Ultralow noise performance of an 8.4-GHz maser-feedhorn system

A total system noise temperature of 6.6 K was demonstrated with an 8.4-GHz traveling wave maser and feedhorn operating in a cryogenic environment. Both the maser and feedhorn were inserted in the helium cryostat, with the maser operating in the 1.6-K liquid bath and the feedhorn cooled in the helium gas, with a temperature gradient along the horn ranging from the liquid bath temperature at its lower end to room temperature at its top. The ruby maser exhibited 43 dB of gain with a bandwidth of 76 MHz(-3 dB) centered at 8400 MHz. Discussions of the maser, cooled feedhorn, and cryostat designs are presented along with a discussion of the noise temperature measurements

Superconducting niobium thin film slow-wave structures

A superconducting comb structure as a slow-wave element in a traveling-wave maser will significantly improve maser noise temperature and gain by reducing the insertion loss. The results of the insertion loss measurements of superconducting niobium slow-wave structures subjected to maser operating conditions at X-Band frequencies are presented

Density-Dependent Regulation of Brook Trout Population Dynamics along a Core-Periphery Distribution Gradient in a Central Appalachian Watershed

Spatial population models predict strong density-dependence and relatively stable population dynamics near the core of a species\u27 distribution with increasing variance and importance of density-independent processes operating towards the population periphery. Using a 10-year data set and an information-theoretic approach, we tested a series of candidate models considering density-dependent and density-independent controls on brook trout population dynamics across a core-periphery distribution gradient within a central Appalachian watershed. We sampled seven sub-populations with study sites ranging in drainage area from 1.3–60 km2and long-term average densities ranging from 0.335–0.006 trout/m. Modeled response variables included per capita population growth rate of young-of-the-year, adult, and total brook trout. We also quantified a stock-recruitment relationship for the headwater population and coefficients of variability in mean trout density for all sub-populations over time. Density-dependent regulation was prevalent throughout the study area regardless of stream size. However, density-independent temperature models carried substantial weight and likely reflect the effect of year-to-year variability in water temperature on trout dispersal between cold tributaries and warm main stems. Estimated adult carrying capacities decreased exponentially with increasing stream size from 0.24 trout/m in headwaters to 0.005 trout/m in the main stem. Finally, temporal variance in brook trout population size was lowest in the high-density headwater population, tended to peak in mid-sized streams and declined slightly in the largest streams with the lowest densities. Our results provide support for the hypothesis that local density-dependent processes have a strong control on brook trout dynamics across the entire distribution gradient. However, the mechanisms of regulation likely shift from competition for limited food and space in headwater streams to competition for thermal refugia in larger main stems. It also is likely that source-sink dynamics and dispersal from small headwater habitats may partially influence brook trout population dynamics in the main stem

The quality of political information

The article conceptualizes the quality of political information and shows how the concept can be used for empirical research. I distinguish three aspects of quality (intelligibility, relevance, validity) and use them to judge the constituent foundations of political information, that is component claims (statements of alleged facts) and connection claims (argumentative statements created by causally linking two component claims). The resulting conceptual map thus entails six manifestations of information quality (component claimintelligibility, connection claim intelligibility, component claimrelevance, connection claim relevance, component claim validity, and connection claim validity). I explain how the conceptual map can be used to make sense of the eclectic variety of existing research, and how it can advance new empirical research, as a guide for determining variation in information quality, as a conceptual template for the analysis of different types of political messages and their common quality deficiencies, and as a generator of new research questions and theoretical expectations

Subthreshold characteristics of pentacene field-effect transistors influenced by grain boundaries.

