ABOUT THIS COLLECTION

This open access archive contains publications from University of Arizona faculty, researchers and staff, primarily open-access versions of formally published journal articles. The collection includes published articles and final accepted manuscripts submitted by UA faculty under the UA Open Access Policy. The collection also includes books, book chapters, book reviews, presentations, data, and other scholarly materials submitters have chosen to make available in the repository.


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Recent Submissions

  • Perceived Barriers and Facilitating Factors in Implementing Delayed School Start Times to Improve Adolescent Sleep Patterns

    Fitzpatrick, Julia M.; Silva, Graciela E.; Vana, Kimberly D.; The University of Arizona, College of Nursing (Wiley, 2020-12-02)
    BACKGROUND: Most adolescents in the United States do not obtain sufficient sleep. Early school start times play a significant role in adolescent sleep deprivation. Most primary and secondary schools begin classes earlier than the 8:30 am. Perceived barriers to implementing a delayed school start time have been suggested in the literature but have not been quantified. This study explored perceived barriers and facilitating factors for implementing delayed high-school start times. METHODS: A cross-sectional study. School administrators who had delayed their school start times were invited to complete an online questionnaire ranking the perceived barriers and facilitating factors for implementing the delayed start times. RESULTS: Most commonly cited perceived barriers were lack of a tiered bus system, school athletes missing more afternoon classes, and less time after school for athletics. Most commonly cited facilitating factors were school-administrator involvement in the decision-making process and sleep education for family members and school administrators. CONCLUSIONS: Participants found that providing sleep education to fellow administrators, teachers, school staff members, families, and students and including them in the decision-making process positively facilitated the implementation of delayed school start times. Perceived barriers to implementation may be overcome with support from stakeholders and planning committees. © 2020, American School Health Association
  • Assessment of High-Temperature Effects on Hypersonic Aerothermoelastic Analysis using Multi-Fidelity Multi-Variate Surrogates

    Sadagopan, Aravinth; Huang, Daning; Duzel, Umran; Martin, Liza E.; Hanquist, Kyle M.; University of Arizona (American Institute of Aeronautics and Astronautics, 2021-01-04)
    This study investigates the impact of the high-temperature effect, esp. the real gas effect and the chemical reactions, on hypersonic aerothermodynamic solutions of double cone and double wedge configurations, as well as the aerothermoelastic behavior of a double wedge configuration in hypersonic flow. First, a high-temperature computational fluid dynamics code was benchmarked and correlated with experimental results, emphasizing the impact of high-temperature effects as well as turbulence modeling on heat flux prediction. Subsequently, an aerothermal surrogate based on the multi-fidelity Gaussian process regression method was developed. The model achieves a balance between model accuracy and computational cost of sample generation, using the combination of a few high-fidelity sample and many low-fidelity samples. Finally, the new aerothermal surrogate was applied to study the impact of the hightemperature effect on the aerothermoelastic response of a hypersonic skin panel, emphasizing the necessity of the accurate characterization of the localized heat flux for reasonable assessment of the response of a compliant structure in high-speed high-temperature flowfield.
  • An Innovative United States–Mexico Community Outreach Initiative for Hispanic and Latino People in the United States: A Collaborative Public Health Network

