The effect of bedrest on various parameters of physiological function. part xi- the effect of bedrest on blood volume, urinary volume, and urinary electrolyte excretion

Effect of bed rest on blood volume, urinary volume, and urinary electrolyte excretio

The effect of bedrest on various parameters of physiological function. part viii- the . . . effect on the cardiovascular tolerance to passive tilt

Effect of short and long term bed rest on cardiovascular tolerance to passive til

The effect of bedrest on various parameters of physiological function. Part XIII - A review of possible mechanisms of orthostatic intolerance to passive tilt

Possible mechanisms of orthostatic intolerance to passive tilt - bed rest and water immersion effects on various parameters of physiological functio

The effect of bedrest on various parameters of physiological function. Part X - The effect of bedrest on the circulatory response to a valsalva maneuver

Quantitative arterial blood pressure change during Valsalva maneuver after bed res

Model of surface instabilities induced by stress

We propose a model based on a Ginzburg-Landau approach to study a strain relief mechanism at a free interface of a non-hydrostatically stressed solid, commonly observed in thin-film growth. The evolving instability, known as the Grinfeld instability, is studied numerically in two and three dimensions. Inherent in the description is the proper treatment of nonlinearities. We find these nonlinearities can lead to competitive coarsening of interfacial structures, corresponding to different wavenumbers, as strain is relieved. We suggest ways to experimentally measure this coarsening.Comment: 4 pages (3 figures included

The effect of bedrest on various parameters of physiological function. part vii- cardiac and ventilatory response to the bicycle ergometer test

Cardiac and ventilatory response to bicycle ergometer tes

The effect of bedrest on various parameters of physiological function. part vi- the effect of the performance of periodic flack maneuvers on preventing cardiovascular deconditioning of bedrest

Preventing cardiovascular deconditioning of bedrest by periodic Flack maneuvers - physiological performance and efficienc

A Robust Numerical Method for Integration of Point-Vortex Trajectories in Two Dimensions

The venerable 2D point-vortex model plays an important role as a simplified version of many disparate physical systems, including superfluids, Bose-Einstein condensates, certain plasma configurations, and inviscid turbulence. This system is also a veritable mathematical playground, touching upon many different disciplines from topology to dynamic systems theory. Point-vortex dynamics are described by a relatively simple system of nonlinear ODEs which can easily be integrated numerically using an appropriate adaptive time stepping method. As the separation between a pair of vortices relative to all other inter-vortex length scales decreases, however, the computational time required diverges. Accuracy is usually the most discouraging casualty when trying to account for such vortex motion, though the varying energy of this ostensibly Hamiltonian system is a potentially more serious problem. We solve these problems by a series of coordinate transformations: We first transform to action-angle coordinates, which, to lowest order, treat the close pair as a single vortex amongst all others with an internal degree of freedom. We next, and most importantly, apply Lie transform perturbation theory to remove the higher-order correction terms in succession. The overall transformation drastically increases the numerical efficiency and ensures that the total energy remains constant to high accuracy.Comment: 21 pages, 4 figure

The effect of quantization on the FCIQMC sign problem

The sign problem in Full Configuration Interaction Quantum Monte Carlo (FCIQMC) without annihilation can be understood as an instability of the psi-particle population to the ground state of the matrix obtained by making all off-diagonal elements of the Hamiltonian negative. Such a matrix, and hence the sign problem, is basis dependent. In this paper we discuss the properties of a physically important basis choice: first versus second quantization. For a given choice of single-particle orbitals, we identify the conditions under which the fermion sign problem in the second quantized basis of antisymmetric Slater determinants is identical to the sign problem in the first quantized basis of unsymmetrized Hartree products. We also show that, when the two differ, the fermion sign problem is always less severe in the second quantized basis. This supports the idea that FCIQMC, even in the absence of annihilation, improves the sign problem relative to first quantized methods. Finally, we point out some theoretically interesting classes of Hamiltonians where first and second quantized sign problems differ, and others where they do not.Comment: 4 pages w/ 2 page appendix, 2 figures, 1 tabl