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Benomyl (0.025% a.i.) and thiabendazole (0.05 % a.i.) applied in July, August and September to apple trees cvs. Sunset and Cox's Orange Pippin gave slightly better control of Gloeosporium spp. rots in stored fruit than captan (0.1% a.i.) applied at similar intervals. On Cox's Orange Pippin, treatment with captan at 0.1 % a.i. in July and at 0.2% a.i. in August was as effective as three sprays at 0.1 % a.i. in July, August and September in controlling both Gloeosporium spp. and Nectria galligena rots. Benomyl applied in the spring and early summer to control apple scab on orchard trees reduced the incidence of Gloeosporium spp. and Monilia fructigena in stored fruit. Pre-harvest sprays of benomyl and captan gave good control of rotting caused by N. galligena but thiabendazole was ineffective. Post-harvest dips of thiabendazole controlled rotting by Gloeosporium spp. butnot byN. galligena.  相似文献   

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Insect-borne diseases are one of the major causes of disease and death in the tropical world. Conventional methods of disease control have proven insufficient and there is pressing need for devising new strategies. One approach that has been explored by several laboratories is to compromise vector fecundity and survivorship through the immunization of vertebrate hosts with the vector's internal organs (concealed antigens). Here, Marcelo Jacobs-Lorena and Francisco J.A. Lemos critically review the results obtained to date by use of this approach. It appears that the published work is less rigorous than would be desirable and the results are contradictory. In contrast to the successes obtained with a similar immunization strategy implemented for tick-borne diseases, it is not yet clear whether or not such an approach can be applied to insect-borne diseases.  相似文献   

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This research compares the performance of bottom-up, self-motivated behavioral interventions with top-down interventions targeted at controlling an "Influenza-like-illness". Both types of interventions use a variant of the ring strategy. In the first case, when the fraction of a person's direct contacts who are diagnosed exceeds a threshold, that person decides to seek prophylaxis, e.g. vaccine or antivirals; in the second case, we consider two intervention protocols, denoted Block and School: when a fraction of people who are diagnosed in a Census Block (resp., School) exceeds the threshold, prophylax the entire Block (resp., School). Results show that the bottom-up strategy outperforms the top-down strategies under our parameter settings. Even in situations where the Block strategy reduces the overall attack rate well, it incurs a much higher cost. These findings lend credence to the notion that if people used antivirals effectively, making them available quickly on demand to private citizens could be a very effective way to control an outbreak.  相似文献   

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Purpose

In this article, we present an innovative way of deriving comparable functional systems for comparative life cycle assessments (LCAs) of food products. We define the functional unit as the contribution of one or more foods to the nutrient composition of a weekly diet and, after a product substitution, employ a product system expansion approach to search for an alternative set of products which provides an equivalent nutritional composition.

Methods

Replacement is regarded within the context of a weekly diet. The comparable diet is a solution to a linear problem which finds the diet that is most similar to the starting one, subject to nutritional and/or other constraints that guarantee a minimum dietary quality. The formulation gives priority to selecting food products according to popularity.

Results

We illustrate our method with two examples. We show that a baseline diet containing 3.6 servings of apples a week is equivalent to a similar diet in which the apples are replaced with 3.6 servings of oranges and servings of strawberry and kiwi are removed. These changes are necessary mainly because of differences in the vitamin C content between apples and oranges. The second example is a replacement of all meat in a weekly diet by a soy-based meat substitute. In this case, additional fish products need to be consumed to make up for a lack of selenium and essential amino acids.

Conclusions

We present an innovative and objective way to overcome the challenge of comparing two or more food products in a comparative LCA. Our approach is systematic and finds the alternative diet that best meets the nutritional criteria as well as reflecting the food preferences of the population. The method selects products according to the role they play in the dietary pattern. Moreover, the method is flexible enough to allow for different selection criteria and other nutritional and non-nutritional constraints.  相似文献   

