Non-linear modeling of active biohybrid materials

Recent advances in engineered muscle tissue attached to a synthetic substrate motivates the development of appropriate constitutive and numerical models. Applications of active materials can be expanded by using robust, non-mammalian muscle cells, such as those of Manduca sexta. In this study, we propose a model to assist in the analysis of biohybrid constructs by generalizing a recently proposed constitutive law for Manduca muscle tissue. The continuum model accounts (i) for the stimulation of muscle fibers by introducing multiple stress-free reference configurations for the active and passive states and (ii) for the hysteretic response by specifying a pseudo-elastic energy function. A simple example representing uniaxial loading-unloading is used to validate and verify the characteristics of the model. Then, based on experimental data of muscular thin films, a more complex case shows the qualitative potential of Manduca muscle tissue in active biohybrid constructs

Epidemiology of toe tip necrosis syndrome in western Canadian feedlot cattle

Lameness continues to cause significant problems in profitability, productivity, and animal welfare in the feedlot industry. Toe tip necrosis syndrome (TTNS) is a new name for a previously reported condition. By definition, TTNS is separation of the apical white line with tissue necrosis and clinical lameness. This definition includes complications such as pedal (P3) osteitis, middle (P2) and proximal (P1) phalangeal osteomyelitis, tendonitis, tenosynovitis, cellulitis, and embolic pneumonia. Anecdotal experiences from practitioners report this lameness in feedlot cattle will develop within weeks after feedlot entry. Often the hindlimbs, specifically the lateral claw, are affected where a separation of the dorsal wall and sole will be noticed. Secondary infections will progress deeper into the foot and become systemic. Unfortunately, despite treatment, these animals can become very lame and will need to be euthanized. The overall objective of this project was to describe the epidemiology of TTNS in western Canadian feedlot cattle. The specific objectives were 1) to use clinical examinations, imaging modalities, and necropsy findings to aid in description, classification, and characterization of TTNS lesions, 2) to describe the epidemiology of TTNS in feedlot cattle, and 3) to evaluate risk factors for TTNS. Upon further investigation into this arrival related condition it became apparent that there were many different descriptors: P3 necrosis, toe abscess, apicus necrotica, apical pedal bone necrosis or toe necrosis. These names and descriptors of toe tip lesions were based on anecdotal experiences and previous case reports. As a result, traditional epidemiological approaches that included field investigations, clinical and necropsy examinations were implemented to identify, characterize and describe this condition. Based on clinical findings, imaging modalities, and necropsy specimens examined during September to December 2012, inclusive, a more specific name and descriptive case definition were introduced. TTNS descriptive epidemiology was described by use of a retrospective database analysis from Feedlot Health Management Services (FHMS) with 702 veterinarian confirmed TTNS cases by necropsy examination. From this database, there were 30% (210/702) of necropsy cases treated for TTNS and 70% of cases (492/702) that were not treated. Of those animals treated, the mean and standard deviation (median) interval from feedlot arrival to first treatment was 18.9 ±1.7 d (12 d). The mean (standard deviation) days on feed until death from TTNS was the earliest in grass-fed calves (32.4 ± 22.1 d), followed by auction-derived (40.6 ± 40.6 d), ranch direct (44.1 ± 53.1 d), and back-grounded calves (69.0 ± 75.6 d) (P < 0.001). Yearlings were on feed for a mean (standard deviation) days of 37.1 ± 32.0 d when compared to calves at 49.5 ± 57.0 d before death (P < 0.001). The greatest proportion of deaths occurred from September to November. There were 96.2% (1,832/1,904) of lots without one case of TTNS and 3.8% (72/1,904) of lots had one or more TTNS cases. A prospective case-control study to identify TTNS risk factors consisted of 148 total necropsy submissions (82 cases, 66 controls) from three feedlot veterinary practices and 16 feedlots during October 2012 to January 2013, inclusive. Confirmation of feet samples by the principal investigator at the Western College of Veterinary Medicine reduced the total to 135 animals: 67 cases and 68 controls. The measure of agreement (kappa) on classification of TTNS cases and controls between the veterinary practice and WCVM was 0.778 (P < 0.001). Bacterial culture results revealed that 75% of pure isolates in TTNS cases were attributed to Escherichia coli, Streptococcus spp., Trueperella pyogenes, Fusobacterium necrophorum. TTNS cases were 3.8 times more likely than control animals to have BVDV isolated (95% CI 1.7-8.5; P < 0.001). TTNS animals were 2.2 times more likely than control animals to have histopathological evidence of vasculitis (95% CI 1.0-4.6; P = 0.04). BVDV samples were 11.2 times more likely to show histopathological evidence of vasculitis than non-BVDV samples (95% CI 4.7-27.0; P < 0.001). A decreased difference was found in sole thickness at the toe tip (P < 0.001). There was no evidence of pedal bone rotation between case and control animals (P = 0.15). In summary, TTNS is a specific term for apical white line separation with tissue necrosis and clinical lameness. A practitioner's field diagnosis of TTNS based on apical white line separation and tissue necrosis is accurate on clinical signs alone. TTNS is a transport or arrival related condition in feedlot cattle that has a propensity for cases to cluster together. Pure bacterial isolates provide an understanding of the pathogens responsible for TTNS and that environmental pathogens contribute to an ascending infection. BVDV, vasculitis and apical sole thickness were risk factors associated with TTNS; however, their exact role requires further investigation

The role of emotion and reflection in the development of student teachers’ self-efficacy when analyzing video lessons

Introduction: Teachers’ self-efficacy is an important indicator of student teachers’ preparedness for teaching. Interventions using video lessons are effective in increasing student teachers’ self-efficacy. However, there is a lack of research on emotional and reflective processes in the context of video-based interventions. Methods: The present study examined emotions and reflection as well as their effects on changes in self-efficacy in a video-based intervention. A total of 159 student teachers participated in the study. The participants were randomly assigned to three groups: Two groups analyzed video lessons in which group roup one received open-ended observation tasks (ig1) and group two received structured observation tasks (ig2). Participants in the control group (cg) analyzed text-based case studies with open-ended observation tasks. Results: The results show that self-efficacy increased with medium effect size (d = 0.68) in video group two (ig2), whose members analyzed videos using structured observation tasks but not in video group one (ig1), whose members analyzed open-ended observation tasks, and in the control group. In addition, there were significant relations between positive arousal and reflection. Finally, regression analyses showed that reflection was a significant predictor for changes in self-efficacy, whereas no significant effect of emotional arousal was detected. Discussion: In conclusion, the findings of this study indicate that video-based interventions with structured observation tasks increased self-efficacy among student teachers. Furthermore, the findings provide novel evidence on the association between reflection, self-efficacy and emotion in video-based interventions in teacher education

Factors Influencing Pre-service Teachers' Intention to Use Digital Learning Materials : A Study Conducted During the COVID-19 Pandemic in Germany

The COVID-19 pandemic necessitated an abrupt change in university teacher education, in that most face-to-face courses were replaced by online education, which had a profound impact on students. Pandemic distance learning required students to possess a high degree of self-regulation concerning their learning environment and to find new ways of communicating with their peers and instructors. At the same time, the novel situation offered opportunities to experience new educational applications. To learn more about the possible benefits of distance learning, this study examines how the first online semester during the pandemic contributed to pre-service teachers' intentions to use digital learning materials in the future. Pre-service teachers enrolled in a German university (n = 348) answered an online questionnaire at the end of the summer term of 2020. Findings from structural equation modeling showed that the perceived quality of teacher training during the online semester and self-reported improvements in digital skills predicted significantly students' intentions to use digital learning materials for future teaching. Moreover, results revealed that attentional regulation predicted perceived quality of teacher training and self-reported improvements in digital skills during distance learning. Thus, attentional regulation had a significant indirect effect on pre-service teachers' behavioral intentions. The indirect effects of other resource management strategies (effort and time management) and intrinsic motivation were not significant. Our results show that the quality of online instruction was an important factor in student teachers' learning processes during the pandemic. Based on our results, we discuss implications for the promotion of pre-service teachers' intentions to use digital learning materials for teaching in schools

Stability of active muscle tissue

In this discussion, the notion of material stability is examined in the context of active muscle tissue modeling, where the nonlinear constitutive law is dependent on both the physiologically-driven muscle contraction and the finite mechanical deformation. First, the governing equations and constitutive laws for a general active-elastic material are linearized about a homogeneous underlying configuration. In order to obtain mathematical restrictions analogous to those found in elastic materials, stability conditions are derived based on the propagation of homogeneous plane waves with real wave speeds, and the generalized acoustic tensor is obtained. Focusing on 2D motions, and considering a simplified, decoupled transversely isotropic energy function, the restriction on the active acoustic tensor is recast in terms of a generally applicable constitutive law, with specific attention paid to the fiber contribution. The implication of the material stability conditions on material parameters, active contraction, and elastic stretch is investigated for prototype material models of muscle tissue

Changes in early career teachers’ technology use for teaching : the roles of teacher self-efficacy, ICT literacy, and experience during COVID-19 school closure

This study examines how early-career teachers' experience and perceived support during the pandemic affected their technology integration self-efficacy and their use of information and communication technology (ICT) after school closure. The results reveal that teachers' positive teaching experiences were associated with their technology integration self-efficacy and their self-reported changes in technology use after the school closure. The results show effects of ICT literacy and general teacher self-efficacy on technology integration self-efficacy. ICT literacy, teacher self-efficacy, and positive experience had indirect effects, whereas support and technology integration self-efficacy had direct effects on changes in teachers’ ICT use for teaching

Pre-service teachers’ beliefs about linguistic and cultural diversity in schools : the role of opportunities to learn during university teacher training

We investigated pre-service teachers’ beliefs about linguistic and cultural diversity in schools and the extent to which these beliefs differ between students at the beginning and at the end of university teacher training using a sample of 1,319 pre-service teachers at different stages of study from a large public university in Germany. Given the cross-sectional nature of our data, comparisons of the different student groups (Semesters 1–2 vs. Semester 6+) were based on a propensity score matching approach. We further examined the relationship between pre-service teachers’ beliefs and their opportunities to learn (OTL) using a subsample of 428 pre-service teachers. The findings suggest that beliefs about language-supportive teaching and egalitarian—but not multicultural—beliefs differed at the beginning and at the end of initial teacher training. Student teachers who studied German as a second language (GSL) more strongly endorsed beliefs about language-supportive teaching and egalitarian and multicultural beliefs than other students