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1.
Phys Rev Lett ; 126(24): 241103, 2021 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-34213924

RESUMO

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.

2.
Nature ; 594(7861): 33-36, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34002091

RESUMO

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.

3.
Thorac Cardiovasc Surg ; 55(1): 19-23, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17285469

RESUMO

BACKGROUND: There are few families with the diagnosis of ascending aortic aneurysm and acute type-A aortic dissection inherited as an autosomal-dominant disorder in the absence of a known genetic syndrome. METHODS: We investigated a family with 26 members in whom ascending aortic aneurysms and acute type-A aortic dissections occurred over three generations. Examinations were performed to identify family members at specific risk. RESULTS: Six members presented with acute type-A aortic dissections and three relatives had ascending aortic aneurysms. Clinical examinations showed no characteristics of a known genetic syndrome. Molecular genetic analysis revealed no mutations known to cause a form of autosomal-dominant inherited aortic disease. CONCLUSION: Adequate diagnostic measures are mandatory in families with ascending aortic aneurysms or type-A aortic dissections to identify or exclude family members at risk for aortic diseases. Even in the absence of identifiable mutations causing isolated aortic aneurysms or aortic dissections, we recommend standardised examinations of all first-degree relatives of affected families. An indication for prophylactic aortic root replacement should be considered for patients at risk.


Assuntos
Aneurisma Dissecante/congênito , Aneurisma da Aorta Torácica/congênito , DNA/genética , Proteínas dos Microfilamentos/genética , Mutação , Adolescente , Adulto , Aneurisma Dissecante/diagnóstico , Aneurisma Dissecante/genética , Aneurisma da Aorta Torácica/diagnóstico , Aneurisma da Aorta Torácica/genética , Proteínas de Ligação ao Cálcio , Diagnóstico Diferencial , Ecocardiografia , Feminino , Fibrilinas , Seguimentos , Predisposição Genética para Doença , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Linhagem , Reação em Cadeia da Polimerase , Prognóstico , Estudos Retrospectivos , Tomografia Computadorizada por Raios X
4.
Clin Radiol ; 61(11): 971-8, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17018311

RESUMO

AIM: Dural ectasia is a major diagnostic criterion for Marfan syndrome using the Ghent nosology. Our aim was to evaluate the efficacy of three different radiological methods previously proposed for the assessment of dural sac diameter in Marfan syndrome. METHODS: Marfan syndrome was diagnosed in our study using the Ghent criteria, disregarding dural ectasia as a criterion. Three proposed radiological methods were applied to measure dural sac diameter, examined for 41 patients (18 patients with and 23 without Marfan syndrome) by computed tomography or magnetic resonance imaging. RESULTS: Using Oosterhof's method, 94% of the patients with and 44% of the patients without Marfan syndrome fulfilled the criteria of dural ectasia. According to Villeirs, dural ectasia was diagnosed in 18% of the patients with and in none of the patients without Marfan syndrome. With Ahn's method, dural ectasia was found in 72% of the patients with and in 44% of the patients without Marfan syndrome. In only two patients with Marfan syndrome was dural ectasia diagnosed by all three methods. CONCLUSION: Our results reveal overt discrepancy between the three methods of assessing dural ectasia. Considering the key role played by dural ectasia in reinforcing the diagnosis of Marfan syndrome according to the Ghent nosology, a standardized and reliable method should be sought.


Assuntos
Dilatação Patológica/diagnóstico , Dura-Máter/patologia , Imageamento por Ressonância Magnética/métodos , Síndrome de Marfan/diagnóstico , Tomografia Computadorizada por Raios X/métodos , Adolescente , Adulto , Estudos de Casos e Controles , Dura-Máter/diagnóstico por imagem , Humanos , Pessoa de Meia-Idade , Interpretação de Imagem Radiográfica Assistida por Computador , Sensibilidade e Especificidade , Coluna Vertebral/diagnóstico por imagem , Coluna Vertebral/patologia
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