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Decarbonation of MgAl-LDHs (layered double hydroxides) using acetate-buffer/NaCl mixed solution.
By using acetate-buffer (sodium acetate and acetic acid)/NaCl mixed solutions, the deintercalation of carbonate ions (CO(2-)3) was conducted on MgAl--LDHs at different Mg/Al ratios-LDH2 (LDH with Mg/Al approximately 2) and LDH3 (LDH with Mg/Al approximately 3). When only an acetate-buffer solution was used, decarbonation did not take place even if the buffer solution was made acidic enough to dissolve LDH itself; however, the addition of NaCl to the buffer solution caused deintercalation of the carbonate ions from the MgAl-LDHs and the reaction was conducted without any morphological and weight change at 25 degrees C. Under the optimum conditions, full decarbonation was attained for the two MgAl-LDHs in minutes, and the obtained LDHs contained Cl(-) in the interlayer space without incorporation of any acetate anions due to their extremely low anion selectivity of acetate ion. The allowable range for the concentration of the decarbonation solution is wide, and the change in pH due to the decarbonation reaction is slight because of the buffering effect. The decarbonation was affected by the Mg/Al ratio of the LDH; i.e., the present LDH2 was slightly more difficult to decarbonate than LDH3, probably due to the higher layer-charge density of LDH2. PMID:18377921
Iyi, Nobuo; Sasaki, Takayoshi
Electrochemical study of carbon steel corrosion in buffered acetic acid solutions with chlorides and H 2S
Microsoft Academic Search
In this work, the corrosion behavior of SAE 1018 carbon steel in buffered acetic acid (HAc) solutions containing chlorides, with and without H2S, was studied. Polarization curves obtained by different electrochemical techniques, indicate negligible modification of anodic slopes when adding H2S; however, the cathodic branch is more sensitive showing an accelerated reduction reaction in the presence of H2S. Interface characterization
M. A. Veloz; I. GonzÃlez
Second Dissociation Constant of Bis[(2-hydroxyethyl)amino]acetic Acid (BICINE) and pH of Its Buffer Solutions from 5 to 55 ¯C
The values of the second dissociation constant, K\\u000a 2, and related thermodynamic quantities of the ampholyte bis[(2-hydroxyethyl)amino]acetic acid (BICINE) have been determined at temperatures from 5 to 55 ?C. The pH values of six equimolal buffer solutions, and four buffer solutions having ionic strengths (I = 0.16 mol?kg?1) similar to those in blood plasma, have been evaluated at 12 temperatures
Lakshmi N. Roy; Rabindra N. Roy; Cole E. Denton; Sean R. LeNoue; Chandra N. Roy; Shahaf Ashkenazi; Thomas B. Williams; Daniel R. Church; Michael S. Fuge; Kartik N. Sreepada
Electrodialysis operation with buffer solution
A new method for improving the efficiency of electrodialysis (ED) cells and stacks, in particular those used in chemical synthesis. The process entails adding a buffer solution to the stack for subsequent depletion in the stack during electrolysis. The buffer solution is regenerated continuously after depletion. This buffer process serves to control the hydrogen ion or hydroxide ion concentration so as to protect the active sites of electrodialysis membranes. The process enables electrodialysis processing options for products that are sensitive to pH changes.
Hryn, John N. (Naperville, IL); Daniels, Edward J. (Orland Park, IL); Krumdick, Greg K. (Crete, IL)
Tested Demonstrations: Buffer Capacity of Various Acetic Acid-Sodium Acetate Systems: A Lecture Experiment.
ERIC Educational Resources Information Center
Background information and procedures are provided for a lecture experiment which uses indicators to illustrate the concept of differing buffer capacities by titrating acetic acid/sodium acetate buffers with 1.0 molar hydrochloric acid and 1.0 molar sodium hydroxide. A table with data used to plot the titration curve is included. (JN)
Donahue, Craig J.; Panek, Mary G.
Ultrasonic Relaxation in Aqueous Acetic Acid Solutions.
National Technical Information Service (NTIS)
Ultrasonic absorption measurements have been made in aqueous acetic solutions at 15 to 85 MHz using pulse echo and pulse send-receive techniques. A weighted nonlinear regression method has been developed for the computation of the relaxation parameters. A...
L. G. Jackopin E. Yeager
Enhancement of organic solar cells efficiency with acetic acid modulated poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) buffer layers.
Bulk-heterojunction organic solar cells (OSCs) based on poly(3-hexylthiophene) as a donor material and (6.6) phenyl-C61-butyric acid methyl ester as an acceptor material were investigated using a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) buffer layer that was modulated with acetic acid. The 1.71 x 10(-1) omega x cm resistivity of the pristine PEDOT:PSS film decreased to 2.29 x 10(-2) omega x cm when acetic acid was applied. This modified PEDOT:PSS buffer layer improved the power conversion efficiency (PCE) of OSCs by reducing their already low series resistance and contact resistance. The PCE of OSCs in which the PEDOT:PSS buffer layers had been treated with acetic acid was 2.91%, an improvement over the 1.82% PCE for cells with pristine PEDOT:PSS layers. We optimized the ratio of acetic acid and PEDOT:PSS solution for high PCE of OSCs in this manuscript. The value of this modification method for hole transporting layer is clearly demonstrated and be applicable to other organic devices. PMID:24758027
Oh, Sang Hoon; Heo, Seung Jin; Kim, Hyun Jae
Structural control of mesoporous silicas with large nanopores in a mild buffer solution
In this study, a simple synthesis strategy has been developed for the systematic control of the structure and pore size of the mesoporous silicas through adjusting the ratio of tetraethoxysilane (TEOS) to tetramethoxysilane (TMOS) in a mild acidic buffer solution (acetic acidsodium acetate pH 4.4) or the pH value using poly(ethylene oxide)poly(propylene oxide)poly(ethylene oxide) (EO20PO70EO20) as a structure-directing agent. By
Jian Liu; Lei Zhang; Qihua Yang
RAPID COMMUNICATION: Chemical solution deposition of highly oriented strontium titanate buffer layers for coated conductors
NASA Astrophysics Data System (ADS)
Highly oriented strontium titanate films have been processed on single-crystal lanthanum aluminate and on textured nickel substrates using solution deposition. Precursor solutions of strontium acetate and titanium IV butoxide in acetic acid and methanol were deposited on substrates using spin coating and heat treated in a reducing atmosphere in a single stage to yield textured strontium titanate films. A dense crack-free microstructure with a grain size of the order of 100 nm was achieved along with a texture of the same order as the underlying substrate. These results offer promise for scalable processing of buffer layers on textured nickel.
Sathyamurthy, Srivatsan; Salama, Kamel
Effect of Tris-acetate buffer on endotoxin removal from human-like collagen used biomaterials.
Protein preparation, which has active ingredients designated for the use of biomaterials and therapeutical protein, is obtained by genetic engineering, but products of genetic engineering are often contaminated by endotoxins. Because endotoxin is a ubiquitous and potent proinflammatory agent, endotoxin removal or depletion from protein is essential for researching any biomaterials. In this study, we have used Tris-acetate (TA) buffer of neutral pH value to evaluate endotoxins absorbed on the Pierce high-capacity endotoxin removal resin. The effects of TA buffer on pH, ionic strength, incubation time as well as human-like collagen (HLC) concentration on eliminating endotoxins are investigated. In the present experiments, we design an optimal method for TA buffer to remove endotoxin from recombinant collagen and use a chromogenic tachypleus amebocyte lysate (TAL) test kit to measure the endotoxin level of HLC. The present results show that, the endotoxins of HLC is dropped to 8.3EU/ml at 25mM TA buffer (pH7.8) with 150mM NaCl when setting incubation time at 6h, and HLC recovery is about 96%. Under this experimental condition, it is proved to exhibit high efficiencies of both endotoxin removal and collagen recovery. The structure of treated HLC was explored by Transmission Electron Microscopy (TEM), demonstrating that the property and structure of HLC treated by TA buffer are maintained. Compared to the most widely used endotoxin removal method, Triton X-114 extraction, using TA buffer can obtain the non-toxic HLC without extra treatment for removing the toxic substances in Triton X-114. In addition, the present study aims at establishing a foundation for further work in laboratory animal science and providing a foundation for medical grade biomaterials. PMID:25063101
Zhang, Huizhi; Fan, Daidi; Deng, Jianjun; Zhu, Chenghui; Hui, Junfeng; Ma, Xiaoxuan
Ozone decomposition in aqueous acetate solutions
SciTech Connect
The acetate radical ion reacts with ozone with a rate constant of k = (1.5 +/- 0.5) x 10Z dmT mol s . The products from this reaction are CO2, HCHO, and O2 . By subsequent reaction of the peroxy radical with ozone the acetate radical ion is regenerated through the OH radical. A chain decomposition of ozone takes place. It terminates when the acetate radical ion reacts with oxygen forming the unreactive peroxy acetate radical. The chain is rather short as oxygen is developed, as a result of the ozone consumption. The inhibiting effect of acetate on the ozone decay is rationalized by OH scavenging by acetate and successive reaction of the acetate radical ion with oxygen. Some products from the bimolecular disappearance of the peroxy acetate radicals, however, react further with ozone, reducing the effectiveness of the stabilization.
Sehested, K.; Holcman, J.; Bjergbakke, E.; Hart, E.J.
On the Preparation of Buffer Solutions.
Presents a method, suitable for use on programmable calculators, which allows calculation of the pH and ionic strength (I) of a mixed solution of salts of an acid or amounts necessary to produce a solution of a particular pH and I. Includes limitations when using the calculations described. (SK)
Thomson, Bruce M.; Kessick, Michael A.
A New Strategy to Stabilize Oxytocin in Aqueous Solutions: I. The Effects of Divalent Metal Ions and Citrate Buffer
In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of\\u000a aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+ and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of
Christina Avanti; Jean-Pierre Amorij; Dewi Setyaningsih; Andrea Hawe; Wim Jiskoot; Jan Visser; Alexej Kedrov; Arnold J. M. Driessen; Wouter L. J. Hinrichs; Henderik W. Frijlink
Seed layer, solution concentration and thickness effects on CSD-derived La 2Zr 2O 7 buffer layers for coated conductors
La2Zr2O7\\/NiW buffer layers as very promising buffer layers for coated conductors were fabricated by chemical solution deposition using cheap precursors, La-acetate and Zr-(IV) n-propoxide (70% w\\/w in n-propanol). The effects on the orientation and microstructure of La2Zr2O7 buffer layers, including seed layer, thickness and solution concentration, were investigated. The results showed that insertion of a seed layer could obviously improve
X. B. Zhu; H. C. Lei; D. Q. Shi; L. Zhang; L. Wang; Y. P. Sun; W. H. Song; Z. R. Yang; J. H. Kim; R. Zeng; S. X. Dou; J. Yang; H. W. Gu
Kinetics of iron(III)-catalyzed autoxidation of sulfur(IV) in acetate buffered medium
The kinetics of the environmentally important oxidation of sulfur(IV) by oxygen in acetate buffered medium in the presence\\u000a of Fe(III) and the pH range 5.275.70 has been studied. The results were in agreement with the rate law:\\u000a \\u000a \\u000a \\u000a \\u000a $$ -\\\\hbox{d}[\\\\hbox{S}(\\\\hbox{IV})]\\/\\\\hbox{d}t=k_{0}[\\\\hbox{S}(\\\\hbox{IV})] +k_{\\\\rm Fe}[\\\\hbox{Fe}(\\\\hbox{III})][\\\\hbox{S}(\\\\hbox{IV})][\\\\hbox{H}^{+}]^{-1} $$\\u000a \\u000a \\u000a \\u000a The role of iron(III) appears to be that of production of SO3? radicals in Fe(III)SO32? complex by an
Sreedharan V. Manoj; Punit K. Mudgal; Krishna S. Gupta
Impact of freezing on pH of buffered solutions and consequences for monoclonal antibody aggregation.
Freezing of biologic drug substance at large scale is an important unit operation that enables manufacturing flexibility and increased use-period for the material. Stability of the biologic in frozen solutions is associated with a number of issues including potentially destabilizing pH changes. The pH changes arise from temperature-associated change in the pK(a)s, solubility limitations, eutectic crystallization, and cryoconcentration. The pH changes for most of the common protein formulation buffers in the frozen state have not been systematically measured. Sodium phosphate buffer, a well-studied system, shows the greatest change in pH when going from +25 to -30 degrees C. Among the other buffers, histidine hydrochloride, sodium acetate, histidine acetate, citrate, and succinate, less than 1 pH unit change (increase) was observed over the temperature range from +25 to -30 degrees C, whereas Tris-hydrochloride had an approximately 1.2 pH unit increase. In general, a steady increase in pH was observed for all these buffers once cooled below 0 degrees C. A formulated IgG2 monoclonal antibody in histidine buffer with added trehalose showed the same pH behavior as the buffer itself. This antibody in various formulations was subject to freeze/thaw cycling representing a wide process (phase transition) time range, reflective of practical situations. Measurement of soluble aggregates after repeated freeze-thaw cycles shows that the change in pH was not a factor for aggregate formation in this case, which instead is governed by the presence or absence of noncrystallizing cryoprotective excipients. In the absence of a cryoprotectant, longer phase transition times lead to higher aggregation. PMID:20039442
Kolhe, Parag; Amend, Elizabeth; Singh, Satish K
Solution behavior and surface properties of carboxymethylcellulose acetate butyrate
Solution behavior of carboxymethylcellulose acetate butyrate (CMCAB) in acetone and ethyl acetate has been investigated by\\u000a small-angle X-ray scattering (SAXS) and capillary viscometry and correlated with the characteristics of CMCAB films. Viscosity\\u000a and SAXS measurements showed that ethyl acetate is a better solvent than acetone for CMCAB. Thin films of CMCAB were deposited\\u000a onto silicon wafers (Si\\/SiO2) by spin coating.
Jorge Amim Jr; Denise F. S. Petri; Francisco C. B. Maia; Paulo B. Miranda
The buffering capacity of crystalloid and colloid resuscitation solutions.
The buffering capacities of common colloid and crystalloid resuscitation solutions were compared in vitro. An equal volume of each resuscitation solution was titrated above and below its initial pH with 0.14 N sodium hydroxide or 0.11 N hydrochloric acid. The volume (+/- S.D.) of titration solution necessary to lower the pH one unit (7.1-6.1) in these solutions was less than 0.5 ml for normal saline, less than 0.5 ml for Ringer's lactate, 1.9 +/- 0.1 ml for Plasmalyte-A, 2.0 +/- 0.23 ml for Plasmalyte-R, 8.8 +/- 0.17 ml for human serum albumin (HSA), 45 +/- 2.2 ml for human fresh frozen plasma (FFP), and 50 +/- 6.6 ml for swine FFP. With the method of this in vitro study, human fresh frozen plasma was 25-50 times better as an acid buffer than the crystalloid solutions and approx. 5 times better than human serum albumin (HSA). On an equal volume basis, it was the superior resuscitation solution as a buffer, probably because of combined bicarbonate and protein content. PMID:2989996
Traverso, L W; Medina, F; Bolin, R B
Cloud Point Extraction of Acetic Acid from Aqueous Solution
A new acetic acid separation method was developed through a successful combination of cloud point extraction and complex extraction technology (CPE-SE), where an acetic acid complex compound formed and was solubilized in a surfactant micelle solution, instead of an organic solvent, and then concentrated into one phase by a phase separation process of the CPE technology. Since no organic solvent
Bingjia Yao; Li Yang
Advanced titania buffer layer architectures prepared by chemical solution deposition
Chemical solution deposition (CSD) was used to grow high-quality (100) oriented films of SrTiO3 (STO) on CSD CaTiO3 (CTO), Ba0.1Ca0.9TiO3 (BCT) and STO seed and template layers. These template films bridge the lattice misfit between STO and the nickel-tungsten (NiW) substrate, assisting in dense growth of textured STO. Additional niobium (Nb) doping of the STO buffer layer reduces oxygen diffusion which is necessary to avoid undesired oxidation of the NiW. The investigated templates offer suitable alternatives to established standard buffer systems like La2Zr2O7 (LZO) and CeO2 for coated conductors.
Kunert, J.; Bðcker, M.; Brunkahl, O.; Wesolowski, D.; Edney, C.; Clem, P.; Thomas, N.; Liersch, A.
Role of the buffer solution in the chemical deposition of CdS films for CIGS solar cell applications
In this work, the effects of NH4Ac on the structural and the electro-optical properties of CdS films were investigated. CdS thin films were deposited on soda-lime glass and indium-tin-oxide (ITO) coated glass from a chemical bath containing 0.025 M cadmium acetate, 0 M ~ 0.2 M ammonium acetate, 0.5 M thiourea, and ammonia. Cadmium acetate was the cadmium source, ammonium acetate served as a buffer, ammonia was the complexing agent, and thiourea was the source of sulfur. A commonl- available chemical bath deposition system was successfully modified to obtain precise control over the pH of the solution at 75 ¯C during the deposition. Chemically deposited CdS films were studied by using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), optical transmittance, and electrical resistivity measurements.
Lee, Sooho; Kim, Donguk; Baek, Dohyun; Hong, Byoungyou; Yi, Junsin; Lee, Jaehyeong; Park, Yong Seob; Choi, Wonseok
Finding the Lost Open-Circuit Voltage in Polymer Solar Cells by UV-Ozone Treatment of the Nickel Acetate Anode Buffer Layer.
Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Voc in comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Voc increases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Voc value of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%. PMID:24878826
Wang, Fuzhi; Sun, Gang; Li, Cong; Liu, Jiyan; Hu, Siqian; Zheng, Hua; Tan, Zhan'ao; Li, Yongfang
Automatic initialisation of buffer composition estimation for on-line analysis of unknown buffer solutions.
An automatic initialisation procedure for extracting useful information about buffer composition from a titration experiment is presented in this paper. The initialisation procedure identifies which buffering components are present in the sample from a relatively long list of buffers expected in the system monitored. The procedure determines approximate pKa values of the buffers and evaluates their maximum and minimum concentrations. This information is then used to start an optimisation procedure to fit the model of the buffer components to the titration data and to accurately determine buffer concentrations and pKa values. The procedure has been integrated as a software layer around the buffer capacity optimum model builder (BOMB) that fits a buffer-capacity model to a measured buffer-capacity curve to estimate model properties (pKa values and concentrations). The reliability and robustness of the resulting buffer capacity software (BCS) were tested using a titrimetric analyser simulator (TAS). The BCS was then validated off-line and on-line. PMID:16184364
Zaher, Usama E; Vanrolleghem, Peter A
Pervaporation characteristics of ethylenevinyl acetate copolymer membranes with different composition for recovery of ethyl acetate from aqueous solution
The degree of crystallization, surface property and density of ethylenevinyl acetate (EVA) copolymer membranes with different vinyl acetate (VA) content were measured by differential scanning calorimetry (DSC), contact angle meter and pycnometer. The pervaporation (PV) characteristics of the EVA copolymer membranes for recovery of ethyl acetate (EA) from aqueous EA solutions have been investigated. The separation factor (?) decreased with
Yunxiang Bai; Jinwen Qian; Quanfu An; Zhihui Zhu; Peng Zhang
Preparation and Monitoring of Lead Acetate Containing Drinking Water Solutions for Toxicity Studies.
The protocols developed and implemented to provide lead acetate containing drinking water solutions for animal toxicity studies are described in detail. The procedure involved preparation of 20 liter batches of high concentration lead acetate solution (20...
W. R. Blair K. L. Jewett F. W. Wang S. B. Schiller
Kinetics and mechanism of cymoxanil degradation in buffer solutions.
The kinetics and mechanism(s) of the hydrolytic degradation of a compound are needed to evaluate a compound's abiotic degradation in the environment. In this paper, the hydrolysis of cymoxanil [2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino) acetamide] was investigated in dark sterile aqueous solutions under a variety of pH conditions (pH 2.8-9.2) and temperatures (15-50 degrees C). Hydrolysis of cymoxanil was described by first-order kinetics, which was dependent on pH and temperature. Cymoxanil degraded rapidly at pH 9 (half-life = 31 min) and relatively slowly at pH 2.8 (half-life = 722 days). The effect of temperature on the rate of cymoxanil degradation was characterized using the Arrhenius equation with an estimated energy of activation of 117.1 kJ mol(-)(1). An increase in temperature of 10 degrees C resulted in a decrease in half-life by a factor of approximately 5. Three competing degradation pathways are proposed for the hydrolysis of cymoxanil, with two of the pathways accounting for approximately 90% of cymoxanil degradation. These two pathways involved either initial cyclization to 1-ethyldihydro-6-imino-2,3,5(3H)-pyrimidinetrione-5-(O-methyloxime) (1, Figure 1) or direct cleavage of the C-1 amide bond to form cyano(methoxyimino) acetic acid (7). The third pathway of degradation involved initial cyclization to 3-ethyl-4-(methoxyimino)-2,5-dioxo-4-imidazolidinecarbonitrile (8), which rapidly degrades into 1-ethyl-5-(methoxyimino)-2,4-imidazoline-2,4-dione (9). All three pathways eventually lead to the formation of the polar metabolite oxalic acid. PMID:14709020
Morrica, Patrizia; Trabue, Steven; Anderson, Jeffrey J; Lawler, Sonya; Seccia, Serenella; Fidente, Paola; Swain, R Scott; Mattson, S Lynne
Determination of the Components of Reagent and Buffer Solutions by Flame Photometry.
An analytical process has been worked out for quantitative determination by flame photometry of sodium-potassium tartrate in a Fehling II and Nylander solution, potassium dehydrophosphate, and sodium monohydrophosphate in buffer phosphate solutions used r...
M. Sarsunova S. Szuesova
Characterization of extracellular peroxidases produced by acetate-buffered cultures of the lignin-degrading basidiomycete Phanerochaete chrysosporium.
Growth of Phanerochaete chrysosporium in a nitrogen-limited medium buffered with sodium acetate, instead of the commonly used 2,2-dimethylsuccinate (DMS), resulted in quantitative and qualitative differences in the production of various extracellular lignin peroxidases (LIPs) and manganese-dependent peroxidases (MNPs) involved in lignin degradation. The results indicate that production of LIPs and MNPs can be selectively enhanced by manipulation of culture conditions. Partial N-terminal analyses of the major LIPs and MNPs have made it possible to assign a specific protein to the specific genes and cDNAs that have been reported recently. The LIPs and MNPs differed widely in their ability to decolorize various dyes that are known to be degraded by the lignin degrading enzyme system of P. chrysosporium. PMID:2210334
Dass, S B; Reddy, C A
In situ XANES study of the passive film formed on iron in borate buffer and in sodium acetate
The passive film formed on Fe in pH 8.4 borate buffer (0. 1 36 M) over a broad potential range was characterized by in situ XANES (x-ray absorption near edge structure). On stepping the potential to a value between -0.6 V and +0.4 V (MSE), a passive film forms without detectable dissolution. The edge position indicates that the valence state of Fe in the film is 10 {+-} 5% Fe{sup 2+} and 90 {+-} 5% Fe{sup 3+}. Formation of a passive film at potentials between -0.8 V and -0.65 V is associated with dissolution prior to passivation, and a lower average valence state of 17 {+-} 5% Fe{sup 2+} and 83 {+-} 5% Fe{sup 3+}. At -0.9 V, the Fe did not passivate. The passive film that forms in pH 8.2 sodium acetate (0.1 M) at +0.4 V gives an edge similar to the high potential passive film formed in borate buffer, but dissolution occurs prior to passivation.
Oblonsky, L.J.; Ryan, M.P.; Isaacs, S. [and others
Electrochemical behavior of superconducting Bi{sub 1.4}Pb{sub 0.6}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} in halide-containing acetate buffer
Electrochemical responses of Bi{sub 1.4}Pb{sub 0.6}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} in various buffered halide solutions were studied. Electrochemical surface alterations in the anodic and cathodic potentials were investigated by x-ray diffraction of the surfaces after potentiostatic exposures in the different media. The principal electrochemical reactions involved in alteration of the surface of the superconductor were identified by considering its potentiodynamic response as well as the post-exposure surface constitution. Formation and stability of bismuth and bismuth trioxide were found to be significant in deciding the surface composition after electrochemical exposure in acetate buffer and buffers containing chloride and fluoride. The electrochemical process was controlled by chemical reaction and diffusion in the presence of iodide.
Chattoraj, I.; Pathak, L.C. [National Metallurgical Lab., Jamshedpur (India)
The Determination of the pH of Standard Buffer Solution: A Laboratory Experiment.
Describes an experiment which shows: (1) how measurements of the reaction electromotive force for the cell (Pt/glass/NaCl(aq,m),buffer/AgCl/Ag/Pt) can be utilized in determining the absolute pH of the buffer; and (2) the demonstration of the use of the Debye-Huckel model of an electrolyte solution in solving an important electrochemical problem.
Harris, K. R.
[Influence of buffer solutions on the performance of microbial fuel cell electricity generation].
Microbial fuel cell (MFC) is a potential green technology due to its application in wastewater treatment and renewable energy generation. Phosphate buffer solution (PBS) has been commonly used in MFC studies to maintain a suitable pH for electricity generating bacteria and/or to increase the solution conductivity. However, it has some drawbacks using PBS in MFC: One is that the addition of a high concentration of phosphate buffer in MFCs is expensive, especially for the application in wastewater treatment; the other is that phosphates can contribute to the eutrophication conditions of water bodies if the effluents are discharged without the removal of phosphates. By adding PBS buffer as the comparison, the study investigated the effect of borax buffer and in the absence of buffer on the performance of electrical power, coulomb efficiency and effluent pH. 200 mmol/L PBS was the best, conductivity was 1.973 mS/cm,the maximum power density was 36.4 mW/m2 and the maximum coulomb efficiency was 2.92%, effluent pH was almost at (7.00 +/- 0.05). 100 mmol/L borax buffer solution, conductivity was 1.553 mS/cm; the maximum power density was 26.2 mW/m2 coulomb efficiency of 6.26%, which was 2.14 times to PBS and greatly increased the electron recovery efficiency with the effluent pH was (7.35 +/- 0.05). While free buffer solution conductivity was 0.314 mS/cm, maximum power density was 27.64 mW/m2; coulomb efficiency was 2.82% and the effluent pH of approximately 7.43. The electrolyte which in absence of buffer solution conductivity was 1/6 of adding PBS buffer, 1/5 of borax buffer, while its power density lower 8.76 mW/mr2 than adding PBS and higher 1.24 mW/m2 than borax buffer. The results showed that adding the suitable concentration of borax buffer may improve the electron recovery efficiency and under batch conditions, MFC run successfully without adding buffer solution to MFC. PMID:21780615
Qiang, Lin; Yuan, Lin-jiang; Ding, Qing
Tissue-dissolving capacity and antibacterial effect of buffered and unbuffered hypochlorite solutions
Objective. The goal of this study was to compare the dissolving potential of Dakin's solution with that of equivalent buffered and unbuffered sodium hypochlorite solutions on fresh and decayed tissues. In addition, the antimicrobial effect of Dakin's solution and equivalent unbuffered hypochlorite was tested. Study design. Tissue specimens were obtained from freshly dissected pig palates. Unbuffered 2.5% and 0.5% sodium
Matthias Zehnder; Daniel Kosicki; Hansueli Luder; Tuomas Waltimo
Objective. The goal of this study was to compare the dissolving potential of Dakin's solution with that of equivalent buffered and unbuffered sodium hypochlorite solutions on fresh and decayed tissues. In addition, the antimicrobial effect of Dakin's solution and equivalent unbuffered hypochlorite was tested. Study Design. Tissue specimens were obtained from freshly dissected pig palates. Unbuffered 2.5% and 0.5% sodium
Matthias Zehnder; Daniel Kosicki; Hansueli Luder; Beatrice Sener; Tuomas Waltimo
Post-steam alkaline flooding using buffer solutions
An enhanced oil recovery process is described for formations that have been subjected to steam flooding, the process comprising: injecting into the formation an alkaline solution having a pH of less than 10, wherein the alkaline solution contains a substantially neutral salt; injecting a non-condensible gas into the formation to form in-situ foams for mobility control; and recovering oil displaced by the alkaline solution and gas.
Ziegler, V.M.
Differential effect of buffering agents on the crystallization of gemcitabine hydrochloride in frozen solutions.
The purpose of this study was to evaluate the differential effect of buffering agents on the crystallization of gemcitabine hydrochloride (GHCl) in frozen solutions. Four buffering agents, viz. citric acid (CA), malic acid (MA), succinic acid (SA) and tartaric acid (TA) were selected and their effect on GHCl crystallization was monitored using standard DSC and low temperature XRD. Onset of GHCl crystallization during heating run in DSC was measured to compare the differential effect of buffering agents. Glass transition temperature (Tg'), unfrozen water content in the freeze concentrate and crystallization propensity of the buffering agents was also determined for mechanistic understanding of the underlying effects. CA and MA inhibited while SA facilitated crystallization of GHCl even at 25mM concentration. Increasing the concentration enhanced their effect. However, TA inhibited GHCl crystallization at concentrations <100mM and facilitated it at concentrations ?100mM. Lyophilization of GHCl with either SA or TA yielded elegant cakes, while CA and MA caused collapse. Tg' failed to explain the inhibitory effects of CA, MA and TA as all buffering agents lowered the Tg' of the system. Differential effect of buffering agents on GHCl crystallization could be explained by consideration of two opposing factors: (i) their own crystallization tendency and (ii) unfrozen water content in the freeze concentrate. In conclusion, it was established that API crystallization in frozen solution is affected by the type and concentration of the buffering agents. PMID:24836665
Patel, Mehulkumar; Munjal, Bhushan; Bansal, Arvind K
Preparation of Buffer Layers on Textured Ni5W Substrates by Chemical Solution Deposition Method
CeO2 caped La2Zr2O7 (LZO) buffer layers on cube-textured Ni5W substrates were fabricated by the method of chemical solution deposition(CSD). The orientation of both LZO film and CeO2\\/LZO buffer layer was investigated using conventional XRD and X-ray four circle diffractometers, respectively. The results reveal that both the LZO film on Ni5W substrates and CeO2 film on LZO buffer layer are grown
Yanling Cheng; Hongli Suo; Dong He; Yue Zhao; Mangmang Gao; Min Liu; Ye Shuai; Yonghua Zhu; Rong Wang; Lin Ma; Meiling Zhou
Chemical solution deposition derived buffer layers for MOCVD-grown GaN films
A polymeric Ga-containing liquid precursor was used for the first time to prepare a buffer layer for the growth of GaN by metalorganic chemical vapor deposition. The buffer layer was prepared by chemical solution deposition (CSD), i.e. spincoating the precursor on a sapphire substrate followed by pyrolysis in ammonia. The GaN films were characterized by optical and electron microscopy, XRD
Manfred Puchinger; Thomas Wagner; Paul Fini; David Kisailus; Ulrich Beck; Joachim Bill; Fritz Aldinger; Eduard Arzt; Frederick F Lange
Myocardial protection against global ischemia with Krebs-Henseleit buffer-based cardioplegic solution
PubMed Central
Background The Krebs-Henseleit buffer is the best perfusion solution for isolated mammalian hearts. We hypothesized that a Krebs-Henseleit buffer-based cardioplegic solution might provide better myocardial protection than well-known crystalloid cardioplegic solutions because of its optimal electrolyte and glucose levels, presence of buffer systems, and mild hyperosmolarity. Methods Isolated Langendorff-perfused rat hearts were subjected to either global ischemia without cardioplegia (controls) or cardioplegic arrest for either 60 or 180 min, followed by 120 min of reperfusion. The modified Krebs-Henseleit buffer-based cardioplegic solution (mKHB) and St. Thomas Hospital solution No. 2 (STH2) were studied. During global ischemia, the temperatures of the heart and the cardioplegic solutions were maintained at either 37¯C (60 min of ischemia) or 22¯C (moderate hypothermia, 180 min of ischemia). Hemodynamic parameters were registered throughout the experiments. The infarct size was determined through histochemical examination. Results Cardioplegia with the mKHB solution at moderate hypothermia resulted in a minimal infarct size (5 Ý 3%) compared to that in the controls and STH2 solution (35 Ý 7% and 19 Ý 9%, respectively; P < 0.001, for both groups vs. the mKHB group). In contrast to the control and STH2-treated hearts, no ischemic contracture was registered in the mKHB group during the 180-min global ischemia. At normothermia, the infarct sizes were 4 Ý 3%, 72 Ý 6%, and 70 Ý 12% in the mKHB, controls, and STH2 groups, respectively (P < 0.0001). In addition, cardioplegia with mKHB at normothermia prevented ischemic contracture and improved the postischemic functional recovery of the left ventricle (P < 0.001, vs. STH2). Conclusions The data suggest that the Krebs-Henseleit buffer-based cardioplegic might be superior to the standard crystalloid solution (STH2).
CCMR: Investigation of Potential Buffer Solutions and Concentrations for an Electrochemical Microfluidic Biosensor
NSDL National Science Digital Library
Biosensors are analytical devices that are being used to detect a variety of analytes including pathogens via antibody recognition. Liposomes have been used in the Baeumner research group for signal generation and amplification. In one detection strategy, electrochemical signals are being reported by entrapping a redox couple in the inner cavity of the liposomes and releasing them upon detection of the pathogen. The main task of this research was the optimization of a buffer system that can be used for the entrapment of the redox couple and does not inhibit the oxidation and reduction reactions on a gold electrode. Potassium ferrihexacyanide and potassium ferrohexacyanide (ferri/ferrohexacyanide) were used as redox couple and dissolved in 0.01M bicarbonate buffer, pH 7.0; 0.01M and 0.1M sodium borate buffers, pH 7.0; and 0.01M and 0.1M phosphate buffers, pH 7.0. The current produced by flowing each of these solutions through a 500ö¥m long by 50ö¥m deep channel in polydimethylsiloxane (PDMS) over the interdigitated ultramicroelectrode array (IDUA) was measured using amperometry. The resulting signal peaks created by the redox cycling of ferri/ferrohexacyanide on the electrode were compared. A 10ö¥M solution of ferri/ferrohexacyanide gave signals of 0.44nA in 0.01M phosphate buffer, 0.41nA in sodium borate, 0.37nA in sodium borate diluted in phosphate buffer, and 0.04nA in 0.01M bicarbonate. Since the phosphate buffer cannot be used for liposome synthesis, it was determined that the sodium borate buffer might be the best alternative.
Wiles, Laura K.
Influence of an acetate- and a lactate-based balanced infusion solution on acid base physiology and hemodynamics: an observational pilot study
Background The current pilot study compares the impact of an intravenous infusion of Ringers lactate to an acetate-based solution with regard to acidbase balance. The study design included the variables of the Stewart approach and focused on the effective strong ion difference. Because adverse hemodynamic effects have been reported when using acetate buffered solutions in hemodialysis, hemodynamics were also evaluated. Methods Twenty-four women who had undergone abdominal gynecologic surgery and who had received either Ringers lactate (Strong Ion Difference 28 mmol/L; n?=?12) or an acetate-based solution (Strong Ion Difference 36.8 mmol/L; n?=?12) according to an established clinical protocol and its precursor were included in the investigation. After induction of general anesthesia, a set of acidbase variables, hemodynamic values and serum electrolytes was measured three times during the next 120 minutes. Results Patients received a mean dose of 4,054?Ý?450 ml of either one or the other of the solutions. In terms of mean arterial blood pressure and norepinephrine requirements there were no differences to observe between the study groups. pH and serum HCO3- concentration decreased slightly but significantly only with Ringers lactate. In addition, the acetate-based solution kept the plasma effective strong ion difference more stable than Ringers lactate. Conclusions Both of the solutions provided hemodynamic stability. Concerning consistency of acid base parameters none of the solutions seemed to be inferior, either. Whether the slight advantages observed for the acetate-buffered solution in terms of stability of pH and plasma HCO3- are clinically relevant, needs to be investigated in a larger randomized controlled trial.
Adverse Effect on Bacteria of Peritoneal Dialysis Solutions that Contain Acetate
Peritoneal dialysis solutions which contained 43 mEq per litre of acetate had a greater antibacterial effect than those containing lactate. Bacteria were isolated from 15 separate clinical infections, each caused by Escherichia coli, Pseudomonas sp., or Staphylo-coccus aureus. Incubation in the dialysate made with acetate substantially reduced the number of viable organisms from all but one of the 45 isolates.
James A. Richardson; Kenneth A. Borchardt
EPA Science Inventory
Presented here are the numerical relationships between incident power densities that produce the same average electric field intensity within a chick brain half immersed in buffered saline solution and exposed to a uniform electromagnetic field at carrier frequencies of 50, 147, ...
Effect of 20% in vitro haemodilution with warmed buffered salt solution and cerebrospinal fluid on coagulation
We have conducted an in vitro coagulation study consisting of two separate groups of 20 subjects using the thrombelastograph. In the first group, haemodilution was performed with a physiological balanced salt solution similar to plasma, with the exception of calcium, and buffered to a normal pH (Plasmalyte B) at 37¯C on blood obtained from consenting volunteers. In the second group,
T. G. Ruttmann; M. F. M. James; K. F. Wells
Demixing and gelation behavior of ternary cellulose acetate solutions
The demixing behavior on cooling of ternary systems of cellulose acetate\\/solvent\\/water has been examined for CA concentrations up to 40 wt% CA in several solvents. Cloud points have been measured as a function of cooling rate. The rapid process of liquid - liquid demixing can be discriminated from the slow process of aggregate formation by examining the dependence of the
A. J. Reuvers; F. W. Altena; C. A. Smolders
Mitochondrial Preservation in Celsior Versus Histidine Buffer Solution During Cardiac Ischemia and Reperfusion
Various stressful conditions such as ischemia in cold cardioplegic solutions and reperfusion occur during heart transplantation.\\u000a Since ATP production is essential for the maintenance of contractile activity, mitochondrial function may be a mediator of\\u000a ischemia and ischemia\\/reperfusion (I\\/R) injury. We aimed at testing the ability of two distinct cardioplegic solutions, Celsior\\u000a (Cs) and Histidine Buffer (HBS), to protect rat heart
Marco G. Alves; Paulo J. Oliveira; Rui A. Carvalho
Comparison of three buffer solutions for amino acid derivatization and following analysis by liquid chromatography electrospray mass spectrometry.
For reversed phase separation amino acids are usually derivatized. Several derivatization reactions are carried out at basic pH. In the present work, influence of three basic buffer solutions on liquid chromatography electrospray ionization mass-spectrometric (LC-ESI-MS) analysis of amino acid derivatives was studied. Borate buffer--the most common derivatization buffer--was found to influence ESI ionization up to 23 min retention time. For 9-fluorenylmethylmethoxycarbonyl chloride (Fmoc-Cl derivatization) carbonate buffer should be preferred as it provides higher responses. Hexafluoroisopropanol (HFIP) buffer improves chromatographic peak shapes and responses for diethyl ethoxymethylenemalonate (DEEMM) derivatives. PMID:22673814
Rebane, Riin; Herodes, Koit
The buffering ability of commonly employed cardiopulmonary bypass solutions and alkalizing agents.
This experiment evaluated the hydrogen ion (H+) buffering capacity (BC) of solutions and alkalizing agents employed during cardiopulmonary bypass (CPB). A solution's BC can be determined when a known quantity of H+ is titrated into the solution and the change () in pH (-log of the hydrogen ion activity ([H+]a)) is measured ([H+]a/mmole H+). Eleven solutions were studied:Lactated Ringers (LR), 0.9% NaCl (NS), Plasma-Lyte A, Hespan (6% hetastarch), banked donor blood with citrate phosphate dextrose adenine (CPDA-1), fresh donor blood, THAM, sodium bicarbonate (NaHCO3; 1 mEq/ml), high potassium crystalloid cardioplegic solution (HKCCPS), oxygenated crystalloid cardioplegic solution (OCCPS), and adult crystalloid priming solution (AP) per institutional protocol. The solutions were studied at three temperatures: 37 degrees C, 28 degrees C, and 18 degrees C. The null hypothesis stated there was no difference in the BC of the solutions studied. The solutions were first titrated to the same starting pH of 8.0. The solutions were then titrated with a predetermined concentration of hydrochloric acid (HCl) to a pH of 7.0. A higher quantity of H+ added to a solution indicated a greater ability of that solution to buffer H+ within pH limits of 8.0 to 7.0. The data was analyzed with a two way ANOVA and Bonferonni method. A p value < 0.05 was considered to be statistically significant. The significant results of our study indicated that THAM demonstrated the best BC, followed in decreasing order by NaHCO3, banked blood, fresh blood, HKCCPS, AP, OCCPS, Plasmalyte, LR, Hespan, and NS. PMID:10155362
Crawford, R E; Bliss, L M; Schneider, M E; Phelps, V K; Gilmore, R V; Harris, H K; Westendorff, B E; Koenig, G K; Mashburn, P C; Galloway, M W
Mitigation of chromatography adsorbent lot performance variability through control of buffer solution design space.
The separation of undesired product-related impurities often poses a challenge in the purification of protein therapeutic species. Product-related impurity species, which may consist of undesirable isoforms, aggregated, or misfolded variants of the desired monomeric form of the product, can be challenging to remove using preparatory scale chromatographic techniques. When using anion exchange chromatography to remove undesirable product-related impurities, the separation can be highly sensitive to relatively small changes in the chromatography operating conditions, including changes to buffer solution pH, buffer solution conductivity protein loading, and operating temperature. When performing difficult separations, slight changes to the chemical and physical properties of the anion exchange adsorbent lot may also impact the separation profile. Such lot-to-lot variability may not be readily measurable by the adsorbent manufacturer, since variability can be highly dependent on a specific protein separation. Consequently, manufacturers of chromatographic adsorbents may not be able to control adsorbent lot to lot variability tightly enough to prevent differences from occurring when performing difficult product-related separations at the preparatory scale. In such cases, it is desirable to design a chromatography step with a control strategy which accounts for adsorbent lot to lot variability in the separation performance. In order to avoid the undesired changes to process consistency and product quality, a proper adjustment of the column operating conditions can be implemented, based on the performance of each adsorbent lot or lot mixture. In this work, we describe how the adjustment of the column buffer solution composition can be used as a design space based-control strategy used to ensure consistent process performance and product quality are achieved for an anion exchange chromatography step susceptible to adsorbent lot to lot performance variability. In addition, a "use test" is described that can be employed to determine the optimal buffer solution compositions for different anion exchange adsorbent lots based on the retention volume of the therapeutic protein during a gradient elution. PMID:24169043
Aono, Hiromasa; Iliescu, Ionela; Cecchini, Doug; Wood, Susanne; McCue, Justin T
Evidence that intrinsic iron but not intrinsic copper determines S-nitrosocysteine decomposition in buffer solution
The present experiments were designed to analyze the influence of copper and iron ions on the process of decomposition of S-nitrosocysteine (cysNO), the most labile species among S-nitrosothiols (RSNO). CysNO fate in buffer solution was evaluated by optical and electron paramagnetic resonance (EPR) spectroscopy, and the consequences on its vasorelaxant effect were studied on noradrenaline-precontracted rat aortic rings. The main
Anatoly F. Vanin; Bernard Muller; Jacicarlos L. Alencar; Irina I. Lobysheva; FranÓoise Nepveu; Jean-Claude Stoclet
Thermal decarboxylation of acetate. Part I. The kinetics and mechanism of reaction in aqueous solution
In an effort to understand the kinetics of the thermal decarboxylation of acetate and the role of catalysis, a series of laboratory experiments were conducted to measure the rate constants for the decomposition of acetate (acetic acid and sodium acetate) in the presence of titanium, silica, stainless steel, gold, and magnetite. Activation energies for decarboxylation of acetic acid and acetate ion range from about 8 kcal mol -1 in stainless steel vessels to 69 kcal mol -1 in silica tubes. Extrapolated rate constants at 100¯C for acetic acid differ by more than fourteen orders of magnitude between the experiments conducted in stainless steel and the catalytically least active titanium vessels. Gold and titanium were the least active catalysts for the acetic acid substrate, while stainless steel, silica, and magnetite showed marked catalytic effects. Methane and carbon dioxide were the predominant reaction products of most of these experiments, although mass spectrometric analyses of the gas phase revealed concentrations of carbon monoxide and hydrocarbons (apparent mass range from 29 to 56) amounting to as much as 55 mole percent of the total volatile products, depending on the catalyst. The reactions were generally first order in acetic acid or acetate ion, except for those involving the acid over silica and magnetite which were zero order. These results and the observed effects of variations in surface area are rationalized in terms of changes in the mode of surface catalysis. The mechanistic assignment is simplified by the existence of three unique straight lines on an isokinetic plot ( i.e., activation enthalpy versus activation entropy) which fit all the respective first- and zeroorder reactions. The results described here provide the nucleus for the discussion in Part II of the role of acetate in the primary migration of methane and the transportation of metals in hydrothermal solutions.
Palmer, Donald A.; Drummond, S. E.
Fluoroalcohols as novel buffer components for basic buffer solutions for liquid chromatography electrospray ionization mass spectrometry: retention mechanisms.
Two fluoroalcohols--1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol (HFTB)--were evaluated as volatile buffer acids in basic mobile phases for LC-ESI-MS determination of acidic and basic compounds. HFIP and HFTB as acidic buffer components offer interesting possibilities to adjust retention behavior of different analytes and expand the currently rather limited range of ESI-compatible buffer systems for basic mobile phases. Comparing with commonly used basic buffer components the fluoroalcohols did not suppress the ionization of the analytes, for several analytes ionization enhancement was observed. RP chromatographic retention mechanisms were evaluated and compared to traditional buffer system. All trends in retention of the acidic and basic analytes can be interpreted by the following model: the neutral fluoroalcohols are quite strongly retained by the stationary phase whereas their anions are less retained, thus their amount on the stationary phase is dependent on mobile phase pH; the anions of the fluoroalcohols form ion pairs in the mobile phase with the basic analytes; the fluoroalcohols on the stationary phase surface compete with acidic analytes thereby hindering their retention; the fluoroalcohols on the stationary phase bind basic analytes thereby favoring their retention. PMID:21968346
Kipper, Karin; Herodes, Koit; Leito, Ivo
Kinetics of hydroxyapatite dissolution in acetic, lactic, and phosphoric acid solutions
Summary The present study was undertaken in an attempt to relate the kinetics of hydroxyapatite dissolution to solution parameters, under experimental conditions relevant to the dental caries process. Thus, the dissolution of hydroxyapatite was studied in acetic, lactic, and dilute phosphoric acid solutions having initial pH values from 4 to 6. Rates of dissolution and the corresponding degree of saturation
H. C. Margolis; E. C. Moreno
Synthesis of silver nanoparticles by gamma-ray irradiation in acetic water solution containing chitosan
Silver nanoparticles were synthesized by gamma-ray irradiation of acetic water solutions containing AgNO3 and chitosan. The resulting particles with the average diameter of 4 5 nm were densely dispersed in the solution due to the protection of chitosan chains. UV vis spectra showed that the irradiation dose would affect the size distribution of nanoparticles.
Peng Chen; Linyong Song; Yankuan Liu; Yue-E. Fang
Synthesis of silver nanoparticles by ?-ray irradiation in acetic water solution containing chitosan
Silver nanoparticles were synthesized by ?-ray irradiation of acetic water solutions containing AgNO3 and chitosan. The resulting particles with the average diameter of 45nm were densely dispersed in the solution due to the protection of chitosan chains. UVvis spectra showed that the irradiation dose would affect the size distribution of nanoparticles.
Peng Chen; Linyong Song; Yankuan Liu; Yue-e Fang
A simple cost-saving measure: 2.5% mafenide acetate solution.
The optimal concentration of mafenide acetate solution for use in the treatment of burns is unknown. Despite data supporting the use of a 2.5% solution, 5% formulation is traditionally used, and has been the highest-costing medication on formulary. The aim of the current study is to evaluate cost and patient outcomes associated with a new policy implementing the use of 2.5% solution in burn patients and restricting the 5% formulation to specific indications only. A retrospective review of all patients receiving mafenide acetate solution at a single pediatric burn hospital was performed before and after the initiation of the new policy on the use of 5 vs 2.5% solution. Duration of therapy, adverse events, cost, incidence of wound infection, and bacteremia were analyzed. In 2009, 69 patients were treated with 5% mafenide acetate solution for a total cost of $125,000 ($1811 per patient). In 2010, after the initiation of the policy, 48 patients were treated: 19 received 5% mafenide acetate solution with appropriate indication, whereas the remaining 29 received 2.5% solution for a total cost of $38,632 ($804 per patient). There were no significant changes in the incidence of bacteremia or wound infection. No side effects of either solution were noted. Under certain conditions, a 2.5% mafenide acetate solution appears sufficient. In this multinational pediatric burn hospital, the use of a 2.5% solution was not associated with increased bacteremia or wound infection, and proved to be more cost-effective. PMID:24043238
Ibrahim, Amir; Fagan, Shawn; Keaney, Tim; Sarhane, Karim A; Hursey, Derek A; Chang, Philip; Sheridan, Rob; Ryan, Colleen; Tompkins, Ronald; Goverman, Jeremy
Highly textured La2Zr2O7 buffer layers for YBCO-coated conductors prepared by chemical solution deposition
Recent results of La2Zr2O7 (LZO) buffer layer development for YBa2Cu3O7-x (YBCO-) coated conductors are presented. The major achievement is the development of a new precursor solution starting from 2,4-pentanedionates of lanthanum and zirconium leading to the formation of highly textured LZO buffer layers at low annealing temperatures. The preparation of the precursor solution using only a carboxylic acid as the solvent is simple and can be carried out at room temperature under atmospheric conditions. Reproducible highly textured buffer layers were obtained at annealing temperatures as low as 900 ¯C. The simplicity of the precursor solution preparation and the low annealing temperature (similar to the processing temperature of the YBCO layer) for preparation of an LZO buffer layer are the main advantages of this new process for cost-effective buffer layer deposition on Ni-RABiTS (rolling-assisted biaxially textured substrates).
