The Protonated Guanine–Cytosine Base Pair

Protonated base pairs were recently implicated in the context of DNA proton transfer and charge migration. The effects of protonating different sites of the guanine–cytosine (GC) base pair are studied here by using the DZP++ B3LYP density functional method. Optimized structures for the protonated GC base pair are compared with those of parent GC and the neutral hydrogenated GC radical (GCH). Proton and hydrogen‐atom additions significantly disturb the structure of the GC base pair. However, the structural perturbations arising from protonation are often less than those arising from hydrogenation of GC. Protonation of the GC base pair causes significant strengthening of the interstrand hydrogen bonds and a concomitant increase in the base dissociation energies. The adiabatic ionization potentials (AIPs), vertical ionization potentials (VIPs), and proton affinities (PAs) for the different protonation sites of the GC base pair are predicted. The N7 site of guanine is the preferred site for protonation of the GC base pair.     

Electrochemical Hydrogen Storage in Ti1.6V0.4Ni1−xCox Icosahedral Quasicrystalline Alloys

The discovery of the icosahedral phase (i‐phase) in rapidly quenched Ti_1.6V_0.4Ni_1?xCo_x (x=0.02–0.1) alloys is described herein. The i‐phase occurs in a similar amount relative to the coexisting β‐Ti phase. The electron diffraction patterns show the distinct spot anisotropy, indicating that the i‐phase is metastable. The electrochemical hydrogen storage performances of these five alloy electrodes are also reported herein. The hydrogen desorption of nonelectrochemical recombination in the cyclic voltammetric (CV) response exhibits the demand for electrocatalytic activity improvement. A discharge capacity of 261.5 mA h g^?1 was measured in a Ti_1.6V_0.4Ni_0.96Co_0.04 alloy electrode at 30 mA g^?1 and 303 K and it is shown that an appropriate amount of Co element addition would enhance the cycling stability at the expense of high‐rate discharging ability.     

Electrogenerated Chemiluminescence Sensor Based on Tris(2,2′‐bipyridine)ruthenium(II)‐Immobilized Natural Clay and Ionic Liquid

A novel electrogenerated chemiluminescence (ECL) sensor based on natural clay and ionic liquid was fabricated. Tris(2,2′‐bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) was immobilized on natural clay surface through simple adsorption. An ECL sensor was prepared by mixing Ru(bpy)₃²⁺‐incorporated clay, graphite powder and an ionic liquid (1‐butyl‐3‐methylimidazolium hexafluorophosphate) as the binder. The electrochemical behavior and ECL of the immobilized Ru(bpy)₃²⁺ was investigated. It was observed that the ECL of immobilized Ru(bpy)₃²⁺ was activated by the ionic liquid. The proposed ECL sensor showed high sensitivity to tri‐n‐propylamine (TPrA) and the detection limit was found to be 20 pM. In addition, the ECL sensor displayed good stability for TPrA detection and long‐term storage stability.     

A New Amperometric Hydrazine Sensor Based on Prussian Blue/Single‐walled Carbon Nanotube Nanocomposites

A slow reaction process has been successfully used to synthesize Prussian blue/single‐walled carbon nanotubes (PB/SWNTs) nanocomposites. Electrochemical and surface characterization by cyclic voltammetry (CV), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV‐vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) confirmed the presence of PB nanocrystallites on SWNTs. PB/SWNTs modified glassy carbon electrode (GCE) exhibits efficient electron transfer ability and high electrochemical response towards hydrazine. The fabricated hydrazine sensor showed a wide linear range of 2.0×10^?6–6.0×10^?3 M with a response time less than 4 s and a detection limit of 0.5 μM. PB/SWNTs modified electrochemical sensors are promising candidates for cost‐effective in the hydrazine assays.     

