Compatibility of poly(vinyl chloride) with epoxidized copolymers of butadiene-styrene

The compatibility of poly(vinyl chloride) (PVC) with epoxidized styrene-butadiene copolymers is examined at different levels of epoxidation. The copolymers modified were a random (SBR) containing 45 wt% styrene and a triblock (SBS) with 30 wt% bound styrene. Blends were examined in the complete composition range and the approximate levels of epoxidation to ensure blend miscibility were determined. Epoxidized SBS (ESBS) was more effective in miscibility compared with ESBR requiring a lesser degree of epoxidation (43 versus 46 mol%). Tensile properties of the ESBS/PVC blends showed the efficiency of ESBS as a polymeric plasticizer even at levels of epoxidation (ca. 35 mol%) where immiscibility sets in.     

Modeling of the NO x trap and experimental validation using ultra-fast NO x analyzers

The present paper employs and validates a NO _x trap model which attempts an optimum compromise between complexity and predictive accuracy. It is shown that using the same set of kinetic data, the model is able to predict the storage rates and the maximum storage amounts as function of temperature. Moreover, the model predicts with reasonable accuracy the NO breakthrough during rich-mode regeneration and the spontaneous/thermal NO₂ release when the temperature is increased in a saturated catalyst. The experimental findings highlight the importance of transient O₂ adsorption/desorption phenomena which are incorporated in the model. The use of ultra-fast responding NO/NO _x analyzers was necessary for the study and modeling of the transient operation following inlet composition switches.     

Hydrogen production via solar-aided water splitting thermochemical cycles: Combustion synthesis and preliminary evaluation of spinel redox-pair materials

Redox-pair-based thermochemical cycles are considered as a very promising option for the production of hydrogen via renewable energy sources like concentrated solar energy and raw materials like water. This work concerns the synthesis of various spinel materials of the iron and aluminum families via combustion reactions in the solid and in the liquid-phase and the testing of their suitability as redox-pair materials for hydrogen production by water splitting via thermochemical cycles. The effects of reactants' stoichiometry (fuel/oxidizer) on the combustion synthesis reaction characteristics and on the products' phase composition and properties were studied. By fine-tuning the synthesis parameters, a wide variety of single-phase, pure and well crystallized spinels could be controllably synthesized. Post-synthesis, high-temperature calcination studies under air and nitrogen at the temperature levels encountered during solar-aided thermochemical cyclic operation have eliminated several material families due to phase composition instabilities and identified among the various compositions synthesized NiFe₂O₄ and CoFe₂O₄ as the two most suitable for cyclic water splitting – thermal reduction operation. First such thermochemical cyclic tests between 800 and 1400 °C with NiFe₂O₄ and CoFe₂O₄ in powder form in a fixed bed laboratory reactor have demonstrated capability for cyclic operation and alternate hydrogen/oxygen production at the respective cycle steps for both materials. Under the particular testing conditions the two materials exhibited hydrogen/oxygen yields of the same magnitude and similar temperatures of oxygen release during thermal reduction.     

A CFD methodology for the design of sedimentation tanks in potable water treatment: Case study: The influence of a feed flow control baffle

Computational fluid dynamics simulations are employed to assess the effect of adding a vertical baffle at the feed section of a full-scale sedimentation tank for the improvement of solids settling in potable water treatment. A general CFD-based simulation strategy is developed based on the specific features and conditions met in practice for potable water treatment. The linearity of the particle conservation equations allows separate calculations for each particle size class – but performed for all classes of interest – leading to the uncoupling of the CFD problem from a particular inlet particle size distribution. The usually unknown and difficult to be measured particle density is found by matching the theoretical to the easily measured experimental total settling efficiency. The proposed strategy is computationally much more efficient than the corresponding strategies used for the simulation of wastewater treatment. This work compares simulations from a standard and a baffle-equipped tank. It is found that the baffle decreases the inlet recirculation zone and enhances the settling of solids by directing them towards the bottom of the tank with high velocities. It is noteworthy that even small differences in the particle velocity can cause large changes in the percent of settled particles; in this work, the overall solids removal efficiency increased when using the baffle from 90.4 to 98.6% leading to a reduction of the effluent solids concentration of approximately 85%.     

Integrated tilt with active lateral secondary suspension control for high speed railway vehicles

This paper presents a novel active suspension control configuration for high speed tilting railway vehicles which integrates tilt with active lateral secondary suspension. The use of the active lateral secondary suspension is to attenuate the vehicle body lateral vibration on straight track, while complementing tilt action during curving. Various control strategies are proposed to accommodate both tilt and active lateral suspension multiple design requirements, whilst considering the strong interaction between vehicle body roll and lateral modes. Compared with the commercial solutions for tilt control, the proposed integration strategy improves the tilting control performance both on curved and straight track as illustrated by simulation tests and control assessments based on given track profiles.     

