text:
Delineation of a volcanic ash body using electrical resistivity profiling
NASA Astrophysics Data System (ADS)
Four lines of electrical resistivity profiling (ERP) were performed to define the extent of a shallow Quaternary volcanic ash deposit being mined in the United States. Inversion results of ERP proved suitable for defining the thickness and lateral extent of the volcanic ash deposit at this testing site. These interpretations were confirmed by shallow borehole drilling. The model sensitivity information indicates that inverted models possess sufficient resolving power down to a depth of 7 m and are fairly consistent in terms of horizontal resolution along the four ERP lines. The bottom of most of the volcanic ash deposit in the study area is less than 7 m in depth. Based on synthesis of the ERP and drill information, the limits of the mineable ash bed resources were clearly defined. Moreover, by integrating the ERP results with a minimal number of optimally placed borings, the volume of the volcanic ash deposit was established at a lesser cost, and with greater accuracy than would be possible with a traditionally designed grid drilling programme.
Xia, Jianghai; Ludvigson, Greg; Miller, Richard D.; Mayer, Lindsay; Haj, Adel
Effective resist profile control
NASA Astrophysics Data System (ADS)
To meet Moore's law, resist resolution improvement has become more and more important. However, it is difficult to improve resist resolution and keep vertical sidewall profile. For example, a high contrast hole resist may cause trench scum, due to very T-top profile. This paper reports several concepts for resist profile tuning without losing performance for lithographic factor , including mask error enhancement factor (MEEF), depth of focus (DOF), and critical dimension uniformity (CDU). To quantitative analysis the resist profile improvement, we define a new factor, Scum fail ratio (F/R%) for new techniques evaluation. The new techniques, including floatable additive, floatable PAG, and new monomer, are discussed. From X-SEM and CD-SEM data, former three concepts could improve resist sidewall profile quantitatively evaluated by Scum fail F/R% and keep lithographic factors. In addition, another key factor, resist residue defect, is also discussed. The high contrast resist with higher receding contact angle (RCA) easily generates more residue defect after development. With the new monomer composition, RCA of Resist E is decreased from 54 to 48 degree after development. Therefore, the residue defect is improved one order.
Liu, Chen-Yu; Wang, Chien-Wei; Huang, Chun-Ching; Chang, Ching-Yu; Ku, Yao-Ching
NSDL National Science Digital Library
An update to the 1996 State Electricity Profiles, this report from the Energy Information Administration (EIA) is "designed to provide basic information about the electricity industry on a State-by-State basis by profiling each State and the District of Columbia with a description of its electricity industry through graphics, and tables." The data for ten states has been changed, with future updates due in the coming weeks.
Teaching Electrical Resistance.
ERIC Educational Resources Information Center
Discusses different approaches to the teaching of electrical resistance as presented by different authors of physics textbooks. Evaluates, compares, and expresses personal preferences for certain approaches. (GA)
Iona, Mario
Electric Resistance Tensometer.
National Technical Information Service (NTIS)
Object of Invention: The electric resistance tensometer for measuring pressures and deformations at higher temperatures or in aggressive media, made in form of a wire or strip of alloy, containing titanium, characterized by the fact, that for the purpose ...
B. A. Galgovskii B. M. Rakhman V. M. Zubkov
Electrical Resistance Experiment
NSDL National Science Digital Library
The Materials Science and Technology Teacher's Workshop (MAST) provides this experiment on electrical resistance and glass. The module involves breaking the glass from a light bulb and then measuring the resistance across the bulb's electrodes. The lesson includes a step by step explanation of the laboratory procedure and a link to a video clip.
Electrical Resistivity Imaging
Electrical resistivity imaging (ERI) is a geophysical method originally developed within the mining industry where it has been used for decades to explore for and characterize subsurface mineral deposits. It is one of the oldest geophysical methods with the first documented usag...
This report covers the electrical resistance tomography (ERT) work performed at the Hanford Reservation, 200 East Area Vadose test (Sisson and Lu) site during the period March 23 through May 5, 2001. The purposes of the ERT work were to: (1) compare and contrast the development of the highly concentrated sodium thio-sulfate plume (FY01 work) with the fresh river water plume observed during FY00; (2) use the resistance images to infer the dynamics of the plume during two or three of the sodium thiosulfate releases and during the water ''chaser'' release; (3) determine the influence of the site's steel casings on the capability to construct reliable ERT images; (4) determine if the steel casings at the site can be used as long electrodes to provide useful images of at least one release; and (5) develop quantitative estimates of the noise in the data and its effect on reconstructed images.
Ramirez, Abelardo L.; Daily, William D.; Binley, Andrew M.
Resistivity Profile in an Urban Setting
NSDL National Science Digital Library
The student works with an electrical resistivity profile and well information (stratigraphy and static water level)taken in an urban area. The goal is to create an integrated subsurface interpretation from geological and geophysical data. The activity gives students practice in using simple quantitative data to create a hypothetical but data-driven picture of the subsurface. Uses online and/or real-time data Has minimal/no quantitative component Uses geophysics to solve problems in other fields
Montgomery, William
Electrically Variable Resistive Memory Devices
NASA Technical Reports Server (NTRS)
Nonvolatile electronic memory devices that store data in the form of electrical- resistance values, and memory circuits based on such devices, have been invented. These devices and circuits exploit an electrically-variable-resistance phenomenon that occurs in thin films of certain oxides that exhibit the colossal magnetoresistive (CMR) effect. It is worth emphasizing that, as stated in the immediately preceding article, these devices function at room temperature and do not depend on externally applied magnetic fields. A device of this type is basically a thin film resistor: it consists of a thin film of a CMR material located between, and in contact with, two electrical conductors. The application of a short-duration, low-voltage current pulse via the terminals changes the electrical resistance of the film. The amount of the change in resistance depends on the size of the pulse. The direction of change (increase or decrease of resistance) depends on the polarity of the pulse. Hence, a datum can be written (or a prior datum overwritten) in the memory device by applying a pulse of size and polarity tailored to set the resistance at a value that represents a specific numerical value. To read the datum, one applies a smaller pulse - one that is large enough to enable accurate measurement of resistance, but small enough so as not to change the resistance. In writing, the resistance can be set to any value within the dynamic range of the CMR film. Typically, the value would be one of several discrete resistance values that represent logic levels or digits. Because the number of levels can exceed 2, a memory device of this type is not limited to binary data. Like other memory devices, devices of this type can be incorporated into a memory integrated circuit by laying them out on a substrate in rows and columns, along with row and column conductors for electrically addressing them individually or collectively.
Liu, Shangqing; Wu, Nai-Juan; Ignatiev, Alex; Charlson, E. J.
State electricity profiles, March 1999
Due to the role electricity plays in the Nation`s economic and social well-being, interested parties have been following the electric power industry`s transition by keeping abreast of the restructuring and deregulation events that are taking place almost daily. Much of the attention centers around the States and how they are restructuring the business of electricity supply within their respective jurisdictions. This report is designed to profile each State and the District of Columbia regarding not only their current restructuring activities, but also their electricity generation and concomitant statistics from 1986 through 1996. Included are data on a number of subject areas including generating capability, generation, revenues, fuel use, capacity factor for nuclear plants, retail sales, and pollutant emissions. Although the Energy Information Administration (EIA) publishes this type of information, there is a lack of a uniform overview for each individual State. This report is intended to help fill that gap and also to serve as a framework for more detailed studies. In addition to basic statistics in tables and graphs, a textual section is provided for each State, discussing some of the points relative to electricity production that are noteworthy in, or unique to, that particular State. Also, each State is ranked according to the place it holds, as compared to the rest of the states, in various relevant areas, such as its average price of electricity per kilowatthour, its population, and its emissions of certain atmospheric pollutants. The final chapter covers the Nation as a whole. 451 figs., 520 tabs.
Electrical Resistivity Features of Compacted Expansive Soils
An electrical resistance apparatus with a highly sensitive alternate current bridge was developed in the paper for the purpose of measuring the electrical resistivity of soils and eliminating the low frequency polarization. The electrical resistivity of Guangxi expansive soils was measured in the laboratory using the developed apparatus. The investigation result demonstrates that the electrical resistivity of the Guangxi expansive
Mingliang Yan; Linchang Miao; Ying Cui
Resist profile aware source mask optimization
NASA Astrophysics Data System (ADS)
In this paper, we present the approach and results of resist profile aware source mask optimization (SMO). In this approach, the cost functions for optimization include the image properties calculated not only from the resist bottom image planes, but also from the top image planes. Consequently, the optimized source and mask shapes are a good balance between the process window for the bottom CD's, and top CD control to ensure a straight resist profile favorable for the etching process. We built up the flow of resist profile aware SMO and implemented it on a 1� nm node back-end layer. Two best candidate sources, SMO1 and SMO2 were generated from the conventional SMO flow and the resist profile aware SMO flow, respectively. The simulation results indicate that a better resist profile is achieved by SMO2, although it gives rise to a relatively smaller overlapping process window evaluated at the resist bottom. Wafer data including bottom CD measurement for critical pattern clips and cross-sectional SEM images from selected patterns have shown good matching with the simulation results, indicating that resist-profile aware SMO is a feasible approach to optimize the illumination sources for a reasonable bottom CD based process window as well as favorable resist profiles.
Chen, Ao; Foong, Yee Mei; Hsieh, Michael; Khoh, Andrew; Hsu, Stephen; Feng, Mu; Qiu, Jianhong; Aquino, Chris
Electrical resistivity of composite superconductors
NASA Technical Reports Server (NTRS)
In addition to its superconducting properties, a superconductor is usually characterized by poor thermal conductivity and relatively high electrical resistivity in the normal state. To remedy this situation a study of superconducting properties of Cu-rich CU-Nb wires prepared by directionally solidified and cold-rolled technique was conducted. Some of the specimens were prepared by melting, directional solidification and diffusing in Tin. A total of 12 wire specimens was tested. Each specimen was analyzed by plotting experimental data into the following curves: the graph of the residual resistivity as a function of the specimen current at 4.3 K; and the graph of the electrical resistivity as a function of the temperature at a constant current.
Davis, J. H.; Lee, J. A.
Dynamic electrical resistance effects in resistance spot welding
The effects of dynamic electrical resistance subject to AC on transport variables, cooling rate and nugget shape during resistance spot welding are realistically investigated. The model accounts for electromagnetic force, heat generations and contact resistances at the faying surface and electrode-workpiece interfaces and bulk resistance in workpieces. Contact resistances are comprised of constriction and film resistances, which are functions of
T. H. Wu; J. E. Ho; P. S. Wei
A GIS Method for Analyzing Electrical Resistivity
NASA Astrophysics Data System (ADS)
Shallow electrical resistivity methods provide a relatively easy and cost-effective way of mapping the subsurface in wetland environments. Traditional ways of analyzing these data include curve matching, analytical methods, and pseudosections, which resemble geologic cross sections. Psuedosections and Three Dimensional (3D) results can be obtained from specialized software, such as RES3DINV or EarthImager. In recent years, ArcGIS has become very popular in environmental studies, but not as popular in electrical resistivity data analysis. In a previous study, we demonstrated that ArcGIS can be used in electrical resistivity analysis. The objective of this project was to assess the performance and accuracy of ArcGIS in analyzing 3D-wetland resistivity data. The study area used for this analysis was located at the Oconee River Greenway, in Milledgeville, Georgia. The area of focus was Alice Basin, which is one of the small basins in the Greenway wetland area. Within the wetland, we observed significant subsurface flow that transported water between basins and from the wetland into nearby Fishing Creek. This subsurface flow is typically restricted to a high permeability layer, and is responsible for most of the water loss within the wetland. To better understand how this wetland functions, electrical resistivity profiling was used to map the subsurface and the extent of the high permeability layer. The data were collected with an ULTRA MiniRes resistivity meter, using the dipole-dipole electrode configuration. We then developed an easy GIS-method for analyzing these data in 3D, and compared the results with those from the specialized resistivity software, RES3DINV. The top layer outputs for both programs were compared to visual observations and soils in the field. The spline interpolation technique in ArcGIS produced a superior match to the observed data, than results from RES3DINV. However, results for the lower layers were similar between the two programs. An additional advantage of the GIS results was that the layers can be assembled in ascending order, and then viewed in a 3D block in ArcScene viewer. The 3D block can also be saved into a video that displays different angles of view. Overall, ArcGIS can be used as a valuable, reliable, and readily available program for visualizing 3D resistivity data.
Hazzard, S. C.; Mutiti, S.; Berry, L. E.; GCSU Hydrogeologists
Resist profile simulation with fast lithography model
NASA Astrophysics Data System (ADS)
A traditional approach to construct a fast lithographic model is to match wafer top-down SEM images, contours and/or gauge CDs with a TCC model plus some simple resist representation. This modeling method has been proven and is extensively used for OPC modeling. As the technology moves forward, this traditional approach has become insufficient in regard to lithography weak point detection, etching bias prediction, etc. The drawback of this approach is from metrology and simulation. First, top-down SEM is only good for acquiring planar CD information. Some 3D metrology such as cross-section SEM or AFM is necessary to obtain the true resist profile. Second, the TCC modeling approach is only suitable for planar image simulation. In order to model the resist profile, full 3D image simulation is needed. Even though there are many rigorous simulators capable of catching the resist profile very well, none of them is feasible for full-chip application due to the tremendous consumption of computational resource. The authors have proposed a quasi-3D image simulation method in the previous study [1], which is suitable for full-chip simulation with the consideration of sidewall angles, to improve the model accuracy of planar models. In this paper, the quasi-3D image simulation is extended to directly model the resist profile with AFM and/or cross-section SEM data. Resist weak points detected by the model generated with this 3D approach are verified on the wafer.
He, Yan-Ying; Chou, Chih-Shiang; Tang, Yu-Po; Huang, Wen-Chun; Liu, Ru-Gun; Gau, Tsai-Sheng
Electrical resistance of muscle capillary endothelium.
A recently developed technique for in vivo determination of the electrical resistance of vascular endothelium in microvessels was applied to the vessels in a thin frog muscle, m. cutaneus pectoris. The technique consists of injection of current via a glass micropipette into a capillary and measurement of the resulting intra- and extravascular potential profiles with another micropipette placed at various distances from the current source. The theory of Peskoff and Eisenberg (1974) was used to handle the problems arising from distributed extravascular resistances and was experimentally shown to describe the external field satisfactorily. With this extension of one-dimensional cable theory the specific electrical resistance of arterial microvessels was 33 omega cm2 and of venous capillaries 23 omega cm2. The "length constants" were 135 and 112 micrometers, respectively. If results from arterial and venous vessels are taken together, the ionic permeabilities at 20 degrees C were PNa = 3.9 X 10(-5) cm X s-1, PK = 5.7 X 10(-5) cm X s-1, PCl = 5.9 X 10(-5) cm X s-1 and PHCO3 = 3.4 X 10(-5) cm X s-1. These figures agree with figures for capillary permeability obtained in tracer experiments on whole muscle. The study bridges a gap between single capillary and whole organ techniques with the conclusion that the two different approaches lead to similar results in muscle capillaries. PMID:6601500
Olesen, S P; Crone, C
Electrical resistance of muscle capillary endothelium.
A recently developed technique for in vivo determination of the electrical resistance of vascular endothelium in microvessels was applied to the vessels in a thin frog muscle, m. cutaneus pectoris. The technique consists of injection of current via a glass micropipette into a capillary and measurement of the resulting intra- and extravascular potential profiles with another micropipette placed at various distances from the current source. The theory of Peskoff and Eisenberg (1974) was used to handle the problems arising from distributed extravascular resistances and was experimentally shown to describe the external field satisfactorily. With this extension of one-dimensional cable theory the specific electrical resistance of arterial microvessels was 33 omega cm2 and of venous capillaries 23 omega cm2. The "length constants" were 135 and 112 micrometers, respectively. If results from arterial and venous vessels are taken together, the ionic permeabilities at 20 degrees C were PNa = 3.9 X 10(-5) cm X s-1, PK = 5.7 X 10(-5) cm X s-1, PCl = 5.9 X 10(-5) cm X s-1 and PHCO3 = 3.4 X 10(-5) cm X s-1. These figures agree with figures for capillary permeability obtained in tracer experiments on whole muscle. The study bridges a gap between single capillary and whole organ techniques with the conclusion that the two different approaches lead to similar results in muscle capillaries.
Olesen, S P; Crone, C
Molecular profiling of platinum resistant ovarian cancer
The aim of this study is to discover a gene set that can predict resistance to platinum-based chemotherapy in ovarian cancer. The study was performed on 96 primary ovarian adenocarcinoma specimens from 2 hospitals all treated with platinum-based chemotherapy. In our search for genes, 24 specimens of the discovery set (5 nonresponders and 19 responders) were profiled in duplicate with
Jozien Helleman; Maurice P. H. M. Jansen; Paul N. Span; Iris L. van Staveren; Leon F. A. G. Massuger; Marion E. Meijer-van Gelder; C. G. J. Sweep; Patricia C. Ewing; Maria E. L. van der Burg; Gerrit Stoter; Kees Nooter; Els M. J. J. Berns
Electrical Trades. Occupational Competency Analysis Profile.
ERIC Educational Resources Information Center
This Occupational Competency Analysis Profile (OCAP), which is one of a series of OCAPs developed to identify the skills that Ohio employers deem necessary to entering a given occupation/occupational area, lists the occupational, academic, and employability skills required of individuals entering the electrical trades. The introduction explains�
Ohio State Univ., Columbus. Vocational Instructional Materials Lab.
Vertical soil profiling using a galvanic contact resistivity scanning approach.
Proximal sensing of soil electromagnetic properties is widely used to map spatial land heterogeneity. The mapping instruments use galvanic contact, capacitive coupling or electromagnetic induction. Regardless of the type of instrument, the geometrical configuration between signal transmitting and receiving elements typically defines the shape of the depth response function. To assess vertical soil profiles, many modern instruments use multiple transmitter-receiver pairs. Alternatively, vertical electrical sounding can be used to measure changes in apparent soil electrical conductivity with depth at a specific location. This paper examines the possibility for the assessment of soil profiles using a dynamic surface galvanic contact resistivity scanning approach, with transmitting and receiving electrodes configured in an equatorial dipole-dipole array. An automated scanner system was developed and tested in agricultural fields with different soil profiles. While operating in the field, the distance between current injecting and measuring pairs of rolling electrodes was varied continuously from 40 to 190 cm. The preliminary evaluation included a comparison of scan results from 20 locations to shallow (less than 1.2 m deep) soil profiles and to a two-layer soil profile model defined using an electromagnetic induction instrument. PMID:25057135
Pan, Luan; Adamchuk, Viacheslav I; Prasher, Shiv; Gebbers, Robin; Taylor, Richard S; Dabas, Michel
Electrical Resistivity of Naphthalene, Phenanthrene and Glucose.
National Technical Information Service (NTIS)
The electrical volume resistivity of naphthalene, phenanthrene and glucose was determined in the region of the melting point and, in the case of glucose, in the glass transition region. Both naphthalene and phenanthrene exhibit abrupt increases in the mag...
R. W. Warfield
Electrical Resistivity of Metal Powder Aggregates
An equation for calculating the electrical resistivity of a compressed powder mass, consisting of oxide-coated metal particles, has been derived. In addition to the intrinsic interest of the problem, the proposed equation is useful for describing the very early stages of electrical sintering processes. The problem is approached in a new way, relating the actual powder system to an equivalent
J. M. Montes; F. G. Cuevas; J. Cintas
Effect of electric shock on capillary resistance
Summary 1.To determine the effect of electric shock on the capillary resistance (CR) a study was made of the CR of 21 female patients treated for different diseases in a mental hospital with a total of 31 electric shocks. The measurements were taken in the infraclavicular region by the suction method.2.The CR was recorded 15 minutes, 1 hour and 6
Rauno Heikinheimo; Osmo Sallas
Anisotropic electric surface resistance of Cu(110)
The electric surface resistance is measured without contacts by grazing incidence of p-polarized infrared (IR) radiation for the adsorbates CO and C{sub 2}H{sub 4}, which settle on top of the close packed atomic ridges of Cu(110) in the <1, -1, 0> direction. Surface resistance has only been observed for the IR electric currents in this direction. This can be explained by the assumption that IR induced currents in the <001> direction can only flow in the second and deeper layers of Cu(110). Therefore, in this direction, there is no friction with the adsorbates and hence no surface resistance.
Otto, A. [Institut f?r Physik der kondensierte Materie, Universit?t D?sseldorf D-40225, Germany; Lilie, P. [Synchrotron SOLEIL; Dumas, P. [Synchrotron SOLEIL; Hirschmugl, C. [University of Wisconsin-Milwaukee; Pilling, M. [University of Wisconsin-Milwaukee; Williams, Gwyn P. [JLAB
Electrical Resistivity of Metal Powder Aggregates
NASA Astrophysics Data System (ADS)
An equation for calculating the electrical resistivity of a compressed powder mass, consisting of oxide-coated metal particles, has been derived. In addition to the intrinsic interest of the problem, the proposed equation is useful for describing the very early stages of electrical sintering processes. The problem is approached in a new way, relating the actual powder system to an equivalent system consisting of deforming spheres in a simple cubic packing, which is much easier to examine. The proposed equation was experimentally verified from measurements of the electrical resistivity for aluminum, bronze, iron, and nickel powders under pressure. The consistency between theoretical predictions and experimental results was reasonably good in all cases.
Montes, J. M.; Cuevas, F. G.; Cintas, J.
Electrical resistances of corn root segments.
Longitudinal electrical resistances have been measured on 2-centimeter segments of corn (Zea mays L.) roots, cut at varying distances from the root apex. The segment resistances vary from 400 to 100 kilohms per centimeter along the root length (apex to 18 cm), with the maximum occurring in the 2- to 4-centimeter segment, and decreasing thereafter toward the root base. Measurements of isolated root cortical sleeves and steles show that the pathway of least resistance is in the cortex, which has a greater cross-sectional area; the specific resistance of the older stele is less than that of the cortex. The anatomical state of the xylem cannot be inferred from electrical resistance determinations. PMID:16659437
Anderson, W P; Higinbotham, N
Molecular profiling of platinum resistant ovarian cancer.
The aim of this study is to discover a gene set that can predict resistance to platinum-based chemotherapy in ovarian cancer. The study was performed on 96 primary ovarian adenocarcinoma specimens from 2 hospitals all treated with platinum-based chemotherapy. In our search for genes, 24 specimens of the discovery set (5 nonresponders and 19 responders) were profiled in duplicate with 18K cDNA microarrays. Confirmation was done using quantitative RT-PCR on 72 independent specimens (9 nonresponders and 63 responders). Sixty-nine genes were differentially expressed between the nonresponders (n=5) and the responders (n=19) in the discovery phase. An algorithm was constructed to identify predictive genes in this discovery set. This resulted in 9 genes (FN1, TOP2A, LBR, ASS, COL3A1, STK6, SGPP1, ITGAE, PCNA), which were confirmed with qRT-PCR. This gene set predicted platinum resistance in an independent validation set of 72 tumours with a sensitivity of 89% (95% CI: 0.68-1.09) and a specificity of 59% (95% CI: 0.47-0.71)(OR=0.09, p=0.026). Multivariable analysis including patient and tumour characteristics demonstrated that this set of 9 genes is independent for the prediction of resistance (p<0.01). The findings of this study are the discovery of a gene signature that classifies the tumours, according to their response, and a 9-gene set that determines resistance in an independent validation set that outperforms patient and tumour characteristics. A larger independent multicentre study should further confirm whether this 9-gene set can identify the patients who will not respond to platinum-based chemotherapy and could benefit from other therapies. PMID:16287073
Helleman, Jozien; Jansen, Maurice P H M; Span, Paul N; van Staveren, Iris L; Massuger, Leon F A G; Meijer-van Gelder, Marion E; Sweep, Fred C G J; Ewing, Patricia C; van der Burg, Maria E L; Stoter, Gerrit; Nooter, Kees; Berns, Els M J J
Electrical resistance of carbon-nanofiber concrete
NASA Astrophysics Data System (ADS)
Concrete is the most widely used construction material, and carbon nanofibers have many advantages in both mechanical and electrical properties such as high strength, high Young's modulus and high conductivity. In this paper, the mechanical and electrical properties of concrete containing carbon nanofibers (CNF) are experimentally studied. The test results indicate that the compressive strength and per cent reduction in electrical resistance while loading concrete containing CNF are much greater than those of plain concrete. Finally, a reasonable concentration of CNF is obtained for use in concrete which not only enhances compressive strength, but also improves the electrical properties required for strain monitoring, damage evaluation and self-health monitoring of concrete.
Gao, Di; Sturm, Mariel; Mo, Y. L.
Synthesis and electrical resistivity of nickel polymethacrylate
This paper reports that synthesis of nickel polymethacrylate was carried out using methanolic solutions of sodium hydroxide and polymethacrylic acid. The electrical resistivity of the pellets made from Ni-polymethacrylate was measured at different voltages and temperatures. Results showed that the electrical resistivity of Ni-polymethacrylate decreases significantly with voltage in high temperature regions but the decrease is insignificant at temperatures nearing room temperature. The activation energy at low temperatures is approximately 0.8 eV whereas at high temperature it is in the range 0.21-0.27 eV.
Chohan, M.H.; Khalid, A.H. (Lab. for Electrical Characterization of Polymers, Dept. of Electronics, Quaid-i-Azam Univ., Islamabad (PK)); Zulfiqar, M.; Butt, P.K.; Khan, F.; Hussain, R. (Dept. of Chemistry, Quaid-i-Azam Univ., Islamabad (PK))
Electrical Resistivity of Metal Powder Aggregates
An equation for calculating the electrical resistivity of a compressed powder mass, consisting of oxide-coated metal particles,\\u000a has been derived. In addition to the intrinsic interest of the problem, the proposed equation is useful for describing the\\u000a very early stages of electrical sintering processes. The problem is approached in a new way, relating the actual powder system\\u000a to an equivalent
J. M. Montes; F. G. Cuevas; J. Cintas
Resistance after firing protected electric match
An electric match having electrical leads embedded in flame-producing compound is protected against an accidental resistance across the leads after firing by a length of heat-shrinkable tubing encircling the match body and having a skirt portion extending beyond the leads. The heat of the burning match and an adjacent thermal battery causes the tubing to fold over the end of the match body, covering the ends of the leads and protecting them from molten pieces of the battery.
Montoya, Arsenio P. (Albuquerque, NM)
Electrical Characteristics of Resistance Welding Tools
Methods of measurement and calculation of resistance welding tools, particularly for the large group of nonstandard type portable welding guns, are contained in this paper. Electrical characteristics have considerable bearing on 1. Kilovolt-amperes at an installation. 2. Required secondary voltage of the welding transformer. 3. Efficiency of the tool. Timesaving means for either measurement or calculation provide accuracies well within
E. M. Callender
Continuous resistivity profiling data from the Corsica River Estuary, Maryland
Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine its importance in nutrient delivery to the Chesapeake Bay. The Corsica River Estuary represents a coastal lowland setting typical of much of the eastern bay. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the lower estuary in April and May 2007. Resource managers are concerned about nutrients that are entering the estuary via SGD that may be contributing to eutrophication, harmful algal blooms, and fish kills. Techniques employed in the study included continuous resistivity profiling (CRP), piezometer sampling of submarine groundwater, and collection of a time series of radon tracer activity in surface water. A CRP system measures electrical resistivity of saturated subestuarine sediments to distinguish those bearing fresh water (high resistivity) from those with saline or brackish pore water (low resistivity). This report describes the collection and processing of CRP data and summarizes the results. Based on a grid of 67.6 kilometers of CRP data, low-salinity (high-resistivity) groundwater extended approximately 50-400 meters offshore from estuary shorelines at depths of 5 to >12 meters below the sediment surface, likely beneath a confining unit. A band of low-resistivity sediment detected along the axis of the estuary indicated the presence of a filled paleochannel containing brackish groundwater. The meandering paleochannel likely incised through the confining unit during periods of lower sea level, allowing the low-salinity groundwater plumes originating from land to mix with brackish subestuarine groundwater along the channel margins and to discharge. A better understanding of the spatial variability and geological controls of submarine groundwater flow beneath the Corsica River Estuary could lead to improved models and mitigation strategies for nutrient over-enrichment in the estuary and in other similar settings.
Cross, V.A.; Bratton, J.F.; Worley, C.R.; Crusius, J.; Kroeger, K.D.
Release Resistant Electrical Interconnections For Mems Devices
A release resistant electrical interconnection comprising a gold-based electrical conductor compression bonded directly to a highly-doped polysilicon bonding pad in a MEMS, IMEMS, or MOEMS device, without using any intermediate layers of aluminum, titanium, solder, or conductive adhesive disposed in-between the conductor and polysilicon pad. After the initial compression bond has been formed, subsequent heat treatment of the joint above 363 C creates a liquid eutectic phase at the bondline comprising gold plus approximately 3 wt % silicon, which, upon re-solidification, significantly improves the bond strength by reforming and enhancing the initial bond. This type of electrical interconnection is resistant to chemical attack from acids used for releasing MEMS elements (HF, HCL), thereby enabling the use of a "package-first, release-second" sequence for fabricating MEMS devices. Likewise, the bond strength of an Au--Ge compression bond may be increased by forming a transient liquid eutectic phase comprising Au-12 wt % Ge.
Peterson, Kenneth A. (Albuquerque, NM); Garrett, Stephen E. (Albuquerque, NM); Reber, Cathleen A. (Corrales, NM)
Estimating soil suction from electrical resistivity
NASA Astrophysics Data System (ADS)
Soil suction and resistivity strongly depend on the degree of soil saturation and, therefore, both are used for estimating water content variations. The main difference between them is that soil suction is measured using tensiometers, which give point information, while resistivity is obtained by tomography surveys, which provide distributions of resistivity values in large volumes, although with less accuracy. In this paper, we have related soil suction to electrical resistivity with the aim of obtaining information about soil suction changes in large volumes, and not only for small areas around soil suction probes. We derived analytical relationships between soil matric suction and electrical resistivity by combining the empirical laws of van Genuchten and Archie. The obtained relationships were used to evaluate maps of soil suction values in different ashy layers originating in the explosive activity of the Mt Somma-Vesuvius volcano (southern Italy). Our findings provided a further example of the high potential of geophysical methods in contributing to more effective monitoring of soil stress conditions; this is of primary importance in areas where rainfall-induced landslides occur periodically.
Piegari, E.; Di Maio, R.
Electrical resistance of a capillary endothelium
The electrical resistance of consecutive segments of capillaries has been determined by a method in which the microvessels were treated as a leaky, infinite cable. A two-dimensional analytical model to describe the potential field in response to intracapillary current injection was formulated. The model allowed determination of the electrical resistance from four sets of data: the capillary radius, the capillary length constant, the length constant in the mesentery perpendicular to the capillary, and the relative potential drop across the capillary wall. Of particular importance were the mesothelial membranes covering the mesenteric capillaries with resistances several times higher than that of the capillary endothelium. 27 frog mesenteric capillaries were characterized. The average resistance of the endothelium was 1.85 omega cm2, which compares well with earlier determinations of the ionic permeability of such capillaries. However, heterogeneity with respect to resistance was observed, that of 10 arterial capillaries being 3.0 omega cm2 as compared with 0.95 omega cm2 for 17 mid- and venous capillaries. The average in situ length constant was 99 micrometers for the arterial capillaries and 57 micrometers for the mid- and venous capillaries. It is likely that the ions that carry the current must move paracellularly, through junctions that are leaky to small solutes.
Tests and Calibration of the Static Electric Resistance Strain Gage.
National Technical Information Service (NTIS)
This article points out problems existing in the techniques of authenticating an electric resistance strain gage. After a brief explanation of technical requirements of the electric resistance strain gage in static strain measurements, the test and calibr...
S. Tsao
Integrating Shear-Wave Reflection and Resistivity Profiling to Improve Subsurface Characterization of Glacial Sediments
NASA Astrophysics Data System (ADS)
In Illinois, both high resolution seismic reflection and 2-D resistivity profiling have become fairly common tools for mapping glacial sediments. Over the past several years we have been using the two methods in combination to improve the characterization of these sediments and to refine geologic and hydrogeologic models. We demonstrate our approach with several case studies where high-resolution shear (S)-wave reflection and electrical resistivity profiling surveys were acquired at the same locations in northern and central Illinois. The two geophysical methods measure the mechanical and the electrical properties of these sediments in the subsurface which together improve our understanding of the sedimentary sequences and the underlying bedrock surface. We present results from measurements made along co-located geophysical lines which vary in length from 400 m to greater than 2300 m. Typically, the S-wave reflection profiles have greater vertical resolution and provide better imaging of depositional surfaces than the corresponding resistivity profiles. On the other hand, the resistivity profiles better express the horizontal variability within individual units compared to the reflection profiles. The reflection profiles more reliably image the bedrock surface, whereas the resistivity profiles are more sensitive to variations in moisture content, mineral content and cementation within the glacial sediments. Together, the overall geometry of depositional packages can be inferred from reflection surfaces, while compositional variations within those packages can be inferred from variations primarily in the resistivity data and secondarily in the seismic data. Geophysical and geological interpretations are constrained by core data and downhole geophysical data from boreholes located on or near the geophysical profiles.
Larson, T. H.; Ismail, A. M.; Thomason, J.; Curry, B.; Stumpf, A.; Dey, W.
Electrical resistivity of copper, gold, palladium, and silver
In this work, recommended values for the electrical resistivity as a function of temperature from the cryogenic region to well beyond the melting point are given for bulk pure copper, gold, palladium, and silver. In addition to the total electrical resistivity values for the solid state, intrinsic electrical resistivity values are presented from cryogenic temperatures to the melting point. The
R. A. Matula
Electrical resistance tomography from measurements inside a steel cased borehole
Electrical resistance tomography (ERT) produced from measurements taken inside a steel cased borehole. A tomographic inversion of electrical resistance measurements made within a steel casing was then made for the purpose of imaging the electrical resistivity distribution in the formation remotely from the borehole. The ERT method involves combining electrical resistance measurements made inside a steel casing of a borehole to determine the electrical resistivity in the formation adjacent to the borehole; and the inversion of electrical resistance measurements made from a borehole not cased with an electrically conducting casing to determine the electrical resistivity distribution remotely from a borehole. It has been demonstrated that by using these combined techniques, highly accurate current injection and voltage measurements, made at appropriate points within the casing, can be tomographically inverted to yield useful information outside the borehole casing.
Daily, William D. (Livermore, CA); Schenkel, Clifford (Walnut Creek, CA); Ramirez, Abelardo L. (Pleasanton, CA)
Electrical resistivity and seismic refraction studies for groundwater in the Jodhpura area, Rajasthan
The results of geophysical investigations carried out for groundwater employing seismic refraction and electrical resistivity methods near Jodhpura (27o47'30?N:75o42'40?E) in the Jhunjhunu District, Rajasthan, are presented. Prominent resistivity low zones, revealed by the resistivity profiles, are indicative of deeper section of unconsolidated sediments overlying the bedrock and are usually favourable locations for groundwater. An equiresistivity and water-level contour map based
P. C. Paul; N. P. Dutta
Electrical Resistance Tomography imaging of concrete
We apply Electrical Resistance Tomography (ERT) for three dimensional imaging of concrete. In ERT, alternating currents are injected into the target using an array of electrodes attached to the target surface, and the resulting voltages are measured using the same electrodes. These boundary measurements are used for reconstructing the internal (3D) conductivity distribution of the target. In reinforced concrete, the metallic phases (reinforcing bars and fibers), cracks and air voids, moisture gradients, and the chloride distribution in the matrix carry contrast with respect to conductivity. While electrical measurements have been widely used to characterize the properties of concrete, only preliminary results of applying ERT to concrete imaging have been published so far. The aim of this paper is to carry out a feasibility evaluation with specifically cast samples. The results indicate that ERT may be a feasible modality for non-destructive evaluation of concrete.
Karhunen, Kimmo [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Seppaenen, Aku, E-mail: email@example.com [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Lehikoinen, Anssi [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California Berkeley, California (United States); Kaipio, Jari P. [Department of Physics, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio (Finland); Department of Mathematics, University of Auckland, Auckland (New Zealand)
Current antimicrobial resistance profiles among methicillin-resistant Staphylococcus aureus encountered in the outpatient setting
The acquisition of the mec gene complex by methicillin-susceptible Staphylococcus aureus in the community and the increased spread of methicillin-resistant Staphylococcus aureus (MRSA) from the health care setting to the community underscore a need to monitor the resistance phenotypes likely to be encountered among outpatient MRSA. Data from the LEADER 2004 surveillance program were analyzed to evaluate current resistance profiles
Deborah C. Draghi; Daniel F. Sheehan; Patricia Hogan; Daniel F. Sahm
Determination of electrical resistivity of dry coke beds
The electrical resistivity of the coke bed is of great importance when producing FeMn, SiMn, and FeCr in a submerged arc furnace. In these processes, a coke bed is situated below and around the electrode tip and consists of metallurgical coke, slag, gas, and metal droplets. Since the basic mechanisms determining the electrical resistivity of a coke bed is not yet fully understood, this investigation is focused on the resistivity of dry coke beds consisting of different carbonaceous materials, i.e., coke beds containing no slag or metal. A method that reliably compares the electrical bulk resistivity of different metallurgical cokes at 1500{sup o} C to 1600{sup o}C is developed. The apparatus is dimensioned for industrial sized materials, and the electrical resistivity of anthracite, charcoal, petroleum coke, and metallurgical coke has been measured. The resistivity at high temperatures of the Magnitogorsk coke, which has the highest resistivity of the metallurgical cokes investigated, is twice the resistivity of the Corus coke, which has the lowest electrical resistivity. Zdzieszowice and SSAB coke sort in between with decreasing resistivities in the respective order. The electrical resistivity of anthracite, charcoal, and petroleum coke is generally higher than the resistivity of the metallurgical cokes, ranging from about two to about eight times the resistivity of the Corus coke at 1450{sup o}C. The general trend is that the bulk resistivity of carbon materials decreases with increasing temperature and increasing particle size.
Eidem, P.A.; Tangstad, M.; Bakken, J.A. [NTNU, Trondheim (Norway)
Determination of Electrical Resistivity of Dry Coke Beds
NASA Astrophysics Data System (ADS)
The electrical resistivity of the coke bed is of great importance when producing FeMn, SiMn, and FeCr in a submerged arc furnace. In these processes, a coke bed is situated below and around the electrode tip and consists of metallurgical coke, slag, gas, and metal droplets. Since the basic mechanisms determining the electrical resistivity of a coke bed is not yet fully understood, this investigation is focused on the resistivity of dry coke beds consisting of different carbonaceous materials, i.e., coke beds containing no slag or metal. A method that reliably compares the electrical bulk resistivity of different metallurgical cokes at 1500 �C to 1600 �C is developed. The apparatus is dimensioned for industrial sized materials, and the electrical resistivity of anthracite, charcoal, petroleum coke, and metallurgical coke has been measured. The resistivity at high temperatures of the Magnitogorsk coke, which has the highest resistivity of the metallurgical cokes investigated, is twice the resistivity of the Corus coke, which has the lowest electrical resistivity. Zdzieszowice and SSAB coke sort in between with decreasing resistivities in the respective order. The electrical resistivity of anthracite, charcoal, and petroleum coke is generally higher than the resistivity of the metallurgical cokes, ranging from about two to about eight times the resistivity of the Corus coke at 1450 �C. The general trend is that the bulk resistivity of carbon materials decreases with increasing temperature and increasing particle size.
Eidem, P. A.; Tangstad, M.; Bakken, J. A.
Deriving electric vehicle charge profiles from driving statistics
The impacts of EV charging on electricity grids is becoming an increasingly important subject of study, but detailed knowledge about the future charging profiles of EVs appears to be missing. In this study we construct EV charge profiles based upon a large dataset of driving patterns. We consider both controlled and uncontrolled charging scenarios, where the main rationale of the
R. A. Verzijlbergh; Z. Lukszo; E. Veldman; J. G. Slootweg; M. Ilic
A model for generating household electricity load profiles
SUMMARY Electricity consumption data profiles that include details on the consumption can be generated with a bottom-up load models. In these models the load is constructed from elementary load components that can be households or even their individual appliances. In this work a simplified bottom-up model is presented. The model can be used to generate realistic domestic electricity consumption data
Jukka V. Paateron; Peter D. Lund
Controlling the electrical resistance of silicon carbide powders
Conclusions A method is specified for determining the specific electrical resistance of silicon carbide powders; the characteristics of the materials used in the production of silicon carbide electric heaters are determined.
V. I. Kolynina; L. G. Gurvich; V. K. Zakharenkov
Improving 3D resist profile compact modeling by exploiting 3D resist physical mechanisms
NASA Astrophysics Data System (ADS)
3D Resist profile aware OPC has becoming increasingly important to address hot spots generated at etch processes due to the mass occurrence of non-ideal resist profile in 28nm technology node and beyond. It is therefore critical to build compact models capable of 3D simulation for OPC applications. A straightforward and simple approach is to build individual 2D models at different image depths either based on actual wafer measurement data or virtual simulation data from rigorous lithography simulators. Individual models at interested heights can be used by downstream OPC/LRC tools to account for 3D resist profile effects. However, the relevant image depths need be predetermined due to the discontinuous nature of the methodology itself. Furthermore, the physical commonality among the individual 2D models may deviate from each other as well during the separate calibration processes. To overcome the drawbacks, efforts are made in this paper to compute the whole bulk image using Hopkins equation in one shot. The bulk image is then used to build 3D resist models. This approach also opens the feasibility of including resist interface effects (for example, top or bottom out-diffusion), which are important to resist profile formation, into a compact 3D resist model. The interface effects calculations are merged into the bulk image Hopkins equation. Simulation experiments are conducted to demonstrate that resist profile heavily rely on interface conditions. Our experimental results show that those interface effects can be accurately simulated with reference to rigorous simulation results. In modeling reality, such a 3D resist model can be calibrated with data from discrete image planes but can be used at arbitrary interpolated planes. One obvious advantage of this 3D resist model approach is that the 3D model is more physically represented by a common set of resist parameters (in contrast to the individual model approach) for 3D resist profile simulation. A full model calibration test is conducted on a virtual lithography process. It is demonstrated that 3D resist profile of the process can be precisely captured by this method. It is shown that the resist model can be carried to a different lithography process with same resist setup but a different illumination source without model any accuracy degradation. In an additional test, the model is used to demonstrate the capability of resist 3D profile correction by ILT.
Fan, Yongfa; Wu, Cheng-En R.; Ren, Qian; Song, Hua; Schmoeller, Thomas
The electrical resistivity method in cased boreholes
The use of downhole current sources in resistivity mapping can greatly enhance the detection and delineation of subsurface features. The purpose of this work is to examine the resistivity method for current sources in wells cased with steel. The resistivity method in cased boreholes with downhole current sources is investigated using the integral equation (IE) technique. The casing and other bodies are characterized as conductivity inhomogeneities in a half-space. For sources located along the casing axis, an axially symmetric Green's function is used to formulate the surface potential and electric field (E-field) volume integral equations. The situations involving off-axis current sources and three-dimensional (3-D) bodies is formulated using the surface potential IE method. The solution of the 3-D Green's function is presented in cylindrical and Cartesian coordinate systems. The methods of moments is used to solve the Fredholm integral equation of the second kind for the response due to the casing and other bodies. The numerical analysis revealed that the current in the casing can be approximated by its vertical component except near the source and the axial symmetric approximation of the casing is valid even for the 3-D problem. The E-field volume IE method is an effective and efficient technique to simulate the response of the casing in a half-space, whereas the surface potential approach is computationally better when multiple bodies are involved. Analyzing several configurations of the current source indicated that the casing response is influenced by four characteristic factors: conduction length, current source depth,casing depth, and casing length. 85 refs., 133 figs., 11 tabs.
Schenkel, C.J.
Spatial considerations on electrical resistance tomography measurements
NASA Astrophysics Data System (ADS)
This work reports experimental evidence of the effect of certain geometrical parameters on the accuracy of electrical resistance tomography (ERT) measurements in two-phase systems. Emphasis is given to millimetre-size electrodes that suffer from significant electric field distortion due to (a) extension of the measuring volume beyond the electrode plane (fringe effect) and (b) the non-uniform distribution of field strength at the electrode plane. Water constitutes the continuous (conductive) phase, whereas Teflon rods constitute the dispersed (non-conductive) phase. The examined parameters include the diameter of the cylindrical test vessel, the size of electrodes and the number and size (radius and length) of the submerged Teflon rods. The variable in these tests is the axial and radial position of the Teflon rods inside the test cell. It is found that for homogeneously (axially and radially) dispersed rods, the void fraction measured by a set of electrodes at a plane agrees pretty well with 2D theoretical predictions. However, in cases of non-homogeneously dispersed rods, void fraction measurements deviate considerably from theoretical values. This is a manifestation of severe electric field distortion associated with the employed small electrodes. Moreover, evidence is provided that in the examined system, the fringe effect is more significant than the topography of the field strength in distorting measurements. To allow a quantitative analysis of the present data, nonlinear regression combined with dimensional analysis is conducted to derive an expression that describes the void fraction measurements by a set of electrodes at a plane for different axial and radial positions of the submerged rods. A parametric analysis of this expression illustrates the significance of different parameters on ERT measurements.
Lioumbas, John S.; Chatzidafni, Ariadni; Karapantsios, Thodoris D.
Non-Contact Electrical Doping Profiling
NASA Astrophysics Data System (ADS)
Monitoring of dopant concentration in the near surface region is very important in semiconductor manufacturing, especially for epi-technology and ion implantation. Two relevant techniques which have been used are Mercury probe and Elastic probe. Both of them allow profiling of dopant concentration by measuring the capacitance of the depletion layer, CD, versus the applied bias. These techniques are contact in nature. In addition Mercury probe uses Hg, which may be considered undesirable in cleanroom environment. The method being presented is non-contact and non-destructive. A deep depletion layer is created by corona charging of the wafer surface. This depletion layer decays to an equilibrium value due to thermal generation of minority carriers. Two transients are simultaneously monitored during this process: 1) the small signal ac surface photovoltage that measures the depletion layer capacitance, and 2) the contact potential difference that measures the voltage drop across the depletion layer. The set of corresponding C-V data is used to calculate the dopant concentration profile. In silicon, the technique is applicable for dopant concentrations in the range from 1e14 to 1e18 cm-3. The probing depth is limited at the upper end by avalanche breakdown in the semiconductor and at the lower end by the minimum surface barrier. Measurements of dopant profiles on bare and oxidized surfaces using this technique are presented for epitaxial p/p+ and n/n+ substrates, n/p structures, and implanted wafers, covering probing depths from 0.05 ?m to 7 ?m. This non-contact technique can be realized in a simple configuration that may be of interest for universities and research and development centers.
Marinskiy, D.; Lagowski, J.; D'Amico, J.; Findlay, A.; Jastrzebski, L.
Psychological Profile of Survival, Evasion, Resistance and Escape Instructor Personnel.
National Technical Information Service (NTIS)
The Psychological Profile of Navy Survival, Evasion, Resistance, and Escape (SERE) Instructor Personnel is critical to the success of this type of training. Sixty-four SERE instructors were administered a clinical interview; the Shipley, MMPI-2, NEO PI-R,...
