How impurity atoms move through a crystal is a fundamental and recurrent question in materials. The previous models of oxygen diffusion in titanium relied on interstitial lattice sites that were recently found to be unstable--leaving no consistent picture of the diffusion pathways. Using first-principles quantum-mechanical methods, we find three oxygen interstitial sites in titanium, and quanti...

A solid-state chemical model is given for the production of O2 by electronic excitation of ice, a process that occurs on icy bodies in the outer solar system. Based on a review of the relevant available laboratory data, we propose that a trapped oxygen atom-water complex is the principal precursor for the formation of molecular oxygen in low-temperature ice at low fluences. Oxygen formation the...

During production of the semisynthetic eicosapeptide Phe-Pro-Arg-Pro-Gly-Gly-Gly-GlyAsn-Gly-Asp-Phe-Glu-Glu-Be-Pro-Glu-Glu-Tyr-Leu, two minor impurities were isolated in which Be-15 had been replaced by other amino acids. The molecular weights of the two peptide minor products were 14 u lower and 14 u higher, respectively, than the major product with the foregoing amino acid sequence. It was de...

This study discussed the effect of oxygen impurity in inlet gas a nitrogen atmospheric pressure plasma jet (APPJ). A numerical model that takes into account fluid dynamics, heat transfer, mass diffusion, and chemical reactions was developed to simulate APPJ. Further, DC APPJ experiment performed verify temperature characteristics on treated surface. The decreased with an increase impurity. More...

We have investigated the interlayer exchange coupling (IEC) in Fe/MgO/Fe(0 0 1) tunnel junctions with and without oxygen vacancies in MgO, using model and density functional calculations. The model predicts that IEC changes sign from ferromagnetic to antiferromagnetic if a defect level matches the Fermi energy. Ab initio calculations show that for perfect junctions, IEC is ferromagnetic and dec...

The influence of the firing conditions on the nanoscale structure of the grain boundaries and on the magnetic properties of polycrystalline MnZn-ferrites is investigated, on specimens of nearly identical microstructures. High oxygen partial pressures favor accumulation of impurity ions at the triple points. Under appropriate oxygen pressures homogeneous accumulation of impurities along the grai...

The randomness of dopant atom distributions in cuprate high-critical temperature superconductors has long been suspected to cause nanoscale electronic disorder. In the superconductor Bi2Sr2CaCu2O8+delta, we identified populations of atomic-scale impurity states whose spatial densities follow closely those of the oxygen dopant atoms. We found that the impurity-state locations are strongly correl...

In this study, a full-potential density functional theory was used to investigate the effects of Ti substitution by different cations. In both rutile and anatase, Ti atom was replaced by Ce, Au, Sn, Ag, Mo, Nb, Zr, and Y. Phase stability, electronic structure and formation energy of oxygen vacancy were compared for rutile and anatase. The results indicated that substitution of Ce and Zr increas...

An unknown impurity in the fermentation-based drug substance lovastatin at 0.52 RRT was observed invariably in all batches when analyzed by HPLC as per the PhEur monograph. This impurity was isolated from the impurity-enriched sample using reversed-phase preparative HPLC and characterized by using spectroscopic (PMR, CMR, MASS, and UV) techniques as the structurally-related compound Monacolin-X...