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Simulation studies have predicted that maximum lipase activity is reached with fed-batch operation strategies. In this work, two different fed-batch operational strategies have been studied: constant substrate feeding rate and specific growth rate control. A constant substrate feeding rate strategy showed that maximum aqueous lipolytic activity (55 U/mL) was reached at low substrate feeding rates, whereas lipase tends to accumulate inside the cell at higher rates of substrate addition. In the second fed-batch strategy studied, a feedback control strategy has been developed based on the estimation of state variables (X and mu) from the measurement of indirect variables such as CER by means of mass spectrometry techniques. An on-off controller was then used to maintain the specific growth rate at the desired value by adjusting the substrate feeding rate. A constant specific growth rate strategy gave higher final levels of aqueous lipolytic activity (117 U/mL) at low specific growth rates. At higher specific growth rates the enzyme remained accumulated inside the cell, as was observed with a constant feeding fed-batch strategy. With a constant specific growth rate strategy, lipase production by Candida rugosa was enhanced 10-fold compared to a batch operation. Purification studies have demonstrated that lipolytic and esterasic specific activity ratios of Candida rugosa isoenzymes can be modified by using different operational conditions. These studies have also showed that the isoenzymes obtained in a controlled growth rate strategy are around three- to four-fold more active than those obtained in a constant feeding rate strategy.  相似文献   

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刘文娟  戴雪伶  姜招峰 《生命科学》2011,(10):1022-1026
β-淀粉样蛋白(amyloid β-peptide,Aβ)的过量表达和异常聚集是引起阿尔茨海默病的重要原因之一。以β-淀粉样蛋白级联假说为线索,阐述分泌酶对Aβ生成的影响,不同聚合状态Aβ的神经毒性以及Aβ毒性作用机制,总结Aβ生成、聚合、清除过程中神经毒性的相应防治措施,对阿尔茨海默病中β-淀粉样蛋白神经毒性最新研究进展作一综述。  相似文献   

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Immersion of apples of the varieties Cox's Orange Pippin and James Grieve for 1 min in solutions of calcium chloride or nitrate reduced the incidence of bitter pit and senescent breakdown that developed during air storage at 3 °C. Calcium nitrate treatments decreased the severity of superficial scald in both Bramley's Seedling and Cox apples probably by slightly delaying the rate of senescence. Calcium chloride caused unacceptable levels of damage when applied to Cox and Grieve at concentrations above 0.125 M; this injury was enhanced in Cox when benomyl was added to this strength of solution. Bramley's Seedling apples were more sensitive to calcium injury than Cox, especially in the presence of benomyl and the scald inhibitor, ethoxyquin; diphenylamine did not increase calcium injury. Calcium nitrate caused more damage to Cox than equimolar concentrations of the chloride without improving the control of bitter pit. Virtually no damage occurred when Cox and Grieve apples were immersed for 10 min in 0.125 M calcium nitrate at 45 °C. The incorporation of calcium in warm water treatments to control rotting and scald may delay sensecent breakdown in heat-treated apples.  相似文献   

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Livestock farming systems are major sources of trace gases contributing to emissions of the greenhouse gases (GHG) nitrous oxide (N2O) and methane (CH4), i.e. N2O accounts for 10% and CH4 for 30% of the anthropogenic contributions to net global warming. This paper presents scenario assessments of whole-system effects of technologies for reducing GHG emissions from livestock model farms using slurry-based manure management. Changes in housing and storage practice, mechanical separation, and incineration of the solid fraction derived from separation were evaluated in scenarios for Sweden, Denmark, France, and Italy. The results demonstrated that changes in manure management can induce significant changes in CH4 and N2O emissions and carbon sequestration, and that the effect of introducing environmental technologies may vary significantly with livestock farming practice and interact with climatic conditions. Shortening the in-house manure storage time reduced GHG emissions by 0–40%. The largest GHG reductions of 49 to, in one case, 82% were obtained with a combination of slurry separation and incineration, the latter process contributing to a positive GHG balance of the system by substituting fossil fuels. The amount and composition of volatile solids (VS) and nitrogen pools were main drivers in the calculations performed, and requirements to improve the assessment of VS composition and turnover during storage and in the field were identified. Nevertheless, the results clearly showed that GHG emission estimates will be unrealistic, if the assumed manure management or climatic conditions do not properly represent a given country or region. The results also showed that the mitigation potential of specific manure management strategies and technologies varied depending on current management and climatic conditions.  相似文献   

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Purpose  

The purpose of the study was to compare three recent Life Cycle Impact Assessment (LCIA) models in prioritizing substances and products from national emission inventories. The focus was on ecotoxic and human toxic impacts. The aim was to test model output against expert judgment on chemical risk assessment.  相似文献   

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Oospores of Phytophthora syringae germinating at 10 and 15°C under artificial light formed one or more sporangia, which yielded zoospores. Furalaxyl and metalaxyl demonstrated eradicant action against infections occurring on zoospore-inoculated apples. Control was obtained at 10°C when treatment was delayed 5–11 days after inoculation. Storage in 5% CO2+ 3% O2 and 0% CO2+ 2% O2 reduced rotting compared with storage in air.  相似文献   

