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排序方式: 共有181条查询结果,搜索用时 31 毫秒
1.
Binary and ternary mixtures of alpha-tocopherol (alphaT), cholesterol and dipalmitoyl phosphatidylcholine (DPPC) in the form of multilamellar liposomes have been investigated by Fourier Transform Infrared Spectroscopy (FTIR). Investigation of frequencies, bandwidths and band shapes of CH(2) stretching and scissoring bands indicate that the effect of alphaT is dominant in comparison with cholesterol and alphaT decreases the interaction of cholesterol with phospholipid membranes. 相似文献
2.
A new Schiff base, N,N′-bis-(2-hydroxy-5-bromobenzyl)-2-hydroxy-1,3-diiminopropane, has been synthesized for the very sensitive
determination of iron(III) and iron(II) in natural water samples. It enabled a very selective and rapid method for iron determination
to be developed. The method has also been applied to total iron determination in sediment samples. In the preconcentration
system, the Schiff base reagent is mixed with the samples and chelates containing iron(III). The complexes are then adsorbed
on silica gel within a column system. Elution of the adsorbed chelate from the silica gel was performed with a small volume
of acetone containing 2.5% nitric acid. The iron is measured off-line by flame atomic absorption spectrometry. The method
can be applied to the preconcentration, separation and speciation of iron. The effects of parameters such as pH, sample flow
rate, eluent flow rate, foreign ions and ligand concentration have been investigated. The effect of humic acid that can produce
complexes with metal ions in natural systems has also been investigated. The results obtained indicate that the method is
not affected by the presence of up to 10 ppm humic acid, which would be a very high concentration to be present in natural
systems. The solid phase extraction method developed has been applied to the determination of iron in both natural water samples
and sediment samples. The LOD was found to be 0.17 mg L−1 when no preconcentration was used, although preconcentration factors of 100 could be achieved. The recovery values for spiked
samples were between 100 and 104%. The results were compared statistically with those from the standard 1,10 phenanthroline
method used for iron speciation in water systems. A Student’s t-test indicated no significant difference between the two methods. In addition, this method was applied to the analysis of
a certified sediment sample, LGC 6156. Generally, a 10-fold preconcentration factor was required for the analysis of natural
water samples. 相似文献
3.
Emel Önal Cheng Zhang Derya Davarcı Ümit İşci Guillaume Pilet Andrew K. Whittaker Fabienne Dumoulin 《Tetrahedron letters》2018,59(6):521-523
A cyclotriphosphazene substituted with six 3,5-bis(trifluoromethyl) benzyloxy units was designed as a novel 19F MRI contrast agent. The resulting molecule has 36 magnetically equivalent fluorine atoms and exhibited suitable MRI properties with high imaging sensitivity, confirming the proof-of-concept as a convenient scaffold for the production of new 19F MRI contrasts agents. 相似文献
4.
5.
We construct a representation of the infinite dimensional complex Clifford algebra on the Hilbert space of square-integrable
complex-valued functions on the Cantor set, which we show to be equivalent to the classical Fock representation. 相似文献
6.
Avcıbaşı Uğur Türkyarar Taner Karadağ Ayşegül Bakan Buket Yavaşoğlu Nefise Ülkü Karabay Kuşat Kevser Akgöl Sinan Gülcemal Derya Tekin Volkan Müftüler Fazilet Zümrüt Biber Topal Gökcen Parlak Yasemin Gümüşer Fikriye Gül 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(2):511-525
Journal of Radioanalytical and Nuclear Chemistry - The aim of this study is the synthesis of a novel 99mTc-labeld graft polymer and the biological evaluation of its in vitro and in vivo properties.... 相似文献
7.
Derya Tarinc Burcu Dogan-Topal Aysegul Golcu Sibel A. Ozkan 《Journal of Analytical Chemistry》2014,69(9):899-908
A voltammetric study of the oxidation of Ceftazidime (CEFT) has been carried out at the glassy carbon electrode by cyclic, differential pulse (DPV) and square wave (SWV) voltammetry. The oxidation of CEFT was irreversible and exhibited diffusion controlled process depending on pH. The oxidation mechanism was proposed and discussed. According to the linear relationship between the peak current and concentration, DPV and SWV voltammetric methods for CEFT assay in pharmaceutical dosage forms and human urine were developed. For analytical purposes, a well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H2SO4 at 1.00 and 1.02 V for differential pulse and square wave voltammetric techniques, respectively. The linear response was obtained within the range of 4 × 10?6?8 × 10?5 M with a detection limit of 6 × 10?7 M for differential pulse and 4 × 10?6–2 × 10?4 M with a detection limit of 1 × 10?6 M for square wave voltammetric technique. The determination of CEFT in 0.1 M H2SO4 was possible over the 2 × 10?6–1 × 10?4 M range in urine sample for both techniques. The standard addition method was used for the recovery studies. 相似文献
8.
A new borophosphate compound with the composition (NH4) χ Mn((3?χ)/2)(H2O)2 [BP2O8]·(1?x)H2O was prepared under mild hydrothermal conditions and characterized by X-ray powder diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) methods. The title compound was synthesized from MnCl2·2H2O, H3BO3, and (NH4)2HPO4 with variable molar ratios by heating at 180 °C for 7 days in an autoclave. The X-ray diffraction data of the water insoluble polycrystalline powder was indexed using the TREOR program in hexagonal system with the unit cell parameters of a = 9.5104, c = 15.7108 Å, Z = 6 and the space group P65 (No.176). (NH4) χ Mn((3?χ)/2)(H2O)2 [BP2O8]·(1?x)H2O is isostructural with (NH4) χ M ((3?χ) 2)/II (H2O)2 [BP2O8]·(1?x)H2O (MII = Co, Cd, Mg; x = 0.5–1). Its unit cell parameters and hkl values were in good agreement with the other isostructural compounds. This is the first report presenting both the synthetic details and the indexed X-ray powder diffraction pattern of this compound along with the characterization by FTIR, thermal gravimetric analysis, scanning electron microscopy and EPR. 相似文献
9.
We present a method for the fabrication of PVTri-BaFe12O19 nanocomposites by in-situ polymerization of PVTri in the presence of synthesized BaFe12O19 nanoparticles. Nanoparticles, polymer and nanocomposite were analyzed by XRD, FTIR, TGA, TEM, NMR, GPC and conductivity techniques for structural and physicochemical characteristics. Crystallographic analysis revealed the phase as hexaferrite and X-ray line profile fitting yielded a crystallite size of 17±5 nm. Conjugation of PVTri to nanoparticle surface was assessed to be via carbonyl groups on the polymer. TG analysis revealed that 45 wt% of nanocomposite is inorganic phase (BaFe12O19). It was found out that the ac conductivity of nanocomposite under a certain frequency increases with temperature. 相似文献
10.
The propagation of phase-locked and non-phase-locked laser array beams of radial and rectangular symmetries in a turbulent
atmosphere are investigated based on the extended Huygens–Fresnel integral. The beamlet used in our paper for constructing
the laser array beams is of elliptical Gaussian mode. Analytical formulae for the average irradiance of phase-locked and non-phase-locked
radial and rectangular laser array beams are derived through vector integration and tensor operation. The irradiance properties
of these laser array beams in a turbulent atmosphere are studied numerically. It is found that both phase-locked and non-phase-locked
radial and rectangular laser array beams eventually become circular Gaussian beams in a turbulent atmosphere, which is much
different from their propagation properties in free space. The propagation properties are closely related to the parameters
of laser array beams and the structure constant of the turbulent atmosphere.
PACS 42.25.Bs; 41.85.Ew; 42.68.Ay 相似文献