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141.
Polymer brushes consisting of hydrophilic and hydrophobic polymer components (poly-4-vinylpyridine, polymethacrylic acid and polystyrene, respectively) change their surface properties (as revealed by contact angles) when they are exposed to various solvents. In brushes prepared via grafting-from methods (using a specific surface initiator) layer thicknesses up to 300 nm were obtained. Copolymerization of the brush component monomers with 2-(4'-styryl)-indene yielded photo-cross-linkable brushes, which were used to fix the brushes in either the hydrophilic or hydrophobic state. Structural patterns differing in surface properties were produced and fixed by photo-cross-linking the hydrophobic component in that samples were irradiated through a mask. The patterns turned out most stable in moderately thick layers. AFM pictures confirm the contact angle results but reveal micro-domains of the two immiscible polymers in the grafted layers. 相似文献
142.
Kredel S Nienhaus K Oswald F Wolff M Ivanchenko S Cymer F Jeromin A Michel FJ Spindler KD Heilker R Nienhaus GU Wiedenmann J 《Chemistry & biology》2008,15(3):224-233
Fluorescent proteins (FPs) emitting in the far-red region of the spectrum are highly advantageous for whole-body imaging applications because scattering and absorption of long-wavelength light is markedly reduced in tissue. We characterized variants of the red fluorescent protein eqFP611 with bright fluorescence emission shifted up to 639 nm. The additional red shift is caused by a trans-cis isomerization of the chromophore. The equilibrium between the trans and cis conformations is strongly influenced by amino acid residues 143 and 158. Pseudo monomeric tags were obtained by further genetic engineering. For the red chromophores of eqFP611 variants, molar extinction coefficients of up to approximately 150,000 were determined by an approach that is not affected by the presence of molecules with nonfunctional red chromophores. The bright fluorescence makes the red-shifted eqFP611 variants promising lead structures for the development of near-infrared fluorescent markers. The red fluorescent proteins performed well in cell biological applications, including two-photon imaging. 相似文献
143.
Yu F Wolff JJ Amster IJ Prestegard JH 《Journal of the American Chemical Society》2007,129(43):13288-13297
A new method is presented for the retrieval of information on the conformation of glycosaminoglycan oligomers in solution. The method relies on the replacement of acetyl groups in isolated native oligomers with 13C labeled acetyl groups and the extraction of orientational constraints from residual dipolar couplings (RDCs) and chemical shift anisotropy (CSA) offsets observed in NMR spectra of partially oriented samples. A novel method for assignment of resonances based on the correlation of resonance intensities with isotope ratios determined from mass spectrometric analysis is also presented. The combined methods are used in conjunction with more traditional NMR structural data to determine the solution structure of a pentasaccharide, GalNAc6S(beta1-4)GlcA(beta1-3)GalNAc4S(beta1-4)GlcA(beta1-3)GalNAc4S-ol, derived by enzymatic hydrolysis of chondroitin sulfate. The geometry derived is compared to that for similar molecules that have been reported in the literature, and prospects for use of the new types of data in the study of protein-bound oligosaccharides are discussed. 相似文献
144.
Wolff H Bredow T Lerch M Schilling H Irran E Stork A Dronskowski R 《The journal of physical chemistry. A》2007,111(14):2745-2749
The geometric and electronic structure of the recently found new polymorph of tantalum oxynitride, gamma-TaON, and its structural stability were studied quantum-chemically at the density functional level. Results obtained by complementary quantum-chemical techniques with wavefunctions either expanded in atom-centered functions or in plane waves were compared, having employed pure density-functional functionals within the generalized gradient approximation as well as density-functional/Hartree-Fock hybrid methods. In particular, several plausible anion distributions were investigated and, in accordance with Pauling's second rule, it was found that the configuration in which nitrogen occupies crystallographic sites with highest coordination numbers is the most stable one. Theoretically generated local structural parameters were used to improve the accuracy of the experimentally derived information. The bonding situation in the most stable configuration was investigated by an analysis of the density of states. 相似文献
145.
