5,787 research outputs found

    Estimations for the Single Diffractive production of the Higgs boson at the Tevatron and the LHC

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    The single diffractive production of the standard model Higgs boson is computed using the diffractive factorization formalism, taking into account a parametrization for the Pomeron structure function provided by the H1 Collaboration. We compute the cross sections at next-to-leading order accuracy for the gluon fusion process, which includes QCD and electroweak corrections. The gap survival probability () is also introduced to account for the rescattering corrections due to spectator particles present in the interaction, and to this end we compare two different models for the survival factor. The diffractive ratios are predicted for proton-proton collisions at the Tevatron and the LHC for the Higgs boson mass of MHM_H = 120 GeV. Therefore, our results provide updated estimations for the diffractive ratios of the single diffractive production of the Higgs boson in the Tevatron and LHC kinematical regimes.Comment: 20 pages, 6 figures, 3 table

    Reducing the Number of Sputum Samples Examined and Thresholds for Positivity: An Opportunity to Optimise Smear Microscopy.

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    SETTING: Urban health clinic, Nairobi. OBJECTIVE: To evaluate the impact on tuberculosis (TB) case detection and laboratory workload of reducing the number of sputum smears examined and thresholds for diagnosing positive smears and positive cases. DESIGN: In this prospective study, three Ziehl-Neelsen stained sputum smears from consecutive pulmonary TB suspects were examined blind. The standard approach (A), > or = 2 positive smears out of 3, using a cut-off of 10 acid-fast bacilli (AFB)/100 high-power fields (HPF), was compared with approaches B, > or = 2 positive smears (> or = 4 AFB/100 HPF) out of 3, one of which is > or = 10 AFB/100 HPF; C, > or = 2 positive smears (> or = 4 AFB/100 HPF) out of 3; D, > or = 1 positive smear (> or = 10 AFB/100 HPF) out of 2; and E, > or = 1 positive smear (> or = 4 AFB/100 HPF) out of 2. The microscopy gold standard was detection of at least one positive smear (> or = 4 AFB/100 HPF) out of 3. RESULTS: Among 644 TB suspects, the alternative approaches detected from 114 (17.7%) (approach B) to 123 cases (19.1%) (approach E) compared to 105 cases (16.3%) for approach A (P < 0.005). Sensitivity ranged between 82.0% (105/128) for A and 96.1% (123/128) for E. The single positive smear approaches reduced the number of smears by 36% compared to approach A. CONCLUSION: Reducing the number of specimens and the positivity threshold to define a positive case increased the sensitivity of microscopy and reduced laboratory workload

    The method of Gaussian weighted trajectories. V. On the 1GB procedure for polyatomic processes

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    In recent years, many chemical reactions have been studied by means of the quasi-classical trajectory (QCT) method within the Gaussian binning (GB) procedure. The latter consists in "quantizing" the final vibrational actions in Bohr spirit by putting strong emphasis on the trajectories reaching the products with vibrational actions close to integer values. A major drawback of this procedure is that if N is the number of product vibrational modes, the amount of trajectories necessary to converge the calculations is ~ 10^N larger than with the standard QCT method. Applying it to polyatomic processes is thus problematic. In a recent paper, however, Czako and Bowman propose to quantize the total vibrational energy instead of the vibrational actions [G. Czako and J. M. Bowman, J. Chem. Phys., 131, 244302 (2009)], a procedure called 1GB here. The calculations are then only ~ 10 times more time-consuming than with the standard QCT method, allowing thereby for considerable numerical saving. In this paper, we propose some theoretical arguments supporting the 1GB procedure and check its validity on model test cases as well as the prototype four-atom reaction OH+D_2 -> HOD+D

    Added value of bleach sedimentation microscopy for diagnosis of tuberculosis: a cost-effectiveness study.

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    SETTING: Bleach sedimentation is a method used to increase the diagnostic yield of sputum microscopy for countries with a high prevalence of human immunodeficiency virus (HIV) infection and limited resources. OBJECTIVES: To compare the relative cost-effectiveness of different microscopy approaches in diagnosing tuberculosis (TB) in Kenya. METHODS: An analytical decision tree model including cost and effectiveness measures of 10 combinations of direct (D) and overnight bleach (B) sedimentation microscopy was constructed. Data were drawn from the evaluation of the bleach sedimentation method on two specimens (first on the spot [1] and second morning [2]) from 644 TB suspects in a peripheral health clinic. Incremental cost per smear-positive detected case was measured. Costs included human resources and materials using a micro-costing evaluation. RESULTS: All bleach-based microscopy approaches detected significantly more cases (between 23.3% for B1 and 25.9% for B1+B2) than the conventional D1+D2 approach (21.0%). Cost per tested case ranged between respectively euro 2.7 and euro 4.5 for B1 and B1+D2+B2. B1 and B1+B2 were the most cost-effective approaches. D1+B2 and D1+B1 were good alternatives to avoid using approaches exclusively based on bleach sedimentation microscopy. CONCLUSIONS: Among several effective microscopy approaches used, including sodium hypochlorite sedimentation, only some resulted in a limited increase in the laboratory workload and would be most suitable for programmatic implementation

