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.
We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (mχ) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on ...time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in mχ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σχNSI at 90% confidence level are derived as 2×10−32∼7×10−35 cm2 for TI analysis at mχ∼50–180 MeV/c2, and 3×10−32∼9×10−38 cm2 for AM analysis at mχ∼75 MeV/c2–3.0 GeV/c2.
Generating ion-photon entanglement is a crucial step for scalable trapped-ion quantum networks. To avoid the crosstalk on memory qubits carrying quantum information, it is common to use a different ...ion species for ion-photon entanglement generation such that the scattered photons are far off-resonant for the memory qubits. However, such a dual-species scheme can be subject to inefficient sympathetic cooling due to the mass mismatch of the ions. Here we demonstrate a trapped-ion quantum network node in the dual-type qubit scheme where two types of qubits are encoded in the S and F hyperfine structure levels of
Yb
ions. We generate ion photon entanglement for the S-qubit in a typical timescale of hundreds of milliseconds, and verify its small crosstalk on a nearby F-qubit with coherence time above seconds. Our work demonstrates an enabling function of the dual-type qubit scheme for scalable quantum networks.
Background
Diet and exercise during pregnancy have been used to prevent gestational diabetes mellitus (GDM) with some success.
Objective
To examine the effectiveness of lifestyle intervention on GDM ...prevention and to identify key effectiveness moderators to improve the prevention strategy.
Search strategy
Pubmed, Scopus, Cochrane, and cross‐references were searched.
Selection criteria
Randomised controlled trials (RCTs) evaluating lifestyle interventions during pregnancy for GDM prevention.
Data collection and analysis
Two independent reviewers extracted data. A random‐effects model was used to analyse the relative risk (RR) and 95% confidence interval (95% CI). Meta‐regressions and subgroup analyses were used to investigate important moderators of effectiveness.
Main results
Forty‐seven RCTs involving 15 745 participants showed that diet and exercise during pregnancy were preventive of GDM (RR 0.77, 95% CI 0.69–0.87). Four key aspects were identified to improve the preventive effect: targeting the high‐risk population; an early initiation of the intervention; the correct intensity and frequency of exercise; and gestational weight gain management. Although 24 RCTs targeted women who were overweight or obese, body mass index (BMI) failed to predict the effectiveness of an intervention. Instead, interventions are most effective in high‐incidence populations rather than simply in women who are overweight or obese. Furthermore, exercise of moderate intensity for 50–60 minutes twice a week could lead to an approximately 24% reduction in GDM.
Conclusion
The best strategy to prevent GDM is to target the high‐risk population predicted by risk evaluation models and to control the gestational weight gain of women through intensified diet and exercise modifications early in their pregnancy.
Tweetable
Four key effectiveness moderators of lifestyle interventions for GDM prevention.
Tweetable
Four key effectiveness moderators of lifestyle interventions for GDM prevention.
Summary
We investigated the secular trends of the incidence and hospitalization cost of hip fracture in Tangshan, China. The incidence of hip fracture and the hospitalization cost were both ...increasing during the observation period.
Introduction
The present study aimed to determine sex-, age-, and fracture type-specific incidence and annual changes in hip fractures in Tangshan, China, between 2007 and 2018.
Methods
We analyzed annual hip fracture incidence using urban hospital data during 2007–2018 and calculated incidence rate/100,000 person years in each age group and sex. We assessed annual changes in incidence among people aged >60 years using linear-by-linear association tests and evaluated hospitalization costs with the Kruskal–Wallis test.
Results
During the study period, we observed an increasing proportion of hip fractures in people >60 years old from 14.2 to 22.79%. Crude hip fracture incidence increased markedly from 140.87 to 306.56/100,000 in women (
p
< 0.01) and from 124.83 to 167.19/100,000 in men (
p
< 0.01) in the age group >60 years. Type-specific analysis indicated significantly increased trends in incidence of cervical and trochanteric fractures among women and cervical fracture among men (
p
< 0.01). In people aged 36–60 years, the trend of hip fracture increased significantly in both sexes. The total and cervical-to-trochanteric ratio in men increased, with significant upward trends (
p
< 0.01). The proportion of cervical fracture was higher than that for trochanteric fracture in women, with stable levels from 2007 to 2018. Hospitalization costs for cervical and trochanteric fractures increased by 51.91% and 53.20%, respectively, during 2011–2018.
