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The thermal stability and electronic structures of anatase TiO2 doped with early transition metals (TM) (group III-B = Sc, Y and La; group IV-B = Zr and Hf; group V-B = V, Nb and Ta) have been studied using first principles calculations. It was found that all doped systems are thermodynamically stable, and their band gaps were reduced by 1–1.3 eV compared to pure TiO2. Doping with transition metals affects the strength of the hybrid orbital of TM–O bonding, and the band gap increases approximately linearly with the MP value of TM–O bonding. [ABSTRACT FROM AUTHOR]

The effects of vertical compressive stress on Sb2Te3 nano-films have been investigated by the first principles calculation, including stability, electronic structure, crystal structure, and bond order. It is found that the band gap of nano-film is sensitive to the stress in Sb2Te3 nano-film and the critical thickness increases under compressive stress. The band gap and band order of Sb2Te3 film has been affected collectively by the surface and internal crystal structures, the contraction ratio between surface bond length of nano-film and the corresponding bond length of bulk decides the band order of Sb2Te3 film. [ABSTRACT FROM AUTHOR]

Based on the features of diode-pumped lasers, a thermal model of the square cross-section of a Yb:KGd(WO4)2 (Yb:KGW) laser crystal was established. According to the latest reports on thermal parameters and considering the heat transfer on side surfaces, temperature distribution pumped-face distortion and thermal lens local length were obtained by solving the anisotropy heal conductive equation. Under pump powers of 16 W, the highest temperature located at the centre of the pumped front surface was 309.9 °C, the maximum distortion was 0.55 µm and the thermal lens focal length at the pump spot was 4.2 cm. It is shown that thermal lensing in b-cut Yb:KGW is quite serious and it can be lessened if the heat transfer is considered. As such, based on the calculations of thermal lens focal length, we designed a plane-concave cavity and then made a further study on the continuous output performances of diode-pumped Yb:KGW lasers. [ABSTRACT FROM AUTHOR]

In this article, we used the Atherton-Todd reaction to synthesize amino acid methyl ester 5'-phosphoamidates of uridine as prodrugs. Their structures were confirmed by 1H NMR, 31P NMR, 13C NMR, IR, and mass spectrometry. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. [ABSTRACT FROM AUTHOR]

The structure and stability of AgXen Z(n=1–3, Z=-1, 0, +1) cluster series at CCSD(T) theoretical level have been investigated. It is shown that the cations are more stable and have more compact geometries than the anions and neutrals. The role of the interaction was explained using the natural bond orbital (NBO) analysis. [ABSTRACT FROM AUTHOR]

The influence of non-uniform Jc distributions on flux jumps in high-temperature superconductors is investigated with the simplified models in the form of a composite superconducting slab consisting of different pinning regions. The magnetization loops and flux jumps for the simplified models are calculated with the modified recursion formulas which could predict the flux-jump fields. The valid ranges of the temperature and sweep rate for Bfj1 are specified and the fields of the subsequent jumps after the first flux jump of the inhomogeneous models are obviously lower than that of the homogeneous models. The results indicate that flux jump instability could be stimulated by non-uniform Jc distributions and with the increase of the discrepancy of Jc between different pinning regions the instability also increase. [ABSTRACT FROM AUTHOR]

Model tetrapeptide system was designed to investigate the cis/trans isomerization of peptidyl-prolyl imide bond of Ser-Pro motif. To establish the side-chain O-phosphorylation effect in regulating the peptides conformations, molecular dynamics (MD) simulations where carried out on the designed tetrapeptides and their corresponding phosphorylated forms by MD Insight II Discovery3 approach. The most stable configurations and the statistic cis/trans concentration distribution demonstrated that the phosphorylation evidently influences the peptidyl-prolyl imide bond isomerization and works as a key effect in regulating the peptide conformations. The charge state and the site provided for the charge of the phosphate moiety might be an important key. The results also demonstrated that phosphorylation changes the cis conformation ratio of the peptide and the maximum cis value is obtained when the phosphate group has no negative charge. [ABSTRACT FROM AUTHOR]

Theoretical studies of the structures of Sn n Cl and Sn n Cl - ( n   =  1–6) clusters have been carried out using density functional theory methods. The geometric structure of each unit is optimized at the B3LYP level, employing the LANL2DZpd for tin and DZP++ for chlorine basis sets. The resulting total energies, fragmentation energies and equilibrium geometries of chlorine–tin clusters are presented and discussed, together with natural populations and natural electron configurations. The impact on internal electron transfer between the (Sn n ) subsystem and Cl atom in Sn n Cl - (Sn n Cl) clusters is investigated. In addition, theoretical results for the electron affinities of Sn n Cl ( n   =  4–6) clusters are in good agreement with experimental results available. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the risk of esophageal carcinoma in a cohort with long-term occupational exposure to sodium nitrite. The method used was a retrospective cohort study. A small wood screw manufacturer was founded in 1977 and closed down in 2000. In their production process, the sodium nitrite solution was used to serve as anticorrosive and coolant fluid. One hundred sixty workers in turning and milling shops had direct exposure to sodium nitrite through skin, mouth, and airway because of lack of occupational protective knowledge (study group), whereas 255 workers from other workshops without direct contact with sodium nitrite served as control group. The incidence, diagnosis, and treatment of esophageal carcinoma as well as other malignant tumors in these two groups were followed until the end of 2007. The sodium nitrite exposure time in the study group ranged from 16 to 23 years, with an average of 22.1 years. During 30 years of follow-up, there were 11 esophageal carcinomas and 10 other malignant tumors (4 hepatic cell carcinomas, 3 lung cancers, 2 breast cancers, and 1 leukemia) documented in the study group, while no cancer developed in the control group. The risk for esophageal carcinoma was significantly increased in the study group compared with the control group (relative risk = 1.26, 95% confidence interval = 1.08-1.46, chi-square = 116.83, P < 0.001). Long-term exposure to sodium nitrite markedly increases the risk of esophageal carcinoma in human body. [ABSTRACT FROM AUTHOR]

erratum [ABSTRACT FROM AUTHOR]