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See detailCoastal Ocean Modelling
Nihoul, Jacques ULg; Djenidi, Salim ULg

in Bordomer 92 (1992)

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See detailCoastal pollution of the Mediterranean and extension of its biomonitoring to trace elements of emerging concern
Richir, Jonathan ULg

Doctoral thesis (2012)

The Mediterranean Sea, a semi-enclosed sea with densely populated coasts, is submitted to numerous anthropogenic pressures: among them, the chemical pollution by traces elements. These pollutants, coming ... [more ▼]

The Mediterranean Sea, a semi-enclosed sea with densely populated coasts, is submitted to numerous anthropogenic pressures: among them, the chemical pollution by traces elements. These pollutants, coming from our continental activities, are transported through rivers or by air and accumulate in seas and oceans where they mainly affect coastal areas. During the 70ies, scientists suggested to use organisms, in particular mussels of the genus Mytilus, in order to evaluate the status of chemical contamination of coastal ecosystems. Biomonitoring was born. Since, many monitoring studies were published using various animal and vegetal species. Two of the most studied bioindicators species in the Mediterranean are the marine magnoliophyte Posidonia oceanica and the Mediterranean mussel Mytilus galloprovincialis. Monitoring studies with these two species have mainly focussed on contaminations by Cr, Ni, Cu, Zn, Cd, Pb (Mytilus galloprovincialis and Posidonia oceanica), Fe (Posidonia oceanica), As, V and Ag (Mytilus galloprovincialis). However, other trace elements like Be, Al, Mn, Co, Se, Mo, Sn, Sb and Bi have been subject to nearly no ecotoxicological survey. Furthermore the worldwide evolution of our technologies and of our lifestyle increases the extraction and production of trace elements (notably to answer needs of developing countries). The biomonitoring of the pollution by trace elements is henceforth a topical subject. The overall objective of this work was therefore to evaluate the potential use of Mytilus galloprovincialis and Posidonia oceanica as bioindicators to monitor the Mediterranean coastal pollution by Be, Al, Mn, Co, Se, Mo, Sn, Sb, Bi, Fe, As, V, and Ag. These trace elements, mostly little studied, can be categorized as elements of “environmental emerging concern”. A time-integrated efficient monitoring of trace elements requires the continuous survey of their environmental levels; we therefore also measured levels of trace elements classically monitored with these two species. Mytilus galloprovincialis and Posidonia oceanica complement each other in monitoring surveys. Both species accumulate pollutants dissolved in the water column. Posidonia oceanica, rooted in the seafloor, accumulates moreover pollutants stored in sediments in the long term. Mytilus galloprovincialis, as a filter feeder, further accumulate particulate pollutants suspended in the water column. The combined use of both bioindicators therefore provides a global view of the health status of the coastal environment (water, sediments, suspended matter). Our first goal was to measure, at the scale of the French Mediterranean littoral, the spatial variability of trace element contents in Posidonia oceanica, and to determine if trace elements of environmental emerging concern threaten the chemical integrity of coastal ecosystems. We observed that the large majority of trace elements little or no monitored with Posidonia oceanica showed an equivalent to higher spatial variability than elements classically monitored with that species. We also showed that the spatial variability could be associated to specific anthropic activities like agriculture (Mo), mining (Sb), storage and refinement of oil products (V), or the presence of harbours and major urban centres (Sn, Bi). Their monitoring, along with the one of trace elements classically studied in the Mediterranean, turns out to be essential. In addition, the in-depth study of the contamination state of the Calvi Bay (Northwestern coast of Corsica, France), enabled us to define (or re-define) this site as a reference site for the monitoring of the chemical pollution by trace elements in the Northwestern Mediterranean. We further studied the physiological mechanisms of accumulation, storage and excretion of trace elements by Posidonia oceanica. In situ contamination of seagrass bed portions allowed us to model the rapid kinetics of accumulation of contaminants by Posidonia oceanica shoots. Compartments of the plant answered differently to pollutant exposures. So, adult and senescent leaves assimilated pollutants less rapidly than young actively growing leaves. Trace elements, once accumulated, could be redistributed between the plant compartments, notably towards the rhizomes-roots systems buried in sediments. Our results experimentally showed that these below-ground organs could therefore play the role of biological archives for many elements. At the end of periods of exposure to pollutants, kinetics of decontaminations of Posidonia oceanica shoots were relatively fast and depended notably on the duration of the exposure to trace elements, on their toxic or essential character and on the studied compartment. We concluded that Posidonia oceanica was a sensitive bioindicator for the monitoring of the past and present coastal pollution by trace elements. We showed that Mytilus galloprovincialis efficiently accumulated trace elements of environmental emerging concern as well as elements classically studied with this bioindicator species. The physiology of mussels further conditioned their answers to pollutant exposures. Their reproductive cycle dissolved trace element concentrations during the massive production of gametes and conducted to differences more or less important between individuals of both sexes. The conservative character of the distribution of trace elements between the different body compartments of Mytilus galloprovincialis suggested an important physiological regulation of their internal levels. Finally, the size of mussels used in this study, harvested from an aquaculture farm, did not noticeably influence inter-individual concentrations, all mussels of a same rope having approximately the same age. In conclusion, this study enabled to improve and enlarge our state of knowledge about the monitoring of the pollution of the Mediterranean coastal environment by trace elements. In particular, both Mytilus galloprovincialis and Posidonia oceanica showed to be good candidates for the monitoring of trace elements of environmental emerging concern. [less ▲]

