On the High-Speed Turn-Off of a Power Transistor by a Small Saturable Core

An effective method for reducing the size and weight of the switching dc-dc converter is to increase the switching frequency. To accomplish this with no deterioration in efficiency, it is necessary to suppress the switching loss per cycle by shortening the switching time. An efficient dc-dc converter operating at the megahertz region is presented. The turn-off time is shortened by using the current feedback and the core saturation. The turn-off mechanism is analyzed with the equivalent circuits. As a result, it is found that the excess carrier in the base region is discharged quickly by the large reverse base current, which flows when the energy stored in the base-emitter capacitance of the power transistor is transferred to the saturated inductance of the core with high frequency oscillation.     

Proliferating cell nuclear antigen (PCNA) expression in oral squamous cell carcinoma - an aid to conventional histological grading?

Decreased oxygen delivery and cellular hypoxia are major factors in the pathophysiology of shock. We studied the effects of 100% O2 at 0.1 and 0.3 MPa (1 and 3 atm abs) in severe hemorrhagic shock in awake, unrestrained rats. Shock was induced by withdrawing 50% of the total blood volume within 120 min. Blood pressure, heart rate, and the electroencephalogram (EEG) were recorded during the first 6 h of the protocol. The animals were observed for 7 days. The shock protocol resulted in 60 and 90% mortality after 1 day and at the end of 7 days, respectively. A single 90-min exposure to O2 at 0.1 and 0.3 MPa, which was started 30 min after bleeding, maintained mean arterial blood pressure at significantly higher values compared to untreated controls throughout the exposure period (P < 0.05). Oxygen therapy at both doses also improved the long-term survival rate and survival time significantly (P < 0.01). No clinical or EEG sign of CNS O2 toxicity was detected in O2-treated animals. Our results indicate that O2 given alone after severe bleeding exerts a beneficial effect on the long-term outcome of hemorrhagic shock in awake, unrestrained rats.     

Identification of benzo[a]pyrene quinone in soybean leaves

Soybean seeds (Glycine max) were grown in soil containing 10 ppm of benzo[a]pyrene (BaP). After 76 days growth, three kinds of quinones, namely BaP-1,6-, 3,6- and 6,12-quinones, were isolated and identified. However, the formative mechanism of the quinones in leaves has yet to be determined.     

Optical feedback in offset-structure optoelectronic integrateddevices

An optical feedback mechanism in offset-structure integrated optoelectronic devices which exhibit light amplification, optical bistability, and regenerated oscillation is discussed. The amount of optical feedback was evaluated by adding a third electrode which allowed each of the integrated devices to be operated separately. Optical feedback control by an additional layer for the absorption of feedback light was demonstrated     

Dura arteriovenous malformation of the posterior fossa-clinical and angiographical analysis of 6 cases

Dural arteriovenous malformation of the posterior fossa was infrequently reported in the literatures. We presented 6 cases of dural arteriovenous malformation of the posterior fossa with the presentation of typical examples. Up to the end February, 1974, 119 cases of intracranial arteriovenous malformation were experienced in our clinic, in which there were 6 cases of dural arteriovenous malformation. The ages of our series ranged from 41 to 75 years old and 57 years old in average. Tinnitus and headache were two main symptoms which developed in most of the cases. As for the older symptoms, visual disturbance was seen in 4 cases, unilateral pulsating exophthalmos in 1 case and papilledema in 3 cases. There wers two cases which progressive dementia was developed by the cerebral anoxia due to arteriovenous shung. On examination, a pulsatile bruit was audible at the mastoid region in all cases and a thrill could be palpated along the occipital arteries. Many kinds of durl and/or tentorial arteries which were drained directly into the sinuses at the occipital portion as the feeding arteries were visualized angiographically. Moreover, the angiographical patterns of feeding arteries into the sinuses showed dynamic changes after the operation. As for the treatments, many kinds of surgery were carried out for the cases by the combination method of the next 6 ways. 1. ligation of external carotid artery 2. ablation of periosteum from occipital bone 3. occipital and/or suboccipital craniectomy 4. clipping of almost of all feeding arteries at dura mater and tentorium 5. ligation of threocervical trunk 6. ventriculo-atrial shunt or ventriculo-peritoneal shunt From our experiences, the most effective treatment is thought to be a direct closure of intradural arteriovenous shunt near the sinus at the occipital portion in the early stage.     

10 watt CW, 5000 h lifetime monolithic AlGaAs laser diode arrays

1 cm-wide monolithic laser diode arrays emitting at about 810 nm with a 3 mm total active aperture width have been life-tested at 10 W constant power at 20 degrees C heat-sink temperature. One array has been operated for over 3000 h and has a projected lifetime in excess of 5000 h.<>     

Enhanced ketogenesis in the kidney during hepatic inflow occlusion with the administration of Ringer's acetate solution

BACKGROUND: The blood levels of ketone bodies, which are synthesized principally in the liver, were maintained even during hepatic inflow occlusion if Ringer's acetate solution (AR) was administered, resulting in an improvement of hepatic energy level in the reperfusion phase, as reported in our previous experimental study. The current study was designed to prove that the kidneys are the organs that contribute to synthesize ketone bodies during hepatic inflow occlusion if AR is administered. METHODS: The arterial, central venous, renal venous, and renal tissue ketone body concentrations were determined in rabbits administered AR or Ringer's lactate solution (LR) at 20 minutes of hepatic ischemia and at 30 minutes of reperfusion. The concentrations were also compared in rabbits under AR infusion with or without hepatic ischemia for 20 minutes. Statistical analyses were performed by means of ANOVA: RESULTS: With AR the renal venous ketone body concentration not only was higher than that with LR (p < 0.001) but also was higher than the arterial concentration (p = 0.05). The renal tissue ketone body concentration was higher than in those with LR (p < 0.001) and also than in those without occlusion (p < 0.001). CONCLUSIONS: Ketogenesis is enhanced in the kidney and may compensate for hepatic loss of ketogenic function during hepatic inflow occlusion under AR administration.     

Fluorination of Hydroxyesters with N,N-Diethyl-1,1,2,3,3,3-Hexafluoro Propaneamine

The reactions of N,N-diethyl-1,1,2,3,3,3-hexafluoro propaneamine (PPDA) with Β-hydroxyl esters gave their corresponding fluorides. For example, methyl (S)-(+)-3-fluorobutyrate was obtained from the reaction of methyl (R)-(-)-3-hydroxybutyrate with PPDA. The reaction ofa-hydroxy esters with PPDA gave a mixture of their corresponding fluorides and 2,3,3,3-tetrafluoropropionate esters. However, γ- and δ-hydroxyesters did not give their fluorinated compounds. Hydrolysis of those racemic monofluoroesters with Lipase MY gave optical active monofluorocarboxylic acids and esters. To whom correspondence should be addressed.