5,192 research outputs found
The Effect of Fluctuations on the QCD Critical Point in a Finite Volume
We investigate the effect of a finite volume on the critical behavior of the
theory of the strong interaction (QCD) by means of a quark-meson model for two
quark flavors. In particular, we analyze the effect of a finite volume on the
location of the critical point in the phase diagram existing in our model. In
our analysis, we take into account the effect of long-range fluctuations with
the aid of renormalization group techniques. We find that these quantum and
thermal fluctuations, absent in mean-field studies, play an import role for the
dynamics in a finite volume. We show that the critical point is shifted towards
smaller temperatures and larger values of the quark chemical potential if the
volume size is decreased. This behavior persists for antiperiodic as well as
periodic boundary conditions for the quark fields as used in many lattice QCD
simulations.Comment: 9 pages, 2 figures, 1 tabl
Mutual interference between memory encoding and motor skills: the influence of motor expertise
In cognitive–motor dual-task situations, the extent of performance decrements
is influenced by the attentional requirements of each task. Well-learned motor
skills should be automatized, leading to less interference. This study presents two
studies combining an episodic memory encoding task with well-practiced motor
tasks in athletes. Study 1 asked 40 rowers (early teenagers to middle adulthood)
to row on ergometers at slow or fast speeds. In study 2, Taekwondo athletes
(n  =  37) of different skill levels performed a well-practiced sequence of martial
arts movements. Performing the motor task during encoding led to pronounced
performance reductions in memory in both studies, with costs of up to 80%.
Cognitive costs were even larger when rowing with the fast compared to the slow
speed in study 1. Both studies also revealed decrements in motor performances
under dual-task conditions: Rowing became slower and more irregular (study 1),
and the quality of the Taekwondo performance was reduced. Although higherlevel athletes outperformed others in motor skills under single-task conditions,
proportional dual-task costs were similar across skill levels for most domains. This
indicates that even well-practiced motor tasks require cognitive resources
On the Phase Structure of QCD in a Finite Volume
The chiral phase transition in QCD at finite chemical potential and
temperature can be characterized for small chemical potential by its curvature
and the transition temperature. The curvature is accessible to QCD lattice
simulations, which are always performed at finite pion masses and in finite
simulation volumes. We investigate the effect of a finite volume on the
curvature of the chiral phase transition line. We use functional
renormalization group methods with a two flavor quark-meson model to obtain the
effective action in a finite volume, including both quark and meson fluctuation
effects. Depending on the chosen boundary conditions and the pion mass, we find
pronounced finite-volume effects. For periodic quark boundary conditions in
spatial directions, we observe a decrease in the curvature in intermediate
volume sizes, which we interpret in terms of finite-volume quark effects. Our
results have implications for the phase structure of QCD in a finite volume,
where the location of a possible critical endpoint might be shifted compared to
the infinite-volume case.Comment: 11 pages, 3 figures, 4 tables; minor text corrections, one figure
added, appendix added, references added, matches PLB versio
Changes in the genetic structure of an invasive earthworm species (Lumbricus terrestris, Lumbricidae) along an urban – rural gradient in North America
European earthworms were introduced to North America by European settlers about 400 years ago. Human-mediated introductions significantly contributed to the spread of European species, which commonly are used as fishing bait and are often disposed deliberately in the wild. We investigated the genetic structure of Lumbricus terrestris in a 100km range south of Calgary, Canada, an area that likely was devoid of this species two decades ago. Genetic relationships among populations, gene flow, and migration events among populations were investigated using seven microsatellite markers and the mitochondrial 16S rDNA gene. Earthworms were collected at different distances from the city and included fishing baits from three different bait distributors. The results suggest that field populations in Alberta established rather recently and that bait and field individuals in the study area have a common origin. Genetic variance within populations decreased outside of the urban area, and the most distant populations likely originated from a single introduction event. The results emphasise the utility of molecular tools to understand the spatial extent and connectivity of populations of exotic species, in particular soil-dwelling species, that invade native ecosystems and to obtain information on the origin of populations. Such information is crucial for developing management and prevention strategies to limit and control establishment of non-native earthworms in North America.Peer reviewe
The problem of repulsive quark interactions - Lattice versus mean field models
We calculate the 2nd and 4th order quark number susceptibilities at zero
baryochemical potential, using a PNJL approach and an approach which includes,
in a single model, quark and hadronic degrees of freedom. We observe that the
susceptibilities are very sensitive to possible quark-quark vector
interactions. Compared to lattice data our results suggest that above any
mean field type of repulsive vector interaction can be excluded from model
calculations. Below our results show only very weak sensitivity on the
strength of the quark and hadronic vector interaction. The best description of
lattice data around is obtained for a case of coexistence of hadronic and
quark degrees of freedom.Comment: 5 pages, 4 figure, version accepted by PL
Crystal Structure of an Anti-Ang2 CrossFab Demonstrates Complete Structural and Functional Integrity of the Variable Domain.
