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Detection of Anomalous Microwave Emission in the Perseus Molecular Cloud with the COSMOSOMAS Experiment
We present direct evidence for anomalous microwave emission in the Perseus molecular cloud, which shows a clear rising spectrum from 11 to 17 GHz in the data from the COSMOSOMAS experiment. By extending the frequency coverage using W ilkinson Microwave Anisotropy Probe maps convolved with the COSMOSOMAS scanning pattern, we reveal a peak flux density of 42+\\/-4 Jy at 22
R. A. Watson; R. Rebolo; J. A. Rubiño-Martín; S. Hildebrandt; C. M. Gutiérrez; S. Fernández-Cerezo; R. J. Hoyland; E. S. Battistelli
We present observations of the known anomalous microwave emission region, G159.6-18.5, in the Perseus molecular cloud at 16 GHz performed with the Arcminute Microkelvin Imager Small Array. These are the highest angular resolution observations of G159.6-18.5 at microwave wavelengths. By combining these microwave data with infrared observations between 5.8 and 160 {mu}m from the Spitzer Space Telescope, we investigate the existence of a microwave-infrared correlation on angular scales of {approx}2'. We find that the overall correlation appears to increase toward shorter infrared wavelengths, which is consistent with the microwave emission being produced by electric dipole radiation from small, spinning dust grains. We also find that the microwave-infrared correlation peaks at 24 {mu}m (6.7{sigma}), suggesting that the microwave emission is originating from a population of stochastically heated small interstellar dust grains rather than polycyclic aromatic hydrocarbons.
Tibbs, C. T. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Scaife, A. M. M. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Dickinson, C.; Davies, R. D.; Davis, R. J.; Watson, R. A. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL (United Kingdom); Paladini, R. [NASA Herschel Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Grainge, K. J. B., E-mail: email@example.com [Astrophysics Group, Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
Planck early results. XX. New light on anomalous microwave emission from spinning dust grains
Anomalous microwave emission (AME) has been observed by numerous experiments in the frequency range ~10-60 GHz. Using Planck maps and multi-frequency ancillary data, we have constructed spectra for two known AME regions: the Perseus and rho Ophiuchi molecular clouds. The spectra are well fitted by a combination of free-free radiation, cosmic microwave background, thermal dust, and electric dipole radiation from
P. A. R. Ade; N. Aghanim; M. Arnaud; M. Ashdown; J. Aumont; C. Baccigalupi; A. Balbi; A. J. Banday; R. B. Barreiro; J. G. Bartlett; E. Battaner; K. Benabed; A. Benoît; J.-P. Bernard; M. Bersanelli; R. Bhatia; J. J. Bock; A. Bonaldi; J. R. Bond; J. Borrill; F. Boulanger; M. Bucher; C. Burigana; P. Cabella; B. Cappellini; J.-F. Cardoso; S. Casassus; A. Catalano; L. Cayón; A. Challinor; A. Chamballu; R.-R. Chary; X. Chen; L.-Y. Chiang; C. Chiang; P. R. Christensen; D. L. Clements; S. Colombi; F. Couchot; A. Coulais; B. P. Crill; F. Cuttaia; L. Danese; R. D. Davies; R. J. Davis; P. de Bernardis; G. de Gasperis; A. de Rosa; G. de Zotti; J. Delabrouille; J.-M. Delouis; C. Dickinson; S. Donzelli; O. Doré; U. Dörl; M. Douspis; X. Dupac; G. Efstathiou; T. A. Enßlin; H. K. Eriksen; F. Finelli; O. Forni; M. Frailis; E. Franceschi; S. Galeotta; K. Ganga; R. T. Génova-Santos; M. Giard; G. Giardino; Y. Giraud-Héraud; J. González-Nuevo; K. M. Górski; S. Gratton; A. Gregorio; A. Gruppuso; F. K. Hansen; D. Harrison; G. Helou; S. Henrot-Versillé; D. Herranz; S. R. Hildebrandt; E. Hivon; M. Hobson; W. A. Holmes; W. Hovest; R. J. Hoyland; K. M. Huffenberger; T. R. Jaffe; A. H. Jaffe; W. C. Jones; M. Juvela; E. Keihänen; R. Keskitalo; T. S. Kisner; R. Kneissl; L. Knox; H. Kurki-Suonio; G. Lagache; A. Lähteenmäki; J.-M. Lamarre; A. Lasenby; R. J. Laureijs; C. R. Lawrence; S. Leach; R. Leonardi; P. B. Lilje; M. Linden-Vørnle; M. López-Caniego; P. M. Lubin; J. F. Macías-Pérez; C. J. MacTavish; B. Maffei; D. Maino; N. Mandolesi; R. Mann; M. Maris; D. J. Marshall; E. Martínez-González; S. Masi; S. Matarrese; F. Matthai; P. Mazzotta; P. McGehee; P. R. Meinhold; A. Melchiorri; L. Mendes; A. Mennella; S. Mitra; M.-A. Miville-Deschênes; A. Moneti; L. Montier; G. Morgante; D. Mortlock; D. Munshi; A. Murphy; P. Naselsky; P. Natoli; C. B. Netterfield; H. U. Nørgaard-Nielsen; F. Noviello; D. Novikov; I. Novikov; I. J. O'Dwyer; S. Osborne; F. Pajot; R. Paladini; B. Partridge; F. Pasian; G. Patanchon; T. J. Pearson; M. Peel; O. Perdereau; L. Perotto; F. Perrotta; F. Piacentini; M. Piat; S. Plaszczynski; P. Platania; E. Pointecouteau; G. Polenta; N. Ponthieu; T. Poutanen; G. Prézeau; P. Procopio; S. Prunet; J.-L. Puget; W. T. Reach; R. Rebolo; W. Reich; M. Reinecke; C. Renault; S. Ricciardi; T. Riller; I. Ristorcelli; G. Rocha; C. Rosset; M. Rowan-Robinson; J. A. Rubiño-Martín; B. Rusholme; M. Sandri; D. Santos; G. Savini; D. Scott; M. D. Seiffert; P. Shellard; G. F. Smoot; J.-L. Starck; F. Stivoli; V. Stolyarov; R. Stompor; R. Sudiwala; J.-F. Sygnet; J. A. Tauber; L. Terenzi; L. Toffolatti; M. Tomasi; J.-P. Torre; M. Tristram; J. Tuovinen; G. Umana; L. Valenziano; J. Varis; L. Verstraete; P. Vielva; F. Villa; N. Vittorio; L. A. Wade; B. D. Wandelt; R. Watson; A. Wilkinson; N. Ysard; D. Yvon; A. Zacchei; A. Zonca
We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1 Degree-Sign radius around R.A. = 56.{sup 0}24, decl. = 23.{sup 0}78 (J2000) is 2.15 {+-} 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected H{alpha} template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 {+-} 0.12 Jy (17.7{sigma}). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 {mu}m data, is found to be 4.36 {+-} 0.17 {mu}K (MJy sr{sup -1}){sup -1}, a value considerably lower than in typical AME clouds, which present emissivities of {approx}20 {mu}K (MJy sr{sup -1}){sup -1}, although higher than the 0.2 {mu}K (MJy sr{sup -1}){sup -1} of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction A{sub V} {approx} 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact, together with the broad knowledge of the stellar content of this region, provides an excellent testbed for AME characterization in physical conditions different from those generally explored up to now.
Genova-Santos, R.; Rebolo, R.; Rubino-Martin, J. A.; Lopez-Caraballo, C. H.; Hildebrandt, S. R. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200 La Laguna, Tenerife (Spain)
Planck intermediate results. XV. A study of anomalous microwave emission in Galactic clouds
NASA Astrophysics Data System (ADS)
Anomalous microwave emission (AME) is believed to be due to electric dipole radiation from small spinning dust grains. The aim of this paper is a statistical study of the basic properties of AME regions and the environment in which they emit. We used WMAP and Planck maps, combined with ancillary radio and IR data, to construct a sample of 98 candidate AME sources, assembling SEDs for each source using aperture photometry on 1°-smoothed maps from 0.408 GHz up to 3000 GHz. Each spectrum is fitted with a simple model of free-free, synchrotron (where necessary), cosmic microwave background (CMB), thermal dust, and spinning dust components. We find that 42 of the 98 sources have significant (>5?) excess emission at frequencies between 20 and 60 GHz. An analysis of the potential contribution of optically thick free-free emission from ultra-compact H ii regions, using IR colour criteria, reduces the significant AME sample to 27 regions. The spectrum of the AME is consistent with model spectra of spinning dust. Peak frequencies are in the range 20-35 GHz except for the California nebula (NGC 1499), which appears to have a high spinning dust peak frequency of (50 ± 17) GHz. The AME regions tend to be more spatially extended than regions with little or no AME. The AME intensity is strongly correlated with the sub-millimetre/IR flux densities and comparable to previous AME detections in the literature. AME emissivity, defined as the ratio of AME to dust optical depth, varies by an order of magnitude for the AME regions. The AME regions tend to be associated with cooler dust in the range 14-20 K and an average emissivity index, ?d, of +1.8, while the non-AME regions are typically warmer, at 20-27 K. In agreement with previous studies, the AME emissivity appears to decrease with increasing column density. This supports the idea of AME originating from small grains that are known to be depleted in dense regions, probably due to coagulation onto larger grains. We also find a correlation between the AME emissivity (and to a lesser degree the spinning dust peak frequency) and the intensity of the interstellar radiation field, G0. Modelling of this trend suggests that both radiative and collisional excitation are important for the spinning dust emission. The most significant AME regions tend to have relatively less ionized gas (free-free emission), although this could be a selection effect. The infrared excess, a measure of the heating of dust associated with H ii regions, is typically >4 for AME sources, indicating that the dust is not primarily heated by hot OB stars. The AME regions are associated with known dark nebulae and have higher 12 ?m/25 ?m ratios. The emerging picture is that the bulk of the AME is coming from the polycyclic aromatic hydrocarbons and small dust grains from the colder neutral interstellar medium phase.
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Arnaud, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Cardoso, J.-F.; Casassus, S.; Catalano, A.; Chamballu, A.; Chen, X.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson; , C.; Diego, J. M.; Donzelli, S.; Doré, O.; Dupac, X.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Ghosh, T.; Giard, M.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lawrence, C. R.; Leonardi, R.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Patanchon, G.; Pearson, T. J.; Peel, M.; Perdereau, O.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reich, W.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Tibbs, C. T.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Verstraete, L.; Vielva, P.; Villa, F.; Wandelt, B. D.; Watson, R.; Wilkinson, A.; Ysard, N.; Yvon, D.; Zacchei, A.; Zonca, A.
Microwave Emission Models of Snow.
National Technical Information Service (NTIS)
This study is concerned with the microwave emission models of dry snow and wet snow. A review of accomplished literature surveys on microwave emission models of snow is presented, which includes the characteristics of the constituents in the snow medium, ...
W. Huining
Evidence for Anomalous Dust-correlated Emission at 8 GHz
NASA Astrophysics Data System (ADS)
In 1969 Edward Conklin measured the anisotropy in celestial emission at 8 GHz with a resolution of 16fdg2 and used the data to report a detection of the cosmic microwave background dipole. Given the paucity of 8 GHz observations over large angular scales and the clear evidence for non-power-law Galactic emission near 8 GHz, a new analysis of Conklin's data is informative. In this paper, we compare Conklin's data to that from Haslam et al. (0.4 GHz), Reich and Reich (1.4 GHz), and the Wilkinson Microwave Anisotropy Probe (WMAP; 23-94 GHz). We show that the spectral index between Conklin's data and the 23 GHz WMAP data is ? = -1.7 ± 0.1, where we model the emission temperature as Tvprop??. Free-free emission has ? ? - 2.15 and synchrotron emission has ? ? - 2.7 to -3. Thermal dust emission (? ? 1.7) is negligible at 8 GHz. We conclude that there must be another distinct non-power-law component of diffuse foreground emission that emits near 10 GHz, consistent with other observations in this frequency range. By comparing to the full complement of data sets, we show that a model with an anomalous emission component, assumed to be spinning dust, is preferred over a model without spinning dust at 5? (??2 = 31). However, the source of the new component cannot be determined uniquely.
Lu, Michelle; Dunkley, Joanna; Page, Lyman
The cut-sky cosmic microwave background is not anomalous
The observed angular correlation function of the cosmic microwave background has previously been reported to be anomalous, particularly when measured in regions of the sky uncontaminated by Galactic emission. Recent work by Efstathiou et al. presents a Bayesian comparison of isotropic theories, casting doubt on the significance of the purported anomaly. We extend this analysis to all anisotropic Gaussian theories with vanishing mean (<{delta}T>=0), using the much wider class of models to confirm that the anomaly is not likely to point to new physics. On the other hand if there is any new physics to be gleaned, it results from low-l alignments which will be better quantified by a full-sky statistic. We also consider quadratic maximum likelihood power spectrum estimators that are constructed assuming isotropy. The underlying assumptions are therefore false if the ensemble is anisotropic. Nonetheless we demonstrate that, for theories compatible with the observed sky, these estimators (while no longer optimal) remain statistically superior to pseudo-C{sub l} power spectrum estimators.
Pontzen, Andrew [Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Cambridge CB3 0HA (United Kingdom); Peiris, Hiranya V. [Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Cambridge CB3 0HA (United Kingdom); Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)
Microwave emission and crop residues
NASA Technical Reports Server (NTRS)
A series of controlled experiments were conducted to determine the significance of crop residues or stubble in estimating the emission of the underlying soil. Observations using truck-mounted L and C band passive microwave radiometers showed that for dry wheat and soybeans the dry residue caused negligible attenuation of the background emission. Green residues, with water contents typical of standing crops, did have a significant effect on the background emission. Results for these green residues also indicated that extremes in plant structure, as created using parallel and perpendicular stalk orientations, can cause very large differences in the degree of attenuation.
Jackson, Thomas J.; O'Neill, Peggy E.
Anomalous Radio Emission from Dust in the Helix
NASA Astrophysics Data System (ADS)
A by-product of experiments designed to map the cosmic microwave background is the recent detection of a new component of foreground Galactic emission. The anomalous foreground at ~10-30 GHz, unexplained by traditional emission mechanisms, correlates with 100 ?m dust emission. We use planetary nebulae (PNs) as astrophysical laboratories to test known radio emission processes and report that in the Helix the emission at 31 GHz and 100 ?m are well correlated and exhibit similar features on sky images, which are absent in H?. Upper limits on the 250 GHz continuum emission in the Helix rule out cold grains as candidates for the 31 GHz emission and provide spectroscopic evidence for an excess at 31 GHz over bremsstrahlung. We estimate that the 100 ?m-correlated radio emission, presumably due to dust, accounts for at least 20% of the 31 GHz emission in the Helix. This result strengthens previous tentative interpretations of diffuse interstellar medium spectra involving a new dust emission mechanism at radio frequencies. Very small grains, thought not to survive in evolved PNs, have not been detected in the Helix, which hampers interpreting the new component in terms of electric dipole emission from spinning grains. The observed iron depletion in the Helix favors considering the identity of this new component to be magnetic dipole emission from hot ferromagnetic grains. The reduced level of free-free continuum that we report also implies an electronic temperature of Te=4600+/-1200 K for the free-free emitting material, which is significantly lower than the temperature of 9500+/-500 K inferred from collisionally excited lines. Partly based on observations collected at the European Southern Observatory, La Silla, Chile.
Casassus, S.; Readhead, A. C. S.; Pearson, T. J.; Nyman, L.-Å.; Shepherd, M. C.; Bronfman, L.
Anomalously delayed stimulated emission in random lasers
In a random laser based on a mixture of Nd{sup 3+}:Ba{sub 5}(PO{sub 4}){sub 3} and Cr{sup 4+}:Y{sub 3}Al{sub 5}O{sub 12} powders, we have observed trains of anomalously delayed stimulated emission pulses, which lasted for several tens of nanoseconds after the end of the pumping pulse. The phenomenon is explained by the color-center formation and reversed-saturable absorption in Cr{sup 4+}:YAG powder.
Zhu, G.; Tumkur, T.; Noginov, M. A. [Center for Materials Research, Norfolk State University, Norfolk, Virginia 23504 (United States)
Thermal Microwave Emission From a Scattering Layer
The microwave radiometric temperature of heterogeneous materials is altered by internal scattering. Radiative transfer theory and a Rayleigh scattering model are used to obtain the microwave temperature and its polarization as a function of view angle for emission from a nonuniformly thick layer containing scatterers. The scatter-induced change in brightness tempera:tare is generally negative and may be many tens of
A. W. England
Soil Moisture Information And Thermal Microwave Emission
This paper presents theoretical and experimental results that demonstrate the depth to which soil moisture can be directly measured using microwave radiometers. The experimental results also document the effect of uniform surface roughness on the response of thermal microwave emission to soil moisture. Experimental measurements were executed in July 1980 at the Texas A&M University Research Farm near College Station,
Richard W. Newton; Quentin Robert Black; Shahab Makanvand; Andrew J. Blanchard; Buford Randall Jean
An Improved Fast Microwave Water Emissivity Model
Satellite measurements from microwave instruments have made a significant contribution to the skill of numerical weather forecasting, on both global and regional scales. A FAST microwave Emissivity Model (FASTEM), which was developed by the Met Office, U.K., has been widely utilized to compute the surface emitted radiation in forward calculations. However, the FASTEM model was developed for frequencies in the
Quanhua Liu; Fuzhong Weng; Stephen J. English
Microwave Emission from Polar Surfaces.
National Technical Information Service (NTIS)
Based on the work described in this report, our observations and modeling work have revealed several considerations which are central to understanding the physical basis for the application and interpretation of thin ice algorithms for passive microwave i...
T. C. Grenfell
Anomalous microwave spectra of snow cover observed from Special Sensor Microwave/Imager measurements
NASA Astrophysics Data System (ADS)
Brightness temperature spectra measured by the Special Sensor Microwave/Imager (SSM/I) flown onboard F8 and F14 satellites of the U.S. Defense Meteorological Satellite Program (DMSP) during the 1987-1988 and 1997-1998 winter periods are analyzed concurrently with the data from snow monitoring stations over the former Soviet Union. Extensive analysis reveals the existence of two anomalies in the microwave thermal radiation spectra of snow cover. It is shown that in the beginning of winter the SSM/I measurements at 19, 37, and 85 GHz generally follow a classical pattern; that is, the brightness temperatures decrease for both increasing snow depth and increasing frequency. Dramatic departures from this behavior is observed around the middle of winter: The brightness temperatures reach a minimum and then begin to increase despite the fact that the snow depth remains constant or even continues to grow. Statistical analysis of the snow pack characteristics and SSM/I measurements is presented around the time when the brightness temperatures reach a minimum. The anomalous spectral characteristics are analyzed using a two-stream radiative transfer model and dense media theory. It is shown how metamorphic changes in the snow crystalline structure are responsible for the brightness temperature minimum. The second departure from the normal snow signature is the inversion of brightness temperature spectra; that is, the higher-frequency brightness temperature is greater than the low-frequency measurements. It is shown that this phenomenon, observed previously over Greenland and Antarctica, is much more extensive. Radiative transfer simulations were used to show that a dense layer of surface crust on top of old coarse-grained snow can produce the invented brightness temperature spectrum.
Rosenfeld, Simon; Grody, Norman
Modeling microwave emission spectra of layered snowpacks
A thermal microwave emission model of layered snowpacks (MEMLS) (Wiesmann and Matzler, 1997) was developed for the frequency range, 5 to 100 GHz. It is based on radiative transfer, using six-flux theory to describe multiple volume scattering and absorption, including radiation trapping due to internal reflection and a combination of coherent and incoherent superpositions of reflections between layer interfaces. The
A. Wiesmann; C. Hatzler; D. Hiltbrunner
Transport process and anomalous membrane potential under microwave conditions
By means of theoretical methods of quantum biology and quantum optics, the microwave induced potential variation of biological membrane has been studied. The membrane potential is related to the unsymmetrical ion distribution. This electric field caused by the ions distribution imposes a force on the ions passing through the membrane, we have found a method of calculating the density of
Cao Deshu; Zhang Kaixi
Origin of anomalous emission in superdense glow discharge
A theory, supported by new experimental data, for recently observed anomalous large pseudospark and backlighted thyratron cathode emission into a superdense glow discharge is reported. The current density at the cathode surface, ~=10 kA\\/cm2, is produced by an ion ``beam,'' extends over a surface area of ~=1 cm2, and is orders of magnitudes larger than that of heated thermionic cathodes.
W. Hartmann; M. A. Gundersen
Anomalous photoelectric emission from Ag on zinc-phthalocyanine film
NASA Astrophysics Data System (ADS)
Photoelectric emission from organic and metal thin films is generally observed with irradiation of photon energy larger than 4 eV. In this paper, however, we report photoelectric emission from Ag on a zinc-phthalocyanine (ZnPc) layer at a photon energy of 3.4 eV. The threshold energy for this photoelectric emission is much smaller than the work function of Ag estimated by conventional photoelectron spectroscopy. The photoelectric emission by low-energy photons is significant for Ag thicknesses of less than 1 nm. Photoelectron spectroscopy and morphological study of the Ag/ZnPc suggest that the anomalous photoelectric emission from the Ag surface is caused by a vacuum level shift at the Ag/ZnPc interface and by surface plasmons of the Ag nanoparticles.
Tanaka, Senku; Otani, Tomohiro; Fukuzawa, Ken; Ogawa, Koji; Azuma, Junpei; Yamamoto, Isamu; Takahashi, Kazutoshi; Kamada, Masao; Hiromitsu, Ichiro
Vacuum field energy and spontaneous emission in anomalously dispersive cavities
Anomalously dispersive cavities, particularly white-light cavities, may have larger bandwidth to finesse ratios than their normally dispersive counterparts. Partly for this reason, they have been proposed for use in laser interferometer gravitational-wave observatory (LIGO)-like gravity-wave detectors and in ring-laser gyroscopes. In this paper we analyze the quantum noise associated with anomalously dispersive cavity modes. The vacuum field energy associated with a particular cavity mode is proportional to the cavity-averaged group velocity of that mode. For anomalously dispersive cavities with group index values between 1 and 0, this means that the total vacuum field energy associated with a particular cavity mode must exceed ({h_bar}/2{pi}){omega}/2. For white-light cavities in particular, the group index approaches zero and the vacuum field energy of a particular spatial mode may be significantly enhanced. We predict enhanced spontaneous emission rates into anomalously dispersive cavity modes and broadened laser linewidths when the linewidth of intracavity emitters is broader than the cavity linewidth.
Bradshaw, Douglas H.; Di Rosa, Michael D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Gyrosynchrotron Microwave Emission From Solar Flares
NASA Astrophysics Data System (ADS)
The subject of this research is decimetric and microwave emission from solar flares. The research deals with gyrosynchrotron emission from a population of fast electrons. Two frequency ranges are investigated: low multiples (1-3) of the cyclotron frequency nu_B , and high multiples ( 6 nu_B and above) of the cyclotron frequency. In the high frequency range a simple geometrical model of a flare loop is investigated. We show that our simple model reproduces observed microwave fluxes and spectra, and present a fit for the microwave spectrum and time evolution of the flare of June 4th 1991. We conclude that the flare spectrum can be explained with a simple model, and that even the time evolution can be fit by changing a single parameter at a time. We also investigate how the observed flare spectrum changes for different locations of the flare on the sun, a question not dealt with previously. The shape of the spectrum is quantified by the ratio of the flux at 10 GHz to the flux at 4 GHz, and this ratio is shown to change by an order of magnitude as the same flare model is moved from the Limb to the Disk center. In the low frequency range we investigate amplification through the Electron Cyclotron Maser (ECM) mechanism in the range 0.5 < nu_p / nu_B < 2, where nu_p is the plasma frequency. The ECM process is widely assumed to produce solar microwave millisecond spike emission. Most previous studies concentrated on the region nu_p / nu_B<1, and claim that spikes are produced there. We show that maser emission should be produced at the foot-points of the flare, where nu_p / nu_B > 1. Previous studies claim emission at 70 degrees to the magnetic field,or more, and emission at the first or second harmonic. We show that spike emission from the foot-points should appear at angles of 30-70 degrees to the magnetic field, and at frequencies near the second cyclotron harmonic, usually at 2.06 nu_B. We also find that ECM emission depends on the temperature and that the unobservable Z-mode quenchs the maser for temperatures above 10(7) Kelvin. These conclusions can be checked by observations of high spatial resolution, especially if performed simultaneously with observations from which the temperature can be estimated.
Stupp, A.
Effects of Salinity on the Microwave Emission of Soils.
National Technical Information Service (NTIS)
Controlled plot experiments were conducted to collect L and C band passive microwave data concurrent with ground observations of salinity and soil moisture. Two dielectric mixing models were used with an emission model to predict the emissivity from a bar...
T. J. Jackson P. E. Oneill
Effects of anomalous permittivity on the microwave heating of zinc oxide
NASA Astrophysics Data System (ADS)
Highly nonuniform heating has been observed in zinc oxide (ZnO) powder compacts exposed to 2.45 GHz microwaves in oxygen deficient atmospheres such as pure nitrogen or argon. This phenomenon manifests as a localized zone of rapid heating which propagates outward from the sample core, and is documented by real-time surface and core temperature measurements performed during the microwave exposure. Measurements of the complex permittivity, ?'', during heating of identical ZnO samples in a conventional furnace and in a nitrogen atmosphere, demonstrated that ?'' experiences at least one significant maximum between 200 and 500 °C. Mass spectrometry results indicate that the peaks in ?'' correlate well with the rate of desorption of chemisorbed water from the surface of the ZnO powder. It was also noted that the nonuniform heating does not manifest when the microwave exposure is performed in air. Similarly, the anomalous peaks in ?'' are almost completely suppressed during heating in air. It is well known that oxygen adsorbs strongly to the surface of ZnO in the temperature range from room temperature to 300 °C, and that this adsorption results in a drastic decrease in the electrical conductivity and, thus, in ?''. It is proposed, therefore, that the effect of water desorption upon the complex permittivity may be, in effect, counterbalanced by the adsorption oxygen from the atmosphere. The effect of this behavior may be significant during microwave processing, where nonuniform power absorption can result in extremely localized heating.
Martin, L. P.; Dadon, D.; Rosen, M.; Gershon, D.; Rybakov, K. I.; Birman, A.; Calame, J. P.; Levush, B.; Carmel, Y.; Hutcheon, R.
Wigner-Ville Analysis of Solar Microwave Emission.
National Technical Information Service (NTIS)
Analysis of low-frequency fluctuations of microwave emission of solar flares at 22 and 37 GHz is performed. Three microwave bursts with duration of about one hour observed in Metsahovi with the time resolution of 100 and 50 ms are investigated. To find ti...
V. V. Zaitsev A. G. Kislyakov S. Urpo A. V. Stepanov E. I. Shkelev
Microwave thermal emission from Iapetus' dark terrains
NASA Astrophysics Data System (ADS)
Because of its large distance from Saturn and its high inclination, the Cassini spacecraft has made only one close (altitude<25 000 km) flyby (IA49) of Iapetus : on September 10, 2007. During this opportunity, the RADAR instrument scanned the antenna beam in a north-south raster pattern, mostly over the dark terrains (named Cassini Regio) of the leading hemisphere of the moon. During this scan, it collected a unique and concurrent set of passive (radiometry) and active (scatterometry) data at 2.2-cm wavelength and with a footprint size of ~120 km (~15% of Iapetus' diameter). The Cassini radiometer measures the surface microwave thermal emission, which varies with the emissivity (or reflectivity) and physical temperature profile of the near-surface. At such a wavelength, it probes several tens of cm up to a few meters below the surface, depending on the absorbing properties of Iapetus' regolith. Combined with the concurrent active data, the radiometry data acquired during IA49 can be used to constrain the electrical and thermal properties of Iapetus' dark region thus providing clues on the physical state (roughness, porosity) and composition of these terrains whose nature and origin are still under debate. In this paper, we will report on the Cassini microwave observations recorded during IA49 in the active and passive modes and describe the radiative transfer model we have developed in order to analyze the radiometry data. Comparison with this model indicates that the thermal inertia sensed by the Cassini radar radiometer at 2.2 cm over Cassini Regio significantly exceeds that measured in the thermal infrared by the Cassini's Composite Infrared Spectrometer (CIRS) instrument (~10 in Rivera-Valentin et al., 2011). This suggests a gradient in density with depth, which is typical for planetary regoliths. The radiometer also captured the temperature asymmetry around the Equator due to heat buried in ground on seasonal timescales while the different local solar times of the equatorial observations seem to be responsible for a variation of less than 10 K in the brightness temperature recorded over Cassini Regio.
Le Gall, A.; Keihm, S.; Janssen, M. A.; Wye, L. C.; Lorenz, R. D.; West, R.
Anomalous conductivity and secondary electron emission in Hall effect thrusters
This paper is devoted to the study of the effects of electron-wall interactions on cross magnetic field electron momentum and energy losses in Hall effect thrusters. By coupling a semianalytical model of the wall sheath similar to models used by several authors in this context, with a two-dimensional hybrid simulation of a Hall effect thruster, we find that the cross magnetic field conductivity enhanced by electron-wall collisions and secondary electron emission is not sufficient to explain the conductivity deduced from experiments. Calculated current-voltage curves including electron-wall collisions from a standard sheath model as the sole 'anomalous' conductivity mechanism do not reproduce the measurements, especially at high discharge voltages, and for various wall ceramics. Results also show that a one-dimensional description of electron-wall collisions with a constant radial plasma density profile as used by many authors leads to an overestimation of the contribution of electron-wall interactions to cross magnetic field conductivity.
Garrigues, L.; Hagelaar, G. J. M.; Boniface, C.; Boeuf, J. P. [Centre de Physique des Plasmas et Applications de Toulouse, CNRS, Universite Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex 4 (France)
Objective Characterization of Snow Microstructure for Microwave Emission Modeling
NASA Technical Reports Server (NTRS)
Passive microwave (PM) measurements are sensitive to the presence and quantity of snow, a fact that has long been used to monitor snowcover from space. In order to estimate total snow water equivalent (SWE) within PM footprints (on the order of approx 100 sq km), it is prerequisite to understand snow microwave emission at the point scale and how microwave radiation integrates spatially; the former is the topic of this paper. Snow microstructure is one of the fundamental controls on the propagation of microwave radiation through snow. Our goal in this study is to evaluate the prospects for driving the Microwave Emission Model of Layered Snowpacks with objective measurements of snow specific surface area to reproduce measured brightness temperatures when forced with objective measurements of snow specific surface area (S). This eliminates the need to treat the grain size as a free-fit parameter.
Durand, Michael; Kim, Edward J.; Molotch, Noah P.; Margulis, Steven A.; Courville, Zoe; Malzler, Christian
Enhancement of LIBS emission using antenna-coupled microwave.
Intensified microwave coupled by a loop antenna (diameter of 3 mm) has been employed to enhance the laser-induced breakdown spectroscopy (LIBS) emission. In this method, a laser plasma was induced on Gd?O? sample at a reduced pressure by focusing a pulsed Nd:YAG laser (532 nm, 10 ns, 5 mJ) at a local point, at which electromagnetic field was produced by introducing microwave radiation using loop antenna. The plasma emission was significantly enhanced by absorbing the microwave radiation, resulting in high-temperature plasma and long-lifetime plasma emission. By using this method, the enhancement of Gd lines was up to 32 times, depending upon the emission lines observed. A linear calibration curve of Ca contained in the Gd?O? sample was made. The detection limit of Ca was approximately 2 mg/kg. This present method is very useful for identification of trace elements in nuclear fuel and radioactive materials. PMID:24514526
Khumaeni, Ali; Motonobu, Tampo; Katsuaki, Akaoka; Masabumi, Miyabe; Ikuo, Wakaida
Aircraft measurements of microwave emission from Arctic Sea Ice
NASA Technical Reports Server (NTRS)
Measurements of the microwave emission from Arctic Sea ice were made with aircraft at 8 wavelengths ranging from 0.510 cm to 2.81 cm. The expected contrast in emissivities between ice and water was observed at all wavelengths. Distributions of sea ice and open water were mapped from altitudes up to 11 km in the presence of dense cloud cover. Different forms of ice also exhibited strong contrasts in emissivity. Emissivity differences of up to 0.2 were observed between two types of ice at 0.811 cm wavelength. The higher emissivity ice type is tentatively identified as having been formed more recently than the lower emissivity ice.
Wilheit, T. T.; Blinn, J.; Campbell, W. J.; Edgerton, A. T.; Nordberg, W.
Microwave land surface emissivities estimated from SSM\\/I observations
Microwave emissivities of land surfaces are estimated from special sensor microwave\\/imager (SSM\\/I) observations by removing the contributions from the atmosphere, clouds, and rain using ancillary satellite data (International Satellite Cloud Climatology Project (ISCCP) and TIROS Operational Vertical Sounder (TOVS) products). In the first step, cloud-free SSM\\/I observations are isolated with the help of collocated visible\\/infrared satellite observations (ISCCP data). The
Catherine Prigent; William B. Rossow; Elaine Matthews
Detection of plutonium with the microwave plasma continuous emissions monitor
The first successful detection of plutonium with a continuous microwave plasma emissions monitor has been demonstrated. Seven plutonium emission peaks in the 362 - 366 nm and 449 - 454 nm ranges were clearly observed. The strongest peak was at 453.62 nm. This peak and five of the other plutonium peaks were easily distinguishable from possible interference from iron emission peaks with a spectrometer resolution of 0.1 nm. 2 refs., 3 figs.
Rhee, D.Y.; Woskov, P.P. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center; Gervais, K.; Surma, J.E. [Pacific Northwest Lab., Richland, WA (United States)
Experimental verification of the anomalous skin effect in copper using emissivity measurements
NASA Astrophysics Data System (ADS)
Spectral directional emissivity has been measured in copper between 3 and 24 ?m above room temperature. The experimental spectrum shows a weak broad peak between 7 and 14 ?m, which is much more acute for higher emission angles. However, the peak width and position are both independent of the emission angle. The experimental results are in very good agreement with the semiclassical theory of the optical properties of metals in the regime of the anomalous skin effect, in particular with the asymptotic approximation. This comparison suggests that this work shows an optical experimental evidence of the anomalous skin effect.
Echániz, T.; Setién-Fernández, I.; Pérez-Sáez, R. B.; Tello, M. J.
Microwave measurement of thermal emission from the sea.
NASA Technical Reports Server (NTRS)
Review of the results of some experimental and theoretical investigations of various limiting factors in microwave measurements of thermal emission from the sea, ranging from instrumentation to surface properties of the ocean. It is shown that absolute measurement of the thermal emission from the sea can be made at 2.69 GHz, with accuracies of better than plus or minus 1 K within the present state of microwave instrument development. The principal uncertainties on interpretation of such observations in terms of molecular temperature of the sea involve: (1) surface contamination such as oil slicks, (2) spray and foaming, (3) salinity variation, and (4) surface waves.
Gray, K. W.; Hall, W. F.; Hardy, W. N.; Hidy, G. M.; Ho, W. W.; Love, A. W.; Van Melle, M. J.; Wang, H.
Planck is expected to answer crucial questions on the early universe, but it also provides further understanding on anomalous microwave emission. Electric dipole emission from spinning dust grains continues to be the favored interpretation of anomalous microwave emission. In this paper, we present a method to calculate the rotational emission from small grains of irregular shape with moments of inertia I{sub 1} {>=} I{sub 2} {>=} I{sub 3}. We show that a torque-free rotating irregular grain with a given angular momentum radiates at multiple frequency modes. The resulting spinning dust spectrum has peak frequency and emissivity increasing with the degree of grain shape irregularity, which is defined by I{sub 1}:I{sub 2}:I{sub 3}. We discuss how the orientation of the dipole moment {mu} in body coordinates affects the spinning dust spectrum for different regimes of internal thermal fluctuations. We show that the spinning dust emissivity for the case of strong thermal fluctuations is less sensitive to the orientation of {mu} than in the case of weak thermal fluctuations. We calculate spinning dust spectra for a range of gas density and dipole moment. The effect of compressible turbulence on spinning dust emission is investigated. We show that the emission in a turbulent medium increases by a factor from 1.2 to 1.4 relative to that in a uniform medium, as the sonic Mach number M{sub s} increases from 2 to 7. Finally, spinning dust parameters are constrained by fitting our improved model to five-year Wilkinson Microwave Anisotropy Probe cross-correlation foreground spectra, for both the H{alpha}-correlated and 100-{mu}m-correlated emission spectra.
Hoang, Thiem; Lazarian, A. [Astronomy Department, University of Wisconsin, Madison, WI 53706 (United States); Draine, B. T. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
The Effect of Intercepted Precipitation on the Microwave Emission of Maize at 1.4 GHz
Terrestrial microwave emission is sensitive to soil moisture. Soil moisture is an important yet unobserved reservoir of the hydrologic cycle linked to precipitation variability. Remote sensing satellites that observe terrestrial microwave emission have the potential to map the spatial and temporal variabilities of soil moisture on a global basis. Unfortunately, terrestrial microwave emission is also sensitive to water within the
Brian K. Hornbuckle; Anthony W. England; Martha C. Anderson
Thermal microwave emission from half-space random media
Brightness temperatures resulting from microwave thermal emission from a half-space random medium are calculated. The random medium has a nonuniform temperature profile and is characterized by correlation functions that possess both vertical and lateral variations. Radiative transfer equations are derived. They are solved with an iterative integral equation approach for small scattering albedo and with a numerical approach for general
L. Tsang; J. A. Kong
A Parameterization of Effective Soil Temperature for Microwave Emission
The observed microwave brightness temperature of soils depends upon the soil temperature profile, which in a remote sensing application will not be known in any detail. In this paper we discuss a parameterization of effe:tive soil temperature, which when divided into the brightness temperature gives the emissivity, in terms of surface (To) and deep (T) soil temperatures as T =
B. J. Choudhury; T. J. Schmugge; T. Mo
Error Sources in Remote Sensing of Microwave Land Surface Emissivity
The retrieval of land surface emissivity from satellite passive microwave measurements often requires the knowledge of various radiative components (e.g., atmospheric upwelling and downwelling radiation) contributed to the measurements. Under a cloud-free condition, atmospheric and surface radiative compo- nents can be derived from atmospheric temperature and water vapor, and surface temperature data. Thus, the quality of these auxiliary data sets
Hu Yang; Fuzhong Weng
The Emissivity of Sea Foam at Microwave Frequencies
A consistent picture of the emission characteristics of sea foam at microwave frequencies has emerged from a survey of published radiometric measurements. The results are summarized, as functions of frequency and angle, by means of simple equations. Available data on the reflection properties of foam are also examined and shown to be qualitatively, but not quantitatively, in agreement with the
A. Stogryn
A search for microwave emission from cosmic ray air showers
NASA Astrophysics Data System (ADS)
At the highest energies, the sources of cosmic rays should be among the most powerful extragalactic accelerators. Large observatories have revealed a flux suppression above a few 1019 eV, similar to the expected effect of the interaction of ultrahigh energy cosmic rays (UHECR) with the cosmic microwave background. The Pierre Auger Observatory has measured the largest sample of cosmic ray induced extensive air showers (EAS) at the highest energies leading to a precise measurement of the energy spectrum, hints of spatial anisotropy, and a surprising change in the chemical composition at the highest energies. To answer the question of the origin of UHECRs a larger sample of high quality data will be required to reach a statistically significant result. One of the possible techniques suggested to achieve this much larger data sample, in a cost effective way, is ultra-wide field of view microwave telescopes which would operate in an analogous way to the already successful fluorescence detection (FD) technique. Detecting EAS in microwaves could be done with 100% duty cycle and essentially no atmospheric effects. This presents many advantages over the FD which has a 10% duty cycle and requires extensive atmospheric monitoring for calibration. We have pursued both prototype detector designs and improved laboratory measurements, the results of which are reported herein, and published in (Alvarez-Muniz et al., 2013; Alvarez-Muniz et al., 2012a; Williams et al., 2013; Alvarez-Muniz et al., 2013). The Microwave Detection of Air Showers (MIDAS) experiment is the first ultra-wide field of view imaging telescope deployed to detect isotropic microwave emission from EAS. With 61 days of livetime data operating on the University of Chicago campus we were able to set new limits on isotropic microwave emission from extensive air showers. The new limits rule out current laboratory air plasma measurements (Gorham et al., 2008) by more than five sigma. The MIDAS experiment continues to take data installed in Argentina, operating in coincidence with the Pierre Auger Observatory. Using the first 70 days of livetime data combined with a sample of EAS events from the Auger surface detector we are able to set a preliminary limit which is even more stringent than that set with the Chicago data set. Test beam efforts performed at Argonne National Lab, The Microwave Air Yield Beam Experiment (MAYBE), have successfully measured a microwave signal which exhibits linear scaling with energy deposit in a frequency range of 1 GHz to 15 GHz. This measurement has produced strong upper limits on the isotropic emission of microwaves from air plasmas.
Williams, Christopher Lee
Anomalous Biophoton Emission during Germination Process of Red Bean
NASA Astrophysics Data System (ADS)
Spontaneous biophoton emission was investigated for the germination and the growth process of a red bean seed. The growth process of the root of a red bean after germination was statistically investigated for a total of 2000 seeds whose average root growth dynamics was well described by a simple logistic equation. Strong biophoton emission was observed at two inflection points of the logistic curve. Namely, when maximum acceleration of the root growth occurred, maximum biophoton emission was observed.
Kai, Shoichi; Mitani, Tomohiko; Fujikawa, Masahiro
Anomalous Biophoton Emission during Germination Process of Red Bean
Spontaneous biophoton emission was investigated for the germination and the growth process of a red bean seed. The growth process of the root of a red bean after germination was statistically investigated for a total of 2000 seeds whose average root growth dynamics was well described by a simple logistic equation. Strong biophoton emission was observed at two inflection points
Shoichi Kai; Tomohiko Mitani; Masahiro Fujikawa
Flutter effect and emission in the region of anomalous and normal doppler effects
This paper investigates the excitation (flutter) of a membrane in the flow of a liquid of finite depth due to the emission of long gravity waves. It is shown that loss of stability occurs due to predominance of emission of gravity waves of negative energy (anomalous Doppler effect) over waves of positive energy. Estimates of typical increments are presented; the instability develops during a period that approximately equals 1/7 sec.
Nemtsov, B.E.
Remote microwave technology for chamber clean to reduce PFC emissions
Applied Materials has developed a new chamber cleaning technology that has the potential to dramatically reduce PFC emissions from chamber cleaning on their D×ZTM platform. The prototype product, known as ?CleanTM, is a remote microwave clean using NF3 that can be retrofitted to a D×Z chamber. Recent tests of ?Clean technology conducted by Air Products and Chemicals, Inc. at Applied
L. Mendicino; S. Filipiak; P. T. Brown; J. Langan; R. Ridgeway; A. Johnson; R. Pearce; P. Maroulis; A. Atherton
Microwave emission of large and small orbit rectangular gyrotron devices
NASA Astrophysics Data System (ADS)
Experiments were conducted on rectangular cross section (RCS) gyrotron devices. Rectangular interaction cavities with both small orbit and large orbit axis encircling electron beams were used in gyrotron mechanisms to generate high power microwaves. The Michigan Electron Long Beam Accelerator (MELBA) produced an annular electron beam with e-beam parameters: V = -0.7 to -1.0 MV, Isb{diode} = 1-10 kA, Isb{tube} = 0.1-3 kA, e-beam pulse length = 0.4-1.0 muS. The small orbit e-beam was spun up into an axis encircling e-beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. The issues under investigation included polarization control of the microwave emission as a function of the interaction cavity magnetic field, microwave power as a function of pulse length, and mode competition. Along with microwave power measurements, frequency analysis was conducted with the use of a heterodyne mixer. Measurements of the optical emission of plasma in the RCS interaction cavity beam dump have also been completed. Experimental results in the small orbit gyrotron demonstrated powers of up to 23 MW in the horizontal polarization with little power measured in the vertical fundamental mode, and hence, polarization control was not obtained. Pulse shortening was observed in the small orbit gyrotron and power efficiency was typically less than 1%. The large orbit gyrotron, operating at a lower current, produced much more successful results. Powers as high as 14 MW were measured in the fundamental TEsb{101} mode at a frequency of 2.18 GHz, and 11 MW in the horizontally polarized TEsb{011} mode at 2.85 GHz. The results showed a high degree of polarization(P(TEsb{101})/P(TEsb{011}) = 1000 or as low as 1/30) as a function of cavity B-fields. The megawatt microwave output shifts from the fundamental TEsb{101} mode to the TEsb{011} mode as the B-field is raised from 1.5 to 1.9 kG. Efficiencies in the large orbit gyrotron were found to be as high as 8%. MAGIC code simulations predicted the ability to shift the linearly polarized output from the fundamental TEsb{10} mode to the orthogonally polarized TEsb{01} mode. The highest power microwave pulses were on the order of 100 ns and demonstrated pulse shortening. Optical emission spectroscopy demonstrated the formation of hydrogen plasma in the cavity or output waveguide; these results imply that microwave pulse shortening could be due to this plasma produced by the e-beam dumping against the output waveguide walls.
Hochman, Jonathan Mark
Anomalous decay of the slow component of Pb2+ emission
A theoretical model is introduced for the experimentally observed nonexponential slow-component decay of Pb2+ ions in potassium halide crystal hosts. It is based on the assumption that the adiabatic approximation is violated for the slow emission process. The Hamiltonian of the model describes the lowest excited state of the system as two energy levels resulting from the Jahn-Teller effect and
B. Gaveau; E. Mihóková; M. Nikl; K. Polák; L. S. Schulman
High-Energy Gamma-Ray Emission from Anomalous X-Ray Pulsars
We study the high-energy gamma-ray radiation from the outer magnetospheres of the anomalous X-ray pulsars. For pulsars with superstrong magnetic fields (B>1014 G), the magnetic field in the region far away from the neutron star surface drops below the quantum critical value, and high-energy gamma-ray emission can be emitted. The electrons\\/positrons produced by collisions between high-energy photons from the outer
K. S. Cheng; L. Zhang
We report on the Ka-band (26-40 GHz) emission properties for 10 star-forming regions in the nearby galaxy NGC 6946. From a radio spectral decomposition, we find that the 33 GHz flux densities are typically dominated by thermal (free-free) radiation. However, we also detect excess Ka-band emission for an outer-disk star-forming region relative to what is expected given existing radio, submillimeter, and infrared data. Among the 10 targeted regions, measurable excess emission at 33 GHz is detected for half of them, but in only one region is the excess found to be statistically significant ({approx}7{sigma}). We interpret this as the first likely detection of so-called 'anomalous' dust emission outside of the Milky Way. We find that models explaining this feature as the result of dipole emission from rapidly rotating ultrasmall grains are able to reproduce the observations for reasonable interstellar medium conditions. While these results suggest that the use of Ka-band data as a measure of star formation activity in external galaxies may be complicated by the presence of anomalous dust, it is unclear how significant a factor this will be for globally integrated measurements as the excess emission accounts for {approx}<10% of the total Ka-band flux density from all 10 regions.
Murphy, E. J.; Chary, R.-R.; Armus, L. [Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125 (United States); Helou, G. [California Institute of Technology, MC 314-6, Pasadena, CA 91125 (United States); Condon, J. J.; Mason, B. S. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Schinnerer, E. [Max Planck Institut fuer Astronomie, Koenigstuhl 17, Heidelberg D-69117 (Germany); Turner, J. L. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States); Beck, R. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel, Bonn (Germany)], E-mail: email@example.com
Physical Foundations of Plasma Microwave Sources Based on Anomalous Doppler Effect.
National Technical Information Service (NTIS)
This project is concerned microwave relativistic plasma electronics, dealing with problems of converting the energy of intense electron beams into high power coherent electromagnetic radiation. This is one of the main topics of AFOSR's interests on basic ...
E. V. Rostomyan
Quantifying Uncertainties in Land Surface Microwave Emissivity Retrievals
NASA Technical Reports Server (NTRS)
Uncertainties in the retrievals of microwave land surface emissivities were quantified over two types of land surfaces: desert and tropical rainforest. Retrievals from satellite-based microwave imagers, including SSM/I, TMI and AMSR-E, were studied. Our results show that there are considerable differences between the retrievals from different sensors and from different groups over these two land surface types. In addition, the mean emissivity values show different spectral behavior across the frequencies. With the true emissivity assumed largely constant over both of the two sites throughout the study period, the differences are largely attributed to the systematic and random errors in the retrievals. Generally these retrievals tend to agree better at lower frequencies than at higher ones, with systematic differences ranging 14% (312 K) over desert and 17% (320 K) over rainforest. The random errors within each retrieval dataset are in the range of 0.52% (26 K). In particular, at 85.0/89.0 GHz, there are very large differences between the different retrieval datasets, and within each retrieval dataset itself. Further investigation reveals that these differences are mostly likely caused by rain/cloud contamination, which can lead to random errors up to 1017 K under the most severe conditions.
