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1.
Particle formation using supercritical fluids
Željko Knez, 2006, pregledni znanstveni članek

Opis: Particle formation and the design of solid particles and powdery composites with unique properties is at the moment one of major the developments of supercritical fluid (synonyms: dense gases, dense fluids, high pressure) applications. Conventional well-known processes for the particle-size redistribution of solid materials are crushing and grinding (which for some compounds are carried out at cryogenic temperatures), air micronization, sublimation, and recrystallization from solution. There are several problems associated with the above-mentioned processes. Some substances are unstable under conventional milling conditions, in recrysfallization processes the product is contaminated with solvent and waste solvent streams are produced. The application of supercritical fluids may overcome the drawbacks of conventional processes, and powders and composites with special characteristics can be produced. Several processes for the formation and design of solid particles using dense gases have been studied intensively. The unique thermodynamic and fluid-dynamic properties of supercritical fluids can also be used for the impregnation of solid particles, for the formation of solid powderous emulsions, particle coatings, e.g. for the formation of solids with unique properties for use in different applications. This review will focus on the fundamentals and on recent advances of particle formation and design processes using supercritical fluids on their applications and the technological advantages and disadvantages of various processes.
Ključne besede: chemical processing, high pressure technology, supercritical CO2, proteinase, thermal stability, pressure stability, enzyme activity, water content, dense gases
Objavljeno: 31.05.2012; Ogledov: 1305; Prenosov: 32
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2.
Relationship between the undrained shear strength, water content, and mineralogical properties of fine-grained soils
Ludvik Trauner, Bojana Dolinar, Miha Mišič, 2005, izvirni znanstveni članek

Opis: The relationship between the undrained shear strength of fine-grained soils and the water content can be described with a nonlinear function in which the type of soil is determined by two parameters. It is well known that these parameters depend mainly on the mineral compositions of soilsč these relationships, however, have not yet been investigated. The findings describedin this paper define those mineralogical properties of soils which determine the values of both parameters. Experimentally obtained results suggest that the parameters primarily depend on the size of the clay minerals,their quantity in soil composition, and the interlayer water quantityin the expanding clay minerals. As this dependence is well defined, the parameters, and thus the undrained shear strength at different water content, can be defined from knowledge of these mineralogical soil properties.
Ključne besede: soil mechanics, clays, fine-grained soils, shear strength, water content, mineralogy
Objavljeno: 01.06.2012; Ogledov: 1669; Prenosov: 58
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3.
Stability of proteinase from Carica papaya latex in dense gases
Maja Leitgeb, Mateja Primožič, Željko Knez, 2005, izvirni znanstveni članek

Opis: Proteinase from Carica papaya latex was tested on its thermal stability at atmospheric pressure and in supercritical carbon dioxide, near-critical propane and dimethyl-ether. In supercritical carbon dioxide at 300 bar thermalactivation of the examined proteinase was improved in the comparison toatmospheric pressure. In propane and dimethyl-ether (300 bar) activity of the examined proteinase decreased. Influence of compressionžexpansion cycles on residual activity of the same proteinase in supercritical carbon dioxide (300 bar and 50 °C) was studied, as well. Different ways of transition from supercritical to low-pressure-state were used which affected residual activityof the proteinase.Addition of water in the system increased activity of proteinase from C. papaya, which was incubated in supercritical carbon dioxide for 24 h. Optimum amount of water was found to be between 0.5 and 0.7 g/L.
Ključne besede: chemical processing, high pressure technology, supercritical CO2, proteinase, thermal stability, pressure stability, enzyme activity, water content, dense gases
Objavljeno: 01.06.2012; Ogledov: 957; Prenosov: 14
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