University of Massachusetts Amherst

About: University of Massachusetts Amherst is a education organization based out in Amherst Center, Massachusetts, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 37274 authors who have published 83965 publications receiving 3834996 citations. The organization is also known as: UMass Amherst & Massachusetts State College.

Hyperbaric-Oxygen Therapy

Abstract: Hyperbaric oxygen — 100 percent oxygen at two to three times the atmospheric pressure at sea level — can result in arterial oxygen tension in excess of 2000 mm Hg1 and oxygen tension in tissue of almost 400 mm Hg.2,3 Such doses of oxygen have a number of beneficial biochemical, cellular, and physiologic effects, and today there are 259 hyperbaric facilities in the United States with 344 single-occupant (“monoplace”) hyperbaric-oxygen chambers.4 In this article, we review the mechanisms of action, evidence of clinical efficacy, and risks of therapy with hyperbaric oxygen. Physiologic Effects For hyperbaric oxygen, pressure is expressed . . .

Radio Properties of Infrared-selected Galaxies in the IRAS 2 Jy Sample

Abstract: The radio counterparts to the IRAS Redshift Survey galaxies are identified in the NRAO VLA Sky Survey (NVSS) catalog. Our new catalog of the IR flux-limited (S60 μm ≥ 2 Jy) complete sample of 1809 galaxies lists accurate radio positions, redshifts, and 1.4 GHz radio and IRAS fluxes. This sample is 6 times larger in size and 5 times deeper in redshift coverage (to z ≈ 0.15) than those used in earlier studies of the radio and far-IR (FIR) properties of galaxies in the local volume. The well-known radio-FIR correlation is obeyed by the overwhelming majority (≥98%) of the IR-selected galaxies, and the radio AGNs identified by their excess radio emission constitute only about 1% of the sample, independent of the IR luminosity. These FIR-selected galaxies can account for the entire population of late-type field galaxies in the local volume, and their radio continuum may be used directly to infer the extinction-free star formation rate in most cases. Both the 1.4 GHz radio and 60 μm IR luminosity functions are reasonably well described by linear sums of two Schechter functions, one representing normal, late-type field galaxies and the other representing starbursts and other luminous IR galaxies. The integrated FIR luminosity density for the local volume is (4.8 ± 0.5) × 107 L☉ Mpc-3, less than 10% of which is contributed by the luminous IR galaxies with LFIR ≥ 1011 L☉. The inferred extinction-free star formation density for the local volume is 0.015 ± 0.005 M☉ yr-1 Mpc-3.

First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole

Abstract: We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ~40 μas, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to select parameters objectively to use when reconstructing images of M87. Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions.

Memristive crossbar arrays for brain-inspired computing

Abstract: With their working mechanisms based on ion migration, the switching dynamics and electrical behaviour of memristive devices resemble those of synapses and neurons, making these devices promising candidates for brain-inspired computing. Built into large-scale crossbar arrays to form neural networks, they perform efficient in-memory computing with massive parallelism by directly using physical laws. The dynamical interactions between artificial synapses and neurons equip the networks with both supervised and unsupervised learning capabilities. Moreover, their ability to interface with analogue signals from sensors without analogue/digital conversions reduces the processing time and energy overhead. Although numerous simulations have indicated the potential of these networks for brain-inspired computing, experimental implementation of large-scale memristive arrays is still in its infancy. This Review looks at the progress, challenges and possible solutions for efficient brain-inspired computation with memristive implementations, both as accelerators for deep learning and as building blocks for spiking neural networks.