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21.
H. Hossienkhani V. Fayaz S. A. A. Terohid N. Azimi Z. Zarei M. Ganji 《Theoretical and Mathematical Physics》2018,194(3):415-438
We study a dilaton scalar field coupled to ghost dark energy in an anisotropic universe. The evolution of dark energy, which dominates the universe, can be completely described by a single dilaton scalar field. This connection allows reconstructing the kinetic energy and also the dynamics of the dilaton scalar field according to the evolution of the energy density. Using the latest observational data, we obtain bounds on the ghost dark energy models and also on generalized dark matter and dark energy. For this, we investigate how the expansion history H(z) is determined by observational quantities. We calculate the evolution of density perturbations in the linear regime for both ghost and generalized ghost dark energy and compare the results with ΛCDM models. We discuss the justification of the generalized second law of thermodynamics in a Bianchi type-I universe. The obtained model is stable for large time intervals but is unstable at small times. 相似文献
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Mohammad Zarei Neda Seyedi Shahab Maghsoudi Mohaddeseh Shahabi Nejad Hassan Sheibani 《中国化学会会志》2020,67(11):1992-2003
In this study, graphene oxide was modified during consecutive functionalization steps with 1,4-diphenylamine, cyanuric chloride, and ethylenediamine. Then, star-shaped CuO nanoparticles were synthesized on modified graphene oxide using the seed-mediated growth method in which nucleation, growth stages, and reduction of graphene oxide to graphene occurred simultaneously. After ensuring successful synthesis of CuO nanoparticles and to facilitate recycling, a magnetization process was utilized by adding iron oxide nanoparticles. This nanocomposite was characterized by transmission electron microscopy, X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The prepared heterogeneous catalyst was investigated for the reduction of organic dyes in the presence of NaBH4 as a reducing reagent. The kinetic data obtained for the reduction of methyl orange (MO), methylene blue (MB), 4-nitrophenol (4-NP), and rhodamine 6G (Rh6G) were fitted to first-order rate equations, and the calculated rate constants for the reduction of MO, MB, 4-NP and Rh6G were as follows: −0.091, −0.071, −0.045, and 0.040, respectively. As star-shaped CuO nanoparticles showed a higher antibacterial effect compared to spherical-shaped CuO nanoparticles, the antibacterial activity of star-shaped CuO nanoparticles immobilized on magnetic functionalized graphene was evaluated against Gram-positive and Gram-negative bacteria through an agar well diffusion assay and demonstrated more antibacterial activity against gram-positive bacteria. 相似文献
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In this paper, an electrochemical sensor was prepared based on the modification of pencil graphite electrode (PGE) by hollow platinum nanoparticles/reduced graphene oxide (HPtNPs/rGO/PGE) for determination of ceftazidime (CFZ). Initially, rGO was electrodeposited on the electrode surface, and then, hollow platinum nanoparticles were placed on the electrode surface via galvanic displacement reaction of Pt(IV) ions with cobalt nanoparticles (CoNPs) that had electrodeposited on the electrode surface. Several significant parameters controlling the performance of the HPtNPs/rGO/PGE were examined and optimized using central composite design as one optimization methodology. The surface morphology and elemental characterization of the bare PGE, rGO/PGE, CoNPs/rGO/PGE, and HPtNPs/rGO/PGE-modified electrodes was analyzed by field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical activity of CFZ on resulting modified electrode was investigated by cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV). Adsorptive differential pulse voltammetry indicates that peak current increases linearly with respect to increment in CFZ concentration. CFZ was determined in the linear dynamic range of 5.0 × 10?13 to 1.0 × 10?9 M, and the detection limit was determined as 2.2 × 10?13 M using AdDPV under optimized conditions. The results showed that modified electrode has high selectivity and very high sensitivity. The method was used to determine of CFZ in drug injection and plasma samples. 相似文献
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Zarei M Kirsch S Müthing J Bindila L Peter-Katalinić J 《Analytical and bioanalytical chemistry》2008,391(1):289-297
The coupling of nano high-performance liquid chromatography (nanoHPLC) with matrix-assisted laser desorption/ionization (MALDI)
mass spectrometry (MS) via an automatic spotting roboter was developed and adapted for the first time for the analysis of
complex mixtures of glycosphingolipids (GSLs). The 2,5-dihydroxybenzoic acid and 6-azo-2-thiothymine matrix systems were adjusted
