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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Scattering of light by dust in bipolar outflow sources

Quinn, Dale Edward, Physics, Australian Defence Force Academy, UNSW January 2001 (has links)
Interstellar dust plays an important role in the physics of the interstellar medium, as well as the formation and evolution of stars. The presence of dust is often indicated in optical images by dark lanes which bisect spiral galaxies, or seen directly as reflection nebulosity around stars or emission nebulosity if sufficient heating is present. Of interest in this thesis is the dust that is associated with bipolar outflow sources. Bipolar outflows can occur in either evolved stars or in young stellar objects, and are so named because they consist of two lobes which are thought to be due to out-flowing dust and gas, with a dark lane between them due to thick dust in a circumstellar disk or shell which often blocks the light from the central star. The spatial distribution of the properties of dust around bipolar outflow sources has been examined using a combination of theoretical and observational techniques. To aid the interpretation of observations of bipolar outflow sources, we have modelled the wavelength dependence of light from 0.36 to 22\um, scattered by dust particles with varying characteristics. The results were then presented in the form of colour excess ratios. These model ratios can be applied to observations if the contribution due to the central star is able to be removed, such that all that remains in the image is the effect of the dust particles. The scattering of light by dust particles was modelled by varying six different characteristics: grain material, size (particle radius from 0.002 to 0.75\um), mantle temperatures and thicknesses, shape, and orientation. Of those characteristics, the largest variation in the colour excess ratios resulted from varying grain composition and size. Different scattering angles also produce a noticeable variation in the colour excess ratios, however the effect is difficult to distinguish from the general extinction due to dust around the source. Water ice mantles were also found to significantly change the colour excess ratios. Grain shape and orientation produced only small variations in the colour excess ratios. Three bipolar outflow sources were studied as part of this thesis, two evolved objects, OH~231.8+4.2 and Mz\,3, and the young T-Tauri object Rno\,91. The observations involved multi-wavelength imaging in the infrared, from which colours and colour excess ratios were obtained at various points of the bipolar outflows and then compared to the predictions made in the modelling. The most extensive data set analysed was seven images of the object OH~231.8+4.2 which were used in a multi-wavelength study in the infrared H to N bands (1.25--12\um). The central source position of the object has been confined to less than an arcsec using the longer wavelength images and an L--M colour image. The two peaks which dominate the lobes in the shorter wavelength images were found to be scattering peaks where the light from the central source is scattered from the walls of the lobes. The spatial distribution of water ice in the nebula has also been constrained to the circumstellar disk which has a torus or disk shape rather than being a spherical shell. The colour excess ratios derived for the nebula from the images also suggest slightly different dust properties between the circumstellar disk, lobe walls and within the lobe cavities. The young T-Tauri star Rno\,91 also contains ice, and was observed between J and L. The central star which illuminates the nebula was shown to be coincident with the brightest point in these images. Using colour excess ratio results for various parts of the nebula, it was shown that the dust close to the central star is likely to contain larger grains than the diffuse ISM, but with a similar composition. Moving away from the central star, the dust becomes more like that observed in the diffuse ISM. The presence of water ice on dust close to the central star was confirmed using images centred in the ice band. The protoplanetary bipolar outflow source Mz\,3 is slightly more evolved than OH 231.8+4.2, and does not have evidence of any water ice in the circumstellar disk. Images of this object were obtained between J and 10\um. The presence of warm dust throughout the inner bipolar lobes of this object is noticeable by the brightness of the lobes in the image at 10\um. Line profiles through the position of the central source of the 10\um\ image demonstrate that there is a circumstellar shell close to the central source which has an inner radius of $\lta\,375$\,AU. Colour excess ratio results for the bipolar lobes suggest that the dust associated with Mz\,3 is generally smaller than that found in the diffuse ISM. The properties of the dust in the bipolar lobes were also observed to be different to the dust closer to the central source and lying in the circumstellar disk. The small sizes for dust in Mz\,3 is consistent with the high velocity outflows that have been associated with the object.
2

Sequência didática sobre dispersão e difração da luz: confecção e utilização de um espectroscópio / Didactic sequence on dispersion and diffraction of light: confection and use of a spectroscope

