4,630 research outputs found
Dynamics of O(N) Model in a Strong Magnetic Background Field as a Modified Noncommutative Field Theory
In the presence of a strong magnetic field, the effective action of a
composite scalar field in an scalar O(N) model is derived using two different
methods. First, in the framework of worldline formalism, the 1PI n-point vertex
function for the composites is determined in the limit of strong magnetic
field. Then, the n-point effective action of the composites is calculated in
the regime of lowest Landau level dominance. It is shown that in the limit of
strong magnetic field, the results coincide and an effective field theory
arises which is comparable with the conventional noncommutative field theory.
In contrast to the ordinary case, however, the UV/IR mixing is absent in this
modified noncommutative field theory.Comment: Latex file, 19 pp, no figur
High-Resolution Imaging and Optical Control of Bose-Einstein Condensates in an Atom Chip Magnetic Trap
A high-resolution projection and imaging system for ultracold atoms is
implemented using a compound silicon and glass atom chip. The atom chip is
metalized to enable magnetic trapping while glass regions enable high numerical
aperture optical access to atoms residing in the magnetic trap about 100
microns below the chip surface. The atom chip serves as a wall of the vacuum
system, which enables the use of commercial microscope components for
projection and imaging. Holographically generated light patterns are used to
optically slice a cigar-shaped magnetic trap into separate regions; this has
been used to simultaneously generate up to four Bose-condensates. Using
fluorescence techniques we have demonstrated in-trap imaging resolution down to
2.5 micronsComment: 4 pages, 5 figures, 12 reference
Effects of cold rolling (CR) and annealing time on microstructure and mechanical properties of AA 5052 aluminum alloy
In this paper, the influences of cold rolling and annealing time on the microstructure and mechanical behaviors of AA 5052 aluminum alloy were investigated. An aluminum sheet was cold-rolled at room temperature at 15, 30, and 45 % rolling reduction. The 45 % cold-rolled sample was subsequently annealed at 370 °C for 2, 4, and 6 h. The microstructure was observed using optical microscopy whereas the mechanical behaviors were evaluated through hardness and tensile tests. It was found that the equiaxed grains are severely elongated along the rolling direction with increased rolling reduction. The hardness and strength increase significantly with an increase of rolling reduction but the ductility decreases. The annealing treatment reduces hardness and strength but improves the ductility
Effects of cold rolling (CR) and annealing time on microstructure and mechanical properties of AA 5052 aluminum alloy
In this paper, the influences of cold rolling and annealing time on the microstructure and mechanical behaviors of AA 5052 aluminum alloy were investigated. An aluminum sheet was cold-rolled at room temperature at 15, 30, and 45 % rolling reduction. The 45 % cold-rolled sample was subsequently annealed at 370 °C for 2, 4, and 6 h. The microstructure was observed using optical microscopy whereas the mechanical behaviors were evaluated through hardness and tensile tests. It was found that the equiaxed grains are severely elongated along the rolling direction with increased rolling reduction. The hardness and strength increase significantly with an increase of rolling reduction but the ductility decreases. The annealing treatment reduces hardness and strength but improves the ductility
The H-alpha Luminosity Function and Star Formation Rate Volume Density at z=0.8 from the NEWFIRM H-alpha Survey
[Abridged] We present new measurements of the H-alpha luminosity function
(LF) and SFR volume density for galaxies at z~0.8. Our analysis is based on
1.18m narrowband data from the NEWFIRM H-alpha Survey, a comprehensive
program designed to capture deep samples of intermediate redshift emission-line
galaxies using narrowband imaging in the near-infrared. The combination of
depth ( erg s cm in H-alpha at
3) and areal coverage (0.82 deg) complements other recent H-alpha
studies at similar redshifts, and enables us to minimize the impact of cosmic
variance and place robust constraints on the shape of the LF. The present
sample contains 818 NB118 excess objects, 394 of which are selected as H-alpha
emitters. Optical spectroscopy has been obtained for 62% of the NB118 excess
objects. Empirical optical broadband color classification is used to sort the
remainder of the sample. A comparison of the LFs constructed for the four
individual fields reveals significant cosmic variance, emphasizing that
multiple, widely separated observations are required. The dust-corrected LF is
well-described by a Schechter function with L*=10^{43.00\pm0.52} ergs s^{-1},
\phi*=10^{-3.20\pm0.54} Mpc^{-3}, and \alpha=-1.6\pm0.19. We compare our
H-alpha LF and SFR density to those at z<1, and find a rise in the SFR density
\propto(1+z)^{3.4}, which we attribute to significant L* evolution. Our H-alpha
SFR density of 10^{-1.00\pm0.18} M_sun yr^{-1} Mpc^{-3} is consistent with UV
and [O II] measurements at z~1. We discuss how these results compare to other
H-alpha surveys at z~0.8, and find that the different methods used to determine
survey completeness can lead to inconsistent results. This suggests that future
surveys probing fainter luminosities are needed, and more rigorous methods of
estimating the completeness should be adopted as standard procedure.Comment: 19 pages (emulate-ApJ format), 16 figures, 5 tables, published in
ApJ. Modified to match ApJ versio
Anomalous metamagnetic-like transition in a FeRh/FePt interface occurring at T120 K in the field-cooled-cooling curves for low magnetic fields
We report on the magnetic properties of a special configuration of a FeRh
thin film. An anomalous behavior on the magnetisation vs. temperature was
observed when low magnetic fields are applied in the plane of a thin layer of
FeRh deposited on ordered FePt. The anomalous effect resembles a
metamagnetic transition and occur only in the field-cooled-cooling
magnetisation curve at temperatures near 120 K in samples without any heat
treatment.Comment: 7 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1008.195
Ultramicrobacteria Genome Database Project
Ultramicrobacteria (UMB) are a largely uncultured, globally abundant, and metabolically active group of bacteria. UMB have cell diameters â€0.3ÎŒm, cell volumes â€0.1 ÎŒm3, and small streamlined genomes. Recent findings indicate that UMB aid in bioremediation and nutrient cycling, but future investigations and comprehension of current findings are skewed by highly variable nomenclature and a lack of databases for functional, genomic, geochemical, or spatial data specific to candidate UMB. We aim to develop a user-friendly open-access database of various UMB candidates linked to an open-access online map where researchers can gather genomic, spatial, and geochemical data. Our comprehensive review of literature and genomic databases revealed several mis-identified UMB candidates, unique highly-conserved fermentation pathways, and novel membrane proteins. We are actively updating this resource and working to link this database to the K-base bioinformatics platform on the Oak Ridge National Laboratory Supercomputer. This database is one of the first steps towards further investigations of the function, structure, and potential biotechnical applications of UMB
- âŠ