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Sample records for field evaluation due

  1. Evaluation of the scattered pressure due to infinite rigid cylinders, infinite elastic cylindrical shells, and rigid spheres in the presence of an ambient noise field

    NASA Astrophysics Data System (ADS)

    Honeycutt, Rebecca L.; Johnson, Steven J.

    1993-04-01

    The sound scattering due to an ambient noise field, approximated by a squared cosine function, is considered for infinite rigid and elastic cylinders and rigid spheres. For the cylinders, it is assumed that the acoustic wave front is parallel to the axis of the cylinder (informally incident). For this assumption, a closed form expression for the scattered sound field-to-incident ambient noise field (signal-to-noise) ratio is obtained not only for the cosine squared directivity, but for any arbitrary directivity which can be expressed in terms of a Fourier series. For the sphere, it is assumed that the noise is circumferentially symmetric which leads to a closed form expression for the signal-to-noise ratio due to a cosine squared directivity.

  2. Combined MRI-PET scanner: A Monte Carlo evaluation of the improvements in PET resolution due to the effects of a static homogeneous magnetic field

    SciTech Connect

    Raylman, R.R.; Hammer, B.E.; Christensen, N.L.

    1996-08-01

    Positron emission tomography (PET) relies upon the detection of photons resulting from the annihilation of positrons emitted by a radiopharmaceutical. The combination of images obtained with PET and magnetic resonance imaging (MRI) have begun to greatly enhance the study of many physiological processes. A combined MRI-PET scanner could alleviate much of the spatial and temporal coregistration difficulties currently encountered in utilizing images from these complementary imaging modalities. In addition, the resolution of the PET scanner could be improved by the effects of the magnetic field. In this computer study, the utilization of a strong static homogeneous magnetic field to increase PET resolution by reducing the effects of positron range and photon noncollinearity was investigated. The results reveal that significant enhancement of resolution can be attained. For example, an approximately 27% increase in resolution is predicted for a PET scanner incorporating a 10-Tesla magnetic field. Most of this gain in resolution is due to magnetic confinement of the emitted positrons. Although the magnetic field does mix some positronium states resulting in slightly less photon noncollinearity, this reduction does not significantly affect resolution. Photon noncollinearity remains as the fundamental limiting factor of large PET scanner resolution.

  3. The magnetic field due to a number of toroidal conductors

    NASA Astrophysics Data System (ADS)

    Caldwell, J.

    1982-03-01

    This is an extension of the work carried out by Gibson and Caldwell on the optimization of the uniformity of the magnetic field produced in the bore of a toroidal conductor of rectangular cross section. In this paper the work is extended to consider the magnetic field due to a number of conductors. The usefulness of the work is assessed by comparing it to the work of Garrett, and numerical results are given for particular coil parameters.

  4. Anisotropy in MHD turbulence due to a mean magnetic field

    NASA Technical Reports Server (NTRS)

    Shebalin, J. V.; Matthaeus, W. H.; Montgomery, D.

    1982-01-01

    The development of anisotropy in an initially isotropic spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops due to the combined effects of an externally imposed dc magnetic field and viscous and resistive dissipation at high wave numbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wave numbers.

  5. Flow damping due to stochastization of the magnetic field

    PubMed Central

    Ida, K.; Yoshinuma, M.; Tsuchiya, H.; Kobayashi, T.; Suzuki, C.; Yokoyama, M.; Shimizu, A.; Nagaoka, K.; Inagaki, S.; Itoh, K.; Akiyama, T.; Emoto, M.; Evans, T.; Dinklage, A.; Du, X.; Fujii, K.; Goto, M.; Goto, T.; Hasuo, M.; Hidalgo, C.; Ichiguchi, K.; Ishizawa, A.; Jakubowski, M.; Kamiya, K.; Kasahara, H.; Kawamura, G.; Kato, D.; Kobayashi, M.; Morita, S.; Mukai, K.; Murakami, I.; Murakami, S.; Narushima, Y.; Nunami, M.; Ohdach, S.; Ohno, N.; Osakabe, M.; Pablant, N.; Sakakibara, S.; Seki, T.; Shimozuma, T.; Shoji, M.; Sudo, S.; Tanaka, K.; Tokuzawa, T.; Todo, Y.; Wang, H.; Yamada, H.; Takeiri, Y.; Mutoh, T.; Imagawa, S.; Mito, T.; Nagayama, Y.; Watanabe, K. Y.; Ashikawa, N.; Chikaraishi, H.; Ejiri, A.; Furukawa, M.; Fujita, T.; Hamaguchi, S.; Igami, H.; Isobe, M.; Masuzaki, S.; Morisaki, T.; Motojima, G.; Nagasaki, K.; Nakano, H.; Oya, Y.; Suzuki, Y.; Sakamoto, R.; Sakamoto, M.; Sanpei, A.; Takahashi, H.; Tokitani, M.; Ueda, Y.; Yoshimura, Y.; Yamamoto, S.; Nishimura, K.; Sugama, H.; Yamamoto, T.; Idei, H.; Isayama, A.; Kitajima, S.; Masamune, S.; Shinohara, K.; Bawankar, P. S.; Bernard, E.; von Berkel, M.; Funaba, H.; Huang, X. L.; Ii, T.; Ido, T.; Ikeda, K.; Kamio, S.; Kumazawa, R.; Moon, C.; Muto, S.; Miyazawa, J.; Ming, T.; Nakamura, Y.; Nishimura, S.; Ogawa, K.; Ozaki, T.; Oishi, T.; Ohno, M.; Pandya, S.; Seki, R.; Sano, R.; Saito, K.; Sakaue, H.; Takemura, Y.; Tsumori, K.; Tamura, N.; Tanaka, H.; Toi, K.; Wieland, B.; Yamada, I.; Yasuhara, R.; Zhang, H.; Kaneko, O.; Komori, A.

    2015-01-01

    The driving and damping mechanism of plasma flow is an important issue because flow shear has a significant impact on turbulence in a plasma, which determines the transport in the magnetized plasma. Here we report clear evidence of the flow damping due to stochastization of the magnetic field. Abrupt damping of the toroidal flow associated with a transition from a nested magnetic flux surface to a stochastic magnetic field is observed when the magnetic shear at the rational surface decreases to 0.5 in the large helical device. This flow damping and resulting profile flattening are much stronger than expected from the Rechester–Rosenbluth model. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that the flow damping is due to the change in the non-diffusive term of momentum transport. PMID:25569268

  6. Tune Variations due to Septum Stray Field F. Pederson &

    SciTech Connect

    Rinolfi, L.

    1986-10-12

    Two types of antiproton instabilities due to trapped ions are harmful in the AA. One is a coherent instability occurring when an ion pocket resonates with a 3-Q mode (hiccups), the other is excitation of 11th and 15th order non-linear resonances due to the non-linear focusing fields from localized ion clouds trapped in uncleared potential well pockets. Accumulation with a good injection yield of antiprotons forces us to locate the tune of the dense core in the general area of the array of 15th order resonances. To avoid harmful blow-up of the dense core the tune is located between the resonances 11Q{sub H} + 4Q{sub V} = 34, 10Q{sub H} + 5Q{sub V} = 34, and 11Q{sub H} = 25, requiring a tune of Q{sub H} = 2.2722 to be maintained with a precision of a few 10{sup -4} (Fig. 4). Different angles of the injection and ejection trajectories require the septum current to be changed from 3860 A during accumulation to 3920 A, during ejection mode. Variations in the septum stray field due to these changes in current cause tune changes in the order of 10{sup -3}. In addition, at a given septum current, a pronounced hysteresis of the stray field causes tune variations of about the same order of magnitude, so also the past history of the septum excitation must be carefully controlled to obtain a reproducible tune.

  7. Biological effects due to weak magnetic field on plants.

    PubMed

    Belyavskaya, N A

    2004-01-01

    Throughout the evolution process, Earth's magnetic field (MF, about 50 microT) was a natural component of the environment for living organisms. Biological objects, flying on planned long-term interplanetary missions, would experience much weaker magnetic fields, since galactic MF is known to be 0.1-1 nT. However, the role of weak magnetic fields and their influence on functioning of biological organisms are still insufficiently understood, and is actively studied. Numerous experiments with seedlings of different plant species placed in weak magnetic field have shown that the growth of their primary roots is inhibited during early germination stages in comparison with control. The proliferative activity and cell reproduction in meristem of plant roots are reduced in weak magnetic field. Cell reproductive cycle slows down due to the expansion of G1 phase in many plant species (and of G2 phase in flax and lentil roots), while other phases of cell cycle remain relatively stable. In plant cells exposed to weak magnetic field, the functional activity of genome at early pre-replicate period is shown to decrease. Weak magnetic field causes intensification of protein synthesis and disintegration in plant roots. At ultrastructural level, changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells were observed in pea roots exposed to weak magnetic field. Mitochondria were found to be very sensitive to weak magnetic field: their size and relative volume in cells increase, matrix becomes electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to weak magnetic field show Ca2+ over-saturation in all organelles and in cytoplasm unlike the control ones. The data presented suggest that prolonged exposures of plants to weak

  8. Biological effects due to weak magnetic field on plants

    NASA Astrophysics Data System (ADS)

    Belyavskaya, N. A.

    2004-01-01

    Throughout the evolution process, Earth's magnetic field (MF, about 50 μT) was a natural component of the environment for living organisms. Biological objects, flying on planned long-term interplanetary missions, would experience much weaker magnetic fields, since galactic MF is known to be 0.1-1 nT. However, the role of weak magnetic fields and their influence on functioning of biological organisms are still insufficiently understood, and is actively studied. Numerous experiments with seedlings of different plant species placed in weak magnetic field have shown that the growth of their primary roots is inhibited during early germination stages in comparison with control. The proliferative activity and cell reproduction in meristem of plant roots are reduced in weak magnetic field. Cell reproductive cycle slows down due to the expansion of G 1 phase in many plant species (and of G 2 phase in flax and lentil roots), while other phases of cell cycle remain relatively stabile. In plant cells exposed to weak magnetic field, the functional activity of genome at early pre-replicate period is shown to decrease. Weak magnetic field causes intensification of protein synthesis and disintegration in plant roots. At ultrastructural level, changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells were observed in pea roots exposed to weak magnetic field. Mitochondria were found to be very sensitive to weak magnetic field: their size and relative volume in cells increase, matrix becomes electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to weak magnetic field show Ca 2+ over-saturation in all organelles and in cytoplasm unlike the control ones. The data presented suggest that prolonged exposures of plants to weak

  9. On the Vertigo Due to Static Magnetic Fields

    PubMed Central

    Mian, Omar S.; Li, Yan; Antunes, Andre; Glover, Paul M.; Day, Brian L.

    2013-01-01

    Vertigo is sometimes experienced in and around MRI scanners. Mechanisms involving stimulation of the vestibular system by movement in magnetic fields or magnetic field spatial gradients have been proposed. However, it was recently shown that vestibular-dependent ocular nystagmus is evoked when stationary in homogenous static magnetic fields. The proposed mechanism involves Lorentz forces acting on endolymph to deflect semicircular canal (SCC) cupulae. To investigate whether vertigo arises from a similar mechanism we recorded qualitative and quantitative aspects of vertigo and 2D eye movements from supine healthy adults (n = 25) deprived of vision while pushed into the 7T static field of an MRI scanner. Exposures were variable and included up to 135s stationary at 7T. Nystagmus was mainly horizontal, persisted during long-exposures with partial decline, and reversed upon withdrawal. The dominant vertiginous perception with the head facing up was rotation in the horizontal plane (85% incidence) with a consistent direction across participants. With the head turned 90 degrees in yaw the perception did not transform into equivalent vertical plane rotation, indicating a context-dependency of the perception. During long exposures, illusory rotation lasted on average 50 s, including 42 s whilst stationary at 7T. Upon withdrawal, perception re-emerged and reversed, lasting on average 30 s. Onset fields for nystagmus and perception were significantly correlated (p<.05). Although perception did not persist as long as nystagmus, this is a known feature of continuous SSC stimulation. These observations, and others in the paper, are compatible with magnetic-field evoked-vertigo and nystagmus sharing a common mechanism. With this interpretation, response decay and reversal upon withdrawal from the field, are due to adaptation to continuous vestibular input. Although the study does not entirely exclude the possibility of mechanisms involving transient vestibular stimulation

  10. On the vertigo due to static magnetic fields.

    PubMed

    Mian, Omar S; Li, Yan; Antunes, Andre; Glover, Paul M; Day, Brian L

    2013-01-01

    Vertigo is sometimes experienced in and around MRI scanners. Mechanisms involving stimulation of the vestibular system by movement in magnetic fields or magnetic field spatial gradients have been proposed. However, it was recently shown that vestibular-dependent ocular nystagmus is evoked when stationary in homogenous static magnetic fields. The proposed mechanism involves Lorentz forces acting on endolymph to deflect semicircular canal (SCC) cupulae. To investigate whether vertigo arises from a similar mechanism we recorded qualitative and quantitative aspects of vertigo and 2D eye movements from supine healthy adults (n = 25) deprived of vision while pushed into the 7T static field of an MRI scanner. Exposures were variable and included up to 135s stationary at 7T. Nystagmus was mainly horizontal, persisted during long-exposures with partial decline, and reversed upon withdrawal. The dominant vertiginous perception with the head facing up was rotation in the horizontal plane (85% incidence) with a consistent direction across participants. With the head turned 90 degrees in yaw the perception did not transform into equivalent vertical plane rotation, indicating a context-dependency of the perception. During long exposures, illusory rotation lasted on average 50 s, including 42 s whilst stationary at 7T. Upon withdrawal, perception re-emerged and reversed, lasting on average 30 s. Onset fields for nystagmus and perception were significantly correlated (p<.05). Although perception did not persist as long as nystagmus, this is a known feature of continuous SSC stimulation. These observations, and others in the paper, are compatible with magnetic-field evoked-vertigo and nystagmus sharing a common mechanism. With this interpretation, response decay and reversal upon withdrawal from the field, are due to adaptation to continuous vestibular input. Although the study does not entirely exclude the possibility of mechanisms involving transient vestibular stimulation

  11. Potential therapeutic misadministration due to inappropriate electron beam field shaping.

    PubMed

    Olch, A J; Fallen, R; Conrad, J; Lavey, R S

    2000-01-01

    Lead or cerrobend blocking strips are used to shape electron treatment fields when an appropriate custom insert is not available. For the Varian 2100C accelerator, the structural supports of the electron applicators impede the free placement of these field-shaping strips on the open custom insert frame while placement at the top of the applicator is unimpeded. We have investigated the dosimetric ramifications of placing field shaping strips at the top level of the 15x15 applicator for 6, 9, and 16 MeV electrons. Our results demonstrate as much as a 30% dose decrease and 2 cm penumbral increase when this is done compared to field shaping at the insert level. The magnitude of this dosimetric error qualifies as a therapeutic misadministration in many states depending on how many treatments are delivered in this manner. Based on this finding, we recommend that routine use of lead strip blocking be discouraged in favor of custom inserts due to the potential for inappropriate placement on some linear accelerators.

  12. Impulse Representation of Sound Field due to a Rigid Wedge

    NASA Astrophysics Data System (ADS)

    Lawu, Tjundewo; Ueda, Mitsuhiro

    2004-05-01

    An impulse representation for calculating a diffraction wave due to a rigid wedge is described. The method is an approximation of the Biot-Tolstoy rigorous closed-form solution for the diffraction of point source radiation by an infinite rigid wedge. The band-limited time-domain function can be reconstructed to the original waveform if it satisfies the sampling theorem, which assumes that sampling takes place at the lowest permissible sampling rate. Therefore, if the energy is concentrated between the first sampling intervals immediately after the rise time of the time-domain function, the rigorous solution can be approximated as a delta function. This paper shows the description methods of the diffraction field near the ridge in three-dimensional space. Using the proposed impulse representation, numerical simulation was performed and the calculation accuracy was examined.

  13. Magnetic Field Fluctuations Due to Diel Vertical Migrations of Zooplankton

    NASA Astrophysics Data System (ADS)

    Dean, C.; Soloviev, A.

    2016-12-01

    Dean et al. (2016) have indicated that at high zooplankton concentrations, diel vertical migrations (DVM) cause velocity fluctuations and a respective increase of the dissipation rate of turbulent kinetic energy (TKE). In this work, we used a 3D non-hydrostatic computational fluid dynamics model with Lagrangian particle injections (a proxy for migrating organisms) via a discrete phase model to simulate the effect of turbulence generation by DVM. We tested a range of organism concentrations from 1000 to 10,000 organisms/m3. The simulation at an extreme concentration of zooplankton showed an increase in dissipation rate of TKE by two to three orders of magnitude during DVM over background turbulence, 10-8 W kg-1. At lower concentrations (<1000 organisms/m3), almost no turbulence above the background level was produced by DVM in the model. The computational fluid dynamics model also produced a small decrease of current velocity due to turbulence generated by DVM. This decrease in current velocity profile appear to be consistent with ADCP measurements from the Straits of Florida during migration times averaged over 11 months of observations (though interpretation of the current velocity measurements is complicated by physical factors such as tides, Florida current meandering, etc.). The deviations in the velocity profiles can in principle be explained by the increase in turbulent mixing during vertical migration periods. In addition, seawater is an electric conductor. Water movements in the magnetic field of the Earth induce electrical currents and, as a result, secondary magnetic fluctuations. The velocity fluctuations produced by DVM are, therefore, supposed to have a magnetic signature. In order to test this hypothesis, we have applied a magnetohydrodnamics add-on module to the hydrodynamic model. The model results indicate that DVM of an extreme concentration of zooplankton may create fluctuations of the total magnetic field on the order of 1 nT, which are

  14. Biological effects due to weak magnetic fields on plants

    NASA Astrophysics Data System (ADS)

    Belyavskaya, N.

    In the evolution process, living organisms have experienced the action of the Earth's magnetic field (MF) that is a natural component of our environment. It is known that a galactic MF induction does not exceed 0.1 nT, since investigations of weak magnetic field (WMF) effects on biological systems have attracted attention of biologists due to planning long-term space flights to other planets where the magnetizing force is near 10-5 Oe. However, the role of WMF and its influence on organisms' functioning are still insufficiently investigated. A large number of experiments with seedlings of different plant species placed in WMF has found that the growth of their primary roots is inhibited during the early terms of germination in comparison with control. The proliferation activity and cell reproduction are reduced in meristem of plant roots under WMF application. The prolongation of total cell reproductive cycle is registered due to the expansion of G phase in1 different plant species as well as of G phase in flax and lentil roots along with2 relative stability of time parameters of other phases of cell cycle. In plant cells exposed to WMF, the decrease in functional activity of genome at early prereplicate period is shown. WMF causes the intensification in the processes of proteins' synthesis and break-up in plant roots. Qualitative and quantitative changes in protein spectrum in growing and differentiated cells of plant roots exposed to WMF are revealed. At ultrastructural level, there are observed such ultrastructural peculiarities as changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells of pea roots exposed to WMF. Mitochondria are the most sensitive organelle to WMF application: their size and relative volume in cells increase, matrix is electron

  15. Evaluating cotton stripper field performance

    USDA-ARS?s Scientific Manuscript database

    Cotton strippers are used primarily in the Southern High Plains due to the specific cotton varieties grown. Typically, cotton strippers cost about two-thirds the price of a cotton picker and range from one-half to one-fourth the horsepower. A cotton stripper also has a higher field and harvesting ef...

  16. Mean-square error due to gradiometer field measuring devices.

    PubMed

    Hatsell, C P

    1991-06-01

    Gradiometers use spatial common mode magnetic field rejection to reduce interference from distant sources. They also introduce distortion that can be severe, rendering experimental data difficult to interpret. Attempts to recover the measured magnetic field from the gradiometer output will be plagued by the nonexistence of a spatial function for deconvolution (except for first-order gradiometers), and by the high-pass nature of the spatial transform that emphasizes high spatial frequency noise. Goals of a design for a facility for measuring biomagnetic fields should be an effective shielded room and a field detector employing a first-order gradiometer.

  17. Induced Magnetic Field Due to Reaction Wheel Shielding

    NASA Astrophysics Data System (ADS)

    Pudney, M. A.; Kapfunde, G.; Trougnou, L.

    2016-05-01

    In situ magnetic field measurements are of critical importance to unanswered questions on the inner heliosphere, such as: how the corona and solar wind are accelerated and heated; how the solar magnetic field evolves over a solar cycle; and how this field links into space. However, accurate spacecraft magnetometer measurements require reliable in-flight calibration. The magnetic interference caused by reaction wheels on magnetometer measurements in space is well known, and a common mitigation method is to use magnetic shielding. However, the presence of high-permeability material in-flight has the side-effect of distorting the true ambient field. We present a theoretical analysis of this distortion, and suggest a transfer function that can be used to recover the ambient field from the distorted dataset. Experimental measurements on a shield prototype for the Solar Orbiter mission agree with predictions to within an order of magnitude, demonstrating a distortion of approximately 1 part in 104.

  18. Rapid dissipation of magnetic fields due to the Hall current

    SciTech Connect

    Vainshtein, S. I.; Chitre, S. M.; Olinto, A. V.

    2000-04-01

    We propose a mechanism for the fast dissipation of magnetic fields which is effective in a stratified medium where ion motions can be neglected. In such a medium, the field is frozen into the electrons, and Hall currents prevail. Although Hall currents conserve magnetic energy, in the presence of density gradients they are able to create current sheets which can be sites for efficient dissipation of magnetic fields. We recover the frequency {omega}{sub MH} for Hall oscillations modified by the presence of density gradients. We show that these oscillations can lead to an exchange of energy between different components of the field. We calculate the time evolution, and show that magnetic fields can dissipate on a time scale of order 1/{omega}{sub MH}. This mechanism can play an important role in magnetic dissipation in systems with very steep density gradients, where the ions are static such as those found in the solid crust of neutron stars. (c) 2000 The American Physical Society.

  19. Domain wall interactions due to vacuum Dirac field fluctuations in 2 +1 dimensions

    NASA Astrophysics Data System (ADS)

    Fosco, C. D.; Mazzitelli, F. D.

    2016-07-01

    We evaluate quantum effects due to a two-component Dirac field in 2 +1 spacetime dimensions, coupled to domain-wall-like defects with a smooth shape. We show that these effects induce nontrivial contributions to the (shape-dependent) energy of the domain walls. For a single defect, we study the divergences in the corresponding self-energy, and also consider the role of the massless zero mode—corresponding to the Callan-Harvey mechanism—by coupling the Dirac field to an external gauge field. For two defects, we show that the Dirac field induces a nontrivial, Casimir-like effect between them, and we provide an exact expression for that interaction in the case of two straight-line parallel defects. As is the case for the Casimir interaction energy, the result is finite and unambiguous.

  20. Evaluating and minimizing noise impact due to aircraft flyover

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.

    1980-01-01

    The results of a study on the evaluation and reduction of noise impact to a community due to aircraft landing and takeoff operations are presented. The case of multiple aircrafts flying on several trajectories, for either approach/landings or takeoffs was examined. An extremely realistic model of the flight path was developed. The annoyance criterion used was the noise impact index (NII). The algorithm was applied to Patrick Henry International Airport.

  1. v-Spread Due to Random Field Errors

    SciTech Connect

    Parzen, G.

    1990-01-01

    Previous work indicated that the random bk, ak field errors can produce a large v-spread within the beam. For the worse case a v-spread of Δv=21x10-3 has been found. The overall results are first presented, without much analysis or breakdown into contributions bk, ak. Later on the contribution of various bk, ak will be studied.

  2. New Manning System Field Evaluation

    DTIC Science & Technology

    1986-03-01

    our Analytic hodel (see Chapter 5, New Manning Svestem Field Evaluacion . Technical Revore No. I, RAJL-, November c t, e number or soldiers retaking...and meaningful performance measures are not only crucial to the WRAIR N Field Evaluacion but also to the Army. To know which unit does betzer than

  3. Far-field errors due to random noise in cylindrical near-field measurements

    NASA Astrophysics Data System (ADS)

    Romeu, Jordi; Jofre, Luis; Cardama, Angel

    1992-01-01

    A full characterization of the far-field noise obtained from cylindrical near- to far-field transformation, for a white Gaussian, space stationary, near-field noise is derived. A possible source for such noise is the receiver additive noise. The noise characterization is done by obtaining the autocorrelation of the far-field noise, which is shown to be easily computed during the transformation process. Even for this simple case, the far-field noise has complex behavior dependent on the measurement probe. Once the statistical properties of the far-field noise are determined, it is possible to compute upper and lower bounds for the radiation pattern for a given probability. These bounds define a strip within the radiation pattern with the desired probability. This may be used as part of a complete near-field error analysis of a particular cylindrical near-field facility.

  4. Aerodynamic sound generation due to vortex-aerofoil interaction. Part 2: Analysis of the acoustic field

    NASA Technical Reports Server (NTRS)

    Parasarathy, R.; Karamcheti, K.

    1972-01-01

    The Lighthill method was the basic procedure used to analyze the sound field associated with a vortex of modified strength interacting with an airfoil. A free vortex interacting with an airfoil in uniform motion was modeled in order to determine the sound field due to all the acoustic sources, not only on the airfoil surfaces (dipoles), but also the ones distributed on the perturbed flow field (quadrupoles) due to the vortex-airfoil interaction. Because inviscid flow is assumed in the study of the interaction, the quadrupoles considered in the perturbed flow field are entirely due to an unsteady flow field. The effects of airfoil thickness on the second radiation are examined by using a symmetric Joukowski airfoil for the vortex-airfoil interaction. Sound radiation in a plane, far field simplification, and computation of the sound field are discussed.

  5. Evaluation of deformations of earth structures due to earthquakes

    NASA Astrophysics Data System (ADS)

    Bastani, Seyed Ali

    Conditions leading to post earthquake-induced deformations of an embankment due to liquefaction were investigated by a physical and numerical modeling program. A set of centrifuge experiments were performed in the National Geotechnical Centrifuge (NGC) and Schaevitz Centrifuge (SC) at the University of California at Davis. A Nevada Sand embankment model overlaid/confined by a clayey Yolo Loam layer was liquefied by an injection system at the base of the embankment model at NGC. The dynamic compaction of liquefiable soil was simulated by the volumetric increase of pore fluid through the water injection system in these tests. Models of the NGC model were also prepared and statically and dynamically tested at the SC facility to compare the deformation patterns between injection- and dynamic-induced liquefactions. The dynamic and static centrifuge models were numerically modeled. In the process a new constitutive model was developed that was utilized in modeling of the injection-induced liquefaction process. The numerical models showed that the void ratio was redistributed during both injection- and shaking-induced liquefaction. The shearing deformations of Nevada Sand were, experimentally and numerically, observed to cease whenever the shaking, water injection, and/or in general the void ratio redistribution within the sand was stopped. The numerical model of injection-induced liquefaction also highlighted that the injection rate has a significant effect on the location of failure surface. A faster rate of injection may induce additional water accumulation/dilation at the base of Nevada Sand layer and induce a deep-seated failure. The injection rate reduction will push the failure towards the interface of less permeable cap and Nevada Sand layer. The concept of residual strength is generally inconsistent with the concept of void ratio redistribution. However, the comparison between the mobilized shear strengths of the centrifuge models and the expected residual shear

  6. Ground penetrating radar field evaluation in Angola

    NASA Astrophysics Data System (ADS)

    Walls, Richard; Brown, Todd; Clodfelter, Fred; Coors, Jeff; Laudato, Stephen; Lauziere, Steve; Patrikar, Ajay; Poole, Michael; Price, Mike

    2006-05-01

    Deminers around the globe are still using handheld metal detectors that lack the capability to distinguish mines from clutter, detect mines containing very little metal, or find mines buried at deeper depths. In the southern African country of Angola, many areas and roads are impassable due to the threat of anti-tank landmines. Some of these mines are undetectable using current metal detector technology. The US Army has funded the development of the NIITEK ground penetrating radar (GPR) for detection of anti-tank (AT) landmines. This radar detects metal and plastic mines as well as mines that are buried too deep for handheld metal detectors to find. The US Department of Defense Humanitarian Demining (HD) Research & Development Program focuses on developing, testing, demonstrating, and validating new technology for immediate use in humanitarian demining operations around the globe. The HD team provided funding and guidance to NIITEK Incorporated for development of a prototype system called Mine Stalker - a relatively light-weight, remote-controlled vehicle outfitted with the NIITEK GPR, detection algorithms, and a marking system. Individuals from the HD team, NIITEK Inc, and the non-governmental organization Meschen Gegen Minen (MgM) participated in a field evaluation of the Mine Stalker in Angola. The primary aim was to evaluate the effectiveness and reliability of the NIITEK GPR under field conditions. The Mine Stalker was extremely reliable during the evaluation with no significant maintenance issues. All AT mines used to verify GPR performance were detected, even when buried to depths as deep as 25-33cm.

  7. Deformed neutron stars due to strong magnetic field in terms of relativistic mean field theories

    NASA Astrophysics Data System (ADS)

    Yanase, Kota; Yoshinaga, Naotaka

    2014-09-01

    Some observations suggest that magnetic field intensity of neutron stars that have particularly strong magnetic field, magnetars, reaches values up to 1014-15G. It is expected that there exists more strong magnetic field of several orders of magnitude in the interior of such stars. Neutron star matter is so affected by magnetic fields caused by intrinsic magnetic moments and electric charges of baryons that masses of neutron stars calculated by using Tolman-Oppenheimer-Volkoff equation is therefore modified. We calculate equation of state (EOS) in density-dependent magnetic field by using sigma-omega-rho model that can reproduce properties of stable nuclear matter in laboratory Furthermore we calculate modified masses of deformed neutron stars.

  8. Distorted orbit due to field errors and particle trajectories in combined undulator and axial magnetic field

    SciTech Connect

    Papadichev, V.A.

    1995-12-31

    Undulator and solenoid field errors cause electron trajectory deviation from the ideal orbit. Even small errors can result in a large lower frequency excursion from the undulator axis of a distorted orbit and of betatron oscillations performed now around it, especially near resonant conditions. Numerical calculation of a trajectory step by step requires large computing time and treats only particular cases, thus lacking generality. Theoretical treatment is traditionally based on random distribution of field errors, which allows a rather general approach, but is not convenient for practical purposes. In contrast, analytical treatment shows explicitly how distorted orbit and betatron oscillation amplitude depend on field parameters and errors and indicates how to eliminate these distortions. An analytical solution of the equations of motion can be found by expanding field errors and distorted orbit in Fourier series as was done earlier for the simplest case of a plane undulator without axial magnetic field. The same method is applied now to the more general case of combined generlized undulator and axial magnetic fields. The undulator field is a superposition of the fields of two plane undulators with mutually orthogonal fields and an arbitrary axial shift of the second undulator relative to the first. Beam space-charge forces and external linear focusing are taken into account. The particle trajectory is a superposition of ideal and distorted orbits with cyclotron gyration and slow drift gyration in the axial magnetic field caused by a balance of focusing and defocusing forces. The amplitudes of these gyrations depend on transverse coordinate and velocity at injection and can nearly double the total deviation of an electron from the undulator axis even after an adiabatic undulator entry. If the wavenumber of any Fourier harmonic is close to the wavenumbers of cyclotron or drift gyrations, a resonant increase of orbit distortion occurs.

  9. Perfect fluid in Lagrangian formulation due to generalized three-form field

    NASA Astrophysics Data System (ADS)

    Wongjun, Pitayuth

    2017-07-01

    A Lagrangian formulation of perfect fluid due to a noncanonical three-form field is investigated. The thermodynamic quantities such as energy density, pressure and the four velocity are obtained and then analyzed by comparing with the k-essence scalar field. The nonrelativistic matter due to the generalized three-form field with the equation of state parameter being zero is realized while it might not be possible for the k-essence scalar field. We also found that nonadiabatic pressure perturbations can be possibly generated. The fluid dynamics of the perfect fluid due to the three-form field corresponds to the system in which the number of particles is not conserved. We argue that it is interesting to use this three-form field to represent the dark matter for the classical interaction theory between dark matter and dark energy.

  10. Far-field optical degradation due to near-field transmission through a turbulent heated jet.

    PubMed

    Cicchiello, J M; Jumper, E J

    1997-09-01

    When a laser beam traverses an optically active, turbulent flow field, the laser wave front is aberrated by the flow. Density variations in a heated two-dimensional jet, for example, correspond to index-of-refraction variations, and this modulation of the index in the fluid can imprint an optical phase disturbance, or phase error, onto the laser wave front. Adaptive-optic systems seek to correct the phase error of the wave front, and thus restore the integrity of the far-field irradiance pattern. Given a near-field spatial mapping of a phase disturbance, the far-field irradiance pattern of the affected wave front can be calculated with Fourier-optics techniques. A Fourier-optics computer code was used to study the far-field irradiance patterns arising from actual time-varying measurements of a fluid-induced phase error. The time-averaged Strehl ratio was studied to provide insight into the spatial and temporal design requirements for adaptive-optic systems applied to the time series of near-field spatial phase-error maps.

  11. New Manning System Field Evaluation

    DTIC Science & Technology

    1985-11-01

    iC -anizat.iuo . The 7th ID(L) merits care£-jl a.tei’tion in future evaluation research. In any caJe., the data at. nand 1joi i. to leadership au Lhe...o ew unItits. IidofuIndad WUtly b j uIliCJ t o Itave di ic u1Lty t al1k I Ig i iot~ f l a1y w i L It theair moldiurt atLsal I I I.tiodad of j ainitig...prelvious war, alterable only by death, wounding, disease , breakdown, or the need to refit end retrain a unit was now changed to one in which a fixed term

  12. Field Evaluation of Programmable Thermostats

    SciTech Connect

    Sachs, O.; Tiefenbeck, V.; Duvier, C.; Qin, A.; Cheney, K.; Akers, C.; Roth, K.

    2012-12-01

    Prior research suggests that poor programmable thermostats usability may prevent their effective use to save energy. We hypothesized that home occupants with a high-usability thermostats would be more likely to use them to save energy than people with a basic thermostat. We randomly installed a high-usability thermostat in half the 77 apartments of an affordable housing complex, installing a basic thermostat in the other half. During the heating season, we collected space temperature and furnace on-off data to evaluate occupant interaction with the thermostats, foremost nighttime setbacks. We found that thermostat usability did not influence energy-saving behaviors, finding no significant difference in temperature maintained among apartments with high- and low-usability thermostats.

  13. Local arrangement of particles in magnetic fluids due to the measurement alternating field

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Marin, C. N.; Malaescu, I.; Raj, K.; Popoiu, C.

    2017-09-01

    Changes in the magnetic susceptibility spectrum of ferrofluids, χ(ω), due to the nanoparticle agglomeration are common when a static magnetic field is superimposed on the measuring field, but here we report on changes which occur in the absence of a static magnetic field, solely in the presence of the measuring field, over the frequency range of 50 Hz-13 MHz and irrespective of the colloidal stability of samples. The result is explained in terms of local rearrangement of particles within ferrofluids subjected to low frequency alternating magnetic field.

  14. Electric field due to velocity space particle loss in field-reversed configurations

    SciTech Connect

    Hsiao, M.; Staudenmeier, J.L.; Chiang, P.

    1989-02-01

    Particle confinement criteria for velocity space particle loss are used to calculate the radial and axial electric potential profiles in field-reversed configurations (FRC's). Assuming Vlasov equilibrium distribution functions for both electrons and ions, the density profile and the potential profile are calculated self-consistently. With rest Maxwellian distribution functions for both species and the Hill's vortex magnetic configuration, a radial electric field of about 0--70 V/cm and an axial electric field of about 0--4 V/cm, depending on positions, have been found for a typical set of experimental parameters: electron temperature T/sub e/ = 100 eV, ion temperature T/sub i/ = 200 eV, magnetic field B/sub 0/ = 5500 G, separatrix radius r/sub s/ = 12 cm, and elongation factor k = 5. The corresponding density profile has behavior similar to profiles observed in the experiments. Cases using rigid-rotor distribution functions with different rigid rotating frequencies are also studied.

  15. Splenic abscess due to blastomycosis: scintigraphic, sonographic, and CT evaluation

    SciTech Connect

    Dubuisson, R.L.; Jones, T.B.

    1983-01-01

    This paper describes the radiologic evaluation of a case of splenic abscess secondary to North American blastomycosis in a known intravenous drug abuser, a disease not believed to be previously reported in the radiologic literature. Dynamic computed tomography proved especially useful in narrowing the diagnostic possibilities and excluding vascular lesions.

  16. Evaluating and minimizing noise impact due to aircraft flyover

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.; Cook, G.

    1979-01-01

    Existing techniques were used to assess the noise impact on a community due to aircraft operation and to optimize the flight paths of an approaching aircraft with respect to the annoyance produced. Major achievements are: (1) the development of a population model suitable for determining the noise impact, (2) generation of a numerical computer code which uses this population model along with the steepest descent algorithm to optimize approach/landing trajectories, (3) implementation of this optimization code in several fictitious cases as well as for the community surrounding Patrick Henry International Airport, Virginia.

  17. Histological evaluation of hair follicle due to papain's depilatory effect.

    PubMed

    Traversa, Eduardo; Machado-Santelli, Gláucia Maria; Velasco, Maria Valéria Robles

    2007-04-20

    Histological alterations in the skin and hair follicle of mice were evaluated as a result of the application of gel and cream formulas containing papain as a harmless treatment for hirsutism. Papain is a proteolytic enzyme and it has been used in pharmaceutical, cosmetic and nutrition areas. The purpose of this study was to evaluate the efficacy of a depilatory product, through histological analysis using light microscopy. Gel and cream formulas containing papain were developed and daily applied on the back of two groups of mice for 31 days. The depilatory effect of the gel formula applied on the first group was less evident. The second group treated with the cream formula presented an intensive depilatory effect; the morphometrical analysis showed dilation of about 55% of the hair follicle lumen and an increase of the thickness of epidermis. Papain cream had a significantly higher depilatory effect than the papain gel.

  18. Evaluation of the annoyance due to helicopter rotor noise

    NASA Technical Reports Server (NTRS)

    Sternfeld, H., Jr.; Doyle, L. B.

    1978-01-01

    A program was conducted in which 25 test subjects adjusted the levels of various helicopter rotor spectra until the combination of the harmonic noise and a broadband background noise was judged equally annoying as a higher level of the same broadband noise spectrum. The subjective measure of added harmonic noise was equated to the difference in the two levels of broadband noise. The test participants also made subjective evaluations of the rotor noise signatures which they created. The test stimuli consisted of three degrees of rotor impulsiveness, each presented at four blade passage rates. Each of these 12 harmonic sounds was combined with three broadband spectra and was adjusted to match the annoyance of three different sound pressure levels of broadband noise. Analysis of variance indicated that the important variables were level and impulsiveness. Regression analyses indicated that inclusion of crest factor improved correlation between the subjective measures and various objective or physical measures.

  19. Evaluation of speech interference due to noise and reverberation

    NASA Astrophysics Data System (ADS)

    Tokuyama, H.

    1988-12-01

    Experiments were conducted to investigate the effect of noise and reverberation on speech intelligibility and to find a simple method for evaluating the quality of speech transmission. Articulation scores and subjectively judged intelligibility of sentences were obtained in a laboratory situation together with the physical measure of the cross-correlation between the source and the listening point. The effect of broadband steady noise was examined by a monosyllable articulation test and subjective judgment of speech interference. A three-syllable articulation test was used to detect the effect of reverberation. These subjective indices showed correspondence with the source to listening point cross-correlation. The measurement of cross-correlation appeared to be effective as an objective method for estimating speech interference.

  20. Image quality evaluation of light field photography

    NASA Astrophysics Data System (ADS)

    Fu, Qiang; Zhou, Zhiliang; Yuan, Yan; Xiangli, Bin

    2011-01-01

    Light field photography captures 4D radiance information of a scene. Digital refocusing and digital correction of aberrations could be done after the photograph is taken. However, capturing 4D light field is costly and tradeoffs between different image quality metrics should be made and evaluated. This paper explores the effects of light field photography on image quality by quantitatively evaluating some basic criteria for an imaging system. A simulation approach was first developed by ray-tracing a designed light field camera. A standard testing chart followed by ISO 12233 was provided as the input scene. A sequence of light field raw images were acquired and processed by light field rendering methods afterwards. Through-focus visual resolution and MTF were calculated and analyzed. As a comparison, the same tests were taken for the same main lens system as the results of conventional photography. An experimental light field system was built up and its performance was tested. This work helps better understanding the pros and cons of light field photography in contrast with conventional imaging methods and perceiving the way to optimize the joint digital-optical design of the system.

  1. Evaluating small-body landing hazards due to blocks

    NASA Astrophysics Data System (ADS)

    Ernst, C.; Rodgers, D.; Barnouin, O.; Murchie, S.; Chabot, N.

    2014-07-01

    Introduction: Landed missions represent a vital stage of spacecraft exploration of planetary bodies. Landed science allows for a wide variety of measurements essential to unraveling the origin and evolution of a body that are not possible remotely, including but not limited to compositional measurements, microscopic grain characterization, and the physical properties of the regolith. To date, two spacecraft have performed soft landings on the surface of a small body. In 2001, the Near Earth Asteroid Rendezvous (NEAR) mission performed a controlled descent and landing on (433) Eros following the completion of its mission [1]; in 2005, the Hayabusa spacecraft performed two touch-and-go maneuvers at (25143) Itokawa [2]. Both landings were preceded by rendezvous spacecraft reconnaissance, which enabled selection of a safe landing site. Three current missions have plans to land on small bodies (Rosetta, Hayabusa 2, and OSIRIS-REx); several other mission concepts also include small-body landings. Small-body landers need to land at sites having slopes and block abundances within spacecraft design limits. Due to the small scale of the potential hazards, it can be difficult or impossible to fully characterize a landing surface before the arrival of the spacecraft at the body. Although a rendezvous mission phase can provide global reconnaissance from which a landing site can be chosen, reasonable a priori assurance that a safe landing site exists is needed to validate the design approach for the spacecraft. Method: Many robotic spacecraft have landed safely on the Moon and Mars. Images of these landing sites, as well as more recent, extremely high-resolution orbital datasets, have enabled the comparison of orbital block observations to the smaller blocks that pose hazards to landers. Analyses of the Surveyor [3], Viking 1 and 2, Mars Pathfinder, Phoenix, Spirit, Opportunity, and Curiosity landing sites [4--8] have indicated that for a reasonable difference in size (a factor

  2. Evaluation of near-field earthquake effects

    SciTech Connect

    Shrivastava, H.P.

    1994-11-01

    Structures and equipment, which are qualified for the design basis earthquake (DBE) and have anchorage designed for the DBE loading, do not require an evaluation of the near-field earthquake (NFE) effects. However, safety class 1 acceleration sensitive equipment such as electrical relays must be evaluated for both NFE and DBE since they are known to malfunction when excited by high frequency seismic motions.

  3. Laser range pole field evaluation report

    NASA Technical Reports Server (NTRS)

    1973-01-01

    A field evaluation was made of the laser pole equipment. The basic plan for the evaluation was to expose the equipment to the actual people and environment for which it was intended and determine, through the use of the equipment, its resultant effectivity in terms of improved performance. Results show the equipment performed better than expected in the high elevation clean air of Colorado, and did as well in Tennessee.

  4. Evaluation of eddy-current probe signals due to cracks in ferromagnetic parts of fast reactor

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Bowler, John R.

    2017-02-01

    Eddy current testing to evaluate the condition of metallic parts in a sodium cooled fast reactor under standby conditions is challenging due to the presence of liquid sodium at 250 °C. The eddy current test system should be sensitive enough to capture small signal changes and hence an advanced inspection systems is needed. We have developed new hardware and improved numerical models to predict the eddy current probe signal due to cracks in metallic fast reactor parts by using volume integral equation method. The analytical expressions are derived for the quasi-static time-harmonic electromagnetic fields of a circular eddy current coil which interacts with conductive plate. Naturally, the method of moment is used to approximate the integral equation and obtain the discrete approximation of the field in the crack domain. A simple and accurate analytical method for dealing with the hyper-singularity element evaluation is also provided. An accurate controlled experiment is carried out on the ferromagnetic stainless steel plate with precision made notch to obtain reference impedance changes for comparison with the theoretical model predictions. Good agreement between predictions and experiment is obtained.

  5. Could field cancerization be interpreted as a biochemical anomaly amplification due to transformed cells?

    PubMed

    Fernández P, Janeth; Méndez-Sánchez, Stelia C; Gonzalez-Correa, C A; Miranda, David A

    2016-12-01

    Field cancerization is a concept used to explain cellular and molecular alterations in tissue associated to neoplasia and cancer. This effect was proposed by Slaughter in order to explain the development of multiple primary tumors and locally recurrent cancer. The particular changes associated with this effect, in each type of cancer, have been detected even at distances greater than 10cm off the tumor, in areas classified as normal by histopathological studies. Early detection of lung, colon, and ovary cancer has been reported by the use of Partial Wave Microscopy Spectroscopy (PWS) and has been explained in terms of the field cancerization effect. Until now, field cancerization has been studied as a field effect and we hypothesize that it can be understood as an amplifying effect of biochemical abnormalities in cells, which leads us to ask the question: Could field cancerization be interpreted as a biochemical anomaly amplification due to transformed cells? We propose this question because the biochemical changes due to field cancerization alter the dynamics of molecules and cells in abnormal tissues in comparison to normal ones, these alterations modify the interaction of intracellular and extracellular medium, as well as cellular movement. We hypothesize that field cancerization when interpreted as an amplification effect can be used for the early detection of cancer by measuring the change of cell dynamics. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Deformation of a nearly hemispherical conducting drop due to an electric field: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Corson, L. T.; Tsakonas, C.; Duffy, B. R.; Mottram, N. J.; Sage, I. C.; Brown, C. V.; Wilson, S. K.

    2014-12-01

    We consider, both theoretically and experimentally, the deformation due to an electric field of a pinned nearly hemispherical static sessile drop of an ionic fluid with a high conductivity resting on the lower substrate of a parallel-plate capacitor. Using both numerical and asymptotic approaches, we find solutions to the coupled electrostatic and augmented Young-Laplace equations which agree very well with the experimental results. Our asymptotic solution for the drop interface extends previous work in two ways, namely, to drops that have zero-field contact angles that are not exactly π/2 and to higher order in the applied electric field, and provides useful predictive equations for the changes in the height, contact angle, and pressure as functions of the zero-field contact angle, drop radius, surface tension, and applied electric field. The asymptotic solution requires some numerical computations, and so a surprisingly accurate approximate analytical asymptotic solution is also obtained.

  7. National Home Start Evaluation: Field Procedures Manual.

    ERIC Educational Resources Information Center

    Nauta, Marrit J.

    This field procedures manual for community interviewers and site coordinators, one of a series of documents on the evaluation of the National Home Start program (NHS), describes specific testing procedures for collecting family data. A federally funded demonstration program, NHS is aimed at providing home-based services (such as health, education,…

  8. Field evaluation of Bemisia parasitoids in Texas

    USDA-ARS?s Scientific Manuscript database

    Two methods were employed to assess the potential of candidate parasitoid species/strains to parasitize B. tabaci under field conditions in Texas. Sleeve cage evaluations were conducted in kale, cantaloupe melons, and cotton in 1994–1995. In kale, the highest parasitism rates were observed for two s...

  9. Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field

    NASA Technical Reports Server (NTRS)

    Sellers, C. C.; Walker, John S.; Szofran, Frank R.; Motakef, Shariar

    2000-01-01

    This paper treats a liquid-metal flow inside an electrically insulating cylinder with electrically conducting solids above and below the liquid region. There is a uniform axial magnetic field, and there is an electric current through the liquid and both solids. Since the lower liquid-solid interface is concave into the solid and since the liquid is a better electrical conductor than the adjacent solid, the electric current is locally concentrated near the centerline. The return to a uniform current distribution involves a radial electric current which interacts with the axial magnetic field to drive an azimuthal flow. The axial variation of the centrifugal force due to the azimuthal velocity drives a meridional circulation with radial and axial velocities. This problem models the effects of Peltier marking during the vertical Bridgman growth of semiconductor crystals with an externally applied magnetic field, where the meridional circulation due to the Peltier Current may produce important mixing in the molten semiconductor.

  10. Surface potential at a ferroelectric grain due to asymmetric screening of depolarization fields

    SciTech Connect

    Genenko, Yuri A. Hirsch, Ofer; Erhart, Paul

    2014-03-14

    Nonlinear screening of electric depolarization fields, generated by a stripe domain structure in a ferroelectric grain of a polycrystalline material, is studied within a semiconductor model of ferroelectrics. It is shown that the maximum strength of local depolarization fields is rather determined by the electronic band gap than by the spontaneous polarization magnitude. Furthermore, field screening due to electronic band bending and due to presence of intrinsic defects leads to asymmetric space charge regions near the grain boundary, which produce an effective dipole layer at the surface of the grain. This results in the formation of a potential difference between the grain surface and its interior of the order of 1 V, which can be of either sign depending on defect transition levels and concentrations. Exemplary acceptor doping of BaTiO{sub 3} is shown to allow tuning of the said surface potential in the region between 0.1 and 1.3 V.

  11. Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field

    NASA Technical Reports Server (NTRS)

    Sellers, C. C.; Walker, John S.; Szofran, Frank R.; Motakef, Shariar

    2000-01-01

    This paper treats a liquid-metal flow inside an electrically insulating cylinder with electrically conducting solids above and below the liquid region. There is a uniform axial magnetic field, and there is an electric current through the liquid and both solids. Since the lower liquid-solid interface is concave into the solid and since the liquid is a better electrical conductor than the adjacent solid, the electric current is locally concentrated near the centerline. The return to a uniform current distribution involves a radial electric current which interacts with the axial magnetic field to drive an azimuthal flow. The axial variation of the centrifugal force due to the azimuthal velocity drives a meridional circulation with radial and axial velocities. This problem models the effects of Peltier marking during the vertical Bridgman growth of semiconductor crystals with an externally applied magnetic field, where the meridional circulation due to the Peltier Current may produce important mixing in the molten semiconductor.

  12. Evaluation of military field-water quality

    SciTech Connect

    Daniels, J.I.; Gallegos, G.M.

    1990-05-01

    This is the first and summary volume of the nine-volume study entitled Evaluation of Military Field-Water Quality. This study is a comprehensive assessment of the chemical, radiological, and biological constituents of field-water supplied that could pose health risks to military personnel around the world; it also provides a detailed evaluation of the field-water-treatment capability of the US Armed Forces. This study identifies as being of concern three physical properties, i.e., turbidity, color, and total dissolved solids; seven chemical constituents, i.e., chloride, magnesium, sulfate, arsenic, cyanide, lindane, and metabolites of algae and associated aquatic bacteria; and over twenty types of water-related pathogenic microorganisms. It also addresses five threat agents, i.e., hydrogen cyanide, radioactivity, organophosphorous nerve agents, the trichotecene mycotoxin T-2, and lewisite. An overview of the criteria and recommendations for standards for these constituents for short- term and long-term exposure periods are presented in this volume, as are health-effects summaries for assessing the potential soldier performance degradation when recommended standards are exceeded. In addition, the existing military field-water-treatment capability is reviewed, and an abbreviated discussion is presented of the general physical, chemical, and biological qualities of field waters in geographic regions worldwide, representing potential theaters of operation for US military forces. Finally, research recommendations are outlined. 18 figs., 6 tabs.

  13. Simplified evaluation of magnetic field fluctuation thermometry

    NASA Astrophysics Data System (ADS)

    Wübbeler, G.; Elster, C.

    2013-11-01

    Recently, a Bayesian approach has been proposed for evaluating magnetic field fluctuation thermometry measurements. The approach provides a coherent use of calibration results in the inference of the temperature from subsequent magnetic field fluctuation thermometry measurements. It does, however, rely on an extensive numerical effort. In this paper, we develop simplified parametric and non-parametric analysis schemes. For all approaches we derive analytic expressions for the resulting temperature estimates and their uncertainties. We assess the new approaches and show in particular that an easy to apply non-parametric analysis yields results which are in good agreement with those obtained by the Bayesian inference.

  14. Observation of megagauss-field topology changes due to magnetic reconnection in laser-produced plasmas.

    PubMed

    Li, C K; Séguin, F H; Frenje, J A; Rygg, J R; Petrasso, R D; Town, R P J; Landen, O L; Knauer, J P; Smalyuk, V A

    2007-08-03

    The spatial structure and temporal evolution of megagauss magnetic fields generated by interactions of up to 4 laser beams with matter were studied with an innovative, time-gated proton radiography method that produces images of unprecedented clarity because it uses an isotropic, truly monoenergetic back-lighter (14.7-MeV protons from D3He nuclear fusion reactions). Quantitative field maps reveal precisely and directly, for the first time, changes in the magnetic topology due to reconnection in a high-energy-density plasma (n(e) approximately 10(20)-10(22) cm(-3), T(e) approximately 1 keV).

  15. Dynamical Effects Due to Fringe Field of the Magnets in Circular Accelerators

    SciTech Connect

    Cai, Y.; Nosochkov, Yu.; /SLAC

    2005-05-16

    The leading Lie generators, including the chromatic effects, due to hard-edge fringe field of single multipole and solenoid are derived from the vector potentials within a Hamiltonian system. These nonlinear generators are applied to the interaction region of PEP-II to analyze the linear errors due to the feed-down from the off-centered quadrupoles and solenoid. The nonlinear effects of tune shifts at large amplitude, the synchro-betatron sidebands near half integer and their impacts on the dynamic aperture are studied in the paper.

  16. Disassociation of electrons from partially stripped ion beams due to strong magnetic fields

    SciTech Connect

    Tepikian, S.; Lee, S.Y.

    1989-01-01

    We study the probability of dissociating an electron from partially stripped ions in the AGS. Our calculation indicates that the probability for electron disassociation due to the strong external magnetic field in the AGS is very small for tightly bounded electrons. Two methods are used to estimate this effect: a one-dimensional JWKB method; an energy density approximation. Both methods yield a consistent picture to support the idea of accelerating the partially stripped ions in the AGS, which requires some upgrade in the vacuum pressure due to other processes such as electron capture and ionization. 5 refs., 4 figs.

  17. The magnetic field inside a layered anisotropic spherical conductor due to internal sources

    NASA Astrophysics Data System (ADS)

    Nieminen, Jaakko O.; Stenroos, Matti

    2016-01-01

    Recent advances in neuronal current imaging using magnetic resonance imaging and in invasive measurement of neuronal magnetic fields have given a need for methods to compute the magnetic field inside a volume conductor due to source currents that are within the conductor. In this work, we derive, verify, and demonstrate an analytical expression for the magnetic field inside an anisotropic multilayer spherically symmetric conductor due to an internal current dipole. We casted an existing solution for electric field to vector spherical harmonic (VSH) form. Next, we wrote an ansatz for the magnetic field using toroidal-poloidal decomposition that uses the same VSHs. Using properties of toroidal and poloidal components and VSHs and applying magnetic scalar potential, we then formulated a series expression for the magnetic field. The convergence of the solution was accelerated by formulating the solution using an addition-subtraction method. We verified the resulting formula against boundary-element method. The verification showed that the formulas and implementation are correct; 99th percentiles of amplitude and angle differences between the solutions were below 0.5% and 0.5°, respectively. As expected, the addition-subtraction model converged faster than the unaccelerated model; close to the source, 250 terms gave relative error below 1%, and the number of needed terms drops fast, as the distance to the source increases. Depending on model conductivities and source position, field patterns inside a layered sphere may differ considerably from those in a homogeneous sphere. In addition to being a practical modeling tool, the derived solution can be used to verify numerical methods, especially finite-element method, inside layered anisotropic conductors.

  18. Field evaluation of internally sealed concrete

    NASA Astrophysics Data System (ADS)

    Spring, R. J.; Smith, D. R.; Neal, B. F.; Woodstrom, J. H.

    1980-02-01

    Portland cement concrete containing wax beads was evaluated. Performance of the deck concrete was evaluated after a little more than three years of service. The deck was found to be badly cracked. From cores, it was determined that the cracks extended at least to the reinforcing steel, and in some cases, entirely through the 8 1/2 inch deck. It is concluded from an examination of the cracked faces of cores that cracking was probably caused by shrinkage of the fresh concrete due to some slight delay in curing. A dry wind was blowing during concrete placement, creating adverse curing conditions.

  19. Additional Enhancement of Electric Field in Surface-Enhanced Raman Scattering due to Fresnel Mechanism

    NASA Astrophysics Data System (ADS)

    Jayawardhana, Sasani; Rosa, Lorenzo; Juodkazis, Saulius; Stoddart, Paul R.

    2013-08-01

    Surface-enhanced Raman scattering (SERS) is attracting increasing interest for chemical sensing, surface science research and as an intriguing challenge in nanoscale plasmonic engineering. Several studies have shown that SERS intensities are increased when metal island film substrates are excited through a transparent base material, rather than directly through air. However, to our knowledge, the origin of this additional enhancement has never been satisfactorily explained. In this paper, finite difference time domain modeling is presented to show that the electric field intensity at the dielectric interface between metal particles is higher for ``far-side'' excitation than ``near-side''. This is reasonably consistent with the observed enhancement for silver islands on SiO2. The modeling results are supported by a simple analytical model based on Fresnel reflection at the interface, which suggests that the additional SERS signal is caused by near-field enhancement of the electric field due to the phase shift at the dielectric interface.

  20. Plasma heating at collisionless shocks due to the kinetic cross-field streaming instability

    NASA Technical Reports Server (NTRS)

    Winske, D.; Quest, K. B.; Tanaka, M.; Wu, C. S.

    1985-01-01

    Heating at collisionless shocks due to the kinetic cross-field streaming instability, which is the finite beta (ratio of plasma to magnetic pressure) extension of the modified two stream instability, is studied. Heating rates are derived from quasi-linear theory and compared with results from particle simulations to show that electron heating relative to ion heating and heating parallel to the magnetic field relative to perpendicular heating for both the electrons and ions increase with beta. The simulations suggest that electron dynamics determine the saturation level of the instability, which is manifested by the formation of a flattop electron distribution parallel to the magnetic field. As a result, both the saturation levels of the fluctuations and the heating rates decrease sharply with beta. Applications of these results to plasma heating in simulations of shocks and the earth's bow shock are described.

  1. Field collapse due to band-tail charge in amorphous silicon solar cells

    SciTech Connect

    Wang, Qi; Crandall, R.S.; Schiff, E.A.

    1996-05-01

    It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain the decrease of FF with the increasing light intensity.

  2. Field collapse due to band-tail charge in amorphous silicon solar cells

    SciTech Connect

    Wang, Qi; Crandall, R S; Schiff, E A

    1996-05-01

    It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain the decrease of FF with the increasing light intensity.

  3. Evaluating Differences in Landscape Interpretation between Webcam and Field-Based Experiences

    ERIC Educational Resources Information Center

    Kolivras, Korine N.; Luebbering, Candice R.; Resler, Lynn M.

    2012-01-01

    Field trips have become less common due to issues including budget constraints and large class sizes. Research suggests that virtual field trips can substitute for field visits, but the role of webcams has not been evaluated. To investigate the potential for webcams to substitute for field trips, participants viewed urban and physical landscapes…

  4. Evaluating Differences in Landscape Interpretation between Webcam and Field-Based Experiences

    ERIC Educational Resources Information Center

    Kolivras, Korine N.; Luebbering, Candice R.; Resler, Lynn M.

    2012-01-01

    Field trips have become less common due to issues including budget constraints and large class sizes. Research suggests that virtual field trips can substitute for field visits, but the role of webcams has not been evaluated. To investigate the potential for webcams to substitute for field trips, participants viewed urban and physical landscapes…

  5. Theoretical and experimental comparisons of nearfield electrogalvanic fields due to nonlinear polarization layers

    NASA Astrophysics Data System (ADS)

    Kasper, R. G.

    1985-02-01

    Based on completed experimental electric-field scans and the corresponding finite-element field predictions, it appears that the finite-element numerical technique presents a strong analytical tool in calculating the nearfield (within 650 micrometers electric-field distributions about active microcells. This was analytically achieved with the new double membrane finite-element configuration representing nonlinear polarization and by using a local tangent slope (impedance) definition dependent on the local potential difference. The experimental determination of the normal current was realized with a newly developed scanning vibrating electrode technique. The finite-element model utilizes a priori measured uncoupled polarization curves for pure iron and pure copper. The current densities and the electric field intensity was calculated for all the grid points within the electrolyte and on its boundaries. Results appear to indicate that first order anodic mass loss can be predicted using finite-element predicted current density distributions on the anodic surface and the imposition of Faraday's law. The electric-field correlation established for the normal current-density vector provides the confidence to proceed in the evaluation of electric fields associated with pitting and crevice corrosion.

  6. Highly Effective Conductance Modulation in Planar Silicene Field Effect Devices Due to Buckling

    PubMed Central

    Al-Dirini, Feras; Hossain, Faruque M.; Mohammed, Mahmood A.; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2015-01-01

    Silicene is an exciting two-dimensional material that shares many of graphene’s electronic properties, but differs in its structural buckling. This buckling allows opening a bandgap in silicene through the application of a perpendicular electric field. Here we show that this buckling also enables highly effective modulation of silicene’s conductance by means of an in-plane electric field applied through silicene side gates, which can be realized concurrently within the same silicene monolayer. We illustrate this by using silicene to implement Self-Switching Diodes (SSDs), which are two-dimensional field effect nanorectifiers realized within a single silicene monolayer. Our quantum simulation results show that the atomically-thin silicene SSDs, with sub-10 nm dimensions, achieve a current rectification ratio that exceeds 200, without the need for doping, representing a 30 fold enhancement over graphene SSDs. We attribute this enhancement to a bandgap opening due to the in-plane electric field, as a consequence of silicene’s buckling. Our results suggest that silicene is a promising material for the realization of planar field effect devices. PMID:26441200

  7. Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals

    DOE PAGES

    Rice, William D.; Liu, Wenyong; Baker, Thomas A.; ...

    2015-11-23

    Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn2+, Co2+ and so on) couple to band carriers via strong sp–d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical √N fluctuations of N spins are expected to generate giant effective magnetic fields Beff, which should dramatically impactmore » carrier spin dynamics, even in the absence of any applied field. In this paper, we directly and unambiguously reveal the large Beff that exist in Mn2+-doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300–600 GHz) spin precession of photoinjected electrons is observed, indicating Beff ~ 15-30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. Finally, these signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn2+ moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials.« less

  8. Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals

    SciTech Connect

    Rice, William D.; Liu, Wenyong; Baker, Thomas A.; Sinitsyn, Nikolai A.; Klimov, Victor Ivanovich; Crooker, Scott A.

    2015-11-23

    Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn2+, Co2+ and so on) couple to band carriers via strong sp–d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical √N fluctuations of N spins are expected to generate giant effective magnetic fields Beff, which should dramatically impact carrier spin dynamics, even in the absence of any applied field. In this paper, we directly and unambiguously reveal the large Beff that exist in Mn2+-doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300–600 GHz) spin precession of photoinjected electrons is observed, indicating Beff ~ 15-30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. Finally, these signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn2+ moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials.

  9. Highly Effective Conductance Modulation in Planar Silicene Field Effect Devices Due to Buckling

    NASA Astrophysics Data System (ADS)

    Al-Dirini, Feras; Hossain, Faruque M.; Mohammed, Mahmood A.; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2015-10-01

    Silicene is an exciting two-dimensional material that shares many of graphene’s electronic properties, but differs in its structural buckling. This buckling allows opening a bandgap in silicene through the application of a perpendicular electric field. Here we show that this buckling also enables highly effective modulation of silicene’s conductance by means of an in-plane electric field applied through silicene side gates, which can be realized concurrently within the same silicene monolayer. We illustrate this by using silicene to implement Self-Switching Diodes (SSDs), which are two-dimensional field effect nanorectifiers realized within a single silicene monolayer. Our quantum simulation results show that the atomically-thin silicene SSDs, with sub-10 nm dimensions, achieve a current rectification ratio that exceeds 200, without the need for doping, representing a 30 fold enhancement over graphene SSDs. We attribute this enhancement to a bandgap opening due to the in-plane electric field, as a consequence of silicene’s buckling. Our results suggest that silicene is a promising material for the realization of planar field effect devices.

  10. Highly Effective Conductance Modulation in Planar Silicene Field Effect Devices Due to Buckling.

    PubMed

    Al-Dirini, Feras; Hossain, Faruque M; Mohammed, Mahmood A; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2015-10-06

    Silicene is an exciting two-dimensional material that shares many of graphene's electronic properties, but differs in its structural buckling. This buckling allows opening a bandgap in silicene through the application of a perpendicular electric field. Here we show that this buckling also enables highly effective modulation of silicene's conductance by means of an in-plane electric field applied through silicene side gates, which can be realized concurrently within the same silicene monolayer. We illustrate this by using silicene to implement Self-Switching Diodes (SSDs), which are two-dimensional field effect nanorectifiers realized within a single silicene monolayer. Our quantum simulation results show that the atomically-thin silicene SSDs, with sub-10 nm dimensions, achieve a current rectification ratio that exceeds 200, without the need for doping, representing a 30 fold enhancement over graphene SSDs. We attribute this enhancement to a bandgap opening due to the in-plane electric field, as a consequence of silicene's buckling. Our results suggest that silicene is a promising material for the realization of planar field effect devices.

  11. Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals

    NASA Astrophysics Data System (ADS)

    Rice, William D.; Liu, Wenyong; Baker, Thomas A.; Sinitsyn, Nikolai A.; Klimov, Victor I.; Crooker, Scott A.

    2016-02-01

    Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn2+, Co2+ and so on) couple to band carriers via strong sp-d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical fluctuations of N spins are expected to generate giant effective magnetic fields Beff, which should dramatically impact carrier spin dynamics, even in the absence of any applied field. Here we directly and unambiguously reveal the large Beff that exist in Mn2+-doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300-600 GHz) spin precession of photoinjected electrons is observed, indicating Beff ˜ 15 -30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. These signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn2+ moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials.

  12. Field evaluation of a VOST sampling method

    SciTech Connect

    Jackson, M.D.; Johnson, L.D.; Fuerst, R.G.; McGaughey, J.F.; Bursey, J.T.; Merrill, R.G.

    1994-12-31

    The VOST (SW-846 Method 0030) specifies the use of Tenax{reg_sign} and a particular petroleum-based charcoal (SKC Lot 104, or its equivalent), that is no longer commercially available. In field evaluation studies of VOST methodology, a replacement petroleum-based charcoal has been used: candidate replacement sorbents for charcoal were studied, and Anasorb{reg_sign} 747, a carbon-based sorbent, was selected for field testing. The sampling train was modified to use only Anasorb{reg_sign} in the back tube and Tenax{reg_sign} in the two front tubes to avoid analytical difficulties associated with the analysis of the sequential bed back tube used in the standard VOST train. The standard (SW-846 Method 0030) and the modified VOST methods were evaluated at a chemical manufacturing facility using a quadruple probe system with quadruple trains. In this field test, known concentrations of the halogenated volatile organic compounds, that are listed in the Clean Air Act Amendments of 1990, Title 3, were introduced into the VOST train and the modified VOST train, using the same certified gas cylinder as a source of test compounds. Statistical tests of the comparability of methods were performed on a compound-by-compound basis. For most compounds, the VOST and modified VOST methods were found to be statistically equivalent.

