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Brain cortical variability, software, and clinical implicationsMikhael, Shadia S. January 2018 (has links)
It is essential to characterize and quantify naturally occurring morphometric changes in the human brain when investigating the onset or progression of neurodegenerative disorders. The aim of this thesis is to characterize the properties and measure the performance of several popular automated magnetic resonance image analysis tools dedicated to brain morphometry. The thesis begins with an overview of morphometric analysis methods, followed by a literature review focusing on cortical parcellation protocols. Our work identified unanimous protocol weaknesses across all packages in particular issues when addressing cortical variability. The next chapters present a ground truth dataset and a dedicated software to analyse manually parcellated data. The dataset (https://datashare.is.ed.ac.uk/handle/10283/2936) includes 10 healthy middle-aged subjects, whose metrics we used as reference against automated tools. To develop the ground truth dataset, we also present a manual parcellation protocol (https://datashare.is.ed.ac.uk/handle/10283/3148) providing step-by-step instructions for outlining three cortical gyri known to vary with ageing and dementia: the superior frontal gyrus, the cingulate gyrus and the supramarginal gyrus. The software, Masks2Metrics (https://datashare.is.ed.ac.uk/handle/10283/3018), was built in Matlab to calculate cortical thickness, white matter surface area, and grey matter volume from 3D binary masks. Characterizing these metrics allowed further understanding of the assumptions made by software when creating and measuring anatomical parcels. Next, we present results from processing the raw T1-weighted volumes in the latest versions of several automated image analysis tools-FreeSurfer (versions 5.1 and 6.0), BrainGyrusMapping, and BrainSuite (version 13a)- against our ground truth. Tool repeatability for the same system was confirmed as multiple runs yielded identical results. Compared to our ground truth, the closest results were generated by BrainGyrusMapping for volume metrics and by FreeSurfer 6.0 for thickness and surface area metrics. In conclusion, our work sheds light on the significance of clearly detailed parcellation protocols and accurate morphometric tools due to the implications that they both will have. We therefore recommend extra caution when selecting image analysis tools for a study, and the use of independent publicly available ground truth datasets and metrics tools to assist with the selection process.
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Design and Characterization of Circularly Polarized Cavity-Backed Slot Antennas in an In-House-Constructed Anechoic ChamberChandak, Mangalam 01 August 2012 (has links)
Small satellites are satellites that weight less than 500 kg. Compared to larger satellites, a small satellite, especially a cube satellite, has limited surface area. The limited surface area casts challenges for allocating essential parts, such as antennas, for the satellite. Therefore, antennas that are conformal to the satellite surface have distinct advantages over other types of antennas that need significant mounting area. One of the very effective conformal antennas is cavity-backed slot antennas that can be integrated around solar cells and do not compete for extra surface area. The previous study performed on cavity-backed slot antennas was mainly a feasibility study and did not address realistic concerns such as effective feeding methods for the antennas. This thesis work is aimed at providing more detailed study on achieving high quality circular polarization (CP) and simplified feed design to initiate effective integration of the antenna with solar panel. In order to accurately characterize an antenna, an effective antenna range in an anechoic chamber is important. Utah State University had an effective near-field range; however, there was not an fully shielded anechoic chamber. As another objective of this thesis work, a state-of-the-art anechoic chamber has been constructed, calibrated, and utilized to measure different antenna parameters. This thesis also shows correct methods to measure important antenna properties such as CP and antenna efficiency.
