Advantages of Surface‐Initiated ATRP (SI‐ATRP) for the Functionalization of Electrospun Materials

Surface‐initiated atom transfer radical polymerization (SI‐ATRP) is successfully applied to electrospun constructs of poly(L ‐lactide). ATRP macroinitiators are adsorbed through polyelectrolyte complexation following the introduction of negative charges on the polyester surface through its blending with a six‐armed carboxy‐terminated oligolactide. SI‐ATRP of glycerol monomethacrylate (GMMA) or 2‐(N,N‐diethylamino)ethyl methacrylate (DEAEMA) allows then to grow surface films with controllable thickness, and in this way also to control the wetting and interactions of the construct.     

Observation of low‐wavenumber out‐of‐plane optical phonon in few‐layer graphene

Few‐layer graphene grown by chemical vapor deposition has been studied by Raman and ultrafast laser spectroscopy. A low‐wavenumber Raman peak of ~120 cm⁻¹ and a phonon‐induced oscillation in the kinetic curve of electron–phonon relaxation process have been observed, respectively. The Raman peak is assigned to the low‐wavenumber out‐of‐plane optical mode in the few‐layer graphene. The phonon band shows an asymmetric shape, a consequence of so‐called Breit‐Wigner‐Fano resonance, resulting from the coupling between the low‐wavenumber phonon and electron transitions. The obtained oscillation wavenumber from the kinetic curve is consistent with the detected low‐wavenumber phonon by Raman scattering. The origin of this oscillation is attributed to the generation of coherent phonons and their interactions with photoinduced electrons. Copyright © 2012 John Wiley & Sons, Ltd.     

3D skyrmion and knot in two-component Bose–Einstein condensates

We present exact solutions to the two-component Bose–Einstein condensates by adopting a method of separating the variables, which exhibit nontrivial topology. These solitonic solutions can form 3D skyrmion and knot in the three-dimensional system.     

Molecular dynamics study on water self-diffusion in aqueous mixtures of methanol,ethylene glycol and glycerol: investigations from the point of view of hydrogen bonding

Molecular dynamics simulations have been performed to investigate the aqueous binary mixtures of alcohols, including methanol, ethylene glycol (EG) and glycerol of molalities ranging from 1 to 5 m at the temperatures of 273, 288 and 298 K, respectively. The primary purpose of this paper is to investigate the mechanism of water self-diffusion in water-alcohol mixtures from the point of view of hydrogen bonding. The effects of temperature and concentration on water self-diffusion coefficient are evaluated quantitatively in this work. Temperature and concentration to some extent affect the hydrogen bonding statistics and dynamics of the binary mixtures. It is shown that the self-diffusion coefficient of water molecules decreases as the concentration increases or the temperature decreases. Moreover, calculations of mean square displacements of water molecules initially with different number n of H-bonds indicate that the water self-diffusion coefficient decreases as n increases. We also studied the aggregation of alcohol molecules by the hydrophobic alkyl groups. The largest cluster size of the alkyl groups clearly increases as the concentration increases, implying the emergence of a closely connected network of water and alcohols. The clusters of water and alcohol that interacted could block the movement of water molecules in binary mixtures. These findings provide insight into the mechanisms of water self-diffusion in aqueous binary mixtures of methanol, EG and glycerol.     

Molecular dynamics simulation studies of cryoprotective agent solutions: the relation between melting temperature and the ratio of hydrogen bonding acceptor to donor number

Molecular dynamics simulations have been carried out for glycerol–water–sodium chloride ternary solution due to its important role in cryopreservation engineering. The radial distribution functions for atom pairs potentially related to C–H ··· O and O–H ··· O hydrogen bonds were calculated. The radial distribution functions for the H (connected to C)–O atom pair do not exhibit peaks between 2 and 3 Å, whereas the radial distribution functions for the C–O atom pair exhibit distinct peaks between 3 and 4 Å. The reason for this is because most C–H ··· O geometries are bent and deviate from linearity. The ratios of acceptor to donor numbers for water and glycerol molecules decrease as the solute concentration increases. A characteristic concentration has been found that divides solutions with different mechanisms. Below the characteristic concentration, the melting temperature is linearly related to the ratio of acceptor to donor number for water molecules, whereas above the characteristic concentration, the melting temperature is linearly related to the ratio of acceptor to donor number for glycerol molecules. Further studies indicate that the relations are independent of hydrogen bonding criteria and temperature.     