  13. On the gravitational potential and field anomalies due to thin mass layers

    NASA Technical Reports Server (NTRS)

    Ockendon, J. R.; Turcotte, D. L.

    1977-01-01

    The gravitational potential and field anomalies for thin mass layers are derived using the technique of matched asymptotic expansions. An inner solution is obtained using an expansion in powers of the thickness and it is shown that the outer solution is given by a surface distribution of mass sources and dipoles. Coefficients are evaluated by matching the inner expansion of the outer solution with the outer expansion of the inner solution. The leading term in the inner expansion for the normal gravitational field gives the Bouguer formula. The leading term in the expansion for the gravitational potential gives an expression for the perturbation to the geoid. The predictions given by this term are compared with measurements by satellite altimetry. The second-order terms in the expansion for the gravitational field are required to predict the gravity anomaly at a continental margin. The results are compared with observations.

  14. Evaluation of PV Module Field Performance

    SciTech Connect

    Wohlgemuth, John; Silverman, Timothy; Miller, David C.; McNutt, Peter; Kempe, Michael; Deceglie, Michael

    2015-06-14

    This paper describes an effort to inspect and evaluate PV modules in order to determine what failure or degradation modes are occurring in field installations. This paper will report on the results of six site visits, including the Sacramento Municipal Utility District (SMUD) Hedge Array, Tucson Electric Power (TEP) Springerville, Central Florida Utility, Florida Solar Energy Center (FSEC), the TEP Solar Test Yard, and University of Toledo installations. The effort here makes use of a recently developed field inspection data collection protocol, and the results were input into a corresponding database. The results of this work have also been used to develop a draft of the IEC standard for climate and application specific accelerated stress testing beyond module qualification. TEP Solar Test Yard, and University of Toledo installations. The effort here makes use of a recently developed field inspection data collection protocol, and the results were input into a corresponding database. The results of this work have also been used to develop a draft of the IEC standard for climate and application specific accelerated stress testing beyond module qualification. TEP Solar Test Yard, and University of Toledo installations. The effort here makes use of a recently developed field inspection data collection protocol, and the results were input into a corresponding database. The results of this work have also been used to develop a draft of the IEC standard for climate and application specific accelerated stress testing beyond module qualification.

  15. Tropical Cyclone Motion Due to Environmental Interactions Represented by Empirical Orthogonal Functions of the Vorticity Fields

    DTIC Science & Technology

    1991-06-01

    values along these lines were extracted and were fit with a fifth-order polynomial (Fig. 35). These curves permit an evaluation of each circulation’s...levels. This midlatitude cyclone continued moving southwestward, and acquired many of the characteristics and dynamics of a TUTT cell. Figs. 44 and 45...Dinah (Figs. 63 and 64) did not have any noticeable interaction with Dinah due to the large separation distance and weaker intensity of the TUTT . Table

  16. Absence of Remote Triggering in Geothermal Fields Due to Human Activity

    NASA Astrophysics Data System (ADS)

    Ge, S.; Zhang, Q.; Lin, G.

    2014-12-01

    Operational geothermal fields typically have high seismicity rates, which could be caused by both tectonic and anthropogenic activities. Due to the high background seismicity and possible interaction between fluid and seismic waves, geothermal areas have been recognized to be susceptible to large remote earthquakes. However, whether human activity (geothermal production) affects remote earthquake triggering by changing the stress state is unclear. Here we choose two geothermal fields, Coso and Salton Sea in southern California, to study the spatiotemporal distributions of the triggered earthquakes following the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes. These two geothermal fields have been in operation since 1980s with comparable net capacity, and have long-term geothermal fluid loss. By analyzing the regional catalog recorded by the Southern California Seismic Network, we find that these two operational geothermal areas remain unaffected by the remote mainshocks, whereas the surrounding areas show vigorous triggered responses. We interpret this phenomenon as a result of human activity, which presumably has brought the stress state away from failure by reducing pore pressure. To further understand how much the human activity can affect the stress state, we also conduct a systematic study on Long Valley Caldera in northern California as a comparison site. Long Valley Caldera hosts an active geothermal field with net capacity about one sixth of that in Coso or Salton Sea geothermal field, and the extraction volume is not constantly larger than the injection. We will show comparisons of the triggered response in Long Valley with the two geothermal fields in southern California.

  17. Enhancement of threshold electric field for relativistic runaway electrons due to magnetic fluctuation and synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Li, Shucai; Wang, Lu; Chen, Zhongyong; Huang, Duwei; Tong, Ruihai

    2016-10-01

    The dynamics of relativistic electrons are analyzed using the relativistic Fokker-Planck equation including deceleration due to synchrotron radiation (SR) and radial diffusion loss caused by magnetic fluctuation (MF). Threshold electric field for avalanche growth is enhanced, and the growth rate is reduced by the combined effect of MF and SR as compared to the case with only SR. The threshold electric field is determined by the time scales balance between momentum evolution and radial diffusion loss induced by MF, and increased with level of MF. More importantly, the hysteresis behavior of runaway pointed out by does not exist anymore. This is because the ``seed electrons'' cannot be sustained as a result of diffusion loss. This work was supported by NSFC Grant No. 11305071, and the Ministry of Science and technology of China, under Contract Nos. 2013GB112002, 2015GB111002 and 2015GB111001.

  18. Observation of Megagauss-Field Topology Changes due to Magnetic Reconnection in Laser-Produced Plasmas

    SciTech Connect

    Li, C. K.; Seguin, F. H.; Frenje, J. A.; Rygg, J. R.; Petrasso, R. D.; Town, R. P. J.; Landen, O. L.; Knauer, J. P.; Smalyuk, V. A.

    2007-08-03

    The spatial structure and temporal evolution of megagauss magnetic fields generated by interactions of up to 4 laser beams with matter were studied with an innovative, time-gated proton radiography method that produces images of unprecedented clarity because it uses an isotropic, truly monoenergetic backlighter (14.7-MeV protons from D{sup 3}He nuclear fusion reactions). Quantitative field maps reveal precisely and directly, for the first time, changes in the magnetic topology due to reconnection in a high-energy-density plasma (n{sub e}{approx}10{sup 20}-10{sup 22} cm{sup -3}, T{sub e}{approx}1 keV)

  19. Linearly polarized radiation from astrophysical masers due to magnetic fields of intermediate strength

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    Previous solutions for polarization of astrophysical maser radiation due to closed-shell molecules in a magnetic field have potentially serious limitations. These solutions are mostly based on the approximation that the Zeeman frequency g-Omega is much greater than the rate for stimulated emission R and the rate for decay Gamma of the molecular state. Others are asymptotic solutions obtained for an angular momentum J = 1-0 transition. It has been unclear whether the polarizations due to plausible Zeeman splittings are adequately represented by the solutions obtained for g-Omega/Gamma much greater than 1 and g-Omega/R much greater than 1. Actual masing transitions tend to involve molecular states with angular momenta that are higher than J = 1 and 0. Numerical solutions for the linear polarization are presented here which do not have the foregoing restrictions on the g-Omega and which are not limited to a J = 1-0 transition.

  20. Dispersive FDTD analysis of induced electric field in human models due to electrostatic discharge.

    PubMed

    Hirata, Akimasa; Nagai, Toshihiro; Koyama, Teruyoshi; Hattori, Junya; Chan, Kwok Hung; Kavet, Robert

    2012-07-07

    Contact currents flow from/into a charged human body when touching a grounded conductive object. An electrostatic discharge (ESD) or spark may occur just before contact or upon release. The current may stimulate muscles and peripheral nerves. In order to clarify the difference in the induced electric field between different sized human models, the in-situ electric fields were computed in anatomically based models of adults and a child for a contact current in a human body following ESD. A dispersive finite-difference time-domain method was used, in which biological tissue is assumed to obey a four-pole Debye model. From our computational results, the first peak of the discharge current was almost identical across adult and child models. The decay of the induced current in the child was also faster due mainly to its smaller body capacitance compared to the adult models. The induced electric fields in the forefingers were comparable across different models. However, the electric field induced in the arm of the child model was found to be greater than that in the adult models primarily because of its smaller cross-sectional area. The tendency for greater doses in the child has also been reported for power frequency sinusoidal contact current exposures as reported by other investigators.

  1. Magnetic field shift due to mechanical vibration in functional magnetic resonance imaging.

    PubMed

    Foerster, Bernd U; Tomasi, Dardo; Caparelli, Elisabeth C

    2005-11-01

    Mechanical vibrations of the gradient coil system during readout in echo-planar imaging (EPI) can increase the temperature of the gradient system and alter the magnetic field distribution during functional magnetic resonance imaging (fMRI). This effect is enhanced by resonant modes of vibrations and results in apparent motion along the phase encoding direction in fMRI studies. The magnetic field drift was quantified during EPI by monitoring the resonance frequency interleaved with the EPI acquisition, and a novel method is proposed to correct the apparent motion. The knowledge on the frequency drift over time was used to correct the phase of the k-space EPI dataset. Since the resonance frequency changes very slowly over time, two measurements of the resonance frequency, immediately before and after the EPI acquisition, are sufficient to remove the field drift effects from fMRI time series. The frequency drift correction method was tested "in vivo" and compared to the standard image realignment method. The proposed method efficiently corrects spurious motion due to magnetic field drifts during fMRI. (c) 2005 Wiley-Liss, Inc.

  2. Temperature fields due to jet induced mixing in a typical OTV tank

    NASA Technical Reports Server (NTRS)

    Hochstein, J. I.; Ji, Hyun-Chul; Aydelott, J. C.

    1987-01-01

    The Eclipse Code is being developed as a general tool for analysis of cryogenic propellant behavior in spacecraft tankage. The focus of the work being reported is on prediction of temperature fields due to introduction of a cold jet along the centerline of a typical Orbit Transfer Vehicle tank. A brief description of the formulations used for modeling heat transfer and turbulent flow is presented. Code performance is verified through comparison to experimental data for mixing in small scale tanks. An unexpected difficulty in computing long duration flows is reviewed. Preliminary results for a partially filled full scale tank are obtained by approximating the free surface by a spherical solid boundary.

  3. Laboratory and field based evaluation of chromatography ...

    EPA Pesticide Factsheets

    The Monitor for AeRosols and GAses in ambient air (MARGA) is an on-line ion-chromatography-based instrument designed for speciation of the inorganic gas and aerosol ammonium-nitrate-sulfate system. Previous work to characterize the performance of the MARGA has been primarily based on field comparison to other measurement methods to evaluate accuracy. While such studies are useful, the underlying reasons for disagreement among methods are not always clear. This study examines aspects of MARGA accuracy and precision specifically related to automated chromatography analysis. Using laboratory standards, analytical accuracy, precision, and method detection limits derived from the MARGA chromatography software are compared to an alternative software package (Chromeleon, Thermo Scientific Dionex). Field measurements are used to further evaluate instrument performance, including the MARGA’s use of an internal LiBr standard to control accuracy. Using gas/aerosol ratios and aerosol neutralization state as a case study, the impact of chromatography on measurement error is assessed. The new generation of on-line chromatography-based gas and particle measurement systems have many advantages, including simultaneous analysis of multiple pollutants. The Monitor for Aerosols and Gases in Ambient Air (MARGA) is such an instrument that is used in North America, Europe, and Asia for atmospheric process studies as well as routine monitoring. While the instrument has been evaluat

  4. Evaluation of pediatric community field trips.

    PubMed

    Molnar, E T; Knasel, A L

    1987-05-01

    A field trip program for junior medical students on a pediatric clinical clerkship acquainted students with the care of normal and handicapped children in community settings of school, day care center, residential treatment, or diagnostic facilities.A program evaluation by pre and post-trip survey demonstrated a positive change in students' knowledge and attitude in general, which was unaffected by such factors as sex, previous experience in a medical setting, and previous experience with handicapped children.As an integral part of the pediatric clerkship, the field trip appears to have been a positive experience for students, as it met their educational and emotional needs. Subjective evaluation indicated that many students formed insightful and compassionate judgments about handicapped children.Although the increase in knowledge and sensitivity of the students, as reflected in the pre-and post-test, was not statistically significant, the benefit to the students, to the personnel of the agencies, and ultimately to the children and families with whom they dealt during their professional careers was important.

  5. Evaluation of Pediatric Community Field Trips

    PubMed Central

    Molnar, Eva T.; Knasel, Anne L.

    1987-01-01

    A field trip program for junior medical students on a pediatric clinical clerkship acquainted students with the care of normal and handicapped children in community settings of school, day care center, residential treatment, or diagnostic facilities. A program evaluation by pre and post-trip survey demonstrated a positive change in students' knowledge and attitude in general, which was unaffected by such factors as sex, previous experience in a medical setting, and previous experience with handicapped children. As an integral part of the pediatric clerkship, the field trip appears to have been a positive experience for students, as it met their educational and emotional needs. Subjective evaluation indicated that many students formed insightful and compassionate judgments about handicapped children. Although the increase in knowledge and sensitivity of the students, as reflected in the pre-and post-test, was not statistically significant, the benefit to the students, to the personnel of the agencies, and ultimately to the children and families with whom they dealt during their professional careers was important. PMID:3586049

  6. Correcting the bias of spike field coherence estimators due to a finite number of spikes.

    PubMed

    Grasse, D W; Moxon, K A

    2010-07-01

    The coherence between oscillatory activity in local field potentials (LFPs) and single neuron action potentials, or spikes, has been suggested as a neural substrate for the representation of information. The power spectrum of a spike-triggered average (STA) is commonly used to estimate spike field coherence (SFC). However, when a finite number of spikes is used to construct the STA, the coherence estimator is biased. We introduce here a correction for the bias imposed by the limited number of spikes available in experimental conditions. In addition, we present an alternative method for estimating SFC from an STA by using a filter bank approach. This method is shown to be more appropriate in some analyses, such as comparing coherence across frequency bands. The proposed bias correction is a linear transformation derived from an idealized model of spike-field interaction but is shown to hold in more realistic settings. Uncorrected and corrected SFC estimates from both estimation methods are compared across multiple simulated spike-field models and experimentally collected data. The bias correction was shown to reduce the bias of the estimators, but add variance. However, the corrected estimates had a reduced or unchanged mean squared error in the majority of conditions evaluated. The bias correction provides an effective way to reduce bias in an SFC estimator without increasing the mean squared error.

  7. Resonance tuning due to Coulomb interaction in strong near-field coupled metamaterials

    SciTech Connect

    Roy Chowdhury, Dibakar; Xu, Ningning; Zhang, Weili; Singh, Ranjan

    2015-07-14

    Coulomb's law is one of the most fundamental laws of physics that describes the electrostatic interaction between two like or unlike point charges. Here, we experimentally observe a strong effect of Coulomb interaction in tightly coupled terahertz metamaterials where the split-ring resonator dimers in a unit cell are coupled through their near fields across the capacitive split gaps. Using a simple analytical model, we evaluated the Coulomb parameter that switched its sign from negative to positive values indicating the transition in the nature of Coulomb force from being repulsive to attractive depending upon the near field coupling between the split ring resonators. Apart from showing interesting effects in the strong coupling regime between meta-atoms, Coulomb interaction also allows an additional degree of freedom to achieve frequency tunable dynamic metamaterials.

  8. Second-order correction to the Bigeleisen–Mayer equation due to the nuclear field shift

    PubMed Central

    Bigeleisen, Jacob

    1998-01-01

    The nuclear field shift affects the electronic, rotational, and vibrational energies of polyatomic molecules. The theory of the shifts in molecular spectra has been studied by Schlembach and Tiemann [Schlembach, J. & Tiemann, E. (1982) Chem. Phys. 68, 21]; measurements of the electronic and rotational shifts of the diatomic halides of Pb and Tl have been made by Tiemann et al. [Tiemann, E., Knöckel, H. & Schlembach, J. (1982) Ber. Bunsenges. Phys. Chem. 86, 821]. These authors have estimated the relative shifts in the harmonic frequencies of these compounds due to the nuclear field shift to be of the order of 10−6. I have used this estimate of the relative shift in vibrational frequency to calculate the correction to the harmonic oscillator approximation to the isotopic reduced partition-function ratio 208Pb32S/207Pb32S. The correction is 0.3% of the harmonic oscillator value at 300 K. In the absence of compelling evidence to the contrary, it suffices to calculate the nuclear field effect on the total isotopic partition-function ratio from its shift of the electronic zero point energy and the unperturbed molecular vibration. PMID:9560183

  9. Biological effects due to weak electric and magnetic fields: the temperature variation threshold.

    PubMed Central

    Weaver, J C; Vaughan, T E; Martin, G T

    1999-01-01

    A large number of epidemiological and experimental studies suggest that prolonged (>100 s) weak 50-60-Hz electric and magnetic field (EMF) exposures may cause biological effects(NIEHS Working Group, NIH, 1998; Bersani, 1999). We show, however, that for typical temperature sensitivities of biochemical processes, realistic temperature variations during long exposures raise the threshold exposure by two to three orders of magnitude over a fundamental value, independent of the biophysical coupling mechanism. Temperature variations have been omitted in previous theoretical analyses of possible weak field effects, particularly stochastic resonance (Bezrukov and Vodyanoy 1997a. Nature. 385:319-321; Astumian et al., 1997 Nature. 338:632-633; Bezrukov and Vodyanoy, 1997b. Nature. 338:663; Dykman and McClintock, 1998. Nature. 391:344; McClintock, 1998;. Gammaitoni et al., 1998. Rev. Mod. Phys. 70:223-287). Although sensory systems usually respond to much shorter (approximately 1 s) exposures and can approach fundamental limits (Bialek, 1987 Annu. Rev. Biophys. Biophys. Chem. 16:455-468; Adair et al, 1998. Chaos. 8:576-587), our results significantly decrease the plausibility of effects for nonsensory biological systems due to prolonged, weak-field exposures. PMID:10354428

  10. Additional Enhancement of Electric Field in Surface-Enhanced Raman Scattering due to Fresnel Mechanism

    PubMed Central

    Jayawardhana, Sasani; Rosa, Lorenzo; Juodkazis, Saulius; Stoddart, Paul R.

    2013-01-01

    Surface-enhanced Raman scattering (SERS) is attracting increasing interest for chemical sensing, surface science research and as an intriguing challenge in nanoscale plasmonic engineering. Several studies have shown that SERS intensities are increased when metal island film substrates are excited through a transparent base material, rather than directly through air. However, to our knowledge, the origin of this additional enhancement has never been satisfactorily explained. In this paper, finite difference time domain modeling is presented to show that the electric field intensity at the dielectric interface between metal particles is higher for “far-side” excitation than “near-side”. This is reasonably consistent with the observed enhancement for silver islands on SiO2. The modeling results are supported by a simple analytical model based on Fresnel reflection at the interface, which suggests that the additional SERS signal is caused by near-field enhancement of the electric field due to the phase shift at the dielectric interface. PMID:23903714

  11. Electron spin relaxation due to reorientation of a permanent zero field splitting tensor.

    PubMed

    Schaefle, Nathaniel; Sharp, Robert

    2004-09-15

    Electron spin relaxation of transition metal ions with spin S> or =1 results primarily from thermal modulation of the zero field splitting (zfs) tensor. This occurs both by distortion of the zfs tensor due to intermolecular collisions and, for complexes with less than cubic symmetry, by reorientational modulation of the permanent zfs tensor. The reorientational mechanism is much less well characterized in previous work than the distortional mechanism although it is an important determinant of nuclear magnetic resonance (NMR) paramagnetic relaxation enhancement phenomena (i.e., the enhancement of NMR relaxation rates produced by paramagnetic ions in solution or NMR-PRE). The classical density matrix theory of spin relaxation does not provide an appropriate description of the reorientational mechanism at low Zeeman field strengths because the zero-order spin wave functions are stochastic functions of time. Using spin dynamics simulation techniques, the time correlation functions of the spin operators have been computed and used to determine decay times for the reorientational relaxation mechanism for S=1. In the zfs limit of laboratory field strengths (H(Zeem)field strengths where H(Zeem) approximately H(zfs) (composite function), and in the vicinity of the Zeeman limit. The results demonstrate that the reorientational electron spin relaxation mechanism is often significant when H(zfs) (composite function)> or =H(Zeem), and that its neglect

  12. Changes in hydrological connectivity due to vegetation recovery and wall collapse in abandoned terraced fields

    NASA Astrophysics Data System (ADS)

    Lana-Renault, Noemí; López-Vicente, Manuel; Oranjuren, Rafael; Ángel Llorente, José; Ruiz-Flaño, Purificación; Arnáez, José

    2017-04-01

    Agricultural terraces have been built in mountain regions worldwide in order to provide a larger surface for cultivation, improve water availability and reduce soil erosion, as they favour infiltration and reduce runoff and sediment connectivity from hillslopes to streams. In many Mediterranean countries, farmland abandonment has led to progressive natural revegetation and, in terraced slopes, due to a lack of maintenance, to a collapse of the water conservation structures, often followed by small mass movements and gullying. Little is known about the effect of such failures on the hydrological system, especially at catchment scale. The aim of this study is to contributing to fill in this gap by exploring the effect of vegetation recovery and terrace failure on hydrological connectivity in a small catchment (192 ha) in northern Spain mostly occupied by abandoned terraced fields. For this purpose, we applied a modified version of the Borselli's index of runoff and sediment connectivity (IC). Besides using the C-RUSLE factor, as used by many authors, we tested the inclusion of an infiltration component (Kf) to assess the landscape-weighting factor. The Kf factor accounted for the high infiltration rates observed in the terraced soils and was estimated using the permeability classes of the K-RUSLE factor. A 2x2 m resolution DEM was used to capture the terraced fields and run the IC model. Following the recommendation of Cavalli et al. (2015), we used the D-infinity flow accumulation algorithm (Tarboton, 1997) to represent the real flow paths, especially on hillslopes, where divergent flow predominates, and on stream channels. To ensure the continuity of the flow path lines, local sinks were filled in with the algorithm of Planchon & Darboux (2001) that preserved a minimum slope gradient of 0.01 degrees. Finally, linear landscape elements such as stonewalls, rock outcrops, and trails and forest roads were also considered. The IC was calculated for the current scenario

  13. Small scale changes of geochemistry and flow field due to transient heat storage in aquifers

    NASA Astrophysics Data System (ADS)

    Bauer, S.; Boockmeyer, A.; Li, D.; Beyer, C.

    2013-12-01

    Heat exchangers in the subsurface are increasingly installed for transient heat storage due to the need of heating or cooling of buildings as well as the interim storage of heat to compensate for the temporally fluctuating energy production by wind or solar energy. For heat storage to be efficient, high temperatures must be achieved in the subsurface. Significant temporal changes of the soil and groundwater temperatures however effect both the local flow field by temperature dependent fluid parameters as well as reactive mass transport through temperature dependent diffusion coefficients, geochemical reaction rates and mineral equilibria. As the use of heat storage will be concentrated in urban areas, the use of the subsurface for (drinking) water supply and heat storage will typically coincide and a reliable prognosis of the processes occurring is needed. In the present work, the effects of a temporal variation of the groundwater temperature, as induced by a local heat exchanger introduced into a groundwater aquifer, are studied. For this purpose, the coupled non-isothermal groundwater flow, heat transport and reactive mass transport is simulated in the near filed of such a heat exchanger. By explicitly discretizing and incorporating the borehole, the borehole cementation and the heat exchanger tubes, a realistic geometrical and process representation is obtained. The numerical simulation code OpenGeoSys is used in this work, which incorporates the required processes of coupled groundwater flow, heat and mass transport as well as temperature dependent geochemistry. Due to the use of a Finite Element Method, a close representation of the geometric effects can be achieved. Synthetic scenario simulations for typical settings of salt water formations in northern Germany are used to investigate the geochemical effects arising from a high temperature heat storage by quantifying changes in groundwater chemistry and overall reaction rates. This work presents the

  14. Estimation of Surface Roughness due to Electrode Erosion in Field-Distortion Gas Switch

    NASA Astrophysics Data System (ADS)

    Liu, Xuandong; Wang, Hu; Li, Xiaoang; Zhang, Qiaogen; Wei, Jin; Qiu, Aici

    2013-08-01

    Field distortion gas switch is one of the crucial elements in a Marx generator, fast linear transformer driver and other pulsed power installations. The performance of the gas switch, which is dramatically affected by the surface roughness due to electrode erosion during the discharge process, directly influences the output parameters, stability and reliability of the pulsed power system. In this paper, an electrode surface roughness (ESR) calculation model has been established based on a great deal of experimental data under operating current. The discharge current waveform, the peak height of the burr, the radius and the depth of etch pits in the electrode erosion region were used to predict the ESR. Also, experimental results indicate that this calculation model can effectively estimate the ESR of the test gas switch.

  15. Field evaluation of prototype electrofibrous filters

    SciTech Connect

    Kuhl, W.D.; Bergman, W.; Biermann, A.H.; Lum, B.Y.

    1982-09-30

    New prototype electrofibrous filters were designed, built and evaluated in laboratory tests and in field installations. Two prototypes were designed for use in nuclear ventilation ducts as prefilters to HEPA filters. One prototype is designed to be a permanent component of the ventilation system while the other is a disposable unit. The disposable electrofibrous prefilter was installed in the exhaust stream of a glove box in which barrels of uranium turnings are burned. Preliminary tests show the disposal prefilter is effectively prolonging the HEPA filter life. An earlier prototype of the rolling prefilter was upgraded to meet the increased requirements for installation in a nuclear facility. This upgraded prototype was evaluated in the fire test facility at LLNL and shown to be effective in protecting HEPA filters from plugging under the most severe smoke conditions. The last prototype described in this report is a recirculating air filter. After demonstrating a high performance in laboratory tests the unit was shipped to Savannah River where it is awaiting installation in a Pu fuel fabrication facility. An analysis of the particulate problem in Savannah River indicates that four recirculating air filter will save $172,000 per year in maintenance costs.

  16. Characterising oil and water in porous media using decay due to diffusion in the internal field.

    PubMed

    Lewis, Rhiannon T; Djurhuus, Ketil; Seland, John Georg

    2015-10-01

    In the method Decay due to Diffusion in the Internal Field (DDIF), the diffusion behaviour of water molecules in the internal magnetic field makes it possible to determine a distribution of pore sizes in a sample. The DDIF experiment can also be extended to a DDIF-Carr-Purcell-Meiboom-Gill (DDIF-CPMG) experiment to measure correlations between the pore size and the transverse relaxation time, T2. In this study we have for the first time applied the DDIF experiment and the DDIF-CPMG experiment to porous materials saturated with both water and oil. Because of the large difference in diffusion rates between water and oil molecules, the DDIF experiment will act as a filter for the signal from oil, and we are left with the DDIF-signal from water only. This has been verified in model systems consisting of glass beads immersed in separate layers of water and oil, and in a sandstone sample saturated with water and oil. The results show that the DDIF and DDIF-CPMG experiments enable the determination of the confining geometry of the water phase, and how this geometry is correlated to T2. Data obtained in the sandstone sample saturated with water and oil also show that with the exception of the smallest pores there is no clear correlation between pore size and the relaxation time of water. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Solar Wind Slowdown Due to Dust Pickup during Interplanetary Field Enhancements

    NASA Astrophysics Data System (ADS)

    Lai, Hairong; Russell, Christopher; Wei, Hanying

    2013-04-01

    The interplanetary field enhancements (IFEs) are characterized by their cusp-shaped enhancement in the magnetic field magnitude. They are observed throughout the inner solar system from 0.72AU by Pioneer Venus Orbiter to 5AU by Ulysses. The annual IFE rate is ten at 0.72AU and around eight at 1AU, i.e., decreases as the heliocentric distance increases. Multiple-spacecraft observations show that IFEs are moving radially away from the Sun at nearly the ambient solar wind speed. During the IFE events, case studies show that while there are correlated diamagnetic compensations in pressure there are no significant correlated changes in the solar wind speed. An IFE formation mechanism that explains most of the IFE features is that IFEs result from interactions between solar wind and clouds of picked up nanoscale charged dust, which is released in interplanetary collisions between objects of 10 to 1000m in diameter. The enhanced magnetic field behaves as a magnetic barrier that can transfer momentum to the charged dust from the solar wind. Momentum lifts the dust outward in the solar gravitational well. A prediction of this hypothesis is that solar wind will be slowed down even when the IFEs have reached exactly the solar wind speed. To test this hypothesis, we perform a superposed analysis on the radial velocity of IFEs observed at 1AU. In contrast to the case studies, the statistical results have a significant change in speed. The velocity on the solar wind side of the IFEs is smaller than the ambient velocity. This slowdown increases for larger IFEs with larger estimated mass. In addition, the amount of momentum due to the solar wind slowdown is quantitatively consistent with the momentum expected to be needed to lift the dust out of the Sun's gravitational potential well, which is in strong support of our IFE formation mechanism.

  18. Hazardous gas model evaluation with field observations

    NASA Astrophysics Data System (ADS)

    Hanna, S. R.; Chang, J. C.; Strimaitis, D. G.

    Fifteen hazardous gas models were evaluated using data from eight field experiments. The models include seven publicly available models (AFTOX, DEGADIS, HEGADAS, HGSYSTEM, INPUFF, OB/DG and SLAB), six proprietary models (AIRTOX, CHARM, FOCUS, GASTAR, PHAST and TRACE), and two "benchmark" analytical models (the Gaussian Plume Model and the analytical approximations to the Britter and McQuaid Workbook nomograms). The field data were divided into three groups—continuous dense gas releases (Burro LNG, Coyote LNG, Desert Tortoise NH 3-gas and aerosols, Goldfish HF-gas and aerosols, and Maplin Sands LNG), continuous passive gas releases (Prairie Grass and Hanford), and instantaneous dense gas releases (Thorney Island freon). The dense gas models that produced the most consistent predictions of plume centerline concentrations across the dense gas data sets are the Britter and McQuaid, CHARM, GASTAR, HEGADAS, HGSYSTEM, PHAST, SLAB and TRACE models, with relative mean biases of about ±30% or less and magnitudes of relative scatter that are about equal to the mean. The dense gas models tended to overpredict the plume widths and underpredict the plume depths by about a factor of two. All models except GASTAR, TRACE, and the area source version of DEGADIS perform fairly well with the continuous passive gas data sets. Some sensitivity studies were also carried out. It was found that three of the more widely used publicly-available dense gas models (DEGADIS, HGSYSTEM and SLAB) predicted increases in concentration of about 70% as roughness length decreased by an order of magnitude for the Desert Tortoise and Goldfish field studies. It was also found that none of the dense gas models that were considered came close to simulating the observed factor of two increase in peak concentrations as averaging time decreased from several minutes to 1 s. Because of their assumption that a concentrated dense gas core existed that was unaffected by variations in averaging time, the dense gas

  19. Attenuation of the NMR signal in a field gradient due to stochastic dynamics with memory

    NASA Astrophysics Data System (ADS)

    Lisý, Vladimír; Tóthová, Jana

    2017-03-01

    The attenuation function S(t) for an ensemble of spins in a magnetic-field gradient is calculated by accumulation of the phase shifts in the rotating frame resulting from the displacements of spin-bearing particles. The found S(t), expressed through the particle mean square displacement, is applicable for any kind of stationary stochastic motion of spins, including their non-markovian dynamics with memory. The known expressions valid for normal and anomalous diffusion are obtained as special cases in the long time approximation. The method is also applicable to the NMR pulse sequences based on the refocusing principle. This is demonstrated by describing the Hahn spin echo experiment. The attenuation of the NMR signal is also evaluated providing that the random motion of particle is modeled by the generalized Langevin equation with the memory kernel exponentially decaying in time. The models considered in our paper assume massive particles driven by much smaller particles.

  20. Blending vocal music with a given sound field due to the characteristics of the running autocorrelation function of singing voices

    NASA Astrophysics Data System (ADS)

    Kato, Kosuke; Fujii, Kenji; Kawai, Keiji; Ando, Yoichi; Yano, Takashi

    2004-05-01

    This is a study to meet music and the opera house acoustics. It is said that singers adjust their interpretation style according to the acoustical condition of the sound field in a room. However, this mechanism of blending of musical performance with the sound field is unknown. In order to obtain a method of performance blending of opera house acoustics, we attempted to develop evaluation criteria for a singing voice in terms of the minimum value of the effective duration of the running autocorrelation function (r-ACF), (te)min, of sound source signals. This temporal factor has shown to have close correlation with the subjective response of both listeners and performers to sound fields [Y. Ando, Architectural Acoustics (AIP Press/Springer-Verlag, New York, 1998)]. As example for the control of (te)min due to performing style, effects of singing style, kind of vowel, relative pitch, vibrato extent, and intonation on the values of (te)min are demonstrated. In addition, the fine structure of the r-ACF is discussed with regard to the identification of vowels of singing voice. a)Now at 1-10-27 Yamanokami, Kumamoto, Japan.

  1. Evanescent field enhancement due to plasmonic resonances of a metamaterial slab.

    PubMed

    Chiu, K P; Kao, T S; Tsai, D P

    2008-02-01

    The characteristics of plasmonic resonance in a dielectric-sandwiched metamaterial film at visible wavelengths of 650 and 568 nm have been investigated (for both p- and s-polarized light). Our calculated results demonstrate that each mode of plasmonic resonance has maximum resonance strength at a particular film thickness of the metamaterial. We also demonstrated that the effect of evanescent field enhancement is due to plasmonic resonances of the sandwiched metamaterial system. And the stronger the plasmonic resonance strength the larger the evanescent field is enhanced at the interfaces of the metamaterial film. Also we see that the plasmonic resonances in a sandwiched metamaterial are influenced not only by the materials that constitute the interfaces but also by the thickness of surrounding dielectrics or distance between evanescent light source and metamaterial film. Finally, our results show that there might be an effective light propagation length that will let the coupling efficiency between evanescent light source and SPs resonance become a maximum. These properties of plasmonic resonances to structure parameters of metamaterial film and its surrounding dielectrics provide a useful way to control the optical responses of an optoelectronic device when the wavelength of light source is fixed. That is, by suitably choosing light polarizations, thickness of the metamaterial thin film or the surrounding dielectrics and the position of evanescent light source, it is possible to modulate the plasmonic resonance wavenumber or resonance strength of the system. Therefore, the optical responses of the system can be modulated. Our results will be helpful for the structure design to control the behaviours of coupled plasmonic resonances and consequently the optical properties of the dielectric-sandwiched metamaterial film.

  2. Magnetostriction of a sphere: stress development during magnetization and residual stresses due to the remanent field

    NASA Astrophysics Data System (ADS)

    Reich, Felix A.; Rickert, Wilhelm; Stahn, Oliver; Müller, Wolfgang H.

    2017-03-01

    Based on the principles of rational continuum mechanics and electrodynamics (see Truesdell and Toupin in Handbuch der Physik, Springer, Berlin, 1960 or Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000), we present closed-form solutions for the mechanical displacements and stresses of two different magnets. Both magnets are initially of spherical shape. The first (hard) magnet is uniformly magnetized and deforms due to the field induced by the magnetization. In the second problem of a (soft) linear-magnetic sphere, the deformation is caused by an applied external field, giving rise to magnetization. Both problems can be used for modeling parts of general magnetization processes. We will address the similarities between both settings in context with the solutions for the stresses and displacements. In both problems, the volumetric Lorentz force density vanishes. However, a Lorentz surface traction is present. This traction is determined from the magnetic flux density. Since the obtained displacements and stresses are small in magnitude, we may use Hooke's law with a small-strain approximation, resulting in the Lamé- Navier equations of linear elasticity theory. If gravity is neglected and azimuthal symmetry is assumed, these equations can be solved in terms of a series. This has been done by Hiramatsu and Oka (Int J Rock Mech Min Sci Geomech Abstr 3(2):89-90, 1966) before. We make use of their series solution for the displacements and the stresses and expand the Lorentz tractions of the analyzed problems suitably in order to find the expansion coefficients. The resulting algebraic system yields finite numbers of nonvanishing coefficients. Finally, the resulting stresses, displacements, principal strains and the Lorentz tractions are illustrated and discussed.

  3. Magnetostriction of a sphere: stress development during magnetization and residual stresses due to the remanent field

    NASA Astrophysics Data System (ADS)

    Reich, Felix A.; Rickert, Wilhelm; Stahn, Oliver; Müller, Wolfgang H.

    2016-12-01

    Based on the principles of rational continuum mechanics and electrodynamics (see Truesdell and Toupin in Handbuch der Physik, Springer, Berlin, 1960 or Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000), we present closed-form solutions for the mechanical displacements and stresses of two different magnets. Both magnets are initially of spherical shape. The first (hard) magnet is uniformly magnetized and deforms due to the field induced by the magnetization. In the second problem of a (soft) linear-magnetic sphere, the deformation is caused by an applied external field, giving rise to magnetization. Both problems can be used for modeling parts of general magnetization processes. We will address the similarities between both settings in context with the solutions for the stresses and displacements. In both problems, the volumetric uc(Lorentz) force density vanishes. However, a uc(Lorentz) surface traction is present. This traction is determined from the magnetic flux density. Since the obtained displacements and stresses are small in magnitude, we may use uc(Hooke's) law with a small-strain approximation, resulting in the uc(Lamé)-uc(Navier) equations of linear elasticity theory. If gravity is neglected and azimuthal symmetry is assumed, these equations can be solved in terms of a series. This has been done by uc(Hiramatsu) and uc(Oka) (Int J Rock Mech Min Sci Geomech Abstr 3(2):89-90, 1966) before. We make use of their series solution for the displacements and the stresses and expand the uc(Lorentz) tractions of the analyzed problems suitably in order to find the expansion coefficients. The resulting algebraic system yields finite numbers of nonvanishing coefficients. Finally, the resulting stresses, displacements, principal strains and the uc(Lorentz) tractions are illustrated and discussed.

  4. Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

    NASA Astrophysics Data System (ADS)

    Bei, N.; Li, G.; Molina, L. T.

    2013-05-01

    The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 μg m-3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but the ratio of the ensemble spread to mean does not change significantly.

  5. Observed Changes in the Gravity Field of Mars Due to Seasonal Atmospheric Processes

    NASA Technical Reports Server (NTRS)

    Smith, David E.; Zuber, M. T.; Dunn, P. J.; Torrence, M. H.; Fricke, S. K.

    2000-01-01

    The atmosphere of Mars deposits approximately 30% of its mass at the winter pole as part of its seasonal cycle of CO2 exchange and sublimes it back to the atmosphere in the spring, thus creating an annual hemispheric cycle of mass re-distribution. Using X-band tracking data of the Mars Global Surveyor (MGS) spacecraft, we have detected the signature of changes in the low degree gravity field from March 1999 through August 2000, corresponding to about three-quarters of a Martian year. The observed variations show a general resemblance to predicted variations from general circulation models. Also observed are irregular changes that appear to be due to transient phenomena in the Martian atmosphere such as large dust storms that provide significant heat into the lower atmosphere, even in the polar regions. In addition, we have identified a change in the rate of rotation of Mars over this same period that appears somewhat smaller than anticipated, but in general agreement with general circulation models.

  6. Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

    NASA Astrophysics Data System (ADS)

    Bei, N.; Li, G.; Molina, L. T.

    2012-12-01

    The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 μg m-3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but the ratio of the ensemble spread to mean does not change significantly.

  7. Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

    NASA Astrophysics Data System (ADS)

    Bei, N.; Li, G.; Molina, L. T.

    2012-07-01

    The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 µg m-3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but has same significance compared to the ensemble mean.

  8. Field evaluations of marine oil spill bioremediation.

    PubMed Central

    Swannell, R P; Lee, K; McDonagh, M

    1996-01-01

    Bioremediation is defined as the act of adding or improving the availability of materials (e.g., nutrients, microorganisms, or oxygen) to contaminated environments to cause an acceleration of natural biodegradative processes. The results of field experiments and trials following actual spill incidents have been reviewed to evaluate the feasibility of this approach as a treatment for oil contamination in the marine environment. The ubiquity of oil-degrading microorganisms in the marine environment is well established, and research has demonstrated the capability of the indigenous microflora to degrade many components of petroleum shortly after exposure. Studies have identified numerous factors which affect the natural biodegradation rates of oil, such as the origin and concentration of oil, the availability of oil-degrading microorganisms, nutrient concentrations, oxygen levels, climatic conditions, and sediment characteristics. Bioremediation strategies based on the application of fertilizers have been shown to stimulate the biodegradation rates of oil in aerobic intertidal sediments such as sand and cobble. The ratio of oil loading to nitrogen concentration within the interstitial water has been identified to be the principal controlling factor influencing the success of this bioremediation strategy. However, the need for the seeding of natural environments with hydrocarbon-degrading bacteria has not been clearly demonstrated under natural environmental conditions. It is suggested that bioremediation should now take its place among the many techniques available for the treatment of oil spills, although there is still a clear need to set operational limits for its use. On the basis of the available evidence, we have proposed preliminary operational guidelines for bioremediation on shoreline environments. PMID:8801437

  9. Overestimation of Crop Root Biomass in Field Experiments Due to Extraneous Organic Matter

    PubMed Central

    Hirte, Juliane; Leifeld, Jens; Abiven, Samuel; Oberholzer, Hans-Rudolf; Hammelehle, Andreas; Mayer, Jochen

    2017-01-01

    Root biomass is one of the most relevant root parameters for studies of plant response to environmental change, soil carbon modeling or estimations of soil carbon sequestration. A major source of error in root biomass quantification of agricultural crops in the field is the presence of extraneous organic matter in soil: dead roots from previous crops, weed roots, incorporated above ground plant residues and organic soil amendments, or remnants of soil fauna. Using the isotopic difference between recent maize root biomass and predominantly C3-derived extraneous organic matter, we determined the proportions of maize root biomass carbon of total carbon in root samples from the Swiss long-term field trial “DOK.” We additionally evaluated the effects of agricultural management (bio-organic and conventional), sampling depth (0–0.25, 0.25–0.5, 0.5–0.75 m) and position (within and between maize rows), and root size class (coarse and fine roots) as defined by sieve mesh size (2 and 0.5 mm) on those proportions, and quantified the success rate of manual exclusion of extraneous organic matter from root samples. Only 60% of the root mass that we retrieved from field soil cores was actual maize root biomass from the current season. While the proportions of maize root biomass carbon were not affected by agricultural management, they increased consistently with soil depth, were higher within than between maize rows, and were higher in coarse (>2 mm) than in fine (≤2 and >0.5) root samples. The success rate of manual exclusion of extraneous organic matter from root samples was related to agricultural management and, at best, about 60%. We assume that the composition of extraneous organic matter is strongly influenced by agricultural management and soil depth and governs the effect size of the investigated factors. Extraneous organic matter may result in severe overestimation of recovered root biomass and has, therefore, large implications for soil carbon modeling and

  10. Overestimation of Crop Root Biomass in Field Experiments Due to Extraneous Organic Matter.

    PubMed

    Hirte, Juliane; Leifeld, Jens; Abiven, Samuel; Oberholzer, Hans-Rudolf; Hammelehle, Andreas; Mayer, Jochen

    2017-01-01

    Root biomass is one of the most relevant root parameters for studies of plant response to environmental change, soil carbon modeling or estimations of soil carbon sequestration. A major source of error in root biomass quantification of agricultural crops in the field is the presence of extraneous organic matter in soil: dead roots from previous crops, weed roots, incorporated above ground plant residues and organic soil amendments, or remnants of soil fauna. Using the isotopic difference between recent maize root biomass and predominantly C3-derived extraneous organic matter, we determined the proportions of maize root biomass carbon of total carbon in root samples from the Swiss long-term field trial "DOK." We additionally evaluated the effects of agricultural management (bio-organic and conventional), sampling depth (0-0.25, 0.25-0.5, 0.5-0.75 m) and position (within and between maize rows), and root size class (coarse and fine roots) as defined by sieve mesh size (2 and 0.5 mm) on those proportions, and quantified the success rate of manual exclusion of extraneous organic matter from root samples. Only 60% of the root mass that we retrieved from field soil cores was actual maize root biomass from the current season. While the proportions of maize root biomass carbon were not affected by agricultural management, they increased consistently with soil depth, were higher within than between maize rows, and were higher in coarse (>2 mm) than in fine (≤2 and >0.5) root samples. The success rate of manual exclusion of extraneous organic matter from root samples was related to agricultural management and, at best, about 60%. We assume that the composition of extraneous organic matter is strongly influenced by agricultural management and soil depth and governs the effect size of the investigated factors. Extraneous organic matter may result in severe overestimation of recovered root biomass and has, therefore, large implications for soil carbon modeling and estimations

  11. Use of field experimental studies to evaluate emergency response models

    SciTech Connect

    Gudiksen, P.H.; Lange, R.; Rodriguez, D.J.; Nasstrom, J.S.

    1985-07-16

    The three-dimensional diagnostic wind field model (MATHEW) and the particle-in-cell atmospheric transport and diffusion model (ADPIC) are used by the Atmospheric Release Advisory Capability to estimate the environmental consequences of accidental releases of radioactivity into the atmosphere. These models have undergone extensive evaluations against field experiments conducted in a variety of environmental settings ranging from relatively flat to very complex terrain areas. Simulations of tracer experiments conducted in a complex mountain valley setting revealed that 35 to 50% of the comparisons between calculated and measured tracer concentrations were within a factor of 5. This may be compared with a factor of 2 for 50% of the comparisons for relatively flat terrain. This degradation of results in complex terrain is due to a variety of factors such as the limited representativeness of measurements in complex terrain, the limited spatial resolution afforded by the models, and the turbulence parameterization based on sigma/sub theta/ measurements to evaluate the eddy diffusivities. Measurements of sigma/sub theta/ in complex terrain exceed those measured over flat terrain by a factor of 2 to 3 leading to eddy diffusivities that are unrealistically high. The results of model evaluations are very sensitive to the quality and the representativeness of the meteorological data. This is particularly true for measurements near the source. The capability of the models to simulate the dispersion of an instantaneously produced cloud of particulates was illustrated to be generally within a factor of 2 over flat terrain. 19 refs., 16 figs.

  12. Evaluation Field Building in South Asia: Reflections, Anecdotes, and Questions

    ERIC Educational Resources Information Center

    Hay, Katherine

    2010-01-01

    This article examines evaluation field building in South Asia and the role of international collaboration in this field building. The article explores aspects of the supply and demand of development evaluation and the political, historical, and systemic factors that bridge or block evaluation use. The article calls for and suggests elements to…

  13. Evaluation Field Building in South Asia: Reflections, Anecdotes, and Questions

    ERIC Educational Resources Information Center

    Hay, Katherine

    2010-01-01

    This article examines evaluation field building in South Asia and the role of international collaboration in this field building. The article explores aspects of the supply and demand of development evaluation and the political, historical, and systemic factors that bridge or block evaluation use. The article calls for and suggests elements to…

  14. Modelling and Evaluation of Environmental Impact due to Continuous Emissions of the Severonickel Plant (Kola Peninsula)

    NASA Astrophysics Data System (ADS)

    Mahura, A.; Gonzalez-Aparicio, I.; Nuterman, R.; Baklanov, A.

    2012-04-01

    In this study, evaluation of potential impact - through concentration, deposition and loadings patterns - on population and environment due to continuous anthropogenic emissions (on example of sulfates) of the Cu-Ni smelters of the Russian North is given. To estimate impact, the Danish Emergency Response Model for Atmosphere (DERMA) was employed to perform long-term simulations of air concentration, time integrated air concentration (TIAC), dry (DD) and wet (WD) deposition patterns resulting from continuous emissions of the Severonickel smelters located on the Kola Peninsula (Murmansk region, Russia). To perform such simulations the 3D meteorological fields (from the European Center for Medium-Range Weather Forecasts, ECMWF) for the year 2000 were used as input. For simplicity, it has been assumed that normalized releases of sulfates from smelters location occurred at a constant rate every day. For each daily release the atmospheric transport, dispersion, dry and wet deposition due to removal processes were estimated during 10 day interval. Output from these long-term simulations is an essential input for evaluation of impact, doses, risks, and short- and long-term consequences, etc. Detailed analyses of simulated concentration and deposition fields allowed evaluating the spatial and temporal variability of resulted patterns on different scales. Temporal variability of both wet and dry deposition as well as their contribution into total deposition have been estimated. On an annual scale, the concentration and deposition patterns were estimated for the most populated cities of the North-West Russia. The modeled annual fields were also integrated into GIS environment as well as layers with population density (from the Center for International Earth Science Information Network, CIESIN) and standard administrative division of the North-West Russia and bordering countries. Furthermore, the estimation of deposited amounts (loadings) of sulfates for selected regions of

  15. Evaluation of military field-water quality

    SciTech Connect

    Daniels, J.I.; Anspaugh, L.R.; Layton, D.W.

    1990-01-01

    The purpose of this report is to develop drinking-water standards for field water for selected threat agents of concern, including radioactivity. The threat agents of concern in addition to radioactivity are the classical chemical-warfare compounds hydrogen cyanide, organophosphorus nerve agents, and lewisite, as well as a fungal metabolite identified only recently as a possible threat agent, the trichothecene mycotoxin. The recommended standards are applicable only to military personnel deployed in the field, and they are meant to protect against performance-degrading effects resulting from the ingestion of the substances in field water. 25 refs., 11 figs., 19 tabs.

  16. Sound propagation through a real jet flow field with scattering due to interaction with turbulence

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Liu, C. H.; Ting, L.; Gunzburger, M.

    1974-01-01

    The sound propagation through a nonuniform turbulent jet flow field is studied by means of a system of linearized equations governing the acoustic variables. These equations depend on the fluctuating flow-field variables which are prescribed by experimental results. It is shown that the redistribution of the acoustic energy in the far field depends on space-time correlation of the turbulent velocities and on the mean flow variables and their gradients.

  17. Primary beam steering due to field leakage from superconducting SHMS magnets

    DOE PAGES

    Moore, Michael H.; Waidyawansa, Buddhini P.; Covrig, Silviu; ...

    2014-11-05

    In this study, simulations of the magnetic fields from the Super High Momentum Spectrometer in Hall C at Thomas Jefferson National Accelerator Facility show significant field leakage into the region of the primary beam line between the target and the beam dump. Without mitigation, these remnant fields will steer the unscattered beam enough to limit beam operations at small scattering angles. Presented here are magnetic field simulations of the spectrometer magnets and a solution using optimal placement of a minimal amount of shielding iron around the beam line.

  18. Primary beam steering due to field leakage from superconducting SHMS magnets

    NASA Astrophysics Data System (ADS)

    Moore, M. H.; Waidyawansa, B. P.; Covrig, S.; Carlini, R.; Benesch, J.

    2014-11-01

    Simulations of the magnetic fields from the Super High Momentum Spectrometer in Hall C at Thomas Jefferson National Accelerator Facility show significant field leakage into the region of the primary beam line between the target and the beam dump. Without mitigation, these remnant fields will steer the unscattered beam enough to limit beam operations at small scattering angles. Presented here are magnetic field simulations of the spectrometer magnets and a solution using optimal placement of a minimal amount of shielding iron around the beam line.

  19. Inner Core Anisotropy Due to the Magnetic Field--induced Preferred Orientation of Iron.

    PubMed

    Karato, S

    1993-12-10

    Anisotropy of the inner core of the Earth is proposed to result from the lattice preferred orientation of anisotropic iron crystals during their solidification in the presence of a magnetic field. The resultant seismic anisotropy is related to the geometry of the magnetic field in the core. This hypothesis implies that the observed anisotropy (fast velocity along the rotation axis) indicates a strong toroidal field in the core, which supports a strong field model for the geodynamo if the inner core is made of hexagonal close-packed iron.

  20. Primary beam steering due to field leakage from superconducting SHMS magnets

    SciTech Connect

    Moore, Michael H.; Waidyawansa, Buddhini P.; Covrig, Silviu; Carlini, Roger; Benesch, Jay

    2014-11-05

    In this study, simulations of the magnetic fields from the Super High Momentum Spectrometer in Hall C at Thomas Jefferson National Accelerator Facility show significant field leakage into the region of the primary beam line between the target and the beam dump. Without mitigation, these remnant fields will steer the unscattered beam enough to limit beam operations at small scattering angles. Presented here are magnetic field simulations of the spectrometer magnets and a solution using optimal placement of a minimal amount of shielding iron around the beam line.

  1. Field Evaluation of Low-E Storm Windows

    SciTech Connect

    Drumheller, S. Craig; Kohler, Christian; Minen, Stefanie

    2007-07-11

    A field evaluation comparing the performance of low emittance (low-e) storm windows with both standard clear storm windows and no storm windows was performed in a cold climate. Six homes with single-pane windows were monitored over the period of one heating season. The homes were monitored with no storm windows and with new storm windows. The storm windows installed on four of the six homes included a hard coat, pyrolitic, low-e coating while the storm windows for the other two homeshad traditional clear glass. Overall heating load reduction due to the storm windows was 13percent with the clear glass and 21percent with the low-e windows. Simple paybacks for the addition of the storm windows were 10 years for the clear glass and 4.5 years forthe low-e storm windows.

  2. Flute stabilization due to ponderomotive force created by an rf field with a variable gradient

    SciTech Connect

    Yasaka, Y.; Itatani, R.

    1986-06-30

    An rf-stabilization experiment was performed in the axisymmetric single-mirror device HIEI by controlling the radial-gradient scale length of the rf field with the aid of an azimuthally phased antenna array. The flute stability depends sensitively on the scale length of the perpendicular rf electric field, which shows that rf stabilization is caused by the ponderomotive force for ions.

  3. Electromagnetic fields in the human body due to switched transverse gradient coils in MRI.

    PubMed

    While, Peter T; Forbes, Larry K

    2004-07-07

    Magnetic resonance imaging scans impose large gradient magnetic fields on the patient. Modern imaging techniques require this magnetic field to be switched rapidly for good resolution. However, it is believed that this can also lead to the unwanted side effect of peripheral nerve stimulation, which proves to be a limiting factor to the advancement of MRI technology. This paper establishes an analytical model for the fields produced within an MRI scanner by transverse gradient coils of known current density. Expressions are obtained for the magnetic induction vector and the electric field vector, as well as for the surface charge and current densities that are induced on the patient's body. The expressions obtained are general enough to allow the study of any combination of gradient coils whose behaviour can be approximated by Fourier series. For a realistic example coil current density and switching function, it is found that spikes of surface charge density are induced on the patient's body as the gradient field is switched, as well as loops of surface current density that mimic the coil current density. For a 10 mT m(-1) gradient field with a rise time of 100 micros, the magnitude of the radial electric field at the body is found to be 10.3 V m(-1). It is also found that there is a finite limit to radial electric field strength as rise time approaches zero.

  4. Magnetic field deformation due to electron drift in a Hall thruster

    NASA Astrophysics Data System (ADS)

    Liang, Han; Yongjie, Ding; Xu, Zhang; Liqiu, Wei; Daren, Yu

    2017-01-01

    The strength and shape of the magnetic field are the core factors in the design of the Hall thruster. However, Hall current can affect the distribution of static magnetic field. In this paper, the Particle-In-Cell (PIC) method is used to obtain the distribution of Hall current in the discharge channel. The Hall current is separated into a direct and an alternating part to calculate the induced magnetic field using Finite Element Method Magnetics (FEMM). The results show that the direct Hall current decreases the magnetic field strength in the acceleration region and also changes the shape of the magnetic field. The maximum reduction in radial magnetic field strength in the exit plane is 10.8 G for an anode flow rate of 15 mg/s and the maximum angle change of the magnetic field line is close to 3° in the acceleration region. The alternating Hall current induces an oscillating magnetic field in the whole discharge channel. The actual magnetic deformation is shown to contain these two parts.

  5. Field Evaluation of a General Purpose Simulator.

    ERIC Educational Resources Information Center

    Spangenberg, Ronald W.

    The use of a general purpose simulator (GPS) to teach Air Force technicians diagnostic and repair procedures for specialized aircraft radar systems is described. An EC II simulator manufactured by Educational Computer Corporation was adapted to resemble the actual configuration technicians would encounter in the field. Data acquired in the…

  6. Field Guide for Evaluating Cottonwood Sites

    Treesearch

    W.M. Broadfoot

    1960-01-01

    Two field methods have been developed at the Stoneville Research Center for estimating the capability of Midsouth soils to grow eastern cottonwood (Populus deltoides Bartr.). Data for establishing the procedures were collected from 155 plots* at the locations indicated in Figure 1.The methods give site index-that is, tree-growing...

  7. Study on magnetic field deviation due to manufacturing errors of the SIS100 superconducting dipole magnet

    NASA Astrophysics Data System (ADS)

    Sugita, Kei; Fischer, Egbert; Mierau, Anna; Roux, Christian; Schnizer, Pierre

    2016-12-01

    An international accelerator project, Facility for Antiproton and Ion Research in Europe (FAIR), is being constructed at Darmstadt, Germany. Central part of the accelerator chain is a superconducting heavy ion synchrotron SIS100, which accelerates injected particles from existing synchrotron SIS18, and provides them to experiment sites and further accelerators. Superconducting magnets in SIS100 are mainly superferric magnet with a Nuclotron cable. After R&D, the First of Series (FoS) main dipole magnet has been manufactured and tested successfully. However, magnetic field quality is unsatisfactory. We report on the investigation of the magnetic field quality by means of magnetic field measurements, geometrical measurements, and electromagnetic simulations.

  8. Nontrivial excited-state coherence due to two uncorrelated partially coherent fields

    NASA Astrophysics Data System (ADS)

    Sadeq, Z. S.

    2015-04-01

    We analyze a model where a closed V system is excited by two uncorrelated partially coherent fields. We use a collisionally broadened cw laser, which is a good model for an experimentally realizable partially coherent field, and show that it is possible to generate excited-state coherences even if the two fields are uncorrelated. This transient coherence can be increased if splitting between the excited states is reduced relative to the radiation coherence time τd. For small excited-state splitting, one can use this scheme to generate a long-lived coherent response in the system.

  9. Circulation in the high-latitude thermosphere due to electric fields and Joule heating

    NASA Technical Reports Server (NTRS)

    Heaps, M. G.; Megill, L. R.

    1975-01-01

    Electric fields in the earth's upper atmosphere are capable of setting the neutral atmosphere in motion via ion-neutral collisions as well as pressure gradients from resultant Joule heating. By means of simple models for the high-latitude thermosphere and electric fields a simplified set of coupled equations is solved which show that moderate electric fields, when present for a period of several hours, are capable of displacing the neutral atmosphere of the order of 50 km in the vertical, a few hundred kilometers in the north-south direction and over 1000 km in the east-west direction.

  10. Circulation in the high-latitude thermosphere due to electric fields and Joule heating

    NASA Technical Reports Server (NTRS)

    Heaps, M. G.; Megill, L. R.

    1975-01-01

    Electric fields in the earth's upper atmosphere are capable of setting the neutral atmosphere in motion via ion-neutral collisions as well as pressure gradients from resultant Joule heating. By means of simple models for the high-latitude thermosphere and electric fields a simplified set of coupled equations is solved which show that moderate electric fields, when present for a period of several hours, are capable of displacing the neutral atmosphere of the order of 50 km in the vertical, a few hundred kilometers in the north-south direction and over 1000 km in the east-west direction.

  11. Electromagnetic field generation in the downstream of electrostatic shocks due to electron trapping.

    PubMed

    Stockem, A; Grismayer, T; Fonseca, R A; Silva, L O

    2014-09-05

    A new magnetic field generation mechanism in electrostatic shocks is found, which can produce fields with magnetic energy density as high as 0.01 of the kinetic energy density of the flows on time scales ∼10(4)ωpe-1. Electron trapping during the shock formation process creates a strong temperature anisotropy in the distribution function, giving rise to the pure Weibel instability. The generated magnetic field is well confined to the downstream region of the electrostatic shock. The shock formation process is not modified, and the features of the shock front responsible for ion acceleration, which are currently probed in laser-plasma laboratory experiments, are maintained. However, such a strong magnetic field determines the particle trajectories downstream and has the potential to modify the signatures of the collisionless shock.

  12. Kilotesla Magnetic Field due to a Capacitor-Coil Target Driven by High Power Laser

    PubMed Central

    Fujioka, Shinsuke; Zhang, Zhe; Ishihara, Kazuhiro; Shigemori, Keisuke; Hironaka, Youichiro; Johzaki, Tomoyuki; Sunahara, Atsushi; Yamamoto, Naoji; Nakashima, Hideki; Watanabe, Tsuguhiro; Shiraga, Hiroyuki; Nishimura, Hiroaki; Azechi, Hiroshi

    2013-01-01

    Laboratory generation of strong magnetic fields opens new frontiers in plasma and beam physics, astro- and solar-physics, materials science, and atomic and molecular physics. Although kilotesla magnetic fields have already been produced by magnetic flux compression using an imploding metal tube or plasma shell, accessibility at multiple points and better controlled shapes of the field are desirable. Here we have generated kilotesla magnetic fields using a capacitor-coil target, in which two nickel disks are connected by a U-turn coil. A magnetic flux density of 1.5 kT was measured using the Faraday effect 650 μm away from the coil, when the capacitor was driven by two beams from the GEKKO-XII laser (at 1 kJ (total), 1.3 ns, 0.53 or 1 μm, and 5 × 1016 W/cm2). PMID:23378905

  13. Analysis of payload bay magnetic fields due to dc power multipoint and single point ground configurations

    NASA Technical Reports Server (NTRS)

    Lawton, R. M.

    1976-01-01

    An analysis of magnetic fields in the Orbiter Payload Bay resulting from the present grounding configuration (structure return) was presented and the amount of improvement that would result from installing wire returns for the three dc power buses was determined. Ac and dc magnetic fields at five points in a cross-section of the bay are calculated for both grounding configurations. Y and Z components of the field at each point are derived in terms of a constant coefficient and the current amplitude of each bus. The dc loads assumed are 100 Amperes for each bus. The ac noise current used is a spectrum 6 db higher than the Orbiter equipment limit for narrowband conducted emissions. It was concluded that installing return wiring to provide a single point ground for the dc Buses in the Payload Bay would reduce the ac and dc magnetic field intensity by approximately 30 db.

  14. Pre- and post-operative evaluations of eight dogs following right nephrectomy due to Dioctophyma renale.

    PubMed

    Mesquita, L R; Rahal, S C; Faria, L G; Takahira, R K; Rocha, N S; Mamprim, M J; Oliveira, H S

    2014-01-01

    Dioctophyma renale is a large nematode distributed worldwide that may cause progressive and severe destruction of renal parenchyma. The present study aimed to evaluate pre- and post-operatively dogs submitted to right nephrectomy due to D. renale and to assess the histopathological damage of the removed kidney. Eight crossbred dogs, aged from 12 to 48 months that were unilaterally nephrectomized due to the presence of D. renale were evaluated. Physical examination, urinalysis, complete blood count, serum biochemistry, and abdominal ultrasound were performed immediately before and one month after nephrectomy. The nephrectomized right kidneys were submitted to macroscopic and microscopic evaluations. Urinalysis preoperatively detected occult blood in all dogs and D. renale eggs in five cases. Complete blood count showed all parameters within the reference range, except one dog post-operatively. Serum biochemistry performed before and after surgery verified that urea, creatinine and sodium were within the reference range values in all dogs. Other findings varied among the dogs. The length and arterial resistive index mean values of the left kidney were similar pre- and post-operatively. Thus, the inconsiderable change in laboratory findings pre- and post-operatively was attributable to compensation by left kidney function for the removed abnormal right kidney. Right kidney histology revealed chronic nephropathy due to D. renale. Imaging diagnosis should be performed on dogs suspected as carrying the disease or on those from an enzootic area since the laboratory findings are not specific except eggs in the urine.

  15. Evaluating 6 ricin field detection assays.

    PubMed

    Slotved, Hans-Christian; Sparding, Nadja; Tanassi, Julia Tanas; Steenhard, Nina R; Heegaard, Niels H H

    2014-01-01

    This study presents data showing the performance of 6 commercial detection assays against ricin around concentrations specified as detection limits by the producers. A 2-fold dilution series of 20 ng/ml ricin was prepared and used for testing the lateral-flow kits: BADD, Pro Strips™, ENVI, RAID DX, Ricin BioThreat Alert, and IMASS™ device. Three of the 6 tested field assays (IMASS™ device, ENVI assay, and the BioThreat Alert assay) were able to detect ricin, although differences in the measured detection limits compared to the official detection limits and false-negative results were observed. We were not able to get the BADD, Pro Strips™, and RAID assays to function in our laboratory. We conclude that when purchasing a field responder assay, there is large variation in the specificity of the assays, and a number of in-house tests must be performed to ensure functionality.

  16. Computation of induced electric field and temperature elevation in human due to lightning current

    NASA Astrophysics Data System (ADS)

    Nagai, T.; Hirata, A.

    2010-05-01

    The present study investigated induced electric field and temperature elevation in specific tissues/organs of an anatomically based human body model for the lightning current. The threshold amplitude of the current inducing ventricular fibrillation and skin burning are estimated from computed induced electric field and temperature elevation with formulas for electrical stimulation and thermal damage. The computational results obtained herein were reasonably consistent with clinical observation.

  17. Alignment of Iron Nanoparticles in a Magnetic Field Due to Shape Anisotropy

    DOE PAGES

    Radhakrishnan, Balasubramaniam; Nicholson, Don M; Eisenbach, Markus; ...

    2015-07-09

    During high magnetic field processing there is evidence for alignment of non-spherical metallic particles above the Curie temperature in alloys with negligible magneto-crystalline anisotropy. The main driving force for alignment is the magnetic shape anisotropy. Current understanding of the phenomenon is not adequate to quantify the effect of particle size, aspect ratio, temperature and the magnetic field on particle alignment. We demonstrate a Monte Carlo approach coupled with size scaling to show the conditions under which alignment is possible.

  18. Alignment of Iron Nanoparticles in a Magnetic Field Due to Shape Anisotropy

    SciTech Connect

    Radhakrishnan, Balasubramaniam; Nicholson, Don M; Eisenbach, Markus; Ludtka, Gerard Michael; Rios, Orlando; Parish, Chad M

    2015-07-09

    During high magnetic field processing there is evidence for alignment of non-spherical metallic particles above the Curie temperature in alloys with negligible magneto-crystalline anisotropy. The main driving force for alignment is the magnetic shape anisotropy. Current understanding of the phenomenon is not adequate to quantify the effect of particle size, aspect ratio, temperature and the magnetic field on particle alignment. We demonstrate a Monte Carlo approach coupled with size scaling to show the conditions under which alignment is possible.

