Albeit of high technological import, epitaxial self-assembly of CdSe/ZnSe QDs is non-trivial and still not clearly understood. The origin and attributes of these QDs are significantly different from those of their III-V and group-IV counterparts. For III-V and group-IV heterosystems, QD-formation is assigned to the Stranski Krastanow (SK) transition, wherein elastic relaxation of misfit strain leads to the formation of coherent three-dimensional (3D) islands, from a supercritically strained two-dimensional (2D) epilayer. Unfortunately, this phenomenon is inconspicuous for the CdSe/ZnSe heterosystem. Well-defined 3D islands are not readily formed in conventional molecular beam epitaxial (MBE) growth of CdSe on ZnSe. Consequently, several alternative approaches have been adopted to induce/enhance formation of QDs. This thesis systematically investigates three such alternative approaches, along with conventional MBE, with emphasis on the formation-mechanism of QDs, and optimization of their morphological and optical attributes. It is shown here that no distinct 3D islands are formed in MBE growth of CdSe on ZnSe. The surface of the CdSe layer represents a rough 2D layer, characterized by a dense array of shallow (<1nm) abutting mounds. In capped samples, the CdSe deposit forms an inhomogeneous CdZnSe quantum well (QW)-like structure. This ternary QW consists of local Cd-rich inclusions, which confine excitons three-dimensionally, and act as QDs. The density of such QDs is very high (~ 1012 cm-2). The QDs defined by the composition inhomogeneities of the CdZnSe QW presumably originate from the shallow mounds of the uncapped CdSe surface. By a technique wherein a CdSe layer is grown at a low temperature (TG = 230 °C) and subsequently annealed at a significantly higher temperature (TA =310 °C), tiny but distinct 3D islands are formed. In this work, the mechanism underlying the formation of these islands is reported. While the CdSe deposit forms a quasi-two-dimensional (quasi-2D) layer at TG = 230 °C, subsequent annealing at TA = 310 °C results in a thermally activated “up-climb” of adatoms onto two-dimensional clusters (or precursors) and concomitant nucleation of 3D islands. The areal density of QDs, achieved by this technique, is at least a decade lower than that typical for conventional MBE growth. It is demonstrated that further reduction is possible by delaying the temperature ramp-up to TA. In the second technique, formation of distinct islands is demonstrated by deposition of amorphous selenium (a-Se) onto a 2D CdSe epilayer at room temperature and its subsequent desorption at a higher temperature (TD = 230 °C). Albeit the self-assembled islands are large, they are severely truncated during subsequent capping with ZnSe, presumably due to segregation of Cd and Zn-alloying of the islands. The segregation phenomenon is analyzed in this work and correlated to the optical properties of the QDs. Additionally, very distinct vertical correlation of QDs in QD-superlattices, wherein the first QD-layer is grown by this technique and the subsequent ones by migration enhanced epitaxy (MEE), is reported. The process steps of the third variant technique, developed in course of this work, are very similar to those of the previous one-the only alteration being the substitution of selenium with tellurium as the cap-forming-material. This leads not only to large alteration of the morphological and optical attributes of the QDs, but also to formation of unique self-assembled island-patterns. Oriented dashes, straight and buckled chains of islands, and aligned island-pairs are formed, depending on the thickness of the Te-cap layer. The islands are partially alloyed with Te and emit luminescence at very low energies (down to 1.7 eV at room temperature). The Te cap layer undergoes (poly)crystallization during temperature ramp-up (from room temperature to TD) for desorption. Here, it is shown that the self-assembled patterns of the island-ensembles