• A Comparison of Electromagnetic Physical Scale and Numerical Modeling for Geophysical Exploration

      Sternberg, Ben K.; Burkart, Riley; Johnson, Roy A.; Rucker, Dale F. (The University of Arizona., 2018)
      Numerical modeling has, in the twenty-first century, become the dominant form of modeling for electromagnetic exploration geophysics, but few studies have been undertaken that compare numerical models with physical scale models to determine the constraints on numerical algorithms. In this thesis, a physical scale model system was constructed and twenty-six profiles run to analyze the strengths and limitations of four algorithms in PetRos EiKon's EMIGMA V8.6 modeling software: Free Space EikPlate (FS Plate), VH Plate, Inductive Localized Non-Linear (ILN), and EMSPHERE. A low-power vertical-array system with a ten-turn square transmitter loop and receiver coils in the Bx, By, and Bz directions with ten turns, ten turns, and two turns, respectively, was designed and constructed for this thesis. Profiles were taken in either a lab setting, which provided more space, or a tank setting, which allowed for lower noise and modeling of a conductive host. A total of twenty-six profiles taken with ten targets are presented here together with their geometric configurations. Through comparison of the measured and the simulated data, the following conclusions are made: (1) The VH Plate and ILN algorithms produce less accurate simulations for small targets; this may be redressed by increasing the scale of the targets. (2) Every algorithm designed to account for galvanic responses, when otherwise operating within its constraints, does so effectively and corroborates the measured data. (3) FS Plate simulations reasonably approximate the measured responses of long sheet targets when the sheet center is distal to the receiver by more than one third the sheet length, but do not approximate the measured data as well when the center of the target is proximal to the receiver. (4) EMSPHERE, which is only supported for dipole sources, does not approximate a target with a loop source well when the target is directly beneath the transmitter, but it does approximate it well when the target is displaced from the transmitter; a sphere may be approximated for the ILN algorithm by a cube that fits flush within the sphere. (5) FS Plate peak responses tend to be smaller than the measured responses by a factor of two, but the side skirts match well; FS plate also appears to diverge from the Kramers-Kronig relations for induction numbers smaller than 2e-4. (6) VH Plate peak responses tend to be larger than the measured responses by a factor of roughly two, and the side skirts do not match well. (7) ILN breaks down for high conductivity contrasts, such as a graphite cube in air; this issue may be avoided by using a more resistive host for the model so long as inductive effects still dominate, which may be determined using LN.
    • A Cooperative Approach to Food Security and Food Sovereignty

      Vásquez-León, Marcela; Oliver, Stephen; Correia, Joel; Finan, Timothy (The University of Arizona., 2019)
      The Paraguayan agrarian sector is highly unequal. With one of the highest levels of land inequality in the world, 94 percent of arable land dedicated to commodity crop agriculture, and entrenched alliances between large-scale agriculture producers and landowners with the country’s political establishment, traditional campesino agriculture is rapidly diminishing across the country. Paraguay’s transition towards a large-scale agro-export model has a raft of implications for both the food security and food sovereignty of its smallholder producers. This research explores the sugarcane cooperative Manduvirá as an alternative model for community development in rural Paraguay. Manduvirá has over 900 members who produce on five to seven hectares of land, they built, own, and operate their own organic sugar mill, and directly export to over 25 countries. Moreover, through a democratic cooperative process, Manduvirá’s members have used their success in the export sugar sector to reinvest in a number of community-based initiatives to address the changing food security and food sovereignty landscape. This research examines the role that Manduvirá fulfills in addressing food security and food sovereignty in attempts to understand the broader role that smallholder agricultural cooperatives can play in the community development process.
    • A Ground Based Optical Survey for GPS Solar Panel Arcing