  19. Simulations of magnetic field gradients due to micro-magnets on a triple quantum dot circuit

    SciTech Connect

    Poulin-Lamarre, G.; Bureau-Oxton, C.; Kam, A.; Zawadzki, P.; Aers, G.; Studenikin, S.; Pioro-Ladrière, M.; Sachrajda, A. S.

    2013-12-04

    To quantify the effects of local magnetic fields on triple quantum dots, the Heisenberg Hamiltonian has been diagonalized for three electrons coupled via the exchange interaction. In particular, we have investigated different geometries of micro-magnets located on top of the triple dot in order to optimize the field gradient characteristics. In this paper, we focus on two geometries which are candidates for an addressable EDSR triple quantum dot device.

  20. Condensing Hybrid Water Heater Monitoring Field Evaluation

    SciTech Connect

    Maguire, J.; Earle, L.; Booten, C.; Hancock, C. E.

    2011-10-01

    This paper summarizes the Mascot home, an abandoned property that was extensively renovated. Several efficiency upgrades were integrated into this home, of particular interest, a unique water heater (a Navien CR240-A). Field monitoring was performed to determine the in-use efficiency of the hybrid condensing water heater. The results were compared to the unit's rated efficiency. This unit is Energy Star qualified and one of the most efficient gas water heaters currently available on the market.

  1. Morphology of blazar-induced gamma ray halos due to a helical intergalactic magnetic field

    SciTech Connect

    Long, Andrew J.; Vachaspati, Tanmay E-mail: tvachasp@asu.edu

    2015-09-01

    We study the characteristic size and shape of idealized blazar-induced cascade halos in the 1–100,GeV energy range assuming various non-helical and helical configurations for the intergalactic magnetic field (IGMF). While the magnetic field creates an extended halo, the helicity provides the halo with a twist. Under simplifying assumptions, we assess the parameter regimes for which it is possible to measure the size and shape of the halo from a single source and then to deduce properties of the IGMF. We find that blazar halo measurements with an experiment similar to Fermi-LAT are best suited to probe a helical magnetic field with strength and coherence length today in the ranges 10{sup −17} ∼< B{sub 0} / Gauss ∼< 10{sup −13} and 10 Mpc ∼< λ ∼< 10 Gpc where H ∼ B{sub 0}{sup 2} / λ is the magnetic helicity density. Stronger magnetic fields or smaller coherence scales can still potentially be investigated, but the connection between the halo morphology and the magnetic field properties is more involved. Weaker magnetic fields or longer coherence scales require high photon statistics or superior angular resolution.

  2. A blood-oxygenation-dependent increase in blood viscosity due to a static magnetic field.

    PubMed

    Yamamoto, Toru; Nagayama, Yuki; Tamura, Mamoru

    2004-07-21

    As the magnetic field of widely used MR scanners is one of the strongest magnetic fields to which people are exposed, the biological influence of the static magnetic field of MR scanners is of great concern. One magnetic interaction in biological subjects is the magnetic torque on the magnetic moment induced by biomagnetic substances. The red blood cell is a major biomagnetic substance, and the blood flow may be influenced by the magnetic field. However, the underlying mechanisms have been poorly understood. To examine the mechanisms of the magnetic influence on blood viscosity, we measured the time for blood to fall through a glass capillary inside and outside a 1.5 T MR scanner. Our in vitro results showed that the blood viscosity significantly increased in a 1.5 T MR scanner, and also clarified the mechanism of the interaction between red blood cells and the external magnetic field. Notably, the blood viscosity increased depending on blood oxygenation and the shear rate of the blood flow. Thus, our findings suggest that even a 1.5 T magnetic field may modulate blood flow.

  3. Possibility of critical field enhancement due to field penetration in high-T/sub c/ sponges and thin films

    SciTech Connect

    Collings, E.W.; Markworth, A.J.; Marken, K.R. Jr.

    1989-03-01

    Magnetic susceptibility measurements of a sample of sintered high-T/sub c/ ceramic superconductor of nominal composition Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-y/ were conducted as function of temperature from liquid-He temperatures to T/sub c/. The fitted form of the susceptibility temperature dependence yielded a sample particle size that was only a few times larger than the field-penetration depth. The particle size was much less than the grain size and commensurate with the thickness of the optical twins. The occurence of field penetration between lamina about 0.2 to 0.7 /mu/m in half-thickness was predicted to lead to a small enhancement of the lower critical field. This prediction was compared with the results of an experiment in which the M(H) field sweep, initially +- 100 gauss, was incremented in small steps up to several kgauss. The results of the enhancement studies are also discussed in the light of Bean's early experiments on Pb sponges (in this case /lambda/ >> particle size) which exhibited spectacular enhancements of H/sub c/ in association with flux trapping at or between the Pb filaments. It is predicted that it should be possible, using presently available film-deposition techniques, to produce high-T/sub c/ films possessing several-fold enhancements of H/sub cl/ beyond the bulk value; and that as with the Pb sponges, the magnetization loops, even when taken within what passes for the Meissner state in such materials, will by hysteretic.

  4. Distortion of magnetic field and magnetic force of a brushless dc motor due to deformed rubber magnet

    NASA Astrophysics Data System (ADS)

    Lee, C. J.; Jang, G. H.

    2008-04-01

    This paper investigates the distortion of magnetic field of a brushless dc (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force is calculated by using the Maxwell stress tensor. When the rubber magnet is globally or locally deformed, the unbalanced magnetic force has the frequencies with the first harmonic and the harmonics of slot number ±1. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry.

  5. Magnetic Field Due to a Finite Length Current-Carrying Wire Using the Concept of Displacement Current

    ERIC Educational Resources Information Center

    Buschauer, Robert

    2014-01-01

    In undergraduate E&M courses the magnetic field due to a finite length, current-carrying wire can be calculated using the Biot-Savart law. However, to the author's knowledge, no textbook presents the calculation of this field using the Ampere-Maxwell law: ?B [multiplied by] dl = µ[subscript 0] (I + e[subscript 0] dF/dt) [multiplied by] 1

  6. Magnetic Field Due to a Finite Length Current-Carrying Wire Using the Concept of Displacement Current

    ERIC Educational Resources Information Center

    Buschauer, Robert

    2014-01-01

    In undergraduate E&M courses the magnetic field due to a finite length, current-carrying wire can be calculated using the Biot-Savart law. However, to the author's knowledge, no textbook presents the calculation of this field using the Ampere-Maxwell law: ?B [multiplied by] dl = µ[subscript 0] (I + e[subscript 0] dF/dt) [multiplied by] 1

  7. Entanglement generation due to the background electric field and curvature of space-time

    NASA Astrophysics Data System (ADS)

    Ebadi, Zahra; Mirza, Behrouz

    2015-02-01

    In Schwinger effect, quantum vacuum instability under the influence of an electric field leads to decay of vacuum into pairs of charged particles. We consider the entanglement of pair produced particles. We will show that the measure of entanglement depends on the geometry of space-time. Using the Schwinger pair production in curved space-time, dS2 and AdS2, we propose and demonstrate that the electric field can generate entanglement. In dS2 space-time, we study entanglement for scalar particles with zero spin in the absence and presence of a constant electric field. We show that the entanglement entropy depends on the choice of the α-vacua. But, for some values of the related parameters (mass, charge, scalar curvature, electric field), the entanglement entropy is independent of α. Also, we consider the generation of entanglement in the presence of a constant electric field for anti-de Sitter space-time. We will show that the positive (negative) curvature of space-time upgrades (degrades) the generated entanglement.

  8. Classroom acoustic evaluation and field study

    NASA Astrophysics Data System (ADS)

    Roy, Kenneth P.; Campos, Micaelina

    2003-10-01

    The Saguaros Corazones de Alameda school in Santiago, Chile had a problem-bad acoustics. Both the background noise levels and reverberation time were much too high. The children had a difficult time understanding the teacher such that their attention was less than exemplary. Teachers had a significant absentee rate due to vocal strain issues. A sound reinforcement system was being considered-but architectural acoustic treatments were substituted with very good results. See the video and hear the results that good architectural design can make.

  9. Evaluation of bioaccumulation using in vivo laboratory and field studies.

    PubMed

    Weisbrod, Annie V; Woodburn, Kent B; Koelmans, Albert A; Parkerton, Thomas F; McElroy, Anne E; Borgå, Katrine

    2009-10-01

    A primary consideration in the evaluation of chemicals is the potential for substances to be absorbed and retained in an organism's tissues (i.e., bioaccumulated) at concentrations sufficient to pose health concerns. Substances that exhibit properties that enable biomagnification in the food chain (i.e., amplification of tissue concentrations at successive trophic levels) are of particular concern due to the elevated long-term exposures these substances pose to higher trophic organisms, including humans. Historically, biomarkers of in vivo chemical exposure (e.g., eggshell thinning, bill deformities) retrospectively led to the identification of such compounds, which were later categorized as persistent organic pollutants. Today, multiple bioaccumulation metrics are available to quantitatively assess the bioaccumulation potential of new and existing chemicals and identify substances that, upon or before environmental release, may be characterized as persistent organic pollutants. This paper reviews the various in vivo measurement approaches that can be used to assess the bioaccumulation of chemicals in aquatic or terrestrial species using laboratory-exposed, field-deployed, or collected organisms. Important issues associated with laboratory measurements of bioaccumulation include appropriate test species selection, test chemical dosing methods, exposure duration, and chemical and statistical analyses. Measuring bioaccumulation at a particular field site requires consideration of which test species to use and whether to examine natural populations or to use field-deployed populations. Both laboratory and field methods also require reliable determination of chemical concentrations in exposure media of interest (i.e., water, sediment, food or prey, etc.), accumulated body residues, or both. The advantages and disadvantages of various laboratory and field bioaccumulation metrics for assessing biomagnification potential in aquatic or terrestrial food chains are discussed

  10. Neoclassical Drift of Circulating Orbits Due toToroidal Electric Field in Tokamaks

    SciTech Connect

    Hong, Qin; Guan, Xiaoyin; Fisch, Nathaniel J.

    2011-07-19

    In tokamaks, Ware pinch is a well known neoclassical effect for trapped particles in response to a toroidal electric field. It is generally believed that there exists no similar neoclassical effect for circulating particles without collisions. However, this belief is erroneous, and misses an important effect. We show both analytically and numerically that under the influence of a toroidal electric field parallel to the current, the circulating orbits drift outward toward the outer wall with a characteristic velocity O ({var_epsilon}{sup -1}) larger than the E x B velocity, where {var_epsilon} is the inverse aspect-ratio of a tokamak. During a RF overdrive, the toroidal electric field is anti-parallel to the current. As a consequence, all charged particles, including backward runaway electrons, will drift inward towards the inner wall.

  11. Infrared near-field detection of a narrow resonance due to molecular vibrations in a nanoparticle

    SciTech Connect

    Romanov, Vyacheslav; Walker, G.C.

    2007-02-27

    Di-iron nonacarbonyl particles on a gold surface have been imaged using an apertureless near-field scanning infrared microscopy. First and second harmonic detection, with and without an auto-homodyning option, have been used to collect the near-field spectrum of a single vibrational mode of the bridging carbonyls in di-iron nonacarbonyl nanocrystalline flakes on a gold surface. The experimental results have been compared to two theoretical models, a static image-dipole effective medium and an image dipole modified by a Fresnel coefficient for the appropriate observation angle. The calculations have taken into account the roughness of the gold film. The phase dependence of the near-field contrast has been investigated using broadband and tunable CO2 lasers. Particle size effects on contrast and spatial resolution have been studied to determine the limits of applicability of the half-space approximation.

  12. Formation of electric dipoles in pea stem tissue due to an electric field

    NASA Astrophysics Data System (ADS)

    Ahmadi, Fatemeh; Farahani, Elham

    2016-07-01

    For examining the effect of an electrical field (DC) on pea seed, we exposed the pea seeds to electric fields with intensities 1, 4 and 7 kV/cm for 30, 230, 430 and 630 seconds. The tests were repeated three times, and each iteration had 5 seeds. Then, the seeds were moved to packaged plates. Finally, microscopic observation of the pea stem tissue showed that the application of a DC electrical field caused a deformation in the pea stem tissue. The results led us to examine the deformation of the tissue theoretically and to address that deformation as an electrostatic problem. In this regard, we modeled the pea stem based on the formation of electric dipoles. Then, theoretically, we calculated the force acting on each xylem section by coding, and the results were consistent with the experimental data.

  13. Cosmic parity violation due to a flavor-space locked gauge field

    NASA Astrophysics Data System (ADS)

    Caldwell, Robert

    2016-05-01

    A flavor-space locked gauge field is shown to behave like a birefringent medium, imparting a preferred left- or right-circular polarization onto gravitational waves. In a cosmological scenario, such a gauge field can cause a primordial spectrum of gravitational waves to develop a net handedness. The degree of chiral asymmetry depends on the wavelength, the abundance of the gauge field, and the strength of the gauge coupling. An asymmetry in the gravitational wave spectrum would be imprinted on the photon polarization pattern of the cosmic microwave background at last scattering. In this scenario, cosmic parity violation is written on the sky, as we predict nonzero correlation of the curl polarization with the temperature, as well as curl with gradient polarization. We compare this phenomena with parity violation in models of chiral gravity, in which the chiral asymmetry is primordial, and with models of quintessence cosmic birefringence, in which parity-violating correlations are induced along the line of sight.

  14. Chiral Magnetic Effect due to Inhomogeneous Magnetic Fields in Noncentrosymmetric Weyl Semimetals

    NASA Astrophysics Data System (ADS)

    Ibe, Yohei; Sumiyoshi, Hiroaki

    2017-05-01

    The chiral magnetic effect is a phenomenon where an electromagnetic current is generated along a magnetic field. Recently, in nonequilibrium systems, negative longitudinal magnetoresistance has been observed experimentally in Dirac/Weyl semimetals, which provides evidence for the chiral magnetic effect as a nonequilibrium current. On the other hand, the emergence of the chiral magnetic effect as an equilibrium current is still controversial. We propose a possible realization of the chiral magnetic effect as an equilibrium current using inhomogeneous magnetic fields. By employing tight-binding calculations and linear response theory, we demonstrate that a finite current density is generated by inhomogeneous magnetic fields, while the spatial integration of the current is equal to zero, which is consistent with the so-called "no-go theorem" of the chiral magnetic effect in real lattice systems. Moreover, we propose an experimental setup to detect the effect in Weyl semimetal materials.

  15. Evolution of a filament due to magnetic-field variations in a complex active region

    NASA Astrophysics Data System (ADS)

    Grigor'Ev, V. M.; Ermakova, L. V.; Khlystova, A. I.

    2006-05-01

    The complex active region NOAA 9672 is studied when it was near the central meridian, from October 21 26, 2001. At that time, there was an emergence of new magnetic flux, with the ongoing formation of a filament. The dynamics of the magnetic field are studied in order to search for their possible manifestations in the filament structure, using SOHO MDI magnetograms, SOHO EIT and TRACE filtergrams in the 171 Å line, and Hα filtergrams available via the Internet. Our earlier conclusion that filaments form at the boundaries of supergranules near polarity-inversion lines is confirmed. The conclusion of Chae that sinistral filaments have positive magnetic helicity is also confirmed. New information about magnetic-field decay processes is obtained. The direction of motion of the magnetic poles and their relative positions suggest that the axial field of a filament forms as a result of either reconnection of cancelling magnetic poles, or emergence of horizontal magnetic-flux tubes.

  16. Transient particle acceleration in strongly magnetized neutron stars. II - Effects due to a dipole field geometry

    NASA Technical Reports Server (NTRS)

    Fatuzzo, Marco; Melia, Fulvio

    1991-01-01

    Sheared Alfven waves generated by nonradial crustal disturbances above the polar cap of a strongly magnetized neutron star induce an electric field component parallel to B. An attempt is made to determine the manner in which the strong radial dependence of B affects the propagation of these sheared Alfven waves, and whether this MHD process is still an effective particle accelerator. It is found that although the general field equation is quite complicated, a simple wavelike solution can still be obtained under the conditions of interest for which the Alfven phase velocity decouples from the wave equation. The results may be applicable to gamma-ray burst sources.

  17. Cancellation of the ion deflection due to electron-suppression magnetic field in a negative-ion accelerator.

    PubMed

    Chitarin, G; Agostinetti, P; Aprile, D; Marconato, N; Veltri, P

    2014-02-01

    A new magnetic configuration is proposed for the suppression of co-extracted electrons in a negative-ion accelerator. This configuration is produced by an arrangement of permanent magnets embedded in one accelerator grid and creates an asymmetric local magnetic field on the upstream and downstream sides of this grid. Thanks to the "concentration" of the magnetic field on the upstream side of the grid, the resulting deflection of the ions due to magnetic field can be "intrinsically" cancelled by calibrating the configuration of permanent magnets. At the same time, the suppression of co-extracted electrons can be improved.

  18. Enhanced excitonic photoconductivity due to built-in internal electric field in TlGaSe{sub 2} layered semiconductor

    SciTech Connect

    Seyidov, MirHasan Yu. Suleymanov, Rauf A.; Şale, Yasin; Balaban, Ertan

    2014-12-07

    The strong enhancement, by several orders of magnitude, of the excitonic peak within the photoconductivity spectrum of TlGaSe{sub 2} semiconductor was observed. The samples were polarized in external dc electric field, which was applied prior to the measurements. Due to the accumulation of charges near the surface, an internal electric field was formed. Electron-hole pairs that were created after the absorption of light are fallen in and then separated by the built-in electric field, which prevents radiative recombination process.

  19. Modified field enhancement and extinction by plasmonic nanowire dimers due to nonlocal response.

    PubMed

    Toscano, Giuseppe; Raza, Søren; Jauho, Antti-Pekka; Mortensen, N Asger; Wubs, Martijn

    2012-02-13

    We study the effect of nonlocal optical response on the optical properties of metallic nanowires, by numerically implementing the hydrodynamical Drude model for arbitrary nanowire geometries. We first demonstrate the accuracy of our frequency-domain finite-element implementation by benchmarking it in a wide frequency range against analytical results for the extinction cross section of a cylindrical plasmonic nanowire. Our main results concern more complex geometries, namely cylindrical and bow-tie nanowire dimers that can strongly enhance optical fields. For both types of dimers we find that nonlocal response can strongly affect both the field enhancement in between the dimers and their respective extinction cross sections. In particular, we give examples of blueshifted maximal field enhancements near hybridized plasmonic dimer resonances that are still large but nearly two times smaller than in the usual local-response description. For the same geometry at a fixed frequency, the field enhancement and cross section can also be significantly more enhanced in the nonlocal-response model.

  20. Excitation of the rossby waves due to the triple polarity reversal of the magnetic field

    NASA Astrophysics Data System (ADS)

    Pataraya, A. D.; Kaghashvili, E. Kh.; Pataraya, T. A.

    It is known that at the given latitude in the "Butterfly Diagram" of Maunder time interval between neighbouring wings is about 2 years (TI), and in this interval magnetic field changes its polarity. From the observed data it is known that in TI: (a) Magnetic field changes its sign once in both hemisphere of the Sun, or (b) There is the triple polarity reversal of the Magnetic field in the one of the hemisphere and single in the another. In another side, during the last two decades quasi bi-annual oscillations (QBAO) have been discovered both in variations of different characteristics of both solar features and geophysical phenomena. The quasi bi-annual oscillations were found out in variations of the solar radius (Sakurai 1981; Delarche et al., 1985), solar radioemission (Toman 1963) and variations of average monthly Wolf numbers (Toman 1963; Robin, 1984). In the present paper exitation of the linear waves is investigated in TI. Ideal MHD equations are used in β - plane considering that the toroidal component of the unperturbed velocity has a shear in the meridional direction. It is found that in case a constant shear there is single polarity reversal of the magnetic field in the both hemisphere. After considering QBAO in case of small amplitudes of QBAO the behavier of the magnetic field is as (a), and in case of large amplitudes as (b). It is found that at the polarity reversal there is strong excitation of the Rossby waves and they propagate from the middle latitudes to equator and poles. Energy flux is calculated.

  1. Relativistic electron loss process by pitch angle scattering due to field curvature

    NASA Astrophysics Data System (ADS)

    Lee, J. J.; Parks, G. K.; Lee, E.; McCarthy, M. P.; Min, K.; Kim, H.; Park, J.; Hwang, J.

    2006-12-01

    Relativistic electron dropout (RED) events are characterized by fast electron flux decrease at the geostationary orbit. It is known that the main loss process is non adiabatic and more effective for the high energy particles. RED events generally start to occur at midnight sector and propagate to noon sector and are correlated with magnetic field stretching. We discuss this kind of event can be caused from pitch angle diffusion induced when the gyro radius of the electrons is comparable to the radius of curvature of the magnetic field and the magnetic moment is not conserved any more. While this process has been studied theoretically, the question is whether electron precipitation could be explained with this process for the real field configuration. This paper will show that this process can successfully explain the precipitation that occurred on June 14, 2004 observed by the low-altitude (680 km) polar orbiting Korean satellite, STSAT-1. In this precipitation event, the energy dispersion showed higher energy electron precipitation occurred at lower L values. This feature is a good indicator that precipitation was caused by the magnetic moment scattering in the geomagnetic tail. This interpretation is supported by the geosynchronous satellite GOES observations that showed significant magnetic field distortion occurred on the night side accompanying the electron flux depletion. Tsyganenko-01 model also shows the magnetic moment scattering could occur under the geomagnetic conditions existing at that time. We suggest the pitch angle scattering by field curvature violating the first adiabatic invariant as a possible candidate for loss mechanism of relativistic electrons in radiation belt.

  2. Modelling of 3D fields due to ferritic inserts and test blanket modules in toroidal geometry at ITER

    NASA Astrophysics Data System (ADS)

    Liu, Yueqiang; Äkäslompolo, Simppa; Cavinato, Mario; Koechl, Florian; Kurki-Suonio, Taina; Li, Li; Parail, Vassili; Saibene, Gabriella; Särkimäki, Konsta; Sipilä, Seppo; Varje, Jari

    2016-06-01

    Computations in toroidal geometry are systematically performed for the plasma response to 3D magnetic perturbations produced by ferritic inserts (FIs) and test blanket modules (TBMs) for four ITER plasma scenarios: the 15 MA baseline, the 12.5 MA hybrid, the 9 MA steady state, and the 7.5 MA half-field helium plasma. Due to the broad toroidal spectrum of the FI and TBM fields, the plasma response for all the n  =  1-6 field components are computed and compared. The plasma response is found to be weak for the high-n (n  >  4) components. The response is not globally sensitive to the toroidal plasma flow speed, as long as the latter is not reduced by an order of magnitude. This is essentially due to the strong screening effect occurring at a finite flow, as predicted for ITER plasmas. The ITER error field correction coils (EFCC) are used to compensate the n  =  1 field errors produced by FIs and TBMs for the baseline scenario for the purpose of avoiding mode locking. It is found that the middle row of the EFCC, with a suitable toroidal phase for the coil current, can provide the best correction of these field errors, according to various optimisation criteria. On the other hand, even without correction, it is predicted that these n  =  1 field errors will not cause substantial flow damping for the 15 MA baseline scenario.

  3. Field evaluation of herbal mosquito repellents.

    PubMed

    Das, N G; Nath, D R; Baruah, I; Talukdar, P K; Das, S C

    1999-12-01

    Repellent properties of Zanthoxylum armatum DC. Syn. Z. alatum Roxb. (Timur), Curcuma aromatica (Jungli haldi) and Azadirachta indica (Neem) oils were evaluated against mosquitoes in mustard (Brassica sp.) and coconut (Cocos sp.) oil base and compared with synthetic repellent. Dimethyl phthalate (DMP) as standard. Timur and jungli haldi afforded better protection in the both the base at all the concentrations. Tepellents in mustard oil gave longer protection time than those in coconut oil. At 0.57 mg/cm2 concentration timur oil gave significantly higher protection both in mustard (445 min) as well as coconut oil (404 min) than the other repellents and DMP.

  4. Energy conversion of the flare due to direct electric fields from the sheared reconnection

    NASA Astrophysics Data System (ADS)

    Hirayama, T.

    In this paper we present a new mechanism of the main energy conversion of the solar flare. Since a flare inducing prominence (flux tube) rises Vz ⩽ 300 km s-1, the plasmas below it cannot continuously eject with Alfvén speeds of VA = 3000 km s-1 but probably with Vz ≈ ±100 km s-1. Plasma up and downflows with VA will within a short duration be blocked between the chromosphere where reconnected flux tubes are piling up, and the slowly rising flux rope. Hence the Petschek slow shock mechanism is difficult to be realized as a major energy converting mechanism. Adopting a conventional reconnecting morphology, we assume a magnetic component parallel to the photospheric neutral line, i.e. sheared fields of By ≠ 0. Then Gauss’s law leads to non-vanishing electric charges σ; 4πσ = -div(V × B/c) ≈ By∂Vz/c∂x where the horizontal inflow velocity Vx changes to vertical down-flow Vz (e.g. By ≈ Bz = 40G and Δx ≈ 104 km). Then the electric field parallel to the magnetic fields E∥ calculated from Coulomb’s law from this σ is found to be far greater than the Dreicer field, and accelerates electrons and protons. Thus the horizontally inflowing Poynting energy flux in area Sx is immediately converted to the kinetic energy of electron beams along the magnetic field in area Sz; BVxSx/4π=12menVbeam3Sz with Sx/Sz ≈ 4. The particle beam energy flux cannot exceed the Poynting energy flux however large E∥ may be. The total energy can be supplied by 10 keV electrons and nbeam = 2 × 107 cm-3 for Vx = 40 km s-1. This inflow velocity Vx, though restricted by the rising prominence speed, explains the short flare duration consistent to observations. The electron beam flux nbeamVbeam will be simultaneously and co-spatially compensated by the slowly back-flowing bulk electrons, avoiding possible enormous charge pile-up. Instead of the conventional diffusion region, which contains serious difficulties if there is the shear as one should normally expect, we propose

  5. Velocity-Space Diffusion Coefficients Due to Full-Wave ICRF Fields in Toroidal Geometry

    SciTech Connect

    Harvey, R.W.; Jaeger, F.; Berry, L.A.; Batchelor, D.B.; D'Azevedo, E.; Carter, M.D.; Ershov, N.M.; Smirnov, A.P.; Bonoli, P.; Wright, J.C.; Smithe, D.N.

    2005-09-26

    Jaeger et al. have calculated bounce-averaged QL diffusion coefficients from AORSA full-wave fields, based on non-Maxwellian distributions from CQL3D Fokker-Planck code. A zero banana-width approximation is employed. Complementing this calculation, a fully numerical calculation of ion velocity diffusion coefficients using the full-wave fields in numerical tokamak equilibria has been implemented to determine the finite orbit width effects. The un-approximated Lorentz equation of motion is integrated to obtain the change in velocity after one complete poloidal transit of the tokamak. Averaging velocity changes over initial starting gyro-phase and toroidal angle gives bounce-averaged diffusion coefficients. The coefficients from the full-wave and Lorentz orbit methods are compared for an ITER DT second harmonic tritium ICRF heating case: the diffusion coefficients are similar in magnitude but reveal substantial finite orbit effects.

  6. Particle acceleration due to shocks in the interplanetary field: High time resolution data and simulation results

    NASA Technical Reports Server (NTRS)

    Kessel, R. L.; Armstrong, T. P.; Nuber, R.; Bandle, J.

    1985-01-01

    Data were examined from two experiments aboard the Explorer 50 (IMP 8) spacecraft. The Johns Hopkins University/Applied Lab Charged Particle Measurement Experiment (CPME) provides 10.12 second resolution ion and electron count rates as well as 5.5 minute or longer averages of the same, with data sampled in the ecliptic plane. The high time resolution of the data allows for an explicit, point by point, merging of the magnetic field and particle data and thus a close examination of the pre- and post-shock conditions and particle fluxes associated with large angle oblique shocks in the interplanetary field. A computer simulation has been developed wherein sample particle trajectories, taken from observed fluxes, are allowed to interact with a planar shock either forward or backward in time. One event, the 1974 Day 312 shock, is examined in detail.

  7. Transmission of electric fields due to distributed cloud charges in the atmosphere-ionosphere system

    NASA Astrophysics Data System (ADS)

    Paul, Suman; De, S. S.; Haldar, D. K.; Guha, G.

    2017-10-01

    The transmission of electric fields in the lower atmosphere by thunder clouds with a suitable charge distribution profile has been modeled. The electromagnetic responses of the atmosphere are presented through Maxwell's equations together with a time-varying source charge distribution. The conductivities are taken to be exponentially graded function of altitude. The radial and vertical electric field components are derived for isotropic, anisotropic and thundercloud regions. The analytical solutions for the total Maxwell's current which flows from the cloud into the ionosphere under DC and quasi-static conditions are obtained for isotropic region. We found that the effect of charge distribution in thunderclouds produced by lightning discharges diminishes rapidly with increasing altitudes. Also, it is found that time to reach Maxwell's currents a maximum is higher for higher altitudes.

  8. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

    PubMed Central

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-01-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter β that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

  9. Field emission current fluctuations due to lithium adsorbed on the W(111) region

    NASA Astrophysics Data System (ADS)

    Biernat, T.; Kleint, Ch.; Mȩclewski, R.

    1991-04-01

    Field emission current fluctuations for lithium adsorbed on the tungsten (111) region were investigated by a probe-hole field emission microscope. The coverage dependence of the noise power as well as spectral density functions W(ƒ) at different temperatures were obtained. The spectral density functions have been analysed in terms of the Timm and van der Ziel concentration fluctuation model. Using Comer's method the surface diffusion energies and prefactors have been determined for submonolayer coverages of lithium. They are strongly coverage dependent. The activation energy varies non-monotonically between 0.41 and 0.53 eV and the prefactor between 2.4 × 10 -4 and 1.3 × 10 -2 cm 2/s in the Li surface concentration interval (0.5-3.7) × 10 14 cm -2. The results are compared with those obtained for the W(111)/K system.

  10. Quasi-static electromagnetic fields due to dipole antennas in bounded conducting media

    NASA Astrophysics Data System (ADS)

    Habashy, T. M.; Kong, J. A.; Tsang, L.

    1985-05-01

    Several techniques are employed to model dipole fields in a two-layer dissipative medium. The upper layer is assumed lossless, the lower lossy. Attention is limited to solutions of integrals over the vertical field by quasi-static approximation (QSA), steepest descent image-source (SDIS), residue and hybrid solution approaches. A comparison of the solutions with experimental data delineates the realms of effectiveness for each computational technique: QSA is good for frequencies below 100 kHz and measurements of less than 1/30 wavelength; SDIS is valid at high frequencies on thick layers; and, normal mode residue is applicable for low frequency thin layers. Finally, intermediate conditions require all three techniques.

  11. Neuromagnetic field strength outside the human head due to impedance changes from neuronal depolarization.

    PubMed

    Ahadzi, G M; Liston, A D; Bayford, R H; Holder, D S

    2004-02-01

    The holy grail of neuroimaging would be to have an imaging system, which could image neuronal electrical activity over milliseconds. One way to do this would be by imaging the impedance changes associated with ion channels opening in neuronal membranes in the brain during activity. In principle, we could measure this change by using electrical impedance tomography (EIT) but it is close to its threshold of detectability. With the inherent limitation in the use of electrodes, we propose a new scheme based on recording the magnetic field resulting from an injected current with superconducting quantum interference devices (SQUIDs), used in magnetoencephalography (MEG). We have performed a feasibility study using computer simulation. The head was modelled as concentric spheres to mimic the scalp, skull, cerebrospinal fluid and brain using the finite element method. The magnetic field 1 cm away from the scalp was estimated. An impedance change of 1% in a 2 cm radius volume in the brain was modelled as the region of depolarization. A constant current of 100 microA was injected into the head from diametrically opposite electrodes. The model predicts that the standing magnetic field is about 10 pT and changed by about 3 fT (0.03%) on depolarization. The spectral noise density in a typical MEG system in the frequency band 1-100 Hz is about 7 fT, so this places the change at the limit of detectability. This is similar to electrical recording, as in conventional EIT systems, but there may be advantages to MEG in that the magnetic field directly traverses the skull and instrumentation errors from the electrode-skin interface will be obviated.

  12. False vacuum bubble nucleation due to a nonminimally coupled scalar field

    SciTech Connect

    Lee, Wonwoo; Park, Chanyong; Lee, Bum-Hoon; Lee, Chul H.

    2006-12-15

    We study the possibility of forming the false vacuum bubble nucleated within the true vacuum background via the true-to-false vacuum phase transition in curved spacetime. We consider a semiclassical Euclidean bubble in the Einstein theory of gravity with a nonminimally coupled scalar field. In this paper we present the numerical computations as well as the approximate analytical computations. We mention the evolution of the false vacuum bubble after nucleation.

  13. VISCOUS EVOLUTION AND PHOTOEVAPORATION OF CIRCUMSTELLAR DISKS DUE TO EXTERNAL FAR ULTRAVIOLET RADIATION FIELDS

    SciTech Connect

    Anderson, Kassandra R.; Adams, Fred C.; Calvet, Nuria

    2013-09-01

    This paper explores the effects of FUV radiation fields from external stars on circumstellar disk evolution. Disks residing in young clusters can be exposed to extreme levels of FUV flux from nearby OB stars, and observations show that disks in such environments are being actively photoevaporated. Typical FUV flux levels can be factors of {approx}10{sup 2}-10{sup 4} higher than the interstellar value. These fields are effective in driving mass loss from circumstellar disks because they act at large radial distance from the host star, i.e., where most of the disk mass is located, and where the gravitational potential well is shallow. We combine viscous evolution (an {alpha}-disk model) with an existing FUV photoevaporation model to derive constraints on disk lifetimes, and to determine disk properties as functions of time, including mass-loss rates, disk masses, and radii. We also consider the effects of X-ray photoevaporation from the host star using an existing model, and show that for disks around solar-mass stars, externally generated FUV fields are often the dominant mechanism in depleting disk material. For sufficiently large viscosities, FUV fields can efficiently photoevaporate disks over the entire range of parameter space. Disks with viscosity parameter {alpha} = 10{sup -3} are effectively dispersed within 1-3 Myr; for higher viscosities ({alpha} = 10{sup -2}) disks are dispersed within {approx}0.25-0.5 Myr. Furthermore, disk radii are truncated to less than {approx}100 AU, which can possibly affect the formation of planets. Our model predictions are consistent with the range of observed masses and radii of proplyds in the Orion Nebula Cluster.

  14. Occupational exposure in MR facilities due to movements in the static magnetic field.

    PubMed

    Andreuccetti, Daniele; Biagi, Laura; Burriesci, Giancarlo; Cannatà, Vittorio; Contessa, Gian Marco; Falsaperla, Rosaria; Genovese, Elisabetta; Lodato, Rossella; Lopresto, Vanni; Merla, Caterina; Napolitano, Antonio; Pinto, Rosanna; Tiberi, Gianluigi; Tosetti, Michela; Zoppetti, Nicola

    2017-08-30

    The exposure of operators moving in the static field of magnetic resonance (MR) facilities was assessed through measurements of the magnetic flux density, which is experienced as variable in time because of the movement. Collected data were processed to allow the comparison with most recent and authoritative safety standards. Measurements of the experienced magnetic flux density B were performed using a probe worn by volunteers moving in MR environments. A total of 55 datasets were acquired nearby a 1.5T, 3T and 7T whole body scanners. Three different metrics were applied: the maximum intensity of B, to be compared with 2013/35/EU Directive exposure limit values for static fields; the maximum variation of the vector B on every 3s-interval, for comparison with the ICNIRP-2014 basic restriction aimed at preventing vertigo effects; two weighted peak indices (for "sensory" and "health" effects: SENS-WP, HLTH-WP), assessing compliance with ICNIRP-2014 and EU Directive recommendations intended to prevent stimulation effects. Peak values of |B| were greater than 2T in 9 of the 55 datasets. All the datasets at 1.5T and 3T were compliant with the limit for vertigo effects, whereas 6 datasets at 7T turned out to be non-compliant. At 7T, all 36 datasets were non-compliant for the SENS-WP index and 26 datasets even for the HLTH-WP one. Results demonstrate that compliance with EU Directive limits for static fields does not guarantee compliance with ICNIRP-2014 reference levels and clearly show that movements in the static field could be the key component of the occupational exposure to EMF in MR facilities. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  15. ¹⁴N Quadrupole Resonance line broadening due to the earth magnetic field, occuring only in the case of an axially symmetric electric field gradient tensor.

    PubMed

    Aissani, Sarra; Guendouz, Laouès; Marande, Pierre-Louis; Canet, Daniel

    2015-01-01

    As demonstrated before, the application of a weak static B0 magnetic field (less than 10 G) may produce definite effects on the ¹⁴N Quadrupole Resonance line when the electric field gradient tensor at the nitrogen nucleus level is of axial symmetry. Here, we address more precisely the problem of the relative orientation of the two magnetic fields (the static field and the radio-frequency field of the pure NQR experiment). For a field of 6G, the evolution of the signal intensity, as a function of this relative orientation, is in very good agreement with the theoretical predictions. There is in particular an intensity loss by a factor of three when going from the parallel configuration to the perpendicular configuration. By contrast, when dealing with a very weak magnetic field (as the earth field, around 0.5 G), this effect drops to ca. 1.5 in the case Hexamethylenetetramine (HMT).This is explained by the fact that the Zeeman shift (due to the very weak magnetic field) becomes comparable to the natural line-width. The latter can therefore be determined by accounting for this competition. Still in the case of HMT, the estimated natural line-width is half the observed line-width. The extra broadening is thus attributed to earth magnetic field. The latter constitutes therefore the main cause of the difference between the natural transverse relaxation time (T₂) and the transverse relaxation time derived from the observed line-width (T₂(⁎)).

  16. Heat flux due to poloidal electric field in the banana regime

    SciTech Connect

    Taguchi, M. )

    1992-02-01

    The heat flux due to poloidally varying electrostatic potential is calculated in the banana regime. This electrostatic potential determined self-consistently from charge neutrality is shown to increase the electron heat flux by a factor {radical}{ital m}{sub {ital i}}/{ital m}{sub {ital e}} compared with that when this potential is neglected, where {ital m}{sub {ital e}} and {ital m}{sub {ital i}} are the masses of electron and ion, respectively.

  17. The onset of layer undulations in smectic A liquid crystals due to a strong magnetic field

    NASA Astrophysics Data System (ADS)

    Contreras, A.; Garcia-Azpeitia, C.; García-Cervera, C. J.; Joo, S.

    2016-08-01

    We investigate the effect of a strong magnetic field on a three dimensional smectic A liquid crystal. We identify a critical field above which the uniform layered state loses stability; this is associated to the onset of layer undulations. In a previous work García-Cervera and Joo (2012 Arch. Ration. Mech. Anal. 203 1-43), García-Cervera and Joo considered the two dimensional case and analyzed the transition to the undulated state via a simple bifurcation. In dimension n  =  3 the situation is more delicate because the first eigenvalue of the corresponding linearized problem is not simple. We overcome the difficulties inherent to this higher dimensional setting by identifying the irreducible representations for natural actions on the functional that take into account the invariances of the problem thus allowing for reducing the bifurcation analysis to a subspace with symmetries. We are able to describe at least two bifurcation branches, highlighting the richer landscape of energy critical states in the three dimensional setting. Finally, we analyze a reduced two dimensional problem, assuming the magnetic field is very strong, and are able to relate this to a model in micromagnetics studied in Alouges et al (2002 ESAIM Control Optim. Calc. Var. 8 31-68), from where we deduce the periodicity property of minimizers.

  18. Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field.

    PubMed

    Zhao, Chuan; Norden, Tenzin; Zhang, Peiyao; Zhao, Puqin; Cheng, Yingchun; Sun, Fan; Parry, James P; Taheri, Payam; Wang, Jieqiong; Yang, Yihang; Scrace, Thomas; Kang, Kaifei; Yang, Sen; Miao, Guo-Xing; Sabirianov, Renat; Kioseoglou, George; Huang, Wei; Petrou, Athos; Zeng, Hao

    2017-08-01

    Exploiting the valley degree of freedom to store and manipulate information provides a novel paradigm for future electronics. A monolayer transition-metal dichalcogenide (TMDC) with a broken inversion symmetry possesses two degenerate yet inequivalent valleys, which offers unique opportunities for valley control through the helicity of light. Lifting the valley degeneracy by Zeeman splitting has been demonstrated recently, which may enable valley control by a magnetic field. However, the realized valley splitting is modest (∼0.2 meV T(-1)). Here we show greatly enhanced valley spitting in monolayer WSe2, utilizing the interfacial magnetic exchange field (MEF) from a ferromagnetic EuS substrate. A valley splitting of 2.5 meV is demonstrated at 1 T by magnetoreflectance measurements and corresponds to an effective exchange field of ∼12 T. Moreover, the splitting follows the magnetization of EuS, a hallmark of the MEF. Utilizing the MEF of a magnetic insulator can induce magnetic order and valley and spin polarization in TMDCs, which may enable valleytronic and quantum-computing applications.

  19. Toroidal response due to strong near-field coupling in planar metamaterials (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Basharin, Alexey A.; Chuguevskiy, Vitaliy; Kafesaki, Maria; Economou, Eleftherios; Ustinov, Alexey V.

    2016-04-01

    The main research efforts in the metamaterials science are focused on achieving negative permittivity and permeability, as well as on effects such as superresolution, subwavelength guiding, enhancement of field localization, nanoantennas etc. At the same time, there is a wide range of interesting problems, beyond the issues of negative refraction. One of them is the problem associated with the excitation of toroidal response in metamaterials and the unusual phenomena associated with such response. In this paper, we demonstrate that, owing to the unique topology of the toroidal dipolar mode, its electric/magnetic field can be spatially confined within sub-wavelength, externally accessible regions of the metamolecules, which makes the toroidal metamaterials a viable platform for sensing, enhancement of light absorption and optical nonlinearities, and, especially, ingredient for qubits and quantum metamaterials. The metamolecules employed in the present study are planar conductive structures consisting of two symmetric split loops. The excited circular currents along the loops lead to a circulating magnetic moment and, as a result, to a toroidal moment. We note that the electric field is strongly localized in the splits of the loops and allows achieving the extremely high Q-factor of such types of resonators.

  20. Inputs of heavy metals due to agrochemical use in tobacco fields in Brazil's Southern Region.

    PubMed

    Zoffoli, Hugo José Oliveira; do Amaral-Sobrinho, Nelson Moura Brasil; Zonta, Everaldo; Luisi, Marcus Vinícius; Marcon, Gracioso; Tolón-Becerra, Alfredo

    2013-03-01

    Only a few studies have assessed the joint incorporation of heavy metals into agricultural systems based on the range of agrochemicals used on a specific agricultural crop. This study was conducted to assess the heavy metals input through application of the main agrochemicals used in Brazilian tobacco fields. A total of 56 samples of different batches of 5 fertilizers, 3 substrates, 8 insecticides, 3 fungicides, 2 herbicides, and 1 growth regulator commonly used in the cultivation of tobacco in Brazil's Southern Region were collected from 3 warehouses located in the States of Rio Grande do Sul, Santa Catarina, and Paraná. The total As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, and Zn content of the samples was then determined and compared with the regulations of different countries and information found in the available literature. The fertilizers were identified as the primary source of heavy metals among the agrochemicals used. Application of pesticides directly to the shoots of tobacco plants contributed very little to the supply of heavy metals. The agrochemicals used in Brazilian tobacco fields provide lower inputs of the main heavy metals that are nonessential for plants than those registered in the international literature for the majority of crop fields in different regions of the world.

  1. Quantization as an emergent phenomenon due to matter-zeropoint field interaction

    NASA Astrophysics Data System (ADS)

    Cetto, A. M.; de la Peña, L.; Valdés-Hernández, A.

    2012-05-01

    Quantization is derived as an emergent phenomenon, resulting from the permanent interaction between matter and radiation field. The starting point for the derivation is the existence of the (continuous) random zero-point electromagnetic radiation field (zpf) of mean energy hslashω/2 per normal mode. A thermodynamic and statistical analysis leads unequivocally (and without quantum assumptions) to the Planck distribution law for the complete field in equilibrium. The problem of the quantization of matter is then approached from the same perspective: A detailed study of the dynamics of a particle embedded in the zpf shows that when the entire system eventually reaches a situation of energy balance thanks to the combined effect of diffusion and dissipation, the particle has acquired its characteristic quantum properties. To obtain the quantum-mechanical description it has been necessary to do a partial averaging and take the radiationless approximation. Consideration of the neglected radiative terms allows to establish contact with nonrelativistic quantum electrodynamics and derive the correct formulas for the first-order radiative corrections. Quantum mechanics emerges therefore as a partial, approximate and time-asymptotic description of a phenomenon that in its original (pre-quantum) description is entirely local and causal.

  2. Reordering of the ridge patterns of a stochastic electromagnetic field by diffraction due to an ideal slit

    NASA Astrophysics Data System (ADS)

    Avendaño, J.; de La Peña, L.

    2005-12-01

    We study the behavior of scarlets of a stochastic radiation field of fixed frequency in the presence of a slit pierced on an infinitely thin metallic screen of ideal conductivity. Our methodology involves the exact solution of the Maxwell equations with appropriate boundary conditions, the only approximations being those due to the numerical procedure. Our numerical simulations show that the field is unfolded into two components, a dominant one that is disordered and a weaker one that is ordered. The former still presents scarlets although modified, while the latter exhibits a pattern of perfectly coherent diffraction. Due to the dominant character of the disordered component, the general appearance of the scattered field is stochastic; however, an underlying order exists. Our results confirm, thus, a novel effect suggested previously in the context of stochastic electrodynamics.

  3. Reordering of the ridge patterns of a stochastic electromagnetic field by diffraction due to an ideal slit.

    PubMed

    Avendaño, J; de la Peña, L

    2005-12-01

    We study the behavior of scarlets of a stochastic radiation field of fixed frequency in the presence of a slit pierced on an infinitely thin metallic screen of ideal conductivity. Our methodology involves the exact solution of the Maxwell equations with appropriate boundary conditions, the only approximations being those due to the numerical procedure. Our numerical simulations show that the field is unfolded into two components, a dominant one that is disordered and a weaker one that is ordered. The former still presents scarlets although modified, while the latter exhibits a pattern of perfectly coherent diffraction. Due to the dominant character of the disordered component, the general appearance of the scattered field is stochastic; however, an underlying order exists. Our results confirm, thus, a novel effect suggested previously in the context of stochastic electrodynamics.

  4. Mechanism-based evaluation of thermal ratchetting due to moving temperature distribution

    SciTech Connect

    Igari, Toshihide; Wada, Hiroshi; Ueta, Masahiro

    1995-12-01

    Recently, a structural design against a new type of thermal ratchetting under null-primary-stress condition has been required. The representative case is the thermal ratchetting caused by the movement of hot sodium level during, operation in the reactor vessel of FBR. In this paper, the mechanism of this ratchetting is proposed, and the evaluation method of ratchetting strain is proposed based on this mechanism. The proposed evaluation method is basically based on the hoop-membrane stress due to the axial temperature distribution, and considers the influence of axial bending stress and moving distance of temperature distribution. Predicted results by this equation correspond to analytical results by FEM and can conservatively estimate the experimental results with several kinds of moving distance, stress level and two types of temperature hold for Type 316 and 316FR stainless steels.

  5. Acoustic radiation force in tissue-like solids due to modulated sound field

    NASA Astrophysics Data System (ADS)

    Dontsov, Egor V.; Guzina, Bojan B.

    2012-10-01

    The focus of this study is the sustained body force (the so-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused ultrasound field (Mach number=O(10-3)) in situations when the latter is modulated by a low-frequency signal. This intermediate-asymptotics problem, which bears relevance to a number of emerging biomedical applications, is characterized by a number of small (but non-vanishing) parameters including the Mach number, the ratio between the modulation and ultrasound frequency, the ratio of the shear to bulk modulus, and the dimensionless attenuation coefficient. On approximating the response of soft tissues as that of a nonlinear viscoelastic solid with heat conduction, the featured second-order problem is tackled via a scaling paradigm wherein the transverse coordinates are scaled by the width of the focal region, while the axial and temporal coordinate are each split into a "fast" and "slow" component with the twin aim of: (i) canceling the linear terms from the field equations governing the propagation of elevated-intensity ultrasound, and (ii) accounting for the effect of ultrasound modulation. In the context of the focused ultrasound analyses, the key feature of the proposed study revolves around the dual-time-scale treatment of the temporal variable, which allows one to parse out the contribution of ultrasound and its modulation in the nonlinear solution. In this way the acoustic radiation force (ARF), giving rise to the mean tissue motion, is exacted by computing the "fast" time average of the germane field equations. A comparison with the existing theory reveals a number of key features that are brought to light by the new formulation, including the contributions to the ARF of ultrasound modulation and thermal expansion, as well as the precise role of constitutive nonlinearities in generating the sustained body force in tissue-like solids by a focused ultrasound beam.

  6. Estimating the change in asymptotic direction due to secular changes in the geomagnetic field

    NASA Technical Reports Server (NTRS)

    Flueckiger, E. O.; Smart, D. F.; Shea, M. A.; Gentile, L. C.; Bathurat, A. A.

    1985-01-01

    The concept of geomagnetic optics, as described by the asymptotic directions of approach, is extremely useful in the analysis of cosmic radiation data. However, when changes in cutoff occur as a result of evolution in the geomagnetic field, there are corresponding changes in the asymptotic cones of acceptance. A method is introduced of estimating the change in the asymptotic direction of approach for vertically incident cosmic ray particles from a reference set of directions at a specific epoch by considering the change in the geomagnetic cutoff.

  7. NASA's New Approach for Evaluating Risk Reduction Due to Space Shuttle Upgrades

    NASA Technical Reports Server (NTRS)

    Safie, Fayssal M.; Belyeu, Rebecca L.

    2000-01-01

    As part of NASA's intensive effort to incorporate quantitative risk assessment (QRA) tools in the Agency's decision-making process concerning Space Shuttle risk, NASA has developed a powerful risk assessment tool called the Quantitative Risk Assessment System (QRAS). The QRAS is a tool designed to estimate Space Shuttle risk and evaluate Space Shuttle upgrades. This paper presents an overview of the QRAS with focus on its application for evaluating the risk reduction due to proposed Space Shuttle upgrades. The application includes a case study from the Space Shuttle main engine (SSME). The QRAS overview section of the paper includes the QRAS development process, the technical approach to model development, the QRA quantification methods and techniques, and observations concerning the complex modeling involved in QRAS. The application section of the paper describes a practical case study using QRAS models for evaluating critical Space Shuttle Program upgrades, specifically a proposed SSME nozzle upgrade. This paper presents the method for evaluating the proposed upgrade by comparing the current nozzle (old design with well-established probabilistic models) to the channel wall nozzle (new design at the preliminary design level).

  8. Measurement of electric fields induced in a human subject due to natural movements in static magnetic fields or exposure to alternating magnetic field gradients

    NASA Astrophysics Data System (ADS)

    Glover, P. M.; Bowtell, R.

    2008-01-01

    A dual dipole electric field probe has been used to measure surface electric fields in vivo on a human subject over a frequency range of 0.1-800 Hz. The low-frequency electric fields were induced by natural body movements such as walking and turning in the fringe magnetic fields of a 3 T magnetic resonance whole-body scanner. The rate-of-change of magnetic field (dB/dt) was also recorded simultaneously by using three orthogonal search coils positioned near to the location of the electric field probe. Rates-of-change of magnetic field for natural body rotations were found to exceed 1 T s-1 near the end of the magnet bore. Typical electric fields measured on the upper abdomen, head and across the tongue for 1 T s-1 rate of change of magnetic field were 0.15 ± 0.02, 0.077 ± 0.003 and 0.015 ± 0.002 V m-1 respectively. Electric fields on the abdomen and chest were measured during an echo-planar sequence with the subject positioned within the scanner. With the scanner rate-of-change of gradient set to 10 T m-1 s-1 the measured rate-of-change of magnetic field was 2.2 ± 0.1 T s-1 and the peak electric field was 0.30 ± 0.01 V m-1 on the chest. The values of induced electric field can be related to dB/dt by a 'geometry factor' for a given subject and sensor position. Typical values of this factor for the abdomen or chest (for measured surface electric fields) lie in the range of 0.10-0.18 m. The measured values of electric field are consistent with currently available numerical modelling results for movement in static magnetic fields and exposure to switched magnetic field gradients.

  9. Measurement of electric fields induced in a human subject due to natural movements in static magnetic fields or exposure to alternating magnetic field gradients.

    PubMed

    Glover, P M; Bowtell, R

    2008-01-21

    A dual dipole electric field probe has been used to measure surface electric fields in vivo on a human subject over a frequency range of 0.1-800 Hz. The low-frequency electric fields were induced by natural body movements such as walking and turning in the fringe magnetic fields of a 3 T magnetic resonance whole-body scanner. The rate-of-change of magnetic field (dB/dt) was also recorded simultaneously by using three orthogonal search coils positioned near to the location of the electric field probe. Rates-of-change of magnetic field for natural body rotations were found to exceed 1 T s(-1) near the end of the magnet bore. Typical electric fields measured on the upper abdomen, head and across the tongue for 1 T s(-1) rate of change of magnetic field were 0.15+/-0.02, 0.077+/-0.003 and 0.015+/-0.002 V m(-1) respectively. Electric fields on the abdomen and chest were measured during an echo-planar sequence with the subject positioned within the scanner. With the scanner rate-of-change of gradient set to 10 T m(-1) s(-1) the measured rate-of-change of magnetic field was 2.2+/-0.1 T s(-1) and the peak electric field was 0.30+/-0.01 V m(-1) on the chest. The values of induced electric field can be related to dB/dt by a 'geometry factor' for a given subject and sensor position. Typical values of this factor for the abdomen or chest (for measured surface electric fields) lie in the range of 0.10-0.18 m. The measured values of electric field are consistent with currently available numerical modelling results for movement in static magnetic fields and exposure to switched magnetic field gradients.

  10. Comparison of induction motor field efficiency evaluation methods

    SciTech Connect

    Hsu, J.S.; Kueck, J.D.; Olszewski, M.; Casada, D.A.; Otaduy, P.J.; Tolbert, L.M.

    1996-10-01

    Unlike testing motor efficiency in a laboratory, certain methods given in the IEEE-Std 112 cannot be used for motor efficiency in the field. For example, it is difficult to load a motor in the field with a dynamometer when the motor is already coupled to driven equipment. The motor efficiency field evaluation faces a different environment from that for which the IEEE-Std 112 is chiefly written. A field evaluation method consists of one or several basic methods according to their physical natures. Their intrusivenesses and accuracies are also discussed. This study is useful for field engineers to select or to establish a proper efficiency evaluation method by understanding the theories and error sources of the methods.

  11. Electron residual energy due to stochastic heating in field-ionized plasma

    SciTech Connect

    Khalilzadeh, Elnaz; Yazdanpanah, Jam Chakhmachi, Amir; Jahanpanah, Jafar; Yazdani, Elnaz

    2015-11-15

    The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is investigated here. Initially, the optical response of plasma is modeled by using two counter-propagating electromagnetic waves. In this case, the solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared with that without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will be significantly changed by applying a minor change in the initial conditions. Extensive kinetic 1D-3V particle-in-cell simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in a proper long pulse length is high enough to act as a second counter-propagating wave and trigger the stochastic electron motion. On the contrary, the analyses of intensity spectrum reveal the fact that the dominant scattering mechanism tends to Thomson rather than Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside and outside of the pulse region.

  12. Screening of external magnetic perturbation fields due to sheared plasma flow

    NASA Astrophysics Data System (ADS)

    Li, L.; Liu, Y. Q.; Liang, Y.; Wang, N.; Luan, Q.; Zhong, F. C.; Liu, Y.

    2016-09-01

    Within the single fluid resistive magnetohydrodynamic model, systematic toroidal modelling efforts are devoted to investigate the plasma response induced screening of the applied external 3D magnetic field perturbations in the presence of sheared toroidal flow. One particular issue of interest is addressed, when the local flow speed approaches zero at the perturbation rational surface inside the plasma. Subtle screening physics, associated with the favourable averaged toroidal curvature effect (the GGJ effect (Glasser et al 1975 Phys. Fluids 7 875)), is found to play an essential role during slow flow near the rational surface by enhancing the screening at reduced flow. A strong cancellation effect between different terms of Ohm’s law is discovered, leading to different screening physics in the GGJ regime, as compared to that of conventional screening of the typical resistive-inertial regime occurring at faster flow. These modelling results may be applicable to interpret certain mode locking experiments, as well as type-I edge localized mode suppression experiments, with resonant magnetic field perturbations being applied to tokamak plasmas at low input toroidal torque.

  13. Excitation of dayside chorus waves due to magnetic field line compression in response to interplanetary shocks

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Li, Wen; Thorne, Richard M.; Bortnik, Jacob; Ma, Qianli; An, Xin; Zhang, Xiao-jia; Angelopoulos, Vassilis; Ni, Binbin; Gu, Xudong; Fu, Song; Zhao, Zhengyu

    2015-10-01

    The excitation of magnetospheric whistler-mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008-2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background magnetic field configurations in the near-equatorial dayside magnetosphere; and therefore, the threshold of nonlinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geomagnetic field line configuration plays a key role in the excitation of dayside chorus.

  14. Suppression of drift wave instability due to sheared field-aligned flow and negative ions

    NASA Astrophysics Data System (ADS)

    Ichiki, Ryuta; Hayashi, Kenichiro; Kaneko, Toshiro; Hatakeyama, Rikizo

    2006-10-01

    Sheared field-aligned plasma flow is a significant topic in space/circumterrestrial plasmas. Taking into account negative ions or dust grains will make the space plasma physics more general and accurate. Using the QT-Upgrade Machine, we have conducted laboratory experiments to examine negative ion effects on shear-modified drift waves. Field-aligned K^+ ion flow and its shear strength are controlled with a concentrically segmented W hot plate. Negative ions SF6^- are produced by introducing SF6 gas in the plasma. The drift wave shows a gradual monotonic decrease in amplitude as the shear strength is increased from zero. However, as the shear strength is decreased from zero to negative values, the amplitude increases up to a certain shear strength and rapidly decreases after the peaking. The negative ion introduction, in general, suppresses this instability while retaining the dependence of the amplitude on the shear. These wave characteristics are interpreted using the theories of current-driven (kinetic) and of D’Angelo (fluid) instabilities.

  15. Electron residual energy due to stochastic heating in field-ionized plasma

    NASA Astrophysics Data System (ADS)

    Khalilzadeh, Elnaz; Yazdanpanah, Jam; Jahanpanah, Jafar; Chakhmachi, Amir; Yazdani, Elnaz

    2015-11-01

    The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is investigated here. Initially, the optical response of plasma is modeled by using two counter-propagating electromagnetic waves. In this case, the solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared with that without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will be significantly changed by applying a minor change in the initial conditions. Extensive kinetic 1D-3V particle-in-cell simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in a proper long pulse length is high enough to act as a second counter-propagating wave and trigger the stochastic electron motion. On the contrary, the analyses of intensity spectrum reveal the fact that the dominant scattering mechanism tends to Thomson rather than Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside and outside of the pulse region.

  16. Excessive magnetic field flux density distribution from overhead isolated powerline conductors due to neutral line current.

    PubMed

    Netzer, Moshe

    2013-06-01

    Overhead isolated powerline conductors (hereinafter: "OIPLC") are the most compact form for distributing low voltage currents. From the known physics of magnetic field emission from 3-phase power lines, it is expected that excellent symmetry of the 120° shifted phase currents and where compact configuration of the 3-phase+neutral line exist, the phase current vectorial summation of the magnetic field flux density (MFFD) is expected to be extremely low. However, despite this estimation, an unexpectedly very high MFFD was found in at least three towns in Israel. This paper explains the reasons leading to high MFFD emissions from compact OIPLC and the proper technique to fix it. Analysis and measurement results had led to the failure hypothsis of neutral line poor connection design and poor grounding design of the HV-LV utility transformers. The paper elaborates on the low MFFD exposure level setup by the Israeli Environmental Protection Office which adopted a rather conservative precaution principal exposure level (2 mG averaged over 24 h).

  17. Vibroacoustic Response of Residential Housing due to Sonic Boom Exposure: A Summary of two Field Tests

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Buehrle, Ralph; Sullivan, Brenda; Gavin, Joseph; Salamone, Joseph; Haering, Edward A., jr.; Miller, Denise M.

    2008-01-01

    Two experiments have been performed to measure the vibroacoustic response of houses exposed to sonic booms. In 2006, an old home in the base housing area of Edwards Air Force Base, built around 1960 and demolished in 2007, was instrumented with 288 transducers. During a 2007 follow-on test, a newer home in the base housing area, built in 1997, was instrumented with 112 transducers. For each experiment, accelerometers were placed on walls, windows and ceilings in bedrooms of the house to measure the vibration response of the structure. Microphones were placed outside and inside the house to measure the excitation field and resulting interior sound field. The vibroacoustic response of each house was measured for sonic boom amplitudes spanning from 2.4 to 96 Pa (0.05 to 2 lbf/sq ft). The boom amplitudes were systematically varied using a unique dive maneuver of an F/A-18 airplane. In total, the database for both houses contains vibroacoustic response data for 154 sonic booms. In addition, several tests were performed with mechanical shaker excitation of the structure to characterize the forced response of the houses. The purpose of this paper is to summarize all the data from these experiments that are available to the research community, and to compare and contrast the vibroacoustic behavior of these two dissimilar houses.

  18. Mobility overestimation due to gated contacts in organic field-effect transistors

    PubMed Central

    Bittle, Emily G.; Basham, James I.; Jackson, Thomas N.; Jurchescu, Oana D.; Gundlach, David J.

    2016-01-01

    Parameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current–voltage characteristics and interpreted by using the classical metal oxide–semiconductor field-effect transistor model. However, in recent reports of devices with ultra-high mobility (>40 cm2 V−1 s−1), the device characteristics deviate from this idealized model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current–voltage characterization are overestimated by one order of magnitude or more. PMID:26961271

  19. Global Simulation of Proton Precipitation Due to Field Line Curvature During Substorms

    NASA Technical Reports Server (NTRS)

    Gilson, M. L.; Raeder, J.; Donovan, E.; Ge, Y. S.; Kepko, L.

    2012-01-01

    The low latitude boundary of the proton aurora (known as the Isotropy Boundary or IB) marks an important boundary between empty and full downgoing loss cones. There is significant evidence that the IB maps to a region in the magnetosphere where the ion gyroradius becomes comparable to the local field line curvature. However, the location of the IB in the magnetosphere remains in question. In this paper, we show simulated proton precipitation derived from the Field Line Curvature (FLC) model of proton scattering and a global magnetohydrodynamic simulation during two substorms. The simulated proton precipitation drifts equatorward during the growth phase, intensifies at onset and reproduces the azimuthal splitting published in previous studies. In the simulation, the pre-onset IB maps to 7-8 RE for the substorms presented and the azimuthal splitting is caused by the development of the substorm current wedge. The simulation also demonstrates that the central plasma sheet temperature can significantly influence when and where the azimuthal splitting takes place.

  20. SOI detector with drift field due to majority carrier flow - an alternative to biasing in depletion

    SciTech Connect

    Trimpl, M.; Deptuch, G.; Yarema, R.; /Fermilab

    2010-11-01

    This paper reports on a SOI detector with drift field induced by the flow of majority carriers. It is proposed as an alternative method of detector biasing compared to standard depletion. N-drift rings in n-substrate are used at the front side of the detector to provide charge collecting field in depth as well as to improve the lateral charge collection. The concept was verified on a 2.5 x 2.5 mm{sup 2} large detector array with 20 {micro}m and 40 {micro}m pixel pitch fabricated in August 2009 using the OKI semiconductor process. First results, obtained with a radioactive source to demonstrate spatial resolution and spectroscopic performance of the detector for the two different pixel sizes will be shown and compared to results obtained with a standard depletion scheme. Two different diode designs, one using a standard p-implantation and one surrounded by an additional BPW implant will be compared as well.

  1. Management of head trauma due to landmine explosions: from battle field to operation room.

    PubMed

    Atabey, Cem; Asir, Alparslan; Ersoy, Turgay

    2012-04-01

    Head injuries due to landmine explosions are not well studied and the management of such injuries is not documented, even though there is, unfortunately, a regrettably high incidence of such injuries in the military and in civilians. The data of 119 patients who underwent surgery for the head injuries due to landmine explosions were reviewed retrospectively. All of these patients were military personnel, and the mean age was 23 years. A total 83 (69.7%) of the cases were injured by the anti-personnel devices and 36 (30.3%) by vehicle landmines. Fifty percent of the patients underwent surgery for depressed skull fracture, intraparenchymal foreign body, epidural haematoma or subdural haematoma. Six (0.05%) patients died in the emergency room. Landmine explosions can produce classic injury patterns from blunt and penetrating mechanisms to several organ systems, including the brain. They also produce unique injury patterns to the brain. Understanding this important difference is critical in management of these injuries. Early surgical treatment and appropriate management could save more lives.

  2. Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields.

    PubMed

    Zradziński, Patryk

    2015-01-01

    Due to the various physical mechanisms of interaction between a worker's body and the electromagnetic field at various frequencies, the principles of numerical simulations have been discussed for three areas of worker exposure: to low frequency magnetic field, to low and intermediate frequency electric field and to radiofrequency electromagnetic field. This paper presents the identified difficulties in applying numerical simulations to evaluate physical estimators of direct and indirect effects of exposure to electromagnetic fields at various frequencies. Exposure of workers operating a plastic sealer have been taken as an example scenario of electromagnetic field exposure at the workplace for discussion of those difficulties in applying numerical simulations. The following difficulties in reliable numerical simulations of workers' exposure to the electromagnetic field have been considered: workers' body models (posture, dimensions, shape and grounding conditions), working environment models (objects most influencing electromagnetic field distribution) and an analysis of parameters for which exposure limitations are specified in international guidelines and standards.

  3. Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields

    PubMed Central

    Zradziński, Patryk

    2015-01-01

    Due to the various physical mechanisms of interaction between a worker's body and the electromagnetic field at various frequencies, the principles of numerical simulations have been discussed for three areas of worker exposure: to low frequency magnetic field, to low and intermediate frequency electric field and to radiofrequency electromagnetic field. This paper presents the identified difficulties in applying numerical simulations to evaluate physical estimators of direct and indirect effects of exposure to electromagnetic fields at various frequencies. Exposure of workers operating a plastic sealer have been taken as an example scenario of electromagnetic field exposure at the workplace for discussion of those difficulties in applying numerical simulations. The following difficulties in reliable numerical simulations of workers’ exposure to the electromagnetic field have been considered: workers’ body models (posture, dimensions, shape and grounding conditions), working environment models (objects most influencing electromagnetic field distribution) and an analysis of parameters for which exposure limitations are specified in international guidelines and standards. PMID:26323781

  4. Evaluation of Transcutaneous Electrical Nerve Stimulation as a Treatment of Neck Pain due to Musculoskeletal Disorders.

