40 research outputs found
Copper-doping effects in electronic structure and spectral properties of SmNiā
The electronic structure and optical properties of the SmNiā
āCux (x = 0, 1, 2) compounds are studied. The
band spectra of the studied intermetallics were calculated with LDA+U+SO method supplementing the local
density approximation with a correction for strong electron interaction on the shell of the rare-earth element. Optical
properties were studied by ellipsometry method in the wide wavelength range. It was found that the substitution
of copper for nickel leads to local changes in the optical conductivity spectra. Both the spectroscopic
measurements and theoretical calculations demonstrate the presence of a broad absorption band around 4 eV associated
with the Cu 3d ā Ni 3d electron transitions and increasing with the grown of copper content. The experimental
dispersion curves of optical conductivity in the interband absorption region were interpreted using the
results of the calculations
QSAR analysis of the toxicity of nitroaromatics in Tetrahymena pyriformis : structural factors and possible modes of action
The Hierarchical Technology for Quantitative Structure - Activity Relationships (HiT QSAR) was applied to 95 diverse nitroaromatic compounds (including some widely known explosives) tested for their toxicity (50% inhibition growth concentration, IGC50) against the ciliate Tetrahymena pyriformis. The dataset was divided into subsets according to putative mechanisms of toxicity. Classification and Regression Trees (CART) approach implemented within HiT QSAR has been used for prediction of mechanism of toxicity for new compounds. The resulting models were shown to have ~80% accuracy for external datasets indicating that the mechanistic dataset division was sensible. Then, Partial Least Squares (PLS) statistical approach was used for the development of 2D QSAR models. Validated PLS models were explored to (i) elucidate the effects of different substituents in nitroaromatic compounds on toxicity; (ii) differentiate compounds by probable mechanisms of toxicity based on their structural descriptors; (iii) analyze the role of various physical-chemical factors responsible for compoundsā toxicity. Models were interpreted in terms of molecular fragments promoting or interfering with toxicity. It was also shown that mutual influence of substituents in benzene ring plays the determining role in toxicity variation. Although chemical mechanism based models were statistically significant and externally predictive (R2ext=0.64 for the external set of 63 nitroaromatics identified after all calculations have been completed), they were also shown to have limited coverage (57% for modeling and 76% for external set)