Showing papers by "University of Arkansas published in 2015"

A Typology of Mixed Methods Sampling Designs in Social Science Research

Abstract: This paper provides a framework for developing sampling designs in mixed methods research. First, we present sampling schemes that have been associated with quantitative and qualitative research. Second, we discuss sample size considerations and provide sample size recommendations for each of the major research designs for quantitative and qualitative approaches. Third, we provide a sampling design typology and we demonstrate how sampling designs can be classified according to time orientation of the components and relationship of the qualitative and quantitative sample. Fourth, we present four major crises to mixed methods research and indicate how each crisis may be used to guide sampling design considerations. Finally, we emphasize how sampling design impacts the extent to which researchers can generalize their findings. Key Words: Sampling Schemes, Qualitative Research, Generalization, Parallel Sampling Designs, Pairwise Sampling Designs, Subgroup Sampling Designs, Nested Sampling Designs, and Multilevel Sampling Designs

Qualitative Analysis Techniques for the Review of the Literature

Abstract: In this article, we provide a framework for analyzing and interpreting sources that inform a literature review or, as it is more aptly called, a research synthesis. Specifically, using Leech and Onwuegbuzie’s (2007, 2008) frameworks, we delineate how the following four major source types inform research syntheses: talk, observations, drawings/photographs/videos, and documents. We identify 17 qualitative data analysis techniques that are optimal for analyzing one or more of these source types. Further, we outline the role that the following five qualitative data analysis techniques can play in the research synthesis: constant comparison analysis, domain analysis, taxonomic analysis, componential analysis, and theme analysis. We contend that our framework represents a first step in an attempt to help literature reviewers analyze and interpret literature in an optimally rigorous way. Keywords: Review of the Literature, Research Synthesis, Qualitative Analysis, Constant Comparison Analysis, Domain Analysis, Taxonomic Analysis, Componential Analysis, Theme Analysis

The Faces of Fungi database: fungal names linked with morphology, phylogeny and human impacts

Abstract: Taxonomic names are key links between various databases that store information on different organisms. Several global fungal nomenclural and taxonomic databases (notably Index Fungorum, Species Fungorum and MycoBank) can be sourced to find taxonomic details about fungi, while DNA sequence data can be sourced from NCBI, EBI and UNITE databases. Although the sequence data may be linked to a name, the quality of the metadata is variable and generally there is no corresponding link to images, descriptions or herbarium material. There is generally no way to establish the accuracy of the names in these genomic databases, other than whether the submission is from a reputable source. To tackle this problem, a new database (FacesofFungi), accessible at www.facesoffungi.org (FoF) has been established. This fungal database allows deposition of taxonomic data, phenotypic details and other useful data, which will enhance our current taxonomic understanding and ultimately enable mycologists to gain better and updated insights into the current fungal classification system. In addition, the database will also allow access to comprehensive metadata including descriptions of voucher and type specimens. This database is user-friendly, providing links and easy access between taxonomic ranks, with the classification system based primarily on molecular data (from the literature and via updated web-based phylogenetic trees), and to a lesser extent on morphological data when molecular data are unavailable. In FoF species are not only linked to the closest phylogenetic representatives, but also relevant data is provided, wherever available, on various applied aspects, such as ecological, industrial, quarantine and chemical uses. The data include the three main fungal groups (Ascomycota, Basidiomycota, Basal fungi) and fungus-like organisms. The FoF webpage is an output funded by the Mushroom Research Foundation which is an NGO with seven directors with mycological expertise. The webpage has 76 curators, and with the help of these specialists, FoF will provide an updated natural classification of the fungi, with illustrated accounts of species linked to molecular data. The present paper introduces the FoF database to the scientific community and briefly reviews some of the problems associated with classification and identification of the main fungal groups. The structure and use of the database is then explained. We would like to invite all mycologists to contribute to these web pages.

