Matching Items (3)
Description
This dissertation describes development of a procedure for obtaining high quality, optical grade sand coupons from frozen sand specimens of Ottawa 20/30 sand for image processing and analysis to quantify soil structure along with a methodology for quantifying the microstructure from the images. A technique for thawing and stabilizing frozen core samples was developed using optical grade Buehler® Epo-Tek® epoxy resin, a modified triaxial cell, a vacuum/reservoir chamber, a desiccator, and a moisture gauge. The uniform epoxy resin impregnation required proper drying of the soil specimen, application of appropriate confining pressure and vacuum levels, and epoxy mixing, de-airing and curing. The resulting stabilized sand specimen was sectioned into 10 mm thick coupons that were planed, ground, and polished with progressively finer diamond abrasive grit levels using the modified Allied HTP Inc. polishing method so that the soil structure could be accurately quantified using images obtained with the use of an optical microscopy technique. Illumination via Bright Field Microscopy was used to capture the images for subsequent image processing and sand microstructure analysis. The quality of resulting images and the validity of the subsequent image morphology analysis hinged largely on employment of a polishing and grinding technique that resulted in a flat, scratch free, reflective coupon surface characterized by minimal microstructure relief and good contrast between the sand particles and the surrounding epoxy resin. Subsequent image processing involved conversion of the color images first to gray scale images and then to binary images with the use of contrast and image adjustments, removal of noise and image artifacts, image filtering, and image segmentation. Mathematical morphology algorithms were used on the resulting binary images to further enhance image quality. The binary images were then used to calculate soil structure parameters that included particle roundness and sphericity, particle orientation variability represented by rose diagrams, statistics on the local void ratio variability as a function of the sample size, and the local void ratio distribution histograms using Oda's method and Voronoi tessellation method, including the skewness, kurtosis, and entropy of a gamma cumulative probability distribution fit to the local void ratio distribution.
ContributorsCzupak, Zbigniew David (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Houston, Sandra (Committee member) / Arizona State University (Publisher)
Created2011
Description
Arid and semiarid ecosystems (known as drylands) cover 45% of global land area and are predicted to expand to encompass half of the world’s land area by the end of the century. Litter decomposition plays a large role in nutrient and carbon cycling in dryland ecosystems, yet it remains poorly understood. Models that accurately predict decomposition in mesic ecosystems fail to accurately describe decomposition in drylands due to differing drivers of decomposition but also because litter in drylands accumulates around litter retention elements (LREs). LREs can be any object or surface that inhibits the movement vectors (e.g., wind) that push litter across drylands, creating a “pool” of litter around the LRE. Litter pooling increases the amount of mixing between litter and soil, creating a microclimate more conducive to microbial decomposition. Due to the increase in microbial decomposition, the decomposition rate for litter around LREs can be markedly different than that of litter not in LREs. To further understand how much litter accumulates in LREs, I studied the differences in litter accumulation between LREs and open areas in five drylands across the Southwestern United States. To do this, I visually analyzed photos of 424 litterbags to determine the cover percentages of four different types of organic litter (grass, broadleaf, reproductive, woody) and rock litter. Visual analysis of litterbags consisted of manually delineating the percent coverage of each of these litter categories. Litterbags had been placed in both open intercanopy areas as well as woody sub-canopy areas in which the plant canopy acted as the LRE. Additionally, 45 of these litterbags were randomly selected for analysis in the computer program FIJI (FIJI is Just ImageJ) to assess the litter area find the percent difference between visual and digital analysis. Areas underneath woody sub-canopies accumulated far more organic matter litter over time than open areas between canopies did but displayed a similar amount of rock litterbag cover. Shrub microsites also displayed far more varied litterbag cover percentages than open microsites. Data also suggested that litter does not always accumulate underneath shrubs or open intercanopy areas and may dissipate as time progresses. These results support the idea that litter accumulation varies throughout drylands, and that soil and litter mix frequently in LREs such as under woody plant canopies. The percent difference between FIJI analysis and visual analysis was generally negative, reflecting that visual estimation of litterbag cover was typically smaller than digital estimates. Cumulatively, litter was shown to accumulate much more around LREs and even move from them – supporting the idea that litter decomposition models need to account for litter movement in drylands to be accurate.
ContributorsNelson, Benjamin (Author) / Throop, Heather (Thesis director) / Ball, Becky (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2022-05
Description
Traumatic brain injury (TBI) poses a significant global health concern with substantial health and economic consequences. Patients often face significant consequences after injury, notably persistent cognitive changes and an increased risk of developing neurodegenerative disease later in life. Apart from the immediate insult, the resulting inflammatory response can lead to neuroinflammation, oxidative stress, tissue death, and long-term neurodegeneration. Microglia and astrocytes play critical roles in these inflammatory processes, emphasizing the unmet need for targeted therapies. Vaccine formulations consisting of poly (a-ketoglutarate) (paKG) microparticles (MPs) encapsulating PFK15 (1-(4-pyridinyl)-3-(2-quinolinyl)-2-propen-1-one) and myelin proteolipid protein (PLP) were developed for prior studies and have demonstrated the production of antigen-specific adaptive T-cell responses in the brain, spleen, and lymph nodes of mice, suggesting that these formulations may be able to prevent neuronal inflammation in mice after TBI. The vaccine efficacy was further evaluated through the image analysis of immunohistochemically stained brain tissue sections from naive, saline, and paKG(PFK15+PLP) MPs or paKG(PFK15) MPs treated mice. Though microglia (Iba1), astrocytes (GFAP) and CD86 were visualized in this method, only Iba1 was found to be significantly reduced in the contralateral hemisphere for paKG(PFK15+PLP) MPs and paKG(PFK15) MPs groups when compared to naive (p=0.0373 and p=0.0186, respectively). However, the naive group also showed an unexpectedly high level of CD86 after thresholding (compared to the TBI groups), indicating flaws were present in the analysis pipeline. Challenges of the image analysis process included thresholding setting optimization, folded tissues, bubbles, and saturated punctate signal. These issues may have impacted data accuracy, underscoring the need for rigorous optimization of experimental techniques and imaging methodologies when evaluating the therapeutic potential of the vaccines in mitigating TBI-induced neuroinflammation. Thus, future analyses should consider microglial morphology and employ more accurate thresholding in FIJI/ImageJ to better measure cellular activation and the overall positive signal.
ContributorsSundem, Andrea (Author) / Stabenfeldt, Sarah (Thesis director) / Willingham, Crystal (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2024-05