Buckling of Si and Ge (111)2×1 Surfaces

Voltage-dependent scanning tunneling microscopy is used to determine the buckling of pi-bonded chains on Si and Ge(111)2x1 surfaces. Images are acquired over a wide range of voltages, and are compared with theoretical constant-density contours generated from first-principles electronic-structure calculations. The theoretical predictions for (2 -1 -1) corrugation shifts are quite different for positive and negative buckling; experimental results for Si are found to agree with the former and those for Ge agree with the latter. In addition to an expected shift in ( 2 -1 -1) corrugation between small-magnitude positive and negative voltages, a further shift is also seen in both experiment and theory between small and large positive voltages. .</p

Band gap of the Ge(111)c(2×8) surface by scanning tunneling spectroscopy

The surface band gap of the Ge(111)c(2×8) surface at low temperature is determined on the basis of scanning tunneling spectroscopy. Electrostatic potential computations permit evaluation of tip-induced band bending, from which a correction to the energy scale of the observed spectra is made. Parameter values in the computations are constrained by comparison of the observed spectrum with known spectral features, including high-lying conduction band features derived from first-principles computations. The surface band gap, lying between the bulk valence band maximum and the minimum of an adatom-induced surface band, is found to have a width of 0.49±0.03 eV.</p

The genetics of blood pressure regulation and its target organs from association studies in 342,415 individuals.

To dissect the genetic architecture of blood pressure and assess effects on target organ damage, we analyzed 128,272 SNPs from targeted and genome-wide arrays in 201,529 individuals of European ancestry, and genotypes from an additional 140,886 individuals were used for validation. We identified 66 blood pressure-associated loci, of which 17 were new; 15 harbored multiple distinct association signals. The 66 index SNPs were enriched for cis-regulatory elements, particularly in vascular endothelial cells, consistent with a primary role in blood pressure control through modulation of vascular tone across multiple tissues. The 66 index SNPs combined in a risk score showed comparable effects in 64,421 individuals of non-European descent. The 66-SNP blood pressure risk score was significantly associated with target organ damage in multiple tissues but with minor effects in the kidney. Our findings expand current knowledge of blood pressure-related pathways and highlight tissues beyond the classical renal system in blood pressure regulation

Novel loci for adiponectin levels and their influence on type 2 diabetes and metabolic traits: a multi-ethnic meta-analysis of 45,891 individuals

Circulating levels of adiponectin, a hormone produced predominantly by adipocytes, are highly heritable and are inversely associated with type 2 diabetes mellitus (T2D) and other metabolic traits. We conducted a meta-analysis of genome-wide association studies in 39,883 individuals of European ancestry to identify genes associated with metabolic disease. We identified 8 novel loci associated with adiponectin levels and confirmed 2 previously reported loci (P = 4.5×10(-8)-1.2×10(-43)). Using a novel method to combine data across ethnicities (N = 4,232 African Americans, N = 1,776 Asians, and N = 29,347 Europeans), we identified two additional novel loci. Expression analyses of 436 human adipocyte samples revealed that mRNA levels of 18 genes at candidate regions were associated with adiponectin concentrations after accounting for multiple testing (p<3×10(-4)). We next developed a multi-SNP genotypic risk score to test the association of adiponectin decreasing risk alleles on metabolic traits and diseases using consortia-level meta-analytic data. This risk score was associated with increased risk of T2D (p = 4.3×10(-3), n = 22,044), increased triglycerides (p = 2.6×10(-14), n = 93,440), increased waist-to-hip ratio (p = 1.8×10(-5), n = 77,167), increased glucose two hours post oral glucose tolerance testing (p = 4.4×10(-3), n = 15,234), increased fasting insulin (p = 0.015, n = 48,238), but with lower in HDL-cholesterol concentrations (p = 4.5×10(-13), n = 96,748) and decreased BMI (p = 1.4×10(-4), n = 121,335). These findings identify novel genetic determinants of adiponectin levels, which, taken together, influence risk of T2D and markers of insulin resistance