243 research outputs found

    Constraining planet formation around 6M⊙-8M⊙ stars

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    Identifying planets around O-type and B-type stars is inherently difficult; the most massive known planet host has a mass of only about 3M⊙. However, planetary systems which survive the transformation of their host stars into white dwarfs can be detected via photospheric trace metals, circumstellar dusty and gaseous discs, and transits of planetary debris crossing our line-of-sight. These signatures offer the potential to explore the efficiency of planet formation for host stars with masses up to the core-collapse boundary at ≈8M⊙, a mass regime rarely investigated in planet formation theory. Here, we establish limits on where both major and minor planets must reside around ≈6M⊙ − 8M⊙ stars in order to survive into the white dwarf phase. For this mass range, we find that intact terrestrial or giant planets need to leave the main sequence beyond approximate minimum star-planet separations of respectively about 3 and 6 au. In these systems, rubble pile minor planets of radii 10, 1.0, and 0.1 km would have been shorn apart by giant branch radiative YORP spin-up if they formed and remained within, respectively, tens, hundreds and thousands of au. These boundary values would help distinguish the nature of the progenitor of metal-pollution in white dwarf atmospheres. We find that planet formation around the highest mass white dwarf progenitors may be feasible, and hence encourage both dedicated planet formation investigations for these systems and spectroscopic analyses of the highest mass white dwarfs

    N-acetyl-B-D-glucosaminidase and inflammatory response after cardiopulmonary bypass

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    OBJECTIVE: To determine the changes in activity of plasma N-acetyl-beta-D-glucosaminidase, a marker for inflammation as well as renal, pulmonary and cardiac damage and proinflammatory cytokines in patients undergoing coronary artery bypass grafting and find out the relationship between their plasma levels with clinical outcome of patients. STUDY DESIGN: Cross-sectional study. PLACE AND DURATION OF STUDY: The Aga Khan University, Karachi, from January to June 2003. PATIENTS AND METHODS: N-acetyl-beta-D-glucosaminidase (NAG) activity and concentrations of tumor necrosis factor-alpha of (TNFalpha), interleukin 6 (IL-6), interleukin 8 (IL8) and granulocyte-macrophage colony stimulating factor (GM-CSF) were monitored in plasma samples of 12 angina patients undergoing coronary artery bypass grafting (CABG), before, immediately after and 5 days post-surgical procedure. Serum glucose concentrations were also monitored in those patients. Patient\u27s clinical condition was monitored during this time period. RESULTS: No significant increase was observed in plasma NAG activity (a marker of inflammation) or in plasma levels of TNFalpha, IL-6, IL-8 and GM-CSF immediately after surgery, indicating that cardiopulmonary bypass itself does not produce any significant amount of inflammation immediately after CABG. However, 5 days post surgery, there was a significant increase in plasma NAG activity (p=0.001), TNFalpha (p=0.047) and GM-CSF (p=0.045). There was no relationship between plasma NAG activity and clinical outcome because various parameters of renal, cardiac and pulmonary functions, though slightly affected, remained within the normal limits. CONCLUSION: Increased levels of NAG and TNFalpha did not affect clinical outcome. However, data suggest that NAG can be a potential marker for inflammation and end organ damage following CABG. An increase in GM-CSF on day 5 following CABG indicates enhanced body\u27s defense mechanism against infection

    Lack of association of methylenetetrahydrofolate reductase 677C\u3eT mutation with coronary artery disease in a Pakistani population