    Flynn, Michael A.; Rodriguez Lainz, Alfonso; Lara, Juanita; Rosales, Cecilia; Feldstein, Federico; Dominguez, Ken; Wolkin, Amy; Sierra Medal, Ivan Roberto; Tonda, Josana; Romero-Steiner, Sandra; et al. (SAGE Publications, 2021-01-21)
    Collaborative partnerships are a useful approach to improve health conditions of disadvantaged populations. The Ventanillas de Salud (VDS) (“Health Windows”) and Mobile Health Units (MHUs) are a collaborative initiative of the Mexican government and US public health organizations that use mechanisms such as health fairs and mobile clinics to provide health information, screenings, preventive measures (eg, vaccines), and health services to Mexican people, other Hispanic people, and underserved populations (eg, American Indian/Alaska Native people, geographically isolated people, uninsured people) across the United States. From 2013 through 2019, the VDS served 10.5 million people (an average of 1.5 million people per year) at Mexican consulates in the United States, and MHUs served 115 461 people from 2016 through 2019. We describe 3 community outreach projects and their impact on improving the health of Hispanic people in the United States. The first project is an ongoing collaboration between VDS and the Centers for Disease Control and Prevention (CDC) to address occupational health inequities among Hispanic people. The second project was a collaboration between VDS and CDC to provide Hispanic people with information about Zika virus infection and health education. The third project is a collaboration between MHUs and the University of Arizona to provide basic health services to Hispanic communities in Pima and Maricopa counties, Arizona. The VDS/MHU model uses a collaborative approach that should be further assessed to better understand its impact on both the US-born and non–US-born Hispanic population and the public at large in locations where it is implemented. © 2021, Association of Schools and Programs of Public Health.
  • The Wikipedia Global Consciousness Index: a measurement of awareness and meaning of the world as one place

    Stieve, Thomas; School of Geography, Development & Environment, University of Arizona (Informa UK Limited, 2021-01-18)
    To supplement current globalization indexes, I propose a new index, the Wikipedia Global Consciousness Index (WikiGCI). The WikiGCI, defined as a measure of awareness and meaning of the world as one place, is founded on Robertson's [(1992). Globalization: Social theory and global culture. Sage] suggestion of global consciousness. Available indexes that measure globalization rely on network definitions for their theoretical frameworks and count objects crossing borders. For the WikiGCI, ideas serve as the empirical units to understand global consciousness. The WikiGCI is based on articles edited in Wikipedia that express ideas on a world level. By geolocating IP address edits to Wikipedia articles, I identified the top 100 articles edited in the most countries (global articles). With this research, I first analyse how global articles affirm a global consciousness as well as define its meaning. Second, I construct an index of this consciousness and measure each country's score on it. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
  • Trash reconsidered: A relational approach to deposition in the Pueblo Southwest

    Fladd, Samantha G.; Hedquist, Saul L.; Adams, E. Charles; School of Anthropology, University of Arizona; Arizona State Museum, University of Arizona (Elsevier BV, 2021-03)
    Deposition creates the archaeological record; however, the social implications of depositional practices are often overlooked, particularly when considering domestic materials found in upper room fill. In this paper, we argue that the term “trash” and its connotations mischaracterize the thought and meaning that motivate decisions about deposition, as exemplified by ethnohistoric and modern accounts of disposal within Pueblo society. Understanding the context and content of deposition can reveal important aspects of the identities, beliefs, and relationships of the individuals and groups who created them. We explore the social role of deposits at Homol'ovi I, an ancestral Hopi pueblo in northeastern Arizona, through detailed analyses of excavation data. Drawing on contemporary Hopi insights, rooms and objects are found to assume distinct social identities, specifically gender, that influence the placement of materials throughout the pueblo. We conclude that patterns of cultural deposition from all contexts have the potential to provide significant insights about the life histories, reuse, and commemoration of spaces and objects when considering archaeological contexts worldwide. © 2021 Elsevier Inc.
  • Unanticipated events, perceptions, and household labor allocation in Zimbabwe

    Josephson, Anna; Shively, Gerald E.; University of Arizona (Elsevier BV, 2021-05)
    This paper investigates labor allocation as a strategy for coping with unanticipated events. We evaluate household responses to unforeseen death and rainfall shocks in Zimbabwe, during a period in which many households were already stressed due to the country's long-term economic crisis. In this context, shocks compound existing stresses. Different types of shocks disparately affect household labor allocation. Household perceptions about the shocks experienced also shift labor use. Perceived rainfall shocks positively affect the share of labor allocated to migration-related activities and negatively affect the share of labor allocated to non-participation. © 2020 Elsevier Ltd
  • On Trapping Sets and Guaranteed Error Correction Capability of LDPC Codes and GLDPC Codes

