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We prove that a branched immersion of a surface with boundary into a differentiable manifold has no false branch points (in fact, no ramified points) if the immersion induces an isomorphism of fundamental groups and some other natural hypotheses are satisfied. This result has immediate applications to Plateau's problem.Work done while the first author was a visiting member of the Max-Planck-Institut für Mathematik at Bonn. Both authors acknowledge the support of Max-Planck-Institut für Mathematik, Bonn and Schwerpunkt Geometrie at Mathematisches Institut, University of Heidelberg 相似文献
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Vladislav?Tomi?i?Email author Vjekoslav?Butorac Jadranka?Viher Vladimir?Simeon 《Journal of solution chemistry》2005,34(6):613-616
The effect of temperature on the π∗←π transition band in the UV absorption spectrum of NO3−(aq) centered at ≈200 nm was studied in the temperature range 10–70 ∘C. The observed temperature independence of this band was in contrast to the significant influence of temperature on the nitrate π∗←n transition reported recently by us. However, taking into account the electronic states involved in both the transitions, it was concluded that this finding was in accordance with our previous assumption that interconversion between spectrally distinct (with respect to π∗←n band) nitrate species included the rupture/formation of hydrogen bond(s) in the hydration shell of the nitrate ion. 相似文献
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Bertosa B Kojić-Prodić B Wade RC Ramek M Piperaki S Tsantili-Kakoulidou A Tomić S 《Journal of chemical information and computer sciences》2003,43(5):1532-1541
The activity of a biological compound is dependent both on specific binding to a target receptor and its ADME (Absorption, Distribution, Metabolism, Excretion) properties. A challenge to predict biological activity is to consider both contributions simultaneously in deriving quantitative models. We present a novel approach to derive QSAR models combining similarity analysis of molecular interaction fields (MIFs) with prediction of logP and/or logD. This new classification method is applied to a set of about 100 compounds related to the auxin plant hormone. The classification based on similarity of their interaction fields is more successful for the indole than the phenoxy compounds. The classification of the phenoxy compounds is however improved by taking into account the influence of the logP and/or the logD values on biological activity. With the new combined method, the majority (8 out of 10) of the previously misclassified derivatives of phenoxy acetic acid are classified in accord with their bioassays. The recently determined crystal structure of the auxin-binding protein 1 (ABP1) enabled validation of our approach. The results of docking a few auxin related compounds with different biological activity to ABP1 correlate well with the classification based on similarity of MIFs only. Biological activity is, however, better predicted by a combined similarity of MIFs + logP/logD approach. 相似文献
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Antibacterial activity of methylated chitosan and chitooligomer derivatives: Synthesis and structure activity relationships 总被引:1,自引:0,他引:1
Ögmundur Vidar Rúnarsson Tapio Nevalainen Tomi Järvinen Jón M. Einarsson Margrét Valdimarsdóttir 《European Polymer Journal》2007,43(6):2660-2671
The purpose of this study was to synthesize series of methylated chitosaccharide derivatives, possessing various degree of methylation, and to determine their structure activity relationship (SAR) with regard to their antibacterial effect against Staphylococcus aureus. Chitosan polymer and chitooligomers were used as starting materials and were methylated by reaction with methyl iodide. Depending on the reaction conditions the degree of N-quaternization ranged from 0% to 74%, with varying degree of N,N-dimethylation, N-monomethylation and O-methylation. More selective N-quaternization could be obtained with protection group strategy. At pH 5.5 the chitosaccharide polymers and their methylated derivatives were active against S. aureus with minimal inhibitory concentration (MIC) ranging from 16 to 512 μg/mL. At pH 7.2 the non-quaternized derivatives were inactive but their highly N-quaternized derivatives showed MIC as low as 8 μg/mL. The chitooligomers, as well as their derivatives, were inactive at both pH’s. The SAR studies revealed that N-quaternization was mainly responsible for the antibacterial effects at pH 7.2, whereas it did not contribute to the antibacterial activity under acidic conditions. 相似文献
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Michèle Postel Félix Tomi Henri Li Kam Wah Laurence Mordenti Patricia Guillaume 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):453-457
Abstract Fe(NO)2XL and Fe(NO)X2L nitrosyl iron complexes, X = Cl, I, and L = HMPA, dppe, PPh3, activate molecular O2 to yield nitrato complexes. The phosphorous ligand is decisive for the oxidative power of these nitrates: with HMPA or dppe, oxygen transfer occurs only to phosphines. On going from HMPA to PPh3 the single nitrato complex obtained, Fe(NO)2X(OPPh3)2 selectively epoxidizes cyclohexene, and this is the first example of oxygen transfer from a nitrato ligand to an olefin. 相似文献
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Tuija Teerinen Timo Lappalainen Tomi Erho 《Analytical and bioanalytical chemistry》2014,406(24):5955-5965
Morphine was used as a model analyte to examine the possibility of using cellulose, physically modified by papermaking and converting techniques, as a capillary matrix in a lateral flow type of diagnostic assay. This research was directed toward low-cost, disposable, and portable paper-based diagnostics, with the aim of addressing the analytical performance of paper as a substrate in the analysis for drugs of abuse. Antibody Fab fragments were used as sensing molecules, and gold nanoparticle detection was employed. Inkjet printing was used to pattern sensing biomolecules as detection zones on paper. To validate the usefulness of paper as a diagnostic platform, the principle of a direct sandwich assay, based on immunocomplex formation between morphine and the anti-morphine Fab fragment and detection of the formed immunocomplex by another Fab fragment, was implemented. Results were compared with that achieved by using nitrocellulose as a reference material. Possible interfering from the sample matrix on assay quality was investigated with spiked oral fluid samples. Under optimized conditions, a visually assessed limit of detection for the sandwich assay was 1 ng/mL, indicating that the paper-based test devices developed in this work can perform screening for drugs of abuse and can fulfill the requirement for a sensitive assay in diagnostically relevant ranges. Fig
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