Preparation of Aligned Polymer Micro/Nanofibres by Electrospinning

Polymer micro/nanofibres are prepared by typical and modified methods of electrospinning. The morphologies and microstructures of the electrospun micro/nanofibres are characterized by a scanning electron microscope （SEM）. The micro/nanofibres prepared by the typical electrospinning are usually collected in the form of nonwoven mats lacking of structural orientation, However, by modifying collector（s） of the electrospinning setup, the resulting polymer fibres show aligned structures to some extent. We analyse all the forces that the fibres experienced during electrospinning and find that the electrostatic force originating from the splitting electric field plays a key role in the alignment of the micro/nanofibres.     

Photoluminescence of Electrospun Poly-Methyl-Methacrylate:Alq3 Composite Fibres

Tris（8-hydroxyquinoline） aluminium doped poly-methyl-methacrylate （PMMA：Alq3） composite nanofibres are fabricated by electrospinning. The morphology of fibres is characterized by scanning electron microscopy. The photoluminescence of a series of the nanofibres with various contents of Alq3 to PMMA is investigated. UVvisible absorption and the PL spectra analysis are employed to analyse the interaction between the polymer and the luminescent molecule.     

Fabrication and magnetic properties of Ni0.50.5Zn0.5Fe2O4 nanofibres by electrospinning

NiZn ferrite/polyvinylpyrrolidone composite fibres were prepared by sol–gel assisted electrospinning.Ni0.5Zn0.5Fe2O4 nanofibres with a pure cubic spinel structure were obtained subsequently by calcination of the composite fibres at high temperatures.This paper investigates the thermal decomposition process,structures and morphologies of the electrospun composite fibres and the calcined Ni0.5Zn0.5Fe2O4 nanofibres at different temperatures by thermogravimetric and differential thermal analysis,x-ray diffraction,Fourier transform infrared spectroscopy and field emission scanning electron microscopy.The magnetic behaviour of the resultant nanofibres was studied by a vibrating sample magnetometer.It is found that the grain sizes of the nanofibres increase significantly and the nanofibre morphology gradually transforms from a porous structure to a necklace-like nanostructure with the increase of calcination temperature.The Ni0.5Zn0.5Fe2O4 nanofibres obtained at 1000 C for 2 h are characterized by a necklace-like morphology and diameters of 100–200 nm.The saturation magnetization of the random Ni0.5Zn0.5Fe2O4 nanofibres increases from 46.5 to 90.2 emu/g when the calcination temperature increases from 450 to 1000 C.The coercivity reaches a maximum value of 11.0 kA/m at a calcination temperature of 600 C.Due to the shape anisotropy,the aligned Ni0.5Zn0.5Fe2O4 nanofibres exhibit an obvious magnetic anisotropy and the ease magnetizing direction is parallel to the nanofibre axis.     

A novel toluene sensor based on ZnO-SnO2 nanofiber web

We proposed in the present work that large-scale synthesis of sensitive ZnO-SnO₂ nanofibres which can be obtained via a simple electrospinning method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction patterns (XRD) showed the average diameter of ZnO-SnO₂ nanofibres ranging between 100 and 200 nm, the mixture of wurtzite (ZnO) and rutile (SnO₂) structure in the composite fibers. The sensitivity of the obtained ZnO-SnO₂ nanofibres to toluene was also investigated. The results showed that under optimal conditions, the calibration curve of response versus toluene concentration was linear in the range of 10-300 ppm, the response and recovery time were only several seconds, and sensitivity for toluene was desirable.     

1-butyl-3-methylimidazolium chloride assisted electrospinning of SAN/MWCNTs conductive reinforced composite membranes

The aim of this research was to investigate how the addition of IL [Bmim]Cl* and MWCNTs** into SAN*** solution will influence the viscosity and the electrical conductivity of the electrospinning solution and to find out the impact of IL and CNTs on the electrical and mechanical properties of the obtained membranes and on the morphology of the produced nanofibres. MWCNTs were added into two types of SAN solutions, with and without [Bmim]Cl, and then electrospinning was performed. All membranes were investigated by SEM analysis. The electrical conductivity and viscosity of the solutions were measured and their effect on the morphology of the fibres, as well as electrical and mechanical properties was estimated.     

