Double neutron star (DNS) merger events are promising candidates of short gamma-ray burst (sGRB) progenitors as well as high-frequency gravitational wave (GW) emitters. On August 17, 2017, such a ...coinciding event was detected by both the LIGO-Virgo gravitational wave detector network as GW170817 and Gamma-Ray Monitor on board NASA's Fermi Space Telescope as GRB 170817A. Here, we show that the fluence and spectral peak energy of this sGRB fall into the lower portion of the distributions of known sGRBs. Its peak isotropic luminosity is abnormally low. The estimated event rate density above this luminosity is at least Formula: see text Gpc
yr
, which is close to but still below the DNS merger event rate density. This event likely originates from a structured jet viewed from a large viewing angle. There are similar faint soft GRBs in the Fermi archival data, a small fraction of which might belong to this new population of nearby, low-luminosity sGRBs.
Electronic structures of graphene oxide (GO) and hydro-thermally reduced graphene oxides (rGOs) processed at low temperatures (120-180°C) were studied using X-ray absorption near-edge structure ...(XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). C K-edge XANES spectra of rGOs reveal that thermal reduction restores C = C sp(2) bonds and removes some of the oxygen and hydroxyl groups of GO, which initiates the evolution of carbonaceous species. The combination of C K-edge XANES and Kα XES spectra shows that the overlapping π and π* orbitals in rGOs and GO are similar to that of highly ordered pyrolytic graphite (HOPG), which has no band-gap. C Kα RIXS spectra provide evidence that thermal reduction changes the density of states (DOSs) that is generated in the π-region and/or in the gap between the π and π* levels of the GO and rGOs. Two-dimensional C Kα RIXS mapping of the heavy reduction of rGOs further confirms that the residual oxygen and/or oxygen-containing functional groups modify the π and σ features, which are dispersed by the photon excitation energy. The dispersion behavior near the K point is approximately linear and differs from the parabolic-like dispersion observed in HOPG.
Background
The aim of this study was to investigate the prevalence of epidemiologic and physician‐diagnosed pollen‐induced AR (PiAR) in the grasslands of northern China and to study the impact of the ...intensity and time of pollen exposure on PiAR prevalence.
Methods
A multistage, clustered and proportionately stratified random sampling with a field interviewer‐administered survey study was performed together with skin prick tests (SPT) and measurements of the daily pollen count.
Results
A total of 6043 subjects completed the study, with a proportion of 32.4% epidemiologic AR and 18.5% PiAR. The prevalence was higher in males than females (19.6% vs 17.4%, P = .024), but no difference between the two major residential and ethnic groups (Han and Mongolian) was observed. Subjects from urban areas showed higher prevalence of PiAR than rural areas (23.1% vs 14.0%, P < .001). Most PiAR patients were sensitized to two or more pollens (79.4%) with artemisia, chenopodium, and humulus scandens being the most common pollen types, which were similarly found as the top three sensitizing pollen allergens by SPT. There were significant regional differences in the prevalence of epidemiologic AR (from 18.6% to 52.9%) and PiAR (from 10.5% to 31.4%) among the six areas investigated. PiAR symptoms were positively associated with pollen counts, temperature, and precipitation (P < .05), but negatively with wind speed and pressure P < .05).
Conclusion
Pollen‐induced AR (PiAR) prevalence in the investigated region is extremely high due to high seasonal pollen exposure, which was influenced by local environmental and climate conditions.
Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances
. It has long been speculated that magnetars are the engine powering ...repeating bursts from FRB sources
, but no convincing evidence has been collected so far
. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft γ-ray bursts
. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft γ-ray/hard-X-ray flare
. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-γ-ray repeater (SGR) bursts were detected in γ-ray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB-SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.
The measurement of the energy spectrum of cosmic ray helium nuclei from 70 GeV to 80 TeV using 4.5 years of data recorded by the Dark Matter Particle Explorer (DAMPE) is reported in this work. A ...hardening of the spectrum is observed at an energy of about 1.3 TeV, similar to previous observations. In addition, a spectral softening at about 34 TeV is revealed for the first time with large statistics and well controlled systematic uncertainties, with an overall significance of 4.3σ. The DAMPE spectral measurements of both cosmic protons and helium nuclei suggest a particle charge dependent softening energy, although with current uncertainties a dependence on the number of nucleons cannot be ruled out.
