@misc{EhrigNowak, author = {Ehrig, Rainald and Nowak, Ulrich}, title = {Algorithmen- und Softwareoptimierung f{\"u}r die Satellitenbahn- und Schwerefeldmodellierung}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5694}, number = {00-01}, abstract = {Dieser Report enth{\"a}lt die Ergebnisse der Untersuchungen, die gem{\"a}ss dem Forschungs-- und Entwicklungsvertrag Gravity zwischen dem GeoForschungsZentrum Potsdam und dem Konrad--Zuse--Zentrum Berlin vorgenommen wurden. Die damit vereinbarte wissenschaftliche Kooperation hat die folgenden Ziele: \item{die am GFZ vorhandenen Algorithmen und Softwaremodule auf ihre Effizienz hisichtlich Nutzung der Rechnerresourcen zu untersuchen und L{\"o}sungen f{\"u}r einen schnelleren Datendurchsatz zu entwickeln und zu implementieren,} \item{Methoden zur Regularisierung und L{\"o}sung schlecht konditionierter Normalgleichungssysteme (f{\"u}r Schwerefeldkoeffizienten) kritisch zu untersuchen und eine mathematisch objektive Strategie der Regularisierung zu entwickeln, und} \item{insbesondere im Hinblick auf die Anforderungen bei GRACE, verschiedene Bahnintegrationsverfahren hinsichtlich ihrer numerischen Genauigkeit und Einsatzm{\"o}glichkeiten zu untersuchen.}}, language = {de} } @misc{SchlegelMarquardtEhrigetal., author = {Schlegel, Martin and Marquardt, Wolfgang and Ehrig, Rainald and Nowak, Ulrich}, title = {Sensitivity analysis of linearly-implicit differential-algebraic systems by one-step extrapolation}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-7052}, number = {02-38}, abstract = {In this work we present an approach for the sensitivity analysis of linearly-implicit differential-algebraic equation systems. Solutions for both, states and sensitivities are obtained by applying an extrapolated linearly implicit Euler discretization scheme. This approach is compared to the widely used sensitivity extensions of multi-step BDF methods by means of case studies. Especially, we point out the benefit of this method in the context of dynamic optimization using the sequential approach.}, language = {en} } @misc{EhrigOfenlochSchaberetal., author = {Ehrig, Rainald and Ofenloch, Oliver and Schaber, Karlheinz and Deuflhard, Peter}, title = {Modelling and Simulation of Aerosol Formation by Heterogeneous Nucleation in Gas-Liquid Contact Devices}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6416}, number = {01-15}, abstract = {This paper describes a new simulation tool for the prediction of aerosol formation and behavior in gas--liquid contact devices such as absorbers, scrubbers, quench coolers, and condensers as well as multistage gas cleaning processes, respectively. Aerosol formation can impact severely the separation efficiency of gas cleaning processes. Aerosol or fog formation can arise by spontaneous condensation or desublimation in supersaturated gas phases. The rigorous description of the mass and energy transfer between the gas phase, the liquid phase, and the growing aerosol droplets leads to a system of partial differential and algebraic equations. For the solution of these systems we have developed the plant simulation tool AerCoDe. This program bases upon the linearly--implicit Euler discretisation, which in combination with extrapolation permits an adaptive step size and order control. Typical simulation results of a multistage industrial flue gas scrubbing process are presented. It is shown, that experimental data can be confirmed if the number concentration of condensation nuclei as an input parameter is roughly known.}, language = {en} } @misc{EhrigNowakDeuflhard, author = {Ehrig, Rainald and Nowak, Ulrich and Deuflhard, Peter}, title = {Highly scalable parallel linearly-implicit extrapolation algorithms}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5405}, number = {TR-96-11}, abstract = {We present parallel formulations of the well established extrapolation algorithms EULSIM and LIMEX and its implementation on a distributed memory architecture. The discretization of partial differential equations by the method of lines yields large banded systems, which can be efficiently solved in parallel only by iterative methods. Polynomial preconditioning with a Neumann series expansion combined with an overlapping domain decomposition appears as a very efficient, robust and highly scalable preconditioner for different iterative solvers. A further advantage of this preconditioner is that all computation can be restricted to the overlap region as long as the subdomain problems are solved exactly. With this approach the iterative algorithms operate on very short vectors, the length of the vectors depends only on the number of gridpoints in the overlap region