Improving rowing performance by adjusting oar blade size and angle.

The principal aim of the work presented here is to investigate and demonstrate that a forward tilted rowing blade would result in a more efficient and effective motion of the blade through the water that would result in a higher boat speed when an equal input power is provided. A 1:5 scaled rowing boat is used to determine the performance of rowing blades with different sizes and blade angles. This is used to validate the results of a previous study where the optimal blade angle of 15 ∘ with respect to the oar shaft was determined ( 1). The input power and speed of the rowing boat can be compared between original and modified oar blades. Measurements in a towing tank demonstrate that a modified rowing blade result in faster rowing by 0.4% at the same input power. Maintaining the same stroke rate, the improvement of the blade efficiency is compensated by using a 4-6% increased blade area to yield the same input power.

Management of ventricular septal defect with associated aortic incompetence.

Twenty-two patients with a ventricular septal defect and aortic incompetence underwent surgical repair. Mean age was 9.6 years (range, 9 to 15 years). Mean follow-up was 32.4 +/- 15.8 months. The ventricular septal defect was perimembranous in 19 patients and doubly committed or juxtaarterial in 3. Most showed only a small left-to-right shunt. Mean diameter was 11.9 +/- 4.8 mm. Aortic incompetence was mild in 6 patients, moderate in 4, and severe in 12. In 16 patients closure of the ventricular septal defect and aortic valvoplasty were both performed through the aortic root. There were no deaths. All patients retained normal sinus rhythm. No complete heart block was found. In 3 patients secondary aortic valve replacement was required for severe incompetence; in 1 the cause was bacterial endocarditis, in another technical failure, and in a third progressive incompetence over an 8-month period. All patients showed substantial clinical improvement, marked decrease or disappearance of the valvar incompetence, diminution of the left ventricular end-diastolic diameter, and decreased cardiothoracic ratio. We conclude that primary repair is the operation of choice for this combination of lesions. This can avoid or delay considerably valvar replacement. The left-sided approach proves safe and is our preferred technique.