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    Pakistanis belong to the South Asian population which has the highest known rate of coronary artery disease. Folic acid deficiency also appears to be highly prevalent in this population. Methylenetetrahydrofolate reductase (MTHFR) 677C\u3eT polymorphism decreases the activity of this enzyme and can be associated with mild to moderate hyperhomocysteinemia in homozygotes, particularly when there is folic acid deficiency, as well as with coronary artery disease. To assess the value of genotyping the MTHFR 677C\u3eT dimorphism, we carried out a case-control study of dimorphism 677C\u3eT for putative association with myocardial infarction (MI) among Pakistani nationals. We investigated a sample population of 622 Pakistanis consisting of 225 controls and 397 patients with clinical diagnosis of acute MI (AMI). MTHFR C677T alleles were determined by assays based on polymerase chain reaction and restriction endonuclease analysis. Frequencies of C alleles were 0.87 among controls and 0.86 among AMI patients. The MTHFR 677C\u3eT dimorphism showed no association with MI (chi(2) = 0.25, 1df, P=0.62), serum levels of folate and vitamin B12 and plasma level of vitamin B6. A significant association, however, was found between homozygous 677T genotype and plasma levels of homocysteine. Multivariate analysis of the data showed that in case of log homocysteine, age and MTHFR genotypes were significantly different (PT polymorphism, though associated with homocysteine levels, confers no significant risk of coronary artery disease in the Pakistani population investigated here. We suggest that the higher incidence of AMI in South Asia occurs through mechanisms other than the MTHFR related pathways

    Prevalence and determinants of human papillomavirus infection and cervical lesions in HIV-positive women in Kenya

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    Background: We assessed the association of human papillomavirus (HPV) infection and cervical intraepithelial neoplasia (CIN) with various characteristics, CD4 count and use of combination antiretroviral therapy (cART) among HIV-positive women. Methods: Cross-sectional study of 498 HIV-positive women who underwent HPV PCR-based testing, cytology, and systematic cervical biopsy. Results: In all, 68.7% of women were HPV-positive, 52.6% had high-risk (hr) HPV, and 40.2% multiple type infections. High-risk human papillomavirus-positivity did not vary significantly by age but it was negatively associated with education level. The most frequent types in 113 CIN2/3 were HPV16 (26.5%), HPV35 (19.5%), and HPV58 (12.4%). CD4 count was negatively associated with prevalence of hrHPV (Po0.001) and CIN2/3 among non-users of cART (P¼0.013). Combination antiretroviral therapies users (X2 year) had lower hrHPV prevalence (prevalence ratio (PR) vs non-users¼0.77, 95% confidence interval (CI): 0.61–0.96) and multiple infections (PR¼0.68, 95% CI: 0.53–0.88), but not fewer CIN2/3. The positive predictive value of hrHPV-positivity for CIN2/3 increased from 28.9% at age o35 years to 53.3% in X45 years. Conclusion: The burden of hrHPV and CIN2/3 was high and it was related to immunosuppression level. Combination antiretroviral therapies (X2 year) use had a favourable effect on hrHPV prevalence but cART in our population may have been started too late to prevent CIN2/3

    Water sanitation and hygiene status in the neighbourhood of Bangladeshi Islamic schools and mosques

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    Faith based interventions have been underutilized to improve water, sanitation and hygiene status and offers promise to promote behaviour in the community. Prior to delivering a faith based WASH intervention, we conducted a survey among the neighbouring households of eight Bangladeshi Islamic schools and associated mosques. We randomly selected 192 families from where any male attend mosque and interviewed adult women from that family. At baseline, almost all households used improved water sources and improved toilets. However, toilet cleanliness was poor. Faecal matter was disposed into the environment after emptying the pit/septic tank. Defecation and disposal among children <3years mostly occurred directly in the open which should be improved using behaviour change recommendations. Presence of hand washing agent in the hand washing place was low. Islamic faith based intervention should be designed and delivered in way that can promote hand washing, safe sanitation practices and safe disposal of child faeces

    Succeeding against the odds: can schools ‘compensate for society’?

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    Education researchers, policy-makers and practitioners in the UK have debated the question of what, and how much, schools can do to mitigate the effects of parental background on educational outcomes over the last half a century. A range of programmes, strategies and interventions have been implemented, and continue to be implemented in an effort to ‘break the link’ between socio-economic disadvantage and low educational outcomes, but educational inequalities have persisted. This paper draws on theoretical and empirical research to offer a new analysis of compensatory education in England across three main phases since the 1960s

    Assessing the perceptions of a biostatistics and epidemiology module: Views of Year 2 medical students from a Malaysian university. A cross-sectional survey

