Archive ouverte UNIGE | last documents for author 'Christian Mazza'https://archive-ouverte.unige.ch/Latest objects deposited in the Archive ouverte UNIGE for author 'Christian Mazza'engA framework for probabilistic numerical evaluation of sensor networks : a case study of a localization protocolhttps://archive-ouverte.unige.ch/unige:32653https://archive-ouverte.unige.ch/unige:32653abstract not availableMon, 23 Dec 2013 11:26:56 +0100On the Storage Capacity of Nonlinear Neural Networkshttps://archive-ouverte.unige.ch/unige:12712https://archive-ouverte.unige.ch/unige:12712abstract not availableTue, 30 Nov 2010 13:17:13 +0100On the Mean Pair Correlation Function of ±J Ising Spin Glasseshttps://archive-ouverte.unige.ch/unige:12680https://archive-ouverte.unige.ch/unige:12680We provide a formula and an upper bound for the average over the disorder of the pair correlation function of ±J Ising spin glasses by using the symmetries of the system, We show the decay of the mean spin pair correlation function when the proportion of antiferromagnetic bonds is larger than the critical parameter associated with the pair dissociation phase transition.Mon, 29 Nov 2010 16:52:58 +0100Gauge symmetries and percolation in ± J Ising spin glasseshttps://archive-ouverte.unige.ch/unige:12564https://archive-ouverte.unige.ch/unige:12564abstract not availableMon, 22 Nov 2010 10:26:14 +0100Simply Generated Trees, B-series and Wigner Processeshttps://archive-ouverte.unige.ch/unige:12229https://archive-ouverte.unige.ch/unige:12229We consider simply generated trees and study multiplicative functions on rooted plane trees. We show that the associated generating functions satisfy differential equations or difference equations. Our approach considers B-series from Butcher's theory, the generating functions are seen as generalized Runge-Kutta methods.Fri, 22 Oct 2010 14:55:58 +0200Angular Gaussian and Cauchy estimationhttps://archive-ouverte.unige.ch/unige:12220https://archive-ouverte.unige.ch/unige:12220This paper proposes a unified treatment of maximum likelihood estimates of angular Gaussian and multivariate Cauchy distributions in both the real and the complex case. The complex case is relevant in shape analysis. We describe in full generality the set of maxima of the corresponding log-likelihood functions with respect to an arbitrary probability measure. Our tools are the convexity of log-likelihood functions and their behaviour at infinity.Fri, 22 Oct 2010 13:14:46 +0200Long time behavior of the solutions to non-linear Kraichnan equationshttps://archive-ouverte.unige.ch/unige:12198https://archive-ouverte.unige.ch/unige:12198We consider the solution of a nonlinear Kraichnan equation $$partial_s H(s,t)=int_t^s H(s,u)H(u,t) k(s,u) du,quad sge t$$ with a covariance kernel $k$ and boundary condition $H(t,t)=1$. We study the long time behaviour of $H$ as the time parameters $t,s$ go to infinity, according to the asymptotic behaviour of $k$. This question appears in various subjects since it is related with the analysis of the asymptotic behaviour of the trace of non-commutative processes satisfying a linear differential equation, but also naturally shows up in the study of the so-called response function and aging properties of the dynamics of some disordered spin systems.Thu, 21 Oct 2010 14:13:34 +0200Strand separation in negatively supercoiled dnahttps://archive-ouverte.unige.ch/unige:12151https://archive-ouverte.unige.ch/unige:12151We consider Benham's model for strand separation in negatively supercoiled circular DNA, and study denaturation as function of the superhelical density k < 0. We propose a statistical version of this model, based on bayesian segmentation methods of current use in bioinformatics; this leads to new algorithms with priors adapted to supercoiled DNA, taking into account the random nature of the free energies needed to denature hydrogen bonds.Tue, 19 Oct 2010 14:33:15 +0200Stochastic Gene Expression in Switching Environmentshttps://archive-ouverte.unige.ch/unige:6274https://archive-ouverte.unige.ch/unige:6274Organisms are known to adapt to regularly varying environments. However, in most cases, the fluctuations of the environment are irregular and stochastic, alternating between favorable and unfavorable regimes, so that cells must cope with an uncertain future. A possible response is population diversification. We assume here that the cell population is divided into two groups, corresponding to two phenotypes, having distinct growth rates, and that cells can switch randomly their phenotypes. In static environments, the net growth rate is maximized when the population is homogeneously composed of cells having the largest growth rate. In random environments, growth rates fluctuate and observations reveal that sometimes heterogeneous populations have a larger net growth rate than homogeneous ones, a fact illustrated recently through Monte-Carlo simulations based on a birth and migration process in a random environment. We study this process mathematically by focusing on the proportionTue, 20 Apr 2010 12:10:11 +0200Clonidine as an adjuvant to intrathecal local anesthetics for surgery: systematic review of randomized trialshttps://archive-ouverte.unige.ch/unige:2168https://archive-ouverte.unige.ch/unige:2168BACKGROUND AND OBJECTIVES: Clonidine is added to intrathecal local anesthetics to improve intraoperative analgesia and to increase the duration of sensory and motor block. The aim of this systematic review is to quantify beneficial and harmful effects of clonidine when used as an adjuvant to intrathecal local anesthetics for surgery. METHODS: We included data from 22 randomized trials (1,445 patients) testing a large variety of doses of clonidine, added to intrathecal bupivacaine, mepivacaine, prilocaine, or tetracaine. RESULTS: Clonidine 15 to 150 microg prolonged in a linear, dose-dependent manner, the time to 2 segment regression (range of means, 14 to 75 minutes) and the time to regression to L2 (range of means, 11 to 128 minutes). The time to first analgesic request (median 101 minutes, range 35 to 310) and of motor block (median 47 minutes, range 6 to 131) was prolonged without evidence of dose-responsiveness. Time to achieve complete sensory or motor block, and extent of cephalic spread remained unchanged. There were fewer episodes of intraoperative pain with clonidine (relative risk, 0.24; 95% confidence interval [CI], 0.09-0.64; number needed to treat, 13) but more episodes of arterial hypotension (relative risk, 1.81; 95% CI 1.44-2.28; number needed to harm, 8) without evidence of dose-responsiveness. The risk of bradycardia was unchanged. CONCLUSIONS: This study may serve as a rational basis to help clinicians decide whether or not to combine clonidine with an intrathecal local anesthetic for surgery. The optimal dose of clonidine, however, remains unknown.Fri, 26 Jun 2009 13:52:46 +0200