References of "Thomassin, Jean-Michel"
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See detailDrug loading of polymer implants by supercritical CO2 assisted impregnation: a review
Champeau, Mathilde; Thomassin, Jean-Michel ULg; Tassaing, Thierry et al

in Journal of Controlled Release (2015), 209

Drug loaded implants also called drug-eluting implants have proven their benefits over simple implants. Among the developed manufacturing processes, the supercritical CO2 (scCO2) assisted impregnation has ... [more ▼]

Drug loaded implants also called drug-eluting implants have proven their benefits over simple implants. Among the developed manufacturing processes, the supercritical CO2 (scCO2) assisted impregnation has attracted growing attention to load Active Pharmaceutical Ingredients into polymer implants since it enables to recover a final implant free of any solvent residue and to operate under mild temperature which is suitable for processing with thermosensitive drugs. This paper is a review of the state-of-the-art and the application of the scCO2 assisted impregnation process to prepare drug-eluting implants. It introduces the process and presents its advantages for biomedical applications. The influences of the characteristics of the implied binary systems and of the experimental conditions on the drug loading are described. Then, the various current applications of this process for manufacturing drug-eluting implants are reviewed. Finally, the new emerging variations of this process are described. [less ▲]

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See detailPrerparation of graphene oxide-poly(methyl methacrylate) nanocompposites by a precipitation polymerization process and their dielectric and rheological characterization
Alkarmo, Walid ULg; Thomassin, Jean-Michel ULg; Macosko, Christopher et al

Poster (2015, May 18)

The graphene sheet, a flat monolayer composed of sp2-bonded carbon atoms packed into a two-dimensional honeycomb structure, has attracted a tremendous attention due to its extraordinary electrical ... [more ▼]

The graphene sheet, a flat monolayer composed of sp2-bonded carbon atoms packed into a two-dimensional honeycomb structure, has attracted a tremendous attention due to its extraordinary electrical, thermal, and mechanical properties. Graphene nanosheets–poly(methyl methacrylate) GN/PMMA nanocomposites were prepared via a precipitation polymerization process in a water/methanol mixture and thermal or chemical reduction of graphene oxide (GO). Scanning electron and transmission electron microscopies confirmed that the precipitate consists of polymer particles (<1μm) surrounded by the GO sheets. The GO sheets acts as a surfactant and adsorbs on the interface between polymerized PMMA particles and solvent mixture. Parallel dielectric and rheological characterization demonstrated that the thermal reduction is a quite fast process without significant degradation of the polymer. In addition, the main increase in electrical conductivity occurred during the first minutes of the thermal treatment but continued for about 30 min. The absence of dramatic change in the storage modulus confirmed that the increase in conductivity was not due to alteration of the particle dispersion. The addition of GO sheets had a dramatic influence on the glass transition (Tg) temperature of PMMA with an increase of 8 °C at only 0.2 wt %. This Tg increase has been attributed to the restricted mobility of PMMA chains which have been grafted onto the graphene surfaces during the in-situ polymerization. However, at GO content higher than 0.7 wt %, the glass transition decreases. This drop may be attributed to the increase in the number of stacked graphene layers. The obtained GN/PMMA composites not only have enhanced mechanical properties but also achieved electrical conductivity higher than 10 −2 S/m at 0.4 wt % of GO. The study should open up new opportunities in the design of GN-based polymer nanocomposites. [less ▲]

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See detailIntercalation of cationic aliphatic polyphosphates between montmorillonite nanosheets towards flame-retardant polymer materials
Carion, Stéphan ULg; Lecomte, Philippe ULg; Thomassin, Jean-Michel ULg et al

Poster (2015, May 18)

Among the strategies used to impart flame-retardant properties to polymer materials, the most effective ones include the addition of phosphorous compounds such as organic polyphosphates and the dispersion ... [more ▼]

