Interaction between an edge dislocation and a semi-circular cut on straight boundary

Interaction between a semi-circular cut on straight boundary and an edge dislocation, placed on the axis of symmetry, in a semi-infinite medium is investigated on the basis of Airy's stress function. The solution is constructed by considering the relation between the real edge dislocation and the imaginary one. Numerical calculations are worked out in some detail and these results are presented graphically in order to clarify the effect of above mentioned interaction.     

Development of mesopores during activation of poly(vinylidene fluoride)-based carbon

Mesoporous carbon films were prepared from poly(vinylidene fluoride) through liquid-phase dehydrofluorination (DHF)-treatment, carbonization at a high temperature and activation in carbon dioxide gas. The adsorption capacity of the resultant carbon was investigated by using nitrogen and methylene blue as adsorbates. The maximum adsorption capacity was obtained for the activated carbon prepared by applying a slight extent of DHF-treatment. The growing process of the pores in this carbon during activation was considered based on the changes of mass, pore volume and surface area. In order to increase the pore size in the activated carbon, it was essential to increase the pore size in the carbon before activation. The application of a slight extent of DHF-treatment was effective to increase the pore size in the carbon before activation.     

Large‐scale parallel finite‐element analysis using the internet: a performance study

This paper describes a parallel finite‐element system implemented using the domain decomposition method on a cluster of remote computers connected via the Internet. This technique is also readily applicable to a grid computing environment. A three‐dimensional finite‐element elastic analysis involving more than one million degrees of freedom was solved using this system, and a good approximate solution was obtained with high parallel efficiency of over 90% using remote computers located in three different countries. Copyright © 2005 John Wiley & Sons, Ltd.     

Fabrication of Transparent Tellurite Glasses Containing Potassium Niobate Crystals by an Incorporation Method

To fabricate transparent oxide glasses containing ferroelectric KNbO₃ crystals, a new method in which KNbO₃ particles are directly incorporated into TeO₂─K₂O─Nb₂O₅ glasses has been developed. Transparent TeO₂-based glasses containing KNbO₃ crystals with a diameter of ∼ 10 μm have been first successfully fabricated by adjusting temperature and time for incorporation. A small difference in the refractive indexes, n , between TeO₂-based matrix glasses ( n = 2.0) and incorporated KNbO₃ crystals ( n = 2.21) is a significant reason for the transparency. This new method is applicable for the fabrication of new transparent glasses containing other functional materials with high refractive indexes.     

Dynamics and control of an activated sludge process as a mixed culture system

One of the difficulties encountered in the operation of an activated sludge process is the phenomenon of bulking sludge. In an activated sludge process which is composed of a completely mixed aeration tank and a sedimentation vessel, the dynamic behavior of the system can be analyzed using a mathematical model. The model developed here is based on the kinetics and settleability of the combination of floc-forming sludge and bulking sludge. The operating conditions that cause the bulking phenomenon are clarified on the phase plane. It is also shown that a type of nonlinear state feedback regulator makes the system stable.     

Enhancement of ethanol production by promoting surface contact between starch granules and arming yeast in direct ethanol fermentation

The specific ethanol production rate of raw starch by arming yeast cells displaying alpha-amylase and glucoamylase increased significantly when the cells and starch granules settled together. The specific ethanol production rate also increased when the size distribution of starch granules was almost same as that of the yeast cells. These results indicate that the surface contact between starch granules and yeast cells is important for increasing the apparent specific activity of alpha-amylase, which was the rate-limiting factor of the direct fermentation.     

Physiological analysis of yeast cells by flow cytometry during serial-repitching of low-malt beer fermentation

At the end of beer brewing fermentation, yeast cells are collected and repitched for economical reasons. Although it is generally accepted that the physiological state of inoculated yeast cells affects their subsequent fermentation performance, the effect of serial-repitching on the physiological state of such yeast cells has not been well clarified. In this study, the fermentation performance of yeast cells during serial-repitching was investigated. After multiple repitchings, the specific growth rate and maximum optical density (OD(660)) decreased, and increases in isoamyl alcohol, which causes an undesirable flavor, and residual free amino acid nitrogen (FAN) concentrations were observed. The physiological state of individual cells before inoculation was characterized by flow cytometry using the fluorescent dyes dehydrorhodamine 123 (DHR) and bis-(1,3-dibutylbarbituric acid) trimethine oxonol (OXN). The fluorescence intensities of DHR, an indicator of reactive oxygen species (ROSs), and OXN, which indicates membrane potential, gradually increased as the number of serial-repitching cycles increased. Fluorescence intensity correlated strongly with cell growth. The subsequent fermentation performance can be predicted from this correlation.     

Expression of C-terminal repeat region of peptidoglycan hydrolase of Lactococcus lactis IL1403 in methylotrophic yeast Pichia pastoris

The C-terminal region of the peptidoglycan hydrolase (CPH) of Lactococcus lactis IL1403 produced intracellularly in Escherichia coli was able to attach to the surface of cells of Lactobacillus casei NRRL B-441, Bacillus subtilis 168, E. coli XL1-blue and Saccharomyces cerevisiae IFO0216. Therefore, this domain is a suitable fusion partner for the adhesion of proteins to cell surfaces. The production of cell-surface adhesive proteins using this domain in Pichia pastoris is particularly attractive, because this organism has better capability to allow the correct folding of the recombinant proteins than prokaryotic hosts. However, when this domain is produced in this yeast, its cell-surface binding activity may be limited by glycosylation. In this study, therefore, we constructed a CPH mutant (CPHM) devoid of the potential N-glycosylation sites by site-directed mutagenesis. CPHM was successfully expressed extracellularly in P. pastoris (GS115) using the methanol inducible AOX1 promoter with an alpha-mating factor signal sequence, whereas the native CPH was not produced in this host. Western blot analysis revealed that the apparent molecular size of CPHM was 18 kDa greater than that of CPH produced in E. coli (32 kDa), which is attributed to O-glycosylation. However, CPHM produced in P. pastoris was capable of binding to the cell surfaces despite its modification by the yeast, and its dissociation rate constant from the surface of L. casei NRRL B-441 cells was 3.5-fold lower than that of CPH produced in E. coli. These results demonstrate the applicability of the constructed domain (CPHM) for the production of cell-surface adhesive proteins in P. pastoris.     

Knowledge-based design and operation of bioprocess systems

Almost twenty years have passed since the first applications of the knowledge-based approach to bioprocess operations were reported. During this period, approaches such as fuzzy logic, artificial neural network modeling, expert systems and genetic algorithms have been extensively studied and successfully used in the design and control of various bioprocesses. The recent development of these approaches in the design and operation of biological processes is summarized and reviewed, especially focusing on the studies reported in biochemical engineering journals.