@misc{ChunSchmidtKucketal., author = {Chun, K. R. Julian and Schmidt, Boris and Kuck, Karl-Heinz and Andresen, Dietrich and Willems, Stefan and Spitzer, Stefan G. and Hoffmann, Ellen and Schumacher, Burghard and Eckardt, Lars and Seidl, Karlheinz and J{\"u}nger, Claus and Horack, Martin and Brachmann, Johannes and Senges, Jochen}, title = {Catheter ablation of atrial fibrillation in the young}, series = {Clinical Research in Cardiology}, volume = {102}, journal = {Clinical Research in Cardiology}, number = {6}, issn = {1861-0684}, doi = {10.1007/s00392-013-0553-6}, pages = {459 -- 468}, language = {en} } @article{WehnerSchmeisserHoffmann, author = {Wehner, Stefan and Schmeißer, Dieter and Hoffmann, Patrick}, title = {Spatiotemporal patterns of external noise-induced transitions in a bistable reaction-diffusion system : Photoelectron Emission Microscopy experiments and modeling}, language = {en} } @article{HoffmannWehnerSchmeisser, author = {Hoffmann, Patrick and Wehner, Stefan and Schmeißer, Dieter}, title = {Noise-Induced Spatiotemporal Patterns in a Bistable Reaction-Diffusion System: Photoelectron Emission Microscopy experiments and Modeling of the CO Oxidation Reaction on Ir(111)}, language = {en} } @inproceedings{SchmeisserWehnerHoffmannetal., author = {Schmeißer, Dieter and Wehner, Stefan and Hoffmann, Patrick and Brand, Helmut R. and K{\"u}ppers, J{\"u}rgen}, title = {Influence of the Substrate on the Pattern Formation of a Surface Reaction}, series = {Nonequilibrium statistical mechanics and nonlinear physics, XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics, Mar del Plata, Argentina, 4 - 8 December 2006}, booktitle = {Nonequilibrium statistical mechanics and nonlinear physics, XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics, Mar del Plata, Argentina, 4 - 8 December 2006}, editor = {Descalzi, Orazio}, publisher = {AIP Publishing}, address = {Melville, New York}, isbn = {978-0-7354-0421-2}, pages = {121 -- 126}, language = {en} } @misc{HoffmannWehnerSchmeisseretal., author = {Hoffmann, Patrick and Wehner, Stefan and Schmeißer, Dieter and Brand, Helmut R. and K{\"u}ppers, J{\"u}rgen}, title = {Noise-induced spatiotemporal patterns in a bistable reaction-diffusion system: Photoelectron emission micrsoscopy experiments and modeling of the CO oxidation reaction on Ir(111)}, series = {Physical Review : E}, volume = {73}, journal = {Physical Review : E}, number = {5}, issn = {1550-2376}, pages = {056123}, language = {en} } @inproceedings{WehnerHoffmannSchmeisseretal., author = {Wehner, Stefan and Hoffmann, Patrick and Schmeißer, Dieter and Brand, Helmut R. and K{\"u}ppers, J{\"u}rgen}, title = {CO oxidation on Ir(111) surfaces: consequences of anisotropic diffusion and noise}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 475}, abstract = {The CO oxidation reaction on Iridium(111) surfaces shows bistability in a limited range of the CO fraction of the reactant gas flux Y and a wide range of temperatures T. The two branches are characterized by their reactivity for CO2 formation. The upper rate (high CO2 formation) rate is related to high oxygen coverage on the surface, the lower rate (little CO2 formation) to high CO coverage. Quadrupol mass spectroscopy and PEEM (photoelectron emission microscopy) was employed to study the influence of a noisy reactant gas flux composition on the spatio-temporal pattern development in the CO oxidation reaction on flat Ir(111) and stepped Ir(977) surfaces. PEEM shows nucleation and growth of few oxygen resp. CO islands at small noise amplitudes. Anisotropic diffusion of CO parallel and normal to the steps causes elliptic shapes of large islands. The long axes of the ellipses are aligned along the steps. At increased noise amplitudes the density of islands becomes larger. 2D modeling of the phenomena based on reaction-diffusion differential equations reproduces the experimental findings quite nicely.}, language = {en} } @misc{TschulikHoffmannFokwaetal., author = {Tschulik, Kristina and Hoffmann, Stefan and Fokwa, Boniface P. T. and Gilleßen, Michael and Schmidt, Peer}, title = {Studies regarding the homogeneity range of the zirconium phosphide telluride Zr2+xPTe2}, series = {Solid State Sciences}, volume = {12}, journal = {Solid State Sciences}, number = {12}, issn = {1293-2558}, doi = {10.1016/j.solidstatesciences.2010.08.022}, pages = {2030 -- 2035}, abstract = {The phosphide tellurides Zr2+δPTe2 (0 ≤ δ ≤ 1) can be synthesized from the elements in a solid state reaction or by thermal decomposition of Z. Zr2PTe2 decomposes under release of Te2(g) + P4(g) forming the homogeneity range Zr2+δPTe2. The growth of single crystals of Zr2+δPTe2 succeeded by chemical vapour transport using iodine as transport agent from 830 °C in direction of