# Brigham Young University - Provo Main Campus

• Provo, Utah, United States
Recent publications
Built-up structures exhibit nonlinear dynamic behavior due to friction between interfaces that are fastened together. On the other hand, aircraft, spacecraft, and even automotive structures consist of thin panels to reduce their weight, which can exhibit geometric nonlinearity for displacements on the order of the thickness. As part of the Tribomechadynamics Research Challenge (TRC), this work seeks to predict these effects a priori, whereas most prior works have focused on tuning a model to experimental measurements. While methods are beginning to mature that can predict micro-slip nonlinearity of structures, and methods are well established for reduced-order modeling of geometrically nonlinear structures, these have not been combined previously. This paper presents a simulation approach used to predict the nonlinear response of a benchmark structure proposed in the TRC, which exhibits both geometric nonlinearity and micro-slip due to friction in the bolted connections. A two-dimensional model of the structure is created to enable a wide range of simulations to be performed with minimal computational cost, including some dynamic simulations where both friction and geometric nonlinearity are considered. The nonlinear modal behavior is predicted using quasi-static modal analysis (QSMA) and a recent extension called single-degree-of-freedom implicit condensation and expansion (SICE). Static load-displacement data is also used to define a non-parametric Iwan element that reproduces the modal behavior with high fidelity and yet with minimal computational cost. Additionally, limited simulations are performed on three-dimensional models, which are much more expensive but should be predictive, at least so long as Coulomb Friction is appropriate to model the interactions at the interfaces.
Background Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study’s purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. Methods After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. Results Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. Conclusions Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.
Bacteria often reside in sessile communities called biofilms, where they adhere to a variety of surfaces and exist as aggregates in a viscous polymeric matrix. Biofilms are resistant to antimicrobial treatments, and are a major contributor to the persistence and chronicity of many bacterial infections. Herein, we determined that the CpxA-CpxR two-component system influenced the ability of enteropathogenic Yersinia pseudotuberculosis to develop biofilms. Mutant bacteria that accumulated the active CpxR~P isoform failed to form biofilms on plastic or on the surface of the Caenorhabditis elegans nematode. A failure to form biofilms on the worm surface prompted their survival when grown on the lawns of Y. pseudotuberculosis . Exopolysaccharide production by the hms loci is the major driver of biofilms formed by Yersinia . We used a number of molecular genetic approaches to demonstrate that active CpxR~P binds directly to the promoter regulatory elements of the hms loci to activate the repressors of hms expression and to repress the activators of hms expression. Consequently, active Cpx-signalling culminated in a loss of exopolysaccharide production. Hence, the development of Y. pseudotuberculosis biofilms on multiple surfaces is controlled by the Cpx-signalling, and at least in part this occurs through repressive effects on the Hms-dependent exopolysaccharide production.
Background The etiology of hamstring strain injury (HSI) in American football is multi-factorial and understanding these risk factors is paramount to developing predictive models and guiding prevention and rehabilitation strategies. Many player-games are lost due to the lack of a clear understanding of risk factors and the absence of effective methods to minimize re-injury. This paper describes the protocol that will be followed to develop the HAMstring InjuRy (HAMIR) index risk prediction models for HSI and re-injury based on morphological, architectural, biomechanical and clinical factors in National Collegiate Athletic Association Division I collegiate football players. Methods A 3-year, prospective study will be conducted involving collegiate football student-athletes at four institutions. Enrolled participants will complete preseason assessments of eccentric hamstring strength, on-field sprinting biomechanics and muscle–tendon volumes using magnetic-resonance imaging (MRI). Athletic trainers will monitor injuries and exposure for the duration of the study. Participants who sustain an HSI will undergo a clinical assessment at the time of injury along with MRI examinations. Following completion of structured rehabilitation and return to unrestricted sport participation, clinical assessments, MRI examinations and sprinting biomechanics will be repeated. Injury recurrence will be monitored through a 6-month follow-up period. HAMIR index prediction models for index HSI injury and re-injury will be constructed. Discussion The most appropriate strategies for reducing risk of HSI are likely multi-factorial and depend on risk factors unique to each athlete. This study will be the largest-of-its-kind (1200 player-years) to gather detailed information on index and recurrent HSI, and will be the first study to simultaneously investigate the effect of morphological, biomechanical and clinical variables on risk of HSI in collegiate football athletes. The quantitative HAMIR index will be formulated to identify an athlete’s propensity for HSI, and more importantly, identify targets for injury mitigation, thereby reducing the global burden of HSI in high-level American football players. Trial Registration The trial is prospectively registered on ClinicalTrials.gov (NCT05343052; April 22, 2022).
