Kinetics and mechanism of the reaction between thiourea and iodate in unbuffered medium

The significances of thiourea and its derivativesnow spill into nonlinear dynamics in chemistry. A re-markable variety of complex dynamical phenomena,including oscillation, oligooscillation, variable stoichio-metries, autoinhibition, autocatalysis, bistability andbirhythmicity, traveling wave and chemical chaos,have been known in thiourea-based reaction systemsfor some time[1—7]. Also, a series of researches on thekinetics and mechanisms of the oxidations of thiourea,thiourea derivatives and …     

An aptasensor for sensitive detection of human breast cancer cells by using porous GO/Au composites and porous PtFe alloy as effective sensing platform and signal amplification labels

A novel aptamer biosensor for cancer cell assay has been reported on the basis of ultrasensitive electrochemical detection. The assay uses the aptamer as a capture probe to recognize and bind the tumor marker on the surface of the cancer cells, forming an aptamer-based sandwich structure for MCF-7 cells detection. Functionalized nanoporous materials, porous graphene oxide/Au composites (GO/Au composites) and porous PtFe alloy have been introduced into the biosensor. Owing to the large surface area and versatile porous structure, the use of nanoporous materials can significantly improve the analysis performance of the biosensors by loading of large amounts of molecules and accelerating diffusion rate. Under the optimized experimental conditions, the proposed aptamer biosensor exhibited excellent analytical performance for MCF-7 cells determination, ranging from 100 to 5.0 × 10⁷ cells mL⁻¹ with the detection limit of 38 cells mL⁻¹. The biosensor showed good selectivity, acceptable stability and reproducibility, and developed a highly sensitive and selective method for cancer cells detection.     

Differentiation of configurations of the phenylbutenoid dimer derivatives from Zingiber cassumunar by tandem mass spectrometry

High‐performance liquid chromatography/electrospray tandem mass spectrometry was developed to distinguish isomers and compounds of similar structures with different configurations in the rhizomes of Z. cassumunar. Energy‐resolved breakdown curves were utilized to differentiate four compounds. Compounds 2 (3R,4S) and 4 (3R,4R) were a pair of stereoisomers which could be distinguished easily by breakdown curves. The breakdown curve of compound 1 was identical to that of compound 2, which suggested that the configuration of compound 1 was (3R,4S) or (3S,4R). The breakdown curve of compound 3 was completely different from those of compounds 1, 2 and 4, and it might be that the configuration of the double bond of compound 3 was different from the other three compounds. Hence, the described method using breakdown curves has great potential in the distinguishing of isomers and compounds of similar structure with different configurations. Copyright © 2009 John Wiley & Sons, Ltd.     

Properties of Polypropylene/Antibacterial Glass Composites

Polypropylene (PP)/antibacterial glass composites were prepared by melt blending PP and silver-doped glass. The antibacterial activity of the PP composites was examined by the method of plate counting, and the crystallization behaviors of pure PP and antibacterial glass/PP composites were compared via hot-stage polarized optical microscopy (POM), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). The results revealed that the antibacterial PP composites had effective antibacterial activity with antibacterial rates more than 90%. The antibacterial agent in the antibacterial glass/PP composites acted as nucleating agents, increasing the crystallization temperature and crystallization rate of PP, but not changing the crystalline modification of PP. The mechanical properties of antibacterial glass/PP composites were also studied, and the results showed that the antibacterial glass improved the stiffness and modulus but decreased the notched impact strength of the PP composites.     

Strain-insensitive and high-temperature long-period gratings inscribed in photonic crystal fiber

We fabricate and demonstrate strain-insensitive and high-temperature long-period gratings in endlessly single-mode photonic crystal fiber by use of focused pulses of a CO2 laser and a periodic stress relaxation technique without geometrical deformation and elongation of the fiber. The thermal dependence of mode coupling at 1299.59 nm is 10.9 pm/degrees C from 24 to 992 degrees C, whereas the coefficient of strain sensitivity is -0.192 pm/muepsilon up to the maximum strain of 2.74%epsilon. It is found for what is believed to be the first time that, in contrast with the traditional fiber case, the coupling resonance shifts toward shorter wavelengths under applied strain, indicating that the refractive index of the core is decreased as a result of the rebuilding of tension attributed to the stress-elastic effect, and the cladding modes is highly dispersive because of airholes arranged in the fiber cladding.     