J. M. Govia
Electrochemical aspects of electrical resistance gages for concrete
An orientation is given about the origin of double layer and a review of the various theoretical models of the double layer. The implications of the double layer for electrical resistance measurements are discussed. Tests were made to study this effect in case of electrical resistance humidity sensors used for moisture measurements in concrete. The influence of double layer was
J. Bhargava; A. Rehnstrom
Evaluation of contact resistance for isotropic electrically conductive adhesives
Electrically conductive adhesives are discussed and studied with ever-increasing interest as an alternative to solder interconnection in microelectronics circuit packaging. A similar level of scrutiny that is used to evaluate contact resistance performance for interconnections made with solder and separable connectors is necessary for electrically conductive adhesives. Experience with solder interconnection and separable connectors shows low initial contact resistance of
Michael A. Gaynes; Russell H. Lewis; R. F. Saraf; Judith M. Roldan
Viscosity and electrical resistivity of Al-Li melts
NASA Astrophysics Data System (ADS)
The kinematic viscosity and electrical resistivity of Al-Li alloys in the liquid state are studied by a combined electrodeless method. Some theoretical calculations performed to determine the viscosity and electrical resistance by comparing the calculated and experimental data are estimated.
Kononenko, V. I.; Razhabov, A. A.; Ryabina, A. V.
Theory of electrical resistance of multivalley semiconductors with screw dislocations
The diffusion theory of electrical resistance in multivalley semiconductors of Si-type with screw dislocations is developed. Intervalley electron transitions are taken into account. The effect of the inhomogeneous dislocation distribution on the electrical resistance of the crystal is considered.
Yu. V. Kornyushin; P. Streda
Electrical insulation performance under thermal and electrical combined stress for resistive fault current limiters
This paper discusses the electrical insulation performance of resistive superconducting fault current limiters (SFCL) under quench condition exposed to thermal and electrical combined stress. Electrical stress of 50 Hz AC was applied to parallel ring electrodes molded with epoxy resin. Thermal stress simulating the quench of the resistive SFCL was simultaneously applied to the ring electrode by an electromagnetic induction
N. Hayakawa; M. Noe; K.-P. Juengst; H. Okubo
Detection of sinkholes using 2D electrical resistivity imaging
Sinkholes in dolomitic areas are notoriously difficult geophysical targets, and selecting an appropriate geophysical solution is not straightforward. Electrical resistivity imaging, or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. RESTOM surveys were conducted at two sinkhole sites near Pretoria, South Africa. The survey
Michael van Schoor
Detection of sinkholes using 2D electrical resistivity imaging
Sinkholes in dolomitic areas are notoriously difficult geophysical targets, and selecting an appropriate geophysical solution is not straightforward. Electrical resistivity imaging, or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. RESTOM surveys were conducted at two sinkhole sites near Pretoria, South Africa. The survey
Michael van Schoor
Electrical-resistivity measurements for evaluating compacted-soil liners
Theoretical relationships suggest that the hydraulic conductivity of compacted soils can be evaluated with electrical resistivity measurements. On the material scale, high resistivity may be indicative of low molding water content, high air-filled porosity, or high sand or gravel content. On the liner scale, resistivity measurements may be useful for identifying desiccation cracking or poor interlift bonding. Methods exist for
R. J. Kalinski; W. E. Kelly
Resistance of Enterobacter sakazakii to pulsed electric fields
The influence of various environmental factors on Enterobacter sakazakii inactivation by pulsed electric fields was studied and the mechanisms underlying the changes in resistance were also explored. E. sakazakii PEF resistance was higher upon entering the stationary growth phase, but it did not significantly change with growth temperature. E. sakazakii cells were also more resistant to PEF in both acidified
Cristina Arroyo; Guillermo Cebri�n; Rafael Pag�n; Santiago Cond�n
Students� understanding of direct current resistive electrical circuits
Research has shown that both high school and university students' reasoning\\u000apatterns regarding direct current resistive electric circuits often differ from\\u000athe currently accepted explanations. At present, there are no standard\\u000adiagnostic examinations in electric circuits. Two versions of a diagnostic\\u000ainstrument called Determining and Interpreting Resistive Electric circuits\\u000aConcepts Tests (DIRECT) were developed, each consisting of 29 questions. The
Paula Vetter Engelhardta; Robert J. Beichner
Nebulised Aerosol Electrostatic Charge Explored Using Bipolar Electrical Mobility Profiles
Electrostatic particle capture methods have been employed to obtain a live-step aerosol electrical-mobility profile for aerosol droplets with inherent charge of both positive and negative polarities. Aerosols were generated using jet and ultrasonic nebulisers. The two nebulisers produce bipolar electrical-mobility distributions that differ dramatically in magnitude, bipolarity and polarity skew, illustrating the diverse nature of aerosol properties nebulised from the
M. O'Leary; W. Balachandran; F. Chambers
Iron aluminide useful as electrical resistance heating elements
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.
Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Oak Ridge, TN); Fleischhauer, Grier S. (Midlothian, VA); Hajaligol, Mohammad R. (Richmond, VA); Lilly, Jr., A. Clifton (Chesterfield, VA)
Iron aluminide useful as electrical resistance heating elements
The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or ZrO.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B, .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.
Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Oak Ridge, TN); Fleischhauer, Grier S. (Midlothian, VA); Hajaligol, Mohammad R. (Richmond, VA); Lilly, Jr., A. Clifton (Chesterfield, VA)
Exploring independent component analysis for electric load profiling
Electric load profile separation is important in the deregulated environment where competing entities need to assess the load demands based on partial knowledge of the system. We show that independent component analysis (ICA) allows us to estimate the loads using only a small set of active line flow measurements. ICA yields an unbiased statistical description of load behavior which can
Huaiwei Liao; Dagmar Niebur
Metamitron-resistant Chenopodium album from sugar beet: cross-resistance profile.
In recent years, in several of the Belgian sugar beet growing regions, farmers have been confronted with unsatisfactory control of fat hen (Chenopodium album L.). Greenhouse bioassays conducted on reference C. album populations and on "suspected" populations from sugar beet fields where poor fat hen control had been observed, revealed that all "suspected" populations were resistant to metamitron, a key herbicide in the modern low rate weed control programs in sugar beet. These metamitron-resistant biotypes were all cross-resistant to atrazine. Since cross-resistance, particularly negative cross-resistance or reversed resistance, is known to play a major role in resistance management, other herbicides used in sugar beet and/or in rotational crops were tested to determine the cross-resistance profile of metamitron-resistant biotypes. Greenhouse bioassays were conducted using herbicides from different chemical families representing different modes of action. Cross-resistance was found for metribuzin, lenacil and chloridazon, all HRAC Group C1 herbicides that inhibit photosynthesis at PS II. The metamitron-resistant C. album populations examined showed negative cross-resistance to S-metolachlor (HRAC Group K3: inhibition of cell division), prosuifocarb (Group N: lipid synthesis, not AC-Case, inhibition), aclonifen and clomazone (both Group F3: inhibition of carotenoid biosynthesis). PMID:17390814
Mechant, E; Bulcke, R
Correlating electrical resistance to growth conditions for multiwalled carbon nanotubes
A correlation between growth temperature and electrical resistance of multiwalled carbon nanotubes (MWNTs) has been established by measuring the resistance of individual MWNTs grown by microwave plasma-enhanced chemical vapor deposition (PECVD) at 800, 900, and 950 deg. C. The lowest resistances were obtained mainly from MWNTs grown at 900 deg. C. The MWNT resistance is larger on average at lower (800 deg. C) and higher (950 deg. C) growth temperatures. The resistance of MWNTs correlated well with other MWNT quality indices obtained from Raman spectra. This study identifies a temperature window for growing higher-quality MWNTs with fewer defects and lower resistance by PECVD.
Lan, Chun; Amama, Placidus B.; Fisher, Timothy S.; Reifenberger, Ronald G. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)
Electrical resistivity of liquid lanthanides using charge hard sphere system
NASA Astrophysics Data System (ADS)
In the present paper, we have studied electrical resistivity (?) of liquid lanthanides. To describe the structural information, the structure factor S(q) due to the charged hard sphere (CHS) reference systems is used along with our newly constructed model potential. To see the influence of exchange and correlation effect on the electrical resistivity (?) have used different local field correction functions like Hartree (H), Sarkar et al (S) and Taylor (T). Lastly we conclude that the proper choice of the model potential along with local field correction function plays a vital role to the study of the electrical resistivity (?).
Sonvane, Y. A.; Thakor, P. B.; Jani, A. R.
Electrical Stimulation for Drug-Resistant Epilepsy
Objective The objective of this analysis was to evaluate the effectiveness of deep brain stimulation (DBS) and vagus nerve stimulation (VNS) for the treatment of drug-resistant epilepsy in adults and children. Data Sources A literature search was performed using MEDLINE, EMBASE, the Cochrane Library, and the Centre for Reviews and Dissemination database, for studies published from January 2007 until December 2012. Review Methods Systematic reviews, meta-analyses, randomized controlled trials (RCTs), and observational studies (in the absence of RCTs) of adults or children were included. DBS studies were included if they specified that the anterior nucleus of thalamus was the area of the brain stimulated. Outcomes of interest were seizure frequency, health resource utilization, and safety. A cost analysis was also performed. Results The search identified 6 studies that assessed changes in seizure frequency after electrical stimulation: 1 RCT on DBS in adults, 4 RCTs on VNS in adults, and 1 RCT on VNS in children. The studies of DBS and VNS in adults found significantly improved rates of seizure frequency, but the study of VNS in children did not find a significant difference in seizure frequency between the high and low stimulation groups. Significant reductions in hospitalizations and emergency department visits were found for adults and children who received VNS. No studies addressed the use of health resources for patients undergoing DBS. Five studies reported on adverse events, which ranged from serious to transient for both procedures in adults and were mostly transient in the 1 study of VNS in children. Limitations We found no evidence on DBS in children or on health care use related to DBS. The measurement of seizure frequency is self-reported and is therefore subject to bias and issues of compliance. Conclusions Based on evidence of low to moderate quality, both DBS and VNS seemed to reduce seizure frequency in adults. In children, VNS did not appear to be as effective at reducing seizure frequency, but children had significantly fewer hospitalizations and ED visits after VNS implantation. Despite the considerable risks associated with these invasive procedures, long-term adverse events appear to be limited. Plain Language Summary Electrical stimulation of specific areas of the brain is a procedure used to control epileptic seizures when more conventional treatments are not working. Most adults and children with epilepsy are able to control their seizures with medication, but for some patients, drugs are not effective and surgery to remove the part of the brain where the seizures start is not an appropriate option. This study looked at the research available on the effectiveness, safety, and cost of two types of electrical stimulation devices currently licensed for treatment of epilepsy for adults and children in Canada: vagus nerve stimulation (VNS) and deep brain stimulation (DBS). Both approaches appear to be effective at reducing the frequency of seizures in adults. However, the evidence on DBS is limited to a single study with adults; we found no studies of DBS with children. Studies on VNS showed that both adults and children had fewer hospitalizations and emergency department visits after the procedure. Both procedures carry serious risks, but several longer-term studies have found that adverse events appear to be limited. The cost of VNS, including the process of assessing whether or not patients are good candidates for the procedure, is estimated to be about $40,000 per person (and higher for DBS because the device is more expensive and the operating time is longer). Of the 70,000 people in Ontario with epilepsy, about 1,400 (300 children and 1,110 adults) may be candidates for VNS to reduce their seizures.
Chambers, A; Bowen, JM
The Physics Classroom: Electrical Resistance: Journey of a Typical Electron
NSDL National Science Digital Library
This is an interactive tutorial for introductory physics on resistance and Ohm's Law. It explores the journey of an electron through the wires of an electric circuit, explaining how countless collisions between the charge carriers and atoms within the wires result in loss of electrical energy. In the second part of the tutorial, students learn about factors affecting resistance, resistivity values, and how to calculate resistance mathematically. This page is part of The Physics Classroom, a comprehensive set of interactive tutorials, labs, and simulations for students of introductory physics. The Physics Classroom is one of the ComPADRE digital library collections.
Henderson, Tom
Detection of Cracks Using 2d Electrical Resistivity Imaging In A Cultivated Soil
NASA Astrophysics Data System (ADS)
Variations of soil structure is significant for the understanding of water and gas trans- fer in soil profiles. In the context of arable land, soil structure can be compacted due to either agriculture operation (wheel tracks), or hardsetting and crusting processes. As a consequence, soil porosity is reduced which may lead to decrease water infiltra- tion and to anoxic conditions. Porosity can be increased by cracks formation due to swelling and shrinking phenomenon. We present here a laboratory experiment based on soil electrical characteristics. Electrical resistivity allows a non destructive three di- mensional and dynamical analysis of the soil structure. Our main objective is to detect cracks in the soil. Cracks form an electrical resistant object and the contrast of resis- tivity between air and soil is large enough to be detected. Our sample is an undisturbed soil block 240mm*170mm*160mm with an initial structure compacted by wheel traf- fic. Successive artificial cracks are generated. Electrodes built with 2 mm ceramic cups permit a good electrical contact at the soil surface whatever its water content. They are installed 15 mm apart and the electrical resistivity is monitored using a dipole-dipole and wenner multi-electrodes 2D imaging method which gives a picture of the subsur- face resistivity. The interpreted resistivity sections show the major soil structure. The electrical response changes with the cracks formation. The structure information ex- tracted from the electrical map are in good agreement with the artificially man-made cracks. These first results demonstrate the relevance of high resolution electrical imag- ing of the soil profile. Further experiments need to be carried out in order to monitor natural soil structure evolution during wetting-drying cycles.
Samou�lian, A.; Cousin, I.; Richard, G.; Bruand, A.
Hygienic quality and antibiotic resistance profile of sliced butchery.
In order to investigate the microbiological quality of different meat products on the Greek market, 200 samples were collected from the following preparations: boiled turkey (n=50), boiled pork ham (n=50), smoked turkey (n=50) and smoked pork ham (n=50). In all cold meat preparations Clostridium perfringens vegetative and spore forms, Staphylococcus aureus, Escherichia coli and other Clostridium sp lec(-), as well as Lactobacillus, Bacillus sp. and Salmonella sp. were recovered. For instance Bacillus cereus was present in 6% of the samples. L. monocytogenes, Campylobacter jejuni and Campylobacter coli were rarely present (1-4%) while Yersinia enterocolitica and Campylobacter lari were absent. Differences in the occurrence of S. aureus, Salmonella sp., E. coli and spore forms of C. perfringens in boiled and smoked samples, reflects either the differences in the processing of the foods or could be associated to the extensive handling by the personnel during the purchasing (storage, slicing, wrapping). Antibiotic resistance on specific antibiotics for each pathogen was also studied. A multiresistance antibiotic profile was effective for most bacterial strains, and pronounced resistance profiles were observed for the commonly used antibiotics as ampicillin, penicillin, cephalothin, streptomycin followed by ceftriaxone and gentamycin. Albeit this high observed resistance profile, the tested strains generally conserved their susceptibility to amikacin, aztreonam, chloramphenicol and tylosin conserved an almost absent resistance. Antibiotics commonly used for therapeutic purposes, as well as antibiotics added to feed stuff of animals for increasing animal flesh production should contribute to the extensive spreading of antibiotic resistance in food and the environment. Systematically monitoring of the microbiological quality of cold butchery preparations must be done, in order to preserve food quality, optimizing the processing and elaboration methods of the product and safeguard the public health. PMID:21722746
Voidarou, C; Alexopoulos, A; Plessas, S; Stavropoulou, E; Fotou, K; Tzora, A; Skoufos, I; Bezirtzoglou, E
Electrical Resistivity of Ten Selected Binary Alloy Systems.
National Technical Information Service (NTIS)
This work compiles, reviews, and discusses the available data and information on the electrical resistivity of ten selected binary alloy systems and presents the recommended values resulting from critical evaluation, correlation, analysis, and synthesis o...
C. Y. Ho M. W. Ackerman, K. Y. Wu T. N. Havill, R. H. Bogaard
Electrical resistance tomography used to monitor subsurface steam injection.
National Technical Information Service (NTIS)
We used electrical resistance tomography (ERT) to map the subsurface distribution of a steam flood as function of time as part of a prototype environmental restoration process performed by the Dynamic Underground Stripping Project. We evaluated the capabi...
A. Ramirez W. Daily E. Owen D. Chesnut D. LaBrecque
Complex electrical resistance tomography of a subsurface PCE plume.
National Technical Information Service (NTIS)
A controlled experiment was conducted to evaluate the performance of complex electrical resistivity tomography (CERT) for detecting and delineating free product dense non-aqueous phase liquid (DNAPL) in the subsurface. One hundred ninety liters of PCE wer...
A. Ramirez W. Daily D. LeBrecque
Electrical Resistivity Imaging to Quantify Spatial Soil Heterogeneity
NASA Astrophysics Data System (ADS)
Electrical resistivity (ER) sounding is increasingly being used as non-invasive technique to reveal and map soil heterogeneity. The objective of this work was to evaluate effects of soil properties on the electric resistivity and to observe these effects in spatial context in coarse-textured soil. The studied soil had the sandy loam texture. The 20x20-m study plot was located at the ARS Beltsville OPE3 site. Relationship between ER, bulk density, and soil water contents was first studied in disturbed 80-cm3 soil samples taken at 10 depths with 20 cm increment. Soil water contents were brought to 6 predefined levels in each sample and were in the range from air dry to 0.27g g-1. Soil bulk density varied in the range from 1.28 to 1.45 g cm-3. The ER in soil samples decreased as the gravimetric water content increased. The ER decrease became more pronounced as bulk density decreased. Next, soil samples were taken at field water contents from 10 depths at 12 locations. Particle size distributions, pH, water content and ER were measured in each sample. Bulk density values in part of the soil profiles below 80 cm ranged from 1.5 to 1.8 g cm- 3 and no dependence between ER and water content could be established in this soil layer where the lowest values of ER were recorded. The increased conductivity of the soil solid phase could be a possible reason for that since soil in this part of the profile had pH values two or more units less than in the upper part. The lowest sand contents corresponded to highest ER values in this soil layer. Finally, the vertical electrical sounding (LandMapper ERM-02) was used to infer spatial distribution of soil resistivity along a 9-m transect for different dates when soil was dry and when it was relatively uniformly wetted with long low- intensity rain. The Wenner-Shlumberger array with 31-electrodes spaced 30-cm apart was used. Soil temperature and water content with multisensor capacitance probes (SENTEC) were monitored at 10 depths down to one meter during ER measurements. High spatial variability of ER was observed. Averaging ER data along the transect resulted in a good correspondence with data from soil samples as described above. The gradual increase in ER values from the surface to the depth of about one meter probably reflected the general increase in bulk density and changes in soil texture. The small ER values found at the lowest depths with sounding were similar to those observed in samples from large depths. Depending on the range of their values, both bulk density and soil texture apparently affected or did not affect the ER. Coupling the information on soil properties in the sounded profile with the sounding data appears to be useful for interpretation of general trends in sounding results.
Guber, A. K.; Hadzick, Z. L.; Garzio, A.; Pachepsky, Y. A.; Hill, R. L.; Rowland, R. A.; Golovko, L. A.
Shipboard electrical-consumption profile analysis. Master's thesis
Department of Navy energy consumption reduction goals have been established for afloat commands and shore installations in order to keep pace with the ever increasing demand and high cost of energy resources. This study examines electrical power consumption data for various Pacific Fleet ships berthed at Naval Station, San Diego, CA. during the period 1 Jan. 1990- 19 Jun 1991, in an effort to construct daily ship consumption profiles from averaged data. These daily profiles are compared for ships of the same class by means of graphical and statistical analysis in order to determine how well daily class profiles will be able to accurately estimate consumption and subsequent costs. Utility savings examples are also discussed with use of these profiles. Class and individual ship daily profiles are constructed from the analysis for the purpose of being useful as a budget forecasting tool for the U.S. Pacific Fleet Comptroller and also as means to examine ways to efficiently use electricity in the future.
Castaneda, W.G.
Electrical resistivity investigations at the Olkaria geothermal field, Kenya
The bipole-dipole, Schlumberger and in line dipole-dipole electrical resistivity configurations were used to delineate the Olkaria geothermal reservoir with the view to site boreholes for the production of electric power using the geopressurized hot water. The dipole-dipole resistivity data provided the least ambiguous and most usable data for assessing the resource. Deep drilling into two of the anomalies outlined by
Four-terminal electrical testing device. [initiator bridgewire resistance
NASA Technical Reports Server (NTRS)
The invention relates to a four-terminal electrical connector device for testing and measuring unknown resistances of initiators used for starting pyrotechnic events aboard the space shuttle. The testing device minimizes contact resistance degradation effects and so improves the reliability of resistance measurements taken with the device. Separate and independent voltage sensing and current supply circuits each include a pair of socket contacts for mating engagement with the pins of the initiator. The unknown resistance that is measured by the device is the resistance of the bridgewire of the initiator which is required to be between 0.95 and 1.15 ohms.
Robinson, Robert L. (inventor); Graves, Thomas J. (inventor); Hoffman, William C., III (inventor)
Electrical resistance tomography using steel cased boreholes as electrodes
An electrical resistance tomography method using steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constain the models.
Daily, William D. (Livermore, CA); Ramirez, Abelardo L. (Pleasanton, CA)
ELECTRICAL RESISTANCE OF ALUMINUM-STEEL ELECTRIC TRANSITION JOINTS vs TIME AND TEMPERATURE
Electrical transition joints (ETJ) are used for welding aluminum to steel in reduction cells. ETJs can experience temperatures up to 600�C which can cause strength loss and resistance increase. This results from formation of brittle, high resistance Fe-Al intermetallics at the bond. Over the time required for mechanical failure to occur, the resistance can increase dramatically. The increase can be
Antoine Nobili; John Banker
Control of the Electric Field Profile in the Hall Thruster
Control of the electric field profile in the Hall Thruster through the positioning of an additional electrode along the channel is shown theoretically to enhance the efficiency. The reduction of the potential drop near the anode by use of the additional electrode increases the plasma density there, through the increase of the electron and ion transit times, causing the ionization in the vicinity of the anode to increase. The resulting separation of the ionization and acceleration regions increases the propellant and energy utilizations. An abrupt sonic transition is forced to occur at the axial location of the additional electrode, accompanied by the generation of a large (theoretically infinite) electric field. This ability to generate a large electric field at a specific location along the channel, in addition to the ability to specify the electric potential there, allows one further control of the electric field profile in the thruster. In particular, when the electron temperature is high, a large abrupt voltage drop is induced at the vicinity of the additional electrode, a voltage drop that can comprise a significant part of the applied voltage.
A. Fruchtman; N. J. Fisch; Y. Raitses
Rolling Resistance of Electric Vehicle Tires from Track Tests.
National Technical Information Service (NTIS)
Special low-rolling-resistance tires were made for DOE's ETV-1 electric vehicle. Tests were conducted on these tires and on a set of standard commercial automotive tires to determine the rolling resistance as a function of time during both constant-speed ...
M. O. Dustin R. J. Slavik
Monitoring an underground steam injection process using electrical resistance tomography
We used electrical resistance tomography (ERT) to map the subsurface distribution of a steam flood as a function of time as part of a prototype environmental restoration process performed by the Dynamic Underground Stripping Project. We evaluated the capability of ERT to monitor changes in the soil resistivity during the steam injection process using a dipole-dipole measurement technique to measure
A. Ramirez; W. Daily; D. LaBrecque; E. Owen; D. Chesnut
Electrical resistance tomography used to monitor subsurface steam injection
We used electrical resistance tomography (ERT) to map the subsurface distribution of a steam flood as function of time as part of a prototype environmental restoration process performed by the Dynamic Underground Stripping Project. We evaluated the capability of ERT to monitor changes in the soil resistivity during the steam injection process using a dipole-dipole measurement technique to measure the
A. Ramirez; W. Daily; E. Owen; D. Chesnut; D. LaBrecque
Single-phase resistive superconductor electrical current limiter
This paper presents the analysis, design, construction and AC test results of low voltage single-phase resistive superconductor electrical current limiters. Two different types of resistive superconductor current limiter are presented: the first one is built with three concentric, cylindrical and helicoidal coils connected in parallel and the second one is built with two superposed cylindrical helicoidal coils connected in series
Roberto P. Homrich; Ernesto R. Filho; Daltro G. Pinatti; Carlos A. Baldan; Carlos Y. Shigue
Electrical resistivity surveys, ascension Island, South Atlantic Ocean
Reconnaissance electrical resistivity surveys, completed on Ascension Island as one part of an integrated geothermal exploration program, define a 5 km2 area of low resistivity within the central part of the island. Dipole-dipole lines help to define the vertical resistivity structure and suggest the incursion of seawater beneath much of the area surveyed. A zone of 5�10 ?m indicated by
Howard P. Ross; Dale J. Green; Claron E. Mackelprang
Electrically Conductive, Heat-Resistant Paint
NASA Technical Reports Server (NTRS)
Improved, sprayable, thermal- and electrostatic-discharge-control coating for titanium possesses excellent adhesion and high resistance to both vibration and thermal shock. Coating is improved formulation of one described in "High-Temperature Coatings for Titanium" (NPO-16222).
Hribar, V. F.; Mell, R. J.
We propose to develop new practical complex resistivity field measurement techniques for pollution characterization and monitoring. For this purpose we will document the detectability of clay-organic interactions with geophysical measurements in the laboratory, develop further un...
Electrical resistivity structure in the mantle across the Mariana subduction system
NASA Astrophysics Data System (ADS)
We have conducted a magnetotelluric (MT) survey across the central Mariana area (around 18�N) to provide a comprehensive electrical resistivity image of the mantle beneath the Mariana subduction zone, fore-arc, arc, and back-arc system, at a depths down to the transition zone. Our transect will address issues of hydration of the mantle wedge and subsequent melting, the origin of arc magmas, and melting processes beneath the slow back-arc spreading ridge axis. Electric and magnetic time series measured with seafloor instruments were cleaned and processed into MT response functions (apparent resistivity and phase), using a bounded influence algorithm with remote reference (Chave and Thomson, 2003, 2004). Topographic effects on the apparent resistivity and phase data were corrected, based on the equation of Nolasco et al. (1998), using correction tensors which were modeled with a three-dimensional forward code (Baba and Seama, 2002). The nonlinear conjugate gradient inversion algorithm, which seeks regularized solutions (Rodi and Mackie, 2001; Baba et al., 2006), was used to find an optimal two-dimensional electrical resistivity structure. This inversion algorithm allows us not only to seek a minimum structure model but also to investigate the effects of electrical anisotropy on the data. In the inversions, the TE mode apparent resistivity data (in which the electric current flow is parallel to the strike of structure) were not used because they are susceptible to resistivity anomalies by off-profile structures, and were seen to be consistently poorly fit. Sensitivity tests were applied to key features found in the obtained structure through inversions of synthetic data. The resultant isotropic electrical resistivity structure shows the following features: (1) a thick resistive Pacific plate lithosphere (roughly 100km in thickness), (2) a high resistivity region roughly in the location of the descending slab (this feature while consistent with the data is not a required feature); (3) a low resistivity region starting at a depth of about 60-70km within the mantle wedge above the slab; (4) a high resistivity region beneath the back-arc spreading ridge axis. The low resistivity feature in the mantle wedge can be attributed to melting initiated by the release of water. We have run tests on the depth to the top of this conductor in an attempt to identify the primary phases responsible for water release. The high resistivity beneath the back-arc spreading center suggests that melt delivery to the ridge crest occurs through segmented (three-dimensional) pathways, reflecting the slow spreading rate of the system. We investigated whether electrical anisotropy is required in our models, but there is no requirement for significant anisotropy either in the mantle wedge or beneath the back-arc basin.
Matsuno, T.; Seama, N.; Baba, K.; Chave, A. D.; Evans, R. L.; Goto, T.; White, A.; Boren, G.; Yoneda, A.; Utada, H.; Heinson, G. S.; Suyehiro, K.
Friction, wear and electrical contact resistance of precious metal alloys
The preferred selection of precious metal electrical contact materials depends on the contact geometry, contact stress, test ambient values of electrical contact resistance and whether friction and/or wear must be controlled. Wiper-type contact couples that operate in dry hydrocarbon-free atmospheres, particularly if low and steady friction coefficients and minimal wear are required, are typically that of a palladium alloy pin (ASTM B540) sliding on a gold alloy plate (ASTM B541). These materials have a contact resistance of approximately ten milliohms and a friction coefficient less than 0.5 for the most common operational environments. Segregation of sulfur up to a few atomic percent to wear tracks formed on the gold alloy is not detrimental. The accumulation of larger concentrations of sulfur can form surface films of cuprous sulfide which increases the contact resistance to a few tens of milliohms. Large electrical contact resistances (greater than one ohm) are measured only when rider wear becomes dominant and ridges of Pd-containing material are formed in wear tracks. Ion implantation of carbon into the Au alloy decreases the friction coefficient without increasing the electrical contact resistance. In contrast, the implantation of nitrogen into the Au alloy increases the friction coefficient, but does not change the electrical contact resistance. In ambients containing hydrocarbons, the implantation of carbon is not recommended because it promotes friction polymer formation. 19 refs., 5 figs., 8 tabs.
Pope, L.E.; Peebles, D.E.; Barton, B.M.
Cross-resistance profile of mesosulfuron-methyl-resistant Italian ryegrass in the southern United States.
Diclofop-resistant Lolium species (ryegrass) is a major weed problem in wheat production worldwide. This study was conducted to determine the resistance pattern of diclofop-resistant ryegrass accessions from the southern United States to mesosulfuron-methyl, a recently commercialized herbicide for ryegrass control in wheat; to determine the cross-resistance pattern of a Lolium multiflorum Lam. (Italian ryegrass) accession, 03-1, to acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibitors; and to determine the resistance mechanism of Italian ryegrass to mesosulfuron-methyl. Seventeen ryegrass accessions from Arkansas and Louisiana, including standard resistant and susceptible accessions, were used in this experiment. Fourteen of the 17 accessions were more resistant (four- to > 308-fold) to diclofop than the standard susceptible biotype. One accession, 03-1, was resistant to mesosulfuron-methyl as well as to other ALS inhibitor herbicides such as chlorsulfuron, imazamox and sulfometuron. Accession 03-1, however, did not show multiple resistance to the ACCase inhibitor herbicides diclofop, fluazifop, clethodim, sethoxydim and pinoxaden, nor to glyphosate. The in vivo ALS activity of the 03-1 biotype was less affected by mesosulfuron-methyl than the susceptible biotype. This indicates that the resistance mechanism of Italian ryegrass to mesosulfuron-methyl is partly due to an alteration in the target enzyme, ALS. It is concluded that diclofop-resistant ryegrass in the southern United States can be generally controlled by mesosulfuron-methyl. However, mesosulfuron-methyl must be used with caution because not all ryegrass populations are susceptible to it. There is a need for more thorough profiling of ryegrass resistance to herbicides. PMID:17315272
Kuk, Yong In; Bugos, Nilda R
Electrical resistivity of iron at high pressure and high temperature
NASA Astrophysics Data System (ADS)
Knowledge of thermal conductivity of iron under high-pressure and temperature conditions is crucial to understand the heat transport and the thermal evolution of planetary interior. However, measurements of thermal conductivity at high pressure and temperature are challenging and experimental data are limited. In this study, we report the measured electrical resistivity of iron at high pressure and temperature. The data are then translated to thermal conductivity through Wiedemann-Franz law. A four-probe method was employed to measure the resistances of a cylindrical wire during heating cycles at high pressure. Experiments at 5, 7 and 13 GPa were performed on an iron wire sample by using a multi-anvil apparatus at the Geophysical Laboratory. At 5, 7 and 13 GPa, the measured electrical resistivity of iron at room temperature are 9.06 m?-cm (bcc phase), 8.85 m?-cm (bcc phase) and 12.72 m?-cm (hcp phase), respectively. The results are in a good agreement with reported room-temperature data. The kinks in electrical resistivity associated with the phase transitions of iron were clearly observed in each run. At 5 and 7 GPa, kinks in the electrical resistivity can be noticed at 677 oC and 652 oC, respectively, due to the bcc to fcc phase transition. At 5 GPa and 1687 oC, melting led to a discontinuous change in electrical resistivity. The temperature dependence of the electrical resistivity for bcc, fcc, and hcp iron are well constrained from these measurements. The hcp iron displays the strongest temperature dependence compared with that of the bcc and fcc phases. Our results provide critical thermodynamic parameters to constrain heat transport in the planetary cores.
Deng, L.; Seagle, C.; Fei, Y.; Shahar, A.
Electrical Resistivity of Liquid Alkali Na-based Binary Alloys
NASA Astrophysics Data System (ADS)
The study of the electrical resistivity rL of alkali Na-based binary alloys Na1-xLix, Na1-xKx, Na1-xRbx and Na1-xCsx have been made by well-recognized model potential of Gajjar et al. The most recent exchange and correlation functions due to Farid et al (F) and Sarkar et al (S) are used for the first time in the study of electrical resistivity of liquid binary mixtures and found suitable for such study. The results, due to the inclusion of Sarkar et al's local field correction function, are found superior to those obtained due to Farid et al's local field correction function. Electrical resistivity of Na-based binary alloys compare well with the experimental data available in the literature.
Vora, Aditya M.
Correlation of geometric factor for slag resistance electric furnaces
NASA Astrophysics Data System (ADS)
The electric resistance of an industrial slag resistance furnace is an important factor in its design and operation. At a certain slag conductivity, the furnace resistance is dependent only on the furnace and electrode geometries; this geometric effect, usually called geometric factor, is a function of the electrode diameter, the depth of electrode immersion, the electrode spacing, and the total depth of slag layer. A correlation of the geometric factor to the above four geometric parameters was developed in this study on the basis of the measurements in a two-electrode salt-solution model. Comparison of the developed correlation to measurements in actual slag resistance electric furnaces shows good agreement between the calculated and measured values.
Jiao, Q.; Themelis, N. J.
High electrical resistivity carbon/graphite fibers
NASA Technical Reports Server (NTRS)
Carbon/graphite fibers were chemically oxidized in the liquid phase to fibers of graphite oxide. Resistivity increases as high as 10,000 times were obtained, the oxidized fiber decomposed on exposure to atmosphere. A factor of 1,000 remained as a stable increment. The largest change observed was 1,000,000 times. Best results were obtained on the most highly graphitized fibers. Electrochemical oxidation yielded a lower increase--about 10 times, but provided a controllable method of synthesis and insight to the mechanism of reaction. Tensile tests indicated that the strength of the fiber on oxidation was decreased by no more than 25 percent.
Vogel, F. L.; Forsman, W. C.
Electrical resistivity measurements of a dense aluminum plasma
In this paper the authors report results of experiments to measure the electrical resistivity for a dense strongly coupled aluminum plasma. These plasmas cover the density and temperature range from near solid density and room temperature to .03x solid and 40 eV. These conditions give values of {Lambda} = 5--6. The results indicate the resistivity is higher in this regime than most theories. Only the results of some density functional calculations give results consistent with the data.
Benage, J.F. Jr.; Shanahan, W.R.; Murillo, M.S.
Using electrical resistance tomography to map subsurface temperatures
A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations. 1 fig.
Ramirez, A.L.; Chesnut, D.A.; Daily, W.D.
Using electrical resistance tomography to map subsurface temperatures
A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely. Distances over which the ERT method can be used to monitor changes in soil temperature range from tens to hundreds of meters from the electrode locations.
Ramirez, Abelardo L. (Pleasanton, CA); Chesnut, Dwayne A. (San Francisco, CA); Daily, William D. (Livermore, CA)
Electrical resistivity of Au-ZnO nanocomposite films
NASA Astrophysics Data System (ADS)
The electrical resistivity of electron beam codeposited gold and zinc oxide (Au-ZnO) films was investigated over the full composition range. The electrical resistivity was shown to increase monotonically with increasing ZnO content, with three characteristic regimes of behavior associated primarily with (1) grain boundary electron scattering due to grain refinement at ZnO volume fractions below 0.3, (2) percolation theory for ZnO volume fractions at and above the percolation threshold (fc = 0.85), and (3) a transition region between these where it was proposed that resistivity was influenced by the formation of Au-Zn complexes due to an oxygen deficiency in the deposited ZnO. The electrical resistivity of the composite films remained below 100 ?? cm for ZnO volume fractions below 0.5. A model combining the general effective media equation and Mayadas-Shatzkes grain boundary electron scattering model was shown to generally describe the composition dependence of electrical resistivity for the investigated oxide dispersion hardened metal-matrix composite thin films.
Argibay, N.; Goeke, R. S.; Dugger, M. T.; Rodriguez, M. A.; Michael, J. R.; Prasad, S. V.
The deep lunar electrical conductivity profile - Structural and thermal inferences
NASA Technical Reports Server (NTRS)
Simultaneous lunar surface and orbital magnetometer records are reexamined, to ascertain intervals which may be suitable for measuring lunar inductive response in the solar wind and terrestrial magnetosheath. Power spectral estimates of the response tangent to the lunar surface, defined in terms of transfer and gain functions, are obtained for the 0.0001-0.01 Hz frequency range. The maximum consistency of estimates from different time intervals is found when the initial analysis is limited to the tangential direction of maximum incident power, or that direction in which the ratio of signal to background noise is greatest. Spherically symmetric plasma confinement theory is used in the interpretation of transfer function data, by way of forward model calculations, under the assumption of continuous electrical conductivity increase with depth. Results are presented for internal electrical conductivity profile, metallic core radius, and selenotherm limits.
Hood, L. L.; Herbert, F.; Sonett, C. P.
On-the- go sensors, designed to measure soil electrical resistivity (ER) or electrical conductivity (EC) are vital for faster non-destructive soil mapping in Precision Agriculture applications. Commercially available contact devices, which utilize a four-electrode principle, are bulky, very expensive, and can be used only on fallow fields. This limits their applications on small and mid-sized farms, which produce perennial horticultural crops,
L. Pozdnyakova; P. V. Oudemans; A. I. Pozdnyakov; M. S. Kelly
Nondestructive evaluation of composite materials by electrical resistance measurement
NASA Astrophysics Data System (ADS)
This dissertation investigates electrical resistance measurement for nondestructive evaluation of carbon fiber (CF) reinforced polymer matrix composites. The method involves measuring the DC electrical resistance in either the longitudinal or through thickness direction. The thermal history and thermal properties of thermoplastic/CF composites were studied by longitudinal and through-thickness resistance measurements. The resistance results were consistent with differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) results. The resistance measurements gave more information on the melting of the polymer matrix than TMA. They were more sensitive to the glass transition of the polymer matrix than DSC. The through-thickness resistance decreased as autohesion progressed. The activation energy of autohesion was 21.2 kJ/mol for both nylon-6 and polyphenylene sulfide (PPS)/CF composites. Adhesive bonding and debonding were monitored in real-time by measurement of the through-thickness resistance between the adherends in an adhesive joint during heating and subsequent cooling. Debonding occurred during cooling when the pressure or temperature during prior bonding was not sufficiently high. A long heating time below the melting temperature (T m) was found to be detrimental to subsequent PPS adhesive joint development above Tm, due to curing reactions below Tm and consequent reduced mass flow response above Tm. A high heating rate (small heating time) enhanced the bonding more than a high pressure. The longitudinal resistance measurement was used to investigate the effects of temperature and stress on the interface between a concrete substrate and its epoxy/CF composite retrofit. The resistance of the retrofit was increased by bond degradation, whether the degradation was due to heat or stress. The degradation was reversible. Irreversible disturbance in the fiber arrangement occurred slightly as thermal or load cycling occurred, as indicated by the resistance decreasing cycle by cycle. This dissertation also addresses the use of the electrical resistance method to observe thermal and mechanical damage in real time. A temperature increase caused the interlaminar contact resistance to decrease reversibly within each thermal cycle, while thermal damage caused the resistance to decrease abruptly and irreversibly, due to matrix molecular movement and the consequent increase in the chance of fibers of one lamina touching those of an adjacent lamina. The through-thickness volume resistivity irreversibly and gradually decreased upon mechanical damage, which was probably fiber-matrix debonding. Moreover, it reversibly and abruptly increased upon matrix micro-structural change, which occurred reversibly near the peak stress of a stress cycle.
Mei, Zhen
Time lapse electrical resistivity and induced polarization monitoring of near-surface CO2 injection
NASA Astrophysics Data System (ADS)
Field experiments were carried out to investigate the efficiency and the reliability of electrical geophysical methods to detect and monitor CO2 leakages at field scale. Each test consisted of injecting CO2 for approximately four hours at five meters depth, corresponding to a cumulative mass of gas of around six kilograms. Electrical resistivity tomography and temporal induced polarization were acquired at the surface before, during and after injections along profiles centered to the injection well. Time lapse measurements were compared to a reference acquisition performed before the injection. We observe that both methods are sensitive to variations in terms of gas saturation, the chargeability measurements being more sensitive to the presence of CO2 than electrical resistivity. During the injection, an increase of chargeability and a decrease of the measured resistivity are observed at depth in the vinicity of the injection well. Afterwards, the medium equilibrates and retrieves its original state, corresponding to the reference acquisition. The temporal variations of electrical resistivity and induced polarization responses are interpreted in terms of gas dissolution and water/gas saturation.
All�gre, V.; Kremer, T.; Williard, E.; Schmutz, M.; Maineult, A. J.
Resistance of a pulsed electrical breakdown channel in ionic crystals
NASA Astrophysics Data System (ADS)
A technique for estimating the resistance of the electrical breakdown channel in ionic crystals is proposed. This technique is based on measuring the channel velocity in a sample when a ballast resistor is connected to the circuit of a needle anode and on using the theoretical dependence of the channel velocity on the channel conductivity. The breakdown channel resistance at a voltage of 140 kV is about 6.5 k? in KCl and about 6.1 k? in KBr. These resistances are shown to characterize a gas phase. The gas-phase resistance is found to be nonuniform along the breakdown channel. The head part �1 mm long has the maximum resistance. This head region is concluded to contain dielectric substance clusters, which then decompose into metal and halogen ions. The cluster lifetime is �10-9 s.
Punanov, I. F.; Emlin, R. V.; Kulikov, V. D.; Cholakh, S. O.
Investigating electrical contact resistance losses in lithium-ion battery assemblies for hybrid and electric vehicles
Lithium-ion (Li-ion) batteries are favored in hybrid-electric vehicles and electric vehicles for their outstanding power characteristics. In this paper the energy loss due to electrical contact resistance (ECR) at the interface of electrodes and current-collector bars in Li-ion battery assemblies is investigated for the first time. ECR is a direct result of contact surface imperfections, i.e., roughness and out-of-flatness, and
Peyman Taheri; Scott Hsieh; Majid Bahrami
Electrical resistivity structure of the upper mantle in the Southern Mariana Trough
NASA Astrophysics Data System (ADS)
We show a 2-D electrical resistivity structure of the upper mantle in the Southern Mariana Trough. The Mariana Trough is an active back-arc basin in which the seafloor spreading has occurred. In the southern region of the Mariana Trough, the seafloor spreading rate is 35-45 km/Myr at present (Kato et al., 2003) that is slow, but there are characteristics of the fast spreading ridge such as an axial topographic high (Martinez et al., 2000) and a nearly constant low mantle Bouguer anomaly along the spreading axis suggesting high magmatic activity with a sheet-like mantle upwelling under the spreading axis (Kitada et al., 2006). We carried out an electromagnetic experiment along a ~120 km length profile across the spreading axis to estimate an electrical resistivity structure, and hence the physical property like temperature, water and melt content in the upper mantle. The observation was made using ten Ocean Bottom Electro-Magnetometers (OBEMs) from August to November in 2010. The data was recorded for ~85 days in two OBEMs and for ~60 days in the rest of the OBEMs. Successfully, eight OBEMs recorded time-variations of the electric and magnetic fields and two OBEMs recorded only those of the magnetic field. The magnetotelluric (MT) method is a base for the data analysis. We carried out the time-series data analysis to estimate the MT responses and correct topographic distortions in the MT responses. We have basically performed a smooth model inversion analysis using the processed MT responses to estimate a minimum electrical resistivity structure, and also have considered a prior constraint in the inversion analysis for the subducted slab inferred from a seismic research (Gudmundsson and Sambridge, 1998). The obtained 2-D electrical resistivity structure shows an asymmetry about the spreading center. The trenchward side shows higher resistivity (~300 Ohm-m), while the opposite side (the west side) shows that intermediate resistivity (~100 Ohm-m) with ~40 km thickness is underlain by lower resistivity (~10 Ohm-m) region down to the subducted slab. The region under the spreading center has low resistivity (~30 Ohm-m) down to the depth of ~40 km. This low resistivity region might be connected to the lower resistivity region located in the west side. These regions may be affected by hydration driven by water release from the subducted slab; that may result in abundant magma supply to support the EPR type axial topographic high. The higher resistivity region in the trenchward side might be a result of low temperature as well as the absence of a significant amount of water in a cold nose within the mantle wedge.
Shindo, H.; Seama, N.; Matsuno, T.; Shibata, Y.; Kimura, M.; Nogi, Y.; Okino, K.
Electrochemical Aspects of Electrical Resistance Gages for Concrete.
National Technical Information Service (NTIS)
The report gives an orientation about the origin of double layer and a review of the various theoretical models of the double layer. The implications of the double layer for electrical resistance measurements are discussed. Tests were made to study this e...
J. Bhargava A. Rehnstrom
Building Better Electrodes for Electrical Resistivity and Induced Polarization Data
In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles\\
P. L. Adkins; D. J. La Brecque
Equivalent Electrical Circuit Representations of AC Quantized Hall Resistance Standards.
National Technical Information Service (NTIS)
We use equivalent electrical circuits to analyze the effects of large parasitic impedances existing in all sample probes on four-terminal-pair measurements of the ac quantized Hall resistance R(H). We will use these predictions to apply small measurable c...
M. E. Cage A. Jeffrey J. Matthews
Relationship Between Tearing Strength and Electrical Resistance in Welded Microjoints
The correlation between electrical resistance and mechanical strength of welded joints is derived, based on a model of the dislocation structure of the heat affected zone. This correlation is confirmed experimentally with a fairly good fit between observed and theoretical results. The possibility of using the derived relationship in the automatic detection of faulty welded elements during production is discussed.
Andrew Rawicz
Mechanical and electrical properties of resistance welds at cryogenic temperatures
The mechanical and electrical properties of resistance welds at cryogenic temperatures for the large superconducting magnet such as the superconducting MHD Dipole system for the National Coal-Fired Flow Facility (CFFF SCMS) at the U. of Tennessee Space Institute are reported.
S. T. Wang; S. H. Kim; N. S. Kim; H. Ludwig
Heat control for electric resistance welding in steel pipe production
A heat control system for electric resistance welding (ERW) for use in pipe manufacturing has been developed. The distinguishing features of the control system are: (1) use of a silicon photodiode array as a heat input sensor, (2) feedback control for steady welding, and (3) open-loop control for transient welding. This control system has been introduced into three ERW mills
I. Komine; I. Takahashi; S. Ishiro
Prediction of electrical contact resistance for anisotropic conductive adhesive assemblies
Anisotropic conductive adhesive (ACA) assembly is emerging as one of the most flexible and cost effective packaging interconnect methods in the microelectronics industry. One of the major impediments to the full realization of the fine pitch (<200 ?m) capabilities of this assembly method is accurate prediction and control of electrical contact resistance. This paper presents a detailed review and direct
Melida Chin; Kaushik A. Iyer; S. Jack Hu
Electrical process tomography with known internal structures and resistivities
In process tomography the aim is to obtain information typically from the interior of the process vessels based on the measurements made on the surface of the vessel. Electrical impedance tomography (EIT) is an imaging modality in which the internal resistivity distribution is reconstructed based on the known injected currents and measured voltages on the surface. Since the reconstructed image
L. M. Heikkinen; M. Vauhkonen; T. Savolainen; K. Leinonen; J. P. Kaipio
Ohmic Electrical Contacts to High-Resistivity Zns Crystals.
National Technical Information Service (NTIS)
Ohmic electrical contacts to high-resistivity ZnS single crystals can be made by annealing crystals at 400-475C with In-Ga contacts in an inert atmosphere. Optimum contacts are obtained by annealing first at about 475C and then at 400C. The following four...
