共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Hans Grisebach 《Die Naturwissenschaften》1977,64(12):619-625
The complete set of enzymes that catalyze the reactions from l-phenylalanine to substituted cinnamyl alcohols is now known. The latter compounds are the primary building stones of lignin. The individual reactions and the possible modes of regulation of this pathway are discussed. The polymerization of cinnamyl alcohols to lignin is mediated by peroxidase. The significance of cell-wall-bound peroxidases in this process and the origin of hydrogen peroxide are reviewed. Finally, the possible role of lignification in relation to disease resistance is discussed. 相似文献
3.
4.
5.
6.
镉免疫毒性机理的初步探讨 总被引:12,自引:1,他引:11
从免疫细胞功能调控因素初步探讨镉免疫毒性机理0.3-2.4mg/kg/d氯化镉连续给小鼠灌胃14d,观察免疫器官重量及免疫功能、淋巴细胞内钙离子浓度、钙调素(CaM)含量、巨噬细胞内NO、O2-、H2O2变化。结果是0.3-2.4mg/kg/d氯化镉对免疫器官重量未见有明显影响,但0.3mg/kg/d组腹腔灌洗液巨噬细胞总数减少、体液免疫和巨噬细胞吞噬功能抑制,淋巴细胞胞内钙离于增加、钙调素呈下降趋势,巨噬细胞NO生成、O2-减少、H2O2有减少趋势体外试验50μmol/L氯化镉出现抑制淋巴细胞转化、IL-2减少、胞内钙离子增加、CaM含量降低趋势认为镉免疫毒性可能与其引起淋巴细胞钙稳态失衡密切相关 相似文献
7.
8.
本文重点研究了清洁生产推进机制,对清洁生产运行机制、技术机制、管理机制、政策机制进行研究和分析,对清洁生产的产生理论和运行管理进行分析。结论是,政策机制的关键是成功地实施技术机制和内部管理机制,在中国清洁生产的实施应该主导的政府执法机制,辅之以必要的经济激励和支持机制应激机制。 相似文献
9.
C. M. Visser 《Die Naturwissenschaften》1980,67(11):549-555
Analysis of the possible evolution of flavin catalysis in succinate dehydrogenase suggests as the ultimate stage an active site that bears one or more acid functions and uses the enediol form of the substrate rather than the carbanion as a nucleophile. In the case of flavoenzyme catalyzed oxidation of fatty acylCoA, α-amino acids and α-hydroxy acids evolution to a similar mechanism seems to be blocked. 相似文献
10.
In this paper,the relationship among land productivity,population pressure and the fluctuation mechanism of ecotone is analyzed,taking coumties and banners of southeast Inner Mongolia plateau as an example,which is the most fragile part in the farming and husbandry interleaving belt of north China due to its severe desertification degree and low level of economic development.The Cv for the total output value of agriculture decreases from southeast to northwest,with the same rule as which the overloading population cumulated distributes,and both indicators have close relation with the high linear coefficient of 0.83.These reveal the fluctuation mechanism for ecotone:fluctuation of the level of economic development is a scientific and practical measure both to weakness degree and to instability of ecotone,because it is a synthesized response to the variation of climate as well as irrational land uses,which reinforce and magnify the fluctuation.In detail,the heavier the population overloading,the severer the grassland reclamation,the stronger the dependence of regional productivity on rainfall,the lower the level of economic development,the rougher the fluctuation of ecotone,but the weaker the PRED system. 相似文献
11.
Michaelowa Axel Fages Emmanuel 《Mitigation and Adaptation Strategies for Global Change》1999,4(2):167-185
The Kyoto Protocol created the Clean Development Mechanism (CDM) to allow industrial countries to reach part of their greenhouse gas (GHG) emission reduction through projects in developing countries. To calculate the achieved emission reduction a reference scenario has to be developed – the baseline. Despite efforts to develop realistic baselines, a certain degree of uncertainty regarding actual reductions will be inevitable. It is therefore necessary to compare the costs (including transaction costs) of developing a baseline against the informational benefit it can be expected to produce. While project-related baselines are already being applied, the proponents of country-related baselines have still to show the applicability of their approach for the CDM. The possibility of quantifying indirect effects and considering market distortions and subsidies through aggregation in the country-related baselines is weighed up by the manipulability and uncertainty of the assumptions required in such a baseline. Thus project-specific baselines are recommended. In cases of severely distorted markets undergoing liberalization or subsidy phase-out, a country-related baseline can be helpful. Sectoral or programme baselines would be suited to large-scale energy and sequestration projects. Moreover it has to be considered whether emission reductions are generally achieved in the context of relocation or done in the context of global emitting capacity expansion. 相似文献
12.
13.
14.
为了深入认识气箱式脉冲袋式除尘器的清灰机理,按可压缩气体绝热状态和等温状态分别计算了脉冲质量流量和气箱中气体压力、密度的变化,进一步推导出穿过滤袋的清灰气流速度方程和清灰剥离力方程.按照在袋式除尘器实验模型上所测定的粉尘剥离率与清灰剥离力之间的特性关系,确定了已知条件下的粉尘剥离率.若预先确定要求达到的粉尘剥离率,可以通过清灰气流速度方程和剥离力方程确定脉冲清灰系统的几何参数、脉冲喷吹压力、脉冲喷吹时间和分室内的过滤面积(或滤袋直径、滤袋长度和滤袋数量等).该理论和实验研究内容为气箱式脉冲袋式除尘器脉冲清灰系统设计计算提供了理论依据. 相似文献
15.
16.
17.
壳聚糖是一种天然高分子聚合物,被广泛地作为絮凝剂用于水处理过程。探讨了壳聚糖的三种絮凝机理。在水处理中,其絮凝性能的发挥受到pH值、壳聚糖的投加量、壳聚糖的分子量以及壳聚糖的脱乙酰度等因素的影响。 相似文献
18.
区域限批是环境保护法运行机制软化的突破 总被引:1,自引:0,他引:1
我国环境管理在建立正式约束(法规、政策)方面已经取得较大的进展,环境保护政策实施机制“软化”是我国制度创新中一个突出的问题。我国建立的环境法规不少,但是形同虚设的现象比较严重。说明环境保护法实施机制的“软化”是环境保护法治建设中的一个不可回避的问题。 相似文献
19.
20.
运用因子分析方法 ,以吉林省为例进行经济与环境耦合机制的探讨 .选取吉林省各城市具有代表性、数据齐全的 16项指标 ,对吉林省 9个城市的经济与环境发展情况进行了定量分析 ,筛选出旋转后具有良好极性的 2个主因子—经济发展与环境保护 ,并对这两个主因子的发展层次和协调程度进行了耦合机制的评价 .在评价的基础上 ,针对吉林省各城市发展的潜力和不足 ,提出了经济与环境协调发展的具体建议 ,也为我国城市经济和环境协调发展的综合决策提供实例 . 相似文献