Implicit collinearity effect in linear regression: Application to basal metabolism rate prediction

Collinearity of predictor variables is a severe problem in the least square regression analysis. It contributes to the instability of regression coefficients and leads to a wrong prediction accuracy. Despite these problems, studies are conducted with a large number of observed and derived variables linked with a response variable. The aim of this study is to highlight a better understanding of the misleading effect of collinearity introduced by derived variables and the efficiency of alternative  methods. Twelve variables selection models were subjected to five parameter estimation methods characterized by their ability to reduce the collinearity effect. The response variable and eight anthropometric variables and two derived variables were collected with 200 children of 5 to 10 years old. We found that the  selection methods do not mitigate the collinearity of selected subset variables, the size of selected subset variables depends on the collinearity of data samples  and no significant correlation exists between sample and selected subset data collinearities. The analysis show that predictive quality did not improve with the  introduction of derived variables. The alternative methods did not result in significant efficiency of prediction quality. We  recommend avoiding the introduction of derived variables for the establishment of regression equation for prediction use.Keywords: Collinearity, prediction, regression, ridge regression, conditional likelihood, basal metabolism rate

Variabilité du taux des lymphocytes CD4 et de la charge virale chez les personnes vivant avec le VIH sous traitement antiretroviral: cas de l’hopital saint Jean De Dieu de Tanguieta (Benin)

L’objectif de cette étude était de mesurer l’impact des traitements antirétroviraux d’importation sur la charge virale et sur le taux des lymphocytes CD4 des personnes vivant avec le Virus de l’Immunodéficience Humaine (PV VIH) en phase du syndrome de l’immunodéficience acquise (SIDA) de l’hôpital de Tanguiéta au Bénin. L’étude était de type transversal, l’échantillonnage exhaustif avec recrutement de tous les malades sous traitement antirétroviral répondant aux critères d’inclusion de l’étude. La durée de l’étude était de 9 mois et la taille de l’échantillon de 94 patients. Les données collectées ont été contrôlées et saisies à l’aide du logiciel SPSS 15.0 For Windows et les tableaux réalisés après conception d’un programme d’analyse. Les résultats obtenus ont montré que la charge virale après quatre mois de traitement devenait indétectable chez 50% des patients et que 79,70% d’entre eux devenaient immunocompétents (r = - 0,5). Après douze mois de traitement, 83,30% et 86% des patients avaient une charge virale indétectable et recouvraient leur immunocompétence respectivement (r = 0,11). De l’analyse des données, il ressort que les antirétroviraux ont une efficacité sur la population étudiée. Le taux des lymphocytes CD4 et la charge virale évoluent en sens inverses au cours du traitement. L’utilisation du coefficient de corrélation r permet de suivre l’efficacité de la thérapie antirétrovirale.Mots clés: ARV, CD4, PV VIH, coefficient de corrélatio

Impacts sanitaires liés à l’usage des eaux de puits, à l’assainissement et à l’aménagement à Gbôdjê dans l’arrondissement de Godomey au Bénin

Cette étude a pour objectif de faire le point sur les ressources en eau utilisées, l’assainissement et l’estimation de l’impact sanitaire pour les populations riveraines de la ville de Cotonou au Bénin. Une enquête méthodologique basée sur des questionnaires a été réalisée du 21 septembre 2010 au 15 janvier 2011, dans l’arrondissement de Godomey au Bénin. Les résultats indiquent que la gestion des ressources en eau et de l’assainissement de l’environnement constituent un véritable problème dans les 2 quartiers déshérités de Gbôdjê/Womey et Rails, à cause d’une forte croissance démographique qui s’accompagne d’un développement spatial anarchique, échappant au contrôle des pouvoirs publics. Sur un échantillon de 122 concessions, 37,50% sont abonnés au réseau public mais la plupart (98,36%) utilise les eaux de puits à diverses fins. Les ouvrages d’assainissement pour les Water Closers (WC) modernes sont de 2,24% contre 97,76% de latrines ; 12,71% des concessions défèquent dans la nature. Pour le nettoyage, 15,57% des concessions sont malsaines. 82,50% des concessions déversent les eaux usées domestiques et ordures dans la nature. La santé de la population semble être menacée par les maladies hydriques avec 82,25%, 12,28% et 4,78%, respectivement pour le paludisme, maladies diarrhéiques et cutanées.Mots clés: Population riveraine, concessions, gestion des ressources, maladies hydrique

