Structure development in biaxially stretched polystyrene film: Part II. Theoretical analysis of orientation development

The present paper describes an analysis of the orientation developed in biaxially stretched polystyrene films in terms of the kinematics of the process and a viscoelastic constitutive equation. It was possible to achieve reasonable agreement of predicted and experimental birefringences through use of a convected Maxwell model and the Rheo-Optical Law.     

The influence of drawing,twisting, heat setting and untwisting on the structure and mechanical properties of melt spun polypropylene filament

The changes in structure and mechanical properties of melt spun polypropylene filaments were determined as the filaments were successively (i) drawn, (ii) twisted, (iii) annealed, and (iv) untwisted. Filaments spun to two different melt draw down levels were studied. The effects of draw temperature and draw ratio, extent of twist, annealing temperature, and the extent of untwisting were examined. Melt spun and twisted filaments (draw ratio of 1) were also considered. Structural characterization techniques used in this study include wide angle (WAXS) and small angle (SAXS) diffraction, scanning electron microscopy (SEM), birefringence and density measurement. Drawing increased crystalline orientation and at low temperatures disrupted the monoclinic unit. cell existing in the melt spun fibers. The drawing produced considerable fibrillation under all conditions even when carried out at 120°C. The fibrillation quid void formation due to low temperature drawing was more pronounced. The variation of WAXS patterns and mechanical properties of twisted drawn filaments was interpreted by presuming that the fibrils act in a manner analogous to that of the filaments in a continuous filament twisted yarn. In the case of incompletely drawn filaments the effect of additional drawing occurring during twistin must be considered. Twisted fibers annealed at 150°C sowed a drastic reduction in tensile properties, while those annealed at 125°C did not set the twist and caused the fibers to tend to untwist. Annealing at 140°C appeared to give satisfactory heat setting. Annealing of cold drawn and cold drawn and twisted fibers increased the density, removed many defects and reformed a well defined monoclinic crystal structure and a lamellar morphology. Untwisting of heat set filaments tended to give back the properties of hot drawn fibers. In some cases, however, the opening of cracks was noted.     

Diffusion on Some Simple Stratified Spaces

A variety of different imaging techniques produce data which naturally lie in stratified spaces. These spaces consist of smooth regions of maximal dimension glued together along lower dimensional boundaries. Diffusion processes are important as they can be used to represent noise in statistical models on spaces for which standard parametric probability distributions do not exist. We consider particles undergoing Brownian motion in some low dimensional stratified spaces, and obtain analytic solutions to the heat equation specifying the distribution of particles. These solutions play the role of prototypical distributions for studying behaviour near singularities. While probabilistic reasoning can be used to solve the heat equation in some straightforward cases, more generally we construct solutions from eigenfunctions of the Laplacian. Specifically, we solve the heat equation on: open books; two-dimensional cones; the Petersen graph with unit edge length; and the cone of this graph which corresponds to a space of evolutionary trees.     

High aspect ratio gold nanopillars on microelectrodes for neural interfaces

Microelectrode arrays (MEA) have become an established tool in applied and fundamental research. Low impedance at the interface between tissue and conducting electrodes is of utmost importance for the electrical recording or stimulation of electrophysiological active cells such as cardiac myocytes and neurons. A common way to improve this interface is to increase the electrochemically active surface area of the electrode. In this paper the fabrication of microelectrodes covered with very high aspect ratio (AR > 100) gold nanopillars is presented and electrode biocompatibility is investigated using cell culture experiments. The nanopillar electrodes show decreased impedance over the entire scanned frequency range of 1 Hz–100 kHz and an impedance improvement of up to 89.5 at 1 kHz depending on nanopillar height. Neurons adhere well to the substrate and electrodes and signals with amplitudes up to ten times higher than with conventional gold electrodes were recorded in cell culture experiments.     

