We studied the trapping of positive and negative charges in the chemical structures of polymers under a high electric field using a space charge measurement system. Positive charges accumulated in low-density polyethylene (LDPE), whereas positive and negative charges accumulated in polyimide (Kapton ® ) and also in ethylene tetrafluoroethylene (ETFE) subjected to electron beam irradiation. To determine the charge-trapping sites in the chemical structures, a quantum chemical calculation was carried out using Density Function Theory (DFT) with Gaussian 09. The relationship between the energy band and the isosurface of orbital electrons at various energy levels was obtained. A threedimensional (3D) electrostatic potential distribution map was obtained for positively and negatively charged polymers to determine the relationship between a trapping site and the charge accumulation center in the 3D potential distribution map. Positive and negative charges in Kapton and ETFE films are trapped in trapping sites in chemical structures and the positive charges in an LDPE film are trapped in physical defects.

No abstract

No abstract

Inhibitors of 3-hydroxy,3-methylglutaryl coenzyme A (HMG-CoA) reductase have been reported to decrease the cholesterol saturation index (CSI) in duodenal bile in humans and to prevent formation of cholesterol gallstones in animal studies. We performed a prospective study to evaluate the role of HMG-CoA reductase inhibitors as gallstone-dissolving agents. Fifty patients with radiolucent gallstones in a gallbladder opacifying at drip infusion cholecystography were treated with either 10 mg/day simvastatin plus 600 mg/day ursodeoxycholic acid (group 1, n=26) or 600 mg/day ursodeoxycholic acid alone (group 2, n=24) for 12 months. The ratio of solitary to multiple gallstone cases was 21:29. Plasma lipid levels were assessed and ultrasonographic examination of the gallbladder was performed at baseline and at 3-month intervals during treatment. Duodenal bile sampling was performed in five patients in each group at baseline and after 12 months of treatment. Plasma cholesterol decreased significantly in group 1 but not in group 2. In solitary gallstone cases, no significant difference in dissolution rates was observed between groups 1 (3 of 9, 33%) and 2 (4 of 12, 33%). In contrast, the dissolution rate in multiple gallstone cases was significantly higher in group 1 (12 of 17, 71%) than in group 2 (3 of 12, 25%) (p < 0.01). Bile cholesterol saturation index was significantly decreased (p < 0.01) but did not significantly differ between the two groups. These results suggest that combination therapy with simvastatin and ursodeoxycholic acid is more effective for cholesterol gallstone dissolution than ursodeoxycholic acid monotherapy in patients with multiple gallstones.

Aim Recently, the accessory middle colic artery (AMCA) has been recognized as the vessel that supplies blood to the splenic flexure. However, the positional relationship between the AMCA and inferior mesenteric vein (IMV) has not been evaluated. Herein, we aimed to evaluate the anatomy of the AMCA and the splenic flexure vein (SFV). Method Two hundred and five patients with colorectal cancer who underwent enhanced CT preoperatively were enrolled in the present study. The locations of the AMCA and IMV were evaluated, focusing on the positional relationship between the vessels and pancreas – below the pancreas or to the dorsal side of the pancreas. Results The AMCA was observed in 74 (36.1%) patients whereas the SFV was found in 177 (86.3%) patients. The left colic artery (LCA) was the major artery accompanying the SFV in 87 (42.4%) of patients. The AMCA accompanied the SFV in 65 (32.7%) patients. In 15 (7.8%) patients, no artery accompanied the SFV. The origin of the AMCA was located on the dorsal side of the pancreas in 15 (20.3%) of these 74 patients. Similarly, the destination of the IMV was located on the dorsal side of the pancreas in 65 (31.7%) of patients. Conclusion The SFV was observed in most patients, and the LCA or AMCA was the common accompanying artery. In some patients these vessels were located on the dorsal side of the pancreas and not below it. Preoperative evaluation of this anatomy may be beneficial for lymph node dissection during left‐sided hemicolectomy.

No abstract

This paper reports on the result of space charge evolution in cross-linked polyethylene (XLPE) planar samples approximately 220 µm thick. The space charge measurement technique used in this study is the pulsed electroacoustic method.There are two phases to this experiment. In the first phase, the samples were subjected to dc 30 kV dc mm −1 and ac (sinusoidal) electric stress levels of 30 kV pk mm −1 at frequencies of 1, 10 and 50 Hz ac. In addition, ac space charge under 30 kV rms mm −1 and 60 kV pk mm −1 electric stress at 50 Hz was also investigated. The volts-off results showed that the amount of charge trapped in XLPE sample under dc electric stress is significantly bigger than samples under ac stress even when the applied ac stresses are substantially higher.The second phase of the experiment involves studying the dc space charge evolution in samples that were tested under ac stress during the first phase of the experiment. Ac ageing causes positive charge to become more dominant over negative charge. It was also discovered that ac ageing creates deeper traps, particularly for negative charge.This paper also gives a brief overview of the data processing methods used to analyse space charge under ac electric stress.

The electric charge accumulation in the dielectric insulation materials under an electron beam irradiation (40 keV and 60 keV) was measured by using the pressure wave propagation (PWP) method. These insulation materials were polar polymeric films such as polycarbonate (PC), polyethylene-naphthalate (PEN), polyimide (PI) and polyethylene-terephthalate (PET), and non-polar polymeric films such as polystyrene (PS), polypropylene (PP), polyethylene (PE) and polytetra-fluoroethylene (PTFE).The PE and PTFE (non-polar polymers) showed the properties of large amount of electric charge accumulation more than 50 C/m 3 and took the time of arrival to saturation of charge accumulation over 80 minutes. On the other hand, it was found the peculiar effect that the charge accumulatuin in PTFE did not observe for the period of 20 minutes after starting electron beam irradiation, as shown Fig. 1 (PTFE). After the period of 20 minutes, the irradiated electric charge was gardually accumulated in PTFE.The PC, PEN, PI and PET (polar polymers) showed properties that smaller amount of charge accumulation about -6 to -14C/m 3 were saturated within the short time about 1.0 minutes after starting beam irradiation as shown Fig. 1 (PC, PI). The PP and PS (non-polar polymer) showed the properties of middle amount of charge accumulation about 20 C/m 3 and took the middle saturation time about 1 to 20 minutes. The PC, PEN, PI and PET (polar polymers) have the benzene ring in principal chain, and have the functional groups of carbonyl group, ester bond, ketone group. These functional groups possess the electrical dipole moment field for trapping an excess electron carrier by irradiation.The PE and PTFE (non-polar polymers) have a carbon-carbon principal chain. And the hydrogen atom was attached to a side chain of PE, the fluorine atom was attached to a side chain of PTFE. There is basically not a trapp site for the excess electron carrier by electron beam irradiation, because these polymers are not a functional group.This paper summarizes the relationship between the properties of irradiated electron charge accumulation and chemical structural formula. Futher more, this paper compares between the electro static potential distribution with negative charged polymer and its chemical structural formula.