and the number of processors, but not on the size of the linear system. As the most reliable and fast iterative methods based on this preconditioning scheme appeared GMRES or FOM and BICGSTAB. To further reduce the number of iterations in GMRES or FOM we can reuse the Krylov-spaces constructed in preceeding extrapolation steps. The implementation of the method within the program LIMEX results in a highly parallel and scalable program for solving differential algebraic problems getting an almost linear speedup up to 64 processors even for medium size problems. Results are presented for a difficult application from chemical engineering simulating the formation of aerosols in industrial gas exhaust purification.}, language = {en} } @misc{EhrigNowakDeuflhard, author = {Ehrig, Rainald and Nowak, Ulrich and Deuflhard, Peter}, title = {Massively Parallel Linearly-Implicit Extrapolation Algorithms as a Powerful Tool in Process Simulation.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3127}, number = {SC-97-43}, abstract = {We study the parallelization of linearly--implicit extrapolation codes for the solution of large scale PDE systems and differential algebraic equations on distributed memory machines. The main advantage of these algorithms is that they enable adapativity both in time and space. Additive Krylov--Schwarz methods yield high parallel perfomance for such extrapolation methods. Our approach combines a slightly overlapping domain decomposition together with a polynomial block Neumann preconditioner and a reduced system technique. Furthermore we get important advantages through the explicit computation of the matrix--products of the preconditioner and the matrix of the linear system. The parallel algorithms exhibit scalability up to 64 processors already for medium--sized test problems. We show that the codes are really efficient in large application systems for chemical engineering problems.}, language = {en} } @misc{EhrigDeuflhard, author = {Ehrig, Rainald and Deuflhard, Peter}, title = {GMERR - an Error Minimizing Variant of GMRES}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3323}, number = {SC-97-63}, abstract = {The paper analyzes a recently proposed iterative error minimizing method for the solution of linear systems. Sufficient and necessary conditions for convergence are studied, which show that the method essentially requires normal matrices. An efficient implementation similar to GMRES has been worked out in detail. Numerical tests on general non--normal matrices, of course, indicate that this approach is not competitive with GMRES. Summarizing, if error minimizing is important, one should rather choose CGNE. A computational niche for GMERR might be problems, where normal but non--symmetric matrices occur, like dissipative quantum mechanics.}, language = {en} } @misc{NowakEhrigOeverdieck, author = {Nowak, Ulrich and Ehrig, Rainald and Oeverdieck, Lars}, title = {Parallel Extrapolation Methods and Their Application in Chemical Engineering}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3387}, number = {SC-97-69}, abstract = {We study the parallelization of linearly--implicit extrapolation methods for the solution of large scale systems of differential algebraic equations arising in a method of lines (MOL ) treatment of partial differential equations. In our approach we combine a slightly overlapping domain decomposi tion together with a polynomial block Neumann preconditioner. Through the explicit computation of the matrix products of the pre conditioner and the system matrix a significant gain in overall efficiency is achieved for medium--sized problems. The parallel algorithm exhibits a good scalability up to 32 proces sors on a Cray T3E. Preliminary results for computations on a workstation cluster are reported.}, language = {en} } @article{BergmannGraichenRohlmannetal.2008, author = {Bergmann, G. and Graichen, F. and Rohlmann, A. and Bender, Alwina and Ehrig, Rainald and Westerhoff, P. and Heinlein, B.}, title = {Design and calibration of load sensing orthopaedic implants}, series = {Journal Biomech. Eng.}, journal = {Journal Biomech. Eng.}, pages = {02109 -- 1-02109-9}, year = {2008}, language = {en} } @article{SchaberKoerberOfenlochetal.2002, author = {Schaber, Karlheinz and Koerber, Jens and Ofenloch, O. and Ehrig, Rainald and Deuflhard, Peter}, title = {Aerosol Formation in Gas-Liquid Contact Devices- Nucleation, Growth and Particle Dynamics}, series = {Chem.Eng.Sci.}, volume = {57}, journal = {Chem.Eng.Sci.