Lowest-order axial and ring mode lasing in confocal quasi-stadium laser diodes

We investigated the lasing modes of quasi-stadium laser diodes that have confocal cavity geometries, with stripe electrode contacts formed either along the cavity axis or a diamond-shaped trajectory. It was clearly demonstrated that by using narrow electrode contact patterns of 2 μm width, the lowest-order axial and ring modes were excited selectively. On the other hand, the second-lowest-order axial and ring modes were excited by using broad electrode patterns of 14 μm width. Experimentally obtained far-field patterns for lasers with broad and narrow electrode contact patterns agree very well with the simulation results obtained using an extended Fox-Li mode calculation method.     

Formation of damascenone derived from glycosidically bound precursors in green tea infusions

Damascenone is well-known for its potent flavour with an extremely low odour threshold. Several glycosidically bound precursors of damascenone have been isolated from several plants, but little is known about their occurrences in green tea infusions. In this work, three major glycosidic precursors of damascenone, 9-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1a), 9-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2a), and 3-O-β-d-glucopyranosyl-3-hydroxy-7,8-didehydro-β-ionol (2b) were isolated and identified in green tea infusions, and the stereochemistries at C-3 and C-9 positions of aglycone parts of the three glycosidic precursors were determined as (3S, 9R)-1a, (3R, 9R)-2a, and (3R, 9R)-2b, respectively. Compounds 1a, 2a, and 2b as well as 3-O-β-d-glucopyranosyl-megastigma-6,7-dien-3,5,9-triol (1b) were hydrolysed to form damascenone in a model system with strong acidic conditions (pH 2.0) and at high temperature (90 °C). In contrast to hydrolysis of 2a and 2b, more damascenone was transformed from 1a and 1b. Furthermore, the β-d-glucosyl moiety at the C-3 position gave a higher dehydration rate from megastigma-6,7-dien-3,5,9-triol to 3-hydroxy-7,8-didehydro-β-ionol than compound 1a carrying the sugar residue at C-9 position. Interestingly, the four glycosidic precursors of damascenone were not hydrolysed to give damascenone under slightly acidic conditions (pH 5.4 and 120 °C for 10 min), but they could be transformed to damascenone in the presence of green tea infusions even under the equal conditions.     

Molecular identification of Anisakis type I larvae isolated from hairtail fish off the coasts of Taiwan and Japan

Anisakid nematodes are known to cause the zoonotic disease, anisakiasis, through the consumption of raw or undercooked fish. The parasites most frequently associated with the disease in humans are categorized as Anisakis type I, which comprise several species of the genus Anisakis. The larvae show primitive forms and lack the detailed morphological characteristics required for precise species identification. Thus, molecular characterization is necessary for determining the species of Anisakis type I larvae and acquiring important clinical and epidemiological information. In this study, we isolated Anisakis type I larvae from hairtail fish caught off the coasts of Taiwan and Japan. The ribosomal DNA (rDNA) internal transcribed spacer (ITS) region was sequenced, and restriction fragment length polymorphism (RFLP) analyses using HinfI and HhaI was carried out for species identification. Most larvae isolated from hairtail caught in Taiwan were Anisakis typica (84%), while those isolated from hairtail caught in Japan were almost exclusively identified either as Anisakis simplex sensu stricto (65%) or Anisakis pegreffii (33%). This is the first report of A. typica in fish obtained from Taiwan. Our results shed the light on the epidemiology of Anisakis type I larvae, which is a potential cause of human anisakiasis in Taiwan and Japan.     

Model comparison for Escherichia coli growth in pouched food

We recently studied the growth characteristics of Escherichia coli cells in pouched mashed potatoes (Fujikawa et al., J. Food Hyg. Soc. Japan, 47, 95-98 (2006)). Using those experimental data, in the present study, we compared a logistic model newly developed by us with the modified Gompertz and the Baranyi models, which are used as growth models worldwide. Bacterial growth curves at constant temperatures in the range of 12 to 34 degrees C were successfully described with the new logistic model, as well as with the other models. The Baranyi gave the least error in cell number and our model gave the least error in the rate constant and the lag period. For dynamic temperature, our model successfully predicted the bacterial growth, whereas the Baranyi model considerably overestimated it. Also, there was a discrepancy between the growth curves described with the differential equations of the Baranyi model and those obtained with DMfit, a software program for Baranyi model fitting. These results indicate that the new logistic model can be used to predict bacterial growth in pouched food.     

Modeling Staphylococcus aureus growth and enterotoxin production in milk

Staphylococcus aureus growth and its enterotoxin production in sterilized milk were modeled with a modification of a new logistic model recently developed by us. The modified model and the Baranyi model described the early exponential phase of a growth curve more accurately than the previous model, at constant temperatures from 14 to 36.5 degrees C. The amount of toxin in milk increased linearly with time from the time the cell population reached about 10(6.5) cfu/ml. The rate of toxin production linearly increased at temperatures between 14 and 32 degrees C. From parameter values obtained at the constant temperatures, the model successfully predicted bacterial growth in the milk at a varying temperature. For toxin level estimation, we postulated that the rate of toxin production might be regulated with the temperature after the cell concentration reached 10(6.5) cfu/ml; the time point when the cell concentration reached that value was predicted with the modified growth model. Introduction of a correction factor in the toxin estimation successfully predicted the toxin level in milk at a varying temperature. These results showed that this prediction system consisting of the modified model and the toxin production algorithm might be a useful tool for modeling bacterial growth and its metabolite production in liquid foods.     

Establishment and evaluation of event-specific quantitative PCR method for genetically modified soybean MON89788

A novel real-time PCR-based analytical method was established for the event-specific quantification of a GM soybean event MON89788. The conversion factor (C(f)) which is required to calculate the GMO amount was experimentally determined. The quantitative method was evaluated by a single-laboratory analysis and a blind test in a multi-laboratory trial. The limit of quantitation for the method was estimated to be 0.1% or lower. The trueness and precision were evaluated as the bias and reproducibility of the relative standard deviation (RSD(R)), and the determined bias and RSD(R) values for the method were both less than 20%. These results suggest that the established method would be suitable for practical detection and quantification of MON89788.     

System of personal identification by using tactile stimuli

This paper proposes a personal identification system that uses tactile stimuli. Recently, scientists have been conducting research in biometrics using biomedical information. However, there is the problem that biomedical information is unchangeable. For example, if a thief steals another user’s biomedical information, that person has no information to register. Due to the problems of sight information and unchangeable biomedical information, we propose a solution that uses the sense of tactile stimuli. Tactile information is difficult to steal and relies on human memory, which is unchangeable. This paper proposes a system that uses a pattern formed by a tactile stimuli time series instead of a password number as the identification key. We also discuss the results of an identification experiment and a memory property experiment. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Effects of oxygen supply condition and specific biofilm interfacial area on phenol removal rate in a three‐phase fluidized bed bioreactor

The effects of oxygen supply conditions and specific biofilm interfacial area on the phenol removal rate in a three‐phase fluidized bed bioreactor were evaluated. The experimental data were well‐explained by the semi‐theoretical equation based on the assumption that the reaction rate follows first‐order reaction kinetics with respect to oxygen and zero‐order one with respect to phenol. Two cases, biological reaction as rate‐controlling step and oxygen absorption as rate‐controlling step, were both explicable by this semi‐theoretical equation. The maximum volumetric phenol removal rate was 27.4 kg·m^?3·d^?1.