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491.
Population declines of anadromous salmonids are attributed to anthropogenic disturbances including dams, commercial and recreational fisheries, and pollutants, such as estrogenic compounds. Nonylphenol (NP), a xenoestrogen, is widespread in the aquatic environment due to its use in agricultural, industrial, and household products. We exposed Atlantic salmon yolk-sac larvae to waterborne 10 or 100 microg L(-1) NP (NP-L or NP-H, respectively), 2 microg L(-1) 17beta-estradiol (E2), or vehicle, for 21 days to investigate their effects on smolt physiology and behavior 1 year later. NP-H caused approximately 50% mortality during exposure, 30 days after exposure, and 60 days after exposure. Mortality rates of NP-L and E2 fish were not affected until 60 days after treatment, when they were 4-fold greater than those of controls. Treatment with NP-L or E2 as yolk-sac larvae decreased gill sodium-potassium-activated adenosine triphosphatase (Na+,K(+)-ATPase) activity and seawater (SW) tolerance during smolt development, 1 year after exposure. Exposure to NP-L and E2 resulted in a latency to enter SW and reduced preference for SW approximately 2- and 5-fold, respectively. NP-L-exposed fish had 20% lower plasma insulin-like growth factor I (IGF-I) levels and 35% lower plasma triiodothyronine (T3). Plasma growth hormone and thyroxine (T4) were unaffected. Exposure to E2 did not affect plasma levels of IGF-I, GH, T3, or T4. Both treatment groups exhibited increased plasma cortisol and decreased osmoregulatory capacity in response to a handling stressor. These results suggest that early exposure to environmentally relevant concentrations of NP, and other estrogenic compounds, can cause direct and delayed mortalities and that this exposure can have long-term, "organizational" effects on life-history events in salmonids. 相似文献
492.
Darren Swanepoel Olinto DelFabbro WalterW. Focke Corrie Conradie 《Propellants, Explosives, Pyrotechnics》2010,35(2):105-113
Manganese metal was evaluated as a fuel for slow‐burning delay compositions press‐filled in aluminium or compaction‐rolled in lead tubes. Oxides of antimony, bismuth, copper, manganese and vanadium were considered as oxidants. Measured burn rates for binary mixtures varied between 5 and 22 mm s−1 but slower burning ternary and quaternary compositions were also found. The addition of fumed silica to the Mn/MnO2 system had little effect on the propagation rate but a low level addition of hollow glass sphere significantly reduced the burn rate. Mn MnO2 mixtures showed reliable burning over a wide stoichiometric range. In this system the fuel and the oxidant share a common metal. They combine to form the more stable intermediate oxide (MnO) releasing considerable quantities of heat in the process. 相似文献
493.
The present study demonstrates the high potential for the application of a novel self assembled positively charged nanofiltration membrane, PA6DT-C, in processes such as the recovery of valuable cationic macromolecules in the bioprocess and pharmaceutical industries or removal of multi-valent cations such as dyes and heavy metals in the paper and pulp, textiles, nuclear, and automotive industries. The nanofiltration membrane, prepared in this laboratory, is further characterised and then tested for the removal and recovery of Methylene Blue from a synthetic dye house wastewater. The characterisation process involved the construction of a rejection profile for NaCl over a wide range of pH and concentration, which illustrates that the optimal process conditions for the removal of small cations using this membrane is in the region pH <8.0 and concentration less than 15 mol m−3. The salt rejection data was used to calculate the magnitude of the effective membrane charge density and this was found to be significantly higher for the PA6DT-C membrane than two commercially available membranes (Desal-DK and Nanomax-50). The membrane flux for this new membrane is also superior to the commercial membranes with an approximate increase of 3-4 fold. The PA6DT-C membrane was successful in removal of Methylene Blue dye from synthetic dye house wastewaters achieving 98% rejection and a membrane flux of ∼17 LMH bar−1. Thus, this new membrane both adds to and complements the existing short supply of positively charged NF membranes. 相似文献
494.
Standard multinomial logit (MNL) and mixed logit (MXL) models are developed to estimate the degree of influence that bicyclist, driver, motor vehicle, geometric, environmental, and crash type characteristics have on bicyclist injury severity, classified as property damage only, possible, nonincapacitating or severe (i.e., incapacitating or fatal) injury. This study is based on 10,029 bicycleinvolved crashes that occurred in the State of Ohio from 2002 to 2008. Results of likelihood ratio tests reveal that some of the factors affecting bicyclist injury severity at intersection and non-intersection locations are substantively different and using a common model to jointly estimate impacts on severity at both types of locations may result in biased or inconsistent estimates. Consequently, separate models are developed to independently assess the impacts of various factors on the degree of bicyclist injury severity resulting from crashes at intersection and non-intersection locations.Several covariates are found to have similar impacts on injury severity at both intersection and non-intersection locations. Conversely, six variables were found to significantly influence injury severity at intersection locations but not non-intersection locations while four variables influenced bicyclist injury severity only at non-intersection locations. In crashes occurring at intersection locations, the likelihood of severe bicyclist injury increases by 14.8 percent if the bicyclist is not wearing a helmet, 82.2 percent if the motorist is under the influence of alcohol, 141.3 percent if the crash-involved motor vehicle is a van, 40.6 percent if the motor vehicle strikes the side of the bicycle, and 182.6 percent if the crash occurs on a horizontal curve with a grade. Results from non-intersection locations show the likelihood of severe injuries increases by 374.5 percent if the bicyclist is under the influence of drugs, 150.1 percent if the motorist is under the influence of alcohol, 53.5 percent if the motor vehicle strikes the side of the bicycle and 99.9 percent if the crash-involved motor vehicle is a heavy-duty truck. 相似文献
495.