Knoth, Kerstin; H■hne, Ruben; Oswald, Steffen; Schultz, Ludwig; Holzapfel, Bernhard
Novel post CMP cleaning using buffered HF solution and ozone water
Post chemical mechanical polishing (CMP) cleaning is a key process for copper (Cu) CMP in dual damascene interconnection technology. During the post CMP cleaning, it is an important issue to minimize organic and Cu contamination residues on the dielectric surface. This study proposed a novel post CMP cleaning using HAL buffer hydrofluoric (BHF) solution and ozone (O 3) water cleaning. The performance of the proposed cleaning technology was investigated and compared to conventional citric solution cleaning, which is currently used in post Cu CMP cleaning. From roughness, contamination residues and electrical characteristics, the proposed cleaning technology showed better performance than citric solution cleaning did. This excellent cleaning performance is attributed to the surface etching and contamination elimination effect of HAL BHF solution and O 3 water. Based on the experimental results, the proposed cleaning technology is feasible and superior to the conventional post CMP cleaning.
Yeh, Ching-Fa; Hsiao, Chih-Wen; Lee, Wen-Shan
Salts of aliphatic carboxylic acids: Raman spectra and ion pairing in hydrothermal solutions containing sodium and calcium acetates
A 2.0 molal solution of sodium acetate and 0.1, 0.5, and 1.0 molal solutions of calcium acetate were investigated by Raman spectroscopy from 22 to 400¯C at 1000 and 2000 bar. Experiments were performed in a special hydrothermal pressure vessel fitted with conical diamond windows. In the case of the sodium acetate solution, perturbations of the internal vibrational modes of
John D Frantz
Chemical degradation of 3H-labeled substance P in tris buffer solution.
Substance P (SP) is an important neuropeptide that has been implicated in several physiological processes, and it is necessary to devise an analytical procedure to measure endogenous SP with a combination of high sensitivity and maximum molecular specificity. However, the unique chemical nature of SP (polarity, chemical stability, ease of oxidation, peptide bond lability) plays a significant role in its analysis, such as in receptor assays, immunoassays, chromatography, and mass spectrometry. In this study, we evaluated in polypropylene and glass assay tubes the effects on the recovery and stability of tritiated SP ([3H]SP) of several pertinent experimental parameters such as buffer, pH, multiple freeze-thaw cycles, and incubation temperature and time. Bovine serum albumin (BSA) effectively reduced the absorption of [3H]SP to polypropylene and glass tube surfaces. Following multiple (6X) freeze-thaw cycles of solutions in BSA-precoated tubes, the recovery of radioactive [3H]SP remained high (greater than 75%) after the last cycle, whereas recovery was minimal in uncoated or siliconized glass tubes. A high level of radioactivity recovery was maintained for 14 days of storage of [3H]SP in triethylamine formate (TEAF) solution in BSA-precoated tubes at 4 and -20 degrees C, but decreased at 37 degrees C to less than 80% in only 3 h. Following storage in Tris-HCl (pH 7.4) buffer, a combination of HPLC and mass spectrometric analyses revealed that a significant amount of peptide bond cleavage occurred to produce the two peptides ArgProLys (RPK) and ArgProLysProGlnGln (RPKPQQ), with only a small amount of remaining intact SP. That decomposition was not observed in triethylamine formate TEAF (pH 3.14) buffer solutions. PMID:2461123
Higa, T; Desiderio, D M
A Comparison of Blood Factor XII Autoactivation in Buffer, Protein Cocktail, Serum, and Plasma Solutions
Activation of blood plasma coagulation in vitro by contact with material surfaces is demonstrably dependent on plasma-volume-to-activator-surface-area ratio. The only plausible explanation consistent with current understanding of coagulation-cascade biochemistry is that procoagulant stimulus arising from the activation complex of the intrinsic pathway is dependent on activator surface area. And yet, it is herein shown that activation of the blood zymogen factor XII (Hageman factor, FXII) dissolved in buffer, protein cocktail, heat-denatured serum, and FXI deficient plasma does not exhibit activator surface-area dependence. Instead, a highly-variable burst of procoagulant-enzyme yield is measured that exhibits no measurable kinetics, sensitivity to mixing, or solution-temperature dependence. Thus, FXII activation in both buffer and protein-containing solutions does not exhibit characteristics of a biochemical reaction but rather appears to be a mechanochemical reaction induced by FXII molecule interactions with hydrophilic activator particles that do not formally adsorb blood proteins from solution. Results of this study strongly suggest that activator surface-area dependence observed in contact activation of plasma coagulation does not solely arise at the FXII activation step of the intrinsic pathway.
Golas, Avantika; Yeh, Chyi-Huey Josh; Pitakjakpipop, Harit; Siedlecki, Christopher A.; Vogler, Erwin A.
Recent results of La2Zr2O7 (LZO) buffer layer development for YBa2Cu3O7-x (YBCO-) coated conductors are presented. The major achievement is the development of a new precursor solution starting from 2,4-pentanedionates of lanthanum and zirconium leading to the formation of highly textured LZO buffer layers at low annealing temperatures. The preparation of the precursor solution using only a carboxylic acid as the
Kerstin Knoth; Ruben H■hne; Steffen Oswald; Ludwig Schultz; Bernhard Holzapfel
Hydrolysis of chlorantraniliprole and cyantraniliprole in various pH buffer solutions.
The hydrolysis reactions of [(14)C]-chlorantraniliprole (CLAP) and cyantraniliprole (CNAP) were investigated in sterile buffer solutions at pH 4, 7, and 9. Both compounds displayed similar degradation reactions. The reactions observed were intramolecular cyclizations and rearrangements instead of the anticipated amide hydrolysis to carboxylic acids. Despite a minor difference in their structures, the degradation rates for the two compounds were substantially different. The reaction rates were examined at multiple temperatures to understand the mechanistic aspects of the underlying transformations. Similarities and differences in the hydrolysis behavior of these compounds in various pH values and temperatures are described. PMID:24694259
Sharma, Ashok K; Zimmerman, William T; Lowrie, Chris; Chapleo, Simon
Compatibility studies on solution of polystyrene and polyvinyl acetate blend by density and viscometric methods
Density and viscometric studies were conducted on solutions of blends of polystyrene (PS) and polyvinyl acetate (PVAc) at 30 ¯C in toluene, methyl ethyl ketone (MEK) and tetrahydrofuran (THF) at 2% total solid content. Experimental densities of the blends were found to be lower than the calculated values assuming additivity of volumes of polymers and solvent. The plots of relative
P. A. A. P. Mamza; F. M. Folaranmi
Extraction equilibria of acetic and propionic acids from dilute aqueous solution by several solvents
Extraction equilibria of acetic acid and propionic acid with hexane solutions of trioctyl amine, trioctyl phosphine oxide, and tributyl phosphate were studied. The species formed in the systems were estimated, and the distribution coefficients and the equilibrium constants for these species were evaluated.s
Fahim, M.A. (Univ. of United Arab Emirates, Al-Ain (United Arab Emirates))
An experimental determination of ferrous chloride and acetate complexation in aqueous solutions to 300¯C
The formation of the monochloroiron(II) complex, FeCl +, was studied potentiometrically from 125 to 295¯C at 25 degree intervals at one molal ionic strength in aqueous solutions containing acetic acid, sodium acetate, and sodium trifluoromethanesulfonate. In this method, competition between chloride and acetate ions for the ferrous cation resulted in a change in solution pH, which in turn was monitored in situ in a hydrogen-electrode, concentration cell. A simple empirical approach was used to extrapolate these formation quotients to infinite dilution. The resulting constants proved to be in excellent agreement with previous spectrophotometric results obtained from 25 to 200¯C. Thus, the present study confirms the validity of the conclusions made based on these earlier data concerning the solubility of Fe-containing minerals in hydrothermal brines. Formation constants at infinite dilution for FeCl + are compared with the stability of ferrous acetate and hydroxide complexes. The original potentiometric titration data for ferrous acetate complex formation were combined in a new fit with values determined from the present study at unit ionic strength. Two empirical treatments (namely the isocoulombic method and the temperature/water density function) were considered for fitting and extrapolating the infinite dilution formation constants to 350¯C.
Palmer, Donald A.; Hyde, K. E.
Chelator-buffered nutrient solution is ineffective in extracting Ni from seeds of Alyssum.
Hyperaccumulator species of the genera Alyssum can accumulate 100 times more Ni than normal crops and are therefore used for phytomining and phytoextraction of nickel contaminated soils. Basic studies on the physiology and metal uptake mechanisms of these plants are needed to increase efficiency and uptake capacity of Nickel (Ni) by hyperaccumulators. Recent attempts to disclose if those hyperaccumulator species require higher Ni level than normal plants failed because of the high Ni content in the seeds (7000-9000 microg g(-1)). In this study, we attempted to use chelator buffered nutrient solution to deplete Ni from the seed/seed coat and to obtain low Ni seedlings of Alyssum cultivars to be used in physiology studies. HEDTA-buffered nutrient solution did not deplete Ni from the seeds, perhaps because Ni was mainly localized within the seedling embryonic tissues with greatest Ni enrichment in the cotyledons and hypocotyls. We could not observe any positive correlation between seed fitness and germination capacity with seed Ni content. Investigation of nickel localization in Alyssum seeds using synchrotron X-ray microfluorescence (micro-SXRF) showed that nickel is localized in the embryonic tissues with greatest Ni enrichment observed in the cotyledons and hypocotyl. PMID:21598774
Centofanti, Tiziana; Tappero, Ryan V; Davis, Allen P; Chaney, Rufus L
Chemical Behaviour of Zirconium Oxychloride Octahydrate and Acetic Acid in Precursor Solution for Zirconia Film Formation on Glass
Precursor solutions for zirconia films on soda lime silica glass substrate were prepared from zirconium oxychloride octahydrate (ZOO) and acetic acid (HOAC) maintaining the mol ratios, [HOAC]\\/[ZOO] = 2, 4, 6, 8 and 10. A characteristic UV absorption band at ~280 nm in the ~120 h aged precursor solutions was identified for acetate group of the zirconium acetato complexed species.
Sunirmal Jana; K. Biswas
Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K
The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.
Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.
Catalytic Deprotection of Acetals In Strongly Basic Solution Usinga Self-Assembled Supramolecular 'Nanozyme'
Acetals are among the most commonly used protecting groups for aldehydes and ketones in organic synthesis due to their ease of installation and resistance to cleavage in neutral or basic solution.[1] The common methods for hydrolyzing acetals almost always involve the use of either Broensted acid or Lewis acid catalysts.[2] Usually aqueous acids or organic solutions acidified with organic or inorganic acids have been used for reconversion of the acetal functionality to the corresponding carbonyl group; however, recently a number of reports have documented a variety of strategies for acetal cleavage under mild conditions. These include the use of Lewis acids such as bismuth(III)[3] or cerium(IV),[4, 5] functionalized silica gel, such as silica sulfuric acid[6] or silica-supported pyridinium p-toluene sulfonate,[7] or the use of silicon-based reagents such as TESOTf-2,6-Lutidine.[8] Despite these mild reagents, all of the above conditions require either added acid or overall acidic media. Marko and co-workers recently reported the first example of acetal deprotection under mildly basic conditions using catalytic cerium ammonium nitrate at pH 8 in a water-acetonitrile solution.[5] Also recently, Rao and co-workers described a purely aqueous system at neutral pH for the deprotection of acetals using {beta}-cyclodextrin as the catalyst.[9] Herein, we report the hydrolysis of acetals in strongly basic aqueous solution using a self-assembled supramolecular host as the catalyst. During the last decade, we have used metal-ligand interactions for the formation of well-defined supramolecular assemblies with the stoichiometry M{sub 4}L{sub 6}6 (M = Ga{sup III} (1 refers to K{sub 12}[Ga{sub 4}L{sub 6}]), Al{sup III}, In{sup III}, Fe{sup III}, Ti{sup IV}, or Ge{sup IV}, L = N,N{prime}-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) (Figure 1).[10] The metal ions occupy the vertices of the tetrahedron and the bisbidentate catecholamide ligands span the edges. The strong mechanical coupling of the ligands transfers the chirality from one metal center to the other, thereby requiring the {Delta}{Delta}{Delta}{Delta} or {Lambda}{Lambda}{Lambda}{Lambda} configurations of the assembly. While the 12- overall charge imparts water solubility, the naphthalene walls of the assembly provide a hydrophobic environment which is isolated from the bulk aqueous solution. This hydrophobic cavity has been utilized to kinetically stabilize a variety of water-sensitive guests such as tropylium,[11] iminium ions,[12] diazonium ions,[13] and reactive phosphonium species.[14] Furthermore, 1 has been used to encapsulate catalysts[15] for organic transformations as well as act as a catalyst for the 3-aza-Cope rearrangement of enammonium substrates[16] and the hydrolysis of acid-labile orthoformates.[17] Our recent work using 1 as a catalyst for orthoformate hydrolysis prompted our investigation of the ability of 1 to catalyze the deprotection of acetals (Scheme 1). With the ability of 1 to favor encapsulation of monocationic guests, we anticipated that the rates of acetal hydrolysis could be accelerated by stabilization of any of the cationic protonated intermediates along the mechanistic pathway upon encapsulation in 1. In contrast to the stability of 2,2-dimethoxypropane in H{sub 2}O at pH 10, addition of the acetal to a solution of 1 at this pH quickly yielded the products of hydrolysis (acetone and methanol). Addition of a strongly binding inhibitor for the interior cavity of 1, such as NEt{sub 4}{sup +} (log (K{sub a}) = 4.55), inhibited the overall reaction, confirming that 1 is active in the catalysis.
Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.
Effect of acetic NaF solution on the corrosion behavior of stainless steel orthodontic brackets.
This study assessed the effect of acetic NaF solutions on stainless steel orthodontic brackets. Acetic acid was added to a 0.1% NaF solution to make two solutions, one with pH 3.5 and the other with pH 6. For the two different stainless steel brackets (Tomy, Dentaurum) used in this study, they had a similar elemental composition--except with Mo (molybdenum) in the Tomy bracket. The brackets were then immersed in the prepared test solutions for three days and their responses evaluated. In terms of hydrofluoric acid (HF) concentration, the 0.1%/pH 3.5 solution showed a high HF concentration at 227 ppm, while that of 0.1%/pH 6 solution was very low at 7 ppm. In terms of color change and element release, only the Dentaurum brackets in 0.1%/pH 3.5 solution showed an appreciable color change (deltaE* = 4.0) and released a great amount of elements (Fe, Cr, Ni, Mn) after three days. Otherwise, regardless of pH value and product, only minor color change (deltaE* < 1.0) and negligible element release occurred. In terms of surface modification, no visible changes in surface morphology were observed in any product after immersion in test solutions. PMID:16916238
Jang, Hee-Song; Son, Woo-Sung; Park, Soo-Byung; Kim, Hyung-Il; Yong, Hoon Kwon
Adsorption of N-alkylpyridinium chlorides from water and salt solutions on cellulose acetate ultrafiltration membranes
A study has been made of the adsorption of three homologues in the N-alkylpyridinium chloride series from water and salt solutions, over a wide range of concentrations, on cellulose acetate ultrafiltration membranes, Grades UAM-500 and UAM-150. When adsorption takes place from true solutions, the membrane surface is hydrophobized. In the region of micellar solutions, nonassociated molecules and micelles are adsorbed in the mesopores and supermicropores, forming a mosaic adsorption layer. The thickness of the modifying layer depends on the length of the hydrophobic radical and on the composition of the system.
Klimenko, N.A.; Yaroshenko, N.A.; Kondratova, T.B.
Ester hydrolysis of cellulose acetate and cellulose acetate phthalate in aqueous suspension and solution, and solid state
The increasing usage of aqueous film coating in the pharmaceutical industry has generated interest concerning the stability of polymer film forming agents to ester hydrolysis. Cellulose acetate phthalate (CAP) and cellulose acetate (CA) are examples of polymers which either have or are being considered for film coating applications in the form of aqueous dispersions. This study was undertaken to determine
Thomas Patrick Garcia
The passivity of Type 316L stainless steel in borate buffer solution
The passivity of Type 316 SS in borate buffer solution (pH 8.35), in the steady-state, has been explored using a variety of electrochemical techniques, including potentiostatic polarization, Mott Schottky analysis, and electrochemical impedance spectroscopy. The study shows that the passive film is an n-type semiconductor with a donor density that is essentially independent of voltage across the passive state. The passive current density is also found to be voltage-independent, but the thickness of the barrier layer depends linearly on the applied voltage. These observations are consistent with the predictions of the Point Defect Model, noting that the point defects within the barrier layer of the passive film are metal interstitials or oxygen vacancies, or both. No evidence for p-type behavior was obtained, indicating that cation vacancies do not have a significant population density in the film compared with the two donors (cation interstitials and oxygen vacancies).
Nicic, Igor; Macdonald, Digby D.
Crystallization process of cubic ZrO 2 in calcium acetate solution
Ultrafine powders of cubic ZrO2 were obtained at about 270¯ C by heating hydrated amorphous ZrO2 in greater than 0.2 molal calcium acetate solutions. Ca2+ ions played a role as nucleii for crystallization and were introduced into distinct sites of the crystalline phases, that is, substituted for Zr4+ ions. Mn2+ ions produced almost the same effects on the crystallization of
H. Imishizawa; T. Tani; K. Matsuoka
Control the polymorphism and morphology of calcium carbonate precipitation from a calcium acetate and urea solution
Two metastable calcium carbonate polymorphs, rod-like aragonite and spherical vaterite are selectively formed in this study. Aragonite rods were synthesized from a calcium acetate (Ca(AC)2) and urea (CO(NH2)2) solution under a given condition. In contrast, the addition of polyacrylamide (PAM) and oleic acid results in the formation of spherical vaterite. The morphology, size and crystal structure were characterized by means
Chengyu Wang
Performance of cellulose acetate butyrate membranes in hyperfiltration of sodium chloride and urea feed solution
NASA Technical Reports Server (NTRS)
Cellulose acetate butyrate (CAB) membranes are shown to give high salt and urea rejection with water flux of about 3 gallons/sq ft per day at 600 psig. Membranes prepared from a formulation containing glyoxal show a significant increase in flux and decrease in salt and urea rejection with drying time. Zero drying time gives maximum urea and salt rejection and is therefore most suitable for hyperfiltration of sodium chloride and urea feed solution.
Wydeven, T.; Leban, M.
Efficient quantum dot light-emitting diodes with solution-processable molybdenum oxide as the anode buffer layer
Quantum dot light-emitting diodes (QD-LEDs) are characterized by pure and saturated emission colors with narrow bandwidth. Optimization of the device interface is an effective way to achieve stable and high-performance QD-LEDs. Here we utilized solution-processed molybdenum oxide (MoOx) as the anode buffer layer on ITO to build efficient QD-LEDs. Using MoOx as the anode buffer layer provides the QD-LED with good Ohmic contact and a small charge transfer resistance. The device luminance is nearly independent of the thickness of the MoOx anode buffer layer. The QD-LEDs with a MoOx anode buffer layer exhibit a maximum luminance and luminous efficiency of 5230 cd m-2 and 0.67 cd A-1 for the yellow emission at 580 nm, and 7842 cd m-2 and 1.49 cd A-1 for the red emission at 610 nm, respectively.
He, Shaojian; Li, Shusheng; Wang, Fuzhi; Wang, Andrew Y.; Lin, Jun; Tan, Zhan'ao
Bicarbonate buffered ultrafiltration leads to a physiologic priming solution in pediatric cardiac surgery.
Pediatric cardiopulmonary bypass (CPB) involves a high ratio of priming blood volume to patient blood volume. The composition of packed red blood cells (RBCs) is very unphysiological in terms of acid-base, electrolyte and metabolite values. Therefore, we tested the hypothesis whether ultrafiltration of the prime and replacement with bicarbonate buffered hemofiltration solution (BB-HS) is sufficient for reducing the metabolic load and reaching a physiologic state. For planned surgery of congenital heart defects with cardiopulmonary bypass, 20 CPB circuits were primed with BB-HS, gelatin and 1 unit of RBCs. The fluid was hemofiltrated using an ultrahemofilter at 300 ml/min until approximately 1000 ml of ultrafiltrate was restored with BB-HS. Blood gas analyses were obtained from the priming blood, once before and once after bicarbonate buffered ultrafiltration (BBUF). The measured substrates decreased significantly (P<0.001) after BBUF (glucose from 13.0+/-2.6 to 6.3+/-1.0 and lactate from 3.8+/-1.5 to 2.3+/-1.0 mmol/l). Acid-base parameters increased (P<0.001) to normal or high normal values (pH from 7.01+/-0.09 to 7.68+/-0.12; HCO(3) from 12.1+/-2.4 to 25.4+/-3.6 mmol/l and BE from -15.4+/-3.6 to -0.8+/-3.7 mmol/l). Even the electrolytes sodium, potassium and calcium changed significantly (P<0.001) toward the physiologic range. BBUF is an efficient method of reducing the metabolic load of priming. After BBUF, even the electrolyte and acid-base balance reached a physiologic state, which is important for minimizing electrolyte and acid-base disturbances after initiation of CPB. PMID:18718953
Osthaus, Wilhelm Alexander; Sievers, Jan; Breymann, Thomas; Suempelmann, Robert
Comparison of peak shape in hydrophilic interaction chromatography using acidic salt buffers and simple acid solutions.
The retention and peak shape of neutral, basic and acidic solutes was studied on hydrophilic interaction chromatography (HILIC) stationary phases that showed both strong and weak ionic retention characteristics, using aqueous-acetonitrile mobile phases containing either formic acid (FA), ammonium formate (AF) or phosphoric acid (PA). The effect of organic solvent concentration on the results was also studied. Peak shape was good for neutrals under most mobile phase conditions. However, peak shapes for ionised solutes, particularly for basic compounds, were considerably worse in FA than AF. Even neutral compounds showed deterioration in performance with FA when the mobile phase water concentration was reduced. The poor performance in FA cannot be entirely attributed to the negative impact of ionic retention on ionised silanols on the underlying silica base materials, as results using PA at lower pH (where their ionisation is suppressed) were inferior to those in AF. Besides the moderating influence of the salt cation on ionic retention, it is likely that salt buffers improve peak shape due to the increased ionic strength of the mobile phase and its impact on the formation of the water layer on the column surface. PMID:24813934
Heaton, James C; Russell, Joseph J; Underwood, Tim; Boughtflower, Robert; McCalley, David V
Viscosity Behavior of ?-Amino Acids in Acetate Salt Solutions at Temperatures (303.15 to 323.15) K
Viscosities of l-lysine monohydrochloride, l-histidine, and l-arginine in 1 m (mol ñ kg-1) aqueous solutions of sodium acetate, potassium acetate, and calcium acetate salts has been determined at (303.15, 308.15, 313.15, 318.15, and 323.15) K. The Falkenhagen coefficient, A, and Jones-Dole coefficient, B, relative viscosity, and specific viscosity of the solutions have also been determined using the measured viscosities. The results are interpreted in terms of solute-solute and solute-solvent interactions occurring in the system under investigation and also discussed in terms of the structure-making/breaking ability of the solute in these salt solutions. The structure making/breaking abilities of the solutes in the studied systems are strongly influenced by temperature.
Siddique, Jamal Akhter; Naqvi, Saeeda
A study of the copper electrode behavior in borax buffer solutions containing chloride ions and benzotriazole-type inhibitors by voltammetry and the photocurrent response method
The electrochemical behavior of the Cu electrode in borax buffer solutions containing chloride ions and benzotriazole (BTA)-type inhibitors was studied by voltammetry and the photocurrent response method. A p-type photoresponse was observed from the Cu electrode in the pure borax buffer solutions. However, an n-type photoresponse was observed in chloride-containing borax buffer solutions if the Cl? concentration exceeded 0.08%. The
Guo-Ding Zhou; Hua Shao; B. H. Loo
La 2Zr 2O 7 and CeGdO buffer layers for YBCO coated conductors using chemical solution deposition
Biaxially textured La2Zr2O7 (LZO) and CeGdO (CGO) buffer layers were grown on Ni-RABiTS (rolling-assisted biaxially textured substrates) to obtain suitable buffer layer architectures for YBa2Cu3O7?x (YBCO) coated conductors. Both buffer systems were prepared using newly developed precursor solutions containing a simple carboxylic acid as solvent. Reproducible highly textured LZO buffer layers were obtained at annealing temperatures as low as 900¯C.
Kerstin Knoth; Brigitte Schlobach; Ruben H■hne; Ludwig Schultz; Bernhard Holzapfel
Monolayer formation of luminescent germanium nanoparticles on silica surface in aqueous buffer solution.
The present paper reports monolayer formation of germanium nanoparticles (Ge NPs) on silica substrate. The NPs were prepared by hydride reduction of GeCl4, which is encapsulated with an inverse micelle of dimethyldioctylammonium bromide, with lithium aluminum hydride, and subsequent hydrogermylation of allylamine in the presence of platinum catalyst. The resultant NPs showed the blue photoluminescence property. Due to the terminal amine, the NPs were soluble highly in aqueous buffer solution. To fabricate a monolayer of Ge NPs, the chemical reactivity of the NPs was studied using a multi-functional microarray in which different kinds of siloxane monolayers were periodically aligned on a silica substrate. We observed using fluorescence microscope whether the terminal amines of the NPs recognize the specific monolayers in the microarray. In terms of fluorescence observation, the entire surface of the monolayer-covered microsize-domains emits uniformly the blue light. This suggests a high degree of coverage of the luminescent NPs covering over the monolayer regions in the microarray, and implies the non-occurrence of quenching through energy transfer between adjacent NPs. PMID:24745276
Shirahata, Naoto
Effect of 20% in vitro haemodilution with warmed buffered salt solution and cerebrospinal fluid on coagulation.
We have conducted an in vitro coagulation study consisting of two separate groups of 20 subjects using the thrombelastograph. In the first group, haemodilution was performed with a physiological balanced salt solution similar to plasma, with the exception of calcium, and buffered to a normal pH (Plasmalyte B) at 37 degrees C on blood obtained from consenting volunteers. In the second group, a protein-poor body fluid (cerebrospinal fluid (CSF)) obtained from parturient patients undergoing spinal anaesthesia for Caesarean section was used as the diluent. There were statistically significant differences between the warmed Plasmalyte B treated samples and their untreated controls for all variables measured by the thrombelastograph, except for maximum amplitude, and between the CSF treated samples and their untreated controls for all variables. We conclude that electrolyte and acid-base composition of the diluent fluid had no effect on the observation that crystalloid haemodilution produces hypercoagulability. The marked increase in coagulability produced by addition of CSF cannot be explained on a simple haemodilution basis and confirms previous suggestions of the presence of a procoagulant factor in CSF. PMID:10325846
Ruttmann, T G; James, M F; Wells, K F
Platinum black coated microdisk electrodes for the determination of high concentrations of hydrogen peroxide in phosphate buffer solutions
The performance of a series of platinum black coated microdisk electrodes (Pt-Bs) was investigated in H2O2 solutions over the concentration range 0.1500mM, in phosphate buffer media pH 7. The Pt-Bs were prepared by electrodeposition of Pt onto the surface of microdisk electrodes 12.5?m of nominal radius, from aqueous solutions containing hexachloroplatinic acid. The resulting roughness factors (RF, i.e., the ratio
Aleksandra Kicela; Salvatore Daniele
Pyrite oxidation in carbonate-buffered solution: 2. Rate control by oxide coatings
The kinetic behaviour of pyrite oxidation in the laboratory was studied over a period of about 10,000 hours in reactors through which a carbonate-buffered solution and air (20% O 2) flowed continuously. Three grain size fractions were monitored. The concentration of sulphate and the mass of the effluent solution were measured periodically to calculate oxidation rates. The results indicate that the rates of reaction decreased significantly with time. The rates initially exhibited an inverse dependence on grain size (within 400 h) then became more linear with the square of the inverse grain size at later times (after 8000 h) suggesting a surface-layer control of the reaction with time. Surface analysis by X-ray Photoelectron Spectroscopy revealed the presence of ferric oxide on the pyrite surfaces, and ion boring with auger electron spectroscopy indicated a layer thickness on the order of 0.6 microns on the 215 micron grains. The data are represented by a shrinking core model which includes the effects of the surface rate constant plus the diffusive resistance to oxygen transfer through the accumulating reaction layer as oxidation proceeds. The three grain sizes (representing different specific surface areas) exhibited consistent estimates of the surface rate constant ( Ks = 3.07 æ 10 -6mh-1 Ý 46%) and the diffusion coefficient for oxygen through the oxide layer ( Ds = 1.08 æ 10 -12m2h-1 Ý 30%). The estimated thickness of the oxide layer at the end of the experiment agreed well with the measured value. Oxide accumulation on the pyrite surfaces under neutral pH conditions results in a significant reduction in oxidation rates over time. This behaviour has important implications for the reduction of the rate of release of oxidation products, including hydrogen ions, to environments where sulphide mineral wastes are exposed to the atmosphere.
Nicholson, R. V.; Gillham, R. W.; Reardon, E. J.
Light scattering and membrane formation studies on polysulfone solutions in NMP and in mixed solvents of NMP and ethyl acetate
The relationship between the characteristics of the polymer dope solution and the skin formation mechanism as well as the performance of the asymmetric membrane has been investigated. The solution characteristics have been studied on the polysulfone (PSf) dope solution as a function of the concentrations of both polymer and the cosolvent, ethyl acetate (EA), by dynamic light scattering. An anomalous
Jongok Won; Yong Soo Kang; Hyun Chae Park; Un Young Kim
Effects of solution temperature on electronic properties of passive film formed on Fe in pH 8.5 borate buffer solution
Effects of solution temperature on the electronic properties of passive film formed on Fe in pH 8.5 borate buffer solution were investigated to clarify why the passive current density of Fe increases with solution temperature. The MottSchottky analysis and photocurrent measurement were employed to determine the electronic properties of the film. The MottSchottky analysis and photocurrent measurement revealed that as
Se Jin Ahn; Hyuk Sang Kwon
Solution-processed MoS(x) as an efficient anode buffer layer in organic solar cells.
We reported a facile solution-processed method to fabricate a MoSx anode buffer layer through thermal decomposition of (NH4)2MoS4. Organic solar cells (OSCs) based on in situ growth MoSx as the anode buffer layer showed impressive improvements, and the power conversion efficiency was higher than that of conventional PEDOT:PSS-based device. The MoSx films obtained at different temperatures and the corresponding device performance were systematically studied. The results indicated that both MoS3 and MoS2 were beneficial to the device performance. MoS3 could result in higher Voc, while MoS2 could lead to higher Jsc. Our results proved that, apart from MoO3, molybdenum sulfides and Mo(4+) were also promising candidates for the anode buffer materials in OSCs. PMID:24018132
Li, Xiaodong; Zhang, Wenjun; Wu, Yulei; Min, Chao; Fang, Junfeng
The stability of DLC film on nitrided CoCrMo alloy in phosphate buffer solution
CoCrMo alloy is often used as the material for metal artificial joint, but metal debris and metal ions are the main concern on tissue inflammation or tissue proliferation for metal prosthesis. In this paper, nitrogen ion implantation and diamond like carbon (DLC) film composite treatment was used to reduce the wear and ion release of biomedical CoCrMo substrate. The mechanical properties and stability of N-implanted/DLC composite layer in phosphate buffer solution (PBS) was evaluated to explore the full potential of N-implanted/DLC composite layer as an artificial joint surface modification material. The results showed that the DLC film on N implanted CoCrMo (N-implanted/DLC composite layer) had the higher surface hardness and wear resistance than the DLC film on virgin CoCrMo alloy, which was resulted from the strengthen effect of the N implanted layer on CoCrMo alloy. After 30 days immersion in PBS, the structure of DLC film on virgin CoCrMo or on N implanted CoCrMo had no visible change. But the adhesion and corrosion resistance of DLC on N implanted CoCrMo (N-implanted/DLC composite layer) was weakened due to the dissolution of the N implanted layer after 30 days immersion in PBS. The adhesion reduction of N-implanted/DLC composite layer was adverse for in vivo application in long term. So researcher should be cautious to use N implanted layer as an inter-layer for increasing CoCrMo alloy load carrying capacity in vivo environment.
Zhang, T. F.; Liu, B.; Wu, B. J.; Liu, J.; Sun, H.; Leng, Y. X.; Huang, N.
Solution-processed nickel acetate as hole collection layer for polymer solar cells.
We report efficient polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and indene-C(60) bisadduct (ICBA) with water soluble nickel acetate (NiAc) instead of acidic poly(ethylenedioxythiophene)?:?poly(styrene sulfonate) (PEDOT : PSS) as hole collection layer (HCL). The NiAc layer after thermal annealing at 150 ¯C for 30 min (?-NiAc) shows high transparency with light transmittance better than PEDOT : PSS in the wavelength range of 500-900 nm, high hole mobility of 1.3 æ 10(-3) cm(2) V(-1) s(-1) and suitable energy levels for application as HCL. The power conversion efficiency of the PSC based on P3HT/ICBA with the ?-NiAc anode buffer layer reached 6.08% under the illumination of AM1.5G 100 mW cm(-2), which is among the best efficiencies of the P3HT-based PSCs. This work gives a new option for HCL selection in designing higher efficiency and more stable PSCs. PMID:22825321
Tan, Zhan'ao; Zhang, Wenqing; Qian, Deping; Cui, Chaohua; Xu, Qi; Li, Liangjie; Li, Shusheng; Li, Yongfang
Photoelectrochemical analysis on the passive film formed on Fe20Cr in pH 8.5 buffer solution
The electronic properties of passive film formed on Fe20Cr stainless steel in pH 8.5 buffer solution were examined by the photocurrent measurements of the film. The passive film on Fe20Cr exhibited an n-type semiconductor, which was confirmed by anodic photocurrent. The photocurrent spectrum for the passive films formed on Fe20Cr was almost same in shape to that for the passive
EunAe Cho; HyukSang Kwon; Digby D. Macdonald
Photo-electrochemical analysis of passive film formed on Cr in pH 8.5 buffer solution
The structure and composition of a passive film formed on Cr in pH 8.5 buffer solution were explored through the photo-electrochemical and impedance analysis of the film. The passive film on Cr was confirmed to be a single layer or duplex layers depending on the film formation potential. At low film formation potentials such as ?300 mV versus saturated calomel
JoonShick Kim; EunAe Cho; HyukSang Kwon
Axially-doped silicon nanowire field effect transistors for real-time sensing in physiologically relevant buffer solutions
This paper present the first measurements of chemically-gated axially-doped n+-p'-n+ silicon nanowire FETs and show stable and reproducible transfer characteristics in physiologically relevant buffer solutions (up to 100 mM KCl). The sensitivity of nanowire FETs having bare oxidized and chemically-functionalized surfaces to changes in pH was greatest when the devices were biased in the subthreshold regime during sensing. Silicon nanowire
Wenchong Hu; Xiahua Zhong; T. Morrow; C. D. Keating; S. Eichfeld; J. M. Redwing; T. S. Mayer
High-performance polymer solar cells with solution-processed and environmentally friendly CuOx anode buffer layer.
Highly efficient polymer solar cells (PSCs) are demonstrated by introducing environmentally friendly CuOx as hole extraction anode buffer layer. The CuOx buffer layer is prepared simply via spin-coating 1,2-dichlorobenzene solution of Copper acetylacetonate on the ITO substrate and thermal transformation (at 80 ¯C) in air. Remarkable improvements in the open-circuit voltage (Voc) and short-circuit current density (Jsc) of the PSCs could be achieved upon the introduction of CuOx buffer layer. The study about the effect of CuOx interfacial layer on the device resistances demonstrates that insertion of CuOx layer can decrease the whole resistance of the PSCs. For the devices based on P3HT:PCBM, the power conversion efficiency (PCE) was increased from 2.8% (the reference device without buffer layer) to 4.1% via introduction of CuOx hole extraction layer. The PCE of the PSC was further increased to 6.72% when ICBA used as an alternative acceptor to PCBM. The much higher PCE of 7.14% can be achieved by adopting PBDTTT-C, a low band gap conjugated polymer, as donor material. The results demonstrate that CuOx has great potential as a hole extraction material for highly efficient PSCs. PMID:24094978
Xu, Qi; Wang, Fuzhi; Tan, Zhan'ao; Li, Liangjie; Li, Shusheng; Hou, Xuliang; Sun, Gang; Tu, Xiaohe; Hou, Jianhui; Li, Yongfang
In situ ellipsometric investigation of stainless steel corrosion behavior in buffered solutions with amino acids
The corrosion of metals is associated both with a release of ions and changes in optical surface properties. In this study, these two effects were correlated by a potentiodynamic corrosion test and in situ probing of the surface by ellipsometry. The studies were carried out with stainless steel (SS) AISI 304 and 316 in phosphate buffered saline (PBS) and in
M. V. Vinnichenko; M. T. Pham; T. Chevolleau; L. V. Poperenko; M. F. Maitz
Effect of Initial Buffer Composition on pH Changes During Far-From-Equilibrium Freezing of Sodium Phosphate Buffer Solutions
Purpose. This study aims to assess the pH changes induced by salt precipitation during far-from-equilibrium freezing of sodium phosphate buffers as a function of buffer composition, under experimental conditions relevant to pharmaceutical applicationssample volumes larger than a few microliters, experiencing large degrees of undercooling and supersaturation.
Gerardo Gµmez; Michael J Pikal; NaÚr RodrÚguez-Hornedo
Physical Compatibility of Magnesium Sulfate and Sodium Bicarbonate in a Pharmacy-compounded Bicarbonate-buffered Hemofiltration Solution
PURPOSE To assess the physical compatibility of magnesium sulfate and sodium bicarbonate in a pharmacy-compounded bicarbonate-buffered hemofiltration solution used at the National Institutes of Health Clinical Center (http://www.cc.nih.gov). METHODS Two hemofiltration fluid formulations with a bicarbonate of 50 mEq/L and a magnesium of 1.5 mEq/L or 15 mEq/L were prepared in triplicate with an automated compounding device. The hemofiltration solution with a bicarbonate of 50 mEq/L and a magnesium of 1.5 mEq/L contains the maximum concentration of additives that we use in clinical practice. The hemofiltration solution of 15 mEq/L of magnesium and 50 mEq/L of bicarbonate was used to study the physicochemical properties of this interaction. The solutions were stored without light protection at 22 to 25 ¯C for 48 hours. Physical compatibility was assessed by visual inspection and microscopy. The pH of the solutions was assayed at 3 to 4 hours and 52 to 53 hours after compounding. In addition, electrolyte and glucose concentrations in the solutions were assayed at two time points after preparation: 3 to 4 hours and 50 to 51 hours. RESULTS No particulate matter was observed by visual and microscopic inspection in the compounded hemofiltration solutions at 48 hours. Electrolyte and glucose concentrations and pH were similar at both time points after solution preparation. CONCLUSION Magnesium sulfate (1.5 mEq/L) and sodium bicarbonate (50 mEq/L) were physically compatible in a pharmacy-compounded bicarbonate-buffered hemofiltration solution at room temperature without light protection at 48 hours.
Moriyama, Brad; Henning, Stacey A.; Jin, Haksong; Kolf, Mike; Rehak, Nadja N.; Danner, Robert L.; Walsh, Thomas J.; Grimes, George J.
Restoration of Normal Glutamic Acid Transport in Vitamin B6-Deficient Lactobacillus Plantarum by Acetate, Ammonium, and Vitamin B6.
A vitamin B6-deficiency in Lactobacillus plantarum markedly reduces the amount of glutamate and other amino acids which can be taken up and accumulated from buffered solutions. The capacity for glutamate accumulation is restored to normal levels when acet...
J. T. Holden
Stability of curcumin in buffer solutions and characterization of its degradation products
The degradation kinetics of curcumin under various pH conditions and the stability of curcumin in physiological matrices were investigated. When curcumin was incubated in 0.1 M phosphate buffer and serum-free medium, pH 7.2 at 37¯C, about 90% decomposed within 30 min. A series of pH conditions ranging from 3 to 10 were tested and the result showed that decomposition was
Ying-Jan Wang; Min-Hsiung Pan; Ann-Lii Cheng; Liang-In Lin; Yuan-Soon Ho; Chang-Yao Hsieh; Jen-Kun Lin
Characterization of gold electrodes in phosphate buffered saline solution by impedance and noise measurements for biological applications.
Impedance spectroscopy and noise measurements have been used to study gold electrodes of three different surface areas in phosphate buffered saline (PBS) solution. The gold-PBS solution interface can be modeled by a charge transfer resistance in parallel with an interfacial constant phase element (CPE) which are in series with the solution resistance. The voltage noise fluctuations were analyzed using the fast Fourier transform (FFT) method. It is found that the voltage noise power is characterized by a 1/f(alpha) spectrum in the low frequency range. The value of alpha is observed to be double that of the CPE coefficient beta. The authors suggest a link between the interface impedance and the measured noise. PMID:17946639
McAdams, E T; Jossinet, J; Subramanian, R; McCauley, R G E
A precise ion chromatography method has been developed for the determination of chloride in high ionic strength ammonium acetate solutions (10-5 M-5 M) using sodium carbonate/sodium bicarbonate as eluent. Negative ion electrospray ionization (ESI) mass spectrometry was used for q...
The Effect of Crystallizing and Non-crystallizing Cosolutes on Succinate Buffer Crystallization and the Consequent pH Shift in Frozen Solutions
Purpose To effectively inhibit succinate buffer crystallization and the consequent pH changes in frozen solutions.\\u000a \\u000a \\u000a \\u000a Methods Using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), the crystallization behavior of succinate buffer\\u000a in the presence of either (i) a crystallizing (glycine, mannitol, trehalose) or (ii) a non-crystallizing cosolute (sucrose)\\u000a was evaluated. Aqueous succinate buffer solutions, 50 or 200 mM, at pH values 4.0 or
Prakash Sundaramurthi; Raj Suryanarayanan
Solution of shallow-water carbonates: An insignificant buffer against rising atmospheric CO2
Model predictions suggest that the saturation state of surface ocean waters with respect to carbonate minerals will decline during the twenty-first century owing to increased invasion of atmospheric CO2. As a result, calcareous organisms may have difficulty calcifying, leading to production of weaker skeletons and greater vulnerability to erosion. Alternatively, it has been suggested that there will be no significant impact on coral reef ecosystems because any changes in saturation state and pH will be restored by dissolution of metastable carbonate minerals. To resolve this controversy, we employ a physical-biogeochemical box model representative of the shallow-water ocean environment. Numerical simulations demonstrate that the carbonate saturation state of surface waters could significantly decrease and hamper the biogenic production of CaCO3 during the twenty-first century. Similarly, the average saturation state of marine pore waters could decline significantly, inducing dissolution of metastable carbonate phases within the pore-water sediment system. Such dissolution could buffer the carbon chemistry of the pore waters, but overlying surface waters of reefs and other shallow-water carbonate environments will not accumulate sufficient alkalinity to buffer pH or carbonate saturation state changes owing to invasion of atmospheric CO2.
Andersson, Andreas J.; MacKenzie, Fred T.; Ver, Leah May
Sol-gel preparation of ZnO films with extremely preferred orientation along (002) plane from zinc acetate solution
ZnO films with preferred orientation along the (002) plane were fabricated by the sol-gel method using Zn(CH3COO)2 ñ 2H2O as starting material. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of 2-methoxyethanol and monoethanolamine. ZnO films highly oriented along the (002) plane were obtained by preheating the dip-coating films at temperatures from 200¯
Masashi Ohyama; Hiromitsu Kouzuka; Toshinobu Yoko
Dialysis solutions buffered with lactate or bicarbonate: in vitro comparison of two dialysis solutions on human peritoneal cell growth from ESRD and non-ESRD patients.
In order to evaluate the injury to the mesothelial cell layer during long-term peritoneal dialysis (PD), a dialysis solution (solution A), buffered with bicarbonate, stabilized with 10 mmol/L glycylglycine, and sterilized by filtration (0.22 micron double filtration, pH = 7.4), was compared to traditional heat sterilized lactate solution (solution B) on human mesothelial cell cultures. The respective effects of both solutions were evaluated on first passage cells by 3H thymidine incorporation after 72-, 96-, 120-, and 144-h contact. Mesothelial cells to be cultured were obtained from the omentum biopsies of 7 end-stage renal disease (ESRD) patients (during first peritoneal catheter placement) and from 7 non-ESRD patients undergoing abdominal surgery. Solution A (diluted 1/5) induced a time-dependent stimulation of growth in 6 cases of ESRD patient cell cultures, and inhibition occurred only in 1 case. Stimulation was also observed in 5 non-ESRD patient cell cultures, and no effect occurred in 2 cases. Solution B inhibited growth in all the cultures except in 1 case of an ESRD patient in which no effect was observed. This study shows that solution A induced mesothelial cell proliferation, while an inhibitory effect of solution B was observed. No significant differences were observed between the sensitivity of mesothelial cells from ESRD and non-ESRD patients. Further analysis will be carried out to identify precisely the cause of the differences observed: buffer or glycylglycine by themselves and/or glucose by-products. PMID:7999836
Fougeray, S; Slingeneyer, A; Bastide, J M; Mion, C; Bastide, M
Production of ethyl acetate from dilute ethanol solutions by Candida utilis
The conversion of ethanol to ethyl acetate has an advantage as a method of ethanol recovery since ethyl acetate is amenable to simple solvent extraction. The potential of Candida utilis in this conversion was studied. The kinetics of accumulation of ethanol and ethyl acetate in glucose-grown C. utilis showed that ester formation resulted from ethanol utilization under appropriate aeration and was inhibited by Fe/sup 3 +/ supplementation. Candida utilis converted ethanol to ethyl acetate optimally at pH 5.0-7.0. The five-hour rate of ester production increased as the ethanol concentration increased to 10 g/L, and rapidly declined to zero at concentrations exceeding 35 g/L. Thus, C. utilis has potential to recover dilute ethanol in the form of ethyl acetate.
Armstrong, D.W.; Martin, S.M.; Yamazaki, H.
Platinum black coated microdisk electrodes for the determination of high concentrations of hydrogen peroxide in phosphate buffer solutions.
The performance of a series of platinum black coated microdisk electrodes (Pt-Bs) was investigated in H(2)O(2) solutions over the concentration range 0.1-500mM, in phosphate buffer media pH 7. The Pt-Bs were prepared by electrodeposition of Pt onto the surface of microdisk electrodes 12.5mum of nominal radius, from aqueous solutions containing hexachloroplatinic acid. The resulting roughness factors (RF, i.e., the ratio of the effective surface area to the geometric electrode area) varied between about 10 and 100. The voltammograms recorded with these electrodes, at relatively low H(2)O(2) concentrations (up to 50-100mM), displayed rather steep mixed anodic-cathodic waves, which attained well-defined and stable current plateaus. At the higher hydrogen peroxide concentrations, additional waves both in the anodic and cathodic region or dramatic current drop phenomena were observed. The wave split phenomenon was attributed to the insufficient buffering capacity of the base electrolyte solution within the pores of the platinum black, induced by the large amounts of hydrogen ions produced in the oxidation process. The current drop was attributed to either the formation of oxygen bubbles, which limit diffusion of H(2)O(2) down the pores, or saturation of the active sites responsible for the decomposition of H(2)O(2) to O(2) and H(2)O. The H(2)O(2) concentration at which the above phenomena occurred depended either on the phosphate buffer concentration in the bulk solution or the RF factor of the electrodes. The latter conditions also affected the dynamic range of detection, the sensitivity and low detection limits. Advantageous analytical characteristics were obtained with a Pt-B of RF of about 24, which provided a dynamic range between 0.5 and 230mM, a sensitivity of 1.93(+/-0.06)AM(-1)cm(-2) and a low detection limit of 0.05mM. The reproducibility was also very good, it being within 2-3%. The usefulness of the Pt-Bs for real samples analysis was tested in an antiseptic solution containing large amounts of H(2)O(2). PMID:18970508
Kicela, Aleksandra; Daniele, Salvatore
The corrosion of metals is associated both with a release of ions and changes in optical surface properties. In this study, these two effects were correlated by a potentiodynamic corrosion test and in situ probing of the surface by ellipsometry. The studies were carried out with stainless steel (SS) AISI 304 and 316 in phosphate buffered saline (PBS) and in Dulbecco's modified minimal essential medium (DMEM) at pH 7.4. In both media, 304 steel is more susceptible to corrosion than 316 grade. The 316 steel shows a higher corrosion potential and higher corrosion current density in PBS than in DMEM, for 304 steel this behavior is vice versa. Ellipsometry demonstrated a higher sensitivity than potentiodynamics to surface modification in the cathodic area. In DMEM the removal of a surface layer at negative potential and a further repassivation with increasing potential was characteristic. In PBS a surface layer started to grow immediately. X-ray photoelectron spectra of this layer formed in PBS are consistent with iron phosphate. Its formation is inhibited in DMEM; the presence of amino acids is discussed as the reason.
Vinnichenko, M. V.; Pham, M. T.; Chevolleau, T.; Poperenko, L. V.; Maitz, M. F.
Better preservation of peritoneal morphologic features and defense in rats after long-term exposure to a bicarbonate/lactate-buffered solution.
