1,315 research outputs found
Finite E x beta Jahn-Teller Systems: A Continued-Fraction Approach
A recursive method is developed to treat electrons coupled to phonons. It is
applied to small systems with Jahn-Teller coupling. Two cases
are considered, a model with one electron and two orbitals on a single site
(related to the Rabi Hamiltonian) and a model with two electrons on two sites.
The corresponding Green's functions are represented by rational functions. It
is found that the spectra change substantially when one phonon couples to the
electron but are relatively robust under an increasing number of phonons.Comment: 15 pages, 7 figure
Spatially resolved simulation of a radio frequency driven micro atmospheric pressure plasma jet and its effluent
Radio frequency driven plasma jets are frequently employed as efficient
plasma sources for surface modification and other processes at atmospheric
pressure. The radio-frequency driven micro atmospheric pressure plasma jet
(APPJ) is a particular variant of that concept whose geometry allows
direct optical access. In this work, the characteristics of the APPJ
operated with a helium-oxygen mixture and its interaction with a helium
environment are studied by numerical simulation. The density and temperature of
the electrons, as well as the concentration of all reactive species are studied
both in the jet itself and in its effluent. It is found that the effluent is
essentially free of charge carriers but contains a substantial amount of
activated oxygen (O, O and O). The simulation results are
verified by comparison with experimental data
Breast cancer risk among first-generation migrants in the Netherlands
We investigated breast cancer incidence in migrants in the Netherlands in 1988-1998. The standardised incidence ratio for breast cancer in Northwest-Netherlands was statistically significantly reduced for women born in Surinam (0.56), Turkey (0.29) and Morocco (0.22). The proportion of women with advanced stages (III and IV) did not differ significantly between migrants and women born in the Netherlands
Jacobson generators, Fock representations and statistics of sl(n+1)
The properties of A-statistics, related to the class of simple Lie algebras
sl(n+1) (Palev, T.D.: Preprint JINR E17-10550 (1977); hep-th/9705032), are
further investigated. The description of each sl(n+1) is carried out via
generators and their relations, first introduced by Jacobson. The related Fock
spaces W_p (p=1,2,...) are finite-dimensional irreducible sl(n+1)-modules. The
Pauli principle of the underlying statistics is formulated. In addition the
paper contains the following new results: (a) The A-statistics are interpreted
as exclusion statistics; (b) Within each W_p operators B(p)_1^\pm, ...,
B(p)_n^\pm, proportional to the Jacobson generators, are introduced. It is
proved that in an appropriate topology the limit of B(p)_i^\pm for p going to
infinity is equal to B_i^\pm, where B_i^\pm are Bose creation and annihilation
operators; (c) It is shown that the local statistics of the degenerated
hard-core Bose models and of the related Heisenberg spin models is p=1
A-statistics.Comment: LaTeX-file, 33 page
Sizes and ages of SDSS ellipticals: Comparison with hierarchical galaxy formation models
In a sample of about 45,700 early-type galaxies extracted from SDSS, we find
that the shape, normalization, and dispersion around the mean size-stellar mass
relation is the same for young and old systems, provided the stellar mass is
greater than 3*10^10 Msun. This is difficult to reproduce in pure passive
evolution models, which generically predict older galaxies to be much more
compact than younger ones of the same stellar mass. However, this aspect of our
measurements is well reproduced by hierarchical models of galaxy formation.
Whereas the models predict more compact galaxies at high redshifts, subsequent
minor, dry mergers increase the sizes of the more massive objects, resulting in
a flat size-age relation at the present time. At lower masses, the models
predict that mergers are less frequent, so that the expected anti-correlation
between age and size is not completely erased. This is in good agreement with
our data: below 3*10^10 Msun, the effective radius R_e is a factor of ~2 lower
for older galaxies. These successes of the models are offset by the fact that
the predicted sizes have other serious problems, which we discuss.Comment: 13 pages, 9 Figures, 1 Table. Accepted by MNRA
High-energy scissors mode
All the orbital M1 excitations, at both low and high energies, obtained from
a rotationally invariant QRPA, represent the fragmented scissors mode. The
high-energy M1 strength is almost purely orbital and resides in the region of
the isovector giant quadrupole resonance. In heavy deformed nuclei the
high-energy scissors mode is strongly fragmented between 17 and 25 MeV (with
uncertainties arising from the poor knowledge of the isovector potential). The
coherent scissors motion is hindered by the fragmentation and for single transitions in this region. The cross
sections for excitations above 17 MeV are one order of magnitude larger for E2
than for M1 excitations even at backward angles.Comment: 20 pages in RevTEX, 5 figures (uuencoded,put with 'figures') accepted
for publication in Phys.Rev.
Methodological considerations in the analysis of fecal glucocorticoid metabolites in tufted capuchins (Cebus apella)
Analysis of fecal glucocorticoid (GC) metabolites has recently become the standard method to monitor adrenocortical activity in primates noninvasively. However, given variation in the production, metabolism, and excretion of GCs across species and even between sexes, there are no standard methods that are universally applicable. In particular, it is important to validate assays intended to measure GC production, test extraction and storage procedures, and consider the time course of GC metabolite excretion relative to the production and circulation of the native hormones. This study examines these four methodological aspects of fecal GC metabolite analysis in tufted capuchins (Cebus apella). Specifically, we conducted an adrenocorticotrophic hormone (ACTH) challenge on one male and one female capuchin to test the validity of four GC enzyme immunoassays (EIAs) and document the time course characterizing GC me- tabolite excretion in this species. In addition, we compare a common field-friendly technique for extracting fecal GC metabolites to an established laboratory extraction methodology and test for effects of storing “field extracts” for up to 1 yr. Results suggest that a corticosterone EIA is most sensitive to changes in GC production, provides reliable measures when extracted according to the field method, and measures GC metabolites which remain highly stable after even 12 mo of storage. Further, the time course of GC metabolite excretion is shorter than that described yet for any primate taxa. These results provide guidelines for studies of GCs in tufted capuchins, and underscore the importance of validating methods for fecal hormone analysis for each species of interest
Compression of Antiproton Clouds for Antihydrogen Trapping
Control of the radial profile of trapped antiproton clouds is critical to
trapping antihydrogen. We report the first detailed measurements of the radial
manipulation of antiproton clouds, including areal density compressions by
factors as large as ten, by manipulating spatially overlapped electron plasmas.
We show detailed measurements of the near-axis antiproton radial profile and
its relation to that of the electron plasma
Genomeâ Wide Study of Subcutaneous and Visceral Adipose Tissue Reveals Novel Sexâ Specific Adiposity Loci in Mexican Americans
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141319/1/oby22074.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141319/2/oby22074_am.pd
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