1,721,314 research outputs found
Drought effects on Helianthus annuus and Glycine max metabolites: from phloem to root exudates
No full textNumerous compounds are exuded by roots that play a central role in microbial decomposition and stabilization of soil carbon. The release of root exudates is sensitive to drought, but it is unclear how compound-specific exudates are related to drought-induced changes in plant metabolism. We investigated drought effects on root exudate quality and quantity for sunflower (Helianthus annuus) and soybean (Glycine max). We analyzed metabolites in phloem and root biomass extracts, to investigate whether root exudation is controlled by above- or below-ground processes. Sunflower and soybean showed different drought responses. Sunflower increased rates of exudation after rewetting (+330% in C) but the composition of metabolites remained unchanged compared to the control (constant moisture). Soybean did not change rates but the composition of metabolites changed with increased concentrations of osmolites (proline and pinitol). For specific groups, positive relationships were observed between exudates and phloem (amino-acids and organic acids) and between exudates and root biomass (sugars). Our results indicate that drought can induce different responses in plant metabolism causing changes in the quantity or composition of root exudates following rewetting. Furthermore, our results suggest that metabolism in shoots can influence exudation of organic acids and amino acids, while roots have a stronger control over exudation of sugars
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
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
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
Performance Analysis of Dynamic Finite Versioning Schemes: Storage Cost vs. Obsolescence
No full textAn Educational Software Suite for Teaching Design Strategies for Multistage Axial Flow Compressors
No full textThe T-AXI turbomachinery design system, an axisymmetric methodology recently developed with an educational purpose, has shown great capabilities in the redesign of existing axial flow gas turbine components. Different turbomachines, single or multistage configurations, have been already reproduced with excellent overall performance results: examples are the NASA/GE E3 HP compressor and LP turbine. In this paper, the authors present a detailed analysis of the results of a "case-study" application of the code as a complementary tool to be used during a turbomachinery design course. The NASA/GE E3 HP compressor has been chosen as the test case. Starting from the data available in open literature the different steps of the redesign have been reported: from the flowpath generation through the thermodynamic properties distributions to the overall turbomachine performance analysis. Particular attention has been given to some critical aero design parameters. The links to some interesting and useful literature sources are reported. The free-vortex, the only vortex law included in the first version of the code has been used for a first EEE compressor redesign. Different design vortex methodologies have been implemented in the new release of the code and their effects on the angular momentum are reported. The corresponding geometries can also be interfaced to a mesh generator and then the turbomachinery configurations analyzed by a 3D Navier-Stokes solver. In this way the flow field can be carefully analyzed and the fluid-dynamic physics better understood. With the above software structure the student has the opportunity to test the effects of different design strategies on the turbomachinery performance and to understand the need of a hierarchy of tools that give complete information for the multistage turbomachinery design. Finally, in the last section of the paper, the authors present how a project such as T-AXI, developed from their research activity in turbomachinery, numerical methods and CFD, can be included in the education tool CompEdu. © 2012 American Society of Mechanical Engineers
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