Electrospray synthesis and properties of hierarchically structured PLGA TI PS microspheres for use as controlled release technologies

Microsphere-based controlled release technologies have been utilized for the long-term delivery of proteins, peptides and antibiotics, although their synthesis poses substantial challenges owing to formulation complexities, lack of scalability, and cost. To address these shortcomings, we used the electrospray process as a reproducible, synthesis technique to manufacture highly porous (>94%) microspheres while maintaining control over particle structure and size. Here we report a successful formulation recipe used to generate spherical poly(lactic-co-glycolic) acid (PLGA) microspheres using the electrospray (ES) coupled with a novel thermally induced phase separation (TIPS) process with a tailored Liquid Nitrogen (LN2) collection scheme. We show how size, shape and porosity of resulting microspheres can be controlled by judiciously varying electrospray processing parameters and we demonstrate examples in which the particle size (and porosity) affect release kinetics. The effect of electrospray treatment on the particles and their physicochemical properties are characterized by scanning electron microscopy, confocal Raman microscopy, thermogravimetric analysis and mercury intrusion porosimetry. The microspheres manufactured here have successfully demonstrated long-term delivery (i.e. 1 week) of an active agent, enabling sustained release of a dye with minimal physical degradation and have verified the potential of scalable electrospray technologies for an innovative TIPS-based microsphere production protocol

Time-varying wing-twist improves aerodynamic efficiency of forward flight in butterflies

PMC3547021Insect wings can undergo significant chordwise (camber) as well as spanwise (twist) deformation during flapping flight but the effect of these deformations is not well understood. The shape and size of butterfly wings leads to particularly large wing deformations, making them an ideal test case for investigation of these effects. Here we use computational models derived from experiments on free-flying butterflies to understand the effect of time-varying twist and camber on the aerodynamic performance of these insects. High-speed videogrammetry is used to capture the wing kinematics, including deformation, of a Painted Lady butterfly (Vanessa cardui) in untethered, forward flight. These experimental results are then analyzed computationally using a high-fidelity, three-dimensional, unsteady Navier-Stokes flow solver. For comparison to this case, a set of non-deforming, flat-plate wing (FPW) models of wing motion are synthesized and subjected to the same analysis along with a wing model that matches the time-varying wing-twist observed for the butterfly, but has no deformation in camber. The simulations show that the observed butterfly wing (OBW) outperforms all the flat-plate wings in terms of usable force production as well as the ratio of lift to power by at least 29% and 46%, respectively. This increase in efficiency of lift production is at least three-fold greater than reported for other insects. Interestingly, we also find that the twist-only-wing (TOW) model recovers much of the performance of the OBW, demonstrating that wing-twist, and not camber is key to forward flight in these insects. The implications of this on the design of flapping wing micro-aerial vehicles are discussed.JH Libraries Open Access Fun

STABILIZING EFFECT OF EMITTED CHARGES ON THE CONE-LIKE SHAPES OF ELECTRIFIED MENISCI

Lorsqu'un ménisque est formé à l'extrémité d'un capillaire et porté à un potentiel électrique suffisamment élevé, le ménisque peut présenter la forme d'un cône. Suivant les conditions expérimentales, on observe à la pointe du cône, l'émission de charges par effet de champ, la production de gouttelettes ou une décharge corona. La forme conique est essentielle car elle permet l'existence des deux premiers phénomènes. Dans le présent travail, les profils des ménisques électrisés ont été calculés en tenant compte de l'effet régulateur que le départ des charges exerce sur le champ électrique au sommet du cône. Les calculs montrent notamment que l'équilibre d'un ménisque conique est possible pour toute une gamme de valeurs du potentiel électrique et de la pression hydrostatique.When a meniscus is formed at the free end of a capillary tube and is subjected to the effect of a sufficiently intense electric field, the meniscus may display the shape of a cone. Depending upon the experiment conditions, a field effect charge emission, the production of droplets or corona discharge may be observed at the apex of the cone. The cone shape is essential to generate the first two phenomena. In this study, the profiles of electrified menisci were calculated taking account of the regulating effect that charge emission may exert on the electric field at the apex of the cone. The calculations particularly show that conical meniscus equilibrium is possible over a whole range of electric potential and hydrostatic pressure values

APPLICATION DES SONDES A FAISCEAU ELECTRONIQUE AUX MESURES LOCALES DE CONCENTRATIONS ET DE TEMPERATURES DE ROTATION

L'article traite des effets d'environnement sur la précision des mesures de masse volumique, et de l'emploi du modèle de Smith pour les mesures de température de rotation.The paper deals with the environment effects on the accuracy of the density measurements, and the use of the Smith model to the rotational temperature measurement