986 resultados para second harmonic generation


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We analyse the access to different institutional pathways to higher education for second-generation students, focusing on youths that hold a higher-education entrance certificate. The alternative vocational pathway appears to compensate to some degree, compared to the traditional academic one, for North-African and Southern-European youths in France, those from Turkey in Germany, and to a lesser degree those from Portugal, Turkey, Ex-Yugoslavia, Albania/Kosovo in Switzerland. This is not the case in Switzerland for Western-European, Italian, and Spanish youths who indeed access higher education via the academic pathway more often than Swiss youths. Using youth panel and survey data, multinomial models are applied to analyse these pathway choices.

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Mode of access: Internet.

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Mode of access: Internet.

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Mode of access: Internet.

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A low-density, male-based linkage map was constructed as one of the objectives of the International Equine Gene Mapping Workshop. Here we report the second generation map based on testing 503 half-sibling offspring from 13 sire families for 344 informative markers using the crimap program. The multipoint linkage analysis localized 310 markers (90%) with 257 markers being linearly ordered. The map included 34 linkage groups representing all 31 autosomes and spanning 2262 cM with an average interval between loci of 10.1 cM. This map is a milestone in that it is the first map with linkage groups assigned to each of the 31 automosomes and a single linkage group to all but three chromosomes.

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Drying is a major and challenging step in the pre-treatment of biomass for production of second generation synfuels for transport. The biomass feedstocks are mostly wet and need to be dried from 30 to 60 wt% moisture content to about 10-15 wt%. The present survey aims to define and evaluate a few of the most promising optimised concepts for biomass pre-treatment scheme in the production of second generation synfuels for transport. The most promising commercially available drying processes were reviewed, focusing on the applications, operational factors and emissions of dryers. The most common dryers applied now for biomass in bio-energy plants are direct rotary dryers, but the use of steam drying techniques is increasing. Steam drying systems enable the integration of the dryer to existing energy sources. In addition to integration, emissions and fire or explosion risks have to be considered when selecting a dryer for the plant. In steam drying there will be no gaseous emissions, but the aqueous effluents need often treatment. Concepts for biomass pre-treatment were defined for two different cases including a large-scale wood-based gasification synfuel production and a small-scale pyrolysis process based on wood chips and miscanthus bundles. For the first case a pneumatic conveying steam dryer was suggested. In the second case the flue gas will be used as drying medium in a direct or indirect rotary dryer.

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Biomass-To-Liquid (BTL) is one of the most promising low carbon processes available to support the expanding transportation sector. This multi-step process produces hydrocarbon fuels from biomass, the so-called “second generation biofuels” that, unlike first generation biofuels, have the ability to make use of a wider range of biomass feedstock than just plant oils and sugar/starch components. A BTL process based on gasification has yet to be commercialized. This work focuses on the techno-economic feasibility of nine BTL plants. The scope was limited to hydrocarbon products as these can be readily incorporated and integrated into conventional markets and supply chains. The evaluated BTL systems were based on pressurised oxygen gasification of wood biomass or bio-oil and they were characterised by different fuel synthesis processes including: Fischer-Tropsch synthesis, the Methanol to Gasoline (MTG) process and the Topsoe Integrated Gasoline (TIGAS) synthesis. This was the first time that these three fuel synthesis technologies were compared in a single, consistent evaluation. The selected process concepts were modelled using the process simulation software IPSEpro to determine mass balances, energy balances and product distributions. For each BTL concept, a cost model was developed in MS Excel to estimate capital, operating and production costs. An uncertainty analysis based on the Monte Carlo statistical method, was also carried out to examine how the uncertainty in the input parameters of the cost model could affect the output (i.e. production cost) of the model. This was the first time that an uncertainty analysis was included in a published techno-economic assessment study of BTL systems. It was found that bio-oil gasification cannot currently compete with solid biomass gasification due to the lower efficiencies and higher costs associated with the additional thermal conversion step of fast pyrolysis. Fischer-Tropsch synthesis was the most promising fuel synthesis technology for commercial production of liquid hydrocarbon fuels since it achieved higher efficiencies and lower costs than TIGAS and MTG. None of the BTL systems were competitive with conventional fossil fuel plants. However, if government tax take was reduced by approximately 33% or a subsidy of £55/t dry biomass was available, transport biofuels could be competitive with conventional fuels. Large scale biofuel production may be possible in the long term through subsidies, fuels price rises and legislation.

