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Search Results: 1 - 10 of 10600 matches for " Matthew Dryden "
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Treatment of complicated skin and soft-tissue infections caused by resistant bacteria: value of linezolid, tigecycline, daptomycin and vancomycin
Christian Eckmann, Matthew Dryden
European Journal of Medical Research , 2010, DOI: 10.1186/2047-783x-15-12-554
Abstract: Tigecycline is an alternative in polymicrobial infections except by diabetic foot infections. Daptomycin might be a treatment option for cases of cSSTI with MRSA bacteremia. cSSTI caused by resistant Gram-negative bacteria are a matter of great concern. The development of new antibiotics in this area is an urgent priority to avoid the risk of a postantibiotic era with no antimicrobial treatment options. An individual approach for every single patient is mandatory to evaluate the optimal antimicrobial treatment regimen.Skin and soft tissue infections (SSTI) are amongst the most common bacterial infections in humans. They represent one of the most common indications for antibiotic treatment and represent about 10% of hospital admissions in the US [1]. Amongst the broad spectrum of skin and soft tissue infections treatment is mainly delivered out of hospital. SSTI have a broad range of aetiology, clinical manifestation and severity [2,3]. At one end of the spectrum the outcome may be spontaneous resolution without antibiotics, but at the other end it may present with sepsis with lethal outcome. SSTI at 10% is the third most frequent focus for severe sepsis or septic shock, after pneumonia (5560%) and abdominal infections (25%) [4].This review aims to discuss the currently available antibiotics active against resistant bacteria (primarily MRSA, VRE, ESBL-producing bacteria and carbapenem-resistant strains) in terms of mechanisms of action, eradication rates and most important clinical outcome.The classification of skin and soft tissue infections is often confusing. Specific SSTI can be sub-categorised according to the causative microbial agents, the main tissue layer affected (i.e. skin, subcutis, fascia and muscle) or according to clinical signs and symptoms. It is to be differentiated, whether the infection is localised or generalised. Useful classifications are those which differentiate SSTI according to urgency of surgical intervention [5,6]. Three categories can be
Isospectral Finiteness of Hyperbolic Orbisurfaces
Emily B. Dryden
Mathematics , 2004,
Abstract: We discuss questions of isospectrality for hyperbolic orbisurfaces, examining the relationship between the geometry of an orbisurface and its Laplace spectrum. We show that certain hyperbolic orbisurfaces cannot be isospectral, where the obstructions involve the number of singular points and genera of our orbisurfaces. Using a version of the Selberg Trace Formula for hyperbolic orbisurfaces, we show that the Laplace spectrum determines the length spectrum and the orders of the singular points, up to finitely many possibilities. Conversely, knowledge of the length spectrum and the orders of the singular points determines the Laplace spectrum. This partial generalization of Huber's theorem is used to prove that isospectral sets of hyperbolic orbisurfaces have finite cardinality, generalizing a result of McKean for Riemann surfaces.
Statistical analysis on high-dimensional spheres and shape spaces
Ian L. Dryden
Mathematics , 2005, DOI: 10.1214/009053605000000264
Abstract: We consider the statistical analysis of data on high-dimensional spheres and shape spaces. The work is of particular relevance to applications where high-dimensional data are available--a commonly encountered situation in many disciplines. First the uniform measure on the infinite-dimensional sphere is reviewed, together with connections with Wiener measure. We then discuss densities of Gaussian measures with respect to Wiener measure. Some nonuniform distributions on infinite-dimensional spheres and shape spaces are introduced, and special cases which have important practical consequences are considered. We focus on the high-dimensional real and complex Bingham, uniform, von Mises-Fisher, Fisher-Bingham and the real and complex Watson distributions. Asymptotic distributions in the cases where dimension and sample size are large are discussed. Approximations for practical maximum likelihood based inference are considered, and in particular we discuss an application to brain shape modeling.
Collars and partitions of hyperbolic cone-surfaces
Emily B. Dryden,Hugo Parlier
Mathematics , 2004, DOI: 10.1007/s10711-007-9172-6
Abstract: For compact Riemann surfaces, the collar theorem and Bers' partition theorem are major tools for working with simple closed geodesics. The main goal of this paper is to prove similar theorems for hyperbolic cone-surfaces. Hyperbolic two-dimensional orbifolds are a particular case of such surfaces. We consider all cone angles to be strictly less than $\pi$ to be able to consider partitions.
Huber's theorem for hyperbolic orbisurfaces
Emily B. Dryden,Alexander Strohmaier
Mathematics , 2005, DOI: 10.4153/CMB-2009-008-0
Abstract: We show that for compact orientable hyperbolic orbisurfaces, the Laplace spectrum determines the length spectrum as well as the number of singular points of a given order. The converse also holds, giving a full generalization of Huber's theorem to the setting of compact orientable hyperbolic orbisurfaces.
