Simulating the effects of intergalactic gray dust

Using a high-resolution cosmological hydrodynamic simulation, we present a method to constrain extinction due to intergalactic gray dust based on the observed magnitudes of distant Type Ia supernovae. We apply several simple prescriptions to relate the intergalactic dust density to the gas density in the simulation, thereby obtaining dust extinctions that may be directly compared with the observed distribution of supernova magnitudes. Our analysis is sensitive to the spatial distribution of gray dust but is not dependent on its intrinsic properties, such as its opacity or grain size. We present an application of our technique to the supernova data of Perlmutter et al., who find that their high-redshift sample is ~0.2 mag fainter than the expectation for a nonaccelerating, low-density universe. We find that for gray dust to be responsible, it must be distributed quite smoothly (e.g., tracing intergalactic gas). More realistic dust distributions, such as dust tracing the metal density, are inconsistent with observations at the 1.5-2 σ level. Upcoming observations and improved modeling of the dust distribution should lead to stronger constraints on intergalactic gray dust extinction

Line versus Flux Statistics -- Considerations for the Low Redshift Lyman-alpha Forest

The flux/transmission power spectrum has become a popular statistical tool in studies of the high redshift ($z > 2$) Lyman-alpha forest. At low redshifts, where the forest has thinned out into a series of well-isolated absorption lines, the motivation for flux statistics is less obvious. Here, we study the relative merits of flux versus line correlations, and derive a simple condition under which one is favored over the other on purely statistical grounds. Systematic errors probably play an important role in this discussion, and they are outlined as well.Comment: 6 pages, to appear in "The IGM/Galaxy Connection: The Distribution of Baryons at z=0", eds. J. L. Rosenberg and M. E. Putma

Needs regarding the hospital care provided to spinal cord injured patients

Study type: descriptive and documentary work. Purpose: to identify the incidence of complications and the care provided by the nursing team to spinal cord injured patients. Method:the records of spinal cord injured patients were analyzed according to the lCD 10, from 1997 to 2000. Data were obtained through the Hospital File Service, through the request of a morbidity report. Afterwards, authors elaborated an instrument containing patient’s identification, basic data on clinical history and physiological alterations, as well as the day these alterations occurred and the care provided by the nursing team. Data were grouped and analyzed through a table and a chart. Results: authõrs observed that these patients were really susceptible to complications as infections, neurogenic bladder, paralytic ileus, priapism, profound venous trombosis, among others. They also found, through the annotatioris of the nursing team, the inexistence of specific care to these complications besides the basic care and the actions of propaedeutic and therapeutic nature that are complementary to the medical act. Authors also verified that six records did not present annotations about discharge orientations and that the notes in nine records were not enough regarding the care that these patients and the ones who provide their care would need at home in order to prevent these complications. Considerations: this study facilitated a broader view of the context involving the spinal cord injured patient. Authors believe that it is important to develop a nursing continuing education program in order to assure that the members of the team will update their knowledge about the needs of each patient and the stage they are going through.Modelo de estudo: Estudo retrospectivo e documental. Objetivo: Identificar a incidência das complicações e quais as ações assistenciais a serem desenvolvidas pela equipe de enfermagem ao paciente com lesão medular. Método: Foram analisados os prontuários dos pacientes com lesão medular, segundo a classificação do CID 10, no período compreendido entre 1997 a 2000; os dados foram obtidos através do Serviço de Arquivo Médico (SAME) da instituição, a partir da solicitação de um relatório de morbidade; elaborou-se um instrumento que continha a identificação do paciente, dados básicos da história clínica e as alterações fisiológicas apresentadas, bem como os dias após a internação em que elas ocorreram e quais os cuidados prestados pela equipe de enfermagem; os dados foram agrupados e analisados através de tabela e quadro. Observou-se que os pacientes com lesão medular ficam realmente susceptíveis às complicações, como infecções, bexiga neurogênica, íleo paralítico, priapismo, trombose venosa profunda, entre outras; também foi constatada, através das anotações da equipe de enfermagem, a inexistência de cuidados específicos a tais complicações, ocorrendo apenas os cuidados básicos e as ações de natureza propedêutica e terapêutica complementares ao ato médico. Neste estudo, também se observou que as anotações das orientações da alta hospitalar, não apareceram em seis prontuários, e que, em nove, as anotações não eram especificas aos cuidados que o paciente e seus cuidadores necessitariam em seu domicilio a fim de prevenir novas intercorrências. Considerações: A realização deste estudo possibilitou-nos uma visão mais ampla do contexto que envolve o cuidado ao paciente com lesão medular. Acredita-se ser importante um programa de educação continuada em enfermagem, de modo a garantir a atualização do conhecimento para toda a equipe, das necessidades de cada paciente e etapa pela qual está passando

