调制激光场中Rydberg原子的电磁感应透明

本文主要研究了调制探测激光场中铯Rydberg 原子阶梯型三能级系统的电磁感应透明(EIT) 效应. 铯原子基态6S_1/2, 第一激发态6P_3/2 和Rydberg 态形成阶梯型三能级系统, 探测光作用于6S_1/2 (F = 4)→6P_3/2(F' = 5) 的跃迁, 耦合光在Rydberg 跃迁线6P_3/2→49S_1/2 附近扫描, 形成Rydberg 原子EIT. 当对探测光频率施加一个几kHz 的调制时, 调制解调后的EIT 信号分裂为两个峰, 双峰间距与调制频率无关,而与调制幅度导致的失谐量大小(频率调制幅度) 成正比, 双峰间隔的一半等于探测光频率调制幅度的λ_p/λ_c = 1.67 倍. 实验结果与理论计算相一致. 本文的研究结果可应用于激光线型和频率抖动的实时监测.     

Quantitative analysis of asymmetrical cortical activity in motor areas during sequential finger movement

Brain asymmetry is a phenomenon well known for handedness and has been studied in motor cortices. However, few quantitative studies on asymmetrical cortical activity in motor areas have been conducted. In this study, we systematically investigated asymmetrical cortical activity in motor areas during sequential finger movement by quantitatively analyzing functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent (BOLD) responses. The norm of BOLD signal percentage of change was introduced to quantitatively measure the BOLD signal intensity change difference between the left and right motor areas. The results of the data collected from six subjects show that the norm of BOLD signal percentage of change in the right motor area is higher than that in the left motor area for two-hand movement (P=.0059) and single-hand movement (P=.0279) with right-handedness. These results from fMRI show the asymmetry of motor areas and may suggest that the left hemisphere motor area comes into being as an adaptation system that needs few neuron cells only to finish any movement task for right-handedness. The activation intensity in the left motor area is reduced with normal right finger movement. The activation intensity in the right motor area is obviously higher than that in the left motor area.     

Enhanced Reproducibility of Positive Temperature Coefficient Effect of CB/HDPE/PVDF Composites with the Addition of Ionic Liquid

Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC) effect is of great significance for large-scale application of polymer based PTC composites, owing to its contribution to the security and reliability. Herein, we developed a carbon black(CB)/high density polyethylene(HDPE)/poly(vinylidene fluoride)(PVDF) composite with outstanding PTC reproducibility, by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([OMIm][NTf_2]) into the composite. After multiple repeated temperature cycles, the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%. Our studies revealed that [OMIm][NTf2] contributes to the improvement of PTC reproducibility in two ways:(i)it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends;(ii) it inhibits the crystallization of PVDF through the dilution effect, leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF. This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.     

Comparative study of Co3O4-ZSM-5 catalysts synthesized by different hydrothermal methods for the catalytic oxidation of dichloromethane

In this work, various Co₃O₄-ZSM-5 catalysts were prepared by the microwave hydrothermal method (MH-Co₃O₄@ZSM-5), dynamic hydrothermal method (DH-Co₃O₄@ZSM-5), and conventional hydrothermal method (CH-Co₃O₄/ZSM-5). Their catalytic oxidation of dichloromethane (DCM) was analyzed. Detailed characterizations such as X-ray diffractometer (XRD), scanning microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), H₂ temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of O₂ (O₂-TPD), temperature-programmed desorption of NH₃ (NH₃-TPD), diffuse reflectance infrared Fourier-transform spectra with NH₃ molecules (NH₃-DRIFT), and temperature-programmed surface reaction (TPSR) were performed. Results showed that with the assistance of microwave, MH-Co₃O₄@ZSM-5 formed a uniform core-shell structure, while the other two samples did not. MH-Co₃O₄@ZSM-5 possessed rich surface adsorbed oxygen species, higher ratio of Co³⁺/Co²⁺, strong acidity, high reducibility, and oxygen mobility among the three Co₃O₄-ZSM-5 catalysts, which was beneficial for the improvement of DCM oxidation. In the oxidation of dichloromethane, MH-Co₃O₄@ZSM-5 presented the best activity and mineralization, which was consistent with the characterizations results. Meanwhile, according to the TPSR test, HCl or Cl₂ removal from the catalyst surface was also promoted in MH-Co₃O₄@ZSM-5 by their abundant Brønsted acid sites and the promotion of Deacon reaction by Co₃O₄ or the synergistic effect of Co₃O₄ and ZSM-5. According to the results of in situ DRIFT studies, a possible reaction pathway of DCM oxidation was proposed over the MH-Co₃O₄@ZSM-5 catalysts.     

铯47D精细能级超冷里德堡原子自由演化的动力学研究

用连续窄线宽激光器将超冷铯里德堡原子分别激发到47D_3/2, 47D_5/2精细态, 观察了处于里德堡精细态的铯原子向超冷铯等离子体自由演化的过程, 详细对比了不同精细态的铯里德堡原子预电离时间、电离速率以及等离子体的转化效率. 将里德堡原子快速转化为等离子体的过程解释为局域势阱内由预电离产生的电子与里德堡原子的快速碰撞导致的雪崩电离.     

