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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.
321

Analysis of side friction impacts on urban roads : Case study Dar-es-Salaam

Chiguma, Masatu L. M. January 2007 (has links)
Side friction factors are defined as all those actions related to the activities taking place by the sides of the road and sometimes within the road, which interfere with the traffic flow on the travelled way. They include but not limited to pedestrians, bicycles, non-motorised vehicles, parked and stopping vehicles. These factors are normally very frequent in densely populated areas in developing countries, while they are random and sparse in developed countries making it of less interest for research and consequently there is comparatively little literature about them. The objective of this thesis is to analyze the effect of these factors on traffic performance measures on urban roads. To carry out this work, a research design was formulated including specific methods and prescribed limitations. An empirical case study methodology was adopted where Dar-es-salaam city in Tanzania was chosen as a representative case. The scope was limited to include only road-link facilities. A sample of these facilities including two-lane two-way and four-lane two-way roads were selected and studied. The study was conducted in two parts, of which each involved a distinctive approach. Part one involved a macroscopic approach where traffic and friction data were collected and analyzed at an aggregated level, whereas part two involved a microscopic approach where data of individual frictional elements were collected and analysed individually. Data collection was mainly performed by application of video method, which proved to be effective for simultaneous collection of traffic and side friction data. Data reduction was conducted chiefly by computer, using standard spreadsheet and statistical software packages, mainly SPSS and some computer macros. The analysis part was based on statistical methods, chiefly regression analysis. In the macroscopic approach, traffic and friction data from all sites were adjusted through a process called ‘normalization’, which enabled the data from the different sites to be merged, and consequently to obtain speed-flow curves for each road type. The individual friction factors through regression analysis were weighted and combined into one unit of measure of friction called "FRIC". The effect of "FRIC" on speed-flow curves was analyzed. The results showed significant impact on speed for both road types. Impact on capacity was identified on two-lane two-way roads while field data on four-lane two-way roads did not allow this. In the microanalysis approach, effect of individual side friction factors on speed was analyzed. The results showed that on two-lane two-way roads, all studied factors exhibited statistically significant impact on speed, while on four-lane two-way roads, only one factor showed the same. The results also identified impact values characteristic to the individual friction factors on some roads. Recommendations were made based on these results that highway capacity studies particularly in developing countries, should include the friction variable, though in the form suitable to their own particular circumstances. Further recommendations were made that these results should be applied to formulate management programs seeking to limit levels of side friction on high mobility urban arterial streets in order to improve traffic safety and operation efficiency. / <p>QC 20100701</p>
322

Air-sea exchange of O2 and CO2 : Processes controlling the transfer efficiency

Andersson, Andreas January 2017 (has links)
World oceans cover more than 70% of the earth surface and constitutes a major sink of atmospheric CO2. Two of the most important gases in the marine carbon cycling are O2 and CO2 and hence accurate descriptions of the air-sea gas exchange of these gases are crucial. Still there is a lack of knowledge of the relative importance of processes controlling the efficiency of the air-sea gas transfer. This is especially true for Arctic and high latitude seas were studies on air-sea gas exchange are few. By studying processes causing water-side turbulence, using gases of different solubility and various measurement techniques, more knowledge on the governing processes can be obtained. Here we present the very first air-sea fluxes of O2 using atmospheric eddy covariance measurements and investigate the dependence between the gas transfer velocity of O2 and turbulence generated by the mean wind. The instrument was found to suffer from the limited precision and time response, causing significant corrections on the O2 flux. After correcting for this, the O2 fluxes displays an anti-correlation with the air-sea fluxes of CO2 in agreement with the measured air-sea gradient of O2. The transfer velocities for O2 indicates a stronger wind dependence than other commonly used parameterizations of the transfer velocity for CO2 and O2, this especially for wind speeds &gt; 5 m s-1 where the typical onset of wave breaking occur. During two winter months eddy covariance measurements were taken over a high Arctic fjord. The data revealed a significant enhancement of the gas transfer velocity for CO2 from water-side convection, generated by cooling of surface waters. The dependence between water-side convection and gas transfer velocity were found for winds as high as 9 m s-1, but were strongest for wind speeds&lt; 7  m s-1.  The data also showed on enhanced air-sea gas transfer of CO2 when conditions were unstable very close to neutral. This enhanced transfer were associated to increased contribution to the CO2 flux from downdraft of air with higher concentrations of CO2.  The combined effect of water-side convection and turbulence generated by wind results in a very effective transfer, thus the air-sea gas exchange at these latitudes may be significantly underestimated.
323

