1,720,969 research outputs found
Zooplancton de la Bahía de Mochima: Retrospectiva y prospectiva | Zooplancton of the Mochima Bay: Retrospective and prospective
Get PDFEn esta recopilación se presenta una síntesis histórica de los trabajos realizados (publicaciones, tesis de grado, trabajos de ascenso) sobre el zooplancton en la Bahía de Mochima, estado Sucre, Venezuela. El Laboratorio de Plancton del Instituto de Zoología y Ecología Tropical (IZET) y el Laboratorio de Zooplancton del Instituto Oceanográfico de Venezuela (IOV) han llevado a cabo numerosos estudios de la comunidad zooplanctónica, en los cuales destacan aspectos taxonómicos y ecológicos incluyendo los efectos de la surgencia costera. Entre éstos, el nivel de información es muy desigual. Se presenta una lista de la composición y riqueza zooplanctónica. Los componentes holoplanctónicos incluyen medusas (19 especies), sifonóforos (5 especies), copépodos (75 especies), cladóceros (4 especies), quetognatos (3 especies), gasterópodos holoplanctónicos (2 especies), misidáceos (2 especies), apendiculados (16 especies). Dentro del meroplancton destacan las larvas de crustáceos decápodos, cirrípedos e ictioplancton. En general, los copépodos constituyeron el grupo más abundante, con diferencias notables en los eventos de surgencia y representaron la mayor proporción de biomasa. Las fluctuaciones temporales y espaciales de la biomasa, abundancia zooplanctónica y las relaciones de estas variables biológicas con variables físico-químicas fueron analizadas; sin embargo, las variables necesarias para estimar la producción, como ciclos anuales y relaciones tróficas han sido pobremente estudiadas. Esta revisión permitió identificar los problemas existentes y así proponer recomendaciones para investigaciones futuras. Palabras clave: Composición, Venezuela, surgencia costera, copepoda, ictioplancton, meroplancton, holoplancton. ABSTRACT This compilation presents a historical synthesis of the studies carried out (publications, thesis, monogrphs) on the zooplankton in the Bay of Mochima, Sucre State, Venezuela. The Plankton Laboratory of the Institute of Zoology and Tropical Ecology (IZET) and the Zooplankton Laboratory of the Venezuelan Oceanographic Institute (IOV) have carried out numerous studies of the zooplankton community, in which they emphasize taxonomic and ecological aspects including the effects of upwelling events. Among these, the level of information is very uneven. A list of zooplankton composition and richness is presented. The holoplankton components include jellyfish (19 species), siphonophores (5 species), copepods (75 species), cladocerans (4 species), chaetognatha (3 species), holoplanktonic mollusks (2 species), mysidacea (2 species), appendicularians (16 species). Within the meroplankton are larvae of decapod crustaceans, cirripedes and ichthyoplankton. In general, copepods were the most abundant group, with differences in upwelling events and represented the highest proportion of biomass. Temporal and spatial biomass fluctuations, zooplankton abundance and related physical and chemical variables were analyzed. However, the variables needed to estimate production, such as annual cycles and trophic relationships, have been poorly studied. Depending on the lack of information, the main problems were identified and recommendations for future research are proposed. Keys words: Composition, Venezuela, copepoda, ictioplancton, meroplancton, holoplancton
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
Distribución temporal y espacial de especies de cladóceros marinos en una zona hipóxica del golfo de Cariaco (mar Caribe suroriental)
No full textCladocerans in coastal environments occupy a predominant place in the pelagic food web after copepods. The composition, abundance and vertical distribution of Cladocera were evaluated in the Guaracayal depression, Gulf of Cariaco, Venezuela. Sampling was carried out bimonthly between April 2012 and April 2013. Water samples were collected with a Niskin bottle (5L) at 5, 25, 45 and 75m, to determine the concentration of dissolved oxygen and Chl a. A conical opening-closing zooplankton net with depth messenger, 300 µm mesh opening, was used; the setting was carried out obliquely, at a speed of 2 knots for 10 min. Temperature and salinity were measured by means of a multiparameter probe (YSI). The phenomenon of coastal upwelling was evident between December 2012 and April 2013, associated with records of low temperature (37) and Chl a. The concentration of dissolved oxygen decreased (37) y Chl a. La concentración de oxígeno disuelto disminuyó (< 1 mg L-1) por debajo