The long-term effects of a standard lactate-buffered dialysis fluid and a new, two-chamber, bicarbonate/lactate-buffered dialysis fluid (with fewer glucose degradation products and a neutral pH) were compared in an in vivo peritoneal exposure model. Rats were given daily injections, via an access port, of 10 ml of standard solution or bicarbonate/lactate-buffered solution for 9 to 10 wk. The omentum, peritoneum, and mesothelial cell layer were screened for morphologic changes. In addition, the bacterial clearing capacity of the peritoneal cells was studied. Significantly more milky spots and blood vessels were observed in the omenta of animals treated with standard solution (P < 0.03 for both parameters). Electron-microscopic analysis demonstrated dramatic changes in the appearance of the vascular endothelial cells of the milky spots and a severely damaged or even absent mesothelium on the peritoneal membrane of the standard solution-treated animals. In contrast, the mesothelium was still present in the bicarbonate/lactate-buffered solution group, although the cells lost microvilli. Both peritoneal dialysis fluids significantly increased the density of mesothelial cells (per square millimeter) on the surface of the liver and the thickness of the submesothelial extracellular matrix of the peritoneum (both P < 0.04 for both fluids versus control). A significantly better ex vivo bacterial clearing capacity was observed with peritoneal cells from the bicarbonate/lactate-buffered solution group, compared with the standard solution group (P < 0.05 in both experiments). These results demonstrate that instillation of bicarbonate/lactate-buffered solution into rats for 9 to 10 wk preserves both morphologic and immune parameters much more effectively, compared with standard solution. These findings may be of considerable clinical importance. PMID:11729248
Hekking, L H; Zareie, M; Driesprong, B A; Faict, D; Welten, A G; de Greeuw, I; Schadee-Eestermans, I L; Havenith, C E; van den Born, J; ter Wee, P M; Beelen, R H
Electrochemical investigation of copper deposition onto silicon from hydrofluoric acid and buffered hydrofluoric acid solutions
For the fabrication of ULSI circuits, the silicon surface should be free of metallic and particulate contamination and be atomically smooth. Heavy metal contaminants have detrimental effects on the yield of microelectronic processing and reliability of solid state devices by increasing the junction leakage current, degrading the integrity of gate oxide and reducing the oxide breakdown voltage. It has been demonstrated that the contamination level for most metals has to be controlled below 10sp{10} atoms/cmsp2 for sub-quarter micron processing. Some transition and noble metal ions such as copper, silver and gold are known to deposit on silicon surfaces in acidic fluoride based solutions. Among them, copper has been the focus of most research due to the widespread use of copper in microelectronic industry. To investigate the mechanisms by which copper deposits on silicon surfaces in HF and BHF solutions, different electrochemical techniques were used, including dc polarization and ac impedance spectroscopy (EIS). The results of electrochemical measurements, in conjunction with various surface characterization techniques, such as TXRF, AFM and TEM, reveal the rates of reactions that occur at silicon/solution interface can be affected by many factors, such as silicon dopant type and doping levels, ionic strength of electrolytes, illumination conditions and the use of additives. For example, under darkness, the amount of copper deposition is nearly one order of magnitude less than that under illumination for p-type silicon in both HF and BHF solutions and n-type silicon in HF solutions. In BHF solutions, n-type silicon is very close to its flat band condition where illumination plays little role. The addition of copper ions in BHF solutions not only causes metal contamination, but also generates severe surface roughness due to the masking effect of copper on the anisotropic etching of silicon in BHF solutions. Local etching rate of 1nm/min was measured on the silicon sample prepared in 100 ppb Cusp{2+} BHF solutions. Some additives such as surfactants and hydrochloric acid can effectively reduce the reaction rates of silicon corrosion and copper deposition by either blocking the active reaction sites or form copper ion complexes.
Li, Guangming
Solubility of the magnetite + hematite buffer assemblage and iron speciation in sodium chloride solutions at 300¯C and 500 bars
The solubility of the buffer assemblage magnetite + hematite in 0.10, 1.00 and 3.00 mol/kg NaCl solutions with various pH values was determined by use of a Dickson gold cell hydrothermal apparatus at 300¯C and 500 bars. Activities of H + and Cl - in the NaCl hydrothermal solution for each determination were approximated. The experimental results show that the solubility is strongly dependent on the pH of the solutions and appears to have no explicit relation to NaCl molality in acidic solutions. The correlation of the measured solubility with pH at 300¯C suggests a change in Fe speciation in solution at pH ? 5.3-5.4. Treatment of the experimental data by a ridge regression program and an iterative procedure indicates that the dominant species in solution under the run condition are FeOH +, Fe(OH) 3Cl -, Fe(OH) 30 and Fe(OH) 4-. Gibbs free energy of formation for these species at 300¯C and 500 bars were derived: ?Gf, Fe( OH) +0 = -250.4 kJ/mol; ?Gf, Fe( OH) 3Cl-0 = -644.7 kJ/mol; ?Gf, Fe( OH) 300 = -552.6 kJ/mol; and ?Gf, Fe( OH) 4-0 = -652.7 kJ/mol. The present study demonstrates that the change in acidity of hydrothermal ore-forming solutions exerts an important influence on the transport and deposition of Fe in nature.
Zeng, Yishan; Ai, Ruiying; Wang, Fengzhen
Chemical solution deposition of La2Zr2O7 and Y2Ti2O7 buffer layers on NiW substrates
La2Zr2O7 and Y2Ti2O7 buffer layers with similar lattice constant and cubic structure were successfully deposited on NiW(2 0 0) substrates using propionic acid as unique chelate through chemical solution deposition method. The results showed that using 900 ¯C-annealing temperature one could obtain highly (4 0 0)-oriented LZO buffer layers with relatively sharp out-of-plane and in-plane orientation and flat microstructure; However,
X. B. Zhu; Y. P. Sun; W. H. Song; J. Yang; H. W. Gu
Capillary electrophoresiselectrospray ionization mass spectrometry using uncoated fused-silica capillaries and alkaline buffer solution for the analysis of small carboxylic acids
A simple and cost-effective capillary electrophoresis\\/mass spectrometric (CE\\/MS) method for the analysis of small carboxylic acids including succinate, malate, tartarate, maleinate and citrate, is described. All CE\\/MS experiments were performed with uncoated fused-silica capillaries and with alkaline volatile buffer solution (ammonium formate buffer, pH 10). Since sheath liquids have significant effects on the sensitivity in typical CE\\/MS applications, the effects
Hirokazu Sawada; Chika Nogami
An evaluation of MES (2(N?Morpholino)ethanesulfonic acid) and amberlite IRC?50 as pH buffers for nutrient solution studies
All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N?Morpholino)ethanesulfonic
Bruce G. Bugbee; Frank B. Salisbury
Decontamination of aquatic vegetable leaves by removing trace toxic metals during pickling process with acetic acid solution.
The heavy-metal content of aquatic plants is mainly dependent upon their ecological system. This study indicated that although the toxic heavy-metal contents could be above the recommended maximum levels depending upon their concentrations in growing water, they can be decontaminated by pickling with 5% acetic acid solution. Almost all Cd, Hg, Ba, or Sb and 99.5% Pb, 96.7% Ag, or 97.1% Al were removed from Water Spinach leaves by soaking in acetic acid solution. For Water-Shield leaves, almost all Cd, Hg, Pb, Ba, or Sb and 95.0% Ag or 96.1% Al were removed. For Watercress leaves, almost all Cd, Hg, Ba, or Sb and 99.0% Pb or 99.7% Ag were removed. For Water Hyacinth leaves, almost all Cd, Ba, or Sb and 99.0% Hg, 98.5% Pb, 95.0% Ag, or 98.7% Al were removed. PMID:21888602
Wu, Wenbiao; Yang, Yixing
Coagulation of chitin and cellulose from 1-ethyl-3-methylimidazolium acetate ionic-liquid solutions using carbon dioxide.
Chemisorption of carbon dioxide by 1-ethyl-3-methylimidazolium acetate ([C2 mim][OAc]) provides a route to coagulate chitin and cellulose from [C2 mim][OAc] solutions without the use of high-boiling antisolvents (e.g., water or ethanol). The use of CO2 chemisorption as an alternative coagulating process has the potential to provide an economical and energy-efficient method for recycling the ionic liquid. PMID:24115399
Barber, Patrick S; Griggs, Chris S; Gurau, Gabriela; Liu, Zhen; Li, Shan; Li, Zengxi; Lu, Xingmei; Zhang, Suojiang; Rogers, Robin D
Impedance and photoelectrochemical study of surface layers on Cu and Cu10Ni in acetate solution containing benzotriazole
The electrochemical behaviour of Cu and Cu10Ni alloy in 1 M sodium acetate solution, pH 5.8 without and in the presence of benzotriazole (BTAH) was investigated by cyclic voltammetry, photopotential measurements and impedance spectroscopy. Both polarization and impedance studies clearly show that BTAH forms the multilayer structure Cu\\/Cu2O-Cu(I)BTA on the electrode surface at a higher concentration of the inhibitor (cBTAH?1
R. Babi?; M. Metiko-Hukovi?; M. Lon?ar
Comparative spectroscopic and mechanistic study of chelation properties of fisetin with iron in aqueous buffered solutions. Implications on in vitro antioxidant activity.
Fisetin (3,3',4',7-tetrahydroxyflavone) has been investigated for its ability to bind iron in a wide range of pH values of acetate and phosphate buffered solutions. To assess the relevant interactions of iron with fisetin, combined spectroscopic (UV/visible, Raman, MS) and theoretical approaches were used. The chelation sites, stoichiometry, stability and the dependence of the complexes structures on pH were defined. The results pointed to the formation of two iron-fisetin complexes with stoichiometries of 1 : 1 and 1 : 2, depending on the pH. Results of vibrational analysis and theoretical calculations implicated the 3-hydroxyl-4-carbonyl group as a chelating site in acidic media while catechol (3'-hydroxyl-4'-hydroxyl) group was identified as the chelating group in neutral and alkaline media. Determined relative, conditional, stability constants with iron-fisetin were in the range from 6 æ 10(4) dm(3) mol(-1) to 7 æ 10(9) dm(6) mol(-2). Competition experiments demonstrated that fisetin bound iron less strongly than EDTA and citric acid under the investigated experimental conditions. Rate constant values calculated for the fast step of the DPPH reduction for fisetin and the iron-fisetin complex are k(1) = 225.75 dm(3) mol(-1) s(-1) and k(1) = 658.00 dm(3) mol(-1) s(-1). These values fit within the interval of the rate constant values which are typical for antioxidants which have a single polyphenolic nucleus. The equilibrium geometries, optimized at the B3LYP/6-311 + G(d,p) and M06/6-311 + G(d,p) levels of theory, predicted structural modifications between the ligand molecule in the free state and in the complex structure. The theoretical model has been validated by both vibrational and electronic spectroscopies. PMID:21431152
Dimitri? Markovi?, Jasmina M; Markovi?, Zoran S; Brdari?, Tanja P; Filipovi?, Nenad D
Growth and Characterization of La2Zr2O7 Buffer Layers Deposited by Chemical Solution Deposition
The deposition and characterization of La2Zr2O7 thin films deposited by metal-organic decomposition method on both single crystal SrTiO3 and cube textured Ni-5 at.%W substrates are presented. Metal acetylacetonates in propionic acid solution was used. The results showed that LZO films are epitaxially grown with smooth surface with rms roughness around 2 nm. YBa2Cu3O7-? films, deposited by pulsed laser deposition technique on LZO buffer layers, showed critical temperature of 90 K and critical current density in self magnetic field Jc = 1.6 and 13 MA/cm2 at 77 K and 4.2 K, respectively. A better Jc retention in magnetic field for YBCO films deposited on LZO/STO than YBCO on bare STO is observed indicating a rather strong vortex pinning as confirmed by microwave measurements.
Armenio, A. Angrisani; Augieri, A.; Fabbri, F.; Freda, R.; Galluzzi, V.; Mancini, A.; Rizzo, F.; Rufoloni, A.; Vannozzi, A.; Sotgiu, G.; Pompeo, N.; Torokhtii, K.; Silva, E.; Bemporad, E.; Contini, G.; Celentano, G.
Plasma acetate, gluconate and interleukin-6 profiles during and after cardiopulmonary bypass: a comparison of Plasma-Lyte 148 with a bicarbonate-balanced solution
INTRODUCTION: As even small concentrations of acetate in the plasma result in pro-inflammatory and cardiotoxic effects, it has been removed from renal replacement fluids. However, Plasma-Lyte 148 (Plasma-Lyte), an electrolyte replacement solution containing acetate plus gluconate is a common circuit prime for cardio-pulmonary bypass (CPB). No published data exist on the peak plasma acetate and gluconate concentrations resulting from the
Paul G Davies; Balasubramanian Venkatesh; Thomas J Morgan; Jeffrey J Presneill; Peter S Kruger; Bronwyn J Thomas; Michael S Roberts; Julie Mundy
Effect of formation conditions of poly(ethylene- co-vinyl acetate) membrane on the membrane physical structure and pervaporation properties in the recovery of ethyl acetate from aqueous solution
The solution properties, intrinsic viscosity [?] and Huggins constant KH of ethylene-vinyl acetate (EVA) copolymer with 38wt% vinyl acetate content (EVA38) in solvents of chloroform (CF), 1,2-dichloroethane (DCE) and cyclohexane (CYH) were measured by an Ubbelohode viscometer. The physical structure and pervaporation performances of the EVA membranes cast from different solvents were also investigated by wide-angle X-ray diffraction (WAXD), contact
Yun-Xiang Bai; Jin-Wen Qian; Qiang Zhao; Zhi-Hui Zhu; Peng Zhang
Colorimetric recognition of acetate anions in aqueous solution using charge neutral azo derivatives
Two novel highly sensitive colorimetric acetate anion receptors: 4-phenylazo-2-hydroxy-benzaldehyde 4-nitrophenylhydrazone ( 1) and 4-phenylazo-2-hydroxy-benzaldehyde 2,4-dinitrophenylhydrazone ( 2) based on azo derivative have been designed and synthesized. UV-vis experiments show that receptor 1 and receptor 2 can selectively recognize acetate in DMSO and even in 9/1 DMSO/H 2O (v/v) mixtures. Meanwhile the color changes induced by anions can provide a way of detection by 'naked-eye'. The further insights to the nature of interactions between receptor 1, 2 and AcO - have been investigated by 1H NMR titration experiments.
Huang, Weiwei; Li, Yaping; Lin, Hai; Lin, Huakuan
Amidolytic, procoagulant, and activation-suppressing proteins produced by contact activation of blood factor XII in buffer solution.
The relative proportions of enzymes with amidolytic or procoagulant activity produced by contact activation of the blood zymogen factor XII (FXII, Hageman factor) in buffer solution depends on activator surface chemistry/energy. As a consequence, chromogenic assay of amidolytic activity (cleavage of amino acid bonds in s-2302 chromogen) does not correlate with the traditional plasma coagulation time assay for procoagulant activity (protease activity inducing clotting of blood plasma). Amidolytic activity did not vary significantly with activator particle surface energy, herein measured as water adhesion tension ?(o)=?(lv)(o)cos?(a) ; where ?(lv)(o) is pure buffer interfacial tension and ?(a) is the advancing contact angle. By contrast, procoagulant activity varied as a parabolic-like function of ?(o), high at both hydrophobic and hydrophilic extremes of activator surface energy and falling through a broad minimum within a 20(o)<40 mJ/m(2) (55¯(a) < 75¯) range, corroborating and expanding previously-published work. It is inferred from these functional assays that an unknown number of protein fragments are produced by contact activation of FXII (a.k.a. autoactivation) rather than just ?FXIIa and ?FXIIa as popularly believed. Autoactivation products produced by activator particles within the 20(o)<40 mJ/m(2) (55¯(a) < 75¯) surface-energy range suppresses production of procoagulant enzymes by activators selected from the hydrophobic or hydrophilic surface-energy extremes through as-yet unknown biophysical chemistry. Suppression proteins may be responsible for the experimentally-observed autoinhibition of the autoactivation reaction. PMID:21955686
Golas, Avantika; Yeh, Chyi-Huey Joshua; Siedlecki, Christopher A; Vogler, Erwin A
Preparation of DNA films for studies under vacuum conditions. The influence of cations in buffer solutions
Experiments were carried out to determine the optimum conditions required for the preparation of uniform films of supercoiled plasmid DNA to be used in irradiation experiments under high vacuum conditions. Investigations reveal that significant damage to the DNA molecules occurs due to the evacuation process when films were formed from DNA samples in ultra high purity water only. A variety of bases were tested for their possible protective capabilities and sodium hydroxide solution was found to be the most effective in maintaining the supercoiled structure of plasmid DNA during the preparation process. Using a transmission electron microscope we also examined the structure of the DNA films which are formed upon evacuation and how the proposed adducts influence the preparation process. It was found that the addition of bases cause the DNA to aggregate, noting that a base is required for the stability of the DNA molecules. The experimental results presented in this paper show that it may not be possible to perform experiments on so-called pure DNA under vacuum with no stabilizers being added to the sample before the evacuation process.
?mia?ek, M. A.; Balog, R.; Jones, N. C.; Field, D.; Mason, N. J.
The specific influence of carbon dioxide and carbamate compounds on the buffer power and Bohr effects in human haemoglobin solutions
1. The difference of pH (?pH) between human deoxygenated haemoglobin (Hb) and oxygenated haemoglobin (O2Hb) solutions when equilibrated with physiological pressures of carbon dioxide is (experimentally) much less than previously supposed. 2. This smaller ?pH is in contradiction to Wyman's (1948) theoretical calculations, wherein no allowance was made for the specific effect of carbamino-compounds on the amount of base neutralized by haemoglobin. Other previous authorities have also neglected this factor, which when properly allowed for restores the role of carbamino-compounds in CO2 transport practically to that previously estimated by Ferguson & Roughton (1934a, b). 3. At a given pH and PCO2, more CO2 is bound by Hb solutions than by O2Hb, the difference increasing with pH. This result provides further, and seemingly decisive, evidence that the bound-CO2 in the blood other than HCO3 (i.e. x-bound CO2) is oxygen-linked. 4. According to a modified form of the HendersonHasselbalch equation for haemoglobin solutions [Formula: see text]. The value of pK1? is the same in Hb as in O2Hb solution and from the data in 3 is found to have the value 6ñ15 at 37¯ C. 5. The difference between the titration curves of O2Hb and Hb (?X?), at a given pH had been hitherto supposed to be the same in presence of CO2 as in its absence. Our experiments show, however, that ?X? is less in presence of CO2 and at pH > 7ñ5 may even change sign. This paradoxical effect is also explicable, at any rate semi-quantitatively, by the effect of carbamino compounds on the buffer power, according to the theory put forward in the paper. 6. The results show that the buffer power (dB/dpH) of haemoglobin solution under physiological conditions is 20-30% greater than previously estimated, and this also is in line with the new theory. 7. In graphs of total CO2 versus PCO2 in haemoglobin solutions (or blood) it has been customary to suppose that points on straight lines radiating from the origin are points of equal pH. Our data, however, show that the iso-pH lines drawn through the experimental points in the pH range, 7ñ2-7ñ4 do not, when produced as straight lines, pass through the origin, but intercept the PCO2 axis significantly to the right thereof. 8. Calculations indicate that most of the x-bound CO2 in haemoglobin solutions at pH 7ñ2-7ñ4 and at 37¯ C can be accounted for by carbaminobound CO2 without the need of postulating the existence of appreciable amounts of yet other forms, i.e. y-bound CO2, in this range.
Rossi-Bernardi, L.; Roughton, F. J. W.
Effects of injecting calcium-buffer solution on [Ca2+]i in voltage-clamped snail neurons.
We have investigated why fura-2 and Ca(2+)-sensitive microelectrodes report different values for the intracellular free calcium ion concentration ([Ca(2+)]i or its negative log, pCa(i)) of snail neurons voltage-clamped to -50 or -60 mV. Both techniques were initially calibrated in vitro, using calcium calibration solutions that had ionic concentrations similar to those of snail neuron cytoplasm. Pressure injections of the same solutions at resting and elevated [Ca(2+)]i were used to calibrate both methods in vivo. In fura-2-loaded cells these pressure injections generated changes in [Ca(2+)]i that agreed well with those expected from the in vitro calibration. Thus, using fura-2 calibrated in vitro, the average resting [Ca(2+)]i was found to be 38 nM (pCa(i) 7.42 +/- 0.05). With Ca(2+)-sensitive microelectrodes, the first injection of calibration solutions always caused a negative shift in the recorded microelectrode potential, as if the injection lowered [Ca2+]i. No such effects were seen on the fura-2 ratio. When calibrated in vivo the Ca(2+)-sensitive microelectrode gave an average resting [Ca2+]i of approximately 25 nM (pCa(i) 7.6 +/- 0.1), much lower than when calibrated in vitro. We conclude that [Ca(2+)]i in snail neurons is approximately 40 nM and that Ca(2+)-sensitive microelectrodes usually cause a leak at the point of insertion. The effects of the leak were minimized by injection of a mobile calcium buffer.
Kennedy, H J; Thomas, R C
Acid neutralizing processes in an alpine watershed front range, Colorado, U.S.A.-1: Buffering capacity of dissolved organic carbon in soil solutions
USGS Publications Warehouse
Soil interstitial waters in the Green Lakes Valley, Front Range, Colorado were studied to evaluate the capacity of the soil system to buffer acid deposition. In order to determine the contribution of humic substances to the buffering capacity of a given soil, dissolved organic carbon (DOC) and pH of the soil solutions were measured. The concentration of the organic anion, Ai-, derived from DOC at sample pH and the concentration of organic anion, Ax- at the equivalence point were calculated using carboxyl contents from isolated and purified humic material from soil solutions. Subtracting Ax- from Ai- yields the contribution of humic substances to the buffering capacity (Aequiv.-). Using this method, one can evaluate the relative contribution of inorganic and organic constituents to the acid neutralizing capacity (ANC) of the soil solutions. The relative contribution of organic acids to the overall ANC was found to be extremely important in the alpine wetland (52%) and the forest-tundra ecotone (40%), and somewhat less important in the alpine tundra sites (20%). A failure to recognize the importance of organic acids in soil solutions to the ANC will result in erroneous estimates of the buffering capacity in the alpine environment of the Front Range, Colorado. ?? 1988.
Iggy, Litaor, M.; Thurman, E. M.
Electrochemical reduction of dioxygen by copper complexes with pyridylalkylamine ligands dissolved in aqueous buffer solution: the relationship between activity and redox potential.
The Cu(II)/Cu(I) redox properties and electrochemical O2 reduction activity of a series of Cu(II)-complexes with pyridylalkylamine ligands were investigated in a neutral buffer solution. The relationship between Cu(II)/Cu(I) redox properties and O2 reduction activity was clearly demonstrated by voltammetric analyses. PMID:24926744
Asahi, Masafumi; Yamazaki, Shin-Ichi; Itoh, Shinobu; Ioroi, Tsutomu
Nanofiltration of rhodium tris(triphenylphosphine) catalyst in ethyl acetate solution
Solvent resistant nanofiltration (SRNF) using polymer membranes has recently received enhanced attention due to the search for cleaner and more energy-efficient technologies. The large size of the rhodium tris(triphenylphosphine) [HRh(CO)(PPh3)3] catalyst (>400 Da) - relative to other components of the hydroformylation reaction provides the opportunity for a membrane separation based on retention of the catalyst species while permeating the solvent. The compatibility of the solvent-polyimide membrane (DuraMem{trade mark, serif} 200 and DuraMem{trade mark, serif} 500) combinations was assessed in terms of the membrane stability in solvent plus non-zero solvent flux at 2.0 MPa. Good HRh(CO)(PPh3)3 rejection (>0.95) and solvent fluxes of 9.9 L/m2.h1 at 2.0 MPa were obtained in the catalyst-ethyl acetate-DuraMem 500 system. The effect of pressure and catalyst concentration on the solvent flux and catalyst rejection was conducted on the catalyst-ethyl acetate-membrane systems. Increasing pressure substantially improved both solvent flux and catalyst rejection, while increasing catalyst concentration was found to be beneficial in terms of substantial increases in catalyst rejection without significantly affecting solvent flux.
Shaharun, Maizatul S.; Mustafa, Ahmad K.; Taha, Mohd F.
Liquid crystalline phase and gel-sol transitions for concentrated microcrystalline cellulose (MCC)/1-ethyl-3-methylimidazolium acetate (EMIMAc) solutions.
Liquid crystalline (LC) phase transition and gel-sol transition in the solutions of microcrystalline cellulose (MCC) and ionic liquid (1-ethyl-3-methylimidazolium acetate, EMIMAc) have been investigated through a combination of polarized optical microscope (POM) observation and rheological measurements. Molecular LC phase forms at the 10 wt % cellulose concentration, as observed by POM, whereas the critical gel point is 12.5 wt % by rheological measurements according to the Winter and Chambon theory, for which the loss tangent, tan ?, shows frequency independence. Dramatic decreases of G' and G'' in the phase transition temperature range during temperature sweep are observed due to disassembling of the LC domain junctions. The phase diagram describing the LC phase and gel-sol transitions is obtained and the associated mechanisms are elucidated. A significant feature shown in the phase diagram is the presence of a narrow lyotropic LC solution region, which potentially has a great importance for the cellulose fiber wet spinning. PMID:21361275
Song, Hongzan; Niu, Yanhua; Wang, Zhigang; Zhang, Jun
Use of aqueous solutions of sodium alginate and calcium acetate as quenching liquids
Aqueous solutions of SA are prepared from a film of it obtained from an algal extract. The algai extract is prepared from seaweed of the species Lc~inaria saccharina and digitata. For the quenching solution 1--3% of the dried seaweeds is infused for 3--5 days in a 1% aqueous sodium carbonate solution. To obtain the SA film sulfuric or hydrochloric acid
M. G. Kurmashov
In situ and simultaneous nanostructural and spectroscopic studies of ZnO nanoparticle and Zn-HDS formations from hydrolysis of ethanolic zinc acetate solutions induced by water
The simultaneous formation of nanometer sized zinc oxide (ZnO), and acetate zinc hydroxide double salt (Zn-HDS) is described.\\u000a These phases, obtained using the sol-gel synthesis route based on zinc acetate salt in alcoholic media, were identified by\\u000a direct characterization of the reaction products in solution using complementary techniques: nephelometry, in situ Small-Angle X-ray Scattering (SAXS), UV-Vis spectroscopy and Extended X-ray
Valerie Briois; Christine Giorgetti; Elisabeth Dartyge; Francois Baudelet; Miriam S. Tokumoto; Sandra H. Pulcinelli; Celso V. Santilli
Experimental determination of portlandite solubility in H sub 2 O and acetate solutions at 100-350C and 500 bars: Constraints on calcium hydroxide and calcium acetate complex stability
The solubility of portlandite was measured in H{sub 2}O and aqueous acetate solutions of varying concentration (1-10 mmolal) at temperatures from 100-350C and 500 bars pressure. Dissolved Ca concentrations increased with decreasing temperature and increasing dissolved acetate concentration. Using known thermodynamic data for portlandite, H{sup +}, OH{sup {minus}}, Ca{sup ++}, CH{sub 3}COO{sup {minus}}, CH{sub 3}COOH{sup 0}, and H{sub 2}O{sub (1)}, stability constants for CaOH{sup +} and CaCH{sub 3}COO{sup +} complexes were determined. These results indicate that the stabilities of CaOH{sup 1} and CaCH{sub 3}COO{sup 1} complex increase with increasing temperature. In the acetate-free experiments, CaOH{sup +} is the dominant form of dissolved Ca in equilibrium with portlandite at 100-350C and 500 bars, while in the acetate-rich experiments (10 mmolal acetate), Ca{sup ++} and CaOH{sup +} are the dominant forms of Ca in equilibrium with portlandite at low temperature (100-200C) and CaCH{sub 3}COO{sup +} and CaOH{sup +} are the dominant forms at relatively high temperature (200-350C). Metal-acetate complexing has long been suggested as an important mechanism for mobilizing base metals during the formation of ore deposits in organic-rich environments. Due to the stability of CaCH{sub 3}COO{sup +} complex in Ca-bearing fluids at elevated temperatures and pressures, however, the effectiveness of dissolved acetate to enhance base metal sulfide solubility is limited.
Seewald, J.S.; Seyfried, W.E. Jr. (Univ. of Minnesota, Minneapolis (United States))
Experimental determination of portlandite solubility in H 2O and acetate solutions at 100-350 ¯C and 500 bars: Constraints on calcium hydroxide and calcium acetate complex stability
The solubility of portlandite was measured in H 2O and aqueous acetate solutions of varying concentration (1-10 mmolal) at temperatures from 100-350¯C and 500 bars pressure. Dissolved Ca concentrations increased with decreasing temperature and increasing dissolved acetate concentration. Using known thermodynamic data for portlandite, H +, OH -, Ca ++, CH 3COO -, CH 3COOH 0, and H 2O (1), stability constants for CaOH + and CaCH 3COO + complexes were determined. Log K values for the reaction Ca ++ + H 2O (1) = CaOH + + H + are, respectively, -10.04, -8.20, -6.88, and -6.35 at 100, 200, 300, and 350¯C and 500 bars pressure and for the reaction CaCH 3COO + = Ca ++ + CH 3COO - are, respectively, -2.53, -3.72, -4.59 at 200, 300, and 350¯C and 500 bars pressure. These results indicate that the stabilities of CaOH + and CaCH 3COO + complex increase with increasing temperature. In the acetate-free experiments, CaOH + is the dominant form of dissolved Ca in equilibrium with portlandite at 100-350¯C and 500 bars, while in the acetate-rich experiments (10 mmolal acetate), Ca ++ and CaOH + are the dominant forms of Ca in equilibrium with portlandite at low temperature (100-200¯C) and CaCH 3COO + and CaOH + are the dominant forms at relatively high temperature (200-350¯C). Metal-acetate complexing has long been suggested as an important mechanism for mobilizing base metals during the formation of ore deposits in organic-rich environments. Due to the stability of CaCH 3COO + complex in Ca-bearing fluids at elevated temperatures and pressures, however, the effectiveness of dissolved acetate to enhance base metal sulfide solubility is limited.
Seewald, Jeffrey S.; Seyfried, William E., Jr.
Introduction As even small concentrations of acetate in the plasma result in pro-inflammatory and cardiotoxic effects, it has been removed from renal replacement fluids. However, Plasma-Lyte 148 (Plasma-Lyte), an electrolyte replacement solution containing acetate plus gluconate is a common circuit prime for cardio-pulmonary bypass (CPB). No published data exist on the peak plasma acetate and gluconate concentrations resulting from the use of Plasma-Lyte 148 during CPB. Methods Thirty adult patients were systematically allocated 1:1 to CPB prime with either bicarbonate-balanced fluid (24 mmol/L bicarbonate) or Plasma-Lyte 148. Arterial blood acetate, gluconate and interleukin-6 (IL-6) levels were measured immediately before CPB (T1), three minutes after CPB commencement (T2), immediately before CPB separation (T3), and four hours post separation (T4). Results Acetate concentrations (normal 0.04 to 0.07 mmol/L) became markedly elevated at T2, where the Plasma-Lyte group (median 3.69, range (2.46 to 8.55)) exceeded the bicarbonate group (0.16 (0.02 to 3.49), P < 0.0005). At T3, levels had declined but the differential pattern remained apparent (Plasma-Lyte 0.35 (0.00 to 1.84) versus bicarbonate 0.17 (0.00 to 0.81)). Normal circulating acetate concentrations were not restored until T4. Similar gluconate concentration profiles and inter-group differences were seen, with a slower T3 decay. IL-6 increased across CPB, peaking at T4, with no clear difference between groups. Conclusions Use of acetate containing prime solutions result in supraphysiological plasma concentrations of acetate. The use of acetate-free prime fluid in CPB significantly reduced but did not eliminate large acetate surges in cardiac surgical patients. Complete elimination of acetate surges would require the use of acetate free bolus fluids and cardioplegia solutions. Trial registration Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12610000267055
Fluorescence quenching of etilefrine by acetate anion
Acid dissociation in the excited state of antihypotensor drug etilefrine [2-(ethylamino1-3-hydroxyphenyl)ethanol] is studied. Fluorescence of etilefrine decreases at pH<7 and is related to phenolic group dissociation. However, intensity of etilefrine fluorescence diminishes as the concentration of the acetate anion increases at pH>7. Analyses of the absorption and fluorescence spectra of aqueous solutions of etilefrine in the presence of acetate anions have been made. Considering the existence of an equilibrium in the excited state the values of 3.47æ10 -9 and 0.216æ10 -9 M -1 s -1 have been obtained for the rate constants for direct and inverse reactions, respectively. Moreover, the lifetime ( ?0'=0.58æ10 -9 s) and quantum yield (0.01) of non-protonated etilefrine have been determined. Our results seem to support the existence of a dynamic quenching process based on a proton transfer mechanism induced by acetate anions. This process could represent a serious inconvenience in analytical fluorimetric techniques taking into account that the acetic acid/acetate pair is commonly used as a buffer. Additional fluorescence quenching by H + ions could be involved in acid aqueous mediums. At high concentrations of acetic acid, a value of 2.98æ10 -9 M -1 s -1 for the bimolecular constant for the quenching by H + has been calculated.
Quintero Osso, B.; Carazo RodrÚguez, F. M.; Morales Domingo, J. J.; Cabeza GonzÃlez, M. C.; Thomas Gµmez, J.
Differences in proton-coupled electron-transfer reactions of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) between buffered and unbuffered aqueous solutions.
The electrochemical reduction mechanisms of flavin mononucleotide (FMN) in buffered aqueous solutions at pH 3-11 and unbuffered aqueous solutions at pH 2-11 were examined in detail using variable-scan-rate cyclic voltammetry (? = 0.1-20 V s(-1)), controlled-potential bulk electrolysis, UV-vis spectroscopy, and rotating-disk-electrode voltammetry. In buffered solutions at pH 3-5, FMN undergoes a two-electron/two-proton (2e(-)/2H(+)) reduction to form FMNH2 at all scan rates. When the buffered pH is increased to 7-9, FMN undergoes a 2e(-) reduction to form FMN(2-), which initially undergoes hydrogen bonding with water molecules, followed by protonation to form FMNH(-). At a low voltammetric scan rate of 0.1 V s(-1), the protonation reaction has sufficient time to take place. However, at a higher scan rate of 20 V s(-1), the proton-transfer reaction is outrun, and upon reversal of the scan direction, less of the FMNH(-) is available for oxidation, causing its oxidation peak to decrease in magnitude. In unbuffered aqueous solutions, three major voltammetric waves were observed in different pH ranges. At low pH in unbuffered solutions, where [H(+)] ? [FMN], (FMN)H(-) undergoes a 2e(-)/2H(+) reduction to form (FMNH2)H(-) (wave 1), similar to the mechanism in buffered aqueous solutions at low pH. At midrange pH values (unbuffered), where pH ? pKa of the phosphate group and [FMN] ? [H(+)], (FMN)H(-) undergoes a 2e(-) reduction to form (FMN(2-))H(-) (wave 2), similar to the mechanism in buffered aqueous solutions at high pH. At high pH (unbuffered), where pH ? pKa = 6.2 of the phosphate group, the phosphate group loses its second proton to be fully deprotonated, forming (FMN)(2-), and this species undergoes a 2e(-) reduction to form (FMN(2-))(2-) (wave 3). PMID:24079606
Tan, Serena L J; Kan, Jia Min; Webster, Richard D
Detailed investigations on La 2Zr 2O 7 buffer layers for YBCO-coated conductors prepared by chemical solution deposition
An extensive study of the growth and properties of La2Zr2O7 (LZO) buffer layers prepared by chemical solution deposition on Ni5at.%W rolling-assisted biaxially textured substrates, which is presently of great interest for the preparation of YBa2Cu3O7?x-coated conductors, is presented. The main focus was on the understanding of the decomposition of the precursor layers, and their growth and texture formation, as well
K. Knoth; R. H■hne; S. Oswald; L. Schultz; B. Holzapfel
Electrochemical behavior of glassy carbon electrodes modified by multi-walled carbon nanotube\\/surfactant films in a buffer solution and an ionic liquid
The electrochemical behavior of glassy carbon (GC) electrodes coated with multi-walled carbon nanotube (MWCNT)\\/surfactant films was studied in an ionic liquid and a phosphate buffer solution (pH=6.86), using cyclic voltammetry. The dispersion of MWCNTs in different media was investigated by scanning and transmission electron microscopy. Cast films of MWCNT\\/zwitterionic dodecyldimethylamine oxide on a GC electrode show a typical redox couple
Yi Li; Xingwang Shi; Jingcheng Hao
Inhibitory effect of hydroxypropyl methylcellulose acetate succinate on drug recrystallization from a supersaturated solution assessed using nuclear magnetic resonance measurements.
We examined the inhibitory effect of hydroxypropyl methylcellulose acetate succinate (HPMC-AS) on drug recrystallization from a supersaturated solution using carbamazepine (CBZ) and phenytoin (PHT) as model drugs. HPMC-AS HF grade (HF) inhibited the recrystallization of CBZ more strongly than that by HPMC-AS LF grade (LF). 1D-1H NMR measurements showed that the molecular mobility of CBZ was clearly suppressed in the HF solution compared to that in the LF solution. Interaction between CBZ and HF in a supersaturated solution was directly detected using nuclear Overhauser effect spectroscopy (NOESY). The cross-peak intensity obtained using NOESY of HF protons with CBZ aromatic protons was greater than that with the amide proton, which indicated that CBZ had hydrophobic interactions with HF in a supersaturated solution. In contrast, no interaction was observed between CBZ and LF in the LF solution. Saturation transfer difference NMR measurement was used to determine the interaction sites between CBZ and HF. Strong interaction with CBZ was observed with the acetyl substituent of HPMC-AS although the interaction with the succinoyl substituent was quite small. The acetyl groups played an important role in the hydrophobic interaction between HF and CBZ. In addition, HF appeared to be more hydrophobic than LF because of the smaller ratio of the succinoyl substituent. This might be responsible for the strong hydrophobic interaction between HF and CBZ. The intermolecular interactions between CBZ and HPMC-AS shown by using NMR spectroscopy clearly explained the strength of inhibition of HPMC-AS on drug recrystallization. PMID:24025080
Ueda, Keisuke; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu
Electrochemical concentration cell (ECC) ozonesonde pump efficiency measurements and tests on the sensitivity to ozone of buffered and unbuffered ECC sensor cathode solutions
On the basis of extensive laboratory and field tests of electrochemical concentration cell (ECC) ozonesondes, a height-dependent artifact in ozone profile measurements was found that is primarily due to side reactions of the phosphate buffers used in the "standard" 1% potassium iodide sensing solution. The influence of the buffers was revealed as a result of new, direct measurements of the ozonesonde pump flow rate efficiency made in an environmental chamber using an oil bubble flowmeter developed at National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL). The new flow rate measurements give pump efficiency correction factors that are 2 and 15% greater at 100 and 5 hPa, respectively, than those used in currently recommended procedures. Profile measurements using ozonesondes with differing ECC sensor solutions, on dual-sonde balloons and experiments in a simulation chamber, show that the impact of the buffers is most pronounced above the ozone partial pressure maximum. The effect is about a 10-15% overmeasurement of ozone at an altitude of 30 km. Careful consideration must be given to the combination of the sensing solution composition and pump efficiency correction if representative ozone profiles are to be obtained from ozonesonde measurements.
Johnson, Bryan J.; Oltmans, Samuel J.; V—Mel, Holger; Smit, Herman G. J.; Deshler, Terry; Kr—Ger, Chris
Removal of chromium from aqueous solution using cellulose acetate and sulfonated poly(ether ether ketone) blend ultrafiltration membranes.
A process for purifying aqueous solutions containing heavy and toxic metals such as chromium has been investigated. Chromium salts are largely used in various industries including leather-manufacturing industry. Ultrafiltration processes are largely being applied for macromolecular and heavy metal ion separation from aqueous streams. Cellulose acetate and sulfonated poly(ether ether ketone) blend ultrafiltration membranes were prepared by precipitation phase inversion technique in 100/0, 90/10, 80/20 and 70/30% polymer blend compositions and subjected to the rejection of chromium at different concentrations such as 200, 400, 600, 800 and 1000 ppm with a water-soluble macroligand (polyvinylalcohol). Factors affecting the percentage rejection and permeate flux such as pH, concentration of solute, concentration of PVA, transmembrane pressure and composition of blend membranes were investigated. It was found that percentage rejection improved at a pH 6 and a macroligand concentration of 2 wt.%. The transmembrane pressure and concentration of solute also have an effect on the separation and product rate efficiencies of the blend membranes. PMID:16860465
Arthanareeswaran, G; Thanikaivelan, P; Jaya, N; Mohan, D; Raajenthiren, M
Resonance Raman characterization of different forms of ground-state 8-bromo-7-hydroxyquinoline caged acetate in aqueous solutions.
The 8-bromo-7-hydroxyquinolinyl group (BHQ) is a derivative of 7-hydroxyquinoline (7-HQ) and BHQ molecules coexisting as different forms in aqueous solution. Absorption and resonance Raman spectroscopic methods were used to examine 8-bromo-7-hydroxyquinoline protected acetate (BHQ-OAc) in acetonitrile (MeCN), H(2)O/MeCN (60:40, v/v, pH 6 approximately 7), and NaOH-H(2)O/MeCN (60:40, v/v, pH 11 approximately 12) to obtain a better characterization of the forms of the ground-state species of BHQ-OAc in aqueous solutions and to examine their properties. The absorption spectra of BHQ-OAc in water show no absorption bands of the tautomeric species unlike the strong band at about 400 nm observed for the tautomeric form in 7-HQ aqueous solution. The resonance Raman spectra in conjunction with Raman spectra predicted from density functional theory (DFT) calculations reveal the observation of a double Raman band system characteristic of the neutral form (the nominal C=C ring stretching, C-N stretching, and O-H bending modes at 1564 and 1607 cm(-1)) and a single Raman band diagnostic of the enol-deprotonated anionic form (the nominal C=C ring, C-N, and C-O(-) stretching modes in the 1593 cm(-1) region). These results suggest that the neutral form of BHQ-OAc is the major species in neutral aqueous solution. There is a modest increase in the amount of the anionic form and a big decrease in the amount of the tautomeric form of the molecules for BHQ-OAc compared to 7-HQ in neutral aqueous solution. The presence of the 8-bromo group and/or competitive hydrogen bonding that hinder the formation and transfer process of a BHQ-OAc-water cyclic complex may be responsible for this large substituent effect. PMID:19296708
An, Hui-Ying; Ma, Chensheng; Nganga, Jameil L; Zhu, Yue; Dore, Timothy M; Phillips, David Lee
Complexation of buffer constituents with neutral complexation agents: part I. Impact on common buffer properties.
The complexation of buffer constituents with the complexation agent present in the solution can very significantly influence the buffer properties, such as pH, ionic strength, or conductivity. These parameters are often crucial for selection of the separation conditions in capillary electrophoresis or high-pressure liquid chromatography (HPLC) and can significantly affect results of separation, particularly for capillary electrophoresis as shown in Part II of this paper series (Bene, M.; RiesovÃ, M.; SvobodovÃ, J.; Tesa?ovÃ, E.; Dubsk», P.; Ga, B. Anal. Chem. 2013, DOI: 10.1021/ac401381d). In this paper, the impact of complexation of buffer constituents with a neutral complexation agent is demonstrated theoretically as well as experimentally for the model buffer system composed of benzoic acid/LiOH or common buffers (e.g., CHES/LiOH, TAPS/LiOH, Tricine/LiOH, MOPS/LiOH, MES/LiOH, and acetic acid/LiOH). Cyclodextrins as common chiral selectors were used as model complexation agents. We were not only able to demonstrate substantial changes of pH but also to predict the general complexation characteristics of selected compounds. Because of the zwitterion character of the common buffer constituents, their charged forms complex stronger with cyclodextrins than the neutral ones do. This was fully proven by NMR measurements. Additionally complexation constants of both forms of selected compounds were determined by NMR and affinity capillary electrophoresis with a very good agreement of obtained values. These data were advantageously used for the theoretical descriptions of variations in pH, depending on the composition and concentration of the buffer. Theoretical predictions were shown to be a useful tool for deriving some general rules and laws for complexing systems. PMID:23889602
RiesovÃ, Martina; SvobodovÃ, Jana; Toner, Zden?k; Bene, Martin; Tesa?ovÃ, Eva; Ga, Bohuslav
TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.
Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol?acetonitrile?acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials. PMID:23822250
Taha, Mohamed; Lee, Ming-Jer
Solution-free, in situ preparation of nano/micro CuO/ZnO in dielectric barrier discharge for sensitive cataluminescence sensing of acetic acid.
The present work describes a new solution-free strategy for preparation of cluster-like nano/micro CuO/ZnO particles in dielectric barrier discharge (DBD) in which the brass acts as the inner electrode. The cataluminescence (CTL) behaviour of such prepared material for acetic acid was studied for analytical application. Under the optimized conditions, the linear range of CTL intensity versus concentration of acetic acid are 6 mg L(-1) to 500 mg L(-1) with the limit of detection (LOD) of 3 mg L(-1), no significant interference was found. The new method shows great advantages because it is a process without any solution and complex equipment. The synthetic material was directly used for the cataluminescence sensing of acetic acid without other preliminary treatment and it shows high selectivity, satisfactory stability, and better sensitivity and linearity. PMID:23671903
Xia, Hui; Zhou, Ronghui; Zheng, Chengbin; Wu, Peng; Tian, Yunfei; Hou, Xiandeng
Inhibition mechanism of hydroxypropyl methylcellulose acetate succinate on drug crystallization in gastrointestinal fluid and drug permeability from a supersaturated solution.
The effects of drug-crystallization inhibitor in bile acid/lipid micelles solution on drug permeation was evaluated during the drug crystallization process. Hydroxypropyl methylcellulose acetate succinate (HPMC-AS) was used as a drug-crystallization inhibitor, which efficiently suppressed dexamethasone (DEX) crystallization in a gastrointestinal fluid model containing sodium taurocholate (NaTC) and egg-phosphatidylcholine (egg-PC). Changes of molecular state of supersaturated DEX during the DEX crystallization process was monitored in real time using proton nuclear magnetic resonance ((1)H NMR). It revealed that DEX distribution to bulk water and micellar phases formed by NaTC and egg-PC was not changed during the DEX crystallization process even in the presence of HPMC-AS. DEX permeation during DEX crystallization was evaluated using dissolution/permeability system. The combination of crystallization inhibition by HPMC-AS and micellar encapsulation by NaTC and egg-PC led to considerably higher DEX concentrations and improvement of DEX permeation at the beginning of the DEX crystallization process. Crystallization inhibition by HPMC-AS can efficiently work even in the micellar solution, where NaTC/egg-PC micelles encapsulates some DEX. It was concluded that a crystallization inhibitor contributed to improvement of permeation of a poorly water-soluble drug in gastrointestinal fluid. PMID:24953904
Ueda, Keisuke; Higashi, Kenjirou; Kataoka, Makoto; Yamashita, Shinji; Yamamoto, Keiji; Moribe, Kunikazu
SEMICONDUCTOR MATERIALS: Morphology dependence of TiO2 nanotube arrays on anodization variables and buffer medium
Vertically oriented TiO2 nanotube arrays were prepared by potentiostatic anodization of Ti foils in HF/acetic acid (HAC) aqueous solution. Anodization variables including anodization electrolyte concentration, anodization voltage, anodization time and buffer medium can be chosen and adjusted to manipulate the nanotube arrays to give the required length and morphology.
Xin, Wen; Meng, Cao; Jie, Wu; Junchao, Tao; Yan, Sun; Ning, Dai
Solid phase extraction of proteins from buffer solutions employing capillary-channeled polymer (C-CP) fibers as the stationary phase.
Polypropylene (PP) capillary-channeled polymer (C-CP) fibers are applied for solid phase extraction (SPE) of proteins from aqueous buffer solutions using a micropipette tip-based format. A process was developed in which centrifugation is used as the moving force for solution passage in the loading/washing steps instead of the previously employed manual aspiration. The complete procedure requires ~15 minutes, with the number of samples run in parallel limited only by the capacity of the centrifuge. The method performance was evaluated based on adsorption and elution characteristics of several proteins (cytochrome c, lysozyme, myoglobin, and glucose oxidase) from 150 mM phosphate buffered saline (PBS) solutions. Protein concentration ranges of ~2 to 100 ?g mL(-1) were employed and the recovery characteristics determined through UV-Vis absorbance spectrophotometry for protein quantification. The protein loading capacities across the range of proteins was ~1.5 ?g for the 5 mg fiber tips. Average recoveries from PBS were determined for each protein sample; cytochrome c ~86%, lysozyme ~80%, myoglobin ~86%, and glucose oxidase ~89%. Recoveries from more complex matrices, synthetic urine and synthetic saliva, were determined to be ~90%. A 10æ dilution study for a fixed 1 ?g protein application yielded 94 Ý 3.2% recoveries. The C-CP tips provided significantly higher recoveries for myoglobin in a 150 mM PBS matrix in comparison to a commercially available protein SPE product, with the added advantages of low cost, rapid processing, and reusability. PMID:23223274
Burdette, Carolyn Q; Marcus, R Kenneth
Strontium titanate buffer layers deposited on rolled Ni substrates with metal organic deposition
SrTiO3 buffer layers have been deposited on rolled Ni substrates using metal organic deposition (MOD) for HTS-coated conductors. The MOD process is based on the formation of the SrTiO3 layer coated on the surface of a Ni substrate using dip-coating as well as spin-coating techniques from a solution-based precursor, which is prepared by dissolving strontium acetate and titanium (IV) butoxide in acetic acid and methanol. The films were annealed at 950 ¯C for 2 h under 5% H2-Ar gas flow. X-ray diffraction (XRD) shows that the buffer layers on the Ni tape are highly oriented. The pole figure indicates a single cube-on-cube texture in addition to SEM and AFM observations revealing a continuous, dense, smooth and crack-free microstructure for the coated buffer. These results offer the potential of further manufacturing coated conductors with high current density.
