芳环羟基化HPLC分离荧光法检测Cu(Ⅱ)-H2O2体系中产生的·OH

采用L-苯丙氨酸为探针,使用液相色谱分离荧光检测(FLD)和荧光分光光度分析(FS)两种方法平行检测Cu(Ⅱ)-H2O2 体系中产生的·OH.试验采用的激发波长277 nm,发射波长306 nm.体系在反应前后的荧光变化,可反映·OH产生量.对FLD与FS所得数据进行了比较分析,结果显示两种方法具有较高一致性.FS使用混合体系检测,易对荧光的产生造成干扰,而FLD法没有干扰.     

Transient free‐surface flow of a viscoelastic fluid in a narrow channel

The interplay between inertia and elasticity is examined for transient free‐surface flow inside a narrow channel. The lubrication theory is extended for the flow of viscoelastic fluids of the Oldroyd‐B type (consisting of a Newtonian solvent and a polymeric solute). While the general formulation accounts for non‐linearities stemming from inertia effects in the momentum conservation equation, and the upper‐convected terms in the constitutive equation, only the front movement contributes to non‐linear coupling for a flow inside a straight channel. In this case, it is possible to implement a spectral representation in the depthwise direction for the velocity and stress. The evolution of the flow field is obtained locally, but the front movement is captured only in the mean sense. The influence of inertia, elasticity and viscosity ratio is examined for pressure‐induced flow. The front appears to progress monotonically with time. However, the velocity and stress exhibit typically a strong overshoot upon inception, accompanied by a plug‐flow behaviour in the channel core. The flow intensity eventually diminishes with time, tending asymptotically to Poiseuille conditions. For highly elastic liquids the front movement becomes oscillatory, experiencing strong deceleration periodically. A multiple‐scale solution is obtained for fluids with no inertia and small elasticity. Comparison with the exact (numerical) solution indicates a wide range of validity for the analytical result. Copyright © 2004 John Wiley & Sons, Ltd.     

Existence results for second order boundary value problem of impulsive dynamic equations on time scales

In this paper, Schaefer's fixed point theorem and nonlinear alternative of Leray-Schauder type are used to investigate the existence of solutions for second order boundary value problem for impulsive dynamic equations on time scales.     

Modification of multiwalled carbon nanotubes by carboxy groups and determination of the degree of functionalization

Multiwalled carbon nanotubes were modified by carboxy groups. Four independent methods for the determination of the degree of functionalization of the surface were proposed: ¹³C NMR spectroscopy, thermogravimetry, titrimetry, and fluorimetry. The first two methods show the total content of carboxy groups in the sample, and the latter two methods give information about the content of the surface groups only. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 291–295, February, 2008.     

Fluorescence Study of Excited-State Relaxation Processes of 2-Pyridyl-5-Aryloxazoles

Anomalously high fluorescence spectrum Stokes' shifts of 2(4-pyridyl)-5-(4-methylphenyl)oxazole, 2(4-pyridyl)-5-(4-methoxyphenyl)oxazole, 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole have been found. The fluorescence spectra of the compounds studied are shifted to longer wavelengths as the solvent dielectric constant increases. The dipole moments of these compounds increase by 3–4 times upon excitation. The fluorescence spectra of the compounds investigated are shifted to shorter wavelengths, and the fluorescence quantum yields increase as the temperature decreases. The fluorescence rate constant of 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole changes slightly as the temperature decreases from 293 K (relaxed state) to 114 K (mainly nonrelaxed state). It was concluded that the anomalously high fluorescence Stokes' shift of 2-pyridyl-5-aryloxazole derivatives is caused by solvent orientation relaxation.     

Dielectric properties of europium-indium oxide solid solution films prepared on Si (100) substrates

Thin Eu-In solid solution oxide films (SS) were grown on Si (P) substrates to form MOS devices. The samples were characterised by X-ray fluorescence and X-ray diffraction techniques. The ac-conductance and capacitance of the devices were studied as a function of frequency in the range 500 Hz to 100 kHz, temperature in the range 293-400 K and gate voltage. The investigation established that: (1) the prepared SS exhibit a sudden reversible structural change at about 370 K, (2) the frequency dependence for f>10 kHz of the ac-conductivity and capacitance of the insulator at room temperature is controlled by the ‘corrected barrier hopping’ CBH model, (3) the temperature dependence of the ac-conductance which shows a small activation energy characterises the hopping process of current carriers between equilibrium sites, and (4) the prepared transparent SS have a sufficiently high relative permittivity ?, around 30, which suggests they are promising candidates for high-? dielectric applications.     

Measuring calcium uptake and inositol 1,4,5-trisphosphate-induced calcium release in cerebellum microsomes using Fluo-3

A simple fluorimetric method is presented for measuring calcium uptake and inositol 1,4,5-trisphosphate (InsP₃)-induced calcium release in microsomes using Fluo-3. This method is used to investigate the amplitude of calcium release (quantal release) induced by InsP₃ from rat cerebellum microsomes.     

电子束装置运行稳定性的测量

 为了验证电子束装置的稳定性,分别对电流波形、电压波形进行了多次测量,对二极管放电时注入腔中电子均匀性进行了探测,最后改变二极管真空度测量了泵浦氩的荧光 谱的稳定性。     

X-ray fluorescence in some rare earth and high Z elements excited by 661.6 keV γ-rays

The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm, Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of ¹³⁷Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other measured values.