Phytochemical Constituents from Ginkgo biloba Exocarp

Chemistry of Natural Compounds -     

块状高温超导体俘获磁通密度实验测试方法

块状单畴高温超导体的重要特性参数之一"俘获磁通密度"决定了单畴超导体能够冻结住的最大磁通俘获场,实际用户在设计装置时必须了解这些参数.然而,这些数值强烈地依赖于测试方法.随着国内块状单畴超导体的研究、生产、应用的不断发展,市场规模的不断扩大以及国际贸易的开展,迫切需要建立一个与国际接轨的测试标准,统一材料提供方与用户之间对单畴块材性能的表征过程.经国家标准化管理委员会批准,2013年全国超导标准化技术委员会将IEC 61788-9国际标准《SUPERCONDUCTIVITY-Measurements for bulk high temperature superconductors-Trapped flux density of large grain bulk oxide superconductors》(《超导电性:块状高温超导体的测量—大晶粒氧化物超导体的俘获磁通密度》)转化为国家标准,本文主要介绍有关"标准"的转化实施过程.     

群的几个幂零性条件

如果G的所有子群都是次正规的,而且G满足下面条件之一,那么G是幂零群.(1)G有一个次正规列1△H△K△G,其中K/H是幂零群,H和G/K是有限生成的;(2)G有一个正规子群N使得,N在其子集的中心化子上满足极小条件,并且G/N是有限生成的.     

Preparation of magnetic poly(vinylimidazole‐co‐divinylbenzene) nanoparticles and their application in the trace analysis of fluoroquinolones in environmental water samples

Nanosized spherical magnetic poly(vinylimidazole‐co‐divinylbenzene) particles were synthesized and used as a sorbent for the enrichment of trace fluoroquinolones (FQs) from environmental water samples. A suspension polymerization procedure was used to prepare the sorbent. The magnetic sorbent was characterized by SEM, transmission electron microscopy, elemental analysis, and FTIR spectroscopy. Analysis of enrofloxacin, marbofloxacin, fleroxacin, lomefloxacin, and sparfloxacin in environmental water samples by the combination of the magnetic sorbent and HPLC with diode array detection was selected as a paradigm for the practical application of the new adsorbent. Several extraction conditions, including desorption solvent, extraction and desorption time, pH value, and ionic strength in sample matrix, were optimized. Results showed that the new sorbent had high affinity for FQs and could be used to extract them effectively. Under the optimum conditions, low detection (S/N = 3) and quantification (S/N = 10) limits were achieved for the target analytes, within the ranges of 0.20–1.46 and 0.68–4.84 μg/L, respectively. Method repeatability was achieved in terms of intra‐ and interday precisions, indicated by the RSDs, which were both <10.0%. The method also showed good linearity, simplicity, practicality, and environmental friendliness for the extraction of FQs. Finally, the developed method was successfully applied to the determination of FQs in lake water, surface water, and reservoir water samples. Acceptable recoveries of spiked target compounds in these water samples were in the range of 52.1–104.5%.     

Light-induced dielectric transparency in single-walled carbon nanotube films

Light-induced difference THz spectroscopy was used to investigate the dielectric response of free-stand single-walled carbon nanotubes (SWCNTs) films in THz region. We observed an enhanced transmission of the peak-signal of THz wave through SWCNTs films under 800 nm pump. In frequency domain, the transparency came from 0.5 to 2.1 THz and the absorption was in 2.1–3.0 THz region. The pump power dependency of the transmission showed this was a nonlinear effect. The dielectric constant response of the SWCNTs films was analyzed theoretically. The analysis suggests that the nonlinear optical properties stem from two factors, which are Drude and Lorentz term for metallic and semiconducting SWCNTs, respectively.     

Fabricating organic transistors based on domain‐ordered copper phthalocyanine film grown on oligothiophene epitaxial substrate

Organic field‐effect transistors were fabricated using a domain‐ordered copper phthalocyanine (CuPc) thin film as the active layer prepared by weak epitaxial growth (WEG) technology. CuPc was deposited onto α‐sexithiophene (α‐6T) and α,ω‐dihexylsexithiophene (α,ω‐DH6T) films acting as the epitaxial substrate to realize the domain‐order growth. As a result, the thin‐film morphology of CuPc exhibits many re‐ gional domain‐ordered structures measured by atomic force microscopy and X‐ray diffraction. The field‐effect mobilities are 0.11 and 0.085 cm²/Vs for the devices with CuPc/α‐6T and CuPc/α,ω‐DH6T, respectively. The threshold voltages were –7 V and –13 V for CuPc/α‐6T and CuPc/α,ω‐DH6T, respectively. The improved device performance could be attributed to the domain‐order structure of the CuPc thin film. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetics for the hydrogen‐abstraction of CH4 with NO2