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Supercritical Carbon Dioxide Aided Preparation of Nickel Oxide/Alumina Aerogel CatalystLi, Haitao 15 February 2005 (has links)
The strength, thermal stability, pore structure and morphology are keys to success for wider deployment of aerogels. Furthermore, co or subsequent functionalization of the surfaces are equally, if not more important. This study addresses these issues through a new method. The path involves successful use of surfactant templating, supercritical extraction and drying, and supercritical fluid aided functionalization of the surface. Alumina support and alumina supported nickel catalyst particles are used to evaluate the approach. Initially thermally stable surfactant alumina was synthesized. The surfactant template was removed completely with the aid of a supercritical solvent mixture. Surfactant-templated alumina aerogel showed remarkable thermal stability and gave specific surface area above 500m2 /g both before and after calcination. The alumina support is subsequently impregnated with nickel. BET and BJH method (Nitrogen adsorption-desorption isotherms) were used to follow the removal of solvents and templates as well as tracking the textural properties for the synthesized gel. Meanwhile, co-precipitated nickel oxide/alumina system was also synthesized for comparison with the supercritical impregnation nickel oxide/alumina system. SEM-EDS and XPS were employed to study the distribution of the nickel on the alumina support and the percentage was compared with the initial mixture of the sol gels.
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Fundamental investigation of fuel cell-based breath alcohol sensors and the cause of sensor degradation in low-humidity conditionsPrest, Laura 01 August 2011 (has links)
The goal of this research project was to characterize the physical and electrochemical properties of a commercially available fuel cell-based breath alcohol sensor. Characteristics of the existing sensor were compared with state of the art power generating fuel cells with the goal of understanding the factors that limit performance, lifetime and cost effectiveness of the sensors. This will guide the development of the next generation of breath alcohol sensors.
The average lifetime of the current sensor falls short of the industry standards. In particular, sensors operating in dry conditions experience more rapid loss of sensitivity and failure. Two primary causes of degradation were investigated in this study. Loss of proton conductivity as a result of membrane dehydration was shown to be reversible by rehydrating the membrane in humid conditions. Loss of electrochemically active surface area of Pt is irreversible and seems to be caused by a change in sensor morphology after long-term exposure to dry conditions. / UOIT
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Cortical Morphology in Children with Alcohol-related Neurodevelopmental DisorderRajaprakash, Meghna 26 November 2012 (has links)
Individuals exposed to alcohol in utero have reduced cortical grey matter volumes. However, the underlying determinants of these reductions have not been investigated exclusively in alcohol-related neurodevelopmental disorder (ARND). Using magnetic resonance imaging scans from 121 participants (57 ARND and 64 controls) aged 8 to 16 years, cortical morphology was analyzed. Results revealed the ARND group had reduced cortical grey matter volumes, but did not differ from controls in cortical thickness. Rather, the cortical abnormalities reflected reductions in global surface area, local surface area reductions in the right occipital-temporal area and right superior temporal gyrus, as well as reduced gyrification. A significant interaction between sex and group was observed, with females showing greater reductions than males in cortical volume and surface area. Results suggest that ARND is characterized by global reductions in cortical surface area and gyrification and females are more vulnerable than males to the teratogenic effects of alcohol.
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Cortical Morphology in Children with Alcohol-related Neurodevelopmental DisorderRajaprakash, Meghna 26 November 2012 (has links)
Individuals exposed to alcohol in utero have reduced cortical grey matter volumes. However, the underlying determinants of these reductions have not been investigated exclusively in alcohol-related neurodevelopmental disorder (ARND). Using magnetic resonance imaging scans from 121 participants (57 ARND and 64 controls) aged 8 to 16 years, cortical morphology was analyzed. Results revealed the ARND group had reduced cortical grey matter volumes, but did not differ from controls in cortical thickness. Rather, the cortical abnormalities reflected reductions in global surface area, local surface area reductions in the right occipital-temporal area and right superior temporal gyrus, as well as reduced gyrification. A significant interaction between sex and group was observed, with females showing greater reductions than males in cortical volume and surface area. Results suggest that ARND is characterized by global reductions in cortical surface area and gyrification and females are more vulnerable than males to the teratogenic effects of alcohol.
