Experimental investigation of model variable-geometry and ogee tip rotors

An experimental investigation was conducted to systematically explore the effects of inter-blade spatial relationships and pitch variations on rotor performance and wake geometry. Variable-geometry rotors consisting of various combinations of blade length, axial spacing, azimuth spacing, and collective pitch were tested at model scale in hover and forward flight. In addition, a hover test of a model rotor with an ogee blade tip design was conducted to determine its performance and wake characteristics. The results of this investigation indicate that properly selected variable geometry rotor configurations can offer substantial improvements in hover performance without adversely affecting forward flight performance. Axial spacing of alternate blades was found to provide the greatest performance benefit, and further improvements were achieved by combining azimuth spacing with axial spacing. The performance benefit appears to be related to the relief of local adverse aerodynamic phenomena produced by vortex interference. The ogee tip design was found to substantially reduce the concentrated core intensity of the tip vortex, and could thus prove beneficial for the relief of blade-vortex interaction problems. However, the ogee tip was found to reduce hover performance at model scale

The Surface Morphology of Normal and Atherosclerotic Coronary Arteries in Male Macaca Fascicularis and the Effect of Coronary Angiography

Selective coronary angiography is one of the procedures used frequently in the diagnosis and management of coronary artery disease. Macaca fascicularis monkeys were used to study the effects of coronary angiography on coronary artery surface morphology. Fourteen M. fascicularis were fed either an atherogenic diet (0.34 mg of cholesterol/kcal and 40 to 43% of the calories as fat) for six to nine months or a control diet. For six of these animals the Judkin method of selective left coronary angiography was done 24 h prior to necropsy. The ascending aorta, right coronary artery, left circumflex (LCX), left anterior descending (LAD) and left main (LM) coronary arteries were examined using scanning electron microscopy (SEM). The animals fed an atherogenic diet had 27% of the ascending aorta and 7% of the coronary arteries covered with raised lesions. The surface of these coronary arteries differed from those of animals fed a control diet in that the surface appeared smoother and often had numerous adherent leukocytes. The animals undergoing coronary angiography had 25% of the ascending aorta and 10% of the LM surface injured by the catheter. These areas were denuded of endothelium and covered with adherent platelets. There were no morphologic changes observed by SEM following angiography within the LCX or LAD arteries. Thus even in a setting of hypercholesterolemia exposure to contrast media during the coronary angiography procedure did not lead to surface alterations

An Unusual Case of Acute Scrotal Pain

Patients frequently present to the emergency department with complaints of scrotal or testicular pain. Generally, there is an algorithmic approach to workup, which includes assessment for torsion, infection, or vascular causes, and musculoskeletal causes of pain are also sometimes considered. Spinal cord pathology, however, is less often explored as a cause of testicular pain. Here, we present a case of a 45-year-old man with end-stage renal disease and hypertension who presented with acute testicular pain. After a comprehensive workup, however, the source of pain was not initially found. Progression of the patient\u27s symptoms led to the diagnosis of spontaneous spinal subdural hematoma. This atypical presentation of a rare diagnosis is also interesting due to the patient\u27s concomitant diagnosis of an otherwise asymptomatic COVID-19 infection. While our case represents an atypical combination of clinical features, it also illustrates the importance of continued vigilance and ongoing workup when patients present with severe pain and unclear causes of their symptoms

「問題導向學習」教案之品質改善：香港大學醫學院一年級生之經驗與回饋

To improve the quality of paper cases used for problem-based learning in the medical curriculum of the University of Hong Kong, Year 1 students were asked at the end of the year to fill in a questionnaire which addresses specific issues related to problem based learning. In addition, for each of the 6 new cases of PBL which were introduced into the first year, tutorials groups were asked to rate which of the learning objectives as specified in the cased were covered under the 4 themes: Biology of Health and Disease (Knowledge Component); Doctors and Patients (Clinical and communication Skills); Medicine and the Community (Societal and Population Medicine) and Professional Development (Medical Ethics and Law). Over eighty percent of the students found the PBL process to facilitate self directed learning and contributed to their learning. Over forty percent found there was unequal representation of the 4 themes with the issue of Professional Development to be the most inadequately covered. Various factors can be identified for the under representation and inadequate coverage of professional development issues. Possible solutions may include case modifications to ensure a fairer balance of 4 themes, alternative formats of enhancing the discussion of professional development issues, tutor training and coaching the students to address professional development issues

Low-level environmental lead exposure in childhood and adult intellectual function: a follow-up study

<p>Abstract</p> <p>Background</p> <p>Early life lead exposure might be a risk factor for neurocognitive impairment in adulthood.</p> <p>Objectives</p> <p>We sought to assess the relationship between early life environmental lead exposure and intellectual function in adulthood. We also attempted to identify which time period blood-lead concentrations are most predictive of adult outcome.</p> <p>Methods</p> <p>We recruited adults in the Boston area who had participated as newborns and young children in a prospective cohort study that examined the relationship between lead exposure and childhood intellectual function. IQ was measured using the Wechsler Abbreviated Scale of Intelligence (WASI). The association between lead concentrations and IQ scores was examined using linear regression.</p> <p>Results</p> <p>Forty-three adults participated in neuropsychological testing. Childhood blood-lead concentration (mean of the blood-lead concentrations at ages 4 and 10 years) had the strongest relationship with Full-Scale IQ (β = -1.89 ± 0.70, p = 0.01). Full-scale IQ was also significantly related to blood-lead concentration at age 6 months (β = -1.66 ± 0.75, p = 0.03), 4 years (β = -0.90 ± 0.41, p = 0.03) and 10 years (β = -1.95 ± 0.80, p = 0.02). Adjusting for maternal IQ altered the significance of the regression coefficient.</p> <p>Conclusions</p> <p>Our study suggests that lead exposure in childhood predicts intellectual functioning in young adulthood. Our results also suggest that school-age lead exposure may represent a period of increased susceptibility. Given the small sample size, however, the potentially confounding effects of maternal IQ cannot be excluded and should be evaluated in a larger study.</p