1,720,990 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
Recommended from our members
Effects of Nutrient Availability on Root Nutrient Uptake and Carbon Exudates of Mature Tetragastris panamensis in a Lowland Humid Tropical Forest
Full text linkEcosystem processes are fundamentally limited by nutrient availability, but the effects of nutrient limitation or co-limitation on key processes like root nutrient uptake and carbon (C) exudation into soils is relatively unknown. New paradigms of nutrient limitation suggest that colimitation by multiple nutrients is more common than single nutrient limitation, therefore the established view that ecosystem processes are limited by phosphosus (P) in lowland tropical forests on highly weathered soils ecosystems should be revisited. Rates of nutrient uptake are of particular importance because these govern downstream plant physiological processes like photosynthesis and basic metabolism. Also, nutrient uptake is directly linked to root C exudates, which are increasingly recognized as an important plant contribution to soil C pools. Here, we explored the effect of changes in nutrient availability on root nutrient uptake in a well-studied Panamanian forest, and linked nutrient uptake to C exudates. We used a long-term factorial nutrient fertilization experiment, and focused our study on a relatively abundant canopy tree species (Tegtragastris panamensis). We found a significant interacting effect of nitrogen (N) and potassium (K) on root uptake rates for ammonium, nitrate, and phosphate. Nitrogen and K added in combination produced uptake rates indistinguishable from control plots, however, N or K added individually increased the uptake rates of all nutrients compared to control and NK plots. No significant effects of N or P addition were observed on root C exudation rates. These results suggest that increased N or K availability may accelerate N and P uptake rates by roots. These results support the growing literature indicating that most ecosystem processes in tropical forests are governed by the availability of multiple nutrients, with implications for understanding plant productivity in this biome
Recommended from our members
Effects of Altered Litter Inputs and Nutrient Additions on Rapidly- and Slowly-Cycling Soil Carbon in a Tropical Forest
Full text linkTropical forests contain a considerable fraction of the global soil carbon (C) stock, but the response of tropical soil C to predicted changes in primary productivity remains poorly understood. Drastic changes in soil C storage and loss are likely to occur if global change alters plant net primary production (NPP). This research assessed the effects of a decade of litter removal and addition on soil C storage in a seasonal tropical forest in Panama. Previous manipulation studies like the one used here have reported strong responses of carbon pools with addition and removal of litter in tropical forest ecosystems. Specifically, total C gains have been observed after addition while corresponding losses of C have been found with litter removal. However, past manipulation experiments fail to account for the heterogeneous nature of carbon cycling in these systems. The overarching hypothesis addressed here, is that changes in net primary production can affect the storage of soil C on various timescales. To address this, a density fractionation scheme was used to assess manipulation effects on rapidly- and slowly-cycling pools of C. Soil samples were collected from 0-5 cm depth in 15 - 45 x 45m plots with litter removal (L-), 2x litter addition (L+), and control (n=5). To account for any potential fertilization effect from added litter, soils from a long-term fertilization experiment were also used. Soil C storage in all pools was significantly different among the three litter treatments, and some seasonality resulted in every pool. L+ increased the oldest, most stable pool of C by 15% in the dry season and 28% during the wet season. Alternatively, L- decreased C concentrations in this long-term pool by 26% in the dry season and 28% in the wet season relative to control. There was no indication of any fertilization effect on the storage of C in this forest. The results here demonstrate that changes in primary productivity have the potential to alter the storage and cycling of C in lowland tropical forest soils
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
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
Recommended from our members
Assessing biotic and abiotic controls of carbon storage in soil
Full text linkUnderstanding the mechanisms of soil carbon (C) formation and loss is essential for predicting the C storage capacity of soils under ongoing global change scenarios. Climatic variables, vegetation structure, microbial activity, soil mineralogy, and tissue C chemistry each have the potential to affect the fate of C in soils, and the interactions among these controls vary in different environments. Our mechanistic understanding of how these factors interact with each other to determine soil C storage is still rudimentary. This dissertation used a series of field and laboratory studies to assess the interacting roles of vegetation, soil mineralogy, microbial activity, C chemistry, and temperature in regulating the fate of C in soils. In the first experiment, we sought to understand how soil mineralogy, soil nutrient and C status, and C chemistry interact to determine warming effects on the fate of newly added soil C using a 13C isotopic tracing approach. By tracking the added 13C label in soil pools at 4 days and 255 days in tropical forest soils with differing weathering and mineralogical conditions, we found that initial microbial uptake of 13C and average carbon use efficiency (CUE) by microbes were strongly correlated with longer-term C retention in mineral soils. Overall, warming had a negative effect on 13C retention in soil in the youngest, least-weathered soil only, with no warming effect on moderately to strongly weathered soils. Thus, soil C stocks in less weathered soils, and with lower microbial CUE, may be most vulnerable to C loss with a warming climate.Our second study assessed the fate of newly added organic 13C-labeled compounds in soils of differing fertility along weathering gradients. Comparing additions of two low molecular weight compounds, 2.9x greater retention occurred for 13C-labeled glucose versus 13C-labeled glycine after two years, suggesting that glucose may be a better precursor for soil organic matter formation. Soil mineralogy and nutrient availability were not significant factors in 13C retention in soil. Soil spectra from 13C NMR revealed an increase in the proportion of alkyl C in glucose and glycine amended soil relative to control soils, and alkyl C are commonly associated with relatively stable organic C. Thus, our results indicate that microbial incorporation of labile organic compounds like glucose into biomass may be associated with greater C retention in stable soil components. Our third study estimated the long-term effect of grass cover loss on soil organic C (SOC) and total nitrogen (TN) storage, and the spatial heterogeneity of SOC and TN in two arid grasslands. The nine years of experimental grass removal resulted in soil deflation and 30% and 35% declines in SOC and TN respectively in 100% grass removal plots (TU100). Grass removal also led to soil deposition in downwind areas of the plot (TD100). Soil organic C and TN concentrations in the deposition plot (TD100) was variable, and likely depended on the structure of the vegetation community trapping wind-blown particulates. Geostatistical analysis showed that weaker and smaller fertile islands, compared to the control, developed in TD100 plots over nine years of aeolian transport. The outcomes of this dissertation will add to the current body of knowledge about mechanisms of soil C stabilization across environmental conditions and with warming
- …
