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Phys Rev Lett ; 128(5): 051102, 2022 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-35179919


Recently, the LHAASO Collaboration published the detection of 12 ultrahigh-energy γ-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV γ rays from astrophysical sources may provide a very sensitive probe of the effect of the Lorentz invariance violation (LIV), which results in decay of high-energy γ rays in the superluminal scenario and hence a sharp cutoff of the energy spectrum. Two highest energy sources are studied in this work. No signature of the existence of the LIV is found in their energy spectra, and the lower limits on the LIV energy scale are derived. Our results show that the first-order LIV energy scale should be higher than about 10^{5} times the Planck scale M_{Pl} and that the second-order LIV scale is >10^{-3}M_{Pl}. Both limits improve by at least one order of magnitude the previous results.

Science ; 373(6553): 425-430, 2021 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-34261813


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 × 1036 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.

Phys Rev Lett ; 126(24): 241103, 2021 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-34213924


We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622+3749 with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of 8.2σ for E>25 TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) =(95.47°±0.11°,37.92°±0.09°), and the extension is 0.40°±0.07°. The energy spectrum can be described by a power-law spectrum with an index of -2.92±0.17_{stat}±0.02_{sys}. No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of ∼160 TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.

Nature ; 594(7861): 33-36, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34002091


The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 1015 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 rays1. 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. 2). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane3-6, 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.

Eur Rev Med Pharmacol Sci ; 21(3): 606-611, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28239805


OBJECTIVE: To observe the efficacy of traditional administration, continuous pump injection, and closed-loop target controlled infusion of cisatracurium to determine the optimal method of drug administration, and to establish the individualized and rational administration of muscle relaxants in elderly patients. PATIENTS AND METHODS: A total of 150 patients who underwent spinal surgery under tracheal intubation general anesthesia in our hospital from August 2013 to April 2015 were selected. All patients were administered with general anesthesia and randomly divided into three groups: group A (n = 50) was treated under closed-loop target controlled infusion (CLTCI), group B (n = 50) was treated under muscle relaxation monitoring, and group C (n = 50) was treated under continuous pump injection. Hemodynamic changes and blood oxygen saturation of the three groups were observed, and the muscle relaxation recovery, dosage, and bleeding of the three groups were compared. RESULTS: MAP and HR of group A were significantly lower than those of group B and group C (p < 0.05). There were no cases of insufficient muscle relaxation in group A, five cases in group C, and 14 cases in group B, and the differences between any two groups were statistically significant (p < 0.05). Regarding muscle relaxation recovery, the time (T¬¬1) of recovery from 10%-25% and 25%-75%, and the time from drug withdrawal to recovery to TOFr from 0.7-0.9 of group A were the shortest, followed by group C and group B. The differences between any two groups were statistically significant (p < 0.05). The total dosage of cisatracurium of group A was the least, followed by group C and group B, and differences between any two groups were statistically significant (p < 0.05). Moreover, the bleeding volume of group A (235.2 ± 141.3 ml) was smaller than in group B (353.1 ± 173.8 ml) and group C (316.5 ± 155.2 ml), and differences between the three groups were statistically significant (p < 0.05). CONCLUSIONS: For spinal surgery of elderly patients, closed-loop target controlled infusion of cisatracurium was superior to continuous infusion and intravenous injection. The time of muscle relaxation recovery was shortened, the dosage of cisatracurium was reduced, and the number of cases of insufficient muscle relaxation was reduced.

Atracúrio/análogos & derivados , Relaxamento Muscular/efeitos dos fármacos , Coluna Vertebral/cirurgia , Idoso , Anestesia Geral , Atracúrio/administração & dosagem , Feminino , Humanos , Injeções Intravenosas , Masculino , Pessoa de Meia-Idade , Bloqueadores Neuromusculares