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Search Results: 1 - 10 of 3109 matches for " Yves Sibaud "
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Photokilling of Escherichia coli Using Hybrid Titania Nanoparticles Suspended in an Aqueous Liquid  [PDF]
Christophe Massard, Muriel Bonnet, Philippe Veisseire, Yves Sibaud, Eric Caudron, Komla Oscar Awitor
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2013, DOI: 10.4236/jbnb.2013.42019
Abstract:

In this work, the photokilling of Escherichia coli using a “one-pot” synthesized suspension of anatase crystallized nanoparticles is evaluated. Preliminary to the biological tests concerning the antibacterial efficiency, the fabricated suspension, using a derived solgel process in soft chemistry condition, is characterized. Structural properties of the nanoparticles are investigated using Electronic Transmission Microscopy (TEM) equipped with Selected Area Electron Diffraction (SAED) probe and X-ray diffraction. The inorganic solid content was evaluated by Thermogravimetric Analysis (TGA). Photodegradation of Acid Orange 7 in aqueous solution was used a probe to assess the photocatalytic activity of the elaborated suspension under UV irradiation. The photokilling of Escherichia coli in presence of hybrid TiO2 nanoparticles suspended in aqueous liquid under UV irradiation is evaluated. Such TiO2 nanoparticles suspension shows a strong bactericidal activity with the total destruction of bacteria after only one hour.

Impact of Annealing Treatment on the Behaviour of Titanium Dioxide Nanotube Layers  [PDF]
Marie Siampiringue, Christophe Massard, Eric Caudron, Yves Sibaud, Mohammed Sarakha, Komla Oscar Awitor
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2016, DOI: 10.4236/jbnb.2016.73015
Abstract: In this work, we study the influence of the annealing treatment on the behaviour of titanium dioxide nanotube layers. The heat treatment protocol is actually the key parameter to induce stable oxide layers and needs to be better understood. Nanotube layers were prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution during 20 minutes and then annealed in air atmosphere. In-situ X-ray diffraction analysis, coupled with thermogravimetry, gives us an inside on the oxidation behaviour of titanium dioxide nanotube layers compared to bulk reference samples. Structural studies were performed at 700°C for 12 h in order to follow the time consequences on the oxidation of the material, in sufficient stability conditions. In-situ XRD brought to light that the amorphous oxide layer induced by anodization is responsible for the simultaneous growths of anatase and rutile phase during the first 30 minutes of annealing while the bulk sample oxidation leads to the nucleation of a small amount of anatase TiO2. The initial amorphous oxide layer created by anodization is also responsible for the delay in crystallization compared to the bulk sample. Thermogravimetric analysis exhibits parabolic shape of the mass gain for both anodized and bulk sample; this kinetics is caused by the formation of a rutile external protective layer, as depicted by the associated in-situ XRD diffractograms. We recorded that titanium dioxide nanotube layers exhibit a lower mean mass gain than the bulk, because of the presence of an initial amorphous oxide layer on anodized samples. In-situ XRD results also provide accurate information concerning the sub-layers behavior during the annealing treatment for the bulk and nanostructured layer. Anatase crystallites are mainly localized at the interface oxide layer-metal and the rutile is at the external interface. Sample surface topography was characterized using scanning electron microscopy (SEM).
Boosted Photoactivity of Titania Nanotube Layers Doped with a Suspension of Gold Nanoparticles  [PDF]
Christophe Massard, Sébastien Pairis, Yves Sibaud, Christelle Blavignac, Oscar Komla Awitor
Advances in Nanoparticles (ANP) , 2017, DOI: 10.4236/anp.2017.63010
Abstract: In the present work, we report on the behavior of synthesized gold nano-particles suspension, incorporated in titanium dioxide nanotube layers (TiO2- NT) and fabricated by electrochemical anodization in 0.4 wt% hydrofluoric acid solution and we study its photocatalytic response. Gold nanoparticles were characterized using Transmission electron microscopy and X-ray diffraction. Scanning electron microscopy was used to study the morphology of TiO2 nanotube layers doped by gold nanoparticles. Boosted photocatalytic performances on the degradation of an azo dye were obtained by using TiO2 nanotube layers doped by gold nanoparticles (Au/TiO2-NT), compared to undoped TiO2 nanotube layer (TiO2-NT) catalysts. Under UV irradiation, this new nanomaterial, with noble metal-semi conductor heterojunction (Au/ TiO2-NT) exhibits a synergetic effect in accelerating the electron transfert, resulting in an enhanced photoactivity recorded in the kinetics of degradation of Acid Orange 7 (AO7). Chronoamperometry was used to highlight higher photocurrent produced by gold-titania interface submited to UV irradiation.
