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251.
Evolutionary biologists are increasingly relying on ancient DNA from archaeological animal bones to study processes such as domestication and population dispersals. As many animal bones found on archaeological sites are likely to have been cooked, the potential for DNA preservation must be carefully considered to maximise the chance of amplification success. Here, we assess the preservation of mitochondrial DNA in a medieval cattle bone assemblage from Coppergate, York, UK. These bones have variable degrees of thermal alterations to bone collagen fibrils, indicative of cooking. Our results show that DNA preservation is not reliant on the presence of intact collagen fibrils. In fact, a greater number of template molecules could be extracted from bones with damaged collagen. We conclude that moderate heating of bone may enhance the retention of DNA fragments. Our results also indicate that ancient DNA preservation is highly variable, even within a relatively recent assemblage from contexts conducive to organic preservation, and that diagenetic parameters based on protein diagenesis are not always useful for predicting ancient DNA survival.  相似文献   
252.
Rural communities in sub‐Saharan Africa rely upon provisioning ecosystem services (ES) to support their livelihoods, yet in areas where rapid land use change is occurring the relationship between environmental change, provisioning ES availability and livelihoods is not fully understood. This relationship is explored here within a typical rural miombo woodland landscape in south‐west Tanzania, which is undergoing rapid land use change due to expanding tobacco cultivation. The types of provisioning ES used, who uses them, changes in their availability, and the possible future impacts of these changes were explored using a mixed‐method approach. Our findings identify 19 provisioning ES used by households regardless of economic status. Firewood, building materials, and fresh water are used by almost all households, and these are perceived to be declining in availability. Households identified this as a negative environmental impact of land use change and that provisioning ES loss would be ‘bad’ for their households. Given the multi‐purpose nature of miombo woodlands, an adaptive co‐management approach, which can achieve multiple objectives through encouraging participation, learning, and empowerment of local communities, could be an appropriate strategy to achieve sustainable land use management and maintain the provision of ES within miombo woodland landscapes of sub‐Saharan Africa.  相似文献   
253.
254.
A comprehensive laboratory study of negatively buoyant discharges is presented. Unlike previous studies, here the focus is on generating data sets where influences of the bottom boundary have been eliminated. There are significant discrepancies in the published dilution data for these flows and a contributing factor is the large variation in the bottom boundary condition. A Laser-induced Fluorescence system is employed to gather flow spread, peak concentration (minimum dilution) and trajectory data for a wide range of densimetric Froude numbers and initial discharge angles. Data from these experiments are compared with previously published data, along with predictions from integral models and a revised form of the previously published semi-analytical solutions. The new data sets are not distorted by mixing processes associated with the bottom boundary and therefore provide the basis for more meaningful assessments of the predictive capabilities of existing models, given that the influences of the bottom boundary on contaminant mixing are not incorporated into these models. In general the models assessed are able to predict key geometric quantities with reasonable accuracy, but their minimum dilution predictions are conservative. Importantly dilution at the return point shows a strong dependence on the initial discharge angle and this could have important implications for the design of discharge systems.  相似文献   
255.
In most mammals, female fertility and reproduction are strongly influenced by nutritional status and, therefore, by foraging conditions. Here, we investigate the relationship between food resources, feeding competition, energy intake and reproduction in a group of wild female Assamese macaques (Macaca assamensis) in northeastern Thailand. Over 2,100 h of data on feeding behaviour, energy intake and activity budgets were combined with data on resource characteristics, female reproduction and physical condition. We found that an increase in food availability had a positive effect on female energy intake and conception rates. In addition, it appeared that females incurred energetic costs during lactation and that females with a better physical condition during the mating season were more likely to conceive. The annual birth season occurred a few months before the annual peak in food availability, causing peak lactation to coincide with a period of high food availability. This suggests that females use the increased food abundance to compensate for the energetic costs of lactation. Neither energy intake rates nor activity budgets were influenced by female dominance rank, even during periods when the levels of contest competition were predicted to be high. In line with this, we found no evidence for rank-related differences in reproduction. The apparently limited influence of feeding competition in female Assamese macaques adds to the debate on the extent to which patterns in feeding competition and fitness can reliably be predicted based on ecological conditions. We suggest that this may partially be resolved by including potential competition-reducing mechanisms into the predictive framework.  相似文献   
256.
