Boron-doped diamond single crystals for probes of the high-vacuum tunneling microscopy

The results of studying the structure of diamond single crystals grown by the temperature gradient method with the aim to obtain samples having maximum uniform characteristics for manufacturing probes for scanning electron microscopes with a specified axial orientation and controlled distribution of the dopant have been considered. It has been shown that the use of similar probes in scanning tunneling microscopy decreases the probability of incidental tunneling channels with participation of the surface states caused by the presence of boron atoms in the diamond structure and increases the reliability of experimental data. The high stability of monocrystalline diamond probes and the possibility to attain the atomic resolution with the help of them have been demonstrated by the investigations of the (0001) graphite plane using scanning tunneling microscopy.     

Oxidation resistance and strength of a molybdenum fiber–oxide matrix composite material

The oxidation kinetics of a composite material, which consists of an Al₂O₃–Al₅Y₃O₁₂ matrix and molybdenum fibers and has a high cracking resistance, is studied. The mass loss of the composite material during oxidation is shown to be several orders of magnitude lower than that of molybdenum. Oxidation in quiet air at 1250°C for several hours weakly changes the strength of the composite material at temperatures from room temperature to 1300°C. It is also shown that the strength of the composite material as a function of the oxide matrix composition (Al: Y ratio) changes nonmonotonically. The maximum strength shifts from the Al₂O₃–Al₅Y₃O₁₂ eutectic point toward garnet.     

Study of phase transformations in silicon by scanning tunneling spectroscopy and nanoindentation

The results have been reported of the experiments on nanoscratching and nanoindentation of the surface of silicon using scanning tunneling microscope equipped with diamond semiconducting probe. Physical phenomena in silicon occurring at various contact pressures have been discussed.     

Graphics processing unit parallel accelerated solution of the discrete ordinates for photon transport in biological tissues

As a widely used numerical solution for the radiation transport equation (RTE), the discrete ordinates can predict the propagation of photons through biological tissues more accurately relative to the diffusion equation. The discrete ordinates reduce the RTE to a serial of differential equations that can be solved by source iteration (SI). However, the tremendous time consumption of SI, which is partly caused by the expensive computation of each SI step, limits its applications. In this paper, we present a graphics processing unit (GPU) parallel accelerated SI method for discrete ordinates. Utilizing the calculation independence on the levels of the discrete ordinate equation and spatial element, the proposed method reduces the time cost of each SI step by parallel calculation. The photon reflection at the boundary was calculated based on the results of the last SI step to ensure the calculation independence on the level of the discrete ordinate equation. An element sweeping strategy was proposed to detect the calculation independence on the level of the spatial element. A GPU parallel frame called the compute unified device architecture was employed to carry out the parallel computation. The simulation experiments, which were carried out with a cylindrical phantom and numerical mouse, indicated that the time cost of each SI step can be reduced up to a factor of 228 by the proposed method with a GTX 260 graphics card.     

Assessment of the resolution of scanning tunneling microscope with a tip of a boron-doped diamond

The assessment of the resolution of scanning tunneling microscope when operated in the scanning mode has been made based on the analysis of the tunneling current on parameters of diamond tip-sample system. The scanning parameters and accuracy of supporting the constant tunneling current by the system of the instrument feedback, at which the presence of the atomic resolution is possible in the case of a single channel of tunneling, have been defined. An alternative (in respect to the best known publications) explanation of the hexagonal structure of the pyrolytic graphite surface observed with atomic resolution has been suggested. The problem of multichannel tunneling caused by the presence of several nanoprotrusions in the diamond probe test zone that initiate tunneling and impair the resolution of a scanning tunneling microscope is discussed.     

Decarboxylation and decarbonylation in the autoxidation of liquid paraffins in the presence of various initiating additives

Summary It has been shown that in the oxidation of liquid paraffins to acids with atmospheric oxygen at 130°C in a dynamic system, the manganese salts of synthetic fatty acids are more effective initiators than KMnO₄. In the case of MnSFA, the undesired processes of decarboxylation and decarbonylation of the desired products, associated with autoxidation, are significantly decreased and a high yield of the acids is attained.