are determined by the pattern of the grain boundaries of the polycrystalline Te layer. Based on an understanding of the mechanism of pattern formation, a simple and “clean” method for controlled positioning of individual QDs and QD-based extended nanostructures, is proposed in this work. The studies carried out in the framework of this thesis provide not only a deeper insight into the microscopic processes governing the heteroepitaxial self-assembly of CdSe/ZnSe(001) QDs, but also concrete approaches to achieve, optimize, and control several technologically-important features of QD-ensembles. Reduction and control of QD-areal-density, pronounced vertical correlation of distinctly-defined QDs in QD-superlattices, and self-assembly of QD-based extended structures, as demonstrated in this work, might turn out to be beneficial for envisioned applications in information-, and communication-technologies. / Trotz ihrer großen technologischen Bedeutung ist die epitaktische Selbstorganisation von CdSe/ZnSe QDs noch immer nicht vollständig verstanden. Die Ursachen und Merkmale dieser QDs unterscheiden sich deutlich von ihren III-V- und IV-IV-Gegenstücken. Für III-V- und IV-IV-Heterosysteme wird die QD-Formation dem Stranski-Krastanow-(SK)-Übergang zugeordnet, bei dem, ausgehend von einer hochverspannten zweidimensionalen (2D) Epitaxieschicht, die elastische Relaxation von durch Gitterfehlanpassung hervorgerufener Verspannung zur Formation von dreidimensionalen (3D) Inseln führt. Im Falle des CdSe/ZnSe-Heterosystems ist es unklar, ob das SK-Modell die Formation von QDs zutreffend beschreibt. Beim Wachstum durch Molekularstrahlepitaxie (engl.: molecular beam epitaxy, MBE) von CdSe auf ZnSe kommt es nicht zur Bildung von 3D-Inseln, wie es für die meisten III-V- und IV-IV-Heterosysteme charakteristisch ist. Infolgedessen wurden mehrere alternative Herangehensweisen eingesetzt, um die Formation der QDs anzuregen bzw. zu verbessern. Diese Doktorarbeit beschreibt die systematische Untersuchung dreier solcher alternativer Ansätze im Zusammenspiel mit konventioneller MBE. Der Schwerpunkt liegt auf dem Formationsmechanismus der QDs und Optimierung ihrer morphologischen und optischen Eigenschaften. Beim MBE-Wachstum von CdSe auf ZnSe findet keine Bildung ausgeprägter, dreidimensionaler Inseln statt. Die Oberfläche der CdSe-Schicht stellt eine rauhe 2D-Schicht dar, gekennzeichnet durch eine dichte Anordung flacher, aneinander angrenzender Hügel. In bedeckten Proben bildet die CdSe-Ablagerung eine inhomogene CdZnSe-quantentrog-ähnliche (engl.: quantum well, QW) Struktur . Dieser ternäre QW enthält lokale Cd-reiche Einschlüsse, die die Bewegung von Exzitonen in drei Dimensionen einschränken und als QDs fungieren. Die Dichte solcher QDs ist sehr hoch (~ 1012 cm-2). Diese durch die Inhomogenität des CdZnSe-QW definierten QDs haben ihren Ursprung in den flachen Hügeln der unbedeckten CdSe-Oberfläche. Mit einer Methode, bei der man eine CdSe-Schicht bei niedriger Temperatur (TG = 230 °C) wachsen lässt und anschießend bei höherer Temperatur (TA = 310 °C) tempert, kommt es zur Bildung winziger, aber ausgeprägter, 3D-Inseln. In dieser Arbeit wird der Mechanismus, der der Bildung dieser Inseln zugrunde liegt, beschrieben. Während die CdSe-Ablagerung eine quasi-zweidimensionale (quasi-2D) Schicht bei TG = 230 °C bildet, führt das darauf folgende Tempern bei TA = 310 °C zu einem thermisch aktivierten „up-climb“ von Adatomen auf zweidimensionale Cluster (oder Vorgänger, engl.: precursor), bei gleichzeitiger Nukleation von 3D-Inseln. Die Flächendichte von QDs, die mit dieser Methode erreicht werden kann, ist mindestens eine Größenordung geringer als es für konventionelles MBE-Wachstum typisch ist. Eine weitere Verringerung ist möglich, indem der Temperaturanstieg auf TA verzögert wird. In einer zweiten Variante wird die Bildung großer und ausgeprägter Inseln durch Aufbringen einer amorphen Selenschicht (&#945;-Se) auf eine 2D-CdSe-Epischicht bei