10-W/mm AlGaN-GaN HFET with a field modulating plate

AlGaN-GaN heterojunction field-effect transistors (HFETs) with a field modulating plate (FP) were fabricated on an SiC substrate. The gate-drain breakdown voltage (BV/sub gd/) was significantly improved by employing an FP electrode, and the highest BV/sub gd/ of 160 V was obtained with an FP length (L/sub FP/) of 1 /spl mu/m. The maximum drain current achieved was 750 mA/mm, together with negligibly small current collapse. A 1-mm-wide FP-FET (L/sub FP/=1 /spl mu/m) biased at a drain voltage of 65 V demonstrated a continuous wave saturated output power of 10.3 W with a linear gain of 18.0 dB and a power-added efficiency of 47.3% at 2 GHz. To our knowledge, the power density of 10.3 W/mm is the highest ever achieved for any FET of the same gate size.     

Exaggerated urinary excretion of aquaporin-2 in the pathological state of impaired water excretion dependent upon arginine vasopressin

The present study was undertaken to determine whether urinary excretion of aquaporin-2 (UAQP-2) is of value to diagnose the pathological state of water retention and hyponatremia. UAQP-2 under ad libitum water drinking was 429 fmol/mg creatinine in the patients with water retention, a value significantly greater than that of 153 fmol/mg creatinine in the normal subjects. An acute oral water load test (20 mL/kg BW) was performed in 7 normal subjects (22-25 yr old) and 10 patients with water retention and hyponatremia (55-75 yr old). The percent excretion of the water load was only 30% in the patient group compared with 70% in the control group (P < 0.01). In the control group, minimal urinary osmolality was as low as 131 mosmol/kg H2O, which was responsible for the decrease in plasma arginine vasopressin (AVP) levels after the reduction in plasma osmolality. In the patient group, minimal urinary osmolality was 320 mosmol/kg H2O, and free water clearance remained below 0.6 mL/min after the water load. This impaired water excretion was consistent with the nonsuppressible levels of plasma AVP despite hypoosmolality. The nadir of UAQP-2 was obtained at 60-90 min. The minimal UAQP-2 was reduced to 284 fmol/mg creatinine, a value significantly greater than that of 76 fmol/mg creatinine in the control group. Similar results were obtained in the 6 patients with hypopituitarism, who had impaired water excretion and marked hyponatremia. Water excretion was totally normalized after the replacement of hydrocortisone (excretion of water load, 31% vs. 102%; P < 0.01). Hydrocortisone replacement also significantly reduced the minimal UAQP-2 from 225 to 49 fmol/mg creatinine after the acute oral water load, a value comparable to that in the control subjects. These results indicate that UAQP-2 is a potent marker to diagnose the pathological state of impaired water excretion and hyponatremia, dependent upon AVP, in patients with water retention and hypopituitarism.     

A surgical case of acute three-channeled aortic dissection in Marfan syndrome

We surgically treated a 35-year-old male with acute 3-channeled aortic dissection in Marfan syndrome. He had acute type A aortic dissection, and underwent Bentall's type operation, simultaneous graft replacement of the ascending aorta and total aortic arch. Pain recurred 5 years and 9 months after the first operation. CT scan showed two adjacent false lumens in the descending aorta. The morphology of the first and second dissections was Stanford type A + B. The second dissection was acute. In the second false lumen, a re-entry formation was observed in the abdominal aorta. Because severe pain was persistent, we immediately replaced the descending aorta using a femoro-femoral partial cardiopulmonary bypass. The patient was doing well and was discharged. When pain recurs in a Marfan patient with an aortic dissection, a 3-channeled aortic dissection should be suspected, and we recommend emergency surgery.     

Nasal insulin delivery in rabbits using soybean-derived sterylglucoside and sterol mixtures as novel enhancers in suspension dosage forms

We describe herein the first successful implementation of intraportal stent placement combined with right portal vein embolization as preoperative management against far advanced gallbladder carcinoma. The patient was a 66-year-old woman with obstructive jaundice, in whom computed tomography confirmed that gallbladder carcinoma had invaded the liver and that massive lymph node metastases involved the hepatoduodenal ligament. Portography also revealed severe stenosis of the main portal trunk to less than 2 mm in diameter. To prevent the contribution of intraportal thrombosis and ensure postoperative liver functional reserve, an intraportal metallic stent implantation was conducted simultaneously with right portal vein embolization via a single route using the percutaneous transhepatic approach. There were no complications following this technique, and the patient subsequently underwent hepato-ligament-pancreatoduodenectomy. The resected specimen disclosed a well-expanded stent containing no thrombus. This method could therefore be an amenable strategy for the preoperative treatment of far advanced biliary malignancies in selected patients.     

A PRELIMINARY STUDY ON CRACK HEALING BEHAVIOUR OF Si3 N4 /SiC COMPOSITE CERAMICS

Ceramic (Si3 N4 /SiC) composites have been produced by sintering. From the sintered block, three point bend specimens were cut out. A semi-circular crack was made on the centre of the tension surface of the test specimen with the aid of a Vicker's indenter. The diameter of the semi-circular crack was about 60–70  μm. The specimens were subsequently heat treated at 1300°C for 1  h in vacuum, nitrogen or air. The bending strength was measured at room temperature, 800 and 1000°C. The specimens heat treated in air recovered considerably their bending strength at 1000°C, several specimens failed at a location different from the healed crack and their average strength showed the same value of that for smooth specimens. From these results, it is concluded that the recovery in bending strength of a cracked specimen was caused by crack healing.     

