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991.
The combination of capillary electrophoresis (CE) and mass spectrometry (MS) is particularly well adapted to bioanalysis due to its high separation efficiency, selectivity, and sensitivity; its short analytical time; and its low solvent and sample consumption. For clinical and forensic toxicology, a two-step analysis is usually performed: first, a screening step for compound identification, and second, confirmation and/or accurate quantitation in cases of presumed positive results. In this study, a fast and sensitive CE-MS workflow was developed for the screening and quantitation of drugs of abuse in urine samples. A CE with a time-of-flight MS (CE-TOF/MS) screening method was developed using a simple urine dilution and on-line sample preconcentration with pH-mediated stacking. The sample stacking allowed for a high loading capacity (20.5% of the capillary length), leading to limits of detection as low as 2 ng mL−1 for drugs of abuse. Compound quantitation of positive samples was performed by CE-MS/MS with a triple quadrupole MS equipped with an adapted triple-tube sprayer and an electrospray ionization (ESI) source. The CE-ESI-MS/MS method was validated for two model compounds, cocaine (COC) and methadone (MTD), according to the Guidance of the Food and Drug Administration. The quantitative performance was evaluated for selectivity, response function, the lower limit of quantitation, trueness, precision, and accuracy. COC and MTD detection in urine samples was determined to be accurate over the range of 10–1000 ng mL−1 and 21–1000 ng mL−1, respectively. 相似文献
992.
昵博铜镍多金属矿位于滇东南地区,大地构造位置属于特提斯―喜马拉雅构造域和环太平洋构造域的交接部位。该区域土壤次生晕测量结果表明,Cu、Fe、Ti、Co、Ni、Cr、V元素背景含量较高,Au、As、Sb、Hg元素背景含量偏低,Au可能来自深源,其分布与反应基性、超基性岩的元素相似。结合矿区地质背景分析并进一步处理土壤次生晕数据,确定区域地球化学背景、元素富集区域及化学异常带,结合地质背景,共划分出两处化学异常带为成矿有利区域,其找矿前景良好。测量数据可为今后进一步的勘查工作提供可靠依据。 相似文献
993.
994.
995.
LIU Lei YAN Shi-Lei 《理论物理通讯》2005,44(4):743-748
We study the ferrimagnetic properties of spin 1/2 and spin-1 systems by means of the effective field theory. The system is considered in the framework of bond dilution mixed Blume-Capel mode/ (BCM) with random single-ion anisotropy. The investigation of phase diagrams and magnetization curves indicates the existence of induced magnetic ordering and single or multi-compensation points. Special emphasis is placed on the influence of bond dilution and random single-ion anisotropy on normal or induced magnetic ordering states and single or multi-compensation points. Normal magnetic ordering states take on new phase diagrams with increasing randomness (bond and anisotropy), while anisotropy induced magnetic ordering states are always occurrence no matter whether concentration of anisotropy is large or small. Existence and disappearance of compensation points rely strongly on bond dilution and random singleion anisotropy. Some results have not been revealed in previous papers and predicted by Néel theory of ferrimagnetism. 相似文献
996.
LED照明自适应驱动电源的研制 总被引:1,自引:0,他引:1
针对半导体发光二极管(LED)作为照明的驱动特性,设计了一种基于开关电源的自适应LED驱动电路。利用高密度电源控制芯片sa7527实现了LED的恒流驱动和过压保护,通过对输出光强和LED温度的检测实现了光衰的自动补偿功能。实际应用表明,该驱动电路可满足LED作为照明的实际需要,并且具有宽电压输入范围、高效率和光衰补偿功能。 相似文献
997.
O. N. Nikulicheva L. M. Pokrovskiy A. P. Krysin V. P. Fadeeva V. A. Logvinenko 《Journal of Thermal Analysis and Calorimetry》2000,60(1):157-161
The present paper deals with thermal decomposition of some spatially hindered phenols, which are in the industry as stabilizers
in synthetic materials used. The investigated stabilizers are separated to two groups in respect to mechanism of decomposition
(group I and II). This assumption was confirmed by chromatomass-spectrometric investigations. It allows a stabilizer for forming
a plastic with variety properties to choose.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
998.
M. Kaplinghat L. Sriramkumar A. Berera P. Chingangbam R. K. Jain M. Joy J. Martin S. Mohanty A. Nautiyal R. Rangarajan S. Ray V. H. S. Kumar 《Pramana》2009,72(1):263-267
This is a summary of the activities of the working group on cosmology at WHEPP-X. The three main problems that were discussed
at some length by the group during the course of the workshop were (i) canceling a ‘large’ cosmological constant, (ii) non-Gaussianities
in inflationary models and (iii) stability of interacting models of dark energy and dark matter. We have briefly outlined
these problems and have indicated the progress made.
相似文献
999.
Tarun Souradeep 《Pramana》2006,67(4):699-710
Measurements of CMB anisotropy and, more recently, polarization have played a very important role in allowing precise determination
of various parameters of the ‘standard’ cosmological model. The expectation of the paradigm of inflation and the generic prediction
of the simplest realization of inflationary scenario in the early Universe have also been established — ‘acausally’ correlated
initial perturbations in a flat, statistically isotropic Universe, adiabatic nature of primordial density perturbations. Direct
evidence for gravitational instability mechanism for structure formation from primordial perturbations has been established.
In the next decade, future experiments promise to strengthen these deductions and uncover the remaining crucial signature
of inflation — the primordial gravitational wave background. 相似文献
1000.