5,795 research outputs found
Inflation and Establishment Turnover
We study a channel through which inflation can have effects on the real economy. Using job creation and destruction data from U.S. manufacturing establishments from 1973-1988, we show that both jobs created by new establishments and jobs destroyed by dying establishments are negatively correlated with inflation. These results are robust to controls for the real-business cycle and monetary policy. Over a longer time frame, data on business failures confirm our results obtained from job creation and destruction data. We discuss how interaction of inflation with financial-markets, nominal-wage rigidities, and imperfect competition could explain the empirical evidence.
Growth-induced blisters in a circular tube
The growth of an elastic film adhered to a confining substrate might lead to
the formation of delimitation blisters. Many results have been derived when the
substrate is flat. The equilibrium shapes, beyond small deformations, are
determined by the interplay between the sheet elastic energy and the adhesive
potential due to capillarity. Here, we study a non-trivial generalization to
this problem and consider the adhesion of a growing elastic loop to a confining
\emph{circular} substrate. The fundamental equations, i.e., the Euler Elastica
equation, the boundary conditions and the transversality condition, are derived
from a variational procedure. In contrast to the planar case, the curvature of
the delimiting wall appears in the transversality condition, thus acting as a
further source of adhesion. We provide the analytic solution to the problem
under study in terms of elliptic integrals and perform the numerical and the
asymptotic analysis of the characteristic lengths of the blister. Finally, and
in contrast to previous studies, we also discuss the mechanics and the internal
stresses in the case of vanishing adhesion. Specifically, we give a theoretical
explanation to the observed divergence of the mean pressure exerted by the
strip on the container in the limit of small excess-length
A stochastic delay differential model of cerebral autoregulation
Mathematical models of the cardiovascular system and of cerebral autoregulation (CAR) have been employed for several years in order to describe the time course of pressures and flows changes subsequent to postural changes. The assessment of the degree of efficiency of cerebral auto regulation has indeed importance in the prognosis of such conditions as cerebro-vascular accidents or Alzheimer. In the quest for a simple but realistic mathematical description of cardiovascular control, which may be fitted onto non-invasive experimental observations after postural changes, the present work proposes a first version of an empirical Stochastic Delay Differential Equations (SDDEs) model. The model consists of a total of four SDDEs and two ancillary algebraic equations, incorporates four distinct delayed controls from the brain onto different components of the circulation, and is able to accurately capture the time course of mean arterial pressure and cerebral blood flow velocity signals, reproducing observed auto-correlated error around the expected drift
Effects of thickness on the spin susceptibility of the 2D electron gas
Using available quantum Monte Carlo predictions for a strictly 2D electron
gas, we have estimated the spin susceptibility of electrons in actual devices
taking into account the effect of the finite transverse thickness and finding a
very good agreement with experiments. A weak disorder, as found in very clean
devices and/or at densities not too low, just brings about a minor enhancement
of the susceptibility.Comment: 4 pages, 3 figure
Delivering real-world ubiquitous location systems
Location-enhanced applications are poised to become the first real-world example of ubiquitous computing. In this paper, we emphasize the practical aspects of getting location-enhanced applications deployed on existing devices, such as laptops, tablets, PDAs, and cell phones, without the need to purchase additional sensors or install special infrastructure. Our goal is to provide readers with an overview of the practical considerations that are currently being faced, and the research challenges that lie ahead. We ground the article with a summary of initial work on two deployments of location- enhanced computing: multi-player location-based games and a guide for the Edinburgh Festival
Comparative analysis of resonant phonon THz quantum cascade lasers
We present a comparative analysis of a set of GaAs-based THz quantum cascade
lasers, based on longitudinal-optical phonon scattering depopulation, by using
an ensemble Monte Carlo simulation, including both carrier-carrier and
carrier-phonon scattering. The simulation shows that the parasitic injection
into the states below the upper laser level limits the injection efficiency and
thus the device performance at the lasing threshold. Additional detrimental
effects playing an important role are identified. The simulation results are in
reasonable agreement with the experimental findings.Comment: 3 pages, 3 figure
Spin Susceptibility of Interacting Two-dimensional Electrons with Anisotropic Effective Mass
We report measurements of the spin susceptibility in dilute (rs up to 10)
AlAs two-dimensional (2D) electrons occupying a single conduction-band valley
with an anisotropic in-plane Fermi contour, characterized by longitudinal and
transverse effective masses, ml and mt. As the density is decreased, the spin
susceptibility is significantly enhanced over its band value, reflecting the
role of interaction. Yet the enhancement is suppressed compared to the results
of quantum Monte Carlo based calculations that take the finite thickness of the
electron layer into account but assume an isotropic effective mass equal to
sqrt(ml.mt). Proper treatment of an interacting 2D system with an anisotropic
effective mass therefore remains a theoretical challenge.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev.
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