      Hart, Michael; Walsh, Shane; Pearce, Eric; Guyon, Olivier (The University of Arizona., 2019)
      In an attempt to confirm electrostatic discharge induced contamination as responsible for the excess power loss of GPS solar arrays, three GPS satellites were observed at the MMT using a sensitive Electron Multiplying CCD (EMCCD) with the aim of catching the microsecond optical emission of solar panel arcing. One of these satellites (NAVSTAR 48) was concurrently observed with the Arecibo radio telescope in the hopes that coincident optical and radio detections would all but confirm the hypothesis. Unfortunately, owing to ∼ 75% transmission losses, optical arc detections could not be conclusively confirmed or ruled out. Detections above the nominal threshold were present more frequently than expected from random fluctuations, but the lack of coincidence with Arecibo detections and the similar number of detections away from the satellite imply a cause other than arcs, most likely non-Gaussian noise behavior. One of the other satellites, NAVSTAR 65, yielded a promising candidate with a brightness consistent with a fully discharging arc of a Block II-F solar array. However, without external confirmation from satellite telemetry, the detection significance is not sufficient to unambiguously label this event as an arc. If the observations could be repeated with transmission losses of 30% or less, the 50% detection efficiency of arcs would improve from 200-photon arcs to 70-photons or better. This would make the difference between being sensitive to some full discharge arcs or most partial discharge arcs, although requiring substantial redesign of the observing strategy.
    • A Hierarchical Framework to Mitigate the Risk of Hazardous Material Transportation

      Fan, Neng; Masoud, Sara; An, Lingling; Niu, Yue (The University of Arizona., 2019)
      An integrated traffic control policy for hazardous materials (hazmat) transportation is devised based on dual toll pricing (DTP) and network design (ND) policies within a two stage simulation-based optimization framework to enhance public safety in a highway. This integrated policy is simultaneously able to restrict hazmat traffic from freeways in densely populated areas via ND and control both regular and hazmat vehicles in tollways via DTP. Moreover, the mixed integer progrmming is employed to find the optimum integrated policy, and linear-relaxation technique based on Kaush-Kahn-Tucker (KKT) conditions is adopted to reduce the search space of the optimization process. In the proposed framework, all suggested policies are evaluated by an agent-based simulation model, which is able to interpret complex interrelationship between road conditions and vehicles. In addition, supervised learning (i.e., random forest algorithm) has been implemented within the agant-based simulation model to predict the risk taking behavior of the drivers considering the drivers' race and gender and transportation network characterstics such as levelness and curviness of the roads. The proposed framework has been demonstrated with a real traffic data of San Antonio, Texas under AnyLogic® platform. The experimental results reveal that the proposed framework is able to efficiently find the optimum integrated policy which effectively reduces the risk of hazmat transportation in a highway.
    • A Method for Analyzing Microclimate Effect of Shaded Transitional Spaces on Outdoor Human Thermal Comfort and Building Performance in a Hot Arid Region

      Chalfoun, Nader; Horn, Patricia; Youssef, Omar; Moeller, Colby (The University of Arizona., 2018)
      Spaces are usually classified as either being indoors – frequently private or public outdoor spaces. Transitional spaces are an important aspect to the built environment as they have great potential to modify the environmental conditions of both indoor and outdoor spaces. They are the connecting space between the outdoor and indoors, between the natural climate and controlled climate. They can aid to building efficiency and to outdoor human thermal comfort. Transitional spaces in a hot arid region are crucial to maintaining the comfort of a user while being outside. The purpose of this investigation is to prove that shaded outdoor transitional spaces can lead to outdoor human thermal comfort and building performance. The problem being addressed is the lack of attention on shaded transitional spaces in a hot arid climate. Being located in such a harsh climatic environment it is important to look into the relationship between the building and its outdoor spaces as well as users. They are used to create a comfortable microclimate while transitioning into the building. A 9 step method will be proposed to defend the idea that shaded transitional spaces can lead to outdoor human thermal comfort and building efficiency. Methods being used are eQUEST Simulations, micro-climate data collection, and calculating outdoor human thermal comfort. The results confirmed the notion that shaded transitional spaces can lead to outdoor human thermal comfort and building performance. The comfort of the user was defined and the performance of the building was established through energy modeling simulations.
    • A Nanometric View into Strengthening Mechanisms of Iron Incorporation in Graphene-Based Nanocomposites

