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Flexure hinges with notches are typical elements in high-precision compliant mechanisms with a wide variety of sizes from macro to micro or nano applications. This paper investigates the elasto-kinematic hinge and mechanism properties in dependence of scaling the geometric parameters regarding the impact of using optimized flexure hinge contours within a unified synthesis method without the need of rerunning simulations. The three performance criteria stiffness, maximum strain, and precision are analyzed among others for a single symmetric flexure hinge and a parallel four-bar linkage. The analytical investigations and FEM simulations include semi-circular, corner-filleted, and special 6th-order polynomial hinge contours. Accordingly, the chosen rigid-body model is transferred into a compliant mechanism through replacing all revolute joints by notch hinges. Geometric scaling is investigated with a parametric non-linear FEM model for factors from 0.1 to 2. To obtain results for comparable relative hinge angles, the defined input displacement is scaled too. Three prototypes are tested to verify the simulations and to validate the influence of scaling by measurement. In addition to general scale dependencies of the properties it is shown, that optimized flexure hinge contours are promising for miniaturized compliant mechanisms with high precision and large stroke at once.

Summary Background Current guidelines recommend potent platelet inhibition with prasugrel or ticagrelor for 12 months after an acute coronary syndrome managed with percutaneous coronary intervention (PCI). However, the greatest anti-ischaemic benefit of potent antiplatelet drugs over the less potent clopidogrel occurs early, while most excess bleeding events arise during chronic treatment. Hence, a stage-adapted treatment with potent platelet inhibition in the acute phase and de-escalation to clopidogrel in the maintenance phase could be an alternative approach. We aimed to investigate the safety and efficacy of early de-escalation of antiplatelet treatment from prasugrel to clopidogrel guided by platelet function testing (PFT). Methods In this investigator-initiated, randomised, open-label, assessor-blinded, multicentre trial (TROPICAL-ACS) done at 33 sites in Europe, patients were enrolled if they had biomarker-positive acute coronary syndrome with successful PCI and a planned duration of dual antiplatelet treatment of 12 months. Enrolled patients were randomly assigned (1:1) using an internet-based randomisation procedure with a computer-generated block randomisation with stratification across study sites to either standard treatment with prasugrel for 12 months (control group) or a step-down regimen (1 week prasugrel followed by 1 week clopidogrel and PFT-guided maintenance therapy with clopidogrel or prasugrel from day 14 after hospital discharge; guided de-escalation group). The assessors were masked to the treatment allocation. The primary endpoint was net clinical benefit (cardiovascular death, myocardial infarction, stroke or bleeding grade 2 or higher according to Bleeding Academic Research Consortium [BARC]) criteria) 1 year after randomisation (non-inferiority hypothesis; margin of 30%). Analysis was intention to treat. This study is registered with ClinicalTrials.gov, number NCT01959451, and EudraCT, 2013-001636-22. Findings Between Dec 2, 2013, and May 20, 2016, 2610 patients were assigned to study groups; 1304 to the guided de-escalation group and 1306 to the control group. The primary endpoint occurred in 95 patients (7%) in the guided de-escalation group and in 118 patients (9%) in the control group (p non-inferiority =0·0004; hazard ratio [HR] 0·81 [95% CI 0·62–1·06], p superiority =0·12). Despite early de-escalation, there was no increase in the combined risk of cardiovascular death, myocardial infarction, or stroke in the de-escalation group (32 patients [3%]) versus in the control group (42 patients [3%]; p non-inferiority =0·0115). There were 64 BARC 2 or higher bleeding events (5%) in the de-escalation group versus 79 events (6%) in the control group (HR 0·82 [95% CI 0·59–1·13]; p=0·23). Interpretation Guided de-escalation of antiplatelet treatment was non-inferior to standard treatment with prasugrel at 1 year after PCI in terms of net clinical benefit. Our trial shows that early de-escalation of antiplatelet treatment can be considered as an alternative approach in patients with acute coronary syndrome managed with PCI. Funding Klinikum der Universitat Munchen, Roche Diagnostics, Eli Lilly, and Daiichi Sankyo.