}, pages = {4345 -- 4356}, year = {2002}, language = {en} } @inproceedings{NowakEhrigOeverdieck1998, author = {Nowak, Ulrich and Ehrig, Rainald and Oeverdieck, Lars}, title = {Parallel Extrapolation Methods and Their Application in Chemical Engineering}, series = {High-Performance Computing and Networking}, volume = {1401}, booktitle = {High-Performance Computing and Networking}, editor = {Sloot, P. and Bubak, Marian and Hertzberger, B.}, publisher = {Springer}, pages = {419 -- 428}, year = {1998}, language = {en} } @article{SchlegelMarquardtEhrigetal.2004, author = {Schlegel, Martin and Marquardt, Wolfgang and Ehrig, Rainald and Nowak, Ulrich}, title = {Sensitivity analysis of linearly-implicit differential-algebraic systems by one-step extrapolation}, series = {Applied Numerical Mathematics}, journal = {Applied Numerical Mathematics}, number = {48}, pages = {83 -- 102}, year = {2004}, language = {en} } @article{EhrigTaylorDudaetal.2006, author = {Ehrig, Rainald and Taylor, William R. and Duda, G. and Heller, Markus O.}, title = {A Survey for Formal Methods for Determining the Centre of Ball Joints}, series = {Journal of Biomechanics}, journal = {Journal of Biomechanics}, number = {39}, pages = {2798 -- 2809}, year = {2006}, language = {en} } @inproceedings{EhrigTaylorDudaetal.2006, author = {Ehrig, Rainald and Taylor, William R. and Duda, G. and Heller, Markus O.}, title = {A New Approach for the Determination of Joint Axes}, series = {Proceedings of the 52th Annual Meeting of the Orthopedic Society}, booktitle = {Proceedings of the 52th Annual Meeting of the Orthopedic Society}, address = {Chicago}, year = {2006}, language = {en} } @inproceedings{EhrigNowakDeuflhard1998, author = {Ehrig, Rainald and Nowak, Ulrich and Deuflhard, Peter}, title = {Massively Parallel Simulation in Chemical Engineering by Extrapolation Algorithms}, series = {Procs. 16th International Workshop on Distributed Data Processing, Novosibirsk, Russia}, booktitle = {Procs. 16th International Workshop on Distributed Data Processing, Novosibirsk, Russia}, editor = {Khoroshevsky, V.}, pages = {1 -- 6}, year = {1998}, language = {en} } @incollection{EhrigNowakOeverdiecketal.1999, author = {Ehrig, Rainald and Nowak, Ulrich and Oeverdieck, Lars and Deuflhard, Peter}, title = {Advanced Extrapolation Methods for Large Scale Differential Algebraic Problems}, series = {High Performance Scientific and Engineering Computing}, volume = {8}, booktitle = {High Performance Scientific and Engineering Computing}, editor = {H.-J. Bungartz, F.}, publisher = {Springer Verlag}, pages = {233 -- 244}, year = {1999}, language = {en} } @article{EhrigOfenlochSchaberetal.2002, author = {Ehrig, Rainald and Ofenloch, O. and Schaber, Karlheinz and Deuflhard, Peter}, title = {Modelling and Simulation of Aerosol Formation by Heterogeneous Nucleation in Gas-Liquid Contact Devices}, series = {Chem.Eng.Sci.}, volume = {57}, journal = {Chem.Eng.Sci.}, number = {7}, pages = {1151 -- 1163}, year = {2002}, language = {en} } @article{HellerDudaEhrigetal.2005, author = {Heller, Markus O. and Duda, Georg and Ehrig, Rainald and Schell, H. and Seebeck, P. and Taylor, William R.}, title = {Muskuloskeletale Belastungen im Schafshinterlauf}, series = {Materialwissenschaft und Werkstofftechnik}, journal = {Materialwissenschaft und Werkstofftechnik}, number = {36}, pages = {775 -- 780}, year = {2005}, language = {en} } @inproceedings{HellerDudaKoenigetal.2005, author = {Heller, Markus O. and Duda, G. and K{\"o}nig, Christian and Taylor, William R. and Ehrig, Rainald and Hinterwimmer, S. and Graichen, H.}, title = {Validation of a New Model of Human Knee Kinematics against in Vivo Data under Physiologic Neuromuscular Activation Patterns}, series = {Proceedings of the 51th Annual Meeting of the Orthopedic Society}, booktitle = {Proceedings of the 51th Annual Meeting of the Orthopedic Society}, address = {Washington}, year = {2005}, language = {en} } @article{HellerKoenigGraichenetal.2007, author = {Heller, Markus O. and K{\"o}nig, Christian and Graichen, F. and Hinterwimmer, S. and Ehrig, Rainald and Duda, G. and Taylor, William R.}, title = {A new model to predict in vivo human knee kinematics under physiological-like muscle activation}, series = {Journal of Biomechanics}, journal = {Journal of Biomechanics}, pages = {45 -- 53}, year = {2007}, language = {en} } @article{KoerberSchaberEhrigetal.1998, author = {Koerber, Jens and Schaber, Karlheinz and Ehrig, Rainald and Deuflhard, Peter}, title = {Modelling and simulation of aerosol formation in absorption processes}, series = {J. Aerosol Sci}, volume = {29}, journal = {J. Aerosol Sci}, pages = {579 -- 580}, year = {1998}, language = {en} } @inproceedings{KratzensteinTaylorEhrigetal.2009, author = {Kratzenstein, Stefan and Taylor, William R. and Ehrig, Rainald and Heller, Markus O.