The ability to form multiple component heterostructures of two-dimensional materials promises to provide access to hybrid materials with tunable properties different from those of the bulk materials or two-dimensional constituents. By taking advantage of the unique properties of different constituents, numerous applications are possible for which none of the individual components are viable. The synthesis of multiple component heterostructures, however, is nontrivial, relying on either the cleaving and stacking of bulk materials in a “scotch tape” type technique or finding coincidentally favorable growth conditions which allow layers to be grown epitaxially on each other in any order. In addition, alloying of miscible materials occurs when the modulation wavelength is small. These synthetic challenges have limited the ability of scientists to fully utilize the potential of multiple component heterostructures. An alternative synthetic route to multiple component heterostructures may be found through expansion of the modulated elemental reactant technique which allows access to metastable products, known as ferecrystals, which are otherwise inaccessible. This work focuses on the expansion of the modulated elemental reactants technique for the formation of ferecrystals containing multiple constituents. As a starting point, the synthesis of the first alloy ferecrystals (SnSe)1.16-1.09([NbxMo1-x]Se2) will be discussed. The structural and electrical characterization of these compounds will then be used to determine the intermixing of the first three component ferecrystal heterojunction ([SnSe]1+δ)([{MoxNb1-x}Se2]1+γ)([SnSe]1+δ)({NbyMo1-y}Se2). Then, by synthesizing ([SnSe]1+δ)m([{MoxNb1-x}Se2]1+γ)1([SnSe]1+δ)m({NbxMo1-x}Se2)1 (m = 0 - 4) compounds with increasing thicknesses of SnSe, the interdiffusion of miscible constituents in ferecrystals will be studied. In addition, by comparison of the ([SnSe]1+δ)m ([{MoxNb1-x}Se2]1+γ)1([SnSe]1+δ)m({NbxMo1-x}Se2)1 (m = 0 - 4) compounds to the ([SnSe]1+δ)m(NbSe2)1 (m = 1 - 8) compounds the electronic interactions of the MoSe2 and NbSe2 layers will be determined. Finally, the effects of different alloying strategies and the interdiffusion of miscible constituents will be further examined by the synthesis of ordered ([SnSe]1.15)1([TaxV1-x]Se2)1([SnSe]1.15)1([VyTa1-y]Se2)1 and ([SnSe]1+δ) ([TaxV1-x]Se2) compounds with the effect of isoelectric doping on the charge density wave transition in (SnSe)1.15(VSe2) also being explored. This work contains previously published and unpublished co-authored material.

Solid state synthesis of layered, rotationally disordered intergrowths consisting of rock salt (MX) and hexagonal (TX2) constituents in various sequences [(MX)1+δ]m[TX2]n is carried out by developing structural and compositional prototypes of the desired product, using fine control of the elemental reactants and then annealing at low temperature to facilitate self-assembly. (M = Sn, La, Eu; T = V, Mo.) The remarkable rotational disorder in these systems - in contrast to traditional misfits - and their proven applications in thermal, electrical and thermoelectric disciplines make them a useful group of materials for demonstrating control of reaction pathways of solid state reactions using low temperatures and short times. The synthesized materials are structurally characterized using X-ray diffraction (XRD), X-ray reflectivity (XRR), and Scanning Transmission Electron Microscopy (STEM). Electrical characterization is carried out on patterned samples using the Van der Pauw method of resistivity and the Hall effect method. Composition of the samples is determined using wavelength dispersive electron probe microanalysis (EPMA). Time domain thermoreflectance is used to determine the cross plane thermal conductivity. The family of [(SnSe)1.05]m(MoSe2)n (m = n = 1, 2, 3, 4), which possess the same composition but different unit cell thicknesses, shows that there is no correlation between c-axis unit cell thickness and cross plane thermal conductivity. The family of structural isomers [(SnSe)1.05]4[MoSe2]4, [(SnSe)1.05]3[MoSe2]3[(SnSe)1.05]1[MoSe2]1, [(SnSe)1.05]3[MoSe2]2[(SnSe)1.05]1[MoSe2]2, [(SnSe)1.05]2[MoSe2]3[(SnSe)1.05]2[MoSe2]1,[(SnSe)1.05]2[MoSe2]1[(SnSe)1.05]1[MoSe2]2[(SnSe)1.05]1[MoSe2]1 and [(SnSe)1.05]2[MoSe2]2[(SnSe)1.05]1[MoSe2]1[(SnSe)1.05]1[MoSe2]1 have the same c-axis lattice thickness and absolute composition but have different numbers of [(SnSe)1.05]/[MoSe2] interfaces. Thermal conductivity studies carried out on these showed no correlation with the interface density. (LaSe1-x)1.17(VSe2-y)n (n = 2, 3, 4) feature a family of compounds that self-assemble at higher than usual temperatures. They form non-stoichiometric moieties with unique structural proclivities including La vacancies and V interstitials compared to other ferecrystals or previous misfits. The designable electrical properties show evidence of charge transfer. (EuSe)1+δ(VSe2)n (n = 1, 2, 3) is a family of materials that complements the investigation of Ln-based ferecrystals. They show evidence of multiple M oxidation states. These compounds highlight the use of rational design of structure and composition to tune properties. This dissertation includes previously published and unpublished co-authored material. / 10000-01-01

