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61.
In spite of large spin coherence length in graphene due to small spin–orbit coupling, the created potential barrier and antiferromagnetic coupling at graphene/transition metal (TM) contacts strongly reduce the spin transport behavior in graphene. Keeping these critical issues in mind in the present work, ferromagnetic (Co, Ni) nanosheets are grown on graphene surface to elucidate the nature of interaction at the graphene/ferromagnetic interface to improve the spin transistor characteristics. Temperature dependent magnetoconductance shows unusual behavior exhibiting giant enhancement in magnetoconductance with increasing temperature. A model based on spin–orbit coupling operated at the graphene/TM interface is proposed to explain this anomalous result. We believe that the device performance can be improved remarkably tuning the spin–orbit coupling at the interface of graphene based spin transistor. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
62.
A.SH. Hussein Z. Hassan S.M. Thahab Abu Hassan M.A. Abid C.W. Chin 《Physica B: Condensed Matter》2011,406(6-7):1267-1271
We have studied the structural properties of undoped and Si-doped AlxGa1?xN/GaN/AlN on Si (1 1 1) substrate prepared by plasma-assisted molecular beam epitaxy (PA-MBE) using high-resolution X-ray diffraction (HR-XRD) and atomic force microscopy (AFM). In comparison with undoped AlGaN, the roughness and dislocation density on the surface of the AlGaN layer decrease with Si doping. Full width half maximum (FWHM) of the undoped and Si-doped samples were equal to 0.69° and 0.52°, respectively. This indicates that the Si doping improves the crystalline quality of the AlxGa1?xN layer compared with the undoped one. Raman scattering measurement reveals that the optical phonon modes of A1(LO) and E2(H) of the AlGaN show a one-mode and two-modes behavior, respectively. The Fourier-transform infrared reflectance (FTIR) investigation confirms the one-mode (two-mode) behavior of the LO (TO) phonon in our samples. This is in good agreement with Raman measurement. Finally, the barrier height (ΦB) of undoped and Si-doped AlxGa1?xN samples was found to be 0.86 and 0.74 eV, respectively. 相似文献
63.
S.Abu el Ata-Doss 《Journal of Mathematical Analysis and Applications》1979,72(1):106-113
Control systems governed by linear parabolic evolution partial differential equations in the case of quadratic cost functions are considered. Sensitivity of the performance of the optimal systems to small parameter variations is studied. It is proved that the cost function sensitivity is the same if the optimal control is implemented in open-loop form or in feedbeck form. 相似文献
64.
Detection limits and reduced mobilities for 12 ribonucleotides and 4 ribonucleosides were measured by ambient pressure electrospray ionization-ion mobility spectrometry (ESI-IMS). With the instrument used in this study it was possible to separate some of these compounds within mixtures. Detection limits reported for ribonucleotides and ribonucleosides ranged from 15 to 300 pmol and the reduced mobilities ranged from 41 to 56 suggesting that ambient pressure ESI-IMS may be used for their rapid and sensitive separation and detection. This report demonstrates that it was possible to use ion mobility spectrometry (IMS) to obtain a spectrum for the separation of nucleotides and nucleosides in less than 1 min. The application holds great promise for nucleotide analysis in the area of separating DNA fragments in genome sequencing and also for forensics DNA typing examinations used for the identification of blood stains in crime scenes and paternity testing. 相似文献
65.
Rosa Pereira Tommy Julianto Peh-Kim Ang Sharon Sheue-Nee Ling Carlos Mauricio Barbosa Kah-Hay Yuen Abu Bakar Abdul Majeed 《Chromatographia》2010,71(5-6):373-381
A sensitive and rapid routine LC method was validated for measuring cefotaxime incorporated in three different pH-sensitive nanoparticles. The drug was chromatographed on a C18 reversed-phase column; the mobile phase used was 0.05 M aqueous ammonium acetate, acetonitrile and tetrahydrofuran (87:11:2, v/v) adjusted to pH 5.5 with acetic acid. The flow rate was 1 mL min?1 and cefotaxime was quantified at 254 nm, with a sensitivity range of 0.005 AUFS. The validated method was specific, linear (R 2 ≥ 0.999), precise and accurate in a concentration range of 0.2–50.0 μg mL?1. The method was rapid, selective and suitable for evaluation of cefotaxime in pH-sensitive Eudragit nanoparticles. 相似文献
66.
