TY  - CHAP
A1  - Abele, Daniel
A1  - Kleefeld, Andreas
ED  - Constanda, Christian
T1  - New Numerical Results for the Optimization of Neumann Eigenvalues
T2  - Computational and Analytic Methods in Science and Engineering
N2  - We present new numerical results for shape optimization problems of interior Neumann eigenvalues. This field is not well understood from a theoretical standpoint. The existence of shape maximizers is not proven beyond the first two eigenvalues, so we study the problem numerically. We describe a method to compute the eigenvalues for a given shape that combines the boundary element method with an algorithm for nonlinear eigenvalues. As numerical optimization requires many such evaluations, we put a focus on the efficiency of the method and the implemented routine. The method is well suited for parallelization. Using the resulting fast routines and a specialized parametrization of the shapes, we found improved maxima for several eigenvalues.
Y1  - 2020
SN  - 978-3-030-48185-8 (Print)
SN  - 978-3-030-48186-5 (Online)
U6  - https://doi.org/10.1007/978-3-030-48186-5_1
SP  - 1
EP  - 20
PB  - Birkhäuser
CY  - Cham
ER  - 
TY  - JOUR
A1  - Bayer, Robin
A1  - Temiz Artmann, Aysegül
A1  - Digel, Ilya
A1  - Falkenstein, Julia
A1  - Artmann, Gerhard
A1  - Creutz, Till
A1  - Hescheler, Jürgen
T1  - Mechano-pharmacological testing of L-Type Ca²⁺ channel modulators via human vascular celldrum model
JF  - Cellular Physiology and Biochemistry
N2  - Background/Aims: This study aimed to establish a precise and well-defined working model, assessing pharmaceutical effects on vascular smooth muscle cell monolayer in-vitro. It describes various analysis techniques to determine the most suitable to measure the biomechanical impact of vasoactive agents by using CellDrum technology. Methods: The so-called CellDrum technology was applied to analyse the biomechanical properties of confluent human aorta muscle cells (haSMC) in monolayer. The cell generated tensions deviations in the range of a few N/m² are evaluated by the CellDrum technology. This study focuses on the dilative and contractive effects of L-type Ca²⁺ channel agonists and antagonists, respectively. We analyzed the effects of Bay K8644, nifedipine and verapamil. Three different measurement modes were developed and applied to determine the most appropriate analysis technique for the study purpose. These three operation modes are called, particular time mode" (PTM), "long term mode" (LTM) and "real-time mode" (RTM). Results: It was possible to quantify the biomechanical response of haSMCs to the addition of vasoactive agents using CellDrum technology. Due to the supplementation of 100nM Bay K8644, the tension increased approximately 10.6% from initial tension maximum, whereas, the treatment with nifedipine and verapamil caused a significant decrease in cellular tension: 10nM nifedipine decreased the biomechanical stress around 6,5% and 50nM verapamil by 2,8%, compared to the initial tension maximum. Additionally, all tested measurement modes provide similar results while focusing on different analysis parameters. Conclusion: The CellDrum technology allows highly sensitive biomechanical stress measurements of cultured haSMC monolayers. The mechanical stress responses evoked by the application of vasoactive calcium channel modulators were quantified functionally (N/m²). All tested operation modes resulted in equal findings, whereas each mode features operation-related data analysis.
Y1  - 2020
U6  - https://doi.org/10.33594/000000225
SN  - 1421-9778
VL  - 54
SP  - 371
EP  - 383
PB  - Cell Physiol Biochem Press
CY  - Düsseldorf
ER  - 
TY  - INPR
A1  - Ringers, Christa
A1  - Bialonski, Stephan
A1  - Solovev, Anton
A1  - Hansen, Jan N.
A1  - Ege, Mert
A1  - Friedrich, Benjamin M.
A1  - Jurisch-Yaksi, Nathalie
T1  - Preprint: Local synchronization of cilia and tissue-scale cilia alignment are sufficient for global metachronal waves
T2  - bioRxiv
N2  - Motile cilia are hair-like cell extensions present in multiple organs of the body. How cilia coordinate their regular beat in multiciliated epithelia to move fluids remains insufficiently understood, particularly due to lack of rigorous quantification. We combine here experiments, novel analysis tools, and theory to address this knowledge gap. We investigate collective dynamics of cilia in the zebrafish nose, due to its conserved properties with other ciliated tissues and its superior accessibility for non-invasive imaging. We revealed that cilia are synchronized only locally and that the size of local synchronization domains increases with the viscosity of the surrounding medium. Despite the fact that synchronization is local only, we observed global patterns of traveling metachronal waves across the multiciliated epithelium. Intriguingly, these global wave direction patterns are conserved across individual fish, but different for left and right nose, unveiling a chiral asymmetry of metachronal coordination. To understand the implications of synchronization for fluid pumping, we used a computational model of a regular array of cilia. We found that local metachronal synchronization prevents steric collisions and improves fluid pumping in dense cilia carpets, but hardly affects the direction of fluid flow. In conclusion, we show that local synchronization together with tissue-scale cilia alignment are sufficient to generate metachronal wave patterns in multiciliated epithelia, which enhance their physiological function of fluid pumping.
