Newly developed foam ceramic body shows promise as thermal insulation material at 3000 deg F

Optimized zirconia foam ceramic body shows promise for use as a thermal insulation material. The insulating media displays low density and thermal conductivity, good thermal shock resistance, high melting point, and mechanical strength

Negative and Positive Assimilation, Skill Transferability, and Linguistic Distance

There are two complementary models of immigrants' economic and social adjustment -- the positive assimilation model of Chiswick (1978, 1979), and the negative assimilation model of Chiswick and Miller (2011). The negative assimilation model is applicable for immigrants from countries that are very similar in terms of the transferability of skills, culture, and labor market institutions to the host country, and has been tested previously primarily using migration among the English-speaking developed countries. This paper generalizes the negative/positive assimilation models through analyzing the post-arrival learnings profiles of immigrants in the US from non-English-speaking countries according to the linguistic distance of their mother tongue from English. Using data on adult male immigrants from the 2000 US Census, it is shown that all groups of immigrants from non English-speaking countries are characterized by positive assimilation. Earnings in the immediate post-arrival period are lowest for the language groups furthest from English, and the increase in earnings with duration is steeper the further the immigrant's mother tongue is from English. The linguistic distance of the immigrants' mother tongue from the destination language appears, therefore, to play a crucial role in generating the inverse relationship between post-arrival earnings growth and the initial earnings disadvantage documented in most studies of immigrant earnings

Distribution, Hybridization, and Taxonomic Status of Two-lined Salamanders (\u3ci\u3eEurycea bislineata\u3c/i\u3e complex) in Virginia and West Virginia

We used three diagnostic protein markers to examine salamanders of the Eurycea bislineata complex at 80 localities in Virginia and West Virginia. Two groups were strongly differentiated and met at a narrow contact zone. Rare hybridization was observed as well as limited introgression up to 5 km north and 10 km south of the contact zone. At the contact zone, 1% F1, 2% F2, 32% backcross, and 66% parental genotypes were observed. This pattern of parapatric distribution with limited hybridization and introgression argues for the recognition of Eurycea bislineata and E. cirrigera as separate species

Is Hyperconjugation Responsible For The Gauche Effect In 1-Fluoropropane And Other 2-Substituted-1-Fluoroethanes?

The energies and geometries of a series of 2-substituted-1-fluoroethanes were computed at the MP2/6-311++G**(6D)//MP2/6-31+G* level of theory for both the maxima and minima of the rotation about the C-C bond. The results did not support the predictions of a hyperconjugative model, that both 1,2-difluoroethane and 1-chloro-2-fluoroethane would strongly prefer a gauche conformation, and that 1-fluoro-2-silylethane would strongly prefer an anti conformation. The existence of competing electrostatic interactions between the fluorine and the substituents at C-2 was indicated by the detailed geometries of the gauche conformers and by the calculated sensitivity of the gauche-anti energy differences to the presence of a polar solvent. However, Fourier analyses of the torsional potential energies were wholly consistent with hyperconjugative electron donation into the C-F sigma* orbital contributing to the conformational preferences of these 1-fluoroethanes. Fourier analyses also showed that hyperconjugation contributes to the small variations in C-C and C-F bond lengths and in fluorine atomic charges that were computed. The torsional potential energies, variations in geometry and atomic charge, and sensitivity to solvent were all in accord with the expected ranking of hyperconjugative electron donating ability of bonds to carbon, C-Si \u3e C-H \u3e C-C \u3e C-Cl \u3e C-F

Growth variation effects in SiGe-based quantum cascade lasers

Epitaxial growth of SiGe quantum cascade (QC) lasers has thus far proved difficult, and nonabrupt Ge profiles are known to exist. We model the resulting barrier degradation by simulating annealing in pairs of quantum wells (QWs). Using a semiclassical charge transport model, we calculate the changes in scattering rates and transition energy between the lowest pair of subbands. We compare results for each of the possible material configurations for SiGe QC lasers. The effects are most severe in n-type (001) Si-rich systems due to the large effective electron mass, and in p-type systems due to the coexistence of light holes and heavy holes. The lower effective mass and conduction band offset of (111) oriented systems minimizes the transition energy variation, and a large interdiffusion length (Ld = 1.49 nm) is tolerated with respect to the scattering rate. Ge-rich systems are shown to give the best tolerance with respect to subband separation (Ld = 3.31 nm), due also to their low effective mass

The "Negative" Assimilation of Immigrants: A Special Case

Research on the economic or labor market assimilation of immigrants has to date focused on the degree of improvement in their economic status with duration in the destination. This pattern has been found for all the immigrant receiving countries, time periods and data sets that have been studied. The theoretical underpinning for this finding is the international transferability of skills. This paper addresses whether positive assimilation will be found if skills are very highly transferable internationally. It outlines the conditions for “negative” assimilation in the context of the traditional immigration assimilation model, and examines the empirical relevance of the hypothesis using data on immigrants from the English-speaking developed countries (i.e., the UK, Ireland, Canada and Australia/New Zealand) to the United States. Comparisons with the native born are also presented to test whether the findings are sensitive to immigrant cohort quality effects. Even after controlling for cohort effects, “negative” assimilation (a decline in earnings with duration) is found for immigrants in the US from the English-speaking developed countries.immigrants, earnings, assimilation

Citizenship in the United States: The Roles of Immigrant Characteristics and Country of Origin

This study develops and estimates a model of the naturalization process in the US. The model is based on both the characteristics of immigrants and features of their countries of origin. The empirical analysis is based on the 2000 US Census. Both the characteristics of immigrants and the origin-country variables are shown to be important determinants of citizenship status. The individual characteristics that have the most influence are educational attainment, age at migration, years since migration, veteran of the US armed forces, living with family, and spouses’ educational attainment. The country of origin variables of most importance are their degree of civil liberties and political rights, GDP per capita, whether the origin country recognizes dual citizenship, and the geographic distance of the origin country from the US.immigrants, human capital, citizenship, country of origin

Earnings and Occupational Attainment: Immigrants and the Native Born

This paper examines the determinants of occupational attainment and the impact of occupation on earnings. Results for both the native born and foreign born are presented, and these provide insights as to the earnings penalties associated with the lessthan- perfect international transferability of human capital skills. It shows that around 50 percent of the earnings gains associated with years of schooling derives from interoccupational mobility. When occupation is held constant, there is a large increase in the effect on earnings of pre-immigration labor market experience for the foreign born, but little change in either the payoff to labor market experience for the native born, or in the premium for post-arrival labor market experience for the foreign born. The estimates of the models of occupational attainment show that years of schooling, and, among the foreign born, proficiency in English, are the key factors determining access to high-paying occupations. Labor market experience has little effect on occupational outcomes among the native born. However, evaluated at 10 years, foreign labor market experience has a modest negative impact on current occupational status. Examination of this negative effect using quantile regression shows that it is concentrated among those in high status jobs.Immigrants, Occupation, Earnings

Does the Choice of Reference Levels of Education Matter in the ORU Earnings Equation?

This paper examines whether the results of the earnings equation developed in the overeducation/required eduation/under-education (ORU) literature are sensitive to whether the usual or reference levels of education are measured using the Realized Matches or Worker Self-Assessment methods. The analyses are conducted for all male native-born and immigrant workers in the US, by level of skill, and by occupation. While point estimates differ, particularly when earnings equations are estimated for the smaller samples of sub-groups of the workforce, the general findings are robust to this measurement issue. Thus, the answers provided to the typical research questions in the ORU literature on the utilization of schooling are independent of the measure of the usual or reference level of education used in the analyses.immigrants, skill, schooling, occupations, earnings, rates of return