    PubMed

    Maayah, Mikhled; Al-Jarrah, Mohammed

    2010-05-19

    This study was designed to evaluate transcutaneous electrical nerve stimulation (TENS) as a treatment for neck pain due to musculoskeletal disorders within the context of a physiotherapy treatment. Thirty subjects with neck pain were randomly allocated to two groups, treated with either TENS (n = 15) or placebo (n = 15). Each subject received one session for one hour. All subjects were evaluated before, during treatment, after switch off and again a week after by using Myometer machine. All subjects completed the follow-up assessment. Subjects referred for out-subjects' physiotherapy department, fulfilling the inclusion and exclusion criteria, took part in the study. The assessments were compared and used to measure outcome treatment. Improvement in their condition was measured in terms of a reduction in the individual's level of pain during the week after the end of the first session. At the end of the first session, the study showed that 11 subjects (73%) in the treatment and 7 subjects (43%) in the control groups had gained marked improvement. These results are statistically highly significant, (P = 0.01) at the end of the follow-up assessment. A conclusion could be drawn that a single intense TENS treatment is an effective treatment for neck pain due to musculoskeletal disorders. On the other hand, TENS showed an effective pain relief with subjects who have a mild neck pain rather than those with severe symptoms. Musculoskeletal disorders; Transcutaneous electrical nerve stimulation; Neck pain.

  5. Evaluating bias due to population stratification in case-control association studies of admixed populations.

    PubMed

    Wang, Yiting; Localio, Russell; Rebbeck, Timothy R

    2004-07-01

    The potential for bias from population stratification (PS) has raised concerns about case-control studies involving admixed ethnicities. We evaluated the potential bias due to PS in relating a binary outcome with a candidate gene under simulated settings where study populations consist of multiple ethnicities. Disease risks were assigned within the range of prostate cancer rates of African Americans reported in SEER registries assuming k=2, 5, or 10 admixed ethnicities. Genotype frequencies were considered in the range of 5-95%. Under a model assuming no genotype effect on disease (odds ratio (OR)=1), the range of observed OR estimates ignoring ethnicity was 0.64-1.55 for k=2, 0.72-1.33 for k=5, and 0.81-1.22 for k=10. When genotype effect on disease was modeled to be OR=2, the ranges of observed OR estimates were 1.28-3.09, 1.43-2.65, and 1.62-2.42 for k=2, 5, and 10 ethnicities, respectively. Our results indicate that the magnitude of bias is small unless extreme differences exist in genotype frequency. Bias due to PS decreases as the number of admixed ethnicities increases. The biases are bounded by the minimum and maximum of all pairwise baseline disease odds ratios across ethnicities. Therefore, bias due to PS alone may be small when baseline risk differences are small within major categories of admixed ethnicity, such as African Americans. Copyright 2004 Wiley-Liss, Inc.

  6. Evaluation of serum myeloperoxidase concentration in dogs with heart failure due to chronic mitral valvular insufficiency.

    PubMed

    Park, Jong-In; Suh, Sang-Il; Hyun, Changbaig

    2017-01-01

    Myeloperoxidase (MPO) is a leukocyte-derived enzyme involved in the process of heart failure and is found to have good diagnostic and prognostic values in humans with chronic heart failure. This study evaluated the relationship between serum MPO levels and the severity of heart failure (HF) due to chronic mitral valvular insufficiency (CMVI) in dogs. Eighty-two client-owned dogs consisting of 69 dogs with different stages of HF due to CMVI and 13 age-matched healthy dogs were enrolled in this study. Serum MPO concentrations in the healthy and CMVI groups were determined by enzyme-linked immunosorbent assay (ELISA) using a canine-specific monoclonal anti-MPO antibody. Serum MPO concentrations were 273.3 ± 179.6 ng/L in the controls, 140.8 ± 114.1 ng/L in the International Small Animal Cardiac Health Council (ISACHC) I group, 109.0 ± 85.2 ng/L in the ISACHC II group, and 106.0 ± 42.3 ng/L in the ISACHC III group. Close negative correlation to serum MPO concentration was found in the severity of heart failure (ISACHC stage). Although this study found a modest relationship between serum MPO levels and the severity of HF due to CMVI in dogs, it also suggested that serum MPO levels decreased as the severity of HF increased.

  7. Experimental observation of increased threshold electric field for runaway generation due to synchrotron radiation losses in the FTU tokamak

    SciTech Connect

    Martin-Solis, Jose Ramon; Sanchez, Raul; Esposito, Basilio

    2010-01-01

    The threshold electric field for runaway generation has been investigated during runaway suppression experiments by means of electron-cyclotron-resonance heating in the flattop phase of FTU discharges. Runaway suppression has been experimentally found to occur at electric fields substantially larger than those predicted by the relativistic collisional theory of runaway generation, E{sub R} = n{sub e}e{sup 3}ln{Lambda}/4{pi}{var_epsilon}{sub 0}{sup 2}m{sub e}c{sup 2}. These experimental results are consistent with an increase of the critical electric field due to the electron synchrotron radiation losses. No runaway electrons are found in FTU experiments below the radiation threshold. These results support evidence for a new threshold electric field for runaway generation that accounts for the effect of the synchrotron losses, and which should be considered when making predictions on runaway generation and mitigation in devices such as ITER.

  8. Field Evaluation of Lethal Ovitrap against Dengue Vectors

    DTIC Science & Technology

    2005-04-01

    AD Award Number: DAMD17-02-1-0217 TITLE: Field Evaluation of Lethal Ovitrap against Dengue Vectors PRINCIPAL INVESTIGATOR: Dr. Lane Foil CONTRACTING...2005 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Field Evaluation of Lethal Ovitrap against Dengue Vectors 5b. GRANT NUMBER DAMD17-02-1-0217 5c. PROGRAM...to effectively sample dengue mosquito vector populations, particularly Aedes aegypti for over a decade. Modifying a standard ovitrap by incorporating

  9. Temporal static stress drop variations due to injection activity at The Geysers geothermal field, California

    NASA Astrophysics Data System (ADS)

    Staszek, M.; Orlecka-Sikora, B.; Leptokaropoulos, K.; Kwiatek, G.; Martínez-Garzón, P.

    2017-07-01

    We use a high-quality data set from the NW part of The Geysers geothermal field to determine statistical significance of temporal static stress drop variations and their relation to injection rate changes. We use a group of 322 seismic events which occurred in the proximity of Prati-9 and Prati-29 injection wells to examine the influence of parameters such as moment magnitude, focal mechanism, hypocentral depth, and normalized hypocentral distances from open-hole sections of injection wells on static stress drop changes. Our results indicate that (1) static stress drop variations in time are statistically significant, (2) statistically significant static stress drop changes are inversely related to injection rate fluctuations. Therefore, it is highly expected that static stress drop of seismic events is influenced by pore pressure in underground fluid injection conditions and depends on the effective normal stress and strength of the medium.

  10. Gyrokinetic Simulations of Electrostatic Turbulence Reduction due to Radial Electric Field Shear in DIII-D

    NASA Astrophysics Data System (ADS)

    Taimourzadeh, Sam; Holod, Ihor; Lin, Zhihong; Nazikian, Raffi

    2015-11-01

    It has been demonstrated that edge localized modes (ELMs) can be fully suppressed in DIII-D H-mode plasmas with the application of resonant magnetic perturbations (RMPs), and that there is a corresponding reduction of pedestal gradients, changes in rotation, and changes in the radial electric field (Er) profile. However, with the application of RMPs there is also an increase in short wavelength, electrostatic turbulence on top of the pedestal, as observed with BES, DBS, and other fluctuation diagnostics. The effects of Er shear on this turbulence, is investigated using gyrokinetic simulations via the gyrokinetic toroidal code (GTC) for in DIII-D shot 158103, at times 3750 ms (RMP on, ELM active) and 3050 ms (RMP on, ELM suppressed).

  11. Variations of Mars gravitational field and rotation due to seasonal CO2 exchange

    NASA Technical Reports Server (NTRS)

    Chao, B. Fong; Rubincam, David Parry

    1990-01-01

    About a quarter of the Martian atmospheric mass is exchanged between the atmosphere and the polar caps in the course of a Martian year: CO2 condenses to form (or add to) the polar caps in winter and sublimes into the atmosphere in summer. This paper studies the effect of this CO2 mass redistribution on Martian rotation and gravitational field. Two mechanisms are examined: (1) the waxing and waning of solid CO2 in the polar caps and (2) the geographical distribution of gaseous CO2 in the atmosphere. In particular, the net peak-to-peak changes in J2 and J3 over a Martian year are both found to be as much as about 6 x 10 to the -9th. A simulation suggests that these changes may be detected by the upcoming Mars Observer under favorable but realistic conditions.

  12. Entanglement production due to quench dynamics of an anisotropic XY chain in a transverse field

    NASA Astrophysics Data System (ADS)

    Sengupta, K.; Sen, Diptiman

    2009-09-01

    We compute concurrence and negativity as measures of two-spin entanglement generated by a power-law quench (characterized by a rate τ-1 and an exponent α ) which takes an anisotropic XY chain in a transverse field through a quantum critical point (QCP). We show that only spins separated by an even number of lattice spacings get entangled in such a process. Moreover, there is a critical rate of quench, τc-1 , above which no two-spin entanglement is generated; the entire entanglement is multipartite. The ratio of the entanglements between consecutive even neighbors can be tuned by changing the quench rate. We also show that for large τ , the concurrence (negativity) scales as α/τ (α/τ) , and we relate this scaling behavior to defect production by the quench through a QCP.

  13. Second Law Violations by Means of a Stratification of Temperature Due to Force Fields

    NASA Astrophysics Data System (ADS)

    Trupp, Andreas

    2002-11-01

    In 1868 J.C. Maxwell proved that a perpetual motion machine of the second kind would become possible, if the equilibrium temperature in a vertical column of gas subject to gravity were a function of height. However, Maxwell had claimed that the temperature had to be the same at all points of the column. So did Boltzmann. Their opponent was Loschmidt. He claimed that the equilibrium temperature declined with height, and that a perpetual motion machine of the second kind operating by means of such column was compatible with the second law of thermodynamics. Extending the general idea behind Loschmidt's concept to other force fields, gravity can be replaced by molecular forces acting on molecules that try to escape from the surface of a liquid into the vapor space. Experiments proving the difference of temperature between the liquid and the vapor phase were conducted in the 19th century already.

  14. Evaluation of uncertainty in the measurement of environmental electromagnetic fields.

    PubMed

    Vulević, B; Osmokrović, P

    2010-09-01

    With regard to Non-ionising radiation protection, the relationship between human exposure to electromagnetic fields and health is controversial. Electromagnetic fields have become omnipresent in the daily environment. This paper assesses the problem of how to compare a measurement result with a limit fixed by the standard for human exposure to electric, magnetic and electromagnetic fields (0 Hz-300 GHz). The purpose of the paper is an appropriate representation of the basic information about evaluation of measurement uncertainty.

  15. Effect of prior performance on subsequent performance evaluation by field independent-dependent raters.

    PubMed

    Sisco, Howard; Leventhal, Gloria

    2007-12-01

    The importance of accurate performance appraisals is central to many aspects of personnel activities in organizations. This study examined threats due to past performance to accuracy of evaluation of subsequent performance by raters differing in scores on field dependence. 162 college students were classified as Field-dependent (n = 81) or Field-independent (n = 81), using a median split on the Group Embedded Figures Test. Past performance (a lecture) was good or poor, presented directly via a videotape or indirectly via a written evaluation to the Field-independent or Field-dependent groups. Analysis indicated the hypothesized contrast effect (ratings in the opposite direction from that of prior ratings) in the Direct condition and an unexpected, albeit smaller, contrast effect in the Indirect condition. There were also differential effects of performance, presentation, and field dependency on rating of lecturer's style and ability.

  16. Mean force on a finite-sized spherical particle due to an acoustic field in a viscous compressible medium

    NASA Astrophysics Data System (ADS)

    Annamalai, Subramanian; Balachandar, S.; Parmar, Manoj K.

    2014-05-01

    An analytical expression to evaluate the second-order mean force (acoustic radiation force) on a finite-sized, rigid, spherical particle due to an acoustic wave is presented. The medium in which the particle is situated is taken to be both viscous and compressible. A far-field derivation approach has been used in determining the force, which is a function of the particle size, acoustic wavelength, and viscous boundary-layer thickness. It is assumed that the viscous length scale is negligibly small compared to the acoustic wavelength. The force expression presented here (i) reduces to the correct inviscid behavior (for both small- and finite-sized particles) and (ii) is identical to recent viscous results [M. Settnes and H. Bruus, Phys. Rev. E 85, 016327 (2012), 10.1103/PhysRevE.85.016327] for small-sized particles. Further, the computed force qualitatively matches the computational fluid dynamics (finite-element) results [D. Foresti, M. Nabavi, and D. Poulikakos, J. Fluid Mech. 709, 581 (2012), 10.1017/jfm.2012.350] for finite-sized particles. Additionally, the mean force is interpreted in terms of a multipole expansion. Subsequently, considering the fact that the force expansion is an infinite series, the number of terms that are required or adequate to capture the force to a specified accuracy is also provided as a function of the particle size to acoustic wavelength ratio. The dependence of the force on particle density, kinematic viscosity, and bulk viscosity of the fluid is also investigated. Here, both traveling and standing waves are considered.

  17. Effect of Combined Loading Due to Bending and Internal Pressure on Pipe Flaw Evaluation Criteria

    NASA Astrophysics Data System (ADS)

    Miura, Naoki; Sakai, Shinsuke

    Considering a rule for the rationalization of maintenance of Light Water Reactor piping, reliable flaw evaluation criteria are essential for determining how a detected flaw will be detrimental to continuous plant operation. Ductile fracture is one of the dominant failure modes that must be considered for carbon steel piping and can be analyzed by elastic-plastic fracture mechanics. Some analytical efforts have provided various flaw evaluation criteria using load correction factors, such as the Z-factors in the JSME codes on fitness-for-service for nuclear power plants and the section XI of the ASME boiler and pressure vessel code. The present Z-factors were conventionally determined, taking conservativity and simplicity into account; however, the effect of internal pressure, which is an important factor under actual plant conditions, was not adequately considered. Recently, a J-estimation scheme, LBB.ENGC for the ductile fracture analysis of circumferentially through-wall-cracked pipes subjected to combined loading was developed for more accurate prediction under more realistic conditions. This method explicitly incorporates the contributions of both bending and tension due to internal pressure by means of a scheme that is compatible with an arbitrary combined-loading history. In this study, the effect of internal pressure on the flaw evaluation criteria was investigated using the new J-estimation scheme. The Z-factor obtained in this study was compared with the presently used Z-factors, and the predictability of the current flaw evaluation criteria was quantitatively evaluated in consideration of the internal pressure.

  18. Evaluating the PM damage cost due to urban air pollution and vehicle emissions in Seoul, Korea.

    PubMed

    Lee, Yong Jin; Lim, Young Wook; Yang, Ji Yeon; Kim, Chang Soo; Shin, Young Chul; Shin, Dong Chun

    2011-03-01

    This study evaluated the prospective damage costs of PM(2.5) inhalation. We performed a health risk assessment based on an exposure-response function to estimate the annual population risk in the Seoul metropolitan city, Korea. Also, we estimated a willingness-to-pay (WTP) amount for reducing the mortality rate in order to evaluate a statistical life value. We combined the annual population risk and the value-of-statistical-life to calculate the damage cost estimate. In the health risk assessment, we applied the PM(2.5) relative risk to evaluate the annual population risk. We targeted an exposure population of 5,401,369 persons who were over the age of 30. Using a Monte-Carlo simulation for uncertainty analysis, we estimated that the population risk of PM(2.5) inhalation during a year in Seoul is 2181 premature deaths for acute exposure and 18,510 premature deaths for chronic exposure. The monthly average WTP for 5/1000 mortality reduction over ten years is $20.20 USD (95% C.I: $16.60-24.50) and the implied value-of-statistical-life (VSL) is $485,000 USD (95% C.I: $398,000-588,000). The damage cost estimate due to risk from PM(2.5) inhalation in Seoul is about $1057 million USD per year for acute exposure, and $8972 million USD per year for chronic exposure. It is important to note that this cost estimate does not reflect all health damage cost estimates in this urban area. This recommendation is a model for evaluating a mortality risk reduction and as such we must re-evaluate an integrated application of morbidity risk. Copyright © 2010 Elsevier Ltd. All rights reserved.

  19. Scavenging of rodent carcasses following simulated mortality due to field applications of anticoagulant rodenticide.

    PubMed

    Montaz, Julie; Jacquot, Marion; Coeurdassier, Michaël

    2014-11-01

    Worldwide, agricultural uses of anticoagulant rodenticides (ARs) cause poisonings of non-target wildlife as observed in France where bromadiolone is used to control water vole outbreaks. Following bromadiolone field application, a part of the vole population may die aboveground of the treated plots and thus, can represent an important risk of secondary poisoning for scavengers. In this study, water voles were trapped in a non-treated area and their carcasses were placed aboveground in plots located in an area where a vole outbreak occurred. Then, the environmental persistence, the diurnal and nocturnal scavenging rates of water vole carcasses were assessed in autumn 2011 and in spring 2012. The diurnal scavenger species were also identified. The environmental persistence of the carcasses to reach at least a scavenging rate of 87.5 % was 0.5-1.5 day. The average rates of diurnal and nocturnal scavenging ranged from 67 to 100 % and 5 to 100 %, respectively. They depended on the composition of the scavenger community present near the monitored plots; diurnal scavenging rates being higher with corvids than with raptors. In autumn, the red kite and the common buzzard were the main scavengers in one of the plots, what suggests a high risk of poisoning for these raptors during post-nuptial migration. So, the collection of vole carcasses after treatments and the limitations of bromadiolone applications when high densities of predators/scavengers are observed could be implemented to mitigate the risks of secondary poisoning.

  20. Enhanced O2 Loss at Mars Due to an Ambipolar Electric Field from Electron Heating

    NASA Technical Reports Server (NTRS)

    Ergun, R. E.; Andersson, L. A.; Fowler, C. M.; Woodson, A. K.; Weber, T. D.; Delory, G. T.; Andrews, D. J.; Eriksson, A. I.; Mcenulty, T.; Morooka, M. W.; hide

    2016-01-01

    Recent results from the MAVEN Langmuir Probe and Waves (LPW) instrument suggest higher than predicted electron temperatures (T sub e) in Mars dayside ionosphere above approx. 180 km in altitude. Correspondingly, measurements from Neutral Gas and Ion Mass Spectrometer (NGIMS) indicate significant abundances of O2+ up to approx. 500 km in altitude, suggesting that O2+ may be a principal ion loss mechanism of oxygen. In this article, we investigate the effects of the higher T(sub e) (which results from electron heating) and ion heating on ion outflow and loss. Numerical solutions show that plasma processes including ion heating and higher T(sub e) may greatly increase O2+ loss at Mars. In particular, enhanced T(sub e) in Mars ionosphere just above the exobase creates a substantial ambipolar electric field with a potential (e) of several k(sub b)T(sub e), which draws ions out of the region allowing for enhanced escape. With active solar wind, electron and ion heating, direct O2+ loss could match or exceed loss via dissociative recombination of O2+. These results suggest that direct loss of O2+ may have played a significant role in the loss of oxygen at Mars over time.

  1. Enhanced O2+ loss at Mars due to an ambipolar electric field from electron heating

    NASA Astrophysics Data System (ADS)

    Ergun, R. E.; Andersson, L. A.; Fowler, C. M.; Woodson, A. K.; Weber, T. D.; Delory, G. T.; Andrews, D. J.; Eriksson, A. I.; McEnulty, T.; Morooka, M. W.; Stewart, A. I. F.; Mahaffy, P. R.; Jakosky, B. M.

    2016-05-01

    Recent results from the MAVEN Langmuir Probe and Waves instrument suggest higher than predicted electron temperatures (Te) in Mars' dayside ionosphere above ~180 km in altitude. Correspondingly, measurements from Neutral Gas and Ion Mass Spectrometer indicate significant abundances of O2+ up to ~500 km in altitude, suggesting that O2+ may be a principal ion loss mechanism of oxygen. In this article, we investigate the effects of the higher Te (which results from electron heating) and ion heating on ion outflow and loss. Numerical solutions show that plasma processes including ion heating and higher Te may greatly increase O2+ loss at Mars. In particular, enhanced Te in Mars' ionosphere just above the exobase creates a substantial ambipolar electric field with a potential (eΦ) of several kBTe, which draws ions out of the region allowing for enhanced escape. With active solar wind, electron, and ion heating, direct O2+ loss could match or exceed loss via dissociative recombination of O2+. These results suggest that direct loss of O2+ may have played a significant role in the loss of oxygen at Mars over time.

  2. Microstructural changes in a cementitious membrane due to the application of a DC electric field.

    PubMed

    Covelo, Alba; Diaz, Belen; Freire, Lorena; Novoa, X Ramon; Perez, M Consuelo

    2008-07-01

    The use of electromigration techniques to accelerate chloride ions motion is commonly employed to characterise the permeability of cementitious samples to chlorides, a relevant parameter in reinforced concrete corrosion. This paper is devoted to the study of microstructure's changes occurring in mortar samples when submitted to natural diffusion and migration experiments. The application of an electric field reduces testing time in about one order of magnitude with respect to natural diffusion experiments. Nevertheless, the final sample's microstructure differs in both tests. Impedance Spectroscopy is employed for real time monitoring of microstructural changes. During migration experiments the global impedance undergoes important increase in shorter period of time compared to natural diffusion tests. So, the forced motion of ions through the concrete membrane induces significant variations in the porous structure, as confirmed by Mercury Intrusion Porosimetry. After migration experiments, an important increase in the capillary pore size (10-100 nm) was detected. Conversely, no relevant variations are found after natural diffusion tests. Results presented in this work cast doubt on the significance of diffusion coefficient values obtained under accelerated conditions.

  3. Microbial contamination of indoor air due to leakages from crawl space: a field study.

    PubMed

    Airaksinen, M; Pasanen, P; Kurnitski, J; Seppänen, O

    2004-02-01

    Mechanical exhaust ventilation system is typical in apartment buildings in Finland. In most buildings the base floor between the first floor apartments and crawl space is not air tight. As the apartments have lower pressure than the crawl space due to ventilation, contaminated air may flow from the crawl space to the apartments. The object of this study was to find out whether a potential air flow from crawl space has an influence on the indoor air quality. The results show that in most cases the concentration of fungal spores was clearly higher in the crawl space than inside the building. The size distribution of fungal spores depended on the fungal species. Correlation between the fungal spores in the crawl space and indoors varied with microbial species. Some species have sources inside the building, which confounds the possible relation between crawl pace and indoor concentrations. Some species, such as Acremonium, do not normally have a source indoors, but its concentration in the crawl space was elevated; our measurements showed also elevated concentrations of Acremonium in the air of the apartments. This consistent finding shows a clear linkage between fungal spores in the indoor air and crawl space. We conclude that a building with a crawl space and pressure difference over the base floor could be a potential risk for indoor air quality in the first floor apartments.

  4. Nonlinear imaging techniques for the observation of cell membrane perturbation due to pulsed electric field exposure

    NASA Astrophysics Data System (ADS)

    Moen, Erick K.; Beier, Hope T.; Thompson, Gary L.; Roth, Caleb C.; Ibey, Bennett L.

    2014-03-01

    Nonlinear optical probes, especially those involving second harmonic generation (SHG), have proven useful as sensors for near-instantaneous detection of alterations to orientation or energetics within a substance. This has been exploited to some success for observing conformational changes in proteins. SHG probes, therefore, hold promise for reporting rapid and minute changes in lipid membranes. In this report, one of these probes is employed in this regard, using nanosecond electric pulses (nsEPs) as a vehicle for instigating subtle membrane perturbations. The result provides a useful tool and methodology for the observation of minute membrane perturbation, while also providing meaningful information on the phenomenon of electropermeabilization due to nsEP. The SHG probe Di- 4-ANEPPDHQ is used in conjunction with a tuned optical setup to demonstrate nanoporation preferential to one hemisphere, or pole, of the cell given a single square shaped pulse. The results also confirm a correlation of pulse width to the amount of poration. Furthermore, the polarity of this event and the membrane physics of both hemispheres, the poles facing either electrode, were tested using bipolar pulses consisting of two pulses of opposite polarity. The experiment corroborates findings by other researchers that these types of pulses are less effective in causing repairable damage to the lipid membrane of cells.

  5. Evaluation of completeness of selected poison control center data fields.

    PubMed

    Jaramillo, Jeanie E; Marchbanks, Brenda; Willis, Branch; Forrester, Mathias B

    2010-08-01

    Poison control center data are used in research and surveillance. Due to the large volume of information, these efforts are dependent on data being recorded in machine readable format. However, poison center records include non-machine readable text fields and machine readable coded fields, some of which are duplicative. Duplicating this data increases the chance of inaccurate/incomplete coding. For surveillance efforts to be effective, coding should be complete and accurate. Investigators identified a convenience sample of 964 records and reviewed the substance code determining if it matched its text field. They also reviewed the coded clinical effects and treatments determining if they matched the notes text field. The substance code matched its text field for 91.4% of the substances. The clinical effects and treatments codes matched their text field for 72.6% and 82.4% of occurrences respectively. This under-reporting of clinical effects and treatments has surveillance and public health implications.

  6. Field evaluation of rice varieties for resistance to major diseases

    USDA-ARS?s Scientific Manuscript database

    The development and use of improved disease resistant rice varieties remains of foremost importance to rice producers, with field evaluation under local environments essential. In this study, we evaluated new and existing varieties, potential releases, and Texas elite breeding lines for resistance t...

  7. An evaluation of recent internal field models. [of earth magnetism

    NASA Technical Reports Server (NTRS)

    Mead, G. D.

    1979-01-01

    The paper reviews the current status of internal field models and evaluates several recently published models by comparing their predictions with annual means of the magnetic field measured at 140 magnetic observatories from 1973 to 1977. Three of the four models studied, viz. AWC/75, IGS/75, and Pogo 8/71, were nearly equal in their ability to predict the magnitude and direction of the current field. The fourth model, IGRF 1975, was significantly poorer in its ability to predict the current field. All models seemed to be able to extrapolate predictions quite well several years outside the data range used to construct the models.

  8. An evaluation of recent internal field models. [of earth magnetism

    NASA Technical Reports Server (NTRS)

    Mead, G. D.

    1979-01-01

    The paper reviews the current status of internal field models and evaluates several recently published models by comparing their predictions with annual means of the magnetic field measured at 140 magnetic observatories from 1973 to 1977. Three of the four models studied, viz. AWC/75, IGS/75, and Pogo 8/71, were nearly equal in their ability to predict the magnitude and direction of the current field. The fourth model, IGRF 1975, was significantly poorer in its ability to predict the current field. All models seemed to be able to extrapolate predictions quite well several years outside the data range used to construct the models.

  9. Scene identification probabilities for evaluating radiation flux errors due to scene misidentification

    NASA Technical Reports Server (NTRS)

    Manalo, Natividad D.; Smith, G. L.

    1991-01-01

    The scene identification probabilities (Pij) are fundamentally important in evaluations of the top-of-the-atmosphere (TOA) radiation-flux errors due to the scene misidentification. In this paper, the scene identification error probabilities were empirically derived from data collected in 1985 by the Earth Radiation Budget Experiment (ERBE) scanning radiometer when the ERBE satellite and the NOAA-9 spacecraft were rotated so as to scan alongside during brief periods in January and August 1985. Radiation-flux error computations utilizing these probabilities were performed, using orbit specifications for the ERBE, the Cloud and Earth's Radiant Energy System (CERES), and the SCARAB missions for a scene that was identified as partly cloudy over ocean. Typical values of the standard deviation of the random shortwave error were in the order of 1.5-5 W/sq m, but could reach values as high as 18.0 W/sq m as computed from NOAA-9.

  10. Scene identification probabilities for evaluating radiation flux errors due to scene misidentification

    NASA Technical Reports Server (NTRS)

    Manalo, Natividad D.; Smith, G. L.

    1991-01-01

    The scene identification probabilities (Pij) are fundamentally important in evaluations of the top-of-the-atmosphere (TOA) radiation-flux errors due to the scene misidentification. In this paper, the scene identification error probabilities were empirically derived from data collected in 1985 by the Earth Radiation Budget Experiment (ERBE) scanning radiometer when the ERBE satellite and the NOAA-9 spacecraft were rotated so as to scan alongside during brief periods in January and August 1985. Radiation-flux error computations utilizing these probabilities were performed, using orbit specifications for the ERBE, the Cloud and Earth's Radiant Energy System (CERES), and the SCARAB missions for a scene that was identified as partly cloudy over ocean. Typical values of the standard deviation of the random shortwave error were in the order of 1.5-5 W/sq m, but could reach values as high as 18.0 W/sq m as computed from NOAA-9.

  11. Evaluation of the cover cracking potential due to ground subsidence at UMTRA Project disposal cells

    SciTech Connect

    Claire, R.F.; Kuo, J.C.; Wanket, D.R.

    1994-03-01

    The US Department of Energy`s Uranium Mill Tailings Remedial Action (UMTRA) Project requires that mill tailings, containing low-level radioactive uranium mill tailings and other waste, be stabilized and controlled by placement in an encapsulated disposal cell. The cover of the cell is a multi-layer system which includes a low-permeability earthen radon/infiltration barrier, a bedding layer, and a erosion protection layer. The radon/infiltration barrier is designed to limit the radon flux and reduce water infiltration. The performance criteria established by the US Environmental Protection Agency in 40 CFR 192 require the cover to be effective for up to 1000 years to the extent reasonably achievable, and in any case, for at least 200 years. One concern that would affect the integrity of the radon/infiltration barrier is the potential for cracking due to the post-construction settlement of underlying compressible materials. To investigate the potential of cover cracking for UMTRA disposal cells, a simplified beam analysis is used to determine the horizontal movements and strains due to the differential settlements at the top surface of a relatively incompressible layer (e.g. radon/infiltration barrier and compacted tailings). The potential of cover cracking is then evaluated by comparing the calculated horizontal tensile strains with the strains that will cause cracking of the cover for a given material.

  12. Dislocation of the third ventricle due to space-occupying stroke evaluated by transcranial duplex sonography.

    PubMed

    Seidel, G; Gerriets, T; Kaps, M; Missler, U

    1996-10-01

    Transcranial color-coded duplex sonography is a recently introduced method for visualizing (1) the blood flow velocity of the basal cerebral arteries and (2) the brain parenchyma as an acoustic impedance image. Dislocation of the third ventricle due to space-occupying stroke is an important clinical marker. This study evaluated the dislocation of the third ventricle from the brain midline by transcranial duplex sonography in 10 healthy volunteers. The mean dislocation was 0.2 +/- 0.3 mm. Eighteen stroke patients were investigated within 12 hours by both duplex sonography and computed tomography (CT) and the dislocation of the third ventricle was measured. Correlation between the two methods was high (r = 0.87, N = 27). Twelve stroke patients divided into three subgroups according to the extent of the space-occupying effects of the lesion were followed for 3 weeks. The increase and decrease of the dislocation of the third ventricle over the time were monitored. In conclusion, transcranial duplex sonography is a reliable tool to monitor dislocation of the third ventricle due to space-occupying stroke.

  13. Laboratory and field evaluations of clad Christmas tree equipment

    SciTech Connect

    Sisak, W.J. ); Gordon, J.R. )

    1991-02-01

    In this paper a methodology is presented for evaluating the corrosion resistance of clad equipment in sour environments. This paper describes the laboratory and field test programs used to evaluate the suitability for sour service of gate valves clad with Alloy UNS NO6625 by weld overlay and by hot, isostatic pressing (HIP). The laboratory tests used to evaluate corrosion and cracking resistance of the clads are reviewed. Experience with actual field installations of both types of clad valves is presented, and the test/inspection methods used to evaluate the equipment during and after the service period are discussed. Finally, laboratory and field results are compared to highlight key findings related to the clad valve bodies and to the trim components.

  14. FIELD EVALUATION OF LOW-EMISSION COAL BURNER TECHNOLOGY ON UTILITY BOILERS VOLUME III. FIELD EVALUATIONS

    EPA Science Inventory

    The report gives results of field tests conducted to determine the emission characteristics of a Babcock and Wilcox Circular burner and Dual Register burner (DRB). The field tests were performed at two utility boilers, generally comparable in design and size except for the burner...

  15. FIELD EVALUATION OF LOW-EMISSION COAL BURNER TECHNOLOGY ON UTILITY BOILERS VOLUME III. FIELD EVALUATIONS

    EPA Science Inventory

    The report gives results of field tests conducted to determine the emission characteristics of a Babcock and Wilcox Circular burner and Dual Register burner (DRB). The field tests were performed at two utility boilers, generally comparable in design and size except for the burner...

  16. Efficient magnetic-field amplification due to the Kelvin-Helmholtz instability in binary neutron star mergers

    NASA Astrophysics Data System (ADS)

    Kiuchi, Kenta; Cerdá-Durán, Pablo; Kyutoku, Koutarou; Sekiguchi, Yuichiro; Shibata, Masaru

    2015-12-01

    We explore magnetic-field amplification due to the Kelvin-Helmholtz instability during binary neutron star mergers. By performing high-resolution general relativistic magnetohydrodynamics simulations with a resolution of 17.5 m for 4-5 ms after the onset of the merger on the Japanese supercomputer "K", we find that an initial magnetic field of moderate maximum strength 1013 G is amplified at least by a factor of ≈103. We also explore the saturation of the magnetic-field energy and our result shows that it is likely to be ≳4 ×1050 erg , which is ≳0.1 % of the bulk kinetic energy of the merging binary neutron stars.

  17. Superior bit error rate and jitter due to improved switching field distribution in exchange spring magnetic recording media.

    PubMed

    Suess, D; Fuger, M; Abert, C; Bruckner, F; Vogler, C

    2016-06-01

    We report two effects that lead to a significant reduction of the switching field distribution in exchange spring media. The first effect relies on a subtle mechanism of the interplay between exchange coupling between soft and hard layers and anisotropy that allows significant reduction of the switching field distribution in exchange spring media. This effect reduces the switching field distribution by about 30% compared to single-phase media. A second effect is that due to the improved thermal stability of exchange spring media over single-phase media, the jitter due to thermal fluctuation is significantly smaller for exchange spring media than for single-phase media. The influence of this overall improved switching field distribution on the transition jitter in granular recording and the bit error rate in bit-patterned magnetic recording is discussed. The transition jitter in granular recording for a distribution of Khard values of 3% in the hard layer, taking into account thermal fluctuations during recording, is estimated to be a = 0.78 nm, which is similar to the best reported calculated jitter in optimized heat-assisted recording media.

  18. Superior bit error rate and jitter due to improved switching field distribution in exchange spring magnetic recording media

    PubMed Central

    Suess, D.; Fuger, M.; Abert, C.; Bruckner, F.; Vogler, C.

    2016-01-01

    We report two effects that lead to a significant reduction of the switching field distribution in exchange spring media. The first effect relies on a subtle mechanism of the interplay between exchange coupling between soft and hard layers and anisotropy that allows significant reduction of the switching field distribution in exchange spring media. This effect reduces the switching field distribution by about 30% compared to single-phase media. A second effect is that due to the improved thermal stability of exchange spring media over single-phase media, the jitter due to thermal fluctuation is significantly smaller for exchange spring media than for single-phase media. The influence of this overall improved switching field distribution on the transition jitter in granular recording and the bit error rate in bit-patterned magnetic recording is discussed. The transition jitter in granular recording for a distribution of Khard values of 3% in the hard layer, taking into account thermal fluctuations during recording, is estimated to be a = 0.78 nm, which is similar to the best reported calculated jitter in optimized heat-assisted recording media. PMID:27245287

  19. Evaluation of World Population-Weighted Effective Dose due to Cosmic Ray Exposure

    PubMed Central

    Sato, Tatsuhiko

    2016-01-01

    After the release of the Report of the United Nations Scientific Committee of the Effects of Atomic Radiation in 2000 (UNSCEAR2000), it became commonly accepted that the world population-weighted effective dose due to cosmic-ray exposure is 0.38 mSv, with a range from 0.3 to 2 mSv. However, these values were derived from approximate projections of altitude and geographic dependences of the cosmic-ray dose rates as well as the world population. This study hence re-evaluated the population-weighted annual effective doses and their probability densities for the entire world as well as for 230 individual nations, using a sophisticated cosmic-ray flux calculation model in tandem with detailed grid population and elevation databases. The resulting world population-weighted annual effective dose was determined to be 0.32 mSv, which is smaller than the UNSCEAR’s evaluation by 16%, with a range from 0.23 to 0.70 mSv covering 99% of the world population. These values were noted to vary with the solar modulation condition within a range of approximately 15%. All assessed population-weighted annual effective doses as well as their statistical information for each nation are provided in the supplementary files annexed to this report. These data improve our understanding of cosmic-ray radiation exposures to populations globally. PMID:27650664

  20. Evaluation of World Population-Weighted Effective Dose due to Cosmic Ray Exposure

    NASA Astrophysics Data System (ADS)

    Sato, Tatsuhiko

    2016-09-01

    After the release of the Report of the United Nations Scientific Committee of the Effects of Atomic Radiation in 2000 (UNSCEAR2000), it became commonly accepted that the world population-weighted effective dose due to cosmic-ray exposure is 0.38 mSv, with a range from 0.3 to 2 mSv. However, these values were derived from approximate projections of altitude and geographic dependences of the cosmic-ray dose rates as well as the world population. This study hence re-evaluated the population-weighted annual effective doses and their probability densities for the entire world as well as for 230 individual nations, using a sophisticated cosmic-ray flux calculation model in tandem with detailed grid population and elevation databases. The resulting world population-weighted annual effective dose was determined to be 0.32 mSv, which is smaller than the UNSCEAR’s evaluation by 16%, with a range from 0.23 to 0.70 mSv covering 99% of the world population. These values were noted to vary with the solar modulation condition within a range of approximately 15%. All assessed population-weighted annual effective doses as well as their statistical information for each nation are provided in the supplementary files annexed to this report. These data improve our understanding of cosmic-ray radiation exposures to populations globally.

  1. EVALUATION OF RADIONUCLIDE ACCUMULATION IN SOIL DUE TO LONG-TERM IRRIGATION

    SciTech Connect

    De Wesley Wu

    2006-04-16

    Radionuclide accumulation in soil due to long-term irrigation is an important part of the model for predicting radiation dose in a long period of time. The model usually assumes an equilibrium condition in soil with a constant irrigation rate, so that radionuclide concentration in soil does not change with time and can be analytically solved. This method is currently being used for the dose assessment in the Yucca Mountain project, which requires evaluating radiation dose for a period of 10,000 years. There are several issues associated with the method: (1) time required for the equilibrium condition, (2) validity of constant irrigation rate, (3) agricultural land use for a long period of time, and (4) variation of a radionuclide concentration in water. These issues are evaluated using a numerical method with a simple model built in the GoldSim software. Some key radionuclides, Tc-99, Np-237, Pu-239, and Am-241 are selected as representative radionuclides. The results indicate that the equilibrium model is acceptable except for a radionuclide that requires long time to accumulate in soil and that its concentration in water changes dramatically with time (i.e. a sharp peak). Then the calculated dose for that radionuclide could be overestimated using the current equilibrium method.

  2. Evaluation of World Population-Weighted Effective Dose due to Cosmic Ray Exposure.

    PubMed

    Sato, Tatsuhiko

    2016-09-21

    After the release of the Report of the United Nations Scientific Committee of the Effects of Atomic Radiation in 2000 (UNSCEAR2000), it became commonly accepted that the world population-weighted effective dose due to cosmic-ray exposure is 0.38 mSv, with a range from 0.3 to 2 mSv. However, these values were derived from approximate projections of altitude and geographic dependences of the cosmic-ray dose rates as well as the world population. This study hence re-evaluated the population-weighted annual effective doses and their probability densities for the entire world as well as for 230 individual nations, using a sophisticated cosmic-ray flux calculation model in tandem with detailed grid population and elevation databases. The resulting world population-weighted annual effective dose was determined to be 0.32 mSv, which is smaller than the UNSCEAR's evaluation by 16%, with a range from 0.23 to 0.70 mSv covering 99% of the world population. These values were noted to vary with the solar modulation condition within a range of approximately 15%. All assessed population-weighted annual effective doses as well as their statistical information for each nation are provided in the supplementary files annexed to this report. These data improve our understanding of cosmic-ray radiation exposures to populations globally.

  3. Evaluating Immunogenicity Risk Due to Host Cell Protein Impurities in Antibody-Based Biotherapeutics.

    PubMed

    Jawa, Vibha; Joubert, Marisa K; Zhang, Qingchun; Deshpande, Meghana; Hapuarachchi, Suminda; Hall, Michael P; Flynn, Gregory C

    2016-11-01

    A potential risk factor for immunogenicity of a biotherapeutic is the low levels of host cell protein (HCP) impurities that remain in the product following the purification process. During process development, significant attention has been devoted to removing HCPs due to their potential safety risk. Samples from different purification steps of several monoclonal antibodies (mAbs) purified by one type of platform were evaluated for their residual Chinese Hamster Ovary (CHO) cell-derived HCP content. HCPs in both in-process (high levels of HCP) and highly purified (low levels of HCP) samples were identified and quantitated by proteomic analysis via mass spectrometry. The responses to HCPs were evaluated in an in vitro assay using PBMC from a population of healthy and disease state individuals. Results indicated that samples with up to 4000 ppm HCP content (levels 200 times greater than the drug substance) did not pose a higher immunogenicity risk than highly purified mAb samples. As an orthogonal method to predict immunogenicity risk, in silico algorithms that probe amino acid sequence for foreign epitope content were used to evaluate over 20 common HCPs (identified in the different mAb samples). Only a few HCPs were identified as high risk by the algorithms; however, the in vitro assay results indicated that the concentration of these HCPs from in-process biotherapeutic mAb samples was not sufficient to stimulate an immune response. This suggests that high levels of HCP in mAb biotherapeutics purified by this type of platform do not increase the potential risk of immunogenicity of these molecules. Insights from these studies can be applied to HCP control and risk assessment strategies.

  4. Evaluation of probe impedance due to thin-skin eddy-current interaction with surface cracks

    SciTech Connect

    Bowler, J.R.; Harfield, N.

    1998-03-01

    Crack detection using eddy-current nondestructive testing is often carried out at frequencies such that the skin depth of the induced current is much smaller than the crack dimensions. The induced current then flows in a thin skin at the conductor surface and at the faces of a surface crack. In the case of a crack that acts as an impenetrable barrier to electric current, the electromagnetic field at the crack surface can be represented, at an arbitrary frequency, in terms of a potential which satisfies a two-dimensional Laplace equation. The boundary conditions required in the solution of the Laplace equation have not yet been determined for the general case, but the authors have derived approximate boundary conditions which are applicable in the thin-skin regime. The conditions derived are valid for cracks in materials of arbitrary permeability. From the harmonic solutions of the Laplace equation, the impedance change of the excitation coil due to the defect has been calculated for cracks in aluminum and ferromagnetic steel. Comparisons between predictions and experimental measurements on rectangular slots show good agreement, thus corroborating the theory and the numerical calculations.

  5. Evaluation of different field methods for measuring soil water infiltration

    NASA Astrophysics Data System (ADS)

    Pla-Sentís, Ildefonso; Fonseca, Francisco

    2010-05-01

    Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the direct measurement of water infiltration rates or its indirect deduction from other soil characteristics or properties has become indispensable for the evaluation and modelling of the previously mentioned processes. Indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, have demonstrated to be of limited value in most of the cases. Direct "in situ" field evaluations have to be preferred in any case. In this contribution we present the results of past experiences in the measurement of soil water infiltration rates in many different soils and land conditions, and their use for deducing soil water balances under variable climates. There are also presented and discussed recent results obtained in comparing different methods, using double and single ring infiltrometers, rainfall simulators, and disc permeameters, of different sizes, in soils with very contrasting surface and profile characteristics and conditions, including stony soils and very sloping lands. It is concluded that there are not methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the surface

  6. Testing the Validity of the Neoclassical Toroidal Viscosity Model of Torque due to 3D Non-Resonant Magnetic Fields

    NASA Astrophysics Data System (ADS)

    McCubbin, A. J.; Smith, S. P.; Ferraro, N. M.; Callen, J. D.; Meneghini, O.

    2012-10-01

    Understanding the torque applied by resonant and non-resonant magnetic perturbations and its effect on rotation is essential to predict confinement and stability in burning plasmas. Non-axisymmetric 3D fields produced in the DIII-D tokamak apply a torque to the plasma, which can be evaluated through its effect on the plasma rotation. One explanation for this torque is Neoclassical Toroidal Viscosity (NTV) acting through non-resonant field components [1]. We have developed a software framework in which magnetic perturbations calculated by the state of the art two fluid MHD code M3D-C1 can be used in NTV calculations. For discharges with applied external magnetic fields in DIII-D, the experimentally determined torques will be analyzed and compared with NTV models.[4pt] [1] J.D. Callen, Nucl. Fusion 51, 094026 (2011).

  7. Rapid evaluation of potential fields in particle systems

    SciTech Connect

    Greengard, L.F.

    1987-01-01

    The evaluation of Coulombic or gravitational interactions in large-scale ensembles of particles is an integral part of the numerical simulation of a large number of physical processes. Examples include celestial mechanics, plasma physics, the vortex method in fluid dynamics, molecular dynamics, and the solution of the Laplace equation via potential theory. In a typical application, a numerical model follows the trajectories of a number of particles moving in accordance with Newton's second law of motion in a field generated by the whole ensemble. In many situations, in order to be of physical interest, the simulation has to involve thousands of particles (or more), and the fields have to be evaluated for a large number of configurations. An algorithm is presented here for the rapid evaluation of the potential and force fields in large-scale systems of particles. Both two- and three-dimensional versions of the algorithm were constructed,and various applications are discussed.

  8. Evaluation of field dental equipment in a deployment environment.

    PubMed

    Charlton, David G; Ehrlich, A Dale; Ragain, James C; Lyles, Mark B; Roberts, Howard W

    2006-03-01

    Dental officers and technicians must have reliable, durable, well-performing field dental equipment to enable them to provide dental care to deployed troops in operational environments. Unfortunately, no organized program exists to test such equipment before its purchase and use in the field. This article presents the results of a project conducted by the Naval Institute for Dental and Biomedical Research and the Air Force Dental Evaluation and Consultation Service to evaluate commercially available field dental equipment through laboratory testing and clinical-user evaluations in theater. The purpose of this 2-year project was to identify the best-performing and most cost-effective field dental equipment for possible future procurement. Initial laboratory testing was performed at the Naval Institute for Dental and Biomedical Research, and the equipment was then shipped to Kuwait for in-theater environmental and clinical-user testing. A seven-member scientific team of military dental officers and technicians was deployed for 1 month to perform in-theater testing under regional environmental conditions and to coordinate clinical-user evaluations. The testing provided beneficial results by identifying equipment that performed properly and equipment that exhibited shortcomings serious enough to render it inadequate for operational use. It is recommended that the project serve as a model for future testing and evaluation of medical/dental equipment by all of the military services.

  9. Evaluation of Vulnerable Zones in Puerto Vallarta due to a Local Tsunami

    NASA Astrophysics Data System (ADS)

    Trejo, E.; Nuñez Cornu, F. J., II; Ortiz, M.

    2015-12-01

    Based in the high possibility of occurrence of a tsunamigenic earthquake of magnitude 8.0Mw offshore from the northern coast of Jalisco and Bahía de Banderas, Mexico. The vulnerability of Puerto Vallarta to a direct flood hazard associated to the tsunami is evaluated. Assuming a simplified model of the seismic source a numerical method is used to calculate the tsunami run-up and the extent of flooding in Puerto Vallarta area. Floods heights and arrival times in the first ten hours after the earthquake and flood boundaries in different watersheds were estimated. This method was previously testing, modeling the October 9, 1995, Jalisco Earthquake and Tsunami, the results obtained were similar to the field observations and testimonies performed in 20 sites along 100 km on the coast of Jalisco, related to the height and flood extension reached during the tsunami. To estimate the vulnerability the following variables were considered: distribution of population density, population by age or physical limitation, housing characteristics, level of education, cost of goods in the affected area, location of key facilities, cost of cleaning the affected area, and change of land use policy in the Puerto Vallarta area. The study indicates that the vulnerability is very high in the Salado basin, and high in the Pitillal and Mascota-Ameca basins.

  10. Evaluation of RF heating due to various implants during MR procedures.

    PubMed

    Muranaka, Hiroyuki; Horiguchi, Takayoshi; Ueda, Yoshitake; Tanki, Nobuyoshi

    2011-01-01

    We evaluated radiofrequency (RF) heating of various implants embedded in a gel phantom during magnetic resonance (MR) procedures. We examined the dependence of RF heating on variation in specific absorption rate (SAR) and angle between the implant and the static magnetic field (B(0)) and on the displacement of the phantom in the irradiation coil using a 1.5-tesla MR system, and we compared the influence of RF heating on the same implant using a 3.0T MR system. Our results support the occurrence of RF heating of implants made of non-magnetizing metal. We observed greater RF heating when the implant was set parallel to B(0), embedded at a shallower depth, and placed at the center of the RF irradiation coil. We also confirmed that the rise in temperature was proportionate to the increase in SAR. We considered the difference in temperature elevation on depth of embedding to reflect the skin-depth effect of RF intensity for both the 1.5- and 3.0-T MR systems.

  11. Use of element model to evaluate transmissibility reduction due to barriers

    SciTech Connect

    Svanes, T.; South, D.; Dronen, O.M.

    1997-08-01

    Water breakthrough has been observed a year earlier than expected in the productive Oseberg Formation in the Veslefrikk Field. Production data revealed extensive water override, whereas the opposite situation was expected based on a homogeneous and coarse flow simulation model. A new model was developed to include geological heterogeneities using a simple upscaling method. The Oseberg Fm. consists of an upper homogeneous unit (zone 2) and a lower unit containing thin barriers of shale and calcite cemented sandstone (zone 1). The barrier content varies laterally. When barriers are distributed in a complex 3D pattern, they reduce the upscaled horizontal transmissibility more than what is obtained by multiplying the sand permeability by the net-to-gross ratio (N/G). However, the transmissibility reduction strongly depends on the spatial distribution of barriers and their geometry. Therefore, a fine scale element model was used to derive the average transmissibility reduction as a function of N/G for alternative geological descriptions of the barriers. A geo-statistical method called General Marked Point Process was used to generate the fine scale descriptions. This work has resulted in a simple upscaling routine for horizontal transmissibility, which represents an effective bridge between geological evaluation of uncertainties and fluid flow simulation. The method combines geo-statistical and deterministic modelling in an elegant manner, recognising that most often these methods complement one another.

  12. Evaluation of fish population effects due to creosote exposure in aquatic mesocosms

    SciTech Connect

    Munro, K.A.; Bestari, K.T.; Robinson, R.D.; Gensemer, R.W.; Solomon, K.R.

    1995-12-31

    Creosote is a coal tar distillate, consisting primarily of a mixture of polycyclic aromatic hydrocarbons (PAHs). Its widespread use as a wood preservative presents a potential risk to aquatic ecosystems. Studying fish responses in mesocosms enabled evaluation of the total impact of creosote exposure, resulting from both direct toxic effects and indirect community-level interactions. Two methods of creosote application were used: liquid creosote treatment and creosote-impregnated pilings treatment. Survival and egg production of adult Fathead minnows (Pimephales promelas) were monitored for two successive 30-day periods (0--30 and 35--65 days posttreatment). In addition, juvenile Fatheads produced during these periods were harvested 90 days posttreatment, to determine impacts to population weight/frequency distributions. Results for both field seasons showed that higher creosote concentrations caused strong decreases in both adult and juvenile survival, as well as egg production. Bile fluorescence levels measured at intervals during the exposure period reflected changes in total aqueous PAH concentrations in the mesocosms. Effects of creosote exposure on survival of adult fish were markedly reduced for fish introduced to ponds 35 days posttreatment compared to those exposed in the initial 0--30 day period.

  13. Evaluation of Microscopic Structural Changes of XLPE Sheets due to Thermal Deterioration

    NASA Astrophysics Data System (ADS)

    Kurihara, Takashi; Takahashi, Toshihiro; Dohi, Kenji; Homma, Hiroya; Okamoto, Tatsuki

    Cross-linked polyethylene (XLPE) sheets were thermally deteriorated in atmospheric air at 180°C for at most 100 hours, and microscopic structural changes due to oxidation such as material density, crystallinity, gel fraction and free volumes were evaluated by the Archimedes' technique, the X-ray diffraction method, the gel fraction measurement and the positron annihilation technique, respectively. As a result, it was found that the crystallinity and free volumes decreased after about 40 hours of heating on the upper surface of XLPE sheets where air supply was sufficient during heating and oxidation degree was high. However, on the lower surface that contacted with a metal plate during heating and was less oxidized, changes of crystallinity and free volumes were small after 40 hours of heating. When the crystallinity and free volumes decreased, the material density increased. It was also found that the gel fraction increased at 100 hours of heating. The observation results of cross-sections of XLPE sheets by the transmission electron microscope showed that lamella crystals disappeared after 40 hours of heating especially near the upper surface of XLPE sheets and agree with the change of the crystallinity. Then, the relationships between the material density, the crystallinity and free volumes in the cases of crystalline polymers such as polyethylene without deterioration and XLPE thermally deteriorated at 180°C were discussed.

  14. Evaluation of Mismatch Losses due to Shunts in industrial Silicon Photovoltaic Modules

    NASA Astrophysics Data System (ADS)

    Somasundaran, P.; Shilpi, M.; Gupta, R.

    2017-05-01

    In order to achieve higher efficiencies in photovoltaic module technology, it is important to characterize the shunts and other defects which degrade the performance of cells and modules as well as decrease their efficiency. These shunts also affect the reliability of cells and modules. It is important to understand how much fill factor and power loss is caused by the presence of shunts in the module. Shunts not only reduce the module power output, but also affect the I-V characteristics of the cell and hence the characteristics of the shunted cells are different from those of the shunt-free cells connected in the module leading to the mismatch effect. This is an interesting effect which has been systematically investigated in the present work. Moreover, the flow of increased shunt current will give rise to increased temperature in the region of shunt, which will affect the cell and hence module performance. In the present study, the distributed diode model has been extended to the module level and applied to evaluate the electrical mismatch losses and thermal mismatch losses due to shunts in industrial Silicon PV modules.

  15. Evaluation of linear registration algorithms for brain SPECT and the errors due to hypoperfusion lesions.

    PubMed

    Radau, P E; Slomka, P J; Julin, P; Svensson, L; Wahlund, L O

    2001-08-01

    The semiquantitative analysis of perfusion single-photon emission computed tomography (SPECT) images requires a reproducible, objective method. Automated spatial standardization (registration) of images is a prerequisite to this goal. A source of registration error is the presence of hypoperfusion defects, which was evaluated in this study with simulated lesions. The brain perfusion images measured by 99mTc-HMPAO SPECT from 21 patients with probable Alzheimer's disease and 35 control subjects were retrospectively analyzed. An automatic segmentation method was developed to remove external activity. Three registration methods, robust least squares, normalized mutual information (NMI), and count difference were implemented and the effects of simulated defects were compared. The tested registration methods required segmentation of the cerebrum from external activity, and the automatic and manual methods differed by a three-dimensional displacement of 1.4+/-1.1 mm. NMI registration proved to be least adversely effected by simulated defects with 3 mm average displacement caused by severe defects. The error in quantifying the patient-template parietal ratio due to misregistration was 2.0% for large defects (70% hypoperfusion) and 0.5% for smaller defects (85% hypoperfusion).

  16. Evaluation of counting error due to colony masking in bioaerosol sampling.

    PubMed

    Chang, C W; Hwang, Y H; Grinshpun, S A; Macher, J M; Willeke, K

    1994-10-01

    Colony counting error due to indistinguishable colony overlap (i.e., masking) was evaluated theoretically and experimentally. A theoretical model to predict colony masking was used to determine colony counting efficiency by Monte Carlo computer simulation of microorganism collection and development into CFU. The computer simulation was verified experimentally by collecting aerosolized Bacillus subtilis spores and examining micro- and macroscopic colonies. Colony counting efficiency decreased (i) with increasing density of collected culturable microorganisms, (ii) with increasing colony size, and (iii) with decreasing ability of an observation system to distinguish adjacent colonies as separate units. Counting efficiency for 2-mm colonies, at optimal resolution, decreased from 98 to 85% when colony density increased from 1 to 10 microorganisms cm-2, in contrast to an efficiency decrease from 90 to 45% for 5-mm colonies. No statistically significant difference (alpha = 0.05) between experimental and theoretical results was found when colony shape was used to estimate the number of individual colonies in a CFU. Experimental colony counts were 1.2 times simulation estimates when colony shape was not considered, because of nonuniformity of actual colony size and the better discrimination ability of the human eye relative to the model. Colony surface densities associated with high counting accuracy were compared with recommended upper plate count limits and found to depend on colony size and an observation system's ability to identify overlapped colonies. Correction factors were developed to estimate the actual number of collected microorganisms from observed colony counts.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. Evaluation of Activity Concentration Values and Doses due to the Transport of Low Level Radioactive Material

    SciTech Connect

    Rawl, Richard R; Scofield, Patricia A; Leggett, Richard Wayne; Eckerman, Keith F

    2010-04-01

    The International Atomic Energy Agency (IAEA) initiated an international Coordinated Research Project (CRP) to evaluate the safety of transport of naturally occurring radioactive material (NORM). This report presents the United States contribution to that IAEA research program. The focus of this report is on the analysis of the potential doses resulting from the transport of low level radioactive material. Specific areas of research included: (1) an examination of the technical approach used in the derivation of exempt activity concentration values and a comparison of the doses associated with the transport of materials included or not included in the provisions of Paragraph 107(e) of the IAEA Safety Standards, Regulations for the Safe Transport of Radioactive Material, Safety Requirements No. TS-R-1; (2) determination of the doses resulting from different treatment of progeny for exempt values versus the A{sub 1}/A{sub 2} values; and (3) evaluation of the dose justifications for the provisions applicable to exempt materials and low specific activity materials (LSA-I). It was found that the 'previous or intended use' (PIU) provision in Paragraph 107(e) is not risk informed since doses to the most highly exposed persons (e.g., truck drivers) are comparable regardless of intended use of the transported material. The PIU clause can also have important economic implications for co-mined ores and products that are not intended for the fuel cycle but that have uranium extracted as part of their industrial processing. In examination of the footnotes in Table 2 of TS-R-1, which identifies the progeny included in the exempt or A1/A2 values, there is no explanation of how the progeny were selected. It is recommended that the progeny for both the exemption and A{sub 1}/A{sub 2} values should be similar regardless of application, and that the same physical information should be used in deriving the limits. Based on the evaluation of doses due to the transport of low-level NORM

  18. Prediction of electron concentration reductions in re-entry flow fields due to electrophilic liquid and water injection.

    NASA Technical Reports Server (NTRS)

    Pergament, H. S.; Mikatarian, R. R.; Kurzius, S. C.

    1972-01-01

    Discussion of an analytical model which leads to predictions of reductions in electron concentrations in reentry flow fields due to the injection of electrophilic liquids and water. The processes incorporated into the model are: penetration and breakup of the liquid jet, droplet acceleration and vaporization, expansion of the liquid spray due to droplet vaporization, electrophilic vapor diffusion, heterogeneous and homogeneous charged species recombination kinetics and homogeneous electron attachment kinetics. Spray boundary calculations are shown to be in good agreement with photographic observations of water and Freon E-3 sprays in wind tunnel tests of a scale model RAM C-III flight vehicle. Fixed-bias electrostatic probe data taken during the RAM C-III flight are interpreted in terms of effective jet penetration distances - which are shown to be consistent with calculations using the present model.

  19. Simulation of permafrost changes due to technogenic influences of different ingeneering constructions used in nothern oil and gas fields

    NASA Astrophysics Data System (ADS)

    Filimonov, M. Yu; Vaganova, N. A.

    2016-10-01

    Significant amount of oil and gas is producted in Russian Federation on the territories with permafrost soils. Ice-saturated rocks thawing due to global warming or effects of various human activity will be accompanied by termocarst and others dangerous geological processes in permafrost. Design and construction of well pads in permafrost zones have some special features. The main objective is to minimize the influence of different heat sources (engineering objects) inserted into permafrost and accounting long-term forecast of development of permafrost degradation due to different factors in particular generated by human activity. In this work on the basis a mathematical model and numerical algorithms approved on 11 northern oil and gas fields some effects obtained by carrying out numerical simulations for various engineering systems are discussed.

  20. First In Situ Evidence of Electron Pitch Angle Scattering Due to Magnetic Field Line Curvature in the Ion Diffusion Region

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Shen, C.; Marchaudon, A.; Rong, Z.; Lavraud, B.; Fazakerley, A. N.; Yao, Z.; Mihaljcic, B.; Ji, Y.

    2016-12-01

    Theory predicts that the first adiabatic invariant of a charged particle may be violated in a region of highly curved field lines, leading to significant pitch angle scattering for particles whose gyroradius are comparable to the radius of the magnetic field line curvature. This scattering generates more isotropic particle distribution functions, with important impacts on the presence or absence of plasma instabilities. Using magnetic curvature analysis (MCA) based on multipoint Cluster spacecraft observations, we present the first investigation of magnetic curvature in the vicinity of an ion diffusion region where reconnected field lines are highly curved. Electrons at energies > 8 keV show a clear pitch angle ordering between bidirectional or trapped distribution in surrounding regions, while we show that in the more central part of the ion diffusion region electrons above such energies become isotropic. By contrast, colder electrons ( 1 keV) retain their bidirectional character throughout the diffusion regions. The calculated adiabatic parameter for these electrons is in agreement with theory. This study provides the first observational evidence for particle pitch angle scattering due to magnetic field lines with well characterized curvature in a space plasma.

  1. First in situ evidence of electron pitch angle scattering due to magnetic field line curvature in the Ion diffusion region

    NASA Astrophysics Data System (ADS)

    Zhang, Y. C.; Shen, C.; Marchaudon, A.; Rong, Z. J.; Lavraud, B.; Fazakerley, A.; Yao, Z.; Mihaljcic, B.; Ji, Y.; Ma, Y. H.; Liu, Z. X.

    2016-05-01

    Theory predicts that the first adiabatic invariant of a charged particle may be violated in a region of highly curved field lines, leading to significant pitch angle scattering for particles whose gyroradius are comparable to the radius of the magnetic field line curvature. This scattering generates more isotropic particle distribution functions, with important impacts on the presence or absence of plasma instabilities. Using magnetic curvature analysis based on multipoint Cluster spacecraft observations, we present the first investigation of magnetic curvature in the vicinity of an ion diffusion region where reconnected field lines are highly curved. Electrons at energies > 8 keV show a clear pitch angle ordering between bidirectional and trapped distribution in surrounding regions, while we show that in the more central part of the ion diffusion region electrons above such energies become isotropic. By contrast, colder electrons (~1 keV) retain their bidirectional character throughout the diffusion regions. The calculated adiabatic parameter K2 for these electrons is in agreement with theory. This study provides the first observational evidence for particle pitch angle scattering due to magnetic field lines with well characterized curvature in a space plasma.

  2. Evaluating winds aloft by a simplified field technique

    Treesearch

    Melvin K. Hull

    1966-01-01

    A field technique for evaluating winds aloft is described. It can be used at remote places--even at the site of a wildfire. It has proved accurate as any known single theodolite technique, and is time-saving because the winds aloft are evaluated in miles per hour from direct readout. The tools required are much lower in cost, more portable, and more multi-purpose than...

  3. Fragmentation due to centrifugal forces in the photodissociation of H{sub 2}{sup +} in intense laser fields

    SciTech Connect

    Fischer, Michael; Schmidt, Ruediger; Lorenz, Ulf; Schmidt, Burkhard

    2011-09-15

    By means of quantum-dynamical and classical trajectory calculations of H{sub 2}{sup +} photodissociation in strong laser fields, it is shown that for certain combinations of pulse durations and intensities the rotational dynamics can lead to fragmentation. In that case, the photofragments exhibit characteristic angular distributions. The classical calculations provide a transparent physical picture of this mechanism which is also very well established in collisions between atomic nuclei or liquid droplets: nonrotating systems are stable, whereas rotating systems fragment due to the decrease of the fragmentation barrier with increasing angular momentum.

  4. Exploration of Quench Initiation Due to Intentional Geometrical Defects in a High Magnetic Field Region of an SRF Cavity

    SciTech Connect

    J. Dai, K. Zhao, G.V. Eremeev, R.L. Geng, A.D. Palczewski; Dai, J.; Palczewski, A. D.; Eremeev, G. V.; Geng, R. L.; Zhao, K.

    2011-07-01

    A computer program which was used to simulate and analyze the thermal behaviors of SRF cavities has been developed at Jefferson Lab using C++ code. This code was also used to verify the quench initiation due to geometrical defects in high magnetic field region of SRF cavities. We built a CEBAF single cell cavity with 4 artificial defects near equator, and this cavity has been tested with T-mapping. The preheating behavior and quench initiation analysis of this cavity will be presented here using the computer program.

  5. Assessment and evaluation in interprofessional education: exploring the field.

    PubMed

    Blue, Amy V; Chesluk, Benjamin J; Conforti, Lisa N; Holmboe, Eric S

    2015-01-01

    The practice of interprofessional education (IPE) is expanding rapidly in the United States and globally. The publication of competencies from the Interprofessional Education Collaborative (IPEC) was a significant step forward to recognize the importance of health professions collaboration and to guide institutions for educational program development. However, there remains substantial difficulty in implementation, as well as considerable variability in assessment of learners' interprofessional collaborative knowledge and skills and evaluation of IPE programs. We conducted a multi-methods project which included 20 key informant interviews, a literature review, and a meeting of an expert panel. Our goals were 1) explore the current field of IPE, 2) identify and disseminate best practices to institutions wishing to implement/augment IPE assessment and evaluation processes, 3) uncover gaps in current IPE assessment and evaluation practices, and 4) recommend next steps for the field. A small and growing literature indicates evidence of the effectiveness of IPE. A diverse collection of methods and tools are used to assess and evaluate IPE learners and programs; these are often used without an explicit program-evaluation framework. For the field to advance and to align with the demands of changing clinical care systems, robust assessment and evaluation methods, standardized use of common tools, and longitudinal assessment from diverse data streams are needed for IPE.

