1,721,071 research outputs found
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
Thermal relationships between body temperature and environment conditions set upper distributional limits on oviparous species
Full text linkWe determined the thermal biology of the oviparous Liolaemus boulengeri and the viviparous Liolaemus lineomaculatus populations localised at high and low latitude sites in Patagonia, Argentina. We present data of body temperatures in the field (Tb) and preferred temperature in the laboratory (Tpref), micro-environmental and operative temperatures and the effectiveness of thermoregulation. Liolaemus boulengeri and L. lineomaculatus choose different heat sources for active selection of suitable thermal micro-environments for thermoregulation, and the oviparous L. boulengeri is a more effective thermoregulator (E=0.55) than the viviparous L. lineomaculatus (E=0.43). Even when L. boulengeri is a better thermoregulator and both species show identical timing in the reproductive cycles, there are constraint factors that impose limitations on the southernmost distribution of the oviparous L. boulengeri.Fil: Medina, Susana Marlin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Scolaro, Jose Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Méndez de la Cruz, Fausto Roberto. Universidad Nacional Autónoma de México; MéxicoFil: Sinervo, Barry Raymond. University of California at Santa Cruz; Estados UnidosFil: Ibarguengoytía, Nora. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma | Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma.; Argentina. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Departamento de Zoología; Argentin
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
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MALE QUALITY INFLUENCES INTERSEXUAL DYNAMICS, BUT NOT FEMALE INTRASEXUAL COMPETITION, IN A MONOGAMOUS, BIPARENTAL FISH
Full text linkFemale preference for higher quality males can influence both intrasexual and intersexual dynamics. In species with biparental care, male quality can influence not only the female's initial gametic investment but also the amount of care each parent provides to the offspring. Here, I describe studies of female reproductive investment in response to male size, an indicator of quality, and the effect of female intrasexual selection on parental behavior in the convict cichlid (Amatitlania siquia), a monogamous, biparental fish. In Chapter 1, I observed breeding patterns in a natural population in Costa Rica and found that females increased their parental care when paired with larger males. Male size was positively correlated with offspring number, indicating a benefit to females from pairing with larger males. In Chapter 2, using a controlled breeding experiment, I investigated trade-offs in female fecundity and parental care within and between breeding events in response to male size. I found that females initially paired with small males had a greater probability of failing to successfully breed. Females did not increase their fecundity when paired with large males, but did increase their parental care and defensive behaviors. However, females did not benefit from pairing with larger males because they had fewer offspring. Male size did not significantly affect female parental care behavior during the second breeding, and fecundity again did not differ between females paired with small and large males. In Chapter 3, I presented breeding pairs with non-reproductive and reproductive female conspecific intruders. I found that parental females behaved more aggressively towards reproductive intruders, which were a threat to their mating status, compared to non-reproductive intruders, which were only a threat to their offspring. Female size, rather than male size, predicted parental female response to intruders, with small females behaving more aggressively. Males preferred to associate with the reproductive intruder, as it represented a potential new mate. The results of this dissertation demonstrate that females increase their parental care, but not their fecundity, for larger males. Moreover, females appear to use their prior breeding experience when allocating resources to the current reproductive event, as females did not increase their parental care when paired with large males during their second mating because large males failed to provide any benefits during the initial breeding. Male quality influences intersexual dynamics, but not intrasexual interactions, suggesting that females may be altering their response to the threat of male desertion. Overall, these results suggest that increased female investment may stabilize the pair-bond between the parents, which ultimately increases female reproductive success
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Conservation biogeography, mechanisms of decline, and climate relationships of California wildlife
Full text linkLife on earth is in the midst of an extinction crisis. Modern rates of extinction are comparable to rates of extinction during the five mass extinction events of the Phanerozoic. While habitat loss and invasive species have been dominant historical drivers of extinction, climate change is projected to emerge as a codominant driver of extinction during the 21st century. This dissertation explores the impacts of climate change, habitat loss, and invasive species on California wildlife with the goal of providing information that will assist in conserving biodiversity. Two themes that unite this dissertation are conservation biogeography and climate change. The first two chapters focus on historical and projected climate-mediated range contraction in a species that appears to be threatened almost entirely by climate change, as opposed to other sources of decline. Chapter three assesses the vulnerability of twenty California mammal species to climate change and includes consideration of land use, hydroclimatic niche, dispersal ability, sea level rise, and species traits. Chapter four explores strategies for recovering one of the first species to be protected under endangered species law in the context of habitat loss, invasive species, climate change, habitat protection, and potential for habitat restoration on retired farmland
