Rate constant for the H˙ + H2O → ˙OH + H2 reaction at elevated temperatures measured by pulse radiolysis.

Maintaining the structural integrity of materials in nuclear power plants is an essential issue associated with safe operation. Hydrogen (H2) addition or injection to coolants is a powerful technique that has been widely applied such that the reducing conditions in the coolant water avoid corrosion and stress corrosion cracking (SCC). Because the radiation-induced reaction of ˙OH + H2 → H˙ + H2O plays a crucial role in these systems, the rate constant has been measured at operation temperatures of the reactors (285-300 °C) by pulse radiolysis, generating sufficient data for analysis. The reverse reaction H˙ + H2O → ˙OH + H2 is negligibly slow at ambient temperature; however, it accelerates considerably quickly at elevated temperatures. Although the reverse reaction reduces the effectiveness of H2 addition, reliable rate constants have not yet been measured. In this study, the rate constants have been determined in a temperature range of 250-350 °C by pulse radiolysis in an aqueous I- solution.

Effects of short-term intensive glycemic control on insulin, glucagon, and glucagon-like peptide-1 secretion in patients with Type 2 diabetes.

BACKGROUND: Short-term intensive insulin therapy (IIT) in patients with Type 2 diabetes mellitus (T2DM) has beneficial effects on insulin secretion. However, IIT effect on glucagon and glucagon-like peptide-1 (GLP-1) secretion is unknown. AIM: We evaluated short-term intensive glycemic control effects on insulin, glucagon, and GLP-1 secretory dynamics in T2DM. MATERIALS AND METHODS: Twenty-six patients with T2DM were hospitalized and treated with IIT for 10-14 days. A meal tolerance test was performed before and after IIT and the differences in serum immunoreactive insulin (IRI) and C-peptide immunoreactivity (CPR) as well as plasma glucagon and active GLP-1 levels were evaluated. RESULTS: Glycoalbumin levels decreased significantly from 23.0% before to 19.6% after IIT (p<0.001). However, pre- and post-IIT, IRI and CPR levels were not significantly different; post-IIT glucose levels were significantly decreased. The post-IIT glucagon levels at 0 and 60 min were lower than pre-IIT levels. Moreover, post- IIT area under the curve (AUC) of glucagon significantly reduced from 6755 ± 996 pg/dl · 60 min to 5796 ± 1074 pg/dl · 60 min (p<0.001). Furthermore, post-IIT GLP-1 levels and AUC were significantly higher than pre-IIT values. CONCLUSIONS: Our results suggest that patients with T2DM who received shortterm IIT demonstrated decreased postprandial glucagon levels and increased GLP-1 levels following a meal tolerance test.