Nature of metastable amorphous-to-crystalline reversible phase transformations in GaSb.

The structural, thermodynamic, and kinetic aspects of the transformations between the metastable amorphous and crystalline phases of GaSb are investigated as a function of pressure at ambient temperature using synchrotron x-ray diffraction experiments in a diamond anvil cell. The results are consistent with the hypothesis that the pressure induced crystallization of amorphous GaSb into the ß-Sn crystal structure near ~5 GPa is possibly a manifestation of an underlying polyamorphic phase transition between a semiconducting, low density and a metallic, high density amorphous (LDA and HDA, respectively) phases. In this scenario, the large differences in the thermal crystallization kinetics between amorphous GaSb deposited in thin film form by sputtering and that prepared by laser melt quenching may be related to the relative location of the glass transition temperature of the latter in the pressure-temperature (P-T) space with respect to the location of the critical point that terminate the LDA ↔ HDA transition. The amorphous → ß-Sn phase transition is found to be hysteretically reversible as the ß-Sn phase undergoes decompressive amorphization near ~2 GPa due to the lattice instabilities that give rise to density fluctuations in the crystal upon decompression.

In situ 3omega techniques for measuring thermal conductivity of phase-change materials.

Knowledge of the thermal conductivity of phase-change materials is essential for accurate modeling of nonvolatile memory devices that incorporate them. The "3omega method" is a well-established and sensitive technique for measuring this property. We report two new extensions of the 3omega technique that feature in situ monitoring of the phase-change material as it transitions from the as-deposited amorphous phase to the crystalline phase. One technique crystallizes the entire sample in a vacuum oven, while using the 3omega voltage to monitor the phase transition. The other technique uses the 3omega heater to crystallize only the material in the region of measurement.

The TNF alpha/G-308A polymorphism influences insulin sensitivity in offspring of patients with coronary heart disease: the European Atherosclerosis Research Study II.

There is accumulating evidence for a role of tumor necrosis factor-alpha (TNF-alpha) in insulin resistance induced by obesity. The purpose of this study was to investigate whether the TNF alpha/G-308A polymorphism was associated with responses to oral glucose and fat tolerance tests in a case--control study comparing male offspring with a paternal history of premature myocardial infarction (cases, n=335) to age-matched controls (n=340) recruited from 14 European university populations. Genotype frequencies did not significantly differ between cases and controls. Among cases, those carrying the A allele exhibited a higher area under the curve for insulin (64.5 vs 55.9 mU h/l, P=0.009), a higher increment between baseline concentration and peak of insulin (63.1 vs 52.8 mU/l, P=0.005) and a greater decrease between peak and insulin at 120 min (49.1 vs 36.8 mU/l, P=0.003) than those with the GG genotype. No such effect was observed in control subjects. No association was observed with response to a fat tolerance test either in cases or in controls. The present results suggest that the TNF alpha/G-308A polymorphism might interact with other susceptibility factors to coronary heart disease to predispose to insulin resistance, and that the ability of TNF-alpha to induce insulin resistance may extend beyond obesity.

Polymorphism screening of four genes encoding advanced glycation end-product putative receptors. Association study with nephropathy in type 1 diabetic patients.

Advanced glycation end-products (AGEs) may play an important role in the pathogenesis and progression of cardiovascular and renal complications of diabetes. Four putative AGE receptors (RAGEs), AGE-R1, AGE-R2, and AGE-R3 have been described. In this study, we scanned the sequence of the genes encoding these AGE receptors in 48 patients with type 1 diabetes and investigated the identified polymorphisms (n = 19) in 199 type 1 diabetic patients with nephropathy and 193 type 1 diabetic patients without nephropathy. Overall, none of the polymorphisms was strongly associated with nephropathy. The minor allele of a polymorphism located in the promoter region of the RAGE gene (C-1152A) conferred a weak protective effect (P < 0.05) and was associated with a longer duration of nephropathy-free diabetes (P = 0.08).