4,888 research outputs found

    Survival and development of Amblypelta nitida Stål, A. l. lutescens Distant (Hemiptera: Coreidae) and the egg parasitoid, Anastatus sp. (Hymenoptera: Eupelmidae) at constant rearing temperatures

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    The effects of constant rearing temperatures on the development and survival of Amblypelta nitida, Amblypelta lutescens lutescens (Hemiptera: Coreidae) and their egg parasitoid, Anastatus sp. (Hymenoptera: Eupelmidae), were studied in the laboratory. Amblypelta nitida and A. l. lutescens survival and development were studied at 10,15, 20, 25,30 and 35 degrees C. The development rate of both species increased linearly with increasing temperature but insects only developed to adults at 20, 25 and 30 degrees C; at these temperatures, mean development times for A. nitida were 87, 64 and 29 days and forA. l. lutescens they were 93, 65 and 31 days respectively. No eggs of either species hatched at 10 degrees C and only A l. lutescens eggs hatched at 35 degrees C At all temperatures at which insects developed beyond the first instar, mortality rates were highest in the second instar for both species. Lower developmental threshold temperatures to complete development were 15.9 degrees C and 17.1 degrees C for A. nitida and A. l. lutescens respectively; A. nitida required 421 degree-days and A.l. lutescens required 404 degree-days to complete development. Anastatus sp. completed development at all six study temperatures and development times decreased from 54 days at 17.5 degrees C to 16 days at 30 degrees C; similarly Anastatus sp, survival increased with increasing temperature. The lower developmental threshold temperature and degree-days required for Anastatus sp. to complete development were 15.0 degrees C and 234 degree-days respectively. Results are discussed with respect to the different geographical distributions of A. nitida and A. l. lutescens and likely interactions with Anastatus sp. (C) 2016 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Published by Elsevier B.V. All rights reserved

    Inflation driven by causal heat flux

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    We find a simple inflationary solution in an inhomogeneous spacetime with heat flux. The heat flux obeys a causal transport equation, and counteracts the inflationary decrease of energy density. At late times, the heat flux tends to zero and the fluid approaches the equation of state p=ρp=-\rho.Comment: Latex 5 pages; to appear Gen. Rel. Gra

    Suspicious Minds: Apportioning and Avoiding Blame for Distrustful Relationships and Deferring Medical Treatment in South Africa

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    This paper examines elements of mistrust, blame and suspicion among patients and providers in the South African health system which affect practice and policy development. Using stories told by patients and providers in Cape Town, Johannesburg and Bushbuckridge, it examines how suspicion is constructed and how others are blamed for adverse outcomes. This paper sets a conceptual framework which examines the attribution of blame in contemporary social and political life, the narratives of 45 patients receiving HIV/AIDS, TB or maternal delivery services and those of 63 providers dealing with similar treatments and arranged across a series of facilities, clinics, hospitals and mobile vans were constructed and shared with participants. These narratives form the basis of the results sections which examines suspicions among both providers and patients with the former seeing the latter as having no respect and regard and providing poor care and access to grants. Providers saw themselves as highly stressed but diligent with service challenges being blamed on patient ignorance, unreasonable demands and failure to follow medical advice. The paper ends with a discussion on how to limit mistrust and reduce suspicion through more co-operative provider-patient relations and what this kind of evidence means for decisionmaker

    Association between childhood adversities and long-term suicidality among South Africans from the results of the South African Stress and Health study: a cross-sectional study

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    Objective: Suicide and suicidal behaviours are significant public health problems and a leading cause of death worldwide and in South Africa. We examined the association between childhood adversities and suicidal behaviour over the life course. Methods: A national probability sample of 4351 South African adult participants (aged 18 years and older) in the South African Stress and Health (SASH) study was interviewed as part of the World Mental Health Surveys initiative. Respondents provided sociodemographic and diagnostic information, as well as an account of suicide-related thoughts and behaviours. Suicidality or suicidal behaviour were defined as were defined as suicide attempts and suicidal ideation in the total sample, and suicide plans and attempts among ideators. Childhood adversities included physical abuse, sexual abuse, parental death, parental divorce, other parental loss, family violence, physical illness and financial adversity. The association between suicidality and childhood adversities was examined using discrete-time survival models. Results: More than a third of the respondents with suicidal behaviour experienced at least one childhood adversity, with physical abuse, parental death and parental divorce being the most prevalent adversities. Physical abuse, sexual abuse and parental divorce were identified as significant risk markers for lifetime suicide attempts, while physical abuse and parental divorce were significantly correlated with suicidal ideation. Two or more childhood adversities were associated with a twofold higher risk of lifetime suicide attempts. Sexual abuse (OR 9.3), parental divorce (OR 3.1) and childhood physical abuse (OR 2.2) had the strongest associations with lifetime suicide attempts. The effect of childhood adversities on suicidal tendencies varied over the life course. For example, sexual abuse was significantly associated with suicide attempts during childhood and teen years, but not during young and later adulthood. Conclusions: Childhood adversities, especially sexual abuse, physical abuse and parental divorce, are important risk factors for the onset and persistence of suicidal behaviour, with this risk being greatest in childhood and adolescence

