Dynamic Model and Control of an Artificial Muscle Based on Contractile Polymers

A dynamic model and control system of an artificial muscle is presented. The artificial muscle is based on a contractile polymer gel which undergoes abrupt volume changes in response to variations in external conditions. The device uses an acid-base reaction to directly convert chemical to mechanical energy. A nonlinear sliding mode control system is proposed to track desired joint trajectories of a single link controlled by two antagonist muscles. Both the model and controller were implemented and produced acceptable tracking performance at 2Hz

Review of Artificial Muscle Based on Contractile Polymers

An artificial muscle with strength and speed equal to that of a human muscle may soon be possible. Polymer gels exhibit abrubt volume changes in response to variations in their external conditions -- shrinking or swelling up to 1000 times their original volume. Through the conversion of chemical or electrical energy into mechanical work, a number of devices have already been constructed which produce forces up to 100N/cm2 and contraction rates on the order of a second. Through the promise of an artificial muscle is real, many fundamental physical and engineering questions remain before the extent or limit of these devices is known

Posttraumatic Stress and Parenting Behaviors: The Mediating Role of Emotion Regulation

Maternal trauma has been linked with problematic parenting, including both harsh and permissive behaviors. However, little is known about mechanisms accounting for this association. The current study examined the potential impact of posttraumatic stress disorder (PTSD) and emotion regulation on dysfunctional parenting behaviors in a sample of community mothers. We hypothesized a mediation model wherein PTSD would be associated with dysfunctional parenting (i.e., lax and overreactive behaviors) indirectly through deficits in maternal emotion regulation. Seventy-eight community mothers of 18- to 36-month-old children were administered the Clinician Administered PTSD Scale for DSM-5 (CAPS-5) and 19 mothers met criteria for PTSD. Mothers also completed self-report measures of difficulties with emotion regulation and maternal laxness and overreactivity in parenting. Results revealed that emotion dysregulation fully mediated relations between PTSD status and lax (but not overreactive) parenting behaviors. Compared to mothers without PTSD, those with PTSD reported greater lax parenting behaviors indirectly through greater emotion dysregulation. Mothers with PTSD may struggle to parent assertively when trauma symptoms interfere with emotion regulation abilities. The current study highlights the need to design interventions focused on helping trauma-exposed mothers manage distress, ultimately aiming to enhance parenting effectiveness and improve child outcomes

Partner Support and Connection Protect Couples during Pregnancy: A Daily Diary Investigation

Objective: The objective of the current study was to examine associations between daily subjective stress and relationship satisfaction as a function of two protective factors—partner support and connection (i.e., intimacy, passion, and commitment)—among couples during pregnancy. Background: Stress brought into the intimate relationship by each partner is often associated with relational dissatisfaction and discord, referred to as stress spillover. Although much research has focused on risk for poor relational outcomes associated with partner stress, it is equally important to focus on resilience. Method: We examined this phenomenon among 154 couples navigating pregnancy. Couples attended an initial laboratory session and then completed daily diary measures from home across 14 days. Results: Multilevel modeling techniques revealed that higher daily subjective stress than usual was negatively associated with relationship satisfaction that day for fathers and mothers, and partner support and connection attenuated this link to a significant degree. As these protective factors increased, the strength of the negative association between daily stress and relationship satisfaction decreased for both parents. Exploratory analyses showed no significant within-person associations between daily stress and next-day relationship satisfaction at any level of support or connection. Conclusion: These findings add innovative components to the investigation of the spillover process, including the examination of this process among couples during pregnancy, utilization of daily diary methods to study this phenomenon on a micro-level over time, and identification of protective factors mitigating daily stress spillover

The effect of an unstructured, moderate to vigorous, before-school physical activity program in elementary school children on academics, behavior, and health

<p>Abstract</p> <p>Background</p> <p>Physical inactivity has been deemed a significant, contributing factor to childhood overweight and obesity. In recent years, many school systems removed recess and/or physical education from their curriculum due to growing pressure to increase academic scores. With the vast majority of children’s time spent in school, alternative strategies to re-introduce physical activity back into schools are necessary. A creative yet underutilized solution to engage children in physical activity may be in before-school programs. The objective of the proposed study is to examine the effect of an unstructured, moderate to vigorous, before-school physical activity program on academic performance, classroom behavior, emotions, and other health related measures.</p> <p>Methods/Design</p> <p>Children in 3rd–5th grade will participate in a before-school (7:30–8:15 a.m.), physical activity program for 12 weeks, 3 days a week. Children will be able to choose their preferred activity and asked to sustain physical activity of moderate to vigorous intensity with individual heart rate monitored during each session.</p> <p>Discussion</p> <p>The proposed study explores an innovative method of engaging and increasing physical activity in children. The results of this study will provide evidence to support the feasibility of an unstructured, moderate to vigorous, before-school physical activity program in children and provide insight regarding the ideal physical activity intensity and duration necessary to achieve a positive increase in academic performance.</p> <p>Trial registration</p> <p>ClinicalTrials.gov Identifier: NCT01505244</p

An Economic Analysis of Twitching Behaviour and Species Rarity

Avid birdwatchers, or ‘twitchers’, expend a considerable amount of money and time pursuing viewing experiences of rare or vagrant species. By vagrant species we mean a species found outside its normal range/distribution. To enhance our understanding of this form of behaviour, we present results from a UK survey of twitchers. First, we examine the relationship between cost and rarity based on actual viewing experiences. Our statistical results reveal that the relationship between cost and rarity is positive and very inelastic. Second, we present results from a hypothetical Best-Worst Scaling exercise examining aspects of species rarity. We find that rarity is a more nuanced construct than simply the frequency with which a vagrant species has appeared. Our results provide insights into the meaning of rarity, as well as the economic value attach to it and why

