1,721,015 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
Proteome response of barnacle larvae to CO2-driven seawater acidification
No full textpublished_or_final_versionBiological SciencesMasterMaster of Philosoph
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
Mechanistic understanding of immunological responses of oysters to ocean acidification
No full textThe anthropogenic activities-driven excessive emission of CO2 can be absorbed in ocean, leading to a continuously changing carbonate chemistry and declining pH of seawater. This progressive alteration is known as ocean acidification (OA). OA usually appears with other biotic and abiotic factors, such as bacterial infection, concomitantly threatening the physiology, immunity and survival of marine organisms such as edible oysters. China, as the main producer of oyster aquaculture, contributing more than 80% of global production, is particularly concerned about this emerging issue. On the other hand, oysters have developed a sophisticated hemocyte-dominated innate immune system and the ability for rapid adaptation within a few generations, which allow them to survive and thrive under the stress of environmental changes and pathogen invasion. Although it is well known that oyster immunity can perform the protective tasks of immune recognition, signalling transduction, phagocytosis and elimination of exogenous pathogens, it is unclear to what extent OA affects the immune response of parents and offspring to pathogen infection in edible oysters, and whether the oyster species from different habitats have specific levels of resistance to OA and infection. Therefore, in this thesis, I systematically and comparatively analysed two oyster species from two habitats: estuarine species Hong Kong oyster (Crassostrea hongkongensis) and coastal species Portuguese oyster (C. angulata) to investigate the effects of long-term OA on oyster immune system and the immunological responses and molecular mechanisms of Vibrio parahaemolyticus infection through three generations under OA exposure. It was found that Hong Kong oyster showed high immune resistance to OA in the first generation, but this resistance gradually decreased in the following generations. On the other hand, Portuguese oyster was vulnerable to OA at the first generation with increasing hemocyte apoptosis, deceasing phagocytosis and bacterial clearance. This adverse effect cannot be ameliorated by adaptive plasticity in the subsequent two generations, suggesting that the OA-resistant species may lose resistance after two successive generations of OA. Interestingly, the negative effects on oyster immune system and gene expression profiles were irreversible after two generations of OA, even when returning the progeny larvae back to normal conditions. Transcriptome analysis revealed that the imbalanced energy metabolism (e.g., carbohydrate metabolism) and altered immune pathways (e.g., lysosome and autophagy) under the combination of long-term OA and bacterial infection were the underpinning molecular mechanisms for the loss of resistance. This study was the first to reveal that oysters with varying initial resistance showed a convergence of immune responses after two successive generations exposed to OA, suggesting that within-generation OA experiments possibly did not fully represent the real biological responses to environmental changes. Even the species that are currently resistant may not be the ultimate winner under climate change. In addition, my research demonstrated the changes in host-pathogen relationships induced by OA, shedding light on the possible intensification of mariculture animal diseases and foodborne human-related diseases in the context of climate change.published_or_final_versionBiological SciencesDoctoralDoctor of Philosoph
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
Reproductive traits and sexual selection in the mangrove littorinid snails, Littoraria ardouiniana and L. melanostoma
No full textAccording to Darwin, any inheritable traits that enhance fitness (i.e. survival and reproductive success) would be adaptive in a given environment, and therefore subject to natural selection. Some traits that enhance reproductive success but not necessarily survival may, however, evolve through the process of sexual selection. The importance of sexual selection has been intensively studied in “higher animals” birds, mammals and insects but has largely been neglected in “lower animals” such as gastropods. Using two mangrove snails, Littoraria ardouiniana HEUDE 1885 and L. melanostoma GRAY 1839 (Littorinidae) as model species, this thesis documents their various reproductive traits and the occurrence of sexual selection, in an attempt to understand how these animals optimize their fitness.
Being one of a few gastropod families that live closely associated with mangrove habitats, various adaptive reproductive traits are likely to have evolved in the genus Littoraria. The two Littoraria species exhibited several, contrasting, reproductive traits (e.g. reproductive mode; length of reproductive season; seasonal fecundity and egg- or larvae-releasing rate), which may represent species-specific strategies to optimize reproductive success. Both species adopted mucus trail following as a mate-searching strategy; with males being able to discriminate the trails laid by conspecific females and trail orientation during the mating season. Since these two snails mate in the complex habitat of mangrove tree canopies, incorporating some cue into mucus trails to aid mate recognition would increase potential encounter rates and hence reproductive success. 1D proteomic techniques identified two potential pheromones in the trail mucus of female L. ardouiniana, but further investigations are needed to confirm their possible role as sex pheromones.
