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31.
Notingher I Bisson I Bishop AE Randle WL Polak JM Hench LL 《Analytical chemistry》2004,76(11):3185-3193
Raman microspectroscopy was used to determine biochemical markers during the differentiation of embryonic murine stem cells (mES) in vitro. Such markers are useful to determine the differentiation status of ES cells cultured on biomaterials. Raman spectra of mES cells as undifferentiated, spontaneously differentiated (4 days), and differentiated cells via formation of embryoid bodies (16, 20 days) were analyzed. Unsupervised hierarchical cluster analysis and principal component analysis were used to determine biochemical differences between mES cells in various states of differentiation. The undifferentiated cells were characterized by high scores of the first principal component (PC1, 49% variance). Similarity between the PC1 loading and the Raman spectrum of RNA indicated a high concentration of RNA in mES cells compared to differentiated cells. The ratio between the peak areas of RNA and proteins was used as a measure of mRNA translation. Using the same peak area ratio, it was possible to differentiate even between mES as undifferentiated and in early stages of differentiation (4 days). These findings were correlated with biological studies reporting high levels of nontranslated mRNA during early embryonic development. Therefore, the RNA translation obtained from the Raman spectra can be used as marker of differentiation state of mES cells. 相似文献
32.
Aerosol lidar intercomparison in the framework of the EARLINET project. 1. Instruments 总被引:1,自引:0,他引:1
Matthais V Freudenthaler V Amodeo A Balin I Balis D Bösenberg J Chaikovsky A Chourdakis G Comeron A Delaval A De Tomasi F Eixmann R Hågård A Komguem L Kreipl S Matthey R Rizi V Rodrigues JA Wandinger U Wang X 《Applied optics》2004,43(4):961-976
In the framework of the European Aerosol Research Lidar Network to Establish an Aerosol Climatology (EARLINET), 19 aerosol lidar systems from 11 European countries were compared. Aerosol extinction or backscatter coefficient profiles were measured by at least two systems for each comparison. Aerosol extinction coefficients were derived from Raman lidar measurements in the UV (351 or 355 nm), and aerosol backscatter profiles were calculated from pure elastic backscatter measurements at 351 or 355, 532, or 1064 nm. The results were compared for height ranges with high and low aerosol content. Some systems were additionally compared with sunphotometers and starphotometers. Predefined maximum deviations were used for quality control of the results. Lidar systems with results outside those limits could not meet the quality assurance criterion. The algorithms for deriving aerosol backscatter profiles from elastic lidar measurements were tested separately, and the results are described in Part 2 of this series of papers [Appl. Opt. 43, 977-989 (2004)]. In the end, all systems were quality assured, although some had to be modified to improve their performance. Typical deviations between aerosol backscatter profiles were 10% in the planetary boundary layer and 0.1 x 10(-6) m(-1) sr(-1) in the free troposphere. 相似文献
33.
34.
Cristofor I. Simionescu Victor Bulacovschi Doina Macocinschi Gheorghe Stoica Ioan I. Neguiescu 《Polymer Bulletin》1988,19(1):59-63
Summary Suspension type PVC was reacted with sodium phenoxide in presence of different quaternary ammonium halides in THF or THF/water mixtures. The competition elimination vs. substitution of chlorine atoms depends on the homogeneity of the system, i.e. the more homogeneous the reaction mixture the less substituted the polymer.Dedicated to the 60th anniversary of Prof. Otto Vogl 相似文献
35.
36.
TMPA 卫星降水数据的评估与校正 总被引:6,自引:1,他引:5
卫星遥感降水由于时空分辨率的优势在现代水文模拟中正起着越来越大的作用。本研究对黄河源区的两套卫星降水产品(TMPA准实时3B42RT和研究数据3B42V6)进行了详细评估,结果表明,3B42RT与3B42V6相比会明显高估地面降水,而两者对降水事件的反演能力基本一致。通过引入"降水重心"的概念,两套卫星降水产品均可以基本反映降水的空间分布及长期演变过程。在两者尤其是3B42RT数据的校正中,首先将卫星数据与地面站点月降水对比,再等比例降尺度回日降水,然后尝试逐步订正和最优插值两种残差处理方法,从而使降水量和降水分布的精度进一步提高。最后用校正后的卫星降水驱动分布式水文模型,利用输出径流间接验证校正的效果。 相似文献
37.
