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The Degradation Gradient Method (DGM) is a sophisticated technique for the assessment of range condition. It applies multivariate analyses of herbaceous species data to detect subtle degrees of overgrazing. The suitability of this multivariate method was tested in the central Highland Savanna of Namibia by comparing its results against a univariate analysis of herbaceous data in a simple but robust Range‐Unit Model. Despite aridity and topographical heterogeneity, the DGM performed unexpectedly well under these conditions. The relative instability of this dry savanna system favoured the applicability of the DGM by promoting a clear grazing gradient. Using species density data only resulted in an incorrect outcome of the multivariate analysis. The sensitivity of the DGM could be improved by combining density and cover data.  相似文献   
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Functionally relevant hepadnavirus-cell surface interactions were investigated with the duck hepatitis B virus (DHBV) animal model by using an in vitro infection competition assay. Recombinant DHBV pre-S polypeptides, produced in Escherichia coli, were shown to inhibit DHBV infection in a dose-dependent manner, indicating that monomeric pre-S chains were capable of interfering with virus-receptor interaction. Particle-associated pre-S was, however, 30-fold more active, suggesting that cooperative interactions enhance particle binding. An 85-amino-acid pre-S sequence, spanning about half of the DHBV pre-S chain, was characterized by deletion analysis as essential for maximal inhibition. Pre-S polypeptides from heron hepatitis B virus (HHBV) competed DHBV infection equally well despite a 50% difference in amino acid sequence and a much-reduced infectivity of HHBV for duck hepatocytes. These observations are taken to indicate (i) that the functionality of the DHBV pre-S subdomain, which interacts with the cellular receptor, is determined predominantly by a defined three-dimensional structure rather than by primary sequence elements; (ii) that cellular uptake of hepadnaviruses is a multistep process involving more than a single cellular receptor component; and (iii) that gp180, a cellular receptor candidate unable to discriminate between DHBV and HHBV, is a common component of the cellular receptor complex for avian hepadnaviruses.  相似文献   
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Purpose

Water footprinting and the assessment of water use in life cycle assessment have become of major interest in sustainability assessments. Various initiatives for combining water resource issues with consumption of products and services have been initiated in the last decade. However, comprehensive databases fulfilling the requirements for addressing these issues have been lacking and are necessary to facilitate efficient and consistent assessments of products and services. To this purpose, ecoinvent focused on integrating appropriate water use data into version 3, since previously water use data has been inconsistently reported and some essential flows were missing. This paper describes the structure of the water use data in ecoinvent, how the data has been compiled and the way it can be used for water footprinting.

Methods

The main changes required for proper assessment of water use are the addition of environmental and product flows in order to allow a water balance over each process. This is in accordance with the strict paradigm in ecoinvent 3 to focus on mass balances, which requires the inclusion of water contents of all products (also for e.g. waste water flows), as well as emissions of water to soil, air and various water bodies. Water inputs from air (e.g. rainwater harvesting) is introduced but is not yet used by any activity.

Results and discussion

Ecoinvent version 3.1 consistently includes the relevant flows to address water use in life cycle assessment (LCA) and calculate water footprints on the product level for most processes including uncertainty information. Although some problems regarding data quality and spatial resolution remain, this is an important step forward and can limit efforts for detailed data collection to the most sensitive processes in the product system. With the combination of data on water use and emissions to water for each process, concentration and corresponding water classes can also be calculated and assessed with existing impact assessment methods.

Conclusions

This comprehensive collection of water use data on the process level facilitates the proper assessment of water use within an LCA and water footprints beyond agricultural production. Especially in LCA, but also in tools for eco-design and specific water footprint, this data is essential and leads to a cost-efficient way of assessing consumption choices and product design decisions with full transparency. It enhances the effectiveness of investing in data collection by performing sensitivity analyses using ecoinvent data to identify the most relevant flows and processes.
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