Showing papers by "University of Bordeaux published in 2013"

Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimer's disease

Abstract: Eleven susceptibility loci for late-onset Alzheimer's disease (LOAD) were identified by previous studies; however, a large portion of the genetic risk for this disease remains unexplained. We conducted a large, two-stage meta-analysis of genome-wide association studies (GWAS) in individuals of European ancestry. In stage 1, we used genotyped and imputed data (7,055,881 SNPs) to perform meta-analysis on 4 previously published GWAS data sets consisting of 17,008 Alzheimer's disease cases and 37,154 controls. In stage 2, 11,632 SNPs were genotyped and tested for association in an independent set of 8,572 Alzheimer's disease cases and 11,312 controls. In addition to the APOE locus (encoding apolipoprotein E), 19 loci reached genome-wide significance (P < 5 × 10−8) in the combined stage 1 and stage 2 analysis, of which 11 are newly associated with Alzheimer's disease.

Habitable Zones Around Main-Sequence Stars: New Estimates

Abstract: Identifying terrestrial planets in the habitable zones (HZs) of other stars is one of the primary goals of ongoing radial velocity (RV) and transit exoplanet surveys and proposed future space missions. Most current estimates of the boundaries of the HZ are based on one-dimensional (1D), cloud-free, climate model calculations by Kasting et?al. However, this model used band models that were based on older HITRAN and HITEMP line-by-line databases. The inner edge of the HZ in the Kasting et?al. model was determined by loss of water, and the outer edge was determined by the maximum greenhouse provided by a CO2 atmosphere. A conservative estimate for the width of the HZ from this model in our solar system is 0.95-1.67?AU. Here an updated 1D radiative-convective, cloud-free climate model is used to obtain new estimates for HZ widths around F, G, K, and M stars. New H2O and CO2 absorption coefficients, derived from the HITRAN 2008 and HITEMP 2010 line-by-line databases, are important improvements to the climate model. According to the new model, the water-loss (inner HZ) and maximum greenhouse (outer HZ) limits for our solar system are at 0.99 and 1.70?AU, respectively, suggesting that the present Earth lies near the inner edge. Additional calculations are performed for stars with effective temperatures between 2600 and 7200?K, and the results are presented in parametric form, making them easy to apply to actual stars. The new model indicates that, near the inner edge of the HZ, there is no clear distinction between runaway greenhouse and water-loss limits for stars with T eff 5000?K, which has implications for ongoing planet searches around K and M stars. To assess the potential habitability of extrasolar terrestrial planets, we propose using stellar flux incident on a planet rather than equilibrium temperature. This removes the dependence on planetary (Bond) albedo, which varies depending on the host star's spectral type. We suggest that conservative estimates of the HZ (water-loss and maximum greenhouse limits) should be used for current RV surveys and Kepler mission to obtain a lower limit on ??, so that future flagship missions like TPF-C and Darwin are not undersized. Our model does not include the radiative effects of clouds; thus, the actual HZ boundaries may extend further in both directions than the estimates just given.

Terminal Complement Inhibitor Eculizumab in Atypical Hemolytic–Uremic Syndrome

Abstract: A b s t r ac t Background Atypical hemolytic–uremic syndrome is a genetic, life-threatening, chronic disease of complement-mediated thrombotic microangiopathy. Plasma exchange or infusion may transiently maintain normal levels of hematologic measures but does not treat the underlying systemic disease. Methods We conducted two prospective phase 2 trials in which patients with atypical hemo lytic–uremic syndrome who were 12 years of age or older received eculizumab for 26 weeks and during long-term extension phases. Patients with low platelet counts and renal damage (in trial 1) and those with renal damage but no decrease in the platelet count of more than 25% for at least 8 weeks during plasma exchange or infu sion (in trial 2) were recruited. The primary end points included a change in the platelet count (in trial 1) and thrombotic microangiopathy event–free status (no de crease in the platelet count of >25%, no plasma exchange or infusion, and no initia tion of dialysis) (in trial 2). Results A total of 37 patients (17 in trial 1 and 20 in trial 2) received eculizumab for a median of 64 and 62 weeks, respectively. Eculizumab resulted in increases in the platelet count; in trial 1, the mean increase in the count from baseline to week 26 was 73×10 9 per liter (P<0.001). In trial 2, 80% of the patients had thrombotic microangiopathy event–free status. Eculizumab was associated with significant improvement in all secondary end points, with continuous, time-dependent increases in the estimated glomerular filtration rate (GFR). In trial 1, dialysis was discontinued in 4 of 5 patients. Earlier intervention with eculiz umab was associated with significantly greater improvement in the estimated GFR. Eculizumab was also associated with improvement in healthrelated quality of life. No cumulative toxicity of therapy or serious infection-related adverse events, including meningococcal infections, were observed through the exten

Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis

Abstract: Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 10 × 10(-4)) In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 subjects with multiple sclerosis and 26,703 healthy controls In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 50 × 10(-8)), 3 of which we found after conditioning on previously identified variants Thus, there are now 110 established multiple sclerosis risk variants at 103 discrete loci outside of the major histocompatibility complex With high-resolution Bayesian fine mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association This study enhances the catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals

Searching for an Operational Definition of Frailty: A Delphi Method Based Consensus Statement. The Frailty Operative Definition-Consensus Conference Project

Abstract: BACKGROUND: There is no consensus regarding the definition of frailty for clinical uses. METHODS: A modified Delphi process was used to attempt to achieve consensus definition. Experts were selected from different fields and organized into five Focus Groups. A questionnaire was developed and sent to experts in the area of frailty. Responses and comments were analyzed using a pre-established strategy. Statements with an agreement more than or equal to 80% were accepted. RESULTS: Overall, 44% of the statements regarding the concept of frailty and 18% of the statements regarding diagnostic criteria were accepted. There was consensus on the value of screening for frailty and about the identification of six domains of frailty for inclusion in a clinical definition, but no agreement was reached concerning a specific set of clinical/laboratory biomarkers useful for diagnosis. CONCLUSIONS: There is agreement on the usefulness of defining frailty in clinical settings as well as on its main dimensions. However, additional research is needed before an operative definition of frailty can be established.

The second fermi large area telescope catalog of gamma-ray pulsars

Abstract: This catalog summarizes 117 high-confidence > 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data, through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

Detection of the characteristic pion-decay signature in supernova remnants

Abstract: Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.

Potential for evolutionary responses to climate change – evidence from tree populations

Abstract: Evolutionary responses are required for tree populations to be able to track climate change. Results of 250 years of common garden experiments show that most forest trees have evolved local adaptation, as evidenced by the adaptive differentiation of populations in quantitative traits, reflecting environmental conditions of population origins. On the basis of the patterns of quantitative variation for 19 adaptation-related traits studied in 59 tree species (mostly temperate and boreal species from the Northern hemisphere), we found that genetic differentiation between populations and clinal variation along environmental gradients were very common (respectively, 90% and 78% of cases). Thus, responding to climate change will likely require that the quantitative traits of populations again match their environments. We examine what kind of information is needed for evaluating the potential to respond, and what information is already available. We review the genetic models related to selection responses, and what is known currently about the genetic basis of the traits. We address special problems to be found at the range margins, and highlight the need for more modeling to understand specific issues at southern and northern margins. We need new common garden experiments for less known species. For extensively studied species, new experiments are needed outside the current ranges. Improving genomic information will allow better prediction of responses. Competitive and other interactions within species and interactions between species deserve more consideration. Despite the long generation times, the strong background in quantitative genetics and growing genomic resources make forest trees useful species for climate change research. The greatest adaptive response is expected when populations are large, have high genetic variability, selection is strong, and there is ecological opportunity for establishment of better adapted genotypes.

Theory of the spontaneous optical emission of nanosize photonic and plasmon resonators.