Raumtemperatur und anschließender Desorption bei höherer Temperatur (TD = 230 °C) demonstriert. Obwohl die selbstorganisierten Inseln groß sind, werden sie durch nachträgliches Bedecken mit ZnSe stark abgeflacht, was durch Segregation von Cd und Legieren der Inseln mit Zn hervorgerufen wird. Das Segregationsphänomen sowie sein Zusammenhang mit den optischen Eigenschaften der QDs wird in dieser Arbeit untersucht. Weiterhin wird vertikale Korrelation von QDs in QD-Übergittern beschrieben, in welchen die erste QD-Schicht mit dieser Methode wachsen gelassen wurde. Darauf folgende Schichten werden duch „migration enhanced epitaxy“ (MEE) aufgebracht. Die Prozessschritte der dritten Variante sind denen der eben beschriebenen sehr ähnlich. Die einzige Abwandlung besteht in der Substitution von Selen mit Tellur als bedeckendes Material. Diese Variation führt nicht nur zu beträchtlicher Veränderung der morphologischen und optischen Eigenschaften der QDs, sondern auch zur Bildung einzigartiger Muster von selbstorganisierten Inseln. Abhängig von der Dicke der Tellurbedeckung kommt es zur Bildung orientierter „dashes“, gerader und gebogener Ketten von Inseln und ausgerichteter Inselpaare. Die Inseln sind teilwese mit Tellur legiert und strahlen Lumineszenz in einem sehr niedrigen Energiebereich ab (bis hinunter zu 1,7 eV bei Raumtemperatur). Im Gegensatz zur &#945;-Se-Bedeckung kommt es in der Te-Schicht während der Temperaturerhöhung (von Raumtemperatur zu TD) zur Polykristallisierung. Es wird gezeigt, dass die selbstorganisierten Muster der Inseln durch die Verteilung der Korngrenzen der polykristallinen Te-Schicht bestimmt werden. Basierend auf dem Verständnis des Mechanismus der Musterbildung wird hier eine einfache und „saubere“ Methode für die kontrollierte Positionierung individueller QDs und QD-basierter, ausgedehnter Nanostrukturen vorgeschlagen.

The study of matter at extreme conditions has been of great importance for modern society. A correct understanding of materials and environments subject to high pressures and temperatures enabled the development of car and jet engines, manufacture of goods, energy production and space travels among other human milestones. Discoveries in magnetism, geology, chemistry, and crystallography have been reported in literature as well, illustrating relevant contributions of this research area. Science at extreme conditions constantly requires to innovate instruments and characterisation methods. Sophisticated proficiencies are needed to explore and reproduce conditions of interest for this field. Since the 1990s, high pressure instruments for neutron scattering have boosted the study of compressed matter. The design and subsequent improvement of the Paris-Edinburgh (PE) press and toroidal anvils successfully impacted this area, currently being the most extensively used instrument for high pressure neutron scattering, commonly used for pressures of the order of 10 GPa. Recent incorporation of toroidal anvils made of Zirconia Toughened Alumina (ZTA) has opened new experimental possibilities. Neutron transparency and mechanical resistance are key properties of this ceramic material. At this point it is essential to understand ZTA anvils design and working conditions in order to increase experimental capabilities and access new frontiers in compressed matter. Computer-based modelling technique Finite Element Analysis (FEA) has been a recent ally for instrumentation design and optimisation. Phenomena such as mechanical stress, deformations, and thermal distributions can be modelled in an object, gathering information regarding its mechanical stability, behaviour and failure. Although this method is popular in industrial and engineering design and applications, it has not been widely employed in high pressure research due to scarce information in material properties under extreme conditions, as well as in innovative ceramics and metallic alloys introduced in these types of scientific devices.

