Electrical Breakdown Properties and Space Charge Formation in High Temperature Region in Ultraviolet Ray Irradiated PVC

Polyvinyl chloride (PVC) is the most popular insulating material for electric wiring instruments. However, an exothermic reaction above 150 °C may cause deterioration of the insulating properties of PVC. Therefore, it is important to clarify the heat degradation in PVC, not only to investigate the ignition of electrical wiring products but also to use electrical products safely. It is known that ultraviolet (UV) irradiation causes chemical deterioration of PVC and an increase in its conductivity. Generally, it has been thought that the electrical breakdown properties, electrical conduction, and insulating performance are affected by space charge accumulation in an insulating material. A high temperature pulsed electroacoustic (PEA) system usable up to 250 °C has been developed, and the PEA system can measure the space charge distribution and conduction current in the high temperature range simultaneously. In this investigation, the space charge distribution and conduction current were measured up to electrical breakdown in a non‐UV irradiated sample (normal PVC) and in 353 nm and 253 nm UV‐irradiated PVC samples in the range from room temperature to 200 °C in a DC electric field. In the short wavelength UV irradiated PVC sample (253 nm, 300 h), a deterioration of breakdown strength at 90 °C to 150 °C and negative packet‐like charges were observed at 60 °C and 100 °C, a positive charge accumulated in front of both the anode and cathode above 90 °C, and a higher electric field near the cathode side because the positive charge of the cathode side was greater.     

Iodine-123-BMIPP myocardial washout and cardiac work during exercise in normal and ischemic hearts

Due to the changes in the frequency of penicillin-resistant strains of S. pneumoniae, it is necessary to perform surveillance studies of bacterial resistance. Isolates from the upper respiratory tract of asymptomatic children have been useful. There is no information about the difference between isolates from children with and without upper respiratory tract infection (URTI). The objective of the authors in this paper is to establish the prevalence of carrier-state, serotype and antimicrobial resistance of S. pneumoniae isolates from children with and without acute upper respiratory tract infection (URTI) in a rural area in Mexico. A cross-sectional comparative study was performed in Tlaxcala, Mexico. Children from one month 5 years of age were included. Nasopharyngeal swabs were obtained. Identification was done by international microbiology standards. Serotyping was done by the capsular Quellung test. The susceptibility testing was performed by the agar dilution method. Four-hundred and fifty patients were included. S. pneumoniae was isolated in 134 children (29.7%). Frequency of carriers was greater in patients with URTI (107/323) than without URTI (27/127) (33.1% vs. 21.1% p = 0.012, OR 1.84, IC 95% 1.1-3.08). The six most frequent serotypes were: 6B (16.4%); 19F (11.9%); 19A (6.7%); 14, 23F, and 35 (5.2% each), with no difference among the groups. Only 3% of the strains had high level resistance to penicillin, and 12.6% had intermediate resistance, and for ampicillin 4%, amoxicillin 4%, amoxicillin-clavulanate 4%, ceftriaxone 3%, cefotaxime 1.5%, erythromycin 6%, miocamycin 3%, chloramphenicol 4%, and vancomycin 0%. Trimethoprim-sulfamethoxazole resistance was very high (42%). In conclusion, colonization is higher in children with URTI. Five of the most frequent serotypes identified in this study were the same as those identified in patients with S. pneumoniae invasive diseases in Mexico City. In Tlaxcala, Mexico, beta-lactams could be the drug of choice for the treatment of S. pneumoniae lower respiratory tract infections. It is necessary to perform clinical assays to evaluate the efficacy of trimethoprim-sulfamethoxazole due to the high resistance in vitro.     

Efficiency of repeated batch penicillin fermentation using two fermentors. Computer simulation and optimisation

Repeated batch operation using two fermentors (RBTF) to penicillin fermentation was demonstrated by computer simulation to improve productivity. Three operation modes were compared: chemostat, repeated batch operation using a single fermentor (RBSF) and RBTF; in each case account was made of the lag period before growth. The simulated fermentor performances were assessed on the basis of the penicillin productivity and concentration; the simulation was based on published batch fermentation data. It was shown that RBTF was superior to RBSF and chemostat. The advantage of RBTF increased as the lag period became greater.     

Comparison of activities in selective catalytic reduction of NOx by C3H8 over Co/MFI, Fe/MFI, and H/MFI zeolite catalysts

The Co/MFI(SiO₂/Al₂O₃ = 30) were prepared by a precipitation method with NaOCl in alkali solutions exhibited high activities to N₂ at 250 °C for the selective catalytic reduction (SCR) of NO_x. These catalysts showed two UV–vis bands at 700 and 400 nm, indicating the presence of octahedral Co(III) as well as tetrahedral Co(II). The high SCR activity over such Co(III, II)/MFI(30) seems to come from Co(III)---O moieties. The Co(II)MFI(30) catalysts prepared from Co(II)Cl₂ exhibited low SCR activities due to the presence of tetrahedral Co(II) ions in MFI. Less CO formation occurred over Co/MFI catalysts. The Fe/MFI(30) catalyst exhibited high activity due to the presence of some Fe---O species in MFI but more amount of CO were produced during SCR. H/MFI(30) catalyst exhibited a good SCR activity. However, more amount of carbonaceous deposits were produced on it. The correlation between acid concentration and SCR activity was discussed over H/MFIs.     