Tian, Yudong; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Prigent, Catherine; Norouzi, Hamidreza; Aires, Filipe; Boukabara, Sid-Ahmed; Furuzawa, Fumie A.; Masunaga, Hirohiko
Subsurface Emission Effects in AMSR-E Measurements: Implications for Land Surface Microwave Emissivity Retrieval
NASA Technical Reports Server (NTRS)
An analysis of land surface microwave emission time series shows that the characteristic diurnal signature associated with subsurface emission in sandy deserts carry over to arid and semi-arid region worldwide. Prior work found that diurnal variation of Special Sensor Microwave/Imager (SSM/I) brightness temperatures in deserts was small relative to International Satellite Cloud Climatology Project land surface temperature (LST) variation and that the difference varied with surface type and was largest in sand sea regions. Here we find more widespread subsurface emission effects in Advanced Microwave Scanning Radiometer-EOS (AMSR-E) measurements. The AMSR-E orbit has equator crossing times near 01:30 and 13 :30 local time, resulting in sampling when near-surface temperature gradients are likely to be large and amplifying the influence of emission depth on effective emitting temperature relative to other factors. AMSR-E measurements are also temporally coincident with Moderate Resolution Imaging Spectroradiometer (MODIS) LST measurements, eliminating time lag as a source of LST uncertainty and reducing LST errors due to undetected clouds. This paper presents monthly global emissivity and emission depth index retrievals for 2003 at 11, 19, 37, and 89 GHz from AMSR-E, MODIS, and SSM/I time series data. Retrieval model fit error, stability, self-consistency, and land surface modeling results provide evidence for the validity of the subsurface emission hypothesis and the retrieval approach. An analysis of emission depth index, emissivity, precipitation, and vegetation index seasonal trends in northern and southern Africa suggests that changes in the emission depth index may be tied to changes in land surface moisture and vegetation conditions
Galantowicz, John F.; Moncet, Jean-Luc; Liang, Pan; Lipton, Alan E.; Uymin, Gennady; Prigent, Catherine; Grassotti, Christopher
Effect of soil texture on the microwave emission from soils
NASA Technical Reports Server (NTRS)
The intensity brightness temperature of the microwave emission from the soil is determined primarily by its dielectric properties. The large difference between the dielectric constant of water and that of dry soil produces a strong dependence of the soil's dielectric constant on its moisture content. This dependence is effected by the texture of the soil because the water molecules close to the particle surface are tightly bound and do not contribute significantly to the dielectric properties. Since this surface area is a function of the particle size distribution (soil texture), being larger for clay soils with small particles, and smaller for sandy soils with larger particles; the dielectric properties will depend on soil texture. Laboratory measurements of the dielectric constant for soils are summarized. The dependence of the microwave emission on texture is demonstrated by measurements of brightness temperature from an aircraft platform for a wide range of soil textures. It is concluded that the effect of soil texture differences on the observed values can be normalized by expressing the soil moisture values as a percent field capacity for the soil.
Schmugge, T. J.
First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission
NASA Technical Reports Server (NTRS)
The WMAP mission has mapped the full sky to determine the geometry, content, and evolution of the universe. Full sky maps are made in five microwave frequency bands to separate the temperature anisotropy of the cosmic microwave background (CMB) from foreground emission, including diffuse Galactic emission and Galactic and extragalactic point sources. We define masks that excise regions of high foreground emission, so CMB analyses can became out with minimal foreground contamination. We also present maps and spectra of the individual emission components, leading to an improved understanding of Galactic astrophysical processes. The effectiveness of template fits to remove foreground emission from the WMAP data is also examined. These efforts result in a CMB map with minimal contamination and a demonstration that the WMAP CMB power spectrum is insensitive to residual foreground emission. We use a Maximum Entropy Method to construct a model of the Galactic emission components. The observed total Galactic emission matches the model to less than 1% and the individual model components are accurate to a few percent. We find that the Milky Way resembles other normal spiral galaxies between 408 MHz and 23 GHz, with a synchrotron spectral index that is flattest (beta(sub s) approx. -2.5) near star-forming regions, especially in the plane, and steepest (beta(sub s) approx. -3) in the halo. This is consistent with a picture of relativistic cosmic ray electron generation in star-forming regions and diffusion and convection within the plane. The significant synchrotron index steepening out of the plane suggests a diffusion process in which the halo electrons are trapped in the Galactic potential long enough to suffer synchrotron and inverse Compton energy losses and hence a spectral steepening. The synchrotron index is steeper in the WMAP bands than in lower frequency radio surveys, with a spectral break near 20 GHz to beta(sub s) less than -3. The modeled thermal dust spectral index is also steep in the WMAP bands, with beta(sub d) approx. = 2.2. Our model is driven to these conclusions by the low level of total foreground contamination at approx. 60 GHz. Microwave and Ha measurements of the ionized gas agree well with one another at about the expected levels. Spinning dust emission is limited to less than 5% of the Ka-band foreground emission. A catalog of 208 point sources is presented. The reliability of the catalog is 98%, i.e., we expect five of the 208 sources to be statistically spurious. The mean spectral index of the point sources is alpha approx. 0(beta approx. -2). Derived source counts suggest a contribution to the anisotropy power from unresolved sources of (15.0 +/- 1.4) x 10(exp -3)micro sq K sr at Q-band and negligible levels at V-band and W-band. The Sunyaev-Zeldovich effect is shown to be a negligible "contamination" to the maps.
Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Nolta, M. R.; Odegard, N.; Page, L.; Spergel, D. N.; Weiland, J. L.; Wright, E. L.; Halpern, M.
Delayed luminescence from ZnO ceramics upon microwave-induced plasma emission
NASA Astrophysics Data System (ADS)
A delayed luminescence from the ZnO ceramics upon microwave-induced plasma emission was observed and its hybridized excitation mechanism was investigated. A phenomenological model of the luminescence is proposed to explain the occurrence of the hybrid excitation process and confirmed that the hybridization is by the photon of luminescence through atomic plasma emission and by the microwave depending on its power. This finding provides a distinctive methodology for studying the physics of the interaction between microwave and matter.
Sonobe, Taro; Hachiya, Kan; Mitani, Tomohiko; Shinohara, Naoki; Ohgaki, Hideaki
Anomalous Emissions of Sulfur Dioxide and Seismicity of San Miguel Volcano, EL Salvador in October, 2006
NASA Astrophysics Data System (ADS)
San Miguel (also known as Chaparrastique) volcano in eastern El Salvador is located 15 km southwest of the city of San Miguel. This volcano has erupted more than 30 times since 1699, with the last gas and ash emission on January 16, 2002. During 2006, San Miguel presented anomalous gas emissions and seismicity. In this work, the seismic parameters reported by SNET (Servicio Nacional de Estudios Territoriales de El Salvador) and the crater gas emissions measured by researchers of the University of El Salvador are compared. For the gas efflux, two types of measurements were done using the Mini-DOAS system (Galle et al., 2002): transects around the crater perimeter (~100 m) and transects following roads located between 5 and 10 km from the crater. Several measurements between October 2005 and May 2006 indicate that the sulfur dioxide efflux during quiet periods is around 20 ton/day. From May to June 2006, a progressive increase in fumarolic activity and noise from gas emissions were observed. From May to August 2006, the sulfur dioxide emissions increased to 60 ton/day. A seismic crisis started on October 9, 2006, increasing the RSAM from 10-20 to 208 on October 10, 2006. During this time, the sulfur dioxide efflux reached a maximum of 492 ton/day. This increase in sulfur dioxide efflux represents 25 times the basic emissions during the previous quiet period and 8 times the values observed from May to August 2006. The correlation coefficient between sulfur dioxide efflux and RSAM values during this period of time was 0.81, which is statistically significant at a level higher than 99.9% . These anomalous changes in seismicity and sulfur dioxide emissions at San Miguel volcano suggest a magmatic reactivation with an increase in the exsolution of magma volatiles, long period seismic events, and volcanic tremor.
Olmos, R.; Barahona, F.; Hernández, A.; Cartagena, R.; Henríquez, B.; López, D.; Cárdenas, C.; Galle, B.
Real-time calibrated microwave plasma mulitmetals emissions monitor
NASA Astrophysics Data System (ADS)
Real-time calibrated atomic emission spectroscopy in stack exhaust using a continuously sustained microwave plasma is under development for trace metals monitoring. The plasma, in a shorted waveguide attached to the stack by a short sample line, is powered at 1.5 kW, 2.45 GHz. An undiluted stack slipstream is isokinetically directed into the plasma at a nominal flow of 14 liters per minute. A pneumatic nebulizer attached to the sample line can momentarily, on command, inject a known concentration of metals solution providing a real-time calibration. Recent testing has been performed on the exhaust stack of an incinerator at the Environmental Protection Agency (EPA) National Risk Management Laboratory in Research Triangle Park. Three hazardous metals were monitored, lead, chromium, and beryllium. These measurements were referenced to EPA Method-29. A total of twenty spiked stack exhaust tests were carried out. Ten one-hour tests at high concentration (40 - 60 (mu) g/actual m3) and ten one and half-hour tests at low concentration (10 - 15 (mu) g/actual m3). The microwave plasma monitor achieved measurement accuracies of approximately 20% for lead and beryllium and 40% for chromium with a threshold detection capability of less than 3 (mu) g/actual m3 for a time response of approximately 1-minute. Laboratory work is continuing to add mercury, arsenic, and cadmium to the monitored metals.
Woskov, Paul P.; Hadidi, Kamal; Thomas, Paul; Green, Karyn; Flores, Guadalupe
Pulsations of microwave flaring emission at low and high frequencies
NASA Astrophysics Data System (ADS)
A wavelet analysis of the flare-intensity variations has been carried out for a solar flare observed with the Nobeyama Radioheliograph at 17 and 34 GHz and the spectrometer of Purple Mountain Observatory at 4.5-7.5 GHz. The signals contain a well-pronounced periodicity with a period of P = 14-17 s and stable, coherent behavior at frequencies higher and lower than the peak frequency. We simulated the modulation of the gyrosynchrotron emission by fast sausage magnetoacoustic oscillations for the cases of low and high plasma density in the radio source. The synchronism of the pulsations at high and low frequencies can be realized only in the case of high plasma density, when the low-frequency turnover of the microwave spectrum is due to the Razin effect, not self-absorption.
Reznikova, V. E.; Melnikov, V. F.; Su, Y.; Huang, G.
Can Charge Exchange Explain Anomalous Soft X-Ray Emission in the Cygnus Loop?
NASA Astrophysics Data System (ADS)
Recent X-ray studies have shown that supernova shock models are unable to satisfactorily explain X-ray emission in the rim of the Cygnus Loop. In an attempt to account for this "anomalously" enhanced X-ray flux, we fit the region with a model including theoretical charge exchange (CX) data along with shock and background X-ray models. The model includes the CX collisions of O8 +, O7 +, N7 +, N6 +, C6 +, and C5 + with H with an energy of 1 keV u-1 (438 km s-1). The observations reveal a strong emission feature near 0.7 keV that cannot fully be accounted for by a shock model, nor the current CX data. Inclusion of CX, specifically O7 + + H, does provide for a statistically significant improvement over a pure shock model.
Cumbee, R. S.; Henley, D. B.; Stancil, P. C.; Shelton, R. L.; Nolte, J. L.; Wu, Y.; Schultz, D. R.
Frequency and angular variations of land surface microwave emissivities: can we estimate SSM\\/T and AMSU emissivities from SSM\\/I emissivities?
To retrieve temperature and humidity profiles from special sensor microwave\\/temperature (SSM\\/T) and advanced microwave sounding units (AMSU), it is important to quantify the contribution of the Earth surface emission. So far, no global estimates of the land surface emissivities are available at SSM\\/T and AMSU frequencies and scanning conditions. The land surface emissivities have been previously calculated for the globe
Catherine Prigent; Jean-Pierre Wigneron; William B. Rossow; Juan R. Pardo-Carrion
Planck intermediate results. XVII. Emission of dust in the diffuse interstellar medium from the far-infrared to microwave frequencies
NASA Astrophysics Data System (ADS)
The dust-Hi correlation is used to characterize the emission properties of dust in the diffuse interstellar medium (ISM) from far infrared wavelengths to microwave frequencies. The field of this investigation encompasses the part of the southern sky best suited to study the cosmic infrared and microwave backgrounds. We cross-correlate sky maps from Planck, the Wilkinson Microwave Anisotropy Probe (WMAP), and the diffuse infrared background experiment (DIRBE), at 17 frequencies from 23 to 3000 GHz, with the Parkes survey of the 21 cm line emission of neutral atomic hydrogen, over a contiguous area of 7500 deg2 centred on the southern Galactic pole. We present a general methodology to study the dust-Hi correlation over the sky, including simulations to quantify uncertainties. Our analysis yields four specific results. (1) We map the temperature, submillimetre emissivity, and opacity of the dust per H-atom. The dust temperature is observed to be anti-correlated with the dust emissivity and opacity. We interpret this result as evidence of dust evolution within the diffuse ISM. The mean dust opacity is measured to be (7.1 ± 0.6) × 10-27 cm2 H-1 × (?/ 353 GHz)1.53 ± 0.03 for 100 ? ? ? 353 GHz. This is a reference value to estimate hydrogen column densities from dust emission at submillimetre and millimetre wavelengths. (2) We map the spectral index ?mm of dust emission at millimetre wavelengths (defined here as ? ? 353 GHz), and find it to be remarkably constant at ?mm = 1.51 ± 0.13. We compare it with the far infrared spectral index ?FIR derived from greybody fits at higher frequencies, and find a systematic difference, ?mm - ?FIR = - 0.15, which suggests that the dust spectral energy distribution (SED) flattens at ? ? 353 GHz. (3) We present spectral fits of the microwave emission correlated with Hi from 23 to 353 GHz, which separate dust and anomalous microwave emission (AME). We show that the flattening of the dust SED can be accounted for with an additional component with a blackbody spectrum. This additional component, which accounts for (26 ± 6)% of the dust emission at 100 GHz, could represent magnetic dipole emission. Alternatively, it could account for an increasing contribution of carbon dust, or a flattening of the emissivity of amorphous silicates, at millimetre wavelengths. These interpretations make different predictions for the dust polarization SED. (4) We analyse the residuals of the dust-Hi correlation. We identify a Galactic contribution to these residuals, which we model with variations of the dust emissivity on angular scales smaller than that of our correlation analysis. This model of the residuals is used to quantify uncertainties of the CIB power spectrum in a companion Planck paper. Appendices are available in electronic form at http://www.aanda.org
Anomalous features in the photo-emission spectrum of heavy- fermion semiconductors
NASA Astrophysics Data System (ADS)
The heavy-fermion semiconductors have a low-temperature insulating state that is characterized by an anomalously small energy gap, varying between 10 and 100 K. The small gap is a many-body renormalized hybridization gap. The dispersion and temperature dependence of the electronic spectral density of states is calculated, using the large Uff limit of the N-fold degenerate Anderson lattice model at half-filling, together with a slave boson 1/ N expansion. The effect of emission and absorption of the slave boson fluctuations is to produce a dispersive asymmetric f 0 peak, and a thermally activated broadening of the f quasi-particle peak in A( k,?) . As the temperature is reduced the structure in the vicinity of the Fermi-energy sharpens up. The theory is compared to experiments on the materials FeSi and Ce 3Bi 4Pt 3.
Riseborough, Peter S.
An SSM/I radiometer simulator for studies of microwave emission from soil. [Special Sensor Microwave/Imager
NASA Technical Reports Server (NTRS)
A ground-based simulator of the defense meterological satellite program special sensor microwave/imager (DMSP SSM/I) is described, and its integration with micrometeorological instrumentation for an investigation of microwave emission from moist and frozen soils is discussed. The simulator consists of three single polarization radiometers which are capable of both Dicke radiometer and total power radiometer modes of operation. The radiometers are designed for untended operation through a local computer and a daily telephone link to a laboratory. The functional characteristics of the radiometers are described, together with their field deployment configuration and an example of performance parameters.
Galantowicz, J. F.; England, A. W.
Characterization of Different Land Classes and Disaster Monitoring Using Microwave Land Emissivity for the Indian Subcontinent
NASA Astrophysics Data System (ADS)
Despite the ability of satellite borne microwave radiometers to measure the atmospheric pa-rameters, liquid water and the microphysical properties of clouds, they have serious limitations over the land owing its large and spatially heterogeneous emissivity compared to the relatively low and homogenous oceans. This calls for determination of the spatial maps of land-surface emissivity with accuracies better than ˜2%. In this study, the characterization of microwave emissivity of different land surface classes over the Indian region is carried out with the forth-coming Indo-French microwave satellite program Megha-Tropiques in focus. The land emissivity is retrieved using satellite microwave radiometer data from Special Sensor Microwave/Imager (SSM/I) and TRMM Microwave Imager (TMI) at 10, 19, 22, 37 and 85 GHz. After identify-ing the clear sky daily data, the microwave radiative transfer computation, is applied to the respective daily atmospheric profile for deducing the upwelling and downwelling atmospheric radiations. This, along with the skin temperature data, is used to retrieve land emission from satellites data. The emissivity maps of placecountry-regionIndia for three months representing winter (January) and post-monsoon (September-October) seasons of 2008 at V and H polar-izations of all the channels (except for 22 GHz) are generated. Though the land emissivity values in V-polarization vary between 0.5 and ˜1, some land surface classes such as the desert region, marshy land, fresh snow covered region and evergreen forest region, etc, show distinct emissivity characteristics. On this basis few typical classes having uniform physical properties over sufficient area are identified. Usually the Indian desert region is dry and shows low emis-sivity (˜0.88 in H-polarisation) and high polarization difference, V-H (˜0.1). Densely vegetated zones of tropical rain forests exhibit high emissivity values (˜0.95) and low polarization dif-ference (lt;0.01). The mangrove forest region and marshy areas exhibit very low emissivities (˜0.8) with very high polarization difference (˜0.2). The usefulness of microwave emissivity to identify and quantify natural disasters such as the inundated regions in the vast Ganga basin during the severe floods in 2008 over country-regionIndia and placecountry-regionBangladesh is also demonstrated as a case study Keywords: Land surface emissivity, Microwave Remote sensing, Megha-Tropiques, Disaster monitoring *corresponding author: email@example.com
Saha, Korak; Raju, Suresh; Antony, Tinu; Krishna Moorthy, K.
Application of microwave energy in the control of DPM, oxides of nitrogen and VOC emissions
NASA Astrophysics Data System (ADS)
The emissions of DPM (diesel particulate matter), NOx (oxides of nitrogen), and toxic VOCs (volatile organic compounds) from diesel engine exhaust gases and other sources such as chemical process industry and manufacturing industry have been a great environmental and health concern. Most control technologies for these emissions require elevated temperatures. The use of microwave energy as a source of heat energy, however, has not been fully explored. In this study, the microwave energy was used as the energy source in three separate emission control processes, namely, the regeneration of diesel particulate filter (DPF) for DPM control, the NOx reduction using a platinum catalyst, and the VOC destruction involving a ceramic based material. The study has demonstrated that microwave heating is an effective method in providing heat for the studied processes. The control efficiencies associated with the microwave-assisted processes have been observed to be high and acceptable. Further research, however, is required for the commercial use of these technologies.
Pallavkar, Sameer M.
Microwave emission in a plasma filled nonuniform backward wave oscillator
High power microwave radiation is used in science, industry, and by the military for a variety of purposes including the acceleration of particles in high energy physics, heating of plasma particles, radiation treatment of surfaces in manufacturing, and for electronic warfare in the military. Among the many sources of high power microwaves, the backward wave oscillator (BWO) is one of
Douglas Talmadge Young
Massive Star Formation, Outflows, and Anomalous H2 Emission in Mol 121 (IRAS 20188+3928)
NASA Astrophysics Data System (ADS)
We have discovered 12 new molecular hydrogen emission-line objects (MHOs) in the vicinity of the candidate massive young stellar object Mol 121, in addition to five that were previously known. H2 2.12-?m/H2 2.25-?m flux ratios indicate another region dominated by fluorescence from a photo-dissociation region (PDR), and one region that displays an anomalously low H2 2.12-?m/H2 2.25-?m flux ratio (<1) and coincides with a previously reported deeply embedded source (DES). Continuum observations at 3 mm reveal five dense cores; the brightest core is coincident with the DES. The next brightest cores are both associated with cm continuum emission. One of these is coincident with the IRAS source; the other lies at the centroid of a compact outflow defined by bipolar MHOs. The brighter of these bipolar MHOs exhibits [Fe II] emission and both MHOs are associated with CH3OH maser emission observed at 95 GHz and 44 GHz. Masses and column densities of all five cores are consistent with theoretical predictions for massive star formation. Although it is impossible to associate all MHOs with driving sources in this region, it is evident that there are several outflows along different position angles, and some unambiguous associations can be made. We discuss implications of observed H2 2.12-?m/H2 2.25-?m and [Fe II] 1.64-?m/H2 2.12-?m flux ratios and compare the estimated total H2 luminosity with the bolometric luminosity of the region. We conclude that the outflows are driven by massive young stellar objects embedded in cores that are likely to be in different evolutionary stages. Submitted to ApJ.
Wolf-Chase, Grace A.; Arvidsson, K.; Smutko, M.; Sherman, R.
Massive Star Formation, Outflows, and Anomalous H2 Emission in Mol 121 (IRAS 20188+3928)
NASA Astrophysics Data System (ADS)
We have discovered 12 new molecular hydrogen emission-line objects (MHOs) in the vicinity of the candidate massive young stellar object Mol 121, in addition to five that were previously known. H2 2.12 ?m/H2 2.25 ?m flux ratios indicate another region dominated by fluorescence from a photodissociation region, and one region that displays an anomalously low H2 2.12 ?m/H2 2.25 ?m flux ratio (<1) and coincides with a previously reported deeply embedded source (DES). Continuum observations at 3 mm reveal five dense cores; the brightest core is coincident with the DES. The next brightest cores are both associated with centimeter continuum emission. One of these is coincident with the IRAS source; the other lies at the centroid of a compact outflow defined by bipolar MHOs. The brighter of these bipolar MHOs exhibits [Fe II] emission and both MHOs are associated with CH3OH maser emission observed at 95 GHz and 44 GHz. Masses and column densities of all five cores are consistent with theoretical predictions for massive star formation. Although it is impossible to associate all MHOs with driving sources in this region, it is evident that there are several outflows along different position angles, and some unambiguous associations can be made. We discuss implications of observed H2 2.12 ?m/H2 2.25 ?m and [Fe II] 1.64 ?m/H2 2.12 ?m flux ratios and compare the estimated total H2 luminosity with the bolometric luminosity of the region. We conclude that the outflows are driven by massive young stellar objects embedded in cores that are likely to be in different evolutionary stages.
Wolf-Chase, Grace; Arvidsson, Kim; Smutko, Michael; Sherman, Reid
Interstellar dust thermal emission at millimeter and microwave wavelengths
NASA Astrophysics Data System (ADS)
Interstellar dust grains are particles of size between a few to hundreds of nanometers, mostly made up of carbon and silicon, found in the vast space between stars within a galaxy. They are important because dust plays a major role in cycling matter and energy between stars and the interstellar medium. Models for interstellar dust thermal emission are fit to a set of 214-channel dust spectra at 60--3000 GHz. Data consist of a new and improved version of dust spectra derived from the measurements of the Far Infrared Absolute Spectrophotometer of the COsmic Background Explorer satellite, sky maps at 100 mum, 140 mum and 240 mum measured by the Diffuse Infrared Background Experiment, also onboard the CUBE satellite, and the 94 GHz dust map measured by the Wilkinson Microwave Anisotropy Probe satellite. A single-component model with its emissivity spectral index fixed at 1.7 is the best among all dust models tested. It fits 88% of the sky with a chi2dof ? 1.13 at 210 degrees of freedom. Within this sky region, temperatures of the dust grains are predicted to be between 16.4 K and 25.1 K, and optical depths are between 1.3 x 10 -6 and 5.1 x 10-4. The uncertainties of the dust temperature are < 10%, while the uncertainties of the optical depth are < 63%. In comparison with the two-component alpha1,2 = 2.0 dust model by Reach et al. (1995b) and the Finkbeiner, Davis & Schlegel (1999, FDS) Model #8, the alpha = 1.7 model is shown to be better able to trace out dust spectral variations over the entire FIRAS frequency coverage in sky regions where these two models are valid. Currently, uncertainties of the best-fit parameters are limited by FIRAS angular resolution and noise, and the angular resolution of the model inherits that of the FIRAS. When data of better quality become available, such as from the Planck mission, this one-component alpha = 1.7 (deltaTdust/ Tdust ? 10%) model can be used to check future dust models.
Liang, Zhuohan
Theory for microwave thermal emission from a layer of cloud or rain
Microwave thermal emission from a layer of cloud or rain consisting of spherical particles has been investigated. Scattering effects are studied in great detail with both numerical and analytical approaches. In the absence of ground emission, it is found that scattering induces brightening for optically thin layers and vice versa for optically thick layers. As a function of observation angle
Leung Tsang; J. Kong; E. Njoku; D. Staelin; J. Waters
Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity.
National Technical Information Service (NTIS)
Foam fraction can be retrieved from space-based microwave radiometric data at frequencies from 1 to 37 GHz. The retrievals require modeling of ocean surface emissivity fully covered with sea foam. To model foam emissivity well, knowledge of foam propertie...
M. D. Anguelova P. W. Gaiser
Field Emission Studies for Microwave and Optical Wave Generation.
National Technical Information Service (NTIS)
We have proposed hybrid electronics based on solid-state and vacuum electron devices for an application to relatively high power and high efficiency active devices in microwave and optical wave regions. The new electronics provides a bunched electron beam...
D. Arslan H. Mimura K. Okamura K. Yokoo O. Yilmazoglu
A Microwave Induced Helium Plasma Emission Detector for Gas Chromatography.
National Technical Information Service (NTIS)
The suitability of the detector for analysis of carbon, fluorine, chlorine, phosphorus and sulfur compounds is investigated. The influence of variations in the microwave power, the helium gas flow, the discharge gas pressure and the observation zone of th...
A. Verweij
A Semi-Empirical Emissivity Model for use in Passive Microwave Precipitation Retrievals Over Land
NASA Astrophysics Data System (ADS)
The upcoming NASA Global Precipitation Measurement Mission (GPM) offers the opportunity for greatly increased understanding of global rainfall and the hydrologic cycle. The GPM algorithm team has made improvement in passive microwave remote sensing of precipitation over land a priority for this mission, and developed a framework allowing for algorithm advancement for individual land surface types as new techniques are developed. An accurate understanding of land surface emissivity in terms of associated surface properties is necessary for any physically-based retrieval scheme over land. This is a complex problem for passive microwave sensors, as the emissivity of land surfaces in the microwave region is large and dynamic, making it difficult to distinguish hydrometeor signal from the highly variable surface emission. In an effort to understand and model the surface emissivity, a semi-empirical technique is developed and tested over the US Southern Great Plains (SGP) area. A physical model is used to calculate emissivity at the 10 GHz frequency, combining contributions from the underlying soil as well as vegetation layers, including the dielectric and roughness effects of each medium. Radiative transfer through each layer is calculated. Adjustments are added for post-precipitation surface water emissivity effects on both the soil and water-coated vegetation. A 5-year dataset of retrieved emissivities from the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) is employed for calculation of a robust set of channel covariances. These covariances, combined with the modeled 10 GHz emissivities, provide emissivity values for each AMSR-E channel, which are then used to compute top of the atmosphere brightness temperatures (TBs). Initial results comparing these calculated TBs to observed values show correlations of 0.87-0.97, with the lowest correlations appearing in the highest frequencies of the microwave window region. Such a modeling system could be easily implemented for the emissivity calculation required for physical precipitation retrievals by GPM over similar land surfaces.
Ringerud, S.; Kummerow, C. D.; Peters-Lidard, C. D.
Satellite Data Analysis System for Searching Microwave Emission Associated with Earthquakes
NASA Astrophysics Data System (ADS)
Recently it was experimentally shown that rock crash by static pressure caused the microwave emission, and this result suggests the microwave would be emitted on the occasion of earthquakes. In order to verify this hypothesis, we have developed the computer system for analyzing the huge satellite database of Institute of Space and Astronautical Science (ISAS). The database includes the orbital parameters and the communication data of all satellites launched by ISAS. As a result, we have found out some anomalies in the data of the S-band (2GHz) microwave power level as for ASCA satellite by this system.
Maeda, Takashi; Takano, Tadashi; Inoue, Kozaburo; Kato, Teruo
Jet-shocked H2 and CO in the Anomalous Arms of Molecular Hydrogen Emission Galaxy NGC 4258
NASA Astrophysics Data System (ADS)
We present a Spitzer Infrared Spectrograph map of H2 emission from the nearby galaxy NGC 4258 (Messier 106). The H2 emission comes from 9.4 ± 0.4 × 106 M ? of warm molecular hydrogen heated to 240-1040 K in the inner anomalous arms, a signature of jet interaction with the galaxy disk. The spectrum is that of a molecular hydrogen emission galaxy (MOHEG), with a large ratio of H2 over 7.7 ?m polycyclic aromatic hydrocarbon emission (0.37), characteristic of shocked molecular gas. We find close spatial correspondence between the H2 and CO emission from the anomalous arms. Our estimate of cold molecular gas mass based on CO emission is 10 times greater than our estimate of 1.0 × 108 M ? based on dust emission. We suggest that the X CO value is 10 times lower than the Milky Way value because of high kinetic temperature and enhanced turbulence. The H2 disk has been overrun and is being shocked by the jet cocoon, and much of the gas originally in the disk has been ejected into the galaxy halo in an X-ray hot outflow. We measure a modest star formation rate of 0.08 M ? yr–1 in the central 3.4 kpc2 that is consistent with the remaining gas surface density.
Ogle, P. M.; Lanz, L.; Appleton, P. N.
Anomalous hydrogen emissions from the San Andreas fault observed at the Cienega Winery, central California
We began continuous monitoring of H2 concentration in soil along the San Andreas and Calaveras faults in central California in December 1980, using small H2/O2 fuel-cell sensors. Ten monitoring stations deployed to date have shown that anomalous H2 emissions take place occasionally in addition to diurnal changes. Among the ten sites, the Cienega Winery site has produced data that are characterized by very small diurnal changes, a stable baseline, and remarkably distinct spike-like H2 anomalies since its installation in July 1982. A major peak appeared on 1-10 November 1982, and another on 3 April 1983, and a medium peak on 1 November 1983. The occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site. In order to methodically assess how these peaks are related to earthquakes, three H2 degassing models were examined. A plausible correlational pattern was obtained by using a model that (1) adopts a hemicircular spreading pattern of H2 along an incipient fracture plane from the hypocenter of an earthquake, (2) relies on the FeO-H2O reaction for H2 generation, and (3) relates the accumulated amount of H2 to the mass of serpentinization of underlying ophiolitic rocks; the mass was tentatively assumed to be proportional to the seismic energy of the earthquake. ?? 1985 Birkha??user Verlag.
Sato, M.; Sutton, A. J.; McGee, K. A.
Dynamics of anomalous temperature-induced emission shift in MOCVD-grown (Al,In)GaN thin films
The authors present a comprehensive study of the optical characteristics of (Al, In)GaN epilayers measured by photoluminescence (PL), integrated PL intensity, and time-resolved PL spectroscopy. For not only InGaN, but also AlGaN epilayers with large Al content, they observed an anomalous PL temperature dependence: (i) an S-shaped PL peak energy shift (decrease-increase-decrease) and (ii) an inverted S-shaped full width at half maximum (FWHM) change (increase-decrease-increase) with increasing temperature. Based on time-resolved PL, the S shape (inverted S shape) of the PL peak position (FWHM) as a function of temperature, and the much smaller PL intensity decrease in the temperature range showing the anomalous emission behavior, the authors conclude that strong localization of carriers occurs in InGaN and even in AlGaN with rather high Al content. They observed that the following increase with increasing Al content in AlGaN epilayers: (i) a Stokes shift between the PL peak energy and the absorption edge, (ii) a redshift of the emission with decay time, (iii) the deviations of the PL peak energy, FWHM, and PL intensity from their typical temperature dependence, and (iv) the corresponding temperature range of the anomalous emission behavior. This indicates that the band-gap fluctuation responsible for these characteristics is due to energy tail states caused by non-random inhomogeneous alloy potential variations enhanced with increasing Al content.
Cho, Y.H.; Gainer, G.H.; Lam, J.B.; Song, J.J.; Yang, W.; Jhe, W.
Inter-Sensor Comparison of Microwave Land Surface Emissivity Products to Improve Precipitation Retrievals
NASA Astrophysics Data System (ADS)
Microwave land surface emissivity acts as the background signal to estimate rain rate, cloud liquid water, and total precipitable water. Therefore, its accuracy can directly affect the uncertainty of such measurements. Over land, unlike over oceans, the microwave emissivity is relatively high and and varies significantly as surface conditions and land cover change. Lack of ground truth measurement of microwave emissivity especially on global scale has made the uncertainty analysis of this parameter very challenging. The present study investigates the consistency among the existing global land emissivity estimates from different microwave sensors. The products are determined from various sensors and frequencies ranging from 7 to 90 GHz. The selected emissivity products in this study are from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) by NOAA - Cooperative remote Sensing and Science and Technology Center (CREST), the Special Sensor Microwave Imager (SSM/I) by The Centre National de la Recherche Scientifique (CNRS) in France, TRMM Microwave Imager (TMI) by Nagoya University, Japan, and WindSat by NASA Jet Propulsion Laboratory (JPL). The emissivity estimates are based on different algorithms and ancillary data sets. This work investigates the difference among these emissivity products from 2003 to 2008 dynamically and spectrally. The similarities and discrepancies of the retrievals are studied at different land cover types. The mean relative difference (MRD) and other statistical parameters are calculated temporally for all five years of the study. Some inherent discrepancies between the selected products can be attributed to the difference in geometry in terms of incident angle, spectral response, and the foot print size which can affect the estimations. The results reveal that in lower frequencies (=<19 GHz) ancillary data especially skin temperature data set is the major source of difference in emissivity retrievals, while in higher frequencies (>19 GHz) the residuals of atmospheric effect on the signal cause inconsistency among the products. The time series and correlation between emissivity maps were analyzed over different land classes to assess the consistency of emissivity variations with geophysical variable such as soil moisture, precipitation, and vegetation.
Norouzi, H.; Temimi, M.; Turk, J.; Prigent, C.; Furuzawa, F.; Tian, Y.
Polarized thermal microwave emission from oxygen in the mesosphere
The thermally emitted microwave spectrum of the terrestrial atmosphere, viewed from above, is calculated for frequencies in the vicinity of a Zeeman-split oxygen line. Previously omitted phase terms are included; their effect on brightness temperature can be as large as 1.5 K for linearly polarized measurements. For the purpose of using oxygen lines as a probe of the atmospheric temperature
P. W. Rosenkranz; D. H. Staelin
Reduction of Perfluorocompound Emissions by Microwave Plasma Torch
Surface cleanings are performed within a reduced pressure chamber by making use of perfluorocompounds (PFC) gases, which eventually contaminate the atmosphere. These contaminant gases are emitted with nitrogen gas, which is used for pump purges. In order to destruct all of the global warming gases including PFCs, we have developed a plasma abatement device, an electrodeless microwave plasma torch operated
Yong C. Hong; J. H. Kim; H. S. Uhm
Use of a characteristic time scale of microwave emission to determine accumulation variability in Antarctica
NASA Astrophysics Data System (ADS)
Relationship of the Passive Microwave Characteristic Time Scale of Emission to Accumulation Rate in Antarctica Authors: Lora S. Koenig1, Eric J. Steig1, Dale P. Winebrenner2 1) Department of Earth and Space Sciences, University of Washington 2) Applied Physics Laboratory, University of Washington Passive microwave sensors offer a potential tool for retrieving accumulation rates over the Greenland and Antarctic ice sheets. However, no retrieval method developed to date is reliable in both temporal and spatial domains. A new retrieval method is presented that shows considerable promise. The characteristic timescale of emission (? 0) is the ratio of the microwave extinction length in the firn, squared, to the firn thermal diffusivity. This characteristic time scale arises in a convolution expression that relates physical temperature to microwave brightness temperature, replacing the "emissivity" term in the traditional Rayleigh-Jeans approximation. ? 0 can be estimated for the entire Antarctic continent by comparing thermal infrared observations of physical surface temperature from the AVHRR satellite with passive microwave brightness temperatures at the 37 GHz vertically polarized channel measured by the Scanning Multichannel Microwave Radiometer (SMMR) and Special Senor Microwave Imager (SSM/I). Comparison between ? 0 and independent estimates of accumulation rate from radar-echo-sounding observations near Byrd Station Antarctica shows a strong linear relationship for accumulation rates over a broad range -- from 10 to 50 cm/year ice equivalent. Averaged over the 18 years of available data, ? 0 varies over this area from a few days to more than three months. Estimates of ? 0 over short time intervals of three years show patterns reminiscent of expected accumulation rate variability, and are of the correct magnitude to plausibly relate to temporal accumulation rate changes. Additional radar accumulation measurements from West Antarctica, which provide temporal as well as spatial estimates of accumulation over broad areas, are currently being compared with calculations of ? 0 to further examine the extent to which the observed spatial relationship holds in the temporal domain.
Koenig, L. S.; Steig, E. J.; Winebrenner, D. P.
Slurry sample introduction with microwave induced plasma atomic emission spectrometry
NASA Astrophysics Data System (ADS)
The successful direct introduction of aqueous slurry samples into a highly efficient TE 101 microwave plasma has been demonstrated. Slurry samples from a spray chamber are fed directly into the cavity with no desolvation apparatus. A V-groove, clog-free Babington-type nebulizer was evaluated for use with high solids content solutions. Slurry concentrations up to 10% m/v were used for the microwave induced plasma work with calibration by the standard additions method. Results are presented for the analysis of two NRCC Standard Reference Materials, i.e. TORT-1 (Lobster Hepatopancreas) and PACS-21 (Marine Sediment). Agreement between analytical results and certified values for the test elements Cd, Cu, Fe and Zn (in the range of 28-850 ?g/g) was good. No memory effects were evident and the nebulizer system had a rapid clean-out time.
Matusiewicz, Henryk; Sturgeon, Ralph E.
Nanophysics of Electron Emission and Breakdown for High Power Microwave Source.
National Technical Information Service (NTIS)
The primary objective of this MURI-funded consortium is to enable the realization of long-lived, low-maintenance, and reliable hard-vacuum high power microwave (HPM) device technologies by establishing new physical understanding of electron emission/absor...
J. H. Booske
Spectral Characteristics of the Microwave Emission From a Wind-Driven Foam-Covered Sea
Aircraft observations of the microwave emission from the Bering Sea show that the spectral character of brightness temperature variation with wind speed in a fully developed sea is due to a combination of surface roughness and a surface layer with varying dielectric constant over a physical depth of a few millimeters. The varying dielectric layer is identified with cusps formed
William J. Webster; Thomas T. Wilheit; Duncan B. Ross; Per Gloersen
Characterization of errors in a coupled snow hydrology-microwave emission model
Traditional approaches to the direct estimation of snow properties from passive microwave remote sensing have been plagued by limitations such as the tendency of estimates to saturate for moderately deep snowpacks and the effects of mixed land cover within remotely sensed pixels. An alternative approach is to assimilate satellite microwave emission observations directly, which requires embedding an accurate microwave emissions model into a hydrologic prediction scheme, as well as quantitative information of model and observation errors. In this study a coupled snow hydrology [Variable Infiltration Capacity (VIC)] and microwave emission [Dense Media Radiative Transfer (DMRT)] model are evaluated using multiscale brightness temperature (TB) measurements from the Cold Land Processes Experiment (CLPX). The ability of VIC to reproduce snowpack properties is shown with the use of snow pit measurements, while TB model predictions are evaluated through comparison with Ground-Based Microwave Radiometer (GBMR), air-craft [Polarimetric Scanning Radiometer (PSR)], and satellite [Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E)] TB measurements. Limitations of the model at the point scale were not as evident when comparing areal estimates. The coupled model was able to reproduce the TB spatial patterns observed by PSR in two of three sites. However, this was mostly due to the presence of relatively dense forest cover. An interesting result occurs when examining the spatial scaling behavior of the higher-resolution errors; the satellite-scale error is well approximated by the mode of the (spatial) histogram of errors at the smaller scale. In addition, TB prediction errors were almost invariant when aggregated to the satellite scale, while forest-cover fractions greater than 30% had a significant effect on TB predictions. ?? 2008 American Meteorological Society.
Andreadis, K. M.; Liang, D.; Tsang, L.; Lettenmaier, D. P.; Josberger, E. G.
Study on microwave emission mechanisms on the basis of hypervelocity impact experiments on various target plates
NASA Astrophysics Data System (ADS)
It was formerly confirmed by experiment that hypervelocity impacts on aluminum plates cause microwave emission. In this study, we have carried out experiments in order to clarify the mechanism of the emission. The microwave is detected by heterodyne detection scheme at 22 and 2 GHz with an intermediate frequency bandwidth of 500 and 120 MHz, respectively. A nylon projectile is accelerated using a light-gas gun to impact a target. First, aluminum plates with ten different thicknesses ranging from 1 to 40 mm were used as a target, and microwave signals were detected. The experimental results are statistically analyzed assuming a Gaussian distribution of the emitted power. The standard deviation of pulse voltage is calculated to show the existence of two kinds of signals: sharp pulse and thermal noise. It is shown that the emitted energy and the dispersion have a relation with the extent of the target destruction. Next, nylon projectiles are impacted on different metals such as aluminum, iron, and copper. These results suggest that microcracks are essential to microwave emission. Finally, in order to clarify the mechanism of charging and discharging across the microcracks, the experimental results are compared with this model for the following factors: (1) the thermally excited electrons and the emitted power, and (2) the bond dissociation energy of target material and emitted power. The analytical results suggest that electrons are excited thermally and by transition from a crystalline state to an atomic state.
Ohnishi, H.; Chiba, S.; Soma, E.; Ishii, K.; Maki, K.; Takano, T.; Hasegawa, S.
Microwave emission from the coronae of late-type dwarf stars
NASA Technical Reports Server (NTRS)
VLA microwave observations of 14 late-type dwarf and subgiant stars and binary systems are examined. In this extensive set of observations, four sources at 6 cm (Chi-1 Ori, UV Cet, YY Gem, and Wolf 630AB) were detected and low upper limits for the remaining stars were found. The microwave luminosities of the nondetected F-K dwarfs are as small as 0.01 those of the dMe stars. The detected emission is slowly variable in all cases and is consistent with gyroresonant emission from thermal electrons spiraling in magnetic fields of about 300 gauss if the source sizes are as large as R/R(asterisk) = 3-4. This would correspond to magnetic fields that are probably in the range 0.001-0.0001 gauss at the photospheric level. An alternative mechanism is gyrosynchrotron emission from a relatively small number of electrons with effective temperature.
Linsky, J. L.; Gary, D. E.
Rock fraction effects on the interpretation of microwave emission from soils
NASA Technical Reports Server (NTRS)
The effects of rock fraction on the relationship between microwave emission and surface soil moisture were investigated through a combination of laboratory dielectric measurements and field observation of emissivity. Field measurements were conducted which included soils with and without rocks. Microwave brightness temperature was measured at L and C band using a truck-mounted radiometer. Dielectric measurements were made at L band. Field observations of emissivity showed that the presence of rocks decreases the range of the measurements. At 21 cm this decrease was relatively small; however, at 6 cm almost all sensitivity to soil moisture was eliminated by the presence of 35 percent rocks. Comparisons between observed and predicted data showed that the effects of rock fraction are not significant in estimating the sample soil moisture for the tested conditions.
Jackson, Thomas J.; Kostov, Kosta; Saatchi, Sasan S.
Microwave H2O emission from young stars
NASA Technical Reports Server (NTRS)
H2O emission has been detected from the Ae or Be stars HD 250550, LkH-alpha 234, and LkH-alpha 198. Comparison of the H2O velocity with that of associated interstellar CO indicates that the H2O originates in an infall region, possibly the contracting parent cloud. H2O emission has also been detected in OH 205.1-14.1, and OH source near the T Tauri star LkH-alpha 308.
Schwartz, P. R.; Buhl, D.
Microwave emission in a plasma filled nonuniform backward wave oscillator
NASA Astrophysics Data System (ADS)
High power microwave radiation is used in science, industry, and by the military for a variety of purposes including the acceleration of particles in high energy physics, heating of plasma particles, radiation treatment of surfaces in manufacturing, and for electronic warfare in the military. Among the many sources of high power microwaves, the backward wave oscillator (BWO) is one of the oldest devices and has undergone a continuous effort to produce higher output power and better efficiency. Motivated by recent experimental observations of an improved efficiency in a BWO by either applying a nonuniform slow wave structure (SWS) or using a plasma filling in a BWO, this dissertation focuses on the combined effects both a nonuniform SWS and plasma filling. The particle-in-cell computer simulation conducted in this study revealed the mechanism of microwave generation through the interaction of an electron beam and slow wave structure, either uniform or nonuniform, with and without the presence of plasma. The first result the simulations is that the electrons within the plasma are quickly driven out of the device by the interaction with the electron beam, leaving the electron beam in the BWO flowing in an ionic background. This result is significant since all analytical treatments of plasma filled BWOs to date have assumed that the electron beam is interacting with the plasma to produce electron plasma waves that, in turn, interact and enhance the output power. From the simulations, this could not be the case, since the plasma electrons are nearly depleted from plasma by the time power production begins. The second major result of this work is that a plasma filled uniform BWO behaves differently than and a plasma filled nonuniform BWO. The uniform BWO does show a substantial power enhancement when filled with plasma, and the radiation frequency is upshifted from 9.75 GHz to 9.91 GHz when plasma is introduced. The power in the nonuniform BWO is also enhanced by the plasma, but not as much as in the uniform BWO. In addition, the nonuniform BWO shows very little frequency shifting with plasma filling.
Young, Douglas Talmadge
Spectral characteristics of the microwave emission from a wind-driven foam-covered sea
NASA Technical Reports Server (NTRS)
Aircraft observations of the microwave emission from the wind-driven foam-covered Bering Sea substantiate earlier results and show that the combination of surface roughness and white water yields a significant microwave brightness temperature dependence on wind speed over a wide range of microwave wavelengths, with a decreasing dependence for wavelengths above 6 cm. The spectral characteristic of brightness temperature as a function of wind speed is consistent with a foam model in which the bubbles give rise to a cusped surface between the foam and the sea. In the fetch-limited situation the contribution of the wave structure at the surface appears to increase as the foam coverage decreases. Although the data show that the thin streaks are the most important part of the white water signature, there is some evidence for the contribution of whitecaps.
Webster, W. J., Jr.; Wilheit, T. T.; Gloersen, P.; Ross, D. B.
Reduction of Perfluorocompound Emissions by Microwave Plasma Torch
NASA Astrophysics Data System (ADS)
Surface cleanings are performed within a reduced pressure chamber by making use of perfluorocompounds (PFC) gases, which eventually contaminate the atmosphere. These contaminant gases are emitted with nitrogen gas, which is used for pump purges. In order to destruct all of the global warming gases including PFCs, we have developed a plasma abatement device, an electrodeless microwave plasma torch operated at the atmosphere pressure. The plasma abatement device is attached to the vacuum pump, which discharges the nitrogen gas with contaminants. The abatement was carried out using oxygen and air as an additive gases. The destruction and removal efficiency (DRE) of more than 98was achieved for tetrafluoromethane(CF4). The detailed characterization of CF4 abatement using Fourier Transform Infrared (FT-IR) and Quadrupole Mass Spectrometer (QMS) showed the major PFC by-products. Finally, experimental results indicate that the plasma abatement device for PFC destruction can be successfully used to abate all of the global warming gases in the semiconductor industry.
Hong, Yong C.; Kim, J. H.; Uhm, H. S.
Microwave backscattering and emission model for grass canopies
NASA Technical Reports Server (NTRS)
A two-layer model is developed that treats the grass canopy as a collection of randomly oriented elliptical dielectric discs over a layer of thatch with underlying soil surface. The distorted Born approximation in conjunction with the Peake formulation is used to calculate the backscattering coefficient and the emissivity from the canopy. Two particular features of this model which are unique for grass canopies are the variation of the canopy structure and the presence of the thatch layer. The basic parameters in the model such as the size and orientation of grass blades, dielectric constant of soil and vegetation, and thickness and water content of the thatch layer have been obtained from ground truth data. To interpret the available experimental observations of grasslands, numerical results from both passive and active models at L-band (1.4 GHz) are generated and various scattering and emission properties of the grass canopies are discussed.
