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151.
Rechthaler J Pelzing M Ingendoh A Kukovecz A Prato M Kuzmany H Allmaier G 《Journal of mass spectrometry : JMS》2011,46(11):1108-1114
An amphiphatic fullerene derivative (8-(N-Methyl-Fullero-Pyrrolidinium-1-yl-chloride)-3,6-Dioxaoctan-1-Ammonium Chloride (MFPDAC)), which is of great interest in nanotechnology due to the fact that it forms self-assembling fullerenic nanorods, has been structurally characterized with emphasis to its purity and thermal treatment of a formed nanorod film (on a LDI target) by means of laser desorption/ionization (LDI) coupled with high-resolution curved field reflectron time-of-flight (TOF) mass spectrometry, and by low energy MS/MS as well as in-source fragmentation experiments applying an quadrupole ion trap (QIT) combined with a two-stage reflectron TOF analyzer. The interpretation of LDI results has been supplemented by ESI QIT MS(n) (n = 1-3), as well as high-resolution ESI reflectron TOF mass spectrometric experiments. Based on the experimental data obtained by both desorption/ionization techniques, various types of analyzers and sample treatments, we could completely characterize MFPDAC and further found out that the investigated sample was not entirely free of impurities. Furthermore, the envisaged loss of the derivative sidechain upon the heat treatment in vacuum of the self-assembled nanorod sample film on a metallic substrate could be successfully monitored by LDI MS. 相似文献
152.
Sikorska J Hau AM Anklin C Parker-Nance S Davies-Coleman MT Ishmael JE McPhail KL 《The Journal of organic chemistry》2012,77(14):6066-6075
Mandelalides A-D are variously glycosylated, unusual polyketide macrolides isolated from a new species of Lissoclinum ascidian collected from South Africa, Algoa Bay near Port Elizabeth and the surrounding Nelson Mandela Metropole. Their planar structures were elucidated on submilligram samples by comprehensive analysis of 1D and 2D NMR data, supported by mass spectrometry. The assignment of relative configuration was accomplished by consideration of homonuclear and heteronuclear coupling constants in tandem with ROESY data. The absolute configuration was assigned for mandelalide A after chiral GC-MS analysis of the hydrolyzed monosaccharide (2-O-methyl-α-L-rhamnose) and consideration of ROESY correlations between the monosaccharide and aglycone in the intact natural product. The resultant absolute configuration of the mandelalide A macrolide was extrapolated to propose the absolute configurations of mandelalides B-D. Remarkably, mandelalide B contained the C-4' epimeric 2-O-methyl-6-dehydro-α-L-talose. Mandelalides A and B showed potent cytotoxicity to human NCI-H460 lung cancer cells (IC(50), 12 and 44 nM, respectively) and mouse Neuro-2A neuroblastoma cells (IC(50), 29 and 84 nM, respectively). 相似文献
153.
Dominik Paukszta Justyna Zielińska-Ma?kowiak 《Journal of Thermal Analysis and Calorimetry》2012,109(2):611-618
Nucleation ability of native and modified rapeseed straw during the polypropylene crystallization from the melt was investigated by the DSC method. Composites were made from isotactic polypropylene and lignocellulosic material using extrusion and injection moulding techniques. They were obtained using polypropylenes differing with respect to melt flow rates and different varieties of rapeseed straw. Chemical modification was carried out in two stages: through mercerisation and treatment with acetic acid anhydride. In the course of investigations, it was found that both native and modified rapeseed straw acted as an active nucleant of polypropylene crystallisation characterised by low values of MFR indices. It was found that for polypropylenes with high MFR values, the values of crystallization temperatures and crystallization half-time in composites were identical when compared with non-filled polymers. The investigations demonstrated that there were insignificant differences among composites containing straw from different varieties of rapeseed. The analysis of crystallization temperatures confirmed that rapeseed straw modification failed to change this parameter of the crystallization process. A similar tendency was observed in the case of changes of the half-time crystallization process. Moreover, the analysis of the crystallization temperature and crystallization half-time showed that the presence in composites of lignified rapeseed straw particles played an important role in the crystallization conditions. 相似文献
154.