Glueball Masses from Hamiltonian Lattice QCD

We calculate the masses of the 0⁺⁺, 0^-- and l^+- glueballs from QCD in 3+1 dimensions using an eigenvalue equation method for Hamiltonian lattice QCD developed and described by S.H. GUO et al. The mass ratios become approximately constants in the coupling region 6/g²∈[6.0,6.4], from which we estimate M(0^--)/M(0⁺⁺) = 2.44 ± 0.05 ± 0.20 and M(l^+-)/M(0⁺⁺) = 1.91 ± 0.05 ± 0.12.     

Reanalysis of the Z_c(4020), Z_c(4025), Z(4050) and Z(4250) as Tetraquark States with QCD Sum Rules

In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the C γμ- Cγνtype scalar, axial-vector and tensor tetraquark states in details with the QCD sum rules. In calculations, we use the formula μ = (M 2X/ Y /Z-(2Mc)2)~(1/2) to determine the energy scales of the QCD spectral densities. The predictions MJ =2=(4.02+0.09-0.09) GeV, MJ =1=(4.02+0.07-0.08) GeV favor assigning the Zc(4020) and Zc(4025) as the JP C= 1+-or 2++diquark-antidiquark type tetraquark states, while the prediction M++J =0=(3.85+0.15-0.09) GeV disfavors assigning the Z(4050) and Z(4250) as the JP C= 0diquark-antidiquark type tetraquark states. Furthermore, we discuss the strong decays of the 0++, 1+-, 2++diquark-antidiquark type tetraquark states in details.     

Homogeneity analysis of sculptured thin films deposited in symmetric style through glancing angle deposition technique

The symmetric deposition technique is often used to improve the uniformity of sculptured thin film （STF）. In this paper, optical properties of STF with the columnar angles 4-/3 are analyzed theoretically, based on the characteristic matrix method for extraordinary waves. Then, the transmittances of uniformity monolayer and bilayer STF in symmetrical style are calculated to show the effect of the bilayer structure on the optical properties of STF. The inhomogeneity of STF is involved in analyzing the differences in transmittance and phase retardation between monolayer and bilayer STF deposited in symmetric style. The results show that optical homogeneity of STF can be improved by depositing in symmetric style at the normal incidence, but it is not the same case as the oblique incidence.     

Characterisation of Electrospun Poly(lactic acid) Nanofibre Networks

Electrospinning has been regarded as a convenient method of manufacturing polymer-based multi-functional and high performance nanofibres that can significantly contribute to the world of advanced materials. The primary requirement of the process is to obtain nanofibres in continuous form with fine diameters and minimum variations. Secondly, the fibre network has to have minimum area occupied by beads to enhance the network's porosity. These two important characteristics, when achieved, render the nanofibre mats acceptable for many membrane type applications. The relationship between processing parameters and microstructures of nanofibrils is still not well understood. The goals of this study are to obtain a set of robust manufacturing parameters that would reduce the variation in quality while electrospinning non-woven mats of nanofibres from poly(L-lactic) acid (PLLA). The study involves sixteen sets of parametric combinations and the scanning electron microscopy of the produced mats. The desirable combination for producing acceptable networks appears to be low concentration of polymer solution, low feed rate, comparatively high applied voltage and a large distance (within the studied range) between the collector and the needle. However, a low concentration of polymer solution may result in some bead formation if other factors are not changed accordingly.     