Bruzadin, Felipe Rodrigues 27 September 2018 (has links)
Submitted by Felipe Rodrigues Bruzadin (felipebruzadin@hotmail.com) on 2018-11-14T15:47:02Z No. of bitstreams: 1 Dissertação Felipe Rodrigues Bruzadin.pdf: 1216866 bytes, checksum: 8f5b1b8d6f77b31f16363a41024cdedc (MD5) / Rejected by ALESSANDRA KUBA OSHIRO ASSUNÇÃO (alessandra@fct.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: - A ficha catalográfica está fora do padrão. Ela deve ser gerada através do link https://www.biblioteca.unesp.br/ficha/ Será gerado um pdf que deverá ser acrescentado ao trabalho - A ficha deve vir antes da folha de aprovação - Nos agradecimentos, de acordo com a portaria nº 206, de 04/09/2018, deverá constar a seguinte frase: O presente trabalho foi realizado com apoio da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Código de Financiamento 001 Agradecemos a compreensão. on 2018-11-14T18:09:34Z (GMT) / Submitted by Felipe Rodrigues Bruzadin (felipebruzadin@hotmail.com) on 2018-11-14T18:58:24Z No. of bitstreams: 1 Dissertação Felipe Rodrigues Bruzadin.pdf: 1223088 bytes, checksum: 6154c5af3c3bf01a650eed314f51f20e (MD5) / Approved for entry into archive by ALESSANDRA KUBA OSHIRO ASSUNÇÃO (alessandra@fct.unesp.br) on 2018-11-14T19:19:22Z (GMT) No. of bitstreams: 1 bruzadin_fr_me_prud.pdf: 1223088 bytes, checksum: 6154c5af3c3bf01a650eed314f51f20e (MD5) / Made available in DSpace on 2018-11-14T19:19:22Z (GMT). No. of bitstreams: 1 bruzadin_fr_me_prud.pdf: 1223088 bytes, checksum: 6154c5af3c3bf01a650eed314f51f20e (MD5) Previous issue date: 2018-09-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta uma sequência didática onde são utilizadas ferramentas de informática e a experimentação como recursos metodológicos, com o intuito de contribuir com o ensino e a prática em sala de aula dos professores. Na sequência, aparece a ordem de como trabalhar a dispersão e a difração da luz, assim como as habilidades e competências necessárias, levando em conta os conhecimentos prévios dos alunos. Os resultados nos mostram que os alunos conseguiram entender a relação entre o espectro e a luz fornecida por diferentes lâmpadas assim como a participação deles nas atividades foi relevante. / This work presents a didactic sequence in which computer tools and experimentation are used as methodological resources, with the aim of contributing to teaching and practice in the teachers' classroom. In the sequence, appears the order of how work the scattering and diffraction of light, as well as the skills and competencies necessary, taking into account the prior knowledge of students. The results show us that students understand the relationship between the spectrum and the light supplied by different light bulbs as well as their participation in activities was relevant.
3

Past pro studium rozptylu světla na prachových zrnech / Dust trap for light scattering study

Bartoň, Petr January 2017 (has links)
Title: Dust trap for light scattering study Author: Petr Bartoň Department: Department of Surface and Plasma Science Supervisor: doc. RNDr. Jiří Pavlů, Ph.D., Department of Surface and Plasma Science Abstract: Light scattering on small grains is common interaction occurring wi- dely in space environments, including Moon surface, dusty nebulas or even the upper atmosphere of the Earth. For experimental measurements of light scatte- ring intensity profiles, we designed and constructed a unique experiment. Using so called acoustic trapping, we are able to capture a single dust grain (or small water droplet) in midair, to irradiate it with the laser beam, and to observe scattered light directly with the photodiode mounted on a precise goniometer. In the thesis, we present not only construction details, but also the first results, which help us to evaluate abilities of the experiment, and provide useful recommendations for further development of all dust-related experiments. Keywords: light scattering, acoustic trap, dust grain, scattering measurement 1
4

Výzkumný 3D skener pro účely skenování problematických povrchů / Research 3D scanner for scanning of problematic surfaces

