Rapid planetesimal formation in turbulent circumstellar discs

The initial stages of planet formation in circumstellar gas discs proceed via dust grains that collide and build up larger and larger bodies (Safronov 1969). How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem (Dominik et al. 2007): boulders stick together poorly (Benz 2000), and spiral into the protostar in a few hundred orbits due to a head wind from the slower rotating gas (Weidenschilling 1977). Gravitational collapse of the solid component has been suggested to overcome this barrier (Safronov 1969, Goldreich & Ward 1973, Youdin & Shu 2002). Even low levels of turbulence, however, inhibit sedimentation of solids to a sufficiently dense midplane layer (Weidenschilling & Cuzzi 1993, Dominik et al. 2007), but turbulence must be present to explain observed gas accretion in protostellar discs (Hartmann 1998). Here we report the discovery of efficient gravitational collapse of boulders in locally overdense regions in the midplane. The boulders concentrate initially in transient high pressures in the turbulent gas (Johansen, Klahr, & Henning 2006), and these concentrations are augmented a further order of magnitude by a streaming instability (Youdin & Goodman 2005, Johansen, Henning, & Klahr 2006, Johansen & Youdin 2007) driven by the relative flow of gas and solids. We find that gravitationally bound clusters form with masses comparable to dwarf planets and containing a distribution of boulder sizes. Gravitational collapse happens much faster than radial drift, offering a possible path to planetesimal formation in accreting circumstellar discs.Comment: To appear in Nature (30 August 2007 issue). 18 pages (in referee mode), 3 figures. Supplementary Information can be found at 0708.389

Health-related characteristics and preferred methods of receiving health education according to dominant language among Latinos Aged 25 to 64 in a large Northern California health plan

<p>Abstract</p> <p>Background</p> <p>Latinos are a fast growing segment of the U.S. health care population. Acculturation factors, including English fluency, result in an ethnic group heterogeneous with regard to SES, health practices, and health education needs. This study examined how demographic and health-related characteristics of Spanish-dominant (SD), Bilingual (BIL), and English-dominant (ED) Latino men and women aged 25–64 differed among members of a large Northern California health plan.</p> <p>Methods</p> <p>This observational study was based on data from cohorts of 171 SD (requiring an interpreter), 181 BIL, and 734 ED Latinos aged 25–64 who responded to random sample health plan member surveys conducted 2005–2006. Language groups were compared separately by gender on education, income, behavioral health risks (smoking, obesity, exercise frequency, dietary practices, health beliefs), health status (overall health and emotional health, diabetes, hypertension, high cholesterol, heartburn/acid reflux, back pain, depression), computer and Internet access, and health education modality preferences.</p> <p>Results</p> <p>Compared with ED Latinos, higher percentages of the SD and BIL groups had very low educational attainment and low income. While groups were similar in prevalence of diabetes, hypertension, and high cholesterol, SD were less likely than ED Latinos to rate overall health and emotional well-being as good, very good, or excellent and more likely to report heartburn and back pain (women only). The groups were similar with regard to smoking and obesity, but among women, SD were more likely to be physically inactive than ED, and BIL were less likely than SD and ED groups to eat <3 servings of fruit/vegetables per day. SD and BIL of both genders were significantly less likely than ED Latinos to believe that health practices had a large impact on health. Compared to ED men and women, SD and BIL Latinos had significantly lower Internet and computer access. As a result, SD Latinos had a greater preference for lower technology health education modalities such as videos and taped phone messages.</p> <p>Conclusion</p> <p>There are important differences among Latinos of different English language proficiency with regard to education, income, health status, health behaviors, IT access, and health education modality preferences that ought to be considered when planning and implementing health programs for this growing segment of the U.S. population.</p

Population attributable risk for diabetes associated with excess weight in Tehranian adults: a population-based cohort study

<p>Abstract</p> <p>Background</p> <p>Little evidence exists regarding the magnitude of contribution of excess weight to diabetes in the Middle East countries. This study aimed at quantification of the impact of overweight and obesity on the incidence of type 2 diabetes mellitus (T2DM) at a population level in Tehran, Iran.</p> <p>Methods</p> <p>Using data of a population-based short-term cohort study in Iran, which began in 1997 with 3.6-year follow-up, we calculated the adjusted odds ratios (OR) and population attributable risks (PAR) of developing T2DM, i.e. the proportion of diabetes that could have been avoided had overweight and/or obesity not been present in the population.</p> <p>Results</p> <p>Of the 4728 subjects studied, aged ≥ 20 years, during the 3.6-year follow-up period, 3.8% (n = 182) developed T2DM. This proportion was 1.4%, 3.6%, and 7.8% for the normal, overweight, and obese subjects, respectively. When compared to normal BMI, the adjusted ORs for incident diabetes were 1.76 [95% confidence interval (CI) 1.07 to 2.89] for overweight and 3.54 (95% CI 2.16 to 5.79) for obesity. The PARs adjusted for family history of diabetes, age, triglycerides, systolic blood pressure was 23.3% for overweight and 37.1% for obesity. These figures were 7.8% and 26.6% for men and 35.3% and 48.3% for women, respectively.</p> <p>Conclusion</p> <p>Incident T2DM is mainly attributable to excess weight, significantly more so in Tehranian women than men. Nonetheless, the contribution of excess weight in developing T2DM was lower in our short-term study than that reported in long-term periods. This probably reflects the significant role of other risk factors of T2DM in a short-term follow-up. Hence, prevention of excess weight probably should be considered as a major strategy for reducing incidence of T2DM; the contribution of other risk factors in developing T2DM in short-term period deserve to be studied and be taken into account.</p

