The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow ...relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size and displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after the merger by using a global network of 32 radio telescopes. The apparent source size is constrained to be smaller than 2.5 milli-arc seconds at the 90% confidence level. This excludes the isotropic outflow scenario, which would have produced a larger apparent size, indicating that GW170817 produced a structured relativistic jet. Our rate calculations show that at least 10% of neutron star mergers produce such a jet.
Human activities are transforming grassland biomass via changing climate, elemental nutrients, and herbivory. Theory predicts that food-limited herbivores will consume any additional biomass ...stimulated by nutrient inputs ('consumer-controlled'). Alternatively, nutrient supply is predicted to increase biomass where herbivores alter community composition or are limited by factors other than food ('resource-controlled'). Using an experiment replicated in 58 grasslands spanning six continents, we show that nutrient addition and vertebrate herbivore exclusion each caused sustained increases in aboveground live biomass over a decade, but consumer control was weak. However, at sites with high vertebrate grazing intensity or domestic livestock, herbivores consumed the additional fertilization-induced biomass, supporting the consumer-controlled prediction. Herbivores most effectively reduced the additional live biomass at sites with low precipitation or high ambient soil nitrogen. Overall, these experimental results suggest that grassland biomass will outstrip wild herbivore control as human activities increase elemental nutrient supply, with widespread consequences for grazing and fire risk.
•Functional nanostructures were prepared via a novel strategy that combines coaxial electrospinning and genipin crosslinking.•Chitosan/PVA core-sheath electrospun nanofibers were successfully ...prepared.•Cross-linked nonwovens exhibited sustained drug release modulated by chitosan structure.•Cross-linked nonwovens exhibited expressive activity against periodontal pathogens.
Core-sheath nanofibers were successfully prepared via coaxial electrospinning by using chitosan with well-defined structural characteristics as the shell layer and poly (vinyl alcohol) (PVA) containing tetracycline hydrochloride (TH) as the core layer. The effects of the average degree of deacetylation (DD‾) of chitosan and the post-electrospinning genipin crosslinking on physicochemical and biological properties of resulting nonwovens were evaluated. Defect-free and geometrically uniform nanofibers with diameters predominantly in the range of 100–300 nm were prepared, and transmission electron microscopy (TEM) revealed the core-sheath structures and its preservation after crosslinking. The mechanical properties, as well as the stability of nonwovens in aqueous medium, were greatly improved by genipin-crosslinking, which enabled a sustained release of TH over 14 days. Results also revealed that the release profile of TH in the presence of lysozyme was affected by the composition of the shell layer, as the TH release rate increases with decreasing of DD‾. Further in vitro antimicrobial activity demonstrated that the cross-linked nonwovens containing TH showed strong activity against bacterial strains associated with periodontal disease. Additionally, the nonwovens did not demonstrate cytotoxic toward fibroblast (HDFn) cells, hence showing their potential for applications as a novel drug delivery platform for periodontitis treatment.
Degradation of solid oxide electrolysis cells (SOECs) is probably the biggest concern in the field of high temperature steam electrolysis (HTSE). Anode supported, YSZ-based microtubular solid oxide ...fuel cells (SOFC) have been tested in fuel cell mode and also at high voltages (up to 2.8
V) under electrolysis mode. At high steam conversion rates the cell voltage tends to saturate. Our hypothesis is that this effect is caused by the electroreduction of the thin YSZ electrolyte which induces electronic conduction losses. YSZ reduction increases the cathode activity and reduces cathode overpotential. Operation of the cell in severe electrolyte reduction conditions induces irreversible damage at the YSZ electrolyte as observed in SEM experiments by the formation of voids at the grain boundaries of the dense YSZ electrolyte. Evidence of this damage was also given by the increase of the ohmic resistance measured by AC impedance. Signs of electrolyte degradation were also found by both EDX analysis and micro-Raman spectroscopy performed along a transverse-cross section of the cell. The observed oxygen electrode delamination is associated to the high oxygen partial pressures gradients that take place at the electrolyte/oxygen electrode interface.
•Nonlinear resonators have a stiffening impact on the dispersion curves.•Perturbation method is limited by the amplitude of waves.•Parameters of the resonators are crucial to evaluate the limit of ...amplitude.•Numerical method proposed shows good coherence compared to the perturbation method.