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Highlights► Biofuel LCAs have high uncertainty and variability, particularly prospective LCAs. ► Variability in biofuel LCAs has two sources: model and methods-induced, and real. ► LCAs of 2nd-generation fuels are so uncertain that no pathway can clearly be preferred. ► Algae biodiesel LCA has greatest variability due to diverse technology, assumptions.  相似文献   

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Impulsive control strategies in biological control of pesticide   总被引:10,自引:0,他引:10  
By presenting and analyzing the pest-predator model under insecticides used impulsively, two impulsive strategies in biological control are put forward. The first strategy: the pulse period is fixed, but the proportional constant E(1) changes, which represents the fraction of pests killed by applying insecticide. For this scheme, two thresholds, E(1)(**) and E(1)(*) for E(1) are obtained. If E(1)>or=E(1)(*), both the pest and predator (natural enemies) populations go to extinction. If E(1)(**)相似文献   

16.
A deltamethrin 'pour-on' insecticide was applied monthly to over 2000 cattle exposed to a high challenge of drug-resistant trypanosomes and high tsetse re-invasion pressure in the Ghibe valley, south-west Ethiopia. Blood samples were taken monthly from an average of 760 cattle for determination of PCV and presence of trypanosomes. The area of the valley is approximately 350 km2 and the cattle grazed in roughly four locations covering about a quarter to half of the area. Two years before the trial commenced, Glossina morsitans submorsitans Newstead (Diptera: Glossinidae) began to invade the valley. Despite the use of the pour-on the mean apparent density of G. m. submorsitans continued to rise, and, during the 4 years of tsetse control, was more than three-fold higher than that recorded during the previous 18 months. Over the same period there was little change in the apparent density of Glossina pallidipes Austen (Diptera: Glossinidae). By contrast, the mean monthly prevalence of trypanosome infections in cattle over 36 months of age decreased from 38.3 to 29.0%, the incidence of new infections decreased from 26.6 to 16.0% (a reduction of 40%), and packed cell volume in cattle increased from 21.7 to 24.1%. Evidence of a change in apparent parasite transmission rate was demonstrated by regression of infection incidence in cattle on the logarithm of apparent density of G. m. submorsitans. Before the trial started the regression coefficient was 45.8 +/- 6.3 and this reduced to 9.2 +/- 2.5% incidence per log(e) (flies/trap/day) during the period of tsetse control. It was concluded that this indicated reductions in tsetse numbers in the immediate vicinities of cattle in a way that was not reflected in overall tsetse catches. Nevertheless, the comparatively high levels of trypanosome prevalence that persisted in the cattle demonstrates that, where invasion prevalence is high, treatment of small pockets of cattle will not eradicate tsetse. To achieve more significant reduction in trypanosome prevalence in cattle, integrated methods of control utilizing target barriers in the major routes of invasion will be needed.  相似文献   

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Eukaryotic cells must contend with a continuous stream of misfolded proteins that compromise the cellular protein homeostasis balance and jeopardize cell viability. An elaborate network of molecular chaperones and protein degradation factors continually monitor and maintain the integrity of the proteome. Cellular protein quality control relies on three distinct yet interconnected strategies whereby misfolded proteins can either be refolded, degraded, or delivered to distinct quality control compartments that sequester potentially harmful misfolded species. Molecular chaperones play a critical role in determining the fate of misfolded proteins in the cell. Here, we discuss the spatial and temporal organization of cellular quality control strategies and their implications for human diseases linked to protein misfolding and aggregation.  相似文献   

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转基因植物的食品安全性问题及评价策略   总被引:4,自引:0,他引:4  
转基因植物经历了20年的快速发展,已经成为21世纪农业的重要支柱之一。转基因植物从诞生以来,其食用安全性一直是科学界、政府和广大消费者关心的焦点问题。各类转基因安全事件层出不穷,严重影响着转基因产业的发展。本文从营养、毒性、过敏性、抗生素抗性、非期望效应等五个方面系统总结了转基因植物食用安全的问题,详细介绍了转基因植物食用安全评价的六大原则以及国际与国内对转基因植物食用安全性评价的内容,最后介绍了我国的转基因植物安全管理体系。以期使读者对转基因植物食用安全问题有一个系统全面的了解。  相似文献   

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