Structure,Phase Composition and Mechanical Properties of Hot-Extruded Ti–3Al–2.5V Pipe After Vacuum Annealing

Metallurgist - The structure and properties of the hot-extruded Ti–3Al–2.5V pipe 90.0 × 20.0 mm in cross section subjected to vacuum annealing are studied using methods of macro-,...     

A general simulation procedure for the electrical characteristics of metal-insulator-semiconductor tunnel structures

The algorithm is suggested for calculating the I–V characteristics of a voltage- or current-controlled metal-tunnel-thin insulator-semiconductor system. The basic underlying physical models are discussed. Applicability of the algorithm is confirmed by a comparison of the simulation results with the measurement data obtained by the authors and borrowed from the literature, for several different structures. The presented information is supposed to suffice for calculating the electrical characteristics of the investigated structures with the various combinations of materials: metal or polysilicon gate, single-layer or stacked insulator, and semiconductor with any doping type and level.     

Effect of aging on structure and properties of quenched alloy based on orthorhombic titanium aluminide Ti2AlNb

Phase and structural transformations that occur upon the aging of a titanium alloy based on the O phase have been investigated. The formation of a special type of arrangement (zigzag or packet ensembles) of the O-phase plates that arise in the course of the β → O transformation has been detected. Using transmission electron microscopy, the multistage character of structural changes during the α₂ → O transformation has been studied, and a schematic of the occurrence of the transformation has been proposed. The microdurometric characteristics of the indicated alloy that were obtained after different aging regimes have been estimated.     

Effect of hydrogen on the formation of the structure and phase composition in the Ti2AlNb-based alloy

Methods of X-ray diffraction, electron microprobe analysis, electron microscopy, differential thermal analysis, and microdurometry were used to study the effect of alloying with 5.2 and 8.5 at % hydrogen on the occurrence of phase and structural transformations in the intermetallic alloy Ti—24.3 Al—24.8 Nb—1.0 Zr—1.4 V—0.6 Mo—0.3 Si (at %) upon heating in the temperature range of 700-1050°C. It has been established that hydrogen favors the stabilization of the ? solid solution, the suppression of the formation of the α ₂ phase, and the reduction of the temperature of heating for quenching, starting with which the formation of an ordered a phase is possible in the alloy structure. Procedures of calculation of the electron concentration in the alloys with hydrogen have been proposed. By the method of the differential scanning calorimetry, the temperatures of disordering have been determined in the alloys.     

Modeling of deep-submicron silicon-based MISFETs with calcium fluoride dielectric

We model the main characteristics of metal-insulator-silicon field-effect transistors (MISFETs) with different gate insulators using the carrier energy distribution function calculated with a Spherical Harmonics Expansion method. In addition to standard devices with Silicon Dioxide or Oxynitride we study a hypothetical MISFET with a rather new crystalline dielectric-Calcium Fluoride. The real physical parameters of the \(\hbox {CaF}_{2}\) /Si tunnel barrier are used in our simulations. The obtained characteristics of the transistors with \(\hbox {CaF}_{2}\) are, in some details, better than those of the devices with traditional oxides. Being a step forward in the context of the industrial implementation of fluorite, this work opens the possibility of simulating the characteristics of different silicon-based devices with crystalline insulators.     

Catalysis of an Essential Step in Vitamin B2 Biosynthesis by a Consortium of Broad Spectrum Hydrolases

An enzyme catalysing the essential dephosphorylation of the riboflavin precursor, 5‐amino‐6‐ribitylamino‐2,4(1H,3H)‐pyrimidinedione 5′‐phosphate ( 6 ), was purified about 800‐fold from a riboflavin‐producing Bacillus subtilis strain, and was assigned as the translation product of the ycsE gene by mass spectrometry. YcsE is a member of the large haloacid dehalogenase (HAD) superfamily. The recombinant protein was expressed in Escherichia coli. It catalyses the hydrolysis of 6 (v_max, 12 μmol mg^?1 min^?1; K_M, 54 μm ) and of FMN (v_max, 25 μmol mg^?1 min^?1; K_M, 135 μm ). A ycsE deletion mutant of B. subtilis was not riboflavin dependent. Two additional proteins (YwtE, YitU) that catalyse the hydrolysis of 6 at appreciable rates were identified by screening 13 putative HAD superfamily members from B. subtilis. The evolutionary processes that have resulted in the handling of an essential step in the biosynthesis of an essential cofactor by a consortium of promiscuous enzymes require further analysis.