    Chilappagari, Shashi Kiran; Nguyen, Dung Viet; Vasic, Bane; Marcellin, Michael W.; Department of Electrical and Computer Engineering, The University of Arizona (Institute of Electrical and Electronics Engineers (IEEE), 2010-04)
    The relation between the girth and the guaranteed error correction capability of ¿ -left-regular low-density parity-check (LDPC) codes when decoded using the bit flipping (serial and parallel) algorithms is investigated. A lower bound on the size of variable node sets which expand by a factor of at least 3 ¿/4 is found based on the Moore bound. This bound, combined with the well known expander based arguments, leads to a lower bound on the guaranteed error correction capability. The decoding failures of the bit flipping algorithms are characterized using the notions of trapping sets and fixed sets. The relation between fixed sets and a class of graphs known as cage graphs is studied. Upper bounds on the guaranteed error correction capability are then established based on the order of cage graphs. The results are extended to left-regular and right-uniform generalized LDPC codes. It is shown that this class of generalized LDPC codes can correct a linear number of worst case errors (in the code length) under the parallel bit flipping algorithm when the underlying Tanner graph is a good expander. A lower bound on the size of variable node sets which have the required expansion is established.
  • FEAST of biosensors: Food, environmental and agricultural sensing technologies (FEAST) in North America

    McLamore, Eric S.; Alocilja, Evangelyn; Gomes, Carmen; Gunasekaran, Sundaram; Jenkins, Daniel; Datta, Shoumen P.A.; Li, Yanbin; Mao, Yu (Jessie); Nugen, Sam R.; Reyes-De-Corcuera, José I.; et al. (Elsevier BV, 2021-04)
    We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics. © 2021 Elsevier B.V.
  • Norovirus detection in water samples at the level of single virus copies per microliter using a smartphone-based fluorescence microscope

    Chung, Soo; Breshears, Lane E.; Gonzales, Alana; Jennings, Christian M.; Morrison, Christina M.; Betancourt, Walter Q.; Reynolds, Kelly A.; Yoon, Jeong-Yeol; Department of Biosystems Engineering, The University of Arizona; Department of Biomedical Engineering, The University of Arizona; et al. (Nature Research, 2021-01-29)
    Norovirus is a widespread public health threat and has a very low infectious dose. This protocol presents the extremely sensitive mobile detection of norovirus from water samples using a custom-built smartphone-based fluorescence microscope and a paper microfluidic chip. Antibody-conjugated fluorescent particles are immunoagglutinated and spread over the paper microfluidic chip by capillary action for individual counting using a smartphone-based fluorescence microscope. Smartphone images are analyzed using intensity- and size-based thresholding for the elimination of background noise and autofluorescence as well as for the isolation of immunoagglutinated particles. The resulting pixel counts of particles are correlated with the norovirus concentration of the tested sample. This protocol provides detailed guidelines for the construction and optimization of the smartphone- and paper-based assay. In addition, a 3D-printed enclosure is presented to incorporate all components in a dark environment. On-chip concentration and the assay of higher concentrations are presented to further broaden the assay range. This method is the first to be presented as a highly sensitive mobile platform for norovirus detection using low-cost materials. With all materials and reagents prepared, a single standard assay takes under 20 min. Although the method described is used for detection of norovirus, the same protocol could be adapted for detection of other pathogens by using different antibodies. © 2021, The Author(s), under exclusive licence to Springer Nature Limited.
  • Widespread fire years in the US–Mexico Sky Islands are contingent on both winter and monsoon precipitation