G. H. Blount M. W. Fisher R. G. Morrison R. H. Bube
Reservoir characterization combining elastic velocities and electrical resistivity measurements
The elastic and electric parameters of rocks that can be obtained from seismic and electromagnetic data depend on porosity, texture, mineralogy, and fluid. However, seismic data seldom allow us to accurately quantify hydrocarbon saturation. On the other hand, in the case of common reservoir rocks (i.e., sandstones and carbonates), resistivity strongly depends on porosity and saturation. Therefore, the recent progress
Carmen Teresa Gomez
Acoustic velocity and electrical resistance of hydrate bearing sediments
Characterization of natural gas hydrate bearing formations is important in the exploration and development of gas hydrate resources in subsea sediments. Solid hydrates can fill the voids of the matrix formed by sand grains and change their cementation condition, which may have a great impact on the electrical resistance and sound velocity of the sand matrix. In this study, experiments
Shao Ran Ren; Yongjun Liu; Yixing Liu; Weidong Zhang
Electrical resistivity survey in soil science: a review
Electrical resistivity of the soil can be considered as a proxy for the spatial and temporal variability of many other soil physical properties (i.e. structure, water content, or fluid composition). Because the method is non-destructive and very sensitive, it offers a very attractive tool for describing the subsurface properties without digging. It has been already applied in various contexts like:
A. Samou�lian; I. Cousin; A. Tabbagh; A. Bruand; G. Richard
Complex electrical resistance tomography of a subsurface PCE plume
A controlled experiment was conducted to evaluate the performance of complex electrical resistivity tomography (CERT) for detecting and delineating free product dense non-aqueous phase liquid (DNAPL) in the subsurface. One hundred ninety liters of PCE were released at a rate of 2 liters per hour from a point 0.5 m below ground surface. The spill was conducted within a double
A. Ramirez; W Daily; D. LeBrecque
Electrical conductivity of the Fennoscandian Shield margin from recent magnetotelluric profiles
NASA Astrophysics Data System (ADS)
During the last decade several magnetotelluric profiles extending from Proterozoic East European Craton into younger domains have been measured. Magnetotelluric TOR profile crosses the Sorgenfrei-Tornquist-Zone (STZ) in the southwestern part of the Fennoscandian Shield. The STZ marks the border between the intact shield in Sweden to the north and the reactivated Danish basin and the Ringkobing-Fyn High (RFH) to the south. The STZ manifests itself electrically very clearly in the lower crust and upper lithospheric mantle as a narrow zone of high conductivity. The thickness of the electric lithosphere decreases across the STZ from about 300 km in the Fennoscandian Shield to about 100 km in the Danish basin. J�mtland-Trondelag magnetotelluric profile crosses the Central Scandinavian Caledonides from Baltic to Norwegian Sea. The results of the data analysis reveal the following main features: (1) An electrically highly conducting layer beneath the Caledonides images alum shales, the autochthonous Cambrian carbon-bearing black shales on top of the Precambrian basement. (2) Beneath the eastern part of the profile in the Fennoscandian Shield, proper, the first upper mantle conductor is detected at the depth of more than 250-300 km. A region of enhanced conductivity is identified at the depth of c.100- 150 km under the Caledonides in the central part of the profile. Further to the west, however, the lithosphere seems to thicken to 150-200 km. A large-scale international electromagnetic experiment has been carried out in northwest Poland and northeast Germany across the Trans European Suture Zone (TESZ), which is the most prominent tectonic boundary in Europe and which constitutes a complex transition between the European Paleozoic Platform towards the southeast and the Precambrian Craton towards the northeast. The results show the presence of highly conductive Cenozoic-Mesozoic sedimentary cover reaching depths up to 3 km. The significant conductivity anomaly in the central part of the TESZ in the Polish Trough at mid-crustal depths is well resolved. The upper mantle of the Precambrian Craton is more resistive than the younger Paleozoic lithosphere by at least one order of magnitude. We can summarize the results from these profiles in the following conclusions. Magnetotelluric data revealed remarkable features at the crustal level along each profile. Some of them were not clearly identified before by other geophysical methods. Conductors like alum shales are very well indicated in the final models. Electrical lithosphere is thick beneath the Fennoscandian Shield and significantly thinner beneath younger domains. The resulting models shows the conductivity contrast at a depth of about 150 km across the cratonic margin to be at least one order of magnitude.
Smirnov, M. Yu.; Korja, T.; Pedersen, L. B.
Correlation between aminoglycoside resistance profiles and DNA hybridization of clinical isolates.
DNA hybridization data and aminoglycoside resistance profiles (AGRPs) were determined for 4,088 clinical isolates from three studies (United States, Belgium, and Argentina). The correlation between susceptibility profiles and hybridization results was determined with nine DNA probes. For each of the seven aminoglycoside resistance profiles which we were able to test, the data suggested at least two distinct genes could encode enzymes which lead to identical resistance profiles. Furthermore, the DNA hybridization data showed that individual strains carried up to six unique aminoglycoside resistance genes. DNA hybridization revealed interesting differences in the frequencies of these genes by organism and by country.
Shaw, K J; Hare, R S; Sabatelli, F J; Rizzo, M; Cramer, C A; Naples, L; Kocsi, S; Munayyer, H; Mann, P; Miller, G H
Protein expression profiles indicative for drug resistance of non-small cell lung cancer
Data obtained from multiple sources indicate that no single mechanism can explain the resistance to chemotherapy exhibited by non-small cell lung carcinomas. The multi-factorial nature of drug resistance implies that the analysis of comprising expression profiles may predict drug resistance with higher accuracy than single gene or protein expression studies. Forty cellular parameters (drug resistance proteins, proliferative, apoptotic, and angiogenic
M Volm; R Koom�gi; J Mattern; T Efferth
Impact of Novel Resistance Profiles in HIV-1 Reverse Transcriptase on Phenotypic Resistance to NVP.
Objective. To clarify the impact of H221Y mutation on drug resistance to NVP. Methods. 646?bp HIV-1 pol gene fragments (from 592 to 1237 nucleotide) with different NNRTIs mutation profiles from AIDS patients receiving antiretroviral therapy containing NVP regimens were introduced into pNL4-3 backbone plasmid. H221Y and (or) Y181C mutations were reverted to wild type amino acids by site-directed mutagenesis, then strains containing various mutation patterns were packaged. Phenotypic drug resistance was analyzed on TZM-bl cells. Results. 12 strains containing different drug-resistant mutation profiles were constructed, including the K101Q series (K101Q/Y181C/H221Y, K101Q/Y181C, K101Q/H221Y, and K101Q), the V179D series (V179D/Y181C/H221Y, V179D/Y181C, V179D/H221Y, and V179D), and the K103N series (K103N/Y181C/H221Y, K103N/Y181C, K103N/H221Y, K103N). For strains containing the mutation profiles (K101Q/Y181C, K101Q, V179D/Y181C, V179D, K103N/Y181C, and K103N), the presence of H221Y reduced NVP susceptibility by 2.1 � 0.5 to 3.6 � 0.5 fold. To the mutation profiles K101Q/H221Y, K101Q, V179D/H221Y, V179D, K103N/H221Y, and K103N, the presence of Y181C reduced NVP susceptibility by 41.9 � 8.4 to 1297.0 � 289.1 fold. For the strains containing K101Q, V179D, and K103N, the presence of Y181C/H221Y combination decreased NVP susceptibility by 100.6 � 32.5 to 3444.6 � 834.5 fold. Conclusion. On the bases of various NNRTIs mutation profiles, Y181C remarkably improved the IC(50) to NVP, although H221Ymutation alone just increases 2.1 ? 3.6-fold resistance to NVP, the mutation could improve 100.6 ? 3444.6-fold resistance to NVP when it copresent with Y181C, the phenotypic drug resistance fold was improved extremely. For strains containing the mutation profiles (K101Q/Y181C, K101Q, V179D/Y181C, V179D, K103N/Y181C, and K103N), the presence of H221Y reduced NVP susceptibility by 2.1 � 0.5 to 3.6 � 0.5 fold. PMID:22536497
Jiao, Liyan; Li, Hanping; Li, Lin; Zhuang, Daomin; Liu, Yongjian; Bao, Zuoyi; Liu, Siyang; Li, Jingyun
Comparison of two years of snowmelt infiltration using electrical resistivity and TDR
NASA Astrophysics Data System (ADS)
Infiltration during snowmelt can be highly heterogeneous due to the formation of ice on the ground surface below the snow cover. In cases where snow is contaminated such as e.g. along highways and airports due to de-icing agents and other contaminants, it is important to be able to predict the zone of infiltration since this will determine the potential for retention and degradation in the unsaturated zone. The infiltration processes was monitored using time-lapse electrical resistivity measured in shallow electrodes in a glacial deposit near Oslo airport. TDR measurements were used to calibrate changes in water contents with changes in electrical resistivity values. In the first snowmelting event (April, 2006) there was hardly any ground frost, while in the second event (March, 2007) ground frost caused redistribution of meltwater and focussed infiltration. The observed infiltration pattern is supported by numerical simulation of infiltration in a 2D unsaturated profile.
French, H. K.; Binley, A.; Leijnse, A.
Influence of different illumination profiles on the on-state resistances of silicon carbide photoconductive semiconductor switches.
Characteristics of a silicon-carbide (SiC) photoconductive switch under different illumination profiles are presented. We triggered a V-doped semi-insulated 6H-SiC switch with lateral geometry using a laser beam of 532-nm wavelength. Photoconductivity tests for different spot profiles and locations show that such switches achieve a minimum on-state resistance when the switching gap is illuminated. The differences between on-state resistances are small for various partial illuminations of the switching gap. Semiconductor modeling is used to simulate the electric field and current profiles for different partial illuminations. The simulation results show poor on-state switch performance when partially illuminated. Based on these results, a more revealing circuit model for the switch matches well with experimental results for partial illuminations. PMID:24784634
Wang, Langning; Xun, Tao; Yang, Hanwu; Liu, Jinliang; Zhang, Yu
Deep Electrical structure along the Meigu-Suijiang profile in the eastern margin of Tibetan plateau
NASA Astrophysics Data System (ADS)
Magnetoteluric (MT) data were collected at 87 locations along a 135km long traverse from Meigu to Suijiang in the eastern margin of Tibetan plateau. This profile yields data in the period range 0.003-2000s across the active tectonic belt of Sichuan-Yunnan block. MT transfer functions were computed after robust processing of single site and remote reference sites. The dimensionality analysis and strike direction are carried out by phase tensor, conjugate transform impedance method and WAL invariants criteria. Only TM mode data is used in two-dimensional inversion. New approaches are adopted in inversion, one is Site-Center Mesh which is used to construct initial model, and another is the determination of regularization parameter by segmental calculation. The validity of inversion model is checked by using effective skin depth of complex structure and invariants of phase tensor. According to horizontal variation of electrical structure, this profile can be divided into two parts. One part in the west is Daliangshan block, the other part in the east is South China block, the electrical boundary between them is Mabian fault. In general, the electrical resistivity of crust in the east is larger than that of the crust in the west.
Cai, J.; Zhao, G.; Tang, J.; Chen, X.
Small-scale electrical resistivity tomography of wet fractured rocks.
This paper describes a series of experiments that tested the ability of the electrical resistivity tomography (ERT) method to locate correctly wet and dry fractures in a meso-scale model. The goal was to develop a method of monitoring the flow of water through a fractured rock matrix. The model was a four by six array of limestone blocks equipped with 28 stainless steel electrodes. Dry fractures were created by placing pieces of vinyl between one or more blocks. Wet fractures were created by injecting tap water into a joint between blocks. In electrical terms, the dry fractures are resistive and the wet fractures are conductive. The quantities measured by the ERT system are current and voltage around the outside edge of the model. The raw ERT data were translated to resistivity values inside the model using a three-dimensional Occam's inversion routine. This routine was one of the key components of ERT being tested. The model presented several challenges. First, the resistivity of both the blocks and the joints was highly variable. Second, the resistive targets introduced extreme changes the software could not precisely quantify. Third, the abrupt changes inherent in a fracture system were contrary to the smoothly varying changes expected by the Occam's inversion routine. Fourth, the response of the conductive fractures was small compared to the background variability. In general, ERT was able to locate correctly resistive fractures. Problems occurred, however, when the resistive fracture was near the edges of the model or when multiple fractures were close together. In particular, ERT tended to position the fracture closer to the model center than its true location. Conductive fractures yielded much smaller responses than the resistive case. A difference-inversion method was able to correctly locate these targets. PMID:14763623
LaBrecque, Douglas J; Sharpe, Roger; Wood, Thomas; Heath, Gail
SEM viewing of gypsiferous material and study of their influence on electrical resistivity
NASA Astrophysics Data System (ADS)
The gypsum rich material is often linked to the cavity formation due to the high solubility of cal-cium carbonate in the presence of acidic media. This work is dedicated to a close-up look to the structure of materials rich of gypsum and material of less or traces of sulfate ions. Electrical resistivity measurements were conducted along extended lines on sections involving cavities and the resulting profiles were examined for any changes. Forms and features of gypsum and minerals containing sulfates were studied and compared to sam-ples tested using SEM (scanning electron microscope). The chemical analyses (EDAX) using electron beam was carried out and the elements present within these samples were established. Quantitative chemical testing for some parameters including sulfate ions was carried out. Structural forms variation and changes are studied in view of the chemical composition. The electrical resistivity was measured using Syscal R1 electerical resis-tivity equipment for several spots near surface. Statistical correlations between sulfate ions content and elec-trical resistivity, for near surface soils, is presented. This study is aiming at utilizing the geophysical testing methods of sulfate rich soils and predicting future cavity formation in areas of high risk to cavities due to chemical weathering.
Dafalla, M.; Fouzan, F. Al
Electrical Resistance Technique to Monitor SiC Composite Detection
NASA Technical Reports Server (NTRS)
Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. The effect of matrix cracking on electrical resistivity for several composite systems will be presented and some initial measurements performed at elevated temperatures under stress-rupture conditions. The implications towards electrical resistance as a technique applied to composite processing, damage detection (health monitoring), and life-modeling will be discussed.
Smith, Craig; Morscher, Gregory; Xia, Zhenhai
The Influence of Basic Physical Properties of Soil on its Electrical Resistivity Value under Loose and Dense Condition
NASA Astrophysics Data System (ADS)
Electrical resistivity technique has become a famous alternative tool in subsurface characterization. In the past, several interpretations of electrical resistivity results were unable to be delivered in a strong justification due to lack of appreciation of soil mechanics. Traditionally, interpreters will come out with different conclusion which commonly from qualitative point of view thus creating some uncertainty regarding the result reliability. Most engineers desire to apply any techniques in their project which are able to provide some clear justification with strong, reliable and meaningful results. In order to reduce the problem, this study presents the influence of basic physical properties of soil due to the electrical resistivity value under loose and dense condition. Two different conditions of soil embankment model were tested under electrical resistivity test and basic geotechnical test. It was found that the electrical resistivity value (ERV, ?) was highly influenced by the variations of soil basic physical properties (BPP) with particular reference to moisture content (w), densities (?bulk/dry), void ratio (e), porosity (?) and particle grain fraction (d) of soil. Strong relationship between ERV and BPP can be clearly presents such as ? ? 1/w, ? ? 1/?bulk/dry, ? ? e and ? ? ?. This study therefore contributes a means of ERV data interpretation using BPP in order to reduce ambiguity of ERV result and interpretation discussed among related persons such as geophysicist, engineers and geologist who applied these electrical resistivity techniques in subsurface profile assessment.
Abidin, M. H. Z.; Ahmad, F.; Wijeyesekera, D. C.; Saad, R.
Improvement of resistance to hydrogen induced cracking in electric resistance welded pipes fabricated with slit coils
The optimization of electric resistance welding (ERW) conditions was studied to improve the resistance to hydrogen induced\\u000a cracking (HIC) at the bondline in small diameter API X60 ERW pipes fabricated with slit coils. The results show that HIC is\\u000a initiated preferentially at the elongated Si, Mn and Al-rich oxide inclusions, normally known as a penetrator on the bondline.\\u000a However, no
Hyun Uk Hong; Jong Bong Lee; Ho Jin Choi
Monitoring an underground steam injection process using electrical resistance tomography
NASA Astrophysics Data System (ADS)
We used electrical resistance tomography (ERT) to map the subsurface distribution of a steam flood as a function of time as part of a prototype environmental restoration process performed by the Dynamic Underground Stripping Project. We evaluated the capability of ERT to monitor changes in the soil resistivity during the steam injection process using a dipole-dipole measurement technique to measure the bulk electrical resistivity distribution in the soil mass. The injected steam caused changes in the soil's resistivity because the steam displaced some of the native pore water, increased the pore water and soil temperatures and changed the ionic content of the pore water. We could detect the effects of steam invasion by mapping changes in the soil resistivity as a function of space and time. The ERT tomographs are compared with induction well logs, formation temperature logs and lithologic logs. These comparisons suggest that the ERT tomographs mapped the formation regions invaded by the steam flood. The data also suggest that steam invasion was limited in vertical extent to a gravel horizon at depth of approximately 43 m. The tomographs show that with time, the steam invasion zone extended laterally to all areas monitored by the ERT technique.
Ramirez, A.; Daily, W.; LaBrecque, D.; Owen, E.; Chestnut, D.
Modeling and analysis of direct-current electrical resistivity in the Durham Triassic basin, North Carolina
Sixty-two Schlumberger electrical soundings were made in the Durham Triassic basin in an effort to determine basin structural geometry, depth of the sedimentary layers, and spatial distribution of individual rock facies. A digital computer program was used to invert the sounding curves of apparent resistivity versus distance to apparent resistivity versus depth. The apparent-resistivity-versus-depth data from the computer-modeling program were used to construct a geoelectric model of the basin that is believed to accurately represent the subsurface geology of the basin. The largest depth to basement in the basin along a resistivity profile (geoelectric section) was determined to be 1,800 m. A resistivity decrease was observed on certain soundings from depths of 100 to 1,000 m; below a 1,000-m depth, apparent resistivity increased to the bottom of the basin. Resistivity values for basement rocks were greater than 1,000 ohm-m and less than 350 ohm-m for the sedimentary layers in the basin. The data suggest that the basin contains a system of step faults near its eastern boundary. ?? 1987.
Brown, C. E.
Combined Electrical and Magnetic Resistivity Tomography: Theory and Inverse Modeling
Electrical Resistivity Tomography (ERT), which has seen increasingly wide use for environmental monitoring, uses the measurement of electrical potentials induced by a low-frequency electric current source. An alternative technique, magnetometric resistivity (MMR), measures the magnetic fields created by the same type of low-frequency electric current source used for ERT. Combining these two methods and thus the two types of data, provides an opportunity for producing improved subsurface images in a wider range of environments. This paper discusses the use of a fully three-dimensional inverse routine that combines magnetic and electric field measurements. The algorithm is based on a 3-D finite difference forward algorithm. The magnetic fields are modeled by applying the reciprocity theorem to model the electric fields induced by a coil of unit moment at a frequency of one radian per second. Using this method, allows for an adjoint formulation for calculating sensitivities of both magnetic and electric fields with respect to changes in the conductivities of individual cells within the finite-difference mesh. In initial model studies, combined MMR/ERT surveys were better able to resolve 3-D structures than ERT alone. The paper also considers design issues and choices of arrays for MMR surveys over a simple 3-D model. In this case, an integral-equation modeling algorithm is used to calculate the expected magnetic fields over a simple 3-D model. Several horizontal and buried vertical electric sources with surface magnetic receivers are employed. This work suggest that in-well horizontal arrays produce the strongest anomalous signals, while vertical dipoles provide the best sensitivity to target location.
Heath, Gail Lynn; Svoboda, John Mark; LaBrecque, Douglas; Sharpe, Roger; Casale, Dan
Electrical resistivity of titanium diboride and zirconium diboride
The electrical resistivities of hot-pressed samples of Ti{sub 1-x}Zr�B� (x = 0.0, 0.3, 0.5, 0.7, 1.0) were measured by a four-point ac technique over the range 298 to 1,573 K in an argon atmosphere. The hot-pressed samples for the intermediate compositions were found to be mixtures of two solid-solution phases. The resistivities for all compositions were found to increase linearly
Matiur Rahman; Ching C. Wang; Weihua Chen; Sheikh A. Akbar; Cathleen Mroz
Acquisition of electrical resistivity data. Application to soil moisture content
NASA Astrophysics Data System (ADS)
Geophysical investigation such as detecting electrical resistivity or conductivity of soil has been applied in other to seek correlations between soil properties and soil state. There may be a lot of reasons for variation of the electrical soil apparent resistivity (bulk density, hydraulic conductivity, pore distribution, porosity), but in the same type of non polluted soil, the changes of electrical resistivity data are mainly due to the differential water retention. Detecting even small modification in soil moisture content (<5?m) it is possible if optimum acquisition and processing techniques are applied. Apparent resistivity acquisition is mainly due by using Wenner, Schlumberger or the hybrid Wenner-Schlumberger and Gradient-Dipol arrays. Investigating the same area with the different array may lead to slight different results (differences of the extent or intensity of the electrical resistivity anomalies). This is mainly a cause of the specific sensitivity functions for each of the above mentioned arrays. Comparing the sensitivity function for various array disadvantages and recommendation for using one or another in a specific site location can be outlined and it is a recommended step before starting the acquisition campaign. Other important parameter that must be considered when geoelectric measurements are designed is the distance between electrodes. Electrical prospecting in DC makes use of metal electrodes implanted into the soil. Consequently, current electrodes, as well as potential electrodes, can only approximately be described as point source electrodes. Geoelectrical measurements made on cultivated soil showed that in case of the improper choose of the distance between the electrodes (1m) small changes in the soil moisture content at shallow depths could not be delineated, resulting an higher estimation of the soil water content, as has been revealed by apparent resistivity measurements made with electrodes positioned at half distance. The results will be of high quality if the distance between electrodes is smaller, but placing too close the electrodes the point-source approximation of the injection electrodes may not accomplish. If the point-source approximation cannot be accomplished certain difficulties in the results interpretation will be encountered. In order to illustrate the difference between values computed under the assumption of a point-electrode, and values obtained under the more realistic assumption that a real electrode, of finite length, was utilized. There has been computed the potential generated in a certain point , by a current source of length , that injected a current of intensity into a homogeneous and isotropic half-space of resistivity . Analyzes made for the Schlumberger array indicates that the apparent resistivity computed in the case of a line-electrode is equal to the apparent resistivity corresponding to a point-electrode only if the distance between the current source and the point (where the electrical potential is measured) is much larger that the electrode burying-depth . The distance between the current source and the point has to be at least four times larger than the electrode burying-depth, in order to secure differences smaller than 5% between the actually computed resistivity values and values existing in the ideal case. In addition, by taking into account the circumstance that both the current electrodes, and the potential electrodes, are actually linear, the electrodes separation must be at least 5-7 times larger than their burying-depth. The latter observation is of utmost importance in carrying out resistivity tomographies for soils, when shallow depth investigation it is needed. The scientific researches were performed with financial support from the CNCSIS-UEFISCU 992/2009 and 998/2009 scientific projects.
Chitea, Florina
Electrical resistivity surveys in Prospect Gulch, San Juan County, Colorado
Prospect Gulch is a major source of naturally occurring and mining related metals to Cement Creek, a tributary of the upper Animas River in southwestern Colorado. Efforts to improve water quality in the watershed have focused on Prospect Gulch because many of its abandoned mines and are located on federal lands. Information on sources and pathways of metals, and related ground-water flow, will be useful to help prioritize and develop remediation strategies. It has been shown that the occurrence of sulfate, aluminum, iron, zinc and other metals associated with historical mining and the natural weathering of pyritic rock is substantial. In this study, direct current resistivity surveys were conducted to determine the subsurface resistivity distribution and to identify faults and fractures that may act as ground-water conduits or barriers to flow. Five lines of resistivity data were collected in the vicinity of Prospect Gulch, and cross-section profiles were constructed from the field data using a two-dimensional inversion algorithm. The conductive anomalies in the profiles are most likely caused by wet or saturated rocks and sediments, clay rich deposits, or high TDS ground water. Resistive anomalies are likely bedrock, dry surficial and sub-surface deposits, or deposits of ferricrete.
McDougal, Robert R.
Two-dimensional carrier profiling of InP structures using scanning spreading resistance microscopy
NASA Astrophysics Data System (ADS)
Scanning spreading resistance microscopy (SSRM) is an analytical technique originally developed for measuring two-dimensional carrier distribution in Si device structures with high spatial resolution. It is in essence an atomic force microscope equipped with a conducting tip that is biased relative to the sample. The spreading resistance value derived from the measured electrical current is a function of the local carrier concentration at the surface region surrounding the probe's tip. In this letter, we report the successful application of SSRM to the analysis of InP semiconductor device structures. We imaged a multilayer epitest structure, and a cross section of a three-dimensional structure in which we observed lateral Zn-dopant diffusion. Comparison of the SSRM profiles with one-dimensional secondary ion mass spectrometry depth profiles shows good qualitative agreement. SSRM analysis of InP-based device structures was found to be much simpler than that of Si structures: there is no need for surface preparation of the cleaved surface, a lower tip force is required, and metal tips, rather than doped diamond can be used.
de Wolf, P.; Geva, M.; Hantschel, T.; Vandervorst, W.; Bylsma, R. B.
Use of Electrical Resistivity to Detect Underground Mine Voids in Ohio.
National Technical Information Service (NTIS)
Electrical resistivity surveys were completed at two sites along State Route 32 in Jackson and Vinton Counties, Ohio. The surveys were done to determine whether the electrical resistivity method could discriminate areas where coal was mined, leaving air- ...
R. A. Sheets
Understanding device performance by incorporating 2D-carrier profiles from high resolution scanning spreading resistance microscopy into device simulations
NASA Astrophysics Data System (ADS)
In this paper we present a procedure and software allowing to predict and understand device performance by incorporating two dimensional (2D)-carrier profiles obtained from high vacuum scanning spreading resistance microscopy (HV-SSRM) into a device simulator. We demonstrate the incorporation of quantified SSRM 2D-carrier profiles obtained on p-MOSFETs into a device simulator. The simulated electrical characteristics (based on the measured 2D-carrier profiles) of the device show nice agreement with the experimentally obtained device results, whereas calculations based on process simulations with available advanced calibration showed significant discrepancies. With this approach the difficult and time consuming calibration step of the process simulation can be circumvented and device results can be interpreted directly based on the details of the real 2D-carrier profiles.
Nazir, Aftab; Eyben, Pierre; Clarysse, Trudo; Hellings, Geert; Schulze, Andreas; Mody, Jay; De Meyer, Kristin; Bender, Hugo; Vandervorst, Wilfried
Development of mixing models using electrical resistance tomography
The network-of-zones concept provides a simplified basis for constructing mixing models appropriate to tomography. For miscible single-phase mixing in three-dimensions, of the order of 104 volume elements (voxels) are needed to interpret mixing results from 16 element electrical resistance tomographic (ERT) sensing rings stacked axially. Experimental mixing and dispersion in passive scalar pulse tests can be acquired at video frame
R. Mann; R. A. Williams; T. Dyakowski; F. J. Dickin; R. B. Edwards
The temperature-dependent electrical resistivities of the alkali metals
This review contains a comprehensive examination of all modern measurements and calculations of the temperature-dependent electrical resistivity rho(T) for the alkali metals-and especially potassium (K)-from their melting points down to below 0.1 K. The simplicity of the electronic structures of these metals makes them unique for testing our fundamental understanding of rho(T). At all temperatures down to a few K,
Jack Bass; William P. Pratt Jr.; Peter A. Schroeder
Continuous resistivity profiling data from Great South Bay, Long Island, New York
An investigation of submarine aquifers adjacent to the Fire Island National Seashore and Long Island, New York was conducted to assess the importance of submarine groundwater discharge as a potential nonpoint source of nitrogen delivery to Great South Bay. Over 200 kilometers of continuous resistivity profiling data were collected to image the fresh-saline groundwater interface in sediments beneath the bay. In addition, groundwater sampling was performed at sites (1) along the north shore of Great South Bay, particularly in Patchogue Bay, that were representative of the developed Long Island shoreline, and (2) at sites on and adjacent to Fire Island, a 50-kilometer-long barrier island on the south side of Great South Bay. Other field activities included sediment coring, stationary electrical resistivity profiling, and surveys of in situ pore water conductivity. Results of continuous resistivity profiling surveys are described in this report. The onshore and offshore shallow hydrostratigraphy of the Great South Bay shorelines, particularly the presence and nature of submarine confining units, appears to exert primary control on the dimensions and chemistry of the submarine groundwater flow and discharge zones. Sediment coring has shown that the confining units commonly consist of drowned and buried peat layers likely deposited in salt marshes. Low-salinity groundwater extends from 10 to 100 meters offshore along much of the north and south shores of Great South Bay based on continuous resistivity profiling data, especially off the mouths of tidal creeks and beneath shallow flats to the north of Fire Island adjacent to modern salt marshes. Human modifications of much of the shoreline and nearshore areas along the north shore of the bay, including filling of salt marshes, construction of bulkheads and piers, and dredging of navigation channels, has substantially altered the natural hydrogeology of the bay's shorelines by truncating confining units and increasing recharge near the shore in filled areas. Better understanding of the nature of submarine groundwater discharge along developed and undeveloped shorelines of embayments such as this could lead to improved models and mitigation strategies for nutrient overenrichment of estuaries.
Cross, V. A.; Bratton, J. F.; Kroeger, K. D.; Crusius, John; Worley, C. R.
Electrical resistivity imaging of the near-surface structure of the Solfatara volcano
NASA Astrophysics Data System (ADS)
We describe the results from an high-resolution study of the near-surface electrical resistivity structures carried out in the Solfatara area, located in the central part of the Campi Flegrei (CF) composite caldera, west of Naples, Italy. This area represents the most active zone within the CF area. It has been the site of an intense hydrothermal activity since Greek times, and currently exhibits the most impressive degassing manifestations. A direct relationship has always been observed between the increase of hydrothermal activity and ground uplift in the caldera. For this reason, dynamic of the Solfatara zone is considered a direct indicator of the volcanism taking place in the CF caldera. Since 2005 a new gradual increase of the hydrothermal activity and ground uplift has been observed. A steep growth of these effects has been recorded from 2012, accompanied by seismic events with hypocentres mostly concentrated below the area of Pozzuoli at depths ranging between 1 and 3 km, and highest magnitude of 1.8. It is thought that a further increase of the activity might lead to more critical conditions, including the occurrence of phreatic explosions. The detailed recovery of the structure and features of the shallow aquifers, mainly in the largest fumarole areas, is a crucial step for interpreting the ground movements and to improve our capability to forecast future pre-eruptive scenarios. Electrical resistivity results particularly sensitive to the presence of aqueous fluids and partial melts. By electrical imaging the volume of subsurface fluids can be constrained and the rheology of the subsoil can be reconstructed. To this aim, we have carried out eight profiles for electrical resistivity imaging, crossing the fumaroles field, deducting an electric model of the structural setting of the hydrothermal system in the first 100 m depth. Six of the profiles were 250 m long, with an electrodic distance of 5 m. Two longer profiles, up to 750 m, characterised by an electrodic distance of 10 m, was also realised, that crosses the whole Solfatara crater in the N-S and NE-WSW direction, respectively. The main electric features has been reconstructed and ERT results have been utilised to the aim of detailing the outlines of the fumarolic field defined by previous ground temperature, CO2 soil degassing, seismic noise, Bouguer anomaly mapping. A further analysis of the correlation between the recorded physical parameters and the main electric discontinuities has been realised.
Giulia Di Giuseppe, Maria; Troiano, Antonio; Fedele, Alessandro; Patella, Domenico; Troise, Claudia; De Natale, Giuseppe
Complex electrical resistance tomography of a subsurface PCE plume
A controlled experiment was conducted to evaluate the performance of complex electrical resistivity tomography (CERT) for detecting and delineating free product dense non-aqueous phase liquid (DNAPL) in the subsurface. One hundred ninety liters of PCE were released at a rate of 2 liters per hour from a point 0.5 m below ground surface. The spill was conducted within a double walled tank where saturated layers of sand, bentonite and a sand/bentonite mixture were installed. Complex electrical resistance measurements were performed. Data were taken before the release, several times during, and then after the PCE was released. Magnitude and phase were measured at 1 and 64 Hz. Data from before the release were compared with those during the release for the purpose of imaging the changes in conductivity resulting from the plume. Conductivity difference tomographs showed a decrease in electrical conductivity as the DNAPL penetrated the soil. A pancake-shaped anomaly developed on the top of a bentonite layer at 2 m depth. The anomaly grew in magnitude and extent during the release and borehole television surveys data confirmed the anomaly to be free-product PCE whose downward migration was stopped by the low permeability clay. The tomographs clearly delineated the plume as a resistive anomaly.
Ramirez, A.; Daily, W,; LeBrecque, D.
Detecting Cracks in Ceramic Matrix Composites by Electrical Resistance
NASA Technical Reports Server (NTRS)
The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of distributed matrix cracks. These cracks initiate near stress concentrations, such as 90o fiber tows or large matrix pores and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a specimen.s electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature. Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or post-damage. A relationship between resistance change and matrix crack density was also determined.
Smith, Craig; Gyekenyesi, Andrew
Rolling resistance of electric vehicle tires from track tests
NASA Technical Reports Server (NTRS)
Special low-rolling-resistance tires were made for DOE's ETV-1 electric vehicle. Tests were conducted on these tires and on a set of standard commercial automotive tires to determine the rolling resistance as a function of time during both constant-speed tires and SAE J227a driving cycle tests. The tests were conducted on a test track at ambient temperatures that ranged from 15 to 32 C (59 to 89 F) and with tire pressures of 207 to 276 kPa (30 to 40 psi). At a contained-air temperature of 38 C (100 F) and a pressure of 207 kPa (30 psi) the rolling resistances of the electric vehicle tires and the standard commercial tires, respectively, were 0.0102 and 0.0088 kilogram per kilogram of vehicle weight. At a contained-air temperature of 38 C (100 F) and a pressure of 276 kPa (40 psi) the rolling resistances were 0.009 and 0.0074 kilogram per kilogram of vehicle weight, respectively.
Dustin, M. O.; Slavik, R. J.
Data acquisition system based on CompactPCI bus and FPGA for electrical resistance tomography
As a kind of visual measurement technique based upon variations in conductivity, electrical resistance tomography has great potential in process application. A new data acquisition system for electrical resistance tomography is described. This data acquisition system is built based on the CompactPCI bus and the FPGA. The application of the CompactPCI bus can make the single plane electrical resistance tomography
Zhiqiang Zhang; Feng Dong; Cong Xu
Temperature and concentration dependence of the electrical resistivity of liquid indium-tin alloys
In this paper, the electrical resistivity (rho) of liquid In-Sn alloys has been measured as a function of temperature during cooling and subsequent heating. The electrical resistivity changes linearly with temperature for all the In-Sn melts within the measuring temperature range (from liquidus to 850 �C or 900 �C). In addition, the concentration dependence of electrical resistivity is presented based
Er-Guang Jia; Li-Jun Guo; Ai-Qing Wu; Wen-Jun Shan; Zhen-Gang Zhu
Evidence for Amorphization in Ni/Ti Multilayers from Electrical Resistivity Changes.
National Technical Information Service (NTIS)
Ni/Ti multilayers of various composition modulation lengths were annealed and studied with in situ electrical resistivity measurements. The resistivity was measured at different temperatures. The temperature coefficient of the resistivity at the annealing...
A. Vandergraaf M. A. Hollanders B. J. Thijsse E. J. Mittemeijer
Electrical Resistivity of an Elasmobranch's Ampullary Jelly in Varying Electric and Magnetic Fields
NASA Astrophysics Data System (ADS)
The ampullae of Lorenzini are believed to function as the electroreceptive organs in elasmobranch fishes. Though the entire excised organs have been the subject of electrical transport measurements, the jelly that fills the ampullae -- composed primarily of glycoproteins with proteins and dissolved salts -- has received less scrutiny. The specific electromagnetic properties of the jelly contribute to electroreception, and we hope to supply useful parameters to modeling efforts via precise electrical characterization. We report preliminary resistivity measurements from ampullary jelly removed, post mortem, from an adult triaenodon obesus (white-tip reef shark). We present data over a broad range of applied electrical currents. We also present data of the resistivity as a function of applied magnetic field strength.
Brown, Brandon; Hughes, Mary E.
Connection equation and shaly-sand correction for electrical resistivity
Estimating the amount of conductive and nonconductive constituents in the pore space of sediments by using electrical resistivity logs generally loses accuracy where clays are present in the reservoir. Many different methods and clay models have been proposed to account for the conductivity of clay (termed the shaly-sand correction). In this study, the connectivity equation (CE), which is a new approach to model non-Archie rocks, is used to correct for the clay effect and is compared with results using the Waxman and Smits method. The CE presented here requires no parameters other than an adjustable constant, which can be derived from the resistivity of water-saturated sediments. The new approach was applied to estimate water saturation of laboratory data and to estimate gas hydrate saturations at the Mount Elbert well on the Alaska North Slope. Although not as accurate as the Waxman and Smits method to estimate water saturations for the laboratory measurements, gas hydrate saturations estimated at the Mount Elbert well using the proposed CE are comparable to estimates from the Waxman and Smits method. Considering its simplicity, it has high potential to be used to account for the clay effect on electrical resistivity measurement in other systems.
Lee, Myung W.
Hydrologic Process-oriented Optimization of Electrical Resistivity Tomography
NASA Astrophysics Data System (ADS)
Electrical resistivity tomography (ERT) is commonly used in hydrologic investigations. Advances in joint and coupled hydrogeophysical inversion have enhanced the quantitative use of ERT to construct and condition hydrologic models (i.e. identify hydrologic structure and estimate hydrologic parameters). However the selection of which electrical resistivity data to collect and use is often determined by a combination of data requirements for geophysical analysis, intuition on the part of the hydrogeophysicist and logistical constraints of the laboratory or field site. One of the advantages of coupled hydrogeophysical inversion is the direct link between the hydrologic model and the individual geophysical data used to condition the model. That is, there is no requirement to collect geophysical data suitable for independent geophysical inversion. The geophysical measurements collected can be optimized for estimation of hydrologic model parameters rather than to develop a geophysical model. Using a synthetic model of drip irrigation we evaluate the value of individual resistivity measurements to describe the soil hydraulic properties and then use this information to build a data set optimized for characterizing hydrologic processes. We then compare the information content in the optimized data set with the information content in a data set optimized using a Jacobian sensitivity analysis.
Hinnell, A.; Bechtold, M.; Ferre, T. A.; van der Kruk, J.
Determining and Interpreting Resistive Electric Circuit Concepts Test (DIRECT)
NSDL National Science Digital Library
This 29-question research-based multiple-choice test is designed to evaluate students' reasoning regarding direct current resistive electric circuits. The test may be administered to students in algebra- or calculus-based introductory physics courses in high school or university settings. The test is based on investigations of students' difficulties with direct current circuits and should be given in a 30-minute period. Statistical results have shown the survey to be reliable and valid. A summary of the construction and analysis of the survey is available in, Students� understanding of direct current resistive electrical circuits, Am. J. Phys. 72 (1), 98-115 (2004). Details are provided in Paula Engelhardt's dissertation, Examining students' understanding of electrical circuits through multiple-choice testing and interviews. This assessment is free for use by instructors in their classroom. However, as it takes years of development effort to create and validate reliable assessment instruments, the file is password-protected. Furthermore, the author requests that 1. students are not given copies following examination; and 2. none of the questions are incorporated into web-based question delivery systems without adequate security to prevent printing or unauthorized access by students. To obtain the password, please send a request with your name, email, institution, and a link to a page at your institution that confirms you are an instructor.
Engelhardt, Paula V.; Beichner, Robert J.
Functional classification of cellular proteome profiles support the identification of drug resistance signatures in melanoma cells.
Drug resistance is a major obstacle in melanoma treatment. Recognition of specific resistance patterns, the understanding of the patho-physiology of drug resistance, and identification of remaining options for individual melanoma treatment would greatly improve therapeutic success. We performed mass spectrometry-based proteome profiling of A375 melanoma cells and HeLa cells characterized as sensitive to cisplatin in comparison to cisplatin resistant M24met and TMFI melanoma cells. Cells were fractionated into cytoplasm, nuclei and secretome and the proteome profiles classified according to Gene Ontology. The cisplatin resistant cells displayed increased expression of lysosomal as well as Ca�? ion binding and cell adherence proteins. These findings were confirmed using Lysotracker Red staining and cell adhesion assays with a panel of extracellular matrix proteins. To discriminate specific survival proteins, we selected constitutively expressed proteins of resistant M24met cells which were found expressed upon challenging the sensitive A375 cells. Using the CPL/MUW proteome database, the selected lysosomal, cell adherence and survival proteins apparently specifying resistant cells were narrowed down to 47 proteins representing a potential resistance signature. These were tested against our proteomics database comprising more than 200 different cell types/cell states for its predictive power. We provide evidence that this signature enables the automated assignment of resistance features as readout from proteome profiles of any human cell type. Proteome profiling and bioinformatic processing may thus support the understanding of drug resistance mechanism, eventually guiding patient tailored therapy. PMID:23713901
Paulitschke, Verena; Haudek-Prinz, Verena; Griss, Johannes; Berger, Walter; Mohr, Thomas; Pehamberger, Hubert; Kunstfeld, Rainer; Gerner, Christopher
Functional Classification of Cellular Proteome Profiles Support the Identification of Drug Resistance Signatures in Melanoma Cells
Drug resistance is a major obstacle in melanoma treatment. Recognition of specific resistance patterns, the understanding of the patho-physiology of drug resistance, and identification of remaining options for individual melanoma treatment would greatly improve therapeutic success. We performed mass spectrometry-based proteome profiling of A375 melanoma cells and HeLa cells characterized as sensitive to cisplatin in comparison to cisplatin resistant M24met and TMFI melanoma cells. Cells were fractionated into cytoplasm, nuclei and secretome and the proteome profiles classified according to Gene Ontology. The cisplatin resistant cells displayed increased expression of lysosomal as well as Ca2+ ion binding and cell adherence proteins. These findings were confirmed using Lysotracker Red staining and cell adhesion assays with a panel of extracellular matrix proteins. To discriminate specific survival proteins, we selected constitutively expressed proteins of resistant M24met cells which were found expressed upon challenging the sensitive A375 cells. Using the CPL/MUW proteome database, the selected lysosomal, cell adherence and survival proteins apparently specifying resistant cells were narrowed down to 47 proteins representing a potential resistance signature. These were tested against our proteomics database comprising more than 200 different cell types/cell states for its predictive power. We provide evidence that this signature enables the automated assignment of resistance features as readout from proteome profiles of any human cell type. Proteome profiling and bioinformatic processing may thus support the understanding of drug resistance mechanism, eventually guiding patient tailored therapy.
Lipid profiles in wheat cultivars resistant and susceptible to tan spot and the effect of disease on the profiles.
Lipid profiles in wheat leaves and the effects of tan spot on the profiles were quantified by mass spectrometry. Inoculation with Pyrenophora tritici-repentis significantly reduced the amount of leaf lipids, including the major plastidic lipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), which together accounted for 89% of the mass spectral signal of detected lipids in wheat leaves. Levels of these lipids in susceptible cultivars dropped much more quickly during infection than those in resistant cultivars. Furthermore, cultivars resistant or susceptible to tan spot displayed different lipid profiles; leaves of resistant cultivars had more MGDG and DGDG than susceptible ones, even in noninoculated plants. Lipid compositional data from leaves of 20 noninoculated winter wheat cultivars were regressed against an index of disease susceptibility and fitted with a linear model. This analysis demonstrated a significant relationship between resistance and levels of plastidic galactolipids and indicated that cultivars with high resistance to tan spot uniformly had more MGDG and DGDG than cultivars with high susceptibility. These findings suggest that lipid composition of wheat leaves may be a determining factor in the resistance response of cultivars to tan spot. PMID:23035632
Kim, Dongwon; Jeannotte, Richard; Welti, Ruth; Bockus, William W
Lipid Profiles in Wheat Cultivars Resistant and Susceptible to Tan Spot and the Effect of Disease on the Profiles
Lipid profiles in wheat leaves and the effects of tan spot on the profiles were quantified by mass spectrometry. Inoculation with Pyrenophora tritici-repentis significantly reduced the amount of leaf lipids, including the major plastidic lipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), which together accounted for 89% of the mass spectral signal of detected lipids in wheat leaves. Levels of these lipids in susceptible cultivars dropped much more quickly during infection than those in resistant cultivars. Furthermore, cultivars resistant or susceptible to tan spot displayed different lipid profiles; leaves of resistant cultivars had more MGDG and DGDG than susceptible ones, even in non-inoculated plants. Lipid compositional data from leaves of 20 non-inoculated winter wheat cultivars were regressed against an index of disease susceptibility and fitted with a linear model. This analysis demonstrated a significant relationship between resistance and levels of plastidic galactolipids and indicated that cultivars with high resistance to tan spot uniformly had more MGDG and DGDG than cultivars with high susceptibility. These findings suggest that lipid composition of wheat leaves may be a determining factor in the resistance response of cultivars to tan spot.
Kim, Dongwon; Jeannotte, Richard; Welti, Ruth; Bockus, William W.
Electrical resistivity tomography monitoring of permafrost in solid rock walls
NASA Astrophysics Data System (ADS)
This article describes the first attempt to conduct electrical resistivity tomography (ERT) in solid permafrost-affected rock faces. Electrode design, instrument settings, and processing routines capable of measuring under relevant conditions were developed. Four transects, with NW, NE, east (E) and south (S) aspects, were installed in solid rock faces between Matter Valley and Turtmann Valley, Switzerland, at 3070-3150 m above sea level. DC resistivity in the transects was measured repeatedly during the summer and compared by applying a time-lapse inversion routine. Resistivity values were calibrated using observed rock surface conditions of thawed, damp rocks (1-8 k? m), deeply frozen rocks (18-80 k? m), and the transition from damp thawed to frozen rocks (8-18 k? m). Mean surface layer resistivities of transects respond to air temperatures below 0�C with a rapid increase by a factor of 1.4 to 2.9 from values of 12-15 k? m to values of 22-31 k? m. Rock layers at depths of 2-6 m display a general trend of resistivity decrease in summer, corresponding to a persistent thawing process. Their response to anomalously cool August temperatures occurs with a time lag of 2 to 4 weeks. Only transects E, NE and NW display persistent, high-resistivity permafrost bodies (>50 k? m) mostly at depths of 6-10 m. The maximum thaw depth of a continuous thawing front above permafrost is 6 m. However, the ERT results emphasize the role of heat transfer by deep-reaching cleft water systems. Thus permafrost occurs in lenses rather than layers. ERT provides rapid detection of ice and water distribution in permafrost-affected bedrock.
Krautblatter, Michael; Hauck, Christian
Upper mantle electrical resistivity structure beneath the Southwest Indian Ridge 37�E
NASA Astrophysics Data System (ADS)
The Southwest Indian Ridge (SWIR) is expected to be interacted with the dynamics of the mantle, for example melt production and thermal structure, through specific mechanisms to the ultraslow spreading ridge system. In addition, the mantle near the SWIR 37�E may be influenced by the mantle upwelling producing the Marion hotspot due to its proximity at present and in the past. To reveal the mantle dynamics of the region by the electrical resistivity that is largely sensitive to melt and water contents and temperature, a marine electromagnetic experiment was carried out on a subsegment of the SWIR at 37�E. The subsegment is not magmatically active as revealed by geophysical surface surveys but may be within an area of high melt production as inferred from the existence of nearby magmatically active segments, an extensive gravity anomaly low, local high axial topography, and rock chemical compositions such as local low Na8. Seven ocean bottom electromagnetometers were deployed along a ~110 km profile across the SWIR axis at 37�E to acquire time variations of the electromagnetic field at the sampling rate of 1 minute for almost one year (from January to December in 2008). Almost all of the acquired time variations data are useful, and they have been processed for a magnetotelluric analysis. The range of frequency of the processed data suggests that the analysis will give an image of the electrical resistivity structure of the upper mantle at depths of a few tenths to a few hundred kilometers. We will present a resultant 2-D electrical resistivity structure to discuss melt and water contents and the thermal structure in the upper mantle. We will also examine possible off-profile 3-D structures related to the SWIR segment structure and the Marion hotspot.
