1,739 research outputs found

    A Simple Novel Method for Determining Mortality Rates in HIV Treatment Programs Worldwide

    Get PDF
    In this Perspective, Gregory Bisson discusses a new article by Matthias Egger and colleagues that introduces a simple method for HIV treatment programs to more accurately estimate the proportion of patients dying in the first year after ART initiation

    Responses of salmonids to habitat changes

    Get PDF
    Streams in western North America provide spawning and rearing habitats for several species of salmon and trout that are of substantial economic importance in the region. Timber that grows on lands through which these streams flow is also economically important, and its harvest can substantially change habitat conditions and aquatic production in salmonid streams. Undisturbed forests, the streams that flow through them, and the salmonid communities in these streams have intrinsic scientific, genetic, and cultural values in addition to their economic importance. The complex relations between salmonids and their physical environment, and the changes in these relations brought about by timber harvest, have been investigated extensively (see the bibliography by Macdonald et al. 1988). However, in spite of considerable evidence of profound changes in channel morphology and in light, temperature, and flow regimes associated with timber harvests, much uncertainty exists about the responses of salmonids to these changes

    Homology modeling and dynamics of the extracellular domain of rat and human neuronal nicotinic acetylcholine receptor subtypes α4ÎČ2 and α7

    Get PDF
    In recent years, it has become clear that the neuronal nicotinic acetylcholine receptor (nAChR) is a valid target in the treatment of a variety of diseases, including Alzheimer's disease, anxiety, and nicotine addiction. As with most membrane proteins, information on the three-dimensional (3D) structure of nAChR is limited to data from electron microscopy, at a resolution that makes the application of structure-based design approaches to develop specific ligands difficult. Based on a high-resolution crystal structure of AChBP, homology models of the extracellular domain of the neuronal rat and human nAChR subtypes α4ÎČ2 and α7 (the subtypes most abundant in brain) were built, and their stability assessed with molecular dynamics (MD). All models built showed conformational stability over time, confirming the quality of the starting 3D model. Lipophilicity and electrostatic potential studies performed on the rat and human α4ÎČ2 and α7 nicotinic models were compared to AChBP, revealing the importance of the hydrophobic aromatic pocket and the critical role of the α-subunit Trp—the homolog of AChBP-Trp 143—for ligand binding. The models presented provide a valuable framework for the structure-based design of specific α4ÎČ2 nAChR subtype ligands aimed at improving therapeutic and diagnostic applications. Figure Electrostatic surface potential of the binding site cavity of the neuronal nicotinic acetylcholine receptor (nAChR). Nicotinic models performed with the MOLCAD program: a rat α7, b rat α4ÎČ2, c human α7, d human α4ÎČ2. All residues labeled are part of the α7 (a,c) or α4 (b,d) subunit with the exception of Phe 117, which belongs to subunit ÎČ2 (d). Violet Very negative, blue negative, yellow neutral, red very positiv

    Material Characterization and Real-Time Wear Evaluation of Pistons and Cylinder Liners of the Tiger 131 Military Tank

    Get PDF
    Material characterisation and wear evaluation of the original and replacement pistons and cylinder-liners of Tiger 131 is reported. Original piston and cylinder-liner were operative in the Tigers’ engine during WWII. The replacement piston and cylinder-liner were used as substitutes and were obtained after failure in two hours of operation in the actual engine. Material characterisation revealed that the original piston was aluminium silicon hypereutectic alloy whereas the replacement piston was aluminium copper alloy with very low silicon content. Both original and replacement cylinder-liners consisted of mostly iron which is indicative of cast iron, a common material for this application. The replacement piston average surface roughness was found to be 9.09 ÎŒm while for replacement cylinder-liner it was 5.78 ÎŒm

    The sticking probability of D2O-water on ice: Isotope effects and the influence of vibrational excitation

    Get PDF
    International audienceThe present study measures the sticking probability of heavy water (D2O) on H2O- and on D2O-ice and probes the influence of selective OD-stretch excitation on D2O sticking on these ices. Molecular beam techniques are combined with infrared laser excitation to allow for precise control of incident angle, translational energy, and vibrational state of the incident molecules. For a translational energy of 69 kJ/mol and large incident angles (Ξ ≄ 45°), the sticking probability of D2O on H2O-ice was found to be 1% lower than on D2O-ice. OD-stretch excitation by IR laser pumping of the incident D2O molecules produces no detectable change of the D2O sticking probability (<10−3). The results are compared with other gas/surface systems for which the effect of vibrational excitation on trapping has been probed experimentally

