Improvement of power system stability by high-speed power control of adjustable speed machines

Large-capacity adjustable speed machines (ASMs) at pumped storage power stations have been put into full operation and their operating characteristics have been highly evaluated from the viewpoint of power system operation. The output power (input power) of ASMs can be controlled very quickly by applying a vector control scheme to the excitation control. This quick responsive feature of ASMs can make it possible to improve the stability of the neighbor subpower system. For improvement of transient stability, the output power of ASMs is reduced very quickly in order to control the acceleration of neighbor generators during and after transmission line faults. For improvement of dynamic stability, the output power of ASMs is modulated in accordance with the stabilizing signals detected from the swing of generator rotor or the power flow fluctuation on the transmission line. This paper describes the design concepts and method of control system for improving the transient and dynamic stability and proposes a power system stabilizing control system. The effects of the proposed stabilizing control system have been verified by a power system simulator. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(2): 27–36, 1997     

Hydriding and electrochemical characteristics of a homogeneous amorphous Mg2Ni-Ni composite

Hydriding and electrochemical characteristics of a homogeneous amorphous Mg₂Ni-Ni composite prepared by ball-milling of Mg₂Ni alloy with Ni (70 wt.% vs. Mg₂Ni) were investigated. It was found that the Mg₂Ni-Ni composite absorbed hydrogen to the amount of 4.0 wt.% vs. Mg₂Ni [2.4 wt.% vs. (Mg₂Ni+70 wt.% Ni)] at a high rate under a hydrogen pressure of 3 MPa at 30°C. Furthermore, this alloy exhibited an extremely high discharge capacity of 1082 mAh g(Mg₂Ni)⁻¹ [636 mAh g(Mg₂Ni+70 wt.% Ni)⁻¹] at 30°C, which exceeded the theoretically calculated value of 999 mAh g(Mg₂Ni)⁻¹ on the basis of Mg₂NiH₄ for crystalline Mg₂Ni.     

Electrochemical characteristics of an amorphous Mg0.9V0.1Ni alloy prepared by mechanical alloying

Electrochemical characteristics of an amorphous MgNi alloy with Mg partially substituted by V were investigated. A Mg_0.9V_0.1Ni alloy prepared by mechanical alloying (MA) exhibited much better cycle life than MgNi alloy. It was found that the partial substitution of Mg in MgNi with V could suppress the formation of Mg(OH)₂ on the alloy surface during the charge–discharge cycling in alkaline solution. This may have unveiled an important factor to improve cycle life of the Mg-based alloy for use in nickel–hydrogen batteries.     

Combined Treatment with Curcumin and Ferulic Acid Suppressed the Aβ-Induced Neurotoxicity More than Curcumin and Ferulic Acid Alone

Alzheimer’s disease (AD) is a neurodegenerative disease that leads to progressive cognitive decline. Several effective natural components have been identified for the treatment of AD. However, it is difficult to obtain conclusive evidence on the safety and effectiveness of natural components, because a variety of factors are associated with the progression of AD pathology. We hypothesized that a therapeutic effect could be achieved by combining multiple ingredients with different efficacies. The purpose of this study was thus to evaluate a combination treatment of curcumin (Cur) and ferulic acid (FA) for amyloid-β (Aβ)-induced neuronal cytotoxicity. The effect of Cur or FA on Aβ aggregation using thioflavin T assay was confirmed to be inhibited in a concentration-dependent manner by Cur single or Cur + FA combination treatment. The effects of Cur + FA on the cytotoxicity of human neuroblastoma (SH-SY5Y) cells induced by Aβ exposure were an increase in cell viability, a decrease in ROS and mitochondrial ROS, and repair of membrane damage. Combination treatment showed an overall higher protective effect than treatment with Cur or FA alone. These results suggest that the combined action mechanisms of Cur and FA may be effective in preventing and suppressing the progression of AD.     

Transformation products of bisphenol A by a recombinant Trametes villosa laccase and their estrogenic activity

A Trametes villosa laccase, produced as a recombinant protein in Aspergillus oryzae, was purified to an electrophoretically homogeneous state and employed in studies on the metabolism of bisphenol A. Structural analysis of the bisphenol A reaction products by the enzyme indicated that the dimer, trimer, tetramer, pentamer, and hexamer of bisphenol A with C? C and/or C? O bonds between phenol moieties, were formed as the result of successive oxidative‐condensation. The reaction mixture also contained oligomers fragments, each with phenol molecules, suggesting the occurrence of cleavage of the formed oligomers to release 4‐isopropenylphenol. A luciferase reporter assay using COS‐7 cells revealed that both the soluble and insoluble fractions of the bisphenol A reaction products had no estrogenic activity even at rather high concentrations. Copyright © 2004 Society of Chemical Industry     

Loop power system control by high-speed phase shifter

Recently, power systems have become larger and more complex. Particularly, the looping of power systems is becoming highly desirable to improve the stability. The main features of such looped power systems are: (i) comparatively fewer losses; and (ii) improved angle stability as well as voltage stability. However, these systems have demerits, such as, in case of route off fault in a loop power system, power disturbances increase more and more, etc. If these demerits are overcome, the loop power systems are going to be more beneficial. In an attempt to obtain a solution to such problems, this paper describes several results of applying a high-speed phase shifter in the control system of a loop power system.     