Matsuno, T.; Mizuma, K.; Seama, N.; Nogi, Y.; Okino, K.
Electrical resistivity of titanium diboride and zirconium diboride
The electrical resistivities of hot-pressed samples of Ti{sub 1{minus}x}Zr{sub x}B{sub 2} (x = 0.0, 0.3, 0.5, 0.7, 1.0) were measured by a four-point ac technique over the range 298 to 1,573 K in an argon atmosphere. The hot-pressed samples for the intermediate compositions were found to be mixtures of two solid-solution phases. The resistivities for all compositions were found to increase linearly with temperature and can be described by {rho}(T) = {rho}{sub 298} + {phi}(T {minus} 298). The room-temperature resistivity {rho}{sub 298} ({mu}{Omega} {center_dot} cm) and the temperature coefficient of resistivity {phi} (n{Omega} {center_dot} cm/K) for ZrB{sub 2} were determined to be 7.8 and 10, both of which increase with the content of TiB{sub 2}. These values for TiB{sub 2} were determined to be 20.4 and 36, respectively.
Rahman, M.; Wang, C.C.; Chen, W.; Akbar, S.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Mroz, C. [Advanced Refractory Technologies, Inc., Buffalo, NY (United States)
Electrical splice resistance measurements and analysis on high purity aluminum
NASA Astrophysics Data System (ADS)
Low temperature electrical splice resistance measurements were performed on samples of high purity aluminum (RRR>5500). The samples were spliced together using two different joint configurations and adhering techniques: 1) soldered lap joints of Cu coated aluminum and 2) TIG welded butt joints. Splice resistance measurements of both the TIG welded butt joints and the Cu coated lap joints were made at 300, 77, and 4.2 K using a dc transport current technique in the absence of an applied magnetic field. Results showed that the soldered samples had splice resistivities ranging from 10 -6 to 10 -7 ?-cm 2 at 4.2 K, and were of the order of 10 -5 ?-cm 2 at room temperature. Results on all of the TIG welded samples showed splice resistivities <10 -8 ?-cm 2 at 4.2 K. An analysis was performed to determine the current flow within a lap joint of non-superconducting materials with rectangular cross sections. A generalized expression describing the current distribution within the lap joint was derived.
Rey, C. M.; Tong, W.; Xu, M. F.
Local Resistance Profiling of Ultra-Shallow Junction with Spike Lamp and Laser Annealing Using Scanning Spreading Resistance Microscopy
NASA Astrophysics Data System (ADS)
Local resistance profiles of ultra-shallow arsenic implanted into silicon with an energy of 3.5 keV and a dose of 1.2�1015 ions/cm2 activated by conventional spike lamp and laser annealing were measured by SSRM in a nitrogen atmosphere with a depth resolution of less than 10 nm for investigating the combination of the conventional spike lamp and laser annealing. Spike lamp annealing at 1050 �C followed by laser annealing at a power density of 0.42 kW/mm2 was found to give the lowest sheet resistance. The resistance profiles obtained by SSRM also indicated the lowest resistance for the sample after spike lamp annealing at 1050 �C followed by laser annealing with a power density of 0.42 kW/mm2. Laser annealing alone with a power density of 0.42 kW/mm2 resulted in the higher sheet resistance, though the shallower resistance profile could be obtained. Spike lamp annealing followed by laser annealing procedures are effective in activating shallow arsenic profiles.
Abo, Satoshi; Tanaka, Yuji; Nishikawa, Kazuhisa; Wakaya, Fujio; Iwamatsu, Toshiaki; Oda, Hidekazu; Takai, Mikio
Building Better Electrodes for Electrical Resistivity and Induced Polarization Data
NASA Astrophysics Data System (ADS)
In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles" heal of the resistivity method. Even stainless steel, a commonly used electrode material because of its durability, showed only average results in laboratory tests for electrode noise. Better results have been found with non-polarizing metal-metal salt electrodes, which are widely used as surface electrodes and in IP surveys. But although they produce small measurement errors, they are not durable enough for in-situ borehole resistivity surveys, and often contain compounds that are toxic to the environment. They are also very seldom used as transmitters. In laboratory studies, we are exploring other materials and configurations for low-noise compound electrodes that will be nontoxic, inexpensive, and durable and can be used as both transmitters and receivers. Testing of the electrical noise levels of electrodes is an arduous task involving repeated measurements under varying conditions at field scales. Thus it is important to find methods of sorting out likely candidates from the mass of possible electrode configurations and construction methods. Testing of electrode impedance versus current density appears to provide simple criteria for predicting the suitability of electrodes. The best electrodes show relatively low overall contact impedance, relatively small changes in impedance with increased current density, and relatively small changes in impedance with time. Furthermore it can be shown that resistivity and induced polarization performance of electrodes is strongly correlated, so that methods of finding electrodes with low impedance and good direct current performance usually provide better quality induced polarization data and vice- versa.
Adkins, P. L.; La Brecque, D. J.
Optical device with low electrical and thermal resistance Bragg reflectors
A compound-semiconductor optical device and method are disclosed. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors. 16 figs.
Lear, K.L.
Optical device with low electrical and thermal resistance bragg reflectors
A compound-semiconductor optical device and method. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors.
Lear, Kevin L. (Albuquerque, NM)
Evaluation of the radiation resistance of electrical insulation materials
NASA Astrophysics Data System (ADS)
The qualification of insulating materials for electrical cables is often accomplished according to the IEC 60544 standard of the International Electrotechnical Commission. The mechanical properties of the polymeric insulators are tested prior and after irradiation at relatively high dose rates. To assess the ageing of selected materials under realistic service conditions, usually at lower dose rate, an IEC Working Group has proposed extrapolation methods (IEC 61244-2), one of which is applied here for a cable sheathing material from Huber+Suhner. The method is found to be suitable to compare radiation resistance data of different materials irradiated under different conditions.
Perrin, Sh.; Sch�nbacher, H.; Tavlet, M.; Widler, R.
Electrical resistivity technique to assess the integrity of geomembrane liners
NASA Astrophysics Data System (ADS)
Two-dimensional electrical modeling of a liner system was performed using computer techiques. The modeling effort examined the voltage distributions in cross sections of lined facilities with different leak locations. Results confirmed that leaks in the liner influenced voltage distributions on the surface of the lined facility. Based on this, a small physical scale model of a lined facility was constructed. Tests were conducted to measure the influence of leaks on the surface voltage distributions of water-filled and earth-filled liner systems. Several leak and current electrode configurations were examined. Plots of measured surface voltages indicated the presence and location of a leak. These tests verified that the electrical resistivity technique could be used for detecting and locating leaks in liners. Larger-scale testing was performed a a 1-acre lined water impoundment.
Shultz, D. W.; Duff, B. M.; Peters, W. R.
Application of electrical resistivity tomography techniques for mapping man-made sinkholes
NASA Astrophysics Data System (ADS)
The suitability of the geophysical prospecting by electrical resistivity tomography to detect and map man-made subsurface cavities and related sinkholes has been studied in the Linares abandoned mining district (Spain). We have selected for this study four mined sectors constituted of different lithologies: granite and phyllites of Paleozoic age, and Triassic shales and sandstones. In three of these sectors, detail underground topographic surveys were carried out to chart the position and dimensions of the mining voids (galleries and chamber), in order to analyze the resolution of this methodology to characterize these cavities by using different electrode arrays. The results are variable, depending on the depth and diameter of the void, the selected electrode array, the spacing between electrodes, geological complexity and data density. These results also indicate that when the cavity is empty, an anomaly with a steep gradient and high resistivity values is registered, because the air that fills the mining void is dielectric, while when the cavities are filled with fine grain sediments, frequently saturated in water, the electrical resistance is lower. In relation with the three different multi-electrode arrays tested, the Wenner-Schlumberger array has resulted to offer the maximum resolution in all these cases, with lower and more stable values for the RMS than the other arrays. Therefore, this electrode array has been applied in the fourth studied sector, a former mine near the city centre of Linares, in an area of urban expansion in which there are problems of subsidence. Two sets of four electrical tomography profiles have been carried out, perpendicular to each other, and which have allowed reaching depths of research between 30-35 m. This net-array allowed the identification of two shallow anomalies of low resistivity values, interpreted as old mining galleries filled with fine material saturated in water. It also allows detecting two fractures, correlated in the profiles and which can be mapped to more than 25 m in depth. As showed by this case study, electrical resistivity tomography can be a suitable tool in sub-surface cavities detection and man-made sinkhole investigations.
Rey, J.; Mart�nez, J.; Hidalgo, C.; Due�as, J.
Reservoir characterization combining elastic velocities and electrical resistivity measurements
NASA Astrophysics Data System (ADS)
The elastic and electric parameters of rocks that can be obtained from seismic and electromagnetic data depend on porosity, texture, mineralogy, and fluid. However, seismic data seldom allow us to accurately quantify hydrocarbon saturation. On the other hand, in the case of common reservoir rocks (i.e., sandstones and carbonates), resistivity strongly depends on porosity and saturation. Therefore, the recent progress of controlled-source-electromagnetic (CSEM) methods opens new possibilities in identifying and quantifying potential hydrocarbon reservoirs, although its resolution is much lower than that of seismic data. Hence, a combination of seismic and CSEM data arguably offers a powerful means of finally resolving the problem of remote sensing of saturation. The question is how to combine the two data sources (elastic data and electrical resistivity data) to better characterize a reservoir. To address this question, we introduce the concept of P-wave impedance and resistivity templates as a tool to estimate porosity and saturation from well log data. Adequate elastic and resistivity models, according to the lithology, cementation, fluid properties must be chosen to construct these templates. These templates can be upscaled to seismic and CSEM scale using Backus average for seismic data, and total resistance for CSEM data. We also measured velocity and resistivity in Fontainebleau samples in the laboratory. Fontainebleau formation corresponds to clean sandstones (i.e., low clay content). We derived an empirical relation between these P-wave velocity and resistivity at 40MPa effective pressure, which is around 3 km depth at normal pressure gradients. We were not able to test if this relation could be used at well or field data scales (once appropriate upscaling was applied), since we did not have a field dataset over a stiff sandstone reservoir. A relationship between velocity and resistivity laboratory data was also found for a set of carbonates. This expression was quadratic, and not linear as in the case of Fontainebleau sandstones. There are other factors that influence this relationship in the case of these carbonates, which include pore geometry, and amount of micritic cement. We observed that the expression is almost linear, but it deviates as we approach lower resistivities. This deviation can be explained by the presence of stiff pores such as moldic or intra-granular pores, which causes high velocity but low resistivity values when water-saturated. In the same way, the effect of micrite cement on velocity is stronger than its effect on resistivity, and that also is responsible for some of the scatter that we observe. We also modeled both velocity and resistivity using self-consistent approximation with the same pore or inclusion geometries in both carbonate and sandstone laboratory datasets. In the case of carbonates, we found that we had to include needle-like pores to explain the low resistivity but high velocities. Needle is one of the geometries that allow us to have connected stiff pores. However, we also found that a fraction of compliant pores also had to be included in order to explain the velocity measurements on the carbonate dataset. The self-consistent model also approximated well the velocity and resistivity laboratory measurements on the Fontainebleau sandstones, using similar aspect ratios for both the velocity and the resistivity. As far as semi-empirical and empirical models, we observed how the stiff-sand model fit well the Fontainebleau data at 40MPa, including S-wave velocities. The Raymer-Hunt-Gardner relation also did a good job at predicting P-wave velocity. Archie's equation with cementation exponent between 1.6 and 2.1 fits the resistivity measurements on the Fontainebleau sandstones. These two relationships can be combined to create a resistivity---P-wave velocity transform for this dataset. When we attempted to use CSEM data to limit the shallow and low-frequency acoustic impedance trend for seismic inversion, we found that appropriate elastic and resistivity models must be chosen in
Gomez, Carmen Teresa
Experimental validation of rigorous, 3D profile models for negative-tone develop resists
NASA Astrophysics Data System (ADS)
The extension of 193nm immersion lithography to the 14nm node and beyond directly encounters a significant reduction in image quality. One of the consequences is that the resist profile varies noticeably, impacting the already limited process window. Resist top-loss, top-rounding, T-top and footing all play significant roles in the subsequent etch process. Therefore, a reliable rigorous model with the capability to correctly predict resist 3D (R3D) profiles is acquiring higher importance. In this paper, we will present a calibrated rigorous model of a negative-tone develop resist. Resist profiles can be well simulated through focus and dose, and cases that match well to the experimental wafer data are validated. Such a model can not only provide early investigation of insights into process limitation and optimization, but can also complement existing OPC models to become R3D-aware in process development.
Gao, Weimin; Klostermann, Ulrich; Kamohara, Itaru; Schmoeller, Thomas; Lucas, Kevin; Demmerle, Wolfgang; De Bisschop, Peter; Mailfert, Julien
Improvement of electrical resistivity tomography for leachate injection monitoring
Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a 'minimum length' constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills.
Clement, R., E-mail: email@example.com [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France); Descloitres, M. [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France); Guenther, T., E-mail: email@example.com [Leibniz Institute for Applied Geophysics, Stilleweg 2, D-30655 Hannover (Germany); Oxarango, L. [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France); Morra, C., E-mail: firstname.lastname@example.com [PROKHEM/Floralis, 6 allee de Bethleem, 38610 Gieres (France); Laurent, J.-P.; Gourc, J.-P. [Laboratoire d'Etude des Transferts en Hydrologie et Environnement, LTHE, UMR 5564, CNRS, INPG, IRD, UJF, B.P. 53, 38041, Grenoble Cedex 9 (France)
Rainfall infiltration process in mountain headwater region using electrical resistivity tomography
NASA Astrophysics Data System (ADS)
Many researchers have studied about the hydrological process, especially rainfall-runoff process, in the headwater region using multi hydrometric methods. Since the possibility has been recognized that bedrock groundwater has important role to play in the rainfall-runoff process, it is important to comprehend the rainfall infiltration process within fluctuations of bedrock groundwater. However, we would need many hydrological instruments to understand this process precisely. So we have applied electrical resistivity tomography (ERT) method to understand rainfall infiltration process in the area that is estimated the contribution of bedrock groundwater for rainfall-runoff processes. Resistivity changes with the saturation rate of the pore fluid in the subsurface material. So it is possible to estimate spatial and temporal distribution of subsurface water by using ERT. In this study, we will estimate rainfall infiltration process in mountain headwater region using resistivity method. The study area is the Mamushi-dani watershed in Shiranui, Kumamoto, Japan. We described the bedrock groundwater storage systems using resistivity method in this watershed previously. Resistivity has been observed at 2 measurement lines in slope areas of this watershed. Both measurement lines have 47m in length, 1m electrode spacing and 48 electrodes. We used the multi-electrode system, NEXT-400(Kowa Co. Ltd., Japan) for measuring apparent resistivity and the application software, E-tomo (Diaconsultant Co. Ltd., Japan) for inversion of apparent resistivity data. The observed resistivity data were compared with water head observed at borehole and specific discharge observed at foot of the watershed. Inverted resistivity profiles and observed hydrological data showed the interface between saturated and unsaturated zone. During rainfall occurs, resistivity in surface area gets lower than that before the rainfall and resistivity in some part of unsaturated area shows increasing tendency. Both variations indicate the movement of subsurface water. Thus, we could estimate spatial and temporal distribution of subsurface water using resistivity data, and understand rainfall infiltration process precisely. Acknowledgements This study was financially supported by THE FUKADA GRANTS-IN-AIDS, Japan.
Ono, M.; Yamamiya, K.; Shimada, J.
Electrical resistivity of fully-relaxed grain boundaries in nanocrystalline Cu
Electrical resistivity of grain boundaries (GBs) was determined in nanocrystalline (nc) Cu specimens prepared by magneto-sputtering and subsequent annealing. Extrapolating the microstrain dependence of GB resistivity, we derived electrical resistivity of GBs in a fully-relaxed state in Cu, being 2.04�10?16 ?m2.
L. H. Qian; Q. H. Lu; W. J. Kong; K. Lua
Modeling Fluid Flow and Electrical Resistivity in Fractured Geothermal Reservoir Rocks
Phase change of pore fluid (boiling\\/condensing) in rock cores under conditions representative of geothermal reservoirs results in alterations of the electrical resistivity of the samples. In fractured samples, phase change can result in resistivity changes that are more than an order of magnitude greater than those measured in intact samples. These results suggest that electrical resistivity monitoring may provide a
R L Detwiler; J J Roberts; W Ralph; B P Bonner
Electrical Resistivity as an Indicator of Saturation in Fractured Geothermal Reservoir Rocks: Experimental Data and Modeling
The electrical resistivity of rock cores under conditions representative of geothermal reservoirs is strongly influenced by the state and phase (liquid\\/vapor) of the pore fluid. In fractured samples, phase change (vaporization\\/condensation) can result in resistivity changes that are more than an order of magnitude greater than those measured in intact samples. These results suggest that electrical resistivity monitoring of geothermal
R L Detwiler; J J Roberts
The effects of dopants on the electrical resistivity in lead magnesium niobate multilayer ceramic capacitors
Electrical resistivity studies were performed on multilayer ceramic capacitors (MLC) based on lead magnesium niobate and containing dopants of lead titanate, lead zinc niobate, and lead cobalt niobate. The results showed that lead titanate and\\/or lead zinc niobate had no effect on the electrical resistivity while lead cobalt niobate decreased the resistivity. In samples without lead cobalt niobate, the authors
D. D. Chang; H. C. Ling
Direct-Current Resistivity Profiling at the Pecos River Ecosystem Project Study Site near Mentone, Texas, 2006
The U.S. Geological Survey, in cooperation with Texas A&M University AgriLife, did a surface geophysical investigation at the Pecos River Ecosystem Project study site near Mentone in West Texas intended to determine shallow (to about 14 meters below the water [river] surface) subsurface composition (lithology) in and near treated (eradicated of all saltcedar) and control (untreated) riparian zone sites during June-August 2006. Land-based direct-current resistivity profiling was applied in a 240-meter section of the riverbank at the control site, and waterborne direct-current continuous resistivity profiling (CRP) was applied along a 2.279-kilometer reach of the river adjacent to both sites to collect shallow subsurface resistivity data. Inverse modeling was used to obtain a nonunique estimate of the true subsurface resistivity from apparent resistivity calculated from the field measurements. The land-based survey showed that the sub-surface at the control site generally is of relatively low resis-tivity down to about 4 meters below the water surface. Most of the section from about 4 to 10 meters below the water surface is of relatively high resistivity. The waterborne CRP surveys convey essentially the same electrical representation of the lithology at the control site to 10 meters below the water surface; but the CRP surveys show considerably lower resistivity than the land-based survey in the subsection from about 4 to 10 meters below the water surface. The CRP surveys along the 2.279-kilometer reach of the river adjacent to both the treated and control sites show the same relatively low resistivity zone from the riverbed to about 4 meters below the water surface evident at the control site. A slightly higher resistivity zone is observed from about 4 to 14 meters below the water surface along the upstream approximately one-half of the profile than along the downstream one-half. The variations in resistivity could not be matched to variations in lithology because sufficient rock samples were not available.
Teeple, Andrew P.; McDonald, Alyson K.; Payne, Jason D.; Kress, Wade H.
Use of electrical resistivity tomography to evaluate processes in soils
NASA Astrophysics Data System (ADS)
Electrical resistivity tomography (ERT) is a non-invasive imaging technique capable of evaluating the distribution of electrical properties within a cross-section or volume of soil specimens. The technique provides an alternative for monitoring processes in soils that otherwise do not yield mechanical or density contrasts. This research presents the development and testing of 2D and 3D ERT imaging systems to map processes in soils and other porous media. The 2D ERT testing cell consisted of 16 electrodes placed along the perimeter of a circular section while the 3D ERT testing cell is composed of 64 electrodes distributed along four planes of the cylindrical testing cell. The 3D ERT testing cell also included 16 bender elements that were used to monitor S-wave propagation parameters to complement the electrical resistivity data. Two different tests were monitored with the ERT systems. The first test involved monitoring chemical diffusion in a 2D soil media by injecting 6 mL of 0.2 mol/L NaCl solution into tap water-saturated Ottawa sand. The ERT system successfully monitored the progression of the chemical diffusion over time. The second test images the injection of sodium pyrophosphate (SPP)-modified bentonite slurry in a sand specimen. Researchers at Purdue University developed this methodology with the intent to reduce liquefaction potential of loose saturated sands. Three tests were conducted to characterize the injected material and the injection processes: (i) electrical impedance analysis were conducted on the SPP-treated bentonite slurries to evaluate the reduction in resistivity with SPP concentration and time, (ii) viscosity measurements of the SPP-treated bentonite slurry were conducted to characterize the mechanical behavior of the slurry and show how increasing SPP concentration decreases and then regains slurry viscosity and (iii) the ERT system and bender elements were used to monitor the injection of bentonite slurry treated with 1% SPP in loose sand specimens. Results show the complementary nature of ERT and bender element data to successfully evaluate the injection process and the effect on the sand-saturated system.
Damasceno, Victor M.
Probabilistic electrical resistivity tomography of a CO2 sequestration analog
NASA Astrophysics Data System (ADS)
Electrical resistivity tomography (ERT) is a well-established method for geophysical characterization and has shown potential for monitoring geologic CO2 sequestration, due to its sensitivity to electrical resistivity contrasts generated by liquid/gas saturation variability. In contrast to deterministic inversion approaches, probabilistic inversion provides the full posterior probability density function of the saturation field and accounts for the uncertainties inherent in the petrophysical parameters relating the resistivity to saturation. In this study, the data are from benchtop ERT experiments conducted during gas injection into a quasi-2D brine-saturated sand chamber with a packing that mimics a simple anticlinal geological reservoir. The saturation fields are estimated by Markov chain Monte Carlo inversion of the measured data and compared to independent saturation measurements from light transmission through the chamber. Different model parameterizations are evaluated in terms of the recovered saturation and petrophysical parameter values. The saturation field is parameterized (1) in Cartesian coordinates, (2) by means of its discrete cosine transform coefficients, and (3) by fixed saturation values in structural elements whose shape and location is assumed known or represented by an arbitrary Gaussian Bell structure. Results show that the estimated saturation fields are in overall agreement with saturations measured by light transmission, but differ strongly in terms of parameter estimates, parameter uncertainties and computational intensity. Discretization in the frequency domain (as in the discrete cosine transform parameterization) provides more accurate models at a lower computational cost compared to spatially discretized (Cartesian) models. A priori knowledge about the expected geologic structures allows for non-discretized model descriptions with markedly reduced degrees of freedom. Constraining the solutions to the known injected gas volume improved estimates of saturation and parameter values of the petrophysical relationship.
Lochb�hler, Tobias; Breen, Stephen J.; Detwiler, Russell L.; Vrugt, Jasper A.; Linde, Niklas
Electrical resistivity imaging study of near-surface infiltration
NASA Astrophysics Data System (ADS)
High resolution electrical resistivity images (ERI method) were obtained during vadose zone infiltration experiments on agricultural soils in cooperation with Cornell University's Agricultural Stewardship Program, Cooperative Extension of Suffolk County, Extension Education Center, Riverhead, New York [ as well as Cornell University's Long Island Horticultural Research & Extension Center (LIHREC) in Riverhead, New York]. One natural soil was also studied. Infiltration was monitored by means of image analysis of two-dimensional array resistivity generated by a Syscal Kid Switch resistivity system (Griffiths et al., 1990). The data was inverted with the computer program RES2DINV (Loke, 2004). The agricultural soils considered were Riverhead sandy loam (RdA), Haven loam (HaA), and Bridgehampton silt loam (BgA). The natural site was located in the Catskill Mountains of New York State. The soils there are classified as Schoharie silty clay loam. The electrical images of the three sites were compared against established soil properties, including particle size distribution, available water capacity, and soluble salts (from the literature), as well as against site-specific soil samples and penetrometer data, which were collected along with the geophysical measurements. This research evaluates the potential of acquiring high resolution, non-destructive measurements of infiltration in the uppermost 1.5 meter of the vadose zone. The results demonstrate that resistivity differences can detect infiltration in soils typical of the north-eastern United States. Temporal and spatial variations of soil water content in the upper 1.5 meters (relevant to agriculture) of the subsurface can be monitored successfully and non-destructively with ERI. The sensitivity of the method is higher in subsurface environments that demonstrate high overall apparent resistivity values (e.g. high sand content). Under conditions of increased soil heterogeneity, instead of the formation of a continuous water plume as occurred in the homogeneous agricultural soils, the location of the infiltrated water seems to be highly influenced by the soil heterogeneity, and the water front is scattered into discontinuous layers and travels in additional directions. The geophysical results during infiltration correlate well with soil compaction data. It follows that the ERI method can be used as a proxy for soil compaction and water content variations in agricultural applications. In a natural environment, ERI successfully maps the tree root zone of mature trees. Applications include continuous water content monitoring in high value cash crops, such as viticulture (precision agriculture).
Lampousis, Angelos
Monitoring Damage Accumulation in Ceramic Matrix Composites Using Electrical Resistivity
NASA Technical Reports Server (NTRS)
The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection and accurate life prediction for high-temperature ceramic matrix composites. Woven silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMC) possess unique properties such as high thermal conductivity, excellent creep resistance, improved toughness, and good environmental stability (oxidation resistance), making them particularly suitable for hot structure applications. In specific, CMCs could be applied to hot section components of gas turbines [1], aerojet engines [2], thermal protection systems [3], and hot control surfaces [4]. The benefits of implementing these materials include reduced cooling air requirements, lower weight, simpler component design, longer service life, and higher thrust [5]. It has been identified in NASA High Speed Research (HSR) program that the SiC/SiC CMC has the most promise for high temperature, high oxidation applications [6]. One of the critical issues in the successful application of CMCs is on-board or insitu assessment of the damage state and an accurate prediction of the remaining service life of a particular component. This is of great concern, since most CMC components envisioned for aerospace applications will be exposed to harsh environments and play a key role in the vehicle s safety. On-line health monitoring can enable prediction of remaining life; thus resulting in improved safety and reliability of structural components. Monitoring can also allow for appropriate corrections to be made in real time, therefore leading to the prevention of catastrophic failures. Most conventional nondestructive evaluation (NDE) techniques such as ultrasonic C-scan, x-ray, thermography, and eddy current are limited since they require structural components of complex geometry to be taken out of service for a substantial length of time for post-damage inspection and assessment. Furthermore, the typical NDE techniques are useful for identifying large interlaminar flaws, but insensitive to CMC materials flaws developed perpendicular to the surface under tensile creep conditions. There are techniques such as piezoelectric sensor [7,8], and optical fiber [9,10] that could be used for on-line health monitoring of CMC structures. However, these systems involve attaching an external sensor or putting special fibers in CMC composites, which would be problematic at high temperature applications.
Smith, Craig E.; Morscher, Gregory N.; Xia, Zhenhai H.
An approach to construct the weathering profile in a hilly granitic terrain based on electrical imaging
NASA Astrophysics Data System (ADS)
For investigation of a granitic hillside at the Kata Noi beach in Phuket, Thailand, a common geotechnical site investigation might not be suitable because it is difficult to bring a drilling rig to make the boreholes on the hillside. As an alternative electrical imaging (EI) survey was proposed. The main issues addressed in this study are how to find the boundary between the weathered and unweathered granites in a gradually changing resistivity pseudo-section and how to assess the effect of hillside topography and the type of electrode array in locating such a boundary. To solve these problems an approach was adopted, including (i) selection of a suitable EI array in the field; (ii) data analysis with topographical correction; and (iii) the incorporation of a conceptual weathering profile in EI data interpretation. As a result, a geological-geoelectrical model was constructed for the weathering profile of granitic rocks at the study site, which can be applied for investigation of similar hilly terrains in Southern Thailand.
Giao, P. H.; Weller, A.; Hien, D. H.; Adisornsupawat, K.
Fabrication of an Electrically-Resistive, Varistor-Polymer Composite
This study focuses on the fabrication and electrical characterization of a polymer composite based on nano-sized varistor powder. The polymer composite was fabricated by the melt-blending method. The developed nano-composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FeSEM), and energy-dispersive X-ray spectroscopy (EDAX). The XRD pattern revealed the crystallinity of the composite. The XRD study also showed the presence of secondary phases due to the substitution of zinc by other cations, such as bismuth and manganese. The TEM picture of the sample revealed the distribution of the spherical, nano-sized, filler particles throughout the matrix, which were in the 10�50 nm range with an average of approximately 11 nm. The presence of a bismuth-rich phase and a ZnO matrix phase in the ZnO-based varistor powder was confirmed by FeSEM images and EDX spectra. From the current-voltage curves, the non-linear coefficient of the varistor polymer composite with 70 wt% of nano filler was 3.57, and its electrical resistivity after the onset point was 861 K?. The non-linear coefficient was 1.11 in the sample with 100 wt% polymer content. Thus, it was concluded that the composites established a better electrical non-linearity at higher filler amounts due to the nano-metric structure and closer particle linkages.
Ahmad, Mansor Bin; Fatehi, Asma; Zakaria, Azmi; Mahmud, Shahrom; Mohammadi, Sanaz A.
Fabrication of an electrically-resistive, varistor-polymer composite.
This study focuses on the fabrication and electrical characterization of a polymer composite based on nano-sized varistor powder. The polymer composite was fabricated by the melt-blending method. The developed nano-composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FeSEM), and energy-dispersive X-ray spectroscopy (EDAX). The XRD pattern revealed the crystallinity of the composite. The XRD study also showed the presence of secondary phases due to the substitution of zinc by other cations, such as bismuth and manganese. The TEM picture of the sample revealed the distribution of the spherical, nano-sized, filler particles throughout the matrix, which were in the 10-50 nm range with an average of approximately 11 nm. The presence of a bismuth-rich phase and a ZnO matrix phase in the ZnO-based varistor powder was confirmed by FeSEM images and EDX spectra. From the current-voltage curves, the non-linear coefficient of the varistor polymer composite with 70 wt% of nano filler was 3.57, and its electrical resistivity after the onset point was 861 K?. The non-linear coefficient was 1.11 in the sample with 100 wt% polymer content. Thus, it was concluded that the composites established a better electrical non-linearity at higher filler amounts due to the nano-metric structure and closer particle linkages. PMID:23443085
Ahmad, Mansor Bin; Fatehi, Asma; Zakaria, Azmi; Mahmud, Shahrom; Mohammadi, Sanaz A
Challenges of using electrical resistivity method to locate karst conduits�A field case in the Inner Bluegrass Region, Kentucky
NASA Astrophysics Data System (ADS)
Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit.
Zhu, Junfeng; Currens, James C.; Dinger, James S.
Urban archaeological investigations using surface 3D Ground Penetrating Radar and Electrical Resistivity Tomography methods
NASA Astrophysics Data System (ADS)
Ongoing and extensive urbanisation, which is frequently accompanied with careless construction works, may threaten important archaeological structures that are still buried in the urban areas. Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) methods are most promising alternatives for resolving buried archaeological structures in urban territories. In this work, three case studies are presented, each of which involves an integrated geophysical survey employing the surface three-dimensional (3D) ERT and GPR techniques, in order to archaeologically characterise the investigated areas. The test field sites are located at the historical centres of two of the most populated cities of the island of Crete, in Greece. The ERT and GPR data were collected along a dense network of parallel profiles. The subsurface resistivity structure was reconstructed by processing the apparent resistivity data with a 3D inversion algorithm. The GPR sections were processed with a systematic way, applying specific filters to the data in order to enhance their information content. Finally, horizontal depth slices representing the 3D variation of the physical properties were created. The GPR and ERT images significantly contributed in reconstructing the complex subsurface properties in these urban areas. Strong GPR reflections and high-resistivity anomalies were correlated with possible archaeological structures. Subsequent excavations in specific places at both sites verified the geophysical results. The specific case studies demonstrated the applicability of ERT and GPR techniques during the design and construction stages of urban infrastructure works, indicating areas of archaeological significance and guiding archaeological excavations before construction work.
Papadopoulos, Nikos; Sarris, Apostolos; Yi, Myeong-Jong; Kim, Jung-Ho
Electrically resistive coating for remediation (regeneration) of a diesel particulate filter and method
A resistively heated diesel particulate filter (DPF). The resistively heated DPF includes a DPF having an inlet surface and at least one resistive coating on the inlet surface. The at least one resistive coating is configured to substantially maintain its resistance in an operating range of the DPF. The at least one resistive coating has a first terminal and a second terminal for applying electrical power to resistively heat up the at least one resistive coating in order to increase the temperature of the DPF to a regeneration temperature. The at least one resistive coating includes metal and semiconductor constituents.
Phelps, Amanda C. (Malibu, CA); Kirby, Kevin K. (Calabasas Hills, CA); Gregoire, Daniel J. (Thousand Oaks, CA)
Study concerning the electrical resistivity of some liquid metals in ultrasonic field
The increasing of the electrical resistivity values for the overheated high-purity liquid aluminium in range 934 K to 1043 K and for aluminium-silicon eutectic alloy in range 850 K to 960 K, during high-energy ultrasonic field presence is reported. We used DC electrical resistivity measurements. The modification of electrical resistivity values in ultrasonic field due to electron-ion interaction processes and
Luminita Moraru
Drug resistance and plasmid profile of shigellae in Taiwan.
One hundred and twenty-eight shigella strains isolated from newborn and infant human faecal specimens at Kaohsiung Medical College Hospital in Taiwan were serogrouped, serotyped and examined for drug-resistance patterns and for the presence of plasmids. Forty-seven per cent of the isolates were found to belong to the Shigella sonnei serogroup, 41% to the S. flexneri group, 9% to the S. boydii group and 3% to the S. dysenteriae group. The serotype with the greatest number of strains was S. sonnei I. (29%) followed by S. flexneri 1 (27%). Each strain was tested for resistance to 11 antimicrobial agents. Eight-eight per cent of the strains were resistant to tetracycline, 87% to chloramphenicol, 84% to streptomycin, 52% to ampicillin, 25% to nalidixic acid, 29% to kanamycin, 11% to cephalothin, 11% to neomycin, 10% to cotrimoxazole, 1% to amikacin and none to gentamicin. The most prevalent resistance pattern was ApCmSmTc (28%). Clinical isolates demonstrating multiple resistance were found to harbour a large transmissible plasmid of 45-75 MDa while isolates without multiple resistance did not. Two large virulence plasmids of 123 and 110 MDa were found in 12 strains of S. flexneri and 4 strains of S. sonnei phase I. Small plasmids of 4.5, 4.2, 3.5, 2.8, 2.5. 2.0 and 1.5 MDa were also present in all strains. These small plasmids were species specific and can be used as marker plasmids to identify species. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4
Lin, S. R.; Chang, S. F.
Numerical analysis for resist profile after thermal process in display manufacturing
NASA Astrophysics Data System (ADS)
The screen size growth of mobile displays is accompanied with the drastically increased resolution. A display should have high pixel resolution to meet demanding readability and legibility expectations. The manufacturing process should be advanced to meet final device requirements. One of the important process steps is the post-development hardbake, where resist reflow is used to tune the final profile which influences subsequent process steps. Moreover, 3D resist profiles become one of critical design factors for mechanical and optical properties of display pixels. The resist reflow is the main time- and temperature-dependent effect of post-development bake process step. Since the resist is in transitional state (crystalline glassy/amorphous rubbery/viscous melt) the resist profile dynamics are very complex and predictive modeling is necessary. The model presented in this paper is based on a lattice-Boltzmann method, where the resist is considered as multicomponent (polymer-solvent) and multiphase (solid-liquid-vapor) mixture. Simulated resist profile dynamics with time are analyzed in dependency of material parameters (solvent diffusivity and evaporation rate, polymer solid fraction and adhesion with substrate). Temperature-dependent parameter descriptions are used for model calibration. Validation against experimental data shows good model consistency and predictability, demonstrating the benefit of simulation in process development and optimization.
Domnenko, Vitaliy; Stock, Hans-J�rgen; Shin, Sangmin; Ryu, Jonghyoek; Choi, Sung Won; Cho, Hyunwoo; Jeong, Eun-Soo; Choi, Jung-Hoe
Changes in electrical resistivity track changes in tectonic plate coupling
NASA Astrophysics Data System (ADS)
coupling on the Hikurangi subduction margin along the east coast of New Zealand's North Island changes north to south from almost uncoupled to locked. Clay-rich sediments and aqueous fluids at the subduction interface have been invoked as key factors in the frictional processes that control interplate coupling. Here we use magnetotelluric data to show that the subduction interface in the weakly coupled region is electrically conductive but is resistive in the locked region. These results indicate the presence of a layer of fluid- and clay-rich sediments in the weakly coupled region and support the idea that the presence of fluid and hydrated clays at the interface is a major factor controlling plate coupling.
Heise, Wiebke; Caldwell, T. Grant; Bertrand, Edward A.; Hill, Graham J.; Bennie, Stewart L.; Ogawa, Yasuo
Monitoring snowmelt induced unsaturated flow and transport using electrical resistivity tomography
NASA Astrophysics Data System (ADS)
The flow and transport of a non-reactive tracer and melt water was monitored in a heterogeneous coarse sandy unsaturated zone in southeastern Norway, during the snowmelt of 2001. Electrical resistivity tomography (ERT) as well as conventional suction cup techniques was employed. A frozen solution of NaBr in water was supplied as a line source on the ground surface above two parallel vertical profiles monitored by the two measurement systems prior to the onset of snowmelt. The two monitored vertical profiles were separated by approximately 1 m. The results were analysed by visual comparison of images and by the use of spatial moments analysis. The two measurement approaches showed that the system was affected by the presence of preferential flow paths during the early stages of the snowmelt, perhaps due to ice near the surface, but the major part of the plume moves uniformly later in the snow-melting period. After most of the tracer plume has reached the depth monitored by both systems (i.e. below 0.4 m depth) there is a good consistency between the two datasets. Spatial moment calculations on the basis of ERT cannot be used to describe the movement of tracer alone, as the resistivity is affected by changes in both saturation levels and tracer concentration. Nevertheless, ERT appears to be an appropriate method to characterise regions of localised high infiltration in this type of soil. The method therefore constitutes a possible alternative and supplement to suction cups in a monitoring system.
French, Helen K.; Hardbattle, Carol; Binley, Andrew; Winship, Peter; Jakobsen, Leif
Combining Inverted Echo Sounder and Horizontal Electric Field Recorder Measurements to Obtain Absolute Velocity Profiles
Profiles of absolute velocity are difficult to obtain in the ocean, especially over long periods of time at the same location. This paper presents a method of estimating full water column absolute horizontal velocity profiles as a function of time by combining historical hydrography with the measurements from two separate instruments, the inverted echo sounder (IES) and the horizontal electric
Christopher S. Meinen; Douglas S. Luther; D. Randolph Watts; Karen L. Tracey; Alan D. Chave; James Richman
Drug resistance, plasmid profile and random amplified polymorphic DNA analysis of Iranian isolates of Salmonella enteritidis.
The aim of this study was to characterize 49 Salmonella Enteritidis (SE) isolates from different sources (poultry, human, cow, poultry house environment) in Iran with respect to drug resistance, plasmid profile, and random amplified polymorphic DNA (RAPD) analysis. Antimicrobial susceptibility test to 29 agents found 33 resistance patterns among the isolates. No resistance was observed to danofloxacin, levofloxacin, norfloxacin, ceftriaxone, imipenem, and amikacin. The highest resistance (38.8%) was observed to flumequine. Thirty (61.2%) isolates were multidrug-resistant. Six plasmid profiles were detected and a 68-kb plasmid was found in 98% of isolates. Two different primers, MK22 and P1254, were used for RAPD analysis which each produced six profiles. For MK22 and P1254 primers, 83 and 86% of the isolates, respectively, belonged to one profile only and the rest distributed among other 5 patterns. The findings of the present study showed that SE isolates from poultry-related sources were closely related to human SE isolates. This study confirmed previous evidence that molecular techniques such as RAPD-PCR or plasmid profile alone do not demonstrate sufficient discriminatory power in epidemiological studies and a combination of patterns obtained by several techniques will provide more discriminatory power. PMID:20402413
Morshed, Rima; Peighambari, Seyed Mostafa
Crystalline electric field effects in the electrical resistivity of PrOs4Sb12
NASA Astrophysics Data System (ADS)
The temperature T and magnetic field H dependences of the electrical resistivity rho of the recently discovered heavy-fermion superconductor PrOs4Sb12 have features that are associated with the splitting of the Pr3+ Hund's rule multiplet by the crystalline electric field (CEF). These features are apparently due to magnetic exchange and aspherical Coulomb scattering from the thermally populated CEF-split Pr3+ energy levels. The rho(T) data in zero magnetic field can be described well by calculations based on CEF theory for various ratios of magnetic exchange and aspherical Coulomb scattering, and yield CEF parameters that are qualitatively consistent with those previously derived from magnetic susceptibility, specific heat, and inelastic neutron scattering measurements. Calculated rho(H) isotherms for a Gamma3 ground state qualitatively account for the 'dome-shaped' feature in the measured rho(H) isotherms.
Frederick, N. A.; Maple, M. B.
Bactericidal activity and resistance development profiling of dalbavancin.
Dalbavancin, a semisynthetic lipoglycopeptide being developed for the treatment of skin and skin structure infections (SSSIs), has a half-life of 5 to 7 days in humans and offers promise for a convenient weekly dosing regimen. We studied the in vitro bactericidal activity of dalbavancin against target organisms, using the concentrations that are maintained in human blood with the proposed dosage regimen. Dalbavancin minimal bactericidal concentrations (MBCs) were
Goldstein, Beth P; Draghi, Deborah C; Sheehan, Daniel J; Hogan, Patricia; Sahm, Daniel F
The Use of Cone-Based Electrical Resistivity Tomography to Image Conductive Contaminants.
NASA Astrophysics Data System (ADS)
Determining the 3D spatial distribution of subsurface contaminants is a challenging task. Most methods sample small regions immediately adjacent to wells or testing devices, thus providing data which are not representative of the entire region of interest. Furthermore, at many sensitive sites invasive methods that are usually employed to characterize contaminants are no longer acceptable, as the risk for exposing workers and spreading contaminants is too high. By integrating geophysical resistivity imaging with cone-penetration testing, we are developing a technology that addresses both of these issues by being minimally invasive while providing information about the 3D distribution of electrically conductive subsurface contamination. This new technique, cone-based electrical resistivity tomography (C-bert), involves placing several permanent current electrodes in the subsurface and using electrodes mounted on the cone-penetrometer to measure the resultant potential field while advancing the cone into the sub-surface. In addition to potential field measurements, we obtain the standard suite of cone-penetration measurements, including high resolution resistivity logs; these data can then be used to constrain the inversion of the potential field data. We recently performed a C-bert experiment to image a salt water intrusion in a fresh water aquifer in Vancouver, British Columbia. A total of nine current electrodes were emplaced at the site and five C-bert profiles were obtained, resulting in approximately 8000 independent data points. Obtaining data at the site proved challenging because of current channeling through the low resistivity salt-water wedge; for certain electrode configurations, this channeling pressed the power limitations of our resistivity unit, resulting in noisy data. In addition, the variation of in-situ resistivity over several orders of magnitude requires specific care be taken with data weighting and model regularization during inversion. To test ways to reduce computational time, we did not explicitly include the effect of the conductive cone in the initial inversion of the data. The inversion results that we obtained, along with forward modeling of the conductive cone, suggest that, for the resistivity structure and measurement geometry at the site, the effect of the cone can be considered second order. We conclude, from this first field test, that this method is a promising new way to image the subsurface.
Pidlisecky, A.; Knight, R.
Novel applications of motif-directed profiling to identify disease resistance genes in plants
Background Molecular profiling of gene families is a versatile tool to study diversity between individual genomes in sexual crosses and germplasm. Nucleotide binding site (NBS) profiling, in particular, targets conserved nucleotide binding site-encoding sequences of resistance gene analogs (RGAs), and is widely used to identify molecular markers for disease resistance (R) genes. Results In this study, we used NBS profiling to identify genome-wide locations of RGA clusters in the genome of potato clone RH. Positions of RGAs in the potato RH and DM genomes that were generated using profiling and genome sequencing, respectively, were compared. Largely overlapping results, but also interesting discrepancies, were found. Due to the clustering of RGAs, several parts of the genome are overexposed while others remain underexposed using NBS profiling. It is shown how the profiling of other gene families, i.e. protein kinases and different protein domain-coding sequences (i.e., TIR), can be used to achieve a better marker distribution. The power of profiling techniques is further illustrated using RGA cluster-directed profiling in a population of Solanum berthaultii. Multiple different paralogous RGAs within the Rpi-ber cluster could be genetically distinguished. Finally, an adaptation of the profiling protocol was made that allowed the parallel sequencing of profiling fragments using next generation sequencing. The types of RGAs that were tagged in this next-generation profiling approach largely overlapped with classical gel-based profiling. As a potential application of next-generation profiling, we showed how the R gene family associated with late blight resistance in the SH*RH population could be identified using a bulked segregant approach. Conclusions In this study, we provide a comprehensive overview of previously described and novel profiling primers and their genomic targets in potato through genetic mapping and comparative genomics. Furthermore, it is shown how genome-wide or fine mapping can be pursued by choosing different sets of profiling primers. A protocol for next-generation profiling is provided and will form the basis for novel applications. Using the current overview of genomic targets, a rational choice can be made for profiling primers to be employed.
Velocity, temperature, and electrical conductivity profiles in hydrogen-oxygen MHD duct flows
NASA Technical Reports Server (NTRS)
This paper presents results of two-dimensional duct flow computations for radial distributions of velocity, temperature, and electrical conductivity. Calculations were carried out for the flow conditions representative of NASA Lewis hydrogen-oxygen combustion driven MHD duct. Results are presented for two sets of computations: (1) profiles of developing flow in a smooth duct, and (2) profiles of fully developed pipe flow with a specified streamwise shear stress distribution. The predicted temperature and electrical conductivity profiles for the developing flows compared well with available experimental data.
Greywall, M. S.; Pian, C. C. P.
On the Intensity Profile of Electric Lamps and Light Bulbs
ERIC Educational Resources Information Center
We demonstrate that the time profile of the light intensity from domestic lighting sources exhibits simple yet interesting properties that foster lively student discussions. We monitor the light intensity of an industrial fluorescent lamp (also known as TL) and an incandescent bulb using a photodetector connected to an oscilloscope. The light�
Bacalla, Xavier; Salumbides, Edcel John
A method for measuring the inductive electric field profile and noninductive current profiles on D3-D
NASA Astrophysics Data System (ADS)
A new technique for determining the parallel electric field profile and noninductive current profile in tokamak plasmas has been developed and applied to two DIII-D tokamak discharges. Central to this technique is the determination of the current density profile, J(rho), and poloidal flux, psi(rho), from equilibrium reconstructions. From time sequences of the reconstructions, the flux surface averaged, parallel electric field can be estimated from appropriate derivatives of the poloidal flux. With a model for the conductivity and measurements of T(sub e) and Z(sub eff), the noninductive fraction of the current can be determined. Such a technique gives the possibility of measuring directly the bootstrap current profile and the noninductively driven current from auxiliary heating such as neutral beam injection or fast wave current drive. Furthermore, if the noninductively driven current is small or if the noninductive current profile is assumed to be known, this measurement provides a local test of the conductivity model under various conditions.