Abstract: We provide a self-consistent electromagnetic theory of the coupling between dipole emitters and dissipative nanoresonators. The theory that relies on the concept of quasinormal modes with complex frequencies provides an accurate closed-form expression for the electromagnetic local density of states of any photonic or plasmonic resonator with strong radiation leakage, absorption, and material dispersion. It represents a powerful tool to calculate and conceptualize the electromagnetic response of systems that are governed by a small number of resonance modes. We use the formalism to revisit Purcell's factor. The new formula substantially differs from the usual one; in particular, it predicts that a spectral detuning between the emitter and the resonance does not necessarily result in a Lorentzian response in the presence of dissipation. Comparisons with fully vectorial numerical calculations for plasmonic nanoresonators made of gold nanorods evidence the high accuracy of the predictions achieved by our semianalytical treatment.

The geographic diversity of nontuberculous mycobacteria isolated from pulmonary samples: an NTM-NET collaborative study

Abstract: A significant knowledge gap exists concerning the geographical distribution of nontuberculous mycobacteria (NTM) isolation worldwide. To provide a snapshot of NTM species distribution, global partners in the NTM-Network European Trials Group (NET) framework (www.ntm-net.org), a branch of the Tuberculosis Network European Trials Group (TB-NET), provided identification results of the total number of patients in 2008 in whom NTM were isolated from pulmonary samples. From these data, we visualised the relative distribution of the different NTM found per continent and per country. We received species identification data for 20 182 patients, from 62 laboratories in 30 countries across six continents. 91 different NTM species were isolated. Mycobacterium avium complex (MAC) bacteria predominated in most countries, followed by M. gordonae and M. xenopi. Important differences in geographical distribution of MAC species as well as M. xenopi, M. kansasii and rapid-growing mycobacteria were observed. This snapshot demonstrates that the species distribution among NTM isolates from pulmonary specimens in the year 2008 differed by continent and differed by country within these continents. These differences in species distribution may partly determine the frequency and manifestations of pulmonary NTM disease in each geographical location.

Herschel view of the Taurus B211/3 filament and striations: evidence of filamentary growth?

Abstract: We present first results from the Herschel Gould Belt survey for the B211/L1495 region in the Taurus molecular cloud. Thanks to their high sensitivity and dynamic range, the Herschel images reveal the structure of the dense, star-forming filament B211 with unprecedented detail, along with the presence of striations perpendicular to the filament and generally oriented along the magnetic field direction as traced by optical polarization vectors. Based on the column density and dust temperature maps derived from the Herschel data, we find that the radial density profile of the B211 filament approaches power-law behavior, ρ ∝ r−2.0± 0.4, at large radii and that the temperature profile exhibits a marked drop at small radii. The observed density and temperature profiles of the B211 filament are in good agreement with a theoretical model of a cylindrical filament undergoing gravitational contraction with a polytropic equation of state: P ∝ ργ and T ∝ ργ−1, with γ = 0.97 ± 0.01 < 1 (i.e., not strictly isothermal). The morphology of the column density map, where some of the perpendicular striations are apparently connected to the B211 filament, further suggests that the material may be accreting along the striations onto the main filament. The typical velocities expected for the infalling material in this picture are ~0.5–1 km s-1, which are consistent with the existing kinematical constraints from previous CO observations.

Controlling the Morphology and Performance of Bulk Heterojunctions in Solar Cells. Lessons Learned from the Benchmark Poly(3-hexylthiophene):[6,6]-Phenyl-C61-butyric Acid Methyl Ester System

Abstract: Heterojunctions in Solar Cells. Lessons Learned from the Benchmark Poly(3-hexylthiophene):[6,6]-Phenyl‐C61-butyric Acid Methyl Ester System Minh Trung Dang,† Lionel Hirsch,‡ Guillaume Wantz,‡ and James D. Wuest*,† †Deṕartement de Chimie, Universite ́ de Montreál, Pavillon J.-Armand Bombardier, 2900 boulevard Édouard-Montpetit, Montreál, Queb́ec H3T 1J4, Canada ‡Laboratoire de l'Inteǵration du Mateŕiau au System̀e, Universite ́ de Bordeaux, UMR CNRS 5218, École Nationale Supeŕieure de Chimie, Biologie et Physique, 16 Avenue Pey Berland, 33607 Pessac Cedex, France

Super-resolution imaging reveals that AMPA receptors inside synapses are dynamically organized in nanodomains regulated by PSD95.

