4,167 research outputs found
Non-LTE Spectral Analysis of Extremely Hot Post-AGB Stars: Constraints for Evolutionary Theory
Spectral analysis by means of Non-LTE model-atmosphere techniques has arrived
at a high level of sophistication: fully line-blanketed model atmospheres which
consider opacities of all elements from H to Ni allow the reliable
determination of photospheric parameters of hot, compact stars. Such models
provide a crucial test of stellar evolutionary theory: recent abundance
determinations of trace elements like, e.g., F, Ne, Mg, P, S, Ar, Fe, and Ni
are suited to investigate on AGB nucleosynthesis. E.g., the strong Fe depletion
found in hydrogen-deficient post-AGB stars is a clear indication of an
efficient s-process on the AGB where Fe is transformed into Ni or even heavier
trans iron-group elements. We present results of recent spectral analyses based
on high-resolution UV observations of hot stars.Comment: 6 pages, 2 figure
Probing Gluonic Spin-Orbit Correlations in Photon Pair Production
We consider photon pair production in hadronic collisions at large mass and
small transverse momentum of the pair, assuming that factorization in terms of
transverse momentum dependent parton distributions applies. The unpolarized
cross section is found to have azimuthal angular dependencies that are
generated by a gluonic version of the Boer-Mulders function. In addition, the
single-transversely polarized cross section is sensitive to the gluon Sivers
function. We present simple numerical estimates for the Boer-Mulders and Sivers
effects in diphoton production at RHIC and find that the process would offer
unique opportunities for exploring transverse momentum dependent gluon
distributions.Comment: 5 pages, 2 figures, minor changes, final version, to be published in
PR
Characterization of a Second Bovine Rotavirus Serotype
Bovine rotavirus (BRV) V 1005 was characterized by two-way cross-neutralization tests as a second serotype of BRV. Virions and inner shell particles of 65 nm and 55 nm diameter respectively, and empty capsids of 65 nm and 55 nm diameter were separated by density gradient centrifugation. Three polypeptides of molecular weight 60,000, 36,000 and 28,000 (minor protein) could be identified in the outer shell of virions and in the larger empty capsids. Inner shell particles contained three polypeptides of molecular weight 105,000, 83,000 and 43,000. Both sizes of empty capsids showed two polypeptides of molecular weight 75,000 and 55,000 not found in virions. Pulse-labelling of infected cells revealed eight major and three minor intracellular viral polypeptides. Viral polypeptide synthesis started at about 6 hours p.i. and correlated in time with double-stranded RNA synthesis. As soon as viral polypeptide synthesis was detectable, newly synthesized viral polypeptides were incorporated into intracellular viral particles. Radioactive viral polypeptides appeared without a longer lag period in extracellular viruses from 6 hours p.i. onward
Linearly Polarized Gluons and the Higgs Transverse Momentum Distribution
We study how gluons carrying linear polarization inside an unpolarized hadron
contribute to the transverse momentum distribution of Higgs bosons produced in
hadronic collisions. They modify the distribution produced by unpolarized
gluons in a characteristic way that could be used to determine whether the
Higgs boson is a scalar or a pseudoscalar particle.Comment: 4 pages, 3 figures, final version, published in PR
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