Octadecyl Chains Immobilized onto Hyaluronic Acid Coatings by Thiol-ene "Click Chemistry" Increase the Surface Antimicrobial Properties and Prevent Platelet Adhesion and Activation to Polyurethane.

Infection and thrombus formation are still the biggest challenges for the success of blood contact medical devices. This work aims the development of an antimicrobial and hemocompatible biomaterial coating through which selective binding of albumin (passivant protein) from the bloodstream is promoted and, thus, adsorption of other proteins responsible for bacterial adhesion and thrombus formation can be prevented. Polyurethane (PU) films were coated with hyaluronic acid, an antifouling agent, that was previously modified with thiol groups (HA-SH), using polydopamine as the binding agent. Octadecyl acrylate (C18) was used to attract albumin since it resembles the circulating free fatty acids and albumin is a fatty acid transporter. Thiol-ene "click chemistry" was explored for C18 immobilization on HA-SH through a covalent bond between the thiol groups from the HA and the alkene groups from the C18 chains. Surfaces were prepared with different C18 concentrations (0, 5, 10, and 20%) and successful immobilization was demonstrated by scanning electron microscopy (SEM), water contact angle determinations, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The ability of surfaces to bind albumin selectively was determined by quartz crystal microbalance with dissipation (QCM-D). Albumin adsorption increased in response to the hydrophobic nature of the surfaces, which augmented with C18 saturation. HA-SH coating reduced albumin adsorption to PU. C18 immobilized onto HA-SH at 5% promoted selective binding of albumin, decreased Staphylococcus aureus adhesion and prevented platelet adhesion and activation to PU in the presence of human plasma. C18/HA-SH coating was established as an innovative and promising strategy to improve the antimicrobial properties and hemocompatibility of any blood contact medical device.

Localized approximation for gaussian beams in elliptical cylinder coordinates.

We establish a localized approximation to evaluate the beam-shape coefficients of a Gaussian beam in elliptical cylinder coordinates. As for the case of spherical coordinates and of circular cylinder coordinates, this approximation provides an efficient way to speed up computations within the framework of a generalized Lorenz-Mie theory for elliptical cylinders.

Scattering of a gaussian beam by an infinite cylinder with arbitrary location and arbitrary orientation: numerical results.

We present numerical results concerning the properties of the electromagnetic field scattered by an infinite circular cylinder illuminated by a circular Gaussian beam. The cylinder is arbitrarily located and arbitrarily oriented with respect to the illuminating Gaussian beam. Numerical evaluations are provided within the framework of a rigorous electromagnetic theory, the generalized Lorenz-Mie theory, for infinite cylinders. This theory provides new insights that could not be obtained from older formulations, i.e., geometrical optics and plane-wave scattering. In particular, some emphasis is laid on the waveguiding effect and on the rainbow phenomenon whose fine structure is hardly predictable by use of geometrical optics.

Cylindrical localized approximation to speed up computations for Gaussian beams in the generalized Lorenz-Mie theory for cylinders, with arbitrary location and orientation of the scatterer.

A cylindrical localized approximation to speed up numerical computations in generalized Lorenz-Mie theory for cylinders, in a special case of perpendicular illumination, was recently introduced and rigorously justified. We generalize this approximation to the case when the cylinder is arbitrarily located and arbitrarily oriented in a Gaussian beam.

Integral localized approximation in generalized lorenz-mie theory.

The generalized Lorenz-Mie theory deals with the interaction between spheres and arbitrarily shaped illuminating beams. An efficient use of the theory requires efficient evaluation of the so-called beam-shape coefficients involved in the description of the illuminating beam. A less time-consuming method of evaluation relies on the localized approximation. However, it lacks flexibility when the description of the illuminating beam is modified. We present a new version of this method, called the integral localized approximation, that exhibits the desired property of flexibility.

Characterization of initial disturbances in a liquid jet by rainbow sizing.

The development of initial disturbances is relevant to the understanding of atomization processes in which droplets are generated by the breakup of a liquid jet. We theoretically and experimentally demonstrate that such disturbances can be characterized by rainbow sizing. More specifically, for a liquid jet with a diameter of 600 mum, disturbances in the range from 10 nm to 0.2 mum are accessible.

Improved algorithm for electromagnetic scattering of plane waves and shaped beams by multilayered spheres.

An efficient numerical procedure for computing the scattering coefficients of a multilayered sphere is discussed. The stability of the numerical scheme allows us to extend the feasible range of computations, both in size parameter and in number of layers for a given size, by several orders of magnitude with respect to previously published algorithms. Exemplifying results, such as scattering diagrams and cross-sectional curves, including the case of Gaussian beam illumination, are provided. Particular attention is paid to scattering at the rainbow angle for which approaches based on geometrical optics might fail to provide accurate enough results.

Discussion of two quadrature methods of evaluating beam-shape coefficients in generalized Lorenz-Mie theory.

A comparison between two quadrature methods of evaluating beam-shape coefficients in generalized Lorenz-Mie theory, in the case of incident Gaussian beams, is carried out. It is shown that, when the electromagnetic description of the Gaussian beams does not perfectly satisfy Maxwell's equations, both quadrature methods are basically flawed. These flaws do not prevent an accurate evaluation of beam-shape coefficients when their nature is correctly identified, because they produce artifacts that can easily be identified and removed.

Prediction of reverse radiation pressure by generalized Lorenz-Mie theory.

Radiation pressure exerted on a spherical particle by one extremely focused Gaussian beam is investigated by the use of generalized Lorenz-Mie theory (GLMT). Particular attention is devoted to reverse radiation pressure. GLMT predictions for different descriptions of the incident beam are compared with electrostriction predictions when the particle size is smaller than the wavelength and with geometric-optics predictions when the particle size is larger than the wavelength.