Diffusion of low molecular weight substances into a fiber with skin-core structure—rigorous solution of the diffusion in a coaxial cylinder of multiple components

The diffusion equation of low molecular weight substances (penetrant) into a coaxial cylinder of multiple components (m) was formulated in general and solved rigorously. As the simplest but a practical case of m = 2, which corresponds to the diffusion of penetrant into fibrous material with skin and core structure, the diffusion of penetrant was analyzed in detail. That is, changes in the penetrant concentration distribution within the coaxial dual cylinder of skin and core components and the total amount of penetrant sorbed within the cylinder both with time after exposing the cylinder to atmosphere of fixed penetrant concentration of C_out were calculated with variation of the diffusion coefficient ratio (D₁/D₂) and the radius ratio (R₂/R₁), where D₁ and D₂ are the diffusion coefficients of penetrant in the core and the skin, and R₂ and R₁ are the radii of the fibrous material and the core, respectively. Keeping (R₂/R₁) at a constant value of 1.2 but varying (D₁/D₂) from 10⁴ to 10^?2, the penetrant concentration distribution was calculated and found to be much different particularly within the core between (D₁/D₂) > 1 and (D₁/D₂) < 1. The sorption curves were also found to deviate in their respective ways from that of Fickian curve of a homogeneous cylinder with (D₁/D₂) = 1 except at initial stage of sorption. Further, by keeping (D₁/D₂) constant but varying (R₂/R₁) from 1.1 to 1.5, the effects of relative skin thickness upon the sorption curve were studied.     

Morphology and orientation of MoS2 clusters on Al2O3 and TiO2 supports and their effect on catalytic performance

The catalytic performance of MoS₂-based hydrotreating catalysts strongly depends on their morphology and orientation on the support. The effects of the morphology and orientation of MoS₂ clusters on supports, typically Al₂O₃ and TiO₂, on the catalytic performance are reviewed here, focusing on recently reported epitaxial relationships at the interface between MoS₂ clusters and the support.     

Preparation and characterization by thermal analysis of magnetic latex particles

Emulsion polymerization of styrene and methyl methacrylate in the presence of a ferrofluid was briefly studied. Thermal properties of the resulted latex particles were investigated by TG–DTA analysis. Determination of the residue weight after the thermal analysis that indicated complete decomposition of the organic components was found to be a facile and practical method to determine the magnetite content in the latex particles. The method was applied to magnetic polystyrene latex particles prepared in the presence of various amounts of the ferrofluid. Analysis of the results suggested that the magnetic content in the latex particles is primarily determined by the weight ratio of the ferrofluid to monomer. © 1993 John Wiley & Sons, Inc.     

Ranges of low energy 119Sb and 125I in metals

Mean ranges of ¹¹⁹Sb in tin and ¹²⁵I in copper have been measured for the energy region of 10 keV to 60 keV by using the samples prepared by ion-implantation of these nuclides into vacuum-evaporated layers of metals. The observed ranges are in good agreement with those predicted by the theory of Lindhard et al. for 0.1 > ? > 0.02, but they are slightly smaller for 0.02 > ? > 0.01 in terms of the dimensionless energy ?.     

Bacterial detection based on polymerase chain reaction and microbead dielectrophoresis characteristics

In this study, an electrical DNA detection method was applied to bacterial detection. DNA was extracted from bacteria and amplified by polymerase chain reaction. The microbeads were labelled with amplicons, altering their surface conductance and therefore their dielectrophoresis characteristics. Amplicon‐labelled microbeads could thus be trapped within a high‐strength electric field, where they formed a pearl chain between the electrodes, resulting in an increased conductance between the electrodes. This method reduces the amplicon detection time from 1–2 h to 15 min, compared with the conventional method. The presented method realised quantitative detection of specific bacteria at concentrations above 1 × 10⁵ and 2.4 × 10⁴ CFU/ml for bacterial solutions with and without other bacterial presence, respectively.Inspec keywords: microorganisms, enzymes, molecular biophysics, biochemistry, electrophoresis, bioelectric phenomena, DNA, biosensors, electrochemical electrodes, electrochemical sensors, microsensors, bioMEMS, surface conductivityOther keywords: bacterial detection, polymerase chain reaction, microbead dielectrophoresis characteristics, electrical DNA detection, surface conductance, amplicon‐labelled microbeads, high‐strength electric field, pearl chain, electrodes, amplicon detection time, quantitative detection, bacterial solutions, time 15 min to 2 h     

Model predictive control of directed‐graph constrained systems

This paper addresses a new type of model predictive control problem for a hybrid system that consists of a continuous‐time linear system and a temporal/spatial directed graph, called a directed‐graph constrained system. Motivated by the obstacle avoidance problem, the problem is newly formulated, where the continuous‐time control input and the waypoints of the state are simultaneously optimized under a temporal/spatial directed graph as well as input/state linear constraints, and a method for efficiently solving this problem is developed. Numerical examples are presented to verify that the proposed approach is effective. Copyright © 2013 John Wiley & Sons, Ltd.     

