Now showing items 12513-12532 of 20330

    • Multiple-pinhole transaxial tomography: A model and analysis.

      Aarsvold, John Nathan.; Barrett, Harrison H.; Dallas, William J.; Denny, Jr., John L. (The University of Arizona., 1993)
      Multiple-pinhole transaxial tomography, a form of single-photon emission computed tomography (SPECT), is performed using novel imagers that have arrays of pinholes for image formation rather than collimators. Some such imagers, the University of Arizona (UA) transaxial systems, consist of coded apertures and modular gamma cameras and acquire data without system motion. They are the only such SPECT systems. This dissertation presents results from studies in which tomography using the UA imagers was simulated and studies in which the singular-value decompositions (SVDs) of multiple-pinhole imagers were calculated. The studies were performed to assess system configurations and to begin characterization of multiple-pinhole tomographs in terms of their SVDs. Our initial study involved simulation of systems consisting of arrays with uniformly spaced pinholes that produce multiplexed data and polygonal detectors comprising sixteen UA modules. This study shows that useful images can be obtained from static systems that have apertures that produce duplexed data and that significantly more useful images can be obtained using detectors that have resolution that is twice as fine as that of the UA modules. Numerical computation of the SVDs of several imagers including a single-pinhole imager and an orthogonal-pinhole imager produced visual displays of the object-space singular vectors of the systems. These displays demonstrate that the SVDs of multiple-pinhole systems can be expressed in terms of the SVDs of single-pinhole systems. The symmetries of all single-slice systems are rotational or reflective. The associated symmetry groups are cyclic groups or dihedral groups. The object-space singular vectors of these systems exhibit the same symmetries as the systems and exhibit multiplicities consistent with the irreducible representations of the associated groups. Results of analysis of the calculated SVDs demonstrate relationships among system symmetries, singular-vector symmetries, and irreducible representations. The results of our final study, a comparison of a system that has 64 pinholes spaced uniformly with one that has 64 pinholes spaced as a dilute uniformly redundant array, show that systems that have pinholes that are not uniformly spaced may prove the most useful.
    • Multiple-resource modelling in the forest and woodland ecosystems of Arizona

      Bojórquez, Luis Antonio,1956-; Ffolliott, Peter F.; Severson, Kieth; Fogel, Martin M.; Guertin, D. Phillip (The University of Arizona., 1987)
      Management, under the concepts of multiple-use and adaptive management, requires the assessment of potentials and limitations of the natural ecosystems to provide satisfaction to human needs, to protect long term productivity, and preserve biological diversity. Overstory-understory relationships were developed for ponderosa pine (Pinus ponderosa) ecosystems to help managers to evaluate herbage production potentials. Secondary data sources from the Beaver Creek and the Heber Watersheds were divided as follows: igneous soils, igneous clay loam, igneous loam-sandy loam, sedimentary soils, alluvium, and sandstone. Regression models were fitted to the raw data by the least squared method. The dependent variables were herbage production (lb/ac) by component; namely total, grass and grass like plants, forbs and half shrubs, and shrubs. The independent variables were total and ponderosa pine basal area (ft 2 /ac). Semilogarithmic models fitted the data from igneous soils, while logarithmic transformations of hyperbolic models fitted the data from sedimentary soils. For igneous soils, ponderosa pine basal area suffice for adequate predictions of herbage production. Significant differences were found between equations for alluvium and sandstone. The resulting equations for ponderosa pine integrate the core of the model UNDER. Mathematical functions developed elsewhere are included in UNDER to compute herbage production in pinyon-juniper and mixed conifer ecosystems. UNDER is linked to other simulators by MICROSIM. MICROSIM, a multiple-resource simulation model, is a tool to assist in the assessment of potentials of forest and woodlands of Arizona. MICROSIM is a menu driven program for IBM or compatibles it contains the module Flora, for estimating plant responses, and module Fauna, to evaluate impacts on animals. Further development of MICROSIM should include the linkage to more modules and models, and to Geographical Information Systems.

      Wyant, James C.; CHENG, YEOU-YEN.; Shannon, R.; Parks, Robert E. (The University of Arizona., 1985)
      The problems of combining ideas of phase shifting interferometry (PSI) and synthetic-wavelength techniques to extend the phase measurement range of conventional single-wavelength PSI are investigated. This combination of PSI and synthetic-wavelengths gives multiple-wavelength phase-shifting interferometry the advantages of: (1) larger phase measurement range and (2) higher accuracy of phase measurement. Advantages, error sources, and limitations of single-wavelength PSI are discussed. Some practical methods to calibrate the piezoelectric transducer (PZT), used to phase shift the reference beam, are presented with experimental results. Two methods of two-wavelength PSI are used to solve the 2π ambiguity problem of single-wavelength PSI. For the first method, two sets of phase data (with 2π ambiguities) for shorter wavelengths are calculated and stored in the computer which calculates the new phase data for the equivalent-wavelength λ(eq). The "error magnification effect," which reduces the measurement precision of the first method, is then investigated. The second, more accurate method, uses the results of the first method as a reference to correct the 2π ambiguities in the single-wavelength phase data. Experimental results are included to confirm theoretical predictions. The enhancement of two-wavelength PSI is investigated, and requires the phase data of a third wavelength. Experiments are performed to verify the capability of multiple-wavelength PSI. For the wavefront being measured, the difference of the optical-path-difference (OPD) between adjacent pixels is as large as 3.3 waves. After temporal averaging of five sets of data, the repeatability of the measurement is better than 2.5 nm (0.0025%) rms (λ = 632.8 nm). This work concludes with recommendations for future work that should make the MWLPSI a more practical technique for the testing of steep aspheric surfaces.
    • Multiplexed acoustic microscopy.

