563 research outputs found

    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

    Current knowledge of external sulfate attack

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    This paper offers an update of the current understanding of sulfate attack, with emphasis on the sulfates present in an external water source percolating through, and potentially reacting with, the cement matrix. The paper considers the explanations put forward to explain sulfate attack, both from a chemical and microstructural perspective. Similarly, this paper reviews work on the physical damage caused by the precipitation of sulfate salts in porous materials. With the increased use of binary and ternary blends, this paper also considers the impact of binder composition on sulfate resistance, and similarly reviews how the nature of the sulfate species can affect the nature and extent of any deterioration. This then leads on to the important consideration of differences between field- and lab-based studies; reviewing the effect of various experimental parameters on sulfate resistance. This latter topic is of great importance to anyone who wishes to carry out such experiments

    Towards the clinical implementation of pharmacogenetics in bipolar disorder.

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    BackgroundBipolar disorder (BD) is a psychiatric illness defined by pathological alterations between the mood states of mania and depression, causing disability, imposing healthcare costs and elevating the risk of suicide. Although effective treatments for BD exist, variability in outcomes leads to a large number of treatment failures, typically followed by a trial and error process of medication switches that can take years. Pharmacogenetic testing (PGT), by tailoring drug choice to an individual, may personalize and expedite treatment so as to identify more rapidly medications well suited to individual BD patients.DiscussionA number of associations have been made in BD between medication response phenotypes and specific genetic markers. However, to date clinical adoption of PGT has been limited, often citing questions that must be answered before it can be widely utilized. These include: What are the requirements of supporting evidence? How large is a clinically relevant effect? What degree of specificity and sensitivity are required? Does a given marker influence decision making and have clinical utility? In many cases, the answers to these questions remain unknown, and ultimately, the question of whether PGT is valid and useful must be determined empirically. Towards this aim, we have reviewed the literature and selected drug-genotype associations with the strongest evidence for utility in BD.SummaryBased upon these findings, we propose a preliminary panel for use in PGT, and a method by which the results of a PGT panel can be integrated for clinical interpretation. Finally, we argue that based on the sufficiency of accumulated evidence, PGT implementation studies are now warranted. We propose and discuss the design for a randomized clinical trial to test the use of PGT in the treatment of BD

    Leprosy among Patient Contacts: A Multilevel Study of Risk Factors

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    Leprosy is an infectious disease that can lead to physical disabilities, social stigma, and great hardship. Transmitted from person to person, it is still endemic in developing countries, like Brazil and India. Effective treatment has been available since 1960, but early diagnosis of the disease remains the most effective way to stop the transmission chain and avoid late diagnoses and subsequent disabilities. Knowledge of the risk factors for leprosy can facilitate early detection; therefore, our study aimed to investigate the factors presented by leprosy patients and their contacts, who are considered at highest risk of contracting the disease. We studied 6,158 contacts of 1,201 patients under surveillance from 1987 to 2007 in a Public Health Care Center in the City of Rio de Janeiro, Brazil. We evaluated the ways patient and contact demographics and epidemiological characteristics were associated with the detection of leprosy. Statistical analyses took into account both individual and group characteristics and their interrelationships. The main characteristics facilitating the contraction of leprosy among contacts were shown to be consanguinity and household association. Conversely, the bacillary load index of leprosy patients was the principle factor leading to disease among their contacts

    Infection rates associated with epidural indwelling catheters for seven days or longer: systematic review and meta-analysis

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    BACKGROUND: To determine infection rate with use of epidural catheters in place for seven days or more. METHODS: Systematic review and pooled analysis of observational studies. RESULTS: Twelve studies with 4,628 patients (median 197 patients) provided information, of which nine (4,334 patients) were published after 1990. Eight studies (3,893 patients) were retrospective, and four studies (735 patients) prospective. Electronic searches identified three studies and searching reference lists nine. There were 257 catheter-related infections in total, of which 211 were superficial and 57 deep, giving rates of 6.1%, 4.6% and 1.2% respectively. Ten of the 12 studies had deep infection rates of 2% or less. The incidence of deep infection was 1 per 2391 days of treatment, or 0.4 per 1000 catheter treatment days. In nine studies (1503 patients), predominantly in cancer, and with average catheter duration of 74 days, the deep infection rate was 2.8%. The proportion of patients with infection of any type was higher in cancer patients with longer catheter duration. Limited numbers of events meant that no reliable estimate of the impact of prospective and retrospective design could be made. There appeared to be a relationship between catheter duration and infection rate from this and other recent estimates. Four of 57 (7%) patients with deep infection died. CONCLUSION: The best estimate is that one person in 35 with an epidural catheter in place for 74 days for relief of cancer pain can be expected to have a deep epidural infection, and that about 1 in 500 may die of infection-related causes. This is a most uncertain estimate given the limited nature of the evidence

