@article{BhattaraiHorbachStaatetal.2022, author = {Bhattarai, Aroj and Horbach, Andreas and Staat, Manfred and Kowalczyk, Wojciech and Tran, Thanh Ngoc}, title = {Virgin passive colon biomechanics and a literature review of active contraction constitutive models}, series = {Biomechanics}, volume = {2}, journal = {Biomechanics}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2673-7078}, doi = {10.3390/biomechanics2020013}, pages = {138 -- 157}, year = {2022}, abstract = {The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel-Gasser-Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill's three-element model, Murphy's four-state cross-bridge chemical kinetic model and Huxley's sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine.}, language = {en} } @article{UysalCreutzFiratetal.2022, author = {Uysal, Karya and Creutz, Till and Firat, Ipek Seda and Artmann, Gerhard and Teusch, Nicole and Temiz Artmann, Ayseg{\"u}l}, title = {Bio-functionalized ultra-thin, large-area and waterproof silicone membranes for biomechanical cellular loading and compliance experiments}, series = {Polymers}, volume = {14}, journal = {Polymers}, number = {11}, publisher = {MDPI}, address = {Basel}, issn = {2073-4360}, pages = {2213}, year = {2022}, abstract = {Biocompatibility, flexibility and durability make polydimethylsiloxane (PDMS) membranes top candidates in biomedical applications. CellDrum technology uses large area, <10 µm thin membranes as mechanical stress sensors of thin cell layers. For this to be successful, the properties (thickness, temperature, dust, wrinkles, etc.) must be precisely controlled. The following parameters of membrane fabrication by means of the Floating-on-Water (FoW) method were investigated: (1) PDMS volume, (2) ambient temperature, (3) membrane deflection and (4) membrane mechanical compliance. Significant differences were found between all PDMS volumes and thicknesses tested (p < 0.01). They also differed from the calculated values. At room temperatures between 22 and 26 °C, significant differences in average thickness values were found, as well as a continuous decrease in thicknesses within a 4 °C temperature elevation. No correlation was found between the membrane thickness groups (between 3-4 µm) in terms of deflection and compliance. We successfully present a fabrication method for thin bio-functionalized membranes in conjunction with a four-step quality management system. The results highlight the importance of tight regulation of production parameters through quality control. The use of membranes described here could also become the basis for material testing on thin, viscous layers such as polymers, dyes and adhesives, which goes far beyond biological applications.}, language = {en} } @article{UysalFiratCreutzetal.2022, author = {Uysal, Karya and Firat, Ipek Serat and Creutz, Till and Aydin, Inci Cansu and Artmann, Gerhard and Teusch, Nicole and Temiz Artmann, Ayseg{\"u}l}, title = {A novel in vitro wound healing assay using free-standing, ultra-thin PDMS membranes}, series = {membranes}, volume = {2023}, journal = {membranes}, number = {13(1)}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/membranes13010022}, pages = {Artikel 22}, year = {2022}, abstract = {Advances in polymer science have significantly increased polymer applications in life sciences. We report the use of free-standing, ultra-thin polydimethylsiloxane (PDMS) membranes, called CellDrum, as cell culture substrates for an in vitro wound model. Dermal fibroblast monolayers from 28- and 88-year-old donors were cultured on CellDrums. By using stainless steel balls, circular cell-free areas were created in the cell layer (wounding). Sinusoidal strain of 1 Hz, 5\% strain, was applied to membranes for 30 min in 4 sessions. The gap circumference and closure rate of un-stretched samples (controls) and stretched samples were monitored over 4 days to investigate the effects of donor age and mechanical strain on wound closure. A significant decrease in gap circumference and an increase in gap closure rate were observed in trained samples from younger donors and control samples from older donors. In contrast, a significant decrease in gap closure rate and an increase in wound circumference were observed in the trained samples from older donors. Through these results, we propose the model of a cell monolayer on stretchable CellDrums as a practical tool for wound healing research. The combination of biomechanical cell loading in conjunction with analyses such as gene/protein expression seems promising beyond the scope published here.