1,720,981 research outputs found
Eco-social Consequences of Disease Management in East African Agro-Pastoral Systems: Policy Implications.
No full textTemperature influences on the functional response of Coenosia attenuata Stein (Diptera, Muscidae) individuals
No full textThe functional response of single Coenosia attenuta Stein (Diptera: Muscidae) adult females to Drosophila melanogaster (Meigen) adults has been investigated at different but constant temperatures and prey densities. The experiments were conducted in cages over a wide range of temperatures between 12 and 42°C. At each experimental temperature, the number of attacks increases with increasing prey density up to a maximum attack rate referred to as demand rate. A ratio-dependent and demand-driven functional response model was appropriate to describe the attack rate at different temperatures. Both the demand and the search rate linearly increased with increasing temperatures throughout the range. Based on these results, a temperature- and prey density-dependent bidimensional attack rate model was developed and parameterized. The resulting response surface shows that C. attenuata is active over a wide range of temperatures (from ≈12 to 36°C) and attacks occur up to 42°C. Thus, C. attenuata may be a promising biological control agent in Mediterranean greenhouses. To support this conclusion, further studies including the evaluation of spatial scale effects on the search rate and the consideration of the economically relevant whitefly prey are recommended
Eco-social analysis of an East African agro-pastoral system : management of tsetse and trypanosomiasis
No full textA key constraint for development of many East African agro-pastoral communities is African animal trypanosomiasis or nagana caused by Trypanosoma spp. and vectored by species of tsetse flies (Glossina spp.). Suppression of trypanosomiasis through trapping of tsetse fly populations was conducted from 1995 to 2005 at and near Luke, Southwest Ethiopia. Odor baited mass trapping technology was used to suppress adult fly populations to very low levels while tryponocidal drugs were used to treat trypanosome infections in cattle. Data on ecological, economic and social variables were collected and analyzed in the context of eco-social dynamics in the community. The bio-economic model of Regev et al. [Regev, U., Gutierrez, A.P., Schreiber, S.J., Zilberman, D., 1998. Biological and Economic Foundations of Renewable Resource Exploitation. Ecological Economics 26, 227-242] and Gutierrez and Regev [Gutierrez, A.P., Regev, U., 2005. The bioeconomics of tritrophic systems: applications to invasive species. Ecological Economics 52, 382-396] was used as a methodological framework for qualitative evaluation of the effects of tsetse/trypanosomiasis suppression on ecological, economic and social aspects. An objective function for single farmers was formulated to determine the optimal harvesting level of cattle, exposed to high and low levels of risk from tsetse/trypanosomiasis, as measured by the discount rate (δ) for a given base level pastoral resource (R = pasture or forage for cattle). The socially optimal objective function for resource exploitation by all farmers is that which maximizes the present value of utility of individuals expending revenues (consumption) from the revenue stream in ways that enhance the quality of life and yet assures the persistence of the resource base over an infinite time horizon (i.e., renewable resource sustainability). The bio-economic model predicts that reducing risk (δ) from tsetse and disease increased the cattle populations and their marginal value. The model also predicts that the interaction of decreased δ and increased productivity (θ) can lead to increased human and cattle populations and hence to over-exploitation of base resources (pastures) that lower environmental carrying capacity and reduced sustainability. Trap catches indicated that tsetse populations were reduced to very low levels, while the disease prevalence decreased from 29% to 10%. This led to a substantial increase in cattle including oxen populations, increased calving rates, increased milk production and increased the per-capita income. The availability of oxen allowed an increase in cultivated land from 12 ha in 1995 to 506 ha in 2005. Revenues (consumption) were invested in the purchase of more cattle and the establishment of a school for educating village children. Increases in land allocated to crops and other sources of income were also found. The bioeconomic model predicts the solution of the trypanosomiasis problems so transforms the East African agro-pastoral communities that new social structures will be required to cope with the ecological, economic and social consequences of this technological changes on sustainable development (sensu [Goodland, R., 1995. The concept of environmental sustainability. Annual Review of Ecology and Systematics 26, 1-24]). This insight should not be lost in international rural development programs
A novel approach based on information theory to rank conservation strategies: an application to amphibian metapopulations.
No full textHabitat fragmentation, reduction and degradation as well as the quality of habitat connecting environments are critical for species persistence. Spatially explicit metapopulation models considering environmental effects are natural candidates for modelling population viability. However, metapopulations share the inherent uncertainties of the population concept with vague field population definitions. The recognition of the fuzzy nature of populations leads to operational definitions for management purposes. To deal with scarce information and uncertainties in predictions of intervention effects, Adaptive Management is useful. Accordingly, the synthesis of monitoring information is performed with models whose features are continuously adapted to the level of available information. To derive useful indices for conservation strategy evaluation, we propose a novel approach based on the Kullback-Leibler information measure. This is used to evaluate strategies aimed at the conservation of amphibians in an alpine Rhine valley region (Canton of the Grisons, Switzerland) and it is applied to outputs from an incidence function model for Bufo bufo and Rana temporaria. For these species, establishing four additional breeding sites along the Rhine river is a better strategy than placing two additional sites in intensively cultivated land. Artificial ponds in residential areas contribute to species conservation, and transfer of individuals to new sites has advantages over reliance on spontaneous colonization. Bufo bufo and R. temporaria reacted similarly to conservation measures, possibly due to their quite similar ecologies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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