Dielectric and infrared properties of SrTiO3 single crystal doped by 3d （V,Mn, Fe,Ni） and 4f （Nd,Sm, Er） ions

In this study, the effects of doping by 3d （V, Mn, Fe, Ni） and 4f （Nd, Sm, Er） ions on dielectric and infrared properties of SrTiO3 （STO） single crystals are investigated. It is well known that doping of the SrTiO3 can change the dielectric properties of the STO from an insulator to an n-type semiconductor, and even to a metallic conductor. Dielectric and infrared （IR） properties of the undoped STO and doped STO single crystals are analyzed using dielectric spectroscopy （80 kHz-5 MHz）, transmission （200 cm^-1-4000 cm^-1）, and reflection spectroscopy （50 cm^-1-2000 cm^-1）. It is found that doping by the 3d ions reduces the value of dielectric permittivity, but the trend of temperature dependence of the dielectric permittivity remains almost unchanged. On the other hand, dielectric spectroscopy measurements for samples doped by 4f ions show the anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition. There are two fractures of temperature dependences of inverse dielectric permittivity εr^-1 （T）. Transmittance spectroscopy measurements show that there are differences in the shape of the spectrum in the mid-IR region between the undoped STO and the one doped by 4f ions. The differences in the reflectance spectrum between the STO：Nd and STO are analyzed in detail.     

Photodetachment of H- Near a Dielectric Surface

Using the closed orbit theory, the photodetachment cross section of H- near a dielectric surface has been derived and calculated. The results show that the dielectric surface has great influence on the photodetachment process of negative ion near the ionization threshold. Above the ionization threshold, the photodetachment cross section starts to oscillate. With the increase of the energy, the oscillating amplitude decreases and the oscillating frequency increases. The oscillation in the photodetachment cross section of H- in the presence of a dielectric surface is either larger or smaller than the photodetachment of H- without the surface. As the photon energy is larger than the critical value Epc, the oscillatory structure disappeared and the cross section approaches to the case of the photodetachment of H- without any external fields. For a given detached-electron energy, the photodetachment cross section becomes decreased with the increase of the ion-surface distance. Besides, the dielectric constant has great influence on the photodetachment of H-. With the increase of the dielectric constant, the oscillation in the cross section becomes increased. As the dielectric constant increases to infinity, the cross section is the same as the photodetachment of H- near a metal surface. This study provides a new understanding on the photodetachment process of H- in the presence of a dielectric surface.     

Electronic and magnetic properties of BiFeO_3 with intrinsic defects:First-principles prediction

The electronic structure, magnetism, and dielectric functions of BiFeO3 with intrinsic vacancies, including Bi-, Fe-, and O-vacancies （denoted as VFe, VBi, and Vo, respectively） are investigated using the first-principles density functional theory plus U calculations. It is revealed that the structural distortions associated with those vacancies impose significant influences on the total density of state and magnetic behaviors. The existence of VBi favors the excitation of the O2p state into the band gap at 0.4 eV, while the O2p and Fe3d orbitals are co-excited into the band gap around 0.45 eV in VFe- Consequently, a giant net magnetic moment of 1.96 P-B is generated in VFe, and a relatively small moment of 0.13 P-B is induced in VBi, whereas Vo seems magnetically inactive. The giant magnetic moment generated in VFe originates from the suppression of the spatially modulated antiferromagnetic spin structure. Furthermore, VFe and VBi have strong influences on dielectric function, and induce some strong peaks to occur in the lower energy level. In contrast, VO has a small effect.     

Novel high-voltage self-adaptive power device based on interface charge＊

This paper presents a novel high-voltage lateral double diffused metal-oxide semiconductor （LDMOS） with self- adaptive interface charge （SAC） layer and its physical model of the vertical interface electric field. The SAC can be self-adaptive to collect high concentration dynamic inversion holes, which effectively enhance the electric field of dielectric buried layer （EI） and increase breakdown voltage （BV）. The BV and EI of SAC LDMOS increase to 612 V and 600 V/tim from 204 V and 90.7 V/ttm of the conventional silicon-on-insulator, respectively. Moreover, enhancement factors of r/which present the enhanced ability of interface charge on EI are defined and analysed.     

