145 research outputs found
A Comparison Between The NORCAT Rover Test Results and the ISRU Excavation System Model Predictions Results
An Excavation System Model has been written to simulate the collection and transportation of regolith on the moon. The calculations in this model include an estimation of the forces on the digging tool as a result of excavation into the regolith. Verification testing has been performed and the forces recorded from this testing were compared to the calculated theoretical data. The Northern Centre for Advanced Technology Inc. rovers were tested at the NASA Glenn Research Center Simulated Lunar Operations facility. This testing was in support of the In-Situ Resource Utilization program Innovative Partnership Program. Testing occurred in soils developed at the Glenn Research Center which are a mixture of different types of sands and whose soil properties have been well characterized. This testing is part of an ongoing correlation of actual field test data to the blade forces calculated by the Excavation System Model. The results from this series of tests compared reasonably with the predicted values from the code
Resonant soft X-ray Raman scattering of NiO
Resonant soft X-ray Raman scattering measurements on NiO have been made at
photon energies across the Ni 2p absorption edges. The details of the spectral
features are identified as Raman scattering due to d-d and charge-transfer
excitations. The spectra are interpreted within the single impurity Anderson
model, including multiplets, crystal-field and charge-transfer effects. At
threshold excitation, the spectral features consists of triplet-triplet and
triplet-singlet transitions of the 3d8 configuration. For excitation energies
corresponding to the charge-transfer region in the Ni 2p X-ray absorption
spectrum of NiO, the emission spectra are instead dominated by charge-transfer
transitions to the 3d9L-1 final state. Comparisons of the final states with
other spectroscopical techniques are also made.Comment: 9 pages, 2 figures, 2 tables,
http://iopscience.iop.org/0953-8984/14/13/32
The electronic structure of polyaniline and doped phases studied by soft X-ray absorption and emission spectroscopies
The electronic structure of the conjugated polymer, polyaniline, has been
studied by resonant and nonresonant X-ray emission spectroscopy using
synchrotron radiation for the excitation. The measurements were made on
polyaniline and a few doped (protonated) phases for both the carbon and
nitrogen contents. The resonant X-ray emission spectra show depletion of the
{\pi} electron bands due to the selective excitation which enhances the effect
of symmetry selection rules. The valence band structures in the X-ray emission
spectra attributed to the {\pi} bands show unambiguous changes of the
electronic structure upon protonation. By comparing to X-ray absorption
measurements, the chemical bonding and electronic configuration is
characterized.Comment: 8 pages, 8 pictures,
http://jcp.aip.org/resource/1/jcpsa6/v111/i10/p4756_s
Polarized x-ray absorption spectra of CuGeO3 at the Cu and Ge K edges
Polarized x-ray absorption near edge structure (XANES) spectra at both the Cu
and the Ge K-edges of CuGeO3 are measured and calculated relying on the
real-space multiple-scattering formalism within a one-electron approach. The
polarization components are resolved not only in the unit cell coordinate
system but also in a local frame attached to the nearest neighborhood of the
photoabsorbing Cu atom. In that way, features which resist a particular
theoretical description can be identified. We have found that it is the
out-of-CuO4-plane p_{z'} component which defies the one-electron calculation
based on the muffin-tin potential. For the Ge K-edge XANES, the agreement
between the theory and the experiment appears to be better for those
polarization components which probe more compact local surroundings than for
those which probe regions with lower atomic density. Paper published in Phys.
Rev. B 66, 155119 (2002) and available on-line at
http://link.aps.org/abstract/PRB/v66/e155119.Comment: 15 pages, 6 figures. Published in Physical Review B, abstract
available on-line at http://link.aps.org/abstract/PRB/e15511
Volatiles from Maruca vitrata (Lepidoptera, Crambidae) host plants influence olfactory responses of the parasitoid Therophilus javanus (Hymenoptera, Braconidae, Agathidinae)
Open Access Article; Published online: 9 Nov 2018.Plants damaged by herbivores are known to release odors attracting parasitoids. However, there is currently no information how leguminous plants damaged by the pod borer Maruca vitrata attract the exotic larval parasitoid Therophilus javanus, which was imported into Benin from the putative area of origin of the pod borer in tropical Asia for assessing its potential as a biological control agent. In this study, we used Y-tube olfactometer bioassays to investigate T. javanus response towards odors emitted by four M. vitrata-damaged host plants: cowpea Vigna unguiculata, the most important cultivated host, and the naturally occurring legumes Lonchocarpus sericeus, Sesbania rostrata and Tephrosia platycarpa. Olfactory attraction of T. javanus was influenced by the species of plant damaged by the pod borer. Moreover, odors released from M. vitrata-infested host plant organs (flowers and pods) were discriminated over non-infested organs in cowpea and T. platycarpa, respectively. These results are discussed in the context of the possible impact of M. vitrata host plants on T. javanus foraging activity and subsequent establishment in natural environments following experimental releases
Welfare Impact of Carbon Dioxide Euthanasia on Laboratory Mice and Rats : A Systematic Review
