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541.
Hamed Rezania Farid Taherkhani 《Applied Physics A: Materials Science & Processing》2012,109(2):343-347
Optical conductivity of a zigzag carbon nanotube is investigated in the context of the Holstein model. Green??s function approach is applied to calculate the optical conductivity as a function of photon frequency, temperature, and electron?Cphonon coupling strength. Based on our results, optical conductivity decreases with electron?Cphonon coupling constant for both metallic and semiconducting carbon nanotubes. Our results show that temperature yields shortening the height of peaks of zigzag CNT optical absorption. 相似文献
542.
Analyses of pesticides and their metabolites in foods and drinks 总被引:10,自引:0,他引:10
Farid E. Ahmed 《Trends in analytical chemistry : TRAC》2001,20(11):649-661
The importance of matrix pretreatment, sample extraction and clean-up in multiresidue methods for pesticide analyses is discussed, with emphasis on alternative new techniques attempted worldwide such as accelerated solvent extraction, microwave-assisted extraction, solid-phase extraction, solid-phase micro-extraction, matrix solid-phase dispersion, supercritical fluid chromatography, ultrasonic extraction and gel permeation chromatography. Detection employing capillary gas chromatography and high-performance liquid chromatography in conjunction with mass spectrometry, capillary electrophoresis, immunoassay techniques and others is summarized. 相似文献
543.
Huda Farid Ernst Haslinger Olaf Kunert Christian Wegner Matthias Hamburger 《Helvetica chimica acta》2002,85(4):1019-1026
Five new steroidal glycosides were isolated from the roots of Balanites aegyptiaca, a widely used African medicinal plant. On the basis of spectroscopic and chemical evidence, their structures were determined as (3β,12α,14β,16β)‐12‐hydroxycholest‐5‐ene‐3,16‐diyl bis(β‐D ‐glucopyranoside) ( 1 ), (3β,20S,22R,25R)‐ and (3β,20S,22R,25S)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurost‐5‐en‐3‐yl β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→4)[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐glucopyranoside ( 2 and 3 , resp.), and (3β,20S,22R,25R)‐ and (3β,20S,22R,25S)‐spirost‐5‐en‐3‐yl β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→4)[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐glucopyranoside ( 4 and 5 , resp.) 相似文献
544.
Citrus aurantium L. Active Constituents,Biological Effects and Extraction Methods. An Updated Review
Sawssan Maksoud Roula M. Abdel-Massih Hiba N. Rajha Nicolas Louka Farid Chemat Francisco J. Barba Esprance Debs 《Molecules (Basel, Switzerland)》2021,26(19)
Citrus genus is a prominent staple crop globally. Long-term breeding and much hybridization engendered a myriad of species, each characterized by a specific metabolism generating different secondary metabolites. Citrus aurantium L., commonly recognized as sour or bitter orange, can exceptionally be distinguished from other Citrus species by unique characteristics. It is a fruit with distinctive flavor, rich in nutrients and phytochemicals which possess different health benefits. This paper presents an overview of the most recent studies done on the matter. It intends to provide an in-depth understanding of the biological activities and medicinal uses of active constituents existing in C. aurantium. Every plant part is first discussed separately with regards to its content in active constituents. All extraction methods, their concepts and yields, used to recover these valuable molecules from their original plant matrix are thoroughly reported. 相似文献
545.
Numerical modelling of electrochemical systems covers length scales from the nanometers up to the macroscopic scale. With finite element methods, the mesh must be extremely fine to describe the diffuse double layer, thus increasing the needed computational resources. We propose a method to describe the diffuse double layer by analytical equations, expressed as boundary conditions for the partial differential equations describing the solution bulk. We apply the method to a one-dimensional system, i. e. to a cell with plane parallel electrodes, in the presence of a redox couple and a supporting electrolyte. We provide evidence of the precision of the method. 相似文献