Bátrla, Martin January 2019 (has links)
This diploma thesis deals with design of 3D scanner for scanning problematic surfaces. The research part introduces the problem of 3D scanning and describes causes of random errors. Further, it contains a description and division of methods that leads to their elimination. The practical part of the thesis deals with design and description of hardware and software parts of the 3D scanner. The output of this work is device that is able to implement and compare quality of codification methods mainly for scanning of problematic surfaces. The functionality of equipment was verified by experimental measurement.
5

Příprava a charakterizace katanionických komplexů / Preparation and characterization of catanionic complexes

Mušková, Alexandra January 2020 (has links)
The diploma thesis deals with the preparation and characterization of catanionic complexes and their possible application to pharmaceutics and medicine. The catanionic complexes were prepared by mixing two oppositely charged surfactants with the concentration of 20 mmol·dm­3 in various volume ratios. Two systems were analyzed – CTAB + SDS and Septonex + SDS. Both systems were prepared in an aqueous and physiological environment. The turbidimetric analyses provided results of the intensity of turbidity of the prepared mixtures. The size and stability of the prepared particles were determined by DLS and ELS measurements. CTAB-rich samples showed significant viscosity changes and they were therefore characterized by rheological measurements. The results of this work show that the asymmetry of alkyl chains, surfactant selection, temperature, and ionic strength have a significant influence on the properties and self-assembly of surfactants in catanionic complexes.
6

Frakcionace a molekulární organizace huminových kyselin / Fractionation and molecular organization of humic acids

Chytilová, Aneta January 2016 (has links)
Humic acids are part of the natural organic matter occurring all around us. The aim of this thesis is to study the molecular organization, conformation of humic acids in aqueous solutions, that always raise a number of questions. For a long time, the scientists all over the world argue, if humic acid are polymers, micelles or supramolecules. Over time, thanks to new technologies, their opinions are moving away from a polymer model and tend rather to supramolecular arrangement of humic acids. Studying humic complex systems is not easy, because they are polydisperse and heterogeneous, which significantly complicates any characterization. Moreover, its molecular organization is affected by many factors such as e.g. pH, ionic strength and etc. For the study of the conformation of humic acids, concentration series of IHSS (International humic substances asociation) Leonardite humic acids stamdards in four different mediums were prepared: 0,1 M NaOH, humic acids in water with pH modified to 12 (basic medium), 0,1 M NaOH + 0,1 M HCl, 0,1 M NaCl (neutral environment). Furthermore it has been performed the fractionation of humic acids for the purpose of simplifying the complicated structure. Prepared concentration series were characterized with several analytical methods such as ultraviolet and visible spectroscopy, dynamic light scattering, electrophoretic light scattering, microrheology, gel permeation chromatography, potentiometric pH determination and direct conductometry. Diploma thesis is built on the previous bachelor thesis in which different sample of humic acids was studied. The measured results indicate that the studied systems show supramolecular behavior and in some cases are subject to aggregation into larger units (micelles).
7

EFFECT OF ATMOSPHERIC PARTICULATES ON AIRBORNE LASER SCANNING FOR TERRAIN-REFERENCED NAVIGATION

Vydhyanathan, Arun January 2006 (has links)
No description available.
8

Collective scattering of light from disordered atomic clouds / Espalhamento coletivo de luz por nuvens atômicas desordenadas