Forest, C. B.; Luce, T. C.; Politzer, P. A.; Lao, L. L.; Kupfer, K.; Wroblewski, D.
DUV resist profile improvement on TiN-deposited metal layer
NASA Astrophysics Data System (ADS)
Over the past several years, there have been many publications concerning the sensitivity of chemically amplified (CA) resist to substrate contamination. Resist footing phenomena are found on SiN, BPSG, TiN...etc stack films. Many approaches, such as varying the film thickness, oxide deposition, etc., have been proposed to solve this problem, with the sacrifice of increasing process complexity. In this study, we tried to improve DUV photoresist profile on TiN/AlSiCu/BPSG stacked layers. A positive tone CA resist was used and the improvement was carried out through both thin-film and lithography treatments. Since many process parameters were optimized, Taguchi design-of-experiment method was utilized to save processing cost, time and effort. The results turned out that passivation of TiN with hydrogen can improve resist footing better than either oxygen passivation or no treatment. However, the improvement was less significant than lithography process parameters. It is believed that since HMDS serves as an interlayer between TiN substrate and DUV resist, optimizing dehydration hot baking, post baking and post-exposure baking processes apparently has a more direct and significant impact on resist profile improvement than thin-film treatments. It is suggested that in this specific problem, the optimization of lithographic parameters can result in satisfactory resist profile.
Lin, Chia-Hui; Chen, Chun-Cho; Jenq, Jhy-Sayang; Op de Beeck, Maaike; Van den Hove, Luc
Electrical Resistance Tomography Field Trials to Image CO2 Sequestration
NASA Astrophysics Data System (ADS)
If geologic formations are used to sequester or store carbon dioxide (CO2) for long periods of time, it will be necessary to verify the containment of injected CO2 by assessing leaks and flow paths, and by understanding the geophysical and geochemical interactions between the CO2 and the geologic minerals and fluids. Remote monitoring methods are preferred, to minimize cost and impact to the integrity of the disposal reservoir. Electrical methods are especially well suited for monitoring processes involving fluids, as electrical properties are most sensitive to the presence and nature of the fluids contained in the medium. High resolution tomographs of electrical properties have been used with success for site characterization, monitoring subsurface migration of fluids in instances of leaking underground tanks, water infiltration events, subsurface steam floods, contaminant movement, and assessing the integrity of subsurface barriers. These surveys are commonly conducted utilizing vertical arrays of point electrodes in a crosswell configuration. Alternative ways of monitoring the reservoir are desirable due to the high costs of drilling the required monitoring boreholes Recent field results obtained using steel well casings as long electrodes are also promising. We have conducted field trials to evaluate the effectiveness of long electrode ERT as a potential monitoring approach for CO2 sequestration. In these trials, CO2 is not being sequestered but rather is being used as a solvent for enhanced oil recovery. This setting offers the same conditions expected during sequestration so monitoring secondary oil recovery allows a test of the method under realistic physical conditions and operational constraints. Field experience has confirmed the challenges identified during model studies. The principal difficulty are the very small signals due to the fact that formation changes occur only over a small segment of the 5000 foot length of the electrodes. In addition, telluric noise can be comparable to the signal levels during periods of geomagnetic activity. Finally, instrumentation stability over long periods is necessary to follow trends in reservoir behavior for several years. Solutions to these and other problems will be presented along with results from the first two years of work at a producing field undergoing CO2 flood. If electrical resistance tomography (ERT) imaging can be performed using existing well casings as long electrodes, it will substantially reduce the cost to monitor CO2 sequestration. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
Newmark, R.
Resistance pattern and antioxidant enzyme profiles of protoporphyrinogen oxidase (PROTOX) inhibitor-resistant transgenic rice
We quantified the resistance levels of transgenic rice plants, expressing Myxococcus xanthus protoporphyrinogen oxidase (PROTOX) in chloroplasts and mitochondria, to PROTOX inhibitors, acifluorfen, oxyfluorfen, carfentrazone-ethyl, and oxadiazon. We also determined whether active oxygen species-scavenging enzymes are involved in the resistance mechanism of transgenic rice. The transgenic rice line M4 was about >200-fold more resistant to oxyfluorfen than the wild-type (WT).
Ha Il Jung; Yong In Kuk; Kyoungwhan Back; Nilda R. Burgos
Exploiting Support Vector Clustering Techniques for Electrical Load Profiling
Many algorithms for load pattern classification have been developed in recent years, addressing various aspects of the energy management process. This paper presents a new application of Support Vector Clustering (SVC) to classify electrical load pattern data. After recalling the details and variants of application of the SVC method, a specific case study is presented and applied to a set
Irinel-Sorin Ilie; Gianfranco Chicco
Shipboard electrical-consumption profile analysis. Master's thesis
Department of Navy energy consumption reduction goals have been established for afloat commands and shore installations in order to keep pace with the ever increasing demand and high cost of energy resources. This study examines electrical power consumption data for various Pacific Fleet ships berthed at Naval Station, San Diego, CA. during the period 1 Jan. 1990- 19 Jun 1991,
Upper mantle electrical resistivity structure beneath the central Mariana subduction system
This paper reports on a magnetotelluric (MT) survey across the central Mariana subduction system, providing a comprehensive electrical resistivity image of the upper mantle to address issues of mantle dynamics in the mantle wedge and beneath the slow back-arc spreading ridge. After calculation of MT response functions and their correction for topographic distortion, two-dimensional electrical resistivity structures were generated using
Tetsuo Matsuno; Nobukazu Seama; Rob L. Evans; Alan D. Chave; Kiyoshi Baba; Antony White; Tada-nori Goto; Graham Heinson; Goran Boren; Asami Yoneda; Hisashi Utada
Study of critical dependence of stable phases in Nitinol on heat treatment using electrical resistivity probe
Phase transformations in 40% cold-worked Nitinol as a function of heat treatment have been studied using electrical resistivity variation with temperature. The stabilisation of austenitic, rhombohedral and martensitic phases is shown to critically depend on the temperatures of heat treatment by the analysis of temperature dependence of electrical resistivity in heating and cooling parts of the cycle. Characteristic values of
J Uchil; K. P Mohanchandra; K. Ganesh Kumara; K. K Mahesh
Position control of shape memory alloy actuators with internal electrical resistance feedback using neural networks
The development of a position control system for a shape memory alloy (SMA) wire actuator using an electrical resistance feedback is presented in this paper. A novel control scheme is implemented to eliminate the need for a position sensor to achieve stable and accurate positioning by utilizing the actuator�s electrical resistance feedback. Experiments are conducted to investigate the relationship between
N Ma; G Song; H-J Lee
Low-temperature electrical resistivity study of deformed Inconel alloy 600
The electrical resistivity of a plastic deformed Inconel alloy 600 (alloy of Ni 72 Cr 16 Fe 8) as function of temperature between 25 K and 300 K was studied. The deformation does not affect the Curie temperature much; it is roughly near 176 K of the deflected point at electrical resistivity, except for the sample with 75% deformation. The
Feng Shiu Chan; Yeong Der Yao; Shing Hoa Wang
Low-temperature electrical resistivity study of deformed Inconel alloy 600
The electrical resistivity of a plastic deformed Inconel alloy 600 (alloy of Ni 72 Cr 16 Fe 8) as function of temperature between 25K and 300K was studied. The deformation does not affect the Curie temperature much; it is roughly near 176K of the deflected point at electrical resistivity, except for the sample with 75% deformation. The ?-type behavior of
Feng Shiu Chan; Yeong Der Yao; Shing Hoa Wang
Shape memory alloy servo actuator system with electric resistance feedback and application for active endoscope
A control system for a shape memory alloy (SMA) servo actuator, and its application to a unique medical tool, are considered. It is thought that the electric resistance value of an SMA can be utilized to monitor the transformation of the SMA directly. Therefore, an antagonistic transformation control scheme using electric resistance feedback is proposed and is verified by several
Koji Ikuta; M. Tsukamoto; Shigeo Hirose
Transformation and detwinning induced electrical resistance variations in NiTiCu
Utilizing electrical resistance measurements in combination with strain observations on single crystals, it was possible to distinguish the austenite to martensite transformation from the detwinning of the martensite behavior during deformation of NiTiCu shape memory alloys. It was found that the electrical resistance change associated with the detwinning of the martensite variants was as high as 45% in deformation experiments
T Kotil; H Sehitoglu; H. J Maier; Y. I Chumlyakov
Optimization of the process of electric resistance welding of metallic strips through an amorphous solder
The main factors of the process of electric resistance welding of a metallic strip through an amorphous solder tape are determined. Regression equations are derived for the determination of the strength of the joint between the coating and the substrate in electric resistance welding through an amorphous solder tape and also the depth of the heat-affected zone in relation to
P. I. Burak; A. V. Serov; R. A. Latypov
3Dimensional spatial monitoring of tanks for the milk processing industry using electrical resistance tomography
The novel application of Electrical Resistance Tomography (ERT) in monitoring milk solutions could have potential applications in various stages of the milk processing industry for monitoring and control of crucial parameters. In this study, Electrical Resistance Tomography has been applied for the first time in 3-dimensional visualization of milk holding tanks for analysis of overall homogeneity or non-homogeneity, total solids
Mohadeseh Sharifi; Brent Young
Electrical Resistivity of TiH/sub X/KClO sub 4.
National Technical Information Service (NTIS)
Various factors affecting the electrical resistivity of the pyrotechnic pressed powder TiH/sub x//KClO sub 4 , which is sensitive to hot wire ignition yet quite spark insensitive, were evaluated. The electrical resistivity of the TiH/sub x/ (x = 0.19-1.9,...
K. White J. W. Reed C. M. Love J. A. Holy J. E. Glaub
Dissecting therapeutic resistance to RAF inhibition in melanoma by tumor genomic profiling.
A detailed understanding of the mechanisms by which tumors acquire resistance to targeted anticancer agents should speed the development of treatment strategies with lasting clinical efficacy. RAF inhibition in BRAF-mutant melanoma exemplifies the promise and challenge of many targeted drugs; although response rates are high, resistance invariably develops. Here, we articulate overarching principles of resistance to kinase inhibitors, as well as a translational approach to characterize resistance in the clinical setting through tumor mutation profiling. As a proof of principle, we performed targeted, massively parallel sequencing of 138 cancer genes in a tumor obtained from a patient with melanoma who developed resistance to PLX4032 after an initial dramatic response. The resulting profile identified an activating mutation at codon 121 in the downstream kinase MEK1 that was absent in the corresponding pretreatment tumor. The MEK1(C121S) mutation was shown to increase kinase activity and confer robust resistance to both RAF and MEK inhibition in vitro. Thus, MEK1(C121S) or functionally similar mutations are predicted to confer resistance to combined MEK/RAF inhibition. These results provide an instructive framework for assessing mechanisms of acquired resistance to kinase inhibition and illustrate the use of emerging technologies in a manner that may accelerate personalized cancer medicine. PMID:21383288
Wagle, Nikhil; Emery, Caroline; Berger, Michael F; Davis, Matthew J; Sawyer, Allison; Pochanard, Panisa; Kehoe, Sarah M; Johannessen, Cory M; Macconaill, Laura E; Hahn, William C; Meyerson, Matthew; Garraway, Levi A
Electrical Resistivity Tomography of the Karstic Aquifer of Bittit spring (Middle Atlas, Morocco)
NASA Astrophysics Data System (ADS)
The Tabular Middle Atlas reservoir is one of the most important aquifers in northern Morocco. It is mainly a water table fractured reservoir consisting of Lias limestone and dolomite. The matrix permeability is very low and water flows essentially along open fractures and karsts. The Bittit Spring belongs to this karstic system and constitutes an important aquifer lying at the junction between the tabular reservoir and the Sais basin. Bittit spring, with an average annual discharge of about 1600 l/s, contributes largely to water supply of the big city of Meknes. Groundwater circulation is complex due to tectonics and to presence of karstic Quaternary travertine overlying Lias carbonate. In Bittit area, travertine is mostly covered by Quaternary basalt. Up to now water flow paths and the underground karst organization remain misknown, and turbidity affects the water quality after rain events. To highlight these issues, an integrated geophysical survey was performed in this area in the framework of a French-Moroccan scientific project. The geophysical imaging was carried out mainly by Electrical Resistivity Tomography (ERT). Resistivity data were acquired by an ABEM Terrameter SAS1000 and a multi-electrode Lund system imaging using a Wenner array configuration of 64 electrodes and 5m spacing, reaching a depth of about 50m. Topographic corrections and 2D inversion models were performed using Res2Dinv software package. Seven 2D resistivity high resolution images have been obtained allowing to detect, delineate important fractures and also to hydrogeological characterization of the underground karst. A borehole of 100m depth was drilled in order to correlate and calibrate geophysical data and proposed models. Two sub-vertical fracture families have been identified with NE-SW and NW-SE directions respectively. These results correlate well with fracture data analysis gathered from remote sensing Spot images at large scale, and from local field fracture scanline surveys. A 3D picture of the fracture system has been drawn showing a mini-graben structure. Geophysical scans and interpreted fractures were displayed with Gocad software leading to geometric construction of aquifer units and to 3D modelling of subsurface architecture. Several horizontal electrical resistivity profiles and electromagnetic VLF profiles were also performed in order to discriminate between dry and favourable hydrological fractures. ERT appears to be an appropriate geophysical method in this issue, especially by improving understanding of fracture geometry. This study initiates a hydrogeophysical research in the Middle Atlas karst in order to improve water resources management and reducing aquifer vulnerability in the region.
Qarqori, Kh.; Rouai, M.; Moreau, F.; Saracco, G.; Hermitte, D.; Boualoul, M.; Dauteuil, O.; Biessy, G.; Sahbi, H.
Time-Lapse Electrical Resistivity Surveys of the Intertidal Zone: Implications for Submarine Groundwater Discharge
NASA Astrophysics Data System (ADS)
Submarine groundwater discharge (SGD) is now widely recognized as a crucial contributor to surface water as it provides a pathway for nutrients and contaminants that can significantly impact coastal ecosystems. Field measurements in the vicinity of the freshwater/seawater interface (FSI) have shown that the spatio-temporal distribution of SGD can be highly heterogeneous. Some numerical models have identified 3 regions (a density-driven circulation cell offshore, an upper saline plume and a freshwater tube in the intertidal zone) which seem to persist over time, such that the distinct regions can be recognized in simulations that average the numerically predicted salinity profiles over the tidal phases. The size and shape of each region are influenced by factors such as the tidal and wave loading, inland hydraulic gradient, beach geometry and aquifer properties. There is a paucity of field data at the FSI on the evolution of the salinity profile during a tidal cycle. To characterize the spatio-temporal heterogeneities of the FSI and compare with numerical predictions, we used electrical resistivity as a proxy for salinity. Electrical resistivity surveys were acquired during a 12-hour cycle in a tidally dominated environment. On September 12 2012, at West Neck Bay (Shelter Island, NY), a 33.4 m long stationary cable with 56 electrodes was extended over land and sea to image the intertidal zone. Hourly measurements were conducted over a full tidal cycle. Our measurements indicate fundamentally different scenarios during high and low tide. At low tide, our resistivity data suggest a strong influx of freshwater from land, forming a plume that rises up and contributes significantly to SGD in the intertidal zone. We also observed the occurrence of 3 regions somewhat analogous to the numerical predictions. However, at high tide, instead of these distinct regions, we observed a diffuse mixing zone that extended along the water/sediment interface and overlaid the freshwater from land. Point measurements of seepage rates and salinity are in basic agreement with the two scenarios. It should also be noted that the phase-averaged section obtained with the resistivity surveys resembles the high tide scenario and therefore differs from the phase-averaged simulations.
Durand, J. M.; Wong, T.
Antimicrobial resistance profile of methicillin resistant staphylococcal aureus from skin and soft tissue isolates
OBJECTIVES: To evaluate resistance rates in methicillin resistant Staphylococcus aureus (MRSA) against clindamycin, cotrimoxazole, tetracycline, fusidic acid, rifampicin and chloramphenicol isolated from skin and soft tissue infections (SSTI).METHODS: Descriptive analysis of SSTI samples yielding MRSA in clinical laboratory of a tertiary care center; receiving specimens across Pakistan from January 2005 to June 2007. MICROBIOLOGICAL METHODS: MRSA were identified using standard
Faiza Idrees; Kauser Jabeen; Muhammad Shoaib Khan; Afia Zafar
Chapter 5 Electrical Capacitance, Electrical Resistance, and Positron Emission Tomography Techniques and Their Applications in Multi-Phase Flow Systems
This article describes the recent progress in research and development on electrical capacitance tomography (ECT), electrical resistance tomography (ERT), and positron emission tomography (PET). Specifically, the article highlights several aspects of the three technologies and illustrates their application and performance through selected demonstration cases studies. The principles and results from the methods provide quantitative and\\/or qualitative assessment of the significance
Fei Wang; Qussai Marashdeh; Liang-Shih Fan; Richard A Williams
Electrical Resistivity of Silicate Glass Melts Calculation Based on the SciGlass Database
The relation between the chemical composition and the electrical resistivity (= 1\\/conductivity) of silicate glass melts at temperatures of 1000 oC to 1400 oC from the SciGlass Database was analyzed statistically. A model including ionic interactions was developed that permits calculating the glass melt electrical resistivity with a standard error of about 0.06 on the logarithmic resistivity scale in ??cm.
Alexander Fluegel; David A. Earl; Arun K. Varshneya
Application of two electrical methods for the rapid assessment of freezing resistance in Salix eriocephala
The importance of early selection of frost-resistant Salix clones makes it desirable to select a rapid and accurate screening method for assessing freezing resistance among several genotypes. Two electrical methods, stem electrical impedance to 1 and 10kHz alternating current, and electrolyte leakage of leaf tissue, were evaluated for detecting freezing resistance on three North America Salix eriocephala Michx., clones after
V. Tsarouhas; W. A. Kenney; L. Zsuffa
Programmed resist sidewall profiles using subresolution binary grayscale masks for Si-photonics applications
NASA Astrophysics Data System (ADS)
In this paper we present a 45-degree mirror created for optical applications utilizing CMOS high-volume manufacturing processes with a gray-scale lithography technique. The process that is presented here was done by creating a 3D pattern in the photoresist and then by transferring the photoresist profile to the Si/SiO2 substrate by specific dry etch processing. We discuss the optimization of the half-tone pattern to achieve the desired resist profile. We achieved smooth sidewalls with various sidewall angles and show that different 3D angles and profiles can be achieved and processed simultaneously.
Gan, Ofir; Allen, Paul; Barkai, Assia; Buck, Peter; Connolly, Brid; Frish, Harel; Pindo, Massimiliano
Electrical resistance sensors record spring flow timing, Grand Canyon, Arizona
Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration.
Adams, E. A.; Monroe, S. A.; Springer, A. E.; Blasch, K. W.; Bills, D. J.
Electrical resistance tomography using steel cased boreholes as long electrodes
Electrical resistance tomography (ERT) using multiple electrodes installed in boreholes has been shown to be useful for both site characterization and process monitoring. In some cases, however, installing multiple downhole electrodes is too costly (e.g., deep targets) or risky (e.g., contaminated sites). For these cases we have examined the possibility of using the steel casings of existing boreholes as electrodes. Several possibilities can be considered. The first case we investigated uses an array of steel casings as electrodes. This results in very few data and thus requires additional constraints to limit the domain of possible inverse solutions. Simulations indicate that the spatial resolution and sensitivity are understandably low but it is possible to coarsely map the lateral extent of subsurface processes such as steam floods. The second case uses an array of traditional point borehole electrodes combined with long-conductor electrodes (steel casings). Although this arrangement provides more data, in many cases it results in poor reconstructions of test targets. Results indicate that this method may hold promise for low resolution imaging where steel casings can be used as electrodes but the merits depend strongly on details of each application. Field tests using these configurations are currently being conducted.
Daily, W; Newmark, R L; Ramirez, A
Electrical resistance tomography using steel cased boreholes as electrodes
Electrical resistance tomography (ERT) using multiple electrodes installed in boreholes has been shown to be useful for both site characterization and process monitoring. In some cases, however, installing multiple downhole electrodes is too costly (e.g., deep targets) or risky (e.g., contaminated sites). For these cases we have examined the possibility of using the steel casings of existing boreholes as electrodes. The first case we investigated used an array of steel casings as electrodes. This results in very few data and thus requires additional constraints to limit the domain of possible inverse solutions. Simulations indicate that the spatial resolution and sensitivity are understandably low but it is possible to coarsely map the lateral extent of subsurface processes such as steam floods. A hybrid case uses traditional point electrode arrays combined with long-conductor electrodes (steel casings). Although this arrangement provides more data, in many cases it results in poor reconstructions of test targets. Results indicate that this method may hold promise for low resolution imaging where steel casings can be used as electrodes.
Newmark, R L; Daily, W; Ramirez, A
Research on Nonlinear Feature of Electrical Resistance of Acupuncture Points
A highly sensitive volt-ampere characteristics detecting system was applied to measure the volt-ampere curves of nine acupuncture points, LU9, HT7, LI4, PC6, ST36, SP6, KI3, LR3, and SP3, and corresponding nonacupuncture points bilaterally from 42 healthy volunteers. Electric currents intensity was increased from 0??A to 20??A and then returned to 0??A again. The results showed that the volt-ampere curves of acupuncture points had nonlinear property and magnetic hysteresis-like feature. On all acupuncture point spots, the volt-ampere areas of the increasing phase were significantly larger than that of the decreasing phase (P < 0.01). The volt-ampere areas of ten acupuncture point spots were significantly smaller than those of the corresponding nonacupuncture point spots when intensity was increase (P < 0.05 ~ P < 0.001). And when intensity was decrease, eleven acupuncture point spots showed the same property as above (P < 0.05 ~ P < 0.001), while two acupuncture point spots showed opposite phenomenon in which the areas of two acupuncture point spots were larger than those of the corresponding nonacupuncture point spots (P < 0.05 ~ P < 0.01). These results show that the phenomenon of low skin resistance does not exist to all acupuncture points.
Wei, Jianzi; Mao, Huijuan; Zhou, Yu; Wang, Lina; Liu, Sheng; Shen, Xueyong
Mapping desiccation fissures using 3-D electrical resistivity tomography
NASA Astrophysics Data System (ADS)
Discontinuities which may form in a soil mass due to desiccation have been shown to be a source of engineering concern in situations where low permeability barriers are required. Current methods for assessing the condition of such geo-barriers, are mainly based on visual inspections, which are inadequate when the soil surface is obscured by vegetation. Electrical Resistivity Tomography (ERT) has been shown to be sensitive to the presence of fissures in 2-D with inversion models mapping the fissure's positions and enabling their growth to be monitored. This paper presents a method for mapping fissured networks in 3-D using miniature arrays under laboratory conditions. The results of two experiments using compacted clay from two separate embankments show a good comparison between the visible surface fissures and the surface model obtained from a 3-D inversion, as well as showing good agreement between the vertical sections of the model and the exposed model interior following dissection. Additionally the results confirm that the 3-D method is suitable for monitoring the onset of fissuring. A comparison of Schlumberger, Dipole-Dipole and combined arrays for visualising the fissures is also presented, indicating that the combined method produces the most accurate image of the subsurface, while the Schlumberger array provides a greater resolution than the Dipole-Dipole array, alongside the added benefit of shorter survey times.
Jones, Gareth; Zielinski, Marcin; Sentenac, Philippe
Detecting leaks in hydrocarbon storage tanks using electrical resistance tomography
Large volumes of hydrocarbons are stored worldwide in surface and underground tanks. It is well documented [1] that all too often these tanks are found to leak, resulting in not only a loss of stored inventory but, more importantly, contamination to soil and groundwater. Two field experiments are reported herein to evaluate the utility of electrical resistance tomography (ERT) for detecting and locating leaks as well as delineating any resulting plumes emanating from steel underground storage tanks (UST). Current leak detection methods for single shell tanks require careful inventory monitoring, usually from liquid level sensors within the tank, or placement of chemical sensors in the soil under and around the tank. Liquid level sensors can signal a leak but are limited in sensitivity and, of course, give no information about the location or the leak or the distribution of the resulting plume. External sensors are expensive to retrofit and must be very densely spaced to assure reliable detection, especially in heterogeneous soils. The rational for using subsurface tomography is that it may have none of these shortcomings.
Daily, W.; Ramirez, A.; LaBrecque, D.; Binley, A.
In Vitro Resistance Profile of the Hepatitis C Virus NS3 Protease Inhibitor BI 201335
The in vitro resistance profile of BI 201335 was evaluated through selection and characterization of variants in genotype 1a (GT 1a) and genotype 1b (GT 1b) replicons. NS3 R155K and D168V were the most frequently observed resistant variants. Phenotypic characterization of the mutants revealed shifts in sensitivity specific to BI 201335 that did not alter susceptibility to alpha interferon. In contrast to macrocyclic and covalent protease inhibitors, changes at V36, T54, F43, and Q80 did not confer resistance to BI 201335.
Lagace, Lisette; White, Peter W.; Bousquet, Christiane; Dansereau, Nathalie; Do, Florence; Llinas-Brunet, Montse; Marquis, Martin; Massariol, Marie-Josee; Maurice, Roger; Spickler, Catherine; Thibeault, Diane; Triki, Ibtissem; Zhao, Songping
Profiling Bortezomib Resistance Identifies Secondary Therapies in a Mouse Myeloma Model
Multiple myeloma is a hematologic malignancy characterized by the proliferation of neoplastic plasma cells in the bone marrow. Although the first-to-market proteasome inhibitor bortezomib (Velcade) has been successfully used to treat patients with myeloma, drug resistance remains an emerging problem. In this study, we identify signatures of bortezomib sensitivity and resistance by gene expression profiling (GEP) using pairs of bortezomib-sensitive (BzS) and bortezomib-resistant (BzR) cell lines created from the Bcl-XL/Myc double-transgenic mouse model of multiple myeloma. Notably, these BzR cell lines show cross-resistance to the next-generation proteasome inhibitors, MLN2238 and carfilzomib (Kyprolis) but not to other antimyeloma drugs. We further characterized the response to bortezomib using the Connectivity Map database, revealing a differential response between these cell lines to histone deacetylase (HDAC) inhibitors. Furthermore, in vivo experiments using the HDAC inhibitor panobinostat confirmed that the predicted responder showed increased sensitivity to HDAC inhibitors in the BzR line. These findings show that GEP may be used to document bortezomib resistance in myeloma cells and predict individual sensitivity to other drug classes. Finally, these data reveal complex heterogeneity within multiple myeloma and suggest that resistance to one drug class reprograms resistant clones for increased sensitivity to a distinct class of drugs. This study represents an important next step in translating pharmacogenomic profiling and may be useful for understanding personalized pharmacotherapy for patients with multiple myeloma.
Stessman, Holly A.F.; Baughn, Linda B.; Sarver, Aaron; Xia, Tian; Deshpande, Raamesh; Mansoor, Aatif; Walsh, Susan A.; Sunderland, John J.; Dolloff, Nathan G.; Linden, Michael A.; Zhan, Fenghuang; Janz, Siegfried; Myers, Chad L.; Van Ness, Brian G.
Profiling bortezomib resistance identifies secondary therapies in a mouse myeloma model.
Multiple myeloma is a hematologic malignancy characterized by the proliferation of neoplastic plasma cells in the bone marrow. Although the first-to-market proteasome inhibitor bortezomib (Velcade) has been successfully used to treat patients with myeloma, drug resistance remains an emerging problem. In this study, we identify signatures of bortezomib sensitivity and resistance by gene expression profiling (GEP) using pairs of bortezomib-sensitive (BzS) and bortezomib-resistant (BzR) cell lines created from the Bcl-XL/Myc double-transgenic mouse model of multiple myeloma. Notably, these BzR cell lines show cross-resistance to the next-generation proteasome inhibitors, MLN2238 and carfilzomib (Kyprolis) but not to other antimyeloma drugs. We further characterized the response to bortezomib using the Connectivity Map database, revealing a differential response between these cell lines to histone deacetylase (HDAC) inhibitors. Furthermore, in vivo experiments using the HDAC inhibitor panobinostat confirmed that the predicted responder showed increased sensitivity to HDAC inhibitors in the BzR line. These findings show that GEP may be used to document bortezomib resistance in myeloma cells and predict individual sensitivity to other drug classes. Finally, these data reveal complex heterogeneity within multiple myeloma and suggest that resistance to one drug class reprograms resistant clones for increased sensitivity to a distinct class of drugs. This study represents an important next step in translating pharmacogenomic profiling and may be useful for understanding personalized pharmacotherapy for patients with multiple myeloma. PMID:23536725
Stessman, Holly A F; Baughn, Linda B; Sarver, Aaron; Xia, Tian; Deshpande, Raamesh; Mansoor, Aatif; Walsh, Susan A; Sunderland, John J; Dolloff, Nathan G; Linden, Michael A; Zhan, Fenghuang; Janz, Siegfried; Myers, Chad L; Van Ness, Brian G
Cucumis melo microRNA expression profile during aphid herbivory in a resistant and susceptible interaction.
Aphis gossypii resistance in melon (Cucumis melo) is due to the presence of a single dominant virus aphid transmission (Vat) gene belonging to the nucleotide-binding site leucine-rich repeat family of resistance genes. Significant transcriptional reprogramming occurs in Vat(+) plants during aphid infestation as metabolism shifts to respond to this biotic stress. MicroRNAs (miRNAs) are involved in the regulation of many biotic stress responses. The role of miRNAs was investigated in response to aphid herbivory during both resistant and susceptible interactions. Small RNA (smRNA) libraries were constructed from bulked leaf tissues of a Vat(+) melon line following early and late aphid infestations. Sequence analysis indicated that the expression profiles of conserved and newly identified miRNAs were altered during different stages of aphid herbivory. These results were verified by quantitative polymerase chain reaction experiments in both resistant Vat(+) and susceptible Vat(-) interactions. The comparative analyses revealed that most of the conserved miRNA families were differentially regulated during the early stages of aphid infestation in the resistant and susceptible interactions. Along with the conserved miRNA families, 18 cucurbit-specific miRNAs were expressed during the different stages of aphid herbivory. The comparison of the miRNA profiles in the resistant and susceptible interactions provides insight into the miRNA-dependent post-transcriptional gene regulation in Vat-mediated resistance. PMID:22375710
Sattar, Sampurna; Song, Yan; Anstead, James A; Sunkar, Ramanjulu; Thompson, Gary A
Monitoring strain and damage in multi-phase composite materials using electrical resistance methods
The variation of the electrical properties of fiber reinforced polymers when subjected to load offer the ability of strain and damage monitoring. This is performed via electrical resistance and electrical potential measurements. On the other hand Carbon Nanotubes (CNTs) have proved to be an efficient additive to polymers and matrices of composites with respect to structural enhancement and improvement of
S. A. Grammatikos; G. Gkikas; A. Paipetis
Laser-induced change of electrical resistivity of metals and its applications
Applying of laser alloying for modification of electrical resistivity of metals with significant importance in electrical and electronic engineering and utilization of this method for producing passive elements of electric circuit have been presented. The alloyed metals were obtained by means of laser beams with different wave length and various mode of working (cw or pulse), by different methods for
Ryszard Pawlak; Franciszek Kostrubiec; Mariusz Tomczyk; Maria Walczak
Three-dimensional electrical resistivity model of a nuclear waste disposal site
A three-dimensional (3D) modeling study was completed on a very large electrical resistivity survey conducted at a nuclear waste site in eastern Washington. The acquisition included 47 pole-pole two dimensional (2D) resistivity profiles collected along parallel and orthogonal lines over an area of 850 m�570 m. The data were geo-referenced and inverted using EarthImager3D (EI3D). EI3D runs on a Microsoft 32-bit operating system (e.g. WIN-2K, XP) with a maximum usable memory of 2 GB. The memory limits the size of the domain for the inversion model to 200 m�200 m, based on the survey electrode density. Therefore, a series of increasing overlapping models were run to evaluate the effectiveness of dividing the survey area into smaller subdomains. The results of the smaller subdomains were compared to the inversion results of a single domain over a larger area using an upgraded form of EI3D that incorporates multi-processing capabilities and 32 GB of RAM memory. The contours from the smaller subdomains showed discontinuity at the boundaries between the adjacent models, which do not match the hydrogeologic expectations given the nature of disposal at the site. At several boundaries, the contours of the low resistivity areas close, leaving the appearance of disconnected plumes or open contours at boundaries are not met with a continuance of the low resistivity plume into the adjacent subdomain. The model results of the single large domain show a continuous monolithic plume within the central and western portion of the site, directly beneath the elongated trenches. It is recommended that where possible, the domain not be subdivided, but instead include as much of the domain as possible given the memory of available computing resources.
Rucker, Dale F.; Levitt, Marc T.; Greenwood, William J.
Insecticide resistance profiles and synergism in field populations of the German cockroach (Dictyoptera: Blattellidae) from Singapore.
The resistance profiles of 22 field-collected populations of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), from various localities in Singapore were determined by topical bioassay against novel and conventional insecticides from six classes: (1) pyrethroid (beta-cyfluthrin, deltamethrin), (2) carbamate (propoxur), (3) organophosphate (chlorpyrifos), (4) phenyl pyrazole (fipronil), (5) neonicotinoid (imidacloprid), and (6) oxadiazine (indoxacarb). Compared with a laboratory susceptible strain, resistance levels ranged from 3.0 to 468.0x for the pyrethroids, from 3.9 to 21.5x for the carbamate, from 1.5 to 22.8X for the organophosphate, from 1.0 to 10.0X for phenyl pyrazole, and were absent or low for the neonicotinoid (0.8-3.8x) and the oxadiazine (1.4-5.3x). One strain demonstrated broad-spectrum resistance to most of the insecticides. Synergism studies using piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) in combination with a discriminating dose (LD99) of selected insecticides were conducted to test for possible resistance mechanisms. Resistance to pyrethroid was reduced with PBO and DEF, suggesting the involvement of P450 monooxygenase and esterases in conferring resistance. Propoxur resistance also was suppressed with PBO and DEF, and coadministration of both synergists resulted in complete negation of the resistance, indicating the involvement of both P450 monooxygenase and esterase. In six B. germanica field strains evaluated, esterases were found to play a role in chlorpyrifos resistance, whereas the P450 monoxygenase involvement was registered in three strains. Additional resistance mechanisms such as kdr-type and Rdl mutation contributing toward pyrethroid and fipronil resistance, respectively, also may be involved in some strains in which the resistance levels were not affected by the synergists. We conclude that insecticide resistance is prevalent in field German cockroach populations in Singapore. PMID:20429463
Chai, Ru-Yuan; Lee, Chow-Yang
Corrosion-resistant, electrically-conductive plate for use in a fuel cell stack
A corrosion resistant, electrically-conductive, durable plate at least partially coated with an anchor coating and a corrosion resistant coating. The corrosion resistant coating made of at least a polymer and a plurality of corrosion resistant particles each having a surface area between about 1-20 m.sup.2/g and a diameter less than about 10 microns. Preferably, the plate is used as a bipolar plate in a proton exchange membrane (PEMFC) fuel cell stack.
Carter, J. David (Bolingbrook, IL) [Bolingbrook, IL; Mawdsley, Jennifer R. (Woodridge, IL) [Woodridge, IL; Niyogi, Suhas (Woodridge, IL) [Woodridge, IL; Wang, Xiaoping (Naperville, IL) [Naperville, IL; Cruse, Terry (Lisle, IL) [Lisle, IL; Santos, Lilia (Lombard, IL) [Lombard, IL
Effect of Coulomb blockade, gold resistance, and thermal expansion on the electrical resistance of ultrathin gold films
NASA Astrophysics Data System (ADS)
Controlling the electrical resistance of granular thin films is of great importance for many applications, yet a full understanding of electron transport in such films remains a major challenge. We have studied experimentally and by model calculations the temperature dependence of the electrical resistance of ultrathin gold films at temperatures between 2 K and 300 K. Using sputter deposition, the film morphology was varied from a discontinuous film of weakly coupled meandering islands to a continuous film of strongly coupled coalesced islands. In the weak-coupling regime, we compare the regular island array model, the cotunneling model, and the conduction percolation model with our experimental data. We show that the tunnel barriers and the Coulomb blockade energies are important at low temperatures and that the thermal expansion of the substrate and the island resistance affect the resistance at high temperatures. At low temperatures our experimental data show evidence for a transition from electron cotunneling to sequential tunneling but the data can also be interpreted in terms of conduction percolation. The resistivity and temperature coefficient of resistance of the meandering gold islands are found to resemble those of gold nanowires. We derive a simple expression for the temperature at which the resistance changes from non-metal-like behavior into metal-like behavior. In the case of strong island coupling, the total resistance is solely determined by the Ohmic island resistance.
Yajadda, M. M. A.; M�ller, K.-H.; Ostrikov, K.
Electrical resistivity and piezoresistivity of Ni-CNT filled epoxy-based composites
NASA Astrophysics Data System (ADS)
This paper investigates properties about electrical resistivity and piezoresistivity of multi-wall carbon nanotubes (MWCNTs)-filled epoxy-based composite and its further use for strain sensing. The MWCNTs dispersed epoxy resin, using MWCNTs in the amount of 1.5~3.0 vol.%, was first prepared by combined high-speed stirring and sonication methods. Then, the MWCNTs dispersed epoxy resin was cast into an aluminum mold to form specimens measuring 10�10�36 mm. After curing, DC electrical resistance measurements were performed along the longitudinal axis using the four-probe method, in which copper nets served as electrical contacts. The percolation threshold zone of resistivity was got as MWCNTs in the amount of 2.00-2.50 vol.%. Further compressive testing of these specimens was conducted with four-probe method for resistance measurements at the same time. Testing results show that the electrical resistivity of the composites changes with the strain's development, namely piezoresistivity. While for practical strain sensing use, signals of electric resistance and current in the acquisition circuits were both studied. Results show that the signal of current, compared with that of resistance, had better linear relationship with the compressive strain, better stability and longer effective section to reflect the whole deformation process of the specimens under pressure. Further works about the effects of low magnetic field on the electrical resistivity and piezoresistivity of Ni-CNTs filled epoxy-based composites were presented briefly at the end of the paper.
Jiang, Jinbao; Xiao, Huigang; Li, Hui
Resolving Large Pre-glacial Valleys Buried by Glacial Sediment Using Electric Resistivity Imaging (ERI)
NASA Astrophysics Data System (ADS)
Two-dimensional electric resistivity imaging (ERI) is the most exciting and promising geological tool in geomorphology and stratigraphy since development of ground-penetrating radar. Recent innovations in 2-D ERI provides a non-intrusive mean of efficiently resolving complex shallow subsurface structures under a number of different geological scenarios. In this paper, we test the capacity of ERI to image two large pre-late Wisconsinan-aged valley-fills in central Alberta and north-central Montana. Valley-fills record the history of pre-glacial and glacial sedimentary deposits. These fills are of considerable economical value as groundwater aquifers, aggregate resources (sand and gravel), placers (gold, diamond) and sometime gas reservoirs in Alberta. Although the approximate locations of pre-glacial valley-fills have been mapped, the scarcity of borehole (well log) information and sediment exposures make accurate reconstruction of their stratigraphy and cross-section profiles difficult. When coupled with borehole information, ERI successfully imaged three large pre-glacial valley-fills representing three contrasting geological settings. The Sand Coulee segment of the ancestral Missouri River, which has never been glaciated, is filled by electrically conductive pro-glacial lacustrine deposits over resistive sandstone bedrock. By comparison, the Big Sandy segment of the ancestral Missouri River valley has a complex valley-fill composed of till units interbedded with glaciofluvial gravel and varved clays over conductive shale. The fill is capped by floodplain, paludal and low alluvial fan deposits. The pre-glacial Onoway Valley (the ancestral North Saskatchewan River valley) is filled with thick, resistive fluvial gravel over conductive shale and capped with conductive till. The cross-sectional profile of each surveyed pre-glacial valley exhibits discrete benches (terraces) connected by steep drops, features that are hard to map using only boreholes. Best quality ERI results were obtained along the Sand Coulee and Onoway transects where the contrast between the bedrock and valley-fill was large and the surficial sediment was homogeneous. The effects of decreasing reliability with depth, 3-D anomalies, principles of equivalence and suppression, and surface inhomogeneity on the image quality are discussed.
Schmitt, D. R.; Welz, M.; Rokosh, C. D.; Pontbriand, M.-C.; Smith, D. G.
The temperature-dependent electrical resistivities of the alkali metals
NASA Astrophysics Data System (ADS)
This review contains a comprehensive examination of all modern measurements and calculations of the temperature-dependent electrical resistivity ?(T) for the alkali metals-and especially potassium (K)-from their melting points down to below 0.1 K. The simplicity of the electronic structures of these metals makes them unique for testing our fundamental understanding of ?(T). At all temperatures down to a few K, ?(T) is dominated by its electron-phonon scattering component, ?ep(T). Current quantitative understanding of ?ep(T) in the alkali metals is examined in detail, including effects of phonon drag at temperatures below ~= 10 K. In the vicinity of 1 K, ?(T) in pure, unperturbed, bulk alkali metals is predicted to be dominated by electron-electron scattering. ?ee(T)=AeeT2. In disagreement with previous reviews, the authors argue that Aee is nearly constant for each alkali metal and-at least for K-also in quantitative agreement with calculation. Below 1 K, alloys based on K and lithium display both previously predicted and completely unexpected effects. Perturbations such as deformation and thinning of K wires induce unusual and interesting behaviors. An unexpected Kondo-like effect appears when K contacts polyethylene. Charge-density-wave-based predictions of contributions to ?(T) in the alkali metals are also considered. Three appendices examine (a) what is involved in a realistic calculation of ?(T) (b) the experimental problems encountered in high-precision measurements of ?(T) at low temperatures and how they are solved; and (c) the most recent experimental data concerning charge-density waves in the alkali metals.
Bass, Jack; Pratt, William P., Jr.; Schroeder, Peter A.
Negative resist profiles in 248 nm photolithography: experiment, modelling and simulation
NASA Astrophysics Data System (ADS)
We consider the effects both of exposure energy dose and of developer temperature on the developed negative resist profiles. The spin-formatted resist film tends to have macromolecules oriented parallel to the substrate surface. The orientation of the resist macromolecules introduces an anisotropic component to the etch rate: higher in the direction parallel to the substrate surface and lower in the perpendicular one. We performed a series of experiments for 400 nm pitch periodic and isolated lines on Shipley SNR-248 negative resist coated Si wafers using a stepper and a deep UV source at 248 nm. We obtained scanning electron micrographs for various developer temperatures and exposure doses. The variation of the lateral etch rate manifested itself in sidewall profile slopes. We used Dill's ABC parameter model to model and quantify the exposure, and cellular automata to model the resist cross-linking during post-exposure bake and the resist etching. Simulation using an algorithm based on this model validated the experimental results.
Karafyllidis, I.; Hagouel, P. I.; Neureuther, A. R.
Accounting for Variable Environmental Conditions in Time-Lapse Electrical Resistivity Images
NASA Astrophysics Data System (ADS)
Time-lapse electrical resistivity imaging (ERI) is being used to monitor salt transport at a remediation site in Alberta, Canada. The goal is to use ERI to produce images of salt concentration in soil. Mapping the salt concentration is possible because soil electrical conductivity (EC) is strongly correlated with salt concentration. However, soil EC is also affected by the temperature of the soil and the soil moisture content. Temperature and soil moisture conditions vary with changing environmental conditions. Three-D ERI results show that dramatically incorrect interpretations will result by neglecting differences in environmental conditions at the time of surveys. These results have two important implications 1) the petrophysical relationship that maps ERI values to salt concentration must be applied to images that have been converted to a standard condition equivalent EC value, and 2) auxiliary field measurements are required to establish temperature and saturation profiles at the time of surveys. We have chosen to standardize our images to 6 Deg. C and saturation of 1 because these values are most representative of the average conditions at the site. Laboratory measurements show that the temperature correction is 3.0% EC per Deg. C. The Waxman-Smits equation is used to correct for saturation differences. Finally, laboratory measurements have established an empirical relationship between soil EC at standard conditions and the regulatory measure of soil paste EC.
Bentley, L. R.; Gharibi, M.; Hayley, K.
First-principles studies of electrical resistivity of iron under pressure
NASA Astrophysics Data System (ADS)
We investigate the temperature and pressure dependences of the electrical resistivity, thermal conductivity and thermal diffusivity for bcc and hcp Fe using the low-order variational approximation and theoretical transport spectral functions calculated from the first-principles linear response linear-muffin-tin-orbital method in the generalized gradient approximation. The calculated values for the electrical resistivity show a strong increase with temperature and decrease with pressure, and are in agreement with high-temperature shock data. We also discuss the behavior of the electrical resistivity for the {bcc \\to hcp} phase transition.
Sha, Xianwei; Cohen, R. E.
Study concerning the electrical resistivity of some liquid metals in ultrasonic field
NASA Astrophysics Data System (ADS)
The increasing of the electrical resistivity values for the overheated high-purity liquid aluminium in range 934 K to 1043 K and for aluminium-silicon eutectic alloy in range 850 K to 960 K, during high-energy ultrasonic field presence is reported. We used DC electrical resistivity measurements. The modification of electrical resistivity values in ultrasonic field due to electron-ion interaction processes and the limited current density in liquid metals is discussed. The effect of cavitation at the high temperature is debated.
Moraru, Luminita
In Vitro Cross-Resistance Profile of Nucleoside Reverse Transcriptase Inhibitor (NRTI) BMS-986001 against Known NRTI Resistance Mutations
BMS-986001 is a novel HIV nucleoside reverse transcriptase inhibitor (NRTI). To date, little is known about its resistance profile. In order to examine the cross-resistance profile of BMS-986001 to NRTI mutations, a replicating virus system was used to examine specific amino acid mutations known to confer resistance to various NRTIs. In addition, reverse transcriptases from 19 clinical isolates with various NRTI mutations were examined in the Monogram PhenoSense HIV assay. In the site-directed mutagenesis studies, a virus containing a K65R substitution exhibited a 0.4-fold change in 50% effective concentration (EC50) versus the wild type, while the majority of viruses with the Q151M constellation (without M184V) exhibited changes in EC50 versus wild type of 0.23- to 0.48-fold. Susceptibility to BMS-986001 was also maintained in an L74V-containing virus (0.7-fold change), while an M184V-only-containing virus induced a 2- to 3-fold decrease in susceptibility. Increasing numbers of thymidine analog mutation pattern 1 (TAM-1) pathway mutations correlated with decreases in susceptibility to BMS-986001, while viruses with TAM-2 pathway mutations exhibited a 5- to 8-fold decrease in susceptibility, regardless of the number of TAMs. A 22-fold decrease in susceptibility to BMS-986001 was observed in a site-directed mutant containing the T69 insertion complex. Common non-NRTI (NNRTI) mutations had little impact on susceptibility to BMS-986001. The results from the site-directed mutants correlated well with the more complicated genotypes found in NRTI-resistant clinical isolates. Data from clinical studies are needed to determine the clinically relevant resistance cutoff values for BMS-986001.
Li, Zhufang; Terry, Brian; Olds, William; Protack, Tricia; Deminie, Carol; Minassian, Beatrice; Nowicka-Sans, Beata; Sun, Yongnian; Dicker, Ira; Hwang, Carey; Lataillade, Max; Hanna, George J.
