Morphology and properties of NR/EPDM rubber blends filled with small amounts of titania nanoparticles

This article describes the results of an investigation on the influence of titania nanoparticles on the morphology and properties of vulcanized natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends. The samples were prepared through roll‐milling and melt‐pressing and diphenyl guianidine was used as vulcanization accelerator. The transmission electron microscopy (TEM) and X‐ray diffraction (XRD) results show that the titania particles are concentrated in the NR phase, and that the presence of titania in EPDM seems to initiate the formation of crystals in the rubber phase. From the dynamic mechanical analysis (DMA) and tensile testing results it is clear that the presence of titania particles inhibited the vulcanization process in both the investigated rubbers, and that the mechanical properties of the nanocomposites were influenced by the interaction between the nanoparticles and the rubber, the reduced vulcanization of the two rubber phases, and the development of crystallinity in EPDM. The thermogravimetric (TGA) results show improved thermal stability of EPDM, and of the EPDM phase in the blend, for the samples containing titania nanoparticles. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Determination of mechanical properties of thin films: a theoretical feasibility study

The aim of this work was to determine the principal mechanical parameters of a thin film on a substrate, i.e. Young's modulus, Poisson's ratio, intrinsic stress, and coefficient of linear thermal expansion. First, standard experiments possibly suitable for this purpose were investigated theoretically. The margin of error of the mechanical parameters determined was estimated as dependent on the geometrical conditions, substrate properties, and error in the respective measurements. In addition, the homogeneity and stability of the parameters were taken into account, for instance inhomogeneity of the film thickness and possible modification of substrate parameters during film growth. To obtain meaningful results, the accuracy of the measurements as well as the homogeneity and stability of several geometrical and physical parameters in general must be extremely high. However, the experimental conditions were found to fulfill these requirements.     

Autogenous welding of Hastelloy X to Mar-M 247 by laser

Mar-M 247, a nickel-base cast alloy, is used widely in aeroengines for parts such as blades, vanes and airfoil. Hastelloy X is one of the most oxidation- and corrosion-resistant nickel-base wrought alloys. In order to join such alloys in aeroengine manufacturing, laser beam welding has been carried out with lap and butt joints using a 1.2 and a 6.0 kW CO₂ laser. Cracks in the fusion zone can be eliminated by deliberate misalignments in the ranging of the laser beam by 0.2−0.3 mm onto Hastelloy X. Correlations between cracking behavior, hardness of the beads and misalignments have been investigated. Metallurgical analysis using electron microscopes has revealed the redistribution of alloy elements, the microstructures of the fusion zone and microfissures in the heat-affected zone (HAZ).     

Structural Insights into the Recognition of N2‐Aryl‐ and C8‐Aryl DNA Lesions by the Repair Protein XPA/Rad14

Aromatic amines are strongly carcinogenic. They are activated in the liver to give reactive nitrenium ions that react with nucleobases within the DNA duplex. The reaction occurs predominantly at the C8 position of the dG base, thereby giving C8‐acetyl‐aryl‐ or C8‐aryl‐dG adducts in an electrophilic aromatic substitution reaction. Alternatively, reaction with the exocyclic 2‐NH₂ group is observed. Although the C8 adducts retain base‐pairing properties, base pairing is strongly compromised in the case of the N² adducts. Here we show crystal structures of two DNA lesions, N²‐acetylnaphthyl‐dG and C8‐fluorenyl‐dG, within a DNA duplex recognized by the repair protein Rad14. The structures confirm that two molecules of the repair protein recognize the lesion and induce a 72 or 78° kink at the site of the damage. Importantly, the same overall kinked structure is induced by binding of the repair proteins, although the structurally different lesions result in distinct stacking interactions of the lesions within the duplex. The results suggest that the repair protein XPA/Rad14 is a sensor that recognizes flexibility. The protein converts the information that structurally different lesions are present in the duplex into a unifying sharply kinked recognition motif.     

Pulsatile Jet Cleaning of Filter Cloths Contaminated with Yeast Cells

The cleaning of filter cloths is necessary to avoid prolonged system downtime and strong fouling. Reliable cleaning concepts are central to the removal of residues from the complex surface of filter cloths. Particle residues, in particular, play a decisive role in the sufficiency of the cleaning performance. Consequently, enhanced particle‐removal cleaning concepts based on pulsatile jets for filter cloths have been developed. By varying the cleaning parameters, it has been demonstrated that increased pulse numbers and velocities improve the cleaning performance. Furthermore, this promising cleaning concept cleaned more effectively than conventional methods. The reduction in the amount of detergent needed is an ecological and economic advantage of pulsatile cleaning.     

