Because of their inherently high flux allowing the detection of clear signals, black hole x-ray binaries are interesting candidates for polarization studies, even if no polarization signals have been ...observed from them before. Such measurements would provide further detailed insight into these sources' emission mechanisms. We measured the polarization of the gamma-ray emission from the black hole binary system Cygnus X-1 with the International Gamma-Ray Astrophysics Laboratory Imager on Board the Integral Satellite (INTEGRAL/IBIS) telescope. Spectral modeling of the data reveals two emission mechanisms: The 250- to 400-keV (kilo-electron volt) data are consistent with emission dominated by Compton scattering on thermal electrons and are weakly polarized. The second spectral component seen in the 400-keV to 2-MeV band is by contrast strongly polarized, revealing that the MeV emission is probably related to the jet first detected in the radio band.
The development of low‐oxygen zones threatening marine life (hypoxia) occurs annually in multiple coastal regions of the world. The largest estuary of the continental United States, the Chesapeake ...Bay, typically has ≈10 km3 of water with dioxygen concentrations <3 mg L−1 in July. As numerical methods for refining model resolutions in targeted areas are becoming common, there is interest in assessing the feasibility of simulating coastal hazards such as hypoxia in Earth System Models (ESMs). These coupled models are typically not constrained by observations and thus likely to feature systematic biases in their land, atmosphere, or ocean components. This study relies on four numerical experiments to evaluate the sensitivity of Chesapeake Bay hypoxia to changes or biases in its external physical forcings. Hypoxia exhibits only a minor decrease (−1.6%) after reducing the Bay's terrestrial freshwater discharge by 9.5% (but keeping terrestrial nutrient loadings the same). Changes in freshwater discharges have their largest impact on hypoxia during one extreme event (−37% during 2011 tropical storm Lee). Similarly, changing oceanic conditions on the shelf or their temporal frequency impact hypoxia by only 5%–6%, indicating that the latter is predominantly dictated by local conditions. Although these results are promising from the perspective of ESMs, additional components of ESMs will need to be evaluated before general conclusions can be reached. We notably speculate that the Bay's hypoxia would exhibit higher sensitivity to other forcings not examined here, notably air temperatures and nutrient loadings.
Plain Language Summary
Many coastal embayments of the world experience the development of “dead zones” during the summer, defined by very low concentrations of oxygen in water. The dead zones negatively affect the ecosystem including commercially‐important fisheries. Such a dead zone can be found every summer in the Chesapeake Bay, the largest and most productive estuary in the continental United States. Although these phenomena are typically the focus of local or regional managers, recent improvements in computer capabilities raise the possibility that dead zones could be successfully represented in the same type of computer simulators used for century‐long projections of the Earth's climate. Such simulators would provide a long term projection for the severity of dead zones throughout the world. The present study examines whether a realistic representation of the Chesapeake Bay dead zone can be obtained using information from these global computer simulations. The results show that the representation of the dead zone is not substantially different when using the global data sets selected for this study. This positive outcome opens the door for additional tests that should focus on other components of the global simulators, notably air temperatures and nutrients inputs from the land to the coastal embayments.
Key Points
Chesapeake Bay hypoxia shows only a weak sensitivity to continental shelf conditions and variability
Changes in shelf hydrography propagate throughout the Bay but surface temperatures are set by the meteorological forcing
Short term hydrological events are not always captured well by global land models which can impact hypoxia substantially
In lung transplant recipients, long-term graft survival relies on the control of inflammation and tissue remodeling to maintain graft functionality and avoid chronic lung allograft dysfunction. ...Although advances in clinical practice have improved transplant success, the mechanisms by which the balance between inflammation and remodeling is maintained are largely unknown.
To assess whether host-microbe interactions in the transplanted lung determine the immunologic tone of the airways, and consequently could impact graft survival.
Microbiota DNA and host total RNA were isolated from 203 bronchoalveolar lavages obtained from 112 patients post-lung transplantation. Microbiota composition was determined using 16S ribosomal RNA analysis, and expression of a set of genes involved in prototypic macrophage functions was quantified using real-time quantitative polymerase chain reaction.
We show that the characteristics of the pulmonary microbiota aligned with distinct innate cell gene expression profiles. Although a nonpolarized activation was associated with bacterial communities consisting of a balance between proinflammatory (e.g., Staphylococcus and Pseudomonas) and low stimulatory (e.g., Prevotella and Streptococcus) bacteria, "inflammatory" and "remodeling" profiles were linked to bacterial dysbiosis. Mechanistic assays provided direct evidence that bacterial dysbiosis could lead to inflammatory or remodeling profiles in macrophages, whereas a balanced microbial community maintained homeostasis.