The aim of this Master’s thesis is to investigate how contemporary Swedish picture-books describe ethnicity. The analysis is based upon eight books that were published during the period 1996 to 2006. The thesis is based upon a qualitative content analysis and a model of analysis that has been constructed with inspiration from Maria Nikolajeva and Pil Dahlerup and their conceptions of analyzing literature. The study’s theoretical framework is primarily based on the sociology of literature and the perspective of the society in literature. We also introduce the conception ethnicity and its connection with nationalism, race, culture, norm, “us and them” and stereotyping. The results show that contemporary Swedish picture-books describe ethnicity stereotyped on the basis of Swedish norms. The picture-books in the study separate the ethnical Swedish from ethical foreign by emphasizing contrasts between the two. These contrasts cause a negative distance between the Swedish and foreign and emphasises the concept of “us and them”. / Uppsatsnivå: D

Many of the wastes associated with the nuclear fuel cycle are toxic to the biosphere; advancing the use of high resolution spectroscopy applied to these materials will provide the chemical speciation of the interaction between nuclear waste and geological material, improving confidence in a permanent disposal method and informing clean-up operations. Luminescence spectroscopy of uranyl(VI) is a well-established technique for the molecular speciation of uranium-mineral interactions. This work explores the use of both micro- and macroscopic luminescence spectroscopy to expose uranyl(VI) speciative heterogeneity in a range of minerals which have been exposed to uranyl(VI) salt solutions. A comprehensive review of the available literature on the interaction of uranyl(VI) with a range of geological media is assessed and compared. The review finds considerable ambiguity in the speciation of uranyl(VI) at the mineral water interface. A database reporting the multi parametric luminescence properties of uranyl(VI) with silica gel, quartz, bayerite, boehmite, muscovite, kaolinite and montmorillonite (SWy-2 and STx-1b) is presented and discussed. Although some of the results are consistent with previously reported values, many newly identified species are reported and their identification speculated. Parallel factor analysis is used to deconvolute the excitationemission matrix of uranyl(VI) sorbed to silica gel between pH 3 and pH 10. The results are used to identify the spectroscopic properties of complexes >(SiO)2UO2 and >(SiO)2UO2OH and thus new complexation coefficients (log(K)) for their formation with the silica gel surface are determined, log(K1) = 9.22 ± 0.02 and log(K2) = 3.45 ± 0.01, respectively. The investigation also provides insight into the fundamental properties of uranyl(VI) excitation pathways, which are not yet fully understood. Confocal microscopy and phosphorescent lifetime image mapping (PLIM) is used to expose the sub-micron heterogeneity of uranyl(VI) sorption complexation across mineral surfaces of silica gel, bayerite and montmorillonite (STx-1b). The results suggest that changes in the uranyl(VI) lifetime can be used to observe and understand submicron changes in uranyl(VI) complexation at hitherto unknown temporal resolution.

Human embryonic stem cells are pluripotent cells that have indefinite replicative potential and ability to differentiate into derivatives of three germ layers. HESCs are conventionally derived and grown on mitotically inactivated mouse embryonic fibroblasts and there are some alternative feeder types of human origin that have been used to replenish hESCs while trying to prevent cross-species contamination. The trophic factors that are secreted by the feeders are found to be important for long-term pluripotency but there are also supportive culture systems for hESCs lacking feeder cells which might suggest that not only the interactions with the feeders affect the behaviour of hESCs but also the components of the niche may take part in the decision of self-renewal or differentiation. Extracellular matrix components are known to exert their stimulatory or inhibitory effects by localising cells into a specific microenvironment in natural niches but have been relatively little investigated for hESCs. The aim of this study was to investigate ECM components which might have a role in the maintenance of hESCs. I have first investigated human placental stromal fibroblasts and immortalised human placental stromal fibroblasts for the support hESC pluripotency as an anlternative feeder type to conventional mouse embryonic fibroblasts. Secondly, the matrices derived from hPSFs and ihPSFs were assessed for their ability to support hESC pluripotency. Tandem mass spectrometry was used to identify ECM components released by human feeders in order to characterise the range of extracellular matrix proteins that support the growth of self-renewing hESCs. The majority of the molecules was shared between the cell types irrespective of hPSF cell derived matrix was not being supportive for hESC pluripotency, with some ECM components being unique ihPSFs. Collagen VI, tenascin C and versican were tested for hESC attachment and as substrates for feeder-free culture system in order to develop an optimised feeder-free system. Furthermore, integrin receptor profile of different hESC lines was also determined in order to identify the mechanisms of substrate attachment. Integrin attachment was shown to be vital for hESC engagement to fibronectin and vitronectin in feeder-free systems. The components of the integrin signalling machinery were identified in hESCs and the significance of integrin-mediated signalling in hESC self-renewal was demonstrated by blocking integrin β1 on fibronectin and integrin aVβ5 on vitronectin. Moreover, intracellular signalling mediator c-Src was shown to involve in ECMregulated signalling by affecting the phosphorylation of Focal Adhesion Kinase. Inhibition of Src led to a decrease in the expression of pluripotency-associated markers. Finally, the effects of growth factor supplementation on the maintenance of pluripotency in defined feeder-free conditions were studied by withdrawal of growth factors and blocking FGF Receptors. FGF-2 was shown to be essential for long-term self-renewal while the effects on pluripotency deteriorated in the absence of both FGF-2 and Activin A. Taken together this project highlighted the importance of substrate attachment and growth factors on the regulation of hESC self-renewal.

