454 research outputs found

    Potential markets for a satellite-based mobile communications system

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    The objective of the study was to define the market needs for improved land mobile communications systems. Within the context of this objective, the following goals were set: (1) characterize the present mobile communications industry; (2) determine the market for an improved system for mobile communications; and (3) define the system requirements as seen from the potential customer's viewpoint. The scope of the study was defined by the following parameters: (1) markets were confined to U.S. and Canada; (2) range of operation generally exceeded 20 miles, but this was not restrictive; (3) the classes of potential users considered included all private sector users, and non-military public sector users; (4) the time span examined was 1975 to 1985; and (5) highly localized users were generally excluded - e.g., taxicabs, and local paging

    A review of data on abundance, trends in abundance, habitat use and diet of ice-breeding seals in the Southern Ocean

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    The development of models of marine ecosystems in the Southern Ocean is becoming increasingly important as a means of understanding and managing impacts such as exploitation and climate change. Collating data from disparate sources, and understanding biases or uncertainties inherent in those data, are important first steps for improving ecosystem models. This review focuses on seals that breed in ice habitats of the Southern Ocean (i.e. crabeater seal, Lobodon carcinophaga; Ross seal, Ommatophoca rossii; leopard seal, Hydrurga leptonyx; and Weddell seal, Leptonychotes weddellii). Data on populations (abundance and trends in abundance), distribution and habitat use (movement, key habitat and environmental features) and foraging (diet) are summarised, and potential biases and uncertainties inherent in those data are identified and discussed. Spatial and temporal gaps in knowledge of the populations, habitats and diet of each species are also identified

    Combining QCD Matrix Elements at Next-to-Leading Order with Parton Showers in Electroproduction

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    We present a method to combine next-to-leading order (NLO) matrix elements in QCD with leading logarithmic parton showers by applying a suitably modified version of the phase-space-slicing method. The method consists of subsuming the NLO corrections into a scale-dependent phase-space-slicing parameter, which is then automatically adjusted to cut out the leading order, virtual, soft and collinear contributions in the matrix element calculation. In this way a positive NLO weight is obtained, which can be redistributed by a parton shower algortihm. As an example, we display the method for single-jet inclusive cross sections at O(alpha_s) in electroproduction. We numerically compare the modified version of the phase-space-slicing method with the standard approach and find very good agreement on the percent level.Comment: 21 pages, 2 eps figures. Revised section 2. To appear in PR

    The State of Theory in LGBTQ Aging: Implications for Gerontological Scholarship

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    Social research in lesbian, gay, bisexual, transgender, and queer (LGBTQ) aging is a rapidly growing field, but an examination of the use of theory has not yet been conducted for its impact on the field’s direction. We conducted a systematic review of empirical articles published in LGBTQ aging in the years 2009–2017 (N = 102). Using a typology of theory use in scholarly articles, we analyzed these articles for the types of theories being used, the degree to which theories were used in each article, and the analytical function they served. We found that 52% of articles consistently applied theory, 23% implied or partially applied theory, and 25% presented as atheoretical. A wide range of theories were used and served multiple analytical functions such as concept development and explanation of findings. We discuss the strengths and weaknesses of theory use in this body of literature, especially with respect to implications for future knowledge development in the field

    Sorghum and Millets Diseases A Second World Review

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    This book is the product of an international workshop held at Harare, Zimbabwe, in Mar 1988. Progress made on sorghum diseases since the first global workshop held in India in 1978 is reviewed; research needs and goals for the next decade are identified; and the strengthening of working relationships among pathologists studying sorghum and millets diseases discussed. Also included are recommendations made by workshop participants and reports on group discussions

    Trajectories of Depressive Symptoms Among a Population of HIV-Infected Men and Women in Routine HIV Care in the United States

