Browsing by Subject "Scanning electron microscopy"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Automated Transmission-Mode Scanning Electron Microscopy (tSEM) for Large Volume Analysis at Nanoscale Resolution(Public Library of Science, 2013-03-26) Kuwajima, Masaaki; Mendenhall, John M.; Lindsey, Laurence F.; Harris, Kristen M.Transmission-mode scanning electron microscopy (tSEM) on a field emission SEM platform was developed for efficient and cost-effective imaging of circuit-scale volumes from brain at nanoscale resolution. Image area was maximized while optimizing the resolution and dynamic range necessary for discriminating key subcellular structures, such as small axonal, dendritic and glial processes, synapses, smooth endoplasmic reticulum, vesicles, microtubules, polyribosomes, and endosomes which are critical for neuronal function. Individual image fields from the tSEM system were up to 4,295 µm2 (65.54 µm per side) at 2 nm pixel size, contrasting with image fields from a modern transmission electron microscope (TEM) system, which were only 66.59 µm2 (8.160 µm per side) at the same pixel size. The tSEM produced outstanding images and had reduced distortion and drift relative to TEM. Automated stage and scan control in tSEM easily provided unattended serial section imaging and montaging. Lens and scan properties on both TEM and SEM platforms revealed no significant nonlinear distortions within a central field of ~100 µm2 and produced near-perfect image registration across serial sections using the computational elastic alignment tool in Fiji/TrakEM2 software, and reliable geometric measurements from RECONSTRUCT™ or Fiji/TrakEM2 software. Axial resolution limits the analysis of small structures contained within a section (~45 nm). Since this new tSEM is non-destructive, objects within a section can be explored at finer axial resolution in TEM tomography with current methods. Future development of tSEM tomography promises thinner axial resolution producing nearly isotropic voxels and should provide within-section analyses of structures without changing platforms. Brain was the test system given our interest in synaptic connectivity and plasticity; however, the new tSEM system is readily applicable to other biological systems.Item Chemical approaches for improved nanoscale organic and polymer thin-film transistors (TFTs)(2022-08-10) McCulley, Calla Mae; Dodabalapur, Ananth, 1963-; Mullins, Charles B; Page, Zachariah A; Roberts, Sean T; Yu, Edward TThin-film transistors (TFTs) function as electrical switches within integrated circuits. Precise control over the on and off states of this switch are crucial for device implementation into the various circuit applications. Currently, organic and polymer thin film semiconductors face challenges that differ from the semiconductors used in modern-day TFTs. However, they have their advantages such as being solution processable, relatively inexpensive, and deposition can be performed on a larger variety of substrates for flexible applications. Therefore, this dissertation consists of many approaches we have explored to overcome the performance challenges (low on-currents and mobilities) of organic and polymer semiconductor-based TFTs. Our approaches were implemented in large- and short-channel TFTs to study the effects of scaling down closer to current dimensions used in state-of-the-art technologies. The modifications to the dielectric layer, the electrical contacts, and the thin-film semiconductor layer were all investigated to highlight the impact each layer contributes to overall electrical TFT performance.Item Nineteenth century concrete in Seguin, Texas: construction materials & techniques(2014-08) Hunter, Sarah Beth; Gale, Frances R.; Holleran, MichaelThis investigation centers on early concrete technology used in Seguin, Texas, during the mid-19th century. Over the course of fifty years, more than ninety concrete structures were built in Seguin. Over the last century, these have dwindled to twenty extant structures. Much of the previous Seguin concrete era research has focused on the historical narrative and architectural description. This study aims to answer questions that previous research has not — it investigated the raw materials used in making Seguin’s concrete. The results provide new information about the Seguin concrete structures, providing guidance for their long-term maintenance. The materials analysis uses instrumental techniques such as scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction to determine the chemical composition and crystalline structure of the cement binder from several extant structures in Seguin. Gathering both qualitative and quantitative data for the binder allowed us to identify the raw materials used in the concrete and better understand the construction methods. Studying the materials and methods increased our understanding of these historic structures and will inform future preservation efforts.