1,721,020 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
THE EFFECTS OF PRENATAL LEAD EXPOSURE ON THE DEVELOPMENT OF BIOMARKERS OF ALZHEIMER’S DISEASE
No full textWhile often well known for its adverse effects on memory, Alzheimer’s disease (AD) is also noteworthy for being the sixth leading cause of death in the United States. An estimated 5.2 million Americans had the disease as of 2013, with the number of cases expected to increase in coming decades. Research into the condition has not revealed its exact cause; however, AD is believed to result from a combination of genetic vulnerabilities and environmental influences. An important aspect of AD and this study is the development of plaques or clumps of amyloid beta (AΒ) protein in the brains of those with AD, with increased concentrations of AΒ indicating a more severe condition. Microglia, resident immune cells of the brain, are thought to influence the level of these proteins in the brain. Prenatal exposure to environmental contaminants may influence the actions of microglia during an organism’s lifetime in a way that encourages the development of AD and its observable plaques. This study explored both the separate and combined effects of environmental agents and genetic predispositions to the disease. This was done by exposing both 3x-Tg-AD mice, that have a genetic predisposition to developing AD, and wild-type mice to lead prenatally. The level of AΒ-42 in brains was measured by ELISA at varying ages, and the differences in AΒ-42 was compared between wild-type and transgenic animals between doses for each age and each sex. The final results showed a significant increase in AB-42 concentration in fully mature 3x-Tg-AD mice that were exposed to lead. This evidence supports our hypothesis that developmental exposure to an exogenous contaminant prenatally would exacerbate the tendency of genetically vulnerable organisms to develop the pathologies of AD.B.S
Investigating the Relationship between Environmental Lead Exposures and the Onset of Alzheimer's Disease Pathologies
No full textIt is been estimated that nearly 5 million Americans suffer from Alzheimer's Disease (AD), making finding its cause one of medicine's top priorities. It has long been known that genetics plays a major role in the development of Alzheimer's Disease, but this does not fully explain why or when the disease manifests itself. Alzheimer's is likely not a single-origin disease, but rather a disease that arises from a combination of both genetic and environmental factors that occur in the "right mix" at the "right time" to produce a phenotype indicative of AD. A major component of Alzheimer's is the plaques of amyloid-_ protein that form in the brains of its victims. One of the cells in the brain that has been shown to control the levels of amyloid-_ is the microglia. Studies show that these microglia experience a "critical window" of heightened susceptibility to environmental contaminants early in development from post-natal day (PND) 5-15. In this study, 3x-Tg-AD mice were dosed during this critical window with a proven neurotoxicant, lead acetate, in the form of drinking water. The levels and states of microglia were observed and compared to the levels of control mice, and the levels of amyloid-_ were tested using enzyme-linked immunosorbent assay (ELISA). This study hoped to uncover the relationship between microglia and amyloid-_ levels as well as determine whether introduction of an environmental toxicant during a period of heightened susceptibility could exacerbate the onset of AD pathologies later in life
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
Effects of PFMOAA, An Understudied PFAS, on Developing Mice
No full textPerfluoro-2-methoxyaacetic acid (PFMOAA) was recently the most prevalent emerging per- and polyfluoroalkyl substance (PFAS) detected in the Cape Fear River of North Carolina (NC). A byproduct of fluorochemical manufacturing, PFMOAA is one of the shortest short-chain PFAS and is understudied with respect to its toxicity although it has been linked with immunotoxicity in mice. Well-studied PFAS are known to be immunosuppressive in both adult and developing organisms. The immune system is sensitive to disruptions and insults during development and may have an influence on immune-related conditions later in life. This study investigated the developmental effects of PFMOAA in mice to better understand the immunotoxicity of this short-chain PFAS on developing organisms. Pregnant C57BL6 mice were given PFMOAA (0.0, 0.05, 0.5, or 1.0 mg/kg with 0.5% Tween) or a 5.0 mg/kg perfluorooctane sulfonic acid (PFOS) positive control via gavage throughout gestation. B6C3F1 offspring were evaluated at postnatal days (PND) 21, 28, and 56 for organ weights, lymphoid organ cellularity was evaluated on PND 28 and 56, and T-cell dependent antibody responses (TDAR) and uterine wall thickness were evaluated on PND 56. Dams were euthanized