Combined study with FDG PET and Tl SPECT in patients with idiopathic dilated cardiomyopathy

This study aimed to determine whether combined examinations of myocardial 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) and stress-redistribution 201Tl single-photon emission computed tomography (Tl SPECT) were useful in clarifying myocardial ischaemia and evaluating the prognosis in patients with idiopathic dilated cardiomyopathy (IDCM). Twenty-two patients with IDCM underwent echocardiography, cardiac catheterization, FDG PET, and Tl SPECT. In scintigraphic analysis, the total defect score (TDS) was semiquantitatively determined as the sum of scores of the 17 left ventricular (LV) segments with a 5-point scale (0 as normal to 4 as absent). Patients were classified according to the scintigraphic findings as follows: eight patients with small defects on Tl and FDG (TDS < or = 20) (group I), eight patients with small defects on FDG (TDS < or = 20) with FDG uptake increased relative to Tl or 'mismatch' (group II), and six patients with large defects on FDG and Tl (TDS >20) (group III). Eleven patients (50%) showed reversible defects on Tl and all showed preserved FDG uptake. The patients in group III had significantly lower LV ejection fraction (LVEF) (P<0.05, respectively) and a poorer prognosis as shown by the Kaplan-Meier event-free curve compared with those in groups I and II (P<0.01, respectively). Although patients in group II had significantly greater TDS on Tl compared with those in group I (P<0.01), no significant differences in LVEF and prognosis were found between patients in groups I and II. In multivariate analysis, a TDS on FDG revealed an independent predictor of subsequent cardiac events. In conclusion, such mismatched areas can be assumed to consist of impaired but viable myocardium, and may be associated with ischaemia of the microvasculature. Impaired myocardial glucose metabolism is a more powerful predictor of future cardiac events than perfusion abnormality in patients with IDCM.     

A 3.3-V 12-ns 16-Mb CMOS SRAM

A 16-Mb CMOS SRAM having an access time of 12 ns under a 3.3-V supply has been developed with a 0.4-μm process technology. An address access time of 12 ns has been achieved by an optimized architecture, the use of an automated transistor size optimizer, and a read-bus midlevel preset scheme (RBMIPS). For better yield and efficient testing, an on-chip test circuit with three test modes has been implemented     

Protective effect of prostaglandin E2 on cerulein-induced rat pancreatitis]

In order to clarify the effect of prostaglandin E2 (PGE2) on cerulein-induced rat pancreatitis, we investigated the interaction of PGE2 with cerulein or secretin. Intravenous infusion of 10 micrograms/kg.h cerulein inhibited external secretion of the pancreas from one hour and caused macroscopic edema at 3 hours. Administration of PGE2 relieved the inhibitory effect of supramaximal dose of cerulein and decreased the pancreatic edema. The 100 micrograms/kg.hr PGE2 had no significant effect on the pancreatic juice volume and amylase secretion stimulated with 0.2 micrograms/kg.hr of cerulein. Intravenous injection of 100 micrograms/kg PGE2 inhibited both the volume and amylase secretion of pancreatic juice stimulated with 1 U/kg.h of secretin. The protective effect of PGE2 on cerulein-induced pancreatitis was not the stimulation on secretion but caused the cytoprotective effect of PG such as stabilization of cytoplasmic and lysosomal membrane.     

Effects of ventilation and pleural effusion on measurements of airway thermal volume and blood flow in dog lungs

We studied the effects of ventilation and pleural effusion on measurements of airway thermal volume (ATV) and pulmonary blood flow (PBF) by using the airway gas thermometry method of V. B. Serikov, M. S. Rumm, K. Kambara, M. I. Bootomo, A. R. Osmack, and N. C. Staub (J. Appl. Physiol. 72: 944-953, 1992) in 39 anesthetized dogs with or without lung edema or pleural effusion. To examine the differential effects of increased-pressure and increased-permeability lung edema on accuracy and sensitivity of ATV and PBF, two models of lung edema were induced by intravenous infusion of a Dextran 70 solution and alloxan monohydrate, respectively. Dogs were hyperventilated for 3 min by using a wide range of minute ventilation (VE) to produce two steady-state conditions of airway temperature. Higher levels of VE increased an estimated amount of ATV. The ATV produced by hyperventilation at VE values of 559, 158, and 72 ml.min-1.kg-1 was consistent with the gravimetric total lung mass, the blood-free wet lung weight, and the extravascular lung water volume, respectively. The coefficient of lung thermal conductivity, a practical index of the rate of heat conduction through tissue from lung vessels, was related to the ratio of the decrease in expired air temperature to VE, and estimated PBF was consistent with the thermodilution cardiac output. Pleural effusion had little effect on measurements of ATV and PBF. However, ATV and PBF showed increased variation in dogs with dextran-induced lung edema.