}, title = {Reduction of the influence of skin marker artefacts using the optimal common shape technique}, series = {Annual meeting of the ESMAC 2009}, booktitle = {Annual meeting of the ESMAC 2009}, address = {London}, year = {2009}, language = {en} } @inproceedings{KassiTaylorSchwarzkopfetal.2004, author = {Kassi, J.-P. and Taylor, William R. and Schwarzkopf, J. and Schell, H. and Duda, G. and Ehrig, Rainald}, title = {Wie sind Osteosynthesesysteme und Defektzonen in vivo belastet?}, series = {68. Jahrestagung der Deutschen Gesellschaft f{\"u}r Unfallchirurgie in Verbindung mit dem Deutschen Orthop{\"a}denkongress}, booktitle = {68. Jahrestagung der Deutschen Gesellschaft f{\"u}r Unfallchirurgie in Verbindung mit dem Deutschen Orthop{\"a}denkongress}, address = {Berlin}, year = {2004}, language = {en} } @article{KratzensteinKornaropoulosEhrigetal.2012, author = {Kratzenstein, Stefan and Kornaropoulos, Evgenios I. and Ehrig, Rainald and Heller, Markus O. and P{\"o}pplau, Berry M. and Taylor, William R.}, title = {Effective marker placement for functional identification of the centre of rotation at the hip}, series = {Gait \& Posture}, volume = {36}, journal = {Gait \& Posture}, number = {3}, doi = {http://dx.doi.org/10.1016/j.gaitpost.2012.04.011}, pages = {482 -- 486}, year = {2012}, language = {en} } @article{StoetzelEhrigBoeretal., author = {St{\"o}tzel, Claudia and Ehrig, Rainald and Boer, H. Marike T. and Pl{\"o}ntzke, Julia and R{\"o}blitz, Susanna}, title = {Exploration of different wave patterns in a model of the bovine estrous cycle by Fourier analysis}, series = {BIOMAT - Proceedings of the 14th International Symposium on Mathematical and Computational Biology, Bedlewo, Poland}, journal = {BIOMAT - Proceedings of the 14th International Symposium on Mathematical and Computational Biology, Bedlewo, Poland}, abstract = {Cows typically have different numbers of follicular waves during their hormonal cycle. Understanding the underlying regulations leads to insights into the reasons for declined fertility, a phenomenon that has been observed during the last decades. We present a systematic approach based on Fourier analysis to examine how parameter changes in a model of the bovine estrous cycle lead to different wave patterns. Even without any biological considerations, this allows to detect the responsible model parameters that control the type of periodicity of the solution, thus supporting experimental planning of animal scientists.}, language = {en} } @article{MoualeuNgangueWeiserEhrigetal., author = {Moualeu-Ngangue, Dany Pascal and Weiser, Martin and Ehrig, Rainald and Deuflhard, Peter}, title = {Optimal control for a tuberculosis model with undetected cases in Cameroon}, series = {Communications in Nonlinear Science and Numerical Simulation}, volume = {20}, journal = {Communications in Nonlinear Science and Numerical Simulation}, number = {3}, doi = {10.1016/j.cnsns.2014.06.037}, pages = {986 -- 1003}, abstract = {This paper considers the optimal control of tuberculosis through education, diagnosis campaign and chemoprophylaxis of latently infected. A mathematical model which includes important components such as undiagnosed infectious, diagnosed infectious, latently infected and lost-sight infectious is formulated. The model combines a frequency dependent and a density dependent force of infection for TB transmission. Through optimal control theory and numerical simulations, a cost-effective balance of two different intervention methods is obtained. Seeking to minimize the amount of money the government spends when tuberculosis remain endemic in the Cameroonian population, Pontryagin's maximum principle is used to characterize the optimal control. The optimality system is derived and solved numerically using the forward-backward sweep method (FBSM). Results provide a framework for designing cost-effective strategies for diseases with multiple intervention methods. It comes out that combining chemoprophylaxis and education, the burden of TB can be reduced by 80 \% in 10 years.}, language = {en} } @article{HengartnerKruegerGeraedtsetal., author = {Hengartner, Michael and Kr{\"u}ger, Tillmann H. C. and Geraedts, Kirsten and Tronci, Enrico and Mancini, Toni and Ille, Fabian and Egli, Marcel and R{\"o}blitz, Susanna and Ehrig, Rainald and Saleh, Lanja and Spanaus, Katharina and Schippert, Cordula and Zhang, Yuanyuan and Leeners, Brigitte}, title = {Negative affect is unrelated to fluctuations in hormone levels across the menstrual cycle: evidence from a multisite observational study across two successive cycles}, series = {Journal of Psychosomatic Research}, volume = {99}, journal = {Journal of Psychosomatic Research}, doi = {10.1016/j.jpsychores.2017.05.018}, pages = {21 -- 27}, language = {en} } @article{MoewisBoethHelleretal., author = {Moewis, Philippe and Boeth, Heide and Heller, Markus O. and Yntema, Caroline and Jung, Tobias and Doyscher, Ralf and Ehrig, Rainald and Zhong, Yanlin and Taylor, William R.