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Abstract  

Semi-batch reactors are widely spread in the fine chemicals and specialties industry. The reason is that, compared to the pure batch operation, the feed of at least one of the reactants provides an additional way of controlling the reaction course, which represents a safety factor and increases the constancy of the product quality. Process temperature and feed rate can be optimized to satisfy safety constraints, i.e. cooling capacity and allowable accumulation. An economically better way of operating a semi-batch reactor is to adapt the feed rate to the allowed accumulation of reactants. An experimental method based on calorimetry will be presented and illustrated by an example.

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The acidic visualization methods most often used for steroids have been optimized and compared. Sulfuric acid at three different concentrations, phosphomolybdic acid, and phosphoric acid, with different heating temperatures for different times, have been examined as reagents for visualization of seven steroids separated by OPLC on HPTLC silica gel as adsorbent. For sulfuric and phosphoric acids the chromatograms were evaluated by inspection under long-wavelength UV light (366 nm). For phosphomolybdic acid the chromatograms were evaluated in daylight. It was found that visualization at higher temperatures for shorter periods usually results in greater sensitivity, although heating for longer periods at lower temperatures results in a more stable, robust visualization.

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Acta Biologica Hungarica
Authors: C. Lizette Del-Toro-Sánchez, S. Villaseñor-Alvarado, Florentina Zurita-Martínez, O. Castellanos-Hernández, Araceli Rodríguez-Sahagún, M. Isabel Torres-Morán, D. Rojas-Bravo, and M. Gutiérrez-Lomelí

Evol. 1999 46 73 79 Padmalatha, K., Prasad, M. N. V. (2006) Optimization of DNA isolation

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Abstract

Aesthetic and utilitarian properties of traditional ceramic wares as well as engineering properties of modern advanced ceramics are attained by maintaining an optimum temperature-time-atmosphere relationship, called firing schedule, in the kiln. The contribution of modern thermal analysis (TA) techniques such as TG/DTG, TG/EGA, TG/MS, DTA, DSC, TDA, etc. in 1) optimizing production steps by raw material quality control, by studying binder burn out, product densification, 2) in simulating appropriate preheating, firing and cooling schedules as well as 3) in developing shorter firing cycles has been extensively reported in recent literature. The paper will first discuss theoretical curves and energy required for ceramic firing and present from the literature selected examples of applications of thermal analysis in ceramic technology.

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Abstract  

When chemical reactions are performed in semi-batch mode and the reaction rate is relatively low, the reactant added may be accumulated. The resulting thermal accumulation is of major concern regarding process safety, as a fault in the cooling system may lead to a run-away reaction. The feed rate in semi-batch processes is usually constant, but this paper discusses methods of optimizing the feed rate interactively, based on the measured heat flow and the calculated amount of compound that has actually reacted. The prerequisite of such procedures is to run the experiments in a reaction calorimeter in which the heat flows can be measured accurately and continuously. For this purpose a ChemiSens reaction calorimeter CPA202, which is calibration free and gives stable, flat ‘zero-line-type’ baselines, was employed.

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experiment ( global optimum ) is achieved [ 1–3 ]. The goal of method optimization is to find the conditions under which the examined system gives the maximal or minimal response, as well as to define the mathematical model that establishes the relationship

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.05). All data are presented as the mean with the standard deviation. In the present study, Design-Expert software version 10.0.7.0 (Statease Inc., Minneapolis, USA) was used for the optimisation of modification parameters of amaranth starch. 3 Results and

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Journal of Thermal Analysis and Calorimetry
Authors: R. Hilfiker, J. Berghausen, F. Blatter, A. Burkhard, S. De Paul, B. Freiermuth, A. Geoffroy, U. Hofmeier, C. Marcolli, B. Siebenhaar, M. Szelagiewicz, A. Vit, and M. von Raumer

Abstract  

Crystal structure (polymorphism) as well as crystal shape (morphology) and size have a huge practical and commercial impact on active substances all the way from research to manufacture of the final product. For an optimal development process, it is important to have an integrated approach to these issues ranging from a systematic polymorphism screening to a controlled scale-up of the crystallization process. The polymorphism program has to be tailored according to the development stage. Particularly suitable for an early development stage is a high-throughput polymorphism screening, which is the basis for a more thorough investigation if the product proceeds further in development. Such a comprehensive polymorphism investigation involves further crystallization experiments and extensive physicochemical characterization of the various forms. In this article the high-throughput polymorphism screening method that we have developed is described. Using carbamazepine as an example, the power of this high-throughput polymorphism screening system is demonstrated. Not only were all published forms found, but also new forms were identified. In the second part of the article, important considerations for crystallization optimization are discussed, again using the example of carbamazepine.

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Optimization of microwave-assisted extraction (MAE) as a method of sample preparation in thin-layer chromatographic (TLC) analysis of a herbicide mixture is described. The extraction was optimized with regard to amount of solvent, duration of microwave extraction, and temperature. In the proposed method the experimental-design technique was used to design initial experiments and a genetic algorithm (GA) was used in the optimization procedure. The general objective was to test a mathematical tool which could facilitate optimization. The optimization procedure was tested in the TLC determination of a mixture of the herbicides atrazine and simazine; determination of recovery revealed results were satisfactory. The GA proved to be an optimization procedure which can be successfully applied to optimization of MAE experiments.

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. Optimized results for a steel beam in (mm), the beam is fixed at both ends during production (prebent) b 1 188.67685 t 7.3591728 t 1 9.427696 b 2 188.67685 h 362.93855 t 2 9.4276958 Input data: L  = 10 (m); F  = 98,100 (N); f y  = 460 (MPa); the

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