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Fyzikální metody ke stanovení struktury povrchové vrstvy funkcionalizovaných mesoporézních silik
Zub, Yu.L. ; Šolcová, Olga
The given report is an attempt to summary the results of composition and structure studying of functionalized mesoporous silicas surface. These results have been received with the help of a number of physical methods (electronic microscopy, the thermal analysis, IR and Raman spectroscopy, solid-state (CP/MAS) NMR spectroscopy (on such nucleus as 1H, 13C, 29Si, 31P), MALDI, metal microprobe method) and also quantum chemistry.
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Charakter proudění v náplňovém superkritickém extraktoru
Rochová, Kristina ; Sovová, Helena
This contribution provides a brief review on the effect of flow direction on SFE and reports our first experiments on axial dispersion measured in the course of extraction; this topic has not been sufficiently discussed in the literature yet. The flow pattern was examined by means of response to tracer injection and the results were expressed in the form of dimensionless variance S2 T,0. Tetracosane deposited on glass beads was extracted and presence of natural convection was observed when the flow was switched from downflow to upflow mode.
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Povaha toku modelových suspenzí
Kulaviak, Lukáš ; Večeř, Marek ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The main object of the present investigation is to test the settling abilities of mixtures of solid particles in liquids. The key quantity here is the magnitude of the viscosity, both of the carrying liquid (water-glycerol solutions) and the effective viscosity of the two-phase mixture. Few model systems were used (glass and polystyrene pellets), to study the settling process. The sedimentation were recorded by a video camera and the resulting deposit structure was photographed. Besides, also a real suspension was tested, of geological materials (calcite, quartz, mixed geological powder, etc.). Immersion rotary viscometer Brookfield with special spindles (RVT and V spindles) was used to measure the effective viscosity of the dispersion.
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Viskozitní charakteristiky geologických suspenzí
Kulaviak, Lukáš ; Večeř, Marek ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The system under study was real geological suspension – ground sedimentary rocks of different chemical composition (calcite, quartz, etc.) dispersed in water-glycerol solutions. The reference one-phase system was a Newtonian liquid (glycerine with water). It is problematic to measure the rheology of settling suspensions, so some specific tools must be used. We used the rotating vane rheometry, with the immersion viscometer Brookfield and two spindles V-71 and V-72. The basic rheological data of solid-liquid system are displayed as flow and effective viscosity curves. The obtained results on rheology were related to the settling behaviour of the geological mixtures, namely to the certain kind of the lateral instability.
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Studium promíchávání ve zkrápěném reaktoru
Bártová, D. ; Jakeš, B. ; Jiřičný, Vladimír ; Kukal, J. ; Staněk, Vladimír ; Stavárek, Petr
Evaluation of axial dispersion flow parameters in trickle bed reactor (TBR) is presented in this contribution. Four axial dispersion models were employed to identify principal flow parameters (mean residence time, Peclet number and transport delay) from experimental data. The impulse-response method was employed to measure the residence time distribution (RTD) in the liquid phase. Isobutanol was chosen as a suitable tracer for the selected liquid phase represented by toluene. Tracer concentration at the outlet from the reactor was continuously monitored by a digital refractometer. Optimal model and the best predictions of the parameters were obtained via non-linear regression and least square method.
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Superkritická extrakce beta-sitosterolu ze slupek a listů rakytníku řešetlákového
Sajfrtová, Marie ; Sovová, Helena ; Bártlová, Milena
Extraction of beta-sitosterol with supercritical carbon dioxide from sea buckthorn pulp and leaves, a by-product of production of sea buckthorn juice, was studied. The effect of operation conditions on the yields and solubility of whole extract and its minor component beta-sitosterol was analysed in a series of experiments at pressures from 15 MPa to 28 MPa and temperatures 40 °C and 60 °C. The consecutively collected extract samples were analysed using HPLC. The selectivity of beta-sitosterol to major component was determined. The content of beta-sitosterol in both plant materials was obtained using Soxhlet extraction with hexane.
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Insekticidní aktivita rostlinných extraktů izolovaných různými metodami
Sajfrtová, Marie ; Sovová, Helena ; Karban, Jindřich ; Pavela, R.
The aim of this study was to compare the insecticidal activity of extracts obtained by SFE and traditional extraction method. Three types of extracts were prepared using the benefit of variable solvent power of supercritical carbon dioxide under different experimental conditions. Composition and product activities of the CO2 extracts were compared with hydrodistillation (HD) and Soxhlet extraction. The composition of volatile compounds in the isolates was determined by gas chromatography, and the toxicity and antifeedant effects of the extracts on larvae of Colorado potato beetle were evaluated.
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