1,417 research outputs found
Fermionic anticommutators for open superstrings in the presence of antisymmetric tensor field
We build up the anticommutator algebra for the fermionic coordinates of open
superstrings attached to branes with antisymmetric tensor fields. We use both
Dirac quantization and the symplectic Faddeev Jackiw approach. In the
symplectic case we find a way of generating the boundary conditions as zero
modes of the symplectic matrix by taking a discretized form of the action and
adding terms that vanish in the continuous limit. This way boundary conditions
can be handled as constraints.Comment: Revision: passage from discrete to continuous clarified, comment on
previous results using Dirac quantization included, typos corrected. Version
to appear in Phys. Lett.
Sodium Atoms in the Lunar Exotail: Observed Velocity and Spatial Distributions
The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations measured the average radial velocity of sodium atoms moving down the lunar tail beyond Earth (i.e., near the anti-lunar point) to be ~ 12.5 km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15 x 15 deg region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights bracketing new Moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3 deg east along the ecliptic per night. Preliminary modeling results suggest the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution. Future observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days
The impact of a population-level school food and nutrition policy on dietary intake and body weights of Canadian children
AbstractObjectiveThe objective of this study is to assess population-level trends in children's dietary intake and weight status before and after the implementation of a provincial school nutrition policy in the province of Nova Scotia, Canada.MethodSelf-reported dietary behavior and nutrient intake and measured body mass index were collected as part of a population-level study with grade 5 students in 2003 (n=5215) and 2011 (5508), prior to and following implementation of the policy. We applied random effects regression methods to assess the effect of the policy on dietary and health outcomes.ResultsIn 2011, students reported consuming more milk products, while there was no difference in mean consumption of vegetables and fruits in adjusted models. Adjusted regression analysis revealed a statistically significant decrease in sugar-sweetened beverage consumption. Despite significant temporal decreases in dietary energy intake and increases in diet quality, prevalence rates of overweight and obesity continued to increase.ConclusionThis population-level intervention research suggests a positive influence of school nutrition policies on diet quality, energy intake and healthy beverage consumption, and that more action beyond schools is needed to curb the increases in the prevalence of childhood obesity
Endovascular Treatment of Ruptured Thoracic Aortic Aneurysm in Patients Older than 75 Years
AbstractObjectivesTo investigate the outcomes of thoracic endovascular aortic repair (TEVAR) for ruptured descending thoracic aortic aneurysm (rDTAA) in patients older than 75 years.MethodsWe retrospectively identified all patients treated with TEVAR for rDTAA at seven referral centres between 2002 and 2009. The cohort was stratified according to age ≤75 and >75 years, and the outcomes after TEVAR were compared between both groups.ResultsNinety-two patients were identified of which 73% (n = 67) were ≤75 years, and 27% (n = 25) were older than 75 years. The 30-day mortality was 32.0% in patients older than 75 years, and 13.4% in the remaining patients (p = 0.041). Patients older than 75 years suffered more frequently from postoperative stroke (24.0% vs. 1.5%, p = 0.001) and pulmonary complications (40.0% vs. 9.0%, p = 0.001). The aneurysm-related survival after 2 years was 52.1% for patients >75 years, and 83.9% for patients ≤75 years (p = 0.006).ConclusionsEndovascular treatment of rDTAA in patients older than 75 years is associated with an inferior outcome compared with patients younger than 75 years. However, the mortality and morbidity rates in patients above 75 years are still acceptable. These results may indicate that endovascular treatment for patients older than 75 years with rDTAA is worthwhile
Human behavior as origin of traffic phases
It is shown that the desire for smooth and comfortable driving is directly
responsible for the occurrence of complex spatio-temporal structures
(``synchronized traffic'') in highway traffic. This desire goes beyond the
avoidance of accidents which so far has been the main focus of microscopic
modeling and which is mainly responsible for the other two phases observed
empirically, free flow and wide moving jams. These features have been
incorporated into a microscopic model based on stochastic cellular automata and
the results of computer simulations are compared with empirical data. The
simple structure of the model allows for very fast implementations of realistic
networks. The level of agreement with the empirical findings opens new
perspectives for reliable traffic forecasts.Comment: 4 pages, 4 figures, colour figures with reduced resolutio
The controlled teleportation of an arbitrary two-atom entangled state in driven cavity QED
In this paper, we propose a scheme for the controlled teleportation of an
arbitrary two-atom entangled state
in driven cavity QED.
