Effects of hydroxyapatite and PDGF concentrations on osteoblast growth in a nanohydroxyapatite-polylactic acid composite for guided tissue regeneration

The technique of guided tissue regeneration (GTR) has evolved over recent years in an attempt to achieve periodontal tissue regeneration by the use of a barrier membrane. However, there are significant limitations in the currently available membranes and overall outcomes may be limited. A degradable composite material was investigated as a potential GTR membrane material. Polylactic acid (PLA) and nanohydroxyapatite (nHA) composite was analysed, its bioactive potential and suitability as a carrier system for growth factors were assessed. The effect of nHA concentrations and the addition of platelet derived growth factor (PDGF) on osteoblast proliferation and differentiation was investigated. The bioactivity was dependent on the nHA concentration in the films, with more apatite deposited on films containing higher nHA content. Osteoblasts proliferated well on samples containing low nHA content and differentiated on films with higher nHA content. The composite films were able to deliver PDGF and cell proliferation increased on samples that were pre absorbed with the growth factor. nHA–PLA composite films are able to deliver active PDGF. In addition the bioactivity and cell differentiation was higher on films containing more nHA. The use of a nHA–PLA composite material containing a high concentration of nHA may be a useful material for GTR membrane as it will not only act as a barrier, but may also be able to enhance bone regeneration by delivery of biologically active molecules

Numerical investigation of an unsteady injection adapted to the continuous detonation wave rocket engine operation

Detonation applied to propulsion could result in a promising increase of the thermodynamic efficiency of the engine cycle. Numerical simulations of the detonation propagating in the Continuous Detonation Wave Rocket Engine (CDWRE) are currently performed but still do not account for realistic injection process. The assumption of an ideal injected premix is generally chosen for convenience to obtain theoretical results. Comparison of the numerical results with experiments is difficult because of the clear difference of the injection configurations. Some physical aspects of the separate injection of the components used in experiments are not clearly assessed. This study is included in a wider numerical project aimed at designing and optimizing a realistic CDWRE. The optimization process is presently focused on the injector. One element of the injection hole pattern is considered assuming that this element is periodically repeated over the injector head. The aim of the work presented here is to model and analyze the refill process of the components in the combustion chamber behind the rotating detonation. The simulation starts just after the passage of the detonation over the considered injection element. This simulation gives information on the way the injected propellants recreate the reactive mixture for the next detonation. In the first step, two-dimensional (2D) computations helped us to set up the methodology and to study the dynamic response of the fresh components injected. A comparison between 2D homogeneous and separate injections is provided. In the second step, three-dimensional (3D) computations have been performed with a separate injection suitable for the CDWRE operation. Some performance parameters are evaluated such as mixing efficiency or filling of the domain

An optimized reciprocity Monte Carlo method for the calculation of radiative transfer in media of various optical thicknesses

An efficient Monte Carlo method for the calculation of radiative transfer in complex geometry systems including semi-transparent media has been achieved and validated. This method, which is based on the reciprocity principle and called optimized reciprocity method (ORM), can be applied to systems discretized in a large number of cells. For each pair of elementary cells exchanging radiative energy, the transfer calculation is carried out by minimizing, for a given computational time, the standard deviation of the radiative power or of the wall flux. The results obtained with ORM have been successfully compared to those obtained with previous approaches in a numerical benchmark

Combustor modeling - A3C operation

3rd European propulsion forum, Cologne (RFA), April 3-5, 1990SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1990 n.65 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Calculs d'ecoulements turbulents reactifs dans les foyers aeronautiques

Paru dans : 80th PEP/AGARD on 'Heat transfer and cooling in turbines', Antalya (Turquie), 12-16 octobre 1992SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1992 n.167 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Cryogenic propellant combustion studies : experimental and analysis aspects

Communication to : Conference internationale sur la propulsion des engins spatiaux, Dublin (Ireland), May 19-20, 1998SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1998 n.99 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc