Micromechanical homogenization of a hydrogel-filled electrospun scaffold for tissue-engineered epicardial patching of the infarcted heart: a feasibility study

For tissue engineering applications, accurate prediction of the effective mechanical properties of tissue scaffolds is critical. Open and closed cell modelling, mean-field homogenization theory, and finite element (FE) methods are theories and techniques currently used in conventional homogenization methods to estimate the equivalent mechanical properties of tissue-engineering scaffolds. This study aimed at developing a formulation to link the microscopic structure and macroscopic mechanics of a fibrous electrospun scaffold filled with a hydrogel for use as an epicardial patch for local support of the infarcted heart. The macroscopic elastic modulus of the scaffold was predicted to be 0.287 MPa with the FE method and 0.290 MPa with the closed-cell model for the realistic fibre structure of the scaffold, and 0.108 MPa and 0.540 MPa with mean-field homogenization for randomly oriented and completely aligned fibres. The homogenized constitutive description of the scaffold was implemented for an epicardial patch in a FE model of a human cardiac left ventricle to assess the effects of patching on myocardial mechanics and ventricular function in the presence of an infarct. Epicardial patching was predicted to reduce maximum myocardial stress in the infarcted LV from 19 kPa (no patch) to 9.5 kPa (patch) and to marginally improve the ventricular ejection fraction from 40% (no patch) to 43% (patch). This study demonstrates the feasibility of homogenization techniques to represent complex multiscale structural features in a simplified but meaningful and effective manner

Weddell Sea iceberg drift: Five years of observations

Since 1999, 52 icebergs have been tagged with GPS buoys in the Weddell Seato enable monitoring of their position. The chosen icebergs were of small tomedium size, with a few icebergs larger than 10 km associatedwith the calving of icebergs A38 and A43 from the Ronne Ice Shelf.The majority of icebergs were tagged off Neumayer Station (8E, 70S).It was found that smaller bergs with edges shorter than 200 m had the shortestlife cycle (< 0.5 yr). Iceberg and thus freshwater export out of theWeddell Sea was found to be highly variable. In one year the majority of buoysdeployed remained in the Weddell Sea, constituting about 40 % of the NCEP P-Efreshwater input, whereas in other years all of the tagged icebergs were exported.The observed drifts of icebergs and sea-ice showed a remarkably coherent motion.The analysis of an iceberg - sea-ice buoy array in the western Weddell Seaand an iceberg array in the eastern Weddell Sea showed a coherent sea-iceiceberg drift in sea-ice concentrations above 86 %. Dynamic kinematic parameter(DKP) during the course of coherent movement were low and deviations from the meancourse associated with the passage of low-pressure system. The length scale ofcoherent movement was estimated to be less than 250km; about half the value found forthe Arctic Ocean

Modeling and simulation in tribology across scales: An overview

This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and micro-scales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions

Can High Levels of Hindrance Demands Increase the Worker’s Intellectual Response?

Job demands are factors that are associated with a physical and psychological cost when it comes to coping with them, but which can also positively affect the motivational process. Demands such as overload, defined as an excessive workload, have not presented positive results in any of the studies that have related it to employee engagement. The present study aims to delve into the possible positive effect of this demand on the intellectual bonding of employees. It is hypothesized that: (a) Initially, the increase in the perception of work overload will show a negative influence on the intellectual engagement of the employees; but (b) high perceptions of overload will change this effect, producing an increase in the intellectual dimension of engagement. The sample is made up of 706 employees of a Spanish multinational company. The results support this asymmetric curvilinear influence. The level of intellectual engagement is significantly reduced when the role overload increases from the lower values of the scale. However, upon reaching high levels of role overload, the intellectual engagement response begins to grow. These results challenge the conceptualization of overload as only negative and opens the door to consider that the positive response to a demand can also occur at high levels of it

Validating the Eating Disorder Inventory-3 (EDI-3): A Comparison Between 561 Female Eating Disorders Patients and 878 Females from the General Population

The Eating Disorder Inventory (EDI) is used worldwide in research and clinical work. The 3rd version (EDI-3) has been used in recent research, yet without any independent testing of its psychometric properties. The aim of the present study was twofold: 1) to establish national norms and to compare them with the US and international norms, and 2) to examine the factor structure, the internal consistency, the sensitivity and the specificity of subscale scores. Participants were Danish adult female patients (N = 561) from a specialist treatment centre and a control group (N = 878) was women selected from the Danish Civil Registration system. Small but significant differences were found between Danish and international, as well as US norms. Overall, the factor structure was confirmed, the internal consistency of the subscales was satisfactory, the discriminative validity was good, and sensitivity and specificity were excellent. The implications from these results are discussed

Supporting genetics in primary care: investigating how theory can inform professional education