  6. Evaluating amber force fields using computed NMR chemical shifts.

    PubMed

    Koes, David R; Vries, John K

    2017-10-01

    NMR chemical shifts can be computed from molecular dynamics (MD) simulations using a template matching approach and a library of conformers containing chemical shifts generated from ab initio quantum calculations. This approach has potential utility for evaluating the force fields that underlie these simulations. Imperfections in force fields generate flawed atomic coordinates. Chemical shifts obtained from flawed coordinates have errors that can be traced back to these imperfections. We use this approach to evaluate a series of AMBER force fields that have been refined over the course of two decades (ff94, ff96, ff99SB, ff14SB, ff14ipq, and ff15ipq). For each force field a series of MD simulations are carried out for eight model proteins. The calculated chemical shifts for the (1) H, (15) N, and (13) C(a) atoms are compared with experimental values. Initial evaluations are based on root mean squared (RMS) errors at the protein level. These results are further refined based on secondary structure and the types of atoms involved in nonbonded interactions. The best chemical shift for identifying force field differences is the shift associated with peptide protons. Examination of the model proteins on a residue by residue basis reveals that force field performance is highly dependent on residue position. Examination of the time course of nonbonded interactions at these sites provides explanations for chemical shift differences at the atomic coordinate level. Results show that the newer ff14ipq and ff15ipq force fields developed with the implicitly polarized charge method perform better than the older force fields. © 2017 Wiley Periodicals, Inc.

  7. Evaluation in the Field: The Need for Site Visit Standards

    ERIC Educational Resources Information Center

    Patton, Michael Quinn

    2015-01-01

    Our understanding of programs is enhanced when trained, skilled, and observant evaluators go "into the field"--the real world where programs are conducted--paying attention to what's going on, systematically documenting what they see, and reporting what they learn. The article opens by presenting and illustrating twelve reasons for…

  8. ADVANCING THE FIELD EVALUATIONS AND APPLICATIONS OF LANDFILL BIOREACTORS

    EPA Science Inventory

    The US Environmental Protection Agency (EPA) is undertaking a long-term program to conduct field evaluations of landfill bioreactors. The near-term effort is focused on the development of appropriate monitoring strategies to ensure adequate control of the landfill bioreactors an...

  9. Evaluation in the Field: The Need for Site Visit Standards

    ERIC Educational Resources Information Center

    Patton, Michael Quinn

    2015-01-01

    Our understanding of programs is enhanced when trained, skilled, and observant evaluators go "into the field"--the real world where programs are conducted--paying attention to what's going on, systematically documenting what they see, and reporting what they learn. The article opens by presenting and illustrating twelve reasons for…

  10. FIELD EVALUATION OF A HIGH-VOLUME DICHOTOMOUS SAMPLER

    EPA Science Inventory

    This study presents the field evaluation of a high-volume dichotomous sampler that collects coarse (PM10-2.5) and fine (PM2.5) particulate matter. The key feature of this device is the utilization of a round-nozzle virtual impactor with a 50% cutpoint at 2.5 5m to split PM10 into...

  11. FIELD TEST AND EVALUATION OF SELECTED ADULT BASIC EDUCATION SYSTEMS.

    ERIC Educational Resources Information Center

    Greenleigh Associates, Inc., New York, NY.

    IN A LARGE-SCALE FIELD TEST WITH FUNCTIONALLY ILLITERATE ADULTS, THIS PROJECT EVALUATED FOUR READING SYSTEMS--LEARNING TO READ AND SPELL, READING IN HIGH GEAR, MOTT BASIC LANGUAGE SKILLS PROGRAM, AND SYSTEMS FOR SUCCESS. TESTING WAS CONDUCTED IN SEVEN COMMUNITIES IN NEW YORK, THREE IN NEW JERSEY, AND FIVE IN CALIFORNIA, PROVIDING A MIXTURE OF…

  12. FIELD EVALUATION OF A HIGH-VOLUME DICHOTOMOUS SAMPLER

    EPA Science Inventory

    This study presents the field evaluation of a high-volume dichotomous sampler that collects coarse (PM10-2.5) and fine (PM2.5) particulate matter. The key feature of this device is the utilization of a round-nozzle virtual impactor with a 50% cutpoint at 2.5 5m to split PM10 into...

  13. Evaluating Potential Exposures to Ecological Receptors Due to Transport of Hydrophobic Organic Contaminants in Subsurface Systems (Final Report)

    EPA Science Inventory

    EPA's Ecological Risk Assessment Support Center (ERASC) announced the release of the final report, Evaluating Potential Exposures to Ecological Receptors Due to Transport of Hydrophobic Organic Contaminants in Subsurface Systems. This technical paper recommends several ty...

  14. Evaluating Potential Exposures to Ecological Receptors Due to Transport of Hydrophobic Organic Contaminants in Subsurface Systems (Final Report)

    EPA Science Inventory

    EPA's Ecological Risk Assessment Support Center (ERASC) announced the release of the final report, Evaluating Potential Exposures to Ecological Receptors Due to Transport of Hydrophobic Organic Contaminants in Subsurface Systems. This technical paper recommends several ty...

  15. Calculation of stochastic broadening in real space due to noise and field errors in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Brodsky, Lisa; Punjabi, Alkesh; Ali, Halima

    2008-11-01

    The equilibrium EFIT data for the DIII-D shot 115467 at 3000 ms is used to construct the equilibrium generating function for magnetic field line trajectories in the DIII-D tokamak in natural canonical coordinates. A canonical transformation is used to construct an area-preserving map for field line trajectories in the natural canonical coordinates in the DIII-D. Maps in natural canonical coordinates have the advantage that natural canonical coordinates can be inverted to calculate real space coordinates (R,Z,φ), and there is no problem in crossing the separatrix. This is not possible for magnetic coordinates. This map is applied to calculate stochastic broadening due to magnetic noise and field errors in the DIII-D. Mode numbers for noise + field errors are (m,n)=(3,1), (4,1), (6,2), (7,2), (8,2), (9,3), (10,3), (11,3), (12,3). The common amplitude δ is varied from 0.8X10-5 to 2.0X10-5. Preliminary results suggest that the width of stochastic layer from noise and field errors in the DIII-D varies from about 7 to 16 cm near X-point, and about 0.6 to 3% of poloidal flux is lost from inside ideal separatrix. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793.

  16. Utilisation of the magnetic sensor in a smartphone for facile magnetostatics experiment: magnetic field due to electrical current in straight and loop wires

    NASA Astrophysics Data System (ADS)

    Septianto, R. D.; Suhendra, D.; Iskandar, F.

    2017-01-01

    This paper reports on the result of a research into the utilisation of a smartphone for the study of magnetostatics on the basis of experiments. The use of such a device gives great measurement result and thus it can replace magnetic sensor tools that are relatively expensive. For the best experimental result, firstly the position of the magnetic sensor in the smartphone has to be considered by way of value mapping of a magnetic field due to permanent magnet. The magnetostatics experiment investigated in this research was the measurement of magnetic field due to electrical currents in two shapes of wire, straight and looped. The current flow, the distance between the observation point and the wire, and the diameter of the loop were the variable parameters investigated to test the smartphone’s capabilities as a measurement tool. To evaluate the experimental results, the measured data were compared with theoretical values that were calculated by using both an analytical and a numerical approach. According to the experiment results, the measured data had good agreement with the results from the analytical and the numerical approach. This means that the use of the magnetic sensor in a smartphone in physics experiments is viable, especially for magnetic field measurement.

  17. Performance evaluation of infrared imaging system in field test

    NASA Astrophysics Data System (ADS)

    Wang, Chensheng; Guo, Xiaodong; Ren, Tingting; Zhang, Zhi-jie

    2014-11-01

    Infrared imaging system has been applied widely in both military and civilian fields. Since the infrared imager has various types and different parameters, for system manufacturers and customers, there is great demand for evaluating the performance of IR imaging systems with a standard tool or platform. Since the first generation IR imager was developed, the standard method to assess the performance has been the MRTD or related improved methods which are not perfect adaptable for current linear scanning imager or 2D staring imager based on FPA detector. For this problem, this paper describes an evaluation method based on the triangular orientation discrimination metric which is considered as the effective and emerging method to evaluate the synthesis performance of EO system. To realize the evaluation in field test, an experiment instrument is developed. And considering the importance of operational environment, the field test is carried in practical atmospheric environment. The test imagers include panoramic imaging system and staring imaging systems with different optics and detectors parameters (both cooled and uncooled). After showing the instrument and experiment setup, the experiment results are shown. The target range performance is analyzed and discussed. In data analysis part, the article gives the range prediction values obtained from TOD method, MRTD method and practical experiment, and shows the analysis and results discussion. The experimental results prove the effectiveness of this evaluation tool, and it can be taken as a platform to give the uniform performance prediction reference.

  18. Field Artillery Ammunition Processing System (FAAPS) concept evaluation study

    SciTech Connect

    Kring, C.T.; Babcock, S.M.; Watkin, D.C.; Oliver, R.P.

    1992-06-01

    The Field Artillery Ammunition Processing System (FAAPS) is an initiative to introduce a palletized load system (PLS) that is transportable with an automated ammunition processing and storage system for use on the battlefield. System proponents have targeted a 20% increase in the ammunition processing rate over the current operation while simultaneously reducing the total number of assigned field artillery battalion personnel by 30. The overall objective of the FAAPS Project is the development and demonstration of an improved process to accomplish these goals. The initial phase of the FAAPS Project and the subject of this study is the FAAPS concept evaluation. The concept evaluation consists of (1) identifying assumptions and requirements, (2) documenting the process flow, (3) identifying and evaluating technologies available to accomplish the necessary ammunition processing and storage operations, and (4) presenting alternative concepts with associated costs, processing rates, and manpower requirements for accomplishing the operation. This study provides insight into the achievability of the desired objectives.

  19. Role of plasma response in displacements of the tokamak edge due to applied non-axisymmetric fields

    SciTech Connect

    Evans, T. E.; Ferraro, N. M.; Orlov, D. M.; Wade, M.; Lao, L. L.; Moyer, R. A.; Wingen, A.; Nazikian, R.; Unterberg, Ezekial A; Shafer, Morgan W

    2013-01-01

    Linear, two-fluid, resistive modelling of the plasma response to applied non-axisymmetric fields shows significant displacement of edge temperature and density profiles. The calculated displacements, often of 2 cm or more in H-mode pedestals with parameters appropriate to DIII-D, are due to the helical distortions resulting from stable edge modes being driven to finite amplitude by the applied fields. In many cases, these displacements are greater in magnitude, and different in phase, than the distortions of the separatrix manifolds predicted from vacuum modelling. Comparison of these results with experimental measurements from Thomson scattering and soft x-ray imaging finds good quantitative agreement. In these experiments, the phase of the applied non-axisymmetric magnetic field was flipped or rotated in order to probe the non-axisymmetric features of the response. The poloidal structures measured by x-ray imaging show clear indications of a helical response, as opposed to simply a change in the axisymmetric transport. Inclusion of two-fluid effects and rotation are found to be important in obtaining quantitative agreement with Thomson scattering data. Modelling shows screening of islands in the H-mode pedestal, but island penetration near the top of the pedestal where the electron rotation vanishes in plasmas with co-current rotation. Enhanced transport due to these islands may provide a mechanism for maintaining the pedestal width below the stability threshold of edge-localized modes. For typical DIII-D parameters, it is shown that the linear approximation is often near or beyond the limit of validity in the H-mode edge; however, the general agreement with experimental measurements indicates that these linear results nevertheless maintain good predictive value for profile displacements.

  20. RF coil optimization: evaluation of B1 field homogeneity using field histograms and finite element calculations.

    PubMed

    Li, S; Yang, Q X; Smith, M B

    1994-01-01

    Two-dimensional (2D) finite element analysis has been used to solve the full set of Maxwell's equations for the 2D magnetic field of radiofrequency (RF) coils. The field histogram method has been applied to evaluate and optimize the magnetic field homogeneity of some commonly used RF coils: the saddle coil, the slotted tube resonator, the multiple elements coil and the birdcage resonator, as well as the radial plate coil. Each coil model represents a cross-section of an infinitely long cylinder. The optimum configuration of each of these five RF coils is suggested. It was found that field homogeneity is more strongly dependent on the coil's window angle than on any other parameter. Additionally, eddy currents in the coil's conductive elements distort the current and magnetic field distribution. The frequency dependence of this eddy current distortion is analyzed and discussed.

  1. Non-Maxwellian electron distribution functions due to self-generated turbulence in collisionless guide-field reconnection

    NASA Astrophysics Data System (ADS)

    Muñoz, P. A.; Büchner, J.

    2016-10-01

    Non-Maxwellian electron velocity space distribution functions (EVDFs) are useful signatures of plasma conditions and non-local consequences of collisionless magnetic reconnection. In the past, EVDFs were obtained mainly for antiparallel reconnection and under the influence of weak guide-fields in the direction perpendicular to the reconnection plane. EVDFs are, however, not well known, yet, for oblique (or component-) reconnection in case and in dependence on stronger guide-magnetic fields and for the exhaust (outflow) region of reconnection away from the diffusion region. In view of the multi-spacecraft Magnetospheric Multiscale Mission (MMS), we derived the non-Maxwellian EVDFs of collisionless magnetic reconnection in dependence on the guide-field strength bg from small ( b g ≈ 0 ) to very strong (bg = 8) guide-fields, taking into account the feedback of the self-generated turbulence. For this sake, we carried out 2.5D fully kinetic Particle-in-Cell simulations using the ACRONYM code. We obtained anisotropic EVDFs and electron beams propagating along the separatrices as well as in the exhaust region of reconnection. The beams are anisotropic with a higher temperature in the direction perpendicular rather than parallel to the local magnetic field. The beams propagate in the direction opposite to the background electrons and cause instabilities. We also obtained the guide-field dependence of the relative electron-beam drift speed, threshold, and properties of the resulting streaming instabilities including the strongly non-linear saturation of the self-generated plasma turbulence. This turbulence and its non-linear feedback cause non-adiabatic parallel electron acceleration. We further obtained the resulting EVDFs due to the non-linear feedback of the saturated self-generated turbulence near the separatrices and in the exhaust region of reconnection in dependence on the guide field strength. We found that the influence of the self-generated plasma turbulence

  2. Transmitted sound field due to an impulsive line acoustic source bounded by a plate followed by a vortex sheet

    NASA Technical Reports Server (NTRS)

    Miura, T.; Chao, C. C.

    1980-01-01

    The propagation of sound due to a line acoustic source in the moving stream across a semiinfinite vortex sheet which trails from a rigid plate is examined in a linear theory for the subsonic case. A solution for the transmitted sound field is obtained with the aid of multiple integral transforms and the Wiener-Hopf technique for both the steady state (time harmonic) and initial value (impulsive source) situations. The contour of inverse transform and hence the decomposition of the functions are determined through causality and radiation conditions. The solution obtained satisfies causality and the full Kutta conditions. The transmitted sound field is composed of two waves in both the stady state and initial value problems. One is the wave scattered from the edge of the plate which is associated with the bow wave and the instability wave. These waves exist in the downstream sectors. The other is the wave transmitted through the vortex sheet which is also associated with the instability wave. Regional divisions of the transmitted sound field are identified.

  3. Evaluation of speech intelligibility in short-reverberant sound fields.

    PubMed

    Shimokura, Ryota; Matsui, Toshie; Takaki, Yuya; Nishimura, Tadashi; Yamanaka, Toshiaki; Hosoi, Hiroshi

    2014-08-01

    The purpose of this study was to explore the differences in speech intelligibility in short-reverberant sound fields using deteriorated monosyllables. Generated using digital signal processing, deteriorated monosyllables can lack the redundancy of words, and thus may emphasize differences in sound fields in terms of speech clarity. Ten participants without any hearing disorders identified 100 monosyllables convolved with eight impulse responses measured in different short-reverberant sound fields (speech transmission index >0.6 and reverberation time <1s), and we compared speech recognition scores between normal and deteriorated monosyllables. Deterioration was produced using low-pass filtering (cut off frequency=1600Hz). Speech recognition scores associated with the deteriorated monosyllables were lower than those for the normal monosyllables. In addition, scores were more varied among the different sound fields, although this result was not significant according to an analysis of variance. In contrast, the variation among sound fields was significant for the normal monosyllables. When comparing the intelligibility scores to the acoustic parameters calculated from eight impulse responses, the speech recognition scores were the highest when the reverberant/direct sound energy ratio (R/D) was balanced. Although our deterioration procedure obscured differences in intelligibility score among the different sound fields, we have established that the R/D is a useful parameter for evaluating speech intelligibility in short-reverberant sound fields. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  4. Evaluation of unintended electrical stimulation from MR gradient fields.

    PubMed

    Bassen, Howard I; Angelone, Leonardo M

    2012-01-01

    Exposure of patients with active implants (e.g. cardiac pacemakers and neurostimulators) to magnetic gradient fields (kHz range) during magnetic resonance imaging presents safety issues, such as unintended stimulation. Magnetically induced electric fields generate currents along the implant's lead, especially high at the distal tip. Experimental evaluation of the induced electric field was previously conducted. This study aimed to perform the same evaluation by means of computational methods, using two commercially available software packages (SemcadX and COMSOL Multiphysics). Electric field values were analyzed 1-3 mm from the distal tip. The effect of the two-electrode experimental probe was evaluated. The results were compared with previously published experimental data with reasonable agreement at locations more than 2-3 mm from the distal tip of the lead. The results were affected by the computational mesh size, with up to one order of magnitude difference for SEMCAD (resolution of 0.1 mm) compared to COMSOL (resolution of 0.5 mm). The results were also affected by the dimensions of the two-electrode probe, suggesting careful selection of the probe dimensions during experimental studies.

  5. Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces

    PubMed Central

    Goldschmidt, Benjamin S.; Rudy, Anna M.; Nowak, Charissa A.; Tsay, Yowting; Whiteside, Paul J. D.; Hunt, Heather K.

    2016-01-01

    Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive. PMID:27500652

  6. [Computational radiofrequency electromagnetic field dosimetry in evaluation of biological effects].

    PubMed

    Perov, S Iu; Kudryashov, Iu B; Rubtsova, N B

    2012-01-01

    Given growing computational resources, radiofrequency electromagnetic field dosimetry is becoming more vital in the study of biological effects of non-ionizing electromagnetic radiation. The study analyzes numerical methods which are used in theoretical dosimetry to assess the exposure level and specific absorption rate distribution. The advances of theoretical dosimetry are shown. Advantages and disadvantages of different methods are analyzed in respect to electromagnetic field biological effects. The finite-difference time-domain method was implemented in detail; also evaluated were possible uncertainties of complex biological structure simulation for bioelectromagnetic investigations.

  7. Numerical evaluation of E-fields induced by body motion near high-field MRI scanner.

    PubMed

    Crozier, S; Liu, F

    2004-01-01

    In modern magnetic resonance imaging (MRI), both patients and radiologists are exposed to strong, nonuniform static magnetic fields inside or outside of the scanner, in which the body movement may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced E-fields in the human model when moving at various positions around the magnet. The numerical calculations are based on an efficient, quasistatic, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively-shielded 4 T magnet system are used and the body model projected through the field profile with normalized velocity. The simulation shows that it is possible to induce E-fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are easy to extrapolate to very high field strengths for the safety evaluation at a variety of field strengths and motion velocities.

  8. EVALUATION OF TEMPORAL VARIATIONS IN HYDRAULIC CAPTURE DUE TO CHANGING FLOW PATTERNS USING MAPPING AND MODELING TECHNIQUES

    SciTech Connect

    SPILIOTOPOULOS AA; SWANSON LC; SHANNON R; TONKIN MJ

    2011-04-07

    Robust performance evaluation represents one of the most challenging aspects of groundwater pump-and-treat (P&T) remedy implementation. In most cases, the primary goal of the P&T system is hydraulic containment, and ultimately recovery, of contaminants to protect downgradient receptors. Estimating the extent of hydraulic containment is particularly challenging under changing flow patterns due to variable pumping, boundaries and/or other conditions. We present a systematic approach to estimate hydraulic containment using multiple lines of evidence based on (a) water-level mapping and (b) groundwater modeling. Capture Frequency Maps (CFMs) are developed by particle tracking on water-level maps developed for each available water level data set using universal kriging. In a similar manner, Capture Efficiency Maps (CEMs) are developed by particle tracking on water-levels calculated using a transient groundwater flow model: tracking is undertaken independently for each stress period using a very low effective porosity, depicting the 'instantaneous' fate of each particle each stress period. Although conceptually similar, the two methods differ in their underlying assumptions and their limitations: their use together identifies areas where containment may be reliable (i.e., where the methods are in agreement) and where containment is uncertain (typically, where the methods disagree). A field-scale example is presented to illustrate these concepts.

  9. Evaluation of different enzyme-linked immunosorbent assays for the diagnosis of brucellosis due to Brucella melitensis in sheep.

    PubMed

    García-Bocanegra, Ignacio; Allepuz, Alberto; Pérez, Julio José; Alba, Anna; Giovannini, Armando; Arenas, Antonio; Candeloro, Luca; Pacios, Alberto; Saez, José Luís; González, Miguel Ángel

    2014-03-01

    Six serological assays for the diagnosis of ovine brucellosis, due to Brucella melitensis were evaluated. Reference serum samples from sheep of known B. melitensis infection status (n=118) were assessed using the Rose Bengal test (RBT), complement fixation test (CFT) and four commercial enzyme-linked immunosorbent assays (ELISAs), including two indirect ELISAs (iELISAs), one competitive ELISA (cELISA) and one blocking ELISA (bELISA). The highest differential positive rates (DPR) were obtained with the cELISA and bELISA, while the lowest DPR was estimated using iELISAs. A latent class analysis was performed to estimate the accuracy of the CFT, RBT and bELISA using 1827 sera from sheep undergoing testing as part of a surveillance and control programme. Lower sensitivity and specificity were obtained for the three serological tests when the field samples were used. A higher DPR was achieved by the CFT, compared to bELISA and RBT. The results suggest that ELISAs, and particularly the bELISA, might be suitable for inclusion in the European Union legislation on intra-community trade for diagnosing B. melitensis infection in sheep, as it has a similar test performance compared to the RBT. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Technical Evaluation of the NASA Model for Cancer Risk to Astronauts Due to Space Radiation

    NASA Technical Reports Server (NTRS)

    2012-01-01

    At the request of NASA, the National Research Council's (NRC's) Committee for Evaluation of Space Radiation Cancer Risk Model1 reviewed a number of changes that NASA proposes to make to its model for estimating the risk of radiation-induced cancer in astronauts. The NASA model in current use was last updated in 2005, and the proposed model would incorporate recent research directed at improving the quantification and understanding of the health risks posed by the space radiation environment. NASA's proposed model is defined by the 2011 NASA report Space Radiation Cancer Risk Projections and Uncertainties--2010 . The committee's evaluation is based primarily on this source, which is referred to hereafter as the 2011 NASA report, with mention of specific sections or tables. The overall process for estimating cancer risks due to low linear energy transfer (LET) radiation exposure has been fully described in reports by a number of organizations. The approaches described in the reports from all of these expert groups are quite similar. NASA's proposed space radiation cancer risk assessment model calculates, as its main output, age- and gender-specific risk of exposure-induced death (REID) for use in the estimation of mission and astronaut-specific cancer risk. The model also calculates the associated uncertainties in REID. The general approach for estimating risk and uncertainty in the proposed model is broadly similar to that used for the current (2005) NASA model and is based on recommendations by the National Council on Radiation Protection and Measurements. However, NASA's proposed model has significant changes with respect to the following: the integration of new findings and methods into its components by taking into account newer epidemiological data and analyses, new radiobiological data indicating that quality factors differ for leukemia and solid cancers, an improved method for specifying quality factors in terms of radiation track structure concepts as

  11. Technical Evaluation of the NASA Model for Cancer Risk to Astronauts Due to Space Radiation

    NASA Technical Reports Server (NTRS)

    2012-01-01

    At the request of NASA, the National Research Council's (NRC's) Committee for Evaluation of Space Radiation Cancer Risk Model reviewed a number of changes that NASA proposes to make to its model for estimating the risk of radiation-induced cancer in astronauts. The NASA model in current use was last updated in 2005, and the proposed model would incorporate recent research directed at improving the quantification and understanding of the health risks posed by the space radiation environment. NASA's proposed model is defined by the 2011 NASA report Space Radiation Cancer Risk Projections and Uncertainties 2010 (Cucinotta et al., 2011). The committee's evaluation is based primarily on this source, which is referred to hereafter as the 2011 NASA report, with mention of specific sections or tables cited more formally as Cucinotta et al. (2011). The overall process for estimating cancer risks due to low linear energy transfer (LET) radiation exposure has been fully described in reports by a number of organizations. They include, more recently: (1) The "BEIR VII Phase 2" report from the NRC's Committee on Biological Effects of Ionizing Radiation (BEIR) (NRC, 2006); (2) Studies of Radiation and Cancer from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2006), (3) The 2007 Recommendations of the International Commission on Radiological Protection (ICRP), ICRP Publication 103 (ICRP, 2007); and (4) The Environmental Protection Agency s (EPA s) report EPA Radiogenic Cancer Risk Models and Projections for the U.S. Population (EPA, 2011). The approaches described in the reports from all of these expert groups are quite similar. NASA's proposed space radiation cancer risk assessment model calculates, as its main output, age- and gender-specific risk of exposure-induced death (REID) for use in the estimation of mission and astronaut-specific cancer risk. The model also calculates the associated uncertainties in REID. The general approach for

  12. Technical Evaluation of the NASA Model for Cancer Risk to Astronauts Due to Space Radiation

    NASA Technical Reports Server (NTRS)

    2012-01-01

    At the request of NASA, the National Research Council's (NRC's) Committee for Evaluation of Space Radiation Cancer Risk Model reviewed a number of changes that NASA proposes to make to its model for estimating the risk of radiation-induced cancer in astronauts. The NASA model in current use was last updated in 2005, and the proposed model would incorporate recent research directed at improving the quantification and understanding of the health risks posed by the space radiation environment. NASA's proposed model is defined by the 2011 NASA report Space Radiation Cancer Risk Projections and Uncertainties 2010 (Cucinotta et al., 2011). The committee's evaluation is based primarily on this source, which is referred to hereafter as the 2011 NASA report, with mention of specific sections or tables cited more formally as Cucinotta et al. (2011). The overall process for estimating cancer risks due to low linear energy transfer (LET) radiation exposure has been fully described in reports by a number of organizations. They include, more recently: (1) The "BEIR VII Phase 2" report from the NRC's Committee on Biological Effects of Ionizing Radiation (BEIR) (NRC, 2006); (2) Studies of Radiation and Cancer from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2006), (3) The 2007 Recommendations of the International Commission on Radiological Protection (ICRP), ICRP Publication 103 (ICRP, 2007); and (4) The Environmental Protection Agency s (EPA s) report EPA Radiogenic Cancer Risk Models and Projections for the U.S. Population (EPA, 2011). The approaches described in the reports from all of these expert groups are quite similar. NASA's proposed space radiation cancer risk assessment model calculates, as its main output, age- and gender-specific risk of exposure-induced death (REID) for use in the estimation of mission and astronaut-specific cancer risk. The model also calculates the associated uncertainties in REID. The general approach for

  13. Technical Evaluation of the NASA Model for Cancer Risk to Astronauts Due to Space Radiation

    NASA Technical Reports Server (NTRS)

    2012-01-01

    At the request of NASA, the National Research Council's (NRC's) Committee for Evaluation of Space Radiation Cancer Risk Model1 reviewed a number of changes that NASA proposes to make to its model for estimating the risk of radiation-induced cancer in astronauts. The NASA model in current use was last updated in 2005, and the proposed model would incorporate recent research directed at improving the quantification and understanding of the health risks posed by the space radiation environment. NASA's proposed model is defined by the 2011 NASA report Space Radiation Cancer Risk Projections and Uncertainties--2010 . The committee's evaluation is based primarily on this source, which is referred to hereafter as the 2011 NASA report, with mention of specific sections or tables. The overall process for estimating cancer risks due to low linear energy transfer (LET) radiation exposure has been fully described in reports by a number of organizations. The approaches described in the reports from all of these expert groups are quite similar. NASA's proposed space radiation cancer risk assessment model calculates, as its main output, age- and gender-specific risk of exposure-induced death (REID) for use in the estimation of mission and astronaut-specific cancer risk. The model also calculates the associated uncertainties in REID. The general approach for estimating risk and uncertainty in the proposed model is broadly similar to that used for the current (2005) NASA model and is based on recommendations by the National Council on Radiation Protection and Measurements. However, NASA's proposed model has significant changes with respect to the following: the integration of new findings and methods into its components by taking into account newer epidemiological data and analyses, new radiobiological data indicating that quality factors differ for leukemia and solid cancers, an improved method for specifying quality factors in terms of radiation track structure concepts as

  14. Seismic fragility analysis of typical pre-1990 bridges due to near- and far-field ground motions

    NASA Astrophysics Data System (ADS)

    Mosleh, Araliya; Razzaghi, Mehran S.; Jara, José; Varum, Humberto

    2016-03-01

    Bridge damages during the past earthquakes caused several physical and economic impacts to transportation systems. Many of the existing bridges in earthquake prone areas are pre-1990 bridges and were designed with out of date regulation codes. The occurrences of strong motions in different parts of the world show every year the vulnerability of these structures. Nonlinear dynamic time history analyses were conducted to assess the seismic vulnerability of typical pre-1990 bridges. A family of existing concrete bridge representative of the most common bridges in the highway system in Iran is studied. The seismic demand consists in a set of far-field and near-field strong motions to evaluate the likelihood of exceeding the seismic capacity of the mentioned bridges. The peak ground accelerations (PGAs) were scaled and applied incrementally to the 3D models to evaluate the seismic performance of the bridges. The superstructure was assumed to remain elastic and the nonlinear behavior in piers was modeled by assigning plastic hinges in columns. In this study the displacement ductility and the PGA are selected as a seismic performance indicator and intensity measure, respectively. The results show that pre-1990 bridges subjected to near-fault ground motions reach minor and moderate damage states.

  15. Quantum corrections to the gravitational potentials of a point source due to conformal fields in de Sitter

    SciTech Connect

    Fröb, Markus B.; Verdaguer, Enric E-mail: enric.verdaguer@ub.edu

    2016-03-01

    We derive the leading quantum corrections to the gravitational potentials in a de Sitter background, due to the vacuum polarization from loops of conformal fields. Our results are valid for arbitrary conformal theories, even strongly interacting ones, and are expressed using the coefficients b and b' appearing in the trace anomaly. Apart from the de Sitter generalization of the known flat-space results, we find two additional contributions: one which depends on the finite coefficients of terms quadratic in the curvature appearing in the renormalized effective action, and one which grows logarithmically with physical distance. While the first contribution corresponds to a rescaling of the effective mass, the second contribution leads to a faster fall-off of the Newton potential at large distances, and is potentially measurable.

  16. Evaluation of Brine Migration Risks Due to CO2 Injection - an Integrated Natural and Social Science Modeling Approach

    NASA Astrophysics Data System (ADS)

    Noack, V.; Kissinger, A.; Class, H.; Knopf, S.; Konrad, W.; Scheer, D.

    2014-12-01

    Evaluation of possible risks for shallow groundwater systems caused by brine displacement due to CO2 injection requires an investigation of possible vertical pathways in regional-scale structural settings. The project CO2BRIM investigates this crucial issue in collaboration with external stakeholders to integrate expert feedback on migration scenarios. To evaluate possible brine displacement scenarios we construct a regional-scale 3D structural model based on data which represent a typical geological setting of the North German Basin. The model has a horizontal size of 39 km times 58 km and includes 11 geological layers from the Permian Zechstein salt up to the Quaternary. It comprises an anticlinal structure on top of a salt pillow and an elongated salt wall that dissect the overburden. For the risk scenarios we include discontinuities in the regionally important Rupelian aquitard (Tertiary) and a transition zone along the salt flank as such discontinuities are supposed to provide permeable pathways for brines which could reach shallow drinking water horizons. Based on this model we develop scenarios in which we vary for example hydro-geological parameters of the geological discontinuities, the injection rate and the initial state of the system in terms of the salinity distribution. Furthermore we compare different levels of model complexity with regard to the physical processes considered and their effects on our results. During the process of scenario development, external experts were invited to participate and share knowledge and concerns on both brine migration risks and possible migration paths and mechanisms. The results may help in site selection as they provide improved knowledge of pressure build-up in the reservoir and the overburden for such complex geological systems. Additionally, we want to identify the level of model complexity which is sufficient for this kind of setting with regard to the limited data availability at hand for the far field.

  17. A Method for Evaluating Volt-VAR Optimization Field Demonstrations

    SciTech Connect

    Schneider, Kevin P.; Weaver, T. F.

    2014-08-31

    In a regulated business environment a utility must be able to validate that deployed technologies provide quantifiable benefits to the end-use customers. For traditional technologies there are well established procedures for determining what benefits will be derived from the deployment. But for many emerging technologies procedures for determining benefits are less clear and completely absent in some cases. Volt-VAR Optimization is a technology that is being deployed across the nation, but there are still numerous discussions about potential benefits and how they are achieved. This paper will present a method for the evaluation, and quantification of benefits, for field deployments of Volt-VAR Optimization technologies. In addition to the basic methodology, the paper will present a summary of results, and observations, from two separate Volt-VAR Optimization field evaluations using the proposed method.

  18. How social context moderates the self-evaluative emotions experienced due to health risk behaviour.

    PubMed

    Grob, Judith D M; Dijkstra, Arie; de Groot, Carla

    2011-10-01

    When people are confronted with the potential negative physical outcomes of their own health risk behaviour, they experience a self-threat. This threat is felt as negative self-evaluative emotions. We hypothesise that the threat will lead to more private self-evaluative emotions (e.g. regret) in a private social context, whereas more public self-evaluative emotions (e.g. embarrassment) will be felt in a public social context with negative norms. Consistent with our hypotheses, we show that participants anticipate feeling more private self-evaluative emotions when confronted with the negative consequences of their unhealthy behaviour when alone, and more public self-evaluative emotions when in a group (Study 1). They further anticipate more public self-evaluative emotions in response to a health self-threat when the group norm is negative, and more private self-evaluative emotions when the group norm is lenient (Study 2). Finally, in a cross-sectional study amongst smokers, we show that private but not public negative self-evaluative emotions concerning their own smoking habits are positively correlated with the intent to quit smoking (Study 3). These studies show that a distinction needs to be made between public and private self-evaluative emotions, in terms of their antecedents and effects. Theoretical implications and further lines of research are discussed.

  19. The emergence of mixing methods in the field of evaluation.

    PubMed

    Greene, Jennifer C

    2015-06-01

    When and how did the contemporary practice of mixing methods in social inquiry get started? What events transpired to catalyze the explosive conceptual development and practical adoption of mixed methods social inquiry over recent decades? How has this development progressed? What "next steps" would be most constructive? These questions are engaged in this personally narrative account of the beginnings of the contemporary mixed methods phenomenon in the field of evaluation from the perspective of a methodologist who was there.

  20. Field evaluation of a modified intervention for overhead drilling.

    PubMed

    Rempel, David; Star, Demetra; Barr, Alan; Blanco, Marco Mendoza; Janowitz, Ira

    2010-04-01

    Drilling holes into concrete or metal ceilings is one of the most physically demanding tasks performed in construction. The work is done overhead with rotary impact hammer drills that weigh up to 40 N. The task is associated with pain and musculoskeletal disorders at the wrist, forearm, shoulder, and back. The mechanism of injury is thought to be the high forces and non-neutral shoulder and wrist postures applied during drilling. Previously, we described a field study of a foot lever and inverted drill press intervention devices that received poor usability ratings compared with the usual method for overhead drilling based on problems with mobility and productivity. Using a participatory intervention model, feedback from construction workers (N = 13) was used to develop a new intervention design that incorporated a wheeled tripod base and a unique method of aligning the drilling column to vertical. A different group of construction workers (N = 23) evaluated usability and fatigue of the new device during their regular overhead drilling in comparison with the usual method. Four of 12 usability ratings were significantly better with the intervention device compared with the usual method. Subjective shoulder fatigue was less with the new intervention (1.1 vs. 3.3; scale 0 to 5; p < 0.001). This difference was supported by objective outcome measures; the mean hand forces during drilling were 26 N with the intervention compared with 245 N with the usual method. The percentage of time with the shoulder flexed or abducted to more than 60 degrees was less with the intervention compared with the usual method (21 vs. 40%; p = 0.007). There was significantly less head extension with the intervention compared with the usual method. There were no significant differences in overall productivity between the two methods. This study demonstrates that a new intervention device for overhead drilling has improved usability and subjective fatigue ratings compared with the usual method

  1. Electrostatic Fields Near the Active Site of Human Aldose Reductase: 2. New Inhibitors and Complications due to Hydrogen Bonds†

    PubMed Central

    Xu, Lin; Cohen, Aina E.; Boxer, Steven G.

    2011-01-01

    Vibrational Stark effect spectroscopy was used to measure electrostatic fields in the hydrophobic region of the active site of human aldose reductase (hALR2). A new nitrile-containing inhibitor was designed and synthesized, and the x-ray structure of its complex, along with cofactor NADP+, with wild-type hALR2 was determined at 1.3 Å resolution. The nitrile is found to be in close proximity to T113, consistent with a hydrogen bond interaction. Two vibrational absorption peaks were observed at room temperature in the nitrile region when the inhibitor binds to wild-type hALR2, indicating that the nitrile probe experiences two different microenvironments, and these could be empirically separated into a hydrogen bonded and non-hydrogen bonded population by comparison with the mutant T113A, where a hydrogen bond to the nitrile is not present. Classical molecular dynamics simulations based on the structure predict a double-peaked distribution in protein electric fields projected along the nitrile probe. The interpretation of these two peaks as a hydrogen bond formation-dissociation process between the probe nitrile group and a nearby amino acid side chain is used to explain the observation of two IR bands, and the simulations were used to investigate the molecular details of this conformational change. Hydrogen bonding complicates the simplest analysis of vibrational frequency shifts as being due solely to electrostatic interactions through the vibrational Stark effect, and the consequences of this complication are discussed. PMID:21859105

  2. Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4

    DOE PAGES

    Yiu, Yuen; Le, Manh Duc; Toft-Peterson, Rasmus; ...

    2017-03-09

    Here, we report on the spin waves and crystal field excitations in single crystal LiFePO 4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below T N = 50 K that are nearly dispersionless and are most intense around magnetic zone centers. Furthermore, we show that these excitations correspond to transitions between thermally occupied excited states of Fe 2 + due to splitting of the S = 2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplifiedmore » by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above T N , magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. This theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and T N . By applying the MF-RPA model to a number of existing spin-wave results from other Li M PO 4 ( M = Mn , Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.« less

  3. Enhanced Valley Zeeman Splitting in MoS2 /EuS due to interfacial exchange field

    NASA Astrophysics Data System (ADS)

    Zhao, Chuan; Scrace, Thomas; Taheri, Payam; Zhang, Peiyao; Norden, Tenzin; Blizzard, Brett; Petrou, Athos; Zeng, Hao; Zhao, Puqin; Kioseoglou, George

    A monolayer transition metal dichalcogenides such as MoS2 with broken inversion symmetry possesses two degenerate yet inequivalent valleys that can be selectively excited by circularly polarized light. The ability to manipulate valley degrees of freedom with light or external magnetic field makes them attractive for optoelectronic and spintronic applications. On the other hand, it has been demonstrated recently that a magnetic insulator such as EuS can induce magnetic exchange field (MEF) on graphene through proximity effect. Thus, construction of a magnetic insulator/TMDC heterostructure may induce large MEF on TMDC, which may lead to giant valley Zeeman splitting. In this work, we report the observation of valley Zeeman splitting in monolayer MoS2 and other TMDCs due to the MEF from EuS substrates. Using magneto-reflectivity, we measured a Zeeman splitting of valley exciton of 2 meV at 7 tesla and 4 K, for monolayer MoS2 on a SiO2 substrate. This is consistent with values reported in monolayer WSe2. However, when EuS is used as the substrate, we observed an increase of valley splitting from 2 to 10 meV. We attribute this enhanced valley splitting to the MEF from the EuS substrate. Utilizing MEF of a magnetic insulator can induce magnetic ordering and giant Zeeman splitting in 2D TMDCs, which might enable novel spintronics applications.

  4. Numerical modelling of thermal effects in rats due to high-field magnetic resonance imaging (0.5 1 GHz)

    NASA Astrophysics Data System (ADS)

    Trakic, Adnan; Crozier, Stuart; Liu, Feng

    2004-12-01

    A finite-difference time-domain (FDTD) thermal model has been developed to compute the temperature elevation in the Sprague Dawley rat due to electromagnetic energy deposition in high-field magnetic resonance imaging (MRI). The field strengths examined ranged from 11.75-23.5 T (corresponding to 1H resonances of 0.5-1 GHz) and an N-stub birdcage resonator was used to both transmit radio-frequency energy and receive the MRI signals. With an in-plane resolution of 1.95 mm, the inhomogeneous rat phantom forms a segmented model of 12 different tissue types, each having its electrical and thermal parameters assigned. The steady-state temperature distribution was calculated using a Pennes 'bioheat' approach. The numerical algorithm used to calculate the induced temperature distribution has been successfully validated against analytical solutions in the form of simplified spherical models with electrical and thermal properties of rat muscle. As well as assisting with the design of MRI experiments and apparatus, the numerical procedures developed in this study could help in future research and design of tumour-treating hyperthermia applicators to be used on rats in vivo.

  5. Numerical modelling of thermal effects in rats due to high-field magnetic resonance imaging (0.5-1 GHZ).

    PubMed

    Trakic, Adnan; Crozier, Stuart; Liu, Feng

    2004-12-21

    A finite-difference time-domain (FDTD) thermal model has been developed to compute the temperature elevation in the Sprague Dawley rat due to electromagnetic energy deposition in high-field magnetic resonance imaging (MRI). The field strengths examined ranged from 11.75-23.5 T (corresponding to 1H resonances of 0.5-1 GHz) and an N-stub birdcage resonator was used to both transmit radio-frequency energy and receive the MRI signals. With an in-plane resolution of 1.95 mm, the inhomogeneous rat phantom forms a segmented model of 12 different tissue types, each having its electrical and thermal parameters assigned. The steady-state temperature distribution was calculated using a Pennes 'bioheat' approach. The numerical algorithm used to calculate the induced temperature distribution has been successfully validated against analytical solutions in the form of simplified spherical models with electrical and thermal properties of rat muscle. As well as assisting with the design of MRI experiments and apparatus, the numerical procedures developed in this study could help in future research and design of tumour-treating hyperthermia applicators to be used on rats in vivo.

  6. Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4

    NASA Astrophysics Data System (ADS)

    Yiu, Yuen; Le, Manh Duc; Toft-Peterson, Rasmus; Ehlers, Georg; McQueeney, Robert J.; Vaknin, David

    2017-03-01

    We report on the spin waves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN=50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2 + due to splitting of the S =2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other Li M PO4 (M =Mn , Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.

  7. Evaluation of DNA Force Fields in Implicit Solvation

    PubMed Central

    Gaillard, Thomas; Case, David A.

    2011-01-01

    DNA structural deformations and dynamics are crucial to its interactions in the cell. Theoretical simulations are essential tools to explore the structure, dynamics, and thermodynamics of biomolecules in a systematic way. Molecular mechanics force fields for DNA have benefited from constant improvements during the last decades. Several studies have evaluated and compared available force fields when the solvent is modeled by explicit molecules. On the other hand, few systematic studies have assessed the quality of duplex DNA models when implicit solvation is employed. The interest of an implicit modeling of the solvent consists in the important gain in the simulation performance and conformational sampling speed. In this study, respective influences of the force field and the implicit solvation model choice on DNA simulation quality are evaluated. To this end, extensive implicit solvent duplex DNA simulations are performed, attempting to reach both conformational and sequence diversity convergence. Structural parameters are extracted from simulations and statistically compared to available experimental and explicit solvation simulation data. Our results quantitatively expose the respective strengths and weaknesses of the different DNA force fields and implicit solvation models studied. This work can lead to the suggestion of improvements to current DNA theoretical models. PMID:22043178

  8. Apparent ionospheric total electron content variations prior to major earthquakes due to electric fields created by tectonic stresses

    NASA Astrophysics Data System (ADS)

    Kelley, Michael C.; Swartz, Wesley E.; Heki, Kosuke

    2017-06-01

    Growing evidence for ionospheric signatures of impending earthquakes comes from electron content measurements along slanted paths from GPS satellites to multiple ground stations located up to 500 km away from the epicenters. These slant total electron content (STEC) measurements deviate from the classic U-shape pattern, starting about 40 min to over an hour before major earthquakes. Unlike other naturally occurring STEC fluctuations at midlatitudes, we show here that these earthquake-induced deviations are simultaneous over a wide geographical area and do not propagate, thereby indicating a ground-based origin. Prior to the 11 March 2011 Tohoku-Oki earthquake (Mw 9.0), the deviations were as much as 10% of the undisturbed STEC. We argue that such deviations must be due to an electric field-forced rise or fall of the main ionosphere with little change in the vertical electron density profile. Hence, "apparent" is used in the title. We show how stress-related underground electric fields penetrate to 80 km altitude (above which penetration to the main ionosphere easily occurs) with magnitudes high enough to create STEC variations comparable to those observed. Since many thousands of GPS receivers exist worldwide, our theory suggests the possibility of early warning systems that could provide 10 to 20 min notice prior to large earthquakes, after allowing time for signal processing. This theory for prequake-induced STEC fluctuations also explains the ground-based ULF magnetic field data acquired by Fraser-Smith et al. 40 min prior to the Loma Prieta earthquake.

  9. Evaluating Field Spectrometer Performance with Transmission Standards: Examples from the USGS Spectral Library and Research Databases

    NASA Astrophysics Data System (ADS)

    Hoefen, T. M.; Kokaly, R. F.; Swayze, G. A.; Livo, K. E.

    2015-12-01

    Collection of spectroscopic data has expanded with the development of field-portable spectrometers. The most commonly available spectrometers span one or several wavelength ranges: the visible (VIS) and near-infrared (NIR) region from approximately 400 to 1000 nm, and the shortwave infrared (SWIR) region from approximately 1000-2500 nm. Basic characteristics of spectrometer performance are the wavelength position and bandpass of each channel. Bandpass can vary across the wavelength coverage of an instrument, due to spectrometer design and detector materials. Spectrometer specifications can differ from one instrument to the next for a given model and between manufacturers. The USGS Spectroscopy Lab in Denver has developed a simple method to evaluate field spectrometer wavelength accuracy and bandpass values using transmission measurements of materials with intense, narrow absorption features, including Mylar* plastic, praseodymium-doped glass, and National Institute of Standards and Technology Standard Reference Material 2035. The evaluation procedure has been applied in laboratory and field settings for 19 years and used to detect deviations from cited manufacturer specifications. Tracking of USGS spectrometers with transmission standards has revealed several instances of wavelength shifts due to wear in spectrometer components. Since shifts in channel wavelengths and differences in bandpass between instruments can impact the use of field spectrometer data to calibrate and analyze imaging spectrometer data, field protocols to measure wavelength standards can limit data loss due to spectrometer degradation. In this paper, the evaluation procedure will be described and examples of observed wavelength shifts during a spectrometer field season will be presented. The impact of changing wavelength and bandpass characteristics on spectral measurements will be demonstrated and implications for spectral libraries will be discussed. *Any use of trade, firm, or product names

  10. Swarm Intelligence Algorithm for Induction Motor Field Efficiency Evaluation

    NASA Astrophysics Data System (ADS)

    Sakthivel, V. P.; Subramanian, S.

    Determining induction motor field efficiency is imperative in industries for energy conservation and cost savings. The induction motor efficiency is generally tested in a laboratories by certain methods defined in IEEE Standard - 112. But these methods cannot be used for motor efficiency evaluations in the field because it disrupts the production process of the industry. This paper proposes a swarm intelligence algorithm, Particle Swarm Optimization (PSO) for efficiency evaluation of in-service induction motor based on a modified induction motor equivalent circuit model. In this model, stray load losses are considered. The proposed efficiency evaluation method combines the PSO and the equivalent circuit method. First, the equivalent circuit parameters are estimated by minimizing the difference between measured and calculated values of stator current and input power of the motor using the PSO algorithm. Based on these parameters, the efficiency of the motor at various load points are evaluated by using the equivalent circuit method. To exemplify the performance of the PSO based efficiency estimation method, a 5 HP motor has been tested, compared with genetic algorithm (GA), torque gauge method, equivalent circuit method, slip method, current method and segregated loss method and found to be superior. Accordingly, the method will be useful for engineers who implement the energy efficiency programs to the electric motor systems in industries.

  11. Permeability enhancement due to cold water injection: A Case Study at the Los Azufres Geothermal Field, Mexico

    SciTech Connect

    Benson, S.M.; Daggett, J.; Ortiz, J.; Iglesias, E.; Comision Federal de Electricidad, Morelia; Instituto de Investigaciones Electricas, Cuernavaca )

    1989-04-01

    Pressure transient buildup and falloff data from 3 wells at the Los Azufres geothermal field have been evaluated to determine the extent to which cold water infection increases the permeability of the near-bore reservoir formation. Simultaneous analysis of the buildup and falloff data provides estimates of the permeability-thickness of the reservoir, the skin factor of the well, and the degree of permeability enhancement in the region behind the thermal front. Estimates of permeability enhancement range from a factor of 4 to 9, for a temperature change of about 150{degree}C. The permeability enhancement is attributed to thermally induced contraction and stress-cracking of the formation. 9 refs., 18 figs.

  12. Field Tests for Evaluating the Aerobic Work Capacity of Firefighters

    PubMed Central

    Lindberg, Ann-Sofie; Oksa, Juha; Gavhed, Désirée; Malm, Christer

    2013-01-01

    Working as a firefighter is physically strenuous, and a high level of physical fitness increases a firefighter’s ability to cope with the physical stress of their profession. Direct measurements of aerobic capacity, however, are often complicated, time consuming, and expensive. The first aim of the present study was to evaluate the correlations between direct (laboratory) and indirect (field) aerobic capacity tests with common and physically demanding firefighting tasks. The second aim was to give recommendations as to which field tests may be the most useful for evaluating firefighters’ aerobic work capacity. A total of 38 subjects (26 men and 12 women) were included. Two aerobic capacity tests, six field tests, and seven firefighting tasks were performed. Lactate threshold and onset of blood lactate accumulation were found to be correlated to the performance of one work task (rs = −0.65 and −0.63, p<0.01, respectively). Absolute (mL·min−1) and relative (mL·kg−1·min−1) maximal aerobic capacity was correlated to all but one of the work tasks (rs = −0.79 to 0.55 and −0.74 to 0.47, p<0.01, respectively). Aerobic capacity is important for firefighters’ work performance, and we have concluded that the time to row 500 m, the time to run 3000 m relative to body weight (s·kg−1), and the percent of maximal heart rate achieved during treadmill walking are the most valid field tests for evaluating a firefighter’s aerobic work capacity. PMID:23844153

  13. Field tests for evaluating the aerobic work capacity of firefighters.

    PubMed

    Lindberg, Ann-Sofie; Oksa, Juha; Gavhed, Désirée; Malm, Christer

    2013-01-01

    Working as a firefighter is physically strenuous, and a high level of physical fitness increases a firefighter's ability to cope with the physical stress of their profession. Direct measurements of aerobic capacity, however, are often complicated, time consuming, and expensive. The first aim of the present study was to evaluate the correlations between direct (laboratory) and indirect (field) aerobic capacity tests with common and physically demanding firefighting tasks. The second aim was to give recommendations as to which field tests may be the most useful for evaluating firefighters' aerobic work capacity. A total of 38 subjects (26 men and 12 women) were included. Two aerobic capacity tests, six field tests, and seven firefighting tasks were performed. Lactate threshold and onset of blood lactate accumulation were found to be correlated to the performance of one work task (r(s) = -0.65 and -0.63, p<0.01, respectively). Absolute (mL · min(-1)) and relative (mL · kg(-1) · min(-1)) maximal aerobic capacity was correlated to all but one of the work tasks (r(s) = -0.79 to 0.55 and -0.74 to 0.47, p<0.01, respectively). Aerobic capacity is important for firefighters' work performance, and we have concluded that the time to row 500 m, the time to run 3000 m relative to body weight (s · kg(-1)), and the percent of maximal heart rate achieved during treadmill walking are the most valid field tests for evaluating a firefighter's aerobic work capacity.

  14. Evaluation of errors due to Compton scattering in gamma-ray emission imaging

    SciTech Connect

    Bruno, M.F.

    1983-12-01

    A set of computer simulation programs were developed to aid in the design of new instrumentation and in the design and evaluation of algorithms for scatter correction in positron emission computed tomography. 14 references, 15 figures, 3 tables. (ACR)

  15. Suspended Education in Massachusetts: Using Days of Lost Instruction Due to Suspension to Evaluate Our Schools

    ERIC Educational Resources Information Center

    Losen, Daniel J.; Sun, Wei-Ling; Keith, Michael A., II

    2017-01-01

    Missed instruction can have a devastating impact on educational outcomes. Some reasons for missed instruction are beyond the control of schools and districts: some students miss school due to mental or physical illness or injury, and transportation problems sometimes are to blame. One major reason for missed instruction that schools can directly…

  16. FDTD analysis of temperature elevation in the lens of human and rabbit models due to near-field and far-field exposures at 2.45 GHz.

    PubMed

    Oizumi, Takuya; Laakso, Ilkka; Hirata, Akimasa; Fujiwara, Osamu; Watanabe, Soichi; Taki, Masao; Kojima, Masami; Sasaki, Hiroshi; Sasaki, Kazuyuki

    2013-07-01

    The eye is said to be one of the most sensitive organs to microwave heating. According to previous studies, the possibility of microwave-induced cataract formation has been experimentally investigated in rabbit and monkey eyes, but not for the human eye due to ethical reasons. In the present study, the temperature elevation in the lens, the skin around the eye and the core temperature of numerical human and rabbit models for far-field and near-field exposures at 2.45 GHz are investigated. The temperature elevations in the human and rabbit models were compared with the threshold temperatures for inducing cataracts, thermal pain in the skin and reversible health effects such as heat exhaustion or heat stroke. For plane-wave exposure, the core temperature elevation is shown to be essential both in the human and in the rabbit models as suggested in the international guidelines and standards. For localised exposure of the human eye, the temperature elevation of the skin was essential, and the lens temperature did not reach its threshold for thermal pain. On the other hand, the lens temperature elevation was found to be dominant for the rabbit eye.

  17. Change in genetic correlation due to selection using animal model evaluation.

    PubMed

    Strandén, I; Mäntysaari, E A; Mäki-Tanila, A

    1993-01-12

    Monte Carlo simulation and analytical calculations were used to study the effect of selection on genetic correlation between two traits. The simulated breeding program was based on a closed adult multiple ovulation and embryo transfer nucleus breeding scheme. Selection was on an index calculated using multi-trait animal model (AM). Analytical formulae applicable to any evaluation method were derived to predict change in genetic (co)variance due to selection under multi-trait selection using different evaluation methods. Two formulae were investigated, one assuming phenotypic selection and the other based on a recursive two-generation AM selection index. The recursive AM method approximated information due to relatives by a relationship matrix of two generations. Genetic correlation after selection was compared under different levels of initial genetic and environmental correlations with two different selection criteria. Changes in genetic correlation were similar in simulation and analytical predictions. After one round of selection the recursive AM method and the simulation gave similar predictions while the phenotypic selection predicted usually more change in genetic correlation. After several rounds of selection both analytical formulae predicted more change in genetic correlation than the simulation. ZUSAMMENFASSUNG: Änderung der genetischen Korrelation bei Selektion mit einem Tiermodell Der Selektionseffekt auf die genetische Korrelation zwischen zwei Merkmalen wurde mit Hilfe von Monte Carlo-Simulation und analytischen Berechnungen untersucht. Ein geschlossener Adulter - MOET (Multiple Ovulation and Embryo Transfer) Zuchtplan wurde simuliert. Die Selektion gründete sich auf einen Index, der die Zuchtwertschätzung des Mehrmerkmals-Tiermodells benutzte. Analytische Formeln für die Voraussage der Änderung der genetischen (Ko)varianz unter multivariate Selektion für verschiedene Zuchtwertschätzungsmethode wurden deduziert. Zwei Formeln wurden studiert

  18. Inclusion of cow records in genomic evaluations and impact on bias due to preferential treatment.

    PubMed

    Dassonneville, Romain; Baur, Aurelia; Fritz, Sébastien; Boichard, Didier; Ducrocq, Vincent

    2012-12-27

    Today, genomic evaluations are an essential feature of dairy cattle breeding. Initially, genomic evaluation targeted young bulls but recently, a rapidly increasing number of females (both heifers and cows) are being genotyped. A rising issue is whether and how own performance of genotyped cows should be included in genomic evaluations. The purpose of this study was to assess the impact of including yield deviations, i.e. own performance of cows, in genomic evaluations. Two different genomic evaluations were performed: one including only reliable daughter yield deviations of proven bulls based on their non-genotyped daughters, and one including both daughter yield deviations for males and own yield deviations for genotyped females. Milk yield, the trait most prone to preferential treatment, and somatic cell count, for which such a bias is very unlikely, were studied. Data consisted of two groups of animals from the three main dairy breeds in France: 11 884 elite females genotyped by breeding companies and 7032 cows genotyped for a research project (and considered as randomly selected from the commercial population). For several measures that could be related to preferential treatment bias, the elite group presented a different pattern of estimated breeding values for milk yield compared to the other combinations of trait and group: for instance, for milk yield, the average difference between estimated breeding values with or without own yield deviations was significantly different from 0 for this group. Correlations between estimated breeding values with or without yield deviations were lower for elite females than for randomly selected cows for milk yield but were very similar for somatic cell count. This study demonstrated that including own milk performance of elite females leads to biased (over-estimated) genomic evaluations. Thus, milk production records of elite cows require specific treatment in genomic evaluation.

  19. Matched-field evaluation of acoustic scattering from Arctic ice

    SciTech Connect

    Kapoor, T.K.; Schmidt, H.

    1997-08-01

    This paper investigates the three-dimensional acoustic scatter from large-scale features under the Arctic ice cover using field data collected during the CEAREX experiments in April 1989. The analysis involves the identification and isolation of the features under the ice canopy, and the simultaneous evaluation of their spatial scattering characteristics. A two-step matched-field processing (MFP) algorithm is used to solve this complex multiparameter estimation problem. Using one large ({approximately}1200m) and four short ({approximately}300m) vertical line arrays, and a crossed horizontal hydrophone array in a matched-field processing scheme, beamforming under the ice sheet was performed to obtain an approximate map of the rough interface between ice and water. This analysis yields estimates for scattering strengths for frequencies ranging between 25 and 105 Hz. It is shown that scatter from the elastic ice surface is a frequency selective phenomenon. This beamformed map is then used to isolate a single discrete scatterer, and subsequently, its scattering characteristics are evaluated. Simultaneously, an idealized environmental model is developed to compute scatter from a canonical protuberance. Matching the theoretical results from the analytical model with the experimental data, which consists of contributions from multiple scatterers, yields the statistics of the distribution of ice protuberances. {copyright} {ital 1997 Acoustical Society of America.}

  20. Improved field experimental designs and quantitative evaluation of aquatic ecosystems

    SciTech Connect

    McKenzie, D.H.; Thomas, J.M.

    1984-05-01

    The paired-station concept and a log transformed analysis of variance were used as methods to evaluate zooplankton density data collected during five years at an electrical generation station on Lake Michigan. To discuss the example and the field design necessary for a valid statistical analysis, considerable background is provided on the questions of selecting (1) sampling station pairs, (2) experimentwise error rates for multi-species analyses, (3) levels of Type I and II error rates, (4) procedures for conducting the field monitoring program, and (5) a discussion of the consequences of violating statistical assumptions. Details for estimating sample sizes necessary to detect changes of a specified magnitude are included. Both statistical and biological problems with monitoring programs (as now conducted) are addressed; serial correlation of successive observations in the time series obtained was identified as one principal statistical difficulty. The procedure reduces this problem to a level where statistical methods can be used confidently. 27 references, 4 figures, 2 tables.

  1. Performance evaluation of RF electric and magnetic field measuring instruments

    NASA Astrophysics Data System (ADS)

    Nesmith, B. C. W.; Ruggers, P. S.

    1982-03-01

    The need to quantify the electromagnetic fields emitted by industrial, scientific, or medical (ISM) products operating in the 10 to 300 MHs region requires the testing of instrumentation suitable for use in RF radiation hazard surveys. To meet this requirement, several procedures were devised to test the accuracy of the RF survey instrumentation. Measurement systems and protocols were developed and evaluated. The electric (E) an magnetic (H) field measuring instruments were tested for linearity, calibration accuracy, amplitude modulation response, directivity, antenna patterns, temperature response, drift and noise, radiofrequency interference and polarization response. Tests were performed on three commercially available RF survey instruments and a one-of-a-kind device over the 10 to 100 MHs region. Complete tests were only performed at the ISM frequency of 27.12 MHs. Errors for each of the tests are presented in tabular form.

  2. Evaluation of potential hydrogen detonation due to postulated hydrogen pipe breaks

    SciTech Connect

    Krishnamurthy, V. [Gilbert Nesbitt, L.

    1995-12-31

    This paper discusses a typical deterministic approach to address the hydrogen detonation issues contained in the U.S. NRC`c Commission`s generic letter 93-06. This letter references a General Electric letter reported on under 10 CFR 21 regarding the potential for the rupture of a hydrogen supply line to the generator. Several BWR plants were evaluated.

  3. Evaluation of Rotordynamic Stability of a Steam Turbine Due to Labyrinth Seal Force

    NASA Astrophysics Data System (ADS)

    Hirano, Toshio; Sasaki, Takashi; Sakakida, Hitoshi; Uchida, Tatsuro; Tsutsui, Masaji; Ikeda, Kazunori

    This paper describes the evaluation of unstable vibration caused by the seal force, which is known as "Steam Whirl" in a steam turbine. Stability of a steam turbine is evaluated by complex eigenvalue analysis of rotordynamics model considering the dynamics of seals, rotor, bearings and pedestals. A commercial CFD program is employed to estimate the dynamic coefficients of labyrinth seal. The labyrinth seal of a large scales steam turbine is taken as an object of analysis and a 3D model with eccentric rotor is solved to obtain the rotordynamic force components. The rotordynamic force is derived by integrating the pressure on the rotor surface. Evaluation formula is formed from the results of numerical calculation, which is used to predict the dynamic coefficient of each seal in a steam turbine. Then rotordynamics model of total system including seal is constructed and stability is evaluated by complex eigenvalue analysis. This procedure is applied to the design of steam turbines and enables the optimization of the turbine structure considering the efficiency and stability.

  4. Geological-engineering evaluation: Castilla and Chichimene Fields, Cubarral Association Contract, Colombia

    SciTech Connect

    Franklin, S.P.; Glick, S.S.; Chou, C.K. ); Dearmas, M. )

    1993-02-01

    A multidisciplinary geological and engineering evaluation project was undertaken for fields within the Chevron Colombia operated Cubarral Association Contract. The goal of the project was to combine geological and engineering evaluations to form a strategy for maximizing the efficiency of ongoing field development, recompletion, and production procedures. The Association Contract is located in the Llanos basin about 100 km southeast of Bogota. The fields: Castilla, Chichimene NE and Chichimene SW contain approximately 2200, 100, and 65 MMBO in place, respectively. The Guadalupe sandstone produces 14-21[degrees] API oil. The geological evaluation consisted of three phases: (1) revision of the structural interpretations, (2) detailed stratigraphic analyses, and (3) delineation of tilted fluid contacts and determination of original-oil-in-place. Structural interpretations show that reservoir properties and continuity are strongly affected by depositional environment which varies between the fields. A major facies change between massive, braided-stream sandstones at Castilla and deltaic to shallow marine sandstones at Chichimene northeast is reflected in production characteristics. The fields show strongly tilted oil-water contacts due to regional hydrodynamic gradients. Geometrical and hydrodynamic calculations were used to delineate the direction and magnitude of the tilts to assess original oil-in-place.

  5. Evaluating Age in the Field Triage of Injured Persons

    PubMed Central

    Nakamura, Yoko; Daya, Mohamud; Bulger, Eileen M.; Schreiber, Martin; Mackersie, Robert; Hsia, Renee Y.; Mann, N. Clay; Holmes, James F.; Staudenmayer, Kristan; Sturges, Zachary; Liao, Michael; Haukoos, Jason; Kuppermann, Nathan; Barton, Erik D.; Newgard, Craig D.

    2012-01-01

    Study Objective In this study, we evaluated (1) trauma under-triage by age group; (2) the association between age and serious injury after accounting for other field triage criteria and confounders; and (3) the potential impact of a mandatory age triage criterion for field triage. Methods This was a retrospective cohort study of injured children and adults transported by 48 EMS agencies to 105 hospitals in 6 regions of the Western U.S. from 2006 through 2008. We used probabilistic linkage to match EMS records to hospital records, including: trauma registries, state discharge databases and emergency department databases. The primary outcome measure was serious injury, as measured by an Injury Severity Score (ISS) ≥ 16. We assessed under-triage (ISS ≥ 16 and triage-negative or transport to a non-trauma center) by age decile and used multivariable logistic regression models to estimate the association (linear and non-linear) between age and ISS ≥ 16, adjusted for important confounders. We also evaluated the potential impact of age on triage efficiency and trauma center volume. Results 260,027 injured patients were evaluated and transported by EMS over the 3-year study period. Under-triage increased for patients over 60 years of age, reaching approximately 60% for those older than 90 years. There was a strong non-linear association between age and ISS ≥ 16. For patients not meeting other triage criteria, the probability of serious injury was most notable after 60 years. A mandatory age triage criterion would have decreased under-triage at the expense of over-triage, with one ISS ≥ 16 patient identified for every 60–65 additional patients transported to major trauma centers. Conclusion Trauma under-triage increases in patients older than 60 years. While the probability of serious injury increases among triage-negative patients with increasing age, the use of a mandatory age triage criterion appears inefficient for improving field triage. PMID:22633339

  6. Reduced spatial focality of electrical field in tDCS with ring electrodes due to tissue anisotropy.

    PubMed

    Suh, Hyun Sang; Lee, Won Hee; Cho, Young Sun; Kim, Ji-Hwan; Kim, Tae-Seong

    2010-01-01

    For effective stimulation with tDCS, spatial focality of induced electrical field (EF) is one of the important factors to be considered. Recently, there have been some studies to improve the spatial focality via different types of electrodes and their new configurations: some improvements using ring electrodes were reported over the conventional pad electrodes. However, most of these studies assumed isotropic conductivities in the head. In this work, we have investigated the effect of tissue anisotropy on the spatial focality of tDCS with the 4+1 ring electrode configuration via a 3-D high-resolution finite element (FE) head model with anisotropic conductivities in the skull and white matter. By examining the profiles of the induced EF from the head models with isotropic and anisotropic conductivities respectively, we found that the spatial focality of the induced EF significantly drops and get diffused due to tissue anisotropy. Our analysis suggests that it is critical to incorporate tissue anisotropy in the stimulation of the brain via tDCS.

