Now showing items 3776-3795 of 14977

    • Dual Field of View Optical System for Colonoscope

      Liang, Rongguang; Katkam, Rajender; Banerjee, Bhaskar; Koshel, Richard J.; Liang, Rongguang (The University of Arizona., 2014)
      The present dual field of view flexible colonoscope can provide both forward view and radial or backward view of the colon to improve detection of cancerous polyps. The colonoscope has its own illumination that illuminates the parts of the colon viewed by imaging optics. The optical system, limited only by the diffraction effects at the exit pupil over the entire visible spectrum, can provide high resolution and is suitable for color imaging. The flexible colonoscope has an on-board sensor at the proximal end of the colonoscope to improve resolution. The proximal end of colonoscope measures only 8 mm in diameter and 20 mm in length. The present colonoscope has the potential to be scaled down to as small as 6 mm inner diameter from the present 8 mm.
    • Dual target effects on the nutating reticle tracking system

      Dereniak, Eustace L.; Tang, Hamilton Roger, 1969- (The University of Arizona., 1993)
      When used in conjunction with an optical system, a nutating reticle can be utilized to track point sources. The position information of a single point source in the field of view is encoded as a phase modulated signal that is demodulated by appropriate electronics to extract the angular position of the single point source for tracking purposes. With two point sources in the field of view, it can be shown that particular types of demodulation electronics will output position information such that the tracking system will track the irradiance weighted centroid of the two sources.
    • Dual-Comb Spectroscopy of Laser-Induced Plasmas

      Jones, R. Jason; Bergevin, Jenna; Jones, R. Jason; Yeak, Jeremy; Sandhu, Arvinder; Schaibley, John (The University of Arizona., 2017)
      Dual-comb spectroscopy (DCS) has widespread applications. It has become a more prominent spectroscopic tool because it has broad spectral coverage with high frequency resolution. We demonstrate the broadband and high resolution of DCS to probe transient events, showing the rst use of DCS of laser-induced plasmas (LIPs). Our measurements span absorption features 7 THz wide, simultaneously detecting Rb D2, K D1 and D2 absorption lines with the ability to resolve the isotope ratios in the Rb D2 line. This technique is more broadband and faster than tunable laser absorption spectroscopy because it eliminates the requirement to scan across transitions. Additionally, DCS makes higher resolution measurements than laser-induced break- down spectroscopy. Our ultimate goal is to use DCS as a technique to ascertain the chemical composition of unknown samples. Our rst demonstration of this technique illustrates that DCS makes broadband, high-resolution measurements with the ability to measure isotope ratios, which is necessary for determining sample composition.
    • Ductility of single plate framing connections

      Caccavale, Salvatore Erasmo, 1951- (The University of Arizona., 1975)
    • Duodenal Gastrinomas Exhibit a Unique Transcriptome and Mutational Profile to Pancreatic Neuroendocrine Tumors

