Critical Collapse in Einstein-Gauss-Bonnet Gravity in Five and Six Dimensions

Einstein-Gauss-Bonnet gravity (EGB) provides a natural higher dimensional and higher order curvature generalization of Einstein gravity. It contains a new, presumably microscopic, length scale that should affect short distance properties of the dynamics, such as Choptuik scaling. We present the results of a numerical analysis in generalized flat slice co-ordinates of self-gravitating massless scalar spherical collapse in five and six dimensional EGB gravity near the threshold of black hole formation. Remarkably, the behaviour is universal (i.e. independent of initial data) but qualitatively different in five and six dimensions. In five dimensions there is a minimum horizon radius, suggestive of a first order transition between black hole and dispersive initial data. In six dimensions no radius gap is evident. Instead, below the GB scale there is a change in the critical exponent and echoing period.Comment: 21 pages, 39 figures, a couple of references and two new figures adde

Restraint-induced Corticosterone Secretion and Hypothalamic CRH mRNA Expression are Augmented During Acute Withdrawal from Chronic Cocaine Administration

Stress responses during cocaine withdrawal likely contribute to drug relapse and may be intensified as a consequence of prior cocaine use. The present study examined changes in stressor-induced activation of the hypothalamic–pituitary–adrenal (HPA) axis during acute withdrawal from chronic cocaine administration. Adult male Sprague–Dawley rats received daily administration of cocaine (30 mg/kg, i.p.) or saline for 14 days. Twenty-four hours after the last injection, rats in each group were sacrificed under stress-free conditions or following 30 min of immobilization. Plasma corticosterone (CORT) was measured in trunk-blood using radioimmunoassay, corticotropin-releasing hormone (CRH) mRNA levels in the paraventricularnucleus (PVN) of the hypothalamus were measured using in situ hybridization and glucocorticoid receptor (GR) protein expression in the pituitary gland and dissected brain regions was measured using Western blot analysis. Basal CRH mRNA in the PVN was unaltered as a result of prior cocaine administration. However, a significant increase in CRH mRNA was observed 90 min following the termination of restraint in cocaine withdrawn, but not saline-treated, rats. Basal CORT was also unaffected by prior cocaine administration, but the CORT response measured immediately after restraint was significantly augmented in cocaine-withdrawn rats. Differences in GR protein expression in number of regions implicated in negative feedback regulation of HPA function, including the hypothalamus, were not observed. These findings indicate that the HPA response to stressors is intensified during early withdrawal from cocaine administration and may be independent of changes in GR-mediated negative feedback

Geometrodynamics of spherically symmetric Lovelock gravity

We derive the Hamiltonian for spherically symmetric Lovelock gravity using the geometrodynamics approach pioneered by Kucha\v{r} in the context of four-dimensional general relativity. When written in terms of the areal radius, the generalized Misner-Sharp mass and their conjugate momenta, the generic Lovelock action and Hamiltonian take on precisely the same simple forms as in general relativity. This result supports the interpretation of Lovelock gravity as the natural higher-dimensional extension of general relativity. It also provides an important first step towards the study of the quantum mechanics, Hamiltonian thermodynamics and formation of generic Lovelock black holes.Comment: 10 pages, references and derivation details added, final version accepted by CQG (Fast Track

Social response to population change and migration: the impact of population change on individuals and institutions

Population change over the last 40 years has greatly redistributed Midwest populations. Migration has long been a social response to change—both to changing capacities in the agricultural system and to socio-cultural attractions and opportunities in the urban-industrial areas. Some of the surplus agricultural population has moved to cities and suburbs. The result is a selective dismembering of many communities and an inordinate growth of others.https://lib.dr.iastate.edu/specialreports/1037/thumbnail.jp

Hamiltonian Formulation of Scalar Field Collapse in Einstein Gauss Bonnet Gravity

We compute the Hamiltonian for spherically symmetric scalar field collapse in Einstein-Gauss-Bonnet gravity in D dimensions using slicings that are regular across future horizons. We first reduce the Lagrangian to two dimensions using spherical symmetry. We then show that choosing the spatial coordinate to be a function of the areal radius leads to a relatively simple Hamiltonian constraint whose gravitational part is the gradient of the generalized mass function. Next we complete the gauge fixing such that the metric is the Einstein-Gauss-Bonnet generalization of non-static Painleve-Gullstrand coordinates. Finally, we derive the resultant reduced equations of motion for the scalar field. These equations are suitable for use in numerical simulations of spherically symmetric scalar field collapse in Gauss-Bonnet gravity and can readily be generalized to other matter fields minimally coupled to gravity.Comment: 14 pages, 0 figure

Modified general relativity as a model for quantum gravitational collapse

We study a class of Hamiltonian deformations of the massless Einstein-Klein-Gordon system in spherical symmetry for which the Dirac constraint algebra closes. The system may be regarded as providing effective equations for quantum gravitational collapse. Guided by the observation that scalar field fluxes do not follow metric null directions due to the deformation, we find that the equations take a simple form in characteristic coordinates. We analyse these equations by a unique combination of numerical methods and find that Choptuik's mass scaling law is modified by a mass gap as well as jagged oscillations. Furthermore, the results are universal with respect to different initial data profiles and robust under changes of the deformation.Comment: 22 pages, 4 figure