Mercer Eric Slind Konrad Amundson Isaac Cofer Darren Babar Junaid Hardin David 《Software and Systems Modeling》2023,22(5):1451-1471
Software and Systems Modeling - Safety-critical systems such as avionics need to be engineered to be cyber resilient meaning that systems are able to detect and recover from attacks or safely... 相似文献
496.
Siddhant Naudiyal Martha Briceno de Gutierrez Richard Greenwood Paul Bowen Mark Simmons Stuart Blackburn Hugh Stitt Darren Gobby Aswani Mogalicherla 《Advanced Engineering Materials》2023,25(16):2201766
Manufacturing honeycomb-structured catalysts require a careful understanding of the microstructure of the solid substrate and its dependence on thermal-processing conditions. Herein, it is the thermal responses of microcracks in an uncoated microcracked aluminum titanate honeycomb catalyst is investigated by analyzing the material's resonance frequency using the high-temperature impulse excitation technique. The resonance frequencies are presented as Young's modulus values to avoid sample size effects. Dynamic Young's modulus measurements show closed-loop hysteresis due to microcracks healing and reopening, causing a reversible response. The hysteresis is further used to understand microcracks’ dependence on critical thermal-processing conditions used in a catalyst manufacturing plant, including peak operating temperature (800–1000 °C), dwell period (1–3 h), and heating rates (1–5 °C min−1). Microcracks are observed to have two healing responses: instantaneous and delayed healing. Both responses significantly influence the design of catalyst manufacturing. Complete reopening of microcracks from their healing temperature (1150 °C) is a very time-consuming process (50–60 h). However, it is shown in the analysis that microcrack relaxation is a critical phenomenon that must be considered in quality-controlled environments. 相似文献
497.
Darren Mc Carthy 《国外电子测量技术》2014,(3):22-26
正先进的的下一代雷达系统受益于数字技术和计算能力的进步。雷达基带部分越来越倾向于使用直接数字合成(direct digital synthesis,DDS)技术,从而具有强大的数字信号处理和宽基带波形生成能力,以便创建软件定义的雷达。DDS雷达优点突出。在评估是否应该将这一技术与有源电子扫描天线(active electronically scanned antenna,AESA)技术相结合时,应该考虑下述潜在的系统优点: 相似文献
498.
499.
Richard Harding-Crooks Darren Smith Séamus Fanning Edward M. Fox 《Comprehensive Reviews in Food Science and Food Safety》2023,22(4):2706-2727
Antimicrobial agents are a critical component of modern healthcare systems, fulfilling a core function in patient care and improving individual patient outcomes and consequently overall public health. However, the efficacy of antimicrobial interventions is being consistently eroded by the emergence and dissemination of various antimicrobial resistance (AMR) mechanisms. One highly valued class of antimicrobial compounds is carbapenems, which retain efficacy in treating most multidrug-resistant infections and are considered “last line” agents. Therefore, recent trends in proliferation of carbapenem resistance (CR) via dissemination of carbapenemase-encoding genes among members of the Enterobacteriaceae family pose a significant threat to public health. While much of the focus relating to this has been on nosocomial environments, community-acquired carbapenemase-producing Enterobacteriaceae (CPE) infections and their associated transmission routes are less well studied. Among these community-associated vectors, the role of food chains and contaminated foods is important, since Enterobacteriaceae occupy niches within these settings. This review examines foodborne CPE transmission by exploring how interactions within and between food, the food chain, and agriculture not only promote and disseminate CPE, but also create reservoirs of mobile genetic elements that may lead to further carbapenemase gene proliferation both within and between microbial communities. Additionally, recent developments regarding the global occurrence and molecular epidemiology of CPEs in food chains will be reviewed. 相似文献
500.
Self-assembled nanoparticle networks have emerged as multifunctional building blocks for a new generation of highly sensitive sensing technologies that offer large surface-to-volume ratios and a range of associated benefits. Unfortunately, with nanoparticle networks often being held together by weak van der Waals forces, the development of useful commercial devices is slowed by the relatively low robustness and poor carrier transport characteristics. This study shows how the application of a single droplet of ethanol can induce capillary forces capability of delivering significant changes to the morphological, structural, optical, and electronic properties of ZnO nanoclusters. It demonstrates how ZnO nanocluster “dendrites” and nanoparticles are forced together to form micro-scale islands and larger nanoparticles, and thereby improve the robustness of the layers and the quality of the junctions between the nanoparticles without significantly reducing the overall porosity of the layer or degrading the structural or optical properties in any way. The commensurate improvement in the electronic transport within the layers is found to greatly improve the photoresponse of UV detectors. It seems likely that the application of ethanol and the exploitation of capillary force can provide a technique that can greatly benefit any nanostructured, ultra-porous device where poor charge transport currently limits performance. 相似文献