Genetic and environmental influence on lung function impairment in Swedish twins

<p>Abstract</p> <p>Background</p> <p>The understanding of the influence of smoking and sex on lung function and symptoms is important for understanding diseases such as COPD. The influence of both genes and environment on lung function, smoking behaviour and the presence of respiratory symptoms has previously been demonstrated for each of these separately. Hence, smoking can influence lung function by co-varying not only as an environmental factor, but also by shared genetic pathways. Therefore, the objective was to evaluate heritability for different aspects of lung function, and to investigate how the estimates are affected by adjustments for smoking and respiratory symptoms.</p> <p>Methods</p> <p>The current study is based on a selected sample of adult twins from the Swedish Twin Registry. Pairs were selected based on background data on smoking and respiratory symptoms collected by telephone interview. Lung function was measured as FEV₁, VC and DLco. Pack years were quantified, and quantitative genetic analysis was performed on lung function data adjusting stepwise for sex, pack years and respiratory symptoms.</p> <p>Results</p> <p>Fully adjusted heritability for VC was 59% and did not differ by sex, with smoking and symptoms explaining only a small part of the total variance. Heritabilities for FEV₁and DLco were sex specific. Fully adjusted estimates were10 and 15% in men and 46% and 39% in women, respectively. Adjustment for smoking and respiratory symptoms altered the estimates differently in men and women. For FEV₁and DLco, the variance explained by smoking and symptoms was larger in men. Further, smoking and symptoms explained genetic variance in women, but was primarily associated with shared environmental effects in men.</p> <p>Conclusion</p> <p>Differences between men and women were found in how smoking and symptoms influence the variation in lung function. Pulmonary gas transfer variation related to the menstrual cycle has been shown before, and the findings regarding DLco in the present study indicates gender specific environmental susceptibility not shown before. As a consequence the results suggest that patients with lung diseases such as COPD could benefit from interventions that are sex specific.</p

Chronic hypothermia and energy expenditure in a neurodevelopmentally disabled patient: a case study

Hypothermia is defined as a core body temperature of \u3c35°C and results in a decrease in measured resting energy expenditure. A 51-year-old mentally disabled patient experienced chronic hypothermia from neurologic sequelae. Because of her continued weight gain and increased body fat in the presence of presumed hypocaloric nutrition, indirect calorimetry measurements were performed twice in a 3-month period. The resting energy expenditure measurements prompted a reduction of her daily caloric intake to prevent further overfeeding. Hypothermia reduces oxygen consumption and, as a consequence, decreases resting energy expenditure. In patients for whom chronic hypothermia is a problem, nutritional intake must be adjusted to prevent overfeeding, excessive weight gain, and the long-term complications of an excess of total calories

Associations of education with 30 year life course blood pressure trajectories: Framingham Offspring Study

Background: Education is inversely associated with cardiovascular disease incidence in developed countries. Blood pressure may be an explanatory biological mechanism. However few studies have investigated educational gradients in longitudinal blood pressure trajectories, particularly over substantial proportions of the life course. Study objectives were to determine whether low education was associated with increased blood pressure from multiple longitudinal assessments over 30 years. Furthermore, we aimed to separate antecedent effects of education, and other related factors, that might have caused baseline differences in blood pressure, from potential long-term effects of education on post-baseline blood pressure changes. Methods: The study examined 3890 participants of the Framingham Offspring Study (mean age 36.7 years, 52.0% females at baseline) from 1971 through 2001 at up to 7 separate examinations using multivariable mixed linear models. Results: Mixed linear models demonstrated that mean systolic blood pressure (SBP) over 30 years was higher for participants with ≤12 vs. ≥17 years education after adjusting for age (3.26 mmHg, 95% CI: 1.46, 5.05 in females, 2.26 mmHg, 95% CI: 0.87, 3.66 in males). Further adjustment for conventional covariates (antihypertensive medication, smoking, body mass index and alcohol) reduced differences in females and males (2.86, 95% CI: 1.13, 4.59, and 1.25, 95% CI: -0.16, 2.66 mmHg, respectively). Additional analyses adjusted for baseline SBP, to evaluate if there may be educational contributions to post-baseline SBP. In analyses adjusted for age and baseline SBP, females with ≤12 years education had 2.69 (95% CI: 1.09, 4.30) mmHg higher SBP over follow-up compared with ≥17 years education. Further adjustment for aforementioned covariates slightly reduced effect strength (2.53 mmHg, 95% CI: 0.93, 4.14). Associations were weaker in males, where those with ≤12 years education had 1.20 (95% CI: -0.07, 2.46) mmHg higher SBP over follow-up compared to males with ≥17 years of education, after adjustment for age and baseline blood pressure; effects were substantially reduced after adjusting for aforementioned covariates (0.34 mmHg, 95% CI: -0.90, 1.68). Sex-by-education interaction was marginally significant (p = 0.046). Conclusion: Education was inversely associated with higher systolic blood pressure throughout a 30-year life course span, and associations may be stronger in females than males.Eric B Loucks, Michal Abrahamowicz, Yongling Xiao, John W Lync

