Dynamics of nonlocal and localized spatiotemporal solitons for a partially nonlocal nonlinear Schrödinger equation

Modern methods of nonlinear dynamics including time histories, phase portraits, power spectra, and Poincaré sections are used to characterize the stability and bifurcation regions of a cantilevered pipe conveying fluid with symmetric constraints at the point of contact. In this study, efforts are made to demonstrate the importance of characterizing the system at the arbitrarily positioned symmetric constraints rather than at the tip of the cantilevered pipe. Using the full nonlinear equations of motion and the Galerkin discretization, a nonlinear analysis is performed. After validating the model with previous results using the bifurcation diagrams and achieving full agreement, the bifurcation diagram at the point of contact is further investigated to select key flow velocities of interest. In addition to demonstrating the progression of the selected regions using primarily phase portraits, a detailed comparison is made between the tip and the point of contact at the key flow velocities. In doing so, period doubling, pitchfork bifurcations, grazing bifurcations, sticking, and chaos that occur at the point of contact are found to not always occur at the tip for the same flow speed. Thus, it is shown that in the case of cantilevered pipes with constraints, more accurate characterization of the system is obtained in a specified range of flow velocities by characterizing the system at the point of contact rather than at the tip.     

基于零价铁的地下水化学还原修复体系中的电子转移有效性和电子竞争机制

近年来,基于零价铁的化学还原技术因其高效性逐渐被应用于受污染地下水的原位修复。但是,该技术在实际应用中仍面临一些亟待解决的问题。零价铁作为一种高活性的电子供体,除了和目标污染物反应外,还可以与地下水中其他的氧化性物质（如O₂、H⁺或NO₃^-等）反应。这些反应所造成的零价铁腐蚀,不仅会降低修复效率还会增加地下水修复成本。此外,同类或多类污染物间也存在对零价铁所释放电子的相互竞争,从而影响各自的去除效率。本文综述了基于零价铁的地下水修复体系中的电子传递过程和氧化物间的电子竞争机制,从零价铁的腐蚀和电子传递、零价铁电子选择性量化指标的提出和量化方法、地下水体中多种共存氧化物间电子竞争作用、电子效率的影响因素以及强化措施等方面进行详细介绍。最后,对该技术今后发展方向作出了展望,以期为其今后实际的地下水修复应用提供参考。     

One-step Construction of Xanthone Scaffold Assisted by Microwave Irradiation to Optimize the Synthesis of DMXAA

An efficient and concise synthesis of 5,6-dimethylxanthenone-4-acetic acid(DMXAA) was developed. The overall yield of this 3-step procedure was 82%. The key reaction is the one-step construction of xanthone scaffold between 2,5-dibromo-3,4-dimethylbenzoic acid and 2-hydroxyphenyl-acetic acid assisted by microwave irradiation.     

螺旋线螺纹模型的有限元分析

针对精细化模型与Abaqus摩擦模型所存在问题, 提出一种基于螺纹几何特征的螺旋线螺纹模型, 采用脚本语言实现了螺旋线螺纹模型生成自动化, 并应用到某发动机机体主轴承盖螺栓螺孔的强度分析. 分析结果表明, 仿真计算得到的螺栓及机体螺孔处的应力很好地表征了螺栓连接结构螺纹处的实际应力分布, 与螺纹精细模型相近, 比Abaqus摩擦模型精度更高, 且计算方便、实用、高效, 验证了本文方法的准确、可行.     

A More Efficient Contextuality Distillation Protocol

Based on the fact that both nonlocality and contextuality are resource theories, it is natural to ask how to amplify them more efficiently. In this paper, we present a contextuality distillation protocol which produces an n-cycle box B ? B ^′ from two given n-cycle boxes B and B ^′. It works efficiently for a class of contextual n-cycle (n ≥?4) boxes which we termed as “the generalized correlated contextual n-cycle boxes”. For any two generalized correlated contextual n-cycle boxes B and B ^′, B ? B ^′ is more contextual than both B and B ^′. Moreover, they can be distilled toward to the maximally contextual box C H _n as the times of iteration goes to infinity. Among the known protocols, our protocol has the strongest approximate ability and is optimal in terms of its distillation rate. What is worth noting is that our protocol can witness a larger set of nonlocal boxes that make communication complexity trivial than the protocol in Brunner and Skrzypczyk (Phys. Rev. Lett. 102, 160403 2009), this might be helpful for exploring the problem that why quantum nonlocality is limited.     

酯基取代的吲哚衍生物的红外和荧光光谱研究

Tryptophan derivatives have long been used as site-specific biological probes. 4-Cyanotryptophan emits in the visible region and is the smallest blue fluorescent amino acid probe for biological applications. Other indole or tryptophan analogs may emit at even longer wavelengths than 4-cyanotryptophan. We performed FTIR, UV-Vis, and steady-state and time-resolved fluorescence spectroscopy on six ester-derivatized indoles in different solvents. Methyl indole-4-carboxylate emits at 450 nm with a long fluorescence lifetime, and is a promising candidate for a fluorescent probe. The ester-derivatized indoles could be used as spectroscopic probes to study local protein environments. Our measurements provide a guide for choosing esterderivatized indoles to use in practice and data for computational modeling of the effect of substitution on the electronic transitions of indole.     