Grain boundaries in polycrystalline pentacene films significantly affect the electrical characteristics of pentacene field-effect transistors (FETs). Upon reversal of the gate voltage sweep direction, pentacene FETs exhibited hysteretic behaviours in the subthreshold region, which was more pronounced for the FET having smaller pentacene grains. No shift in the flat-band voltage of the metal-insulator-semiconductor capacitor elucidates that the observed hysteresis was mainly caused by the influence of localized trap states existing at pentacene grain boundaries. From the results of continuous on/off switching operation of the pentacene FETs, hole depletion during the off period is found to be limited by pentacene grain boundaries. It is suggested that the polycrystalline nature of a pentacene film plays an important role on the dynamic characteristics of pentacene FETs

Study of perturbed periodic systems of differential equations - The Stroboscopic method

Stroboscopic method for solving perturbed periodic systems of differential equation

Using parent metaphors for learning about the neonatal care experience: an interpretive perspective

© 2019 The Author(s). The final, definitive version of this paper has been published in Journal of Child Health Care by Sage Publications Ltd. All rights reserved. It is available at: https://doi.org/10.1177/1367493519875853.This study focuses on how metaphors are used by parents who have had a premature baby to describe their neonatal care experience and how these can contribute to empathic learning of health professionals. In health, metaphors are commonly used to communicate and explain difficult topics. When patients tell their story, metaphor can be a means of expression from which we can learn about their experience of illness or hospitalisation. Limited research exits on how metaphor can improve our understanding of parent’s emotional experience in neonatal care and subsequently inform education in this field. Employing narrative inquiry within an interpretive, constructivist paradigm, 20 narrative interviews with 23 parents of premature babies were analysed using a process of metaphor identification. Findings revealed common metaphors used to describe experience. Metaphor clusters used by parents in order of frequency were journeying, altered reality, darkness, breaking, connections, fighting, salvation and being on the edge. Parents widely used compelling and emotive metaphors to describe and express both difficult and challenging times as well as progression forward. Metaphors serve as a powerful way for health professionals to learn about the emotional experiences of parents and potentially enhance their empathic understanding.Peer reviewe

Impacto sobre a aprendizagem dos alunos: Perspectivas sobre a Comissão Nacional de Certificação de Professores

The purpose of this study is to report National Board Certified Teachers’ (NBCTs) perceived impact on student learning. The guiding research question for this study, “How do teachers perceive the influence of the National Board Certification process on student learning in their own classrooms?” was explored. A total of 496 NBCTs currently teaching in North Carolina public schools completed the survey questionnaire in which they responded to demographic questions, Likert item questions, and open-ended questions. More than 80% of the study’s participants reported the certification process had positively influenced student learning in their classrooms. Thematic analysis revealed several reoccurring themes that NBCTs reported having impact on student learning in their classrooms. These included impact on academic achievement, improved teaching, and/or an increase of effective evaluation and assessment strategies.El propósito de este estudio es informar sobre la percepción del impacto de la Comisión Nacional de Certificación Docente (por su sigla en inglés NBCTs) en el aprendizaje de los estudiantes. La pregunta de investigación que guía este estudio es "¿Cómo perciben los profesores la influencia del proceso de Certificación de la NBCTs en el aprendizaje de los estudiantes en las aulas de su país”. Un total de 496 docentes que cuentan con su NBCTs en las escuelas públicas de Carolina del Norte completó la encuesta en la que respondieron a preguntas demográficas, preguntas usando escalas Likert y preguntas abiertas. Más del ochenta por ciento de los participantes del estudio informó que el proceso de certificación ha influido positivamente en el aprendizaje de los estudiantes en sus clases. Análisis temático reveló varios temas recurrentes que los docentes NBCTs reportaron influyen en el aprendizaje de los estudiantes, incluidos rendimiento académico, mejora de la enseñanza, y/o un aumento de estrategias de evaluación y evaluación eficaces.O objetivo deste estudo é relatar sobre as percepções de impacto da Comissão Nacional de Certificação de Professores (sigla em Inglês NBCTs) nos aprendizagens dos alunos. A questão de pesquisa que orientou este estudo foi "Como é que os professores percebem a influência do processo de certificação NBCTs na aprendizagem dos alunos nas salas de aula do seu país". Um total de 496 professores têm seus NBCTs nas escolas públicas da Carolina do Norte responderam as perguntas sobre dados demográficos, perguntas usando uma escala Likert e perguntas abertas. Mais de oitenta por cento dos participantes do estudo relataram que o processo de certificação tem efeitos positivos na aprendizagem dos alunos em suas aulas. A análise temática revelou vários temas recorrentes que os professores NBCTs indicaram que influenciam a aprendizagem dos alunos, incluindo desempenho acadêmico, melhoras na educação, e/ou um aumento de estratégias de avaliação e de avaliação eficazes