Y1  - 2021
U6  - https://doi.org/10.1101/2021.11.23.469646
N1  - Veröffentlicht in eLife 12:e77701 (https://doi.org/10.7554/eLife.77701).
ER  - 
TY  - JOUR
A1  - Akimbekov, Nuraly S.
A1  - Digel, Ilya
A1  - Abdieva, Gulzhamal
A1  - Ualieva, Perizat
A1  - Tastambek, Kuanysh
T1  - Lignite biosolubilization and bioconversion by Bacillus sp.: the collation of analytical data
JF  - Biofuels
N2  - The vast metabolic potential of microbes in brown coal (lignite) processing and utilization can greatly contribute to innovative approaches to sustainable production of high-value products from coal. In this study, the multi-faceted and complex coal biosolubilization process by Bacillus sp. RKB 7 isolate from the Kazakhstan coal-mining soil is reported, and the derived products are characterized. Lignite solubilization tests performed for surface and suspension cultures testify to the formation of numerous soluble lignite-derived substances. Almost 24% of crude lignite (5% w/v) was solubilized within 14 days under slightly alkaline conditions (pH 8.2). FTIR analysis revealed various functional groups in the obtained biosolubilization products. Analyses of the lignite-derived humic products by UV-Vis and fluorescence spectrometry as well as elemental analysis yielded compatible results indicating the emerging products had a lower molecular weight and degree of aromaticity. Furthermore, XRD and SEM analyses were used to evaluate the biosolubilization processes from mineralogical and microscopic points of view. The findings not only contribute to a deeper understanding of microbe–mineral interactions in coal environments, but also contribute to knowledge of coal biosolubilization and bioconversion with regard to sustainable production of humic substances. The detailed and comprehensive analyses demonstrate the huge biotechnological potential of Bacillus sp. for agricultural productivity and environmental health.
KW  - humic acid
KW  - Bacillus sp
KW  - lignite
KW  - Biosolubilization
Y1  - 2021
SN  - 1759-7277
VL  - 12
IS  - 3
SP  - 247
EP  - 258
PB  - Taylor & Francis
CY  - London
ER  - 
TY  - JOUR
A1  - Hunker, Jan L.
A1  - Gossmann, Matthias
A1  - Raman, Aravind Hariharan
A1  - Linder, Peter
T1  - Artificial neural networks in cardiac safety assessment: Classification of chemotherapeutic compound effects on hiPSC-derived cardiomyocyte contractility
JF  - Journal of Pharmacological and Toxicological Methods
Y1  - 2021
U6  - https://doi.org/10.1016/j.vascn.2021.107044
SN  - 1056-8719
VL  - 111
IS  - Article number 107044
PB  - Elsevier
CY  - New York
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Staat, Manfred
T1  - FEM shakedown analysis of Kirchhoff-Love plates under uncertainty of strength
T2  - Proceedings of UNCECOMP 2021
N2  - A new formulation to calculate the shakedown limit load of Kirchhoff plates under stochastic conditions of strength is developed. Direct structural reliability design by chance con-strained programming is based on the prescribed failure probabilities, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem. We restrict uncertainty to strength, the loading is still deterministic. A new formulation is derived in case of random strength with lognormal distribution. Upper bound and lower bound shakedown load factors are calculated simultaneously by a dual algorithm.
Y1  - 2021
SN  - 978-618-85072-6-5
U6  - https://doi.org/10.7712/120221.8041.19047
N1  - UNCECOMP 2021, 4th International Conference on Uncertainty Quantification in Computational Sciences and Engineering, streamed from Athens, Greece, 28–30 June 2021.
SP  - 323
EP  - 338
ER  - 
TY  - JOUR
A1  - Hackl, Michael
A1  - Nacov, Julia
A1  - Kammerlohr, Sandra
A1  - Staat, Manfred
A1  - Buess, Eduard
A1  - Leschinger, Tim
A1  - Müller, Lars P.