Among the strategies used to impart flame-retardant properties to polymer materials, the most effective ones include the addition of phosphorous compounds such as organic polyphosphates and the dispersion of layered silicates (nanoclays). The aim of this work is to combine both approaches by the dispersion of nanoclays, organomodified by cationic aliphatic polyphosphates, into a polymer matrix. In this work, the synthesis of an aliphatic polyphosphate end-capped by an imidazolium cation followed by its intercalation between montmorillonite nanoclays sheets is reported. In a first step, the polyphosphate was synthesized by ring-opening polymerization of the corresponding cyclic phosphate using 1-(11-hydroxy-undecyl)-3-methylimidazolium bromide as initiator. This polymerization was catalyzed by DBU and a thiourea derivative. This polymer was characterized by different techniques (31P and 1H NMR, SEC, TGA, DSC). Finally, the cationic end-functionalized polymer was exchanged with sodium cations present in montmorillonite. The intercalation of the polyphosphate between the clay nanosheets was proved by X-Ray Diffraction (XRD) and thermogravimetric analysis (TGA). This last technique was also used to determine the influence of the intercalation on the thermal stability of the polyphosphate.polyphosphates, into a polymer matrix. In this work, the synthesis of an aliphatic polyphosphate end-capped by an imidazolium cation followed by its intercalation between montmorillonite nanoclays sheets is reported. In a first step, the polyphosphate was synthesized by ring-opening polymerization of the corresponding cyclic phosphate using 1-(11-hydroxy-undecyl)-3-methylimidazolium bromide as initiator. This polymerization was catalyzed by DBU and a thiourea derivative. This polymer was characterized by different techniques (31P and 1H NMR, SEC, TGA, DSC). Finally, the cationic end-functionalized polymer was exchanged with sodium cations present in montmorillonite. The intercalation of the polyphosphate between the clay nanosheets was proved by X-Ray Diffraction (XRD) and thermogravimetric analysis (TGA). This last technique was also used to determine the influence of the intercalation on the thermal stability of the polyphosphate. [less ▲]

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See detailDouble thermo-responsive hydrogels from poly(vinylcaprolactam) containing diblock and triblock copolymers
Thomassin, Jean-Michel ULg; Mathieu, Kevin ULg; Kermagoret, Anthony ULg et al

in Polymer Chemistry (2015), 6(10), 1856-1864

The thermally-induced gelation and gel properties of concentrated aqueous solutions of double thermoresponsive poly(N-vinylamide)-based di- and triblock copolymers are studied by rheology. The copolymers ... [more ▼]

The thermally-induced gelation and gel properties of concentrated aqueous solutions of double thermoresponsive poly(N-vinylamide)-based di- and triblock copolymers are studied by rheology. The copolymers under investigation, prepared by cobalt-mediated radical polymerization and coupling reactions, are composed of poly(vinylcaprolactam) (PNVCL) blocks and of a statistical poly(vinylcaprolactam-stat-vinylpyrrolidone) segment with a cloud point temperature (TCP) higher than that of PNVCL. Heating the di- and triblock solutions beyond the first phase transition temperature favors gel formation while heating above the second TCP leads to opaque gels without macroscopic demixing. Moduli of the triblock hydrogels are systematically higher than those of the corresponding diblocks, even above the second transition. Rheological data suggest distinct micellar structures for each copolymer architecture: densely packed micelles of diblocks and 3-D networks of bridged micelles for triblocks. Strain sweep experiments also emphasize the positive effect of the micelle bridging on the elasticity and stability of the hydrogels. The formation and properties of the obtained gels are also shown to depend on the copolymer concentration, block length, and composition. Addition of salt also allows us to tune the phase transition temperatures of these double thermoresponsive hydrogels. [less ▲]

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See detailIn situ investigation of scCO2 assisted impregnation of drug into polymer by high pressure FTIR micro-spectroscopy
Champeau, Mathilde ULg; Thomassin, Jean-Michel ULg; Jérôme, Christine ULg et al

in Analyst (2015), 140(3), 869-879

An original experimental set-up combining a FTIR microscope with a high pressure cell has been built in order to analyze in-situ the impregnation of solute into microscopic polymer samples, such as fibers ... [more ▼]