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See detailCoastal-open ocean exchange in the Black Sea: Observations and modelling
Stanev, Emil; Beckers, Jean-Marie ULg; Lancelot, Christiane et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 601-620

The interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems. The complexity of processes in these areas requires detailed studies ... [more ▼]

The interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems. The complexity of processes in these areas requires detailed studies combining modelling and surveying efforts. One promising step in this direction was undertaken in the framework of the EROS 21 project, focusing on the shelf part of the north-western Black Sea. In the present paper, we focus on the results of physical studies aiming to improve the understanding of the fundamental exchange processes in the ocean margins, as well as to quantify some of them in the Black Sea. We illustrate the capabilities of circulation models to reproduce physical processes with different time- and space-scales: coastal waves, internal waves, baroclinic Rossby and topographic waves. Another class of important phenomena in the coastal zone is associated with convection. Sources at the sea surface and in the outflow areas give rise to plume dynamics that play a crucial role in the vertical mixing and provide the mechanism for water-mass formation. Most of the results are illustrated for the shelf part of the Black Sea. The verification of simulations is performed by comparison with survey data, altimeter data from the Topex/Poseidon mission and radiotracer observations. The latter, in combination with simulations from circulation models, are used to trace the penetration of tracers into the intermediate and deep layers. We show that although most Sr-90 is introduced by river runoff, large amounts of this signal penetrate the halocline in the Bosphorus Straits area and along the southern coast. Another important fraction of the river water penetrates the intermediate layers at the shelf edge in the north-western Black Sea. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailCoating of gold nanoparticles by thermosensitive poly(N-isopropylacrylamide) end-capped by biotin
Aqil, Abdelhafid ULg; Qiu, Hongjin; Greisch, Jean-François ULg et al

in Polymer (2008), 49(5), 1145-1153

Gold nanoparticles (NPs) were prepared by reduction of HAuCl4 in aqueous solution and stabilized by poly(N-isopropylacrylamide) (PNIPAM). PNIPAM was prepared by two distinct routes: (i) conventional free ... [more ▼]

Gold nanoparticles (NPs) were prepared by reduction of HAuCl4 in aqueous solution and stabilized by poly(N-isopropylacrylamide) (PNIPAM). PNIPAM was prepared by two distinct routes: (i) conventional free-radical polymerization leading to polymer without any reactive end-group, and (ii) Reversible Addition–Fragmentation chain Transfer (RAFT) polymerization with 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP) as a RAFT agent. PNIPAM with low polydispersity was then end-capped by an α-carboxylic acid and an ω-trithiocarbonate that was converted into an ω-thiol upon hydrolysis. This hetero-telechelic polymer was analyzed by mass spectroscopy, size exclusion chromatography (SEC) and 1H NMR. Even without thiol end-group, known for chemisorption onto gold, PNIPAM was effective in stabilizing gold NPs (1–5 nm). The thermosensitivity of PNIPAM at the surface of gold NPs was, however, dependent on the molecular weight of the chains. Finally, the α-carboxyl end-group of PNIPAM was used to anchor biotin, which is indeed known for complexation with avidin, which is a possible strategy for the coated gold NPs to be involved as building blocks in supramolecular assemblies. TEM and UV–vis spectroscopy were used to characterize the gold nanoparticles. [less ▲]

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See detailCobalt mediated radical coupling (CMRC) : an unusual route to midchain-functionalized symmetrical macromolecules
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

in Chemistry : A European Journal (2010), 16(5), 1799-1811

Cobalt-mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3-diene compounds onto polymer precursors preformed by ... [more ▼]

Cobalt-mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3-diene compounds onto polymer precursors preformed by cobalt-mediated radical polymerization (CMRP). Mechanistic features that make this process so efficient for radical polymer coupling are reported here. The mechanism was established on the basis of NMR spectroscopy and MALDI-MS analyses of the coupling product and corroborated by DFT calculations. A key feature of CMRC is the preferential insertion of two diene units in the middle of the chain of the coupling product mainly according to a trans-1,4-addition pathway. The large tolerance of CMRC towards the diene structure is demonstrated and the impact of this new coupling method on macromolecular engineering is discussed, especially for midchain functionalization of polymers. It is worth noting that the interest in CMRC goes beyond the field of polymer chemistry, since it constitutes a novel carbon-carbon bond formation method that could be applied to small organic molecules. [less ▲]

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See detailCobalt mediated radical polymerization (CMRP) using bis(acetylacetonato)cobalt(II): a unique tool for controlling the radical polymerization of conjugated and unconjugated vinyl monomers
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

Poster (2009, September 17)

