Quasibound states and transport characteristics of Au chains with a substitutional S impurity.

Electronic transport properties of short gold atom chains with a single sulfur impurity were studied using density functional theory. It is found that the role of the impurity atom in the transport properties is twofold. First, it acts as a scattering center in the dominating 6s-orbital transmission channel and generally leads to a decrease of the transmission function in a wide energy region around the Fermi level. Second, it gives rise to a quasibound state manifesting as a peak near the Fermi level both in the partial density of states as well as in the transmission function. Because of the hybridization of the sulfur 3p and gold 5d orbitals in its formation, the quasibound state moves locally upward in the gold 5d transmission channel and brings about an enhancement of the transmission function in a narrow energy region near the Fermi level. The height of the peak of the quasibound state in the transmission function depends significantly on the position of the impurity in the chain and its energy varies with the bias voltage. The current-voltage (I-V) characteristics become asymmetric with a departure of the impurity from the central position in the chain and they are nonlinear for small values of the voltage (V < 0.1 V). It is proposed that a careful analysis of the I-V characteristics or the voltage dependence of the differential conductance may be used for unambiguous location of the light impurity in experiments with gold chains.

Defect-induced conductance oscillations in short atomic chains.

Electronic transport through a junction made of two gold electrodes connected with a gold chain containing a silver impurity is analyzed with a tight binding model and the density-functional theory. It is shown that the conductance depends in a simple way on the position of the impurity in the chain and the parity of the total number of atoms of the chain. For an odd chain the conductance takes on a higher value when the Ag impurity substitutes an even Au atom in the chain, and a lower one for an odd position of the Ag atom. In the case of an even chain the conductance hardly depends on the position of the Ag atom. This new kind of a defect-induced parity oscillation of the conductance is significantly more prominent than the well-known even-odd effect related to the dependence of the conductance on the parity of number of atoms in perfect chains.

[The morphofunctional changes in the internal organs in the modelling of poisonings by psilocybine-containing mushrooms]. / Morfofunktsional'nye izmeneniia vnutrennikh organov pri modelirovanii otravlenii psilotsibinsoderzhashchimi gribami.

Histological analysis of the viscera in experimental poisoning with psilocybin-containing mushrooms showed nonspecific changes in all examined organs, presenting as expressed hemocirculatory disorders and intracellular dystrophy. Quantitative histochemical analysis showed appreciable shifts in the activities of enzymes involved in the cytoplasmic and mitochondrial redox processes and of specific enzymes involved in nerve tissue metabolism. This may reflect some features in the direct effects of narcotic alkaloids contained in psilocybin-producing mushrooms.

[The forensic chemical study of psilocybine-containing fungi]. / Sudebno-khimicheskoe issledovanie psilotsibinsoderzhashchikh gribov.

A method for isolating the main components (psilocybin and psilocine) from Psilocybe semilanceata mushrooms, their identification and measurement by thin-layer and gas-liquid chromatography, chromatographic mass-spectrometry, and inverse-phase high-performance liquid chromatography is developed.

[The toxicological aspects of poisonings by psilocybine-containing mushrooms]. / Toksikologicheskie aspekty otravlenii psilotsibinsoderzhashchimi gribami.

Cases involving the investigation of psylocybin-containing mushrooms became more frequent in forensic chemical and criminological expert evaluation in recent years. The authors present the data on the main chemical factors contained in these mushrooms, on the mechanism of their toxic effect, clinical picture of poisoning, and methods of chemical and toxicological analysis.