      Kuhn, William Paul.; Barrett, Harrison H.; Dallas, William J.; Hickernell, Fred S. (The University of Arizona., 1995)
      There is much biological evidence that mechanical forces play a significant role in controlling normal cell growth and proliferation. This evidence has motivated many researchers to use scanning acoustic microscopes to study the mechanical properties of cells. Multiplexing techniques are used in a variety of imaging systems. This dissertation presents the results of the application of multiplexing concepts to acoustic microscopy. The introduction to this dissertation reviews evidence for the biological role of mechanical forces and relevant acoustic imaging techniques. This is followed by an introduction to multiplexing techniques that leads to the conceptual design of a multiplexed acoustic microscope (MAM). The results from simulating and prototyping a small MAM are used to perform a simulation of a large MAM. Data from a large MAM is either impractical to process or requires assumptions that produce unacceptable results. The ultimate solution requires the design of a MAM having a small point spread function.
    • Multiplication Achievement and Self-Efficacy in Third- and Fifth-Grade Students: Effects of Cross-Age Peer Tutoring and Skill Training

      Summers, Jessica J.; Dennis, Lisa Marie Giles; Wood, Marcy B.; Burross, Heidi L.; Summers, Jessica J. (The University of Arizona., 2013)
      Self-efficacy is the belief an individual has about his or her capabilities to successfully complete an activity. Self-efficacy stems from four sources: verbal persuasion, physiological states, past experiences, and vicarious experiences. Increases in self-efficacy in education are connected with an increase in academic achievement. The current study sought to answer the question of which of three treatment options would have the most positive effect on mathematical achievement and self-efficacy for correctly answering problems on a multiplication math test. Participants were third- and fifth-grade students identified by their teachers as struggling in math. Students either received training on skills designed to increase self-efficacy, participated in cross-age peer tutoring, or received a combination of both treatments. Achievement and self-efficacy were measured before and after treatment and four weeks following the end of treatment to measure the lasting effects.
    • A multirate DS-CDMA system

      Schooley, Larry C.; Hu, Teck Hon, 1965- (The University of Arizona., 1997)
      A rapidly growing interest in third generation Personal Communication Networks has underlined the importance of wireless multimedia systems that can support voice, video, images, files, or any combinations thereof. In order to ensure satisfactory quality of service (QoS) for individual multimedia traffic, a new analysis with a new user model based on circuit-switched direct-sequence Code Division Multiple Access (DS-CDMA) system is presented. The new user model is introduced to allow users to transmit data at multiple bit rates and to switch to other bit rates at any time. To facilitate performance analysis, each traffic type with rate s is assumed a probability ps for user k. To ensure satisfactory QoS, a new power control scheme is further proposed for a multimedia circuit-switched DS-CDMA system. Specifically, a new closed-form power control function is introduced to ensure quality of service for each traffic type and to achieve a better overall throughput at the same time. Central to the new closed-form power control function is a parameter called the traffic exponent. By introducing this parameter, the difficulty in obtaining an optimal closed-form power control function is reduced which simplifies the information feedback process from the base station to the mobile stations.

      Hetrick, David L.; Keepin, William North. (The University of Arizona., 1980)
      Simulation of large physical systems often leads to initial value problems in which some of the solution components contain high frequency oscillations and/or fast transients, while the remaining solution components are relatively slowly varying. Such a system is referred to as two-time-scale (TTS), which is a partial generalization of the concept of stiffness. When using conventional numerical techniques for integration of TTS systems, the rapidly varying components dictate the use of small stepsizes, with the result that the slowly varying components are integrated very inefficiently. This could mean that the computer time required for integration is excessive. To overcome this difficulty, the system is partitioned into "fast" and "slow" subsystems, containing the rapidly and slowly varying components of the solution respectively. Integration is then performed using small stepsizes for the fast subsystem and relatively large stepsizes for the slow subsystem. This is referred to as multirate integration, and it can lead to substantial savings in computer time required for integration of large systems having relatively few fast solution components. This study is devoted to multirate integration of TTS initial value problems which are partitioned into fast and slow subsystems. Techniques for partitioning are not considered here. Multirate integration algorithms based on explicit Runge-Kutta (RK) methods are developed. Such algorithms require a means for communication between the subsystems. Internally embedded RK methods are introduced to aid in computing interpolated values of the slow variables, which are supplied to the fast subsystem. The use of averaging in the fast subsystem is discussed in connection with communication from the fast to the slow subsystem. Theoretical support for this is presented in a special case. A proof of convergence is given for a multirate algorithm based on Euler's method. Absolute stability of this algorithm is also discussed. Four multirate integration routines are presented. Two of these are based on a fixed-step fourth order RK method, and one is based on the variable step Runge-Kutta-Merson scheme. The performance of these routines is compared to that of several other integration schemes, including Gear's method and Hindmarsh's EPISODE package. For this purpose, both linear and nonlinear examples are presented. It is found that multirate techniques show promise for linear systems having eigenvalues near the imaginary axis. Such systems are known to present difficulty for Gear's method and EPISODE. A nonlinear TTS model of an autopilot is presented. The variable step multirate routine is found to be substantially more efficient for this example than any other method tested. Preliminary results are also included for a pressurized water reactor model. Indications are that multirate techniques may prove fruitful for this model. Lastly, an investigation of the effects of the step-size ratio (between subsystems) is included. In addition, several suggestions for further work are given, including the possibility of using multistep methods for integration of the slow subsystem.
    • A multireference coupled-cluster method using a single-reference formalism.