Saatchi, Sasan S.; Lang, Roger H.; Levine, David M.
Control of nitric oxide, nitrous oxide, and ammonia emissions using microwave plasmas
The subject of this paper is mitigation of the undesirable side-effects of selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR): ammonia slip, residual NOx, and N2O emissions. The use of microwave-plasma discharge within the flue gas was explored as a potential pollution-control method. The key issues addressed were: (1) N2O, NH3, and NO removal efficiencies; and (2) sustaining a
Marek A. Wójtowicz; Francis P. Miknis; R. W. Grimes; Wayne W. Smith; Michael A. Serio
Giant microwave bursts emitted from a field-emission, relativistic-electron-beam magnetron
A magnetron operating at a wavelength of 10 cm has been constructed with six resonant cavities cut in a cylindrical anode block. A graphite cylinder acting as a field-emission cathode delivers approx.12 kA in an accelerating radial potential of approx.360 kV. The magnetic field directed along the diode axis is approx.8 kG. Linearly polarized microwaves of 30 nsec duration at
G. Bekefi; T. J. Orzechowski
Simulation of electron emission from conformal boundaries for applications to high-power microwave sources
The finite difference time domain (FDTD) approach for electromagnetic particle-in-cell (EM-PIC) is a proven method for many problems involving interactions of charged particles with electromagnetic fields. Applying these methods to complex geometries that occur in high-power microwave (HPM) sources requires methods to accurately model fields and deal with particle emission and absorption at complex boundaries. We have recently developed conformal
Chet Nieter; David Smithe; Peter H. Stoltz; John R. Cary
Impact of Conifer Forest Litter on Microwave Emission at L-Band
NASA Technical Reports Server (NTRS)
This study reports on the utilization of microwave modeling, together with ground truth, and L-band (1.4-GHz) brightness temperatures to investigate the passive microwave characteristics of a conifer forest floor. The microwave data were acquired over a natural Virginia Pine forest in Maryland by a ground-based microwave active/passive instrument system in 2008/2009. Ground measurements of the tree biophysical parameters and forest floor characteristics were obtained during the field campaign. The test site consisted of medium-sized evergreen conifers with an average height of 12 m and average diameters at breast height of 12.6 cm. The site is a typical pine forest site in that there is a surface layer of loose debris/needles and an organic transition layer above the mineral soil. In an effort to characterize and model the impact of the surface litter layer, an experiment was conducted on a day with wet soil conditions, which involved removal of the surface litter layer from one half of the test site while keeping the other half undisturbed. The observations showed detectable decrease in emissivity for both polarizations after the surface litter layer was removed. A first-order radiative transfer model of the forest stands including the multilayer nature of the forest floor in conjunction with the ground truth data are used to compute forest emission. The model calculations reproduced the major features of the experimental data over the entire duration, which included the effects of surface litter and ground moisture content on overall emission. Both theory and experimental results confirm that the litter layer increases the observed canopy brightness temperature and obscure the soil emission.
Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Cosh, Michael H.; Joseph, Alicia T.; Jackson, Thomas J.
Rough-sea microwave emissivities measured with the SSM\\/I
The combination of sea surface roughness and whitewater causes a change in emissivity from an undisturbed sea surface. Previous measurements of this effect have covered the frequency range 1-37 GHz. The seven-channel SSM\\/I (Special Sensor Microwave\\/Imager) on the Block 5D-2 spacecraft extends this range to 85.5 GHz, at a fixed viewing angle of 53° from normal. To correct for atmospheric
P. W. Rosenkranz
Measurements of Microwave Emission from a Foam-Covered, Wind-Driven Sea
Measurements were made from aircraft of the 1.55-cm microwave emission from the North Sea and North Atlantic at surface wind speeds ranging from less than 5 to 25 m sec1. Brightness temperatures in the nadir direction increased almost linearly with wind speed from 7 to 25 m sec1 at a rate of about 1.2C (m sec1)1. At 70° from nadir
W. Nordberg; J. Conaway; Duncan B. Ross; T. Wilheit
Synthesis, field emission and microwave absorption of carbon nanotubes filled with ferromagnetic nanowires
Carbon nanotubes filled with ferromagnetic metal nanowires (M-CNTs) were synthesized by using chlorine-contained benzene (e.g.\\u000a trichlorobenzene) as precursor. The wall thicknesses of M-CNTs synthesized by trichlorobenzene are much thinner than those\\u000a by precursor without Cl (e.g. benzene). As-synthesized thin-walled M-CNTs exhibit remarkably enhanced field electron emission\\u000a performance with a low turn-on field of 0.3 V\\/?m and better field-emission stability. Microwave-absorption
RuiTao Lv; FeiYu Kang; JiaLin Gu; KunLin Wang; DeHai Wu
Anomalous Visible Emission Observed from the Rear Side of Laser-Irradiated Thin Transparent Targets.
National Technical Information Service (NTIS)
Visible emission measurements from the rear surface of laser-irradiated thin transparent target foils show a transient light flash followed by secondary light emission due to rear surface heating. This temporal signature is different from that reported in...
S. H. Gold E. A. McLean
Microwave Interstellar Medium Emission in the Green Bank Galactic Plane Survey: Evidence for Spinning Dust
NASA Astrophysics Data System (ADS)
We observe significant dust-correlated emission outside of H II regions in the Green Bank Galactic Plane Survey (-4degemission as majority constituents at 14 GHz, and the amplitude is at least 500 times higher than expected thermal dust emission. When combined with the Rhodes (2.326 GHz) and Wilkinson Microwave Anisotropy Probe (23-94 GHz) data, it is possible to fit dust-correlated emission at 2.3-94 GHz with only soft synchrotron, free-free, thermal dust, and an additional dust-correlated component similar to Draine & Lazarian spinning dust. The rising component generally dominates free-free and synchrotron for ?>~14 GHz and is overwhelmed by thermal dust at ?>~60 GHz. The current data fulfill most of the criteria laid out by Finkbeiner and coworkers for detection of spinning dust.
Finkbeiner, Douglas P.; Langston, Glen I.; Minter, Anthony H.
The anomalous 3.43 and 3.53 micron emission features toward HD 97048 and Elias 1 - C-C vibrational modes of polycyclic aromatic hydrocarbons?
NASA Technical Reports Server (NTRS)
The 5-8 micron spectra obtained toward the two protostellar sources, HD 97048 and Elias 1 exhibit strong anomalous emission features at 3.43 and 3.53 microns. Combining these results with earlier data established that the emission in the general IR features is extended on at least a 20-arcsec scale. In view of the high energy density in the emission zone, as well as the apparent correspondence of the anomalous 3.43 and 3.53 micron features with weak emission shoulders associated with the general family of IR emission bands, an explanation for these observations in terms of C-C overtones and combination tones of large or dehydrogenated polycyclic aromatic hydrocarbons is judged to be provisionally suitable.
Schutte, W. A.; Tielens, A. G. G. M.; Allamandola, L. J.; Wooden, D. H.; Cohen, M.
A Test for Coronal Thick Target Hard X-ray Emissions Using Microwave Spectrum
NASA Astrophysics Data System (ADS)
Hard X-ray (HXR) sources located in the corona may be regarded as evidence for the collisionally thick target in the corona. We investigated whether this idea can be independently verified by microwave radiations that have been known as the best companion to HXRs. Although the sensitivity of microwave radiations to magnetic field has been of main emphasis, there are two other spectral features sensitive to thermal density, the Razin suppression and free-free emission. These density sensitive features may not be significant at typical coronal densities, but become prominent at very high densities that are considered necessary for the collisionally thick target model. In addition, we stress that there is an absolute cut-off of microwave radiation at the plasma frequency which is a sole function of thermal density. These three spectral features make microwave spectral observations an essential tool for testing the thick target models for coronal HXR sources. The test has been made for the 2002 September 9 flare that was observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Owens Valley Solar Array.
Lee, Jeongwoo
Impact of the seasonal evolution of snow properties on microwave emission model performance
NASA Astrophysics Data System (ADS)
Snow cover exhibits great spatio-temporal variability, and is dynamically coupled with global hydrological and climatological processes. Accounting for snowpack evolution related to snow accumulation, metamorphosis, and melt are essential for both modeling and remote sensing applications. Microwave emission has frequency dependant relationships with snow water equivalent (SWE), but snow grain-size, snowpack layering, and snow liquid-water content can confuse the estimation of snow parameters with empirical stand-alone algorithms. This work presents an overview of seasonal snow and multi-frequency dual-polarization microwave emission measurements collected during the 2009-2010 winter season at a network of sites near Churchill, Manitoba, Canada. These observations were used to parameterize and evaluate model simulations of microwave snow emission using the multiple-layer version of the Helsinki University of Technology (HUT) microwave emission model. The HUT model is utilized in the European Space Agency's (ESA) GlobSnow global snow monitoring service, applied to SWE and snow depth (SD) retrievals for the Northern Hemisphere. The HUT model used for forward brightness temperature simulations in the GlobSnow retrieval scheme is currently limited to one layer which necessitates idealizing physical properties of the entire snow pack. In this study, we explore the performance of simulations with the addition of a depth hoar layer and, when appropriate, an ice lens. Simulations for forest, lake, and open environments were synthesized through a scene simulation formulation of the HUT model to produce output suitable for comparison with measured brightness temperatures from the Advanced Microwave Scanning Radiometer (AMSR-E). While the multi-layer model better represents the vertical complexities of grain size and layering, implementation of a multi-layer approach remains a challenge due to model sensitivity with regard to the method of generalization of a complex snow pack into multiple layers. The addition of a second snow layer had a notable impact on 37 GHz simulations because of model sensitivity to the determination of grain size. By reserving one model layer for an ice lens, notable improvements can be made with horizontal polarization simulations at both 19 and 37 GHz.
Fuller, M.; Derksen, C.; Lemmetyinen, J.; Yackel, J.
Anomalous pressure dependence of emission in Si-doped InGaN/GaN quantum wells
NASA Astrophysics Data System (ADS)
In this work we have investigated the effect of pressure on Si-doped In_0.15Ga_0.85N/GaN multiple quantum wells (MQWs) by monitoring the shift in the well peak emission energy (E_p). These experiments reveal an anomalous pressure dependence of E_p, which initially shifts at a rate dE_p/dp = 26 meV/GPa and that increases to values greater than 45 meV/GPa at pressures in excess of 8 GPa. The change in dE_p/dp is reversible, ruling out any damage to the sample. The pressure at which dE_p/dp increases decreases with increasing Si doping of the GaN barrier. This behavior is interpreted as being due to screening of the built-in electric field by carriers delocalized from the barrier states. This interpretation of the results is supported by excitation intensity dependent measurements.
Patel, D.; Vaschenko, G.; Menoni, C. S.; Minsky, M. S.; Keller, S.; Hu, E.; Mishra, U. K.; Denbaars, S. P.
Microwave emission from the coronae of late-type dwarf stars
We present VLA microwave observatios of 14 late-type dwarf and subgiant stars ad binary systems. In this extensive set of observations we detected four sources at 6 cm (chi/sup 1/ Ori, UV Cet, YY Gem, and Wolf 630AB) and found low upper limits for the remaining stars. The microwave luminosities of the nondetected F--K dwarfs are as small as 10/sup -2/ those of the dMe stars. The detected emission is slowly variable in all cases and is consistent with gyroresonant emission from thermal electrons spiralig in magnetic fields of about 300 gauss if the source sizes are as large as R/R/sub asterisk/roughly-equal3--4. This would correspond to magnetic fields that are probably in the range 10/sup 3/--10/sup 4/ gauss at the photospheric level. These photospheric field strengths are somewhat larger than have been observed so far in G--K dwarfs. An alternative mechanism is gyrosynchrotron emission from a relatively small number of electrons (only 10/sup -3/ the number of ambient electrons) with effective temperature, T/sub eff/>10/sup 8/ K. This mechanism is consistent with much smaller and presumably more realistic source sizes. Observations of YY gem dMle+dMle) at a number of phase are consistent with maximum but variable microwave flux at the same phase as miximum plage and central meridian passage of a large starspot of the secondary star. If confirmed by subsequent observations, this provides the first direct evidence that the emission process is magnetic in character on dMe stars.
Linsky, J.L.; Gary, D.E.
Constraints on the Emission and Viewing Geometry of the Transient Anomalous X-ray Pulsar XTE J1810-197
NASA Technical Reports Server (NTRS)
The temporal decay of the flux components of the transient anomalous X-ray pulsar XTE J1 810-197 following its 2002 outburst presents a unique opportunity to probe the emission geometry of a magnetar. Toward this goal, we model the magnitude of the pulsar's modulation in narrow spectral bands over time. Following previous work, we assume that the postoutburst flux is produced in two distinct thermal components arising from a hot spot and a warm concentric ring. We include general relativistic effects on the blackbody spectra due to gravitational redshift and light bending near the stellar surface, which strongly depend on radius. This affects the model fits for the temperature and size of the emission regions. For the hot spot, the observed temporal and energy-dependent pulse modulation is found to require an anisotropic, pencil-beamed radiation pattern. We are able to constrain an allowed range for the angles that the line of sight (psi) and the hot spot pole (xi) make with respect to the spin axis. Within errors, this is defined by the locus of points in the xi-psi plane that lie along the line [xi + beta(R)] [psi + [beta(R)] = const, where beta(R) is a function of the radius R of the star. For a canonical value of R = 12 km, the viewing parameters range from psi = xi = 37deg to (psi, xi) = (85deg, 15deg). We discuss our results in the context of magnetar emission models.
Perna, Rosalba; Gotthelf, E. V.
Unique Properties of Thermally Tailored Copper: Magnetically Active Regions and Anomalous X-ray Fluorescence Emissions
When high-purity copper (?99.98%wt) is melted, held in its liquid state for a few hours with iterative thermal cycling, then allowed to resolidify, the ingot surface is found to have many small regions that are magnetically active. X-ray fluorescence analysis of these regions exhibit remarkably intense lines from "sensitized elements" (SE), including in part or fully the contiguous series V, Cr, Mn, Fe, and Co. The XRF emissions from SE are far more intense than expected from known impurity levels. Comparison with blanks and standards show that the thermal "tailoring" also introduces strongly enhanced SE emissions in samples taken from the interior of the copper ingots. For some magnetic regions, the location as well as the SE emissions, although persistent, vary irregularly with time. Also, for some regions extraordinarily intense "sensitized iron" (SFe) emissions occur, accompanied by drastic attenuation of Cu emissions.
Analyses of the cosmic microwave background (CMB) radiation maps made by the Wilkinson Microwave Anisotropy Probe (WMAP) have revealed anomalies not predicted by the standard inflationary cosmology. In particular, the power of the quadrupole moment of the CMB fluctuations is remarkably low, and the quadrupole and octopole moments are aligned mutually and with the geometry of the solar system. It has been suggested in the literature that microwave sky pollution by an unidentified dust cloud in the vicinity of the solar system may be the cause for these anomalies. In this paper, we simulate the thermal emission by clouds of spherical homogeneous particles of several materials. Spectral constraints from the WMAP multi-wavelength data and earlier infrared observations on the hypothetical dust cloud are used to determine the dust cloud's physical characteristics. In order for its emissivity to demonstrate a flat, CMB-like wavelength dependence over the WMAP wavelengths (3 through 14 mm), and to be invisible in the infrared light, its particles must be macroscopic. Silicate spheres of several millimeters in size and carbonaceous particles an order of magnitude smaller will suffice. According to our estimates of the abundance of such particles in the zodiacal cloud and trans-Neptunian belt, yielding the optical depths of the order of 10{sup -7} for each cloud, the solar system dust can well contribute 10 muK (within an order of magnitude) in the microwaves. This is not only intriguingly close to the magnitude of the anomalies (about 30 muK), but also alarmingly above the presently believed magnitude of systematic biases of the WMAP results (below 5 muK) and, to an even greater degree, of the future missions with higher sensitivities, e.g., Planck.
Dikarev, Valeri; Preuss, Oliver; Solanki, Sami; Krueger, Harald [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany); Krivov, Alexander [Friedrich-Schiller Universitaet Jena (Germany)
Search for High-energy Gamma-ray Emission from an Anomalous X-ray Pulsar, 4U 0142+61
Until 2004, anomalous X-ray pulsars (AXPs) were known as strong emitters of soft X-rays only (<10 keV). The discovery of hard X-ray component from AXPs provided important insight about their emission properties while it posed a serious challenge to explain its origin. The physical mechanism of the hard emission component has still not been fully resolved. We investigate the high-energy
Sinem Sasmaz Mus; Ersin Goegues
Determination of n-butylated trialkyllead compounds by gas chromatography with microwave plasma emission detection
An analytical gas chromatographic procedure is described for the determination of trialkyllead compounds in aqueous media. The analyte compounds are extracted into benzene from an aqueous solution saturated with sodium chloride. They are then quantitatively converted into n-butyltrialkyllead derivatives by reaction with an n-butyl Grignard reagent. Precolumn Tenax trap enrichment of the derived trialkylbutylleads enables determination to low parts per billion levels to be carried out. Also investigated are extraction efficiencies and injection split ratios onto a fused silica capillary column. Lead specific detection is by atmospheric pressure microwave induced plasma spectrometric emission. Data are presented for a wastewater effluent sample. 3 figures.
Estes, S.A.; Uden, P.C.; Barnes, R.M.
Determination of n-butylated trialkyllead compounds by gas chromatography with microwave plasma emission detection
An analytical gas chromatographic procedure is described for the determination of trialkyllead compounds in aqueous media. The analyte compounds are extracted into benzene from an aqueous solution saturated with sodium chloride. They are then quantitatively converted into n-butyltrialkyllead derivatives by reaction with an n-butyl Grignard reagent. Precolumn Tenax trap enrichment of the derived trialkylbutylleads enables determination to low ppB levels to be carried out. Also investigated are extraction efficiencies and injection split ratios onto a fused silica capillary column. Lead specific detection is by atmospheric pressure microwave induced plasma spectrometric emission. Data are presented for a wastewater effluent sample. 21 references, 3 figures.
Estes, S.A.; Uden, P.C.; Barnes, R.M.
A model describing the microwave emission from a multi-layer snowpack at 37 GHz
NASA Technical Reports Server (NTRS)
A multilayer emission model is described and applied to emission measurements obtained at 37 GHz and H polarization using a microwave radiometer attached to a truck-mounted boom in Steamboat Springs, Colorado in 1977. Estimated absorption and scattering coefficients and their dependence on wetness were obtained using calculated values of the dielectric constant at 37 GHz along with the model. It was found that the scattering coefficient is comparable in value to the absorption coefficient for dry snow however, the absorption coefficient increases linearly with increasing snow wetness while the scattering coefficient decreases linearly with increasing wetness. The emission from each layer of the snowpack was also calculated using the estimated coefficients. It is shown that for dry snow, the ground underneath the snowpack contributes about 45% of all measured emission while the rest is due to emission from all the layers within the snowpack. When the wetness of the top 5 cm layer of snowpack increases to about 2% by volume, this top 5 cm snowlayer contributes more than 90% of all the measured emission.
Abdelrazik, M.; Ulaby, F.; Stiles, H.
MASSIVE STAR FORMATION, OUTFLOWS, AND ANOMALOUS H{sub 2} EMISSION IN Mol 121 (IRAS 20188+3928)
We have discovered 12 new molecular hydrogen emission-line objects (MHOs) in the vicinity of the candidate massive young stellar object Mol 121, in addition to five that were previously known. H{sub 2} 2.12 {mu}m/H{sub 2} 2.25 {mu}m flux ratios indicate another region dominated by fluorescence from a photodissociation region, and one region that displays an anomalously low H{sub 2} 2.12 {mu}m/H{sub 2} 2.25 {mu}m flux ratio (<1) and coincides with a previously reported deeply embedded source (DES). Continuum observations at 3 mm reveal five dense cores; the brightest core is coincident with the DES. The next brightest cores are both associated with centimeter continuum emission. One of these is coincident with the IRAS source; the other lies at the centroid of a compact outflow defined by bipolar MHOs. The brighter of these bipolar MHOs exhibits [Fe II] emission and both MHOs are associated with CH{sub 3}OH maser emission observed at 95 GHz and 44 GHz. Masses and column densities of all five cores are consistent with theoretical predictions for massive star formation. Although it is impossible to associate all MHOs with driving sources in this region, it is evident that there are several outflows along different position angles, and some unambiguous associations can be made. We discuss implications of observed H{sub 2} 2.12 {mu}m/H{sub 2} 2.25 {mu}m and [Fe II] 1.64 {mu}m/H{sub 2} 2.12 {mu}m flux ratios and compare the estimated total H{sub 2} luminosity with the bolometric luminosity of the region. We conclude that the outflows are driven by massive young stellar objects embedded in cores that are likely to be in different evolutionary stages.
Wolf-Chase, Grace; Arvidsson, Kim [Astronomy Department, Adler Planetarium, 1300 South Lake Shore Drive, Chicago, IL 60605 (United States)] [Astronomy Department, Adler Planetarium, 1300 South Lake Shore Drive, Chicago, IL 60605 (United States); Smutko, Michael [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)] [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Sherman, Reid, E-mail: firstname.lastname@example.com [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)] [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
Anomalous enhanced emission from PbS quantum dots on a photonic-crystal microcavity
We report up to 75 times enhancement in emission from lithographically produced photonic crystals with postprocessing close-packed colloidal quantum-dot incorporation. In our analysis, we use the emission from a close-packed free-standing film as a reference. After discounting the angular redistribution effect, our analysis shows that the observed enhancement is larger than the combined effects of Purcell enhancement and dielectric enhancement with the microscopic local field. The additional enhancement mechanisms, which are consistent with all our observations, are thought to be spectral diffusion mediated by phonons and local polarization fluctuations that allow off-resonant excitons to emit at the cavity wavelengths.
Luk, Ting Shan; Xiong, Shisheng; Chow, Weng W.; Miao, Xiaoyu; Subramania, Ganesh; Resnick, Paul J.; Fischer, Arthur J.; Brinker, Jeffrey C.
First detection of nonflare microwave emissions from the coronae of single late-type dwarf stars
NASA Technical Reports Server (NTRS)
Results are presented of a search for nonflare microwave radiation from the coronae of nearby late-type dwarf stars comparable to the sun: single stars without evidence for either a large wind or circumstellar envelope. The observing program consisted of flux measurements of six stars over a 24-h period with the VLA in the C configuration at a wavelength of 6 cm with 50 MHz bandwidth. Positive detections at 6 cm were made for Chi 1 Ori (0.6 mJy) and the flare star UV Cet (1.55 mJy), and upper limits were obtained for the stars Pi 1 UMa, Xi Boo A, 70 Oph A and Epsilon Eri. It is suggested that Chi 1 Ori, and possibly UV Cet, represent the first detected members of a new class of radio sources which are driven by gyroresonance emission, i.e. cyclotron emission from nonrelativistic Maxwellian electrons.
Gary, D. E.; Linsky, J. L.
Simulation of electron emission from conformal boundaries for applications to high-power microwave sources
NASA Astrophysics Data System (ADS)
The finite difference time domain (FDTD) approach for electromagnetic particle-in-cell (EM-PIC) is a proven method for many problems involving interactions of charged particles with electromagnetic fields. Applying these methods to complex geometries that occur in high-power microwave (HPM) sources requires methods to accurately model fields and deal with particle emission and absorption at complex boundaries. We have recently developed conformal boundaries for the FDTD electromagnetic solver in the VORPAL code that have be shown to be 2nd order accurate in space. VORPAL also has models for the field emission of electrons as well as models for secondary electron emission. In order to use these advances to study particle effects in HPM devices we have begun modifying the particle boundaries in VORPAL so they can be used with the conformal geometry. We will present the current results of this work including the addition of current correction algorithms to prevent the build up of unphysical image charges when particles are removed and simulations involving field emission and secondary emission of electrons from conformal surfaces.
Nieter, Chet; Smithe, David; Stoltz, Peter H.; Cary, John R.
Anomalous Spectral and Yield Features of Auger Emission from Symmetric Molecules
Proton-induced sulfur LMM and carbon KLL Auger yields from SF6, CF4, and CCl4 gaseous targets are found to be substantially reduced from the corresponding yields observed using H2S, SO2, and CH4. Speculations about the observed dependence on chemical species include inelastic scattering of the Auger electron during its transit out of the molecule and double Auger emission to the continuum.
Dennis L. Matthews; Forrest Hopkins
We report the detection and successful modeling of the unusual 9.7 {mu}m Si-O stretching silicate emission feature in the type 1 (i.e., face-on) LINER nucleus of M81. Using the Infrared Spectrograph (IRS) instrument on Spitzer, we determine the feature in the central 230 pc of M81 to be in strong emission, with a peak at {approx}10.5 {mu}m. This feature is strikingly different in character from the absorption feature of the galactic interstellar medium, and from the silicate absorption or weak emission features typical of galaxies with active star formation. We successfully model the high signal-to-noise ratio IRS spectra with porous silicate dust using laboratory-acquired mineral spectra. We find that the most probable fit uses micron-sized, porous grains of amorphous silicate and amorphous carbon. In addition to silicate dust, there is weak polycyclic aromatic hydrocarbon (PAH) emission present (particularly at 11.3 {mu}m, arising from the C-H out-of-plane bending vibration of relatively large PAHs of {approx}500-1000 C atoms) whose character reflects the low-excitation active galactic nucleus environment, with some evidence that small PAHs of {approx}100-200 C atoms (responsible for the 7.7 {mu}m C-C stretching band) in the immediate vicinity of the nucleus have been preferentially destroyed. Analysis of the infrared fine structure lines confirms the LINER character of the M81 nucleus. Four of the infrared H{sub 2} rotational lines are detected and fit to an excitation temperature of T {approx} 800 K. Spectral maps of the central 230 pc in the [Ne II] 12.8 {mu}m line, the H{sub 2} 17 {mu}m line, and the 11.3 {mu}m PAH C-H bending feature reveal arc- or spiral-like structures extending from the core. We also report on epochal photometric and spectroscopic observations of M81, whose nuclear intensity varies in time across the spectrum due to what is thought to be inefficient, sub-Eddington accretion onto its central black hole. We find that, contrary to the implications of earlier photometry, the nucleus has not varied over a period of two years at these infrared wavelengths to a precision of about 1%.
Smith, Howard A.; Ashby, M. L. N.; Fazio, G. G.; Huang, J.-S.; Marengo, M.; Wang, Z.; Willner, S.; Zezas, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Li, Aigen; Li, M. P.; Koehler, M. [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); Spinoglio, L. [Istituto di Fisica dello Spazio Interplanetario, CNR, via Fosso del Cavaliere, 100, I-00133 Rome (Italy); Wu, Y. L., E-mail: email@example.com, E-mail: email@example.com [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91101 (United States)
In search of water vapor on Jupiter: Laboratory measurements of the microwave properties of water vapor and simulations of Jupiter's microwave emission in support of the Juno Mission
NASA Astrophysics Data System (ADS)
This research has involved the conduct of a series of laboratory measurements of the centimeter-wavelength opacity of water vapor along with the development of a hybrid radiative transfer ray-tracing simulator for the atmosphere of Jupiter which employs a model for water vapor opacity derived from the measurements. For this study an existing Georgia Tech high-sensitivity microwave measurement system (Hanley and Steffes, 2007) has been adapted for pressures ranging from 12--100 bars, and a corresponding temperature range of 293--525°K. Water vapor is measured in a mixture of hydrogen and helium. Using these measurements which covered a wavelength range of 6--20 cm, a new model is developed for water vapor absorption under Jovian conditions. In conjunction with our laboratory measurements, and the development of a new model for water vapor absorption, we conduct sensitivity studies of water vapor microwave emission in the Jovian atmosphere using a hybrid radiative transfer ray-tracing simulator. The approach has been used previously for Saturn (Hoffman, 2001), and Venus (Jenkins et al., 2001). This model has been adapted to include the antenna patterns typical of the NASA Juno Mission microwave radiometer (NASA/Juno-MWR) along with Jupiter's geometric parameters (oblateness), and atmospheric conditions. Using this adapted model we perform rigorous sensitivity tests for water vapor in the Jovian atmosphere. This work will directly improve our understanding of microwave absorption by atmospheric water vapor at Jupiter, and improve retrievals from the Juno microwave radiometer. Indirectly, this work will help to refine models for the formation of Jupiter and the entire solar system through an improved understanding of the planet-wide abundance of water vapor which will result from the successful opreation of the Juno Microwave Radiometer (Juno-MWR).
Karpowicz, Bryan Mills
L-Band H Polarized Microwave Emission During the Corn Growth Cycle
NASA Technical Reports Server (NTRS)
Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (T(sub B))'s measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These T(sub B)'s measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly T(sub B)'s could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly T(sub B). Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, h(sub r), on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on T(sub B) simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent h(sub r) parameterization was responsible for the largest error reduction of T(sub B) simulations in the early growth cycle.
Joseph, A. T.; va der Velde, R.; O'Neill, P. E.; Kim, E.; Lang, R. H.; Gish, T.
Element-specific derivatization for enhanced detectability by the gas chromatograph-microwave emission detector (GC-MED)
NASA Astrophysics Data System (ADS)
The applicability or using the gas chromatograph-microwave plasma emission detector (GC-MED) in combination with chemical derivatization based on unique elements for enhanced detectability of selected compounds in complex samples is discussed. A number of potential derivatization schemes are surveyed and results for two specific approaches are presented. In addition to high sensitivity and element selectivity, the possibility of determining empirical formulas by plasma emission will be an advantage unique to this approach.
Delaney, Michael F.; Warren, F. Vincent
Investigations on the on-line determination of metals in air flows by capacitively coupled microwave plasma atomic emission spectrometry
Plasma optical emission spectrometry with a capacitively coupled microwave plasma (CMP) operated with air has been investigated with respect to its possibilities for real-time environmental monitoring of combustion processes. The unique feature is the possibility to operate the CMP with air as working gas, as is usually the case in exhaust gases of combustion processes. The CMP also is shown
M. Seelig; J. A. C Broekaert
Measurement of hot-electron production and microwave emission by laser-irradiated CH targets
This work was an experimental study on hot-electron production and microwave emission by laser irradiated targets. The laser was a neodymium glass laser (1.06-..mu..m wavelength). Typically the laser beam consisted of a weak 3-mJ prepulse followed by a strong 30-J main pulse 8ns later. Both pulses had a temporal duration of 150 psec and were focused to a 30-..mu..m diameter spot. The majority of the data presented were obtained using exploding-foil-type targets, which had either copper or tin foils attached to the side pointed away from the laser. These foils emitted x-rays that were used to diagnose hot electron temperature, energy and transport. Other targets used were plastic, brass, and copper disks. Specific goals of the experiment included: measurement of the hot-electron temperature and energy, determination of how the hot electrons spread from the point of their generation, and measurement of the microwave energy spectrum and total energy emitted from the targets.
Heidrich, J.E.; Ault, S.K.; Koehler, H.A.; Pollaine, S.M.; Slivinsky, V.W.; Zacharias, R.A.; Kilkenny, J.D.
Contribution of thermal bremsstrahlung to microwave emission of solar flare loops
NASA Astrophysics Data System (ADS)
The contribution of thermal bremsstrahlung to the total microwave flux of a solar flare loop is considered. The total-flux data were obtained on the Nobeyama Radio Heliograph. The calculation of the thermal bremsstrahlung radio flux was based on determining the integrated temperature and number density of the hot flare-loop plasma from its soft X-ray flux, obtained using data from the GOES-10 and GOES-12 satellites. The effect of thermal bremsstrahlung on the total flux and the spectral index of the microwave radiation is insignificant at the burst maximum ( F th/ F tot < 3%, ? ? < 0.2), while the contribution of bremsstrahlung can be substantial during the decay phase of the burst (up to 80%). This results in an appreciable decrease in the observed spectral index (to ? ? ˜ 1.5). Therefore, when diagnosing the parameters of the accelerated electrons based on the characteristics of their gyrosynchrotron radiation, the most accurate results can be obtained using the emission characteristics obtained near the burst maximum.
Morgachev, A. S.; Polyakov, V. E.; Melnikov, V. F.
A comparison of radiative transfer models for predicting the microwave emission from soils
NASA Technical Reports Server (NTRS)
Two general types of numerical models for predicting microwave emission from soils are compared-coherent and noncoherent. In the former, radiation in the soil is treated coherently, and the boundary conditions on the electric fields across the layer boundaries are used to calculate the radiation intensity. In the latter, the radiation is assumed to be noncoherent, and the intensities of the radiation are considered directly. The results of the two approaches may be different because of the effects of interference, which can cause the transmitted intensity at the surface (i.e., emissivity) to be sometimes higher and sometimes lower for the coherent case than for the noncoherent case, depending on the relative phases of reflected fields from the lower layers. This coupling between soil layers in the coherent models leads to greater soil moisture sampling depths observed with this type of model, and is the major difference that is found between the two types of models. In noncoherent models, the emissivity is determined by the dielectric constraint at the air/soil interface. The subsequent differences in the results are functions of both the frequency of the radiation being considered and the steepness of the moisture gradient near the surface. The calculations were performed at frequencies of 1.4 and 19.4 GHz and for two sets of soil profiles. Little difference was observed between the models at 19.4 GHz; and only at the lower frequency were differences apparent because of the greater soil moisture sampling depth at this frequency.
Schmugge, T. J.; Choudhury, B. J.
Theory for microwave thermal emission from a layer of cloud or rain
NASA Technical Reports Server (NTRS)
Microwave thermal emission from a layer of cloud or rain consisting of spherical particles has been investigated. Scattering effects are studied in great detail with both numerical and analytical approaches. In the absence of ground emission, it is found that scattering induces brightening for optically thin layers and vice versa for optically thick layers. As a function of observation angle, brightening occurs near nadir, while darkening occurs at large angles in the case of small optical thickness. For large optical thickness, darkening occurs at all angles because of backscattering effects. When the layer of cloud or rain is above an air layer and an ocean surface at a higher temperature, it is found that the darkening effect at large optical thickness is much more pronounced. The darkening effect is also larger for vertical polarizations because the ocean emits more vertically polarized components. The effect of thermal emission and molecular absorption by atmospheric gases is also taken into account. Results obtained from analytical formulas under single-scattering assumptions are compared and illustrated.
Tsang, L.; Kong, J. A.; Staelin, D. H.; Njoku, E.; Waters, J. W.
Enhancement of microwave emission in magnetic tunnel junction oscillators through in-plane field orientation
NASA Astrophysics Data System (ADS)
We observe giant enhancement of microwave emission in MgO-based magnetic tunnel junction nano-oscillators through in-plane magnetic field orientation. At an optimal in-plane field angle, the output power reaches up to 240 nW, two orders of magnitude higher compared to the vicinity of the easy axis (~1 nW). Moreover, in this condition, the linewidth is significantly narrowed (<100 MHz) and the additional precession modes are suppressed. Analysis of the data indicates that the optimal field angle is influenced by the field-like torque. The results demonstrate that controlling the in-plane magnetic field orientation can be an important strategy for developing high-power spin-torque oscillators.
Zeng, Z. M.; Upadhyaya, P.; Khalili Amiri, P.; Cheung, K. H.; Katine, J. A.; Langer, J.; Wang, K. L.; Jiang, H. W.
Snow-cover environmental monitoring and assessment in Northeast China using passive microwave emission models.
In this study, we present the application of the passive microwave emission models to snow-cover environment monitoring and assessment in Northeast China. The study employs the radiative transfer function and strong fluctuation theory to develop the models. We used the exponential form of a spherical symmetric correlation function to describe random permittivity fluctuations. From strong fluctuation, we then obtained the phase matrix and extinction coefficients of snow-packs for the spherical symmetric correlation function. We also used the vector radiative transfer formula for the layer of a random medium by solving Gaussian quadrature and eigen analysis. By comparing the brightness temperatures at 5, 10.7, 18, and 37 GHz, the modelling results agreed with experimental data of dry-snow physical parameters as measured in the fieldwork. PMID:17671847
Song, Kaishan; Zhang, Yuanzhi
Passive L-Band H Polarized Microwave Emission During the Corn Growth Cycle
NASA Astrophysics Data System (ADS)
Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (TB's) measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These TB measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly TB's could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly TB. Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, hr, on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on TB simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent hr parameterization was responsible for the largest error reduction of TB simulations in the early growth cycle. A.T. Joseph, R. Van der Velde, P.E. O'Neill, R.H. Lang, and T. Gish, "Soil moisture retrieval during a corn growth cycle using L-band (1.6 GHz) radar observations", IEEE Transactions on Geoscience and Remote Sensing, vol. 46, DOI:10.1109/TGRS.2008.917214, Aug. 2008. M.C. Dobson, F.T. Ulaby, M.T. Hallikainen and M.A. El-Rayes, "Microwave dielectic behavior of wet soil - Part II: Dielectric mixing models", IEEE Transactions on Geoscience and Remote Sensing, vol. GE-23, pp. 35- 46, Jan., 1985. A.K. Fung, Z. Li and K.S. Chen, "Backscattering from a randomly rough dielectric surface", IEEE Transactions on Geoscience Remote Sensing, vol. 30, pp. 356-369, Mar., 1992.
Joseph, A. T.; van der Velde, R.; O'Neill, P. E.; Kim, E. J.; Lang, R. H.; Gish, T. J.
Comparison among physical process based snow models in estimating SWE and upwelling microwave emission
NASA Astrophysics Data System (ADS)
Snowpack serves as a critical water resource and an important climate indicator. Accurately estimating snow water equivalent (SWE) and melt timing has both civil and scientific merits. Physical process based multi-layer land surface models (LSM) characterize snowpack by tracking the energy balance and mass balance in each layer. However, in terms of the number of layers used to model the snowpack stratigraphy, as well as the complexity of the simulated mass/energy exchanges in each single layer, significant variances exist among different LSMs. Previous work has largely focused on assessing the impact of layering and stratigraphy representation on mass and energy balance, with little attention paid to the implications of these factors on predicted microwave brightness temperature (Tb). In this paper, three LSMs with varying snow layer schemes: SSiB (3-layer), CoLM (5-layer), and SNOWPACK (N-layer), are coupled to the Microwave Emission from Multi-Layer Snowpacks (MEMLS) radiative transfer model (RTM) to simulate the snowpack mass/energy budgets and microwave signature over a full season. The simulations are performed at five in-situ gage locations in the Kern River Basin, Sierra Nevada, CA where it is known that large snow events occur that can be problematic to represent using a small number of snow layers. A particular emphasis is placed on assessment of the impact of layering scheme on the results. Preliminary results show that even for SSiB which has a relative simple empirical layering scheme, the modeled annual SWE could be highly correlated with the in-situ SWE (r¬2=0.91) if the precipitation bias is corrected, also, the comparison between the Tb simulated by SSiB+MEMLS and the downscaled AMSR-E Tb measurements shows a correlation coefficient of 0.94 during the snow accumulation season (Oct to Apr) if the grain growth parameters and the soil snow reflectivity is properly calibrated. Future work includes comparing SWE and Tb from all threemodels and quantitatively determining how the more complex models (SNOWPACK) could possibly further improve the Tb estimates, and how they will increase the computational loads, which are highly relevant to the ultimate goal of estimation of SWE via assimilation of multi-frequency passive microwave observations.
Li, D.; Durand, M. T.; Margulis, S. A.
Snow stratigraphic heterogeneity within ground-based passive microwave radiometer footprints: Implications for emission modeling
NASA Astrophysics Data System (ADS)
measurements of snowpack properties (stratigraphic layering, density, grain size, and temperature) were used as inputs to the multilayer Helsinki University of Technology (HUT) microwave emission model at a centimeter-scale horizontal resolution, across a 4.5 m transect of ground-based passive microwave radiometer footprints near Churchill, Manitoba, Canada. Snowpack stratigraphy was complex (between six and eight layers) with only three layers extending continuously throughout the length of the transect. Distributions of one-dimensional simulations, accurately representing complex stratigraphic layering, were evaluated using measured brightness temperatures. Large biases (36 to 68 K) between simulated and measured brightness temperatures were minimized (-0.5 to 0.6 K), within measurement accuracy, through application of grain scaling factors (2.6 to 5.3) at different combinations of frequencies, polarizations, and model extinction coefficients. Grain scaling factors compensated for uncertainty relating optical specific surface area to HUT effective grain size inputs and quantified relative differences in scattering and absorption properties of various extinction coefficients. The HUT model required accurate representation of ice lenses, particularly at horizontal polarization, and large grain scaling factors highlighted the need to consider microstructure beyond the size of individual grains. As variability of extinction coefficients was strongly influenced by the proportion of large (hoar) grains in a vertical profile, it is important to consider simulations from distributions of one-dimensional profiles rather than single profiles, especially in sub-Arctic snowpacks where stratigraphic variability can be high. Model sensitivity experiments suggested that the level of error in field measurements and the new methodological framework used to apply them in a snow emission model were satisfactory. Layer amalgamation showed that a three-layer representation of snowpack stratigraphy reduced the bias of a one-layer representation by about 50%.
Rutter, Nick; Sandells, Mel; Derksen, Chris; Toose, Peter; Royer, Alain; Montpetit, Benoit; Langlois, Alex; Lemmetyinen, Juha; Pulliainen, Jouni
Snow stratigraphic heterogeneity within ground-based passive microwave radiometer footprints: implications for emission modelling
NASA Astrophysics Data System (ADS)
Remote sensing of snow mass remains a challenging area of research. Scattering of electromagnetic radiation is sensitive to snow mass, but is also affected by contrasts in the dielectric properties of the snow. Although the argument that errors from simple algorithms average out at large scales has been used to justify current retrieval methods, it is not obvious why this should be the case. This hypothesis needs to be tested more rigorously. A ground-based field experiment was carried out to assess the impact of sub-footprint snow heterogeneity on microwave brightness temperature, in Churchill, Canada in winter in early 2010. Passive microwave measurements of snow were made using sled-mounted radiometers at 75cm intervals over a 5m transect. Measurements were made at horizontal and vertical polarizations at frequencies of 19 and 37 GHz. Snow beneath the radiometer footprints was subsequently excavated, creating a snow trench wall along the centrepoints of adjacent footprints. The trench wall was carefully smoothed and photographed with a near-infrared camera in order to determine the positions of stratigraphic snow layer boundaries. Three one-dimensional vertical profiles of snowpack properties (density and snow specific surface area) were taken at 75cm, 185cm and 355cm from the left hand side of the trench. These profile measurements were used to derive snow density and grain size for each of the layers identified from the NIR image. Microwave brightness temperatures for the 2-dimensional map of snow properties was simulated with the Helsinki University of Technology (HUT) model at 1cm intervals horizontally across the trench. Where each of five ice lenses was identified in the snow stratigraphy, a decrease in brightness temperature was simulated. However, the median brightness temperature simulated across the trench was substantially higher than the observations, of the order of tens of Kelvin, dependent on frequency and polarization. In order to understand and quantify possible sources of error in the simulations, a number of experiments were carried out to investigate the sensitivity of the brightness temperature to: 1) uncertainties in field observations, 2) representation of ice lenses, 3) model layering structure, and 4) near-infrared derived grain size representing snow grain size at microwave wavelengths. Field measurement error made little difference to the simulated brightness temperature, nor did the representation of ice lenses as crusts of high density snow. As the number of layers in the snow was reduced to 3, 2, or 1, the simulated brightness temperature increased slightly. However, scaling of snow grain size had a dramatic effect on the simulated brightness temperatures, reducing the median bias of the simulations to within measurement error for the statistically different brightness temperature distributions. This indicated that further investigation is required to define what is meant by the microwave grain size, and how this relates to the grain size that is used in the microwave emission model.
Sandells, M.; Rutter, N.; Derksen, C.; Langlois, A.; Lemmetyinen, J.; Montpetit, B.; Pulliainen, J. T.; Royer, A.; Toose, P.
Soft X-ray, microwave, and hard X-ray emission from a solar flare - Implications for electron heating and acceleration in current channels
The soft X-ray, microwave, and hard X-ray emissions from the solar flare of May 14, 1980 are studied. The flare consists of a gradual component in soft X-rays and microwaves and a superposed impulsive burst accompanied by hard X-ray emission. The impulsive phase of the flare appears in the soft X-ray emission as a temperature spike and as an increased
Gordon D. Holman; Mukul R. Kundu; Sharad R. Kane
Spatial Variability of Barrow-Area Shore-Fast Sea Ice and Its Relationships to Passive Microwave Emissivity
NASA Technical Reports Server (NTRS)
Aircraft-acquired passive microwave data, laser radar height observations, RADARSAT synthetic aperture radar imagery, and in situ measurements obtained during the AMSR-Ice03 experiment are used to investigate relationships between microwave emission and ice characteristics over several space scales. The data fusion allows delineation of the shore-fast ice and pack ice in the Barrow area, AK, into several ice classes. Results show good agreement between observed and Polarimetric Scanning Radiometer (PSR)-derived snow depths over relatively smooth ice, with larger differences over ridged and rubbled ice. The PSR results are consistent with the effects on snow depth of the spatial distribution and nature of ice roughness, ridging, and other factors such as ice age. Apparent relationships exist between ice roughness and the degree of depolarization of emission at 10,19, and 37 GHz. This depolarization .would yield overestimates of total ice concentration using polarization-based algorithms, with indications of this seen when the NT-2 algorithm is applied to the PSR data. Other characteristics of the microwave data, such as effects of grounding of sea ice and large contrast between sea ice and adjacent land, are also apparent in the PSR data. Overall, the results further demonstrate the importance of macroscale ice roughness conditions such as ridging and rubbling on snow depth and microwave emissivity.
Maslanik, J. A.; Rivas, M. Belmonte; Holmgren, J.; Gasiewski, A. J.; Heinrichs, J. F.; Stroeve, J. C.; Klein, M.; Markus, T.; Perovich, D. K.; Sonntag, J. G.; Tape, K.
Microwave and hard X-ray emissions during the impulsive phase of solar flares: Nonthermal electron spectrum and time delay
NASA Technical Reports Server (NTRS)
On the basis of the summing-up and analysis of the observations and theories about the impulsive microwave and hard X-ray bursts, the correlations between these two kinds of emissions were investigated. It is shown that it is only possible to explain the optically-thin microwave spectrum and its relations with the hard X-ray spectrum by means of the nonthermal source model. A simple nonthermal trap model in the mildly-relativistic case can consistently explain the main characteristics of the spectrum and the relative time delays.
Gu, Ye-Ming; Li, Chung-Sheng
First detection of nonflare microwave emission from the coronae of single late-type dwarf stars
We report on an observing program with the VLA in its C configuration to detect microwave radiation from the coronae of nearby late-type dwarf stars which are not members of close binary systems and do not have large winds. Six stars, chosen on the basis of strong apparent X-ray flux, were observed during a 24 hour period, and two stars were detected chi/sup 1/ Orionis (G0 V) was detected as a 0.6 mJy source (S/Nroughly-equal7) at 6 cm, and we obtained an upper limit at 2 cm. The flare star UV Cet (dM 5.5e) was detected as a steady 1.55 mJy source (S/Nroughly-equal17) at 6 cm during a 2.5 hour observation. We obtained upper limits at 6 cm for the other stars observed: ..pi../sup 1/ UMa (G0 V), zeta Boo A (G8 V), 70 Oph A (K0 V), and epsilon Eri (K2 V). We believe that the most likely emission mechanism is gyro-resonance emission, i.e., cyclotron emission from nonrelativistic Maxwellian electrons. Assuming a coronal temperature of 0.5--0.1 x 10/sup 7/ K consistent with the X-ray data, we find that the observed 6 cm fluxes are consistent with emission in the sixth or lower harmonics with coronal magnetic fields roughly-equal300 gauss or larger covering a large fraction of the star. It is likely that chi/sup 1/ Ori, solar active regions (plages), and perhaps UV Cet, are the first detected members of a new class of radio sources.
Gary, D.E.; Linsky, J.L.