Effect of hot pressing on the ionic conductivity of the PEO/LiCF3SO3 based electrolyte membranes

PEO/LiCF₃SO₃ (LiTFS) /Ethylene carbonate (EC) polymer electrolyte membranes were prepared with a solution casting method followed by a hot pressing process. The effect of the hot pressing process on the in-plane conductivity of the PEO electrolyte membranes was evaluated using a four-electrode AC impedance method. The composition, morphology, and microstructure of the composite polymer electrolyte were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The AC impedance measurement results indicate that the hot pressing process can increase the room temperature conductivity of the membranes 14 times to 1.7 × 10^− 3 S cm^− 1 depending upon the duration of the hot pressing process. The SEM, FTIR, XRD, and DSC results indicate that the hot pressing process could increase the amorphous part of the polymer electrolyte membrane or convert large spherulite crystals into nano-sized crystals.     

超热电子产生Kα辐射的参数影响

 超短超强激光与固体靶相互作用,可以产生大量的Kα特征谱线发射。这种Kα线光源在背光照相、医学成像和超快诊断等方面具有显著优势。为了寻求获得Kα线高产额的方法,利用ITS蒙卡模拟程序,对超短超强激光产生的超热电子在固体靶中产生的Kα线发射进行了模拟。系统研究了Kα线发射强度随出射角度、靶厚度和超热电子温度等参数的变化情况。研究发现在恒定的激光功率密度或超热电子温度下,存在最佳的靶厚度,使得Kα线光子产额最大,并用模拟结果对已有实验数据进行了解释。     

Differential loop for measuring 1 MA/1O0 ns pulsed high current

“强光一号”加速器能输出上升沿约100 ns、幅值约2 MA的电流脉冲.实验中通常采用自积分式Rogowski线圈监测负载电流.为与该线圈比对校验,研制了一种快响应、结构简单、抗电磁干扰性能较好的微分环.标定实验给出,微分环测量的响应时间约1.2 ns,频谱响应范围10 kHz～100 MHz,灵敏度为6.13×10-11(V· s)/A.其快时间响应将有助于监测与负载物理特性有关的瞬态电流变化.在加速器二极管短路状态对微分环和积分式Rogowski线圈进行了实验比对,数值积分给出的电流波形与后者基本相符,峰值偏差小于10％,表明微分环的设计合理,同时校验了电流测量的可信度.     

快前沿直线脉冲变压器驱动源模块中开关同步对放电电流的影响

介绍了4支路并联快前沿直线脉冲变压器驱动源(FLTD)模块的初步实验结果,在工作电压160 kV时,次级短路放电电流幅值达到103.4 kA,电流前沿为78 ns(10%~90%)。利用微分环测量了4只开关在工作电压120 kV时的同步情况,研究分析了开关同步对放电电流幅值和波形的影响。开关同步小于15ns时,放电电流幅值变化不明显,电流幅值的标准偏差约3.62 kA,电流波形没有明显畸变;开关同步15~25ns时,放电电流幅值略有下降,电流幅值的标准偏差约8.59 kA,电流波形有一定程度畸变;开关同步大于25ns时,放电电流幅值明显降低,电流的标准偏差显著增大,电流波形发生严重畸变。     

Super-π-Brauer Characters and Super-π-Regular Classes

Supercharacter theories for an arbitrary finite group were developed by Diaconis and Isaacs. Let G* denote the set of all π-regular elements of G. Set I^π(G) = {χ* | χ ∈Irr(G) and χ* ≠ α* + β* for characters α, β of G}, where χ* means the restriction of χ to G*. In this paper, we consider the partitions of I^π(G) and G* for a π-separable group G. We obtain some results which generalize those of Diaconis and Isaacs.