Zhou, Y. X.; Bhuiyan, S.; Scruggs, S.; Fang, H.; Mironova, M.; Salama, K.
Buffer Biology.
Presents a science experiment in which students test the buffering capacity of household products such as shampoo, hand lotion, fizzies candy, and cola. Lists the standards addressed in this experiment and gives an example of a student lab write-up. (YDS)
Morgan, Kelly
Cube textured CeO2, BaZrO3 and LaAlO3 buffer layers on Ni based Substrates
CeO2, BaZrO3 as well as LaAlO3 buffer layers were deposited on {100}<001> Ni + 5 weight-% W substrates by a wet chemical technique. The solutions were prepared by dissolving the metal nitrates or acetates and zirconiumacetylacetonate, respectively, in mixtures of acetic acid, methanol and water. The solutions were applied by dip- or spincoating, dried at 135 ¯C and annealed at temperatures between 900 and 1 400 ¯C depending on the buffer layer for 15 min. under Ar-5% H2 gas flow. Pole-figure measurements proved the exact texture of each buffer layer. Electron microscopy showed dense and smooth buffer layers.
Deinhofer, C.; Gritzner, G.
Natural dissolved organic matter mobilizes Cd but does not affect the Cd uptake by the green algae Pseudokirchneriella subcapitata (Korschikov) in resin buffered solutions.
Natural dissolved organic matter (DOM) can have contrasting effects on metal bioaccumulation in algae because of complexation reactions that reduce free metal ion concentrations and because of DOM adsorption to algal surfaces which promote metal adsorption. This study was set up to reveal the role of different natural DOM samples on cadmium (Cd) uptake by the green algae Pseudokirchneriella subcapitata (Korschikov). Six different DOM samples were collected from natural freshwater systems and isolated by reverse osmosis. In addition, one (13)C enriched DOM sample was isolated from soil to trace DOM adsorption to algae. Algae were exposed to standardized solutions with or without these DOM samples, each exposed at equal DOM concentrations and at equal non-toxic Cd(2+) activity (?4nM) that was buffered with a resin. The DOM increased total dissolved Cd by factors 3-16 due to complexation reactions at equal Cd(2+) activity. In contrast, the Cd uptake was unaffected by DOM or increased maximally 1.6 fold ((13)C enriched DOM). The (13)C analysis revealed that maximally 6% of algal C was derived from DOM and that this can explain the small increase in biomass Cd. It is concluded that free Cd(2+) and not DOM-complexed Cd is the main bioavailable form of Cd when solution Cd(2+) is well buffered. PMID:24874007
Verheyen, Liesbeth; Versieren, Liske; Smolders, Erik
Internal acid buffering in San Joaquin Valley fog drops and its influence on aerosol processing
Although several chemical pathways exist for S(IV) oxidation in fogs and clouds, many are self-limiting: as sulfuric acid is produced and the drop pH declines, the rates of these pathways also decline. Some of the acid that is produced can be buffered by uptake of gaseous ammonia. Additional internal buffering can result from protonation of weak and strong bases present in solution. Acid titrations of high pH fog samples (median pH=6.49) collected in California's San Joaquin Valley reveal the presence of considerable internal acid buffering. In samples collected at a rural location, the observed internal buffering could be nearly accounted for based on concentrations of ammonia and bicarbonate present in solution. In samples collected in the cities of Fresno and Bakersfield, however, significant additional, unexplained buffering was present over a pH range extending from approximately four to seven. The additional buffering was found to be associated with dissolved compounds in the fogwater. It could not be accounted for by measured concentrations of low molecular weight ( C1- C3) carboxylic acids, S(IV), phosphate, or nitrophenols. The amount of unexplained buffering in individual fog samples was found to correlate strongly with the sum of sample acetate and formate concentrations, suggesting that unmeasured organic species may be important contributors. Simulation of a Bakersfield fog episode with and without the additional, unexplained buffering revealed a significant impact on the fog chemistry. When the additional buffering was included, the simulated fog pH remained 0.3-0.7 pH units higher and the amount of sulfate present after the fog evaporated was increased by 50%. Including the additional buffering in the model simulation did not affect fogwater nitrate concentrations and was found to slightly decrease ammonium concentrations. The magnitude of the buffering effect on aqueous sulfate production is sensitive to the amount of ozone present to oxidize S(IV) in these high pH fogs.
Collett, Jeffrey L.; Hoag, Katherine J.; Rao, Xin; Pandis, Spyros N.
Evolution of a physiological pH 6.8 bicarbonate buffer system: application to the dissolution testing of enteric coated products.
The use of compendial pH 6.8 phosphate buffer to assess dissolution of enteric coated products gives rise to poor in vitro-in vivo correlations because of the inadequacy of the buffer to resemble small intestinal fluids. A more representative and physiological medium, pH 6.8 bicarbonate buffer, was developed to evaluate the dissolution behaviour of enteric coatings. The bicarbonate system was evolved from pH7.4 Hanks balanced salt solution to produce a pH 6.8 bicarbonate buffer (modified Hanks buffer, mHanks), which resembles the ionic composition and buffer capacity of intestinal milieu. Prednisolone tablets were coated with a range of enteric polymers: hypromellose phthalate (HP-50 and HP-55), cellulose acetate phthalate (CAP), hypromellose acetate succinate (HPMCAS-LF and HPMCAS-MF), methacrylic acid copolymers (EUDRAGITÛ L100-55, EUDRAGITÛ L30D-55 and EUDRAGITÛ L100) and polyvinyl acetate phthalate (PVAP). Dissolution of coated tablets was carried out using USP-II apparatus in 0.1M HCl for 2h followed by pH 6.8 phosphate buffer or pH 6.8 mHanks bicarbonate buffer. In pH 6.8 phosphate buffer, the various enteric polymer coated products displayed rapid and comparable dissolution profiles. In pH 6.8 mHanks buffer, drug release was delayed and marked differences were observed between the various coated tablets, which is comparable to the delayed disintegration times reported in the literature for enteric coated products in the human small intestine. In summary, the use of pH 6.8 physiological bicarbonate buffer (mHanks) provides more realistic and discriminative in vitro release assessment of enteric coated formulations compared to compendial phosphate buffer. PMID:21255647
Liu, Fang; Merchant, Hamid A; Kulkarni, Rucha P; Alkademi, Maram; Basit, Abdul W
In vitro effects of bicarbonate and bicarbonate-lactate buffered peritoneal dialysis solutions on mesothelial and neutrophil function.
The inclusion of bicarbonate in the formulation of peritoneal dialysis solutions may avoid the in vitro impairment of certain cell functions seen with acidic lactate-based fluids. The supranormal physiological levels of HCO3- and PCO2 inherent in such formulations may, however, not be biocompatible. This study compared the in vitro biocompatibility of a pH 5.2 lactate-based formulation with formulations containing either 40 mM lactate at pH 7.4, 38 mM HCO3- at pH 6.8 (PCO2 at approximately 240 mm Hg) or 7.4 (PCO2 at approximately 60 mm Hg), and 25 mM HCO3- plus 15 mM lactate at pH 6.8 (PCO2 at approximately 160 mm Hg) or 7.4 (PCO2 at approximately 40 mm Hg). Significant release of lactate dehydrogenase or decreases in ATP content by human peritoneal mesothelial cells (HPMC) and human peripheral polymorphonuclear leukocytes (PMN) after a 30-min exposure to each test solution was only seen with the pH 5.2 lactate-based fluid. The ATP content of HPMC exposed to this fluid returned to control levels after 30 min of recovery in M199 control medium but showed a trend toward decreasing ATP content at 240 min. Similarly, interleukin (IL)-1 beta-induced IL-6 synthesis by HPMC was also only significantly reduced by the pH 5.2 lactate solution. PMN chemiluminescence was unaffected by 30-min exposure to all test solutions except for the pH 5.2 lactate formulation. Staphylococcus epidermidis phagocytosis was reduced to between 46 to 57% of control with all test solutions except the pH 5.2 lactate solution, which further suppressed the chemiluminescence response to 17% of control. These data suggest that short exposure to supranormal physiological levels of HCO3- and PCO2 does not impair HPMC or PMN viability and function. Furthermore, neutral pH lactate-containing solutions show equivalent biocompatibility to bicarbonate-based ones. PMID:8785390
Topley, N; Kaur, D; Petersen, M M; J—rres, A; Williams, J D; Faict, D; Holmes, C J
Continuous venovenous haemofiltration with citrate-buffered replacement solution is safe and efficacious in patients with a bleeding tendency: a prospective observational study
Background There is ongoing controversy concerning optimum anticoagulation and buffering in continuous venovenous haemofiltration (CVVH). Regional anticoagulation with trisodium citrate also acting as a buffer in the replacement fluid has several advantages and disadvantages over prefilter citrate administration alone. We analysed a large cohort of patients with acute kidney injury (AKI) treated by the former method and hypothesized that it is safe and efficacious. Methods Patients admitted at the intensive care unit with AKI and a high bleeding risk, without exclusion of liver disease, treated by CVVH with citrate in a custom-made replacement solution were prospectively included. Patient and CVVH characteristics, including citrate accumulation, were evaluated in outcome groups. A standardized mortality rate (SMR) was calculated using the simplified acute physiology score II. Results Ninety-seven patients were included; metabolic control was adequate and did not differ between outcome groups, apart from lower pH/bicarbonate in non-survivors. Citrate accumulation was proven in 9% and was timely identified. These patients had about threefold higher plasma transaminases and higher CVVH dose and mortality. The hospital mortality was 60% with a SMR of 1.1 (95% confidence interval 0.90-1.40): age and hyperlactatemia, rather than CVVH-characteristics and citrate accumulation, predicted mortality in multivariable analysis. Conclusion In critically ill, patients with AKI at high risk of bleeding, CVVH with citrate-containing replacement solution is safe and efficacious. The risk for citrate accumulation is 9% and best predicted by levels of transaminases. It carries, when citrate is discontinued, no attributable mortality.
Application of the Pitzer Model to Assignment of pH to Phthalate Standard Buffer Solutions
Stoichiometric ionization constants of phthalic acid have been determined in potassium chloride solutions at temperatures\\u000a from 10 to 40?¯C, with molalities up to 3 mol?kg?1, from potentiometric titrations of potassium hydrogen phthalate. The procedure described by Gans and OSulliven (Talanta\\u000a 51:3337, 2000) was followed to calibrate the electrochemical cell in terms of hydrogen ion concentration and the SUPERQUAD\\u000a program was used
M. I. A. Ferra; J. R. GraÓa; A. M. M. Marques
Liquid-liquid extraction of ethanol from aqueous solutions with amyl acetate, benzyl alcohol, and methyl isobutyl ketone at 298. 15. Kappa
Experimental mutual solubility and tie-line data were determined for three ternary liquid-liquid systems containing water, ethanol, and amyl acetate, benzyl alcohol, and methyl isobutyl ketone at 298.15{Kappa} in order to obtain their complete phase diagrams and to determine which is the most suitable solvent for extraction of ethanol from aqueous solutions. Tie lines were determined correlating the density of the binodal curve as a function of composition and the plait points using the Othmer and Tobias method. The experimental data were also correlated with the UNIFAC group contribution method. A qualitative agreement was obtained. Experimental results show that amyl acetate is a better solvent than methyl isobutyl ketone and benzyl alcohol.
Solimo, H.N. (Instituto de Fisica, Facultad de Ciencias Exactas y Tecnologia, Universidad Nacional de Tucuman, 4000 San Miguel de Tucuman (AR)); Martinez, H.E.; Riggio, R. (Facultad de Ciencias Naturales, Universidad Nacional de Salta, 4400 Salta (AR))
Molecular Structure of Sodium acetate
Sodium acetate is known for its ability to supercool. It freezes at 130 degrees, but can exist as a liquid at a much lower temperature. In order to melt solidified sodium acetate, however, every single crystal must liquify, otherwise the material will recrystallize. Sodium acetate has been used as a deicer for roads and runways. It is also used a component of buffer systems and in the manufacture of pharmaceuticals and heat pads. The compound is quite stable. It may act as an irritant and be harmful if inhaled or absorbed through the skin.
Composite Ferric Oxyhydroxide-Containing Phases Formed in Neutral Aqueous Solutions of Tryptophan and Indole3Acetic Acid
M—ssbauer, FTIR and XRD analyses showed that in aqueous medium in air in the presence of L-tryptophan (Trp) or indole-3-acetic acid (IAA) the ambient-temperature ageing of the precipitates formed from ferrous sulphate at pH7 gave composite phases with varying proportions of -FeOOH (a dominating crystalline phase), -FeOOH (both fine-grained, showing superparamagnetic behaviour at 298 K, and relatively better crystallized) and
A. A. Kamnev; E. Kuzmann; Yu. D. Perfiliev; A. VÕrtes; M. Risti?; S. Popovi?
Solubility and speciation of atmospheric iron in buffer systems simulating cloud conditions
The solubility of iron (Fe) in atmospheric particulate matter (PM) is important to understand its chemistry and potential bioavailability to ocean phytoplankton. However, current studies on Fe solubility and its speciation are highly uncertain partly due to inconsistencies in analytical protocols. In this study, cloud-processing of atmospheric PM was simulated in acetate, formate, and oxalate buffers (pH = 4.30 Ý 0.05) at 0.5, 1, 5, and 20 mM. Colorimetric analysis of Fe(II)-ferrozine complex showed that Fe solubility increased by an order of magnitude when acetate and formate concentrations increased from 0.5 mM to 5 mM, with a higher fraction of soluble Fe in acetate than in formate at lower buffer concentration (0.5 mM). Measured pH of sample extracts revealed that weak buffers are unable to maintain pH, presumably due to acidic or alkaline components of PM, requiring an optimum concentration (5 mM in this study) of acetate and formate for Fe solubility measurements. Similar extraction procedures revealed that oxalate buffer inhibits the formation of Fe(II)-ferrozine complex, especially with Fe(III)-containing solutions, rendering it unsuitable for Fe solubility measurements by Ferrozine method. Application of the optimized analytical method to PM samples from different environments showed quite variable Fe solubility, with the lowest (<1%) in dust-impacted samples and the highest (5%) in urban samples. The highest solubility (6.8%) was observed in ambient PM2.5 samples influenced by anthropogenic sources (car emissions) with more than 90% of soluble Fe in the form of Fe(II). Results from this study highlight the importance of the type and strength of buffer at a given pH for Fe solubility and provide further evidence of a higher Fe solubility in urban PM samples compared to desert dust.
Upadhyay, Nabin; Majestic, Brian J.; Herckes, Pierre
Proton transfer between acetic acid and methylamine in aqueous solution. Ab initio and molecular dynamics study of free energies of hydration
The free energy difference between the neutral and ionic forms of the complex of acetic acid with methylamine, surrounded by 253 SPC water molecules, is calculated by a combination of molecular dynamics (MD) and ab initio methods. The ab initio energy calculations (4-31G* basis set) were carried out on instantaneous values, extracted from MD trajectories. The ionic form turns out to be more stable than the neutral form by 6.7 Ý 1.9 kcal mol -1. This result compares well with the difference in pKa values. The stabilization of the ionic form is mainly due to the superior water-solute interaction energy of this form.
Mavri, Janez; Hadz?i, Dus?an
Treatment of otitis externa associated with Corynebacterium kroppenstedtii in a peach-faced lovebird (Agapornis roseicollis) with an acetic and boric acid commercial solution.
A 5-year-old lovebird (Agapornis roseicollis) was presented with scaly crusts around both external ear openings and exudate present around the left ear. The bird had been treated with ivermectin and enrofloxacin without success. A pure culture of Corynebacterium kroppenstedtii was isolated from both ears. After susceptibility testing, a treatment of an acetic and boric acid solution administered topically 3 times daily was prescribed. The scaly appearance disappeared after 14 days of treatment and C kroppenstedtii could not be reisolated. PMID:19673461
Martel, An; Haesebrouck, Freddy; Hellebuyck, Tom; Pasmans, Frank
Interaction of povidone with aromatic compounds III: Thermodynamics of the binding equilibria and interaction forces in buffer solutions at varying pH values and varying dielectric constant.
The complex formation of a series of aromatic compounds with povidone was studied in buffer solutions and organic solvent mixtures by equilibrium dialysis. For all the ligand molecules studied, a linear relationship was found between r, the number of moles of bound ligand per mole of povidone, and the free ligand concentration. The binding constants and the free energies of binding (-delta F), were greater for compounds in the nonionic state and increased with the number of hydroxyl groups which were capable of forming hydrogen bonds. They decreased with temperature elevation. The thermodynamic data showed entropy gains during the binding process accompanied by small negative enthalpy values. The increased ability to form hydrogen bonds and the increase in ionization of the ligand molecule was reflected in more negative delta H and decreasing delta S values. (The thermodynamic values were interpreted on the basis of the "iceberg" concept of water structure.) From these entropy and enthalpy changes, hydrogen and hydrophobic bondings appeared to be the most important types of binding. In organic solvent mixtures, the association constants lowered with increasing ethanol or propylene glycol concentration; a line relationship between the free energy and the dielectric constant of the solvent mixtures was observed. PMID:7097503
Plaizier-Vercammen, J A; De NÒve, R E
Effect of synovial fluid, phosphate-buffered saline solution, and water on the dissolution and corrosion properties of CoCrMo alloys as used in orthopedic implants.
The corrosion and dissolution of high- and low-carbon CoCrMo alloys, as used in orthopedic joint replacements, were studied by immersing samples in phosphate-buffered saline (PBS), water, and synovial fluid at 37 degrees C for up to 35 days. Bulk properties were analyzed with a fine ion beam microscope. Surface analyses by X-ray photoelectron spectroscopy and Auger electron spectroscopy showed surprisingly that synovial fluid produced a thin oxide/hydroxide layer. Release of ions into solution from the alloy also followed an unexpected pattern where synovial fluid, of all the samples, had the highest Cr concentration but the lowest Co concentration. The presence of carbide inclusions in the alloy did not affect the corrosion or the dissolution mechanisms, although the carbides were a significant feature on the metal surface. Only one mechanism was recognized as controlling the thickness of the oxide/hydroxide interface. The analysis of the dissolved metal showed two mechanisms at work: (1) a protein film caused ligand-induced dissolution, increasing the Cr concentration in synovial fluid, and was explained by the equilibrium constants; (2) corrosion at the interface increased the Co in PBS. The effect of prepassivating the samples (ASTM F-86-01) did not always have the desired effect of reducing dissolution. The release of Cr into PBS increased after prepassivation. The metal-synovial fluid interface did not contain calcium phosphate as a deposit, typically found where samples are exposed to calcium rich bodily fluids. PMID:15900610
Lewis, A C; Kilburn, M R; Papageorgiou, I; Allen, G C; Case, C P
Solution and solid state characterization of oxo-centered trinuclear iron(III) acetate complexes [Fe3(?3-O)(?-OAc)6(L)3]+.
[Fe(3)(?(3)-O)(?-OAc)(6)(py)(3)][FeBr(4)](2)[pyñH], complex (1), (OAc is acetate) was prepared from the reaction of FeBr(3) with pyridine in 1.2 molar aqueous HBr and 2.4 molar aqueous CH(3)COOH. Recrystallization of 1 in acetonitrile produced the [Fe(3)(?(3)-O)(?-OAc)(6)(py)(3)][FeBr(4)] complex (2). Both complexes were characterized by IR and (1)H NMR spectroscopies and their structures were studied using the single-crystal diffraction method. There is a lack of thorough characterization of the titled compounds in solution. Paramagnetic (1)H NMR is introduced as a good probe for the characterization of a family of titled compounds in solution when the L ligand coordinated to iron varies as: CH(3)OH, CH(3)CN, DMSO, H(2)O, py and acetone. PMID:22020165
Amani, Vahid; Safari, Nasser; Khavasi, Hamid Reza
Solution and solid state characterization of oxo-centered trinuclear iron(III) acetate complexes [Fe 3(? 3-O)(?-OAc) 6(L) 3] +
[Fe 3(? 3-O)(?-OAc) 6(py) 3][FeBr 4] 2[pyñH], complex ( 1), (OAc is acetate) was prepared from the reaction of FeBr 3 with pyridine in 1.2 molar aqueous HBr and 2.4 molar aqueous CH 3COOH. Recrystallization of 1 in acetonitrile produced the [Fe 3(? 3-O)(?-OAc) 6(py) 3][FeBr 4] complex ( 2). Both complexes were characterized by IR and 1H NMR spectroscopies and their structures were studied using the single-crystal diffraction method. There is a lack of thorough characterization of the titled compounds in solution. Paramagnetic 1H NMR is introduced as a good probe for the characterization of a family of titled compounds in solution when the L ligand coordinated to iron varies as: CH 3OH, CH 3CN, DMSO, H 2O, py and acetone.
An experimental study of zinc chloride speciation from 300 to 600 ??C and 0.5 to 2.0 kbar in buffered hydrothermal solutions
The solubility of sphalerite (ZnS) was measured in KCl-HCl-H2O solutions at 300-600??C and 0.5-2.0 kbar. The silicate assemblage K-feldspar-muscovite (or andalusite)-quartz was used to buffer the solution to acid conditions, resulting in the total solubility reaction 2K+ + KAl2AlSi3O10(OH)2 + 6SiO2 + ZnS + nCl- = ZnCln(2-n) + 3KAlSi3O8 + H2S. (muscovite) (quartz) (sphalerite) (K-feldspar) A computer retrieval technique was used to derive average chloride ligand numbers for chlorozinc species at 0.25-2.0 molal total chloride. This technique mathematically solves for the average ligand number using a series of pertinent chemical relations at P and T. Mono- and di-chlorozinc species were found to predominate throughout the pressure-temperature-composition range investigated. The logarithms of the first and second dissociation constants for ZnCl20 were evaluated over the P-T range; for example, at 1 kbar, the values -0.41 and -1.42 were computed for the logarithm of the first dissociation constant, while -7.62 and -10.57 were computed for the logarithm of the second dissociation constant, for 400 and 500??C, respectively. Results are compared to past studies conducted at subcritical conditions and differ in that we find no evidence for more highly coordinated chloro-zinc species except possibly for ZnCl3- at 600??C, 1 and 2 kbar. Our results are consistent with electrostatic theory, which favors lower charged to neutral molecules in low dielectric-constant media. ?? 1994.
Cygan, G. L.; Hemley, J. J.; d'Angelo, W. M.
Electrofocusing in Buffers.
Methods of electrofocusing in amphoteric or non-amphoteric buffers is disclosed. In such methods, buffers are employed as carrier constituents, and optionally as anolyte and catholyte. Using a buffer electrofocusing system, stability with time has been ac...
A. Chrambach N. Y. Nguyen
Abiraterone acetate.
Abiraterone acetate (CB 7630; CB7630; JNJ-212082), the 3?-acetate prodrug of abiraterone, is structurally related to ketoconazole and is being developed by Cougar Biotechnology as a hormonal therapy for advanced prostate and breast cancers. As a selective inhibitor of adrenal androgens, it is thought to be a safer product than existing second-line hormonal therapies. This review discusses the key development milestones and therapeutic trials of this drug. PMID:21171672
The variation of viscosity, refractive indices, compressibility, intermolecular free length, and excess molar volume of the acetophenoneethyl acetate solutions at 303.15-323.15 K
Densities, viscosities, refractive indices and ultrasonic velocities of the binary mixtures of acetophenone with ethyl acetate were measured over the entire mole fractions at 303.15, 313.15, and 323.15 K. From the experimental results, excess molar volumes V E, viscosity deviation ??, refractive index deviation ? n D , deviations in isentropic compressibility ?? s and excess intermolecular free length ? L f are calculated. The viscosity values were fitted to the models of Krishnan-Laddha and McAllister. The thermophysical properties under study were fit to the Jouyban-Acree model. The excess values were correlated using Redlich-Kister polynomial equation to obtain their coefficients and standard deviations. The data obtained fitted with the values correlated by the corresponding models very well. The results are interpreted in terms of molecular interactions occurring in the solution.
Saravanakumar, K.; Baskaran, R.; Kubendran, T. R.
An all chemical solution deposition approach for the growth of highly textured CeO2 cap layers on La2Zr2O7-buffered long lengths of biaxially textured Ni W substrates for YBCO-coated conductors
A reel-to-reel, dip coating process has been developed to continuously deposit epitaxial La2Zr2O7 (LZO) and CeO2 on 5 m long cube-textured {100} (001)Ni tapes. Recent results for La2Zr2O7 and CeO2 buffer layers deposited on long lengths of Ni substrate for the realization of YBa2Cu3O7-x (YBCO)-coated conductors are presented. The major achievement is the development of a new all chemical solution deposition (CSD) process leading to the formation of highly textured buffer layers at moderate annealing temperatures. Reproducible highly textured, dense and crack-free LZO buffer layers and CeO2 cap layers were obtained for annealing temperatures as low as 900 ¯C in a reducing atmosphere (Ar-5 at.%-H2). The thickness of the LZO buffer layers was determined to be (200 Ý 10) nm per single coating; prepared cerium oxide layers showed a thickness of 60 nm Ý 10 nm. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. A Tc 0 of T = 90.5 K and ?Tc = 1.4 K was obtained on PLD-YBCO/CSD-CeO2 /CSD-LZO/Ni-5 at.% W, which shows the outstanding features of this new buffer layer architecture processed by CSD. The large layer thickness combined with low annealing temperatures is the main advantage of this new process for low-cost buffer layer deposition on Ni-RABiTS (rolling-assisted biaxially textured substrates).
Engel, S.; Knoth, K.; H■hne, R.; Schultz, L.; Holzapfel, B.
The properties of aqueous solutions of some short chain cosurfactants used for radical polymerization of vinyl acetate
The refractive index and excess molar volume, of the following short hydrocarbon chain cosurfactants were studied: ethylene\\u000a glycol, ethylene glycol monomethyl ether, ethanol, n-, i-propanol, acrylic acid, ethyl monomethylmaleate and acrylamide. The refractive indexes of the aqueous solutions of these\\u000a compounds vary nonlinearly with composition. The maximum variation of refractive indexes occurs up to a cosurfactant\\/water\\u000a molar ratio equal to
D. Donescu; L. Fusulan; C. Petcu; M. Vasilescu
Vapor pressures of phenethyl alcohol and phenethyl acetate in aqueous solutions of sodium xylene sulfonate and polyvinylpyrrolidone
Vapor pressures of two fragrance materials in aqueous solutions of polyvinylpyrrolidone and sodium xylenesulfonate were determined\\u000a using gas chromatography of head space samples. The association between polymer and hydrotrope was evaluated from the values\\u000a of surface tension and electrical conductance. The result showed an association of the hydrotrope and the polymer leading\\u000a to enhanced surface tension after addition of polymer
S. Friberg; L. Fei
1-Naphthyl Acetate-Dependent Medium Acidification by Zea mays L. Coleoptile Segments 1
Zea mays L. cv INRA 5a coleoptile segments ecidify the incubation medium on the addition of 1-naphthyl acetate (1-NA). The buffering capacity of the bathing solution increases during 1-NA stimulated medium acidification. The solution bathing the 1-NA treated coleoptile segment was analyzed by high performance liquid chromatography. A considerable amount of acetic acid was detected in the bathing solution used to measure 1-NA-dependent medium acidification. For the first time, the data demonstrate directly the release of acetic acid from 1-NA. The extent of medium acidification was proportional to 1-NA concentration. Simultaneous measurement of medium acidification and acetate content upon addition of 1-NA showed that both processes were temporally correlated. The stoichiometry of proton equivalents to acetate ion was 0.966. Addition of 50 micromolar N,N?-dicyclohexylcarbodiimide had little effect on 1-NA-dependent medium acidification. The results indicate that 1-NA is hydrolyzed in the extracellular space of coleoptile cells.
Salguero, Julio; Calatayud, Angeles; Gonzalez-Daros, Francisco; del Valle-Tascon, Secundino
Hemodynamic Effects of Peritoneal Dialysis Solutions on the Rat Peritoneal Membrane: Role of Acidity, Buffer Choice, Glucose Concentration, and Glucose Degradation Products
Conventional peritoneal dialysis fluids (PDF) are unphysiologic because of their hypertonicity, high glucose and lactate concentrations, acidic pH, and presence of glucose degradation products (GDP). Long-term exposure to conven- tional PDF may cause functional and structural alterations of the peritoneal membrane. New PDF have a neutral pH, a low GDP content, and contain bicarbonate or lactate as the buffer. Intravital
Molecular Structure of Phenylmercuric acetate
Phenylmercuric acetate is white to white-yellow crystalline powder that is odorless. This phenyl mercury compound is used mainly as a fungicide, herbicide, slimicide and bacteriocide. Phenylmercuric acid serves as a preservative in canned paint, eye ointments and drops, injectable solutions, skin disinfectants and in cosmetics products such as hair shampoos, mouthwashes and toothpastes. It is also used in contraceptive gels and foams. Phenylmercuric acetate is prepared by interaction of benzene with mercuric acetate in glacial acetic acid. Phenylmercuric acetate's former production and use as a fungicide and as a mildew inhibitor in paints may have resulted in its direct release to the environment. This substance is very toxic to aquatic organisms and may be hazardous to the environment.
Method for the preparation of cellulose acetate flat sheet composite membranes for forward osmosisDesalination using MgSO 4 draw solution
A lab scale method for the preparation of defect free flat sheet composite membranes for forward osmosis (FO) has been developed. Membranes containing a thin layer of cellulose acetate (CA) cast on a nylon fabric of 50?m thick were prepared by phase inversion in water. Cellulose acetate (CA) membranes with an overall thickness of 7080?m have been prepared with lactic
M. Sairam; E. Sereewatthanawut; K. Li; A. Bismarck; A. G. Livingston
A Buffer that Mimics the SMP Buffer for Determining Lime Requirement of Soil
The Shoemaker-McLean-Pratt (SMP) buffer used for determining lime requirement of soil contains chromium and p-nitrophenol, which classifies the solution as a hazardous waste. A buffer without hazard- ous chemicals producing the same pH as SMP buffer would eliminate hazardous waste and have no effect on agronomic interpretation. Chemicals chosen to replace chromium and p-nitrophenol were 2-(N- morpholino)ethanesulfonic acid monohydrate (MES)
F. J. Sikora
A selective chromogenic probe for mercury(II) and cyanide in aqueous buffered solution from a cycloaddition reaction of an ynamine to polycyclic dithiolethiones.
The synthesis of some new polysulfur-nitrogen heterocycles by cycloaddition of an ynamine to bisdithiolothiazine ketothiones or dithiones is described and the interconversion between regioisomers is studied by DFT calculations, showing that the double bond isomerizes at room temperature. This series is a new selective and sensitive chromogenic probe for the naked-eye detection of mercury(II) cation and cyanide anion in buffered (HEPES 0.05 M, pH 7.14) water/acetonitrile 1:1 mixture, with sub-micromolar sensitivity, and constitutes the first example of a new class of colorimetric chemical probes for Hg(2+) and CN(-). PMID:20533432
Fuertes, Pedro; Moreno, Daniel; Cuevas, JosÕ V; GarcÚa-Valverde, MarÚa; Torroba, TomÃs
A reel-to-reel, dip coating process has been developed to continuously deposit epitaxial La2Zr2O7 (LZO) and CeO2 on 5 m long cube-textured {100} (001)Ni tapes. Recent results for La2Zr2O7 and CeO2 buffer layers deposited on long lengths of Ni substrate for the realization of YBa2Cu3O7-x (YBCO)-coated conductors are presented. The major achievement is the development of a new all chemical solution
S. Engel; K. Knoth; R. H■hne; L. Schultz; B. Holzapfel
Very High Selective Etching of GaAs\\/Al0.2Ga0.8As for Gate Recess Process to Pseudomorphic High Electron Mobility Transistors (PHEMT) Applications Using Citric Buffer Solution
Highly selective wet etching of GaAs on Al0.2Ga0.8As can be realized using citric buffer (citric acid\\/H2O2\\/H2O) solutions. The selectivity can be up to 256, which is distinct from the previous non-selectivity inference, due to consulting the role of H2O2 in this etching system. The etch stop mechanism is demonstrated by X-ray photoelectron spectroscopy (XPS) and indicates the formation of dense
Chin-I. Liao; Po-Wen Sze; Mau-Phon Houng; Yeong-Her Wang
Chemical solution deposition (CSD) of CeO2 and La2Zr2O7 buffer layers on cube textured NiW substrates
We present results of crack free layers of CeO2 and La2Zr2O7 deposited by means of CSD on cube textured Ni-4 at.% W substrates. EBSD-data show histograms with very good inplane- and out-of-plane textures and were used to simulate the critical current density in the YBCO layer. The surface roughness, a sensitive feature for good deposition results, was analyzed with a profilometer. In the CSD process we applied, the 2, 4-pentanedionates of the metal cations in glacial acetic acid and methanol served as starting substances.
Kotzyba, G.; Obst, B.; Nast, R.; Goldacker, W.; Holzapfel, B.
Formation of indium-doped zinc oxide thin films using chemical spray techniques: The importance of acetic acid content in the aerosol solution and the substrate temperature for enhancing electrical transport
Indium-doped zinc oxide (ZnO:In) thin films were grown on glass substrates using the chemical spray technique. The effects of the acetic acid content in the starting solution (cAA), as well as the substrate temperature (TS), were studied. Our results demonstrate that when cAA is extremely low, the resistivity values of the zinc oxide (ZnO) thin films become relatively high (in
L. Castaneda; A. Garciavalenzuela; E. P. Zironi; J. Canetasortega; M. Terrones; A. Maldonado
Queueing analysis of finite buffer token networks
This paper introduces analytic models for evaluating demand assignment protocols in realistic finite buffer\\/finite station network configurations. We present a solution for implicit and explicit token passing systems enabling us to model local area networks, such as Token Bus. We provide, for the first time, a tractable approximate solution by using an approach based on restricted occupancy urn models. The
Aura Ganz; Imrich Chlamtac
Tri-State Buffer
This interactive presentation, created by Terry Bartelt and hosted by the Electromechanical Digital Library, discusses the tri-state buffer used in devices employing digital circuitry. A tri-state buffer is "one type of device that is used in digital circuits receiving two logic states but producing three different types of output signals." The presentation is filled with useful flash animations presenting the buffer's use. Furthermore, a series of slides presents the application of this device in different situations. Once complete, a short four-question quiz is provided to test the full understanding of the different concepts.
Bartelt, Terry L.
Method for regeneration of electroless nickel plating solution
An electroless nickel(EN)/hypophosphite plating bath is provided employing acetic acid/acetate as a buffer and which is, as a result, capable of perpetual regeneration while avoiding the production of hazardous waste. A regeneration process is provided to process the spent EN plating bath solution. A concentrated starter and replenishment solution is provided for ease of operation of the plating bath. The regeneration process employs a chelating ion exchange system to remove nickel cations from spent EN plating solution. Phosphites are then removed from the solution by precipitation. The nickel cations are removed from the ion exchange system by elution with hypophosphorous acid and the nickel concentration of the eluate adjusted by addition of nickel salt. The treated solution and adjusted eluate are combined, stabilizer added, and the volume of resulting solution reduced by evaporation to form the bath starter and replenishing solution.
Eisenmann, Erhard T. (5423 Vista Sandia, NE., Albuquerque, NM 87111)
An electroless nickel(EN)/hypophosphite plating bath is provided employing acetic acid/acetate as a buffer and which is, as a result, capable of perpetual regeneration while avoiding the production of hazardous waste. A regeneration process is provided to process the spent EN plating bath solution. A concentrated starter and replenishment solution is provided for ease of operation of the plating bath. The regeneration process employs a chelating ion exchange system to remove nickel cations from spent EN plating solution. Phosphites are then removed from the solution by precipitation. The nickel cations are removed from the ion exchange system by elution with hypophosphorus acid and the nickel concentration of the eluate adjusted by addition of nickel salt. The treated solution and adjusted eluate are combined, stabilizer added, and the volume of resulting solution reduced by evaporation to form the bath starter and replenishing solution. 1 fig.
Eisenmann, E.T.
Miscibility of cellulose acetate with vinyl polymers
Binary blend films of cellulose acetate (CA) with flexible syntheticpolymers including poly(vinyl acetate) (PVAc), poly(N-vinyl pyrrolidone) (PVP),and poly(N-vinyl pyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] were preparedfrommixed polymer solutions by solvent evaporation. Thermal analysis by DSC showedthat CA of any degree of substitution (DS) was not miscible with PVAc, but CAwith DS less than 2.8 was miscible with PVP to form homogeneous blends. Thestate
Yoshiharu Miyashita; Tetsuya Suzuki; Yoshiyuki Nishio
An acetate bound cobalt oxide catalyst for water oxidation: role of monovalent anions and cations in lowering overpotential
Co(II) dissolved in acetate buffer at pH 7 is found to be a good water oxidation catalyst (WOC) showing electrocatalytic water oxidation current significantly greater than Co(II) in phosphate buffer under the same conditions owing to the higher solubility of the former. When electrodeposited on ITO/FTO electrodes it forms acetate bound cobalt(II)oxide based material (Co-Ac-WOC) showing catalytic water oxidation current density of 0.1 mA/cm$^{2}$ at 830 mV and 1 mA/cm$^{2}$ at 1 V in a pH 7 buffer solution. The morphology of Co-Ac-OEC is investigated with AFM, HR-TEM and SEM (at different times and electrodeposition potentials). The chemical composition of Co-Ac-OEC is investigated using XPS, EDX, combustion analysis and ATR-FTIR which indicates that this material has a CoO core with chloride and acetate anions bound to the Co center. Sodium is found to be integrated in the Co-Ac-WOC. The presence of the sodium ions and the chloride ions lowers the onset potential for oxygen evolution reaction (OER) by 240 mV relative to the classic Co-Pi at pH 7. The lower onset potential and higher OER current lowers the exchange current density to 10$^{-6.7}$ in Co-Ac-WOC relative to 10$^{-8}$-10$^{-10}$ in Co-Pi and its derivatives.
Dey, Subal; Mondal, Biswajit; Dey, Abhishek
Combined effects of hydrostatic pressure, temperature, and pH on the inactivation of spores of Clostridium perfringens type A and Clostridium sporogenes in buffer solutions.
To develop a spore inactivation strategy, the effect of 15-min hydrostatic pressure treatments (550 and 650 MPa) at 55 and 75 degrees C in citric acid buffer (4.75 and 6.5 pH) on spores of 5 isolates of Clostridium perfringens type A carrying the gene that encodes the C. perfringens enterotoxin (cpe) on the chromosome (C-cpe), 4 isolates carrying the cpe gene on a plasmid (P-cpe), and 2 strains of C. sporogenes were investigated. Treatments at 650 MPa, 75 degrees C and pH 6.5 were moderately effective against spores of P-cpe (approximately 3.7 decimal reduction, DR) and C. sporogenes (approximately 2.1 DR) but not for C-cpe (approximately 1.0 DR) spores. Treatments at pH 4.75 were moderately effective against spores of P-cpe (approximately 3.2 DR) and C. sporogenes (approximately 2.5 DR) but not of C-cpe (approximately 1.2 DR) when combined with 550 MPa at 75 degrees C. However, when pressure was raised to 650 MPa under the same conditions, high inactivation of P-cpe (approximately 5.1 DR) and C. sporogenes (approximately 5.8 DR) spores and moderate inactivation of C-cpe (approximately 2.8 DR) spores were observed. Further advances in high-pressure treatment strategies to inactivate spores of cpe-positive C. perfringens type A and C. sporogenes more efficiently are needed. PMID:17995687
Paredes-Sabja, D; Gonzalez, M; Sarker, M R; Torres, J A
Role of ethylene diamine tetra-acetic acid (EDTA) in catheter lock solutions: EDTA enhances the antifungal activity of amphotericin B lipid complex against Candida embedded in biofilm
Ethylene diamine tetra-acetic acid (EDTA) is an anticoagulant with antibiofilm-enhancing activity. We therefore used an in vitro biofilm model to determine the activity of amphotericin B lipid complex (ABLC) with or without EDTA against Candida embedded in biofilm on silicone disk surfaces. Clinical blood isolates from cancer patients infected with Candida albicans or Candida parapsilosis were used. Silicone disks were
Issam I. Raad; Ray Y. Hachem; Hend A. Hanna; Xiang Fang; Ying Jiang; Tanya Dvorak; Robert J. Sherertz; Dimitrios P. Kontoyiannis
Electrochemical deposition of zinc oxide films from non-aqueous solution: a new buffer\\/window process for thin film solar cells
Zinc oxide is a wide band gap semiconductor with wide application in thin film devices such as n-type window layers for thin film solar cells, piezoelectric and luminescent devices, and for catalytic applications. We have cathodically electrodeposited films of ZnO by reduction of dissolved oxygen in a non-aqueous solution (dimethylsulfoxide) containing a Zn salt. This method allows a large deposition
D. Gal; G Hodes; D Lincot; H.-W Schock
Cytosolic Ca2+ Buffers
Ca2+ buffers, a class of cytosolic Ca2+-binding proteins, act as modulators of short-lived intracellular Ca2+ signals; they affect both the temporal and spatial aspects of these transient increases in [Ca2+]i. Examples of Ca2+ buffers include parvalbumins (? and ? isoforms), calbindin-D9k, calbindin-D28k, and calretinin. Besides their proven Ca2+ buffer function, some might additionally have Ca2+ sensor functions. Ca2+ buffers have to be viewed as one of the components implicated in the precise regulation of Ca2+ signaling and Ca2+ homeostasis. Each cell is equipped with proteins, including Ca2+ channels, transporters, and pumps that, together with the Ca2+ buffers, shape the intracellular Ca2+ signals. All of these molecules are not only functionally coupled, but their expression is likely to be regulated in a Ca2+-dependent manner to maintain normal Ca2+ signaling, even in the absence or malfunctioning of one of the components.
Schwaller, Beat
Tris-sucrose buffer system: a new specially designed medium for extracellular invertase production by immobilized cells of isolated yeast Cryptococcus laurentii MT-61.
The aims of the present study were to isolate new yeasts with high extracellular (exo) invertase activity and to investigate the usability of buffer systems as invertase production media by immobilized yeast cells. Among 70 yeast isolates, Cryptococcus laurentii MT-61 had the highest exo-invertase activity. Immobilization of yeast cells was performed using sodium alginate. Higher exo-invertase activity for immobilized cells was achieved in tris-sucrose buffer system (TSBS) compared to sodium acetate buffer system and potassium phosphate buffer system. TSBS was prepared by dissolving 30 g of sucrose in 1 L of tris buffer solution. The optimum pH, temperature, and incubation time for invertase production with immobilized cells were determined as 8.0, 35 ¯C and 36 h in TSBS, respectively. Under optimized conditions, maximum exo-invertase activity was found to be 28.4 U/mL in sterile and nonsterile TSBS. Immobilized cells could be reused in 14 and 12 successive cycles in sterile and nonsterile TSBS without any loss in the maximum invertase activity, respectively. This is the first report which showed that immobilized microbial cells could be used as a biocatalyst for exo-invertase production in buffer system. As an additional contribution, a new yeast strain with high invertase activity was isolated. PMID:23722276
Aydogan, Mehmet Nuri; Taskin, Mesut; Canli, Ozden; Arslan, Nazli Pinar; Ortucu, Serkan
The molecular mechanism of neural induction: neural differentiation of Triturus ectoderm exposed to Hepes buffer
Ectoderm was isolated from early gastrula stages of Triturus alpestris and cultured in salt solution buffered with either bicarbonate or Hepes as the principal buffer substance. When bicarbonate was the principal buffer substance or when bicarbonate was omitted, the isolated ectoderm formed atypical epidermis. When Hepes was added as a buffer substance, neural tissue was formed in a high percentage
Hildegard Tiedemann
Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases
The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.
Kim, Hyunjung [University of Tennessee, Knoxville (UTK); Kaczmarski, Krzysztof [University of Tennessee and Rzeszow University of Technology, Poland; Guiochon, Georges A [ORNL
Stability of ertapenem in aqueous solutions.
The kinetics of degradation of ertapenem was studied in aqueous solutions at 303, 313, 323 and 333 K and pH 0.42-12.5. Degradation was studied using two methods: HPLC (LiChrospher RP-18 column, 5 microm, 250 mm x 4 mm; mobile phase: methanol-phosphate buffer 25 mmol l(-1), pH 6.5 (15:85, v/v); flow rate--1.2 ml/min; detection UV--298 nm) and UV (294 nm). Specific acid-base catalysis involves: (a) hydrolysis of ertapenem, catalysed by hydrogen ions; (b) hydrolysis of ertapenem dianions catalysed by hydroxide ions; (c) spontaneous hydrolysis of zwitter ions and dianions of ertapenem under the influence of water. The thermodynamic parameters of these reactions--energy, enthalpy and entropy of activation were calculated. It was observed that buffer catalysis occurred in acetate, phosphate and borate buffers. PMID:16914282
Zajac, Marianna; Cielecka-Piontek, Judyta; Jeli?ska, Anna
Buffering as a means for increasing growth and butanol production by Clostridium acetobutylicum
Summary The objective of this work was to optimize butanol formation in the acetone-butanol-ethanol (ABE) fermentation by examining the level of buffering as it affects the dissociation of butyric acid to the less toxic butyrate anion. Experiments were carried out in batch culture using chemically defined (P2) or complex media containing various buffering agents. These included salts of acetate, citrate,
Dennis L. Bryant; Hans P. Blaschek
Use of 1.0% or 0.5% KI-buffered Cathode Solution in ECC Ozonesondes: An Analysis of Dual-Ozonesonde Flights Over McMurdo Station, Antarctica Through Comparison With Remote Measurements and a Transfer Function to Convert Between Solution
Balloon-borne electrochemical concentration cell ozonesondes have been used to measure vertical profiles of ozone concentration from 0 to ~ 35km above McMurdo Station, Antarctica since 1986. These instruments have precisions of ~ 5%. The accuracy partially depends on the concentration of potassium- iodide (KI) cathode solution used in the electrochemical concentration cell. The use of 1.0% KI sensing solution has been maintained at McMurdo, even though in 1996 the manufacturer recommended reducing the concentration to 0.5%. Since then, laboratory studies (Smit et al., 2006) and field comparisons (Deshler et al., 2006) have indicated that the use of 1.0% KI cathode sensing solution can lead to an overestimation of ozone of up to 5% below 20 km, and up to 10% above 20 km. However, these overestimations are thought to be dependent on the amount of ozone entering the chamber, and thus could be less for measurements taken during times of polar ozone depletion. Here, we present the results of dual ozonesonde flights over McMurdo Station, Antarctica (78¯ S) using 1.0% and 0.5% buffered KI solution. Comparison between vertical ozone profiles from dual flights shows that 0.5% buffered solution consistently gives lower values of ozone than the 1.0% buffered solution when ozone partial pressure is > 5mPa. Total column ozone values are calculated from balloon flight measurements and compared with total column ozone measured by the Total Ozone Mapping Spectrometer (TOMS) on NASA's Earth Probe satellite and by a Dobson spectrophotometer operated approximately 1 km from McMurdo station. When total column ozone is > 250DU, the 0.5% solution compares better with the TOMS and Dobson spectrophotometer data. However, in most cases where total ozone is < 250DU, measurements with 1.0% solution compare better with both TOMS and Dobson spectrophotometer measurements. Recent analysis of dual-ozonesonde flights in mid- and polar latitudes has led to the development of a simple linear transfer function where the Ratio (1.0KI/0.5KI) = 1.106 - 0.027 æ log10(Pressure). This transfer function has been suggested for homogenizing long-term data sets where both 1.0% and 0.5% KI-sensing solutions have been used, and thus its application is investigated here.
Mercer, J. L.; Deshler, T.; Wood, S. W.; Nichol, S.
Kinetics of pyrite to pyrrhotite reduction by hydrogen in calcite buffered solutions between 90 and 180 ¯C: Implications for nuclear waste disposal
The kinetics of abiotic redox reactions induced by hydrogen are poorly documented although it represents a growing area of interest in terms of both nuclear waste storage assessment and the comprehensive study of hydrogen-rich fluid in mid-ocean ridge hydrothermal systems. We present an experimental kinetics study of pyrite reduction into pyrrhotite under significant H 2 pressure and mid-hydrothermal conditions. We describe the mechanism and kinetic behavior of this reaction by combining textural and solution analyses under various conditions of temperature, pyrite particles size, H 2 pressure and pH. When pH is controlled by calcite, the reaction presents all the characteristics of a coupled dissolution-precipitation mechanism occurring at the pyrite-pyrrhotite interface. By considering the chemical affinity of the coupled reaction as a function of reaction extent, we demonstrate that the spatial coupling is induced both by pyrite as a substrate for pyrrhotite nucleation and by the role of fluid chemistry at the reaction front. Far from equilibrium with respect to pyrite, the kinetics of sulfide production associated with the reaction are linearly related to the square root of time with an activation energy of 53 kJ/mol. This value is higher than what is expected for a diffusion-controlled kinetic regime. We suggest that the reaction rate is controlled both by pyrite reductive dissolution and by sulfide diffusion through the porous pyrrhotite microstructure. We provide a simple sulfide production-rate expression on the basis of our measured rate constants that can be used in geochemical modeling to further evaluate the impact of hydrogen on pyrite under nuclear waste disposal conditions.