Vad berättar ljud för oss? Olika ljud ger olika konnotationer beroende på vem som lyssnar, vad den har för förkunskaper och erfarenheter. Lyssnandet är i allra högsta grad subjektivt. Vad har en filmmusikkompositör för ansvar? Är det viktigt att vara tydlig i vilka val av ljud kompositören gjort och varför just de ljuden valts ut? Spelar det egentligen någon roll när det subjektiva lyssnandet träder in? Behöver de ljud vi hör vara det vi tror att de är? Det här är några av de frågor som intresserar mig och ligger till grund för det ämne som jag har valt: experimenterande med ljud i filmberättande. I mitt examensarbete har jag både konstnärligt och i denna text reflekterat kring ämnet. / <p>Till uppsatsen följer bilagor i form av ljudfiler och en dokumentär kortfilm, <em>Vi Andra</em>, regi: Sharmarke Binyusuf och Manolo Diaz Rämö, klipp: Jakob Åsell, ljud: Gustaf Forsberg, produktion: Beatrice Pourbagher Garcia.</p><p>Länk till filmen går att få vid meljkontakt.</p>

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-07-21T16:25:18Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_SistemaLiberacaoControlada.pdf: 1661147 bytes, checksum: baf9d5ff827500cf82f2018daaf113c2 (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-09-08T14:37:56Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_SistemaLiberacaoControlada.pdf: 1661147 bytes, checksum: baf9d5ff827500cf82f2018daaf113c2 (MD5) / Made available in DSpace on 2014-09-08T14:37:56Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_SistemaLiberacaoControlada.pdf: 1661147 bytes, checksum: baf9d5ff827500cf82f2018daaf113c2 (MD5) Previous issue date: 2012 / A utilização do antígeno Vi em vacinas é bastante promissor devido a este proporcionar um alto nível de imunidade em vacinas parenterais. A necessidade pela busca por alternativas para administração de vacinas levou à aplicação da tecnologia da liberação controlada de fármacos no campo da imunização. Nestes sistemas de liberação controlada, as doses administradas são diminuídas, porém o período de imunidade aumenta, já que prolonga a quantidade liberada do antígeno ao longo do tempo. O presente estudo propôs desenvolver e caracterizar um sistema de liberação controlada contendo antígeno Vi, utilizando como polímero veiculador a quitosana. As técnicas de RMN H-1 e espectroscopia de infravermelho mostraram que o método de extração do antígeno Vi empregado foi satisfatório qualitativamente. A caracterização da quitosana e das nanopartículas através de ensaios de análise térmica mostrou maior estabilidade das partículas em relação à quitosana, além do aumento da temperatura de degradação nas nanopartículas à medida que aumenta a concentração da quitosana. Em relação ao potencial zeta todas as nanopartículas tiveram cargas positivas em pH 7,2, enquanto que, no tamanho, as partículas foram menores à medida que aumentou a quantidade de quitosana no sistema. Na microscopia eletrônica de transmissão, as partículas mostraram-se morfologicamente homogêneas e com formato esférico. Na cinética de adsorção o antígeno, contido em solução, sofreu uma adsorção de 55% nas partículas de quitosana. Com isso, observou-se que é possível criar um sistema de liberação controlada envolvendo nanopartículas de quitosana e antígeno Vi de Salmonella enterica sorotipo Typhi. / The use of the Vi antigen in vaccines is very promising because this provides a high level of immunity in parenteral vaccines. The need for the search for alternatives for administration of vaccines has led to the application of technology controlled release of drugs in the field of immunization. In such controlled delivery systems, the doses are decreased, but the period of immunity increases, extending the amount of antigen released over time. This study aimed to develop and characterize a controlled delivery system containing Vi antigen, using as disseminator polymer chitosan. The techniques of H-1 NMR and infrared spectroscopy showed that the method of extracting the Vi antigen used was qualitatively satisfactory. The characterization of chitosan and nanoparticles by tests thermal analysis showed greater stability of the particles in relation to chitosan, besides increasing the degradation temperature of the nanoparticles increases as the concentration of chitosan. Regarding the zeta potential nanoparticles were all positive charges at pH7.2, while the particles were smaller size as they increased the amount of chitosan in the system. In transmission electron microscopy showed the particles are morphologically homogeneous and spherical. In the adsorption kinetics of antigen contained in solution, suffered a 55% adsorption of the particles of chitosan. With this, we observed that it is possible to create a controlled delivery system involving nanoparticles of chitosan and Vi antigen of Salmonella enterica serotype Typhi.