Abstract: The spatiotemporal organization of neurotransmitter receptors in postsynaptic membranes is a fundamental determinant of synaptic transmission and information processing by the brain. Using four independent super-resolution light imaging methods and EM of genetically tagged and endogenous receptors, we show that, in rat hippocampal neurons, AMPARs are often highly concentrated inside synapses into a few clusters of ∼70 nm that contain ∼20 receptors. AMPARs are stabilized reversibly in these nanodomains and diffuse freely outside them. Nanodomains are dynamic in their shape and position within synapses and can form or disappear within minutes, although they are mostly stable for up to 1 h. AMPAR nanodomains are often, but not systematically, colocalized with clusters of the scaffold protein PSD95, which are generally of larger size than AMPAR nanoclusters. PSD95 expression level regulates AMPAR nanodomain size and compactness in parallel to miniature EPSC amplitude. Monte Carlo simulations further indicate the impact of AMPAR concentration in clusters on the efficacy of synaptic transmission. The observation that AMPARs are highly concentrated in nanodomains, instead of diffusively distributed in the PSD as generally thought, has important consequences on our understanding of excitatory neurotransmission. Furthermore, our results indicate that glutamatergic synaptic transmission is controlled by the nanometer-scale regulation of the size of these highly concentrated nanodomains.

Magnetic responsive polymer composite materials

Abstract: Magnetic responsive materials are the topic of intense research due to their potential breakthrough applications in the biomedical, coatings, microfluidics and microelectronics fields. By merging magnetic and polymer materials one can obtain composites with exceptional magnetic responsive features. Magnetic actuation provides unique capabilities as it can be spatially and temporally controlled, and can additionally be operated externally to the system, providing a non-invasive approach to remote control. We identified three classes of magnetic responsive composite materials, according to their activation mode and intended applications, which can be defined by the following aspects. (A) Their ability to be deformed (stretching, bending, rotation) upon exposure to a magnetic field. (B) The possibility of remotely dragging them to a targeted area, called magnetic guidance, which is particularly interesting for biomedical applications, including cell and biomolecule guidance and separation. (C) The opportunity to use magnetic induction for thermoresponsive polymer materials actuation, which has shown promising results for controlled drug release and shape memory devices. For each category, essential design parameters that allow fine-tuning of the properties of these magnetic responsive composites are presented using key examples.

An overview of the last advances in probiotic and prebiotic field

Abstract: Probiotics and prebiotics play an important role in human nutrition. In recent years there has been a significant increase in research on the characterization and verification potential health benefits associated with the use of probiotic and prebiotic. The main effects attributed to selected probiotics/prebiotic products have been proved by clinical trials, while others have been acquired on the basis of in vitro tests which require in vivo transposition in order to be validated. The main clinical reports in the literature for the application of probiotic have been done for the treatment of infectious diseases including viral, bacterial or antibiotic associated diarrhoea, relief of chronic bowel inflammatory diseases, immuno-modulation, lowering of serum cholesterol, decreased risk of colon cancer, improve lactose digestion, reduce allergies, and effect on intestinal microbiota. Although the large investigation for the health benefits, information on probiotic species, a specific strain-therapeutic application, and sufficient dosages, is not sufficiently studied to allow practical and rational consumption. Moreover, prebiotic oligosaccharides although provided curative and nutritional values, they are poorly understood in regard to their origin, the processes employed to generate them, their fermentation profiles, and dosages required for health effects. The present review summarizes guidelines reported on the literature in regard to clinician or therapeutic trials of probiotic and prebiotic.

