Additives distribution and electrical properties in zinc oxide varistor prepared by a wet chemical method

Cobalt-, praseodymium-added zinc oxide varistor was prepared through a wet chemical method followed by sintering with or without calcination. Changes in grain size, compact density, additives distribution, and voltagecurrent/ capacitance-voltage relations were investigated for the characterization of the samples sintered at temperatures from 1473 to 1573 K without calcination or with calcination at 773 K for 2 h. The electrical properties were compared with nhose of samples prepared by two types of ball mill methods. The wet chemical method provided almost the same additives-distribution profile and less impurities in comparison with the ball grinding method carried out for 10–100 h. The donor concentration and the potential-barrier height for the samples were evaluated by Double Schottky Barrier Model. Addition of small amount of both cobalt and praseodymium in preparation by the wet chemical method was effective for a better nonlinearity relation between voltage and current, which has potential for a smaller sized varistor.     

Pericardial effusion after primary percutaneous transluminal coronary angioplasty in first Q-wave acute myocardial infarction

To evaluate the incidence and clinical significance of infarction-associated pericardial effusion in patients with successful primary percutaneous transluminal coronary angioplasty, we studied 214 consecutive patients with a first Q-wave acute myocardial infarction. Based on 9 clinical variables, multivariate analysis was performed to determine the important variables related to the occurrence of pericardial effusion. Pericardial effusion was detected by echocardiography in 45 patients (21%); pericardial rub (p <0.001), number of advanced asynergic segments (p <0.001), ventricular aneurysmal motion (p = 0.03), and pulmonary capillary wedge pressure (p = 0.04) were found to be the important variables related to pericardial effusion. Among 45 patients with pericardial effusion, 29 patients with no pericardial rub had significantly higher pulmonary capillary wedge pressure than those with pericardial rub, whereas 16 patients with pericardial rub had a higher incidence of angiographic no reflow and ventricular aneurysmal motion than those without pericardial rub. Patients with pericardial effusion and a pericardial rub had a higher mortality rate than those without pericardial effusion (19% vs 3%; p = 0.02). Thus, pericardial effusion is still a relatively common clinical finding after primary percutaneous transluminal coronary angioplasty, and those with pericardial effusion and a pericardial rub were associated with more severe transmural myocardial damage and higher in-hospital mortality.     

Effect of Charge State in Nearby Quantum Dots on Quantum Hall Systems

Transport properties have been measured on two-dimensional electron system (2DES) with a nearby InAs self-assembled quantum dot layer, in order to clarify the anomalous behavior of magnetoresistance, ρ _xx , and Hall resistance, ρ _xy at $\nu=\frac{1}{3}$ , which was an unsolved problem in our previous paper (Takehana et al.: J. Phys. Soc. Jpn. 75, 114713, 2006). The significant suppression of both ρ _xx and ρ _xy was found to be reduced in the vicinity of $\nu=\frac{1}{3}$ , which indicates that the fractional quantum Hall effect prevent the spin-flip process between localized electrons and that extended 2DES, according to the discussion of the previous paper.     

Photocatalytic properties of titanium dioxide sputtered on a nanostructured substrate

The effective one-step physical approach is demonstrated for the fabrication of anatase titanium dioxide nanotubes through r.f. magnetron sputtering of TiO₂ on a highly ordered nanoporous anodic alumina template. The nanostructured TiO₂ benefited from the combination of unique properties of both the sputtering technique that provided well-controlled environment for the fabrication of anatase phase TiO₂ and the porous anodic alumina (PAA) that provided uniform and ordered nanopores. The photocatalytic properties of TiO₂ films were characterized following the degradation of methylene blue molecules under UV light irradiation. The photocatalytic activity of the nanostructured TiO₂ films has been found to be approximately twice higher in comparison with the flat TiO₂ films fabricated at the same conditions.     

Resolution of late potentials with improvement in left ventricular systolic function in patients with first acute myocardial infarction

BACKGROUND: Little has been written about the use of computed tomography (CT) in the evaluation of small bowel obstruction (SBO) in children. The purpose of this study is to review the CT findings of SBO in a pediatric series and to increase awareness of CT as potential problem-solving tool for SBO in children. METHODS: The medical, surgical, radiographic, and CT scan records of 20 consecutive children with surgically proven SBO were retrospectively reviewed. Duodenal and neonatal obstruction was excluded. CT scans were evaluated for small and large bowel caliber, bowel wall thickening, the appearance of the mesentery, extraluminal abnormalities, and the ability to detect the cause of obstruction. RESULTS: Causes of obstruction included adhesions (nine), small bowel intussusception (four), abscess (two), segmental volvulus (two), Crohn disease (one), focal stricture (one), and internal hernia (one). Small bowel dilatation was present in 19/20 children. Small bowel caliber transition was noted in 17/19 children. Two children with no small bowel caliber transition had a collapsed colon. The colon appeared normal in caliber in nine children, collapsed in nine, and filled with stool proximally and collapsed distally in two. Small bowel thickening was present in six children and mesenteric venous engorgement in three. Specific causes of obstruction were identified on CT in nine children (45%) and could be correctly predicted in seven of nine children with adhesions. In four children, the causes were either not evident or alternate diagnoses could be made. CONCLUSION: CT can be a useful adjunct in evaluating the presence or causes of SBO in children.     

