Slowing Down and Scattering of Ions in Solids

The interaction of particle beams with solids yields three parts, i.e. reflected particles, penetrating particles and trapped particles. At very low energies particle reflection is dominant, at very high energies penetration is the most important effect. Trapped particles are the result of energy loss processes, which on the other hand cause radiation damage in the solid. In the energy range discussed here, i.e. above energies where quantum effects, diffraction etc. are important and below energies where nuclear reactions, relativistic effects etc. may occur, the particle trajectories are classical. The energy loss process can be treated separately as nuclear and electronic stopping power. The collisions of the projectiles with target atoms are hence binary collisions involving a properly chosen screened Coulomb-potential. In single crystals the structural properties enable channeling, which is a very useful tool in sol id state analysis. The electronic stopping includes contributions from single collision processes and collective excitations. Both effects can be described by a dielectric response function. The range of applications covers analytical methods, means to modify solid state properties and also the production of thin films

SPUTTER DEPTH PROFILING OF OPTICAL WAVEGUIDES USING SECONDARY ION MASS SPECTROMETRY

The technique of sputter depth profiling by means of secondary ion mass spectrometry of samples with high resistivity is reviewed. As examples we discuss optical waveguides made in lithium niobate by titanium indiffusion and implantation and also yttrium iron garnet waveguides grown by liquid phase epitaxy on gadolinium gallium garnet. Depth profiling of these waveguide structures has been performed and the necessary precautions to prevent charging by the primary ion beam are discussed. In some cases, coating with a metallic layer is adequate, but a more universal method is charge neutralization by an additional electron beam

A low-rank solution method for Riccati equations with indefinite quadratic terms

Algebraic Riccati equations with indefinite quadratic terms play an important role in applications related to robust controller design. While there are many established approaches to solve these in case of small-scale dense coefficients, there is no approach available to compute solutions in the large-scale sparse setting. In this paper, we develop an iterative method to compute low-rank approximations of stabilizing solutions of large-scale sparse continuous-time algebraic Riccati equations with indefinite quadratic terms. We test the developed approach for dense examples in comparison to other established matrix equation solvers, and investigate the applicability and performance in large-scale sparse examples.Comment: 19 pages, 2 figures, 5 table

Weight-Related Behavior among Adolescents: The Role of Peer Effects

To investigate whether social interactions in friendship networks influence the following weight-related behaviors of adolescents: exercising regularly, playing an active sport, hours of TV/Video viewing, sleeping six or fewer hours, eating breakfast on weekdays, frequency of eating at fast food restaurants, eating five servings of fruits/vegetables daily, and consuming calorie-dense snacks.Data from a nationally representative sample of adolescents are used to examine the association between peer and individual weight-related behaviors. Evidence from multivariate regression analysis controlling for an extensive list of individual- and family-level factors as well as school-level unobserved heterogeneity is obtained.We find a significant positive association between individuals' and friends' behaviors in terms of sports, exercise and fast food consumption. The estimated associations are robust to controls for individual- and family-level factors, unobserved heterogeneity at the school level and our attempts to account for non-random peer selection.The social transmission of weight-related behaviors is a viable explanation for the spread of obesity in friendship networks documented in recent research. Traditional weight reduction interventions may be fruitfully complemented with strategies that focus on harnessing peer support to modify behaviors

Have We Finally Achieved Actuarial Fairness of Social Security Retirement Benefits and Will It Last?

Working Paper: WP 2014-307This paper develops a framework to analyze the actuarial adjustments faced by American workers who claim Social Security benefits before or after their Full Retirement Age (FRA). We derive the conditions under which these adjustments are “actuarially fair” (or “neutral”) and develop measures to characterize the deviation from the fair form. Fair adjustment schedules are increasing at an increasing rate in take-up age and become flatter as longevity rises. We document that the actuarial fit has improved across generations. Our baseline 3% discount rate scenario estimates that the current schedule deviates from its fair form by less than 1% for average-mortality beneficiaries, compared to 5.1% and 4.0% for male and female beneficiaries in 1980, respectively. The improvement is largely due to the increases in the Delayed Retirement Credit. For men, gains in life expectancy combined with the increase in the FRA also contributed to the improved fit. We predict that the designated increase in the FRA to age 67 will have little effect on the actuarial fit. We investigate schedules reflecting (further) increases in the retirement ages, as recommended by the President’s 2010 Fiscal Commission, and propose alternatives. We also discuss results from the analysis of the adjustments to spousal and widow(er) benefits.Social Security Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/109395/1/wp307.pdfDescription of wp307.pdf : Working pape

Disability Crossover: Is There a Hispanic Immigrant Health Advantage that Reverses from Working to Old Age?

BACKGROUND Hispanic immigrants have been found to be more likely to have a disability than US-born populations. Studies have primarily focused on populations aged 60 and older; little is known about immigrant disability at younger ages. OBJECTIVE Taking a broader perspective, we investigate whether Hispanic immigrants have lower disability rates in midlife; if so, at what ages this health advantage reverses; and the correlates of this pattern. METHODS Using American Community Survey 2010–2014 data, we estimate age-specific disability prevalence rates by gender, nativity, education, and migration age from age 40 to 80. We also present estimates by six types of disability. RESULTS Compared to non-Hispanic whites, disability prevalence among foreign-born Mexican women is lower until age 53 (men: 61) and greater after 59 (66). Similar patterns hold for other foreign-born Hispanics. Crossovers are observed in rates of ambulatory, cognitive, independent living, and self-care disability. Evidence of a steeper age– disability gradient among less-educated immigrants is found. Minimal differences are noted by migration age, challenging an acculturation explanation for the crossover. CONTRIBUTION The paper contributes to a better understanding of immigrant–native disability patterns in the United States. It is the first to systematically document a Hispanic immigrant health advantage in disability that reverses from working to old age. Hispanic immigrants (particularly foreign-born Mexican women), may face steeper risk trajectories, consistent with their greater concentration in low-skill manual occupations. We call for increased scholarly attention to this phenomenon

Electronic structure of the muonium center as a shallow donor in ZnO

The electronic structure and the location of muonium centers (Mu) in single-crystalline ZnO were determined for the first time. Two species of Mu centers with extremely small hyperfine parameters have been observed below 40 K. Both Mu centers have an axial-symmetric hyperfine structure along with a [0001] axis, indicating that they are located at the AB_{O,//} and BC_{//} sites. It is inferred from their small ionization energy (~6 meV and 50 meV) and hyperfine parameters (~10^{-4} times the vacuum value) that these centers behave as shallow donors, strongly suggesting that hydrogen is one of the primary origins of n type conductivity in as-grown ZnO.Comment: 4 pages, 4 figures, submitted to PR