N-Heterocyclic carbenes (NHCs) as organocatalysts and structural components in metal-free polymer synthesis

Abstract: The chemistry of N-heterocyclic carbenes (NHCs) has witnessed tremendous development in the past two decades: NHCs have not only become versatile ligands for transition metals, but have also emerged as powerful organic catalysts in molecular chemistry and, more recently, in metal-free polymer synthesis. To understand the success of NHCs, this review first presents the electronic properties of NHCs, their main synthetic methods, their handling, and their reactivity. Their ability to activate key functional groups (e.g. aldehydes, esters, heterocycles, silyl ketene acetals, alcohols) is then discussed in the context of molecular chemistry. Focus has been placed on the activation of substrates finding analogies with monomers (e.g. bis-aldehydes, multi-isocyanates, cyclic esters, epoxides, N-carboxyanhydrides, etc.) and/or initiators (e.g. hydroxy- or trimethylsilyl-containing reagents) employed in such “organopolymerisation” reactions utilizing NHCs. A variety of metal-free polymers, including aliphatic polyesters and polyethers, poly(α-peptoid)s, poly(meth)acrylates, polyurethanes, or polysiloxanes can be obtained in this way. The last section covers the use of NHCs as structural components of the polymer chain. Indeed, NHC-based photoinitiators, chain transfer agents or functionalizing agents, as well as bifunctional NHC monomer substrates, can also serve for metal-free polymer synthesis.

The PRESERVE mortality risk score and analysis of long-term outcomes after extracorporeal membrane oxygenation for severe acute respiratory distress syndrome

Abstract: Purpose This study was designed to identify factors associated with death by 6 months post-intensive care unit (ICU) discharge and to develop a practical mortality risk score for extracorporeal membrane oxygenation (ECMO)-treated acute respiratory distress syndrome (ARDS) patients. We also assessed long-term survivors’ health-related quality of life (HRQL), respiratory symptoms, and anxiety, depression and post-traumatic stress disorder (PTSD) frequencies.

Xylem embolism threshold for catastrophic hydraulic failure in angiosperm trees

Abstract: Hydraulic failure is one of the main causes of tree mortality in conditions of severe drought. Resistance to cavitation is known to be strongly related to drought tolerance and species survival in conifers, but the threshold of water-stress-induced embolism leading to catastrophic xylem dysfunction in angiosperms has been little studied. We investigated the link between drought tolerance, survival and xylem cavitation resistance in five angiosperm tree species known to have contrasting desic cation resistance thresholds. We exposed seedlings in a greenhouse to severe drought to generate extreme water stress. We monitored leaf water potential, total plant water loss rate, leaf transpiration, stomatal conductance and CO2 assimilation rate during drought exposure and after rewatering (recovery phase). The time required for the recovery of 50% of the maximum value of a given ecophysiological variable after rewatering was used to determine the critical water potential corresponding to the threshold beyond which the plant failed to recover. We also investigated the relationship between this potential and stem xylem cavitation resistance, as assessed from vulnerability curves. This minimum recoverable water potential was consistent between ecophysiological variables and varied considerably between species, from −3.4 to −6.0 MPa. This minimum recoverable water potential was strongly correlated with P50 and P88, the pressures inducing 50 and 88% losses of stem hydraulic conductance, respectively. Moreover, the embolism threshold leading to irreversible drought damage was found to be close to 88%, rather than the 50% previously reported for conifers. Hydraulic failure leading to irreversible droughtinduced global dysfunction in angiosperm tree species occurred at a very high level of xylem embolism, possibly reflecting the physiological characteristics of their stem water-transport system.

