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421.
Symonds JP Arnolds H Zhang VL Fukutani K King DA 《The Journal of chemical physics》2004,120(15):7158-7164
CO on Ru[1010] was investigated by broadband femtosecond sum-frequency spectroscopy at 200 K. Approximately half of the frequency shift of 71 cm(-1) over the coverage range from 0.15 to 1.22 monolayers is shown to originate from dipole-dipole coupling, with the remainder due to a chemical shift. Despite low adlayer-surface registration at the highest coverages, the linewidth of the C-O stretch is comparatively low, and is described by homogeneous broadening according to sum-frequency free-induction decay measurements in the time domain. This can be explained by the dominance of the CO dipole coupling strength over the static disorder present in a coincidence structure. As the coverage decreases below 0.3 monolayer, the linewidth increases considerably, indicative of inhomogeneous broadening. Supported by a concomitant frequency change we suggest that at low coverages CO molecules form chains of irregular length in the [0001] direction, as has been shown for other surfaces with similar symmetry. 相似文献
422.
Antje Widmann Heike Kahlert Harm Wulff Fritz Scholz 《Journal of Solid State Electrochemistry》2005,9(5):380-389
Electrochemical reduction/oxidation cycles of immobilised powder mixtures of KCu[hcc] and KZn[hcf] as well as their mechanical milling lead to the formation of a quaternary solid solution (mixed crystals) with Cu2+ and Zn2+ on the nitrogen coordinated sites and Fe3+ and Co3+ on the carbon coordinated sites. The reaction products were studied by the X-ray diffractometry and voltammetric techniques. The formation of solid solutions of the general formula KCuxZn1-x[hcc]x[hcf]1-x is the first example of an electrochemical and mechanochemical reaction leading to mixed hexacyanometalates.Dedicated to Professor Dr. G. Horányi on the occasion of his 70th birthday. 相似文献
423.
The interferences from Cd, Cu, Hf, Pb, Sr, Zn, Zr and Y on the inductively coupled plasma quadrupole mass spectrometry (ICP-MS) determination of Pt, Pd, Rh, Ru and Ir in geological (Pt-ore SARM-7, abundance range for platinum metals 0.07-3.74 μg/g) and environmental samples (sediment JSd-2 abundance range for Pt and Pd 0.0167-0.021 μg/g; road dust and plant sample) are evaluated using model solutions, real samples and comparison to inductively coupled plasma atomic emission spectrometry (ICP-AES) results. Pt, Rh, Ru and Ir can be determined usually after introduction of corrections for the interference in all investigated materials though in sediments the direct determination of Pt might be a problem depending on the actual Hf concentrations. The direct determination of Pd (after microwave-assisted acid digestion) is possible in ores using all investigated isotopes (, , ), in plants using and correction for the interferences of Zr, Mo and Cd, and not possible in sediments and road dust. Therefore, we developed a procedure for isolation of Pd using its diethyl-dithio-carabamate (DDTC) complex. The detection limits for Pt, Pd and Ir are 0.015 ng/g, and for Ru and Rh 0.03 ng/g. 相似文献
424.
Musshoff F Junker HP Lachenmeier DW Kroener L Madea B 《Journal of chromatographic science》2002,40(6):359-364
This study describes a fully automated procedure using alkaline hydrolysis and headspace (HS) solid-phase microextraction (SPME) followed by on-fiber derivatization and gas chromatographic (GC)-mass spectrometric (MS) detection of amphetamine, methamphetamine, methylendioxyamphetamine, methylendioxymethamphetamine, methylendioxyethylamphetamine, methylendioxyphenylbutanamine, and methylmethylendioxyphenylbutanamine in human hair samples. Ten milligrams of hair is washed with deionized water, petroleum ether, and dichloromethane. After the addition of deuterated internal standards the sample is hydrolyzed with sodium hydroxide and directly submitted to HS-SPME. After the absorption of analytes for an on-fiber derivatization procedure the fiber is directly placed into the HS of a second vial containing N-methyl-bis(trifluoroacetamide) before GC-MS analysis. The limits of detection are determined between 0.01 and 0.17 ng/mg. Absolute analyte recoveries are in the range between 0.3% and 7.5%. Linearity is proven over a range from 0.1 to 50 ng/mg with coefficients of correlation from 0.998 to 1. In comparison with conventional methods of hair analysis, this fully automated HS-SPME-GC-MS procedure is substantially faster and easier to perform without using solvents. It uses minimal sample amounts and has the same degree of sensitivity and reproducibility. 相似文献
425.
