14,430 research outputs found
Unraveling quantum dissipation in the frequency domain
We present a quantum Monte Carlo method for solving the evolution of an open
quantum system. In our approach, the density operator evolution is unraveled in
the frequency domain. Significant advantages of this approach arise when the
frequency of each dissipative event conveys information about the state of the
system.Comment: 4 pages, 4 Postscript figures, uses RevTe
Ceramides: a new player in the inflammation-insulin resistance paradigm?
No abstract available
The Nature of Superfluidity in Ultracold Fermi Gases Near Feshbach Resonances
We study the superfluid state of atomic Fermi gases using a BCS-BEC crossover
theory. Our approach emphasizes non-condensed fermion pairs which strongly
hybridize with their (Feshbach-induced) molecular boson counterparts. These
pairs lead to pseudogap effects above and non-BCS characteristics below.
We discuss how these effects influence the experimental signatures of
superfluidity.Comment: 4 pages, 3 figures, submitted to PRA Rapid Communications;
introduction rewritten, figure replace
An Updated Ultraviolet Calibration for the Swift/UVOT
We present an updated calibration of the Swift/UVOT broadband ultraviolet
(uvw1, uvm2, and uvw2) filters. The new calibration accounts for the ~1% per
year decline in the UVOT sensitivity observed in all filters, and makes use of
additional calibration sources with a wider range of colours and with HST
spectrophotometry. In this paper we present the new effective area curves and
instrumental photometric zeropoints and compare with the previous calibration.Comment: 4 pages, 3 figures, 2 tables. Presented at GRB 2010 symposium,
Annapolis, November 2010 to be published in American Institute of Physics
Conference Serie
Effect of continuous gamma-ray exposure on performance of learned tasks and effect of subsequent fractionated exposures on blood-forming tissue
Sixteen monkeys trained to perform continuous and discrete-avoidance and fixed-ratio tasks with visual and auditory cues were performance-tested before, during, and after 10-day gamma-ray exposures totaling 0, 500, 750, and 1000 rads. Approximately 14 months after the performance-test exposures, surviving animals were exposed to 100-rad gamma-ray fractions at 56-day intervals to observe injury and recovery patterns of blood-forming tissues. The fixed-ratio, food-reward task performance showed a transient decline in all dose groups within 24 hours of the start of gamma-ray exposure, followed by recovery to normal food-consumption levels within 48 to 72 hours. Avoidance tasks were performed successfully by all groups during the 10-day exposure, but reaction times of the two higher dose-rate groups in which animals received 3 and 4 rads per hour or total doses of 750 and 1000 rads, respectively, were somewhat slower
Enhanced winnings in a mixed-ability population playing a minority game
We study a mixed population of adaptive agents with small and large memories,
competing in a minority game. If the agents are sufficiently adaptive, we find
that the average winnings per agent can exceed that obtainable in the
corresponding pure populations. In contrast to the pure population, the average
success rate of the large-memory agents can be greater than 50 percent. The
present results are not reproduced if the agents are fed a random history,
thereby demonstrating the importance of memory in this system.Comment: 9 pages Latex + 2 figure
Resonances in Ferromagnetic Gratings Detected by Microwave Photoconductivity
We investigate the impact of microwave excited spin excitations on the DC
charge transport in a ferromagnetic (FM) grating. We observe both resonant and
nonresonant microwave photoresistance. Resonant features are identified as the
ferromagnetic resonance (FMR) and ferromagnetic antiresonance (FMAR). A
macroscopic model based on Maxwell and Landau-Lifschitz equations reveals the
macroscopic nature of the FMAR. The experimental approach and results provide
new insight in the interplay between photonic, spintronic, and charge effects
in FM microstructures.Comment: 4 pages, 4 figure
HST/STIS Imaging of the Host Galaxy of GRB980425/SN1998bw
We present HST/STIS observations of ESO 184-G82, the host galaxy of the
gamma-ray burst GRB 980425 associated with the peculiar Type Ic supernova
SN1998bw. ESO 184-G82 is found to be an actively star forming SBc sub-luminous
galaxy. We detect an object consistent with being a point source within the
astrometric uncertainty of 0.018 arcseconds of the position of the supernova.
The object is located inside a star-forming region and is at least one
magnitude brighter than expected for the supernova based on a simple
radioactive decay model. This implies either a significant flattening of the
light curve or a contribution from an underlying star cluster.Comment: 12 pages, 2 figures, AASTeX v5.02 accepted for publication in ApJ
Letter
Resonance superfluidity in a quantum degenerate Fermi gas
We consider the superfluid phase transition that arises when a Feshbach
resonance pairing occurs in a dilute Fermi gas. We apply our theory to consider
a specific resonance in potassium-40, and find that for achievable experimental
conditions, the transition to a superfluid phase is possible at the high
critical temperature of about 0.5 T_F. Observation of superfluidity in this
regime would provide the opportunity to experimentally study the crossover from
the superfluid phase of weakly-coupled fermions to the Bose-Einstein
condensation of strongly-bound composite bosons.Comment: 4 pages, 3 figure
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The best wildflowers for wild bees
Governmental agri-environment schemes (AES) aim to improve pollinator abundance and diversity on farmland by sowing wildflower seed mixes. These often contain high proportions of Fabaceae, particularly Trifolium (clovers), which are attractive to some bumblebee species, but not to most of the ~ 240 solitary bee species in the UK. Here we identify wildflowers that are attractive to a greater range of wild bee species. Forty-five wildflower species being farmed for commercial seed production on a single farm were surveyed for native bees. Bee walks were conducted through discrete wildflower areas from April until August in 2018. The results indicate that including a range of Apiaceae, Asteraceae, and Geraniaceae in seed mixes would cater for a wide diversity of bee species. A total of 14 wildflower species across nine families attracted 37 out of the 40 bee species recorded on the farm, and accounted for 99.7% of all visitations. Only two of these 14 species are included in current AES pollinator mixes. Unexpectedly, few visits were made by bumblebees to Trifolium spp. (0.5%), despite their being considered an important food source for bumblebees, while Anthyllis vulneraria and Geranium pratense were highly attractive. For solitary bees, Crepis capillaris, Sinapsis arvensis, Convolvulus arvensis and Chaerophyllum temulum were amongst the best performing species, none of which are usually included in sown flower mixes. We suggest that the standard ‘pollinator’ mixes used in AES might be updated to include some of these wildflower species, and trialled as seed mixes on farmland
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