High performance in refolding of Streptomyces griseus trypsin by the aid of a mutant of Streptomyces subtilisin inhibitor designed as trypsin inhibitor

The platelet glycoprotein (GP) IIb/IIIa receptor antagonist appears to reduce the need for revascularization after coronary angioplasty. However, since the effect of GP IIb/IIIa receptor antagonist on the in-stent neointimal thickening has not been clarified, we examined it in the canine model. The beagle dogs were assigned to the control (n=7) or the GP IIb/IIIa receptor antagonist FK633 group (n=7). FK633 was administered by subcutaneous osmotic pumps (0.2 mg. kg-1. h-1) and an intravenous bolus injection (1 mg/kg) before stenting. A coil stent was implanted in the left circumflex coronary arteries. The platelet aggregation capability was significantly (<5%) and consistently reduced by FK633 except for the mild elevation (10% to 30%) on the next day of stenting. Hearts were excised 3 months after stent implantation. The area of intima and media and the area stenosis were obtained from the sections of the stented arteries. The area of intima and media and the area stenosis (1.3+/-0.2 mm2, 41.8+/-7.5% and 1.3+/-0.2 mm2, 33.9+/-6.7% in the FK633 and the control group, respectively) were not different between the groups. We conclude that, although GP IIb/IIIa antagonist FK633 prevented the platelet aggregation significantly and consistently, it could not prevent the neointimal thickening after stent implantation in canine coronary artery.     

Relationship between the morphological changes of Japanese cedar (Cryptomeria japonica) pollen grains and the release of major allergens from the pollen

Release of major allergens (Cry j 1, Cry j 2) from Japanese cedar (C. japonica) pollen grains treated with high pressure was investigated. C. japonica pollen grains crushed by high pressure treatment using FRENCH Pressure Cell Press released greater amounts of major allergens, particularly Cry j 2, compared to those without crush. This suggests that the cytoplasm of C. japonica pollen grains contains more Cry j 2 than previously reported. The effect of nasal fluid on the release of major allergens from C. japonica pollen grains was analyzed in vitro. Nasal fluid from patients with nasal allergy remarkably increased the release of major allergens from pollen grains, compared to controls, and the amount of Cry j 1 was greater than Cry j 2. Further studies revealed that nasal fluid affects the outer wall of pollen grains, where Cry j 1 is located, to a greater extent than its effect on the cytoplasm, where Cry j 2 is located.     

In vitro effects of CINC/gro, a member of the interleukin-8 family, on interleukin-6 secretion by rat posterior pituitary cells

We investigated the effects of CINC/gro on IL-6 secretion by rat posterior pituitary cells. CINC/gro immunoreactivity was already detected in 1-h conditioned medium of normal posterior pituitary cells, and it increased significantly in a time-dependent manner during the first 24 h of culture. This immunoreactivity could be induced by TNF-alpha in a dose-dependent manner. On the other hand, CINC/gro stimulated IL-6 secretion by posterior pituitary monolayer cultures in a concentration dependent manner. Thus, CINC/gro significantly (P < 0.01) increased the secretion of IL-6 within 13 h of incubation, and this effect continued throughout 24 h of incubation. The stimulatory effect of 100 ng/ml CINC/gro on IL-6 secretion was completely blocked by 24-h incubation with 100 ng/ml IAP. These data demonstrate a new biological activity for CINC/gro in the posterior pituitary system.     

Topochemical Photodimerization of 4-(3-Oxo-3-phenyl-l-propenyl)benzoic Acid and Its Esters

The photodimerization behaviors of 4-(3-oxo-3-phenyl-1-propenyl)benzoic acid (1) and its esters (2–7) in the crystalline state are investigated. These crystals, except that of the phenyl ester (7), dimerize photochemically to yield the corresponding cyclobutane derivatives in a typical topochemical fashion. Head-to-head type cyclobutane derivatives are obtained from crystals of the acid and ethyl ester (1 and 3), whereas head-to-tail type derivatives are formed from the other ester crystals (2, 4, 5, and 6). The temperature dependences of these reaction behaviors and the configurations of the photoproducts are correlated with the molecular arrangement in the reactant crystals. Reversible or irreversible behavior of as-formed dimer crystals, derived from 2 or 4 crystals, is interpreted in terms of accumulated strain energy in the course of the topochemical process.