Carlos Eduardo Maximo 26 October 2017 (has links)
In this thesis, we investigate the coherent scattering of light by atoms randomly distributed in space. As described by a model of coupled dipoles, the cooperation in the spontaneous emission process results from purely optical interactions between the atomic internal degrees of freedom. In the optically dilute regime, where the atomic medium can be described by a refractive index, we have shown that light can be deflected with the application of a gradient of magnetic field. In the dense regime, short-range interactions appear to suppress Anderson localization of light even in two dimensions, a result which disassembles the common belief that all waves are localized in two dimensions. We also find that the fringe pattern, resulting from the interference between light scattered by an atomic cloud and that of its specular image, is robust to both disorder averaging and saturation. Finally, we demonstrate two-atom bound states in the two-dimensional motion through the long-range optical coupling. This optical binding effect with an atom pair will be important to investigate the all-optical stabilization of large clouds. / Nesta tese, investigamos o espalhamento coerente de luz por átomos distribuídos aleatoriamente no espaço. Conforme descrito por um modelo de dipolos acoplados, a cooperação no processo de emissão espontânea resulta de interações puramente ópticas entre os graus internos de liberdade dos átomos. No regime opticamente diluído, onde o meio atômico pode ser descrito por um índice de refração, mostramos que a luz pode ser desviada com a aplicação de um gradiente de campo magnético. No regime denso, as interações de curto alcance parecem suprimir a localização de Anderson da luz mesmo em duas dimensões, resultado que desmonta a crença comum de que todas as ondas estão localizadas em duas dimensões. Também descobrimos que o padrão de franjas, resultante da interferência entre a luz espalhada por uma nuvem atômica e a de sua imagem especular, é robusto tanto contra a média em disordem quanto contra saturação. Finalmente, demonstramos estados ligados de dois átomos no movimento bidimensional através do acoplamento óptico de longo alcance. Este optical binding effect com um par de átomos será importante para investigar a estabilização totalmente óptica de nuvens extensas.
9

Collective scattering of light from disordered atomic clouds / Espalhamento coletivo de luz por nuvens atômicas desordenadas

Maximo, Carlos Eduardo 26 October 2017 (has links)
In this thesis, we investigate the coherent scattering of light by atoms randomly distributed in space. As described by a model of coupled dipoles, the cooperation in the spontaneous emission process results from purely optical interactions between the atomic internal degrees of freedom. In the optically dilute regime, where the atomic medium can be described by a refractive index, we have shown that light can be deflected with the application of a gradient of magnetic field. In the dense regime, short-range interactions appear to suppress Anderson localization of light even in two dimensions, a result which disassembles the common belief that all waves are localized in two dimensions. We also find that the fringe pattern, resulting from the interference between light scattered by an atomic cloud and that of its specular image, is robust to both disorder averaging and saturation. Finally, we demonstrate two-atom bound states in the two-dimensional motion through the long-range optical coupling. This optical binding effect with an atom pair will be important to investigate the all-optical stabilization of large clouds. / Nesta tese, investigamos o espalhamento coerente de luz por átomos distribuídos aleatoriamente no espaço. Conforme descrito por um modelo de dipolos acoplados, a cooperação no processo de emissão espontânea resulta de interações puramente ópticas entre os graus internos de liberdade dos átomos. No regime opticamente diluído, onde o meio atômico pode ser descrito por um índice de refração, mostramos que a luz pode ser desviada com a aplicação de um gradiente de campo magnético. No regime denso, as interações de curto alcance parecem suprimir a localização de Anderson da luz mesmo em duas dimensões, resultado que desmonta a crença comum de que todas as ondas estão localizadas em duas dimensões. Também descobrimos que o padrão de franjas, resultante da interferência entre a luz espalhada por uma nuvem atômica e a de sua imagem especular, é robusto tanto contra a média em disordem quanto contra saturação. Finalmente, demonstramos estados ligados de dois átomos no movimento bidimensional através do acoplamento óptico de longo alcance. Este optical binding effect com um par de átomos será importante para investigar a estabilização totalmente óptica de nuvens extensas.
10

Studium interakce záporně nabitých vezikulárních systémů s polykationty / Study of interaction of negatively charged vesicular systems with polycations

Repová, Romana January 2020 (has links)
This diploma thesis deals with the preparation and characterization of negatively charged catanionic vesicular systems and their combination with selected polycations. The catanionic vesicular system was prepared by mixing of two oppositely charged surfactants SDS and CTAB. The negative charge as well as the stability of the vesicular system was provided by the incorporation of phosphatidic acid. Polycations, DEAE and TMC, have been selected for use in a pharmaceutical applications. Characterization of the prepared systems was performed by measuring DLS and ELS. The results indicate that we were able to prepare stable negatively charged vesicles that were eligible to non-covalently interact with selected polycations.

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