Anomalous resistivity effect on multiple ion beam emission and hard x-ray generation in a Mather type plasma focus device
Multi ion beam and hard x-ray emissions were detected in a high inductance (more than 100 nH) Mather type plasma focus (PF) device at different filling gas pressures and charging voltages. The signal analysis was performed through the current trace, as it is the fundamental signal from which all of the phenomena in a PF device can be extracted. Two different fitting processes were carried out according to Lee's computational (snow-plow) model. In the first process, only plasma dynamics and classical (Spitzer) resistances were considered as energy consumer parameters for plasma. This led to an unsuccessful fitting and did not answer the energy transfer mechanism into plasma. A second fitting process was considered through the addition of anomalous resistance, which provided the best fit. Anomalous resistance was the source of long decrease in current trace, and multi dips and multi peaks of high voltage probe. Multi-peak features were interpreted considering the second fitting process along with the mechanisms for ion beam production and hard x-ray emission. To show the important role of the anomalous resistance, the duration of the current drop was discussed.
Behbahani, R. A.; Aghamir, F. M. [Department of Physics, University of Tehran, N. Kargar Ave, Tehran 14399 (Iran, Islamic Republic of)
Establishing a Calibration for a Microwave Plasma Continuous Emissions Monitor For Stack Exhaust Metals
NASA Astrophysics Data System (ADS)
A real-time continuous emissions monitor for hazardous metals in stack exhaust is in development to replace the regulatory standard, EPA Method 29. A microwave plasma is sustained in ambient stack exhaust flow for real-time atomic emission spectroscopy. A metals injection calibration subsystem using a pneumatic nebulizer and standard metals solution is attached to the exhaust flow for real-time span calibration of the monitored metals. A novel approach to determine the nebulizer injection efficiency during plasma operation was tested. A known metal mass on a tungsten filament attached to an alumina rod was introduced into a nitrogen plasma at different axial positions. These signals were then correlated to masses of metals aspirated into the plasma by the nebulizer. The metals injection efficiency as a function of rod insertion position was calculated by dividing the correlated mass by the total mass aspirated by the nebulizer, and extrapolated to the end of the sample line. The resulting efficiency was compared to samples collected directly by Gelman Science Type A/E glass fiber filters off line from the plasma. The results to date give the nebulizer metals injection efficiencies less than one percent.
Flores, G. J., III; Green, K. M.; Woskov, P. P.; Hadidi, K.; Thomas, P.
We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground contamination outside of the updated (KQ85y7) foreground mask. We place a 15 {mu}K upper bound on rms foreground contamination in the cleaned maps used for cosmological analysis. Further, the cleaning process requires only three power-law foregrounds outside of the mask. We find no evidence for polarized foregrounds beyond those from soft (steep-spectrum) synchrotron and thermal dust emission; in particular we find no indication in the polarization data of an extra 'haze' of hard synchrotron emission from energetic electrons near the Galactic center. We provide an updated map of the cosmic microwave background (CMB) using the internal linear combination method, updated foreground masks, and updates to point source catalogs using two different techniques. With additional years of data, we now detect 471 point sources using a five-band technique and 417 sources using a three-band CMB-free technique. In total there are 62 newly detected point sources, a 12% increase over the five-year release. Also new are tests of the Markov chain Monte Carlo foreground fitting procedure against systematics in the time-stream data, and tests against the observed beam asymmetry. Within a few degrees of the Galactic plane, the behavior in total intensity of low-frequency foregrounds is complicated and not completely understood. WMAP data show a rapidly steepening spectrum from 20 to 40 GHz, which may be due to emission from spinning dust grains, steepening synchrotron, or other effects. Comparisons are made to a 1 deg 408 MHz map (Haslam et al.) and the 11 deg ARCADE 2 data (Singal et al.). We find that spinning dust or steepening synchrotron models fit the combination of WMAP and 408 MHz data equally well. ARCADE data appear inconsistent with the steepening synchrotron model and consistent with the spinning dust model, though some discrepancies remain regarding the relative strength of spinning dust emission. More high-resolution data in the 10-40 GHz range would shed much light on these issues.
Gold, B.; Bennett, C. L.; Larson, D. [Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Odegard, N.; Weiland, J. L.; Hill, R. S. [Adnet Systems, Inc., 7515 Mission Dr., Suite A1C1 Lanham, MD 20706 (United States); Kogut, A.; Hinshaw, G. [Code 665, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Chen, X. [Infrared Processing and Analysis Center, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Dunkley, J. [Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Halpern, M. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Jarosik, N.; Page, L.; Spergel, D. N. [Department of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544-0708 (United States); Komatsu, E. [Department of Astronomy, University of Texas, Austin, 2511 Speedway, RLM 15.306, Austin, TX 78712 (United States); Limon, M. [Columbia Astrophysics Lab, Columbia University, Mail Code 5247, 550 W. 120th St., New York, NY 10027 (United States); Meyer, S. S. [Departments of Astrophysics and Physics, KICP and EFI, University of Chicago, Chicago, IL 60637 (United States); Nolta, M. R. [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON, Canada M5S 3H8 (Canada); Smith, K. M. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544-1001 (United States); Tucker, G. S., E-mail: email@example.com [Department of Physics, Brown University, 182 Hope St., Providence, RI 02912-1843 (United States)
The Effect of the Melting Layer on the Microwave Emission of Clouds over the Ocean.
NASA Astrophysics Data System (ADS)
A study was carried out in order to estimate the effect of melting particles on simulated brightness temperatures at microwave frequencies between 10.7 and 85.5 GHz for precipitation over the ocean. The meteorological model framework is based on the assumption that the strongest radiometric effect is due to the drastically increased permittivity of melting particles driven by the volume fraction of liquid water. Thus, effects caused by particle aggregation and breakup are neglected.Different approaches for calculating the effective permittivity of mixed particles are compared. The resulting extinction coefficients, single scattering albedos, and asymmetry parameters indicate a maximum effect when the particle is composed of a water matrix with air-ice inclusions. In particular the extinction coefficient may vary by more than two orders of magnitude right below the freezing level dependent on frequency and the applied mixing formula. In the melting region also the strongest dependence of the optical properties on the droplet spectrum is observed. Extreme local differences of 100% between the particle optical properties employing either a Marshall-Palmer or gamma-type drop size distribution occur.When radiative transfer calculations are carried out, average deviations of 20-30 K at low frequencies (10.7 and 19.35 GHz) are observed, mainly due to the strong dependence of the extinction coefficient on the implemented melting process. However, this effect is driven by the applied mixing formula rather than the drop size distribution; that is, for particles composed of a water matrix and air-ice inclusions independently of melting stage the emission excess seems to be overexpressed.The systematic effect of including the melting process in radiative transfer calculations for the development of surface rain retrievals was also investigated. Over 550 model atmospheres were used to estimate the relative deviation of surface rain-rate estimates using a set of operational rain retrieval algorithms. Neglecting the melting effect may lead to severe overestimations of surface rain rates by up to 100% in stratiform conditions. However, if the melting layer is either weakly expressed or nonuniformly distributed in space, the relative overestimation is much lower. If the effective permittivity of melting particles is calculated using the weighted mixing approach of Meneghini and Liao, considerably less effect of melting particles on passive microwave emission is observed.
Bauer, P.; Poiares Baptista, J. P. V.; de Iulis, M.
High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations
We analyse the polarized emission at 1.4 GHz in a 3°× 3° area at high Galactic latitude (b~-40°). The region, centred in (alpha= 5h, delta=-49°), was observed with the Australia Telescope Compact Array (ATCA) radio-interferometer, whose 3-30 arcmin angular sensitivity range allows the study of scales appropriate for cosmic microwave background polarization (CMBP) investigations. The angular behaviour of the diffuse
E. Carretti; G. Bernardi; R. J. Sault; S. Cortiglioni; S. Poppi
Microwave emission and beam propagation measurements in a high-power relativistic electron beam-plasma system
Microwave emission was measured from a system consisting of an unmagnetized plasma and a propagating electron beam. A 93-cm2 velvet cathode, with an anode-cathode gap of 5.9 cm, injects the electron current into the plasma through an aluminized Mylar anode. Measurements were made of the diode voltage and current in the 6-?V water dielectric accelerator and net current through the
M. S. Di Capua; J. F. Camacho; E. S. Fulkerson; D. Meeker
Stimulated microwave emission from E×B drifting electrons in slow-wave cavities: A quantum approach
Stimulated microwave emission from E×B drifting electrons in slow-wave cavities occurs when the Doppler-shifted radiation frequency is either near zero or the electron cyclotron frequency. The former case, characterized by the synchronous drift velocity u, omega-ku~=0, corresponds to the ``pure drift'' instability, while the latter, satisfying omega-ku~=+\\/-Omega, is termed the ``drift-cyclotron'' mode. In both cases the drift kinetic energy and
Spilios Riyopoulos
Superslow Self-Organized Motions in a Multimode Microwave Phonon Laser (Phaser) under Resonant Destabilization of Stationary Acoustic Stimulated Emission
Two qualitatively different kinds of resonant destabilization of phonon stimulated emission (SE) are experimentally revealed for periodically forced multimode ruby phaser (phonon laser) operating at SE frequencies about 9 GHz, i.e. at microwave acoustic wavelengths of 1 micron. The inversion state of Cromium(3+) spin-system in ruby was created by electromagnetic pump at 23 GHz. Under deep modulation of pump power
D. N. Makovetskii
Effects of varying soil moisture contents and vegetation canopies on microwave emissions
NASA Technical Reports Server (NTRS)
Results of NASA airborne passive microwave scans of bare and vegetated fields for comparison with ground truth tests are discussed and a model for atmospheric scattering of radiation by vegetation is detailed. On-board radiometers obtained data at 21, 2.8, and 1.67 cm during three passes over each of 46 fields, 28 of which were bare and the others having wheat or alfalfa. Ground-based sampling included moisture in five layers down to 15 cm in addition to soil temperature. The relationships among the brightness temperature and soil moisture, as well as the surface roughness and the vegetation canopy were examined. A model was developed for the dielectric coefficient and volume scattering for a vegetation medium. L- to C-band data were found useful for retrieving soil information directly. A surface moisture content of 5-35% yielded an emissivity of 0.9-0.7. The data agreed well with a combined multilayer radiative transfer model with simple roughness correction.
Burke, H.-H. K.; Schmugge, T. J.
Emission of non-thermal microwave radiation by a Martian dust storm
NASA Astrophysics Data System (ADS)
We report evidence for the emission of non-thermal microwave radiation by a deep Martian dust storm. The observations were made using an innovative detector that can discriminate between radiation of thermal and non-thermal origin by measuring the high order moments of its electric field strength. Measurements with this detector, installed in a 34 m radio telescope of the Deep Space Network (DSN), were made for about 5 hours a day over a dozen days between 22 May and 16 June 2006. Non-thermal radiation was detected for a few hours only when a 35 km deep Martian dust storm was within the field of view of the radio telescope on 8 June 2006. The spectrum of the non-thermal radiation has significant peaks around predicted values of the lowest three modes of the Martian Schumann Resonance (SR). The SR results from electromagnetic standing waves formed in the concentric spherical cavity between the Martian surface and its ionosphere and forced by large-scale electric discharge. Thus, the non-thermal radiation was probably caused by electric discharge in the Martian dust storm.
Ruf, Christopher; Renno, Nilton O.; Kok, Jasper F.; Bandelier, Etienne; Sander, Michael J.; Gross, Steven; Skjerve, Lyle; Cantor, Bruce
Objects in the Edgeworth-Kuiper Belt and the main asteroid belt should emit microwaves that may give rise to extra anisotropy signals in the multipole of the cosmic microwave background (CMB) experiment. Constraints are derived from the absence of positive detection of such anisotropies for l {approx}< 50, meaning the total mass of Edgeworth-Kuiper Belt objects is smaller than 0.2 M{sub +}. This limit is consistent with the mass extrapolated from the observable population with the size of a {approx}> 15 km, assuming that the small-object population follows the power law in size dN/da {approx} a{sup -q} with the canonical index expected for collisional equilibrium, q {approx_equal} 3.5, with which 23% of the mass is ascribed to objects smaller than are observationally accessible down to grains. A similar argument applied to the main asteroid belt indicates that the grain population should not increase more quickly than q {approx_equal} 3.6 toward smaller radii, if the grain population follows the power law that continues to observed asteroids with larger radii. Both cases are at or only slightly above the limit that can be physically significant, implying the importance of further tightening the CMB anisotropy limit, which may be attained with observation at higher radio frequencies.
Ichikawa, Kazuhide; Fukugita, Masataka [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582 (Japan)
A proposal to explain strong optical emission from single walled carbon nanotubes triggered by intense microwave radiation
NASA Astrophysics Data System (ADS)
A mechanism to explain interaction of microwaves (300W,12.1 cm) with single walled nanotubes (SWNT,average d ˜1.1nm), in vacuum, is discussed. Visible light emission from the SWNTs shows a maximum indicating a black body temperature near 6000^o with spectral components for H+ and C++ species.The nanotubes,remain intact to allow their post-experiment microscopic and Raman-spectroscopic analysis. Microscopic analysis shows partial doubling. The energy of the microwave field appears to be insufficient to achieve the temperatures encountered. Inverse r-square dependence of surface tension shows that the internal energy needed is released when two 1 nm size nanotubes coalesce. The surface tension energy transfers to the H and C atoms and is released in diameter doubling: The microwaves provide initial energy to overcome the barrier. Microwaves may also excite mechanical vibrations and acoustic shock waves. [1] T. J. Imholt, C. A. Dykes, B. Hasslacher, J. M. Perez, D. W. Price, J. A. Roberts, J. B. Scott, A. Wadhawan, Z. Ye and J. M. Tour, Chem. Mater. 15, 3969 (2003).[2] D. Sanchez-Portal, et al., Phys. Rev. B 59, 12678 (1999.3A. Pantano, et al., Phys. Rev. Lett. 91, 14405 (2003).
Roberts, James A.; Deering, Bill; Krokhin, Arkady; Ye, Zhao; McDaniel, Floyd
CREST-Snow Analysis and Field Experiment (CREST-SAFE): Continuous In Situ Observations of Snow Physical Properties and Microwave Emission
NASA Astrophysics Data System (ADS)
The CREST-Snow Analysis and Field Experiment (CREST-SAFE) is being carried out for two winter seasons (2011 and 2012) at the research site of the National Weather Service office, Caribou ME, USA. In this ground experiment, dual polarized microwave (37 and 89 GHz) observations are conducted continuously from the time of snow onset to snow melt off along with detailed synchronous observations of snowpack physical properties. The objective of this long term field experiment is to improve our understanding of the effect of changing snow characteristics (grain size, density, temperature) under various meteorological conditions on the microwave emission of snow and hence to improve retrievals of snow cover properties from satellite observations in the microwave spectral range. In this presentation, we give an overview of the field experiment and of available datasets. We also present the analysis of microwave observations collected during the two years of experiment along with observations of the snowpack properties. The simulations of seasonal changes of the snow pack physical properties were simulated with the SNTHERM model whereas to simulate the snowpack emission in the microwave we have used from SNTHERM and the HUT (Helsinki University of Technology) snow emission model. For different snow conditions simulated microwave brightness temperatures were compared with brightness temperatures observed in situ and with satellite based brightness temperature. The analysis of microwave observations has revealed a large difference in the microwave brightness temperature over fresh and aged snow pack even under the same snow depth. This suggests a substantial impact of other physical parameters on the microwave emission of snow as snow grain size, ice layer formation and density.
Munoz, J.; Lakhankar, T.; Romanov, P.; Powell, A. M.; Khanbilvardi, R.
Effects of tapered tubes on long-pulse microwave emission from intense e-beam gyrotron-backward-wave-oscillators
Experiments are reported on tapered-tube versus uniform-tube, gyrotron-backward-wave-oscillators (4.5--6 GHz) driven by an intense electron beam with parameters: 0.8 MV, 1--4 kA, and pulselength (0.5--1 [mu]s). Results show that, compared to a uniform interaction tube, a gyro-BWO with a 10% downtapered tube produces the following effects: (1) highest microwave peak-power (up to about 100 MW in internal tube), a factor of 2 higher than the uniform tube, (2) more reproducible long-pulse (400--500 ns) emission, and (3) the largest inferred-integrated energy (factor of 2.5--3 increase). Experiments show high power microwave spikes with lower power plateaus. Experimental observations are in qualitative agreement with MAGIC code simulations of uniform and tapered-tube gyro-BWOs.
Walter, M.T.; Gilgenbach, R.M. (Univ. of Michigan, Ann Arbor, MI (United States). Intense Energy Beam Interaction Lab.); Menge, P.R. (Univ. of Michigan, Ann Arbor, MI (United States). Intense Energy Beam Interaction Lab. Sandia National Labs., Albuquerque, NM (United States)); Spencer, T.A. (Univ. of Michigan, Ann Arbor, MI (United States). Intense Energy Beam Interaction Lab. Air Force Phillips Lab., Kirtland AFB, NM (United States))
Direct introduction of aqueous samples into a low-powered microwave-induced plasma for atomic emission spectrometry
The direct introduction of aqueous samples into a low-power microwave plasma is achieved with the use of a highly efficient TM/sub 010/ microwave plasma. A toroidal plasma is sustained in the cavity solely by the Ar gas output of the nebulizer. Samples from a concentric glass nebulizer/Scott type spray chamber are fed directly into the cavity with no desolvation apparatus. A toroidal plasma can be sustained from the output of the nebulizer while 1 mL/min water is being aspirated at power levels of 36 W. This plasma is characterized as an atom cell by the study of emission profiles, working curves, and limits of detection. Also, ionization and vaporization interferences that occur with the use of this plasma are discussed.
Long, G.L.; Perkins, L.D.
Microwave emission and beam propagation measurements in a high-power relativistic electron beam-plasma system
The authors measured microwave emission from a system consisting of an unmagnetized plasma (T/sub e/ approx. = 1 eV, 0.8 < n/sub e/ < 2.3 x 10/sup 11/ cm/sup -3/) and a propagating electron beam (I/sub b/ approx. = 50 kA, V/sub b/ approx. = 1.4 MV, J/sub b/ approx. = 280 A/cm/sup 2/, t/sub rise/ approx. = 35 ns, t/sub pulse/ approx. = 60 ns). A 93-cm/sup 2/ velvet cathode, with an anode-cathode gap of 5.9 cm, injects the electron current into the plasma through an aluminized Mylar anode. The authors measure diode voltage and current in the 6-..cap omega.. water dielectric accelerator and net current through the beam-plasma system. The plasma is produced by a 90-..mu..s, 90-A current pulse, emitted from a thermionic LaB/sub 6/ electron source, which preionizes a 0.8 < rho/sub o/ < 4.6 mT argon fill in a 1-m-long, 15-cm-diameter Lucite tube. A microwave spectrometer detects the radio-frequency output in the 2-18, 18-26, and 26-47 GHz bands, which a set of filters then separates into narrower subbands. The emission takes place in two distinct phases. The 2-6-GHz output, which includes f/sub rho/, rises promptly with the current pulse and then decays. At 6 GHz and above, a low-level microwave prepulse appears simultaneously with the 2-6-GHz output. This output rises sharply 25 ns after the current pulse begins and includes frequencies out to and beyond 40 GHz. The radio-frequency output falls off before the current pulse ends. The microwave intensity decays monotonically with frequency.
Di Capua, M.S.; Camacho, J.F.; Fulkerson, E.S.; Meeker, D.
Effects of foam on ocean surface microwave emission inferred from radiometric observations of reproducible breaking waves
WindSat, the first satellite polarimetric microwave radiometer, and the NPOESS Conical Microwave Imager\\/Sounder both have as a key objective the retrieval of the ocean surface wind vector from radiometric brightness temperatures. Available observations and models to date show that the wind direction signal is only 1-3 K peak-to-peak at 19 and 37 GHz, much smaller than the wind speed signal.
Sharmila Padmanabhan; Steven C. Reising; William E. Asher; L. Allen Rose; Peter W. Gaiser
Coupling the snow thermodynamic model SNOWPACK with the microwave emission model of layered snowpacks for subarctic and arctic snow water equivalent retrievals
NASA Astrophysics Data System (ADS)
Satellite-passive microwave remote sensing has been extensively used to estimate snow water equivalent (SWE) in northern regions. Although passive microwave sensors operate independent of solar illumination and the lower frequencies are independent of atmospheric conditions, the coarse spatial resolution introduces uncertainties to SWE retrievals due to the surface heterogeneity within individual pixels. In this article, we investigate the coupling of a thermodynamic multilayered snow model with a passive microwave emission model. Results show that the snow model itself provides poor SWE simulations when compared to field measurements from two major field campaigns. Coupling the snow and microwave emission models with successive iterations to correct the influence of snow grain size and density significantly improves SWE simulations. This method was further validated using an additional independent data set, which also showed significant improvement using the two-step iteration method compared to standalone simulations with the snow model.
Langlois, A.; Royer, A.; Derksen, C.; Montpetit, B.; Dupont, F.; GoïTa, K.
A large scale microwave emission model for forests. Contribution to the SMOS algorithm
NASA Astrophysics Data System (ADS)
1. INTRODUCTION It is well known that surface soil moisture plays an important role in the water cycle and the global climate. SMOS is a L-Band multi-angle dual-polarization microwave radiometer for global monitoring of this variable. In the areas covered by forests, the opacity is relatively high, and the knowledge of moisture remains problematic. A significant percentage of SMOS pixels at global scale is affected by fractional forest. Whereas the effect of the vegetation can be corrected thanks a simple radiative model, in case of dense forests the wave penetration is limited and the sensitivity to variations of soil moisture is poor. However, most of the pixels are mixed, and a reliable estimate of forest emissivity is important to retrieve the soil moisture of the areas less affected by forest cover. Moreover, there are many sparse woodlands, where the sensitivity to variations of soil moisture is still acceptable. At the scale of spaceborne radiometers, it is difficult to have a detailed knowledge of the variables which affect the overall emissivity. In order to manage effectively these problems, the electromagnetic model developed at Tor Vergata University was combined with information available from forest literature. Using allometric equations and other information, the geometrical and dielectric inputs required by the model were related to global variables available at large scale, such as the Leaf Area Index. This procedure is necessarily approximate. In a first version of the model, forest variables were assumed to be constant in time, and were simply related to the maximum yearly value of Leaf Area Index. Moreover, a unique sparse distribution of trunk diameters was assumed. Finally, the temperature distribution within the crown canopy was assumed to be uniform. The model is being refined, in order to consider seasonal variations of foliage cover, subdivided into arboreous foliage and understory contributions. Different distributions of trunk diameter are being considered. Also the effects of temperature gradients within the crown canopy are being considered. The model was tested against radiometric measurements carried out by towers and aircrafts. A new test has been done using the brightness temperatures measured over some forests in Finland by the AMIRAS radiometer, which is an airborne demonstrator of the MIRAS imaging radiometer to be launched with SMOS. The outputs produced by the model are used to fit the parameters of the simple radiative transfer model which will be used in the Level 2 soil moisture retrieval algorithm. It is planned to compare model outputs with L1C data, which will be made available during the commissioning phase. To this end, a number of adequate extended forest sites are being selected: the Amazon rain forest, the Zaire Basins, the Argentinian Chaco forest, and the Finland forest. 2. PARAMETRIC STUDIES In this paper, results of parametric simulations are shown. The emissivity at vertical and horizontal polarization is simulated as a function of soil moisture content for various conditions of forest cover. Seasonal effects are considered, and the values of Leaf Area Index in winter and summer are taken as basic inputs. The difference between the two values is attributed partially to arboreous foliage and partially to understory, while the woody biomass is assumed to be constant in time. Results indicate that seasonal effects are limited, but not negligible. The simulations are repeated for different distributions of trunk diameters. If the distributions is centered over lower diameter values, the forest is optically thicker, for a given biomass. Also the variations of brightness temperature due to a temperature gradient within the crown canopy have been estimated. The outputs are used to predict the values of a simple first order RT model. 3. COMPARISONS WITH EXPERIMENTAL DATA Results of previous comparisons between model simulations and experimental data are summarized. Experimental data were collected by tower, in the Julich and Les Landes forest (Bray site) and by aircraft, ove
Rahmoune, R.; Della Vecchia, A.; Ferrazzoli, P.; Guerriero, L.; Martin-Porqueras, F.
Superslow Self-Organized Motions in a Multimode Microwave Phonon Laser (Phaser) under Resonant Destabilization of Stationary Acoustic Stimulated Emission
Two qualitatively different kinds of resonant destabilization of phonon\\u000astimulated emission (SE) are experimentally revealed for periodically forced\\u000amultimode ruby phaser (phonon laser) operating at SE frequencies about 9 GHz,\\u000ai.e. at microwave acoustic wavelengths of 1 micron. The inversion state of\\u000aCromium(3+) spin-system in ruby was created by electromagnetic pump at 23 GHz.\\u000aUnder deep modulation of pump power
D. N. Makovetskii
[Determination of trace metals by direct solid sample introduction and high power microwave induced nitrogen plasma atomic emission spectrometry].
The possibility of using direct solid sample introduction coupled with high power microwave induced nitrogen plasma atomic emission spectrometry to determine trace metals in solid samples was investigated. The experimental results show that the solid powder sample could be readily introduced into the plasma with good stability and reproducibility by using a self-assembled solid sample introduction system. The relative standard deviation of the measurements could be controlled to be less than 1% for major components and less than 10% for minor components in the solid samples. PMID:12961896
Zhang, Zhan-en; Wagatsuma, Kazuaki
Determination of silver in nano-plastic food packaging by microwave digestion coupled with inductively coupled plasma atomic emission spectrometry or inductively coupled plasma mass spectrometry
The detection of silver in nano-plastic food packaging by microwave digestion coupled with either inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) was investigated. Microwave digestion was optimised by trialling different acid mixtures. Both ICP-AES and ICP-MS showed good reproducibility, repeatability and recovery. For ICP-AES the limit of detection of the method (LODm) was
Q.-B. Lin; B. Li; H. Song; H.-J. Wu
Optical emission spectroscopy of plasma generated by a waveguide-supplied microwave plasma source operated at 915 MHz
NASA Astrophysics Data System (ADS)
In this paper we present the results of an optical emission spectroscopic study of an atmospheric pressure microwave (915 MHz) nitrogen and nitrogen with carbon dioxide (1%) plasma at high working gas flow rate. This study was aimed at determining rotational Trot and vibrational Tvib temperatures of N2+ ions and N2, CN molecules. The plasma was generated in a waveguide-supplied cavity-resonant type microwave plasma source. All experimental tests were performed with working gas flow rates QN2 between 80 and 320 l min?1 and a power PA absorbed by the plasma microwave varied from 1.5 to 3 kW. The Trot and Tvib temperatures of selected heavy species were determined by comparing the measured and simulated spectra. The measured temperatures of N2+ ions and N2, CN molecules were 6800 to 7500 K (± 250 K), 5000 to 5200 K (± 150 K) and 6100 to 6600 K (± 100 K), respectively, depending on the PA.
Miotk, Robert; Jasinski, Mariusz; Mizeraczyk, Jerzy
Microwave remediation of electronic circuitry waste and the resulting gaseous emissions
NASA Astrophysics Data System (ADS)
The global community has become increasingly dependent on computer and electronic technology. As a result, society is faced with an increasing amount of obsolete equipment and electronic circuitry waste. Electronic waste is generally disposed of in landfills. While convenient, this action causes a substantial loss of finite resources and poses an environmental threat as the circuit board components breakdown and are exposed to the elements. Hazardous compounds such as lead, mercury and cadmium may leach from the circuitry and find their way into the groundwater supply. For this dissertation, a microwave waste remediation system was developed. The system was designed to remove the organic components from a wide variety of electronic circuitry. Upon additional heating of the resulting ash material in an industrial microwave, a glass and metal product can be recovered. Analysis of the metal reveals the presence of precious metals (gold, silver) that can be sold to provide a return on investment. a glass and metal product can be recovered. Analysis of the metal reveals the presence of precious metals (gold, silver) that can be sold to provide a return on investment. Gaseous organic compounds that were generated as a result of organic removal were treated in a microwave off gas system that effectively reduced the concentration of the products emitted by several orders of magnitude, and in some cases completely destroying the waste gas. Upon further heating in an industrial microwave, a glass and metal product were recovered. In order to better understand the effects of processing parameters on the efficiency of the off-gas system, a parametric study was developed. The study tested the microwave system at 3 flow rates (10, 30, and 50 ft 3/min) and three temperatures (400, 700 and 1000°C. In order to test the effects of microwave energy, the experiments were repeated using a conventional furnace. While microwave energy is widely used, the mechanisms of interaction with materials is not well understood. In an effort to better understand how microwaves couple with materials, a newly developed molecular orbital model was investigated. The model proposed an interaction mechanism associated with the development of coupled oscillators upon application of microwave energy. The model was used to model several of the waste gases that appear in the waste stream. Results from experimentation support the data generated thus far.
Schulz, Rebecca L.
Attenuation of soil microwave emissivity by corn and soybeans at 1.4 and 5 GHz
NASA Technical Reports Server (NTRS)
Theory and experiments have shown that passive microwave radiometers can be used to measure soil moisture. However, the presence of a vegetative cover alters the measurement that might be obtained under bare conditions. Deterministically accounting for the effect of vegetation and developing algorithms for extracting soil moisture from observations of a vegetable-soil complex present significant obstacles to the practical use of this approach. The presence of a vegetation canopy reduces the sensitivity of passive microwave instruments to soil moisture variations. The reduction in sensitivity, as compared to a bare-soil relationship, increases as microwave frequency increases, implying that the longest wavelength sensors should provide the most information. Sensitivity also decreases as the amount of vegetative wet biomass increases for a given type of vegetation.
Jackson, Thomas J.; O'Neill, Peggy E.
Tunable one-dimensional microwave emissions from cyclic-transition three-level artificial atoms
By strongly driving a cyclic-transition three-level artificial atom, demonstrated by such as a flux-based superconducting circuit, we show that coherent microwave signals can be excited along a coupled one-dimensional transmission line. Typically, the intensity of the generated microwave is tunable via properly adjusting the Rabi frequencies of the applied strong-driving fields or introducing a probe field with the same frequency. In practice, the system proposed here could work as an on-chip quantum device with controllable atom-photon interaction to implement a total-reflecting mirror or switch for the propagating probe field.
Jia, W. Z. [Quantum Optoelectronics Laboratory, School of Physics and Technology, Southwest Jiaotong University, Chengdu 610031 (China); Wei, L. F. [Quantum Optoelectronics Laboratory, School of Physics and Technology, Southwest Jiaotong University, Chengdu 610031 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Wang, Z. D. [Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Pokfulam Road (Hong Kong)
Field emission from bias-grown diamond thin films in a microwave plasma
A method of producing diamond or diamond like films in which a negative bias is established on a substrate with an electrically conductive surface in a microwave plasma chemical vapor deposition system. The atmosphere that is subjected to microwave energy includes a source of carbon, nitrogen and hydrogen. The negative bias is maintained on the substrate through both the nucleation and growth phase of the film until the film is continuous. Biases between -100V and -200 are preferred. Carbon sources may be one or more of CH.sub.4, C.sub.2 H.sub.2 other hydrocarbons and fullerenes.
Gruen, Dieter M. (Downers Grove, IL); Krauss, Alan R. (Naperville, IL); Ding, Ming Q. (Beijing, CN); Auciello, Orlando (Bolinbrook, IL)
Field emission from bias-grown diamond thin films in a microwave plasma
US Patent & Trademark Office Database
A method of producing diamond or diamond like films in which a negative bias is established on a substrate with an electrically conductive surface in a microwave plasma chemical vapor deposition system. The atmosphere that is subjected to microwave energy includes a source of carbon, nitrogen and hydrogen. The negative bias is maintained on the substrate through both the nucleation and growth phase of the film until the film is continuous. Biases between -100V and -200 are preferred. Carbon sources may be one or more of CH.sub.4, C.sub.2 H.sub.2 other hydrocarbons and fullerenes.
The Contribution of Galactic Free-Free Emission to Anisotropies in the Cosmic Microwave Background Radiation Measured by MSAM
NASA Astrophysics Data System (ADS)
The Medium Scale Anisotropy Measurement (MSAM) experiment has detected anisotropies in the cosmic microwave background radiation with an rms between about 30 mu K and 90 mu K. MSAM uses double-difference and single-difference demodulation signals from a chopped, 30(') beam at a number of frequencies between 170 and 680 GHz. We observed the region covered by MSAM using the Virginia Tech Spectral Line Imaging Camera (SLIC), a wide-field camera sensitive to faint interstellar H? emission. We duplicated the MSAM chopping and demodulation procedure using samples from our H? image (after the subtraction of a continuum image and smoothing to a 30(') beam). The rms in our double-difference and single-difference demodulation signals are 4.4 and 3.0 Rayleighs, respectively. The implied rms for the microwave brightness temperature of the interstellar plasma is <1 mu K at 170 GHz. Thus the MSAM anisotropies are not significantly contaminated by foreground Galactic emission irregularities. This research was supported by NSF grant AST-9319670 and a grant from the Horton Foundation to Virginia Tech.
Simonetti, J. H.; Topasna, G. A.; Dennison, B.
Signal Analysis of Microwave Radiometric Emissions in Hurricanes: Part 1 - Ocean Wind Speed Dependence
Electrical engineering communications technologies contribute significantly to environmental remote sensing. In fact, microwave remote sensing is a primary tool for the measurement of critical environmental parameters, such as oceanic surface wind speed and rain rate, in hurricanes. Our understanding of hurricanes and, ultimately, the safety of people and property depend on our ability to monitor hurricanes as they develop and
Salem Fawwaz El-Nimri; James W. Johnson; W. Linwood Jones
Thermal Microwave Emissions from Vegetated Fields: A Comparison Between Theory and Experiment.
National Technical Information Service (NTIS)
The radiometric measurements over bare field and fields covered with grass, soybean, corn, and alfalfa were made with 1.4 GHz and 5 GHz microwave radiometers during August - October 1978. The measured results are compared with radiative transfer theory tr...
J. R. Wang J. C. Shiue S. L. Chuang M. Dombrowski
Total organochloride and organobromide determinations in aqueous samples by microwave induced plasma-optical emission spectrometry
The element specific detection of the adsorbable organic halogen (AOX) parameter in waters has been investigated by adsorption of the halogenated analytes on activated carbon, incineration to yield carbon dioxide and hydrogen halide, trapping of the halide on a 0.01 M sodium hydroxide solution and online introduction of the halogen formed by continuous oxidation into a microwave induced plasma (MIP).
Bernt Koschuh; Maria Montes; Jose Francisco Camufia; Rosario Pereiro; Alfredo Sanz-Medel
Microwave emission from high Arctic Sea ice during freeze-up
A cooperative sea ice remote sensing experiment was conducted in the eastern Beaufort Sea and Mould Bay area during the freeze-up period in October 1981. Airborne millimeter-wave imagery at 90, 140, and 220 GHz, and nadir microwave radiometric measurements at 19, 22, and 31 GHz, were made from a U. S. Naval Research Laboratory aircraft, while the Canadian Atmospheric Environmental
J. P. Hollinger; B. E. Troy; R. O. Ramseier; K. W. Asmus; M. F. Hartman; C. A. Luther
Microwave Radiometer (MWR) Handbook
The Microwave Radiometer (MWR) provides time-series measurements of column-integrated amounts of water vapor and liquid water. The instrument itself is essentially a sensitive microwave receiver. That is, it is tuned to measure the microwave emissions of the vapor and liquid water molecules in the atmosphere at specific frequencies.
Morris, VR
Microwave radio emissions of negative cloud-to-ground lightning flashes
NASA Astrophysics Data System (ADS)
We report preliminary results of a new observational study of microwave-frequency electromagnetic radiation that is emitted by lightning discharge processes. Radiation was observed with a ceramic patch antenna and a digital radio receiver tuned to a center frequency of 1.63 GHz and a bandwidth of 2 MHz. The recorded radiation waveforms are compared with data collected by the Oklahoma Lightning Mapping Array (OKLMA) lightning mapping system and the co-located Earth Networks Total Lightning Network (ENTLN) broadband electric field antenna. Microwave radiation was observed to occur during preliminary breakdown, negative stepped leader breakdown, negative dart leader breakdown, and return strokes. Characteristic radiation signatures were observed, including trains of individually resolvable impulses during breakdown and brief but intense trains of noise-like bursts during return strokes.
Petersen, D.; Beasley, W.
Fast polarization changes in mm microwave emission of weak multistructured solar bursts
NASA Technical Reports Server (NTRS)
Circular polarization of weak multistructured solar bursts was measured at mm microwaves with unprecedented sensitivity (0.03 sfu rms) and high time resolution (1ms). It was shown that sudden changes occur in the degree of polarization with time scales of 0.04 to 0.3 s. In most cases the degree of polarization attained maximum values before the maximum flux in both mm microwaves and hard X-rays with time scales of 0.04 to 1.0 s. The timing accuracy in determining the degree of polarization was 40 ms. Physical phenomena are discussed invoking one or a combination of various possible causes for the observed effects. The bursts at mm microwaves were weak compared to the contribution of the preexisting active regions, and therefore the changes in magnetoionic propagation conditions for emerging radiation plays an important role in the observed effects. Composite effects due to more than one polarizing mechanism or more than one polarized spots within the antenna beam are discussed.
Kaufmann, P.; Strauss, F. M.; Costa, J. E. R.; Dennis, B. R.
Design of red/green emissive lanthanide activated nano-materials by supersonic and microwave co-irradiations
NASA Astrophysics Data System (ADS)
ZnSnO3:Eu3+ and Sr1-xCaxMoO4:Tb3+ nanocrystals with controlled shape have been assembled in the presence of two driving forces (supersonic microwave co-assistance, abbreviated as SMC) simultaneously in less than 60 min at very low temperature (80 °C). Scanning Electronic Microscope (SEM) images further supported the existence of cubic crystals and shuttle-like structures. More interestingly, Eu(III) ion has been encapsulated into zinc stannate for the first time and ZnSnO3:Eu3+ can exhibit red emissions excited by long wavelength (395 nm). Similarly, it was found that Sr1-xCaxMoO4:Tb3+ had striking green luminescence. The parameters to improve the optical properties have been studied in detail. This convenient approach may be applicable to construct other phosphors with well-defined crystalline structures.
Wang, Qianming; Huo, Jiansheng; Zheng, Yuhui; Pang, Shuting; He, Zhouzhi
Manifestation of large-scale kink oscillations of coronal loops in the low frequency modulations of solar microwave emission
NASA Astrophysics Data System (ADS)
Very-low-frequency fluctuations (¡ 0.01 Hz) of solar microwave radiation were analysed by means of a "sliding window" Fourier transform combined with the Wigner-Ville technique. In view of the fact that slow variations of the magnetic field in the radiation source, as well as a large-scale motion of the source, can modulate the intensity of the received radio signal, we considered large-scale kink-type oscillatory motions of coronal loops which were accompanied also by periodic magnetic stress, created near the loops footpoints during each inclination of loop, i.e. two times per the oscillation cycle. In such cases a properly located observer, besides of the modulation caused by motion of the emission diagram pattern at the main oscillation frequency, may see also modulation at a double frequency of the loop oscillation as well as much weaker higher harmonics. Therefore, the presence in the very-low-frequency spectra of the lines at the main and double frequency of the loop oscillation ("modulation pairs") may indicate about a kink-type oscillatory dynamics of the loop. Special attention in the present study has been paid to the analysis of modulations of microwave emission recorded at the same time when TRACE EUV telescope observed large scale oscillations of coronal loops. The applied data analysis technique, besides of the modulations connected with loop kink oscillations seen by TRACE, enables to detect also the modulations associated with kink oscillations of smaller (invisible for TRACE) loops. Acknowledgements: MLK and TZ acknowledge Austrian Fond zur Fürderung der wissenschaftlichen Forschung (project P21197-N16); MP and HOR acknowledge Austrian Fond zur Fürderung der wissenschaftlichen Forschung (project P20680-N16).
Khodachenko, Maxim; Kislyakova, Kristina; Zaqarashvili, Teimuraz; Kislyakov, Albert; Panchenko, Mykhaylo; Zaitsev, Valerii; Rucker, Helmut
The Air Microwave Yield (AMY) experiment to measure the GHz emission from air shower plasmas
NASA Astrophysics Data System (ADS)
The AMY experiment aims to measure the Microwave Bremsstrahlung Radiation (MBR) emitted by air-showers secondary electrons accelerating in collisions with neutral molecules of the atmosphere. The measurements are performed at the Beam Test Facility (BTF) of Frascati INFN National Laboratories and the final purpose is to characterize the process to be used in a next generation detectors of ultra-high energy cosmic rays (up to 1020eV). We describe the experimental set-up and the first test measurement performed in November 2011.
Alvarez-Muñiz, J.; Bohacova, M.; Cataldi, G.; Coluccia, M. R.; Creti, P.; De Mitri, I.; Di Giulio, C.; Engel, R.; Facal San Luis, P.; Iarlori, M.; Martello, D.; Monasor, M.; Perrone, L.; Petrera, S.; Privitera, P.; Riegel, M.; Rizi, V.; Rodriguez Fernandez, G.; Salamida, F.; Salina, G.; Settimo, M.; Smida, R.; Verzi, V.; Werner, F.; Williams, C.
Microwave emission from snow and glacier ice. [brightness temperature for snow fields
NASA Technical Reports Server (NTRS)
The microwave brightness temperature for snow fields was studied assuming that the snow cover consists of closely packed scattering spheres which do not interact coherently. The Mie scattering theory was used to compute the volume scattering albedo. It is shown that in the wavelength range from 0.8 to 2.8 cm, most of the micro-radiation emanates from a layer 10 meters or less in thickness. It is concluded that it is possible to determine snow accumulation rates as well as near-surface temperature.
Chang, T. C.; Gloersen, P.; Schmugge, T.; Wilheit, T. T.; Zwally, H. J.
The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study
NASA Astrophysics Data System (ADS)
Satellite observations of microwave brightness temperatures between 19 GHz and 85 GHz are the main data sources for operational sea-ice monitoring and retrieval of ice concentrations. However, microwave brightness temperatures depend on the emissivity of snow and ice, which is subject to pronounced seasonal variations and shows significant hemispheric contrasts. These mainly arise from differences in the rate and strength of snow metamorphism and melt. We here use the thermodynamic snow model SNTHERM forced by European Re-Analysis (ERA) interim data and the Microwave Emission Model of Layered Snowpacks (MEMLS), to calculate the sea-ice surface emissivity and to identify the contribution of regional patterns in atmospheric conditions to its variability in the Arctic and Antarctic. The computed emissivities reveal a pronounced seasonal cycle with large regional variability. The emissivity variability increases from winter to early summer and is more pronounced in the Antarctic. In the pre-melt period (January-May, July-November) the standard deviations in surface microwave emissivity due to diurnal, regional and inter-annual variability of atmospheric forcing reach up to ?? = 0.034, 0.043, and 0.097 for 19 GHz, 37 GHz and 85 GHz channels, respectively. Between 2000 and 2009, small but significant positive emissivity trends were observed in the Weddell Sea during November and December as well as in Fram Strait during February, potentially related to earlier melt onset in these regions. The obtained results contribute to a better understanding of the uncertainty and variability of sea-ice concentration and snow-depth retrievals in regions of high sea-ice concentrations.
Willmes, S.; Nicolaus, M.; Haas, C.
Rock fraction effects on the interpretation of microwave emission from soils
NASA Technical Reports Server (NTRS)
The effect of the rock fraction of soil on emissivity is presently investigated through a combination of laboratory dielectric measurements and field observation of emissivity from soils with and without rocks. The rock fraction reduced the range of emissivity; beyond this, it appears to be important only in determining the moisture in the soil component. Data gathered at 6 cm indicate that the presence of rocks renders this and shorter wavelengths useless as soil-moisture sensors. Modeling of the 21-cm case suggest that rock-fraction effects on soil dielectric properties can be compensated for by the greater surface roughness.
Jackson, Thomas J.; Kostov, Kosta G.; Saatchi, Sasan S.
Study on anti-emission materials for non-emitting grid applications in microwave power tubes
Hafnium and platinum were deposited onto molybdenum grids by ion-beam assisted deposition method. Electron-emission characteristics from molybdenum grids with Hf and Pt films, which were contaminated by active electron-emission substances (Ba, BaO) of the cathode, were measured using analogous diode method. The surfaces of grids were analyzed by X-ray diffraction. The results revealed that the reaction between BaO and Hf
J. Jiang; B. Y. Jiang; C. X. Ren; F. M. Zhang; T. Feng; X. Wang; X. H. Liu; S. C. Zou
Miniaturized dielectric barrier discharge carbon atomic emission spectrometry with online microwave-assisted oxidation for determination of total organic carbon.
A simple, rapid, and portable system consisted of a laboratory-built miniaturized dielectric barrier discharge atomic emission spectrometer and a microwave-assisted persulfate oxidation reactor was developed for sensitive flow injection analysis or continuous monitoring of total organic carbon (TOC) in environmental water samples. The standard/sample solution together with persulfate was pumped to the reactor to convert organic compounds to CO2, which was separated from liquid phase and transported to the spectrometer for detection of the elemental specific carbon atomic emission at 193.0 nm. The experimental parameters were systematically investigated. A limit of detection of 0.01 mg L(-1) (as C) was obtained based on a 10 mL sample injection volume, and the precision was better than 6.5% (relative standard deviation, RSD) at 0.1 mg L(-1). The system was successfully applied for TOC analysis of real environmental water samples. The obtained TOC value of 30 test samples agreed well with those by the standard high-temperature combustion coupled nondispersive infrared absorption method. Most importantly, the system showed good capability of in situ continuous monitoring of total organic carbon in environmental water. PMID:24862626
Han, Bingjun; Jiang, Xiaoming; Hou, Xiandeng; Zheng, Chengbin
Asymmetric absorption and emission of energy by a macroscopic mechanical oscillator in a microwave circuit optomechanical system
NASA Astrophysics Data System (ADS)
We measure the asymmetry in rates for emission and absorption of mechanical energy in an electromechanical system composed of a macroscopic suspended membrane coupled to a high-Q, superconducting microwave resonant circuit. This asymmetry is inherently quantum mechanical because it arises from the inability to annihilate the mechanical ground state. As such, it is only appreciable when the average mechanical occupancy approaches one. This measurement is now possible due to the recent achievement of ground state cooling of macroscopic mechanical oscillators [1,2]. Crucially, we measure the thermal cavity photon occupancy and account for it in our analysis. Failure to correctly account for the interference of these thermal photons with the mechanical signal can lead to a misinterpretation of the data and an overestimate of the emission/absorption asymmetry. [4pt] [1] J. D. Teufel, T. Donner, Dale Li, J. W. Harlow, M. S. Allman, K. Cicak, A. J. Sirois, J. D. Whittaker, K. W. Lehnert, R. W. Simmonds, ``Sideband Cooling Micromechanical Motion to the Quantum Ground State,'' Nature, 475, 359-363 (2011).[0pt] [2] Jasper Chan, et al, ``Laser cooling of a nanomechanical oscillator into its quantum ground state,'' Nature, 478, 89-92 (2011).
Harlow, Jennifer; Palomaki, Tauno; Kerckhoff, Joseph; Teufel, John; Simmonds, Raymond; Lehnert, Konrad
Thermal microwave emission from vegetated fields - A comparison between theory and experiment
NASA Technical Reports Server (NTRS)
The radiometric measurements over bare field and fields covered with grass, soybean, corn, and alfalfa were made with 1.4- and 5-GHz microwave radiometers during August-October 1978. The measured results are compared with radiative transfer theory treating the vegetated fields as a two-layer random medium. It is found that the presence of a vegetation cover generally gives a higher brightness temperature T sub B than that expected from a bare soil. The amount of this T sub B excess increases with increase in the vegetation biomass and in the frequency of the observed radiation. The results of radiative transfer calculations, which include a parameter characterizing ground surface roughness, generally match well with the experimental data.
Wang, J. R.; Shiue, J. C.; Dombrowski, M.; Chuang, S. L.; Shin, R. T.
Frequency and Angular Variations of Land Surface Microwave Emissivities: Can we Estimate SSM/T and AMSU Emissivities from SSM/I Emissivities?
NASA Technical Reports Server (NTRS)
To retrieve temperature and humidity profiles from SSM/T and AMSU, it is important to quantify the contribution of the Earth surface emission. So far, no global estimates of the land surface emissivities are available at SSM/T and AMSU frequencies and scanning conditions. The land surface emissivities have been previously calculated for the globe from the SSM/I conical scanner between 19 and 85 GHz. To analyze the feasibility of deriving SSM/T and AMSU land surface emissivities from SSM/I emissivities, the spectral and angular variations of the emissivities are studied, with the help of ground-based measurements, models and satellite estimates. Up to 100 GHz, for snow and ice free areas, the SSM/T and AMSU emissivities can be derived with useful accuracy from the SSM/I emissivities- The emissivities can be linearly interpolated in frequency. Based on ground-based emissivity measurements of various surface types, a simple model is proposed to estimate SSM/T and AMSU emissivities for all zenith angles knowing only the emissivities for the vertical and horizontal polarizations at 53 deg zenith angle. The method is tested on the SSM/T-2 91.655 GHz channels. The mean difference between the SSM/T-2 and SSM/I-derived emissivities is less than or equal to 0.01 for all zenith angles with an r.m.s. difference of approx. = 0.02. Above 100 GHz, preliminary results are presented at 150 GHz, based on SSM/T-2 observations and are compared with the very few estimations available in the literature.