Dual Mechanism Analgesia-Enhancing Agents

Young, Shawquia Elithia 01 January 2005 (has links)
Currently, there is an increasing need for novel analgesics that are potent but lack undesired side effects. Recent studies have shown that both 5-HT3 receptors and α2B- adrenoceptors play a role in antinociception. MD-354, N-(3-chlorophenyl)guanidine, has a high-affinity both for 5-HT3 and α2B- adrenoceptors and could be viewed as the first example of a rather selective 5-HT3/α2B- adrenoceptor ligand. MD-354, inactive by itself, potentiates the antinociceptive effects of an inactive dose of clonidine in the mouse tail- flick assay. An attempt to determine the underlying mechanism of this potentiating effect was the purpose of the present investigation. The studies focused on an examination of: i) MD-354 in the mouse hot-plate assay, ii) a more lipophilic analog of MD-354 in the tail-flick assay, iii) various analogs of MD-354 with different binding profiles in both mouse tail-flick and hot-plate assays. The present investigation suggests that both 5-HT3 and α2B- adrenoceptors are playing a role in the potentiation of clonidine analgesia by arylguanidines such as MD-354. Arylguanidines might represent a unique class of analgesia-enhancing agents with a dual (5-HT3/α2- adrenoceptor) mechanism of action.
324

Optimal multi-drug chemotherapy control scheme for cancer treatment : design and development of a multi-drug feedback control scheme for optimal chemotherapy treatment for cancer : evolutionary multi-objective optimisation algorithms were used to achieve the optimal parameters of the controller for effective treatment of cancer with minimum side effects

Algoul, Saleh January 2012 (has links)
Cancer is a generic term for a large group of diseases where cells of the body lose their normal mechanisms for growth so that they grow in an uncontrolled way. One of the most common treatments of cancer is chemotherapy that aims to kill abnormal proliferating cells; however normal cells and other organs of the patients are also adversely affected. In practice, it's often difficult to maintain optimum chemotherapy doses that can maximise the abnormal cell killing as well as reducing side effects. The most chemotherapy drugs used in cancer treatment are toxic agents and usually have narrow therapeutic indices, dose levels in which these drugs significantly kill the cancerous cells are close to the levels which sometime cause harmful toxic side effects. To make the chemotherapeutic treatment effective, optimum drug scheduling is required to balance between the beneficial and toxic side effects of the cancer drugs. Conventional clinical methods very often fail to find drug doses that balance between these two due to their inherent conflicting nature. In this investigation, mathematical models for cancer chemotherapy are used to predict the number of tumour cells and control the tumour growth during treatment. A feedback control method is used so as to maintain certain level of drug concentrations at the tumour sites. Multi-objective Genetic Algorithm (MOGA) is then employed to find suitable solutions where drug resistances and drug concentrations are incorporated with cancer cell killing and toxic effects as design objectives. Several constraints and specific goal values were set for different design objectives in the optimisation process and a wide range of acceptable solutions were obtained trading off among different conflicting objectives. Abstract v In order to develop a multi-objective optimal control model, this study used proportional, integral and derivative (PID) and I-PD (modified PID with Integrator used as series) controllers based on Martin's growth model for optimum drug concentration to treat cancer. To the best of our knowledge, this is the first PID/I-PD based optimal chemotherapy control model used to investigate the cancer treatment. It has been observed that some solutions can reduce the cancer cells up to nearly 100% with much lower side effects and drug resistance during the whole period of treatment. The proposed strategy has been extended for more drugs and more design constraints and objectives.
325

Oral contraceptives, weight control, and fat patterning in young college women

Litchfield, Ruth Edson January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas State University Libraries / Department: Foods and Nutrition.
326

The short-term effects of polymethyl methacrylate and rigid gas permeable contact lens wear on keratometric behaviour

17 September 2013 (has links)
M.Phil.(Optometry) / The concept of contact lenses was conceived over 500 years ago and has now evolved into a fundamental component of optometric practice. Soft contact lenses have become a convenient, aesthetically pleasing and comfortable alternative to spectacles that are becoming increasingly popular. The use of rigid contact lenses is imperative in the management of conditions such as keratoconus due to spectacles being insufficient in providing adequate vision. Placing a contact lens onto the cornea is an invasive procedure. The contact lens is a foreign body to the eye hence it is expected that the eye would react to that foreign body. Literature has revealed that the general reactions of the eye to contact lens wear are initial tearing, alteration of the tear layer and oedema due to reduced oxygen transmission but these are just a few of the known consequences amongst the multitude of the unknown consequences. What exactly goes on under a contact lens remains an enigma which contact lens researchers have strived to uncover over the past century. The consequence of contact lens wear is a vast area of research and can best be investigated by focusing on one aspect at a time. The aim of this study was to use dioptric power matrices and multivariate statistics to explore the effects of both gas permeable and gas non-permeable rigid contact lenses on corneal curvature. This study involves auto-keratometric measurements of the corneal curvature before and after lens wear to establish if there are any curvature changes induced by the contact lens. Keratometric data was collected with an automated keratometer (Nidek ARK-700) and was analysed correctly and completely using multivariate statistics. This thesis presents the findings of a study done in an effort to establish the short-term effects of rigid contact lens wear on keratometric behaviour by using complete methods of multivariate statistical analysis. Twenty four subjects were equally divided into three groups. One group wore polymethyl methacrylate (PMMA) rigid lenses, another group wore rigid gas permeable (RGP) contact lenses and the third group served as the control. The control group was included in the study to establish a reference for normal diurnal changes in keratometric behaviour. Fifty autoii keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the experimental groups and 50 auto-keratometric measurements were taken before and immediately after three hours of no lens wear for the control group. Data collected was analysed using multivariate statistical methods that in the past have been used infrequently in this area of research.
327

