Synthesis and characterization of binary copolymers of methyl methacrylate with glycidyl methacrylate and 2‐hydroxy ethyl methacrylate as carriers for cellulase

Cellulase was immobilized directly on methyl methacrylate‐glycidyl methacrylate copolymer (MMA‐co‐GMA) and methyl methacrylate‐2‐hydroxy ethyl methacrylate copolymer (MMA‐co‐HEMA) by covalent attachment and crosslinking methods. The properties of the immobilized cellulase were investigated and compared with those of the free one. For the assays carried out through crosslinking method at 25°C and pH 7, the retained activities were found to be 91.92% and 74.63%, respectively, for MMA‐co‐GMA and MMA‐co‐HEMA crosslinked with 0.1% of 1‐cyclohexyl‐3‐(2‐morpholino‐ethyl) carbodiimide metho‐p‐toluenesulfonate (CMCT), respectively. The immobilized cellulase had better stability and higher retained activities with respect to pH, temperature, and storage stability than the free one. In the repeated use experiments, the immobilized cellulase using (MMA‐co‐GMA)‐CMCT (0.1%) and (MMA‐co‐HEMA)‐CMCT (0.1%) did not change after 10 and eight times of repeated use and maintained 67% and 62% from their original activities after 25 times, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The influence of fiber fineness on physical characteristics of staple polypropylene fibers spun at different pumping speeds

Melt spinning and pump speed conditions are described for five samples of staple polypropylene PP fibers of different fineness. The influence of fiber fineness or denier on the physical characteristics of staple PP fibers spun at different pump speeds was studied. Optical anisotropy was measured using two‐beam interference microscopy. Enthalpy and degree of crystallinity were measured using differential scanning calorimetry technique for studied fibers. The relation between the fiber diameter, crimp ratio, tenacity, and degree of orientation with the fiber denier are given. A selection of microinterferograms of fibers is given for illustration. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improvement of mechanical performance of epoxy resins filled with cobalt and chromium powders

Epoxy/ powder metal composites have interesting electrical properties, becoming conductors above the percolation threshold. To complete this study, mechanical investigations have been carried out to show the influence of the fillers on the mechanical performance of these composites. In this framework, different epoxy/metallic powders (Cobalt, Chromium) composites were prepared. Scanning Electron Microscopy showed that the dispersion of the metallic fillers in the matrix is almost homogeneous. The dynamic mechanical thermal analysis (DMTA) measurements showed the dependence of the viscoelastic parameters with the frequency, temperature, nature, and content of fillers. The main relaxations observed are the primary α relaxation (associated to the glass transition, T_g) and a secondary β relaxation. A second DMTA run on the same samples showed a slight increase of the T_g. It clearly showed that the used metallic fillers improve the mechanical properties of the obtained composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Membrane‐Surface Anchoring of Charged Diacylglycerol‐Lactones Correlates with Biological Activities

Synthetic diacylglycerol‐lactones (DAG‐lactones) are effective modulators of critical cellular signaling pathways, downstream of the lipophilic second messenger diacylglycerol, that activate a host of protein kinase C (PKC) isozymes and other nonkinase proteins that share similar C1 membrane‐targeting domains with PKC. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study examines the biological properties of charged DAG‐lactones exhibiting different alkyl groups attached to the heterocyclic nitrogen of an α‐pyridylalkylidene chain, and particularly the relationship between membrane interactions of the substituted DAG‐lactones and their respective biological activities. Our results suggest that bilayer interface localization of the N‐alkyl chain in the R² position of the DAG‐lactones inhibits translocation of PKC isoenzymes onto the cellular membrane. However, the orientation of a branched alkyl chain at the bilayer surface facilitates PKC binding and translocation. This investigation emphasizes that bilayer localization of the aromatic side residues of positively charged DAG‐lactone derivatives play a central role in determining biological activity, and that this factor contributes to the diversity of biological actions of these synthetic biomimetic ligands.     

A method for preparation and application of micronized ferrite pigments in anticorrosive solvent-based paints

This work presents a method of preparing single-, double-, and triple-cation ferrite pigments by employing simple chemical techniques to study their corrosion protection properties. The prepared pigments were characterized using X-ray diffraction and scanning electron microscopy. All prepared ferrite pigments were evaluated using ASTM methods. Anticorrosive paint formulations were performed using different prepared pigment loadings. The physico-mechanical and corrosion properties of dry paint films were examined. The tests revealed that the prepared ferrite pigments show excellent anticorrosive behavior, and that the best among them in performance are zinc and zinc magnesium. Calcium, zinc–calcium, and zinc–magnesium–calcium ferrites show better performance in high pigment loadings, while magnesium ferrite pigments show good results only in low pigment loading.     

