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.
Dysbiotic oral microbiota has been associated with multiple sclerosis. However, the role and mechanism of oral microbiota in the development of multiple sclerosis are still elusive. Here, we ...demonstrated that ligature-induced periodontitis (LIP) aggravated experimental autoimmune encephalomyelitis (EAE) in mice, and this was likely dependent on the expansion of T helper 17 (Th17) cells. LIP increased the splenic richness of Enterobacter sp., which was able to induce the expansion of splenic Th17 cells and aggravate EAE in mice. LIP also led to enrichment of Erysipelotrichaceae sp. in the gut and increased Th17 cells in the large intestinal lamina propria of EAE mice. Fecal microbiota transplantation from EAE mice with LIP also promoted EAE symptoms. In conclusion, periodontitis exacerbates EAE, likely through ectopic colonization of oral pathobionts and expansion of Th17 cells.
Background
Increased left atrium diameter (LAD) is associated with an elevated risk of cardiovascular diseases. The relationship between nutrition status and left atrial enlargement (LAE) is still ...unclear. The present study aimed to investigate the association of famine exposure in early life with LAE in adulthood.
Methods
Participants were divided into non‐exposed, fetal, early, middle and late childhood exposed groups according to birth data. LAE was defined when LAD was ≥3.9 cm in women and ≥4.1 cm in men, or ≥2.3 cm m−2 by a sex‐independent cut‐off normalised for body surface area. Multivariate logistic regression was performed to calculate the odds ratio (OR) and confidence interval (CI) between famine exposure and LAE.
Results
In total, 2522 905 male, mean (SD) age 59.1 (3.65) years subjects were enrolled, including 392 (15.5%) LAE subjects. The prevalence of LAE in non‐exposed, fetal, early, middle and late childhood exposed groups was 55 (10.8%), 38 (11.2%), 88 (18.1%), 102 (16.7%) and 109 (19.0%), respectively. Compared to the non‐exposed group, the ORs for LAE were in fetal (OR = 0.956, 95% CI = 0.605–1.500, P = 0.847), late (OR = 1.748, 95% CI = 1.208–2.555, P = 0.003), middle (OR = 1.647, 95% CI = 1.140–2.403, P = 0.008) and early (OR = 1.630, 95% CI = 1.116–2.399, P = 0.012) childhood exposed groups after adjusting potential cofounders. When stratified by gender, smoking, body mass index, hypertension and diabetes, we found that the effect of famine exposure on LAE was only modified by diabetes (Pinteraction = 0.007).
Conclusions
Famine exposure during childhood stage might increase the risk of LAE in adults, and this effect interacts with diabetes.
Famine exposure during childhood stage might increase the risk of left atrial enlargement in adults, and this effect interacts with diabetes.
Two-dimensional (2D) materials have been studied extensively as monolayers, vertical or lateral heterostructures. To achieve functionalization, monolayers are often patterned using soft lithography ...and selectively decorated with molecules. Here we demonstrate the growth of a family of 2D materials that are intrinsically patterned. We demonstrate that a monolayer of PtSe
can be grown on a Pt substrate in the form of a triangular pattern of alternating 1T and 1H phases. Moreover, we show that, in a monolayer of CuSe grown on a Cu substrate, strain relaxation leads to periodic patterns of triangular nanopores with uniform size. Adsorption of different species at preferred pattern sites is also achieved, demonstrating that these materials can serve as templates for selective self-assembly of molecules or nanoclusters, as well as for the functionalization of the same substrate with two different species.
Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating rice diseases worldwide. In this study, a rice introgression line (IL), FF329, which was ...identified from a BC₁F₄population derived from the cross between donor PSBRC66 (P66) and recipient Huang‐Hua‐Zhan (HHZ), exhibited a typical hypersensitive response (HR) when inoculated with all 21 representative Xoo strains, consisting of 14 Philippines races and seven Chinese pathotypes. By contrast, the parents were highly susceptible to 10 of the tested strains and resistant or moderately susceptible to 11 strains, but without HR symptoms. Genetic analysis of the F₂population derived from the HHZ/FF329 cross with virulent Philippines race 6 (P6) and Chinese pathotype V (CV) revealed that BB resistance in FF329 was controlled by a single dominant gene. Because FF329 showed broad‐spectrum BB resistance, different from both parents, the gene identified was novel and was designated Xa39. Two SSR markers, RM21 and RM206, located on rice chromosome 11, were linked to the target gene by bulked segregant analysis. A further six markers linked to Xa39 were identified in the region between RM21 and RM206 for fine gene mapping, and the Xa39 locus was refined to a 97·4 kb interval flanked by markers RM26985 and DM13 using a large F₂population. This gene provides rice breeders with a new option to incorporate BB resistance into newly developed cultivars.
The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium
, which is assumed to dominate the total extragalactic dispersion. ...Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs
, in at least one case there is evidence for an extreme magneto-ionic local environment
and a compact persistent radio source
. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately Formula: see text parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies
, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications.
A new alpha-emitting isotope U-214, produced by the fusion-evaporation reaction W-182(Ar-36,4n) U-214, was identified by employing the gas-filled recoil separator SHANS and the recoil-a correlation ...technique. More precise a-decay properties of even-even nuclei U-216,U-218 were also measured in the reactions of Ar-40, Ca-40 beams with W-180,W-182,W- 184 targets. By combining the experimental data, improved alpha-decay reduced widths delta(2) for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N = 126 are deduced. Their systematic trends are discussed in terms of the N-p N-n scheme in order to study the influence of protonneutron interaction on a decay in this region of nuclei. It is strikingly found that the reduced widths of( 214,216)U are significantly enhanced by a factor of two as compared with the NpNn systematics for the 84 <= Z <= 90 and N < 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the pi 1f (7/2) and nu 1f(5/2) spin-orbit partner orbits, which is supported by the large-scale shell model calculation.
Periodontitis is a common infectious disease. Recent studies have indicated that the progression of periodontitis may be regulated by interactions between host immunity and periodontopathic bacteria. ...Although periodontopathic bacteria can destroy periodontal tissue, a dysfunctional host immune response triggered by the bacteria can lead to more severe and persistent destruction. Toll‐like receptors (TLRs), a type of pattern recognition receptor (PRR) that recognizes pathogens, have been implicated in host innate immune responses to periodontopathic bacteria and in the activation of adaptive immunity. TLR‐targeted drugs may hold promise to treat periodontal disease. This review summarizes recent studies on the role of TLRs in periodontitis and discusses areas needing further research. We believe TLRs may be an effective biomarker for the prevention, diagnosis, and treatment of periodontitis in the near future.
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.
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