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201.
Jing‐Zheng Song Lok Man Cheung Xin Liu Chun‐Feng Qiao Yan Zhou Song‐Lin Li Shi‐Lin Chen Hong‐Xi Xu 《Journal of separation science》2010,33(13):1909-1915
(+)‐Pinoresinol 4,4′‐di‐O‐β‐D ‐glucopyranoside ((+)‐PDG) is one of the major lignans with various pharmacological activities which could be isolated from Duzhong and other plant species. In this study, a diastereomeric impurity, (?)‐pinoresinol 4,4′‐di‐O‐β‐D ‐glucopyranoside ((?)‐PDG), the main impurity was identified in (+)‐PDG chemical reference substance (CRS) and a reliable chromatographic method for rapid purity determination of (+)‐PDG CRS was firstly developed. The optimal chromatographic condition was found to be using ACN/1,4‐dioxane–water (2.5:6:91.5, v/v/v) as mobile phase on a Waters Acquity UPLC HSS T3 column (2.1 mm×100 mm, 1.8 μm) with column temperature of 37°C. The method was validated and applied to determine the chromatographic purity of five (+)‐PDG CRS samples. The content of (?)‐PDG in four commercial (+)‐PDG CRS was 8.47–20.30%, whereas no (?)‐PDG was detected in our in‐house prepared (+)‐PDG CRS in which purity was confirmed to be 99.80%. The above results confirmed that this method is fast and highly efficient for purity determination of the (+)‐PDG CRS. 相似文献
202.
Yongguang Li Keith Man‐Chung Wong Dr. Anthony Yiu‐Yan Tam Dr. Lixin Wu Prof. Dr. Vivian Wing‐Wah Yam Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8690-8698
A series of photochromic spironaphthoxazine derivatives has been designed, synthesized, and characterized by using 1H NMR spectroscopy, FAB mass spectrometry, and elemental analysis. Their photophysical and photochromic behavior have been investigated. Two of the compounds (G12‐en‐SA‐SO and G16‐en‐SA‐SO) have been shown to be capable of forming stable thermoreversible organogels in organic solvents, tested by the “stable‐to‐inversion of a test tube” method. Addition of p‐toluenesulfonic acid was found to induce the formation of stable organogels at concentrations below that of the critical gelation concentration (c.g.c.), with a concomitant change in color from colorless to purple. Transmission electron microscopy and scanning electron microscopy of the xerogels showed typical fibrous structures in the micrometer scale. The activation parameters for the bleaching reaction of G8‐en‐SA‐SO in the solution state and G16‐en‐SA‐SO in the gel state have been determined in ethanol through kinetic studies at various temperatures. The results showed that the rate of the bleaching reaction in the gel state was much slower than that in the solution state. 相似文献
203.
Data fusion in multivariate calibration transfer 总被引:1,自引:0,他引:1
We report the use of stacked partial least-squares regression and stacked dual-domain regression analysis with four commonly used techniques for calibration transfer to improve predictive performance from transferred multivariate calibration models. The predictive performance from three conventional calibration transfer methods, piecewise direct standardization (PDS), orthogonal signal correction (OSC) and model updating (MUP), requiring standards measured on both instruments, was significantly improved from data fusion either by stacking of wavelet scales or by stacking of spectral intervals, as demonstrated by transfer of calibrations developed on near-infrared spectra of synthetic gasoline. Stacking did not produce as significant an improvement for calibration transfer using a finite impulse response (FIR) filter, but application of SPLS regression to FIR-transferred spectra improves predictive performance of the transferred model. 相似文献
204.
