Topic
Rarefaction
About: Rarefaction is a research topic. Over the lifetime, 1852 publications have been published within this topic receiving 26943 citations.
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TL;DR: In this paper, the authors considered a two-dimensional model of a laser with a ring-like active region and compared the characteristics of its modes with the modes of an active microring, a similar disk with a concentric hole.
Abstract: Microcavity lasers shaped as thin circular disks are famous for the ultra-low thresholds of their whispering-gallery modes. We considered a two-dimensional model of such a laser in free space with a ring-like active region and compared the characteristics of its modes with the modes of an active microring, i.e. a similar disk with a concentric hole. The comparison showed that a microring has considerable rarefaction effect in terms of emission thresholds, accompanied by the blue-shift of emission spectra. If the ring becomes narrower than a half-wavelength in material, then all lasing modes obtain catastrophically high thresholds.
29 citations
TL;DR: Capillary rarefaction has not only been reported in established essential hypertension, but also in borderline essential hypertension and young adults with a predisposition to high blood pressure, which suggests that defective angiogenesis/ arteriogenesis may be an etiological component in the inheritance of highBlood pressure.
Abstract: The established phase of human essential hypertension is characterized by a normal cardiac output and an elevation in peripheral resistance. A considerable part of this increase in vascular resistance is determined by the structure of the microvasculature, in particular the small arteries and precapillary arterioles, where increases in the wall thickness : lumen ratios are frequently observed [1]. In addition, other abnormalities in the microvasculature are also known to occur, such as a reduction in microvessels. Rarefaction of capillaries and arterioles has been reported in many animal models of hypertension [2,3], and may also be involved in increasing peripheral resistance in essential hypertension [4]. Rarefaction of capillaries is caused by an absence of capillaries or a functional rarefaction, in which the capillaries are present but not perfused. Capillary rarefaction has not only been reported in established essential hypertension [4], but also in borderline essential hypertension [5] and young adults with a predisposition to high blood pressure [6]. This latter observation suggests that defective angiogenesis/ arteriogenesis may be an etiological component in the inheritance of high blood pressure, and raises the possibility that genetic factors may be responsible for at least a component of microvascular rarefaction.
29 citations
TL;DR: In this article, the authors investigated the effect of rarefaction on heat transfer characteristics, at a distance from the inlet where Nu becomes constant, for two cases: (i) including and (ii) neglecting the viscous dissipation effect.
29 citations
TL;DR: In this article, the effect of rarefaction acceleration on the propagation dynamics and structure of relativistically hot jets is studied through relativistic hydrodynamic simulations, and it is shown that a decrease in the relativism due to the interacting rare faction waves in the central zone of the jet transiently yields a more powerful boost of the bulk jet than that expected from single rare fraction acceleration.
Abstract: The effect of rarefaction acceleration on the propagation dynamics and structure of relativistically hot jets is studied through relativistic hydrodynamic simulations. We emphasize the nonlinear interaction of rarefaction waves excited at the interface between a cylindrical jet and the surrounding medium. From simplified one-dimensional (1D) models with radial jet structure, we find that a decrease in the relativistic pressure due to the interacting rarefaction waves in the central zone of the jet transiently yields a more powerful boost of the bulk jet than that expected from single rarefaction acceleration. This leads to a cyclic in situ energy conversion between thermal and bulk kinetic energies, which induces radial oscillating motion of the jet. The oscillation timescale is characterized by the initial pressure ratio of the jet to the ambient medium and follows a simple scaling relation, τoscillation(P jet, 0/P amb, 0)1/2. Extended two-dimensional simulations confirm that this radial oscillating motion in the 1D system manifests as modulation of the structure of the jet in a more realistic situation where a relativistically hot jet propagates through an ambient medium. We find that when the ambient medium has a power-law pressure distribution, the size of the reconfinement region along the propagation direction of the jet in the modulation structure λ evolves according to a self-similar relation λt α/2, where α is the power-law index of the pressure distribution.
29 citations
01 Jan 2001
TL;DR: A shock wave is a surface of discontinuity propagating in a gas at which density and velocity experience abrupt changes as discussed by the authors, and it can be divided into two types: compression and rarefaction.
Abstract: A shock wave is a surface of discontinuity propagating in a gas at which density and velocity experience abrupt changes. One can imagine two types of shock waves: (positive) compression shocks which propagate into the direction where the density of the gas is a minimum, and (negative) rarefaction waves which propagate into the direction of maximum density. 1
Gyozy Zemplen University of Budapest 1905
29 citations