The Swift X-Ray Te1escope: Status and Performance

We present science highlights and performance from the Swift X-ray Telescope (XRT), which was launched on November 20,2004. The XRT covers the 0.2-10 keV band, and spends most of its time observing gamma-ray burst (GRB) afterglows, though it has also performed observations of many other objects. By mid-August 2007, the XRT had observed over 220 GRB afterglows, detecting about 96% of them. The XRT positions enable followup ground-based optical observations, with roughly 60% of the afterglows detected at optical or near IR wavelengths. Redshifts are measured for 33% of X-ray afterglows. Science highlights include the discovery of flaring behavior at quite late times, with implications for GRB central engines; localization of short GRBs, leading to observational support for compact merger progenitors for this class of bursts; a mysterious plateau phase to GRB afterglows; as well as many other interesting observations such as X-ray emission from comets, novae, galactic transients, and other objects

Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)

Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame is defined by the positions and proper motions at epoch 2016.0 for a specific set of extragalactic sources in the (E)DR3 catalogue. Aims. We describe the construction of Gaia-CRF3 and its properties in terms of the distributions in magnitude, colour, and astrometric quality. Methods. Compact extragalactic sources in Gaia DR3 were identified by positional cross-matching with 17 external catalogues of quasi-stellar objects (QSO) and active galactic nuclei (AGN), followed by astrometric filtering designed to remove stellar contaminants. Selecting a clean sample was favoured over including a higher number of extragalactic sources. For the final sample, the random and systematic errors in the proper motions are analysed, as well as the radio-optical offsets in position for sources in the third realisation of the International Celestial Reference Frame (ICRF3). Results. Gaia-CRF3 comprises about 1.6 million QSO-like sources, of which 1.2 million have five-parameter astrometric solutions in Gaia DR3 and 0.4 million have six-parameter solutions. The sources span the magnitude range G = 13-21 with a peak density at 20.6 mag, at which the typical positional uncertainty is about 1 mas. The proper motions show systematic errors on the level of 12 μas yr-1 on angular scales greater than 15 deg. For the 3142 optical counterparts of ICRF3 sources in the S/X frequency bands, the median offset from the radio positions is about 0.5 mas, but it exceeds 4 mas in either coordinate for 127 sources. We outline the future of Gaia-CRF in the next Gaia data releases. Appendices give further details on the external catalogues used, how to extract information about the Gaia-CRF3 sources, potential (Galactic) confusion sources, and the estimation of the spin and orientation of an astrometric solution

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Modeling the Relationship among Gray Matter Atrophy, Abnormalities in Connecting White Matter, and Cognitive Performance in Early Multiple Sclerosis

BACKGROUND AND PURPOSE: Quantitative assessment of clinical and pathologic consequences of white matter abnormalities in multiple sclerosis is critical in understanding the pathways of disease. This study aimed to test whether gray matter atrophy was related to abnormalities in connecting white matter and to identify patterns of imaging biomarker abnormalities that were related to patient processing speed. MATERIALS AND METHODS: Image data and Symbol Digit Modalities Test scores were collected from a cohort of patients with early multiple sclerosis. The Network Modification Tool was used to estimate connectivity irregularities by projecting white matter abnormalities onto connecting gray matter regions. Partial least-squares regression quantified the relationship between imaging biomarkers and processing speed as measured by the Symbol Digit Modalities Test. RESULTS: Atrophy in deep gray matter structures of the thalami and putamen had moderate and significant correlations with abnormalities in connecting white matter (r = 0.39–0.41, P < .05 corrected). The 2 models of processing speed, 1 for each of the WM imaging biomarkers, had goodness-of-fit (R(2)) values of 0.42 and 0.30. A measure of the impact of white matter lesions on the connectivity of occipital and parietal areas had significant nonzero regression coefficients. CONCLUSIONS: We concluded that deep gray matter regions may be susceptible to inflammation and/or demyelination in white matter, possibly having a higher sensitivity to remote degeneration, and that lesions affecting visual processing pathways were related to processing speed. The Network Modification Tool may be used to quantify the impact of early white matter abnormalities on both connecting gray matter structures and processing speed

Elaboration of Consensus Clinical Endpoints to Evaluate Antimicrobial Treatment Efficacy in Future Hospital-acquired/Ventilator-associated Bacterial Pneumonia Clinical Trials

Background: Randomized clinical trials (RCTs) in hospital-acquired and ventilator-associated bacterial pneumonia (HABP and VABP, respectively) are important for the evaluation of new antimicrobials. However, the heterogeneity in endpoints used in RCTs evaluating treatment of HABP/VABP may puzzle clinicians. The aim of this work was to reach a consensus on clinical endpoints to consider in future clinical trials evaluating antimicrobial treatment efficacy for HABP/VABP. Methods: Twenty-six international experts from intensive care, infectious diseases, and the pharmaceutical industry were polled using the Delphi method. Results: The panel recommended a hierarchical composite endpoint including, by priority order, (1) survival at day 28, (2) mechanical ventilation-free days through day 28, and (3) clinical cure between study days 7 and 10 for VABP; and (1) survival (day 28) and (2) clinical cure (days 7-10) for HABP. Clinical cure was defined as the combination of resolution of signs and symptoms present at enrollment and improvement or lack of progression of radiological signs. More than 70% of the experts agreed to assess survival and mechanical ventilation-free days though day 28, and clinical cure between day 7 and day 10 after treatment initiation. Finally, the hierarchical order of endpoint components was reached after 3 Delphi rounds (72% agreement). Conclusions: We provide a multinational expert consensus on separate hierarchical composite endpoints for VABP and HABP, and on a definition of clinical cure that could be considered for use in future HABP/VABP clinical trials. © 2019 The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: [email protected]

Elaboration of Consensus Clinical Endpoints to Evaluate Antimicrobial Treatment Efficacy in Future Hospital-acquired/Ventilator-associated Bacterial Pneumonia Clinical Trials.

Randomized clinical trials (RCTs) in hospital-acquired and ventilator-associated bacterial pneumonia (HABP and VABP, respectively) are important for the evaluation of new antimicrobials. However, the heterogeneity in endpoints used in RCTs evaluating treatment of HABP/VABP may puzzle clinicians. The aim of this work was to reach a consensus on clinical endpoints to consider in future clinical trials evaluating antimicrobial treatment efficacy for HABP/VABP. Twenty-six international experts from intensive care, infectious diseases, and the pharmaceutical industry were polled using the Delphi method. The panel recommended a hierarchical composite endpoint including, by priority order, (1) survival at day 28, (2) mechanical ventilation-free days through day 28, and (3) clinical cure between study days 7 and 10 for VABP; and (1) survival (day 28) and (2) clinical cure (days 7-10) for HABP. Clinical cure was defined as the combination of resolution of signs and symptoms present at enrollment and improvement or lack of progression of radiological signs. More than 70% of the experts agreed to assess survival and mechanical ventilation-free days though day 28, and clinical cure between day 7 and day 10 after treatment initiation. Finally, the hierarchical order of endpoint components was reached after 3 Delphi rounds (72% agreement). We provide a multinational expert consensus on separate hierarchical composite endpoints for VABP and HABP, and on a definition of clinical cure that could be considered for use in future HABP/VABP clinical trials