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61.
Flow field-flow fractionation (flow FFF), a separation technique for particles and macromolecules, has been used to separate carbon nanotubes (CNT). The carbon nanotube ropes that were purified from a raw carbon nanotube mixture by acidic reflux followed by cross-flow filtration using a hollow fiber module were cut into shorter lengths by sonication under a concentrated acid mixture. The cut carbon nanotubes were separated by using a modified flow FFF channel system, frit inlet asymmetrical flow FFF (FI AFIFFF) channel, which was useful in the continuous flow operation during injection and separation. Carbon nanotubes, before and after the cutting process, were clearly distinguished by their retention profiles. The narrow volume fractions of CNT collected during flow FFF runs were confirmed by field emission scanning electron microscopy and Raman spectroscopy. Experimentally, it was found that retention of carbon nanotubes in flow FFF was dependent on the use of surfactant for CNT dispersion and for the carrier solution in flow FFF. In this work, the use of flow FFF for the size differentiation of carbon nanotubes in the process of preparation or purification was demonstrated. 相似文献
62.
Kang K Bae SJ Kim WM Lee DH Cho U Lee MH Lee MS Nam S Kuettner KE Schwartz DE 《Experimental & molecular medicine》2000,32(3):146-154
Nonsteroidal antiinflammatory drugs(NSAIDs) are known as clinically effective agents for treatment of inflammatory diseases. Inhibition of cyclooxygenase has been thought to be a major facet of the pharmacological mechanism of NSAIDs. However, it is difficult to ascribe the antiinflammatory effects of NSAIDs solely to the inhibition of prostaglandin synthesis. Human neutrophil elastase (HNElastase; HNE, EC 3.4.21.37) has been known as a causative factor in inflammatory diseases. To investigate the specific relationship between HNElastase inhibition and specificity of molecular structure of several NSAIDs, HNElastase was purified by Ultrogel AcA54 gel filtration, CM-Sephadex ion exchange, and HPLC (with TSK 250 column) chromatography. HNElastase was inhibited by aspirin and salicylate in a competitive manner and by naproxen, ketoprofen, phenylbutazone, and oxyphenbutazone in a partial competative manner, but not by ibuprofen and tolmetin. HNElastase-phenylbutazone-complex showed strong Raman shifts at 200, 440, 1124, 1194, 1384, 1506, and 1768 cm(-1). The Raman bands 1194, 1384, and 1768 cm(-1) may represent evidences of the conformational change at -N=N-phi radical, pyrazol ring, and -C=O radical of the elastase-drug complex, respectively. Phenylbutazone might be bound to HNElastase by ionic and hydrophobic interaction, and masked the active site. Inhibition of HNElastase could be another mechanism of action of NSAIDs besides cyclooxygenase inhibition in the treatment of inflammatory diseases. Different inhibition characteristics of HNE-lastase by NSAIDs such as aspirin, phenylbutazone-like drugs and ineffective drugs could be important points for drawing the criteria for appropriate drugs in clinical application. 相似文献
63.
The electroosmotic flow through an annulus is analyzed under the situation when the two cylindrical walls carry high zeta potentials. The analytical solutions for the electric potential profile and the electroosmotic flow field in the annulus are obtained by solving the Poisson-Boltzmann equation and the Stokes equation under an analytical scheme for the hyperbolic sine function. A mathematical expression for the average electroosmotic velocity is derived in a fashion similar to the Smoluchowski equation. Hence, a correction formula is introduced to modify the Smoluchowski equation, taking into account contributions due to the finite thickness of the electric double layer (EDL) and the geometry ratio-dependent correction. Specifically, under a circumstance when the two annular walls are oppositely charged, the flow direction can be determined from the sign of such correction formula, and there exists a zero-velocity plane inside the annulus. With the assumption of large electrokinetic diameters, the location of the zero-velocity plane can be estimated from the analytical expression for the velocity distribution. In addition, the characteristics of the electroosmotic flow through the annulus are discussed under the influences of the EDL parameters and geometric ratio of the inner radius to the outer radius of the annulus. 相似文献
64.
Bo Jiang Hui Song Yunqing Kang Shengyao Wang Qi Wang Xin Zhou Kenya Kani Yanna Guo Jinhua Ye Hexing Li Yoshio Sakka Joel Henzie Yamauchi Yusuke 《Chemical science》2020,11(3):791
Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO2 into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.Generating high surface area mesoporous transition metal boride is challenging but interesting because incorporation of boron atoms can generate lattice distortion to form amorphous metal boride which has unique properties in catalysis. 相似文献
65.