  7. Enhanced electro-magnetic energy transfer between a hot and cold body at close spacing due to evanescent fields

    SciTech Connect

    Raynolds, J.E.

    1998-10-01

    Theoretical studies have demonstrated that the energy transfer between a hot and cold body at close spacing (on the order of the radiation wavelength) can greatly exceed the limit for black body radiation (ie, Power = {sigma}T{sup 4}). This effect, due to the coupling of evanescent fields, presents an attractive option for thermo-photovoltaic (TPV) applications (assuming the considerable technical challenges can be overcome). The magnitude of the enhanced energy transfer depends on the optical properties of the hot and cold bodies as characterized by the dielectric functions of the respective materials. The present study considers five different situations as specified by the materials choices for the hot/cold sides: metal/metal, metal/insulator, metal/semiconductor, insulator/insulator, and semiconductor/semiconductor. For each situation, the dielectric functions are specified by typical models. An increase in energy transfer (relative to the black body law) is found for all situations considered, for separations less than one micron, assuming a temperature difference of 1,000 C. The metal/metal situation has the highest increase vs. separation while the semiconductor/semiconductor has the lowest. Factor-of-ten increases are obtained at roughly 0.1 microns for the metal/metal and roughly 0.02 microns for the metal/semiconductor. These studies are helping to increase the understanding of the close-spaced effect in the context of a radiator/TPV context.

  8. Dust mobilization due to density currents in the Atlas region: Observations from the Saharan Mineral Dust Experiment 2006 field campaign

    NASA Astrophysics Data System (ADS)

    Knippertz, P.; Deutscher, C.; Kandler, K.; Müller, T.; Schulz, O.; Schütz, L.

    2007-11-01

    Evaporation of precipitation is a ubiquitous feature of dry and hot desert environments. The resulting cooling often generates density currents with strong turbulent winds along their leading edges, which can mobilize large amounts of dust. Mountains support this process by triggering convection, by downslope acceleration of the cool air, and by fostering the accumulation of fine-grained sediments along their foothills through the action of water. For the Sahara, the world's largest dust source, this mechanism has been little studied because of the lack of sufficiently high resolution observational data. The present study demonstrates the frequent occurrence of density currents along the Sahara side of the Atlas Mountain chain in southern Morocco using the unique data set collected during the Saharan Mineral Dust Experiment (SAMUM) field campaign in May/June 2006. The density currents are related to convection over the mountains in the afternoon hours and have lifetimes on the order of 10 h. The passage of the sharp leading edge that sometimes reaches several hundred kilometers in length is usually associated with a marked increase in dew point and wind speed, a change in wind direction, and a decrease in temperature and visibility due to suspended dust. It is conceivable that this mechanism is relevant for other mountainous regions in northern Africa during the warm season. This would imply that simulations of the dust cycle with numerical models need a reliable representation of moist convective processes in order to generate realistic dust emissions from the Sahara.

  9. MRI of trabecular bone using a decay due to diffusion in the internal field contrast imaging sequence.

    PubMed

    Mintzopoulos, Dionyssios; Ackerman, Jerome L; Song, Yi-Qiao

    2011-08-01

    To characterize the DDIF (Decay due to Diffusion in the Internal Field) method using intact animal trabecular bone specimens of varying trabecular structure and porosity, under ex vivo conditions closely resembling in vivo physiological conditions. The DDIF method provides a diffusion contrast which is related to the surface-to-volume ratio of the porous structure of bones. DDIF has previously been used successfully to study marrow-free trabecular bone, but the DDIF contrast hitherto had not been tested in intact specimens containing marrow and surrounded by soft tissue. DDIF imaging was implemented on a 4.7 Tesla (T) small-bore, horizontal, animal scanner. Ex vivo results on fresh bone specimens containing marrow were obtained at body temperature. Control measurements were carried out in surrounding tissue and saline. Significant DDIF effect was observed for trabecular bone samples, while it was considerably smaller for soft tissue outside the bone and for lipids. Additionally, significant differences were observed between specimens of different trabecular structure. The DDIF contrast is feasible despite the reduction of the diffusion constant and of T(1) in such conditions, increasing our confidence that DDIF imaging in vivo may be clinically viable for bone characterization. Copyright © 2011 Wiley-Liss, Inc.

  10. Pulmonary Hypertension Due to Common Respiratory Conditions: Classification, Evaluation and Management Strategies

    PubMed Central

    Fein, Daniel G.; Zaidi, Ali N.; Sulica, Roxana

    2016-01-01

    Pulmonary hypertension (PH) due to chronic respiratory disease and/or hypoxia is classified as World Health Organization (WHO) Group III pulmonary hypertension. The patients most commonly encountered in clinical practice with group III PH include those with chronic obstructive lung disease (COPD), diffuse parenchymal lung disease, and sleep-disordered breathing. The purpose of this review is to outline the variable clinical significance of pulmonary hypertension in the most common pulmonary disease states and how a clinician may approach the management of these patients. PMID:27571110

  11. Evaluation of ocular hazards due to electric arc flash at an in-line switch.

    PubMed

    Chou, B R; Cullen, A P

    1991-10-01

    We investigated the ocular damage resulting from operation of a solid blade pole-mounted in-line electrical switch at between 16 and 17 kV with current loads between 38 A and 340 A. Spectroradiometric data for the electric arcs produced as the switch was opened were obtained over the waveband 200 to 1500 nm. The eyes of adult pigmented rabbits were exposed to the arc flash at a distance of 2 m. The ocular tissues were assessed clinically and histologically up to 48 h postexposure. Threshold damage was clinically detectable only in eyes exposed to a 340 A arc. We conclude that at the normal current loads on a 17-kV electric power transmission line, the principal oculovisual hazards are due to molten metal fulminated from the switch by the arc, and after-images due to the bright visible light flash. At a working distance of 2 m, the ultraviolet ocular hazard is negligible. Adequate eye protection is provided by clear polycarbonate safety lenses.

  12. Evaluation of abutment scour prediction equations with field data

    USGS Publications Warehouse

    Benedict, S.T.; Deshpande, N.; Aziz, N.M.

    2007-01-01

    The U.S. Geological Survey, in cooperation with FHWA, compared predicted abutment scour depths, computed with selected predictive equations, with field observations collected at 144 bridges in South Carolina and at eight bridges from the National Bridge Scour Database. Predictive equations published in the 4th edition of Evaluating Scour at Bridges (Hydraulic Engineering Circular 18) were used in this comparison, including the original Froehlich, the modified Froehlich, the Sturm, the Maryland, and the HIRE equations. The comparisons showed that most equations tended to provide conservative estimates of scour that at times were excessive (as large as 158 ft). Equations also produced underpredictions of scour, but with less frequency. Although the equations provide an important resource for evaluating abutment scour at bridges, the results of this investigation show the importance of using engineering judgment in conjunction with these equations.

  13. Photovoltaic performance models: an evaluation with actual field data

    NASA Astrophysics Data System (ADS)

    TamizhMani, Govindasamy; Ishioye, John-Paul; Voropayev, Arseniy; Kang, Yi

    2008-08-01

    Prediction of energy production is crucial to the design and installation of the building integrated photovoltaic systems. This prediction should be attainable based on the commonly available parameters such as system size, orientation and tilt angle. Several commercially available as well as free downloadable software tools exist to predict energy production. Six software models have been evaluated in this study and they are: PV Watts, PVsyst, MAUI, Clean Power Estimator, Solar Advisor Model (SAM) and RETScreen. This evaluation has been done by comparing the monthly, seasonaly and annually predicted data with the actual, field data obtained over a year period on a large number of residential PV systems ranging between 2 and 3 kWdc. All the systems are located in Arizona, within the Phoenix metropolitan area which lies at latitude 33° North, and longitude 112 West, and are all connected to the electrical grid.

  14. A diagram for evaluating multiple aspects of model performance in simulating vector fields

    NASA Astrophysics Data System (ADS)

    Xu, Zhongfeng; Hou, Zhaolu; Han, Ying; Guo, Weidong

    2016-12-01

    Vector quantities, e.g., vector winds, play an extremely important role in climate systems. The energy and water exchanges between different regions are strongly dominated by wind, which in turn shapes the regional climate. Thus, how well climate models can simulate vector fields directly affects model performance in reproducing the nature of a regional climate. This paper devises a new diagram, termed the vector field evaluation (VFE) diagram, which is a generalized Taylor diagram and able to provide a concise evaluation of model performance in simulating vector fields. The diagram can measure how well two vector fields match each other in terms of three statistical variables, i.e., the vector similarity coefficient, root mean square length (RMSL), and root mean square vector difference (RMSVD). Similar to the Taylor diagram, the VFE diagram is especially useful for evaluating climate models. The pattern similarity of two vector fields is measured by a vector similarity coefficient (VSC) that is defined by the arithmetic mean of the inner product of normalized vector pairs. Examples are provided, showing that VSC can identify how close one vector field resembles another. Note that VSC can only describe the pattern similarity, and it does not reflect the systematic difference in the mean vector length between two vector fields. To measure the vector length, RMSL is included in the diagram. The third variable, RMSVD, is used to identify the magnitude of the overall difference between two vector fields. Examples show that the VFE diagram can clearly illustrate the extent to which the overall RMSVD is attributed to the systematic difference in RMSL and how much is due to the poor pattern similarity.

  15. Evaluation of physical health effects due to volcanic hazards: human studies

    SciTech Connect

    Buist, A.S.; Bernstein, R.S.; Johnson, L.R.; Vollmer, W.M.

    1986-03-01

    Despite certain gaps in the knowledge that has been gained from the studies done in the aftermath of Mount St. Helens and following previous major volcanic eruptions, we can be confident that the health effects of both short- and long-term exposures to the relatively low levels of airborne volcanic ash that are typical following such a volcanic eruption are minor. These effects seem to relate more to the irritating effect of the ash on mucous membranes and airway epithelia than to the potential of the ash (due to its free crystalline silica content) to initiate a fibrotic response. Nevertheless, common sense dictates that exposures should be minimized whenever possible by use of appropriate preventive measures, such as wetting the sedimented ash before disturbing it, and using commercially available disposable paper masks meeting NIOSH code TC-23 for dusts for light exposures and industrial half- and full-faced respirator and goggles for more extensive and heavy exposure.

  16. Numerical simulation of visibility degradation due to particulate matter: model development and evaluation

    SciTech Connect

    Pilinis, C.

    1989-07-20

    The model presented predicts visibility degradation due to aerosol, using thermodynamic equilibrium calculations and Mie theory. Observed scattering coefficients /ital b//sub sca/ at Mead View, Nevada, are successfully predicted. The model is used to examine the dependence of /ital b//sub sca/ on certain changes in the ambient sulfate concentrations, as well as the sensitivity of /ital b//sub sca/ to the ambient relative humidity. The model predicts that aerosol water plays an important role in the visibility degradation at relative humidities higher than the deliquescent point of the aerosol particles. We have also shown that reduction in the ambient sulfate levels does not necessarily result in improvements in the ambient visibility, unless it is accompanied by reductions in the ambient nitrate concentrations. (copyright) American Geophysical Union 1989

  17. Risk factors in fatal cases of anaphylaxis due to contrast media: a forensic evaluation.

    PubMed

    Palmiere, Cristian; Reggiani Bonetti, Luca

    2014-01-01

    Fatalities following contrast medium exposure are extremely rare in clinical routine, though they may occur as an exception. Some may fall under the purview of the inquiring authorities and forensic pathologists due to their in-hospital occurrence. The purpose of this study was to assess the risk factors for anaphylaxis due to contrast medium administration that can be identified in fatal cases. Fatalities occurred during the course of clinical investigations with contrast media described in the literature and fatal reactions to contrast agents that had undergone forensic investigations in our medicolegal center were reviewed with respect to patient characteristics, administered contrast medium, performed biochemical investigations and potential risk factors identified based on clinical history and medical records. Biochemical investigations into the fatal cases examined in our facility revealed increased mast cell tryptase, total IgE and activated mast cells in all subjects. Data obtained from the literature and our own investigations indicated that in only a minority of the fatal cases had there been previous exposure to contrast compounds, while most cases of severe anaphylaxis involved patients who apparently reacted on initial exposure. Most fatal cases failed to present any identifiable predisposing conditions out of those traditionally considered as risk factors for an anaphylactic reaction to contrast compounds in the medical histories of the patients. Comprehensive clinical histories and thorough reviews of medical data, along with exhaustive forensic investigations, provide information that is relevant in order to better appreciate the interwoven relationships linking all factors potentially involved in the pathogenesis of fatal anaphylaxis to contrast media. © 2014 S. Karger AG, Basel.

  18. Ionizing radiation exposure among kidney transplant recipients due to medical imaging during the pretransplant evaluation.

    PubMed

    Nguyen, Kim N; Patel, Anup M; Weng, Francis L

    2013-05-01

    Kidney transplant recipients are at increased risk for malignancies. One recognized risk for malignancy is ionizing radiation. The purpose of this study was to determine, among kidney transplant recipients, the medical imaging procedures that contribute to radiation exposure and their cumulative radiation exposure, as a result of their pretransplant evaluation. Medical records of patients who received a first, kidney-alone transplant during 2008 at a single transplant center were examined. This study identified medical imaging procedures that were performed as prerequisites for deceased donor wait-listing or receipt of live donor kidney transplants and to maintain active status on the wait list. Frequencies of medical imaging procedures and cumulative effective doses of radiation were calculated. Among the 172 kidney transplant recipients, 905 procedures were performed. Seventy patients (40.7%) were exposed to low dose (0-20 mSv), 51 (29.7%) were exposed to moderate dose (>20-50 mSv), 28 (16.3%) were exposed to high dose (>50-100 mSv), and 23 (13.4%) were exposed to very high dose (>100 mSv) cumulative effective radiation. Nuclear stress tests accounted for 82.9% of the total radiation exposure. In multivariate analysis, older age, diabetes, and black race were associated with exposure to >20 mSv radiation during the pretransplant evaluation. Kidney transplant recipients are exposed to large amounts of ionizing radiation from medical imaging during the pretransplant evaluation. The effects of radiation upon malignancy risk and strategies to reduce this radiation exposure warrant further investigation.

  19. Infrared image to evaluate the selective (directional) freezing due to localized injection of thermally important solutions.

    PubMed

    Yan, Jing-Fu; Liu, Jing; Zhou, Yi-Xin

    2005-01-01

    Cryosurgery is a minimally invasive surgical technique that employs the destructive effect of freezing to eradicate benign or malignant tumors which are difficult or even impossible to be extirpated by conventional surgery. Recently, we proposed a method for flexibly controlling the freezing scale during cryosurgery by percutaneously injecting thermally important functional solutions into the target tissues. This method can also help modify the direction of the iceball formation which is desirable for a successful cryosurgery for treating tumors with complex anatomical structure. To evaluate the effect of controlling the size, shape and direction of the iceball formation by injecting solutions with specific thermal properties into the target tissues, a medical infrared thermometer was introduced in this paper to map the temperature profile over the whole surface above the treated area. The cryosurgical procedure was performed using a minimally invasive cryoprobe cooled by liquid nitrogen in order to obtain a deep regional freezing. Meanwhile, one thermocouple was also amounted in the tip of the probe to record the transient temperature in order to detect the freezing and thawing effect on the tissues. The obtained infrared image was applied to monitor and evaluate the whole process. Simulation experiments on biological tissues (fresh pork and liver) were performed in vitro and four different liquids were injected into the test materials, which were distilled water, an aqueous suspension of aluminum nano-particles in water, ethanol and a 10% solution of the cryoprotective agent dimethylsulfoxide, (Me2SO), respectively. It was clearly demonstrated that the localized injection of an appropriate solution could effectively regulate the tumor-killing area via directional freezing. The study also suggested that infrared imaging can be used as an effective way to monitor and evaluate the selective freezing process, which will provide important information to help enhance

  20. Evaluation of thermal effects due to back-streaming electrons in the IAE RF gun

    NASA Astrophysics Data System (ADS)

    Kii, Toshiteru; Masuda, Kai; Amazaki, Satoshi; Horii, Tomohiro; Toku, Hisayuki; Yoshikawa, Kiyoshi; Ohgaki, Hideaki; Yamazaki, Tetsuo

    2002-05-01

    Back-streaming electrons in thermionic RF guns give a serious thermal effect to a cathode. In this study, the back-streaming beam power onto a thermionic cathode of the IAE RF gun was evaluated quantitatively by using an infrared radiation thermometer. Time evolutions of cathode surface temperature during RF macro-pulse were also calculated by using a simple 1-dimensional heat conduction model and results of a 2-dimensional particle simulation for several methods expected to reduce back-bombardment effect.

  1. Evaluation of sound field systems in elementary school classrooms

    NASA Astrophysics Data System (ADS)

    Vigeant, Michelle C.; Kruger, Kelly

    2003-10-01

    Our primary purpose in this study was to determine the relevant ergonomic issues associated with daily use of sound field systems in elementary school classrooms, in order to develop a purchasing guideline and technical specification. The secondary purpose was to evaluate these systems to identify if one or more acoustical parameters could be used to determine the quality and effectiveness of a system. Six sound field systems, with varying numbers and types of speakers, were chosen as a cross-section of available systems on the market. Six representative classrooms, currently in use, were selected based on a range of reverberation times and background noise levels. All systems were installed for two weeks in each classroom. Student speech intelligibility (SI) tests using phonetically balanced word lists were conducted, as well as teacher interviews. The acoustical parameters measured were clarity ratios C50 and C80, speech transmission indices STI and R(rapid)STI, sound pressure level (SPL) uniformity and frequency response. An improvement in SI was found for all systems. Only SPL uniformity and frequency response were found to be useful distinguishing performance parameters between systems. Ergonomic design aspects of sound field systems had a significant influence on the acceptance and usage in the classroom.

  2. A metric for the evaluation of dense vector field visualizations.

    PubMed

    Matvienko, Victor; Krüger, Jens

    2013-07-01

    In this work, we present an intuitive image-quality metric that is derived from the motivation of DVF visualization. It utilizes the features of the resulting image and effectively measures the similarity between the output of the visualization method and the input flow data. We use the angle between the gradient direction and the original vector field as a measure of such similarity and the gradient magnitude as an importance measure. Our metric enables the automatic evaluation of images for a given vector field and allows the comparison of different methods, parameters sets, and quality improvement strategies for a specific vector field. By integrating the metric into the image-computation process, our approach can be used to generate improved images by choosing the best parameter set. To verify the effectiveness of our method, we conducted an extensive user study that demonstrated the metric’s applicability to various situations. For instance, our approach elucidated the robustness of a DVF visualization in the presence of data-altering filters, such as resampling.

  3. Evaluation of free-field transfer functions in anomalous reverberant fields

    NASA Astrophysics Data System (ADS)

    Cheng, Guo; He, Lin; Xu, Rongwu

    2017-01-01

    The structural-acoustic transfer functions of complex structures are often measured in anomalous reverberant environments. Aiming to eliminating the influences of these reverberant fields on structural-acoustic transfer functions, an impulse-based synchronization average evaluation method is proposed. Structures are actuated according to an impulse signal, and the response signals are synchronized in time and averaged in space. This method does not require complex data processing, and the free-field transfer functions can be obtained based on the measurements in reverberant fields and the transfer characteristics of the structures are preserved. Moreover, in combination with the principle of reciprocity, the proposed method does not require the installation of impulse actuators in structures. The proposed method is verified numerically and validated in a deep lake experiment using a cylindrical model. The results show that the structural-acoustic transfer functions in the profundal zone can be effectively evaluated using the data collected in the shallow zone, and the error is less than 3 dB at most frequencies.

  4. Laboratory or Field Tests for Evaluating Firefighters' Work Capacity?

    PubMed Central

    Lindberg, Ann-Sofie; Oksa, Juha; Malm, Christer

    2014-01-01

    Muscle strength is important for firefighters work capacity. Laboratory tests used for measurements of muscle strength, however, are complicated, expensive and time consuming. The aims of the present study were to investigate correlations between physical capacity within commonly occurring and physically demanding firefighting work tasks and both laboratory and field tests in full time (N = 8) and part-time (N = 10) male firefighters and civilian men (N = 8) and women (N = 12), and also to give recommendations as to which field tests might be useful for evaluating firefighters' physical work capacity. Laboratory tests of isokinetic maximal (IM) and endurance (IE) muscle power and dynamic balance, field tests including maximal and endurance muscle performance, and simulated firefighting work tasks were performed. Correlations with work capacity were analyzed with Spearman's rank correlation coefficient (rs). The highest significant (p<0.01) correlations with laboratory and field tests were for Cutting: IE trunk extension (rs = 0.72) and maximal hand grip strength (rs = 0.67), for Stairs: IE shoulder flexion (rs = −0.81) and barbell shoulder press (rs = −0.77), for Pulling: IE shoulder extension (rs = −0.82) and bench press (rs = −0.85), for Demolition: IE knee extension (rs = 0.75) and bench press (rs = 0.83), for Rescue: IE shoulder flexion (rs = −0.83) and bench press (rs = −0.82), and for the Terrain work task: IE trunk flexion (rs = −0.58) and upright barbell row (rs = −0.70). In conclusion, field tests may be used instead of laboratory tests. Maximal hand grip strength, bench press, chin ups, dips, upright barbell row, standing broad jump, and barbell shoulder press were strongly correlated (rs≥0.7) with work capacity and are therefore recommended for evaluating firefighters work capacity. PMID:24614596

  5. Noncontact Elastic Wave Imaging Optical Coherence Elastography for Evaluating Changes in Corneal Elasticity Due to Crosslinking.

    PubMed

    Singh, Manmohan; Li, Jiasong; Vantipalli, Srilatha; Wang, Shang; Han, Zhaolong; Nair, Achuth; Aglyamov, Salavat R; Twa, Michael D; Larin, Kirill V

    2016-01-01

    The mechanical properties of tissues can provide valuable information about tissue integrity and health and can assist in detecting and monitoring the progression of diseases such as keratoconus. Optical coherence elastography (OCE) is a rapidly emerging technique, which can assess localized mechanical contrast in tissues with micrometer spatial resolution. In this work we present a noncontact method of optical coherence elastography to evaluate the changes in the mechanical properties of the cornea after UV-induced collagen cross-linking. A focused air-pulse induced a low amplitude (μm scale) elastic wave, which then propagated radially and was imaged in three dimensions by a phase-stabilized swept source optical coherence tomography (PhS-SSOCT) system. The elastic wave velocity was translated to Young's modulus in agar phantoms of various concentrations. Additionally, the speed of the elastic wave significantly changed in porcine cornea before and after UV-induced corneal collagen cross-linking (CXL). Moreover, different layers of the cornea, such as the anterior stroma, posterior stroma, and inner region, could be discerned from the phase velocities of the elastic wave. Therefore, because of noncontact excitation and imaging, this method may be useful for in vivo detection of ocular diseases such as keratoconus and evaluation of therapeutic interventions such as CXL.

  6. Evaluations of effects due to low-frequency noise in a low demanding work situation

    NASA Astrophysics Data System (ADS)

    Bengtsson, J.; Persson Waye, K.; Kjellberg, A.

    2004-11-01

    Noise sources with a dominating content of low frequencies (20-200 Hz) are found in many occupational environments. This study aimed to evaluate effects of moderate levels of low-frequency noise on attention, tiredness and motivation in a low demanding work situation. Two ventilation noises at the same A-weighted sound pressure level of 45 dB were used: one of a low-frequency character and one of a flat frequency character (reference noise). Thirty-eight female subjects worked with six performance tasks for 4 h in the noises in a between-subject design. Most of the tasks were monotonous and routine in character. Subjective reports were collected using questionnaires and cortisol levels were measured in saliva. The major finding in this study was that low-frequency noise negatively influenced performance on two tasks sensitive to reduced attention and on a proof-reading task. Performances of tasks aimed at evaluating motivation were not significantly affected. The difference in work performance was not reflected by the subjective reports. No effect of noise was found on subjective stress or cortisol levels.

  7. [Methodological studies on the evaluation of family burden due to injuries].

    PubMed

    Lu, F; Zeng, G; Zhong, T

    2001-08-01

    To evaluate the method for describing the burden and dimensions of injury on family. Eighty-four families of patients with injury from the selected families were studied. Status on family function, including before and after the suffering disease, were measured with Family APGAR index. Present family function was re-measured one week after the initial study. The burden of injury on these families was measured with Family Burden Score. There were significant differences (P < 0.01) between scores of APGAR before and after the onset of injury. Forty-one point six seven percent of the families were with dysfunctions prior to the injuries, while 89.29% of families having dysfunctions for the time being. There were universal burden on the families of patients with injury in multi-dimensions, including economic status, routine life, entertainment, relationship between members, physiological and psychological health of the members, and social relationship of and within the families. Injury may bring impacts to the patient's family in multi-dimensions and induce dysfunction to patient's family. Both patients and their families should be involved when providing health care to and evaluating burden of injury on them.

  8. Evaluation of membrane filter field monitors for microbiological air sampling

    NASA Technical Reports Server (NTRS)

    Fields, N. D.; Oxborrow, G. S.; Puleo, J. R.; Herring, C. M.

    1974-01-01

    Due to area constraints encountered in assembly and testing areas of spacecraft, the membrane filter field monitor (MF) and the National Aeronautics and Space Administration-accepted Reyniers slit air sampler were compared for recovery of airborne microbial contamination. The intramural air in a microbiological laboratory area and a clean room environment used for the assembly and testing of the Apollo spacecraft was studied. A significantly higher number of microorganisms was recovered by the Reyniers sampler. A high degree of consistency between the two sampling methods was shown by a regression analysis, with a correlation coefficient of 0.93. The MF samplers detected 79% of the concentration measured by the Reyniers slit samplers. The types of microorganisms identified from both sampling methods were similar.

  9. Evaluation of membrane filter field monitors for microbiological air sampling

    NASA Technical Reports Server (NTRS)

    Fields, N. D.; Oxborrow, G. S.; Puleo, J. R.; Herring, C. M.

    1974-01-01

    Due to area constraints encountered in assembly and testing areas of spacecraft, the membrane filter field monitor (MF) and the National Aeronautics and Space Administration-accepted Reyniers slit air sampler were compared for recovery of airborne microbial contamination. The intramural air in a microbiological laboratory area and a clean room environment used for the assembly and testing of the Apollo spacecraft was studied. A significantly higher number of microorganisms was recovered by the Reyniers sampler. A high degree of consistency between the two sampling methods was shown by a regression analysis, with a correlation coefficient of 0.93. The MF samplers detected 79% of the concentration measured by the Reyniers slit samplers. The types of microorganisms identified from both sampling methods were similar.

  10. Initial urological evaluation and management of children with neurogenic bladder due to myelomeningocele.

    PubMed

    Sager, Cristian; Burek, Carol; Corbetta, Juan Pablo; Weller, Santiago; Ruiz, Javier; Perea, Ramiro; Lago, Enrique; Gomez, Yesica; Durán, Victor; López, Juan Carlos

    2017-06-01

    The proactive management of children with myelomeningocele (MMC) has contributed to decreasing their progression to end-stage renal disease, thanks to early urological evaluation and timing implementation of treatments. To demonstrate that early urological evaluation of the urinary tract in MMC shows functional alterations in most cases, and that it requires medical intervention, even when in some cases the complementary imaging studies do not show any abnormalities. A retrospective study including 60 patients aged <1 year with MMC who were followed by a multidisciplinary team. All of them underwent renal/bladder ultrasound, videourodynamic studies, renal scintigraphy/dimercaptosuccinic acid (DMSA), and laboratory tests for kidney function. The studied variables were: bladder capacity and pressure, presence of overactivity, vesicoureteral reflux (VUR), urinary dilations and abnormalities on renal scintigraphy/DMSA. All the patients received clean intermittent catheterization (CIC). See Summary Table all the patients showed alterations in at least some of the assessed urodynamic variables: reduced cystometric capacity, 21.6%; detrusor overactivity, 55%; end filling detrusor pressure >20 cm H2O, 43.3%; inefficient bladder voiding, 98.3%; indirect dyssynergic patterns, 28.8%. The high-risk videourodynamic findings were observed in 28 cases (46.6%). DMSA was abnormal in 30%. Renal impairment was detected in 6.6% of cases. A total of 66% of cases received oxybutynin. Almost all the children in this sample population showed urinary dysfunction, and approximately half of them had high-risk videourodynamic findings. Although many cases showed reflex urinary contractions, almost the entire sample had inefficient bladder voiding. An important limitation of this work was the lack of simultaneity in obtaining each of the requested studies. In the initial urological evaluation of patients with myelomeningocele, almost all the urodynamic studies showed abnormalities and one

  11. Field observations of seismic velocity changes caused by shaking-induced damage and healing due to mesoscopic nonlinearity

    NASA Astrophysics Data System (ADS)

    Gassenmeier, M.; Sens-Schönfelder, C.; Eulenfeld, T.; Bartsch, M.; Victor, P.; Tilmann, F.; Korn, M.

    2016-03-01

    To investigate temporal seismic velocity changes due to earthquake related processes and environmental forcing in Northern Chile, we analyse 8 yr of ambient seismic noise recorded by the Integrated Plate Boundary Observatory Chile (IPOC). By autocorrelating the ambient seismic noise field measured on the vertical components, approximations of the Green's functions are retrieved and velocity changes are measured with Coda Wave Interferometry. At station PATCX, we observe seasonal changes in seismic velocity caused by thermal stress as well as transient velocity reductions in the frequency range of 4-6 Hz. Sudden velocity drops occur at the time of mostly earthquake-induced ground shaking and recover over a variable period of time. We present an empirical model that describes the seismic velocity variations based on continuous observations of the local ground acceleration. The model assumes that not only the shaking of large earthquakes causes velocity drops, but any small vibrations continuously induce minor velocity variations that are immediately compensated by healing in the steady state. We show that the shaking effect is accumulated over time and best described by the integrated envelope of the ground acceleration over the discretization interval of the velocity measurements, which is one day. In our model, the amplitude of the velocity reduction as well as the recovery time are proportional to the size of the excitation. This model with two free scaling parameters fits the data of the shaking induced velocity variation in remarkable detail. Additionally, a linear trend is observed that might be related to a recovery process from one or more earthquakes before our measurement period. A clear relationship between ground shaking and induced velocity reductions is not visible at other stations. We attribute the outstanding sensitivity of PATCX to ground shaking and thermal stress to the special geological setting of the station, where the subsurface material

  12. Dynamic evaluation of environmental impact due to tritium accidental release from the fusion reactor.

    PubMed

    Nie, Baojie; Ni, Muyi; Jiang, Jieqiong; Wu, Yican

    2015-10-01

    As one of the key safety issues of fusion reactors, tritium environmental impact of fusion accidents has attracted great attention. In this work, the dynamic tritium concentrations in the air and human body were evaluated on the time scale based on accidental release scenarios under the extreme environmental conditions. The radiation dose through various exposure pathways was assessed to find out the potential relationships among them. Based on this work, the limits of HT and HTO release amount for arbitrary accidents were proposed for the fusion reactor according to dose limit of ITER. The dynamic results aim to give practical guidance for establishment of fusion emergency standard and design of fusion tritium system. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Damage evaluation in metal structures subjected to high energy deposition due to particle beams

    NASA Astrophysics Data System (ADS)

    Scapin, Martina; Peroni, Lorenzo; Dallocchio, Alessandro

    2011-07-01

    The unprecedented energy intensities of modern hadron accelerators yield special problems with the materials that are placed close to or into the high intensity beams. The energy stored in a single beam of LHC particle accelerator is equivalent to about 80 kg of TNT explosive, stored in a transverse beam area with a typical value of 0.2 mm×0.2 mm. The materials placed close to the beam are used at, or even beyond, their damage limits. However, it is very difficult to predict structural efficiency and robustness accurately: beam-induced damage for high energy and high intensity occurs in a regime where practical experience does not exist. The interaction between high energy particle beams and metals induces a sudden non uniform temperature increase. This provokes a dynamic response of the structure entailing thermal stress waves and thermally induced vibrations or even the failure of the component. This study is performed in order to estimate the damage on a copper component due to the impact with a 7 TeV proton beam generated by LHC. The case study represents an accidental case consequent to an abnormal release of the beam: the energy delivered on the component is calculated using the FLUKA code and then used as input in the numerical simulations, that are carried out via the FEM code LS-DYNA.

  14. Evaluating the prognostic value of selected prognostic scales in patients operated on due to peritonitis.

    PubMed

    Paduszyńska, Katarzyna; Kaczka, Krzysztof; Dworzyńska, Agnieszka; Sieniawski, Karol; Pomorski, Lech

    2014-12-18

    The aim of the study was to assess the usefulness of prognostic scales: ASA (American Society of Anesthesiologist), MPI (Meinheim Peritonitis Index), MOFS (the Multiple Organ Failure Score) and SPI (the Simple Prognostic Index) in the prognosis of the course of disease in patients operated on for peritonitis. The study was conducted in the Clinical Department of General and Oncological Surgery of the Medical University in Łódź between January 2009 to December 2010. During this period 263 patients were operated on for peritonitis. Before surgery all patients were classified into particular groups according to the above mentioned prognostic scales according to their criteria. There were 29 (11%) deaths. ASA ≥4 (p<0.0001), MPI >30 (p<0.0001) MOFS ≥2 (p<0.0001), SPI II, III, IV (p<0.0001) were important risk factors of death. 1. ASA, MPI, MOFS and SPI scales are of high significance in predicting the outcome in patients operated on for peritonitis. 2. The ASA scale in spite and due to its simplicity is adequate enough to be used in everyday practice in patients operated on for peritonitis. 3. The MPI scale is most suitable in the scientific aims and in comparing the outcomes of patients operated on for peritonitis.

  15. Molecular Evaluation of a Case of Visceral Leishmaniasis Due to Leishmania tropica in Southwestern Iran.

    PubMed

    Sarkari, Bahador; Bavarsad Ahmadpour, Niloofar; Moshfe, Abdolali; Hajjaran, Homa

    2016-01-01

    We describe a case of visceral leishmaniasis (VL) due to Leishmania tropica in a 50-year-old Iranian man lived in a VL-endemic area in southwest of Iran. The patient presented with a 3-month history of fever and splenomegaly. Clinical signs and serological findings were suggestive of VL. Spleen biopsy was taken from the patient and intracellular forms of Leishmania amastigotes was seen in Giemsa stained smears. The patient was treated with pentavalent antimonial compound with complete resolution of his systemic signs and symptoms. DNA was extracted from the microscopic slides of the spleen biopsy and the nagt (N-Acetylglucosamine-1-Phosphate Transferase) gene of Leishmania was PCR-amplified. Sequence analysis of the PCR product demonstrated that the case has 99% identity with those of available sequences of L. tropica. Intra-species variation within isolate was 0-0.1%; whereas, inter-species differences of the isolate with those of L. major and L. infantum was significantly higher.

  16. [Clinical evaluation of ureteral stenting for managing extrinsic ureteral obstruction due to gynecological and gastrointestinal cancer].

    PubMed

    Takehara, Kosuke; Onita, Toru; Mochizuki, Yasushi; Miyata, Yasuyoshi; Igawa, Tsukasa; Sakai, Hideki

    2014-01-01

    We retrospectively reviewed patients who were treated with an indwelling ureteral stent to manage extrinsic ureteral obstruction due to advanced gynecological and gastrointestinal cancers. A total of 34 patients, including 17 with gynecological cancer and 17 with gastrointestinal cancer, underwent a successful initial ureteral stent placement from January 2007 to December 2011. Functional ureteral stent failures, which required percutaneous nephrostomy within 3 months after initial ureteral stenting, occurred in 14 of the 34 patients (41%) during follow-up. The risk factors of functional ureteral stent failure were bilateral ureteral obstruction, elevated serum creatinine level, poor performance status, subsequent therapy for primary cancer after ureteral stent placement, presence of peritonitis carcinomatosa, and gastrointestinal cancer. Patients with gastrointestinal cancer had a higher rate of stent failure than did those with gynecological cancer (p = 0.01). Median survival from the diagnosis of hydronephrosis for patients with gastrointestinal and gynecological cancers was 9 and 23 months, respectively (p = 0. 02). Retrograde ureteral stenting is a useful treatment for malignant ureteral obstruction. However, patients with gastrointestinal cancer had a high stent failure rate and a short survival time from the diagnosis of hydronephrosis. Indications for retrograde ureteral stenting for malignant ureteral obstruction should be carefully considered while taking into account stent failure risk, patient prognosis and quality of life.

  17. Evaluation of undesirable deformations in complex, hollow aluminium extrusions due to roll bending

    NASA Astrophysics Data System (ADS)

    Farstad, Jan Magnus Granheim; Netland, Øyvind; Welo, Torgeir

    2016-10-01

    This paper presents a series of experiments where an aluminium extrusion with a complex, hollow cross-section was formed by roll bending. The extrusion is intended to be used as a rail for a mobile instrumentation platform that requires both straight and bent rail sections in different configurations. In order to develop the system to be highly accurate, precise and functional under all operating conditions, it is vital to know the `nominal' local cross-sectional deformations due to the bending process, and the associated tolerances that can be achieved. The results presented herein are based on nine rail segments that underwent identical bending operations. The differences between the rails were found to be relatively small as seen from a product functionality perspective; thus, the observed deformations are considered acceptable for the application considered. These results will also serve as a reference for future experiments with other bending parameters and methods in the efforts to identify the most technically and commercially viable solution.

  18. Evaluation of Alternative Field Buses for Lighting ControlApplications

    SciTech Connect

    Koch, Ed; Rubinstein, Francis

    2005-03-21

    The Subcontract Statement of Work consists of two major tasks. This report is the Final Report in fulfillment of the contract deliverable for Task 1. The purpose of Task 1 was to evaluate existing and emerging protocols and standards for interfacing sensors and controllers for communicating with integrated lighting control systems in commercial buildings. The detailed task description follows: Task 1. Evaluate alternative sensor/field buses. The objective of this task is to evaluate existing and emerging standards for interfacing sensors and controllers for communicating with integrated lighting control systems in commercial buildings. The protocols to be evaluated will include at least: (1) 1-Wire Net, (2) DALI, (3) MODBUS (or appropriate substitute such as EIB) and (4) ZigBee. The evaluation will include a comparative matrix for comparing the technical performance features of the different alternative systems. The performance features to be considered include: (1) directionality and network speed, (2) error control, (3) latency times, (4) allowable cable voltage drop, (5) topology, and (6) polarization. Specifically, Subcontractor will: (1) Analyze the proposed network architecture and identify potential problems that may require further research and specification. (2) Help identify and specify additional software and hardware components that may be required for the communications network to operate properly. (3) Identify areas of the architecture that can benefit from existing standards and technology and enumerate those standards and technologies. (4) Identify existing companies that may have relevant technology that can be applied to this research. (5) Help determine if new standards or technologies need to be developed.

  19. Evaluation of Potential pH-Driven Metal Release Due to Elevated Groundwater CO2 Concentrations

    NASA Astrophysics Data System (ADS)

    Tinnacher, R. M.; Varadharajan, C.; Zheng, L.; Spycher, N.; Birkholzer, J. T.; Trautz, R. C.; Pugh, J. D.; Esposito, R.; Nico, P. S.

    2012-12-01

    The injection of carbon dioxide (CO2) emissions from industrial sources into deep geologic formations is a potential option for the control of CO2 concentrations in the atmosphere. While the risk of CO2 migration from the storage reservoir into potable groundwater is low considering the safeguards of site characterization and permitting, it is important to understand what type of potential impacts could occur and how to identify these impacts. Elevated CO2 concentrations may potentially lead to a decrease in groundwater pH and the subsequent release of metals and ions from natural sediments into the groundwater solution. In this risk scenario, potential metal release processes, such as enhanced mineral dissolution, metal desorption and/or ion exchange reactions, may be driven by changes in groundwater pH, the presence of carbonate ligands in solution or a combination of the two. However, a detailed understanding and a distinction of pH-driven and carbonate-driven metal release reactions are important for the development of site monitoring plans and remediation strategies, required by regulations in the unlikely event of a release. Hence, in this study we characterized metal release from natural sediments into synthetic groundwater solutions at two pH conditions in order to mimic the native groundwater pH (pH ~8.5) and the low pH conditions expected in the event of elevated CO2 concentrations (pH~5). In addition, results are compared between tests performed in the presence and absence of elevated CO2. Metal release was investigated in lab-scale sequential leaching experiments using two sediment types with different organic carbon contents over a time-frame of 25 days. Supernatant solutions were monitored for pH and characterized in terms of metal concentrations (ICP-MS), total inorganic carbon (TIC) and anion composition. Furthermore, experimental results were compared with data from a field study involving the controlled release of groundwater containing dissolved

  20. Evaluation of photobioreactor heat balance for predicting changes in culture medium temperature due to light irradiation.

    PubMed

    Morita, M; Watanabe, Y; Saiki, H

    2001-09-20

    Microalgal photosynthesis requires appropriate culture medium temperatures to achieve high photosynthetic performance and to maintain production of a high-quality biomass product. Enclosed systems, such as our conical, helical tubular photobioreactor (HTP), can accomplish high photosynthetic efficiency and the small amount of culture medium used by these systems means that the culture medium temperature may be effectively controlled. On the other hand, because a high ratio of surface area to culture medium volume leads to rapid heating under the illumination condition and substantial heat loss at night, maintaining a suitable culture medium temperature is necessary to achieve efficient, commercially practical biomass production. In order to predict changes in the culture medium temperature caused by changes in solar irradiance and ambient temperature, it is necessary to understand the heat balance within the photobioreactor. We therefore investigated the heat balance in three major parts (photostage, degasser, and helical heat exchanger) of our conical HTP, analyzed the time-dependent changes in medium temperature at various room temperatures and radiant energy inputs, and predicted changes in the culture medium temperature based on the characteristics of heat transfer among the three parts. Using this model, the predicted changes in culture medium temperature were very similar to the changes observed experimentally in the laboratory and under field conditions. This means that by calculating the time-dependent changes in the culture medium temperature, based on measurements of solar energy input and ambient temperature, we should be able to estimate the energy required to maintain the culture medium temperature within a range where photosynthetic performance of microalgae is high. Copyright 2001 John Wiley & Sons, Inc.

  1. Evaluation of dermal and eye irritation and skin sensitization due to carbon nanotubes.

    PubMed

    Ema, Makoto; Matsuda, Akitaka; Kobayashi, Norihiro; Naya, Masato; Nakanishi, Junko

    2011-12-01

    The present paper summarizes the results of our studies on dermal and eye irritation and skin sensitization due to carbon nanotubes (CNTs), whose potential applications and uses are wide and varied, including CNT-enhanced plastics, electromagnetic interference/radio-frequency (EMI/RFI) shielding, antistatic material, flexible fibers and advanced polymers, medical and health applications, and scanning probe microscopy. Skin and eyes have the highest risk of exposure to nanomaterials, because deposition of nanomaterials to the surficial organs has the potential to be a major route of exposure during the manufacturing, use, and disposal of nanomaterials. Two products composed of single-walled carbon nanotubes (SWCNTs) and two products composed of multi-walled carbon nanotubes (MWCNTs) were tested regarding acute dermal and acute eye irritation using rabbits, and skin sensitization using guinea pigs. The concentrations of the CNTs in the substances were the maximum allowable for administration. The two products of SWCNTs and one of the products of MWCNTs were not irritants to the skin or eyes. The other product of MWCNTs caused very slight erythema at 24h, but not at 72h, after patch removal in the dermal irritation experiments and conjunctival redness and blood vessel hyperemia at 1h, but not at 24h, in eye irritation experiments. These findings showed that one product of MWCNTs was a very weak acute irritant to the skin and eyes. No products of SWCNTs and MWCNTs exhibited skin-sensitization effects. Our knowledge of the toxicological effects of CNTs is still limited. Further information is needed to clarify the potential for irritation and sensitization given the complex nature of CNTs. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Evaluation of the uncertainty due to land cover observation and conversion into plant functional types

    NASA Astrophysics Data System (ADS)

    Georgievski, Goran; Hartley, Andrew; MacBean, Natasha; Hagemann, Stefan

    2016-04-01

    Land surface processes represented in the latest generation of climate models (IPCC AR5) use the concept of Plant Functional Types (PFTs) to group different vegetation types and species according to similar physiological, biochemical and structural characteristics. The 5th IPCC Assessment Report recognizes the role of the Land Surface Models (LSMs) as one of the key contributors to uncertainty in climate change impacts projections. In the frame of the European Space Agency (ESA) Climate Change Initiative (CCI), a new global land cover (LC) data set was derived. We aim to investigate two sources of uncertainties in LSMs and their ranges: (i) uncertainty of ESA-CCI state of the art satellite observation of LC classes, and (ii) uncertainty due to LC conversion ("cross-walking (CW) procedure") into PFTs. Therefore, we have derived 5 perturbations of PFTs maps: (i) reference map (REF), (ii) map that minimizes biomass in LC observation and CW procedure (MinLC MinCW), (iii) map that minimizes biomass in LC observation with reference CW procedure (MinLC RefCW), (iv) map that maximizes biomass in LC observation with reference CW procedure (MaxLC RefCW), and (v) map that maximizes biomass in LC observation and CW procedure (MaxLC MaxCW). Our analysis demonstrates that there is still considerable uncertainty in the methods used to convert LC classes into the PFTs used by LSMs. Furthermore, uncertainty in the labelling of LC classes has an equal magnitude compared to the cross-walking uncertainty. In the next phase, we aim to quantify the sensitivity of the carbon, hydrological and energy cycles to LC and CW uncertainty with 3 LSMs (JSBACH, JULES, and ORHCIDEE). This work will enable us to both advice the land cover mapping community about the accuracy requirements for land cover maps, and to provide insights to the earth system modelling community on the implications of decisions taken when converting from land cover classes to PFTs.

  3. Evaluation of the tapered PMMA fiber sensor response due to the ionic interaction within electrolytic solutions

    NASA Astrophysics Data System (ADS)

    Batumalay, M.; Rahman, H. A.; Kam, W.; Ong, Y. S.; Ahmad, F.; Zakaria, R.; Harun, S. W.; Ahmad, H.

    2014-01-01

    A tapered plastic multimode fiber (PMMA) optical sensor is proposed and demonstrated for continuous monitoring of solutions based on different concentration of sodium chloride and glucose in deionized water The tapered PMMA fiber was fabricated using an etching method involving deionized water and acetone to achieve a waist diameter and length of 0.45 mm and 10 mm, respectively, and was used to investigate the effect of straight, U-shape, and knot shape against concentration for both sodium chloride and glucose. The results show that there is a strong dependence of the electrolytic and non-electrolytic nature of the chemical solutions on the sensor output. It is found that the sensitivity of the sodium chloride concentration sensor with the straight tapered fiber probe was 0.0023 mV/%, which was better than the other probe arrangements of U-shape and knot. Meanwhile, the glucose sensor performs with the highest sensitivity of 0.0026 mV/wt % with the knot-shaped tapered fiber probe. In addition, a tapered PMMA probe which was coated by silver film was fabricated and demonstrated using calcium hypochlorite (G70) solution. The working mechanism of such a device is based on the observed increment in the transmission of the sensor that is immersed in solutions of higher concentration. As the concentration varies from 0 ppm to 6 ppm, the output voltage of the sensor increases linearly from 3.61 mV to 4.28 mV with a sensitivity of 0.1154 mV/ppm and a linearity of more than 99.47%. The silver film coating increases the sensitivity of the proposed sensor due to the effective cladding refractive index, which increases with the coating and thus allows more light to be transmitted from the tapered fiber.

  4. Enhancement of electron-positron pair creation due to transient excitation of field-induced bound states

    NASA Astrophysics Data System (ADS)

    Jiang, M.; Lv, Q. Z.; Sheng, Z. M.; Grobe, R.; Su, Q.

    2013-04-01

    We study the creation of electron-positron pairs induced by two spatially separated electric fields that vary periodically in time. The results are based on large-scale computer simulations of the time-dependent Dirac equation in reduced spatial dimensions. When the separation of the fields is very large, the pair creation is caused by multiphoton transitions and mainly determined by the frequency of the fields. However, for small spatial separations a coherence effect can be observed that can enhance or reduce the particle yield compared to the case of two infinitely separated fields. If the travel time for a created electron or positron between both field locations becomes comparable to the period of the oscillating fields, we observe peaks in the energy spectrum which can be explained in terms of field-induced transient bound states.

  5. Evaluation of the Contamination in Vacuum Due to Plume Effects and Materials Outgassing

    NASA Astrophysics Data System (ADS)

    Delamare, B.; Palerm, S. Carrat, J.-M.

    2009-01-01

    This paper is devoted to the methodoloy and techniques used by ASTRIUM-ST to estimate the contamination in vacuum. This estimation is particularly important for the proper operation of the optical instruments and solar arrays of space vehicles such as the international space station (ISS). The contamination in vacuum has two main sources: plume effects and materials outgassing. Regarding the estimation of plume effects, the gas flow inside the nozzel is first computer using a parabolized Navier-Stokes turbulent numerical code (PNSTURDI). The resulting flow at the nozzel exit section is then used as an input to simulate the plume expansion in vacuum with the Direct Simulation Monte Carlo (DSMC) technique (IEMC code). The Plume is next approximated by a classical form of radial straight streamlines coming from a common source point. The resulting fitting function is implemented in the RAYJET code with uses a "ray launch" technique. Indeed, the impacted body is decribed by simple elementary surfaces, and when a ray coming from the nozzle impacts on one of these surfaces, the impingement effects (pressure, thermal and molecular fluxes) are evaluated through local models. Since the relative motion of the body with regard to the nozzle is taken into account, the integrated plume effects (energy, mass deposits) are estimated along its whole trajectory. As an application of this technique, the evaluation of the contamination on the ISS during the approach phase of the automatic transfer vehicle (ATV) is presented. As for the estimation of outgassing, two calculation methods are used. The first on considers the view factors theory based on the Lambertian law and uses the RAYOUT code. In the second technique, the intermolecular collisions between the molecules emitted by the materials and their interactions with the walls are computed using a DSMC approach. As an application, the case of the ATV solar generation system (SGS) outgassing is presented with input data supplied

  6. [Cost evaluation of hospital inpatient stays induced by injuries due to falls for elderly people].

    PubMed

    Di Pierdomenico, Lionel; Uwiteka, Ines; Senterre, Christelle; Leclercq, Pol; Mendes Da Costa, Élise; Pepersack, Thierry; Pirson, Magali

    2015-03-01

    Thirty percent of people aged 65 and older, living at home fall at least once a year. Few economic data are available in Belgium on this issue. We evaluated the cost borne by social security. 823 inpatient stays aged 65 and more, from home and admitted for injuries after a fall were selected. We observe an average (SD) age of 81 years. The proportion of women is 76%. 75% of admissions are related to fractures. 18% of patients are 'institutionalized' after falls. The death rate is 6%. The median (Q1-Q3) of cost is € 4.182 (2.385-6.820), for a length of stay median (Q1-Q3) of 11 days (4-25). The cost of hospital stays is estimated at €135 millions. Based on population projections, the cost could be estimated at € 243 millions in 2050. The overall cost of the treatment of these lesions is much more important, because costs are also generated after the hospitalization.

  7. Cinephotogrammetric Evaluation Of Thoracic Deformation Due To Safety Belt Action During A Crash Test

    NASA Astrophysics Data System (ADS)

    Verriest, J. P.

    1983-07-01

    In order to estimate the thoracic injury tolerance of a belted automobile occupant and to get a better knowledge about the mechanical behaviour of the belt/torso system, the dynamic deformation of the thorax is evaluated under the action of a safety belt load. Therefore, during the whole duration of a crash test (about 120 ms) the relative displacement of a set of points drawn on the thorax surface is measured by cinephotogrammetry. Five 16 mm cine-photo cameras (3 fix around the impact area and 2 on board the sled) filming at 500 frames per second permit to cover the whole trunk surface. Synchronization of film data is done by interpolating on a common time base. The three-dimensional coordinates of the measurement points enable the reconstruction of the thorax surface as a set of contiguous triangular plane facets which can be projected on various reference planes for display purposes. For clarity of drawings, an algorithm determines hidden lines not to be plotted. Cuts parallel to the projection plane are performed. By changing the orientation of this plane and the number and the pace of the cuts, either contour maps or transversal cuts are obtained providing a visualization of deformation which can then be related to compressive forces and resulting injuries.

  8. Evaluation of edge effect due to phase contrast imaging for mammography.

    PubMed

    Matsuo, Satoru; Katafuchi, Tetsuro; Tohyama, Keiko; Morishita, Junji; Yamada, Katsuhiko; Fujita, Hiroshi

    2005-08-01

    It is well-known that the edge effect produced by phase contrast imaging results in the edge enhancement of x-ray images and thereby sharpens those images. It has recently been reported that phase contrast imaging using practical x-ray tubes with small focal spots has improved image sharpness as observed in the phase contrast imaging with x-ray from synchrotron radiation or micro-focus x-ray tubes. In this study, we conducted the phase contrast imaging of a plastic fiber and plant seeds using a customized mammography equipment with a 0.1 mm focal spot, and the improvement of image sharpness was evaluated in terms of spatial frequency response of the images. We observed that the image contrast of the plastic fiber was increased by edge enhancement, and, as predicted elsewhere, spectral analysis revealed that as the spatial frequencies of the x-ray images increased, so did the sharpness gained through phase contrast imaging. Thus, phase contrast imaging using a practical molybdenum anode tube with a 0.1 mm-focal spot would benefit mammography, in which the morphological detectability of small species such as microcalcifications is of great concern. And detectability of tumor-surrounded glandular tissues in dense breast would be also improved by the phase contrast imaging.

  9. Stochastic Modeling Approach for the Evaluation of Backbreak due to Blasting Operations in Open Pit Mines

    NASA Astrophysics Data System (ADS)

    Sari, Mehmet; Ghasemi, Ebrahim; Ataei, Mohammad

    2014-03-01

    Backbreak is an undesirable side effect of bench blasting operations in open pit mines. A large number of parameters affect backbreak, including controllable parameters (such as blast design parameters and explosive characteristics) and uncontrollable parameters (such as rock and discontinuities properties). The complexity of the backbreak phenomenon and the uncertainty in terms of the impact of various parameters makes its prediction very difficult. The aim of this paper is to determine the suitability of the stochastic modeling approach for the prediction of backbreak and to assess the influence of controllable parameters on the phenomenon. To achieve this, a database containing actual measured backbreak occurrences and the major effective controllable parameters on backbreak (i.e., burden, spacing, stemming length, powder factor, and geometric stiffness ratio) was created from 175 blasting events in the Sungun copper mine, Iran. From this database, first, a new site-specific empirical equation for predicting backbreak was developed using multiple regression analysis. Then, the backbreak phenomenon was simulated by the Monte Carlo (MC) method. The results reveal that stochastic modeling is a good means of modeling and evaluating the effects of the variability of blasting parameters on backbreak. Thus, the developed model is suitable for practical use in the Sungun copper mine. Finally, a sensitivity analysis showed that stemming length is the most important parameter in controlling backbreak.

  10. Evaluation of alignment error due to a speed artifact in stereotactic ultrasound image guidance.

    PubMed

    Salter, Bill J; Wang, Brian; Szegedi, Martin W; Rassiah-Szegedi, Prema; Shrieve, Dennis C; Cheng, Roger; Fuss, Martin

    2008-12-07

    Ultrasound (US) image guidance systems used in radiotherapy are typically calibrated for soft tissue applications, thus introducing errors in depth-from-transducer representation when used in media with a different speed of sound propagation (e.g. fat). This error is commonly referred to as the speed artifact. In this study we utilized a standard US phantom to demonstrate the existence of the speed artifact when using a commercial US image guidance system to image through layers of simulated body fat, and we compared the results with calculated/predicted values. A general purpose US phantom (speed of sound (SOS) = 1540 m s(-1)) was imaged on a multi-slice CT scanner at a 0.625 mm slice thickness and 0.5 mm x 0.5 mm axial pixel size. Target-simulating wires inside the phantom were contoured and later transferred to the US guidance system. Layers of various thickness (1-8 cm) of commercially manufactured fat-simulating material (SOS = 1435 m s(-1)) were placed on top of the phantom to study the depth-related alignment error. In order to demonstrate that the speed artifact is not caused by adding additional layers on top of the phantom, we repeated these measurements in an identical setup using commercially manufactured tissue-simulating material (SOS = 1540 m s(-1)) for the top layers. For the fat-simulating material used in this study, we observed the magnitude of the depth-related alignment errors resulting from the speed artifact to be 0.7 mm cm(-1) of fat imaged through. The measured alignment errors caused by the speed artifact agreed with the calculated values within one standard deviation for all of the different thicknesses of fat-simulating material studied here. We demonstrated the depth-related alignment error due to the speed artifact when using US image guidance for radiation treatment alignment and note that the presence of fat causes the target to be aliased to a depth greater than it actually is. For typical US guidance systems in use today, this will

  11. Evaluation of Field-in-Field Technique for Total Body Irradiation

    SciTech Connect

    Onal, Cem; Sonmez, Aydan; Arslan, Gungor; Sonmez, Serhat; Efe, Esma; Oymak, Ezgi

    2012-08-01

    Purpose: To evaluate the clinical use of a field-in-field (FIF) technique for total body irradiation (TBI) using a treatment-planning system (TPS) and to verify TPS results with in vivo dose measurements using metal-oxide-semiconductor field-effect transistor (MOSFET) detectors. Methods and Materials: Clinical and dosimetric data of 10 patients treated with TBI were assessed. Certain radiation parameters were measured using homogenous and regular phantoms at an extended distance of 380 cm, and the results were compared with data from a conventional standard distance of 100 cm. Additionally, dosimetric validation of TPS doses was performed with a Rando phantom using manual calculations. A three-dimensional computed tomography plan was generated involving 18-MV photon beams with a TPS for both open-field and FIF techniques. The midline doses were measured at the head, neck, lung, umbilicus, and pelvis for both open-field and FIF techniques. Results: All patients received planned TBI using the FIF technique with 18-MV photon energies and 2 Gy b.i.d. on 3 consecutive days. The difference in tissue maximum ratios between the extended and conventional distances was <2%. The mean deviation of manual calculations compared with TPS data was +1.6% (range, 0.1-2.4%). A homogenous dose distribution was obtained with 18-MV photon beams using the FIF technique. The mean lung dose for the FIF technique was 79.2% (9.2 Gy; range, 8.8-9.7 Gy) of the prescribed dose. The MOSFET readings and TPS doses in the body were similar (percentage difference range, -0.5% to 2.5%) and slightly higher in the shoulder and lung (percentage difference range, 4.0-5.5%). Conclusion: The FIF technique used for TBI provides homogenous dose distribution and is feasible, simple, and spares time compared with more-complex techniques. The TPS doses were similar to the midline doses obtained from MOSFET readings.

  12. A tool to evaluate local biophysical effects on temperature due to land cover change transitions

    NASA Astrophysics Data System (ADS)

    Perugini, Lucia; Caporaso, Luca; Duveiller, Gregory; Cescatti, Alessandro; Abad-Viñas, Raul; Grassi, Giacomo; Quesada, Benjamin

    2017-04-01

    Land Cover Changes (LCC) affect local, regional and global climate through biophysical variations of the surface energy budget mediated by albedo, evapotranspiration, and roughness. Assessment of the full climate impacts of anthropogenic LCC are incomplete without considering biophysical effects, but the high level of uncertainties in quantifying their impacts to date have made it impractical to offer clear advice on which policy makers could act. To overcome this barrier, we provide a tool to evaluate the biophysical impact of a matrix of land cover transitions, following a tiered methodological approach similar to the one provided by the IPCC to estimate the biogeochemical effects, i.e. through three levels of methodological complexity, from Tier 1 (i.e. default method and factors) to Tier 3 (i.e. specific methods and factors). In particular, the tool provides guidance for quantitative assessment of changes in temperature following a land cover transition. The tool focuses on temperature for two main reasons (i) it is the main variable of interest for policy makers at local and regional level, and (ii) temperature is able to summarize the impact of radiative and non-radiative processes following LULCC. The potential changes in annual air temperature that can be expected from various land cover transitions are derived from a dedicated dataset constructed by the JRC in the framework of the LUC4C FP7 project. The inputs for the dataset are air temperature values derived from satellite Earth Observation data (MODIS) and land cover characterization from the ESA Climate Change Initiative product reclassified into their IPCC land use category equivalent. This data, originally at 0.05 degree of spatial resolution, is aggregated and analysed at regional level to provide guidance on the expected temperature impact following specific LCC transitions.

  13. Experiments evaluating subsidence generated within a subaqueous deformable substrate due to varying differential sediment loading patterns

    NASA Astrophysics Data System (ADS)

    Foreman, B.; Chatmas, E. S.; Abeyta, A.; Paola, C.

    2013-12-01

    The intraslope areas of many passive margins display a complex bathymetry of topographic depressions and crests that form series of minibasins. These minibasins are linked to the deformation of subsurface salt layers and act as localized sediment traps. Many mechanisms have been proposed for the initiation of minibasins, including tectonic forces (both extensional and contractional), regional gravitational sliding, density inversion between salt layers and overburden, and differential sediment loading. Regardless of initiation mechanism, it is widely recognized that synkinematic deposition plays a active role in determining subsidence patterns and sediment routing within and among the minibasins. We undertook a series of simplified 1-D and 2-D experiments 1) to evaluate the feasibility of developing a series of well-defined minibasins created exclusively by differential sediment loading and 2) to quantitatively determine the effects of substrate thickness, density contrast, and sedimentation rate on the resultant subsidence pattern. We also present an initial non-dimensionalized formulation of the problem that relates density contrasts, clinoform thickness, substrate thickness, progradation rate, and viscosity of the deformable substrate. Two sets of experiments were performed. The first set (1-D) vertically loaded a subaqueous corn syrup substrate (capturing the rheology of subsurface salt as a Newtonian fluid) with walnut sand. The second set (2-D) of experiments prograded a walnut sediment clinoform across a corn syrup substrate. We systematically varied sedimentation rate, substrate thickness, and, in the case of the prograding clinoform, base level. In no cases did we successfully reproduce a series of minibasins similar to those observed in natural settings. Instead the substrate was simply displaced laterally as sediment was deposited, forming a single depression. High sedimentation rates tended to produce wider zones of subsidence, however, if given

  14. Spectrally Enhanced Lighting Program Implementation for Energy Savings: Field Evaluation

    SciTech Connect

    Gordon, Kelly L.; Sullivan, Gregory P.; Armstrong, Peter R.; Richman, Eric E.; Matzke, Brett D.

    2006-08-22

    This report provides results from an evaluation PNNL conducted of a spectrally enhanced lighting demonstration project. PNNL performed field measurements and occupant surveys at three office buildings in California before and after lighting retrofits were made in August and December 2005. PNNL measured the following Overhead lighting electricity demand and consumption, Light levels in the workspace, Task lighting use, and Occupant ratings of satisfaction with the lighting. Existing lighting, which varied in each building, was replaced with lamps with correlated color temperature (CCT) of 5000 Kelvin, color rendering index (CRI) of 85, of varying wattages, and lower ballast factor electronic ballasts. The demonstrations were designed to decrease lighting power loads in the three buildings by 22-50 percent, depending on the existing installed lamps and ballasts. The project designers hypothesized that this reduction in electrical loads could be achieved by the change to higher CCT lamps without decreasing occupant satisfaction with the lighting.

  15. Army nurse readiness instrument: psychometric evaluation and field administration.

    PubMed

    Reineck, C; Finstuen, K; Connelly, L M; Murdock, P

    2001-11-01

    The purpose of this study was to construct and evaluate the psychometric properties of an instrument to estimate the level of individual readiness among U.S. Army nurses. This study constitutes phase II of congressionally sponsored research to establish the degree to which Army nurses are prepared for the expectations of deployment. An expert panel established the validity of the initial readiness questionnaire. Changes were then incorporated into the first Readiness Estimate and Deployability Index (READI) questionnaire. Internal consistency and test-retest techniques assessed multiple reliabilities from pilot administrations. The READI was refined based on the results. Analysis of field administrations of the revised READI to three separate groups of nurses replicated earlier reliability results. Principle component analyses appear to support the hypothesized dimensional structure underlying questionnaire attitude items. The READI produced psychometrically stable ratings and results with great utility for the Army and potential adaptation for other military services.

  16. Results of field testing the cement evaluation tool

    SciTech Connect

    Leigh, C.A.; Finlayson, C.G.; Van der Kolk, C.

    1984-01-01

    The Cement Evaluation Tool (CET) developed by Schlumberger employs a pulse-echo technique using eight sonic transducers to investigate the casing cement bond. The tool has been widely field tested in a clastic environment in Brunei (N.W. Borneo), across both oil and gas bearing reservoirs. Numerous comparisons of the CET with conventional CBL/VDL logs have been made. Across oil and water bearing intervals the CET is shown to compare favourably with the CBL/VDL and yields significant additional information on channeling, cement distribution, and the success of casing centralization. In addition, the accuracy of the acoustic calipers have proved sufficient to be used in assisting drilling and completion operations. The response of the tool to a microannulus has also been demonstrated by multiple runs under varying wellbore pressures.

  17. Medium and Heavy Duty Vehicle Field Evaluations (Presentation)

    SciTech Connect

    Walkowicz, K.

    2014-06-01

    This presentation discusses field evaluations of medium- and heavy-duty vehicles performed by NREL. The project provides medium-duty (MD) and heavy-duty (HD) test results, aggregated data, and detailed analysis, including 3rd party unbiased data (data that would not normally be shared by industry in an aggregated and detailed manner). Over 5.6 million miles of advanced technology MD and HD truck data have been collected, documented, and analyzed on over 240 different vehicles since 2002. Data, analysis, and reports are shared within DOE, national laboratory partners, and industry for R&D planning and strategy. The results help guide R&D for new technology development, help define intelligent usage of newly developed technology, and help fleets/users understand all aspects of advanced technology.

  18. Evaluation of an electric field sensor for nondestructive material inspection

    NASA Astrophysics Data System (ADS)

    Kalyanasundaram, Kayatri; Arunachalam, Kavitha

    2013-01-01

    An electric field sensor is fabricated on a 125 micron thick flexible dielectric substrate for electromagnetic (EM) nondestructive material inspection at 915 MHz. The sensor consists of an electrically short dipole antenna and a radio frequency (RF) diode detector connected to a pair of high impedance screen printed carbon lines. The DC component of the rectified diode voltage conveyed across the high impedance lines is measured using a data acquisition circuit. Sensor measurements are validated with simulated data for a conformal patch antenna operating at 915 MHz. Sensor performance for EM nondestructive testing (NDT) is evaluated using phantom defects in low loss dielectric slabs. Preliminary results indicate sensor utility for EM NDT and support further testing on realistic defects.

