Relationship between axial compression strength and longitudinal microvoid size for PAN-based carbon fibers

Single fiber axial compression strength has been determined on a series of polyacrylonitrile-based carbon fibers using micro compression test at a gage length of about 10 μm and a detailed analysis has been made on the distribution and the fiber diameter dependence of the axial compression strength. The length of the unsupported region of carbon layer stack calculated from the axial compression strength was well comparable with the longitudinal length of the microvoids determined with small-angle X-ray scattering. This indicated that the fracture of carbon fibers is initiated from the buckling of the unsupported region of carbon layer stack which is formed where the microvoid adjoins it. The tensile and the axial compression strengths of the carbon fibers showed different relationships between the coefficient of variation and the average. This indicated that the tensile and the axial compression strengths are governed by different factors although they showed a correlation. Comparison has also been made between the longitudinal length of the microvoid and the microvoid sizes perpendicular to the fiber axis.     

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.     

Anthracene‐Containing Binaphthol Chromophores for Light‐Emitting Diode (LED) Fabrication

Non‐crystalline anthracene‐containing binaphthol chromophores were synthesized, characterized, and used in the fabrication of organic light‐emitting diodes (OLEDs). Specifically, the target molecules were 2,2′‐dihexyloxy‐1,1′‐binaphthol‐6,6′‐bisanthracene ( BA1 ) and 2,2′‐dimethoxyy‐1,1′‐binaphthol‐6,6′‐bisanthracene ( BA2 ). Molecules BA1 and BA2 provide amorphous solids, as determined by their glass‐transition temperature (T_g) measured by differential scanning calorimetry (DSC). Efficient multilayer OLEDs containing BA1 and BA2 were fabricated by evaporation techniques. Differences in the electroluminescence frequencies of these devices suggests that the degree of alkoxide substitution controls the mobility within the binaphthol material, and therefore the recombination region in the device. Compound BA2 can also be used to dope CBP ((4,4′‐bis(carbazol‐9‐yl)biphenyl)) in the fabrication of highly efficient OLEDs.     

Cyclic batch biological wastewater treatment

The possibility of using cyclic batch operations to replace conventional continuous stirred tank reactors for biological wastewater treatment is considered.Using mathematical models the efficiencies of cyclic batch, fed batch and continuous stirred tank processing, are compared. A cyclic batch is shown to have a large kinetic advantage, especially when the final substrate concentration is low. A graphical method is developed from theory which makes use of either an experimental batch kinetics curve or a suitable kinetic model. From the graphical calculation the total volume requirement and the optimal retained volume can be determined.     

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.     

On‐Line Estimation and Control of Apparent Extract Concentration in Low‐Malt Beer Fermentation

Apparent extract concentration, which is defined as the apparent total dry matter concentration in the media calculated by measurement of the specific gravity, is a very important variable in the process of beer and low‐malt beer fermentation. In the present study, ethanol formation and the residual apparent extract concentration were estimated using the CO₂ concentration in the exhaust gas. A simple mathematical model involving the CO₂ production rate, temperature and cell activity was constructed and a novel system for on‐line estimation and control of apparent extract concentration was developed. In the control system for the residual apparent extract concentration, cell activity was estimated by monitoring the differences in actual CO₂ production rate. In addition, the future trajectory of the apparent extract concentration was predicted. The degree of fermentation, i.e., the residual apparent extract concentration trajectory, was controlled by raising or lowering the temperature, taking into account the estimated cell activity at that time. The residual apparent extract concentration reached the target value at a given time, using the on‐line estimation of apparent extract concentration and temperature control.     

Lipid Oxidations in Ordinary and Dark Muscles of Fish: Influences on Rancid Off-odor Development and Color Darkening of Yellowtail Flesh During Ice Storage

We investigated the role of lipid oxidation in the development of a rancid off‐odor in the early stage of ice storage in both ordinary and dark muscles of cultured yellowtail (Seriola quinqueradiata). The total lipid hydroperoxide content and thiobarbituric acid‐reactive substances (TBARS) of the dark muscle were significantly higher (P < 0.01) than those of the ordinary muscle during 2 d of ice storage. The increase in the metmyoglobin content of the dark muscle was accompanied by gradual darkening of the muscle color during ice storage. To distinguish the changes in odor characteristics of the muscles, sensory evaluation was carried out. Slight changes in the intensity of 7 different odors were noted in the ordinary muscles, and there was a significant increase in the overall, fishy, spoiled, and rancid smells of the dark muscle during 2 d of ice storage. No correlation was found between the total content of lipid hydroperoxide and the odor intensities in ordinary muscle; however, there was a significant correlation between the total lipid hydroperoxide content and rancid off‐odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related to meat darkening and development of the rancid off‐odor during the early stage of ice storage.     

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.     

Interactions between Lactobacillus kefiranofaciens and Saccharomyces cerevisiae in mixed culture for kefiran production

Since a positive effect on the growth and kefiran production of Lactobacillus kefiranofaciens was observed in a mixed culture with Saccharomyces cerevisiae, the elucidation of the interactions between L. kefiranofaciens and S. cerevisiae may lead to higher productivity. Hence, the microbial interaction of each strain was investigated. Apart from the positive effect of a reduction in the amount of lactic acid by S. cerevisiae, a positive effect of S. cerevisiae on the growth and kefiran production of L. kefiranofaciens in a mixed culture was observed. Various experiments were carried out to study this effect. In this study, the observed increase in capsular kefiran in a mixed culture with inactivated S. cerevisiae correlated well to that in an anaerobic mixed culture. Differences in capsular kefiran production were observed for different initial S. cerevisiae concentrations under anaerobic conditions. From these fermentation results, it was concluded that the physical contact with S. cerevisiae mainly enhanced the capsular kefiran production of L. kefiranofaciens in a mixed culture. Therefore, in an anaerobic mixed culture, this direct contact resulted in higher capsular kefiran production than that in pure culture.     

A penny-shaped crack in piezoelectrics: resolved

This paper reconsiders the problem of a penny-shaped crack in a piezoelectric medium under uniform mechanical as well as electric loadings applied at infinity (mode I). The analysis is based on the general solution of three-dimensional piezoelasticity, which is represented by four quasi-harmonic displacement functions. It is shown that these harmonics can be expressed in terms of two potentials of a simple layer. By using the previous results in potential theory, exact solution of the mode I crack is obtained. In particular, the solution is complete and in terms of elementary functions.