1,040 research outputs found
A biomechanical model of anther opening reveals the roles of dehydration and secondary thickening
Understanding the processes that underlie pollen release is a prime target for controlling fertility to enable selective breeding and the efficient production of hybrid crops. Pollen release requires anther opening, which involves changes in the biomechanical properties of the anther wall. In this research, we develop and use a mathematical model to understand how these biomechanical processes lead to anther opening
Long-term health benefits and costs of measurement of carotid intima-media thickness in prevention of coronary heart disease
OBJECTIVE: Recently, it was demonstrated that information on carotid intima-media thickness (CIMT) and plaque may improve coronary heart disease (CHD) risk prediction through reclassification of some individuals to the correct risk category using the Framingham risk score. Our objective was to assess the currently unknown cost-effectiveness of CIMT measurements in primary prevention. METHODS: A hypothetical cohort of men and women aged 50-59 years and at intermediate or high CHD risk based on data from the Atherosclerosis Risk in Communities Study was simulated using a Markov model. Myocardial infarction (MI) events were used as a proxy for CHD. The effectiveness of pharmaceutical treatment was varied in the analysis. Sensitivity analysis was performed to obtain robust results. RESULTS: CIMT-based reclassification induced a 1% lower absolute risk of MI and 0.01-0.02 increase in quality-adjusted life years (QALYs) for men, and a 1-3% lower risk, and 0.03-0.05 increase in QALYs for women, over a period of 20-30 years. Corresponding costs were an additional 200-300 per woman. Over a 10-year period CIMT measurements were cost-effective with a probability of 66% (men), and 94% (women). Over a 30-year period, CIMT measurements had acceptable cost-effectiveness for men and women. CONCLUSION: Performing CIMT measurements in asymptomatic men and women aged 50-59 years results in additional, but small, health benefits. It takes time for these health benefits to outweigh the initial CIMT measurement costs. Our results support CIMT measurements for cardiovascular risk stratification, in particular for women, when focusing on long-term health
Reaction pathways and textural aspects of the replacement of anhydrite by calcite at 25 °C
The replacement of sulfate minerals by calcium carbonate polymorphs (carbonation) has important implications in various geological processes occurring in Earth surface environments. In this paper we report the results of an experimental study of the interaction between anhydrite (100), (010), and (001) surfaces and Na₂CO₃ aqueous solutions under ambient conditions. Carbonation progress was monitored by glancing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM). We show that the reaction progresses through the dissolution of anhydrite and the simultaneous growth of calcite. The growth of calcite occurs oriented on the three anhydrite cleavage surfaces and its formation is accompanied by minor vaterite. The progress of the carbonation always occurs from the outer-ward to the inner-ward surfaces and its rate depends on the anhydrite surface considered, with the (001) surface being much more reactive than the (010) and (100) surfaces. The thickness of the formed carbonate layer grows linearly with time. The original external shape of the anhydrite crystals and their surface details (e.g., cleavage steps) are preserved during the carbonation reaction. Textural characteristics of the transformed regions, such as the gradation in the size of calcite crystals, from ~2 μm in the outer region to ~17 μm at the calcite-anhydrite interface, the local preservation of calcite crystalographic orientation with respect to anhydrite and the distribution of the microporosity mainly within the carbonate layer without development of any significant gap at the calcite-anhydrite interface. Finally, we compare these results on anhydrite carbonation with those on gypsum carbonation and can explain the differences on the basis of four parameters: (1) the molar volume change involved in the replacement process in each case, (2) the lack/existence of epitactic growth between parent and product phases, (3) the kinetics of dissolution of the different surfaces, and (4) the chemical composition (amount of structural water) of the parent phases
Некоторые проблемы добычи полезных ископаемых на глубоких горизонтах недр
Cardiovascular screening may benefit middle-aged sportsmen, as coronary artery disease (CAD) is the main cause of exercise-related sudden cardiac death. Arterial stiffness, as measured by pulse wave velocity (PWV), may help identify sportsmen with subclinical CAD. We examined the additional value of PWV measurements to traditional CAD risk factors for identifying CAD.From the Measuring Athlete's Risk of Cardiovascular events (MARC) cohort of asymptomatic, middle-aged sportsmen who underwent low-dose Cardiac CT (CCT) after routine sports medical examination (SME), 193 consecutive sportsmen (aged 55 ± 6.6 years) were included with additional PWV measurements before CCT. Sensitivity, specificity and predictive values of PWV values (>8.3 and >7.5 m/s) assessed by Arteriograph were used to identify CAD (coronary artery calcium scoring ≥ 100 Agatston Units or coronary CT angiography luminal stenosis ≥ 50%) and to assess the additional diagnostic value of PWV to established cardiovascular risk factors.Forty-seven sportsmen (24%) had CAD on CCT. They were older (58.9 vs. 53.8 years, p<0.001), had more hypertension (17 vs. 4%, p=0.003), higher cholesterol levels (5.7 vs. 5.4 mmol/l) p=0.048), and more often were (ever) smokers (55 vs. 34%, p=0.008). Mean PWV was higher in those with CAD (8.9 vs. 8.0 m/s, p=0.017). For PWV >8.3m/s respectively >7.5 m/s sensitivity to detect CAD on CT was 43% and 74%, specificity 69% and 45%, positive predictive value 31% and 30%, and negative predictive value 79% and 84%. Adding PWV to traditional risk factor models did not change the area under the curve (from 0.78 (95% CI = 0.709-0.848)) to AUC 0.78 (95% CI 0.710-0.848, p = 0.99)) for prediction of CAD on CCT.Limited additional value was found for PWV on top of established risk factors to identify CAD. PWV might still have a role to identify CAD in middle-aged sportsmen if risk factors such as cholesterol are unknown
Феномен мастурбации: негативное или позитивное явление?