The work describes the wave propagation in a periodic structure formed by a linear spring-mass chain with local Duffing non-linear resonators. The wave propagation of the system is studied using the Floquet-Bloch theorem combined with a perturbation approach to identify the dispersion relations in the nonlinear periodic structure. The theoretical model is benchmarked by a numerical approach based on imposing a wave number on a finite resonant spring-mass system as an initial condition, and then obtaining the corresponding frequency from the chain amplitude in the time domain. The perturbation and the numerical methods are compared to discuss the behaviour of the wave propagation in the nonlinear resonators periodic chain considered in this work. The results from the perturbation techniques are also compared with the ones generated through an Harmonic Balance Method previously used in open literature.
Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium, which is referred to as a ...'secondary source'. Positrons might also originate in objects such as pulsars and microquasars or through dark matter annihilation, which would be 'primary sources'. Previous statistically limited measurements of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.
Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from
the collapsing cores of dying massive stars. They are characterized by an initial phase
of bright and highly ...variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C. Here we report multifrequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10^(−6) to 10^(12) electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.
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High molecular weight Chi modulates the orientation of SF groups (Try and Try).Chi and SF LbL films were successfully used as template for phytase immobilization.The matrix ...improved the performance of phytic acid biosensing.
In this paper, we show that chitosan may induce conformation changes in silk fibroin (SF) in layer-by-layer (LbL) films, which were used as matrix for immobilization of the enzyme phytase to detect phytic acid. Three chitosan (CH) samples possessing distinct molecular weights were used to build CH/SF LbL films, and a larger change in conformation from random coils to β-sheets for SF was observed for high molecular weight chitosan (CHH). The CHH/SF LbL films deposited onto interdigitated gold electrodes were coated with a layer of phytase, with which phytic acid could be detected down to 10⿿9M using impedance spectroscopy as the principle of detection and treating the data with a multidimensional projection technique. This high sensitivity may be ascribed to the suitability of the CHH/SF matrix, thus indicating that the molecular-level interactions between chitosan and SF may be exploited in other biosensors and biodevices.
Precise time-dependent measurements of the Z = 2 component in the cosmic radiation provide crucial information about the propagation of charged particles through the heliosphere. The PAMELA ...experiment, with its long flight duration (2006 June 15-2016 January 23) and the low energy threshold (80 MeV/n) is an ideal detector for cosmic-ray solar modulation studies. In this paper, the helium nuclei spectra measured by the PAMELA instrument from 2006 July to 2009 December over a Carrington rotation time basis are presented. A state-of-the-art three-dimensional model for cosmic-ray propagation inside the heliosphere was used to interpret the time-dependent measured fluxes. Proton-to-helium flux ratio time profiles at various rigidities are also presented in order to study any features that could result from the different masses and local interstellar spectra shapes.
Growing numbers of indications for intravenous immunoglobulins (IVIg) in recent years has resulted in an increase in the consumption of these products. A lack of raw material has led to IVIg ...shortage. The objective of this work was to evaluate the impact of this situation on patient care in one French referral centre considering practice modifications and clinical impact.
All patients treated with IVIg for chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy and myasthenia gravis from October 2017 to October 2018 were included.
Out of 142 patients, 111 (78%) had a modification of their IVIg treatment. We noted that 75 (68%) patients had a delay in IVIg treatment, 41 (37%) patients had a decrease in IVIg doses and 31 (28%) experienced IVIg treatment interruption. Thirty percent of patients for whom IVIg treatment was discontinued were switched to other treatments mainly plasma exchange (16%) or corticosteroids (13%). Switches to plasma exchange or corticosteroids were carried out in order to save immunoglobulins for patients who had no other alternatives. Fifty-eight (52%) patients presented a deterioration of their clinical score after IVIg treatment changes including 31 (28%) patients who had a moderate or a clinically significant deterioration. Concerning practice modifications, we noted a substantial though not significant decrease in median IVIg dose for myasthenia gravis and a significant increase in the delay between IVIg courses for chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy (P=0.011 and P=0.018 respectively).
Our study showed a rather important number of changes in IVIg treatment related to IVIg shortage during the period considered. These changes had a negative impact on the clinical status of some patients.
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