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991.
Wolfram Fuchs Hubert Kalbacher Wolfgang Voelter 《Magnetic resonance in chemistry : MRC》1981,17(3):157-162
The 13C data of several new amino protecting groups of the urethane structure are reported. The speeds of acidolytic cleavage are correlated with the 13C parameters. 相似文献
992.
993.
Different isotopic modifications of deuterated products of 1-t-butlyl-4-methoxycarbonyl cyclohexene (d4-3,3,6,6), cis- and trans-3-methyl-4-cyanocyclohexene (d3-3,6,6), cis- and trans-3-methyl-4-cyanocyclohexene (d3,6,6), cis- and trans-3-t-butyl-4-methoxycarbonylcyclohexene (d3,-3,6,6) are shown by nuclear magnetic resonance spectral analysis. By comparison of 3J and 4J coupling constants of model molecules and molecules with large gauche interactions, we obtain proof that the latter are in a chair conformation with moderate cycle deformations. 相似文献
994.
Hubert de Rugy Philippe Saliot Roland Pantel 《Fresenius' Journal of Analytical Chemistry》1989,333(4-5):331-332
Conclusion Due to their complementary character, AES and RBS can give a very rich set of information when they are combined for profiling thin films. The interpretation of data is easier and more accurate when a same simulated structure is fitted successively to the RBS and AES data.
Quantifizierung von Auger-Tiefenprofilen mit Hilfe der Rutherford-Rückstreu-Spektrometrie相似文献
995.
Two neutrino double beta decay of 150Nd to the first 0+ excited state in 150Sm is investigated with the 400 cm3 low-background HPGe detector. Data analysis for 11320.5 h shows the excess of events at 333.9 and 406.5 keV. This makes it possible to estimate the half-life of the investigated process as [1.4 ?0.2 +.04 (stat)±0.3(syst)]×1020yr. 相似文献
996.
D.M.?BubbEmail author J.S.?Horwitz S.B.?Qadri S.W.?Kirchoefer C.?Hubert J.?Levy 《Applied Physics A: Materials Science & Processing》2004,79(1):99-101
We report a method for producing BST films with consistently high figures of merit for tunable microwave applications. (Ba1-x,Srx)TiO3 (x=0.4, target doped with 1% W) thin films have been deposited using pulsed laser deposition onto (100)MgO substrates. Films were deposited at low partial pressures of oxygen (50 mTorr) at a substrate temperature of 730 °C. An analysis of the X-ray diffraction data indicates that the film has a nearly cubic structure, with the overall lattice parameter enlarged relative to the bulk material due to the presence of oxygen vacancies. A post-deposition anneal of the film in flowing oxygen (1000 °C for 6 h) resulted in a decrease in the lattice parameter while remaining nearly cubic. An analysis of the microwave dielectric properties (1–20 GHz) showed that the annealed film exhibited about 10% tunability for an applied bias field of 67 kV/cm with a dielectric Q(1/tan)>600. Investigation of the films by time-resolved confocal scanning optical microscopy (CSOM) has revealed that there is an out-of-plane polarization at zero applied field (EDC=0). The results show that the paraelectric response is relatively insensitive to applied field, while the ferroelectric response is correlated with the growth of in-plane nanodomains. We find these results to be consistent with a large number of studies that show that strain-relief is of paramount importance if ferroelectric films are to be developed as microwave circuit components. PACS 81.15.Fg; 85.50.-n 相似文献
997.
Dehouck P Vander Heyden Y Smeyers-Verbeke J Massart DL Marini RD Chiap P Hubert P Crommen J Van de Wauw W De Beer J Cox R Mathieu G Reepmeyer JC Voigt B Estevenon O Nicolas A Van Schepdael A Adams E Hoogmartens J 《Journal of chromatography. A》2003,1010(1):63-74
Erythromycin is a mixture of macrolide antibiotics produced by Saccharopolyspora erythreas during fermentation. A new method for the analysis of erythromycin by liquid chromatography has previously been developed. It makes use of an Astec C18 polymeric column. After validation in one laboratory, the method was now validated in an interlaboratory study. Validation studies are commonly used to test the fitness of the analytical method prior to its use for routine quality testing. The data derived in the interlaboratory study can be used to make an uncertainty statement as well. The relationship between validation and uncertainty statement is not clear for many analysts and there is a need to show how the existing data, derived during validation, can be used in practice. Eight laboratories participated in this interlaboratory study. The set-up allowed the determination of the repeatability variance, s(2)r and the between-laboratory variance, s(2)L. Combination of s(2)r and s(2)L results in the reproducibility variance s(2)R. It has been shown how these data can be used in future by a single laboratory that wants to make an uncertainty statement concerning the same analysis. 相似文献
998.
