1,721,050 research outputs found
Optimization of a heterogeneous reaction system for the production of optically active D-amino acids using thermostable D-hydantoinase
No full textA thermostable D-hydantoinase from Bacillus stearothermophilus SD-1 was previously mass-produced by batch cultivation of the recombinant E. coil harboring the gene encoding the enzyme (Lee et al., 1997). In this work, we attempted to optimize the process for the production of N-carbamoyl-D-p-hydroxyphenylglycine, which is readily hydrolyzed to D-p-hydroxyphenylglycine under acidic conditions, from 5-(4-hydroxyphenyl)hydantoin using the mass-produced D-hydantoinase. In an effort to overcome the low solubility of the substrate, enzyme reaction was carried out in a heterogeneous system consisting of a high substrate concentration up to 300 g/L. In this reaction system, most of substrate is present in suspended particles. Optimal temperature and pH were determined to be 45 degrees C and 8.5, respectively, by taking into account the reaction rate and conversion yield. When the free enzyme was employed as a biocatalyst, enzyme loading higher than 300 unit/g-substrate was required to achieve maximum conversion. Use of whole cell enzyme resulted in maximum conversion even at lower enzyme loadings than the free enzyme, showing 96% conversion yield at 300 g/L substrate. The heterogeneous reaction system used in this work might be applied to the enzymatic production of other valuable compounds from a rarely water-soluble substrate. (C) 1998 John Wiley & Sons
Use of methicillin and ampicillin mixture as a selective pressure in the cultivation of recombinant E. coli
No full textAmpicillin was rapidly degraded by an extracellular beta-lactamase, and was therefore ineffective to isolate plasmid-harboring cells in the cultivation of recombinant E. coli for the production of thermostable D-hydantoinase. An effective way of preventing the degradation of ampicillin, methicillin was employed as a beta-lactamase inhibitor. A mixture of methicillin and ampicillin was observed to effectively function as a selective pressure, and consequently plasmid stability and enzyme productivity of recombinant E. coli were highly maintained
A design criterion for the vibration isolation of a marine diesel generator set
No full textThe resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the engine operation range. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and elastic potential energy index stored in the mounts. A case study is also presented in which a diesel engine generator, which had an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis of the test model was performed by using a single mass 6 degree of freedom system. Actual measurements of mechanical vibration of the engine and its foundation onboard were carried out, which showed the importance of including the flexibility of the engine support structure in the model
The mechanical behavior of optical fiber sensors embedded within the smart composite materials
No full textDynamic behaviour and transmission characteristics of structure-borne noise of marine diesel generator with resilient rubber mounts and elastic foundation
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Vibration isolation of a marine diesel generator set
No full textThe resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the operation range of the engine. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and an index of elastic potential energy stored in the mounts. A case study is also presented in which a diesel engine generator, which has an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis involved a single rigid body with 6 degrees of freedom. Actual measurements of mechanical vibration of the engine and its foundation were carried out onboard, and showed the importance of including the flexibility of the engine support structure in the model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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