基于复杂网络的北半球遥相关 年代际变化特征研究

基于北半球中高纬度环流系统关联网络, 研究了冬季北半球各种遥相关年代际尺度的变化特征及其与气候突变的可能联系等. 研究结果表明, NAO, EUPA和WP 等遥相关的作用中心在1970年代中后期和1990年代初期均对应有显著的跃变过程, 且主要空间模态也发生一定的变化. 结合网络顶点度, 定义直接体现遥相关作用强弱的指数并分析其随时间的变化:1980年代以前以PNA, EUPA和WP三种模态的共同作用为主导, 1980年代以后NAO的作用显著增强, 1987年以后AO的作用显著增强, 其他模态的作用则相对较弱. 因此, 多种遥相关年代际尺度的调整可能是1970年代中后期和1990年代初期气候突变的重要表现形式之一.     

Lateral field excitation properties of langasite single crystal

In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation (LFE) on langasite substrate, namely the (yxl)65o (pure-LFE mode), (yxl)45o (quasi-LFE mode), and (yxl)0o (pseudo-LFE mode). Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the (yxl)65o langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, (yxl)0o langasite LFE device is also found suitable for liquid phase sensing applications.     

The (e, 2e) triple differential cross sections of Cu+ (3p) in coplanar asymmetric geometry

The three-body distorted-wave Born approximation has been used to calculate the (e,2e) triple differential cross sections (TDCSs) of Cu+ (3p) in different kinematical variables in coplanar asymmetric geometry.The angles 4,10 and 20 were selected as the scattering electron angles.Under high incident energy (≥ 500 eV) and high asymmetric detection energy,the binary peaks showed abnormal splits.Such abnormal splits have not been observed in atomic target and outer valence orbitals of ionic target,which indicates that an (e,2e) process for inner valence orbitals of ionic target would be more complicated than outer valence orbitals.Furthermore,some pronounced peaks appeared at certain ejected angles.We considered that these pronounced peaks are probably related to one kind of double-binary collision.     

Complexes between C.I. Acid Orange 6 and human serum albumin, a multi-spectroscopic approach to investigate the binding behavior

The interaction mechanism of Acid Orange 6 (AO6) with human serum albumin (HSA) was investigated firstly by using fluorescence quenching technique, UV absorbance, circular dichroism (CD), Fourier transform infrared (FT-IR), three-dimensional fluorescence spectroscopy in combination with molecular modeling method under simulative physiological conditions. Fluorescence data indicated that there is a single class of binding sites between AO6 and HSA, and the alterations of HSA secondary structure in the presence of AO6 was confirmed by synchronous fluorescence, UV, CD, FT-IR and three-dimensional fluorescence spectra. The efficiency of fluorescence resonance energy transfer provided the binding distance (r) of 2.83 nm for AO6-HSA system. Furthermore, the thermodynamic parameters enthalpy change (ΔH⁰) and entropy change (ΔS⁰) for the reaction were calculated to be −5.77 kJ mol⁻¹ and 109.42 J mol⁻¹ K⁻¹, respectively, according to Van't Hoff equation, these data suggested that both hydrophobic forces and hydrogen bonding play a major role in the binding of AO6 to HSA, which agrees well with the results of molecular modeling study. Experimental results showed that the interaction between AO6 and HSA induced a conformational change of HSA, which was proved by the qualitative and quantitative analysis data of different spectroscopic techniques under simulative physiological conditions.     

Synthesis and Characterization of Novel Poly(1‐Naphthylamine)‐Montmorillonite Nanocomposites Intercalated by Emulsion Polymerization

Nanocomposites of montmorillonite (MMT) with poly(1‐naphthylamine) (PNA) is investigated for the first time by emulsion polymerization using three different oxidants. Polymerization of PNA was confirmed by Fourier transformation infrared (FT‐IR) as well as UV‐visible spectra. The in situ intercalative polymerization of PNA within MMT layers was confirmed by FT‐IR, X‐ray diffraction, conductivity; scanning electron microscopy (SEM) as well as transmission electron microscopy studies. X‐ray diffraction revealed intercalated as well as exfoliated structures of PNA/MMT nanocomposites, which were compared with the reported polyaniline‐MMT nanocomposites. It was found that the increase in the concentration of PNA in the interlayer galleries of MMT led to destruction of the layered clay structure resulting in exfoliation of the nanocomposite. Conductivity of the nanocomposites was found to be in the range of 10^?3 to 10^?2 S cm^?1 which was found to be higher than the ones reported for polyaniline‐clay nanocomposites as well as PEOA‐OMMT nanocomposites at similar concentrations of intercalated species. The morphology of PNA/MMT nanocomposites was found to be governed by the nature of the oxidant used.     