    Stellar models with Schwarzschild and non-Schwarzschild vacuum exteriors

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    A striking characteristic of non-Schwarzschild vacuum exteriors is that they contain not only the total gravitational mass of the source, but also an {\it arbitrary} constant. In this work, we show that the constants appearing in the "temporal Schwarzschild", "spatial Schwarzschild" and "Reissner-Nordstr{\"o}m-like" exteriors are not arbitrary but are completely determined by star's parameters, like the equation of state and the gravitational potential. Consequently, in the braneworld scenario the gravitational field outside of a star is no longer determined by the total mass alone, but also depends on the details of the internal structure of the source. We show that the general relativistic upper bound on the gravitational potential M/R<4/9M/R < 4/9, for perfect fluid stars, is significantly increased in these exteriors. Namely, M/R<1/2M/R < 1/2, M/R<2/3M/R < 2/3 and M/R<1M/R < 1 for the temporal Schwarzschild, spatial Schwarzschild and Reissner-Nordstr{\"o}m-like exteriors, respectively. Regarding the surface gravitational redshift, we find that the general relativistic Schwarzschild exterior as well as the braneworld spatial Schwarzschild exterior lead to the same upper bound, viz., Z<2Z < 2. However, when the external spacetime is the temporal Schwarzschild metric or the Reissner-Nordstr{\"o}m-like exterior there is no such constraint: Z<Z < \infty. This infinite difference in the limiting value of ZZ is because for these exteriors the effective pressure at the surface is negative. The results of our work are potentially observable and can be used to test the theory.Comment: 19 pages, 3 figures and caption

    Renormalization Group Approach to Causal Viscous Cosmological Models

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    The renormalization group method is applied to the study of homogeneous and flat Friedmann-Robertson-Walker type Universes, filled with a causal bulk viscous cosmological fluid. The starting point of the study is the consideration of the scaling properties of the gravitational field equations, of the causal evolution equation of the bulk viscous pressure and of the equations of state. The requirement of scale invariance imposes strong constraints on the temporal evolution of the bulk viscosity coefficient, temperature and relaxation time, thus leading to the possibility of obtaining the bulk viscosity coefficient-energy density dependence. For a cosmological model with bulk viscosity coefficient proportional to the Hubble parameter, we perform the analysis of the renormalization group flow around the scale invariant fixed point, therefore obtaining the long time behavior of the scale factor.Comment: 19 pages. RevTeX4. Revised version. Accepted in Classical and Quantum Gravit

    A causal model of radiating stellar collapse

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    We find a simple exact model of radiating stellar collapse, with a shear-free and non-accelerating interior matched to a Vaidya exterior. The heat flux is subject to causal thermodynamics, leading to self-consistent determination of the temperature TT. We solve for TT exactly when the mean collision time τc\tau_{c} is constant, and perturbatively in a more realistic case of variable τc\tau_{c}. Causal thermodynamics predicts temperature behaviour that can differ significantly from the predictions of non-causal theory. In particular, the causal theory gives a higher central temperature and greater temperature gradient.Comment: Latex [ioplppt style] 9 pages; to appear Class. Quantum Gra

    Acceptable care? Illness constructions, healthworlds, and accessible chronic treatment in South Africa

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    Achieving equitable access to health care is an important policy goal, with access influenced by affordability, availability, and acceptability of specific services. We explore patient narratives from a 5-year program of research on health care access to examine relationships between social constructions of illness and the acceptability of health services in the context of tuberculosis treatment and antiretroviral therapy in South Africa. Acceptability of services seems particularly important to the meanings patients attach to illness and care, whereas—conversely—these constructions appear to influence what constitutes acceptability and hence affect access to care. We highlight the underestimated role of individually, socially, and politically constructed healthworlds; traditional and biomedical beliefs; and social support networks. Suggested policy implications for improving acceptability and hence overall health care access include abandoning patronizing approaches to care and refocusing from treating “disease” to responding to “illness” by acknowledging and incorporating patients’ healthworlds in patient–provider interactions
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