An ab initio self-consistent calculation has been carried out for the electronic properties of BaC6. Energy bands and charge densities are presented for BaC6 and compared with those of LiC6. The results show that the band originating from Ba states has a mixture of s and d character and the d component hybridizes appreciably with the π bands of graphite. The Fermi level intersects this band as well as the graphite π bands, giving rise to a complicated Fermi surface with several types of carriers. Depending on the type of volumetric partitioning, the charge transfer from Ba to graphite layers is determined to be between 0.7 and 1.0 electron per Ba atom. The calculated results are consistent with available transport and optical measurements. 相似文献
A simple, selective, precise and accurate reversed phase-HPLC assay for analysis of gemfibrozil in tablets was developed and validated. Separation and quantification were achieved on a Phenomenex C18 column under isocratic conditions using a mobile phase (methanol:water, 80:20, v/v) maintained at 1.1 mL min−1. UV-detection was at 280 nm. Atorvastatin was selected as an internal standard. The standard curves were linear over the range of 0.5–3.0 μg mL−1 (r > 0.999). The limits of detection and quantification were 0.20 and 0.51 μg mL−1, respectively. The recoveries for gemfibrozil were above 99.01%. The intra-day and inter-day precision (RSD) for gemfibrozil were below 1.74 and 1.83%, respectively. No chromatographic interferences from the tablet excipients were found. The results of the developed procedure in tablets were compared with those of the reference method to assess gemfibrozil content. Statistical comparison of the results with the reference method using spectrofluorimetric method showed excellent agreement and proved no significant difference in accuracy and precision. This HPLC method is fast and simple for the analysis of gemfibrozil in pharmaceutical preparations. 相似文献
A new complex of diaquabis(5-methoxyindole-2-carboxylato)bis(3-picoline)nickel(II) (Ni(5-MeOI2CA)2(3-pic)2(H2O)2), was synthesized for the first time and characterized by elemental analysis, FT-IR and electronic spectroscopy (UV-Vis) and single-crystal X-ray diffraction (XRD) techniques. The thermal degradation of the Ni(II) complex was investigated using thermogravimetric and differential thermal analyses techniques in oxygen atmosphere. The molecular structure of the complex was determined by single crystal X-ray diffraction technique. Hirshfeld surface analysis (HSA) investigated the packing modes and intermolecular interactions in molecular crystals, as they provide a visual picture of intermolecular interactions. In addition, all computational studies at B3LYP/6-311++G(d,p) were carried out for theoretical characterization of Ni(II) complex. The optimized geometry results, which were well represented the X-ray data, were shown that the chosen of DFT/B3LYP/6-311++G(d,p) was a successful choice for title compound. After a successful optimization, FMOs, chemical activity, non-linear optical properties (NLO), molecular electrostatic potential (MEP), Mulliken population (MPA), natural population analyses (NPA), Fukui function analysis (FFA) and natural bond orbital analysis (NBO), which could not obtained by experimental ways, were calculated and investigated. The computed of net charges and chemical activity studies which helped to identifying the electrophilic/nucleophilic nature. 相似文献
Cytochrome P450 monooxygenases (CYPs) form a vast and diverse enzyme class of particular interest in drug development and
a high biotechnological potential. Although very diverse in sequence, they share a common structural fold. For the comprehensive
and systematic comparison of protein sequences and structures the Cytochrome P450 Engineering Database (CYPED) was established.
It was built up based on an extensible data model that enables its functions readily enhanced. 相似文献
Summary: Thermally curable benzoxazine ring‐containing polystyrene macromonomers were synthesized and characterized. 1,4‐Dibromo‐2,5‐bis(bromomethyl)benzene and 1,4‐dibromo‐2‐(bromomethyl)benzene were used as initiators in the atom transfer radical polymerization of styrene. The resulting polymers were used in combination with 3‐aminophenylboronic acid hemisulfate, for a Suzuki coupling. The obtained polymers, with amino groups in the middle or end of the chains, were reacted with formaldehyde and phenol to yield benzoxazine ring‐containing macromonomers. In addition to the glass transition temperature of the polystyrene segment observed at ca. 105 °C, differential scanning calorimetry thermograms exhibit an exotherm at ca. 276 °C corresponding to the oxazine thermal polymerization. Both macromonomers undergo thermal curing with the formation of thermosets having polystyrene segments.
Structure of the benzoxazine‐functionalized polystyrene. 相似文献
The title compound, [Cu(C6H2Br3O)2(NH3)2], a monomeric centrosymmetric CuII complex, crystallizes in the monoclinic system. The CuO2N2 coordination sphere is trans planar, [Cu—O 1.943 (5) Å and Cu—N 1.977 (6) Å], with the fifth and sixth coordination sites occupied by Br atoms from the phenoxide ions [Cu—Br 3.129 (1) Å], resulting in an elongated distorted octahedral structure for the CuO2N2Br2 coordination. Each of the NH3 groups forms two hydrogen bonds with the Br and O atoms of the CuO2N2Br2 moiety of a neighbouring molecule. This arrangement constitutes a one‐dimensional chain along the x axis of the unit cell. 相似文献
The control problem of axially moving strings occurs in a large class of mechanical systems. In addition to the longitudinal displacement, the strings are subject to undesirable transversal vibrations. In this work, in order to suppress these vibrations, we consider a control by a hydraulic touch-roll actuator at the right boundary. We prove uniform stability of the system using a viscoelastic material and an appropriate boundary control force applied to the touch rolls of the actuator. The features of the present work are: taking into account the mass flow entering in and out at the boundaries due to the axial movement of the string and overcoming the difficulty raised by the Kirchhoff coefficient which does not allow us to profit from the dissipativity of the system (as in the existing works so far). We shall make use of an inequality which is new in this theory. 相似文献