Water-induced effects of hydrogen adsorption on Ru(001)

Adsorption and desorption of hydrogen and coadsorption of H₂ with H₂O and CO over Ru(00l) surface have been studied under UHV conditions using the technique of TDS. Surface hydrogen interacts with adsorbed water resulting in an additional desorption state at 510 K which is not easily displaced by CO, but the total number of adsorption sites for hydrogen adsorption is independent of the amount of H₂O predosed at room temperature. Hydrogen adsorption is blocked easily by CO dose (more than 0.5 L) or a small amount of O(a) formed from dissociative adsorption of water, and adsorbed hydrogen formed in the absence of significant water is easily displaced by CO dose at even room temperature.     

Mössbauer studies of illites and heat-treated illite as related to coal-conversion processes

Mossbauer spectra of iron species in the following illites were studied: Grundite, Fithian, Minerva, and New Albany. Spectra of samples of Fithian illite heated at temperatures of 225, 700, and 1000 °C were also obtained. Analyses of these spectra provide Mössbauer parameter values of iron species in the illites and heat-transformed illite for comparison with similar species found in coals containing illites and in coal process residues derived from them. The illites contain both ferric and ferrous species. Mössbauer parameters for one of the ferric species, designated M(2), are virtually the same as those of pyrite. The two species are therefore difficult to distinguish from one another. Values of the concentration of pyrite in coals and shales may be inflated if the pyrite concentration is measured by Mössbauer spectroscopy. Mössbauer spectra of the heat-treated illite samples reveal changes in iron distribution, principally at the 700 and 1000 °C levels, where there are found three and six different iron species respectively. These changes are accompanied by reduction of ferric to ferrous iron. This process should be integrated into any assessment of the iron chemistry which accompanies coal-conversion processes.     

Investigation of structure development in polyamide 11 and polyamide 12 tubular film extrusion

The processability of single bubble polyamide 11 and polyamide 12 films was investigated. The development of crystalline structure and chain orientation of polyamide 11 and polyamide 12 films in single bubble film blowing was studied by differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXS), infrared (IR) spectroscopy, and birefringence. DSC measurements of both films revealed a spontaneous increase in glass transition temperature (T_g) and cold crystallization temperature (T_c) during aging at room conditions, with crystallinity and melting point remaining constant. Single bubble polyamide 11 and polyamide 12 films exhibited triclinic α and monoclinic γ crystals, respectively. The level of biaxial orientation was evaluated by calculating White‐Spruiell biaxial orientation factors with pole figure data. We were not able to produce biaxially oriented double bubble films with either polyamide 11 or polyamide 12.     

Prediction of DNA-binding regulatory proteins in bacteriophage T7

The high-resolution structure of several specific DNA-bindingproteins have been determined, and they display a common structuralmotif which mediates their binding to DNA. This motif consistsof two -helices connected by a sharp turn, and its amino acidsequence has several distinguishing features. A computer searchof the proteins coded by the genome of bacteriophage T7 hasbeen performed in an attempt to identify those proteins thatpotentially contain this motif. Eight proteins were found tohave regions similar to that of the motif. Of these, three arerelatively small, have no known function and are good candidatesfor being DNA-binding regulatory proteins. The methods describeduse commonly available computer programs and databases, andare therefore easy to implement.     

Mass transport effects on the electrodeposition of iron-nickel alloys at the presence of additives

Iron-nickel (Fe-Ni) plating bath solution chemistry was studied by determining the Fe-Ni equilibrium concentrations at various pH levels. It was found that the alloy composition is determined by solution equilibria, mass transfer of the electroactive species within the diffusion layer and by the surface coverage of the additives on the electrode. The effect of the rotation speed of the disc electrode and the presence of organic additives on the deposition of Fe-Ni alloys are evaluated. Boric acid increases the absolute iron deposition rate, while it inhibits the rate of nickel reduction. Saccharin and ethylene diamine influence the metal deposition rate but are not as effective as boric acid.