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We propose a new method for calculating the dressed fermion propagator at finite chemical potential in QED3 under the rainbow approximation of Dyson-Schwinger equation. In the above approximation, we show that the dressed fermion propagator at finite chemical potentialμ has the form S (p) = iγ. pA (p2) B (p2) with pμ = (p, p3 iμ).Using this form of fermion propagator at nonzero chemical potential, we investigate the Dyson-Schwinger equation for the dressed fermion propagator at finite chemical potential and study the effects of the chemical potential on the critical number of the fermion flavors. 相似文献
63.
高信噪比的动态光谱(dynamic spectrum, DS)提取是实现高精度动态光谱血液成分无创检测的一个关键。为了进一步提高提取的精度和速度,从原理上分析了各单波长光电容积脉搏波(photoelectric plethysmography,PPG)的线性相似性,并基于此性质提出了补偿拟合法:首先按照PPG单周期采样点数进行滑动平均得到漂移基线进行补偿,除去基线漂移;其次用各波长对数PPG与全波长叠加平均模板PPG进行最小二乘拟合,提取一次项系数构成DS。利用拟合提取法对近红外和可见光波段各25组PPG数据样本进行DS提取实验验证,并将结果与单沿提取法进行平滑性指标的对比,结果表明:近红外和可见光波段补偿拟合法获取DS的平均方差分别为单沿提取法的77.9%和59.5%,稳定提高了DS的平滑性;近红外和可见光波段补偿拟合法处理时间分别可以达到单沿提取法的10%和20%,处理速度得到显著改善。补偿拟合法在单沿提取法的基础上稳定提高了DS的信噪比,改善了DS提取质量,缩减了提取时间,并简化了处理步骤,有望推动DS无创血液成分检测的发展。 相似文献
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Near-infrared spectroscopy (NIRS) is a spectroscopic method that is frequently used in health care and sports medicine to monitor oxygenation parameters in biological tissue. This tutorial provides a coherent derivation of equations for differential spectroscopy and spatially resolved spectroscopy, from basic theories to implementable equations. The basic theories are applicable to any kind of tissue oximeter but mainly focus on continuous-wave instruments. 相似文献
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Summary The physicochemical properties of biogenic monoamines, their polar character, lability and trace amounts found in the biological
material create great analytical difficulties in their identification and separation. The selective chromatographic separation
of those amines is greatly facilitated by their derivatization [1]. Based on theoretical considerations, 4-dipropylaminodiazabenzene-4′-isothiocyanate
(DPABITC) was synthetized and applied to the preparation of thiocarbamoyl derivatives of the amines. The coloured derivatives
were separated by TLC.
Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
69.
The purge and trap (P&T) method of analysis has been interfaced with fused silica capillary column gas chromatography. This interfacing has been accomplished without splitting the P&T trap desorption carrier gas. Thus, 100% of the purged compounds are transferred to the column. The analytes are cryofocussed on the column using whole column cryotrapping (WCC) at ?80°C. The resulting P&T/WCC procedure is extremely well-suited to the analysis of trace purgeable aqueous organic compounds. Samples and standards containing a variety of aromatic standard compounds were analyzed. The standards included benzene, toluene, ethylbenzene, xylenes, C3-C4-benzenes, and naphthalene, as well as three P&T internal standard compounds. Chromatographic peak widths were uniformly less than 6 s at the base and excellent precision was obtained in the relative retention time data for all compounds. The chromatogram of a groundwater sample contaminated with aromatic gasoline compounds is also presented. Since P&T/WCC works well with fused silica capillary columns, the full sensitivity and chromatographic efficiency of capillary gas chromatography is made available to P&T analyses. 相似文献
70.
Claudia Barba Daniel Montané Xavier Farriol Jacques Desbrières Marguerite Rinaudo 《Cellulose (London, England)》2002,9(3-4):327-335
This paper concerns the rheological behavior of carboxymethylcelulloses(CMC) derived after one and two successive steps from different non-woodbleached cellulose pulps. CMC rheological characterization was achieved in0.1M NaCl solution, as a function of polymer concentration. Theevidence of a critical concentration (C* < 1 g/L) is discussedfromsteady shear and dynamic experiments. Rheological properties of the CMC werefound to depend on the cellulose source reactivity and on their degree ofsubstitution (DS). Higher molecular weight of initial cellulose was accompaniedby higher apparent intrinsic viscosity of the CMC produced. Depending on theCMCconcentration and on the degree of etherification, the system behaves as asolution or as a gel. In the case of abaca CMC sample, it is shown that afteronly one step of chemical modification and above a polymer concentration of20 g/L, the system behaves as a gel. The gel behavior was studied asafunction of temperature. In the temperature range from 25 to 45°C, the rheological behavior was found to remain almostconstant due to the existence of dispersed swollen aggregates. This unusualcharacteristic represents an advantage for applications such as oil recovery inthe petroleum industry, where viscosity of the recovered fluid should not diminishwith temperature. 相似文献