Tento pokus je považován za pilotní projekt. Nikdo nezkoušel aplikovat pouze KPO do rybničního prostředí. Metodicky bylo postupováno v souladu s projektem Aquaexcel. Výzkum byl zaměřen na 6 modelových rybníků na území pokusnictví VÚRH ve Vodňanech. Zde byla vysazena obsádka K1, L1 a L2. Od 26.6.2013 do 1.8.2013 byly pravidelně odebírány vzorky ryb pro parazitologické vyšetření. 2 tyto rybníky byly označeny jako kontrolní a ve zbývajících 4 došlo k aplikaci KPO v koncentraci 1 mg×l-1.K aplikaci docházelo 1 x nebo 2 x denně.V období od 30.5. do 4.6.2013 zasáhly Jihočeský kraj povodně a dešťové srážky. Dešťová voda společně se splachy z okolí promíchala a zvířila vodní sloupec všech těchto rybníků. Tato událost byla důvodem zvýšeného výskytu parazitární prevalence v počátcích odběrů vzorků, v porovnání s pozdějšími odběry vzorků. Celková incidence parazitů byla však velmi nízká. Líni byli zasaženi více parazitárními druhy, ale v mnohem menším počtu než v případě kaprů. Kaprům byla věnována největší pozornost a tedy i grafické a statistické vyhodnocení. U kaprů byli nalezeni parazité Trichodina sp. na žábrách a kůži, Ichthyophthirius multifiliis na žábrách a kůži, Apiosoma sp. na kůži, Gyrodactylus sp. na kůži. Po aplikaci KPO došlo k statisticky významnému snížení (P<0,01) pouze u Trichodina sp. na žábrách při porovnání kontrolních rybníků s rybníky. Rybniční prostředí se svými fyzikálně chemickými vlastnostmi liší od vody použité v průtočných systémech či v RAS. Pokus nevyšel dle očekávání, ale vzhled k tomu, že byl pilotní, tak nelze označit jako neúspěšný. Tento výzkum dává prostor pro další studie zaměřené na danou tématiku.

<p> Government programs now underway in Ontario aim at removing phosphates from waste-waters at sewage treatment plants. At present, removal of phosphates is commonly accomplished by chemical precipitation with lime, alum, or iron. Lanthanum, a rare earth element, has been found to be an effective precipitant of phosphates. If lanthanum precipitate can be collected, and the lanthanum then regenerated so that it could be recycled for further phosphate precipitation, a very advantageous alternative to the above schemes would result.</p> <p> In this study, phosphates were precipitated from both distilled water and secondary effluent using lanthanum. For the two cases, a regeneration scheme for lanthanum was examined. The basic regeneration reactions were carried out to evaluate the kinetics and equilibria for different ratios of reactants and different reaction temperatures. Techniques for phase separation of reacted reagents were studied. Process design calculations were carried out to obtain order of magnitude figures for amounts and costs of chemicals required, amounts of sludge produced, and reactor sizes.</p> / Thesis / Master of Engineering (MEngr)

The search for clean and efficient combustors is motivated by the increasingly stringent emissions regulations. New gas turbine engines are designed to operate under lean conditions with inhomogeneous reactants to ensure cleanliness and stability of the combustion. This ushers in a new mode of combustion, called the inhomogeneous reactants premixed combustion. The present study investigates the effects of inhomogeneous reactants on premixed combustion, specifically on the interactions of an initially planar flame with field of inhomogeneous reactants. Unsteady and unstrained laminar methane-air flames are studied in one- and two-dimensional simulations to investigate the effects of normally and tangentially (to the flame surface) stratified reactants. A three-dimensional DNS of turbulent inhomogeneous reactants premixed combustion is performed to extend the investigation into turbulent flames. The methaneair combustion is represented by a complex chemical reaction mechanism with 18 species and 68 steps. The flame surface density (FSD) and displacement speed S_d have been used as the framework to analyse the inhomogeneous reactants premixed flame. The flames are characterised by an isosurface of reaction progress variable. The unsteady flames are compared to the steady laminar unstrained reference case. An equivalence ratio dip is observed in all simulations and it can serve as a marker for the premixed flame. The dip is attributed to the preferential diffusion of carbon- and hydrogen- containing species. Hysteresis of S_d is observed in the unsteady and unstrained laminar flames that propagate into normally stratified reactants. Stoichiometric flames propagating into lean mixture have a larger S_d than lean flames propagating into stoichiometric mixtures. The cross-dissipation term contribution to S_d is small (~~10%) but its contribution to the hysteresis of S_d is not (~~50%). Differential propagation of the flame surface is observed in the laminar flame that propagates into tangentially stratified reactants. Stretch on the flame surface is induced by the differential propagation, which in turn increases the flame surface area.

