Polysaccharide separation mechanism in polysulfone-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic composite membranes

Polysulfone (PSF)-Fe3O4 composite membranes were prepared by the phase-inversion process and their polysaccharide separation mechanism was explored using chondroitin sulfate (CS) and dextran. The mechanism was analyzed from constraints on the magnetic field and geometric deformation. It was found that variations in dextran rejection from 58% to 46% were mainly influenced by the geometric deformation of the composite membrane, while the magnetic field had a significant influence on variations in CS rejection from 82% to 35%. The results indicate that it is possible to continuously separate different types of polysaccharide with a composite membrane by adjusting the external magnetic field.     

One-pot synthesis of PVP-coated Ni<Subscript>0.6</Subscript>Fe<Subscript>2.4</Subscript>O<Subscript>4</Subscript> nanocrystals

Novel poly(N-vinyl-2-pyrrolidone) (PVP)-coated nickel ferrite nanocrystals were prepared by simultaneously pyrolyzing nickel(II) acetylacetonate (Ni(acac)₂) and iron(III) acetylacetonate (Fe(acac)₃) in N-vinyl-2-pyrrolidone (NVP). The PVP coating was formed in situ through polymerization of NVP. The crystalline structure of the resultant nickel ferrite was analyzed by high-resolution transmission electron microscopy, electron diffraction patterns, and powder X-ray diffraction. In addition, the valence state of Ni and the metal contents of Ni and Fe in different valence states were analyzed by X-ray photoelectron spectroscopy (XPS), atomic absorption and the phenanthroline method. The surface coating layer of PVP and its binding states were characterized by Fourier transform infrared spectroscopy in combination with XPS. Colloidal stability experiments revealed that the nanocrystals could be dispersed well in both phosphate-buffered saline and Dulbecco’s Modified Eagle Medium.     

Decay dynamics of excited CS<Subscript>2</Subscript> and NH<Subscript>3</Subscript> investigated by femtosecond laser

By using the home-made femtosecond laser system and the time-of-flightmass spectrometer, the decay dynamics of excited carbon disulfide (CS2) and ammonia (NH3) are investigated in real time by pump-probe multiphoton ionization detection. The estimated lifetime constant of the NH3 state (514 fs) agreed quite well with the literature report. For the first time, the decay lifetime constants of the NH3 ′1A′1 state (93793 fs), the CS2 state (153 ± 10 fs), and the CS2 Rydberg state[2-3]6sσg(3Ⅱg)(948 ± 23 fs) are obtained.     

Investigation of solvatochromism and aggregation behavior of C_(60)(C_4H_(10)N~+)I~- in binary solvent mixtures

Solvatochromism was observed in some solutions of C60 or C70, which was thought to arise from the formation of fullerene clusters[1—6]. This special type of solvato- chromism has aroused much interest because it has some potential applications in material science and sensor tech- nology. On the other hand, C60 or C70 can be made soluble in water by connecting it to various functional groups[7—20]. Those functionalized fullerenes not only have been found a number of important applicati…     

Laser induced photoemission electron and the generation of high Rydberg states of atoms and molecules

Laser induced photoemission electron was produced by directing 532 nm and/or 355 nm onto stainless steel plate on a time of flight mass spectrometer. Multiple charged ions and high Rydberg states of atoms or molecules were successfully generated by impacts of the photoemission electrons. The high Rydberg states ( n ～40-100) thus produced were separated from ions, produced by direct electron impact ionization, by a 3 V DC electric field and then ionized by a delayed pulsed HV electric field in a ZEKE-PFI manner. Relationship between generation/property of high Rydberg states of atoms/molecules and experimental conditions could be investigated. Relationship between the electron accelerating voltage and high Rydberg states of Ar was described.     

Ar原子(J=0)的高激发态结构

本文依据多通道量子亏损理论对Ar原子J=0的高激发态结构进行了理论分析,确定了基本结构参量,得到Lu-Fano图和全部分立态能位、通道混合系数,预言了自电离共振结构。     

Chemical quenching and inhibition of positronium in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The pore structure of Cr2O3/Al2O3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ4 and τ3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3 content, both τ4 and its intensity I4 show sharp decrease, while τ3 and its intensity I3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr2O3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3 content. This indicates that the change of o-Ps lifetime τ4 is due to the chemical quenching by Cr2O3 but not spin-conversion of positronium. The decrease of o-Ps intensity I4 indicates that Cr2O3 also inhibits positronium formation.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3sf</Subscript> addition on the friction and wear properties of (SiC<Subscript>p</Subscript>+Al<Subscript>2</Subscript>O<Subscript>3sf</Subscript>)/Al2024 composites fabricated by pressure infiltration