椭圆偏振强激光场中准直的乙炔分子的高次谐波发射

We perform an experimental study on high-order harmonic generation (HHG) of aligned acetylene molecules induced by a 35-fs 800-nm strong laser field, by using a home-built HHG spectrometer. It is observed that the molecular HHG probability declines with increasing the laser ellipticity, which is in consistence with the deduction from the well-known tunneling-plus-rescattering scenario. By introducing a weak femtosecond laser pulse to nonadiabatically align the molecules, we investigated the molecular orbital effect on the HHG in both linearly and elliptically polarized driving laser fields. The results show that the harmonic intensity is maximum for the molecular axis aligned perpendicularly to the laser electric field. It indicates that both the highest occupied molecular orbitals (HOMO) and HOMO-1 contribute to the strong-field HHG of acetylene molecules. Our study should pave the way for understanding the interaction of molecules with ultrafast strong laser fields.     

Free-standing WS<Subscript>2</Subscript><Emphasis Type="Strikethrough">-</Emphasis>MWCNTs hybrid paper integrated with polyaniline for high-performance flexible supercapacitor

As two-dimensional layered nanomaterials, the tungsten disulfide (WS₂) nanosheets can be used as building blocks of paper-like electrodes for high-performance FSs. However, poor conductivity and mechanical property of WS₂ nanosheets (NSs) paper greatly hinders their capacitance and/or rate performance. To solve these problems, we fabricated the WS₂-multiwalled carbon nanotubes (MWCNTs)/polyaniline (PANI) composite papers based on liquid exfoliation and electrochemical deposition for high-performance flexible supercapacitors. The WS₂-MWCNTs/PANI with conductive PANI chains linked WS₂ NSs and MWCNTs takes the advantages of high-electronic double-layer capacitance originated from the internal surface areas of MWCNTs and effective pseudocapacitance generated by exfoliated WS₂ NSs and PANI. Electrochemical studies showed that the gravimetric-specific capacitance of WS₂-MWCNTs/PANI can reach ~760.1 F/g at a current density of 1 A/g. A symmetric flexible solid-state supercapacitor was also assembled and studied. The WS₂-MWCNTs/PANI-assembled FS device also has an excellent area specific capacitance of 1158.7 mF/cm² at a current density of 0.5 mA/cm² together with a high-capacity retention of ~82.5% after 2000 cycles.     

A facile in situ solvothermal method for two-dimensional layered g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>/SnS<Subscript>2</Subscript> p-n heterojunction composites with efficient visible-light photocatalytic activity

To overcome the fast recombination rate of electron-hole pairs of individual SnS₂, p-n heterojunction g-C₃N₄/SnS₂ composites were fabricated as high-efficiency visible-light photocatalyst to photodegradate the organic dye MB. The morphologies, structures, compositions, and photocatalytic properties were characterized. The SnS₂ shows two-dimensional layer structure with an average thickness of 20 nm and diameter size of about 2 μm, and the g-C₃N₄ nanoflakes were uniformly deposited on the surface of SnS₂ nanosheets. In comparison with the bare g-C₃N₄ and SnS₂, the composites show improved photocatalytic activity under visible light, which is sensitive to the content of g-C₃N₄. In particular, the 15% g-C₃N₄/SnS₂ composites exhibit the highest photocatalytic activity and outstanding reusability, which can degrade 88.01% MB after only 1 h in the visible light (λ?>?420 nm) range. The g-C₃N₄/SnS₂ heterojunction composites show outstanding reusability after four times cycling experiments. The improved photocatalytic activities of composites are attributed to abundant active species, increased charge separation, and decreased electron-hole pair recombination, which originated from the large specific surface area and efficient interfacial transport of photo-induced charge carriers between SnS₂ and g-C₃N₄. These results suggest that the two-dimensional layered g-C₃N₄/SnS₂ p-n heterojunction composites are promised to be a high-efficiency visible-light photocatalyst.     

Superfluid-superradiant mixed phase of the interacting degenerate Fermi gas in an optical cavity

We investigate the ground-state properties of an attractively interacting degenerate Fermi gas coupling with a high-finesse optical cavity. We predict a new mixed phase with both the superfluid and superradiant properties for the intermediate fermion-fermion interaction and fermion-photon coupling strengths. Moreover, in this mixed phase a relatively large ratio of the scaled polarization to the dimensionless mean-field gap, which is in contrast to that in the conventional superfluid regime can be obtained. We also figure out rich phase diagrams depending crucially on the atomic resonant frequency (effective Zeeman field) and address briefly the experimental detection of our predicted quantum phases.