Optimization of Digital Growth of Thick N-Polar InGaN by MOCVD

Smooth 200 nm thick N-polar InGaN films were grown by metal–organic chemical vapor deposition (MOCVD) on sapphire using a digital approach consisting of a constant In, Ga, and N precursor flow with pulsed injection of H2 into the N2 carrier gas. Using this growth scheme, the H2 injection time was altered and the effect on the morphology and indium incorporation in the films observed. The effect of periodic insertion of additional GaN inter-layers on the surface morphology of the InGaN layers was also studied.     

Properties of syndiotactic-rich poly(vinyl alcohol) thin film in water. V. Effect of initial temperature of heating on elongation

The effect of the initial temperature of heating on the elongation of syndiotactic-rich poly(vinyl alcohol) thin films was investigated in water under a load. The elongation ratios E_i after 4 h at fixed temperatures increased roughly with an increase in the initial temperature T_i and a decrease in the annealing temperature. E_i after 4 h was the smallest at T_i = 45°C for the films annealed at temperatures below 100°C. E_i was 6.8 at T_i = 60°C for the unannealed film and 1.12 at T_i = 70°C for the film annealed at 200°C. The elongation at break decreased and the temperature at break increased with an increase in annealing temperature, but those at the annealing temperature of 100°C were the smallest. The films annealed at 200°C did not break even at 98°C (boiling temperature) in water and the elongation ratio was 1.42–1.97 in the initial temperature range of 10–70°C. From these results, the relation between the elongation in water and the state of polymer chains in film was discussed.     

Porous cellulose acetate membrane prepared by thermally induced phase separation

Microporous cellulose acetate membranes were prepared by a thermally induced phase separation (TIPS) process. Two kinds of cellulose acetate with acetyl content of 51 and 55 mol % and two kinds of diluents, such as 2‐methyl‐2,4‐pentandiol and 2‐ethyl‐1,3‐hexanediol, were used. In all polymer‐diluent systems, cloud points were observed, which indicated that liquid–liquid phase separation occurred during the TIPS process. The growth of droplets formed after the phase separation was followed using three cooling conditions. The obtained pore structure was isotropic, that is, the pore size did not vary across the membrane. In addition, no macrovoids were formed. These pore structures were in contrast with those usually obtained by the immersion precipitation method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3951–3955, 2003     

Background lead and cadmium exposure of adult women in Xian City and two farming villages in Shaanxi Province, China

The objectives of the present study are: (a) to clarify the current levels of environmental exposure to lead (Pb) and cadmium (Cd) in Shaanxi Province in China in comparison with levels in other parts of mainland China; (b) to examine if there is any urban-rural difference in Pb and Cd exposure; and (c) to quantify the role of cereals as the dietary source of environmental exposure to these metals. For this purpose, triplet surveys on lead and cadmium exposure were conducted in the provincial capital of Xian and two farming villages A and B in Shaanxi Province, China in 1997. The grand geometric mean for lead (Pb) intake via foods (Pb-F), Pb in blood (Pb-B) and Pb in urine as corrected for creatinine concentration (Pb-Ucr) were 30 micrograms/day, 33 micrograms/l and 5 micrograms/g creatinine, respectively, with significant differences among the survey sites, e.g. Pb-B being higher in Xian (43 micrograms/l) than in the two villages (38 and 22 micrograms/l). The counterpart values for cadmium (Cd) intake via foods (Cd-F), Cd in blood (Cd-B) and Cd in urine (Cd-Ucr) were 6.1 micrograms/day, 0.46 microgram/l and 2.8 micrograms/g creatinine, respectively, with no substantial inter-survey site difference. Thus, it was possible to conclude that, from comparison with the values reported in 1990s literature, the exposure of Shaanxi people to Pb and Cd is no higher than, and even possibly lower than, the levels reported for people in other parts of mainland China. The exposure to Cd was almost exclusively from foods, whereas the exposure to air-borne Pb was large enough in Xian to explain higher Pb-B and Pb-Ucr than the level in Village B despite lower Pb-F in Xian than in Village B. Cereals (wheat, rice, maize and foxtail millet) contributed 26 and 84% of dietary Pb and Cd intake, respectively.     

