One-dimensional Bi<Subscript>2</Subscript>Mo<Subscript>x</Subscript>W<Subscript>1-x</Subscript>O<Subscript>6</Subscript> sosoloids: controllable synthesis by electrospinning process and enhanced photocatalytic performance

One-dimensional Bi₂Mo_xW_1-xO₆ (x = 0, 0.2, 0.5, 0.67, and 1) photocatalysts have been successfully synthesized for the first time by a straightforward electrospinning technique with a calcination process. The as-formed Bi₂Mo_xW_1-xO₆ nanofibers are composed of inter-linked nanosheets of 30–50 nm in size and characterized by thermogravimetric and differential scanning calorimetric, Fourier transform infrared, Raman spectra, X-ray powder diffraction, scanning electron microscope, Brunauer-Emmett-Teller, transmission electron microscope, UV-Vis spectroscopy, photoluminescence, HPLC, and EIS. The photodegradation behaviors towards organic dyes, including rhodamine B (RhB) and methylene blue (MB) are investigated, and the results illustrate that Bi₂Mo_0.25W_0.75O₆ nanofibers exhibit the highest photocatalytic performance under visible light irradiation than Bi₂Mo_xW_1-xO₆ (x = 0, 0.2, 0.5, 0.67, and 1) samples. The possible mechanisms of the enhanced photocatalytic properties are discussed in detail.     

基于MSP430的直线导轨定位装置的设计与实现

直线导轨是数控技术的重要组成部件,它的精确程度非常重要。以MSP430单片机为核心,设计了一个直线导轨精确定位装置。此装置采用两相四线的ST57型步进电机和60CM的螺纹丝杆组成一个直线导轨组,选用M7128驱动器驱动步进电机,使用PWM波精确定位算法程序精确控制电机转速。MSP430的IO端口控制步进电机的正反转,使得步进电机带动螺纹丝杆转动,让滚动丝杠上的物体往复移动,并在电脑上显示当前位移值。试验证明,其定位精度为0.01cm,具有较高的可靠性和准确性,低成本,稳定性好。     

Scale-invariant structure of energy fluctuations in real earthquakes

Earthquakes are obviously complex phenomena associated with complicated spatiotemporal correlations, and they are generally characterized by two power laws: the Gutenberg-Richter (GR) and the Omori-Utsu laws. However, an important challenge has been to explain two apparently contrasting features: the GR and Omori-Utsu laws are scale-invariant and unaffected by energy or time scales, whereas earthquakes occasionally exhibit a characteristic energy or time scale, such as with asperity events. In this paper, three high-quality datasets on earthquakes were used to calculate the earthquake energy fluctuations at various spatiotemporal scales, and the results reveal the correlations between seismic events regardless of their critical or characteristic features. The probability density functions (PDFs) of the fluctuations exhibit evidence of another scaling that behaves as a q-Gaussian rather than random process. The scaling behaviors are observed for scales spanning three orders of magnitude. Considering the spatial heterogeneities in a real earthquake fault, we propose an inhomogeneous Olami-Feder-Christensen (OFC) model to describe the statistical properties of real earthquakes. The numerical simulations show that the inhomogeneous OFC model shares the same statistical properties with real earthquakes.     

A search for sterile neutrinos with the latest cosmological observations

We report the result of a search for sterile neutrinos with the latest cosmological observations. Both cases of massless and massive sterile neutrinos are considered in the \(\Lambda \)CDM cosmology. The cosmological observations used in this work include the Planck 2015 temperature and polarization data, the baryon acoustic oscillation data, the Hubble constant direct measurement data, the Planck Sunyaev–Zeldovich cluster counts data, the Planck lensing data, and the cosmic shear data. We find that the current observational data give a hint of the existence of massless sterile neutrino (as dark radiation) at the 1.44\(\sigma \) level, and the consideration of an extra massless sterile neutrino can indeed relieve the tension between observations and improve the cosmological fit. For the case of massive sterile neutrino, the observations give a rather tight upper limit on the mass, which implies that actually a massless sterile neutrino is more favored. Our result is consistent with the recent result of neutrino oscillation experiment done by the Daya Bay and MINOS collaborations, as well as the recent result of cosmic ray experiment done by the IceCube collaboration.     