A Transfer Matrix Method for Resonances in Randall-Sundrum Models

In this paper we discuss in detail a numerical method to study resonances in membranes generated by domain walls in Randall-Sundrum-like scenarios. It is based on similar works to understand the quantum mechanics of electrons subject to the potential barriers that exist in heterostructures in semiconductors. This method was used recently to study resonances of a three form field and lately generalized to arbitrary forms. We apply it to a lot of important models, namely those that contain the Gauge, Gravity and Spinor fields. In many cases we find a rich structure of resonances which depends on the parameters involved.Comment: 25 pages, 17 figure

Direct and Inverse Variational Problems on Time Scales: A Survey

We deal with direct and inverse problems of the calculus of variations on arbitrary time scales. Firstly, using the Euler-Lagrange equation and the strengthened Legendre condition, we give a general form for a variational functional to attain a local minimum at a given point of the vector space. Furthermore, we provide a necessary condition for a dynamic integro-differential equation to be an Euler-Lagrange equation (Helmholtz's problem of the calculus of variations on time scales). New and interesting results for the discrete and quantum settings are obtained as particular cases. Finally, we consider very general problems of the calculus of variations given by the composition of a certain scalar function with delta and nabla integrals of a vector valued field.Comment: This is a preprint of a paper whose final and definite form will be published in the Springer Volume 'Modeling, Dynamics, Optimization and Bioeconomics II', Edited by A. A. Pinto and D. Zilberman (Eds.), Springer Proceedings in Mathematics & Statistics. Submitted 03/Sept/2014; Accepted, after a revision, 19/Jan/201

The current status of observational cosmology

Observational cosmology has indeed made very rapid progress in recent years. The ability to quantify the universe has largely improved due to observational constraints coming from structure formation. The transition to precision cosmology has been spearheaded by measurements of the anisotropy in the cosmic microwave background (CMB) over the past decade. Observations of the large scale structure in the distribution of galaxies, high red-shift supernova, have provided the required complementary information. We review the current status of cosmological parameter estimates from joint analysis of CMB anisotropy and large scale structure (LSS) data. We also sound a note of caution on overstating the successes achieved thus far.Comment: 13 pages, 3 figures, Latex style files included, To appear in the proceedings of ICGC-04. Minor rewording in the abstract and introductio

Fibrinogen is not elevated in the cerebrospinal fluid of patients with multiple sclerosis

<p>Abstract</p> <p>Background</p> <p>Elevated plasma fibrinogen levels are a well known finding in acute infectious diseases, acute stroke and myocardial infarction. However its role in the cerebrospinal fluid (CSF) of acute and chronic central (CNS) and peripheral nervous system (PNS) diseases is unclear.</p> <p>Findings</p> <p>We analyzed CSF and plasma fibrinogen levels together with routine parameters in patients with multiple sclerosis (MS), acute inflammatory diseases of the CNS (bacterial and viral meningoencephalitis, BM and VM) and PNS (Guillain-Barré syndrome; GBS), as well as in non-inflammatory neurological controls (OND) in a total of 103 patients. Additionally, MS patients underwent cerebral MRI scans at time of lumbar puncture.</p> <p>CSF and plasma fibrinogen levels were significantly lower in patients with MS and OND patients as compared to patients with BM, VM and GBS. There was a close correlation between fibrinogen levels and albumin quotient (rho = 0.769, <it>p </it>< 0.001) which strongly suggests passive transfer of fibrinogen through the blood-CSF-barrier during acute inflammation. Hence, in MS, the prototype of chronic neuroinflammation, CSF fibrinogen levels were not elevated and could not be correlated to clinical and neuroradiological outcome parameters.</p> <p>Conclusions</p> <p>Although previous work has shown clear evidence of the involvement of fibrinogen in MS pathogenesis, this is not accompanied by increased fibrinogen in the CSF compartment.</p

Compensation in Preclinical Huntington's Disease: Evidence From the Track-On HD Study

BACKGROUND: Cognitive and motor task performance in premanifest Huntington's disease (HD) gene-carriers is often within normal ranges prior to clinical diagnosis, despite loss of brain volume in regions involved in these tasks. This indicates ongoing compensation, with the brain maintaining function in the presence of neuronal loss. However, thus far, compensatory processes in HD have not been modeled explicitly. Using a new model, which incorporates individual variability related to structural change and behavior, we sought to identify functional correlates of compensation in premanifest-HD gene-carriers. METHODS: We investigated the modulatory effects of regional brain atrophy, indexed by structural measures of disease load, on the relationship between performance and brain activity (or connectivity) using task-based and resting-state functional MRI. FINDINGS: Consistent with compensation, as atrophy increased performance-related activity increased in the right parietal cortex during a working memory task. Similarly, increased functional coupling between the right dorsolateral prefrontal cortex and a left hemisphere network in the resting-state predicted better cognitive performance as atrophy increased. Such patterns were not detectable for the left hemisphere or for motor tasks. INTERPRETATION: Our findings provide evidence for active compensatory processes in premanifest-HD for cognitive demands and suggest a higher vulnerability of the left hemisphere to the effects of regional atrophy