      Merchant, Juanita L.; Rico, Karen; Heinmark, Ronald; Pandey, Ritu (The University of Arizona., 2019)
      Gastrinomas are malignant gastroenteropancreatic neuroendocrine tumors (GEP-NETs) that occur more commonly in the duodenum than in the pancreas and are associated with mutations in MEN1. Neuroendocrine cells, which give rise to GEP-NETs, are thought to arise from endodermally-derived cells. We previously showed that duodenal gastrinomas express glial cell markers, suggesting that duodenal neuroendocrine tumors (DNETs) and pancreatic neuroendocrine tumors (PNETs) may have a different origin. AIM: To determine if DNETs and PNETs exhibit a transcriptome that reflects parallel mechanisms for the development of GEP-NETs and whether MEN1 influences the tissue-specific differences. METHODS: Blood and tumor whole exome sequencing (WES) was performed in three PNETs, three DNETs, and two ileal carcinoids. RNA-Seq was performed on two of the DNET gastrinomas and two non-functional PNETs. We conducted a western blot and immunohistochemistry of menin to determine if mutations led to a loss of the protein or change in location. RESULTS: All four tumor samples showed elevated but equivalent levels of RNA transcripts for neuroendocrine markers such as chromogranin A, neuron-specific enolase and synaptophysin. Gastrin mRNA was 700-fold greater in both DNETs compared to the PNETs, which is consistent with their clinical diagnoses of gastrinoma. The non-functional PNETs expressed >25-fold higher mRNA levels of vasoactive intestinal peptide relative to the DNETs. DNETs expressed elevated mRNA levels of genes related to gastrin-cell specification (e.g., NKX6-3). In PNETs, elevated transcripts were related to genes expressed during the early stages of enteroendocrine cell differentiation (ASCL-1, IRX2). WES analysis of all samples showed a germline mutation of MEN1Ala541Thr. The minor allele frequency of the MEN1Ala541Thr mutation is 16.2%. In addition, a germline frameshift at MEN1 Arg 521 was identified in a DNET. A germline non-frameshift deletion at Glu363 and two somatic insertions consisting of 14 and 32 nucleotides at Gly2 and Met1 respectively, were identified in a PNET. All DNETs exhibited germline and somatic MEN1 mutations in the C-terminus of the protein near the nuclear export signal within exon 10. By contrast, in the non-functional PNETs, the mutations were located near the N-terminus of the protein. Surprisingly, a MEN1 mutation was present in the ileal carcinoids at MEN1Ala541Thr. Menin protein expression was observed in GEP-NETs and was cytoplasmic. CONCLUSION: The transcriptome and mutation profiles of DNET gastrinomas differed from PNETs. Elevated levels of transcripts in DNETs were related to gastrin cell specification, while elevated PNET transcripts were related to neuronal and enteroendocrine cell differentiation. Regardless of the MEN1 mutation profile, menin protein was expressed in all samples. MEN1 mutations may not be sufficient to initiate tumorigenesis, suggesting that other parallel mechanisms might inactivate the function of menin.
    • Duration of zoospore motility of pythium species in situ

      Stanghellini, Michael E.; Quaempts, Rex Matthew, 1962- (The University of Arizona., 1987)
      Motile zoospores of P. dissotocum and P. catenulatum were added to 20 and 60 mesh silica sand and a sandy loam soil to investigate the duration of motility. Both Pythium species remained motile for up to 24 hours in all soil textures tested. However, the duration and percentage of the motile population varied depending upon the soil type and species tested. The duration of survival of motile and encysted zoospores of P. dissotocum and P. catenulatum in air dried and saturated sterile silica sand was also tested. P. dissotocum, under air dried conditions, did not survive while P. catenulatum was capable of surviving 4 and 16 days as motile and encysted zoospores, respectively. Both fungi could be recovered at high percentages after 5 weeks under saturated conditions. The survival structure is believed to be in the form of a zoospore cyst.

      Li, Beirong (The University of Arizona., 2003)
    • DVFS-Aware Asymmetric-Retention STT-RAM Caches for Energy-Efficient Multicore Processors

      Adegbija, Tosiron; Gajaria, Dhruv Mayur; Lysecky, Roman; Akoglu, Ali (The University of Arizona., 2019)
      Spin-transfer torque RAMs (STT-RAMs) have been studied as a promising alternative to SRAMs in emerging caches and main memories due to their low leakage power and high density. However, STT-RAMs, also have drawbacks of high dynamic write energy and long write latency. Relaxing the retention time of the non-volatile STT-RAM has been widely studied as a way to reduce STT-RAM's write energy and latency. However, since different applications may require different retention times, STT-RAM retention times must be critically explored to satisfy various applications' needs. This process can be challenging due to exploration overhead, and exacerbated by the fact that STT-RAM caches are emerging and are not readily available for design time exploration. This work explores using known statistics (e.g., SRAM statistics) to predict the appropriate STT-RAM retention times, in order to minimize exploration overhead. We propose an STT-RAM Cache Retention Time (SCART) model, which utilizes machine learning to enable design time or runtime prediction of best STT-RAM retention times for latency or energy optimization. Furthermore, we analyze the impacts of dynamic voltage and frequency scaling (DVFS)---a common optimization in modern processors---on STT-RAM L1 cache design. Our analysis reveals that, apart from the fact that different applications may require different retention times, the clock frequency, which is typically ignored in most STT-RAM studies, may also significantly impact applications' retention time needs. Based on our findings, we propose an asymmetric-retention core (ARC) design for multicore architectures. ARC features retention time heterogeneity to specialize STT-RAM retention times to applications' needs. We also propose a runtime prediction model to determine the best core on which to run an application, based on the applications' characteristics, their retention time requirements, and available DVFS settings. Results reveal that the proposed approach can reduce the average cache energy by 39.21% and overall processor energy by 13.66%, compared to an SRAM-based system, and by 20.19% and 7.66%, respectively, compared to a homogeneous STT-RAM cache design.

