Search results for "hole"
showing 10 items of 2900 documents
A quantum model of Schwarzschild black hole evaporation
1996
We construct a one-loop effective metric describing the evaporation phase of a Schwarzschild black hole in a spherically symmetric null-dust model. This is achieved by quantising the Vaidya solution and by chosing a time dependent quantum state. This state describes a black hole which is initially in thermal equilibrium and then the equilibrium is switched off, so that the black hole starts to evaporate, shrinking to a zero radius in a finite proper time. The naked singularity appears, and the Hawking flux diverges at the end-point. However, a static metric can be imposed in the future of the end-point. Although this end-state metric cannot be determined within our construction, we show tha…
Symmetries and solvable models for evaporating 2D black holes
1997
We study the evaporation process of a 2D black hole in thermal equilibrium when the ingoing radiation is suddenly switched off. We also introduce global symmetries of generic 2D dilaton gravity models which generalize the extra symmetry of the CGHS model. © Elsevier Science B.V
Worldwide burden of LDL cholesterol: Implications in cardiovascular disease
2020
Abstract Background and aim an increased value of low-density lipoprotein cholesterol (LDL-C) is now universally considered a major cardiovascular disease (CVD) risk factor. LDL-C is included in the vast majority of worldwide cardiovascular risk prediction algorithms, as well as in the guidelines for cardiovascular risk prevention. We aimed to provide an overview of the worldwide adverse healthcare impact of low-density lipoprotein cholesterol (LDL-C). Methods and results Data on the epidemiologic burden of LDL-C >1.3 mmol/L were retrieved from Global Health Data Exchange (GHDx) registry. The current burden is 94.92 million disability-adjusted life years (DALYs), with an exponential increas…
Associations of Maternal Cell-Phone Use During Pregnancy With Pregnancy Duration and Fetal Growth in 4 Birth Cohorts
2019
Results from studies evaluating potential effects of prenatal exposure to radio-frequency electromagnetic fields from cell phones on birth outcomes have been inconsistent. Using data on 55,507 pregnant women and their children from Denmark (1996-2002), the Netherlands (2003-2004), Spain (2003-2008), and South Korea (2006-2011), we explored whether maternal cell-phone use was associated with pregnancy duration and fetal growth. On the basis of self-reported number of cell-phone calls per day, exposure was grouped as none, low (referent), intermediate, or high. We examined pregnancy duration (gestational age at birth, preterm/postterm birth), fetal growth (birth weight ratio, small/large size…
Cholesterol Modulates the Interaction of β-Amyloid Peptide with Lipid Bilayers
2009
The interaction of an amphiphilic, 40-amino acid beta-amyloid (Abeta) peptide with liposomal membranes as a function of sterol mole fraction (X(sterol)) was studied based on the fluorescence anisotropy of a site-specific membrane sterol probe, dehydroergosterol (DHE), and fluorescence resonance energy transfer (FRET) from the native Tyr-10 residue of Abeta to DHE. Without Abeta, peaks or kinks in the DHE anisotropy versus X(sterol) plot were detected at X(sterol) approximately 0.25, 0.33, and 0.53. Monomeric Abeta preserved these peaks/kinks, but oligomeric Abeta suppressed them and created a new DHE anisotropy peak at X(sterol) approximately 0.38. The above critical X(sterol) values coinci…
Cross-circulation and Cell Distribution Kinetics in Parabiotic Mice
2011
Blood-borne nucleated cells participate not only in inflammation, but in tissue repair and regeneration. Because progenitor and stem cell populations have a low concentration in the blood, the circulation kinetics and tissue distribution of these cells is largely unknown. An important approach to tracking cell lineage is the use of fluorescent tracers and parabiotic models of cross-circulation. Here, we investigated the cross-circulation and cell distribution kinetics of C57/B6 GFP(+)/wild-type parabionts. Flow cytometry analysis of the peripheral blood after parabiosis demonstrated no evidence for a "parabiotic barrier" based on cell size or surface characterstics; all peripheral blood cel…
Occupational health disparities among U.S. long-haul truck drivers: the influence of work organization and sleep on cardiovascular and metabolic dise…
2018
Objective The organization of work has undergone vast transformations over the past four decades in the United States and has had profound impacts on worker health and wellbeing. The profession of commercial truck driving is one of the best examples. Particularly for long-haul truck drivers, changes in work organization have led to disproportionately poor physiological, psychological, and sleep health outcomes. Methods The present study examined disparities in cardiometabolic disease risk among long-haul truck drivers and the general population, and the influence of work organization and sleep in generating these outcomes. Researchers collected survey data from 260 drivers, and blood assay …
Tuneable multicoloured patterns from photonic cross-communication between cholesteric liquid crystal droplets
2014
Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets—which thus act as spherically symmetric self-assembled photonic crystals—and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications.
Vertical distribution of pharmaceuticals in lake sediments-citalopram as potential chemomarker
2012
The use of pharmaceuticals has increased enormously over the last few decades and serious concerns about their environmental fate and effects have arisen. Thus far, there is little knowledge about the historical pollution of the environment by pharmaceuticals. In the present study, sediment columns from three lake sites adjacent to wastewater treatment plants were collected, further divided in 2- or 2.5-cm slices, and analyzed for 15 pharmaceuticals by liquid chromatography-tandem mass spectrometry. In addition, sediment columns were historically interpreted by analyzing fecal sterols (coprostanol and cholesterol) as well as organic material and organic carbon. Several pharmaceuticals were …
Whole body vibrations during field operations in the vineyard
2013
Human exposure to mechanical vibration can be a significant risk factor for exposed workers and this also occurs in the agricultural sector, in particular with reference to the driver of the tractor during field operations. The aim of this paper is the evaluation of Whole Body Vibrations for the operator driving tractors during the field operations in the vineyard. The experimental tests were performed using a wheeled and a track-laying tractor. They were coupled to four different machines: rototilling (RT), chisel plough (CP), flail mowers (FM) and vibro farmer (VF). Two homogeneous plots of vineyard, about 200 m long, were identified different only for slope: 0% and 30%. The tests were pe…