An arbitrary two-atom entangled state can be teleported perfectly with the help
of the cooperation of the third side by constructing a three-atom GHZ entangled
state as the controlled channel. This scheme does not involve apparent (or
direct) Bell-state measurement and is insensitive to the cavity decay and the
thermal field. The probability of the success in our scheme is 1.0.Comment: 10 page
Holographic principle in the BDL brane cosmology
We study the holographic principle in the brane cosmology. Especially we
describe how to accommodate the 5D anti de Sitter Schwarzschild (AdSS)
black hole in the Binetruy-Deffayet-Langlois (BDL) approach of brane cosmology.
It is easy to make a connection between a mass of the AdSS black hole
and a conformal field theory (CFT)-radiation dominated universe on the brane in
the moving domain wall approach. But this is not established in the BDL
approach. In this case we use two parameters in the Friedmann
equation. These arise from integration and are really related to the choice of
initial bulk matter. If one chooses a bulk energy density to account
for a mass of the AdSS black hole and the static fifth dimension, a
CFT-radiation term with comes out from the bulk
matter without introducing a localized matter distribution on the brane. This
means that the holographic principle can be established in the BDL brane
cosmology.Comment: 9 pages, a version to appear in PR
Imperfect nesting and transport properties in unconventional density waves
We consider the effect of imperfect nesting in quasi-one dimensional
unconventional density waves.
The phase diagram is very close to those in a conventional DW. The linear and
non-linear aspects of the electric conductivity are discussed. At T=0 the
frequency dependent electric conductivity develops a small dip at low
frequencies.
The threshold electric field depends strongly on the imperfect nesting
parameter, allowing us to describe the measured threshold electric field in the
low temperature phase of the quasi-two dimensional organic conductor,
alpha-(BEDT-TTF)_2KHg(SCN)_4 very well.Comment: 9 pages, 9 figure
Growth performance and fecal microflora of rats offered metabolites from lactic acid bacteria.
The objectives of this experiment were to study the effect of metabolites produced from lactic acid bacteria(LAB) on the growth performance, Enterobacteriaceae and LAB counts in the faeces, faecal pH and plasma cholesterol. A total of 30 female postweaning rats were randomly assigned to five groups of diet: basal diet + 100% drinking water (DW), basal diet + 90% DW + 10% ULA metabolite, basal diet + 80% DW + 20% UL4 metabolite, basal diet + 90% DW+ 10% RW18 metabolite and basal diet + 80% DW + 20% RW18 metabolite for a period of four weeks. The metabolites affected only Enterobacteriaceae counts and faecal pH, which were lower than the control groups. In conclusion, addition of lactic acid bacterial metabolites in the drinking water had only antibacterial effect in rats
A Review of Controlling Motivational Strategies from a Self-Determination Theory Perspective: Implications for Sports Coaches
The aim of this paper is to present a preliminary taxonomy of six controlling strategies, primarily based on the parental and educational literatures, which we believe are employed by coaches in sport contexts. Research in the sport and physical education literature has primarily focused on coaches’ autonomysupportive behaviours. Surprisingly, there has been very little research on the use of controlling strategies. A brief overview of the research which delineates each proposed strategy is presented, as are examples of the potential manifestation of the behaviours associated with each strategy in the context of sports coaching. In line with self-determination theory (Deci & Ryan, 1985; Ryan & Deci, 2002), we propose that coach behaviours employed to pressure or control athletes have the potential to thwart athletes’ feelings of autonomy, competence,and relatedness, which, in turn, undermine athletes’ self-determined motivation and contribute to the development of controlled motives. When athletes feel pressured to behave in a certain way, a variety of negative consequences are expected to ensue which are to the detriment of the athletes’ well-being. The purpose of this paper is to raise awareness and interest in the darker side of sport participation and to offer suggestions for future research in this area
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