Polar Mixing Optical Phonon Spectra in Wurtzite GaN Cylindrical Quantum Dots： Quantum Size and Dielectric Effects

The interface-optical-propagating （IO-PR） mixing phonon modes of a quasi-zero-dimensional （QOD） wurtzite cylindrical quantum dot （QD） structure are derived and studied by employing the macroscopic dielectric continuum model. The analytical phonon states of IO-PR mixing modes are given. It is found that there are two types of IO-PR mixing phonon modes, i.e. p-IO//z-PR mixing modes and the z-IO//p-PR mixing modes existing in QOD wurtzite QDs. And each IO-PR mixing modes also have symmetrical and antisymmetrieal forms. Via a standard procedure of field quantization, the Frohlich Hamiltonians of electron-（IO-PR） mixing phonons interaction are obtained. Numerical calculations on a wurtzite GaN cylindrical QD are performed. The results reveal that both the radial-direction size and the axial-direction size as well as the dielectric matrix have great influence on the dispersive frequencies of the IO-PR mixing phonon modes. The limiting features of dispersive curves of these phonon modes are discussed in depth. The phonon modes ＂reducing＂ behavior of wurtzite quantum confined systems has been observed obviously in the structures. Moreover, the degenerating behaviors of the IO-PR mixing phonon modes in wurtzite QOD QDs to the IO modes and PR modes in wurtzite Q2D QW and QID QWR systems are analyzed deeply from both of the viewpoints of physics and mathematics.     

Beam transport design for a 1 MeV prototype dielectric wall accelerator

The beam transport design of a novel proton dielectric wall accelerator is introduced in this paper. The protons will be accelerated from 40 keV to nearly 1 MeV under an accelerating gradient that is as high as 20 MV/m. A consideration of the beam line as well as the transport simulation is presented. The influences of the injection timing jitter and the accelerating pulse timing jitter are also discussed.     

Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature

In order to investigate of cobalt-doped interracial polyvinyl alcohol （PVA） layer and interface trap （Dit） effects, A1/p- Si Schottky barrier diodes （SBDs） are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance （Rs）, and interfacial layer. Both the real and imaginary parts of dielectric constant （er and err） and electric modulus （Mr and Mrr）, loss tangent （tan~）, and AC electrical conductivity （aac） are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance （C） and conductance （G/w） values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si （MPS） type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance （CLF-CHF） method.     

A Proposal on the Search for the Hybrid with I^G（J^PC）=1^—（1—＋）in the Process J／ψ→ρωππ at Upgraded BEPC／BES

We give the moment expressions for the boson resonances X with spin-parity JXPXC=0 ,1- ,1 and 2 posibly produced in the process J/ψ→ρX,X→b1(1235)π,b1→ωπ in terms of the generalized moment analysis method .The resonance with JXPXC=1- can e distingguished from other resonances by means of these moments exceptfor some rather special cases.The suggestion that the search for the hybrid with IG(JPC)=1-(1- ) can be performed in the decay channl J/ψ→ρωππat upgraded BEPC/BES is presented.     

Search for Theta++ pentaquarks in the exclusive reaction gammap-->K+K-p

The reaction gammap --> pK+K- was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a Theta++ pentaquark, a narrow, doubly charged baryon state having strangeness S=+1 and isospin I=1, in the pK+ invariant mass spectrum. No statistically significant evidence of a Theta++ was found. Upper limits on the total and differential cross section for the reaction gammap --> K-Theta++ were obtained in the mass range from 1.5 to 2.0 GeV/c2, with an upper limit for a narrow resonance with a mass M(Theta++) = 1.54 GeV/c2 of about 0.15 nb, 95% C.L.. This result places a stringent upper limit on the Theta++ width Gamma(Theta++) <0.1 MeV/c2.     

