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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.
71

Different methods for particle diameter determination of low density and high density lipoproteins-Comparison and evaluation

Vaidyanathan, Vidya 15 May 2009 (has links)
Predominance of small dense Low Density Lipoprotein (LDL) is associated with a two to threefold increase in risk for Coronary Heart Disease (CVD). Small, dense HDL (High Density Lipoprotein) particles protect small dense LDL from oxidative stress. Technological advancements have introduced an array of techniques for measuring diameters of LDL and HDL as well as estimating overall particle heterogeneity. However, there is lack of comparative studies between these techniques, and, hence, no conclusive evidence to establish the merits of one method relative to others. The primary purpose of this study was to compare Nondenaturing Gradient Gel Electrophoresis (NDGGE) and Dynamic Laser Light Scattering (DLLS) methods in determining LDL and HDL particle diameter. Our comparison entailed: 1) Evaluating the two methods in terms of their reproducibility 2) Correlating the two methods(in future studies method selection would be driven by time and cost considerations if the two methods correlate), and 3) Evaluating the two methods in terms of their ability to identify bi-modal samples. A secondary purpose of this research was to investigate the effect of refrigerated plasma storage on particle diameter. Reproducibility was measured as Coefficient of Variance (CV). Within and between runs, CV for LDL and HDL for NDGGE were <6% and <15%, respectively and for DLLS, CV within runs were <3% and <5.5%, respectively. No correlation was observed between LDL diameter from the two methods. NDGGE showed two bands for 157 HDL samples of which only 24 samples showed bimodal peaks in DLLS. In order to study the effect of storage, three sample sets of LDL and two sample sets of HDL were used. NDGGE showed a significant difference between mean diameter of fresh and stored LDL and HDL sample for all sets, whereas DLLS showed a significant difference in only one LDL sample set and none for HDL sample sets. We conclude that DLLS may be a better method for measuring LDL diameter because NDGGE overestimated LDL diameter. However, NDGGE was able to resolve subpopulation better in an HDL sample than DLLS. Thus, NDGGE may be a better choice for measuring HDL diameter than DLLS.
72

The Chemistry of Atherogenic High Density Lipoprotein

Moore, D'Vesharronne J. 2011 May 1900 (has links)
An array of analytical methods including density gradient ultracentrifugation, capillary electrophoresis, and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), were utilized to analyze serum high density lipoprotein (HDL) subfractions from two cohorts of normolipidemic individuals, which included subjects with diagnosed coronary artery disease (CAD), and angiographically proven non-CAD controls. These methods collectively provided characteristic information about the two populations of individuals including composition, electrophoretic mobilities, molecular weights, isoforms, and post-translational modifications of HDL apolipoproteins. This information proved useful in identifying potential biomarkers for CAD risk, and understanding the biological functions of a novel atherogenic HDL phenotype in individuals with CAD. Through the implementation of the aforementioned methodologies, new isoforms of apoC-I were identified. MALDI-MS, detected a shifting of approximately 90 Da in the mass to charge ratios corresponding to apoC-I peaks in the serum subfractions from all CAD cohort patients. This shifting was not observed in the non-CAD cohort, which displayed apoC-I peaks in accordance with the known mass of this protein. In addition to the shifting observed in the CAD cohort, some CAD patients showed further modifications of apoC-I that were indicative of oxidative processes. Interestingly, one patient, who has not been diagnosed with CAD, and has a family history of the disease, contained the apoC-I isoforms. This feature could underlie this subject’s known family history of CAD, and serve as an initial screening that could indicate the future development of CAD in this individual. Through collaborative work with Johns Hopkins University, it was initially observed that apoC-I enriched HDL induced apoptosis of aortic smooth muscle cells. Conversely, apoC-I depleted HDL induced minimal to no apoptosis, which led to the hypothesis that apoC-I is a contributor to atherogenic HDL and is a potential risk factor for CAD. Further collaborative work with Johns Hopkins assessed the apoptosis levels induced by HDL from both cohorts of patients. A distinct difference in apoptosis was identified between the two cohorts. High density lipoprotein subfractions from subjects in the CAD cohort, all of which contained the apoC-I isoforms, induced marked apoptosis compared to the non-CAD controls. These results further supported the hypothesis that apoC-I compromises the functionality of HDL and showed that through the induction of apoptosis, apoC-I can contribute to the destabilization of atherosclerotic plaque and the acceleration of CAD.
73

Establishment of zero-water exchange cultivation technology in the white shrimp, Litopenaeus vannamei

