Two-stream-like instability in dilute hot relativistic beams and astrophysical relativistic shocks

Relativistic collisionless shocks are believed to be efficient particle accelerators. Nonlinear outcome of the interaction of accelerated particles that run ahead of the shock, the so-called "precursor", with the unperturbed plasma of the shock upstream, is thought to facilitate additional acceleration of these particles and to possibly modify the hydrodynamic structure of the shock. We explore here the linear growth of kinetic modes appearing in the precursor-upstream interaction in relativistic shocks propagating in non and weakly magnetized plasmas: electrostatic two-stream parallel mode and electrostatic oblique modes. These modes are of particular interest because they are the fastest growing modes known in this type of system. Using a simplified distribution function for a dilute ultra-relativistic beam that is relativistically hot in its own rest frame, yet has momenta that are narrowly collimated in the frame of the cold upstream plasma into which it propagates, we identify the fastest growing mode in the full $k$-space and calculate its growth rate. We consider all types of plasma (pairs and ions-electrons) and beam (charged and charge-neutral). We find that unstable electrostatic modes are present in any type of plasma and for any shock parameters. We further find that two modes, one parallel ($k_\perp=0$) and the other one oblique ($k_\perp \sim k_\|$), are competing for dominance and that either one may dominate the growth rate in different regions of the phase space. The dominant mode is determined mostly by the perpendicular spread of the accelerated particle momenta in the upstream frame, which reflects the shock Lorentz factor. The parallel mode becomes more dominant in shocks with lower Lorentz factors (i.e., with larger momentum spreads). We briefly discuss possible implications of our results for external shocks in gamma-ray burst sources

X-shooter, NACO, and AMBER observations of the LBV Pistol Star \footnote{Based on ESO runs 85.D-0182A, 085.D-0625AC}

We present multi-instruments and multi-wavelengths observations of the famous LBV star Pistol Star. These observations are part of a larger program about early O stars at different metallicities. The Pistol star has been claimed as the most massive star known, with 250 solar masses. We present the preliminary results based on X-Shooter spectra, as well as the observations performed with the VLTI-AMBER and the VLT-NACO adaptive optics. The X-shooter spectrograph allows to obtain simultaneously a spectrum from the UV to the K-band with a resolving power of $\sim$15000. The preliminary results obtained indicate that Pistol Star has similar properties of Eta Car, including shells of matter, but also the binarity. Other objects of the program, here briefly presented, were selected for their particular nature: early O stars with mass discrepancies between stellar evolution models and observations, discrepancies with the wind momentum luminosity relation.Comment: Poster at the 39th LIAC, submitted version of the proceeding

Peristomal Skin Complications Are Common, Expensive, and Difficult to Manage: A Population Based Cost Modeling Study

BACKGROUND: Peristomal skin complications (PSCs) are the most common post-operative complications following creation of a stoma. Living with a stoma is a challenge, not only for the patient and their carers, but also for society as a whole. Due to methodological problems of PSC assessment, the associated health-economic burden of medium to longterm complications has been poorly described. AIM: The aim of the present study was to create a model to estimate treatment costs of PSCs using the standardized assessment Ostomy Skin Tool as a reference. The resultant model was applied to a real-life global data set of stoma patients (n = 3017) to determine the prevalence and financial burden of PSCs. METHODS: Eleven experienced stoma care nurses were interviewed to get a global understanding of a treatment algorithm that formed the basis of the cost analysis. The estimated costs were based on a seven week treatment period. PSC costs were estimated for five underlying diagnostic categories and three levels of severity. The estimated treatment costs of severe cases of PSCs were increased 2-5 fold for the different diagnostic categories of PSCs compared with mild cases. French unit costs were applied to the global data set. RESULTS: The estimated total average cost for a seven week treatment period (including appliances and accessories) was 263€ for those with PSCs (n = 1742) compared to 215€ for those without PSCs (n = 1172). A co-variance analysis showed that leakage level had a significant impact on PSC cost from 'rarely/never' to 'always/often' p<0.00001 and from 'rarely/never' to 'sometimes' p = 0.0115. CONCLUSION: PSCs are common and troublesome and the consequences are substantial, both for the patient and from a health economic viewpoint. PSCs should be diagnosed and treated at an early stage to prevent long term, debilitating and expensive complications

