Effects of Geomaterial-Originated Fillers on Microstructure and Mechanical/Physical Properties of α- and ß-Chitosan-Based Films.

Edible films and coatings with good mechanical/physical properties are highly required for carrying medical substances and food packaging. So, solvent-cast films of α- or ß-chitosan filled with palygorskite, montmorillonite or geopolymer-containing material (GCM), were prepared, and the effects of their clay contents (up to 50 wt.%) on the mechanical/physical properties were assessed. The microstructure of the films was investigated using FT-IR spectroscopy, SEM and thermal analysis. The results showed that, except for the films composed of GCM and ß-chitosan, the mechanical properties of the films with limited (up to 5 wt.%) to moderate (5-25 wt.%) amounts of fillers increased as a result of the attractive electrostatic forces formed between the fillers and chitosan functional groups (-NH3+, CH2OH and NHCOCH3). However, due to the occurrence of coarse aggregates, the strength of filler-rich films declined. The addition of fillers led to an increase in porosity and water absorption of the films, but it had irregular effects on their wettability and water vapor transmission rate. These observations as well as the thermal stability of the films were discussed in relation to the characterization results.

Retention and release of hexavalent and trivalent chromium by chitosan, olive stone activated carbon, and their blend.

Shrimp shells and waste of olive stones were used as feedstock for the preparation of chitosan and activated carbon. The adsorption of CrVI and CrIII species in aqueous solution by the materials prepared and their blend were studied by using the well-known kinetic and isotherm models, Fourier transform infrared spectroscopy and scanning electron microscope. It was demonstrated that the rates of adsorption were controlled by diffusion inside particles and throughout the liquid film, and adsorption occurred spontaneously (- 26 < ∆G° < - 15 kJ/mol) in the range of 298-333 K, except for that involving CrIII species and activated carbon. The maximum amounts of Cr species retained by the composite (146 mg of CrVI/g and 33 mg of CrIII/g at 298 K) were three times greater than those of the basic constituents. Adsorption was markedly affected by temperature and pH, and CrVI species were substantially desorbed in acid mediums, particularly in acetic acid solution. The recovery of CrIII species varied according to the adsorbent and the solution used. The immobilization of CrVI species (HCrO4- and CrO42-) and CrIII species (Cr(OH)2+ and Cr3(OH)45+) by chitosan was accomplished by means of amine moieties and hydroxyls of D-glucosamine units of the biopolymer. The adsorption of CrVI species on activated carbon involved π electrons of aromatic rings as well as oxygenated sites (C-OH, C=O, C-O-C). In such a condition, CrVI was partially reduced into CrIII. For the composite, the amino functional groups of chitosan and hydroxyls of both constituents were implicated in the linkage of the biopolymer and activated carbon, and the C-O-H and C-O-C functional groups of chitosan were involved in the retention of CrVI species. For CrIII species, adsorption occurred preferentially on hydroxyls of the components, and consequently, the chains of the biopolymer recovered some flexibility.

Combining Haar Wavelet and Karhunen Loeve Transforms for medical images watermarking.

This paper presents a novel watermarking method, applied to the medical imaging domain, used to embed the patient's data into the corresponding image or set of images used for the diagnosis. The main objective behind the proposed technique is to perform the watermarking of the medical images in such a way that the three main attributes of the hidden information (i.e., imperceptibility, robustness, and integration rate) can be jointly ameliorated as much as possible. These attributes determine the effectiveness of the watermark, resistance to external attacks, and increase the integration rate. In order to improve the robustness, a combination of the characteristics of Discrete Wavelet and Karhunen Loeve Transforms is proposed. The Karhunen Loeve Transform is applied on the subblocks (sized 8 × 8) of the different wavelet coefficients (in the HL2, LH2, and HH2 subbands). In this manner, the watermark will be adapted according to the energy values of each of the Karhunen Loeve components, with the aim of ensuring a better watermark extraction under various types of attacks. For the correct identification of inserted data, the use of an Errors Correcting Code (ECC) mechanism is required for the check and, if possible, the correction of errors introduced into the inserted data. Concerning the enhancement of the imperceptibility factor, the main goal is to determine the optimal value of the visibility factor, which depends on several parameters of the DWT and the KLT transforms. As a first step, a Fuzzy Inference System (FIS) has been set up and then applied to determine an initial visibility factor value. Several features extracted from the Cooccurrence matrix are used as an input to the FIS and used to determine an initial visibility factor for each block; these values are subsequently reweighted in function of the eigenvalues extracted from each subblock. Regarding the integration rate, the previous works insert one bit per coefficient. In our proposal, the integration of the data to be hidden is 3 bits per coefficient so that we increase the integration rate by a factor of magnitude 3.