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991.
《Analytical letters》2012,45(11):1620-1631
Abstract A rapid, simple, and efficient liquid-phase microextraction (LPME) method coupled with high-performance liquid chromatography and ultraviolet detection for the analysis of triazine herbicides was developed in this study. Under the optimum conditions, the enrichment factors and extraction recoveries were 33.0–72.6 and 11.2–23.2%, respectively. The detection limits (LODs) were in the range of 0.03–0.10 µg L?1. The relative standard deviations for the determination of the triazine herbicides at μg L?1 levels varied in the range 2.05–8.15%. The method was successfully applied in the determination of the triazine herbicides in aqueous samples with satisfactory results. 相似文献
992.
《Analytical letters》2012,45(7):1437-1444
Abstract We report the use of solid phase microextraction (SPME) combined with ion mobility spectrometry (IMS) for sampling, screening and identification of organic compounds that are readily detected by IMS. This is a new SPME application. SPME has emerged recently as an excellent sample preparation technique for gas chromatography (GC) and high performance liquid chromatography (HPLC). We have found that SPME can be used very conveniently with IMS. An example of SPME-IMS is described using SPME headspace sampling at room temperature with 0.1 mL vials containing 1.0 microgram or less of either cocaine freebase or cocaine hydrochloride. This is followed by analysis using IMS. A hole, drilled in the IMS sample ticket holder, serves as the SPME-IMS interface. 相似文献
993.
994.
Abstract: We demonstrate that wax-embedded models of tissue-engineered oral mucosa can be effectively dewaxed using xylene for Raman spectroscopic analysis. Tissue sections of 20 μm thickness were cut and mounted onto glass slides. Sections were placed in xylene for increasing lengths from 2 to 45 min. Acquired Raman spectra revealed the wax contribution in the fingerprint region until 28-min treatment in xylene. Good quality and wax-free spectra were recorded at 30, 35, 40, and 45 min in xylene with no significant differences among them. It is essential to collect uncontaminated Raman spectra in order to achieve authentic results because the fingerprint region of biological tissues holds extremely vital information that is of diagnostic significance in cancer. 相似文献
995.
AbstractWith 135 references, this review presents the recent application of various preconcentration and separation techniques in atomic fluorescence spectrometry for the sensitive determination and speciation of various elements and their species. It focuses on sample pretreatment, separation, and enrichment-related techniques, including liquid–liquid extraction, solid-phase (micro)extraction, microwave/ultrasound-assisted extraction, pressurized liquid extraction, as well as chemical vapor generation. In this review, the historical development and overview of these preconcentration and separation methodologies are briefly discussed, together with a comprehensive collection of application of these methods in combination with atomic fluorescence spectrometry for determination of ultratrace amounts of elements and their species in various sample matrices (liquids and solids). 相似文献
996.
衍射增强相位衬度成像中的信息分离研究一直以来都是相关研究人员重点关注的方向之一. 本文在利用余弦函数拟合衍射增强成像中的摇摆曲线的基础上, 推导出了峰位像、左腰像和右腰像的余弦函数表达式以及吸收像、折射角像和散射角方差像的解析表达式, 形成了一种基于衍射增强成像的简便信息分离方法. 该方法只需利用摇摆曲线左腰、右腰和峰位三幅图像, 就能提取出样品的吸收、折射和散射信息, 具有方法简便、样品所受辐射剂量低等优点. 对模型样品和真实样品的实验结果表明, 本文所提方法可成功对样品进行信息分离, 并且所获得的信息分离结果可以和目前常用的多图统计方法(至少需要7张图像)获得的实验结果相比较.
关键词:
衍射增强成像
相位衬度成像
样品信息提取 相似文献
997.
《随机分析与应用》2013,31(4):853-869
Abstract For bootstrap sample means resulting from a sequence {X n , n ≥ 1} of random variables, very general weak laws of large numbers are established. The random variables {X n , n ≥ 1} do not need to be independent or identically distributed or be of any particular dependence structure. In general, no moment conditions are imposed on the {X n , n ≥ 1}. Examples are provided that illustrate the sharpness of the main results. 相似文献
998.
《Journal of computational and graphical statistics》2013,22(2):368-383
In this article we consider posterior simulation in models with constrained parameter or sampling spaces. Constraints on the support of sampling and prior distributions give rise to a normalization constant in the complete conditional posterior distribution for the (hyper-) parameters of the respective distribution, complicating posterior simulation. To mitigate the problem of evaluating normalization constants, we propose a computational approach based on model augmentation. We include an additional level in the probability model to separate the (hyper-) parameter from the constrained probability model, and we refer to this additional level in the probability model as a shadow prior. This approach can significantly reduce the overall computational burden if the original (hyper-) prior includes a complicated structure, but a simple form is chosen for the shadow prior, for example, if the original prior includes a mixture model or multivariate distribution, and the shadow prior defines a set of shadow parameters that are iid given the (hyper-) parameters. Although introducing the shadow prior changes the posterior inference on the original parameters, we argue that by appropriate choices of the shadow prior, the change is minimal and posterior simulation in the augmented probability model provides a meaningful approximation to the desired inference. Data used in this article are available online. 相似文献
999.
Adjustable microwave absorption properties of flake shaped (Ni0.5Zn0.5)Fe2O4/Co nanocomposites with stress induced orientation 总被引:1,自引:0,他引:1
Flake shaped (Ni0.5Zn0.5)Fe2O4/Co nanocomposites were successfully fabricated by co-precipitating of Ni-Zn ferrite on the surface of cobalt nanoflakes. The electromagnetic characteristics of the samples were studied at the frequency of 0.1–14 GHz. The results showed that the cobalt nanoflakes in compacted nanocomposites were well orientated, and the nanocomposites were characterized with low optimal reflection loss (RL) of −33.8 dB at 11.5 GHz and broad RL bandwidth for <−20 dB in the frequency range of 7.6–12.1 GHz. At the same time, the position of the absorptive band can be adjusted by changing the mass ratio of ferrite to cobalt in the nanocomposites. It is proposed that the excellent microwave absorption properties are related to the combination of strong shape anisotropy of cobalt nanoflakes and adjustable dielectric loss. 相似文献
1000.
Gil García MD Belmonte Gallegos A Valverde RS Martínez Galera M 《Journal of separation science》2012,35(7):823-831
An analytical method based on online enrichment using coupled-column liquid chromatography with fluorescence detection has been developed to determine marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, norfloxacin, lomefloxacin, oxolinic acid, and nalidixic acid at trace levels in surface water. The sample containing the pharmaceuticals was pumped through a short C18 column in such a way that the analytes were retained on the column, whereas polar interferences, eluting at the first of the chromatogram, were discarded to waste. Then, the analytes were transferred by the chromatographic mobile phase to a second C18 analytical column, where they were separated following a conventional chromatography. The optimized approach allowed to preconcentrate 15 mL of sample volume adjusted at acid pH with phosphoric acid and modified with 5% of methanol, at a flow rate of 1.5 mL/min in 10 min. R(2) values were between 0.994 and 0.998, detection and quantitation limits ranged between 0.001 and 0.080 and between 0.002 and 0.100 μg/L, respectively, and the interday precision was below 9.8%. Recoveries in three different surface water samples, spiked at concentration levels between 0.002 and 0.500 μg/L (n = 3 for each spiking level), ranged from 82.1 to 125.8% with the relative standard deviation lower than 12%. 相似文献