319 research outputs found
6-Methyl-7,7,9-tripropargyl-7H-1,2,4-triazolo[4,3-b][1,2,4]triazepin-8(9H)-one
The title compound, C15H13N5O, features a triazolyl ring fused with a seven-membered triazepinyl ring; the latter ring adopts a boat conformation (with the propargyl-bearing C atom as the prow and the fused-ring C/N atoms as the stern)
1-Benzyl-3-[(dimethylamino)methylene]-4-phenyl-1H-1,4-benzodiazepin-2(3H)-one
The title compound, C25H23N3O, features a benzene ring fused with a seven-membered 1,4-diazepine ring; the latter ring adopts a boat conformation with the (dimethylamino)methyl-bearing C atom as the prow and the fused-ring C atoms as the stern. There are two independent molecules in the asymmetric unit with similar conformations
7,9-Diallyl-6-methyl-7H-1,2,4-triazolo[4,3-b][1,2,4]triazepin-8(9H)-one
The title compound, C12H15N5O, features a triazolyl ring fused with a seven-membered triazepinyl ring; the latter ring adopts a boat conformation with the allyl-bearing C atom as the prow and the C and N fused-ring atoms as the stern
Influence of Previous Exposure to Antibiotic Therapy on the Susceptibility Pattern of Pseudomonas aeruginosa Bacteremic Isolates
Many patients who present with Pseudomonas aeruginosa bacteremia have been previously exposed to antibiotics. To assess whether resistance of bacteremic strains to antipseudomonal antibiotics (piperacillin, ceftazidime, imipenem, ciprofloxacin, or aminoglycosides) is associated with previous exposure to these drugs, a case-control study including 267 cases of P. aeruginosa bacteremia was conducted. Twenty-five percent of the episodes had been preceded by the exposure to an antipseudomonal antibiotic. Eighty-one strains were resistant to at least 1 antibiotic; 186 were susceptible to all drugs. Via univariate analysis, the risks of resistance to ceftazidime and imipenem were found to be significantly associated with previous receipt of these agents. Using multivariate analysis, exposure to any antipseudomonal antibiotic as a monotherapy was found to be associated with an increased risk of subsequent resistance to itself (odds ratio, 2.5; P = .006). Therefore, clinicians should avoid readministering previously prescribed antibiotics when initiating empiric therapies for possible P. aeruginosa bacteremia, especially when they have been given as monotherapie
Outcome of treated and untreated asymptomatic bacteriuria in renal transplant recipients
Background. No guidelines exist concerning treatment of asymptomatic bacteriuria in renal transplant recipients (RTR). Because of scarce clinical symptoms and fear of complications, such episodes are frequently treated based on subjective criteria without clear clinical benefit, with the risk of selecting resistant pathogens. Methods. We retrospectively analysed the outcome of 334 asymptomatic Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) bacteriuria that occurred in 77 RTR later than 1 month post-transplantation. We distinguished: Type I, high-grade bacteriuria with pyuria; Type II, high-grade bacteriuria without pyuria; Type III, low-grade bacteriuria with pyuria and Type IV, low-grade bacteriuria without pyuria. Results. None of the 334 episodes was followed by acute rejection or chronic pyelonephritis. One hundred and one (30%) episodes were treated [32 (62%) Type I, 38 (45%) Type II, 13 (36%) Type III and 18 (11%) Type IV]. Evolution to symptomatic urinary tract infection (UTI) was similar between treated and untreated episodes (0/101 versus 4/233, P = 0.32). The four UTI resolved favourably without further complication upon treatment. Persistent asymptomatic bacteriuria occurred in 45 (46%) treated episodes (2 Type I, 27 Type II, 8 Type III and 9 Type IV), with selection of resistant pathogen in 35 cases (78%). Spontaneous bacterial clearance occurred in 138 (59%) untreated episodes (15 Type I, 23 Type II, 9 Type III and 91 Type IV). Negative control cultures tended to be more frequent in treated Type I (P = 0.09) and in untreated Type II episodes (P = 0.08). Conclusion. Restricting antibiotic treatments for asymptomatic low-grade bacteriuria and high-grade bacteriuria in the absence of pyuria, occurring later than 1 month posttransplantation, might be safe in RT
Mean-field equations for stochastic firing-rate neural fields with delays: Derivation and noise-induced transitions
In this manuscript we analyze the collective behavior of mean-field limits of
large-scale, spatially extended stochastic neuronal networks with delays.
Rigorously, the asymptotic regime of such systems is characterized by a very
intricate stochastic delayed integro-differential McKean-Vlasov equation that
remain impenetrable, leaving the stochastic collective dynamics of such
networks poorly understood. In order to study these macroscopic dynamics, we
analyze networks of firing-rate neurons, i.e. with linear intrinsic dynamics
and sigmoidal interactions. In that case, we prove that the solution of the
mean-field equation is Gaussian, hence characterized by its two first moments,
and that these two quantities satisfy a set of coupled delayed
integro-differential equations. These equations are similar to usual neural
field equations, and incorporate noise levels as a parameter, allowing analysis
of noise-induced transitions. We identify through bifurcation analysis several
qualitative transitions due to noise in the mean-field limit. In particular,
stabilization of spatially homogeneous solutions, synchronized oscillations,
bumps, chaotic dynamics, wave or bump splitting are exhibited and arise from
static or dynamic Turing-Hopf bifurcations. These surprising phenomena allow
further exploring the role of noise in the nervous system.Comment: Updated to the latest version published, and clarified the dependence
in space of Brownian motion
Warped Riemannian metrics for location-scale models
The present paper shows that warped Riemannian metrics, a class of Riemannian
metrics which play a prominent role in Riemannian geometry, are also of
fundamental importance in information geometry. Precisely, the paper features a
new theorem, which states that the Rao-Fisher information metric of any
location-scale model, defined on a Riemannian manifold, is a warped Riemannian
metric, whenever this model is invariant under the action of some Lie group.
This theorem is a valuable tool in finding the expression of the Rao-Fisher
information metric of location-scale models defined on high-dimensional
Riemannian manifolds. Indeed, a warped Riemannian metric is fully determined by
only two functions of a single variable, irrespective of the dimension of the
underlying Riemannian manifold. Starting from this theorem, several original
contributions are made. The expression of the Rao-Fisher information metric of
the Riemannian Gaussian model is provided, for the first time in the
literature. A generalised definition of the Mahalanobis distance is introduced,
which is applicable to any location-scale model defined on a Riemannian
manifold. The solution of the geodesic equation is obtained, for any Rao-Fisher
information metric defined in terms of warped Riemannian metrics. Finally,
using a mixture of analytical and numerical computations, it is shown that the
parameter space of the von Mises-Fisher model of -dimensional directional
data, when equipped with its Rao-Fisher information metric, becomes a Hadamard
manifold, a simply-connected complete Riemannian manifold of negative sectional
curvature, for . Hopefully, in upcoming work, this will be
proved for any value of .Comment: first version, before submissio
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