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71.
Polythene sheeting is a major litter component on estuarine beaches and river banks. Sanitary towel backing strips, which
are one of the commonest items of sewage related debris found on beaches, enter the riverine system via combined sewer overflows.
Investigations on these items, positioned at natural riverine stranding levels, showed that after an initial rapid breakdown
little further loss of tensile strength occurred. Experiments carried out on backing strips, buried in the bank suspended
from a tree and tethered to the bank, showed significant change. Buried samples retained the greatest tensile strength retention,
dropping no lower than 90 %, the other samples showed similar retention rates at 80%. The difference is probably due to photodegradation
as biodegradation effects were minimal. Probably, the longevity of such plastics is a major reason for their abundance and
widespread distribution both on river banks and beaches. 相似文献
72.
Sperm competition is predicted to generate opposing selection pressures on males. On one hand, selection should favour ‘defensive’ adaptations that protect a male’s ejaculate from displacement, while, on the other hand, selection should favour ‘offensive’ adaptations that overcome paternity assurance mechanisms of rivals. Here, we use the sterile male technique to assess sperm precedence when a male dung beetle Onthophagus taurus mates in both a defensive (first male) and an offensive (second male) role. Significant variation in a male’s sperm precedence (both P
1 and P
2) was detected, and an individual’s defensive (P
1) and offensive (P
2) abilities were positively correlated. Thus, it appears that sexual selection simultaneously selects for ‘defensive’ and ‘offensive’ adaptations in O. taurus. We discuss a variety of male traits in O. taurus that potentially contribute to a male’s ability to be successful when mating in an ‘offensive’ and a ‘defensive’ role. 相似文献
73.
John M. Graham Jr. Eileen F. Rawnsley G. Millard Simmons Doris H. Wurster-Hill Jonathan P. Park Miguel Marin-Padilla Harte C. Crow 《黑龙江环境通报》1989,9(6):409-419
Seven cases of triploidy were encountered by the Prenatal Diagnosis Program at Dartmouth–Hitchcock Medical Center over an 8-year period through associated pregnancy complications. We describe the characteristic findings that facilitate prenatal diagnosis and management. Our experience includes fetuses with major central nervous system abnormalities (spina bifida aperta, holoprosencephaly) and anterior abdominal wall defects, which are detectable with routine prenatal diagnostic screening examinations (ultrasound and AFP). In addition, we stress the importance of recognizing obstetric complications and associated cystic placental changes, which are quite common among triploid conceptuses. Molar changes associated with triploidy have a more benign prognosis than that associated with diploid moles. Such molar changes may relate to the presence of a diploid paternal chromosome complement. The usefulness of cytofluorometric DNA determinations in helping to confirm a clinical suspicion of triploidy is emphasized. These cases are presented in an effort to facilitate prenatal recognition and management of this common cytogenetic condition and prevent unnecessary Caesarean section deliveries. 相似文献
74.
Hydrogen production by anaerobic microbial communities exposed to repeated heat treatments. 总被引:2,自引:0,他引:2
T Duangmanee S I Padmasiri J J Simmons L Raskin S Sung 《Water environment research》2007,79(9):975-983
Biological hydrogen production by anaerobic mixed communities was studied in laboratory-scale bioreactors using sucrose as the substrate. A bioreactor in which a fraction of the return sludge was exposed to repeated heat treatments performed better than a control bioreactor without repeated heat treatment of return sludge and produced a yield of 2.15 moles of hydrogen per mole of sucrose, with 50% hydrogen in the biogas. Terminal restriction fragment length polymorphism analysis showed that two different Clostridium groups (comprised of one or more species) were dominant during hydrogen production. The relative abundance of two other non-Clostridium groups increased during periods of decreased hydrogen production. The first group consisted of Bifidobacterium thermophilum, and the second group included one or more of Bacillus, Melissococcus, Spirochaeta, and Spiroplasma spp. 相似文献
75.
Simmons RW Pongsakul P Saiyasitpanich D Klinphoklap S 《Environmental geochemistry and health》2005,27(5-6):501-511
Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence
communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous
mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual
entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated
rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken.
Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg−1 and 100 to 8036 mg kg−1, respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to
fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field’s proximity
to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60–100% of the Cd and Zn loading
associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged
from 0.05 to 7.7 mg kg−1. Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives
and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg−1. In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 μg Cd per kg Body.
This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based
field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values
via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated
rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate
the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific ‘high risk’
areas. 相似文献
76.
Christopher W. Simmons Hongyun Guo Joshua T. Claypool Megan N. Marshall Kristen M. Perano James J. Stapleton Jean S. VanderGheynst 《Waste management (New York, N.Y.)》2013,33(5):1090-1096
Soil solarization is a method of soil heating used to eradicate plant pathogens and weeds that involves passive solar heating of moist soil mulched (covered) with clear plastic tarp. Various types of organic matter may be incorporated into soil prior to solarization to increase biocidal activity of the treatment process. Microbial activity associated with the decomposition of soil organic matter may increase temperatures during solarization, potentially enhancing solarization efficacy. However, the level of organic matter decomposition (stability) necessary for increasing soil temperature is not well characterized, nor is it known if various amendments render the soil phytotoxic to crops following solarization. Laboratory studies and a field trial were performed to determine heat generation in soil amended with compost during solarization. Respiration was measured in amended soil samples prior to and following solarization as a function of soil depth. Additionally, phytotoxicity was estimated through measurement of germination and early growth of lettuce seedlings in greenhouse assays. Amendment of soil with 10% (g/g) compost containing 16.9 mg CO2/g dry weight organic carbon resulted in soil temperatures that were 2–4 °C higher than soil alone. Approximately 85% of total organic carbon within the amended soil was exhausted during 22 days of solarization. There was no significant difference in residual respiration with soil depth down to 17.4 cm. Although freshly amended soil proved highly inhibitory to lettuce seed germination and seedling growth, phytotoxicity was not detected in solarized amended soil after 22 days of field solarization. 相似文献
77.
