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91.
Insertion of elemental selenium or tellurium into the Csp2-Zr bond of alkenylchlorozirconocenes followed by oxidation in air affords (E)-divinyl diselenides or (E)-divinyl ditellurides. 相似文献
92.
《Mendeleev Communications》2021,31(6):807-809
Two new heptamethine cyanine dye–fullerene C60 covalently- linked dyads, which absorb in far-red and NIR spectral regions, have been synthesized by esterification click reaction and characterized by physicochemical methods. No significant fluorescence quenching was found due to weak electronic coupling between heptamethine moiety and fullerene core, which was confirmed by photophysical and electrochemical methods. Such dyads can be useful for cell imaging and fluorescence diagnostics of various fullerene derivatives. 相似文献
93.
Derivatives of N-acetylgalactosamine and N-acetylglucosamine in which the 4-OH group could be selectively labelled have been prepared from a common precursor. 相似文献
94.
Recently it has been shown experimentally by the authors that a highly twisted thin nematic cell at low temperatures can separate into a smectic A region in the middle of the cell surrounded by twisted nematic layers at the boundaries. In this case the twist is expelled into the nematic layers and the nematic–smectic A transition temperature is strongly depressed. We present a thermodynamic theory of such a phase transition in a twisted nematic cell, taking into account that the smectic A slab inside the nematic cell can be stable only if the decrease of free energy in the smectic region overcomes the increase in distortion energy of the twist deformation in the nematic layers plus the energy of the nematic–smectic A interface. In such a system the equilibrium thickness of the smectic A slab corresponds to the minimum of the total free energy of the whole cell, which includes all the bulk and surface contributions. Existing experimental data are at least qualitatively explained by the results of the present theory. This opens a unique possibility to study the properties of the nematic–smectic interface which is perpendicular to the smectic layers. 相似文献
95.
We present a numerical algorithm for pricing derivatives on electricity prices. The algorithm is based on approximating the generator of the underlying price process on a lattice of prices, resulting in an approximation of the stochastic process by a continuous time Markov chain. We numerically study the rate of convergence of the algorithm for the case of the Merton jump-diffusion model and apply the algorithm to calculate prices and sensitivities of both European and Bermudan electricity derivatives when the underlying price follows a stochastic process which exhibits both fast mean-reversion and jumps of large magnitude. 相似文献
96.
Fred Espen Benth 《Applied Mathematical Finance》2018,25(1):36-65
The recent introduction of wind power futures written on the German wind power production index has brought with it new interesting challenges in terms of modelling and pricing. Some particularities of this product are the strong seasonal component embedded in the underlying, the fact that the wind index is bounded from both above and below and also that the futures are settled against a synthetically generated spot index. Here, we consider the non-Gaussian Ornstein–Uhlenbeck type processes proposed by Barndorff-Nielsen and Shephard in the context of modelling the wind power production index. We discuss the properties of the model and estimation of the model parameters. Further, the model allows for an analytical formula for pricing wind power futures. We provide an empirical study, where the model is calibrated to 37 years of German wind power production index that is synthetically generated assuming a constant level of installed capacity. Also, based on 1 year of observed prices for wind power futures with different delivery periods, we study the market price of risk. Generally, we find a negative risk premium whose magnitude decreases as the length of the delivery period increases. To further demonstrate the benefits of our proposed model, we address the pricing of European options written on wind power futures, which can be achieved through Fourier techniques. 相似文献
97.
Kew-Yu Chen 《Molecular Crystals and Liquid Crystals》2016,625(1):212-220
The title compound 2-(2-hydroxyphenyl)benzo[d]oxazole-6-carbaldehyde (1a) was synthesized and characterized by single-crystal X-ray diffraction. Compound 1a possesses intramolecular C–H···O and O–H···N hydrogen bonds, which generate S(5) and S(6) rings, respectively. Intermolecular π–π stacking is observed in the crystal structure, which links a pair of molecules into a cyclic centrosymmetric dimer. The crystal structure is further stabilized by three different intermolecular C–H···O hydrogen bonds, which link the molecules into a continuous three-dimensional framework. Its spectroscopic properties and complementary density functional theory (DFT) calculations are also reported. 相似文献
98.
Felix Katzsch Tobias Gruber Edwin Weber 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(9):679-684
The syntheses of three bis(benzo[b]thiophen‐2‐yl)methane derivatives, namely bis(benzo[b]thiophen‐2‐yl)methanone, C17H10OS2, (I), 1,1‐bis(benzo[b]thiophen‐2‐yl)‐3‐(trimethylsilyl)prop‐2‐yn‐1‐ol, C22H20OS2Si, (II), and 1,1‐bis(benzo[b]thiophen‐2‐yl)prop‐2‐yn‐1‐ol, C19H12OS2, (III), are described and their crystal structures discussed comparatively. The conformation of ketone (I) and the respective analogues are rather similar for most of the compounds compared. This is true for the interplanar angles, the Caryl—Cbridge—Caryl angles and the dihedral angles. The best resemblance is found for a bioisotere of (I), viz. 2,2′‐dinaphthyl ketone, (VII). By way of interest, the crystal packings also reveal similarities between (I) and (VII). In (I), the edge‐to‐face interactions seen between two napthyl residues in (VII) are substituted by S…π contacts between the benzo[b]thiophen‐2‐yl units in (I). In the structures of the bis(benzo[b]thiophen‐2‐yl)methanols, i.e. (II) and (III), the interplanar angles are also quite similar compared with analogues and related active pharmaceutical ingredients (APIs) containing the dithiophen‐2‐ylmethane scaffold, though the dihedral angles show a larger variability and produce unsymmetrical molecules. 相似文献
99.
Luca Deseri Mario Di Paola Massimiliano Zingales 《International Journal of Solids and Structures》2014
Complex materials, often encountered in recent engineering and material sciences applications, show no complete separations between solid and fluid phases. This aspect is reflected in the continuous relaxation time spectra recorded in cyclic load tests. As a consequence the material free energy cannot be defined in a unique manner yielding a significative lack of knowledge of the maximum recoverable work that can extracted from the material. The non-uniqueness of the free energy function is removed in the paper for power-laws relaxation/creep function by using a recently proposed mechanical analogue to fractional-order hereditariness. 相似文献
100.
Firouz Matloubi Moghaddam Zohreh Mirjafary Marjan Jebeli Javan Sara Motamen Hamid Saeidian 《Tetrahedron letters》2014
A mild and efficient tandem process for the synthesis of new highly substituted 2-pyrones starting from commercially available 2-arylacetic acids has been developed. The synthesis is based on the Knoevenagel condensation of 1,3-cyclohexadiones with various β-formyl-esters, followed by lactonization in the presence of nano ZnO (20 mol %). Moderate to high yields and readily available cheap starting materials are the key features of the present method. 相似文献