Space charge behavior in polymer film based on increment of capacitance under AC high field

Polymer materials have excellent dielectric and insulation properties; however, those properties in AC high field region have not been known well. Recently we established an evaluation method of high‐field AC dissipation current waveform of polymer materials 1 . AC dissipation current waveforms of polyethylene and polypropylene films show nonlinear distortion in AC high‐field region. This nonlinearity was thought to be related to the behavior of AC space charge formation in the sample near electrodes. The properties of space charge formed under AC high field at power frequency seem to differ from those formed under DC high field. The measurement of AC space charge distribution is not so easy due to the resolution limit of the space charge measurement. We studied the dielectric properties of biaxially oriented polypropylene (BOPP) film under AC high field up to 120 °C. It was found that tan δ, AC dissipation current (Ixr), and unbalanced component of capacitive current (ΔIxc) increased when the temperature became higher. In particular, ΔIxc increased above some threshold field and was considered to be due to the AC space charge formation. This AC space charge layer near electrode is thought to be formed due to carrier injection under AC high‐field application. Usually, the carrier mobility becomes smaller on lowering the temperature. Most of the carriers injected from the electrode are trapped near the electrode in the sample film. But in the high‐temperature region, the carrier mobility becomes larger and the carrier injection starts to increase from lower field. Many more carriers are injected from the electrode. It is thought that some of the injected carriers are trapped inside the sample film; the others go through the sample to the opposite side. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 8–16, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10018     

Diet-induced hypercholesterolemia increases endothelin-1 release by aortic endothelial cells

Thrombotic thrombocytopenic purpura (TTP) is a disorder of unknown etiology affecting the microcirculation of multiple organ systems. Plasma therapy has significantly reduced the mortality rate; thus, an increased incidence of recurrence has been noted. Since corticosteroids, antiplatelet agents, and splenectomy do not prevent recurrences, monthly plasma infusion have been instituted to decrease the risk of recurrence. However, in pregnancy, increase in frequency of plasma infusions to weekly or biweekly intervals has been associated with avoidance of placental infarcts. This is the first report of a successful pregnancy in which bimonthly prophylactic single plasma-exchange plasmapheresis was the treatment regimen with no obvious maternal-fetal morbidity.     

Nucleotide sequencing analysis of the 146-kilobase segment around the IkBL and MICA genes at the centromeric end of the HLA class I region

The biomechanics of medialization laryngoplasty are not well understood. An excised canine larynx model was used to test the effects of various sized silicon implants. The vocal fold length, position, and tension were measured. Medialization laryngoplasty did not affect vocal fold length. At the mid-membranous vocal fold, larger shims resulted in greater medialization and tension. Medialization laryngoplasty neither medialized nor stiffened the vocal process to resist lateralizing forces. We conclude that medialization laryngoplasty provides bulk and support for defects of the membranous region of the vocal fold, but does not appear to close a posterior glottal gap. The selection of a surgical procedure to treat glottal incompetence should take into account the unique biomechanical properties of the anterior (membranous vocal folds) and posterior (cartilaginous portion) glottis.     

Characterization of endothelium-dependent relaxation independent of NO and prostaglandins in guinea pig coronary artery

In the presence of N omega-nitro-L-arginine and indomethacin, acetylcholine (ACh) induced endothelium-dependent relaxation in guinea pig coronary artery preconstricted with 9,11-dideoxy-9 alpha, 11 alpha-epoxymethano prostaglandin F2 alpha. Dexamethasone and arachidonyltrifluoromethyl ketone, inhibitors of phospholipase A2, and 17-octadecynoic acid, an inhibitor of cytochrome P450 epoxygenase, had no effect on the response to ACh. Although proadifen, which is used widely as an inhibitor of cytochrome P450-dependent enzymes, suppressed the ACh-induced relaxation, the drug also inhibited the relaxation induced by cromakalim, a K+ channel opener. In isolated smooth muscle cells of guinea pig coronary artery, proadifen, but not 17-octadecynoic acid, almost abolished delayed rectifier K+ current. Epoxyeicosatrienoic acids failed to relax the artery. Apamin and iberiotoxin, inhibitors of small- and large-conductance Ca(++)-activated K+ channels, respectively, did not affect the relaxation induced by ACh. A combination of charybdotoxin plus apamin, but not iberiotoxin plus apamin, abolished the response. However, the combination of charybdotoxin plus apamin had no effect on ACh-induced increase in intracellular free Ca++ concentration in endothelial cells. These results suggest that epoxyeicosatrienoic acids do not contribute to N omega-nitro-L-arginine/indomethacin-resistant relaxation induced by ACh in the guinea pig coronary artery. The present study also proposes that K+ channels on vascular smooth muscle cells, which both charybdotoxin and apamin must affect for inhibition to occur, are the target for endothelium-derived hyperpolarizing factor.     

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells

Neuropsychological profiles were assessed in a large group of nondemented control subjects (n = 261) and individuals with dementia of the Alzheimer type (DAT) (n = 407) by subjecting their psychometric test results to a factor analysis. Nondemented control subjects were functionally homogeneous with only one factor accounting for the results. The results of the factor analysis on the very mild DAT and mild DAT groups, however, yielded a mental control/frontal factor, a memory-verbal/temporal factor, and a visuospatial/parietal factor. Forty-one of the original set of participants came to autopsy an average of 5.1 years after psychometric testing and had neurofibrillary tangles, total senile plaques, and cored senile plaques estimated from frontal, temporal, and parietal regions. The results of correlations indicated that the relative burden of cored senile plaques was systematically related to the three psychometric factors. These results suggest a connection between the specific functions as defined by neuropsychological measures and specific neuropathology occurring in associated areas of cortex.     

