High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes and may enable the observation of ...phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a 'smoothly broken power-law' model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.
•MSTN−/− pigs subcutaneous adipose tissue clearly showed characteristic multilocular lipid droplets like beige adipose in contrast to the tissues from WT pigs.•MSTN gene deletion in adipose tissue ...activates the browning of white fat via the AMPK signaling pathway.•MSTN−/− skeletal muscle secretes IL-6 and modulates the AMPK pathway in adipocytes, and induces white adipose conversion into beige adipose in pigs.
Myostatin (MSTN) is primarily expressed in skeletal muscle and plays an important role in the regulation of muscle growth and development as well as fat deposition; however, little is known about the molecular mechanism through which MSTN regulates body fat deposition. Therefore, in this study, we sought to identify the signaling pathways through which MSTN regulates fat accumulation in pigs. MSTN knockout (MSTN−/−) pigs showed increased muscle mass, decreased fat mass, and a leaner body composition. In this study, we found that the adipose tissue of MSTN−/− pigs exhibits the characteristics of beige adipose tissue, and the mRNA expression levels of beige adipose marker genes, including UCP3, Cidea, and CD137, were significantly increased. Remarkably, the observed beige phenotype was not adipocyte autonomous but rather caused by muscle-secreted myokine interleukin (IL)-6. This occurrence results in increased AMP-activated protein kinase (AMPK) phosphorylation in adipose tissue, which subsequently activates peroxisome proliferator-activated receptor gamma coactivator 1α and the conversion of white adipocytes to beige in pigs. Therefore, we concluded that MSTN deficiency leads to increased IL-6 secretion in skeletal muscle and activates AMPK in adipocytes, thereby increasing the beige adipose tissue in MSTN−/− pigs.
Background
The expression of chronic rhinosinusitis (CRS) is multidimensional. Disease heterogeneity in patients with CRS remains poorly understood. This study aimed to identify endotypes of CRS ...using cluster analysis by integrating multidimensional characteristics and to explore their association with treatment outcomes.
Methods
A total of 28 clinical variables and 39 mucosal cellular and molecular variables were analyzed using principal component analysis. Cluster analysis was performed on 246 prospectively recruited Chinese CRS patients with at least 1‐year postoperative follow‐up. Difficult‐to‐treat CRS was characterized in each generated cluster.
Results
Seven subject clusters were identified. Cluster 1 (13.01%) was comparable to the classic well‐defined eosinophilic CRS with polyps, having severe disease and the highest proportion of difficult‐to‐treat CRS. Patients in cluster 2 (16.26%) and cluster 4 (13.82%) had relatively lower proportions of presence of polyps and presented mild inflammation with moderate proportions of difficult‐to‐treat cases. Subjects in cluster 2 were highly atopic. Cluster 3 (7.31%) and cluster 6 (21.14%) were characterized by severe or moderate neutrophilic inflammation, respectively, and with elevated levels of IL‐8 and high proportions of difficult‐to‐treat CRS. Cluster 5 (4.07%) was a unique group characterized by the highest levels of IL‐10 and lacked difficult‐to‐treat cases. Cluster 7 (24.39%) demonstrated the lowest symptom severity, a low proportion of difficult‐to‐treat CRS, and low inflammation load. Finally, we found that difficult‐to‐treat CRS was associated with distinct clinical features and biomarkers in the different clusters.
Conclusions
Distinct clinicopathobiologic clusters of CRS display differences in clinical response to treatments and characteristics of difficult‐to‐treat CRS.
A novel fast electron beam emitting along the surface of a target irradiated by intense laser pulses is observed. The beam is found to appear only when the plasma density scale length is small. ...Numerical simulations reveal that the electron beam is formed due to the confinement of the surface quasistatic electromagnetic fields. The results are of interest for potential applications of fast electron beams and deep understanding of the cone-target physics in the fast ignition related experiments.
The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This ...work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2
/
years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.
The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10
electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV ...energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays
. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref.
). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane
, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.
