1,721,100 research outputs found
A Review of Sediment Toxicity Bioassays Using the Amphipods and Polychaetes
No full textSeveral bioassay methods have been developed since the US EPA/COE (United States Environmental Protection Agency/ Army Corps of Engineers) testing protocol was devised, involving a great variety of test species. The amphipods and the polychates are now beginning to be used routinely as standard bioassay organisms for assessing the toxicity of marine sediments for regulatory purposes. The present review has confirmed the potential of both the amphipods and the polychaetes for sediments toxicity bioassays
Studies on the uptake of copper, zinc and cadmium by the amphipod Corophium volutator (Pallas) in the laboratory
No full textIn this study, accumulation of copper, zinc and cadmium at varying concentrations trom sea water and sediment under the laboratory conditions was assessed by bioaccumulation tests, using the marine crustacean Corophium volutator (Pallas). Concentrations of these metals in the whole tissues of C. volutator were determined at intervals of 3, 6, 24, 48, 72 and 96 h. There is positive correlation between metal levels in C. volutator and metal levels in sea water and sediment. The results also show that the accumulation of copper, zinc and cadmium in C. volutator from the sea water is higher than those from sediment
Poliket Arenicola marina ’nın Ağır Metal Alımında Sedimanın Etkisi
No full textIn this study, the suitability of the polychaete
Arenicola marina
as a test organism using clean intertidal sediment
contaminated with copper, zinc and cadmium was evaluated. Metal levels in casts were significantly lower than in unworked sedim
ent
indicating that the bioturbatory activity of lugworms might be significant in the distribution of the pollutants. This study sh
owed
that sediments contaminated with specific pollutants affected the uptake of these pollutants by
Arenicola
in a predictable and
dose–dependant way and gave further justification for the use of this species in sediment toxicity tests.Mevcut çalışmada poliket
Arenicola marina
bakır, çinko ve kadmiyumla kirletilen temiz sedimanla yapılan deneylerde test
organizması olarak kullanılmıştır.
Cast
adı verilen atıklardaki metal düzeyleri, organizma tarafından kullanılmamış sedimandaki metal
düzeylerinden önemli ölçüde daha az bulunmuştur. Bu da halkalı deniz kurtlarının biyolojik aktivitelerinin kirleticilerin dağıl
ımında
önemli olabileceğini göstermektedir. Mevcut çalışma özel kirleticilerle kirletilmiş sedimanın, bu kirleticilerin
Arenicola
tarafından
alımını doza bağlı olarak etkilediğini göstermiş ve bu türün sediman zehirlilik deneylerinde kullanımlarını desteklemiştir
The composition and seasonal distribution of zooplankton in the region of Sinop cape of the Black Sea, Turkey
No full textMevcut çalışmada, zooplanktonun mevsimsel dağılımı ve kompozisyonu, güney Karadeniz Bölgesi Sinop açıklarında yer alan iki istasyonda (kıyı ve açık) 2002-2004 yıllarında karşılaştırmalı olarak incelenmiştir. Zooplankton örneklemesi 210 um ağ göz ve 50 cm ağız açıklığına sahip standart net plankton kepçesi kullanılarak dikey olarak gerçekleştirilmiştir. Sinop bölgesinde 2002-2004 yıllarında toplam 27 zooplankton türü tanımlanmıştır. Besin zooplanktonunun en yüksek biyokütle değerleri, kıyısal istasyonda 2002 yılında Eylül (1.618 mg/m2), 2003 yılında Şubat (4.083 mg/m2) ve 2004 yılında Ağustos ayında (4.353 mg/m2) belirlenmiştir. Noctiluca scintillans, kıyısal istasyonda Mayıs 2002-2004 ve Ocak 2003 yılında en baskın tür olduğu belirlenmiştir. Kopepodlar tüm sene boyunca her iki istasyonda da eşit oranda rapor edilmiştir. Meroplankton, özellikle kıyısal istasyonda önemli miktarlarda bulunurken, maksimum değerlerine Aralık 2002, Şubat 2003 ve Ocak 2004 tarihlerinde ulaşmıştır. Kladoserlerin sıcak aylan tercih ettikleri görülürken, en baskın kladoser türü Penilia avirostris olarak tespit edilmiştir. Appendicularia, kıyısal istasyonda yüksek bolluk ve biyokütle değerleri 2002 ve 2003 yılında Eylül, 2004 yılında Kasım ayında bulunmuştur. Sagitta setosa açık istasyonda yüksek biyokütle değeri göstermiştir.in the present study, seasonality and composition of zooplankton was comparatively studied at two stations (inshore and offshore) off Sinop, in southern Black Sea in 2002- 2004. Samplings of zooplankton were carried out vertically with standard type plankton net with 210 \ı mesh size and 50 cm diameter. A total of 27 zooplankton species were identified in the Sinop region in 2002-2004. The highest inshore and offshore biomass values of the fbdder zooplankton were 2,618 mg/m2 in Septeraber 2002, 4,083 mg/m2 in February 2003 and 4,353 mg/m2 2004. Noctiluca scintillans dominated the zooplankton May 2002-2004 and January 2003 in inshore station. Copepods had no preference betvveen the inhore and offshore stations and existed throughout the year. Meroplankton had a higher preference for the inshore station, reaching peak values in December 2002, February 2003 and January 2004. Cladocerans mainly existed during warm months, the dominant species being Penilia avirostris. The maximum abundance and biomass value of the Appendicularia in inshore station were found in September 2002-2003 and November 2004. Sagitta setosa was showed highest biomass values in offshore sation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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