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The main goal of this numerical study is to assess the impact of geometric design perturbations on the performance of a representative coronary stent platform. In this context, first, a design parameterization model was defined for the stent under study. After, a set of metrics characterizing stent performance, namely, vessel injury, radial recoil, bending resistance, longitudinal resistance, radial strength, the risk of fracture, prolapse index, and dogboning were evaluated within the context of a finite element analysis. Afterwards, accurate surrogate models were developed, using the efficient global optimization algorithm, as predictive tools in the execution of tasks that normally require a high number of model evaluations, such as global sensitivity analysis and visualization. In the end, the dependence of the output response surfaces on the geometric parameters was mechanically interpreted, which allowed us to understand the complex interplay that exists between the considered design variables and the defined performance metrics.

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Left atrium function is essential for cardiovascular performance and is evaluable by two-dimensional speckle-tracking echocardiography (2D-STE). Our aim was to determine how echocardiographic parameters interrelate with exercise capacity and ventilatory efficiency in subjects with no structural heart disease. Asymptomatic volunteers, in sinus rhythm and with normal biventricular size and function, were recruited from a community-based population. Individuals with moderate-to-severe valvular disease, pulmonary hypertension, and history of cardiac disease were excluded. We performed a transthoracic echocardiogram and assessed left atrial (LA) and left ventricular (LV) mechanics via 2D-STE. Cardiopulmonary exercise testing by treadmill took place immediately thereafter. Peak oxygen uptake (VO) served as measure of functional capacity and ventilation/carbon dioxide output (VE/VCO) slope as surrogate of ventilation/perfusion mismatch. 20 subjects were included (age 51 ± 14 years, male gender 65%). Peak VO strongly correlated with age (r = -0.83; P < 0.01), with E/e' ratio (r = -0.72; P < 0.01), and with LA reservoir- and conduit-phase mechanics, particularly with LA conduit strain rate (SR) (r = -0.82; P < 0.01), but showed no correlation with LA volume index or LV mechanics. A similar pattern of associations was identified for VE/VCO slope. In multivariate analysis, LA conduit SR (β = -0.69; P = 0.02) emerged as sole independent correlate of peak VO, adjusted for age and for E/e' ratio (adjusted r = 0.76; P< 0.01). Conduit and reservoir components of LA mechanics displayed strong associations with peak VO and VE/VCO slope. LA conduit-phase SR seems best suited as echocardiographic marker of functional capacity in subjects with no structural heart disease.

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This paper describes the development of a computational model to calculate wear rates in total shoulder prostheses, for a 5-150 degrees arm abduction. Anatomical keeled and pegged prosthesis as well as reversed prosthesis were the studied implants. The bone models were built based on computed tomography (CT) images and using a computer aided design-based modelling pipeline. The finite element method was used to solve the contact problem between the surface of the polyethylene (PE) components and the corresponding articular component. The aim of this work was to determine linear and volumetric PE wear, for several radial mismatches, in conditions of pathological (rheumatoid arthritis) and non-pathological bone. Results showed that contact pressures and linear wear developed in anatomical prosthesis were higher than those visualised in reversed prosthesis. However, anatomical prosthesis exhibited a better volumetric wear performance. Moreover, our findings indicated higher values of volumetric wear in higher congruent models and on pathological bone conditions.

PurposeThis paper aims at understanding the action of pilot entities, in order to ultimately infer about their role to the overall reform process of public sector accounting (PSA).Design/methodology/approachTaking the Portuguese case as a reference, the new institutional theory (isomorphism perspective) and institutional logics are used to explain the action and stance of pilot entities in the implementation process of reforms.FindingsPilot experiments are expected to provide feedback on the main difficulties felt in the implementation of a new PSA system, helping to define a global strategy to overcome those problems and to improve the system to be generally and finally put into practice. Nevertheless, entities seem to find it important to be pilots, more for individual advantages than for the common benefit of the reform as a whole. Therefore, in order for them to actually be important actors in the reform process, pilots need to be included in the decision process, better realizing the benefits of the new IPSAS-based system and be provided with the proper technical, human and financial support.Research limitations/implicationsThis research suffers from some limitations, namely concerning the use of questionnaires. The findings may, in some points, reflect the perceptions of the respondents and not the actual reality. Additionally, the respondents were not asked about any personal background factors, which may influence their answers. Also, they did not allow relating the new PSA system features with the way pilot entities (re)acted. In regard to the implications for practice, the study points to a need for decision-makers and external support bodies to work more closely with pilot entities in the overall design and implementation of PSA reforms. Pilot entities need to understand the importance and usefulness of changes, and reform authorities need to better recognize their institutional reality and the support they require. Only in this way, the use of pilots can make a difference in the implementation of PSA innovations.Originality/valueThis paper contributes to theory by adding to a better understanding of the role of the ones acting in the development and implementation of PSA innovations, enlightening on how pilot entities can act/react. Despite several studies on PSA reforms, very few so far have addressed pilot entities in particular, their attitude and actual contribution toward PSA reforms, and why. The case of Portugal as a frontrunner in adopting an IPSAS-based system within the EU helps contribute to that understanding in the setting of European countries.