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  • 1
    Electronic Resource
    Electronic Resource
    Wet oxidation of AlAs grown by molecular beam epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2717-2719 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 1 μm thick n-type GaAs layer with Si doping density of 1×1017/cm3 and a 1000 A(ring) thick undoped AlAs layer was subsequently grown by molecular beam epitaxy on the n+ GaAs substrate. To perform selective oxidation of the AlAs layer, the wafer was oxidized in N2 bubbled H2O vapor ambient at 370 °C, 400 °C, and 430 °C, each for 3 hours. It is found that the defect-free selective oxidation of AlAs is very critically dependent on oxidation temperature. Both GaAs and AlAs layers were oxidized at the oxidation temperature of 430 °C, and some defects were found by scanning electron microscopy (SEM) on the surface oxidized at 370 °C. Oxidation was, however, stopped at the AlAs/GaAs interface at the oxidation temperature of 400 °C, and no defects were found on the surface. By the slow ramp rate (5 mV/sec) high frequency (100 kHz) C-V measurement, the fixed charge density was estimated to be about 1×1011/cm2 for the metal-oxide-semiconductor (MOS) capacitor fabricated from the oxidized sample at 400 °C. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112545
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  • 2
    Electronic Resource
    Electronic Resource
    Raman spectra of indium nitride thin films grown by microwave-excited metalorganic vapor phase epitaxy on (0001) sapphire substrates (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 937-939 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report Raman scattering study on InN single crystalline films with wurtzite form. The films were grown on sapphire substrates by microwave-excited metalorganic vapor phase epitaxy and optical phonon properties of the films were investigated. Both A1(LO) and E2(2) peaks, which are related to a longitudinal optical phonon mode and a doubly degenerated mode, respectively, were observed at 596 cm−1 with the full width of 36 cm−1 at half maximum intensity and at 495 cm−1 with the full width of 20 cm−1 at half maximum intensity. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116949
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanism of the enzymatic hydrolysis of cellulose: Effects of major structural features of cellulose on enzymatic hydrolysis (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 22 (1980), S. 177-199 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The susceptibility of cellulose to enzymatic hydrolysis is affected by the structural features of cellulosic materials. It has been suggested that the crystallinity and surface area of cellulose fibers are the most important structural features in this regard. This study investigated in depth the relative effects of these two structural features upon the enzymatic hydrolysis of cellulose and the change of the structural parameters of cellulose during the course of hydrolysis. It was found that the hydrolysis rate is mainly dependent upon the fine structural order of cellulose which can best be represented by the crystallinity rather than the simple surface area. Monitoring the changes in the structural parameters during the course of reaction showed that surface area is not a major limiting factor that slows hydrolysis in its late stages as has been suggested. This information concerning structural features is used to elucidate the mode of action of cellulase.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260220113
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetic studies of enzymatic hydrolysis of insoluble cellulose: Analysis of the initial rates (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 24 (1982), S. 2383-2406 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study was conducted on the kinetics of enzymatic hydrolysis of pure insoluble cellulose using unpurified culture filtrate Trichoderma reesei, with the emphasis on the initial reaction period. The initial hydrolysis rate and extent of enzyme (soluble protein)adsorption, either apparent or initial, were evaluated under various experimental conditions. It has been found that the various mass-transfer steps do not control the overall hydrolysis rate and that the hydrolysis rate is mainly controlled by the surface reaction step promoted by the adsorbed enzyme. It has also been found that the initial hydrolysis rate strongly depends on the initial extent of soluble protein adsorption and the effectiveness of the adsorbed soluble protein to promote the hydrolysis. The initial extent of soluble protein adsorption, in turn, is related to the initial cellulose concentration, enzyme concentration, and specific surface area of cellulose, whereas the effectiveness of the initially adsorbed soluble protein to promote the derived to interrelate these parameters without resorting to the Michaelis-Menten kinetics. The present result appear to imply that the role of enzyme-substrate complex formation should not be ignored in deriving a mechanistic kinetic model for enzymatic hydrolysis of cellulose.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260241107
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  • 5
    Electronic Resource
    Electronic Resource
    Structural modification of lignocellulosics by pretreatments to enhance enzymatic hydrolysis (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 157-172 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this work an evaluation was made of a wide variety of single and multiple pretreatment methods for enhancing the rate of enzymatic hydrolysis of wheat straw. A multiple pretreatment consisted of a physical pretreatment followed by a chemical pretreatment. The structural features of wheat straw, including the specific surface area, crystallinity index, and lignin content, were measured to understand the mechanism of the enhancement in the hydrolysis rate upon pretrement. It has been found that, in general, multiple pretreatments were not promising, since the hydrolysis rates rarely exceeded those achieved by single pretreatments. Ballmilling pretreatment was found to be effective in increasing the specific surface area and decreasing the crystallinity index. Treatment with ethylene glycol was highly effective in increasing the specific surface area, in addition to a high degree of delignification. Peracetic acid pretreatment was highly effective in delignifying substrate. Among multiple pretreatments, those involving peracetic acid treatment generally had lower crystallinity indices and lignin content values. The relationship between the hydrolysis rate and the set of structural features indicated that an increase in surface area and a decrease in the crystallinity and lignin content enhance the hydrolysis; the specific surface area is the most influential of the structural features, followed by the lignin content.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260250113