Prigent, Catherine; Wigneron, Jean-Pierre; Rossow, William B.; Pardo-Carrion, Juan R.
Frequency and Angular Variations of Land Surface Microwave Emissivities: Can we Estimate SSM/T and AMSU Emissivities from SSM/I Emissivities.
National Technical Information Service (NTIS)
To retrieve temperature and humidity profiles from SSM/T and AMSU, it is important to quantify the contribution of the Earth surface emission. So far, no global estimates of the land surface emissivities are available at SSM/T and AMSU frequencies and sca...
C. Prigent J. P. Wigneron W. B. Rossow J. R. Pardo-Carrion
Connecting Surface Emissions, Convective Uplifting, and Long-Range Transport of Carbon Monoxide in the Upper Troposphere: New Observations from the Aura Microwave Limb Sounder
NASA Technical Reports Server (NTRS)
Two years of observations of upper tropospheric (UT) carbon monoxide (CO) from the Aura Microwave Limb Sounder are analyzed; in combination with the CO surface emission climatology and data from the NCEP analyses. It is shown that spatial distribution, temporal variation and long-range transport of UT CO are closely related to the surface emissions, deep-convection and horizontal winds. Over the Asian monsoon region, surface emission of CO peaks in boreal spring due to high biomass burning in addition to anthropogenic emission. However, the UT CO peaks in summer when convection is strongest and surface emission of CO is dominated by anthropogenic source. The long-range transport of CO from Southeast Asia across the Pacific to North America, which occurs most frequently during boreal summer, is thus a clear imprint of Asian anthropogenic pollution influencing global air quality.
Jiang, Jonathan H.; Livesey, Nathaniel J.; Su, Hui; Neary, Lori; McConnell, John C.; Richards, Nigel A. D.
Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 108 2
NASA Technical Reports Server (NTRS)
This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1 SIN 108, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).
Valdez, A.
Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 109
NASA Technical Reports Server (NTRS)
This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 109, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).
Valdez, A.
Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A2, S/N 108, 08
NASA Technical Reports Server (NTRS)
This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A2, S/N 108, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).
Valdez, A.
Determining the microwave emissivity of sea-ice at AMSU-B frequencies for use in operational numerical weather prediction assimilation schemes
NASA Astrophysics Data System (ADS)
Possible methods for improving the way in which the emissivity of sea ice is represented in numerical weather prediction (NWP) assimilation schemes, and hence allowing increased exploitation of satellite data in these traditionally data sparse regions, are investigated by comparing emissivities retrieved from in-situ, airborne observations in the arctic and those derived from two different models. Further information is provided by sea ice type and concentration products derived from Special Sensor Microwave Imager (SSM/I) observations. Analysis of the aircraft derived emissivities shows a definite relationship between the emissivities at 157 GHz and 183 GHz irrespective of the ice type (R2 = 0.97), and while this is not the case for the window channel at 89 GHz and the two higher frequencies (R2 = 0.55), it will be shown that by sub setting the emissivities according to ice type results in a stronger relationship between these frequencies for first year ice (R2 = 0.66 between 89 and 183 GHz) while the relationships for multi year ice are weaker. The retrieved emissivities are also compared with two emissivity models, the fast emissivity model (FASTEM) which assigns an emissivity to a prescribed ice type and a model from the NOAA (National Oceanographic and Atmospheric Administration) which uses an empirical approach based on retrievals from Advanced Microwave Sounding Unit (AMSU) brightness temperatures. The NOAA model performed better than FASTEM, although FASTEM performance was improved by weighting the emissivity spectra by the sea ice type and concentration information given by the SSM/I derived products.
Pollard, David F.
Emissivity measurements in thin metallized membrane reflectors used for microwave radiometer sensors
NASA Astrophysics Data System (ADS)
This paper is concerned with electromagnetic losses in metallized films used for inflatable reflectors. An inflatable membrane is made of tough elastic material such as Kapton, and it is not electromagnetically reflective by design. A film of conducting metal is added to the membrane to enhance its reflective properties. Since the impetus for use of inflatables for spacecraft is the light weight and compact packaging, it is important that the metal film be as thin as possible. However, if the material is not conductive or thick enough, the radiation due to the emissivity of the reflector could be a significant part of the radiation gathered by the radiometer. The emissivity would be of little consequence to a radar or solar collector; but for a radiometer whose signal is composed of thermal radiation, this contribution could be severe. Bulk properties of the metal film cannot be used to predict its loss. For this reason, a program of analysis and measurement was undertaken to determine the emissivities of a number of candidate metallized film reflectors. This paper describes the three types of measurements which were performed on the metallized thin films: (1) a network analyzer system with an L-band waveguide; (2) an S-band radiometer; and (3) a network analyzer system with a C-band antenna free-space transmission system.
Schroeder, Lyle C.; Cravey, Robin L.; Scherner, Michael J.; Hearn, Chase P.; Blume, Hans-Juergen C.
Calculations of the spectral nature of the microwave emission from soils. [Arizona and Georgia
NASA Technical Reports Server (NTRS)
The brightness temperatures for a set of soil profiles observed at USDA facilities in Arizona and Georgia were calculated at the wavelengths of 2.8, 6, 11, 21, and 49 cm using a coherent radiative transfer model. The soil moisture sampling depth is found to be a function of wavelength and is in the range 0.06 to 0.1 of a wavelength. The thermal sampling depth also depends on wavelength and is approximately equal to one wavelength at dry soil condition and 0.1 - 0.5 wavelengths at wet soil conditions. Calculated values of emissivity show strong diurnal variations when the soils are wet, while there is little diurnal change when the soil is dry. The soil moistures within the four depth intervals of 0-2, 0-5, 0-9, and 0-15 cm were parameterized as function of the calculated emissivity and brightness temperature. Best-fit parameters and correlation coefficients are presented for five wavelengths. Interrelationships among the effective temperature, surface temperature, and emissivity are displayed.
Mo, T.; Schmugge, T. J.; Choudhury, B. J. (principal investigators)
Angular and polarization measurements of snow and bare soil microwave reflective and emissive characteristics by ka-band (37GHz), combined scatterometer-radiometer system
NASA Astrophysics Data System (ADS)
In this paper the results of spatio-temporally collocated polarization measurements of snow and bare soil (covered by old and dry lying stems of wheat and weed) microwave reflective (radar backscattering coefficient) and emissive (brightness temperature) characteristics angular dependences at ~37GHz are presented. As well as a structure and operational features of utilized Ka-band, multi-polarization, combined scatterometer-radiometer system, measuring and calibration facilities are discussed.
Grigoryan, Malanya L.; Arakelyan, Artashes K.; Hambaryan, Astghik K.; Arakelyan, Arsen A.
Gyro-synchrotron emission in a magnetic dipole field for the application to the center-to-limb variation of microwave impulsive bursts
In order to interpret the observed center to limb variations of spectrum and polarization of microwave impulsive bursts, gyro-synchrotron emission from nonthermal electrons trapped in a magnetic dipole field is computed. The theoretical spectrum and polarization are consistent with observed ones if we put an outer boundary of the radio source at a layer of 100-60 G or (7–9) ×
Tatsuo Takakura; Eugenio Scalise
The self absorption of gyro-synchrotron emission in a magnetic dipole field: Microwave impulsive burst and hard X-ray burst
The gyro-synchrotron emission from a model source with a non-uniform magnetic field is computed taking into account the self absorption. This model seems adequate not only to interpret the radio spectrum and its time variation of microwave impulsive bursts but also to solve the discrepancy between the numbers of non-thermal electrons emitting radio burst and those emitting hard X-ray burst.
Tatsuo Takakura
Enhancement of secondary electron emission by annealing and microwave hydrogen plasma treatment of ion-beam-damaged diamond films
NASA Astrophysics Data System (ADS)
In this work we investigate the influence of annealing and microwave (MW) hydrogen plasma exposure of ion-beam-irradiated diamond film surfaces. In particular, we are interested in the recovery of secondary electron emission (SEE) and negative electron affinity (NEA) by removal of the damaged layer. To this aim, we correlate the SEE of variously treated Xe+ ion-damaged diamond films with their bonding structure in the near-surface region, as identified by near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and x-ray photoelectron spectroscopy. The 30 keV Xe+ ion bombardment of hydrogenated polycrystalline diamond films to a dose of 2×1015 cm-2 results in the transformation of the near-surface region of a diamond film to sp2-bonded amorphous carbon, increased oxygen adsorption, shift of the electron affinity from negative to positive, and strong degradation of its electron emission properties, although it does not induce a pronounced depletion of hydrogen. Exposure of the ion-bombarded films to MW hydrogen plasma treatment for 30 min produces NEA diamond surfaces, but only partially regenerates SEE properties, retains some imperfection in the near-surface atomic layers, as determined by NEXAFS, and the concentration of oxygen remains relatively high. Subsequent annealing to 610 °C produces oxygen-free diamond films and somewhat increases their SEE. Annealing to 1000 °C results in desorption of the surface hydrogen, formation of positive electron affinity surfaces, and drastically degrades their electron emission properties. Prolonged (up to three hours) MW hydrogen plasma treatment of as-implanted diamond films gradually improves their crystal quality and results in a further increase of SEE intensity. The SEE intensity after three hours MW hydrogen plasma exposure of the ion-beam-irradiated films was found to be ~50% above the value obtained for the as-deposited diamond films. This treatment does not, however, substantially reduce the concentration of oxygen in the previously damaged diamond, indicating its bulk diffusion during or after ion bombardment. Our results show that removal of damage from a highly disordered diamond surface and recovery of its electron emission properties are possible by MW hydrogen plasma. However, it is a slow process. This is most likely due to the very low etching rate of the low-level damage at the end of the ion beam range.
Laikhtman, A.; Hoffman, A.
Partial microwave-assisted wet digestion of animal tissue using a baby-bottle sterilizer for analyte determination by inductively coupled plasma optical emission spectrometry
NASA Astrophysics Data System (ADS)
A procedure for partial digestion of bovine tissue is proposed using polytetrafluoroethylene (PTFE) micro-vessels inside a baby-bottle sterilizer under microwave radiation for multi-element determination by inductively coupled plasma optical emission spectrometry (ICP OES). Samples were directly weighed in laboratory-made polytetrafluoroethylene vessels. Nitric acid and hydrogen peroxide were added to the uncovered vessels, which were positioned inside the baby-bottle sterilizer, containing 500 mL of water. The hydrogen peroxide volume was fixed at 100 µL. The system was placed in a domestic microwave oven and partial digestion was carried out for the determination of Ca, Cu, Fe, Mg, Mn and Zn by inductively coupled plasma optical emission spectrometry. The single-vessel approach was used in the entire procedure, to minimize contamination in trace analysis. Better recoveries and lower residual carbon content (RCC) levels were obtained under the conditions established through a 2 4-1 fractional factorial design: 650 W microwave power, 7 min digestion time, 50 µL nitric acid and 50 mg sample mass. The digestion efficiency was ascertained according to the residual carbon content determined by inductively coupled plasma optical emission spectrometry. The accuracy of the proposed procedure was checked against two certified reference materials.
Matos, Wladiana O.; Menezes, Eveline A.; Gonzalez, Mário H.; Costa, Letícia M.; Trevizan, Lilian C.; Nogueira, Ana Rita A.
Microwave scattering and emission properties of large impact craters on the surface of Venus
NASA Technical Reports Server (NTRS)
Many of the impact craters on Venus imaged by the Magellan synthetic aperture radar (SAR) have interior floors with oblique incidence angle backscatter cross sections 2 to 16 times (3 dB to 12 dB) greater than the average scattering properties of the planet's surface. Such high backscatter cross sections are indicative of a high degree of wavelength-scale surface roughness and/or a high intrinsic reflectivity of the material forming the crater floors. Fifty-three of these (radar) bright floored craters are associated with 93 percent of the parabolic-shaped radar-dark features found in the Magellan SAR and emissivity data, features that are thought to be among the youngest on the surface of Venus. It was suggested by Campbell et al. that either the bright floors of the parabolic feature parent craters are indicative of a young impact and the floor properties are modified with time to a lower backscatter cross section or that they result from some property of the surface or subsurface material at the point of impact or from the properties of the impacting object. As a continuation of earlier work we have examined all craters with diameters greater than 30 km (except 6 that were outside the available data) so both the backscatter cross section and emissivity of the crater floors could be estimated from the Magellan data.
Stacy, N. J. S.; Campbell, D. B.; Devries, C.
Lower hybrid resonance acceleration of electrons and ions in solar flares and the associated microwave emission
NASA Technical Reports Server (NTRS)
The particle acceleration processes here studied are driven by the relaxation of unstable ion ring distributions; these produce strong wave activity at the lower hybrid resonance frequency which collapses, and forms energetic electron and ion tails. The results obtained are applied to the problem posed by the production of energetic particles by solar flares. The numerical simulation results thus obtained by a 2 1/2-dimensional particle-in-cell code show a simultaneous acceleration of electrons to 10-500 keV energies, and of ions to as much as the 1 MeV range; the energy of the latter is still insufficient to account for gamma-ray emission in the 4-6 MeV range, but furnish a seed population for further acceleration.
Mcclements, K. G.; Bingham, R.; Su, J. J.; Dawson, J. M.; Spicer, D. S.
Impact of Hillslope-Scale Organization of Topography, Soil Moisture, Soil Temperature, and Vegetation on Modeling Surface Microwave Radiation Emission
Microwave radiometry will emerge as an important tool for global remote sensing of near-surface soil moisture in the coming decade. In this modeling study, we find that hillslope-scale topography (tens of meters) influences microwave brightness temperatures in a way that produces bias at coarser scales (kilometers). The physics underlying soil moisture remote sensing suggests that the effects of topography on
Alejandro N. Flores; Valeriy Y. Ivanov; Dara Entekhabi; Rafael L. Bras
In search of water vapor on Jupiter: Laboratory measurements of the microwave properties of water vapor and simulations of Jupiter's microwave emission in support of the Juno Mission
This research has involved the conduct of a series of laboratory measurements of the centimeter-wavelength opacity of water vapor along with the development of a hybrid radiative transfer ray-tracing simulator for the atmosphere of Jupiter which employs a model for water vapor opacity derived from the measurements. For this study an existing Georgia Tech high-sensitivity microwave measurement system (Hanley and
Bryan Mills Karpowicz
Anomalous conductivity in Hall thrusters: Effects of the non-linear coupling of the electron-cyclotron drift instability with secondary electron emission of the walls
NASA Astrophysics Data System (ADS)
With the help of an implicit particle-in-cell code, we have shown in a previous paper that the electron-cyclotron drift instability was able to induce anomalous conductivity as well as anomalous heating. As such it can be a major actor among the mechanisms involved in the operation of Hall thrusters. However, experimental results show that the nature of wall material has a significant effect on the behavior of the thruster. The purpose of this paper is to study the plasma-wall interaction in the case where the plasma is heated self-consistently by electrostatic fluctuations induced by the electron-cyclotron drift instability.
Héron, A.; Adam, J. C.
Anomalous conductivity in Hall thrusters: Effects of the non-linear coupling of the electron-cyclotron drift instability with secondary electron emission of the walls
With the help of an implicit particle-in-cell code, we have shown in a previous paper that the electron-cyclotron drift instability was able to induce anomalous conductivity as well as anomalous heating. As such it can be a major actor among the mechanisms involved in the operation of Hall thrusters. However, experimental results show that the nature of wall material has a significant effect on the behavior of the thruster. The purpose of this paper is to study the plasma-wall interaction in the case where the plasma is heated self-consistently by electrostatic fluctuations induced by the electron-cyclotron drift instability.
Héron, A.; Adam, J. C. [Centre de physique théorique, CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex (France)] [Centre de physique théorique, CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex (France)
Investigation of electrochemical hydride generation coupled to microwave plasma torch optical emission spectrometry for the determination of arsenic: analytical figures of merit, interference studies and applications to environmentally relevant samples
A continuous flow thin layer electrolysis cell with a Pt cathode in combination with a microwave plasma torch operated with Ar as working gas was used for the optical emission spectrometric determination of As with the hydride technique. Under the optimised conditions the limit of detection (3?) in the case of the As(I) 228.81 nm emission line was 81 ng
Martin A. Amberger; Nicolas H. Bings; Pawel Pohl; José A. C. Broekaert
Effects of buckyballs and cosmic strings on the cosmic microwave background
NASA Astrophysics Data System (ADS)
This thesis consists of two Cosmic Microwave Background related projects: a simulation of an anomalous foreground component, and a search for a distinct background signature. The Cosmic Microwave Background forms one of the three major pillars of support for the Big Bang theory of the origin of the universe, and is an important source of information about the early universe. The first of two components of this thesis proposes a possible explanation for an anomalous component of our Galaxy's foreground contribution to the Cosmic Microwave Background. The second component of this thesis searches for signatures of early universe phase transition products called Cosmic strings. We propose that Fullerene molecules, or, buckyballs, may compose part of the interstellar medium. Their thermal rotational angular velocity is on the order of GHz, which lies within the range of the "anomalous free-free emission" that is correlated with interstellar dust found in Galactic foreground maps of the Cosmic Microwave Background. We have written a Monte Carlo code to simulate the radiation from spinning partially hydrogenated fullerene molecules. We quantify the emission, compare it to the Galactic foreground, and find that if C 20 comprises 0.5% of the Galactic carbon budget, then there are sufficient buckyballs to make it possible for fullerene molecules be responsible for the anomalous free-free emission. We also performed a search for signatures of cosmic strings in the Cosmic Microwave Background data from the Wilkinson Microwave Anisotropy Probe. We used a digital filter designed to search for individual cosmic strings and found no evidence for them in the WMAP CMB anisotropies to a level of ? T / T ˜ 0.29 mK. This corresponds to an absence of cosmic strings with G ? [Special characters omitted.] 1.07 =D7 10 -5 for strings moving with velocity v = c /[Special characters omitted.] . We have searched the WMAP data for evidence of a cosmic string recently reported as the CSL-1 object. We found that if the signatures at CSL-1 were produced by cosmic strings, these strings would have to move with a velocity [Special characters omitted.] 0.94c. We also present preliminary limits on the CMB data that will be returned by the PLANCK satellite for comparison. With the available information on the PLANCK satellite, we calculated that it would be twice as sensitive to cosmic strings as WMAP.
Lo, Amy Shiu-Mei
X-radiation /E greater than 10 keV/, H-alpha and microwave emission during the impulsive phase of solar flares.
NASA Technical Reports Server (NTRS)
A study has been made of the variation in hard (E greater than 10 keV) X-radiation, H-alpha and microwave emission during the impulsive phase of solar flares. Analysis shows that the rise-time in the 20-30-keV X-ray spike depends on the electron hardness. The impulsive phase is also marked by an abrupt, very intense increase in H-alpha emission in one or more knots of the flare. Properties of these H-alpha kernels include: (1) a luminosity several times greater than the surrounding flare, (2) an intensity rise starting about 20-30 sec before, peaking about 20-25 sec after, and lasting about twice as long as the hard spike, (3) a location lower in the chromosphere than the remaining flare, (4) essentially no expansion prior to the hard spike, and (5) a position within 6000 km of the boundary separating polarities, usually forming on both sides of the neutral line near both feet of the same tube of force. Correspondingly, impulsive microwave events are characterized by: (1) great similarity in burst structure with 20-32 keV X-rays but only above 5000 MHz, (2) typical low frequency burst cutoff between 1400-3800 MHz, and (3) maximum emission above 7500 MHz.
Vorpahl, J. A.
LIRAS mission for lunar exploration by microwave interferometric radiometer: Moon's subsurface characterization, emission model and numerical simulator
NASA Astrophysics Data System (ADS)
The "Lunar Interferometric Radiometer by Aperture Synthesis" (LIRAS) mission is promoted by the Italian Space Agency and is currently in feasibility phase. LIRAS' satellite will orbit around the Moon at a height of 100 km, with a revisiting time period lower than 1 lunar month and will be equipped with: a synthetic aperture radiometer for subsurface sounding purposes, working at 1 and 3 GHz, and a real aperture radiometer for near-surface probing, working at 12 and 24 GHz. The L-band payload, representing a novel concept for lunar exploration, is designed as a Y-shaped thinned array with three arms less than 2.5 m long. The main LIRAS objectives are high-resolution mapping and vertical sounding of the Moon subsurface by applying the advantages of the antenna aperture synthesis technique to a multi-frequency microwave passive payload. The mission is specifically designed to achieve spatial resolutions less than 10 km at surface and to retrieve thermo-morphological properties of the Moon subsurface within 5 m of depth. Among LIRAS products are: lunar near-surface brightness temperature, subsurface brightness temperature gross profile, subsurface regolith thickness, density and average thermal conductivity, detection index of possible subsurface discontinuities (e.g. ice presence). The following study involves the preliminary design of the LIRAS payload and the electromagnetic and thermal characterization of the lunar subsoil through the implementation of a simulator for reproducing the LIRAS measurements in response to observations of the Moon surface and subsurface layers. Lunar physical data, collected after the Apollo missions, and LIRAS instrument parameters are taken as input for the abovementioned simulator, called "LIRAS End-to-end Performance Simulator" (LEPS) and obtained by adapting the SMOS End-to-end Performance Simulator to the different instrumental, orbital, and geophysical LIRAS characteristics. LEPS completely simulates the behavior of the satellite when it becomes operational providing the extrapolation of lunar brightness temperature maps in both Antenna frame (the cosine domain) and on the Moon surface and allowing an accurate analysis of the instrument performance. The Moon stratigraphy is reproduced in LEPS environment through three scenarios: a macro-layer of regolith; two subsequent macro-layers of regolith and rock; three subsequent macro-layers of regolith, ice and rock, respectively. These scenarios are studied using an incoherent approach, taking into account the interaction between the upwelling and downwelling radiation contributions from each layer to model the resulting brightness temperature at the surface level. It has been considered that the radiative behavior of the Moon varies over time, depending on solar illumination conditions, and it is also function of the material properties, layer thickness and specific position on the lunar crust; moreover it has been examined its variation with frequency, observation angle, and polarization. Using the proposed emission model it has been possible to derive a digital thermal model in the microwave frequency of the Moon, allowing in-depth analysis of the lunar soil consistency; this collected information could be related with a lunar digital elevation model in order to achieve global coverage information on topological aspects. The main results of the study will be presented at the conference.
Pompili, Sara; Silvio Marzano, Frank; Di Carlofelice, Alessandro; Montopoli, Mario; Talone, Marco; Crapolicchio, Raffaele; L'Abbate, Michelangelo; Varchetta, Silvio; Tognolatti, Piero
Long wavelength (>1.55 {mu}m) room temperature emission and anomalous structural properties of InAs/GaAs quantum dots obtained by conversion of In nanocrystals
We demonstrate that molecular beam epitaxy-grown InAs quantum dots (QDs) on (100) GaAs obtained by conversion of In nanocrystals enable long wavelength emission in the InAs/GaAs material system. At room temperature they exhibit a broad photoluminescence band that extends well beyond 1.55 {mu}m. We correlate this finding with cross-sectional scanning tunneling microscopy measurements. They reveal that the QDs are composed of pure InAs which is in agreement with their long-wavelength emission. Additionally, the measurements reveal that the QDs have an anomalously undulated top surface which is very different to that observed for Stranski-Krastanow grown QDs.
Urbanczyk, A.; Keizer, J. G.; Koenraad, P. M. [COBRA Research Institute on Communication Technology, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)] [COBRA Research Institute on Communication Technology, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Noetzel, R. [Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), ETSI Telecommunication, Technical University of Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)] [Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), ETSI Telecommunication, Technical University of Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)
Vacuum Ultraviolet Emission Spectrum Measurement of a Microwave-discharge Hydrogen-flow Lamp in Several Configurations: Application to Photodesorption of CO Ice
NASA Astrophysics Data System (ADS)
We report measurements of the vacuum ultraviolet (VUV) emission spectra of a microwave-discharge hydrogen-flow lamp (MDHL), a common tool in astrochemistry laboratories working on ice VUV photoprocessing. The MDHL provides hydrogen Ly-? (121.6 nm) and H2 molecular emission in the 110-180 nm range. We show that the spectral characteristics of the VUV light emitted in this range, in particular the relative proportion of Ly-? to molecular emission bands, strongly depend on the pressure of H2 inside the lamp, the lamp geometry (F type versus T type), the gas used (pure H2 versus H2 seeded in He), and the optical properties of the window used (MgF2 versus CaF2). These different configurations are used to study the VUV irradiation of CO ice at 14 K. In contrast to the majority of studies dedicated to the VUV irradiation of astrophysical ice analogs, which have not taken into consideration the emission spectrum of the MDHL, our results show that the processes induced by photons in CO ice from a broad energy range are different and more complex than the sum of individual processes induced by monochromatic sources spanning the same energy range, as a result of the existence of multistate electronic transitions and discrepancy in absorption cross sections between parent molecules and products in the Ly-? and H2 molecular emission ranges.
Chen, Y.-J.; Chuang, K.-J.; Muñoz Caro, G. M.; Nuevo, M.; Chu, C.-C.; Yih, T.-S.; Ip, W.-H.; Wu, C.-Y. R.
The Contribution of Galactic Free-Free Emission to Anisotropies in the Cosmic Microwave Background Radiation Measured by MSAM
The Medium Scale Anisotropy Measurement (MSAM) experiment has detected anisotropies in the cosmic microwave background radiation with an rms between about 30 mu K and 90 mu K. MSAM uses double-difference and single-difference demodulation signals from a chopped, 30(') beam at a number of frequencies between 170 and 680 GHz. We observed the region covered by MSAM using the Virginia
J. H. Simonetti; G. A. Topasna; B. Dennison
Measurements of plasma temperatures in H\\/sub 2\\/\\/carbon\\/AR microwave plasma by UV emission spectroscopy
Summary form only given. We have developed a microwave plasma at atmospheric pressure in the mixtures of hydrogen, carbon, and argon in order to study the hydrogasification reaction of coal. A coal gasification is a newly highlighted research field because coal is abundant energy source for methane or hydrogen. However, the coal gasification process has encountered technical barriers because no
Yongho Kim; S. Abbate; G. Anderson; L. Rosocha; H. Ziock
High power microwave generator
A microwave generator efficiently converts the energy of an intense relativistic electron beam (REB) into a high-power microwave emission using the Smith-Purcell effect which is related to Cerenkov radiation. Feedback for efficient beam bunching and high gain is obtained by placing a cylindrical Smith-Purcell transmission grating on the axis of a toroidal resonator. High efficiency results from the use of a thin cold annular highly-magnetized REB that is closely coupled to the resonant structure.
Ekdahl, Carl A. (Albuquerque, NM) [Albuquerque, NM
Simultaneous determination of macro and trace elements in biological reference materials by microwave induced plasma optical emission spectrometry with slurry sample introduction
NASA Astrophysics Data System (ADS)
A slurry sampling technique (SST) has been utilized for simultaneous multi-element analysis by microwave-induced plasma optical emission spectrometry (MIP-OES). Slurry samples from a spray chamber are fed directly into the microwave cavity-torch assembly (power 300 W) with no desolvation apparatus. The performance of SST-MIP-OES was demonstrated by the determination of macro (Na, K, Ca, Mg, P) and trace (Cd, Cu, Mn, Sr, Zn) elements in three biological certified reference materials using a V-groove, clog-free Babington-type nebulizer. Slurry concentrations up to 1% m/v (particles <20 ?m), prepared in 10% HNO 3 (pH 1.2) containing 0.01% of Triton X-100, were used with calibration by the standard additions method. The method offers relatively good precision (R.S.D. ranged from 7 to 11%) with measured concentrations being in satisfactory agreement with certified values for NRCC TORT-1 (Lobster hepatopancreas), NRCC LUTS-1 (Lobster hepatopancreas) and IAEA-153 (Milk powder). The concentrations of Na, K, Ca, Mg, P and Cd, Cu, Mn, Sr, Zn were determined in the range 90-22 000 ?g/g and 1-420 ?g/g, respectively. The method could be useful as a routine procedure.
Matusiewicz, Henryk; Golik, Bartosz
Multi-frequency and polarimetric measurements of perturbed water surface microwave reflective and emissive characteristics by C-, and Ku-band combined scatterometric-radiometric systems
NASA Astrophysics Data System (ADS)
In this paper the results of simultaneous and spatially coincident, multi-frequency, polarimetric, spatio-temporally collocated measurements of waved pool water surface microwave reflective (radar backscattering coefficient) and emissive (brightness temperature) characteristics angular dependences at 5.6GHz and 15GHz will be represented. Angular measurements were carried out for various water surface roughness parameters at clear air, cloudy and rain conditions. For these measurements C-, and Ku-band, polarimetric, combined scatterometric-radiometric systems were used, set jointly on a mobile buggy moving along the measuring platform. Structures, operational features and the main technical characteristics of the utilized systems are presented too. The paper has an aim as well to attract attention of interested researchers and to invite them to perform their own or joint researches using available devices and facilities.
Arakelyan, Artashes K.; Hambaryan, Astghik K.; Hambaryan, Vardan K.; Karyan, Vanik V.; Manukyan, Mushegh R.; Grigoryan, Melanya L.; Hovhannisyan, Gagik G.; Arakelyan, Arsen A.; Darbinyan, Sargis A.
The theory of an auto-resonant field emission cathode relativistic electron accelerator for high efficiency microwave to direct current power conversion
NASA Technical Reports Server (NTRS)
A novel method of microwave power conversion to direct current is discussed that relies on a modification of well known resonant linear relativistic electron accelerator techniques. An analysis is presented that shows how, by establishing a 'slow' electromagnetic field in a waveguide, electrons liberated from an array of field emission cathodes, are resonantly accelerated to several times their rest energy, thus establishing an electric current over a large potential difference. Such an approach is not limited to the relatively low frequencies that characterize the operation of rectennas, and can, with appropriate waveguide and slow wave structure design, be employed in the 300 to 600 GHz range where much smaller transmitting and receiving antennas are needed.
Manning, Robert M.
Continuous-flow determination of aqueous sulfur by atmospheric-pressure helium microwave-induced plasma atomic emission spectrometry with gas-phase sample introduction
NASA Astrophysics Data System (ADS)
A simple continuous-flow generation of volatile hydrogen sulfide and sulfur dioxide by acidification of aqueous sulfide and sulfite ions, respectively, is described for the determination of low concentrations of sulfur by atmospheric-pressure helium microwave-induced plasma atomic emission spectrometry (MIP-AES) in the normal ultraviolet (UV) and vacuum ultraviolet (VUV) regions of the spectrum. For measuring spectral lines in the VUV region, the monochromator and the enclosed external optical path between the MIP source and the entrance slit of the monochromator have both been purged with nitrogen to minimize oxygen absorption below 190 nm. Sulfur atomic emission lines at 180.73, 182.04 and 217.05 nm have been selected as the analytical lines. Of the various acids examined, 1.0 M hydrochloric acid is the most favorable for both the generation of hydrogen sulfide from sulfide ions and sulfur dioxide from sulfite ions. Either generated hydrogen sulfide or sulfur dioxide is separated from the solution in a simple gas-liquid separator and swept into the helium stream of a microwave-induced plasma for analysis. The best attainable detection limits (3 ? criterion) for sulfur at 180.73 nm were 0.13 and 1.28 ng ml -1 for the generation of hydrogen sulfide and sulfur dioxide, respectively, with the corresponding background equivalent concentrations of 20.9 and 62.2 ng ml -1 in sulfur concentration. The typical analytical working graphs obtained under the optimized experimental conditions were rectilinear over approximately four orders of magnitude in sulfur concentration. The present method has been successfully applied to the recovery test of the sulfide spiked to waste water samples and to the determination of sulfite in some samples of commercially available wine.
Nakahara, Taketoshi; Mori, Toshio; Morimoto, Satoru; Ishikawa, Hiroshi
NASA Astrophysics Data System (ADS)
Brownian motion is widely considered the quintessential model of diffusion processes—the most elemental random transport processes in Science and Engineering. Yet so, examples of diffusion processes displaying highly non-Brownian statistics-commonly termed "Anomalous Diffusion" processes-are omnipresent both in the natural sciences and in engineered systems. The scientific interest in Anomalous Diffusion and its applications is growing exponentially in the recent years. In this Paper we review the key statistics of Anomalous Diffusion processes: sub-diffusion and super-diffusion, long-range dependence and the Joseph effect, Lévy statistics and the Noah effect, and 1/f noise. We further present a theoretical model-generalizing the Einstein-Smoluchowski diffusion model-which provides a unified explanation for the prevalence of Anomalous Diffusion statistics. Our model shows that what is commonly perceived as "anomalous" is in effect ubiquitous.
Eliazar, Iddo; Klafter, Joseph
Effects of tapered tubes on long-pulse microwave emission from intense e-beam gyrotron-backward-wave-oscillators
Experiments are reported on tapered-tube versus uniform-tube, gyrotron-backward-wave-oscillators (4.5-6 GHz) driven by an intense electron beam with parameters: 0.8 MV, 1-4 kA, and pulselength (0.5-1 ?s). Results show that, compared to a uniform interaction tube, a gyro-BWO with a 10% downtapered tube produces the following effects: 1) highest microwave peak-power (up to about 100 MW in internal tube), a factor
M. T. Walter; R. M. Gilgenbach; P. R. Menge; T. A. Spencer
Hard X-ray emission cutoff in the anomalous X-ray pulsar 4U 0142+61 detected by INTEGRAL
NASA Astrophysics Data System (ADS)
The anomalous X-ray pulsar 4U 0142+61 has been studied with observations from INTEGRAL. The hard X-ray spectrum in the range 18–500 keV for 4U 0142+61 was derived using nearly nine years of INTEGRAL/IBIS data. We obtained the average hard X-ray spectrum of 4U 0142+61 with all available data. The spectrum of 4U 0142+61 can be fitted with a power law that includes an exponential high energy cutoff. This average spectrum is well fitted by a power law with ? ~ 0.51 ± 0.11 plus a cutoff energy at 128.6 ± 17.2 keV. The hard X-ray flux of the source from 20–150 keV showed no significant variations (within 20%) from 2003–2011. The spectral profiles have some variability over the nine years such that the photon index varies from 0.3–1.5 and the cutoff energies from 110–250 keV. The detection of the high energy cutoff around 130 keV shows some constraints on the radiation mechanisms of magnetars and possibly probes the differences between magnetar and accretion models for this special class of neutron stars. Future HXMT observations could provide stronger constraints on the hard X-ray spectral properties of this source and other magnetar candidates.
Wang, Wei; Tong, Hao; Guo, Yan-Jun
Microwave Dielectric Model for Aggregated Soils
In order to understand the interactions of soil properties and microwave emission better, a series of field experiments were conducted in 1984. Small plots were measured with a truck-mounted passive microwave radiometer operating at 1.4 GHz. The microwave data were collected concurrently with ground observations of soil moisture and bulk density. Treatment effects included different soil moisture contents and bulk
A determination of the spectra of Galactic components observed by the Wilkinson Microwave Anisotropy Probe
NASA Astrophysics Data System (ADS)
Wilkinson Microwave Anisotropy Probe (WMAP) data when combined with ancillary data on free-free, synchrotron and dust allow an improved understanding of the spectrum of emission from each of these components. Here, we examine the sky variation at intermediate latitudes using a cross-correlation technique. In particular, we compare the observed emission in 15 selected sky regions to three `standard' templates. The free-free emission of the diffuse ionized gas is fitted by a well-known spectrum at K and Ka band, but the derived emissivity corresponds to a mean electron temperature of ~4000-5000 K. This is inconsistent with estimates from Galactic HII regions although a variation in the derived ratio of H? to free-free intensity by a factor of ~2 is also found from region to region. The origin of the discrepancy is unclear. The anomalous emission associated with dust is clearly detected in most of the 15 fields studied. The anomalous emission correlates well with the Finkbeiner, Davis & Schlegel model 8 predictions (FDS8) at 94 GHz, with an effective spectral index between 20 and 60 GHz, of ? ~ -2.85. Furthermore, the emissivity varies by a factor of ~2 from cloud to cloud. A modestly improved fit to the anomalous dust at K band is provided by modulating the template by an estimate of the dust colour temperature, specifically FDS8 × Tn. We find a preferred value n ~ 1.6, although there is a scatter from region to region. Nevertheless, the preferred index drops to zero at higher frequencies where the thermal dust emission dominates. The synchrotron emission steepens between GHz frequencies and the WMAP bands. There are indications of spectral index variations across the sky but the current data are not precise enough to accurately quantify this from region to region. Our analysis of the WMAP data indicates strongly that the dust-correlated emission at the low WMAP frequencies has a spectrum which is compatible with spinning dust; we find no evidence for a synchrotron component correlated with dust. The importance of these results for the correction of cosmic microwave background data for Galactic foreground emission is discussed.
Davies, R. D.; Dickinson, C.; Banday, A. J.; Jaffe, T. R.; Górski, K. M.; Davis, R. J.
Peak Frequency Dynamics in Solar Microwave Bursts
NASA Astrophysics Data System (ADS)
We analyze the dynamics of the broadband frequency spectrum of 338 microwave bursts observed in the years 2001 - 2002 with the Owens Valley Solar Array. A subset of 38 strong microwave bursts that show a single spectral maximum are studied in detail. Our main goal is to study changes in spectral peak frequency ? pk with time. We show that, for a majority of these simple bursts, the peak frequency shows a high positive correlation with flux density - it increases on the rise phase in ?83% of 24 bursts where it could be cleanly measured, and decreases immediately after the peak time in ?62% of 34 bursts. This behavior is in qualitative agreement with theoretical expectations based on gyrosynchrotron self-absorption. However, for a significant number of events (?30 - 36%) the peak frequency variation is much smaller than expected from self-absorption, or may be entirely absent. The observed temporal behavior of ? pk is compared with a simple model of gyrosynchrotron radio emission. We show that the anomalous behavior is well accounted for by the effects of Razin suppression, and further show how an analysis of the temporal evolution of ? pk can be used to uniquely determine the relative importance of self-absorption and Razin suppression in a given burst. The analysis technique provides a new, quantitative diagnostic for the gyrosynchrotron component of solar microwave bursts. Applying this analysis technique to our sample of bursts, we find that in most of the bursts (60%) the spectral dynamics of ? pk around the time of peak flux density is caused by self-absorption. On the other hand, for a significant number of events (?70%), the Razin effect may play the dominant role in defining the spectral peak and dynamics of ? pk, especially on the early rise phase and late decay phase of the bursts.
Melnikov, V. F.; Gary, Dale E.; Nita, Gelu M.
Thermal microwave emissions from vegetated fields: A comparison between theory and experiment. [Agricultural Research Center, Beltsville, MD.
NASA Technical Reports Server (NTRS)
The radiometric measurements over bare field and fields covered with grass, soybean, corn, and alfalfa were made with 1.4 GHz and 5 GHz microwave radiometers during August - October 1978. The measured results are compared with radiative transfer theory treating the vegetated fields as a two layer random medium. It is found that the presence of a vegetation cover generally gives a higher brightness temperature T(B) than that expected from a bare soil. The amount of this T(B) excess increases in the vegetation biomass and in the frequency of the observed radiation. The results of radiative transfer calculations generally match well with the experimental data, however, a detailed analysis also strongly suggests the need of incorporating soil surface roughness effect into the radiative transfer theory in order to better interpret the experimental data.
Wang, J. R.; Shiue, J.; Chuang, S. L.; Dombrowski, M.
Anomalous Retinal Correspondence.
National Technical Information Service (NTIS)
This paper presents an overview of anomalous retinal correspondence in strabismus. Definitions, certain testing techniques, and a review of underlying theory are outlined. It is concluded that ARC is not well understood and represents an area still open f...
M. R. Lattimore
National Technical Information Service (NTIS)
Recent developments in anomalous water research in England are summarized indicating experimental approaches used, observations made, and questions still unanswered. A partial bibliography on the subject is included and a list of interested investigators ...
R. A. Burton
Anomalous Ferroelectric Hysteresis Loops.
National Technical Information Service (NTIS)
Materials that exhibit anomalous ferroelectric hysteresis loops appear throughout the literature. These loops have irregular shapes that diverge from the normal hysteresis loop which is characteristic of most ferroelectrics. The observation of a unique hy...
F. J. Murdoch
High frequency thermal emission from the lunar surface and near surface temperature of the Moon from Chang'E-2 microwave radiometer
NASA Astrophysics Data System (ADS)
Near surface temperature of the Moon and thermal behaviors of the lunar regolith can provide important information for constraining thermal and magmatic evolution models of the Moon and engineering constrains for in situ lunar exploration system. In this study, China's Chang'E-2 (CE-2) microwave radiometer (MRM) data at high frequency channels are used to investigate near surface temperature of the Moon given the penetration ability of microwave into the desiccated and porous lunar regolith. Factors that affect high frequency brightness temperature (TB), such as surface slope, solar albedo and dielectric constant, are analyzed first using a revised Racca's temperature model. Radiative transfer theory is then used to model thermal emission from a semi-infinite regolith medium, with considering dielectric constant and temperature profiles within the regolith layer. To decouple the effect of diurnal temperature variation in the uppermost lunar surface, diurnal averaged brightness temperatures at high frequency channels are used to invert mean diurnal surface and subsurface temperatures based on their bilinear profiles within the regolith layer. Our results show that, at the scale of the spatial resolution of CE-2 MRM, surface slope of crater wall varies typically from about 20° to 30°, and this causes a variation in TB about 10-15 K. Solar albedo can give rise to a TB difference of about 5-10 K between maria and highlands, whereas a ?2-8 K difference can be compensated by the dielectric constant on the other hand. Inversion results indicate that latitude (?) variations of the mean diurnal surface and subsurface temperatures follow simple rules as cos0.30? and cos0.36?, respectively. The inverted mean diurnal temperature profiles at the Apollo 15 and 17 landing sites are also compared with the Apollo heat flow experiment data, showing an inversion uncertainty <4 K for surface temperature and <1 K for subsurface temperature.
Fang, Tuo; Fa, Wenzhe
Review of unprecedented ULF electromagnetic anomalous emissions possibly related to the Wenchuan MS = 8.0 earthquake, on 12 May 2008
NASA Astrophysics Data System (ADS)
This work presents ground based ultra low frequency (ULF) electromagnetic field measurements in the frequency range 0.1-10 Hz from January 2007 to December 2008. In this time period a strong earthquake series hits the Wenchuan region with a main shock of magnitude MS = 8.0 on 12 May 2008. The Hebei ULF electromagnetic observation network includes eight observation stations in north China and the observation system named E-EM is employed to record the electric potential difference between two electrodes with an analog automatic real-time continuous pen recorder. First, weak electric signals appeared on 11 October 2007 at Ningjin station, most of which are with relative long periods ~0.4-3 s and unequal amplitudes ~0.5-20 mm. Then, similar signals appeared at Gaobeidian station at the end of October. Abnormal behavior with various time intervals appeared randomly and not every day. At the beginning of April 2008, one and a half months before the Wenchuan MS = 8.0 earthquake, the anomalies were gradually subject to an intensive increase mainly in Gaobeidian SN direction and Ningjin EW direction. The abnormal behavior appeared almost every day and the amplitudes of electric signals, with short periods of ~0.1-0.3 s, enhanced to ~3-30 mm. Qingxian station started to record marginally high frequency signals in SN and EW components in the middle of April. On 9 May, 3 days before the main shock, the amplitude of high frequency information increased sharply at the same time in two components at Gaobeidian station and the maximum amplitude was up to 70 mm, i.e. 1.3 mV m-1 for the electric field. This situation did not stop until 17 May, 5 days after the main event. However, this kind of climax phenomena did not happen at Ningjin station and Qingxian station. Then weak anomalous information lasted about four months again, and strong signals appeared again for a short time before several powerful aftershocks. It is the first time that an abnormity with so large an amplitude and so long a duration time in the observation history of this network though several strong earthquakes were recorded. Furthermore, no obvious interferences have been found during this period. So this event is possibly related to this shock although all these three stations are more than 1300 km away from the Wenchuan earthquake epicenter.
Li, M.; Lu, J.; Parrot, M.; Tan, H.; Chang, Y.; Zhang, X.; Wang, Y.
Translational anisotropy in the cosmic microwave background radiation and far-infrared emission by galactic dust clouds
NASA Technical Reports Server (NTRS)
The predicted emission spectrum of galactic dust at about 10 K is compared with the spectrum of 2.8-K universal blackbody radiation and with the spectrum of the anisotropy expected in the 2.8-K radiation due to motion of earth with respect to the coordinate system in which the radiation was last scattered. The extremely anisotropic galactic-dust emission spectrum may contribute a significant background to anisotropy measurements which scan through the galactic plane. The contamination would appear in an 8-mm scan around the celestial equator, for example, as a spurious 200 km/s velocity toward declination 0 deg, right ascension 19 hr, if predictions are correct. The predicted spectrum of dust emission in the galactic plane at longitudes not exceeding about 30 deg falls below the total 2.8-K cosmic background intensity at wavelengths of at least 1 mm.
Forman, M. A.
Brownian motion is widely considered the quintessential model of diffusion processes-the most elemental random transport processes in Science and Engineering. Yet so, examples of diffusion processes displaying highly non-Brownian statistics-commonly termed 'Anomalous Diffusion' processes-are omnipresent both in the natural sciences and in engineered systems. The scientific interest in Anomalous Diffusion and its applications is growing exponentially in the recent years. In this Paper we review the key statistics of Anomalous Diffusion processes: sub-diffusion and super-diffusion, long-range dependence and the Joseph effect, Levy statistics and the Noah effect, and 1/f noise. We further present a theoretical model-generalizing the Einstein-Smoluchowski diffusion model-which provides a unified explanation for the prevalence of Anomalous Diffusion statistics. Our model shows that what is commonly perceived as 'anomalous' is in effect ubiquitous. - Highlights: > The article provides an overview of Anomalous Diffusion (AD) statistics. > The Einstein-Smoluchowski diffusion model is extended and generalized. > The generalized model universally generates AD statistics. > A unified 'universal macroscopic explanation' for AD statistics is established. > AD statistics are shown to be fundamentally connected to robustness.
Eliazar, Iddo, E-mail: email@example.com [Department of Technology Management, Holon Institute of Technology, P.O. Box 305, Holon 58102 (Israel); Klafter, Joseph, E-mail: email@example.com [School of Chemistry, Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel)
MAXI GSC detection of an enhanced X-ray emission from Anomalous X-ray Pulsar 4U 0142+61
NASA Astrophysics Data System (ADS)
The MAXI/GSC detected an enhanced X-ray emission from a position consistent with 4U 0142+61 during the scan transit of 53 seconds centered at 2011-07-29 11:23:15 (UT). The scan started 214 seconds later than the Swift/BAT trigger of a short burst from this source (GCN 12209). The GSC light curve during the scan transit showed no significant spiky structure and the averaged X-ray flux was 69 +- 16 mCrab in the 4-10 keV band.
Morii, M.; Tomida, H.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakahira, S.; Yamamoto, T.; Sootome, T.; Matsuoka, M.; Ueno, S.; Kohama, M.; Ishikawa, M.; Kawai, N.; Sugimori, K.; Usui, R.; Toizumi, T.; Yoshida, A.; Yamaoka, K.; Tsunemi, H.; Kimura, M.; Kitayama, H.; Negoro, H.; Nakajima, M.; Suwa, F.; Ueda, Y.; Hiroi, K.; Shidatsu, M.; Tsuboi, Y.; Matsumura, T.; Yamazaki, K.
Measurement of Anomalously Strong Emission from the 1s-9p Transition in the Spectrum of H-like Phosphorus Following Charge Exchange with Molecular Hydrogen
NASA Technical Reports Server (NTRS)
We have measured K-shell x-ray spectra of highly ionized argon and phosphorus following charge exchange with molecular hydrogen at low collision energy in an electron beam ion trap using an x-ray calorimeter array with approx.6 eV resolution. We find that the emission at the high-end of the Lyman series is greater by a factor of two for phosphorus than for argon, even though the measurement was performed concurrently and the atomic numbers are similar. This does not agree with current theoretical models and deviates from the trend observed in previous measurements.
Leutenegger, M. A.; Beiersdorfer, P.; Brown, G. V.; Kelley, R. L.; Porter, F. S.
