Electrical and dielectric behaviors and their origins in the three-dimensional polyvinyl alcohol/MWCNT composites with low percolation threshold

The electrical conductivity and dielectric behavior of a three-dimensional composite of polyvinyl alcohol (PVA) and multiwalled nanotubes (MWCNTs) were measured and an extremely low percolation threshold was observed. Two established theories were used to investigate the behaviors of the composites near the percolation threshold, and then the results indicated that the intercluster polarization effect is more reasonable to explain the electrical property of our system in the frequency range of measurement. The high value of the dielectric constant of the composites was attributed to interfacial polarization within the bulk sample and DC conductance based on charge injection at electrode-sample interface. Thus an equivalent circuit was established by separating the behavior of the bulk sample from that of the electrode-sample interface. The introduction of the concept of Constant Phase Element into the equivalent circuit model gave a fit in good agreement with the experimental data and implied the influence of a fractal interface on the real capacitance. The interfacial polarization and the relaxation processes were fully studied. As a result, the activation energy associated with those relaxation processes in the composites was thought to be the energy needed for the charges accumulating and bounded on the interfaces between MWCNT and PVA.     

Pulsed electrical breakdown in liquid helium in the μs range

Information about breakdown time-lags under pulsed voltage stress is prerequisite to the insulation design of superconducting devices. Experiments have been carried out using a pulse generator which provides a step voltage with 200 ns rise time and a long decay time constant of more than 1 ms. The present experiments may bridge the information gap between time lag measurements in the ns range using extremely high field strengths, and existing data found with usual lightning impulse voltage. The test device is described in the paper, and some typical results are discussed in detail     

Deletion and insertion of a 192-residue peptide in the active-site domain of glycosyl hydrolase family-2 beta-galactosidases

The monomeric multimetal-binding beta-galactosidase of Saccharopolyspora rectivirgula (srbg), a glycosyl hydrolase family-2 enzyme, has a unique sequence consisting of 192 amino acid residues with no similarity to known proteins. This 192-residue sequence (termed the "iota [iota] sequence") appears to be inserted into a sequence homologous to the active-site domain of the Escherichia coli lacZ enzyme (lacZbg). To assess the effects of the t sequence at specific sites of beta-galactosidase on the catalytic functioning and molecular properties of beta-galactosidase, deletion or insertion mutants of beta-galactosidases were constructed, expressed in LacZ- E. coli strains, and characterized: srbgdelta in which the iota sequence was deleted from srbg, and lacZbgI, in which the 192-residue iota sequence was inserted into the corresponding position (between Asp591 and Phe592) in the active-site domain of lacZbg. srbgdelta was a catalytically inactive, dimeric protein which retained multimetal-binding characteristics, suggesting that the iota sequence is very important for maintaining the structure necessary for the catalytic functioning and the monomeric structure of srbg but is not responsible for the unique metal ion requirements of srbg. On the other hand, lacZbgI existed as a mixture of a monomer, a tetramer, and higher multimers. The monomeric species was inactive, whereas the tetramer and other multimers were catalytically active (V(max )K(m) value, 25% of that of lacZbg) and highly specific for beta-D-galactoside. The tetrameric lacZbgI was activated by Mg2+ and Mn2+ with lowered metal affinities, and the stoichiometry of metal binding was unchanged from that of lacZbg. These results, along with the published stereo structure of lacZbg, suggest that, in lacZbgI, the inserted 192-residue iota peptide could fold independently of the lacZbg domains into a "sub-domain," lying distant from the active site and subunit interfaces.     

Novel sugar phosphotransferase system applicable to the efficient labeling of the compounds synthesized via the non-mevalonate pathway in Escherichia coli

It is known that 1-deoxy-D-xylulose taken up by Escherichia coli is used as the precursor of the compounds synthesized via the non-mevalonate pathway, such as isoprenoids, probably after conversion into 1-deoxy-D-xylulose 5-phosphate. In this report, we show that a novel phospho(enol) pyruvate-dependent phosphotransferase system catalyzes the uptake and phosphorylation of 1-deoxy-D-xylulose.     

Discovering Emerging Topics from WWW

Discovering emerging topics from WWW has been attracting attention of business professionals, especially marketing researchers. For this purpose, WWW can be a valuable source of information because it reflects the dynamics of human society. In this paper we aim at revealing the structure of WWW by using KeyGraph, a visualization method of hidden structure behind data, for understanding emerging topics.     