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INTRODUCTION: Bipolar disorder requires long-term treatment but non-adherence is a common problem. Antipsychotic long-acting injections (LAIs) have been suggested to improve adherence but none are licensed in the UK for bipolar. However, the use of second-generation antipsychotics (SGA) LAIs in bipolar is not uncommon albeit there is a lack of systematic review in this area. This study aims to systematically review safety and efficacy of SGA LAIs in the maintenance treatment of bipolar disorder. METHODS AND ANALYSIS: The protocol is based on Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) and will include only randomised controlled trials comparing SGA LAIs in bipolar. PubMed, EMBASE, CINAHL, Cochrane Library (CENTRAL), PsychINFO, LiLACS, http://www.clinicaltrials.gov will be searched, with no language restriction, from 2000 to January 2016 as first SGA LAIs came to the market after 2000. Manufacturers of SGA LAIs will also be contacted. Primary efficacy outcome is relapse rate or delayed time to relapse or reduction in hospitalisation and primary safety outcomes are drop-out rates, all-cause discontinuation and discontinuation due to adverse events. Qualitative reporting of evidence will be based on 21 items listed on standards for reporting qualitative research (SRQR) focusing on study quality (assessed using the Jadad score, allocation concealment and data analysis), risk of bias and effect size. Publication bias will be assessed using funnel plots. If sufficient data are available meta-analysis will be performed with primary effect size as relative risk presented with 95% CI. Sensitivity analysis, conditional on number of studies and sample size, will be carried out on manic versus depressive symptoms and monotherapy versus adjunctive therapy.

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We present a novel optical comb generation technique based on the use of a multi-harmonic electrical signal for driving the MZM. The proposed scheme is highly power efficient and gives rise to square shaped combs of advanced flatness and side mode suppression ratio while maintaining a stable performance over a long time period. © 2012 OSA.

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The rise in diversity and numbers of U.S. immigrants since 1965 has spawned a number of studies about the education of these immigrants and their children. Most of this research finds that school-age immigrants arriving in the last 20 years have the highest drop-out rates, lowest test scores, and are less likely than their native born peers to go to college. This dissertation examines the experiences of Nicaraguan immigrant youth living in Miami and the factors that make some of these adolescents feel positive about education, while others have negative attitudes about education. The method for this study combined structured and unstructured interviews, participant observation, focus groups, and data collected from a larger data set to understand the academic orientation of 25 Nicaraguan youths over a 4-year period. One of the independent variables is length of time in the United States. During the time of my initial contact with the subjects, 6 had been living in the United States for less than 3 years, 14 had been living in the United States between 6 and 12 years, and 6 had been living in the in the United States most or all of their lives (either they were born in the United States or had resided here for over 12 years). ^ Results are based on the students' particular experiences, which influence the dependent variable, academic orientation. Besides length of time, the independent variables also include ethnic self-identity, perceived discrimination, social capital in Miami, and peer influence. The study finds that those who are very recent arrivals have a “dual frame of reference,” that is, they directly compare their educational opportunities here in the United States, with their prior, often less favorable, situation in their homeland. Many of those who were born in Nicaragua, but have been residing in Miami most of their lives, have a less favorable view of education based on a higher degree of perceived discrimination. However, those who are second generation Nicaraguans deliberately take advantage of the strength inherent in their co-ethnic community unique to Miami. Recognition of this ethnic community prompts them to perceive education as worthwhile. ^

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Prices of U.S. Treasury securities vary over time and across maturities. When the market in Treasurys is sufficiently complete and frictionless, these prices may be modeled by a function time and maturity. A cross-section of this function for time held fixed is called the yield curve; the aggregate of these sections is the evolution of the yield curve. This dissertation studies aspects of this evolution. ^ There are two complementary approaches to the study of yield curve evolution here. The first is principal components analysis; the second is wavelet analysis. In both approaches both the time and maturity variables are discretized. In principal components analysis the vectors of yield curve shifts are viewed as observations of a multivariate normal distribution. The resulting covariance matrix is diagonalized; the resulting eigenvalues and eigenvectors (the principal components) are used to draw inferences about the yield curve evolution. ^ In wavelet analysis, the vectors of shifts are resolved into hierarchies of localized fundamental shifts (wavelets) that leave specified global properties invariant (average change and duration change). The hierarchies relate to the degree of localization with movements restricted to a single maturity at the base and general movements at the apex. Second generation wavelet techniques allow better adaptation of the model to economic observables. Statistically, the wavelet approach is inherently nonparametric while the wavelets themselves are better adapted to describing a complete market. ^ Principal components analysis provides information on the dimension of the yield curve process. While there is no clear demarkation between operative factors and noise, the top six principal components pick up 99% of total interest rate variation 95% of the time. An economically justified basis of this process is hard to find; for example a simple linear model will not suffice for the first principal component and the shape of this component is nonstationary. ^ Wavelet analysis works more directly with yield curve observations than principal components analysis. In fact the complete process from bond data to multiresolution is presented, including the dedicated Perl programs and the details of the portfolio metrics and specially adapted wavelet construction. The result is more robust statistics which provide balance to the more fragile principal components analysis. ^

