1,720,955 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
The Impact of Mycorrhizal Networks on Quercus rubra Seedling Recruitment
Get PDFMain Objectives – Mycorrhizal fungi are ubiquitous plant mutualists and can be classified into two types: ecto- (EMF) - dominant in temperate forests and arbuscular (AMF) - globally dominant. Both types form mycorrhizal networks (MN), consisting of fungal hyphae that connect plants of the same and different species. The degree to which the MN of adult trees facilitate or inhibit other plants, specifically seedlings, is unclear. This study examines how the MN associated with different species of adult trees affect mycorrhizal colonization, growth, survival, and root fungal community of Quercus rubra seedlings, an EMF tree species.
Methods – Seedlings were planted under four adult tree species of varying mycorrhizal types: Q. rubra (EMF), Q. velutina (EMF), Carya glabra (EMF), and Acer saccharum (AMF). Before field transplant, two thirds of the seedlings were grown within micromesh bags that allow hyphae to pass while blocking roots. Seedlings were separated into treatment groups: no bag control (C), bagged control (BC), and disturbed (D). C and BC groups were transplanted and allowed to grow undisturbed. Seedlings in the D group had their connection to the MN disrupted every 2-3 days. Seedlings were collected at the end of the growing season and survival and biomass were recorded. A subset of the seedlings was examined for EMF colonization, and all colonized tips were collected. Collected tips had fungal DNA extracted, amplified, and sequenced to determine the EMF community present on the roots of the seedlings.
Results – Seedlings in the D treatment were colonized by a different suite of mycorrhizae than the two control groups, complicating interpretation of the effect of the MN on seedlings performance. Q. rubra seedlings benefited from MN connection when grown under con-specific and hetero-specific trees; but the effect of EMF colonization when connected to the MN was negative under C. glabra. Furthermore, under A. saccharum, seedlings benefited more from the EMF community that colonized the roots when they were disconnected, than from the EMF community when connected to the MN.
Conclusions – The findings in this study underline the importance of MNs in the recruitment of Q. rubra, a common canopy tree in the temperate forests of eastern North America. The effects are highly variable, ranging from facilitation to inhibition, and vary on the species and mycorrhizal type associated with neighboring canopy trees. Overall, this study highlights the importance of the MN in structuring temperate forest ecosystems.Master of Science (MS)School for Environment and SustainabilityUniversity of Michiganhttps://deepblue.lib.umich.edu/bitstream/2027.42/154868/1/Schaffer-Morrison, Sam_Thesis.pd
Above- and Belowground Functional Trait Variation and Its Effect on Tree Seedling Response to Environmental Change
No full textTo predict forest composition and function under global change, it is important to understand tree responses to environmental shifts. This is especially true for seedlings, as the seedling stage represents a forest recruitment bottleneck. By studying how seedlings of different tree species respond to environmental changes, we can gain insights into future forest composition. Tree responses are influenced by their ecological strategies, which are shaped by the functional traits of their leaves and roots, the key organs for resource acquisition above- and belowground. Prior work at the interspecific level suggests that traits align along three independent axes: one each for above- and belowground resource conservation, which reflect plant’s efficiency in resource uptake and investment in organ construction, and a third for belowground collaboration, which describes the degree to which plants rely on mycorrhizal fungi – important root symbionts that assist with nutrient capture. However, no study has yet tested weather the proposed collaboration axis accurately captures how plants interact with mycorrhizal fungi. As a result, we still lack understanding of how roots and their symbiotic partners contribute to nutrient uptake within species. My dissertation addresses this gap by exploring patterns of plant functional trait variation and their implications for seedlings success in four chapters.
In Chapter 1, I review the current understanding of the relationships between tree roots and mycorrhizal fungi, arguing that because roots and mycorrhizal fungi operate together in resource acquisition, we should study them simultaneously for a more complete understanding of belowground resource acquisition strategies. In Chapter 2, I investigate whether the collaboration axis exists independently of the two resource conservation axes intraspecifically within seedlings of Quercus rubra, Acer rubrum, A. saccharum, and Prunus serotina collected across Michigan. My findings show that while aboveground traits are independent of belowground traits, belowground traits align along on a single axis, raising questions about the functionality of the collaboration axis.
In Chapter 3, I explore how plant functional traits of tree seedlings vary with mycorrhizal communities along a nitrogen (N) gradient. Both plants and mycorrhizal fungi are impacted by changes in N, but no study to date has examined both simultaneously. I collected seedlings of two different mycorrhizal types: Q. rubra (ectomycorrhizal; EcM), and A. rubrum and P. serotina (arbuscular mycorrhizal; AM). Some EcM fungi provide access to organic N, whicht is otherwise unavailable to plants, offering an advantage in low N conditions. I found that seedlings were often more acquisitive belowground at higher N, EcM access to organic N decreased with increasing N, and traits not included in the collaboration axis changed with mycorrhizal function, suggesting that the proposed collaboration axis is inadequate for describing plant reliance on mycorrhizae.
In Chapter 4, I apply the trait patterns observed in previous chapters to assess how trait variation affects seedling growth under multiple environmental stresses. While prior studies have examined plant responeses to a single stresses, stresses rarely occurs in isolation. I grew seedlings of Q. rubra, A. rubrum, and A. saccharum in the greenhouse under three levels of water and light conditions, measuring their growth and functional traits. I found that growth under multiple stresses declined less than expected based on the effects of individual stresses. Additionally, different species exhibited distinct trait strategies to cope with multiple stressors.PhDEcology and Evolutionary BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/199355/1/samsm_1.pd
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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