A1  - Wegmann, Kilian
T1  - Intratendinous Strain Variations of the Supraspinatus Tendon Depending on Repair Technique: A Biomechanical Analysis Regarding the Cause of Medial Cuff Failure
JF  - The American Journal of Sports Medicine
Y1  - 2021
U6  - https://doi.org/10.1177/03635465211006138
SN  - 1552-3365
SN  - 0363-5465
VL  - 49
IS  - 7
SP  - 1847
EP  - 1853
PB  - Sage
CY  - London
ER  - 
TY  - JOUR
A1  - Tran, Ngoc Trinh
A1  - Staat, Manfred
T1  - Direct plastic structural design under random strength and random load by chance constrained programming
JF  - European Journal of Mechanics - A/Solids
Y1  - 2021
U6  - https://doi.org/10.1016/j.euromechsol.2020.104106
SN  - 0997-7538
VL  - 85
IS  - Article 104106
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Hugenroth, Kristin
A1  - Borchardt, Ralf
A1  - Ritter, Philine
A1  - Groß‑Hardt, Sascha
A1  - Meyns, Bart
A1  - Verbelen, Tom
A1  - Steinseifer, Ulrich
A1  - Kaufmann, Tim A. S.
A1  - Engelmann, Ulrich M.
T1  - Optimizing cerebral perfusion and hemodynamics during cardiopulmonary bypass through cannula design combining in silico, in vitro and in vivo input
JF  - Scientific Reports
N2  - Cardiopulmonary bypass (CPB) is a standard technique for cardiac surgery, but comes with the risk of severe neurological complications (e.g. stroke) caused by embolisms and/or reduced cerebral perfusion. We report on an aortic cannula prototype design (optiCAN) with helical outflow and jet-splitting dispersion tip that could reduce the risk of embolic events and restores cerebral perfusion to 97.5% of physiological flow during CPB in vivo, whereas a commercial curved-tip cannula yields 74.6%. In further in vitro comparison, pressure loss and hemolysis parameters of optiCAN remain unaffected. Results are reproducibly confirmed in silico for an exemplary human aortic anatomy via computational fluid dynamics (CFD) simulations. Based on CFD simulations, we firstly show that optiCAN design improves aortic root washout, which reduces the risk of thromboembolism. Secondly, we identify regions of the aortic intima with increased risk of plaque release by correlating areas of enhanced plaque growth and high wall shear stresses (WSS). From this we propose another easy-to-manufacture cannula design (opti2CAN) that decreases areas burdened by high WSS, while preserving physiological cerebral flow and favorable hemodynamics. With this novel cannula design, we propose a cannulation option to reduce neurological complications and the prevalence of stroke in high-risk patients after CPB.
Y1  - 2021
U6  - https://doi.org/10.1038/s41598-021-96397-2
SN  - 2045-2322
VL  - 11
IS  - Art. No. 16800
SP  - 1
EP  - 12
PB  - Springer
CY  - Berlin
ER  - 
TY  - CHAP
A1  - Olderog, M.
A1  - Mohr, P.
A1  - Beging, Stefan
A1  - Tsoumpas, C.
A1  - Ziemons, Karl
T1  - Simulation study on the role of tissue-scattered events in improving sensitivity for a compact time of flight compton positron emission tomograph
T2  - 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)
N2  - In positron emission tomography improving time, energy and spatial detector resolutions and using Compton kinematics introduces the possibility to reconstruct a radioactivity distribution image from scatter coincidences, thereby enhancing image quality. The number of single scattered coincidences alone is in the same order of magnitude as true coincidences. In this work, a compact Compton camera module based on monolithic scintillation material is investigated as a detector ring module. The detector interactions are simulated with Monte Carlo package GATE. The scattering angle inside the tissue is derived from the energy of the scattered photon, which results in a set of possible scattering trajectories or broken line of response. The Compton kinematics collimation reduces the number of solutions. Additionally, the time of flight information helps localize the position of the annihilation. One of the questions of this investigation is related to how the energy, spatial and temporal resolutions help confine the possible annihilation volume. A comparison of currently technically feasible detector resolutions (under laboratory conditions) demonstrates the influence on this annihilation volume and shows that energy and coincidence time resolution have a significant impact. An enhancement of the latter from 400 ps to 100 ps leads to a smaller annihilation volume of around 50%, while a change of the energy resolution in the absorber layer from 12% to 4.5% results in a reduction of 60%. The inclusion of single tissue-scattered data has the potential to increase the sensitivity of a scanner by a factor of 2 to 3 times. The concept can be further optimized and extended for multiple scatter coincidences and subsequently validated by a reconstruction algorithm.
Y1  - 2021
SN  - 978-1-7281-7693-2
U6  - https://doi.org/10.1109/NSS/MIC42677.2020.9507901
N1  - 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 31 Oct.-7 Nov. 2020, Boston, MA, USA
PB  - IEEE
CY  - New York, NY
ER  -