Truche, Laurent; Berger, Gilles; Destrigneville, Christine; Guillaume, Damien; Giffaut, Eric
[Fe3(?3-O)(?-OAc)6(py)3][FeBr4]2[pyñH], complex (1), (OAc is acetate) was prepared from the reaction of FeBr3 with pyridine in 1.2 molar aqueous HBr and 2.4 molar aqueous CH3COOH. Recrystallization of 1 in acetonitrile produced the [Fe3(?3-O)(?-OAc)6(py)3][FeBr4] complex (2). Both complexes were characterized by IR and 1H NMR spectroscopies and their structures were studied using the single-crystal diffraction method. There is a lack of
Vahid Amani; Nasser Safari; Hamid Reza Khavasi
Buffered Telemetry Demodulator
Buffered telemetry demodulator (BTD) is radio receiver designed mainly for recovery of low-rate data binery phase-modulated onto square-wave subcarrier on sinusoidal or suppressed sinusoidal carrier signal and received at low symbol-to-noise ratio. In BTD, received signal not only processed in real time but also recorded and subsequently reprocessed to recover data otherwise lost. BTD could be implemented on general-purpose computer workstation.
Tsou, Haiping; Hinedi, Sami M.; Shah, Biren; Lee, Robert
Electrochemical sensor for 2,4-dichlorophenoxy acetic acid using molecularly imprinted polypyrrole membrane as recognition element
An electrochemical sensor based on molecularly imprinted polypyrrole membranes is reported for the determination of 2,4-dichlorophenoxy\\u000a acetic acid (2,4-D). The sensor was prepared by electropolymerization of pyrrole on a glassy carbon electrode in the presence\\u000a of 2,4-D as a template. The template was removed by overoxidation at +1.3 V in buffer solution. The sensor can effectively\\u000a improve the reductive properties of
Chenggen Xie; Shan Gao; Qingbao Guo; Ke Xu
Simultaneous routing and buffer insertion with restrictions on buffer locations
During the routing of global interconnects, macro blocks formuseful routing regions which allow wires to go through but forbidbuffers to be inserted. They give restrictions on bufferlocations. In this paper, we take these buffer location restrictionsinto consideration and solve the simultaneous mazerouting and buffer insertion problem. Given a block placementdefining buffer location restrictions and a pair of pins(a source and
Hai Zhou; D. F. Wong; I-Min Liu; Adnan Aziz
Pallidol hexa-acetate ethyl acetate monosolvate
The entire molÙecule of pallidol hexaÙacetate {systematic name: (Ý)-(4bR,5R,9bR,10R)-5,10-bisÙ[4-(acetÙyloxy)phenÙyl]-4b,5,9b,10-tetraÙhydroÙindenoÙ[2,1-a]indene-1,3,6,8-tetrayl tetraÙacetate} is completed by the application of twofold rotational symmetry in the title ethyl acetate solvate, C40H34O12ñC4H8O2. The ethyl acetate molÙecule was highly disordered and was treated with the SQUEEZE routine [Spek (2009 ?). Acta Cryst. D65, 148155]; the crystallographic data take into account the presence of the solvent. In pallidol hexaÙacetate, the dihedral angle between the fused five-membered rings (r.m.s. deviation = 0.100?é) is 54.73?(6)¯, indicating a significant fold in the molÙecule. Significant twists between residues are also evident as seen in the dihedral angle of 80.70?(5)¯ between the five-membered ring and the pendent benzene ring to which it is attached. Similarly, the acetate residues are twisted with respect to the benzene ring to which they are attached [CO(carbÙoxy)CC torsion angles = ?70.24?(14), ?114.43?(10) and ?72.54?(13)¯]. In the crystal, a three-dimensional architecture is sustained by CH?O interÙactions which encompass channels in which the disordered ethyl acetate molÙecules reside.
Mao, Qinyong; Taylor, Dennis K.; Ng, Seik Weng; Tiekink, Edward R. T.
Optimization of protein solution by a novel experimental design method using thermodynamic properties.
In this study, the structural stability of hen egg white lysozyme in solution at various pH levels and in different types of buffers, including acetate, phosphate, histidine, and Tris, was investigated by means of differential scanning calorimetry (DSC). Reasonable pH values were selected from the buffer ranges and were analyzed statistically through design of experiment (DoE). Four factors were used to characterize the thermograms: calorimetric enthalpy (?H), temperature at maximum heat flux (T( m )), van't Hoff enthalpy (?H( V )), and apparent activation energy of protein solution (E(app)). It was possible to calculate E(app) through mathematical elaboration from the Lumry-Eyring model by changing the scan rate. The transition temperature of protein solution, T( m ), increased when the scan rate was faster. When comparing the T( m ), ?H( V ), ?H, and E(app) of lysozyme in various pH ranges and buffers with different priorities, lysozyme in acetate buffer at pH 4.767 (scenario 9) to pH 4.969 (scenario 11) exhibited the highest thermodynamic stability. Through this experiment, we found a significant difference in the thermal stability of lysozyme in various pH ranges and buffers and also a new approach to investigate the physical stability of protein by DoE. PMID:23054718
Kim, Nam Ah; An, In Bok; Lee, Sang Yeol; Park, Eun-Seok; Jeong, Seong Hoon
Mechanisms of retardation of rigid spherical particles with 3 to 1,085 nm radius in capillary electrophoresis, using buffered polyacrylamide (molecular weight 5 x 10(6)) solutions.
Subjecting particles in the size range of 3 to 1085 nm radius (R) to capillary electrophoresis in buffered solution of entangled uncrosslinked polyacrylamide (M(r) 5 x 10(6)), it was found that particle size-dependent retardation ("molecular sieving") becomes electric field- and particle size range-dependent once the particle size exceeds 15-20 nm in radius. The field strength dependence of the retardation coefficient [KR = d(log mobility)/ d(polymer concentration] and the positive or negative sign of dKR/dR suggest the existence of two different mechanisms of molecular sieving depending on the particle size range: particles with diameters less than the screening length (or blob size) of the polymer network are thought to penetrate into the available spaces within a discontinuous polymer network; particles with diameters larger than the screening length (or blob size) of the polymer network are thought to undergo size-dependent retardation by exerting shear stress against polymer chains, and displacing them, so as to cause local deformations in a continuous polymer network. A limit in the separating capacity of molecular sieving, due to a sharp increase in the rate of band widening with polymer concentration, was found when the value of the retardation coefficient exceeded 60 (mL/g). PMID:8832177
Radko, S P; Chrambach, A
[Preparation and testing of buffers for fibrinogen].
Chloride-citrate-glucose solution was used in fibrinogen preparation for intravenous administration. Concentrated hydrochloric acid previously used for preparation of buffers for fibrinogen has been replaced by the diluted one enabling easier and more precise buffer pH regulation and faster fibrinogen dissolution. Procedure for spectrophotometric determination of the total citrate ion buffer system, sodium-citrate and citric acid was developed. Obtained results were within the prescribed limits but the ones obtained by officinal titration in non-aqueous medium were significantly decreased. Glucose was determined before sterilization by polymetric, and after sterilization by iodometric procedure. Chloride content was determined by coulometric titration and sodium content by flame photometry. Used analytic methods are simple and obtained results accurate and reproducible. PMID:8553608
Poprzen, V; Popovi?, R; Antunovi?, M
Cellulose acetate electrospun fiber mats for controlled release of silymarin.
In this research, the silymarin-loaded electrospun cellulose acetate (CA) fibers were prepared which containing silymarin in various amounts (i.e., 2.5-20 wt.% based on the weight of CA powder). Incorporation of silymarin in the neat CA solution did not affect the morphology of the resulting fibers, as both the neat and the silymarin-loaded CA fibers were smooth. The average diameters of silymarin-loaded CA fiber ranged between 550-900 nm. No presence of the silymarin aggregates of any kind was observed on the surfaces of these fibers, suggesting that the silymarin was encapsulated well within the fibers. These results were confirmed by lowering the glass transition temperature and the melting temperature of the silymarin-loaded electrospun CA fibers which is determined by DSC technique. The release characteristic of silymarin from the silymarin-loaded CA fiber mats was investigated by the total immersion in the solution of 1/1 phosphate buffer/methanol medium pH 7.4 at 37 degrees C. The silymarin release from the silymarin-loaded electrospun CA fiber mat is monotonously increased to reach the maximum value at 480 min. The maximum amount of silymarin released from these materials increases with the increasing of initial silymarin loading in the spinning CA solutions. Since no aggregation of silymarin was found on the surface of the silymarin-loaded fibers, the release of the silymarin from fiber mats was mainly by the diffusion. PMID:22524059
Phiriyawirut, Manisara; Phaechamud, Thawatchai
Valuation of forested buffers
The research concentrated on two fronts: (1) defining relationships between land use complex and nitrate and sediment concentrations; and (2) developing a method for assessing the extent of potential and water quality improvements available through land management options and their associated costs. In this work, selected basins of the Fish River (Alabama) were delineated, land use/land cover types were classified, and "contributing zones" were delineated using Geographic Information System (GIS) and Remote Sensing (RS) analytical tools. Water samples collected from these basins were analyzed for their nutrient contents. Based on measured nitrate and sediment concentrations in basin streams, a linkage model was developed. This linkage model relates land use/land cover with the pollution levels in the stream. The linkage model was evaluated at three different scales: (1) the basin scale; (2) the contributing zone scale; and (3) the stream buffer/riparian zone scale. The contributing zone linkage model suggests that forests act as a sink or transformation zone. Residential/urban/built-up areas were identified as the strongest contributors of nitrate in the contributing zones model and active agriculture was identified as the second largest contributor. Regression results for the "land use/land cover diversity" model (stream buffer/riparian zone scale) suggest that areas that are close (adjacent) to the stream and any disturbances in these areas will have major impacts on stream water quality. The economic model suggests the value of retiring lands from agricultural land uses to forested buffers varies from 0 to 3067 per hectare, depending on the types of crops currently grown. Along with conversion costs, this land value forms the basis for estimates of the costs of land management options for improving (or maintaining) water quality throughout the study area. The model also shows the importance of stream-side management zones, which are key to maintenance of stream water quality.
Basnyat, Prakash
Liquid Chromatography-Tandem Mass Spectrometry for Analysis of Intestinal Permeability of Loperamide in Physiological Buffer
Analysis of in vitro samples with high salt concentrations represents a major challenge for fast and specific quantification with liquid chromatography-tandem mass spectrometry (LC-MS/MS). To investigate the intestinal permeability of opioids in vitro employing the Ussing chamber technique, we developed and validated a fast, sensitive and selective method based on LCMS/MS for the determination of loperamide in HEPES-buffered Ringer's solution. Chromatographic separation was achieved with an Atlantis dC18 column, 2.1 mmæ20 mm, 3 çm particle size and a gradient consisting of methanol/0.1% formic acid and ammonium acetate. The flow rate was 0.7 ml/min, and the total run time was 3 min. For quantification, two mass transitions for loperamide and a deuterated internal standard (methadone-d3) were used. The lower limit of loperamide quantification was 0.2 ng/ml. This new LC-MS/MS method can be used for the detection of loperamide in any experimental setup using HEPES-buffered Ringer's solution as a matrix compound.
Rubelt, Miriam S.; Amasheh, Salah; Grobosch, Thomas; Stein, Christoph
Highly textured La 2 Zr 2 O 7 and CeO 2 buffer layers by ink jet printing for coated conductors
The objective of this paper is to prove the possibility to produce single side buffered substrates for coated conductors.\\u000a We report for the first time the production of highly textured NiW\\/La2Zr2O7\\/CeO2 system by all-chemical solution deposition means using an in-house built drop-on-demand ink-jet printer. Lanthanum zirconate\\u000a precursor ink was produced using lanthanum acetate and zirconium n-propoxide modified with propionic and
M. C. Cordero-Cabrera; T. Mouganie; B. A. Glowacki; M. Bðcker; M. Falter; B. Holzapfel; J. Engell
The physicochemical property characterization of agar acetate.
A series of agar acetates with different degree of substitution (DS) were prepared, and their properties were determined and analyzed. The results showed that the gelling temperature, the gel melting temperature, the gel strength, the gel hardness, the gel fracturability, the gel springiness and the solution apparent viscosity of agar acetates all decreased except that their gel cohesiveness increased with the increase of DS. The variation process of agar molecules in solution from coil to helix could be also observed by measuring solution optical rotation in a lower concentration at which even the solution could not form a gel. The gel skeleton structures of agar acetates were of porous network structures, and the pores became smaller and denser with the increase of DS. After acetylation, the water holding capacity of the agar was improved, but its thermal stability was lowered. PMID:24906725
Xia, Kai; Liu, Xin; Zhao, Jingkun; Zhang, Xiaodong
Single-biomolecule observation with micro one-way valves for rapid buffer exchange
This paper describes a method for the rapid exchange of buffer solution during single-molecule observation. We use a simple, transparent, all-plastic one-way valve integrated on a coverslip on a flow cell. The valve is formed using a membrane made of parylene covering a microhole. It opens when a buffer solution is introduced from the microhole (the flow pushes the cover membrane) and closes when suctioning the buffer solution (the membrane is pulled back and seals the microhole to prevent the diffusion of the solution). To check valve performance, we observed the response of a rotary biomotor, F1-ATPase, for several buffer solutions in the fabricated chamber.
Hirono-Hara, Yoko; Noji, Hiroyuki; Takeuchi, Shoji
Preparation of vinyl acetate
This invention pertains to the preparation of vinyl acetate by contacting a mixture of hydrogen and ketene with a heterogeneous catalyst containing a transition metal to produce acetaldehyde, which is then reacted with ketene in the presence of an acid catalyst to produce vinyl acetate.
Tustin, Gerald Charles (Kingsport, TN); Zoeller, Joseph Robert (Kingsport, TN); Depew, Leslie Sharon (Kingsport, TN)
Tustin, G.C.; Zoeller, J.R.; Depew, L.S.
Blending effects on adsorption and micellization of different membrane protein solubilizers II. A thermodynamic study on a mixed system of CHAPS with a bile salt in pH 7.4 phosphate buffer solution.
For a mixed system of a typical membrane protein solubilizer CHAPS (a derivative of a bile acid cholic acid) combined with a bile salt (sodium salt of glycocholic acid, NaGC), which is also a candidate as a membrane protein solubilizer, micellization and adsorbed film formation in a phosphate buffer solution of pH 7.4 at 303 K were studied paying special attention to the synergistic effect upon mixing. The collection of sufficient data based on plots of surface tension (gamma) versus logarithmic concentration (C(t) or m(t)) in total molality at discrete mole fractions (X(2)) in the mixture of surfactants 1 and 2 (where 1 and 2 correspond to CHAPS and NaGC, respectively) allowed us to accurately determine critical micelle concentration (CMC), minimum surface tension at CMC (gamma(CMC)), and the slope (dgamma/dlnC(t)) from the gamma-lnC(t) curves in the concentration range just below CMC. These data enabled us to estimate surface excess (Gamma(t)), and mean molecular area (A(m)) in addition to such parameters as the minimum surface Gibbs energy (G(min)((S))), pC(20) and CMC/C(20) related to synergism accompanied by blending. Applying the regular solution theory (RST), the relation of compositions of the singly dispersed phase (X(2)) and the micellar phase (Y(2)) as well as the interaction parameter (omega(R)) (by using the Rubingh's equations) were estimated. The relation between the composition in the adsorbed film (Z(2)) and X(2) together with the interaction parameter (omega(A)) in the adsorbed film was also estimated. The partial molecular area (PMA), gamma(CMC), and G(min)((S)) were examined as functions of X(2) and/or Z(2.) The resultant CMC-X(2) and CMC-Y(2) curves and omega(R) and omega(A) values have demonstrated that mixed micelles and adsorbed film formation are attained accompanying to some extent enhanced intermolecular interaction (with negative omega(R) and omega(A) values). Comparing with previous results for mixed systems of CHAPS with n-acyl (octanoly, nonanoyl, and decanoyl)-N-methylglucamides [MEGA-n's (n=8, 9, and 10)] and of sodium chenodeoxycholate (NaCDC) with sodium ursodeoxycholate (NaUDC), the synergism observed for the mixed system of CHAPS with NaGC lies between both combinations. However the expected properties as a membrane protein solubilizer are judged to be sufficient. PMID:17997082
Oh, Se-Woung; Na, Jin-Su; Ko, Jeong-Soo; Nagadome, Shigemi; Sugihara, Gohsuke
Doped with Sodium Acetate and Metallic Sodium
We have investigated the thermoelectric properties of p-type Na-doped Mg2 Si0.25Sn0.75 solid solutions prepared by liquid-solid reaction and hot-pressing methods. Na was introduced into Mg2Si0.25Sn0.75 by using either sodium acetate (CH3COONa) or metallic sodium (2 N). The samples doped with sodium acetate consisted of phases with antifluorite structure and a small amount of MgO as revealed by x-ray diffraction, whereas the sample doped with metallic sodium contained the Sn, MgO, and Mg2SiSn phases. The hole concentrations of Mg1.975Na0.025Si0.25Sn0.75 doped by sodium acetate and metallic sodium were 1.84 æ 1025 m-3 and 1.22 æ 1025 m-3, respectively, resulting in resistivities of 4.96 æ 10-5 ? m (sodium acetate) and 1.09 æ 10-5 ? m (metallic sodium). The Seebeck coefficients were 198 ?V K-1 (sodium acetate) and 241 ?V K-1 (metallic sodium). The figures of merit for Mg1.975Na0.025Si0.25Sn0.75 were 0.40 æ 10-3 K-1 (sodium acetate) and 0.25 æ 10-3 K-1 (metallic sodium) at 400 K. Thus, sodium acetate is a suitable Na dopant for Mg2Si1- x Sn x .
Tada, Satoki; Isoda, Yukihiro; Udono, Haruhiko; Fujiu, Hirofumi; Kumagai, Shunji; Shinohara, Yoshikazu
Isoelectric buffers for capillary electrophoresis. 2. Bismorpholine derivative of a carboxylic acid as a low molecular weight isoelectric buffer.
A new compound class of synthetic isoelectric buffers is introduced, designed as a small molecule with one fully or prevailingly dissociated acidic group (such as sulfonic or carboxylic) and two partly pronated (buffering) basic amino groups attached onto a hydrophilic UV-transparent backbone. As an example, a new isoelectric compound 2,2-bis(4-morpholinylmethyl)propanoic acid (BMMPA) was synthesized by attaching two morpholine groups onto a molecule of pivalic acid. It was characterized as having an isoelectric point pI = 6.5 and exhibiting satisfactory buffering capacity at the pI. Solutions of BMMPA are transparent down to the low-UV spectral region, thus making it a potentially suitable buffer for a number of separation methods. Its use in capillary electrophoresis was demonstrated in a separation system for indirect photometric detection of anions based on an electrolyte with the anionic dye Orange G as the indirect detection probe and using BMMPA as a buffer. The use of an isoelectric buffering compound brings the advantages of a buffered electrolyte without the concomitant introduction of co-ions that would be detrimental to the indirect detection process. Submicromole per liter limits of detection for a number of inorganic and small organic ions were achieved. Optimal structural properties of the isoelectric buffer with respect to its buffering properties are discussed. PMID:15623286
Rodemann, Thomas; Johns, Cameron; Yang, Wen-Schu; Haddad, Paul R; Macka, Miroslav
Effects of Buffer Loading for Electrospray Ionization Mass Spectrometry of a Noncovalent Protein Complex that Requires High Concentrations of Essential Salts
Electrospray ionization (ESI) mass spectrometry (MS) is a powerful method for analyzing the active forms of macromolecular complexes of biomolecules. However, these solutions often contain high concentrations of salts and/or detergents that adversely effect ESI performance by making ion formation less reproducible, causing severe adduction or ion suppression. Many methods for separating complexes from nonvolatile additives are routinely used with ESI-MS, but these methods may not be appropriate for complexes that require such stabilizers for activity. Here, the effects of buffer loading using concentrations of ammonium acetate ranging from 0.22 to 1.41 M on the ESI mass spectra of a solution containing a domain truncation mutant of a ?54 activator from Aquifex aeolicus were studied. This 44.9 kDa protein requires the presence of millimolar concentrations of Mg2+, BeF3?, and ADP, (at ?60 ¯C) to assemble into an active homo-hexamer. Addition of ammonium acetate can improve signal stability and reproducibility, and can significantly lower adduction and background signals. However, at higher concentrations, the relative ion abundance of the hexamer is diminished, while that of the constituent monomer is enhanced. These results are consistent with loss of enzymatic activity as measured by ATP hydrolysis and indicate that the high concentration of ammonium acetate interferes with assembly of the hexamer. This shows that buffer loading with ammonium acetate is effective for obtaining ESI signal for complexes that require high concentrations of essential salts, but can interfere with formation of, and/or destabilize complexes by disrupting crucial electrostatic interactions at high concentration.
Sterling, Harry J.; Batchelor, Joseph D.; Wemmer, David E.; Williams, Evan R.
Nanofabrication in cellulose acetate.
We have demonstrated nanofabrication with commercialized cellulose acetate. Cellulose acetate is used for bulk nanofabrication and surface nanofabrication. In bulk nanofabrication, cellulose acetate reacts with an e-beam and permanent patterns are formed in it instead of being transferred to other substrates. We have studied the nano relief modulation performance of cellulose acetate before and after development. The depth of the nanopatterns is magnified after development, and is varied by exposing dosage and line width of the pattern. The thinnest 65 nm wide line is achieved in the bulk fabrication. We also demonstrate a binary phase Fresnel lens array which is directly patterned in a cellulose acetate sheet. Because of its unique mechanical and optical properties, cellulose is a good candidate for a template material for soft imprinting lithography. In the surface nanofabrication, cellulose acetate thin film spin-coated on silicon wafers is employed as a new resist for e-beam lithography. We achieved 50 nm lines with 100 nm pitches, dots 50 nm in diameter, and single lines with the smallest width of 20 nm. As a new resist of e-beam lithography, cellulose acetate has high resolution comparable with conventional resists, while having several advantages such as low cost, long stock time and less harmfulness to human health. PMID:19224020
Zeng, Hongjun; Lajos, Robert; Metlushko, Vitali; Elzy, Ed; An, Se Young; Sautner, Joshua
Application of solution deposition techniques to coated conductor fabrication
Coated conductors offer a viable alternative to the BSCCO PIT tapes. However, at the current juncture, results are being reported for conductors with buffer layers and superconductor layers processed using conventional thin film deposition which are vacuum based. Also these conductors are fabricated using four or five buffer layers between the superconductor and the metal substrate. These aspects of the fabrication route drive the cost of the process to prohibitively high values. This work is directed at the development of fabrication routes for cube textured nickel substrates, and metallorganic decomposition (MOD) routes for buffer layers and Y123 layers using simple solution based techniques which can be readily scaled. Studies of cube texturing of nickel using rolling and recrystallization showed that it is possible to produce textured nickel substrates with a FWHM of 8--10¯. The substrate quality of the nickel is determined by the purity of the cube texture and the cleanliness of the surface. Processing of oriented buffer layers of barium zirconate and strontium titanate using simple metal organic decomposition routes have been studied. These processes, which use precursor solutions made by dissolution of simple acetates in common solvents like acetic acid and methanol, produce highly oriented buffer layers even when processed in a partially reducing atmosphere. Therefore, these MOD routes for buffer layer processing are compatible with nickel substrates and produce buffer layers oriented as sharply as the underlying nickel substrate. Y123 processing using fluorinated precursors, as in the TFA process, effectively circumvents the BaCO3 problem associated with most MOD routes for Y123 processing. This route, under optimized process conditions, yields Y123 films with Jc of the order of 106 A/cm2 on single crystal substrates. Studies of the compatibility of the TFA process with the MOD buffer layers showed that current density of the order of 106 A/cm 2 can be obtained for Y123 on buffered single crystals. These results give promise to the applicability of these scaleable solution deposition techniques to coated conductor fabrication.
Sathyamurthy, Srivatsan
The Endogenous Calcium Buffer and the Time Course of Transducer Adaptation in Auditory Hair Cells
anism that is sensitive to the level of internal calcium buffer. We have used the properties of transducer adaptation to compare the effects of exogenous calcium buffers in the patch electrode solution with those of the endogenous buffer assayed with perforated-patch recording. The endogenous buffer of the hair bundle was equivalent to 0.1-0.4 mM BAPTA and, in a majority of
A. J. Ricci; R. Fettiplace
Oracle Log Buffer Queueing
The purpose of this document is to investigate Oracle database log buffer queuing and its affect on the ability to load data using a specialized data loading system. Experiments were carried out on a Linux system using an Oracle 9.2 database. Previous experiments on a Sun 4800 running Solaris had shown that 100,000 entities per minute was an achievable rate. The question was then asked, can we do this on Linux, and where are the bottlenecks? A secondary question was also lurking, how can the loading be further scaled to handle even higher throughput requirements? Testing was conducted using a Dell PowerEdge 6650 server with four CPUs and a Dell PowerVault 220s RAID array with 14 36GB drives and 128 MB of cache. Oracle Enterprise Edition 188.8.131.52 was used for the database and Red Hat Linux Advanced Server 2.1 was used for the operating system. This document will detail the maximum observed throughputs using the same test suite that was used for the Sun tests. A detailed description of the testing performed along with an analysis of bottlenecks encountered will be made. Issues related to Oracle and Linux will also be detailed and some recommendations based on the findings.
Rivenes, A S
Mechanisms of buffer therapy resistance
Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit.
Bailey, Kate M.; Wojtkowiak, Jonathan W.; Cornnell, Heather H.; Ribeiro, Maria C.; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J.
Determination of Indole Acetic Acid by the Salkowsky Reaction
RECENTLY attention has been focused on the reaction of indole acetic acid with ferric ions. Cohen et al.1 have shown that indole acetic acid forms a chelate with iron at acid pH and this has been confirmed by Recaldin and Heath2. The latter state that at pH 2.6 iron slowly decomposes the indole acetic acid in the solution. The oxidation
A. M. Mayer
Effect of Ethylene diamine tetra acetic acid and sodium hypochlorite solution conditioning on microtensile bond strength of one-step self-etch adhesives
Background: Attempts to improve bond strength of self-etch adhesives can enhance the durability of composite restorations. Aims: The aim of the present study was to evaluate the effect of collagen and smear layer removal with sodium hypochlorite solution (NaOCl) and EDTA on micro-tensile bond strength (?TBS) of self-etch adhesives to dentin. Settings and Design: It was an in-vitro study. Materials and Methods: Seventy-two teeth were divided into eight groups and their crowns were ground perpendicular to their long axis to expose dentin. The teeth were polished with silicon-carbide papers. The groups were treated as follows: No conditioning, 0.5-M EDTA conditioning, 2.5% NaOCl conditioning, NaOCl + EDTA conditioning. The surfaces were rinsed and blot-dried. Clearfil S3 and I-Bond were applied according to manufacturers instructions and restored with Z100 composite. After 500 cycles of thermo-cycling between 5¯C and 55¯C, the samples were sectioned and tested for ?TBS. Statistical Analysis: Data were analyzed by two-way ANOVA and Tukey-HSD test. Results: The highest ?TBS was recorded with Clearfil S3 + NaOCl + EDTA, and the lowest was recorded with I-Bond without conditioning. ?TBS in EDTA-and EDTA + NaOCl-treated groups was significantly higher than the control and NaOCl-conditioned groups. Conclusions: Application of EDTA or EDTA + NaOCl before one-step self-etch adhesives increased ?TBS.
Kasraei, Shahin; Azarsina, Mohadese; Khamverdi, Zahra
Growth Conditions of Sequentially Electrodeposited Buffer Layers for YBCO Superconductor
We report recent technical advances in the fabrication by sequential electrodeposition (ED) of Gd2O3\\/Gd2Zr2O7 buffer architecture. A systematic study is performed for a fundamental understanding of the buffer structure grown by ED. The electrolyte composition, solution flow rate, composition\\/concentration of chemicals, and annealing conditions are found to affect considerably the deposition of the layer, formation of the pyrochlore oxide, and
Sovannary Phok; Wenjun Zhao; Raghu Bhattacharya
Mechanisms of acetate formation and acetate activation in halophilic archaea
The halophilic archaea Halococcus (Hc.) saccharolyticus, Haloferax (Hf.) volcanii, and Halorubrum (Hr.) saccharovorum were found to generate acetate during growth on glucose and to utilize acetate as a growth substrate. The mechanisms of acetate formation from acetyl-CoA and of acetate activation to acetyl-CoA were studied. Hc. saccharolyticus, exponentially growing on complex medium with glucose, formed acetate and contained ADP-forming acetyl-CoA
Christopher Brðsen; Peter Sch—nheit
Effect of light and heat on the stability of montelukast in solution and in its solid state
The chemical stability of montelukast (Monte) in solution and in its solid state was studied. A simultaneous measurement of Monte and its degradation products was determined using a selective HPLC method. The HPLC system comprised a reversed phase column (C18) as the stationary phase and a mixture of ammonium acetate buffer of pH 3.5 and methanol (15:85v\\/v) as the mobile
Mahmoud M. Al Omari; Rufaida M. Zoubi; Enas I. Hasan; Tariq Z. Khader; Adnan A. Badwan
Buffer effects on the zeta potential of ultrafiltration membranes
Membrane charge can have a large effect on the performance of many ultrafiltration processes. Previous studies of membrane charge have generally been performed using solutions of simple monovalent salts; however, the effective surface charge can be strongly influenced by the binding or adsorption to the membrane surface of specific buffer ions present in actual process solutions. Experimental data were obtained
Douglas B. Burns; Andrew L. Zydney
Analysis of a buffer strip laminate with a cutout
Stress concentration at holes results in a loss of strength of composite structures, as much as one-third in tension and one-half in compression. A model based on the classical shear lag theory for predicting the fracture behavior of a unidirectional laminate with a pair of (hybrid) buffer strips and with a transverse crack in the form of broken fiber is extended to include a circular cutout. An assessment of the buffer strips, soft or stiff, is presented. A simplified model consisting of two half-planes and three finite-width unidirectional strips is analyzed. The basic solution required in the analysis of this problem is the solution of a unidirectional half-plane with a circular cutout and a longitudinal matrix split between two arbitrary fibers. By letting the split length approach infinity, the solution of the finite-width strip with a circular cutout is obtained. The final solution to the buffer strip laminate is obtained by making use of the half-plane and the finite-width strip solutions. The results show that the use of softening strips in composite laminates with circular cutouts will reduce the stress concentration at the hole. However, the stress concentration in the undamaged main panel is increased with a decrease in the buffer strip stiffness; thus, there is a cutoff after which further softening of the buffer strip will not increase the notched strength of the laminate.
Meyer, E. S.; Dharani, L. R.
Vinyl acetate polymerization by ionizing radiation
For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000g\\/mol, respectively. >From the characterization
A. C. Mesquita; M. N. Mori; J. M. Vieira; L. G. Andrade e. Silva
For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000g\\/mol, respectively. From the characterization
A. C Mesquita; M. N Mori; J. M Vieira; L. G. Andrade e Silva
Fatal Hemorrhagic Shock and Acetate Solutions.
One-half of deaths among trauma victims occur within 1 hour of injury and are due to rapid hemorrhage or CNS trauma. We developed a rapid hemorrhage model in unanesthetized swine to simulate human exsanguination. We compared the ability of four crystalloi...
L. W. Traverso W. P. Lee M. J. Langford L. D. Witcher
Buffer gas acquisition and storage
The acquisition and storage of buffer gases (primarily argon and nitrogen) from the Mars atmosphere provides a valuable resource for blanketing and pressurizing fuel tanks and as a buffer gas for breathing air for manned missions. During the acquisition of carbon dioxide (CO2), whether by sorption bed or cryo-freezer, the accompanying buffer gases build up in the carbon dioxide acquisition system, reduce the flow of CO2 to the bed, and lower system efficiency. It is this build up of buffer gases that provide a convenient source, which must be removed, for efficient capture of CO2. Removal of this buffer gas barrier greatly improves the charging rate of the CO2 acquisition bed and, thereby, maintains the fuel production rates required for a successful mission. Consequently, the acquisition, purification, and storage of these buffer gases are important goals of ISRU plans. Purity of the buffer gases is a concern e.g., if the CO2 freezer operates at 140 K, the composition of the inert gas would be approximately 21 percent CO2, 50 percent nitrogen, and 29 percent argon. Although there are several approaches that could be used, this effort focused on a hollow-fiber membrane (HFM) separation method. This study measured the permeation rates of CO2, nitrogen (N2), and argon (Ar) through a multiple-membrane system and the individual membranes from room temperature to 193 K and 10 kPa to 300 kPa. Concentrations were measured with a gas chromatograph. The end result was data necessary to design a system that could separate CO2, N2, and Ar. .
Parrish, Clyde F.; Lueck, Dale E.; Jennings, Paul A.
Radiation sterilization of hydrocortisone acetate.
The feasibility of using high energy ionizing radiation for the sterilization of hydrocortisone acetate was investigated. Hydrocortisone acetate in the form of powder was exposed to different dose levels of gamma radiation using a Cobalt-60 source. The ir...
A. Charef A. Boussaha
An adaptive predictor for media playout buffering
Receiver playout buffers are required to smooth network delay variations for multimedia streams. Playout buffer algorithms such as those commonly used in the Internet, autoregressively measure the network delay and variation and adjust the buffer delay accordingly, to avoid packets arriving too late. In this work, we attempt to adjust the buffer delay based on a prediction of the network
Phillip Deleon; Cormac J. Sreenan
Acetate Production by Methanogenic Bacteria
Methanosarcina barkeri MS and 227 and Methanosarcina mazei S-6 produced acetate when grown on H2-CO2, methanol, or trimethylamine. Marked differences in acetate production by the two bacterial species were found, even though methane and cell yields were nearly the same. M. barkeri produced 30 to 75 ?mol of acetate per mmol of CH4 formed, but M. mazei produced only 8 to 9 ?mol of acetate per mmol of CH4.
Westermann, Peter; Ahring, Birgitte K.; Mah, Robert A.
Levulinyl cellulose esters have been produced as an effective renewable binder for architectural coatings. The title compound, C7H10O4 (systematic name: 2-methyl-5-oxoÙtetraÙhydroÙfuran-2-yl acetate), assigned as the esterifying species, was isolated and crystallized to confirm the structure. In the crystal, the molÙecules pack in layers parallel to (102) utilizing weak CH?O interÙactions.
Tristram, Cameron; Gainsford, Graeme J.; Hinkley, Simon
Evaluation of hypromellose acetate succinate (HPMCAS) as a carrier in solid dispersions.
The utility of hypromellose acetate succinate (HPMCAS), a cellulosic enteric coating agent, as a carrier in a solid dispersion of nifedipine (NP) was evaluated in comparison with other polymers, including hypromellose (HPMC), hypromellose phthalate (HPMCP), methacrylic acid ethyl acrylate copolymer (MAEA), and povidone (PVP). An X-ray diffraction study showed that the minimum amount of HPMCAS required to make the drug completely amorphous was the same as that of other cellulosic polymers, and less than that in dispersions using non-cellulosic polymers. Hypromellose acetate succinate showed the highest drug dissolution level from its solid dispersion in a dissolution study using a buffer of pH 6.8. This characteristic was unchanged after a storage test at high temperature and high humidity. The inhibitory effect of HPMCAS on recrystallization of NP from a supersaturated solution was the greatest among all the polymers examined. Further, the drug release pattern could be modulated by altering the ratio of succinoyl and acetyl moieties in the polymer chain. Our results indicate that HPMCAS is an attractive candidate for use as a carrier in solid dispersions. PMID:15000425
Tanno, FumiÕ; Nishiyama, Yuichi; Kokubo, Hiroyasu; Obara, SakaÕ
Recovery of acetic acid from waste streams by extractive distillation.
Wastes have been considered to be a serious worldwide environmental problem in recent years. Because of increasing pollution, these wastes should be treated. However, industrial wastes can contain a number of valuable organic components. Recovery of these components is important economically. Using conventional distillation techniques, the separation of acetic acid and water is both impractical and uneconomical, because it often requires large number of trays and a high reflux ratio. In practice special techniques are used depending on the concentration of acetic acid. Between 30 and 70% (w/w) acetic acid contents, extractive distillation was suggested. Extractive distillation is a multicomponent-rectification method similar in purpose to azeotropic distillation. In extractive distillation, to a binary mixture which is difficult or impossible to separate by ordinary means, a third component termed an entrainer is added which alters the relative volatility of the original constituents, thus permitting the separation. In our department acetic acid is used as a solvent during the obtaining of cobalt(III) acetate from cobalt(II) acetate by an electrochemical method. After the operation, the remaining waste contains acetic acid. In thiswork, acetic acid which has been found in this waste was recovered by extractive distillation. Adiponitrile and sulfolane were used as high boiling solvents and the effects of solvent feed rate/solution feed rate ratio and type were investigated. According to the experimental results, it was seem that the recovery of acetic acid from waste streams is possible by extractive distillation. PMID:12862234
Demiral, H; Yildirim, M Ercengiz
Plasma acetate turnover and oxidation.
Plasma acetate turnover and oxidation were determined in 11 healthy subjects by the constant infusion of a trace amount of [1-14C]acetate for 6 h. The subjects ages ranged from 22 to 57 yr. There was a positive correlation (P less than 0.001) between plasma acetate concentration and turnover rate, and a negative correlation (P less than 0.001) between turnover and age. The plasma acetate concentration in the subjects 22--28 yr old was 0.17 vs. 0.13 mM (P less than 0.02) in subjects 40--57 yr old. The plasma acetate turnover rate was also greater in the younger age group (8.23 +/- 0.66 vs. 4.98 +/- 0.64 mumol/min . kg, P less than 0.01). Approximately 90% of the plasma acetate turnover was immediately oxidized to CO2 in both age groups, however, 13.2 +/- 0.89% of the CO2 output in the younger group was derived from plasma acetate oxidation compared to 7.9 +/- 0.94% in the older group (P less than 0.01). The mean plasma acetate concentration, turnover, and oxidation in six cancer patients 47--63 yr old were similar to the values observed in the age-matched healthy subjects. Uptake or output of acetate by various tissues was measured by arterial-venous plasma acetate concentration differences. In seven of eight subjects undergoing elective surgery, the arterial-portal venous concentration difference was negative, which indicated that the gastrointestinal tract can contribute to plasma acetate production. Uptake of plasma acetate by both the leg and liver appeared to be dictated by the arterial acetate concentration. Net production of acetate by both the leg and liver was most often observed at arterial plasma acetate concentrations less than 0.08 mM.
Skutches, C L; Holroyde, C P; Myers, R N; Paul, P; Reichard, G A
Determination of thalidomide in transport buffer for Caco-2 cell monolayers by high-performance liquid chromatography with ultraviolet detection
We report simple validated HPLC methods for the determination of thalidomide in the transport buffer for the human colonic cell line (Caco-2) cell monolayers. An aliquot of 50 ?l of the mixture was injected onto a Spherex C18 column (150æ4.6 mm; 5 ?m) at a flow-rate of 0.5 ml\\/min of mobile phase consisting of acetonitrile10 mM ammonium acetate buffer (24:76,
Shufeng Zhou; Yan Li; Phillip Kestell; James W Paxton
Development of a differential pulse voltammetric method for the determination of Silymarin/Vitamin E acetate mixture in pharmaceuticals.
Differential pulse voltammetric method was developed for determination of Silymarin (SMR)/Vitamin E acetate (VEA) mixture in pharmaceuticals. SMR and VE gave well-resolved diffusion-controlled anodic peaks at +756 and +444mV, respectively (versus Ag/AgCl) in Britton-Robinson buffer at pH 2.8. The solution conditions and instrumental parameters were optimized for their quantitative determination. The linear response was obtained in the range 0.1-4.0mgL(-1) with a detection limit of 0.03mgL(-1) for SMR and 0.05-4.0mgL(-1) with a detection limit of 0.01mgL(-1)for VEA. PMID:18371708
Hassan, Ekram M; Khamis, Essam F; El-Kimary, Eman I; Barary, Magda A
Investigation on isobaric vapor liquid equilibrium for acetic acid + water + ( n-propyl acetate or iso-butyl acetate)
Isobaric vaporliquid equilibrium (VLE) data for acetic acid+water, acetic acid+n-propyl acetate, acetic acid+iso-butyl acetate, acetic acid+water+n-propyl acetate, acetic acid+water+iso-butyl acetate are measured at 101.33kPa with a modified Rose still. The nonideal behavior in vapor phase caused by the association of acetic acid are corrected by the chemical theory and HaydenOConnell method, and analyzed by calculating the second virial coefficients and
Chundong Zhang; Hui Wan; Lijun Xue; Guofeng Guan
Buffered electrochemical polishing of niobium
The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a damaged\\u000a surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance\\u000a of the cavities is characterized by a sharp degradation of the quality factor at high surface magnetic field, a phenomenon\\u000a referred to as Q-drop. In
Gianluigi Ciovati; Hui Tian; Sean G. Corcoran
The effect of decaying leaves on the ph and buffer capacity of waters
Acid rain has become a significant environmental problem in the United States. The survival of aquatic life depends on the ability of the aquatic's system to withstand acidic rainwater. This in turn is very dependant on the buffer capacity of the system. Understanding the factors that effect buffer capacity would be very valuable in formulating solutions for the protection of
Paula M. Deano; J. W. Robinson
Buffer Replacement Algorithms for Multimedia Storage Systems
In a disk-based storage system, a buffer cache is usedto reduce the number of disk I\\/O. The buffer manageris responsible for buffer replacement to free memoryin order to accommodate new data blocks from disk.An optimal buffer replacement algorithm is one whichyields the lowest number of cache misses and as a resultthe lowest number of disk I\\/O. In general, optimalbuffer replacement
Banu øzden; Rajeev Rastogi; Abraham Silberschatz
A comparison of Tris-glycine and Tris-tricine buffers for the electrophoretic separation of major serum proteins.
This paper compares different buffer systems for the electrophoretic separation of the five most abundant serum proteins on native-PAGE gel and cellulose membranes. A modified Tris-tricine system was shown to be superior for the separation of these serum proteins in a 7% m/v native-PAGE gel as compared with the traditionally used Tris-glycine and Tris-tricine methods. This modified Tris-tricine buffer system was also employed for the separation of serum proteins using a cellulose acetate membrane and very effective separation was observed as compared with the traditionally used Tris-barbital and Tris-glycine buffer systems. PMID:21818850
Haider, Syed R; Sharp, Barry L; Reid, Helen J
The effect of oral sodium acetate administration on plasma acetate concentration and acid-base state in horses
Aim Sodium acetate (NaAcetate) has received some attention as an alkalinizing agent and possible alternative energy source for the horse, however the effects of oral administration remain largely unknown. The present study used the physicochemical approach to characterize the changes in acid-base status occurring after oral NaAcetate/acetic acid (NAA) administration in horses. Methods Jugular venous blood was sampled from 9 exercise-conditioned horses on 2 separate occasions, at rest and for 24 h following a competition exercise test (CET) designed to simulate the speed and endurance test of 3-day event. Immediately after the CETs horses were allowed water ad libitum and either: 1) 8 L of a hypertonic NaAcetate/acetic acid solution via nasogastric tube followed by a typical hay/grain meal (NAA trial); or 2) a hay/grain meal alone (Control trial). Results Oral NAA resulted in a profound plasma alkalosis marked by decreased plasma [H+] and increased plasma [TCO2] and [HCO3-] compared to Control. The primary contributor to the plasma alkalosis was an increased [SID], as a result of increased plasma [Na+] and decreased plasma [Cl-]. An increased [Atot], due to increased [PP] and a sustained increase in plasma [acetate], contributed a minor acidifying effect. Conclusion It is concluded that oral NaAcetate could be used as both an alkalinizing agent and an alternative energy source in the horse.
Waller, Amanda; Lindinger, Michael I
Sizing Buffers for Pipelined Forwarding Engine
Packet buffers in routers constitute a central element of packet networks. Selecting appropriate buffer size is an important and open research problem. This paper aims to size buffers for forwarding engine known as one of the main parts of a router. First, a high-speed pipeline which is designed for forwarding engine is presented, and its memory analysis model is also
Yufeng Li; Peng Yi; Han Qiu; Julong Lan
Doped LZO buffer layers for laminated conductors
A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the substrate, the biaxially textured buffer layer comprising LZO and a dopant for mitigating metal diffusion through the LZO, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.
Paranthaman, Mariappan Parans (Knoxville, TN) [Knoxville, TN; Schoop, Urs (Westborough, MA) [Westborough, MA; Goyal, Amit (Knoxville, TN) [Knoxville, TN; Thieme, Cornelis Leo Hans (Westborough, MA) [Westborough, MA; Verebelyi, Darren T. (Oxford, MA) [Oxford, MA; Rupich, Martin W. (Framingham, MA) [Framingham, MA
Exploiting a buffer overflow using metasploit framework
Buffer overflow has been used for many years as an effective mean for system penetration to gain remote access [2, 3, 5, 6, 7]. Buffer overflow exploitation takes advantage of weak software programming such as boundary check for memory usage of declared buffers somewhere in the program to undermine software security and exploit its vulnerability so that attacker can remotely
Mustapha Refai
Buffer Management for Wireless Media Streaming
We study playout buffer management at the receiver for supporting multimedia streaming services over unreliable wireless links. On one hand, memory is a precious resource on portable wireless devices and must be used judiciously. On the other hand, allocating a big playout buffer to a media streaming application reduces the probability of a playout in- terruption\\/freeze due to buffer underflow,
Aditya Dua; Nicholas Bambos
Study of Buffer Size in Internet Routers.
In this report, we summarize the results of our small buffer project. The goals of the project were (1) to model the behavior of TCP in a network where the routers have very small buffers, (2) to determine a rule for sizing buffers in such networks, and (...
D. Towsley
[Nomegestrol acetate: clinical pharmacology].
Progestogens are used in clinical practice in some conditions. Their effects depend on their chemical structure, pharmacokinetics, pharmacodynamics, with important differences among various progestogens. Generally, progestins are classified according to their parent molecule, of which often they keep some features. Derivatives of 19-nor-progesterone are characterized by high selectivity of action on progestin receptor. In particular, nomegestrol acetate (NomAc) shows an important progestational potency, neutral gluco-lipid profile, and antigonadotropic activity. It is used for treating menstrual cycle disorders and for hormone replacement therapy in menopause in association with an estrogen. In future, thanks to its antigonadotropic activity, NomAc will be used in estroprogestin combinations in fertile women, thus taking advantage of its tolerability profile and obtaining numerous non-contraceptive benefits as well. PMID:19749678
Lello, S
Electrodialytic membrane suppressors for ion chromatography make programmable buffer generators.
The use of buffer solutions is immensely important in a great variety of disciplines. The generation of continuous pH gradients in flow systems plays an important role in the chromatographic separation of proteins, high-throughput pK(a) determinations, etc. We demonstrate here that electrodialytic membrane suppressors used in ion chromatography can be used to generate buffers. The generated pH, computed from first principles, agrees well with measured values. We demonstrate the generation of phosphate and citrate buffers using a cation-exchange membrane (CEM) -based anion suppressor and Tris and ethylenediamine buffers using an anion-exchange membrane (AEM) -based cation suppressor. Using a mixture of phosphate, citrate, and borate as the buffering ions and using a CEM suppressor, we demonstrate the generation of a highly reproducible (avg RSD 0.20%, n = 3), temporally linear (pH 3.0-11.9, r(2) > 0.9996), electrically controlled pH gradient. With butylamine and a large concentration (0.5 M) of added NaCl, we demonstrate a similar linear pH gradient of large range with a near-constant ionic strength. We believe that this approach will be of value for the generation of eluents in the separation of proteins and other biomolecules and in online process titrations. PMID:22103670
Chen, Yongjing; Srinivasan, Kannan; Dasgupta, Purnendu K
Buffer Layer R&D for YBCO Coated Conductor Composite Wires
Buffer layers play a key role in the YBa2Cu3O7-? (YBCO) coated conductor composite wire technology. The important buffer layer characteristics are: these buffers should prevent metal diffusion into the superconductor from the substrate; possibly act as oxygen diffusion barriers; should be smooth, continuous, crack-free, highly aligned and dense. In order to develop low-cost alternative buffer layer architectures to the standard architecture of YBCO/CeO2/YSZ/Y2O3/Ni/Ni-W, LaMnO3 (LMO) and La2Zr2O7 (LZO) buffers were chosen for this study. These buffers were grown epitaxially on biaxially textured and strengthened Ni-W3% metal tapes by scalable vapor and/or solution techniques. LaMnO3 buffers were grown epitaxially on Ni-W substrates by rf sputtering, and La2Zr2O7 buffers were grown by a Metal-Organic Deposition (MOD). Detailed microstructural characterizations indicate that both of these buffers were excellent Ni diffusion barrier layers and high current YBCO films were grown on both LMO and LZO buffer templates.
Paranthaman, M. Parans; Sathyamurthy, S.; Aytug, T.; Leonard, K. J.; Goyal, A.; Zhai, H. Y.; Kroeger, D. M.; Christen, D. K.; Li, X.; Verebelyi, D. T.; Schoop, U.; Thieme, C.; Kodenkandath, T.; Zhang, W.; Rupich, M. W.; Ericson, R. E.
Effects of buffer concentration on voltage-gated H+ currents: does diffusion limit the conductance?