Singlet—triplet oscillations of spin-correlated radical pairs due to the Larmor precession in low magnetic fields

Singlet—triplet oscillations in spin-correlated radical pairs have been studied at magnetic field strengths low for one radical and high for the other. Oscillations with frequencies close to the Larmor frequency ω₀ of electron spin precession have been predicted under these conditions. Both numerical and exact analytical solutions in arbitrary magnetic fields are presented for three cases of hyperfine couplings in wide-spectrum radical. For the case of unresolved spectrum, singlet—triplet evolution was found to contain a single oscillating term with frequency ω₀. In the case of one spin-I magnetic nucleus, there are two low frequency oscillating terms with frequencies ω_? = ω₀ ? ω₀/(2I + 1) and ω₊ = ω₀ + ω₀/(2I + 1), the amplitude of the first term being larger than that of the second. The case of a number of equivalent protons also has been analysed as a superposition of one-nucleus oscillations. The predicted oscillations were observed in a time resolved magnetic field effect for several radical ion pairs produced by X-ray irradiation of alkane solutions with charge acceptors. For pairs (p-terphenyl-d ₁₄)^?./(isooctane)^+. and (p-terphenyl-d ₁₄)^?./(2,4-dimethylpentane)^+. the oscillation frequency in a field B ₀ of 0.5–4mT is about 20% lower than ω₀. Oscillations were observed also in pairs with equivalent nuclei: (p-terphenyl-d ₁₄)^+./(C₆F₆)^?. and (p-terphenyl-d ₁₄)^?./(hexamethylethane)^+.     

Statistical mechanics of inhomogeneous model colloid—polymer mixtures

We describe two strategies for tackling the equilibrium statistical mechanics of inhomogeneous colloid—polymer mixtures treated in terms of the simple Asakura—Oosawa—Vrij (AO) model, in which colloid—colloid and colloid—polymer interactions are hard-sphere like, whereas the polymer—polymer interaction is zero (perfectly interpenetrating polymer spheres). The first strategy is based upon integrating out the degrees of freedom of the polymer spheres to obtain an effective one-component Hamiltonian for the colloids. This is particularly effective for small size ratios q = σ_p/σ_c < 0.1547, where σ_p and σ_c are the diameters of colloid and polymer spheres, respectively, since in this regime three and higher body contributions to the effective Hamiltonian vanish. In the second strategy we employ a geometry based density functional theory (DFT), specifically designed for the AO model but based on Rosenfeld's fundamental measure DFT for additive mixtures of hard-spheres, that treats colloid and polymer on an equal footing and which accounts for the fluid-fluid phase separation occurring for larger values of q. Using the DFT we investigate the properties of the ‘free’ interface between colloid-rich (liquid) and colloid-poor (gas) fluid phases and adsorption phenomena at the interface between the AO mixture and a hard-wall, for a wide range of size ratios. In particular, for q = 0.6 to 1.0, we find rich interfacial phenomena, including oscillatory density profiles at the free interface and novel wetting and layering phase transitions at the hard-wall-colloid gas interface. Where appropriate we compare our DFT results with those from computer simulations and experiment. We outline several very recent extensions of the basic AO model for which geometry based DFTs have also been developed. These include a model in which the effective polymer sphere—polymer sphere interaction is treated as a repulsive step function rather than ideal and one in which the depletant is a fluid of infinitely thin rods (needles) with orientational degrees of freedom rather than (non-interacting) polymer spheres. We comment on the differences between results obtained from these extensions and those of the basic AO model. Whilst the interfacial properties of the AO model share features in common with the those of simple (atomic) fluids, with the polymer reservoir density replacing the inverse temperature, we emphasize that there are important differences which are related to the many-body character of the effective one-component Hamiltonian.     

