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51.
Patrik Vrábel 《Journal of luminescence》2006,118(2):283-292
Capillary electrophoresis with laser-induced fluorescence detection (CELIF) is a powerful tool for separation and sensitive determination of fluorescent species. Biologically active compounds, such as amino acids, peptides and proteins may exhibit native fluorescence, which is however often low and/or an expensive laser is required for excitation in UV. Therefore, labelling of the analytes with a fluorescent dye is usually necessary.In this work, a home-built CELIF instrument with diode pumped frequency-doubled continuous wave Nd:YAG excitation laser with feedback power regulation (532 nm) was constructed. The suitability of this type of laser for LIF detection in a separation method was found excellent. A limit of detection (LOD) (S/N=3) of 2×10−13 mol/l was achieved with rhodamine B, which is comparable to those obtained using similar instruments with Ar+ laser [Y.F. Cheng, N.J. Dovichi, Science 242 (1988) 562, E.S. Yeung et al., J. Chromatogr. 608 (1992) 73]. LOD of a protein derivatized according to modified procedures [M.J. Little et al., Anal. Chim. Acta 339 (1997) 279, A. Chersi et al., Biochim. Biophys. Acta 1336 (1997) 83] was determined. Detection of the derivatives was found to be limited by insufficient reaction recovery at low analyte concentration, chemical noise, separation efficiency and quality of the derivatizing reagent rather than by the detector performance. As a consequence, a huge gap between the detection ability of CELIF instruments and LOD determined in real samples is revealed. 相似文献
52.
The effect of filling high density polyethylene (HDPE) with calcium carbonate (up to 50% by weight) on the stress relaxation and the creep in uniaxial extension at room temperature was investigated. The addition of CaCO3 was found to have a strong influence on the flow behaviour of HDPE. In particular, it was observed that the internal stress level, calculated from relaxation data, increased markedly with the filler content. The reduction in creep rate of the filled samples suggested that the CaCO3-particles induce a change in the structure of the HDPE-interphase close to the filler surface. This was supported by dynamic mechanical measurements performed at low temperatures on swollen HDPE-CaCO3 samples. 相似文献
53.
The Quest for Polysulfides in Lithium–Sulfur Battery Electrolytes: An Operando Confocal Raman Spectroscopy Study 下载免费PDF全文
Dr. Julien Hannauer Dr. Johan Scheers Julien Fullenwarth Dr. Bernard Fraisse Prof. Dr. Lorenzo Stievano Prof. Dr. Patrik Johansson 《Chemphyschem》2015,16(13):2755-2759
Confocal Raman spectra of a lithium–sulfur battery electrolyte are recorded operando in a depth‐of‐discharge resolved manner for an electrochemical cell with a realistic electrolyte/sulfur loading ratio. The evolution of various possible polysulfides is unambiguously identified by combining Raman spectroscopy data with DFT simulations. 相似文献
54.
Cover Picture: The Quest for Polysulfides in Lithium–Sulfur Battery Electrolytes: An Operando Confocal Raman Spectroscopy Study (ChemPhysChem 13/2015) 下载免费PDF全文
55.
56.
Six derivatives ( 1 , 2 , 3 , 4 , 5 , 6 ) of 2‐phenyl‐1H‐imidazole were tested as catalysts of Henry reaction. Three new ( 4 , 5 , 6 ) 2‐phenyl‐1H‐imidazole derivatives, differently substituted (thio)ureas, were synthesized and determined by 1H NMR and IR spectroscopy and elemental analysis. Two types of catalysis, homogeneous and heterogeneous, were examined and compared. Clay minerals Ca‐MMT and Cu‐MMT were used as solid supports for heterogeneous catalysis. The best results were obtained using compound 2 under conditions of heterogeneous method D from the point of view of yield and reaction time. J. Heterocyclic Chem., (2011) 相似文献
57.
Highly ordered mixed V(2)O(5)-TiO(2) nanotubes can be formed by self-organizing anodization of Ti-V alloys with vanadium content of up to 18 at%. In the resulting oxide nanotube arrays, the vanadium is electrochemically switchable leading to a specific capacitance that can reach up to 220 F g(-1) and an energy density of 19.56 Wh kg(-1) with perfect reversibility and long-term stability. Thus these mixed oxide nanotubes may be considered as a promising candidate for supercapacitors. 相似文献
58.
Ek M Borgstr?m MT Karlsson LS Hetherington CJ Wallenberg LR 《Microscopy and microanalysis》2011,17(5):752-758
The twin interface structure in twinning superlattice InP nanowires with zincblende structure has been investigated using electron exit wavefunction restoration from focal series images recorded on an aberration-corrected transmission electron microscope. By comparing the exit wavefunction phase with simulations from model structures, it was possible to determine the twin structure to be the ortho type with preserved In-P bonding order across the interface. The bending of the thin nanowires away from the intended 110 axis could be estimated locally from the calculated diffraction pattern, and this parameter was successfully taken into account in the simulations. 相似文献
59.
Bryan Ek 《Journal of Difference Equations and Applications》2019,25(2):262-293
The q-binomial coefficients were conjectured to be unimodal as early as the 1850's but it remained unproven until Sylvester's 1878 proof using invariant theory. In 1982, Proctor gave an ‘elementary’ proof using linear algebra. Finally, in 1989, Kathy O'Hara provided a combinatorial proof of the unimodality of the q-binomial coefficients. Very soon thereafter, Doron Zeilberger translated the argument into an elegant recurrence. We introduce several perturbations to the recurrence to create a larger family of unimodal polynomials. We analyse how these perturbations affect the final polynomial and analyse some specific cases. 相似文献
60.
Shanshan Qin Nikita Denisov Hyesung Kim Prof. Patrik Schmuki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(10):e202316660
When using single atoms (SAs) as a co-catalyst in photocatalytic H2 generation, achieving a well-dispersed, evenly distributed and adjustable SA surface density on a semiconductor surface is a challenging task. In the present work we use the planar adsorption of tetrakis-(4-carboxyphenyl)-porphyrin (TCPP) and its platinum coordinated analogue, Pt-TCPP, onto anatase TiO2 surfaces to establish a spatially controlled decoration of SAs. We show that the surface Pt SA density can be very well controlled by co-adsorption of Pt-TCPP and TCPP in the planar monolayer regime, and by adjusting the Pt-TCPP to TCPP ratio a desired well dispersed surface density of SAs up to 2.6×105 atoms μm−2 can be established (which is the most effective Pt SA loading for photocatalysis). This distribution and the SA state are maintained after a thermal treatment in air, and an optimized SA density as well as a most active form of Pt for photocatalytic H2 evolution can be established and maintained. 相似文献