higher temperatures up to 900 °C. Zr2+δPTe2 crystallizes in the rhombohedral space group R-3m (no. 166) with lattice parameters a = 383(1)…386(1) pm and c = 2935(4)…2970(4) pm for δ = 0…1, respectively. Single crystal data have been determined for Zr2.40(2)PTe2 with lattice parameters a = 385.24(4) pm and c = 2967.8(4) pm. The electronic structure and chemical bonding in Zr2+δPTe2 was investigated by the linear muffin-tin orbital (LMTO) method. Both Zr2PTe2 and Zr3PTe2 show non-vanishing DOS values at the Fermi level (EF) indicating metallic character. According to COHP bonding analyses, mainly the heteroatomic Zr-P and Zr-Te bonds are responsible for the structural stability of Zr3PTe2. The new Zr2-Te bond, which is not present in Zr2PTe2, is stronger than Zr1-Te and is thought to be responsible for the stability of phases having Zr in excess.}, language = {en} } @misc{AckerBueckerHoffmann, author = {Acker, J{\"o}rg and B{\"u}cker, Stefan and Hoffmann, Volker}, title = {Impact of the chemical form of different fluorine sources on the formation of AlF molecules in a C2H2/N2O flame}, series = {Journal of Analytical Atomic Spectrometry}, volume = {31}, journal = {Journal of Analytical Atomic Spectrometry}, issn = {0267-9477}, doi = {10.1039/C5JA00470E}, pages = {902 -- 911}, abstract = {The formation of diatomic AlF molecules was studied in a C2H2/N2O flame by means of a high-resolution continuum source flame absorption spectrometer using different fluorine containing compounds HF, H2SiF6, HBF4 and CF3COOH as fluorine sources. The fragmentation of these fluorine sources, as well the resulting impact on the AlF molecule formation, was derived from flame height distribution studies of the atomic and molecular species Al, AlO, Si, SiO, SiF, B and BF as a function of the fluorine concentration, the molar Al : F ratio and the burner gas composition. As a consequence, the used fluorine sources HF, H2SiF6, HBF4 and CF3COOH have been divided into two major groups. The first group of fluorine sources, covering HF, H2SiF6 and HBF4, decomposes during the drying of the aerosol under the formation of AlF3, which is the dominating species for the transport of aluminium into the flame. Its decomposition into AlF results in a high sensitivity of AlF molecular absorption at low flame observation heights. The second group of fluorine sources is exemplarily given by CF3COOH. In the upper parts of the flame the cleavage of the very stable C-F bond proceeds incompletely so that the sensitivity of the AlF molecular absorption is considerably lower than that for the other fluorine sources. In consequence, the AlF molecules are formed by the reaction between the fluorine atoms and the aluminium atoms, which are transported into the flame without the aid of fluorine, presumably via oxidic and/or carbidic species. The present investigations show that the sensitivity of the AlF molecular absorption and the pathway of AlF formation depend on the chemical form of the fluorine in the studied samples.}, language = {en} } @misc{AckerBueckerHoffmann, author = {Acker, J{\"o}rg and B{\"u}cker, Stefan and Hoffmann, Volker}, title = {The Formation of AlF Molecules and Al Atoms in a C2H2/N2O Flame Studied by Absorption and Emission Spectrometry of Molecules and Atoms}, series = {Current Analytical Chemistry}, volume = {10}, journal = {Current Analytical Chemistry}, number = {3}, issn = {1875-6727}, pages = {418 -- 425}, abstract = {The absorption of the diatomic molecule AlF in the C2H2/N2O flame at 227.66 nm reveals an interesting feature. The calibration curve of the AlF absorption plotted against a rising concentration of hydrofluoric acid in solutions of constant aluminum content consists of two subsequent linear sections of different slopes. The bend position is reproducibly found at a molar fluorine-to-aluminum ratio of 3, calculated from the composition of the studied solutions. To explain this behavior, the most prominent aluminum flame species Al, AlF, and AlO were recorded as a function of the burner gas composition and flame observation height, using a high-resolution continuum source flame absorption spectrometer. As a result, the two-sectioned calibration curve is explained by two different pathways of AlF molecule formation: At a molar fluorine-to-aluminum ratio of below 3, aluminum is transported into the flame by two parallel pathways. One is the common pathway in absence of fluorine via the reduction of oxidic and/or carbidic species by the flame gases. The second pathway comprises the formation of gaseous AlF3 and its decomposition into AlF molecules and, subsequently, Al atoms. The fractionation of AlF3 releases Al atoms much faster than through the reduction of the oxidic and/or carbidic species. At molar fluorine-to-aluminum ratios of above 3, all aluminum is introduced to the flame via gaseous AlF3. A further increase of the hydrofluoric acid concentration increases the fluorine atom concentration in the flame, so that the AlF formation is determined by the recombination of aluminum and fluorine atoms.