Structural and Tribological Properties of Polytetrafluoroethylene Composites Filled with Glass Fiber and Al2O3 in Atomic Oxygen Environment

Effects of atomic oxygen (AO) irradiation on the structural and tribological behaviors of polytetrafluoroethylene (PTFE) composites filled with both glass fibers and Al₂O₃ were investigated in a ground-based simulation facility, in which the average energy of AO was about 5 eV and the flux was 5.0 × 10¹⁵/cm² s. It was found that AO irradiation first induced the degradation of PTFE molecular chains on the sample surface, and then resulted in a change of surface morphology. The addition of Al₂O₃ filler significantly increased the AO resistance property of PTFE composites. Friction and wear tests indicated that AO irradiation affected the wear rate and increased the friction coefficient of specimens. The PTFE composite containing 10% Al₂O₃ exhibit the best AO resistance and lower wear rate after long time AO irradiation.     

LATTICE BOLTZMANN EQUATION MODEL IN THE CORIOLIS FIELD

In a large-scale field of rotational fluid, various unintelligible and surprising dynamic phenomena are produced due to the effect of the Coriolis force. The lattice Boltzmann equation (LBE) model in the Coriolis field is developed based on previous works.^[1-4] Geophysical fluid dynamics equations are derived from the model. Numerical simulations have been made on an ideal atmospheric circulation of the Northern Hemisphere by using the model and they reproduce the Rossby wave motion well. Hence the applicability of the model is verified in both theory and experiment.     

Structural and Tribological Properties of Polyimide/Al2O3/SiO2 Composites in Atomic Oxygen Environment

Effects of atomic oxygen (AO) irradiation on the structural and tribological behaviors of polyimide/Al₂O₃/SiO₂ composites were investigated in a ground-based simulation facility, in which the energy of AO was about 5 eV and the flux was 7.2 × 10¹⁵ cm^?2.s^?1. The structural changes were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total-reflection FTIR (FTIR-ATR), while the tribological changes were evaluated by friction and wear tests as well as scanning electron microscopy (SEM) analysis of the worn surfaces. It was found that AO irradiation induced the oxidation and degradation of polyimide (PI) molecular chains. The destructive action of AO changed the surface chemical structure, which resulted in changes of the surface morphology and chemical composition of the samples. Friction and wear tests indicated that AO irradiation decreased the friction coefficient but increased the wear rate of both pure and Al₂O₃/SiO₂ filled PIs.     

Soft X-ray photoemission study of nitrogen diffusion in TiN/HfO:N gate stacks

The impact of HfO:N post nitridation anneal (PNA) and gate fabrication on the physico-chemical properties of the TiN/HfO:N/SiO₂/Si stack are investigated using Soft X-ray Photoelectron Spectroscopy (S-XPS) and Vacuum UltraViolet Spectroscopic Ellipsometry (VUV-SE). Defects created in the high-k during plasma nitridation are passivated by PNA under O₂. Both oxygen and nitrogen diffusion is observed towards the bottom SiO₂/Si interface together with a regrowth of the SiO₂. These defects play a major role regarding nitrogen diffusion during gate fabrication. Without PNA, no diffusion is observed because O and N atoms are trapped inside the high-k. With PNA and simultaneous defects passivation, nitrogen from both metal gate and high-k diffuses towards the bottom SiO₂/Si interface.     

变权小世界生物神经网络的兴奋及优化特性

根据实际生物神经网络具有小世界连接和神经元之间的连接强度随时间变化的特点,首先构造了一个以Hodgkin-Huxley方程为节点动力学模型的动态变权小世界生物神经网络模型,然后研究了该模型神经元的兴奋特性、权值变化特点和不同的学习系数对神经元的兴奋统计特性的影响.最有意义的结果是,在同样的网络结构、网络参数及外部刺激信号的条件下,学习系数b存在一个最优值b^*,使生物神经网络的兴奋度在b=b^*时达到最大. 关键词： 动态变权生物神经网络 小世界网络 Hodgkin-Huxley方程     

Impact parameter description of the charge exchange process π+ p → π° (π+ p)

The “Reggeometry” model — universal impact parameter profile and Reggen behaviour — is applied to recent data on π⁺ p → π° (π⁺ p) at different energies and (π⁺p) missing masses, including Δ production. We are able, in particular, to explain the filling of the dips and the variation of the slope with respect to the missing mass.     