Promotion Effect of Bismuth on Nickel Electrodeposition and Its Electrocatalysis to Glucose Oxidation

Metallic Bi and Ni were co‐deposited onto the surface of glass carbon electrode (GCE) from the electrolyte solution containing their respective nitrate to fabricate a Bi/Ni alloy modified GCE (Bi/Ni‐GCE). The purpose is to study the influence of Bi³⁺ on the deposition of Ni and that of deposited Bi on the electrocatalytic performance of Ni to glucose in alkali solution. The results show that both redox signal of Ni(OH)₂/NiOOH and Ni(OH)₂/NiOOH mediated electrocatalysis to glucose is remarkably increased in the presence of Bi. It seems that there is a synergistic effect between Bi and Ni on each other’s redox electrochemistry. It’s possible that the firstly deposited Bi on GCE surface helps to the following nucleation and growth of Ni, leading to the deposition of more metallic Ni on GCE surface. An extremely attractive feature of Bi/Ni‐GCE is reflected by the fast response time to the electrocatalytic oxidation of glucose. The electrode nearly responses immediately after glucose is added and it reaches a steady‐state level within only 2 seconds, demonstrating a good electrocatalytic property of Bi/Ni‐GCE. The calibration plot is linear over the wide concentration range of 0–5.8 mM with a sensitivity of 33.96 µA/mM and a correlation coefficient of 0.9985. The detection limit of the glucose was found to be 0.59 µM at a signal‐to‐noise ratio of 3. The fabricated Bi/Ni‐GCE was successfully employed to analyze the glucose level in blood samples, exhibiting high accuracy, strong resistance against inference and good reliability in the practical applications.     

Structural elucidation of new urinary tamoxifen metabolites by liquid chromatography quadrupole time‐of‐flight mass spectrometry

In this study, tamoxifen metabolic profiles were investigated carefully. Tamoxifen was administered to two healthy male volunteers and one female patient suffering from breast cancer. Urinary extracts were analyzed by liquid chromatography quadruple time‐of‐flight mass spectrometry using full scan and targeted MS/MS techniques with accurate mass measurement. Chromatographic peaks for potential metabolites were selected by using the theoretical [M + H]⁺ as precursor ion in full‐scan experiment and m/z 72, 58 or 44 as characteristic product ions for N,N‐dimethyl, N‐desmethyl and N,N‐didesmethyl metabolites in targeted MS/MS experiment, respectively. Tamoxifen and 37 metabolites were detected in extraction study samples. Chemical structures of seven unreported metabolites were elucidated particularly on the basis of fragmentation patterns observed for these metabolites. Several metabolic pathways containing mono‐ and di‐hydroxylation, methoxylation, N‐desmethylation, N,N‐didesmethylation, oxidation and combinations were suggested. All the metabolites were detected in the urine samples up to 1 week. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of CuI Trifluoromethylselenates for Trifluoromethylselenolation of Aryl and Alkyl Halides

The development of new strategies for synthesis of trifluoromethylthiolate compounds is of considerable importance in pharmaceuticals, agrochemicals, and advanced materials. Accordingly, currently much attention is being devoted to the development of effective methods and reagents for their synthesis. In contrast, considerably less effort has been afforded to the development of preparing C?SeCF₃ bonds. Herein we report a concise route to synthesize a family of copper(I) trifluoromethylselenolate reagents by the reaction of CuI with the Ruppert’s reagent (Me₃SiCF₃), KF, and elemental selenium in the presence of dinitrogen ligands in CH₃CN at room temperature. The reagent [Cu(bpy)(SeCF₃)]₂ was proven to be air‐stable and highly efficient for nucleophilic trifluoromethylthselenolation of a broad range of (hetero)aryl halides and alkyl halides. This method represents a powerful protocol for the construction trifluoromethylselenolate compounds.     

Theory Study of the Adsorption of Hydrocyanic Acid onto Small Silver Clusters

Density functional theory calculations have been performed to study the interaction of small silver clusters, Ag2 ~Ag9, with HCN. The adsorption of HCN on-top site of the silver cluster, among various possible sites, is energetically preferred. The adsorption energies of HCN on the silver clusters reach a local maximum at n = 4, which is only about 0.450 eV, indicating that the adsorbed HCN molecule is weakly perturbed. The adsorbed C–N and C–H stretching frequencies are blue- and red-shifted compared with the values of free HCN, respectively.     

Phase behavior of amphiphiles at liquid crystals/water interface: A coarse-grained molecular dynamics study

We present a coarse-grained molecular dynamics simulation study of phase behavior of amphiphilic monolayers at the liquid crystal （LC）/water interface. The results revealed that LCs at interface can influence the lateral ordering of amphiphiles. Particularly, the amphiphile tails along with perpendicularly penetrated LCs between tails undergo a two-dimension phase transition from liquid-expanded into a liquid-condensed phase as their area density at interface reaches 0.93. While, the liquid-condensed phase of the monolayer never appears at oil/water interface with isotropic shape oil particles. These findings reveal the penetration of anisotropic LC can promote ordered lateral organization of amphiphiles. Moreover, we find the phase transition point is shifted to lower surface coverage of amphiphiles when the LCs have larger affinity to the amphiphile tails.