12,981 research outputs found
Recent developments in classical density functional theory: Internal energy functional and diagrammatic structure of fundamental measure theory
An overview of several recent developments in density functional theory for
classical inhomogeneous liquids is given. We show how Levy's constrained search
method can be used to derive the variational principle that underlies density
functional theory. An advantage of the method is that the Helmholtz free energy
as a functional of a trial one-body density is given as an explicit expression,
without reference to an external potential as is the case in the standard
Mermin-Evans proof by reductio ad absurdum. We show how to generalize the
approach in order to express the internal energy as a functional of the
one-body density distribution and of the local entropy distribution. Here the
local chemical potential and the bulk temperature play the role of Lagrange
multipliers in the Euler-Lagrange equations for minimiziation of the
functional. As an explicit approximation for the free-energy functional for
hard sphere mixtures, the diagrammatic structure of Rosenfeld's fundamental
measure density unctional is laid out. Recent extensions, based on the
Kierlik-Rosinberg scalar weight functions, to binary and ternary non-additive
hard sphere mixtures are described.Comment: 15 pages, 6 figure
The quantum Casimir operators of \Uq and their eigenvalues
We show that the quantum Casimir operators of the quantum linear group
constructed in early work of Bracken, Gould and Zhang together with one extra
central element generate the entire center of \Uq. As a by product of the
proof, we obtain intriguing new formulae for eigenvalues of these quantum
Casimir operators, which are expressed in terms of the characters of a class of
finite dimensional irreducible representations of the classical general linear
algebra.Comment: 10 page
Spherical codes, maximal local packing density, and the golden ratio
The densest local packing (DLP) problem in d-dimensional Euclidean space Rd
involves the placement of N nonoverlapping spheres of unit diameter near an
additional fixed unit-diameter sphere such that the greatest distance from the
center of the fixed sphere to the centers of any of the N surrounding spheres
is minimized. Solutions to the DLP problem are relevant to the realizability of
pair correlation functions for packings of nonoverlapping spheres and might
prove useful in improving upon the best known upper bounds on the maximum
packing fraction of sphere packings in dimensions greater than three. The
optimal spherical code problem in Rd involves the placement of the centers of N
nonoverlapping spheres of unit diameter onto the surface of a sphere of radius
R such that R is minimized. It is proved that in any dimension, all solutions
between unity and the golden ratio to the optimal spherical code problem for N
spheres are also solutions to the corresponding DLP problem. It follows that
for any packing of nonoverlapping spheres of unit diameter, a spherical region
of radius less than or equal to the golden ratio centered on an arbitrary
sphere center cannot enclose a number of sphere centers greater than one more
than the number that can be placed on the region's surface.Comment: 12 pages, 1 figure. Accepted for publication in the Journal of
Mathematical Physic
A pilot validation in 10 European Union Member States of a point prevalence survey of healthcare-associated infections and antimicrobial use in acute hospitals in Europe, 2011
Microjansky radio sources in DC0107-46 (Abell 2877)
The cluster DC0107-46 (Abell 2877) lies within the Phoenix Deep Survey, made
at 1.4 GHz with the Australia Telescope Compact Array. Of 89 known optical
cluster members, 70 lie within the radio survey area. Of these 70 galaxies, 15
(21%) are detected, with luminosities as faint as 10^20 W/Hz. Spectroscopic
observations are available for 14/15 of the radio-detected cluster galaxies.