Improved kinetic model for water splitting thermochemical cycles using Nickel Ferrite

In a previous work of the authors (AIChE Journal 2013; 59(4): 1213-1225) on the characterization of the performance of redox material compositions during two-step thermochemical splitting of water, it was observed that fitting of the obtained hydrogen and oxygen concentration profiles with a reaction model based on simple first order reaction rates could describe adequately only the first part of the evolution curves. This suggested that more complicated reaction models taking into account the structure of the redox material are needed to describe the whole extent of the experimental data. Based on the above, a minimum set of experiments for water splitting thermochemical cycles over a Nickel-ferrite was deigned and performed involving an increased duration of the reaction steps. A new extended model was derived for the water splitting and thermal reduction reactions, which considers two oxygen storage regions of the redox material communicating to each other by a solid state diffusion mechanism. The inclusion of two state variables instead of one has a significant effect on the reaction dynamics and renders the model capable to explain the dynamics of the convergence of the thermochemical cycles to a periodic steady state, observed experimentally in the previous work.     

Hydrodynamic characteristics in an inverse internal-loop airlift-driven fibrous-bed bioreactor

An inverse internal loop airlift-driven fibrous bed bioreactor (ALFBB) was designed by combining the advantages of an internal loop airlift bioreactor and packed bed bioreactor into one column. This bioreactor, with a high degree of design flexibility, is expected to handle genetically engineered cells as well as fragile cells, which are shear-sensitive. The hydrodynamic characteristics of the combined system have been investigated. Woven cotton was set in the downcomer of the I-IL-ALB to represent the fibrous bed packed bed and the outcome results were compared with those of the polyurethane foam (PUF) packed system and the unpacked I-IL-ALB system. The effects of the packing nature, packing height, packing top and bottom clearances, gaps between adjacent fiber surfaces, and superficial gas velocities were investigated. The hydrodynamic output variables included the gas holdup and liquid circulation velocity. Gas holdup for all packed systems continuously increased with increases in packing height, packing top clearance and superficial gas velocity. It was found highest in the downcomer of the cotton packed system than in the PUF counter part due to the roughness and hydrophilicity of the woven cotton fibrous material. Increased amounts of packing in the I-IL-ALB, whether in the form of cotton or PUF decreased the liquid circulation velocity in the bioreactor because of the increased frictional resistance and tortuosity. The reduction in liquid circulation velocity was significant for large packing with small gaps between fiber surfaces and increased bottom clearances of the cotton packed system. Empirical models based on packing properties are presented which accurately predict the gas holdup, whereas energy based model was proposed to predict liquid circulation velocities. The optimum hydrodynamic conditions were observed with cotton packing.     

Design,characterisation and drug release study of polymeric,drug‐eluting single layer thin films on the surface of intraocular lenses

To design, develop and study a novel drug delivery system for intraocular applications. The spin coating technique was applied to develop a polymeric, drug‐eluting thin film consisting of a blend of organic polymers [poly (D, L lactide coglycolide) lactide: glycolide 75: 25, PLGA and polycaprolactone, PCL] and dexamethasone on the surface of intraocular lenses (IOLs). The initial durability of the IOLs during spinning was assessed. Information about the structural and optical properties of the modified IOLs was extracted using atomic force microscopy, scanning electron microscopy and spectroscopic ellipsometry. A drug release study was conducted for 8 weeks. The IOLs were durable in spinning speeds higher than the ones used to develop thin films. Single‐layer thin films were successfully developed on the optics and the haptics of the lenses. The films formed nanopores with encapsulated aggregates of dexamethasone. The spectroscopic ellipsometry showed an acceptable optical transparency of the lenses regardless of the deposition of the drug‐eluting films on their surface. The drug release study demonstrated gradual dexamethasone release over the selected period. In conclusion, the novel drug‐eluting IOL system exhibited desired properties regarding its transparency and drug release rate. Further research is necessary to assess their suitability as an intraocular drug delivery system.Inspec keywords: ellipsometry, encapsulation, nanoporous materials, spin coating, polymer blends, biodegradable materials, surface treatment, polymer films, atomic force microscopy, transparency, nanomedicine, durability, scanning electron microscopy, drug delivery systemsOther keywords: drug release, intraocular lenses, intraocular applications, spin coating technique, modified IOLs, spectroscopic ellipsometry, dexamethasone release, transparency, drug release rate, intraocular drug delivery system, drug‐eluting IOL system, polymeric drug‐eluting single‐layer thin films, optical properties, structural properties     

Kappa-Carrageenan Gel Immobilisation of Lager Brewing Yeast

Kappa-carrageenan has been found to be a suitable carrier for yeast immobilisation for continuous fermentation systems due to its unique properties. Brewing lager yeast immobilised in kappa-carrageenan beads was studied both in batch and in a continuously fermenting gas lift bioreactor. The cells were monitored over a six month period of continuous fermentation. Viability (methylene blue), immobilised cell concentration and distribution, and the morphological characteristics of the cells (electron microscopy) were investigated. Viability of cells within the beads was found to decline to less than 50% after six months of continuous wort fermentation and maximum bead population did not exceed 10⁹ cells/mL of gel bead.