1,721,021 research outputs found
Bioaccumulation of the estrogenic compound 4-nonylphenol in the clam Tapes philippinarum
No full textDespite the widespread use of nonylphenol ethoxylates (NPEs) in many household and industrial
detergents and their accumulation in aquatic environments, mostly as nonylphenol (NP), very few
data are available about bioaccumulation of NP in bivalves. Considering that NP can exert estrogenic
effects in marine organisms, it is of great concern to improve the knowledge on their capability
of bioaccumulating the contaminant. In the present study, bioaccumulation of 4-NP was evaluated in the clam Tapes philippinarum after exposure for 7 and 14 days to 0, 0.025, 0.05, 0.1, and 0.2 mg
NP/L. NP concentrations were also determined before and after water renewal in the experimental
tanks. NP concentrations measured after water renewal ranged from 52% to 96% of the nominal
concentrations, whereas the values fell to 20–59 % after 24 h.
NP was not detected (DL = 0.05 mg/kg FW) in control clams. The highest NP concentration
(180.12 mg/kg FW) was measured in the clams exposed for 7 days to 0.2 mg NP/L.
In the clams exposed to the lowest NP concentrations in water (0.025 and 0.05 mg/L), accumulation
of NP was not completed in 7 days, whereas NP tissue concentrations observed in 0.1 and
0.2 mg NP/L-exposed clams after 7 days of exposure were maintained after 14 days.
The bioconcentration factor (BCF), calculated using the mean NP water concentration, ranged
from 1098, for the clams exposed for 7 days to 0.025 mg NP/L, to 1918, for the clams exposed for 14
days to 0.05 mg NP/L
Chemistry and isotopic composition of precipitation and surface waters in Khumbu valley (Nepal Himalaya): N dynamics of high elevation basins
No full textWe monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050 m a.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry
and to obtain insights regarding ecosystem responses to atmospheric inputs.
The major cations in the precipitation were NH4+ and Ca2+, whereas the main anion was HCO3−, which constituted approximately 69% of the anions, followed by NO3−, SO42− and Cl-. Data analysis suggested that Na+, Cl− and K+ were derived from the long-range transport of marine aerosols. Ca2+, Mg2+ and HCO3− were related to rock and soil dust contributions and the NO3− and SO42− concentrations were derived from anthropogenic sources. Furthermore, NH4+ was derived from gaseous NH3 scavenging. The isotopic composition of weekly precipitation ranged from −1.9 to −23.2‰
in δ18O, and from −0.8 to −174‰ in δ2H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation,which suggested
that other water sources contributed to the stream flow. Precipitation contentsfor all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while
in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source.
The calculated atmospheric N load (0.30 kg ha−1y−1) was considerably lower than the levels that were measured in other high-altitude environments. Nevertheless, the NO3− concentrations in the surface waters (from 2 to 17
μeq L−1) were greater than expected based on the low N inputs from wet deposition
A note on the ice crystallography and geochemistry of a debris cone, Northern Foothills, Antarctica
No full textEvolutionary toxicology as a tool to assess the ecotoxicological risk in freshwater ecosystems
No full textBorrowing the approaches of population genetics, evolutionary toxicology was particularly useful in assessing the transgenerational effects of a substance at sublethal concentrations, as well as evaluating genetic variation in populations exposed to pollutants. Starting from assays in controlled conditions, in recent years this approach has also found successful applications multi-stressed natural systems. It is also able to exploit the huge amount of data provided by Next Generation Sequencing (NGS) techniques. Similarly, the focus has shifted from effects on the overall genetic variability, the so-called "genetic erosion", to selective effects induced by contaminants at more specific pathways. In the aquatic context, effects are usually assessed on non-model species, preferably native fish or macroinvertebrates. Here we provide a review of current trends in this specific discipline, with a focus on population genetics and genomics approaches. In addition, we demonstrate the potential usefulness of predictive simulation and Bayesian techniques. A focused collection of field and laboratory studies is discussed to demonstrate the effectiveness of this approach, covering a range of molecular markers, different endpoints of genetic variation, and different classes of chemical contaminants. Moreover, guidelines for a future implementation of evolutionary perspective into Ecological Risk Assessment are provided
Vitellogenin induction in the clam Tapes philippinarum after exposure to 4-nonylphenol.
No full textNonylphenol (NP) is reported to exert estrogenic effects in marine organisms, being able to mimic
the action of endogenous estrogens. As a consequence, NP can induce vitellogenin (Vg) synthesis, the
major precursor of the egg-yolk proteins. In our previous study [Matozzo and Marin, 2005. Environ.
Res., 97, 43–49], we found that exposure for 7 days of the clams Tapes philippinarum to NP caused a
dose-related induction of Vg in both haemolymph and digestive gland of males. In the present study,
Vg induction was evaluated in sexually undifferentiated clams exposed to NP: for 7 days to 0,
0 + acetone, 0.025, 0.05, 0.1, and 0.2 mg NP/L and for 14 days to 0, 0 + acetone, 0.025, 0.05, and
0.1 mg NP/L. Vg was determined in both haemolymph and digestive gland by the alkali-labile
phosphate (ALP) assay. In the haemolymph Ca
2+
levels were also measured. Exposure for 7 days to
0.2 mg NP/L resulted in significant increases (p < 0.05) in ALP in both haemolymph and digestive
gland with respect to controls, whereas no difference was observed in Ca
2+
levels. After 14 days
exposure, ALP significantly (p < 0.05) increased in digestive gland from 0.05 and 0.1 mg NP/Lexposed clams. Increases (p < 0.05) in Ca
2+
levels were recorded in haemolymph from clams exposed
to 0.025 and 0.05 mg NP/L. Results obtained demonstrates that NP induces Vg synthesis in T.
philippinarum also far from the reproductive period. As endocrine disruption may cause fertility
reduction and alteration in sex ratio, a condition of potential risk for clam populations in estuarine
areas is highlighted. This study was supported by grants from Co.Ri.La (Second Research Programme, 2004–2006)
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
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