Management of Ingested Foreign Bodies in Children: A Clinical Report of the NASPGHAN Endoscopy Committee

Abstract: Foreign body ingestions in children are some of the most challenging clinical scenarios facing pediatric gastroenterologists. Determining the indications and timing for intervention requires assessment of patient size, type of object ingested, location, clinical symptoms, time since ingestion, and myriad other factors. Often the easiest and least anxiety-producing decision is the one to proceed to endoscopic removal, instead of observation alone. Because of variability in pediatric patient size, there are less firm guidelines available to determine which type of object will safely pass, as opposed to the clearer guidelines in the adult population. In addition, the imprecise nature of the histories often leaves the clinician to question the timing and nature of the ingestion. Furthermore, changes in the types of ingestions encountered, specifically button batteries and high-powered magnet ingestions, create an even greater potential for severe morbidity and mortality among children. As a result, clinical guidelines regarding management of these ingestions in children remain varied and sporadic, with little in the way of prospective data to guide their development. An expert panel of pediatric endoscopists was convened and produced the present article that outlines practical clinical approaches to the pediatric patient with a variety of foreign body ingestions. This guideline is intended as an educational tool that may help inform pediatric endoscopists in managing foreign body ingestions in children. Medical decision making, however, remains a complex process requiring integration of clinical data beyond the scope of these guidelines. These guidelines should therefore not be considered to be a rule or to be establishing a legal standard of care. Caregivers may well choose a course of action outside of those represented in these guidelines because of specific patient circumstances. Furthermore, additional clinical studies may be necessary to clarify aspects based on expert opinion instead of published data. Thus, these guidelines may be revised as needed to account for new data, changes in clinical practice, or availability of new technology.

Mechanical properties of carbon nanotube/polymer composites

Abstract: The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.

Mobile application usability: conceptualization and instrument development

Abstract: This paper presents a mobile application usability conceptualization and survey instrument following the 10- step procedure recommended by MacKenzie et al. (2011). Specifically, we adapted Apple's user experience guidelines to develop our conceptualization of mobile application usability that we then developed into 19 first-order constructs that formed 6 second-order constructs. To achieve our objective, we collected four datasets: content validity (n = 318), pretest (n = 440), validation (n = 408), and cross-validation (n = 412). The nomological validity of this instrument was established by examining its impact on two outcomes: continued intention to use and mobile application loyalty. We found that the constructs that represented our mobile application usability conceptualization were good predictors of both outcomes and compared favorably to an existing instrument based on Microsoft's usability guidelines. In addition to being an exemplar of the recent procedure of MacKenzie et al. to validate an instrument, this work provides a rich conceptualization of an instrument for mobile application usability that can serve as a springboard for future work to understand the impacts of mobile application usability and can be used as a guide to design effective mobile applications.

Effect of warming temperatures on US wheat yields

Abstract: Climate change is expected to increase future temperatures, potentially resulting in reduced crop production in many key production regions. Research quantifying the complex relationship between weather variables and wheat yields is rapidly growing, and recent advances have used a variety of model specifications that differ in how temperature data are included in the statistical yield equation. A unique data set that combines Kansas wheat variety field trial outcomes for 1985–2013 with location-specific weather data is used to analyze the effect of weather on wheat yield using regression analysis. Our results indicate that the effect of temperature exposure varies across the September−May growing season. The largest drivers of yield loss are freezing temperatures in the Fall and extreme heat events in the Spring. We also find that the overall effect of warming on yields is negative, even after accounting for the benefits of reduced exposure to freezing temperatures. Our analysis indicates that there exists a tradeoff between average (mean) yield and ability to resist extreme heat across varieties. More-recently released varieties are less able to resist heat than older lines. Our results also indicate that warming effects would be partially offset by increased rainfall in the Spring. Finally, we find that the method used to construct measures of temperature exposure matters for both the predictive performance of the regression model and the forecasted warming impacts on yields.

Reducing greenhouse gas emissions, water use, and grain arsenic levels in rice systems.

Abstract: Agriculture is faced with the challenge of providing healthy food for a growing population at minimal environmental cost. Rice (Oryza sativa), the staple crop for the largest number of people on earth, is grown under flooded soil conditions and uses more water and has higher greenhouse gas (GHG) emissions than most crops. The objective of this study was to test the hypothesis that alternate wetting and drying (AWD--flooding the soil and then allowing to dry down before being reflooded) water management practices will maintain grain yields and concurrently reduce water use, greenhouse gas emissions and arsenic (As) levels in rice. Various treatments ranging in frequency and duration of AWD practices were evaluated at three locations over 2 years. Relative to the flooded control treatment and depending on the AWD treatment, yields were reduced by <1-13%; water-use efficiency was improved by 18-63%, global warming potential (GWP of CH4 and N2 O emissions) reduced by 45-90%, and grain As concentrations reduced by up to 64%. In general, as the severity of AWD increased by allowing the soil to dry out more between flood events, yields declined while the other benefits increased. The reduction in GWP was mostly attributed to a reduction in CH4 emissions as changes in N2 O emissions were minimal among treatments. When AWD was practiced early in the growing season followed by flooding for remainder of season, similar yields as the flooded control were obtained but reduced water use (18%), GWP (45%) and yield-scaled GWP (45%); although grain As concentrations were similar or higher. This highlights that multiple environmental benefits can be realized without sacrificing yield but there may be trade-offs to consider. Importantly, adoption of these practices will require that they are economically attractive and can be adapted to field scales.