The lake-rich glacial landscapes of north-eastern central Europe play an important role in the preservation and use of water resources, including protection of biodiversity, carbon storage and promotion of tourism. With a view to the last c. 20 years and the future, a regional ‘syndrome of water shortage’ has been frequently stated, which impairs particularly peatlands, flowing waters and lakes. Accordingly, the overall question addressed in this study is: What can regional and local gauging records tell us about decadal hydrological changes of lakes and their catchments? In the study area, most of the gauging records of lakes begin only in the late 1990s. Forty-five lake-level records were analysed by hierarchical agglomerative clustering, looking for the trend in the 1999–2008 time window. The analyses show that lake levels had varying dynamics, namely a negative, unclear or even a positive trend. The proportional shares of these three groups are 23 (51 %) to 15 (34 %) to 7 lakes (15 %), respectively. In group 1, largely groundwater-fed lakes, lake-level changes depend on groundwater-level changes. These are controlled by decreasing groundwater recharge in the catchments, which are caused by specific seasonal weather conditions in the observation period, and the impact of the dominating pine forests, which consume high quantities of water. In group 2, mainly stream lakes, direct human impact drives the lake levels through the management of weirs and ground sills. Nearly all lakes in group 3, consisting of river, stream and spring lakes, were subject to impoundment measures initiated by local rewetting projects. Thus, an important finding with respect to the impact of climate and land use is the fact that the (‘natural’) lakes of the region, primarily fed by groundwater and precipitation, show a predominantly negative lake-level trend in the period studied. Beyond the 10-year-time window analysed, further regional data show that periodic lake-level fluctuations with amplitudes of c. 1–2(–3) m are characteristic for regional groundwater-fed lakes.  相似文献   
257.
The availability of reliable, accurate and precise monitoring methods for toxic volatile organic compounds (VOCs) is a primary need for state and local agencies addressing daily monitoring requirements related to odor complaints, fugitive emissions, and trend monitoring. The canister-based monitoring method for VOCs is a viable and widely used approach that is based on research and evaluation performed over the past several years. This activity has involved the testing of sample stability of VOCs in canisters and the design of time-integrative samplers. The development of procedures for analysis of samples in canisters, including the procedure for VOC preconcentration from whole air, the treatment of water vapor in the sample, and the selection of an appropriate analytical finish has been accomplished. The canister-based method was initially summarized in the EPA Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air as Method TO-14. Modifications and refinements are being added to Method TO-14 in order to obtain a Statement of Work for the Superfund Contract Laboratory Program for Air. This paper discusses the developments leading to the current status of the canisterbased method and provides a critique of the method using results obtained in EPA monitoring networks.  相似文献   
258.
The rapid expansion of the dimension stone and black granite industry in Zimbabwe in the 1990s, a result of increasing domestic and international demand for black granite, has ushered in new challenges and opportunities for producers and beneficiaries alike. This article investigates the social, environmental and economic challenges emanating from the export boom, the economic opportunities presented by the expanding market and the potential role the robust industry could play in regional economic development and poverty alleviation. The article evaluates the long-term sustainability of the dimension stone industry and recommends the reinvestment of revenues into diversification of the regional economic base, upgrading of local infrastructure, further processing of rough stone before export and encouragement of micro-businesses to enhance sustainability. The author argues for modification of economic incentives to incorporate environmental and social objectives in order to enhance sustainability. The need for a holistic approach to policies affecting the exploitation, processing and marketing of granite resources and their products is recognized. More research on the operations of the industry is called for.  相似文献   
259.
Dilly O  Blume HP  Sehy U  Jimenez M  Munch JC 《Chemosphere》2003,52(3):557-569
Land use and agricultural practices modify both the amounts and properties of C and N in soil organic matter. In order to evaluate land use and management-dependent modifications of stable and labile C and N soil pools, (i). organic C and total N content, (ii). microbial (C(mic)) and N (N(mic)) content and (iii). C and N mineralisation rates, termed biologically active C and N, were estimated in arable, grassland and forest soils from northern and southern Germany. The C/N-ratios were calculated for the three levels (i)-(iii) and linked to the eco-physiological quotients of biotic-fixed C and N (C(mic)/C(org), N(mic)/N(t)) and biomass-specific C and N mineralisation rate (qCO(2), qN(min)). Correlations could mainly be determined between organic C, total N, C(mic), N(mic) and C mineralisation for the broader data set of the land use systems. Generally, the mineralisation activity rate at 22 degrees C was highly variable and ranged between 0.11 and 17.67 microg CO(2)-C g(-1) soil h(-1) and -0.12 and 3.81 microg (deltaNH(4)(+)+deltaNO(3)(-))-N g(-1) soil h(-1). Negative N data may be derived from both N immobilisation and N volatilisation during the experiments. The ratio between C and N mineralisation rate differed significantly between the soils ranging from 5 to 37, and was not correlated to the soil C/N ratio and C(mic)/N(mic) ratio. The C/N ratio in the 'biologically active' pool was significantly smaller in soils under conventional farming than those under organic farming systems. In a beech forest, it increased from the L, Of to the Ah horizon. The biologically active C and N pools refer to the current microbial eco-physiology and are related to the need for being C and N use efficient as indicated by metabolic qCO(2) and qN(min) quotients.  相似文献   
260.
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