The variation in the concentration and fatty acid composition of lipid classes during the molting cycle of the prawn Penaeus japonicus was investigated. The lipid concentration of the whole body reached a maximum at mid-premolt (Stage D2) and then decreased to low level at late premolt (Stage D3–4). The accumulation of lipids during the premolt period seemed to be attributable to the increase of both polar and neutral lipids. The increase of neutral lipids at Stage D2 was derived from not only triglycerides but also free sterols and free fatty acids. Regarding the fatty acid composition of every lipid class, a marked variation occurred mainly at the intermolt (Stage C). In this stage, the polar lipids were rich in monoenoic acids such as 18:1 and poor in polyenoic acids such as 20:53 and 22:63. The triglycerides were rich in polyenoic acids at Stage C, but poor in monoenoic acids such as 16:1 and 18:1. The steryl esters contained large amounts of saturated acids such as 16:0 and 18:0 throughout the molting cycle, however the level of polyenoic acids increased at Stage C. 相似文献
Lack of information from vehicle-to-child pedestrian impacts provides considerable challenges when developing vehicle countermeasures for the pediatric population. Crash reconstructions of real-world incidents provide useful information about the vehicle damage and injury outcome but do not permit definitive and quantitative measures of the impact severity given the high level of uncertainty in the initial conditions of the pedestrian and the vehicle prior the impact. This paper develops an advanced methodology for reconstructing child pedestrian–vehicle impacts that combines the crash data with multi-body simulations and optimization techniques for identifying the pedestrian posture and vehicle speed prior to impact. For the child pedestrian posture, a continuous sequence of the running gait was developed based on the literature data and simulations. Using vehicle damage information from an actual child pedestrian crash, an objective function was developed that minimized the difference between vehicle and pedestrian contact points for the simulated child postures, pedestrian, and vehicle speeds. Simulated annealing and genetic optimization algorithms were used to identify sets of potential solutions for the pedestrian and vehicle initial conditions. Local minimums were observed for several response surfaces of the objective function which shows the non-convex nature of the crash reconstruction optimization problem with the chosen objective function. Based on the results of the real-world reconstruction, this study indicates that numerical simulations coupled with heuristic optimization algorithms can be used to reconstruct child pedestrian and vehicle pre-impact conditions. 相似文献
The photo-Fenton reactions, which could yield hydroxyl radicals via the catalytic degradation of H2O2 by Fe(II), were focused as one of the abiotic degradation processes of bisphenol A (BPA) in surface waters. At pH 6, in the presence of H2O2 only, 32% of BPA was degraded after 120?min of irradiation. However, 97% of BPA was degraded in the presence of both H2O2 and Fe(II). Without light irradiation, no BPA degradation was observed even in the presence of Fe(II) and H2O2. These results show that photo-Fenton processes are effective in the natural attenuation of BPA in surface water. In addition, the presence of humic acids (HAs), which were of more aliphatic nature, resulted in enhancing BPA degradation via the photo-Fenton processes. Therefore, HAs can be one of the important factors in enhancing the degradation of BPA in surface water via the photo-Fenton processes. 相似文献
In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition. 相似文献
Many planktonic organisms have adaptations such as floats or lighter substances to obtain buoyancy to help them remain in
the surface layer of the ocean where photosynthetic primary production occurs and food is most abundant. The almost totally
transparent eel larvae, called leptocephali, are a unique member of the planktonic community of the surface layer, but their
ecology and physiology are poorly understood. We conducted a comparative study on the specific gravity of planktonic animals
including 25 taxa of 7 phyla of marine invertebrates and 6 taxa of leptocephali (vertebrate) to gain a broad perspective on
the buoyancy of the eggs and larval stages of the Japanese eel. The specific gravity values of the various freshly caught
marine invertebrate taxa varied widely from 1.020 to 1.425, but leptocephali had some of the lowest values (1.028–1.043).
Artificially cultured live leptocephali had even greater buoyancies with specific gravities of 1.019–1.025 that were close
to or lower than seawater, and their buoyancy showed ontogenetic changes among the different early life history stages. Leptocephali
appear to have a unique mechanism of buoyancy control by chloride cells all over body surface through osmoregulation of body
fluid contained in the extracellular matrix of transparent gelatinous glycosaminoglycans filling their bodies. This adaptation
is likely a key factor for their survival by helping them to remain in the surface layer where food particles are the most
abundant, while being transparent for predator avoidance. The ontogenetic change in buoyancy of eel eggs, leptocephali and
glass eels likely enhances their larval survival, transport, and recruitment to terrestrial freshwater habitats. 相似文献
The rates of photochemical generation of hydroxyl radical at 313 nm in aqueous solutions containing ferric ion at acidic pH were measured by the competitive kinetic method using 2-chlorophenol as a test compound and 1-octanol as a radical scavenger. The quantum yield of hydroxyl radical generation calculated from the rates was about 0.02. From the results, it was suggested that this system could be used as a method of wastewater treatment. 相似文献
Dissolved humic substances (DHSs) are the major components of organic matter in the aquatic environment. DHSs are well known to considerably affect the speciation, solubility, and toxicity of a wide variety of pollutants in the aquatic environment. In this study, the effects of the toxicity of heavy metals and hydrophobic organic pollutants (HOPs) on Chlamydomonas reinhardtii in the presence of humic acid (HA) were examined by a microscale algal growth inhibition (μ-AGI) test based on spectrophotometric detection. To clarify the relationship between the chemical properties of HAs and the toxicity change of pollutants, eight HAs from different sources were prepared and used. HAs were responsible for mitigating the toxicity of Hg, Cu, pesticides (γ-HCH, 2,4-D, and DDT), and polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap), anthracene (Ant), and benzo[a]pyrene (BaP). In particular, an approximately 100-fold decrease in the toxicity of BaP was observed in the presence of 10 ppm HAs extracted from tropical peat. The results indicated that the carboxylic group content and the HA molecular weight are correlated to the changes in the heavy metal toxicity. For HOPs, the aromaticity and polarity of HAs are crucial for mitigating their toxicity. Furthermore, it was clearly shown that the lake water including a high concentration of DHSs collected from Central Kalimantan, Indonesia, reduced the toxicity of Hg and γ-HCH on Chlamydomonas reinhardtii.
The combination of ultraviolet light and hydrogen peroxide was demonstrated to be a useful method for removing COD and TOC in aqueous phenol solutions. Both COD and TOC decreased to nearly zero in the presence of hydrogen peroxide. 相似文献