The detailed mechanism of the NO₂+CH₄ reaction has been computationally investigated at the M06‐2X/MG3S, B3LYP/6‐311G(2d,d,p), and MP2/6‐311+G(2df,p) levels. The direct dynamics calculations were preformed using canonical transition state theory with tunneling correction and scaled generalized normal‐mode frequencies including anharmonic torsion. The calculated results indicate that the NO₂+CH₄ reaction proceeds by three distinct channels simultaneously, leading to the formation of trans‐HONO (1a), cis‐HONO (1b), and HNO₂ (1c), and each channel involves the formation of intermediate having lower energy than the final product. The anti‐Hammond behavior observed in channel 1a is well analyzed. Proper treatment of anharmonic torsions about the C···H···O (or N) axis in the transition structures greatly improves the accuracy of kinetics predictions. The activation energy for each channel increases substantially with temperature, but is not strictly a linear function of temperature. Therefore, the thermal rate constants are fitted to the four‐parameter expression recommended for this case over the wide temperature range 400–4000 K. © 2012 Wiley Periodicals, Inc.     

Immobilization of Chiral Catalyst on Amorphous Al2O3 for the Selective Hydrogenation of Ethyl 1H-Indole-2-carboxylate

Ru-B/γ-Al2O3 catalyst was prepared by reductant impregnation method,which was applied in the selective hydrogenation of ethyl 1H-indole-2-carboxylate for producing ethyl 2,3,3a,7a-tetrahydro-1H-indole-2-carboxylate with hydrogen as reductant.Furthermore,we discussed the influences of substrate concentration,reaction solvent,hydrogenation temperature,initial hydrogen pressure and reaction time on the catalytic performance of the as-prepared catalyst.The obtained Ru-B/γ-Al2O3 catalyst showed a high-efficiency for the selective hydrogenation of ethyl 1H-indole-2-carboxylate（＞99％ conversion and selectivity） in i-propanol used as solvent at a concentration of 10％（mass fraction） of ethyl 1H-indole-2-carboxylate,a pressure of hydrogen of 6 MPa and a reaction temperature of 373 K.     

Determination of fentanyl in human breath by solid-phase microextraction and gas chromatography–mass spectrometry

Fentanyl, a kind of intravenous narcotic analgesic, is widely used in clinical anesthesia. As a potential pollution, it was detected in both the air of the cardiothoracic operating room and patients' expiratory circuit. However, whether the fentanyl in patients' expiratory circuit is exhaled by patients is unknown. In this study, breath samples were taken from the expiratory circuits of anesthetic machine linked to the patients who received intravenous fentanyl, a solid-phase microextraction (SPME) coupled with gas chromatography–mass spectrometry (GC–MS) method was developed to detect and quantify fentanyl in breath samples. The parameters influencing adsorption (extraction time, temperature,) and desorption (desorption time) of the analyte on the fiber were investigated and validated for method development. The developed method was proved to be simple, easy, and inexpensive and offer high sensitivity and reproducibility. Linear range was obtained from 0.05 ng/mL to 0.8 ng/mL. The limit of detection was 0.01 ng/mL while an interday precision of less than 12.13% (n = 5) could be achieved. Six patients were involved in this study; results showed presence of fentanyl in the breath of patients who received intravenous fentanyl, and fentanyl concentrations in breath varied from 6.00 to 20.89 pg/mL. In conclusion, fentanyl can be exhaled by patients who received intravenous fentanyl.     

Propagations of Airy Beams and Nonlinear Accelerating Optical Beams in Photorefractive Crystals with Asymmetric Nonlocality

The impact of the asymmetric nonlocal diffusion nonlinearity of Airy beams and nonlinear accelerating beams supported by photorefractive crystals is addressed. It is revealed how the asymmetric nonlocal response alters the evolution of these optical beams. It is found that the evolution of these beams presents a bending action under the influence of the diffusion nonlinearity. It is also shown that nonlinear accelerating beams can exist in photorefractive crystals with asymmetric nonlocality. These accelerating solutions have the same Airy‐like tail, and accelerate along parabolic trajectories. Soliton states are formed in the interaction of both in‐phase and out‐of‐phase Airy beams and nonlinear accelerating beams and also present a bending action because of the action of diffusion nonlinearity.