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    Depressive symptoms vary in severity and chronicity. We used group-based trajectory models to describe trajectories of depressive symptoms (measured using the Patient Health Questionnaire-9) and predictors of trajectory group membership among 1493 HIV-infected men (84%) and 292 HIV-infected women (16%). At baseline, 29% of women and 26% of men had depressive symptoms. Over a median of 30 months of follow-up, we identified four depressive symptom trajectories for women (labeled “low” [experienced by 56% of women], “mild/moderate” [24%], “improving” [14%], and “severe” [6%]) and five for men (“low” [61%], “mild/moderate” [14%], “rebounding” [5%], “improving” [13%], and “severe” [7%]). Baseline antidepressant prescription, panic symptoms, and prior mental health diagnoses were associated with more severe or dynamic depressive symptom trajectories. Nearly a quarter of participants experienced some depressive symptoms, highlighting the need for improved depression management. Addressing more severe or dynamic depressive symptom trajectories may require interventions that additionally address mental health comorbidities

    Intergenerational Education: The significance of 'reciprocity' and 'place'

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    In this article, the case is made for greater clarity in the definition of intergenerational practice and intergenerational education. Theoretically, the effects of all-age reciprocity and the significance of attending to 'place' are explored. Taken together, they help point to what is distinctive about the scope and purpose of intergenerational education. The author argues that any intergenerational practice must always involve an educative element that is focused, at least in part, on the on-going reciprocal production of new relations between generations through the way challenges are purposefully responded to in some specific place

    Fertility, Living Arrangements, Care and Mobility

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    There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed

    A brain-infecting parasite impacts host metabolism both during exposure and after infection is established

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    Metabolic costs associated with parasites should not be limited to established infections. Even during initial exposure to questing and attacking parasites, hosts can enact behavioural and physiological responses that could also incur metabolic costs. However, few studies have measured these costs directly. Hence, little is known about metabolic costs arising from parasite exposure. Furthermore, no one has yet measured whether and how previous infection history modulates metabolic responses to parasite exposure. Here, using the California killifish Fundulus parvipinnis and its brain‐infecting parasite Euhaplorchis californiensis, we quantified how killifish metabolism, behaviour and osmoregulatory phenotype changed upon acute exposure to parasite infectious stages (i.e. cercariae), and with long‐term infection. Exposure to cercariae caused both naïve and long‐term infected killifish to acutely increase their metabolic rate and activity, indicating detection and response to parasite infectious stages. Additionally, these metabolic and behavioural effects were moderately stronger in long‐term infected hosts than naïve killifish, suggesting that hosts may develop learned behavioural responses, nociceptor sensitization and/or acute immune mechanisms to limit new infections. Although established infection altered the metabolic response to parasite exposure, established infection did not alter standard metabolic rate, routine metabolic rate, maximum metabolic rate, aerobic scope or citrate synthase enzyme activity. Unexpectedly, established infection reduced lactate dehydrogenase enzyme activity in killifish brains and relative Na+/K+‐ATPase abundance in gills, suggesting novel mechanisms by which E. californiensis may alter its hosts\u27 behaviour and osmoregulation. Thus, we provide empirical evidence that parasites can disrupt the metabolism of their host both during parasite exposure and after infection is established. This response may be modulated by previous infection history, with probable knock‐on effects for host performance, brain energy metabolism, osmoregulation and ecology. A free Plain Language Summary can be found within the Supporting Information of this article

    Theory in highly cited studies of sexual minority parent families: variations and implications

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    This paper includes a systematic review and citation analysis of the literature regarding sexual minority parent families, particularly attending to what theories have been used, and how. We consider the importance of theoretical frameworks for future research and implications for policy, practice, and law related to sexual minority parent families. Our review targets 30 highly cited studies located through Google Scholar (as an interdisciplinary search engine) and published within a specific time frame (2005-2010). We highlight the dominant theoretical models employed across disciplines studying sexual minority parent families. While the majority of studies reviewed referred to theoretical models or perspectives, explicit theoretical grounding was frequently lacking. Instead, the empirical work reviewed appeared to have a predominantly applied focus in addressing public debates on sexual minority parent families. We provide recommendations for how theory might be more fully integrated into the social science literature on sexual minority parents and their children
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