The effect of two applications of atrazine on the water quality of freshwater enclosures

To simulate runoff from agricultural lands, atrazine was applied to aquatic enclosures (112 m(3)) on 1 June 1983 at a concentration of 0.1 mg litre(-1). Thirty-five days later the nominal concentration was increased to 0.155 mg litre(-1). Treated enclosures became clearer with Secchi disc readings of 3.6 m compared to non-treated controls (2.9 m). Less than 5% of the first atrazine addition disappeared during the first 35 days and little effect on biological activity was observed. However, with the second enrichment the rate of loss of atrazine was rapid (t(1/2) = 150 days), ammonium, calcium, dissolved inorganic carbon and nitrate levels were higher, while oxygen, chlorophyll, dissolved organic carbon and particulate organic carbon concentrations were lower in the treated enclosures. These water quality changes cannot be explained by herbicide-water chemistry interactions alone, thereby suggesting an indirect effect as a consequence of atrazine inhibition on photosynthesis and possibly other microbial processes.     

Current indirect fitness benefits associated with philopatry in juvenile prairie voles

Summary Prairie vole (Microtus ochrogaster) family groups were examined to determine possible indirect fitness benefits from the presence of juvenile helpers at the natal nest. The reproductive performance of family groups retaining two juveniles was compared with that of families in which all juveniles were removed when the subsequent litter was born. Litter sizes at birth of the second litter and pup survival rates were the same in the two treatments. Offspring quality was affected by the presence of juveniles however. Pups reared with juveniles weighed 13% more at weaning than pups reared without juveniles. Pups also opened their eyes sooner when juveniles were present. Differences in growth and development may have been affected by the amount of time pups were alone in the nest since pups in families with juveniles were left alone less frequently than were pups without juveniles. Maternal behavior patterns were not affected by the presence of juveniles. In contrast, fathers in families with juveniles spent more time in non-parental behaviors such as feeding, drinking, and foraging. In families with large litters, mothers delivered a subsequent litter sooner if juveniles were present. Subsequent litter sizes were the same in both treatments. Overall, both infants and parents benefited from the presence of juveniles, suggesting that helping may enhance the helper's indirect fitness in multiple ways.     

A pre/post evaluation of fatigue,stress and vigilance amongst commercially licensed truck drivers performing a prolonged driving task

Purpose. The main purpose of this research study was to evaluate changes in fatigue, stress and vigilance amongst commercially licensed truck drivers involved in a prolonged driving task. The secondary purpose was to determine whether a new ergonomic seat could help reduce both physical and cognitive fatigue during a prolonged driving task. Two different truck seats were evaluated: an industrial standard seat and a new truck seat prototype. Methods. Twenty male truck drivers were recruited to attend two testing sessions, on two separate days, with each session randomized for seat design. During each session, participants performed two 10-min simulated driving tasks. Between simulated sessions, participants drove a long-haul truck for 90 min. Fatigue and stress were quantified using a series of questionnaires whereas vigilance was measured using a standardized computer test. Results. Seat interactions had a significant effect on fatigue patterns. Conclusion. The new ergonomic seat design holds potential in improving road safety and vehicle accidents due to fatigue-related accidents.     

Morphology-Related Isometric Trunk Strength of South African Manual Workers: Implications for Prevention of Occupational Low-Back Stress

Occupational back stress among manual workers in South Africa is now a cause of governmental concern. Yet no data on the back strength of the South African workforce have been published. This study represents a first step in reporting the trunk strength of Xhosa workers in South Africa, in absolute and size-relative terms. Thirty-five male manual workers were tested isometrically while making maximal extension and flexion efforts at 0°, 23°, 46°, 69°, and 92° of stoop. The results show nonlinearity of the extensor-to-flexor (E/F) ratio of the trunk musculature. The E/F ratio increases in deep stoop because of a drop in flexor torques. The data suggest that predictions of flexor from extensor torques or vice versa can confidently be made so long as testing is done away from the fully flexed position. Significant differences between morphologically gracile and robust workers in this sample are discussed. The study has implications for occupational rehabilitation and for prophylaxis, for whereas muscular strength alone may not protect the spine from occupational injury, muscular weakness certainly predisposes it.     

卟啉作为人体早期砷暴露生物标志的研究

采用氢化物发生原子吸收分析了贵州省燃煤污染型砷中毒区和非砷中毒区（对照）居民尿样中砷浓度,采用高效液相色谱法分析了卟啉浓度,考察了燃煤污染造成的人体砷暴露与尿液中卟啉排泄改变的关系,寻求慢性砷中毒早期健康效应的生物标志物.结果显示,与对照组相比,砷暴露组尿卟啉Ⅲ（uroporphyrin-Ⅲ）和粪卟啉Ⅲ（coproporphyrin-Ⅲ）显著增高（P＜0.01,P＜0.01）,粪卟啉Ⅰ（coproporphyrin-Ⅰ）比对照组增高,但不显著;不同性别组间比较,对照组和暴露组的中龄（20～40岁）群体尿液中,尿卟啉Ⅲ的浓度在男性和女性群体之间呈显著性的差异（P<0.01）,其它年龄组中,这一指标在不同性别群体之间未见显著性差异;不同年龄分层比较,低龄组（＜20岁）尿卟啉Ⅲ和粪卟啉Ⅲ比对照显著增高（P＜0.01,P＜0.01）,中龄组（20～40岁）和高龄组（＞40岁）粪卟啉Ⅲ比对照显著增高（P＜0.05,P＜0.05）;此外,砷暴露组尿液中砷与总粪卟啉和总卟啉呈正相关（r=0.623,r=0.549）.结果表明,人体砷暴露会导致尿液中卟啉排泄的改变,提示卟啉有可能作为慢性砷中毒早期健康效应的生物标志.