Perturbation of matrices and non-negative rank with a view toward statistical models

In this paper we study how perturbing a matrix changes its non-negative rank. We prove that the non-negative rank is upper-semicontinuos and we describe some special families of perturbations. We show how our results relate to Statistics in terms of the study of Maximum Likelihood Estimation for mixture models.Comment: 13 pages, 3 figures. A theorem has been rewritten, and some improvements in the presentations have been implemente

Complementarity of Entanglement and Interference

A complementarity relation is shown between the visibility of interference and bipartite entanglement in a two qubit interferometric system when the parameters of the quantum operation change for a given input state. The entanglement measure is a decreasing function of the visibility of interference. The implications for quantum computation are briefly discussed.Comment: Final version, to appear on IJMPC; minor revision

Square Root Actions, Metric Signature, and the Path-Integral of Quantum Gravity

We consider quantization of the Baierlein-Sharp-Wheeler form of the gravitational action, in which the lapse function is determined from the Hamiltonian constraint. This action has a square root form, analogous to the actions of the relativistic particle and Nambu string. We argue that path-integral quantization of the gravitational action should be based on a path integrand $\exp[ \sqrt{i} S ]$ rather than the familiar Feynman expression $\exp[ i S ]$, and that unitarity requires integration over manifolds of both Euclidean and Lorentzian signature. We discuss the relation of this path integral to our previous considerations regarding the problem of time, and extend our approach to include fermions.Comment: 32 pages, latex. The revision is a more general treatment of the regulator. Local constraints are now derived from a requirement of regulator independenc

On the dimensions of secant varieties of Segre-Veronese varieties

This paper explores the dimensions of higher secant varieties to Segre-Veronese varieties. The main goal of this paper is to introduce two different inductive techniques. These techniques enable one to reduce the computation of the dimension of the secant variety in a high dimensional case to the computation of the dimensions of secant varieties in low dimensional cases. As an application of these inductive approaches, we will prove non-defectivity of secant varieties of certain two-factor Segre-Veronese varieties. We also use these methods to give a complete classification of defective s-th Segre-Veronese varieties for small s. In the final section, we propose a conjecture about defective two-factor Segre-Veronese varieties.Comment: Revised version. To appear in Annali di Matematica Pura e Applicat

Down-Hole Heat Exchangers: Modelling of a Low-Enthalpy Geothermal System for District Heating

In order to face the growing energy demands, renewable energy sources can provide an alternative to fossil fuels. Thus, low-enthalpy geothermal plants may play a fundamental role in those areas—such as the Province of Viterbo—where shallow groundwater basins occur and conventional geothermal plants cannot be developed. This may lead to being fuelled by locally available sources. The aim of the present paper is to exploit the heat coming from a low-enthalpy geothermal system. The experimental plant consists in a down-hole heat exchanger for civil purposes and can supply thermal needs by district heating. An implementation in MATLAB environment is provided in order to develop a mathematical model. As a consequence, the amount of withdrawable heat can be successfully calculated

Actin Gene Family Evolution and the Phylogeny of Coleoid Cephalopods (Mollusca: Cephalopoda)

Phylogenetic analysis conducted on a 784-bp fragment of 82 actin gene sequences of 44 coleoid cephalopod taxa, along with results obtained from genomic Southern blot analysis, confirmed the presence of at least three distinct actin loci in coleoids. Actin isoforms were characteri zed through phylogenetic analysis of representative cephalopod sequences from each of the three isoforms, along with translated actin cDNA sequences from a diverse array of metazoan taxa downloaded from GenBank. One of the three isoforms found in cephalopods was closely related to actin sequences expressed in the muscular tissues of other molluscs. A second isoform was most similar to cytoplasmic-specific actin amino acid sequences. The muscle type actins of molluscs were found to be distinct from those of arthropods, suggesting at least two independent derivations of muscle actins in the protostome lineage, although statistical support for this conclusion was lacking. Parsimony and maximum-likelihood analyses of two of the isoforms from which \u3e30 orthologous coleoid sequences had been obtained (one of the cytoplasmic actins and the muscle actin) supported the monophyly of several higher-level coleoid taxa. These included the superorders Octopodiformes and Decapodiformes, the order Octopoda, the octopod suborder Incirrata, and the teuthoid suborder Myopsida. The monophyly of several taxonomic groups within the Decapodiformes was not supported, including the orders Teuthoidea and Sepioidea and the teuthoid suborder Oegopsida. Parametric bootstrap analysis conducted on the simulated cytoplasmic actin data set provided statistical support to reject the monophyly of the Sepioidea. Although parametric bootstrap analysis of the muscle actin isoform did not reject sepioid monophyly at the 5% level, the results (rejection at P = 0.068) were certainly suggestive of sepioid nonmonophyly

Geoestatística aplicada à atividade pecuária brasileira.

Este trabalho, portanto, tem como objetivo analisar geoestatísticamente os dados da pecuária brasileira e gerar mapas com informações interpoladas. Dessa maneira, pode-se inferir dependência espacial das variáveis, avaliando se estas possuem comportamento regional, e permitir uma leitura dos dados que considere as tendências no espaço. físico

Immature platelet fraction as predictive index of sepsis

Introduction The incidence of sepsis is reported around 37% in European ICUs [1]. The mortality rate depends on the severity of organ failure, up to 65% if four or more organs are involved. Multiple organ failure (MOF) is due to microcirculatory dysfunction with microthrombosis resulting from coagulation disorders including platelets’ activation. An early diagnosis should identify the microcirculatory dysfunction before MOF became clinically evident. The diagnosis of sepsis is commonly based on clinical criteria, pathogen identifi cation and use of markers like procalcitonin (PCT) and C-reactive protein (PCR) associated with infection. The aim of our study is to evaluate whether the routine measurement of immature platelet fraction (IPF), considered a precocious marker of platelet production, is associated with sepsis and its severity and/or whether it could be used as a predicting marker of sepsis. Methods We enrolled 66 consecutive patients admitted to the ICU, dividing them into two groups: septic (n = 44) and no septic (n = 22). The severity of sepsis was evaluated. The exclusion criterion was a platelet count <150,000/mm3. Blood count, coagulation, PCR, PCT, and IPF were collected every day. Results The IPF values between septic (4.6 ± 3.1) and no septic patients (3.3 ± 1.5) did not diff er (P = 0.16). No correlation was found between IPF values and the severity of septic condition (no sepsis 11.7 ± 10.1; sepsis 14.3 ± 10.5; severe sepsis 10.5 ± 9.1; septic shock 19.5 ± 12.4; P = 0.3). When we considered only subjects who did not have sepsis at the ICU admission we found that patients who developed sepsis during the recovery had IPF values higher than patients who did not develop sepsis (Table 1). Conclusions From our results IPF cannot be considered a marker of sepsis. Conversely it could be used as predictive index of sepsis because it can identify patients who will develop sepsis. References 1. Vincent et al.: Sepsis in European intensive care units: results of the SOAP study. Intensive Care Med 2006, 34:344-353