Governing the physical and chemical characteristics of contact area among solid substrate and liquid droplets is a widely used strategy to fabricate superhydrophobic and superhydrophilic surfaces. While both surface morphology and surface free energy of a solid substrate conclude its wettability, designing the surface with right topology has reserved immense focus by researchers in last few decades. In the pursuit to achieve such goals of immaculate surfaces, some intriguing question need to be answered, for instance, what will happen if one takes same material for the solid substrate but having different morphological features? Irrespective of chemical nature, how the physical appearance of a rough surface controls the wettability? To unravel these questions, we examine the wettability of different surrogate models using coarse-grain (CG) simulations. Interesting results were obtained for apparent contact angles on varying the morphology of a particular surface with different geometrical shapes. Different surface geometries such as square, nail, solid sphere, hollow sphere, rod, and hollow sphere of hydrophobic (poly(dimethylsiloxane)) (PDMS) and hydrophilic (poly (vinyl alcohol)) (PVA) polymers were created. In hydrophobic case, the square followed by nail shape corrugated surface demonstrated least wettability by restricting the penetration of water beads inside the grooves. Whereas, for hydrophilic case, the shell shaped surface showed excellent wetting condition due to maximum availability of unoccupied volume. It was concluded from the present study that hollow cylinder and square shaped corrugated surface could be respectively used to obtain the maximum and the least surface wettability possible. This investigation, through the evolved understanding of the role of surface geometry at the nano level could guide researchers and materials scientists to develop effective materials with desired wetting conditions.
The combustion behavior of biomass as a fuel varies dependent on source of the raw material, but also on the type of pre-treatment. In this work steam exploded and torrefied woody biomass were studied with respect to NOx formation in co-firing experiments. Most of the reported data is based on small scale experiments and simulations. In this work, however, have three different cases been investigated experimentally in a 1.5MWth combustor supported by reaction simulations. One case corresponds to firing 100% Utah bituminous coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Two of the cases was also studied in a utility scale 1.3 GWth industrial boiler. In both units did the case with pure coal result in the highest amount of NO formed, which was expected due to the higher amount of fuel-bound nitrogen in the coal, as compared to the biomass fuels. The fuel analyses indicate that the nitrogen content is the same in the two investigated biofuels. However, the amount of NO formed differed. Gas composition measurements reveal that the partitioning of volatile nitrogen species (HCN and NH3) varies between the biomass co-firing cases. This was investigated further using detailed reaction simulations and is suggested as the main reason for the observed difference in NO formation.
In this paper, we give a survey of methods used to calculate values of resistance distance (also known as effective resistance) in graphs. Resistance distance has played a prominent role not only in circuit theory and chemistry, but also in combinatorial matrix theory and spectral graph theory. Moreover resistance distance has applications ranging from quantifying biological structures, distributed control systems, network analysis, and power grid systems. In this paper, we discuss both exact techniques and approximate techniques and for each method discussed we provide an illustrative example. We also present some open questions and conjectures.
Chemical looping ammonia generation (CLAG) is a promising NH3 production technology due to its potential for high yield of NH3 and low CO2 emission footprint. However, the stabilities of the existing N-carriers are problematic during the cyclic N-sorption/desorption. This research was designed to overcome that challenge through use of elemental doping and depositing the N-carrier on a support. The experimental results show that the N-sorption/desorption performance of γ-Al2O3 N-carriers decreased with cycling due to the deterioration of the pore structure and phase transformation. A Si-modified alumina-based N-carrier, with a Si: Al molar ratio of 1:20 prepared by co-precipitation, was much more resistant to high-temperature phase transition and collapse of pore structure, resulting in highly stable cyclic N-sorption/desorption performance. Use of ZrO2 as a support for the Si-modified Al-based N-carrier further reduced NH3 decomposition and thus increased the NH3 yield and selectivity by 85.6% and 53.6% compared to that obtained with the pure γ-Al2O3 N-carrier.