    Arizpe, Alexis H.; Falk, Donald A.; Woodhouse, Connie A.; Swetnam, Thomas W.; Univ Arizona, Lab Tree Ring Res; Univ Arizona, Sch Nat Resources & Environm; Univ Arizona, Sch Geog Dev & Environm (CSIRO PUBLISHING, 2020)
    The climate of the south-western United States and northern Mexico borderlands is marked by a bimodal precipitation regime with the majority of moisture arriving during the cool season via Pacific frontal storm systems, and intense convective storms during the North American Monsoon (NAM). The fire season occurs primarily during the arid foresummer in May and June, before the development of the NAM. Most tree-ring studies of fire climatology in the region have evaluated only the role of winter precipitation. We used tree-ring-width-based reconstructions of both winter and monsoon precipitation, coupled with fire scar reconstructions of fire history from mountain ranges in the US and Mexico, to quantify the historical role and interactions of both seasons of precipitation in modulating widespread fire years. Winter precipitation was the primary driver of widespread fire years in the region, but years with drought in both seasons had the highest fire frequency and most widespread fires. These relationships define a unique monsoon fire regime, in which the timing and amount of monsoon precipitation are important factors in limiting the length of fire season and regulating widespread fire years.
  • Projected Climate-Fire Interactions Drive Forest to Shrubland Transition on an Arizona Sky Island

    O’Connor, Christopher D.; Falk, Donald A.; Garfin, Gregg M.; School of Natural Resources and the Environment, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Frontiers Media SA, 2020-08-21)
    Climate stressors on the forests of the American Southwest are shifting species distributions across spatial scales, lengthening potential fire seasons, and increasing the incidence of drought and insect-related die-off. A legacy of fire exclusion in forests once adapted to frequent surface fires is exacerbating these changes. Reducing stand densities and surface fuel loads has been proposed as a means of moderating fire behavior while reducing competition for water, but it is not established whether thinning treatments and restoration of surface fire regimes will be enough to offset the multiple manifestations of a changing climate. We examined the potential for prescribed fuel treatments and restoration of historical fire frequencies to mitigate the effects of climate on forest species distributions, composition, total biomass, and fire severity. We used an ecosystem process model to simulate the effects of projected climate, fire, and active management interactions along an ecological gradient of shrublands, woodlands, and forests on a mountain range in Arizona in the United States. We used historical climate conditions as a baseline to compare results from projected climate for the period 2005–2055 with and without fire and with no fuel treatments, a single-entry fuel treatment, and a second fuel treatment after 20 years. Simulated desert grassland and shrub communities remained compositionally stable and maintained or expanded their extents while woodland and forest communities lost basal area and total biomass and receded to the coolest and wettest aspects and drainages even without fire. Initial fuel treatments reduced the extent and relative mortality of high-severity patches for the first two decades, and secondary treatments at simulation year 20 extended these effects for the remaining 30 years of simulation. Immediate and future fuel treatments showed potential to mitigate the severity of fire effects under projected conditions and slow the transition from forest to shrubland in some vegetation types, however, a reduction in basal area and spatial extent of some forest species occurred regardless of management actions. Results are being used to inform local land managers and partners of potential landscape changes resulting from climate alone and from climate–fire interactions and to coordinate active management of fuels across ownerships.
  • Smartphones and Social Support: Longitudinal Associations Between Smartphone Use and Types of Support

    Lapierre, Matthew A.; Zhao, Pengfei; University of Arizona (SAGE Publications, 2021-02-03)
    Smartphones provide users with a vast array of tools to reach out to the world. Smartphones can be used to reach out interpersonally with family, friends, and acquaintances, they can be used to scroll through social networking platforms where one can post comments on a friend’s status update or read about the personal lives of their favorite celebrity, and they can be used to surf the web or read the news. Yet, research has also shown that problematic smartphone use (PSU) can be harmful. Of interest in the current study is whether smartphones can help or harm social bonds longitudinally via social support. Working with a sample of 221 college students who were surveyed twice over a 3-month span, this study explored whether various types of smartphone use (e.g., person-to-person, social networking, and mass-mediated) along with PSU predicted different types of social support over time. The results showed that person-to-person smartphone use was associated with greater belonging support (i.e., feeling accepted by people around you) and tangible support (i.e., feeling that you can find people to help with practical needs) over time. In addition, increased PSU was associated with less tangible support longitudinally. Lastly, there were no effects for social networking or mass-mediated smartphone use on any type of social support. These results offer important insights into how smartphones potentially affect our ability to connect with others along with greater detail about specific kinds of use are implicated. © The Author(s) 2021.
  • Guidelines For Pursuing and Revealing Data Abstractions

