多偏振飞秒激光制备彩色铁

采用四个不同偏振方向的线偏振和圆偏振态飞秒激光扫描处理金属铁表面来制备不同的彩色铁。从不同角度观察被处理区域时,线偏振扫描处理的彩色区域呈现不同的色彩,而圆偏振扫描处理的区域没有明显的颜色变化。扫描电子显微镜图片显示,线偏振激光扫描处理金属铁表面形成了nm量级的激光诱导周期表面结构,其方向始终与激光偏振方向垂直;圆偏振激光扫描处理金属铁表面形成的条纹结构不明显且有大量的纳米颗粒结构。     

Detecting hidden spatial and spatio-temporal structures in glasses and complex physical systems by multiresolution network clustering

We elaborate on a general method that we recently introduced for characterizing the “natural” structures in complex physical systems via multi-scale network analysis. The method is based on “community detection” wherein interacting particles are partitioned into an “ideal gas” of optimally decoupled groups of particles. Specifically, we construct a set of network representations (“replicas”) of the physical system based on interatomic potentials and apply a multiscale clustering (“multiresolution community detection”) analysis using information-based correlations among the replicas. Replicas may i) be different representations of an identical static system, ii) embody dynamics by considering replicas to be time separated snapshots of the system (with a tunable time separation), or iii) encode general correlations when different replicas correspond to different representations of the entire history of the system as it evolves in space-time. Inputs for our method are the inter-particle potentials or experimentally measured two (or higher order) particle correlations. We apply our method to computer simulations of a binary Kob-Andersen Lennard-Jones system in a mixture ratio of A₈₀B₂₀ , a ternary model system with components “A”, “B”, and “C” in ratios of A₈₈B₇C₅ (as in Al₈₈Y₇Fe₅ , and to atomic coordinates in a Zr₈₀Pt₂₀ system as gleaned by reverse Monte Carlo analysis of experimentally determined structure factors. We identify the dominant structures (disjoint or overlapping) and general length scales by analyzing extrema of the information theory measures. We speculate on possible links between i) physical transitions or crossovers and ii) changes in structures found by this method as well as phase transitions associated with the computational complexity of the community detection problem. We also briefly consider continuum approaches and discuss rigidity and the shear penetration depth in amorphous systems; this latter length scale increases as the system becomes progressively rigid.     

High-speed camera study of Stage III crack propagation in chemically strengthened glass

Thermally or chemically strengthened glass is more resistant to damage and breakage compared to non-strengthened glass. Both strengthening mechanisms are based on incorporation of a compressive stress profile in the surface of the glass, which must be balanced by an equivalent amount of integrated tensile stress in the interior of the glass. This tensile stress is believed to affect the kinetics of Stage III crack propagation upon fracture of the sample. In this study, we use a high-speed camera to perform direct measurement of the kinetics of Stage III fracture in a strengthened glass sample. Data including crack propagation speed, crack bifurcation distance, and bifurcation angles are collected at a rate of 500,000 frames per second and then characterized. The authors believe that these data will provide a foundation for understanding the physics of Stage III fracture in strengthened glass samples.     

Structural, optical and electronic properties of P doped p-type ZnO thin film

P doped ZnO films were grown on quartz by radio frequency-magnetron sputtering method using a ZnO target mixed with 1.5 at% P₂O₅ in the atmosphere of Ar and O₂ mixing gas. The as-grown P doped ZnO film showed n-type conductivity, which was converted to p-type after 800 °C annealing in Ar gas. The P doped ZnO has a resistivity of 20.5 Ω cm (p∼2.0×10¹⁷ cm⁻³) and a Hall mobility of 2.1 cm² V⁻¹ s⁻¹. XRD measurement indicated that both the as-grown and the annealed P doped ZnO films had a preferred (0 0 2) orientation. XPS study agreed with the model that the P_Zn-2V_Zn acceptor complex was responsible for the p-type conductivity as found in the annealed P-doped ZnO. Temperature-dependent photoluminescence (PL) spectrum showed that the dominant band is located at 3.312 eV, which was attributed to the free electronic radiative transition to neutral acceptor level (FA) in ZnO. The P_Zn-2V_Zn acceptor complex level was estimated to be at E_V=122 meV.     

γ-MnO2/polyaniline composites: Preparation, characterization, and applications in microwave absorption

MnO₂/doped polyaniline (PANI) is prepared by an in situ polymerization method using γ-MnO₂ as the addition agent and hydrochloric acid as the doping agent. Products are characterized by FT-IR, UV-vis, XRD, and TEM. Conductivity, electromagnetic properties, and microwave absorption properties are first discussed on the basis of structural characterization. The as-prepared products of MnO₂/PANI are partially crystalline in nature and spherical in pattern with grain sizes of 50-70 nm. MnO₂ particles are successfully decorated with doped PANI. MnO₂/PANI displays moderate electric conduction, excellent dielectric losses, and microwave absorption capabilities. Compared to pure MnO₂, the dielectric and reflection loss properties of MnO₂/PANI composites exhibit significant improvements, with an effective absorption band at 5 GHz under −10 dB and maximum reflection loss of −21 dB at 13.56 GHz. Pure MnO₂ shows an effective absorption band of 3 GHz under −10 dB and a maximum reflection loss of −14.20 dB at 11.5 GHz. Thus, MnO₂/PANI composites are found to be a promising microwave absorption material.     