Depigmenting activity and low cytotoxicity of alkoxy benzoates or alkoxy cinnamte in cultured melanocytes 总被引:2,自引:0,他引:2
To obtain effective and safe topical depigmenting agents, we synthesized hydroxybenzoates, alkoxybenzoates, and 3,4,5-trimethoxycinnamate containing a thymol moiety and screened then for high-level inhibitory activity against melanin synthesis in cultured melanocytes. Eight compounds were tested for their depigmenting effect and cytotoxicity using a murine melanocyte cell line. We found that 3,4,5-trialkoxybenzoates and 3,4,5-trimethoxycinnamate, synthesized by conjugating 3,4,5-trialkoxybenzoic acids and 3,4,5-trimethoxycinnmic acid with thymol, showed a potent depigmenting effect and low cytotoxicity. Compound 4h, 5-methyl-2-(methylethyl)phenyl (2E)-3-(3,4,5-trimethoxyphenyl)prop-2-enoate, showed the most potent depigmenting effect (IC50=10 microM) with low cytotoxicity (IC50=200 microM). 相似文献
66.
K. H. Kim J. H. Lee M. Y. Ko K. S. Shin J. S. Kang W. C. Mar J. R. Youm 《Chromatographia》2002,55(1-2):81-85
Summary A method for the assay of R-(+)- and S-(−)- metoprolol in human urine has been developed using gas chromatography-mass spectrometry.
The method involved purification by liquid-liquid extraction and derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide
to form an O-silyl ether, followed by subsequent chiral derivatization with (−)-α-methoxy-α-(trifluoromethyl)phenylacetyl
chloride to form diastereomeric amide. The reaction was rapid and the diastereomeric derivatives were well resolved. Quantitation
was performed by selected-ion monitoring of fragment ions of the diastereomers in electron impact ionization mode. No racemization
was found during the reaction. The detection limit was 0.5 ng·mL−1. The intra-day variation ranged between 0.38 and 7.86% in relation to the measured concentration and inter-day variation
was 2.26–8.06%. The method has been applied to the determination of R-(+)-and S-(−)- metoprolol in human urine from healthy
volunteers dosed with racemic metoprolol tartrate. 相似文献
67.
Fashui?HongEmail author Xuefeng?Wang Chao?Liu Guoxing?Su Weiping?Song Kang?Wu Ye?Tao Guiwen?Zhao 《中国科学B辑(英文版)》2003,46(1):42-50
It was studied by spectroscopy that PSII reaction center complex consisting of three polypeptides, D1, D2 and Cytb559, were purified from PSII particle of CeCl3 treated spinach. The results of the experiment show that Ce3+ could improve the growth of spinach, and accelerate electron transport of PSII particles. Of chl-a of UV-Vis spectrum of
D1/D2/Cytb559 complex, Soret band was blue-shifted by 3 nm and Q band by 2 nm, respectively, and the fluorescence emission
peak was blue-shifted by 5 nm in CeCl3-treated spinach compared with the one in control. By the extended X-ray absorption fine structure (EXAFS) spectroscopy methods,
it has been found that Ce3+ is coordinated with 8 nitrogen atoms in the first coordination shell with Ce-N bond length of 0.253 nm, and Ce3+ with 6 oxygen atoms in the second coordination shell with Ce-O bond length of 0.32 nm. However, the secondary structure of
D1/D2/Cytb559 complex by circular dichroism (CD) spectroscopy has no significant change after CeCl3 treated. It might be that Ce3+ binds to porphyrin rings of chlorophyll and oxygen of amino acid residue of polypeptide in D1/D2/Cytb559 complex, and then
accelerates the primary reaction of PSII, intensifies function of P680+ primary electron donor of D1/D2/Cytb559, but there is little change in conformation of PSII reaction center complex. 相似文献
68.
针对医用高值耗材种类繁多、管理难度大的问题,为减少人力成本、提高医用高值耗材的智能化管理水平。本文提出了基于物联网的高值医用耗材智能屋的管理系统,介绍了智能屋的整体架构、系统功能、核心业务及流程设计,主要分为结构模块、RFID模块、数据库模块、控制系统模块四大模块,具体有用户管理、出入库管理、综合查询、预警管理四大业务,通过GM(1,1)模型对2022年全年高值医用耗材的月消耗量进行预测分析,并且检验得该预测模型的精度等级为一级,模型预测效果很好,能够为医院采购人员采购提供了一个参考,避免因过度的主观估计而造成的耗材浪费。该系统能够有效地提高医院对于高值医用耗材的管理水平,减少人力、物力和财力的消耗,为广大患者提供更加优质的医疗服务。本文所提的高值医用耗材智能屋管理系统解决了传统的高值医用耗材管理的诸多难题。 相似文献
69.
Kang Zhao 《Numerical Algorithms》1995,9(1):141-156
Implicit and explicit characterizations of the solutions to the following constrained best interpolation problem $$\min \left\{ {\left\| {Tx - z} \right\|:x \in C \cap A^{ - 1} d} \right\}$$ are presented. Here,T is a densely-defined, closed, linear mapping from a Hilbert spaceX to a Hilbert spaceY, A: X→Z is a continuous, linear mapping withZ a locally, convex linear topological space,C is a closed, convex set in the domain domT ofT, andd∈AC. For the case in whichC is a closed, convex cone, it is shown that the constrained best interpolation problem can generally be solved by finding the saddle points of a saddle function on the whole space, and, if the explicit characterization is applicable, then solving this problem is equivalent to solving an unconstrained minimization problem for a convex function. 相似文献
70.