Porcine pancreatic lipase immobilized on polysiloxane–polyvinyl alcohol hybrid matrix: catalytic properties and feasibility to mediate synthesis of surfactants and biodiesel

Polysiloxane–polyvinyl alcohol hybrid matrix was prepared by a sol–gel technique and its capacity to bind porcine pancreatic lipase investigated. The loading of 250 units g^?1 support was shown to be effective, resulting in an immobilized lipase with high catalytic activity. Both free and immobilized lipases were characterized by determining the activity profile as a function of pH, temperature, substrate concentration and thermal stability. Application of the immobilized lipase in non‐conventional biocatalysis for the synthesis of surfactants and biodiesel was also analyzed. Production of sugar fatty acid esters was found to be dependent on the carbohydrate and the highest molar conversion (50% in 3–4 h of reaction) was achieved for substrates containing fructose and lauric or oleic acids. Biodiesel synthesis from babassu oil and ethanol, propanol or butanol was feasible and regardless of the kind of alcohols, results revealed that the immobilized PPL could efficiently convert triglycerides to fatty acid alkyl esters attaining yields varying from 75 to 95%. Copyright © 2007 Society of Chemical Industry     

A multi-agent architecture for plug and produce on an industrial assembly platform

Modern manufacturing companies face increased pressures to adapt to shorter product life cycles and the need to reconfigure more frequently their production systems to offer new product variants. This paper proposes a new multi-agent architecture utilising “plug and produce” principles for configuration and reconfiguration of production systems with minimum human intervention. A new decision-making approach for system reconfiguration based on tasks re-allocation is presented using goal driven methods. The application of the proposed architecture is described with a number of architectural views and its deployment is illustrated using a validation scenario implemented on an industrial assembly platform. The proposed methodology provides an innovative application of a multi-agent control environment and architecture with the objective of significantly reducing the time for deployment and ramp-up of small footprint assembly systems.     

A theoretical analysis of a buffer frame size conversion algorithm for audio applications ensuring minimum latency

In implementing digital signal processing (DSP) algorithms for audio real-time applications, one is frequently faced with problems regarding incompatibilities between the hardware buffer length (the internal buffer of a professional sound card) and the software buffer size imposed by the underlying algorithm (due to i.e. multirate or FFT constraints). This mismatch is solved by proper frame size conversion algorithms which inevitably introduce delay. In this context, this paper presents a buffering scheme together with a theoretical proof of the minimum delay property shown by it. Some examples derived from frequently encountered issues in DSP applications are reported.     

Dynamical Behavior in a DPCM System with an Order 2 Predictor. Case of a Constant Input

This paper deals with a differential pulse code modulation (DPCM) transmission system. It includes an encoder which uses a coupling between a transversal predictor and a nonlinear quantizer. This paper studies, from a dynamical point of view, an order 2 DPCM system modeled via a noninvertible two-dimensional map. Chaotic phenomena can be observed; depending on the kind of application, it can be interesting to avoid chaos or to use it. In both cases, it is necessary to understand the mechanisms which give rise to it. For that, the usual tools of chaotic dynamics are used (bifurcation structures, critical and invariant manifolds).     

CFD simulations of hydrogen combustion in a simplified EPR containment with CFX and REACFLOW

The prediction of over-pressures and temperatures that are generated by hydrogen explosions in case of a severe nuclear accident is a crucial stage of the safety analysis of the containment. The investigation presented in this paper is a continuation of the numerical studies of validation and benchmarking that were carried out in the European co-sponsored project HYCOM. In the present work, numerical simulations of hydrogen deflagrations within a simplified, real-scale European Pressure Reactor (EPR) containment have been performed with two CFD codes, CFX4 and REACFLOW. The analysis has been focused not only on overpressure peaks and pressure oscillations, but also on pressure differences between the two sides of the same wall of internal compartments. Different geometrical configurations have been considered in term of presence of vents between internal compartments and in term of vents number, size and position. Single and multiple ignition points have also been taken into account. The paper describes the main results of the investigation and it is a demonstration of how CFD modelling can provide significant indications for real-scale safety applications within the limits of uncertainty of the accident scenarios.     

Robust design via simulation experiments: a modified dual response surface approach

The existing procedures for robust design, devised for physical experiments, may be too limiting when the system can be simulated by a computer model. In this paper we introduce a modification of the dual response surface modelling, which incorporates the option of stochastically simulating some of the noise factors when their probabilistic behaviour is known. Our method generalizes both the crossed and the combined array approaches and finds a natural application to integrated parameter and tolerance design. The method appears suitable for designing complex measurement systems and in this paper is applied to the design of a high‐precision optical profilometer. Copyright © 2008 John Wiley & Sons, Ltd.     

New photoactive oligo- and poly-alkylthiophenes

A new type of ω-methoxy-functionalized oligo-(OCT) and poly-(PQ) hexylthiophene characterized by a tetrameric repeating unit was synthesized and characterized. The configurational regularity and the mean degree of functionalization per thiophenic ring, lower than in commonly synthesized PATs, permitted the obtainment of more ordered chain conformations especially in the solid (film) state. Solar cells based on OCT and PQ films (as p-donor polymeric layer) mixed with Single-walled Carbon Nanotubes (SWCNTs, used as electron-acceptor system) were prepared and investigated. A power conversion efficiency of 0.52% with a fill factor of 0.42, an open-circuit voltage of 0.48 V and a short-circuit current of 1.93 mA/cm² under 70 mW/cm² white light illumination is reported for the polymeric sample. The obtained performance is comparable with that of devices made with regioregular P3HT but the easiness of the monomer synthesis and polymer preparation, giving OCT and PQ with good yields, as well as the enhanced workability and filmability of the latters from diluted solutions of common organic solvents together with their low sensitivity to the environmental conditions (air oxygen, moisture, temperature) makes the synthesized materials very promising for the set-up of polymer photovoltaic cells.     

Nondegradative microextrusion of resorbable polyesters for pharmaceutical and biomedical applications: The cases of poly‐lactic‐acid and poly‐caprolactone

In recent years biodegradable polymers, particularly polyesters such as the poly(lactic acid) (PLA) and polycaprolactone (PCL), have gained high interests for their applicability in the biomedical and pharmaceutical fields where they're used for manufacturing various different resorbable devices, from tissue engineering scaffolds to controlled drug release systems. Despite many positive characteristics, processability of these materials still remains a critical issue as they easily tend to degrade during manufacturing. In this article we aimed to assess microextrusion as a nondegradative process for manufacturing PLA and PCL. The results we experimentally obtained, that are hereby presented, set a new point in the on‐going debate on degradation during processing of resorbable polymers as they allow to affirm that microextrusion leaves unmodified molecular weight distributions without producing any evident reductions in mean molecular weight. Microextrusion thus represents a risk‐free high molecular weight polymer processing solution for obtaining nondegraded products within pharmaceutical and biomedical production lines, such as for scaffolds for tissue engineering applications or drug delivery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008