• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • 1
  • Tagged with
  • 8
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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

On M-spaces and M*-spaces

Nuckols, Thomas Ryland January 1970 (has links)
In this thesis we investigate the properties of M-spaces and M*-spaces, which are generalized metric spaces. Chapter II is devoted to preliminary results, and in Chapter III we prove the characterization for M-spaces theorem of K. Morita [12]. This theorem states that a space X is an M-space if and only if there exists a quasi-perfect map from X onto a metrizable space T. Chapter IV is concerned with the relationships between M-spaces and M*-spaces. We first prove an M-space is an expandable, M*'-space and then show that every normal, expandable, M*-space is an M-space. Using Katetov's Theorem, we show that in a collectionwise normal space, X is an M-space if and only if it is an M*-space. We conclude by generalizing this to the following. In a normal space X, X is an M-space if and only if it is an M*-space. Chapter V is concerned with the study of M-spaces and M*-spaces under quasi-perfect maps. We also prove the Closed Subspace Theorem for M-spaces and M*-spaces and establish the Locally Finite Sum Theorem for M-spaces and M*-spaces. In Chapter VI, we give an example of a T₂, locally compact M-space X, which is not normal and therefore not metrizable. We also give an example of a T₂, locally compact M*-space Y, which is not an M-space, but is however the image of X under a quasi-perfect mapping. / Master of Science
2

New reactions under homogeneous conditions

Núñez Magro, Ángel Alberto January 2007 (has links)
BDTBPMB has been proven to be an essential ligand in carbonylation chemistry. Its two tert-butyl groups and wide bite angle give it the ideal characteristics for this kind of chemistry, and leads to high activity and selectivity with use of its complexes. During this work the group of reactions where this ligand has been proven to be active has been extended with two new protocols for hydroxycarbonylation and aminocarbonylation. In the hydroxycarbonylation process, a large variety of unsaturated compounds were studied. Dioxane was found to be the ideal solvent, due to its properties in terms of coordinability, and miscibility with water. Using this solvent as the medium, a BDTBPMB complex of palladium was found to be highly active and selective under mild conditions. Initial attempts to address the aminocarbonylation of alkenes catalysed by the Pd/BDTBPMB system did not give high activity. This problem was overcome by the addition of an arylalcohol. Under those conditions, high selectivity and conversion was obtained in a wide variety of amides. However, attempts to address the aminocarbonylation of alkenes with ammonia gas to generate primary amides did not result in any conversion. The generation of these primary amides was obtained with transamidation of N-phenylnonamides which can be prepared by aminocarbonylation. Amides have been successfully hydrogenated to amines catalysed by a Ru/Triphos system. This system has been proven to be highly active in this reaction. High selectivities have been obtained in the generation of secondary amine. However, initial results of the hydrogenation of primary amides resulted in no formation of primary amines. A careful analysis of the mechanism of the formation of various products from the hydrogenation of primary amides allows the selective formation of primary amines by the ruthenium/Triphos system in the presence of ammonia. The possibility of the generation of primary amides in situ from acids under hydrogenation conditions, giving primary amines was explored with high conversion and moderate selectivities. To complete this work, a system based on a palladium complex for the decarboxylation of benzoic acids was developed. Usually, the decarboxylation reactions catalysed by copper require high temperatures. However, palladium complexes of highly electron donating ligands such as BDTBPMB or P([superscript]tBu)₃ were found to be highly active under milder conditions. This catalytic system was proven to be active in desulfonation reactions giving high conversion.
3

