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631.
The results of studies on the radial increment of larch and pine in central Yakutia are presented. The application of dendroclimatological methods to the study of tree-ring chronologies has made it possible to evaluate tree growth response to the dynamics of climatic factors over the past 120 years. The results of analysis of radial tree increment show that the onset of the growing season has shifted to earlier dates by the end of the 20th century.  相似文献   
632.
The purpose of this paper is to study the redistribution of chemical species (OH, HO2, H2O2, HNO3 and H2SO4) over West Africa, where the cloud cover is ubiquitously present, and where deep convection often develops. In this area, because of these cloud systems, chemical species are redistributed by the ascending and descending flow, or leached if they are soluble. So, we carry out a mesoscale study using the Regional Atmospheric Modelling System (RAMS) coupled to a code of gas and aqueous chemistry (RAMS_Chemistry). It takes into account all processes under mesh. We examine several cases following the period (November and July), with inputs emissions (anthropogenic, biogenic and biomass burning). The radicals OH and HO2 are an indicator of possibilities for chemical activity. They characterize the oxidizing power of the atmosphere and are very strong oxidants. The acids HNO3 and H2SO4 are interesting in their transformation into nitrates and sulfates in precipitation. In November, when photochemistry is active during an event of biomass burning, concentrations of chemical species are higher than those of November in the absence of biomass burning. The concentrations of nitric acid double and sulfuric acid increases 70 times. In addition, the concentrations are even lower in July if there is a deep convection. Compared to measures of the African Monsoon Multidisciplinary Analysis (AMMA), the results and observations of radicals OH and HO2 are the same order of magnitude. Emissions from biomass burning increase the concentrations of acid and peroxide, and a deep convection cloud allows the solubility and the washing out of species, reducing their concentration. Rainfalls play a major role in solubility and washing out acids, peroxides and radicals in this region.  相似文献   
633.
Synthesis and characterization of novel biodegradable, water soluble and optically active DL-malic acid (DMA) and citric acid (CA) copolymers were studied for possible use as antibacterial agents. The copolymers were synthesized by direct bulk melt condensation in the absence of a catalyst above 150 °C. Characterization of obtained copolymers was carried out with the help of infrared absorption spectra, differential scanning calorimetry and thermo gravimetric analysis. The antibacterial activity of copolymers against bacteria was investigated. The results obtained shows the above copolymers possess a broad wound dressing activity against different types of bacteria and may be useful as antibacterial agents.  相似文献   
634.
Environmental change is likely to have a strong impact on biodiversity, and many species may shift their distribution in response. In this study, we aimed at projecting the availability of suitable habitat for an endangered amphibian species, the Fire-bellied toad Bombina bombina, in Brandenburg (north-eastern Germany). We modelled a potential habitat distribution map based on (1) a database with 10,581 presence records for Bombina from the years 1990 to 2009, (2) current estimates for ecogeographical variables (EGVs) and (3) the future projection of these EGVs according to the statistical regional model, respectively, the soil and water integrated model, applying the maximum entropy approach (Maxent). By comparing current and potential future distributions, we evaluated the projected change in distribution of suitable habitats and identified the environmental variables most associated with habitat suitability that turned out to be climatic variables related to the hydrological cycle. Under the applied scenario, our results indicate increasing habitat suitability in many areas and an extended range of suitable habitats. However, even if the environmental conditions in Brandenburg may change as predicted, it is questionable whether the Fire-bellied toad will truly benefit, as dispersal abilities of amphibian species are limited and strongly influenced by anthropogenic disturbances, that is, intensive agriculture, habitat destruction and fragmentation. Furthermore, agronomic pressure is likely to increase on productive areas with fertile soils and high water retention capacities, indeed those areas suitable for B. bombina. All these changes may affect temporary pond hydrology as well as the reproductive success and breeding phenology of toads.  相似文献   
635.
This paper uses a sensitivity framework approach to look at the probabilistic impacts of climate change on 20-year return period flood peaks, by applying a set of typical response surfaces alongside the probabilistic UK Climate Projections (UKCP09) for 10 river-basin regions over Scotland. The first paper of the pair used the same approach for 10 river-basin regions over England and Wales. This paper develops the methodology for Scotland, by first enabling better estimation of the response type of Scottish catchments. Then, as for England and Wales, the potential range of impacts is shown for different types of catchment in each river-basin region in Scotland, and regional average impact ranges are estimated. Results show clear differences in impacts between catchments of different types and between regions. The Argyll and West Highland regions show the highest impacts, while the North-East Scotland region shows the lowest impacts. The overall ranges are generally smaller for Scotland than England and Wales.  相似文献   
636.