Lipoprotein(a) levels in the Japanese population: influence of age and sex, and relation to atherosclerotic risk factors. The Jichi Medical School Cohort Study

The authors studied the distribution of lipoprotein(a) (Lp(a)) levels with stratification for age and sex, as well as the relation between Lp(a) and atherosclerotic risk factors in a large Japanese population between 1992 and 1993. The subjects were 1,235 males and 1,762 females over 30 years old. Lp(a) was measured by an enzyme-linked immunosorbent assay. Lp(a) levels were higher in females than in males. The increase in Lp(a) with age was statistically significant, and the proportion of subjects with Lp(a) levels > 30 mg/dl also increased with age. In the obese subjects (body mass index (BMI) (kg/m2) > 26), Lp(a) levels were lower than in the non-obese subjects (BMI < or = 26) (p < 0.01 in males; p < 0.05 in females). Male alcohol drinkers had lower Lp(a) levels than nondrinkers (p < 0.05). Age, low density lipoprotein subtracting Lp(a) cholesterol [Lp(a) x 0.3], and fibrinogen level were all positively correlated with Lp(a) in both sexes. Alcohol consumption (g/day) and triglycerides were inversely correlated with Lp(a) in males, while total cholesterol subtracting Lp(a) cholesterol [Lp(a) x 0.3], high density lipoprotein, and factor VII were positively correlated in females. Multiple logistic regression analysis showed that triglycerides in males and BMI and fibrinogen in females were significant independent variables. The authors conclude that Lp(a) level is affected by various factors, such as alcohol drinking, BMI, sex, and age, and is not only correlated with lipid levels but also with hemostatic factors such as fibrinogen and factor VII.     

Model-based surgical planning and simulation of cranial base surgery

Plastic skull models of seven individual patients were fabricated by stereolithography from three-dimensional data based on computed tomography bone images. Skull models were utilized for neurosurgical planning and simulation in the seven patients with cranial base lesions that were difficult to remove. Surgical approaches and areas of craniotomy were evaluated using the fabricated skull models. In preoperative simulations, hand-made models of the tumors, major vessels and nerves were placed in the skull models. Step-by-step simulation of surgical procedures was performed using actual surgical tools. The advantages of using skull models to plan and simulate cranial base surgery include a better understanding of anatomic relationships, preoperative evaluation of the proposed procedure, increased understanding by the patient and family, and improved educational experiences for residents and other medical staff. The disadvantages of using skull models include the time and cost of making the models. The skull models provide a more realistic tool that is easier to handle than computer-graphic images. Surgical simulation using models facilitates difficult cranial base surgery and may help reduce surgical complications.     

Sero-epidemiological study on equine influenza in Japan

Ten male subjects performed five maximal treadmill running tests at 7 mph. Tests included two (test-retest) progressive, step increment (2 1/2% grade elevation), discontinuous tests (DCT); a progressive, step increment, continuous test (ct) and two constant load tests (CL and CL +2 1/2%). A DCT test was performed first for establishment of peak elevation levels as constant load tests were performed at the peak elevation level attained (CL) and at a level 2 1/2% higher (CL + 2 1/2%). The second DCT test and the remaining three tests were administered randomly. Peak preformance capability (operationally defined as duration at highest grade elevation) was markedly reduced during progressive tests as compared with constant load tests. There was a similar reduction in peak performance capability during the CT test as compared with DCT test. Maximal oxygen uptake (VO2max) was quite similar among the various tests. It was concluded that VO2max attained during progressive, step increment, tests is unaffected by cumulative submaximal work. Discontinuous and continuous progressive tests provide similar VO2max results.     

Advantages of counter-current operation for hydrodesulfurization in trickle bed reactors

The deep desulfurization of oil fraction is a central matter of concern to every refinery. Hydrogen sulfide is the product of hydrodesulfurization reaction and it is the inhibiter of the reaction. When products inhibit the reaction, the counter-current operation is expected to have an advantage over the co-current operation. Hydrodesulfurization of vacuum gas oil in a trickle bed reactor was simulated for both models of co-current operation and counter-current operation. The models were simulated on high and low gas and liquid velocities. Hydrogen sulfide was affected by mass transfer resistance in both gas-liquid and liquid-catalyst interface. The other component mass transfer resistances were negligible. When the deep desulfurization was required, simulation results showed that the counter-current operation was superior to the co-current operation in organic sulfur conversion     

Factors affecting the oxidative activity of laccase towards biphenyl derivatives in homogeneous aqueous-organic systems

Catalytic oxidation of biphenyl derivatives was investigated using laccase in a homogeneous aqueous-organic system. A thermostable laccase from Trametes sp. showed the highest catalytic activity for the oxidation of 4-hydroxybiphenyl (4-HB) at a reaction temperature of 60 degrees C when dimethylsulfoxide (DMSO) was employed as a co-solvent. Furthermore, the catalytic performance was successfully enhanced by the incorporation of a laccase mediator system (LMS) into the aqueous-DMSO media. The catalytic performance strongly depended on the type of mediator, and the highest activity was observed with 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as mediator, suggesting the importance of the selection of a suitable mediator. It was verified that this mediator system is applicable to the oxidation of several biphenyl derivatives with hydroxyl groups.