The crosstalk between bacterial communities and innate immune cells potentially determines the function of the transplanted lung offering novel pathways for intervention strategies.
Epidemiological data point toward a critical period in early life during which environmental cues can set an individual on a trajectory toward respiratory health or disease. The neonatal immune ...system matures during this period, although little is known about the signals that lead to its maturation. Here we report that the formation of the lung microbiota is a key parameter in this process. Immediately following birth, neonatal mice were prone to develop exaggerated airway eosinophilia, release type 2 helper T cell cytokines and exhibit airway hyper-responsiveness following exposure to house dust mite allergens, even though their lungs harbored high numbers of natural CD4(+)Foxp3(+)CD25(+)Helios(+) regulatory T (Treg) cells. During the first 2 weeks after birth, the bacterial load in the lungs increased, and representation of the bacterial phyla shifts from a predominance of Gammaproteobacteria and Firmicutes towards Bacteroidetes. The changes in the microbiota were associated with decreased aeroallergen responsiveness and the emergence of a Helios(-) Treg cell subset that required interaction with programmed death ligand 1 (PD-L1) for development. Absence of microbial colonization(10) or blockade of PD-L1 during the first 2 weeks postpartum maintained exaggerated responsiveness to allergens through to adulthood. Adoptive transfer of Treg cells from adult mice to neonates before aeroallergen exposure ameliorated disease. Thus, formation of the airway microbiota induces regulatory cells early in life, which, when dysregulated, can lead to sustained susceptibility to allergic airway inflammation in adulthood.
Context. It is well established that between 380 000 and 1 billion years after the Big Bang the Inter Galactic Medium (IGM) underwent a “phase transformation” from cold and fully neutral to warm ...(≈ 104 K) and ionized. Whether this phase transformation was fully driven and completed by photoionization by young hot stars is a question of topical interest in cosmology. Aims. We propose here that besides the ultraviolet radiation from massive stars, feedback from accreting black holes in high-mass X-ray binaries (BH-HMXBs) was an additional, important source of heating and reionization of the IGM in regions of low gas density at large distances from star-forming galaxies. Methods. We use current theoretical models on the formation and evolution of primitive massive stars of low metallicity, and the observations of compact stellar remnants in the near and distant universe, to infer that a significant fraction of the first generations of massive stars end up as BH-HMXBs. Results. The total number of energetic ionizing photons from an accreting stellar black hole in an HMXB is comparable to the total number of ionizing photons of its progenitor star. However, the X-ray photons emitted by the accreting black hole are capable of producing several secondary ionizations and the ionizing power of the resulting black hole could be greater than that of its progenitor. Feedback by the large populations of BH-HMXBs heats the IGM to temperatures of ≈ 104 K and maintains it ionized on large distance scales. Conclusions. BH-HMXBs determine the early thermal history of the universe and maintain it as ionized over large volumes of space in regions of low density. This has a direct impact on the properties of the faintest galaxies at high redshifts, the smallest dwarf galaxies in the local universe, and on the existing and future surveys at radio wavelengths of atomic hydrogen in the early universe.
The rapid thinning of the ice shelves in the Amundsen Sea is generally attributed to basal melt driven by warm water originating from the continental slope. We examine the hypothesis that processes ...taking place on the continental shelf contribute significantly to the interannual variability of the ocean heat content and ice shelf melt rates. A numerical model is used to simulate the circulation of ocean heat and the melt of the ice shelves over the period 2006–2013. The fine model grid (grid spacing 1.5 km) explicitly resolves the coastal polynyas and mesoscale processes. The ocean heat content of the eastern continental shelf exhibits recurrent decreases around September with a magnitude that varies from year to year. The heat loss is primarily caused by surface heat fluxes along the eastern shore in areas of low ice concentration (polynyas). The cold winter water intrudes underneath the ice shelves and reduces the basal melt rates. Ocean temperatures upstream (i.e., at the shelf break) are largely constant over the year and cannot account for the cold events. The cooling is particularly marked in 2012 and its effect on the ocean heat content remains visible over the following years. The study suggests that ocean‐atmosphere interactions in coastal polynyas contribute to the interannual variability of the melt of Pine Island Glacier.