after weaning, liver weights were recorded, and the thickness of the uterine wall of dams was evaluated. Liver weights of dams and PND 21 female offspring exposed to PFOS were increased by 17.9% and 9.9%, respectively, compared to controls. There were increases in several relative organ weights across dose groups as well as a decrease in relative kidney weight in the 0.05 mg/kg dose group at PND 21 for female offspring. There were increases in relative heart, kidney, and brain weights at PND 56 in males of the 0.5 mg/kg dose group and increases in relative heart, kidney, and spleen weights as well as a decrease in relative uterus weight for 0.05 mg/kg group females. At PND 28, both sexes had an increase in thymus cellularity in the 0.5 mg/kg dose group as did females in the PFOS dose group when compared to controls. Females in the 0.5 mg/kg dose group had decreases in spleen cellularity at PND 28 and 56, and males in the 0.5 mg/kg dose group had a decrease in spleen cellularity at PND 56. These data suggest that at the administered doses, PFMOAA has potential to induce developmental toxicity and additional studies are warranted to determine further health effects of gestational exposure to PFMOAA and other emerging short-chain PFAS
30-Day Immunotoxicity Study of PFMOAA in C57BL/6 Mice
No full textWithin the past five years, two classes of per- and polyfluoroalkyl substances (PFAS) were phased out of production in the U.S., which led to the development and production of PFAS to replace these two major classes. One family of these PFAS are perfluoro-ether carboxylic acids (PFECA), which have emerged in the public and scientific arenas due to their presence in drinking water systems across the U.S., including Wilmington, NC. Although manufacturers have touted them as having more favorable environmental and toxicological properties very little is known about the toxicity and environmental fate these emerging PFECA. One compound, perfluoro-2-methoxyacetic acid (PFMOAA), was identified as the dominant PFECA in the Cape Fear River, in concentrations as high as 35,000 ng/L. There is very little mention of PFMOAA in the publicly available scientific literature and to our knowledge, we are the first to investigate its potential for toxic effects. In this 30-day study, we orally administered 25,000, 2,500,000, or 250,000,000 ng/L of PFMOAA in water to male and female C57BL/6 mice and investigated immune and liver alterations following exposure. Mice given PFMOAA showed no signs of overt toxicity during the study and no evident changes were observed in liver mass or peroxisomal enzyme activity. While mild alterations in splenic and thymic lymphocyte sub-populations were observed in males, these results do not point to any definitive alterations in immune function. Ultimately, we concluded that the doses administered were too low to achieve an internal dose sufficient to induce changes to immune endpoints, likely due to rapid excretion of PFMOAA in mice. Further investigation into serum and organ concentrations of PFMOAA as well its effects on antibody production will be more conclusive of immunotoxic effects
The Immunotoxicity of Two Novel Perfluoroether Acids Found in North Carolina’s Cape Fear River
No full textNovel perfluoroether acids (PFEAs) have been identified in surface waters of North Carolina and in the blood of some North Carolina residents. As some per- and polyfluoroalkyl substances (PFAS) are presumed immune hazards to humans, markers of immunotoxicity in young adult female and male C57BL/6 mice were observed following either 30-day oral exposure to perfluoro-2-methoxyacetic acid (PFMOAA), 30-day oral exposure to Nafion by-product 2 (NBP2), or 15-day oral exposure to a mixture of PFMOAA and NBP2. In-life observations were collected and endpoints included: organ weights, immunophenotype of lymphoid organs, natural killer (NK) cell cytotoxicity, liver peroxisomal enzyme activity, and the T-cell dependent antibody response (TDAR). In animals exposed to PFMOAA orally for 30 days the following changes were observed: liver weight statistically increased, in male animals peroxisomal enzyme activity statistically increased, and in male animals the TDAR was statistically suppressed. In animals exposed to NBP2 orally for 30 days the following changes were observed: liver weight statistically increased, spleen and thymus weight statistically decreased, NK cytotoxicity statistically decreased, liver peroxisomal enzyme activity statistically increased, and the TDAR was statistically decreased. In animals exposed to PFMOAA and NBP2 mixtures for 30 days the following changes were observed: one male group had statistically decreased bodyweight, some groups had alterations in organ weights. Our results indicate these novel PFEAs have immunosuppressive and immunomodulatory potential
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
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