de los 60 m de profundidad entre octubre y noviembre 2012 (período de estratificación). Se identificaron 4 especies de cladóceros: Penilia avirostris, Pseudoevadne tergestina, Evadne spinifera y Pleopis polyphemoides. Se observó la mayor abundancia en abril 2012 y 2013 a nivel superficial (5m) y las menores abundancias se hallaron en octubre 2012. P. tergestina fue la especie más abundante, registrándose en todos los meses muestreados e incluso se halló en el estrato anóxico, seguido de P. avirostris; en menor proporción se reconocieron a E. spinifera y P. polyphemoides. Dos factores fisicoquímicos, la temperatura y salinidad, fueron los principales impulsores de los cambios en la composición de los Cladocera
Bloom algal y abundancia de copépodos en el golfo de Cariaco, Venezuela (Caribe Suroriental)
No full textAmong the zooplankton, copepods are one of the main consumers of phytoplankton and, as such, these organisms are potential consumers of the dinoflagellate species that produce toxins. In this sense, the relationship between harmful algal blooms (HAB) on the copepods were studied in the eastern area of the Gulf of Cariaco, Venezuela. Monthly samples were collected from June 2009 to May 2010, in 9 stations distributed in three areas. Zooplankton was collected by a standard 333 µm plankton mesh, whereas phytoplankton were collected by water bottle (250 mL). Temperature (ºC), salinity (UPS), dissolved oxygen (mL.L-1), phytoplankton abundance (cel.mL-1), chlorophyll a concentration (mg.m-3) and inorganic nutrients (nitrate, nitrite, phosphate and silicate) were measured. Salinity, dissolved oxygen, phosphate and silicate concentrations were significantly different according to the multifactorial model of two factors: sampling period and geographic zones with two and three levels, respectively. The highest concentrations of Chl- a (ND - 26.49 mg.m-3) and phytoplankton abundance (37 – 1.247cel.mL-1) were reported during the rainy season (junio-julio 2009). The zooplankton community was dominated by copepods (78 % relative abundance), with total abundance varying between 2 - 4543 ind.m-3 and did not show temporal or spatial differences. During the study, a single algal bloom was observed during the rainy period, dominated by Prorocentrum mexicanum and G. catenatum. A positive correlation was observed between the maximum abundance of Acartia tonsa and Temora turbinata with the highest presence of toxic dinoflagellates. The richness of copepods was relatively low, due to the dominance of more than 90 % of A. tonsa and T. turbinata. It is suggested that A. tonsa is able to ingest these dinoflagellates and use them without suffering apparent deleterious effects.Dentro del zooplancton, los copépodos son uno de los principales consumidores de fitoplancton. Por tanto, estos organismos son potenciales consumidores de las especies de dinoflagelados que producen toxinas. En este sentido, se estudiaron los efectos de las floraciones de algas nocivas (FAN) sobre los copépodos de la zona oriental del golfo de Cariaco, Venezuela. Se recolectaron muestras mensuales de junio de 2009 a mayo de 2010, en nueve estaciones distribuidas en tres zonas. Para el zooplancton, se empleó una red estándar de plancton de 333 μm, mientras que el fitoplancton se colectó a través de botella de agua (250 mL). Se midieron la temperatura (ºC), la salinidad (UPS), el oxígeno disuelto (mL.L-1), la abundancia fitoplanctónica (cel.mL-1), la concentración de clorofila a (mg.m-3) y los nutrientes inorgánicos (nitrato, nitrito, fosfato y silicato). La salinidad y el oxígeno disuelto resultaron significativamente diferentes de acuerdo con el modelo multifactorial de dos factores: períodos y zonas con dos y tres niveles, respectivamente. Las mayores concentraciones de Cl-a (0-26,49 mg.m-3) y de la abundancia fitoplanctónica (37-1,247 cel.mL-1) se reportaron en el período de lluvia (junio-julio de 2009). La comunidad zooplanctónica estuvo dominada por los copépodos (78 % de abundancia relativa), con abundancias totales entre 2 – 4,543 ind.m-3, y no mostró diferencias temporales ni espaciales. Durante el estudio se observó una sola floración algal durante junio-julio de 2009, dominada por Prorocentrum mexicanum y Gymnodinium catenatum. Se observó una correlación positiva entre los máximos de abundancia de Acartia tonsa y Temora turbinata con la mayor presencia de dinoflagelados tóxicos. La riqueza de copépodos fue relativamente baja debido a la dominancia de más del 90 % de A. tonsa y T. turbinata. Se sugiere que A. tonsa es capaz de ingerir estos dinoflagelados y utilizarlos sin sufrir efectos deletéreos aparentes
- …
