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241.
A scheme for watershed protection and landscape enhaneement(WPLE) by utilization of fiver water was proposed to renovate water resources and protect ecological environment in Qiongshan City, Hainan Province, China. Utilization of fiver water may diminish the drought and flood risks. The scheme is benefieial to solve the problems of water resources shortage, groundwater declines and saltwater intrusion in the watershed. The object of the WPLE scheme is to aehieve a sustainable integrated development of environment, ecology, economy and society.A kind of physieally beautiful and funetionally vivid landscape may exert its synthetieal funetion on the diversity of landscape and the enjoyment of inhabitants. Feasibility of the scheme will be demonstrated by more exoeriments and tests, as well as observations in a long term. 相似文献
242.
A familial pericentric inversion of chromosome 19 was detected prenatally in a young primagravida. As far as the authors are aware there are no previous published reports of this rare abnormality being ascertained in this manner. The problems of counselling such a family are considered. 相似文献
243.
This study was designed to test the usefulness of the common definitions for maternal cell contamination, true mosaicism, and pseudomosaicism for amniotic fluid specimens processed by in situ culture and robotic harvesting. We prospectively studied 4309 consecutive amniotic fluid specimens processed with these methods and found that 0.84 per cent had maternal cell contamination, 0.28 per cent had true mosaicism, and 5.4 per cent had pseudomosaicism. Although the frequencies of maternal cell contamination and true mosaicism were comparable to those in similar published studies, the frequency of pseudomosaicism was more than twice as high as that in previous reports. This finding is most likely not due to the method, but rather to a more accurate estimate of the actual frequency of pseudomosaicism in amniotic fluid cultures than reported heretofore. Follow-up clinical information was available on 72 per cent of the cases. In three cases of true mosaicism involving structural anomalies, the results of cytogenetic follow-up studies on the neonates were normal. None of the pseudomosaic cases involving trisomy 8, 13, 18, or 21; triple X; or monosomy X were associated with newborns who had birth defects. 相似文献
244.
金属浓度,半透膜孔径,水温及配位体对半透膜囊吸收铜的影响 总被引:2,自引:1,他引:2
在实验室条件下,研究了影响树脂-半透膜囊吸收铜的主要因素,重点探讨了水相铜含量,半透膜孔径,温度以及天然河水中的有机配位体对吸收的影响。结果表明,半透膜囊吸收量与水相游离铜浓度,水温及半透膜孔径的非整数次幂成正比,其中包括EDTA,河水富里酸,以及河水中的各种天然有机物在内的配位体均与铜生成不能被半透膜囊吸收的络合物,研究结果进一步证实了半透膜囊对水环境中游离态微量金属进行长期监测的可行性。 相似文献
245.
Reproductive marine algae with complex life histories may respond differently to water motion depending upon whether the spore-producing or gamete-producing phase is considered. Two such species, the kelp Alaria esculenta (L.) Greville (Phaeophyceae) and Ulva lactuca L. (Chlorophyta), were examined experimentally in the laboratory. The kelp was collected in April–June 2000 and U. lactuca was collected in July–August 2000, from four intertidal habitats at Schoodic Point, Maine, USA. Orbital shakers were used to generate water motion. Sporophylls of A. esculenta released more zoospores under shaken versus calm conditions, whereas fewer antheridia on the microscopic male gametophytes released sperm under shaken versus calm conditions when male and female gametophytes were placed together. However, antheridial sperm release was equivalent when male gametophytes were exposed to undiluted media from dense cultures of mature female gametophytes under shaken versus calm conditions. These data suggest that water motion inhibited sperm release by diluting the sperm-releasing pheromone produced by ripe eggs below a threshold required to cause sperm release. Water motion stimulated both gamete and zoospore release from U. lactuca. This is the first report in an alga of stimulation of gamete release by increased water motion, but it is notable that parthenogenesis occurs in Ulva spp.; thus, gametes may develop into gametophytes (1 N) or parthenosporophytes (2 N). This study demonstrates that water motion has strong effects upon algal reproduction, but that the effects may vary between species, possibly due to their different life histories.Communicated by J.P. Grassle, New Brunswick 相似文献
246.
Net photosynthetic O2 evolution by five marine macroalgae:Ulva lactuca L.,Enteromorpha sp.,Ceramium strictum Harvey,Fucus serratus L., andF. vesiculosus L., collected from Danish waters in the summer of 1983 was followed at increasing O2 and with pH either fixed close to pH 7, 8 or 9, or drifting upwards during photosynthesis in a closed chamber to determine the effects of changing O2, pH and DIC (dissolved inorganic carbon) on photosynthesis. Increasing O2, increasing pH and decreasing DIC together limited O2 evolution. Raising the O2 concentration with pH and DIC held constant resulted in less inhibition of net-O2 evolution than when all three factors acted together. The O2 inhibition of photosynthesis was similar to the reported O2 inhibition of ribulose 1,5-bisphosphate carboxylase isolated from lower and higher plants. Net-O2 evolution as a function of the molar ratio of O2 to HCO–
3 + CO2 in solution provided a general, linear relationship (r
2 = 0.72 to 0.84), predicting inhibition of photosynthesis based on O2 pH and DIC changing together. Slopes of this relationship, representing competition between O2 and carbon based on external concentrations, were similar for the five taxonomically different algae, suggesting that similar processes act to reduce net-O2 evolution. 相似文献
247.
