Effects of stress and phenotypic variation on inbreeding depression in Brassica rapa

Stressful environments are often said to increase the expression of inbreeding depression. Alternatively, Crow's "opportunity for selection" (the squared phenotypic coefficient of variation) sets a limit to how much selection can occur, constraining the magnitude of inbreeding depression. To test these hypotheses, we planted self- and cross-fertilized seeds of Brassica rapa into a factorial experiment that varied plant density and saline watering stresses. We then repeated the experiment, reducing the salt concentration. We observed considerable inbreeding depression, particularly for survival in the first experiment and growth in the second. Both stresses independently depressed plant performance. Families differed in their amounts of inbreeding depression and reaction norms across environments. Outcrossed progeny were sometimes more variable. Stresses had small and inconsistent effects on inbreeding depression and, when significant, tended to diminish it. Levels of phenotypic variability often predicted whether inbreeding depression would increase or decrease across environments and were particularly effective in predicting which traits display the most inbreeding depression. Thus, we find little support for the stress hypothesis and mixed support for the phenotypic variability hypothesis. Variable levels of phenotypic variation provide a parsimonious explanation for shifts in inbreeding depression that should be tested before invoking more complex hypotheses.     

Simple example of structure versus property relationship applied to a reduced-friction biosystem, a quite personal opinion

Structure versus property (small-scale) relationship enters when something interesting is going to happen in a biosystem. This special-type "happening" is actually appearing to be manifested at both micro- and mesoscopic levels of always productive soft-matter organization under dynamic response, especially the one characteristic of the articular cartilage--an efficient, designed-by-nature multi-membrane, and virtually, with-ion-channels equipped, absorber and load relaxor.     

蔗渣浆CEH漂白废水的毒性及毒性污染负荷的研究

采用发光细菌法对蔗渣浆CEH三段漂白废水进行了毒性研究 ,其中C段废水的毒性最大 ,其EC50 为 2 8.83% ,属于强毒级别 ;E段、H段废水的EC50 分别为 6 8.92 %、2 6 7.9% ,分别属于毒、无毒级别 ;其中C段的毒性排放负荷约占总废水毒性排放负荷的 6 7.5 %左右 ;结果表明 ,漂白废水的毒性排放负荷较大 ,约为 4 2 3.92 (TU·m3 吨浆 ) ,相当于 4 2 .93(gHgCl2 吨浆 ) ,对其治理不容忽视     

Environmental Load from Dutch Private Consumption: How Much Damage Takes Place Abroad?

This article describes a method for determining the environmental load of Dutch private consumption. The method generates detailed information about consumption-related environmental impacts. The environmental load of households (direct) and production (indirect) was determined for 360 expenditure categories reported in the Dutch Expenditure Survey. The indirect environmental load was calculated with linked input-output tables covering worldwide production and trade. The environmental load per Euro turnover of industries was linked to consumer expenditures. With this method we can quantify several types of environmental load per expenditure category and per economic production region.
It was found that food production, room heating, and car use are the most important elements in the environmental load of Dutch private consumption. The impacts taking place abroad were—with the exception of emission of greenhouse gases and road traffic noise—found to be larger than domestic impacts. Most land use was found to take place in developing (non-OECD) countries, whereas most emissions occur in industrialized (OECD) countries.     

Introduction of captive breeders to the wild: Harmful or beneficial?

This work focuses on the consequences on thegenetic load and the risk of extinction when anendangered population is exposed to recurrentintroductions from a captive population whereselection is somewhat relaxed. Our findingssuggest that, although selection pressuresmight be reduced in captivity, which leads tohigher frequency of deleterious alleles innatural populations (Lynch and O'Hely 2001),such a population structure could have positiveeffects on population fitness when threeconditions are met: (i) the time length of thesupplementation program does not exceed areasonable time frame, e.g., 20 generations (ii)introduction of captive individuals is kept ata low level, i.e., one or two individuals pergeneration (iii) the size of the captivepopulation is reasonably large, e.g., more than20 individuals. The positive effect is due tothe fact that the supplementation programdelays the increase of homozygosity of thenatural population. When migration from thewild towards captivity is also allowed, thebenefits with regard to genetic load increasesignificantly even for larger numbers ofcaptive immigrants and a higher number ofgenerations. We also worked out a model withexplicit demographic considerations(fluctuating population sizes, captive migrantsincrease the size of the wild population),which shows that the probability of extinctiondecreases significantly with the number ofintroduced individuals when short-termsupplementation programs are applied (up totwenty generations). Furthermore, anappropriate genetic management of the captivepopulation, such as the equalization of familysizes, could enhance the positive effects ofsuch supplementation programs.     

