1,721,007 research outputs found
Potentiodynamic study of Al-Mg alloy with superhydrophobic coating in photobiologically active/not active natural seawater
No full textSuperhydrophobic coating technology is regarded as an attractive possibility for the protection of materials in a sea environment. DC techniques are a useful tool to characterize metals' behavior in seawater in the presence/absence of coatings and/or corrosion inhibitors. In this work, investigations concerning Al-5%Mg alloy with and without a sprayed superhydrophobic coating were carried out with potentiodynamic scans in photobiologically active and not active seawater (3 weeks of immersion).In not photobiologically active seawater, the presence of the superhydrophobic coating did not prevent pitting corrosion. With time, the coating underwent local exfoliations, but intact areas still preserved superhydrophobicity. In photobiologically active seawater, on samples without the superhydrophobic coating (controls) pitting was inhibited, probably due to the adsorption of organic compounds produced by the photobiological activity. After 3 weeks of immersion, the surface of the coating became hydrophilic due to diatom coverage. As suggested by intermediate observations, the surface below the diatom layer is suspected of having lost its superhydrophobicity due to early stages of biofouling processes (organic molecule adsorption and diatom attachment/gliding). Polarization curves also revealed that the metal below the coating underwent corrosion inhibiting phenomena as observed in controls, likely due to the permeation of organic molecules through the coating.Hence, the initial biofouling stages (days) occurring in photobiologically active seawater can both accelerate the loss of superhydrophobicity of coatings and promote corrosion inhibition on the underlying metal. Finally, time durability of superhydrophobic surfaces in real seawater still remains the main challenge for applications, where the early stages of immersion are demonstrated to be of crucial importance
Assessing the neurotoxic effects of Ostreopsis cf. ovata by using microelettrode array based platform
No full textIn the last decade, the occurrence of harmful Ostreopsis cf. ovata blooms has increased both in frequency and in geographic distribution. This resulted in adverse impacts on public health and the
economy and has become a global concern. Until now, the data required for the evaluation of real toxicological hazard related to naturally occurring phenomena, such as algal blooms, require time
and resources. Existing data are mainly derived on in vivo mouse assay and are related to acute effects of palytoxin without considering that the toxicity of the dinoflagellates is due to a mixture of
biotoxins whose composition is not only strongly species dependent, but may also differ according to region of occurrence, specific environmental conditions and biological cycles.
In this study, we investigated for the first time the effect of cultured O. cf. ovata cells and their naturally released toxins mixture in the growth medium on rat cortical neuronal networks grown on
multi-electrode arrays (MEA). By means of the multiparametric analysis of neuronal network activity, the approach revealed different toxicological characteristics of the cellular component and
the algal conditioned growth medium, highlighting the higher toxic potential of the first treatment. Overall, the high sensitivity, the rapidity and the throughput make MEA-based method a valuable
tool to be used to facilitate the toxicity evaluation of marine toxic algae in due time and at regulatory level
Adverse effects of the SSRI antidepressant sertraline on early life stages of marine invertebrates
No full textWidespread contamination of coastal environments by emerging compounds includes low concentrations of pharmaceuticals. These pollutants are not currently incorporated in monitoring programs despite their effects on non-target organisms are very little documented. Among the selective serotonin reuptake inhibitor (SSRI) antidepressants, sertraline (SRT) is one of the most prescribed globally. In this work, earlier life stages of Amphibalanus amphitrite, Brachionus plicatilis and Mytilus galloprovincialis were exposed to environmental concentrations of SRT in order to study both sub-lethal and lethal responses in 24/48 h-tests. Low concentrations of SRT altered significantly swimming behavior in A. amphitrite and B. plicatilis giving 48 h-EC50 (μg/L) of 113.88 and 282.23, respectively whereas higher values were observed for mortality and immobilization. EC50 embryotoxicity with M. galloprovincialis was 206.80 μg/L. This work add new data about SRT ecotoxicity on marine invertebrates and confirms the applicability of behavioral endpoints to evaluate the environmental impact of antidepressants in marine organisms
Ag and AgCu as brazing materials for Ti6Al4V-Y 3 Al 5 O 12 joints: Does ennoblement affect the galvanic behaviour in seawater?
