1,549 research outputs found
Investigating L-Amino Acid Enantiomeric Excess in CM and CR Carbonaceous Chondrites
The Ninth Symposium on Polar Science/Ordinary sessions: [OA] Antarctic meteorites / Hayabusa, Wed. 5 Dec. / Conference hall of the Research/Administration Building (2nd floor) at the JAXA Sagamihara Campu
Theory of Neutron Diffraction from the Vortex Lattice in UPt3
Neutron scattering experiments have recently been performed in the
superconducting state of UPt3 to determine the structure of the vortex lattice.
The data show anomalous field dependence of the aspect ratio of the unit cell
in the B phase. There is apparently also a change in the effective coherence
length on the transition from the B to the C phases. Such observations are not
consistent with conventional superconductvity. A theory of these results is
constructed based on a picture of two-component superconductivity for UPt3. In
this way, these unusual observations can be understood. There is a possible
discrepancy between theory and experiment in the detailed field dependence of
the aspect ratio.Comment: 11 pages; uses REVTEX, APS and PRABIB styles; 2 Postscript figure
files include
High-energy Auger line shapes of Pd and Rh: experiment and theory
FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSWe compare nonrelativistic atomic multiplet calculations of the L1,2,3M4,5M4,5 spectra of Rh and Pd in the jj intermediate-coupling scheme with high-resolution experimental spectra excited with a Ti anode, indicating general, good agreement even for these open valence shell metals: the simplicity of the calculations indicates their suitability for experimental analyses. Comparison with relativistic calculations, including configuration interaction, for Rh indicates that the nonrelativistic spectra appear to agree better with the experimental data than do the relativistic ones. The influence of relativistic and correlation effects on the intensities does not seem to be important. The major influence on the forms of the spectra is that of the relative positions of the multiplet components. Satellites of all three spectra would seem to be produced by shake-up, rather than Coster-Kronig processes. The positions and forms of these satellites are consistent with a model in which spectator vacancies in the 4d band exist in both the initial and final states of the Auger transitionWe compare nonrelativistic atomic multiplet calculations of the L1,2,3M4,5M4,5 spectra of Rh and Pd in the ii intermediate-coupling scheme with high-resolution experimental spectra excited with a Ti anode, indicating general, good agreement even for these open valence shell metals: the simplicity of the calculations indicates their suitability for experimental analyses. Comparison with relativistic calculations, including configuration interaction, for Rh indicates that the nonrelativistic spectra appear to agree better with the experimental data than do the relativistic ones. The influence of relativistic and correlation effects on the intensities does not seem to be important. The major influence on the forms of the spectra is that of the relative positions of the multiplet components. Satellites of all three spectra would seem to be produced by shake-up, rather than Coster-Kronig processes. The positions and forms of these satellites are consistent with a model in which spectator vacancies in the 4d band exist in both the initial and final states of the Auger transition. [S0163-1829(98)02548-X].58241610316109FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSSem informaçãoSem informaçãoSem informaçã
Stress balance in nano-patterned N/Cu(001) surfaces
We employ helium atom scattering (HAS) and density functional theory (DFT)
based on the ultrasoft pseudopotential scheme and the plane-wave basis set to
investigate the strain and stress balance in nano-patterned N/Cu(001) surfaces.
