A high-performance liquid chromatographic method has been developed for the simultaneous analysis of the flavonols myricitrin (1), avicularin (2), and juglanin (3) in rat plasma and urine after oral administration of the total flavonoids from Polygonum aviculare. Samples were prepared by solid-phase extraction then separated on a C18 reversed-phase column by use of a mobile-phase gradient prepared from methanol and aqueous formic acid solution. The flow rate was 1 mL min−1. Detection was performed at 254 nm. The calibration range was 11–1,100 μg mL−1 for both 2 and 3 in plasma; in urine the calibration ranges for 1, 2, and 3 were 32–1,600, 11–1,100, and 22–1,100 μg mL−1, respectively. Intra-day and inter-day RSD were less than 4.33 and 3.62% for 2 and 3, respectively, in plasma, and no more than 4.03 and 2.22% for all the analytes in urine. The analytical sensitivity and selectivity of the assay enabled successful application to pharmacokinetic studies of flavonols 1–3 in rats.
In this paper the convergence behavior of an epidemic model with time-varying delays are considered. Some sufficient conditions are established to ensure that all solutions of the epidemic model with permitted initial conditions converge exponentially to zero, which are new and complement previously known results. 相似文献
A series of dicyanovinyl‐substituted aromatic compounds (Ar‐DCV; Ar=9‐anthracenyl, 1‐naphthyl, 1‐pyrenyl) with dual fluorescence are prepared, and their emission properties—when molecularly dispersed in a polymer medium—are investigated under pressure perturbation. The total emission intensity is enhanced drastically from ambient pressure up to 70 kbar. Emission 30–107 times more intense than that at ambient pressure is observed at higher pressure. In dual emission, the enhancement of the local excited state (LE state) is significantly different from that of the intramolecular charge‐transfer state (ICT state). The intensity of the ICT emission increases faster (30–370 times) than that of the LE emission (less than 20 times). In accordance with spectroscopic data, emission dynamics at different pressures, and computational studies on the molecular conformations of these compounds, a kinetic model is proposed to explain the effect of pressure on the emissive properties of the Ar‐DCV compounds from the point of view of pressure‐dependent populations of the species in the ground state. 相似文献
The binary alloy/ferromagnetic metal heterostructure has drawn extensive attention in the research field of spin–orbittorque(SOT)due to the potential enhancement of SOT efficiency via composition engineering.In this work,the magneticproperties and SOT efficiency in the Pt100?xNix/Ni78Fe22 bilayers were investigated via the spin-torque ferromagneticresonance(ST-FMR)technique.The effective magnetic anisotropy field and effective damping constant extracted by analyzing the ST-FMR spectra show a weak dependence on the Ni concentration.The effective spin-mixing conductanceof 8.40×1014??1·m?2and the interfacial spin transparency Tin of 0.59 were obtained for the sample of Pt70Ni30/NiFebilayer.More interestingly,the SOT efficiency that is carefully extracted from the angular dependence of ST-FMR spectrashows a nonmonotonic dependence on the Ni concentration,which reaches the maximum at x=18.The enhancement ofthe SOT efficiency by alloying the Ni with Pt shows potential in lowering the critical switching current.Moreover,alloyingrelatively cheaper Ni with Pt may promote to reduce the cost of SOT devices. 相似文献
In reverse-mode polymer-stabilised cholesteric texture (PSCT), the dynamic response is derived from local director reorientation governed by dielectric coupling effect/self-assembly and polymer network deformation. A double exponential rise/decay model is proposed to investigate the underlying physical mechanisms. Through simulation of the transient rise and decay processes, the polymer network deformation in PSCT can be quantitatively evaluated. Less deformation and faster restoration speed of the polymer network can suppress hysteresis. These results provide useful guidelines for future PSCT fabrication and performance optimisation. 相似文献
A nonenzymatic amperometric sensor for sensitive and selective detection of glucose has been constructed by using highly dispersed Pt nanoparticles supported onto mesoporous carbons (MCs). The Pt nanoparticles/mesoporous carbons (Pt/MCs) composites modified electrode displayed high electrocatalytic activity towards the oxidation of glucose. At an applied potential of 0.1 V, the Pt/MCs electrode has a linear dependence (R=0.996) in the glucose concentration up to 7.5 mM with a sensitivity of 8.52 mA M?1 cm?2. The Pt/MCs electrode has also shown highly resistant toward poisoning by chloride ions and without interference from the oxidation of common interfering species. 相似文献
A new Cu(II) coordination polymer [Cu(3,5-pdc)(H2O)4·H2O]n1 (3,5-pdc=3,5-pyridinedicarboxylic acid) has been synthesized by hydrothermal method and characterized by IR, elemental analysis,
TG technique and X-ray crystallography. The crystallographic data for the compound 1: monoclinic P21/n, a = 11.361(5) ?, b = 7.095(3) ?, c = 14.575(6) ?, β = 107.630(4)°, V = 1,119.7(8) ?3, Z = 4, Dc = 1.891 Mg/m3, F(000) = 652, R1 = 0.0374, wR2 = 0.1083. Cu(II) atom has an distorted octahedral environment with N2O4 donor set of Cu(1) and O6 donor set of Cu(2), respectively. Each ligand is bound to two Cu(II) ions and each copper atom is coordinated by two ligands
thereby generating a 1D zigzag chain. The 1D chain was interacted each other feathering three-dimensional supramolecular network
through π···π interactions and multiform intermolecular hydrogen bonds. The luminescent properties of the title complex in
the solid state were investigated. 相似文献