Rejection of emerging organic micropollutants in nanofiltration-reverse osmosis membrane applications. 总被引:1,自引:0,他引:1
Pei Xu J?rg E Drewes Christopher Bellona Gary Amy Tae-Uk Kim Marc Adam Thomas Heberer 《Water environment research》2005,77(1):40-48
The rejection of emerging trace organics by a variety of commercial reverse osmosis (RO), nanofiltration (NF), and ultra-low-pressure RO (ULPRO) membranes was investigated using TFC-HR, NF-90, NF-200, TFC-SR2, and XLE spiral membrane elements (Koch Membrane Systems, Wilmington, Massachusetts) to simulate operational conditions for drinking-water treatment and wastewater reclamation. In general, the presence of effluent organic matter (EfOM) improved the rejection of ionic organics by tight NF and RO membranes, as compared to a type-II water matrix (adjusted by ionic strength and hardness), likely as a result of a decreased negatively charged membrane surface. Rejection of ionic pharmaceutical residues and pesticides exceeded 95% by NF-90, XLE, and TFC-HR membranes and was above 89% for the NF-200 membrane. Hydrophobic nonionic compounds, such as bromoform and chloroform, exhibited a high initial rejection, as a result of both hydrophobic-hydrophobic solute-membrane interactions and steric exclusion, but rejection decreased significantly after 10 hours of operation because of partitioning of solutes through the membranes. This resulted in a partial removal of disinfection byproducts by the RO membrane TFC-HR. In a type-II water matrix, the effect of increasing feed water recoveries on rejection of hydrophilic ionic and nonionic compounds was compound-dependent and not consistent for different membranes. The presence of EfOM, however, could neutralize the effect of hydrodynamic operating condition on rejection performance. The ULPRO and tight NF membranes were operated at lower feed pressure, as compared to the TFC-HR, and provided a product water quality similar to a conventional RO membrane, regarding trace organics of interest. 相似文献
248.
Chang FT Lin YC Bai H Pei BS 《Journal of the Air & Waste Management Association (1995)》2003,53(11):1384-1390
The use of a honeycomb zeolite concentrator and an oxidation process is one of the most popular methods demonstrated to control volatile organic compound (VOCs) emissions from waste gases in semiconductor manufacturing plants. This study attempts to characterize the performance of a concentrator in terms of the removal efficiencies of semiconductor VOCs (isopropyl alcohol [IPA], acetone, propylene glycol methyl ether [PGME], and propylene glycol monomethyl ether acetate [PGMEA]) under several parameters that govern the actual operations. Experimental results indicated that at inlet temperatures of under 40 degrees C and a relative humidity of under 80%, the removal efficiency of a zeolite concentrator can be maintained well over 90%. The optimal rotation speed of the concentrator is between 3 and 4.5 rph in this study. The optimal rotation speed increases with the VOCs inlet concentration. Furthermore, reducing the concentration ratio helps to increase the removal efficiency, but it also increases the incineration cost. With reference to competitive adsorption, PGMEA and PGME are more easily adsorbed on a zeolite concentrator than are IPA and acetone because of their high boiling points and molecular weights. 相似文献
249.
250.
Cumulative ecological and socioeconomic effects of forest policies in coastal Oregon. 总被引:1,自引:0,他引:1
Thomas A Spies K Norman Johnson Kelly M Burnett Janet L Ohmann Brenda C McComb Gordon H Reeves Pete Bettinger Jeffrey D Kline Brian Garber-Yonts 《Ecological applications》2007,17(1):5-17
Forest biodiversity policies in multi-ownership landscapes are typically developed in an uncoordinated fashion with little consideration of their interactions or possible unintended cumulative effects. We conducted an assessment of some of the ecological and socioeconomic effects of recently enacted forest management policies in the 2.3-million-ha Coast Range Physiographic Province of Oregon. This mountainous area of conifer and hardwood forests includes a mosaic of landowners with a wide range of goals, from wilderness protection to high-yield timber production. We projected forest changes over 100 years in response to logging and development using models that integrate land use change and forest stand and landscape processes. We then assessed responses to those management activities using GIS models of stand structure and composition, landscape structure, habitat models for focal terrestrial and aquatic species, timber production, employment, and willingness to pay for biodiversity protection. Many of the potential outcomes of recently enacted policies are consistent with intended goals. For example, we project the area of structurally diverse older conifer forest and habitat for late successional wildlife species to strongly increase. 'Other outcomes might not be consistent with current policies: for example, hardwoods and vegetation diversity strongly decline within and across owners. Some elements of biodiversity, including streams with high potential habitat for coho salmon (Oncorhynchus kisutch) and sites of potential oak woodland, occur predominately outside federal lands and thus were not affected by the strongest biodiversity policies. Except for federal lands, biodiversity policies were not generally characterized in sufficient detail to provide clear benchmarks against which to measure the progress or success. We conclude that land management institutions and policies are not well configured to deal effectively with ecological issues that span broad spatial and temporal scales and that alternative policies could be constructed that more effectively provide for a mix of forest values from this region. 相似文献