Coline Pinese Said Jebors Pierre Emmanuel Stoebner Vincent Humblot Pascal Verdié Léa Causse Xavier Garric Hubert Taillades Jean Martinez Ahmad Mehdi Gilles Subra 《Materials Today Chemistry》2017
The need for bioactive dressings increases with the population aging and the prevalence of chronic diseases. In contrast, there are very few dressings on the market which are designed to display a chosen bioactivity. In this context, we investigated the surface-functionalization of silicone wound dressing with bioactive peptides. One of the challenges was to avoid multistep grafting reactions involving catalysts, solvents or toxic reagents, which are not suitable for the fabrication of medical devices at an industrial scale. In the other hand, a covalent bonding was necessary to avoid the loss of the biological effect by progressive removal of the peptide in biological fluids generated by the wound. To solve these limitations, we developed a strategy allowing an easy and direct functionalization of silicone. This strategy relies on hybrid silylated bioactive peptides, which chemoselectively react with plasma-activated silicone surfaces. We synthesized three hybrid peptides with wound healing properties, which were grafted on commercially available silicone dressings Cerederm® and Mepitel®. Grafted dressings were evaluated in vitro and enabled a quicker scare recovery and extracellular matrix deposition with human dermal fibroblasts. These results were confirmed by in vivo studies showing an enhanced wound-healing of the pig skin. By this simple method, we transformed inert dressing into bioactive dressing which showed properties of wound healing. 相似文献
999.
Selective Coordination of Gallium(III), Zinc(II), and Copper(II) by an Asymmetric Dinucleating Ligand: A Model for Metallophosphatases 下载免费PDF全文
Dr. Simone Bosch Prof. Dr. Peter Comba Prof. Lawrence R. Gahan Dr. Christopher Noble Prof. Dr. Gerhard Schenk Prof. Dr. Hubert Wadepohl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18269-18279
Complexation studies of the dinucleating ligand H3L (H3L=2‐{[bis(pyridin‐2‐ylmethyl)amino]methyl}‐6‐{[bis(6‐pivaloylamidopyridin‐2‐ylmethyl)amino]methyl}‐4‐methylphenol), with metal‐binding sites A and B, which both provide four donors to a metal ion; a tertiary amine; two pyridines (substituted with amide hydrogen‐bond donors in site B), and a bridging phenolate, with ZnII, CuII, and GaIII are reported. The titration of H3L with the three metal ions in solution was monitored by NMR spectroscopy or EPR and UV/Vis/near‐IR spectroscopy, as well as by ESI‐MS to analyze the selectivity of the two metal‐ion sites A and B of this model ligand for metallophosphatases; the spectroscopic assignments are supported by X‐ray crystallography results. The first ZnII ion coordinates to site A with unsubstituted pyridine donors and, upon addition of a second equivalent of ZnII, this coordinates to the sterically less accessible site B. From a similar titration with GaIII, it emerges that only a mononuclear complex is obtained, with the GaIII center coordinated to site A. When one equivalent of GaIII is reacted with the mononuclear ZnII complex, ZnII is forced by GaIII to exchange the site; this results in a dinuclear complex with GaIII in site A and ZnII in site B. With CuII, two isomers are observed: one with and the other without a bridging phenolate; these differ significantly in their spectroscopic and magnetic properties. 相似文献
1000.
Azaphilic versus Carbophilic Coupling at CN Bonds: Key Steps in Titanium‐Assisted Multicomponent Reactions 下载免费PDF全文
Torsten Roth Prof. Hubert Wadepohl Dr. Eric Clot Prof. Lutz H. Gade 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18730-18738
Consecutive C‐ and N‐arylation of N‐heterocyclic nitriles is mediated by titanium(IV) alkoxides. The carbo‐ and azaphilic arylation step may be separated by choosing the order in which the two equivalents of aryl transfer reagent are added. In the course of this transformation, the ancillary N‐heterocycle acts as both a directing anchor group and electron reservoir. In the selectivity‐determining step, the selectivity is governed by a choice between (direct) C‐ and Ti‐arylation; the latter opens up a reaction pathway that allows further migration to the nitrogen atom. The isolation of metal‐containing aggregates from the reaction mixture and computational studies gave insights into the reaction mechanism. Subsequently, a multicomponent one‐pot protocol was devised to rapidly access complex quaternary carbon centers. 相似文献