@article{MennickenPeterKaulenetal.2020, author = {Mennicken, Max and Peter, Sophia K. and Kaulen, Corinna and Simon, Ulrich and Karth{\"a}user, Silvia}, title = {Transport through Redox-Active Ru-Terpyridine Complexes Integrated in Single Nanoparticle Devices}, series = {The Journal of Physical Chemistry C}, volume = {124}, journal = {The Journal of Physical Chemistry C}, number = {8}, publisher = {ACS Publications}, address = {Washington, DC}, issn = {1932-7455}, doi = {10.1021/acs.jpcc.9b11716}, pages = {4881 -- 4889}, year = {2020}, abstract = {Transition metal complexes are electrofunctional molecules due to their high conductivity and their intrinsic switching ability involving a metal-to-ligand charge transfer. Here, a method is presented to contact reliably a few to single redox-active Ru-terpyridine complexes in a CMOS compatible nanodevice and preserve their electrical functionality. Using hybrid materials from 14 nm gold nanoparticles (AuNP) and bis-{4′-[4-(mercaptophenyl)-2,2′:6′,2″-terpyridine]}-ruthenium(II) complexes a device size of 30² nm² inclusive nanoelectrodes is achieved. Moreover, this method bears the opportunity for further downscaling. The Ru-complex AuNP devices show symmetric and asymmetric current versus voltage curves with a hysteretic characteristic in two well separated conductance ranges. By theoretical approximations based on the single-channel Landauer model, the charge transport through the formed double-barrier tunnel junction is thoroughly analyzed and its sensibility to the molecule/metal contact is revealed. It can be verified that tunneling transport through the HOMO is the main transport mechanism while decoherent hopping transport is present to a minor extent.}, language = {en} } @article{VoegeleGrajewskiGovorukhaetal.2020, author = {V{\"o}gele, Stefan and Grajewski, Matthias and Govorukha, Kristina and R{\"u}bbelke, Dirk}, title = {Challenges for the European steel industry: Analysis, possible consequences and impacts on sustainable development}, series = {Applied Energy}, volume = {264}, journal = {Applied Energy}, number = {Article number: 114633}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0306-2619}, doi = {10.1016/j.apenergy.2020.114633}, year = {2020}, abstract = {The steel industry in the European Union (EU), important for the economy as a whole, faces various challenges. These are inter alia volatile prices for relevant input factors, uncertainties concerning the regulation of CO₂-emissions and market shocks caused by the recently introduced additional import duties in the US, which is an important sales market. We examine primary and secondary effects of these challenges on the steel industry in the EU and their impacts on European and global level. Developing and using a suitable meta-model, we analyze the competitiveness of key steel producing countries with respect to floor prices depending on selected cost factors and draw conclusions on the impacts in the trade of steel on emissions, energy demand, on the involvement of developing countries in the value chain as well on the need for innovations to avoid relocations of production. Hence, our study contributes to the assessment of sustainable industrial development, which is aimed by the Sustainability Development Goal "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation countries". By applying information on country-specific Human Development Indexes (reflecting aspects of life expectancy, education, and per capita income), we show that relocating energy-intensive industries from the EU may not only increase global energy demand and CO₂-emissions, but may also be to the disadvantage of developing countries.}, language = {en} } @article{KnoxBruggemannGossmannetal.2020, author = {Knox, Ronald and Bruggemann, Andrea and Gossmann, Matthias and Thomas, Ulrich and Horv{\´a}th, Andr{\´a}s and Dragicevic, Elena and Stoelzle-Feix, Sonja and Fertig, Niels and Jung, Alexander and Raman, Aravind Hariharan and Staat, Manfred and Linder, Peter}, title = {Combining physiological relevance and throughput for in vitro cardiac contractility measurement}, series = {Biophysical Journal}, volume = {118}, journal = {Biophysical Journal}, number = {Issue 3, Supplement 1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0006-3495}, doi = {10.1016/j.bpj.2019.11.3104}, pages = {570a}, year = {2020}, abstract = {Despite increasing acceptance of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in safety pharmacology, controversy remains about the physiological relevance of existing in vitro models for their mechanical testing. We hypothesize that existing signs of