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  • 1
    Digitale Medien
    Digitale Medien
    Novel high-power and coherent semiconductor laser with a shaped unstable resonator (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2048-2050 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We describe a novel high power semiconductor laser that employs a shaped unstable resonator waveguide to maintain fundamental spatial mode operation at high power levels. We call this device the SHUR (shaped unstable resonator) laser. By photoetching and regrowth we locate a secondary, nonplanar antiguide, beneath the main part of the waveguide. The lasing mode couples to this secondary guide and experiences lateral antiguiding, which is the basis of the unstable resonator action. Prototype versions of the SHUR laser show a maximum pulsed output power of 770 mW per facet. The focused beam is dominated by a single lobe that contains 47% of the output power. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.113688
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  • 2
    Digitale Medien
    Digitale Medien
    High-power spatially coherent operation of unstable resonator semiconductor lasers with regrown lens trains (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1272-1274 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have obtained high-power spatially coherent operation in wide-stripe InGaAs/GaAs/AlGaAs semiconductor lasers using a monolithic unstable resonator [consisting of diverging lens elements incorporated above an asymmetric graded-index separate confinement heterostructure (AGRIN-SCH)]. The fabrication involves MOCVD regrowth after wet-chemical etching of lens-like patterns in a GaAs layer above the active region. Pulsed output powers of 175 and 490 mW have been obtained in 170- and 100-μm-wide lasers, respectively, with spatial coherence in the near field exceeding 60%. We observe good lateral mode discrimination up to 3.5 times threshold in the 100-μm stripes with a round-trip magnification of 6.4.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.107615
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  • 3
    Digitale Medien
    Digitale Medien
    Application of response-surface methodology to evaluate the optimum environmental conditions for the enhanced production of surfactin (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 358-363 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Response-surface methodology was applied to determine the effect of the fermentation process conditions, namely pH, temperature, rates of agitation and aeration, on surfactin production. The effects of the mutual interactions between these parameters were extensively studied to optimize the process conditions for the maximum production of surfactin. With a view to simultaneously reducing the number of experiments and obtaining the mutual interactions between the variables required for achieving the optimal experimental conditions, a 24 full-factorial central composite design followed by multi-stage Monte-Carlo optimization was employed for experimental design and analysis of the results. The optimum process conditions for the enhanced production of surfactin were as follows: pH = 6.755, temperature = 37.4 °C, agitation = 140 rpm and aeration = 0.75 vvm. Relative surfactin concentrations were denoted by the reciprocal of the critical micelle concentrations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002530050940
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  • 4
    Digitale Medien
    Digitale Medien
    Extended monod kinetics for substrate inhibited systems (1994)
    Springer
    Bioprocess and biosystems engineering 11 (1994), S. 185-188 
    Details
    ISSN: 1432-0797
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The biochemical route is identified to be one of the simplest and cheapest means by which valuable chemicals are being synthesized. Microorganisms play a vital role in carrying out these processes. However, the kinetic studies relevant to this process is scarce. Most often inhibition effects due to either cells or substrates or products affect the performance of such processes. This paper deals with the study of various model equations for substrate inhibition kinetics. An attempt has been made to study the applicability of various model equations for substrate inhibited systems by fitting their experimental data and evaluating various parameters including the standard deviations in each case. Finally, a new model has been brought out which gives the best fit for almost all the systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369628
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of urea on the production of 2,3-butanediol by K. oxytoca (1995)
    Springer
    Bioprocess and biosystems engineering 13 (1995), S. 49-50 
    Details
    ISSN: 1432-0797
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract This paper deals with the production of 2,3- butanediol by K. oxytoca in batch cultures. The effect of urea on various kinetic parameters was studied by replacing the ammonium salts in the medium with the corresponding nitrogen equivalent in the form of urea. The specific growth rate and the product yield in an unacclimatised batch culture were found to be 0.29 h−1 and 0.26 g·g−1 respectively. The acclimatised batch cultures on the other hand behaved similar to that grown using the original medium with a specific growth rate of 0.66 h−1 and the product yield of 0.345 g·g−1. However the cultures were unable to grow when urea was used both as the carbon and nitrogen source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00368766
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  • 6
    Digitale Medien
    Digitale Medien
    Studies on biodegradation of a mixture of toxic and nontoxic pollutant using Arthrobacter species (1996)
    Springer
    Bioprocess and biosystems engineering 15 (1996), S. 195-199 
    Details
    ISSN: 1432-0797