Identification of molecular mechanisms for cellular drug resistance by combining drug activity and gene expression profiles
Acquired drug resistance is a major problem in cancer treatment. To explore the genes involved in chemosensitivity and resistance, 10 human tumour cell lines, including parental cells and resistant subtypes selected for resistance against doxorubicin, melphalan, teniposide and vincristine, were profiled for mRNA expression of 7400 genes using cDNA microarray technology. The drug activity of 66 cancer agents was evaluated on the cell lines, and correlations between drug activity and gene expression were calculated and ranked. Hierarchical clustering of drugs based on their drug�gene correlations yielded clusters of drugs with similar mechanism of action. Genes correlated with drug sensitivity and resistance were imported into the PathwayAssist software to identify putative molecular pathways involved. A substantial number of both proapoptotic and antiapoptotic genes such as signal transducer and activator of transcription 1, mitogen-activated protein kinase 1 and focal adhesion kinase were found to be associated to drug resistance, whereas genes linked to cell cycle control and proliferation, such as cell division cycle 25A and signal transducer of activator of transcription 5A, were associated to general drug sensitivity. The results indicate that combined information from drug activity and gene expression in a resistance-based cell line panel may provide new knowledge of the genes involved in anticancer drug resistance and become a useful tool in drug development.
Rickardson, L; Fryknas, M; Dhar, S; Lovborg, H; Gullbo, J; Rydaker, M; Nygren, P; Gustafsson, M G; Larsson, R; Isaksson, A
Characterizing heterogeneous coastal groundwater pathways using multi-scale onshore-to-offshore electrical resistivity surveys
NASA Astrophysics Data System (ADS)
Electrical resistivity (ER) imaging techniques are useful for investigating porewater salinity distributions and dynamics within coastal environments. However, complex coastal geology can obscure the hydrologic target of ER surveys. We investigated the geologic controls on groundwater pathways in Rarotonga, a high volcanic island with a carbonate fringe. We used three ER survey configurations to explore this hydrogeologic setting: 1) waterborne, continuous resistivity profiling in the lagoon, 2) submerged cable surveys across the terrestrial-marine interface, and 3) traditional surveys on land. We designed overlapping portions of these surveys to reveal differences in how the deployment methods image subsurface ER structure. Using both the field data and forward modeling, we quantified the resolvability of ER features imaged by overlapping configurations, where the sensitivity changed both as a function of electrode spacing and boundary conditions (i.e. influence of seawater). Waterborne ER results revealed large scale variations in the ER structure of the lagoon geology. These heterogeneities are products of Rarotonga's volcanic history and reef diagenesis that change both the electrical signature and hydrogeologic properties of the subsurface. Time-lapse, submersed ER surveys imaged groundwater salinity dynamics and resolved select ER features more effectively than the waterborne surveys. Terrestrial ER surveys traced the extent of the freshwater lens and the transition from the unsaturated-saturated conditions, i.e., the water table. The ER responses of the three field configurations were concordant but imaged different scales hydrogeologic variability. The unique spatial signatures of both methodology and the geologic setting must be incorporated into future coastal ER applications.
Befus, K. M.; Cardenas, M.; Tait, D. R.; Erler, D.
Lifetime and resistivity modifications induced by helium implantation in silicon: Experimental analysis with an ac profiling technique
The effect of He ion bombardment on silicon based devices can be seen observing a change of their electric properties, that are relevant for their application, as well as through the modification of some local properties, in particular, resistivity and recombination lifetime, that in turn reflect the microscopic modification of their structure. The knowledge of the relation between these two aspects of the modifications induced by ion implantation would represent a powerful tool to design new devices and processes. This paper presents the results of an experimental analysis, where the modifications of the electrical properties of power devices, induced by helium implantation, were correlated to both the local recombination lifetime and the resistivity depth profile measured using a differential ac technique. Various measurements were performed for a wide range of temperatures to obtain information on the energy levels of the recombination centers which are responsible for the observed variations of the local properties of the device. The investigation was performed varying both the beam energy (from 3.5 to 5.8 MeV) and dose (1x10{sup 8}-5x10{sup 11} ions/cm{sup 2}), providing a complete picture of the implantation effects. Finally, an application to the switching behavior of a fast recovery power diode is presented.
Daliento, S.; Mele, L.; Spirito, P. [Department of Electronic Engineering, University of Naples 'Federico II', Via Claudio 21, 80125 Naples (Italy); Gialanella, L. [INFN Sezione di Napoli, Via Cinthia, 80125 Naples (Italy); Limata, B. N. [INFN Sezione di Napoli, Via Cinthia, 80125 Naples (Italy); Department of Physics, University of Naples 'Federico II', Via Claudio 21, 80125 Naples (Italy)
Mechanistic and predictive profiling of 5-Fluorouracil resistance in human cancer cells.
Gene expression was analyzed in five pairs of 5-fluorouracil (5-FU) resistant and parental cancer cell lines on DNA microarrays. In unsupervised analysis, a prediction rule was built from the expression profiles of 29 genes, and 5-FU sensitivity class was predicted with 100% accuracy and high predictive strength. In supervised analysis of key 5-FU pathways, expression of 91 genes was associated with 5-FU sensitivity phenotype and segregated samples accordingly in hierarchical analysis. Key genes involved in 5-FU activation were significantly down-regulated (thymidine kinase, 2.9-fold; orotate phosphoribosyltransferase, 2.3-fold; uridine monophosphate kinase, 3.2-fold; pyrimidine nucleoside phosphorylase 3.6-fold) in resistant cells. Overexpression of thymidylate synthase and its adjacent gene, c-Yes, was detected in the resistant cell lines. The mRNA and protein overexpression of nuclear factor kappaB (NFkappaB) p65 and related antiapoptotic c-Flip gene was detected in resistant cells. The 5-FU-resistant cell lines also showed high NFkappaB DNA-binding activity. Cotransfection of NFkappaB p50 and p65 cDNA induced 5-FU resistance in MCF-7 cells. Both NFkappaB- and 5-FU-induced resistant cell lines manifested reduced expression of genes governing G(1)-S and S-phase transition. Expression of genes involved in DNA replication was also down-regulated in resistant cell lines. These findings were highly consistent with the slower growth rate, higher proportion of G(1), and lower proportion of S-phase cells in the resistant cell lines. This phenotype may protect resistant cells from cell death induced by incorporation of 5-FU into DNA chains, by allowing time to repair 5-FU-induced damage. Our findings may provide novel targets for tackling 5-FU resistance. PMID:15548681
Wang, Weiguang; Cassidy, James; O'Brien, Vincent; Ryan, Kevin M; Collie-Duguid, Elaina
Statistical properties of the electrically induced contact resistance between two stainless steel balls
NASA Astrophysics Data System (ADS)
The electrical contact resistance between two stainless steel balls was measured to study the electrical conduction of a metallic contact separated by a thin oxide layer. Through a statistical approach, the contact resistance was found to have a bimodal log-normal distribution. This result reflects conduction by tunneling and electrically induced metal bridge, which was explained by the simulation of a random circuit breaker model, inside the insulating layer. Based on the results of this study, we suggest an effective conduction model to explain macroscopic electrical contact systems with a nano- or microscopic filamentary conduction mechanism.
Kim, Sang-Kuk; Sung Lee, Jae; Kwak, Han; Kang, Sung-Oong; Lee, Jongjin; Yu, In-Suk
An electrically modifiable synapse array of resistive switching memory
This paper describes the resistive switching of a cross-point cell array device, with a junction area of 100 nm � 100 nm, fabricated using ultraviolet nanoimprinting. A GdOx and Cu-doped MoOx stack with platinum top and bottom electrodes served as the resistive switching layer, which shows analog memory characteristics with a resistance ratio greater than 10. To demonstrate a neural
Hyejung Choi; Heesoo Jung; Joonmyoung Lee; Jaesik Yoon; Dong-jun Seong; Wootae Lee; Musarrat Hasan; Gun-Young Jung; Hyunsang Hwang
An efficient, low profile, electrically small, three-dimensional, very high frequency magnetic EZ antenna
NASA Astrophysics Data System (ADS)
A very high frequency version of the electrically small, coax-fed, three-dimensional magnetic EZ antenna was designed and tested. The fabricated antenna was formed by integrating a capacitively loaded loop element with a coaxially-fed, electrically small, semicircular loop antenna. This low profile antenna (height ~?/25) had an electrical size that was ka~0.46 at 105.2 MHz (where a is the radius of the minimum enclosing hemisphere). Nearly complete matching to the 50 ? source and a high overall efficiency (nearly 95%) were achieved. The numerically predicted and the measured results were in good agreement.
Lin, Chia-Ching; Ziolkowski, Richard W.; Nielsen, Jean A.; Tanielian, Minas H.; Holloway, Christopher L.
Fluid upwelling beneath arc volcanoes above the subducting Philippine Sea Plate: Evidence from regional electrical resistivity structure
NASA Astrophysics Data System (ADS)
At subduction zones, aqueous fluids released from the subducting slab play an important role in island arc volcanism, triggering partial melting and accretion magmatism. We used the Network-magnetotelluric (MT) method to obtain the deep (>100 km), large-scale electrical resistivity structure beneath Kyushu, Japan, with the aim of identifying regions of deep fluids and magma that feeds subduction zone volcanoes in the region. Network-MT observations, in which dipoles of about 10-30 km in length were used to measure the electric potential difference, were performed over all of Kyushu, in the Southwest Japan Arc, where the Philippine Sea Plate (PSP) is subducting beneath the Eurasian Plate at a high angle. Using the Network-MT data, we obtained the large-scale electrical resistivity structure along four profiles across each of four Quaternary active volcanoes at the volcanic front of the Kyushu subduction zone. The resistivity models have two features in common: a conductor beneath each volcano, whose base extends to the backarc side, and a resistor along the hinge line of the subducting PSP in the forearc. The conductor indicates regions of fluid released from the slab or partial melting of the mantle, representing a magma source for subduction zone volcanoes in this region.
Hata, Maki; Oshiman, Naoto; Yoshimura, Ryokei; Tanaka, Yoshikazu; Uyeshima, Makoto
An Ultra-Precise System for Electrical Resistivity Tomography Measurements
The objective of this research was to determine the feasibility of building and operating an ERT system that will allow measurement precision that is an order of magnitude better than existing systems on the market today and in particular if this can be done without significantly greater manufacturing or operating costs than existing commercial systems. Under this proposal, we performed an estimation of measurement errors in galvanic resistivity data that arise as a consequence of the type of electrode material used to make the measurements. In our laboratory, measurement errors for both magnitude and induced polarization (IP) were estimated using the reciprocity of data from an array of electrodes as might be used for electrical resistance tomography using 14 different metals as well as one non-metal - carbon. In a second phase of this study, using archival data from two long-term ERT surveys, we examined long-term survivability of electrodes over periods of several years. The survey sites were: the Drift Scale Test at Yucca Mountain, Nevada (which was sponsored by the U. S. Department of Energy as part of the civilian radioactive waste management program), and a water infiltration test at a site adjacent to the New Mexico Institute of Mines and Technology in Socorro, New Mexico (sponsored by the Sandia/Tech vadose program). This enabled us to compare recent values with historical values and determine electrode performance over the long-term as well as the percentage of electrodes that have failed entirely. We have constructed a prototype receiver system, made modifications and revised the receiver design. The revised prototype uses a new 24 bit analog to digital converter from Linear Technologies with amplifier chips from Texas Instruments. The input impedance of the system will be increased from 107 Ohms to approximately 1010 Ohms. The input noise level of the system has been decreased to approximately 10 Nanovolts and system resolution to about 1 Nanovolt at the highest gain range of 125 to 1. The receiver also uses very high precision and high temperature stability components. The goal is to improve the accuracy to better than 0.1%. The system has more receiver channels, eight, to allow efficient data collection at lower base frequencies. We are also implementing a frequency-domain acquisition mode in addition to the time-domain acquisition mode used in the earlier systems. Initial field tests were started in the fall of 2008. We conducted tests on a number of types of cable commonly used for resistivity surveys. A series of different tests were designed to determine if the couplings were primarily resistive, capacitive, or inductive in nature and to ascertain that the response was due to the cable cross-talk and did not depend on the receiver electronics. The results show that the problem appears to be primarily capacitive in nature and does not appear to be due to problems in the receiver electronics. Thus a great deal of emphasis has been placed on finding appropriate cables as well as stable electrodes that have low contact impedance at the very low current flows observed at the receiver. One of the issues in survey design and data collection has been determining how long one must wait before using the same electrode as a transmitter and as a receiver. A series of tests was completed in the laboratory sand tank where four-electrode measurements were made using the same dipole transmitters and dipole receivers (the dipoles used adjacent electrodes). For each data series, a single set of normal measurements were collected with no reciprocals and electrodes were never reused as a receiver after being used as a transmitter. After waiting a specified length of time, the reciprocal measurements were collected using a schedule of measurements. The order of this second schedule was rearranged such that if this second set of measurements were performed without first using the normal schedule, no electrode would be used as a receiver after being used as a transmitter. For this study, we cannot conclude that increasing the
LaBrecque, Douglas J; Adkins, Paula L
Fracture network characterisation of a landslide by electrical resistivity tomography
NASA Astrophysics Data System (ADS)
In contrary to most of the landslide studies which concentrate to the sliding surface in this paper the fracture system of a loess landslide is investigated. The continuity and geometry, orientation and dip of the major fractures are crucial parameters for assessing rock stability and landslide evolution. Rain infiltrating moreover easily into the rock mass through fractures providing lubrication for the material to slide, and increases the self-mass of the material increasing the slumping rate. Fracture maps enable beside of the characterisation of the fractured area the delineation of the endangered area of slow-moving landslides in due time and getting information about its inner structure. For constructing such maps Electrical Resistivity Tomography (ERT) measurements have been carried out using different geoelectric configurations. In spite of the high density of the fractures and their changing physical parameters in function of their water content - which make the interpretation rather difficult - a number of fractures have been detected and more or less well localised. On the basis of the present research the application of the Schlumberger and the Pole-Dipole arrays is recommended to fulfil the aim of the study. The optimised Stummer array is at the same time the only array which presents conductive anomalies (supposedly water filled fractures), as well, and indicates that fractures elongate deep downwards. Because these features seem to be realistic based on field observations or theoretical considerations the Stummer array may be a very good tool for completing e.g. P-Dp measurements. The study area could have been divided by all arrays into differently fractured zones, which assists a lot in understanding the landslide structure and evolution. It was shown, moreover, that in the still passive area there are thick fractures, too, verifying its dangerousness, as well. The ERT results enabled localising the rupture surfaces of future slumps which proved to be distributed uniformly with about 10 m distance between them and predicting mass movements which may prevent the slump along the visible fracture. Similar unidirectional fracture systems could be investigated by the ERT method for any hydrogeological or engineering geological aim.
Szalai, S.; Szokoli, K.; Nov�k, A.; T�th, �.; Metwaly, M.; Pr�cser, E.
Electrical Resistivity as an Indicator of Saturation in Fractured Geothermal Reservoir Rocks: Experimental Data and Modeling.
National Technical Information Service (NTIS)
The electrical resistivity of rock cores under conditions representative of geothermal reservoirs is strongly influenced by the state and phase (liquid/vapor) of the pore fluid. In fractured samples, phase change (vaporization/condensation) can result in ...
R. L. Detwiler J. J. Rpberts
Quartz resonator for simultaneously measuring changes in the mass and electrical resistance of a polyaniline film.
A novel quartz resonator was developed to measure, simultaneously, changes in the mass and electrical resistance of a polyaniline film during the absorption of water vapor. Interdigitated gold electrodes were vacuum-deposited on the sensing surfaces of the quartz crystals, and polyaniline films were drop-cast on the electrodes used to measure the changes in the electrical resistance. Two symmetric semicircular gold electrodes were deposited on the bottom surface of the quartz crystal. These electrodes were used to measure the changes in the mass of absorbed water based on the changes in the resonance frequency. The simultaneous measurements of mass and electrical resistance shed light on the interactions between the water vapor and the polyaniline film. The resonator was exposed to various organic gases, including ethanol, acetone, or chloroform, and each gas was found to produce characteristic changes in the normalized electrical resistance. PMID:22931237
Yim, Changyong; Yun, Minhyuk; Jung, Namchul; Jeon, Sangmin
Composite Materials with Distinctive Behaviors under High Electric Fields: I - Material Switches to 'High Resistive' State
NASA Technical Reports Server (NTRS)
Electrically conductive silver filled epoxy ECF-563 preform, sandwiched between gold contact pads exhibits intermittent current-voltage characteristics with switching to 'high resistive' state under applied bias voltage.
Javadi, H.
Electrical Resistivity and Thermal Conductivity of Nine Selected AISI Stainless Steels.
National Technical Information Service (NTIS)
This technical report reviews the available experimental data and information on the electrical resistivity and thermal conductivity of nine selected AISI stainless steels and presents the recommended values from near absolute zero (1 K) to above the melt...
C. Y. Ho T. K. Chu
The Use of Electrical Resistivity to Determine Porosity of Marine Sediments.
National Technical Information Service (NTIS)
A method using electrical resistivity measurements to determine the in situ porosity of marine sediments was investigated in the laboratory, and equipment for this purpose was designed, fabricated and tested. Formation Factor-porosity relationships determ...
R. A. Erchul
PCR-based identification of methicillin-resistant Staphylococcus aureus strains and their antibiotic resistance profiles
Objective To evaluated the PCR for mecA gene compared with the conventional oxacillin disk diffusion method for methicillin-resistant Staphylococcus aureus (S. aureus) identification. Methods A total of 292 S. aureus strains were isolated from various clinical specimens obtained from hospitalized patients. Susceptibility test to several antimicrobial agents was performed by disk diffusion agar according to Clinical and Laboratory Standards Institute guidelines. The PCR amplification of the mecA gene was carried out in all the clinical isolates. Results Among antibiotics used in our study, penicillin showed the least anti-staphylococcal activity and vancomycin was the most effective. The rate of methicillin-resistant S. aureus prevalence determined by oxacillin disk diffusion method was 47.6%; whereas, 45.1% of S. aureus isolates were mecA- positive in the PCR assay. Conclusions This study is suggestive that the PCR for detection of mecA gene is a fast, accurate and valuable diagnostic tool, particularly in hospitals in areas where methicillin-resistant S. aureus is endemic.
Pournajaf, Abazar; Ardebili, Abdollah; Goudarzi, Leyla; Khodabandeh, Mahmoud; Narimani, Tahmineh; Abbaszadeh, Hassan
Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials
A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700�C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 ?-cm2 at RT, decreasing continuously to ~1-10 ?-cm2 at 700�C. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by ~1/2.
Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.
High-temperature electrical resistivity of rare-earth metals with variable valence
The electrical resistivity of compounds of rare-earth metals at high temperatures is calculated on the basis of allowance for the background mechanism of scattering and the hybridization of local electron states with the states of conduction electrons. An analytic expression is obtained for resistivity in a strong hybridization approximation. It follows from the expression that electrical resistivity may have a negative temperature coefficient within a broad range of high temperatures. The use of a three-band (s, d, f) model makes it possible to explain experimental data on the resistivity of certain rare-earth metals, particularly the connection between the sign of the temperature coefficient of electrical resistivity and the curvature of the relation (T).
Povzner, A.A.; Abel'skii, S.S.
Highly electrical resistive SiTiNx heating layers and diffusion barriers for PCRAM
Highly electrical resistive amorphous SiTiNx films were explored as both heating layers and diffusion barriers for the cells of phase-change random-access memory (PCRAM). The measured electrical resistivity of SiTiNx films, determined by the nitrogen content x tunable up to 38.68%, is between 0.039-0.69 Omega cm which fulfils the requirements of a suitable heating layer suggested by simulations. SiTiNx films with
Huai-Yu Cheng; Yi-Chen Chen; Ren-Jei Chung; Tsung-Shune Chin
Measurement of Specific Heat Capacity and Electrical Resistivity of Industrial Alloys Using Pulse Heating Techniques
The determination of the specific heat capacity and electrical resistivity of Inconel 718, Ti-6Al-4V, and CF8M stainless steel, from room temperature to near the melting temperatures of the alloys, is described. The method is based on rapid resistive self-heating of a solid cylindrical specimen by the passage of a short-duration electric current pulse through it while simultaneously measuring the pertinent
D. Basak; R. A. Overfelt; D. Wang
Welding time effect on mechanical properties of automotive sheets in electrical resistance spot welding
In this study, the effects of welding time on the tensile-peel strength and tensile-shear strength of welding joints in electrical resistance spot welding of chromate micro-alloyed steel sheets having 1.2mm thicknesses were investigated. A timer and current controlled electrical resistance spot welding machine having 120kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the
S. Aslanlar; A. Ogur; U. Ozsarac; E. Ilhan
In this study, electrical resistance method was used to detect the damage of IM7\\/8552 carbon graphite-reinforced composites under mechanical loadings. Both two-probe and four-probe measurement methods were used. In order to study the feasibility of the two measurement methods, we performed the tensile and three-point bending tests on 1-D strip specimens; the electrical resistance change was recorded by both methods.
Ercan Sevkat; Jackie Li; Benjamin M. Liaw; Feridun Delale; Jaycee H. Chung
Correlation between Electrical Resistivity and Soil-Water Content based Artificial Intelligent Techniques
NASA Astrophysics Data System (ADS)
By using a artificial intelligent approaches, the purpose of this study is to compare water content of soils obtained from electrical resistivity in order to better results from conventional techniques system. The input variables for this system are the electrical resistivity reading, the water content laboratory measurements. The output variable is water content of soils. In this study, 148 data sets are clustered into 120 training sets and 28 testing sets for constructing the fuzzy system and validating the ability of system prediction, respectively. Soil is a heterogeneous medium consisted of liquid, solid, and gaseous phases. The solid and liquid phases play an essential role in soil spontaneous electrical phenomena and in behavior of electrical fields, artificially created in soil. For our aim, study area is selected in Istanbul (Yesilkoy, Florya, Basinkoy) and Golcuk. In this area, it is measured the electrical resistivity by VES (Vertical Electrical Sounding) in many points of these locations by field resistivity equipment. For geotechnical purposes, on the soil samples from borings, it was applied soil mechanics laboratory procedures and is determined the soil water contents from these samples. Relationships between soil water content and electrical parameters were obtained by curvilinear models. The ranges of our samples are changed between 1-50 ohm.m (for resistivity) and 20-60 (%, for water content). A artificial intelligent system (artificial neural networks, Fuzzy logic applications: Mamdani and Sugeno approaches) based on some comparisons about correlation between electrical resistivity and soil-water content, for Istanbul and Golcuk Soils in Turkey was constructed for identifying water content with electrical resistivity of soils.
Ozcep, Ferhat; Yildirim, Eray; Tezel, Okan; Asci, Metin; Karabulut, Savas
Electric field polarization around Ioannina VAN station, Greece, inferred from a resistivity mapping
NASA Astrophysics Data System (ADS)
In the summer of 1997, we made a bipole-dipole mapping survey around Ioannina station of VAN (Varotsos, Alexopoulos, and Nomicos), where detection of the pre-seismic electric signal (SES) has been repeatedly reported. Since we had found the characteristic directional properties of the electric field in the previous study, the present study was aimed to examine it by investigating the shallow electric structure around the station. The apparent resistivity tensor was derived from two sets of measured voltages at each receiver position. From a rough sketch of the resistivity tensor distribution, we found that the electric field was enhanced along the direction parallel to the trend of the basin at receivers located in the conductive basin, and perpendicular to it at receivers in the resistive mountainside. Conductance distribution models with thin plates were constructed by using the measured voltages. The results showed that the VAN station is located on the resistive portion near the contact between the conductive and the resistive part. Furthermore, we simulated the apparent resistivity tensor near the VAN station on the inferred conductance distribution model. Although the directional property similar to those of magnetotelluric (MT) and lightning electric field was not reproduced there, we found that the electric field polarization is affected by heterogeneous structure not only around receivers but also around the source.
Kanda, Wataru; Uyeshima, Makoto; Makris, John; Orihara, Yoshiaki; Hase, Hideaki; Nagao, Toshiyasu; Uyeda, Seiya
Predicting drug sensitivity and resistance: profiling ABC transporter genes in cancer cells.
For analysis of multidrug resistance, a major barrier to effective cancer chemotherapy, we profiled mRNA expression of the 48 known human ABC transporters in 60 diverse cancer cell lines (the NCI-60) used by the National Cancer Institute to screen for anticancer activity. The use of real-time RT-PCR avoided artifacts commonly encountered with microarray technologies. By correlating the results with the growth inhibitory profiles of 1,429 candidate anticancer drugs tested against the cells, we identified which transporters are more likely than others to confer resistance to which agents. Unexpectedly, we also found and validated compounds whose activity is potentiated, rather than antagonized, by the MDR1 multidrug transporter. Such compounds may serve as leads for development. PMID:15324696
Szak�cs, Gergely; Annereau, Jean-Philippe; Lababidi, Samir; Shankavaram, Uma; Arciello, Angela; Bussey, Kimberly J; Reinhold, William; Guo, Yanping; Kruh, Gary D; Reimers, Mark; Weinstein, John N; Gottesman, Michael M
Sheet resistance determination of electrically symmetric planar four-terminal devices with extended contacts
NASA Astrophysics Data System (ADS)
This paper reports an analytic method to determine the sheet resistance Rsq of symmetric planar four-terminal devices based on resistance measurements. Using the technique of conformal mapping it is first shown that any such device is electrically equivalent to a corresponding symmetric unit disk with the same Rsq and invariant under rotations by 90�. Two independent resistances measurable on these devices are expressed analytically as a function of Rsq and of the contact opening angle ?. These two resistances fully characterize the electrical properties of such planar conductive devices. A simple procedure to extract both ? and Rsq from the resistance values is then presented. These findings are corroborated by the experimental characterization of four-contact devices of ten different geometries fabricated using a commercial complementary metal oxide semiconductor process. From these widely different devices, the sheet resistance of a n-well is extracted to be 1042 ? with a relative uncertainty of only 0.45%.
Cornils, Martin; Paul, Oliver
An in vitro assessment and a pilot clinical study of electrical resistance of demineralized enamel.
Electrical resistance measurement was evaluated in vitro and in vivo as a method for comparing the remineralizing performance of toothpastes. In the in vitro study, areas of sound enamel on 12 unrestored, mature, extracted human molars and bicuspids, with electrical resistance readings greater than 99.99 M omega, were demineralized to an electrical resistance of 1 to 4 M omega. The teeth were divided into three groups. The change in electrical resistance was measured following a 15 cycle regimen of treatment, demineralization and salivary soaking. Treatments were five-minute exposures to either a 1:2 slurry in saliva of Enamelon (E), a remineralizing fluoride-toothpaste also containing soluble calcium and phosphate ions, a 1:2 slurry in saliva of Crest (C), a conventional fluoride toothpaste (P), or to saliva alone. Demineralization was performed with a 30-minute exposure to 0.1 M lactic acid 50% saturated with calcium hydroxyapatite. The salivary soaking was 1 hour in duration. The mean electrical resistance of the E, C and the saliva treated sites was 63.9 +/- 4.3, 37.6 +/- 9.5 and 2.1 +/- 0.7 M omega, respectively. The final resistance was statistically different for each group (p < 0.05). A pilot clinical study was then conducted to assess the electrical resistance technology in vivo. Eighteen adult subjects with at least one site of early enamel caries with an electrical resistance between 1.0 M omega and 20.00 M omega were randomly assigned to either Enamelon, Crest, or a non-fluoride placebo toothpaste and asked to brush twice daily. After three months, the mean resistance of the test sites was 23.57 M omega for E, 9.61 M omega for C and 13.24 M omega for P. However, the mean resistance changes did not proceed consistently over time. At the end of the study, the electrical resistance measurements on four sites out of twelve in Group E were suggestive of remineralization, whereas measurements on one site out of ten were suggestive of remineralization in Group C and two or three sites out of twelve were suggestive of remineralization in Group P. Progression of demineralization was possibly indicated in only one site, which was in Group C. There were insufficient subjects for statistical significance in the pilot clinical study. There were apparent problems with the variability of some measurements between visits in the in vivo study. Overall, however, the results of both studies indicate that with modifications to the equipment, electrical resistance measurements may be a means of comparing the remineralization performance of toothpastes. PMID:10686859
Wolinsky, L E; Gnagne-Agnero, N D; Chamkasem, P; Jason, S; Triol, C W; Winston, A E
Study on Optimal Location of a Resistive SFCL Applied to an Electric Power Grid
This paper describes a study on the optimal location of a resistive superconducting fault current limiter (SFCL) applied to an electric power grid. The resistive SFCL, which is designed to provide the quick system protection in the event of a fault, can have different effects on the planning and operation of a power system depending on its location. To select
Byung Chul Sung; Dong Keun Park; Jung-Wook Park; Tae Kuk Ko
Electric-field-induced resistance switching universally observed in transition-metal-oxide thin films
We show that polarity-dependent, nonvolatile resistance switching by electric field occurs in the thin film of various transition-metal oxides in almost the same manner. This result indicates that, contrary to the general acceptance, perovskite manganite is by no means a special compound for this phenomenon. It is also suggested that the resistance switching is not dominated by a detailed electronic
M. Hamaguchi; K. Aoyama; S. Asanuma; Y. Uesu; T. Katsufuji
Influence of Degree of Saturation in the Electric Resistivity-Hydraulic Conductivity Relationship
The relationship between aquifer hydraulic conductivity and aquifer resistivity, either measured on the ground surface by vertical electrical sounding (VES) or from resistivity logs, or measured in core samples have been published for different types of aquifers in different locations. Generally, these relationships are empirical and semi-empirical, and confined in few locations. This relation has a positive correlation in some
Mohamed Ahmed Khalil; Fernando A. Monterio Santos
An electric double-layer capacitor with high capacitance and low resistance
The development of the electric double-layer capacitor with ultra-high capacitance and extremely low DC resistance is described. The capacitance ranges from 1 to 500 F and the DC resistance is less than one fifth of that of the conventional capacitor with organic electrolytes. The capacitor consists of an activated carbon layer on aluminum foil collector electrodes, a separator, and an
Akihiko Yoshida; Kiyoaki Imoto; Hajime Yoneda; A. Nishimo
Effect of pressure on the electrical resistivity of water-saturated crystalline rocks
Electrical r.esistivity of eight igneous rocks and two crystalline limestones was measured at pressures to 10 kb. The rocks were saturated with tap water or salt solution, and the pore pressure was maintained near zero. The dependence of resistivity on temperature, porosity, and pore fluid salinity suggested that conduction was primarily electrolytic through- out the .entire pressure range, even though
W. F. Brace; A. S. Orange; T. R. Madden
In situ electrical resistivity and bulk porosity of the oceanic crust Costa Rica Rift
In situ electrical resistivity was measured in DSDP Hole 504B to a depth of 1,013 m into oceanic basement. Apparent resistivities are about 10 Omega m in about 600 m of pillow lavas, sharply increasing to nearly 1,000 Omega m in the underlying dykes. Bulk porosities calculated from resistivities show a distinct layering, apparently corresponding to geophysical layers 2A, 2B
Keir Becker; R. P. von Herzen; T. J. G. Francis; R. N. Anderson; J. Honnorez; A. C. Adamson; J. C. Alt; R. Emmermann; P. D. Kempton; H. Kinoshita; C. Laverne; M. J. Mottl; R. L. Newmark
Electrical resistivity of AuIn2 thin films at 4.2 K
Electrical resistivity and grain size of AuIn2 thin films, which are used as resistors in Pb-alloy Josephson integrated circuits, were investigated as a function of film thickness, substrate temperature, and pressure during deposition and annealing time. The effect of grain boundary on film resistivity was estimated and the dominant scattering mechanism was determined. The resistivity at 4.2 K is 2�15
Yuji Hasumi; Kunihiro Arai; Takao Waho; Fumihiko Yanagawa
Electric-pulse-induced reversible resistance in doped zinc oxide thin films
Nonvolatile, electric-pulse-induced resistance switching is reported on S and Co doped ZnO thin films deposited on different substrates using magnetron sputtering and laser ablation. Two resistance states were obtained by applying voltage pulses of different polarity. The switching was observed regardless of the substrate, dopant species, or microstructure of the samples. In the Co doped ZnO samples, the two resistance
M. Villafuerte; S. P. Heluani; G. Ju�rez; G. Simonelli; G. Braunstein; S. Duhalde
Organic acids make Escherichia coli more resistant to pulsed electric fields at acid pH
Stationary growth phase cells of Escherichiacoli were more pulsed electric fields (PEF) resistant in citrate�phosphate McIlvaine buffer at pH 4.0 than at pH 7.0. The greater PEF resistance was also confirmed in fruit juices of similar acid pH. In this work we studied whether the higher PEF resistance of E. coli at acid pH was due to the low pH
M. Somolinos; D. Garc�a; P. Ma�as; S. Cond�n; R. Pag�n
Focused subsurface flow in the Amargosa Desert characterized by direct-current resistivity profiling
NASA Astrophysics Data System (ADS)
Environmental-tracer studies have shown that ground-water recharge in the thick alluvial fill of the Amargosa Desert is localized beneath ephemeral stream channels and anthropogenic sources of water, with little recharge beneath native vegetation on interfluvial areas under current climatic conditions. These borehole-based studies provided relatively robust but limited, one-dimensional (vertical) information that can be only tentatively regionalized using geomorphologic, pedologic, and vegetational mapping. The ability of direct-current (DC) resistivity profiling to complement and extend studies of the spatial distribution of subsurface flow was examined by making surface-based measurements ("soundings") along one transect normal to the depositional fabric in each of three geomorphologically distinct settings: a well-incised ephemeral channel system, a poorly incised (distributory) ephemeral channel system, and an interfluvial upland. Linear arrays of 32 to 80 electrodes were deployed with a uniform 2 to 5-m spacing between adjacent electrodes. A multiplexing 8-channel resistivity instrument made automated inverse-Schlumberger-array soundings along the deployed line, using up to 10 electrodes at a time. The line was shifted piecemeal until composite transects consisted of 168 to 232 electrode positions. This approach allowed rapid profiling of long transects at high resolution. Numerical inversions assumed horizontal constancy normal to the vertical slices being imaged, producing solution sets of optimized resistivity values for several thousand points within each modeled slice. Imaged slices were �30 to 80 m deep and �1 km wide. RMS errors between apparent resistivities in the model inversions and field-measured apparent resistivities were �10%. On the basis of borehole studies, inverted resistivity (? ) values denoted three categories of alluvium: (1) low-water-content coarse gravel and highly desiccated surface materials, with ? > �200 ? -m, (2) vertical plumes of moist alluvium in areas of active recharge, with ? < �20 ? -m, and (3) other low to low-medium water-content alluvium in areas without active recharge, with intermediate values of ? . The upland profile revealed a laterally extensive gravel layer (category 1 alluvium) at a depth of �25 m that intersects instrumented boreholes at the Amargosa Desert Research Site. This layer coincides with peak concentrations of radioactive gases and volatile organic compounds moving through the unsaturated zone from a nearby waste-disposal facility. DC-resistivity profiling appears useful for locating areas of active ground-water recharge as well as potential passageways for preferential gas transport in the Amargosa Desert and similar environments.
Stonestrom, D. A.; Abraham, J. D.; Lucius, J. E.; Prudic, D. E.
Evaluation of antimicrobial resistance profiles of Salmonella isolates from broiler chickens at slaughter in Alberta, Canada.
Antimicrobial-resistant Salmonella species are threatening to become a serious public health problem. Therefore, surveillance and prudent use of antimicrobials is needed in both the agricultural and human health sectors. The aim of this study was to describe the antimicrobial susceptibility profiles of Salmonella isolates recovered from healthy broiler chickens at slaughter from November 2004 to April 2005. Salmonella isolates recovered from 36 broiler flocks in Alberta, Canada, were serotyped and tested for antimicrobial susceptibility against 15 antimicrobials. Of 272 Salmonella isolates tested, 64.0% were resistant to one or more antimicrobials, 10.0% were resistant to three or more antimicrobials, and 1.8% were resistant to five antimicrobials. All isolates were susceptible to amikacin, amoxicillin-clavulanic acid, ceftiofur, cefoxitin, ceftriaxone, ciprofloxacin, and nalidixic acid. The highest prevalence of resistance was to tetracycline (54.8%), followed by streptomycin (24.2%) and sulfisoxazole (8.4%). The most common multiantimicrobial resistance patterns were to streptomycin-tetracycline (24.3%), streptomycin-sulfisoxazole-tetracycline (6.6%), and ampicillin-streptomycin-sulfisoxazole-tetracycline (3.7%). The strongest associations were observed between resistance to kanamycin and tetracycline (odds ratio = 65.7, P = 0.001) and to ampicillin and sulfisoxazole (odds ratio = 62.9, P = 0.001). Salmonella Hadar and Salmonella Heidelberg were the two most common serovars accounting for 40.4 and 13.6% of the total isolates, respectively. Eighty-one percent and 12.7% of Salmonella Hadar isolates and 62.0 and 8.1% of Salmonella Heidelberg isolates were resistant to 1 or more and three or more antimicrobials, respectively. The flock level prevalence of resistance ranged from 5.6% for trimethoprim-sulfamethoxazole to 83.3% for tetracycline. This study provides baseline information on antimicrobial susceptibility of Salmonella isolates of broiler chickens at slaughter in Alberta that can serve as a benchmark for future research. PMID:24674442
Mainali, C; McFall, M; King, R; Irwin, R
Seasonal Variation of Moisture Content in Unsaturated Sandstone Inferred From Borehole Radar and Resistivity Profiles
NASA Astrophysics Data System (ADS)
Understanding the processes controlling recharge to aquifers is critical if accurate predictions are to be made on the fate of contaminants in the subsurface environment. In order to fully understand the hydrochemical mechanisms in the vadose zone it is essential that the dynamics of the hydrology can be suitably characterized. The correlation between moisture content and both bulk dielectric and resistivity properties of porous media is well established. Using suitably placed sensors in boreholes detailed depth profiles of dielectric and resistivity behaviour have been monitored over a period of over two years at a Triassic Sherwood Sandstone aquifer field site at Hatfield, England. The borehole-borehole transmission radar and borehole resistivity profiles show a significant correlation. Through appropriate petrophysical relationships, derived from core samples, seasonal dynamics of the vadose zone are seen to illustrate the migration of wetting and drying fronts over the monitoring period. At a second field site in Eggborough, located 17 km from Hatfield, similar temporal changes in moisture content in the sandstone were observed using borehole radar profiles. Travel times of seasonal wetting fronts through the sandstone at both sites appear to be approximately 2 m per month. The retardation of this front propagation in the top 3 m is also common to both sites, suggesting that pollutant transport may be principally controlled by near surface sediments. The results have important consequences to existing groundwater modelling programmes that are being utilized to predict transfer of agricultural chemicals through the vadose zone.
Binley, A.; Winship, P.; Middleton, R.; Middleton, R.; West, L. J.; Pokar, M.
Seasonal variation of moisture content in unsaturated sandstone inferred from borehole radar and resistivity profiles
NASA Astrophysics Data System (ADS)
Understanding the processes controlling recharge to aquifers is critical if accurate predictions are to be made on the fate of contaminants in the subsurface environment. In order to understand fully the hydrochemical mechanisms in the vadose zone it is essential that the dynamics of the hydrology can be suitably characterised. The correlation between moisture content and both bulk dielectric and resistivity properties of porous media is well established. Using suitably placed sensors in boreholes detailed depth profiles of dielectric and resistivity behaviour have been monitored over a period of two years at a Triassic Sherwood Sandstone aquifer field site at Hatfield, England. The borehole-borehole transmission radar and borehole resistivity profiles show a significant correlation. Through appropriate petrophysical relationships, derived from core samples, seasonal dynamics of the vadose zone are seen to illustrate the migration of wetting and drying fronts over the monitoring period. At a second field site in Eggborough, located 17 km from Hatfield, similar temporal changes in moisture content in the sandstone were observed using borehole radar profiles. Travel times of seasonal wetting fronts through the sandstone at both sites appear to be approximately 2 m per month. The retardation of this front propagation in the top 3 m is also common to both sites, suggesting that pollutant transport may be principally controlled by near surface sediments. The results have important consequences to existing groundwater modelling programmes that are being utilised to predict transfer of agricultural chemicals through the vadose zone.
Binley, Andrew; Winship, Peter; West, L. Jared; Pokar, Magdeline; Middleton, Roy
Gene Expression Profiling in the Thiamethoxam Resistant and Susceptible B-biotype Sweetpotato Whitefly, Bemisia tabaci
Thiamethoxam has been used as a major insecticide to control the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Due to its excessive use, a high level of resistance to thiamethoxam has developed worldwide over the past several years. To better understand the molecular mechanisms underlying this resistance in B. tabaci, gene profiles between the thiamethoxam-resistant and thiamethoxam-susceptible strains were investigated using the suppression subtractive hybridization (SSH) library approach. A total of 72 and 52 upand down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These expressed sequence tags (ESTs) belong to several functional categories based on their gene ontology annotation. Some categories such as cell communication, response to abiotic stimulus, lipid particle, and nuclear envelope were identified only in the forward library of thiamethoxam-resistant strains. In contrast, categories such as behavior, cell proliferation, nutrient reservoir activity, sequence-specific DNA binding transcription factor activity, and signal transducer activity were identified solely in the reverse library. To study the validity of the SSH method, 16 differentially expressed genes from both forward and reverse SSH libraries were selected randomly for further analyses using quantitative realtime PCR (qRT-PCR). The qRT-PCR results were fairly consistent with the SSH results; however, only 50% of the genes showed significantly different expression profiles between the thiamethoxam-resistant and thiamethoxam-susceptible whiteflies. Among these genes, a putative NAD-dependent methanol dehydrogenase was substantially over-expressed in the thiamethoxamresistant adults compared to their susceptible counterparts. The distributed profiles show that it was highly expressed during the egg stage, and was most abundant in the abdomen of adult females.
Xie, Wen; Yang, Xin; Wang, Shao-Ii; Wu, Qing-jun; Yang, Ni-na; Li, Ru-mei; Jiao, Xiaoguo; Pan, Hui-peng; Liu, Bai-ming; Feng, Yun-tao; Xu, Bao-yun; Zhou, Xu-guo; Zhang, You-jun
A Coupled-Field Simulation of an Electrical Contact during Resistance Welding
This paper deals with the study of the electrical contact between two OFHC copper pieces in the assembling process of resistance welding. A coupled-field simulation is developed with the ANSYS software to observe the coupled phenomena - mechanical, electrical and thermal - occurring in the contact when a high current (up to 100 kA) flows through it. It takes into
A. Monnier; B. Froidurot; C. Jarrige; R. Meyer; P. Teste
A simple apparatus for measuring electrical resistance of materials at high temperatures
Electrical resistance measurements in a wide temperature range are very important for understanding the physical properties of materials. It is often difficult to carry out the measurements at high temperatures since taking electrical leads reliably from specimens is a nontrivial problem. In this note we describe in detail a simple apparatus which can be used for studying any foil or
G. V. Narasimha Rao; V. S. Sastry; T. S. Radhakrishnan; V. Seshagiri
Wear resistance of parts clad with sintered layers welded on by the electric contact technique
1.It is shown that ferrochromium, ferromanganese, and ferrotitanium can be successfully used as hardening components in powder mixtures for the production of cladding layers to be welded by the electric contact technique onto parts operating under severe wear conditions.2.It has been established that materials clad with sintered layers welded on by the electric contact process possess high wear resistance under
E. V. Rymorov; L. Kh. Dyn'kin
A novel method of modeling and simulation for electrical resistance tomography system
A new method of modeling and simulation for electrical resistance tomography (ERT) system applied to two phase flow measurement is presented in the paper. Based on the Matlab PDE (partial differential equations) tool box, the mathematical model is established, the forward problem is solved and the distributions of electric potential and current density in sensitive field are obtained. The results
Xiang Deng; Zengwei Yan; Zheng Wei
Monitoring chemical diffusion in a porous media using electrical resistivity tomography
Electrical resistivity tomography (ERT) is a non-invasive imaging technique capable of evaluating the distribution of electrical properties within cross-sections of soil specimens. The technique provides an alternative for the monitoring of processes in soils that may not yield mechanical or density contrasts. In this paper, a series of experimental test results is presented, where the diffusion of chemical fronts, in
V. Damasceno; D. Fratta
Electrical resistivity surveys to delineate groundwater potential aquifers in Peddavanka watershed, Anantapur District, Andhra Pradesh, India
Vertical electrical resistivity soundings were conducted in order to delineate groundwater potential aquifers in Peddavanka watershed, which is a catchment of about 398�km 2 in Anantapur District, Andhra Pradesh, India. The main lithologic units in the watershed are quartzite, limestone, shale, and alluvium. Ninety-nine vertical electrical soundings were conducted using the Schlumberger configuration, covering the entire watershed. The data were
S. Srinivasa Gowd
Method and device with adjustable focusing for measuring the electric resistivity of geological formations
The method of the invention comprises determining the variation of the electric potential on both sides of a central electrode in a borehole, detecting the two levels of the borehole where the potential gradient is zero, and measuring the electric resistivity of the geological formation between these two levels.
Desbrandes, R.
Spatial and temporal monitoring of soil water content with an irrigated corn crop cover using surface electrical resistivity tomography
NASA Astrophysics Data System (ADS)
A nondestructive and spatially integrated multielectrode method for measuring soil electrical resistivity was tested in the Beauce region of France during a period of corn crop irrigation to monitor soil water flow over time and in two-dimensional (2-D) with simultaneous measurements of soil moisture and thermal profiles. The results suggested the potential of surface electrical resistivity tomography (ERT) for improving soil science and agronomy studies. The method was able to produce a 2-D delimitation of soil horizons as well as to monitor soil water movement. Soil drainage through water uptake by the roots, the progression of the infiltration front with preferential flow zones, and the drainage of the plowed horizon were well identified. At the studied stage of corn development (3 months) the soil zones where infiltration and drainage occurred were mainly located under the corn rows. The structural soil characteristics resulting from agricultural practices or the passage of agricultural equipment were also shown. Two-dimensional sections of soil moisture content were calculated using ERT. The estimates were made by using independently established "in situ" calibration relationships between the moisture and electrical resistivity of typical soil horizons. The thermal soil profile was also considered in the modeling. The results showed a reliable linear relationship between the calculated and measured water contents in the crop horizon. The precision of the calculation of the specific soil water content, quantified by the root mean square error (RMSE), was 3.63% with a bias corresponding to an overestimation of 1.45%. The analysis and monitoring of the spatial variability of the soil moisture content with ERT represent two components of a significant tool for better management of soil water reserves and rational irrigation practices.
Michot, Didier; Benderitter, Yves; Dorigny, Abel; Nicoullaud, Bernard; King, Dominique; Tabbagh, Alain
Electrical Resistance of Ceramic Matrix Composites for Damage Detection and Life-Prediction
NASA Technical Reports Server (NTRS)
The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection or inspection of a component during "down time". The correlation of damage with appropriate failure mechanism can then be applied to accurate life prediction for high-temperature ceramic matrix composites.
Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai
Two-dimensional electrical modeling of a liner system was performed using computer techniques. The modeling effort examined the voltage distributions in cross sections of lined facilities with different leak locations. Results confirmed that leaks in the liner influenced voltage ...
Electrical resistivity tomography at the search of groundwater near Anapa town in the south of Russia.
