Relation between mortality of young walleye (Stizostedion vitreum) and recruitment with different forms of compensation

The relation between mortality of young fish and recruitment is important for assessment of the environmental effects of facilities that kill large numbers of young fish, such as electric power stations and hydropower plants. A simulation model with a bioenergetic growth component was applied to examine the relation between mortality of young and recruitment for walleye (Stizostedion vitreum) with different forms of population regulation, including: food limited growth, food limited growth with size-dependent mortality, and food limited growth with age at maturity dependent on size. With food limited growth small increases in mortality of young reduced recruitment considerably, but the population slowly approached a new equilibrium. If mortality of young increased when growth was food limited, the population approached a new equilibrium of natality and mortality because with fewer individuals there was more food per individual, and individuals were larger in size and produced more eggs; this feedback adjusted natality to equal mortality. With either mortality or age at maturity dependent on size, large increases in mortality of young resulted in only small decreases in recruitment.     

Hunger, poverty and food aid in Sub-Saharan Africa: Retrospect and potential

Frustrations and failures will continue to mount if we do not immediately summon the courage to revise the ways we think and take action-as well as maintaining essential services to support life and health … Saving hundreds of thousands … who are at risk of dying from malnutrition or infection is an immediate imperative. But it must be only one stage in the progress toward other activities, and one element in the truly comprehensive approach… The main intent of this paper is to explore aspects of the nature and evolution of poverty in Sub-Saharan Africa with special reference to food and hunger and their interaction with macro-economic policy. An attempt is made to outline the overall context within which food aid needs to be used in order to have a greater developmental impact. Following an Introductory Section I, Section II provides a sketch map of how recession and lagging food production - with cyclical weather crises superimposed - affect the human condition of poor people. Section III reviews die interaction between "standard" IMF stabilization and World Bank structural adjustment strategies and poverty/hunger. Improvements in the design of stabilization and adjustment programmes, and of the inter-relationship with them of emergency programmes, can be identified. A number turn on the broadened and more innovative or catalytic use of food aid. Section IV reviews aspects of facing a continuing series of emergencies and of designing life support programmes to facilitate rehabilitation of the households directly affected as well as of the national economies. From this base it explores a series of elements in achieving renewed development. The concluding Section seeks to explore the strengths, limitations and potentials of food aid in the context set by the previous sections. The standard criticisms of food aid appear to be overstated and/or to relate to particular modalities or approaches rather than to anything intrinsic. A number of criteria for improving the effectiveness of food aid - especially in respect to rehabilitation, recovery and renewed development - are set out.     

SWOT analysis of renewable energy sector in Mazowieckie Voivodeship (Poland): current progress,prospects and policy implications

Environment, Development and Sustainability - Renewable energy (RE) plays an increasingly important role in the economy of almost every country in the world. In order to examine the state of...     

pH值对亚硝酸盐氧化菌动力学及功能基因的影响

为探究pH值对亚硝酸盐氧化菌（NOB）活性动力学影响,本试验采用序批式活性污泥（SBR）反应器,以富含NOB的活性污泥为对象,基于Monod模型考察不同pH值对NOB活性动力学的影响并进行统计学分析.结果表明,Monod方程可较好地反映不同pH值条件下基质底物浓度对NOB比亚硝态氮氧化速率（SNiOR）的影响,且pH=7.0时动力学参数Ks为（6.167mg/L）,r_max为[1.134g/（g·d）],此时NOB活性最好.利用钟形经验模型进行非线性回归拟合,最大比降解速率（r_max）随pH值的增大呈钟形变化,本试验NOB的最佳pH值为（6.9±0.1）,其中r_max维持在r_opt一半以上的pH值范围（ω）为（3.26±0.4）.以亚硝酸盐氧化还原酶类基因（nxrA、nxrB）为引物,基于荧光定量PCR技术分析结果显示,在不同pH值条件下nxrA基因和nxrB基因拷贝数的变化趋势均与动力学参数（Ks、r_max）的规律一致,且nxrA和nxrB基因在系统的降解过程中起协同作用.