      Adamowicz, Ludwik; Oliphant, Nevin Horace; Armstrong, Neal R.; Wigley, David E.; Salzman, William R.; Smith, Mark A. (The University of Arizona., 1991)
      The coupled-cluster (CC) equations including single, double, triple and quadruple excitations (CCSDTQ) are qraphically derived using Feynman diagrams. These equations are programmed and an iterative reduced linear equation method is used to solve these equations. A few points on the potential curves for the dissociation of some model systems with a single bond (LiH and Li₂) are calculated using CC doubles (CCD), singles and doubles (CCSD), singles, doubles and triples (CCSDT) and CCSDTQ. These calculations demonstrate the magnitude of the CC contributions arising from triple and quadruple excitation amplitudes to the stretching of a chemical bond. A multi-reference coupled-cluster singles and doubles (MRCCSD) method utilizing two reference determinants, which differ by a two electron excitation, is then proposed. One of these determinants is selected as the formal reference determinant. The proposed method is based on the single-reference coupled-cluster equations truncated after quadruples with appropriate restrictions placed on the triple and quadruple amplitudes to allow only those amplitudes which correspond to single and double excitations from the second reference determinant. The computational expense of this method is no more than twice that of singles and doubles from a single reference (CCSD). These equations are programmed and the potential curves for the dissociation of a few model systems with single bonds (LiH, BH, and H₂O) are calculated to demonstrate the correct bond dissociation properties of this method. These calculations also demonstrate how much of the CC energy contribution arising from the triple and quadruple excitation amplitudes can be attributed to single and double excitations from the second reference determinant.
    • A multiresolution approach to computer verification of handwritten signatures.

      Qi, Yingyong.; Hunt, Bobby R.; Strickland, Robin N.; Rodriguez, Jeffrey J. (The University of Arizona., 1993)
      This dissertation presents procedures and results of works on computer signature verification. Two methods were developed and evaluated. First, verification was made using multi-resolution feature representation. This multi-resolution feature representation included global geometric characteristics and wavelet transformations of a signature image. A number of algorithms were developed to extract the global geometric features. A vector quantization classifier and a neural-network classifier were designed to use the multi-resolution representation for verification. Second, verification was made using a grid approach. In this approach, a signature image was divided by a grid and verification was made based on grid features that approximate local structures of a signature image. The grid feature comparison was made using dynamic programming procedures. Results indicated that both systems could detect free-handed forgeries accurately and could also monitor simulated forgeries with reasonable accuracy.
    • Multiscale Analytical Solutions and Homogenization of n-Dimensional Generalized Elliptic Equations

      Warrick, Arthur W.; Sviercoski, Rosangela; Warrick, Arthur W.; Brio, Moysey; Neuman, Shlomo; Ferre, Paul; Winter, Larry (The University of Arizona., 2005)
      In this dissertation, we present multiscale analytical solutions, in the weak sense, to the generalized Laplace's equation in Ω ⊂ Rⁿ, subject to periodic and nonperiodic boundary conditions. They are called multiscale solutions since they depend on a coefficient which takes a wide possible range of scales. We define forms of nonseparable coefficient functions in Lᵖ(Ω) such that the solutions are valid for the periodic and nonperiodic cases. In the periodic case, one such solution corresponds to the auxiliary cell problem in homogenization theory. Based on the proposed analytical solution, we were able to write explicitly the analytical form for the upscaled equation with an effective coefficient, for linear and nonlinear cases including the one with body forces. This was done by performing the two-scale asymptotic expansion for linear and nonlinear equations in divergence form with periodic coefficient. We proved that the proposed homogenized coefficient satisfies the Voigt-Reiss inequality. By performing numerical experiments and error analyses, we were able to compare the heterogeneous equation and its homogenized approximation in order to define criteria in terms of allowable heterogeneity in the domain to obtain a good approximation. The results presented, in this dissertation, have laid mathematical groundwork to better understand and apply multiscale processes under a deterministic point of view.
    • Multiscale anaylses of permeability in porous and fractured media