NASA Astrophysics Data System (ADS)
Electrical resistivity tomography at the search of groundwater near Anapa town in the south of Russia. Kvon D. A.(1)*, Shevnin V.A.(1), Nikulin B. A.(1), Ryjov A. A.(2), Skobelev A. O.(1) (1)Geophysical dept., Faculty of Geology, Moscow state university; (2)VSEGINGEO Due to acute shortage of fresh drinking water near Anapa town (not far from the Black Sea), geophysical investigations were performed for searching and mapping aquifers in the area, where, according to rare wells exist probability to find fresh underground water. Geophysical explorations were carried out by Electrical resistivity tomography (ERT) method and water resistivity measurements. The resistivity of fresh groundwater is 15 Ohm.m, its salinity is 0.4 g/l. The structure of the area has been obtained by previous geological and hydrogeological studies and boreholes drilling. Geological structure of the area consists of two parts: the upper part of cross-section presented by loose lacustrine-alluvial sediments of Upper Pleistocene - Holocene, the lower part presented by hard rocs of carbonate-flysch formation of Upper Cretaceous age consisted of marl and limestone. Prospective areas to find underground water are: water-bearing horizon of upper Pleistocene-Holocene sediments, which is presented by gravel layer (base layer of modern lacustrine-alluvial sediments), and fractured zones in hard rocks of the carbonate-flysch formation of Maastricht age (Supseh formation). Analysis of rocks' resistivity obtained from Electrical resistivity tomography followed by calculation of rock resistivity on known petrophysical parameters (in Petrowin program created by A. A. Ryjov) [Shevnin et al., 2007]. The calculation showed that there is low clay content in carbonate rocks of the studied area, and the rock is limestone, not marl. Measurement of rock samples with X-ray radiometric method showed high calcium content (30-35%) or 75-87.5% limestone. This fact shows that flysch formation of the area is mainly carbonate, which is fit to results of petrophysical modeling with Petrowin program, which calculated rock resistivity from porosity and clay content. On the base of Electrical resistivity tomography results, calculated rocks' resistivity and drilling data, table of rocks' resistivity was created and resistivity intervals promising to search for underground water were determined. Electric resistivity of rocks in cross-section according to histogram obtained on Electrical resistivity tomography data varies from 20 to 600 Ohm.m and clear divides into two sections: 20-100 Ohm.m for loose sediments and 70-600 Ohm.m for hard rocks. On geoelectrical resistivity sections, which were obtained from Electrical resistivity tomography inversion, we draw isolines of boundary values for resistivity (50-100 Ohm.m for sandy-gravel layer, 100-150 Ohm.m for fractured carbonate-flysch), which detached promising areas to search for underground water taking with account aquifers position according to wells. As a result the Electrical resistivity tomography method succeeded to search groundwater and to determine aquifers position. We pointed out several areas for subsequent drilling found with Electrical resistivity tomography, and we are waiting confirmation of underground water findings. Reference Shevnin V., Mousatov A., Ryjov A. and Delgado-Rodriquez O. Estimation of clay content in soil based on resistivity modeling and laboratory measurements. Geophysical Prospecting, 2007, 55, p.265-275
Kvon, Dina; Vladimir, Shevnin; Boris, Nikulin; Albert, Ryjov; Alexey, Skobelev
Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques
Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid though the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution.
Daily, William D. (Livermore, CA); Laine, Daren L. (San Antonio, TX); Laine, Edwin F. (Alamo, CA)
Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques
Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid though the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution. 6 figs.
Daily, W.D.; Laine, D.L.; Laine, E.F.
Methods for detecting and locating leaks in containment facilities using electrical potential data and electrical resistance tomographic imaging techniques
Methods are provided for detecting and locating leaks in liners used as barriers in the construction of landfills, surface impoundments, water reservoirs, tanks, and the like. Electrodes are placed in the ground around the periphery of the facility, in the leak detection zone located between two liners if present, and/or within the containment facility. Electrical resistivity data is collected using these electrodes. This data is used to map the electrical resistivity distribution beneath the containment liner or between two liners in a double-lined facility. In an alternative embodiment, an electrode placed within the lined facility is driven to an electrical potential with respect to another electrode placed at a distance from the lined facility (mise-a-la-masse). Voltage differences are then measured between various combinations of additional electrodes placed in the soil on the periphery of the facility, the leak detection zone, or within the facility. A leak of liquid through the liner material will result in an electrical potential distribution that can be measured at the electrodes. The leak position is located by determining the coordinates of an electrical current source pole that best fits the measured potentials with the constraints of the known or assumed resistivity distribution.
Daily, William D. (Livermore, CA); Laine, Daren L. (San Anotonio, TX); Laine, Edwin F. (Penn Valley, CA)
Electrical resistance of CNT-PEEK composites under compression at different temperatures
Electrically conductive polymers reinforced with carbon nanotubes (CNTs) have generated a great deal of scientific and industrial interest in the last few years. Advanced thermoplastic composites made of three different weight percentages (8%, 9%, and 10%) of multiwalled CNTs and polyether ether ketone (PEEK) were prepared by shear mixing process. The temperature- and pressure-dependent electrical resistance of these CNT-PEEK composites have been studied and presented in this paper. It has been found that electrical resistance decreases significantly with the application of heat and pressure.
Electrical resistance of CNT-PEEK composites under compression at different temperatures
NASA Astrophysics Data System (ADS)
Electrically conductive polymers reinforced with carbon nanotubes (CNTs) have generated a great deal of scientific and industrial interest in the last few years. Advanced thermoplastic composites made of three different weight percentages (8%, 9%, and 10%) of multiwalled CNTs and polyether ether ketone (PEEK) were prepared by shear mixing process. The temperature- and pressure-dependent electrical resistance of these CNT-PEEK composites have been studied and presented in this paper. It has been found that electrical resistance decreases significantly with the application of heat and pressure.
Mohiuddin, Mohammad; van Hoa, Suong
The resistivity image of the Mur�? fault zone (Central Western Carpathians) obtained by electrical resistivity tomography
NASA Astrophysics Data System (ADS)
The paper describes the application of geophysical prospecting techniques for estimation of the fault's inclination. The field survey was carried out across the Mur�? fault structure in the Slovensk� rudohorie Mts (central Slovakia). Three different geophysical methods were used to map the fault zone: Electrical Resistivity Tomography (ERT), induced polarization (IP) and radon emanometry. All these methods have been used to locate the fault zone area, but the principal aims of this research are to test the efficiency of the 2D ERT technique to recognize the geometrical characterization of the fault and to improve our tectonic knowledge of the investigated area. For the synthetic cases, three geometric contexts were modelled at 60, 90 and 120 degrees and computed with the l2 norm inversion method, the l1 norm with standard horizontal and vertical roughness filter and the l1 norm with diagonal roughness filter. In the second phase this geophysical methodology was applied to fieldwork data. Our results confirm that the ERT technique is a valuable tool to image the fault zone and to characterize the general geometry, but also the importance of setting up the right inversion parameters. The main contribution of the geophysical investigations in this case was the determination of the location and confirmation of the inclination of the Mur�? fault. The result of this study is the ability to make a visual estimation of the direction and dip of the fault. Pursuant to this work the dipole-dipole electrode configuration produces the best resolution, particularly for the location of vertical and dipping structures. The advantage of this array is that it shows the ability to assess the trend of the dip and therefore it can be strongly recommended. The result is also a case study of a small scale tectonic survey involving geophysical methods.
Puti�ka, Ren�; Dost�l, Ivan; Mojze�, Andrej; Gajdo�, Vojtech; Rozimant, Kamil; Vojtko, Rastislav
Monitoring strain and damage in multi-phase composite materials using electrical resistance methods
NASA Astrophysics Data System (ADS)
The variation of the electrical properties of fiber reinforced polymers when subjected to load offer the ability of strain and damage monitoring. This is performed via electrical resistance and electrical potential measurements. On the other hand Carbon Nanotubes (CNTs) have proved to be an efficient additive to polymers and matrices of composites with respect to structural enhancement and improvement of the electrical properties. The induction of CNTs increases the conductivity of the matrix, transforming it to an antistatic or a conducting phase. The key issue of the structural and electrical properties optimization is the dispersion quality of the nano-scale in the polymer phase. Well dispersed CNTs provide an electrical network within the insulating matrix. If the fibers are conductive, the CNT network mediates the electrical anisotropy and reduces the critical flaw size that is detectable by the change in conductivity. Thus, the network performs as an inherent sensor in the composite structure, since every invisible crack or delamination is manifested as an increase in the electrical resistance. The scope of this work is to further exploit the information provided by the electrical properties with a view to identify strain variation and global damage via bulk resistance measurements. The aforementioned techniques were employed to monitor, strain and damage in fiber reinforced composite laminates both with and without conductive nanofillers.
Grammatikos, S. A.; Gkikas, G.; Paipetis, A.
Effects of contact resistance on electrical conductivity measurements of SiC-based materials
A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance (Rc) and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from room temperature (RT) to ?973 K. The Rc-values behaved similarly for each type of metallic electrode: Rc > ?1000 ? cm2 at RT, decreasing continuously to ?1�10 ? cm2 at 973 K. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ?0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.
Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.
Electrical resistance measurements in a diamond anvil cell to 40 GPa on ytterbium
NASA Astrophysics Data System (ADS)
An easily assembled setup employing diamond anvil cell, stainless steel gasket and leads, and mylar embedded Al2O3 (alumina) pressure medium for the measurement of electrical resistance of materials under pressure is described. The use of a mylar sheet prevents the alumina layer from sticking to the anvil in the precompacting stage of Al2O3 and also reduces the pressure gradients in the final assembly. The technique is used to reproduce the known transition in Si, Ge, and Fe. The results of measurements of electrical resistance of ytterbium up to 40 GPa are reported. In the hcp phase of ytterbium the electrical resistance increases with pressure. Efforts are made to explain the variation of resistance with pressure from known band structure calculations.
Garg, Alka B.; Vijayakumar, V.; Godwal, B. K.
Electrical contact resistances of thermoelectric thin films measured by Kelvin probe microscopy
NASA Astrophysics Data System (ADS)
This work presents an approach for measuring cross plane electrical contact resistances directly using Kelvin Probe Microscopy. With this technique we were able to measure the electrical contact resistances of a cross section of a thermoelectric thin film made of Bi2Te3 sandwiched between two gold electrodes. On the one hand, the bottom gold electrode, which is located on top of the silicon substrate, was used as a cathode in electro-deposition process to grow the sample. On the other hand, the gold electrode on top was made via physical evaporation. The electrical contact resistances measured at both interfaces were 0.11 +/- 0.01? and 0.15 +/- 0.01?, respectively. These differences are related to differences between the top and bottom gold/bismuth-telluride film, obtaining smaller contact resistance where the film was grown by electro-deposition.
Mu�oz-Rojo, Miguel; Caballero-Calero, Olga; Mart�n-Gonz�lez, Marisol
Cross-section electrical resistance tomography of La Soufri�re of Guadeloupe lava dome
NASA Astrophysics Data System (ADS)
The electrical resistivity distribution at the base of La Soufri�re of Guadeloupe lava dome is reconstructed by using transmission electrical resistivity data obtained by injecting an electrical current between two electrodes located on opposite sides of the volcano. Several pairs of injection electrodes are used in order to constitute a data set spanning the whole range of azimuths, and the electrical potential is measured along a cable covering an angular sector of ?120� along the basis of the dome. The data are inverted to perform a slice electrical resistivity tomography (SERT) with specific functions implemented in the EIDORS open source package dedicated to electrical impedance tomography applied to medicine and geophysics. The resulting image shows the presence of highly conductive regions separated by resistive ridges. The conductive regions correspond to unconsolidated material saturated by hydrothermal fluids. Two of them are associated with partial flank collapses and may represent large reservoirs that could have played an important role during past eruptive events. The resistive ridges may represent massive andesite and are expected to constitute hydraulic barriers.
Lesparre, Nolwenn; Grychtol, Bart?omiej; Gibert, Dominique; Komorowski, Jean-Christophe; Adler, Andy
Cross-section electrical resistance tomography of La Soufri�re of Guadeloupe lava dome
NASA Astrophysics Data System (ADS)
The electrical resistivity distribution at the base of La Soufri�re of Guadeloupe lava dome is reconstructed by using transmission electrical resistivity data obtained by injecting an electrical current between two electrodes located on opposite sides of the volcano. Several pairs of injection electrodes are used in order to constitute a data set spanning the whole range of azimuths, and the electrical potential is measured along a cable covering an angular sector of ?120� along the basis of the dome. The data are inverted to perform a slice electrical resistivity tomography (SERT) with specific functions implemented in the EIDORS open source package dedicated to electrical impedance tomography applied to medicine and geophysics. The resulting image shows the presence of highly conductive regions separated by resistive ridges. The conductive regions correspond to unconsolidated material saturated by hydrothermal fluids. Two of them are associated with partial flank collapses and may represent large reservoirs that could have played an important role during past eruptive events. The resistive ridges may represent massive andesite and are expected to constitute hydraulic barriers.
Lesparre, Nolwenn; Grychtol, Bart?omiej; Gibert, Dominique; Komorowski, Jean-Christophe; Adler, Andy
Fault Detection Using Resistivity Image Profiling Method at Taoyuan and Hsinchu, Taiwan
NASA Astrophysics Data System (ADS)
As Taiwan is located in the Neotectonic belt along the western Pacific Ocean, the detection of active faults is important for it provides the information for the analysis of earthquake risk. In addition, some active faults in Taiwan lie typically at the bases of urban or industrial area, their identifications are often challengeable because of environmental changes and interferences, etc. The Taoyuan and Hsinchu county are most important high technology sites in Taiwan. Based on previous geophysical and geologic surveys, the well-known active Hukou fault right crosses the site, although the exact location of active fault zone remains unclear. The detection of an active fault can be done by different geophysical methods. However, a successful recognition of a fault depends on the physical properties such as density contrast acoustic impedance and reisitivity contrast, etc. of the targets and its surroundings. Due to a large resistivity contrast between the hanging wall (low resistivity Choulan shale) and the footwall (high resistivity Toukoshan gravel beds) of the Hsinchen fault, geoelectrical sounding may well be one of the best ways to trace this fault. For the above reasons, the resistivity image profiling method was used to investigate the fault and to relate these resistivity measurements to the fault parameters. All of the field measurements to be discussed were made during the period of 2003 and 2004. Fifteen RIP survey lines were deployed in the study area. RIP results indicate that the thickness of the high resistivity gravel layer is increased between the northern cliff of the Hu-Kou terrace and southern edge of Yangmei graben. An obvious difference of altitude is found among low resistivity zones. It may associate with the disturbance or dislocation of layers in the past. Combined the RIP sounding results to the local topographic maps, geologic data, and formal open pits information, fault zones are being recognized. Keywords: active fault; resistivity change; Hukou fault; Taiwan
Hsung-Chang, L.; Chieh-Hou, Y.; Yan-Hao, H.
High definition cross-well electrical resistivity imaging using seismoelectric focusing and image-guided inversion
NASA Astrophysics Data System (ADS)
We propose a new, simple and efficient method to image electrical resistivity between a set of wells. Our procedure consists of two steps: first, we map the interfaces between various subsurface formations using seismoelectric conversions; second, we derive the formation resistivity using image-guided cross-well electric tomography. In the first step, we focus seismic energy at a set of points located on a regular grid between wells, which enables us to map the geological formations in terms of heterogeneities in electrical, hydraulic and/or seismic properties. The density of the scanning points (i.e. the seismoelectric image resolution) is related to the wavelength of the seismic impulse used to scan the formations. Each time the seismic energy is focused at a point, the resulting electrical potential burst (equivalent to the one generated by a volumetric seismic source) is recorded remotely at a set of electrodes positioned in wells (the reference electrode can be located on the ground surface or far enough to be considered at infinity). We construct a high-resolution `seismoelectric' image by assigning the electrical potential simulated at these fixed electrodes to the location of the seismic focus. In a follow-up step, the structure of this image is used in image-guided inversion to improve electrical resistivity tomography between the two wells. The structural information from the seismoelectric image is used to impose constraints on the model covariance matrix used in the inversion of the electrical resistivity data. This approach offers new perspectives in recovering fine structure of resistivity (high definition resistivity tomography) between the wells, which cannot be resolved through conventional cross-well resistivity or from seismic tomography alone.
Sava, P.; Revil, A.; Karaoulis, M.
Electrical resistivity and hydrogen permeation of dip-coated Er 2O 3 on JLF-1
NASA Astrophysics Data System (ADS)
Liquid blanket systems are very promising directions for future fusion reactors. A ceramic coating on the ducts would solve issues for the liquid blankets such as MHD pressure drop and tritium permeation through structure materials. In this study, an Er 2O 3 coating was fabricated on JLF-1 (Fe-9Cr-2W based reduced activation ferritic/martensitic steel), SUS430 (18Cr based commercial ferritic steel) by dip-coating method with metal organic decomposition (MOD) liquid followed by baking in air. XRD patterns indicated that good crystallinity of the Er 2O 3 coating was obtained for the baking temperature of 600 �C. The highest electrical resistivity was about 10 11 ? m. Below the coating, a substrate oxidation layer was also formed according to a XPS elemental depth profile. Hydrogen permeability of the coated sample was decreased only by 1/15 compared with bare JLF-1 sample. The reason might be oxidation of the substrate surface for degrading the coating barrier performance.
Zhang, Dongxun; Tanaka, Teruya; Muroga, Takeo
The effect of cyanide and carbon monoxide on the electrical potential and resistance of cell membranes.
The rapid reduction in cell electropotentials induced by metabolic inhibitors is strong evidence for an electrogenic ion pump. According to Ohm's law, such a depolarization might be explained by a reduction in electric current, I, with unidirectional transport of a given ion, or an increase in permeability (decrease in resistance). With cells of etiolated seedlings of Pisum sativum L. cv. Alaska and Zea mays cv. Golden Bantam, carbon monoxide inhibition, which occurs only in the dark and is readily reversed by light, allows repeated cycling of depolarization and repolarization; there is no effect on cell membrane resistance. In contrast, cyanide inhibition results in a marked increase in membrane electrical resistance; with cyanide following repeated pulses of current used in measuring cell membrane resistance, the resistance eventually (about 10 minutes) shows an abrupt drop as in the "punch-through" effect reported by H. G. L. Coster (1965. Biophys. J. 5: 669-686). PMID:16658958
Anderson, W P; Hendrix, D L; Higinbotham, N
Strategies of ARP application (Automatic Resistivity Profiling) for viticultural precision farming
NASA Astrophysics Data System (ADS)
Introduction Viticultural precision farming needs detailed soil information, which can be obtained by means of remote as well as proximal sensors, besides traditional invasive soil survey. Nevertheless, the use of the new technologies is still in its infancy, because of their costs and the lack of knowledge about the detail actually needed for the viticultural husbandry. The main aim of this work was to test the sensitivity of the ARP methodology (Automatic Resistivity Profiling) in supporting soil survey for viticultural precision farming. In addition, we tried to optimize the detail of geoelectrical measurements and soil sampling to reduce the cost of the integrated survey, maintaining a significant information accuracy for viticulture. Materials and methods Two vineyards in coastal Tuscany (central Italy), about 3.5 ha each, were selected. Vineyard 1 was cultivated with Cabernet Sauvignon and Cabernet Franc, while vineyard 2 only had Cabernet Sauvignon. Soil survey and geoelectrical investigation were conducted in may 2007. The ARP methodology consists in the injection in soil of electric current through one pair of electrodes mounted on teeth wheels and measuring the resulting potential with other three pairs of electrodes, placed of the same mobile equipment. The electrical resistance of the soil (ER) is expressed as ohm per m. The depth of investigation is a function of the geometry of the electrodes and the soil being probed. Increasing the distance between electrodes will increase the depth while decreasing the measured potential. The innovative character of the ARP technique is represented by the passage of a mobile machinery, able to perform 30,000 measurements per hectare, with a measurement every 0.2 m. The ARP system, equipped with a digital encoder and DGPS system, is transported by a four-wheeled vehicle. It is fitted with three sensors that contemporaneously analyse three distinct levels of the soil, the values of which are represented by maps of apparent resistivity, from the surface to 0.5 m, 1 m and 1.7 m depth respectively. Soil sampling at 0.1-0.3 m and 0.5-0.7 m was carried out with hand auger on a regular grid sampling scheme (35-40 m per 20 m). Soil samples were analysed for moisture, particle size, and electrical conductivity in water. The spatial viticultural behaviour was appreciated in both vineyards through image analysis of aerial photographs and, in vineyard 2, by means of a grape sampling and analysis of the must at harvest. The vines chosen for the sampling were selected according to the results of the geoelectrical survey. Results and discussion Laboratory analysis showed that the most frequent texture class in both vineyards was clay loam, followed by clay. ER spatial variability however was different in the two vineyards. In vineyard 1, the occurrence of low ER values at 0-0.5 and 0-1 m depths correlated with the presence of clayey and saline soil horizons. In vineyard 2, only ER at 0-1 m depth correlated with clay and soil water content. In vineyard 1, the relationship between ER and clay content allowed the evaluation of the loss of accuracy caused by the reduction of the number of analysed soil samples. Passing from the initial 51 samples, to 25, 12, and 6, the accuracy in clay prediction passed from 100% to 79.4, 79.1, and 74%, respectively. The reduction of accuracy of ER prediction at less intense surveys, was limited, in spite of the relatively high soil variability. In fact, doubling the distance between the passages of the machinery between the vine rows, the accuracy of ER prediction was still of 74%, and even widening it at 24 m, from the initial 6 m, the accuracy remained 64%. The density of vegetation in vineyard 1 was positively correlated with ER, while it was inverse in vineyard 2. The opposite behaviour was due to the soil salinity of vineyard 1, which inversely correlated with ER and vegetation vigour. In vineyard 2, on the other hand, the lack of soil salinity enhanced the relationship between vine vigour and water content. In the same vineyard, the sugar content of
Costantini, E. A. C.; Andrenelli, M. C.; Bucelli, P.; Magini, S.; Natarelli, L.; Pellegrini, S.; Perria, R.; Storchi, P.; Vignozzi, N.
Species distribution and resistance profiles of coagulase-negative staphylococci isolated from bovine mastitis in Switzerland.
Coagulase-negative staphylococci (CNS) are the predominant cause of bovine intra-mammary infections. They can lead to chronic infections and were reported to significantly increase milk somatic cell counts. The goal of our study was to determine the species distribution and antimicrobial susceptibility profiles of CNS in bovine mastitis milk samples in Switzerland. Between March 2011 and February 2012, a total of 120 CNS were isolated from mastitis milk samples from 117 different animals at 77 farms. The isolates were identified by matrix-assisted laser desorption ionization - time of flight mass spectrometry (MALDI-TOF MS) and subsequently tested for sensitivity to various antibiotic agents by disk diffusion. Antimicrobial agents were selected mainly based on their relevance to the treatment of bovine mastitis in Switzerland. MALDI-TOF MS assigned the 120 isolates to 12 different staphylococcal species - S. chromogenes (33 %), S. xylosus (28 %), S. sciuri (13 %), S. haemolyticus (9 %), S. epidermidis (4 %), S. simulans (4 %), S. warneri (3 %), S. equorum (2 %), S. hyicus (2 %), S. cohnii (1 %), S. succinus (1 %), and S. fleuretti (1 %). Resistance rates in CNS were high, with 39% of isolates exhibiting resistance to ampicillin and penicillin, 6% of isolates being resistant to amoxicillin with clavulanic acid, ceftiofur, cephalothin, and cefoxitin, and 5 % being resistant to erythromycin. In rare cases resistance to gentamicin (2 %), kanamycin (2 %), and kanamycin-cefalexin (1 %) was detected. PMID:23732379
Moser, A; Stephan, R; Ziegler, D; Johler, S
Rolling Resistance of Electric-Vehicle Tires from Track Tests.
National Technical Information Service (NTIS)
Two sets of low-rolling-resistance tires were track tested to obtain realistic tire characteristics for use in programming the Road Load Simulator, a special dynamometer facility located at the NASA Lewis Research Center. One set was specially made by Goo...
M. O. Dustin R. J. Slavik
Module Three: Resistance; Basic Electricity and Electronics Individualized Learning System.
ERIC Educational Resources Information Center
In this module the student will learn of the opposition offered to electron flow, what this opposition does, why it is needed, and how it is used. The module is divided into four lessons: characteristics of resistance, resistors, resistor values, and ohmmeters. Each lesson consists of an overview, a list of study resources, lesson narratives,�
Bureau of Naval Personnel, Washington, DC.
Electrical resistivity structure at the SAFOD site from magnetotelluric exploration
The magnetotelluric dataset collected on the San Andreas Fault at Parkfield has been re-analyzed using superior inversion algorithms that have been developed in recent years. A combination of constrained inversion, forward modeling and synthetic inversion studies are used, and show that at the SAFOD site, the low resistivity fault zone extends to a depth of 2-3 km. An extended zone
Martyn Unsworth; Paul A. Bedrosian
Electrical Resistivity Study of a Pleistocene Riverbed in Saltville, VA
A shallow capacitively coupled resistivity survey was performed in Saltville, VA, in an area of suspected buried Pleistocene river deposits. Previous excavations in the sediments beneath the Saltville valley floor had been performed to recover late Pleistocene megafaunal remains and possible Clovis-age human artifacts. These digs encountered a zone, one to two meters deep, of gravel-sized rock fragments, including some
R. B. Herman; R. C. Whisonant
Determining concentration depth profiles in fluorinated networks by means of electric force microscopy
By means of electric force microscopy, composition depth profiles were measured with nanometric resolution for a series of fluorinated networks. By mapping the dielectric permittivity along a line going from the surface to the bulk, we were able to experimentally access to the fluorine concentration profile. Obtained data show composition gradient lengths ranging from 30 nm to 80 nm in the near surface area for samples containing from 0.5 to 5 wt. % F, respectively. In contrast, no gradients of concentration were detected in bulk. This method has several advantages over other techniques because it allows profiling directly on a sectional cut of the sample. By combining the obtained results with x-ray photoelectron spectroscopy measurements, we were also able to quantify F/C ratio as a function of depth with nanoscale resolution.
Miccio, Luis A. [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), JB. Justo 4302, Mar del Plata, Buenos Aires (Argentina); Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Kummali, Mohammed M.; Alegria, Angel [Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Departamento de Fisica de Materiales UPV/EHU, Facultad de Quimica, 20080 San Sebastian (Spain); Montemartini, Pablo E.; Oyanguren, Patricia A. [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), JB. Justo 4302, Mar del Plata, Buenos Aires (Argentina); Schwartz, Gustavo A. [Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Colmenero, Juan [Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Departamento de Fisica de Materiales UPV/EHU, Facultad de Quimica, 20080 San Sebastian (Spain); Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain)
Schumann resonance effects of electrical conductivity perturbations in an exponential atmospheric/ionospheric profile
NASA Astrophysics Data System (ADS)
An examination of the Schumann resonance effects of conductivity disturbances superimposed on an exponential vertical conductivity profile in the atmosphere is presented. Differential equations are defined for the radial segment of the eigenfunctions of the earth ionosphere system in the case of spherically symmetric, isotropic dielectric of arbitrary radial profile. Integration of the eigenfunctions produces the vertical and tangential electric field components, and thereby the Joule dissipation profile. It is found that the Schumann resonances have a two-level structure in the Joule dissipation profile, with maximum dissipation happening at the mesospheric height of 50 km. A secondary maximum is situated at 90 km. The vertical component of the electric field of the Schumann modes is constant from the ground up to 40 km, then decreases rapidly. Moderate perturbation conductivity enhancements below 65 km lead to depressed Schumann eigenfrequencies, but below 50 km and between 70-85 km causes depressed Q-values. Between 50-70 km and over 85 km, enhanced conductivity increases the Q-values.
Sentman, D. D.
Determination of ovulation time in sows based on skin temperature and genital electrical resistance changes.
Different physical and physiological parameters may be used to determine ovulation time in sows. In the present study, we analysed the ear and vulvar skin temperature fluctuations, and the changes in genital electrical resistance, at a distance of 4, 8 and 12 cm from the vulva during oestrus in order to predict the time of ovulation. Multiparous sows were checked by transrectal real-time ultrasonography and luteinising hormone (LH) plasma concentration was determined. Temperature was measured using a thermoprecision infrared thermometer, and the electrical resistance was measured with a commercial resistance probe. All measurements were carried out every 12 hours from one day after the weaning to three days after oestrus onset. Skin temperature showed significant difference around periovulatory period. The electrical resistance at 4 cm from the vulva showed marked changes during oestrus, which were different from those described at 8 and 12 cm from the vulva. At 12 hours before ovulation time, skin temperature decreased significantly, and negative correlation (P<0.05) was found between vulvar skin temperature and vaginal resistance. There was no relationship between skin temperature, electrical resistance and LH plasma concentration. The measurement of several physiological traits may provide more accurate predictions of the moment of ovulation. PMID:23709092
Lu�o, V; Gil, L; Jerez, R A; Malo, C; Gonz�lez, N; Grand�a, J; de Blas, I
Bounds on the electrical resistance between contacting elastic rough bodies
A method is developed for placing bounds on the electrical contact conductance between contacting elastic bodies with rough surfaces. An analogy is � rst estab- lished between contact conductance and the incremental sti� ness in the mechanical contact problem. Results from contact mechanics and the reciprocal theorem are then used to bracket the mechanical load{displacement curve between those for two
J. R. Barber
Resistance welding of metals with high electrical and thermal conductivity
A simple device for welding metals with high electrical and thermal conductivity is described. The use of the device, which was adapted from a commercially available carbon deposition unit, for welding 0.0127 and 0.0507-cm-diam Ag, Au, and Pt wires is discussed.
R. Ekern; A. W. Czanderna
Analysis of temperature-dependent electrical resistivity of ZnO nano-structures
NASA Astrophysics Data System (ADS)
The temperature-dependent electrical resistivity ?(T) in metallic and semiconducting phase of ZnO nanostructures is theoretically analysed. ?(T) shows semiconducting phase in low temperature regime (140 K
Choudhary, K. K.
Noninvasive Imaging of Head-Brain Conductivity Profiles Using Magnetic Resonance Electrical Impedance Imaging
Magnetic resonance electrical impedance tomography (MREIT) is a recently introduced non-invasive conductivity imaging modality, which combines the magnetic resonance current density imaging (CDI) and the traditional electrical impedance tomography (EIT) techniques. MREIT is aimed at providing high spatial resolution images of electrical conductivity, by avoiding solving the well-known ill-posed problem in the traditional EIT. In this paper, we review our research activities in MREIT imaging of head-brain tissue conductivity profiles. We have developed several imaging algorithms and conducted a series of computer simulations for MREIT imaging of the head and brain tissues. Our work suggests MREIT brain imaging may become a useful tool in imaging conductivity distributions of the brain and head.
Zhang, Xiaotong; Yan, Dandan; Zhu, Shanan; He, Bin
Electrical resistance anomalies and hydrogen solubilities in the disorder-order system Pd/sub 3/Mn
The maximum in electrical resistance is caused by a combination of two factors which affect the resistance oppositely, i.e., the scattering of electrons from the boundaries between the partially ordered domains and the disordered matrix increases resistance, and the growth and ordering of the domains decreases the resistance. Electron diffraction and TEM studies of samples quenched from temperatures corresponding to the maximum in resistance confirm that ordering occurs and that domains grow as resistance decreases.
Baba, K.; Sakamoto, Y.; Flanagan, T.B.; Kuji, T.; Craft, A.P.
Resistive Fault Current Limiter Prototypes: Mechanical and Electrical Analyses
NASA Astrophysics Data System (ADS)
The problem of excessive short-circuit currents has become an important issue for power systems operators and there are clear indications for a growing interest in superconducting fault current limiter devices for MV and HV grids. In this work, we report on both simulation and electrical testing on single-phase SFCL prototypes developed in the framework of an Italian RTD project to be completed with a 3-phase SFCL unit by the end of 2005.
Martini, L.; Arcos, I.; Bocchi, M.; Brambilla, R.; Dalessandro, R.; Frigerio, A.; Rossi, V.
Anisotropic electrical resistivity of YBCO/PBCO superlattice films grown on miscut substrates
Anisotropic electrical resistivity is studied in epitaxial superlattice films of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}/PrBa{sub 2}Cu{sub 3}O{sub 7-{epsilon}} grown in situ by laser ablation on SrTiO{sub 3} surfaces aligned slightly away from the (100) direction. Layer thicknesses of each compound range from two to eight atomic cells. Electrical resistivity of these superlattice films always shows a peak at some cryogenic temperature that decreases with increasing PrBa{sub 2}Cu{sub 3}O{sub 7-{epsilon}} layer thickness. Clear evidence is seen of vortex pinning or of supercurrent blocking by the step edges or by twin boundaries. The ratio of electrical resistivities for current directions parallel and perpendicular to these boundaries shows a large step-like change just above the superconductive critical temperature. The possibility is discussed that the Kosterlitz-Thouless explains this anisotropy change.
Kerchner, H.R.; Klabunde, C.E.; Christen, D.K.; Budai, J.D.; Lowndes, D.H.; Norton, D. [Oak Ridge National Lab., TN (United States); Thomson, J.O. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy
The gene expression profiles of medulloblastoma cell lines resistant to preactivated cyclophosphamide.
The total expression profiles of two medulloblastoma cell lines resistant to the preactivated form of cyclophosphamide (4-hydroperoxycyclophosphamide, 4-HC) were examined using the Affymetrix GeneChip U133A array. Our primary objective was to look for possible genes, other than the well-studied aldehyde dehydrogenases (ALDH) that may be involved in cyclophosphamide (CP) resistance in medulloblastomas. We present here the lists of the most highly upregulated [30 for D341 MED (4-HCR); 20 for D283 MED (4-HCR)] and downregulated [19 for D341 MED (4-HCR); 15 for D283 MED (4-HCR)] genes which may be involved in conferring CP-resistance to the two medullobalstoma cell lines. The lists of genes from the two sublines almost had no overlap, suggesting different mechanisms of CP-resistance. One of the most noteworthy upregulated gene is TAP1 [90-fold increase in D341 MED (4-HCR) relative to D341 MED]. TAP1, a protein belonging to the ABC transporter family is normally involved in major histocompatibility class I (MHC I) antigen processing. This suggests the possible role of multidrug resistance (MDR), albeit atypical (which means it does not involve the usual MDR1 and MRP glycoproteins), in medulloblastoma's CP-resistance. Apart from TAP1, a number of other genes involved in MHC1 processing were upregulated in D341 MED (4HCR). D341 MED (4-HCR) also had a 20-fold increase in the expression of the aldo-keto reductase gene, AKR1B10, which may deactivate the reactive cyclophosphamide metabolite, aldophosphamide. For D283 MED (4-HCR), the most notable increase in expression is that of ALDH1B1, a member of the aldehyde dehydrogenase (ALDH) family of proteins. PMID:18473730
Bacolod, M D; Lin, S M; Johnson, S P; Bullock, N S; Colvin, M; Bigner, D D; Friedman, H S
Antimicrobial resistance and toxin gene profiles of Staphylococcus aureus strains from Holstein milk.
Isolation of Staphylococcus aureus (Staph.�aureus) from Holstein milk samples with mastitis and nonmastitis was conducted to estimate its prevalence, antimicrobial resistance and toxin genes. A total of 353 milk samples were collected from three Chinese Holstein herds. Fifty-three Staph.�aureus isolates collected from 29 Staph.�aureus-positive samples were characterized via antimicrobial susceptibility, toxin genes and Pulsed-field Gel Electrophoresis (PFGE) profiles. The prevalence of Staph.�aureus was 4�0-9�5% in mastitic and 7�3-11�5% in nonmastitic samples in the analysed herds. Approximately 61�0% of Staph.�aureus strains isolated from mastitis cows were resistant to ?10 antimicrobials compared with 0% of isolates with nonmastitis. The most frequently observed super antigenic toxin gene was pvl (41�5%) followed by seh�+�pvl (13�2%). We did not find mecA-positive methicillin-resistant Staph.�aureus (MRSA) strains, while mecA-negative MRSA strains were identified in the three herds. PFGE results suggested potential transmission of Staph.�aureus strains in different farms. These results open new insights into Staph.�aureus transmission and antimicrobial resistance of Holstein dairy cows and into developing strategies for udder health improvement of dairy cattle. PMID:24460961
Wang, X; Wang, X; Wang, Y; Guo, G; Usman, T; Hao, D; Tang, X; Zhang, Y; Yu, Y
Metagenomic Profiling of Microbial Composition and Antibiotic Resistance Determinants in Puget Sound
Human-health relevant impacts on marine ecosystems are increasing on both spatial and temporal scales. Traditional indicators for environmental health monitoring and microbial risk assessment have relied primarily on single species analyses and have provided only limited spatial and temporal information. More high-throughput, broad-scale approaches to evaluate these impacts are therefore needed to provide a platform for informing public health. This study uses shotgun metagenomics to survey the taxonomic composition and antibiotic resistance determinant content of surface water bacterial communities in the Puget Sound estuary. Metagenomic DNA was collected at six sites in Puget Sound in addition to one wastewater treatment plant (WWTP) that discharges into the Sound and pyrosequenced. A total of ?550 Mbp (1.4 million reads) were obtained, 22 Mbp of which could be assembled into contigs. While the taxonomic and resistance determinant profiles across the open Sound samples were similar, unique signatures were identified when comparing these profiles across the open Sound, a nearshore marina and WWTP effluent. The open Sound was dominated by ?-Proteobacteria (in particular Rhodobacterales sp.), ?-Proteobacteria and Bacteroidetes while the marina and effluent had increased abundances of Actinobacteria, ?-Proteobacteria and Firmicutes. There was a significant increase in the antibiotic resistance gene signal from the open Sound to marina to WWTP effluent, suggestive of a potential link to human impacts. Mobile genetic elements associated with environmental and pathogenic bacteria were also differentially abundant across the samples. This study is the first comparative metagenomic survey of Puget Sound and provides baseline data for further assessments of community composition and antibiotic resistance determinants in the environment using next generation sequencing technologies. In addition, these genomic signals of potential human impact can be used to guide initial public health monitoring as well as more targeted and functionally-based investigations.
Port, Jesse A.; Wallace, James C.; Griffith, William C.; Faustman, Elaine M.
In Vitro Efficacies and Resistance Profiles of Rifampin-Based Combination Regimens for Biofilm-Embedded Methicillin-Resistant Staphylococcus aureus
To compare the in vitro antibacterial efficacies and resistance profiles of rifampin-based combinations against methicillin-resistant Staphylococcus aureus (MRSA) in a biofilm model, the antibacterial activities of vancomycin, teicoplanin, daptomycin, minocycline, linezolid, fusidic acid, fosfomycin, and tigecycline alone or in combination with rifampin against biofilm-embedded MRSA were measured. The rifampin-resistant mutation frequencies were evaluated. Of the rifampin-based combinations, rifampin enhances the antibacterial activities of and even synergizes with fusidic acid, tigecycline, and, to a lesser extent, linezolid, fosfomycin, and minocycline against biofilm-embedded MRSA. Such combinations with weaker rifampin resistance induction activities may provide a therapeutic advantage in MRSA biofilm-related infections.
Tang, Hung-Jen; Chen, Chi-Chung; Cheng, Kuo-Chen; Wu, Kuan-Ying; Lin, Yi-Chung; Zhang, Chun-Cheng; Weng, Tzu-Chieh; Yu, Wen-Liang; Chiu, Yu-Hsin; Toh, Han-Siong; Chiang, Shyh-Ren; Su, Bo An
Relation between serotype distribution and antibiotic resistance profiles of Listeria monocytogenes isolated from ground turkey.
The objectives of this study were to determine the serotype distribution of Listeria monocytogenes isolated from ground turkey using a multiplex PCR assay and to determine antimicrobial resistance profiles of the isolates using the disc diffusion method. Of 78 isolates, 35 (44.9%), 29 (37.2%), 7 (9.0%), and 7 (9.0%) were identified as serotypes 1/2a (or 3a), 4b (or 4d or 4e), 1/2b (or 3b), and 1/2c (or 3c), respectively. Overall, 63 isolates (80.8%) were resistant to penicillin G, and 53 (67.9%) were resistant to ampicillin. All 1/2c (or 3c) serotype isolates were resistant to penicillin G and ampicillin, and all 1/2b (or 3b) serotype isolates were resistant to penicillin G. In addition, 91.4% (32 of 35) of 1/2a (or 3a), 57.1% (4 of 7) of 1/2b (or 3b), and 37.9% (11 of 29) of 4b (or 4d or 4e) serotype isolates were resistant to ampicillin, and 85.7% (30 of 35) of 1/2a (or 3a) and 65.5% (19 of 29) of 4b (or 4d or 4e) serotype isolates were resistant to penicillin G. In conclusion, most of the L. monocytogenes isolates identified were serotype 1/2a (or 3a) and 4b (or 4d or 4e). Serotype 1/2c (or 3c) isolates were highly resistant to antibiotics compared with isolates of serotypes 1/2a (or 3a), 1/2b (or 3b), and 4b (or 4d or 4e). Increasing resistance of L. monocytogenes to ampicillin and penicillin is an especially serious concern for public health because of the common use of these antibiotics in treatment of human listeriosis cases. PMID:20501050
Ayaz, Naim Deniz; Erol, Irfan
Electrical resistance and macromolecular permeability of brain endothelial monolayer cultures.
Electrophysiological measurements were made on endothelial cells initially isolated as individual clones from bovine brain microvessels, and then grown as monolayers on a permeable support of glutaraldehyde-treated collagen gel. When transendothelial cell resistance (R) of the clones was measured, there was a range of values from a low of 157.4 +/- 4.5 omega.cm2 (n = 6) to a high of 783.2 +/- 7.0 omega.cm2 (n = 34). With the high-resistance cells, there was also a small potential difference of -0.46 +/- 0.03 mV luminal-side negative (n = 34). In comparison, endothelial cells from bovine aortas and rat epididymal fat pads cultured on the collagen gels had transendothelial R values of 13.5 +/- 0.2 (n = 62) and 0.45 +/- 0.03 (n = 10) omega.cm2, respectively. Exposure of the high-resistance brain endothelial cell monolayers to a Ca2+-free medium for 10 min decreased the R to 75% of the control values. Addition of Ca2+ back to the medium caused a return of the transendothelial R to control values within 1 h. Endothelial cells were also grown to confluency on microcarrier beads for permeability measurements to Evans blue dye-bovine serum albumin. Microcarriers with no cells (control) and microcarriers with bovine and epididymal endothelial cell monolayers showed no difference in the amount of adsorbed dye. Microcarriers with brain endothelial monolayers excluded up to 80% of the dye. This mammalian brain endothelial culture system will be a useful model for studies of the electrophysiological and permeability properties of the blood-brain barrier. PMID:3427432
Rutten, M J; Hoover, R L; Karnovsky, M J
Computational Analysis of HIV1 Resistance Based on Gene Expression Profiles and the Virus-Host Interaction Network
A very small proportion of people remain negative for HIV infection after repeated HIV-1 viral exposure, which is called HIV-1 resistance. Understanding the mechanism of HIV-1 resistance is important for the development of HIV-1 vaccines and Acquired Immune Deficiency Syndrome (AIDS) therapies. In this study, we analyzed the gene expression profiles of CD4+ T cells from HIV-1-resistant individuals and HIV-susceptible
Tao Huang; Zhongping Xu; Lei Chen; Yu-Dong Cai; Xiangyin Kong
Electrical resistivity investigations at Memphis, and Bolivar, Tennessee
This geophysical investigation was undertaken upon request of Elliott M. Cushing of the Ground Water Division Office at Memphis, Tennessee. The field work was performed during the period March 13 to 28, 1947; the apparent resistivity curves were interpreted during November and December; and the report was written subsequent to the interpretation of the curves. The writer is grateful to Elliott M. Cushing and his staff for the splendid cooperation and generous assistance extended to him in obtaining the measurements. It is also a pleasure to acknowledge the assistance of George J. Edwards in obtaining the field measurements.
Spicer, H. Cecil
Mechanical stress and electrical resistance of CrSi-O thin films
An apparatus for simultaneous measurement of the temperature dependence of mechanical stress and electrical resistance was constructed to obtain information about intrinsic and thermal stresses in correlation with resistance changes of (Cr0.286Si0.714)1?xOx thin films (0 < x < 0.5). Together with Auger electron spectroscopy and factor analysis the results provide insights into the as-grown amorphous film structure (pre-demixed in O-poor
W. Br�ckner; G. Sobe; H. Grie?mann; G. Reiss
Stable hole doping of graphene for low electrical resistance and high optical transparency
We report on the p doping of graphene with the polymer TFSA ((CF3SO2)2NH). Modification of graphene with TFSA decreases the graphene sheet resistance by 70%. Through such modification, we report sheet resistance values as low as 129 Omega, thus attaining values comparable to those of indium-tin oxide (ITO), while displaying superior environmental stability and preserving electrical properties over extended time
S. Tongay; K. Berke; M. Lemaitre; Z. Nasrollahi; D. B. Tanner; A. F. Hebard; B. R. Appleton
Semiconductorlike Behavior of Electrical Resistivity in Heusler-type Fe2VAl Compound
An anomalous negative temperature dependence of electrical resistivity has been observed in \\\\(Fe1-xVx\\\\)3Al alloys with V compositions up to x = 0.35. In particular, the Heusler-type Fe2VAl compound is found to be on the verge of magnetic ordering and to exhibit a semiconductorlike behavior with the resistivity reaching 3000 muOmega cm at 2 K, in spite of the possession of
Y. Nishino; M. Kato; S. Asano; K. Soda; M. Hayasaki; U. Mizutani
Electric-Pulse-Induced Resistance Switching in Magnetoresistive Manganite Films Grown by Metalorganic Chemical Vapor Deposition
Pr1-xCaxMnO3 (PCMO) films with the desired atomic composition were deposited at low temperature (480 degC) by metalorganic chemical vapor deposition (MOCVD) using in situ infrared spectroscopic monitoring. The electric-pulse-induced resistance switching was observed in PCMO-based devices with various kinds of metal electrodes. The resistance change was dependent on the Ca\\/(Pr+Ca) composition ratio of the films and the kind of the
Toshihiro Nakamura; Kohei Homma; Ryusuke Tai; Akira Nishio; Kunihide Tachibana
Influence of Degree of Saturation in the Electric Resistivity�Hydraulic Conductivity Relationship
The relationship between aquifer hydraulic conductivity and aquifer resistivity, either measured on the ground surface by\\u000a vertical electrical sounding (VES) or from resistivity logs, or measured in core samples have been published for different\\u000a types of aquifers in different locations. Generally, these relationships are empirical and semi-empirical, and confined in\\u000a few locations. This relation has a positive correlation in some
Mohamed Ahmed Khalil; Fernando A. Monterio Santos
Influence of Degree of Saturation in the Electric Resistivity-Hydraulic Conductivity Relationship
NASA Astrophysics Data System (ADS)
The relationship between aquifer hydraulic conductivity and aquifer resistivity, either measured on the ground surface by vertical electrical sounding (VES) or from resistivity logs, or measured in core samples have been published for different types of aquifers in different locations. Generally, these relationships are empirical and semi-empirical, and confined in few locations. This relation has a positive correlation in some studies and negative in others. So far, there is no potentially physical law controlling this relation, which is not completely understood. Electric current follows the path of least resistance, as does water. Within and around pores, the model of conduction of electricity is ionic and thus the resistivity of the medium is controlled more by porosity and water conductivity than by the resistivity of the rock matrix. Thus, at the pore level, the electrical path is similar to the hydraulic path and the resistivity should reflect hydraulic conductivity. We tried in this paper to study the effect of degree of groundwater saturation in the relation between hydraulic conductivity and bulk resistivity via a simple numerical analysis of Archie�s second law and a simplified Kozeny-Carmen equation. The study reached three characteristic non-linear relations between hydraulic conductivity and resistivity depending on the degree of saturation. These relations are: (1) An inverse power relation in fully saturated aquifers and when porosity equals water saturation, (2) An inverse polynomial relation in unsaturated aquifers, when water saturation is higher than 50%, higher than porosity, and (3) A direct polynomial relation in poorly saturated aquifers, when water saturation is lower than 50%, lower than porosity. These results are supported by some field scale relationships.
Khalil, Mohamed Ahmed; Monterio Santos, Fernando A.
SiC Epitaxial Layer Resistivity Monitoring; A look at Existing and Novel Electrical Methods
NASA Astrophysics Data System (ADS)
In this paper three electrical methods for SiC resistivity measurement are discussed. The primary method is based on the Elastic Material Probe (EM-Probe) or Elastic Probe CV (ECV). Also we discuss the specifics of the advanced Mercury CV (MCV) and Spreading Resistance (SRP) techniques. Measurement results of 4H-SiC Epitaxial samples are presented, showing a good correlation between various methods.
