1,721,177 research outputs found
Insight into the early steps of root hair formation revealed by the procuste1 cellulose synthase mutant of Arabidopsis thaliana
Get PDFBackground: formation of plant root hairs originating from epidermal cells involves selection of a polar initiation site and production of an initial hair bulge which requires local cell wall loosening. In Arabidopsis the polar initiation site is located towards the basal end of epidermal cells. However little is currently understood about the mechanism for the selection of the hair initiation site or the mechanism by which localised hair outgrowth is achieved. The Arabidopsis procuste1 (prc1-1) cellulose synthase mutant was studied in order to investigate the role of the cell wall loosening during the early stages of hair formation. Results: the prc1-1 mutant exhibits uncontrolled, preferential bulging of trichoblast cells coupled with mislocalised hair positioning. Combining the prc1-1 mutant with root hair defective6-1 (rhd6-1), which on its own is almost completely devoid of root hairs results in a significant restoration of root hair formation. The pEXPANSIN7::GFP (pEXP7::GFP) marker which is specifically expressed in trichoblast cell files of wild-type roots, is absent in the rhd6-1 mutant. However, pEXP7::GFP expression in the rhd6-1/prc1-1 double mutant is restored in a subset of epidermal cells which have either formed a root hair or exhibit a bulged phenotype consistent with a function for EXP7 during the early stages of hair formation. Conclusion: these results show that RHD6 acts upstream of the normal cell wall loosening event which involves EXP7 expression and that in the absence of a functional RHD6 the loosening and accompanying EXP7 expression is blocked. In the prc1-1 mutant background, the requirement for RHD6 during hair initiation is reduced which may result from a weaker cell wall structure mimicking the cell wall loosening events during hair formation
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
Zero Knowledge Proofs and Their Applications in Cryptography
No full textZero Knowledge Proofs (ZKPs), cryptographic protocols that allow a party to authenticate a transaction to another without disclosing additional information beyond the authenticity of the transaction, continue to have a significant impact on privacy, security, and integrity in applications. It addresses constraints such as computing costs, trust dimensions, and integration complexity, and proposes possible methods and techniques for future research. It emphasizes the importance of ZKP for improving privacy and security in digital systems highlights, the article emphasizes the importance of continuous innovation and further development of their standardization efforts. Proofs (ZKPs) have emerged as a powerful tool in cryptography, offering innovative solutions to privacy, security, and authentication challenges. This article provides an in-depth review of ZKPs, exploring their progress, challenges and future prospects in cryptography. It examines the basic concepts of ZKPs, their applications, and their impact on cryptographic protocols
Cell adhesion in Arabidopsis thaliana is mediated by ECTOPICALLY PARTING CELLS 1 – a glycosyltransferase (GT64) related to the animal exostosins
No full textDespite the fact that several hundred glycosyltransferases have been identified from sequencing of plant genomes, the biological functions of only a handful have been established to date. A Poplar glycosyltransferase 64 (GT64) family member that is differentially expressed during the cell division and elongation phases of cambial growth was identified from previously generated transcript profiling of cambium tissues. The predicted Poplar GT64 protein has a closely related Arabidopsis homolog ECTOPICALLY PARTING CELLS (EPC1). Mutation of the EPC1 gene, one of three Arabidopsis GT64 family members, results in plants with a dramatically reduced growth habit, defects in vascular formation and reduced cell–cell adhesion properties in hypocotyl and cotyledon tissues. Secondary growth is enhanced in epc1 hypocotyl tissues and it is proposed that this results from the abnormal cell–cell adhesion within the cortical parenchyma cell layers. Loss of cell–cell contacts within cotyledon and leaf tissues is also proposed to account for vascular patterning defects and the fragile nature of epc1 tissues. The EPC1 protein thus plays a critical role during plant development in maintaining the integrity of organs via cell–cell adhesion, thereby providing mechanical strength and facilitating the movement of metabolites throughout the plant
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