TY - JOUR A1 - Geith, Markus A. A1 - Nothdurfter, Laurenz A1 - Heiml, Manuel A1 - Agrafiotis, Emmanouil A1 - Gruber, Markus A1 - Sommer, Gerhard A1 - Schratzenstaller, Thomas A1 - Holzapfel, Gerhard A. T1 - Quantifying stent-induced damage in coronary arteries by investigating mechanical and structural alterations JF - Acta Biomaterialia N2 - Vascular damage develops with diverging severity during and after percutaneous coronary intervention with stent placement and is the prevailing stimulus for in-stent restenosis. Previous work has failed to link mechanical data obtained in a realistic in vivo or in vitro environment with data collected during imaging processes. We investigated whether specimens of porcine right coronary arteries soften when indented with a stent strut shaped structure, and if the softening results from damage mechanisms inside the fibrillar collagen structure. To simulate the multiaxial loading scenario of a stented coronary artery, we developed the testing device ‘LAESIO’ that can measure differences in the stress-stretch behavior of the arterial wall before and after the indentation of a strut-like stamp. The testing protocol was optimized according to preliminary experiments, more specifically equilibrium and relaxation tests. After chemical fixation of the specimens and subsequent tissue clearing, we performed three-dimensional surface and second-harmonic generation scans on the deformed specimens. We analyzed and correlated the mechanical response with structural parameters of high-affected tissue located next to the stamp indentation and low-affected tissue beyond the injured area. The results reveal that damage mechanisms, like tissue compression as well as softening, fiber dispersion, and the lesion extent, are direction-dependent, and the severity of them is linked to the strut orientation, indentation pressure, and position. The findings highlight the need for further investigations by applying the proposed methods to human coronary arteries. Additional data and insights might help to incorporate the observed damage mechanisms into material models for finite element analyses to perform more accurate simulations of stent-implantations. KW - Percutaneous coronary intervention KW - Stent KW - Mechanical properties KW - Damage mechanism KW - Vascular injury KW - Coronary artery KW - Indentation test KW - Softening KW - Second-harmonic generation imaging KW - Micro-structure Y1 - 2020 U6 - https://doi.org/10.1016/j.actbio.2020.08.016 VL - 116 IS - October SP - 285 EP - 301 PB - Elsevier ER - TY - CHAP A1 - Hauser, Florian A1 - Reiß, Markus A1 - Nivala, Markus A1 - Mottok, Jürgen A1 - Gruber, Hans T1 - Eye tracking applied: Visual expertise in code reviews T2 - 9th International Conference on Education and New Learning Technologies, EDULEARN17, 3-5 July, 2017, Barcelona, Spain, Proceedings Y1 - 2017 U6 - https://doi.org/10.21125/edulearn.2017.1084 SP - 379 EP - 389 ER - TY - CHAP A1 - Nivala, Markus A1 - Hauser, Florian A1 - Jossberger, Helen A1 - Reiß, Markus A1 - Mottok, Jürgen A1 - Gruber, Hans T1 - Detecting errors in program flow diagrams: Comparing novices and advanced programmers T2 - EARLI Biennial Conference 2017, 17th European Association for Research on Learning and Instruction, 29 August - 2 September, 2017 - University of Tampere, Finland Y1 - 2017 ER - TY - CHAP A1 - Nivala, Markus A1 - Hauser, Florian A1 - Mottok, Jürgen A1 - Gruber, Hans T1 - Developing visual expertise in software engineering: An eye tracking study T2 - IEEE Global Engineering Education Conference (EDUCON), 10-13 April 2016, Abu Dhabi, UAE N2 - Program comprehension and the ability to find program errors are key skills of software engineering. The aim of this pilot study was to examine the visual processes of novice and advanced programmers in authentic tasks. Fifteen novices and eight advanced programmers were given eight short pieces of code. Their task was to either identify an error or give the output of the code. Eye movements and keyboard activity were recorded. On average, the novices spent more time reading the code than composing the response, whereas the more advanced programmers started composing the response sooner and spent more time on it. In general, the advanced programmers had shorter fixations and saccades. The results suggest that the advanced programmers are quicker to grasp the essence of the code and able to see more details in it. The advanced programmers had shorter fixations and saccade lengths during the second phase which might indicate the process of chunking. KW - program comprehension KW - debugging KW - software engineering KW - visual expertise KW - eye tracking Y1 - 2016 U6 - https://doi.org/10.1109/EDUCON.2016.7474614 SP - 613 EP - 620 ER -