Measurement of Anomalously Strong Emission from the 1s-9p Transition in the Spectrum of H-Like Phosphorus Following Charge Exchange with Molecular Hydrogen
We have measured K-shell x-ray spectra of highly ionized argon and phosphorus following charge exchange with molecular hydrogen at low collision energy in an electron beam ion trap using an x-ray calorimeter array with {approx}6 eV resolution. We find that the emission at the high end of the Lyman series is greater by a factor of 2 for phosphorus than for argon, even though the measurement was performed concurrently and the atomic numbers are similar. This does not agree with current theoretical models and deviates from the trend observed in previous measurements.
Leutenegger, M. A.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S. [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Beiersdorfer, P. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Space Sciences Laboratory, University of California, Berkeley, California 96720 (United States); Brown, G. V. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
The Swift/Burst Alert Telescope detected the first burst from 1E 1841-045 in 2010 May with intermittent burst activity recorded through at least 2011 July. Here we present Swift and Fermi/Gamma-ray Burst Monitor observations of this burst activity and search for correlated changes to the persistent X-ray emission of the source. The T {sub 90} durations of the bursts range between 18 and 140 ms, comparable to other magnetar burst durations, while the energy released in each burst ranges between (0.8-25) x 10{sup 38} erg, which is on the low side of soft gamma repeater bursts. We find that the bursting activity did not have a significant effect on the persistent flux level of the source. We argue that the mechanism leading to this sporadic burst activity in 1E 1841-045 might not involve large-scale restructuring (either crustal or magnetospheric) as seen in other magnetar sources.
Lin Lin [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Goegues, Ersin; Kaneko, Yuki [Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli-Tuzla, Istanbul 34956 (Turkey); Van der Horst, Alexander J. [Universities Space Research Association, NSSTC, Huntsville, AL 35805 (United States); Watts, Anna L.; Wijers, Ralph A. M. J.; Van der Klis, Michiel [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, 1090 GE Amsterdam (Netherlands); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, Houston, TX 77251 (United States); Woods, Peter M. [Corvid Technologies, Huntsville, AL 35806 (United States); Barthelmy, Scott; Gehrels, Neil; Mcenery, Julie [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Michael Burgess, James; Chaplin, Vandiver; Goldstein, Adam; Guiriec, Sylvain; Preece, Robert D. [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Granot, Jonathan [Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Tierney, David, E-mail: firstname.lastname@example.com [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)
Observation of the Askaryan Effect: Coherent Microwave Cherenkov Emission from Charge Asymmetry in High-Energy Particle Cascades
We present the first direct experimental evidence for the charge excess in high-energy particle showers and corresponding radio emission predicted nearly 40 years ago by Askaryan. We directed picosecond pulses of GeV bremsstrahlung photons at the SLAC Final Focus Test Beam into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3 to 6GHz detected strong, subnanosecond radio-frequency pulses produced by the showers. Measurements of the polarization, coherence, timing, field strength vs shower depth, and field strength vs frequency are completely consistent with predictions. These measurements thus provide strong support for experiments designed to detect high-energy cosmic rays such as neutrinos via coherent radio emission from their cascades.
Saltzberg, David; Gorham, Peter; Walz, Dieter; Field, Clive; Iverson, Richard; Odian, Allen; Resch, George; Schoessow, Paul; Williams, Dawn
Observation of the Askaryan Effect: Coherent Microwave Cherenkov Emission from Charge Asymmetry in High-Energy Particle Cascades
We present the first direct experimental evidence for the charge excess in high-energy particle showers and corresponding radio emission predicted nearly 40 years ago by Askaryan. We directed picosecond pulses of GeV bremsstrahlung photons at the SLAC Final Focus Test Beam into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3
David Saltzberg; Peter Gorham; Dieter Walz; Clive Field; Richard Iverson; Allen Odian; George Resch; Paul Schoessow; Dawn Williams
Numerical simulations of emission for two-dimensional randomly rough surfaces with an inhomogeneous layered medium are presented. The inhomogeneous layered medium is modeled by a generalized n-layered stratified media. The numerical method was adopted from the physics-based two-grid method (PBTG). To ensure the strict accuracy requirement while to relief the memory and CPU resources, the PBTG in conjunction with the sparse-matrix
Kun-Shan Chen; Leung Tsang; J. C. Shi
Foundations for statistical-physical precipitation retrieval from passive microwave satellite measurements. Part II: Emission-source and generalized weighting-function properties of a time-dependent cloud-radiation model
The authors present the second part of a study on the development of a framework for precipitation retrieval from space-based passive microwave measurements using a three-dimensional time-dependent cloud model to establish the microphysical setting. The first developed the theory needed to interpret the vertically distributed radiative sources and the emission-absorption-scattering processes responsible for the behavior of frequency-dependent top-of-atomsphere brightness temperatures
Alberto Mugnai; Eric A. Smith; Gregory J. Tripoli
Foundations for Statistical Physical Precipitation Retrieval from Passive Microwave Satellite Measurements. Part II: Emission-Source and Generalized Weighting-Function Properties of a Time-dependent Cloud-Radiation Model
We present the second part of a study on the development of a framework for precipitation retrieval from space-based passive microwave measurements using a three-dimensional time-dependent cloud model to establish the microphysical setting. We first develop the theory needed to interpret the vertically distributed radiative sources and the emission-absorption-scattering processes responsible for the behavior of frequency-dependent top-of-atmosphere brightness temperatures TB's.
Alberto Mugnai; Eric A. Smith; Gregory J. Tripoli
Evaluation of different derivatization methods for the multi-element detection of Hg, Pb and Sn compounds by gas chromatography-microwave induced plasma-atomic emission spectrometry in environmental samples
A multi-element, element-specific detector for gas chromatography (GC) based on atomic emission spectroscopy (AES) with a microwave induced plasma (MIP) source was tested on some environmental samples. As derivatization procedure, direct aqueous phase ethylation and chelation\\/extraction followed by Grignard reaction were tested on the following ions: methylmercury, ethylmercury, phenylmercury, mercury(II), trimethyllead, dimethyllead, lead(II), trimethyltin, dimethyltin, triethyltin, tripropyltin, tributyltin, dibutyltin, butyltin,
V. Minganti; R. Capelli; R. De Pellegrini
Growth, microstructure, and field-emission properties of synthesized diamond film on adamantane-coated silicon substrate by microwave plasma chemical vapor deposition
Diamond nucleation on unscratched Si surface is great importance for its growth, and detailed understanding of this process is therefore desired for many applications. The pretreatment of the substrate surface may influence the initial growth period. In this study, diamond films have been synthesized on adamantane-coated crystalline silicon {l_brace}100{r_brace} substrate by microwave plasma chemical vapor deposition from a gaseous mixture of methane and hydrogen gases without the application of a bias voltage to the substrates. Prior to adamantane coating, the Si substrates were not pretreated such as abraded/scratched. The substrate temperature was {approx}530 deg. C during diamond deposition. The deposited films are characterized by scanning electron microscopy, Raman spectrometry, x-ray diffraction, and x-ray photoelectron spectroscopy. These measurements provide definitive evidence for high-crystalline quality diamond film, which is synthesized on a SiC rather than clean Si substrate. Characterization through atomic force microscope allows establishing fine quality criteria of the film according to the grain size of nanodiamond along with SiC. The diamond films exhibit a low-threshold (55 V/{mu}m) and high current-density (1.6 mA/cm{sup 2}) field-emission (FE) display. The possible mechanism of formation of diamond films and their FE properties have been demonstrated.
Tiwari, Rajanish N.; Chang Li [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan 300 (China)
Low temperature anomalous field effect in SrxBa1-xNb2O6 uniaxial relaxor ferroelectric seen via acoustic emission
NASA Astrophysics Data System (ADS)
Sr0.75Ba0.25Nb2O6 [100]-oriented uniaxial tungsten bronze relaxor crystals have been studied by means of dedicated acoustic emission during their thermal cycling in 150-300 K temperature range under dc electric field (E). A 1st order transition in a modulated incommensurate tetragonal phase has been successfully detected at Tmi = 198 K on heating and Tmi = 184 K on cooling, respectively. As field E enhances, a thermal hysteresis gradually narrows and vanishes in the critical point at Eth = 0.31 kV/cm, above which a phase transition becomes to 2nd order. The Tmi(E) dependence looks as a V-shape dip, not similar that previously has been looked as a smeared minimum between both the two polar and nonpolar tetragonal phases near Tm = 220 ÷ 230 K in the same crystals (Dul'kin et al., J Appl. Phys. 110, 044106 (2011)). Due to such a V-shape dip is characteristic for Pb-based multiaxial perovskite relaxor, a rhombohedral phase is waited to be induced by a field E in the critical point temperature range. The emergence of this rhombohedral phase as a crucial evidence of an orthorhombic phase presumably existing within the modulated incommensurate tetragonal phase in tungsten bronze SrxBa1-xNb2O6 relaxor is discussed.
Dul'kin, E.; Kojima, S.; Roth, M.
An automated analysis of DEMETER ionospheric plasma waves observations and its application to the search for anomalous emissions over the Great Sichuan EQ region
NASA Astrophysics Data System (ADS)
Electric field observations in the VLF range from the ICE experiment onboard the CNES DEMETER micro-satellite have been analyzed to search for anomalies possibly related to the Great Sichuan Earthquake of May 12, 2008. This work was undertaken using results from a dedicated data processing that has been recently developed at LATMOS to perform an automated recognition and characterization of the various wave emissions that are regularly detected along the orbit of DEMETER. The data processing method and the associated algorithms will be first presented and a few typical results will be shown in order to provide a detailed understanding of the algorithm capabilities. As a first full-scale application of this method, a statistical study was conducted to analyze the plasma waves observed in day-time half orbits over a region of ~1000 kilometres extent centred on the Sichuan EQ epicentre and during a period of 20 days encompassing the day of the EQ. 5 years of observations have been used to derive the statistical distribution of various types of ionospheric plasma waves that can be compared to the signals detected during the seismic active period. The first outcome of our study was the detection of a localized variation in the characteristics of the electrostatic turbulence 6 days before the EQ that appears to be unique in the whole 5 year reference observations data base. We will discuss this result and its possible interpretations.
Onishi, Tatsuo; Berthelier, Jean-Jacques
Anomalous pulmonary venous connections.
Developmental lung anomalies are classified into 3 main categories: bronchopulmonary (lung bud) anomalies, vascular anomalies, and combined lung and vascular anomalies. These anomalies are uncommon, and patients are at times asymptomatic; hence, identifying a developmental lung anomaly in the adult can be a challenge. Pulmonary vascular anomalies include interruption or absence of the main pulmonary artery, anomalous origin of the left pulmonary artery from the right pulmonary artery, anomalous pulmonary venous drainage (partial or complete), and pulmonary arteriovenous malformations. Systemic vascular anomalies comprise persistent left superior vena cava, anomalies of azygos and hemiazygos systems, and anomalies of the thoracic aorta and its major branches. In this article, we present embryology, classification, epidemiology, clinical presentation, and imaging features of anomalous pulmonary venous connections, with special emphasis on multidetector computed tomography and magnetic resonance imaging. These state-of-art imaging techniques have facilitated accurate and prompt diagnosis of these anomalies. PMID:23168060
Katre, Rashmi; Burns, Stephanie K; Murillo, Horacio; Lane, Michael J; Restrepo, Carlos S
The presence of ferromagnetic or ferrimagnetic nanoparticles in the interstellar medium would give rise to magnetic dipole radiation at microwave and submillimeter frequencies. Such grains may account for the strong millimeter-wavelength emission observed from a number of low-metallicity galaxies, including the Small Magellanic Cloud. We calculate the absorption and scattering cross sections for such grains, with particular attention to metallic Fe, magnetite Fe{sub 3}O{sub 4}, and maghemite {gamma}-Fe{sub 2}O{sub 3}, all potentially present in the interstellar medium. The rate of Davis-Greenstein alignment by magnetic dissipation is also estimated. We determine the temperature of free-flying magnetic grains heated by starlight and calculate the polarization of the magnetic dipole emission from both free-fliers and inclusions. For inclusions, the magnetic dipole emission is expected to be polarized orthogonally relative to the normal electric dipole radiation. Magnetic dipole radiation will contribute significantly to the 20-40 GHz anomalous microwave emission only if a large fraction of the Fe is in metallic Fe iron nanoparticles with extreme elongations. Finally, we present self-consistent dielectric functions for metallic Fe, magnetite Fe{sub 3}O{sub 4}, and maghemite {gamma}-Fe{sub 2}O{sub 3}, enabling calculation of absorption and scattering cross sections from microwave to X-ray wavelengths.
Draine, B. T.; Hensley, Brandon, E-mail: firstname.lastname@example.com [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States)
Streamlined Modeling for Characterizing Spacecraft Anomalous Behavior
Anomalous behavior of on-orbit spacecraft can often be detected using passive, remote sensors which measure electro-optical signatures that vary in time and spectral content. Analysts responsible for assessing spacecraft operational status and detecting detrimental anomalies using non-resolved imaging sensors are often presented with various sensing and identification issues. Modeling and measuring spacecraft self emission and reflected radiant intensity when the
B. Klem; D. Swann
Microwave off-gas treatment apparatus and process
The invention discloses a microwave off-gas system in which microwave energy is used to treat gaseous waste. A treatment chamber is used to remediate off-gases from an emission source by passing the off-gases through a susceptor matrix, the matrix being exposed to microwave radiation. The microwave radiation and elevated temperatures within the combustion chamber provide for significant reductions in the qualitative and quantitative emissions of the gas waste stream.
Schulz, Rebecca L. (Aiken, SC); Clark, David E. (Gainesville, FL); Wicks, George G. (North Aiken, SC)
Recent Advancements in Microwave Imaging Plasma Diagnostics
Significant advances in microwave and millimeter wave technology over the past decade have enabled the development of a new generation of imaging diagnostics for current and envisioned magnetic fusion devices. Prominent among these are revolutionary microwave electron cyclotron emission imaging (ECEI), microwave phase imaging interferometers, imaging microwave scattering and microwave imaging reflectometer (MIR) systems for imaging electron temperature and electron density fluctuations (both turbulent and coherent) and profiles (including transport barriers) on toroidal devices such as tokamaks, spherical tori, and stellarators. The diagnostic technology is reviewed, and typical diagnostic systems are analyzed. Representative experimental results obtained with these novel diagnostic systems are also presented.
H. Park; C.C. Chang; B.H. Deng; C.W. Domier; A.J.H. Donni; K. Kawahata; C. Liang; X.P. Liang; H.J. Lu; N.C. Luhmann, Jr.; A. Mase; H. Matsuura; E. Mazzucato; A. Miura; K. Mizuno; T. Munsat; K. and Y. Nagayama; M.J. van de Pol; J. Wang; Z.G. Xia; W-K. Zhang
Microwave radiometric observations of snowpacks
NASA Technical Reports Server (NTRS)
Models for the microwave emission from snowpacks were generated on the basis of radiometric observations made at 10.7 GHz, 37 HGz, and 94 GHz at a test site near Steamboat Springs, Colorado. In addition to conducting measurements on an approximately daily basis over a six week observation period, measurements were made over several diurnal cycles during which the change in snow wetness was tracked by the microwave radiometers. Also, the variation in emissivity with snow water equivalent was examined, as was the sensitivity to changes in snow surface geometry. The microwave emissivity was observed to (1) decrease exponentially with snow water equivalent and (2) increase with snow wetness. Thus, the emission behavior is the reverse of the backscattering behavior observed by the radar. By fitting the models to the measured data, the variation of the optical depth with snow wetness was estimated.
Ulaby, F. T.; Stiles, W. H.
A microwave detector is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite produces a magnetization field flux that links a B-dot loop. The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.
Meldner, H.W.; Cusson, R.Y.; Johnson, R.M.
Anomalous Diffusion Near Resonances
Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations. Transport of particles near resonances is still not a well understood phenomenon. Often, without justification, phase space motion is assumed to be a normal diffusion process although at least one case of anomalous diffusion in beam dynamics has been reported [1]. Here we will focus on the motion near synchro-betatron resonances which can be excited by several means, including beams crossing at an angle at the collision points as in the LHC. We will consider low order resonances which couple the horizontal and longitudinal planes, both for simplicity and to observe large effects over short time scales. While the tunes we consider are not practical for a collider, nonetheless the transport mechanisms we uncover are also likely to operate at higher order resonances.
Sen, Tanaji; /Fermilab
Observational and theoretical advances in cosmological foreground emission
NASA Astrophysics Data System (ADS)
Observational and theoretical work towards the separation of foreground emission from the cosmic microwave background is described. The bulk of this work is in the design, construction, and commissioning of the C-Band All-Sky Survey (C-BASS), an experiment to produce a template of the Milky Way Galaxy's polarized synchrotron emission. Theoretical work is the derivation of an analytical approximation to the emission spectrum of spinning dust grains. The performance of the C-BASS experiment is demonstrated through a preliminary, deep survey of the North Celestial Pole region. A comparison to multiwavelength data is performed, and the thermal and systematic noise properties of the experiment are explored. The systematic noise has been minimized through careful data processing algorithms, implemented both in the experiment's Field Programmable Gate Array (FPGA) based digital backend and in the data analysis pipeline. Detailed descriptions of these algorithms are presented. The analytical function of spinning dust emission is derived through the application of careful approximations, with each step tested against numerical calculations. This work is intended for use in the parameterized separation of cosmological foreground components and as a framework for interpreting and comparing the variety of anomalous microwave emission observations.
Stevenson, Matthew A.
Interpretation of observed cosmic microwave background radiation
The Alfven and Mendis (1977) conclusion that dust grains in galaxies render the universe opaque to cosmic microwave background at a red shift ratio equal to 40 is challenged by a calculation of the opacity of galactic dust grains to the microwave background radiation from the time of decoupling at emission red shift ratio equal to 1500 to the present
... sold in the United States are responsible for compliance with the Federal Food, Drug and Cosmetic Act ( ... Control . Manufacturers of microwave ovens are responsible for compliance with all applicable requirements of Title 21 Code ...
A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit there through effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators. 6 figs.
Kwan, T.J.T.; Snell, C.M.
Microwave Ovens RadTown USA Topics Personal Exposure : Airport Security Scanning Cosmic Radiation During Flights X-Rays in CT Scans Dental X-ray Diagnostic Nuclear Medicine Electromagnetic Fields from Power Lines Internal Radiotherapy ...
NASA Astrophysics Data System (ADS)
Microwave annealing of dopants in Si has been reported to produce highly activated junctions at temperatures far below those needed for comparable results using conventional thermal processes. However the details of the kinetics and mechanisms for microwave annealing are far from well understood. Comparisons between MWA and RTA of dopants in implanted Si has been investigated to produce highly activated junctions. First, As, 31P, and BF2 implants in Si substrate were annealed by MWA at temperatures below 550 °C.
Lee, Yao-Jen; Cho, T.-C.; Chuang, S.-S.; Hsueh, F.-K.; Lu, Y.-L.; Sung, P.-J.; Chen, S.-J.; Lo, C.-H.; Lai, C.-H.; Current, Michael I.; Tseng, T.-Y.; Chao, T.-S.; Yang, F.-L.
Determination of bis-carboxyethyl germanium sesquioxide by gas chromatography with microwave-induced plasma-atomic emission detection after derivatization with alkyl chloroformates.
Organic germanium compounds, especially Ge-132, more corrctly denoted as bis-beta-carboxyethyl germanium sesquioxide ([Ge(=O)CH2CH2CO2H]2O), are of continued interest as they are said to promote health and display anticancer activity. Although these beneficial effects have never been substantiated by comprehensive clinical studies, this drug can still be obtained through various sources and is usually marketed as a nutritional supplementation rather than an anticancer medication. As the quality standards under which this drug is produced are unknown, the need for an effective quality control of these products arises. To date, Ge-132 is considered generally as a safe compound for application in contrast to inorganic germanium which demonstrates severe renal toxicity. In this paper, a new approach to the determination of Ge-132, based on derivatization by ethyl chloroformate reagent (ECF), in the presence of ethanol and pyridine in the mixture, and subsequent analysis by gas chromatography coupled with microwave-induced plasma-atomic emission detection (GC-MIP-AED), is reported. Reaction conditions of the derivatization procedure were optimized with particular respect to the reagent (ECF) and catalyst (pyridine) concentrations. The proposed method is capable of distinguishing Ge-132 from inorganic germanium. The derivatization procedure was also tested with the use of methyl chloroformate (MCF) as alternative reagent, providing interesting additional information about the nature of the final product and the proposed reaction scheme. Among the two types of chloroformates, i.e., MCF and ECF, the latter proved to be more suitable for the proposed method, providing a calibration curve of superior sensitivity and linearity compared with the one obtained with MCF. The method was applied successfully in three real samples, two food supplements, and one commercially available fertilizer. The analysis of the Ge-132 derivative showed good linearity in the concentration of 1-250 mg L(-1) (r (2)?=?0.9986) and a satisfactory precision (RSD?=?6.8%), which qualifies the proposed method for the speciation analysis of Ge in various matrices. PMID:24748447
Trikas, E; Zachariadis, G A; Rosenberg, E
Beta function and anomalous dimensions
We demonstrate that it is possible to determine the coefficients of an all-orders beta-function linear in the anomalous dimensions using as data the 2-loop coefficients together with the first one of the anomalous dimensions which are universal. The beta function allows us to determine the anomalous dimension of the fermion masses at the infrared fixed point, and the resulting values compare well with the lattice determinations.
Pica, Claudio; Sannino, Francesco [CP3-Origins, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark)
Height of the Slowly Varying Component of Radio Emission at 9.1 cm During the Quiet Sun Years.
National Technical Information Service (NTIS)
The slowly varying component of solar microwave emission is associated with plage and sunspot regions seen optically. Under the assumption that the microwave emission originates radially above the associated optical feature the height of the microwave emi...
A. C. Riddle
Investigation of Plasma Generators for Microwave Devices.
National Technical Information Service (NTIS)
An experimental study on the Penning Ionization Gauge (PIG) discharge and ion emission from beta-eucryptite was conducted with a view toward the production of plasmas suitable for microwave application. Langmuir probe measurements on the PIG were obtained...
M. Weiner R. M. True E. V. Edwards
Microwave Depolarization above Sunspots
NASA Astrophysics Data System (ADS)
Microwave emissions from sunspots are circularly polarized in the sense of rotation (right or left) determined by the polarity (north or south) of coronal magnetic fields. However, they may convert into unpolarized emissions under certain conditions of magnetic field and electron density in the corona, and this phenomenon of depolarization could be used to derive those parameters. We propose another diagnostic use of microwave depolarization based on the fact that an observed depolarization strip actually represents the coronal magnetic polarity inversion line (PIL) at the heights of effective mode coupling, and its location itself carries information on the distribution of magnetic polarity in the corona. To demonstrate this diagnostic utility we generate a set of magnetic field models for a complex active region with the observed line-of-sight magnetic fields but varying current density distribution and compare them with the 4.9 GHz polarization map obtained with the Very Large Array (VLA). The field extrapolation predicts very different locations of the depolarization strip in the corona depending on the amount of electric currents assumed to exist in the photosphere. Such high sensitivity of microwave depolarization to the coronal magnetic field can therefore be useful for validating electric current density maps inferred from vector magnetic fields observed in the photosphere.
Lee, Jeongwoo; White, Stephen M.
A New Neural Network Approach Including First-Guess for Retrieval of Atmospheric Water Vapor, Cloud Liquid Water Path, Surface Temperature and Emissivities Over Land From Satellite Microwave Observations
NASA Technical Reports Server (NTRS)
The analysis of microwave observations over land to determine atmospheric and surface parameters is still limited due to the complexity of the inverse problem. Neural network techniques have already proved successful as the basis of efficient retrieval methods for non-linear cases, however, first-guess estimates, which are used in variational methods to avoid problems of solution non-uniqueness or other forms of solution irregularity, have up to now not been used with neural network methods. In this study, a neural network approach is developed that uses a first-guess. Conceptual bridges are established between the neural network and variational methods. The new neural method retrieves the surface skin temperature, the integrated water vapor content, the cloud liquid water path and the microwave surface emissivities between 19 and 85 GHz over land from SSM/I observations. The retrieval, in parallel, of all these quantities improves the results for consistency reasons. A data base to train the neural network is calculated with a radiative transfer model and a a global collection of coincident surface and atmospheric parameters extracted from the National Center for Environmental Prediction reanalysis, from the International Satellite Cloud Climatology Project data and from microwave emissivity atlases previously calculated. The results of the neural network inversion are very encouraging. The r.m.s. error of the surface temperature retrieval over the globe is 1.3 K in clear sky conditions and 1.6 K in cloudy scenes. Water vapor is retrieved with a r.m.s. error of 3.8 kg/sq m in clear conditions and 4.9 kg/sq m in cloudy situations. The r.m.s. error in cloud liquid water path is 0.08 kg/sq m . The surface emissivities are retrieved with an accuracy of better than 0.008 in clear conditions and 0.010 in cloudy conditions. Microwave land surface temperature retrieval presents a very attractive complement to the infrared estimates in cloudy areas: time record of land surface temperature will be produced.
Aires, F.; Prigent, C.; Rossow, W. B.; Rothstein, M.; Hansen, James E. (Technical Monitor)
Applicability of microwave acid digestion to sample preparation of biological materials for analysis by particle-induced X-ray emission (PIXE).
A microwave acid digestion method for the preparation of biological samples for PIXE analysis is presented. The precision and accuracy of the entire PIXE analytical procedure, including the microwave digestion step, were evaluated by analyzing eight certified reference materials. For elements heavier than K, and for concentration levels from 2 micrograms/g upward, the total random error of a single analysis is in the range of 2-5%. The accuracy is better than 5%. The detection limits are down to 0.3 micrograms/g. PMID:1704766
Pinheiro, T; Duflou, H; Maenhaut, W
Stromvil Photometry: Peculiar Stars and Anomalous Reddening
NASA Astrophysics Data System (ADS)
Possibilities of the Stromvil photometric system in identifying peculiar stars of various types are reviewed. The system can identify in the presence of interstellar reddening the following types of peculiar stars: F--G--K--M subdwarfs, G--K--M metal-deficient giants, cool carbon, barium and zirconium stars, chemically peculiar B and A stars, emission-line stars (Be, Ae/Be, WR, T Tauri, etc.), white dwarfs, a fraction of horizontal-branch stars and many types of unresolved binaries. Also, the system can identify stars affected by anomalous interstellar reddening and classify them correctly.
Straizys, V.
Microwave furnace having microwave compatible dilatometer
An apparatus for measuring and monitoring a change in the dimension of a sample being heated by microwave energy is described. The apparatus comprises a microwave heating device for heating a sample by microwave energy, a microwave compatible dilatometer for measuring and monitoring a change in the dimension of the sample being heated by microwave energy without leaking microwaves out of the microwave heating device, and a temperature determination device for measuring and monitoring the temperature of the sample being heated by microwave energy.
Kimrey, Jr., Harold D. (Knoxville, TN); Janney, Mark A. (Knoxville, TN); Ferber, Mattison K. (Oak Ridge, TN)
How useful is anomalous correspondence?
In anomalous retinal correspondence (ARC), retinal points in the right and left eyes which receive stimuli from one object in space have the same visual direction despite a manifest motor deviation. The mode of cooperation of these anomalously corresponding retinal points depends on their relative eccentricity or their relative functional level. If there is a great difference, as for the
Volker Herzau
Anomalous transport in toroidal plasmas
When the magnetic moment of particle is conserved, there are three mechanisms which cause anomalous transport. These are: variation of magnetic field strength in flux surface, variation of electrostatic potential in flux surface, and destruction of flux surface. The anomalous transport of different groups of particles resulting from each of these mechanisms is different. This fact can be exploited to
Alkesh Punjabi
Anomalous thresholds of reaction amplitudes
Summary Anomalous thresholds of reaction amplitudes are studied without recourse to a partial wave expansion. Ft is shown that the\\u000a behavior of the amplitudes is quite similar to that of the partial wave projections even though the Legendre series does not\\u000a converge near the anomalous threshold.
P. G. O. Freund; R. Karplus
Anomalous properties of an RF discharge in humid air
The behavior of an rf discharge in water vapor is studied experimentally. A physical explanation is given for the processes that occur and their effect on the passage of high-current electron beams is examined. It is shown that water molecules cause sharp changes in the plasma properties; the recombination time of the plasma increases anomalously, the emission spectrum changes, and
V. P. Grigorev; E. T. Protasevich; V. I. Tolmachev
An Accretion Model for Anomalous X-Ray Pulsars
We present a model for the anomalous X-ray pulsars (AXPs) in which the emission is powered by accretion from a fossil disk, established from matter falling back onto the neutron star following its birth. The time-dependent accretion drives the neutron star toward a ``tracking'' solution in which the rotation period of the star increases slowly, in tandem with the declining
Pinaki Chatterjee; Lars Hernquist; Ramesh Narayan
Microwave remote sensing of soil moisture
NASA Technical Reports Server (NTRS)
Knowledge of soil moisture is important to many disciplines, such as agriculture, hydrology, and meteorology. Soil moisture distribution of vast regions can be measured efficiently only with remote sensing techniques from airborne or satellite platforms. At low microwave frequencies, water has a much larger dielectric constant than dry soil. This difference manifests itself in surface emissivity (or reflectivity) change between dry and wet soils, and can be measured by a microwave radiometer or radar. The Microwave Sensors and Data Communications Branch is developing microwave remote sensing techniques using both radar and radiometry, but primarily with microwave radiometry. The efforts in these areas range from developing algorithms for data interpretation to conducting feasibility studies for space systems, with a primary goal of developing a microwave radiometer for soil moisture measurement from satellites, such as EOS or the Space Station. These efforts are listed.
Shiue, J. C.; Wang, J. R.
NASA Technical Reports Server (NTRS)
Research on the use of active microwaves in remote sensing, presented during plenary and poster sessions, is summarized. The main highlights are: calibration techniques are well understood; innovative modeling approaches have been developed which increase active microwave applications (segmentation prior to model inversion, use of ERS-1 scatterometer, simulations); polarization angle and frequency diversity improves characterization of ice sheets, vegetation, and determination of soil moisture (X band sensor study); SAR (Synthetic Aperture Radar) interferometry potential is emerging; use of multiple sensors/extended spectral signatures is important (increase emphasis).
Evans, D.; Vidal-Madjar, D.
A limited evaluation was made of two commonly found microwave interconnections: microstrip-to-microstrip and coaxial-to-microstrip. The evaluation attempted to select the interconnection technique which worked best for the particular interface type. short ribbon wires worked best for the microstrip-to-microstrip interconnection. A published method of compensating the microstrip conductor had the best performance for the coaxial-to-microstrip interconnection. The work was conducted under the Microwave Technology process Capability Assurance Program at Allied-Signal Inc., Kansas City Division.
Fry, P.E.
The long-wavelength emission of interstellar PAHs: characterizing the spinning dust contribution
NASA Astrophysics Data System (ADS)
Context. The emission of cold dust grains at long wavelengths will soon be observed by the Planck and Herschel satellites and will provide new constraints on the nature of interstellar dust. In particular, the microwave galactic anomalous foreground detected between 10 to 90 GHz, proposed as coming from small spinning grains (PAHs), should help to define these species better. Moreover, understanding the fluctuations of the anomalous foreground quantitatively over the sky is crucial for CMB studies. Aims: We focus on the long-wavelength emission of interstellar PAHs in their vibrational and rotational transitions. We present here the first model that coherently describes the PAH emission from the near-IR to microwave range. Methods: We take quantum effects into account to describe the rotation of PAHs and compare our results to current models of spinning dust to assess the validity of the classical treatment used. Between absorptions of stellar photons, we followed the rovibrational radiative cascade of PAHs. We used the exact-statistical method of Draine & Li to derive the distribution of PAH internal energy and followed a quantum approach for the rotational excitation induced by vibrational (IR) transitions. We also examined the influence of the vibrational relaxation scheme and of the low-energy cross-section on the PAH emission. We study the emissivity of spinning PAHs in a variety of physical conditions (radiation field intensity and gas density), search for specific signatures in this emission that can be looked for observationally, and discuss how the anomalous foreground may constrain the PAH size distribution. Results: Simultaneously predicting the vibrational and rotational emission of PAHs, our model can explain the observed emission of the Perseus molecular cloud from the IR to the microwave range with plausible PAH properties. We show that for ? ? 3 mm the PAH vibrational emission no longer scales with the radiation field intensity (G0), unlike the mid-IR part of the spectrum (which scales with G0). This emission represents less than 10% of the total dust emission at 100 GHz. Similarly, we find the broadband emissivity of spinning PAHs per carbon atom to be rather constant for G_0? 100 and for proton densities n_H<100 cm-3. In the diffuse ISM, photon exchange and gas-grain interactions play comparable roles in exciting the rotation of PAHs, and the emissivity of spinning PAHs is dominated by the contribution of small species (bearing less than 100 C atoms). We show that the classical description of rotation used in previous works is a good approximation and that unknowns in the vibrational relaxation scheme and low-energy cross-section affect the PAH rotational emissivity around 30 GHz by less than 15%. Conclusions: The contrasted behaviour of the PAH vibrational and rotational emissivities with G0 provides a clear prediction that can be tested against observations of anomalous and dust mid-IR emissions: this is the subject of a companion paper. Comparison of these emissions complemented with radio observations (21 cm or continuum) will provide constraints on the fraction of small species and the electric dipole moment of interstellar PAHs.
Ysard, N.; Verstraete, L.
Observing Saturn's Rings in the Microwave with Cassini
NASA Astrophysics Data System (ADS)
We will present an initial calibration and analysis of microwave radiometry observation of Saturn's rings from the Cassini RADAR. Microwave emission is the ideal waveband for studying the scattering properties of cm-scale ring particles and for constraining the thermal emission from (possibly buried) rocky ring contaminants, which, unlike water ice, behave like blackbodies at cm- wavelengths.
Zhang, Z.; Hayes, A. G.; Janssen, M. A.; Cuzzi, J. N.; Nicholson, P. D.
NSDL National Science Digital Library
This University of Washington Web site "is intended to serve both as an introductory tutorial to anomalous scattering and as a general tool for designing experiments based on anomalous scattering." Visitors can find a periodic table and a chart supplying X-ray absorption edge data. Students needing assistance with the concept of anomalous scattering will find the tutorial explaining the interactions of incident photons having relatively high and low energy with scattering electrons very instructive. The site also supplies users with information about Friedel's Law and MAD experiments.
The PASER (Particle Acceleration by Stimulated Emission of Radiation) concept for particle acceleration entails the direct transfer of energy from an active medium to a charged particle beam. The PASER was originally formulated for optical (laser) media; we are planning a PASER demonstration experiment based on an optically pumped X-band paramagnetic medium consisting of porphyrin or fullerene (C{sub 60}) derivatives in a toluene solution or polystyrene matrix. We discuss the background of this project and report on the status of the experiment to measure the acceleration of electrons using the microwave PASER.
Schoessow, P.; Kanareykin, A. [Euclid Techlabs, 1375 Piccard Dr Rockville MD 20850 (United States); Antipov, S.; Poluektov, O. [Argonne National Laboratory 9700 S Cass Ave Argonne IL 60439 (United States); Jing, C. [Euclid Techlabs, 1375 Piccard Dr Rockville MD 20850 (United States); Argonne National Laboratory 9700 S Cass Ave Argonne IL 60439 (United States)
L-band Microwave Emission of the Biosphere (L-MEB) Model: Description and calibration against experimental data sets over crop fields
In the near future, the SMOS (Soil Moisture and Ocean Salinity) mission will provide global maps of surface soil moisture (SM). The SMOS baseline payload is an L-band (1.4 GHz) two dimensional interferometric microwave radiometer which will provide multi-angular and dual-polarization observations. In the framework of the ground segment activities for the SMOS mission an operational SMOS Level 2 Soil Moisture
J.-P. Wigneron; Y. H. Kerr; P. Waldteufel; K. Saleh; M.-J. Escorihuela; P. Richaume; P. Ferrazzoli; P. de Rosnay; R. Gurney; J.-C. Calvet; J. P. Grant; M. Guglielmetti; B. Hornbuckle; C. Mätzler; T. Pellarin; M. Schwank
Anomalous two-state model for anomalous diffusion.
An anomalous two-state model (ATSM) with the anomalous long-tailed kinetics of transitions between states is proposed to describe the specific features of anomalous diffusion (AD) and AD-assisted transitions (ADAT) in the double-well potential. In the ATSM the system is assumed to undergo the conventional diffusion in both states but with different diffusion coefficients. The anomalous features of diffusion result from the modulation of the diffusion coefficient caused by transitions between ATSM states. The anomalous space-time evolution predicted by the ATSM is treated within the continuous time random walk theory. With the use of the proposed ATSM the transient behavior of the AD and the ADAT is analyzed in detail. We found a large variety of different (and sometimes peculiar) types of the space-time behavior of the free AD and ADAT. The free AD is found to be of subdiffusion or superdiffusion type for fairly long time depending on the relation between the parameters of the ATSM. The kinetics of the ADAT can be either conventional (exponential) or anomalous (of inverse power type) for different parameters of the model and time. PMID:11735901
Shushin, A I
A study of passive microwave techniques applied to geologic problems
NASA Technical Reports Server (NTRS)
Passive microwave techniques were applied to geologic problems, in order to establish the microwave properties of representative rocks and minerals, and to examine the feasibility of using microwave radiometry for geologic mapping problems. A review of microwave pertaining to geology was conducted, coupled with laboratory and field investigations of the microwave emission characteristics of various geologic features. The laboratory studies consisted of dielectric constant measurements of rocks and minerals. A majority of field investigations conducted in the western United States, involved the microwave emission charateristics of rock types, and a portion of the study was concerned with microwave properties of mineralized areas. Experiments were also conducted in the vicinity of a coal seam fire in Colorado and across the San Andreas Fault Zone near the Salton Sea, in Southern California.
Edgerton, A. T.
Passive microwave observations of asteroids
NASA Technical Reports Server (NTRS)
The advances made since 1979 in the quantity and quality of the radio observations of asteroids and in the understanding of the physics of asteroidal microwave emission are reviewed. Radio continuum spectra analyses are now available for the four largest asteroids (Ceres, Vesta, Pallas, and Hygiea) at several wavelengths and several smaller asteroids (including Interamnia and Eunomia) at one wavelength. The spectra show that most asteroids are covered by a layer of material with physical properties of finely divided dust. This surface material is in layers of variable depth and has dielectric properties which vary from asteroid to asteroid. The effect of instrumentation on the interpretation of microwave observations is examined.
Webster, William J., Jr.; Johnston, Kenneth J.
Anomalous - viscosity current drive
An apparatus and method for maintaining a steady-state current in a toroidal magnetically confined plasma. An electric current is generated in an edge region at or near the outermost good magnetic surface of the toroidal plasma. The edge current is generated in a direction parallel to the flow of current in the main plasma and such that its current density is greater than the average density of the main plasma current. The current flow in the edge region is maintained in a direction parallel to the main current for a period of one or two of its characteristic decay times. Current from the edge region will penetrate radially into the plasma and augment the main plasma current through the mechanism of anomalous viscosity. In another aspect of the invention, current flow driven between a cathode and an anode is used to establish a start-up plasma current. The plasma-current channel is magnetically detached from the electrodes, leaving a plasma magnetically insulated from contact with any material obstructions including the cathode and anode.
Stix, Thomas H. (Princeton, NJ); Ono, Masayuki (Princeton Junction, NJ)
Element analysis and characteristic identification of non-fumigated and sulfur-fumigated Fritillaria thunbergii Miq. using microwave digestion-inductively coupled plasma atomic emission spectrometry combined with Fourier transform infrared spectrometry
Background: Sulfur-fumigation may induce chemical transformation of traditional Chinese medicines leading to harmful effects following patient ingestion. For quality control, it is urgently needed to develop a reliable and efficient method for sulfur-fumigation identification. Materials and Methods: The spectrochemical identification of non-fumigated and sulfur-fumigated Fritillaria thunbergii Miq. was carried out to evaluate inorganic elements and organic components. The concentrations of 12 elements, including Zn, Mn, Cu, Fe, Li, Mg, Sr, Pb, As, Cd, Hg, and S of samples were determined by microwave digestion - inductively coupled plasma atomic emission spectrometry (ICP-AES). Meanwhile, Fourier transform infrared spectrometry (FTIR) was used for the study of chemical group characteristic reactions after sulfur-fumigation. Results: The concentrations of Fe, Mg, Hg, and S elements showed significant differences between non-fumigated and sulfur-fumigated Fritillaria thunbergii Miq. The characteristic stretching vibrations of some groups in FTIR spectra, such as -OH, -S = O and -S-O, provided the identification basis for the discrimination of non-fumigated and sulfur-fumigated Fritillaria thunbergii Miq. Conclusion: The application of microwave digestion - ICP-AES was successfully used in combination with FTIR to authenticate and evaluate the quality of medicinal Fritillaria thunbergii Miq. Further applications of this technique should be explored.
Lou, Yajing; Cai, Hao; Liu, Xiao; Tu, Sicong; Pei, Ke; Zhao, Yingying; Cao, Gang; Li, Songlin; Qin, Kunming; Cai, Baochang
Improvement of AOAC Official Method 984.27 for the determination of nine nutritional elements in food products by Inductively coupled plasma-atomic emission spectroscopy after microwave digestion: single-laboratory validation and ring trial.
A single-laboratory validation (SLV) and a ring trial (RT) were undertaken to determine nine nutritional elements in food products by inductively coupled plasma-atomic emission spectroscopy in order to improve and update AOAC Official Method 984.27. The improvements involved optimized microwave digestion, selected analytical lines, internal standardization, and ion buffering. Simultaneous determination of nine elements (calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, and zinc) was made in food products. Sample digestion was performed through wet digestion of food samples by microwave technology with either closed or open vessel systems. Validation was performed to characterize the method for selectivity, sensitivity, linearity, accuracy, precision, recovery, ruggedness, and uncertainty. The robustness and efficiency of this method was proved through a successful internal RT using experienced food industry laboratories. Performance characteristics are reported for 13 certified and in-house reference materials, populating the AOAC triangle food sectors, which fulfilled AOAC criteria and recommendations for accuracy (trueness, recovery, and z-scores) and precision (repeatability and reproducibility RSD and HorRat values) regarding SLV and RT. This multielemental method is cost-efficient, time-saving, accurate, and fit-for-purpose according to ISO 17025 Norm and AOAC acceptability criteria, and is proposed as an improved version of AOAC Official Method 984.27 for fortified food products, including infant formula. PMID:19916387
Poitevin, Eric; Nicolas, Marine; Graveleau, Laetitia; Richoz, Janique; Andrey, Daniel; Monard, Florence
Dual Frequency Microwave Radiometer Measurements of Soil Moisture for Bare and Vegetated Rough Surfaces.
National Technical Information Service (NTIS)
Controlled ground-based passive microwave radiometric measurements on soil moisture were conducted to determine the effects of terrain surface roughness and vegetation on microwave emission. Theoretical predictions were compared with the experimental resu...
S. L. Lee
Compact Microwave Fourier Spectrum Analyzer
NASA Technical Reports Server (NTRS)
A compact photonic microwave Fourier spectrum analyzer [a Fourier-transform microwave spectrometer, (FTMWS)] with no moving parts has been proposed for use in remote sensing of weak, natural microwave emissions from the surfaces and atmospheres of planets to enable remote analysis and determination of chemical composition and abundances of critical molecular constituents in space. The instrument is based on a Bessel beam (light modes with non-zero angular momenta) fiber-optic elements. It features low power consumption, low mass, and high resolution, without a need for any cryogenics, beyond what is achievable by the current state-of-the-art in space instruments. The instrument can also be used in a wide-band scatterometer mode in active radar systems.
Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry
Policy Manual - Microwave Ovens
All containers used in microwave devices should be made from microwave-transparent material. Examples of microwave-transparent materials include ceramics, sodium borosilicate glass, unleaded quartz, fluoropolymers, and nonpolar plastics such as polypropylene, polyethylene and PTFE compounds.
Microwave Hydrology: A Trilogy.
National Technical Information Service (NTIS)
Microwave hydrology, as the term in construed in this trilogy, deals with the investigation of important hydrological features on the Earth's surface as they are remotely, and passively, sensed by orbiting microwave receivers. Microwave wavelengths penetr...
J. M. Stacey E. J. Johnston M. A. Girard H. A. Regusters
Tandem microwave waste remediation and decontamination system
The invention discloses a tandem microwave system consisting of a primary chamber in which microwave energy is used for the controlled combustion of materials. A second chamber is used to further treat the off-gases from the primary chamber by passage through a susceptor matrix subjected to additional microwave energy. The direct microwave radiation and elevated temperatures provide for significant reductions in the qualitative and quantitative emissions of the treated off gases. The tandem microwave system can be utilized for disinfecting wastes, sterilizing materials, and/or modifying the form of wastes to solidify organic or inorganic materials. The simple design allows on-site treatment of waste by small volume waste generators.
Wicks, George G. (North Aiken, SC); Clark, David E. (Gainesville, FL); Schulz, Rebecca L. (Gainesville, FL)
Experimental study of matrix carbon field-emission cathodes and computer aided design of electron guns for microwave power devices, exploring these cathodes
The experimental study of matrix carbon field-emission cathodes (MCFECs), which has led to the stable operation of the cathodes with current emission values up to 100 mA, is described. A method of computer aided design of TWT electron guns (EGs) with MCFEC, based on the results of the MCFEC emission experimental study, is presented. The experimental MCFEC emission characteristics are used to define the field gain coefficient K and the cathode effective emission area S{sub eff}. The EG program computes the electric field upon the MCFEC surface, multiplies it by the K value and uses the Fowler{endash}Nordheim law and the S{sub eff} value to calculate the MCFEC current; the electron trajectories are computed as well. {copyright} {ital 1997 American Vacuum Society.}
Grigoriev, Y.A.; Petrosyan, A.I.; Penzyakov, V.V.; Pimenov, V.G.; Rogovin, V.I.; Shesterkin, V.I.; Kudryashov, V.P.; Semyonov, V.C. [Research Production Co. ALMAZ, Panfilova 1, Saratov 410033 (Russia)] [Research Production Co. ALMAZ, Panfilova 1, Saratov 410033 (Russia)
Wideband Agile Digital Microwave Radiometer
NASA Technical Reports Server (NTRS)
The objectives of this work were to take the initial steps needed to develop a field programmable gate array (FPGA)- based wideband digital radiometer backend (>500 MHz bandwidth) that will enable passive microwave observations with minimal performance degradation in a radiofrequency-interference (RFI)-rich environment. As manmade RF emissions increase over time and fill more of the microwave spectrum, microwave radiometer science applications will be increasingly impacted in a negative way, and the current generation of spaceborne microwave radiometers that use broadband analog back ends will become severely compromised or unusable over an increasing fraction of time on orbit. There is a need to develop a digital radiometer back end that, for each observation period, uses digital signal processing (DSP) algorithms to identify the maximum amount of RFI-free spectrum across the radiometer band to preserve bandwidth to minimize radiometer noise (which is inversely related to the bandwidth). Ultimately, the objective is to incorporate all processing necessary in the back end to take contaminated input spectra and produce a single output value free of manmade signals to minimize data rates for spaceborne radiometer missions. But, to meet these objectives, several intermediate processing algorithms had to be developed, and their performance characterized relative to typical brightness temperature accuracy re quirements for current and future microwave radiometer missions, including those for measuring salinity, soil moisture, and snow pack.
Gaier, Todd C.; Brown, Shannon T.; Ruf, Christopher; Gross, Steven
Simultaneous Excess Power And Anomalous Radiation
NASA Astrophysics Data System (ADS)
Experimental studies of a Pd/D2O + LiOD/Pt electrolysis cell displayed the characteristics of the excess power effect during seven occasions over a 22-day period. These measurements clearly show the anomalous increase in the cell temperature from two thermistors despite the steadily decreasing electrical input power during electrolysis. During this same time period, the cell thermistor located close to the palladium cathode showed strange temperature excursions that suggest electromagnetic radiation emissions from this cathode. These sudden temperature excursions ranged from 1 to 16 ^oC and quickly returned to normal^2. The second thermistor in this cell that was located at a more distant position, where any electromagnetic radiation from the cathode would have to pass through the platinum anode, showed only normal temperature behavior. Later studies using a set of five thermistors also showed anomalous temperature excursions for any thermistors placed in close contact with a Cs-137 radioactive source (b-decay, 94% 0.511 MeV energy). However, the number of such temperature excursions using Cs-137 was much less than the number observed in the active Pd/D2O electrolysis cell for the same time period.
Miles, Melvin H.