荧光法快速检测有机磷农药残留总量 总被引:1,自引:0,他引:1
在pH4.60的B-R缓冲溶液中,中性红(NR)与一定浓度的十二烷基苯磺酸钠(SDBS)发生荧光增强反应,在该体系中加入有机磷农药后,在激发波长560 nm,发射波长604 nm处体系的荧光强度明显降低,且降低程度与有机磷农药的加入量呈良好的线性关系,其线性范围和检出限分别为0.024~0.40 mg/L,0.014 mg/L。据此建立了测定有机磷农药残留总量的新方法。方法已用于面粉和土壤中有机磷农药残留总量的检测,回收率在92.0%~100.5%之间,RSD在1.1~1.9%之间。 相似文献
205.
The symplectic tomograms of coherent states of a charged particle moving in a constant uniform magnetic field are obtained
in explicit form. The tomograms are shown to coincide with normal probability distributions of two random variables. The means
and dispersions of the variables are found and expressed in terms of means and dispersions of the charged particle coordinates
and momenta. The characteristic function of the tomographic probability distribution is found. The center of mass tomogram
of the coherent state of charge in magnetic field is also found and the relation of the symplectic tomogram and the center
of mass tomogram is established. 相似文献
206.
In this paper, a desirably simple, convenient and inexpensive saturable absorber mirror has been fabricated based on graphene, which has no wavelength selectivity. Moreover, there are no changes in the structure and characteristics of graphene. By inserting the graphene-PMMA SA mirror to the Nd: YAG laser, the shortest pulse width of 260 ns can be obtained with the single-pulse energy of about 8.32 μJ. The experimental results prove that our graphene-PMMA SA mirror is feasible and suitable for Q-switched lasers. 相似文献
207.
The new inequality recently found by Trifonov and called the state-extended inequality is considered in the tomographic-probability
representation of quantum mechanics. The Trifonov uncertainty relations are expressed in terms of optical tomograms and can
be checked in experiments on homodyne detection of the photon states. 相似文献
208.
Zorica Marinković Stanojević Z. Branković Z. Jagličić M. Jagodič L. Mančić S. Bernik A. Rečnik G. Branković 《Journal of nanoparticle research》2011,13(8):3431-3439
We have studied the formation of BiMnO3 (BMO) nanocrystalline perovskite powder produced by high-energy milling of the constituent
oxides. The crystal structure and the amount of crystalline and amorphous phases in the powder as a function of the milling
time were determined with XRPD using Rietveld refinement. BMO perovskite formed directly from highly activated nano-sized
constituent oxides after 240 min of milling and subsequently grew during prolonged milling. The morphology, structure, and
chemical composition of the powder were investigated by SEM and TEM. A clear ferromagnetic transition was observed at T
C ~66 K for a sample milled for 240 min and increased with milling time. The magnetic hysteresis behavior is similar to that
of a soft ferromagnet. The magnetic properties of the obtained BMO powders were found to change as a function of milling time
in a manner consistent with variations in the nanocomposite microstructure. 相似文献
209.
B. HuB.Y. Man C. YangM. Liu C.S. ChenX.G. Gao S.C. XuC.C. Wang Z.C. Sun 《Applied Surface Science》2011,258(1):525-529
Mn-doped GaN films (Ga1−xMnxN) were grown on sapphire (0 0 0 1) using Laser assisted Molecular Beam Epitaxy (LMBE). High-quality nanocrystalline Ga1−xMnxN films with different Mn concentration were then obtained by thermal annealing treatment for 30 min in the ammonia atmosphere. Mn ions were incorporated into the wurtzite structure of the host lattice by substituting the Ga sites with Mn3+ due to the thermal treatment. Mn3+, which is confirmed by XPS analysis, is believed to be the decisive factor in the origin of room-temperature ferromagnetism. The better room-temperature ferromagnetism is given with the higher Mn3+ concentration. The bound magnetic polarons (BMP) theory can be used to prove our room-temperature ferromagnetic properties. The film with the maximum concentration of Mn3+ presents strongest ferromagnetic signal at annealing temperature 950 °C. Higher annealing temperature (such as 1150 °C) is not proper because of the second phase MnxGay formation. 相似文献
210.