immaturity of the cell models result from an improper mechanical environment. We cultured hiPSC-CMs in a 96-well format on hyperelastic silicone membranes imitating their native mechanical environment, resulting in physiological responses to compound stimuli.We validated cell responses on the FLEXcyte 96, with a set of reference compounds covering a broad range of cellular targets, including ion channel modulators, adrenergic receptor modulators and kinase inhibitors. Acute (10 - 30 min) and chronic (up to 7 days) effects were investigated. Furthermore, the measurements were complemented with electromechanical models based on electrophysiological recordings of the used cell types.hiPSC-CMs were cultured on freely-swinging, ultra-thin and hyperelastic silicone membranes. The weight of the cell culture medium deflects the membranes downwards. Rhythmic contraction of the hiPSC-CMs resulted in dynamic deflection changes which were quantified by capacitive distance sensing. The cells were cultured for 7 days prior to compound addition. Acute measurements were conducted 10-30 minutes after compound addition in standard culture medium. For chronic treatment, compound-containing medium was replaced daily for up to 7 days. Electrophysiological properties of the employed cell types were recorded by automated patch-clamp (Patchliner) and the results were integrated into the electromechanical model of the system.Calcium channel agonist S Bay K8644 and beta-adrenergic stimulator isoproterenol induced significant positive inotropic responses without additional external stimulation. Kinase inhibitors displayed cardiotoxic effects on a functional level at low concentrations. The system-integrated analysis detected alterations in beating shape as well as frequency and arrhythmic events and we provide a quantitative measure of these.}, language = {en} } @article{GrajewskiHronTurek2005, author = {Grajewski, Matthias and Hron, Jaroslav and Turek, Stefan}, title = {Dual weighted a posteriori error estimation for a new nonconforming linear finite element on quadrilaterals}, series = {Applied Numerical Mathematics}, volume = {54}, journal = {Applied Numerical Mathematics}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0168-9274}, doi = {10.1016/j.apnum.2004.09.016}, pages = {504 -- 518}, year = {2005}, abstract = {After a short introduction of a new nonconforming linear finite element on quadrilaterals recently developed by Park, we derive a dual weighted residual-based a posteriori error estimator (in the sense of Becker and Rannacher) for this finite element. By computing a corresponding dual solution we estimate the error with respect to a given target error functional. The reliability and efficiency of this estimator is analyzed in several numerical experiments.}, language = {en} } @article{GrajewskiHronTurek2006, author = {Grajewski, Matthias and Hron, Jaroslav and Turek, Stefan}, title = {Numerical analysis for a new non-conforming linear finite element on quadrilaterals}, series = {Journal of Computational and Applied Mathematics}, volume = {193}, journal = {Journal of Computational and Applied Mathematics}, number = {1}, issn = {0377-0427}, doi = {10.1016/j.cam.2005.05.024}, pages = {38 -- 50}, year = {2006}, language = {en} } @article{GrajewskiKoesterTurek2010, author = {Grajewski, Matthias and K{\"o}ster, Michael and Turek, Stefam}, title = {Numerical analysis and implementational aspects of a new multilevel grid deformation method}, series = {Applied Numerical Mathematics}, volume = {60}, journal = {Applied Numerical Mathematics}, number = {8}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0168-9274}, doi = {10.1016/j.apnum.2010.03.017}, pages = {767 -- 781}, year = {2010}, abstract = {Recently, we introduced and mathematically analysed a new method for grid deformation (Grajewski et al., 2009) [15] we call basic deformation method (BDM) here. It generalises the method proposed by Liao et al. (Bochev et al., 1996; Cai et al., 2004; Liao and Anderson, 1992) [4], [6], [20]. In this article, we employ the BDM as core of a new multilevel deformation method (MDM) which leads to vast improvements regarding robustness, accuracy and speed. We achieve this by splitting up the deformation process in a sequence of easier subproblems and by exploiting grid hierarchy. Being of optimal asymptotic complexity, we experience speed-ups up to a factor of 15 in our test cases compared to the BDM. This gives our MDM the potential for tackling large grids and time-dependent problems, where possibly the grid must be dynamically deformed once per time step according to the user's needs. Moreover, we elaborate on implementational aspects, in particular efficient grid searching, which is a key ingredient of the BDM.