Evidence indicates that many barriers exist to the integration of genetic case finding into primary care. We conducted an exploratory study of the determinants of three specific behaviours related to using breast cancer genetics referral guidelines effectively: 'taking a family history', 'making a risk assessment', and 'making a referral decision'. We developed vignettes of primary care consultations with hypothetical patients, representing a wide range of genetic risk for which different referral decisions would be appropriate. We used the Theory of Planned Behavior to develop a survey instrument to capture data on behavioural intention and its predictors (attitude, subjective norm, and perceived behavioural control) for each of the three behaviours and mailed it to a sample of Canadian family physicians. We used correlation and regression analyses to explore the relationships between predictor and dependent variables. The response rate was 96/125 (77%). The predictor variables explained 38-83% of the variance in intention across the three behaviours. Family physicians' intentions were lower for 'making a risk assessment' (perceived as the most difficult) than for the other two behaviours. We illustrate how understanding psychological factors salient to behaviour can be used to tailor professional educational interventions; for example, considering the approach of behavioural rehearsal to improve confidence in skills (perceived behavioural control), or vicarious reinforcement as where participants are sceptical that genetics is consistent with their role (subjective norm)

Development of a planar multi-body model of the human knee joint

The aim of this work is to develop a dynamic model for the biological human knee joint. The model is formulated in the framework of multibody systems methodologies, as a system of two bodies, the femur and the tibia. For the purpose of describing the formulation, the relative motion of the tibia with respect to the femur is considered. Due to their higher stiffness compared to that of the articular cartilages, the femur and tibia are considered as rigid bodies. The femur and tibia cartilages are considered to be deformable structures with specific material characteristics. The rotation and gliding motions of the tibia relative to the femur can not be modeled with any conventional kinematic joint, but rather in terms of the action of the knee ligaments and potential contact between the bones. Based on medical imaging techniques, the femur and tibia profiles in the sagittal plane are extracted and used to define the interface geometric conditions for contact. When a contact is detected, a continuous non-linear contact force law is applied which calculates the contact forces developed at the interface as a function of the relative indentation between the two bodies. The four basic cruciate and collateral ligaments present in the knee are also taken into account in the proposed knee joint model, which are modeled as non-linear elastic springs. The forces produced in the ligaments, together with the contact forces, are introduced into the system’s equations of motion as external forces. In addition, an external force is applied on the center of mass of the tibia, in order to actuate the system mimicking a normal gait motion. Finally, numerical results obtained from computational simulations are used to address the assumptions and procedures adopted in this study.Fundação para a Ciência e a Tecnologia (FCT

Efficacy of a training intervention on the quality of practitioners' decision support for patients deciding about place of care at the end of life: A randomized control trial: Study protocol

<p>Abstract</p> <p>Background</p> <p>Most people prefer home palliation but die in an institution. Some experience decisional conflict when weighing options regarding place of care. Clinicians can identify patients' decisional needs and provide decision support, yet generally lack skills and confidence in doing so. This study aims to determine whether the quality of clinicians' decision support can be improved with a brief, theory-based, skills-building intervention.</p> <p>Theory</p> <p>The Ottawa Decision Support Framework (ODSF) guides an evidence based, practical approach to assist clinicians in providing high-quality decision support. The ODSF proposes that decisional needs [personal uncertainty, knowledge, values clarity, support, personal characteristics] strongly influence the quality of decisions patients make. Clinicians can improve decision quality by providing decision support to address decisional needs [clarify decisional needs, provide facts and probabilities, clarify values, support/guide deliberation, monitor/facilitate progress].</p> <p>Methods/Design</p> <p>The efficacy of a brief education intervention will be assessed in a two-phase study. In phase one a focused needs assessment will be conducted with key informants. Phase two is a randomized control trial where clinicians will be randomly allocated to an intervention or control group. The intervention, informed by the needs assessment, knowledge transfer best practices and the ODSF, comprises an online tutorial; an interactive skills building workshop; a decision support protocol; performance feedback, and educational outreach. Participants will be assessed: a) at baseline (quality of decision support); b) after the tutorial (knowledge); and c) four weeks after the other interventions (quality of decision support, intention to incorporate decision support into practice and perceived usefulness of intervention components). Between group differences in the primary outcome (quality of decision support scores) will be analyzed using ANOVA.</p> <p>Discussion</p> <p>Few studies have investigated the efficacy of an evidence-based, theory guided intervention aimed at assisting clinicians to strengthen their patient decision support skills. Expanding our understanding of how clinicians can best support palliative patients' decision-making will help to inform best practices in patient-centered palliative care. There is potential transferability of lessons learned to other care situations such as chronic condition management, advance directives and anticipatory care planning. Should the efficacy evaluation reveal clear improvements in the quality of decision support provided by clinicians who received the intervention, a larger scale implementation and effectiveness trial will be considered.</p> <p>Trial registration</p> <p>This study is registered as NCT00614003</p