      Hyun, Yunjung.; Neuman, Shlomo P.; Maddock, Thomas; Frantziskonis, George; Myers, Donald E. (The University of Arizona., 2002)
      It has been shown by Neuman [1990], Di Federico and Neuman [1997, 1998a,b] and Di Federico et al. [1999] that observed multiscale behaviors of subsurface fluid flow and transport variables can be explained within the context of a unified stochastic framework, which views hydraulic conductivity as a random fractal characterized by a power variogram. Any such random fractal field is statistically nonhomogeneous but possesses homogeneous spatial increments. When the field is statistically isotropic, it is associated with a power variogram γ(s) = Cs²ᴴ where C is a constant, s is separation distance, and If is a Hurst coefficient (0 < H< 1). If the field is Gaussian it constitutes fractional Brownian motion (fBm). The authors have shown that the power variogram of a statistically isotropic or anisotropic fractal field can be constructed as a weighted integral from zero to infinity of exponential or Gaussian vario grams of overlapping, homogeneous random fields (modes) having mutually uncorrelated increments and variance proportional to a power 2H of the integral (spatial correlation) scale. Low- and high-frequency cutoffs are related to length scales of the sampling window (domain) and data support (sample volume), respectively. Intermediate cutoffs account for lacunarity due to gaps in the multiscale hierarchy, created by a hiatus of modes associated with discrete ranges of scales. In this dissertation, I investigate the effects of domain and support scales on the multiscale properties of random fractal fields characterized by a power variogram using real and synthetic data. Neuman [1994] and Di Federico and Neuman [1997] have concluded empirically, on the basis of hydraulic conductivity data from many sites, that a finite window of length-scale L filters out (truncates) all modes having integral scales λ larger than λ = μL where μ ≃ 1/3. I confii in their finding computationally by generating truncated fBm realizations on a large grid, using various initial values of μ, and demonstrating that μ ≃ 1/3 for windows smaller than the original grid. My synthetic experiments also show that generating an fl3m realization on a finite grid using a truncated power variogram yields sample variograms that are more consistent with theory than those obtained when the realization is generated using a power variogram. Interpreting sample data from such a realization using wavelet analysis yields more reliable estimates of the Hurst coefficient than those obtained when one employs variogram analysis. Di Federico et al. [1997] developed expressions for the equivalent hydraulic conductivity of a box-shaped support volume, embedded in a log-hydraulic conductivity field characterized by a power variogram, under the action of a mean uniform hydraulic gradient. I demonstrate that their expression and empirically derived value of μ ≃ 1/3 are consistent with a pronounced permeability scale effect observed in unsaturated fractured tuff at the Apache Leap Research Site (ALRS) near Superior, Arizona. I then investigate the compatibility of single-hole air permeability data, obtained at the ALRS on a nominal support scale of about 1 m, with various scaling models including fBm, fGn (fractional Gaussian noise), fLm (fractional Lévy motion), bfLm (bounded fractional Lévy motion) and UM (Universal Multifractals). I find that the data have a Lévy-like distribution at small lags but become Gaussian as the lag increases (corresponding to bfLm). Though this implies multiple scaling, it is not consistent with the UM model, which considers a unique distribution. If one nevertheless applies a UM model to the data, one obtains a very small codimension which suggests that multiple scaling is of minor consequence (applying the UM model to permeability rather than log-permeability data yields a larger codimension but is otherwise not consistent with these data). Variogram and resealed range analyses of the log-permeability data yield comparable estimates of the Hurst coefficient. Resealed range analysis shows that the data are not compatible with an fGn model. I conclude that the data are represented most closely by a truncated fBm model.
    • Multiscale Lanthanide-Containing Materials: MOFs, Clusters, and Nanomaterials

