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Search Results: 1 - 10 of 6225 matches for " Vincent Raspal "
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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.
Tunable Functionality and toxicity studies of Titanium Dioxide Nanotube Layers
E. Feschet-Chassot,V. Raspal,O. K. Awitor,F. Bonnemoy,J. L. Bonnet,J. Bohatier
Physics , 2010, DOI: 10.1016/j.tsf.2010.12.184
Abstract: In this work, we have developed economic process to elaborate scalable titanium dioxide nanotube layers which show a tunable functionality. The titanium dioxide nanotube layers was prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution. The nanotube layers structure and morphology were characterized using x-ray diffraction and scanning electron microscopy. The surface topography and wettability was studied according to the anodization time. The sample synthesized while the current density reached a local minimum displayed higher contact angle. Beyond this point, the contact angles decrease with the anodization time. Photo-degradation of acid orange 7 in aqueous solution was used as a probe to assess the photo-catalytic activity of titanium dioxide nanotube layers under UV irradiation. We obtained better photocatalitic activity for the sample elaborate at higher current density. Finally we use the Ciliated Protozoan T. pyriformis, an alternative cell model used for in vitro toxicity studies, to predict the toxicity of titanium dioxide nanotube layers in biological system. We did not observe any characteristic effect in the presence of the titanium dioxide nanotube layers on two physiological parameters related to this organism, non-specific esterases activity and population growth rate.
Eigenvector Sensitivity: A Kharitonov Result  [PDF]
Vincent Winstead
American Journal of Computational Mathematics (AJCM) , 2013, DOI: 10.4236/ajcm.2013.32024
Abstract:

This study is motivated by a need to effectively determine the difference between a system fault and normal system operation under parametric uncertainty using eigenstructure analysis. This involves computational robustness of eigenvectors in linear state space systems dependent upon uncertain parameters. The work involves the development of practical algorithms which provide for computable robustness measures on the achievable set of eigenvectors associated with certain state space matrix constructions. To make connections to a class of systems for which eigenvalue and characteristic root robustness are well understood, the work begins by focusing on companion form matrices associated with a polynomial whose coefficients lie in specified intervals. The work uses an extension of the well known theories of Kharitonov that provides computational efficient tests for containment of the roots of the polynomial (and eigenvalues of the companion matrices) in desirable regions, such as the left half of the complex plane.

Dealing with Complex Management Problems  [PDF]
Vincent Omachonu
Open Journal of Business and Management (OJBM) , 2014, DOI: 10.4236/ojbm.2014.21002
Abstract: Dealing with Complex Management Problems
The Unemployment Volatility Puzzle: A Note on the Role of Reference Points  [PDF]
Vincent Boitier
Theoretical Economics Letters (TEL) , 2015, DOI: 10.4236/tel.2015.51013
Abstract: This theoretical note aims at studying the role of reference points in generating unemployment volatility. For this purpose, I introduce the notion of reference points in a standard Mortensen-Pissarides model. I obtain two results. First, I find that the obtained model is similar to the one found by Pissarides in 2009. Second, I show that the introduction of reference points can increase significantly unemployment volatility through a mechanism à la Hagerdorn and Manovskii.
Review Article: Remote Sensing, Surface Residue Cover and Tillage Practice  [PDF]
Obade Vincent de Paul
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.32026
Abstract: A growing world population and possible liquid fuel energy shortages are likely to result in worldwide agricultural intensification, and the possible expansion of non-sustainable practices. The adoption of non-sustainable practices could result in the loss of currently productive land, with potential impacts on human welfare and economic viability. One of the easiest techniques to maintain productivity is to maintain surface soil organic matter. However, developing reliable, cost effective and accurate methods for quantifying and monitoring crop residue cover (a major source of soil organic matter) that remains on top of the soil over large spatial extents constitutes a significant challenge. This article reviews potential remote sensing approaches for estimating surface residue cover with a view to mapping tillage practice.
Managerial Skills, Financial Capability and Strategic Planning in Organizations  [PDF]
Vincent Bagire, Juliana Namada
American Journal of Industrial and Business Management (AJIBM) , 2013, DOI: 10.4236/ajibm.2013.35055
Abstract:

This study sought to establish the relationship between managerial skills, financial capability and the level of strategic planning. The study was premised on the increasing focus on strategic planning in Ugandan organizations. There was however, a lack of local empirical studies on the factors driving this trend. Data were obtained from organizations in various sectors that included government institutions, private and family business organizations. The findings confirmed that organizations were involved in significant level of strategic planning. There was a positive and significant relationship with managerial skills. However, there was a very weak relationship with the financial capability. The implication of the findings for management was to give more attention to managerial skills to ensure congruence of operations.

An Integrative Framework for Customizations on Satisfaction: The Case of an Online Jewelry Business in China  [PDF]
Vincent Cho, Candy Lau
Journal of Service Science and Management (JSSM) , 2014, DOI: 10.4236/jssm.2014.72013
Abstract:

Upon the technological advancement of production flexibility, supply chain agility, and customer behavioral tracking, many online businesses now develop their customization strategies. In this regard, this study proposes an integrative framework for customization of product information, transaction handling, product attribute, and sales’ service. We are interested in how these customizations affect customer satisfaction. From our web-based survey on a renowned online jewelry company in China, we collected 1383 responses from its customer database. Our findings showed that information, product and sales’ service customizations have significant influence on customer satisfaction. Moreover, ordinary members as compared with VIP members feel more satisfied once they receive customized services.

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