An original experimental set-up combining a FTIR microscope with a high pressure cell has been built in order to analyze in-situ the impregnation of solute into microscopic polymer samples, such as fibers or films, subjected to supercritical CO2. Thanks to this experimental set-up, key factors governing the impregnation process can be simultaneously followed such as the swelling of the polymeric matrix, the CO2 sorption, the kinetic of impregnation and the drug loading into the matrix. Moreover, the solute/polymer interactions and the speciation of the solute can be analyzed. We have monitored in situ the impregnation of aspirin and ketoprofen into PEO (Polyethylene Oxide) platelets at T=40°C and P=5; 10 and 15 MPa. The kinetic of impregnation of aspirin was quicker than the one of ketoprofen and the final drug loading was also higher in case of aspirin. Whereas the CO2 sorption and the PEO swelling remain constant when PEO is just subjected to CO2 under isobaric conditions, we noticed that both parameters can increase while the drug impregnates PEO. Coupling these results with DSC measurements, we underlined the plasticizing effect of the drug that also leads to decrease the crystallinity of PEO in situ thus favoring the sorption of CO2 molecules into the matrix and the swelling of the matrix. The plasticizing effect increases with the drug loading. Finally, the speciation of drug was investigated considering the shift of the carboxyl bands of the drugs. Both drugs were found to be mainly homogeneously dispersed into PEO. [less ▲]

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See detailNanocomposite foams of polypropylene and carbon nanotubes: preparation, characterization, and evaluation of their performance as EMI absorbers
Tran, Minh-Phuong; Thomassin, Jean-Michel ULg; Alexandre, Michaël et al

in Macromolecular Chemistry and Physics (2015), 216(12), 1302-1312

Highly expanded nanocomposite foams of polypropylene and carbon nanotubes (PP/CNT) are formed using supercritical carbon dioxide (scCO 2 ) technology. The foaming parameters (temperature, pressure) are ... [more ▼]

Highly expanded nanocomposite foams of polypropylene and carbon nanotubes (PP/CNT) are formed using supercritical carbon dioxide (scCO 2 ) technology. The foaming parameters (temperature, pressure) are investigated to establish their infl uence on the morphology of the resulting foams and their impact on the electrical con- ductivity. As promising electromagnetic-interference (EMI) absorbers, the EMI shielding performance of the foams is determined, and a preliminary relationship is established between foam morphology and the EMI shielding perfor- mance. The best candidates are highly expanded foams with a volume expansion of >25, containing 0.1 vol% CNTs; they are able to absorb more than 90% of the incident radiation between 25 and 40 GHz. [less ▲]

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See detailNanocomposites based on MWCNT and polystyrene, styrene-acrylonitrile copolymer, or polymethylmethacrylate, obtained by miniemulsion polymerization
Donescu, Dan; Corobea, Mihai Cosmin; Petcu, Cristian et al

in Journal of Applied Polymer Science (2014), 131(23), 411481-10

Free radical miniemulsion polymerization of styrene (St), St/acrylonitrile 3 : 1 mixture or methylmethacrylate in the presence of multiwalled carbon nanotubes (MWCNT) was proven as a convenient way to ... [more ▼]

Free radical miniemulsion polymerization of styrene (St), St/acrylonitrile 3 : 1 mixture or methylmethacrylate in the presence of multiwalled carbon nanotubes (MWCNT) was proven as a convenient way to obtain homogenous hybrids with perspectives in associated applications like foams specialties materials. Miniemulsion polymerization was viable up to 2% wt. MWCNT to monomer, without agglomerations. The grafting on MWCNT during the polymerization occurs without the need for supplementary functionalization and the polymer grafted nanotubes showed stable dispersions in the polymer solvent. Monomer polarity affected the grafting ability during the polymerization process. The nanocomposites obtained after purification and drying were used in foaming process. MWCNT presence in the related nanocomposites decreased the pore sizes in foam-like materials (for all three different matrices). At 1 wt % MWCNT content, low density (< 0.3 g/cm3), low pore size (< 10 μm) and high cell density (>109 cell/cm3) were achieved. [less ▲]