}, title = {Towards understanding knee joint laxity: Errors in non-invasive assessment of joint rotation can be corrected}, series = {Medical Engineering and Physics}, volume = {36}, journal = {Medical Engineering and Physics}, number = {7}, doi = {doi.org/10.1016/j.medengphy.2014.03.017}, pages = {889 -- 895}, language = {en} } @article{EhrigHeller, author = {Ehrig, Rainald and Heller, Markus O.}, title = {On intrinsic equivalences of the finite helical axis, the instantaneous helical axis, and the SARA approach. A mathematical perspective.}, series = {Journal of Biomechanics}, volume = {84}, journal = {Journal of Biomechanics}, doi = {10.1016/j.jbiomech.2018.12.034}, pages = {4 -- 10}, language = {en} } @article{LangVolkamerBehmetal., author = {Lang, Annemarie and Volkamer, Andrea and Behm, Laura and R{\"o}blitz, Susanna and Ehrig, Rainald and Schneider, Marlon and Geris, Lisbet and Wichard, Joerg and Buttgereit, Frank}, title = {In silico Methods - Computational Alternatives to Animal Testing}, series = {ALTEX}, volume = {35}, journal = {ALTEX}, number = {1}, doi = {10.14573/altex.1712031}, pages = {126 -- 128}, abstract = {A seminar and interactive workshop on "In silico Methods - Computational Alternatives to Animal Testing" was held in Berlin, Germany, organized by Annemarie Lang, Frank Butt- gereit and Andrea Volkamer at the Charit{\´e}-Universit{\"a}tsmedizin Berlin, on August 17-18, 2017. During the half-day seminar, the variety and applications of in silico methods as alternatives to animal testing were presented with room for scientific discus- sions with experts from academia, industry and the German fed- eral ministry (Fig. 1). Talks on computational systems biology were followed by detailed information on predictive toxicology in order to display the diversity of in silico methods and the potential to embrace them in current approaches (Hartung and Hoffmann, 2009; Luechtefeld and Hartung, 2017). The follow- ing interactive one-day Design Thinking Workshop was aimed at experts, interested researchers and PhD-students interested in the use of in silico as alternative methods to promote the 3Rs (Fig. 2). Forty participants took part in the seminar while the workshop was restricted to sixteen participants.}, language = {en} } @inproceedings{TaylorKratzensteinKornaropoulosetal.2009, author = {Taylor, William R. and Kratzenstein, Stefan and Kornaropoulos, Evgenios I. and Ehrig, Rainald and Moewis, Philippe and Heller, Markus O.}, title = {Non-invasive Assessment of Skeletal Kinematics}, series = {Measurement and Sensing in Medicine and Health}, booktitle = {Measurement and Sensing in Medicine and Health}, address = {London}, year = {2009}, language = {en} } @inproceedings{TaylorKornaropoulosKratzensteinetal.2011, author = {Taylor, William R. and Kornaropoulos, Evgenios I. and Kratzenstein, Stefan and Ehrig, Rainald and Plank, F. and Heller, Markus O.}, title = {Targeted Marker Placement for the Functional Identification of the Hip Joint Centre}, series = {Transactions Vol. 36, 2011 Annual Meeting of the Orthopedic Society}, booktitle = {Transactions Vol. 36, 2011 Annual Meeting of the Orthopedic Society}, address = {Long Beach}, year = {2011}, language = {en} } @inproceedings{TaylorKoenigSpeirsetal.2006, author = {Taylor, William R. and K{\"o}nig, Christian and Speirs, A. and Ehrig, Rainald and Duda, G. and Heller, Markus O.}, title = {The medio-lateral force distribution in the sheep knee during walking}, series = {5. World Congress of Biomechanics, Munich, Journal of Biomechanics}, booktitle = {5. World Congress of Biomechanics, Munich, Journal of Biomechanics}, number = {39, Suppl. 1}, pages = {S491}, year = {2006}, language = {en} } @inproceedings{TaylorKoenigSpeirsetal.2006, author = {Taylor, William R. and K{\"o}nig, Christian and Speirs, A. and Ehrig, Rainald and Duda, G. and Heller, Markus O.}, title = {Die medio-laterale Kraftverteilung im Schafsknie}, series = {Deutscher Kongress f{\"u}r Orthp{\"a}die und Unfallchirurgie, Berlin}, booktitle = {Deutscher Kongress f{\"u}r Orthp{\"a}die und Unfallchirurgie, Berlin}, year = {2006}, language = {en} } @inproceedings{TaylorKassiSchwarzkopfetal.2005, author = {Taylor, William R. and Kassi, J.-P. and Schwarzkopf, J. and Ehrig, Rainald and Schell, H. and Duda, G.