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  • 1
    Electronic Resource
    Electronic Resource
    An efficient enzymatic preparation of 4(S)-hydroxy-1 (R)-acetoxy-cyclopent-2-ene by using new yeast isolate (1992)
    Springer
    Biotechnology letters 14 (1992), S. 785-788 
    Details
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The Enzymatic enantioselective hydrolysis of prochiral 1,4-cyclopent-2-ene diacetate (3) was carried out using yeast and fungal cultures from inhouse culture collection. Of all the cultures tested, the yeast sp. NCIM 3574 gave 4 (S)-hydroxy-1 (R)- acetoxy-cyclopent-2-ene (4b) in high optical yields (99% ee).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029139
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  • 2
    Electronic Resource
    Electronic Resource
    The Problem of Liquid Sodium-Amalgams (1932)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 36 (1932), S. 2474-2482 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150339a009
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of coherent electromagnetic radiation on the ultrafast electron dynamics of laser excited bulk photoconductors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3215-3218 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze the role of coherent terahertz radiation on the ultrafast electron dynamics of laser excited photoconductors. Generation of electromagnetic radiation is included within the framework of the usual hot carrier transport theory. A Monte Carlo scheme is used to study the resulting changes in the nonequilibrium electronic energy and transient drift velocity. Our results reveal a density dependent decrease in both quantities, due to reductions in the internal electric fields caused by radiative energy outflow. At densities above 2×1017 cm−3, we obtain a decrease in the transient velocity and expect delays in the onset of phonon emission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354593
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  • 4
    Electronic Resource
    Electronic Resource
    Studies of high field conduction in diamond for electron beam controlled switching (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4781-4787 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental studies on a vertical metal-diamond-silicon switch structure have been conducted for potential pulsed power applications. Both the dc current-voltage characteristics and the transient switching response have been measured for a range of voltages. With a 1 μm diamond film, the switch has been seen to withstand electric fields up to 1.8 MV/cm. Our results show a polarity dependence which can be associated with current injection at the asymmetric contacts. Polarity effects were also observed in the presence of e-beam excitation, and arise due to nonuniform carrier generation near the diamond-silicon interface. Our switching transients were seen to follow the shape of the e-beam for a negative bias at the silicon substrate. For positive voltage values exceeding about 80 V however, the switch is seen to go into a persistent-photocurrent mode. This effect is a result of free carrier trapping within diamond and is enhanced by the double injection process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352090
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanisms controlling temperature dependent mechanical and electrical behavior of SiH4 reduced chemically vapor deposited W (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5625-5629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of deposition temperature on growth, composition, structure, adhesion properties, stress, and resistivity of chemically vapor deposited W deposited purely by SiH4 reduction of WF6 are discussed. At lower deposition temperatures, due to incomplete Si reduction reaction, a small amount of Si is incorporated in the film. This elemental Si in W is responsible for the observed high stresses and high resistivities over a wide temperature range. With the increase in the deposition temperature, the conversion of incorporated Si as well as the initial Si reduction are taking place, stimulating increased grain growth and thereby relieving stress and reducing resistivity. The optimum values for stress and resistivity are achieved around 500 °C, as Si content is at its minimum. At higher temperatures the reaction between residual Si and W, is the prime cause of resistivity increase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346974
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  • 6
    Electronic Resource
    Electronic Resource
    Non-self-limiting nature of silicon reduction of WF6 in cold wall systems (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1428-1441 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper addresses the kinetics and related mechanisms of non-self-limiting nature of Si reduction of WF6 in cold wall systems for the first time. The growth of such films in low-pressure chemical-vapor deposition (LPCVD) and ultrahigh vacuum (UHV) systems is compared. Both systems produce non-self-limiting, uniform, controllable, nonporous films. The growth is controlled by process parameters such as the wafer temperature and WF6 concentration at the wafer surface. The order of the Si reduction reaction is 0.5 in the concentration of WF6. The tungsten films deposited in the LPCVD system contaminated with water vapor are thicker than the films grown in the UHV system even when the temperature is below 450 °C. Such thicker films are produced as a result of the formation of an amorphous W-O layer. From the thermodynamic considerations, the origin of W-O layer is attributed to a parallel