Aluminum (Al) 2024 matrix composites reinforced with alumina short fibers (Al₂O_3sf) and silicon carbide particles (SiC_p) as wear-resistant materials were prepared by pressure infiltration in this study. Further, the effect of Al₂O_3sf on the friction and wear properties of the as-synthesized composites was systematically investigated, and the relationship between volume fraction and wear mechanism was discussed. The results showed that the addition of Al₂O_3sf, characterized by the ratio of Al₂O_3sf to SiC_p, significantly affected the properties of the composites and resulted in changes in wear mechanisms. When the volume ratio of Al₂O_3sf to SiC_p was increased from 0 to 1, the rate of wear mass loss (K_m) and coefficients of friction (COFs) of the composites decreased, and the wear mechanisms were abrasive wear and furrow wear. When the volume ratio was increased from 1 to 3, the COF decreased continuously; however, the K_m increased rapidly and the wear mechanism became adhesive wear.     

Ba原子6pnd自电离态的光谱研究

采用三台可调谐激光器和孤立实激发技术,是将处于基态的Ba原子分三步激发到6p1/2nd和6p3/2nd(J=1,3)自电离态上,并通过频率扫描获得了这些自电离态的光谱.本文着重研究了从钡原子的6 snd3D2Rydberg态激发的那些较低的自电离态的光谱.通过对实验光谱的线形拟合,得到了上述原子态的能级位置和宽度等实验数据,进而获得了量子亏损和约化宽度等微观信息.通过对这些自电离光谱的分析和比较,讨论了它们在6p1 /2电离限附近的光谱特征及其产生机制.     

Influence of Ag doping on the microstructure and electrical properties of ZnO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-based varistor ceramics

Silver in the form of AgNO₃ was added to ZnO-based varistor ceramics prepared by the solid-state reaction method. The effects of AgNO₃ on both the microstructure and electrical properties of the varistors were studied in detail. The optimum addition amount of AgNO₃ in ZnO-based varistors was also determined. The mechanism for grain growth inhibition by silver doping was also proposed. The results indicate that the varistor threshold voltage increases substantially along with the AgNO₃ content increasing from 0 to 1.5mol%. Also, the introduction of AgNO₃ can depress the mean grain size of ZnO, which is mainly responsible for the threshold voltage. Furthermore, the addition of AgNO₃ results in a slight decrease of donor density and a more severe fall in the density of interface states, which cause a decline in barrier height and an increase in the depletion layer.     

Thermal performance and reduction kinetic analysis of cold-bonded pellets with CO and H<Subscript>2</Subscript> mixtures

Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H₂–CO mixtures with different H₂/CO molar ratios (1:0, 5:2, 1:1, 2:5, and 0:1) under various temperatures (1023, 1123, 1223, 1323, and 1423 K) in a thermogravimetric analysis apparatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstructure of reduced pellets was observed by scanning electron microscopy–energy-dispersive spectrometry (SEM-EDS). The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hinder effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could maintain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overall equilibrium constant to the promotion effect depends on the gas composition.     

Electro-deoxidation of V<Subscript>2</Subscript>O<Subscript>3</Subscript> in molten CaCl<Subscript>2</Subscript>-NaCl-CaO

The electro-deoxidation of V₂O₃ precursors was studied. Experiments were carried out with a two-terminal electrochemical cell, which was comprised of a molten electrolyte of CaCl₂ and NaCl with additions of CaO, a cathode of compact V₂O₃, and a graphite anode under the potential of 3.0 V at 1173 K. The phase constitution and composition as well as the morphology of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 3 g of V₂O₃ could be converted to vanadium metal powder within the processing time of 8 h. The kinetic pathway was investigated by analyzing the product phase in samples prepared at different reduction stages. CaO added in the reduction path of V₂O₃ formed the intermediate product CaV₂O₄.     

Photoluminescence and cathodoluminescence properties of CaLaGa<Subscript>3</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>3+</Superscript> phosphors

The CaLaGa₃O₇:Eu³⁺ phosphor was prepared by a chemical co-precipitation method. Field emission scanning electron microscopy (FE-SEM), laser particle size analysis, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphor. The results revealed that the phosphor was composed of microspheres with a slight agglomerate phenomenon and was spherically shaped. The average grain size was about 1.0 μm. Eu³⁺ ions, as luminescent centers, substituted La³⁺ ions into the single crystal lattice of CaLaGa₃O₇ with the sites of C_s. Although the CL spectrum was greatly different from the PL spectrum, it had the strongest red emission corresponding to the ⁵D₀ →⁷F₂ transition of Eu³⁺. Under the excitation of UV light (287 nm) and electron beams (1.0–7.0 kV), the chromaticity coordinates of the phosphor were found to be in the nearly red and orange light regions, respectively.     