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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Evolutionary consequences of Cenozoic climate change on African lacertid lizards (Squamata: Lacertidae)
Full text linkThe evolutionary diversification of many terrestrial vertebrate groups is strongly linked to climatic events in the Cenozoic, the period from 65 Million years ago to today when modern animals first appeared. I investigated the effects of Cenozoic climate change on the taxonomic and morphological diversification of the Old World lizard family Lacertidae, with particular emphasis on the African radiation. African lacertids exhibit an unusual pattern of diversification, in which their highest species richness occurs in deserts north and south of the equator, despite being spread throughout the continent. This disparity is particularly surprising given that desert lacertids are thought to be evolutionarily younger than their mesic-dwelling relatives, suggesting increased diversification rates in arid habitats. To identify the evolutionary factors underlying this pattern, I use a combination of phylogenetic, morphological and ecological techniques. In Chapter 1, I apply Bayesian methods and fossil-based calibrations to molecular sequence data to construct a time-calibrated phylogeny for Lacertidae. I estimate that the family arose in the early Cenozoic, with the majority of their African radiation occurring in the Eocene and Oligocene. In Chapter 2, I describe changes in lacertid body shape across biomes and substrates, and find widespread morphological convergence in similar habitat types. I suggest that in addition to foraging demands, fluctuating and extreme climatic conditions, largely driven by precipitation and temperature, contribute to morphological convergence across independent arid-dwelling clades. Finally, I test if ancestral transitions in ecology, morphology, and rates of diversification temporally coincide with paleoclimatic events in the Cenozoic. I use High Resolution X-ray Computed Tomography to characterize changes in the skull related to life in arid habitats, and apply maximum likelihood methods to test if the origins of those traits temporally coincide with significant shifts in habitat, diversification rates and climatic changes. My results show that African lacertids experienced three major peaks in diversification, accompanied by the evolution of suites of arid-adapted morphological traits. These changes coincide with climatic shifts in Africa, including the transition from closed forests to open grasslands and savanna in the late Oligocene, prior to the peak temperatures of the mid-Miocene Climatic Optimum, and following the formation of the Benguela current leading to hyper-aridity in southern Africa. I conclude that deserts are important centers for reptile evolution, but that expected changes in climate due to global warming may outpace the ability of arid-dwelling species to adapt and persist in the future
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Climate change and a little brown lizard: the impact of climate on maternal thermoregulation, offspring phenotype, and host-parasite interactions in the viviparous European common lizard (Zootoca vivipara)
Full text linkClimate change is predicted to severely impact species distributions and extinction risk in the coming decades. Ectotherms, such as lizards, are of particular concern due to their dependence on environmental temperatures to survive and reproduce. The predictions of extreme weather events and increases in global mean temperatures will affect the ability of these organisms to carry out important functions such as feeding or breeding. While we predict that these organisms will face challenges from climate change, examining whether they show evidence of coping with these changes is critical for determining extinction risk and making conservation decisions. In this dissertation, I use treatments of 3-hour (short), 6-hour (mid/control), and 9-hour (long) access to basking heat to investigate how different climate extremes, predicted to increase and worsen under climate change, would impact various aspects of pregnant viviparous European common lizards (Zootoca vivipara). The 3-hour treatments reflect an unusually long series of cool days limiting thermoregulation, 6-hours reflects the “normal” period of contemporary climate and 9-hours reflects periods of long-duration heat spells. In Chapter 1, I look at the flexibility of females to modify their behavior to different basking treatments and how intraspecific variation between populations plays a role. My results demonstrate these lizards exhibit plasticity in basking behavior in response to varying thermal opportunity. However, the magnitude to which they modify their behavior is significantly tempered by environmental characteristics of their population of origin. In Chapter 2, I investigate how basking treatments influence gestation and offspring phenotype, as the offspring life history stage is one of great importance. We found that offspring phenotype was significantly affected by mother basking treatments with local population differences and sex-dependent outcomes on size and viability in juveniles. My findings indicate that cooler and warmer temperatures have different effects on progeny phenotype and may have cascading impacts under climate change in the next generation. In Chapter 3, I examine how parasite load varies between populations and whether basking treatments influence a lizard’s ability to fight infection. The basking treatments influenced changes in parasite load in three of the five populations, where we observed a relatively small increase in parasite abundance in lizards in the short and mid/control basking treatment compared to the long treatment. This difference between populations suggests a context-dependent impact of basking opportunities on the capability of lizards to clear parasite infections, under the warm environment treatment (9-h) and provides further evidence that ectothermic host-blood parasite relationships are likely to be impacted by future and contemporary climate change. The results of this dissertation ultimately highlight the complex impacts climate change can have on these organisms and will hopefully encourage further research while raising awareness of this pressing issue
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