Synthesis of RGO/Cu8S5/PPy Composite Nanosheets with Enhanced Peroxidase‐Like Activity for Sensitive Colorimetric Detection of H2O2 and Phenol

In this paper, a novel strategy for the fabrication of reduced graphene oxide (rGO)/Cu₈S₅/polypyrrole (PPy) composite nanosheets with Cu₈S₅ nanoparticles and PPy layer anchored on the surface of rGO as peroxidase‐like nanocatalyst is reported. During the synthesis, graphene oxide (GO)/CuO composite nanosheets are prepared first and used as templates, then the sulfuration of CuO and polymerization of pyrrole are accompanied with the reduction of GO, resulting in ternary rGO/Cu₈S₅/PPy composite nanosheets. The synthesized Cu₈S₅ nanoparticles with a diameter in the range from tens to hundreds of nanometers are dispersed within PPy decorated rGO nanosheets. The resultant ternary rGO/Cu₈S₅/PPy composite nanosheets exhibit a higher peroxidase‐like catalytic activity toward the oxidation of 3,3′,5,5′‐tetramethylbenzidine in the presence of H₂O₂ than GO/CuO and rGO/CuS composite nanosheets, revealing a synergistic effect on their activity. The as‐prepared rGO/Cu₈S₅/PPy platform provides a simple colorimetric approach for the detection of H₂O₂ and phenol with a high sensitivity. This work offers a new way for the fabrication of rGO‐based nanocomposite with superior enzyme‐like activity, which displays great potential applications in biocatalysis and environmental monitoring.     

Targeting Upconversion Nanoprobes for Magnetic Resonance Imaging of Early Colon Cancer

Colon cancer (CC) is one of the most common intestinal malignancies and is difficult to detect in its early stage by magnetic resonance imaging (MRI) with currently used contrast agents (CAs). The development of targeted CAs contributes to the early diagnosis of CC and thereby enables early intervention and timely therapy. Considering the outstanding performance of upconversion nanoprobes (UCNPs) in high‐performance MR and fluorescence imaging, a new type of nanoprobes with considerably enhanced imaging performance is developed herein. Carcinoembryonic antigen (CEA) antibody is conjugated onto the surface of UCNPs to achieve the targeted imaging of early CC tumors, which overexpress CEA. Both toxicity tests and histological/hematological examinations demonstrate the excellent biocompatibility of these CC‐targeting nanoprobes, which possess great potential for clinical application in the early diagnosis of CC.     

Raman spectroscopy based on a single-crystal sapphire fiber

We demonstrate the advantages of using a single-crystal sapphire fiber to perform Raman spectroscopy over using a standard glass fiber. The narrow Raman peaks and the low background signal of a single-crystal sapphire fiber allow for the detection of weaker Raman signals or Raman signals much closer to the incident laser wavelength than with a standard glass fiber, which has a strong broadband Raman spectrum of its own. The Raman spectra of calcite, single-walled carbon nanotubes, and aqueous sodium carbonate solution were collected using a 50 cm long, 200 μm diameter sapphire fiber, and then they were compared with the results using a 50 cm long, 100 μm diameter glass fiber. The Raman spectrum of each tested material becomes indistinguishable due to the background Raman signal of the glass fiber but can easily be seen using the sapphire fiber, which has only a few narrow Raman peaks of its own.     

A General Cavitation Model for the Highly Nonlinear Mie-Grüneisen Equation of State

A general one-fluid cavitation model is proposed for a family of Mie-Grüneisen equations of state (EOS), which can provide a wide application of cavitation flows, such as liquid-vapour transformation and underwater explosion. An approximate Riemann problem and its approximate solver for the general cavitation model are developed. The approximate solver, which provides the interface pressure and normal velocity by an iterative method, is applied in computing the numerical flux at the phase interface for our compressible multi-medium flow simulation on Eulerian grids. Several numerical examples, including Riemann problems and underwater explosion applications, are presented to validate the cavitation model and the corresponding approximate solver.     

飞秒激光烧蚀LiNbO3晶体的形貌特征与机理研究

采用了不同能量的单脉冲和多脉冲飞秒激光对LiNbO₃晶体进行烧蚀，并刻蚀了表面衍射型光栅.通过扫描电镜和原子力显微镜观察了烧蚀点的形貌特征，首次发现利用单束飞秒激光脉冲对LiNbO₃晶体烧蚀，可以得到超衍射极限的烧蚀点，当聚焦光斑直径约为2μm、能量为170nJ的单脉冲飞秒激光作用时，烧蚀点的直径约为400nm，100nJ，17个脉冲作用时烧蚀点的直径约为800nm.同时可以观察到在能量较低的多脉冲飞秒激光作用下， LiNbO₃晶体呈现出大约200nm周期性分布的波纹状结构.实验结果表明，选择合适参数的飞秒激光脉冲可以对LiNbO₃晶体进行超衍射极限加工，这对于利用飞秒激光制作LiNbO₃基质的微纳光电子器件有十分重要的意义.