The single-channel proton conductance of the voltage-gated H(+)-selective channel, like that of the F0 component of the H(+)-ATPase, is nearly constant over a wide range of pH encompassing the physiological range. To examine the possible contributions of buffer diffusion and buffer-channel proton transfer reactions to this phenomenon, the effects of buffer concentration on voltage-activated H+ currents were explored in voltage-clamped rat alveolar epithelial cells. Changes in the external buffer concentration ([B]o), evaluated using the whole-cell configuration, had only small effects on H+ currents (IH). Lowering [B]o from 100 to 1 mM did not alter the voltage-activation curve or reversal potential (Vrev) but reduced IH, typically by 10-30%. Changes in internal buffer concentration ([B]i), examined in inside-out patches, usually altered IH more distinctly and subtly changed the kinetics. Overall, the effects of changing buffer concentration were small and subtle. The maximum attenuation of the single-channel H+ current at 1 mM buffer was estimated to be approximately 20% at either mouth of the H+ channel. Therefore, the rate-determining step in H+ permeation is neither deprotonation of buffer at the inner mouth of the channel nor protonation of buffer at the external surface. Evidently the rate of H+ permeation through the channel is itself small enough that diffusion of buffer in bulk solution does not directly limit the conductance significantly.
DeCoursey, T E; Cherny, V V
Thermogravimetric analysis of the relationship among calcium magnesium acetate, calcium acetate and magnesium acetate
Thermal decomposition characteristic of calcium magnesium acetate (CMA), calcium acetate (CA) and magnesium acetate (MA) are investigated through thermogravimetric (TG) analysis at the heating rates of 5Kmin?1, 7.5Kmin?1, 10Kmin?1 and 15Kmin?1. After dehydration, the evaporation of carboxylic radical and carbon dioxide of CMA and CA exist in two separate segments, but for MA, this occurs together in just one segment
Shengli Niu; Kuihua Han; Chunmei Lu; Rongyue Sun
Glucose buffer is suitable for blood group conversion with ?-N acetylgalactosaminidase and ?-galactosidase
Background It is well known that the buffer plays a key role in the enzymatic reaction involved in blood group conversion. In previous study, we showed that a glycine buffer is suitable for A to O or B to O blood group conversion. In this study, we investigated the use of 5% glucose and other buffers for A to O or B to O blood group conversion by ?-N-acetylgalactosaminidase or ?-galactosidase. Materials and methods We compared the binding ability of ?-N-acetylgalactosaminidase/?-galactosidase with red blood cells (RBC) in different reaction buffers, such as normal saline, phosphate-buffered saline (PBS), a disodium hydrogen phosphate-based buffer (PCS), and 5% commercial glucose solution. The doses of enzymes necessary for the A/B to O conversion in different reaction buffers were determined and compared. The enzymes ability to bind to RBC was evaluated by western blotting, and routine blood typing and fluorescence activated cell sorting was used to evaluate B/A to O conversion efficiency. Results The A to O conversion efficiency in glucose buffer was similar to that in glycine buffer with the same dose (>0.06 mg/mL pRBC). B to O conversion efficiency in glucose buffer was also similar to that in glycine buffer with the same dose (>0.005 mg/mL pRBC). Most enzymes could bind with RBC in glycine or glucose buffer, but few enzymes could bind with RBC in PBS, PCS, or normal saline. Conclusion These results indicate that 5% glucose solution provides a suitable condition for enzymolysis, especially for enzymes combining with RBC. Meanwhile, the conversion efficiency of A/B to O was similar in glucose buffer and glycine buffer. Moreover, 5% glucose solution has been used for years in venous transfusion, it is safe for humans and its cost is lower. Our results do, therefore, suggest that 5% glucose solution could become a novel suitable buffer for A/B to O blood group conversion.
Gao, Hong-Wei; Li, Su-Bo; Bao, Guo-Qiang; Zhang, Xue; Li, Hui; Wang, Ying-Li; Tan, Ying-Xia; Ji, Shou-Ping; Gong, Feng
Stabilized Calcium Acetate Oil Dispersions.
A lubricating composition is imparted with improved load-carrying ability and anti-wear properties by incorporation of calcium acetate. The composition consists of a base lubricant, 0.1 to 50 percent by weight calcium acetate and 0.01 to 20 percent by wei...
R. H. Davis
[Formulation of calcium acetate tablets].
The results of the testing of calcium acetate tablets, produced by direct compression and by wet granulation (Ph. Jug. IV) are presented. Tablet hardness, friability and disintegration were determined. The best properties were observed in the tablets produced with maize starch. This procedure is fast and simple, and compound tablets of calcium acetate fulfill the current requirements for this type of preparation. PMID:11521467
Obrenovic, D; Gazikalovic, E; Ognjanovic, J; Nidzovic Z, Z
Improving Water Quality With Conservation Buffers
Conservation buffer technologies are new approaches that need wider application. In-field buffer practices work best when used in combination with other buffer types and other conservation practices. Vegetative barriers may be used in combination with edge-of-field buffers to protect and improve their function and longevity by dispersing runoff and encouraging sediment deposition upslope of the buffer. It's important to understand how buffers can be managed to help reduce nutrient transport potential for high loading of nutrients from manure land application sites, A restored riparian wetland buffer retained or removed at least 59 percent of the nitrogen and 66 percent of the phosphorus that entered from an adjacent manure land application site. The Bear Creek National Restoration Demonstration Watershed project in Iowa has been the site of riparian forest buffers and filter strips creation; constructed wetlands to capture tile flow; stream-bank bioengineering; in-stream structures; and controlling livestock grazing. We need field studies that test various widths of buffers of different plant community compositions for their efficacy in trapping surface runoff, reducing nonpoint source pollutants in subsurface waters, and enhancing the aquatic ecosystem. Research is needed to evaluate the impact of different riparian grazing strategies on channel morphology, water quality, and the fate of livestock-associated pathogens and antibiotics. Integrating riparian buffers and other conservation buffers into these models is a key objective in future model development.
Lowrance, R.; Dabney, S.; Schultz, R.
Weak acid transport across bilayer lipid membrane in the presence of buffers. Theoretical and experimental pH profiles in the unstirred layers.
This paper presents a simple model to describe experimental data on weak acid transport across planar bilayer lipid membrane separating two buffered solutions. The model takes into account multiple proton-transfer reactions occurring in the unstirred layers (ULs) adjacent to the membrane. Differential equations of the model are shown to be reduced to a set of nonlinear algebraic equations. Since the latter equations depend monotonically on unknown variables, they can be easily solved numerically, using bisection method. For the particular system studied experimentally (with acetate as the weak acid and TRIS+MES as the buffer mixture) pH profiles in the ULs are calculated from the model. These results are compared with experimental data obtained using pH microelectrode. The agreement between theoretical and experimental pH profiles is found to be satisfactory. The most pronounced deviations are observed at the UL/bulk solution boundary. To obtain a better correlation between the theoretical and experimental results, two other, less idealized models are considered. They take into account, respectively, (a) the electric field arising in the ULs from ion diffusion and (b) finiteness of the rates of proton-transfer reactions. However, both acetate membrane fluxes and pH profiles in the ULs computed from these models are found to be close to those of the simple model. One can thus conclude that the difference between experimental and theoretical pH profiles is due to the inconsistency of the generally accepted model of the "unstirred layer", assuming the existence of a strict boundary between the regions of "pure diffusion" and "ideal stirring".
Antonenko, Y N; Denisov, G A; Pohl, P
Buffered Electrochemical Polishing of Niobium
The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop'. In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature ({approx} 120 C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.
Gianluigi Ciovati, Hui Tian, Sean Corcoran
Chapter 21 Architecture of Hydrates and Local Structure of Acetic Acid Aqueous Solution: Ab Initio Calculations and CarParrinello Molecular Dynamics (CPMD) Simulations on Hydrogen-Bonding Rings, Network, and Intra-Hydrate Protonation in Multi-Hydrates of Acetic Acid Monomer
The protonation and deprotonation phenomena and molecular association of solute molecule with water via intermolecular hydrogen bonding forming various hydration compounds are very common in aqueous solution and in biological cell in nature. In the aqueous solution, more complicated type of hydrogen bond, hydrogen-bonding rings, various kinds of hydration compounds (hydrates), and even hydrogen-bonding network can be expected. The nature
Liang Pu; Qing Wang; Yong Zhang; Qiang Miao; Yang-Soo Kim; Zhibing Zhang
Triamcinolone acetonide acetate.
IN THE CRYSTAL STRUCTURE OF THE TITLE COMPOUND [SYSTEMATIC NAME: 2-(4b-fluoro-5-hy-droxy-4a,6a,8,8-tetra-methyl-2-oxo-2,4a,4b,5,6,6a,9a,10,10a,10b,11,12-dodeca-hydro-7,9-dioxa-penta-leno[2,1-a]phenanthren-6b-yl)-2-oxoethyl acetate], C(26)H(33)FO(7), the mol-ecules are connected by inter-molecular O-H?O hydrogen bonds into an infinite supra-molecular chain along the b axis. The mol-ecular framework consists of five condensed rings, including three six-membered rings and two five-membered rings. The cyclo-hexa-2,5-dienone ring is nearly planar [maximum deviation = 0.013?(3)?é], while the cyclo-hexane rings adopt chair conformations. The two five-membered rings, viz. cyclo-pentane and 1,3-dioxolane, display envelope conformations. PMID:21523039
Lu, Xiao; Tang, Gu-Ping; Gu, Jian-Ming; Hu, Xiu-Rong
Triamcinolone acetonide acetate
In the crystal structure of the title compound [systematic name: 2-(4b-fluoro-5-hyÙdroxy-4a,6a,8,8-tetraÙmethyl-2-oxo-2,4a,4b,5,6,6a,9a,10,10a,10b,11,12-dodecaÙhydro-7,9-dioxaÙpentaÙleno[2,1-a]phenanthren-6b-yl)-2-oxoethyl acetate], C26H33FO7, the molÙecules are connected by interÙmolecular OH?O hydrogen bonds into an infinite supraÙmolecular chain along the b axis. The molÙecular framework consists of five condensed rings, including three six-membered rings and two five-membered rings. The cycloÙhexa-2,5-dienone ring is nearly planar [maximum deviation = 0.013?(3)?é], while the cycloÙhexane rings adopt chair conformations. The two five-membered rings, viz. cycloÙpentane and 1,3-dioxolane, display envelope conformations.
Ion selective permeation through cellulose acetate membranes in forward osmosis.
Solute-solute interactions can have a dramatic impact on the permeation of solutes through dense polymeric membranes. In particular, understanding how solute-solute interactions can affect the design of osmotically driven membrane processes (ODMPs) is critical to the successful development of these emerging water treatment and energy generation processes. In this work, we investigate the influence that solute-solute interactions have on nitrate permeation through an asymmetric cellulose acetate forward osmosis membrane. A series of experiments that included systematic modifications to the cation paired with nitrate, the identity of the draw solute, and the solution pH were conducted. These experiments reveal that in the unique operating geometry of ODMPs, where solute containing solutions are present on both sides of the membrane, nitrate fluxes are significantly higher (>15 times in some cases) than predicted by existing models for solute permeation in ODMPs. The identity of the cation paired with nitrate influences the flux of nitrate; the identity of the cation in the draw solution does not affect the flux of nitrate; however, the identity of the anion in the draw solution has the most significant impact on the flux of nitrate. These results suggest that an ion exchange mechanism, which allows nitrate to switch rapidly with anions from the draw solution, is present when cellulose acetate based membranes are used in ODMPs. PMID:24152190
Irvine, Gavin J; Rajesh, Sahadevan; Georgiadis, Michael; Phillip, William A
Simultaneous determination of 2-naphthoxyacetic acid and indole-3-acetic acid by first derivation synchronous fluorescence spectroscopy
A simple, rapid, sensitive and selective method for simultaneously determining 2-naphthoxyacetic acid (BNOA) and Indole-3-Acetic Acid (IAA) in mixtures has been developed using derivation synchronous fluorescence spectroscopy based on their synchronous fluorescence. The synchronous fluorescence spectra were obtained with ?? = 100 nm in a pH 8.5 NaH2PO4-NaOH buffer solution, and the detected wavelengths of quantitative analysis were set at 239 nm for BNOA and 293 nm for IAA respectively. The over lapped fluorescence spectra were well separated by the synchronous derivative method. Under optimized conditions, the limits of detection (LOD) were 0.003 ?g/mL for BNOA and 0.012 ?g/mL for IAA. This method is simple and expeditious, and it has been successfully applied to the determination of 2-naphthoxyacetic acid and indole-3-acetic acid in fruit juice samples with satisfactory results. The samples were only filtrated through a 0.45 ?m membrane filter, which was free from the tedious separation procedures. The obtaining recoveries were in the range of 83.88-87.43% for BNOA and 80.76-86.68% for IAA, and the relative standard deviations were all less than 5.0%. Statistical comparison of the results with high performance liquid chromatography Mass Spectrometry (HPLC-MS) method revealed good agreement and proved that there were no significant difference in the accuracy and precision between these two methods.
Liu, Xiangxiang; Wan, Yiqun
An automated system for monitoring and regulating the pH of bicarbonate buffers.
The bicarbonate buffer is considered as the most biorelevant buffer system for the simulation of intestinal conditions. However, its use in dissolution testing of solid oral dosage forms is very limited. The reason for this is the thermodynamic instability of the solution containing hydrogen carbonate ions and carbonic acid. The spontaneous loss of carbon dioxide (CO(2)) from the solution results in an uncontrolled increase of the pH. In order to maintain the pH on the desired level, either a CO(2) loss must be completely avoided or the escaped CO(2) has to be replaced by quantitative substitution, i.e. feeding the solution with the respective amount of gas, which re-acidifies the buffer after dissociation. The present work aimed at the development of a device enabling an automatic pH monitoring and regulation of hydrogen carbonate buffers during dissolution tests. PMID:23468339
Garbacz, Grzegorz; Ko?odziej, Bartosz; Koziolek, Mirko; Weitschies, Werner; Klein, Sandra
Unit 8: Buffers for Biochemical Reactions
The last of an eight-unit teaching and training module from Promega, this "introductory buffers laboratory is for use in undergraduate or highschool courses that cover basic topics in molecular biology or biochemistry" and includes "laboratories to illustrate basic chemistry concepts related to buffers and their functions." This unit is math-intensive, aimed at helping students feel comfortable performing laboratory calculations. It includes a lecture presentation ("Buffers for Biological Systems") and a students' and instructors' laboratory protocol.
Self-assembly of diorganotin(IV) 2-{[( E)-1-(2-oxyaryl)alkylidene]amino}acetates: An investigation of structures by X-ray diffraction, solution and solid-state tin NMR, and electrospray ionization MS
The diorganotin(IV) compounds, [Me2SnL2(OH2)]2 (1), [nBu2SnL2(OH2)]2 (2), [nBu2SnL1]3ñ0.5C3H6O (3), [nBu2SnL3]3ñ0.5C6H6 (4) and [Ph2SnL3]nñ0.5C6H6 (5) (L=carboxylic acid residue, i.e., 2-{[(E)-1-(2-oxyaryl)alkylidene]amino}acetate), were synthesized by treating the appropriate diorganotin(IV) dichloride with the potassium salt of the ligand in anhydrous methanol.The reaction of Ph2SnL2 (L=2-{[(E)-1-(2-oxyphenyl)ethylidene]amino}acetate) with 1,10-phenanthroline (Phen) yielded a 1:1 adduct of composition, [Ph2SnL2(Phen)] (6).The crystal structures of 16 were determined.The crystal of
Tushar S. Basu Baul; Cheerfulman Masharing; Rudolph Willem; Monique Biesemans; Michal Hol?apek; Robert JirÃsko; Anthony Linden
All-optical buffering for DPSK packets
Advanced modulation formats, such as DPSK, DQPSK, QAM, have become the mainstream technologies in the optical network over 40Gb/s, the DPSK format is the fundamental of all advanced modulation formats. Optical buffers, as a key element for temporarily storing packets in order to synchronization or contention resolution in optical nodes, must be adapted to this new requirement. Different from other current buffers to store the NRZ or RZ format, an all-optical buffer of storing DPSK packets based on nonlinear polarization rotation in SOA is proposed and demonstrated. In this buffer, a section of PMF is used as fiber delay line to maintain the polarization states unchanged, the driver current of SOA is optimized, and no amplifier is required in the fiber loop. A packet delay resolution of 400ns is obtained and storage for tens rounds is demonstrated without significant signal degradation. Using proposed the new tunable DPSK demodulator, bit error rate has been measured after buffering for tens rounds for 10Gb/s data payload. Configurations for First-in First-out (FIFO) buffer or First-in Last-out (FILO) buffer are proposed based on this buffer. The buffer is easy control and suitable for integration. The terminal contention caused by different clients can be mitigated by managing packets delays in future all-optical network, such as optical packet switching network and WDM switching network.
Liu, Guodong; Wu, Chongqing; Liu, Lanlan; Wang, Fu; Mao, Yaya; Sun, Zhenchao
Evaluation of stainless steel cathodes and a bicarbonate buffer for hydrogen production in microbial electrolysis cells using a new method for measuring gas production
Microbial electrolysis cells (MECs) are often examined for hydrogen production using non-sustainable phosphate buffered solutions (PBS), although carbonate buffers have been shown to work in other bioelectrochemical systems with a platinum (Pt) catalyst. Stainless steel (SS) has been shown to be an effective catalyst for hydrogen evolution in MECs, but it has not been tested with carbonate buffers. We evaluated
Jack R. Ambler; Bruce E. Logan
Reaction of nerve agents with phosphate buffer at pH 7.
Chemical weapon nerve agents, including isopropyl methylphosphonofluoridate (GB or Sarin), pinacolyl methylphosphonofluoridate (GD or Soman), and S-(2-diisopropylaminoethyl) O-ethyl methylphosphonothioate (VX), are slow to react in aqueous solutions at midrange pH levels. The nerve agent reactivity increases in phosphate buffer at pH 7, relative to distilled water or acetate buffer. Reactions were studied using (31)P NMR. Phosphate causes faster reaction to the corresponding alkyl methylphosphonic acids, and produces a mixed phosphate/phosphonate compound as an intermediate reaction product. GB has the fastest reaction rate, with a bimolecular rate constant of 4.6 æ 10(-3) M(-1)s(-1)[PO(4)(3-)]. The molar product branching ratio of GB acid to the pyro product (isopropyl methylphosphonate phosphate anhydride) is 1:1.4, independent of phosphate concentration, and the pyro product continues to react much slower to form GB acid. The pyro product has two doublets in the (31)P NMR spectrum. The rate of reaction for GD is slower than GB, with a rate constant of 1.26 æ 10(-3) M(-1)s(-1) [PO(4)(3-)]. The rate for VX is considerably slower, with a rate constant of 1.39 æ 10(-5) M(-1)s(-1) [PO(4)(3-)], about 2 orders of magnitude slower than the rate for GD. The rate constant of the reaction of GD with pyrophosphate at pH 8 is 2.04 æ 10(-3) min(-1) at a concentration of 0.0145 M. The rate of reaction for diisopropyl fluorophosphate is 2.84 æ 10(-3) min(-1) at a concentration of 0.153 M phosphate, a factor of 4 slower than GD and a factor of 15 slower than GB, and there is no detectable pyro product. The half-lives of secondary reaction of the GB pyro product in 0.153 and 0.046 M solution of phosphate are 23.8 and 28.0 h, respectively, which indicates little or no dependence on phosphate. PMID:22667763
Creasy, William R; Fry, Roderick A; McGarvey, David J
Acetate catabolism by Methanosarcina barkeri
Cell suspensions of Methanosarcina barkeri convert the carboxyl and methyl group carbons of acetate to carbon dioxide and methane at pH 6 under an atmosphere of 100% CO/sub 2/. The rate of loss of radioactivity from (1-/sup 14/C)acetate was over three times greater than that from (2-/sup 14/C)acetate under these conditions. Control experiments with both labeled substrates present showed that the rates were additive. Addition of a high level of 2-bromoethanesulfonate to selectively inhibit methane formation largely inhibited release of /sup 14/C from methyl-labeled acetate but only marginally decreased the rate of loss from (1-/sup 14/C)acetate. Thus, in the absence of the inhibitor loss of /sup 14/C from (1-/sup 14/C)acetate likely reflects an isotopic exchange reaction with CO/sub 2/ superimposed on the overall conversion of acetate to CO/sub 2/ and CH/sub 4/. The exchange reaction was inhibited by uncouplers such as 2,4-dinitrophenol, CCCP, and FCCP. Cells permeabilized by treatment with nonionic detergents or disrupted by passage through a French pressure cell failed to catalyze the exchange reaction. Exchange activity was not restored by addition of ATP or by use of (1-/sup 14/C)acetyl CoA as substrate. No evidence for involvement of carbon monoxide dehydrogenase in the exchange was found in these experiments when CO/sub 2/ was replaced by CO. However, the soluble extracts retained the ability to convert acetate to methane in the presence of H/sub 2/ and ATP.
Grahame, D.A.
Activity of octreotide acetate in a total nutrient admixture.
The activity of octreotide acetate in a total nutrient admixture (TNA) and the effect of the drug on the stability of lipid emulsion in the TNA were studied. Octreotide acetate injection was added to a standard solution containing 3% lipids, amino acids, dextrose, electrolytes, vitamins, and trace elements to achieve a theoretical concentration of 45 micrograms/dL. Samples were stored at room temperature for 48 hours. Octreotide concentrations were determined in triplicate by radioimmunoassay; physical stability of the solutions was assessed by lipid particle-size determination, pH measurement, and visual observation of emulsion integrity at 0, 12, 24, and 48 hours. The activity of octreotide in two samples of each solution (with and without lipid) was analyzed immediately after preparation and after seven days under refrigeration. There was no evidence of emulsion breakdown or pH change in any solution over the study period. In addition, particle-size distributions at 48 hours and 7 days were comparable to those at time zero, suggesting physical stability. Octreotide acetate activity was not consistently greater than 90% (mean +/- S.D.) after storage for 48 hours. Octreotide acetate at a theoretical concentration of 45 micrograms/dL in a TNA solution containing 3% lipids appeared to be physically compatible for 48 hours at room temperature and for 7 days under refrigeration. However, the chemical activity of octreotide in TNA was not consistent after storage for 48 hours. PMID:1781474
Ritchie, D J; Holstad, S G; Westrich, T J; Hirsch, J D; O'Dorisio, T M
1 H and 13 C NMR observation of the reaction of acetic acid with titanium isopropoxide
Hydrogen and carbon NMR spectroscopy have been used to investigate the chemical modification process of titanium isopropoxide by acetic acid. The spectra confirm the belief that the titanium isopropoxide exchanges isopropyl groups with modifying acetate groups to form a molecule with approximate stoichiometry Ti(OiPr)2(OAc)2. This stoichiometry results even when enough acetic acid is present in solution to allow for significantly
Dunbar P Birnie III; Norbert J. Bendzko
Degradation of acetic acid with sulfate radical generated by persulfate ions photolysis
The photolysis of S2O82- was studied for the removal of acetic acid in aqueous solution and compared with the H2O2\\/UV system. The SO4- radicals generated from the UV irradiation of S2O82- ions yield a greater mineralization of acetic acid than the OH radicals. Acetic acid is oxidized by SO4- radicals without significant formation of intermediate by-products. Increasing system pH results
Justine Criquet; Nathalie Karpel Vel Leitner
Comparison of three buffers used in the formulation of buffered charcoal yeast extract medium.
Growth of Legionella spp. on buffered charcoal yeast extract medium supplemented with alpha-ketoglutarate and formulated with 3-(n-morpholino)propanesulfonic acid (MOPS), 3-(n-morpholino)-2-hydroxypropanesulfonic acid (MOPSO), or n-(2-acetamido)-2-aminoethanesulfonic acid (ACES) buffer was similar. With three exceptions, growth was no different in buffered yeast extract broth supplemented with alpha-ketoglutarate and formulated with MOPS or ACES buffer. PMID:8308131
Edelstein, P H; Edelstein, M A
Investigation on isobaric vaporliquid equilibrium for acetic acid + water + methyl ethyl ketone + isopropyl acetate
Isobaric vaporliquid equilibrium (VLE) data for acetic acid+water, acetic acid+methyl ethyl ketone (MEK), MEK+isopropyl acetate, acetic acid+MEK+water and acetic acid+MEK+isopropyl acetate+water are measured at 101.33kPa using a modified Rose cell. The nonideal behavior in vapor phase of binary systems measured in this work is analyzed through calculating fugacity coefficients since mixture containing acetic acid deviates from ideal behavior seriously in
Qiang Xie; Hui Wan; MingJuan Han; GuoFeng Guan
Experimental acidification of two biogeochemically-distinct neotropical streams: buffering mechanisms and macroinvertebrate drift.
Research into the buffering mechanisms and ecological consequences of acidification in tropical streams is lacking. We have documented seasonal and episodic acidification events in streams draining La Selva Biological Station, Costa Rica. Across this forested landscape, the severity in seasonal and episodic acidification events varies due to interbasin groundwater flow (IGF). Streams that receive IGF have higher concentrations of solutes and more stable pH (~6) than streams that do not receive IGF (pH ~5). To examine the buffering capacity and vulnerability of macroinvertebrates to short-term acidification events, we added hydrochloric acid to acidify a low-solute, poorly buffered (without IGF) and a high-solute, well buffered stream (with IGF). We hypothesized that: 1) protonation of bicarbonate (HCO(3)(-)) would neutralize most of the acid added in the high-solute stream, while base cation release from the sediments would be the most important buffering mechanism in the low-solute stream; 2) pH declines would mobilize inorganic aluminum (Ali) from sediments in both streams; and 3) pH declines would increase macroinvertebrate drift in both streams. We found that the high-solute stream neutralized 745 ?eq/L (96% of the acid added), while the solute poor stream only neutralized 27.4 ?eq/L (40%). Protonation of HCO(3)(-) was an important buffering mechanism in both streams. Base cation, Fe(2+), and Ali release from sediments and protonation of organic acids also provided buffering in the low-solute stream. We measured low concentrations of Ali release in both streams (2-9 ?eq/L) in response to acidification, but the low-solute stream released double the amount Ali per 100 ?eq of acid added than the high solute stream. Macroinvertebrate drift increased in both streams in response to acidification and was dominated by Ephemeroptera and Chironomidae. Our results elucidate the different buffering mechanisms in tropical streams and suggest that low-solute poorly buffered streams might be particularly vulnerable to episodic acidification. PMID:23201647
Ardµn, Marcelo; Duff, John H; RamÚrez, Alonso; Small, Gaston E; Jackman, Alan P; Triska, Frank J; Pringle, Catherine M
Resilience to suicidality: The buffering hypothesis
Recent years have seen a growing interest into resilience to suicidality, which has been described as a perception or set of beliefs which buffer individuals from suicidality in the face of stressors. The current review extends this research by introducing the buffering hypothesis, a framework for the investigation of resilience to suicidality. The key proposal of this is that psychological
Judith Johnson; Alex M. Wood; Patricia Gooding; Peter J. Taylor; Nicholas Tarrier
Shaking table testing of geofoam seismic buffers
The paper describes the experimental design and results of tests used to investigate the use of compressible EPS (geofoam) seismic buffers to attenuate dynamic loads against rigid retaining wall structures. The tests were carried out using 1-m-high models mounted on a large shaking table. Three different geofoam buffer materials retaining a sand soil were tested under idealized dynamic loading conditions.
Richard J. Bathurst; Saman Zarnani; Andrew Gaskin
Modeling buffer layer IGBTs for circuit simulation
The dynamic behavior of commercially available buffer layer IGBTs is described. It is shown that buffer layer IGBTs become much faster at high voltages than nonbuffer layer IGBTs with similar low voltage characteristics. Because the fall times specified in manufacturers' data sheets do not reflect the voltage dependence of switching speed, a new method of selecting devices for different circuit
Database buffer paging in virtual storage systems
Three models, corresponding to different sets of assumptions, are analyzed to study the behavior of a database buffer in a paging environment. The models correspond to practical situations and vary in their search strategies and replacement algorithms. The variation of I\\/O cost with respect to buffer size is determined for the three models. The analysis is valid for arbitrary database
TomÃs Lang; Christopher Wood; Eduardo B. FernÃndez
Derivation and systematic calculation of buffer capacity is a topic that seems often to be neglected in chemistry courses and given minimal treatment in most texts. However, buffer capacity is very important in the chemistry of natural waters and potable water. It affects corro...
Buffer Management for Video Database Systems
Future multimedia information systems are likely to manage thousands of videos with various lengths and display requirements. Mismatch of playback and delivery rates of compressed video data requires sophisticated buffer management algorithms to guarantee smooth playback of video data. In this paper, we address some of the many design and operational issues including buffer size requirements, refreshing policies, and support
Doron Rotem; J. Leon Zhao
The buffer capacity of airway epithelial secretions
The pH of airway epithelial secretions influences bacterial killing and mucus properties and is reduced by acidic pollutants, gastric reflux, and respiratory diseases such as cystic fibrosis (CF). The effect of acute acid loads depends on buffer capacity, however the buffering of airway secretions has not been well characterized. In this work we develop a method for titrating micro-scale (30 ?l) volumes and use it to study fluid secreted by the human airway epithelial cell line Calu-3, a widely used model for submucosal gland serous cells. Microtitration curves revealed that HCO?3 is the major buffer. Peak buffer capacity (?) increased from 17 to 28 mM/pH during forskolin stimulation, and was reduced by >50% in fluid secreted by cystic fibrosis transmembrane conductance regulator (CFTR)-deficient Calu-3 monolayers, confirming an important role of CFTR in HCO?3 secretion. Back-titration with NaOH revealed non-volatile buffer capacity due to proteins synthesized and released by the epithelial cells. Lysozyme and mucin concentrations were too low to buffer Calu-3 fluid significantly, however model titrations of porcine gastric mucins at concentrations near the sol-gel transition suggest that mucins may contribute to the buffer capacity of ASL in vivo. We conclude that CFTR-dependent HCO?3 secretion and epithelially-derived proteins are the predominant buffers in Calu-3 secretions.
Kim, Dusik; Liao, Jie; Hanrahan, John W.
Carbon dioxide concentrates in containers are frequently controlled by using a diethanolamine-bicarbonate buffer. Current studies show that this buffer produces ethylene and that the production increases with increasing pH and/or time in the incubation vessel. Ethylene is not pro...
Buffer control scheme in multimedia synchronization
We present a complete synchronization scheme for multimedia information systems. The playout schedule is ensured by setting medium retrieval schedule based on the suitable control time at each different medium servers and by providing a suitable buffer for each medium at the client side. Because of the asynchronous nature of the network and the host operating system, certain buffer management
A. Hac; Cindy X. Xue
Optimization of protein buffer cocktails using Thermofluor.
The stability and homogeneity of a protein sample is strongly influenced by the composition of the buffer that the protein is in. A quick and easy approach to identify a buffer composition which increases the stability and possibly the conformational homogeneity of a protein sample is the fluorescence-based thermal-shift assay (Thermofluor). Here, a novel 96-condition screen for Thermofluor experiments is presented which consists of buffer and additive parts. The buffer screen comprises 23 different buffers and the additive screen includes small-molecule additives such as salts and nucleotide analogues. The utilization of small-molecule components which increase the thermal stability of a protein sample frequently results in a protein preparation of higher quality and quantity and ultimately also increases the chances of the protein crystallizing. PMID:23385769
Reinhard, Linda; Mayerhofer, Hubert; Geerlof, Arie; Mueller-Dieckmann, Jochen; Weiss, Manfred S
[Mechanical buffering characteristics of feline paw pads].
In the long time of natural evolution, the bodies of some animals, such as feline, that live in the wild and complicate surroundings have evolved to possess outstanding buffering characteristics, which make the animals adapt to the environment perfectly. These animals generally have well-developed paw pads under their soles to play an important role in attenuating the intensity of impact when they land on the ground. Investigating the buffering characteristics of these animals' paw pads could help us to design "bionic" buffering and energy-absorption devices. In this paper, based on observations of animal jumping test, a simple mass-spring-buffer model was proposed to explore the buffering characteristics of the animals' paw pads. By analytically solving the differential equations of this model, the parameters concerned with paw pads functions were discussed and some significant results were obtained. PMID:23469538
Zhang, Xiaopeng; Yang, Jialing; Yu, Hui
Studies on Cellulose Acetate Phthalate. 3. Osmotic Pressure Measurements
Osmotic pressure measurements of aqueous solutions of cellulose acetate phthalate (CAP) were carried out with the help of a highspeed membrane osmometer. The value of the osmotic coefficient, g, for different concentrations of CAP, as well as at different degree of neutralization for various concentrations, were estimated. The effect of concentration and degree of neutralization on the value of g
C. P. Patel; H. C. Trivedi; K. C. Patel; R. D. Patel
Alkaline buffers release EDRF from bovine cultured aortic endothelial cells.
1. Release of endothelium-derived relaxing factor (EDRF) and prostacyclin (PGI2) from bovine cultured aortic endothelial cells (EC) was measured by bioassay and radioimmunoassay, respectively. 2. Bradykinin (BK, 3-30 pmol), adenosine diphosphate (ADP, 2-6 nmol) or the sodium ionophore monensin (40-100 nmol) injected through a column of EC released EDRF. L-Arginine free base (FB; 10-20 mumol) or D-arginine FB (10-20 mumol) injected through the column of EC released similar amounts of EDRF and also caused an increase in pH of the Krebs solution perfusing the EC from 7.5-8.0 to 8.6-9.5. Sodium carbonate (Na2CO3) an alkaline buffer which caused the same changes in the pH of the Krebs solution also induced the same release of EDRF. The hydrochloride salts of L- or D-arginine did not cause either release of EDRF when injected through the column of EC or increases in the pH of the Krebs solution. 3. Inhibitors of either diacylglycerol lipase (RHC 80267) or kinase (R59022) inhibited the release of EDRF induced by BK or ADP but potentiated the release induced by L-arginine FB, monensin (40-100 nmol) or alkaline buffer (Na2CO3). R59022 and RHC 80267 infused through the EC increased the basal release of EDRF. 4. When calcium chloride was omitted from the Krebs solution the release of EDRF induced by alkaline buffer (Na2CO3; pH 8.6-9.5) or L-arginine FB (10-20 mumol) was selectively inhibited when compared to that induced by BK (3-30 pmol) or ADP (2-6 nmol). This inhibition was reversed when calcium (2.5 mM) was restored. 5. NG-monomethyl-L-arginine (NMMA; 30 microM) inhibited release of EDRF induced by BK (10-30 pmol) or alkaline buffers (Na2CO3 or D-arginine FB; pH 8.6-9.5). This inhibition was partially reversed by L- but not D-arginine FB or HCl (30-100 microM). 6. Prostacyclin was released when BK (10 pmol), ADP (2 nmol) or arachidonic acid (30 nmol) were injected through the column of EC. However, monensin (40 nmol) or alkaline buffers (pH 8.6-9.5) did not release detectable amounts of PGI2 as measured by radioimmunoassay for 6-oxo-prostaglandin F1 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)
Mitchell, J. A.; de Nucci, G.; Warner, T. D.; Vane, J. R.
Morphological Properties and Antibacterial Activity of Nano-Silver-Containing Cellulose Acetate Phthalate Films
Modification of the rheological properties of cellulose acetate phthalate in 2-methoxyethanol\\/acetone\\/water, at different compositions of solvent mixtures, allowed the identification of optimal composition of solvent mixtures for obtaining fibers with controlled diameters. Changing the solvent content in the casting solutions favors modification of the morphological aspects of cellulose acetate phthalate (CAP) films, as observed from atomic force microscopy images. Silver
Adina Maria Necula; Simona Dunca; Iuliana Stoica; Niculae Olaru; Liliana Olaru; Silvia Ioan
Sodium acetate as a replacement for sodium bicarbonate in medical toxicology: a review.
Sodium bicarbonate is central to the treatment of many poisonings. When it was placed on the FDA drug shortage list in 2012, alternative treatment strategies to specific poisonings were considered. Many hospital pharmacies, poison centers, and medical toxicologists proposed sodium acetate as an adequate alternative, despite a paucity of data to support its use in medical toxicology. The intention of this review is to educate the clinician on the use of sodium acetate and to advise them on the potential adverse events when given in excess. We conducted a literature search focused on the pharmacology of sodium acetate, its use as a buffer in pathologic acidemia and dialysis baths, and potential adverse events associated with excess sodium acetate infusion. It appears safe to replace sodium bicarbonate infusion with sodium acetate on an equimolar basis. The metabolism of acetate, however, is more complex than bicarbonate. Future prospective studies will be needed to confirm the efficacy of sodium acetate in the treatment of the poisoned patient. PMID:23636658
Neavyn, Mark J; Boyer, Edward W; Bird, Steven B; Babu, Kavita M
LC determination of octreotide acetate in compound formulations of Sandostatin Û and diamorphine hydrochloride
The determination of octreotide acetate in compound formulations of SandostatinÛ and diamorphine hydrochloride by RPLC is described. Octreotide acetate, diamorphine hydrochloride and their respective degradants, [des-Thr-ol8]-octreotide and 6-O-acetylmorphine, were baseline resolved using a Lichrospher-60 RP-select B column with a mobile phase composition of acetonitrile\\/phosphate buffer (pH 7.4, 20 mM) (35:65 v\\/v) with UV detection at 210 nm. The method is
N Kyaterekera; J. N. A Tettey; G. G Skellern; D. G Watson; J Urie; J. R McDade; H Fielding
Buffering effect of a prophylactic gel on dental plaque.
The aim of this study was to evaluate the effect of a new prophylactic gel on plaque pH and plaque fluoride concentration. Twelve participants with normal (n=6, >or=0.7 ml/min) and low (n=6, <0.7 ml/min) stimulated whole salivary secretion rate were included. After 3 days of plaque accumulation, at random the participants were (1) treated with Profylin fluoride gel with buffering components (active gel), (2) treated with Profylin fluoride gel without buffering components (placebo gel), (3) asked to rinse with water, and (4) given no treatment. All test series were followed by rinsing with a nutrition solution; after which registration of plaque pH was performed during 60 min. There were two drop outs with low salivary secretion rate in the water session. The overall least pronounced pH fall was found after the use of the prophylactic gel. Significant differences between the prophylactic gel and the placebo gel were found for the participants with normal secretion rate. Fluoride plaque concentrations evaluated in 12 individuals after (1) application of the active gel, (2) rinsing with 0.2% NaF, and (3) rinsing with water showed significantly higher values after rinsing with the NaF solution. It can be concluded that application of the active gel, particularly in subjects with normal salivary secretion rate, in general, buffered plaque pH to higher levels. Factors like concentration of buffering agent and solubility of the gel need to be further evaluated to improve the effect. PMID:16937109
Persson, Anitha; Lingstr—m, Peter; Bergdahl, Maud; van Dijken, Jan W V
Sediment retention in rangeland riparian buffers.
Controlling nonpoint-source sediment pollution is a common goal of riparian management, but there is little quantitative information about factors affecting performance of rangeland riparian buffers. This study evaluated the influence of vegetation characteristics, buffer width, slope, and stubble height on sediment retention in a Montana foothills meadow. Three vegetation types (sedge wetland, rush transition, bunchgrass upland) were compared using twenty-six 6- x 2-m plots spanning 2 to 20% slopes. Plots were clipped moderately (10-15 cm stubble) or severely (2-5 cm stubble). Sediment (silt + fine sand) was added to simulated overland runoff 6, 2, or 1 m above the bottom of each plot. Runoff was sampled at 15-s to > 5-min intervals until sediment concentrations approached background levels. Sediment retention was affected strongly by buffer width and moderately by vegetation type and slope, but was not affected by stubble height. Mean sediment retention ranged from 63 to > 99% for different combinations of buffer width and vegetation type, with 94 to 99% retention in 6-m-wide buffers regardless of vegetation type or slope. Results suggest that rangeland riparian buffers should be at least 6 m wide, with dense vegetation, to be effective and reliable. Narrower widths, steep slopes, and sparse vegetation increase risk of sediment delivery to streams. Vegetation characteristics such as biomass, cover, or density are more appropriate than stubble height for judging capacity to remove sediment from overland runoff, though stubble height may indirectly indicate livestock impacts that can affect buffer performance. PMID:12809315
Hook, Paul B
Buffer-regulated biocorrosion of pure magnesium.
Magnesium (Mg) alloys are being actively investigated as potential load-bearing orthopaedic implant materials due to their biodegradability in vivo. With Mg biomaterials at an early stage in their development, the screening of alloy compositions for their biodegradation rate, and hence biocompatibility, is reliant on cost-effective in vitro methods. The use of a buffer to control pH during in vitro biodegradation is recognised as critically important as this seeks to mimic pH control as it occurs naturally in vivo. The two different types of in vitro buffer system available are based on either (i) zwitterionic organic compounds or (ii) carbonate buffers within a partial-CO(2) atmosphere. This study investigated the influence of the buffering system itself on the in vitro corrosion of Mg. It was found that the less realistic zwitterion-based buffer did not form the same corrosion layers as the carbonate buffer, and was potentially affecting the behaviour of the hydrated oxide layer that forms on Mg in all aqueous environments. Consequently it was recommended that Mg in vitro experiments use the more biorealistic carbonate buffering system when possible. PMID:22190196
Kirkland, Nicholas T; Waterman, Jay; Birbilis, Nick; Dias, George; Woodfield, Tim B F; Hartshorn, Richard M; Staiger, Mark P
A novel structure of optical buffer
Optical buffers are critical for low packet-loss probability in future photonic packet-switched networks. In particular, they would be required to store packets during rate conversion and header processing, and to overcome the receiver's bottleneck. They would be required for queuing packets while transmitters await access to the network. In this paper, we present a novel structure of optical buffer with compact size. This kind of optical buffer is based on a collinear 3x3 fiber coupler in which three fibers are completely in the same plane and weakly coupled. A SOA is used as its nonlinear element as well as an amplifier in it.The experiment result will be also given in the paper. Storage results obtained with this novel structure optical buffer at 100Mb/s will be presented first and then its capacity is extended to higher data rates of 2.5Gb/s, more compatible with present optical networks. Storage has been observed for time up to 1.568ms(more than 32 circulations) in both cases without obvious degration. The novel structure of optical buffer could be a more compact device which makes it possible to be integrated in a chip. SOA in the buffer is used as a nonlinear element as well as an amplifier to compensate loss in the buffer loop. The buffer needs low control power for switch operation. It is easy to control 'write' and 'erase' operation because the same TOAD switch in the buffer can be used for both 'write' and 'erase' operation.
Liu, AiMing; Wu, Chongqing; Gao, Huali; Gong, Yandong; Shum, Ping
Tractable analytic models of demand assignment protocols in networks with arbitrary buffer capacity
The authors introduce analytic models for evaluating demand assignment protocols in realistic finite-buffer\\/finite-station network configurations. A solution for protocols with gated and nongated service disciplines that enables one to model demand assignment protocols as found, for example, in local and metropolitan area networks and in satellite communication systems is presented. A tractable approximate solution based on linear equations whose number
The use of static and dynamic physical property measurements to infer structural properties of associated liquids: Acetic acidwater
The anomalies which occur in most static and dynamic physical property measurements on solutions of water in acetic acid can be used with critical analysis to infer associative molecular structures. The anomalies indicate significant structural changes. Proton magnetic resonance chemical shifts for acetic acidwater solutions show a significant structural change occurring in the region of equal molar concentration. Literature values
Robert W. Sims; M. Robert Willicott III; R. R. Inners
The use of static and dynamic physical property measurements to infer structural properties of associated liquids: Acetic acid-water
The anomalies which occur in most static and dynamic physical property measurements on solutions of water in acetic acid can be used with critical analysis to infer associative molecular structures. The anomalies indicate significant structural changes. Proton magnetic resonance chemical shifts for acetic acid-water solutions show a significant structural change occurring in the region of equal molar concentration. Literature values
Buffering Capacity of Crystalloid and Colloid Resuscitation Solutions.
Rapid loss of a critical blood volume is 100% fatal if not treated. After hemostasis, the rapid replacement of shed blood with volume is the only current treatment that provides survival. The method of replacement involves either crystalloid or colloid so...
L. W. Traverso F. Medina R. B. Bolin
Regeneration of Cellulose Acetate Membranes.
Several simple methods for in situ one-step regeneration of both flux and salt-retention properties of service-deteriorated membranes have been developed. Membranes have been successfully regenerated using hot, 4% acetic acid, and a one-step cleaning meth...
P. A. Cantor W. S. Higley C. W. Saltonstall
Lead Acetate, Teratology Study - Rabbits.
Three groups of 15 females rabbits were mated. Two groups were fed lead acetate in their diet at lead concentrations of 54.6 and 546 ppm from day 6 through day 16 of their gestation period. The third group of females and all males received the basal labor...
D. C. Jessup
Spacecraft Optical Disk Recorder Memory Buffer Control.
The goal of this project is to develop an Application Specific Integrated Circuit (ASIC) for use in the control electronics of the Spacecraft Optical Disk Recorder (SODR). Specifically, this project is to design an extendable memory buffer controller ASIC...
R. F. Hodson
Certifying the Absence of Buffer Overflows.
Despite increased awareness and efforts to reduce buffer overflows, they continue to be the cause of most software vulnerabilities. In large part, these problems are due to the widespread use of unsafe library routines among programmers. For reasons of ef...
S. Chaki S. Hissam
In Situ Formation of Cellulose Acetate Carbamate Dry-RO (Trade Name) Membranes.
The in situ formation of cellulose acetate (CA) carbamates was investigated to increase the performance of Dry-RO membranes of CA. The CA casting solutions were charged with reversibly blocked isocyanate monomers, which when heated, formed CA carbamates. ...
R. E. Kesting J. Ditter A. Murray J. Newman
Baroreflex Buffering and Susceptibility to Vasoactive Drugs
BackgroundThe overall effect of vasoactive drugs on blood pressure is determined by a combination of the direct effect on vascular tone and an indirect baroreflex-mediated effect, a baroreflex buffering of blood pressure. Differences in baroreflex function affect the responsiveness to vasoactive medications, particularly baroreflex buffering of blood pressure; however, the magnitude is not known. Methods and ResultsWe characterized baroreflex function
Jens Jordan; Jens Tank; John R. Shannon; Andre Diedrich; Axel Lipp; Christoph Schr—der; Guy Arnold; Arya M. Sharma; Italo Biaggioni; David Robertson; Friedrich C. Luft
Implementing Virtual Buffer for Electric Power Grids
The electric power grid is a vital network for every aspect of our life. The lack of buffer between generation and consumption\\u000a makes the power grid unstable and fragile. While large scale power storage is not technically and economically feasible at\\u000a present stage, we argue that a virtual buffer could be effectively implemented through a demand side management strategy built
Rong Gao; Lefteri H. Tsoukalas
Beltway Buffers: Avoiding the OS Traffic Jam
Beltway buffers are operating system I\\/O paths optimised for high-throughput network applications. The key architec- tural feature of Beltway buffers is that all I\\/O takes place in long-lived, allocation-free, shared ringbuffers. Advantages of this design are (1) improved throughput through system-wide copy, context-switch and allocation avoidance and judicious use of the data cache, (2) transparent integration of peripheral hardware and
Willem De Bruijn; Herbert Bos
Efficient Quality-Based Playout Buffer Algorithm
Playout buffers are used in VoIP systems to compensate for network delay\\u000ajitter by making a trade-off between delay and loss. In this work we propose a\\u000aplayout buffer algorithm that makes the trade-off based on maximization of\\u000aconversational speech quality, aiming to keep the computational complexity\\u000alowest possible. We model the network delay using a Pareto distribution and\\u000ashow
Emine Zerrin Sakir; Christian Feldbauer
Contraction of rat thoracic aorta strips induced by phorbol 12-myristate 13-acetate
Phorbol 12-myristate 13-acetate (PMA) induced a slow and progressive increase in tension of rat thoracic aorta strips in the presence of extracellular CaS . Complete relaxation could not be obtained in CaS -free buffer containing 1 mM ethyleneglycol-bis(US -aminoethylether)-N,N'-tetraacetic acid (EGTA) and 10 X M PMA. In the absence of extracellular CaS , PMA (10 X M) induced a small
H. Itoh; K. Lederis
Acetate free biofiltration (AFB): from theory to clinical results.