      Muralidharan, Krishna; Rand, Matthew; Manga, Venkateswara; Potter, Barrett; Runge, Keith (The University of Arizona., 2018)
      Recent advances in the ability to synthesize metal-ion coagulated graphene oxide (GO) colloidal dispersions have provided new avenues for fabrication of GO based thin films and membranes. Additionally, new fabrication techniques have recently emerged that enable the ability to intercalate and reduce metal halides in bulk graphite crystals, leading to metal-based graphite intercalated compounds (GICs). To this end, a fundamental study on the interplay between composition, atomic-scale structure and mechanical properties of metal-GO as well as metal-GIC composite materials was carried out employing molecular dynamics (MD) simulations. Specifically, the transition metal iron (Fe) was considered in this study; MD investigations reveal that Fe ions act as strong cross-linkers between individual GO sheets, increasing elastic modulus as well as tensile strength of the Fe-GO composite. Investigations of Fe intercalated GIC (Fe-GIC) showed interesting trends in its mechanical properties due to bond formation between the intercalated Fe atoms and the ‘sandwiching’ graphene sheets. In particular, with increasing iron concentration, there is strengthening in the out-of-plane direction, while reduction in the in-plane direction of the Fe-GIC lattice. While the Fe-C bonding ensures out-of-plane strengthening, it is equally detrimental to the strength of the in-plane C-C bonds within the graphene sheets. Valuable lessons learned from this work provide important insights into the design and development of GO and GIC composites for targeted mechanical and chemical applications.
    • A Nonparametric Multiple Imputation Approach For MNAR Mechanism Using the Sample Selection Model Framework

      Hsu, Paul; Jia, Ziyue; Bell, Melanie; Hu, Chengcheng (The University of Arizona., 2019)
      Missing data is an unavoidable issue when performing data analysis. If the missing probability is related to unobserved variables, missingness is considered as missing not at random (MNAR). It is challenging to analyze data subject to MNAR. There are two ways to induce MNAR mechanism: sample selection model and pattern mixture model. Under the sample se-lection model framework, we develop a nonparametric multiple imputation (NNMI) method to estimate the marginal mean of an outcome subject to MNAR mechanism, where the sample se-lection model is only used as a working model to define the imputing set for each missing indi-vidual. We perform simulation studies to compare the performance of the proposed approach with a parametric multiple imputation approach, which directly uses the sample selection model to impute missing individuals. The results show that our method performs well for data subject to MNAR mechanism. Due to the limitations of current estimation method, we have not found solid proof to demonstrate the proposed method has better performance than parametric multi-ple imputation to handle MNAR when the sample selection model is misspecified. We also ap-ply the proposed approach to a real dataset to estimate the marginal mean of HbA1c level for carotid patients, whose HbA1c is subject to missingness.
    • A Novel Pathology Device for the Improvement of Intraoperative Breast-Cancer Tissue Gross Examination

      Arabyan, Ara; Kachur, Xenia; (The University of Arizona., 2011)
      The aim of this study was to design and test key aspects of a novel device, consisting of a polymer referencing enclosure (hardware) and a gel component, for the standardization of intraoperative gross pathology examination of excised breast cancer tissue. The proposed device improves the current practice of tissue preparation for radiographic and pathological examination without changing the existing process and without imposing retraining requirements on professional staff involved in the current process. To identify the optimal composition of the gel component to be used, 32 gel formulations were tested to determine setting times and maximum temperature reached during setting. The radiographic properties of 12 gel formulations and 15 plastic materials for potential use in the hardware were also tested. A negative correlation was found to exist between setting time and maximum temperature reached, narrowing down gel selections to those setting in <10 minutes with a temperature peak of <54 °C. The radiographic properties of the tested and downselected gels and plastics were found to be such that these materials are unlikely to interfere with lesion identification in radiological examinations. A completed tissue study for examination of gel effects on tissue properties revealed no effects, thereby clearing this device for potential clinical applications.
    • A Penetration and Safety Assay for Generic Ophthalmic Drugs