      BRITTAIN, RICHARD GRAY (The University of Arizona., 1979)
    • Dynamic and continuous annalysis of SO₂-Air mixtures by infrared spectroscopy

      Nuttall, H. E. (Herbert Ericksen), 1944- (The University of Arizona., 1968)
    • The dynamic behavior of an artificial satellite stabilized by gravity-gradient

      Skelding, Robert Matthew, 1933- (The University of Arizona., 1962)
    • Dynamic behavior of flow during leaching of copper ores

      Harpalani, Satya; Sainath, Narayana Rangaiah, 1968- (The University of Arizona., 1991)
      The objective of this investigation was to experimentally determine the variation in the flow characteristics of tactite copper ores during the leaching process. The laboratory work involved estimation of porosity and permeability of cores before leaching, and after various intervals of leaching. The tests were carried out using specimens of diameter 1.5 and 4.0 inches, prepared from boulders obtained from the Cyprus Casa Grande mine. A solution containing about 25 grams of sulfuric acid per liter was used as the lixiviant. Porosity was determined using the water saturation method. The permeability was estimated using either helium or water with the specimens stressed triaxially to simulate in situ conditions. The rate of copper recovery from the specimen during the leaching process was also determined by estimating the copper content in the solution used for leaching. The results indicate that the permeability and porosity of the specimens increased with leaching, but both tend to remain constant after most of the soluble material in the core was dissolved. The rate of copper recovery was high initially but dropped as leaching progressed and the copper in the specimen was depleted.
    • Dynamic calibration of intracardiac pressure transducer systems

      Burton, Donald Luther, 1935- (The University of Arizona., 1965)
    • Dynamic control of traffic input into an urban complex

      Rabin, William David, 1941- (The University of Arizona., 1967)
    • Dynamic interactive modelling in elasticity problems

      Tantraphol, Boonrut, 1945- (The University of Arizona., 1972)
    • Dynamic load factors with damping

      Toriello, Michael Raymond, 1947- (The University of Arizona., 1976)
    • Dynamic point relocation: An enhancement for traveling salesman problem initial tour construction procedures

      Rozenblit, Jerzy W.; Gale, Andrew Dent, 1955- (The University of Arizona., 1993)
      Traditional solving techniques for the traveling salesman problem are carried out in two phases. First an initial tour is constructed, then this tour is improved using some form of optimization. The procedure introduced in this research applies a simple optimization technique which minimally increases the runtime of the initial tour construction procedure. At the same time it greatly improves the quality of the tour which is constructed. It does this by globally searching the tour after each insertion for points which require repositioning and performing point relocations where necessary.
    • Dynamic response of structures with geometrically softening components including foundation interaction

      Kiousis, Panos; Stapleton-Hart, Nicole Colette, 1965- (The University of Arizona., 1990)
      The effects of material nonlinearity and geometric instabilities of a bracing system of a dynamically loaded steel frame, as well as nonlinear soil-structure interaction are studied in this thesis. To investigate the response of a frame subjected to severe dynamic loads, a model of the force-displacement relationship of the bracing system is developed to account for the inelastic, post-buckling behavior of a brace subjected to strong compressive loads. This thesis also develops a model of the force-deformation relationship of the foundation-soil interface, confining the study only to the slide mode of failure. From these models, a softening behavior for the bracing system and a hyperbolic load-deformation behavior of the interface are proposed. It is shown that the structural response of a frame is significantly affected when the analysis includes both the effects of softening of the bracing system and soil-structure interaction.