HAS shows that, with increasing N coverage (and decreasing stripe widths), the
stress-relief-driven lateral expansion of the averaged lattice parameter within
finite-sized N-containing patches reduces from 3.5% to 1.8% and that, beyond a
critical exposure, the lateral expansion of the patches increases again
slightly, to 2.4%. The latter implies that in this higher coverage range the
compressive stress is partially relieved via another mechanism, which turns out
to be nucleation of Cu-vacancy trenches. In full agreement with the above and
previous experimental observations, DFT calculations show that an optimized
N-induced c(2\times2) structure has a net surface stress level of 4.2 N/m and
such stress is effectively relieved when stripes of clean Cu(001) form along
the direction or when trench-like steps of Cu atoms form along the
direction. Additionally, the calculations demonstrate that (contrary to earlier
suggestions) rumpling displacements within the outermost Cu layer do not act to
relieve the compressive surface stress levels and that, while clock-like
displacements could relieve stress levels, such displacements are energetically
unstable
STUDY OF AMORPHOUS GERMANIUM-NITROGEN ALLOYS THROUGH X-RAY PHOTOELECTRON AND AUGER ELECTRON SPECTROSCOPIES
In this work, experimentally determined values of electron spectroscopic shifts induced by nitrogen in Ge core levels of substoichiometric amorphous germanium-nitrogen (a-GeN) alloys are discussed and presented. X-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XAES) are employed to study the behavior of the Ge 3d and LMM spectra, respectively, and combined the corresponding XPS and Auger core levels shifts to determine Δα′, the modified Auger parameter shift, which is exempt from problems inherent in the interpretation of XPS and XAES shifts. It is demonstrated how one can use Δα′ to reliably estimate ΔnGe, the change in Ge valence charge in the alloys, and how one can calibrate XPS shifts of Si and Ge based alloys in terms of approximate values of ΔnGe
Arithmetically Cohen-Macaulay Bundles on complete intersection varieties of sufficiently high multidegree
Recently it has been proved that any arithmetically Cohen-Macaulay (ACM)
bundle of rank two on a general, smooth hypersurface of degree at least three
and dimension at least four is a sum of line bundles. When the dimension of the
hypersurface is three, a similar result is true provided the degree of the
hypersurface is at least six. We extend these results to complete intersection
subvarieties by proving that any ACM bundle of rank two on a general, smooth
complete intersection subvariety of sufficiently high multi-degree and
dimension at least four splits. We also obtain partial results in the case of
threefolds.Comment: 15 page
Review of Multi-Person Exposure Calls to a Regional Poison Control Center
Objective: Poisoning events, including exposures to hazardous materials, can involve multiple victims. Regional poison centers often are contacted in such events involving multiple victims. Methods: We searched our poison center database over a nine-year time period for all calls involving a poisoning event in which more than two people were exposed to the same substance. We then matched each product to the generic category used by the National Poison Data System. We analyzed this data to find the most frequent substances reported as primary substances in the multiple exposures. Results: We identified 6,695 calls between 2000 and 2008 that had more than two people exposed to the same substance. In these calls, 25,926 people were exposed (3.6 % of the 715,701 human exposure calls for this period). These calls involved 64 of the 67 NPDS substance group codes. Some substances were much more commonly involved than others. The top three categories causing the most exposures were Fumes/Gases/Vapors, Food Products/Food Poisoning and Pesticides. Of the patients exposed, 69.4 % were not followed due to minimal effects possible or judged as nontoxic, 0.3 % had major effects, 8.6 % had no effects, and 9.3 % had minimal to moderate effects. Eight people expired. Conclusion: Fumes, gases, and vapors make up the majority of multi-exposure calls. The overall mortality from multi-exposures, based on our data, is low. Analysis of these calls can help poison centers better understand these events and direct training. [West J Emerg Med. 2010; 11(3):291-293.
Nonrelativistic double photoeffect on lithiumlike ions at high energies
The total cross section for double ionization of lithiumlike ions by a
high-energy photon is calculated in leading order of the nonrelativistic
perturbation theory. The partial contributions due to simultaneous and
sequential emissions of two electrons are taken into account. The cross section
under consideration is shown to be related to those for double photoeffect on
the ground and excited 2^{1,3}S states of heliumlike ions. The double-to-single
ionization ratio is equal to R = 0.288/Z^2 for lithiumlike ions with moderate
nuclear charge numbers Z. However, even for the lightest three-electron targets
such as Li and Be^+, analytical predictions are found to be in good agreement
with the numerical calculations performed within the framework of different
rather involved approaches.Comment: 12 pages, 2 figures. to be published in Physics Letters
Mechanism of thermally activated c-axis dissipation in layered High-T superconductors at high fields
We propose a simple model which explains experimental behavior of -axis
resistivity in layered High-T superconductors at high fields in a limited
temperature range. It is generally accepted that the in-plane dissipation at
low temperatures is caused by small concentration of mobile pancake vortices
whose diffusive motion is thermally activated. We demonstrate that in such
situation a finite conductivity appears also in -direction due to the phase
slips between the planes caused by the mobile pancakes. The model gives
universal relation between the components of conductivity which is in good
agreement with experimental data.Comment: RevTeX, 4 pages, 2 Postscript figure
Integral Grothendieck-Riemann-Roch theorem
We show that, in characteristic zero, the obvious integral version of the
Grothendieck-Riemann-Roch formula obtained by clearing the denominators of the
Todd and Chern characters is true (without having to divide the Chow groups by
their torsion subgroups). The proof introduces an alternative to Grothendieck's
strategy: we use resolution of singularities and the weak factorization theorem
for birational maps.Comment: 24 page
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