Molten salts are being widely considered for use as high-temperature coolants in advanced nuclear reactors. There are a serious lack of experimental data pertaining to their thermophysical properties, especially thermal conductivity, which are paramount to safe thermal hydraulic design. This study seeks to measure the thermal conductivity of several molten fluoride and chloride salts using a modified transient hot-wire needle probe. Building on previous work by the same authors, the multilayered heat transfer model is expanded to account for thermal radiation interactions across the salt layer and is validated using a commercial finite-element package. Sensitivity and correlation analyses are performed to assess the time-dependent influence of critical parameters in the model, including the new radiative terms. Finally, thermal conductivity measurements are presented for LiF–NaF–KF, NaF–KF–MgF2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{2}$$\end{document}, and LiCl–KCl up to 750 °C and are compared against reference correlations. Total measurement uncertainty is also quantified and tabulated, with the resulting range between ± 14.2 % and ± 29.0 %.
Digital soil mapping (DSM) can be used to predict soils at unvisited sites, but problems arise when predictions are needed in areas without any soil observations. In such situations, DSM can still extend the results from reference areas with soil data to target areas that are alike in terms of soil-forming factors and obey the same rules. Such DSM methods have low accuracy due to the complexity of spatial variation in soil, and the difficulty of matching soil-forming factors exactly between reference and target areas. A new approach for extrapolating soil information from reference to target areas is proposed in the current research. We evaluated the ability of a semi-supervised learning (SSLR→T) approach compared to a supervised learning (SLR→T) approach for extrapolating soil classes in two areas (reference and target areas) in central Iran. The SSLR→T used soil observations from the reference area and covariates from both areas. Then, the learned knowledge produced by SSLR→T was transferred to the target area to estimate soil classes. The findings revealed that SSLR→T resulted in higher overall accuracy (0.65) and kappa index (0.44) in the target area compared to the SLR→T (overall accuracy=0.40 and kappa index=0.18). Furthermore, the SSLR→T produced the lower values of the confusion index (mean=0.66) compared to the SLR→T (mean=0.80). This indicated that the SSLR→T could not only increase the accuracy but also decrease the uncertainty of the soil class predictions, compared to the spatial extrapolation predictions derived from the SLR→T. Generally, these findings indicated that leveraging covariate information from the target area during the training of DSM models in the reference area could successfully improve the generalization power of the models, indicating the effectiveness of SSLR→T for spatial extrapolation.
Therapists often conceptualize resistance as client behaviors that impede progress; this perspective threatens the therapeutic alliance, especially in couple and family therapy where increased resistance and multiple alliances are present. Polyvagal theory reframes and normalizes resistant behaviors as preconscious, protective responses emerging from our autonomic nervous system. The theory also explains how humans reciprocate safety cues to connect with each other; therapists can use concepts of polyvagal theory to manage their own emotional regulation and foster safety and connection in therapy. Polyvagal concepts deepen our understanding of protective behaviors presenting in couple and family therapy; therapists can help couple and family clients to recognize protective behaviors in their own relationships and facilitate safer connection and engagement. Clinical implications are presented: psychoeducation can help clients normalize and understand their protective processes; therapist presence and immediacy acknowledges and normalizes protective behaviors as they arise; therapist and client self-regulation skills support connection; therapist genuineness is a precondition to client safety; and understanding of polyvagal theory enhances assessment of conflict and enactments in couple and family therapy.
