Аномальные кинетические характеристики транспорта водорода через Pd-Cu-мембраны, модифицированные пентадвойникованными цветкообразными нанокристаллитами с высокоиндексными гранями

A technique that made it possible for the first time to achieve fivefold symmetry in palladium nanocrystallites grown on the surface of a Pd-Cu film has been developed. Pd-40%Cu membrane modification with pentatwinned nanocrystallites with high-index facets made it possible to achieve ultra-high hydrogen permeability up to 10.1 mmol s-1 m-2 at 100 °C. Such permeability, comparable in value to high-temperature analogs, is anomalous, since the predicted values should be more than 2 times lower than those obtained. This result is due to the acceleration of surface dissociative adsorption and recombinative desorption as a result of the pentatwinned particles ultra-high activity in reactions involving hydrogen, which is confirmed by the data on the selectivity of the developed membranes.

Single Amino Acid Substitutions Surrounding the Icosahedral Fivefold Symmetry Axis Are Critical for Alternative Receptor Usage of Foot-and-Mouth Disease Virus

The integrins function as the primary receptor molecules for the pathogenic infection of foot-and-mouth disease virus (FMDV) in vivo, while the acquisition of a high affinity for heparan sulfate (HS) of some FMDV variants could be privileged to facilitate viral infection and expanded cell tropism in vitro. Here, we noted that a BHK-adapted Cathay topotype derivative (O/HN/CHA/93tc) but not its genetically engineered virus (rHN), was able to infect HS-positive CHO-K1 cells and mutant pgsD-677 cells. There were one or three residue changes in the capsid proteins of O/HN/CHA/93tc and rHN, as compared with that of their tissue-originated isolate (O/HN/CHA/93wt). The phenotypic properties of a set of site-directed mutants of rHN revealed that E83K of VP1 surrounding the fivefold symmetry axis was necessary for the integrin-independent infection of O/HN/CHA/93tc. L80 in VP2 was essential for the occurrence of E83K in VP1 during the adaptation of O/HN/CHA/93wt to BHK-21 cells. L80M in VP2 and D138G in VP1 of rHN was deleterious, which could be compensated by K83R of VP1 for restoring an efficient infection of integrin-negative CHO cell lines. These might have important implications for understanding the molecular and evolutionary mechanisms of the recognition and binding of FMDV with alternative cellular receptors.

Interdependence of shape and magnetic properties in Al-nanoparticles doped with Ni and Pt

By means of ab initio molecular dynamics, we investigate the magnetic behaviour of Al, AlNi and AlPt nanoparticles of 19 atoms. New geometrical shapes are detected and a depression of the total magnetization is associated with geometrical reconstructions where the fivefold symmetry character is lost, independently of the chemical doping.

Quasi-fivefold symmetric electron diffraction patterns due to multiple twinning in silicon thin films grown from hexamethyldisiloxane

Unusual quasi-fivefold symmetric electron diffraction patterns are observed for silicon thin films grown by plasma-enhanced chemical vapour deposition and containing oxygen and carbon impurities in the range of 0.3–5.5%. These films were grown on crystalline (100) silicon wafers using a liquid precursor, hexamethyldisiloxane (HMDSO), mixed with silane, hydrogen and diborane diluted in argon. The occurrence of this quasi-fivefold symmetry is explained by multiple twinning and imperfect epitaxy. A quantitative method performed on the diffraction patterns is developed to evaluate the number of twin operations. This method is also used to discriminate twin positions from random microcrystalline ones in the diffraction patterns and thus to estimate their respective ratios for different growth conditions. Quite remarkably, the random microcrystalline part remains in the range of a few per cent and the diffracted intensities are the sum of two main contributions: multiple (micro-) twinned and amorphous. Increasing the amount of HMDSO decreases the microtwinned part directly to the benefit of the amorphous part with no significant microcrystalline phase. The causes of twinning are presented and discussed by comparing the observations with the literature; dynamical considerations where the system tends to align {111} planes with the growth direction would explain multiple twinning and, in turn, the fivefold symmetry.