Surface runoff and tile drainage transport of phosphorus in the midwestern United States.

Abstract: The midwestern United States offers some of the most productive agricultural soils in the world. Given the cool humid climate, much of the region would not be able to support agriculture without subsurface (tile) drainage because high water tables may damage crops and prevent machinery usage in fields at critical times. Although drainage is designed to remove excess soil water as quickly as possible, it can also rapidly transport agrochemicals, including phosphorus (P). This paper illustrates the potential importance of tile drainage for P transport throughout the midwestern United States. Surface runoff and tile drainage from fields in the St. Joseph River Watershed in northeastern Indiana have been monitored since 2008. Although the traditional concept of tile drainage has been that it slowly removes soil matrix flow, peak tile discharge occurred at the same time as peak surface runoff, which demonstrates a strong surface connection through macropore flow. On our research fields, 49% of soluble P and 48% of total P losses occurred via tile discharge. Edge-of-field soluble P and total P areal loads often exceeded watershed-scale areal loadings from the Maumee River, the primary source of nutrients to the western basin of Lake Erie, where algal blooms have been a pervasive problem for the last 10 yr. As farmers, researchers, and policymakers search for treatments to reduce P loading to surface waters, the present work demonstrates that treating only surface runoff may not be sufficient to reach the goal of 41% reduction in P loading for the Lake Erie Basin.

Superior Optical Properties of Perovskite Nanocrystals as Single Photon Emitters.

Abstract: The power conversion efficiency of photovoltaic devices based on semiconductor perovskites has reached ∼20% after just several years of research efforts. With concomitant discoveries of other promising applications in lasers, light-emitting diodes, and photodetectors, it is natural to anticipate what further excitement these exotic perovskites could bring about. Here we report on the observation of single photon emission from single CsPbBr3 perovskite nanocrystals (NCs) synthesized from a facile colloidal approach. Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit nearly 2 orders of magnitude increase in their absorption cross sections at similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is greatly shortened at both room and cryogenic temperatures to favor an extremely fast output of single photons. The above superior optical properties have paved the way toward quantum-light applications of perovskite NCs in various quantum information processing schemes.

Propagation Dynamics of a Light Beam in a Fractional Schrödinger Equation.

Abstract: The dynamics of wave packets in the fractional Schrodinger equation is still an open problem. The difficulty stems from the fact that the fractional Laplacian derivative is essentially a nonlocal operator. We investigate analytically and numerically the propagation of optical beams in the fractional Schrodinger equation with a harmonic potential. We find that the propagation of one- and two-dimensional input chirped Gaussian beams is not harmonic. In one dimension, the beam propagates along a zigzag trajectory in real space, which corresponds to a modulated anharmonic oscillation in momentum space. In two dimensions, the input Gaussian beam evolves into a breathing ring structure in both real and momentum spaces, which forms a filamented funnel-like aperiodic structure. The beams remain localized in propagation, but with increasing distance display an increasingly irregular behavior, unless both the linear chirp and the transverse displacement of the incident beam are zero.

Religion, spirituality, and physical health in cancer patients: A meta-analysis.

Abstract: Although religion/spirituality (R/S) is important in its own right for many cancer patients, a large body of research has examined whether R/S is also associated with better physical health outcomes. This literature has been characterized by heterogeneity in sample composition, measures of R/S, and measures of physical health. In an effort to synthesize previous findings, a meta-analysis of the relation between R/S and patient-reported physical health in cancer patients was performed. A search of PubMed, PsycINFO, the Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library yielded 2073 abstracts, which were independently evaluated by pairs of raters. The meta-analysis was conducted for 497 effect sizes from 101 unique samples encompassing more than 32,000 adult cancer patients. R/S measures were categorized into affective, behavioral, cognitive, and 'other' dimensions. Physical health measures were categorized into physical well-being, functional well-being, and physical symptoms. Average estimated correlations (Fisher z scores) were calculated with generalized estimating equations with robust variance estimation. Overall R/S was associated with overall physical health (z = 0.153, P < .001); this relation was not moderated by sociodemographic or clinical variables. Affective R/S was associated with physical well-being (z = 0.167, P < .001), functional well-being (z = 0.343, P < .001), and physical symptoms (z = 0.282, P < .001). Cognitive R/S was associated with physical well-being (z = 0.079, P < .05) and functional well-being (z = 0.090, P < .01). 'Other' R/S was associated with functional well-being (z = 0.100, P < .05). In conclusion, the results of the current meta-analysis suggest that greater R/S is associated with better patient-reported physical health. These results underscore the importance of attending to patients' religious and spiritual needs as part of comprehensive cancer care.

