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Larissa Rosa Nogarol Ana Luiza Brossi-Garcia Raphael Bastão de Souza 《International journal of environmental analytical chemistry》2016,96(4):387-403
Due to their benthic filter-feeding habits and high bioaccumulation potential of metals and organic compounds, bivalve molluscs have been widely used in studies in the field and laboratory to assess the toxic effects of several compounds discharged in rivers, oceans and estuaries. However, most ecotoxicological studies use invasive exotic species, while the response of native species is poorly known. The Brazilian endemic species Diplodon expansus occurs in rivers near areas of intense agricultural activity, and atrazine is currently one of the main residues of pesticides found in water bodies of the Brazilian territory. This study was aimed at examining the toxicity of different atrazine concentrations to a Brazilian native mollusc by analysing the histology, histochemistry and ultrastructure of its gill filaments. The cells that comprise the frontal and intermediary regions of gill filaments were the most affected by the herbicide and responses associated with damage and protection were observed. The response of tissues and cells were dose-dependent. Higher concentrations of herbicide caused more severe alterations in large areas of the gills. The persistence of the alterations observed might result in severe functional problems in the gills of these animals, negatively affecting their performance and health. 相似文献
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Dr. Logesh Mathivathanan Dr. Guillaume Rogez Dr. Nadia Ben Amor Prof. Vincent Robert Prof. Raphael G. Raptis Dr. Athanassios K. Boudalis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(56):12769-12784
Previously reported ferromagnetic triangles (NnBu4)2[Cu3(μ3-Cl)2(μ-4-NO2-pz)3Cl3] ( 1 ), (PPN)2[Cu3(μ3-Cl)2(μ-pz)3Cl3] ( 2 ), (bmim)2[Cu3(μ3-Cl)2(μ-pz)3Cl3] ( 3 ) and newly reported (PPh4)2[Cu3(μ3-Cl)2(μ-4-Ph-pz)3Cl3] ( 4 ) were studied by magnetic susceptometry, electron paramagnetic resonance (EPR) spectroscopy and ab initio calculations to assess the origins of their ferromagnetism and of the magnetic anisotropy of their ground S=3/2 state (PPN+=bis(triphenylphosphine)iminium, bmim+=1-butyl-3-methylbenzimidazolium, pz−=pyrazolate). Ab initio studies revealed the d character of the magnetic orbitals of the compressed trigonal bipyramidal copper(II) ions. Ferromagnetic interactions were attributed to weak orbital overlap via the pyrazolate bridges. From the wavefunctions expansions, the ratios of the magnetic couplings were determined, which were indeterminate by magnetic susceptometry. Single-crystal EPR studies of 1 were carried out to extend the spin Hamiltonian with terms which induce zero-field splitting (zfs), namely dipolar interactions, anisotropic exchange and Dzyaloshinskii–Moriya interactions (DMI). The data were treated through both a giant-spin model and through a multispin exchange-coupled model. The latter indicated that ≈62 % of the zfs is due to anisotropic and ≈38 % due to dipolar interactions. The powder EPR data of all complexes were fitted to a simplified form of the multispin model and the anisotropic and dipolar contributions to the ground state zfs were estimated. 相似文献
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Matthieu Emond Thomas Le Saux Dr. Sylvie Maurin Jean‐Bernard Baudin Prof. Dr. Raphael Plasson Dr. Ludovic Jullien Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8822-8831
This paper evaluates the 2‐hydroxyazobenzene platform for tailoring proton concentration pulses and oscillations with monochromatic light. The easily prepared 2‐hydroxyazobenzenes exhibit large absorptions in the near‐UV range. Photoisomerization was investigated by UV/Vis absorption, 1H NMR spectroscopy, and steady‐state fluorescence emission. In the whole investigated series, the trans stereoisomer of the 2‐hydroxyazobenzene motif provides the corresponding cis derivative with an action cross section in the 103 M ?1 cm?1 range. At the same time, photoisomerization is accompanied by a significant pK drop of the phenol group. According to the phenyl‐substituent pattern, cis‐to‐trans thermal back‐isomerization can be tuned in the 10 ms–100 s range. Up to 2 units of reversible pH drops or pH oscillations on the 10 s timescale have been obtained by appropriately tailoring single‐wavelength illumination of 2‐hydroxyazobenzene solutions. 相似文献
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This review covers the recent marine chemical ecology literature for phytoplankton, macroalgae, sponges and other benthic invertebrates; 249 references are cited. 相似文献
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Raphael Yuster 《Discrete Mathematics》2006,306(1):166-170
For an oriented graph G with n vertices, let f(G) denote the minimum number of transitive subtournaments that decompose G. We prove several results on f(G). In particular, if G is a tournament then and there are tournaments for which f(G)>n2/3000. For general G we prove that f(G)?⌊n2/3⌋ and this is tight. Some related parameters are also considered. 相似文献
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An edge-coloring of a connected graph is monochromatically-connecting if there is a monochromatic path joining any two vertices. How “colorful” can a monochromatically-connecting coloring be? Let mc(G) denote the maximum number of colors used in a monochromatically-connecting coloring of a graph G. We prove some nontrivial upper and lower bounds for mc(G) and relate it to other graph parameters such as the chromatic number, the connectivity, the maximum degree, and the diameter. 相似文献
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