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Immigrants from Jamaica represent the largest number of migrants to the United States from the English speaking Caribbean. Research indicates that of all Caribbean immigrants they are most likely to retain the ethnic identity of their home country for the longest period of time. This dissertation explored the nature of ethnic identity and sought to determine its impact upon the additional variables of self-esteem and academic factors. A secondary analysis was carried out using data collected in the Spring of 1992 by Portes and Rumbaut on the children of immigrants attending the eighth and ninth grades in local schools in San Diego and southern Florida. A sample of 151 second-generation Jamaican immigrants was selected from the data set. ^ Six hypotheses yielded mixed results. Both parents who have a Jamaican ethnic identity present in the household are the best predictor Jamaican youth who retain a Jamaican ethnic identity. It was expected that ethnic identity would be a predictor of positive academic factors. The study showed that ethnic identity was not associated with one of the academic factors which were examined: help given with homework. ^ Neither family economic status nor parents' level of education played a significant role in the retention of Jamaican identity. Other findings were that there was no mean difference in the self-esteem scores of respondents who had similar ethnic identities to their parents and those who did not. There was also no difference found in the academic factors of either group. The study also showed that there was a small correlation between parent-child conflict and self-esteem. Specifically, the study found that the higher the conflict between youth and their parents, the lower the self-esteem of the youth. Finally it found that time lived in the U.S. was the best predictor of a higher GPA and it was also related to lower self-esteem. ^ Surprisingly, the study found that the relationship between ethnic identity and SES was the opposite of what was expected in that it found that SES was higher when there was no Jamaican identity. ^

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The purpose of this dissertation was to determine the interactions of sexuality and education among low socioeconomic status first and second generation Mexican immigrant adolescent girls. Much of the existing research differentiates between immigrant generations with little examination of the differences within a particular immigrant generation. This study utilized qualitative methods to examine how various social institutions intersected to influence the young women's decisions about education and sexuality. The methodology included more than three years of participant observation in a South Florida high school and surrounding community; structured and unstructured interviews with twenty young women, their family members, school personnel, and community activists; and surveys conducted with the young women and their parent or guardian. ^ Moving beyond the limits of essentialist immigration theories, this project revealed within group (i.e. immigrant generation) complexities as well as between group similarities. The data included in this dissertation delineate how relationships of power and control permeated the lives of first and second generation Mexican immigrant adolescent girls. The lens of this dissertation is focused on the salient issues of sexuality and education: two dominant forces in many adolescent lives. ^ I found the young women represented a variety of positions on the academic orientation and sexuality continuums and engaged in activities that both reinforced and countered their stated positions on each of these issues. Specifically, first and second generation immigrants are often viewed as maintaining opposing viewpoints about both education and female sexuality however, for these young women the within group variation was larger than the between group variation. While all the young women in this study expressed a belief in the value of education, they engaged in activities that both fortified and contradicted that expressed position. Additionally, although acculturation can lead to increased sexual activity and decreased engagement with education, the first generation immigrant young women in this study became pregnant and/or withdrew from school in equal proportions to their second generation counterparts. In summary, structural forces combined, often inadvertently, and contributed to these young women's spiraling negative academic orientation and/or rational choice of motherhood. Finally, the findings are linked to policy implications. ^

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We report on generation of harmonic oscillations with frequencies of hundreds of MHz and radio-frequency linewidth of 13 Hz in unidirectional ring laser oscillator. This high stability makes these oscillators a suitable substitute for existing quartz resonators used in high frequency optoelectronics applications.