Coronary MR angiography at 3T: fat suppression versus water-fat separation

Objectives: To compare Dixon water-fat suppression with spectral pre-saturation with inversion recovery (SPIR) at 3T for coronary magnetic resonance angiography (MRA) and to demonstrate the feasibility of fat suppressed coronary MRA at 3T without administration of a contrast agent. Materials and methods: Coronary MRA with Dixon water-fat separation or with SPIR fat suppression was compared on a 3T scanner equipped with a 32-channel cardiac receiver coil. Eight healthy volunteers were examined. Contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), right coronary artery (RCA), and left anterior descending (LAD) coronary artery sharpness and length were measured and statistically compared. Two experienced cardiologists graded the visual image quality of reformatted Dixon and SPIR images (1: poor quality to 5: excellent quality). Results: Coronary MRA images in healthy volunteers showed improved contrast with the Dixon technique compared to SPIR (CNR blood-fat: Dixon = 14.9 ± 2.9 and SPIR = 13.9 ± 2.1; p = 0.08, CNR blood-myocardium: Dixon = 10.2 ± 2.7 and SPIR = 9.11 ± 2.6; p = 0.1). The Dixon method led to similar fat suppression (fat SNR with Dixon: 2.1 ± 0.5 vs. SPIR: 2.4 ± 1.2, p = 0.3), but resulted in significantly increased SNR of blood (blood SNR with Dixon: 19.9 ± 4.5 vs. SPIR: 15.5 ± 3.1, p < 0.05). This means the residual fat signal is slightly lower with the Dixon compared to the SIPR technique (although not significant), while the SNR of blood is significantly higher with the Dixon technique. Vessel sharpness of the RCA was similar for Dixon and SPIR (57 ± 7 % vs. 56 ± 9 %, p = 0.2), while the RCA visualized vessel length was increased compared to SPIR fat suppression (107 ± 21 vs. 101 ± 21 mm, p < 0.001). For the LAD, vessel sharpness (50 ± 13 % vs. 50 ± 7 %, p = 0.4) and vessel length (92 ± 46 vs. 90 ± 47 mm, p = 0.4) were similar with both techniques. Consequently, the Dixon technique resulted in an improved visual score of the coronary arteries in the water fat separated images of healthy subjects (RCA: 4.6 ± 0.5 vs. 4.1 ± 0.7, p = 0.01, LAD: 4.1 ± 0.7 vs. 3.5 ± 0.8, p = 0.007). Conclusions: Dixon water-fat separation can significantly improve coronary artery image quality without the use of a contrast agent at 3T

Using a Markov simulation model to assess the impact of changing trends in coronary heart disease incidence on requirements for coronary artery revascularization procedures in Western Australia

<p>Abstract</p> <p>Background</p> <p>The population incidence of coronary heart disease (CHD) has been declining in Australia and many other countries. This decline has been due to reduced population levels of risk factors for CHD and improved medical care for those at higher risk of CHD. However, there are signs that there may be a slowing down or even reversal in the decline of CHD incidence due to the 'obesity epidemic' and other factors and this will have implications for the requirements for surgical treatments for those with CHD.</p> <p>Methods</p> <p>Using a validated Markov simulation model applied to the population of Western Australia, different CHD incidence trend scenarios were developed to explore the effect of changing CHD incidence on requirements for coronary artery bypass graft (CABG) and percutaneous coronary interventions (PCI), together known as coronary artery revascularization procedures (CARPs).</p> <p>Results</p> <p>The most dominant component of CHD incidence is the risk of CHD hospital admission for those with no history of CHD and if this risk leveled off and the trends in all other risks continued unchanged, then the projected numbers of CABGs and PCIs are only minimally changed. Further, the changes in the projected numbers remained small even when this risk was increased by 20 percent (although it is an unlikely scenario). However, when the other CHD incidence components that had also been declining, namely, the risk of CABG and that of CHD death for those with no history of CHD, were also projected to level off as these were declining in 1998-2000 and the risk of PCI for those with no history of CHD (which was already increasing) was projected to further increase by 5 percent, it had a substantial effect on the projected numbers of CARPs.</p> <p>Conclusion</p> <p>There needs to be dramatic changes to several CHD incidence components before it has a substantial impact on the projected requirements for CARPs. Continued monitoring of CHD incidence and also the mix of initial presentation of CHD incidence is required in order to understand changes to future CARP requirements.</p

‘Maintaining balance and harmony’: Javanese perceptions of health and cardiovascular disease

Community intervention programmes to reduce cardiovascular disease (CVD) risk factors within urban communities in developing countries are rare. One possible explanation is the difficulty of designing an intervention that corresponds to the local context and culture