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The effect of a nontoxic easily degradable substrate, glucose, on the biodegradation of toxic pollutant, phenol, was studied in batch reactors using a phenol degrading culture (Arthrobacter species). The effect of glucose on phenol degradation was determined at different glucose concentrations. The effect of different inoculum on substrate removal in a phenol and glucose mixture was also studied. Results indicated that when a mixed substrate (phenol and glucose) was used, phenol acclimated population showed an initial preference for phenol and utilised glucose after phenol removal. However phenol degradation rate was reduced in the presence of glucose. It was also observed that phenol degradation was completely inhibited when the glucose concentration exceeds 2 g/l. The substrate removal pattern changed completely when inoculum was drawn from mixed substrate acclimatised culture. The glucose utilisation started immediately and the rate of glucose utilisation was not affected by the presence of phenol. The phenol degradation also started simultaneously. In presence of phenol only, the rate of phenol degradation for the culture acclimatised to mixed substrates was lower than that of phenol acclimatised culture. These results indicate that nontoxic substrate can affect the biodegradation of toxic pollutants is suitable and acclimatisation may be necessary for biodegradation of mixed substrate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369481
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  • 7
    Digitale Medien
    Digitale Medien
    Extended monod kinetics for substrate inhibited systems (1994)
    Springer
    Bioprocess engineering 11 (1994), S. 185-188 
    Details
    ISSN: 0178-515X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  The biochemical route is identified to be one of the simplest and cheapest means by which valuable chemicals are being synthesized. Microorganisms play a vital role in carrying out these processes. However, the kinetic studies relevant to this process is scarce. Most often inhibition effects due to either cells or substrates or products affect the performance of such processes. This paper deals with the study of various model equations for substrate inhibition kinetics. An attempt has been made to study the applicability of various model equations for substrate inhibited systems by fitting their experimental data and evaluating various parameters including the standard deviations in each case. Finally, a new model has been brought out which gives the best fit for almost all the systems. List of symbols C s g/l substrate concentration C s0 g/l threshold substrate concentration K I g/l inhibition constant K M, K s g/l half saturation constant of growth kinetics m, n – constants μ 1/h specific growth rate μmax 1/h maximal specific growth rate
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369628
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  • 8
    Digitale Medien
    Digitale Medien
    Biodegradation of phenol by arthrobacter and modelling of the kinetics (1995)
    Springer
    Bioprocess engineering 12 (1995), S. 227-229 
    Details
    ISSN: 0178-515X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  The toxic effects of phenol, a common constituent of many industrial effluents, necessitates treatment of the polluted streams. Biodegradation is a popular technique and enjoys many advantages. The degradation of phenol with Arthrobacter species is studied in batch cultures and it is observed that the substrate is inhibiting. The fit of various models, including the model proposed earlier by us [17], to the experimental data is studied. The model is used to fit available data in literature, which unfortunately is very sparse. In all the cases the present model fits the data best. List of Symbols S mg/l substrate concentration S 0 mg/l threshold substrate concentration K I mg/l inhibition constant K m , K S mg/l half saturation constant of growth kinetics m, n constants μ 1/h specific growth rate μ m 1/h maximal specific growth rate X mg/l biomass concentration at time t X 0 mg/l initial biomass concentration Abbreviations MTCC Microbial Type Culture Collection IMTECH Institute of Microbial Technology
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369495
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  • 9
    Digitale Medien
    Digitale Medien
    Optimisation of lignin peroxidase production from Phanerochaete chrysosporium using response surface methodology (1999)
    Springer
    Bioprocess engineering 21 (1999), S. 465-468 
    Details
    ISSN: 0178-515X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The ligninolytic white rot fungus Phanerochaete chrysosporium, holds good promise as a biological treatment tool due to its ability to produce the lignin peroxidase enzyme which has the potential to degrade a wide variety of hazardous compounds. The effective application of this technique requires optimisation of the process variables to maximise the enzyme production. Response surface methodology was applied to determine the effects of glucose, ammonium tartarate and ferrous sulphate and their mutual interactions on lignin peroxidase production. With a view to simultaneously reducing the number of experiments and obtaining more information on the mutual interactions between the variables, a 23 full-factorial central composite experimental design was adopted. The experimental data were fitted to a second order polynomial equation using multiple regression analysis and also analysed by appropriate statistical methods. Solving the regression equation using the multi-stage monte-carlo optimisation techniques, the optimum process conditions for enhanced production of lignin peroxidase were obtained as: glucose 0.9728 kg/m3, ammonium tartarate 0.288 kg/m3, and ferrous sulphate 0.097 kg/m3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00009085
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  • 10
    Digitale Medien
    Digitale Medien
    Effect of urea on the production of 2,3-butanediol by K. oxytoca (1995)
    Springer
    Bioprocess engineering 13 (1995), S. 49-50 
    Details
    ISSN: 0178-515X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  This paper deals with the production of 2, 3-butanediol by K. oxytoca in batch cultures. The effect of urea on various kinetic parameters was studied by replacing the ammonium salts in the medium with the corresponding nitrogen equivalent in the form of urea. The specific growth rate and the product yield in an unacclimatised batch culture were found to be 0.29 h-1 and 0.26 g.g-1 respectively. The acclimatised batch cultures on the other hand behaved similar to that grown using the original medium with a specific growth rate of 0.66 h-1 and the product yield of 0.345 g.g-1. However the cultures were unable to grow when urea was used both as the carbon and nitrogen source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00368766
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