Six galaxies show only absorption features and are typical low-luminosity AGN
radio sources. One galaxy hosts a Seyfert 2 nucleus, two are star-forming
galaxies, and the remaining five may be star-forming galaxies, AGNs, or both.Comment: 14 pages, 3 figures, Accepted by ApJS (v128n2p JUN 2000 issue
Diffuse supernova neutrinos: oscillation effects, stellar cooling and progenitor mass dependence
We estimate the diffuse supernova neutrino background (DSNB) using the recent
progenitor-dependent, long-term supernova simulations from the Basel group and
including neutrino oscillations at several post-bounce times. Assuming
multi-angle matter suppression of collective effects during the accretion
phase, we find that oscillation effects are dominated by the matter-driven MSW
resonances, while neutrino-neutrino collective effects contribute at the 5-10%
level. The impact of the neutrino mass hierarchy, of the time-dependent
neutrino spectra and of the diverse progenitor star population is 10% or less,
small compared to the uncertainty of at least 25% of the normalization of the
supernova rate. Therefore, assuming that the sign of the neutrino mass
hierarchy will be determined within the next decade, the future detection of
the DSNB will deliver approximate information on the MSW-oscillated neutrino
spectra. With a reliable model for neutrino emission, its detection will be a
powerful instrument to provide complementary information on the star formation
rate and for learning about stellar physics.Comment: 19 pages, including 4 figures and 1 table. Clarifying paragraphs
added; results unchanged. Matches published version in JCA
System data communication structures for active-control transport aircraft, volume 2
The application of communication structures to advanced transport aircraft are addressed. First, a set of avionic functional requirements is established, and a baseline set of avionics equipment is defined that will meet the requirements. Three alternative configurations for this equipment are then identified that represent the evolution toward more dispersed systems. Candidate communication structures are proposed for each system configuration, and these are compared using trade off analyses; these analyses emphasize reliability but also address complexity. Multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems
System data communication structures for active-control transport aircraft, volume 1
Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems
Lactobacillus fermentum (PCC®) supplementation and gastrointestinal and respiratory-tract illness symptoms: a randomised control trial in athletes
BACKGROUND Probiotics purportedly reduce symptoms of gastrointestinal and upper respiratory-tract illness by modulating commensal microflora. Preventing and reducing symptoms of respiratory and gastrointestinal illness are the primary reason that dietary supplementation with probiotics are becoming increasingly popular with healthy active individuals. There is a paucity of data regarding the effectiveness of probiotics in this cohort. The aim of this study was to evaluate the effectiveness of a probiotic on faecal microbiology, self-reported illness symptoms and immunity in healthy well trained individuals. METHODS Competitive cyclists (64 males and 35 females; age 35 ± 9 and 36 ± 9 y, VO2max 56 ± 6 and 52 ± 6 ml.kg-1.min-1, mean ± SD) were randomised to either probiotic (minimum 1 × 109 Lactobacillus fermentum (PCC®) per day) or placebo treatment for 11 weeks in a double-blind, randomised, controlled trial. The outcome measures were faecal L. fermentum counts, self-reported symptoms of illness and serum cytokines. RESULTS Lactobacillus numbers increased 7.7-fold (90% confidence limits 2.1- to 28-fold) more in males on the probiotic, while there was an unclear 2.2-fold (0.2- to 18-fold) increase in females taking the probiotic. The number and duration of mild gastrointestinal symptoms were ~2-fold greater in the probiotic group. However, there was a substantial 0.7 (0.2 to 1.2) of a scale step reduction in the severity of gastrointestinal illness at the mean training load in males, which became more pronounced as training load increased. The load (duration×severity) of lower respiratory illness symptoms was less by a factor of 0.31 (99%CI; 0.07 to 0.96) in males taking the probiotic compared with placebo but increased by a factor of 2.2 (0.41 to 27) in females. Differences in use of cold and flu medication mirrored these symptoms. The observed effects on URTI had too much uncertainty for a decisive outcome. There were clear reductions in the magnitude of acute exercise-induced changes in some cytokines. CONCLUSION L. fermentum may be a useful nutritional adjunct for healthy exercising males. However, uncertainty in the effects of supplementation on URTI and on symptoms in females needs to be resolved. TRIAL REGISTRATION The trial was registered in the Australia and New Zealand Clinical Trials Registry (ACTRN12611000006943).The study was funded by Christian Hansen A/S, Probiomics and the Australian Institute of Sport
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