Dual V-type resonators to enhance beam quality of Yb:YAG thin-disk lasers.

In this paper, the operating characteristics of a Yb:YAG thin-disk laser using double V-type resonators are reported. The laser maintained stable performance by independently activating either the main or the auxiliary V-type resonator depending on the pumping laser power. Experimental investigations revealed that by reducing the dynamic range in which the main resonator was used for stability and instead employing the auxiliary resonator, the laser beam quality factor M2 could be reduced from 40.2 to 32.3, representing a beam quality enhancement of approximately 20%.

Zinc deficiency aggravates abnormal glucose metabolism in thalassemia major patients.

BACKGROUND: The aim was to determine whether reduced serum zinc level has a contributory effect on impairment of insulin secretion in beta-thalassemic patients with transfusion-induced iron overload. MATERIAL/METHODS: Seventy thalassemia patients who received deferoxamine chelation therapy and 69 healthy individuals as the control group were evaluated. A standard oral glucose tolerance test (OGTT) was performed and blood samples for measurement of serum ferritin, zinc, and insulin concentrations were obtained. RESULTS: Although the fasting serum insulin concentrations were quite similar between the patient and the control groups, serum insulin levels were significantly lower in the thalassemia patients one hour and two hours after oral glucose load ingestion compared with the healthy controls. Among the thalassemic adults, zinc deficiency (present in 37% of patients) resulted in significantly lower fasting and 1-hour post-OGTT serum insulin concentrations. The serum zinc level in patients with impaired OGTT was also considerably lower than in patients with normal OGTT. CONCLUSIONS: These data support the assumption that zinc deficiency might lead to an exacerbation of the inability of the pancreas to secrete sufficient amounts of insulin in response to glucose stimulation in beta-thalassemia patients. We suggest that serum zinc levels be routinely monitored in these patients as it might provide useful complementaly information regarding glucose metabolism.