University of Virginia

About: University of Virginia is a education organization based out in Charlottesville, Virginia, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 52543 authors who have published 113268 publications receiving 5220506 citations. The organization is also known as: U of V & UVa.

Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar

Abstract: Despite its importance to our understanding of physics at supranuclear densities, the equation of state (EoS) of matter deep within neutron stars remains poorly understood. Millisecond pulsars (MSPs) are among the most useful astrophysical objects in the Universe for testing fundamental physics, and place some of the most stringent constraints on this high-density EoS. Pulsar timing—the process of accounting for every rotation of a pulsar over long time periods—can precisely measure a wide variety of physical phenomena, including those that allow the measurement of the masses of the components of a pulsar binary system1. One of these, called relativistic Shapiro delay2, can yield precise masses for both an MSP and its companion; however, it is only easily observed in a small subset of high-precision, highly inclined (nearly edge-on) binary pulsar systems. By combining data from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 12.5-yr data set with recent orbital-phase-specific observations using the Green Bank Telescope, we have measured the mass of the MSP J0740+6620 to be $${\mathbf{2}}{\mathbf{.14}}_{ - {\mathbf{0}}{\mathbf{.09}}}^{ + {\mathbf{0}}{\mathbf{.10}}}$$ M⊙ (68.3% credibility interval; the 95.4% credibility interval is $${\mathbf{2}}{\mathbf{.14}}_{ - {\mathbf{0}}{\mathbf{.18}}}^{ + {\mathbf{0}}{\mathbf{.20}}}$$ M⊙). It is highly likely to be the most massive neutron star yet observed, and serves as a strong constraint on the neutron star interior EoS. Cromartie et al. have probably found the most massive neutron star discovered so far by combining NANOGrav 12.5-yr data with radio data from the Green Bank Telescope. Millisecond pulsar J0740+6620 has a mass of 2.14 M⊙, ~0.1 M⊙ more massive than the previous record holder, and very close to the upper limit on neutron star masses from Laser Interferometer Gravitational-Wave Observatory measurements.

The Legion vision of a worldwide virtual computer

Abstract: of a Worldwide Virtual Computer Long a vision of science fiction writers and distributed systems researchers, the notion of a worldwide computer, now taking shape through the Legion project, distributes computation like the World-Wide Web distributes multimedia, creating the illusion for users of a very, very powerful desktop computer. T ODAY’S DRAMATIC INCREASE IN AVAILABLE NETWORK BANDWIDTH WILL qualitatively change how the world computes, communicates, and collaborates. The rapid expansion of the World-Wide Web and the changes it has wrought are just the beginning. As high-bandwidth connections become available, they shrink distances and change our modes of computation, storage, and interaction. Inevitably, users will operate in a wide-area environment transparently consisting of workstations, PCs, graphics-rendering engines, supercomputers, and nontraditional computing devices, such as televisions. The relative physical locations of users and their resources is increasingly irrelevant. Realization of such an environment, sometimes called a “metasystem,” is not without problems. Today’s experimental high-speed networks, such as the Very

Investigating variation in replicability: A “Many Labs” replication project

Abstract: Although replication is a central tenet of science, direct replications are rare in psychology. This research tested variation in the replicability of 13 classic and contemporary effects across 36 independent samples totaling 6,344 participants. In the aggregate, 10 effects replicated consistently. One effect – imagined contact reducing prejudice – showed weak support for replicability. And two effects – flag priming influencing conservatism and currency priming influencing system justification – did not replicate. We compared whether the conditions such as lab versus online or US versus international sample predicted effect magnitudes. By and large they did not. The results of this small sample of effects suggest that replicability is more dependent on the effect itself than on the sample and setting used to investigate the effect.