306 research outputs found

    3-Ethyl 5-methyl 4-(2,3-dichloro­phen­yl)-2,6-dimethyl­pyridine-3,5-dicarboxyl­ate

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    In the title compound, C18H17Cl2NO4, an oxidation product of felodipine, the dihedral angle between the benzene and pyridine rings is 75.3 (4)°. The crystal structure is stabilized by intermolecular C—H⋯O interactions

    Adsorption of phenylacetylene on Si(100)-2×1: Reaction mechanism and formation of a styrene-like π-conjugation system

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    This is the published version. Copyright 2003 American Physical SocietyThe interactions of phentylacetylene and phenylacetylene−α−d1 with Si(100)−2×1 have been studied as a model system to mechanistically understand the adsorption of conjugated π-electron aromatic substitutions on Si(100)−2×1. Vibrational signatures show that phenylacetylene covalently binds to the surface through a [2+2]-like cycloaddition pathway between the external C≡C and Si=Si dimer, forming styrene-like conjugation structure which was further supported by the chemical-shift of C 1s core level. These experimental results are consistent with the density-functional theory [B3LYP/6−311//+G(d)] calculations. The resulting styrene-like conjugation structures may possibly be employed as an intermediate for further organic syntheses and fabrication of molecular architecture for modification and functionalization of Si surfaces, or as a monomer for polymerization on Si surfaces

    Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory

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    Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by Duan-Lukin-Cirac-Zoller protocol, many improved quantum-repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multi-photons (multi-photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Here, we demonstrate the storage of deterministic single photons emitted from a quantum dot in a polarization-maintaining solid-state quantum memory; in addition, multi-temporal-mode memory with 11, 2020 and 100100 narrow single-photon pulses is also demonstrated. Multi-photons are eliminated, and only one photon at most is contained in each pulse. Moreover, the solid-state properties of both sub-systems make this configuration more stable and easier to be scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devicesComment: Published version, including supplementary materia

    Effect of P450 Oxidoreductase Polymorphisms on the Metabolic Activities of Ten Cytochrome P450s Varied by Polymorphic CYP Genotypes in Human Liver Microsomes

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    Background/ Aims: Little is known about the effect of P450 oxidoreductase (POR) gene polymorphisms on the activities of CYPs with multiple genotypes. Methods: We genotyped 102 human livers for 18 known POR single nucleotide polymorphisms (SNPs) with allelic frequencies greater than 1% as well as for 27 known SNPs in 10 CYPs. CYP enzyme activities in microsomes prepared from these livers were determined by measuring probe substrate metabolism by high performance liquid chromatograph. Results: We found that the effects of the 18 POR SNPs on 10 CYP activities were CYP genotype-dependent. The POR mutations were significantly associated with decreased overall Km for CYP2B6 and 2E1, and specific genotypes within CYP1A2, 2A6, 2B6, 2C8, 2D6 and 2E1 were identified as being affected by these POR SNPs. Notably, the effect of a specific POR mutation on the activity of a CYP genotype could not be predicted from other CYP genotypes of even the same CYP. When combining one POR SNP with other POR SNPs, a hitherto unrecognized effect of multiple-site POR gene polymorphisms (MSGP) on CYP activity was uncovered, which was not necessarily consistent with the effect of either single POR SNP. Conclusions: The effects of POR SNPs on CYP activities were not only CYP-dependent, but more importantly, CYP genotype-dependent. Moreover, the effect of a POR SNP alone and in combination with other POR SNPs (MSGP) was not always consistent, nor predictable. Understanding the impact of POR gene polymorphisms on drug metabolism necessitates knowing the complete SNP complement of POR and the genotype of the relevant CYPs

    Multiple configurations of N-methylpyrrole binding on Si(111)-7×7

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    The adsorption configurations of N-methylpyrrole on Si(111)-7×7 were investigated using high-resolution electron energy-loss spectroscopy, x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and density function theory calculations. Compared to physisorbed N-methylpyrrole, chemisorbed molecules present a different vibrational feature at 2886 cm-1 attributable to ν[(Si)Csp3-H] in addition to the vibrational features of (sp2)Cα-H (3106 cm-1), (sp2)Cβ-H (3050 cm-1), and C—H of CH3 (2944 cm-1) stretching modes, demonstrating the direct interaction between C=C bonds and Si(111)-7×7. The major change of N 1s XPS spectrum of N-methylpyrrole upon chemisorption strongly suggests the coexistence of two chemisorption states, further confirmed in the strong dependence of STM image features on the sample bias together with statistical analysis. The concurrent occurrence of [4+2] and [2+2] cycloadditions is proposed to account for these two adsorption configurations of N-methylpyrrole on Si(111)-7×
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