Daily intake of TBT, Cu, Zn, Cd and As for fishermen in Taiwan

The consumption of contaminated seafood has been reported as an important route of human exposure to metals in Taiwan. We consider the concentrations of TBT, Cu, Zn, Cd, As, and the consumption of oysters of Taiwanese to be the important information related to public health in Taiwan. Therefore, the aim of this study was to evaluate the public health risks associated with TBT, Cu, Zn, Cd and As from shellfish for the general population and fishermen of Taiwan. In general, TBT concentrations in various oysters ranging from 0.32 to 1.51 microg/g dry wt. varied with sampling locations. The highest TBT, Cu, and Zn geometric mean (GM) concentrations in oysters of 1.51, 1180 and 1567 microg/g dry wt. were obtained from the Hsiangshan coastal area. The values of oyster consumption for fishermen were 94.1 and 250 g/day for typically and maximally exposed individuals, respectively. In particular, the highest intake (250 g/day) from fishermen was almost two times greater than that of the general population (139 g/day). The THQ (target hazard quotient) values of Hsiangshan's fishermen are 3.87 and 20.50 for TBT and Cu for maximally exposed individuals are higher than other oyster culture areas. It is interesting that those consuming oysters from Hsiangshan, Lukang, Taishi caused abnormally high THQs of TBT and other metals (100% over 1.0), and TBT was attributed to only 3-21% of the total THQs in different fishermen of Taiwan. Our results suggest that current environmental levels of TBT and other metals are associated with a significant potential threat to human health for fishermen resident in coastal areas of Taiwan.     

消泡剂、增稠剂和有机硅添加剂

1消泡剂对涂料来说，起泡总是要不得的。起泡的问题在涂料制造过程本身中就是存在的。起泡使投料量不得不降低，设备有效利用率不得不减少。但起泡的问题更多地发生在施工过程中，使漆膜出现种种弊病。而且，起泡造成的不仅仅限于对视觉的干扰，还会使涂层的保护功能难以正常发挥。于是，在涂料配方中，消泡剂就是一个不可缺少的组成成分几乎所有的涂料体系的组成成分都会对起泡现象发生影响，有的影响是正面的，有的是反面的。此外，基材性质和施工方法对起泡的表现也是有影响的。必须认识到，消泡在很大程度上是一个有着极强针对性的问题…     

Methods of Modifying the Brittle Behavior of Cementitious Composites

We put forward effective methods of increasing the tensile strain of cementitious composites with 2% PVA fiber and high fly ash content. The test results show that curing condition has a significantly effect on the tensile performance. It is approved that the specimens incorporated appropriate volume fraction rubber powder and lightweight aggregate greatly increase the tensile strain of composites at medium-term age, but indefinitely at long-term age. To a certain extent, EVA can limitedly enhance the tensi...     

High-resolution crystal structures of delta5-3-ketosteroid isomerase with and without a reaction intermediate analogue

Bacterial Delta5-3-ketosteroid isomerase (KSI) catalyzes a stereospecific isomerization of steroid substrates at an extremely fast rate, overcoming a large disparity of pKa values between a catalytic residue and its target. The crystal structures of KSI from Pseudomonas putida and of the enzyme in complex with equilenin, an analogue of the reaction intermediate, have been determined at 1.9 and 2.5 A resolution, respectively. The structures reveal that the side chains of Tyr14 and Asp99 (a newly identified catalytic residue) form hydrogen bonds directly with the oxyanion of the bound inhibitor in a completely apolar milieu of the active site. No water molecule is found at the active site, and the access of bulk solvent is blocked by a layer of apolar residues. Asp99 is surrounded by six apolar residues, and consequently, its pKa appears to be elevated as high as 9.5 to be consistent with early studies. No interaction was found between the bound inhibitor and the residue 101 (phenylalanine in Pseudomonas testosteroni and methionine in P. putida KSI) which was suggested to contribute significantly to the rate enhancement based on mutational analysis. This observation excludes the residue 101 as a potential catalytic residue and requires that the rate enhancement should be explained solely by Tyr14 and Asp99. Kinetic analyses of Y14F and D99L mutant enzymes demonstrate that Tyr14 contributes much more significantly to the rate enhancement than Asp99. Previous studies and the structural analysis strongly suggest that the low-barrier hydrogen bond of Tyr14 (>7.1 kcal/mol), along with a moderate strength hydrogen bond of Asp99 ( approximately 4 kcal/mol), accounts for the required energy of 11 kcal/mol for the transition-state stabilization.     

Sample size calculations for studies with correlated observations

Correlated data occur frequently in biomedical research. Examples include longitudinal studies, family studies, and ophthalmologic studies. In this paper, we present a method to compute sample sizes and statistical powers for studies involving correlated observations. This is a multivariate extension of the work by Self and Mauritsen (1988, Biometrics 44, 79-86), who derived a sample size and power formula for generalized linear models based on the score statistic. For correlated data, we appeal to a statistic based on the generalized estimating equation method (Liang and Zeger, 1986, Biometrika 73, 13-22). We highlight the additional assumptions needed to deal with correlated data. Some special cases that are commonly seen in practice are discussed, followed by simulation studies.     

Racial differences in Helicobacter pylori seroprevalence in Singapore: correlation with differences in peptic ulcer frequency

The aim of this study was to determine, first, whether racial differences exist in the seroprevalence of Helicobacter pylori infection in Singapore, and second, whether these differences correlate with racial differences in peptic ulcer frequency. A commercial serological test for immunoglobulin (Ig)G antibody to H. pylori which was 90% sensitive and 83% specific in our population was used to screen 403 adult blood donors of Chinese, Malay and Indian origin, aged between 15-60 years. Serum specimens from 84 paediatric patients admitted to the Paediatrics Department, National University of Singapore, with non-gastroenterological illnesses were also tested. In all three races, seroprevalence of H. pylori increased with age. Indians have the highest prevalence of infection followed by Chinese and Malays. Peptic ulcer prevalences are known to be highest in Chinese, followed by Indians and Malays. The Malays have the lowest prevalence of H. pylori and peptic ulcer among the three races in Singapore. Indians have a higher prevalence of H. pylori antibodies but a lower frequency of peptic ulcer than the Chinese. Racial differences in peptic ulcer frequency between Chinese and Indians are not explained by the prevalence of H. pylori infection; other environmental or genetic factors may be involved.