光声喇曼光谱的理论分析

对光声喇曼光谱(PARS)作了系统的理论分析,分别导出固体和液体介质中的光声喇曼光谱的信号表达式,并进行了数值估算。 关键词：     

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Solvent and concentration effects on the properties of electrospun poly(ethylene terephthalate) nanofiber mats

This study describes the preparation and characterization of nanofibrous mats obtained by electrospinning poly(ethylene terephthalate) (PET) solutions in trifluoroacetic acid/dichloromethane (TFA/DCM). Special attention was paid to the effect of polymer concentration and solvent properties on the morphology, structure, and mechanical and thermal properties of the electrospun nonwovens. The results show that the spinnable concentration of PET solution in TFA/DCM solvents is above 10 wt %. Mats have nanofibrous morphology with fibers having an average diameter in the range of 200–700 nm (depending on polymer concentration and solvent composition) and an interconnected pore structure. Higher solution concentration favors the formation of uniform fibers without beads and with higher diameter. Morphology and fiber assembly changed with the solvent properties. Solvent mixtures rich in TFA, i.e., those with higher dielectric constant and lower surface tension, originated fibers with small diameter. However, due to the lower volatility, those solvent mixtures also produced more branched and crosslinking fibers, with less morphologic uniformity. Mechanical properties (Young's modulus, ultimate strength, and elongation at break) and thermal properties (glass transition, crystallization, and melting) have been studied for the PET electrospun nanomats and compared with those of the original polymer. Solvent effect on fiber crystallinity was not significant, but a complex effect was observed on the mechanical properties of the electrospun mats, as a consequence of the different structural organization of the fibers within the mat network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 460–471, 2008     

The inverse scattering transform: Tools for the nonlinear fourier analysis and filtering of ocean surface waves

Surface wave data from the Adriatic Sea are analysed in the light of new data analysis techniques which may be viewed as a nonlinear generalization of the ordinary Fourier transform. Nonlinear Fourier analysis as applied herein arises from the exact spectral solution to large classes of nonlinear wave equations which are integrable by the inverse scattering transform (IST). Numerical methods are discussed which allow for implementation of the approach as a tool for the time series analysis of oceanic wave data. The case for unidirectional propagation in shallow water, where integrable nonlinear wave motion is governed by the Korteweg-deVries (KdV) equation with periodic/quasi-periodic boundary conditions, is considered. Numerical procedures given herein can be used to compute a nonlinear Fourier representation for a given measured time series. The nonlinear oscillation modes (the IST ‘basis functions’) of KdV obey a linear superposition law, just as do the sine waves of a linear Fourier series. However, the KdV basis functions themselves are highly nonlinear, undergo nonlinear interactions with each other and are distinctly non-sinusoidal. Numerical IST is used to analyse Adriatic Sea data and the concept of nonlinear filtering is applied to improve understanding of the dominant nonlinear interactions in the measured wavetrains.     

The micro water/1,2-dichloroethane interface as a transducer for creatinine assay

Facilitated ammonium ion transfer reactions, using the crown ether dibenzo-18-crown-6, at a single microhole supported water/1,2-dichloroethane interface were used as the transducer to detect the biomolecule creatinine. The ammonium ion was produced during the enzymatic action of creatinine deiminase on creatinine. A prototype sensing device incorporating a Teflon gas permeable membrane, to exclude possible interferents, yielded a linear amperometric response to added creatinine from 20 M to 1 mM. This range is sufficient for that required for the determination of creatinine in serum.     

Cesium chromate,Cs2CrO4: heat capacity and thermodynamic properties from 5 to 350 K

The heat capacity of a sample of Cs₂CrO₄ was determined in the temperature range 5 to 350 K by aneroid adiabatic calorimetry. The heat capacity at constant pressure C_p^o(298.15 K), the entropy S^o(298.15 K), the enthalpy {H^o(298.15 K) - H^o(0)} and the function $\text{? {G}{}^{\mathrm{o}}\text{(298.15}\text{K}\text{) - H}{}^{\mathrm{o}}\text{(0)}}\text{298.15}\text{K}$ were found to be (146.06 ± 0.15) J K^?1 mol^?1, (228.59 ± 0.23) J K^?1 mol^?1, (30161 ± 30) J mol^?1, and (127.43 ± 0.13) J K^?1 mol^?1, respectively. The heat capacity C_p^o(298.15 K) and entropy S^o(298.15 K) and entropy S^o(298.15 K) of Rb₂CrO₄ are estimated to be (146.0 ± 1.0) J K^?1 mol^?1 and (217.6 ± 3.0) J K^?1 mol^?1, respectively.     

香豆素类化合物的一种新合成方法

香豆素类化合物是一类重要的有生物活性的天然产物,也可用作香料、阻凝剂和三线态光敏剂。用 Meldrum 酸合成该类化合物,已有一些报道。我们在研究 Meldrum 酸系列     

十二烯基丁二酸改性氧化锆色谱固定相性能研究

本文用十二烯基丁二酸（DSA）改性氧化锆得到一种新的锆基质色谱固定相。改性前后的红外光谱的差异表明，DSA以两个羧基与氧化锆结合，由于多位点结合方式提高了固定相的稳定性，因此固定相可以在碱性（pH8．5）条件下稳定使用。锆基质色谱固定相具有较强的疏水性，用于中性及碱性化合物的分离取得了满意的结果。