}, title = {The Profile of Mechanical Loading is Independent of Fracture Fixation Principle}, series = {Proceedings of the 51th Annual Meeting of the Orthopedic Society}, booktitle = {Proceedings of the 51th Annual Meeting of the Orthopedic Society}, address = {Washington}, year = {2005}, language = {en} } @article{SchaberOfenlochEhrigetal.2004, author = {Schaber, Karlheinz and Ofenloch, Oliver and Ehrig, Rainald and Deuflhard, Peter}, title = {Aerosolbildung in Gas/Fl{\"u}ssigkeits-Kontaktapparaten - Modellierungsstrategien und Simulation}, series = {Chemie Ingenieur Technik}, volume = {76}, journal = {Chemie Ingenieur Technik}, number = {9}, pages = {1358 -- 1359}, year = {2004}, language = {en} } @inproceedings{TaylorEhrigDudaetal.2006, author = {Taylor, William R. and Ehrig, Rainald and Duda, G. and Heller, Markus O.}, title = {The determination of joint axes}, series = {5. World Congress of Biomechanics, Munich, Journal of Biomechanics}, booktitle = {5. World Congress of Biomechanics, Munich, Journal of Biomechanics}, number = {39, Suppl. 1}, pages = {S571 -- S572}, year = {2006}, language = {en} } @inproceedings{TaylorEhrigDudaetal.2006, author = {Taylor, William R. and Ehrig, Rainald and Duda, G. and Heller, Markus O.}, title = {The Symmetrical Axis of Rotation Approach (SARA) for Determination of Joint Axes in Clinical Gait Analysis}, series = {1st Joint ESMAC-GCMAS Meeting, Amsterdam}, booktitle = {1st Joint ESMAC-GCMAS Meeting, Amsterdam}, year = {2006}, language = {en} } @inproceedings{TaylorEhrigHelleretal.2004, author = {Taylor, William R. and Ehrig, Rainald and Heller, Markus O. and Schell, H. and Duda, G.}, title = {Can Skin Markers Determine the Kinematics of Underlying Bones?}, series = {Proceedings of the 50th Annual Meeting of the Orthopedic Society}, booktitle = {Proceedings of the 50th Annual Meeting of the Orthopedic Society}, address = {San Francisco}, year = {2004}, language = {en} } @article{TaylorEhrigHelleretal.2005, author = {Taylor, William R. and Ehrig, Rainald and Heller, Markus O. and Schell, H. and Klein, P. and Duda, G.}, title = {On the Influence of Soft Tissue Coverage in the Determination of Bone Kinematics using Bone Markers}, series = {Journal of Orthopedic Research}, journal = {Journal of Orthopedic Research}, number = {23}, pages = {726 -- 734}, year = {2005}, language = {en} } @inproceedings{TaylorEhrigHelleretal.2005, author = {Taylor, William R. and Ehrig, Rainald and Heller, Markus O. and Schell, H. and Seebeck, P. and Duda, G.}, title = {Animal Models for Knee Injury Frequently Underestimate the Mechanical Conditions of the Clinical Situation}, series = {Proceedings of the 51th Annual Meeting of the Orthopedic Society}, booktitle = {Proceedings of the 51th Annual Meeting of the Orthopedic Society}, address = {Washington}, year = {2005}, language = {en} } @article{TaylorEhrigHelleretal.2006, author = {Taylor, William R. and Ehrig, Rainald and Heller, Markus O. and Schell, H. and Seebeck, P. and Duda, G.}, title = {Tibio-femoral Joint Contact Forces in Sheep}, series = {Journal of Biomechanics}, journal = {Journal of Biomechanics}, number = {39}, pages = {791 -- 798}, year = {2006}, language = {en} } @article{WixSchaberOfenlochetal.2007, author = {Wix, A. and Schaber, Karlheinz and Ofenloch, O. and Ehrig, Rainald and Deuflhard, Peter}, title = {Simulation of Aerosol Formation in Gas-Liquid Contact Devices}, series = {Chem. Eng. Comm.}, volume = {194}, journal = {Chem. Eng. Comm.}, pages = {565 -- 577}, year = {2007}, language = {en} } @misc{StoetzelEhrigBoeretal., author = {St{\"o}tzel, Claudia and Ehrig, Rainald and Boer, H. Marike T. and Pl{\"o}ntzke, Julia and R{\"o}blitz, Susanna}, title = {Exploration of different wave patterns in a model of the bovine estrous cycle by Fourier analysis}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-57039}, abstract = {Cows typically have different numbers of follicular waves during their hormonal cycle. Understanding the underlying regulations leads to insights into the reasons for declined fertility, a phenomenon that has been observed during the last decades. We present a systematic approach based on Fourier analysis to examine how parameter changes in a model of the bovine estrous cycle lead to different wave patterns. Even without any biological considerations, this allows to detect the responsible model parameters that control the type of periodicity of the solution, thus supporting experimental planning of animal scientists.}, language = {en} } @inproceedings{HajizadehSchuetzListetal., author = {Hajizadeh, Maryam and Sch{\"u}tz, Pascal and List, Renate and Boeth, Heide and Ehrig, Rainald and Postolka, Barbara and Freeman, Michael A. R. and Taylor, William R.