Anomalous absorption in H_{2}CO molecule
NASA Astrophysics Data System (ADS)
Formaldehyde (H_2CO) is the first organic molecule identified in a number of galactic and extragalactic radio sources through its transition 1_{10}-1_{11} at 4.830 GHz in absorption in 1969. Later on, this transition was found in anomalous absorption. In some cosmic objects, this transition however was found in emission and even as a maser radiation. Since the transition 1_{10}-1_{11} of ortho-H_2CO is considered as a unique probe of high density gas at low temperature, the study of H_2CO has always been of great importance for astrophysicists as well as for spectroscopists. In the present investigation, we have solved a set of statistical equilibrium equations coupled with the equations of radiative transfer for H_2CO. Since the kinetic temperature in the medium where H_2CO is identified is few tens of Kelvin, we have considered 22 rotational levels of ortho-H_2CO in the ground vibrational and ground electronic states. The input data required in the present investigation are the radiative transition probabilities and the collisional rates. Using the latest data for radiative transition probabilities and the collisional rates, we have found anomalous absorption of 1_{10}-1_{11}, 2_{11}-2_{12} and 3_{12} - 3_{13} transitions of ortho-H_2CO.
Sharma, Monika; Kumar Sharma, Mohit
Anomalous transport with overlap fermions
NASA Astrophysics Data System (ADS)
Anomalous correlators of vector and axial currents which enter the Kubo formulae for the chiral magnetic and the chiral separation conductivities are explicitly calculated for free overlap fermions on the lattice. The results are confronted with continuum calculations in the finite-temperature regularization, and a subtle point of such regularization for chiral magnetic conductivity related to the correct counting of the chiral states is highlighted. In agreement with some previous claims in the literature, we find that in a lattice regularization which respects gauge invariance, the chiral magnetic conductivity vanishes. We point out that the relation of anomalous transport coefficients to axial anomaly is nontrivial due to the non-commutativity of their infrared limit and the Taylor expansion in baryon or chiral chemical potential. In particular, we argue that the vector and axial Ward identities fix the asymptotic behavior of anomalous current-current correlators in the limit of large momenta. Basing on the work of Knecht et al. on the perturbative non-renormalization of the transverse part of the correlator of two vector and one axial currents, we demonstrate that the relation of the anomalous vector-vector correlator to axial anomaly holds perturbatively in massless QCD but might be subject to non-perturbative corrections. Finally, we identify kinematical regimes in which the anomalous transport coefficients can be extracted from lattice measurements.
Buividovich, P. V.
Microwave technologies in coal power engineering
NASA Astrophysics Data System (ADS)
An analysis of the modern state and prospects of using microwave radiation in the processes of drying, dispersion, burning, and fine processing of low-rank coals for the purpose of increasing the energy efficiency of coal technologies and decreasing harmful emissions from them has been carried out. It is shown that the use of microwave-radiation energy in coal power engineering is a promising method of complex action on coal in the process of its preparation and burning.
Salomatov, V. V.; Sladkov, S. O.; Pashchenko, S. É.
Catastrophic extraction of anomalous events
NASA Astrophysics Data System (ADS)
In this paper we discuss extraction of anomalous events based on the theory of catastrophes, a mathematical theory of continuous geometrical manifolds with discrete singularities called catastrophes. Intelligence exploitation systems and technologies include such novel data mining techniques as automatic extraction of discrete anomalous events by software algorithms based on the theory of catastrophes, that can reduce complex problems to a few essential so-called state variables. This paper discusses mostly corank-1 catastrophes with only one state variable, for simplicity. As an example we discuss mostly avionics platforms and catastrophic failures that can be recorded by flight instruments.
Jannson, Tomasz; Forrester, Thomas; Ro, Sookwang; Kostrzewski, Andrew
NSDL National Science Digital Library
This fact card presents an overview of cosmic microwaves, light waves left over from the Big Bang after they have been stretched out by the expansion of the universe. The energy from microwave ovens are used as a reference point from everyday life. Microwaves in space are contrasted with the energy produced by microwave ovens.
The nature of microwave technology is defined in the discovery of microwave, which was initially used for military purposes. The invention of radar and microwave ovens are both attributed to this significant discovery. This paper explores significant applications of microwave technology and analyzed the impact on various aspects of this high technology. The new paradigm shift has resulted in tremendous
Joseph Z Bih
We find a unique direction in the cosmic microwave background sky around which giant rings have an anomalous mean temperature profile. This direction is in very close alignment with the afore measured anomalously large bulk flow direction. Using Monte Carlo simulations, we estimate the significance of the giant rings at the 3{sigma} level and the alignment with the bulk flow at 2.5{sigma}. We argue that a cosmic defect seeded by a pre-inflationary particle could explain the giant rings, the large bulk flow, and their alignment.
Kovetz, Ely D.; Ben-David, Assaf; Itzhaki, Nissan, E-mail: email@example.com, E-mail: email@example.com, E-mail: email@example.com [Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel-Aviv University, Ramat-Aviv, 69978 (Israel)
NASA Astrophysics Data System (ADS)
We consider deeply virtual Compton scattering (DVCS) on a photon target, in the generalized Bjorken limit, at the Born order and in the leading logarithmic approximation. This leads us to the extraction of the photon anomalous generalized parton distributions (GPDs) [S. Friot, B. Pire and L. Szymanowski, Phys. Lett. B 645 153 (2007)].
Friot, S.; Pire, B.; Szymanowski, L.
Anomalous-viscosity current drive
The present invention relates to a method and apparatus for maintaining a steady-state current for magnetically confining the plasma in a toroidal magnetic confinement device using anomalous viscosity current drive. A second aspect of this invention relates to an apparatus and method for the start-up of a magnetically confined toroidal plasma.
Stix, T.H.; Ono, M.
Anomalous dispersion of cylindrical longitudinal guided modes
NASA Astrophysics Data System (ADS)
Anomalous dispersion, phase velocity increases with frequency, of longitudinal modes in five cylindrical waveguides are numerically analyzed and summarized in this paper. The aim is to study the types and characteristics of modes exhibit anomalous dispersion, and the factors affect the anomalous. The analyses results show anomalous dispersion is relative to the surface and interface waves, and it could reflect the variations of shear modulus, density, and geometric structures.
Cui, H.; Zhang, B.; Trevelyan, J.; Johnstone, S.; Millman, S.
Surface and Bulk Characteristics of Cesium Iodide (CsI) coated Carbon (C) Fibers for High Power Microwave (HPM) Field Emission Cathodes
NASA Astrophysics Data System (ADS)
CsI coated C fibers [1] are promising field emission cathodes for HPM applications. Ab initio computational modeling has shown that atomically-thin CsI coatings reduce the work function of C substrates by a surface dipole mechanism [2]. Characterization measurements of the composition and morphology of the CsI-coated C fibers are underway for determining the properties and characteristics of the following important regions of the fiber: (i) the surface on the tip of the fiber where the majority of electron emission is believed to occur, (ii) the surface covering the body of the fiber and its role on the emission properties of the system, and (iii) the interior volume of the fiber and its effects on the CsI surface re-supply process and rate. The results will be interpreted in terms of surface electronic properties and theoretical electron emission models. [1]D. Shiffler, et al., Phys. Plasmas 11 (2004) 1680. [2]V.Vlahos et al., Appl. Phys. Lett. 91 (2007) 144102.
Vlahos, Vasilios; Morgan, Dane; Booske, John H.; Shiffler, Don
Lateralized Anomalous Perceptual Experiences in Schizophrenia
Four cases of schizophrenia are described, in which subjects reported anomalous perceptual experiences confined to one visual field, in all cases the left visual field. The pattern, content and laterality of such anomalous perceptions point to the presence of right hemisphere dysfunction in schizophrenia. Further evidence to this effect comes from examining the type of anomalous perceptual experiences reported by
R. Persaud; J. Cutting
Greener steel maldng process by microwave irradiation with discharges
Highly pure pig irons were produced from powdered iron ores and carbons in a multimode microwave reactor. Microwaves create two different steps that enhance chemical reactions at the grain boundaries very rapidly to finish the reduction process. The visible light spectroscopic monitored the progress of the reactions. The powders absolve and radiate the continuous spectrum of blackbody emission under the
M. Sato; K. Nagata; A. Matsubara; S. Takayama
Reduction of magnetite in air by use of microwave heating
Microwave technology is not a mere substitute for conventional heating, but it resides in the new domain of materials science, namely, microscopic and strong thermal non-equilibrium systems. The key factor for application of microwaves in the iron industry, is its high potential for an essential reduction of carbon dioxide emission. Iron ore refinement by means of blast furnaces was realized
Sadatsugu Takayama; Guido Link; M. Thumm; A. Matsubara; M. Sato
Fan-shaped microwave plasma for mail decontamination
A microwave torch is designed to produce fan-shaped plasma, which extends about 140 mm laterally. This torch produces an abundance of reactive atomic oxygen in the plasma effluent as evidenced by its emission spectroscopy. The results of the spectral intensity measurements show that the produced atomic oxygen outside the microwave cavity distributes quite uniformly over a width of about 80
Spencer P. Kuo; S. Popovic; Olga Tarasenko; M. Rubinraut; M. Raskovic
The Upper Atmosphere Research Satellite Microwave Limb Sounder Instrument
The microwave limb sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is the first satellite experiment using limb sounding techniques at microwave frequencies. Primary measure- ment objectives are stratospheric C10, 03, H20, temperature, and pressure. Measurements are of thermal emission: all are performed simultaneously and continuously and are not degraded by ice clouds or volcanic aerosols. The instrument has
F. T. Barath; M. C. Chavez; R. E. Cofield; D. A. Flower; M. A. Frerking; M. B. Gram; W. M. Harris; J. R. Holden; R. F. Jarnot; W. G. Kloezeman; G. J. Klose; G. K. Lau; M. S. Loo; B. J. Maddison; R. J. Mattauch; R. P. McKlnney; G. E. Peckham; H. M. Pickett; G. Siebes; F. S. Soltis; R. A. Suttie; J. A. Tarsala; J. W. Waters; W. J. Wilson
Unexpected behavior of crossing microwave beams.
An anomalous effect in the near field of crossed microwave beams, consisting in an unexpected transfer of modulation from one beam to the other, cannot be fully interpreted, at least not in a simple way, in terms of the usual electromagnetic or related framework. It is hypothesized that a local breaking of the Lorentz invariance, already invoked for an alternative interpretation of superluminal behaviors in these kinds of systems, could provide a partial explanation of the present results, although other interpretations cannot be completely ruled out. PMID:14995593
Ranfagni, A; Mugnai, D; Ruggeri, R
Tracking Jupiter at microwave frequencies after the 2009 impact
NASA Astrophysics Data System (ADS)
On 19 July 2009, amateur astronomer Anthony Wesley located near Canberra, Australia, discovered an anomalous dark feature near Jupiter's south pole. It was soon confirmed with additional observations that the new feature was an impact site created by an unknown object. The only other observed collision with Jupiter occurred 15 years earlier with the catastrophic impact of the Shoemaker-Levy 9 Comet (SL9). Unlike the well-predicted SL9 event, the biggest question to answer this time is whether the impact body was a comet or an asteroid. We started a campaign to track Jupiter at microwave frequencies with NASA's Deep Space Network (DSN), in Canberra, Goldstone (California), and Madrid, and the Allen Telescope Array (ATA) in California. A 34m DSN radio telescope at Goldstone was operated by students through GAVRT program. Our primary goal was first to detect molecular radio emissions possibly originating from cometary core components, such as OH, H2O, and NH3, and second to detect radio burst in non-thermal continuum emissions, as observed after the SL-9 impact 15 years ago. We used a 70m radio telescope in Canberra and another 70m in Madrid to search for molecular emissions at 1.6 GHz for OH, 22 GHz for water vapors, 23 GHz for ammonia. Several radio spectroscopy observing sessions have been successfully conducted from 23 July to 1 August. We also started continuum emission monitoring, mainly at 2.3 GHz and 8.4 GHz using 34m and 70m DSN telescopes and the ATA. At early stage of this still on-going monitoring, joint observations were conducted with two 34m telescopes in Canberra and the ATA on 30 July and 9 August in order to have long continuous time coverage and to check flux density scales using a common calibrator source. To highlight this campaign, on 22 November we undertook the Jupiter: Project 24 for the International Year of Astronomy. This campaign was over 24 hours of continuous observation of Jupiter using all three DSN complexes around the world. A couple of DSN 34m telescopes were operated by students organized by two educational programs: GAVRT in California and PARTNeR in Madrid. The Jupiter: Project 24 observations were broadcasted to the world in real time via the Internet. In this talk, we will present a summary of results from the molecular emission search and the continuum flux density monitoring. The evolution of the non-thermal Jupiter radio emission after the July 2009 impact will be discussed, along with a comparison to the increase in the synchrotron radiation caused by the SL9 impact in 1994.
Horiuchi, Shinji; García-Miró, Cristina; Rizzo, Ricardo; Forster, James; Hofstadter, Mark; Dorcey, Ryan; Jauncey, David; de Pater, Imke; Baines, Graham; Sotuela, Ioanna
Low pressure gas discharges for electric field intensity monitoring in microwave resonant cavities
This paper introduces a new concept in the detection and monitoring of the electric field intensity in high power microwave cavities. It is proposed that the optical emission intensity of a low-pressure gas plasma discharge can be used to describe the strength of the microwave electric field that is powering the plasma. This paper discusses the principles of microwave generated
Ahmed Al-Shamma'a; Colin Fitzpatrick; Jim Lucas; Ionnais Pandithas; Elfed Lewis
Microwave Remote Sensing of Planetary Atmospheres: From Staelin and Barrett to the Nasa Juno Mission
Early seminal contributions by Staelin helped initiate the field of microwave remote sensing as a key tool for the study of planetary atmospheres. Recent studies of the microwave emission from the neutral atmosphere of Venus have been used to identify the abundance and spatial distribution of microwave absorbing constituents such as sulfuric acid vapor and sulfur dioxide. A new mission
Paul G. Steffes; Bryan M. Karpowicz
Microwave Imaging Reflectometry for the Visualization of Turbulence in Tokamaks
Understanding the mechanism of anomalous transport in magnetically confined plasmas requires the use of sophisticated diagnostic tools for the measurement of short-scale turbulent fluctuations. This paper describes the conceptual design of an experimental technique for the global visualization of density fluctuations in tokamaks. The proposed method is based on microwave reflectometry and consists in using a large diameter probing beam, collecting the reflected waves with a large aperture antenna, and forming an image of the reflecting plasma layer onto a 2D array of microwave receivers. Based on results from a series of numerical simulations, the theoretical feasibility conditions of the proposed method are discussed.
E. Mazzucato
Laboratory measurement of the millimeter wave properties of liquid sulfuric acid (H2SO4). [study of microwave emission from Venus
NASA Technical Reports Server (NTRS)
The methodology and the results of laboratory measurements of the millimeter wave properties of liquid sulfuric acid are presented. Measurements conducted at 30-40 and 90-100 GHz are reported, using different concentrations of liquid H2SO4. The measured data are used to compute the expected opacity of H2SO4 condensates and their effects on the millimeter wave emission from Venus. The cloud condensate is found to have an effect on the emission from Venus. The calculated decrease in brightness temperature is well below the observed decrease in brightness temperature found by de Pater et al. (1991). It is suggested that other constituents such as gaseous H2SO4 also affect the observed variation in the brightness temperature.
Fahd, Antoine K.; Steffes, Paul G.
Microwave based method of monitoring crack formation
NASA Astrophysics Data System (ADS)
The formation of cracks in glass particles was monitored by application of linearly polarized microwaves. The breakage behavior of glass spheres coated with a thin gold layer of about 50 nm, i.e. a thickness that is lower than the microwave penetration depth, was tested. In this way the investigation of fracture behavior of electronic circuits was simulated. A shielding current was induced in the gold layer by the application of microwaves. During the crack formation the distribution of this current changed abruptly and a scattered microwave signal appeared at the frequency of the incident microwaves. The time behavior of the scattered signal reflects the microscopic processes occurring during the fracture of the specimen. The duration of the increasing signal corresponds to the crack formation time in the tested specimen. This time was estimated as particle size divided by crack development speed in glass. An intense emission of electrons occurs during the formation of cracks. Due to this, coherent Thomson scattering of microwaves by emitted electrons becomes significant with a delay of a few microseconds after the initial phase of crack formation. In this time the intensity of the microwave signal increases.
Aman, Sergej; Aman, Alexander; Majcherek, Soeren; Hirsch, Soeren; Schmidt, Bertram
Microwave remote sensing: Active and passive. Volume 1 - Microwave remote sensing fundamentals and radiometry
NASA Technical Reports Server (NTRS)
The three components of microwave remote sensing (sensor-scene interaction, sensor design, and measurement techniques), and the applications to geoscience are examined. The history of active and passive microwave sensing is reviewed, along with fundamental principles of electromagnetic wave propagation, antennas, and microwave interaction with atmospheric constituents. Radiometric concepts are reviewed, particularly for measurement problems for atmospheric and terrestrial sources of natural radiation. Particular attention is given to the emission by atmospheric gases, clouds, and rain as described by the radiative transfer function. Finally, the operation and performance characteristics of radiometer receivers are discussed, particularly for measurement precision, calibration techniques, and imaging considerations.
Ulaby, F. T.; Moore, R. K.; Fung, A. K.
Combined Foam-Spray Model for Ocean Microwave Radiometry.
National Technical Information Service (NTIS)
Passive microwave emissions from oceanic dispersed media are considered. The spray is modeled by the aggregates of spherical water droplets, and the foam is represented by a macroscopic system of hollow spherical water shells. Dielectric properties of foa...
V. Raizer
Interpretation of observed cosmic microwave background radiation
NASA Technical Reports Server (NTRS)
The Alfven and Mendis (1977) conclusion that dust grains in galaxies render the universe opaque to cosmic microwave background at a red shift ratio equal to 40 is challenged by a calculation of the opacity of galactic dust grains to the microwave background radiation from the time of decoupling at emission red shift ratio equal to 1500 to the present in the standard big bang model. In the present calculation, evolutionary effects on grain opacity and abundance are estimated. At wavelengths used in studying the microwave background, the optical depth of the grains is found to be 0.18 when the deceleration parameter equals 0.03, and 0.05 when the deceleration parameter equals 0.5. The results indicate that microwave background can provide information on an early dense phase of the universe.
Pollaine, S.
NASA Astrophysics Data System (ADS)
By using an on-chip microwave sensor employing spintronic and spin caloritronic principles, a spintronic technique has been developed for microwave imaging. This novel technique allows microwave fields to be directly rectified on chip into dc voltage signals. This imaging technique does not require complicated and expensive microwave systems to operate, yet it can still electrically detect scattered microwave fields accurately enough to image embedded defects and hidden objects. By varying the experimental setup, apparatuses based on spintronic sensors have been developed for achieving both near- and far-field imaging (at microwave frequencies) as well as for performing on-chip dielectric analysis.
Cao, Z. X.; Lu, W.; Fu, L.; Gui, Y. S.; Hu, C.-M.
Microwave processing improvements for methane conversion to ethylene
This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project`s objective was to investigate microwave enhanced catalysis. Published work by others had demonstrated improved selectivity in microwave-driven catalytic conversion of 2-methylpentane to its isomers. We reproduced their experiment, discovering that there is no improvement in selectivity using microwaves. The selectivity at a given conversion was the same for both microwave heated and conventionally heated catalyst beds. Meetings with the authors of the previously published work led to the conjecture that their catalyst was not being prepared properly, leading to anomalously low selectivity for their conventional heating runs. An optical temperature diagnostic suitable for use on a microwave applicator was developed and characterized in this project. This pyrometer can measure the temperature of small scale features on the catalyst bed, and it has a fast response that can follow the rapid heating often encountered in a microwave processing system. The behavior of the microwave applicator system was studied, and theoretical models were developed to yield insight about the stability and control of the system.
Stringfield, R.; Ott, K.; Nelson, E.; Anderson, G.; Chen, Dye-Zone; Dyer, T. [Los Alamos National Lab., NM (United States); Thomas, J. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)
Determination of soluble toxic arsenic species in alga samples by microwave-assisted extraction and high performance liquid chromatography-hydride generation-inductively coupled plasma-atomic emission spectrometry.
A microwave-based procedure for arsenic species extraction in alga samples (Sargassum fulvellum, Chlorella vulgaris, Hizikia fusiformis and Laminaria digitata) is described. Extraction time and temperature were tested in order to evaluate the extraction efficiency of the process. Arsenic compounds were extracted in 8 ml of deionised water at 90 degrees C for 5 min. The process was repeated three times. Soluble arsenic compounds extracted accounted for about 78-98% of total arsenic. The results were compared with those obtained in a previous work, where the extraction process was carried out by ultrasonic focussed probe for 30 s. Speciation studies were carried out by high performance liquid chromatography-hydride generation-inductively coupled plasma-atomic emission spectrometry (HPLC-HG-ICP-AES). The chromatographic method allowed us to separate As(III), As(V), monomethylarsonic acid and dimethylarsinic acid in less than 13 min. The chromatographic analysis of the samples allowed us to identify and quantify As(V) in Hizikia sample and Sargasso material, while the four arsenic species studied were found in Chlorella sample. In the case of Laminaria sample, none of these species was identified by HPLC-HG-ICP-AES. However, in the chromatographic analysis of this alga by HPLC-ICP-AES, an unknown arsenic species was detected. PMID:16876177
García Salgado, S; Quijano Nieto, M A; Bonilla Simón, M M
Partial anomalous pulmonary venous return.
Partial anomalous pulmonary venous return (PAPVR) is an uncommon congenital abnormality that occurs in 0.4 to 0.7% of postmortem examinations. Ninety percent of these anomalies are associated with an atrial septal defect. Partial anomalous pulmonary venous return occurs more commonly on the right than the left and is manifested by abnormal return of the pulmonary veins to the central venous circulation. Most patients are asymptomatic, but when symptoms are present they are due to shunting of oxygenated blood to the venous circulation. We submit the case of a recently activated solider who presented with dyspnea on exertion refractory to inhaled corticosteroids and an 8.5-mm solitary pulmonary nodule. Further diagnostic imaging revealed PAPVR. Our case appears to be the first report of a solitary pulmonary nodule as the initial presentation of a right upper lobe PAPVR with return to the superior vena cava in the absence of associated atrial septal defect. PMID:18595412
Broy, Charles; Bennett, Steven
Magnetic effects in anomalous dispersion
Spectacular enhancements of magnetic x-ray scattering have been predicted and observed experimentally. These effects are the result of resonant phenomena closely related to anomalous dispersion, and they are strongest at near-edge resonances. The theory of these resonances will be developed with particular attention to the symmetry properties of the scatterer. While the phenomena to be discussed concern magnetic properties the transitions are electric dipole or electric quadrupole in character and represent a subset of the usual anomalous dispersion phenomena. The polarization dependence of the scattering is also considered, and the polarization dependence for magnetic effects is related to that for charge scattering and to Templeton type anisotropic polarization phenomena. It has been found that the strongest effects occur in rare-earths and in actinides for M shell edges. In addition to the scattering properties the theory is applicable to ``forward scattering`` properties such as the Faraday effect and circular dichroism.
Blume, M.
Anomalous free electron laser interaction
Free electron lasers (FELs) are considered, typically, as fast wave devices. The normal FEL interaction satisfies the tuning condition ??(kz+kW)Vz , where ? and kz are the em-wave angular frequency and longitudinal wave number, respectively, Vz is the electron axial speed, and kW is the wiggler periodicity. This paper presents an anomalous FEL interaction, which may occur in slow-wave FELs
M. Einat; E. Jerby; A. Kesar
Defrosting Shrimp with Microwaves.
National Technical Information Service (NTIS)
Laboratory experiments and results lead to the conclusion that microwave defrosting is particularly suited to the defrosting of raw, headless shrimp for the following reasons: (1) Microwave defrosting would allow compliance with the present GMP guideline ...
A. Bezanson R. Learson W. Teich
Mikroaaltoalueen Instrumentit (Microwave Instruments).
National Technical Information Service (NTIS)
Numerous microwave telemapping instruments usable in flight have been designed and built. Microwave radiometers and radars are used in campaigns to measure forests, snow and the sea. Up to the present these measurements were taken from helicopters. Instru...
M. Hallikainen E. Panula-Ontto P. Ahola J. Koivula L. Kurvonen
Causes of anomalous line-splitting in RV Tauri stars
NASA Astrophysics Data System (ADS)
Data on the anomalous absorption-line splitting and emission in the RV Tauri stars AC Her, U Mon, and R Sct are examined. It is shown that the Karp line-splitting mechanism for cepheids cannot explain the highly redshifted lines that appear without antecedents in some RV Tauri stars and that the veiling that occurs during rising light appears to affect the bluer absorption components more than the high redshift ones. Evidence is reviewed showing strong shock waves must be present in RV Tauri star atmospheres, and a two-shock picture to explain the anomalous line splitting is presented based on a model for long-period variables by Hill and Willson. Advantages and difficulties of the model are discussed.
Baird, S. R.
Anomalous sounds from the entry of meteor fireballs.
A very bright fireball observed over New South Wales in 1978 produced anomalous sounds clearly audible to some of the observers. An investigation of the phenomenon indicates that bright fireballs radiate considerable electromagnetic energy in the very-low-frequency (VLF) region of the spectrum. A mechanism for the production of VLF emissions from the highly energetic wake turbulence of the fireball is proposed. Trials with human subjects revealed a very extended range of thresholds for the perception of electrically excited sounds among a sample population, particularly when the VLF electric field excites surface acoustic waves in surrounding objects. This fact, together with variable propagation effects and local conditions, can account for the sporadic distribution of reports of anomalous sounds from fireballs and auroras. PMID:17751127
Keay, C S
Wave-particle interaction and peculiarities of propagation and emission of accelerated particles in solar flares
NASA Astrophysics Data System (ADS)
Consequences of wave-particle interaction in the propagation and emission of accelerated particles in solar flares are considered. i. Strong diffusion energetic particles on small-scale waves (Trakhtengerts 1984) gives time delays of gamma ray line emission vs hard X-ray emission when electron and protons are accelerated simultaneously. ii. Anomalous propagation of relativistic electrons along the flare loop with velocity of 30 times less compared with light velocity (Yokoyama et al 2002) is explained in terms of the collective effects of interaction of electrons with plasma turbulence. A cloud of high-energetic electrons responsible for microwave emission generates whistler waves and a turbulent "wall" in the loop is formed. The electrons undergo strong resonant scattering and the emission front propagates with the wave phase velocity, which is much lower than particle velocity. iii. Absence of linear polarization (? 0.07%) in H? emission of some flares (Bianda et al 2005) is interpreted in terms of pitch-angle scattering of proton beams on small-scale Alfven waves. References Bianda M., Benz F.O., Stenflo J.O. et al 2005, A&A, 434, 1183 Trakhtengerts V.Yu. 1984, Relaxation of Plasma with Anisotropic Velocity Distribution, in A.A.Galeev and R.N.Sudan (eds.) Basic Plasma Physics II, North-Holland Physics Publishing Yokoyama T., Nakajima H., Shibasaki K, et al. 2002, ApJ, 576, L87
Stepanov, A. V.; Tsap, Yu. T.
Microwave Remote Sensing Resources
NSDL National Science Digital Library
This module provides background information on microwave remote sensing with polar-orbiting satellites. It reviews coverage, orbits, and data latency issues of current operational and selected research satellites and notes improvements expected in the NPP and NPOESS era. The module contrasts active vs. passive remote sensing, discusses advantages and limitations of different microwave instrument scanning strategies, and addresses viewing geometry with implications for spatial resolution and swath coverage. Finally, it offers a review of the microwave spectrum and special characteristics of microwave energy important for understanding microwave imagery and derived products. This module takes about 1 hour to complete.
Spangler, Tim
Microwave sintering of ceramics
Successful adaptation of microwave heating to the densification of ceramic materials require a marriage of microwave and materials technologies. Using an interdisciplinary team of microwave and materials engineers, we have successfully demonstrated the ability to density ceramic materials over a wide range of temperatures. Microstructural evolution during microwave sintering has been found to be significantly different from that observed in conventional sintering. Our results and those of others indicate that microwave sintering has the potential to fabricate components to near net shape with mechanical properties equivalent to hot pressed or hot isostatically pressed material. 6 refs., 11 figs.
Snyder, W.B.
Raman lidar calibration for the DMSP SSM\\/T-2 microwave water vapor sensor
Campaigns were conducted at the Pacific Missile Range Facility, Barking Sands, Kauai, investigating Raman lidar as a method to improve calibration of the DMSP SSM\\/T-2 microwave water vapor profiling instrument. Lidar mixing ratios were calibrated against AIR and Vaisala radiosondes and the calibration was tested in the vicinity of clouds. Above 6 km, radiosondes reported anomalously low relative humidity in
John Wessel; Steven M. Beck; Yat C. Chan; Robert W. Farley; Jerry A. Gelbwachs
Anomalous phosphenes in ocular protontherapy
NASA Astrophysics Data System (ADS)
We have undertaken a clinical ground study of proton-induced light flashes (phosphenes). Patients treated at the Institut Curie - Centre de Protonthérapie in Orsay, France, received radiation therapy to cure ocular and skull-base cancers. Sixty percent of the patients treated for choroidal melanomas using 73 MeV protons report anomalous phosphenes. Delivering a radiation dose on the retina only is not sufficient to trigger the light flash. The present study may be the first indication of phosphenes triggered by protons of few tens of MeV.
Khan, E.; Maréchal, F.; Dendale, R.; Mabit, C.; Calugaru, V.; Desjardin, L.; Narici, L.
Anomalous transport in toroidal plasmas
When the magnetic moment of particle is conserved, there are three mechanisms which cause anomalous transport. These are: variation of magnetic field strength in flux surface, variation of electrostatic potential in flux surface, and destruction of flux surface. The anomalous transport of different groups of particles resulting from each of these mechanisms is different. This fact can be exploited to determine the cause of transport operative in an experimental situation. This approach can give far more information on the transport than the standard confinement time measurements. To implement this approach, we have developed Monte Carlo codes for toroidal geometries. The equations of motion are developed in a set of non-canonical, practical Boozer co-ordinates by means of Jacobian transformations of the particle drift Hamiltonian equations of motion. Effects of collisions are included by appropriate stochastic changes in the constants of motion. Effects of the loop voltage on particle motions are also included. We plan to apply our method to study two problems: the problem of the hot electron tail observed in edge region of ZT-40, and the energy confinement time in TOKAPOLE II. For the ZT-40 problem three situations will be considered: a single mode in the core, a stochastic region that covers half the minor radius, a stochastic region that covers the entire plasma. A turbulent spectrum of perturbations based on the experimental data of TOKAPOLE II will be developed. This will be used to simulate electron transport resulting from ideal instabilities and resistive instabilities in TOKAPOLE II.
Punjabi, A.
Anomalous thermodynamics at the microscale.
Particle motion at the microscale is an incessant tug-of-war between thermal fluctuations and applied forces on one side and the strong resistance exerted by fluid viscosity on the other. Friction is so strong that completely neglecting inertia--the overdamped approximation--gives an excellent effective description of the actual particle mechanics. In sharp contrast to this result, here we show that the overdamped approximation dramatically fails when thermodynamic quantities such as the entropy production in the environment are considered, in the presence of temperature gradients. In the limit of vanishingly small, yet finite, inertia, we find that the entropy production is dominated by a contribution that is anomalous, i.e., has no counterpart in the overdamped approximation. This phenomenon, which we call an entropic anomaly, is due to a symmetry breaking that occurs when moving to the small, finite inertia limit. Anomalous entropy production is traced back to futile phase-space cyclic trajectories displaying a fast downgradient sweep followed by a slow upgradient return to the original position. PMID:23368546
Celani, Antonio; Bo, Stefano; Eichhorn, Ralf; Aurell, Erik
Kinetic studies of anomalous transport
Progress in achieving a physics-based understanding of anomalous transport in toroidal systems has come in large part from investigations based on the proposition that low frequency electrostatic microinstabilities are dominant in the bulk ( confinement'') region of these plasmas. Although the presence here of drift-type modes dependent on trapped particle and ion temperature gradient driven effects appears to be consistent with a number of important observed confinement trends, conventional estimates for these instabilities cannot account for the strong current (I{sub p}) and /or q-scaling frequently found in empirically deduced global energy confinement times for auxiliary-heated discharges. The present paper deals with both linear and nonlinear physics features, ignored in simpler estimates, which could introduce an appreciable local dependence on current. It is also pointed out that while the thermal flux characteristics of drift modes have justifiably been the focus of experimental studies assessing their relevance, other transport properties associated with these microinstabilities should additionally be examined. Accordingly, the present paper provides estimates and discusses the significance of anomalous energy exchange between ions and electrons when fluctuations are present. 19 refs., 3 figs.
Tang, W.M.
Anomalous work function anisotropy in ternary acetylides
NASA Astrophysics Data System (ADS)
Anomalous anisotropy of work function values in ternary alkali metal transition metal acetylides is reported. Work function values of some characteristic surfaces in these emerging semiconducting materials may differ by more than 2 eV as predicted by density functional theory calculations. This large anisotropy is a consequence of the relative orientation of rodlike [MC2]? negatively charged polymeric subunits and the surfaces, with M being a transition metal or metalloid element and C2 refers to the acetylide ion C22-, with the rods embedded into an alkali cation matrix. It is shown that the conversion of the seasoned Cs2Te photoemissive material to ternary acetylide Cs2TeC2 results in substantial reduction of its ?3 eV work function down to 1.71-2.44 eV on the Cs2TeC2(010) surface, while its high quantum yield is preserved. Similar low work function values are predicted for other ternary acetylides as well, allowing for a broad range of applications from improved electron and light sources to solar cells, field emission displays, detectors, and scanners.
Terdik, Joseph Z.; Németh, Károly; Harkay, Katherine C.; Terry, Jeffrey H., Jr.; Spentzouris, Linda; Velázquez, Daniel; Rosenberg, Richard; Srajer, George
Microwave amplification with nanomechanical resonators.
The sensitive measurement of electrical signals is at the heart of modern technology. According to the principles of quantum mechanics, any detector or amplifier necessarily adds a certain amount of noise to the signal, equal to at least the noise added by quantum fluctuations. This quantum limit of added noise has nearly been reached in superconducting devices that take advantage of nonlinearities in Josephson junctions. Here we introduce the concept of the amplification of microwave signals using mechanical oscillation, which seems likely to enable quantum-limited operation. We drive a nanomechanical resonator with a radiation pressure force, and provide an experimental demonstration and an analytical description of how a signal input to a microwave cavity induces coherent stimulated emission and, consequently, signal amplification. This generic scheme, which is based on two linear oscillators, has the advantage of being conceptually and practically simpler than the Josephson junction devices. In our device, we achieve signal amplification of 25 decibels with the addition of 20 quanta of noise, which is consistent with the expected amount of added noise. The generality of the model allows for realization in other physical systems as well, and we anticipate that near-quantum-limited mechanical microwave amplification will soon be feasible in various applications involving integrated electrical circuits. PMID:22170682
Massel, F; Heikkilä, T T; Pirkkalainen, J-M; Cho, S U; Saloniemi, H; Hakonen, P J; Sillanpää, M A
Decimetric Spike Bursts versus Microwave Continuum
NASA Astrophysics Data System (ADS)
We analyze properties of decimetric spike bursts occurring simultaneously with microwave gyrosynchrotron continuum bursts. We found that all of the accompanying microwave bursts were highly polarized in the optically thin range. The sense of polarization of the spike clusters is typically the same as that of the optically thin gyrosynchrotron emission, implying preferential extraordinary wave-mode spike polarization. Optically thick spectral indices of the continuum in spike-producing events were not observed to be larger than 2.5, suggesting low or absent Razin suppression. This implies that the plasma frequency-to-gyrofrequency ratio is systematically lower in the spike-producing bursts than in other bursts. The spike cluster flux density is found to be tightly correlated with the high-frequency spectral index of the microwave continuum for each event, while the flux-to-flux correlation may not be present. We discovered strong evidence that the trapped fast electrons producing the microwave gyrosynchrotron continuum have an anisotropic pitch-angle distribution of the loss cone type in the spike-producing bursts. The spike clusters are mainly generated when the trapped electrons have the hardest and the most anisotropic distributions. The new properties are discussed against the currently available ideas about emission processes and models for spike generation. We conclude that the findings strongly support the electron cyclotron maser mechanism of spike emission, with characteristics agreeing with expectations from the local-trap model.
Fleishman, Gregory D.; Gary, Dale E.; Nita, Gelu M.
Microwave power generation by magnetic superlattices
NASA Astrophysics Data System (ADS)
We report on microwave power emission by ballistic electrons as they cross a region of spatially inhomogeneous magnetic field. Magnetic finger gates were fabricated at the surface of high mobility GaAs/AlGaAs Hall bars embedded in a coplanar waveguide. By modulating the current injected through the Hall bar and measuring the second harmonic of the signal rectified by a Schottky detector, we obtain the microwave power emitted by the superlattice. This power (~6 W m-2) is compared to the fluorescence of electron spins that undergo spin resonance as they cross domains of opposite magnetic field.
Littlejohn, S.; Nogaret, A.; Davies, S. R.; Henini, M.; Beere, H. E.; Ritchie, D. A.
Receivers for the Microwave Radiometer on Juno
NASA Technical Reports Server (NTRS)
Six receivers for the MicroWave Radiometer (MWR) are currently under development at JPL. These receivers cover a frequency range of 0.6 to 22 GHz in approximately octave steps, with 4 % bandwidth. For calibration and diagnosis three noise diodes and a Dicke switch are integrated into each receiver. Each receiver is connected to its own antenna which is mounted with its bore sights perpendicular to the spin axis of the spacecraft. As the spacecraft spins at 2 RPM, the antenna field of view scans Jupiter's atmosphere from limb to nadir to limb, measuring microwave emission down to 1000-bar.
Maiwald, F.; Russell, D.; Dawson, D.; Hatch, W.; Brown, S.; Oswald, J.; Janssen, M.
Wanted: A Positive Control for Anomalous Subdiffusion
Anomalous subdiffusion in cells and model systems is an active area of research. The main questions are whether diffusion is anomalous or normal, and if it is anomalous, its mechanism. The subject is controversial, especially the hypothesis that crowding causes anomalous subdiffusion. Anomalous subdiffusion measurements would be strengthened by an experimental standard, particularly one able to cross-calibrate the different types of measurements. Criteria for a calibration standard are proposed. First, diffusion must be anomalous over the length and timescales of the different measurements. The length-scale is fundamental; the time scale can be adjusted through the viscosity of the medium. Second, the standard must be theoretically well understood, with a known anomalous subdiffusion exponent, ideally readily tunable. Third, the standard must be simple, reproducible, and independently characterizable (by, for example, electron microscopy for nanostructures). Candidate experimental standards are evaluated, including obstructed lipid bilayers; aqueous systems obstructed by nanopillars; a continuum percolation system in which a prescribed fraction of randomly chosen obstacles in a regular array is ablated; single-file diffusion in pores; transient anomalous subdiffusion due to binding of particles in arrays such as transcription factors in randomized DNA arrays; and computer-generated physical trajectories.
Saxton, Michael J.
Thermochromism, photochromism and anomalous temperature dependence of luminescence in Poly(3Alkylthiophene) film
Thermochromism and anomalous temperature dependence of emission spectra have been observed in poly(3-alkylthiophene) films, and are explained in terms of the transition of poly(3-alkylthiophene) conformation. The spectral change by laser irradiation and its memory have also been confirmed. The application of this phenomenon as an optical active element is proposed.
Katsumi Yoshino; Shigeaki Nakajima; Dae Hee Park; Ryu-Ichi Sugimoto
Spatial behavior of anomalous transport.
We present a general derivation of one-dimensional spatial concentration distributions for anomalous transport regimes. Such transport can be captured in the framework of a continuous time random walk with a broad transition time distribution. This general theory includes a Fokker-Planck equation as a particular limiting case. All of the concentration profiles, as well as the associated temporal first passage time distributions, can be written in terms of a single special function (that belongs to the class of Fox functions). In addition, we consider the first two moments of the spatial concentration distributions, and determine not only their scaling behavior with time but also the coefficients and correction terms. PMID:11909023
Margolin, Gennady; Berkowitz, Brian
Anomalous magnetic relaxation in ferritin
NASA Astrophysics Data System (ADS)
We report measurements in natural horse-spleen ferritin that provide a detailed mapping of the blocking temperature, TB, as a function of magnetic field over a broad range up to 20 kOe. Unlike most superparamagnetic materials where it decreases with applied field, TB increases with increasing field at small fields, reaching a maximum at ~3 kOe before exhibiting the expected decrease. The hysteresis loops are anomalously ``pinched'' near zero field. Both observations are consistent with an effective energy barrier that is smaller at zero field than in small finite fields. This may arise from tunneling between pairs of states on opposite sides of the anisotropy barrier that are in resonance in zero magnetic field, regardless of particle size. However, direct measurements of the magnetic viscosity yield ambiguous results, leaving open other possible explanations.
Friedman, Jonathan R.; Voskoboynik, U.; Sarachik, M. P.
Considerations for Microwave Remote Sensing of Ocean-Surface Salinity
Parametric calculations of the microwave emission from the ocean surface are presented to determine the optimum electromagnetic wavelength for measuring salinity. At 800 MHz, a target accuracy of 240 parts per million is within the state of the art provided that emission due to surface roughness is negligible, or correctable, and that the error resulting from galactic radiation can be
Calvin T. Swift; Robert E. Mcintosh
Lossless anomalous dispersion and an inversionless gain doublet via dressed interacting ground states
Transparent media exhibiting anomalous dispersion have been of considerable interest since Wang, Kuzmich, and Dogariu [Nature 406, 277 (2000)] first observed light propagate with superluminal and negative group velocities without absorption. Here, we propose an atomic model exhibiting these properties, based on a generalization of amplification without inversion in a five-level dressed interacting ground-state system. The system consists of a {Lambda} atom prepared as in standard electromagnetically induced transparency (EIT), with two additional metastable ground states coupled to the {Lambda} atom ground states by two rf-microwave fields. We consider two configurations by which population is incoherently pumped into the ground states of the atom. Under appropriate circumstances, we predict a pair of new gain lines with tunable width, separation, and height. Between these lines, absorption vanishes but dispersion is large and anomalous. The system described here is a significant improvement over other proposals in the anomalous dispersion literature in that it permits additional coherent control over the spectral properties of the anomalous region, including a possible 10{sup 4}-fold increase over the group delay observed by Wang, Kuzmich, and Dogariu.
Weatherall, James Owen [Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States); Department of Mathematical Sciences, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States); Department of Logic and Philosophy of Science, University of California Irvine, 3151 Social Science Plaza A, Irvine, California 92697 (United States); Search, Christopher P. [Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States)
The observation of more rapid reaction and/or sintering during microwave processing of ceramics has lead to speculation that microwave processing results in enhanced diffusion.'' The loss mechanisms by which microwaves interact with a crystal lattice have been reviewed. These mechanisms were evaluated with regard to the atomic theory of diffusion. The potential for these loss mechanisms to influence atomic diffusion, and thus produce enhancement will be discussed. Existing evidence, both direct and indirect, regarding microwave enhanced diffusion has been reviewed and will be discussed along with recent experimental data. 15 refs., 5 figs.
Katz, J.D.; Blake, R.D. (Los Alamos National Lab., NM (USA)); Kenkre, V.M. (New Mexico Univ., Albuquerque, NM (USA))
During the last decades the use of microwaves has been common in the industry, medicine, household and armed forces. According to the literature microwaves may especially cause lens opacities and other serious health disturbances. The authors of this paper examined 121 radar workers, but nothing was found which could be connected to microwaves. For example, the amount of lens opacities had correlation only to the age of the patients, but not to the exposure time of microwaves. The exposure duration varied from 0 to 28 years and the age of the patients between 18 and 59 years. PMID:7158323
Castrén, J; Lauteala, L; Antere, E; Aho, J; Torvi, K
Photoinduced spin polarization and microwave technology
NASA Astrophysics Data System (ADS)
We report here on studies of optically pumped active microwave media based on various fullerene derivatives, with an emphasis on the use of these materials in microwave electronics. We have investigated a class of optically excited paramagnetic materials that demonstrate activity in the X-band as candidate materials. We found that a particular fullerene derivative, Phenyl-C61-butyric acid methyl ester (PCBM), produced the largest electron paramagnetic resonance (EPR) emission signal compared to other organic compounds that have been suggested for use as microwave active materials. We also studied the effects of concentration, temperature, solvent etc. on the activity of the material. In these experiments, EPR studies using a commercial spectrometer were followed up by measurements of an RF signal reflected from a resonator loaded with the PCBM-based material. The activity was directly demonstrated through the change in the quality factor and RF coupling between the resonator and waveguide feed. At the inception of these experiments the primary interest was the development of a microwave PASER. The PASER (particle acceleration by stimulated emission of radiation [1]) is a novel acceleration concept that is based on the direct energy transfer from an active medium to a charged particle beam. While the previous work on the PASER has emphasized operations at infrared or visible wavelengths, operating in the microwave regime has significant advantages in terms of the less stringent quality requirements placed on the electron beam provided an appropriate microwave active medium can be found. This paper is focused on our investigation of the possibility of a PASER operating in the microwave frequency regime [2] using active paramagnetic materials. While a high level of gain for PCBM was demonstrated compared to other candidate materials, dielectric losses and quenching effects were found to negatively impact its performance for PASER applications. We present results on development and bench testing for these new fullerene-based materials along with some conceptual designs for microwave PASERs. Other possible applications for active paramagnetic materials are suggested including low noise microwave amplifiers and tunable RF absorbers.
Antipov, Sergey; Poluektov, Oleg; Schoessow, Paul; Kanareykin, Alexei; Jing, Chunguang
Anomalous and classical neutral beam fast ion diffusion on JET
NASA Astrophysics Data System (ADS)
Trace tritium experiments (TTE) on JET were analysed using Monte Carlo modelling of the neutron emission resulting from the neutral beam injection (NBI) of short (~300 ms) tritium (T) beam blips into reversed shear, hybrid ELMy H-mode and L-mode deuterium plasmas for a wide range of plasma parameters. The calculated neutron fluxes from deuterium-tritium (DT) reactions could only be made consistent with all plasmas by applying an artificial reduction of the T beam power in the modelling of between 20% and 40%. A similar discrepancy has previously been observed in both JET (Gorini et al 2004 Proc. 31st EPS Conf. on Plasma Physics (London, UK) vol 28G (ECA)) and TFTR (Ruskov et al 1999 Phys. Rev. Lett. 82 924), although no mechanism has yet been found that could explain such a difference in the measured T beam power. Applying this correction in the T beam power, good agreement between calculated and measured DT neutron emission profiles was obtained in low to moderate line averaged density (\\overline {n_\\rme} <4\\times 10^{19}\\,m^{-3}) ELMy H-Mode plasmas assuming that the fast beam ions experience no, or relatively small, anomalous diffusion (Dan Lt 0.5 m2 s-1). However, the modelled neutron profiles do not agree with measurements in higher density plasmas using the same assumption and the disagreement between the measured and calculated shape of the neutron profile increases with plasma density. In this paper it is demonstrated that large anomalous losses of fast ions have to be assumed in the simulations to improve agreement between experimental and simulated neutron profiles, characterized by the goodness of fit. Various types of fast ion losses are modelled to explain aspects of the data, though further investigation will be required in order to gain a more detailed understanding of the nature of those anomalous losses.
Baranov, Yu F.; Jenkins, I.; Alper, B.; Challis, C. D.; Conroy, S.; Kiptily, V.; Ongena, J.; Popovichev, S.; Smeulders, P.; Surrey, E.; Zastrow, K.-D.; JET EFDA contributors
Effects of Microwave Radiation on Oil Recovery
NASA Astrophysics Data System (ADS)
A variety of oil recovery methods have been developed and applied to mature and depleted reservoirs in order to improve the efficiency. Microwave radiation oil recovery method is a relatively new method and has been of great interest in the recent years. Crude oil is typically co-mingled with suspended solids and water. To increase oil recovery, it is necessary to remove these components. The separation of oil from water and solids using gravitational settling methods is typically incomplete. Oil-in-water and oil-water-solid emulsions can be demulsified and separated into their individual layers by microwave radiation. The data also show that microwave separation is faster than gravity separation and can be faster than conventional heating at many conditions. After separation of emulsion into water and oil layers, water can be discharged and oil is collected. High-frequency microwave recycling process can recover oil and gases from oil shale, residual oil, drill cuttings, tar sands oil, contaminated dredge/sediments, tires and plastics with significantly greater yields and lower costs than are available utilizing existing known technologies. This process is environmentally friendly, fuel-generating recycler to reduce waste, cut emissions, and save energy. This paper presents a critical review of Microwave radiation method for oil recovery.
