Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: a case for Caustic Radio Emission?

We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the \emph{Fermi} Large Area Telescope (LAT) and timing solutions based on radio observations conducted at the Westerbork and Nan\c{c}ay radio telescopes. In addition, we analyzed archival \emph{RXTE} and \emph{XMM-Newton} X-ray data for the two MSPs, confirming the X-ray emission properties of PSR B1937+21 and finding evidence ($\sim 4\sigma$) for pulsed emission from PSR B1957+20 for the first time. In both cases the gamma-ray emission profile is characterized by two peaks separated by half a rotation and are in close alignment with components observed in radio and X-rays. These two pulsars join PSRs J0034-0534 and J2214+3000 to form an emerging class of gamma-ray MSPs with phase-aligned peaks in different energy bands. The modeling of the radio and gamma-ray emission profiles suggests co-located emission regions in the outer magnetosphere.Comment: Accepted for publication in the Astrophysical Journa

A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope

Globular clusters with their large populations of millisecond pulsars (MSPs) are believed to be potential emitters of high-energy gamma-ray emission. Our goal is to constrain the millisecond pulsar populations in globular clusters from analysis of gamma-ray observations. We use 546 days of continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope to study the gamma-ray emission towards 13 globular clusters. Steady point-like high-energy gamma-ray emission has been significantly detected towards 8 globular clusters. Five of them (47 Tucanae, Omega Cen, NGC 6388, Terzan 5, and M 28) show hard spectral power indices $(0.7 < \Gamma <1.4)$ and clear evidence for an exponential cut-off in the range 1.0-2.6 GeV, which is the characteristic signature of magnetospheric emission from MSPs. Three of them (M 62, NGC 6440 and NGC 6652) also show hard spectral indices $(1.0 < \Gamma < 1.7)$, however the presence of an exponential cut-off can not be unambiguously established. Three of them (Omega Cen, NGC 6388, NGC 6652) have no known radio or X-ray MSPs yet still exhibit MSP spectral properties. From the observed gamma-ray luminosities, we estimate the total number of MSPs that is expected to be present in these globular clusters. We show that our estimates of the MSP population correlate with the stellar encounter rate and we estimate 2600-4700 MSPs in Galactic globular clusters, commensurate with previous estimates. The observation of high-energy gamma-ray emission from a globular cluster thus provides a reliable independent method to assess their millisecond pulsar populations that can be used to make constraints on the original neutron star X-ray binary population, essential for understanding the importance of binary systems in slowing the inevitable core collapse of globular clusters.Comment: Accepted for publication in A&A. Corresponding authors: J. Kn\"odlseder, N. Webb, B. Pancraz

The polymorphism L412F in TLR3 inhibits autophagy and is a marker of severe COVID-19 in males

The polymorphism L412F in TLR3 has been associated with several infectious diseases. However, the mechanism underlying this association is still unexplored. Here, we show that the L412F polymorphism in TLR3 is a marker of severity in COVID-19. This association increases in the sub-cohort of males. Impaired macroautophagy/autophagy and reduced TNF/TNFα production was demonstrated in HEK293 cells transfected with TLR3L412F-encoding plasmid and stimulated with specific agonist poly(I:C). A statistically significant reduced survival at 28 days was shown in L412F COVID-19 patients treated with the autophagy-inhibitor hydroxychloroquine (p = 0.038). An increased frequency of autoimmune disorders such as co-morbidity was found in L412F COVID-19 males with specific class II HLA haplotypes prone to autoantigen presentation. Our analyses indicate that L412F polymorphism makes males at risk of severe COVID-19 and provides a rationale for reinterpreting clinical trials considering autophagy pathways. Abbreviations: AP: autophagosome; AUC: area under the curve; BafA1: bafilomycin A1; COVID-19: coronavirus disease-2019; HCQ: hydroxychloroquine; RAP: rapamycin; ROC: receiver operating characteristic; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; TLR: toll like receptor; TNF/TNF-α: tumor necrosis factor

GELS IN THE SYSTEM CaO-Al2O3-SiO2 PREPARATION AND STRUCTURAL EVOLUTION

Les gels du système CaO-Al2O3-SiO2 ont été élaborés par la méthode de destabilisation d'un sol. Les ions aluminium et calcium sont ajoutés sous forme de solutions aqueuses de nitrates à une solution colloïdale de silice. Afin d'éviter toute précipitation sélective d'hydroxydes de calcium et d'aluminium, la gélification est effectuée à des pH bien définis. Les domaines de formation des gels des binaires Al2O-SiO2 et CaO-SiO2 ont été établis et s'étendent respectivement de la silice pure à 75 % molaire en SiO2 et de 100 % à 25 % molaire en SiO2. Le domaine de formation des gels du système ternaire CaO-Al2O3-SiO2 s'étend du côté de l'oxyde de calcium et des gels contenant jusqu'à 75 % molaire en CaO ont été synthétisés. L'ion calcium diminue le temps de prise alors que l'ion aluminium l'augmente. L'évolution structurale des gels a été suivie en fonction de la température par diffraction des rayons X. Des nitrates de calcium cristallisés apparaissent à basse température et se décomposent avec un accroissement de température. Cette décomposition s'effectue d'autant plus facilement que la composition du gel est riche en alumine.Gels in the system CaO-Al2O3-SiO2 were prepared by the sol destabilization method. Aqueous solutions of calcium and aluminium nitrate were added to a colloïdal silica solution. In order to avoid a selective precipitation of calcium and aluminium hydroxide, the gelation was done at definite pH. The ranges of gel formation in the binary systems Al2O3-SiO2 and CaO-SiO2 have been established. They lie from 100 to 75 mole % SiO2 and from 100 to 25 mole % SiO2 respectively. The range of formation in the ternary system CaOAl2O3-SiO2 was displaced towards the compositions rich in calcium and gels containing up to 75 mole % CaO were prepared. The gelation time was reduced by calcium ions while the aluminium ions increased it. The structural evolution of these gels were followed as a function of temperature by X-ray diffraction. Calcium nitrate crystals occured at low temperature and decomposed as the temperature increased. This decomposition was facilited in the composition domain rich in aluminium

Computed tomography colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications.

Colorectal cancer (CRC) represents one of the most relevant causes of morbidity and mortality in Western societies. CRC screening is actually based on faecal occult blood testing, and optical colonoscopy still remains the gold standard screening test for cancer detection. However, computed tomography colonography (CT colonography) constitutes a reliable, minimally-invasive method to rapidly and effectively evaluate the entire colon for clinically relevant lesions. Furthermore, even if the benefits of its employment in CRC mass screening have not fully established yet, CT colonography may represent a reasonable alternative screening test in patients who cannot undergo or refuse colonoscopy. Therefore, the purpose of our review is to illustrate the most updated recommendations on methodology and the current clinical indications of CT colonography, according to the data of the existing relevant literature