    Bigelow, Alex; Williams, Katy; Isaacs, Katherine E.; University of Arizona (Institute of Electrical and Electronics Engineers (IEEE), 2021-02)
    Many data abstraction types, such as networks or set relationships, remain unfamiliar to data workers beyond the visualization research community. We conduct a survey and series of interviews about how people describe their data, either directly or indirectly. We refer to the latter as latent data abstractions. We conduct a Grounded Theory analysis that (1) interprets the extent to which latent data abstractions exist, (2) reveals the far-reaching effects that the interventionist pursuit of such abstractions can have on data workers, (3) describes why and when data workers may resist such explorations, and (4) suggests how to take advantage of opportunities and mitigate risks through transparency about visualization research perspectives and agendas. We then use the themes and codes discovered in the Grounded Theory analysis to develop guidelines for data abstraction in visualization projects. To continue the discussion, we make our dataset open along with a visual interface for further exploration.
  • Constructing a desert labyrinth: The psychological and emotional geographies of deterrence strategy on the U.S. / Mexico border

    Chambers, Samuel N.; Boyce, Geoffrey Alan; Jacobs, W. Jake; School of Geography, Development & Environment, The University of Arizona; Department of Psychology, The University of Arizona (Elsevier BV, 2021-02)
    Confinement, hindrance, and time bring anxiety, fear, and stress, often accompanied by confusion and desperation. In the case of undocumented immigrants in the Sonoran Desert, such conditions are manipulated by way of surveillance and policing. These conditions, in combination with physical exertion, augment a physiological stress response that coalesces with existing traumas and fear. We undertake a critical mapping of relations among enforcement infrastructure, migration routes, and measurable features of the physical landscape to demonstrate that a corridor in the region functions as a labyrinth, an outcome of a combination of threats and stressors determined by the spaces migrants find themselves in after crossing the U.S./Mexico border. We argue a biopolitical understanding of current border policies indicates it reduces migrants to bare life rather than using threat, stressors, or trauma as instruments for manipulating behavior. We discuss how this labyrinth works in combination with other mechanisms, including criminalization, detention, abuse, separation, and deportation, to deliver consequences that may deter migration. Despite these efforts, migration routes remain plastic, indicating the continued potential to resist and evade the surveillance technologies and enforcement deployed in the borderlands. We assert that an inevitable result of the desert labyrinth is human mortality. © 2021 Elsevier Ltd
  • The effect of direct cognitive assessment in the Medicare annual wellness visit on dementia diagnosis rates

    Lind, Kimberly E.; Hildreth, Kerry; Lindrooth, Richard; Morrato, Elaine; Crane, Lori A.; Perraillon, Marcelo Coca; Mel and Enid Zuckerman College of Public Health, University of Arizona (Wiley, 2021-01-22)
    Objective: To evaluate the relationship between direct cognitive assessment introduced with the Medicare Annual Wellness Visit (AWV) and new diagnoses of dementia, and to determine if effects vary by race. Data Sources: Medicare Limited Data Set 5% sample claims 2003-2014 and the HRSA Area Health Resources Files. Study Design: Instrumental Variable approach estimating the relationship between AWV utilization and new diagnoses of dementia using county-level Welcome to Medicare Visit rates as an instrument. Data Collection/Extraction Methods: Three hundred twenty-four thousand three hundred and eighty-five fee-for-service Medicare beneficiaries without dementia when the AWV was introduced in 2011. Principal Findings: Annual Wellness Visit utilization was associated with an increased probability of new dementia diagnosis with effects varying by racial group (categorized as white, black, Hispanic/Latino, or Asian based on Social Security Administration data). Hazard ratios (95% confidence intervals) for new dementia diagnosis within 6 months of AWV utilization were as follows: 2.34 (2.13, 2.58) white, 2.22 (1.71, 2.89) black, 4.82 (2.94, 7.89) Asian, and 6.14 (3.70, 10.19) Hispanic (P <.001 for each). Our findings show that estimates that do not control for selection underestimate the effect of AWV on new diagnoses. Conclusions: Dementia diagnosis rates increased with AWV implementation with heterogenous effects by race and ethnicity. Current recommendations by the United States Preventive Services Task Force state that the evidence is insufficient to recommend for or against screening for cognitive impairment in older adults. © 2021 Health Research and Educational Trust
  • The concept of responsibility in the ethics of self-defense and war