}, language = {en} } @article{GrajewskiKoesterTurek2009, author = {Grajewski, Matthias and K{\"o}ster, Michael and Turek, Stefan}, title = {Mathematical and Numerical Analysis of a Robust and Efficient Grid Deformation Method in the Finite Element Context}, series = {SIAM Journal on Scientific Computing}, volume = {31}, journal = {SIAM Journal on Scientific Computing}, number = {2}, publisher = {Society for Industrial and Applied Mathematics}, address = {Philadelphia, Pa.}, doi = {10.1137/050639387}, pages = {1539 -- 1557}, year = {2009}, language = {en} } @article{GoeddekeStrzodkaMohdYusofetal.2007, author = {G{\"o}ddeke, Dominik and Strzodka, Robert and Mohd-Yusof, Jamaludin and McCormick, Patrick and Buijssen, Sven H.M. and Grajewski, Matthias and Turek, Stefan}, title = {Exploring weak scalability for FEM calculations on a GPU-enhanced cluster}, series = {Parallel Computing}, volume = {33}, journal = {Parallel Computing}, number = {10-11}, issn = {0167-8191}, doi = {10.1016/j.parco.2007.09.002}, pages = {685 -- 699}, year = {2007}, language = {en} } @article{DadfarCamozziDarguzyteetal.2020, author = {Dadfar, Dryed Mohammadali and Camozzi, Denise and Darguzyte, Milita and Roemhild, Karolin and Varvar{\`a}, Paola and Metselaar, Josbert and Banala, Srinivas and Straub, Marcel and G{\"u}ver, Nihan and Engelmann, Ulrich M. and Slabu, Ioana and Buhl, Miriam and Leusen, Jan van and K{\"o}gerler, Paul and Hermanns-Sachweh, Benita and Schulz, Volkmar and Kiessling, Fabian and Lammers, Twan}, title = {Size-isolation of superparamagnetic iron oxide nanoparticles improves MRI, MPI and hyperthermia performance}, series = {Journal of Nanobiotechnology}, volume = {18}, journal = {Journal of Nanobiotechnology}, number = {Article number 22}, publisher = {Nature Portfolio}, issn = {1477-3155}, doi = {10.1186/s12951-020-0580-1}, pages = {1 -- 13}, year = {2020}, abstract = {Superparamagnetic iron oxide nanoparticles (SPION) are extensively used for magnetic resonance imaging (MRI) and magnetic particle imaging (MPI), as well as for magnetic fluid hyperthermia (MFH). We here describe a sequential centrifugation protocol to obtain SPION with well-defined sizes from a polydisperse SPION starting formulation, synthesized using the routinely employed co-precipitation technique. Transmission electron microscopy, dynamic light scattering and nanoparticle tracking analyses show that the SPION fractions obtained upon size-isolation are well-defined and almost monodisperse. MRI, MPI and MFH analyses demonstrate improved imaging and hyperthermia performance for size-isolated SPION as compared to the polydisperse starting mixture, as well as to commercial and clinically used iron oxide nanoparticle formulations, such as Resovist® and Sinerem®. The size-isolation protocol presented here may help to identify SPION with optimal properties for diagnostic, therapeutic and theranostic applications.}, language = {en} } @article{AbelKahmannMellonetal.2020, author = {Abel, Alexander and Kahmann, Stephanie Lucina and Mellon, Stephen and Staat, Manfred and Jung, Alexander}, title = {An open-source tool for the validation of finite element models using three-dimensional full-field measurements}, series = {Medical Engineering \& Physics}, volume = {77}, journal = {Medical Engineering \& Physics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1350-4533}, doi = {10.1016/j.medengphy.2019.10.015}, pages = {125 -- 129}, year = {2020}, abstract = {Three-dimensional (3D) full-field measurements provide a comprehensive and accurate validation of finite element (FE) models. For the validation, the result of the model and measurements are compared based on two respective point-sets and this requires the point-sets to be registered in one coordinate system. Point-set registration is a non-convex optimization problem that has widely been solved by the ordinary iterative closest point algorithm. However, this approach necessitates a good initialization without which it easily returns a local optimum, i.e. an erroneous registration. The globally optimal iterative closest point (Go-ICP) algorithm has overcome this drawback and forms the basis for the presented open-source tool that can be used for the validation of FE models using 3D full-field measurements. The capability of the tool is demonstrated using an application example from the field of biomechanics. Methodological problems that arise in real-world data and the respective implemented solution approaches are discussed.}, language = {en} }