The secretome of skeletal muscle cells: A systematic review

peer reviewedBackground Proteomic studies of the secretome of skeletal muscle cells can help us understand the processes that govern the synthesis, systemic interactions and organization of skeletal muscle and identify proteins that are involved in muscular adaptations to exercise, ageing and degeneration. In this systematic review, we aimed to summarize recent mass-spectrometry based proteomics discoveries on the secretome of skeletal muscle cells in response to disease, exercise or metabolic stress. Methods A literature search was performed in the Medline/Ovid and Scopus electronic bibliographic databases. Only papers reporting the analysis of the secretome by mass spectrometry were included. Results A total of 19 papers met the inclusion criteria for this systematic review. These papers included comparative analysis of differentially expressed proteins between healthy and unhealthy muscle cells and comparison of the secretome of skeletal muscle cells during myogenesis and after insulin stimulation or exercising. The proteins were separated into several categories and their differential secretion was compared. In total, 654 proteins were listed as being present in the secretome of muscle cells. Among them, 30 proteins were differentially regulated by physical exercise, 130 during myogenesis, 114 by dystrophin deficiency, 26 by muscle atrophy, 27 by insulin stimulation and finally 176 proteins secreted by insulin-resistant muscle cells. Conclusions This systematic review of the secretome of skeletal muscle cell in health and disease provides a comprehensive overview of the most regulated proteins in pathological or physiological conditions. These proteins might be therapeutic targets or biochemical markers of muscle diseases.Projet DEMAI

High-angular resolution observations of the Pistol Star

First results of near-IR adaptive optics (AO)-assisted imaging, interferometry, and spectroscopy of this Luminous Blue Variable (LBV) are presented. They suggest that the Pistol Star is at least double. If the association is physical, it would reinforce questions concerning the importance of multiplicity for the formation and evolution of extremely massive stars.Comment: poster at IAUS27

Loss-of-function alleles of P2RX7 and TLR4 fail to affect the response to chemotherapy in non-small cell lung cancer

The success of anticancer chemotherapy relies at least in part on the induction of an immune response against tumor cells. Thus, tumors growing on mice that lack the pattern recognition receptor TLR4 or the purinergic receptor P2RX7 fail to respond to chemotherapy with anthracyclins or oxaliplatin in conditions in which the same neoplasms growing on immunocompetent mice would do so. Similarly, the therapeutic efficacy (measured as progression-free survival) of adjuvant chemotherapy with anthracyclins is reduced in breast cancer patients bearing loss-of-function alleles of TLR4 or P2RX7. TLR4 loss-of-function alleles also have a negative impact on the therapeutic outcome of oxaliplatin in colorectal cancer patients. Here, we report that loss-of-function TLR4 and P2RX7 alleles do not affect overall survival in non-small cell lung cancer (NSCLC) patients, irrespective of the administration and type of chemotherapy. The intrinsic characteristics of NSCLC (which near-to-always is chemoresistant and associated with poor prognosis) and/or the type of therapy that is employed to treat this malignancy (which near-to-always is based on cisplatin) may explain why two genes that affect the immune response to dying cells fail to influence the clinical progression of NSCLC patients

Luminous blue variables: An imaging perspective on their binarity and near environment

Luminous blue variables (LBVs) are rare massive stars with very high luminosity. They are characterized by strong photo-metric and spectroscopic variability related to transient eruptions. The mechanisms at the origin of these eruptions is not well known. In addition, their formation is still problematic and the presence of a companion could help to explain how they form. Aims. This article presents a study of seven LBVs (about 20% of the known Galactic population), some Wolf-Rayet stars, and massive binaries. We probe the environments that surround these massive stars with near-, mid-, and far-infrared images, investigating potential nebula/shells and the companion stars. Methods. To investigate large spatial scales, we used seeing-limited and near diffraction-limited adaptive optics images to obtain a differential diagnostic on the presence of circumstellar matter and to determine their extent. From those images, we also looked for the presence of binary companions on a wide orbit. Once a companion was detected, its gravitational binding to the central star was tested. Tests include the chance projection probability, the proper motion estimates with multi-epoch observations, flux ratio, and star separations. Results. We find that two out of seven of LBVs may have a wide orbit companion. Most of the LBVs display a large circumstellar envelope or several shells. In particular, HD168625, known for its rings, possesses several shells with possibly a large cold shell at the edge of which the rings are formed. For the first time, we have directly imaged the companion of LBV stars

Validation of standard and alternative satellite ocean-color chlorophyll products off Western Iberia