One-pot Synthesis of TiO2 Nanoparticles in Suspensions for Quantification of Titanium Debris Release in Biological Liquids  [PDF]
Christophe Massard, Daniel Bourdeaux, Vincent Raspal, Emmanuelle Feschet-Chassot, Yves Sibaud, Eric Caudron, Thierry Devers, Kolma Oscar Awitor
Advances in Nanoparticles (ANP) , 2012, DOI: 10.4236/anp.2012.13012
Abstract: In this work we have developed an analytical method to measure potential titanium debris released from TiO2 nanotube layers devices immersed in biological fluids. This quantitative study is highly required to ensure both the security and non toxicity of the nanostructured surfaces used as future implantable medical devices in the living. A one-pot synthesis process is developed to produce high quality standard solutions of titanium dioxide nanoparticles in aqueous medium. The elaborated dispersion is then used to fabricate standard solutions in both aqueous and human blood plasma media. The synthesized nanoparticles dispersion was characterized by granulometry. The nanoparticles structure and morphology were then observed using Transmission Electron Microscopy (TEM). Thermogravimetric Analysis (TGA) was used to evaluate the concentration of TiO2 in the suspension. A quantitative routine by the use of Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) is developed. The quantification threshold of titanium species is found to be in the 30 - 40 ppb range. None interference is detected between the particles and the human blood plasma. Using the established quantitative routine, the titanium species release from titania nanotube layers in human blood plasma is evaluated.
Feasibility of a Chronic Foreign Body Infection Model Studying the Influence of TiO2 Nanotube Layers on Bacterial Contamination  [PDF]
Charles Vorilhon, Christophe Massard, Vincent Raspal, Yves Sibaud, Christiane Forestier, Nicolas Charbonnel, Stéphane Descamps, Komla Oscar Awitor
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2016, DOI: 10.4236/jbnb.2016.71006
Abstract:

Bacterial infections on the surface of medical devices are a significant problem in therapeutic approach, especially when implants are used in the living. In cardiology, pacemaker generator pocket surfaces, made in titanium alloy can be colonized by pathogen microorganism. This contamination represents a major risk of sepsis, endocarditis and localized infections for patients. A way to limit this bacterial contamination is to modify the surface topography using nano-structuration process of the titanium alloy surface of the implanted devices. The aim of this study is to evaluate the influence of TiO2 nanotube layers on bacterial infection in the living, considering the feasibility of an animal model of chronic foreign body infection. TiO2 nanotube layers prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution were implanted subcutaneously in Wistar rats. Three weeks after implantation, TiO2 implants were contaminated by a Staphylococcus epidermilis strain using two different concentrations at 106 and 108 colony forming unit (CFU) in order to induce a sufficient infection level and to avoid unwanted over infection consequences on rats health during the experiments. After 28 days in the living, 75% of nanotube layers initially submitted to the 108 CFU inoculum were contaminated while only 25% nanotube layers initially submitted to the 106 CFU inoculum remained infected. This significant result underlines the influence of TiO2 nanotube layers in decreasing the infection level. Our in vitro experiments showed that the synthesized TiO2 nanotubes indeed decreased the Staphylococcus epidermilis adhesion compared to unanodized Ti foil.

Cytotoxicity Study of Gold Nanoparticles on the Basal-Like Triple-Negative HCC-1937 Breast Cancer Cell Line  [PDF]
Christophe Massard, Clémence Dubois, Vincent Raspal, Pierre Daumar, Yves Sibaud, Emmanuelle Mounetou, Mahchid Bamdad, Oscar Komla Awitor
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2018, DOI: 10.4236/jbnb.2018.91002
Abstract: The Triple Negative “Basal-like” breast cancer (TNBL) tumours have a high proliferative capacity and develop a resistance phenotype associated with metastases. However, the management of TNBL carcinomas is still not standardized. Among the promising trails, gold nanoparticles could be a relevant tool for the development of a targeted treatment for this breast cancer subtype in monotherapy, associated and/or conjugated with other drugs. In this work, we report the cytotoxicity impact of gold nanoparticles wrapped in Poly-Ethylene Glycol (PEG) on the TNBL HCC-1937 breast cancer cell line. PEG-coated gold nanoparticles (PEG-Au NPs) were synthesized by a two-step method using a reduction process followed by a post-functionalization called PEGylation. PEG-Au NPs were characterized using transmission electron microscopy and X-ray diffraction. The gold content of the samples was determined using atomic absorption spectrometer. The cytotoxicity tests were performed using Sulforhodamine B survival test and resazurin viability test. PEG-Au NPs impact analysis on HCC1937 TNBL cell line showed a clear toxic action of type dose dependent and at long term. These PEGylated gold nanoparticles present a promising tool for the development of tumor-specific radiosensitizing vectors, with or without the association of other treatment strategies.
H2 and CH4 Sorption on Cu-BTC Metal Organic Frameworks at Pressures up to 15 MPa and Temperatures between 273 and 318 K  [PDF]
Yves Gensterblum
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2011, DOI: 10.4236/jsemat.2011.12004
Abstract: Sorption isotherms of methane and hydrogen on Cu3(BTC)2 have been measured in the temperature range from 273 to 318 K and at pressures up to 15 MPa. H2 excess sorption capacities of the Cu3(BTC)2 amounted to 3.9 mg/g at 14 MPa. Promising maximum CH4 excess sorption capacities on the same sample were reached at approximately 5 MPa. They amounted to 101, 100, 92 and 80 mg/g at 273, 278, 293 and 318 K, respectively. The sorbed phase density was essestially the same for all temperatures and amounted to ~600 kg/m3. Structural changes of the Cu3(BTC)2 samples after thermal activation and treatment with high pressure H2 and CH4 were tested. It was found that the initial micropore structure has virtually disappeared as evidenced by a decrease of the Langmuir specific surface area by a factor ~3 and CO2 micropore volume by a factor of ~4 for H2 and ~3 for CH4. This is in line with an increase in the average pore diameter from initially 9.2 to 15.7 for H2 and 12.8 for CH4.