Renewable and alternative fuels have numerous advantages compared with fossil fuels, as they are renewable and biodegradable, and provide food and energy security and foreign exchange savings besides addressing environmental concerns and socio-economic issues. In this context, present work was carried out to investigate the feasibility of alternative and renewable fuels derived from biomass feedstock of different origin for engine applications. The present study was also extended to study the effect of producer gas composition derived from different biomass feedstock on the performance, combustion and emission characteristics of a single-cylinder, four-stroke, direct injection stationary diesel engine operated on a dual-fuel mode using Honge oil methyl ester (HOME) and producer gas induction. The performance of the engine was evaluated with a constant injection timing of 27° before top dead centre, an injection pressure of 205 bar for the diesel–producer gas combination and 230 bar for the HOME–producer gas combination and a compression ratio of 17.5. The results showed that the performance of the dual-fuel engine varies with the composition of the producer gas and depends on the type of biomass feedstock used in the gasifier. Experimental investigations on the dual-fuel engine showed that brake thermal efficiency values for the engine operated using HOME–producer gas derived from babul, neem and honge woods were found to be 17.2, 14.3 and 11.56% respectively, compared to 23.8% for diesel–producer gas operation at 80% load. However, the results showed better engine performance with lower exhaust emission levels for the operation of HOME–producer gas derived from the ordinary or babul wood compared with the operation of that derived from the neem and Honge woods. In view of this, present study reveals that use of alternative and renewable fuels for dual fuel engine can be considered as an immediate solution for the development of rural areas and emergency use in the event of severe diesel fuel shortage.  相似文献   
637.
The diminishing resources and continuously increasing cost of petroleum in association with their alarming pollution levels from diesel engines has led to an interest in finding alternative fuels to diesel. Emission control and engine efficiency are two of the most important parameters in current engine design. The impending introduction of emission standards such as Euro IV and Euro V has forced research towards developing new technologies for combating engine emissions. This paper examines the effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of compressed natural gas (CNG) blended with Honge oil methyl esters (HOME) in a dual fuel engine. The present results show that the combustion of HOME and 15% ethanol blend with CNG induction in a dual-fuel engine operated in optimized parameters at an injection timing of 27° Before Top Dead Centre and a compression ratio of 17.5 resulted in acceptable combustion emissions and improved brake thermal efficiencies. The implementation of swirl augmentation techniques increased brake thermal efficiencies (BTEs) and considerably reduced combustion emissions such as smoke, HC, CO and NOx. The addition of ethanol also increased BTEs. However, at more than 15% of ethanol in HOME, NOx emissions increased dramatically.  相似文献   
638.
Identifying effective adaptation strategies for coastal communities dependent on marine resources and impacted by climate change can be difficult due to the dynamic nature of marine ecosystems. The task is more difficult if current and predicted shifts in social and economic trends are considered. Information about social and economic change is often limited to qualitative data. A combination of qualitative and quantitative models provide the flexibility to allow the assessment of current and future ecological and socio-economic risks and can provide information on alternative adaptations. Here, we demonstrate how stakeholder input, qualitative models and Bayesian belief networks (BBNs) can provide semi-quantitative predictions, including uncertainty levels, for the assessment of climate and non-climate-driven change in a case study community. Issues are identified, including the need to increase the capacity of the community to cope with change. Adaptation strategies are identified that alter positive feedback cycles contributing to a continued decline in population, local employment and retail spending. For instance, the diversification of employment opportunities and the attraction of new residents of different ages would be beneficial in preventing further population decline. Some impacts of climate change can be combated through recreational bag or size limits and monitoring of popular range-shifted species that are currently unmanaged, to reduce the potential for excessive removal. Our results also demonstrate that combining BBNs and qualitative models can assist with the effective communication of information between stakeholders and researchers. Furthermore, the combination of techniques provides a dynamic, learning-based, semi-quantitative approach for the assessment of climate and socio-economic impacts and the identification of potential adaptation strategies.  相似文献   
639.
Comparative analysis of the structure of small mammal communities has been performed in two European cities located in different biomes: Chisinau (2008?C2009) and Yaroslavl (1994?C2002). The parameters studied included abundance, species composition, similarity and difference of faunas, species diversity, and proportions of groups differing in predisposition to synanthropy. It has been found that the structure of small mammal communities in these cities depends on specific physiographic conditions of the surrounding areas and on the distinctive features of the cities themselves (their structure, age, etc.). The similarity between the faunas is accounted for by the common ecological patterns of fauna formation in the biota of urban cenoses.  相似文献   
640.
In industrialized countries, the idea of degrowth has emerged as a response to environmental, social, and economic crises. Realizing environmental limits to and failures of more than half a century of continual economic growth in terms of social progress and environmental sustainability, the degrowth paradigm calls for a downscaling of consumption and production for social equity and ecological sustainability. The call for economic degrowth is generally considered to be delimited to rich countries, where reduced consumption can save “ecological space” enabling people in poor countries to enjoy the benefits of economic growth. China, as one of the economically most expanding countries in the world, has dramatically improved its living standards, particularly along the Eastern coast, over the latest 30 years. However, China is absent from the international debates on growth. This article discusses the implications of the Western degrowth debates for China. Given the distinctive features of China’s development, the paper aims to enrich the degrowth debates, which have hitherto been dominated by Western perspectives. Based upon reflections on social, environmental, and moral dimensions of economic growth, the paper argues that limited natural resources may not continuously support universal affluence at the current level of the rich countries, a level that China is likely to reach within a few decades. Priority for growth in China should therefore be given to the poor regions of the country, and future growth should be beneficial to social and environmental development.  相似文献   
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