Etude et intégration de matériaux avancés pour la passivation face arrière de cellules photovoltaïques minces / Investigation and integration of advanced materials for back passivation of thin solar cells

Bounaas, Lotfi 30 June 2014 (has links)
L'objectif d'amélioration des performances de cellules solaires sur des substrats de silicium cristallin de plus en plus en minces (< 200 µm) est indispensable à la réduction des coûts du module et donc à l'essor du photovoltaïque à l'échelle mondiale. Cette thèse se propose de répondre à la problématique d'amincissement des plaquettes sur substrats monocristallins (Cz) de type p de grande surface (239 cm2 - 180 µm) par le développement d'une structure en face arrière capable de générer un rendement de conversion élevé tout en limitant le degré de complexité du procédé de fabrication de la cellule. La solution explorée est celle des cellules à face arrière passivée et contacts localisés et les schémas de passivation étudiés s'appuient sur l'utilisation d'empilements diélectriques à base d'oxydes de silicium (SiO2) et d'aluminium (Al2O3) couplés au nitrure de silicium (SiNx). Ces travaux ont pour objectif d'optimiser les propriétés de passivation des couches diélectriques tout autant que les briques technologiques nécessaires à leur intégration dans la structure de cellule finale (conditionnement de surface, ablation laser sélective, métallisation par sérigraphie). Le procédé de fabrication résultant a permis d'obtenir des cellules avec un rendement de conversion de 19.1% pour l'empilement SiO2/SiNx. Il est cependant démontré que les limitations des performances de cette structure peuvent être partiellement compensées en introduisant une couche d'alumine, permettant d'atteindre un rendement remarquable de 19.5% (+0.4% par rapport à une structure standard). / Improving the solar cell efficiency on thin wafers (< 200 µm) has become a must in the industry in order to reduce the module cost and enhance the photovoltaics field growth worldwide. This work addresses the issues regarding the thickness reduction of large monocrystalline p-type wafers (239 cm2 - 180 µm) by developing a back side architecture capable of increasing the efficiency while limiting the cell fabrication level of complexity. Thus back passivated and local contacts, also known as PERC-type, solar cells are investigated. Those include passivation schemes relying on the use of dielectric stacks based on silicon oxide (SiO2), aluminum oxide (Al2O3) both coupled with silicon nitride layers (SiNx). This PhD study attempts to carry out an optimization of the passivation properties as well as of the technological steps required for a proper integration in the final cell structure (surface preparation, selective laser ablation, screen-printing metallization). The resulting optimized process led to the fabrication of solar cells displaying an 19.1% conversion efficiency by using SiO2/SiNx layers. Nevertheless it was shown evidence that the limited electrical performances can be overcome by introducing an Al2O3 layer, eventually reaching a remarkable 19.5% efficiency. This represents an absolute gain efficiency of +0.4% compared to the standard full-area Al-BSF solar cell architecture.
328

Plasticidade das fibras amielínicas na tubulização látero-terminal / Plasticity of unmyelinated fibers using side-to-end tubulisation