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See detailDouble thermoresponsive di- and triblock copolymers based on N-vinylcaprolactam and N-vinylpyrrolidone: synthesis and comparative study of solution behaviour
Kermagoret, Anthony ULg; Mathieu, Kevin ULg; Thomassin, Jean-Michel ULg et al

in Polymer Chemistry (2014), 5(22), 6534-6544

Poly(N-vinylcaprolactam) (PNVCL) and poly(N-vinylpyrrolidone) (PNVP) are water soluble polymers of interest especially in the biomedical field. Moreover, PNVCL is characterized by a lower critical ... [more ▼]

Poly(N-vinylcaprolactam) (PNVCL) and poly(N-vinylpyrrolidone) (PNVP) are water soluble polymers of interest especially in the biomedical field. Moreover, PNVCL is characterized by a lower critical solution temperature close to 36 °C in water, which makes it useful for the design of thermoresponsive systems. In this context, we used the cobalt-mediated radical polymerization (CMRP) and reaction coupling (CMRC) for synthesizing a series of well-defined NVCL and NVP-based copolymers, including statistical copolymers as well as double thermoresponsive diblocks and triblocks. Dynamic light scattering and turbidimetry analyses highlighted the crucial impact of the copolymer composition and architecture on the cloud point temperature (TCP) of each segment and also their influence on the multistep assembly behaviour of block copolymers. Addition of NaCl enabled us to adjust the inter-TCP range of the di- and triblock in which selective precipitation of one block and self-assembly of the copolymer were favoured. Overall, data presented here provide a basis for the synthesis of a broad range of NVCL/NVP based copolymer architectures with a tunable thermal response in water. [less ▲]

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See detailA facile and fast electrochemical route to produce functional few-layer graphene sheets for lithium battery anode application
Ouhib, Farid ULg; Aqil, Abdelhafid ULg; Thomassin, Jean-Michel ULg et al

in Journal of Materials Chemistry A (2014), 2(37), 15298-15302

A simple approach for the production of polymer functionalized graphene nanosheets is reported. The resulting polyacrylonitrile chemisorbed on graphene sheets is made of 1 to 2 layers, with a large ... [more ▼]

A simple approach for the production of polymer functionalized graphene nanosheets is reported. The resulting polyacrylonitrile chemisorbed on graphene sheets is made of 1 to 2 layers, with a large majority of graphene single-layers. This novel functionalized graphene exhibits good cycling stability as an anode in Li-ion batteries without a conductive additive or binder. [less ▲]

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See detailSupercritical CO2, impregnation to prepare drug-loaded implants: inpregantion of anti-inflammatory drugs into sutures
Champeau, Mathilde; Tassaing, Thierry; Thomassin, Jean-Michel ULg et al

Conference (2014, July 10)

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See detailIn situ FTIR micro-spectroscopy to investigate polymeric fibers under supercritical carbon dioxide: CO2 sorption and swelling measurements
Champeau, Mathilde; Thomassin, Jean-Michel ULg; Jérôme, Christine ULg et al

in Journal of Supercritical Fluids (2014), 90

An original experimental set-up combining a FTIR (Fourier Transformed InfraRed) microscope with a high pressure cell has been built in order to analyze in situ and simultaneously the CO2 sorption and the ... [more ▼]

