Extraction and isolation of catechins from tea

Tea is a major source of catechins, which have become well known for their antioxidant potential. Numerous human, animal, and in vitro studies have linked tea catechins with prevention of certain types of cancers, reduction of the risks for obesity, diabetes, and cardiovascular disease, and improvement of the immune system. Tea catechins are widely used in various neutraceuticals, pharmaceuticals, and cosmetics for either enhancing product shelf-life or for enhancing human health. Thus, the demand for catechins has increased considerably. Catechins have been extracted and isolated from tea leaves by numerous methods through several steps including: treatment of the tea leaves, extraction of catechins from teas into solvents, isolation of catechins from other extracted components, and drying the preparations to obtain catechin extracts in a powder form. This paper outlines the physical and chemical properties of the tea catechins and reviews the extraction steps of the various extraction methods, as a basis to improve and further develop the extraction and isolation of the tea catechins.     

Formation and characterization of a hydrophilic polymer hydrogel under gamma irradiation

Formation and characterization of hydrogel of a hydrophilic polymer in a wide range of gamma absorbed doses is reported. An aqueous solution contains 2% polyvinyl alcohol (PVA) by mass irradiated under gamma rays of ⁶⁰Co was chosen for study. The hydrogel was synthesized without using any additives. It was found that gel fraction is an exponential saturation function that increases with an increase of absorbed dose while swelling ratio is an exponential saturation function that decreases with an increase of absorbed dose. The results are described by energy transfer model.     

Designing an intelligent teaching simulator for learning to teach by practicing

Learning to teach is difficult for prospective teachers because of the complex nature of the work of teaching. Practicing (Lampert in J Teach Educ 61(1–2):21–34, 2010), interacting with the practice of teaching from a first-person perspective, may give them a unique experience in learning to teach. Computer-based simulators in which the apprentice teacher can interact with virtual students may be used to create that kind of experience. In this paper, we show how to apply techniques in artificial intelligence to design an intelligent learning environment. We show how to model the apprentice’s decision making and resources that can help him or her improve the practice of teaching.     

On an optimal robust digital image watermarking based on SVD using differential evolution algorithm

It is shown that the optimal robust digital image watermarking based on singular value decomposition using differential evolution algorithm proposed by Veysel Aslantas [Opt. Commun. 282(5):769-777 (2009)] has a serious fundamental flaw and should not be used for proof of ownership application.     

Projected viscosity subgradient methods for variational inequalities with equilibrium problem constraints in Hilbert spaces

In this paper, we introduce and study some low computational cost numerical methods for finding a solution of a variational inequality problem over the solution set of an equilibrium problem in a real Hilbert space. The strong convergence of the iterative sequences generated by the proposed algorithms is obtained by combining viscosity-type approximations with projected subgradient techniques. First a general scheme is proposed, and afterwards two practical realizations of it are studied depending on the characteristics of the feasible set. When this set is described by convex inequalities, the projections onto the feasible set are replaced by projections onto half-spaces with the consequence that most iterates are outside the feasible domain. On the other hand, when the projections onto the feasible set can be easily computed, the method generates feasible points and can be considered as a generalization of Maingé’s method to equilibrium problem constraints. In both cases, the strong convergence of the sequences generated by the proposed algorithms is proven.     

Comparison of three methods for fractionation and enrichment of low molecular weight proteins for SELDI-TOF-MS differential analysis

In most diseases, the clinical need for serum/plasma markers has never been so crucial, not only for diagnosis, but also for the selection of the most efficient therapies, as well as exclusion of ineffective or toxic treatment. Due to the high sample complexity, prefractionation is essential for exploring the deep proteome and finding specific markers.In this study, three different sample preparation methods (i.e., highly abundant protein precipitation, restricted access materials (RAM) combined with IMAC chromatography and peptide ligand affinity beads) were investigated in order to select the best fractionation step for further differential proteomic experiments focusing on the LMW proteome (MW inferior to 40,000 Da). Indeed, the aim was not to cover the entire plasma/serum proteome, but to enrich potentially interesting tissue leakage proteins. These three methods were evaluated on their reproducibility, on the SELDI-TOF-MS peptide/protein peaks generated after fractionation and on the information supplied.The studied methods appeared to give complementary information and presented good reproducibility (below 20%). Peptide ligand affinity beads were found to provide efficient depletion of HMW proteins and peak enrichment in protein/peptide profiles.     

A proof of zelevinski’s structure theorem for psh algebras 1

We give a new proof of the structure theorem for PSH—algebras, and of a formula for primitives     

Temperature-responsive self-assembly of charged and uncharged hydroxyethylcellulose-<Emphasis Type="Italic">graft</Emphasis>-poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) copolymer in aqueous solution

Temperature-induced interchain association and contraction of species in aqueous solutions of charged (MHEC(−)-g-PNIPAAM) and uncharged (MHEC-g-PNIPAAM) modified hydroxyethylcellulose-graft-poly(N-isopropylacrylamide) copolymer have been studied with the aid of turbidimetry and dynamic light scattering (DLS). It was shown that by attaching PNIPAAM chains to the backbone of a hydrophilic cellulose derivative, a strongly temperature-responsive copolymer could be prepared. The results show an intriguing interplay between interchain association and contraction of the multichain species. The transition zone for compression is narrow, and the compaction effect is promoted by a low polymer concentration and charges on the polymer moieties. The findings from DLS revealed two populations of species, namely molecularly dispersed molecules or small clusters and interchain complexes, which exhibit temperature-induced collapse. The magnitude of the cluster contraction can be modulated by changing the polymer concentration and charge density of the copolymer.