Biosynthesis of the Myxobacterial Antibiotic Corallopyronin A

Corallopyronin A is a myxobacterial compound with potent antibacterial activity. Feeding experiments with labelled precursors resulted in the deduction of all biosynthetic building blocks for corallopyronin A and revealed an unusual feature of this metabolite: its biosynthesis from two chains, one solely PKS‐derived and the other NRPS/PKS‐derived. The starter molecule is believed to be carbonic acid or its monomethyl ester. The putative corallopyronin A biosynthetic gene cluster is a trans‐AT‐type mixed PKS/NRPS gene cluster, containing a β‐branching cassette. Striking features of this gene cluster are a NRPS‐like adenylation domain that is part of a PKS‐type module and is believed to be responsible for glycine incorporation, as well as split modules with individual domains occurring on different genes. It is suggested that CorB is a trans‐acting ketosynthase and it is proposed that it catalyses the Claisen condensation responsible for the interconnection of the two chains. Additionally, the stereochemistry of corallopyronin A was deduced by a combination of a modified Mosher's method and ozonolysis with subsequent chiral GC analyses.     

Structural Influence of the Ligand Geometry on Construction of Coordination Polymers Formed from Silver(I) Chloride Ribbons and Bipodal Nitrogen Donor Ligands

An assembly of adducts of silver nitrate and KCl and bipodal nitrogen donor ligands, 4,4′-bipyridine (bpy), trans-1,2-bis(4-pyridyl)ethylene (tbpe) or 1,2-bis(4-pyridyl)ethane (bpe), at room temperature affords new supramolecular coordination polymers (SCP), [AgCl·bpy] (1), [(AgCl)₂·tbpe] (2) and [(AgCl)₃·(bpe)₂] (3). X-ray single crystal analyses reveal that 1–3 have 3D-supramolecular networks composed of different types of infinite 1D-ribbons of ladder, 1, and staircase, 2 and 3, structures formed from fused minicyle {Ag₂(μ₃-Cl)₂} motifs, which are bridged by the nitrogen donor ligands to form 2D-layers. The 2D-layers are interconnected by extensive hydrogen bonds and π–π stacking thereby creating 3D-networks. The products are also characterized by IR and electronic absorption spectra. SCP 1–3 display strong fluorescence in the solid state at room temperature.     

Preparation and physicochemical characterization of hydroxyapatite coatings on zinc surfaces

This work presents a study on an alternative coating method based on electrochemical techniques which are designed to form a crystalline hydroxyapatite layer very similar to the process corresponding to the formation of natural bone. In this study, a sample electrochemical method of coating the solid surfaces of zinc, with a film of apatite, was developed. The hydroxyapatite deposit was investigated by means of scanning electron microscopy, X-ray diffraction, infrared spectroscopy, and chemical analysis. The data suggest that the method utilized in this work can be successfully applied to obtain deposition of uniform coatings of crystalline hydroxyapatite on zinc substrates. As a result, both the lattice parameters a and c of the apatite layer decreased with increasing Zn fraction.     

An Environmentally Benign,Highly Efficient Catalytic Reduction of p‐Nitrophenol using a Nano‐Sized Nickel Catalyst Supported on Silica‐Alumina

A green and effective method is reported for the reduction of p‐nitrophenol to p‐aminophenol using a nano‐sized nickel catalyst supported on silica‐alumina in the presence of hydrazine hydrate as an alternative source of hydrogen. It was found that nickel loaded on a silica‐alumina support is a very effective catalyst in the hydrogenation of p‐nitrophenol to p‐aminophenol. Thus it attained 100% conversion in only 69 seconds instead of 260 seconds for commercial Raney nickel. In addition, the possibility to reuse it more than one time with great efficiency gives it another advantage over commercial Rainey nickel which cannot be used more than once. This economical and environmentally friendly method provides a potentially new approach for the synthesis of the intermediate product of paracetamol in industry, which overcomes the drawbacks of the known reduction methods. The prepared catalysts were fully characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), and electron spin resonance (ESR) tehniques.     

Influence of Ag micro-particle additions on the microstructure, hardness and tensile properties of Sn-9Zn binary eutectic solder alloy

In this study, an addition of Ag micro-particles (8-10 μm) with a content in the range between 0 and 1.5 wt.% to Sn-9Zn eutectic solder, were examined in order to understand the effect of Ag additions as the particulate reinforcement on the microstructural and mechanical properties as well as the thermal behavior of the newly developed composite solders. Here, an approach to prepare a micro-composite solder alloy by mixing Ag micro-particles with a molten Sn-Zn solder alloy was developed. The composite solder was prepared by mechanically mixing Ag micro-particles into the Sn-9Zn alloy melt to ensure a homogeneous distribution of the reinforcing particles. The distribution of the Ag micro-particles in the matrix was found to be fairly uniform. The Ag particles reacted with the Zn and formed ε-AgZn₃ intermetallic compounds (IMC) in the β-Sn matrix. It was found that the more Ag particles added to the Sn-9Zn solder, the more Ag-Zn compound formed. In the Sn-9Zn/XAg composite solder, the microstructure was composed of AgZn₃ IMC and α-Zn phase in the β-Sn matrix. Interestingly, as the Ag particles in the composite solder increased, the α-Zn phase was found to be depleted from the matrix. The average tensile strength of the composite solders increased with the Ag micro-particles content up to a certain limit. Beyond this limit, the addition of Ag particles actually decreased the strength.