J Trzaskowski C Rabe K Vogtt M Krumova G Goerigk M Ballauff S Mecking 《Chemical communications (Cambridge, England)》2012,48(73):9153-9155
Nanoparticles of precisely branched polyethylenes possess a distinct oblate shape resulting from a crystalline lamella in the particle as revealed by SAXS and TEM, and display controllable and well-behaved thermal behaviour. 相似文献
155.
We prove stability of the spectral gap for gapped, frustration-free Hamiltonians under general, quasi-local perturbations. We present a necessary and sufficient condition for stability, which we call Local Topological Quantum Order and show that this condition implies an area law for the entanglement entropy of the groundstate subspace. This result extends previous work by Bravyi et al. on the stability of topological quantum order for Hamiltonians composed of commuting projections with a common zero-energy subspace. We conclude with a list of open problems relevant to spectral gaps and topological quantum order. 相似文献
156.
Justyna Czupryniak Aleksandra Fabiańska Piotr Stepnowski Tadeusz Ossowski Robert Bogdanowicz Marcin Gnyba Ewa M. Siedlecka 《Central European Journal of Physics》2012,10(5):1183-1189
The aim of the presented study is to investigate the applicability of electrochemical oxidation of aromatic compounds containing heteroatoms, e.g. waste from production of pesticides or pharmaceutics, at a borondoped diamond (BDD) electrode. The BDD electrodes were synthesized by microwave plasma enhanced chemical vapour deposition (MW PE CVD). Investigation of the electrode surface by optical microscopy and scanning electron microscopy (SEM) confirmed that the synthesized layer was continuous and formed a densely packed grain structure with an average roughness of less than 0:5 ??m. The influence of important electrochemical parameters: current density, kind of reactor, pH or mixing operation, on the efficiency of the oxidation was investigated. The fouling of electrode??s surface caused by the deposition of organic material was observed during CV and galvanostatic experiments. At low current density the oxidation rate constant k was low, but the current efficiency was relatively high. The BDD can be used successfully to remove heterogeneous aromatic compounds existing either as molecules or cations. During 4 h of electrolysis 95% of aromatic compounds were electrochemically decomposed to mineral forms. It was observed that the influence of the initial pH on mineralization was marginal. 相似文献
157.
158.
Grzegorz Graff Agnieszka Kaczkowska Piotr Nowak-Przygodzki Justyna Signerska 《Topology and its Applications》2012,159(10-11):2728-2735
Let f be a self-map of a compact connected manifold M. We characterize Lefschetz periodic point free continuous self-maps of M for several classes of manifolds and generalize the results of Guirao and Llibre [J.L.G. Guirao, J. Llibre, On the Lefschetz periodic point free continuous self-maps on connected compact manifolds, Topology Appl. 158 (16) (2011) 2165–2169]. 相似文献
159.
Marcin Palusiak Arno Pfitzner Manfred Zabel Sawomir J. Grabowski Jan Epsztajn Justyna A. Kowalska 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(4):o239-o241
In methyl [5‐methoxy‐4‐(4‐methoxyphenyl)isochroman‐3‐yl]acetate, C20H22O5, (I), and methyl [4‐(2,5‐dimethoxyphenyl)‐8‐methoxyisochroman‐3‐yl]acetate, C21H24O6, (II), the heterocyclic rings adopt half‐chair conformations. The substituents at the 3‐ and 4‐positions are in a trans configuration in both (I) and (II), being in an axial conformation in (I) and in an equatorial conformation in (II). The crystal structure of (I) is stabilized by weak C—H⋯O hydrogen bonding, leading to the formation of an infinite three‐dimensional network. Compound (II) crystallizes in a chiral space group. This feature, which was also found in previously investigated isochroman derivatives, is related to the arrangement of substituents attached to the isochroman moiety. 相似文献
160.
Waldemar Iwanek Alicja Wzorek Zdzisława Nowakowska Grzegorz Schroeder 《Monatshefte für Chemie / Chemical Monthly》2009,140(3):359-364
Abstract Synthesis of chelates from selected l-amino acids and triethylborane, and the mass spectra of the chelates, are described. Conditions for forming dimers between
the chelates and the sodium ion are discussed, and structures are proposed for the dimers.
Graphical abstract
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