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetic studies of enzymatic hydrolysis of insoluble cellulose: (II). Analysis of extended hydrolysis times (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 939-966 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of enzymatic hydrolysis of pure insoluble cellulose by means of unpurified culture filtrate of Trichoderma reesei was studied, emphasizing the kinetic characteristics associated with the extended hydrolysis times. The changes in the hydrolysis rate and extent of soluble protein adsorption during the progress of reaction, either apparent or intrinsic, were investigated. The hydrolysis rate declined drastically during the initial hours of hydrolysis. The factors causing the reduction in the hydrolysis rate were examined; these include the transformation of cellulose into a less digestible form and product inhibition. The structural transformation can be partially explained by changes in the crystallinity index and surface area. The product inhibition was caused by the deactivation of the adsorbed soluble protein by the products, which essentially represents the so-called “un-competitive” inhibition. The kinetics of β-glucosidase were also studied. The result has shown that the action of β-glucosidase is competitively inhibited by glucose. It has been found that the integrated form of the initial rate expression cannot be used in predicting the progress of reaction because the digestibility of cellulose changes drastically as the hydrolysis proceeds, and that the rate expression for enzymatic hydrolysis of cellulose cannot be simplified or approximated by resorting to the pseudo-steady-state assumption. A mechanistic kinetic model of cellulose hydrolysis should include the following major influencing factors: (1)mode of action of enzyme, (2) structure of cellulose, and (3) mode of interaction between the enzyme and cellulose molecules.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260250406
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  • 7
    Electronic Resource
    Electronic Resource
    Evaluation of organosolv processes for the fractionation and modification of corn stover for bioconversion (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 572-581 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Corn stover was pretreated for compositional fractionation and structural modification for maximum conversion of carbohydrate to soluble sugars. The process scheme consisted of three steps: (1) mild prehydrolysis in dilute sulfuric acid, (2) delignification with various organosolv solvents, and (3) enzymatic hydrolysis in an agitated bead reactor. Prehydrolysis of corn stover can be achieved at temperatures ranging from 95 to 120°C, which is a much milder condition than must be applied to wood. Various organosolv solvents, including several alcohols with acid as catalyst, ethylene glycol, and its derivatives, and amines were used for delignification of the prehydrolyzed corn stover. Aromatic alcohols were found to be more effective in solubilizing the prehydrolyzed corn stover than were the aliphatic alcohols. Butanol was the most effective among the aliphatic alcohols; on the other hand, phenol was the best among the aromatic alcohols. Ethylene glycol, methylcellosolv, and ethylcellosolv were effective in solubilizing the prehydrolyzed corn stover but not for enhancing the enzymatic hydrolysis. Various amines achieved delignification at the mild temperature of 95°C, but they tended to solubilize substantial amounts of carbohydrate in addition to lignin. n-Butylamine was effective in enhancing the conversion during enzymatic hydrolysis; it was a good delignifying agent as well as one that achieved a concomitant swelling of the cellulose structure. The low enzymic conversion (20-37%) of prehydrolyzed and solvent-extracted corn stover that was achieved implies that lignin is not the only major barrier for enzymatic hydrolysis. Modification of cellulose structure also should be accomplished to achieve a high degree of conversion. Enzymatic hydrolysis in the agitated bead system increased the rate and extent of conversion of corn stover substantially compared to systems without beads.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260290506
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic studies of enzymatic hydrolysis of insoluble cellulose: Derivation of a mechanistic kinetic model (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 2707-2733 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comprehensive mechanistic kinetic model for enzymatic hydrolysis of insoluble cellulose has been synthesized by combining models for several key aspects which have been derived independent of each other. The model takes into account the major contributing factors: the nature of the enzyme system, the structure of cellulose, and the mode of interaction between the enzyme and cellulose molecules. It consists of a set of simultaneously occurring ordinary differential equations with ten kinetic constants. All of the kinetic constants have been determined independently by carrying out critically designed experiments, and they appear in the comprehensive model without any arbitrary manipulations. The governing equations of the model have been numerically simulated by means of the computer subroutine CSMP III. The model predicts the progress of hydrolysis of cellulose over a wide range of experimental conditions and hydrolysis times reasonably well. The model can even be applied to predict the progress of hydrolysis for intensively pretreated cellulose with a minor adjustment. The applicability of the model for the actual process development is also discussed.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260251115
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  • 9
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    Wet oxidation of AlAs grown by molecular beam epitaxy (1994)
    American Institute of Physics
    Details
    Publication Date: 1994-11-21
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Raman spectra of indium nitride thin films grown by microwave‐excited metalorganic vapor phase epitaxy on (0001) sapphire substrates (1996)
    American Institute of Physics
    Details
    Publication Date: 1996-08-12
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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