Development of a pumped-storage power station model for power system stability study

Since a pumped-storage power station generally is located far from the load center, it frequently encounters problems of power system stability, especially at the pumping operation mode. Capacity of units constructed in recent years is as large as a few hundred megawatts, and water head is as high as 500 m. The period of water pressure oscillation of such a high head station becomes longer and closer to power system swing. Under such condition the output is affected by the conduit system dynamics and becomes different from analytical results using the classical model which assumes constant torque or output during power system disturbance at the pumping operation mode. This paper describes the newly developed simplified pumped-storage plant model based on the elastic theory of the conduit system and the complete characteristics of the turbine, which has necessary accuracy to be analyzed because it is connected to bulk power system. Comparison with the real plant test result verifies the validity of the developed model. The interaction with power system is examined by linearized analysis and simulation study.     

Calcium signals in helper T cells after interaction with antigen-specific and antigen-nonspecific B cells

By confocal fluorescence microscopy we have studied the rises of the intracellular free calcium ion concentration ([Ca2+]i) in helper T cells (KLH-specific, I-Ak-restricted Th1 cells, 28-4) after interaction with antigen-specific and antigen-nonspecific B cells (antigen-presenting cells). Antigen-specific and antigen-nonspecific B cells were prepared by the preincubation of TNP (trinitrophenol)-specific B cell hybridomas (TP67.21 I-Ak) with TNP-conjugated KLH and KLH alone, respectively. Calcium signals in Th1 cells (28-4) were induced by antigen-specific B cells one hundred times more efficiently as those by antigen-nonspecific B cells. Herbimycin A, a tyrosine kinase inhibitor, suppressed the former signals but not the latter. These results indicated that tyrosine phosphorylation was involved in the antigen processing of antigen-specific B cells but not in the processing of antigen-nonspecific B cells.     

High-resolution 3-D shape integration of dentition and face measured by new laser scanner

Face and dentition were measured using a high-resolution three-dimensional laser scanner to circumvent problems of radiation exposure and metal-streak artifacts associated with X-ray computed tomography. The resulting range data were integrated in order to visualize the dentition relative to the face. The acquisition interval for dentition by laser scanner was 0.18 mm, and complicated morphologies of the occlusal surface could be sufficiently reproduced. Reproduction of occlusal condition of upper and lower dentitions was conducted by matching the surface of the occlusal impression record with upper dentition data. To integrate dentition and face, a marker plate interface was devised and adopted on the lower dental cast or by the subject directly. Integration was performed by matching both sets of interface data. Reproduction of the occlusal condition and integration of the dentition and face were accomplished and visualized satisfactorily by computer graphics. The integration accuracy was examined by changing the attachment angle of the marker plate, and the marker plate attached at 45 degrees showed the smallest error of 0.2 mm. The current noninvasive method is applicable to clinical examination, diagnosis and explanation to the patient when dealing with the physical relationship between face and dentition.     

The filamentous fungusmortierella alpina,high in arachidonic acid

Arachidonic acid is not available readily, although it is widely distributed in animal tissue. We found that in some strains ofMortierella alpina, arachidonic acid accounted for 68.5–78.8% of the total fatty acids. This is more than twice the arachidonic acid content of any organism previously reported. The content of arachidonic acid per dry cell weight was about 25%. Our findings offer a method for the efficient isolation of arachidonic acid in large amounts.     

Formation of cleavage products by autoxidation of lycopene

The cleavage products formed by autoxidation of lycopene were evaluated in order to elucidate possible oxidation products of lycopene in biological tissues. Lycopene solubilized at 50 μM in toluene, aqueous Tween 40, or liposomal suspension was oxidized by incubating at 37°C for 72 h. Among a number of oxidation products formed, eight products in the carbonyl compound fraction were identified as 3,7,11-trimethyl-2,4,6,10-dodecatetraen-1-al, 6,10,14-trimethyl-3,5,7,9,13-pentadecapentaen-2-one, acycloretinal, apo-14′-lycopenal, apo-12′-lycopenal, apo-10′-lycopenal, apo-8′-lycopenal, and apo-6′-lycopenal. These correspond to a series of products formed by cleavage in the respective 11 conjugated double bonds of lycopene. The maximal formation of acycloretinal was 135 nM in toluene, 49 nM in aqueous Tween 40, and 64 nM in liposomal suspension. Acycloretinoic acid was also formed by autoxidation of lycopene, although its formation was lower in the aqueous media than in toluene. The pig liver homogenate had the ability to convert acycloretinal to acycloretinoic acid, comparable to the conversion of all-trans-retinal to all-trans-retinoic acid. These results suggest that lycopene might be cleaved to a series of apolycopenals and short-chain carbonyl compounds under the oxidative conditions in biological tissues and that acycloretinal is further enzymatically converted to acycloretinoic acid.     

Quantitative analysis of swarming pulsive microdischarges by using very low frequency voltage application

Partial discharge (PD) degradation phenomena is one of the most important factors to decide the performance and the lifetime of the high voltage apparatus. During PD degradation tests of an epoxy specimen with an internal void, PD often change to a large number of very small PD known as swarming pulsive microdischarges (SPMD). Because the appearance of SPMD is concerned with the degradation of the insulating materials, the insulation diagnosis with the detection of SPMD becomes possible. However, SPMD cannot be detected with the conventional PD Detector because the PD magnitude of SPMD is too small. The computer-aided partial discharge analyzing system (CAPDAS) has been developed to detect and analyze the SPMD. Furthermore, a new PD parameter, the SPMD ratio has been introduced for quantitative analysis of SPMD. In this paper, the time variation of SPMD characteristics of a CIGRE Method-II specimen are investigated by using the CAPDAS. Further, the effect of the frequency of the applied voltage on SPMD is also investigated at 60 Hz and a very low frequency of 0.1 Hz. As a result, the comparison of PD magnitudes measured at 60 Hz with those at 0.1 Hz enables a quantitative analysis of SPMD characteristics to be possible by using only the conventional PD detector.     

ATM video signal multiplexer with congestion control function

ATM (asynchronous transfer mode) is a key technology in the construction of the broadband ISDN. In the ATM network, encoded video signals with burstiness are divided into short fixed length packets called cells, and can be transferred efficiently maintaining high quality by the statistical multiplexing of cells. However, in the congestion state, an appropriate congestion control is needed to avoid deterioration of transfer quality due to the loss of cells. This paper proposes a new congestion control scheme and evaluates characteristics of an ATM video signal multiplexer with the proposed congestion control function. In this paper, the amount of encoded video information per frame is approximated by the auto-regressive model, and the characteristics are evaluated by computer simulation. Particularly, the obtained circuit gain, the effect of congestion control and the optimum cell length are shown from the results of evaluation. Nearly double circuit gain can be obtained by the statistical multiplexing of cells and a throughput improvement of nearly 10% can be obtained by introducing the proposed congestion control in the multiplexing of cells.     

The effect of GABAergic system activity on hyperthermia-induced seizures in rats

Developing rats were given GABA antagonists and agonist before electrical seizure discharges were induced by heating the brain of a rat with infra-red rays. The thresholds for the GABA antagonist groups were significantly lower than that for the control, and the threshold for the GABA agonist group was significantly higher than that for the control. These results support the hypothesis that reduced GABAergic system activity underlies febrile seizures.