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971.
Vinyl sugar ester, 6-O-vinyladipoyl-d-glucose (VAG), was polymerized with vinyl fatty acid esters in dimethylformamide (DMF) with azobisisobutyronitrile (AIBN) to produce new amphiphilic polymers having branches of sugar and fatty acid esters. The influence of structural variations by changing the length of the alkyl chain of fatty acid moiety was examined by measurements of the surface tension and biodegradability. 相似文献
972.
浅谈事故查处遵循的原则及善后处理需把握的关键问题 总被引:2,自引:0,他引:2
苏景云 《中国安全科学学报》2000,10(4):31-35
通过安全工作实践 ,总结归纳了事故查处应遵循的若干原则和善后处理的主要内容 ,提出了事故善后处理过程中需要把握的几个关键问题 ,对于事故管理有一定的借鉴和指导意义。 相似文献
973.
Effect of electrokinetic transport on the vulnerability of PAH-degrading bacteria in a model aquifer
There has been increasing interest in employing electro-bioremediation, a hybrid technology of bioremediation and electrokinetics,
to overcome the low bioavailability of hydrophobic organic contaminants (HOC) by homogenizing sorption-retarded HOC and immobilised
microorganisms. Present electro-remediation approaches mainly aim at macroscale pollutant extraction and tend to neglect possible
impacts of direct current (DC) on the physiology of microorganisms. The effect of weak electric fields (X = 1 V cm−1) on the fitness of electrokinetically dispersed fluorene-degrading Sphingomonas sp. LB126 in bench-scale model aquifers was investigated by flow cytometry using propidium iodide (PI) as an indicator that
distinguishes between PI-permeable (cells with porous membranes, i.e. dead or vulnerable) and PI-impermeable bacteria. After
15.5 h of DC treatment 56% of all cells recovered were dispersed at the centimetre scale relative to 29% in the absence of
DC. There was no overall negative effect of the 15.5-h DC treatment on cell vulnerability, as 7.0% of the DC-treated bacteria
exhibited PI-staining compared to 6.5% of the control population. Minor differences were observed in the subpopulation that
had been mobilised by electroosmosis with an approximately twofold increase in the percentage of PI-stained cells relative
to the control. Enhanced PI staining did not correlate with reduced culturability of the cells on rich-medium agar plates.
Relative to the control, DC-treated cells mobilised by electroosmosis were threefold more culturable, confirming earlier data
that that PI-cell membrane permeability does not always indicate reduced viability of oligotrophic environmental bacteria.
Our findings suggest that electrokinetics is a valuable mechanism to transport viable and culturable polycyclic aromatic hydrocarbon
(PAH)-degrading bacteria in soil or sediments. 相似文献
974.
A general model for the phase-averaged velocity field in wind-induced countercurrent flow is proposed. The influence of waves
on the time-averaged velocity is accounted for by introducing a skewness factor in a parabolic eddy viscosity model. The skewness
factor represents the net effect of the wavy surface in the engineering model for velocity. The coherent velocity components
are described separately by an orbital velocity obtained from linear wave theory and are added to the time-averaged components
to give a complete model for the phase-averaged velocity field. The proposed model collapses to the standard model for deep-water
conditions, but is also shown to yield the correct behavior for intermediate conditions. Moreover, the bed shear stress, derived
from the proposed velocity model, is also shown to be in agreement with experiments. 相似文献
975.
Axel Strauß Katrin Y. Solmsdorff Roger Pech Jens Jacob 《Behavioral ecology and sociobiology》2008,62(10):1551-1558
Predators can strongly influence the microhabitat use and foraging behaviour of prey. In a large-scale replicated field experiment
in East Gippsland, Australia, we tested the effects of reduced alien red fox (Vulpes vulpes) and alien wild dog (Canis lupus familiaris) abundance (treatment) on native bush rat (Rattus fuscipes) behaviour. Bush rats are exposed to two main guilds of predators, namely mammalian carnivores and birds of prey. Tracking
rat movements using the spool-and-line technique revealed that, in treatment sites, rats used ground cover, which provides
shelter from predators, less often than at unmanipulated fox and wild dog abundance (non-treatment sites). In treatment sites,
rats more frequently moved on logs where they would have been exposed to hunting foxes and dogs than in non-treatment sites.
Furthermore, in treatments, rats showed a preference for understorey but not in non-treatments. Hence, bush rats adapted their
behaviour to removal of alien terrestrial predators. Giving-up densities (GUDs) indicated no treatment effects on the marginal
feeding rate of bush rats. Interestingly, GUDs were higher in open patches than in sheltered patches, suggesting higher perceived
predation risk of bush rats during foraging at low versus high cover. The lack of treatment effects on GUDs but the clear
response of bush rats to cover may be explained by the impact of predators other than foxes and wild dogs. 相似文献
976.