A Spatial-Epistemic Logic for Reasoning about Security Protocols

Reasoning about security properties involves reasoning about where the information of a system is located, and how it evolves over time. While most security analysis techniques need to cope with some notions of information locality and knowledge propagation, usually they do not provide a general language for expressing arbitrary properties involving local knowledge and knowledge transfer. Building on this observation, we introduce a framework for security protocol analysis based on dynamic spatial logic specifications. Our computational model is a variant of existing pi-calculi, while specifications are expressed in a dynamic spatial logic extended with an epistemic operator. We present the syntax and semantics of the model and logic, and discuss the expressiveness of the approach, showing it complete for passive attackers. We also prove that generic Dolev-Yao attackers may be mechanically determined for any deterministic finite protocol, and discuss how this result may be used to reason about security properties of open systems. We also present a model-checking algorithm for our logic, which has been implemented as an extension to the SLMC system.Comment: In Proceedings SecCo 2010, arXiv:1102.516

A Booster Vaccine Expressing a Latency-Associated Antigen Augments BCG Induced Immunity and Confers Enhanced Protection against Tuberculosis

BACKGROUND: In spite of a consistent protection against tuberculosis (TB) in children, Mycobacterium bovis Bacille Calmette-Guerin (BCG) fails to provide adequate protection against the disease in adults as well as against reactivation of latent infections or exogenous reinfections. It has been speculated that failure to generate adequate memory T cell response, elicitation of inadequate immune response against latency-associated antigens and inability to impart long-term immunity against M. tuberculosis infections are some of the key factors responsible for the limited efficiency of BCG in controlling TB. METHODS/PRINCIPAL FINDINGS: In this study, we evaluated the ability of a DNA vaccine expressing α-crystallin--a key latency antigen of M. tuberculosis to boost the BCG induced immunity. 'BCG prime-DNA boost' regimen (B/D) confers robust protection in guinea pigs along with a reduced pathology in comparison to BCG vaccination (1.37 log(10) and 1.96 log(10) fewer bacilli in lungs and spleen, respectively; p<0.01). In addition, B/D regimen also confers enhanced protection in mice. Further, we show that B/D immunization in mice results in a heightened frequency of PPD and antigen specific multi-functional CD4 T cells (3(+)) simultaneously producing interferon (IFN)γ, tumor necrosis factor (TNF)α and interleukin (IL)2. CONCLUSIONS/SIGNIFICANCE: These results clearly indicate the superiority of α-crystallin based B/D regimen over BCG. Our study, also demonstrates that protection against TB is predictable by an increased frequency of 3(+) Th1 cells with superior effector functions. We anticipate that this study would significantly contribute towards the development of superior booster vaccines for BCG vaccinated individuals. In addition, this regimen can also be expected to reduce the risk of developing active TB due to reactivation of latent infection

Minimality results for the spatial logics

1 Introduction Over the last 15 years, a lot of research has gone into calculi of mobile processes.Among these, the ss-calculus is the best known. A number of other calculi, how-ever, have been put forward to study aspects of mobility not directly covere

A complete axiomisation for quantifier-free separation logic

We present the first complete axiomatisation for quantifier-free separation logic. The logic is equipped with the standard concrete heaplet semantics and the proof system has no external feature such as nominals/labels. It is not possible to rely completely on proof systems for Boolean BI as the concrete semantics needs to be taken into account. Therefore, we present the first internal Hilbert-style axiomatisation for quantifier-free separation logic. The calculus is divided in three parts: the axiomatisation of core formulae where Boolean combinations of core formulae capture the expressivity of the whole logic, axioms and inference rules to simulate a bottom-up elimination of separating connectives, and finally structural axioms and inference rules from propositional calculus and Boolean BI with the magic wand

On the almighty wand

We investigate decidability, complexity and expressive power issues for (first-order) separation logic with one record field (herein called SL) and its fragments. SL can specify properties about the memory heap of programs with singly-linked lists. Separation logic with two record fields is known to be undecidable by reduction of finite satisfiability for classical predicate logic with one binary relation. Surprisingly, we show that second-order logic is as expressive as SL and as a by-product we get undecidability of St.. This is refined by showing that SL without the separating conjunction is as expressive as SL, whence undecidable too. As a consequence, in SL the separating implication (also known as the magic wand) can simulate the separating conjunction. By contrast, we establish that SL without the magic wand is decidable, and we prove a non-elementary complexity by reduction from satisfiability for the first-order theory over finite words. This result is extended with a bounded use of the magic wand that appears in Hoare-style rules. As a generalization, it is shown that kSL, the separation logic over heaps with k &gt;= 1 record fields, is equivalent to kSO, the second-order logic over heaps with k record fields. (C) 2012 Elsevier Inc. All rights reserved

