Regulated plus and minus power supply using approximately 2DOF robust digital control

A plus and minus switching power supply is needed for many applications, for example an audio power supply. Since the changes in the output voltage of such loaded power amplifiers are large, the voltage of the power supply is also subject to large changes. In order to suppress these changes, a capacitor with a large capacity is usually used at the output end. If the capacities are reduced, the power supplies can be compacted. In this article, we show that the capacities can be reduced by using robust digital control using approximately 2DOF. The resulting controller is actually implemented on a digital signal processor (DSP). We show from experiments that the power supplies can be compacted by a robust controller.     

Complete dechlorination of 1-chloronaphthalene by electrochemical reduction with naphthalene radical anion as mediator

The possibility of electrochemical reduction for the complete dechlorination of toxic chlorinated aromatic compounds was investigated using 1-chloronaphthalene as a substrate. Sufficient current was obtained at the reduction potential of naphthalene rather than that of the substrate, and complete (>99.99%) dechlorination was achieved in tetra-n-butylammonium perchlorate/dimethylformamide solution in less than 1 h. The reaction was considered to proceed autocatalytically with the naphthalene radical anion, which was derived from the reduction of the initial dechlorination product (naphthalene) of the substrate, as mediator. The reaction rate was increased by the use of an excess of naphthalene at the start of the reaction, and complete dechlorination was possible without significant loss of current efficiency even if the water concentration was 0.3% v/v. The order of reaction of the mediated reduction was determined kinetically to be 0.5 for the substrate and 1 for naphthalene. Although the reaction of the naphthalene radical anion with 1-chloronaphthalene was very fast, it was considered to be the rate-determining step.     

Transformation of cellobiose to 3-ketocellobiose by the EDTA-treated Agrobacterium tumefaciens cells

Agrobacterium tumefaciens cells treated with EDTA were used as a biocatalyst for the transformation of cellobiose to 3-ketocellobiose. The effects of pH of the reaction medium and temperature on the reaction rate and the selectivity during the transformation by the cells were examined, and it was found that the optimum reaction conditions were pH 6 and 15 degrees C. The selectivity was about 0.8 under these conditions. The substrate concentration had no significant effect on the selectivity up to 300 mmol/I.     

Secondary calcium-binding parameter of Bacillus amyloliquefaciens alpha-amylase obtained from inhibition kinetics

Calcium is required for the stabilization of alpha-amylase because of primary binding (essential binding), but has been shown to inhibit hydrolytic catalysis due to secondary binding at the catalytic site in the enzyme. The role of calcium in the hydrolysis of soluble amylose by Bacillus amyloliquefaciens alpha-amylase was characterized using the equilibrium dissociation constant (K(m)) and k(cat) for the hydrolytic catalysis. The enzymatic hydrolysis was inhibited by a relatively high concentration of calcium ions ([Ca2+] > or = 2.0 mM). The dissociation constant (Km) was increased with increasing calcium ion concentration. Because k(cat) was practically constant at the high calcium concentration range, a competitive inhibition kinetic model was applied to calculate the inhibition parameters in terms of the secondary calcium binding to the alpha-amylase. The enthalpy and entropy changes for the secondary binding were 54.8 kJ/mol and 215 J/mol.K, respectively, and these values suggest a strong entropic affinity for the bivalent ion binding to the enzyme. The thermodynamical analysis clearly shows the conformational changes in this a-amylase during the primary and secondary calcium ion binding.     

Nutraceutical functions of sesame: a review

The results of recent food chemical and nutraceutical studies on the traditionally well-known health value of sesame are described, including some aspects of the utilization of sesame. The highly antioxidative activity of sesame oil was clarified and found to involve newly discovered lignans. The antiaging effect of sesame was elucidated to be due to the strong vitamin E activity caused by a novel synergistic effect of sesame lignans with tocopherols resulting from the inhibition of metabolic decomposition of tocopherols by sesame lignans. The specific inhibitory action of sesame lignans on Delta5 desaturase in polyunsaturated fatty acid synthesis was found in studies on the microbial production of polyunsaturated fatty acids. This effect of sesame lignans was extended to various effects on fatty acid metabolism involving lowering fatty acid concentration in liver and serum due to acceleration of fatty acid oxidation and suppression of fatty acid synthesis, and the controlling influence on the ratio of n-6/n-3 polyunsaturated fatty acids under excess intake of either n-6 or n-3 fatty acids in the diet. Sesame lignans lowered the cholesterol concentration in serum, especially in combination with tocopherol, due to the inhibition of absorption from the intestine and suppression of synthesis in the liver. Sesame lignans also showed other useful functions such as acceleration of alcohol decomposition in the liver, antihypertensive activity, immunoregulatory activities, anticarcinogenic activity, and others.     

Degradation of natural estrogen and identification of the metabolites produced by soil isolates of Rhodococcus sp. and Sphingomonas sp.