Electrical characterization of homoepitaxial diamond p–n junction

Electrical properties of homoepitaxial diamond p–n⁺ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 10⁵ at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density N_i of the p–n⁺ junction is not uniform and N_i at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce N_i at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n⁺ interface and incorporating during the growth of p-type layer, which makes to reduce N_i at the vicinity of the p–n⁺ interface.     

Analysis of distribution of Campylobacter jejuni and Campylobacter coli in broilers by using restriction fragment length polymorphism of flagellin gene

The incidence of Campylobacter jejuni and Campylobacter coli in broiler farms was 33.9% (19/56). C. jejuni-positive flocks accounted for 20.0% (17/85) and C. coli-positive ones was 4.7% (4/85). There were 14 patterns (fla type) of restriction fragment length polymorphism (RFLP) of flagellin A gene among these 22 strains of C. jejuni and C. coli including the standard strain C. jejuni ATCC 33560. Different fla types of Campylobacter were isolated from broilers in different growing cycles on the same farms. Four strains of C. jejuni were isolated from four breeder farms and four fla types of C. jejuni were detected from their progenies reared on growing farms. Three fla types of C. jejuni detected from the progenies were different from those of each breeder. Also, the other three fla types of C. jejuni were detected from different progenies of each growing farm during the next growing cycle. These findings indicate that the RFLP analysis may contribute to epidemiological studies of C. jejuni and C. coli contamination of broilers and suggest the risk of contamination with different types of Campylobacter in every growing cycle of broilers on the farm even on the same farm. They also supported that there was little likeliness of the vertical transmission of C. jejuni and C. coli from breeders to broilers.     

An automatic torque ripple compensation system for direct drive motors

A serious problem in motion control is the occurrence of torque ripple. Since a direct drive (DD) motor with a magnet rotor uses a rare-earth magnet, the torque ripple is more serious than that of conventional servomotors. This paper presents an auto-compensation of torque ripple using a software-implemented torque observer. The frequency and amplitude of torque ripple can be obtained in the controller by using the estimated torque from an observer, and the autonomous generation of a compensating current component for a torque ripple is possible. The proposed algorithm has been verified by experiments.     

Preferential Oxidation of CO in H2-Rich Gas at Low Temperatures over Au Nanoparticles Supported on Metal Oxides

We investigated Au catalysts supported on TiO₂, Fe₂O₃, and ZnO for their preferential oxidation of CO in a H₂-rich atmosphere. Both full conversion and selectivity were achieved over Au/Fe₂O₃ and Au/ZnO around room temperature, but at higher temperatures the CO conversion was suppressed due to competition between CO and H₂.     

An all-digital analog-to-digital converter with 12-/spl mu/V/LSB using moving-average filtering

A compact, high-resolution analog-to-digital converter (ADC) especially for sensors is presented. The basic structure is a completely digital circuit including a ring-delay-line with delay units (DUs), along with a frequency counter, latch, and encoder. The operating principles are: (1) the delay time of the DU is modulated by the analog-to-digital (A/D) conversion voltage and (2) the delay pulse passes through a number of DUs within a sampling (= integration) time and the number of DUs through which the delay pulse passes is output as conversion data. Compact size and high resolution were realized with an ADC having a circuit area of 0.45 mm/sup 2/ (0.8-/spl mu/m CMOS) and a resolution of 12 /spl mu/V (10 kS/s). Its nonlinearity is /spl plusmn/0.1% FS per 200-mV span (1.8-2.0 V), for 14-b resolution. Sample holds are unnecessary and a low-pass filter function removes high-frequency noise simultaneously with A/D conversion. Thus, the combination of this ADC and a digital filter that follows can eliminate an analog prefilter to prevent the aliasing before A/D conversion. Also, both this ADC can be shrunk and operated at low voltages, so it is an ideal means to lower the cost and power consumption. Drift errors can be easily compensated for by digital processing.     

Mechanism for high singlemode stability of gain-coupled DFB laserswith periodically etched quantum wells

The sidemode suppression ratio of gain-coupled DFB lasers with periodically etched quantum wells is analysed by a more accurate model for amplified spontaneous emission. It is shown that the periodic etching of quantum wells is very effective for providing a high side-mode suppression. The mechanism for the high singlemode stability is explained by the effective modal gain. which has an enhancement at the longer wavelength side of the Bragg stopband