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An Analysis of the Surface Area of the Western Roman Empire until CE 476Roncone, Laura Antonia January 2012 (has links)
In 1968, Rein Taagepera created growth curves of four empires by measuring the surface area of each and plotting his data on a graph of area versus time. He used his growth curves to analyse the development of empires quantitatively, as he considered surface area to be the best measurable indicator of an empire’s strength. His growth curve of the Roman Empire, in particular, has been referenced numerous times by scholars researching the decline and fall of complex civilizations to support their individual analyses of the collapse of Rome. While this thesis surveys only the territories of the Western Roman Empire, many of the parameters used by Taagepera have been either borrowed or adapted in order to define, measure, and graph the surface area of the Western Empire as precisely as possible. This thesis also adds further precision and validity to Bryan Ward-Perkins’ theory that surface area can be used to analyse and quantify the collapse of a complex society accurately.
In order to demonstrate the extent to which differing circumstances and outcomes of provincial history impacted the total surface area of the Western Roman Empire, it was essential to include not only an overview of Rome’s extensive history, but also to establish the chronology, as it related to the Roman Empire, of each individual province, territory, and client kingdom within the Western Empire. Detailed chronologies of Noricum and Britannia have been included to serve as case studies as they comprise a broad range of distinct characteristics and so represent typical western provinces.
My research of the history and geography of the Roman Empire has generated a comprehensive inventory that includes all the pertinent onomastic and chronological data needed to measure the surface area of each of Rome’s western provinces and client kingdoms. When plotted on a graph of area versus time, my data not only produced an accurate representation of the actual surface area of the Western Roman Empire, but also one that facilitates temporal analyses of territorial fluctuations at any given point in the Empire’s history until the fall of the Western Empire in CE 476.
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Early stage sintering and PLAL fragmentation of micro-scale CaCO3Lin, Peng-Wen 04 July 2012 (has links)
In the first part of this thesis, CaCO3 (calcite) powder ball-milled to micro/nano scale were subjected to isothermal firing in the temperature range of 450-600 ¢XC in an open air furnace in order to study specific-surface area reduction as a result of early-stage sintering/coarsening/coalescence/repacking (denoted as SCCR process) of the fine particles. The surface area and pore size distributions were obtained from the BET and BJH methods, respectively. The H1 type adsorption/desorption hysteresis loop of the type IV isotherm was used as an indicator of cylindrical pore formation upon dry pressing and firing of the powder. The apparent activation energy for the onset SCCR of the dry-pressed calcite powder turned out to be 57.5¡Ó1.0 kJ/mol based on t0.5, i.e. time for 50 % specific surface area reduction. The minimum temperature for such an incipient SCCR process was estimated to be 590K (317¢J) by extrapolating the specific-surface-area reduction rate to null. The mechanism of specific surface area change includes the Brownian motion, coarsening and coalescence/repacking of calcite particles besides sintering via synchronizing diffusion of calcium ion and carbonic acid ion along grain surface and boundary. In the second part of this thesis, pulsed laser ablation on micrometer-sized calcite (type I) powder in liquid H2O (PLAL) was conducted to study the structure and optical property change of calcium carbonate under a dynamic high-temperature.
high-pressure aqueous condition. X-ray diffraction (XRD) indicated the fragmented calcite I powder via such a PLAL process change predominantly into a metastable CaCO3 II phase presumably by a displacive type transformation from calcite I and/or nucleated from atom clusters. The refined XRD lattice parameters indicate a significant internal compressive stress (up to 1.5 GPa) was retained for the predominant CaCO3 II nanoparticles having well-developed (013), (010) and (013) faces as revealed by transmission electron microscopy (TEM). Minor calcium carbonate nanoparticles were also identified by TEM to be other high-pressure polymorphs (type III and aragonite), hydrated (monohydrocalcite, ikaite), amorphized (amorphous calcium carbonate), and even decomposed as cubic lime (CaO). Monohydrocalcite occasionally occurred as epitaxial intergrowths within the predominant CaCO3 II matrix. Vibrational spectroscopy (Raman and FTIR) indicated
the structure units of the overall nanoparticles by the PLAL process were considerably modified as a combined results of size miniature, protonation and internal compressive stress. The UV-visible absorption results further indicate that the minimum band gap of the colloidal solution was narrowed down to ca. 5 eV and 3 eV for the predominant CaCO3 II and minor accessory phases, respectively, thus shedding light on their potential opto-catalytic applications.