Male dung beetles, Onthophagus taurus, are dimorphic for a secondary sexual trait, head horns. Horned males participate in the production of brood masses while
hornless male do not. Here we examine the reproductive performance of females mated with males exhibiting alternative horn
morphologies. We found that exposure to males may be costly for females in that it reduced the total number of brood masses
produced. However, females paired with horned males produced significantly larger brood masses than females paired with hornless
males or females producing broods alone. We discuss the possible selection pressures that may underly horn evolution in this
genus.
Received: 22 August 1997 / Accepted after revision: 19 January 1998 相似文献
78.
Marcussen H Joergensen K Holm PE Brocca D Simmons RW Dalsgaard A 《Environmental monitoring and assessment》2008,139(1-3):77-91
Extensive aquatic or semi-aquatic production of water spinach (Ipomoea aquatica Forssk.) for human consumption takes place in Southeast Asia. The aim of this study was to assess the concentrations of 38
elements in soil and water spinach cultivated under different degrees of wastewater exposure in Hanoi, Vietnam. The results
showed no effect of wastewater use on the overall element concentrations in soil and water spinach. Mean soil concentrations
for selected potentially toxic elements at the studied field sites had the following ranges 9.11–18.7 As, 0.333–0.667 Cd,
10.8–14.5 Co, 68–122 Cr, 34.0–62.1 Cu, 29.9–52.8 Ni, 32.5–67.4 Pb, 0.578–0.765 Tl and 99–189 Zn mg kg−1 dry weight (d.w.). In all samples Cd, Pb and Zn soil concentrations were below the Vietnamese Guideline Values (TCVN 7209-2002)
for agricultural soils whereas As and Cu exceeded the guideline values. Maximum site element concentrations in water spinach
were 0.139 As, 0.032 Cd, 0.135 Cr, 2.01 Cu, 39.1 Fe, 57.3 Mn, 0.16 Ni, 0.189 Pb and 6.01 Zn mg kg−1 fresh weight (f.w.). The site and soil content of organic carbon were found to have high influence on the water spinach element
concentrations whereas soil pH and the total soil element concentrations were of less importance. The estimated average daily
intake of As, Cd, Cu, Fe, Pb and Zn for adult Vietnamese consumers amounts to <11% of the maximum tolerable intake proposed
by FAO/WHO for each element. It is assessed that the occurrence of the investigated elements in water spinach will pose low
health risk for the consumers. 相似文献
79.
Behavior and lifestyle characteristics of male Kuwaiti drivers 总被引:1,自引:0,他引:1
Ali M. Al-Hemoud Author Vitae Rodney J. Simmons Author Vitae Author Vitae 《Journal of Safety Research》2010,41(4):307-313
Introduction: The high traffic accident risk among young drivers is a well-known and well-documented fact in most countries. Lifestyle has proven to affect driving behavior as well as accident risk. This study covers the lifestyle component of the problems related to young male Kuwaiti drivers’ accident risk. Methods: The purpose of the study is to measure the relationship between lifestyle and accident risk. Lifestyle is measured through a questionnaire, where 302 male Kuwaiti drivers (mean age = 28 years; range 25-35 years) answer 39 questions related to behavioral and social factors, road conditions, police enforcement, and life satisfaction. They also report their involvement in accidents and traffic violations. Results: The questionnaire's validity and reliability (Cronbach's alpha = 0.7) were achieved. Principal component analysis reduced the 39 items on the questionnaire to 5 factors. Inadequate police enforcement is strongly correlated (r = 0.862) to accident risk and traffic violations and is thus considered the best predictor of traffic accidents in Kuwait. Impact on Industry: As driving-related incidents (on-the-job and off-the-job) are a significant source of fatalities and lost-work-days, the study points to the importance of considering cultural factors in the design of comprehensive safety programs for industry. 相似文献
80.
In the distributed signal detection theoretic (DSDT) model, the human operator and the warning mechanism are independent decision makers who work together as a team. The DSDT demonstrates that the optimal warning threshold, in general, differs from the signal detection theoretic (SDT) threshold, which assumes a single decision maker. This prediction was tested in an experiment where drivers received monetary rewards for making safe passing decisions on a driving simulator. The experiment focused on evaluating the quality of the decision making of the drivers, and not on perceptual issues. A collision avoidance system provided a warning when the probability of an inadequate overtaking gap exceeded a threshold. Three thresholds were tested. The control threshold resulted in no detections or false alarms. The DSDT threshold resulted in some misses but no false alarms. The SDT threshold resulted in no misses but frequent false alarms. As predicted, (1) drivers performed the best when the warning system used the DSDT threshold, and (2) use of the SDT threshold improved performance over the control threshold, even though four of the 10 drivers occasionally ignored the warning and made risky passing attempts in the SDT conditions, possibly because of earlier false alarms. These findings support the conclusion that the DSDT model is a useful, quantitative tool that should be used by warning designers. 相似文献