38,771 research outputs found
Effects of Nitrogen Quenching Gas on Spin-Exchange Optical Pumping of He-3
We consider the degree of conservation of nuclear spin polarization in the
process of optical pumping under typical spin-exchange optical pumping
conditions. Previous analyses have assumed that negligible nuclear spin
precession occurs in the brief periods of time the alkali-metal atoms are in
the excited state after absorbing photons and before undergoing quenching
collisions with nitrogen molecules. We include excited-state hyperfine
interactions, electronic spin relaxation in collisions with He and N_2,
spontaneous emission, quenching collisions, and a simplified treatment of
radiation trapping
Electromagnetic Polarizabilities: Lattice QCD in Background Fields
Chiral perturbation theory makes definitive predictions for the extrinsic
behavior of hadrons in external electric and magnetic fields. Near the chiral
limit, the electric and magnetic polarizabilities of pions, kaons, and nucleons
are determined in terms of a few well-known parameters. In this limit, hadrons
become quantum mechanically diffuse as polarizabilities scale with the inverse
square-root of the quark mass. In some cases, however, such predictions from
chiral perturbation theory have not compared well with experimental data.
Ultimately we must turn to first principles numerical simulations of QCD to
determine properties of hadrons, and confront the predictions of chiral
perturbation theory. To address the electromagnetic polarizabilities, we
utilize the background field technique. Restricting our attention to
calculations in background electric fields, we demonstrate new techniques to
determine electric polarizabilities and baryon magnetic moments for both
charged and neutral states. As we can study the quark mass dependence of
observables with lattice QCD, the lattice will provide a crucial test of our
understanding of low-energy QCD, which will be timely in light of ongoing
experiments, such as at COMPASS and HI\gamma S.Comment: 3 pages, talk given by B. C. Tiburzi at PANIC 201
Extracting Electric Polarizabilities from Lattice QCD
Charged and neutral, pion and kaon electric polarizabilities are extracted
from lattice QCD using an ensemble of anisotropic gauge configurations with
dynamical clover fermions. We utilize classical background fields to access the
polarizabilities from two-point correlation functions. Uniform background
fields are achieved by quantizing the electric field strength with the proper
treatment of boundary flux. These external fields, however, are implemented
only in the valence quark sector. A novel method to extract charge particle
polarizabilities is successfully demonstrated for the first time.Comment: 17 pages, 6 figures, a few clarifications added, published versio
Hydrocarbons identified in extracts from estuarine water accommodated no. 2 fuel oil by gas chromatography-mass spectrometry
Results are presented on a computerized gas chromatograph-mass spectrometer analysis of methylene chloride and n-heptane extracts of a No. 2 fuel oil accommodated estuarine water sample. The analytical method is briefly described, and the limitations on the identifications are categorized. Some attempt was made to determine major and trace constituents in the water accommodate. Altogether 66 hydrocarbon compounds were identified specifically, and 75 compounds were partially identified. Seven compounds could be recognized as major constituents of the water accommodated oil and ten were present only as traces. The aromatic compounds found were alkyl benzenes, naphthalene, tetralin, indane, biphenyl, fluorene, anthracene, and some of their alkyl substituted isomers in the range of carbon numbers C7 to C15. Four n-alkanes, C10 to C13, were found along with four other assorted hydrocarbons
Static axisymmetric spacetimes with non-generic world-line SUSY
The conditions for the existence of Killing-Yano tensors, which are closely
related to the appearance of non-generic world-line SUSY, are presented for
static axisymmetric spacetimes. Imposing the vacuum Einstein equation, the set
of solutions admitting Killing-Yano tensors is considered. In particular, it is
shown that static, axisymmetric and asymptotically flat vacuum solutions
admitting Killing-Yano tensors are only the Schwarzschild solution.Comment: 10 pages (RevTeX), TIT/HEP-253/COSMO-4
Methodology of measuring internal contamination in spacecraft hardware Final report
Methodology of measuring internal contamination in spacecraft hardwar
Electromagnetic and spin polarisabilities in lattice QCD
We discuss the extraction of the electromagnetic and spin polarisabilities of
nucleons from lattice QCD. We show that the external field method can be used
to measure all the electromagnetic and spin polarisabilities including those of
charged particles. We then turn to the extrapolations required to connect such
calculations to experiment in the context of finite volume chiral perturbation
theory. We derive results relevant for lattice simulations of QCD,
partially-quenched QCD and quenched QCD. Our results for the polarisabilities
show a strong dependence on the lattice volume and quark masses, typically
differing from the infinite volume limit by ~10% for current lattice volumes
and quark masses.Comment: Minor change
Evaluation of a Brazilian fuel alcohol yeast strain for Scotch whisky fermentations
Traditionally, distilling companies in Scotland have employed a very limited number of yeast strains in the production of alcohol for Scotch whiskies. Recent changes such as the decline in availability of brewers’ yeast as a secondary yeast strain and the availability of yeast in different formats (e.g., dried and cream yeast as alternatives to compressed yeast) have promoted interest in alternative Scotch whisky distilling yeasts. In previous work, we investigated different strains of yeasts, specifically Brazilian yeasts which had been isolated from and used in fuel alcohol distilleries. One of the Brazilian yeasts (CAT 1) showed a comparable fermentation performance and superior stress tolerance compared with a standard commercial Scotch whisky distilling yeast (M Type). The Brazilian CAT 1 yeast isolate was further assessed in laboratory scale fermentations and subsequent new make spirit was subjected to sensory analyses. The spirits produced using the Brazilian strain had acceptable flavour profiles and exhibited no sensory characteristics that were atypical of Scotch whisky new make spirit. This study highlights the potential of exploiting yeast biodiversity in traditional Scotch whisky distillery fermentation processes
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