Static and dynamic deformation mechanisms of a high-density polyethylene having rownucleated crystalline texture of a-axis orientation as observed by orientation distribution function of crystallites

The rheo-optical properties of a high-density polyethylene having a row-nucleated crystalline texture of a-axis orientation were investigated in the machine direction (MD) and transverse direction (TD) of fabricating the specimen. The tensile complex dynamic compliance function $\text{J1}$ displays two dispersions designated as the α₂ and α₂ mechanical retardation processes with activation energies of about 21 and 35 kcal mol^?1, respectively, for both MD and TD specimens, and the complex dynamic stress-optical coefficient function $\text{M1}$ exhibits a single discrete dispersion designated as the α optical retardation process with an activation energy of about 24 kcal mol^?1 for both specimens over the same frequency and temperature ranges as those covered for the dynamic mechanical measurements. The real and imaginary components of $\text{M1}$ converge from positive values to almost zero at the highest frequencies and lowest temperatures covered for both specimens, with the exception of the real component of the MD specimen which converges to a small but definitely negative value. The analysis of this anomalous behaviour of the MD specimen in terms of the optical retardation time spectrum has ascribed the negative convergence to a negative form birefringence that arises from a dynamic lamellar splaying or bending process responding in phase with the dynamic bulk stress. The dynamic X-ray diffraction studies have revealed the α optical dispersion and possibly the α mechanical dispersion to be mostly attributed to the crystal orientation dispersions involving intralamellar shearing processes, i.e. detwisting and tilting processes of the lamellar segments for the MD and TD specimens, respectively. The optical dispersion, if any, associated with the lamellar splaying or bending process may be expected at higher frequencies or lower temperatures than those covered here to assign the β mechanical dispersion to the interlamellar shearing process.     

A study on hydroxyl groups in polyethylene

The possibility of the presence of hydroxyl groups in polyethylene molecular chains has been investigated in observations of infrared spectra of O? H and C? O stretching vibrations in olefinic molecular chains. n-Paraffins and fresh medium-pressure process polyethylenes containing the primary alcohols were used as a model of polyethylene containing hydroxyl groups in the molecular chains. The characteristic wavenumber of the hydroxyl groups slightly contained in the polyethylene in the region 3600–3200 cm^?1 becomes constant over about 10 of carbon-atom number of the alcohols, approximately 3336 cm^?1. The wavenumber does not agree with ～3370 cm^?1, which has been hitherto assigned to hydroxyl groups in polyethylene molecular chains. Although the absorption due to the hydroxyl groups must appear in the region of C? O stretching band in the vicinity of 1050 cm^?1 if the absorption around 3370 cm^?1 is due to the hydroxyl groups, the absorption has not been observed. Changes in infrared spectra of polyethylene absorbing water as much as 10 ppm corresponding to the water absorbing capacity are not observed in comparison with those of extremely dried polyethylene. It is concluded that the absorption at 3370 cm^?1 in polyethylene is not due to the hydroxyl groups and that the groups are not contained at least in fresh polyethylene.     

Nickel-containing catalysts for hydroprocessing of aromatic oils

A series of nickel-containing catalysts was prepared by a sequence of impregnation and calcining steps using a γ-alumina support. The calcined catalysts were reduced in a flow of hydrogen and mixtures of hydrogen with hydrogen sulfide. Both the calcining temperature and nickel loading strongly influenced the hydrogenation activity. The changes in surface species which resulted from some of the preparation steps were identified by spectroscopy. The catalysts containing nickel without molybdenum were quickly poisoned by sulfur, but a certa in sulfur tolerance was achieved by a two-step impregnation and calcining procedure. Improved hydrogenation activity and high hydrogenation vs. hydrocracking selectivity of nickel—molybdenum catalysts were obtained with relatively low loading of molybdenum and high loading of nickel. A three-step impregnation and calcining procedure appeared to produce the most effective catalysts.     

Recent advances in high temperature catalytic combustion

Catalytic combustion of methane has been investigated for the application to gas turbines. As the combustion is operated at high temperatures and high space velocity, heterogeneous reaction and surface-initiated gas phase reaction proceed concurrently. Thermal resistance to maintain large surface area is, therefore, requested to attain high combustion efficiency above 1000°C. Hexaaluminate compounds were effective in maintaining large surface area. On the other hand, palladium catalysts were generally employed for the combustion of methane below 1000°C. The prototype catalyst combustors were successfully tested with their high combustion efficiency and low NO_x emission by using Pd based- and/or hexaaluminate catalysts.