Title: Comparison of educational and compensation exercise programmes for ankylosing spondylitis patients Objective: The objective of the research was to determine the effect of two educational and compensation exercise programmes on the mobility of the axial system, the functional status and disease activity (including inflammatory process activity) in individuals with ankylosing spondylitis. Methods: The research group included men and women (average age of 35.42 ± 7.15 years), all out-patients of the Institute of Rheumatology in Prague. This characteristic sample (n ═ 38) consisted of respondents who were randomised into three groups: The first experimental group (n ═ 13) attended an educational and compensation exercise programme in a group setting in a gym (twice a week) and an educational and compensation exercise programme in the form of a group exercise in a pool - hydrokinesiotherapy (once a week); the second experimental group (n ═ 13) attended the same educational and compensation exercise programme in a group setting in a gym (twice a week); the control group educational and compensation exercise programme in a group setting in a gym (twice a week) received no exercise intervention but its members were allowed to use "passive" physiotherapeutic procedures (e.g. hydrotherapy or...

A new approach to the growth of MoSe2 thin films on epitaxial graphene on SiC(0001) by the use of modulated elemental reactants (MER) precursors has been reported. The synthesis applies a two-step process, where first an amorphous precursor is deposited on the substrate which self-assembles upon annealing. Films with a nominal thickness of about 1ML are successfully grown on epitaxial graphene monolayer as well as buffer layer samples. Characterization of the films is performed using XPS, LEED, AFM, and Raman spectroscopy. The films are nanocrystalline and show randomly rotated domains. This approach opens up an avenue to synthesize a number of new van-der-Waals systems on epitaxial graphene and other substrates.

Title: Comparison of educational and compensation exercise programmes for ankylosing spondylitis patients Objective: The objective of the research was to determine the effect of two educational and compensation exercise programmes on the mobility of the axial system, the functional status and disease activity (including inflammatory process activity) in individuals with ankylosing spondylitis. Methods: The research group included men and women (average age of 35.42 ± 7.15 years), all out-patients of the Institute of Rheumatology in Prague. This characteristic sample (n ═ 38) consisted of respondents who were randomised into three groups: The first experimental group (n ═ 13) attended an educational and compensation exercise programme in a group setting in a gym (twice a week) and an educational and compensation exercise programme in the form of a group exercise in a pool - hydrokinesiotherapy (once a week); the second experimental group (n ═ 13) attended the same educational and compensation exercise programme in a group setting in a gym (twice a week); the control group educational and compensation exercise programme in a group setting in a gym (twice a week) received no exercise intervention but its members were allowed to use "passive" physiotherapeutic procedures (e.g. hydrotherapy or...