Summary
Porcine reproductive and respiratory syndrome virus (PRRSV) is a major economically significant pathogen that has adversely affected China's swine industry. Currently, a novel type 2 PRRSV, ...called the NADC30‐like strain, is epidemic in numerous provinces of China, and commercial vaccines provide limited protection for infected animals. The extensive recombination phenomenon among NADC30‐like PRRSVs is identified as a unique molecular characteristic of the virus. However, our understanding of how recombination influences NADC30‐like PRRSVs is largely inadequate. In this study, we analysed the genetic characteristics of a recombinant NADC30‐like PRRSV (SC‐d) and examined its pathogenicity compared with a non‐recombinant NADC30‐like PRRSV (SD‐A19) and a highly pathogenic PRRSV (HuN4). SC‐d has three discontinuous deletions in nsp2, consistent with NADC30 isolated from the United States in 2008. Furthermore, we identified four recombination breakpoints in the SC‐d genome, which separated the SC‐d genome into four regions (regions A, B, C and D). Regions A and C are closely related to the JXA1‐like strain, one of the earliest Chinese HP‐PRRSV strains, and regions B and D are closely related to the NADC30 strain. Moreover, SC‐d inoculated piglets exhibited a persistent fever, moderate weight loss, mild thymus atrophy and obvious microscopic lung lesions. In summary, the recombinant NADC30‐like PRRSV SC‐d strain displayed a higher pathogenicity than the non‐recombinant NADC30‐like PRRSV SD‐A19 strain; however, the pathogenicity of the NADC30‐like PRRSV SC‐d was lower compared with the HP‐PRRSV HuN4 strain in piglets. Our findings demonstrate that recombination is responsible for the enormous genetic diversity and pathogenicity variance of the NADC30‐like PRRSV in China. This study provides a theoretical basis for developing a more reasonable PRRSV control and prevention strategy.
We report a study of the processes of e^{+}e^{-}→K^{+}D_{s}^{-}D^{*0} and K^{+}D_{s}^{*-}D^{0} based on e^{+}e^{-} annihilation samples collected with the BESIII detector operating at BEPCII at five ...center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7 fb^{-1}. An excess of events over the known contributions of the conventional charmed mesons is observed near the D_{s}^{-}D^{*0} and D_{s}^{*-}D^{0} mass thresholds in the K^{+} recoil-mass spectrum for events collected at sqrts=4.681 GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5_{-2.6}^{+1.8}±2.1) MeV/c^{2} and (12.8_{-4.4}^{+5.3}±3.0) MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 σ over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into D_{s}^{-}D^{*0} and D_{s}^{*-}D^{0}. However, the properties of the excess need further exploration with more statistics.
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•The phase composition rule has been clarified for the TiZrNbMoV HEAs.•The HEAs with low content of Mo and V have single bcc phase and excellent phase stability.•The compressive ...mechanical properties for these HEAs have been evaluated.•TiZrNbMo0.3V0.3 has excellent specific yield strength, strain and phase stability.•A new parameter, named as shear modulus mismatch, has been proposed.
TiZrNbMoxVy high-entropy alloys (HEAs) with x=0–2, y=1 and y=0.3, respectively, were designed and prepared by copper mold casting technology. The phase composition and stability of these HEAs were investigated. It is shown that the HEAs with low content of V are composed of only one type of bcc solid solution phase (SSP), and demonstrate excellent phase stability at 1273K. The high content of V and Mo results in the formation of two types of bcc SSPs and the decrease of phase stability in the HEAs. Based on the previously proposed criteria, the formation ability of solid solution phase for this kind of HEAs was comprehensively evaluated. The compressive mechanical properties of the as-cast and annealed HEAs were measured. It has been found that Mo plays a strong solid solution strengthening effect on this kind of HEAs. Especially, TiZrNbMo0.3V0.3 has the yield strength and plastic strain of 1312MPa and >50%, respectively, and still maintains the excellent plastic deformation ability even after annealed at 1273K for 72h. The strengthening effect in this kind of HEAs is considered to be due to the shear modulus mismatch. The solubility limit of HEAs is correspondent to shear modulus mismatch of 29.
A novel refractory Hf25Nb25Ti25Zr25 high entropy alloy (HEA) with single body centered cubic (BCC) structure was prepared by copper mold cast method. This HEA still holds the single BCC phase even ...after furnace cooling from homogenization at 1573K for 6h. The fracture strength and plastic strain of this HEA reach about 969MPa and 14.9%, respectively. There is significant work hardening effect in this HEA, which is considered as resulting from the movement and multiplication of dislocations.
•A novel refractory Hf25Nb25Ti25Zr25 high entropy alloy was prepared by conventional arc-melting method.•The prepared high entropy alloy possesses single body centered cubic phase and high thermal stability.•The prepared high entropy alloy exhibit tensile fracture strength up to 969MPa.•The prepared high entropy alloy exhibit tensile plastic strain of 14.9%.•The fracture manner and strengthen mechanism were investigated.
Abstract
1
T
-TaS
2
undergoes successive phase transitions upon cooling and eventually enters an insulating state of mysterious origin. Some consider this state to be a band insulator with interlayer ...stacking order, yet others attribute it to Mott physics that support a quantum spin liquid state. Here, we determine the electronic and structural properties of 1
T
-TaS
2
using angle-resolved photoemission spectroscopy and X-Ray diffraction. At low temperatures, the 2π/2c-periodic band dispersion, along with half-integer-indexed diffraction peaks along the
c
axis, unambiguously indicates that the ground state of 1
T
-TaS
2
is a band insulator with interlayer dimerization. Upon heating, however, the system undergoes a transition into a Mott insulating state, which only exists in a narrow temperature window. Our results refute the idea of searching for quantum magnetism in 1
T
-TaS
2
only at low temperatures, and highlight the competition between on-site Coulomb repulsion and interlayer hopping as a crucial aspect for understanding the material’s electronic properties.
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