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S. R. Zinzadze H. Kleinmann H. Neubauer O. Lemmermann L. Fresenius J. König und J. Hasenbäumer 《Fresenius' Journal of Analytical Chemistry》1930,82(10):383-385
Ohne Zusammenfassung 相似文献
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A part of homotopy theory is applied to classify planar structures in chiral nematic liquid crystals confined to cylindrical cavities. The resulting classification is exact in the approximation of undeformed chiral nematic surfaces. Within this approach the relative stability of possible planar structures with surface and bulk disclination lines is discussed. The number and the shape of these disclinations, which in some cases form spiral structures, are predicted. Further approximate analytical expressions for non-singular director fields close to disclination lines with integral strength are introduced. Our predictions, which are also in agreement with some previously suggested pictures of such director fields, are used to improve stability considerations of the confined planar chiral nematic structures in tubes and droplets. 相似文献
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Bradley J Turner Dirk Bäumer Nicholas J Parkinson Jakub Scaber Olaf Ansorge Kevin Talbot 《BMC neuroscience》2008,9(1):104
Background
Redistribution of nuclear TAR DNA binding protein 43 (TDP-43) to the cytoplasm and ubiquitinated inclusions of spinal motor neurons and glial cells is characteristic of amyotrophic lateral sclerosis (ALS) pathology. Recent evidence suggests that TDP-43 pathology is common to sporadic ALS and familial ALS without SOD1 mutation, but not SOD1-related fALS cases. Furthermore, it remains unclear whether TDP-43 abnormalities occur in non-ALS forms of motor neuron disease. Here, we characterise TDP-43 localisation, expression levels and post-translational modifications in mouse models of ALS and spinal muscular atrophy (SMA). 相似文献67.
More than activity, selectivity of catalytic reactions is the focus of research in the 21(st) century. We review studies on model systems that address the issue of directing a catalytic reaction on disperse metal catalysts by controlling the specific surface site. Three examples are explored: methanol dehydrogenation over Pd/alumina, NO dissociation on Pd/alumina, and reaction studies for molecules relevant in a Fischer-Tropsch scenario on a bimetallic Pd/Co/alumina model catalyst. We show how surface science can be used by combining a variety of experimental techniques to study the chemistry of model catalysts at the atomic level. 相似文献
68.
Polymorphic and Pseudosymmetrical Hydrates MSeO3 · H2O (M = Mn, Co, Ni, Zn, Cd) By crystallization from aqueous solutions of MSeO3 and M(HSeO3)2, the selenites MSeO3 · H2O (M = Mn, Co, Ni, Zn, Cd) were obtained and characterized by means of X-ray diffraction and IR-spectroscopy. The crystal structure of ZnSeO3 · H2O was determined. The IR spectra indicate that the hydrates are isotypic and contain H2O molecules of symmetry mm2. However, the X-ray data show different structure types with H2O molecules of site symmetry m or 1. CdSeO3 · H2O and MnSeO3 · H2O are isotypic (o.rh., MnSeO3 · D2O type). CoSeO3 · H2O (mon.) as well as the isotypic NiSeO3 · H2O and ZnSeO3 · H2O (mon.) form new structure types. These findings are discussed on the basis of the crystal structure of ZnSeO3 · H2O (P21/n, a = 477.9(1), b = 1319.4(5), c = 570.1(1) pm, β = 90.84(2)°, Z = 4, Dx = 3.886 g · cm?3, R = 0.035 for 722 reflections with I > 2σ1) and the local pseudosymmetry of its components, i.e., layers [ZnSeO3 · H2O] of ZnO6 octahedra sharing four equatorial vertices, SeO32? anions and H2O molecules. 相似文献
69.
Lear T Marshall R Lopez-Sanchez JA Jackson SD Klapötke TM Bäumer M Rupprechter G Freund HJ Lennon D 《The Journal of chemical physics》2005,123(17):174706
Five alumina-supported palladium catalysts have been prepared from a range of precursor compounds [palladium(II) nitrate, palladium(II) chloride, palladium(II) acetylacetonate, and tetraamminepalladium(II) tetraazidopalladate(II)] and at different metal loadings (1-7.3 wt %). Collectively, this series of catalysts provides a range of metal particle sizes (1.2-8.5 nm) that emphasize different morphological aspects of the palladium crystallites. The infrared spectra of chemisorbed CO applied under pulse-flow conditions reveal distinct groupings between metal crystallites dominated by low index planes and those that feature predominantly corner/edge atoms. Temperature-programmed infrared spectroscopy establishes that the linear CO band can be resolved into contributions from corner atoms and a combination of (111)(111) and (111)(100) particle edges. Propene hydrogenation has been used as a preliminary assessment of catalytic performance for the 1 wt % loaded catalysts, with the relative inactivity of the catalyst prepared from palladium(II) chloride attributed to a diminished hydrogen supply due to decoration of edge sites by chlorine originating from the preparative process. It is anticipated that refinements linking the vibrational spectrum of a probe molecule with surface structure and accessible adsorption sites for such a versatile catalytic substrate provide a platform against which structure/reactivity relationships can be usefully developed. 相似文献
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Robin Heckershoff Garrett May Janika Däumer Lukas Eberle Petra Krämer Dr. Frank Rominger Dr. Matthias Rudolph Dr. Florian F. Mulks Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(55):e202201816
New N-heterocyclic compounds for organic functional materials and their efficient syntheses are highly demanded. A surprising entropy-induced selectivity switch in the gold-catalyzed intramolecular hydroarylation of 2-ethynyl N-aryl indoles was found and its exploitation led to straightforward syntheses of indolo[1,2-a]quinolines. Experimental and computational mechanistic investigations gave insight into this uncommon selectivity phenomenon and into the special reactivity of the indolo[1,2-a]quinolines. The high functional group tolerance of this methodology enabled access to a diverse scope with high yields. In addition, bidirectional approaches, post-functionalization reactions, and π-extension of the core structure were feasible. An in-depth study of the photophysical properties explored the structure-effect relationship for different derivatives and revealed a high potential of these compounds for future applications as functional materials. 相似文献