Chang, Chun-ming 13 July 2005 (has links)
White shrimp (Litopenaeus vannamei) were cultured in isolated environment using zero-water exchange to investigate optimum cultivation method. Except density experiment, culture density was 100 shrimps/m2 in all other experiments. The results indicated that simple quarantine facility could prevent virus infection of pond shrimps. After 83 days of cultivation, survival rate, final weight, yield and growth rate (90.7%, 16.8 g, 1.52 kg/m2, 1.36 g/week) of zero-water exchange group was not significantly different from those of water exchange group, but FCR was lower (p<0.05) instead. Addition of brown sugar increased final weight and growth rate of shrimp and lowered FCR (18.6 g, 1.60 kg/m2, 1.64 ¡Ó 0.04) (p<0.05), but nitrification was inhibited. Application of two mats per tank gave highest increases in final weight and yield and lowest FCR (p<0.05). Bottom sand increased final weight and yield and lowered FCR (p<0.05), stabilized pH and increased de-nitrification efficiency. Salinity of 25 ppt had highest final weight and yield and lowest FCR (p<0.05). Density of 200 shrimps/m2 had highest final weight and lowest FCR (p<0.05) and yield twice as that of density of 100 shrimps/m2. At the end of cultivation, water quality condition between 37% and 32% protein feed were not significantly different. But, the shrimps of 37% protein feed had higher final weight, lower FCR (p<0.05) and 26% more yield. The above results indicated that the risk of shrimps infected by virus could be prevented using zero-water exchange culture method. As long as solid was held suspending by sufficient agitating, good water quality could be maintained. Hence, zero-water exchange culture could not only decrease electricity of water pump and quantity of water use, but also increase the value of product and incorporation efficiency of feeds.
74

Serum High Sensitivity C-Reactive Protein, White Blood Cell Count, and High-Density Lipoprotein Cholesterol Levels are Associated with Coronary Artery Lesions in Kawasaki Disease

Ou, Chum-yen 04 July 2007 (has links)
Background: Kawasaki disease (KD) affects mainly children younger than five years of age, leading to coronary artery lesions, and even to life-threatening myocardial infarctions. Since 1976, Kawasaki disease has occurred among thousands of children in Taiwan. Evidence suggests that inflammation plays a key role in the pathogenesis of atherosclerosis. Significant determinants of high sensitivity C-reactive protein (hs-CRP), which is a sensitive indicator of inflammation, as well as white blood cell (WBC) count, and high-density lipoprotein cholesterol (HDLc) and coronary artery lesion were identified. The relationships between these factors¡¦ concentration and arterial lesion were likewise investigated and had reported. The aim of this study was to determine the serum levels of the hs-CRP, WBC count, and plasma HDLc levels in patients with later phase of KD. Methods and Materials: From July 2005 to June 2006, 97 children with Kawasaki disease at least 1 year after diagnosis were recruited in this study. These participated children had been diagnosed as KD and collected at the interval of 2001 to 2004. Diagnosis was based on the 1984 revised by the KD Research Committee in Japan. The participants were grouped into 45 patients with KD and coronary aneurysms (Group I), 52 patients with KD and normal coronary arteries (Group II), and 50 healthy age-matched children (Control Group III). Their WBC count, systemic and diastolic blood pressures, body mass index, age, sex, fasting total cholesterol concentrations, triglyceride, high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol, serum hs-CRP levels, and coronary artery lesion by cardioechography were recorded and compared. The analytical differences between hs-CRP, WBC count, and plasma HDLc levels and the coronary artery events in KD were examined. Results: Serum hs-CRP levels of Group I patients (mean 0.264 mg/dl) was significantly greater than that of Group II (mean 0.155 mg/dl, p=0.006) and Group III patients (mean 0.116 mg/dl, p =0.017). Similarly, the WBC count of Group I patients (mean 6,543.11/mm3) was significantly greater than that of Group II (mean 5,720.19/mm3, p=0.029), and Group III patients (mean 5,611.27/mm3, p =0.012). However, plasma HDLc levels of Group I patients (mean 41.42 mg/dl) was significantly lesser than that of Group II (mean 44.79 mg/dl, p=0.035), and Control Group III patients (mean 46.58 mg/dl, p=0.027). There was a positive association between hs-CRP and WBC count levels (r = 0.641, p < 0.05), but none between hs-CRP and plasma HDLc levels. Conclusions: There is the possibility of ongoing low-grade inflammation late after the convalescent phase of Kawasaki disease in children with coronary aneurysms, which may have a role in increasing coronary artery dysfunction. These results also suggest that hs-CRP, WBC count, and plasma HDLc levels are useful parameters for predicting formation of coronary artery lesion even in children after onset of KD.
75

