Reactivation kinetics of boron acceptors in hydrogenated silicon during zero bias anneal

The reactivation kinetics of passivated boron accepters in hydrogenated silicon during zero bias annealing in the temperature range of 65-130 degrees C are reported, For large annealing times and high annealing temperatures, the reactivation process follows second-order kinetics and is rate limited by a thermally activated <(H)over tilde (2)> complex formation process, For short annealing times and low annealing temperatures, the reactivation rate is found to be larger than that due to <(H)over tilde (2)> complex formation alone. We conclude that the faster reactivation is caused by the diffusion of the liberated hydrogen atoms into the bulk as well as <(H)over tilde (2)> complex formation. The effective diffusion coefficient of hydrogen is measured and found to obey the Arrhenius relation with an activation energy (1.41 +/- 0.1) eV. (C) 1997 American Institute of Physics.

Synthesis based on cyclohexadienes .21. Total synthesis of (+/-)-hinesol and (+/-)-10-epi-hinesol

An efficient strategy for the construction of the spiro[4,5]decane and eremane systems is described which involves an acid-catalysed rearrangement of an endo alcohol, followed by an oxidative cleavage resulting in the generation of a spiro-system, as the key step, This methodology is extended to the total synthesis of (+/-)-hinesol and (+/-)-10-epi-hinesol 2.

R-parity violation in neutralino decays at an e gamma collider

At an e gamma collider, a selectron (e) over tilde(L,R) may be produced in association with a (lightest) neutralino <(chi)over tilde>(0)(1). Decay of the selectron may be expected to yield a final state with an electron and another <(chi)over tilde>(0)(1). If R-parity is violated, these two neutralinos will decay, giving rise to distinctive signatures, which are identified and studied. (C) 1998 Published by Elsevier Science B.V.

Precise measurement of hyperfine intervals using avoided crossing of dressed states

We demonstrate a technique for precisely measuring hyperfine intervals in alkali atoms. The atoms form a three-level system in the presence of a strong control laser and a weak probe laser. The dressed states created by the control laser show significant linewidth reduction. We have developed a technique for Doppler-free spectroscopy that enables the separation between the dressed states to be measured with high accuracy even in room temperature atoms. The states go through an avoided crossing as the detuning of the control laser is changed from positive to negative. By studying the separation as a function of detuning, the center of the level-crossing diagram is determined with high precision, which yields the hyperfine interval. Using room temperature Rb vapor, we obtain a precision of 44 kHz. This is a significant improvement over the current precision of similar to1 MHz.

Sustainable biomass production for energy in selected Asian countries

This paper presents a synthesis of assessment of sustainable biomass production potential in six Asian countries-China, India, Malaysia, Philippines, Sri Lanka and Thailand, and is based on the detailed studies carried out in these countries under the Asian Regional Research Programme in Energy, Environment and Climate (ARRPEEC). National level studies were undertaken to estimate land availability for biomass production, identify and evaluate the biomass production options in terms of yield per hectare and financial viability, estimate sustainable biomass production for energy, and estimate the energy potential of biomass production in the six Asian countries. Sustainable biomass production from plantation is estimated to be in the range of 182.5-210.5, 62-310, 0.4-1.7, 3.7-20.4, 2.0-9.9 and 11.6-106.6 Mt yr(-1) for China, India, Malaysia, Philippines, Sri Lanka and Thailand, respectively. The maximum annual electricity generation potential, using advanced technologies, from the sustainable biomass production is estimated to be about 27, 114, 4.5, 79, 254 and 195 percentage of the total electricity generation in year 2000 in China, India, Malaysia, Philippines, Sri Lanka and Thailand, respectively. Investment cost for bioenergy production varies from US$381 to 1842 ha(-1) in the countries considered in this study; investment cost for production of biomass varies from US$5.1 to 23 t(-1). (C) 2003 Elsevier Ltd. All rights reserved.

Thermodynamics of CuAlO2 and CuAl2O4 and phase equilibria in the system Cu2O CuO-Al2O3

The standard Gibbs free energies of formation of CuAlO2 and CuAl2O4 were determined in the range 700° to 1100°C, using emf measurements on the galvanic cells (1) Pt,CuO +] Cu2O/CaO-ZrO2/O2,Pt; (2) Pt,Cu +] CuAlO2+] Al2O3/CaO-ZrO2/ Cu +] Cu2O,Pt; and (3) Pt,CuAl2O4+] CuAlO2+]Al2O3/CaO-ZrO2/O2,Pt. The results are compared with published information on the stability of these compounds. The entropy of transformation of CuO from tenorite to the rock-salt structure is evaluated from the present results and from earlier studies on the entropy of formation of spinels from oxides of the rock-salt and corundum structures. The temperatures corresponding to 3-phase equilibria in the system Cu2O-CuO-Al2O3 at specified O2 pressures calculated from the present results are discussed in reference to available phase diagrams.

Gibbs energy of formation of CuCrO4 and phase relations in the system Cu-Cr-O below 735 K

A solid state galvanic cell incorporating yttria-stabilized zirconia electrolyte and ruthenium(IV) oxide electrodes has been used to measure the equilibrium chemical potential of oxygen corresponding to the decomposition of CuCrO4 in the range 590–760 K. For the reaction CuO(tenorite) + CuCr2O4(spinel) + 1.5O2(g)→2CuCrO4(orth), ΔGXXX = −183540 + 249.6T(±900) J mol−1. The decomposition temperature of CuCrO4 in pure oxygen at a pressure of 1.01 × 105 Pa is 735(±1) K. By combining the results obtained in this study with data on the Gibbs energy of formation of CuCr2O4 and CuCrO2 reported earlier, the standard Gibbs energy of formation of CuCrO4 and the phase relations in the system Cu-Cr-O at temperatures below 735 K have been deduced. Electron microscopic studies have indicated that the decomposition of CuCrO4 to CuCr2O4 is topotactic.

Ferro electriclike and pyroelectric behavior of CaCu3Ti4O12 ceramics

A ferroelectriclike hysteresis loop was obtained at room temperature for CaCu3Ti4O12 (CCTO) ceramic. The remnant polarization and coercive field for 1100 °C/5 h sintered CaCu3Ti4O12 ceramics were 0.063 μC/cm2 and 195 V/cm, respectively. Remnant polarization increased while the coercive field decreased with increase in sintering temperature/duration, implying that these were microstructural dependent. The observation of the hysteresis loop for CCTO ceramic was corroborated by its pyroelectric behavior, and the pyroelectric current at room temperature was −0.0028 nA. These findings were attributed to the presence of mixed-valent Ti ions, apart from off center displacement of Ti ions in TiO6 octahedra.