Acetate free biofiltration (AFB) is a hemodiafiltration technique based on a buffer-free dialysate and bicarbonate infusion in the postdilution mode. The performance of AFB requires a dialysis machine equipped with an automatic control system to balance the infusion rate to that of ultrafiltration. The filters employed are usually polyacrylonitrile hollow-fiber hemodialyzers. A 145 mEq/l sodium bicarbonate solution is generally used and the infusion rate is regulated at about 8-10 liters per session to ensure optimal convective removal of toxins as well as to compensate for the bicarbonate lost in the dialysate. During AFB bicarbonate transfer results from the balance between diffusive and convective bicarbonate losses in the dialyzer and the amount of bicarbonate infused in the venous return. Thus bicarbonate supply can increase along with the rise in plasma bicarbonate concentration until a steady state is reached when the rate of infused bicarbonate equals bicarbonate losses into the dialyzer. A mild alkalosis may sometimes occur which can be avoided by slightly reducing bicarbonate concentration and/or infusion rate during the session. In spite of the large amount of sodium infused and the unusual high chloride concentration in the dialysate, no difference in the postdialysis plasma sodium levels nor in chloremia has been observed between AFB and bicarbonate dialysis. This is essentially due to the very large removal of these anions by convection (chloride and sodium) and by diffusion (sodium) into the dialyzer. Similarly the significant convective losses of calcium suggest a high dialysate calcium concentration to avoid negative intradialytic calcium balance. Polyacrylonitrile membranes, regularly employed in AFB, allow the passage of endotoxin fragments to the blood circuit in a lesser extent than other membranes. Coupled with the fact that a buffer-free dialysate and a sterile bicarbonate infusion are used AFB can be considered a highly biocompatible dialysis technique. As compared to conventional dialysis AFB allows adequate removal of small molecules and better removal of larger molecules such as beta2-microglobulin. In the short run AFB is characterized by an increase in cardiovascular stability: it improves dialysis symptoms and the subjective well-being of patients. A better acid-base correction is regularly reported together with a rise in some nutritional indices like serum albumin levels. The reasons for these favorable results are not well defined yet. A number of multicenter studies on the effects of AFB have been published with quite similar results, but most of them are non-randomized, and use historical controls. Only one prospective, cross-over study comparing bicarbonate dialysis with AFB in diabetic dialysis patients is available. It concludes that in a six-month observation period with AFB it is possible to better control some metabolic aspects and to improve both treatment tolerance and patients' life quality. However, it is not known whether these positive effects may entail better long-term prognosis; moreover, comparisons between AFB and conventional dialysis were never designed to ascertain the role of the dialysis membrane from that of the other components of AFB on clinical results. Therefore, large prospective trials with long observation periods are necessary to clarify the mechanisms through which AFB might be superior to conventional dialysis as well as the impact of these techniques on long-term prognosis. In such studies other relevant factors such as rehabilitation and life quality of the patients, which have been generally neglected in previous surveys, must also be included to evaluate cost-effectiveness of this therapy. PMID:9710344
Galli, G; Panzetta, G
Acetate and Formate Stress: Opposite Responses in the Proteome of Escherichia coli
Acetate and formate are major fermentation products of Escherichia coli. Below pH 7, the balance shifts to lactate; an oversupply of acetate or formate retards growth. E. coli W3110 was grown with aeration in potassium-modified Luria broth buffered at pH 6.7 in the presence or absence of added acetate or formate, and the protein profiles were compared by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Acetate increased the steady-state expression levels of 37 proteins, including periplasmic transporters for amino acids and peptides (ArtI, FliY, OppA, and ProX), metabolic enzymes (YfiD and GatY), the RpoS growth phase regulon, and the autoinducer synthesis protein LuxS. Acetate repressed 17 proteins, among them phosphotransferase (Pta). An ackA-pta deletion, which nearly eliminates interconversion between acetate and acetyl-coenzyme A (acetyl-CoA), led to elevated basal levels of 16 of the acetate-inducible proteins, including the RpoS regulon. Consistent with RpoS activation, the ackA-pta strain also showed constitutive extreme-acid resistance. Formate, however, repressed 10 of the acetate-inducible proteins, including the RpoS regulon. Ten of the proteins with elevated basal levels in the ackA-pta strain were repressed by growth of the mutant with formate; thus, the formate response took precedence over the loss of the ackA-pta pathway. The similar effects of exogenous acetate and the ackA-pta deletion, and the opposite effect of formate, could have several causes; one possibility is that the excess buildup of acetyl-CoA upregulates stress proteins but excess formate depletes acetyl-CoA and downregulates these proteins.
Kirkpatrick, Christopher; Maurer, Lisa M.; Oyelakin, Nikki E.; Yoncheva, Yuliya N.; Maurer, Russell; Slonczewski, Joan L.
Optimization of a model of red blood cells for the study of anti-oxidant drugs, in terms of concentration of oxidant and phosphate buffer
The aggression of erythrocytes by an oxidative stress induces hemolysis. This paper aims to valid a model of erythrocytes in terms of composition of the phosphate buffer solution and of concentration of a well-known oxidant, AAPH. Three compositions of phosphate buffer solution are mixed with three concentrations of oxidant. The influence of these two parameters on hemolysis is independently studied
A. Bureau; J.-J. Lahet; F. Lenfant; F. Bouyer; M. Petitjean; B. Chaillot; M. Freysz
ACS Science Data Buffer Check/Self-Tests for CS Buffer RAM and MIE RAM
The ACS Science Buffer RAM is checked for bit flips during SAA passages. This is followed by a Control Section {CS} self-test consisting of writing/reading a specified bit pattern from each memory location in Buffer RAM and a similar test for MIE RAM. The MIE must be placed in BOOT mode for its self-test. The CS Buffer RAM self-test as well as the bit flip tests are all done with the CS in Operate.
Balzano, V.
Experimental study of the hydrothermal reactivity of organic acids and acid anions: II. Acetic acid, acetate, and valeric acid
Organic acids and acid anions occur in substantial concentrations in many aqueous geologic fluids and are thought to take part in a variety of geochemical processes ranging from the transport of metals in ore-forming fluids to the formation of natural gas to serving as a metabolic energy source for microbes in subsurface habitats. The widespread occurrence of organic acids and their potential role in diverse geologic processes has led to numerous experimental studies of their thermal stability, yet there remain substantial gaps in our knowledge of the factors that control the rates and reaction pathways for the decomposition of these compounds under geologic conditions. In order to address some of these uncertainties, a series of laboratory experiments were conducted to examine the behavior of organic acids and acid anions under hydrothermal conditions in the presence of minerals. Reported here are results of experiments where aqueous solutions of acetic acid, sodium acetate, or valeric acid ( n-pentanoic acid) were heated at 325¯C, 350 bars in the presence of the mineral assemblages hematite + magnetite + pyrite, pyrite + pyrrhotite + magnetite, and hematite + magnetite. The results indicate that aqueous acetic acid and acetate decompose by a combination of two reaction pathways: decarboxylation and oxidation. Both reactions are promoted by minerals, with hematite catalyzing the oxidation reaction while magnetite catalyzes decarboxylation. The oxidation reaction is much faster, so that oxidation dominates the decomposition of acetic acid and acetate when hematite is present. In contrast to previous reports that acetate decomposed more slowly than acetic acid, we found that acetate decomposed at slightly faster rates than the acid in the presence of minerals. Although longer-chain monocarboxylic acids are generally thought to decompose by decarboxylation, valeric acid appeared to decompose primarily by "deformylation" to 1-butene plus formic acid. Subsequent decomposition of 1-butene and formic acid generated a variety of short-chain (?C 4) hydrocarbons and moncarboxylic acids as well as CO 2. Valeric acid decomposition proceeded more rapidly (by a factor of 2) in the presence of hematite-magnetite-pyrite than with the other mineral assemblages, with the greater reaction rate apparently attributable to the effects of fluid chemistry. Valeric acid was observed to decompose at a substantially faster rate than acetic acid under similar conditions. The results suggest that decomposition of aqueous monocarboxylic acids may make a significant contribution to the conversion of petroleum to light hydrocarbons in natural gas and thermal fluids.
McCollom, Thomas M.; Seewald, Jeffrey S.
The compatibility and stability of octreotide acetate in the presence of diamorphine hydrochloride in polypropylene syringes.
Varying concentrations of octreotide acetate (Sandostatin) and diamorphine hydrochloride were prepared and stored in polypropylene syringes at 37 degrees C in the dark. The solutions were analysed for octreotide acetate content using a validated HPLC method at regular intervals over a 48-h period. The results indicate that octreotide acetate remains stable in the presence of diamorphine hydrochloride at 37 degrees C for 24 h. In addition, the solutions prepared maintained their clarity, with no signs of precipitation upon visual examination under normal light conditions. PMID:10858828
Fielding, H; Kyaterekera, N; Skellern, G G; Tettey, J N; McDade, J R; Msuya, Z; Watson, D G; Urie, J
Migration of ethylene glycol from polyethylene terephthalate bottles into 3% acetic acid.
Migration of ethylene glycol (EG) from polyethylene terephthalate (PET) bottles into the food simulate 3% acetic acid was studied using 32 fluid oz PET bottles filled with 3% acetic acid and stored at 32 degrees C for 6 months. Final concentration of EG in the 3% acetic acid migration solution was about 100 ppb, which is equivalent to about 94 microgram EG/bottle. A gas-liquid chromatographic procedure for quantitating EG was developed which is capable of measuring EG levels as low as 50 ppb in the migration solution. PMID:6448834
Kashtock, M; Breder, C V
Synthesis and regeneration of lead (IV) acetate
Lead acetate [Pb(O{sub 2}CMe){sub 4}] was easily synthesized from a warm solution of Pb{sub 3}O{sub 4}, HO{sub 2}CMe and O(OCMe){sub 2} following literature preparations when the appropriate measures to minimize water contamination were followed. Furthermore, Pb(O{sub 2}CMe){sub 4} which has been decomposed (evidenced by the appearance of a purple color due to oxidation) can be regenerated using a similar preparatory route. Introduction of Pb(O{sub 2}CMe){sub 4} from the two routes outlined above into the IMO process for production of PZT thin films gave films with comparable ferroelectric properties to commercially available Pb(O{sub 2}CMe){sub 4} precursors. However, the freshly synthesized material yields PZT films with better properties compared to the recycled material.
Boyle, T.J.; Al-Shareef, H.N.; Moore, G.J. [Sandia National Labs., Albuquerque, NM (United States). Advanced Materials Lab.
Biofiltration of ethyl acetate and amyl acetate using a composite bead biofilter.
Biodegradation kinetic behaviors of ethyl acetate and amyl acetate in a composite bead biofilter were investigated. The composite bead was the spherical PVA/peat/KNO3/GAC composite bead which was prepared in our previous works. Both microbial growth rate and biochemical reaction rate were inhibited at higher inlet concentration. For the microbial growth process, the microbial growth rate of ethyl acetate was greater than that of amyl acetate in the inlet concentration range of 100-400ppm. The degree of inhibitive effect was almost the same for ethyl acetate and amyl acetate in this concentration range. The half-saturation constant Ks values of ethyl acetate and amyl acetate were 16.26 and 12.65ppm, respectively. The maximum reaction rate Vm values of ethyl acetate and amyl acetate were 4.08 and 3.53gCh(-1)kg(-1) packed material, respectively. Zero-order kinetic with the diffusion limitation could be regarded as the most adequate biochemical reaction model. For the biochemical reaction process, the biochemical reaction rate of ethyl acetate was greater than that of amyl acetate in the inlet concentration range of 100-400ppm. The inhibitive effect for ethyl acetate was more pronounced than that for AA in this concentration range. The maximum elimination capacity of ethyl acetate and amyl acetate were 82.3 and 37.93gCh(-1)m(-3) bed volume, respectively. Ethyl acetate degraded by microbial was easier than amyl acetate did. PMID:18445522
Chan, Wu-Chung; Su, Mei-Qi
Carbon-isotopic analysis of dissolved acetate
Heating of dried, acetate-containing solids together with oxalic acid dihydrate conveniently releases acetic acid for purification by gas chromatography. For determination of the carbon-isotopic composition of total acetate, the acetate-containing zone of the chromatographic effluent can be routed directly to a combustion furnace coupled to a vacuum system allowing recovery, purification, and packaging of CO2 for mass-spectrometric analysis. For analysis of methyl carbon, acetic acid can be cryogenically trapped from the chromatographic effluent, then transferred to a tube containing excess NaOH. The tube is evacuated, sealed, and heated to 500 degrees C to produce methane by pyrolysis of sodium acetate. Subsequent combustion of the methane allows determination of the 13C content at the methyl position in the parent acetate. With typical blanks, the standard deviation of single analyses is less than 0.4% for acetate samples larger than 5 micromoles. A full treatment of uncertainties is outlined.
Gelwicks, J. T.; Hayes, J. M.
Cationic surfactant as a sensitizer for the spectrophotometric determination of hydrogen sulphide in air and evaluation of a new absorbing medium containing triethanolamine-zinc acetate-sodium hydroxide.
An extractive spectrophotometric method for the determination of trace amounts of hydrogen sulphide after fixing the gas in triethanolamine (TEA)-zinc acetate-sodium hydroxide solution is described. The method is based on the reaction of iodate with hydrogen sulphide in the presence of acid and excess chloride ion leading to the formation of ICl2- species which is used to iodinate 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein. The iodinated product formed is extracted into an organic solvent and sensitized by equilibrating with a cationic surfactant, cetrimide, in the presence of acetate buffer (pH 5.9 +/- 0.1). The colour system obeys Beer's law over the range 0-1 microg of hydrogen sulphide and the relative standard deviation is 2.4% for 10 determinations at 0.75 microg of hydrogen sulphide. The effect of interfering gases on the determination is discussed. The proposed absorbing solution has been evaluated using a hydrogen sulphide permeation device. This absorbing solution has an absorption efficiency of > 93% at a flow rate of 1.5 litre min(-1) for a sampling period of 2 h. The fixed H2S is stable for 40 days. The method has been applied to determine residual H2S levels in a laboratory fume hood and in the vicinity of sewage pumping station. The method can be used to determine as little as 0.05 microg of hydrogen sulphide. PMID:15093484
Pandurangappa, M; Balasubramanian, N
Heating of dried, acetate-containing solids together with oxalic acid dihydrate conveniently releases acetic acid for purification by gas chromatography. For determination of the carbon-isotopic composition of total acetate, the acetate-containing zone of the chromatographic effluent can be routed directly to a combustion furnace coupled to a vacuum system allowing recovery, purification, and packaging of COã for mass-spectrometric analysis. For analysis
Jeffrey T. Gelwicks; J. M. Hayes
21 CFR 184.1185 - Calcium acetate.
Code of Federal Regulations, 2011 CFR
, CAS Reg. No. 62-54-4), also known as acetate of lime or vinegar salts, is the calcium salt of acetic acid. It may be produced by the calcium hydroxide neutralization of acetic acid. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed. (1981),...
Code of Federal Regulations, 2010 CFR
Transport and release of transition elements during early diagenesis: Sequential leaching of sediments from MANOP Sites M and H. Part I. pH 5 acetic acid leach
Sediments from MANOP sites M and H in the eastern tropical Pacific Ocean can be partitioned into operationally defined phases by means of a sequential leach procedure. This paper reports the results of the first leach in the sequence, an acetic acid solution buffered as p H 5 with sodium acetate. This leach is designed to remove carbonate-bound and sorbed cations. The only cation bound in a consistent ratio to calcium in the carbonate is strontium. The molar ratio is 2 æ 10 -3. In contrast, transition metals are sorbed onto the surfaces of other sedimentary particles. The proportions sorbed range from 2 to 10% of the total manganese, about 10% of the total nickel and copper, and less than 1% of the total iron. The pool of sorbed metals in surface sediments is sufficiently large and the rate of biological stirring is sufficiently rapid for this metal reservoir potentially to dominate the porewater reservoir in supplying metals to ferromanganese nodules. A simple model for nodule growth based upon transfer of metals through this reservoir suggests that only 1% of the sedimentary sorbed metals within a radius of 2 to 9 cm is required to support typical nodule growth rates.
Lyle, Mitchell; Heath, G. Ross; Robbins, James M.
Transports of acetate and haloacetate in Burkholderia species MBA4 are operated by distinct systems
Background Acetate is a commonly used substrate for biosynthesis while monochloroacetate is a structurally similar compound but toxic and inhibits cell metabolism by blocking the citric acid cycle. In Burkholderia species MBA4 haloacetate was utilized as a carbon and energy source for growth. The degradation of haloacid was mediated by the production of an inducible dehalogenase. Recent studies have identified the presence of a concomitantly induced haloacetate-uptake activity in MBA4. This uptake activity has also been found to transport acetate. Since acetate transporters are commonly found in bacteria it is likely that haloacetate was transported by such a system in MBA4. Results The haloacetate-uptake activity of MBA4 was found to be induced by monochloroacetate (MCA) and monobromoacetate (MBA). While the acetate-uptake activity was also induced by MCA and MBA, other alkanoates: acetate, propionate and 2-monochloropropionate (2MCPA) were also inducers. Competing solute analysis showed that acetate and propionate interrupted the acetate- and MCA- induced acetate-uptake activities. While MCA, MBA, 2MCPA, and butyrate have no effect on acetate uptake they could significantly quenched the MCA-induced MCA-uptake activity. Transmembrane electrochemical potential was shown to be a driving force for both acetate- and MCA- transport systems. Conclusions Here we showed that acetate- and MCA- uptake in Burkholderia species MBA4 are two transport systems that have different induction patterns and substrate specificities. It is envisaged that the shapes and the three dimensional structures of the solutes determine their recognition or exclusion by the two transport systems.
Phase Equilibria in the Systems Oxolane + Vinyl Acetate, Oxolane + Ethyl 1,1-Dimethylethyl Ether and Vinyl Acetate + Ethyl 1,1-Dimethylethyl Ether
Vapor-liquid equilibrium at 94kPa has been determined for the binary systems oxolane (THF) + vinyl acetate, oxolane + ethyl 1,1-dimethylethyl ether (ETBE) and vinyl acetate + ethyl 1,1-dimethylethyl ether. The three systems present slight to moderate positive deviations from ideal behavior and, to a first approximation, can be considered to behave like regular solutions. An azeotrope is present in the
Jaime Wisniak; Hugo Segura
Redox buffered hydrofluoric acid etchant for the reduction of galvanic attack during release etching of MEMS devices having noble material films
Etchant solutions comprising a redox buffer can be used during the release etch step to reduce damage to the structural layers of a MEMS device that has noble material films. A preferred redox buffer comprises a soluble thiophosphoric acid, ester, or salt that maintains the electrochemical potential of the etchant solution at a level that prevents oxidation of the structural material. Therefore, the redox buffer preferentially oxidizes in place of the structural material. The sacrificial redox buffer thereby protects the exposed structural layers while permitting the dissolution of sacrificial oxide layers during the release etch.
Hankins, Matthew G. (Albuquerque, NM)
Buffer-gas cooling of diatomic molecules
Development of novel methods of molecular cooling and progress towards a general technique for molecular trapping are reported. Buffer-gas cooling of laser-ablated molecules is used to produce 1012 molecules of lead monoxide PbO in the ground X1Sigma(v? = 0) state at 4 K, opening a possibility for improved sensitivity of searches for the electric dipole moment of the electron. A new method of loading atoms and molecules into a buffer gas cell is developed, and is used to produce 1012 Rb atoms at 4.5 K and 1012 molecules of imidogen NH X3Sigma-(v? = 0) at <6 K. A next-generation trapping apparatus combining a molecular-beam loaded buffer gas cell with an in-vacuum 4.5-Tesla magnetic trap is developed. A critical parameter in buffer-gas-based magnetic trapping, the Zeeman relaxation rate in molecule-helium collisions, is measured for collisions of calcium monofluoride CaF with He. Up to 5 x 10 13 CaF X2Sigma+(v? = 0) molecules are produced via laser ablation at temperature of 2 K in helium buffer gas; the Zeeman relaxation rate is found to be 7.7 x 10 -15 cm3s-1. The result is consistent with a recent theoretical prediction, which indicates that the theory may be successfully used to predict suitability of molecular candidates for buffer-gas based trapping experiments and supports the continued use of new theoretical approaches to the calculation of molecular collisional processes.
Egorov, Dimitri Michael
Flexible and Adaptable Buffer Management Techniques for Database Management Systems
The problem of buffer management in database management systems is concerned with theefficient main memory allocation and management for answering database queries. Previous workson buffer allocation are based either exclusively on the availability of buffers at runtime or on theaccess patterns of queries. In this paper, we first propose a unified approach for buffer allocation inwhich both of these considerations
Christos Faloutsos; Raymond T. Ng; Timos K. Sellis
Buffer Standards for the Physiological pH of the Zwitterionic Compound, DIPSO from 5 to 55 degrees C.
The values of the second dissociation constant, pK(2), and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55 degrees C including 37 degrees C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I = 0.16 mol.kg(-1). Conventional pa(H) values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37 degrees C after correcting the liquid junction potentials with the flowing junction cell. PMID:20160870
Roy, Lakshmi N; Roy, Rabindra N; Lenoue, Sean R; Denton, Cole E; Fuge, Michael S; Dunseth, Craig D; Roy, Chandra N; Hayden, Shawn M; Wollen, Joshua T; Sreepada, Kripa
Buffer Standards for the Physiological pH of the Zwitterionic Compound, DIPSO from 5 to 55?C
The values of the second dissociation constant, pK2, and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55¯C including 37¯C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I = 0.16 molñkg?1. Conventional paH values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37¯C after correcting the liquid junction potentials with the flowing junction cell.
Roy, Lakshmi N.; Roy, Rabindra N.; LeNoue, Sean R.; Denton, Cole E.; Fuge, Michael S.; Dunseth, Craig D.; Roy, Chandra N.; Hayden, Shawn M.; Wollen, Joshua T.; Sreepada, Kripa
Thin La{sub 2}Zr{sub 2}O{sub 7} films made from a water-based solution
Thin films of La{sub 2}Zr{sub 2}O{sub 7} (LZO) are highly regarded as possible buffer layers in the coated conductor configuration. This report describes a new synthesis for thin crystalline LZO films, based on a largely water-based solution, mainly containing metal acetates, acetic acid and an organic amine-base: triethanolamine. Initially, a thin layer of amorphous material is deposited on the textured Ni-5 at%W substrate by means of dip-coating. Only by careful control of the thermal treatment can the layer be transformed into a crystalline layer. Important parameters in this respect are the heating rate and the dwell time. The amorphous gel is analysed by HR-TGA/DTA and HR-TEM. The textured layers are analysed by XRD, pole figures, RHEED, AFM and SEM. - Grapical Abstract: Thin films of La2Zr2O7 (LZO) are produced via a water-based solution, containing metal acetates, acetic acid and triethanolamine. The thin layer is deposited on the textured Ni-5 at%W substrate by dip-coating. The amorphous gel is analysed by HR-TGA/DTA and HR-TEM. The textured layers are analysed by XRD, pole figures, RHEED analysis, AFM and SEM.
Cloet, V. [Ghent University, Krijgslaan 281-S3, 9000 Gent (Belgium)], E-mail: firstname.lastname@example.com; Feys, J. [Ghent University, Krijgslaan 281-S3, 9000 Gent (Belgium); Huehne, R. [Institute for Metallic Materials, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany); Hoste, S.; Van Driessche, I. [Ghent University, Krijgslaan 281-S3, 9000 Gent (Belgium)
Advanced treatment of sodium acetate in water by ozone oxidation.
Ozone oxidation is an advanced oxidation process for treatment of organic and inorganic wastewater. In this paper, sodium acetate (according to chemical oxygen demand [COD]) was selected as the model pollutant in water, and the degradation efficiencies and mechanism of sodium acetate in water by ozone oxidation were investigated. The results showed that the ozone oxidation was an effective treatment technology for advanced treatment of sodium acetate in water; the COD removal rate obtained the maximum value of 45.89% from sodium acetate solution when the pH value was 10.82, ozone concentration was 100 mg/L, reaction time was 30 minutes, and reaction temperature was 25 degrees C. The COD removal rate increased first and decreased subsequently with the bicarbonate (HCO3-) concentration from 0 to 200 mg/L, the largest decline being 20.35%. The COD removal rate declined by 25.38% with the carbonate (CO3(2-)) concentration from 0 to 200 mg/L; CO3(2-) has a more obvious scavenging effect to inhibit the formation of hydroxyl free radicals than HCO3-. Calcium chloride (CaCl2) and calcium hydroxide (Ca(OH)2) could enhance the COD removal rate greatly; they could reach 77.35 and 96.53%, respectively, after a reaction time of 30 minutes, which was increased by 31.46 and 50.64%, respectively, compared with only ozone oxidation. It was proved that the main ozone oxidation product of sodium acetate was carbon dioxide (CO2), and the degradation of sodium acetate in the ozone oxidation process followed the mechanism of hydroxyl free radicals. PMID:24645544
Yang, De-Min; Yuan, Jian-Mei
Electrospun cellulose acetate-garnet nanocomposite magnetic fibers for bioseparations.
Cellulose acetate fibers with magnetic properties have recently attracted much attention because of their potential novel applications in biomedicine such as for cell and protein separations, magnetic resonance imaging contrast agents, and magnetic filters. In this work, as synthesized yttrium iron garnet and gadolinium substituted yttrium iron garnet nanoparticles have been used to generate magnetic filter paper. Garnet nanoparticles dispersed in cellulose acetate polymer solutions were electrospun as free-standing nonwoven fiber mats as well as on cellulose filter paper substrates resulting in magnetic filter papers. The magnetic fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and superconducting quantum interference device (SQUID) magnetic property measurements. The resulting magnetic polymer nanocomposites can be easily picked up by an external magnet from a liquid medium. Fluorescein isothiocyanate (FITC) labeled bovine serum albumin (BSA) was separated from solution by using the magnetic filter paper. PMID:24341636
Munaweera, Imalka; Aliev, Ali; Balkus, Kenneth J
High-performance multiqueue buffers for VLSI communication switches
A type of buffer called a dynamically allocated multiqueue (DAMQ) buffer, designed for use in næn switches, is presented. This buffer provides efficient handling of variable-length packets and the forwarding of packets in non-FIFO (first-in-first-out) order. The microarchitecture of the DAMQ buffer and its controller is described in the context of the ComCoBB communication coprocessor for multicomputers. The DAMQ buffer
Y. Tamir; Gregory L. Frazier
Performance Analysis of Buffering Schemes on Wormhole Routers
Wormhole switched input-buffered and middle-buffered routers with virtual channels are analyzed in this paper. Middle buffering refers to the placement of virtual channels between the demultiplexers and multiplexers of a crossbar switch. An analytical model for multistage interconnection networks using middle-buffered switches is developed. In addition, extensive simulation is conducted to assess the performance of the two buffering techniques in
Younes M. Boura; Chita R. Das
Complexation of chitosan with acetic acid according to Fourier transform Raman spectroscopy data
The results of the interaction between the protonated chitosan (CHI) macromolecule and the acetate ion in dilute acetic acid solutions were studied by Fourier transform Raman spectroscopy and quantum-chemical modeling. The complexation of CHI with the acetate ion showed itself as the 934 cm-1 band in the Raman spectrum, which suggests the formation of [CHI+ ñ CH3COO-] type ion pairs. It was concluded that a comparative analysis of the integrated intensities of the Raman bands in the range 880-940 cm-1 makes it possible to judge about the relative content of hydrated acetate ions, CHI macromolecules of the [CHI+ ñ CH3COO-] complex, and acetic acid molecules not involved in CHI protonation.
Mikhailov, G. P.; Tuchkov, S. V.; Lazarev, V. V.; Kulish, E. I.
Buffered DDA command generation in a CNC
In a computerized numerical controller (CNC), interpolating more than one block in a sampling interval, increases the feed rate. Some commands skipped by the generator are pre-saved in a circular buffer, to provide faster operation than that of a conventional digital differential analyzer. The feed rate can be increased when programmed distances are short. The high feed rate is confirmed
Yih-Fang Chang
Antibody buffering of a ligand in vivo
Clearance is the practical limit on drug action. Here we propose a means of slowing clearance, thereby extending drug lifetime in vivo by "antibody buffering." In this process, a drug and an anti-drug antibody are coadministered. Most of the drug is bound to the antibody, preventing the drug from acting, but also preventing its elimination. A dynamic free drug pool is established by reversible dissociation from the antibody. The free drug is active and can be eliminated, but the free pool is constantly replenished by reequilibration from the antibody-drug complex, giving a long effective lifetime. Here we explore antibody buffering experimentally by using a model compound, 2-phenyloxazol-5-one--aminobutyrate (Ox), as a drug proxy. We show that antibody buffering can extend by an order of magnitude the plasma lifetime of Ox in rats, and that the steady-state Ox level depends on the molecular properties of the antibody used to buffer the Ox. In addition, the anti-Ox antibody can be recharged with drug in vivo to extend Ox lifetime without additional antibody administration, making this technique even more suitable for possible clinical application. drug delivery | pharmacokinetics | immunotherapy | antibody-antigen interactions
O'Hear, Carol E.; Foote, Jefferson
Stochastic analysis of moisture buffering in rooms
SUMMARY: This paper presents a stochastic method to obtain design values for the necessary moisture buffering of wall materials in order to prevent moisture damage. The difference in maximal and minimal relative humidity in the room during a day is chosen as an indicator for the moisture damage risk. Choosing an acceptable probability of occurrence of moisture damage allows then
Jan Carmeliet; Dominique Derome
Buffer layers on biaxially textured metal substrates
A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.
Shoup, Shara S. (Woodstock, GA); Paranthamam, Mariappan (Knoxville, TN); Beach, David B. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)
Delay Reduction Techniques for Playout Buffering
Receiver synchronization of continuous mediastreams is required to deal with delay differences and variationsresulting from delivery over packet networks suchas the Internet. This function is commonly provided usingper-stream playout buffers which introduce additionaldelay in order to produce a playout schedule which meetsthe synchronization requirements. Packets which arrive aftertheir scheduled playout time are considered late and arediscarded. In this paper, we
Cormac J. Sreenan; Jyh-cheng Chen; Prathima Agrawal; B. Narendran
A new view-buffer splatting algorithm
Splatting is an important object-order direct volume rendering algorithm which projects each voxel onto the view plane and composite it into a accumulating image by using a preintegrated interpolation kernels called footprint. Popular sheet-buffer based splatting algorithms overcome most problems at the cost of leading to popping artifacts. In this paper we present a new splatting volume rendering method which
Zhigang Sun; Jiawan Zhang; Jizhou Sun; Zunce Wei
Biodegradable cellulose acetate nanofiber fabrication via electrospinning.
Nanofiber manufacturing is one of the key advancements in nanotechnology today. Over the past few years, there has been a tremendous growth of research activities to explore electrospinning for nanofiber formation from a rich variety of materials. This quite simple and cost effective process operates on the principle that the solution is extracted under the action of a high electric field. Once the voltage is sufficiently high, a charged jet is ejected following a complicated looping trajectory. During its travel, the solvent evaporates leaving behind randomly oriented nanofibers accumulated on the collector. The combination of their nanoscale dimensionality, high surface area, porosity, flexibility and superior strength makes the electrospun fibers suitable for several value-added applications, such as filters, protecting clothes, high performance structures and biomedical devices. In this study biodegradable cellulose acetate (CA) nanofibrous membranes were produced using electrospinning. The device utilized consisted of a syringe equipped with a metal needle, a microdialysis pump, a high voltage supply and a collector. The morphology of the yielded fibers was determined using SEM. The effect of various parameters, including electric field strength, tip-to-collector distance, solution feed rate and composition on the morphological features of the electrospun fibers was examined. The optimum operating conditions for the production of uniform, non-beaded fibers with submicron diameter were also explored. The biodegradable CA nanofiber membranes are suitable as tissue engineering scaffolds and as reinforcements of biopolymer matrix composites in foils by ultrasonic welding methods. PMID:21133179
Christoforou, Theopisti; Doumanidis, Charalabos
An MEC-MFC-coupled system for biohydrogen production from acetate.
Microbial fuel cells (MFCs) are devices that use bacteria as the catalysts to oxidize organic and inorganic matter and generate current whereas microbial electrolysis cells (MECs) are a reactor for biohydrogen production by combining MFC and electrolysis. In an MEC, an external voltage must be applied to overcome the thermodynamic barrier. Here we report an MEC-MFC-coupled system for biohydrogen production from acetate, in which hydrogen was produced in an MEC and the extra power was supplied by an MFC. In this coupled system, hydrogen was produced from acetate without external electric power supply. At 10 mM of phosphate buffer, the hydrogen production rate reached 2.2 +/- 0.2 mL L(-1) d(-1), the cathodic hydrogen recovery (RH2) and overall systemic Coulombic efficiency (CEsys) were 88 to approximately 96% and 28 to approximately 33%, respectively, and the overall systemic hydrogen yield (Y(sysH2)) peaked at 1.21 mol-H2 mol-acetate(-1). The hydrogen production was elevated by increasing the phosphate buffer concentration, and the highest hydrogen production rate of 14.9 +/- 0.4 mL L(-1) d(-1) and Y(sysH2) of 1.60 +/- 0.08 mol-H2 mol-acetate(-1) were achieved at 100 mM of phosphate buffer. The performance of the MEC and the MFC was influenced by each other. This MEC-MFC-coupled system has a potential for biohydrogen production from wastes, and provides an effective way for in situ utilization of the power generated from MFCs. PMID:19031908
Sun, Min; Sheng, Guo-Ping; Zhang, Lei; Xia, Chang-Rong; Mu, Zhe-Xuan; Liu, Xian-Wei; Wang, Hua-Lin; Yu, Han-Qing; Qi, Rong; Yu, Tao; Yang, Min
Vitamin-loaded electrospun cellulose acetate nanofiber mats as transdermal and dermal therapeutic agents of vitamin A acid and vitamin E.
The present contribution reports the use of mats of electrospun cellulose acetate (CA; acetyl content=39.8%; Mw=30,000 Da) nanofibers as carriers for delivery of the model vitamins, all-trans retinoic acid or vitamin A acid (Retin-A) and alpha-tocopherol or vitamin E (Vit-E). The amounts of Vit-E and Retin-A loaded in the base CA solution [17% w/v in 2:1 v/v acetone/N,N-dimethylacetamide (DMAc)] were 5 and 0.5 wt% (based on the weight of CA), respectively. Cross-sectionally round and smooth fibers were obtained. The average diameters of these fibers ranged between 247 and 265 nm. The total immersion of the vitamin-loaded as-spun CA fiber mats in the acetate buffer solutions containing either 0.5 vol % Tween 80 or 0.5 vol % Tween 80 and 10 vol % methanol was used to arrive at the cumulative release of the vitamins from the fiber mat samples. The same was also conducted on the vitamin-loaded solution-cast CA films for comparison. In most cases, the vitamin-loaded as-spun fiber mats exhibited a gradual and monotonous increase in the cumulative release of the vitamins over the test periods (i.e., 24 h for Vit-E-loaded samples and 6 h for Retin-A-loaded ones), while the corresponding as-cast films exhibited a burst release of the vitamins. PMID:17498935
Taepaiboon, Pattama; Rungsardthong, Uracha; Supaphol, Pitt
Polymerization of vinyl acetate in fatty acids and properties of poly (vinyl alcohols) derived from the poly (vinyl acetates)
Polymerization of vinyl acetate (VAc) in various fatty acids (carbon numbers 418) was carried out. Chain transfer constants to the acids were determined to be 2035æ10-4, from which the constant to a methylene group was obtained to be 0.73æ10-4. Viscometry in aqueous solution of derived poly (vinyl alcohol) (PVA) showed the usual behavior in terms of Huggins constant obtained by
Takeshi Ishijima; Yoshiki Mizumori; Kenji Kikuchi; Atsushi Suzuki; Takuji Okaya
Biochar contribution to soil pH buffer capacity
Biochar as ecologically clean and stable form of carbon has complex of physical and chemical properties which make it a potentially powerful soil amendment (Mutezo, 2013). Therefore during the last decade the biochar application as soil amendment has been a matter for a great number of investigations. For the ecological viewpoint the trend of decreasing of soil organic matter in European agricultural land is a major problem. Society is faced with the task to find possibilities to stabilize or increase soil organic matter content in soil and quality. The availability of different functional groups (e.g. carboxylic, phenolic, acidic, alcoholic, amine, amide) allows soil organic matter to buffer over a wide range of soil pH values (Krull et al. 2004). Therefore the loss of soil organic matter also reduces cation exchange capacity resulting in lower nutrient retention (Kimetu et al. 2008). Biochar can retain elements in soil directly through the negative charge that develops on its surfaces, and this negative charge can buffer acidity in the soil. There are lack of investigations about the effect of biochar to soil pH buffering properties, The aim of our investigation was to investigate the changes in soil pH buffer capacity in a result of addition of carbonizated material to temperate region soils. In the experiment different kind of softwood biochars, activated carbon and different soil types with various organic matter and pH were used. The study soils were Albeluvisols, Leptosols, Cambisols, Regosols and Histosols . In the experiment the series of the soil: biochar mixtures with the biochar content 0 to 100% were used. The times of equiliberation between solid and liquid phase were from 1 to 168 hours. The suspension of soil: biochar mixtures was titrated with HCl solution. The titration curves were established and pH buffer capacities were calculated for the pH interval from 3.0 to 10.0. The results demonstrate the dependence of pH buffer capacity from soil type, organic matter and type of added carbonizated material. Our study showed that the biochar content has significant role in total pH buffer capacity in soil:biochar system . References. Kimetu, J.M., Lehmann, J., Ngoze, S.O., Mugendi, D.N., Kinyangi, J., Riha, S.J., Verchot, L., Recha, J.W., Pell, A.N. 2008. Reversibility of Soil Productivity Decline with Organic Matter of Differing Quality Along a Degradation Gradient. Ecosystems, 11, 726-739. Krull, E. S., Skjemstad, J.O., Baldock, J.A. 2004 'Functions of Soil Organic Matter and the Effect on Soil Properties'. GRDC report. Project CSO 00029. Mutezo, W.T., 2013. Early crop growth and yield responses of maize (Zea mays) to biochar applied on soil. International Working Paper Series, 13/03, 50 pp.
Tonutare, Tonu; Krebstein, Kadri; Utso, Maarius; Rodima, Ako; Kolli, Raimo; Shanskiy, Merrit
COS Science Data Buffer Check/Self-Tests for CS Buffer RAM and DIB RAM
The COS Science Buffer RAM is checked for bit flips during SAA passages. This is followed by a Control Section {CS} self-test consisting of writing/reading a specified bit pattern from each memory location in Buffer RAM and a similar test for DIB RAM. The DIB must be placed in BOOT mode for its self-test. The CS Buffer RAM self-test as well as the bit flip tests are all done with the CS in Operate. Supports Activity COS-03;
Welty, Alan
Comparison of zwitterionic N-alkylaminomethanesulfonic acids to related compounds in the Good buffer series
Summary Several N-alkyl and N,N-dialkylaminomethanesulfonic acids were synthesized (as zwitterions and/or sodium salts) to be tested for utility as biological buffers at lower pH levels than existing Good buffer compounds (aminoalkanesulfonates with a minimum of two carbons between amine and sulfonic acid groups as originally described by Norman Good, and in common use as biological buffers). Our hypothesis was that a shorter carbon chain (one carbon) between the amino and sulfonic acid groups should lower the ammonium ion pK a values. The alkylaminomethanesulfonate compounds were synthesized in aqueous solution by reaction of primary or secondary amines with formaldehyde/sodium hydrogensulfite addition compound. The pK a values of the ammonium ions of this series of compounds (compared to existing Good buffers) was found to correlate well with the length of the carbon chain between the amino and sulfonate moeties, with a significant decrease in amine basicity in the aminomethanesulfonate compounds (pK a decrease of 2 units or more compared to existing Good buffers). An exception was found for the 2-hydroxypiperazine series which shows only a small pK a decrease, probably due to the site of protonation in this compound (as confirmed by X-ray crystal structure). X-ray crystallographic structures of two members of the series are reported. Several of these compounds have pK a values that would indicate potential utility for buffering at pH levels below the normal physiological range (pK a values in the range of 3 to 6 without aqueous solubility problems) a range that is problematic for currently available Good buffers. Unfortunately, the alkylaminomethanesulfonates were found to degrade (with loss of their buffering ability) at pH levels below the pK a value and were unstable at elevated temperature (as when autoclaving) thus limiting their utility.
Hilliard, Newton P; Chhatre, Suneel A; Timofeeva, Tatiana V; Yakovenko, Andrey A; Dei, Daniel K; Mensah, Enoch A
Spectrophotometric Determination of Lorsartan Potassium and its Dosage Form by Bromothymol Blue and Phosphate Buffer
Simple, rapid and accurate, spectrophotometric method for the determination of losartan potassium by using bromothymol blue as a chromogen and phosphate buffer solution (pH 3-4) as a diluting agent was developed. The developed colour shows maximum absorbance at 620 nm and it was observed that the absorbance of different dilution from the plots the calibration curve between the concentrations in
Analysis of Memory Interference in Buffered Multiprocessor Systems in Presence of Hot Spots and Favorite Memories
We present a discrete Markov chain model for analyzing the effect of memory interference in processor-memory in- terconnections of buffered multiprocessor systems. Each module is assumed to be one of the following three types - hot memory, favorite memory and memory which is neither hot nor favorite. The analytical solutions are restricted to 2 and 2 systems, where and are
Sajal K. Das; Sanjoy K. Sen
Playout buffering of speech packets based on a quality maximization approach
To combat jitter problems in voice streaming over packet networks, playout buffering algorithms are used at the receiver side. Most of the proposed solutions rely on two main operations: prediction of delay statistics for future packets; setting of the end-to-end delay so as to limit or avoid packet losses. In recent years, a new approach has been presented, which is
Luigi Atzori; Mirko Luca Lobina; Marco Corona
Characterization of the spherical intermediates and fibril formation of hCT in HEPES solution using solid-state 13C-NMR and transmission electron microscopy.
Human calcitonin (hCT) is a 32-amino acid peptide hormone that contains an intrachain disulfide bridge between Cys1 and Cys7 and a proline amide at the C-terminus. hCT tends to associate to form a fibril precipitate of the same type as amyloid fibrils, and hence has been studied as a model of amyloid fibril formation. The fibrillation process in N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid (HEPES) solution was examined using transmission electron microscopy. The rate of hCT fibrillation in HEPES solution was much lower than in phosphate buffer and acetic acid solution. Spherical intermediate aggregates (nuclei) were observed during the early stage of fibril formation. Short proto-fibrils appeared on the surface of the spherical intermediates. Subsequently, the spherical intermediates transformed directly into long proto-fibrils, which then elongated into mature hCT fibrils. The fibrillation process was also examined using solid-state (13)C-NMR spectroscopy, which indicated that the fibril structure was a ?-sheet in the central region and a mixture of random coils and ?-sheets at the C-terminus. The kinetics of fibril formation was examined in terms of a two-step autocatalytic reaction mechanism. The first-step nucleation rate (k1) was lower in HEPES solution than in phosphate buffer and acetic acid solution because the half-life of the intermediates is significantly longer in HEPES solution. In contrast, the second-step fibril elongation rate (k2) was similar in HEPES solution and acidic solutions. Specific interaction of HEPES molecules with hCT may stabilize the spherical intermediates and consequently inhibit the fibril elongation process of hCT. PMID:24002168
Itoh-Watanabe, Hikari; Kamihira-Ishijima, Miya; Kawamura, Izuru; Kondoh, Masashi; Nakakoshi, Masamichi; Sato, Michio; Naito, Akira
Acetate biodegradation by anaerobic microorganisms at high pH and high calcium concentration.
Acetate biodegradation at a high pH and a high calcium concentration was examined to clarify the effect of bacterial activity on the migration of organic (14)C compounds in cementitious repositories. Tamagawa river sediment or Teganuma pond sediment was anaerobically cultured with 5 mM acetate and 10 mM nitrate at pH 9.5-12 at 30 ¯C. After 20 and 90 days, the acetate concentration of the culture medium was analyzed and found to have decreased below 5 mM at pH ? 11. On the other hand, it did not decrease when either sediment was incubated in the absence of nitrate. These results suggest that nitrate-reducing bacteria can biodegrade acetate under more alkaline conditions than the reported pH range in which nitrate-reducing bacteria can exhibit activity. Acetate biodegradation was also examined at a high calcium concentration. Sediments were anaerobically cultured at pH 9.5 with 5 mM acetate and 10 mM nitrate in solution, equilibrated with ordinary Portland cement hydrate, in which the Ca concentration was 14.6 mM. No decrease in acetate concentration after incubation of the sediments was observed, nor was it lower than in the absence of cementitious composition, suggesting that kinetics of acetate biodegradation by anaerobic microorganisms is lowered by a high Ca concentration. PMID:21130545
Yoshida, Takahiro
Computer aided design of reactive distillation processes for the treatment of waste waters polluted with acetic acid
A theoretical study of reactive distillation processes to remove acetic acid from its 30wt% aqueous solution by esterification with n-butanol is presented. Two different column structures were identified rendering theoretically close to 100 percent conversion of acetic acid. A model capable of precisely predicting the potential phase split is used. Total costs for the new processes are estimated and compared
Jignesh Gangadwala; G. Radulescu; Achim Kienle; K. Sundmacher
Radical addition of methyldichlorosilane to vinyl acetate
The GC-MS method was used to identify the addition products of methyldichlorosilane to vinyl acetate. Radiation-induced addition of methyldichlorosilane to vinyl acetate produces 2-methyldichlorosilylethyl ethyl ether. The reaction follows a radical-chain mechanism. The ratio of the rate constants of methyldichlorosilyl radical addition to C=C and C=O to vinyl acetate amounts to 0.4Ý0.1 (303 K).
Yu. M. Lugovoi; N. P. Tarasova; G. Bourgeois; N. V. Bryantseva; V. V. Kostikov; C. Filliatre; A. G. Shostenko
Graft polymerization of vinyl acetate onto silica
The free-radical graft polymerization of vi- nyl acetate onto nonporous silica particles was studied ex- perimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free-rad- ical graft polymerization of vinyl acetate in ethyl acetate with 2,2-azobis(2,4-dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by vol- ume and the reaction was spanned from 50 to
Van Nguyen; Wayne Yoshida; Yoram Cohen
[Synthesis of ethriolophospholipids of acetal type].
New analogues of acetal-type phospholipids were obtained on the basis of ethriol (2-hydroxymethyl-2-ethyl-1,3-propanediol). The starting triol originally was condensed with decanal or dodecanal to form acetals, which were then phosphorylated with tetraethyldiamidophosphorous acid chloride. The amidophosphites were further oxidized with iodosobenzene or sulfurized to the corresponding acetal-type phospholipids and their thio analogues. PMID:17042275
Savin, G A
Oxidative reaction of oxindole-3-acetic acids.
The oxindole-3-acetic acids, oxidative metabolites of indole-3-acetic acid, were isolated from a byproduct of a corn starch manufacturing plant, and were further converted to the 3-hydroxyl derivatives in the presence of metal ion. The mechanical study was followed by a chemical analysis including other byproducts, and suggested the presence of an intermediate that had a radical at the C-3 position of oxindole-3-acetic acids. PMID:14519969
Niwa, Toshio; Ishii, Sayuri; Hiramatsu, Atsushi; Osawa, Toshihiko
Biocompatibility and buffers: Effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function
Biocompatibility and buffers: Effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function.BackgroundConventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in
Achim J—rres; Thorsten O Bender; AndrÕ Finn; Janusz Witowski; Sibylle Fr—hlich; Gerhard M Gahl; Ulrich Frei; Heiko Keck; Jutta Passlick-Deetjen
Removal of HãS by spray-calcined calcium acetate
The effectiveness of wet-spraying calcium acetate as an alternative to limestone and dolomite for the desulfurization of flue gases (in particular, HãS removal from coal gas) has been investigated by experimental studies using drop tube (DTR) and fixed-bed flow reactors (FBR). Calcium acetate solution was spray-calcined in the DTR at temperatures of 1073 and 1323 K. At the lower temperature,
William Nimmo; Jonathan Agnew; Edward Hampartsoumian; Jenny M. Jones
Accelerated ripening of Dhakki dates by artificial means: ripening by acetic acid and sodium chloride
The effectiveness of sodium chloride and acetic acid for initiation\\/acceleration of the ripening of Dhakki dates has been investigated. Each treatment was applied individually and\\/or in combined form at different proportions varying from 0.25% to 3.5% and 0.25% to 2.5% for sodium chloride and acetic acid respectively. Dhakki dates at the Doka stage were immersed in treatment solutions for 5min
Shahzada A. Saleem; Ahmad K. Baloch; Musa Kaleem Baloch; Waqar A. Baloch; Abdul Ghaffoor
Characterization of iron(III) oxide nanoparticles prepared by using ammonium acetate as precipitating agent
The effect of precipitating agent on the preparation of iron(III) oxide particles was investigated. Iron(III) oxide particles\\u000a were prepared by precipitation of aqueous ferric nitrate solution by using ammonium acetate and ammonium hydroxide as precipitating\\u000a agents. Particle size, shape, chemical composition, crystalline formation rate, crystallinity and magnetic property were measured\\u000a for Fe2O3 particles obtained by precipitating with ammonium acetate, and
Ji Young Park; Seong Geun Oh; Baik Hyon Ha
Synthesis and characterization of cellulose acetatecalcium carbonate hybrid nanocomposite
A hybrid nanocomposite composed of calcium carbonate (CaCO3) and cellulose acetate (CA) was fabricated by bubbling CO2 gas into the mixture of CA and Ca(OH)2 solution. Cellulose acetatecalcium carbonate (CACC) nanocomposite was characterized by spectral, thermal and optical methods. FTIR and XRD analysis confirmed the formation of the hybrid nanocomposite and XRD confirmed the formation of CaCO3 with calcite polymorph.
Amalraj John; Yi Chen; Jaehwan Kim
Catalytic oxidation of carbon\\/carbon composite materials in the presence of potassium and calcium acetates
The catalytic effects of potassium acetate (KAC) and calcium acetate (CaAC) on the oxidation of carbon\\/carbon composites (C\\/C composites) used in aircraft brake system have been characterized. Potassium exhibited a very strong catalytic effect on the oxidation of the selected carbon samples, including C\\/C composite blocks impregnated with aqueous KAC solution and graphite powder physically mixed with KAC powder. The
Xianxian Wu; Ljubisa R. Radovic
Synthesis and antimicrobial activities of polymer\\/montmorillonitechlorhexidine acetate nanocomposite films
The PDMS\\/montmorillonitechlorhexidine acetate (PDMS\\/OMMT) nanocomposite films were successfully obtained by intercalation from solution. Organo-montmorillonite (OMMT) with antibacterial activity was prepared from Na+-montmorillonite (Na+-MMT) and chlorhexidine acetate (CA) by ion exchange. The microstructure of these nanocomposite films were characterized by TEM and XRD. The effect of OMMT on mechanical properties and thermal stability of the nanocomposites was investigated. When the OMMT
Na Meng; Ning-Lin Zhou; Shuang-Quan Zhang; Jian Shen
Filtrates & Residues: A "Semimicro" Spectrophotometric Determination of the Ksp of Silver Acetate at Various Temperatures.