Chlorophyll a concentration (Chl) product validation off theWestern Iberian coast is here undertaken by directly comparing remote sensing data with in situ surface reference values. Both standard and recently developed alternative algorithms are considered for match-up data analysis. The investigated standard products are those produced by the MERIS (algal 1 and algal 2) and MODIS (OC3M) algorithms. The alternative data products include those generatedwithin the CoastColour Project and Ocean Color Climate Change Initiative (OC-CCI) funded by ESA, as well as a neural net model trained with field measurements collected in the Atlantic off Portugal (MLPATLP). Statistical analyses showed that satellite Chl estimates tend to be larger than in situ reference values. The study also revealed that a non-uniform Chl distribution in the water column can be a concurring factor to the documented overestimation tendency when considering larger optical depth match-up stations. Among standard remote sensing products, MODIS OC3M and MERIS algal 2 yield the best agreement with in situ data. The performance of MLPATLP highlights the capability of regional solutions to further improve Chl retrieval by accounting for environmental specificities. Results also demonstrate the relevance of oceanographic regions such as the Nazaré area to evaluate how complex hydrodynamic conditions can influence the quality of Chl products.This studywas performed in the framework of HabSpot FCT Project, PTDC/MAR/100348/2008 and European Space Agency projects DUE CoastColour (ESRIN/AO/1-6141/09/l-EC) and Climate Change Iniciative — Ocean Color (AO-1/6207/09/I-LG). The work has been also partially supported by the European Space Agency within the framework of the MERIS Validation Activities under contract n. 12595/09/I-OL, and sampling activities benefited from European projects HERMES (GOCE-CT-2005-511234) and Hermione (EC contract 226354) support. We would like to thank NASA OBPG for the MODIS data and ESA Project AOPT-2423 for providing MERIS full resolution images. Ana C. Brito was funded by a Portuguese Post-doc grant from FCT (BPD/63017/2009) and by the Investigador FCT Program (IF/00331/2013). Davide D'Alimonte was funded by Investigador FCT Program (IF/00541/2013).info:eu-repo/semantics/publishedVersio

CO or no CO? Narrowing the CO abundance constraint and recovering the H2O detection in the atmosphere of WASP-127 b using SPIRou

Precise measurements of chemical abundances in planetary atmospheres are necessary to constrain the formation histories of exoplanets. A recent study of WASP-127b, a close-in puffy sub-Saturn orbiting its solar-type host star in 4.2 d, using HST and Spitzer revealed a feature-rich transmission spectrum with strong excess absorption at 4.5 um. However, the limited spectral resolution and coverage of these instruments could not distinguish between CO and/or CO2 absorption causing this signal, with both low and high C/O ratio scenarios being possible. Here we present near-infrared (0.9--2.5 um) transit observations of WASP-127 b using the high-resolution SPIRou spectrograph, with the goal to disentangle CO from CO2 through the 2.3 um CO band. With SPIRou, we detect H2O at a t-test significance of 5.3 sigma and observe a tentative (3 sigma) signal consistent with OH absorption. From a joint SPIRou + HST + Spitzer retrieval analysis, we rule out a CO-rich scenario by placing an upper limit on the CO abundance of log10[CO]<-4.0, and estimate a log10[CO2] of -3.7^(+0.8)_(-0.6), which is the level needed to match the excess absorption seen at 4.5um. We also set abundance constraints on other major C-, O-, and N-bearing molecules, with our results favoring low C/O (0.10^(+0.10)_(-0.06)), disequilibrium chemistry scenarios. We further discuss the implications of our results in the context of planet formation. Additional observations at high and low-resolution will be needed to confirm these results and better our understanding of this unusual world.Comment: 23 pages, 13 figures, Submitted for publication in the Monthly Notice of the Royal Astronomical Societ

Microarcsecond astrometric observatory Theia: from dark matter to compact objects and nearby earths

Theia is a logical successor to Gaia, as a focused, very high precision astrometry mission which addresses two key science objectives of the ESA Cosmic Vision program: the nature of dark matter and the search for habitable planets. Theia addresses a number of other science cases strongly synergistic with ongoing/planned missions, such as the nature of compact objects, motions of stars in young stellar clusters, follow-up of Gaia objects of interest. Theia s "point and stare" operational mode will enable us to answer some of the most profound questions that the results of the Gaias survey will ask. Extremely-high-precision astrometry at 1-μas level can only be reached from space. The Theia spacecraft, which will carry a 0.8-m telescope, is foreseen to operate at L2 for 3,5 years. The preliminary Theia mission assessment allowed us to identify a safe and robust mission architecture that demonstrates the mission feasibility within the Soyuz ST launch envelope and a small M-class mission cost cap. We present here these features of the mission that has been submitted to the last ESA M4 call in January 2015