      Zheng, Zhiping; Tomat, Elisa; Fairley, Melissa C.; Lichtenberger, Dennis; Loy, Doug (The University of Arizona., 2018)
      Lanthanide-containing functional materials are an important class of compounds with interesting chemical properties. Lanthanide f-electrons give rise to interesting magnetic and photoluminescence properties that make these materials optimal for single-molecule magnets, magnetocaloric effect, and light emitting diodes. Lanthanides have a flexible coordination sphere that allows production of multiple structure types. The incorporation of Ni2+ and Ln3+ into the same structure expands the study of these properties. The work herein focuses on both the synthetic approach to and properties of novel lanthanide metal-organic frameworks, gigantic heterometallic clusters, and nanomaterials. Chapter 1 provides a fundamental background of lanthanides, properties of lanthanides, lanthanide-based materials, and potential applications of lanthanide-containing materials. This chapter gives a summary of synthetic approaches and methods for understanding the properties of these unique metal materials. Chapter 2 discusses the synthesis and structural characterization series of a 2D lanthanide metal-organic frameworks. These metal-organic frameworks were produced under ambient conditions. Eu3+ and Tb3+ were doped into the parent metal-organic framework without disruption of the framework. Tunable luminescence was achieved by the production of five mixed Eu/Tb metal-organic frameworks. In chapter 3 two novel lanthanide metal-organic frameworks are structurally characterized and studied for proton conduction. These include a 2D cerium metal-organic framework and a series of 3D lanthanide metal-organic frameworks with hydrophilic channels and pores respectively with interchelated water molecules allowing for a proton conduction pathway. The proton conductivities of these metal-organic frameworks were analyzed using pellets and single crystal samples. The proton conduction was determined via activation energy to follow a Grotthus mechanism. Chapter 4 focuses on the synthesis and structural characterization of novel gigantic 3d-4f clusters. A range of clusters using Ni2+ and Ln3+ (Ln=Er, Ho, Dy, Gd, Sm, Eu, Nd, Pr, and La) were produced under hydrothermal conditions and iminodiacetic acid as the supporting ligand. This novel cluster series of Ni2+ and Ln3+ revealed an interesting trend based on the atomic radius of Ln3+ ion utilized. When incorporating a larger Ln3+ ion, a larger cluster with more Ni2+ ions is obtained. The magnetic studies of Er3+ cluster showed significant magnetic anisotropy and/or population of low-lying excited states. Chapter 5 explores a facile hydrothermal synthetic approach to porous and non-porous lanthanide hydroxide nanorods. These nanorods were characterized using powder X-ray diffraction and transmission electron microscopy. These nanomaterials have potential use as catalysts, magnetic resonance imaging contrast agents, and drug delivery systems. The final chapter summarizes the importance of the presented novel lanthanide-containing materials. The work herein shows the use of multiple synthetic approaches and methods of testing lanthanide-based functional materials for potential applications in solid state light emitting devices, magnetic cooling, and single-molecule magnets. This chapter also discusses potential expansion of these projects for future experiments. Appendices A, B, C, and D provide the supporting information for these projects. Appendix A contains single-crystal X-ray diffraction information. Appendix B entails excitation and emission scans for all mixed Eu/Tb metal-organic frameworks presented in chapter 2. Appendix C provides an additional Ln coordination polymer referenced in chapter 3. Appendix D provides the experimental powder X-ray diffraction patterns for clusters 1 – 5 and 7 – 13 from chapter 4.
    • Multiscale Remote Sensing Analysis To Monitor Riparian And Upland Semiarid Vegetation

      Glenn, Edward P.; Nguyen, Uyen; Glenn, Edward P.; Fitzsimmons, Kevin; Wissler, Craig (The University of Arizona., 2015)
      The health of natural vegetation communities is of concern due to observed changes in the climatic-hydrological regime and land cover changes particularly in arid and semiarid regions. Monitoring vegetation at multi temporal and spatial scales can be the most informative approach for detecting change and inferring causal agents of change and remediation strategies. Riparian communities are tightly linked to annual stream hydrology, ground water elevations and sediment transport. These processes are subject to varying magnitudes of disturbance overtime and are candidates for multi-scale monitoring. My first research objective focused on the response of vegetation in the Upper San Pedro River, Arizona, to reduced base flows and climate change. I addressed the correlation between riparian vegetation and hydro-climate variables during the last three decades in one of the remaining undammed rivers in the southwestern U.S. Its riparian forest is threatened by the diminishing base flows, attributed by different studies either to increases in evapotranspiration (ET) due to conversion of grasslands to mesquite shrublands in the adjacent uplands, or to increased regional groundwater pumping to serve growing populations in surrounding urban areas and or to some interactions of those causes. Landsat 5 imagery was acquired for pre- monsoon period, when riparian trees had leafed out but before the arrival of summer monsoon rains in July. The result has showed Normalized Difference Vegetation Index (NDVI) values from both Landsat and Moderate Resolution Imaging Spectrometer (MODIS) had significant decreases which positively correlated to river flows, which decreased over the study period, and negatively correlated with air temperatures, which have increased by about 1.4°C from 1904 to the present. The predictions from other studies that decreased river flows could negatively impact the riparian forest were supported by this study. The pre-monsoon Normalized Different Vegetation Index (NDVI) average values in the adjacent uplands also decreased over thirty years and were correlated with the previous year's annual precipitation. Hence an increase in ET in the uplands did not appear to be responsible for the decrease in river flows in this study, leaving increased regional groundwater pumping as a feasible alternative explanation for decreased flows and deterioration of the riparian forest. The second research objective was to develop a new method of classification using very high-resolution aerial photo to map riparian vegetation at the species level in the Colorado River Ecosystem, Grand Canyon area, Arizona. Ground surveys have showed an obvious trend in which non-native saltcedar (Tamarix spp.) has replaced native vegetation over time. Our goal was to develop a quantitative mapping procedure to detect changes in vegetation as the ecosystem continues to respond to hydrological and climate changes. Vegetation mapping for the Colorado River Ecosystem needed an updated database map of the area covered by riparian vegetation and an indicator of species composition in the river corridor. The objective of this research was to generate a new riparian vegetation map at species level using a supervised image classification technique for the purpose of patch and landscape change detection. A new classification approach using multispectral images allowed us to successfully identify and map riparian species coverage the over whole Colorado River Ecosystem, Grand Canyon area. The new map was an improvement over the initial 2002 map since it reduced fragmentation from mixed riparian vegetation areas. The most dominant tree species in the study areas is saltcedar (Tamarix spp.). The overall accuracy is 93.48% and the kappa coefficient is 0.88. The reference initial inventory map was created using 2002 images to compare and detect changes through 2009. The third objective of my research focused on using multiplatform of remote sensing and ground calibration to estimate the effects of vegetation, land use patterns and water cycles. Climate change, hydrological and human uses are also leading to riparian, upland, grassland and crop vegetation changes at a variety of temporal and spatial scales, particularly in the arid and semi-arid ecosystems, which are more sensitive to changes in water availability than humid ecosystems. The objectives of these studies from the last three articles were to evaluate the effect of water balance on vegetation indices in different plant communities based on relevant spatial and temporal scales. The new methodology of estimating water requirements using remote sensing data and ground calibration with flux tower data has been successfully tested at a variety sites, a sparse desert shrub environment as well as mixed riparian and cropland systems and upland vegetation in the arid and semi-arid regions. The main finding form these studies is that vegetation-index methods have to be calibrated with ground data for each new ecosystem but once calibrated they can accurately scale ET over wide areas and long time spans.
    • Multisensor Translation and Continuity of Vegetation Indices Using Hyperspectral Data