      Orsinger, Gabriel; (The University of Arizona., 2010)
      Generic topical ophthalmic medications are poorly regulated by the Food and Drug Administration, resulting in an uncertainty of generics' efficacy and safety and unnecessarily placing patients at risk. In 1999, more than 200 documented cases of corneal damage as severe as corneal melting were linked to the use of a generic formulation of diclofenac, which was consequently pulled from the market. These devastating iatrogenic effects demonstrate the need for stricter testing of generic ophthalmic drugs prior to reaching the public. This report addresses this urgent need by proposing an in vitro model for simultaneously predicting corneal penetration and epithelial toxicity of topical ophthalmic formulations. Penetration and safety of ophthalmic medications have been studied separately, but until now, the development of an assay to accurately predict both penetration and safety in parallel has been overlooked. In this report, recent and ongoing research will be reviewed to (1) elucidate the complexities of corneal penetration and the effects of topical ophthalmic formulations on corneal penetration, and (2) identify important characteristics of existing models to incorporate in the proposed in vitro penetration and safety assay. Critical features of the model proposed here include a trephinated porcine cornea from tissue discards affixed in a Franz diffusion cell, permitting concurrent drug penetration and epithelial health monitoring. A robust, cost-effective penetration and safety assay such as this would provide drug companies with a valuable tool to eliminate chances of future iatrogenic effects due to topical ophthalmic drugs.
    • A Predictive Model for the Production Rates of a Bioregenerative Life Support System

      Furfaro, Roberto; Gellenbeck, Sean Christian; Giacomelli, Gene; Lepore, Robert (The University of Arizona., 2018)
      Future long-term human space flight will require systems that are reliable, sustainable, and can continue to function for the entire length of the mission. Included in these possibilities are a relatively short two-year expedition to Mars as well as the indefinite colonization of another celestial body. Life support presents a significant challenge to this concept as many of the systems currently in use would require bringing a prohibitively heavy and bulky amount of supplies and consumables. An additional challenge is what to do with all the refuse from humans and other systems within the habitat. An innovative solution that addresses both of these problems is the use of bioregenerative life support (BLS). This type of life support utilizes the evolutionarily refined abilities of biological organisms to produce oxygen and sequester carbon dioxide through photosynthesis, purify water through transpiration, and produce edible biomass and calories for human consumption. In addition to being reliable, these systems operate at ambient conditions which reduces risk, and also provide psychological benefits to the crew. A successful BLS system will likely include many subsystems of which a higher plants production chamber will be one. The inclusion of biology as part of a life support system introduces complexity and mathematical models that can accurately predict the production rates of these systems is necessary. One such model that describes the production of a higher plants growth system is the Modified Energy Cascade Model (MEC) which was developed by James Cavazzoni in the early 2000’s. Around this model, a wrapper was developed to allow a user or system designer to input parameters for a hypothetical design and receive graphics depicting the production rates of said system over the entire course of the proposed mission for two different harvest strategies. This allows the user to accurately predict the production of any design and optimize to find the solution that best fits the needs of the mission. Four different BLS system example analogues were analyzed to show this utility and to allow for the further discussion of the design process surrounding such a system. This tool could also be modified to allow the design to identify deficiencies in the astronauts’ diets and show the effect of variable environmental conditions. In its current form, this tool would have the most potential benefit during the system and concept of operations (ConOps) design phases of a life support system for a long duration human space flight mission.
    • A Qualitative Study of Adult Recipients of the Deferred Action for Childhood Arrivals (DACA) Program: A Community Cultural Wealth and Life Course Perspective