Electrochromic properties of the n-heptyl viologen-ferrocyanide system

Electrochromic properties of the mixed solution of n-heptyl viologen dibromide (HV), Fe(CN) ₆ ^4– and NaH₂PO₂ or KBr were investigated by cyclic voltammetry and the transparency-time relation. When Fe(CN) ₆ ^4– is added to a HV solution the mixture colours violet without inputting any voltage. However, the colour fades gradually by further addition of NaH₂PO₂, and the transparency of the mixture increases with addition of larger amounts of NaH₂PO₂. The same effect was observed by addition of KBr to the HV-Fe(CN) ₆ ^4– solution. The input voltage required for the electrochromism of HV is lowered considerably by addition of Fe(CN) ₆ ^4– , when NaH₂PO₂ or KBr plays a role in controlling the colouringerasing phenomena. The HV-Fe(CN) ₆ ^4– -KBr system showed some HV residue in the cyclic voltammogram on an indium-tin oxide (ITO) electrode, while no such HV residue was observed in the HV-Fe(CN) ₆ ^4– -NaH₂PO₂ system. The HV-Fe(CN) ₆ ^4– -NaH₂PO₂ system is superior in colouring-erasing reproducibility and in response time to the HV solution or the HV-Fe(CN) ₆ ^4– system.     

Propane gas leak detection by infrared absorption using carbon infrared emitter and infrared camera

The present study investigated the ability of a system using a carbon infrared emitter (CIE) and an infrared (IR) camera to detect a combustible gas, propane. The CIE transmitted infrared at wavelengths ranging from 1 to 5 μm, and the infrared absorption band of propane gas (3.37 μm) was obtained using a bandpass filter to remove other infrared wavelengths. The intensity of infrared radiation passing through the propane gas decreased as a result of infrared absorption. A clear, real-time image of the gas leak was also obtained using this system. Furthermore, a hazard evaluation of the leakage propane gas was made from a correlation between infrared intensity and the concentration–pathlength product.     

A study of zero-sequence current induced in a cable system

Large zero-sequence currents found in an actual crossbonded cable system led to a study of their causes and a solution to the problem. Measured values were compared to calculated results by the BPA-EMTP circuit analysis program. It was found that the zero-sequence currents were circulating between different circuits in the cable system and that they were being generated by the induction between phases in the same cable route. It was determined that the zero-sequence currents could be greatly reduced in a twin circuit (six phases) by symmetrical configuration of the cables. However, in a four-circuit system, no significant reduction could be achieved even by the symmetrical configuration     

Magneto-optical measurements with a hybrid magnet

An FFT spectrometer has been constructed to measure magneto-optical spectra in the far-infrared region (3 to 40 cm^?1) with a hybrid magnet system. The magneto-absorption was studied in the spin-Peierls cuprate CuGeO₃ at various magnetic fields. Coil constants of superconducting magnet and resistive one, of which a hybrid magnet consists, were calibrated by ESR spectra at the constant field.     

Protective effects of glutathione isopropyl ester on the sensitivity of cultured cells to UVB irradiation

The effect of glutathione (GSH) isopropyl ester on cellular sensitivity to UVB irradiation was investigated in HeLaS3 cells. Pretreatment with 0.1-0.5 mM GSH isopropyl ester for 4 h significantly inhibited the decrease of thymidine (TdR) incorporation caused by UVB irradiation at a dose of 500 J/m2, whereas pretreatment with a high dose (1 mM) had no effect. The colony formation ability of the pretreated cells (0.3 mM) was significantly better than that of cells that received irradiation only. When the cells were treated with GSH isopropyl ester, their intracellular GSH level increased dose-dependently over a 4 h period, suggesting that GSH isopropyl ester was transported into the cells and there converted to GSH. Within 2 min of exposure, the intracellular GSH level depleted rapidly to about 75% of that in non-irradiated normal cells. In contrast, the GSH level in cells pretreated with 0.3 mM GSH isopropyl ester was maintained at the same level as that in normal cells, indicating that the maintenance of intracellular GSH level is due to converted GSH from GSH isopropyl ester. These results clearly show that intracellular GSH is involved in cell protection against photodamage, and that GSH isopropyl ester is a useful antioxidant for protection against photooxidative injury.