Giant Negative Electrocaloric Effect in Antiferroelectric La‐Doped Pb(ZrTi)O3 Thin Films Near Room Temperature

Abstract: Antiferroelectric thin films are demonstrated as a new class of giant electrocaloric materials that exhibit a negative electrocaloric response of about -5 K near room temperature. The giant negative electrocaloric effect may open up a new paradigm for light, compact, reliable, and high-efficiency refrigeration devices.

Future agriculture with minimized phosphorus losses to waters: Research needs and direction

Abstract: The series of papers in this issue of AMBIO represent technical presentations made at the 7th International Phosphorus Workshop (IPW7), held in September, 2013 in Uppsala, Sweden. At that meeting, the 150 delegates were involved in round table discussions on major, predetermined themes facing the management of agricultural phosphorus (P) for optimum production goals with minimal water quality impairment. The six themes were (1) P management in a changing world; (2) transport pathways of P from soil to water; (3) monitoring, modeling, and communication; (4) importance of manure and agricultural production systems for P management; (5) identification of appropriate mitigation measures for reduction of P loss; and (6) implementation of mitigation strategies to reduce P loss. This paper details the major challenges and research needs that were identified for each theme and identifies a future roadmap for catchment management that cost-effectively minimizes P loss from agricultural activities.

Enhancing privacy through caching in location-based services

Abstract: Privacy protection is critical for Location-Based Services (LBSs). In most previous solutions, users query service data from the untrusted LBS server when needed, and discard the data immediately after use. However, the data can be cached and reused to answer future queries. This prevents some queries from being sent to the LBS server and thus improves privacy. Although a few previous works recognize the usefulness of caching for better privacy, they use caching in a pretty straightforward way, and do not show the quantitative relation between caching and privacy. In this paper, we propose a caching-based solution to protect location privacy in LBSs, and rigorously explore how much caching can be used to improve privacy. Specifically, we propose an entropy-based privacy metric which for the first time incorporates the effect of caching on privacy. Then we design two novel caching-aware dummy selection algorithms which enhance location privacy through maximizing both the privacy of the current query and the dummies' contribution to cache. Evaluations show that our algorithms provide much better privacy than previous caching-oblivious and caching-aware solutions.

The Association between Sustainability Governance Characteristics and the Assurance of Corporate Sustainability Reports

Abstract: SUMMARY: This study provides evidence on whether sustainability-oriented corporate governance mechanisms impact the voluntary assurance of corporate sustainability reports. Specifically, we consid...

Adaptation to sensory input tunes visual cortex to criticality

Abstract: Sensory nervous systems adapt to their environment—a mechanism thought to ensure network dynamics remain critical. Visual cortex experiments show that adaptation maintains criticality even as sensory input drives the system away from this regime. A long-standing hypothesis at the interface of physics and neuroscience is that neural networks self-organize to the critical point of a phase transition, thereby optimizing aspects of sensory information processing1,2,3. This idea is partially supported by strong evidence for critical dynamics observed in the cerebral cortex4,5,6,7,8,9,10, but the impact of sensory input on these dynamics is largely unknown. Thus, the foundations of this hypothesis—the self-organization process and how it manifests during strong sensory input—remain unstudied experimentally. Here we show in visual cortex and in a computational model that strong sensory input initially elicits cortical network dynamics that are not critical, but adaptive changes in the network rapidly tune the system to criticality. This conclusion is based on observations of multifaceted scaling laws predicted to occur at criticality4,11. Our findings establish sensory adaptation as a self-organizing mechanism that maintains criticality in visual cortex during sensory information processing.