Experiment study for heat transfer of high density electronic multichip array by transient heat transfer method with with thermochromic liquid crystal

Lee, Hsu-Fu 10 July 2002 (has links)
Abstract This investigate is designated to the viewpoint that arrangement array of multichip modules are both staggered and in-line. Moreover, here we will discuss and compare the effects and differences of the relevantparameters caused by change Reynolds number (Re) in the experiment.In this experiment, I adopt ¡§transient heat transfer method with thermochromic liquid crystal¡¨ to research multichip modules array change to 3 ¡Ñ 5 and in-line or staggered multichip modules array to probe into the effects of over high density electronic multichip array space to length ratio to heat transfer effects when over high density electronic multichip array space to length ratio are S/L= 4/20,6/20,8/20 in the 8mm¡B12m¡B16mm respectively. The conditions are as following when every row center of chip convection heat transfer coefficient are measured: standard height to length ratio is H/L=10/20 and the height is 20mm. By observing the relationship of the varying parameters, as we can see in the analyze multichip of the experiment Re range form 1394 to 5025, we are able to improve thermal management. The experimentresule: (1) At higher values of Re the heat transfer effects are gain more,atteribute main flow field separation and reattachment is form behind the downstream modules. (2) In over high density multichip array 12S (S/L=6/20) proper are use for Re higher 4135 more than, at 8S (S/L=4/20)the lower Re can be thermocumulate in chip center. (3)When Re is 4135~5025,the heat transfer effects from staggered array is superior to in-line array. If Re range is 1394~3210,the thermal conduction is opposite. Therefore, Re is still the key that decides the efficacy of over high density electronic multichip array heat transfer effects.
76

High-density capacitor array fabrication on silicon substrates

Sethi, Kanika 19 November 2010 (has links)
System integration and miniaturization demands are driving integrated thin film capacitor technologies with ultra-high capacitance densities for power supply integrity and efficient power management. The emerging need for voltage conversion and noise-free power supply in bioelectronics and portable consumer products require ultra high-density capacitance of above 100 μF/cm2 with BDV 16-32 V ,independent capacitor array terminals and non-polar dielectrics. The aim of this research,therefore, is to explore a new silicon- compatible thin film nanoelectrode capacitor technology that can meet all these demands. The nanoelectrode capacitor paradigm has two unique advances. The first advance is to achieve ultra-high surface area thin film electrodes by sintering metallic particles directly on a silicon substrate at CMOS- compatible temperatures. The second advance of this study is to conformally- deposit medium permittivity dielectrics over such particulate nanoelectrodes using Atomic Layer Deposition (ALD) process. Thin film copper particle nanoelectrode with open-porous structure was achieved by choosing a suitable phosphate-ester dispersant, solvent and a sacrificial polymer for partial sintering of copper particles to provide a continuous high surface area electrode. Capacitors with conformal ALD alumina as the dielectric and Polyethylene dioxythiophene (PEDT) as the top electrode showed 30X enhancement in capacitance density for a 20-30 micron copper particulate bottom electrode and 150X enhancement of capacitance density for a 75 micron electrode. These samples were tested for their mechanical and electrical properties by using characterization techniques such as SEM, EDS, I-V and C-V plots. A capacitance density of 30 μF/cm2 was demonstrated using this approach. The technology is extensible to much higher capacitance densities with better porosity control, reduction in particle size and higher permittivity dielectrics.
77

Thin-film trench capacitors for silicon and organic packages

Wang, Yushu 29 August 2011 (has links)
The continuous trend towards mega-functional, high-performance and ultra-miniaturized system has been driving the need for advances in novel materials with superior properties leading to thin components, high-density interconnect substrates and interconnections. Power supply and management is becoming a critical bottleneck for the advances in such mega-functional systems because power components do not scale down with the rest of the system resulting in bulky and stand-alone power modules. Amongst the power components, thin film capacitors are considered the most challenging to integrate because of several manufacturability concerns. The challenges are related to process compatibility of high permittivity dielectrics with substrates and high surface area electrodes, yield, leakage and losses. This thesis focuses on novel thin film capacitor technologies that address some of these critical challenges. / Thesis advisor has approved the addition of errata to this item. The abstract text in the metadata record has been modified to match the document text.
78