Measurement of specific movement power application: evaluation of weight lifters

A new dynamometer was developed for the measurement of specific movement power (SMP) exerted by mono- or multi-articular movements. To determine the reproducibility of SMP, two identical test protocols were carried out on separate days for six movement types on seven adult males. The movement types were arm pull (AP), leg rise (LR), knee extension (KE), elbow flexion (EF), hip extension (HE) and squat movement (SQ). Variations in peak power obtained in two tests ranged from 0.7% (AP) to 9.6% (SQ). Coefficients of the test-re-test correlation in peak power ranged from 0.805 (SQ) to 0.961 (AP) and standard errors ranged from 4 W (EF) to 14 W (SQ). SMP in upper extremities increased from 166 W (EF) to 307 W (AP) resulting from the increase in velocity. However, in the movements of lower extremities, SMP increased from 506 W (KE) to 1351 W (SQ) as a result of the increase in force. To evaluate the validity of the SMP, a pull movement in weightlifting was tested and related to the athletic performance on weightlifters. Positive linear correlation (r = 0.862, p<0.001) was observed between SMP and the total weight best records. It is concluded that this newly developed dynamometer has enough reproducibility and validity for evaluating the SMP, which is developed by various joint movement patterns related to the sport. The feasibility of applying this measuring protocol to the testing and training programmes for improving the daily living activities and athletic performances should now be assessed.     

Isolation, characterization and identification of polyhydroxyalkanoate-accumulating bacteria from activated sludge

Two novel gram-positive bacteria capable of accumulating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [poly(3HB-co-3HV)] were isolated from an anaerobic-oxic activated sludge system fed with acetate. Strains Lpha5 and Lpha7 are motile cocci, 1-2 microm in diameter, occurring singly or in pairs. These isolates have doubling times ranging from 0.4-1.7 d and can accumulate in high levels of poly(3HB-co-3HV) (up to 44.7% of cell dry weight) when grown on complex media. Furthermore, these two strains exhibited the rapid substrate uptake and accumulation of storage granules as observed in situ. Under aerobic conditions, about 14.4% (cell dry weight) polyhydroxyalkanoate and 82% (carbon dry weight) cellular carbohydrate were produced from acetate and glucose, respectively. Under anaerobic conditions, poly(3HB-co-3HV) and cellular carbohydrate accumulated when glucose but not acetate was fed. The result of analysis of 16S rRNA sequence revealed that both strains belong to the gram-positive high-G + C group, but are significantly different from their closest phylogenetic relatives, Dermatophilus sp. and Terrabacter sp., to warrant classification as a new species.     

A monoarthritis model in rabbits induced by repeated intra-articular injections of lipopolysaccharide

In recent years, states have increasingly turned to managed care arrangements for financing and delivering health services to Medicaid beneficiaries. In 1996, approximately 40% of all Medicaid recipients were enrolled in some form of managed care. The rapid escalation of managed care in this population has been fueled by states' desire to slow the growth of Medicaid expenditures and by the trend toward managed care enrollment in the private health insurance industry. The effect of managed care on cost containment in the Medicaid program may be limited, however, because 85% to 90% of Medicaid managed care enrollees are women of childbearing age and children, who together account for 69% of Medicaid recipients, but only 26% of program costs. Nonetheless, the increase in managed care enrollment in this population may have a profound impact on health service delivery and health outcomes for U.S. children, approximately 20% of whom received health benefits through the Medicaid program in 1995. In the future, the proportion of Medicaid-eligible children enrolled in managed care will likely increase as a result of recent legislation that relaxed the requirement that states seek federal approval prior to mandating managed care enrollment for Medicaid beneficiaries. More states are relying on fully capitated arrangements as the preferred type of managed care for Medicaid recipients, despite the relative lack of experience many of these plans have in serving this low-income population. Moreover, managed care organizations have few incentives to enroll chronically or disabled children with higher-than-average expected costs. Without mechanisms in place that adequately adjust capitated rates to account for these higher-cost enrollees, managed care organizations may lose money, and children with the greatest health care needs may be underserved. As mandatory managed care enrollment for Medicaid recipients increases nationwide, states should carefully monitor changes in program costs and quality as well as implications for the delivery of pediatric health services and health outcomes.     

Reference values for bisphosphoglycerate mutase protein content and specific activity in human erythrocytes

Cytomegalovirus (CMV) gastritis has been reported in transplant patients. Symptoms are considered nonspecific, and gastroscopy with biopsy is usually performed to establish the diagnosis. Three patients are described here 1 to 3 months after solid organ transplantation, with primary CMV gastritis, confirmed by gastroscopy, histopathologic examination and cultures. The clinical presentation in all three cases was sharp epigastric pain that decreased in a supine position, increased while sitting and further increased when standing or walking. The epigastric pain completely resolved after treatment with ganciclovir. To the best of our knowledge, such postural epigastric pain has not been described as a specific symptom in any other clinical entity and may be a unique sign of primary CMV gastritis.     

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.