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    Background In the era of evidence based medicine, biostatistics and epidemiology are considered as the main elements aiding the health professional to design a research study, understand the literature, and make decisions about patient care. The aim of the study is to explore students' perception about this subject because it plays an important role in determining educational outcome. Methods Data were collected from a self-administered questionnaire distributed among 164 Year 2 medical students. The 5-point Likert scale anchored by Strongly disagree = 1 and Strongly agree = 5 included 36 questions in four domains designed to assess the perception of a biostatistics and epidemiology module amongst students. Results 138 students with ages ranging from 20 to 24 years (Mean = 20.7; SD = 0.62) returned their responses to the questionnaire. This was a response rate of 84.14%. Of the 138 students, 80.7% realized the relevance of the subject to real health issues at the end of the module, while 89.8% believed the module focused on interpretation more than calculation. More than three quarters (78.1%) agreed that lack of practicing exercises was the cause for declining interest in the subject, while only 26.1% believed that lectures were not interesting. Another three quarters (75.4%) believed that there were too many lectures for one day of teaching activities, while 84.6% recommended practical sessions for designing research and data collection. Conclusions This study found that students perceived the relevance of biostatistics and epidemiology to real health issues. The major cause of poor interest in the subject was attributed to the short duration of the course, lack of practicing exercises, and the need for practical data collection sessions. Emphasis should be given to early introduction of projects for data collection and analysis

    Burosumab vs conventional therapy in children with X-linked hypophosphatemia:results of the open-label, phase 3 extension period

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    In a randomized, open-label phase 3 study of 61 children aged 1–12 years old with X-linked hypophosphatemia (XLH) previously treated with conventional therapy, changing to burosumab every 2 weeks (Q2W) for 64 weeks improved the phosphate metabolism, radiographic rickets, and growth compared with conventional therapy. In this open-label extension period (weeks 64–88), 21 children continued burosumab Q2W at the previous dose or crossed over from conventional therapy to burosumab starting at 0.8 mg/kg Q2W with continued clinical radiographic assessments through week 88. Efficacy endpoints and safety observations were summarized descriptively for both groups (burosumab continuation, n = 6; crossover, n = 15). At week 88 compared with baseline, improvements in the following outcomes were observed in the burosumab continuation and crossover groups, respectively: mean (SD) RGI-C rickets total score (primary outcome), +2.11 (0.27) and +1.89 (0.35); mean (SD) RGI-C lower limb deformity score, +1.61 (0.91) and +0.73 (0.82); and mean (SD) height Z-score + 0.41 (0.50) and +0.08 (0.34). Phosphate metabolism normalized rapidly in the crossover group and persisted in the continuation group. Mean (SD) serum alkaline phosphatase decreased from 169% (43%) of the upper limit of normal (ULN) at baseline to 126% (51%) at week 88 in the continuation group and from 157% (33%) of the ULN at baseline to 111% (23%) at week 88 in the crossover group. During the extension period, treatment-emergent adverse events (AEs) were reported in all 6 children in the burosumab continuation group and 14/15 children in the crossover group. The AE profiles in the randomized and extension periods were similar, with no new safety signals identified. Improvements from baseline in radiographic rickets continued in the extension period among children with XLH who remained on burosumab. Children who crossed over from conventional therapy to burosumab demonstrated a rapid improvement in phosphate metabolism and improved rickets healing over the ensuing 22 weeks

    Grand Challenges in Protoplanetary Disc Modelling

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    The Protoplanetary Discussions conference --- held in Edinburgh, UK, from 7th --11th March 2016 --- included several open sessions led by participants. This paper reports on the discussions collectively concerned with the multiphysics modelling of protoplanetary discs, including the self-consistent calculation of gas and dust dynamics, radiative transfer and chemistry. After a short introduction to each of these disciplines in isolation, we identify a series of burning questions and grand challenges associated with their continuing development and integration. We then discuss potential pathways towards solving these challenges, grouped by strategical, technical and collaborative developments. This paper is not intended to be a review, but rather to motivate and direct future research and collaboration across typically distinct fields based on \textit{community driven input}, to encourage further progress in our understanding of circumstellar and protoplanetary discs
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