Highly efficient optically pumped vertical-emitting semiconductor laser with more than 20 W average output power in a fundamental transverse mode.

We have demonstrated an optically pumped vertical-external-cavity surface-emitting laser (OP-VECSEL) generating more than 20 W of cw output power in a fundamental transverse mode (M2 approximately 1.1) at 960 nm. The laser is highly efficient with a slope efficiency of 49%, a pump threshold of 4.4 W, and an overall optical-to-optical efficiency of 43%.

Comparing a simplified FEM approach with the mass-spring model for surgery simulation.

Virtual reality based surgical simulators offer a very elegant approach to enhancing traditional training in endoscopic surgery. In this context a realistic soft tissue model is of central importance. The most accurate procedures for modeling elastic deformations of tissue use the Finite Element Method (FEM) to solve the governing mechanical equations. An alternative are mass-spring models which are a crude approximation of the real physical behavior. The main reason given when using the mass-spring approach is the computational complexity of FEM. In this study we show that an optimized linear FEM model requires computation time similar to the mass-spring approach, while giving better results.

Haemodynamic characterization of young normotensive men carrying the 825T-allele of the G-protein beta3 subunit.

A C825T polymorphism was recently identified in the gene for the G-protein beta3 subunit, the T-allele being associated with hypertension. To better understand the underlying pathophysiological mechanisms, we compared the haemodynamics of young healthy males with and without the T-allele. In three studies, subjects were investigated with regard to cardiac and vascular function at rest and following intravenous administration of the beta-adrenoceptor antagonist, propranolol, and the alpha2-adrenoceptor agonist, alpha-methylnoradrenaline, and with regard to local venous vasoconstriction in the dorsal hand vein in situ following infusion of the alpha2-adrenoceptor agonist, azepexol. alpha2-Adrenoceptor agonists were chosen as vasoconstrictor drugs since alpha2-adrenoceptors couple to pertussis toxin (PTX)-sensitive G-proteins and since in-vitro studies have demonstrated enhanced signal transduction of PTX-dependent pathways in the presence of the T-allele. Total peripheral resistance was determined as a parameter of vasoconstrictor tone and heart rate, stroke volume and systolic time intervals for cardiac function. T-allele carriers had a significantly elevated stroke volume and lower total peripheral resistance at baseline. After propranolol, their fall in stroke volume was significantly greater. During alpha-methylnoradrenaline infusion, elevation of total peripheral resistance was not increased relative to controls. Similarly, the constriction response of the dorsal hand vein to azepexol was not different. Our study does not support the idea of increased vasoconstrictor tone in T-allele carriers either at rest or during stimulation of alpha2-adrenoceptors. However, this allele may be associated with elevated cardiac stroke volume.

[Familial Mediterranean fever]. / Familiäres Mittelmeerfieber.

BACKGROUND: Familial Mediterranean fever (FMF) is characterized by febrile attacks, acute abdominal pain, pleuritis or arthritis and predominantly observed in ethnic groups of the Mediterranean area (Sephardic Jews, Turks, Armenians). Its most ominous manifestation is amyloidosis potentially leading to chronic renal failure. FMF is an inherited disorder caused by mutations of the FMF-gene, which first was described in 1997. CASE REPORT: We report a 10-year old turkish boy and his family presenting with an increased blood sedimentation rate (WBC) and recurrent attacks of acute abdominal pain. A molecular analysis was carried out, confirming a typical mutation of the FMF-gene. The patient remained free of symptoms after starting therapy with colchicine. CONCLUSION: Investigation of the FMF gene enables an early diagnosis in case of clinical suspect findings, subsequent colchicine administration may prevent amyloidosis.

[Effect of nifedipine on proximal tubular function in patients with essential hypertension]. / Wplyw nifedypiny na funkcje cewki proksymalnej u chorych z nadcisnieniem tetniczym.

The effect of a single 20 mg sublingual dose of nifedipine on function of proximal tubule of nephron in patients with essential hypertension was studied by measuring changes in renal excretion of water, sodium, uric acid and beta-2-microglobulin (B2m) after nifedipine administration. Fifteen patients at the mean age of 40.1 +/- 7 years, with mild to moderate essential hypertension were studied. Systolic (SBP) and diastolic (DBP) blood pressure as well as heart rate (HR) were recorded every hour. Urine was sampled over 60-min, four times. The first two periods were regarded controls and the last two periods followed the administration of a 20 mg sublingual nifedipine dose. Blood samples were taken 1 h before and 1 h after that. Sodium, uric acid, B2m and creatinine in urine and plasma were determined. Nifedipine caused a significant fall in SBP and DBP (p < 0.001) and a marked increase in HR (p < 0.001). Diuresis, sodium (CNa) and uric acid (Cua) clearances were significantly increased (p < 0.001). Similarly, fractional excretion of sodium (FENa) was higher (p < 0.01). B2m excretion (UB2m) showed a two fold increase after nifedipine administration (p < 0.01). A positive correlations were found between the changes in CNa and Cua (r = 0.835, p < 0.001) and between the changes in UB2m and CNa (r = 0.747, p < 0.001). The results indicate that nifedipine induces an increase in diuresis, natriuresis and excretion of uric acid and B2m. These findings and the relationship between the changes in UB2m and Cua proves effect of nifedipine on proximal tubular function.

Dialysis hypoxemia. Role of dialyzer membrane and dialysate delivery system.

Arterial blood gas values, carbon monoxide diffusion capacity, oxygen consumption, carbon dioxide production, respiratory quotient, minute ventilation, and pulmonary capillary blood flow were determined before and during hemodialysis. In addition, the effect of single passage through the dialyzer on blood carbon dioxide tension, pH, and bicarbonate concentration was evaluated. Acetate-based dialysate was used in all experiments. Cellulosic dialyzer with single-pass dialysate delivery system was used in one group, and polyacrylonitrile dialyzers with recirculating delivery system in another. Although hypoxemia occurred in both groups, it was more severe in the former group. Dialyzer carbon dioxide loss was significantly greater with single-pass dialysate delivery system and cellulosic dialyzers than with recirculating delivery system and polyacrylonitrile dialyzer. To differentiate the role of dialysate delivery system from that of the membrane, the experiments were repeated using recirculating delivery system and cellulosic dialyzer. This resulted in marked attenuation of hypoxemia and dialyzer carbon dioxide tension losses. Since other experimental conditions were the same, the observed differences were thought to be due to the difference in the mode of dialysate delivery. It thus appears that the mode of dialysate delivery per se can modify the changes in arterial oxygen tension during hemodialysis and should be added to the list of factors implicated in the genesis of dialysis hypoxemia.

[Choice of the point of attack in the light of the differential diagnosis in class III cases]. / Wahl der Angriffsorte im Lichte der Differentialdiagnose in Klasse-III-Fällen

The author points out that therapy has to be based upon a highly qualified differential diagnosis. In three class III-cases the consecutive steps--differential diagnosis, location of therapeutic attack, adequate design of the appliance--are demonstrated. On the basis of the treatment result the initial treatment goal is discussed.