Five bacterial strains capable of utilizing 17β-estradiol (E2) and estrone (E1) were isolated from soil samples. Using their morphological and physiological features and 16S rDNA sequences, we classified these isolates into two groups: Group A (Rhodococcus sp. strains ED6, ED7, and ED10) and Group B (Sphingomonas sp. strains ED8 and ED9). All isolates used E2 and E1 as the sole carbon sources and showed high E1 and E2 degradation activities. In all strains, more than 50% of 0.8 mg of E1 or E2 was degraded in 4 mL of inorganic medium over 24 h, and 90% was degraded over 120 h. By incubating the resting ED8 cells with E2 and the meta-cleavage inhibitor 3-chlorocatechol, we identified two metabolites, 4-hydroxyestrone (4-OH-E1) and 4-hydroxyestradiol (4-OH-E2), and confirmed their identity using authentic chemicals. The 4-OH-E1 and 4-OH-E2 compounds were assumed to be intermediate metabolites formed before meta-cleavage, as they were not identified in culture without 3-chlorocatechol. Degradation of E2 by strain ED8 can be initiated by hydroxylation of the C-4 position, followed by meta-cleavage of the benzene ring. When strains ED8 degraded E2, we further identified hydroxy-E2, keto-E1 and -E2, and an additional degradation product via mass spectrometry. The presence of these compounds implied degradation through a second pathway initiated through an attack of the saturated ring.     

Polybrominated diphenyl ethers and organochlorines in archived northern fur seal samples from the Pacific coast of Japan, 1972-1998

The present study clearly indicated possible prolonged and chronic marine pollution by polybrominated diphenyl ethers (PBDEs) unless the international regulatory measures are reinforced substantially. Fat tissues of female northern fur seals (Callorhinus ursinus), collected at 10 time periods between 1972 and 1998 from the Pacific coast of northern Japan, were analyzed for PBDEs and organochlorine compounds (OCs). PCBs and DDTs were the predominant contaminants in the fur seal samples. PBDEs were detected in all the samples analyzed, the values ranging from 0.33 to 100 ng/g lipid wt. with predominance of BDE-47. The lowest PBDE levels were in the fur seals collected in 1972, with the peak concentration around 1991-1994 and then decreased to about 50% in 1997-1998. Compositions of higher brominated congeners increased since 1972, while some lower brominated congeners decreased, implying a change in the pattern of use, particularly the increased use of highly brominated diphenyl ethers during 1972-1998. In the meantime, PCB compositions in fur seals showed no temporal variation, suggesting a continuous input of PCBs into the marine environment in significant quantities. As peak concentrations of PBDEs occurred later than OCs, it is essential to follow up the patterns of PBDEs pollution that may be of great concern in the future. To our knowledge, this is the first report on the contamination by PBDEs in marine mammals from the Asia-Pacific waters.     

HEAT TRANSFER CONTROL IN QUIESCENT AIR WITH THERMAL GRADIENT BY MAGNETIZING FORCE UNDER BOTH GRAVITATIONAL AND NONGRAVITATIONAL FIELDS

ABSTRACT

Two-dimensional numerical computations were carried out to clarify the influence of magnetizing force on quiescent air with thermal gradient in a vertical cylindrical container under both gravitational and nongravitational fields. Several sizes and axial positions of a circular electric coil were tested so that the magnetizing force depended on the magnetic gradient. Under both gravitational and nongravitational fields, the convection was induced in quiescent air with thermal gradient by the magnetizing force; however, flow pattern and Nusselt number depended strongly on the size and the axial position of the circular electric coil in addition to the magnetic strength.     

In vitro inhibition of α-glucosidases and glycogen phosphorylase by catechin gallates in green tea

We investigated in vitro inhibition of mammalian carbohydrate-degrading enzymes by green tea extract and the component catechins, and further evaluated their inhibitory activities in cell cultures. The extract showed good inhibition toward rat intestinal maltase and rabbit glycogen phosphorylase (GP) b, with IC₅₀ values of 45 and 7.4 μg/ml, respectively. The polyphenol components, catechin 3-gallate (CG), gallocatechin 3-gallate (GCG), epicatechin 3-gallate (ECG), and epigallocatechin 3-gallate (EGCG), were good inhibitors of maltase, with IC₅₀ values of 62, 67, 40, and 16 μM, respectively, and EGCG also showed good inhibition toward maltase expressed on Caco-2 cells, with an IC₅₀ value of 27 μM. The ungallated catechins, such as catechin, gallocatechin (GC), epicatechin (EC), and epigallocatechin (EGC), showed no significant inhibition toward GP b, whereas the gallated catechins CG, GCG, ECG, and EGCG inhibited the enzyme, with IC₅₀ values of 35, 6.3, 27, and 34 μM. From multiple inhibition studies by Dixon plots, GCG appears to bind a new allostelic site, the indole inhibitor site. These gallated catechins also inhibited glucagon-stimulated glucose production dose-dependently, with IC₅₀ values ranging from 33 to 55 μM. Dietary supplementation with these gallated catechins or the green tea extract containing them, which inhibits both α-glucosidases and GP in vitro and in cell culture, would contribute to the protection or improvement of type 2 diabetes.     

Effects of methanol feeding methods on chimeric alpha-amylase expression in continuous culture of Pichia pastoris

The effects of two types of methanol feeding methods in a continuous culture of Pichia system on the cell growth and recombinant protein expression were studied using chimeric alpha-amylase as a model protein. With the feeding of methanol by a DO-stat method, the alpha-amylase concentration in the fermentation broth increased with decreasing dilution rate and reached 173 mg/l at a dilution rate of 0.013 h(-1), at which the maximum volumetric productivity of alpha-amylase was obtained. Although almost the same productivity was attained at 0.04 h(-1) with continuous methanol feeding, the alpha-amylase concentration was one third that compared with feeding by the DO-stat method, that is, 55 mg/l. Furthermore, at this dilution rate, the medium volume needed per unit time was three times that required when DO-stat was used. Therefore, continuous culture with methanol feeding by the DO-stat method may be a promising method for the production of recombinant proteins on an industrial scale by Pichia pastoris.