New developments in chromatographic NMR

Lucena Alcalde, Guillermo January 2018 (has links)
Analysis in chemistry has always been hindered by the presence of impurities in samples or mixtures that are difficult to separate. Nuclear magnetic resonance has proven to be one of the most powerful analysis techniques to enable the study of mixtures by pseudoseparation using molecular parameters such as the diffusion coefficient through the application of the DOSY technique. In order to extend the application of this technique, an improvement has been proposed know as matrix-assisted DOSY (MAD-DOSY) or chromatographic NMR. This technique is based on the addition of a sample modifier that will interact differently with the molecules, varying and separating their diffusion coefficients, or even changing slightly the chemical shifts. To extend the application of chromatographic NMR, size exclusion stationary phases have been combined with DOSY experiments. These studies have been applied to analyze mixtures modifying the diffusion coefficient in terms of size exclusion behavior and to increase the understanding of the interactions between the analytes and the stationary phase. These studies have been published in Magnetic Resonance in Chemistry. One of the main issues when using DOSY is spectral overlapping, which is the main cause of poor resolution. In addition to this problem, a consequence of using stationary phases is the appearance of increased broadening of the signals due to differences in magnetic susceptibility. Thus, to achieve the aim, the study of diffusion properties have been performed under HR-MAS conditions which can help to remove susceptibility effect, but has complicating effects on the DOSY experiment. A method to obtain reliable diffusion measurements under HR-MAS have been developed using a D2O sample. Different conditions have been investigated including different pulse sequences, variation of parameters of the pulse sequence (diffusion delay or gradient strength), spinning rate and synchronization of the pulse sequence with the sample spinning. Also improvements in sample preparation as the addition of spacers in different locations of the sample rotor, to both reduce radial field variations and the sample volume, in order to obtain the most accurate diffusion values. This method have been published in Magnetic Resonance in Chemistry. The method have been applied to a wide range of molecules to extend the understanding of diffusion under HR-MAS conditions. In order to extend the range of application of NMR chromatography, a complementary study of the analysis of a mixture of different enantiomers including ethylenediamine cobalt complexes, aminoacids and some other organic small molecules adding to the sample a chiral stationary phase as a sample modifier is included in the final chapter of this thesis.
4

The adoption and enforcement of a technological regime. The case of the First IT Regime.

Hölzl, Werner, Reinstaller, Andreas January 2000 (has links) (PDF)
In this paper we explore the process of adoption and enforcement of a number of new information processing technologies, such as the typewriter, calculators, tabulation gears and book-keeping machines, starting from the 1880s in the United States. We show that their innovation and diffusion was inexorably coupled to the economic development in the USA in the late 19th century. It is a complex and contradictory consequence of underlying socio-economic processes that led to the formation of modern organisational structures in large scale manufacturing which required systematic and efficient information processing. The typewriter and all the complementary office automation devices that entered the scene shortly after were part of a socio-technical regime that started being established: the office work regime or as we prefer to call it the first IT regime, as for the first time a technology was set up to process information on large scale. The logic of large scale manufacturing to produce standardised products in large series and to apply labour saving techniques was cast into the organisation of administration. This required a convergence of technical practices. The lock-in to the inferior QWERTY-keyboard is hence the outcome of the diffusion and hardening of the First IT Regime. (author's abstract) / Series: Working Papers Series "Growth and Employment in Europe: Sustainability and Competitiveness"
5

Optimization Of Water Distribution Networks Using Genetic Algorithm

Guc, Gercek 01 April 2006 (has links) (PDF)
This study gives a description about the development of a computer model, RealPipe, which relates genetic algorithm (GA) to the well known problem of least-cost design of water distribution network. GA methodology is an evolutionary process, basically imitating evolution process of nature. GA is essentially an efficient search method basically for nonlinear optimization cases. The genetic operations take place within the population of chromosomes. By means of various operators, the genetic knowledge in chromosomes change continuously and the success of the population progressively increases as a result of these operations. GA optimization is also well suited for optimization of water distribution systems, especially large and complex systems. The primary objective of this study is optimization of a water distribution network by GA. GA operations are realized on a special program developed by the author called RealPipe. RealPipe optimizes given water network distribution systems by considering capital cost of pipes only. Five operators are involved in the program algorithm. These operators are generation, selection, elitism, crossover and mutation. Optimum population size is found to be between 30-70 depending on the size of the network (i.e. pipe number) and number of commercially available pipe size. Elitism rate should be around 10 percent. Mutation rate should be selected around 1-5 percent depending again on the size of the network. Multipoint crossover and higher rates are advisable. Also pressure penalty parameters are found to be much important than velocity parameters. Below pressure penalty parameter is the most important one and should be roughly 100 times higher than the other. Two known networks of the literature are examined using RealPipe and expected results are achieved. N8.3 network which is located in the northern side of Ankara is the case study. Total cost achieved by RealPipe is 16.74 percent lower than the cost of the existing network / it should be noted that the solution provided by RealPipe is hydraulically improved.
6