Fluorescence sensor for nitrofurazone using 4-methyl-7-allyloxynaphtho[1,2-b]pyran-2-ketone as sensing carrier

4-methyl-7-allyloxynaphtho[1,2-b]pyran-2-ketone (MANPK), a naphthopyran derivative, was synthesized as a fluorescent carrier for the preparation of an optical chemical sensor for nitrofurazone. To prevent the leakage of the fluorophore, MANPK with a terminal double bond was photo-copolymerized with 2-hydroxypropyl methacrylate on the silanized glass surface. The response of the sensor is based on fluorescence quenching of MANPK by nitrofurazone. The sensor shows sufficient reproducibility, selectivity and a long lifetime. Nitrofurazone can be determined in the range from 6.0 × 10⁻⁶ to 8.0 × 10⁻⁴ M with a detection limit of 4.5 × 10⁻⁶ M at pH 6.0. The sensor has been applied to the direct determination of nitrofurazone in pharmaceutical preparations and urine samples.     

Thermomagnetic natural convection of thermo-sensitive magnetic fluids in cubic cavity with heat generating object inside

Experiment and numerical study were conducted to investigate the heat transfer characteristics of a thermo-sensitive magnetic fluid (TSMF) filled in a cubic container with a heat generating square cylinder stick inside and under a uniform magnetic field. The experimental results show that, regardless of the heat generating object sizes, the heat transfer characteristic of the TSMF is enhanced when the magnetic field is applied to the TSMF. However, the heat transfer of the TSMF becomes poor as the size of the inside heat generating object increases because the space where the fluids go through becomes narrower and the flow is obstructed when the heat generating object size becomes bigger. Numerical simulation based on the Lattice Boltzmann method confirmed the experimental findings, and disclosed more flow details of the natural convection of the TSMF inside cavity.     

Stability of thermal convection of an Oldroyd-B fluid in a porous medium with Newtonian heating

A linear stability analysis determining the onset of oscillatory convection of an Oldroyd-B fluid in a bounded two-dimensional rectangular porous medium generated by Newtonian heating is conducted. Influences of viscoelastic parameters and Biot number on the onset of oscillatory convection, preferred modes and patterns of disturbed temperature contours are discussed.     

Morphology-controlled growth of tetrapod ZnO nanostructures by direct arc discharge

A novel buttress-root shaped ZnO tetrapod-like nanostructure and a classic tetrapod ZnO nanostructure were synthesized by a direct reaction of high-purity Zn granules with oxygen using an arc discharge method. The morphology of the products could be controlled by adjusting the oxygen partial pressure. The buttress-root shaped tetrapod-like nanostructure contains three triangular nanosheets, the diameters of nanoarms vary between 50 and 80 nm, and the angle between every two arms is about 109.5°. A nanorod-centered growth model has been proposed to explain the novel nanostructure. An ultraviolet (UV) emission band located at 389 nm (3.18 eV) and a broad blue emission band centered at 484 nm (2.57 eV) were observed at room temperature.     

Spin polarized field emission from Fe and Co-coated W tips

Spin polarized field emission from thin film Fe- and Co-coated W(001) and W(111) tips has been investigated. A transverse spin polarization component is detected in each case. For W(111) tips, the azimuthal orientation of polarization showed only a weak preference for the set of 〈1?10〉 and 〈112?〉 tip directions due to the competing influence of magnetocrystalline anisotropy and tip morphology on tip magnetization. On the contrary, the polarization direction for W(001) tips exhibited a strong preference for alignment with the transverse low-index crystallographic directions, i.e. the 〈110〉 for Co and 〈100〉 for Fe. Superparamagnetic fluctuations of the tip magnetization are evident in the polarization direction of emitted electrons when film coatings are very thin. At marginally larger thickness, long-term stability of the polarization magnitude and direction is observed at 300 K. A method for changing the stable spin polarization direction is also presented that exploits spontaneous flipping of the tip magnetization at elevated temperature.     

高剥离态Fe Ⅹ Ⅵ离子能级寿命测量

在原子能院串列加速器上,利用束箔方法,测量了能量为30 MeV Fe离子产生的高剥离态谱线跃迁结构的寿命值.在30 MeV时,Fe通过箔膜的电荷态分布在7+到17+,我们选择Fe XⅥ2p~6(~1S)4p—2p~6(~1S)5d(~2P_(3/2)~o—~2D_(3/2))的谱线,谱线波长124.696(?),能级寿命为79±4 ps.最后对实验误差进行了分析.