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A Phenotypic Evaluation of 61 Mutated Lines of TAM 94L-25Brown, Ismael Ning 2010 December 1900 (has links)
Among the available methods of creating selectable variation, induced mutagenesis has been historically under-utilized in cotton improvement. Dick Auld showed that chemical mutagenesis could be used to enhance fiber length of a medium staple cotton cultivar without sacrificing yield. The goal of this project was to determine if mutagenesis could be used to improve the fiber quality of a germplasm line already considered to be at the upper-limits of fiber length.
Seed of TAM 94 L-25 were treated with EMS in 2001 and the M2 generation was produced at Lubbock, Texas in 2002. More than 1200 M3 plants were grown at College Station, Texas in 2004, harvested individually, and HVI fiber properties determined. The top and bottom 1 percent for UHML, strength, and elongation were selected and the seeds of these individuals planted as an M4 progeny row nursery in 2005. Approximately ten individual plants per progeny row were harvested for re-evaluation of fiber parameters. From the approximately 1600 individual TAM 94L-25 M4 plants harvested in 2005, 61 were selected and subsequently treated as pure lines. Agronomic performance trials were conducted on 61 of those TAM 94L-25 M lines along with the M0 check and two commercial cultivar checks, Fiber Max 832 and Phytogen 355, in 2008 and 2009 in College Station and Weslaco, Texas. Within-boll yield components were examined for 13 representative mutant lines and the three checks.
TAM 94L-25 averaged 751 kg lint ha^-1, 31.1 mm UHML, 303 kN m kg^-1 fiber bundle strength, and 6.0 percent elongation. The 61 mutant lines yielded from 366 to 932 kg lint ha^-1, exhibited UHML from 24.3 to 34.9 mm, fiber bundle strengths of 261 to 333 kN m kg^-1, and elongations from 5.4 to 8.1 percent. Seed surface area of the TAM 94L-25 M-lines was between 99 and 124 mm^2, and fibers per unit seed surface area from 123 to 168 fibers mm^-2. The M0 parent, TAM 94L-25 averaged 125 mm^2 seed-1, and 128 fibers mm^-2. The data presented herein demonstrate that EMS-induced mutagenesis was successful in creating TAM 94L-25 M-lines with superior fiber and yield traits to that of the non-mutated, high fiber quality parent, TAM 94L-25.
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Effects Of Granulated Blast Furnace Slag Trass And Limestone Fineness On The Properties Of Blended CementsDelibas, Tughan 01 January 2012 (has links) (PDF)
The aim of this research was to determine the effects of the fineness of different mineral additives on loss on ignition, heat of hydration, physical, mechanical and chemical properties of blended cements. For that purpose, portland cement clinker was replaced with granulated blast furnace slag (GBFS), natural pozzolan (NP) and limestone (L) at 6%, 20% and 35% replacement levels. Blended cements containing GBFS and NP were ground to a fineness of 3000, 5000 and 6000 cm2/g. Cements containing L were ground to 3000 cm2/g, 4000 cm2/g and 4500 cm2/g. All of the blended cement types mentioned above were both interground and separately ground to the specified fineness levels. Therefore, a total of 57 different cements were produced. Loss on ignition, heat of hydration, chemical, mechanical and physical analyses were performed on the produced cements. Moreover, the chemical analyses of the cements were obtained for cement particles finer (-45&mu / m) and coarser (+45&mu / m) than 45 &mu / m in order to determine the ingredients of -45 &mu / m, which is known to be more reactive.
As a result it was shown that the grindability differences of the cement ingredients affect the properties of blended cements. An increase in the specific surface area increases both the compressive strength and heat of hydration values and adversely affects the loss on ignition
values. The results also showed that if the cement particles were ground finer, it was more prone to moisture which resulted in higher loss on ignition values after longer periods.
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