A cycle of American educational reform : Garfield and Bellingham High Schools in the state of Washington, 1958-1983

Nuzum, Kathleen A. January 2004 (has links)
This thesis examines the educational experience from 1958 to 1983 in two Washington State high schools: Bellingham High School and Garfield High School, Seattle. It focuses on what happened to the structure, curriculum content and environment within these schools, and also discusses the process of centralisation in Washington State educational administration. The period of study was bounded by two reports: James Bryant Conant's The American High School Today (January 1959), and A Nation at Risk (issued in 1983) by the U.S. Secretary of Education, Terrell Bell, and the National Commission on Excellence in Education, reports which were issued in response to the Cold War and to growing international economic competition. Conant and his generation of educators sought a system of secondary education that, by opening educational opportunities to all young Americans, would close the critical Soviet- US gap in missile and space technology, and would give the Cold War victory to the United States. However, national policies, state administration and socio-cultural change in American life all contributed to a shift in classroom emphasis away from traditional academics and measures of students' achievement during the quarter-century after Conant - a condition made clear by the National Commission in 1983. Whatever the other values of these educational reforms, they had a negative effect on student attitudes towards academic achievement, resulting in a disengagement from all aspects of school life. Despite cultural differences, the parallel institutional experiences of Bellingham and Garfield, and the similarities that emerged between the schools' administrative structures, educational goals, teaching strategies and learning styles, imply that class was also an important factor shaping the educational experience in the United States during the 1960s and 1970s.
7

Potentialytan av N8: En kvantkemisk studie / Potential Energy Surface of N8: A Quantum Chemical Study

GUSTAFSSON STJERNQVIST, FRED January 2015 (has links)
In this study, quantum chemical methods have been used to study two isomers of the proposed high energy density material N8. It has been suggested as a green substitute for conventional solid rocket fuel. Several techniques were used to study the barrier height towards decomposition along reaction path of four N8 isomers. The potential energy surfaces around the transition states of two of the isomers were further investigated. Results show that the bond length of the isomers may have been overestimated, and one of the isomers has a lower barrier and may have a more complicated reaction route. Furthermore, there is a rather large difference in barrier height between calculations at the CCSD and CCSD(T) levels of theory / I den här studien har kvantkemiska beräkningsmetoder använts för att studera två isomerer av N8. På grund av sitt höga energiinnehåll har N8 föreslagits som ett grönt alternativ till konventionellt fast racketbränsle. Flera tekniker har använts för att studera barriären för nedbrytning utefter reaktionskoordinaten för fyra N8-isomerer. Potentialytan runt aktiveringstillståndet för två av isomererna studerades närmare. Resultaten visar att bindningslängden hos isomererna kan ha överskattats och en av isomererna har en lägre barriär samt kan ha en mer komplicerad reaktionsväg. Vidare är det en tämligen stor skillnad i aktiveringsenergi mellan CCSD- och CCSD(T)- nivåerna.
8

Advanced light-sheet and structured illumination microscopy techniques for neuroscience and disease diagnosis

Nylk, Jonathan January 2016 (has links)
Optical microscopy is a cornerstone of biomedical research. Advances in optical techniques enable specific, high resolution, sterile, and biologically compatible imaging. In particular, beam shaping has been used to tailor microscopy techniques to enhance microscope performance. The aim of this Thesis is to investigate the use of novel beam shaping techniques in emerging optical microscopy methods, and to apply these methods in biomedicine. To overcome the challenges associated with high resolution imaging of large specimens, the use of Airy beams and related techniques are applied to light-sheet microscopy. This approach increases the field-of-view that can be imaged at high resolution by over an order of magnitude compared to standard Gaussian beam based light-sheet microscopy, has reduced phototoxicity, and can be implemented with a low-cost optical system. Advanced implementations show promise for imaging at depth within turbid tissue, in particular for neuroscience. Super-resolution microscopy techniques enhance the spatial resolution of optical methods. Structured illumination microscopy is investigated as an alternative for electron microscopy in disease diagnosis, capable of visualising pathologically relevant features of kidney disease. Separately, compact optical manipulation methods are developed with the aim of adding functionality to super-resolution techniques.

Page generated in 0.0257 seconds