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241.
生态系统服务研究进展 总被引:23,自引:5,他引:18
工业革命以来对地球进行的大范围开发 ,导致人类与自然的尖锐对立 ,全球气候在变暖、土地的生产力在下降、水资源的短缺日益突出、生态系统在大范围改变 (水生生态系统衰退、草原荒漠化、森林生态系统退化 )、生物多样性在减少、环境质量在下降。伴随着这些全球性和区域性的生态环境危机的发生 ,人类本身的生存与发展受到威胁 ,表现在 :自然生产的食物越来越少、可用于医疗保健的天然药物越来越少、许多相伴人类的动植物正濒临灭绝、灾难性的水旱灾害日益频繁、清洁的空气和清澈的河溪正变成奢侈品、人类活动产生的废物正在充斥和破坏着环境… 相似文献
242.
Biomphalaria sudanica (intermediate host of Schistosoma mansoni) were raised in the laboratory in media with seven different calcium concentrations ranging from 0.02 to 2.0 mmol/l. After 10 weeks, snails were killed and shell diameter, inorganic dry weight, ash free dry weight and crushing resistance were measured. Snails raised at lower calcium concentrations were found to be significantly smaller than snails raised at higher concentrations. Furthermore, relatively thinner shells were developed at low concentrations and crushing resistance relative to snail size was found to be lower for these snails. The ratio between crushing resistance and ash free dry weight (as a measure for the energetic cost/benefit-ratio) was also found to be correlated with calcium concentration. The relevance of the results for predation risk of B. sudanica is discussed. 相似文献
243.
蒙古栎伴生种及邻体物种多样性的研究 总被引:4,自引:0,他引:4
采用点样地法对四个地点蒙古栎树种的邻体多样性进行了研究,结果表明,随着调查样点数的增加,蒙古栎邻体的物种丰富度和Shannon -Wiener(H′)物种多样性指数逐渐增加,最后趋于一固定值。用物种共同出现百分率测定了蒙古栎与其伴生种的种间联结值(PC值),并引入LS值来测定单株蒙古栎相邻物种的平均个体数目,结果发现,不同地点蒙古栎邻体多样性不同,其相邻乔木和灌木种类也有较大差异,联结系数各有高低,比较PC值的大小,得出了蒙古栎的主要伴生乔木和主要伴生灌木物种(结构和组成)。物种(乔木和灌木)与蒙古栎伴生的原因主要是相似的环境需求和互惠互利,说明蒙古栎处在不同的群落演替阶段。 相似文献
244.
This study estimates the economic values of and the dominant contributors to five key ecosystem services of wetlands in Beijing, by using the wetland inventory data in 2014 and economic valuation methods. Results indicate that the 51,434 ha of wetlands in Beijing annually provide 2.07 billion m3 of flood regulation, 944.01 million m3 of water provision, 42,154 tons of chemical oxygen demand (COD) purification, 3.03 PJ of heat absorption, and 9587 ha of habitat. Their economic values are estimated to be 15.89 billion RMB, 1.19 billion RMB, 169 million RMB, 421 million RMB, and 1.08 billion RMB in 2014 (RMB: Chinese currency, US$1 = RMB 6.14), respectively. The total values of five key wetland ecosystem services reach 18.76 billion RMB. In addition, the reservoir and river wetlands in Miyun, Yanqing, Fangshan, Huairou, and Mentougou Districts contribute 78% of key ecosystem services, whereas the urban wetlands in Xicheng, Dongcheng, Haidian, Chaoyang, and Tongzhou Districts more conveniently serve densely local people, hence they should be given particular attentions. In this paper, we develop the valuation methods of wetland ecosystem services, and recommend diversified strategies, regulations, and programs to protect the remaining wetlands in Beijing. This work can also provide a reference for the valuating of wetland ecosystem services for other urban-rural areas. 相似文献
245.
The kinetic properties of rat liver nuclear lysozyme, earlier purified to homogeneity in our laboratory, have been studied.
The enzyme was found to be maximally active in the pH range 4.2 to 5.4 in 0.02 M buffer. Its Km was found to be 333 mg/litre.