No full textTransparent ceramic materials may be used as optical windows, sensors, gas-tight components, etc. in specific marine applications by integration into metallic structures through joining procedures. In such systems the evaluation of galvanic effects between base alloys and compounds obtained during brazing is crucial. In this work, the galvanic behaviour of Ag and AgCu brazes, used to obtain Ti6Al4V-Y3Al5O12 joints, was investigated in natural seawater for the first time. Two test sessions lasting 4 weeks each were performed. During the first, the AgCu brazed joint showed Cu selective depletion from both the interlayer and the diffusion zone, while the Ag brazed one appeared intact. Hence, the second session was devoted to a further study of the Ag brazed joint. Active-passive alloys are well known to undergo important OCP positive shift induced by the biofilm growth, commonly referred as ennoblement. The risk of Ti6Al4V to act as ennobling cathode, with acceleration of the Ag anodic dissolution in the interlayer, was simulated with Ti6Al4V and Ag freely corroding and coupled electrodes. In parallel, a 254 SMO stainless steel/Ag system was used as reference for ennoblement. OCP data were evaluated in the framework of inferential statistic in order to highlight the consistence with galvanic coupling data. The results were: 1) when coupled to Ti6Al4V, Ag showed occasional and reversible anodic inversions with galvanic current z 10-6 A x cm-2, 2) when coupled to 254 SMO, Ag inverted irreversibly as anode with galvanic current up to 10-5 A x cm-2. These differences depended on Ti6Al4V not ennobling, contrary to SS, which ennobled acting as a more powerful cathode. Finally, about dissimilar joints in natural seawater with Ti6Al4V as base alloy, AgCu is confirmed to be unsuitable as brazing material due to early Cu depletion from the interfacial zone. Differently, Ag is promising in relation to generally stable interfaces, even when there is a risk of ennoblement, thanks to Ti6Al4V not ennobling
Morpho-functional approach to neurotransmission and osmoregulation in Amphibalanus amphitrite cyprid (Cirripedia, Crustacea)
No full textAcorn barnacles are cirripedian crustacea with a sessile adult stage, that live in a calcareous shell attached to a submersed substrate and filter food with its limbs. Barnacles show various naupliar stages and a cyprid, the final lecithotrophic stage competent for settlement. Due to their ability to adhere, barnacles are important constituents of biofouling. To obtain biological data useful to develop antifouling strategies, many studies are focused on cyprid anatomy and neuroendocrinology, especially in Amphibalanus amphitrite due to its worldwide distribution. With our work we wanted to map the distribution of neurotransmitters in the cyprid to provide data for research on barnacle development, new antifouling strategies and the use of cyprid as a model organism in ecotoxicology. We focused on the distribution of neuroactive substances related to different systems: serotonergic, cholinergic, FMRFamidergic-like, GABAergic, glutamatergic and nitrergic. Also the functional aspects were investigated through physiological assessment, pointing out on swimming and settling activities. The cholinergic (our data) and the octopaminergic (from the literature) systems are known as potential target in antifouling strategies; moreover we suggest that serotonergic and GABAergic systems could be pharmacologically targeted as well, because they are widely present in the cyprid sensory and nervous structures. We are now focusing also on osmoregulative processes, attempting to characterize the presence and distribution of aquaporins, as they could be of interest in both antifouling strategies and ecotoxicology. To date, our data are consistent with the literature about ion-exchanging sites in the cyprid
Effect of silver nanoparticles on marine organisms belonging to different trophic levels
No full textSilver nanoparticles (Ag-NPs) are increasingly used in a wide range of consumer products and such an extensive use raises questions about their safety and environmental toxicity. We investigated the potential toxicity of Ag-NPs in the marine ecosystem by analyzing the effects on several organisms belonging to different trophic levels. Algae (Dunaliella tertiolecta, Skeletonema costatum), cnidaria (Aurelia aurita jellyfish), crustaceans (Amphibalanus amphitrite and Artemia salina) and echinoderms (Paracentrotus lividus) were exposed to Ag-NPs and different end-points were evaluated: algal growth, ephyra jellyfish immobilization and frequency of pulsations, crustaceans mortality and swimming behavior, and sea urchin sperm motility. Results showed that all the end-points were able to underline a dose-dependent effect. Jellyfish were the most sensitive species, followed by barnacles, sea urchins, green algae, diatoms and brine shrimps. In conclusion, Ag-NPs exposure can influence different trophic levels within the marine ecosystem
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
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