      Romero, Andrea J.; Rascon, Michelle; Henry, Kevin; Ottusch, Timothy (The University of Arizona., 2019)
      This study focuses on the experiences of adults who are beneficiaries of the Deferred Action for Childhood Arrivals ("DACA") Program. The rescission of the DACA Program announced in 2017, and subsequent legal battle to reinstate DACA (Duke, 2017; IEIYC & Arreola v. Duke, 2017), once again poses new untenable terrains for the many who received temporary reprieve by DACA but may return to being undocumented. Informed by the Life Course Theory (Elder & Rockwell, 1979) and Community Cultural Wealth Theory (Yosso, 2005), semi-structured qualitative interviews were conducted in a sample of adult college students (age: M = 23) who are DACA recipients (n = 15) enrolled in colleges. The interviews revealed how DACA recipients have come to understand their undocumented status, their transition to the DACA reprieve, and how they are navigating the uncertainty of the program. This study identified forms of Community Cultural Wealth Theory (Yosso, 2005) accessed by DACA recipients through retrospective interviews. Community Cultural Wealth Theory (CCW), from educational research, is an array of knowledge, skills, abilities, and resources utilized by Communities of Color to survive and resist exclusionary practices in institutions not created with them in mind (Yosso, 2005). The findings of this study will contribute to the literature on immigration policy and to new empirical research exploring how DACA recipients have come to understand their undocumented status, DACA reprieve, and how they access community wealth in academic settings.
    • A Study of Adversarial Attacks Against an LSTM Language Model and the Impact of Normalization in SNN

      Ditzler, Gregory; Liang, Zhengzhong; Tandon, Ravi; Koyluoglu, Onur Ozan; Fellous, Jean-Marc (The University of Arizona., 2018)
      Artificial Neural Networks (ANNs) have been used to many application-driven fields and have been shown to be quite successful, however, some aspects of ANNs are not well understood. One such area is learning an ANN in the presence of an adversary.In such a context, it is assumed that the attacker can manipulate the training (also referred to causative attack or poison) or testing data (also referred to exploratory attack) to disrupt its normal functionality. In turn, the defender aims at reducing the impact of such attacks as much as possible. The first part of this thesis focuses on causative attacks against an Long Short-Term Memory (LSTM) neural network in a language model. In causative attacks, it is assumed that the attacker can only change the training text in the language model. We study the behavior of the LSTM language model under different causative attacks and propose several simple measures that can reduce the impact of the attacks. Our results show that the poisoning ratio, the poisoning position and the generation of poisoned text can all influence the performance the LSTM language model. Furthermore, we show that proper use of dropout and gradient clipping can reduce the impact of poisoning the training data to some extent. We also contribute to understanding how to globally learn a Spiking Neural Network (SNN). SNNs are a type of ANN; however SNNs are much more biologically realistic than other ANNs. SNNs have not been widely adopted because of several critical issues of SNNs that are not well studied. One such effect is the training of SNNs and the encoding/decoding of signals in SNNs. In the second part of this thesis, we build an SNN based image classifier to study the encoding/decoding of signals and compare several learning rules for training an SNN. Results reveal that (i) classical STDP learning windows generally obtain the best performance using different decoding schemes; (ii) first-spike decoding has worse accuracy than count decoding classifier does when no normalization rules are applied, although first-spike decoding classifier consumes much less time than count decoding classifier; (iii) the performance of first-spike decoding classifier can be largely enhanced with proper use of normalization rules.
    • A Systematic Review of Recruitment and Retention Strategies Used in Dietary Randomized Controlled Interventions in Cancer Survivors

