Design of polymeric materials for culturing human pluripotent stem cells: Progress toward feeder-free and xeno-free culturing

This review describes recent developments regarding the use of natural and synthetic polymers to support the propagation of human pluripotent stem cells (hPSCs), human embryonic stem cells (hESCs), and induced pluripotent stem cells (hiPSCs) while maintaining pluripotency in feeder-free and xeno-free cultures. The development of methods for culturing these cells without using mouse embryonic fibroblasts (MEFs) as a feeder layer will enable more reproducible culture conditions and reduce the risk of xenogenic contaminants, thus increasing the potential clinical applications of differentiated hPSCs. Human or recombinant fibronectin, laminin-511, and vitronectin, which are components of the extracellular matrix (ECM), have been used instead of Matrigel for the feeder-free growth of undifferentiated hPSCs. Successful hPSC cultures have been described for the following conditions: on oligopeptide-immobilized surfaces derived from vitronectin, on microcarriers prepared from synthetic polymers, and encapsulated within three-dimensional (3D) hydrogels composed of alginate and other hydrophilic natural polymers. Recently, synthetic biomaterials that allow hPSCs to maintain pluripotency by secreting endogenous ECM components have been designed. The combination of human ECM proteins or cell adhesion molecules (e.g., oligopeptides and poly-d-lysine) and synthetic biomaterials with well-designed surfaces and/or structures (e.g., scaffolds, hydrogels, microcarriers, microcapsules, or microfibers) in the presence of a chemically defined medium containing recombinant growth factors would offer a xeno-free alternative to feeder cells for culturing hPSCs and maintaining their pluripotency.     

Preparation and Properties of Novel Quaternized Metal–Polymer Matrix Nanocomposites

A new class of PANI/Sn(II)SiO₃/FCNTs nanocomposite was synthesized by mixing polyaniline into the gel of Sn(II)SiO₃ followed by FCNTs (Polyaniline/Sn(II)SiO₃/Functionalized Carbon nanotubes). The physico-chemical characterization was carried out by scanning electron microscope, XRD (X-ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), ultraviolet–visible spectroscopy, and simultaneous thermogravimetric analysis studies. The ion-exchange capacity (1.2 meq/g) and distribution studies were also determined to understand the ion-exchange capabilities. The DC electrical conductivity studies revile it in the range of 3–5 × 10^?3 S/cm. On the basis of distribution studies, ion-selective membrane electrode was designed for Hg(II). The analytical utility of this membrane was established by using it as an indicator electrode in electrometric titrations.     

Solubilization of graphene flakes through covalent modification with well‐defined azido‐terminated poly(ε‐caprolactone)

A well‐defined poly(ε‐caprolactone) (PCL) with terminal azido group was prepared. Grafting‐on reaction between the azido‐terminated PCL (N₃? PCL) and ultrasonication‐assisted exfoliated graphene flakes (GF) was carried out to obtain PCL‐grafted‐GF (PCL‐g‐GF) which showed good dispersibility in a wide variety of organic solvents. Gel permeation chromatography, ¹H NMR, IR, Raman, UV‐vis, and TEM measurements indicated that PCL macromolecules were covalently introduced on the surface of GF without disrupting the structure of GF. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41569.     

The cutting tool stresses in finish turning of hardened steel with mixed ceramic tool

Precision hard machining is an interesting topic in manufacturing die and mold, automobile parts, and scientific research. While the hard machining has benefit advantages such as short cutting cycle time, process flexibility, and low surface roughness, there are several disadvantages such as high tooling cost, need of rigid machine tool, high cutting stresses, and residual stresses. Especially, tool stresses should be understood and dealt with to achieve successful performance of finish hard turning with ceramic cutting tool. So, the influence of cutting parameters on cutting stresses during dry finish turning of hardened (52 HRC) AISI H13 hot work steel with ceramic tool is investigated in this paper. For this aim, a series finish turning tests were performed, and the cutting forces were measured in tests. After literature procedure about finite element model (FEM), FEM is established to predict cutting stresses in finish turning of hardened AISI H13 steel with Ceramic 650 grade insert. As shown, effect of the cutting parameters on cutting tool stresses in finish turning of AISI H13 steel is obtained. The suggested results are helpful for optimizing the cutting parameters and decreasing the tool failure in finish turning applications of hardened steel.     

An Investigation on the Tribological Behaviors of Al 6061–B4C Metal Matrix Composites

Protection of Metals and Physical Chemistry of Surfaces - Ceramic reinforcements are used in metal matrix composite materials to enhance the mechanical properties. Ceramic particles also improve...     

Structure and Disorder in Squaraine–C60 Organic Solar Cells: A Theoretical Description of Molecular Packing and Electronic Coupling at the Donor–Acceptor Interface

Organic solar cells based on the combination of squaraine dyes (as electron donors) and fullerenes (as electron acceptors) have recently garnered much attention. Here, molecular dynamics simulations are carried out to investigate the evolution of a squaraine–C₆₀ bilayer interface as a function of the orientation and order of the underlying squaraine layer. Electronic couplings between the main electronic states involved in exciton dissociation and charge (polaron pair) recombination are derived for donor–acceptor complexes extracted from the simulations. The results of the combined molecular‐dynamics?quantum‐mechanics approach provide insight into how the degree of molecular order and the dynamics at the interface impact the key processes involved in the photovoltaic effect.     

Performance of Object Classification Using Zernike Moment

Moments have been used in all sorts of object classification systems based on image. There are lots of moments studied by many researchers in the area of object classification and one of the most preference moments is the Zernike moment. In this paper, the performance of object classification using the Zernike moment has been explored. The classifier based on neural networks has been used in this study. The results indicate the best performance in identifying the aggregate is at 91.4% with a ten orders of the Zernike moment. This encouraging result has shown that the Zernike moment is a suitable moment to be used as a feature of object classification systems.     

Carbonization behavior of oxidized viscose rayon fibers in the presence of boric acid–phosphoric acid impregnation

The oxidation and carbonization stages of viscose rayon fibers were performed in the presence of 3 % phosphoric acid and 4 % boric acid (PA–BA) impregnation. The results showed that PA–BA impregnation enhanced thermal stability and prevented the evolution of volatile by-products. During the oxidation stage carried out at 250 °C, the cellulose II crystalline structure was totally lost due to the decrystallization process. Carbonization was carried out in a pure nitrogen atmosphere at temperatures ranging from 600 to 1000 °C. The results obtained from the fiber thickness, linear density, carbon fiber yield, elemental analysis, volume density, X-ray diffraction, infrared (IR) and Raman spectroscopy, tensile testing, and electrical conductivity measurements showed that the carbonization temperature had a significant effect on the structure and properties of the resulting carbon fibers. Carbon fibers obtained from the oxidized viscose rayon fibers showed physical and chemical transformations with increasing carbonization temperature and were characterized by a reduction in fiber thickness and linear density values due to the removal of non-carbon elements together with increases in the carbon content, carbon to hydrogen ratio (C/H), volume density, tensile strength, tensile modulus, and electrical conductivity values. X-ray diffraction analysis showed that the interplanar d-spacing (d ₀₀₂) decreased, and that the apparent crystallite thickness (L _c) and the apparent crystallite width (L _a) increased with increasing temperature. IR spectroscopy in agreement with the elemental analysis showed the total loss of OH, CH, C=O, CH₂, C–O, and C–O–C groups arising from the completion of dehydration and dehydrogenation reactions indicating total elimination of the cellulose structure and the formation of amorphous carbon during high temperature treatment.