Ion mobility spectrometry detection for gas chromatography 总被引:2,自引:0,他引:2
The hyphenated analytical method in which ion mobility spectrometry (IMS) is coupled to gas chromatography (GC) provides a versatile alternative for the sensitive and selective detection of compounds after chromatographic separation. Providing compound selectivity by measuring unique gas phase mobilities of characteristic analyte ions, the separation and detection process of gas chromatography-ion mobility spectrometry (GC-IMS) can be divided into five individual steps: sample introduction, compound separation, ion generation, ion separation and ion detection. The significant advantage of a GC-IMS detection is that the resulting interface can be tuned to monitor drift times/ion mobilities (as a mass spectrometer (MS) can be tuned to monitor ion masses) of interest, thereby tailoring response characteristics to fit the need of a given separation problem. Because IMS separates ions based on mobilities rather than mass, selective detection among compounds of the same mass but different structures are possible. The most successful application of GC-IMS to date has been in the international space station. With the introduction of two-dimensional gas chromatography (2D-GC), and a second type of mobility detector, namely differential mobility spectrometry (DMS), GC prior to mobility measurements can now produce four-dimensional analytical information. Complex mixtures in difficult matrices can now be analyzed. This review article is intended to provide an overview of the GC-IMS/DMS technique, recent developments, significant applications, and future directions of the technique. 相似文献
67.
Isothiochromene[3,4‐d] pyrimidine derivatives 2 , 3 , and 4a , b were synthesized from the reaction of 3‐amino‐1‐(pyridin‐4‐yl)‐5‐(pyridin‐4‐ylmethylene)‐5,6,7,8‐tetrahydro‐1H‐isothiochromene‐4‐carbonitrile 1 with acetic anhydride, formamide, urea, or thiourea in appropriate experimental conditions. Combination of 1 with carbon acid derivatives afforded isothiochromene [3,4‐b]pyridine 6 – 8 in good yield. A simple approach for N‐substituted fused isothiochromene derivatives has been explored. A POCl3‐mediated direct amination of isothiochromene amide 2 with NH2‐heterocycles, secondary amines, and carbohydrazides is described and compared with classical method, yielding 10 – 14 . The structures of the newly synthesized compounds were elucidated on the basis of elemental analysis, and spectral data. 相似文献
68.
Abdul Amir H. Kadhum Bilal A. Wasmi Abu Bakar Mohamad Ahmed A. Al-Amiery Mohd S. Takriff 《Research on Chemical Intermediates》2012,38(2):659-668
Environmentally friendly manufacture of organic compounds has been intensively reexamined in recent years. Many excellent methods have been devised to produce organic compounds from renewable resources. Azelaic acid has been produced by ozonolysis of oleic acid. The reaction was performed in a Bach bubbling reactor, with fine bubbles, at high temperature (150 °C) without utilizing any catalyst or any solvent. Yield of the reaction was 20% after 2 h. Production of azelaic acid was confirmed by use of FT-IR and 1H NMR spectroscopic data and high-performance liquid chromatography of both synthesized and reference azelaic acid. A theoretical study was performed to obtain quantum chemical data for azelaic acid and to optimize the molecule’s geometry. 相似文献
69.
G. Schwedt Abu Baker Tawali Kerstin Koch 《Analytical and bioanalytical chemistry》1998,360(5):589-594
After the application of simulated digestive fluids (gastric and intestinale fluid) as extraction solutions, AAS and differential pulse anodic-stripping voltammetry (DPASV) were used as analytical methods in combination with ion-exchange procedures for the determination of zinc species and total zinc contents. The ion exchange procedure and the shifting of electrochemical potentials as well as changes of the calibration slope after standard addition in the polarographic analysis allowed discriminating statements with regard to a possible resorption of zinc. On the basis of these methods, a strategy is presented for in vitro investigations of the bioavailability of zinc in foodstuffs. 相似文献
70.
In the presence of triethylamine, 2-mercaptobenzoic acid readily adds onto acylhydrazonoyl chlorides (1a-c) (precursors of the reactive nitrile imine 1,3-dipolar species) to afford good yields of the corresponding 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto]benzoic acids (2a-c). The latter acyclic adducts, in THF in the presence of 1,1'-carbonyldiimidazole, undergo intramolecular cyclization involving the activated carboxy and the enol functionality to deliver the respective 2-(N-arylhydrazono)-3-oxobenzothiophenes (3a-c). In the solid state, the latter compounds adopt the (Z)-geometry around the C=N double bond as evidenced by single crystal X-ray structure determination for 3b. 相似文献