Chemical alteration of poly(vinyl fluoride) Tedlar by hyperthermal atomic oxygen

In this study the erosion of poly(vinyl fluoride) Tedlar by hyperthermal atomic oxygen (AO) has been examined using X-ray photoelectron spectroscopy (XPS). Initially the Tedlar film had F/C and O/C atom ratios of 0.45 and 0.11, which decrease to 0.018 and 0.04, respectively, after a 2-h exposure to a flux of 2 × 10¹⁵ atoms/cm² s AO with an average kinetic energy of 5 eV. This exposure essentially produced a graphitic or amorphous carbon-like layer with a carbon content greater than 90 at.%. Longer AO exposures do not alter the composition of this layer significantly. Exposure to O₂ or air nearly doubles the oxygen content in the near-surface region. This is due to dissociative oxygen adsorption at reactive sites formed at the polymer surface during AO exposure. Further exposure to AO removes this chemisorbed oxygen.     

Pulse width compression and enhancement of peak power in a diode-pumped doubly Q-switched Nd:GdVO<Subscript>4</Subscript> 1.34 μm laser with AO and V<Superscript>3+</Superscript>:YAG saturable absorber

By using both acousto-optic (AO) modulator and V³⁺:YAG saturable absorber, a diode-pumped doubly Q-switched a-cut Nd:GdVO₄ laser at 1.34 μm is realized. The average output power and the pulse width for different AO repetition rate f have been measured. The experimental results show that the doubly Q-switched laser can compress the pulse width and improve the pulsed peak power in comparison to the singly Q-switched laser with AO or V³⁺:YAG saturable absorber. At the pump power 10.34 W and f = 10 kHz, the greatest pulse width compression ratio 72% and the highest peak power improvement 8.8 times have been obtained, respectively.     

Effect of solvent on the characteristics of nanostructured composites of poly (1-naphthylamine) with poly (vinyl alcohol)

Efficient utilization of inherently conducting polymers in nano technological applications faces the challenge to assemble them into highly ordered structures which may yield novel properties. The present study reports for the first time the synthesis and characterization of nanostructured poly (1-naphthylamine) (PNA) dispersed polyvinyl alcohol (PVA) composites. The composites were prepared by loading PNA from 2 wt% to 10 wt% in PVA in aqueous as well as nonaqueous media. The composites were characterized by UV–visible spectroscopy, TEM, stress–strain studies, electrical conductivity measurements and moisture absorption studies under controlled humidity. A discrete but uniform distribution of nanoparticles was obtained in PNA/PVA composites synthesized in water having particle size between 5 and 30 nm. A self assembled network of nanostructured PNA particles was obtained in case of PNA/PVA composites synthesized in N-methylpyrolidone (NMP) with particle sizes between 10 and 65 nm. The variation in the nanostructured morphology of PNA particles in PVA matrix in the two cases resulted from the pronounced interaction of PVA with NMP through hydrogen bonding. This leads to the formation of a homogeneous matrix that facilitates the formation of a self assembled network of PNA nano particles. In case of PNA/PVA composites synthesized in water, lower affinity of PVA towards water was responsible for a discrete, agglomerate free distribution of PNA particles. We have found that the PNA/PVA nano composite synthesized in water exhibited good mechanical properties and electrical conductivity (8.1 × 10⁻¹ S/cm) as well as lowest moisture absorption (4 wt%) which holds potential for use in semiconductor and biomedical devices.     

Laser-diode-pumped doubly Q-switched Nd:GdVO4/KTA intracavity optical parametric oscillator

By using an acousto-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber, a high repetition rate doubly Q-switched noncritically phase-matched KTiOAsO₄ (KTA) intracavity optical parametric oscillator (IOPO) at 1.50 μm is realized. In comparison to AO Q-switched IOPO, the lower threshold energy, the higher output average power, the narrower pulse width and the higher peak power from the doubly Q-switched IOPO can be obtained.     