Hillard, Robert J.; Tsidilkovski, Edward
Electrical resistivity of iron-silicon alloys under high pressure and temperature
NASA Astrophysics Data System (ADS)
Very recent experiments and calculations of electrical resistivity of the Earth's core (Gomi et al. 2011; de Koker et al. 2012; Pozzo et al. 2013) suggest the thermal conductivity of the outer core to be a factor of 2-3 higher than previous estimates. This renews interest and calls for electrical conductivity measurements on iron and iron alloys in order to better understand core heat flow. Considering silicon as a strong candidate for a light alloying element in the Earth's core, electrical resistivity measurements on iron silicon alloys up to 17wt% silicon have been carried out at pressure up to 5 GPa and at temperatures beyond melting in a 1000 ton cubic anvil press. These findings show that in contrast to the electrical resistivity behavior of pure iron, iron-silicon alloys of ~ 17 wt% silicon undergo a drop in resistivity at the melting temperature. The application of these results on iron silicon alloys to the thermal conductivity of the outer core is based on the tendency for resistivity to saturate at very high temperatures. By using the Wiedemann-Franz law, we compare our results with the recent high thermal conductivity estimates of the Earth's core.
Kiarasi, S.; Secco, R.
High pressure and temperature electrical resistivity of iron and implications for planetary cores (Invited)
NASA Astrophysics Data System (ADS)
Electrical resistivity measurements of polycrystalline iron have been performed at 5, 7 and 15 GPa and in the temperature range 293-2200 K by employing a four-wired method. The kinks in electrical resistivity associated with solid iron phase transitions and the solid to liquid transition were clearly observed upon increasing temperature. Geometry corrections due to volume variations with pressure and temperature were applied to the entire data set. High pressure and temperature thermal conductivity were calculated by fitting resistivity data through the Wiedemann-Franz law. The temperature dependences of electrical resistivity and thermal conductivity for ?, ? and ? solid iron have been determined at high pressure conditions. Our study provides the first experimental constraint on the heat flux conducted at Mercury's outmost core, estimated to be 0.29-0.36 TW, assuming an adiabatic core. Extrapolations of our data to Martian outer core conditions yield a series of heat transport parameters (eg. electrical resistivity, thermal conductivity and heat flux), which are in reasonable comparison with various geophysical estimates.
Deng, L.; Seagle, C. T.; Fei, Y.; Shahar, A.
Size and temperature effects on the thermoelectric power and electrical resistivity of bismuth telluride thin films
NASA Astrophysics Data System (ADS)
Thermoelectric power and electrical resistivity measurements have been carried out as a function of temperature in the range 300-470 K on well-annealed thin films of Bi2Te3 of various thicknesses in the range 400-1900 Å. The films of a given thickness for both the measurements have been prepared simultaneously in a single evaporation so that the results of the thermoelectric power and the electrical resistivity measurements can be combined to evaluate useful material parameters. Annealed Bi2Te3 thin films of all thicknesses exhibit semiconducting behavior, viz., an exponential decrease of resistivity with increasing temperature and a mildly temperature-dependent thermoelectric power, the latter's magnitude increasing with increasing temperature. (The thermoelectric power of all the Bi2Te3 thin films is negative, indicating that the majority of carriers are electrons.) The effective-mean-free-path model and least-squares fitting by local (spline) functions have been used to analyze the thickness dependence of thermoelectric power and electrical resistivity of Bi2Te3 thin films. Both are found to be linear functions of inverse thickness. By combining the results of analyses of electrical resistivity data and thermoelectric power data, material parameters like mean free path, carrier concentration, their effective mass, and Fermi energy have been evaluated.
Das, V. Damodara; Soundararajan, N.
Electrical resistivity well-logging system with solid-state electronic circuitry
An improved 4-channel electrical resistivity well-logging system for use with a passive probe with electrodes arranged in the 'normal' configuration has been designed and fabricated by Westinghouse Electric Corporation to meet technical specifications developed by the U.S. Geological Survey. Salient features of the system include solid-state switching and current regulation in the transmitter circuit to produce a constant-current source square wave, and synchronous solid-state switching and sampling of the potential waveform in the receiver circuit to provide an analog dc voltage proportions to the measured resistivity. Technical specifications and design details are included in this report.
Scott, James Henry; Farstad, Arnold J.
Online Monitoring of the Electrical Power Transfer Stability and Voltage Profile Stability Margins in Electric Power Transmission Systems Using Phasor Measurement Units Data Sets
An innovative method to monitor the electric power transfer stability on power transmission paths and the voltage profile stability at the power systems nodes in real time modus is proposed. Based on the laws of electric circuit theory, the transfer operating mode of each relevant transmission line is formulated in an active power-voltage PV characteristic. The relevant transmission line parameters
Yves Nguegan; Albert Claudi; Carsten Strunge
Electrical Resistivity Study of a Pleistocene Riverbed in Saltville, VA
NASA Astrophysics Data System (ADS)
A shallow capacitively coupled resistivity survey was performed in Saltville, VA, in an area of suspected buried Pleistocene river deposits. Previous excavations in the sediments beneath the Saltville valley floor had been performed to recover late Pleistocene megafaunal remains and possible Clovis-age human artifacts. These digs encountered a zone, one to two meters deep, of gravel-sized rock fragments, including some boulders up to 75 cm. in diameter. These large clasts are rounded, show some imbrication (shingle-like overlapping indicative of current flow), and have been interpreted as river channel deposits. Carbon 14 dates from the megafaunal bones within and just above the gravel bed yielded dates of 14,500 years BP. Resistivity signals in a number of locations were consistent with cobbles and boulders deposited in a river channel. These signals are generally bowl- shaped areas with large circular (2-d scans) anomalies near the center, and smaller circular anomalies tapering out towards both sides. The bowl-shaped anomalies are within 3 meters of the surface. With several lines imaged in this survey a rough path of the riverbed, along with a number of branchings is traceable in the survey area. An exploratory hole confirmed the presence of a layer of rounded cobbles and boulders 1.3 meters deep beneath one of the survey lines.
Herman, R. B.; Whisonant, R. C.
The effect of electromagnetic forces on the penetrator formation during high-frequency electric resistance welding
During high-frequency electric resistance welding (HF-ERW), the electromagnetic force induced by the high-frequency electric current was studied to improve the understanding of penetrator formation mechanism. ERW melting zone behavior is investigated by the cinematography and the three-dimensional numerical analysis of electromagnetic field around molten metal bridge. Based on the results, the penetrator formation is mainly influenced by the narrow gap
Choong-Myeong Kim; Jung-Kyu Kim
Assessment of Continuous Resistivity Profiling for the Characterization of Paved Roads
NASA Astrophysics Data System (ADS)
We have assessed the continuous resistivity profiling method using towed arrays as a diagnostic NDT method for the evaluation of pavements. Whether the pavement consists of a sequence of asphalt, concrete slab and subgrade layer (rigid pavement) or a layer of asphalt overlying a subgrade and grade base layers (flexible pavement) defects within those different layers can cause pavement deterioration that must be identified. We first examine the response of the method to the various problems using numerical modeling. It is shown that with an optimally designed system the method allows the determination of the thickness and the location of cracks in the asphalt cover. It is also sensitive to the presence of cracks, internal defects and chloride ions (de-icing salt) within the concrete slab below. For reinforced concrete it is possible to estimate the concrete resistivity related directly to its composition (quality) and the thickness of the top coating over the level of rebars. A low resistivity of concrete will usually be diagnostic of advanced stage of rebar corrosion and delamination could occur. However it is shown that the rebars cause current channeling and the depth of investigation is limited then to the depth of the first row of rebars. Finally heterogeneities within the foundation reflecting subsidence, bad drainage, frost-defrost cycles or cavities can be mapped. The optimal design is based on a system with 10 to 20 receiver dipoles and one transmitter dipole (first or last of the array) with a dipole length typically of 10 cm that can be used in equatorial or in-line mode. Static resistivity measurements have been carried out at the laboratory scale over concrete slabs built to verify results obtained from the numerical modeling. Observed data fit very well the modeled data and validate the overall conclusions. Tests have been performed in December 2003 in some selected streets (6 visited, 3 re-visited) of Montreal using a CORIM system (Iris Instruments, France), a capacitively-coupled resistivity towed equatorial array that continuously record data collected with six receiver dipoles and one transmitter dipole. Typical acquisition sampling and velocity were 0,20-0,50 m and 1 to 2 km/h respectively. Although the system is not optimally designed for the applications described above it provides useful diagnostic information about the state of deterioration of pavement. Data have been imaged using 2D resistivity inversion. In general it shows a high resistivity for the shallow depth related to the asphalt layer and a decreasing resistivity with depth related to the concrete slab first and the granular foundation below. Lateral variations appear to be correlated with degradation of the concrete slab.
Chouteau, M.; Vallieres, S.; Miralles, M.
Characterization of profile dependency on nitride substrate thickness for a chemically amplified I-line negative resist
NASA Astrophysics Data System (ADS)
During implementation of a chemically amplified I-line negative resist (INR) into the eight- inch-wafer manufacturing line at IBM's facility in Essex Junction, Vermont we found that the resist profiles were being undercut during development on silicon-nitride surfaces. The undercut was attributed to a `poisoning' of the photoacid generated in the resist during exposure by the nucleophilic characteristics of the silicon-nitride surface. A second-generation negative resist has since been formulated by IBM, which greatly reduces these undercut effects but does not eliminate them. This newer version of INR is referred to as INR2. To further understand the effects of silicon nitride on the I-line negative-resist profiles, we used Prolith/2 (v3.05)3 to model the underlying stack and evaluate the performance of INR2. Silicon monitors with oxide and different nitride thicknesses were patterned with INR2 using 4-Mb DRAM manufacturing ion-implant block masks and associated photo processing. The results indicated that the undercut observed by this chemically amplified negative resist on silicon nitride was not only chemical in nature, but related to the optical properties of the nitride substrate. Simulation results obtained using Prolith/2 are give and compared with resist profiles obtained from wafers processed with INR2; the accuracy of the Prolith/2 model to predict slope profiles for INR2 is also discussed.
Puttlitz, Erik A.; Collins, James P.; Glynn, Thomas M.; Linehan, Leo L.
Negative Temperature Coefficient of Electrical Resistivity in B2Type Ti Ni Alloys
A negative temperature coefficient of electrical resistivity (TCR) has been observed in Ti50-XNi50+X (at.%; X=1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5) in the temperature range between 20 and 350 K. The resistivity vs temperature curve has no hysteresis and the relative resistivity at 20 K (rho20 K\\/rho350 K) decreases with increasing Ni content. X-ray diffraction and magnetic susceptibility measurements show
Tomoyuki Kakeshita; Takashi Fukuda; Hiroki Tetsukawa; Toshio Saburi; Koichi Kindo; Tetsuya Takeuchi; Makoto Honda; Shoichi Endo; Toshifumi Taniguchi; Yoshihito Miyako
Immersion scatterometry for improved feature resolution and high speed acquisition of resist profiles
NASA Astrophysics Data System (ADS)
Specular-mode spectroscopic scatterometry is currently being used as an in-line metrology tool for wafer-to-wafer process monitoring and control in lithography and etch processes. Experimental real-time, in situ demonstrations of critical dimension monitoring and control have been made for reactive ion etching. There have been no similar demonstrations of real-time control in the critical step of resist development. In this paper, we will show the results of a simulation study on the use of scatterometry in an immersion mode both to improve resolution and to act as a real-time monitor for photoresist topography evolution during development. We have performed realistic simulations of the experimental performance by using Prolith to generate developing resist profiles vs. time and a rigorous couple wave algorithm (RCWA) simulator (modified to include the immersion ambient) to generate simulated scatterometry data. We have examined several modes of operation of the proposed measurement including specular and 1st order scattered modes using spectroscopic ellipsometry and reflectometry. For our simulations, we have used pure water to approximate the developer refractive index. We have created realistic simulation data by adding appropriate amounts of random noise to perfect simulations, and then used regression analysis to extract profiles from these data. Water immersion increases feature shape resolution for small period gratings by increasing the scattering into real diffracted modes.
Terry, Fred L., Jr.; Bendik, Joseph J.
Delineation of shallow resistivity structure in the city of Burdur, SW Turkey by vertical electrical sounding measurements
NASA Astrophysics Data System (ADS)
The city of Burdur, which is built on an alluvium aquifer, is located in one of the most seismically active zones in southwestern Turkey. The soil properties in the study site are characterized by unconsolidated and water-saturated sediments including silty, clayey and sandy units, and shallow groundwater level is the other characteristic of the site. Thus, the city is under soil liquefaction risk during a large earthquake. A resistivity survey including 189 vertical electrical sounding (VES) measurements was carried out in 2000 as part of a multi-disciplinary project aiming to investigate settlement properties in Burdur city and its vicinity. In the present study, the VES data acquired by using a Schlumberger array were re-processed with 1D and 2D inversion techniques to determine liquefaction potential in the study site. The results of some 1D interpretations were compared to the data from several wells drilled during the project. Also, the groundwater level map that was previously obtained by hydrological studies was extended toward north by using the resistivity data. 2D least-squares inversions were performed along nine VES profiles. This provided very useful information on vertical and horizontal extends of geologic units and water content in the subsurface. The study area is characterized by low resistivity distribution (<150 ?m) originating from high fluid content in the subsurface. Lower resistivity (3-30 ?m) is associated with the Quaternary and the Tertiary lacustrine sediments while relatively high resistivity (40-150 ?m) is related to the Quaternary alluvial cone deposits. This study has also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information on the groundwater level and the fluid content in the subsurface. Based on this, we obtained a liquefaction hazard map for the study area. The liquefaction potential was classified by considering the resistivity distributions from 2D inversion of the VES profiles, the types of the sediments and the extended groundwater level map. According to this map, the study area was characterized by high liquefaction hazard risk.
Balkaya, �a?layan; Kaya, M. Ali; G�kt�rkler, G�khan
On the Modeling of Electrical Effects Experienced by Space Explorers During Extra Vehicular Activities: Intracorporal Currents, Resistances, and Electric Fields
NASA Technical Reports Server (NTRS)
Recent research has shown that space explorers engaged in Extra Vehicular Activities (EVAs) may be exposed, under certain conditions, to undesired electrical currents. This work focuses on determining whether these undesired induced electrical currents could be responsible for involuntary neuromuscular activity in the subjects, possibly caused by either large diameter peripheral nerve activation or reflex activity from cutaneous afferent stimulation. An efficient multiresolution variant of the admittance method along with a millimeter-resolution model of a male human body were used to calculate induced electric fields, resistance between contact electrodes used to simulate the potential exposure condition, and currents induced in the human body model. Results show that, under realistic exposure conditions using a 15V source, current density magnitudes and total current injected are well above previously reported startle reaction thresholds. This indicates that, under the considered conditions, the subjects could experience involuntary motor response.
Cela, Carlos J.; Loizos, Kyle; Lazzi, Gianluca; Hamilton, Douglas; Lee, Raphael C.
Application of resistivity image profiling method and laser scanning to monitor landside
NASA Astrophysics Data System (ADS)
Taiwan, located at the Western Pacific, bears the threats from both typhoons and earthquakes. The 921 earthquake resulted in the unstable ground so that typhoons or torrential rain could cause serious disasters. Currently, the hazard mitigation is the target of the authorities. However, using the traditional approaches not only wastes a lot of time but also is ineffectively. The deformation of slope terrain is detected by physical measured instrument traditionally. Collecting deformation data of tiltmeter and piezometer inner well drilling. A few of wells are limited by terrain and cost. The wells can not cover all landslide area. The results of analysis data are debated. The collapse slope once has more probabilistic collapse. Particularly designing engineering against natural calamities with debated conclusion and the rebuilt slope will be instable. This paper demonstrates the possibility of using resistivity image profiling method (RIP) and 3d laser scanning to monitor a landside at No.3 freeway of 85 km in Taiwan. The slope was rebuilt by grid-beam engineering, spraying concrete engineering and cut-slope engineering. The first, exploring underground substance by resistivity image profiling method . To obtain the destructive sliding position of slope, the range of slope with the same sliding position and groundwater data. Time-lapse RIP sections for different time period also indicate that the obvious resistivity change zones were limited under a strongest topography change surface.Fitting 3d laser scanner on suitable site for scanning research target. To analyze overlay scanning data by correcting the cloud-points with the different periods. The study utilizes the 3d scanning technology and geoelectric resistivity technology to obtain analysis information of slope probability and terrain deformation trend. The way of detecting deformation of rebuilt slope that combines RIP and 3D laser scanner is overall technology. The RIP detects the sensitive area of underground and the 3D laser scanner detects terrain surface of slope. Especial collecting the data by period observation. The data can provide the trend of rebuilt slope creeping and the policy decision of remaking engineering. Keyword�Gresistivity image profiling ,3d laser scanning,landslide
Liu, H.; Yang, C.
Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag.
Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35???�cm at room temperature after 3?mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior. PMID:24965478
Kim, Ji Young; Oh, Min-Wook; Lee, Seunghun; Cho, Yong Chan; Yoon, Jang-Hee; Lee, Geun Woo; Cho, Chae-Ryong; Park, Chul Hong; Jeong, Se-Young
Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag
Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35???�cm at room temperature after 3?mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior.
Kim, Ji Young; Oh, Min-Wook; Lee, Seunghun; Cho, Yong Chan; Yoon, Jang-Hee; Lee, Geun Woo; Cho, Chae-Ryong; Park, Chul Hong; Jeong, Se-Young
A upper mantle electrical conductivity profile beneath the Australian continent and a comparison with a laboratory-based model
NASA Astrophysics Data System (ADS)
To investigate the standard electrical conductivity profile beneath a continental craton, we conducted magnetotelluric observations with long dipole span near Alice Springs, central Australia. Central Australia is located in mid-geomagnetic latitudes, which makes it suitable to conduct magnetotelluric studies and its location in the center of a continent means we can expect the oceanic effect to be minimized. Moreover, seismic tomographic studies detect no lower mantle upwelling beneath Australia. We utilized geomagnetic data acquired at the Alice Springs geomagnetic observatory maintained by Geoscience Australia. The power spectrum densities of 3 components of the geomagnetic data are not distinctive at four principal tidal constituents (M2, S2, O1, and K1) frequencies except S2, which suggest the observed electromagnetic field variations are not affected by motional induction. Using the BIRRP processing code (Chave and Thomson, 2004), we estimated the MT and GDS transfer functions from 100 to 106 sec in period. The MT-compatible response functions converted from GDS response functions are resistive compared to the Canadian Shield (Chave et al., 1993) around 105 sec in period. The calculated MT responses have also resistive apparent resistivity values in overall period range. We inverted the average MT responses into a one-dimensional conductivity structure with the Occam inversion (Constable et al., 1987). We compared the resultant one-dimensional structure with the electrical conductivity profiles predicted from the compositional models of the earth's upper mantle by calculating phase diagrams in the CFMAS (CaO-FeO-MgO-Al2O3-SiO2) system. The on-craton and off-craton chemical composition models (Rudnick et al., 1998) were adopted for tectosphere. The Perple_X (e.g. Connolly, 2005) programs were utilized for obtaining mineral proportions and compositions with depth by minimizing the total Gibbs free energy. The used thermodynamic data base was SFO05 (Stixrude and Lithgow-Bertelloni, 2005; Fabrichnaya, 1998; Ono and Oganov, 2005). The adiabat, which passes through the pressure and temperature conditions constrained by both of the olivine-wadsleyite (Katsura et al., 2004) and ringwoodite-perovskite (Ito and Takahashi, 1989) phase transitions, is considered to be appropriate for the upper mantle. The appropriate adiabat itself was adopted to the thermal structure of oceanic upper mantle. On the other hand, the thermal structure of sub-continents was obtained by incorporating the effect of the mechanical boundary layer and of the crustal double heat production layers into the appropriate adiabat by means of McKenzie et al.(2005). Newly compiled laboratory data for electrical conductivity of minerals were as followings: olivine (Constable, 2006), garnet-majorite (Romano et al., 2006), wadsleyite (Yoshino et al., 2008), ringwoodite (op. cit.), and akimotoite (Katsura et al., 2007). We referred to Xu et al.(2000) for other minerals' data. The calculated conductivity profiles with on- and off-craton models still show significantly lower magnitude than the observed.
Ichiki, M.; Fujita, K.; Wang, L.; Hitchman, A. P.
Direct current resistivity profiling to study distribution of water in the unsaturated zone near the Amargosa Desert Research Site, Nevada
In order to study the distribution of water in the unsaturated zone and potential for ground-water recharge near the Amargosa Desert Research Site south of Beatty, Nevada, the U.S. Geological Survey collected direct-current resistivity measurements along three profiles in May 2003 using an eight-channel resistivity imaging system. Resistivity data were collected along profiles across the ADRS, across a poorly incised (distributary) channel system of the Amargosa River southwest of the ADRS, and across a well-incised flood plain of the Amargosa River northwest of the ADRS. This report describes results of an initial investigation to estimate the distribution of water in the unsaturated zone and to evaluate the shallow subsurface stratigraphy near the ADRS. The geophysical method of dc resistivity was employed by using automated data collection with numerous electrodes. 'Cross sections' of resistivity, produced by using an inversion algorithm on the field data, at the three field sites are presented and interpreted.
Abraham, Jared D.; Lucius, Jeffrey E.
Effector Genomics Accelerates Discovery and Functional Profiling of Potato Disease Resistance and Phytophthora Infestans Avirulence Genes
Potato is the world's fourth largest food crop yet it continues to endure late blight, a devastating disease caused by the Irish famine pathogen Phytophthora infestans. Breeding broad-spectrum disease resistance (R) genes into potato (Solanum tuberosum) is the best strategy for genetically managing late blight but current approaches are slow and inefficient. We used a repertoire of effector genes predicted computationally from the P. infestans genome to accelerate the identification, functional characterization, and cloning of potentially broad-spectrum R genes. An initial set of 54 effectors containing a signal peptide and a RXLR motif was profiled for activation of innate immunity (avirulence or Avr activity) on wild Solanum species and tentative Avr candidates were identified. The RXLR effector family IpiO induced hypersensitive responses (HR) in S. stoloniferum, S. papita and the more distantly related S. bulbocastanum, the source of the R gene Rpi-blb1. Genetic studies with S. stoloniferum showed cosegregation of resistance to P. infestans and response to IpiO. Transient co-expression of IpiO with Rpi-blb1 in a heterologous Nicotiana benthamiana system identified IpiO as Avr-blb1. A candidate gene approach led to the rapid cloning of S. stoloniferum Rpi-sto1 and S. papita Rpi-pta1, which are functionally equivalent to Rpi-blb1. Our findings indicate that effector genomics enables discovery and functional profiling of late blight R genes and Avr genes at an unprecedented rate and promises to accelerate the engineering of late blight resistant potato varieties.
Vleeshouwers, Vivianne G. A. A.; Rietman, Hendrik; Krenek, Pavel; Champouret, Nicolas; Young, Carolyn; Oh, Sang-Keun; Wang, Miqia; Bouwmeester, Klaas; Vosman, Ben; Visser, Richard G. F.; Jacobsen, Evert; Govers, Francine; Kamoun, Sophien; Van der Vossen, Edwin A. G.
Clonality and Antimicrobial Resistance Gene Profiles of Multidrug- Resistant Salmonella enterica Serovar Infantis Isolates from Four Public Hospitals in Rio de Janeiro, Brazil
In Brazil, Salmonella enterica serovar Infantis resistant to various antimicrobials, including cephalosporins, has been identified as an etiological agent of severe gastroenteritis in hospitalized children since 1994. In this study, 35 serovar Infantis strains, isolated from children admitted to four different Rio de Janeiro, Brazil, hospitals between 1996 and 2001, were characterized by pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing in order to determine their genetic relatedness and antimicrobial resistance profiles. Thirty-four serovar Infantis strains were resistant to at least two antibiotic classes, and all 35 strains were susceptible to fluoroquinolones, cephamycin, and carbapenem. Extended-spectrum beta-lactamase (ESBL) screening by double-disk diffusion indicated that 32 serovar Infantis strains (91.4%) produced beta-lactamases that were inhibited by clavulanic acid. Antimicrobial resistance gene profiles were determined by PCR for a subset of 11 multidrug-resistant serovar Infantis strains, and putative ESBLs were detected by isoelectric focusing. Ten serovar Infantis strains carried blaTEM, catI, ant(3")Ia and/or ant(3")Ib, sulI and/or sulII, and tet(D) genes as well as an integron-associated aac(6?)-Iq cassette. Eight strains possessed at least four different beta-lactamases with pI profiles that confirmed the presence of both ESBLs and non-ESBLs. Our PFGE profiles indicated that 33 serovar Infantis strains isolated from Rio de Janeiro hospitals came from the same genetic lineage.
Fonseca, E. L.; Mykytczuk, O. L.; Asensi, M. D.; Reis, E. M. F.; Ferraz, L. R.; Paula, F. L.; Ng, L. K.; Rodrigues, D. P.
Three-dimensional monitoring of soil water content in a maize field using Electrical Resistivity Tomography
NASA Astrophysics Data System (ADS)
A good understanding of the soil water content (SWC) distribution at the field scale is essential to improve the management of water, soil and crops. Recent studies proved that Electrical Resistivity Tomography (ERT) opens interesting perspectives in the determination of the SWC distribution in 3 dimensions (3-D). This study was conducted (i) to check and validate how ERT is able to monitor SWC distribution in a maize field during the late growing season; and (ii) to investigate how maize plants and rainfall affect the dynamics of SWC distribution. Time Domain Reflectometry (TDR) measurements were used to validate ERT-inverted SWC values. Evolution of water mass balance was also calculated to check whether ERT was capable of giving a reliable estimate of soil water stock evolution. It is observed that ERT was able to give the same average SWC as TDR (R2 = 0.98). In addition, ERT gives better estimates of the water stock than TDR thanks to its higher spatial resolution. The high resolution of ERT measurements also allows for the discrimination of SWC heterogeneities. The SWC distribution showed that alternation of maize rows and inter-rows was the main influencing factor of the SWC distribution. The drying patterns were linked to the root profiles, with drier zones under the maize rows. During short periods, with negligible rainfall, the SWC decrease took place mainly in the two upper soil horizons and in the inter-row area. In contrast, rainfall increased the SWC mostly under the maize rows and in the upper soil layer. Nevertheless, the total amount of rainfall during the growing season was not sufficient to modify the SWC patterns induced by the maize rows. During the experimental time, there was hardly any SWC redistribution from maize rows to inter-rows. Yet, lateral redistribution from inter-rows to maize rows induced by potential gradient generates SWC decrease in the inter-row area and in the deeper soil horizons.
Beff, L.; G�nther, T.; Vandoorne, B.; Couvreur, V.; Javaux, M.
Electrical resistivity characterization and defect detection on a geosynthetic clay liner (GCL) on an experimental site
NASA Astrophysics Data System (ADS)
In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serves to ensure the impermeability of a landfill cap by DC electrical methods. The imaging of the GCL geoelectrical properties is a challenging problem because it is a very thin (between 4 and 7 mm thick) and resistive layer (from 100,000 to 2,000,000 ?�m) depending on meteorological conditions and aging. We compare results obtained using electrical resistivity tomography (ERT) using two different kinds of arrays (dipole-dipole DD and Wenner-Schlumberger) on an experimental site with engineered defects. To confirm these results and to find the real onsite GCL resistivity we have performed sampling of the posterior distribution of this parameter using vertical electrical sounding (VES) inversions. Different VES methods were extracted from ERT with DD array and converted into a Schlumberger array. As a main conclusion the dipole-dipole array provides a better resistivity resolution of the defects than the Wenner-Schlumberger array. On ERT images, the defect detection seems to be impossible if the GCL has very high resistivity, as it happened when it was put in place. Taking into account the equivalence rules, the inversions are in both cases (ERT and VES) compatible. The GCL resistivity estimated from PSO (particle swarm optimization) varies from 3.0 105 to 1.106 ?�m depending on saturation conditions during the twenty first months of its placing. Then, the resistivity dropped to 4.104-9.104 ?�m, indicating a probable chemical damage of the GCL due to aging. Finally the fact that the VES inversions are solved via PSO sampling allows for the detection of a very thin and resistive layer and opens the possibility of performing micro VES surveys along the landfill to detect possible GCL defects.
Sirieix, C.; Fern�ndez Mart�nez, J. L.; Riss, J.; Genelle, F.
Electrical resistance determination of actual contact area of cold welded metal joints
NASA Technical Reports Server (NTRS)
Method measures the area of the bonded zone of a compression weld by observing the electrical resistance of the weld zone while the load changes from full compression until the joint ruptures under tension. The ratio of bonding force to maximum tensile load varies considerably.
Hordon, M. J.
Electrical resistivity tomography for early vadose leak detection under single shell storage tanks.
National Technical Information Service (NTIS)
This document describes planned testing with Electrical Resistivity Tomography (ERT). It is prepared in support of TTP RL46WT51 Rev. 1, funded by the Tank Focus Area through the Office of Technology Integration. The primary goal of the testing for fiscal ...
S. M. Narbutovskih
Urban archaeological investigations using surface 3D Ground Penetrating Radar and Electrical Resistivity Tomography methods
Ongoing and extensive urbanisation, which is frequently accompanied with careless construction works, may threaten important archaeological structures that are still buried in the urban areas. Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) methods are most promising alternatives for resolving buried archaeological structures in urban territories. In this work, three case studies are presented, each of which involves an
Nikos Papadopoulos; Apostolos Sarris; Myeong-Jong Yi; Jung-Ho Kim
Electrical contact resistance as a diagnostic tool for MEMS contact interfaces
The electrical contact resistance (ECR) was evaluated as an in situ diagnostic tool for the contact interface behavior of microelectromechanical systems (MEMS). Special polycrystalline silicon (polysilicon) MEMS devices fabricated by surface micromachining were used to study polysilicon\\/native oxide\\/polysilicon contact interfaces. ECR measurements obtained during monotonic contact loading and unloading and cyclic contact loading are interpreted in the context of a
Ari Lumbantobing; Lior Kogut; Kyriakos Komvopoulos
Relationship between Electrical Resistance Measurements and Microradiographic Variables during Remineralization of Softened Enamel Lesions
The purpose of this study was to investigate the relationship between electrical resistance (ECM) measurements and microradiographic variables during remineralization of softened enamel lesions. Sound bovine enamel blocks were demineralized and, subsequently, were remineralized for 3, 4, 5, 7 or 14 days. All the specimens were assessed by ECM and transversal microradiography. The mean ECM values in each group increased
Jing Wang; Yoshiko Someya; Daisuke Inaba; Chris Longbottom; Hideo Miyazaki
Change in electrical resistivity and thermo-emf during the deformation of iron saturated with hydrogen
The electrical resistivity and thermo-emf were determined on wire specimens of Armco iron (i mm in diameter, 200 mm long) after annealing in vacuo at 930~ for 1 h. The specimens were deformed in air and during saturation with hydrogen on a laboratory testing machine at a rate of 2 mm\\/min. A 26% solution of sulfuric acid was used to
M. M. Shved; I. S. Slabkovskii; N. Ya. Yaremchenko; R. S. Kozemchuk; B. M. Yatsyk
Assessment of the performance and reliability of older ERW (electric resistance welding) pipelines
On December 24, 1988, a failure occurred in the Ozark Pipeline System in Maries County, Missouri, and resulted in a spill of over 800,000 gallons of crude oil, causing serious contamination of the Gasconade and Missouri Rivers. The pipeline had been in operation since 1949 and the failure occurred in a section of steel pipe produced by electric resistance welding
R. J. Fields; E. N. Pugh; D. T. Read; J. H. Smith
The role of electrical resistance tomography in the U.S. nuclear waste site characterization program
Several tests are being conducted in the densely welded Topopah Springs tuff within Yucca Mountain, Nevada to study the thermomechanical and thermo-hydrological behavior of this horizon and its suitability as a storage unit of the high level nuclear waste for the USA. One of the methods used to monitor the hydraulic response of the rockmass is electrical resistance tomography (ERT).
W D Daily; A Ramirez
An integration of aeromagnetic and electrical resistivity methods in dam site investigation
Aeromagnetic map and electrical resistivity sounding data obtained along eight traverses were examined at two sites across the Katsina-Ala River. The principal goals of this exercise were to define depths to the bedrock, bedrock relief, geologic structures, define the nature of the superficial deposit, and select probable minor and major axes for hydroelectric power dams. The aeromagnetic map shows that
Adebayo Aina; M. O. Olorunfemi; J. S. Ojo
Electric Pulse Induced Resistive Switching, Electronic Phase Separation, and Possible Superconductivity in a Mott insulator
Metal-insulator transitions (MIT) belong to a class of fascinating physical phenomena, which includes superconductivity, and colossal magnetoresistance (CMR), that are associated with drastic modifications of electrical resistance. In transition metal compounds, MIT are often related to the presence of strong electronic correlations that drive the system into a Mott insulator state. In these systems the MIT is usually tuned by
C. Vaju; L. Cario; B. Corraze; E. Janod; V. Dubost; T. Cren; D. Roditchev; D. Braithwaite; O. Chauvet
Effects of scandium addition on electrical resistivity and formation of thermal hillocks in aluminum thin films
This study investigates the effects of doping aluminum (Al) films with minor amounts of scandium (Sc) on the electrical resistivity and the formation of thermal hillocks. The pure Al and Al�Sc films, prepared via sputtering deposition, before and after isochronal annealing are examined using a scanning electron microscope and a transmission electron microscope. In-situ thermal stress analyses of the films
Sheng-Long Lee; Jeng-Kuei Chang; Yin-Chun Cheng; Kent-Yi Lee; Wen-Chi Chen
Monitoring snowmelt induced unsaturated flow and transport using electrical resistivity tomography
The flow and transport of a non-reactive tracer and melt water was monitored in a heterogeneous coarse sandy unsaturated zone in southeastern Norway, during the snowmelt of 2001. Electrical resistivity tomography (ERT) as well as conventional suction cup techniques was employed. A frozen solution of NaBr in water was supplied as a line source on the ground surface above two
Helen K. French; Carol Hardbattle; Andrew Binley; Peter Winship; Leif Jakobsen
Monitoring hydraulic processes with automated time-lapse electrical resistivity tomography (ALERT)
Hydraulic processes in porous media can be monitored in a minimally invasive fashion by time-lapse electrical resistivity tomography (ERT). The permanent installation of specifically designed ERT instrumentation, telemetry and information technology (IT) infrastructure enables automation of data collection, transfer, processing, management and interpretation. Such an approach gives rise to a dramatic increase in temporal resolution, thus providing new insight into
Oliver Kuras; Jonathan D. Pritchard; Philip I. Meldrum; Jonathan E. Chambers; Paul B. Wilkinson; Richard D. Ogilvy; Gary P. Wealthall
Does Temperature Affect Electric Resistivity of Rocks in the Larderello Region.
National Technical Information Service (NTIS)
The geoelectric resistivity method has been applied extensively in the Larderello region since 1950. From 1950--1969, 6,792 vertical electrical soundings (VES) were made with an electrode separation of 2 to 6 km. The more than 300 deep wells drilled in th...
M. Albo G. M. Cameli R. Cataldi
Characterization and monitoring of subsurface processes using parallel computing and electrical resistivity imaging
This newsletter discusses recent advancement in subsurface resistivity characterization and monitoring capabilities. The BC Cribs field desiccation treatability test resistivity monitoring data is use an example to demonstrate near-real time 3D subsurface imaging capabilities. Electrical resistivity tomography (ERT) is a method of imaging the electrical resistivity distribution of the subsurface. An ERT data collection system consists of an array of electrodes, deployed on the ground surface or within boreholes, that are connected to a control unit which can access each electrode independently (Figure 1). A single measurement is collected by injecting current across a pair of current injection electrodes (source and sink), and measuring the resulting potential generated across a pair of potential measurement electrodes (positive and negative). An ERT data set is generated by collecting many such measurements using strategically selected current and potential electrode pairs. This data set is then processed using an inversion algorithm, which reconstructs an estimate (or image) of the electrical conductivity (i.e. the inverse of resistivity) distribution that gave rise to the measured data.
Johnson, Timothy C.; Truex, Michael J.; Wellman, Dawn M.; Marble, Justin
Te+ implanted silicon structure and electrical resistance dependence on high frequency electromagnetic field annealing
NASA Astrophysics Data System (ADS)
A strong dependence of the electrical resistance of Te+ implanted (100) silicon was established on annealing by high-frequency (0.45 MHz) electromagnetic field for 30 and 60 minutes. The implantation was performed at 50 keV and fluence of 1�1017 cm-2. Cross-sectional high-resolution transmission electron microscopy of the 30 minutes treated samples shows a planar network of amorphous nanoclusters embedded in the amorphous silicon layer created by the implantation. As a result of a 60 minutes high-frequency electromagnetic field treatment, the nanoclusters formation dynamics changes and larger individual nanoclusters separated by highly resistive areas of amorphous silicon are formed. Crystallization of some of the nanoclusters is also observed. The structural changes are correlated with the corresponding electrical resistance measured by alternative current impedance spectroscopy at frequencies of 1 Hz up to 100 KHz. After 30 minutes treatment, the sample electrical resistance dropped by about four orders of magnitude as compared to the as-implanted sample. The situation after 60 minutes treatment is totally different: the sample resistance increased by about seven orders of magnitude in the low-frequencies range, as compared to the as-implanted sample. In the high-frequencies range the increase is about three orders of magnitude.
Kalitzova, M.; Gesheva, K.; Vlakhov, E.; Marinov, Y.; Ivanova, T.; Lebedev, O.
Aerodynamic resistance reduction of electric and hybrid vehicles
NASA Technical Reports Server (NTRS)
The generation of an EHV aerodynamic data base was initiated by conducting full-scale wind tunnel tests on 16 vehicles. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current 4-passenger prototype automobile which was designed with aerodynamics as an integrated parameter. Characteristic effects of aspect ratio or fineness ratio which might appear if electric vehicle shape proportions were to vary significantly from current automobiles were identified. Some preliminary results indicate a 5 to 10% variation in drag over the range of interest. Effective drag coefficient wind-weighting factors over J227a driving cycles in the presence of annual mean wind fields were identified. Such coefficients, when properly weighted, were found to be from 5 to 65% greater than the zero-yaw drag coefficient in the cases presented. A vehicle aerodynamics bibliography of over 160 entries, in six general categories is included.
Roles apparent resistivity amplitude and phase play in an aquifer's electrical-hydraulic conductivity correlation
NASA Astrophysics Data System (ADS)
This paper argues how the spectral characteristics of two borehole apparent resistivity traces further corroborate two statistically significant electrical-hydraulic (eh) conductivity correlations previously reported in Nevada's fractured welded tuffs. Even though the eh conductivity correlation is positive in one borehole and negative in the other, as explained by low pore water electrical conductivity and the absence or presence of alteration minerals, both apparent resistivity amplitude spectra are identically power-law structured. This is interpreted to mean that eh flow is occurring along rock fractures of a common regional fractal dimension. Furthermore, both apparent resistivity phase spectra are strikingly linear, as mandated by the condition of incompressible fluids. Linear phase implies a groundwater flow that is geostatistically nonstationary in the wide sense, a complication normally not considered by hydrogeologists.
Purvance, David T.
On electrical resistivity of AISI D2 steel during various stages of cryogenic treatment
NASA Astrophysics Data System (ADS)
The effect of dislocation densities and residual stresses is well known in tool steels. Measurement of electrical resistivity in order to monitor dislocation densities or residual stresses has seldom been used in investigating the effect of cryogenic treatment on tool steels. Monitoring residual stresses during cryogenic treatment becomes important as it is directly related to changes due to cryogenic treatment of tool steels. For high carbon high chromium (HCHC- AISI D2) steels, not only wear resistance but dimensional stability is an important issue as the steels are extensively used in dies, precision measuring instruments. This work comprises of study of measurement of electrical resistivity of AISI D2 steel at various stages of cryogenic treatment. Use of these measurements in order to assess the dimensional stability of these steels is discussed in this paper.
Lomte, Sachin Vijay; Gogte, Chandrashekhar Laxman; Peshwe, Dilip
3D Electrical Resistivity Imaging to Predict Slope Failure in USM Campus, Penang, Malaysia
NASA Astrophysics Data System (ADS)
3D electrical resistivity imaging was carried out to monitor slope failure in the USM campus. The natural disasters that occur suddenly such as landslides can cause loss of life, and money by damaging roads and cars. The prediction of a landslide before it occurs will reduce or stop these hazards. Geophysical techniques can be used to image slopes and monitor slope failure. The geophysical technique that was used in this study is electrical resistivity imaging. The results from the resistivity sections show that there are two different regions made up of granite, and sand zone. The results show that there are two factors which make the landslide possible. The first factor is the subsurface boulders and the other factor is saturated sand which may results subsidence of the surface.
Moussa, Hussein A.; Nawawi, Mohd M. N.; Abdullah, Khiruddin
Electrical resistivity investigations for guiding and controlling fresh water well drilling in semi-arid region in Khanasser Valley, Northern Syria
NASA Astrophysics Data System (ADS)
Electrical resistivity survey is conducted in the Khanasser Valley, considered as a semi-arid region in Northern Syria, to guide and control fresh water well drilling. Vertical Electrical Soundings (VES) are carried out near the existing wells, which were also used to measure salinity and conductivity of water samplings. Resistivity and hydrogeological data combination made it possible to establish empirical relationships between earth resistivity, water resistivity, and the amount of total dissolved solids (TDS). These relationships are used in the present research in order to follow the TDS salinity variations, both in lateral and depth directions, along the longitudinal profile LP3, located in Khanasser Valley. Apparent salinity map under this profile is established for Quaternary and Paleogene deposits, and boundaries of suitable areas for fresh water well drilling in the totality of the Khanasser Valley are drawn. It was shown that excessive fresh-water depletion may affect the groundwater quality by upward seepage of saline water. Therefore, it is important to keep the fresh-salt water interface in a stationary situation. The geoelectrical methods widely contribute in determining the position of such interface, and can be easily applied in similar arid areas.
Asfahani, Jamal
Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements
The mechanical properties in superalloys are controlled by the distribution of the {gamma}{prime} precipitate phase. Electrical measurements have been shown to be sensitive to certain aspects of the precipitation process and show promise for predicting the evolving microstructural state in superalloys. Aging experiments were conducted on Waspaloy samples for temperatures between 600 and 950 C for times ranging from 2min to 500h. Particle size distributions were obtained by modeling of small angle scattering (SAS) data, whereas, small precipitate size information, strain, and lattice mismatch data were obtained from X-ray diffraction. The microstructural information was then used to create a figure of merit of electron scattering intended to correlate electrical properties to the precipitate microstructure. The proposed figure of merit shows an empirical correlation with the electrical resistivity data, demonstrating the sensitivity of the resistivity measurements to the precipitation process and coarsening behavior.
Whelchel, R. [Georgia Institute of Technology; Gerhardt, Dr. Rosario [Georgia Institute of Technology; Littrell, Ken [ORNL
Global Transcriptional Profiling of Longitudinal Clinical Isolates of Mycobacterium tuberculosis Exhibiting Rapid Accumulation of Drug Resistance
The identification of multidrug resistant (MDR), extensively and totally drug resistant Mycobacterium tuberculosis (Mtb), in vulnerable sites such as Mumbai, is a grave threat to the control of tuberculosis. The current study aimed at explaining the rapid expression of MDR in Directly Observed Treatment Short Course (DOTS) compliant patients, represents the first study comparing global transcriptional profiles of 3 pairs of clinical Mtb isolates, collected longitudinally at initiation and completion of DOTS. While the isolates were drug susceptible (DS) at onset and MDR at completion of DOTS, they exhibited identical DNA fingerprints at both points of collection. The whole genome transcriptional analysis was performed using total RNA from H37Rv and 3 locally predominant spoligotypes viz. MANU1, CAS and Beijing, hybridized on MTBv3 (BuG@S) microarray, and yielded 36, 98 and 45 differentially expressed genes respectively. Genes encoding transcription factors (sig, rpoB), cell wall biosynthesis (emb genes), protein synthesis (rpl) and additional central metabolic pathways (ppdK, pknH, pfkB) were found to be down regulated in the MDR isolates as compared to the DS isolate of the same genotype. Up regulation of drug efflux pumps, ABC transporters, trans-membrane proteins and stress response transcriptional factors (whiB) in the MDR isolates was observed. The data indicated that Mtb, without specific mutations in drug target genes may persist in the host due to additional mechanisms like drug efflux pumps and lowered rate of metabolism. Furthermore this population of Mtb, which also showed reduced DNA repair activity, would result in selection and stabilization of spontaneous mutations in drug target genes, causing selection of a MDR strain in the presence of drug pressures. Efflux pump such as drrA may play a significant role in increasing fitness of low level drug resistant cells and assist in survival of Mtb till acquisition of drug resistant mutations with least fitness cost.
Chatterjee, Anirvan; Saranath, Dhananjaya; Bhatter, Purva; Mistry, Nerges
Gene and cytokine profile analysis of macrolide-resistant Mycoplasma pneumoniae infection in Fukuoka, Japan
Background Recent epidemiologic data suggest that the prevalence of macrolide resistant Mycoplasma pneumoniae (MR-M. pneumoniae) is increasing rapidly worldwide. This study assessed the present status of M. pneumoniae infection in Japan and clinical end-points to distinguish children with MR-M. pneumoniae. Methods During an outbreak of M. pneumoniae infections in Fukuoka, Japan in 2010�11, a total of 105 children with clinically suspected M. pneumoniae infection were enrolled. M. pneumoniae was analyzed for macrolide resistance in domain V of the 23S rRNA gene. Sixty -five patients with PCR positive for M. pneumoniae were analyzed with regard to clinical symptoms, efficacy of several antimicrobial agents and several laboratory data. Results Causative pathogens were detected in 81.0% (85 of 105) and M. pneumoniae was identified 61.9% (65 of 105). The resistance rate of M. pneumoniae was 89.2% (58 of 65) in this general pediatric outpatient setting. Patients infected with MR-M. pneumoniae showed longer times to resolution of fever and required frequent changes of the initially prescribed macrolide to another antimicrobial agent. We observed three different genotypes of M. pneumoniae including the rarely reported A2063T mutation (A2063G: 31 strains, A2063T: 27 strains, no mutation: 7 strains). Drug susceptibility testing showed different antimicrobial susceptibility profiles for each genotype. Serum IFN-gamma, IL-6 and IP-10 levels were higher in patients with MR-genotypes than in those infected with no-mutation strains (p?0.001). Conclusions Macrolide resistance is more common than previously thought and a small epidemic of rarely reported A2063T mutation was observed in Fukuoka, Japan. Furthermore our results reveal the possibility that levels of certain inflammatory cytokines may be a candidate to predict MR-M.pneumoniae infection.
Electrical Insulating and Heat-Resistive Properties of PDMS-TEOS Hybrid with Different Molar Ratio of TEOS to PDMS
The hybrids prepared from polydimethylsiloxane (PDMS) and tetraethoxysilane (TEOS) have been well known to be rubbery hybrid materials. In this report, the authors have investigated the electrical insulating and heat resistive properties of the hybrids by changing the molar ratio of TEOS to PDMS. The electrical insulating properties are evaluated by volume resistivity and AC breakdown strength at room temperature.
Makoto Sugiura; Fumitoshi Imasato; Atsushi Ohno; Yusuke Aoki; Shuhei Nakamura; Tetsushi Okamoto; Takuya Shindou
Anomalous pressure dependence of the electrical resistance and thermal expansion of UGe2 in the paramagnetic state
The electrical resistivity of single-crystalline UGe2 has been measured under high pressure. It is found that the