Als van-der-Waals Heterostrukturen werden vertikale Stapelfolgen quasi-zweidimensionaler Kristalle bezeichnet. Durch die Kombination von Schichten mit unterschiedlichen physikalischen Eigenschaften eröffnen sich vielfältige Möglichkeiten für die Grundlagenforschung und potentielle Anwendungen neuer Materialien. Für die Synthese solcher Schichtstrukturen haben sich in der Vergangenheit hauptsächlich zwei Methoden etabliert. Dies ist zum einen die manuelle Stapelung mechanisch exfolierter Lagen und zum anderen das sequentielle Schichtwachstum mittels chemischer oder physikalischer Gasphasenabscheidung. Ein entscheidender Nachteil bei der mechanischen Exfoliation ist dabei, dass die verwendeten zweidimensionalen Schichten unter Transportbedingungen stabil sein müssen. Die sequentielle Synthese wird dadurch limitiert, dass die idealen Wachstumsbedingungen für verschiedene Lagen nicht immer kompatibel sind. Einen alternativen Ansatz zur Herstellung von van-der-Waals Heterostrukturen verfolgt die MER-Synthese (engl. modulated elemental reactants). Dabei wird die gewünschte Schichtstruktur durch einen amorphen Precursor vorgegeben, welcher aus elementaren Schichten mit exakt kalibrierter Teilchenzahl aufgebaut wird. Aufgrund der Vorstrukturierung kann die Kristallisation beim anschließenden Tempern bei deutlich niedrigeren Wachstumstemperaturen erfolgen als bei klassischen Festkörpersynthesen. Auf diese Weise sind auch metastabile Verbindungen mit variablen Stapelfolgen zugänglich, jedoch Verbunden mit einem Verlust der langreichweitigen kristallinen Ordnung. Daher werden solche Heterostrukturen auch als Ferekristalle bezeichnet (nach dem lateinischen fere, zu Deutsch „fast“). Die vorliegende Arbeit widmet sich der Untersuchung verschiedener Ferekristalle mittels Methoden der Oberflächenphysik. Der Fokus liegt dabei auf der elektronischen Struktur und den Wechselwirkungen zwischen den einzelnen Schichten, welche über die Photoelektronenspektroskopie zugänglich sind. Insbesondere Ladungstransferphänomene lassen sich über die Analyse der atomaren Rumpfniveauspektren untersuchen. Dabei können zwei grundlegende Prozesse unterschieden werden: In Ferekristallen, die PbSe oder SnSe enthalten, zeigt sich eine Modulationsdotierung durch Elektronenübertrag in die benachbarten Übergangsmetalldichalkogenide. Verbindungen mit BiSe zeigen hingegen ein deutlich komplexeres Verhalten, da neben dem Ladungstransfer in benachbarte Schichten auch eine Lokalisation von Ladungsträgern an Antiphasendomänengrenzen erfolgen kann. In Kombination mit Molybdändiselenid treten bei entsprechend großem Elektronenübertrag aus BiSe gemischte Bereiche der halbleitenden 2H- und (metastabilen) metallischen 1T-Phase von MoSe2 auf. Durch eine Variation der Zusammensetzung und Stapelfolge der betrachteten Ferekristalle lassen sich diese Phänomene systematisch untersuchen. Zum Abschluss der Arbeit wird zudem die Anwendbarkeit der MER-Synthese für die Herstellung ultradünner Filme mit einer Dicke im Bereich von ein bis zwei Monolagen untersucht. Als Wachstumssubstrate kommen dabei Silizium und epitaktisches Graphen auf Siliziumcarbid zum Einsatz. Dabei konnte sowohl das Wachstum von Monolagen von MoSe2 als auch von Bilagen aus MoSe2 und Bi2Se3 erfolgreich demonstriert werden. / Vertical stacks of quasi-two-dimensional crystals are commonly referred to as van-der-Waals heterostructures. By combining layers with different physical properties, one opens up a variety of possibilities for fundamental research as well as the application of new materials. In the past, two prominent methods have been established for the synthesis of such layered structures: manual stacking of mechanically exfoliated layers and sequential layer-by-layer growth via chemical or physical vapor deposition. A decisive disadvantage of the mechanical exfoliation is that the two-dimensional layers that are to be stacked have to be stable under transport conditions. Sequential synthesis is limited by the fact that the ideal growth conditions for different layers are not always compatible. An alternative approach to the preparation of van-der-Waals heterostructures is the MER-synthesis. MER stands for modulated elemental reactants. Here, an amorphous precursor mimicking the desired structure is built up from elemental layers with a precisely calibrated number of atoms. Due to the prestructuring of the precursor, crystallization during subsequent annealing can take place at significantly lower growth temperatures compared to classical solid-state syntheses. With this approach, metastable compounds with variable stacking sequences become accessible, but at the expense of losing the long-range crystalline order. Therefore, such heterostructures are also referred to as ferecrystals (from the latin fere, meaning „almost“). The present work is devoted to the study of a variety of ferecrystals by means of surface science methods. The main focus is put on the electronic structure of and the interactions between the individual layers, which are accessible via photoelectron spectroscopy. In particular, charge transfer phenomena can be studied by analyzing the atomic core level spectra. Here, two distinct fundamental processes can be distinguished: In ferecrystals that contain PbSe or SnSe, electrons are transferred into the neighboring transition metal dichalcogenide layers, which can be applied in the form of controlled modulation doping. On the other hand, compounds with BiSe show a much more complex behavior. In addition to charge transfer into neighboring layers, localization of charge carriers can occur at antiphase domain boundaries. When combined with molybdenum diselenide, electron donation from BiSe can lead to a mixture of the semiconducting 2H- and (metastable) metallic 1T-phase of MoSe2. By varying the composition and layering sequence of the heterostructures, these phenomena can be investigated systematically. To conclude the thesis, the applicability of the MER synthesis for the preparation of ultrathin films with thicknesses in the range of one to two monolayers is investigated. In this study, silicon and epitaxial graphene on silicon carbide are used as growth substrates. The growth of monolayers of MoSe2 as well as bilayers of MoSe2 and Bi2Se3 is demonstrated successfully.

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