一价铝离子3sns(J=0)系列的高激发态结构

本文利用本征通道量子亏损理论方法计算了一价铝离子3sns(J=0)里德伯系列的激发态结构,给出了高激发态结构的具体数值结果,并讨论了干状态的影响.     

Mechanism of skeletal reorganization of 1,6-enynes catalyzed by GaCl<Subscript>3</Subscript>

The mechanism of skeletal reorganization of 1,6-enynes catalyzed by GaCI3 has been studied with the density functional method at the B3LYP/6-31G* level. The structures and energies of the stationary points were calcu-lated to identify the activation barriers. The transition stateswere testified with vibration analysis and IRC calculations.The results of calculation show that the conversion of 1,6-enynes is a step-wise reaction. The whole reaction process is formation and migration of three-membered cycle involvinga three-center and two-electron (3c-2e) bond. High stereose-lectivity of the reaction is in good agreement with experimental results.     

Effects of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> on the properties of ceramics from steel slag

Ferric oxide is one of the key factors affecting both the microstructure and the properties of CaO-MgO-SiO₂-based ceramics. Research on this effect is significant in the utilization of iron-rich solid wastes in ceramics. Ceramic samples with various Fe₂O₃ contents (0wt%, 5wt%, and 10wt%) were prepared and the corresponding physical properties and microstructure were studied. The results indicated that Fe₂O₃ not only played a fluxing role, but also promoted the formation of crystals. Ceramics with 5wt% of Fe₂O₃ addition attained the best mechanical properties with a flexural strength of 132.9 MPa. Iron ions were dissolved into diopside, consequently causing phase transformation from diopside and protoenstatite to augite, thereby contributing to the enhancement of its properties. An excess amount of Fe₂O₃ addition (10wt% or more) resulted in deteriorated properties due to the generation of an excess volume of liquid and the formation of high-porosity structures within ceramics.     

Synthesis and characterization of Pt-MoO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>-TiO<Subscript>2</Subscript> electrodes for direct ethanol fuel cells

To enhance the CO-tolerance performance of anode catalysts for direct ethanol fuel cells, carbon nanotubes were modified by titanium dioxide (donated as CNTs@TiO₂) and subsequently served as the support for the preparation of Pt/CNTs@TiO₂ and Pt-Mo/CNTs@TiO₂ electrocatalysts via a UV-photoreduction method. The physicochemical characterizations of the catalysts were carried out by using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy of adsorbed probe ammonia molecules. The electrocatalytic properties of the catalysts for methanol oxidation were investigated by the cyclic voltammetry technique. The results show that Pt-Mo/CNTs@TiO₂ electrode exhibits the highest performance in all the electrodes. It is explained that, the structure, the oxidation states, and the acid-base properties of the catalysts are influenced due to the strong interaction between Ti and Mo species by adding TiO₂ and MoO _x to the Pt-based catalysts.     

Inverse relationship of the durations of adjacent open and shut intervals for C1 and K channels

Ion channels in cell membranes, whether voltage-dependent or activated by ligands, make repeated transitions among open and shut states during activity. Information about the number of states and the transitional pathways between them can be obtained from the durations of open and shut intervals, as transitions to states of different lifetimes result in intervals of different mean durations. If there is only one open conformation, or state, then the durations of open intervals would be independent of the durations of adjacent shut intervals. On the other hand, if a channel has two or more open states with different mean lifetimes, and if each open state is entered directly from a different shut state with a different mean lifetime, then the open intervals should be related to the adjacent shut intervals. We now report that the durations of adjacent open and shut intervals for both a C1 channel and a large conductance Ca-activated K channel in skeletal muscle are inversely related; shorter open intervals are adjacent to longer shut intervals. These findings indicate that two or more shut states make direct transitions to two or more open states, and suggest that the lifetimes of adjacent open and shut states are inversely related.     

Effects of metal binder on the microstructure and mechanical properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-based micro-nanocomposite ceramic tool material

The Al₂O₃-(W,Ti)C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases Al₂O₃ and (W,Ti)C were detected by XRD. Compound MoNi also existed in sintered nanocomposites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.     

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO<Subscript>2</Subscript> electrodes

The ZnO-modified TiO₂ electrode was prepared by adding Zn(CH₃COO)₂·2H₂O to the TiO₂ colloid during the sol-gel production process, and was used in dye-sensitized solar cells (DSCs). The open circuit voltage (V _OC) and fill factor (ff) of the cells were improved significantly. The performances of the ZnO-modified TiO₂ electrode such as dark current, transient photocurrent, impedance, absorption spectra, and flat band potential (V _fb) were investigated. It is found that the interface charge recombination impedance increases and V _fb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO₂ film.