Key Points:
Model study with an eddy‐resolving ice‐ocean model covering entire Amundsen Sea
Winter cooling within polynyas is responsible for cold anomalies in September
Coastal processes contribute to interannual variability of melt of glaciers
The nature of the prompt gamma-ray emission of gamma-ray bursts (GRBs) is still far from being completely elucidated. The measure of linear polarization is a powerful tool that can be used to put ...further constraints on the content and magnetization of the GRB relativistic outflows, as well as on the radiation processes at work. To date, only a handful of polarization measurements are available for the prompt emission of GRBs. Here we present the analysis of the prompt emission of GRB 140206A, obtained with INTEGRAL/IBIS, Swift/BAT, and Fermi/GBM. Using INTEGRAL/IBIS as a Compton polarimeter, we were able to constrain the linear polarization level of the second peak of this GRB as being larger than 28 per cent at 90 per cent c.l. We also present the GRB afterglow optical spectroscopy obtained at the Telescopio Nazionale Galileo, which allowed us to measure the distance of this GRB, z = 2.739. This distance value together with the polarization measure obtained with IBIS allowed us to derive the deepest and most reliable limit to date (ξ < 1 × 10−16) on the possibility of Lorentz invariance violation, measured through the vacuum birefringence effect on a cosmological source.
Transition-metal dichalcogenide monolayers and heterostructures are highly tunable material systems that provide excellent models for physical phenomena at the two-dimensional (2D) limit. While most ...studies to date have focused on electrons and electron–hole pairs, phonons also play essential roles. Here, we apply ultrafast electron diffraction and diffuse scattering to directly quantify, with time and momentum resolution, electron–phonon coupling (EPC) in monolayer molybdenum disulfide and phonon transport from the monolayer to a silicon nitride substrate. Optically generated hot carriers result in a profoundly anisotropic distribution of phonons in the monolayer within ∼5 ps. A quantitative comparison with ab initio ultrafast dynamics simulations reveals the essential role of dielectric screening in weakening EPC. Thermal transport from the monolayer to the substrate occurs with the phonon system far from equilibrium. While screening in 2D is known to strongly affect equilibrium properties, our findings extend this understanding to the dynamic regime.
•A new method was developed for measuring the void fraction for two-phase flows in debris beds.•This technology, based on the use of a capacitance probe, was validated by comparison to a weighing ...method.•Integral tests have been performed subsequently on single-size debris beds made of 4mm and 8mm glass beads.•The data demonstrate the strong impact of interfacial friction phenomena.
The modeling of pressure drop for two-phase flows through porous media is a key point to assess the coolability of debris beds resulting from nuclear severe accidents. Models involve several parameters which are non-linear functions of the void fraction, e.g. relative permeabilities. Their identification requires that experimental data include the measurement of void fraction. This paper presents a new technique developed to reach this objective. The method is based on the use of a capacitance probe and has been validated by comparison with a weighing method. The validation has shown that the accuracy is better than 10%. The measurement device has been implemented in the CALIDE facility, at IRSN, which has been designed to perform air–water flow through debris bed. Tests have been carried out with beds made of single size 4mm and 8mm beads. Measurements of pressure drop and average void fraction are reported in the paper, for air and water flow rates representative of flows that would result of either the reflooding of the damaged core or the cooling of corium debris in a stagnant pool of water. Finally, the pressure drop models used in severe accident simulation codes, based on generalizations of the single-phase Ergun law, have been assessed against the new data. It has been observed that generalized Ergun laws including an interfacial drag term accurately predict the pressure drop and the void fraction for flows with a zero net water velocity.
Since the MOSAIC study, oxaliplatin-based adjuvant chemotherapy has been the standard treatment of stage III colon cancer. Combination therapy with fluoropyrimidines and oxaliplatin has improved ...overall survival (OS) and reduced the risk of recurrence in patients with resected stage III colon cancer. However, only 20% of patients really benefit from adjuvant chemotherapy, exposing 80% of patients to unnecessary toxicity. Recent analyses of large multicenter adjuvant studies have focused on the prognostication of OS and disease-free survival in stage III colon cancer in order to reduce over-treatment and to find more accurate prognostic tools than those used for adjuvant treatment decision-making in stage II disease. Indeed, clinical and pathological prognostic factors, although important, are not sufficient to decide which stage III patients will benefit from adjuvant therapy, and biomarkers will help select patient that need adjuvant treatment. Molecular markers such as microsatellite status and BRAF and KRAS mutations have recently been explored, and molecular signatures have been identified as promising prognostic factor for OS. Furthermore, recent studies have highlighted the prognostic value of immune infiltration. This review focuses on pathologic, immunologic and molecular prognostic markers for stage III colon cancer that could help clinicians tailor adjuvant treatment in a comprehensive transversal approach.
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