Examines a solubility laboratory experiment using silver acetate and spectrophotometers for an Advanced Placement chemistry course. Covers experimental procedure, analysis of saturated solutions, and a discussion of chemistry involved. Includes an absorbance curve for silver ions and solution preparation suggestions. (ML)
Liebermann, John, Jr.; Yun, Ki J.
Controlled release of triprolidine using ethylene-vinyl acetate membrane and matrix systems
The studies on the permeability of triprolidine through ethylene-vinyl acetate (EVA) copolymer membrane using two-chamber diffusion cell was carried out to develop the controlled delivery system. To evaluate the effect of drug concentration in reservoir, polyethylene glycol (PEG) 400 was added to saline solution as a solubilizer and a sink condition was maintained in the receptor solution. The permeation rate
Sang-Chul Shin; Hyun-Jin Lee
Precipitation of calcium carbonate from a calcium acetate and ammonium carbamate batch system
In this paper, we report a novel approach for preparing precipitated calcium carbonate using solutions of ammonium carbamate and calcium acetate as the sources of calcium and carbon dioxide, respectively. Two different concentrations of the starting solutions at three different temperatures (15, 25 and 50¯C) were used for the reaction. The influence of temperature and concentration on the polymorphism and
J. Prah; J. Macek; G. Drazic
Creatininium 2-chloro-acetate
In the title compound (systematic name: 2-amino-1-methyl-4-oxo-4,5-dihydro-1H-imidazol-3-ium 2-chloroÙacetate), C4H8N3O+ñC2H2ClO2 ?, the molÙecular aggregations are stabilÙized through classical (NH?O) and non-classical (CH?O and CH?N) hydrogen-bonding interÙactions. The cations are linked to the anions, forming ion pairs through two NH?O bonds that produce characteristic R 2 2(8) ring motifs. These cationanion pairs are connected through another NH?O hydrogen bond, leading to an R 4 2(8) ring motif. Further weak CH?N interÙactions link the molÙecules along the a axis, while other CH?O interÙactions generate zigzag chains extending along b.
Ali, A. Jahubar; Athimoolam, S.; Bahadur, S. Asath
Coupled microrings data buffer using fast light
We present a theoretical study of a trap-door optical buffer based on a coupled microrings add/drop filter (ADF) utilizing the white light cavity (WLC). The buffer "trap-door" can be opened and closed by tuning the resonances of the microrings comprising the ADF and trap/release optical pulses. We show that the WLC based ADF yields a maximally flat filter which exhibits superior performances in terms of bandwidth and flatness compared to previous design approaches. We also present a realistic, Silicon-over-Insulator based, design and performance analysis taking into consideration the realistic properties and limitations of the materials and the fabrication process, leading to delays exceeding 850ps for 80GHz bandwidth, and a corresponding delay-bandwidth product of approximately 70.
Scheuer, Jacob; Shahriar, Selim
Spacecraft optical disk recorder memory buffer control
This paper discusses the research completed under the NASA-ASEE summer faculty fellowship program. The project involves development of an Application Specific Integrated Circuit (ASIC) to be used as a Memory Buffer Controller (MBC) in the Spacecraft Optical Disk System (SODR). The SODR system has demanding capacity and data rate specifications requiring specialized electronics to meet processing demands. The system is being designed to support Gigabit transfer rates with Terabit storage capability. The complete SODR system is designed to exceed the capability of all existing mass storage systems today. The ASIC development for SODR consist of developing a 144 pin CMOS device to perform format conversion and data buffering. The final simulations of the MBC were completed during this summer's NASA-ASEE fellowship along with design preparations for fabrication to be performed by an ASIC manufacturer.
Hodson, Robert F.
Measurement of pH by NMR Spectroscopy in Concentrated Aqueous Fluoride Buffers
An NMR spectroscopic technique has been developed to give rapid, accurate pH measurements on tenth-milliliter samples of concentrated acidic aqueous solutions buffered by fluoride ion in the pH 1.5 4.5 range. The fluoride 19F chemical shift has been calibrated as a function of pH at 0.1 and 1.0 M concentration by reference to an internal 3-fluoropyridine standard. Subsequent measurements of fluoride buffer pH required no additives and only two NMR spectra in the presence of an external reference standard.
Gerken, James B.
Chemically deposited La2Zr2O7 buffer layers for YBCO-coated conductors: film growth and microstructure
An adequate buffer layer architecture is of great importance for YBa2Cu3O7-delta (YBCO)-coated conductor fabrication. We present a transmission electron microscopy (TEM) analysis of La2Zr2O7 (LZO) buffer layers on biaxially textured Ni-5 at.%W substrates for YBCO-coated conductors prepared by chemical solution deposition (CSD). The LZO thin films were heat-treated at 900 and 1050 ¯C respectively. Electron diffraction patterns, and bright and
L. Molina; K. Knoth; S. Engel; B. Holzapfel; O. Eibl
Effect of Temperature and Film Thickness on Residual Stress and Texture of Buffer Layers for YBCO Coated Conductor
Re2O3 (Re = Er, Gd, Ho, Y and Yb) was prepared by sol-gel synthesis using metal-organic precursors. Residual stress and microstructure in the Re2O3 buffer layers were investigated as a function of temperature and film thickness. Textured Re2O3 buffer layers were grown on biaxially textured-Ni (100) substrates using chemical solution deposition. Films were annealed at 1150degC under a flowing 4%
Lutfi Arda; S. Ataoglu; O. Bulut
How Close Is Safe? Buffer Zone Development
The effects of volcanoes on both the environment and people are the focus of this investigation. Students are introduced to the term "buffer" and are tasked with creating a possible buffer zone around Mount St. Helens. Students begin by assigning 32 pre-written statements related to volcanoes into categories of cause, effect and human responses. The chart, along with true-color and false-color LandSat images from 1980 and 1999, are used to study the eruption of Mount St. Helens to determine that possible buffer zone. The URL opens to the investigation directory, with links to teacher and student materials, lesson extensions, resources, teaching tips, and assessment strategies. As the first investigation in this module entitled, "Volcanoes- Local Hazard, Global Issue," the teacher's guide will begin with a two-page module overview and list of all standards addressed. This is Investigation 1 of three found in the Grades 5-8 Module 1 of Mission Geography. The Mission Geography curriculum integrates data and images from NASA missions with the National Geography Standards. Each of the three investigations in Module 1, while related, can be done independently.
Estimating the buffer capacity of forest soils
The organic-matter content of New England soils is an index of buffer capacity, and can be measured to indicate how forest soils might respond to acid precipitation. Buffer capacity, as defined herein, is the milliequivalents of H/sup +/ or OH/sup -/ that must be added to a kilogram of soil to change its pH by one unit. As such, it is an index of how soil pH will respond to H/sup +/ in acid precipitation. At four locations in New England, the buffer capacity of organic and mineral horizons for well-drained forest soils under second-growth forests and in new and regrowing clearcuts was measured. The sites included a spruce-fir forest in central Maine, two northern hardwood forests in northern New Hampshire, and a central hardwood forest in southern Connecticut. Soil materials were titrated by adding known amounts of HCl or NaOH and measuring the pH after 24 hours. Details on methods were given in this paper. 1 table.
Hornbeck, J.W.; Federer, C.A.
A freshwater anaerobe coupling acetate oxidation to tetrachloroethylene dehalogenation.
Strain TT4B has been isolated from anaerobic sediments known to be contaminated with a variety of organic solvents. It is a gram-negative, rod-shaped bacterium and grew anaerobically with acetate as the electron donor and tetrachloroethylene as the electron acceptor in a mineral medium. cis-Dichloroethylene was the halogenated product. This strain did not grow fermentatively and used only acetate or pyruvate as electron donors. Tetrachloroethylene and trichloroethylene were used as electron acceptors, as were ferric nitriloacetate and fumarate. Nitrogen and sulfur oxyanions were not able to substitute as the electron acceptor for this organism. Modest growth occurred in a two-phase system with 1 ml of hexadecane containing 50 to 200 mM tetrachloroethylene (aqueous concentrations, 25 to 100 microM) and 10 ml of anaerobic mineral solution with Na2S as the reducing agent. Growth was completely inhibited at tetrachloroethylene levels above 100 microM.
Krumholz, L R; Sharp, R; Fishbain, S S
Effects of buffers on milk fatty acids and mammary arteriovenous differences in dairy cows fed Ca salts of fatty acids.
Ten Holstein cows in early lactation were used in a replicated 5 x 5 Latin square design to study the effects of MgO and three buffers added to diets containing Ca salts of canola oil fatty acids. Treatments were 1) control (basal diet; no buffer). 2) 1.1% NaHCO3 plus 1.1% KHCO3, 3) 1.9% NaHCO3, 4) 0.5% MgO, and 5) 2.0% Na sesquicarbonate (percentage of dry matter). The control diet contained 53% grass silage, 43% concentrate, and 4% Ca salts. Body weight, intake, milk yield, and percentages of milk fat, protein, and lactose were unaffected by treatments. Buffers and MgO tended to increase triacylglycerol extraction by the mammary gland and changed the proportions of some fatty acids in milk. Arterial concentrations of acetate and triacylglycerol were correlated with their respective arteriovenous differences. Extraction by the mammary gland was high for acetate (approximately equal to 58.2%), triacylglycerol (approximately equal to 47.3%) propionate (approximately equal to 34.6%), and glucose (approximately equal to 24.3%). Extraction of free fatty acids, phospholipids, or cholesterol was negligible. Mammary triacylglycerol arteriovenous difference tended to be higher than when MgO was fed than when NaHCO3 was fed. Sodium sesquicarbonate, NaHCO3, and the blend of bicarbonate buffers increased C18:2 in milk fat when compared with the control treatment. The concentration of C18:2 in milk fat decreased when MgO was fed, but the ratio of cis-C18:1 to trans-C18:1 increased compared with effects of dietary NaHCO3. Medium-chain fatty acids in milk fat tended to be higher than Na sesquicarbonate than with NaHCO3. Buffers and MgO modified the profiles of fatty acids in milk. PMID:9710770
Thivierge, M C; Chouinard, P Y; LÕvesque, J; Girard, V; Seoane, J R; Brisson, G J
Stability of exenatide in poly(D,L-lactide-co-glycolide) solutions: a simplified investigation on the peptide degradation by the polymer.
A solution model can be used to elucidate drug stability issues in a complex system. The aim of this study was to investigate the interaction between poly(D,L-lactide-co-glycolide) (PLGA) and exenatide in organic solvent-acetate buffer saline (ABS) solutions. The effect of solvent composition on exenatide stability was investigated first. In the selected 90:10 dimethyl sulfoxide (DMSO):ABS solution, exenatide stability was examined as a function of PLGA comonomer ratios, molecular weight (Mw) and concentrations. The specific rotation analysis and second derivative UV absorbance spectroscopy were used to monitor the variation of exenatide higher order structure. The effect of ABS pH on the interaction was also investigated. Exenatide degradation products were characterized by HPLC-MS/MS. It was found that exenatide was relatively stable in glacial acetic acid (HAc)-ABS solutions, whereas DMSO content had a strong influence on the conformation state and stability of exenatide. PLGA 50:50 promoted exenatide degradation more than PLGA 75:25 and poly(D,L-lactide) (PLA). Lower Mw and higher concentration of PLGA were beneficial for exenatide degradation. Exenatide was more stable in 90:10 DMSO:ABS (pH 3.0) solution than in 90:10 DMSO:ABS (pH 4.5 and 3.0) solutions during the incubation. HPLC-MS/MS analysis of exenatide demonstrated that acylation was the main degradation route of the peptide. PMID:23994054
Liang, Rongcai; Zhang, Renyu; Li, Xiang; Wang, Aiping; Chen, Daquan; Sun, Kaoxiang; Liu, Wanhui; Li, Youxin
A study of carbon steel corrosion inhibition by phosphate ions and by an organic buffer using a scanning vibrating electrode
The scanning vibrating reference electrode technique (SVET) has been used to map anodic and cathodic currents in solutions over freely corroding type Cl020 carbon steel. All solutions contained millimolar concentrations of chloride and were sterilized. The effect of phosphate and an organic buffer on the corrosion of carbon steel in liquid media were studied because they were added to promote
Riparian buffer zones, the vegetated region adjacent to streams and wetlands, are thought to be effective at intercepting and controlling nitrogen loads entering water bodies. Riparian buffer width may be positively related to nitrogen removal effectiveness by influencing nitrog...
Multiphasic Buffer Systems. Instructions for Use of the Systems Catalogue.
The terminology of the 'Systems Catalogue' is explained. Instructions are given for the procedure by which a multiphasic buffer system, optimal for the particular application, can be identified by System Number for retrieval from the Multiphasic Buffer Sy...
T. M. Jovin M. L. Dante A. Chrambach
Buffer Standards for the Physiological pH of the Zwitterionic Compound, ACES from 5 to 55?C
The values of the second dissociation constant pK2 and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over the temperature range 5 to 55¯C including 37¯C. This paper reports the paH values of four chloride ion free buffer solutions and eight buffer solutions with I = 0.16 molñkg ?1, matching closely to that of the physiological sample. Conventional paH values for all twelve buffer solutions from 5 to 55¯C, are reported. The residual liquid junction potential correction for two widely used temperatures, 25 and 37¯C, has been made. The flowing-junction calomel cell method has been utilized to measure Ej, the liquid junction potential. The operational pH values for four buffer solutions at 25 and 37¯C are calculated using the physiological phosphate buffer standard based on NBS/NIST convention. These solutions are recommended as pH standards in the pH range of 6.8 to 7.2 for physiological fluids.
Roy, Rabindra N.; Roy, Lakshmi N.; Fuge, Michael S.; Roy, Chandra N.; Himes, Curtis A.; Bryant, Paul A.; Robinson, Kyle T.; Kaufmann, Daniel A.; Grove, Colby H.; Ghosh, Toshi; Bwashi, Adonis
Photo- and Thermal Degradation of Piroxicam in Aqueous Solution
Light and temperature have considerable effect on the degradation of piroxicam in aqueous solutions. The pH and acetate buffer ions also affect the degradation process. The apparent first-order rate constants for the photochemical and thermal degradation of piroxicam have been determined as 2.0410.01 and 0.86-3.06æ103 min1, respectively. The first-order plots for the degradation of piroxicam showed good linearity within a range of 20-50% loss of piroxicam at pH 2.0-12.0. The rate-pH profile for the photodegradation of piroxicam is a U-shaped curve and for the thermal degradation a bell-shaped curve in the pH range of 2.0-12.0. The thermal degradation of piroxicam was maximum around pH 6.0. It is increased in the presence of acetate ions but was not affected by citrate and phosphate ions.
Aminuddin, M.; Nazim, U.; Ahmad, I.
(Acetoxy)(2-methylphenyl)methyl acetate
In the title compound, C12H14O4, the two acetÙoxy groups are inclined by 57.92?(5)¯ and 62.71?(6)¯ to the benzene ring. An interÙmolecular CH?O interÙaction involving the two acetÙoxy groups generates a centrosymmetric dimer via an R 2 2(16) ring motif.
Kanchanadevi, J.; Anbalagan, G.; Saravanan, V.; Mohanakrishnan, A. K.; Manivannan, V.
Biodegradable Plastics Based on Cellulose Acetate
It is generally known that secondary cellulose acetate (with 53 to 56% acetyl groups) is suitable for thermoplastic processing. With appropriate plasticizers a plastic material is obtained which excels in transparency and pleasant texture, and it is therefore often used for tool handles, combs, spectacle frames, and the like. In principle, cellulose acetate with such a degree of substitution is
Alexander Ach
Heating of dried, acetate-containing solids together with oxalic acid dihydrate conveniently releases acetic acid for purification by gas chromatography. For determination of the carbon-isotopic composition of total acetate, the acetate-containing zone of the chromatographic effluent can be routed directly to a combustion furnace coupled to a vacuum system allowing recovery, purification, and packaging of CO{sub 2} for mass-spectrometric analysis. For analysis of methyl carbon, acetic acid can be cryogenically trapped from the chromatographic effluent, then transferred to a tube containing excess NaOH. The tube is evacuated, sealed, and heated to 500{degree}C to produce methane by pyrolysis of sodium acetate. Subsequent combustion of the methane allows determination of the {sup 13}C content at the methyl position in the parent acetate. With typical blanks, the standard deviation of single analyses is less than 0.4{per thousand} for acetate samples larger than 5 {mu}mol. A full treatment of uncertainties is outlined.
Gelwicks, J.T. (Merck and Co., Inc., Rahway, NJ (USA)); Hayes, J.M. (Indiana Univ., Bloomington (USA))
Defending Embedded Systems Against Buffer Overflow via Hardware\\/Software
Buffer overflow attacks have been causing serious secu- rity problems for decades. With more embedded systems networked, it becomes an important research problem to defend embedded systems against buffer overflow attacks. In this paper, we propose the Hardware\\/Software Address Protection (HSAP) technique to solve this problem. We first classify buffer overflow attacks into two categories (stack smashing attacks and function
Zili Shao; Qingfeng Zhuge; Yi He; Edwin Hsing-mean Sha
On the design of power buffer and its applications
A power electronics-based buffer is examined in which through control of its PWM converters, the buffer-load combination is driven to operate under either constant power or constant impedance modes. A battery, incorporated within the buffer, provides the energy storage facility to facilitate the necessary power flow control. Real power demand from upstream supply is regulated under fault condition, and the
S. S. Choi; X. Y. Wang; D. M. Vilathgamuwa
Effect of Tris-HCl buffer on DNA adsorption by a variety of soil constituents.
We investigated the effect of tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer (pH 7.0) as a bulk solution on the adsorption of DNA by gibbsite, goethite, montmorillonite, kaolinite, synthetic and natural allophanes, two humic acids and two andosols. The natural allophane, gibbsite, kaolinite and an andosol adsorbed significantly more DNA in a 0.1 M Tris-HCl buffer than in a 0.1 M NaCl solution (t-test, P<0.005). In contrast, montmorillonite adsorbed significantly less DNA in the Tris-HCl than NaCl solution (P<0.05). Care should be taken when using Tris-HCl in studies on the adsorption of extracellular DNA molecules by soil particles. PMID:21487209
Saeki, Kazutoshi; Kunito, Takashi; Sakai, Masao
Enhanced dielectric properties from barium strontium titanate films with strontium titanate buffer layers
In order to enhance the permittivity and tunability of the dielectric component, a thin film dielectric composite consisting of a radio frequency sputtered SrTiO3 (STO) buffer layer and metalorganic solution deposited Mg-doped BaxSr1-xTiO3 (Mg-BST) thin film overgrowth was developed using affordable industry standard processes and materials. The effect of the STO buffer layer thickness on the dielectric response of the heterostructure was investigated. Our results demonstrate that the composite film heterostructure, evaluated in the metal-insulator-metal configuration Pt/STO/Mg-BST/Pt on sapphire substrate, with the thinner (9-17 nm) STO buffer layers possessed enhanced permittivity (?r 491) with respect to the thicker 41 nm buffer layer (?r 360) and that of a control Mg-BST film without a STO buffer layer (?r 380). Additionally, the composite film with the thinner buffer layers were shown to have low losses (tan ? 0.02), low leakage characteristics (J = 7.0 æ 10-9 A/cm2), high breakdown voltage (VBR > 10 V), a large grain microstructure (125 nm), and smooth pin-hole free surfaces. The enhanced permittivity of the composite dielectric film resulted from three major factors: (i) the template-effect of the thin STO buffer layer on the thicker Mg-BST over-layer film to achieve a large grain microstructure, (ii) the low viscosity of the metallo-organic solution deposition (MOSD) solution, which ensured heterogeneous nucleation of the Mg-BST overgrowth film on the surface of the STO buffer layer, and (iii) minimization of the low permittivity grain boundary phase (TiO2-x phase). The dielectric response of the BST can be explained using a thermodynamic model taking into account interlayer electrostatic and electromechanical interactions. Additionally, Mg doping of the BST enabled low loss and low leakage characteristics of the heterostructure. The large permittivity, low loss, low leakage characteristics, and defect free surfaces of the composite dielectric heterostructure promote tunable device miniaturization and hold the potential to enable enhanced electromagnetic coupling in ferromagnetic/high permittivity dielectric heterostructures, which in turn would facilitate the realization of integrated charge mediated voltage controlled magnetic radio frequency/microwave communication devices.
Cole, M. W.; Ngo, E.; Hubbard, C.; Hirsch, S. G.; Ivill, M.; Sarney, W. L.; Zhang, J.; Alpay, S. P.
Length scales involved in decoherence of trapped bosons by buffer-gas scattering
We ask and answer a basic question about the length scales involved in quantum decoherence: how far apart in space do two parts of a quantum system have to be before a common quantum environment decoheres them as if they were entirely separate? We frame this question specifically in a cold atom context. How far apart do two populations of bosons have to be before an environment of thermal atoms of a different species ("buffer gas") responds to their two particle numbers separately? An initial guess for this length scale is the thermal coherence length of the buffer gas; we show that a standard Born-Markov treatment partially supports this guess, but predicts only inverse-square saturation of decoherence rates with distance, and not the much more abrupt Gaussian behavior of the buffer gas's first-order coherence. We confirm this Born-Markov result with a more rigorous theory, based on an exact solution of a two-scatterer scattering problem, which also extends the result beyond weak scattering. Finally, however, we show that when interactions within the buffer-gas reservoir are taken into account, an abrupt saturation of the decoherence rate does occur, exponentially on the length scale of the buffer gas's mean free path.
Gilz, Lukas; Rico-PÕrez, Luis; Anglin, James R.
Buffer for a gamma-insensitive optical sensor with gas and a buffer assembly
A buffer assembly for a gamma-insensitive gas avalanche focal plane array operating in the ultra-violet/visible/infrared energy wavelengths and using a photocathode and an avalanche gas located in a gap between an anode and the photocathode. The buffer assembly functions to eliminate chemical compatibility between the gas composition and the materials of the photocathode. The buffer assembly in the described embodiment is composed of two sections, a first section constructed of glass honeycomb under vacuum and a second section defining a thin barrier film or membrane constructed, for example, of Al and Be, which is attached to and supported by the honeycomb. The honeycomb section, in turn, is supported by and adjacent to the photocathode.
Kruger, Hans W. (Walnut Creek, CA)
A buffer assembly is disclosed for a gamma-insensitive gas avalanche focal plane array operating in the ultra-violet/visible/infrared energy wavelengths and using a photocathode and an avalanche gas located in a gap between an anode and the photocathode. The buffer assembly functions to eliminate chemical compatibility between the gas composition and the materials of the photocathode. The buffer assembly in the described embodiment is composed of two sections, a first section constructed of glass honeycomb under vacuum and a second section defining a thin barrier film or membrane constructed, for example, of Al and Be, which is attached to and supported by the honeycomb. The honeycomb section, in turn, is supported by and adjacent to the photocathode. 7 figures.
Kruger, H.W.
Ulipristal acetate in emergency contraception.
Despite the widespread availability of highly effective methods of contraception, unintended pregnancy is common. Unplanned pregnancies have been linked to a range of health, social and economic consequences. Emergency contraception reduces risk of pregnancy after unprotected intercourse, and represents an opportunity to decrease number of unplanned pregnancies and abortions. Emergency contraception pills (ECP) prevent pregnancy by delaying or inhibiting ovulation, without interfering with post fertilization events. If pregnancy has already occurred, ECPs will not be effective, therefore ECPs are not abortificants. Ulipristal acetate (17alpha-acetoxy-11beta-(4N-N,N-dymethilaminophenyl)-19-norpregna--4,9-diene-3,20-dione) is the first drug that was specifically developed and licensed for use as an emergency contraceptive. It is an orally active, synthetic, selective progesterone modulator that acts by binding with high affinity to the human progesterone receptor where it has both antagonist and partial agonist effects. It is a new molecular entity and the first compound in a new pharmacological class defined by the pristal stem. Up on the superior clinical efficacy evidence, UPA has been quickly recognized as the most effective emergency contraceptive pill, and recently recommended as the first prescription choice for all women regardless of the age and timing after intercourse. This article provides literature review of UPA and its role in emergency contraception. PMID:24851646
Goldstajn, Marina Sprem; Baldani, Dinka Pavici?; Skrgati?, Lana; Radakovi?, Branko; Vrbi?, Hrvoje; Cani?, Tomislav
Preparation, characterization and effect of annealing on performance of cellulose acetate\\/sulfonated polysulfone and cellulose acetate\\/epoxy resin blend ultrafiltration membranes
Polymeric membranes based on cellulose acetate (CA)sulfonated polysulfone blends at three different polymer compositions were prepared by solution blending and phase inversion technique, characterized and subjected to annealing at 70, 80 and 90 ¯C. The permeate water flux, separation of bovine serum albumin and its flux by the blend membranes before and after thermal treatment, have been compared and discussed.
R Mahendran; R Malaisamy; D Mohan
Anaerobic model for high-solids or high-temperature digestion - additional pathway of acetate oxidation.
Current anaerobic digestion models cannot properly simulate processes that are operated under high solids concentrations or high temperatures. A modification to existing models has been implemented by adding important missing degradation pathways, to accommodate these systems without artificially recalibrating the model parameters. Specifically, we implemented the alternate acetate oxidizing mechanism that is more tolerant to ammonia than the standard aceticlastic pathway. Inhibition values were estimated and an empirical function has been used to apply ammonia inhibition. The model also relates metabolic activity to un-ionised species such as undissociated acetic acid as substrate (although not obligatory for all organisms) and unionised ammonia as inhibitor. The model relies on an equilibrium chemistry module (e.g. including the phosphate buffer), resulting in more accurate pH predictions, which is crucial for proper modeling of CO2 and NH3 stripping. Calibration results from three case-studies modeling thermal hydrolysis and subsequent digestion of sludge are presented. PMID:24759522
Wett, B; TakÃcs, I; Batstone, D; Wilson, C; Murthy, S
Concentrated Flow through a Riparian Buffer: A Case Study
Riparian buffers are often used for in-situ treatment of agricultural runoff. Although the benefits of riparian buffers are well recongized, concentration of flow can restrict the efficiency of contaminant removal. This study evaluates flow concentration at a agricultural site near Manhattan, Kansas. Manual and automated GIS analyses of a high-resolution digital elevation model were used to determine the fraction of runoff contributing to each buffer segment. Subsequent simulation of the system in WEPP (Water Erosion and Prediction Project) demonstrates the extent to which flow concentration affects buffer efficiency. Recommendations are presented for the design of adaptive-width buffers.
Young, C. B.; Nogues, J. P.; Hutchinson, S. L.
Magnetorheological elastomer and its application on impact buffer
In this study, a new magnetorheological elastomer (MRE) based buffer is proposed and its vibration isolation performance is investigated. The MRE buffer with a compact structure is first designed in order to accomplish the maximization of the variable stiffness range. The working characteristics of the MRE buffer are then measured and the model of MRE is established. On the basis of the experimental data, the control model of the MRE buffer is also formulated. A two-degree-of-freedom dynamic model with an MRE buffer is then developed. An intelligent control strategy, human simulated intelligent control (HSIC), is proposed to reduce the impact during the drop crash. Finally, the proposed MRE buffer and controller are validated numerically and experimentally. The results show that the proposed MRE buffer and the control strategy can reduce the impact acceleration effectively.
Fu, J.; Yu, M.; Dong, X. M.; Zhu, L. X.
36 CFR 1232.24 - Unstable cellulose-acetate film.
...2009-07-01 2009-07-01 false Unstable cellulose-acetate film. 1232.24 Section 1232...Audiovisual Records Management ôÏ 1232.24 Unstable cellulose-acetate film. Cellulose-acetate film, also known as safety...
21 CFR 172.833 - Sucrose acetate isobutyrate (SAIB).
... 2009-04-01 2009-04-01 false Sucrose acetate isobutyrate (SAIB). 172.833...CONSUMPTION Multipurpose Additives ôÏ 172.833 Sucrose acetate isobutyrate (SAIB). Sucrose acetate isobutyrate may be safely used in...
...3 2010-01-01 2009-04-01 true Sucrose acetate isobutyrate (SAIB). 172.833...CONSUMPTION Multipurpose Additives ôÏ 172.833 Sucrose acetate isobutyrate (SAIB). Sucrose acetate isobutyrate may be safely used in...
Addition of a nitric oxide inhibitor to a more biocompatible peritoneal dialysis solution in a rat model of chronic renal failure.
Biocompatible dialysis solutions have been developed to preserve peritoneal membrane morphology and function. Compared with a conventional solution, a combination of glycerol, amino acids, and dextrose in a bicarbonate/lactate buffer (GLAD) led to less peritoneal fibrosis and fewer vessels in a chronic peritoneal exposure model in the rat. However, no concomitant reduction in small-solute transport was observed. We hypothesized that this result could be attributable to peritoneal vasodilation induced by vasoactive substances such as nitric oxide. The aim of the present study was to investigate whether fast transport of small solutes and proteins induced by exposure to GLAD could be influenced by Ngamma -methyl-L-arginine acetate (L-NMMA), an inhibitor of NO. These investigations used our rat model of long-term peritoneal exposure with chronic renal failure. All rats underwent peritoneal catheter implantation and a 70% nephrectomy. Thereafter, the rats were allocated to 3 groups: 16 weeks of peritoneal exposure to GLAD and L-NMMA, to GLAD only, or to buffer (bicarbonate/lactate without any osmotic agent). Afterward, a standard peritoneal permeability analysis adjusted for the rat was performed. Subsequently, the rats were euthanized, and tissue samples were obtained for morphometric determinations. No effect of L-MNNA on the transport of small solutes and proteins was found. Also, no effect on morphology was found. Our findings make it unlikely that NO is directly involved, being more in favor of a direct effect of amino acids on peritoneal transport. PMID:21348371
de Graaff, Marijke; Vlijm, Anniek; Zweers, Machteld M; Coester, Annemieke M; Vandemaele, FrÕderic; Struijk, Dirk G; Krediet, Raymond T
A new process for producing calcium acetate from vegetable wastes for use as an environmentally friendly deicer.
A new process for producing calcium acetate, a non-corrosive deicer, is proposed. The process consists of a two-step continuous-flow hydrothermal conversion of vegetable wastes into acetic acid and the production of calcium acetate, followed by the separation and condensation of the product. The experiments for acetic acid production showed that there were almost no significant differences in acetic acid yields for the five different kinds of vegetables selected for the batch experiments or for their mixture in batch and continuous-flow experiments. Electrodialysis was chosen as a satisfactory method for separating and condensing the calcium acetate produced from the acetic acid solution obtained from the vegetable wastes. After purification by reverse-osmosis, the residual, depleted acid solution could be safely discharged. The calculation of the carbon balance for the proposed process showed that 21.3% of the TOC from vegetable wastes could be used as calcium/magnesium acetate (CMA) and over 22% as an environmentally friendly deicer. PMID:20483594
Jin, Fangming; Zhang, Guangyi; Jin, Yujia; Watanabe, Yosiyuki; Kishita, Atsushi; Enomoto, Heiji
The effect of desoxycorticosterone acetate (DCA) on the granulation tissue of healing and healed linear laparotomy wounds was studied in young adult male guinea pigs maintained on a complete diet and on a known intake of ascorbic acid. DCA induces the production of an excessive amount of granulation tissue, as evidenced by a relatively great number of fibroblasts and by a larger amount of ground substance. This effect was accompanied by a slight to moderate lag in the maturation process of both cellular and intercellular elements. These changes were observed when DCA administration was begun 5 days prior to operation, but were less obvious or absent if DCA was injected, beginning on the 5th or 10th postoperative day. The results indicate that the action of DCA on immature, proliferating connective tissue is marked, and is considerably less or absent when connective tissue elements have reached partial or almost complete maturity. The effect of DCA on connective tissue does not appear to rest on the basis of an altered nutritional status. Chemical and histochemical studies of the adrenals suggest that the action of DCA on connective tissue is probably mediated through a disturbance of adrenocortical function, namely an imbalance between hormones of the zona glomerulosa (excess of DCA) and those of the zona fasciculata (deficiency of glucocorticoids). The presence of changes in granulation tissue and the lack of them in mature resting connective tissue of DCA-treated guinea pigs confirm the view that a profound difference in the response mechanism exists between resting and actively proliferating connective tissue.
Pirani, Conrad L.; Stepto, Robert C.; Sutherland, Kenneth
The pharmacology of nomegestrol acetate.
Nomegestrol acetate (NOMAC) is a 19-norprogesterone derivative with high biological activity at the progesterone receptor, a weak anti-androgenic effect, but with no binding to estrogen, glucocorticoid or mineralocorticoid receptors. At dosages of 1.5mg/day or more, NOMAC effectively suppresses gonadotropic activity and ovulation in women of reproductive age. Hemostasis, lipids and carbohydrate metabolism remain largely unchanged. In normal and cancerous human breast cells, NOMAC has shown favorable effects on estrogen metabolism. Like natural progesterone (but in contrast to some other synthetic progestogens), it does not appear stimulate the proliferation of cancerous breast cells. While there has been some experience of the use of NOMAC in combination with estrogens as a hormone replacement therapy, most of the data on the compound are reported in the context of its inclusion as a component of a new contraceptive pill comprising 2.5mg NOMAC combined with 1.5mg estradiol. Because of its strong endometrial efficacy, and due to its high antigonadotropic activity and long elimination half-life (about 50h), the contraceptive efficacy of the new pill is maintained even when dosages are missed. Furthermore, for the first time with a monophasic 24/4 regimen containing estradiol, cyclical stability can be achieved comparable with that obtained using pills containing ethinyl estradiol and progestogens like levonorgestrel or drospirenone. The addition of NOMAC to estradiol means that the beneficial effects of estrogen are not lost, which is of especial importance in relation to the cardiovascular system. On the basis both of its pharmacology and of studies performed during the development of the NOMAC/estradiol pill, involving some 4000 women in total, good long-term tolerability can be expected for NOMAC, although its safety profile is still to be fully ascertained, as the clinical endpoint studies are yet to be completed. PMID:22364709
Ruan, Xiangyan; Seeger, Harald; Mueck, Alfred O
Correlation between acetic acid resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria.
In this study, we compared the growth properties and molecular characteristics of pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) among highly acetic acid-resistant strains of acetic acid bacteria. Gluconacetobacter europaeus exhibited the highest resistance to acetic acid (10%), whereas Gluconacetobacter intermedius and Acetobacter pasteurianus resisted up to 6% of acetic acid. In media with different concentrations of acetic acid, the maximal acetic acid production rate of Ga. europaeus slowly increased, but specific growth rates decreased concomitant with increased concentration of acetic acid in medium. The lag phase of A. pasteurianus was twice and four times longer in comparison to the lag phases of Ga. europaeus and Ga. intermedius, respectively. PQQ-dependent ADH activity was twice as high in Ga. europaeus and Ga. intermedius as in A. pasteurinus. The purified enzymes showed almost the same specific activity to each other, but in the presence of acetic acid, the enzyme activity decreased faster in A. pasteurianus and Ga. intermedius than in Ga. europaeus. These results suggest that high ADH activity in the Ga. europaeus cells and high acetic acid stability of the purified enzyme represent two of the unique features that enable this species to grow and stay metabolically active at extremely high concentrations of acetic acid. PMID:16133326
Trcek, Janja; Toyama, Hirohide; Czuba, Jerzy; Misiewicz, Anna; Matsushita, Kazunobu
Transport Parameters in a Porous Cellulose Acetate Membrane
The transport parameters of a cellulose acetate membrane prepared from a mixture of cellulose acetate, formamide, and acetone, 25:25:50 by weight, were studied. The membrane consists of a thin, porous layer, the skin, in series with a thick, highly porous layer, the coarse support. In the skin the diffusional permeability coefficient, ?, of a number of small amides and alcohols depends critically upon the partition coefficient, Ks, the size of the molecule, and the apparent hydrogen-bonding ability, Ns, of the solute. These observations are in general agreement with our earlier conclusions on the properties of nonporous membranes. On the other hand, the corrected reflection coefficient, ?', is not a very sensitive function of either Ns or Ks taken separately. The correlation between ?' and molecular diameter is reasonably good; however, it is much improved when both Ns and Ks are taken into consideration. Isotope interaction was also studied in the present preparation and was found to provide only a small (58%) contribution to the diffusional permeability coefficient of ethylene glycol. The contribution of solute-water friction was found to be less than 24% of the total solute friction.
DiPolo, R.; Sha'afi, R. I.; Solomon, A. K.
Buffer Standards for the Biological pH of the Amino Acid N-[2 hydroxyethyl]piperazine-N'-[3-propanesulfonic acid], HEPPS, From (278.15 to 328.15) K
For the HEPPS buffer under investigation, there are seven buffer solutions without NaCl and eight buffer solutions that contain Cl? and have an ionic strength (I = 0.16 molñkg?1), which is similar to that of blood plasma. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended Debye- H■ckel equation and the Bates-Guggenheim convention. The previously determined Ej values have been used to determine the operational pH values of HEPPS buffer solutions at (298.15 and 310.15) K. These are recommended as secondary standard reference solutions for pH measurements in saline media with an isotonic ionic strength of I = 0.16 molñkg?1.
Roy, Lakshmi N.; Roy, Rabindra N.; Wollen, Joshua T.; Harmon, Meagan A.; Stegner, Jessica M.; Shah, Ankita A.; Henson, Isaac B.
Density Functional Theory Study of Selective Deacylation of Aromatic Acetate in the Presence of Aliphatic Acetate under Ammonium Acetate Mediated Conditions.
Aromatic acetates can be selectively deprotected in the presence of aliphatic acetates under ammonium acetate mediated condition. B3LYP/6-31++G** level of theory was demonstrated to be successfully used to model the relative reaction rates for deacylation reactions for aliphatic and aromatic ester systems. On the basis of the mechanistic studies, acetate anion is most likely to be the active catalyst for the ester deacylation reactions under ammonium acetate mediated condition. PMID:24956355
Xia, Shijing; Zhang, Haoyu
Buffer allocation in an ATM switch with output buffer and speed constraints
A synchronous nonblocking N times N switch for asynchronous transfer mode (ATM) networks or high speed packet switching networks transporting fixed length packets called cells is considered. Such a switch with output queuing achieves the optimal performance, however it requires the switch fabric to work at the speed of N. In practice the switch may operate L times faster than the input/output trunk. It is assumed that queues at each output port have a limited buffer space and whenever an output queue is full, the back-pressure is applied and the packets are retained at the head of the input queues. The upper bound on the packet loss probability at the input queues in such a switch are computed. To achieve a given packet loss rate, the switch with L equals 2 requires almost the same amount of input and output buffers as with L equals 4 up to 70 percent input load, but as the load increases beyond 70 percent the switch with L equals 4 would require more output buffers and less input buffers in comparison with a switch operating at L equals 2. The performance of a switch with L equals 3 is very similar to that for L equals 4 and is not considered.
Gupta, Anil K.; Georganas, N. D.
Acetate Causes Alcohol Hangover Headache in Rats
Background The mechanism of veisalgia cephalgia or hangover headache is unknown. Despite a lack of mechanistic studies, there are a number of theories positing congeners, dehydration, or the ethanol metabolite acetaldehyde as causes of hangover headache. Methods We used a chronic headache model to examine how pure ethanol produces increased sensitivity for nociceptive behaviors in normally hydrated rats. Results Ethanol initially decreased sensitivity to mechanical stimuli on the face (analgesia), followed 4 to 6 hours later by inflammatory pain. Inhibiting alcohol dehydrogenase extended the analgesia whereas inhibiting aldehyde dehydrogenase decreased analgesia. Neither treatment had nociceptive effects. Direct administration of acetate increased nociceptive behaviors suggesting that acetate, not acetaldehyde, accumulation results in hangover-like hypersensitivity in our model. Since adenosine accumulation is a result of acetate formation, we administered an adenosine antagonist that blocked hypersensitivity. Discussion Our study shows that acetate contributes to hangover headache. These findings provide insight into the mechanism of hangover headache and the mechanism of headache induction.
Maxwell, Christina R.; Spangenberg, Rebecca Jay; Hoek, Jan B.; Silberstein, Stephen D.; Oshinsky, Michael L.
Water dispersible microbicidal cellulose acetate phthalate film
BACKGROUND: Cellulose acetate phthalate (CAP) has been used for several decades in the pharmaceutical industry for enteric film coating of oral tablets and capsules. Micronized CAP, available commercially as \\
A Robert Neurath; Nathan Strick; Yun-Yao Li
Modification of gel architecture and TBE/TAE buffer composition to minimize heating during agarose gel electrophoresis.
Agarose gel electrophoresis of DNA and RNA is routinely performed using buffers containing either Tris, acetate, and EDTA (TAE) or Tris, borate, and EDTA (TBE). Gels are run at a low, constant voltage (?10 V/cm) to minimize current and asymmetric heating effects, which can induce band artifacts and poor resolution. In this study, alterations of gel structure and conductive media composition were analyzed to identify factors causing higher electrical currents during horizontal slab gel electrophoresis. Current was reduced when thinner gels and smaller chamber buffer volumes were used, but was not influenced by agarose concentration or the presence of ethidium bromide. Current was strongly dependent on the amount and type of EDTA used and on the concentrations of the major acid-base components of each buffer. Interestingly, resolution and the mobilities of circular versus linear plasmid DNAs were also affected by the chemical form and amount of EDTA. With appropriate modifications to gel structure and buffer constituents, electrophoresis could be performed at high voltages (20-25 V/cm), reducing run times by up to 3-fold. The most striking improvements were observed with small DNAs and RNAs (10-100 bp): high voltages and short run times produced sharper bands and higher resolution. PMID:24637158
Sanderson, Brian A; Araki, Naoko; Lilley, Jennifer L; Guerrero, Gilberto; Lewis, L Kevin
Nomegestrol acetate/estradiol: in oral contraception.
Nomegestrol acetate/estradiol is a combined oral contraceptive with approval in many countries. This fixed-dose combination tablet contains nomegestrol acetate, a highly selective progestogen, and estradiol, a natural estrogen. It is the first monophasic combined oral contraceptive to contain estradiol, and is taken in 28-day cycles, consisting of 24 active therapy days with 4 placebo days (i.e. 24/4-day cycles). In two large, 1-year, randomized, open-label, multicentre, phase III trials in healthy adult women (aged 18-50 years), nomegestrol acetate/estradiol was at least as effective as drospirenone/ethinylestradiol as contraceptive therapy, as the pregnancy rates in women aged 18-35 years (primary efficacy population) in terms of the Pearl Index (primary endpoint) were numerically lower with nomegestrol acetate/estradiol, although the between-group difference was not statistically significant. In both trials, nomegestrol acetate/estradiol was given in a 24/4-day cycle, and drospirenone/ethinylestradiol was given in a 21/7-day cycle. The criteria for using condoms in case of forgotten doses were less stringent in the nomegestrol acetate/estradiol group than in the drospirenone/ethinylestradiol group. Nomegestrol acetate/estradiol therapy for up to 1 year was generally well tolerated in healthy adult women, with an acceptable tolerability profile in line with that expected for a combined oral contraceptive. The most commonly reported adverse events were acne and abnormal withdrawal bleeding (most often shorter, lighter or absent periods). Overall, compared with drospirenone/ethinylestradiol, nomegestrol acetate/estradiol appeared to be associated with less favourable acne-related outcomes, and shorter, lighter or absent periods. PMID:22950535
Yang, Lily P H; Plosker, Greg L
Processing aspects of MOD strontium titanate buffer layers for coated conductor applications
Recent trends in HTS research have been geared toward development of coated conductors. In these conductors, a flexible metallic substrate, typically a nickel alloy, is covered successively with one or more thin buffer layers such as YSZ, STO, MgO, etc., and a relatively thick film of Y123. To make the fabrication of such conductors scalable and cost effective, this paper demonstrates the application of a solution based metallorganic decomposition (MOD) process for deposition of strontium titanate buffer layers. We present results on the effect of precursor chemistry and heat treatment variables on the densification behavior, texture, and microstructure of the strontium titanate films. Highly oriented strontium titanate films with good coverage across the substrate surface have been processed using this method. Thus, this process offers promise to the application of scalable solution deposition techniques to coated conductor fabrication.
Density data for copolymer systems: butyl acrylate\\/vinyl acetate homo- and copolymerization in ethyl acetate
A study was performed to provide precise density data, badly needed for on-line measurements and control of polymerization reactors, e.g. for densimetry studies. Data was obtained for one copolymer of butyl acrylate\\/vinyl acetate, the homopolymers of vinyl acetate and butyl acrylate, plus the two monomers and ethyl acetate. In addition, the hypothesis of the linear dependence of the density of
I Barudio; G FÕvotte; T. F McKenna
Impact of scheduling algorithms on performances of buffered crossbar switch fabrics
In this paper, the impacts of different scheduling algorithms on buffered crossbar switch (BCS) performances are analyzed. Four BCSs are considered: combined input- and crosspoint-queued (CICQ) switch, output-queued with speed-up N (OQ-N) switch virtual ouput-queued with iterative longest input part first (VOQ) switch and virtual output-queued with longest input port first and with throughput maximization (VOQL) switch. As solutions for
Igor Radusinovic; Milica Pejanovic; Zoran Petrovic
Factors affecting coal solubilization by the bacterium Streptomyces setonii 75Vi2 and by alkaline buffers
Streptomyces setonii 75Vi2 produces an extracellular coal-solubilizing component(s) in the absence of coal. The heat stability, relatively low molecular weight, and insensitivity to proteases of the substance(s) responsible for coal solubilization indicate that the mechanism is nonenzymatic. This report describes factors affecting the production and activity of this substance(s) and the similarity in action to alkaline buffer solutions in solubilizing coal.
Strandberg, G.W.; Lewis, S.N.
NCI-Frederick PHL - Fixatives and Solutions
Services Price List Courier Services & Shipment Procedures Scheduling Contact Information Related Links Establishing an Account PHL Forms PHL Portal Fixatives and Solutions Routine fixatives: 10% Neutral Buffered Formalin (NBF) 37 - 40% Formaldehyde
1000mL distilled
Platelet additive solutions: a future perspective.
Platelet additive solutions (PASs) were first developed in the 1980s, and continued to be improved over the following years. The use of PASs as replacement for plasma has a number of benefits, both for the quality of the platelet concentrates and for the patients. However, some PASs have been associated with a lower platelet yield in the PCs, a shorter storage time, and a lower increment in the patient when compared to PCs in plasma. A number of reformulations of the PASs have taken place to counteract these disadvantages. Most PASs use acetate as nutrient for the platelets, which has the benefit of generating bicarbonate when oxidized by the platelets, thus supplying its own buffering capacity. Alternatively, glucose is used, but may cause deterioration of pH in the stored PCs due to the formation of lactic acid. Addition of other buffering substances, such as phosphate, can be added to ensure maintenance of neutral pH. An important finding was the inhibiting effect of potassium and magnesium on platelet activation. The initially developed PASs lacked these two ingredients and showed reduced storage times of the PCs in PAS when compared to those stored in plasma. However, when these constituents are included in the PAS, storage time is similar and even exceeds those seen for PCs in plasma. Considerable research is done in further formulating the optimal PAS. Bicarbonate is being considered as buffer for these PASs. Also, L-carnitine appears to have a favorable effect on stored platelets, including a reduction of platelet metabolism, and inhibition of apoptosis. Another area of optimization is lowering of plasma content needed for maintaining platelet quality. Where current PASs still need at least 30% residual plasma, there is a trend towards lowering the plasma content to less than 5% with the newer PASs. Preservation of purinergic platelet receptor functionality by ADP-degrading activities in plasma appears to play an important role in this respect. Development of PASs are usually based on in vitro studies alone. It is important to realize that only clinical studies can give definitive answers about the quality of platelets stored in PASs. Sofar, only limited clinical evaluations have been published that either studied the effectiveness of platelets in initially-developed PASs, or were specifically done in combination with pathogen reduction technologies. Thus, PASs seem to be an excellent replacement for (part of) the plasma when producing PCs, and allow extended storage with maintenance of quality, but more clinical studies are needed to substantiate in vitro results. PMID:18420439
van der Meer, P F
Design and implementation of Single-Buffered routers
A Single-Buffered (SB) router is a router where only one stage of shared buffering is sandwiched between two interconnects\\u000a in comparison of a Combined Input and Output Queued (CIOQ) router where a central switch fabric is sandwiched between two\\u000a stages of buffering. The notion of SB routers was firstly proposed by the High-Performance Networking Group (HPNG) of Stanford\\u000a University, along
Ximing Hu; Jing Qu; Binqiang Wang; Jiangxing Wu
O-Buffer: A Framework for Sample-Based Graphics
Abstract, We present an innovative modeling and rendering primitive, called the O-buffer, as a framework for sample-based graphics. The 2D or 3D O-buffer is, in essence, a conventional image or a volume, respectively, except that samples are not restricted to a regular grid. A sample position in the O-buffer is recorded as an offset to the nearest grid point of
Huamin Qu; Arie E. Kaufman
Economics of buffer space provisioning in data communication systems
In data communication systems, system designers often face the quintessential dilemma of how much buffer space for storing packet or