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Characterization of polyelectrolyte complexes using structural and thermal analysis
Řiháčková, Barbora ; Smilek, Jiří (referee) ; Krouská, Jitka (advisor)
This master thesis deals with study of chitosan-lignohumate, chitosan-polystyrenesulfonate, chitosan-alginate and chitosan-carrageenan polyelectrolyte complexes. The work was motivated by research of finding suitable alternative substance for lignohumate. The molecular weights of substances were characterized using SEC-MALLS. A degree and a character of the interactions between polyelectrolyte were studied by isothermal titration calorimetry and dynamic light scattering method. The calorimetric experiments proved that decreasing concentration of samples causes decreasing of heat flow. The best calorimetric measurements were provided by adding chitosan into polymer solution. The interactions between chitosan and polyanions and influence of mixing order were proved also by measuring intensity of zeta potential, Z-average of particle size and turbidity. New chitosan-based materials have a big potential in agriculture and medicine.
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Microstructure and Anisotropy of Creep in Ti-46Al-2W-0.5Si Castings
Dlouhý, Antonín ; Kuchařová, Květa ; Svoboda, Milan ; Válek, Robert ; Březina, Josef
The present study investigates microstructure and creep behaviour of the cast alloy Ti-46A1-2W-0.5Si (at-%) at temperatures 700, 750 and 800°C and applied stresses between 250-420 MPa. Solidification of the alloy during precision casting is associated with two processes: (i) the growth of the [0001].alpha. oriented columnar grains from the mould wall into the cast interior and (ii) the enrichment of the central part of the cast with aluminium. The first process results in a fully lamellar microstructure where lamellae are preferentially oriented parallel to the cast surface. The second process contributes to the development of the duplex microstructure in the central part of the cast. It is shown that distinct microstructural types in different regions of the cast result in different creep strengths. Specimens taken from inside of the cast and oriented parallel to the cast bar axis exhibited the lowest creep strength while similarly oriented specimens cut from the fully lamellar region near the cast surface were the strongest. The third type of the creep specimens cut out of the central region of the cast and oriented perpendicular to the cast bar axis showed the intermediate creep strength. The observed variations of the creep strength are associated with the preferential orientation of the lamellas and with the fraction of equiaxed .gamma.-grains in the duplex regions of the cast.
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Lightweight concrete with reinforcement
Plochý, Ondřej ; Hubertová,, Michala (referee) ; Hela, Rudolf (advisor)
This bachelor thesis summarizes the current knowledge regarding to the design and properties of lightweight concrete and concrete with reinforcement. Also deals with research of lightweight aggregate concrete with Liapor and its interaction with dispersed steel fibers. The work examined recipes of volume classes D1,6 and D1,8 and strength classes SFRLC 20/22 and SFRLC 25/28. Recipes are monitored by physical-mechanical and rheological properties.
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Transparent polycrystalline ceramics for ballistic and high-temperature applications
Malík, Petr ; Pouchlý, Václav (referee) ; Trunec, Martin (advisor)
Alumina based transparent ceramic bodies were prepared within this diploma thesis by the gel casting process followed by presintering to closed porosity stage with subsequent hot isostatic pressing. The problematic drying of large bodies was solved by means of careful temperature and relative humidity control and by osmotic drying. Almost perfectly dense ceramics were achieved thanks to colloidal processing of TM-DAR and TM-UF ceramic powders providing a final structure with grain size of 381 nm, resp. 302 nm. High real in-line transmission of 72,3 % was achieved at wavelength of 632,8 nm and thickness of 0,8 mm. Among mechanical properties high values of hardness HV10 = 22,5 GPa, fracture toughness KIC = 3,99 MPam0,5, Young’s modulus E = 400 GPa a bending strength o = 494 MPa were achieved.
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Position and Perspectives of the Company BUKOCEL, a. s. on European Markets
Nováková, Silvia ; Němečková, Iveta (advisor) ; Gilan, Milan (referee)
The only non-integrated pulp mill in Slovakia BUKOCEL, a. s. is 100% exporter of its product short fiber kraft bleached paper pulp. Pulp is intermediate product, which is used primarily in paper sector. Export of this company is mainly directed to European markets. The aim of this paper is to state the position and perspectives of this company on European markets. The evaluation of its status is based on paper sector's point of view. And by analysing the European pulp and paper industry, its evolution as well as by outlining future prospects, together with the evaluation of Slovak market and by comparing the company with its competition and stating its weaknesses and strengths, as well as, its opportunities and threats and lastly, analysing European environment by conducting PEST analysis, fulfills this paper's goal of stating the position of this company on the pulp market, as well as its further growth opportunities. Pulp and paper industry is showing up to be a perspective industry with broad possibilities of growth of its product portfolio, mainly in segment of packaging and tissue paper as well as in innovative ways of using cellulose fibre outside of paper sector.
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On geotechnical design according to residual shear strength
Koudelka, Petr
The paper consider on possibility and effectivity of a new concept of ULS design on residual shear strength based. Values of residual shear strength are the most reliable and in opposite, applied peak values of shear strength are the most favorable and applicable for states of small deformations only. The paper presents results of a prior analysis of slope stability and compares designs applying values of residual shear strength and peak shear strength. Some recommendations are included.
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Occurence and importance of the "molten globule" structure in proteins
Plutinský, Martin ; Hudeček, Jiří (advisor) ; Martínek, Václav (referee)
One part of my work focus on literature review on molten globule theme. This conformational state is generally formed in solution of some proteins under mild denaturation conditions as a thermodynamically stable state. Molten globule-like intermediate is also transiently formed during refolding of proteins. It is assumed and even it was proved for some proteins that kinetic (refolding) intermediate and equilibrium unfolding molten globule is identical. The second part of my work presents conformational study of horse heart ferricytochrome c under acidic conditions in low and high ionic strenght (addition of 0,5 M sodium chloride). Cytochrome c is a mitochondrial protein which mediates electron transfer in respiratory chain. These conformational changes were monitored by UV/VIS and derivative spectrophotometry in four wavelength ranges of absorption spectra - aromatic amino acids absorption range, Soret band, Q-band and CT band. Under high ionic strength probably a molten globule state is stabilized in the pH range 1,90-2,60. However, under low ionic strength, changes in polarity of tryptophane and tyrosine residues vicinity (between pH 2,60 and 2,30) and in spin state of iron atom (around pH 2,10) were observed due to putative denaturation of the protein. (in Czech) (in Czech)
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