Sharp Threshold of Global Existence for a Nonlocal Nonlinear Schrödinger System in ℝ3

In this paper, the authors investigate the sharp threshold of a three-dimensional nonlocal nonlinear Schr\"{o}dinger system. It is a coupled system which provides the mathematical modeling of the spontaneous generation of a magnetic field in a cold plasma under the subsonic limit. The main difficulty of the proof lies in exploring the inner structure of the system due to the fact that the nonlocal effect may bring some hinderance for establishing the conservation quantities of the mass and of the energy, constructing the corresponding variational structure, and deriving the key estimates to gain the expected result. To overcome this, the authors must establish local well-posedness theory, and set up suitable variational structure depending crucially on the inner structure of the system under study, which leads to define proper functionals and a constrained variational problem. By building up two invariant manifolds and then making a priori estimates for these nonlocal terms, the authors figure out a sharp threshold of global existence for the system under consideration.     

Two-dimensional Sb cluster superlattice on Si substrate fabricated by a two-step method

Nanoclusters consisting of a few atoms have attracted a lot of research interests due to their exotic size-dependent properties. Here, well-ordered two-dimensional Sb cluster superlattice was fabricated on Si substrate by a two-step method and characterized by scanning tunneling microscopy. High resolution scanning tunneling microscope measurements revealed the fine structures of the Sb clusters, which consist of several Sb atoms ranging from 2 to 7. Furthermore, the electronic structure of the nanocluster displays the quantized energy-level which is due to the single-electron tunneling effects. We believe that the fabrication of Sb cluster superlattice broadens the species of the cluster superlattice and provides a promising candidate to further explore the novel physical and chemical properties of the semimetal nanocluster.     

Preparation of High-performance Polyimide Fibers with Wholly Rigid Structures Containing Benzobisoxazole Moieties

In this work, a fully rigid coplanar symmetric heterocyclic unit was introduced into the rigid polyimide macromolecular backbone structure to prepare high-performance polyimide fibers. The novel co-polyimide(co-PI) fibers based on 3,3',4,4'-biphenyltetracarboxylic anhydride(BPDA), p-phenylenediamine(PDA) and 2,6-(4,4'-diaminodiphenyl) benzo[1,2-d:5,4-d'] bisoxazole(PBOA) were fabricated via a twostep wet-spinning method. The effects of benzobisoxazole moiety on spinnability, aggregation structure, and mechanical properties of fibers were systematically discussed. The detailed structural analysis revealed that the well-defined aggregation structures of co-PI fibers were obtained from initial amorphous structure when post hot-drawing temperature was higher than 460 ℃ under proper drawing ratio, and the incorporation PBOA into BPDA-PDA structures produced more compact structural co-PI fiber than homo BPDA-PDA fiber. The BPDA-PDA/PBOA co-PI fibers exhibited optimum tensile strength and modulus of 2.65 and 103 GPa, which increased by 182% and 84% compared to the homo BPDA-PDA fiber, respectively.     

In-situ optical pumping for polarizing 3He neutron spin filters at the China Spallation Neutron Source

In this paper,we present the performance of a recently developed in-situ spin-exchange optically pumped³He-neutron spin filter system at the China Spallation Neutron Source(CSNS).The system achieved a³He polarization of over 74%at the beamline BL-20.Analysis of neutron transmission experiment results reveals a neutron polarization of>90%and an average transmission of 27%for 2.2?neutrons,which were maintained for a duration of 120 h of beam time.To the best of our knowledge,this is the first in-situ hyperpolarized³He system incorporated on a neutron beamline in China.This technology is expected to provide stable,wide-angle,and highly polarized neutrons at the CSNS for materials research and fundamental neutron physics.     

Selective O-difluoromethylation of 1,3-diones using S-(difluoromethyl) sulfonium salt

A facile and highly efficient approach for selective O-difluoromethylation of 1,3-diones with S-(difluoromethyl)sulfonium salt was developed, and a wide variety of difluoromethyl enol ethers were readily synthesized.     

Convergence of complex martingale for a branching random walk in an independent and identically distributed environment

We consider anR^d-valued discrete time branching random walk in an independent and identically distributed environment indexed by time n∈N.Let W_n(z)(z∈C^d)be the natural complex martingale of the process.We show necessary and sufficient conditions for the L^α-convergence of W_n(z)forα>1,as well as its uniform convergence region.     

High dense views auto-stereoscopic three-dimensional display based on frontal projection with LLA and diffused screen

We present a high dense views auto-stereoscopic three-dimensional display method with the projectors array and lenticular lens array(LLA) screen. The principle and configuration are demonstrated. This display method utilizes lenticular screen to modulate the information of projectors. To increase the dense of views, we propose a novel arrangement way of projectors array. In the experiment, the viewer can obtain smooth motion parallax and evident stereo feeling at optimal distance. Through analyzing and observation, the maximum display depth is found to be more than 50 cm.     

A simple method for determining water content in organic solvents based on cobalt(Ⅱ)complexes

A method to determine water content in organic solvents was developed based on the color change of cobalt(Ⅱ) nitrate in different solvents.The color-change mechanism and optimal conditions for determining the water content were investigated.The results showed that there was a good linear relationships between the absorbance of cobalt(Ⅱ) complexes in organic solvents and water contents withγin 0.9989～0.9994.This method has the advantages of low cost,good reproducibility,good sensitivity,simple in operation,fast in detection,friendly to the environment and no limitation on linear range for determining water content.It was used to determine water in samples with a satisfactory recovery in 97.81%～101.24%.     

Synthesis of CdS multipods from cadmium xanthate in ethylenediamine solution

CdS nanocrystals of various shapes were synthesized by using cadmium ethyldithiocarbonatio(xanthate)as a single precursor under solvothermal condition.The reaction temperature,cadmium concentration,and solvents determine the CdS morphology.Multipodal CdS structures of different fractions of all particles were obtained at temperatures ranging from 100 to 180 ℃ with the corresponding precursor concentrations in ethylenediamine(EDA) solution.This approach is different from that reported in the literature,where EDA is regarded as a solvent favorable to the formation of CdS nanorods instead of pods.Uniform CdS multipods were prepared at 160℃ with 1.0g of cadmium xanthate.The formation of CdS multipods in EDA solution may be attributed to a synergistic effect between the reaction temperature and Cd concentration,i.e.,thermodynamicaily and kinetically controlled growth of the CdS wurtzite(WZ)and zinc blende(ZB) phases,as confirmed by the structural characterization of the component CdS crystals.EDA and xanthate ligands act as co-assisted capping agents in the growth of CdS multipods.When using N,N-dimethylformamide(DMF) and ethylene glycol(EG) as solvents,the CdS appears as triangular particles and flower-like microspheres assembled by polyhedrons,respectively.     

Facile synthesis and properties of alkali-clearable azo disperse dye containing a carboxylic ester moiety

A yellow, alkali-clearable azo disperse dye containing a carboxylic ester moiety was readily synthesized from the reactant p-aminobenzoic acid by successive diazotization, coupling reaction, chlorination and esterification with ethanol. Then its molecular structure was characterized by FTIR,1H NMR,13 C NMR,mass spectrometry and elemental analysis. The synthesized dye and a similar control dye containing the acylamide moiety（I） were applied to dyeing poly（ethylene terephthalate） fabric and their washing and rubbing fastness properties with different post-treatment methods（reduction clearing and alkali clearing） were examined and compared. It is found that the ester-containing disperse dye shows good alkali-clear ability on poly（ethylene terephthalate） fabric and contaminates little to environment due to the absence of reductants, as well as low toxicity and easy recycling of the hydrolysates.