Wolfgang A. Herrmann John M. Huggins Christine Bauer Manfred L. Ziegler Heike Pfisterer 《Journal of organometallic chemistry》1984,262(2):253-262
The μ-ethylidene complex (μ-CHCH3)[(η5-C5Me5)Co(μ-CO)]2 (Me CH3) accessible along the diazoalkane route from [(η5-C5Me5)Co(μ-CO)]2 and diazoethane exhibits both in solution (IR spectroscopy) and in the crystalline state (X-Ray diffraction) a nearly Cs-symmetrical structure with a triply bridged metal—metal bond. This compound thus differs from the parent μ-methylene complex of analogous composition, which latter compound exists as a mixture of the isomers A and B with terminal and edge-bridging carbonyl ligands, respectively (IR spectra, X-Ray diffraction). A structural comparison with closely related alkylidene- and carbonyl-bridged derivatives reveals a striking lack of correlation between metal—metal bond lengths and formal bond orders as they result from the EAN rule. 相似文献
426.
427.
Oliver Schütze Víctor Adrián Sosa Hernández Heike Trautmann Günter Rudolph 《Journal of Heuristics》2016,22(3):273-300
We present a new hybrid evolutionary algorithm for the effective hypervolume approximation of the Pareto front of a given differentiable multi-objective optimization problem. Starting point for the local search (LS) mechanism is a new division of the decision space as we will argue that in each of these regions a different LS strategy seems to be most promising. For the LS in two out of the three regions we will utilize and adapt the Directed Search method which is capable of steering the search into any direction given in objective space and which is thus well suited for the problem at hand. We further on integrate the resulting LS mechanism into SMS-EMOA, a state-of-the-art evolutionary algorithm for hypervolume approximations. Finally, we will present some numerical results on several benchmark problems with two and three objectives indicating the strength and competitiveness of the novel hybrid. 相似文献
428.
Evaluating Shielding‐Based Ring‐Current Models by Using the Gauge‐Including Magnetically Induced Current Method
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Magnetically induced current densities and integrated ring‐current strength susceptibilities have been calculated at the density functional theory (DFT) level for a test set consisting of 17 ring‐shaped molecules using the gauge‐including magnetically induced current (GIMIC) method. Reliable values for the ring‐current strengths have been obtained by performing numerical integration of the current‐density susceptibility passing a cut plane perpendicularly to the molecular ring. The current densities and ring current strengths were calculated at the DFT level using the B3LYP functional and def2‐TZVP basis sets. Current densities and ring‐current strengths have also been calculated at the Hartree‐Fock self‐consistent field (HF‐SCF) level using Dunning’s aug‐cc‐pVTZ basis sets, which allow a direct comparison with ring‐current strengths that have previously been estimated using ring‐current models based on magnetic shielding calculations. Current density calculations at both levels of theory show that the magnetic shielding based ring‐current models are not a very accurate means to estimate the magnetically induced ring current strengths, whereas they provide qualitatively the correct aromaticity trends for the studied molecules. 相似文献
429.
M. Sc. Paul Kahl M. Sc. J. Philipp Wagner Ciro Balestrieri Dr. Jonathan Becker Dr. Heike Hausmann Prof. Dr. Graham J. Bodwell Prof. Dr. Peter R. Schreiner 《Angewandte Chemie (International ed. in English)》2016,55(32):9277-9281
The fusion of the sp3‐hybridized parent diamondoid adamantane with the sp2‐hybridized pyrene results in a hybrid structure with a very large dipole moment which arises from bending the pyrene moiety. Presented herein is the synthesis, study of the electronic and optical properties, as well as the dynamic behavior of this new hydrocarbon. 相似文献
430.
Xiaoyue Cheng Dianne Cook Heike Hofmann 《Journal of computational and graphical statistics》2016,25(4):1057-1076
Temporal data are information measured in the context of time. This contextual structure provides components that need to be explored to understand the data and that can form the basis of interactions applied to the plots. In multivariate time series, we expect to see temporal dependence, long term and seasonal trends, and cross-correlations. In longitudinal data, we also expect within and between subject dependence. Time series and longitudinal data, although analyzed differently, are often plotted using similar displays. We provide a taxonomy of interactions on plots that can enable exploring temporal components of these data types, and describe how to build these interactions using data transformations. Because temporal data are often accompanied other types of data we also describe how to link the temporal plots with other displays of data. The ideas are conceptualized into a data pipeline for temporal data and implemented into the R package cranvas. This package provides many different types of interactive graphics that can be used together to explore data or diagnose a model fit. 相似文献