Background: There has been increased concern about the suitability of CO as a method for euthanasia of laboratory mice and rats, including the potential discomfort, pain or distress that animals may experience prior to loss of consciousness; time to loss of consciousness; best methods for use of CO; and the availability of better alternatives. These discussions have been useful in providing new information, but have resulted in significant confusion regarding the acceptability of CO for rodent euthanasia. In some cases, researchers and veterinarians have become uncertain as to which techniques to recommend or use for euthanasia of laboratory mice and rats. Methods: The International Association of Colleges of Laboratory Animal Medicine (IACLAM) convened a taskforce to examine the evidence for adverse welfare indicators in laboratory rats and mice undergoing CO euthanasia using a SYRCLE-registered systematic review protocol. Of 3,772 papers identified through a database search (PubMed, Web of Science, CAB Direct, Agricola, and grey literature) from 1900 to 2017, 37 studies were identified for detailed review (some including more than one species or age group), including 15 in adult mice, 21 in adult rats, and 5 in neonates of both species. Experiments or reports were excluded if they only assessed parameters other than those directly affecting animal welfare during CO induction and/or euthanasia. Results: Study design and outcome measures were highly variable and there was an unclear to high risk of bias in many of the published studies. Changes in the outcome measures evaluated were inconsistent or poorly differentiated. It is likely that repeated exposures to carbon dioxide inhalation are aversive to adult rats and mice, based on avoidance behavior studies; however, this effect is largely indistinguishable from aversion induced by repeated exposures to other inhalant anesthetic gasses. Conclusion: There is insufficient evidence to permit an unbiased assessment of the effect of CO inhalation during euthanasia on welfare indicators in laboratory mice and rats. Additional well-designed, unbiased, and adequately powered studies are needed to accurately assess the welfare of laboratory mice and rats undergoing euthanasia via CO gas
Resonant inelastic soft-x-ray scattering spectra at the N1s and C1s edges of poly(pyridine-2,5-diyl)
Resonant inelastic scattering measurements of poly(pyridine-2,5-diyl) have
been performed at the N1s and C1s edges using synchrotron radiation. For
comparison, molecular orbital calculations of the spectra have been carried out
with the repeat unit as a model molecule of the polymer chain. The resonant
emission spectra show depletion of the p electron bands which is consistent
with symmetry selection and momentum conservation rules. The depletion is most
obvious in the resonant inelastic scattering spectra of carbon while the
nitrogen spectra are dominated by lone pair n orbital emission of s symmetry
and are less excitation energy dependent. By comparing the measurements to
calculations an isomeric dependence of the resonant spectra is found giving
preference to two of the four possible isomers in the polymer.Comment: 6 pages, 3 figures,
http://www.sciencedirect.com/science/article/pii/S036820489800354
The electronic structure of poly(pyridine-2,5-diyl) investigated by soft x-ray absorption and emission spectroscopies
The electronic structure of the poly-pyridine conjugated polymer has been
investigated by resonant and nonresonant inelastic X-ray scattering and X-ray
absorption spectroscopies using synchrotron radiation. The measurements were
made for both the carbon and nitrogen contents of the polymer. The analysis of
the spectra has been carried out in comparison with molecular orbital
calculations taking the repeat-unit cell as a model molecule of the polymer
chain. The simulations indicate no significant differences in the absorption
and in the non-resonant X-ray scattering spectra for the different isomeric
geometries, while some isomeric dependence of the resonant spectra is
predicted. The resonant emission spectra show depletion of the {\pi} electron
bands in line with symmetry selection and momentum conservation rules. The
effect is most vizual for the carbon spectra; the nitrogen spectra are
dominated by lone pair n orbital emission of {\sigma} symmetry and are less
frequency dependent.Comment: 11 pages, 7 figures, 1 table,
http://www.sciencedirect.com/science/article/pii/S030101049800262
A Spontaneous Mutation of the Rat Themis Gene Leads to Impaired Function of Regulatory T Cells Linked to Inflammatory Bowel Disease
Spontaneous or chemically induced germline mutations, which lead to Mendelian phenotypes, are powerful tools to discover new genes and their functions. Here, we report an autosomal recessive mutation that occurred spontaneously in a Brown-Norway (BN) rat colony and was identified as causing marked T cell lymphopenia. This mutation was stabilized in a new rat strain, named BNm for “BN mutated.” In BNm rats, we found that the T cell lymphopenia originated in the thymus, was intrinsic to CD4 T lymphocytes, and was associated with the development of an inflammatory bowel disease. Furthermore, we demonstrate that the suppressive activity of both peripheral and thymic CD4+ CD25bright regulatory T cells (Treg) is defective in BNm rats. Complementation of mutant animals with BN Treg decreases disease incidence and severity, thus suggesting that the impaired Treg function is involved in the development of inflammatory bowel disease in BNm rats. Moreover, the cytokine profile of effector CD4 T cells is skewed toward Th2 and Th17 phenotypes in BNm rats. Linkage analysis and genetic dissection of the CD4 T cell lymphopenia in rats issued from BNm×DA crosses allowed the localization of the mutation on chromosome 1, within a 1.5 megabase interval. Gene expression and sequencing studies identified a frameshift mutation caused by a four-nucleotide insertion in the Themis gene, leading to its disruption. This result is the first to link Themis to the suppressive function of Treg and to suggest that, in Themis-deficient animals, defect of this function is involved in intestinal inflammation. Thus, this study highlights the importance of Themis as a new target gene that could participate in the pathogenesis of immune diseases characterized by chronic inflammation resulting from a defect in the Treg compartment
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