1,588 research outputs found
Exact renormalisation group flow for ultracold Fermi gases in unitary limit
We study the exact renormalisation group flow for ultracold Fermi-gases in
unitary regime. We introduce a pairing field to describe the formation of the
Cooper pairs, and take a simple ansatz for the effective action. Set of
approximate flow equations for the effective couplings including boson and
fermionic fluctuations is derived. At some value of the running scale, the
system undergoes a phase transition to a gapped phase. The values of the energy
density, chemical potential, pairing gap and the corresponding proportionality
constants relating the interacting and non-interacting Fermi gases are
calculated. Standard mean field results are recovered if we omit the boson
loops.Comment: 11 pages, Revtex, misprints corrected, references and comments adde
Serum procalcitonin for discrimination of blood contamination from bloodstream infection due to coagulase-negative staphylococci
The diagnostic value of serum procalcitonin (PCT) to distinguish blood contamination from bloodstream infection (BSI) due to coagulase-negative staphylococci was evaluated. Patients with BSI had higher PCT concentration than those with blood contamination at day -1, day 0 and day +1 with regard to blood culture collection (p > 0.05), whereas serum C-reactive protein values were significantly higher only on day +1. At a cutoff of 0.1 ng/dl, PCT had a sensitivity of 86% and 100%, and a specificity of 60% and 80% for the diagnosis of BSI on day -1 and 0, respectively. In addition to clinical and microbiological parameters, PCT may help discriminating blood contamination from BSI due coagulase-negative staphylococci
Serum Procalcitonin for Discrimination of Blood Contamination from Bloodstream Infection due to Coagulase-Negative Staphylococci
Abstract : The diagnostic value of serum procalcitonin (PCT) to distinguish blood contamination from bloodstream infection (BSI) due to coagulase-negative staphylococci was evaluated. Patients with BSI had higher PCT concentration than those with blood contamination at day -1, day 0 and day +1 with regard to blood culture collection (p < 0.05), whereas serum C-reactive protein values were significantly higher only on day +1. At a cutoff of 0.1 ng/dl, PCT had a sensitivity of 86% and 100%, and a specificity of 60% and 80% for the diagnosis of BSI on day -1 and 0, respectively. In addition to clinical and microbiological parameters, PCT may help discriminating blood contamination from BSI due coagulase-negative staphylococc
Mixed population of competing TASEPs with a shared reservoir of particles
We introduce a mean-field theoretical framework to describe multiple totally
asymmetric simple exclusion processes (TASEPs) with different lattice lengths,
entry and exit rates, competing for a finite reservoir of particles. We present
relations for the partitioning of particles between the reservoir and the
lattices: these relations allow us to show that competition for particles can
have non-trivial effects on the phase behavior of individual lattices. For a
system with non-identical lattices, we find that when a subset of lattices
undergoes a phase transition from low to high density, the entire set of
lattice currents becomes independent of total particle number. We generalize
our approach to systems with a continuous distribution of lattice parameters,
for which we demonstrate that measurements of the current carried by a single
lattice type can be used to extract the entire distribution of lattice
parameters. Our approach applies to populations of TASEPs with any distribution
of lattice parameters, and could easily be extended beyond the mean-field case.Comment: 12 pages, 8 figure
Diffusion algebras
We define the notion of "diffusion algebras". They are quadratic
Poincare-Birkhoff-Witt (PBW) algebras which are useful in order to find exact
expressions for the probability distributions of stationary states appearing in
one-dimensional stochastic processes with exclusion. One considers processes in
which one has N species, the number of particles of each species being
conserved. All diffusion algebras are obtained. The known examples already used
in applications are special cases in our classification. To help the reader
interested in physical problems, the cases N=3 and 4 are listed separately.Comment: 29 pages; minor misprints corrected, few references adde
Efficient modularity optimization by multistep greedy algorithm and vertex mover refinement
Identifying strongly connected substructures in large networks provides
insight into their coarse-grained organization. Several approaches based on the
optimization of a quality function, e.g., the modularity, have been proposed.
We present here a multistep extension of the greedy algorithm (MSG) that allows
the merging of more than one pair of communities at each iteration step. The
essential idea is to prevent the premature condensation into few large
communities. Upon convergence of the MSG a simple refinement procedure called
"vertex mover" (VM) is used for reassigning vertices to neighboring communities
to improve the final modularity value. With an appropriate choice of the step
width, the combined MSG-VM algorithm is able to find solutions of higher
modularity than those reported previously. The multistep extension does not
alter the scaling of computational cost of the greedy algorithm.Comment: 7 pages, parts of text rewritten, illustrations and pseudocode
representation of algorithms adde
The solution space of metabolic networks: producibility, robustness and fluctuations
Flux analysis is a class of constraint-based approaches to the study of
biochemical reaction networks: they are based on determining the reaction flux
configurations compatible with given stoichiometric and thermodynamic
constraints. One of its main areas of application is the study of cellular
metabolic networks. We briefly and selectively review the main approaches to
this problem and then, building on recent work, we provide a characterization
of the productive capabilities of the metabolic network of the bacterium E.coli
in a specified growth medium in terms of the producible biochemical species.
While a robust and physiologically meaningful production profile clearly
emerges (including biomass components, biomass products, waste etc.), the
underlying constraints still allow for significant fluctuations even in key
metabolites like ATP and, as a consequence, apparently lay the ground for very
different growth scenarios.Comment: 10 pages, prepared for the Proceedings of the International Workshop
on Statistical-Mechanical Informatics, March 7-10, 2010, Kyoto, Japa
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