}, title = {Interpretation of tibio-femoral kinematics critically depends upon the kinematic analysis approach}, series = {ISB 2015, 25th congress of the International Society of Biomechanics, Glasgow}, booktitle = {ISB 2015, 25th congress of the International Society of Biomechanics, Glasgow}, language = {en} } @misc{MoualeuNgangueRoeblitzEhrigetal., author = {Moualeu-Ngangue, Dany Pascal and R{\"o}blitz, Susanna and Ehrig, Rainald and Deuflhard, Peter}, title = {Parameter Identification for a Tuberculosis Model in Cameroon}, issn = {1438-0064}, doi = {10.1371/journal.pone.0120607}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-43087}, abstract = {A deterministic model of tuberculosis in sub-Saharan Africa in general and Cameroon in particular including lack of access to the treatment and weak diagnose capacity is designed and analyzed with respect to its transmission dynamics. The model includes both frequency- and density-dependent transmissions. It is shown that the model is mathematically well-posed and epidemiologically reasonable. Solutions are non-negative and bounded whenever the initial values are non-negative. A sensitivity analysis of model parameters is performed and most sensitive parameters of the model are identified using a state-of-the-art Gauss-Newton Method. In particular, parameters representing the proportion of individuals having access to medical facilities have a large impact on the dynamics of the disease. It has been shown that an increase of these parameter values over the time can significantly reduce the disease burden in the population within the next 15 years.}, language = {en} } @misc{MoualeuNgangueWeiserEhrigetal., author = {Moualeu-Ngangue, Dany Pascal and Weiser, Martin and Ehrig, Rainald and Deuflhard, Peter}, title = {Optimal control for a tuberculosis model with undetected cases in Cameroon}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-43142}, abstract = {This paper considers the optimal control of tuberculosis through education, diagnosis campaign and chemoprophylaxis of latently infected. A mathematical model which includes important components such as undiagnosed infectious, diagnosed infectious, latently infected and lost-sight infectious is formulated. The model combines a frequency dependent and a density dependent force of infection for TB transmission. Through optimal control theory and numerical simulations, a cost-effective balance of two different intervention methods is obtained. Seeking to minimize the amount of money the government spends when tuberculosis remain endemic in the Cameroonian population, Pontryagin's maximum principle is used to characterize the optimal control. The optimality system is derived and solved numerically using the forward-backward sweep method (FBSM). Results provide a framework for designing cost-effective strategies for diseases with multiple intervention methods. It comes out that combining chemoprophylaxis and education, the burden of TB can be reduced by 80 \% in 10 years}, language = {en} } @article{MoualeuNgangueRoeblitzEhrigetal., author = {Moualeu-Ngangue, Dany Pascal and R{\"o}blitz, Susanna and Ehrig, Rainald and Deuflhard, Peter}, title = {Parameter Identification in a Tuberculosis Model for Cameroon}, series = {PLOS ONE}, journal = {PLOS ONE}, doi = {10.1371/journal.pone.0120607}, abstract = {A deterministic model of tuberculosis in Cameroon is designed and analyzed with respect to its transmission dynamics. The model includes lack of access to treatment and weak diagnosis capacity as well as both frequency- and density-dependent transmissions. It is shown that the model is mathematically well-posed and epidemiologically reasonable. Solutions are non-negative and bounded whenever the initial values are non-negative. A sensitivity analysis of model parameters is performed and the most sensitive ones are identified by means of a state-of-the-art Gauss-Newton method. In particular, parameters representing the proportion of individuals having access to medical facilities are seen to have a large impact on the dynamics of the disease. The model predicts that a gradual increase of these parameters could significantly reduce the disease burden on the population within the next 15 years.