    Sartorio, Carolina (Springer Science and Business Media LLC, 2021-02-03)
    The focus of this paper is an influential family of views in the ethics of self-defense and war: views that ground the agent’s liability to be attacked in self-defense in the agent’s moral responsibility for the threat posed (“Responsibility Views”). I critically examine the concept of responsibility employed by such views, by looking at potential connections with the contemporary literature on moral responsibility. I start by uncovering some of the key assumptions that Responsibility Views make about the relevant concept of responsibility, and by scrutinizing those assumptions under the lens of more general theorizing about responsibility. I identify an important conflict that arises at that point. The problem is that the concept presupposed by Responsibility Views is in tension with the standard way of understanding the connection between the neutral and non-neutral forms of moral responsibility. I draw attention to a particular strategy that could be used to address this challenge, but I also identify some important obstacles that stand in the way. © 2021, The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature.
  • Shifts in plant composition mediate grazing effects on carbon cycling in grasslands

    Liang, Maowei; Smith, Nicholas G.; Chen, Jiquan; Wu, Yantao; Guo, Zhiwei; Gornish, Elise S.; Liang, Cunzhu; School of Natural Resources and the Environment, University of Arizona (Wiley, 2021-01-31)
    Carbon cycling in grasslands can be impacted by livestock grazing, partially as an indirect result of herbivory-induced compositional shifts in the plant community. However, the underlying mechanisms of how these shifts impact carbon cycling are not well-documented. We conducted a long-term grazing experiment with four sheep stocking rates in the semi-arid grasslands of Inner Mongolia, China, to examine grazing effects on the ratio of C3 to C4 species (C3:C4), shoot biomass, root biomass, root:shoot, soil respiration, soil C, soil N and soil C:N between 2014 and 2018. We explored the responses of these carbon metrics to C3:C4 under different grazing treatments and the mechanisms driving grazing-induced carbon loss using structural equation models. Livestock grazing directly shifted plant community composition (i.e. increasing C3:C4) and reduced vegetation carbon (i.e. shoot biomass), whereas grazing effects on below-ground carbon were mediated by the interactions of the soil profile (i.e. depth dependence) and year-to-year variation (e.g. rainfall regulation). Grazing-induced increases in C3:C4 suppressed soil carbon loss by inhibiting the rate of soil respiration. Furthermore, grazing intensity indirectly altered these relationships. Specifically, C3:C4 was positively related to shoot biomass and negatively associated with root:shoot, soil C and soil N, whereas these relationships were only significant in no-grazed plots. Meanwhile, soil respiration was negatively associated with C3:C4, soil C, soil N and soil C:N, but a positive relationship with shoot biomass; these relationships were significant only in grazed plots. Synthesis and applications. Our study highlights the importance of the functional linkages between community characteristics and ecosystem processes, that is, shifts in plant community composition play a key role in regulating grassland carbon cycling. These findings provide a useful field-observed resource for model development and could improve the guidelines for livestock management and policies regarding climate mitigation. © 2021 British Ecological Society
  • Identifying restoration opportunities beneath native mesquite canopies