to concurrently meet the requirements for reproducible and homogeneous crystal formation with the liquid chromatography (LC)
eluent under the variable LC solvent composition over the course gradient and high ionization efficiency of the GSL species,
without the need for recrystallization. Precise adjustment of the automatic spotting parameters in terms of matrix flow rate,
on-tip collection time of the matrix/LC eluent solution and the matrix spotting mode, i.e., continuous and discontinuous,
was accomplished to collect individually nanoHPLC-separated species within distinct spots and consequently recover by MALDI
MS screening all major and minor GSL species in the mixtures. The nanoHPLC/MALDI MS coupling protocol was developed and applied
to a mixture of neutral GSLs purified from human erythrocytes and a monosialoganglioside mixture expressed by the murine MDAY-D2
cell line. Additionally, on-line nanoHPLC/MALDI doping with lithium cations of individually separated neutral GSLs was introduced
to enhance data interpretation of the GSL MS pattern, while preserving the same level of information and ultimately to enhance
structural assignment of components of interest. The method is demonstrated to be highly sensitive, reaching the low femtomole
level of detection of individual GSL species and is highlighted as a versatile analytical tool for glycolipidomic studies.
Figure
Automatic LC/MALDI MS profiling of glycosphingolipids
Mostafa Zarei and Stephan Kirsch contributed equally to this work. 相似文献
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A convenient and efficient procedure for the Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P2O5/SiO2 is described. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones. The use of non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields of the products are the advantages of this method. 相似文献
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A. A. Ensafi H. Rahimi Mansour K. Zarei 《Fresenius' Journal of Analytical Chemistry》1999,363(7):646-650
A novel method for the determination of cobalt(II) by stripping voltammetry is described. It involves an adsorptive accumulation
of the cobalt(II)-2-aminocyclopentene-1-dithiocarboxylic acid complex on a hanging mercury drop electrode, followed by a stripping
voltammetric measurement of the catalytic reduction current of the complex at –1.4 V at pH = 9 (vs. Ag/AgCl). The effects
of various experimental parameters on the catalytic current were investigated. An accumulation time of 60 s results in a low
experimental limit of detection of 0.1 ng/mL of Co(II), and 0.50 to 40.0 ng/mL of cobalt can be determined. The relative
standard deviation at 0.50 ng/mL is 2.8%. Possible interferences from co-existing ions were also investigated.
Received: 17 August 1998 / Revised: 16 November 1998 / Accepted: 20 November 1998 相似文献
29.
A number of 2-azetidinones were synthesized in good to excellent yields by a novel reaction between Schiff bases, substituted acetic acids and alkoxymethylene-N,N-dimethyliminium salts, the adduct formed from DMF and O-alkylating agents. The advantages of this new method are mild reaction conditions, low cost, avoiding the use of chlorinating agents and easy purification of the products. The best results were obtained when DMF and dimethyl sulfate were used at room temperature. 相似文献
30.
Modern microfluidic devices are currently introduced in electrospray (ESI) mass spectrometry (MS), tending to substitute the classical capillary-based ESI infusion. Automated systems using the combination of robotized sample handling and chip-based ESI are significantly increasing the analysis reproducibility, precision, throughput, and efficiency. In the last couple of years our group developed the chip-based ESI-MS approach for glycomics in biomedical research and applied it for oligosaccharide, glycopeptide and ganglioside investigation. Here we report upon the optimization and application of this modern technique for the analysis of differential ganglioside expression patterns in human fetal and adult hippocampus. By this methodology, ganglioside species exhibiting high degree of heterogeneity in the ceramide motifs and biologically-relevant modifications could be identified in human hippocampus. The ultra-high reproducibility of the experiments uniquely provided by the chip-ESI approach allowed for a reliable MS-based ganglioside comparative assay. Moreover, the particular feature of chip ESI-tandem MS to provide structural information at high sensitivity was useful for detailed characterization of hippocampus-associated species. The experimental data presented in this study indicate the benefits of microfluidic/MS for determination of the topospecific brain ganglioside composition and development-related changes in their expression, which might be of high value in clinical investigation and for studies related to ganglioside-based therapy of central nervous system diseases. 相似文献