Bayesian matching of unlabelled point sets using Procrustes and configuration models
Kim Kenobi,Ian L. Dryden
Statistics , 2010,
Abstract: The problem of matching unlabelled point sets using Bayesian inference is considered. Two recently proposed models for the likelihood are compared, based on the Procrustes size-and-shape and the full configuration. Bayesian inference is carried out for matching point sets using Markov chain Monte Carlo simulation. An improvement to the existing Procrustes algorithm is proposed which improves convergence rates, using occasional large jumps in the burn-in period. The Procrustes and configuration methods are compared in a simulation study and using real data, where it is of interest to estimate the strengths of matches between protein binding sites. The performance of both methods is generally quite similar, and a connection between the two models is made using a Laplace approximation.
Mapping properties of the heat operator on edge manifolds
Eric Bahuaud,Emily B. Dryden,Boris Vertman
Mathematics , 2011, DOI: 10.1002/mana.201300188
Abstract: We consider the heat operator acting on differential forms on spaces with complete and incomplete edge metrics. In the latter case we study the heat operator of the Hodge Laplacian with algebraic boundary conditions at the edge singularity. We establish the mapping properties of the heat operator, recovering and extending the classical results from smooth manifolds and conical spaces. The estimates, together with strong continuity of the heat operator, yield short-time existence of solutions to certain semilinear parabolic equations. Our discussion reviews and generalizes earlier work by Jeffres and Loya.
Bayesian registration of functions and curves
Wen Cheng,Ian L. Dryden,Xianzheng Huang
Statistics , 2013,
Abstract: Bayesian analysis of functions and curves is considered, where warping and other geometrical transformations are often required for meaningful comparisons. We focus on two applications involving the classification of mouse vertebrae shape outlines and the alignment of mass spectrometry data in proteomics. The functions and curves of interest are represented using the recently introduced square root velocity function, which enables a warping invariant elastic distance to be calculated in a straightforward manner. We distinguish between various spaces of interest: the original space, the ambient space after standardizing, and the quotient space after removing a group of transformations. Using Gaussian process models in the ambient space and Dirichlet priors for the warping functions, we explore Bayesian inference for curves and functions. Markov chain Monte Carlo algorithms are introduced for simulating from the posterior, including simulated tempering for multimodal posteriors. We also compare ambient and quotient space estimators for mean shape, and explain their frequent similarity in many practical problems using a Laplace approximation. A simulation study is carried out, as well as shape classification of the mouse vertebra outlines and practical alignment of the mass spectrometry functions.
Penalized Euclidean Distance Regression
D. Vasiliu,T. Dey,I. L. Dryden
Statistics , 2014,
Abstract: A new method is proposed for variable screening, variable selection and prediction in linear regression problems where the number of predictors can be much larger than the number of observations. The method involves minimizing a penalized Euclidean distance, where the penalty is the geometric mean of the $\ell_1$ and $\ell_2$ norms of the regression coefficients. This particular formulation exhibits a grouping effect, which is useful for screening out predictors in higher or ultra-high dimensional problems. Also, an important result is a signal recovery theorem, which does not require an estimate of the noise standard deviation. Practical performances of variable selection and prediction are evaluated through simulation studies and the analysis of a dataset of mass spectrometry scans from melanoma patients, where excellent predictive performance is obtained.
Rank-based model selection for multiple ions quantum tomography
Madalin Guta,Theodore Kypraios,Ian Dryden
Statistics , 2012, DOI: 10.1088/1367-2630/14/10/105002
Abstract: The statistical analysis of measurement data has become a key component of many quantum engineering experiments. As standard full state tomography becomes unfeasible for large dimensional quantum systems, one needs to exploit prior information and the "sparsity" properties of the experimental state in order to reduce the dimensionality of the estimation problem. In this paper we propose model selection as a general principle for finding the simplest, or most parsimonious explanation of the data, by fitting different models and choosing the estimator with the best trade-off between likelihood fit and model complexity. We apply two well established model selection methods -- the Akaike information criterion (AIC) and the Bayesian information criterion (BIC) -- to models consising of states of fixed rank and datasets such as are currently produced in multiple ions experiments. We test the performance of AIC and BIC on randomly chosen low rank states of 4 ions, and study the dependence of the selected rank with the number of measurement repetitions for one ion states. We then apply the methods to real data from a 4 ions experiment aimed at creating a Smolin state of rank 4. The two methods indicate that the optimal model for describing the data lies between ranks 6 and 9, and the Pearson $\chi^{2}$ test is applied to validate this conclusion. Additionally we find that the mean square error of the maximum likelihood estimator for pure states is close to that of the optimal over all possible measurements.
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