Multicompartmentalized polymeric systems: towards biomimetic cellular structure and function

Abstract: The cell is certainly one of the most complex and exciting systems in Nature that scientists are still trying to fully understand. Such a challenge pushes material scientists to seek to reproduce its perfection by building biomimetic materials with high-added value and previously unmatched properties. Thanks to their versatility, their robustness and the current state of polymer chemistry science, we believe polymer-based materials to constitute or represent ideal candidates when addressing the challenge of biomimicry, which defines the focus of this review. The first step consists in mimicking the structure of the cell: its inner compartments, the organelles, with a multicompartmentalized structure, and the rest, i.e. the cytoplasm minus the organelles (mainly cytoskeleton/cytosol) with gels or particular solutions (highly concentrated for example) in one compartment, and finally the combination of both. Achieving this first structural step enables us to considerably widen the gap of possibilities in drug delivery systems. Another powerful property of the cell lies in its metabolic function. The second step is therefore to achieve enzymatic reactions in a compartment, as occurs in the organelles, in a highly controlled, selective and efficient manner. We classify the most exciting polymersome nanoreactors reported in our opinion into two different subsections, depending on their very final concept or purpose of design. We also highlight in a thorough table the experimental sections crucial to such work. Finally, after achieving control over these prerequisites, scientists are able to combine them and push the frontiers of biomimicry further: from cell structure mimics towards a controlled biofunctionality. Such a biomimetic approach in material design and the future research it will stimulate, are believed to bring considerable enrichments to the fields of drug delivery, (bio)sensors, (bio)catalysis and (bio)technology.

P2-NaxVO2 system as electrodes for batteries and electron-correlated materials

Abstract: Layered oxides are important as electrode materials for batteries and because of the strong electronic correlations resulting from their unique structure. Electrochemical investigations of the layered P2-NaxVO2 system in sodium batteries together with in situ X-ray diffraction experiments now result in the elucidation of the room-temperature phase diagram of this system.

Evaluating theories of drought‐induced vegetation mortality using a multimodel–experiment framework

Abstract: 'Summary' 305 I. 'Background' 305 II. 'Model–experiment approach' 306 III. 'Simulations of hydraulic failure and carbon starvation' 310 IV. 'On thresholds vs duration of stress as drivers of mortality' 311 V. 'Interdependence of hydraulic failure and carbon starvation' 314 VI. 'Next-generation, traditional, and empirical models' 316 VII. 'A path forward' 317 VIII. 'Conclusions' 318 'Acknowledgements' 318 References 318 Summary Model–data comparisons of plant physiological processes provide an understanding of mechanisms underlying vegetation responses to climate. We simulated the physiology of a pinon pine–juniper woodland (Pinus edulis–Juniperus monosperma) that experienced mortality during a 5 yr precipitation-reduction experiment, allowing a framework with which to examine our knowledge of drought-induced tree mortality. We used six models designed for scales ranging from individual plants to a global level, all containing state-of-the-art representations of the internal hydraulic and carbohydrate dynamics of woody plants. Despite the large range of model structures, tuning, and parameterization employed, all simulations predicted hydraulic failure and carbon starvation processes co-occurring in dying trees of both species, with the time spent with severe hydraulic failure and carbon starvation, rather than absolute thresholds per se, being a better predictor of impending mortality. Model and empirical data suggest that limited carbon and water exchanges at stomatal, phloem, and below-ground interfaces were associated with mortality of both species. The model–data comparison suggests that the introduction of a mechanistic process into physiology-based models provides equal or improved predictive power over traditional process-model or empirical thresholds. Both biophysical and empirical modeling approaches are useful in understanding processes, particularly when the models fail, because they reveal mechanisms that are likely to underlie mortality. We suggest that for some ecosystems, integration of mechanistic pathogen models into current vegetation models, and evaluation against observations, could result in a breakthrough capability to simulate vegetation dynamics.

