1,720,970 research outputs found
Watching Trees Grow: Observations of Radial Tree Growth Across Multiple Temporal Scales in Northern Labrador
Get PDFThis research assesses whether a refinement of the temporal resolution of tree-ring data can improve our understanding of the radial growth-climate relationship. Two study sites in Northern Labrador were chosen, one coastal (Nain), and the other inland (Kamestastin). In Nain, microcore samples were taken weekly from the same five white spruce (Picea glauca) trees over the 2014 growing season. After cross sections were made and stained, the resulting 10µm thin radii provided a direct view of active ring development. In coastal Labrador, radial growth was initiated during the last week of June 2014, and ceased by August 25th.
Circumference band dendrometers were installed on white spruce trees at both the Nain and Kamestastin sites. The dendrometers were used to measure micrometre-scale changes over the 2014 growing season. Analogous records of temperature were collected with equal temporal resolution, from an Environment Canada climate station (#8502800), and via a programmable data logger (UX120-006M, Onset HOBO). Correlation function analysis determined the relationship between daily temperature variables and daily variations in stem size. A strong relationship was found between minimum daily temperature and daily stem size at both sites over the eight week long growing season.
Traditional dendrochronological sampling methods were utilized to retrieve tree cores from white spruce and eastern larch (Larix laricina) in Nain and Kamestastin. Site-specific master growth chronologies were created using crossdating and standardization techniques. After establishing long term records of monthly temperature and accumulated growing degree-days (GDD) at both study sites, a linear regression analysis was undertaken to determine the suitability of these two variables as predictors of annual-radial growth. An accumulated June/July GDD index was identified as an overall better predictor of annual ring-width than mean monthly temperature variables in northern Labrador.
Exploring radial growth on an intra-annual scale helped to improve our understanding of the complex radial growth-climate relationship in Labrador. This allows for a strengthening of tree rings as a proxy climate indicator in remote regions of the northern boreal forest. The findings from this thesis provide the tools necessary to improve upon long-term climate reconstruction and forecasts of boreal forest structure in the face of climate change
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
Synchrotron dendrochemistry: Exploring the comparison of multi-dimensional elemental analysis methodologies on tree cores using synchrotron techniques
Get PDFThe research conducted in this thesis assesses the feasibility of using X-ray fluorescence (XRF) spectroscopy to determine concentrations (i.e., ppm and ppb) of heavy metals in tree core samples. The samples used to determine this feasibility came from the arsenic (As)-laden region of Yellowknife, NT, which has had past gold mining activity for several decades. With an area of known As contamination, it was hoped that the element could be used as a tracer to determine if XRF counts could in fact be compared directly to concentrations obtained from inductively coupled plasma-mass spectrometry (ICP-MS). There were eight sample locations within the study site, and they all bordered different cardinal directions of the perimeter of the Giant Mine. At each site multiple tree cores and soil samples were taken, as well as heights and diameters of the sampled trees.
The first manuscript is focussed on determining the best parameters for XRF spectroscopy tree core scans. Determining a methodology of conducting synchrotron dendrochemistry is important because there is little-to-no research on the best parameters to use to obtain meaningful, repeatable results. Using the IDEAS beamline at the CLS synchrotron allowed us to test XRF scanning parameters on tree cores using different preparation methods, dwell times, and core orientations with respect to incoming incident light. We were able to determine the most accurate and time-efficient way to scan tree cores using XRF without sampling and preparation methods leaving contamination on the core that could be picked up by the hypersensitive detector on the beamline. We determined that a perpendicular orientation, with a dwell time of 2 s and a jog distance of 0.25 mm resulted in the best line scans that used cores that were sanded flat by iterations of subsequent sandpaper grits.
The second manuscript is focussed on creating a relationship between the results obtained from two heavy metal analysis methodologies used in dendrochemistry; XRF and ICP-MS. Using a synchrotron, we obtained results of what elements were present in the wood by measuring photons emitted by the individual elements when excited by incident X-rays. Using ICP-MS we sampled the same tree from the same location in time to obtain precise concentrations of heavy metals from different portions of the same tree core. Although hypothesized that a relationship between the two methodologies could be found, no correlation was found; instead, two-dimensional maps of the tree cores suggested a reason why the hypothesis was not confirmed. Two-dimensional maps indicated that elements within trees likely vary in all three dimensions in a much more random fashion than was originally expected. This variation has implications for not only specific questions in dendrochemistry like radial translocation but necessarily alters the way all past and future synchrotron dendrochronological studies should be viewed
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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