磷模型在千岛湖水体污染预测中的应用研究

运用国际上通用的多个经验统计磷模型预测千岛湖目前的磷浓度水平,其中第6个模型最适合用于千岛湖的预测预报．利用该模型预测了磷负荷量分别减少1/4、1/2、3/4情况下,千岛湖水体中总磷浓度的响应．同时针对千岛湖营养水平控制的短、长期目标,利用模型计算出了所允许的总磷负荷量及入湖磷浓度．     

QoS-based Architectures for Geographically Replicated Web Servers

In this paper, we discuss strategies for providing World Wide Web service users with adequate Quality of Service (QoS). We argue that QoS can be provided by distributing the service requests processing load among replicated Web servers (WSs), that can be geographically distributed across the Internet. In order to support our argument, we compare and contrast several load distribution strategies, and assess their effectivness when deployed within the context of a geographically replicated Web service; the principal figure of merit we use in this assessment is the response time experienced by the users of that service. As a result of this comparison, we propose a specific strategy, named QoS-based, that implements load distribution among WS replicas by binding a user to the replica that provides the shortest user response time. We examine several architectures that exploit our QoS-based strategy. Two of these architectures, named, respectively, Browser-based and Load Distribution-based, are described in detail as they are particularly appropriate for implementing our strategy.     

Influence of up-flow velocity on the performance of an anaerobic filter under oleic acid overloads

An upflow velocity of 0.21 m h^–1 was optimal to minimize the effect of organic shocks (from 6 to 30 kg COD m^–3 d^–1) when operating an upflow anaerobic filter for the treatment of an oleic acid-based effluent (50% w/v COD). This value represented the transition between a mass transfer controlled regime and a kinetic regime. Under hydraulic shock loads, an increase in upflow velocity from 0.3 to 0.4m h^–1 decreased the removal efficiency from 68 to 51%.     

Stabilization of threonine production in an Escherichia coli overproducing strain using tightly regulated T7 promoter system

The industrial production of compounds by E. coli strains is often accompanied with variability in yield levels. To investigate the mechanism of such instability the over-production of threonine was used as a model. The instability in this strain appears to be caused by a metabolic burden resulting in occurrence of low producing revertants. A successful application of the tightly regulated T7 expression system is presented as a possible solution providing a substantial stabilization of the threonine production.     

Drought and Oxidative Load in the Leaves of C3 Plants: a Predominant Role for Photorespiration?

Although active oxygen species are produced at high rates inboth the chloroplasts and peroxisomes of the leaves of C₃ plants,most attention has focused on the potentially damaging consequencesof enhanced chloroplastic production in stress conditions suchas drought. This article attempts to provide quantitative estimatesof the relative contributions of the chloroplast electron transportchain and the glycolate oxidase reaction to the oxidative loadplaced on the photosynthetic leaf cell. Rates of photorespiratoryH₂O₂ production were obtained from photosynthetic and photorespiratoryflux rates, derived from steady-state leaf gas exchange measurementsat varying irradiance and ambient CO₂. Assuming a 10 % allocationof photosynthetic electron flow to the Mehler reaction, photorespiratoryH₂O₂ production would account for about 70 % of total H₂O₂ formedat all irradiances measured. When chloroplastic CO₂ concentrationrates are decreased, photorespiration becomes even more predominantin H₂O₂ generation. At the increased flux through photorespirationobserved at lower ambient CO₂, the Mehler reaction would haveto account for more than 35 % of the total photosynthetic electronflow in order to match the rate of peroxisomal H₂O₂ production.The potential signalling role of H₂O₂ produced in the peroxisomesis emphasized, and it is demonstrated that photorespiratoryH₂O₂ can perturb the redox states of leaf antioxidant pools.We discuss the interactions between oxidants, antioxidants andredox changes leading to modified gene expression, particularlyin relation to drought, and call attention to the potentialsignificance of photorespiratory H₂O₂ in signalling and acclimation.