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Beer foam stabilization using biosurfactants
Jandrtová, Sabina ; Diviš, Pavel (referee) ; Pořízka, Jaromír (advisor)
This diploma thesis focuses on a research of the foam stability of the beer. We specifically observed the influence of ethanol and surface tension on the foam stability, and influence of ethanol and surface tension on the height of the foam. It was observed the influence of the hop acids in non-alcoholic beers. Furthermore, different biosurfactants were added into to the beer to observe better stability of the foam. The theoretical part of this work describes the foam from the physical aspect. There are described fourth key events involved in foam formation. Then it focuses on the beer foam – its structure, substances that influence its behavior and measurement of the foam stability. In this part there are described biosurfactants as well – their characteristics, qualities, distribution and applications. The experimental part is dedicated to the influence of ethanol, surface tension, the amount of iso- acids on foam stability in beer. There is observed the influence of biosurfactants of the foam stability and surface tension, which are added into to the beer. For the measurement of the foam stability was used the Rudin method. Liquid chromatography with DAD detector was used for the measurement the amount of the hop acids. The surface tension was determined by tensiometer. According to the results addition of ethanol changed the characteristics of the foam stability, but it’s not easy to find correlation between the increasing amount of ethanol and its stability. It was found out, that there is connection between the amount of ethanol and surface tension. On the other hand, there is not much connection between the surface tension and foam height. Within the framework of addition of biosurfactants was observed, that these foaming agents interacted the surface tension of the beer (lowering), however these agents accelerated the fall of the beer foam.
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Structure and properties of bacterial biofilms
Mrázová, Kateřina ; Sedláček, Petr (referee) ; Obruča, Stanislav (advisor)
This thesis deals with the study of basic properties of cells of bacterial biofilm produced by PHA producing bacteria, specifically Burkholderia cepacia and Burkholderia sacchari. Two cultivation approaches were used to compare different types of cells: at first, the cells were cultivated in bioreactor providing both planktonic and biofilm attached cells, secondly, cells grown on Petri dishes were also included in the study. In experimental part the affinity of each type of cells to hydrophobic phase was studied using BATH method. It was found that sessile cells, either biofilm associated cells as well as cells taken from Petri dishes, prefer hydrophobic phases more than planktonic cells. Also size and Zeta potential were measured using Dynamic Light Scattering (DLS). It was found for studied samples that, cells in these samples tend to aggregate and the difference of size between both types of cells occurs only for biofilm of the strain Burkholderia cepacia. Finally the impact of presence various bacterial cells types on surface tension of water as well as amount of PHA cumulated in different types of cells were observed.
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EFFECT OF FLOW PARAMETERS OF WATER AND AIR ATOMIZED SPRAYS ON COOLING INTENSITY OF HOT SURFACES
Boháček, Jan ; Střasák,, Pavel (referee) ; Rudolf, Pavel (referee) ; Horský, Jaroslav (advisor)
Práce komplexně popisuje vodní a vodovzdušné chlazení pomocí metod CFD (Computational Fluid Dynamics) konkrétně s využitím software ANSYS FLUENT. Skládá se ze dvou hlavních částí, z nichž první se zabývá numerickým popisem jediné vodní kapky a druhá popisem směsí kapek představující paprsek válcové a ploché trysky. Je založena převážně na vícefázových modelech proudění a vlastních uživatelsky definovaných funkcí (User Defined Functions, UDF) představujících stěžejní část práce. Uvedené výpočtové modely jsou ve většině případů verifikovány pomocí experimentálních dat nebo jiných numerických modelů. V první části práce jsou teoreticky postupně rozebrány všechny tři použité vícefázové modely proudění. První z nich, Volume Of Fluid model (VOF), byl použit pro modelování jediné kapky (mikromodel). Zatímco zbývající dva, Euler-Euler model a Euler-Lagrange model, byly aplikovány v modelu celého paprsku trysky (makromodel). Mikromodel popisuje dynamiku volného pádu vodní kapky. Pro malé průměry kapek (~100µm) standardní model povrchového napětí (Continuum Surface Force, CSF) způsoboval tzv. parazitní proudy. Z toho důvodu je v práci rozebrána problematika výpočtu normál, křivostí volných povrchů a povrchového napětí jako zdroje objemových sil v pohybových rovnicích. Makromodel se zabývá studiem dynamiky celého paprsku tj. oblastí od ústí trysky po dopad na horký povrch, bere v úvahu kompletní geometrii, tzn. např. podpůrné válečky, bramu, spodní část krystalizátoru apod. V práci je rozebrána 2D simulace dopadu paprsku válcové trysky pomocí VOF modelu Euler-Lagrange modelu na horký povrch. Pro případ s VOF modelem byl navržen model blánového varu. Euler-Euler model a Euler-Lagrange model byly využity pro simulaci paprsku ploché trysky horizontálně ostřikující horkou bramu přímo pod krystalizátorem nad první řadou válečků. Pro Euler-Euler model byl navržen model sekundárního rozpadu paprsku založený na teorii nejstabilnější vlnové délky (Blob jet model). Jelikož diskrétní Lagrangeovy částice tvořily v určitých místech spíše kontinuální fázi, byl navržen a otestován model pro konverzi těchto částic do VOF.