The First FERMI-LAT Gamma-Ray Burst Catalog

Abstract: In three years of observations since the beginning of nominal science operations in August 2008, the Large Area Telescope (LAT) on board the Fermi Gamma Ray Space Telescope has observed high-energy (>20 MeV) \gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ~ 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared to emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

Methods for measuring plant vulnerability to cavitation: a critical review

Abstract: Xylem cavitation resistance has profound implications for plant physiology and ecology. This process is characterized by a ‘vulnerability curve’ (VC) showing the variation of the percentage of cavitation as a function of xylem pressure potential. The shape of this VC varies from ‘sigmoidal’ to ‘exponential’. This review provides a panorama of the techniques that have been used to generate such a curve. The techniques differ by (i) the way cavitation is induced (e.g. bench dehydration, centrifugation, or air injection), and (ii) the way cavitation is measured (e.g. percentage loss of conductivity (PLC) or acoustic emission), and a nomenclature is proposed based on these two methods. A survey of the literature of more than 1200 VCs was used to draw statistics on the usage of these methods and on their reliability and validity. Four methods accounted for more than 96% of all curves produced so far: bench dehydration– PLC, centrifugation–PLC, pressure sleeve-PLC, and Cavitron. How the shape of VCs varies across techniques and species xylem anatomy was also analysed. Strikingly, it was found that the vast majority of curves obtained with the reference bench dehydration-PLC method are ‘sigmoidal’. ‘Exponential’ curves were more typical of the three other methods and were remarkably frequent for species having large xylem conduits (ring-porous), leading to a substantial overestimation of the vulnerability of cavitation for this functional group. We suspect that ‘exponential’ curves may reflect an open-vessel artefact and call for more precautions with the usage of the pressure sleeve and centrifugation techniques.

High-volume versus standard-volume haemofiltration for septic shock patients with acute kidney injury (IVOIRE study): a multicentre randomized controlled trial

Abstract: Purpose Septic shock is a leading cause of death among critically ill patients, in particular when complicated by acute kidney injury (AKI). Small experimental and human clinical studies have suggested that high-volume haemofiltration (HVHF) may improve haemodynamic profile and mortality. We sought to determine the impact of HVHF on 28-day mortality in critically ill patients with septic shock and AKI.

Risk Factors and Outcomes for Late Presentation for HIV-Positive Persons in Europe: Results from the Collaboration of Observational HIV Epidemiological Research Europe Study (COHERE).

Abstract: Background: Few studies have monitored late presentation (LP) of HIV infection over the European continent, including Eastern Europe. Study objectives were to explore the impact of LP on AIDS and mortality. Methods and Findings: LP was defined in Collaboration of Observational HIV Epidemiological Research Europe (COHERE) as HIV diagnosis with a CD4 count ,350/mm 3 or an AIDS diagnosis within 6 months of HIV diagnosis among persons presenting for care between 1 January 2000 and 30 June 2011. Logistic regression was used to identify factors associated with LP and Poisson regression to explore the impact on AIDS/death. 84,524 individuals from 23 cohorts in 35 countries contributed data; 45,488 were LP (53.8%). LP was highest in heterosexual males (66.1%), Southern European countries (57.0%), and persons originating from Africa (65.1%). LP decreased from 57.3% in 2000 to 51.7% in 2010/2011 (adjusted odds ratio [aOR] 0.96; 95% CI 0.95–0.97). LP decreased over time in both Central and Northern Europe among homosexual men, and male and female heterosexuals, but increased over time for female heterosexuals and male intravenous drug users (IDUs) from Southern Europe and in male and female IDUs from Eastern Europe. 8,187 AIDS/deaths occurred during 327,003 person-years of follow-up. In the first year after HIV diagnosis, LP was associated with over a 13-fold increased incidence of AIDS/death in Southern Europe (adjusted incidence rate ratio [aIRR] 13.02; 95% CI 8.19–20.70) and over a 6-fold increased rate in Eastern Europe (aIRR 6.64; 95% CI 3.55–12.43). Conclusions: LP has decreased over time across Europe, but remains a significant issue in the region in all HIV exposure groups. LP increased in male IDUs and female heterosexuals from Southern Europe and IDUs in Eastern Europe. LP was associated with an increased rate of AIDS/deaths, particularly in the first year after HIV diagnosis, with significant variation across Europe. Earlier and more widespread testing, timely referrals after testing positive, and improved retention in care strategies are required to further reduce the incidence of LP. Please see later in the article for the Editors’ Summary.