}, language = {en} } @article{DefosseKleinschmidtSchmutzetal.2022, author = {Defosse, Jerome and Kleinschmidt, Joris and Schmutz, Axel and Loop, Torsten and Staat, Manfred and Gatzweiler, Karl-Heinz and Wappler, Frank and Schieren, Mark}, title = {Dental strain on maxillary incisors during tracheal intubation with double-lumen tubes and different laryngoscopy techniques - a blinded manikin study}, series = {Journal of Cardiothoracic and Vascular Anesthesia}, volume = {36}, journal = {Journal of Cardiothoracic and Vascular Anesthesia}, number = {8, Part B}, publisher = {Elsevier}, address = {New York, NY}, issn = {1053-0770}, doi = {10.1053/j.jvca.2022.02.017}, pages = {3021 -- 3027}, year = {2022}, language = {en} } @article{MalinowskiFournierHorbachetal.2022, author = {Malinowski, Daniel and Fournier, Yvan and Horbach, Andreas and Frick, Michael and Magliani, Mirko and Kalverkamp, Sebastian and Hildinger, Martin and Spillner, Jan and Behbahani, Mehdi and Hima, Flutura}, title = {Computational fluid dynamics analysis of endoluminal aortic perfusion}, series = {Perfusion}, volume = {0}, journal = {Perfusion}, number = {0}, publisher = {Sage}, address = {London}, issn = {1477-111X}, doi = {10.1177/02676591221099809}, pages = {1 -- 8}, year = {2022}, abstract = {Introduction: In peripheral percutaneous (VA) extracorporeal membrane oxygenation (ECMO) procedures the femoral arteries perfusion route has inherent disadvantages regarding poor upper body perfusion due to watershed. With the advent of new long flexible cannulas an advancement of the tip up to the ascending aorta has become feasible. To investigate the impact of such long endoluminal cannulas on upper body perfusion, a Computational Fluid Dynamics (CFD) study was performed considering different support levels and three cannula positions. Methods: An idealized literature-based- and a real patient proximal aortic geometry including an endoluminal cannula were constructed. The blood flow was considered continuous. Oxygen saturation was set to 80\% for the blood coming from the heart and to 100\% for the blood leaving the cannula. 50\% and 90\% venoarterial support levels from the total blood flow rate of 6 l/min were investigated for three different positions of the cannula in the aortic arch. Results: For both geometries, the placement of the cannula in the ascending aorta led to a superior oxygenation of all aortic blood vessels except for the left coronary artery. Cannula placements at the aortic arch and descending aorta could support supra-aortic arteries, but not the coronary arteries. All positions were able to support all branches with saturated blood at 90\% flow volume. Conclusions: In accordance with clinical observations CFD analysis reveals, that retrograde advancement of a long endoluminal cannula can considerably improve the oxygenation of the upper body and lead to oxygen saturation distributions similar to those of a central cannulation.}, language = {en} } @inproceedings{AllalBannisterBuismanetal.2022, author = {Allal, D. and Bannister, R. and Buisman, K. and Capriglione, D. and Di Capua, G. and Garc{\´i}a-Patr{\´o}n, M. and Gatzweiler, Thomas and Gellersen, F. and Harzheim, Thomas and Heuermann, Holger and Hoffmann, J. and Izbrodin, A. and Kuhlmann, K. and Lahbacha, K. and Maffucci, A. and Miele, G. and Mubarak, F. and Salter, M. and Pham, T.D. and Sayegh, A. and Singh, D. and Stein, F. and Zeier, M.}, title = {RF measurements for future communication applications: an overview}, series = {2022 IEEE International Symposium on Measurements \& Networking (M\&N)}, booktitle = {2022 IEEE International Symposium on Measurements \& Networking (M\&N)}, publisher = {IEEE}, isbn = {978-1-6654-8362-9}, issn = {2639-5061}, doi = {10.1109/MN55117.2022.9887740}, pages = {1 -- 6}, year = {2022}, abstract = {In this paper research activities developed within the FutureCom project are presented. The project, funded by the European Metrology Programme for Innovation and Research (EMPIR), aims at evaluating and characterizing: (i) active devices, (ii) signal- and power integrity of field programmable gate array (FPGA) circuits, (iii) operational performance of electronic circuits in real-world and harsh environments (e.g. below and above ambient temperatures and at different levels of humidity), (iv) passive inter-modulation (PIM) in communication systems considering different values of temperature and humidity corresponding to the typical operating conditions that we can experience in real-world scenarios. An overview of the FutureCom project is provided here, then the research activities are described.