Semiconfocal optical disk readout with one linear-spread beam

A novel, to our knowledge, optics pickup for semiconfocal optical disk is proposed. Five tracks are imaged simultaneously by use of one linear-shaped beam that extends over the tracks in the radial direction with the focusing and the tracking position controlled. We also show how the cross talk between tracks is eliminated automatically. The approximately diffraction-limited width of the beam and the small-signal detector elements make semiconfocal detection possible in the tangential direction.     

Effects of amrinone on left ventricular function following open heart surgery--analysis with left ventricular pressure volume loops

The effects of Amrinone on cardiac function soon after extracorporeal circulation (ECC) were studied in 5 patients including mitral valvuloplasty, VSD closure, Fontan operation and coronary AV fistel closure. In all patients, left ventricular volume load decreased postoperatively. To evaluate the efficacy, we obtained left ventricular pressure-volume loops (P-V loop) before and after ECC and after intravenous administration of Amrinone (1 mg/kg) following ECC. P-V loops were produced by measuring left ventricular pressure using a Miller catheter which was retrogradely advanced from the ascending aorta into the left ventricle and by measuring left ventricular diameter to calculate left ventricular volume with Teichholtz' formula. Although no apparent difference of Emax was recognized before and after ECC, Emax increased from 3.2 +/- 2.5 mmHg/cm3 to 5.9 +/- 4.7 mmHg/cm3 after the administration of Amrinone. The left ventricular "systolic" pressure-volume area (PVA) which is the sum of stroke work (SW) and elastic potential energy decreased from 34.4 +/- 16.4 gm to 30.9 +/- 17.8 gm after Amrinone. No difference was also recognized in left ventricular end-diastolic pressure. Ejection fraction increased from 50 +/- 17.5% to 56.1 +/- 17.3%. These results suggested that Amrinone could improve the left ventricular function without prominent change in myocardial oxygen consumption immediately after open heart surgery.     

On‐off discrete control of series capacitors for power system stability with torsional oscillation countermeasure

Application of controlled series capacitors with antiparallel thyristor combination across the capacitor segment is a new and promising countermeasure for enhancement of power system stability. The line reactance can be directly controlled by the controlled series capacitors; hence, it is very effective to apply the capacitors for damping power system disturbances. However, the segmented series capacitors may cause subsynchronous resonance (SSR) that can lead to turbine‐generator shaft failure and electrical instability at oscillation frequencies lower than normal system frequency as well as the conventional capacitor may cause. In this paper, we describe the following. (1) The response of turbine‐generator shaft torque is analytically discussed when the number of inserted series capacitors in the power system is changed. (2) It is proposed for SSR countermeasure that the control system will be designed to avoid the number of series capacitor segments which may cause SSR in addition to selecting better on‐off timing of series capacitors. (3) The effects of the proposed countermeasures are confirmed by the results of EMTP simulations using both simplified two‐mass shaft model and detailed five‐mass shaft model of turbine‐generator. © 1999 Scripta Technica, Electr Eng Jpn, 128(3): 31–42, 1999     

Numerical analysis for conduction mechanism of thinoxide-nitride-oxide films formed on rough poly-Si

The conduction mechanism of thin oxide-nitride-oxide films formed on rough poly-Si, in which grain sizes are not uniform, is studied for low and negative applied voltage. By assuming an electric field concentration at the convex edge of the plate electrode, the numerical analysis for direct tunneling (D.T.) is carried out. From the results, it is thought that the D.T. currents to the convex edge of the plate electrode dominate the total leakage currents     

Evaluation of small caliber vascular prostheses implanted in small children: activated angiogenesis and accelerated calcification

Healing characteristics of small-caliber vascular prostheses used in small children have rarely been observed because removing specimens are troublesome. Modified Blalock Taussig shunt procedures were performed using small caliber expanded polytetrafluoroethylene (ePTFE) vascular grafts and fabric grafts in 13 patients with congenital heart disease. At the time of total corrective procedures, a piece of 10 ePTFE grafts in 10 patients and six fabric grafts in four patients were removed from the distal pulmonary anastomosis, and evaluated. The implantation duration was from 11 months to 5 years and 7 months (mean, 2 years and 6 months). At removal, average patient age was 4 years and all grafts were patent. Microscopically, the wall of three ePTFE grafts were calcified, and macrophages were immunohistologically observed in the graft wall. Thrombus formation, intimal hyperplasia, and pannus detachment was common. In the fabric grafts, many capillaries infiltrated the interstices and often reached the lumen from the perigraft side. These results suggested that in cyanotic small children, angiogenesis in and around fabric grafts was active and calcification was accelerated in ePTFE grafts. Complete endothelialization throughout the length, caused by angiogenesis, might be possible in small children when highly porous fabric vascular prostheses are used.     

A study on the effect of stacking fault energy on fatigue crack propagation as deduced from dislocation patterns

Fatigue tests of crack growth rates and transmission electron microscopy in the immediate vicinity of crack tips were performed on specimens of copper and 70/30 brass. In brass, very dense dislocations accumulated on the primary and the conjugate slip planes were observed just ahead of the crack tips, and they appeared to be not easy to move because of the difficulty of cross slip. In copper, well-defined cells were observed around the crack tips and there were frequently found cracks propagating along or across cell boundaries. On the basis of these observation results, an interpretation is put on the effect of stacking fault energy on fatigue crack growth.