TY - GEN A1 - Chun, K. R. Julian A1 - Schmidt, Boris A1 - Kuck, Karl-Heinz A1 - Andresen, Dietrich A1 - Willems, Stefan A1 - Spitzer, Stefan G. A1 - Hoffmann, Ellen A1 - Schumacher, Burghard A1 - Eckardt, Lars A1 - Seidl, Karlheinz A1 - Jünger, Claus A1 - Horack, Martin A1 - Brachmann, Johannes A1 - Senges, Jochen T1 - Catheter ablation of atrial fibrillation in the young T2 - Clinical Research in Cardiology Y1 - 2013 U6 - https://doi.org/10.1007/s00392-013-0553-6 SN - 1861-0684 SN - 1861-0692 VL - 102 IS - 6 SP - 459 EP - 468 ER - TY - JOUR A1 - Wehner, Stefan A1 - Schmeißer, Dieter A1 - Hoffmann, Patrick T1 - Spatiotemporal patterns of external noise-induced transitions in a bistable reaction-diffusion system : Photoelectron Emission Microscopy experiments and modeling Y1 - 2005 ER - TY - JOUR A1 - Hoffmann, Patrick A1 - Wehner, Stefan A1 - Schmeißer, Dieter T1 - Noise-Induced Spatiotemporal Patterns in a Bistable Reaction-Diffusion System: Photoelectron Emission Microscopy experiments and Modeling of the CO Oxidation Reaction on Ir(111) Y1 - 2006 ER - TY - CHAP A1 - Schmeißer, Dieter A1 - Wehner, Stefan A1 - Hoffmann, Patrick A1 - Brand, Helmut R. A1 - Küppers, Jürgen ED - Descalzi, Orazio T1 - Influence of the Substrate on the Pattern Formation of a Surface Reaction T2 - Nonequilibrium statistical mechanics and nonlinear physics, XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics, Mar del Plata, Argentina, 4 - 8 December 2006 Y1 - 2007 SN - 978-0-7354-0421-2 SP - 121 EP - 126 PB - AIP Publishing CY - Melville, New York ER - TY - GEN A1 - Hoffmann, Patrick A1 - Wehner, Stefan A1 - Schmeißer, Dieter A1 - Brand, Helmut R. A1 - Küppers, Jürgen T1 - Noise-induced spatiotemporal patterns in a bistable reaction-diffusion system: Photoelectron emission micrsoscopy experiments and modeling of the CO oxidation reaction on Ir(111) T2 - Physical Review : E Y1 - 2006 SN - 1550-2376 VL - 73 IS - 5 SP - 056123 ER - TY - CHAP A1 - Wehner, Stefan A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter A1 - Brand, Helmut R. A1 - Küppers, Jürgen T1 - CO oxidation on Ir(111) surfaces: consequences of anisotropic diffusion and noise T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41 N2 - 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. Y1 - 2006 UR - http://www.dpg-verhandlungen.de/year/2006/conference/dresden/part/o/session/14/contribution/37 SN - 0420-0195 SP - S. 475 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Tschulik, Kristina A1 - Hoffmann, Stefan A1 - Fokwa, Boniface P. T. A1 - Gilleßen, Michael A1 - Schmidt, Peer T1 - Studies regarding the homogeneity range of the zirconium phosphide telluride Zr2+xPTe2 T2 - Solid State Sciences N2 - 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. KW - Zirconium phosphide telluride KW - Homogeneity range KW - Thermal decomposition KW - Crystal structure KW - Chemical bonding Y1 - 2010 UR - http://www.sciencedirect.com/science/article/pii/S1293255810003614 U6 - https://doi.org/10.1016/j.solidstatesciences.2010.08.022 SN - 1293-2558 VL - 12 IS - 12 SP - 2030 EP - 