    The Prevalence of Norovirus in returning international travelers with diarrhea

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    Background: There is a high incidence of diarrhea in traveling populations. Norovirus (NV) infection is a common cause of diarrhea and is associated with 7% of all diarrhea related deaths in the US. However, data on the overall prevalence of NV infection in traveling populations is limited. Furthermore, the prevalence of NV amongst travelers returning to Europe has not been reported. This study determined the prevalence of NV among international travelers returning to Germany from over 50 destinations in and outside Europe. Methods: Stool samples of a total of 104 patients with a recent (&lt; 14days) history of international travel (55 male, mean age 37 yrs.) were tested for the presence of NV genogroup (GG) I and II infection using a sensitive and well established quantitative RT PCR method. 57 patients experienced diarrhea at the time of presentation at the Department of Infectious Diseases & Tropical Medicine. The remaining 47 patients had no experience of diarrhea or other gastrointestinal symptoms for at least 14 days prior to their date of presentation at our institute. Results: In our cohort, NV infection was detected in 15.7% of returning travelers with diarrhea. The closer to the date of return symptoms appeared, the higher the incidence of NV, ranging as high as 21.2% within the first four days after return. Conclusions: In our cohort, NV infection was shown to be frequent among returning travelers especially in those with diarrhea, with over 1/5 of diarrhea patients tested positive for NV within the first four days after their return to Germany. Due to this prevalence, routine testing for NV infection and hygienic precautions may be warranted in this group. This is especially applicable to patients at an increased risk of spreading the disease, such as healthcare workers, teachers or food-handlers

    Comparison of diet consumption, body composition and lipoprotein lipid values of Kuwaiti fencing players with international norms

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    <p>Abstract</p> <p>Background</p> <p>No published data is currently available that describes the dietary patterns or physiological profiles of athletes participating on the Kuwaiti national fencing team and its potential impact on health and physical performance. The purpose of this investigation was to: 1) collect baseline data on nutrient intake 2) collect, analyze and report baseline for body composition, plasma lipid and lipoprotein concentrations during the competitive season, 3) compare the results with the international norms, 4) and provide necessary health and nutritional information in order to enhance the athletes' performance and skills.</p> <p>Methods</p> <p>Fifteen national-class fencers 21.5 ± 2.6 years of age participated in this study. Food intake was measured using a 3-day food record. Body composition was estimated using both the BOD POD and Body Mass Index (BMI). Total blood lipid profiles and maximum oxygen consumption was measured for each of the subjects during the competitive season.</p> <p>Results</p> <p>The results of the present study showed significant differences in dietary consumption in comparison with the recommended dietary allowances (RDA). The blood lipids profile and body composition (BMI and % body fat) were in normal range in comparison with international norms However, the average VO<sub>2 max </sub>value was less than the value of the other fencers.</p> <p>Conclusion</p> <p>Due to the results of the research study, a dietary regimen can be designed that would better enhance athletic performance and minimize any health risks associated with nutrition. Percent body fat and BMI will also be categorized for all players. In addition, the plasma blood tests will help to determine if any of the players have an excessive level of lipids or any blood abnormalities. The outcomes of present study will have a direct impact on the players health and therefore their skills and athletic performance.</p

    Homocysteine, Grey Matter and Cognitive Function in Adults with Cardiovascular Disease

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    Background: Elevated total plasma homocysteine (tHcy) has been associated with cognitive impairment, vascular disease and brain atrophy. Methods: We investigated 150 volunteers to determine if the association between high tHcy and cerebral grey matter volume and cognitive function is independent of cardiovascular disease. Results: Participants with high tHcy ($15 mmol/L) showed a widespread relative loss of grey matter compared with people with normal tHcy, although differences between the groups were minimal once the analyses were adjusted for age, gender, diabetes, hypertension, smoking and prevalent cardiovascular disease. Individuals with high tHcy had worse cognitive scores across a range of domains and less total grey matter volume, although these differences were not significant in the adjusted models. Conclusions: Our results suggest that the association between high tHcy and loss of cerebral grey matter volume and decline in cognitive function is largely explained by increasing age and cardiovascular diseases and indicate that th
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