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1.
The determination of the enantiomeric purity of 2 or 3-substituted cyclanones, particularly cyclohexanones, is conveniently achieved by derivatisation into cyclic aminals with commercially available (R, R)-1,2-diphenylethylenediamine. The derivatisation procedure is directly done into the NMR tube, instantaneously, and 13C NMR allows an accurate measure of the ee. 相似文献
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Thermogravimetric determination of magnesium,potassium and lead by precipitation with dilituric acid
The thermolysis curves of magnesium, potassium, and lead diliturate have established that either the hydrated or anhydrous forms of these precipitates are stable enough for their gravimetric use to be possible. Magnesium and lead were determined by precipitation with dilituric acid while potassium was precipitated with trimethylamine diliturate. 相似文献
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Véronique Dupuis Nils Blanc Luis E. Diaz-Sanchez Arnaud Hillion Alexandre Tamion Florent Tournus Gustavo M. Pastor Andrei Rogalev Fabrice Wilhelm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2013,67(2):1-4
In this paper, the one-way absorption property in one-dimensional dielectric/metal photonic crystal structure with a dielectric defect layer is studied. The effects of incident angle and state of polarization on one-way absorption behaviour of the anti-resonant (AR) mode are investigated. The normally incident wave from left to right propagation is totally allowed to penetrate to the structure but right to left propagation totally reflected at the same wavelength. It is found that, with increasing of the incident angle, the AR mode shifts to the lower wavelengths and its intensity decreases. Simultaneously, another AR mode with reversed one-way property appears at higher wavelength. The one-way behaviour on absorption is observed at the both states of polarizations but is localized on different wavelengths. Those effects, are suggesting that the proposed structure can be used as a direction sense polarization splitter or reflector/antireflector device. 相似文献
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Topological properties of native folds are obtained from statistical analysis of 160 low homology proteins covering the four structural classes. This is done analyzing one, two and three-vertex joint distribution of quantities related to the corresponding network of amino acid residues. Emphasis on the amino acid residue hydrophobicity leads to the definition of their center of mass as vertices in this contact network model with interactions represented by edges. The network analysis helps us to interpret experimental results such as hydrophobic scales and fraction of buried accessible surface area in terms of the network connectivity. Moreover, those networks show assortative mixing by degree. To explore the vertex-type dependent correlations, we build a network of hydrophobic and polar vertices. This procedure presents the wiring diagram of the topological structure of globular proteins leading to the following attachment probabilities between hydrophobic–hydrophobic 0.424(5), hydrophobic-polar 0.419(2) and polar–polar 0.157(3) residues. 相似文献
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Vianney O. Santos Isabela R. Leite Alexandre G. Brolo Joel C. Rubim 《Journal of Raman spectroscopy : JRS》2016,47(6):674-680
The electrochemical conversion of CO2 into value‐added products using room temperature ionic liquids as solvent/electrolyte has been proposed as an alternative to minimize the environmental effects of CO2 emissions. A key issue in the design of electrochemical systems for the reduction of CO2 is the in situ identification of intermediate surface species as well as reaction products. Copper electrodes, besides being used as cathodes in the electrochemical reduction of CO2, present surface‐enhanced Raman scattering (SERS) when properly activated. In this sense, the electrochemical reduction of CO2 over a copper electrode in the room temperature ionic liquids 1‐n‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMI.BF4) was investigated by cyclic voltammetry and by in situ SERS. The cyclic voltammetries have shown that the presence of CO2 on the BMI.BF4 anticipates the reduction of BMI+ to the corresponding carbene. Fourier‐transform‐SERS spectra excited at 1064 nm and SERS spectra excited at 632.8 nm have shown vibrational signals from adsorbed CO. These SERS results indicated that CO adsorbs on the copper surface at two different surface sites. The observation of a 2275 cm−1 vibration in the SERS spectra also confirmed the presence of chemically adsorbed CO2. Other products of CO2 reduction in BMI.BF4, besides CO, were identified, including BMI carbene and the BMI‐CO2 adduct. The SERS results also suggest that the presence of a thin film of Cu2O on the copper surface anticipates the reduction of CO2 to CO, an important component of syngas. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
9.
We present exact solutions for the position-dependent mass Schrödinger equation (PDMSE) in an annular billiard with impenetrable walls where the mass is allowed to depend on the radial position, i.e., μ=μ(r). Exact wavefunctions are calculated explicitly for four mass distributions. 相似文献
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