No description available.

This dissertation explores the impact of HOPE VI (Housing Opportunities for People Everywhere), a Housing and Urban Development (HUD) program, on Tampa's Greenwood neighborhood. The program represents a policy shift away from traditional public housing toward a "mixed income" model that has effectively privatized public housing. Through a HOPE VI program implemented in Tampa in 2000, two public housing complexes were demolished and redeveloped in this way. While some former residents of public housing relocated to other public housing complexes, many moved to apartments and houses in the private rental market with Section 8 subsidized housing vouchers-many to Tampa's Greenwood neighborhood. In the dissertation, I examine how these policy changes affect both those relocated to the neighborhood and those already living in the neighborhood. The dissertation also examines the social dynamics of Greenwood in order to understand an actual mixed income neighborhood. In addition, the dissertation is concerned with the intersection of HOPE VI with other neoliberal trends in Greenwood-such as models for social order and particular discourses.

The USEPA Maximum Contaminant Level (MCL) for Total Chromium in drinking water is 100 μg/L. Total chromium includes both trivalent chromium (Cr(III), a trace nutrient) and hexavalent chromium (Cr(VI), a probable human carcinogen). The State of California set a Cr(VI)-specific MCL of 10 μg/L in 2014, and USEPA is considering a new federal MCL for Cr(VI). This would have a significant impact on drinking water systems across the US, with estimated annual cost of compliance between $0.6 to 5.1 billion per year. While Cr(VI) is the species of concern for health effects, water utilities must also consider Cr(III) since it can be oxidized to Cr(VI) by various chemicals. This oxidation has been documented for commonly used disinfectants. However, past studies were conducted with higher levels of chromium (e.g., 20 to 500 μg/L) and it is unknown if the reactions proceed at the same rate and extent at the lower concentrations relevant to most water treatment plants (< 10 μg/L). This project, funded by the Water Research Foundation, systematically evaluated the extent of oxidation of Cr(III) by drinking water oxidants under conditions relevant to drinking water utilities. Five oxidants (chlorine, monochloramine, chlorine dioxide, potassium permanganate, and ozone) were tested. Two doses were used for each chemical with their respective reaction times reflecting the typical application of the chemical in treatment. Three different water qualities were evaluated, each at pH 5.5, 7, and 9, and at two different temperatures (5 and 16 °C). Chlorine consistently oxidized an average of 80% of the available Cr(III), with the majority of the oxidation happening within the first 7 hours. Monochloramine did not significantly oxidize Cr(III) at any of the conditions tested. Chlorine dioxide was an effective oxidant at pH 7, with complete oxidation occurring in 6 hours, but was less effective at pH 5.5 and 9. Potassium permanganate achieved complete oxidation in 4 hours at each pH, with pH 7 experiencing the fastest oxidation. Ozone oxidized all available Cr(III) within minutes at all pH values. Quantifying the Cr(III) oxidation as a result of using these oxidants provides understanding of potential Cr(VI) addition into drinking water.