为了评价全氟辛烷磺酸(PFOS)和多壁碳纳米管(MWCNTs)对水环境及鱼类的影响,以斑马鱼为模式生物,研究了PFOS和MWCNTs复合对斑马鱼外周血红细胞的DNA损伤。将成年斑马鱼暴露于PFOS(0.2、0.4、0.8、1.6 mg·L-1)、MWCNTs(50 mg·L-1)、PFOS+MWCNTs(0.2+50、0.4+50、0.8+50、1.6+50 mg·L-1)和对照溶液中30 d后,断尾取血进行微核试验和彗星试验。结果表明:PFOS和MWCNTs均可造成斑马鱼外周血红细胞的DNA损伤。1.6 mg·L-1PFOS处理组的微核率、Olive尾矩及尾长分别为(36.3±0.25)‰、(87.91±14.90)μm和(250.49±34.71)μm。PFOS与MWCNTs复合后,斑马鱼外周血红细胞的DNA损伤效应明显降低。复合处理组斑马鱼外周血红细胞的微核率、Olive尾矩及尾长均低于PFOS单独处理相。1.6 mg·L-1复合处理组的微核率、Olive尾矩及尾长比PFOS单独处理组分别降低了24.7%、68.9%、52.4%。因此,在实验浓度范围内,MWCNTs可以降低PFOS对斑马鱼外周血红细胞的DNA损伤。 相似文献
977.
Mengnjo J. Wirmvem Takeshi Oh Wilson Y. Fantong Samuel N. Ayonghe Jonathan N. Hogarh Justice Y. Suil Asobo Nkengmatia E. Asaah Seigo Ooki Gregory Tanyileke Joseph V. Hell 《环境科学学报(英文版)》2014,26(4):801-809
Rainwater characteristics can reveal emissions from various anthropogenic and natural sources into the atmosphere. The physico-chemical characteristics of 44 monthly rainfall events (collected between January and December 2012) from 4 weather stations (Bamenda, Ndop plain, Ndawara and Kumbo) in the Bamenda Highlands (BH) were investigated. The purpose was to determine the sources of chemical species, their seasonal inputs and suitability of the rainwater for drinking. The mean pH of 5 indicated the slightly acidic nature of the rainwater. Average total dissolved solids (TDS) were low (6.7 mg/L), characteristic of unpolluted atmospheric moisture/air. Major ion concentrations (mg/L) were low and in the order K+ 〉 Ca2+ 〉 Mg2~ 〉 Na+ for cations and NO3 〉〉 HCO3 〉 SO] 〉 CI- 〉 PO3- 〉 F- for anions. The average rainwater in the area was mixed Ca-Mg-SO4-CI water type. The CI-/Na+ ratio (1.04) was comparable to that of seawater (1.16), an indication that N a+ and CI originated mainly from marine (Atlantic Ocean) aerosols. High enrichments of Ca2+, Mg2+ and SO2- to Na+ ratios relative to seawater ratios (constituting 44% of the total ions) demonstrated their terrigenous origin, mainly from Saharan and Sahelian arid dusts. The K+/Na+ ratio (2.24), which was similar to tropical vegetation ash (2.38), and NO3 was essentially from biomass burning. Light (〈 100 mm) pre-monsoon and post-monsoon convective rains were enriched in major ions than the heavy (〉 100 mm) monsoon rains, indicating a high contribution of major ions during the low convective showers. Despite the acidic nature, the TDS and major ion concentrations classified the rainwater as potable based on the WHO guidelines. 相似文献
978.
979.
980.
Light microscopic study of different body organs of cat-fish following exposure to HgCl2 0.2 mg/L in water for 30 days revealed that focal degeneration of liver cells and disorganization of hepatic cords occurred at places. Furthermore, centrilobular atrophy and compensatory hypertrophy of some hepatic cells were also observed. In the kidneys disintegration of renal epithelium along with displacement of nuclei, shrinkage of glomeruli, breakdown of Bowman's capsule and heavy infiltration by inflammatory cells were observed. The histopathological changes noted in the intestine included degeneration of lining epithelium, and diminution of goblet cells. Microscopic section of ovaries exhibited reduction of ooplasm leading to formation of atypical oocytes. An increase in the occurrence of atretic oocytes and interfolicular spaces was also discernible. No histopathological lesions could be detected in testes of male fish probably because of the difference in the maturity of the control and experimental groups. The pathomorphological alterations in relation to mercury toxicity in spleen were associated with the disorganization of the splenic cords resulting in the displacement of lymphatic tissue cells within the substance of splenic pulp. Marked depletion of the red pulp was noticeable. 相似文献