      Huete, Alfredo R.; Kim, Youngwook; Huete, Alfredo R.; Glenn, Edward; Thome, Kurtis J.; Van Leeuwen, Willem J. D. (The University of Arizona., 2007)
      The earth surface is monitored periodically by numerous satellite sensors which have different spectral response functions, image acquisition heights, atmosphere correction schemes, overpass times, and sun/view angle geometries. Temporal and spatial variations of land surface properties, such as vegetation index, Leaf Area Index (LAI), land surface temperature, and soil moisture, have been provided by long-term time series of various remote sensing datasets. Inter-sensor translation equations are required to build long-term time series by the combination of multiple sensors from historical to advanced and new satellite datasets. In the first chapter, inter-sensor translation equations of band reflectances and two vegetation indices (e.g. Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI)) were derived using linear regression equations relative to Moderate Resolution Imaging Spectroradiometer (MODIS) values. The consistency and validation of inter-sensor transforms were investigated through statistical student's t-test and the root mean square error (RMSE).In the second chapter, cross-sensor extension of EVI and a 2-band EVI (without the blue band; EVI2) were investigated based on the continuity of both EVI's. Sensor specific red-blue coherencies were examined for the possibility of the EVI and EVI2 extension from MODIS sensor. The EVI continuity to MODIS was particularly problematic for the Visible Infrared Imager / Radiometer Suite (VIIRS) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) that have dissimilar blue bands from that of MODIS. The cross-sensor extension and compatibility of EVI2 were improved and provided the possibility to be lengthened to the Advanced Very High Resolution Radiometer (AVHRR) using its translation equation.Finally, we evaluated the use of sensor-specific EVI and NDVI data sets, using a time sequence of Hyperion images over Amazon rainforest in Tapajos National Forest, Brazil for the 2001 and 2002 dry seasons. We computed NDVI, EVI, and EVI2 with the convolution data of different global monitoring and high temporal resolution sensor systems (AVHRR, MODIS, VIIRS, SPOT-VGT, and SeaWiFS) from Hyperion, and evaluated their spectral deviations and continuity in the characterization of tropical forest phenology. Our analyses show that EVI2 maintains the desirable properties of increased sensitivity in high biomass forests across all sensor systems evaluated.
    • Multisensory Processing in the Primate Amygdala