}, language = {en} } @article{HerssensCowburnAlbrachtetal.2022, author = {Herssens, Nolan and Cowburn, James and Albracht, Kirsten and Braunstein, Bjoern and Cazzola, Dario and Colyer, Steffi and Minetti, Alberto E. and Pavei, Gaspare and Rittweger, J{\"o}rn and Weber, Tobias and Green, David A.}, title = {Movement in low gravity environments (MoLo) programme - the MoLo-L.O.O.P. study protocol}, series = {PLOS ONE / Public Library of Science}, volume = {17}, journal = {PLOS ONE / Public Library of Science}, number = {11}, editor = {Cattaneo, Luigi}, publisher = {Plos}, address = {San Francisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0278051}, pages = {e0278051}, year = {2022}, abstract = {Exposure to prolonged periods in microgravity is associated with deconditioning of the musculoskeletal system due to chronic changes in mechanical stimulation. Given astronauts will operate on the Lunar surface for extended periods of time, it is critical to quantify both external (e.g., ground reaction forces) and internal (e.g., joint reaction forces) loads of relevant movements performed during Lunar missions. Such knowledge is key to predict musculoskeletal deconditioning and determine appropriate exercise countermeasures associated with extended exposure to hypogravity.}, language = {en} } @article{StaeudleSeynnesLapsetal.2022, author = {St{\"a}udle, Benjamin and Seynnes, Olivier and Laps, Guido and Br{\"u}ggemann, Gert-Peter and Albracht, Kirsten}, title = {Altered gastrocnemius contractile behavior in former achilles tendon rupture patients during walking}, series = {Frontiers in Physiology}, volume = {13}, journal = {Frontiers in Physiology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-042X}, doi = {10.3389/fphys.2022.792576}, pages = {12 Seiten}, year = {2022}, abstract = {Achilles tendon rupture (ATR) remains associated with functional limitations years after injury. Architectural remodeling of the gastrocnemius medialis (GM) muscle is typically observed in the affected leg and may compensate force deficits caused by a longer tendon. Yet patients seem to retain functional limitations during—low-force—walking gait. To explore the potential limits imposed by the remodeled GM muscle-tendon unit (MTU) on walking gait, we examined the contractile behavior of muscle fascicles during the stance phase. In a cross-sectional design, we studied nine former patients (males; age: 45 ± 9 years; height: 180 ± 7 cm; weight: 83 ± 6 kg) with a history of complete unilateral ATR, approximately 4 years post-surgery. Using ultrasonography, GM tendon morphology, muscle architecture at rest, and fascicular behavior were assessed during walking at 1.5 m⋅s-1 on a treadmill. Walking patterns were recorded with a motion capture system. The unaffected leg served as control. Lower limbs kinematics were largely similar between legs during walking. Typical features of ATR-related MTU remodeling were observed during the stance sub-phases corresponding to series elastic element (SEE) lengthening (energy storage) and SEE shortening (energy release), with shorter GM fascicles (36 and 36\%, respectively) and greater pennation angles (8° and 12°, respectively). However, relative to the optimal fascicle length for force production, fascicles operated at comparable length in both legs. Similarly, when expressed relative to optimal fascicle length, fascicle contraction velocity was not different between sides, except at the time-point of peak series elastic element (SEE) length, where it was 39 ± 49\% lower in the affected leg. Concomitantly, fascicles rotation during contraction was greater in the affected leg during the whole stance-phase, and architectural gear ratios (AGR) was larger during SEE lengthening. Under the present testing conditions, former ATR patients had recovered a relatively symmetrical walking gait pattern. Differences in seen AGR seem to accommodate the profound changes in MTU architecture, limiting the required fascicle shortening velocity. Overall, the contractile behavior of the GM fascicles does not restrict length- or velocity-dependent force potentials during this locomotor task.