59,810 research outputs found
Structure of a thermal quasifermion in the QCD/QED Medium
In this paper we carried out a nonperturbative analysis of a thermal
quasifermion in the chiral symmetric thermal QCD/QED medium by studying its
self-energy function through the Dyson-Schwinger equation with the
hard-thermal-loop resummed improved ladder kernel. Our analysis reveals several
interesting results, two in some of which may force us to change the image of
thermal quasifermions: (1) The thermal mass of a quasifermion begins to
decrease as the strength of the coupling gets stronger and finally disappears
in the strong coupling region, thus showing a property of a massless particle,
and (2) its imaginary part (i.e., the decay width) persists to have behavior. These results suggest that in the recently produced
strongly coupled quark-gluon plasma, the thermal mass of a quasiquark should
vanish. Taking into account the largeness of the imaginary part, it seems very
hard for a quark to exist as a qausiparticle in the strongly coupled
quark-gluon plasma phase. Other important findings are as follows: (3) The
collective plasmino mode disappears also in the strongly coupled system, and
(4) there exists an ultrasoft third peak in the quasifermion spectral density
at least in the weakly coupled QED/QCD plasma, indicating the existence of the
ultrasoft fermionic mode.Comment: 20 pages, 28 figure
Work-rate of substitutes in elite soccer: A preliminary study
The aim of this study was to investigate the work-rate of substitutes in professional soccer. A computerised player tracking system was used to assess the work-rates of second-half substitutes (11 midfielders and 14 forwards) in a French Ligue 1 club. Total distance, distance covered in five categories of movement intensity and recovery time between high-intensity efforts were evaluated. First- and second-half work-rates of the replaced players were compared. The performance of substitutes was compared to that of the players they replaced, to team-mates in the same position who remained on the pitch after the substitution and in relation to their habitual performances when starting games. No differences in work-rate between first- and second-halves were observed in all players who were substituted. In the second-half, a non-significant trend was observed in midfield substitutes who covered greater distances than the player they replaced whereas no differences were observed in forwards. Midfield substitutes covered a greater overall distance and distance at high-intensities (p<0.01) and had a lower recovery time between high-intensity efforts (p<0.01) compared to other midfield team-mates who remained on the pitch. Forwards covered less distance (p<0.01) in their first 10-minutes as a substitute compared to their habitual work-rate profile in the opening 10-minutes when starting matches while this finding was not observed in midfielders. These findings suggest that compared to midfield substitutes, forward substitutes did not utilise their full physical potential. Further investigation is warranted into the reasons behind this finding in order to optimise the work-rate contributions of forward substitutes
Expansion-maximization-compression algorithm with spherical harmonics for single particle imaging with X-ray lasers
In 3D single particle imaging with X-ray free-electron lasers, particle
orientation is not recorded during measurement but is instead recovered as a
necessary step in the reconstruction of a 3D image from the diffraction data.
Here we use harmonic analysis on the sphere to cleanly separate the angu- lar
and radial degrees of freedom of this problem, providing new opportunities to
efficiently use data and computational resources. We develop the
Expansion-Maximization-Compression algorithm into a shell-by-shell approach and
implement an angular bandwidth limit that can be gradually raised during the
reconstruction. We study the minimum number of patterns and minimum rotation
sampling required for a desired angular and radial resolution. These extensions
provide new av- enues to improve computational efficiency and speed of
convergence, which are critically important considering the very large datasets
expected from experiment
Determination of population structure and stock composition of chum salmon (Oncorhynchus keta) in Russia determined with microsatellites
Variation at 14 microsatellite loci was examined in 34 chum
salmon (Oncorhynchus keta) populations from Russia and evaluated for its use in the determination of population
structure and stock composition in simulated mixed-stock fishery samples. The genetic differentiation index (Fst) over all populations and loci was 0.017, and individual locus values ranged from 0.003 to 0.054. Regional population structure was observed, and populations from Primorye, Sakhalin Island, and northeast Russia were the most distinct. Microsatellite variation provided evidence of a more fine-scale population structure than those that had previously been demonstrated with other genetic-based markers. Analysis of simulated mixed-stock samples indicated that accurate and precise regional estimates of stock composition were produced when the microsatellites
were used to estimate stock compositions. Microsatellites can be used to determine stock composition in geographically separate Russian coastal chum salmon fisheries and provide a greater resolution of stock
composition and population structure than that previously provided with other techniques
Silver Nanoparticle Aggregates as Highly Efficient Plasmonic Antennas for Fluorescence Enhancement
The enhanced local fields around plasmonic structures can lead to enhancement of the excitation and modification of the emission quantum yield of fluorophores. So far, high enhancement of fluorescence intensity from dye molecules was demonstrated using bow-tie gap antenna made by e-beam lithography. However, the high manufacturing cost and the fact that currently there are no effective ways to place fluorophores only at the gap prevent the use of these structures for enhancing fluorescence-based biochemical assays. We report on the simultaneous modification of fluorescence intensity and lifetime of dye-labeled DNA in the presence of aggregated silver nanoparticles. The nanoparticle aggregates act as efficient plasmonic antennas, leading to more than 2 orders of magnitude enhancement of the average fluorescence. This is comparable to the best-reported fluorescence enhancement for a single molecule but here applies to the average signal detected from all fluorophores in the system. This highlights the remarkable efficiency of this system for surface-enhanced fluorescence. Moreover, we show that the fluorescence intensity enhancement varies with the plasmon resonance position and measure a significant reduction (300×) of the fluorescence lifetime. Both observations are shown to be in agreement with the electromagnetic model of surface-enhanced fluorescence
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