}, language = {en} } @article{WeberFischerDamerauetal., author = {Weber, Marie-Christin and Fischer, Lisa and Damerau, Alexandra and Ponomarev, Igor and Pfeiffenberger, Moritz and Gaber, Timo and G{\"o}tschel, Sebastian and Lang, Jens and R{\"o}blitz, Susanna and Buttgereit, Frank and Ehrig, Rainald and Lang, Annemarie}, title = {In vitro and in silico modeling of cellular and matrix-related changes during the early phase of osteoarthritis}, series = {BioRxiv}, journal = {BioRxiv}, doi = {10.1101/725317}, abstract = {Understanding the pathophysiological processes of osteoarthritis (OA) require adequate model systems. Although different in vitro or in vivo models have been described, further comprehensive approaches are needed to study specific parts of the disease. This study aimed to combine in vitro and in silico modeling to describe cellular and matrix-related changes during the early phase of OA. We developed an in vitro OA model based on scaffold-free cartilage-like constructs (SFCCs), which was mathematically modeled using a partial differential equation (PDE) system to resemble the processes during the onset of OA. SFCCs were produced from mesenchymal stromal cells and analyzed weekly by histology and qPCR to characterize the cellular and matrix-related composition. To simulate the early phase of OA, SFCCs were treated with interleukin-1β (IL-1β), tumor necrosis factor α (TNFα) and examined after 3 weeks or cultivated another 3 weeks without inflammatory cytokines to validate the regeneration potential. Mathematical modeling was performed in parallel to the in vitro experiments. SFCCs expressed cartilage-specific markers, and after stimulation an increased expression of inflammatory markers, matrix degrading enzymes, a loss of collagen II (Col-2) and a reduced cell density was observed which could be partially reversed by retraction of stimulation. Based on the PDEs, the distribution processes within the SFCCs, including those of IL-1β, Col-2 degradation and cell number reduction was simulated. By combining in vitro and in silico methods, we aimed to develop a valid, efficient alternative approach to examine and predict disease progression and new therapeutic strategies.}, language = {en} } @article{LangFischerWeberetal., author = {Lang, Annemarie and Fischer, Lisa and Weber, Marie-Christin and Gaber, Timo and Ehrig, Rainald and R{\"o}blitz, Susanna and Buttgereit, Frank}, title = {Combining in vitro simulation and in silico modelling towards a sophisticated human osteoarthritis model}, series = {Osteoarthritis and Cartilage}, volume = {27}, journal = {Osteoarthritis and Cartilage}, doi = {10.1016/j.joca.2019.02.277}, pages = {S183}, abstract = {Our project aimed at building an in silico model based on our recently developed in vitro osteoarthritis (OA) model seeking for refinement of the model to enhance validity and translatability towards the more sophisticated simulation of OA. In detail, the previously 3D in vitro model is based on 3D chondrogenic constructs generated solely from human bone marrow derived mesenchymal stromal cells (hMSCs). Besides studying the normal state of the model over 3 weeks, the in vitro model was treated with interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNFα) to mimic an OA-like environment.}, language = {en} } @article{WeberFischerDamerauetal., author = {Weber, Marie-Christin and Fischer, Lisa and Damerau, Alexandra and Ponomarev, Igor and Pfeiffenberger, Moritz and Gaber, Timo and G{\"o}tschel, Sebastian and Lang, Jens and R{\"o}blitz, Susanna and Buttgereit, Frank and Ehrig, Rainald and Lang, Annemarie}, title = {Macroscale mesenchymal condensation to study cytokine-driven cellular and matrix-related changes during cartilage degradation}, series = {Biofabrication}, volume = {12}, journal = {Biofabrication}, number = {4}, doi = {10.1088/1758-5090/aba08f}, abstract = {Understanding the pathophysiological processes of cartilage degradation requires adequate model systems to develop therapeutic strategies towards osteoarthritis (OA). Although different in vitro or in vivo models have been described, further comprehensive approaches are needed to study specific disease aspects. This study aimed to combine in vitro and in silico modeling based on a tissue-engineering approach using mesenchymal condensation to mimic cytokine-induced cellular and matrix-related changes during cartilage degradation. Thus, scaffold-free cartilage-like constructs (SFCCs) were produced based on self-organization of mesenchymal stromal cells (mesenchymal condensation) and i) characterized regarding their cellular and matrix composition or secondly ii) treated with interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) for 3 weeks to simulate OA-related matrix degradation. In addition, an existing mathematical model based on partial differential equations was optimized and transferred to the underlying settings to simulate distribution of IL-1β, type II collagen degradation and cell number reduction. By combining in vitro and in silico methods, we aim to develop a valid, efficient alternative approach to examine and predict disease progression and effects of new therapeutics.}, language = {en} }