Dynamic avalanche breakdown of a p-n junction: deterministic triggering of a plane streamer front

We discuss the dynamic impact ionization breakdown of high voltage p-n junction which occurs when the electric field is increased above the threshold of avalanche impact ionization on a time scale smaller than the inverse thermogeneration rate. The avalanche-to-streamer transition characterized by generation of dense electron-hole plasma capable to screen the applied external electric field occurs in such regimes. We argue that the experimentally observed deterministic triggering of the plane streamer front at the electric field strength above the threshold of avalanche impact ionization but yet below the threshold of band-to-band tunneling is generally caused by field-enhanced ionization of deep-level centers. We suggest that the process-induced sulfur centers and native defects such as EL2, HB2, HB5 centers initiate the front in Si and GaAs structures, respectively. In deep-level free structures the plane streamer front is triggered by Zener band-to-band tunneling.Comment: 4 pages, 2 figure

Electroplastic Processing of Titanium Implants

The results of experimental studies of samples of titanium for implants when exposed to pulsed electric currents. Excitation of longitudinal and transverse vibrations to the sample under these influences can be used in their electroplastic processing and introduction into the bone tissue. When exposed to pulses of surface layers of titanium sample are experiencing significant dynamic load. The possibility of increasing amplitudes with decreasing duration of pulses of electric current was shown. This allows to exclude the heating of implants during such impacts. The peculiarities of ponderomotive effects in titanium samples related to its uniqueelectrical and mechanical properties, precluding the practical manifestation of the classic skin-effect and its impact on the generation of oscillatory processes in the moments of passage of the leading and trailing edges of current pulse. Keywords: titanium, implant, vibration, acceleration, magnetic field, skin effect

Patterns of calcium oxalate monohydrate crystallization in complex biological systems

The paper presents the features of calcium oxalate crystallization in the presence of additives revealed through experimental modeling. The patterns of phase formation are shown for the Ca{2+} – C[2]O[4]{ 2–} – H[2]O and Ca{2+} – C[2]O[4]{2–} – PO[4]{3–} – H[2]O systems with the components and pH of the saline varying over a wide concentrations range. The effect of additives on crystallization of calcium oxalate monohydrate was investigated. It was found that the ionic strength and magnesium ions are inhibitors, and calcium oxalate and hydroxyapatite crystals are catalysts of calcium oxalate monohydrate crystallization. The basic calcium phosphate (apatite) was found to be most thermodynamically stable, which indicates its special role in kidney stone formation since it is found in virtually all stones