1,720,972 research outputs found
Desarrollo, validación e implementación de metodología analítica para la determinación de contaminantes emergentes mediante el sistema de extracción de fase sólida y espectrometría de masas en tejidos de ostras y mejillones cultivados en el Golfo de Nicoya
No full textTesis (licenciatura en química)--Universidad de Costa Rica. Facultad de Ciencias Básicas. Escuela de Química, 2024El consumo de productos farmacéuticos ha incrementado de manera significativa a través de los años. Esto ha provocado, que, a nivel mundial, muchas de estas sustancias lleguen a matrices naturales como aguas subterráneas, aguas superficiales, aguas residuales, sedimentos, entre otros, convirtiéndose en contaminantes emergentes de rápido crecimiento. Actualmente, se están empleando organismos bivalvos como ostras y mejillones para el biomonitoreo de las zonas costeras. Esto debido a que estos, al alimentarse por medio de la filtración tienen capacidad de absorber xenobióticos. En Costa Rica la investigación en torno de la presencia de estos contaminantes se ha centrado en aguas residuales y superficiales y hay muy poca investigación en torno a la presencia de estas sustancias en zonas costeras y organismos acuáticos. En el Golfo de Nicoya se está dando como actividad productiva la producción de ostras y mejillones. Por esta razón, en este trabajo, se buscó implementar un método para la determinación de estas sustancias en tejidos de ostras (Magallana gigas) y mejillones (Mytella guyanensis) cultivados en el Golfo de Nicoya, específicamente en Isla Chira, Costa de Pájaros y Punta Cuchillo. Se analizaron nueve moléculas de seis clases terapéuticas diferentes: antibióticos (levofloxacina, sulfametazina, clindamicina), antidepresivos (venlafaxina), antilépticos (carbamazepina), antifúngico (fluconazol), β-bloqueadores (atenolol y metoprolol) y otros (cafeína). Se realizó la validación del método y se determinó que el método presenta linealidad (R2 < 0,995), reproducibilidad (% recuperación: 74 % - 131 % en mejillones y de 67 % - 101 % en ostras) y límites de detección de 0,30-3,50 ng/g en mejillones y 0,40 – 3,35 ng/g en ostras y límites de cuantificación de entre 0,5 – 5,00 ng/g en ambos organismos. Sin embargo, se determinó que hay que realizar mejoras al proceso de purificación de la muestra...UCR::Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic
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
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
Occurrence and transformation products of drug residues in the aquatic environment, media and organisms, by targeted and non-targeted approach in mass spectrometry
No full textLa croissance démographique et l'urbanisation exercent des pressions anthropiques sur les ressources en eau et leurs écosystèmes. Parmi les polluants anthropiques, les produits pharmaceutiques à usage humain sont rejetés dans l'environnement principalement par les eaux usées traitées et non traitées. Plusieurs études ont déterminé l’occurrence de ces composés dans les eaux continentales en Europe et en Amérique du Nord. Cependant, dans les pays du Sud, peu d’informations sont connues ce qui justifie de poursuivre les efforts pour renseigner l’état de contamination des milieux aquatiques par les résidus de médicaments. L'exposition continue des organismes aquatiques à ces substances biologiquement actives peut favoriser leur bioaccumulation. Des publications récentes suggèrent qu’il est nécessaire d'élaborer des scénarios sur l’exposition et les implications, en termes de risques, des résidus de médicaments et de leurs produits de transformation sur ces organismes non ciblés. Dans ce contexte, les approches ciblées et plus récemment les approches non ciblées à l'aide de la chromatographique liquide couplée à la spectrométrie de masse sont des méthodologies prometteuses à utiliser pour renseigner l'état de contamination des eaux et des organismes marins par les produits pharmaceutiques. Compte tenu de ce qui précède, ce travail s'est appuyé sur des analyses dirigées et non dirigées qui ont été appliquées sur des échantillons environnementaux (matrices aqueuses et biote). Au final, cette étude a permis: 1) de faire le premier diagnostic du niveau de contamination des eaux de surface et souterraines par les produits pharmaceutiques au Cameroun, autour de sa capitale Yaoundé et 2) de caractériser les métabolites de l'antidépresseur Venlafaxine dans les moules (Mytilus Galloprovincialis).Population growth and urbanization are exerting anthropogenic pressures on water resources and their ecosystems. Among anthropogenic pollutants, pharmaceuticals for human use are released into the environment mainly through treated and untreated wastewater. Several studies have determined the occurrence of these compounds in inland waters in Europe and North America. However, in the countries of the South, little information is known, which justifies continuing efforts to inform the state of contamination of aquatic environments by drug residues. Continued exposure of aquatic organisms to these biologically active substances can promote their bioaccumulation. Recent publications suggest the need to develop scenarios on the exposure and risk implications of drug residues and their transformation products on these non-target organisms. In this context, targeted approaches and, more recently, non-targeted approaches using liquid chromatography coupled with mass spectrometry are promising methodologies to be used to inform the state of pharmaceutical contamination of waters and marine organisms.In view of the above, this work was based on directed and non-directed analyses that were applied to environmental samples (aqueous matrices and biota). In the end, this study made it possible: 1) to make the first diagnosis of the level of contamination of surface and groundwater by pharmaceutical products in Cameroon, around its capital Yaoundé and 2) to characterize the metabolites of the antidepressant Venlafaxine in mussels (Mytilus Galloprovincialis)
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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