Miguel, Vânia Tognon 25 November 2014 (has links)
A tubulização representa uma possível alternativa para reparo de lesões de nervos periféricos, por permitir a aplicação local de fatores de crescimento e neurorregenerativos assim como por facilitar o estudo dos mecanismos de ação relacionados à regeneração das fibras nervosas. O objetivo do presente estudo foi verificar se há crescimento de fibras amielínicas no nervo fibular comum de ratas Wistar adultas após a tubulização látero-terminal (TLT) sem a utilização de indutores de crescimento, através de análise morfológica e morfométrica das referidas fibras. Para tanto, o nervo fibular comum direito foi seccionado a 3 mm da sua emergência, o coto proximal sepultado e suturado na musculatura adjacente e um tubo de silicone (6 mm) interposto entre o coto distal do fibular e a lateral do nervo tibial (grupo TLT). O controle usado foi o segmento distal esquerdo do nervo fibular (grupo GN). Setenta dias após, foram realizados cortes semifinos e ultrafinos para análise de aspectos morfológicos e morfométricos através de microscopia de luz e microscopia eletrônica de transmissão (MET). Houve evidente brotamento axonal de fibras amielínicas, que cresceram a partir do nervo tibial intacto no grupo TLT em comparação ao grupo GN, sendo que o número total de axônios amielínicos foi similar nos dois grupos. Estudo morfométrico evidenciou diferenças significativas (p<=0,05) em relação à maior densidade de axônios amielínicos regenerados e em relação ao diâmetro mínimo axonal. No presente estudo os axônios amielínicos no nervo receptor, usando o modelo da TLT, foram quantificados. Esse modelo poderá ser útil e importante para estudo da plasticidade do sistema nervoso periférico. / Side-to-end tubulisation is a model recently developed in our laboratory to study nerve plasticity. In this model, collateral sprouting of fibers grow from intact donor nerve fibers to the distal stump of a receptor nerve. The objective of the present study was to study unmyelinated fibers using this model. Adults female Wistar rats were used and morphological and morphometric analysis were done. The fibular common nerve was sectioned 3 mm from its origin. The proximal stump was buried and sutured in the adjacent musculature. A silicone tube (6 mm) was fixed on the adjacent lateral portion of the intact tibial nerve and the fibular common nerve distal stump was sutured in the other extremity of the tube (SET group). The left fibular common nerve distal segment was used as control. Semithin and ultrathin sections were obtained and studied using light and transmission electron microscopy. Seventy days after, there was profuse axonal sprouting of unmyelinated fibers that grew from the nerve tibial, reaching the same number of axons when compared with the controls. In the present study unmyelinated axons in the receptor nerve using SET were quantified. SET is an important tool to study plasticity of peripheral nerve fibers.
329

Return to the Gateway: Enshrining the Immigrant in 1980s America

Cannella, Katherine January 2008 (has links)
Thesis advisor: David Quigley / This thesis will explore the factors that contributed to the enshrinement of the immigrant, in relation to places relevant to the Old World immigrant narrative. The chapters concentrate on the area around New York Harbor, often referred to as "the gateway," where turn-of-the-century immigrants sailed and settled and to where public memory made its return in the late sixties, seventies, and eighties. Public attentiveness to ethnic identity affected the character of historic preservation, prompting the creation of new symbols of American history. Many Americans' own Roots narratives brought them here, to the very place the immigrants began their American stories. Chapter One puts the spotlight on New Jersey, exploring how Jersey City claimed its part in the immigrant narrative, and how the state government organized its multi-ethnic character. Chapter Two opens to the national level, illustrating how the enshrinement of Ellis Island and the Statue of Liberty Centennial embodied the nationalism that came with the rise of conservatism. Chapter Three surveys immigrant memory in the Lower East Side, the quintessential neighborhood of nations, exploring what the Lower East Side Tenement Museum has done to pay homage to the "urban pioneers" of American history, using the past to affect contemporary immigration issues. The public memory that took shape at these historic sites resulted from not solely a revived interest in Old World ethnicity, but through a combination of factors. This thesis will also show how the ethnic revival helped draw attention to aspects of American life such as urban living, and provoked public discourse and scholarly research to attend to the people that history previously overlooked. / Thesis (BA) — Boston College, 2008. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: History. / Discipline: History Honors Program.
330

Cost-Effectiveness of Electricity Energy Efficiency Programs: Demand-Side Management's (DSM) Future Role in Energy Markets and Feasibility of Smart Meters in New York City

Huang, Zhixing January 2011 (has links)
Thesis advisor: Scott Fulford / Can smart metering program and time-of-use (TOU) prices help reduce energy consumption in New York City? Being able to track electricity consumption levels and to modify consumer usage patterns are important for policy makers to efficiently manage the energy markets. Unfortunately, no reliable and up-to-date data have been brought to bear on this question. I study the effects of time-of-use (TOU) prices and smart metering for the residents of Shanghai and I investigate further what can policy makers do in order to adapt and transfer this successful DSM experience from Shanghai to the residential sector in New York City. The primary objective of my study is to characterize the realistic short-term and long-term potential for the smart metering program in New York City given my empirical findings that the smart metering program has had brought great benefits to the residents of Shanghai. People respond to incentives; if electricity is charged at different prices throughout a day, consumers are likely to shift their usage to when it is cheaper. My findings suggest that policy makers should think harder about designing a pricing scheme that can optimize the social plus. / Thesis (BA) — Boston College, 2011. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Economics Honors Program. / Discipline: Economics.

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