1,721,003 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Population differentiation, dispersal limitation, and local adaptation in the gametophytic fern Vittaria appalachiana
Get PDFSpecies\u27 distributions are driven by a variety of abiotic and biotic factors. As these factors become altered by global climate change, species are believed to respond to these projected environmental changes in four different ways. One response is the shifting of the species\u27 geographic range to higher latitudes and elevations, which will be unlikely for those species that have limited dispersal potential. Alternatively, organisms may tolerate the change, which will be unlikely for those organisms that are not phenotypically plastic. A third potential response is to adapt to the new environment via rapid evolution, an unlikely response for those organisms that are isolate and genetically depauperate. Therefore, those species that are characterized by limited dispersal potential and populations that are differentially adapted may be especially sensitive to the anticipated environmental changes associated with global climate change. Here, we used a variety of field and common garden experiments to understand how a fern species will respond to global climate change. Specifically, we tested for dispersal limitation at the northern range boundary, population differentiation, and phenotypic plasticity. Our focal species, Vittaria appalachiana, is an asexual, gametophytic fern species, that occupies patchily distributed, non-calcareous rock shelters in the Appalachian Mountains of eastern North America. In each experiment, we used six different populations that span the species\u27 geographic range. To test for dispersal limitation, transplants were placed in a site beyond the northern range boundary that does not contain any known V. appalachiana populations. Transplants from each of these populations were also reciprocally transplanted amongst each population to test for local adaptation. Finally, explants from each of the six source populations were exposed to various temperature and humidity conditions, to test for phenotypic plasticity in response to temperature and humidity. Cumulative results from these three studies indicate that dispersal limitation heavily influences the contemporary northern range boundary of V. appalachiana and that populations are differentially adapted. However, this differentiation is not driven by temperature or humidity. Additionally, our results also indicate that southern populations may be locally adapted, while the most northern population is composed of robust genotypes. Finally, it appears that the species as a whole prefers cooler temperatures and lower humidity levels, suggesting that global climate change may negatively impact this species. Broader implications of this study suggest that abiotic factors other than temperature may drive species\u27 distribution patterns, and must therefore be included in modeling efforts to understand species response to climate change. Additionally, these results indicate that conservation efforts should consider population-level differences, as they may exhibit different responses to the stressors associated with global climate change
Effects of temperature and pollinator availability on plant reproductive success in the Indiana spring ephemeral community
Get PDFTemperature is a key driver of phenology in both plants and insects, and even small changes in temperature can impact the reproductive success of insect-pollinated plants by influencing access to pollinator services. While it is well-established that temperature variation directly impacts the flowering phenology of many plant species, the mechanisms by which it ultimately influences seed production via the pollinator community are not well understood. Climate change has the potential to disrupt the temporal synchrony between plants and their primary pollinators, especially if the two rely on different seasonal cues for the timing of their life history events. If the plants and their primary pollinators respond differently to environmental change, the plants may switch pollinators (host switching), obtain services or resources from other sources (e.g., self-pollination), or face extinction. The goal of this dissertation was to experimentally test the hypothesis that temperature-mediated variation in flowering time influences seedset by determining access to a pool of active pollinators, and the extent to which a flower experiences competitive or facilitative interactions for pollinators with co-flowering plant species. Three separate field studies were conducted using Claytonia virginica and Anemone acutiloba—members of the spring ephemeral community of deciduous forests in the eastern United States. This plant community is characterized by a brief 4 – 6 week reproductive period in the late winter and early spring, when the temperatures are rising but the tree canopy has not yet developed, so substantial sunlight still reaches the forest floor. Only a few pollinating insects are tolerant of the low temperatures that characterize early spring in this ecosystem, potentially generating competition for pollinators among co-flowering plants in the community. The first study evaluated the impacts of temperature, phenology, and co-flowering community diversity on the extent of pollen limitation experienced by the perennial herb C. virginica, a relatively abundant member of the spring ephemeral community. The study was conducted over two consecutive years that had markedly different spring temperature patterns. I observed a major advancement in the timing of flowering throughout the plant community in response to the warmer spring temperatures during the second year. However, seedset in C. virginica was not limited by pollen availability and was not influenced by the abundance and diversity of the co-flowering community. The second field experiment investigated temperature as a driver of plant phenology and the effects of shifted phenology on the reproductive output of A. acutiloba—the earliest flowering member of the spring ephemeral community. Individuals of A. acutiloba were transplanted into artificially warmed plots and monitored over two growing seasons. Increasing soil temperature resulted in advanced flowering time by at least 5 days in both years. However, despite this relatively large shift in flowering phenology, seed production in A. acutiloba was not affected by the temperature treatment. The third study evaluated the degree to which C. virginica functions as a generalist in the plant-pollinator network. This was done by characterizing the insect pollinator community that occurs in flowering C. virginica populations, and evaluating the relative abundance and diversity of the pollen from different co-flowering species on the bodies of the insects. I found that C. virginica pollen was present on all species of pollinators collected during its flowering period, and its pollen comprised the largest proportion of the total pollen abundance on all species of insect pollinators. Collectively, the results of this dissertation suggest that both C. virginica and A. acutiloba maintain access to sufficient pollinator services across high levels of temperature-mediated variation in flowering phenology and co-flowering community structure. Furthermore, high relative abundances of C. virginica pollen on all of the pollinating insects in the community reflect the generalist strategy of this species within the plant-pollinator network of the spring ephemeral community. While successful pollination in these two species is robust across dramatic shifts in temperature and phenology, I suspect that other species—especially those that are relatively rare, that rely on specialist insect pollinators, or that have narrower flowering windows—could be more likely to be subject to phenological mismatching across years with different temperature profiles. Additional experiments that explicitly compare plant species with different levels of relative abundance, different pollinators, and different phenological windows could make it possible to generate a predictive framework for anticipating which species in a community are most likely to be vulnerable to phenological mismatching with their pollinators in response to climate change
Refining phylogenetic hypotheses using chloroplast genomics and incomplete data sets in Lasthenia (Madieae, Asteraceae)
Get PDFThe genus Lasthenia (Madieae, Asteraceae), consists of predominantly annual plant species that are largely endemic to the California Floristic Province of western North America and occupy a large range of habitat types. With high levels of morphological and ecological diversity, Lasthenia is a robust tool, capable of providing a natural non-model organism for answering a diverse array of ecological and evolutionary questions. Future studies would benefit greatly from a strong phylogenetic hypothesis and more molecular resources, such as the whole plastome sequence for a representative species in the genus. Over a decade ago there was a study that laid a strong foundation for a molecular phylogenetic hypothesis, however, many critical nodes still remained ambiguous. Since that study was conducted, there have emerged new statistical and biological methods to maximize the information obtained from the sequence data. With the advent of next-generation sequencing, it is now simpler than ever to obtain molecular resources for a genus, and it is possible to apply some of those molecular resources to resolving the phylogenetic relationships in Lasthenia. My research has two specific outcomes: 1) I have provided the first whole plastome in the tribe Madieae of the Asteraceae and used the plastome to analyze rates of evolution across the regions of other sequenced plastomes in the Asteraceae, and 2) Through the use of modern phylogenetic methods and incomplete data sets consisting of freely available and newly obtained sequence data, I have for the first time resolved all seven sections of the Lasthenia genus with moderate to high bootstrap support
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