5,879 research outputs found
Observation of a possible superflare on Proxima Centauri
We report the observation on UT 2017 July 1 of an unusually powerful flare detected in near-infrared continuum photometry of Proxima Centauri. During a campaign monitoring the star for possible exoplanet transits, we identified an increase in Sloan i' flux leading to an observed peak at BJD 2457935.996 that was at least 10 per cent over pre-flare flux in this band. It was followed by a two-component rapid decline in the first 100 s that became a slower exponential decay with time constant of 1350 s. A smaller flare event 1300 s after the first added an incremental peak flux increase of 1 per cent of pre-flare flux. Since the onset of the flare was not fully time resolved at a cadence of 62 s, its actual peak value is unknown but greater than the time average over a single exposure of 20 s. The i' band is representative of broad optical and near-IR continuum flux over which the integrated energy of the flare is 100 times the stellar luminosity. This meets the criteria that established the concept of superflares on similar stars. The resulting implied ultraviolet flux and space weather could have had an extreme effect on the atmospheres of planets within the star's otherwise habitable zone
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Property Rights and the Nature of the Firm
This paper provides a framework for addressing the question of when transactions should be carried out within a firm and when through the market. Following Grossman and Hart, we identify a firm with the assets that its owners control. We argue that the crucial difference for party 1 between owning a firm (integration) and contracting for a service from another party 2 who owns this firm (nonintegration) is that, under integration, party 1 can selectively fire the workers of the firm (including party 2), whereas under nonintegration he can "fire" (i.e., stop dealing with) only the entire firm: the combination of party 2, the workers, and the firm's assets. We use this idea to study how changes in ownership affect the incentives of employees as well as those of owner-managers. Our frame- work is broad enough to encompass more general control structures than simple ownership: for example, partnerships and worker and consumer cooperatives all emerge as special cases.Economic
Continuous Blooming of Convex Polyhedra
We construct the first two continuous bloomings of all convex polyhedra.
First, the source unfolding can be continuously bloomed. Second, any unfolding
of a convex polyhedron can be refined (further cut, by a linear number of cuts)
to have a continuous blooming.Comment: 13 pages, 6 figure
Bleomycin increases neutrophil adhesion to human vascular endothelial cells independently of upregulation of ICAM-1 and E-selectin
© 2016 Taylor & Francis. Aim of the Study: Bleomycin-induced lung disease is a serious complication of therapy characterized by alveolar injury, cytokine release, inflammatory cell recruitment, and eventually pulmonary fibrosis. The mechanisms underlying bleomycin-induced pulmonary fibrosis may be relevant to other progressive scarring diseases of the lungs. Pulmonary vascular endothelial cells are critically involved in immune cell extravasation at sites of injury through adhesion molecule expression and cytokine release. We sought to determine the effects of bleomycin on adhesion molecule expression and cytokine release by pulmonary vascular endothelial cells, and their functional relevance to inflammatory cell recruitment. Materials and Methods: The effects of pharmacologically relevant concentrations of bleomycin on adhesion molecule expression and cytokine release by human vascular endothelial cells in vitro were studied by flow cytometry, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay. A flow chamber model was used to assess the functional consequences on adhesion of flowing human neutrophils to endothelial cell monolayers. Results: Bleomycin increased intercellular adhesion molecule 1 (ICAM-1; CD54), vascular cell adhesion molecule (VCAM-1; CD106), and E-selectin (CD62E) expression, and increased monocyte chemoattractant protein (MCP-1) and interleukin (IL-8) release by endothelial cells. Increases in protein expression were accompanied by increased mRNA transcription. In contrast, there was no direct effect of bleomycin on the profibrotic cytokines transforming growth factor-beta (TGF-β), platelet-derived growth factor-BB (PDGF-BB), or endothelin-1. Under flow conditions, endothelial cells exposed to bleomycin supported increased neutrophil adhesion which was independent of ICAM-1 or E-selectin. Conclusion: Our findings demonstrate that bleomycin promotes endothelial-mediated inflammation and neutrophil adhesion. These mechanisms may contribute to the development of pulmonary fibrosis by supporting immune cell recruitment in the lungs
The Gribov Ambiguity for Maximal Abelian and Center Gauges in SU(2) Lattice Gauge Theory
We present results for the fundamental string tension in SU(2) lattice gauge
theory after projection to maximal abelian and direct maximal center gauges. We
generate 20 Gribov copies/configuration. Abelian and center projected string
tensions slowly decrease as higher values of the gauge functionals are reached.Comment: 3 pages, latex, 1 postscript figure, presented at Lattice
2000(Topology and Vacuum
Abelian Links, Monopoles and Glueballs in SU(2) Lattice Gauge Theory
We investigate the masses of 0+ and 2+ glueballs in SU(2) lattice gauge
theory using abelian projection to the maximum abelian gauge. We calculate
glueball masses using both abelian links and monopole operators. Both methods
reproduce the known full SU(2) results quantitatively. Positivity problems
present in the abelian projection are discussed. We study the dependence of the
glueball masses on magnetic current loop size, and find that the 0+ state
requires a much greater range of sizes than does the 2+ state.Comment: 18 pages, latex, 4 postscript figure
Waves in Radial Gravity Using Magnetic Fluid
We are beginning laboratory experiments using magnetically active ferrofluids to study surface waves in novel geometries. Terrestrial gravity is eliminated from the dynamics, and the magnetic body force felt by ferrofluid in the presence of a magnetic field gradient is used to create a geopotential field which is a section of or an entire sphere or cylinder. New optical, electromagnetic and ultrasonic diagnostic techniques are under development to initially study capillary-gravity wave propagation and interaction in such geometries
Regulation and Measurement of Nitrification in Terrestrial Systems
Nitric oxide (NO) is a relatively short-lived trace gas that reacts with oxygen in the troposphere to produce the air pollutant ozone. It also reacts with water vapor to form nitric and nitrous acids, which acidify precipitation and increase N deposition. Models currently used to predict soil NO fluxes are based on the assumption that NO flux is proportional to the gross rate of nitrification or N mineralization; however, this assumption has not been tested because of the difficulty in measuring gross N-cycling rates in situ. We measured soil NO fluxes, gross and net N-cycling rates, and a variety of other soil characteristics in the forest floor and intact soil cores at nine undisturbed forest and rangeland ecosystems of New Mexico, Utah, and Oregon, USA, to determine which soil variables were most closely related to soil NO flux. Soil NO fluxes ranged from a low of 0.02 ng N·m22·s21, prior to wetting in a western hemlock–sitka spruce forest on the Oregon coast, to a high of 6.74 ng N·m22·s21, one hour after soil wetting in a juniper woodland of central Oregon. In contrast to our expectations, neither gross nitrification nor gross mineralization was correlated with soil NO flux. Fluxes were positively correlated with net rates of mineralization and nitrification, soil NO3 2 concentrations, bulk density, and pH, and negatively correlated with gross rates of NO3 2 consumption in the forest floor, soil organic carbon (SOC), soil C:N, and soil water content. Principal-component analysis showed that NO flux after water addition (2 cm of water) had a strong negative correlation with microbial demand for N (as indicated by net mineralization, net nitrification, SOC, and C:N). Our results suggest that, even in well-drained soils, NO efflux is limited more by NO consumption than by NO production. As a result, models utilizing the more easily measured net rates, rather than gross rates, may be better predictors of soil NO fluxes across a range of ecosystems
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