Band-to-band tunneling in a carbon nanotube metal-oxide-semiconductor field-effect transistor is dominated by phonon-assisted tunneling

Band-to-band tunneling (BTBT) devices have recently gained a lot of interest due to their potential for reducing power dissipation in integrated circuits. We have performed extensive simulations for the BTBT operation of carbon nanotube metal-oxide-semiconductor field-effect transistors (CNT-MOSFETs) using the nonequilibrium Green's function formalism for both ballistic and dissipative quantum transport. In comparison with recently reported experimental data (J. Am. Chem. Soc. 2006, 128, 3518-3519), we have obtained strong evidence that BTBT in CNT-MOSFETs is dominated by optical phonon assisted inelastic transport, which can have important implications on the transistor characteristics. It is shown that, under large biasing conditions, two-phonon scattering may also become important.     

Phase composition and structure of molybdenum-, copper-, and cesium-containing sodium aluminophosphate glassy materials for immobilization of high level wastes of nuclear reactors

Molybdenum-, copper-, and cesium-containing glass based on aluminophosphate designed to immobilize high-active wastes (HAWs), which are formed at the reprocessing of spent nuclear fuel (SNF) from Atom Peaceful Big (AMB) nuclear reactor, have been synthesized and studied by means of the X-ray diffraction and electron-microscopy methods. After quenching the melts, glass, which partially crystallizes at annealing, is formed. The introduction of magnesium oxide in aluminophosphate glass increases its crystallization resistance; and molybdenum oxide, decreases. The samples crystallize after heat treatment with the formation of aluminum and sodium-aluminum orthophosphates and solid solution of the (Na,Cs)_3?3x Al _x PO₄ composition.     

Temperature dependence of diffusion length in MCT epitaxial layers

The temperature dependence of the minority charge carriers diffusion length in the active photosensitive layer of a matrix photodetector based on MCT heteroepitaxial structure grown by molecular beam epitaxy is studied.     

Coprecipitation of Transuranium Elements from Alkaline Solutions by the Method of Arising Agents: XXII. Coprecipitation of Pu(IV) with Sodium Uranate

The behavior of approximately 5 × 10^{- 7} M Pu(IV) in precipitation of sodium uranate produced by catalytic decomposition of peroxouranium(VI) ion with copper(II) in 0.5-4 M NaOH was studied radiometrically. Plutonium is efficiently coprecipitated, and the decontamination factors of the solutions from plutonium K _d are 200-100. Carbonate and organic ions cause a decrease in K _d.     

Operation and Modeling of Semiconductor Spintronics Computing Devices

Semiconductor spintronic devices are considered from the point of view of suitability for digital logic. Functionality of earlier proposed devices is reviewed for cascadability and signal gain. Spin gain transistor, which uses electronic control of ferromagnetism in semiconductors, is treated in more detail via semiconductor Bloch equations for both localized and free-carrier magnetic moments. Dependence of the steady state magnetization and temporal switching characteristics on material parameters is determined. Finally, fundamental physical limits for spintronic devices are determined via use of an idealized model. They are compared with similar limits for electronic devices. It is found that, though spintronic devices switch slower, their switching energy is smaller, therefore they scale with size on a curve with lower power dissipation.     

Ribosomal structure: RNA-protein and protein-protein interactions

Vitamin A and its derivatives have been postulated to play an important role in renal tubulogenesis and compensatory hypertrophy. This study examined the effects of two carboxylic derivatives of vitamin A on Lewis lung carcinoma-porcine kidney-1 (LLC-PK1) renal tubular epithelial cell mito- and motogenesis and cell size. It was found that all-trans and 13-cis retinoic acids exerted modest, dose-dependent effects to stimulate incorporation of 3H-thymidine into acid-precipitable material of LLC-PK1 cells. The effects of all-trans retinoic acid to promote 3H-thymidine uptake in LLC-PK1 cells modestly enhanced that seen with acidic fibroblastic growth factor. Similar findings of these two retinoic acid derivatives to promote 3H-thymidine uptake and to enhance 3H-thymidine uptake stimulated by another growth factor (platelet-derived growth factor BB) were also observed in cultured bovine aortic smooth muscle cells. Both retinoic acids promoted healing of denuded areas made within confluent monolayers of serum-starved LLC-PK1 cells. All-trans retinoic acid also stimulated recovery of mechanically denuded areas within bovine aortic smooth muscle monolayers. Neither all-trans nor 13-cis retinoic acids s affected cell size as assessed by forward light scatter with flow cytometry, suggesting lack of effect to induce hypertrophy. These results demonstrate that two carboxylic acid derivatives of vitamin A are capable of stimulation of basal and growth factor-induced incorporation of 3H-thymidine uptake into acid-precipitable material and healing of denuded areas in disparate cell types. These findings are compatible with a role for vitamin A and its analogues in the tissue repair process.     

Structure of borosilicate glassy materials with high concentrations of sodium,iron, and aluminum oxides

Alkali borosilicate glassy materials, which contain high iron and aluminum oxide concentrations and simulate vitrified high-level wastes of the Savannah River Site (United States), are investigated using X-ray powder diffraction, optical and electron microscopies, and infrared spectroscopy. The materials prepared by induction melting in cold crucibles operating in pilot and industrial facilities at the State Unitary Enterprise “Moscow Research and Production Association Radon” consist of a glass matrix with distributed individual or aggregated crystals of spinel similar in composition to trevorite. The maximum content of the crystalline phase in the glassy material from a “dead volume” of the cold crucible with an industrial size reaches ～13 vol %. The texture of the glass phase is complex and determined by the direction of flows in cold crucibles under the action of eddy currents, the character of outflow of the glass melt stream during pouring into canisters, and the interaction of the stream with the glass solidified in the canister after preceding pourings. The structure of the anionic motif of the glass phase is predominantly built up of metasilicate chains and boron-oxygen fragments with threefold-coordinated boron.     

Application of physicomechanical methods of separation to the decontamination of contaminated soils

The physicomechanical methods of separation of conventional mineral raw materials, including uranium-containing stock, can be used successfully to decontaminate soils and remediate territories contaminated by mining companies. Using its many years of scientific and applied experience in the development and commercial adoption of technology for reprocessing uranium-containing raw materials, the All-Russia Research Institute of Heat Sources is restoring radioactively contaminated territories within the Russian Federation and the Commonwealth of Independent States. The results of investigations of the decontamination of contaminated soils and territories, including radiometric separation, fine classification in hydrocyclones, and magnetic separation, are described. Effective technological schemes and their hardware implementation have been developed. __________ Translated from Atomnaya énergiya, Vol. 101, No. 4, pp. 296–301, October, 2006.     

Oxidation of Pu(VI) with ozone and stability of the oxidation products,Pu(VII) and Pu(VIII), in concentrated alkali solutions

Oxidation of Pu(VI) with ozone and stability of the oxidation products, Pu(VII) and Pu(VIII), in 4–15 M NaOH solutions were studied. In a wide range of alkali concentrations, from 1 to 15 M, the Pu(VI) ozonation yields a mixture of Pu(VII) and Pu(VIII). It was proved that Pu(VII) exists in aqueous alkali solutions in the form different from that suggested previously. Pu(VII) is readily reduced with ?2? in aqueous alkali solutions with the NaOH concentration of up to 8 M, whereas at [NaOH] + 8 M it is fairly stable. On the contrary, Pu(VIII) is noticeably reduced with water at room temperature throughout the examined range of NaOH concentrations from 1 to 15 M.