    Cryptococcus and Lymphocytic Meningitis in Botswana

    Get PDF
    We retrospectively reviewed microbiology data from a tertiary care hospital in Botswana and found that Cryptococcus neoformans was cultured from 15% (193/1307) of all cerebrospinal (CSF) fluid specimens submitted for analysis, making it the most common diagnosed cause of meningitis in this population. Moreover, almost 70% of CSF samples with significant lymphocytosis did not yield a pathogen, suggesting that many causes of lymphocytic meningitis are going undiagnosed

    Estimation de l'Ă©quivalent en eau du couvert nival au moyen d'images radar satellitaires

    Get PDF
    L'objectif de cette Ă©tude est de vĂ©rifier le potentiel des images radar Ă  synthĂšse d'ouverture (RSO) pour estimer l'Ă©quivalent en eau du couvert nival sur le bassin de la riviĂšre La Grande (Baie de James, QuĂ©bec). Il s'agit d'un milieu dominĂ© par une forĂȘt ouverte d'Ă©pinettes noires, des brĂ»lis et des tourbiĂšres. Cette information intĂ©resse grandement Hydro-QuĂ©bec qui gĂšre plusieurs installations hydro-Ă©lectriques dans cette rĂ©gion subarctique. Durant deux ans, six campagnes de terrain ont Ă©tĂ© rĂ©alisĂ©es sur le bassin de la riviĂšre La Grande et une dizaine d'images RSO du satellite europĂ©en ERS-1 ont Ă©tĂ© acquises, Ă©talonnĂ©es et gĂ©orĂ©fĂ©rencĂ©es, afin de dĂ©terminer la relation entre les coefficients de rĂ©trodiffusion des images radar (hiver et automne) et la rĂ©sistance thermique du couvert nival. Cette relation constitue la premiĂšre partie d'un algorithme d'estimation de l'Ă©quivalent en eau. Elle utilise plus spĂ©cifiquement le rapport de rĂ©trodiffusion, qui est la diffĂ©rence entre une image avec neige et une image sans neige. La deuxiĂšme partie de cette algorithme dĂ©duit l'Ă©quivalent en eau du couvert de neige Ă  partir de sa rĂ©sistance thermique et de sa densitĂ©, en se basant sur la relation physique Ă©tablie par les mesures de terrain. L'Ă©quivalent en eau du couvert nival a donc Ă©tĂ© estimĂ© pour quatre images de fĂ©vrier et mars 1994 et 1995. L'erreur moyenne sur l'estimation de l'Ă©quivalent en eau de la neige au sol est de 2% Ă  3% (-5 Ă  7mm) sur l'ensemble des sites d'Ă©chantillonnage avec un Ă©cart-type de 14 Ă  19% (-35 Ă  45mm). Ces rĂ©sultats ont encouragĂ© Hydro-QuĂ©bec Ă  poursuivre la recherche avec les donnĂ©es du satellite canadien RADARSAT (opĂ©rationnel depuis le 1er avril 1996) et Ă  dĂ©velopper un prototype pour la cartographie de l'Ă©quivalent en eau du couvert nival Ă  partir d'images radar.The goal of this study was to evaluate the potential of synthetic aperture radar (SAR) images for estimating the snow water equivalent (SWE) on the La Grande river watershed (James Bay area, QuĂ©bec). This information is of major interest for Hydro-QuĂ©bec, which exploits many hydroelectric complexes throughout this subarctic region. The La Grande watershed is composed of moderately dense to opened black spruce forests, opened areas, burned areas and peat bogs. Over two years (1994-1995), six field campaigns were carried out on a study site located between the LG4 and Laforge1 reservoir, in the center of the La Grande river watershed. The field measurements were of two types: 20 snow lines (depth, snow water equivalent (SWE), density) and 8 snow profiles (depth, density, grain size, temperature, dielectric constant). With these data, the thermal resistance of the snowpack was calculated for every test-site, using the depth, density and thermal conductivity of each layer. Concurrently, more than 10 SAR images (European Satellite ERS-1) of the study site were acquired, calibrated and georeferenced. The backscattering coefficients of all winter images were extracted. Using a reference image (snow-free), backscattering ratios were calculated. They are the difference between a winter image and a snow-free image. This process is used to reduce the impact of vegetation and topography. Then, the relationship between the backscattering ratios and the snowpack thermal resistance of february and march 1994 are established, as the first part of an algorithm developed to estimate the snow water equivalent. The second part of the algorithm infers the snowpack water equivalent from its thermal resistance and density, based on the physical relationship established with field data. This approach is based on studies conducted by INRS-Eau in a southern Quebec agricultural area (BERNIER and FORTIN (1998)). The hypothesis are based on the following: - The snowpack characteristics influence the underlying soil temperature;- The dielectric constant of the soil varies with the soil temperature under 0°C;- The radar signal is influenced by the soil dielectric constant;- Thus, the snowpack characteristics (thermal resistance) influence the radar signal. However, due to variations of soil humidity on the date of the reference image (september 1994), two slightly different relationships were obtained. One for open areas and open forests and one for burned areas and peat bogs. This shows the importance of using a good reference image, with homogeneous soil conditions. It could be better to obtain an image later in the fall, when the soil is frozen. The relationships established here are preliminary, as they use a small dataset. It is estimated that a better regression should be obtained with the acquisition of more images and with a greater range of snow characteristics. However, the algorithm is applied to test the applicability of the method. First, the algorithm was applied on the test-sites, using the images from February and March of 1994 and 1995. The mean error on the estimation of the snow water equivalent is 2% to 3% ( 5 to 7mm), with a deviation of 14% to 19% ( 35 to 45mm). The results are comparable for both years, even if the algorithm is based on 1994 data only. Secondly, the algorithm is applied on the whole images. A classification of a Landsat-TM image is used to identify the land cover of every pixel, which determines the regression and the snow density to be used in the algorithm. Four maps of the SWE are produced and resampled to a resolution of 500m. These are compared with the field measurements from the four nearest Hydro-Quebec snow survey sites. The SWE measured by Hydro-Quebec are all within the most dominant SWE class of each map. Further validation of the results will be possible when the algorithm can be applied on a sub-watershed, which is the actual scale used by Hydro-Quebec. However, the results of this study were sufficiently promising to Hydro-Quebec to support a follow up research with data from the canadian satellite RADARSAT (operational since april 1996). Meanwhile, to improve the algorithm, it is important to obtain a good and homogeneous reference image, to better assess the impact of the land cover and to acquire a dataset with a greater range of snow characteristics

