1,721,277 research outputs found
Light capture efficiency decreases with increasing tree age and size in the southern hemisphere gymnosperm Agathis australis
No full textWe investigated leaf and shoot architecture in relation to growth irradiance (Qint) in young and mature trees of a New Zealand native gymnosperm Agathis australis (D. Don) Lindl. to determine tree size-dependent and age-dependent controls on light interception efficiency. A binomial 3-D turbid medium model was constructed to distinguish between differences in shoot light interception efficiency due to variations in leaf area
density, angular distribution and leaf aggregation. Because of the positive effect of light on leaf dry mass per area (MA), nitrogen content per area (NA) increased with
increasing irradiance in both young and mature trees. At a common irradiance, NA, MA and the components of MA, density and thickness, were larger in mature trees,
indicating a greater accumulation of photosynthetic biomass per unit area, but also a larger fraction of support biomass in older trees. In both young and mature trees,
shoot inclination angle relative to orizontal, and leaf number per unit stem length decreased, and silhouette to total leaf area ratio (SS) increased with decreasing irradiance, demonstrating more efficient light harvesting in low light. The shoots of young trees were more horizontal and less densely leafed with a larger SS than
those of mature trees, signifying greater light interception efficiency in young plants. Superior light harvesting in young trees resulted from more planar leaf arrangement and less clumped foliage. These results suggest that the age-dependent and/or size-dependent decreases in stand
productivity may partly result from reduced light interception efficiency in larger mature relative to smaller and younger plants
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
Size‐dependent variation in shoot light‐harvesting efficiency in shade‐intolerant conifers
Full text linkShoots and foliage elements of shade-intolerant conifers strongly vary in size, but the effects of size on shoot light-harvesting efficiency have not been quantified. We investigated shoot adaptation to seasonal average integrated quantum flux density in gymnosperms Pinus palustris Mill., P. patula Schlect. & Cham., and P. radiata D. Don. and angiosperm Casuarina glauca Sieb. ex Spreng. In addition, P. sylvestris L., sampled from infertile and fertile sites, and P. taeda L. were included to test for general correlations among shoot architecture and size. All studied species possess needle-like photosynthetic elements. A shoot model was fitted to the data to separate the determinants of shoot light-harvesting efficiency. The model estimated shoot light harvesting on the basis of angular distribution of foliage surface areas, degree of spatial clumping, foliage area density in shoot volume, and beam path length in shoot volume. Increases in irradiance primarily led to greater foliage aggregation, greater foliage area density in shoot volume, and to a minor degree, to changes in foliage area angular distribution. Greater foliage aggregation resulted in lower efficiency of light harvesting but greater investment of foliar biomass in high light where the photosynthetic returns are greater. The species behave similarly except that the light-harvesting characteristics of P. patula, which has long, strongly bending needles, were independent of light. In all species, the shoots were larger in higher irradiance, and the fraction of biomass in shoot axis increased with increasing irradiance, indicating greater costs for light harvesting in high light. There were further significant species differences in light-harvesting efficiency that were linked to differences in foliage and shoot size. Foliage element length varied between 1.1 and 31.4 cm and shoot axis length between 1.2 and 36.5 cm among the species, leading to 4 orders of magnitude variation in shoot cylinder volume and three orders of magnitude variation in foliage area density (ρ); ρ decreased with increasing foliage element length and shoot volume. The degree of foliage clumping scaled positively with ρ and negatively with foliage element length. Foliage clumping was positively associated with foliage dry mass to shoot silhouette area ratio, signifying a trade-off between efficient light harvesting and large photosynthetic biomass accumulation. These data demonstrate a general increase of light-harvesting efficiency with increasing length of foliage elements, but they also demonstrate that this increase is limited by enhanced bending of longer foliage elements and by augmented support cost
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
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
- …