There is substantial evidence that employees build relationships with coworkers who provide them with assistance and distance themselves from coworkers who behave unethically. We consider how employees respond when coworkers provide them with benefits that violate ethical standards—a phenomenon we refer to as pro-coworker unethical behavior (PCUB). Building on social exchange theory, we explore how recipients of PCUB may simultaneously experience both a sense of increased indebtedness toward their coworker, given the beneficial nature of PCUB, and reduced perceptions of their coworker's integrity, given the unethical nature of PCUB. We theorize that these diverging reactions will have countervailing indirect effects on the social exchange relationship between the recipient and PCUB provider. In turn, these effects on the social exchange relationship will influence whether the recipient responds favorably toward the provider, in the form of interpersonal citizenship. Our theoretical model incorporates the PCUB provider's prosocial versus self-interested motives as a critical contingency that shapes recipients’ perceptions of indebtedness and integrity. The results of a multi-wave field study of employee–coworker dyads and an experimental study provide converging support for our hypothesized model. This article is protected by copyright. All rights reserved
Relationship power, which refers to the ability to influence one’s romantic partner, is an important organizing principle in the assessment and treatment of couples. Power imbalance is predictive of various dimensions of marital quality, which explains why it is often a central focus of couple therapy. Despite the importance of relationship power in couple therapy, assessing power in clinical settings has been hindered by the lack of a validated measure of power that has high clinical utility. Data from 640 married couples associated with the Flourishing Families Project were used to develop the Perceived Power Imbalance Scale by conducting exploratory factor analysis, confirmatory factor analysis, dyadic predictive validity analysis, and measurement equivalence analysis. Although power has been conceptualized as consisting of both outcome power and process power, results indicated that the final scale consisted of four items that only tapped aspects of process power. The scale demonstrated good reliability and was a significant predictor of marital quality, marital instability, and depression.
We have previously shown that schizophrenia (SCZ) participants with high community functioning demonstrate better verbal working memory (vWM) performance relative to those with low community functioning. In the present study, we investigated whether neuroanatomical differences in regions supporting vWM also exist between schizophrenia groups that vary on community functioning. Utilizing magnetic resonance imaging, shape features of deep-brain nuclei known to be involved in vWM were calculated in samples of high functioning (HF-SCZ, n = 23) and low functioning schizophrenia participants (LF-SCZ, n = 18), as well as in a group of healthy control participants (CON, n = 45). Large deformation diffeomorphic metric mapping was employed to characterize surface anatomy of the caudate nucleus, globus pallidus, hippocampus, and thalamus. Statistical analyses involved linear mixed-effects models and vertex-wise contrast mapping to assess between-group differences in structural shape features, and Pearson correlations to evaluate relationships between shape metrics and vWM performance. We found significant between-group main effects in deep-brain surface anatomy across all structures. Post-hoc comparisons revealed HF-SCZ and LF-SCZ groups significantly differed on both caudate and hippocampal shape, however, significant correlations with vWM were only observed in hippocampal shape for both SCZ groups. Specifically, more abnormal hippocampal deformation was associated with lower vWM suggesting hippocampal shape is both a neural substrate for vWM deficits and a potential biomarker to predict or monitor the efficacy of cognitive rehabilitation. These findings add to a growing body of literature related to functional outcomes in schizophrenia by demonstrating unique shape patterns across the spectrum of community functioning in SCZ.
Methods for predicting autoignition temperatures (AIT) have been historically inaccurate and are rarely based on the underlying physical phenomena leading to observed AIT. Previous attempts at predicting AIT have been developed based on Quantitative Structure–Property Relationships (QSPR) and additive group contribution methods. This work presents an improved method for predicting AIT based on the method originally developed by the late Dr. William H. Seaton. The method of Seaton is described in detail including its use of first principles to predict AIT. A comprehensively evaluated data set is used for a new regression of Seaton method parameters. Improvements on the model of Seaton and underlying principles are presented and discussed. Finally, an improved AIT prediction model and parameter sets based on Seaton’s method are recommended.
Evaluating the liquefaction potential of gravelly soils using in-situ testing remains a challenge in geotechnical engineering practice. The Chinese Dynamic Cone Penetration (DPT) test provides an alternative for in-situ testing in gravelly soils to Becker Penetration Test (BPT) and the Standard Penetration test (SPT). The Chinese DPT was recently correlated with liquefaction resistance based on field performance data from the Mw 7.9 Wenchuan earthquake. In this study, liquefaction resistance was evaluated using the DPT and shear wave velocity measurements at eight sites in Seward and Old Valdez, Alaska, where gravel liquefaction took place and two sites in Valdez, where no liquefaction occurred in the 1964 Alaska earthquake. The DPT-based liquefaction triggering curve predicted liquefaction potential at all test sites with moderate accuracy. N′120 blow counts from SPT hammers were generally consistent with those from the DPT hammer after energy correction. Back-calculated energy correction factors were typically within 10% of the theoretical energy correction factor. These results suggest that the DPT can provide liquefaction hazard evaluations accurately and economically for many gravelly soils. Liquefaction evaluations using currently available Vs-based triggering curves developed for sands often indicated no liquefaction at sites where liquefaction occurred at the Alaska sites. In contrast, a Vs-based triggering curve developed from a data set of gravelly soil sites correctly predicted liquefaction at all sites.