Effect of Coal Type and Residence Time on the Submicron Aerosol Distribution from Pulverized Coal Combustion

Three types of pulverized coal were burned in a laboratory furnace under various combustion configurations. Pulverized samples of Utah bituminous, Beulah (North Dakota) lignite, and Texas lignite coals were burned at a rate of 2.5 kg/hr in a laboratory furnace. Aerosol size distributions were measured at various positions within the convection section, and temperature and gas compositions were measured throughout. The evolution of the submicron particle size distribution within the convection section for the three coals was similar, although the location of the initial particle mode at the convection section inlet varied with coal type. While staged combustion of Utah bituminous coal had a variable effect on the volume of submicron aerosol produced, staged combustion of the lignites caused a definite increase in the submicron aerosol volume. Vapor enhancement due to a localized reducing atmosphere, which would effect coals of higher ash volatility, is thought to explain this behavior.     

Mathematical Description of Experimentally Determined Charge Distributions of a Unipolar Diffusion Charger

The charge distributions of an improved opposed flow unipolar diffusion charger were measured using a tandem differential mobility analyzer (DMA) set up in a size range of approximately 20–400 nm. The charger is intended to be used in a portable aerosol sizer to measure particle size distributions. The determined charge distributions were represented by lognormal distributions, and a set of equations and coefficients was developed to calculate the charge distributions. These equations can be easily implemented in software for size distribution measurements. The agreement between the mathematically derived and measured charge distributions is very good, with regression coefficients R ² > 0.96. The investigations showed that approximately 55% of 20-nm particles remain uncharged, while up to 25 elementary charges need to be considered for multiple charge correction of 400-nm particles. Comparison with the Fuchs theory delivered satisfying agreement with the measured average charge levels, but charge distributions cannot be described by the Fuchs theory, likely caused by the charger geometry.

Copyright 2012 American Association for Aerosol Research     

Benign oxidants and single-site solid catalysts for the solvent-free selective oxidation of toluene

Two types of single-site heterogeneous catalysts have been designed so as to facilitate either the side-chain oxidation or ring-hydroxylation of toluene in O₂ (solvent-free) or by employing aqueous (H₂O₂) or organic (cumene hydroperoxide) hydroperoxides in high yield. The use of H₂O₂ and cumene hydroperoxide in particular, facilitates the ring-hydroxylation of toluene when zeolite-encapsulated metal complexes, such as perhalogenated or tetra-nitro-substituted phthalocyanines, are used as catalysts. Nanoporous, redox molecular sieves, display a higher tendency for the side-chain oxidation of toluene with air as an oxidant, with benzoic acid as the predominant product.     

Tungsten hexacarbonyl and hydrogen peroxide as precursors for the growth of tungsten oxide thin films on titania nanoparticles

W(CO)₆ and H₂O₂ were used in an atomic layer deposition (ALD)‐like process to grow thin WO_x films onto TiO₂ powders in a fluidized bed reactor. Carbonyl precursors are not widely used in this application, so that deviations from an ideal ALD process, previously not examined with W(CO)₆, were identified. The resulting WO_x films were a result of both ALD‐like and chemical vapor deposition‐based growth modes. A chemical reaction mechanism incorporating a combination of these two growth modes was inferred. As the move to expand the range of ALD precursors meets with the desire to scale up these processes, the simultaneous appearance of both these growth modes is likely to become more and more common, and so understanding the interaction of these two types of surface reactions is key to progress in the field. The films were observed to inhibit the anatase‐to‐rutile phase transformation in the TiO₂ powders upon high temperature annealing, while crystallization of the amorphous WO₃ was also not observed. Changes in the local bonding within the WO₃ were observed and associated with changes in the structural nature of the film and its interface to the substrate. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1278–1286, 2014     

Small‐Molecule Proteomimetic Inhibitors of the HIF‐1α–p300 Protein–Protein Interaction

The therapeutically relevant hypoxia inducible factor HIF‐1α–p300 protein–protein interaction can be orthosterically inhibited with α‐helix mimetics based on an oligoamide scaffold that recapitulates essential features of the C‐terminal helix of the HIF‐1α C‐TAD (C‐terminal transactivation domain). Preliminary SAR studies demonstrated the important role of side‐chain size and hydrophobicity/hydrophilicity in determining potency. These small molecules represent the first biophysically characterised HIF‐1α–p300 PPI inhibitors and the first examples of small‐molecule aromatic oligoamide helix mimetics to be shown to have a selective binding profile. Although the compounds were less potent than HIF‐1α, the result is still remarkable in that the mimetic reproduces only three residues from the 42‐residue HIF‐1α C‐TAD from which it is derived.