On Symbolic Heaps Modulo Permission Theories

International audienceWe address the entailment problem for separation logic with symbolic heaps admitting list predicates and permissions for memory cells that are essential to express ownership of a heap region. In the permission-free case, the entailment problem is known to be in P. Herein, we design new decision procedures for solving the satisfiability and entailment problems that are parameterised by the permission theories. This permits the use of solvers dealing with the permission theory at hand, independently of the shape analysis. We also show that the entailment problem without list predicates is coNP-complete for several permission models, such as counting permissions and binary tree shares but the problem is in P for fractional permissions. Furthermore, when list predicates are added, we prove that the entailment problem is coNP-complete when the entail-ment problem for permission formulae is in coNP, assuming the write permission can be split into as many read permissions as desired. Finally, we show that the entailment problem for any Boolean permission model with infinite width is coNP-complete. 1 Introduction Separation logics with permissions. In program verification, proving properties of the memory is one of the most difficult tasks and separation logic has been devised for this goal [14]. Separation logic with permissions [4] can express that the ownership of a given heap region is shared with other threads. A permission can be thought of as a "quantity of ownership" associated to each cell of the heap. This quantity prescribes whether write accesses are allowed or not on this cell and how such a write access may be restored in the future. This abstract notion has lead to many permission theories and separation logics, including fractional permissions [5], token-based permissions [4], combinations of the two, binary tree shares [7], and yet some other models. Separation logic with permissions is supported by several tools like VeriFast [12], Hip/Sleek [11], or Heap-Hop [16]. Usually, these tools support only one permission model and demand that permissions are explicit values. For instance, in a tool that supports fractional permissions, to express that a cell x is shared by two threads for read access, one may write x 0.3 → y and x 0.7 → y making an arbitrary choice for permissions (0.3 and 0.7) when a better approach would use x α → y and x β → y and the constraint 1 = α + β (as it is done in the paper). This hides the logical structure of the proof and ties it to a specific arbitrary permission model. Our motivations. We wish to get rid of the use of explicit permission models and to provide a separation logic with permissions which can use symbolic permission expression

Induction of cytotoxic T-cell responses against culture filtrate antigens in Mycobacterium bovis bacillus Calmette-Guérin-infected mice.

CD8+ T cells are essential for protection against mycobacteria, as is clearly demonstrated by the fatal outcome of experimental infection of beta-2 microglobulin knockout mice. However, the mechanisms and antigens (Ags) leading to CD8+ T-cell activation and regulation have been poorly characterized. Here we show that, upon immunization of major histocompatibility complex (MHC)-congenic mice with Mycobacterium bovis bacillus Calmette-Guérin (BCG), a cytotoxic response against BCG culture filtrate (CF) Ags (CFAgs) is induced in H-2b and H-2bxd haplotypes but not in H-2d haplotype. This response is mediated by CD8+ T cells and absolutely requires the activation of CD4+ T cells and their secretion of interleukin 2. The lack of cytotoxic response in H-2d mice cannot be explained by impaired cytokine production or by a defect in Ag presentation by H-2d macrophages. Using the MHC class I mutant B6.C-H-2bm13 mouse strain, we demonstrate that cytotoxic T lymphocytes (CTLs) recognize CFAgs exclusively in association with D(b) molecules. These Ags are cross-reactive in mycobacteria, since BCG-induced CTLs also recognize macrophages pulsed with CF from Mycobacterium tuberculosis H37Rv and H37Ra and from two virulent strains of M. bovis. Moreover, immunization with Mycobacterium kansasii induces CTLs able to lyse macrophages pulsed with BCG CF. Finally, we have found that these Ags can be characterized as hydrophilic proteins, since they do not bind to phenyl-Sepharose CL-4B. Our results indicate that MHC-linked genes exert a profound influence on the generation of CD8+ CTLs following BCG vaccination