Time dependent response of pulled-in-place HDPE pipes

Chehab, Abdul Ghafar 19 June 2008 (has links)
Horizontal directional drilling is increasingly used to install pipes without costs and disruptions associated with conventional ‘cut and cover’ installations. This technique, which was developed by industrial innovators, feature complex soil and pipe response which is not well understood. The success of this operation depends on knowledge of the pulling forces applied, level of ground disturbance, ground expansion or fracture from mud pressure, and the effect of the pulling operation on the pipes. Tensile stresses in the pipe vary with time during and after installation, and along the pipe. This applies especially to polymer pipes where the stresses during insertion and those over the service life of the pipe may influence its performance. The main objective of this study is to model the short term and long term response of pipes installed using horizontal directional drilling and to investigate the effect of the time dependent behaviour of polymer pipes, as well as other installation variables on the performance of the pipe during and after installation. The mechanical behaviour of high density polyethylene used to manufacture a significant portion of pipes installed using horizontal directional drilling is investigated and two sophisticated constitutive models are developed to simulate the time-dependent behaviour of high density polyethylene. The interaction between the pipe and the surrounding soil during horizontal directional drilling installations is also investigated and modelled. A FORTRAN algorithm is developed to calculate the short and long term response of elastic and polymeric pipes installed using horizontal directional drilling. The program uses the HDPE constitutive models as well as the pipe-soil interaction model developed in the study. After evaluation, the developed program is employed in a parametric study on the sensitivity of short term and long term pipe response to different parameters, including the effect of overstressing the pipe during installation. As Multiaxial modeling is necessary for accurate analysis of some applications including the swagelining method, a uniaxial constitutive model developed in the current study is generalized to a multi-axial model that can simulate the response to biaxial stress-strain fields. The multi-axial model is implemented in a finite element code and its performance in simulating multiaxial stress-strain fields is evaluated. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2008-06-12 18:03:43.501
79

Strategic repositioning of Safripol in the South African polymer industry / W.A. du Plessis

Du Plessis, Willem Adriaan January 2010 (has links)
Safripol is a South African polymer company producing mainly high density polyethylene and polypropylene for the South African market. Safripol used to be part of a global chemical company Dow Chemicals. Dow Chemical's divested in South Africa in 2006 and Safripol lost all the advantages of being part of a global corporate enterprise. The company is faced with a unique situation in that it is receiving monomer from Sasol, which is also its main competitor in the polymer market. The price of monomer and its low availability is putting pressure on Safripol's product margins, with a negative effect on the company's sustainability. The above was also defined as the research problem that threatens to undermine the company's competitive edge in the polymer market. It was clear from this research study that monomer and specifically propylene was the biggest burning point for Safripol regarding the price and availability thereof. Research into the South African polymer market has shown that Safripol will lose significant market share if the company is not showing additional growth in the market. The research problem is investigated through interviews, monomer availability investigations, plant capacity increasing and potential technology partner's discussions. A specific scenario planning process was also followed to help Safripol identify potential present and future scenarios that the company can investigate. The research problem was addressed by developing a strategy for Safripol to address the research objectives. Recommendations were done regarding the following: 1) Recommendations for additional propylene supply. 2) Recommendations to increase the polypropylene plant capacity. 3) Recommendations with regards to technology partners. 4) Recommendations regarding the scenario planning process. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011. (Mag eers in 2014 gepubliseer word)
80

Strategic repositioning of Safripol in the South African polymer industry / W.A. du Plessis

Du Plessis, Willem Adriaan January 2010 (has links)
Safripol is a South African polymer company producing mainly high density polyethylene and polypropylene for the South African market. Safripol used to be part of a global chemical company Dow Chemicals. Dow Chemical's divested in South Africa in 2006 and Safripol lost all the advantages of being part of a global corporate enterprise. The company is faced with a unique situation in that it is receiving monomer from Sasol, which is also its main competitor in the polymer market. The price of monomer and its low availability is putting pressure on Safripol's product margins, with a negative effect on the company's sustainability. The above was also defined as the research problem that threatens to undermine the company's competitive edge in the polymer market. It was clear from this research study that monomer and specifically propylene was the biggest burning point for Safripol regarding the price and availability thereof. Research into the South African polymer market has shown that Safripol will lose significant market share if the company is not showing additional growth in the market. The research problem is investigated through interviews, monomer availability investigations, plant capacity increasing and potential technology partner's discussions. A specific scenario planning process was also followed to help Safripol identify potential present and future scenarios that the company can investigate. The research problem was addressed by developing a strategy for Safripol to address the research objectives. Recommendations were done regarding the following: 1) Recommendations for additional propylene supply. 2) Recommendations to increase the polypropylene plant capacity. 3) Recommendations with regards to technology partners. 4) Recommendations regarding the scenario planning process. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011. (Mag eers in 2014 gepubliseer word)

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