  19. A Strategy to Estimate the Systematic Uncertainty of Eddy Covariance Fluxes due to the Post-field Raw Data Processing

    NASA Astrophysics Data System (ADS)

    Sabbatini, Simone; Fratini, Gerardo; Fidaleo, Marcello; Papale, Dario

    2017-04-01

    Among several sources of uncertainty characterising the fluxes of atmospheric constituents to and from a given ecosystem calculated using the eddy covariance (EC) methodology, the systematic error due to the corrections applied in the post-field raw data processing is still relatively unknown. We performed an extensive analysis aiming at quantifying this portion of the uncertainty for the CO2 exchange, and at defining a strategy of processing to be generically applied as to understand this uncertainty. We selected 11 years of raw EC data from 9 stations all over the Europe, corresponding to 4 different setups. Then we chose 2 or 3 possible valid options for each of the 8 most relevant corrections to be applied to the raw data, and produced as many outputs (1-year-long calculated hourly and half-hourly fluxes) as the combinations of all the different options (full-factorial design). Statistical analysis was used to quantify and characterise the uncertainty (n-way ANOVA) both on the (half-)hourly and the yearly cumulative fluxes. Factorial design of Experiment (DOE) was used to select a relatively small sub-group of combinations of processing options (fractional factorial design) to be applied to a given dataset in order to quantify the processing uncertainty, with a limited loss of information as compared to the full factorial. Our results show that: (i) the variability as expressed by the inter-quartile range (IQR) of the cumulate CO2 flux is between 50 and 400 gC m-2 year-1. (ii) The importance of the single corrections (factors) in terms of variance explained is not constant among datasets, but a general trend is found such that the coordinate rotation (CR) and the trend removal (TR) have often a high weight on the overall uncertainty (i.e. between 10% and 50%), while the importance of the time-lag compensation (TL) is highly variable. (iii) 2x2 interactions between factors have some importance, mostly between the most relevant ones. (iv) The percentage error of

  20. Improving detection and identification of seismic signals due to landslides: a methodology based on field scale controlled experiments

    NASA Astrophysics Data System (ADS)

    Yfantis, G.; Carvajal, H. E.; Pytharouli, S.; Lunn, R. J.

    2013-12-01

    A number of published studies use seismic sensors to understand the physics involved in slope deformation. In this research we artificially induce failure to two meter scaled slopes in the field and use 12 short period 3D seismometers to monitor the failure. To our knowledge there has been no previous controlled experiments that can allow calibration and validation of the interpreted seismic signals. Inside the body of one of the artificial landslides we embed a pile of glass shards. During movement the pile deforms emitting seismic signals due to friction among the glass shards. Our aim is twofold: First we investigate whether the seismic sensors can record pre-cursory and failure signals. Secondly, we test our hypothesis that the glass shards produce seismic signals with higher amplitudes and a distinct frequency pattern, compared to those emitted by common landslide seismicity and local background noise. Two vertical faces, 2m high, were excavated 3m apart in high porous tropical clay. This highly attenuating material makes the detection of weak seismic signals challenging. Slope failure was induced by increasing the vertical load at the landslide's crown. Special care was taken in the design of all experimental procedures to not add to the area's seismic noise. Measurements took place during 18 hours (during afternoon and night) without any change in soil and weather conditions. The 3D sensors were placed on the ground surface close to the crown, forming a dense microseismic network with 5-to-10m spacing and two nanoseismic arrays, with aperture sizes of 10 and 20 m. This design allowed a direct comparison of the recorded signals emitted by the two landslides. The two faces failed for loading between 70 and 100kN and as a result the pile of glass shards was horizontally deformed allowing differential movement between the shards. After the main failure both landslides were continuing to deform due to soil compaction and horizontal displacement. We apply signal

  1. Microbial Community Shifts due to Hydrofracking: Observations from Field-Scale Observations and Laboratory-Scale Incubations

    NASA Astrophysics Data System (ADS)

    Mouser, P. J.; Ansari, M.; Hartsock, A.; Lui, S.; Lenhart, J.

    2012-12-01

    The use of fluids containing chemicals and variable water sources during the hydrofracking of unconventional shale is the source of considerable controversy due to perceived risks from altered subsurface biogeochemistry and the potential for contaminating potable water supplies. Rapid shifts in subsurface biogeochemistry are often driven by available macronutrients combined with the abundance and metabolic condition of the subsurface microbiota. While the depth that fracturing occurs in the Marcellus formation is reasonably deep to pose little risk to groundwater supplies, no published studies have systematically characterized the indigenous microbial population and how this community is altered through variable fluid management practices (e.g., chemical composition, source water makeup). In addition, limited information is available on how shallower microbial communities and geochemical conditions might be affected through the accidental release of these fluids to groundwater aquifers. Our measurements indicate field-applied and laboratory-generated fracking fluids contain levels of organic carbon greater than 300 mg/l and nitrogen concentrations greater than 80 mg/l that may differentially stimulate microbial growth in subsurface formations. In contrast to certain inorganic constituents (e.g., chloride) which increase in concentration through the flowback period; dissolved organic carbon levels decrease with time after the fracturing process through multiple attenuation processes (dilution, sorption, microbial utilization). Pyrosequencing data of the 16S rRNA gene indicate a shift from a more diverse source water microbial community to a less diverse community typical of a brine formation as time after fracturing increases. The introduction of varying percentages of a laboratory-generated fracking fluid to microcosm bottles containing groundwater and aquifer media stimulated biogeochemical changes similar to the introduction of landfill leachate, another

  2. Evaluation of PCR Systems for Field Screening of Bacillus anthracis

    PubMed Central

    Ozanich, Richard M.; Colburn, Heather A.; Victry, Kristin D.; Bartholomew, Rachel A.; Arce, Jennifer S.; Heredia-Langner, Alejandro; Jarman, Kristin; Kreuzer, Helen W.

    2017-01-01

    There is little published data on the performance of hand-portable polymerase chain reaction (PCR) systems that can be used by first responders to determine if a suspicious powder contains a potential biothreat agent. We evaluated 5 commercially available hand-portable PCR instruments for detection of Bacillus anthracis. We used a cost-effective, statistically based test plan to evaluate systems at performance levels ranging from 0.85-0.95 lower confidence bound (LCB) of the probability of detection (POD) at confidence levels of 80% to 95%. We assessed specificity using purified genomic DNA from 13 B. anthracis strains and 18 Bacillus near neighbors, potential interference with 22 suspicious powders that are commonly encountered in the field by first responders during suspected biothreat incidents, and the potential for PCR inhibition when B. anthracis spores were spiked into these powders. Our results indicate that 3 of the 5 systems achieved 0.95 LCB of the probability of detection with 95% confidence levels at test concentrations of 2,000 genome equivalents/mL (GE/mL), which is comparable to 2,000 spores/mL. This is more than sufficient sensitivity for screening visible suspicious powders. These systems exhibited no false-positive results or PCR inhibition with common suspicious powders and reliably detected B. anthracis spores spiked into these powders, though some issues with assay controls were observed. Our testing approach enables efficient performance testing using a statistically rigorous and cost-effective test plan to generate performance data that allow users to make informed decisions regarding the purchase and use of field biodetection equipment. PMID:28192050

  3. Field evaluations of hearing protection devices at surface mining environments

    SciTech Connect

    Not Available

    1993-12-31

    A study was conducted to evaluate the effectiveness of circumaural hearing protection devices and their predictability when they were being worn by mine employees performing normal work duties. The method employed relied on a physical measurement of the noise reduction of the hearing protectors by utilizing two FM-wireless transmitting and receiving systems. One system measured the outside hearing protector noise level, the second system measured the inside hearing protector noise level. The noise level data of both systems was transmitted back to the corresponding receivers and was recorded onto a two-channel tape recorder. Three methods of evaluating hearing protector performance were explored and compared to the Environmental Protection Agency, Noise Reduction Rating (EPA NRR) values. They were, (1) predicted National Institute for occupational Safety and Health`s (NIOSH) method No. 1 values, (2) field-calculated NIOSH No. 1 values, and (3) measured dBA reduction values, which was the arithmetic A-weighted differences between both microphone locations. The majority of the data was obtained on operators of mobile strip equipment, such as bulldozers, front-end-loaders, and overburden drills. A total of 107 individual tests were conducted using 11 different hearing protectors. The results indicate that the amount of protection, which can vary significantly, is related either to the spectrum shape of the noise, or the C-weighted minus the A-weighted (C-A) value. This is consistent with other researchers. The field measured noise reductions were equivalent to the EPA NRR values when the C-A values were negative or approaching zero. When the C-A values increased, the measured noise reductions significantly decreased.

  4. Field evaluation of an avian risk assessment model

    USGS Publications Warehouse

    Vyas, N.B.; Spann, J.W.; Hulse, C.S.; Borges, S.L.; Bennett, R.S.; Torrez, M.; Williams, B.I.; Leffel, R.

    2006-01-01

    We conducted two laboratory subacute dietary toxicity tests and one outdoor subacute dietary toxicity test to determine the effectiveness of the U.S. Environmental Protection Agency's deterministic risk assessment model for evaluating the potential of adverse effects to birds in the field. We tested technical-grade diazinon and its D Z N- 50W (50% diazinon active ingredient wettable powder) formulation on Canada goose (Branta canadensis) goslings. Brain acetylcholinesterase activity was measured, and the feathers and skin, feet. and gastrointestinal contents were analyzed for diazinon residues. The dose-response curves showed that diazinon was significantly more toxic to goslings in the outdoor test than in the laboratory tests. The deterministic risk assessment method identified the potential for risk to birds in general, but the factors associated with extrapolating from the laboratory to the field, and from the laboratory test species to other species, resulted in the underestimation of risk to the goslings. The present study indicates that laboratory-based risk quotients should be interpreted with caution.

  5. Evaluation of the field-in-field technique with lung blocks for breast tangential radiotherapy

    PubMed Central

    Tanaka, Hidekazu; Hayashi, Shinya; Kajiura, Yuichi; Kitahara, Masashi; Matsuyama, Katsuya; Kanematsu, Masayuki; Hoshi, Hiroaki

    2015-01-01

    ABSTRACT Several studies have reported the advantages of the field-in-field (FIF) technique in breast radiotherapy, including dose reduction in the lungs by using lung field blocks. We evaluated the FIF technique with lung blocks for breast tangential radiotherapy. Sixteen patients underwent free breathing (FB) computed tomography (CT), followed by two CT procedures performed during breath hold after light inhalation (IN) and light exhalation (EX). Three radiotherapy plans were created using the FIF technique based on the FB-CT images: one without lung blocks (LB0) and two with lung blocks whose monitor units (MUs) were 5 (LB5) and 10 (LB10), respectively. These plans were copied to the IN-CT and EX-CT images. V20Gy, V30Gy, and V40Gy of the ipsilateral lung and V100%, V95%, and the mean dose (Dmean) to the planning target volume (PTV) were analyzed. The extent of changes in these parameters on the IN-plan and EX-plan compared with the FB-plan was evaluated. V20Gy, V30Gy, and V40Gy were significantly smaller for FB-LB5 and FB-LB10 than for FB-LB0; similar results were obtained for the IN-plan and EX-plan. V100%, V95%, and Dmean were also significant smaller for FB-LB5 and FB-LB10 than for FB-LB0. The extent of changes in V20Gy, V30Gy, and V40Gy on the IN-plan and EX-plan compared with the FB-plan was not statistically significant. Lung blocks were useful for dose reduction in the lung and a simultaneous PTV decrease. This technique should not be applied in the general population. PMID:26412879

  6. Application of PCR-denaturing-gradient gel electrophoresis (DGGE) method to examine microbial community structure in asparagus fields with growth inhibition due to continuous cropping.

    PubMed

    Urashima, Yasufumi; Sonoda, Takahiro; Fujita, Yuko; Uragami, Atsuko

    2012-01-01

    Growth inhibition due to continuous cropping of asparagus is a major problem; the yield of asparagus in replanted fields is low compared to that in new fields, and missing plants occur among young seedlings. Although soil-borne disease and allelochemicals are considered to be involved in this effect, this is still controversial. We aimed to develop a technique for the biological field diagnosis of growth inhibition due to continuous cropping. Therefore, in this study, fungal community structure and Fusarium community structure in continuously cropped fields of asparagus were analyzed by polymerase chain reaction/denaturing-gradient gel electrophoresis (PCR-DGGE). Soil samples were collected from the Aizu region of Fukushima Prefecture, Japan. Soil samples were taken from both continuously cropped fields of asparagus with growth inhibition and healthy neighboring fields of asparagus. The soil samples were collected from the fields of 5 sets in 2008 and 4 sets in 2009. We were able to distinguish between pathogenic and non-pathogenic Fusarium by using Alfie1 and Alfie2GC as the second PCR primers and PCR-DGGE. Fungal community structure was not greatly involved in the growth inhibition of asparagus due to continuous cropping. By contrast, the band ratios of Fusarium oxysporum f. sp. asparagi in growth-inhibited fields were higher than those in neighboring healthy fields. In addition, there was a positive correlation between the band ratios of Fusarium oxysporum f. sp. asparagi and the ratios of missing asparagus plants. We showed the potential of biological field diagnosis of growth inhibition due to continuous cropping of asparagus using PCR-DGGE.

  7. Application of PCR-Denaturing-Gradient Gel Electrophoresis (DGGE) Method to Examine Microbial Community Structure in Asparagus Fields with Growth Inhibition due to Continuous Cropping

    PubMed Central

    Urashima, Yasufumi; Sonoda, Takahiro; Fujita, Yuko; Uragami, Atsuko

    2012-01-01

    Growth inhibition due to continuous cropping of asparagus is a major problem; the yield of asparagus in replanted fields is low compared to that in new fields, and missing plants occur among young seedlings. Although soil-borne disease and allelochemicals are considered to be involved in this effect, this is still controversial. We aimed to develop a technique for the biological field diagnosis of growth inhibition due to continuous cropping. Therefore, in this study, fungal community structure and Fusarium community structure in continuously cropped fields of asparagus were analyzed by polymerase chain reaction/denaturing-gradient gel electrophoresis (PCR-DGGE). Soil samples were collected from the Aizu region of Fukushima Prefecture, Japan. Soil samples were taken from both continuously cropped fields of asparagus with growth inhibition and healthy neighboring fields of asparagus. The soil samples were collected from the fields of 5 sets in 2008 and 4 sets in 2009. We were able to distinguish between pathogenic and non-pathogenic Fusarium by using Alfie1 and Alfie2GC as the second PCR primers and PCR-DGGE. Fungal community structure was not greatly involved in the growth inhibition of asparagus due to continuous cropping. By contrast, the band ratios of Fusarium oxysporum f. sp. asparagi in growth-inhibited fields were higher than those in neighboring healthy fields. In addition, there was a positive correlation between the band ratios of Fusarium oxysporum f. sp. asparagi and the ratios of missing asparagus plants. We showed the potential of biological field diagnosis of growth inhibition due to continuous cropping of asparagus using PCR-DGGE. PMID:22200640

  8. Anomalous Hanle effect due to optically created transverse overhauser field in single InAs/GaAs quantum dots.

    PubMed

    Krebs, O; Maletinsky, P; Amand, T; Urbaszek, B; Lemaître, A; Voisin, P; Marie, X; Imamoglu, A

    2010-02-05

    We report on experimental observations of an anomalous Hanle effect in individual self-assembled InAs/GaAs quantum dots. A sizable electron spin polarization photocreated under constant illumination is maintained in transverse magnetic fields as high as approximately 1 T, up to a critical field where it abruptly collapses. These striking anomalies of the Hanle curve point to a novel mechanism of dynamic nuclear spin polarization giving rise to an effective magnetic field generated perpendicular to the optically injected electron spin polarization. This transverse Overhauser field, confirmed by the cancellation of electron Zeeman splitting below the critical field, is likely to be a consequence of the strong inhomogeneous quadrupolar interactions typical for strained quantum dots.

  9. PRELIMINARY FIELD EVALUATION OF MERCURY CONTROL USING COMBUSTION MODIFICATIONS

    SciTech Connect

    Vitali Lissianski; Antonio Marquez

    2004-02-19

    In this project General Electric Energy and Environmental Research Corporation conducts a preliminary field evaluation of a novel technology, referred to as Hg/NO{sub x}, that can reduce emissions of both mercury (Hg) and oxides of nitrogen (NO{sub x}) from coal-fired power plants. The evaluation takes place in Green Station Unit 2 operated by Western Kentucky Energy. Reduction of Hg and NO{sub x} emissions in Unit 2 is achieved using coal reburning. Activities during first project year (January 23, 2003--January 22, 2004) included measurements of baseline Hg emissions in Unit 2 and pilot-scale testing. Baseline testing of Hg emissions in Green Unit 2 has been completed. Two fuels were tested with OFA system operating at minimum air flow. Mercury emissions were measured at ESP inlet and outlet, and at the stack using Ontario Hydro revised method. Testing demonstrated that baseline Hg reductions at ESP outlet and stack were 30-45% and 70-80%, respectively. Pilot-scale testing demonstrated good agreement with baseline measurements in Unit 2. Testing showed that fuel composition had an effect on the efficiency of Hg absorption on fly ash. Maximum achieved Hg removal in reburning was close to 90%. Maximum achieved Hg reduction at air staging conditions was 60%. Testing also demonstrated that lowering ESP temperature improved efficiency of Hg removal.

  10. Preliminary Field Evaluation of Mercury Control Using Combustion Modifications

    SciTech Connect

    V. Lissianski; P. Maly; T. Marquez

    2005-01-22

    In this project EER conducted a preliminary field evaluation of the integrated approach for mercury (Hg) and NO{sub x} control. The approach enhanced the 'naturally occurring' Hg capture by fly ash through combustion optimization, increasing carbon in ash content, and lowering ESP temperature. The evaluation took place in Green Station Units 1 and 2 located near Henderson, Kentucky and operated by Western Kentucky Energy. Units 1 and 2 are equipped with cold-side ESPs and wet scrubbers. Green Station Units 1 and 2 typically fire two types of fuel: a bituminous coal and a blend of bituminous coals based on availability. Testing of Hg emissions in Unit 2 without reburning system in operation and at minimum OFA demonstrated that efficiencies of Hg reduction downstream of the ESP were 30-40%. Testing also demonstrated that OFA system operation at 22% air resulted in 10% incremental increase in Hg removal efficiency at the ESP outlet. About 80% of Hg in flue gas at ESP outlet was present in the oxidized form. Testing of Hg emissions under reburning conditions showed that Hg emissions decreased with LOI increase and ESP temperature decrease. Testing demonstrated that maximum Hg reduction downstream of ESP was 40-45% at ESP temperatures higher than 300 F and 60-80% at ESP temperatures lower than 300 F. The program objective to demonstrate 80% Hg removal at the ESP outlet has been met.

  11. Small wind systems field evaluation. Volume 2: Institutional issues

    NASA Astrophysics Data System (ADS)

    Dodge, D. M.; Liske, C.

    1983-07-01

    The operation, management, and results of the field evaluation program (FEP) for small wind systems is described. The FEP was initiated in early 1979 with the objective to install wind systems in the states and territories to assist local governments in evaluating and addressing the institutional concerns associated with the proliferation of small wind systems in utility interconnected applications. Institutional issues defined, encountered and addressed by Rocky Flats in operating the FEP are summarized. Information dissemination, which includes briefings of state and local governments and utility personnel is outlined. The scope and acievements of the program are detailed. Specific problems encountered and addressed are described which includes height restrictions posed by proximity to airports and requirements for state and local approvals of various types. Other barriers include lack of public knowledge, lack of data sources, local wind resource uncertainties, lack of industry standards, and low institutional and consumer confidence. Regulatory barriers which would impact other federal projects and large private wind farm development efforts are considered.

  12. Handheld standoff mine detection system (HSTAMIDS) field evaluation in Namibia

    NASA Astrophysics Data System (ADS)

    Doheny, Robert C.; Burke, Sean; Cresci, Roger; Ngan, Peter; Walls, Richard; Chernoff, Jeff

    2006-05-01

    The Humanitarian Demining Research and Development Program of the US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate (NVESD), under the direction of the Office of Assistant Secretary of Defense for Special Operations and Low-Intensity Conflict (OASD SO/LIC) and with participation from the International Test and Evaluation Program (ITEP) for humanitarian demining, conducted an in-country field evaluation of the Handheld Standoff Mine Detection System (HSTAMIDS) in the southern African country of Namibia. Participants included the US Humanitarian Demining Team of NVESD; ITEP personnel from several member countries; deminers from two non-governmental organizations in Angola, Menschen Gegen Minen (MgM) and HALO Trust; and CyTerra Corporation. The primary objectives were to demonstrate the performance of the U.S. Army's newest handheld multisensor mine detector, the HSTAMIDS, to the performance of the metal detector being used by local demining organizations and also to assess the performance of deminers using the HSTAMIDS after limited experience and training.

  13. [Methods of dosimetry in evaluation of electromagnetic fields' biological action].

    PubMed

    Rubtsova, N B; Perov, S Iu

    2012-01-01

    Theoretical and experimental dosimetry can be used for adequate evaluation of the effects of radiofrequency electromagnetic fields. In view of the tough electromagnetic environment in aircraft, pilots' safety is of particular topicality. The dosimetric evaluation is made from the quantitative characteristics of the EMF interaction with bio-objects depending on EM energy absorption in a unit of tissue volume or mass calculated as a specific absorbed rate (SAR) and measured in W/kg. Theoretical dosimetry employs a number of computational methods to determine EM energy, as well as the augmented method of boundary conditions, iterative augmented method of boundary conditions, moments method, generalized multipolar method, finite-element method, time domain finite-difference method, and hybrid methods combining several decision plans modeling the design philosophy of navigation, radiolocation and human systems. Because of difficulties with the experimental SAR estimate, theoretical dosimetry is regarded as the first step in analysis of the in-aircraft conditions of exposure and possible bio-effects.

  14. Field evaluation of mosquito control devices in southern Louisiana.

    PubMed

    Collier, Brett W; Perich, Michael J; Boquin, Gerardo J; Harrington, Scott R; Francis, Mike J

    2006-09-01

    The effect of 2 mosquito traps and 2 repellent systems on the catch of adult mosquitoes in American Biophysics Corporation (ABC) light traps was evaluated over a 14-month period at 3 locations in Louisiana. Devices evaluated included 1) ABC Mosquito Magnet with dry ice and octanol; 2) the BioSensory 500 cc Dragonfly Biting Insect Trap with CO2, octenol, and Mosquito Cognito, which uses Conceal inhibitor; 3) the SC Johnson OFF! Mosquito Lantern; and 4) the ThermaCell cordless mosquito repellent system. The number of adult mosquitoes caught in the ABC light traps, at the SC Johnson OFF! Mosquito Lantern, and ThermaCell cordless mosquito repellent treatment sites was significantly lower than the number collected at the ABC Mosquito Magnet or the Dragonfly/Mosquito Cognito trap system sites. When the 2 repellent devices were placed in combination with the ABC traps, mosquito numbers were significantly reduced when compared with sites with ABC traps alone. These data indicate that the SC Johnson OFF! Mosquito Lantern and ThermaCell cordless mosquito system may reduce attack from biting mosquitoes due to the reduction in their numbers. In the same study, the mosquito counts of the trapping devices also were reported.

  15. Strong and large area field enhancement outside a microcavity due to propagating surface plasmons and standing wave effect

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Wang, Bin; Sun, Xin; Li, Haoyu; Wang, Feng; Zhang, Yunxia; Huang, Senpeng; Xu, Xiaoxuan; Wang, Yufang; Zhang, Cunzhou

    2016-10-01

    We investigated the optical property of periodic inverted pyramidal microcavities and observed large area field enhancement outside a cavity when the incident wavelength and structure parameters match certain relations. The mechanism of this phenomenon has been studied. Propagating surface plasmons and the standing wave effect both contribute to the field enhancement outside the cavity. The relations between the incident wavelength and structure parameters have been clarified. Based on the relations, one can control the field enhancement outside the cavity for a specific laser wavelength.

  16. Far field intensity distributions due to spatial self phase modulation of a Gaussian beam by a thin nonlocal nonlinear media.

    PubMed

    Ramirez, E V Garcia; Carrasco, M L Arroyo; Otero, M M Mendez; Cerda, S Chavez; Castillo, M D Iturbe

    2010-10-11

    In this work we present a simple model that can be used to calculate the far field intensity distributions when a Gaussian beam cross a thin sample of nonlinear media but the response can be nonlocal.

  17. External magnetic field dependent shift of superparamagnetic blocking temperature due to core/surface disordered spin interactions

    NASA Astrophysics Data System (ADS)

    Lee, Kwan; Jang, Jung-tak; Nakano, Hiroshi; Nakagawa, Shigeki; Paek, Sun Ha; Bae, Seongtae

    2017-02-01

    Although the blocking temperature of superparamagnetic nanoparticles (SPNPs) is crucial for various spintronics and biomedical applications, the precise determination of the blocking temperature is still not clear. Here, we present ‘intrinsic’ and ‘extrinsic’ characteristics of the blocking temperature in SPNP systems. In zero-field-cooled/field-cooled (ZFC-FC) curves, there was no shift of ‘intrinsic blocking temperature’ at different applied external (excitation) magnetic fields. However, ‘extrinsic blocking temperature’ shift is clearly dependent on the external (excitation) magnetic field. According to our newly proposed physical model, the ‘intermediate spin layer’ located between the core and surface disordered spin layers is primarily responsible for the physical nature of the shift of extrinsic blocking temperature. Our new findings offer possibilities for characterizing the thermally induced physical properties of SPNPs. Furthermore, these findings provide a new empirical approach to indirectly estimate the qualitative degree of the disordered surface spin status in SPNPs.

  18. External magnetic field dependent shift of superparamagnetic blocking temperature due to core/surface disordered spin interactions.

    PubMed

    Lee, Kwan; Jang, Jung-Tak; Nakano, Hiroshi; Nakagawa, Shigeki; Paek, Sun Ha; Bae, Seongtae

    2017-02-17

    Although the blocking temperature of superparamagnetic nanoparticles (SPNPs) is crucial for various spintronics and biomedical applications, the precise determination of the blocking temperature is still not clear. Here, we present 'intrinsic' and 'extrinsic' characteristics of the blocking temperature in SPNP systems. In zero-field-cooled/field-cooled (ZFC-FC) curves, there was no shift of 'intrinsic blocking temperature' at different applied external (excitation) magnetic fields. However, 'extrinsic blocking temperature' shift is clearly dependent on the external (excitation) magnetic field. According to our newly proposed physical model, the 'intermediate spin layer' located between the core and surface disordered spin layers is primarily responsible for the physical nature of the shift of extrinsic blocking temperature. Our new findings offer possibilities for characterizing the thermally induced physical properties of SPNPs. Furthermore, these findings provide a new empirical approach to indirectly estimate the qualitative degree of the disordered surface spin status in SPNPs.

  19. Field evaluation of nitrogen availability from fresh and composted manure.

    PubMed

    Muñoz, Gabriela R; Kelling, Keith A; Rylant, Karen E; Zhu, Jun

    2008-01-01

    Prediction of manure nitrogen availability to crops is key to ensuring adequate production while minimizing potential adverse environmental impacts. This field study estimated first-year and residual N availability from several manures subjected to various levels of processing, and evaluated the applicability of the pre-sidedress soil N test (PSNT) in fields receiving the different manures using corn (Zea mays L.) as the test crop. Plots received several rates of fresh (FP), dried (DP), or composted (CP) poultry (Gallus gallus domesticus) manure, composted cow (Bos taurus) (CC) manure, ammonium nitrate (AN), or no N. Crop yields and N uptake from plots where CC was applied were undistinguishable from controls in most years, whereas poultry manures significantly increased corn production. Average apparent first-year N availability, as measured by fertilizer equivalence, was 57, 53, 14, and 4% for FP, DP, CP, and CC respectively. Apparent second-year N availability, as measured by relative effectiveness, was 18, 19, 12, and 7% for FP, DP, CP, and CC; however, for CC both first- and second-year estimates of apparent N recovery (ANR) could statistically not be separated from the controls. Apparent nitrogen avail-ability was greater for less processed manures and for CP compared to CC, emphasizing that producers should know the source and level of compost stability when these materials are used as a primary nutrient source. The PSNT successfully (87% correct) identified sites with a critical value of 24 mg kg(-1) that were N sufficient across a variety of N amendments from those that would have benefitted from additional N input.

  20. Regional rigorous 3-D modelling of ground geoelectric field due to realistic geomagnetic disturbances. An approach and implementation.

    NASA Astrophysics Data System (ADS)

    Ivannikova, Elena; Kruglyakov, Mikhail; Kuvshinov, Alexey; Rastaetter, Lutz; Pulkkinen, Antti

    2017-04-01

    Strong eruptions at the Sun's surface produce large release of plasma, which with a high speed (solar wind) flows into space. Solar wind interaction with the Earth's magnetosphere and the ionosphere leads to a continuous disturbance of the geomagnetic field. This fluctuating geomagnetic field induces a ground geoelectric field that in turn generates geomagnetically induced currents (GICs) in technological systems, such as power grids and pipelines. It is well known that GICs are one of the most dangerous factors affecting the operation of the above systems. Thus, an accurate modelling of the spatio-temporal evolution of the geoelectric field during abnormal (storm-time) geomagnetic activity is a key consideration in estimating the hazard to technological systems from space weather. We present a numerical tool for regional modelling of the space weather influence on ground geoelectric field. The tool exploits realistic regional and global three-dimensional (3-D) models of Earth's electrical conductivity, and realistic global models of the spatio-temporal evolution of magnetospheric and ionospheric current systems responsible for geomagnetic disturbances. The tool involves four steps. First, we compute the spatio-temporal distribution of external magnetic field on a regular grid at the surface of the Earth using a magnetohydrodynamic model of the magnetosphere coupled to an electrostatic model of the ionosphere. Second, from the external magnetic field we compute the global source in the form of equivalent currents flowing in a thin shell above the Earth. Third, for a given global source and a given global 3-D conductivity model of the Earth we compute ground geoelectric field globally at a coarse grid (using spherical geometry). Finally, for a given source and a given regional 3-D conductivity model(s) of the Earth we compute geoelectric field regionally (using Cartesian geometry) at a dense grid utilizing the results from the global modelling. Both global and

  1. Health risks of electromagnetic fields. Part I: Evaluation and assessment of electric and magnetic fields.

    PubMed

    Habash, Riadh W Y; Brodsky, Lynn M; Leiss, William; Krewski, Daniel; Repacholi, Michael

    2003-01-01

    Exposure to electric and magnetic fields (EMF) emanating from the generation, distribution, and utilization of electricity is widespread. The major debate in recent years has focused on the possibility that exposure to EMF may result in adverse health consequences, including the development of cancer. This article provides a review and evaluation of potential health risks associated with residential and occupational exposure to EMF. In addition to reviewing data from laboratory, epidemiology, and clinical studies, we examine exposure data from field measurement surveys and exposure guidelines that have been established for EMF. Currently, the evidence in support of an association between EMF and childhood cancer is limited, although this issue warrants further investigation. Evidence of an association between EMF exposure and adult cancers, derived largely from occupational settings, is inconsistent, precluding clear conclusions. There is little evidence of an association between EMF and noncancer health effects. Epidemiological studies of EMF and population health are limited by exposure measurement error and the lack of a clear dose/response relationship in studies suggesting possible health risks. Further research is needed to clarify the ambiguous findings from present studies and to determine if EMF exposure poses a health risk.

  2. Change of ionospheric plasma parameters under the influence of electric field which has lithospheric origin and due to radon emanation

    NASA Astrophysics Data System (ADS)

    Rapoport, Y.; Grimalsky, V.; Hayakawa, M.; Ivchenko, V.; Juarez-R, D.; Koshevaya, S.; Gotynyan, O.

    A mechanism of electric-photochemistry channel of seismo-ionospheric coupling is investigated. In particular, the penetration of electric field from the lithospheric source into the ionosphere and effect of this field on the photochemistry coefficient and ionospheric parameters in the altitude range in the lower D region are modeled numerically. It is shown that observable effects can be expected when lithospheric electric source strength is of the order of 1.5 kV/m. In this case, variations of electron temperature and electron concentration will be of the order of (40-60)% and (25-40)% respectively at the range of altitudes 60-70 km. An increase of near-ground conductivity (caused by increasing humidity and/or radon emanation) by ∼2.3 times can cause increase of electric field intensity by ∼2 times in altitude ranges of 60-70 km. Corresponding relative change of Te increases up to ∼50%, as compared with the case of lower near-ground temperature. Spatial shapes of relative distribution of electron temperature and the ratio of negative ion-electron concentration map the spatial shape of the lithospheric electric field distribution. Spatial shapes of electron concentration distribution and electric field strength distribution of the lithospheric source are “opposite” to each other.

  3. Multiple crossovers between positive and negative magnetoresistance versus field due to fragile spin structure in metallic GdPd3

    NASA Astrophysics Data System (ADS)

    Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Johnston, D. C.

    2017-02-01

    Studies on the phenomenon of magnetoresistance (MR) have produced intriguing and application-oriented outcomes for decades–colossal MR, giant MR and recently discovered extremely large MR of millions of percents in semimetals can be taken as examples. We report here the discovery of novel multiple sign changes versus applied magnetic field of the MR in the cubic intermetallic compound GdPd3. Our study shows that a very strong correlation between magnetic, electrical and magnetotransport properties is present in this compound. The magnetic structure in GdPd3 is highly fragile since applied magnetic fields of moderate strength significantly alter the spin arrangement within the system–a behavior that manifests itself in the oscillating MR. Intriguing magnetotransport characteristics of GdPd3 are appealing for field-sensitive device applications, especially if the MR oscillation could materialize at higher temperature by manipulating the magnetic interaction through perturbations caused by chemical substitutions.

  4. Multiple crossovers between positive and negative magnetoresistance versus field due to fragile spin structure in metallic GdPd3

    PubMed Central

    Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Johnston, D. C.

    2017-01-01

    Studies on the phenomenon of magnetoresistance (MR) have produced intriguing and application-oriented outcomes for decades–colossal MR, giant MR and recently discovered extremely large MR of millions of percents in semimetals can be taken as examples. We report here the discovery of novel multiple sign changes versus applied magnetic field of the MR in the cubic intermetallic compound GdPd3. Our study shows that a very strong correlation between magnetic, electrical and magnetotransport properties is present in this compound. The magnetic structure in GdPd3 is highly fragile since applied magnetic fields of moderate strength significantly alter the spin arrangement within the system–a behavior that manifests itself in the oscillating MR. Intriguing magnetotransport characteristics of GdPd3 are appealing for field-sensitive device applications, especially if the MR oscillation could materialize at higher temperature by manipulating the magnetic interaction through perturbations caused by chemical substitutions. PMID:28211520

  5. Field Collection Methods for an EPA Pilot Study Evaluating ...

    EPA Pesticide Factsheets

    This compilation of field collection standard operating procedures (SOPs) was assembled for the U.S. Environmental Protection Agency’s (EPA) Pilot Study add-on to the Green Housing Study (GHS). A detailed description of this add-on study can be found in the peer reviewed research protocol entitled “An EPA Pilot Study Evaluating Personal, Housing, and Community Factors Influencing Children’s Potential Exposures to Indoor Contaminants at Various Lifestages –Research Protocol” 1. Briefly, the Centers for Disease Control and Prevention’s (CDC) Green Housing Study (GHS) follows changes in environmental measurements [pesticides, volatile organic compounds (VOCs), particulate matter (i.e., PM2.5 and 1.0), indoor allergens, and fungi] in both U.S. Department of Housing and Urban Development (HUD) green-renovated and comparison (no renovation) homes and relates these changes to asthma morbidity in children ages 7-12 years. Green-renovations include (but are not limited to) use of low VOC materials, use of energy efficient appliances, and integrated pest management. The EPA has leveraged this opportunity to collect additional multimedia measurements and questionnaire data from the index children actively participating in the GHS and a sibling in order to characterize personal, housing, and community factors. The purpose of this document is to publish the methodology EPA used for a specific study for reference and use by other scientists both within the Agency

  6. Technology evaluation center assessment synopsis: full-field digital mammography.

    PubMed

    Rothenberg, Barbara M; Ziegler, Kathleen M; Aronson, Naomi

    2006-08-01

    Full-field digital mammography (FFDM) is proposed as an alternative to screen-film mammography (SFM). The ability to separate and optimize the acquisition, storage, and display of images may allow greater visualization of breast cancers at equal or lower radiation doses, especially in younger women and those with denser breasts. This is a synopsis of a systematic review by the Blue Cross Blue Shield Association Technology Evaluation Center. This updated systematic review primarily incorporated the results of the ACR Imaging Network(R) Digital Mammographic Imaging Screening Trial (DMIST), which provided results on 42,760 asymptomatic women who underwent both FFDM and SFM and showed with reasonable certainty that there was no difference in the accuracy of the 2 modalities for asymptomatic women in general, with some advantages of FFDM in certain subgroups. There were no strong, new studies on the use of digital mammography compared with film mammography in a diagnostic population. However, the DMIST results indicated that tumors detected by FFDM, but not by SFM, were likely to be invasive carcinomas or medium-grade to high-grade ductal carcinoma in situ. On the basis of the suppositions that these are the cancers of greatest interest and the ones more likely to be found in a diagnostic population and that the diagnostic population may be younger on average than the screening population, it was concluded that there is sufficient evidence to support the use of FFDM for diagnostic purposes.

  7. Transient electrical field characteristics due to polarization of domains in bulk LiNbO{sub 3} during Czochralski growth

    SciTech Connect

    Bermudez, V.; Dutta, P.S.; Serrano, M.D.; Dieguez, E.

    1997-01-01

    The transient behavior of the electric field during simultaneous growth and {ital in situ} poling of LiNbO{sub 3} has been studied. The transient features have been correlated with the poling of the multidomain seed and crystal, and domain reversal in poled seed. A steady-state condition is obtained after the shoulder region of the crystal is terminated and the crystal reaches its final diameter. Finally, the critical values of field parameters necessary to obtain complete monodomain crystals without causing melt electrolysis at the solid{endash}liquid interface have been analyzed. {copyright} {ital 1997 American Institute of Physics.}

  8. Evaluation of the productivity decrease risk due to a future increase in tropical cyclone intensity in Japan.

    PubMed

    Esteban, Miguel; Longarte-Galnares, Gorka

    2010-12-01

    A number of scientists have recently conducted research that shows that tropical cyclone intensity is likely to increase in the future. This would result in an increase in the damage along with a decrease in economic productivity due to precautionary cessation of the economic activity of the affected areas during the passage of the cyclone. The economic effect of this stop in economic activity is a phenomenon that has not received much attention in the past, and the cumulative effect that it can have on the Japanese economy over the next 75 years has never been evaluated. The starting point for the evaluation of the economic risks is the change in the patterns of tropical cyclone intensity suggested by Knutson and Tuleya. The results obtained show how a significant decrease in the overall productivity of the country could be expected, which could lower GDP by between 6% and 13% by 2085. © 2010 Society for Risk Analysis.

  9. Measuring frequency changes due to microwave power variations as a function of C-field setting in a rubidium frequency standard

    NASA Technical Reports Server (NTRS)

    Sarosy, E. B.; Johnson, Walter A.; Karuza, Sarunas K.; Voit, Frank J.

    1992-01-01

    It has been shown in previous studies that in some cesium frequency standards there exist certain C-field settings that minimize frequency changes that are due to variations in the microwave power. In order to determine whether similar results could be obtained with rubidium (Rb) frequency standards (clocks), we performed a similar study, using a completely automated measurement system, on a commercial Rb standard. From our measurements we found that changing the microwave power to the filter cell resulted in significant changes in frequency, and that the magnitude of these frequency changes at low C-field levels went to zero and decreased as the C-field was increased.

  10. Variable resolution electromagnetic tomography (VARETA) in evaluation of compression of cerebral arteries due to deep midline brain lesions.

    PubMed

    Fernández-Bouzas, Antonio; Harmony, Thalía; Fernández, Thalía; Ricardo-Garcell, Josefina; Santiago, Efraín

    2004-01-01

    Hemispheric tumors produced electroencephalographic (EEG) delta activity mainly due to deafferentation of cerebral cortex. In small, deep midline lesions that compressed cerebral arteries, the most important abnormality should have been in EEG theta band that selectively responded to brain ischemia. Frequency domain-variable resolution electromagnetic tomography (FD-VARETA) has been applied satisfactorily to the study of brain tumors, cerebral infarcts, and brain hemorrhages and was shown to localize areas of hypoperfusion. Twelve patients with deep midline lesions compressing different cerebral arteries were studied. Computer tomography (CT) and/or magnetic resonance imaging (MRI) as well as quantitative EEG with source calculation in frequency domain were obtained. Brain electromagnetic tomographies (BETs) were calculated to evaluate localization and extension of functional abnormalities. Ten of twelve cases presented abnormal sources in theta band as main abnormal source. In only two cases was the main source in delta band, but these cases also had abnormal Z values in theta band. In four patients there were only abnormal values in theta range. Sources of abnormal theta activity were observed in regions irrigated by the arteries compressed. In deep midline lesions, compression of cerebral arteries producing relative ischemia may explain abnormal EEG sources in theta band. Patients with main source in theta band showed vascular compression and some patients exhibited vasogenic edema. Thus, theta might be due to relative ischemia produced by both hypoperfusion and edema. Once again, VARETA has found to be very useful in evaluation of functional abnormalities.

  11. Accidental Strangulation Due to Entrapment of Saree in Crop Thrasher Machine in an Elderly Women Working at Agricultural Field.

    PubMed

    Parchake, Manoj Bhausaheb; Kumre, Vikas; Kachare, Rajesh V

    2016-09-01

    Strangulation is generally considered as homicidal death and in accidental strangulation circumstantial evidence alone can point toward the accidental nature of incidence. In present case, a 71-year-old woman, wearing a saree (garment worn by traditional women in India) working in agricultural field, got entangled in the crop thrasher machine and got strangled. Immediately, she was taken to the nearest hospital, where she survived for 6 to 8 hours and then died. The autopsy reveals cross ribbon-shaped ligature mark on neck and anterior chest along with 1 puncture wound at the right lateral aspect of the neck. A lack of proper precaution and safety measures at agricultural field are other contributing factors. Accidental strangulation by saree is extremely rare, hence, this case is presented for its rarity and pattern of injury.

  12. Force field analysis suggests a lowering of diffusion barriers in atomic manipulation due to presence of STM tip.

    PubMed

    Emmrich, Matthias; Schneiderbauer, Maximilian; Huber, Ferdinand; Weymouth, Alfred J; Okabayashi, Norio; Giessibl, Franz J

    2015-04-10

    We study the physics of atomic manipulation of CO on a Cu(111) surface by combined scanning tunneling microscopy and atomic force microscopy at liquid helium temperatures. In atomic manipulation, an adsorbed atom or molecule is arranged on the surface using the interaction of the adsorbate with substrate and tip. While previous experiments are consistent with a linear superposition model of tip and substrate forces, we find that the force threshold depends on the force field of the tip. Here, we use carbon monoxide front atom identification (COFI) to characterize the tip's force field. Tips that show COFI profiles with an attractive center can manipulate CO in any direction while tips with a repulsive center can only manipulate in certain directions. The force thresholds are independent of bias voltage in a range from 1 to 10 mV and independent of temperature in a range of 4.5 to 7.5 K.

  13. Purity loss and degradation of qubit-field correlations and entanglement due to phase noise in nonlinear interaction

    NASA Astrophysics Data System (ADS)

    Hessian, H. A.; Mohamed, A.-B. A.

    2014-09-01

    Numerical simulations and calculation of both the total entropy and the sub-entropies are used to investigate the purity loss in nonlinear interaction of a qubit with coherent field. While, the mutual entropy is used as a measure of the total correlations and the negativity as a measure to the entanglement. We show that the purity and entanglement behave different for standard energy dissipation as compared to an energy preserving phase noise coupling as introduced by Milburn. It is found that a very strong sensitivity of the degradation both total correlation with entanglement to the amount of phase damping and the chosen coupling. In particular for a coherent initial field state the maximum obtainable correlation is strongly reduced even for very weak noise.

  14. Variation of Magnetic Fluctuation due to Gas Puffing in Edge Region of Reversed-Field Pinch Plasma

    NASA Astrophysics Data System (ADS)

    Yambe, Kiyoyuki; Hirano, Yoichi; Sakakita, Hajime; Koguchi, Haruhisa

    2016-09-01

    We measured the variation of magnetic and electrostatic fluctuations observed during the gas puffing in the edge region of the toroidal pinch experiment-reversed experiment (TPE-RX) reversed-field pinch plasma. In the short period in which the electron density increased slowly just after the gas puffing, the confinement of fast electrons in the core region was maintained by the decrease in the fast radial magnetic fluctuation with the deepening of the reversal of the toroidal field. During the following period in which the electron density increased rapidly, the radial gradient of electron density decreased, and the loss of fast electrons from the core region increased owing to the increase in the toroidal and radial magnetic fluctuations in the high-frequency band, although the poloidal magnetic fluctuation decreased. Therefore, the confinement of fast electrons would be maintained by keeping the radial gradient of plasma thermal pressure with a moderate neutral particle supply of small quantity in a short time.

  15. Multicomponent seismic monitoring of stress arching in the overburden due to hydraulic fracturing in the Montney Shale at Pouce Coupe Field, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Vinal, Irene

    Recent studies have shown convincing evidence that time-lapse changes in seismic data occur not only within the reservoir interval but also in the overburden. Observations that production at the reservoir level and subsequent decrease in pore pressure lead to modifications in the stress field and variations in the overburden have been documented (Hatchell et al., 2003; Hudson et al., 2005). The study of the opposite case, that is, the analysis of the effect in the overburden of an increase in pore pressure in the reservoir has not been so well documented yet and is the focus of this work; the possibility that the hydraulic fracturing process causes seismically detectable changes in the overburden in a time-lapse sense is studied at Pouce Coupe Field, Alberta, and the results are shown. The analysis is performed using multicomponent data from three seismic surveys acquired to evaluate the hydraulic stimulations of two horizontal wells in the Montney Shale. The time-lapse time shifts between the data of the two monitor surveys and the baseline have been calculated and constitute the main tool to study the injection-induced changes above the reservoir interval. The hypothesis is that the increase in the reservoir pressure due to the hydraulic well treatment might produce upward overburden compaction, leading to an increase in stresses that would be translated into an increase in the seismic velocities and therefore, into positive time shifts (considering monitor data subtracted from baseline data) if a time window for the overburden is analyzed. The study shows strong differences in the magnitude of the PS response to the stimulations compared to that of the PP data. The fact that mode-converted (PS) waves are more sensitive to azimuthal anisotropy than compressional waves explains the stronger character of the response observed in PS data, allowing for a more detailed interpretation of the stress-arching distribution. The time-lapse time shifts in the overburden

  16. Evaluating the Field Emission Characteristics of Aluminum for DC High Voltage Photo-Electron Guns

    NASA Astrophysics Data System (ADS)

    Taus, Rhys; Poelker, Matthew; Forman, Eric; Mamun, Abdullah

    2013-10-01

    High current photoguns require high power laser light, but only a small portion of the laser light illuminating the photocathode produces electron beam. Most of the laser light (~ 65%) simply serves to heat the photocathode, which leads to evaporation of the chemicals required to create the negative electron affinity condition necessary for photoemission. Photocathode cooling techniques have been employed to address this problem, but active cooling of the photocathode is complicated because the cooling apparatus must float at high voltage. This work evaluates the field emission characteristics of cathode electrodes manufactured from materials with high thermal conductivity: aluminum and copper. These electrodes could serve as effective heat sinks, to passively cool the photocathode that resides within such a structure. However, literature suggests ``soft'' materials like aluminum and copper are ill suited for photogun applications, due to excessive field emission when biased at high voltage. This work provides an evaluation of aluminum and copper electrodes inside a high voltage field emission test stand, before and after coating with titanium nitride (TiN), a coating that enhances surface hardness. National Science Foundation Award Number: 1062320 and the Department of Defence ASSURE program.

  17. Evaluating the Field Emission Characteristics of Aluminum for DC High Voltage Photo-Electron Guns

    NASA Astrophysics Data System (ADS)

    Taus, Rhys; Poelker, Matthew; Forman, Eric; Mamun, Abdullah

    2014-03-01

    High current photoguns require high power laser light, but only a small portion of the laser light illuminating the photocathode produces electron beam. Most of the laser light (~ 65%) simply serves to heat the photocathode, which leads to evaporation of the chemicals required to create the negative electron affinity condition necessary for photoemission. Photocathode cooling techniques have been employed to address this problem, but active cooling of the photocathode is complicated because the cooling apparatus must float at high voltage. This work evaluates the field emission characteristics of cathode electrodes manufactured from materials with high thermal conductivity: aluminum and copper. These electrodes could serve as effective heat sinks, to passively cool the photocathode that resides within such a structure. However, literature suggests ``soft'' materials like aluminum and copper are ill suited for photogun applications, due to excessive field emission when biased at high voltage. This work provides an evaluation of aluminum and copper electrodes inside a high voltage field emission test stand, before and after coating with titanium nitride (TiN), a coating that enhances surface hardness. National Science Foundation Award Number: 1062320 and the Department of Defence ASSURE program.

  18. Magnetic phase diagram of CeAu2Ge2: High magnetic anisotropy due to crystal electric field

    NASA Astrophysics Data System (ADS)

    Fritsch, V.; Pfundstein, P.; Schweiss, P.; Kampert, E.; Pilawa, B.; v. Löhneysen, H.

    2011-09-01

    CeAu2Ge2 single crystals (with tetragonal ThCr2Si2 structure) have been grown in Au-Ge flux (AGF) as well as in Sn flux (SF). X-ray powder diffraction and EDX measurements indicate that in the latter case, Sn atoms from the flux are incorporated in the samples, leading to a decrease of the lattice constants by ≈0.3% compared to AGF samples. For both types of samples, a strong anisotropy of the magnetization M for the magnetic field B parallel and perpendicular to the c direction is observed with M||/M⊥≈6--7 in low fields just above 10 K. This anisotropy is preserved to high fields and temperatures and can be quantitatively explained by crystal electric field effects. Antiferromagnetic ordering sets in around 10 K as previously found for polycrystalline samples. From the magnetization data of our single crystals we obtain the phase diagrams for the AGF and SF samples. The magnetic properties depend strongly on the flux employed. While the AGF samples exhibit a complex behavior indicative of several magnetic transitions, the SF samples adopt a simpler antiferromagnetic structure with a single spin-flop transition. This effect of a more ordered state induced by disorder in form of Sn impurities is qualitatively explained within the anisotropic next-nearest neighbor Ising (ANNNI) model, which assumes ferromagnetic and antiferromagnetic interactions in agreement with the magnetic structure previously inferred from neutron-scattering experiments on polycrystalline CeAu2Ge2 by Loidl [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.46.9341 46, 9341 (1992)].

  19. Evaluation of the functional results after different techniques for treatment of retinal detachment due to macular holes.

    PubMed

    Rashed, O; Sheta, S

    1989-01-01

    A total of 50 eyes with retinal detachment due to macular holes were treated in the period from July 1986 to December 1987. In all, 10 eyes underwent pneumatic retinopexy using plain room air. A total of 30 eyes were treated by pars plana vitrectomy, followed by fluid/air exchange, with no treatment of the macular break; in 9 of these the detachment recurred, reflattening of the retina by air tamponade followed by laser photo-coagulation. The other 10 eyes underwent pars plana vitrectomy followed by silicone oil tamponading because of proliferative vitreoretinopathy (PVR). This paper compares the functional results for each group. The parameters used included visual acuity, color vision and visual fields.

  20. Anomalous spin-orbit torque switching due to field-like torque-assisted domain wall reflection.

    PubMed

    Yoon, Jungbum; Lee, Seo-Won; Kwon, Jae Hyun; Lee, Jong Min; Son, Jaesung; Qiu, Xuepeng; Lee, Kyung-Jin; Yang, Hyunsoo

    2017-04-01

    Spin-orbit torques (SOTs) allow the electrical control of magnetic states. Current-induced SOT switching of the perpendicular magnetization is of particular technological importance. The SOT consists of damping-like and field-like torques, and understanding the combined effects of these two torque components is required for efficient SOT switching. Previous quasi-static measurements have reported an increased switching probability with the width of current pulses, as predicted considering the damping-like torque alone. We report a decreased switching probability at longer pulse widths, based on time-resolved measurements. Micromagnetic analysis reveals that this anomalous SOT switching results from domain wall reflections at sample edges. The domain wall reflection was found to strongly depend on the field-like torque and its relative sign to the damping-like torque. Our result demonstrates a key role of the field-like torque in deterministic SOT switching and the importance of the sign correlation of the two torque components, which may shed light on the SOT switching mechanism.

  1. Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

    NASA Astrophysics Data System (ADS)

    Kostin, V. A.; Vvedenskii, N. V.

    2015-03-01

    We present a way for generating coherent tunable electromagnetic radiation through dc to ac field conversion by an ionization front. The conversion is caused by the excitation of leaky waves behind the transversely limited ionization front propagating in a uniform electrostatic field. This differs significantly from the well-known dc-to-ac-radiation-converter models which consider Doppler-like frequency conversion by a transversely unlimited ionization front propagating in a spatially periodic electric field. We explore the dispersion properties and excitation of these leaky waves radiated through the transverse plasma boundary at the Cherenkov angle to the direction of propagation of a superluminal ionization front as dependent on the parameters of the plasma produced and on the speed of the ionization front. It is shown that not only the center frequency but also the duration and waveform of the generated pulse may significantly depend on the speed of the ionization front. The results indicate the possibility of using such converters based on planar photoconductive antennas to create sources of microwave and terahertz radiation with controllable waveforms that are transformed from video to radio pulse when the angle of incident ionizing radiation is tuned.

  2. Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

    SciTech Connect

    Ciaccio, G. Spizzo, G.; Schmitz, O. Frerichs, H.; Abdullaev, S. S.; Evans, T. E.; White, R. B.

    2015-10-15

    The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted by simulations with the Hamiltonian guiding center code ORBIT. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for these effects. An analytical model for the plasma potential is implemented in the code ORBIT, and analyses of ion and electron radial diffusion show that both ion- and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggest that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

  3. Evaluation of seismic performance of reinforced concrete (RC) buildings under near-field earthquakes

    NASA Astrophysics Data System (ADS)

    Moniri, Hassan

    2017-03-01

    Near-field ground motions are significantly severely affected on seismic response of structure compared with far-field ground motions, and the reason is that the near-source forward directivity ground motions contain pulse-long periods. Therefore, the cumulative effects of far-fault records are minor. The damage and collapse of engineering structures observed in the last decades' earthquakes show the potential of damage in existing structures under near-field ground motions. One important subject studied by earthquake engineers as part of a performance-based approach is the determination of demand and collapse capacity under near-field earthquake. Different methods for evaluating seismic structural performance have been suggested along with and as part of the development of performance-based earthquake engineering. This study investigated the results of illustrious characteristics of near-fault ground motions on the seismic response of reinforced concrete (RC) structures, by the use of Incremental Nonlinear Dynamic Analysis (IDA) method. Due to the fact that various ground motions result in different intensity-versus-response plots, this analysis is done again under various ground motions in order to achieve significant statistical averages. The OpenSees software was used to conduct nonlinear structural evaluations. Numerical modelling showed that near-source outcomes cause most of the seismic energy from the rupture to arrive in a single coherent long-period pulse of motion and permanent ground displacements. Finally, a vulnerability of RC building can be evaluated against pulse-like near-fault ground motions effects.

  4. Evaluation of seismic performance of reinforced concrete (RC) buildings under near-field earthquakes

    NASA Astrophysics Data System (ADS)

    Moniri, Hassan

    2017-01-01

    Near-field ground motions are significantly severely affected on seismic response of structure compared with far-field ground motions, and the reason is that the near-source forward directivity ground motions contain pulse-long periods. Therefore, the cumulative effects of far-fault records are minor. The damage and collapse of engineering structures observed in the last decades' earthquakes show the potential of damage in existing structures under near-field ground motions. One important subject studied by earthquake engineers as part of a performance-based approach is the determination of demand and collapse capacity under near-field earthquake. Different methods for evaluating seismic structural performance have been suggested along with and as part of the development of performance-based earthquake engineering. This study investigated the results of illustrious characteristics of near-fault ground motions on the seismic response of reinforced concrete (RC) structures, by the use of Incremental Nonlinear Dynamic Analysis (IDA) method. Due to the fact that various ground motions result in different intensity-versus-response plots, this analysis is done again under various ground motions in order to achieve significant statistical averages. The OpenSees software was used to conduct nonlinear structural evaluations. Numerical modelling showed that near-source outcomes cause most of the seismic energy from the rupture to arrive in a single coherent long-period pulse of motion and permanent ground displacements. Finally, a vulnerability of RC building can be evaluated against pulse-like near-fault ground motions effects.

  5. Evaluation of Aqua-Ammonia Chiller Technologies and Field Site Installation

    SciTech Connect

    Zaltash, Abdolreza

    2007-09-01

    The Naval Facilities Engineering Service Center (NFESC) has sponsored Oak Ridge National Laboratory (ORNL) to review, select, and evaluate advanced, gas-fired, 5-ton, aqua-ammonia, chiller technologies. The selection criteria was that units have COP values of 0.67 or better at Air-conditioning and Refrigeration Institute (ARI) 95 F outdoor rating conditions, an active refrigerant flow control, and a variable-speed condenser fan. These features are expected to allow these units to operate at higher ambient temperatures (up to the maximum operating temperature of 110 F) with minimal degradation in performance. ORNL evaluated three potential manufacturers of advanced, gas-fired, 5-ton, aqua-ammonia chillers-Robur, Ambian, and Cooling Technologies. Unfortunately, Robur did not meet the COP requirements and Cooling Technologies could not deliver a unit to be tested at the U.S. Department of Energy (DOE)-ORNL environmental chamber testing facility for thermally activated heat pumps. This eliminated these two technologies from further consideration, leaving only the Ambian chillers for evaluation. Two Ambian chillers were evaluated at the DOE-ORNL test facility. Overall these chillers operated well over a wide range of ambient conditions with minimal degradation in performance due to several control strategies used such as a variable speed condenser fan, a modulating burner, and active refrigerant flow control. These Ambian pre-commercial units were selected for installation and field testing at three federal facilities. NFESC worked with ORNL to assist with the site selection for installation and evaluation of these chillers. Two sites (ORNL and Naval Surface Warfare Center [NSWC] Corona) had a single chiller unit installed; and at one site (Naval Amphibious Base [NAB] Little Creek), two 5-ton chillers linked together were installed to provide 10 tons of cooling. A chiller link controller developed under this project was evaluated in the field test at Little Creek.

  6. Field Evaluation of the Pedostructure-Based Model (Kamel®)

    USDA-ARS?s Scientific Manuscript database

    This study involves a field evaluation of the pedostructure-based model Kamel and comparisons between Kamel and the Hydrus-1D model for predicting profile soil moisture. This paper also presents a sensitivity analysis of Kamel with an evaluation field site used as the base scenario. The field site u...

  7. The Administrative Experiment: A Special Case of Field Testing or Evaluation.

    ERIC Educational Resources Information Center

    Thompson, Charles W. N.; Rath, Gustave J.

    This paper describes administrative experimentation--a particular strategy and method of field testing or evaluation. Administrative experimentation can best be described as a specialized form of field testing, field experimentation or evaluation which emphasizes the dual role of administrator and experimenter. This method is first defined in…

  8. Static magnetic field effect on the arterial baroreflex-mediated control of microcirculation: implications for cardiovascular effects due to environmental magnetic fields.

    PubMed

    Gmitrov, Juraj

    2007-08-01

    Increasing evidence suggests that time-varying and static magnetic fields in the environment might affect the cardiovascular system. To explore the underlying physiology, the effect of static magnetic fields (SMFs) on the carotid baroreflex control of microcirculation was studied. Twenty-four hemodynamic monitorings were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h) during experiments that lasted 120 min. Mean femoral artery blood pressure, heart rate, and ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after a 40 min exposure of the sinocarotid baroreceptors to Nd(2)-Fe(14)-B alloy magnets (n = 14) or sham magnets (n = 10, control series). The local SMF field was 350 mT, at the baroreceptors' site. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. A significant positive correlation was found between the SMF-induced increase in BRS (DeltaBRS = BRS(afterSMF) - BRS(priorSMF)) and the increment in microvascular blood flow (DeltaMPPG = MPPG(afterSMF) - MPPG(priorSMF)) (r = 0.66, p < 0.009). The SMF probably modulated the arterial baroreflex-mediated microcirculatory control. This could represent one possible mechanism how environmental magnetic fields act on the cardiovascular system, and a method how to complexly adjust macro- and microcirculation with potential clinical implementation.

  9. Evaluation of the angular spectrum approach for simulations of near-field pressures.

    PubMed

    Zeng, Xiaozheng; McGough, Robert J

    2008-01-01

    The implementation of the angular spectrum approach based on the two-dimensional fast Fourier transform is evaluated for near-field pressure simulations of square ultrasound transducers, where the three-dimensional pressure field is calculated from the normal velocity distribution on the transducer surface. The pressure field is propagated in the spatial frequency domain with the spatial propagator or the spectral propagator. The spatial propagator yields accurate results in the central portion of the computational grid while significant errors are produced near the edge due to the finite extent of the window applied to the spatial propagator. Likewise, the spectral propagator is inherently undersampled in the spatial frequency domain, and this causes high frequency errors in the computed pressure field. This aliasing problem is alleviated with angular restriction. The results show that, in nonattenuating media, the spatial propagator achieves smaller errors than the spectral propagator after the region of interest is truncated to exclude the windowing error. For pressure calculations in attenuating media or with apodized pistons as sources, the spatial and spectral propagator achieve similar accuracies. In all simulations, the angular spectrum calculations with the spatial propagator take more time than calculations with the spectral propagator.

  10. Linearly polarized radiation from astrophysical masers due to magnetic fields when the rate for stimulated emission exceeds the Zeeman frequency

    NASA Technical Reports Server (NTRS)

    Deguchi, Shuji; Watson, William D.

    1990-01-01

    The results are presented of reformulating the treatment of polarized maser radiation in the presence of magnetic fields in a way that seems somewhat more convenient for calculations with masing states having angular momenta greater than J = 1 and 0. Calculations are then performed for the case of small Zeeman splitting using idealizations which are equivalant to those made previously in calculations for a J = 1-0 transition. The results provide a complete, general description of the polarization characteristics of astrophysical maser radiation involving states of higher angular momentum of closed-shell molecules.

  11. Ion heating by kinetic cross-field streaming instability due to reflected ions at a quasiperpendicular shock

    NASA Technical Reports Server (NTRS)

    Yoon, Peter H.; Wu, C. S.; Mandt, M. E.

    1992-01-01

    The present paper shows that the reflected ion at a supercritical quasi-perpendicular shock wave can excite a purely growing mode propagating parallel to the ambient magnetic field. To discuss the ion heating by such an unstable mode, the self-consistent quasi-linear kinetic equation is solved with the assumption that the present purely growing mode is the dominant unstable mode in the system. In the quasi-linear analysis of the instability, two particular cases are considered: the case of low initial ion beta and that of a high initial ion beta.

  12. A new framework for evaluating potential risk of back disorders due to whole body vibration and repeated mechanical shock.

    PubMed

    Waters, Thomas; Rauche, Christin; Genaidy, Ash; Rashed, Tarek

    2007-03-01

    A number of studies have examined the potential relationship between exposure to occupational vibration and low back pain associated with operation of vehicles. Only a handful of studies, however, have attempted to differentiate between the relative contributions of the steady state and transient mechanical shock components (the latter also being known as 'jarring and jolting', 'high acceleration event', 'multiple shocks' and 'impact') of the vibration exposure. The primary objective of this paper is to present a review of current studies that examine mechanical shock, present a case for the importance of evaluating both steady state and mechanical shock components and propose a new framework for evaluating the health effects due to occupational vibration exposure. A computerized bibliographical search of several databases was performed with special reference to the health effects of mechanical shock in relation to lower back disorders. Based on the analysis, eight experimental studies and nine epidemiological studies with relevance to exposure to 'mechanical shock' were identified. These studies suggested that rough vehicle rides are prevalent and that repeated exposure to mechanical shock may increase the risk of lower back pain. There is an urgent need for assessing the health effects of mechanical shocks in epidemiological studies. In particular, the new ISO 2631-5: International Organization for Standardization 2004 standard for shock exposure assessment should be evaluated with regard to musculoskeletal health effects.

  13. Comparative evaluation of two vaccine candidates against experimental leishmaniasis due to Leishmania major infection in four inbred mouse strains.

    PubMed

    Benhnini, Fouad; Chenik, Mehdi; Laouini, Dhafer; Louzir, Hechmi; Cazenave, Pierre André; Dellagi, Koussay

    2009-11-01

    Experimental leishmaniasis in BALB/c and C57BL/6 mice are the most investigated murine models that were used for the preclinical evaluation of Leishmania vaccine candidates. We have previously described two new inbred mouse strains named PWK and MAI issued from feral founders that also support the development of experimental leishmaniasis due to L. major. In this study, we sought to determine whether different mouse inbred strains generate concordant or discordant results when used to evaluate the potential of Leishmania proteins to protect against experimental leishmaniasis. To this end, two Leishmania proteins, namely, LACK (for Leishmania homolog of receptor for activated C kinase) and LmPDI (for L. major protein disulfide isomerase) were compared for their capacity to protect against experimental leishmaniasis in PWK, MAI, BALB/c, and C57BL/6 inbred mouse strains. Our data show that the capacity of Leishmania proteins to confer protection depends on the mouse strain used, stressing the important role played by the genetic background in shaping the immune response against the pathogen. These results may have important implications for the preclinical evaluation of candidate Leishmania vaccines: rather than using a single mouse strain, a panel of different inbred strains of various genetic backgrounds should be tested in parallel. The antigen that confers protection in the larger range of inbred strains may have better chances to be also protective in outbred human populations and should be selected for clinical trials.

  14. Listing of 502 Times When the Ulysses Magnetic Fields Instrument Observed Waves Due to Newborn Interstellar Pickup Protons

    NASA Astrophysics Data System (ADS)

    Cannon, Bradford E.; Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J.; Joyce, Colin J.; Murphy, Neil; Nuno, Raquel G.

    2017-05-01

    In two earlier publications we analyzed 502 intervals of magnetic waves excited by newborn interstellar pickup protons that were observed by the Ulysses spacecraft. Due to the considerable effort required in identifying these events, we provide a list of the times for the 502 wave event intervals previously identified. In the process, we provide a brief description of how the waves were found and what their properties are. We also remind the reader of the conditions that permit the waves to reach observable levels and explain why the waves are not seen more often.