Рассмотрены разные взгляды на роль мастурбации в становлении сексуальности человека. Представлены результаты собственных исследований автора, проведенных с целью установить значение этого феномена для формирования сексуального поведения и сексуального здоровья.Various opinions about the role of masturbation in human sexuality development are discussed. The findings of the original research performed to evaluate the significance of this phenomenon in formation of sexual behavior and sexual health are reported
Flow-mediated vasodilation is not impaired when HDL-cholesterol is lowered by substituting carbohydrates for monounsaturated fat
Low-fat diets, in which carbohydrates replace some of the fat, decrease serum cholesterol. This decrease is due to decreases in LDL-cholesterol but in part to possibly harmful decreases in HDL-cholesterol. High-oil diets, in which oils rich in monounsaturated fat replace some of the saturated fat, decrease serum cholesterol mainly through LDL-cholesterol. We used these two diets to investigate whether a change in HDL-cholesterol would change flow-mediated vasodilation, a marker of endothelial function. We fed thirty-two healthy volunteers two controlled diets in a 2x3.5 weeks' randomised cross-over design to eliminate variation in changes due to differences between subjects. The low-fat diet contained 59.7 % energy (en%) as carbohydrates and 25.7 en% as fat (7.8 en% as monounsaturates); the oil-rich diet contained 37.8 en% as carbohydrates and 44.4 en% as fat (19.3 en% as monounsaturates). Average (sd) serum HDL-cholesterol after the low-fat diet was 0.21 (sd 0.12) mmol/l (8.1 mg/dl) lower than after the oil-rich diet. Serum triacylglycerols were 0.22 (sd 0.28) mmol/l (19.5 mg/dl) higher after the low-fat diet than after the oil-rich diet. Serum LDL and homocysteine concentrations remained stable. Flow-mediated vasodilation was 4.8 (SD 2.9) after the low-fat diet and 4.1 (SD 2.7) after the oil-rich diet (difference 0.7 %; 95 % CI -0.6, 1.9). Thus, although the low-fat diet produced a lower HDL-cholesterol than the high-oil diet, flow-mediated vasodilation, an early marker of cardiovascular disease, was not impaired
Sequentially based analysis versus image based analysis of Intima Media Thickness in common carotid arteries studies - Do major IMT studies underestimate the true relations for cardio- and cerebrovascular risk?
<p>Abstract</p> <p>Background</p> <p>Image-based B-mode ultrasound has gained popularity in major studies as a non-invasive method of measuring cardio- and cerebrovascular risk factors. However, none of the major studies appears to have paid sufficient attention to the variation in end diastolic wall process. By using sequentially based analyses (SBA) of Intima-Media Thickness (IMT), the general purpose of this study was to show that the current image based (ECG tracked) analysis (IBA) has some major variations and might underestimate the true relations for cardiovascular events and stroke for IMT measurement.</p> <p>Method</p> <p>The study group consisted of 2500 healthy male subjects aged between 35 to 55 years. 4 sequences (300 images) were analyzed per subject. 750,000 images were analysed throughout the course of this study.</p> <p>Results</p> <p>IBA showed significantly lower mean, maximal, and minimal values for IMT in CCA than for SBA. The correlation analysis between IBA and SBA with the cardio- and cerebrovascular risk factors showed a higher correlation of SBA for all risk factors. The Pearson coefficient was 0.81, p < 0.01, for SBA versus Framingham CHD risk level (FCRL) and 0.49, p = 0.01, for IBA versus FCRL.</p> <p>Conclusion</p> <p>IBA did not measure the true maximal values of the IMT in this study. Together with the correlation analysis, this indicates that IBA might underestimate the true relations for IMT and risk factors.</p
Prevalence of atherosclerosis and association with 5-year outcome: The Norwegian Stroke in the Young Study
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Периоды апробации метода прогноза интегральной метанообильности шахты
Розроблені аналітичній та натурній методи урахування метанового потенціалу вугільних шахт, апробація яких в умовах діючих об’єктів вдовж 5 термінів (1967 – 2009 рр.) показала високу надійність метода прогнозу інтегральної метанообільності шахт ІМА (~9 тис. порівнянь). На базі цього методу пропонується розробить державний нормативний документ для урахування метанового потенціалу вугільних шахт та реалізувати науково-технічні проекти авторів, які включені в програму науково-технічного розвитку Донецької області до 2020 р.Analytic and nature methods of calculation of methane potential of the collieries which check in the conditions of operating objects during 5 periods (1967 – 2009 years) has shown high reliability concerning of the method integrated methane of abundance of object IMA (~9 000 results) are developed. On the basis of this method it is offered to develop the state standard document for calculation of methane potential of collieries and to realize author’s projects to be conclusion to the science-technical program of development of Donetsk region to 2020 year
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