Cobalt-Mediated Radical Polymerization (CMRP) imparts a high level of control on the polymerization of acrylic and vinylic esters, acrylic acid and acrylonitrile. However, each class of monomers appears ... [more ▼]

Cobalt-Mediated Radical Polymerization (CMRP) imparts a high level of control on the polymerization of acrylic and vinylic esters, acrylic acid and acrylonitrile. However, each class of monomers appears to be controlled by one class of cobalt complexes. For example, the polymerization of acrylates and acrylic acid is mediated by cobalt porphyrin complexes while vinyl acetate (VAc) and acrylonitrile are efficiently controlled by bis(acetylacetonato)cobalt(II) (Co(acac)2). Therefore, a challenging issue in CMRP remains to broaden the range of monomers that can be controlled by the same cobalt complex. Recently, the controlled random copolymerization of butyl acrylate (BuA) with VAc was performed using the conventional V-70/Co(acac)2 CMRP system, but the homopolymerization of BuA remained uncontrolled. In this work, we used a new alkylcobalt(III) adduct to initiate and control the copolymerization of BuA with VAc. This achievement resulted in a significant improvement over the V-70/Co(acac)2 pair regarding the molecular weight control and the polydispersity indexes. Moreover, for the first time, the alkylcobalt(III) adduct was also efficient in controlling the homopolymerization of BuA and yielded low polydispersity PBuA even in the absence of VAc. These results indicate that Co(acac)2 is a versatile mediator for the CMRP of both unconjugated vinyl monomers (VAc, N-vinylpyrrolidone) and conjugated monomers such as acrylates. It gives access to copolymers that cannot be prepared by other controlled radical polymerization techniques. [less ▲]

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See detailCobalt(II) complexes as controlling agents for the radical polymerization of vinyl monomers
Debuigne, Antoine ULg; Sciannaméa, Valérie; Piette, Yasmine ULg et al

Poster (2007, August 31)

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See detailCobalt-assisted synthesis of novel block copolymers
Debuigne, Antoine ULg

Scientific conference (2009, February 05)

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See detailCobalt-mediated radical (co)polymerization of vinyl chloride and vinyl acetate
Piette, Yasmine; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

in Polymer Chemistry (2012), 3(10), 2880-2891

The cobalt mediated radical polymerization (CMRP) of vinyl chloride (VC) in the presence of bis(acetylacetonato)cobalt(II) (Co(acac)2) as a controlling agent is presented for the first time. Using an ... [more ▼]

The cobalt mediated radical polymerization (CMRP) of vinyl chloride (VC) in the presence of bis(acetylacetonato)cobalt(II) (Co(acac)2) as a controlling agent is presented for the first time. Using an alkyl-Co(III) compound (R0–(CH2–CHOAc)<4–Co(acac)2; R0 = (H3C)2(OCH3)C–CH2–C(CH3)(CN)–) as an initiator, the bulk polymerization under non-isotherm conditions is controlled. 1H NMR spectra of the resulting PVC show that the CMRP process does not significantly affect the level of defects compared to a PVC prepared by a conventional free radical polymerization at the same temperature. Using the same alkyl-cobalt(III) compound, the copolymerization of VC and VAc is controlled at 40 °C provided that enough VAc (about 40 mol%) is present in the polymerization medium to moderate the VC polymerization. In line with reactivity ratios, VC is preferentially incorporated in the polymer at the early stages of the polymerization, leading to copolymers with a high VC content at moderate conversions. This is the first report of a CMRP of VC and of the synthesis of well-defined statistical PVC-co-PVAc copolymers by this technique. [less ▲]

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See detailCobalt-mediated radical copolymerization of conjugated and non-conjugated monomers
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Fustin, Charles-André et al

in Polymer Preprints (2011), 52(2), 626-627

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See detailCobalt-mediated radical polymerization
Debuigne, Antoine ULg; Jérôme, Robert ULg; Jérôme, Christine ULg et al

in Schlüter, Dieter A.; Hawker, Craig; Sakamoto, Junji (Eds.) Synthesis of polymers: new structures and methods (2012)

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See detailCobalt-mediated radical polymerization (CMRP) and coupling reaction (CMRC): mechanistic advances ans synthetic opportunities
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

Poster (2009, December 14)

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See detailCobalt-mediated radical polymerization (CMRP) of vinyl acetate initiated by redox systems: Toward the scale-up of CMRP
Bryaskova, Rayna ULg; Detrembleur, Christophe ULg; Debuigne, Antoine ULg et al

in Macromolecules (2006), 39(24), 8263-8268

A redox initiating system was developed in order to bypass 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate ... [more ▼]

A redox initiating system was developed in order to bypass 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) in the presence of cobalt(II) acetylacetonate (Co(acac)(2)). It is indeed a problem to stock up with V70 because of needed storage at -20 degrees C during transportation. This paper reports on the controlled CMRP of VAc initiated by ascorbic acid combined with either lauroyl peroxide or benzoyl peroxide at 30 degrees C. Substitution of citric acid for ascorbic acid results in faster polymerization whereas the polymerization control is maintained. All these improvements facilitate the implementation of the vinyl acetate CMRP and open the door to the scale-up of the process. [less ▲]

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