Surface properties and biocompatibility of cellulose acetates

The article describes some properties of cellulose acetates (CAs) with different substitution degrees. The hydrophilic/hydrophobic properties, morphological aspects, and interface properties with red blood cells and platelets are affected by the substitution degree, synthesis conditions, history of the formed films from solutions in acetone/water nonsolvent/nonsolvent mixtures, and low pressure plasma treatment. The results obtained are useful in biomedical applications, including evaluation of bacterial adhesion onto surfaces, or utilization of CA for semipermeable membranes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Engineering Biomaterials for Myocardial Regeneration and Repair

Augmentation of myocardial tissue regeneration processes in injured hearts represents a major challenge in cardiology as current therapeutic approaches do not regenerate the myocardial tissue. Herein, we describe three emerging biomaterial-based strategies to treat heart injuries, as stand-alone therapies or in combination with regeneration-inducing signals and/or cells. One strategy relies on the injection of acellular biomaterials, at an early stage after myocardial infarction (MI); these materials replace the damaged extracellular matrix, maintain left ventricular (LV) thickness, and prevent the negative LV remodeling and progression to heart failure. This strategy is currently being investigated in advanced clinical trials using a novel alginate-based biomaterial. The second strategy employs engineered biomaterials, spatially presenting multiple regeneration-inducing factors, to promote myocardial tissue regeneration in chronic infarcted hearts. The recent attempts to understand the “natural capacity” of the myocardium to heal and the factors involved in these processes are promising to advance this therapy. The third strategy applies biomaterials to promote cardiac tissue engineering and create a pre-vascularized cardiac patch to replace damaged or missing myocardial tissue. Collectively, this review emphasizes the increasing importance of biomaterials in cardiology, describes the engineering schemes used in their fabrication, and their implementation in various therapeutic strategies aimed at cardiac tissue regeneration and repair. It mainly highlights the contribution of our group in developing these strategies.     

Stress-induced structural changes in La-doped BiFeO3–PbTiO3 high-temperature piezoceramics

High-temperature piezoelectric polycrystalline ceramics of the system (1 ? x)(Bi_1?yLa_y)FeO₃-xPbTiO₃ (BF–PT), which are mixed phase in their consolidated state, have been investigated by in situ neutron diffraction during the application of uniaxial compressive stress. It is suggested that the achievable strain in BF–PT is largely generated by straining of the rhombohedral phase. The results of the neutron diffraction measurements are compared and discussed with respect to the measured macroscopic ferroelastic constitutive behavior for various compositions of BF–PT.     

Local versus Global in Quasi-Conformal Mapping for Medical Imaging

A method and algorithm of flattening folded surfaces, for two-dimensional representation and analysis of medical images, are presented. The method is based on an application to triangular meshes of classical results of Gehring and Väisälä regarding the existence of quasi-conformal and quasi-isometric mappings.The proposed algorithm is basically local and, therefore, suitable for extensively folded surfaces encountered in medical imaging. The theory and algorithm guarantee minimal distance, angle and area distortion. Yet, the algorithm is relatively simple, robust and computationally efficient, since it does not require computational derivatives. Both random-starting-point and curvature-based versions of the algorithm are presented.We demonstrate the algorithm using medical data obtained from real CT images of the colon and MRI scans of the human cortex. Further applications of the algorithm, for image processing in general are also considered. The globality of this algorithm is also studied, via extreme length methods for which we develop a technique of computing straightest geodesics on polyhedral surfaces.     

Synthesis and properties of photosensitive poly(urethane‐acrylate) containing anil groups with application in the chemosensors area

Some aspects of the enol‐imine to keto‐enamine photoisomerism and fluorescent behavior of the new monomer with urethane and anil units in its structure, namely, methacryloyloxyethyl‐2‐carbamoyloxy(m‐methyl, o‐hydroxybenziliden)aniline (UAN), were studied comparatively with the corresponding copolymer poly (methacryloyloxyethyl‐2‐carbamoyloxy(m‐methyl, o‐hydroxybenziliden)aniline)‐co‐methyl methacrylate) (COP‐UAN). The structure, thermal properties, and morphology of the anil compounds were investigated by Fourier transform infrared, proton nuclear magnetic resonance, fluorescence spectroscopies, UV spectrophotometry, thermogravimetric analysis, differential scanning calorimetry, and atomic force microscopy. The photochromic behavior of salicylideneanil units was investigated by UV/laser irradiation, and an inspection of their photophysical properties suggested that such structures could function as fluorescent chemosensors for some transition metals, a fluorescence quenching in the presence of different metal cations (Fe³⁺, Fe²⁺, Cu²⁺, and Ni²⁺) being evidenced. The direct observation of an enhancement in the fluorescence emission caused of the presence of Zn²⁺ (solution) or Fe²⁺, Cu²⁺, and Zn²⁺ (thin film) would be rather suitable for the production of turn‐on fluorescent chemosensors. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The investigation of fly ash based asphalt binders using atomic force microscope

Atomic Force Microscope (AFM) is a relatively new technique for investigation of construction materials. In this study AFM was used to investigate the interaction of asphalt binder with fly ash. Fly ash is a coal combustion byproduct of electric power utilities having pozzolanic properties and commonly used in Portland cement concrete. In this study, an investigation was made by using different types of fly ash with two types of asphalt binders such as PG 58-28 and PG 64-28. Asphalt microstructure is divided into four subgroups such as Saturates, Aromatics, Resins and Asphaltenes (SARA). These four phases can be distinguished by the atomic force microscope. The interaction of these phases affected by introducing fly-ash was investigated and correlation with rheological properties was observed.     

Transformation of coherence and of the spectrum of light by a moving diffuser

Abstract

Effects of a diffuser on the spectral degree of coherence and on the spectrum of light produced by transmitting light through the diffuser are described. Both stationary and uniformly moving diffusers are considered and the analysis applies to dielectric as well as to absorbing diffusers. The results are illustrated by numerical examples.