    Gornish, Elise S.; Ganjurjav, Hasbagan; Liang, Maowei; Simonis, Juniper L.; McClaran, Mitchel P.; School of Natural Resources and the Environment, University of Arizona (Wiley, 2021-02)
    Effective restoration strategies are needed to address habitat degradation that accompanies worldwide environmental change. One method used to enhance restoration outcomes is the leveraging of beneficial relationships (facilitation) among plants. In the southwestern United States, native mesquite trees (Prosopis spp.) are commonly planted to stabilize soil, but the value of using mesquite canopies for enhancing restoration success is unknown. We explored this possibility in an attempt to understand how common species, that both are and are not typically used for restoration, might differentially respond to mesquite canopies. We used a Bayesian multivariate generalized mixed model structure to analyze a dataset describing natural vegetation density in the Santa Rita Experimental Range, Arizona, United States. We found that more dominant species were not more likely to be distributed under mesquite. We also found that, while all of the focal species were more likely to be under mesquite with increased mesquite cover, they varied in the strength of their responses and the degree of saturation. Finally, we found that the aggressive invasive grass Eragrostis lehmanniana was found at lower incidences with increasing mesquite canopy cover, compared to the total species average as well as several of the natives investigated in this study. This work highlights the importance of being conscious of canopy size and continuity when considering understory species for restoration. This work also suggests that mesquite canopies can be used to provide a “safe site” for restoration species because competitive pressure from invasives is slightly reduced. © 2020 Society for Ecological Restoration
  • The importance of nutrients for microbial priming in a bog rhizosphere

    Waldo, Nicholas B.; Tfaily, Malak M.; Anderton, Christopher; Neumann, Rebecca B.; Department of Environmental Science, University of Arizona (Springer Science and Business Media LLC, 2021-01-26)
    Wetlands host anaerobic microbes which convert organic carbon into methane (CH4), a powerful greenhouse gas. Wetland plants can influence which carbon compounds are available for microbial processing by exuding freshly fixed carbon from their roots. Exudation of carbon from plant roots can trigger microbial priming: the process of new carbon stimulating the microbial community into processing more soil carbon than they otherwise would have. This study utilized high resolution Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) analysis to probe the composition of soil organic compounds from the rhizosphere of Carex aquatillis, a common wetland sedge, which is known to have stimulated microbial priming within peat soil. The goal was to identify what types of molecules were created or lost during microbial priming in the wetland rhizosphere and thus advance mechanistic understanding of the process. FT-ICR-MS analysis demonstrated that more microbial transformations of carbon occurred among water-soluble compounds than among hydrophobic compounds, but that some hydrophobic compounds were processed. Crucially for understanding microbial priming, the root exudates triggered increased processing of high molecular weight molecules regardless of nutrient content but processed low molecular weight compounds only if they contained nitrogen or sulfur, essential nutrients for plant growth. The importance of sulfur in determining molecular utilization is noteworthy because priming literature typically focuses on nitrogen-mining. The fact that some molecules were processed and others were not is evidence for a selective priming effect in which some carbon compounds with specific properties are used at an increased rate, while others are left unaltered. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG part of Springer Nature.
  • MetroSets: Visualizing Sets as Metro Maps

    Jacobsen, Ben; Wallinger, Markus; Kobourov, Stephen; Nollenburg, Martin; University of Arizona (Institute of Electrical and Electronics Engineers (IEEE), 2021-02)
    We propose MetroSets, a new, flexible online tool for visualizing set systems using the metro map metaphor. We model a given set system as a hypergraph H=(V,S), consisting of a set V of vertices and a set S, which contains subsets of V called hyperedges. Our system then computes a metro map representation of H, where each hyperedge E in S corresponds to a metro line and each vertex corresponds to a metro station. Vertices that appear in two or more hyperedges are drawn as interchanges in the metro map, connecting the different sets. MetroSets is based on a modular 4-step pipeline which constructs and optimizes a path-based hypergraph support, which is then drawn and schematized using metro map layout algorithms. We propose and implement multiple algorithms for each step of the MetroSet pipeline and provide a functional prototype with easy-to-use preset configurations. Furthermore, using several real-world datasets, we perform an extensive quantitative evaluation of the impact of different pipeline stages on desirable properties of the generated maps, such as octolinearity, monotonicity, and edge uniformity. © 1995-2012 IEEE.

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