5,558 research outputs found
Reducing the Number of Sputum Samples Examined and Thresholds for Positivity: An Opportunity to Optimise Smear Microscopy.
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
Evolution of the decay mechanisms in central collisions of + from = 8 to 29
Collisions of Xe+Sn at beam energies of = 8 to 29 and leading to
fusion-like heavy residues are studied using the INDRA multidetector.
The fusion cross section was measured and shows a maximum at = 18-20
. A decomposition into four exit-channels consisting of the number of
heavy fragments produced in central collisions has been made. Their relative
yields are measured as a function of the incident beam energy. The energy
spectra of light charged particles (LCP) in coincidence with the fragments of
each exit-channel have been analyzed. They reveal that a composite system is
formed, it is highly excited and first decays by emitting light particles and
then may breakup into 2- or many- fragments or survives as an evaporative
residue. A quantitative estimation of this primary emission is given and
compared to the secondary decay of the fragments. These analyses indicate that
most of the evaporative LCP precede not only fission but also breakup into
several fragments.Comment: Invited Talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
The method of Gaussian weighted trajectories. V. On the 1GB procedure for polyatomic processes
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
Un procedimiento para obtener clusters utilizando la D.V.S. de una matriz. Comparaciones con el biplot y con el modelo Q-factorial
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 artÃculo 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
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
Added value of bleach sedimentation microscopy for diagnosis of tuberculosis: a cost-effectiveness study.
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
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
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