      Gothard, Katalin M.; Morrow, Jeremiah Kegley; Fuglevand, Andrew; Barnes, Carol; Cai, Haijiang (The University of Arizona., 2019)
      The ability to make use of the diverse sensory information present in the natural world is critical for every living creature from single-cell organisms to humans. In the primate brain, signals from different sensory modalities begin to intermix as early as the primary sensory cortices and become intricately interwoven along a myriad of parallel processing routes. Many of these routes pass through a temporal lobe structure called the amygdala. This subcortical cluster of nuclei is involved in a host of functions ranging from regulation of the autonomic nervous system to the generation of social behaviors. Despite the diverse inputs and varied functions of the amygdala, most of what is known about this structure in primates comes from studies that relied on visual stimuli. More must be done to assess how the primate amygdala processes multisensory information in order to better understand how this structure contributes to higher order cognitive functions. The three chapters of this dissertation report the outcome of experiments that are a logical progression of my research. The first experiment presented here examined how the amygdala processes visual information as monkeys scanned complex arrays of images. While some theories suggested that neural activity in the amygdala should alert an organism to potentially important stimuli before the animal attends to them, we found that the activity of neurons in the amygdala was gated by attention. Some neurons were found to be tuned to specific categories of stimuli (e.g., monkey faces or flowers); however, many cells responded to some degree across a range of categories. The complexity of the responses seen in this study have become increasingly common observations in neuroscience experiments. In order to link the work in the visual domain with ongoing work in the laboratory that focused on touch, we designed an experiment that involved both visual and tactile stimuli. We also added auditory stimuli in order to cover a wider subset of sensory domains. In these experiments, we examined the responses of neurons in the amygdala to stimuli that were devoid of any obvious emotional or social meaning to the monkeys (neurons in the amygdala are known to respond to these abstract features). As expected, we found neurons that responded to stimuli of all three sensory domains; however, we were surprised by the large proportion of responsive cells (~70%) given the low salience of the stimuli. Furthermore, we found that many neurons appeared to differentiate the sensory modality of the stimulus by varying different parameters of their spiking activity. The high number of multisensory responses from neurons in the amygdala suggests that researchers may be missing many crucial functions of this structure when the stimulus space is small or focuses on stimuli from a single sensory domain. The second chapter of the dissertation reports the outcome of this experiment. In the third chapter, I report the outcome of applying a data analysis method, new to the study of local field potentials (LFPs), to data recorded in response to multisensory stimuli. It has been notoriously difficult to extract meaningful information from LFPs in the primate amygdala, primarily because the amygdala lacks the layered anatomical organization of the neocortex or the hippocampus. A small number of reports suggest a functional relevance of theta and gamma oscillations in rodents and cats during anticipatory anxiety, fear, and reward learning tasks but attempts to quantify or interpret amygdala LFP in primates are almost non-existent. By simultaneously recording field potentials from the entire dorsal-ventral axis of the amygdala, we were able to isolate statistically distinct signals likely related to the underlying neural structure of the amygdala. We used a non-orthogonal covariance-based decomposition method, called generalized eigendecomposition (GED), that maximizes the differences between experimental conditions (e.g., baseline and stimulus delivery) to extract statistically dissociable components of LFP activity related to sensory processing. The activity captured by these components reflects electrophysiological structure likely generated by networks of neurons in the amygdala. The activity of these component signals often differentially processed the three sensory modalities tested. Importantly, the signals extracted with these methods frequently showed dramatic changes at the anatomical boundaries between the nuclei in the amygdala, suggesting that these networks are spatially defined by these boundaries. These experiments demonstrate that meaningful LFP signals can be readily extracted from the amygdala with sophisticated analysis techniques. Taken together, the work contained in this dissertation deepens our understanding of the ways in which the primate amygdala may contribute to higher order cognitive functions. For example, in order to understand how the amygdala contributes to social communication we must know how attending to social stimuli modulates activity of amygdala neurons (chapter 1). Furthermore, we need to have an idea of how information from multiple sensory modalities is processed (chapters 2 and 3) as sight, sound, and touch can all provide valuable information about the emotional state and intentions of others. These functions are severely impaired by amygdala damage, therefore, the neural processes reported here might be the substrate, or neural foundation, of these behaviors.
    • The multiskilled health practitioner: Educational preparedness and effects of technology on organizational work practices in hospital settings

      Rhoades, Gary; Tossell, Renee Fayhe (The University of Arizona., 2000)
      This paper investigates the multiskilled health practitioner (i.e., imaging specialist) how they are trained for what they do and the way their traditional role as a generalist in radiologic technology has been impacted by advancing technologies. This dissertation consists of multiple case studies, which is primarily qualitative and exploratory in nature. It does not test a hypothesis in a strict sense and is grounded in analytical categories and theories derived from the literature on technology, work, occupations, and organizations. The data analysis section consists of four sections: perceptions of the MSHPs' work, the impact of technology (i.e., incentive structures, wages, issues of autonomy/authority, task difficulty/responsibility and patterns of interaction), the enskilling/deskilling findings for all MSHPs in general and each hospital subgroup, and the MSHPs perceptions about the effectiveness of their formal education programs. With regards to a cultural examination of the workplace, the most significant sociological perspective identified were in the patterns of interaction. Specifically, three primary stylistic differences are noted. In relation to the effects of technology, an institutionalized practice of the incentive structure and the homogeneity of three broad skills were noted among our cohort. Additionally, three contextual factors that condition social action and thereby affect a technology's tendency to enskill or deskill are revealed. In light of the attributes and deficiencies noted by the interviewees regarding their formal educational programs and skills required for their new roles, the researcher provides five recommendations for strengthening technology transfer programs in which to better prepare the MSHP.
    • Multispecies Thinking from Alexander von Humboldt to Leslie Marmon Silko: Intercultural Communication Toward Cosmopolitics