Turning up by turning over : the change of scenery effect in major league baseball

Purpose: This study examined a “change of scenery” effect on performance in major league baseball (MLB). We also tested this effect for voluntary versus involuntary employee departures, as well as employees returning to a past employer. Design/Methodology/Approach: This study uses publicly available MLB performance data from 2004 to 2015. The data comprise 712 team changes for players following two consecutive years with the same organization. Data were analyzed using MANCOVA to assess the impact of changing teams on player performance. Findings: Results indicate players with declining performance benefited significantly from a change of scenery. Following a team change, these players experienced a significant increase in their performance that remained stable through a subsequent season. The effect was not different for players who changed teams via trade and free agency and was modest for those returning to a past organization. Analysis also showed that players leaving while their performance was improving suffered a subsequent performance drop-off in the new organization. Implications: As the war for talent escalates and employees change jobs more frequently, extending our understanding of how performance can be influenced by work context may provide new insight into organization staffing policies. Originality/Value: Results extend field theory by highlighting how past performance interacts with new work contexts to influence performance. This is one of the few studies evaluating the job change-performance relationship, and perhaps the first to account for the effects of performance trends prior to exit

The economics of species extinction: An economist’s viewpoint

There is growing evidence to suggest that there is an increase in species extinction occurring globally. In this article, we briefly review the literature on the economics of species extinction, examining what is meant by extinction before explaining how economics has conceptualised this. The initial economics literature on species extinction focuses largely on renewable resources, in particular fisheries, but has subsequently evolved to cover many aspects of biodiversity across all physical scales, employing an increasing array of methodological tools. We also consider aspects of cultural and societal extinctions (e.g. local languages, local knowledge) and how this is positively correlated with loss of biodiversity, as well as an economist’s outlook on the potential to re-capture value post-extinction

Navigator channel adaptation to reconstruct three dimensional heart volumes from two dimensional radiotherapy planning data

BACKGROUND: Biologically-based models that utilize 3D radiation dosimetry data to estimate the risk of late cardiac effects could have significant utility for planning radiotherapy in young patients. A major challenge arises from having only 2D treatment planning data for patients with long-term follow-up. In this study, we evaluate the accuracy of an advanced deformable image registration (DIR) and navigator channels (NC) adaptation technique to reconstruct 3D heart volumes from 2D radiotherapy planning images for Hodgkin's Lymphoma (HL) patients. METHODS: Planning CT images were obtained for 50 HL patients who underwent mediastinal radiotherapy. Twelve image sets (6 male, 6 female) were used to construct a male and a female population heart model, which was registered to 23 HL "Reference" patients' CT images using a DIR algorithm, MORFEUS. This generated a series of population-to-Reference patient specific 3D deformation maps. The technique was independently tested on 15 additional "Test" patients by reconstructing their 3D heart volumes using 2D digitally reconstructed radiographs (DRR). The technique involved: 1) identifying a matching Reference patient for each Test patient using thorax measurements, 2) placement of six NCs on matching Reference and Test patients' DRRs to capture differences in significant heart curvatures, 3) adapting the population-to-Reference patient-specific deformation maps to generate population-to-Test patient-specific deformation maps using linear and bilinear interpolation methods, 4) applying population-to-Test patient specific deformation to the population model to reconstruct Test-patient specific 3D heart models. The percentage volume overlap between the NC-adapted reconstruction and actual Test patient's true heart volume was calculated using the Dice coefficient. RESULTS: The average Dice coefficient expressed as a percentage between the NC-adapted and actual Test model was 89.4 ± 2.8%. The modified NC adaptation technique made significant improvements to the population deformation heart models (p = 0.01). As standard evaluation, the residual Dice error after adaptation was comparable to the volumetric differences observed in free-breathing heart volumes (p = 0.62). CONCLUSIONS: The reconstruction technique described generates accurate 3D heart models from limited 2D planning data. This development could potentially be used to retrospectively calculate delivered dose to the heart for historically treated patients and thereby provide a better understanding of late radiation-related cardiac effects

Chemical characteristics of macroscopic pyrogenic carbon following millennial-scale environmental exposure

Pyrogenic Carbon (PyC) is ubiquitous in global environments, and is now known to form a significant, and dynamic component of the global carbon cycle, with at least some forms of PyC persisting in their depositional environment for many millennia. Despite this, the factors that determine the turnover of PyC remain poorly understood, as do the physical and chemical changes that this material undergoes when exposed to the environment over tens of thousands of years. Here, we present the results of an investigation to address these knowledge gaps through chemical and physical analysis of a suite of wood PyC samples exposed to the environment for varying time periods, to a maximum of >90,000 years. This includes an assessment of the quantity of resistant carbon, known as Stable Polyaromatic Carbon (SPAC) versus more chemically labile carbon in the samples. We find that, although production temperature is likely to determine the initial ‘degradation potential’ of PyC, an extended exposure to environmental conditions does not necessarily mean that remaining PyC always progresses to a ‘SPAC-dominant’ state. Instead, some ancient PyC can be composed largely of chemical components typically thought of as environmentally labile, and it is likely that the depositional environment drives the trajectory of preservation versus loss of PyC over time. This has important implications for the size of global PyC stocks, which may have been underestimated, and also for the potential loss of previously stored PyC, when its depositional environment alters through environmental or climatic changes