Wyniki wyszukiwania - Biblioteka Nauki

1

Simplified solution of lactate dehydrogenase catalysed reaction

100%

Kuczek M.

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nr 2

EN

The lactate dehydrogenase catalysed reaction shows lag phase. This lag phase is easy for explanation if the consecution of first and second order equilibrium reactions were assumed for calculation of pyruvate trace concentration. The same explanation was accepted for calculation of significant pyruvate concentration. For calculation significant pyruvate concentration the consecution of simple Michaelis - Menten type and second order reactions was assumed. The exact solution of reaction rate equations system for this complex reaction was counted.

2

Application of lipase in shaping Al2O3-mullite composites

51%

Szafran M. , Bednarek P. , Piwowarski P.

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tom R. 11, nr 1

90-94

EN

The paper presents the method of Direct Coagulation Casting (DCC) which is a recently developed method of near-netshaping of ceramic components at low costs. The process relies on electrostatic stabilized ceramic suspensions and their destabilization owing to time delayed in situ reactions. In the method, the enzyme-catalized reaction is used to shift the pH of the ceramic suspension to the isoelectric point, which causes coagulation of the slurry. The aim of this work is the research on shaping alumina-mullite composites with the application of a lipase-catalyzed decomposition of glycerin triacetate. Zeta potential measurements in relation to pH were performed and the appropriate substrate and enzyme was chosen to conduct controlled coagulation of ceramic slurry. In the DCC method, the optimal composition of ceramic suspension was experimentally chosen. The slip gaining a high concentration of ceramic powders, small amount of organic additives, good flow properties and the shortest time after which the intensive increase of viscosity, was considered as optimal. The paper also presents the results of the viscosity of slurries with different concentrations of dispersant and lipase. The sintering temperature leading to the best density and mechanical strength parameters was found to be 1600°C. The relative densities of DCC sintered samples were higher than 95%. The Vickers hardness and fracture toughness KIC for DCC sintered samples were measured. The main conclusion is that the DCC method, using the lipaze-catalyzed decomposition of glycerin triacetate, can be successfully applied to the formation of complex-shaped alumina-mullite composites. Very good mechanical properties can be achieved due to the low content of binders and other additives.

PL

W ostatnich latach prowadzone są intensywne badania nad zastosowaniem technik formowania elementów ceramicznych opartych na układach koloidalnych. Do jednych z takich metod należy bezpośrednie odlewanie koagulacyjne (Direct Coagulation Casting, DCC), dzięki któremu można formować elementy o skomplikowanej geometrii, stosując ceramiczne masy lejne o wysokim stężeniu fazy stałej i małej ilości dodatków organicznych. Metoda DCC jest alternatywą dla formowania metodą wtrysku, wymagającą stosowania wysokich ciśnień oraz znacznej ilości dodatków organicznych oraz dla tradycyjnego formowania przez odlewanie do porowatych form gipsowych. W artykule przedstawiono wyniki badań nad formowaniem kształtek z kompozytów tlenek glinu-mullit z wykorzystaniem reakcji enzymatycznego rozkładu trójoctanu glicerolu lipazą. Wykonano pomiary potencjału zeta w funkcji pH dla czystych proszków tlenku glinu i mullitu oraz dla kompozytu wraz z pozostałymi składnikami ceramicznej masy lejnej. Na podstawie otrzymanych wyników dobrano substrat oraz enzym, pozwalające na przeprowadzenie kontrolowanej koagulacji masy lejnej. Na drodze eksperymentalnej dobrano optymalny skład masy lejnej tak, aby lepkość układu była stosunkowo niska, a czas koagulacji masy relatywnie krotki. Przedstawiono wyniki pomiarów lepkości ceramicznych mas lejnych w funkcji czasu dla rożnych ilości upłynniacza i lipazy w masie. Otrzymane elementy spieczono w temperaturze 1600°C. Uzyskano spieki o gęstości względnej powyżej 95% oraz o wysokich wartościach twardości mierzonej metodą Vickersa i odporności na kruche pękanie KIC mierzonej metodą pomiaru długości pęknięć wykonanych wgłębnikiem diamentowym Vickersa.

3

System-level modeling of a Lab-On-Chip for micropollutants detection

51%

Guiton S. , Rezgui A. , Madec M. , Lallement C. , Rufi F. , Haiech J.

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tom Vol. 5, nr 3

116--125

EN

The issue addressed by this paper is system-level modeling of Lab-On-Chip (LOC) level. These microsystems integrate within a single chip many functions from several domains such as electronics, thermic, biochemistry or microﬂuidics. The modeling of these systems in a single environment and the interface between different domains is very challenging. In this paper, we propose some methods to model the entire system in VHDL-AMS. The models are developed and assembled from elementary building blocks, with a validation through experiments or numerical simulation on a reference tool, toward the complete LOC. For each domain, the modeling methodology is described. The principle is applied to a specific use case: a LOC designed for the detection of micro-pollutants in drinking water. It is based on the ELISA test leading to a pH-shift which is in turn detected by an Ion-Sensitive Field Effect Transistor (ISFET). In the last part of the paper, the ﬁrst results obtained with the complete zero-order model of the LOC are described. Of course, this model has to be improved in order to be faithful to the actual LOC but it will undoubtedly be a major asset for the optimization and reliability improvement of the LOC.