1,720,967 research outputs found
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
Occurrence and Distribution of Urban Organic Pollutants in the Pohick Region of the Potomac River Watershed (Virginia, USA)
Get PDFPolycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs) and several Endocrine Disrupting Compounds were examined in the Pohick Bay region of the Potomac River, Virginia, USA. Urban Organic Pollutants (UOPs) were found in nanogram/gram quantities in whole fish tissue, bed sediment and suspended sediment. Analytes of interest were extracted from environmental samples using Microwave Assisted Extraction using acetone:hexane as the solvent. Replicate samples from the Pohick Bay region were examined by Gas Chromatography/Mass Spectroscopy. Concentrations of UOPs in the Lower Pohick watershed reveal that the upstream wastewater treatment plant (WWTP) is a possible point source of certain chemicals including triclosan and bisphenol A, PCBs, and PAHs. Loading of creeks and streams from WWTPs that feed into larger water bodies adds to the complexity of modeling a tidal water body such as the Potomac River. Consensus-based Threshold Effect Concentrations (TECs) have also been compared to analyte concentrations of PCBs and PAHs in bed sediment. Human and watershed health implications, including exposure to endocrine disrupting compounds, should be analyzed to determine possible detrimental effects of utilization of the watershed
Bioavailability of Persistent Organic Pollutants in Fish from Gunston Cove (Potomac River Watershed, Virginia)
Get PDFThree classes of Persistent Organic Pollutants (POPs): Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs) and Organochlorine Pesticides (OCPs) were investigated in aquatic biota and bed sediments from an embayment-river mainstem of the Potomac River. Mean sediment concentrations ranged from 2.85 * 10^3 to 3.27 * 10^3 ng g^-1 for total-PAHs, 27.9 to 29.6 ng g-^1 for total-PCBs, 1.42 to 1.66 ng g^-1 for 4,4’-DDE and 0.65-0.66 ng g^-1 for γ-chlordane. A greater portion of high molecular weight PAHs were present in the bed sediments indicating high contribution of pyrogenically-derived PAHs. Consensus-based Threshold Effect Concentrations (TECs) have been compared to concentrations of total-PAHs, individual PAHs, total-PCBs and individual OCPs. Mean concentrations of POPs in fish tissue ranged from 5.4 to 34.3 ng g^-1 for total-PAHs, 40 to 116 ng g^-1 for total-PCBs, 14.0 to 28.9 ng g^-1 for 4,4’-DDE and <LOD to 1.8 ng g^-1 for γ-chlordane. The highest total-PCB and 4,4’-DDE concentrations were observed in White Perch (Morone americana) and Spottail Shiner (Notropis hunsonius) indicating strong correlation with their dietary consumptions. The median biota-sediment accumulation factor (BSAF) estimated in all fish species for total-PCBs was 1.88. However, some individual and co-eluting PCB congeners had median BSAFs that were substantially greater (e.g. congener numbers 44, 84, 91, 138/164, 151, 158 and 183) or lower (e.g. congener numbers 22, 56/60, 191 and 208) than the total-PCB average. Bioaccumulation for PCB congeners showed a somewhat parabolic relation with n-octanol/water partition coefficients, confirming some previous investigations. The median BSAF value for 4,4’-DDE was 9.58, higher than all other analytes of interest indicating an exceptionally high affinity to partition into aquatic biota. No clear trend was observed between apparent bioaccumulation factors and trophic level
Endocrine Disrupting Chemicals in Water, Sediments and Fish Observed in Urban Tributaries of the Freshwater Tidal Potomac River: Occurrence, Bioaccumulation and Tissue Distribution
Get PDFThe goal of the present study was to assess the ecological impacts of legacy and contemporary endocrine disrupting chemicals (EDCs) in the upper tidal Potomac River associated with WWTP discharge. Legacy EDCs includes polychlorinated biphenyls (PCBs) and the present study quantified total-PCBs and dioxin like PCBs (dl-PCBs), which are the more toxic PCB congeners, in bed sediments and biota from Hunting Creek and Gunston cove to evaluate the significance of dl-PCBs in the upper Potomac River
Allocating the Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Surficial Sediments from the Washington, DC Region with Particular Emphasis on Coal Tar Sealcoat
Get PDFVarious sources of polycyclic aromatic hydrocarbons (PAHs) were analyzed that potentially influenced contamination levels in sediments from the Anacostia River in Washington, DC and surrounding area. Sources of PAHs allocated in this study included coal tar sealcoat, asphalt, rubber tire, gasoline soot, diesel soot, and coal power fly ash. Extraction of sources and sediments was accomplished by microwave assisted extraction (MAE) and analyzed on gas chromatography mass spectrometry (GC-MS). Two methods were conducted to identify major sources of PAHs. The first used isomer ratios, unique ratios exhibited by studied sources helped identify major contributors of PAH contamination in sediments. The other method used was a chemical mass balance model developed by the U.S. EPA, CMB 8.2. This method apportioned major sources of PAHs. The findings from the methods showed that the major contributors of PAH contamination in area sediments were from gasoline soot, coal tar sealcoats, and coking emissions
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