}, language = {en} } @article{QuittmannAbelAlbrachtetal.2022, author = {Quittmann, Oliver J. and Abel, Thomas and Albracht, Kirsten and Str{\"u}der, Heiko K.}, title = {Biomechanics of all-out handcycling exercise: kinetics, kinematics and muscular activity of a 15-s sprint test in able-bodied participants}, series = {Sports Biomechanics}, volume = {21}, journal = {Sports Biomechanics}, number = {10}, publisher = {Taylor \& Francis}, address = {London}, issn = {1752-6116 (Onlineausgabe)}, doi = {10.1080/14763141.2020.1745266}, pages = {1200 -- 1223}, year = {2022}, abstract = {This study aims to quantify the kinematics, kinetics and muscular activity of all-out handcycling exercise and examine their alterations during the course of a 15-s sprint test. Twelve able-bodied competitive triathletes performed a 15-s all-out sprint test in a recumbent racing handcycle that was attached to an ergometer. During the sprint test, tangential crank kinetics, 3D joint kinematics and muscular activity of 10 muscles of the upper extremity and trunk were examined using a power metre, motion capturing and surface electromyography (sEMG), respectively. Parameters were compared between revolution one (R1), revolution two (R2), the average of revolution 3 to 13 (R3) and the average of the remaining revolutions (R4). Shoulder abduction and internal-rotation increased, whereas maximal shoulder retroversion decreased during the sprint. Except for the wrist angles, angular velocity increased for every joint of the upper extremity. Several muscles demonstrated an increase in muscular activation, an earlier onset of muscular activation in crank cycle and an increased range of activation. During the course of a 15-s all-out sprint test in handcycling, the shoulder muscles and the muscles associated to the push phase demonstrate indications for short-duration fatigue. These findings are helpful to prevent injuries and improve performance in all-out handcycling.}, language = {en} } @article{AngermannGuenthnerHanssenetal.2022, author = {Angermann, Susanne and G{\"u}nthner, Roman and Hanssen, Henner and Lorenz, Georg and Braunisch, Matthias C. and Steubl, Dominik and Matschkal, Julia and Kemmner, Stephan and Hausinger, Renate and Block, Zenonas and Haller, Bernhard and Heemann, Uwe and Kotliar, Konstantin and Grimmer, Timo and Schmaderer, Christoph}, title = {Cognitive impairment and microvascular function in end-stage renal disease}, series = {International Journal of Methods in Psychiatric Research (MPR)}, volume = {31}, journal = {International Journal of Methods in Psychiatric Research (MPR)}, number = {2}, publisher = {Wiley}, issn = {1049-8931 (Print)}, doi = {10.1002/mpr.1909}, pages = {1 -- 10}, year = {2022}, abstract = {Objective Hemodialysis patients show an approximately threefold higher prevalence of cognitive impairment compared to the age-matched general population. Impaired microcirculatory function is one of the assumed causes. Dynamic retinal vessel analysis is a quantitative method for measuring neurovascular coupling and microvascular endothelial function. We hypothesize that cognitive impairment is associated with altered microcirculation of retinal vessels. Methods 152 chronic hemodialysis patients underwent cognitive testing using the Montreal Cognitive Assessment. Retinal microcirculation was assessed by Dynamic Retinal Vessel Analysis, which carries out an examination recording retinal vessels' reaction to a flicker light stimulus under standardized conditions. Results In unadjusted as well as in adjusted linear regression analyses a significant association between the visuospatial executive function domain score of the Montreal Cognitive Assessment and the maximum arteriolar dilation as response of retinal arterioles to the flicker light stimulation was obtained. Conclusion This is the first study determining retinal microvascular function as surrogate for cerebral microvascular function and cognition in hemodialysis patients. The relationship between impairment in executive function and reduced arteriolar reaction to flicker light stimulation supports the involvement of cerebral small vessel disease as contributing factor for the development of cognitive impairment in this patient population and might be a target for noninvasive disease monitoring and therapeutic intervention.}, language = {en} }