      Evers, Larry; Gemein, Mascha Nicola; Fatzinger, Amy; Washburn, Franci; Adamson, Joni; Evers, Larry (The University of Arizona., 2013)
      The concept of cosmopolitics identifies a multispecies political practice within the framework of multinaturalism. The dissertation, "Multispecies Thinking from Alexander von Humboldt to Leslie Marmon Silko: Intercultural Communication Toward Cosmopolitics," is concerned with understandings of multispecies relationships, with the human intercultural communication that could prepare for a cosmopolitical practice, and with the ways Native American fiction supports this endeavor. This research draws from Native American literary studies and ecocritical scholarship to illustrate the potential of transdisciplinary thinking about multispecies ethnography, cosmopolitics, and Indigenous paradigms as providing a promising communication zone against the grain of scientific imperialism. It thus traces the development of pluralist and multispecies-oriented thought and its points of connection to Indigenous paradigms from Alexander von Humboldt's Cosmos Studies of the early 19th century to 21st century Indigenous cosmopolitics. First, this study discusses the insights and obstructions to Western pluralist and multispecies thinking in relation to Native American paradigms from Humboldt via 19th century nature writers-Henry David Thoreau, Margaret Fuller, and John Muir-to contemporary interdisciplinary research. Opening to wide potential with Humboldt's holistic Cosmos Studies, intercultural communication was tempered by the colonial enterprise in the 19th century United States, including a nature-culture dualism and the notion of degenerated, vanishing Indigenous peoples. The resulting conceptual understandings, terms, and attitudes have been influential until today and are what contemporary Native American authors and activists are confronted with when engaged in their work. Detailed textual analysis of exemplary Native American literature outlines how contemporary authors criticize, counter-narrate, and/or integrate Western intellectual traditions. Furthermore, this study outlines 20th and 21st century scientific concepts that refine much earlier ideas, provide helpful terminology regarding Western approaches to Indigenous ontologies and multispecies thinking, and facilitate a new, insightful reading of contemporary Native American fiction as cosmopolitical texts. The analyses of works by Louise Erdrich, Linda Hogan, Louis Owens, and Leslie Marmon Silko demonstrate the value of these works to enhance multispecies thinking and respective political practices. Therefore, Native American literature plays a major role worldwide as an educational and critical tool for an intercultural communication toward cosmopolitics.

      Hunt, Bobby R.; GRAY, ROBERT TERRY. (The University of Arizona., 1983)
      A multispectral image data compression scheme has been investigated in which a scene is imaged onto a detector array whose elements vary in spectral sensitivity. The elements are staggered such that the scene is undersampled within any single spectral band, but is sufficiently sampled by the total array. Compression thus results from transmitting only one spectral component of a scene at any given array coordinate. The pixels of the mosaic array may then be directly transmitted via PCM or undergo further compression (e.g. DPCM). The scheme has the advantages of attaining moderate compression without compression hardware at the transmitter, high compression with low-order DPCM processing, and a choice of reconstruction algorithms suitable to the application at hand. Efficient spatial interpolators such as parametric cubic convolution may be employed to fill in the missing pixels in each spectral band in cases where high resolution is not a requirement. However, high-resolution reconstructions are achieved by a space-variant minimum-mean-square spectral regression estimation of the missing pixels of each band from the adjacent samples of other bands. In this case, reconstruction accuracy is determined by the local spectral correlations between bands, the estimates of which include the effects of interband contrast reversal. Digital simulations have been performed on three-band aerial and four-band Landsat multispectral images. Spectral regressions of mosaic array data can provide reconstruction errors comparable to second-order DPCM processing and lower than common intraband interpolators at data rates of approximately 2 bits per pixel. When the mosaic data is itself DPCM-coded, the radiometric accuracy of spectral regression is superior to direct DPCM for equivalent bit rates.
    • Multispectral fluorescence imaging of atherosclerosis.

      Davenport, Carolyn Marie Connor.; Gmitro, Arthur F.; Greivenkamp, Jr., John E.; Roehrig, Hans (The University of Arizona., 1992)
      Multispectral fluorescence imaging is a new diagnostic technique with the potential to provide improved detection and classification of atherosclerotic disease. This technique involves imaging the fluorescence response of a tissue region through a tunable band-pass filtering device. The result is a set of images in which each individual image is composed of the fluorescence emission within a specified band of wavelengths. Multispectral imaging combined with angioscopic technology allows direct access to important spectral information and spatial attributes providing the potential for more informed clinical decisions about which, if any, treatment modality is indicated. In this dissertation, the system requirements for an angioscopic system with multispectral imaging capability are identified. This analysis includes a description of the necessary optical components and their characteristics as well as the experimental determination of spectral radiance values for the fluorescence response of human aorta specimens and the estimation of anticipated signal-to-noise ratios for the spectral images. Other issues investigated include the number of spectral images required to provide good classification potential and the best normalization method to be utilized. Finally, the potential utility of the information contained within a multispectral data set is demonstrated. Two methods of utilizing the multispectral data are presented. The first method involves generating a ratio-image from the ratio of the intensities of two spectrally filtered images. The second method consists of using histologically verified training data to train a projector and then applying that projector to a set of spectral images. The result (a weighted sum of the spectral images) provides improved contrast between normal and diseased tissue, and is called an optimized-contrast image. White-light images (generated using an incandescent light source), total-fluorescence images (the fluorescence response without spectral filtering), ratio-images, and optimized contrast images are compared. The results indicate that angioscopic fluorescence imaging appears to be a feasible and potentially useful technique in terms of providing improved detection of atherosclerotic disease. This technique warrants further investigation to further define the system requirements and to evaluate its clinical usefulness including the collection of a more extensive data set and the development of a prototype system.