Nursing faculty are challenged to integrate immunization content in prelicensure nursing curricula. Historically, most immunization content has been delivered in pediatrics courses, with less emphasis on other populations across the lifespan. Skills related to vaccine administration may be prioritized over the most current immunization science, such as pathophysiology, immunology, and epidemiology. As the most trusted profession rated by the public (Saad, 2020), nurses are ideally suited to address vaccine hesitancy and promote vaccination in the communities they serve. Nurses apply active listening, problem solving, and communication skills with patients and their families, contributing to a person's confidence in their decision to be vaccinated. The Centers for Disease Control and Prevention and the Association for Prevention Teaching and Research collaborated to develop a framework for immunization content and teaching resources, Immunization Resources for Undergraduate Nursing (IRUN), for faculty to use in designing the nursing curricula. Content includes a curriculum framework, curriculum mapping tool, multiple teaching resources, and a dedicated website (IRUNursing.org). The framework provides guidance for faculty on integrating immunization content into a curriculum. Teaching resources include case studies, simulation scenarios, and PowerPoint slide decks. Although primarily focused on prelicensure nursing education, resources are also relevant to advanced professional nursing education.
Critical care nurses who care for postoperative cardiac surgery patients need such specialty knowledge as atrial electrograms (AEGs). An inadequate audit trail exists for psychometric performance of instruments to measure knowledge of AEGs. The aim of this study was to revise a previously tested instrument and assess evidence for content validity (content validity index), internal consistency (Cronbach α), and stability (correlation coefficient, r) reliability against the a priori criterion of 0.80. The multiple-choice response, self-administered, paper-and-pencil instrument was revised to 20 items and named the Drake Atrial Electrogram Assessment Survey (DAEGAS). A panel of 6 AEG experts reviewed the DAEGAS for content validity evidence. The instrument was further revised to 19 items (13 knowledge and 6 AEG interpretation) and tested with 76 critical care nurses from the greater Houston metropolitan area. The content validity index was 0.93. Cronbach α was .51, and test-retest r was 0.74. Cronbach α increased to .60 and r was 0.73 with removal of 3 items: 2 items with a negative item-total correlation and 1 item that was transitioned to a sample question. Content validity evidence exceeded the a priori criterion. Internal consistency and stability reliability estimates did not meet the criterion, albeit the latter met the criterion recommended by psychometricians for a new instrument. Recommendations include further development of the DAEGAS to improve internal consistency estimates and testing for evidence of other forms of validity. Reliable and valid assessment of critical care nurse knowledge of AEGs will require improved psychometric performance of the DAEGAS.
Purpose Certain strains, called adverse childhood experiences (ACE), have continually been found to influence delinquency, but how these ACEs affect delinquency during adolescence and whether middle childhood experiences mediate this relationship remain unclear. Further, racial/ethnic differences in the ACEs to delinquency link remain understudied. The purposes of this study are threefold: (1) to understand the association of different levels of ACEs experienced by age five with adolescent delinquency, (2) explore potential middle childhood mechanisms that may mediate this association, and (3) examine whether the effects vary by race/ethnicity. Methods Negative binomial regression models were used to examine the relationship between early cumulative ACEs and adolescent delinquency by race/ethnicity. Karlson-Holm-Breen (KHB) method was used examine the extent to which middle childhood mechanisms mediated the relationship between early ACEs and adolescent delinquency by race/ethnicity. Results Our findings support the established relationship between early childhood ACEs and youth delinquency but show that different middle childhood mechanisms – such as prior delinquency, low self-control, and cumulative ACEs – mediate the relationship differently across racial/ethnic groups. Conclusions This study highlights the importance of early ACEs as an explanation for adolescent delinquency as well as the importance of considering middle childhood mechanisms and race/ethnicity in these relationships.
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• Department of Educational Leadership & Foundations
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• Department of Psychology
• Department of Psychology
• Department of Counseling Psychology and Special Education
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