Synthesis, Crystal Structure, Interaction with BSA and Antibacterial Activity of La(III) and Sm(III) Complexes with Enrofloxacin

Two new La(III) and Sm(III) complexes with enrofloxacin (HER, 1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid, C(19)H(21)FN(3)O(3)), [La(2)(ER)(6)(H(2)O)(2)]·14H(2)O(1) and [Sm(2)(ER)(6)(H(2)O)(2)]·14H(2)O(2) have been synthesized and characterized by elemental analysis, FT-IR, TG-DTG and X-ray single crystal diffraction. Both of the complexes are triclinic system with space group Pī. The structure of the complexes show that each rare earth atom in both complexes was nine-coordinated. Two of the enrofloxacin ions acted as tridentate chelate and bridging ligands, while the others as bidentate chelate ligands. The binding reaction between the complexes and bovine serum albumin (BSA) was studied by UV-vis absorption spectra and fluorescence spectroscopy. The results indicated that the two complexes had a quite strong ability to quench the fluorescence from BSA and the binding reaction was mainly a static quenching process. The binding constants K ( A )/(L·mol(-1)) were 1.46 × 10(5)(1) and 8.59 × 10(6)(2) and one binding site was formed. The synchronous spectroscopy suggested that tryptophan residues were placed in BSA. It was also found that the two complexes exhibited greater antimicrobial activity than enrofloxacin at given concentrations.     

Electronic structure and magnetism in full-Heusler compound Mn2ZnGe

The first-principle calculations within density functional theory are used to investigate the electronic structure and magnetism of the Mn₂ZnGe Heusler alloy with CuHg₂Ti-type structure. The half-metallic ferrimagnets (HMFs) in Mn₂ZnGe are predicted. The energy gap lies in the minority-spin band for the Mn₂ZnGe alloy. The calculated total spin magnetic moment is −2μ_B per unit cell for Mn₂ZnGe alloy, the magnetic moments of Zn and Mn(B) are antiparallel to that of Mn(A), and we also found that the half-metallic properties of Mn₂ZnGe are insensitive to the dependence of lattice within the wide range of 5.69 and 5.80 Å where exhibiting perfect 100% spin polarization at the Fermi energy.     

Synchronization of complex community networks with nonidentical nodes and adaptive coupling strength

In this Letter, the complex dynamical networks with community structure and nonidentical nodes are considered. The globally asymptotical synchronization of the time-delayed complex community networks onto any uniformly smooth state is studied. Some simple and useful criteria are derived by constructing an effective control scheme and adjusting automatically the adaptive coupling strength. Finally, the developed techniques are applied to two complex community networks which are respectively synchronized to a chaotic trajectory and a periodic orbit, and numerical simulations are provided to show the feasibility of the developed methods.     

大气折射对可见光波段辐射传输特性的影响

折射是影响辐射传输的重要因素. 为分析大气折射对辐射传输的影响, 基于Monte Carlo方法, 给出了考虑大气折射的矢量辐射传输模型, 实现了均匀气层和耦合面处光子随机运动过程的模拟, 实现了直射光及漫射光Stokes矢量、偏振度和辐射通量等参数的计算. 在考虑和不考虑大气折射两种条件下, 验证了模型的准确性; 在纯瑞利散射条件下, 讨论了大气折射对不同方向漫射光Stokes矢量的影响; 在不同太阳天顶角、大气廓线、气溶胶及含云大气条件下, 分析了大气折射对辐射传输过程的影响. 结果表明: 大气折射对漫射光Stokes矢量的影响主要体现在天顶角70°–110°区间, 且随着太阳入射角增大, 其影响更为显著; 不同大气廓线情形下, 大气折射对Stokes矢量的影响不一致, 其原因是不同大气廓线对应的折射率廓线存在差异. 含云及含气溶胶大气条件下, 大气折射对辐射传输的影响变弱, 沙尘型及海盐型气溶胶条件下, 折射对辐射传输的影响强于可溶型气溶胶情形; 不同形状气溶胶条件下, 大气折射对辐射传输的影响也存在显著差异; 不同云高条件下, 大气折射对漫射光Stokes矢量的影响无显著差异, 但随着云光学厚度增大, 大气折射的影响减弱.     

Epitaxial growth and thermostability of cubic and hexagonal SrMnO3 films on SrTiO3(111)

The growth of SrMnO₃ films on SrTiO₃(111) substrates by pulsed laser deposition was studied and found to produce cubic and hexagonal (4H) structures in the SrMnO₃ films. By adjusting the substrate temperature and oxygen pressure, the stability of the two phases was fine-tuned, resulting in the growth of cubic-SrMnO₃(111) or 4H-SrMnO₃(0001) film, with the 4H phase being the more stable at room temperature and ambient pressure in the bulk form. The growth temperature of the cubic phase was also further lowered relative to the bulk thermodynamics by strain at the heterointerface, and once obtained, it was stable at temperatures of up to 800 °C.