      Thomson, Cynthia A.; Lavelle, Sarah Arline; Marian, Mary J.; Hingle, Melanie D. (The University of Arizona., 2018)
      Interpretation of results of dietary intervention trials in cancer survivors may be limited by insufficient recruitment or retention of study participants. This systematic review describes recruitment strategies, accrual of participants, and attrition (withdrawal) rates for dietary interventions conducted in breast, prostate, and colorectal cancer survivors. PubMed, CINAHL, Cochrane Central Register of Controlled Trials, Embase, PsychINFO, and Web of Science databases were searched. Eligible studies included national and international dietary randomized controlled trials (RCTs), with at least 12 weeks of intervention and 6 months of follow-up. Trials were required to include a CONSORT (CONsolidated Standards of Reporting Trials) diagram. Twenty cohorts were included: breast cancer (BC) survivors (n=11), prostate cancer (PC) (n=3), colorectal cancer (CRC) (n=1), and combined (n=5). Primary recruitment methods included health care providers (n=13) or cancer registries (n=9). Of studies that set a priori sample sizes, 12 met accrual targets and five did not. Attrition rates averaged 18.6% at 6 months, 16.3% at 12-13 months, and 20.3% at 2 years. Among completed studies (n=18), seven trials met a priori retention targets, three trials did not, one assessed feasibility, and seven trials did not provide a clearly defined retention goal. There were few trials in PC and CRC survivors. Missing CONSORT diagrams reduced the eligible studies. The majority of studies met recruitment goals (n=12). Overall, attrition rates averaged approximately 17.4%. Improved understanding of effective recruitment and retention strategies requires more diligent reporting. Qualitative research may allow for more systematic and detailed evaluation of challenges that contribute to insufficient recruitment and retention of cancer survivors in dietary intervention trials. Registration can be found at PROSPERO ref: CRD42018070396.
    • A Visual Analysis of Local Food Taste Regime in Conventional and Unconventional Marketplaces

      Mars, Matthew M.; Thorp, Tyler; Torres, Robert; Hingle, Melanie (The University of Arizona., 2018)
      The Local Food Movement (LFM) is composed of a complex network of actors including producers (e.g., farmers, ranchers, processors), purveyors (e.g., farmers’ market vendors, retailers, restaurateurs), organizers (e.g., farmers’ market operators, food bank administrators) and narrators (e.g., local food journalists). Limited governance within local food systems (LFSs) and a lack of consensus on the definition of ‘local food’ provide such actors with notable latitude in how they frame the meaning of ‘local’ in the products they produce, market, and sell. The expansion of food products that are framed as being local within conventional retail sites may be further convoluting the meaning and representation of local food across the disparate market sites that operate within a single LFS (e.g. community gardens, farmers’ markets, festivals, grocery stores, roadside stands, you-picks). Thus, consumers are left to sort through a variety of elements (e.g., activist, aesthetic, community, cultural, ecological, economic, health and wellness) that converge and compete to shape their understanding of local food and guide their consumption decisions. Here, I use a structured photo analysis design to explore the elements that influence the visual representation of local food within five farmers’ markets and five grocery stores within the Southern Arizona Local Food System (SALFS). The theoretical principles of institutional logics guide my identification and analysis of the beliefs, motives, practices and values that guide the framing practices and strategies of local food actors within various retail settings. Commodification, the act of turning something with intrinsic value into a exchangeable good, is used to reveal how the various elements that underpin the LFM are (or are not) being leveraged to support the representation of local food products across different retail settings. The theoretical principles of taste regimes, the concept that social groups with high levels of cultural capital have the greatest influence over the meaning and legitimacy of products within an aesthetically oriented culture of consumption, is used to analyze the similarities and differences between the representations of local food within and across the 10 retail locations. The findings illustrate how local food framing practices and strategies across conventional and unconventional retail sites foster a local food taste regime that is mostly inconsistent with the fundamental principles and values of the LFM. Recommendations for local food practitioners and further research are provided.
    • Abe Lincoln in Illinois: from historical figure to state character

      Cook, Harlin Maurice, 1925- (The University of Arizona., 1952)
    • ABERRATION FIELD PROPERTIES OF SIMPLE NON-AXIALLY SYMMETRIC OPTICAL SYSTEMS.

      Jewell, Tatiana Emelianovna. (The University of Arizona., 1984)
    • ABILITY GROUPING IN A COLLEGE CHEMISTRY LABORATORY COURSE.

      Chambers, Rebecca Anne. (The University of Arizona., 1985)
    • The ability of a group of prospective teachers in speech skills

      Cook, Robert Verne, 1923- (The University of Arizona., 1951)