Dielectric loss of half-doped manganite Lao.sCao.sMnO3＊

The dielectric loss tanfi of half-doped manganite Lao.sCao.sMnO3 is investigated using Green＇s function technique. The Lao.sCao.sMnO3 is described by the Kondo-lattice model in the double exchange limit, taking into account the Jahn- Teller distortion and the super-exchange interaction between the localized electrons. It is found that the intensity of tans decreases with increasing [e]TI, V, and U. It is also observed that the transition temperature Tp rises as l eJTI and U increase. It is worth noting that Tp remains unchanged and the strength of tans increases with increasing g. The calculated dielectric loss results are explained theoretically, and these behaviors are in qualitative agreement with the experimental results.     

催化前驱体亚硝酰硝酸钌中杂质元素的质谱分析

钌催化前驱体是影响负载型钌催化剂催化性能最重要因素。前驱体中的部分杂质会对催化性能产生抑制作用，尤其是S，P，Cl，As等杂质元素含量过高会降低催化剂的活性，严重时会造成催化剂中毒；因此，必须严格控制催化前驱体中杂质元素的含量。建立了快速准确测定催化前驱体亚硝酰硝酸钌（Ru(NO)(NO₃)₃）中杂质元素的分析方法。Ru(NO)(NO₃)₃经稀硝酸溶解后采用电感耦合等离子体串联质谱（ICP-MS/MS）直接测定其中的8个杂质元素（P，S，Ti，V，Cr，Mn，Fe，As）。为防止Ru(NO)(NO₃)₃溶液水解形成Ru(NO)(NO₃)x(OH)_3-x，采用稀硝酸介质有效维持了样品溶液的稳定性。在MS/MS模式下，通过一级四极杆质量过滤器（Q₁）控制进入碰撞/反应池（CRC）的离子，仅允许与待测元素具有相同质荷比（m/z）的离子进入CRC，从而将来自样品基质和等离子气Ar所形成的干扰离子阻止在CRC外，消除了大量质谱干扰。通过向CRC内通入O₂为反应气，目标离子P+，S+，Ti+，V+，As+与O₂的反应为放热过程（31P++O₂→31P16O++O，ΔH_r=-3.17 eV；32S++O₂→32S16O++O，ΔH_r=-0.34 eV；48Ti++O₂→48Ti16O++O，ΔH_r=-1.63 eV；51V++O₂→51V16O++O，ΔH_r=-0.85 eV；75As++O₂→75As16O++O，ΔH_r=-0.63 eV），能自发反应生成氧化物离子；目标离子Cr+，Mn+与O₂的反应为吸热过程（52Cr++ O₂→52Cr16O++O，ΔH_r=+1.38 eV；55Mn++O₂→55Mn16O++O，ΔH_r=+2.15 eV）。为促进Cr+，Mn+与O₂发生反应，通过调整CRC的工作参数，设置八极杆偏置电压为较大的负电压，使Cr+和Mn+在与O₂反应前被加速，提高Cr+和Mn+的动能，促进了反应的发生，通过吸热反应生成氧化物离子；而P+，S+，Ti+，V+，Cr+，Mn+，As+干扰离子在CRC内不能与O₂发生反应，仍然保持原始的m/z。通过二级四极杆质量过滤器（Q₂）将这些干扰离子阻止在外，仅允许所形成的氧化物离子进入检测器，几乎完全消除了元素P，S，Ti，V，Cr，Mn，As的所有质谱干扰。NH₃因含一对孤对电子而具有高反应活性，能与很多金属离子反应形成团簇离子。通过向CRC内通入NH₃/He为反应气，目标离子Fe+与NH₃发生质量转移反应，在所形成多个团簇离子中，Fe(NH₃)+₂的丰度最高且无干扰，通过NH₃质量转移法消除干扰。结果显示，8个元素在0～500 μg·L-1范围内具有良好的线性关系，线性相关系数≥0.999 8。方法的检出限为0.29～485 ng·L-1，按所建立的方法分析了实际样品中8个杂质元素的含量，各元素的加标回收率为93.2%～107.5%，相对标准偏差（RSD）≤3.9%。方法具有样品处理简单、分析速度快和精密度高的特点，适合催化前驱体亚硝酰硝酸钌中多个杂质元素的准确测定，为制备负载型钌催化剂提供了质量保障。