Design criterion for fatigue strengthening of riveted beams in a 120-year-old railway metallic bridge using pre-stressed CFRP plates

Abstract: This study presents a design criterion developed for fatigue strengthening of a 120-year-old metallic railway bridge in Switzerland and presents a pre-stressed un-bonded reinforcement (PUR) system developed to apply the strengthening. The PUR system uses carbon fiber reinforced polymer (CFRP) plates; however, unlike conventional pre-stressed CFRP reinforcement methods, preparation of the existing metallic bridge surface is not required. This decreases the time required for on-site strengthening procedures. The principle of the constant life diagram (CLD) and two fatigue failure criteria (Johnson and Goodman) are described. Analytical formulations are developed based on the CLD method to determine the minimum CFRP pre-stress level required to prevent fatigue crack initiation. The PUR system uses an applied pre-stress force to reduce the mean stress level (and stress ratio) to shift an existing fatigue-susceptible metallic detail from the 'at risk' finite life regime to the 'safe' infinite life regime. The applied CLD method is particularly valuable when the stress history of the detail is not known and it is difficult to assess the remaining fatigue life. Moreover, it is shown that the currently adopted approach in many structural codes which emphasizes stress range as the dominant parameter influencing fatigue life are non-conservative for tension-tension stress patterns (i.e., stress ratios of 0 < R < 1). Analyses show that the modified Johnson formula accurately reflects the combined effect of stress range, mean stress level, and material properties, and offers a relatively easy design procedure. Details of a retrofit field application on members of a riveted wrought iron railway bridge are given. A wireless sensor network (WSN) system is used for long-term monitoring of the on-site CFRP stress levels and temperature of the retrofitted details. WSN measurements indicate that increases in ambient temperature result in increased CFRP pre-stress levels. © 2014 Elsevier Ltd. All rights reserved.

Development and Applications of Portable Biosensors

Abstract: The significance of microfluidics-based and microelectromechanical systems-based biosensors has been widely acknowledged, and many reviews have explored their potential applications in clinical diagnostics, personalized medicine, global health, drug discovery, food safety, and forensics. Because health care costs are increasing, there is an increasing need to remotely monitor the health condition of patients by point-of-care-testing. The demand for biosensors for detection of biological warfare agents has increased, and research is focused on ways of producing small portable devices that would allow fast, accurate, and on-site detection. In the past decade, the demand for rapid and accurate on-site detection of plant disease diagnosis has increased due to emerging pathogens with resistance to pesticides, increased human mobility, and regulations limiting the application of toxic chemicals to prevent spread of diseases. The portability of biosensors for on-site diagnosis is limited due to various issues, including sample preparation techniques, fluid-handling techniques, the limited lifetime of biological reagents, device packaging, integrating electronics for data collection/analysis, and the requirement of external accessories and power. Many microfluidic, electronic, and biological design strategies, such as handling liquids in biosensors without pumps/valves, the application of droplet-based microfluidics, paper-based microfluidic devices, and wireless networking capabilities for data transmission, are being explored.

Good habits gone bad: Explaining negative consequences associated with the use of mobile phones from a dual-systems perspective

Abstract: Information technology use is typically assumed to have positive effects for users, yet information technology use may also lead to negative consequences with various degrees of gravity. In the current work, we build on dual-systems theories to investigate negative consequences associated with mobile phones use MPU, defined as the extent to which the use of mobile phones is perceived to create problems in managing one's personal and social life. According to dual-system theories, human behaviour is guided by two systems: reflexive automatic and reflective control, which most of the time work in harmony. But when the two systems come into conflict, they will both complete to exert their influences over behaviour. Thus, we view the negative consequences associated with MPU as an outcome of the tug-of-war between the two systems influencing our day-to-day behaviours, where reflexive system is represented in our study by MPU habits and reflective system is represented by self-regulation. We hypothesise that the influence of habit and self-regulation on these negative consequences will be mediated through MPU. A partial least square analysis of 266 responses was used to validate and test our model. The study results generally support our model. The theoretical and practical implications of our study are discussed.

Discovery of stable skyrmionic state in ferroelectric nanocomposites

Abstract: Non-coplanar swirling field textures, or skyrmions, are now widely recognized as objects of both fundamental interest and technological relevance. So far, skyrmions were amply investigated in magnets, where due to the presence of chiral interactions, these topological objects were found to be intrinsically stabilized. Ferroelectrics on the other hand, lacking such chiral interactions, were somewhat left aside in this quest. Here we demonstrate, via the use of a first-principles-based framework, that skyrmionic configuration of polarization can be extrinsically stabilized in ferroelectric nanocomposites. The interplay between the considered confined geometry and the dipolar interaction underlying the ferroelectric phase instability induces skyrmionic configurations. The topological structure of the obtained electrical skyrmion can be mapped onto the topology of domain-wall junctions. Furthermore, the stabilized electrical skyrmion can be as small as a few nanometers, thus revealing prospective skyrmion-based applications of ferroelectric nanocomposites.