Neuromuscular facilitation in proprioceptive juvenile dermatomyositis: a case report

Introd ução: Dermatomiosite Juvenil (DMJ) é uma doença muscular inflamatória de etiologia desconhecida, auto-imune, e que se manifesta nos pequenos vasos sanguíneos dos músculos e pele. A incidência varia entre 0,8 e 4,1 por milhão de crianças nascidas por ano, com prevalência do sexo feminino. São cinco os critérios de diagnóstico: fraqueza simétrica proximal progressiva, enzimas musculares elevadas, anormalidades no eletromiograma, padrão inflamatório na amostra da biópsia muscular, e associação com distúrbios cutâneos. OBJETIVO: Relatar a Facilitação Neuromuscular Proprioceptiva (FNP) em um caso de DMJ. MÉTODO: Foi avaliada uma paciente do sexo feminino, nove anos de idade, com quadro de DMJ e com sintomas de: fraqueza muscular, dificuldade em atividades de vida diária e quedas freqüentes, que se encontra em acompanhamento médico ambulatorial no Hospital Foram realizadas três avaliações, antes (AV-1), durante (AV-2) e após (AV-3) a intervenção fisioterapêutica. Após a primeira avaliação, foi aplicado um tratamento com 24 sessões, com duração de uma hora cada sessão, durante 12 semanas, que constou de Facilitação Neuromuscular Proprioceptiva (FNP) com técnicas de estímulo de estiramento e reversões lentas nas diagonais primitiva e funcional, bem como alongamentos associados. RESULTADOS: Aumento da força muscular em membros inferiores, diminuição de contraturas, ganho de amplitude de movimento articular e melhor qualidade de vida para a paciente. CONCLUSÃO: Em vista dos resultados expostos, a utilização da FNP foi satisfatória, e estudos longitudinais são necessários para que se comprove a eficácia a longo prazo.Introduction : Juvenile dermatomyositis (DM) is an inflammatory muscle disease of unknown etiology, autoimmune disorder, which manifests itself in small blood vessels of the muscles and skin. The incidence varies between 0.8 and 4.1 per million children born each year with a prevalence of females. Five criteria are considered for diagnosis: progressive proximal symmetrical weakness, elevated muscle enzymes, abnormal electromyogram and inflammatory pattern in the muscle biopsy sample, and association with cutaneous disorders. OBJECTIVE: To report the Neuromuscular Facilitation Proprioceptive (PFN) procedure in a case of juvenile DM. METHODS: We evaluated a female patient, nine years old, with part of JDM, who manifested: muscle weakness, difficulty in daily activities and frequent falls. She attended the out patient service at our Hospital Three evaluations were performed before (AV-1), during (AV-2) and after (AV-3) to physiotherapy intervention. After the first evaluation, a treatment was applied in 24 sessions over 12 weeks, lasting an hour each, which consisted of Neuromuscular Facilitation proprioceptive (FNP) with stimulating techniques of stretching and slow reversals in diagonal primitive and functional as well as associated stretching. RESULTS: Increased muscle strength in lower limbs, reduction of contractures, gain range of motion and better quality of life for the patient. CONCLUSION: Considering the above results, longitudinal studies are required to prove efficacy in long-term

A New Family of Covariate-Adjusted Response Adaptive Designs and their Asymptotic Properties

It is often important to incorporating covariate information in the design of clinical trials. In literature, there are many designs of using stratification and covariate-adaptive randomization to balance on certain known covariate. Recently Zhang, Hu, Cheung and Chan (2007) have proposed a family of covariate-adjusted response-adaptive (CARA) designs and studied their asymptotic properties. However, these CARA designs often have high variabilities. In this paper, we propose a new family of covariate-adjusted response-adaptive (CARA) designs. We show that the new designs have smaller variabilities and therefore more efficient

What Is the Role of Astrocyte Calcium in Neurophysiology?

Astrocytes comprise approximately half of the volume of the adult mammalian brain and are the primary neuronal structural and trophic supportive elements. Astrocytes are organized into distinct nonoverlapping domains and extend elaborate and dense fine processes that interact intimately with synapses and cerebrovasculature. The recognition in the mid 1990s that astrocytes undergo elevations in intracellular calcium concentration following activation of G protein-coupled receptors by synaptically released neurotransmitters demonstrated not only that astrocytes display a form of excitability but also that astrocytes may be active participants in brain information processing. The roles that astrocytic calcium elevations play in neurophysiology and especially in modulation of neuronal activity have been intensely researched in recent years. This review will summarize the current understanding of the function of astrocytic calcium signaling in neurophysiological processes and discuss areas where the role of astrocytes remains controversial and will therefore benefit from further study