An original experimental set-up combining a FTIR (Fourier Transformed InfraRed) microscope with a high pressure cell has been built in order to analyze in situ and simultaneously the CO2 sorption and the polymer swelling of microscopic polymer samples, such as fibers, subjected to supercritical carbon dioxide. Thanks to this experimental set-up, we have determined as a function of the CO2 pressure (from 2 to 15 MPa) the CO2 sorption and the polymer swelling at T = 40 °C of four polymer samples, namely PEO (polyethylene oxide), PLLA (poly-l-lactide acid), PET (polyethylene terephtalate) and PP (polypropylene). The quantity of CO2 sorbed in all the studied polymers increases with pressure. PEO and PLLA display a significant level of CO2 sorption (20 and 25% respectively, at P = 15 MPa). However, we observe that a lower quantity of CO2 can be sorbed into PP and PET (7 and 8% respectively, at P = 15 MPa). Comparing their thermodynamic behaviors and their intrinsic properties, we emphasize that a high CO2 sorption can be reach if on one hand, the polymer is able to form specific interaction with CO2 in order to thermodynamically favor the presence of CO2 molecules inside the polymer and on the other, displays high chains mobility in the amorphous region. PLLA and PEO fulfilled these two requirements whereas only one property is fulfilled by PET (specific interaction with CO2) and PP (high chains mobility). Finally, we have found that for a given CO2 sorption, the resulting swelling of the polymer depends mainly on its crystallinity. [less ▲]

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See detailUse of supercritical carbon dioxide to prepare drug-laoded polymer implants: impregnation of anti-inflammatory drugs into sutures
Champeau, Mathilde; Tassaing, Thierry; Thomassin, Jean-Michel ULg et al

Conference (2014, May 19)

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See detailSupercritical CO2 and polycarbonate based nanocomposites: A critical issue for foaming
Monnereau, Laure; Urbanczyk, Laetitia; Thomassin, Jean-Michel ULg et al

in Polymer (2014), 55(10), 2422-2431

Supercritical carbon dioxide readily induced foaming of various polymers. In that context, supercritical CO2 was applied to carbon nanotubes based polycarbonate nanocomposites to ensure their foaming ... [more ▼]

Supercritical carbon dioxide readily induced foaming of various polymers. In that context, supercritical CO2 was applied to carbon nanotubes based polycarbonate nanocomposites to ensure their foaming. Surprisingly, efficient foaming only occurs when low pressure is applied while at high pressure, no expansion of the samples was observed. This is related to the ability of supercritical carbon dioxide to induce crystallization of amorphous polycarbonate. Moreover, this behaviour is amplified by the presence of carbon nanotubes that act as nucleating agents for crystals birth. The thermal behaviour of the composites was analysed by DSC and DMA and was related to the foaming observations. The uniformity of the cellular structure was analysed by scanning electron microscopy (SEM). By saturating the polycarbonate nanocomposites reinforced with 1 wt% of MWNTs at 100 bar and 100 °C during 16 h, microcellular foams were generated, with a density of 0.62, a cell size ranging from 0.6 to 4 μm, and a cellular density of 4.1 × 1011 cells cm−3. The high ability of these polymeric foams to absorb electromagnetic radiation was demonstrated at low MWNT content as the result of the high affinity of the polycarbonate matrix for MWNTs, and therefore to the good MWNTs dispersion. [less ▲]

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See detailPoly(methyl methacrylate)/graphene oxide nanocomposites by a precipitation polymerization process and their dielectric and rheological characterization
Thomassin, Jean-Michel ULg; Trifkovic, Milana; Alkarmo, Walid et al

in Macromolecules (2014), 47(6), 2149-2155

We report a method for achieving controlled dispersion of graphene oxide (GO) in poly(methyl methacrylate) (PMMA) via the precipitation polymerization process in a water/ methanol mixture. GO acts as a ... [more ▼]

We report a method for achieving controlled dispersion of graphene oxide (GO) in poly(methyl methacrylate) (PMMA) via the precipitation polymerization process in a water/ methanol mixture. GO acts as a surfactant and adsorbs on the interface between polymerized PMMA particles and solvent mixture. Scanning electron and transmission electron microscopy confirmed that the precipitate consists of polymer particles (<1 μm) surrounded by the GO sheets. Compression molding of the precipitate yields a polymer nanocomposite with the GO organized into a regularly spaced 3D network which percolates at 0.2 wt % GO. Simple thermal reduction of the GO sheets dispersed in PMMA at relatively low temperature (210 °C) achieved electrical conductivity higher than 10−2 S/m at 0.4 wt % of GO. Parallel dielectric and rheological characterization demonstrated that the thermal reduction is a quite fast process without significant degradation of the polymer. The study should open up new opportunities in the design of GO-based polymer nanocomposites. [less ▲]