Esmaeili, Abdollah
Satellite microwave observations of soil moisture variations. [by the microwave radiometer on the Nimbus 5 satellite
NASA Technical Reports Server (NTRS)
The electrically scanning microwave radiometer (ESMR) on the Nimbus 5 satellite was used to observe microwave emissions from vegetated and soil surfaces over an Illinois-Indiana study area, the Mississippi Valley, and the Great Salt Lake Desert in Utah. Analysis of microwave brightness temperatures (T sub B) and antecedent rainfall over these areas provided a way to monitor variations of near-surface soil moisture. Because vegetation absorbs microwave emission from the soil at the 1.55 cm wavelength of ESMR, relative soil moisture measurements can only be obtained over bare or sparsely vegetated soil. In general T sub B increased during rainfree periods as evaporation of water and drying of the surface soil occurs, and drops in T sub B are experienced after significant rainfall events wet the soil. Microwave observations from space are limited to coarse resolutions (10-25 km), but it may be possible in regions with sparse vegetation cover to estimate soil moisture conditions on a watershed or agricultural district basis, particularly since daily observations can be obtained.
Schmugge, T. J.; Rango, A.; Neff, R.
The presence of astrophysical emissions between the last scattering surface and our vantage point requires us to apply a foreground mask on cosmic microwave background (CMB) sky maps, leading to large cuts around the Galactic equator and numerous holes. Since many CMB analysis, in particular on the largest angular scales, may be performed on a whole-sky map in a more straightforward and reliable manner, it is of utmost importance to develop an efficient method to fill in the masked pixels in a way compliant with the expected statistical properties and the unmasked pixels. In this Letter, we consider the Monte Carlo simulation of a constrained Gaussian field and derive it CMB anisotropy in harmonic space, where a feasible implementation is possible with good approximation. We applied our method to simulated data, which shows that our method produces a plausible whole-sky map, given the unmasked pixels, and a theoretical expectation. Subsequently, we applied our method to the Wilkinson Microwave Anisotropy Probe foreground-reduced maps and investigated the anomalous alignment between quadrupole and octupole components. From our investigation, we find that the alignment in the foreground-reduced maps is even higher than the Internal Linear Combination map. We also find that the V-band map has higher alignment than other bands, despite the expectation that the V-band map has less foreground contamination than other bands. Therefore, we find it hard to attribute the alignment to residual foregrounds. Our method will be complementary to other efforts on in-painting or reconstructing the masked CMB data, and of great use to Planck surveyor and future missions.
Kim, Jaiseung; Naselsky, Pavel [Niels Bohr Institute and Discovery Center, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Mandolesi, Nazzareno, E-mail: firstname.lastname@example.com [INAF/IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, Istituto Nazionale di Astrofisica, via Gobetti 101, I-40129 Bologna (Italy)
Development of radar absorbing nano crystals by microwave irradiation
Single phase M-type barium hexaferrite nano crystals of radar absorbing material i.e., BaFe12O19 were synthesized by a modified flux method under cyclic microwave irradiation. Uniform and ultrafast morphological transformation from spherical to pyramidal-faced nano crystals were noticed in field emission electron microscopy during the cyclic microwave irradiation power for constant time. The reflection loss of nano crystals in Ku band
Rahul Sharma; R. C. Agarwala; Vijaya Agarwala
Correlation between galactic HI and the cosmic microwave background
We revisit the issue of a correlation between the atomic hydrogen gas in our local galaxy and the cosmic microwave background, a detection of which has been claimed in some literature. We cross correlate the 21-cm emission of galactic atomic hydrogen as traced by the Leiden/Argentine/Bonn Galactic Hi survey with the 3-year cosmic microwave background data from the Wilkinson microwave anisotropy probe. We consider a number of angular scales, masks, and Hi velocity slices and find no statistically significant correlation.
Land, Kate [Astrophysics, Denys Wilkinson Building, University of Oxford, Keble Road, OX3RH1, Oxford (United Kingdom); Slosar, Anze [Astrophysics, Denys Wilkinson Building, University of Oxford, Keble Road, OX3RH1, Oxford (United Kingdom); Faculty of Mathematics and Physics, University of Ljubljana (Slovenia)
Variable frequency microwave heating apparatus
A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).
Bible, D.W.; Lauf, R.J.; Johnson, A.C.; Thigpen, L.T.
Variable frequency microwave heating apparatus
A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).
Bible, Don W. (Clinton, TN); Lauf, Robert J. (Oak Ridge, TN); Johnson, Arvid C. (Lake in the Hills, IL); Thigpen, Larry T. (Angier, NC)
Coaxial microwave plasma source
Physical principles underlying the operation of a pulsed coaxial microwave plasma source (micro-wave plasmatron) are considered. The design and parameters of the device are described, and results of experimental studies of the characteristics of the generated plasma are presented. The possibility of application of this type of plasmatron in gas-discharge physics is discussed.
Gritsinin, S. I. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Gushchin, P. A. [Gubkin State University of Oil and Gas (Russian Federation); Davydov, A. M.; Kossyi, I. A. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Kotelev, M. S. [Gubkin State University of Oil and Gas (Russian Federation)
Microwave shielding measurement method
A simple system for measuring the attenuation of microwaves in the frequency range of 700 MHz to 13 GHz is described. It has been used to test a large number of commercially available microwave shielding materials. The standard system for such measurements would require IEEE STD 299 2006. This standard requires a number of different sources and receivers depending on
L. L. Hatfield; B. Schilder
ERIC Educational Resources Information Center
Since it became a reality just before World War II, terrestrial microwave has improved in systems and equipments, but with the improvements have come higher costs. Television microwave costs are so high because users are demanding more capability, land prices have increased, operating costs are higher, and there is frequency congestion along many…
Peterson, Roger E.
This paper presents a compilation of the important milestones in the development and applications of microwave technology from the time of Hertz until 1980. The years from 1980 to the present are not addressed since this period will be covered in depth in other papers of this Transactions. The primary technology areas addressed are electromagnetics, guided microwave structures, free-space propagation,
Harold Sobol; Kiyo Tomiyasu
National Technical Information Service (NTIS)
Pulsed microwave therapy is a method based on using very short (2 or 8 microseconds) but powerful (up to 15 kilovolts) pulses of an electrical field of microwaver alternating with pauses one one-thousandth as long as a pulse (2,000 and 8,000 microseconds)...
L. A. Skurikhina
China needs microwave research to realize its grand goal of four modernizations. Microelectronics, bioengineering, new materials, new sources of energy, oceanographic engineering and astronavigation have shown their importance and will boost our productive forces in the future. Microwave research in China plays an active role in all these fields, is an area where talented people temper themselves through new experience
Weigan Lin
Microwave processing of ceramics
Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.
Katz, J.D.
Microwave processing of ceramics
Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.
Katz, J.D.
Electromagnetic and acoustic emission associated with rock fracture
To understand the physical mechanism of the anomalous electromagnetic emissions observed before earthquakes, we carried out some laboratory experiments on electromagnetic and acoustic emission from a rock. Granitic samples were loaded at a constant strain rate and electromagnetic and acoustic emission were simultaneously recorded during deformation of the sample. Ten to 20% of the acoustic emissions detected during the experiment
I. Yamada; K. Masuda; H. Mizutani
Simultaneous Measurements of Atmospheric Emissions at 10, 33 and 90 GHz.
National Technical Information Service (NTIS)
As part of a larger experiment to measure the cosmic microwave background radiation spectrum, frequent simultaneous measurements of the microwave thermal emission from the earth's atmosphere were made at three fixed frequencies, namely, 10 GHz, 33 GHz and...
J. B. Costales
STIS MAMA Recovery from Anomalous Shutdown
NASA Astrophysics Data System (ADS)
This proposal is designed to permit recovery of the FUV- or NUV-MAMA detector after an anomalous shutdown. Anomalous shutdowns can occur as a result of bright object violations which trigger the Bright Scene Detection or Software Global Monitors. Anomalous shutdowns can also occur as a result of MAMA hardware problems. The anomalous recovery procedure consists of three separate tests where each must be successfully completed before proceeding onto the next: {1} a signal processing electronics check, {2} high voltage ramp-up to an intermediate voltage, and {3} high voltage ramp-up to the full operating voltage and fold analysis test During each of the two high voltage ramp-ups, diagnostics are performed during dark and flat field ACCUMs. This proposal executes the same steps as were in proposals 10036 during cycle 12.;
Wheeler, Thomas
Anomalous Seismic Signals from Novaya Zemlya.
National Technical Information Service (NTIS)
Broad band seismic signals from several underground explosions on Novaya Zemlya have been analysed to determine the reason for some anomalous broad band signals from the same location. (Atomindex citation 09:357927)
R. W. Hurley
ACS SBC Recovery from Anomalous Shutdown
NASA Astrophysics Data System (ADS)
This proposal is designed to permit recovery of the SBC {FUV MAMA} detector after an anomalous shutdown. Anomalous shutdowns can occur as a result of bright object violations which trigger the Bright Scene Detection or Software Global Monitor. Anomalous shutdowns can also occur as a result of SBC hardware problems. The recovery from anomalous shutdown procedure consists of four tests: 1} a signal processing electronics check, 2} a slow high voltage ramp-up to an intermediate voltage, 3} a slow high-voltage ramp-up to the full operating voltage, and 4} a Fold Test. During the two high-voltage ramp-ups, dark ACCUM exposures are taken. At high voltage, dark ACCUM exposures and diagnostics are taken. This proposal is based on Proposal 12738 from Cycle 19.;
Wheeler, Thomas
Anomalous Skin Effect in a Gaseous Plasma.
National Technical Information Service (NTIS)
Experimental data are presented for the skin effect in a plasma in which the electron thermal motions are sufficient to increase the field penetration. The results are consistent with the Weibel criteria for the existence of anomalous penetration and with...
M. J. Kofoid
Anomalous diffraction in crystallographic phase evaluation.
X-ray diffraction patterns from crystals of biological macromolecules contain sufficient information to define atomic structures, but atomic positions are inextricable without having electron-density images. Diffraction measurements provide amplitudes, but the computation of electron density also requires phases for the diffracted waves. The resonance phenomenon known as anomalous scattering offers a powerful solution to this phase problem. Exploiting scattering resonances from diverse elements, the methods of MAD (multiwavelength anomalous diffraction) and SAD (single-wavelength anomalous diffraction) now predominate for de novo determinations of atomic-level biological structures. This review describes the physical underpinnings of anomalous diffraction methods, the evolution of these methods to their current maturity, the elements, procedures and instrumentation used for effective implementation, and the realm of applications. PMID:24726017
Hendrickson, Wayne A
Anomalous Force on the Map Spacecraft.
National Technical Information Service (NTIS)
The Microwave Anisotropy Probe (MAP) orbits the second Earth-Sun libration point (L2)-about 1.5 million kilometers outside Earth's orbit-mapping cosmic microwave background radiation. To achieve orbit near L2 on a small fuel budget, the MAP spacecraft nee...
S. R. Starin J. R. ODonnell D. K. Ward E. J. Wollack P. M. Bay D. R. Fink
Microwave bonding of MEMS component
NASA Technical Reports Server (NTRS)
Bonding of MEMs materials is carried out using microwave. High microwave absorbing films are placed within a microwave cavity, and excited to cause selective heating in the skin of the material. This causes heating in one place more than another. Thereby minimizing the effects of the bonding microwave energy.
Barmatz, Martin B. (Inventor); Mai, John D. (Inventor); Jackson, Henry W. (Inventor); Budraa, Nasser K. (Inventor); Pike, William T. (Inventor)
First results from the microwave air yield beam experiment (MAYBE): Measurement of GHz radiation for ultra-high energy cosmic ray detection
NASA Astrophysics Data System (ADS)
We present measurements of microwave emission from an electron-beam induced air plasma performed at the 3 MeV electron Van de Graaff facility of the Argonne National Laboratory. Results include the emission spectrum between 1 and 15 GHz, the polarization of the microwave radiation and the scaling of the emitted power with respect to beam intensity. MAYBE measurements provide further insight on microwave emission from extensive air showers as a novel detection technique for Ultra-High Energy Cosmic Rays.
Williams, C.; Bohá?ová, M.; Bonifazi, C.; Cataldi, G.; Chemerisov, S.; de Mello Neto, J. R. T.; Facal San Luis, P.; Fox, B.; Gorham, P. W.; Hojvat, C.; Hollon, N.; Meyhandan, R.; Monasor, M.; Rouillé d'Orfeuil, B.; Santos, E. M.; Pochez, J.; Privitera, P.; Spinka, H.; Verzi, V.; Zhou, J.
Emissivity corrected infrared method for imaging anomalous structural heat flows
A method for detecting flaws in structures using dual band infrared radiation is disclosed. Heat is applied to the structure being evaluated. The structure is scanned for two different wavelengths and data obtained in the form of images. Images are used to remove clutter to form a corrected image. The existence and nature of a flaw is determined by investigating a variety of features. 1 fig.
Del Grande, N.K.; Durbin, P.F.; Dolan, K.W.; Perkins, D.E.
Emissivity corrected infrared method for imaging anomalous structural heat flows
A method for detecting flaws in structures using dual band infrared radiation. Heat is applied to the structure being evaluated. The structure is scanned for two different wavelengths and data obtained in the form of images. Images are used to remove clutter to form a corrected image. The existence and nature of a flaw is determined by investigating a variety of features.
Del Grande, Nancy K. (San Leandro, CA); Durbin, Philip F. (Livermore, CA); Dolan, Kenneth W. (Livermore, CA); Perkins, Dwight E. (Livermore, CA)
Microwave plasma torches used for hydrogen production
NASA Astrophysics Data System (ADS)
A microwave plasma torch operating at 2.45 GHz and atmospheric pressure has been used as a medium and a tool for decomposition of alcohol in order to produce molecular hydrogen. Plasma in a gas mixture of argon and ethanol/methanol, with or without water, has been created using a waveguide surfatron launcher and a microwave generator delivering a power in the range 0.2-2.0 kW. Mass, Fourier Transform Infrared, and optical emission spectrometry have been applied as diagnostic tools. The decomposition yield of methanol was nearly 100 % with H2, CO, CO2, H2O, and solid carbon as the main reaction products. The influence of the fraction of Ar flow through the liquid ethanol/methanol on H2, CO, and CO2 partial pressures has been investigated, as well as the dependence of the produced H2 flow on the total flow and power. The optical emission spectrum in the range 250–700 nm has also been detected. There is a decrease of the OH(A-X) band intensity with the increase of methanol in the mixture. The emission of carbon atoms in the near UV range (240–300 nm) exhibits a significant increase as the amount of alcohol in the mixture grows. The obtained results clearly show that this microwave plasma torch at atmospheric pressure provides an efficient plasma environment for hydrogen production.
Dias, F. M.; Bundaleska, N.; Henriques, J.; Tatarova, E.; Ferreira, C. M.
Microwave photonic signal processing.
Photonic signal processing offers the advantages of large time-bandwidth capabilities to overcome inherent electronic limitations. In-fibre signal processors are inherently compatible with fibre optic microwave systems that can integrate with wireless antennas, and can provide connectivity with in-built signal conditioning and electromagnetic interference immunity. Recent methods in wideband and adaptive signal processing, which address the challenge of realising programmable microwave photonic phase shifters and true-time delay elements for phased array beamforming; ultra-wideband Hilbert transformers; single passband, widely tunable, and switchable microwave photonic filters; and ultra-wideband microwave photonic mixers, are described. In addition, a new microwave photonic mixer structure is presented, which is based on using the inherent frequency selectivity of the stimulated Brillouin scattering loss spectrum to suppress the carrier of a dual-phase modulated optical signal. Results for the new microwave photonic mixer demonstrate an extremely wide bandwidth operation of 0.2 to 20 GHz and a large conversion efficiency improvement compared to the conventional microwave photonic mixer. PMID:24104178
Minasian, R A; Chan, E H W; Yi, X
The small scale power asymmetry in the cosmic microwave background
NASA Astrophysics Data System (ADS)
We investigate the hemispherical power asymmetry in the cosmic microwave background on small angular scales. We find an anomalously high asymmetry in the multipole range l = 601-2048, with a naive statistical significance of 6.5?. However, we show that this extreme anomaly is simply a coincidence of three other effects, relativistic power modulation, edge effects from the mask applied, and inter-scale correlations. After correcting for all of these effects, the significance level drops to ~ 1?, i.e., there is no anomalous intrinsic asymmetry in the small angular scales. Using this null result, we derive a constraint on a potential dipolar modulation amplitude, A(k) < 0.0045 on the ~ 10 Mpc-scale, at 95% C.L. This new constraint must be satisfied by any theoretical model attempting to explain the hemispherical asymmetry at large angular scales.
Flender, Samuel; Hotchkiss, Shaun
NASA Technical Reports Server (NTRS)
Microwave Vision (MV), a concept originally developed in 1985, could play a significant role in the solution to robotic vision problems. Originally our Microwave Vision concept was based on a pattern matching approach employing computer based stored replica correlation processing. Artificial Neural Network (ANN) processor technology offers an attractive alternative to the correlation processing approach, namely the ability to learn and to adapt to changing environments. This paper describes the Microwave Vision concept, some initial ANN-MV experiments, and the design of an ANN-MV system that has led to a second patent disclosure in the robotic vision field.
Lewandowski, Leon; Struckman, Keith
The present invention is directed to a microwave coupler for enhancing the heating or metallurgical treatment of materials within a cold-wall, rapidly heated cavity as provided by a microwave furnace. The coupling material of the present invention is an alpha-rhombohedral-boron-derivative-structure material such as boron carbide or boron silicide which can be appropriately positioned as a susceptor within the furnace to heat other material or be in powder particulate form so that composites and structures of boron carbide such as cutting tools, grinding wheels and the like can be rapidly and efficiently formed within microwave furnaces.
Holcombe, C.E.
NASA Technical Reports Server (NTRS)
Stable reference tones aid testing and calibration of microwave receivers. Signal generator puts out stable tones in frequency range of 2 to 10 GHz at all multiples of reference input frequency, at any frequency up to 1 MHz. Called "comb generator" because spectral plot resembles comb. DC reverse-bias current switched on and off at 1 MHz to generate sharp pulses in step-recovery diode. Microwave components mounted on back of special connector containing built-in attenuator. Used in testing microwave and spread-spectrum wide-band receivers.
Sigman, E. H.
Superconducting microwave transmission lines
Superconducting microwave transmission lines can be designed to have lower loss, lower dispersion, and lower phase velocity than conventional metal lines. These properties make superconducting transmission lines attractive for use in many devices and systems such as filters and analog to digital converters. The problem with designing microwave circuits which utilizes these lines is that accurate circuit models do not exist. This paper present models for the microwave transmission line parameters (phase velocity, attenuation, and characteristic impedance) of superconducting lines as a function of temperature and geometry. An experiment to verify these models is also presented.
McClay, C.P.; Soares, S.; Weitzman, P.S.
Microwave and Nuclear Excitations of Alkali Metal Vapors
NASA Astrophysics Data System (ADS)
Alkali metals have been evaluated as the most promising candidates with the highest photon production efficiency (40-50%) in the visible-to-infrared region for flashlamps. Alkali metal excimers with a bound-free transition are proposed as the agents for such an efficient photon -generating process. In this study, these issues are examined by microwave excitation with sodium and rubidium, and nuclear excitation with only sodium. Microwave-excited alkali metal fluorescence has been demonstrated by a microwave-driven alkali metal lamp with a specially designed heat-pipe confinement. Two major emissions are studied: (1) atomic emission, as the major contribution in microwave excitation and electric discharge, and (2) excimer emission, as the agent for high efficiency and potential applications for high power, tunable lasers. Atomic emission dominated the microwave-excited alkali metal spectra, especially the D line. The suppression of atomic emission occurred while increasing the vapor pressure. Self-absorption and line broadening of the D line at high vapor pressure were observed. The experimental fluorescence efficiency of alkali metal vapors, obtained in microwave excitation, was in good agreement with the theoretical predictions. The branching ratio for pumping the upper level state of the excimer transition is the key point for obtaining practically efficient excimer fluorescers. The alkali metal excimer emission was not identified with certainty in microwave excitation due to the ambiguous structure. However, the considerable elevation of the peak base at 436 and 452 nm for the sodium spectra, and the red shift of the primary peak in the broad continuum for the rubidium spectra, confirmed the existence of alkali metal excimer emissions. The nuclear excitation experiment was performed in a TRIGA reactor with a double-encapsulated heat pipe to generate the sodium vapor. ^3He was used as a nuclear volume energy source. The first observation of nuclear-excited sodium excimer emission at 436 nm was successfully obtained with 810 Torr of ^3He at 924 K (Na = 52.7 Torr). Similar suppression and self-absorption of the 3D to 3P atomic line confirms the results of microwave excitation. This experiment established the physical feasibility of nuclear-driven alkali metal excimer lamps.
Lin, Li-Te Steven
Heat transfer in microwave heating
NASA Astrophysics Data System (ADS)
Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite, which is a typical magnetic dielectric, was simulated by using an explicit finite-difference approach. It is demonstrated that the heat generation due to microwave irradiation dominates the initial temperature rise in the heating and the heat radiation heavily affects the temperature distribution, giving rise to a hot spot in the predicted temperature profile. Microwave heating at 915 MHz exhibits better heating homogeneity than that at 2450 MHz due to larger microwave penetration depth. To minimize/avoid temperature nonuniformity during microwave heating the optimization of object dimension should be considered. The calculated reflection loss over the temperature range of heating is found to be useful for obtaining a rapid optimization of absorber dimension, which increases microwave absorption and achieves relatively uniform heating. To further improve the heating effectiveness, a function for evaluating absorber impedance matching in microwave heating was proposed. It is found that the maximum absorption is associated with perfect impedance matching, which can be achieved by either selecting a reasonable sample dimension or modifying the microwave parameters of the sample.
Peng, Zhiwei
Design of high-speed digital correlator in fully polarimetric microwave radiometer
Fully polarimetric microwave radiometer is a new type of passive microwave sensor for measuring ocean wind vector. Digital correlation technology is used in it to get all the four Stokes parameters of ocean emission in this paper. Digital correlator is the main part of fully polarimetric radiometer. In the paper, design of a novel digital correlator is presented. Two high-speed,
Lu Hao; Wang Zhen-Zhan; Liu Jing-Yi; Jiang Jing-Shan
New microwave spectrometer/imager has possible applications for pollution monitoring
NASA Technical Reports Server (NTRS)
Microwave imager forms thermal-emissivity image of solid portion of planet Venus and provides data on the planet's atmosphere, surface, terminator, and temperature changes. These thermally produced multifrequency microwaves for image production of temperature profiles can be applied to water pollution monitoring, agriculture, and forestry survey.
Tooley, R. D.
Numerical simulation of microwave transmission in the presence of an electron cloud
Electron cloud effects on the transmission of microwaves through beam pipes in the CERN SPS experiment and the PEP-II Low Energy Ring (LER) at SLAC have been recently observed. Electrons within the vacuum chamber generated primarily via secondary electron emission have been observed to cause a phase shift in microwaves injected into the vacuum chamber. Understanding this effect may provide
Kiran Sonnad; Seth Veitzer; Peter Stoltz; Miguel Furman; John Cary
Improved Detectability in Medical Microwave Radio-Thermometers as Obtained by Active Antennas
Microwave radiometry is a spectral measurement technique for resolving blackbody radiation of heated matter above absolute zero. The emission levels vary with frequency and are at body temperatures maximized in the infrared spectral band. Medical radio-thermometers are mostly noninvasive short-range instruments that can provide temperature distributions in subcutaneous biological tissues when operated in the microwave region. However, a crucial limitation
Svein Jacobsen; O. Klemetsen
Atmospheric water vapor over Antarctica derived from Special Sensor Microwave\\/Temperature 2 data
In polar regions, satellite microwave radiometry has not been successful in measuring the total water vapor (TWV) in the atmosphere. The difficulties faced in these regions arise from the very low water vapor burden of the atmosphere and the large and highly variable emissivities of ice surfaces in the microwave frequency range. By exploiting the advantages of the Special Sensor
Jungang Miao; Klaus Kunzi; Georg Heygster; Tom A. Lachlan-Cope; John Turner
Measurement of the cosmic microwave background using BEAST for the determination of cosmological parameters
The Background Emission Anisotropy Scanning Telescope (BEAST) is a millimeter wavelength experiment designed to generate maps of fluctuations in the cosmic microwave background (CMB). The telescope is composed of an off-axis Gregorian optical system with a 2.2 meter primary that focuses the collected microwave radiation onto an array of cryogenically cooled high electron mobility transistor (HEMT) receivers. This array is
Jeffery Dale Childers
Reduction of weather effects in the calculation of sea ice concentration from microwave radiances
A technique is presented which improves existing methods of calculating sea ice concentrations from microwave radiances by reducing weather-related effects over open ocean areas and in the vicinity of marginal sea ice zones. Winds, atmospheric water vapor, cloud liquid water, and rain increase the microwave emission over these regions and thus result in erroneous values of computed sea ice concentration.
P. Gloersen; D. J. Cavalieri
Steady state temperature profile in a sphere heated by microwaves
NASA Technical Reports Server (NTRS)
A new theory has been developed to calculate the microwave absorption and resultant temperature profile within a sphere positioned in a single mode rectangular cavity. This theory is an extension of a total absorption model based on Mie scattering results. Temperature profiles have been computed for alumina spheres at the center of a rectangular cavity excited in the TM354 mode. Parametric studies reveal significant structure in those profiles under special conditions that are associated with electromagnetic resonances inside the spheres. Anomalous behavior similar to thermal runaway occurs at moderate temperatures when there is enhanced absorption associated with resonant conditions in the sphere.
Barmatz, M.; Jackson, H. W.
NASA Technical Reports Server (NTRS)
Microwave sensors, used in conjunction with the traditional sensors of visible and infrared light to extend present capabilities of global weather forecasts and local storm watches, are discussed. The great advantage of these sensors is that they can penetrate or 'see' through cloud formations to monitor temperature, humidity and wind fields below the clouds. Other uses are that they can penetrate the earth deeper than optical and IR systems; they can control their own angle of incidence; they can detect oil spills; and they can enhance the studies of the upper atmosphere through measurement of temperature, water vapor and other gaseous species. Two types of microwave sensors, active and passive, are examined. Special attention is given to the study of the microwave radiometer and the corresponding temperature resolution as detected by the antenna. It is determined that not only will the microwave remote sensors save lives by allowing close monitoring of developing storms, but also save approximately $172 million/year.
Kritikos, H. N.; Shiue, J.
NASA Technical Reports Server (NTRS)
Information on microwave beam power is given in viewgraph form. Information is given on orbit transfer proulsion applications, costs of delivering 100 kWe of usable power, and costs of delivering a 1 kg payload into orbit.
Faymon, Karl A.
The invention comprises a new class of device, driven by electron or other charged particle flow, for producing coherent microwaves by utilizing the interaction of electromagnetic waves with electron flow in diodes not requiring an external magnetic field. Anode and cathode surfaces are electrically charged with respect to one another by electron flow, for example caused by a Marx bank voltage source or by other charged particle flow, for example by a high energy charged particle beam. This produces an electric field which stimulates an emitted electron beam to flow in the anode-cathode region. The emitted electrons are accelerated by the electric field and coherent microwaves are produced by the three dimensional spatial and temporal interaction of the accelerated electrons with geometrically allowed microwave modes which results in the bunching of the electrons and the pumping of at least one dominant microwave mode.
Craig, G.D.; Pettibone, J.S.; Drobot, A.T.
Correlating anomalies of the microwave sky
NASA Astrophysics Data System (ADS)
At the largest angular scales the presence of a number of unexpected features has been confirmed by the latest measurements of the cosmic microwave background (CMB). Among them are the anomalous alignment of the quadrupole and octopole with each other as well as the stubborn lack of angular correlation on scales >60°. We search for correlations between these two phenomena and demonstrate their absence. A Monte Carlo likelihood analysis confirms previous studies and shows that the joint likelihood of both anomalies is incompatible with the best-fit ? cold dark matter model at >99.95% C.L. Extending also to higher multipoles, a common special direction (the "Axis of Evil") has been identified. In the search for an explanation of the anomalies, several studies invoke effects that exhibit an axial symmetry. We find that this interpretation of the "Axis of Evil" is inconsistent with three-year data from the Wilkinson Microwave Anisotropy Probe (WMAP). The data require a preferred plane, whereupon the axis is just the normal direction. Rotational symmetry within that plane is ruled out at high confidence.
Raki?, Aleksandar; Schwarz, Dominik J.
Correlating anomalies of the microwave sky
At the largest angular scales the presence of a number of unexpected features has been confirmed by the latest measurements of the cosmic microwave background (CMB). Among them are the anomalous alignment of the quadrupole and octopole with each other as well as the stubborn lack of angular correlation on scales >60 deg. We search for correlations between these two phenomena and demonstrate their absence. A Monte Carlo likelihood analysis confirms previous studies and shows that the joint likelihood of both anomalies is incompatible with the best-fit {lambda} cold dark matter model at >99.95% C.L. Extending also to higher multipoles, a common special direction (the 'Axis of Evil') has been identified. In the search for an explanation of the anomalies, several studies invoke effects that exhibit an axial symmetry. We find that this interpretation of the 'Axis of Evil' is inconsistent with three-year data from the Wilkinson Microwave Anisotropy Probe (WMAP). The data require a preferred plane, whereupon the axis is just the normal direction. Rotational symmetry within that plane is ruled out at high confidence.
Rakic, Aleksandar; Schwarz, Dominik J. [Fakultaet fuer Physik, Universitaet Bielefeld, Postfach 100131, D-33501 Bielefeld (Germany)
Microwave sintering process model.
In order to simulate and optimize the microwave sintering of a silicon nitride and tungsten carbide/cobalt toolbits process, a microwave sintering process model has been built. A cylindrical sintering furnace was used containing a heat insulating layer, a susceptor layer, and an alumina tube containing the green toolbit parts between parallel, electrically conductive, graphite plates. Dielectric and absorption properties of the silicon nitride green parts, the tungsten carbide/cobalt green parts, and an oxidizable susceptor material were measured using perturbation and waveguide transmission methods. Microwave absorption data were measured over a temperature range from 20 degrees C to 800 degrees C. These data were then used in the microwave process model which assumed plane wave propagation along the radial direction and included the microwave reflection at each interface between the materials and the microwave absorption in the bulk materials. Heat transfer between the components inside the cylindrical sintering furnace was also included in the model. The simulated heating process data for both silicon nitride and tungsten carbide/cobalt samples closely follow the experimental data. By varying the physical parameters of the sintering furnace model, such as the thickness of the susceptor layer, the thickness of the allumina tube wall, the sample load volume and the graphite plate mass, the model data predicts their effects which are helpful in optimizing those parameters in the industrial sintering process. PMID:15323110
Peng, Hu; Tinga, W R; Sundararaj, U; Eadie, R L
High-voltage virtual-cathode microwave simulations
In contrast to a conventional microwave tube, a virtual-cathode device operates above the space-charge limit where the depth of the space-charge potential is sufficiently large to cause electron reflection. The region associated with electron reflection is referred to as a virtual cathode. Microwaves can be generated through oscillations in the position of the virtual cathode and by reflexing electrons trapped in the potential well formed between the real and virtual cathodes. A virtual-cathode device based on the first mechanism is a vircator while one based on latter mechanism is a reflex diode. A large number of low-voltage virtual-cathode microwave configurations have been investigated. Initial simulations of a high-voltage virtual-cathode device using a self-consistent particle-in-cell code indicated reasonable conversion efficiency with no frequency chirping. The nonchirping character of the high-voltage virtual-cathode device lead to the interesting possibility of locking four very-high-power microwave devices together using the four transmission lines available at Aurora. Subsequently, in support of two high-voltage experiments, simulations were used to investigate the effect of field-emission threshold and velvet position on the cathode; anode and cathode shape; anode-cathode gap spacing; output waveguide radius; diode voltage; a cathode-coaxial-cavity resonator; a high-frequency ac-voltage drive; anode foil scattering and energy loss; and ion emission on the microwave frequency and power. Microwave
Thode, L.; Snell, C.M.
Photometric Properties of Thermally Anomalous Terrain on Icy Saturnian Satellites
NASA Astrophysics Data System (ADS)
Spectral maps of thermal emission from Mimas obtained by Cassini's Composite InfraRed Spectrometer (CIRS) show that a V-shaped boundary, centered at 0° N and 180° W, divides relatively warm daytime temperatures from an anomalously cooler region at low to mid-latitudes on the leading hemisphere (Howett et al. 2011 Icarus 216, 211). This cooler region is also warmer at night, indicating that it has high thermal inertia, and also coincides in shape and location with that of high-energy electron deposition from Saturn's magnetosphere (Roussos et al. 2007 JGR 112, A06214; Schenk et al. 2011 Icarus 211, 740). Global IR/UV color ratio maps assembled from Cassini Imaging Science Subsystem (ISS) images revealed a lens-shaped region of relatively blue terrain centered on the leading hemisphere (Schenk et al. 2011, Icarus). The area with low IR/UV ratio also coincides in shape and location with the region of high thermal inertia. A preliminary photometric analysis of Cassini ISS CL1 CL2 filter (centered at 611 nm) images using the Hapke (2008) model suggests that the high thermal inertia region on Mimas is rougher and more strongly backscattering than terrain with lower thermal inertia. Particles on the surface of the thermally anomalous terrain may have a more complex microtexture due to the high-energy electron bombardment. This work is supported by the NASA Cassini Data Analysis Program.
Annex, Andrew; Verbiscer, A. J.; Helfenstein, P.; Howett, C.; Schenk, P.
Analytical solutions for anomalous dispersion transport
NASA Astrophysics Data System (ADS)
Groundwater flow and transport often occur in a highly heterogeneous environment (potentially heterogeneous at multiple spatial scales) and is impacted by geochemical reactions, advection, diffusion, and other pore scale processes. All these factors can give rise to large-scale anomalous dispersive behavior that can make complex model representation and prediction of plume concentrations challenging due to difficulties unraveling all the complexities associated with the governing processes, flow medium, and their parameters. An alternative is to use upscaled stochastic models of anomalous dispersion, and this is the approach used here. Within a probabilistic framework, we derive a number of analytical solutions for several anomalous dispersion models. The anomalous dispersion models are allowed to be either non-Gaussian (?-stable Lévy), correlated, or nonstationary from the Lagrangian perspective. A global sensitivity analysis is performed to gain a greater understanding of the extent to which uncertainty in the parameters associated with the anomalous behavior can be narrowed by examining concentration measurements from a network of monitoring wells and to demonstrate the computational speed of the solutions. The developed analytical solutions are encoded and available for use in the open source computational framework MADS (http://mads.lanl.gov).
O'Malley, D.; Vesselinov, V. V.
More than a century ago, astronomers using transit telescopes to determine precise stellar positions were hampered by an unexplained periodic shifting of the stars they were observing. With the advent of CCD transit telescopes in the past three decades, this unexplained motion, termed 'anomalous refraction' by these early astronomers, is again being observed. Anomalous refraction is described as a low-frequency, large angular scale ({approx}2 Degree-Sign ) motion of the entire image plane with respect to the celestial coordinate system as observed and defined by astrometric catalogs. These motions, of typically several tenths of an arcsecond amplitude with timescales on the order of 10 minutes, are ubiquitous to ground-based drift-scan astrometric measurements regardless of location or telescopes used and have been attributed to the effect of tilting of equal-density layers of the atmosphere. The cause of this tilting has often been attributed to atmospheric gravity waves, but this cause has never been confirmed. Although theoretical models of atmospheric refraction show that atmospheric gravity waves are a plausible cause of anomalous refraction, an observational campaign specifically directed at defining this relationship provides clear evidence that anomalous refraction is not consistent with the passage of atmospheric gravity waves. The source of anomalous refraction is found to be meter-scale, slowly evolving quasi-coherent dynamical structures in the boundary layer below 60 m above ground level.
Taylor, M. Suzanne [Department of Natural and Environmental Sciences, Western State Colorado University, 128 Hurst Hall, Gunnison, CO 81230 (United States); McGraw, John T.; Zimmer, Peter C. [Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131 (United States); Pier, Jeffrey R., E-mail: email@example.com [Division of Astronomical Sciences, NSF 4201 Wilson Blvd, Arlington, VA 22230 (United States)
Identifying the Radio Bubble Nature of the Microwave Haze
NASA Astrophysics Data System (ADS)
Using seven-year data from the Wilkinson Microwave Anisotropy Probe, I identify a sharp "edge" in the microwave haze at high southern Galactic latitude (-55° < b < -35°) that is spatially coincident with the southern edge of the "Fermi haze/bubbles." This finding proves conclusively that the edge in the gamma rays is real (and not a processing artifact), demonstrates explicitly that the microwave haze and the gamma-ray bubbles are indeed the same structure observed at multiple wavelengths, and strongly supports the interpretation of the microwave haze as a separate component of Galactic synchrotron (likely generated by a transient event) as opposed to a simple variation of the spectral index of disk synchrotron. In addition, combining these data sets allows for the first determination of the magnetic field within a radio bubble using microwaves and gamma rays by taking advantage of the fact that the inverse Compton gamma rays are primarily generated by scattering of cosmic microwave background photons at these latitudes, thus minimizing uncertainty in the target radiation field. Assuming uniform volume emissivity, I find that the magnetic field within the southern Galactic microwave/gamma-ray bubble is ~5 ?G above 6 kpc off of the Galactic plane.
Dobler, Gregory
Streamlined Modeling for Characterizing Spacecraft Anomalous Behavior
NASA Astrophysics Data System (ADS)
Anomalous behavior of on-orbit spacecraft can often be detected using passive, remote sensors which measure electro-optical signatures that vary in time and spectral content. Analysts responsible for assessing spacecraft operational status and detecting detrimental anomalies using non-resolved imaging sensors are often presented with various sensing and identification issues. Modeling and measuring spacecraft self emission and reflected radiant intensity when the radiation patterns exhibit a time varying reflective glint superimposed on an underlying diffuse signal contribute to assessment of spacecraft behavior in two ways: (1) providing information on body component orientation and attitude; and, (2) detecting changes in surface material properties due to the space environment. Simple convex and cube-shaped spacecraft, designed to operate without protruding solar panel appendages, may require an enhanced level of preflight characterization to support interpretation of the various physical effects observed during on-orbit monitoring. This paper describes selected portions of the signature database generated using streamlined signature modeling and simulations of basic geometry shapes apparent to non-imaging sensors. With this database, summarization of key observable features for such shapes as spheres, cylinders, flat plates, cones, and cubes in specific spectral bands that include the visible, mid wave, and long wave infrared provide the analyst with input to the decision process algorithms contained in the overall sensing and identification architectures. The models typically utilize baseline materials such as Kapton, paints, aluminum surface end plates, and radiators, along with solar cell representations covering the cylindrical and side portions of the spacecraft. Multiple space and ground-based sensors are assumed to be located at key locations to describe the comprehensive multi-viewing aspect scenarios that can result in significant specular reflection from both the sun and the underlying earth surface. The objects are modeled to be either tumbling or spin stabilized at key orientations in order to capture the complexity of the solar/earth incident illumination and the sensor viewing aspect conditions. Although these geometries and processes appear to be specialized and limited, they are sufficient to capture the principal observable features that are necessary for gaining insight into the complex issues of interpreting non-imaging sensor signals for monitoring the actual on-orbit spacecraft behavior changes. This talk has been prepared as a poster paper, to allow for engagement with conference participants on the presentation contents, and discussions for expansion of the material to include additional topical areas for future work, as appropriate. All discussions have been limited only to topics that could be discussed in the open format of the conference.
Klem, B.; Swann, D.
Application of Monte Carlo algorithms to the Bayesian analysis of the Cosmic Microwave Background
NASA Technical Reports Server (NTRS)
Power spectrum estimation and evaluation of associated errors in the presence of incomplete sky coverage; nonhomogeneous, correlated instrumental noise; and foreground emission are problems of central importance for the extraction of cosmological information from the cosmic microwave background (CMB).
Jewell, J.; Levin, S.; Anderson, C. H.
Using Microwave Sample Decomposition in Undergraduate Analytical Chemistry
NASA Astrophysics Data System (ADS)
A shortcoming of many undergraduate classes in analytical chemistry is that students receive little exposure to sample preparation in chemical analysis. This paper reports the progress made in introducing microwave sample decomposition into several quantitative analysis experiments at Truman State University. Two experiments being performed in our current laboratory rotation include closed vessel microwave decomposition applied to the classical gravimetric determination of nickel and the determination of sodium in snack foods by flame atomic emission spectrometry. A third lab, using open-vessel microwave decomposition for the Kjeldahl nitrogen determination is now ready for student trial. Microwave decomposition reduces the time needed to complete these experiments and significantly increases the student awareness of the importance of sample preparation in quantitative chemical analyses, providing greater breadth and realism in the experiments.
Griff Freeman, R.; McCurdy, David L.
Anomalous convergence of Lyapunov exponent estimates
Numerical experiments reveal that estimates of the Lyapunov exponent for the logistic map {ital x}{sub {ital t}+1}={ital f}({ital x}{sub {ital t}})=4{ital x}{sub {ital t}}(1{minus}{ital x}{sub {ital t}}) are anomalously precise: they are distributed with a standard deviation that scales as 1/{ital N}, where {ital N} is the length of the trajectory, not as 1/ {radical}{ital N} , the scaling expected from an informal interpretation of the central limit theorem. We show that this anomalous convergence follows from the fact that the logistic map is conjugate to a constant-slope map. The Lyapunov estimator is just one example of a ``chaotic walk``; we show that whether or not a general chaotic walk exhibits anomalously small variance depends only on the autocorrelation of the chaotic process.
Theiler, J. [Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); [Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States); Smith, L.A. [Mathematical Institute, University of Oxford, Oxford, OX13LB (United Kingdom)] [Mathematical Institute, University of Oxford, Oxford, OX13LB (United Kingdom)
NUV Detector Recovery After Anomalous Shutdown
NASA Astrophysics Data System (ADS)
This proposal is designed to permit recovery of the NUV-MAMA detector after an anomalous shutdown. Anomalous shutdowns can occur as a result of bright object violations which trigger the Bright Scene Detection or Software Global Monitor. Anomalous shutdowns can also occur as a result of MAMA hardware problems. The Initial MAMA turn-on consists of three tests: a signal processing electronics check, a slow high voltage ramp-up to an intermediate voltage, and a slow high voltage ramp-up to the full operating voltage. During each of the two high voltage ramp-ups, diagnostics are performed during a dark time-tag exposure. The turn-on is followed by a MAMA Fold Analysis Test. The complete sequence is contained in visits 1 through 4. This proposal is based on SMOV proposal 11355, visit 01 and visits 03-05.;
Wheeler, Thomas
Determination of soluble toxic arsenic species in alga samples by microwave-assisted extraction and high performance liquid chromatography–hydride generation–inductively coupled plasma-atomic emission spectrometry
A microwave-based procedure for arsenic species extraction in alga samples (Sargassum fulvellum, Chlorella vulgaris, Hizikia fusiformis and Laminaria digitata) is described. Extraction time and temperature were tested in order to evaluate the extraction efficiency of the process. Arsenic compounds were extracted in 8ml of deionised water at 90°C for 5min. The process was repeated three times. Soluble arsenic compounds extracted
S. García Salgado; M. A. Quijano Nieto; M. M. Bonilla Simón
A potassium Faraday anomalous dispersion optical filter
NASA Technical Reports Server (NTRS)
The characteristics of a potassium Faraday anomalous dispersion optical filter operating on the blue and near infrared transitions are calculated. The results show that the filter can be designed to provide high transmission, very narrow pass bandwidth, and low equivalent noise bandwidth. The Faraday anomalous dispersion optical filter (FADOF) provides a narrow pass bandwidth (about GHz) optical filter for laser communications, remote sensing, and lidar. The general theoretical model for the FADOF has been established in our previous paper. In this paper, we have identified the optimum operational conditions for a potassium FADOF operating on the blue and infrared transitions. The signal transmission, bandwidth, and equivalent noise bandwidth (ENBW) are also calculated.
Yin, B.; Shay, T. M.
Cassini RADAR: prospects for Titan surface investigations using the microwave radiometer
The Radar instrument on the Cassini spacecraft can be used in a passive radiometric mode to map the microwave emission from Titan: these will be the 5rst resolved microwave emission measurements of an icy satellite. Observation plans and the theory for their interpretation is presented: these data should be able to provide crude composition maps of Titan's surface, con5rm equator-to-pole
Ralph D. Lorenz; Michael A. Janssen; Richard D. West; Duane O. Muhleman
Design of a microwave calorimeter for the microwave tokamak experiment
The initial design of a microwave calorimeter for the Microwave Tokamak Experiment is presented. The design is optimized to measure the refraction and absorption of millimeter rf microwaves as they traverse the toroidal plasma of the Alcator C tokamak. Techniques utilized can be adapted for use in measuring high intensity pulsed output from a microwave device in an environment of ultra high vacuum, intense fields of ionizing and non-ionizing radiation and intense magnetic fields. 16 refs.
Marinak, M. (California Univ., Berkeley, CA (USA))
The European Microwave Week 2008 and its Microwave Conferences
Under the auspices of the European Microwave Association (EuMA) the 11th annual European Microwave Week was organized in the Amsterdam RAI Congress Centre, The Netherlands, 27-31 October 2008. This major event consisted this year of five conferences, an exhibition, and various side events. The 38th European Microwave Conference (EuMC), the Third European Microwave Integrated Circuits Conference (EuMIC), the Fifth European
P. Hoogeboom; F. Van Vliet
Anomalous Excess Heat by D2O\\/Pd Cell under LH Mode Electrolysis
A Pd sheet cathode centered within a Pt-wired anode in D2O\\/LiOD electrolyte was used with the L-H mode pulse operation. Anomalously large excess heat (32 watts in average for 2 months, 100 - 130 watts at peaks and averaged output\\/input power ratio 1.7) was once observed, associated with very low neutron emission (~1 n\\/s). To investigate the reproducibility of this
Akito TAKAHASHI; Akimasa MEGA; Takayuki TAKEUCHI; Hiroyuki MIYAMARU; Toshiyuki IIDA
Anomalous NMR Line Shapes in Solid Ordered OrthoHydrogen and Para-Deuterium
Some highly anomalous features have been observed in the low-temperature NMR spectrum of high-purity (> 99% J=1), solid para-deuterium. The intensity of the low-frequency side of the Pake doublet is enhanced and that of the high-frequency side reduced, sometimes becoming negative, corresponding to an emission of power. The anomaly is particularly pronounced and of the opposite sign for the I=2
Walter N. Hardy; A. John Berlinsky
P-type electrical, photoconductive, and anomalous ferromagnetic properties of Cu2O nanowires
Cu2O nanowires are synthesized by reduction of CuO nanowires with hydrogen gas. Strong green photoluminescence dominated by band-edge emission is observed. Field effect transistors fabricated from individual Cu2O nanowires present high on-off ratio (>106) and high mobility (>95 cm2\\/V s). Furthermore, the device demonstrates a fast photoelectric response to blue illumination in air at room temperature. In addition, anomalous ferromagnetism
L. Liao; B. Yan; Y. F. Hao; G. Z. Xing; J. P. Liu; B. C. Zhao; Z. X. Shen; T. Wu; L. Wang; J. T. L. Thong; C. M. Li; W. Huang; T. Yu
Measurements of the GHz emission by a 3 MeV electron beam
NASA Astrophysics Data System (ADS)
The MAYBE (Microwave Air Yield Beam) Experiment is dedicated to the study of the microwave emission from particle beams in light of its possible use for the detection of ultra high energy cosmic rays. Measurements of the microwave emission were performed at the 3 MeV electron beam in the Van de Graaff facility at the Argonne National Laboratory. Results include the measured spectrum between 1 and 15 GHz, the polarization, and the scaling of the emission power with respect to the beam intensity. MAYBE measurements provide further insight on microwave emission as a detection technique for ultra-high energy cosmic rays.
San Luis, P. Facal; Bohá?ová, M.; Bonifazi, C.; Cataldi, G.; Chemerisov, S.; de Mello Neto, J. R. T.; Fox, B.; Gorham, P. W.; Hojvat, C.; Hollon, N.; Meyhandan, R.; Monasor, M.; d'Orfeuil, B. Rouillé; Santos, E. M.; Pochez, J.; Privitera, P.; Spinka, H.; Verzi, V.; Zhou, J.