The extremely cold 2009–2010 winter and its relationship with the Arctic oscillation

The Northern-Hemisphere high-latitude continents experienced extremely cold weathers in winter 2009 2010. In the present paper, we show that the cold winter was associated with the activity of tile Arctic oscillation （AO）, which demonstrated the strongest negative polarity over the past six decades and persisted from December, 2009 to March, 2010. It is found that variations of the surface AO was closely linked to stratospheric polar vortex anomalies, and that the surface AO phases followed downward propagation of stratospheric Northern-Hemisphere Annular mode （NAM） anomalies during the winter. The case of 2009-2010 winter provides us with a typical example that anomalous stratospheric signals can be used to improve skills of long-range weather forecast and intra-seasonal climate prediction in winter time. We also show that the E1 Nifio event, which started developing from May 2009, might contribute the formation of exceptionally negative and persistent AO and stratospheric NAM, particularly over North Pacific and North America.     

Preparation and biodistribution of <Superscript>59</Superscript>Fe-radiolabelled iron oxide nanoparticles

We report on the ⁵⁹Fe radiolabelling of iron oxide nanoparticle cores through post-synthetic isotope exchange (⁵⁹Fe-IONP_ex) and precursor labelling (⁵⁹Fe-IONP_pre). Scanning electron microscopy and dynamic light scattering measurements showed no impact of radiolabelling on nanoparticle size or morphology. While incorporation efficiencies of these methods are comparable—83 and 90% for precursor labelling and post-synthetic isotope exchange, respectively—⁵⁹Fe-IONP_pre exhibited much higher radiochemical stability in citrated human plasma. Quantitative ex vivo biodistribution study of ⁵⁹Fe-IONP_pre coated with triethylene glycol was performed in Wistar rats. Following the intravenous administration, high ⁵⁹Fe concentration was observed in the lung and the organs of the reticuloendothelial system such as the liver, the spleen and the femur.     

Sonochemical assisted hydrothermal synthesis of ZnO: Cr nanoparticles loaded activated carbon for simultaneous ultrasound-assisted adsorption of ternary toxic organic dye: Derivative spectrophotometric,optimization, kinetic and isotherm study

Chromium doped zinc oxide nanoparticles (ZnO: Cr-NPs) was synthesized by ultrasonically assisted hydrothermal method and characterized by FE-SEM, XRD and TEM analysis. Subsequently, this composite ultrasonically assisted was deposited on activated carbon (ZnO: Cr-NPs-AC) and used for simultaneous ultrasound-assisted removal of three toxic organic dye namely of malachite green (MG), eosin yellow (EY) and Auramine O (AO). Dyes spectra overlap in mixture (major problem for simultaneous investigation) of this systems was extensively resolved by derivative spectrophotometric method. The magnitude of variables like initial dyes concentration, adsorbent mass and sonication time influence on dyes removal was optimized using small central composite design (CCD) combined with desirability function (DF) approach, while pH was studied by one-a-time approach. The maximized removal percentages at desirability of 0.9740 was set as follow: pH 6.0, 0.019 g ZnO: Cr-NPs-AC, 3.9 min sonication at 4.5, 4.8 and 4.7 mg L⁻¹ of MG, EY and AO, respectively. Above optimized points lead to achievement of removal percentage of 98.36%, 97.24%, and 99.26% correspond to MG, EY and AO, respectively. ANOVA for each dyes based p-value less than (<0.0001) suggest highly efficiency of CCD model for prediction of data concern to simultaneous removal of these dyes within 95% confidence interval, while their F-value for MG, EY and AO is 935, 800.2, and 551.3, respectively, that confirm low participation of this them in signal. The value of multiple correlation coefficient R², adjusted and predicted R² for simultaneous removal of MG is 0.9982, 0.9972 and 0.9940, EY is 0.9979, 0.9967 and 0.9930 and for AO is 0.9970, 0.9952 and 0.9939. The adsorption rate well fitted by pseudo second-order and Langmuir model via high, economic and profitable adsorption capacity of 214.0, 189.7 and 211.6 mg g⁻¹ for MG, EY and AO, respectively.