    Active duty and ex-serving military personnel with post-traumatic stress disorder treated with psychological therapies: systematic review and meta-analysis

    Get PDF
    Background: Post-traumatic stress disorder (PTSD) is a major cause of morbidity amongst active duty and ex-serving military personnel. In recent years increasing efforts have been made to develop more effective treatments. Objective: To determine which psychological therapies are efficacious in treating active duty and ex-serving military personnel with post-traumatic stress disorder (PTSD). Method: A systematic review was undertaken according to Cochrane Collaboration Guidelines. The primary outcome measure was reduction in PTSD symptoms and the secondary outcome dropout. Results: Twenty-four studies with 2386 participants were included. Evidence demonstrated that CBT with a trauma focus (CBT-TF) was associated with the largest evidence of effect when compared to waitlist/usual care in reducing PTSD symptoms post treatment (10 studies; n = 524; SMD −1.22, −1.78 to −0.66). Group CBT-TF was less effective when compared to individual CBT-TF at reducing PTSD symptoms post treatment (1 study; n = 268; SMD −0.35, −0.11 to −0.59). Eye Movement Desensitization and Reprocessing (EMDR) therapy was not effective when compared to waitlist/usual care at reducing PTSD symptoms post treatment (4 studies; n = 92; SMD −0.83, −1.75 to 0.10). There was evidence of greater dropout from CBT-TF therapies compared to waitlist and Present Centred Therapy. Conclusions: The evidence, albeit limited, supports individual CBT-TF as the first-line psychological treatment of PTSD in active duty and ex-serving personnel. There is evidence for Group CBT-TF, but this is not as strong as for individual CBT-TF. EMDR cannot be recommended as a first line therapy at present and urgently requires further evaluation. Lower effect sizes than for other populations with PTSD and high levels of drop-out suggest that CBT-TF in its current formats is not optimally acceptable and further research is required to develop and evaluate more effective treatments for PTSD and complex PTSD in active duty and ex-serving military personnel
    • 

    corecore