reaction between water vapor, WF6, and substrate Si. The beneficial role played by the W-O layer is that it prevents any volume shrinkage of the converted layer and restricts lateral encroachment. In the absence of such a layer as in the case of the UHV system, severe volume shrinkage and encroachment are observed. A theoretical model together with physical mechanisms explaining the non-self-limiting phenomenon are proposed. The mechanism suggests that a fine-grained W structure surrounded by a W-O layer, formed in the LPCVD system, assists faster out-diffusion of Si through the tungsten films compared to the UHV system. The higher values of the diffusion coefficient for Si out-diffusion through films grown in the LPCVD system as compared with the UHV system support this mechanism. The out-diffused Si is substituted to W by reduction reaction to complete the film growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351265
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  • 7
    Electronic Resource
    Electronic Resource
    Studies of electron-beam penetration and free-carrier generation in diamond films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1568-1574 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental observations of the energy-dependent electron-beam penetration in type II-A natural diamond are reported. The experimental data are compared with results obtained from numerical Monte Carlo simulations, and the results are in very good agreement. The results also reveal that a threshold energy of about 125 keV is necessary for complete penetration for a 35 μm sample. It is found that over the 30–180 keV range, the energy dependence of the penetration depth and total path length exhibits a power-law relation. Monte Carlo simulations have also been performed to investigate the excess carrier-generation profiles within diamond for a set of incident e-beam energy distributions. The simulation results demonstrate the feasibility of tailoring the internal source function, and hence influencing the diffusion currents, the internal electric fields, and charge injection through the contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354829
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  • 8
    Electronic Resource
    Electronic Resource
    Microscopic calculations of density and field-dependent electronic trapping via attractive Coulomb centers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1810-1817 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We examine the dynamics of electronic transitions into the shallow states of attractive impurity centers in GaAs through numerical simulations. The molecular dynamics based formulation circumvents the difficulty of having to evaluate "sticking functions,'' enables accurate computations of the phase-space distribution function, and allows microscopic treatment of both the carrier-phonon and carrier-carrier phenomena on an equal footing. Energy dependent trapping rates with and without the presence of external electric fields are obtained, and we consider situations involving both singly- and doubly-charged impurity centers. We show that initial trapping is reduced as a result of free-carrier screening, and hence detailed knowledge of both the trap density and the electronic concentration is necessary for a meaningful prediction of the trapping behavior. Finally, we also focus on modifications caused by electron-electron scattering, and find trapping enhancements due to the additional energy loss channel created by Auger-like phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354786
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  • 9
    Electronic Resource
    Electronic Resource
    Intersubband relaxation dynamics in ternary/binary quantum wells: Role of the electron-optical phonon interaction (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3827-3835 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ensemble Monte Carlo calculations of the intersubband dynamics in binary-ternary double-heterostructure systems are presented. The presence of a ternary alloy has been explicitly incorporated to account for complexities arising from the multimode nature of phonons in real heterostructures. Electronic scattering rates are derived as a function of energy and quantum-well width for both confined and interface modes on the basis of a continuum model. Results of Monte Carlo simulations yield an intersubband time constant that is in reasonable agreement with the experimental value, but only when details of the phonon modes and their dispersion, spreading of the electronic wave functions due to poor confinement, and the phonon amplification effects are comprehensively included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350872
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  • 10
    Electronic Resource
    Electronic Resource
    Monte Carlo study of minority electronic transport in InGaAs: Effects of phonon mode splitting and dynamically screened electron-hole interactions (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4322-4324 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an ensemble Monte Carlo simulation of electronic transport in p-type In0.53Ga0.47As. The effects of mixed phonon modes and of dynamically screened electron-hole scattering on the velocity-field characteristics are examined. Our results show that a two phonon model yields smaller velocities at low fields and higher values beyond the intervalley transfer threshold. The dynamic screening leads to a field dependent velocity enhancement at moderate carrier densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347164
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