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See detailUse of supercritical carbon dioxide to prepare drug-loaded polymeric sutures
Champeau, Mathilde; Tassaing, Thierry; Jérôme, Christine ULg et al

Conference (2014, March 19)

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See detailUse of supercritical carbon dioxide to prepare drug-loaded polymer implants
Champeau, Mathilde; Tassaing, Thierry; Thomassin, Jean-Michel ULg et al

Conference (2013, November 20)

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See detailRheological characterization of double thermo-responsive block copolymer hydrogels
Thomassin, Jean-Michel ULg; Mathieu, Kevin ULg; Kermagoret, Anthony ULg et al

Poster (2013, November 20)

The ability of double thermoresponsive block copolymers to form hydrogels has been thoroughly studied by rheology. These copolymers having two discrete LCSTs were synthesized following a one-pot strategy ... [more ▼]

The ability of double thermoresponsive block copolymers to form hydrogels has been thoroughly studied by rheology. These copolymers having two discrete LCSTs were synthesized following a one-pot strategy based on the sequential cobalt mediated radical polymeryzation of N-vinylcaprolactam (NVCL) followed by the copolymerization of N-vinylpyrrolidone (NVP) with the residual NVCL.Moreover, the very efficient cobalt mediated radical coupling of the growing chains was advantageously used to design triblock copolymers with similar morphological characteristics than the diblock copolymers (same external block length, copolymer ratio…) allowing direct comparison between their respective gels to be established. Different parameters have been compared such as the block length and the copolymer concentration. Temperature ramps were first performed to distinguish the different states, i.e., solubilized copolymers (below the two LCSTs), micelles (between the two LCSTs) and precipitated polymers (above the two LCSTs). [less ▲]

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See detailCarbon nanotubes/polypropylene nanocomposites foams for EMI shielding applications
Tran, Minh Phuong ULg; Detrembleur, Christophe ULg; Thomassin, Jean-Michel ULg et al

Conference (2013, September 12)

In order to reduce the undesired effect of the electromagnetic interference, the developing of the materials with high capacity of electromagnetic interference (EMI) shielding has attracted a great ... [more ▼]

In order to reduce the undesired effect of the electromagnetic interference, the developing of the materials with high capacity of electromagnetic interference (EMI) shielding has attracted a great attention to scientific and industrial communities during last two decades.Indeed, polymer carbon nanotubes (CNTs) nanocomposites foams are addressed due to their high electrical conductivity and a great potential applications in electrostatic dissipation (ESD) and in electromagnetic interferences (EMI) shielding. However, the shortcoming of the addition of CNTs is that it usually leads to an increase of permittivity which results in enhancing undesirably the electromagnetic reflectivity due to the mismatch between the wave impedances for the signal propagating into air and into the absorbing material, respectively. To solve this problem, the introduction of air into these nanocomposites by the formation of foam will be favorable in order to reduce the permittivity of conductive composites. A good understanding of the influence of the foam structural parameters on the electrical properties of the foam will ultimately enable the optimum design of these materials for the targeted applications. A wide range of poly (propylene)/CNTs nanocomposites foams were synthesized using the supercritical CO2 technology. Different foaming parameters, such as the temperature, impregnation pressure will be controlled to modify the foam structure. Nanocomposite foams show higher electrical conductivity than non-foamed nanocomposites at the same volume content of CNTs. Effects of foam morphology such as cell density, pore size, volume expansion, and cell-wall thickness on electrical conductivity were comprehensively assessed. Similarly to our previous study on PMMA foam nanocomposites, the electrical conductivity of foams show higher value when the volume expansion is increased and when the average pore size is decreased. The preliminary EMI performances have highlighted that PP/CNTs foams containing 0.1 vol%CNTs are able to absorb about 90% of the incident radiation in the 25 to 40 GHz frequency range. [less ▲]

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