It was heat sensitive even in the acidic pH range. The enzyme exhibited tissue specific differences when compared with the
rat kidney nuclear lysozyme. 相似文献
246.
《Saudi Journal of Biological Sciences》2022,29(10):103374
The liver is more prone to infections that cause fibrosis, such as steatosis, non-alcoholic steatohepatitis, hepatotoxicity, cirrhosis, and hepatocellular carcinoma. Also, Viral hepatitis is a common condition worldwide it worsens into chronic inflammation of the liver. One of the healthiest fruits is the pomegranate for the body and health, as it contains a high nutritional value of minerals, vitamins, antioxidants, so we worked on this investigation to magnify the therapeutic applications of pomegranate fruits (POF) and peel (POP) in carbon tetrachloride-injected rats (Ccl4). The experiment was carried out in a caged animal. All rats were fed a basal diet for one week before the study, and they were divided into seven groups, each with six rats. As a control negative group (C–ve), the first group sample was fed only the basal diet for 28 days. The remaining rats (n = 36) were injected with carbon tetrachloride (Ccl4). Five groups were fed varying concentrations of (5 %, 10 %, 15 % POF, 5 %, and 10 % pomegranate peel (POP)), whereas one group was diagnosed with the illness and disease, and didn't even feed the experimental diet. The results revealed significant increases in T.BIL, D.BIL, and BIL in the serum of rats injected by CC14 to induce hepatopathy compared to the healthy group (normal rats). Also, the best treatment considering the serum D.BIL was recorded for the 5 % POF. 相似文献
247.
《Saudi Journal of Biological Sciences》2020,27(11):3161-3168
Despite widespread and its local available as a naturalized hedge and shade plant, the potential of Trichilia emetica was not utilized in soap making by the majority of local community in various parts of Dodoma, Tanzania. This study aimed to assess the quantity (yields) and quality (Acid Values (AVs), %Free Fatty Acids (%FFAs) and Saponification Values (SVs) of seed oil from water plant (T. emetica), suitable for soap making application. Solvent extraction method was used during oil extraction, where by 50gm of preheated and powdered seed materials were immersed in 250 ml of n-hexane in 1:5 (w/v) to dissolve the oil contained in the seed cake. The oil was collected by vaporizing solvent out through Rotary evaporation at 60 °C. Also standard titration methods were used to obtain SVs, AVs and %FFAs of the extracted oil. Results showed that T. emetica seeds contained higher quantity of oil (48.4%−50.2%) than many reported commercial plant seed oils. Also, the study found higher AV (7.4 mgKOH/g−7.8 mgKOH/g), %FFA (3.7% to 3.9%) and SVs (189.5 mgKOH/g − 191.4 mgKOH/g) than the maximum acceptable limits of 0.50 mg KOH/g, 0.020% and 175 mgKOH/g − 187 mgKOH/g prescribed by ASTM standards (2002). The obtained results showed that, T. emetica seeds yielded high oil quantity with low qualities due to higher levels of acidity. But high SVs guarantees the possibility of using T. emetica seed oil in soap making. However, the oil requires purification in order to bring levels of acidity to acceptable standards and guarantee its normal use in soap making. 相似文献
248.
249.
This paper focuses on the analysis and evaluation of resilience anchored in an economic perspective. Resilience, as well as
most of the benefits provided by ecosystems, is not priced on current markets. However, this does not mean that resilience
is of no value for humans. On the contrary, the interest of using an economic perspective, and the respective scientific methodology,
will be put forward in terms of resilience relevance for ecosystem functioning, and its impact on human welfare. The economic
perspective is anchored in an anthropocentric analysis evaluating resilience in terms of provision of natural capital benefits.
These in turn are interpreted as insurance against the risk of ecosystem malfunctioning and the consequent interruption of
the provision of goods and services to humans. For this analysis, we make use of a conceptual framework that identifies and
describes the different value components of resilience. Finally, we present an illustration that discusses the economic analysis
of resilience benefits in the context of the Venice Lagoon. 相似文献
250.
Fisher information for a multivariate extreme value distribution 总被引:7,自引:0,他引:7
Explicit algebraic formulae for the Fisher information matrixof the multivariate extreme value distribution with generalisedextreme value margins and logistic dependence structure aregiven. 相似文献