Nonlocal control of pulse propagation in excitable media

We study the effects of nonlocal control of pulse propagation in excitable media. As a generic example for an excitable medium the FitzHugh-Nagumo model with diffusion in the activator variable is considered. Nonlocal coupling in form of an integral term with a spatial kernel is added. We find that the nonlocal coupling modifies the propagating pulses of the reaction-diffusion system such that a variety of spatio-temporal patterns are generated including acceleration, deceleration, suppression, or generation of pulses, multiple pulses, and blinking pulse trains. It is shown that one can observe these effects for various choices of the integral kernel and the coupling scheme, provided that the control strength and spatial extension of the integral kernel is appropriate. In addition, an analytical procedure is developed to describe the stability borders of the spatially homogeneous steady state in control parameter space in dependence on the parameters of the nonlocal coupling

Global algebras of nonlinear generalized functions with applications in general relativity

We give an overview of the development of algebras of generalized functions in the sense of Colombeau and recent advances concerning diffeomorphism invariant global algebras of generalized functions and tensor fields. We furthermore provide a survey on possible applications in general relativity in light of the limitations of distribution theory

Physics with Like-Sign Muon Beams

We point out that both the specific lepton number content and the high energies potentially attainable with muon-muon colliders make it advisable to consider the technical feasibility of including an option of like-sign incoming beams in the studies towards a proposal to build a muon-muon collider with center-of-mass energies in the TeV region. This capability will add some unique physics capabilities to the project. Special attention will have to be paid to polarization retention for the muons.Comment: 13 pages, uuencoded postscript file, also available from ftp://gluon.hep.physik.uni-muenchen.de/preprints/scipp9534.u

Convective regularization for optical flow

We argue that the time derivative in a fixed coordinate frame may not be the most appropriate measure of time regularity of an optical flow field. Instead, for a given velocity field $v$ we consider the convective acceleration $v_t + \nabla v v$ which describes the acceleration of objects moving according to $v$. Consequently we investigate the suitability of the nonconvex functional $\|v_t + \nabla v v\|^2_{L^2}$ as a regularization term for optical flow. We demonstrate that this term acts as both a spatial and a temporal regularizer and has an intrinsic edge-preserving property. We incorporate it into a contrast invariant and time-regularized variant of the Horn-Schunck functional, prove existence of minimizers and verify experimentally that it addresses some of the problems of basic quadratic models. For the minimization we use an iterative scheme that approximates the original nonlinear problem with a sequence of linear ones. We believe that the convective acceleration may be gainfully introduced in a variety of optical flow models

Time-Bound Labor Access to the United States: A Four-Way Win for the Middle Class, Low-Skill Workers, Border Security, and Migrants

The US economy needs low-skill workers now more than ever, and that requires a legal channel for the large-scale, employment-based entry of low-skill workers. The alternative is what the country has now: a giant black market in unauthorized labor that hinders job creation and harms border security. A legal time-bound labor-access program could benefit the American middle class and low-skill workers, improve US border security, and create opportunities for foreign workers

Deep space monitor communication satellite system Patent

Elimination of tracking occultation problems occurring during continuous monitoring of interplanetary missions by using Earth orbiting communications satellit

The Suppression of Diversity

Is it a systematic strategy or a mutation of millennial ferver that drives the escalating challenges to the civil rights of this nation\u27s racial, linguistic, and national origin minorities? Increasing juridical, legislative, and popular assaults on affirmative action policies coupled with the sometimes less heralded emergence of a de facto U.S. language policy are sweeping through the states. These activities draw on a consistent repertoire of approaches from the invocation of the very language and concepts of the civil rights movement to the isolationist buzz-words of early twentieth century advocates of Americanization. In an effort to legitimize their efforts this new breed of assailants has lifted the terms equality of opportunity, color blind, and merit directly from the lips of civil rights heroes of the past, retrofitting concepts that resonate from the very core of the civil rights movement into an arsenal of weapons that threaten the extinction of that movement. In that same vein opponents of bilingual education have reached further back into our history dredging up de-contextualized quotations from icons of American history to evoke nostalgia and patriotism and to resuscitate the fear of the dissolution of national unity in the wake of the infusion of diverse languages and cultures. The introductory portion of this article treats the failure of anti-civil rights movements to acknowledge either the rich cultural legacy of people of color or the deeply engrained cultural and political limitations that this nation has imposed on their civil rights. We discuss the re-packaged language of equality and equity used by these movements and their success and attempts at success in reversing the progress of civil rights at the polls and in legislatures across the nation. We next examine the anti-affirmative action and anti-bilingual movements sweeping the U.S. today, analyzing qualitative and quantitative data from multiple sources including data from the the 2000 U.S. Census to track current anti-affirmative action and anti-bilingual/English only developments among the states to demonstrate the coexistence of these developments in those areas where people of color are concentrated

A Tariff-Growth Paradox? Protection's Impact the World Around 1875-1997

This paper uses a new database to establish two findings covering the first globalization boom before World War I, the second since World War II, and the autarkic interlude in between. First, there is strong evidence supporting a Tariff-Growth Paradox: protection was associated with fast growth before World War II, while it was associated with slow growth thereafter. Second, there is strong evidence supporting regional asymmetry: while the tariff-growth association was powerful and positive in the Core and rich New World before World War II, it was typically weak and negative in the poor Periphery. The paper offers explanations for the Paradox by controlling for a changing world economic environment. It shows how the oft-quoted Sachs-Warner results for 1970-1989 are significantly revised when one controls for trading partners' growth, trading partners' tariffs and the effective distance between them over the longer half-century 1950-1997. Falling partners' tariffs was the most important force accounting for the switch in sign on the tariff-growth connection after 1950. An increase in own tariffs after 1950 hurt growth, but it would not have hurt growth in a world where partners' tariffs were much higher, trading partners' growth much slower, and the world less closely connected by transportation. World environment matters. Leader-country reaction to big world events (like the Great Depression) matter. Followers take notice.