Higher-order symplectic Born-Oppenheimer molecular dynamics

The extended Lagrangian formulation of time-reversible Born-Oppenheimer molecular dynamics (TR-BOMD) enables the use of geometric integrators in the propagation of both the nuclear and the electronic degrees of freedom on the Born-Oppenheimer potential energy surface. Different symplectic integrators up to the 6th order have been adapted and optimized to TR-BOMD in the framework of ab initio self-consistent-field theory. It is shown how the accuracy can be significantly improved compared to a conventional Verlet integration at the same level of computational cost, in particular for the case of very high accuracy requirements

Fast crystallization of chalcogenide glass for rewritable memories

Natural Science Foundation of Fujian Province of China [2008J0166]; Xiamen University [X071I4]By ab initio molecular dynamics simulations, we unraveled the unique network structure of amorphous Ge(1)Sb(2)Te(4), which shows high rank of ordering and mostly consists of distorted defective octahedrons with a small portion of distorted tetrahedrons. The phase transition from amorphous to cubic Ge(1)Sb(2)Te(4) would be mainly a process of angle rearrangements of tetrahedrons to octahedrons and vice versa. (C) 2008 American Institute of Physics

Formation of Large Voids in the Amorphous Phase-Change Memory Ge2Sb2Te5 Alloy

Natural Science Foundation of Fujian Province of China [2008J0166]; Xiamen UniversityOn the basis of ab initio molecular dynamics simulations, large voids mainly surrounded by Te atoms are observed in molten and amorphous Ge2Sb2Te5, which is due to the clustering of two- and threefold coordinated Te atoms. Furthermore, pressure shows a significant effect on the clustering of the under coordinated Te atoms and hence the formation of large voids. The present results demonstrate that both vacancies and Te play an important role in the fast reversible phase transition process

One-carbon metabolism biomarkers and risk of urothelial cell carcinoma in the European prospective investigation into cancer and nutrition

Published associations between dietary folate and bladder cancer risk are inconsistent. Biomarkers may provide more accurate measures of nutrient status. This nested case-control analysis within the European Prospective Investigation into Cancer and Nutrition (EPIC) investigated associations between pre-diagnostic serum folate, homocysteine, vitamins B6 and B12 and the risk of urothelial cell carcinomas of the bladder (UCC). A total of 824 patients with newly diagnosed UCC were matched with 824 cohort members. Serum folate, homocysteine, and vitamins B6 and B12 were measured. Odds ratios (OR) and 95% confidence intervals (CI) for total, aggressive, and non-aggressive UCC were estimated using conditional logistic regression with adjustment for smoking status, smoking duration and intensity, and other potential confounders. Additionally, statistical interaction with smoking status was assessed. A halving in serum folate concentrations was moderately associated with risk of UCC (OR: 1.18; 95% CI: 0.98-1.43), in particular aggressive UCC (OR: 1.34; 95% CI: 1.02-1.75; p-heterogeneity = 0.19). Compared to never smokers in the highest quartile of folate concentrations, this association seemed only apparent among current smokers in the lowest quartile of folate concentrations (OR: 6.26; 95% CI: 3.62-10.81, p-interaction = 0.07). Dietary folate was not associated with aggressive UCC (OR: 1.26; 95% CI: 0.81-1.95; p-heterogeneity = 0.14). No association was observed between serum homocysteine, vitamins B6 and B12 and risk of UCC. This study suggests that lower serum folate concentrations are associated with increased UCC risk, in particular aggressive UCC. Residual confounding by smoking cannot be ruled out and these findings require confirmation in future studies with multiple measurements.Peer reviewe

Sex specific associations in genome wide association analysis of renal cell carcinoma.

Renal cell carcinoma (RCC) has an undisputed genetic component and a stable 2:1 male to female sex ratio in its incidence across populations, suggesting possible sexual dimorphism in its genetic susceptibility. We conducted the first sex-specific genome-wide association analysis of RCC for men (3227 cases, 4916 controls) and women (1992 cases, 3095 controls) of European ancestry from two RCC genome-wide scans and replicated the top findings using an additional series of men (2261 cases, 5852 controls) and women (1399 cases, 1575 controls) from two independent cohorts of European origin. Our study confirmed sex-specific associations for two known RCC risk loci at 14q24.2 (DPF3) and 2p21(EPAS1). We also identified two additional suggestive male-specific loci at 6q24.3 (SAMD5, male odds ratio (ORmale) = 0.83 [95% CI = 0.78-0.89], Pmale = 1.71 × 10-8 compared with female odds ratio (ORfemale) = 0.98 [95% CI = 0.90-1.07], Pfemale = 0.68) and 12q23.3 (intergenic, ORmale = 0.75 [95% CI = 0.68-0.83], Pmale = 1.59 × 10-8 compared with ORfemale = 0.93 [95% CI = 0.82-1.06], Pfemale = 0.21) that attained genome-wide significance in the joint meta-analysis. Herein, we provide evidence of sex-specific associations in RCC genetic susceptibility and advocate the necessity of larger genetic and genomic studies to unravel the endogenous causes of sex bias in sexually dimorphic traits and diseases like RCC

Firm Strategy, Location and MNE-networks

This paper asks three explicit questions, where the first one concerns the impact of a firm’s choice of innovation strategy and knowledge resources. The study aims at confirming that firms with a strategy with R&D persistency have a markedly higher productivity, profitability and wage level than other firms. The second question is focused on the location of firms, with a distinction between firms dwelling in a metropolitan region and other firms. The hypothesis is that a metropolitan knowledge milieu may augment the performance of firms. The third question concerns knowledge exchange in regional and global networks that pertain to multinational affiliates. Applying Swedish data on individual firms and their location, the paper shows that firm performance is significantly higher when the three factors R&D persistency, metropolitan location and affiliation to a multinational group are combined.R&D; knowledge; productivity; profitability; regional milieu