}, language = {en} } @misc{BueckerHoffmannAcker, author = {B{\"u}cker, Stefan and Hoffmann, Volker and Acker, J{\"o}rg}, title = {Determination of Fluorine by Molecular Absorption Spectrometry of AlF Using a High-Resolution Continuum Source Spectrometer and a C2H2/N2O Flame}, series = {Current Analytical Chemistry}, volume = {10}, journal = {Current Analytical Chemistry}, number = {3}, issn = {1573-4110}, pages = {426 -- 434}, abstract = {The molecular absorption of the diatomic AlF molecule in the C2H2/N2O flame was studied using a highresolution continuum source flame atomic absorption spectrometer. AlF has a structured absorption spectrum in the range of 227.30 nm and 227.80 nm. From this band system, the remarkably narrow absorption band at 227.66 nm proved to be the optimum for analytical purposes. The signal intensity was studied as a function of the C2H2 : N2O ratio, the aspiration flow, and the aluminum concentration added to the analytical solution to generate the AlF molecules in the flame. The AlF molecule formation is significantly affected by the bonding state of the fluorine source used. Compared to ionic bound fluorine, organic bound fluorine leads to a markedly less sensitive molecular absorbance of AlF. Furthermore, several ions, such as Na+, K+ and NH4+, and acids, such as HCl, CH3COOH, and HNO3, affect the AlF signal intensity severely. It has to be concluded that the determination of fluorine by AlF F MAS only leads to reliable analytical results in simple matrices.}, language = {en} } @misc{KuenzelHoffmannWeberetal., author = {K{\"u}nzel, Stephan R. and Hoffmann, Maximilian and Weber, Silvio and K{\"u}nzel, Karolina and K{\"a}mmerer, Susanne and G{\"u}nscht, Mario and Klapproth, Erik and Rausch, Johanna S. E. and Sadek, Mirna S. and Kolanowski, Tomasz and Meyer-Roxlau, Stefanie and Piorkowski, Christopher and Tugtekin, Sems M. and Rose-John, Stefan and Yin, Xiaoke and Mayr, Manuel and Kuhlmann, Jan Dominik and Wimberger, Pauline and Gr{\"u}tzmann, Konrad and Herzog, Natalie and K{\"u}pper, Jan-Heiner and O'Reilly, Molly and Kabir, S. Nashitha and Sommerfeld, Laura C. and Guan, Kaomei and Wielockx, Ben and Fabritz, Larissa and Nattel, Stanley and Ravens, Ursula and Dobrev, Dobromir and Wagner, Michael and El-Armouche, Ali}, title = {Diminished PLK2 Induces Cardiac Fibrosis and Promotes Atrial Fibrillation}, series = {Circulation Research}, volume = {129}, journal = {Circulation Research}, number = {8}, issn = {1524-4571}, doi = {10.1161/CIRCRESAHA.121.319425}, pages = {804 -- 820}, abstract = {Rationale: Fibrosis promotes the maintenance of atrial fibrillation (AF), making it resistant to therapy. Improved understanding of the molecular mechanisms leading to atrial fibrosis will open new pathways toward effective antifibrotic therapies. Objective: This study aims to decipher the mechanistic interplay between PLK2 (polo-like kinase 2) and the profibrotic cytokine OPN (osteopontin) in the pathogenesis of atrial fibrosis and AF. Methods and Results: Atrial PLK2 mRNA expression was 10-fold higher in human fibroblasts than in cardiomyocytes. Compared with sinus rhythm, right atrial appendages and isolated right atrial fibroblasts from patients with AF showed downregulation of PLK2 mRNA and protein, along with increased PLK2 promotor methylation. Genetic deletion as well as pharmacological inhibition of PLK2 induced profibrotic phenotype conversion in cardiac fibroblasts and led to a striking de novo secretion of OPN. Accordingly, PLK2-deficient (PLK2 knockout) mice showed cardiac fibrosis and were prone to experimentally induced AF. In line with these findings, OPN plasma levels were significantly higher only in patients with AF with atrial low-voltage zones (surrogates of fibrosis) compared with sinus rhythm controls. Mechanistically, we identified ERK1/2 as the relevant downstream mediator of PLK2 leading to increased OPN expression. Finally, oral treatment with the clinically available drug mesalazine, known to inhibit ERK1/2, prevented cardiac OPN overexpression and reversed the pathological PLK2 knockout phenotype in PLK2 knockout mice. Conclusions: Abnormal PLK2/ERK1/2/OPN axis function critically contributes to AF-related atrial fibrosis, suggesting reinforcing PLK2 activity and/or OPN inhibition as innovative targets to prevent fibrosis progression in AF. Mesalazine derivatives may be used as lead compounds for the development of novel anti-AF agents targeting fibrosis.}, language = {en} }