Minkowskian Solution of General Relativity with Cosmological Constant and the Accelerating Universe  [PDF]
Yves Pierseaux
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.516172
Abstract: A Minkowskian solution of the equation of General Relativity (as written by Einstein in 1915) is trivial because it simply means that both members of the equation are equal to zero. However, if alternatively, one considers the complete equation with a non-zero constant Λ (Einstein 1917), a Minkowskian solution is no longer trivial because it amounts to impose a constraint on the right hand side of the equation (i.e. a non-null stress-energy tensor). If furthermore one identifies (as usual) this tensor to the one of a perfect fluid, one finds that this fluid has a positive energy density and a negative pressure that depend on the three constants of the equation (i.e. gravitational constant G, cosmological constant Λ and velocity of light c). When doing that (§1), one has to consider the “Minkowskian Vacuum” as a physical object of GR (an enigmatic non-baryonic Minkowskian fluid). Can one build a model of this object on the basis of a dynamical equilibrium between the effective gravitational attraction due to the positive energy density versus the negative pressure repulsion? We propose to study such a model, where the (enigmatic) fluid is assumed to exist only in a limited sphere whose surface acts like a “test body” sensitive to the gravitational field created by the fluid. No static equilibrium exists, but a pseudoNewtonian “dynamical equilibrium” (§2) can be reached if the pseudoEuclidean fluid is in state of expansion. Up to there, we have simply constructed a model of an “abstract Universe” (i.e. the limited sphere: There is no fluid outside this sphere!) that gives to a (purely mathematical) constant Λ a concrete physical meaning. We discover finally that our expanding fluid has not only dynamical (gravitational) properties (§3) but also optical properties that are connected with Doppler Redshift (§4). Remembering that recent observations in Cosmology indicate that the “real Universe” seems to be “Flat” and in “Accelerated Expansion”; remembering also (after all) that the archetypal Flat Universe is simply a Minkowskian Universe, we logically wonder if the unexpected Minkowskian global solution, could not be also a significant cosmological model (conclusion).
PAPR Reduction Scheme with SOCP for MIMO-OFDM Systems  [PDF]
Basel RIHAWI, Yves LOUET
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2008, DOI: 10.4236/ijcns.2008.11005
Abstract: Combination of multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) has become a promising candidate for high performance wireless communications. However one major disadvantage of MIMO-OFDM systems lies in a prohibitively large peak-to-average power ratio (PAPR) of the transmitted signal on each antenna. In this paper we extend from SISO to MIMO systems a method based on allocating dedicated subcarriers for PAPR mitigation. These subcarriers are located on unused subcarriers of OFDM spectrum under the assumption they all fall under the power mask. This is originally implemented with a SOCP optimization algorithm applied before space time coding scheme. This jointly mitigates PAPR on each MIMO branch scheme. This approach does not degrade the bit-error-rate (BER) and the data bit rate and no side information (SI) transmission is required. Simulation results are presented in the IEEE 802.16 WiMAX standard contexts: an Alamouti space time code with two transmitted antennas and 256 OFDM subcarriers are considered where 56 of which are unused and allocated for PAPR reduction. PAPR gains up to 7dB are obtained depending on mean power increase limitation. Moreover, with a spectrum mask constraint, this method is standard compliant.
Contribution of Topographically Explicit Descriptors of Landscape Measures for Application in the Vector Data Environment  [PDF]
Auda Yves, Jomaa Ihab
Journal of Geographic Information System (JGIS) , 2010, DOI: 10.4236/jgis.2010.23023
Abstract: Digital terrain models (DTMs) are not commonly used to integrate for landscape spatial analysis. Two dimensional patchcorridormatrix models are prototypes in landscape spatial ecology analysis. Previous studies have motivated ecologists to integrate terrain models in landscape analysis through 1) adjusting areas and distance calculations prior computing landscape indices; 2) designing new indices to capture topography and 3) searching the possible relationship between topographic characteristics and vegetation patterns. This study presents new indices called Relative number of Topographic Faces (RTF) and Simplicity of topographic Faces (STF) that can be easily computed in a GIS environment, capturing topographical features of landscapes. Digital terrain model was first prepared and topographic units were extracted and installed in computing the suggested indices. Mountainous and rugged topography in Lebanon was chosen on a forested landscape for the purpose of this study. The indices were useful in monitoring changes of topographic features on patch and landscape level. Both indices are ecologically useful if integrated in landscape pattern analysis, especially in areas of rugged terrains.
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