Evidence for sexual selection was found in L. ardouiniana through male mate choice and male-male competition. Large male L. ardouiniana showed a preference for mucus trails laid by large (= more fecund) females, but this preference was not seen in small males, suggesting a size-based male mate preference. Males of this species also mated with larger females for a longer duration and they showed physical aggression (i.e. they pushed each other) when they encountered a female. These sexual selection mechanisms may drive size-assortative mating patterns in littorinid species and in other animals.
Conversely, L. melanostoma exhibited no obvious male mate preference or male aggression. Such differences in sexual selection patterns from L. ardouiniana were proposed to be a result of differences in operational sex ratio and variation in female quality. As many gastropods show similar mating behaviour to littorinids (i.e. trail following, shell mounting and copulation), sexual selection may operate in a comparable manner in other gastropods. By revealing the complexity of sex roles of males and females (e.g. the mutual occurrence of male mate choice and male-male competition) and condition-dependent male mate preference in these mangrove snails, this thesis has contributed to a missing link between sexual selection and the “lower animals” and provides new insights into the operation of sexual selection in animals.HKU 3 Minute Thesis Award, Champion (2012)published_or_final_versionBiological SciencesDoctoralDoctor of Philosoph
The microstructure, crystallography and mechanical performances of biomineralized oyster shell materials : ocean acidification perspective
No full textMarine calcifiers, such as oysters, build structurally complex shells to defend against predators using CaCO3 crystals through biomineralization. However, they are now facing a novel threat from ocean acidification (OA) in the process of which their biomineralization is damaged by the decreasing availability of carbonate ions in the unfavourable CO2-induced chemical environment. The inability to form their protective shell, with proper structure and mechanical features, is a major threat to marine biodiversity, shellfish aquaculture industries, coastal fisheries and thus global food security. It is not possible to predict the impact that OA will have on these species unless we understand the response of the shell structural mechanics to changing seawater chemistry. For these reasons, my thesis is particularly focused on a unique biological material, oyster shell, and the responses of their hierarchical microstructure to the near-future level of OA. I borrowed tools from marine biology, climate change science and aquaculture to obtain biological minerals from a variety of ecologically and economically important oyster species with unique structural and mechanical features. I then, mapped the architecture of CaCO3 crystals embedded in an organic matrix in those materials, and also modeled its mechanical features using tools borrowed from mechanical engineering (e.g. nanoindentation and finite element modelling). Beyond the immediate benefit to marine climate change science and aquaculture industry, the interdisciplinary knowledge gained here will provide novel insights for the materials science design of light and strong biomaterials.
My research, combining laboratory experiments and biomaterial analysis, is structured around four tasks or chapters. In chapter 2, the integrated comparison of structural and mechanical features of shells of two related species, Hong Kong oyster (Crassostrea hongkongensis) and the Portuguese oyster (C. angulata), demonstrates that the superior microstructure and organization of CaCO3 crystals in foliated layer are contributed to a stronger shell (Hong Kong oyster), which draws a baseline for the rest OA-related Chapters. In chapter 3, I have found that Portuguese oyster shells are highly vulnerable to OA due to their porous microstructure which directly leads less stiff and softer foliated layers at a near-future level of OA at pH 7.8. In chapter 4, Hong Kong oysters keep their superiority in structural and mechanical resistance to OA even at the pH 7.6 by realignments of crystal units in foliated layers. Indeed, I have found, in the final chapter 5, that the Pacific oyster (C. gigas) shells show a high degree of plasticity, in terms both microstructure (i.e. shorter laminas but unchanged porosity) and crystal orientation, in response to OA at pH levels from 7.6 to 8.1.
Thus, this hypothesis-driven (based on chapter 2), interdisciplinary (science and engineering) and comparative (three different species) study has illustrated the trade-offs between the microstructural and crystallographic characteristics and the mechanical features in oyster shells of different species in near-future coastal oceans with elevated anthropogenic CO2-driven OA, which not only unveils the intriguing capability of calcifiers in biomineralization but also provides critical knowledge for accurate forecasting the survival and production of edible oysters in the near-future ocean.published_or_final_versionBiological SciencesDoctoralDoctor of Philosoph
- …