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Interactions between Hyaluronan and Surface Active Substances
Krouská, Jitka ; Burgert,, Ladislav (referee) ; Lehocký,, Marián (referee) ; Vikegard,, Peter (referee) ; Pekař, Miloslav (advisor)
Vliv hyaluronanu na micelizaci tenzidů byl studován různými fyzikálně-chemickými metodami. Byly zvoleny dva kationaktivní tenzidy, a to tetradecyltrimethylammonium bromid (TTAB) a cetyltrimethylammonium bromid (CTAB). Metoda izotermické titrační kalorimetrie byla využita pro stanovení entalpie micelizace, tenziometrie popisuje povrchové vlastnosti daných vzorků. Byl sledován také vliv různé molekulové hmotnosti použitého hyaluronanu a délka alkylového řetězce tenzidu na agregační chování daného systému. Výsledkem jsou hodnoty kritické micelární nebo agregační koncentrace tenzidu. V neposlední řadě se diskutuje využití agregátů hyaluronan-tenzid jako možné nosiče pro cílenou distribuci léčiv.
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Study of surface tension of systems applied in ultrasonography.
Říkovská, Klára ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
Surface tension of sonography systems was investigated using several experiments. These experiments were comprised of measurements of surface tension using BPA-800P tensiometer. The influence of surface tension of commercial substance SonoVue®, which contains in its structure two types of phospholipids, was studied more detailed. Other phospholipids were studied to comparison with SonoVue®. All substances were dissolved in saline (0,15 M NaCl). Effect of gas type on microbubbles formation and surface tension was investigated. Some samples were studied using du Nüy ring method. It was found that gas constructing the microbubbles (air or SF6) has no impact to the surface tension value. Production of foam on the surface of solutions has an impact on the value of the surface tension. This foam degreases the surface tension. Gas pressure is significant to comparison of measured data.
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Fixed-charge examination by surface energy measurement
Mojrová, Barbora ; Boušek, Jaroslav (referee) ; Hégr, Ondřej (advisor)
This work is deal with development of alternative method measuring fixed charge in thin dielectric layers by surface tension. Presence fixed charge takes effect so-called Back Surface Field (BFS), which helps to decrease surface recombination velocity on back side of solar cell. In work is described experimental measuring on dielectric layers Al2O3, AlN, SiNx, Y2O3 and PSG deposit on crystalline silicon wafers. Surface tension (it is the same like surface free energy) is analyzed from contact angle size using See System.
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Optical measurement of liquid surface tension
Malá, Kateřina ; Pech, Ondřej (referee) ; Malý, Milan (advisor)
This bachelor thesis explores the topic of measuring surface tension of liquids. The theoretical section explains the basic principles as well as possibilities of application of several measuring methods. In the next part, the most suitable method is selected in terms of ease of use, accuracy and purchase cost. The pendent drop method has been found to fit these criteria. The experimental section of the thesis describes the measuring apparatus and the analytic tool used. The results comprise an analysis of the factors which may affect the measurement precision as well as a comparison of an automatic and a manual analysis, and a reference measurement that confirms the aperture as efficient at measuring surface tension of liquids.
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Utilization of methods of physicochemical and structural analysis in characterization of biosurfactants
Nešpor, Tomáš ; Hurčíková, Andrea (referee) ; Sedláček, Petr (advisor)
This bachelor thesis deals with the very actual topic of biosurfactants. In the theoretical part of the thesis, a literature review on this topic was carried out and on the basis of this research, physicochemical and structural analysis techniques suitable for testing these substances were selected. In the practical part, the model biosurfactants were first characterized by standard methods used to study these compounds. Fourier transform infrared spectrometry was chosen as a standard technique of structural analysis. As an example of a universal technique for the study of aggregation behavior was used tensiometry. In the next part of the thesis there were designed and optimized alternative techniques usable for fast and inexpensive physicochemical analysis of these substances. It was mainly a microplate assay and its modified alternatives. Thus, the methods of low sample consumption, but also effective in confirming the presence and a possible amount determination of the biosurfactant content in the solution. The result of this work is a few simple methods that have been proven effective in studying biosurfactants.
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Properties and application of ferrofluids
Vaverka, Jakub ; Šedivý, Dominik (referee) ; Zbavitel, Jan (advisor)
Ferrofluids are substances that can change their properties through an external magnetic field. The theoretical part of this bachelor thesis explains the nature and properties of these liquids, and how they are made. The next chapter provides concrete examples of ferrofluid use, and where it is possible to direct current research. The principal objective of the experimental part is to measure and evaluate the surface tension of two different samples of kerosene-based ferrofluids.
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