Bispecific antibodies are considered as a promising class of future biotherapeutic molecules. They comprise binding specificities for two different antigens, which may provide additive or synergistic modes of action. There is a wide variety of design alternatives for such bispecific antibodies, including the "CrossMab" format. CrossMabs contain a domain crossover in one of the antigen-binding (Fab) parts, together with the "knobs-and-holes" approach, to enforce the correct assembly of four different polypeptide chains into an IgG-like bispecific antibody. We determined the crystal structure of a hAng-2-binding Fab in its crossed and uncrossed form and show that CH1-CL-domain crossover does not induce significant perturbations of the structure and has no detectable influence on target binding
No indication of porcine reproductive and respiratory syndrome virus (PRRSV) infection in Brazilian swine herds.
Porcine reproductive and respiratory syndrome virus (PRRSV) is a globally important pathogen of economic and veterinary concern. Recent studies estimate a cost of US$664m yearly to United States swine industry 3. PRRS is present throughout the world, with the exception of Australia, New Zealand, Finland, Norway, Sweden and Switzerland 5. Although Brazilian swine production is expressive (fourth pork producer and exporter), there has been no evidence of PRRSV infection in those herds 1. Most of the analysis used serology by commercial ELISA tests in breeding herds to perform prevalence surveys. The objective of this work was to detect PRRSV in samples of sera, plasma or oral fluids (OF) from swine herds, quarantined imported boars and feral pigs from 2008 ? 2012
Mid-infrared Period-Luminosity Relations of RR Lyrae Stars Derived from the WISE Preliminary Data Release
Interstellar dust presents a significant challenge to extending
parallax-determined distances of optically observed pulsational variables to
larger volumes. Distance ladder work at mid-infrared wavebands, where dust
effects are negligible and metallicity correlations are minimized, have been
largely focused on few-epoch Cepheid studies. Here we present the first
determination of mid-infrared period-luminosity (PL) relations of RR Lyrae
stars from phase-resolved imaging using the preliminary data release of the
Wide-Field Infrared Survey Explorer (WISE). We present a novel statistical
framework to predict posterior distances of 76 well-observed RR Lyrae that uses
the optically constructed prior distance moduli while simultaneously imposing a
power-law PL relation to WISE-determined mean magnitudes. We find that the
absolute magnitude in the bluest WISE filter is M_W1 = (-0.421+-0.014) -
(1.681+-0.147)*log(P/0.50118 day), with no evidence for a correlation with
metallicity. Combining the results from the three bluest WISE filters, we find
that a typical star in our sample has a distance measurement uncertainty of
0.97% (statistical) plus 1.17% (systematic). We do not fundamentalize the
periods of RRc stars to improve their fit to the relations. Taking the
Hipparcos-derived mean V-band magnitudes, we use the distance posteriors to
determine a new optical metallicity-luminosity relation which we present in
Section 5. The results of this analysis will soon be tested by HST parallax
measurements and, eventually, with the Gaia astrometric mission.Comment: 33 pages, 12 figures, 2 tables. Accepted for publication in ApJ, June
27th, 201
Supernova Properties from Shock Breakout X-rays
We investigate the potential of the upcoming LOBSTER space observatory (due
circa 2009) to detect soft X-ray flashes from shock breakout in supernovae,
primarily from Type II events. LOBSTER should discover many SN breakout
flashes, although the number is sensitive to the uncertain distribution of
extragalactic gas columns. X-ray data will constrain the radii of their
progenitor stars far more tightly than can be accomplished with optical
observations of the SN light curve. We anticipate the appearance of blue
supergiant explosions (SN 1987A analogs), which will uncover a population of
these underluminous events. We consider also how the mass, explosion energy,
and absorbing column can be constrained from X-ray observables alone and with
the assistance of optically-determined distances. These conclusions are drawn
using known scaling relations to extrapolate, from previous numerical
calculations, the LOBSTER response to explosions with a broad range of
parameters. We comment on a small population of flashes with 0.2 < z < 0.8 that
should exist as transient background events in XMM, Chandra, and ROSAT
integrations.Comment: 14 pages, 9 figures, accepted by MNRAS, presented at AAS 203rd
meetin
- …