Thermally stable epoxy polymers from new tetraglycidyl amine-based resin

Journal of Thermal Analysis and Calorimetry - A tetraglycidyl amines-based epoxy resin, namely 4-(2-(4-(bis(oxiran-2-ylmethyl)amino)phenoxy)ethoxy)-N,N-bis(oxiran-2-ylmethyl)benzenamine (TGAE), was...     

An Improvement of Ostrowski’s and King’s Techniques with Optimal Convergence Order Eight

In this paper, we first establish a new class of three-point methods based on the two-point optimal method of Ostrowski. Analysis of convergence shows that any method of our class arrives at eighth order of convergence by using three evaluations of the function and one evaluation of the first derivative per iteration. Thus, this order agrees with the conjecture of Kung and Traub (J. ACM 643–651, 1974) for constructing multipoint optimal iterations without memory. We second present another optimal eighth-order class based on the King’s fourth-order family and the first attained class. To support the underlying theory developed in this work, we examine some methods of the proposed classes by comparison with some of the existing optimal eighth-order methods in literature. Numerical experience suggests that the new classes would be valuable alternatives for solving nonlinear equations.     

A profound density functional theory study to unravel the spectroscopic and molecular properties of two Flavanols differing in α-pyrone ring position

A comprehensive theoretical model was designed for two new flavanols that have been reported from Glycosmis pentaphylla, differing in the placement of α-pyrone ring. The density functional theory (DFT) approach was utilized for computing different properties of these compounds to validate the experimental findings and stereochemical assignments. Electronic properties, geometric parameters, frontier molecular orbitals (FMOs), molecular electrostatic potential (MESP), and natural bond orbital analysis were performed for the first time at the PBE0-D3BJ/def2-TZVP level of theory for the compounds under study. The simulated vibrational frequencies for compounds 1 and 2 were computed and compared with the experimental results. nuclear magnetic resonance (NMR) (¹H and ¹³C) chemical shift values were computed at the PBE0-D3BJ/def2-TZVP/SMD_DMSO level of theory and showed a very good agreement with the experimental results for both the compounds. The electronic circular dichroism (ECD) and ultraviolet–visible (UV) spectra for both the compounds were obtained using time-dependent DFT in methanol, whose results exhibited excellent correlation with experimental data. The intermolecular interaction effect on geometric parameters, vibrational frequencies, and electronic properties were studied for the first time.     

Consistent and asymptotically normal estimators for cyclically time-dependent linear models

We consider a general class of time series linear models where parameters switch according to a known fixed calendar. These parameters are estimated by means of quasi-generalized least squares estimators. conditions for strong consistency and asymptotic normality are given. Applications to cyclical ARMA models with non constant periods are considered.     

On the stability and causality of general time-dependent bilinear models

In this Note, sufficient conditions are given for the existence of a causal stable solution for general bilinear time series with time-dependent coefficients. To cite this article: A. Bibi, C. R. Acad. Sci. Paris, Ser. I 338 (2004).     

A methodology for an accurate evaluation of the linearization procedures in nonlinear mean field homogenization

A systematic methodology for the evaluation of the linearization procedures sustaining mean field homogenization theories for nonlinear composite materials is proposed and applied as an illustration to various recently proposed ‘affine’ and ‘second-order’ formulations for nonlinear elasticity. It relies on the analysis of composites for which both the exact nonlinear homogenization problem and the homogenization problem associated with the ‘linear comparison material’ defined by the linearization procedure can be solved numerically with the same accuracy and for the same microstructure. The comparison of the results then provides a rigorous evaluation of the effects of the sole linearization method. To cite this article: A. Rekik et al., C. R. Mecanique 333 (2005).     

The role of ligands on protein retention in adsorption chromatography: A surface energetics approach

Protein adsorption onto hydrophobic chromatographic supports has been investigated using a colloid theory surface energetics approach. The surface properties of commercially available chromatographic beads, Toyopearl Phenyl 650‐C, and Toyopearl Butyl 650‐C, have been experimentally determined by contact angle and zeta potential measurements. The adsorption characteristics of these beads, which bear the same backbone matrix but harbor different ligands, have been studied toward selected model proteins, in the hydrated as well as dehydrated state. There were two prominent groups of proteins observed with respect to the chromatographic supports presented in this work: loosely retained proteins, which were expected to have lower average interaction energies, and the strongly retained proteins, which were expected to have higher average interaction energies. Results were also compared and contrasted with calculations derived from adsorbent surface energies determined by inverse liquid chromatography. These results showed a good qualitative agreement, and the interaction energy minima obtained from these extended Derjaguin, Landau, Verwey and Overbeek calculations were shown to correlate well with the experimentally determined adsorption behavior of each protein.     

Interaction of magnetic cobalt based titanium dioxide nanofibers with muscle cells: in vitro cytotoxicity evaluation

Titanium dioxide and magnetic cobalt based materials are one of the most attractive materials for investigation due to their dramatic photocatalytic, optical, biomedical, magnetic and electrical applications. However, there is limited or no information about the possible impact of cobalt based titanium dioxide (Co-doped TiO₂) nanofibers on muscle cells. This study focuses on the interaction of magnetic cobalt based titanium dioxide nanofibers with C2C12 cell line. C2C12 mouse myoblasts were used to evaluate the beneficial/or toxicological effects of Co-doped TiO₂ on cells. The effects of Co-doped TiO₂ nanofibers on the morphology, cytotoxicity and adhesion ability of C2C12 cells, as well as on the cell death were evaluated. To examine the in vitro cytotoxicity, mouse myoblast C2C12 cells were treated with different concentrations of synthesized Co-doped TiO₂ nanofibers and the viability of cells was analyzed by cell counting Kit-8 assay at regular time intervals. The morphological features of the cells were examined by microscopy and cell attachment with nanofibers was observed by scanning electron microscopy respectively. Experiments indicate that the mouse myoblast cells could attach to the nanofibers after being cultured. Cell viability was determined as a function of incubation time; with increasing concentration of Co-doped TiO₂, the cell viability decreased. Thus from the obtained results it was concluded that Co-doped TiO₂ nanofibers could support cell adhesion and growth of myoblast cells, however the cell compatibility decreases with high doses and after sustained exposure.