Laures AM Wolff JC Eckers C Borman PJ Chatfield MJ 《Rapid communications in mass spectrometry : RCM》2007,21(4):529-535
The results of an investigation of the parameters which have the most significant effect on the accuracy of mass measurements on a quadrupole orthogonal acceleration time-of-flight mass spectrometer (q-oaToF) are reported. The influence of eight factors is investigated: ion abundances of reference and analyte compounds, mass difference between analyte and reference compounds, quality of calibration, number of reference acquisitions averaged and TDC (time-to-digital converter) settings (resolution, Np multiplier (number of pushes correction factor), minimum number of points, i.e. minimum acquisition width which defines a peak). To extract the maximum information from as few experiments as possible, a Design of Experiment approach was used. The data will be used as a basis for developing guidance on accurate mass measurement on q-oaToF instruments. 相似文献
146.
Simultaneous temperature and 2D velocity measurements in a turbulent heated jet using combined laser-induced fluorescence and LDA 总被引:1,自引:0,他引:1
This paper presents an efficient technique for the characterization of thermal transport properties in turbulent flows. The
method is based on the temperature dependence of fluorescence, induced by laser radiation, of an organic dye. The laser-induced
fluorescence technique is combined with 2D laser Doppler anemometry, in order to measure in the same sample volume simultaneously
and instantaneously the temperature and velocity. The technique is demonstrated on a turbulent heated round jet: the mean
and fluctuating dynamic and thermal fields are investigated, and the temperature-velocity cross-correlations are determined
in order to characterize the turbulent diffusivity and the turbulent Prandtl number.
Received: 30 October 1997/Accepted: 14 July 1998 相似文献
147.
A concept of teaching basic mathematical knowledge and skills related to the vocational training of master craftsmen in the field of electrical engineering and metal engineering is described. The provision of application-oriented mathematics is pointed out as an important basis of competence needed by master craftsmen in their professional surroundings. A framework for the development of training supporting materials for mathematics learning is explained on the basis of earlier experiences as well as on newer constructivitically oriented instructional approaches of educational psychology and in consideration of current professional guidelines and examination regulations of the Chambers of Industry and Commerce. These materials are developed into three CBT-units which are to be of fundamentally different design in order to enable learning on different levels using the material on the learners' own initiative. Active self-organization is offered to the course participants via the use of interactive multimedia-based presentations. 相似文献
148.
149.
150.
Mario Glanz Sebastian Dechert Herbert Schumann Dietmar Wolff Dietmar Wolff Jürgen Springer 《无机化学与普通化学杂志》2000,626(12):2467-2477
The Influence of the Coordination Sphere of Samarocenes on the Synthesis of Liquid Crystalline Polymethacrylates (C5Me5)2Sm(THF)2 ( 1 ) reacts with 1,3‐Diisopropyl‐4,5‐dimethylimidazoline‐2‐ylidene C3N2Me2iPr2 (iPr‐carben) with formation of (C5Me5)2Sm(iPr‐carben) ( 3 ). The reaction of (C5Me4Et)2Sm(THF)2 ( 2 ) with Al2Me6 in toluene yields [(C5Me4Et)2Sm(CH3)Al(CH3)3]2 ( 6 ). 3 and 6 were characterized by single crystal X‐ray structure analysis. Via living polymerization of mesogenic methacrylates with the organosamarium complexes 1 , 2 , 3 , (C5Me5)2Sm(C3H5) ( 4 ), (C5Me5)2Sm(CH3)(THF) ( 5 ), 6 , and (C5Me4Et)2SmCH(SiMe3)2 ( 7 ), liquid crystalline homo‐ and blockcopolymers were obtained with narrow molecular mass distribution indexes in high yield. Partial competitive mechanisms are observed dependend of the structure of the catalyst and the polarity of the solvents. 相似文献