Evaluation of bridge function for hard sphere fluid confined in a narrow slit-pore via TMMC Mayer-sampling

The bridge function required to yield a singlet integral equation (IE) up to the second order in density expansion for the hard sphere fluid confined in a slit-pore is evaluated. The slit-fluid bridge function can be divided into wall-particle bridge diagrams with h _b-bond, which were evaluated by recently proposed Transition Matrix Monte Carlo (TMMC) Mayer-sampling method. The bulk-fluid total correlation function h _b(r) used in cluster integrals is determined by solution of the bulk-fluid Ornstein–Zernike (OZ) equation with a hypernetted chain closure (HNC). The calculation is performed for the reduced density of bulk fluid in equilibrium with the fluid in slit-pores from 0.3 to 0.7 with narrow slit width of 3.0σ and 4.0σ. The quantity of the slit-fluid bridge function is assessed by comparison of the density profile obtained from the singlet IE theory and the grand canonical Monte Carlo (GCMC) simulation. Good agreement between the proposed approach and the GCMC data is observed. The reduced normal pressure is also calculated, and agrees well with the simulation data at low to medium densities but becomes a little larger at high density. It is expected that the result can be improved by adding higher order bridge coefficients. The direct evaluation of the slit-fluid bridge function seems to be practical since a great improvement of the quality of the singlet IE theory has been achieved for predicting the structural and thermodynamic properties of fluids confined in narrow slit pores.     

Polarization-Entanglement Purification for Ideal Sources Using Weak Cross-Kerr Nonlinearity

We propose an entanglement purification protocol (EPP) for ideal entangled photon sources resorting to weak cross-Kerr nonlinearities. The key element of this EPP is the quantum nondemolition detector (QND) which uses weak cross-Kerr nonlinearity effect to generate phase shifts on the coherent states conditionally. By exploiting the double cross-phase modulation (XPM) method in QND, we present an efficient EPP protocol, which reduces the requirement for coupling strength of the cross-Kerr nonlinearity medium. The proposed protocol may open up promising possibilities for the practicability of quantum information processing using weak cross-Kerr nonlinearities.     

One-step synthesis of flower-like Au-ZnO microstructures at room temperature and their photocatalytic properties

In this paper, 3D flower-like Au-ZnO microstructures with controlled morphology and dimensions were synthesized by a facile one-step aqueous solution route at room temperature, and the photocatalytic properties of these structures were investigated. The as-prepared flower-like Au-ZnO structures with a diameter of about 3 μm consisted of many ZnO nanosheets which interacted with each other. These nanosheets, which were successfully decorated by Au NPs, showed an average thickness of 10 nm and a single-crystalline structure with {2-1-10} planar surfaces. The growth process of Au-ZnO structures and the effects of trisodium citrate on the nucleation and growth of ZnO were investigated. The formation of Au NPs in this experiment was discussed too. The Au-ZnO structures showed higher photocatalytic activity than that of pure ZnO.     

新型稀磁半导体Mn掺杂LiZnAs的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法, 对纯LiZnAs, Mn掺杂的LiZnAs, Li过量和不足下Mn掺杂的LiZnAs体系进行几何结构优化, 计算并对比分析了体系的电子结构、半金属性、光学性质及形成能.结果表明新型稀磁半导体Li (Zn_0.875Mn_0.125) As, Li_1.1 (Zn_0.875Mn_0.125) As和Li_0.9 (Zn_0.875Mn_0.125) As均表现为100%自旋注入, 材料均具有半金属性, Li过量和不足下体系的半金属性明显增强. Li过量可以提高体系的居里温度, 改善材料的导电性, 使体系的形成能降低. 说明LiZnAs半导体可以实现自旋和电荷注入机理的分离, 磁性和电性可以分别通过Mn的掺入和Li的含量进行调控. 进一步对比分析光学性质发现, 低能区的介电函数虚部和复折射率函数明显受到Li的化学计量数的影响. 关键词： Mn掺杂LiZnAs 电子结构 光学性质 第一性原理