Blood lead levels of the general populations of three Chinese cities

Blood samples were obtained from 537 adults (age greater than or equal to 16 years) living in three cities in China; in Hefei in 1985, and in Shenyang and Jinxi in 1987. The samples were subjected to blood lead (Pb-B) analyses. The subjects were factory workers either in solvent-synthesizing or solvent application plants with no known exposure to metals (including lead). Their smoking and drinking habits were confirmed in medical interviews. Blood lead was significantly higher in smokers than in non-smokers, although no dose-dependency was observed. The Pb-B values in non-smokers were log-normally distributed. The Pb-B among non-smokers was significantly higher in men [104.0 micrograms l-1 (1.428) 87] [geometric mean (geometric standard deviation) number of determinations] than in women [75.5 micrograms l-1 (1.358) 225] when the data from the three cities were combined. There was a significant difference in the Pb-B levels of non-smoking men in the three cities studied, suggesting that regional food habits should be considered as a possible contributory factor of a non-occupational nature. The present findings are compared with observations from Korea and Japan from the viewpoint of environmental health.     

Non-occupational lead and cadmium exposure of adult women in Bangkok, Thailand

This survey was conducted to examine the extent of the exposure of Bangkok citizens to lead (Pb) and cadmium (Cd), and to evaluate the role of rice as the source of these heavy metals. In practice, 52 non-smoking adult women in an institution in the vicinity of Bangkok, volunteered to offer blood, spot urine, boiled rice and 24-h total food duplicate samples. Samples were wet-ashed, and then analyzed for Pb and Cd by ICP-MS. Geometric means for the levels in blood (Pb-B and Cd-B) and urine (Pb-U and Cd-U as corrected for creatinine concentration), and also for dietary intake (Pb-F and Cd-F) were 32.3 micrograms/l for Pb-B, 0.41 microgram/l for Cd-B, 2.06 micrograms/g creatinine for Pb-U, 1.40 micrograms/g creatinine for Cd-U, 15.1 micrograms/day for Pb-F and 7.1 micrograms/day for Cd-F. Rice contributed 30% and 4% of dietary Cd and Pb burden, respectively. When compared with the counterpart values obtained in four neighboring cities in southeast Asia (i.e. Nanning, Tainan, Manila, and Kuala Lumpur), dietary Pb burden of the women in Bangkok was middle in the order among the values for the five cities. Pb level in the blood was the lowest of the levels among the five cities and Pb in urine was also among the low group. This apparent discrepancy in the order between Pb-B (i.e. the fifth) and Pb-F (the third) might be attributable to recent reduction of Pb levels in the atmosphere in Bangkok. Regarding Cd exposure, Cd levels in blood and urine as well as dietary Cd burden of Bangkok women were either the lowest or the next lowest among those in the five cities.     

Levels of copper in the urine of women from nonpolluted farming regions of Japan.

Nearly 1500 spot urine samples were collected in the winter of 1987-1988 from women of seven farming prefectures located throughout Japan. Samples were analyzed for copper by flameless atomic absorption spectrometry. The copper content of the urine samples (Cu-U) distributed log-normally with a geometric mean (geometric standard deviation) of 36.9 (1.47) micrograms/l after adjustment for the specific gravity of urine of 1.016. The 95% confidence range was 17.1-79.7 micrograms/l. Neither alcohol consumption nor smoking habit affected the Cu-U. A literature survey showed that the observed level appears to be somewhat higher than previously reported values.     

Proposal for selective isotope transmutation of long-lived fission products using quasi-monochromatic γ-ray beams

We have proposed a new selective isotope transmutation method using photonuclear reactions with quasi-monochromatic γ-ray beams. This method is based on the fact that the particle threshold of a long-lived fission product (LLFP) such as ⁹³Zr, ¹⁰⁷Pd, or ⁷⁹Se is lower than those of stable isotopes of the same chemical element. Therefore, this method has the excellent advantage that LLFPs cannot, in principle, be produced newly even if the target materials include stable isotopes in addition to LLFPs. Furthermore, this method is effective for ¹²⁶Sn, ^{135, 137}Cs, ⁹⁰Sr, and ³H. The nuclear data involved and suitable γ-ray sources are discussed. Laser Compton scattering γ-ray sources and neutron capture γ-rays in nuclear reactors are candidates for this method.     

High speed and reproducible analysis of nitrosamines by capillary electrophoresis with a sulfonated capillary

Recently environmental control is regarded as important for good human health conditions, and toxic substances, including carcinogens and endocrine disruptors should be eliminated from our living environment. Hence easy quantitative methods are expected for a high level of environmental control. Our previous paper describes an easy quantitative analysis of nitrosamines (NAs) by capillary electrophoresis with an untreated fused silica capillary installed in an ordinary apparatus. In this paper, utilizing a novel type capillary column having sulfonated inner wall was investigated for improvements of separation performance and reproducibility. A sulfonated capillary causes fast and stabile electroosmotic flow because its inner wall is strongly negative charged. On a performance comparison of a sulfonated capillary with an untreated fused silica, analysis time reduction of c.a. forty percent was achieved, and relative standard deviations of migration times and peak responses were less than one third. In addition sample concentrations giving detection and quantitation limits were also reduced to a half.