2035 ER - TY - GEN A1 - Acker, Jörg A1 - Bücker, Stefan A1 - Hoffmann, Volker T1 - Impact of the chemical form of different fluorine sources on the formation of AlF molecules in a C2H2/N2O flame T2 - Journal of Analytical Atomic Spectrometry N2 - 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. KW - flame molecular absorption spectrometry KW - diatomic molecule KW - aluminum monofluoride KW - C2H2/N2O flame KW - hexafluorosilicic acid KW - tetrafluoro boric acid KW - trifluoro acetic acid KW - species fragmentation Y1 - 2016 UR - http://pubs.rsc.org/en/Content/ArticleLanding/2016/JA/C5JA00470E#!divAbstract U6 - https://doi.org/10.1039/C5JA00470E SN - 0267-9477 SN - 1364-5544 VL - 31 SP - 902 EP - 911 ER - TY - GEN A1 - Acker, Jörg A1 - Bücker, Stefan A1 - Hoffmann, Volker T1 - The Formation of AlF Molecules and Al Atoms in a C2H2/N2O Flame Studied by Absorption and Emission Spectrometry of Molecules and Atoms T2 - Current Analytical Chemistry N2 - 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. KW - AlF KW - AlF3 KW - AlO KW - diatomic molecule KW - high-resolution continuum source absorption spectrometry KW - molecular absorption spectrometry KW - molecular emission spectrometry KW - air-acetylene flame Y1 - 2014 SN - 1875-6727 SN - 1573-4110 VL - 10 IS - 3 SP - 418 EP - 425 ER - TY - GEN A1 - Bücker, Stefan A1 - Hoffmann, Volker A1 - Acker, Jörg T1 - Determination of Fluorine by Molecular Absorption Spectrometry of AlF Using a High-Resolution Continuum Source Spectrometer and a C2H2/N2O Flame T2 - Current Analytical Chemistry N2 - 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. KW - AlF KW - fluorine determination KW - high resolution continuum source absorption spectrometry KW - molecular absorption spectrometry KW - non-spectral interference KW - diatomic molecule Y1 - 2014 SN - 1573-4110 SN - 1875-6727 VL - 10 IS - 3 SP - 426 EP - 434 ER - TY - GEN A1 - Künzel, Stephan R. A1 - Hoffmann, Maximilian A1 - Weber, Silvio A1 - Künzel, Karolina A1 - Kämmerer, Susanne A1 - Günscht, Mario A1 - Klapproth, Erik A1 - Rausch, Johanna S. E. A1 - Sadek, Mirna S. A1 - Kolanowski, Tomasz A1 - Meyer-Roxlau, Stefanie A1 - Piorkowski, Christopher A1 - Tugtekin, Sems M. A1 - Rose-John, Stefan A1 - Yin, Xiaoke A1 - Mayr, Manuel A1 - Kuhlmann, Jan Dominik A1 - Wimberger, Pauline A1 - Grützmann, Konrad A1 - Herzog, Natalie A1 - Küpper, Jan-Heiner A1 - O’Reilly, Molly A1 - Kabir, S. Nashitha A1 - Sommerfeld, Laura C. A1 - Guan, Kaomei A1 - Wielockx, Ben A1 - Fabritz, Larissa A1 - Nattel, Stanley A1 - Ravens, Ursula A1 - Dobrev, Dobromir A1 - Wagner, Michael A1 - El-Armouche, Ali T1 - Diminished PLK2 Induces Cardiac Fibrosis and Promotes Atrial Fibrillation T2 - Circulation Research N2 - 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. KW - atrial fibrillation KW - fibroblasts KW - fibrosis KW - mesalamine KW - osteopontin Y1 - 2021 UR - https://www.ahajournals.org/doi/full/10.1161/CIRCRESAHA.121.319425 U6 - https://doi.org/10.1161/CIRCRESAHA.121.319425 SN - 1524-4571 SN - 0009-7330 VL - 129 IS - 8 SP - 804 EP - 820 ER -