Salnave Elementary playground during COVID-19

I wanted to share this image to capture what now feels like a forgotten moment in the pandemic -- for the first few days of statewide lockdown, I had taken my daughter to this playground at her elementary school in Cheney, since playing outside was about the only safe thing we knew to do. But then an order was issued to close playgrounds out of fear of the spread of covid-19, so this is a picture taken on March 23 -- you can see not only the big sign, but the faint yellow caution tape that\u27s wrapped around all of the playground equipment. There was something very chilling about it -- at the time it seemed ominous but no one was sure yet how bad things would get. And now, with the playgrounds having been open for many months (though we wear a mask and hand sanitize, etc.), this picture feels more like a dream I had than like a memory.https://dc.ewu.edu/covid/1000/thumbnail.jp

Virtual dielectric waveguide mode description of a high-gain free-electron laser I: Theory

A set of mode-coupled excitation equations for the slowly-growing amplitudes of dielectric waveguide eigenmodes is derived as a description of the electromagnetic signal field of a high-gain free-electron laser, or FEL, including the effects of longitudinal space-charge. This approach of describing the field basis set has notable advantages for FEL analysis in providing an efficient characterization of eigenmodes, and in allowing a clear connection to free-space propagation of the input (seeding) and output radiation. The formulation describes the entire evolution of the radiation wave through the linear gain regime, prior to the onset of saturation, with arbitrary initial conditions. By virtue of the flexibility in the expansion basis, this technique can be used to find the direct coupling and amplification of a particular mode. A simple transformation converts the derived coupled differential excitation equations into a set of coupled algebraic equations and yields a matrix determinant equation for the FEL eigenmodes. A quadratic index medium is used as a model dielectric waveguide to obtain an expression for the predicted spot size of the dominant system eigenmode, in the approximation that it is a single gaussian mode.Comment: 14 page

From Illegal to Legal: Estimating Previous Illegal Experience among New Legal Immigrants to the United States

This paper develops a framework for estimating previous illegal experience among annual cohorts of new legal immigrants to the United States – using public-use administrative microdata alone, survey data alone, and the two jointly – and provides estimates for the FY 1996 cohort of new immigrants, based on both administrative and survey data. Our procedures enable assessment of type of illegal experience, including entry without inspection, visa overstay, and unauthorized employment. We compare our estimates of previous illegal experience to estimates that would be obtained using administrative data alone; examine the extent of previous illegal experience by country of birth, immigrant class of admission, religion, and geographic residence in the United States; and estimate multivariate models of the probability of having previous illegal experience. To further assess origins and destinations, we carry out two kinds of contrasts, comparing formerly illegal new legal immigrants both to fellow immigrants who do not have previous illegal experience and also to the broader unauthorized population, the latter using estimates developed by DHS (2002), Passel (2002), and Costanzo et al. (2002).administrative data, legal immigration, illegal immigration, survey data

Immigration, health, and New York City: early results based on the U.S. new immigrant cohort of 2003

This article was presented at a conference organized by the Federal Reserve Bank of New York in April 2005, "Urban Dynamics in New York City." The goal of the conference was threefold: to examine the historical transformations of the engine-of-growth industries in New York and distill the main determinants of the city's historical dominance as well as the challenges to its continued success; to study the nature and evolution of immigration flows into New York; and to analyze recent trends in a range of socioeconomic outcomes, both for the general population and recent immigrants more specifically.Immigrants - New York (N.Y.) ; Medical care - New York (N.Y.) ; Economic conditions - New York (N.Y.) ; Federal Reserve District, 2nd

Immigrant Health--Selectivity and Acculturation

This paper explores some salient issues concerning immigrant health. Ethnic health disparities are inherently linked to immigration since ethnic identities often are traced to the country of origin of one's immigrant ancestors. Two of the central questions that have dominated the medical and social science literature on immigrant health are the central focus of this paper. These issues involve the magnitude and mechanisms shaping health selectivity and the determinants of health trajectories following immigration. As part of this paper, we also developed a theoretical model that attempts to explain the diversity in health selection among immigrants.

Characterization of plasma accelerators with RF linac terminology

Abstract The physics of plasma acceleration is described by using RF linac terminology such as shunt impedance, filling time, transit time factor, etc. It is shown that some differences between conventional RF accelerators and plasma accelerators make it difficult to import the RF linac terminology directly into the new field. For example, the shunt impedance is of limited use and the filling time is no use in wake-field accelerators with single-drive beams or single-pump pulses. The beatwave accelerator, a driven oscillator system, has in a sense more similarity to RF linacs than wake-field accelerators. It was shown that plasma wave decay due to collisions and modulational instability seriously deteriorate the quality factor

Microscopic kinetic analysis of space-charge induced optical microbunching in a relativistic electron beam

Longitudinal space-charge forces from density fluctuations generated by shot noise can be a major source of microbunching instability in relativistic high brightness electron beams. The gain in microbunching due to this effect is broadband, extending at least up to optical frequencies, where the induced structure on the beam distribution gives rise to effects such as coherent optical transition radiation. In the high-frequency regime, theoretical and computational analyses of microbunching formation require a full three-dimensional treatment. In this paper we address the problem of space-charge induced optical microbunching formation in the high-frequency limit when transverse thermal motion due to finite emittance is included for the first time. We derive an analytical description of this process based on the beam's plasma dielectric function. We discuss the effect of transverse temperature on the angular distribution of microbunching gain and its connection to the physics of Landau damping in longitudinal plasma oscillations. Application of the theory to a relevant experimental scenario is discussed. The analytical results obtained are then compared to the predictions arising from high resolution three-dimensional molecular dynamics simulations