    From angle-action to Cartesian coordinates: A key transformation for molecular dynamics

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    The transformation from angle-action variables to Cartesian coordinates is a crucial step of the (semi) classical description of bimolecular collisions and photo-fragmentations. The basic reason is that dynamical conditions corresponding to experiments are ideally generated in angle-action variables whereas the classical equations of motion are ideally solved in Cartesian coordinates by standard numerical approaches. To our knowledge, the previous transformation is available in the literature only for triatomic systems. The goal of the present work is to derive it for polyatomic ones.Comment: 10 pages, 11 figures, submitted to J. Chem. Phy

    Un procedimiento para obtener clusters utilizando la D.V.S. de una matriz. Comparaciones con el biplot y con el modelo Q-factorial

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    Durante las últimas décadas, el análisis de un conjunto de n individuos medidos en p variables, proporcionando una matriz de datos Xn,p, mediante técnicas de representación que utilizan la Descomposición en Valores Singulares de la matriz Xn,p (o alguna derivada), han permitido resumir la información que aportan los datos en alguna forma óptima, siendo muy útil para indicar la presencia de clusters entre los n individuos y/o para prevenir ante posibles clasificaciones erróneas producidas por técnicas de agrupamiento más complejas. En este artículo estudiaremos un procedimiento que puede utilizarse en ocasiones para obtener clasificaciones naturales de un conjunto de datos, basado en la representación biplot y en el modelo Q-factorial que puede obtenerse a partir de la DVS

    Effect of the reservoir size on gas adsorption in inhomogeneous porous media

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    We study the influence of the relative size of the reservoir on the adsorption isotherms of a fluid in disordered or inhomogeneous mesoporous solids. We consider both an atomistic model of a fluid in a simple, yet structured pore, whose adsorption isotherms are computed by molecular simulation, and a coarse-grained model for adsorption in a disordered mesoporous material, studied by a density functional approach in a local mean-field approximation. In both cases, the fluid inside the porous solid exchanges matter with a reservoir of gas that is at the same temperature and chemical potential and whose relative size can be varied, and the control parameter is the total number of molecules present in the porous sample and in the reservoir. Varying the relative sizes of the reservoir and the sample may change the shape of the hysteretic isotherms, leading to a "reentrant" behavior compared to the grand-canonical isotherm when the latter displays a jump in density. We relate these phenomena to the organization of the metastable states that are accessible for the adsorbed fluid at a given chemical potential or density.Comment: 16 page

    Desenvolvimento de modelos de regressão como contribuição para a análise de risco de resíduos de pesticidas em maçã.

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    O Plano Nacional de Controle de Resíduos e Contaminantes (PNCRC) do Ministério da Agricultura Pecuária e Abastecimento (MAPA) é um programa federal de fiscalização de alimentos que visa quantificar resíduos químicos potencialmente nocivos à saúde do consumidor. Os dados coletados pelo PNCRC provêm de uma amostragem homogênea e aleatória, em âmbito nacional, de diversos produtos de origem vegetal e animal, seguida de análises em laboratórios oficiais e credenciados pelo MAPA. Este trabalho objetiva o tratamento dos dados gerados pelo PNCRC, coletados no período de 2008 a 2011, relativos à análise de risco de resíduos de pesticidas em maçã, visando evidenciar correlações espaço-temporais relevantes quanto à concentração de diferentes resíduos químicos.CIIC 2014. Nº 14604

    Death rates from malaria epidemics, Burundi and Ethiopia.

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    Death rates exceeded emergency thresholds at 4 sites during epidemics of Plasmodium falciparum malaria in Burundi (2000-2001) and in Ethiopia (2003-2004). Deaths likely from malaria ranged from 1,000 to 8,900, depending on site, and accounted for 52% to 78% of total deaths. Earlier detection of malaria and better case management are needed
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