Conclusion
Tangshan will have an increasing burden on health care resources attributable to a considerable rise in hip fracture incidence and the older population. Further investigation of risk factors and subsequent implementation of effective measures to prevent hip fracture are needed.
We present improved germanium-based constraints on sub-GeV dark matter via dark matter-electron (χ-e) scattering using the 205.4 kg·day dataset from the CDEX-10 experiment. Using a novel calculation ...technique, we attain predicted χ-e scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for m_{χ} larger than 80 MeV/c^{2} compared to previous germanium-based χ-e results. We also present the most stringent χ-e cross-section limit to date among experiments using solid-state detectors for m_{χ} larger than 90 MeV/c^{2} with heavy mediators and m_{χ} larger than 100 MeV/c^{2} with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new χ-e detection method with high-purity germanium detectors in ultralow radioactive background.
We report a measurement of electron antineutrino oscillation from the Daya Bay Reactor Neutrino Experiment with nearly 4 million reactor νover ¯_{e} inverse β decay candidates observed over 1958 days ...of data collection. The installation of a flash analog-to-digital converter readout system and a special calibration campaign using different source enclosures reduce uncertainties in the absolute energy calibration to less than 0.5% for visible energies larger than 2 MeV. The uncertainty in the cosmogenic ^{9}Li and ^{8}He background is reduced from 45% to 30% in the near detectors. A detailed investigation of the spent nuclear fuel history improves its uncertainty from 100% to 30%. Analysis of the relative νover ¯_{e} rates and energy spectra among detectors yields sin^{2}2θ_{13}=0.0856±0.0029 and Δm_{32}^{2}=(2.471_{-0.070}^{+0.068})×10^{-3} eV^{2} assuming the normal hierarchy, and Δm_{32}^{2}=-(2.575_{-0.070}^{+0.068})×10^{-3} eV^{2} assuming the inverted hierarchy.
Trapped ions constitute one of the most promising systems for implementing quantum computing and networking1,2. For large-scale ion-trap-based quantum computers and networks, it is critical to have ...two types of qubit: one for computation and storage, and another for auxiliary operations such as qubit detection3, sympathetic cooling4–7 and entanglement generation through photon links8,9. Although the two qubit types can be implemented using two different ion species3,10–13, this approach introduces substantial complexity into creating and controlling each qubit type14,15. Here we resolve these challenges by implementing two coherently convertible qubit types using one ion species. We encode the qubits into two pairs of clock states of the 171Yb+ ions, and achieve microsecond-level conversion rates between the two types with one-way fidelities of 99.5%. We further demonstrate that operations on one qubit type, including sympathetic laser cooling, single-qubit gates and qubit detection, have crosstalk errors less than 0.06% on the other type, which is below the best-known error threshold of ~1% for fault-tolerant quantum computing using the surface code1,16. Our work establishes the feasibility and advantages of using coherently convertible dual-type qubits with the same ion species for large-scale quantum computing and networking.Quantum computing with trapped ions requires qubits that can store and manipulate quantum information, and others that can be used for destructive incoherent operations. Different states of ytterbium-171 ions can be used to realize both qubit types
Abstract
We report the discovery of an ultrahigh-energy (UHE) gamma-ray source, LHAASO J2108+5157, by analyzing the LHAASO-KM2A data of 308.33 live days. A significant excess of gamma ray–induced ...showers is observed in both energy bands of 25−100 and >100 TeV with 9.5
σ
and 8.5
σ
, respectively. This source is not significantly favored as an extended source with an angular extension smaller than the point-spread function of KM2A. The measured energy spectrum from 20 to 200 TeV can be approximately described by a power-law function with an index of −2.83 ± 0.18
stat
. A harder spectrum is demanded at lower energies considering the flux upper limit set by Fermi-LAT observations. The position of the gamma-ray emission is correlated with a giant molecular cloud, which favors a hadronic origin. No obvious counterparts have been found, and deeper multiwavelength observations will help to cast new light on this intriguing UHE source.
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