Biodegradable polyesters reinforced with triclosan loaded polylactide micro/nanofibers: Properties, release and biocompatibility

Mechanical properties and drug release behavior were studied for three biodegradable polyester matrices (polycaprolactone, poly(nonamethylene azelate) and the copolymer derived from 1,9-nonanediol and an equimolar mixture of azelaic and pimelic acids) reinforced with polylactide (PLA) fibers. Electrospinning was used to produce suitable mats constituted by fibers of different diameters (i.e. from micro- to nanoscale) and a homogeneous dispersion of a representative hydrophobic drug (i.e. triclosan). Fabrics were prepared by a molding process, which allowed cold crystallization of PLA micro/nanofibers and hot crystallization of the polyester matrices. The orientation of PLA molecules during electrospinning favored the crystallization process, which was slightly enhanced when the diameter decreased. Incorporation of PLA micro/nanofibers led to a significant increase in the elastic modulus and tensile strength, and in general to a decrease in the strain at break. The brittle fracture was clearer when high molecular weight samples with high plastic deformation were employed. Large differences in the release behavior were detected depending on the loading process, fiber diameter size and hydrophobicity of the polyester matrix. The release of samples with the drug only loaded into the reinforcing fibers was initially fast and then became slow and sustained, resulting in longer lasting antimicrobial activity. Biocompatibility of all samples studied was demonstrated by adhesion and proliferation assays using HEp-2 cell cultures

Combined microwave–convective drying of saccharomyces cerevisiae based yeast

Attention is paid to drying as a downstream processing of foodstuff as it is used finally for human consumption. In some cases the conventional (convective, contact or infrared) drying processes can damage the quality of food due to crusting phenomena, overheating or protein denaturation. Better results can be obtained using combined microwave–convective dehydration.The paper mainly focuses on the investigation of drying Saccharomyces cerevisiaepulp using the method of dielectric dehydration. A dried product with a residual fermentative activity of over 80% was produced with the application of a microwave–convective drying system. As a result the moisture content was lower than 10% calculated on dry basis. We permanently regulated the incident microwave power manually in order to eliminate the mentioned disadvantageous effects. This type of regulation was applied when the surface temperature reached 45 °C

Stochastic modelling and prediction of fatigue crack propagation using piecewise-deterministic Markov processes

Fatigue crack propagation is a stochastic phenomenon due to the inherent uncertainties originating from material properties, environmental conditions and cyclic mechanical loads. Stochastic processes offer thus an appropriate framework for modelling and predicting crack propagation. In this paper, the fatigue crack growth is modelled and predicted by a piecewise-deterministic Markov process associated with deterministic crack laws. First, a regime-switching model is used to express the transition between Paris' regime and rapid propagation which occurs before failure. Both regimes of propagation are governed by a deterministic equation whose parameters are randomly selected in a finite state space. This one has been adjusted from real data available in the literature. The crack growth behaviour is well-captured and the transition between both regimes is well-estimated by a critical stress intensity factor range. The second purpose of our investigation deals with the prediction of the fatigue crack path and its variability based on measurements taken at the beginning of the propagation. The results show that our method based on this class of stochastic models associated with an updating method provides a reliable prediction and can be an efficient tool for safety analysis of structures in a large variety of engineering applications. In addition, the proposed strategy requires only few information to be effective and is not time-consuming

INTERACTION BETWEEN 3D STRESS CORROSION CRACKS

ABSTRACT To predict the time to failure of a structure due to stress corrosion crack network, overall crack growth behavior must be studied. When many cracks are initiated in an enclosed area, neighboring cracks may affect the stress field ahead the crack tips and then affect their crack growth rates. The interactions between cracks depend on their relative positions and on their sizes. The present work presents the experimental behavior of crack networks by in-situ observations and proposed a finite element analysis of interacting 3D cracks

Drying parameters of an adhesive coating with respect to quality

International audienc

Parc des ventilateurs et des résistances dans les techniques de séchage adaptées à l'environnement tropical

Fans and Resistances Park in Drying Technologies Appropriate for Tropical Environment. To design a dryer, it is necessary to master its elements. Fan and resistance are parts of heated and convective dryer. Catalogues analysis of 33 and 14 french suppliers of fans and resistances respectively showed 773 fans and 226 resistances suitable for drying technologies. Fans are classified as follows in decreasing order : axial (58 %), centrifugal (42 %) and tangential (1 %). Specifications of fans used in pilots dryers adapted for developing countries in the literature are presented. Centrifugal fan appeared to be the most used. Optimisation of fan parameters (rating fan, air circulation) are presented as a function of drying time

Electrochemical characterization of a mechanically stressed passive layer

The electrochemical behavior of the stainless steel 304L was studied under static mechanical stress. In a first approach, the elastic domain of the material was investigated by using the scanning electrochemical microscope (SECM). The Fe(CN)63− was used as mediator to characterize the electrochemical reactivity of the passive layer of SS 304L under various stress strengths. Keywords: Scanning electrochemical microscopy, Heterogeneous electron transfer, Stress corrosion, Passive laye

Drying parameters of an adhesive coating with respect to quality

International audienc

Drying parameters of an adhesive coating with respect to quality

International audienc