We report a new spectroscopic technique that combines step-scanning Fourier transform infrared spectroscopy with opto-thermal transient emission radiometry (OTTER) in order to provide near-surface depth-resolved spectra in the range 700-1800 cm(-1). It works nondestructively, without contact, with samples of arbitrary shape and size, without requiring prior preparation. The depth of surface probed depends on the thermal diffusivity of the sample; for organic materials it is approximately 10 microm. With homogeneous samples, absolute absorption coefficients can be measured. With two-layered samples, the technique proved able to distinguish between the spectral properties of the top layer and the substrate and to estimate the thickness of the top layer. We present a theoretical analysis with the main design features of the instrumentation and software, together with studies of homogeneous and layered samples, to validate the methods and illustrate the potential of the technique for practical applications. 相似文献
38.
Cleopatra Vasiliu-Oprea Ioan Marcu Sorin Ciovica Florin Dan 《Polymer-Plastics Technology and Engineering》2013,52(4):609-620
Poly(acrylonim1e) fibers were preoxidated under stress, in the presence of air, then saponified by boiling in alkaline solutions. The chemomechani-cal behavior of these fibers, expressed as contraction and mechanical work, under different loads and in different solvent-nonsolvent and/or base-acid systems were investigated. Total nitrogen content, carboxyl groups content, tensile strength, and cross-link density were determined. Both contraction and mechanical work were expressed as functions of applied load in every studied system. The results of chemomechanical measurements were connected to those of chemical and physical investigations. Significant differences in chemomechanical behavior were found to be the result of different stress conditions during the preoxidation stage. 相似文献
39.
Ana-Maria Stanciuc Christoph Martin Sprecher Jérôme Adrien Lucian Ioan Roiban Mauro Alini Laurent Gremillard Marianna Peroglio 《Journal of the European Ceramic Society》2018,38(3):845-853
Zirconia-toughened alumina (ZTA) is the gold-standard ceramic in hip arthroplasty, but still lacks direct osseointegration and a metal shell, often coated with a bioactive layer, is currently required. The latter could potentially be replaced by a thinner, architectured ZTA layer, thereby allowing for larger acetabular components, with larger range of motion and lower dislocation risk. Robocasting may be an adequate technique to fabricate the architectured layer. Therefore, as a first step, this study aimed to produce ZTA scaffolds (3D-ZTA) by robocasting and assess their in vitro response. Shape retention was achieved by using a stable, well-dispersed, high solid loading ink injected in acid pH waterbath. 3D-ZTA exhibit regularly spaced microporous, rough struts and fully interconnected macroporosity. Human primary osteoblasts were homogenously distributed inside 3D-ZTA and showed increased osteogenic marker expression compared to 2D-ZTA control. Further work will focus on optimizing scaffold design to improve cell retention and extracellular matrix maturation. 相似文献
40.
The bulk polymerization reaction of N-vinylcarbazole (VK) at 70 °C in the presence of single-walled carbon nanotubes (SWNTs) leads to a new composite, whose optical properties were studied by photoluminescence (PL), surface enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopies. A dramatic reduction of the poly(N-vinylcarbazole) (PVK) PL efficiency and a change in the vibrational structure of the PL spectrum of this polymer were observed by adding SWNTs to the synthesis mixture. Steric hindrance effects were evidenced both in SERS spectra of the VK when it interacts mechanico-chemically with SWNTs and in FTIR spectra of the un-doped PVK/SWNTs' composites. Cyclic voltammetry was used to demonstrate the doping process of PVK in PVK/SWNTs' composite. 相似文献