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In this paper we consider a damping control of low-frequency oscillations in an electric power system. On the basis of the hypothesis that an auto-parametric resonance model can explain a power oscillation, we propose a new model for a robust damping control, by which the system maintains stability even if some auto-parametric resonance happens. With this model, we can express a parametric variation of a principal oscillation mode and a class of uncertainties which cover neglected dynamics. Since the model has a certain structure of uncertain parameters, we design a robust controller via µ-synthesis. The robust controller which can be obtained from the presented design strategy has the property that the control performances are more sophisticated in comparison to controllers designed with other existing methods based on the H∞ control. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 42–49, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10069

Background The impulse oscillometry is increasingly used for assessing the oscillatory mechanics of the respiratory system. The within-breath behaviour of the oscillatory mechanics in chronic obstructive pulmonary disease (COPD) is a well-known physiological feature. The purpose of this study was to develop a new approach for assessing this feature using impulse oscillometry. Methods The oscillatory mechanics were assessed by a commercially available impulse oscillometry device. The respiratory system resistance (Rrs) and reactance (Xrs) were measured during tidal breathing in patients with COPD (n=39) and healthy subjects (n=5). Selected data, the Rrs at 5 Hz (R5), Rrs at 20 Hz (R20), Xrs at 5 Hz (X5), and resonant frequency of Xrs (Fres) every 0.2 s, were extracted from the device. These data were divided into eight time fractions during the respiratory cycle to form averaged respiratory phases. Results The time courses of the R5 and X5 were notably dependent on the respiratory cycles in patients with COPD, while there was little such dependency in healthy subjects. Irrespective of respiratory phase, R5 and Fres increased, and X5 fell to a more negative level in patients with COPD in a severity-dependent fashion. The increase in the R5 and negative level in the X5 were more prominent in the middle of the expiratory phase. The severity dependence in the R20 was relatively small compared with that in the R5. Conclusions The results of this study suggest that impulse oscillometry can assess the within-breath behaviour of the oscillatory mechanics with high temporal resolution, which may be helpful for evaluating the severity of COPD. Further studies are needed to reveal which biomarkers obtained with this approach would be suitable for evaluating the airway obstruction., Article summary Article focus To develop a new approach for assessing the within-breath behaviour of the oscillatory mechanics in patients with chronic obstructive pulmonary disease (COPD) using impulse oscillometry. Key messages Impulse oscillometry provides a means of evaluating within-breath behaviour of oscillatory mechanics at high temporal resolution. Since it is possible that the oscillatory flow resistance varies markedly within a breathing cycle in patients with COPD, differences between the inspiratory and expiratory phases must be taken into account. Strengths and limitations of this study The within-breath behaviour of the oscillatory mechanics can be assessed by a commercially available impulse oscillometry device. Owing to the small number of subjects, the findings related to the pathophysiology of COPD were very limited.

Background The forced oscillation technique (FOT) is a simple method for assessing the oscillatory mechanics of the respiratory system. The oscillatory properties, respiratory system resistance (Rrs) and reactance (Xrs), are calculated from the oscillatory pressure/flow relationship. Although the FOT has been a well-established technique, some detailed experimental conditions would be different among institutions. Methods We evaluated whether time lags produced by the experimental conditions such as different positions of the sensors can affect the accuracy of the FOT. If the position of the pressure sensor is different from the flow sensor, a time lag may occur in the measurements. The effect of the time lag was studied by numerical analysis. Results Rrs was estimated to be increased and Xrs decreased with an increase in the time lag, especially at a high oscillatory frequency of the medium-frequency range (5-35 Hz). At the high-frequency range (10-500 Hz), Rrs and Xrs were strikingly different in the values of the time lag. Conclusion A time lag between the oscillatory pressure and flow may be involved in the accuracy of the FOT, suggesting that it needs to be minimized or compensated for with signal processing. Researchers should pay attention to such detailed experimental conditions of the FOT apparatus.

In order to obtain 1-β-D-arabinofuranosylcytosine derivatives with better antitumor effect, 12 kinds of saturated fatty acyl groups were introduced at the N4-position of 1-β-D-arabinofuranosylcytosine. The presence of a great excess of water and about two-fold equivalents of carboxylic anhydride was found to be most desirable for selective N4-acylation. This simple method of one-step N4-acylation should be generally applicable to cytosine nucleosides and a variety of carboxylic anhydrides.

In connection with our studies on the roles of heteroatoms (N, S, O) in solvolytic reactions, the effects of the heteroatoms in ring openings of epoxides, methylenecyclohexane epoxide (4), 3-methylene epoxides of tetrahydropyran (5), N-methylpiperidine (6) and tetrahydrothiopyran (7), were examined. All epoxides were synthesized according to Corey's procedure from the corresponding cyclanones. Ring-opening reactions of epoxides were carried out as follows : a) Reduction with lithium aluminum hydride, b) reduction with lithium metal in ethylenediamine, c) reduction with borane-lithium borohydride, d) acetic acid-catalyzed opening, e) hydrochloric acidcatalyzed opening, and f) reaction of 7 with Lewis acid (boron trichloride). No appreciable effects of heteroatoms were observed in the reactions a and b for 4, 5, and 6. The reactions c, d, and f for 7 resulted in the predominant formation of ring-contracted 5-membered ring derivatives. These results strongly suggest that an enormous amount of participation, particularly by the sulfur atom, is also involved in the ring-opening reactions of epoxides as well as that observed in solvolysis.

The participation of acetate and propionate to the biosynthesis of aureothin, one of the metabolites of Streptomyces thioluteus and S. luteoreticuli containing an aryl-nitro group has been proved by the use of 13C tracer technique and 13C-NMR spectrometry.

Cytosine arabinoside is one of the most reliable drugs for treatment of leukemia and lymphoma, and is also used for the treatment of solid tumours as a component of their combination treatments. In order to find a better congener of this drug, numerous derivatives have been widely examined for their antitumour activity. This presentation deals with the antitumour effect of a series of N4-acyl derivatives of cytosine arabinoside.