We study the e^{+}e^{-}→γωJ/ψ process using 11.6 fb^{-1} e^{+}e^{-} annihilation data taken at center-of-mass energies from sqrts=4.008 GeV to 4.600 GeV with the BESIII detector at the BEPCII ...storage ring. The X(3872) resonance is observed for the first time in the ωJ/ψ system with a significance of more than 5σ. The relative decay ratio of X(3872)→ωJ/ψ and π^{+}π^{-}J/ψ is measured to be R=1.6_{-0.3}^{+0.4}±0.2, where the first uncertainty is statistical and the second systematic (the same hereafter). The sqrts-dependent cross section of e^{+}e^{-}→γX(3872) is also measured and investigated, and it can be described by a single Breit-Wigner resonance, referred to as the Y(4200), with a mass of 4200.6_{-13.3}^{+7.9}±3.0 MeV/c^{2} and a width of 115_{-26}^{+38}±12 MeV. In addition, to describe the ωJ/ψ mass distribution above 3.9 GeV/c^{2}, we need at least one additional Breit-Wigner resonance, labeled as X(3915), in the fit. The mass and width of the X(3915) are determined. The resonant parameters of the X(3915) agree with those of the Y(3940) in B→KωJ/ψ and of the X(3915) in γγ→ωJ/ψ observed by the Belle and BABAR experiments within errors.
High-energy photons from the Crab Nebula
The Crab Nebula contains a pulsar that excites the surrounding gas to emit high-energy radiation. The combination of the pulsar's youth and nearby location ...makes the nebula the brightest gamma-ray source in the sky. The LHAASO Collaboration report observations of this source at energies of tera– to peta–electron volts, extending the spectrum of this prototypical object. They combine these data with observations at lower energies to model the physics of the emission process. The multiwave-length data can be explained by a combination of synchrotron radiation and inverse Compton scattering.
Science
, abg5137, this issue p.
425
Detection of the Crab Nebula at peta–electron volt energies constrains the gamma-ray emission mechanism.
The Crab Nebula is a bright source of gamma rays powered by the Crab Pulsar’s rotational energy through the formation and termination of a relativistic electron-positron wind. We report the detection of gamma rays from this source with energies from 5 × 10
−4
to 1.1 peta–electron volts with a spectrum showing gradual steepening over three energy decades. The ultrahigh-energy photons imply the presence of a peta–electron volt electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron’s size between 0.025 and 0.1 parsecs and the magnetic field to ≈110 microgauss. The production rate of peta–electron volt electrons, 2.5 × 10
36
ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta–electron volt protons to the production of the highest-energy gamma rays.
The complicated structure of the neutron cannot be calculated using first-principles calculations due to the large colour charge of quarks and the self-interaction of gluons. Its simplest structure ...observables are the electromagnetic form factors1, which probe our understanding of the strong interaction. Until now, a small amount of data has been available for the determination of the neutron structure from the time-like kinematical range. Here we present measurements of the Born cross section of electron–positron annihilation reactions into a neutron and anti-neutron pair, and determine the neutron’s effective form factor. The data were recorded with the BESIII experiment at centre-of-mass energies between 2.00 and 3.08 GeV using an integrated luminosity of 647.9 pb−1. Our results improve the statistics on the neutron form factor by more than a factor of 60 over previous measurements, demonstrating that the neutron form factor data from annihilation in the time-like regime is on par with that from electron scattering experiments. The effective form factor of the neutron shows a periodic behaviour, similar to earlier observations of the proton form factor. Future works—both theoretical and experimental—will help illuminate the origin of this oscillation of the electromagnetic structure observables of the nucleon.Form factors encode the structure of nucleons. Measurements from electron–positron annihilation at BESIII reveal an oscillating behaviour of the neutron electromagnetic form factor, and clarify a long-standing photon–nucleon interaction puzzle.
In this work, the type, composition and distribution of inclusions contained in an API5L X100 steel were characterized by scanning electron microscopy and energy-dispersive x-ray analysis. A ...hydrogen-charging at various current densities was used to introduce hydrogen into the steel, and the correlation between HIC and the inclusions was established. The microstructure of the steel consists of a leather-like bainitic ferrite matrix, with martensite/austenite as the second phase particles. At least four types of inclusions are contained in API5L X100 steel, elongated MnS inclusions and spherical Al-, Si- and Ca-Al-O-S-enriched inclusions. In particular, the majority of inclusions in the steel are Al-enriched. Upon hydrogen-charging, hydrogen blisters and HIC could be caused in the steel in the absence of external stress. The cracks are primarily associated with the Al- and Si-enriched inclusions, rather than the elongated MnS inclusion. The critical amount of hydrogen resulting in HIC of the tested API5L X100 steel is determined to be 3.24 ppm under condition in this work.
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