  15. Experimental Evidence of Change in Sheath Properties due to Secondary Electron Emission in a Crossed Field Plasma Setup

    NASA Astrophysics Data System (ADS)

    Sawlani, Kapil; Foster, John

    2013-09-01

    The nature of plasma transport across the magnetic field in crossed-field (CF) devices remains largely an unsolved problem. This can be further complicated by the presence of secondary electrons derived from electron impact on walls. The coupling of these electrons to the bulk plasma and their role in CF plasma transport is also not well understood. The emission of secondary electrons from wall surfaces also affects the sheath potential, thus impacting energy transport to the wall. In this work, a benchtop apparatus is used to elucidate the role that secondary electrons play in regards to CF transport and energy flow to the walls. An electron beam is used to generate a secondary electron plume at the surface of an insulating target. The CF device plasma response to these secondary electrons is assessed by measuring changes to the potential distribution in the sheath of the irradiated target and the measured electron energy distribution function. The variation in the discharge voltage at fixed emission current is also determined which yields insight into CF impedance. The effect of the variation of the electron beam's angle of incidence on the CF current is also characterized. An attempt is made to relate phenomena and trends observed in this work with those in Hall thrusters. Work supported by Air Force Office of Scientific Research (AFOSR).

  16. In field damage of high and low cyanogenic cassava due to a generalist insect herbivore Cyrtomenus bergi (Hemiptera: Cydnidae).

    PubMed

    Riis, Lisbeth; Bellotti, Anthony Charles; Castaño, Oscar

    2003-12-01

    The hypothesis that cyanogenic potential in cassava roots deters polyphagous insects in the field is relevant to current efforts to reduce or eliminate the cyanogenic potential in cassava. To test this hypothesis, experiments were conducted in the field under natural selection pressure of the polyphagous root feeder Cyrtomenus bergi Froeschner (Hemiptera: Cydnidae). A number of cassava varieties (33) as well as 13 cassava siblings and their parental clone, each representing a determined level of cyanogenic potential (CNP), were scored for damage caused by C. bergi and related to CNP and nonglycosidic cyanogens, measured as hydrogen cyanide. Additionally, 161 low-CNP varieties (< 50 ppm hydrogen cyanide, fresh weight) from the cassava germplasm core collection at Centro Internacional de Agricultura Tropical (CIAT) were screened for resistance/tolerance to C. bergi. Low root damage scores were registered at all levels of CNP. Nevertheless, CNP and yield (or root size) partly explained the damage in cassava siblings (r2 = 0.82) and different cassava varieties (r2 = 0.42), but only when mean values of damage scores were used. This relation was only significant in one of two crop cycles. A logistic model describes the underlying negative relation between CNP and damage. An exponential model describes the underlying negative relation between root size and damage. Damage, caused by C. bergi feeding, released nonglycosidic cyanogens, and an exponential model fits the underlying positive relation. Fifteen low-CNP clones were selected for potential resistance/tolerance against C. bergi.

  17. Preliminary Evaluation of a Field and Non-Field Based Social Studies Preservice Teacher Education Program

    ERIC Educational Resources Information Center

    Napier, John D.; Vansickle, Ronald L.

    1978-01-01

    Comparison of pre-service social studies teachers in field and non-field based methods courses indicated no significant differences with regard to teaching skills, attitudes, or behaviors teachers should exhibit in the classroom. (Author/DB)

  18. Preliminary Evaluation of a Field and Non-Field Based Social Studies Preservice Teacher Education Program

    ERIC Educational Resources Information Center

    Napier, John D.; Vansickle, Ronald L.

    1978-01-01

    Comparison of pre-service social studies teachers in field and non-field based methods courses indicated no significant differences with regard to teaching skills, attitudes, or behaviors teachers should exhibit in the classroom. (Author/DB)

  19. Field and laboratory evaluation of a diffusive emitter for semipassive release of PCE to an aquifer

    SciTech Connect

    Arildskov, N.P.; Devlin, J.F.

    2000-02-01

    In controlled field experiments or model aquifers, it is sometimes desirable to introduce solutes below the water table without perturbing the flow system. Diffusive emitters offer a means of achieving that goal. In this study, two laboratory experiments were conducted to evaluate nylon tubing as a diffusive emitter for tetrachloroethene (PCE). The initial approach was to pump a saturated aqueous PCE solution through a piece of nylon tubing immersed in a flow-through contractor vessel. Millipore water was pumped through the contractor vessel at a constant rate. Due to PCE diffusion through the nylon, a steady-state concentration in the contractor vessel eventually developed. The process was well described by a computer model that accounted for retarded diffusion through the nylon. In a second experiment, pieces of nylon tubing were exposed to a relatively low concentration of PCE in water for 10 days in gently rotated hypovials. With the aid of a second diffusion model, the bulk diffusion coefficient was obtained from the concentration history of the solution. With the different experimental conditions taken into account, there was reasonably good agreement between the bulk diffusion coefficients in the two experiments. The results were used in the field design of a semipassive release system. Evaluation of this system showed a lower than expected steady-state concentration of PCE inside the releasing wells. The difference is likely due to lower temperature, variable PCE concentrations in the nylon tubing, and nonideal mixing in the wells. The work has shown that laboratory derived diffusion coefficients for polymeric materials are likely to be larger than, but within an order of magnitude of, the effective diffusion coefficients exhibited by emitters in the field. Nevertheless, with temperature corrections taken into account and proper well development, these values could be used to design emitters that would suit most practical applications.

  20. On Ambition, Learning, and Co-Evolution: Building Evaluation as a Field

    ERIC Educational Resources Information Center

    Sridharan, Sanjeev; De Silva, Soma

    2010-01-01

    The papers in this dialogue help develop evaluation as a field (both in South Asia and other regions). What comes through in all of the papers is both humility of where evaluation is as a field and imagination and ambition of where evaluators could be in the near future. Reading the papers in this forum makes them enthusiastic about being…

  1. On Ambition, Learning, and Co-Evolution: Building Evaluation as a Field

    ERIC Educational Resources Information Center

    Sridharan, Sanjeev; De Silva, Soma

    2010-01-01

    The papers in this dialogue help develop evaluation as a field (both in South Asia and other regions). What comes through in all of the papers is both humility of where evaluation is as a field and imagination and ambition of where evaluators could be in the near future. Reading the papers in this forum makes them enthusiastic about being…

  2. Documenting the Impact of Multisite Evaluations on the Science, Technology, Engineering, and Mathematics Field

    ERIC Educational Resources Information Center

    Roseland, Denise; Greenseid, Lija O.; Volkov, Boris B.; Lawrenz, Frances

    2011-01-01

    This chapter discusses the impact that four multisite National Science Foundation (NSF) evaluations had on the broader field of science, technology, engineering, and mathematics education and evaluation. Three approaches were used to investigate the broader impact of these evaluations on the field: (a) a citation analysis, (b) an on-line survey,…

  3. Documenting the Impact of Multisite Evaluations on the Science, Technology, Engineering, and Mathematics Field

    ERIC Educational Resources Information Center

    Roseland, Denise; Greenseid, Lija O.; Volkov, Boris B.; Lawrenz, Frances

    2011-01-01

    This chapter discusses the impact that four multisite National Science Foundation (NSF) evaluations had on the broader field of science, technology, engineering, and mathematics education and evaluation. Three approaches were used to investigate the broader impact of these evaluations on the field: (a) a citation analysis, (b) an on-line survey,…

  4. Focusing, Situating, and Grounding Micro-Level Evaluation Field Experiences: An Instructional Tool

    ERIC Educational Resources Information Center

    Skolits, Gary J.; Woodard, Thelma; Morrow, Jennifer Ann; Kaesbauer, Susanne

    2012-01-01

    Evaluator training field experiences seek to reinforce applicable content knowledge and promote applied skills. For students, even a small-scale field experience focusing on limited components of a larger evaluation process can seem particularly challenging. Students often do not recognize the relevance of established evaluation resources capable…

  5. Evaluating Sound Field Amplification Technology in New Brunswick Schools

    ERIC Educational Resources Information Center

    Rubin, Rhonda; Aquino-Russell, Catherine; Flagg-Williams, Joan

    2007-01-01

    (Purpose) The purpose of this study was to investigate the effects of classroom sound field amplification on communication in kindergarten through grade 3 classrooms. (Methodology) Sixty classrooms were involved in the study; half of the classrooms were provided with sound field amplification. The flow of communication was measured through…

  6. Field Test Evaluation Report on Introduction to Polymer Chemistry.

    ERIC Educational Resources Information Center

    Chapman, Kenneth; Fleming, Janice

    1981-01-01

    After describing a continuing education course in polymer chemistry, summarizes materials, methods, and results of an extensive evaluation of the course. Includes a discussion of benefits for participants and a list of 14 recommendations based on the evaluation. (JN)

  7. Field Test Evaluation Report on Introduction to Polymer Chemistry.

    ERIC Educational Resources Information Center

    Chapman, Kenneth; Fleming, Janice

    1981-01-01

    After describing a continuing education course in polymer chemistry, summarizes materials, methods, and results of an extensive evaluation of the course. Includes a discussion of benefits for participants and a list of 14 recommendations based on the evaluation. (JN)

  8. Field evaluation of hazardous waste site bioassessment protocols

    SciTech Connect

    Thomas, J.M.; Cline, J.F.; Cushing, C.E.; McShane, M.C.; Rogers, J.E.; Rogers, L.E.; Simpson, J.C.; Skalski, J.R.

    1983-04-01

    The goals were: (1) determine the variability (both within and between laboratories) for the various bioassay procedures using contaminated soil samples from the Rocky Mountain Arsenal (RMA); (2) assess variability within and between plots for several assessment techniques (for sampling small mammals, plants, insects including honeybees and microarthropods) so that field studies could be designed to detect a defined biotic change; (3) establish three field plant transects which are apparently (a) contaminated, (b) appear contaminated and (c) could serve as a control; (4) assess the feasibility (in the laboratory) of using Basin F water to contaminate RMA soil artificially, and to supply information for the design of a field plot study in 1983; (5) attempt to obtain preliminary data on any promising field or laboratory bioassessment techniques not currently mentioned in the statement of work; and (6) obtain field data to assess the ecological status of RMA lakes and compare these observations to results from bioassessment testing.

  9. Electromagnetic Scattered Field Evaluation and Data Compression Using Imaging Techniques

    NASA Technical Reports Server (NTRS)

    Gupta, I. J.; Burnside, W. D.

    1996-01-01

    This is the final report on Project #727625 between The Ohio State University and NASA, Lewis Research Center, Cleveland, Ohio. Under this project, a data compression technique for scattered field data of electrically large targets is developed. The technique was applied to the scattered fields of two targets of interest. The backscattered fields of the scale models of these targets were measured in a ra compact range. For one of the targets, the backscattered fields were also calculated using XPATCH computer code. Using the technique all scattered field data sets were compressed successfully. A compression ratio of the order 40 was achieved. In this report, the technique is described briefly and some sample results are included.

  10. Watching the wind: seismic data contamination at long-periods due to atmospheric pressure-field-induced tilting

    NASA Astrophysics Data System (ADS)

    de Angelis, S.; Bodin, P.; Hagel, K.; Fletcher, D.

    2010-12-01

    Long-period noise generated by the elastic response of the Earth to atmospheric pressure fluctuations has long been recognized as a limiting factor for seismic investigations. The quality of seismic data recorded by sensitive, near-surface broadband seismometers can be severely corrupted by this effect. During the recent installation of a new broadband site on the Olympic Peninsula in Washington, the Pacific Northwest Seismic Network recorded and investigated elevated daytime noise levels at periods exceeding 30 seconds. Substantial power spectral density variations of the background noise field, 15-20 dB, were observed in the horizontal component seismograms. The pattern of the long-period noise exhibited striking correlations with local fluctuations of the air temperature and wind speed as measured nearby the seismic station by the National Weather Service Forecast Office, Seattle, Washington, and the National Oceanic and Atmospheric Administration. Several past studies have demonstrated that local wind systems may lead to variations of the atmospheric pressure field that deform the ground and perturb seismograms. The rotational component of this motion is detected by horizontal-component seismometers because at periods longer than the sensor’s low corner frequency the sensor is acting essentially as a tiltmeter. We obtained a transfer function that describes the response of the broadband seismometer to a tilt step change and estimated the amplitude of tilt noise to be on the order of 10-9 - 10-8 radians. Within the seismic pass-band of the sensor, it is not possible to remove the tilt signal from the observed seismograms because the details of the tilting depend on the pressure field variations, the compliance of the near surface to pressure variations, and the design and construction of the seismometer vault itself. At longer periods, using the seismic data to recover tilts of tectonic origin is made challenging because of the needed instrument correction

  11. Evaluation of some GRIN fiber parameters and the associated fraction mode loss due to mechanically induced optical anisotropy

    NASA Astrophysics Data System (ADS)

    El-Diasty, Fouad

    2003-09-01

    Some of the optical parameters of the bent multimode graded-index (GRIN) optical fiber in terms of indices of refraction, where the bending stresses broke the radial symmetry, are evaluated by use of multiple-beam Fizeau fringes. The variation of the index difference between the cladding index and core index in both the compression and tensile fiber regions is measured. The accuracy of measuring the index is +/-1 × 10-4. The spatial resolution of the method is 1.39 μm. Evaluation of the acceptance angle, the numerical aperture, and the V number profiles of the bent fiber from the interference pattern at both sides of the bent fiber are presented. The fraction of the mode number lost has been evaluated. The method was used to study the influence of compression on diminishing the index difference that leads to a dissipation of energy and a considerable mode loss. It is obvious from the experimental data that the change of the index difference due to bending strongly affects the fraction of propagating mode number, especially at the small radii of curvature. Ignoring the variation of the index difference we evaluating the number of propagated modes number leads to an insufficient determination of the mode loss. It subsequently leads to an incorrect determination of the mode dispersion and the interface loss in bent GRIN fibers. The study confirms that the deviation of the guide axis from straightness with the radius of curvature of less than 1 cm could lead to a significant fraction mode loss.

  12. Suppression of the vortex glass transition due to correlated defects with a persistent direction perpendicular to an applied magnetic field

    NASA Astrophysics Data System (ADS)

    Ikeda, Ryusuke; Myojin, Kiyokazu

    2004-05-01

    It is found in terms of the lowest Landau level approach for the Ginzburg Landau model that, in bulk type II superconductors with correlated defects, such as columnar defects, with a persistent direction perpendicular to an applied field H, a continuous vortex-glass transition should be depressed to a low enough temperature in the limit of weak point disorder. Based on this finding, remarkable reductions of the glass transition temperatures, seen in twin-free YBCO with columnar defects in H⊥c and twinned YBCO in H‖c, are discussed. It is pointed out that, in both of these two situations, the critical scaling of vanishing resistivities is anisotropic in spite of an isotropic scaling of correlation lengths and hence, makes it possible to determine two critical exponents by changing the relative angle between the current and the correlated defects.

  13. Ion temperature anisotropy due to perpendicular heating by Alfvén wave propagating along magnetic field lines

    NASA Astrophysics Data System (ADS)

    Choi, C.-R.; Woo, M.-H.; Dokgo, K.; Min, K.-W.; Lee, D.-Y.; Yoon, Peter H.; Hwang, J.; Lee, J.-J.; Park, Y.-D.

    2016-09-01

    The perpendicular heating and acceleration of ions by linearly polarized Alfvén wave, which is propagating along constant background magnetic field, is studied. The perpendicular diffusion coefficient of ions is calculated through the autocorrelation function based on linear perturbation theory, which unambiguously demonstrates that ion heating is attained by non-resonant wave-particle interaction. It is found that the perpendicular heating and acceleration of ions occur by the Alfvén wave during a relatively short time interval, i.e., approximately 20 ion gyro period (Ωi0t ) even though the perturbation amplitude is quite low. Also, it is shown that the temperature anisotropy of ions A , where A =T⊥/T∥-1 , increases with the increasing perturbation amplitude while the parallel ion heating does not occur. Test particle simulation is also carried out in order to investigate the non-resonant perpendicular heating process.

  14. Density profile steepening due to self-generated magnetic fields in plasmas produced by laser irradiation of spherical targets

    SciTech Connect

    Vyas, P.; Srivastava, M.P.

    1995-07-01

    The density variation of plasmas produced by irradiation with laser beams on spherical targets has been studied in the steady state. This study used an adiabatic plasma model with self-generated magnetic fields included in a phenomenological manner. The density variation with a radial coordinate is found to have a steep rise through the critical density, which reaches a plateau in the overdense region, then a density minimum and finally, a rise. This variation has been compared with experimentally observed values in earlier works and is found to be in fairly good agreement. The variation of plateau density with the intensity of the laser is also compared with the experimentally observed variation. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  15. Control of clinical coccidiosis of calves due to Eimeria bovis and Eimeria zuernii with toltrazuril under field conditions.

    PubMed

    Mundt, H-C; Bangoura, B; Mengel, H; Keidel, J; Daugschies, A

    2005-10-01

    The efficacy of metaphylactic treatment with toltrazuril (Baycox 5% suspension) against natural infections with Eimeria bovis and/or Eimeria zuernii in calves was investigated. The study was conducted with 208 calves on five calf-rearing farms in Germany and the Czech Republic. All participating farms had a notable incidence of coccidiosis. Animals were treated 14 days after stabling in the respective facility. One group was treated with 15 mg toltrazuril/kg body weight, and a second group served as the sham-treated control. Assessment of efficacy was based on faecal consistency and oocyst excretion of E. bovis and E. zuernii, both investigated throughout the study. Duration and rate of oocyst excretion as well as number of scour days with E. bovis or E. zuernii oocyst shedding and the severity of diarrhoea were significantly lower in the toltrazuril-treated groups. It is concluded that a single metaphylactic treatment with toltrazuril controls coccidiosis of housed calves under various field conditions.

  16. F layer postsunset height rise due to electric field prereversal enhancement: 1. Traveling planetary wave ionospheric disturbance effects

    NASA Astrophysics Data System (ADS)

    Fagundes, P. R.; Bittencourt, J. A.; Abalde, J. R.; Sahai, Y.; Bolzan, M. J. A.; Pillat, V. G.; Lima, W. L. C.

    2009-12-01

    An ionospheric sounding station is operational at Palmas (10.2°S, 48.2°W, dip latitude 5.5°S), Brazil, since 2002. Observations of F layer virtual height day-to-day variations during evening hours (1800 LT to 2000 LT) show a strong variability, even during geomagnetically quiet periods. From the ionospheric multifrequency virtual height variations (at 3, 4, 5, 6, 7, and 8 MHz), observed from July 2003 to May 2004, it is found that the virtual height day-to-day variability presents oscillations with periods of days during the evening hours. The thermospheric wind component perpendicular to the magnetic meridian (zonal wind) is one of the primary sources that generate the F region dynamo near sunset, which causes the zonal electric field prereversal enhancement (PRE) that induces the E × B vertical F layer postsunset height rise. Therefore, the planetary wave (PW) component that flows superposed on the thermospheric wind induces a traveling planetary wave ionospheric disturbance (TPWID) on the vertical F layer displacement. This indicates that the postsunset ionospheric height rise can be strongly modulated by TPWID oscillations. Our study shows that TPWIDs with periods of several days control the strength of the electric field PRE and, therefore, slowly push the F layer heights up or down, according to the TPWID phase. Also, simultaneous virtual height variations at Sao José dos Campos (low latitude) and Palmas (equatorial region) for October and November show similar behavior. This suggests that TPWID oscillation is a manifestation of atmospheric equatorial Kelvin waves that modulate the thermospheric wind.

  17. Evaluation of the Effect of Glibenclamide in Patients With Diffuse Axonal Injury Due to Moderate to Severe Head Trauma

    PubMed Central

    Zafardoost, Peyman; Ghasemi, Amir Abbas; Salehpour, Firooz; Piroti, Chia; Ziaeii, Ehsan

    2016-01-01

    Background Traumatic brain injury (TBI) is a major health problem worldwide. Secondary injuries after TBI, including diffuse axonal injury (DAI) often occur, and proper treatments are needed in this regard. It has been shown that glibenclamide could reduce secondary brain damage after experimental TBI and improve outcomes. Objectives We aim to evaluate the role of glibenclamide on the short-term outcome of patients with DAI due to moderate to severe TBI. Patients and Methods In this controlled randomized clinical trial, 40 patients with moderate to severe TBI were assigned to glibenclamide (n = 20) and control (n = 20) groups. Six hours after admission the intervention group received 1.25 mg glibenclamide every 12 hours. The Glasgow coma scale (GCS) was administered at admission, in the first 24 and 48 hours, at one week post-trauma and at discharge. The Glasgow outcome scale (GOS) was also administered at discharge. All results were evaluated and compared between groups. Results Patients treated with glibenclamide compared to the control group had a significantly better GCS score one week post-trauma (P = 0.003) and at discharge (P = 0.004), as well as a better GOS score at discharge (P = 0.001). The glibenclamide group also had a shorter length of hospital stay compared to the control group (P = 0.03). In the control group, two patients (10%) died during the first week post-trauma, but there was no mortality in the glibenclamide group (P = 0.48). Conclusions Treatment with glibenclamide in patients with DAI due to moderate to severe TBI significantly improves short-term outcomes. PMID:28184360

  18. Evaluation of uncertainties in lung measurement of actinides due to non-uniform distribution of activity in lungs.

    PubMed

    Nadar, M Y; Akar, D K; Rao, D D; Kulkarni, M S; Pradeepkumar, K S

    2017-09-01

    Various parameters can introduce uncertainties in the lung activity measurements of actinides. In this study, uncertainties due to non-uniform distribution of activity in the lungs are evaluated. To study the effect of non-uniform distribution, lungs of ICRP male thorax voxel and resized phantoms are divided into upper and lower parts of both right and left lungs as well as into anterior and posterior lung regions. Simulation of uniform and non-uniform distribution of activity in lungs is carried out using thorax voxel phantoms in FLUKA for Phoswich and an array of three HPGe detectors for 18-238keV photons. Source sampling for non-uniform distribution of activity is carried out by selecting the source points by varying the weightage to 0.4, 0.5, 0.6 and 1 in different parts of lungs. Uncertainties in lung activity estimation at different energies are quantified in the form of scattering factors (SFs) which are geometric standard deviations. The SFs due to non-uniform distribution of activity of the order of 0.4-0.6 in different parts of the lungs are found to be ~ 1.25 for Phoswich and HPGe array detectors above 18keV. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Evaluation of detectors for the small field measurements used for clinical radiation dosimetry

    NASA Astrophysics Data System (ADS)

    Markovic, Miljenko

    Advanced radiation therapy treatments with very small field sizes are complex. Increasingly higher doses delivered in single or few fractions are being commonly used for the treatments of the small target volume. Absolute or relative small field dosimetry is difficult due to radiation transport. Therefore it is very important to understand characteristics of the small field, detector selection as well as correction factors that have to be taken into account for the accurate measurements. Reducing uncertainty in relative dose measurement and modeling dose on treatment planning systems are factors contributing to the accuracy of the small field radiation treatments. Several challenges in small field dosimetry arise because of the lack of lateral charge particle equilibrium as well as the occlusion of the direct photon beam source and collimator settings. Presence of low-density media in irradiation geometry does complicate dosimetry even more. All those conditions are representing the challenge when it comes to dosimetric measurements. Size and construction are crucial when it comes to choice of the detector. Depending on beam energy, resolving the beam profile and penumbra for the small field sizes are a challenge and practically impossible with detectors commonly used in clinics. With decreasing field size and due to changes in particle spectrum, variations in radiological parameters have to be taken into account. To measure percent depth dose, tissue maximum ratios, tissue phantom ratios as well as output factors for the small field size experimental studies and Monte Carlo simulations have been conducted to determine appropriate detectors for the measurements. The primary goal of Specific Aim 1 was experimental quantification of the performance parameters for single detectors used for dosimetric verification of the small fields in radiotherapy. The proposed method and qualitative value for appropriate detectors selection defined by field size has been set. The

  20. Applications of gas chemistry in evaluating physical processes in the Southern Negros (Palinpinon) geothermal field, Philippines

    SciTech Connect

    D`Amore, F.; Nuti, S.; Ramos-Candelaria, M.N.; Seastres, J.S. Jr.; Ruaya, J.R.

    1993-10-01

    Three major physical processes have occurred in the Palinpinon geothermal system due to exploitation from 1985 to 1991. They were identified using gas compositions and equilibria involving H{sub 2}, H{sub 2}S, CH{sub 4} and CO{sub 2} to calculate temperature and vapor fraction in the reservoir. The first process is pressure drawdown in the southern part of the field, producing a local increase in the vapor fraction, with the liquid maintaining a high measured temperature, close to 300 C. The second process is vapor loss from an original liquid phase during its ascent through fractures. Wells affected by this process show high degrees of vapor loss (> 10%) when evaluated at the original high temperature of the liquid (290--300 C). But if vapor loss is modeled to occur at much lower temperatures (220--250 C), more realistic vapor losses (1--3%) are calculated. The last process involves mixing and cooling due to injection fluid returns to wells located in the northeastern part of the field. For some wells the fraction of injected brine in total temperatures can decline from 290 to 300 C to as low as 215--220 C, corresponding to periods when most of the produced fluids are derived from injected brine. Gas geothermometry gives a more reliable temperature estimate than quartz geothermometry for fluids with high fractions of injected brine, as the gas equilibria reflects the local reservoir temperature.

  1. Field evaluation of hazardous waste site bioassessment protocols. Volume 2

    SciTech Connect

    Thomas, J.M.; Cline, J.F.; Gano, K.A.; McShane, M.C.; Rogers, J.E.; Rogers, L.E.; Simpson, J.C.; Skalski, J.R.

    1984-04-01

    The overall goal of the plan was to demonstrate that honeybees could be used in detecting likely areas of chemical pollution, to demonstrate the usefulness of microbial and plant phytoassays, and to demonstrate a relationship between laboratory derived phytotoxicity results and field observations of plant community structure and diversity. Field studies were conducted through a cooperative arrangement with the US Army arsenal in Commerce City, Colorado.

  2. Evaluation of the denitrification rate of terraced paddy fields

    NASA Astrophysics Data System (ADS)

    Onishi, Takeo; Nakamura, Kimihito; Horino, Haruhiko; Adachi, Toru; Mitsuno, Toru

    2012-05-01

    SummaryRice is one of the most important staple foods in the world. Lowland paddy fields are well known for functioning as denitrification areas, but few studies have been conducted of paddy fields situated on hill slopes (terraced paddy fields). These terraced paddy fields have a characteristic artificial stepped shape, and this unique shape and periodic ponding from rice production may configure unique hydrological properties that might be different from lowland paddy fields. The shape and hydrological properties may also affect transport of nutrients such as nitrogen. This study is particularly focused on the denitrification rate in terraced paddy fields. To understand the hydrological properties of terraced paddy fields, a detailed water budget including the subsurface flow components was calculated. Combining the water budget components and chemical measurements of surface and subsurface water, a nitrogen budget was calculated. The results showed that about 10% of the total nitrogen input, mainly from fertilizers, was lost, suggesting the occurrence of denitrification in the area. The average denitrification rate of the study site was estimated at about 0.53-0.67 g N m-2 year-1. Spatial variations in the measured groundwater nitrate concentration suggest that denitrification is important in both the plough layer and the sloping area. The denitrification rate in the sloping area was estimated at 0.67-0.78 g N m-2 year-1, which is slightly higher than the estimates of denitrification rate in paddy lots, i.e., 0.56-0.61 g N m-2 year-1. The result indicates the importance of sloping areas for denitrification in terraced paddy fields.

  3. An Evaluation of Tropical Cyclogenesis Theories through Intercomparison of Field Experiment Observations

    NASA Astrophysics Data System (ADS)

    Helms, C. N.; Hart, R. E.

    2011-12-01

    The process by which tropical cyclones evolve from loosely organized convective clusters into well organized systems is still poorly understood. A number of theories have been proposed to explain this evolution based on vortex dynamics, adiabatic processes, and diabatic processes. Due to the data sparse location in which many of these systems develop, many studies of tropical cyclogenesis theory are limited to either a few case studies or are forced to rely on simulations to critically evaluate the theories. The recent PREDICT and GRIP field experiments have provided a new opportunity to examine these theories using unusually dense observations. The present study aims at using this new data in conjunction with data from previous field experiments, such as NAMMA, GATE, and TOGA COARE, to evaluate three existing theories: top-down vortex merger (Ritchie and Holland, 1997; Simpson et al., 1997), top-down shower-head (Emanuel, 1993; Bister and Emanuel, 1997), and bottom-up vortex merger (Montgomery and Enagonio, 1998; Enagonio and Montgomery, 2001). Additionally, these observations are used to briefly examine the newer marsupial framework for tropical cyclogenesis in African easterly waves (Dunkerton et al. 2009). The processes associated with each of these theories create unique signatures in wind, vorticity, potential temperature, and humidity fields. Timelines of these fields, created from composited mean dropsonde soundings, are used to determine the system-wide evolution. Further, the temporal evolution of sub-system processes, which are minimized or removed as a result of the compositing process, are identified in isobaric surface plot series. While previous studies have shown that no theory completely explains tropical cyclogenesis, it is hoped that a thorough analysis of these data sets will highlight both consistencies and inconsistencies between theory and observation.

  4. Topographic/isostatic evaluation of new-generation GOCE gravity field models

    NASA Astrophysics Data System (ADS)

    Hirt, C.; Kuhn, M.; Featherstone, W. E.; GöTtl, F.

    2012-05-01

    We use gravity implied by the Earth's rock-equivalent topography (RET) and modeled isostatic compensation masses to evaluate the new global gravity field models (GGMs) from European Space Agency (ESA)'s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite gravimetry mission. The topography is now reasonably well-known over most of the Earth's landmasses, and also where conventional GGM evaluation is prohibitive due to the lack (or unavailability) of ground-truth gravity data. We construct a spherical harmonic representation of Earth's RET to derive band-limited topography-implied gravity, and test the somewhat simplistic Airy/Heiskanen and Pratt/Hayford hypotheses of isostatic compensation, but which did not improve the agreement between gravity from the uncompensated RET and GOCE. The third-generation GOCE GGMs (based on 12 months of space gravimetry) resolve the Earth's gravity field effectively up to spherical harmonic degree ˜200-220 (˜90-100 km resolution). Such scales could not be resolved from satellites before GOCE. From the three different GOCE processing philosophies currently in use by ESA, the time-wise and direct approaches exhibit the highest sensitivity to short-scale gravity recovery, being better than the space-wise approach. Our topography-implied gravity comparisons bring evidence of improvements from GOCE to gravity field knowledge over the Himalayas, Africa, the Andes, Papua New Guinea and Antarctic regions. In attenuated form, GOCE captures topography-implied gravity signals up to degree ˜250 (˜80 km resolution), suggesting that other signals (originating, e.g., from the crust-mantle boundary and buried loads) are captured as well, which might now improve our knowledge on the Earth's lithosphere structure at previously unresolved spatial scales.

  5. Variation of bulk Lorentz factor in AGN jets due to Compton rocket in a complex photon field

    NASA Astrophysics Data System (ADS)

    Vuillaume, T.; Henri, G.; Petrucci, P.-O.

    2015-09-01

    Radio-loud active galactic nuclei are among the most powerful objects in the universe. In these objects, most of the emission comes from relativistic jets getting their power from the accretion of matter ontosupermassive black holes. However, despite the number of studies, a jet's acceleration to relativistic speeds is still poorly understood. It is widely known that jets contain relativistic particles that emit radiation through several physical processes, one of them being the inverse Compton scattering of photons coming from external sources. In the case of a plasma composed of electrons and positrons continuously heated by the turbulence, inverse Compton scattering can lead to relativistic bulk motions through the Compton rocket effect. We investigate this process and compute the resulting bulk Lorentz factor in the complex photon field of an AGN composed of several external photon sources. We consider various sources:the accretion disk, the dusty torus, and the broad line region. We take their geometry and anisotropy carefully into account in order to numerically compute the bulk Lorentz factor of the jet at every altitude. The study, made for a broad range of parameters, shows interesting and unexpected behaviors of the bulk Lorentz factor, exhibiting acceleration and deceleration zones in the jet. We investigate the patterns of the bulk Lorentz factor along the jet depending on the source sizes and on the observation angle and we finally show that these patterns can induce variability in the AGN emission with timescales going from hours to months.

  6. Reexamination of relaxation of spins due to a magnetic field gradient: Identity of the Redfield and Torrey theories

    NASA Astrophysics Data System (ADS)

    Golub, R.; Rohm, Ryan M.; Swank, C. M.

    2011-02-01

    There is an extensive literature on magnetic-gradient-induced spin relaxation. Cates, Schaefer, and Happer, in a seminal publication, have solved the problem in the regime where diffusion theory (the Torrey equation) is applicable using an expansion of the density matrix in diffusion equation eigenfunctions and angular momentum tensors. McGregor has solved the problem in the same regime using a slightly more general formulation using the Redfield theory formulated in terms of the autocorrelation function of the fluctuating field seen by the spins and calculating the correlation functions using the diffusion-theory Green’s function. The results of both calculations were shown to agree for a special case. In the present work, we show that the eigenfunction expansion of the Torrey equation yields the expansion of the Green’s function for the diffusion equation, thus showing the identity of this approach with that of the Redfield theory. The general solution can also be obtained directly from the Torrey equation for the density matrix. Thus, the physical content of the Redfield and Torrey approaches are identical. We then introduce a more general expression for the position autocorrelation function of particles moving in a closed cell, extending the range of applicability of the theory.

  7. Annoyance and self-reported sleep disturbance due to night-time railway noise examined in the field.

    PubMed

    Pennig, Sibylle; Quehl, Julia; Mueller, Uwe; Rolny, Vinzent; Maass, Hartmut; Basner, Mathias; Elmenhorst, Eva-Maria

    2012-11-01

    Railway noise interferes with daytime activities and disturbs sleep leading to annoyance of exposed residents. The main objective of this paper was to establish exposure-response relationships between nocturnal railway noise exposure and annoyance and to examine self-reported sleep disturbances as short-term reactions to noise. In a field study 33 residents living close to railway tracks in the Cologne/Bonn area (Germany) were investigated. Railway noise was measured indoors during nine consecutive nights at each site. Questionnaires referring to annoyance and non-acoustical factors were performed. Annoyance ratings increased significantly with the total number of trains and freight trains per night, and non-significantly with rising number of passenger trains and energy equivalent sound pressure level (L(Aeq)), when adjusting the model for non-acoustical variables. The total number of trains and the number of freight trains also significantly affected self-reported awakening frequency, but no other aspects of subjective sleep disturbances. The responses of this subject sample referring to railway noise in the previous night point to rather low impairments of exposed residents.

  8. Using forward calculations of the magnetic field perturbation due to a realistic vascular model to explore the BOLD effect.

    PubMed

    Marques, José P; Bowtell, R W

    2008-07-01

    This paper assesses the reliability of the infinite cylinder model used previously in the literature to simulate blood oxygenation level dependent (BOLD) signal changes. A three-dimensional finite element method was applied to a realistic model of the cortical vasculature, and the results compared with those generated from a simple model of the vasculature as a set of independent, randomly oriented, infinite cylinders. The realistic model is based on scanning electron microscopy measurements of the terminal vascular bed in the superficial cortex of the rat. Good agreement is found between the two models with regard to the extravascular R(2)* and R(2) dependence on the cerebral blood volume and blood oxygenation fraction. Using the realistic model, it is also possible to gain further understanding of the relative importance of intravascular and extravascular BOLD contrast. A simple parameterisation of the dependence of the relaxation rates on relative cerebral blood volume and blood-tissue susceptibility difference was carried out, allowing discussion of the variation in the form of the haemodynamic response with field strength.

  9. Evaluation of SAR in a human body model due to wireless power transmission in the 10 MHz band.

    PubMed

    Laakso, Ilkka; Tsuchida, Shogo; Hirata, Akimasa; Kamimura, Yoshitsugu

    2012-08-07

    This study discusses a computational method for calculating the specific absorption rate (SAR) due to a wireless power transmission system in the 10 MHz frequency band. A two-step quasi-static method comprised of the method of moments and the scalar potential finite-difference method are proposed. The applicability of the quasi-static approximation for localized exposure in this frequency band is discussed by comparing the SAR in a lossy dielectric cylinder computed with a full-wave electromagnetic analysis and the quasi-static approximation. From the computational results, the input impedance of the resonant coils was affected by the existence of the cylinder. On the other hand, the magnetic field distribution in free space and considering the cylinder and an impedance matching circuit were in good agreement; the maximum difference in the amplitude of the magnetic field was 4.8%. For a cylinder-coil distance of 10 mm, the difference between the peak 10 g averaged SAR in the cylinder computed with the full-wave electromagnetic method and our quasi-static method was 7.8%. These results suggest that the quasi-static approach is applicable for conducting the dosimetry of wireless power transmission in the 10 MHz band. With our two-step quasi-static method, the SAR in the anatomically based model was computed for different exposure scenarios. From those computations, the allowable input power satisfying the limit of a peak 10 g averaged SAR of 2.0 W kg(-1) was 830 W in the worst case exposure scenario with a coil positioned at a distance of 30 mm from the chest.

  10. Self-contained self-rescuer long term field evaluation: combined eighth and ninth phase results

    SciTech Connect

    2006-10-15

    The National Institute for Occupational Safety and Health (NIOSH) National Personal Protective Technology Laboratory (NPPTL) and the Mine Safety and Health Administration (MSHA) conduct a Long Term Field Evaluation (LTFE) program to evaluate deployed self-contained self rescuers (SCSRs). The objective of the program is to evaluate how well SCSRs endure the underground coal mining environment with regard to both physical damage and aging when they are deployed in accordance with Federal regulations (30 CFR 75.1714). This report presents findings of the combined eighth and ninth phases of the LTFE. For these phases, over four hundred SCSRs were evaluated. The units tested include the CSE SR-100, Draeger Oxy K-Plus, MSA Life-saver 60, and the OCENCO EBA 6.5. The OCENCO 20 was evaluated only in Phase 9. Testing was performed between December 2000 and April 2004. Results of the evaluation indicate that all SCSRs experience some performance degradation due to the mining environment. Observed degradation varies from elevated levels of carbon dioxide, high breathing resistance, and reduced capacity. Mechanical degradation to the SCSR components included breathing hoses, chemical beds, outer cases and seals. The LTFE tests discussed in this report are different from tests performed for SCSR certification to the requirements of 42 Code of Federal Regulations, Part 84 (42 CFR, Part 84). LTFE tests reported here are conducted to an end point, oxygen depletion, to enable comparison of the duration of new and deployed SCSRs. The method for obtaining deployed SCSRs for this evaluation was not a random selection from the deployed population of SCSRs. Although the results of these tests are useful for observing performance of the tested SCSRs, they are not representative of all deployed SCSRs. 9 refs., 10 figs., 9 tabs., 3 apps.

  11. Field-based evaluation of a male-specific (F+) RNA coliphage ...

    EPA Pesticide Factsheets

    Fecal contamination of water poses a significant risk to public health due to the potential presence of pathogens, including enteric viruses. Thus, sensitive, reliable and easy to use methods for the detection of microorganisms are needed to evaluate water quality. In this study, we performed a field evaluation of an anion-exchange resin based platform to concentrate F-RNA coliphages (fecal/enteric virus indicators) from diverse fecally impacted environmental waters. In this platform, F-RNA coliphages are adsorbed to anion-exchange resin and direct nucleic acid isolation is performed, yielding a sample amenable to real-time reverse transcriptase PCR detection. Matrix-dependent inhibition was evaluated using known quantities of spiked F-RNA coliphage genogroups GI, GII, GII and GIV. Detection was successful in 97%, 72%, 85% and 98% of the samples for spiked F-RNA coliphage GI, GII, GIII and GIV, respectively, and was differentially affected by inhibitory properties specific to each water sample. No association between inhibition and the water samples’ physicochemical properties was apparent. Parallel evaluations of the spiked samples with internal amplification control (IAC) reactions (a widely used control to assess inhibition) demonstrated that IAC reaction inhibition was not agreement with that observed for spiked samples, suggesting that testing of spiked samples allows for better assessments of matrix-dependent inhibition. Additionally, the anion-

  12. Field significance of performance measures in the context of regional climate model evaluation. Part 1: temperature

    NASA Astrophysics Data System (ADS)

    Ivanov, Martin; Warrach-Sagi, Kirsten; Wulfmeyer, Volker

    2017-03-01

    A new approach for rigorous spatial analysis of the downscaling performance of regional climate model (RCM) simulations is introduced. It is based on a multiple comparison of the local tests at the grid cells and is also known as "field" or "global" significance. New performance measures for estimating the added value of downscaled data relative to the large-scale forcing fields are developed. The methodology is exemplarily applied to a standard EURO-CORDEX hindcast simulation with the Weather Research and Forecasting (WRF) model coupled with the land surface model NOAH at 0.11 ∘ grid resolution. Monthly temperature climatology for the 1990-2009 period is analysed for Germany for winter and summer in comparison with high-resolution gridded observations from the German Weather Service. The field significance test controls the proportion of falsely rejected local tests in a meaningful way and is robust to spatial dependence. Hence, the spatial patterns of the statistically significant local tests are also meaningful. We interpret them from a process-oriented perspective. In winter and in most regions in summer, the downscaled distributions are statistically indistinguishable from the observed ones. A systematic cold summer bias occurs in deep river valleys due to overestimated elevations, in coastal areas due probably to enhanced sea breeze circulation, and over large lakes due to the interpolation of water temperatures. Urban areas in concave topography forms have a warm summer bias due to the strong heat islands, not reflected in the observations. WRF-NOAH generates appropriate fine-scale features in the monthly temperature field over regions of complex topography, but over spatially homogeneous areas even small biases can lead to significant deteriorations relative to the driving reanalysis. As the added value of global climate model (GCM)-driven simulations cannot be smaller than this perfect-boundary estimate, this work demonstrates in a rigorous manner the

  13. Integrating a MRI scanner with a 6 MV radiotherapy accelerator: impact of the surface orientation on the entrance and exit dose due to the transverse magnetic field.

    PubMed

    Raaijmakers, A J E; Raaymakers, B W; van der Meer, S; Lagendijk, J J W

    2007-02-21

    At the UMC Utrecht, in collaboration with Elekta and Philips Research Hamburg, we are developing a radiotherapy accelerator with integrated MRI functionality. The radiation dose will be delivered in the presence of a lateral 1.5 T field. Although the photon beam is not affected by the magnetic field, the actual dose deposition is done by a cascade of secondary electrons and these electrons are affected by the Lorentz force. The magnetic field causes a reduced build-up distance: because the trajectory of the electrons between collisions is curved, the entrance depth in tissue decreases. Also, at tissue-air interfaces an increased dose occurs due to the so-called electron return effect (ERE): electrons leaving tissue will describe a circular path in air and re-enter the tissue yielding a local dose increase. In this paper the impact of a 1.5 T magnetic field on both the build-up distance and the dose increase due to the ERE will be investigated as a function of the angle between the surface and the incident beam. Monte Carlo simulations demonstrate that in the presence of a 1.5 T magnetic field, the surface dose, the build-up distance and the exit dose depend more heavily on the surface orientation than in the case without magnetic field. This is caused by the asymmetrical pointspread kernel in the presence of 1.5 T and the directional behaviour of the re-entering electrons. Simulations on geometrical phantoms show that ERE dose increase at air cavities can be avoided using opposing beams, also when the air-tissue boundary is not perpendicular to the beam. For the more general case in patient anatomies, more problems may arise. Future work will address the possibilities and limitations of opposing beams in combination with IMRT in a magnetic field.

  14. Integrating a MRI scanner with a 6 MV radiotherapy accelerator: impact of the surface orientation on the entrance and exit dose due to the transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Raaijmakers, A. J. E.; Raaymakers, B. W.; van der Meer, S.; Lagendijk, J. J. W.

    2007-02-01

    At the UMC Utrecht, in collaboration with Elekta and Philips Research Hamburg, we are developing a radiotherapy accelerator with integrated MRI functionality. The radiation dose will be delivered in the presence of a lateral 1.5 T field. Although the photon beam is not affected by the magnetic field, the actual dose deposition is done by a cascade of secondary electrons and these electrons are affected by the Lorentz force. The magnetic field causes a reduced build-up distance: because the trajectory of the electrons between collisions is curved, the entrance depth in tissue decreases. Also, at tissue-air interfaces an increased dose occurs due to the so-called electron return effect (ERE): electrons leaving tissue will describe a circular path in air and re-enter the tissue yielding a local dose increase. In this paper the impact of a 1.5 T magnetic field on both the build-up distance and the dose increase due to the ERE will be investigated as a function of the angle between the surface and the incident beam. Monte Carlo simulations demonstrate that in the presence of a 1.5 T magnetic field, the surface dose, the build-up distance and the exit dose depend more heavily on the surface orientation than in the case without magnetic field. This is caused by the asymmetrical pointspread kernel in the presence of 1.5 T and the directional behaviour of the re-entering electrons. Simulations on geometrical phantoms show that ERE dose increase at air cavities can be avoided using opposing beams, also when the air-tissue boundary is not perpendicular to the beam. For the more general case in patient anatomies, more problems may arise. Future work will address the possibilities and limitations of opposing beams in combination with IMRT in a magnetic field.

  15. Characterization of carbonate reservoir property changes due to dissolution for far-field conditions of CO2 storage

    NASA Astrophysics Data System (ADS)

    Mangane, P. O.; Gouze, P.; Luquot, L.

    2012-12-01

    Geological storage of CO2 in reservoir pore fluid (e.g. deep saline aquifers), is one of the diverse technologies being explored for deacreasing atmospheric CO2 concentration. After injecting the CO2 as a supercritical fluid at depth, it will slowly dissolve into the pore water producing low pH fluids with a high capacity for dissolving carbonates and consequently changing irreversibly the hydrodynamical properties of the reservoir. Characterizing these changes is essential for modelling flow and CO2 transport during and after the CO2 injection. Here we report experimental results from the injection of the CO2-saturated brine into two distinct limestone cores (a bioclastic carbonate and an oolitic carbonate) of 9 mm diameter, 18 mm length. 3D high-resolution X-ray microtomography (XRMT) of the rock sample have been performed before and after the experiments. The experiments were performed using in-situ sequestration conditions (P = 12MPa and T = 100°C), and notably, under chemical conditions given at the position far away from the well injection site (i.e area where the volume of dissolved CO2 into the brine is low, due to CO2 consumption by the dissolution processes occured during its transport from the well injection site). Permeability k is calculated from the pressure drop across the sample and porosity Φ is deduced from chemical concentration of the outlet fluid. The change of the pore structure is analysed in terms of connectivity, tortuosity and fluid-rock interface from processing the XRMT images. These experiments show that far from the well injection site, dissolution processes are characterized by slow mass tranfer including, in the case of carbonate rock, transport of fine particles, which locally clog the porous space. Then, that leads to the damage of the carbonate reservoir both in terms of connectivity of the porous space and CO2 hydrodynamical storage capacity. In fact, the results of the two experiments show that the porosity decreased locally

  16. HPV8 Field Cancerization in a Transgenic Mouse Model Is due to Lrig1+ Keratinocyte Stem Cell Expansion.

    PubMed

    Lanfredini, Simone; Olivero, Carlotta; Borgogna, Cinzia; Calati, Federica; Powell, Kathryn; Davies, Kelli-Jo; De Andrea, Marco; Harries, Sarah; Tang, Hiu Kwan Carolyn; Pfister, Herbert; Gariglio, Marisa; Patel, Girish K

    2017-10-01

    β-Human papillomaviruses (HPVs) cause near ubiquitous latent skin infection within long-lived hair follicle (HF) keratinocyte stem cells. In patients with epidermodysplasia verruciformis, β-HPV viral replication is associated with skin keratosis and cutaneous squamous cell carcinoma. To determine the role of HF keratinocyte stem cells in β-HPV-induced skin carcinogenesis, we utilized a transgenic mouse model in which the keratin 14 promoter drives expression of the entire HPV8 early region (HPV8tg). HPV8tg mice developed thicker skin in comparison with wild-type littermates consistent with a hyperproliferative epidermis. HF keratinocyte proliferation was evident within the Lrig1+ keratinocyte stem cell population (69 vs. 55%, P < 0.01, n = 7), and not in the CD34+, LGR5+, and LGR6+ keratinocyte stem cell populations. This was associated with a 2.8-fold expansion in Lrig1+ keratinocytes and 3.8-fold increased colony-forming efficiency. Consistent with this, we observed nuclear p63 expression throughout this population and the HF infundibulum and adjoining interfollicular epidermis, associated with a switch from p63 transcriptional activation isoforms to ΔNp63 isoforms in HPV8tg skin. Epidermodysplasia verruciformis keratosis and in some cases actinic keratoses demonstrated similar histology associated with β-HPV reactivation and nuclear p63 expression within the HF infundibulum and perifollicular epidermis. These findings would suggest that β-HPV field cancerization arises from the HF junctional zone and predispose to squamous cell carcinoma. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Assessing hydrological changes due to the Hemlock Woolly Adelgid infestation in New England using field measurements and ecohydrological modeling

    NASA Astrophysics Data System (ADS)

    Kim, J.; Hwang, T.; Schaaf, C.; David, O.; Boose, E.; Munger, J. W.

    2016-12-01

    In the northeastern US, eastern hemlock (Tsuga canadensis) is known as a foundation species, playing a key role in controlling regional hydrological and biogeochemical cycles. The Hemlock Woolly Adelgid (HWA; Adelges tsugae) currently infests about half of the entire eastern hemlock forests in the region, causing a significant increase in mortality of eastern hemlock trees over the past decade. Although warmer winter temperatures are expected to promote its northward expansion, the effect of the ongoing hemlock declines on local hydrologic regime is not yet fully understood. Here, we first report the ongoing HWA infestation and its effect on the hydrologic fluxes at the Harvard Forest Long Term Ecological Research (LTER) site in central Massachusetts. For the last five years (2009-2014), the HWA infestation has increased from 17.2% to 96.5%, inducing foliar loss by 50%. Based on the eddy-covariance flux measurements, we estimated that the evapotranspiration (ET) flux over the hemlock-dominated area has decreased by 23-37%. The annual stream discharge of a mixed-forest headwater catchment has increased by 4.2-15.8 mm as compared to an adjacent catchment with 22.4% less hemlock cover. We used a mechanistic ecohydrological model (RHESSys: Regional Hydro-Ecologic Simulation System) to scale up the plot-scale HWA effect into catchment-scale hydrological changes, and assessed the net amount of the annual stream discharge changed due to the HWA infestation. This study highlights that the local hydrological regimes in the northeastern US will be significantly altered by the complete mortality of eastern hemlock forests.

  18. Modeling the (Sub)surface Deformation Field Evolution Due to Production from a Hydrocarbon Reservoir Overlain by Rocksalt

    NASA Astrophysics Data System (ADS)

    Marketos, G.; Govers, R. M. A.; Spiers, C. J.

    2014-12-01

    Rocksalt is an important caprock for sealing or trapping hydrocarbons. Given its relatively low viscosity, it may flow during and after production and result in time-dependent surface deformation. To predict the consequences of alternative production strategies, we seek to understand the primary controls on stress-driven flow and surface deformation of hydrocarbon extraction from a reservoir topped by rocksalt. The mechanical properties of rock salt are a key influence, but complicated. Depending on grain size, temperature, and stress, salt can deform mainly elastically, by power law viscous creep, and/or by linear viscous diffusion creep. In this study, we evaluate the evolution of production induced deformation using generic geo-mechanical models. Our strategy is to start with simplified geometries, rheologies, and forcing, and to increase model complexity slowly. Our results show that there are two distinctly different time scales that dominate the evolution of the models: short term subsidence and longer term partial rebound. The shortest time scale corresponds to stress-driven flow in the vicinity of the reservoir. The longest time scale is controlled by resistance to viscous flow and stress relaxation within a wider region of the rocksalt layer. We discuss the sensitivity to the thickness of the rocksalt seal, the geometry of the reservoir, and the distance between the source and the seal.

  19. Nonprofits and Evaluation: Empirical Evidence from the Field

    ERIC Educational Resources Information Center

    Carman, Joanne G.; Fredericks, Kimberly A.

    2008-01-01

    The authors explore what evaluation looks like, in practice, among today's nonprofit organizations on the basis of their survey results. The types of evaluation activities nonprofit organizations are engaging in on a regular basis, as well as the types of data they are collecting and how they are using these data, are described. How nonprofits…

  20. Amplified hazard of small-volume monogenetic eruptions due to environmental controls, Orakei Basin, Auckland Volcanic Field, New Zealand

    NASA Astrophysics Data System (ADS)

    Németh, Károly; Cronin, Shane J.; Smith, Ian E. M.; Agustin Flores, Javier

    2012-11-01

    Orakei maar and tuff ring in the Auckland Volcanic Field is an example of a basaltic volcano in which the style and impacts of the eruption of a small volume of magma were modulated by a fine balance between magma flux and groundwater availability. These conditions were optimised by the pre-85 ka eruption being hosted in a zone of fractured and variably permeable Plio-Pleistocene mudstones and sandstones. Orakei maar represents an end-member in the spectrum of short-lived basaltic volcanoes, where substrate conditions rather than the magmatic volatile content was the dominant factor controlling explosivity and eruption styles. The eruption excavated a crater ≫80 m deep that was subsequently filled by slumped crater wall material, followed by lacustrine and marine sediments. The explosion crater may have been less than 800 m in diameter, but wall collapse and wave erosion has left a 1,000-m-diameter roughly circular basin. A tuff ring around part of the maar comprises dominantly base surge deposits, along with subordinate fall units. Grain size, texture and shape characteristics indicate a strong influence of magma-water and magma-mud interactions that controlled explosivity throughout the eruption, but also an ongoing secondary role of magmatic gas-driven expansion and fragmentation. The tuff contains >70 % of material recycled from the underlying Plio-Pliestocene sediments, which is strongly predominant in the >2 ϕ fraction. The magmatic clasts are evolved alkali basalt, consistent with the eruption of a very small batch of magma. The environmental impact of this eruption was disproportionally large, when considering the low volume of magma involved (DRE < 0.003 km3). Hence, this eruption exemplifies one of the worst-case scenarios for an eruption within the densely populated Auckland City, destroying an area of ~3 km2 by crater formation and base surge impact. An equivalent scenario for the same magma conditions without groundwater interaction would yield a

  1. Mars Pathfinder Near-Field Rock Distribution Re-Evaluation

    NASA Technical Reports Server (NTRS)

    Haldemann, A. F. C.; Golombek, M. P.

    2003-01-01

    We have completed analysis of a new near-field rock count at the Mars Pathfinder landing site and determined that the previously published rock count suggesting 16% cumulative fractional area (CFA) covered by rocks is incorrect. The earlier value is not so much wrong (our new CFA is 20%), as right for the wrong reason: both the old and the new CFA's are consistent with remote sensing data, however the earlier determination incorrectly calculated rock coverage using apparent width rather than average diameter. Here we present details of the new rock database and the new statistics, as well as the importance of using rock average diameter for rock population statistics. The changes to the near-field data do not affect the far-field rock statistics.

  2. A method for evaluating personal dosemeters in workplace with neutron fields.

    PubMed

    de Freitas Nascimento, Luana; Cauwels, Vanessa; Vanhavere, Filip

    2012-04-01

    Passive detectors, as albedo or track-etch, still dominate the field of neutron personal dosimetry, mainly due to their low-cost, high-reliability and elevated throughput. However, the recent appearance in the market of electronic personal dosemeters for neutrons presents a new option for personal dosimetry. In addition to passive detectors, electronic personal dosemeters necessitate correction factors, concerning their energy and angular response dependencies. This paper reports on the results of a method to evaluate personal dosemeters for workplace where neutrons are present. The approach here uses few instruments and does not necessitate a large mathematical workload. Qualitative information on the neutron energy spectrum is acquired using a simple spectrometer (Nprobe), reference values for H*(10) are derived from measurements with ambient detectors (Studsvik, Berthold and Harwell) and angular information is measured using personal dosemeters (electronic and bubbles dosemeters) disposed in different orientations on a slab phantom.

  3. Effects of rippled fields due to ferritic inserts and ELM mitigation coils on energetic ion losses in a 15 MA inductive scenario in ITER

    NASA Astrophysics Data System (ADS)

    Shinohara, K.; Tani, K.; Oikawa, T.; Putvinski, S.; Schaffer, M.; Loarte, A.

    2012-09-01

    The energetic ion loss has been assessed using the F3D-OFMC code for a 15 MA inductive scenario with Q = 10 and the latest information on the first wall geometry, the implementation of ferritic inserts (FI) and the ELM mitigation/control coils. Alpha particles and NB ions generated by the neutral beam injectors with the injection energy of 1 MeV are well confined and the heat load on the first wall is negligibly small and allowable for the magnetic background by the toroidal field coils and FI. However, an increase in the loss of these energetic ions is observed when the magnetic field by the ELM coils is applied. The increase in the loss fraction is larger for NB ions than for alpha particles under the ELM coil field. The origin of the expelled NB ions is dominantly trapped ions generated in the peripheral region due to a high-density plasma of the 15 MA scenario.

  4. Increased particle transport due to resonant magnetic perturbations modelled with a vacuum field line tracing code and a 2D fluid code

    SciTech Connect

    Mordijck, S.; Owen, L. W.; Moyer, R. A.

    2010-02-23

    In this paper we compare the pedestal density changes in resonant magnetic perturbations (RMP) H-modes at low collisionality with enhanced free streaming due to the creation of open field lines. First, we derive the effective radial transport coefficients by matching an ELMing (edge localized mode) H-mode using SOLPS5. Next, a vacuum field line tracing code, TRIP3D, is employed to calculate free streaming of particles along open field lines inside the traditional 2D axisymmetric separatrix. These coefficients are added to the effective radial transport coefficients from the ELMing H-mode and inserted in SOLPS5 to compute midplane profiles. Finally, we compare the SOLPS5 results with the experimental data from RMP H-modes and find good agreement. This good agreement was achieved not only for one single case, but also for two different experiments, with different triangularities, where the high triangularity case contains two RMP H-modes that give good agreement.

  5. Evaluation and Mitigation of the Risk Due to Climate Change at the Department of Energy's Savannah River Site

    NASA Astrophysics Data System (ADS)

    Werth, D. W.

    2016-12-01

    The state of South Carolina, home to the Department of Energy's (DOE) Savannah River Site (SRS), has been identified as facing an `above average' risk due to extreme heat, and the threat due to wildfire is expected to nearly double by 2050. To comply with DOE requirements that each of its sites prepares for climate change, the Savannah River National Laboratory (SRNL) is involved in an ongoing process to evaluate the site vulnerability and establish policies to mitigate those effects. This requires close cooperation between the managers of various site facilities and on-site climate researchers. The Atmospheric Technologies Group at SRNL currently provides short-term weather forecasts to support outdoor activities on site, but is also now working with site decision-makers to achieve DOE's goals of climate change mitigation and adaptation. We will discuss the results of our climate vulnerability assessment, which includes the effects of climate change on the energy requirements for mission critical infrastructure, the health, safety and productivity of the outdoor workforce, the danger of fire in the SRS forest, and the levels of surface water impoundments. (The latter of which must be maintained to avoid the release of radioactive contaminants sequestered beneath them). For each of these, existing climate change projections were carefully studied and `translated' into numerical indices relevant to facility personnel at SRS, along with a vulnerability rating (also based on conversations with site workers) to estimate the most endangered `assets'. We will also explain the process we have developed to facilitate effective communication between researchers and managers - involving them both in the development of the climate vulnerability assessment and the next steps toward planning, resource allocation, actions to mitigate rising costs, and safety considerations as well as helping the site remain sustainable throughout the future of its missions.

  6. Long term field evaluation reveals HLB resistance in Citrus relatives

    USDA-ARS?s Scientific Manuscript database

    Citrus huanglongbing (HLB) is a destructive disease with no known cure. To identify sources of HLB resistance in the subfamily Aurantioideae to which citrus belongs, we conducted a six-year field trial under natural disease challenge conditions in an HLB endemic region. The study included 65 Citrus ...

  7. Field evaluation of timber preservation treatments for highway applications

    Treesearch

    Jake J. Bigelow; Carol A. Clausen; Stan T. Lebow; Lowell Greimann

    2007-01-01

    Timber material repair and replacement cost for timber bridges is a considerable expense to highway agencies in Iowa, especially to county road departments. To address these needs, the objectives of this investigation was to study the field effectiveness of various treatment alternatives used on Iowa roadway projects and to determine if the current specifications and...

  8. FIELD ANALYTICAL SCREENING PROGRAM: PCP METHOD - INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    The Field Analytical Screening Program (FASP) pentachlorophenol (PCP) method uses a gas chromatograph (GC) equipped with a megabore capillary column and flame ionization detector (FID) and electron capture detector (ECD) to identify and quantify PCP. The FASP PCP method is design...

  9. Evaluation and field load testing of timber railroad bridge

    Treesearch

    Terry J. Wipf; Michael A. Ritter; Douglas L. Wood

    2000-01-01

    Several spans of a 60-year-old open-deck timber railroad bridge on the Southern Pacific Railroad Line (now the Union Pacific) in Southwest Texas were field tested. The tests were conducted with the sponsorship and cooperation of the Association of American Railroads to determine the vertical live load distribution characteristics of the...

  10. BIOREMEDIATION FIELD EVALUATION - HILL AIR FORCE BASE, UTAH

    EPA Science Inventory

    In 1990, the U.S. Environmental Protection Agency (EPA) established the Bioremediation Field Initiative as part of its overall strategy to increase the use of bioremediation to treat hazardous wastes at Comprehensive Environmental Response, Compensation, and Liabil- ity Act (C...

  11. Design, Development and Evaluation of a Field Learning Video Blog

    ERIC Educational Resources Information Center

    Petrovic, Otto

    2016-01-01

    The research question in this paper is how a Field Learning Video Blog (FLvlog) has to be designed in order to optimize learning processes taking into account changed everyday communication habits of students. The system is designed to meet pedagogical as well as functional requirements for learning in fieldwork settings. The main difference to…

  12. Field Evaluation of a Mini Learning Resource Aided Instruction System.

    ERIC Educational Resources Information Center

    Attala, Emile E.; Howard, James A.

    Very little work has been done in the broad field of computer-assisted instruction (CAI) to exploring the use of a minicomputer as another learning resource in the instructional process. Accordingly a cost-effective Learning Resource Aided Instruction (LRAI) System centered around a Data General NOVA minicomputer augmented with slide…

  13. FIELD ANALYTICAL SCREENING PROGRAM: PCP METHOD - INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    The Field Analytical Screening Program (FASP) pentachlorophenol (PCP) method uses a gas chromatograph (GC) equipped with a megabore capillary column and flame ionization detector (FID) and electron capture detector (ECD) to identify and quantify PCP. The FASP PCP method is design...

  14. Developing and evaluating rapid field methods to estimate peat carbon

    Treesearch

    Rodney A. Chimner; Cassandra A. Ott; Charles H. Perry; Randall K. Kolka

    2014-01-01

    Many international protocols (e.g., REDD+) are developing inventories of ecosystem carbon stocks and fluxes at country and regional scales, which can include peatlands. As the only nationally implemented field inventory and remeasurement of forest soils in the US, the USDA Forest Service Forest Inventory and Analysis Program (FIA) samples the top 20 cm of organic soils...

  15. BIOREMEDIATION FIELD EVALUATION - HILL AIR FORCE BASE, UTAH

    EPA Science Inventory

    In 1990, the U.S. Environmental Protection Agency (EPA) established the Bioremediation Field Initiative as part of its overall strategy to increase the use of bioremediation to treat hazardous wastes at Comprehensive Environmental Response, Compensation, and Liabil- ity Act (C...

  16. FIELD EVALUATION OF DNAPL EXTRACTION TECHNOLOGIES: PROJECT OVERVIEW

    EPA Science Inventory

    Five DNAPL remediation technologies were evaluated at the Dover National Test Site, Dover AFB, Delaware. The technologies were cosolvent solubilization, cosolvent mobilization, surfactant solubilization, complex sugar flushing and air sparging/soil vapor extraction. The effectiv...

  17. FIELD EVALUATION OF DNAPL EXTRACTION TECHNOLOGIES: PROJECT OVERVIEW

    EPA Science Inventory

    Five DNAPL remediation technologies were evaluated at the Dover National Test Site, Dover AFB, Delaware. The technologies were cosolvent solubilization, cosolvent mobilization, surfactant solubilization, complex sugar flushing and air sparging/soil vapor extraction. The effectiv...

  18. FIELD VALIDATION OF SEDIMENT TOXCITY IDENTIFCATION AND EVALUATION METHODS

    EPA Science Inventory

    Sediment Toxicity Identification and Evaluation (TIE) methods have been developed for both porewaters and whole sediments. These relatively simple laboratory methods are designed to identify specific toxicants or classes of toxicants in sediments; however, the question of whethe...

  19. Evaluation study of the suitability of instrumentation to measure ambient NH3 concentrations under field conditions

    NASA Astrophysics Data System (ADS)

    Twigg, Marsailidh

    2017-04-01

    The uncertainties in emissions of ammonia (NH3) in Europe are large, partially due to the difficulty in monitoring of ambient concentrations due to its sticky nature. In the European Monitoring and Evaluation Program (EMEP) the current recommended guidelines to measure NH3 are by coated annular denuders with offline analysis. This method, however, is no longer used in most European countries and each one has taken a different strategy to monitor atmospheric ammonia due to the increase of commercial NH3 monitoring instrumentation available over the last 20 years. In June 2014, a 3 year project funded under the European Metrology Research Programme, "Metrology for Ammonia in Ambient Air" (MetNH3), started with the aim to develop metrological traceability for the measurement of NH3 in air from primary gas mixtures and instrumental standards to field application. This study presents the results from the field intercomparison (15 instruments) which was held in South East Scotland in August 2016 over an intensively managed grassland. The study compared active sampling methods to a meteorological traceable method which was developed during the project with the aim to produce a series of guidelines for ambient NH3 measurements. Preliminary results highlight both the importance of inlets and management of relative humidity in the measurement of ambient NH3 and of the requirement to carry out frequent intercomparison of NH3 instrumentation. Overall, it would be recommended from this study that a WMO-GAW world centre for NH3 would be established and support integration of standards into both routine and research measurements.

  20. BIOREMEDIATION FIELD EVALUATION: EIELSON AIR FORCE BASE, ALASKA (EPA/540/R-95/533)

    EPA Science Inventory

    This publication, one of a series presenting the findings of the Bioremediation Field Initiatives bioremediation field evaluations, provides a detailed summary of the evaluation conducted at the Eielson Air Force Base (AFB) Superfund site in Fairbanks, Alaska. At this site, the ...