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排序方式: 共有185条查询结果,搜索用时 15 毫秒
81.
82.
Nima Khosravi Hamid Reza Sepangi Babak Vakili 《General Relativity and Gravitation》2010,42(5):1081-1102
We employ the familiar canonical quantization procedure in a given cosmological setting to argue that it is equivalent to
and results in the same physical picture if one considers the deformation of the phase-space instead. To show this we use
a probabilistic evolutionary process to make the solutions of these different approaches comparable. Specific model theories
are used to show that the independent solutions of the resulting Wheeler–DeWitt equation are equivalent to solutions of the
deformation method with different signs for the deformation parameter. We also argued that since the Wheeler–DeWitt equation
is a direct consequence of diffeomorphism invariance, this equivalence is only true provided that the deformation of phase-space
does not break such an invariance. 相似文献
83.
84.
Hakimeh Sharafi Mahya Abdoli Hamidreza Hajfarajollah Nima Samie Leila Alidoust Habib Abbasi Jamshid Fooladi Hossein Shahbani Zahiri Kambiz Akbari Noghabi 《Applied biochemistry and biotechnology》2014,173(5):1236-1249
A biosurfactant-producing thermophile was isolated from the Kahrizak landfill of Tehran and identified as a bacterium belonging to the genus Aneurinibacillus. A thermostable lipopeptide-type biosurfactant was purified from the culture medium of this bacterium and showed stability in the temperature range of 20–90 °C and pH range of 5–10. The produced biosurfactant could reduce the surface tension of water from 72 to 43 mN/m with a CMC of 1.21 mg/mL. The strain growing at a temperature of 45 °C produces a substantial amount of 5 g/L of biosurfactant in the medium supplemented with sunflower oil as the sole carbon source. Response surface methodology was employed to optimize the biosurfactant production using sunflower oil, sodium nitrate, and yeast extract as variables. The optimization resulted in 6.75 g/L biosurfactant production, i.e., 35 % improved as compared to the unoptimized condition. Thin-layer chromatography, FTIR spectroscopy, 1H-NMR spectroscopy, and biochemical composition analysis confirmed the lipopeptide structure of the biosurfactant. 相似文献
85.
Nabil Vaeli Nadia Esfandiari Zahra Arab Aboosadi 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2019,25(3):261-283
The experimental feasibility of extracting carvacrol or cymophenol from local and medicinal Oliveria decumbens by supercritical carbon dioxide through using ultrasound waves was investigated in this study. The extraction modelling was carried out in two forms: Internal and external. The internal model was adopted to simulate the concentration distribution of the phytochemicals in the plant particles. In this model, the extracted cell was assumed to be a filled substrate and two mechanisms of molecular permeability and mass transfer had the greatest effect. The comparison of the experimental data obtained from modelling revealed that both the internal and external models are compatible with the experimental data as much as 80%, indicating an acceptable accuracy. Furthermore, the empirical data is completely in line with the model at the final time (40 min), which is the time to reach the equilibrium. 相似文献
86.
Ionics - A ferrocene-derivative compound, 2, 7-bis (ferrocenyl ethynyl) fluoren-9-one (2,7-BFE), was synthesized and used to construct a modified graphene paste electrode. The electrooxidation of... 相似文献
87.
基于纳米结构的电化学传感器用于伏安法测定苄丝肼、尿酸和叶酸(英文) 总被引:1,自引:0,他引:1
Sakineh Esfandiari Baghbamidi Hadi Beitollahi Seyed Zia Mohammadi Somayeh Tajik Somayeh Soltani-Nejad Vahhab Soltani-Nejad 《催化学报》2013,34(10):1869-1875
A carbon paste electrode modified with carbon nanotubes and ferrocene was fabricated.An electrochemical study of the modified electrode and an investigation into its efficiency for the electrocatalytic oxidation of benserazide,uric acid and folic acid were undertaken.The electrode was also used to study the electrocatalytic oxidation of benserazide using cyclic voltammetry,chronoamperometry,and square wave voltammetry(SWV).We found that the oxidation of benserazide at the surface of the modified electrode occurs at a potential about 285 mV lower than that of unmodified carbon paste electrode.SWV gave a linear dynamic range from 8.0×10-7 to 7.0×10 4 mol/L.The detection limit was 1.0×10-7 mol/L for benserazide.This modified electrode was used for the determination of benserazide,uric acid,and folic acid in an urine sample. 相似文献
88.
Masoud Rahman Dr. Fariba Tajabadi Leyla Shooshtari Dr. Nima Taghavinia 《Chemphyschem》2011,12(5):966-973
Hollow structures show both light scattering and light trapping, which makes them promising for dye‐sensitized solar cell (DSSC) applications. In this work, nanoparticulate hollow TiO2 fibers are prepared by layer‐by‐layer (LbL) self‐assembly deposition of TiO2 nanoparticles on natural cellulose fibers as template, followed by thermal removal of the template. The effect of LbL parameters such as the type and molecular weight of polyelectrolyte, number of dip cycles, and the TiO2 dispersion (amorphous or crystalline sol) are investigated. LbL deposition with weak polyelectrolytes (polyethylenimine, PEI) gives greater nanoparticle deposition yield compared to strong polyelectrolytes (poly(diallyldimethylammonium chloride), PDDA). Decreasing the molecular weight of the polyelectrolyte results in more deposition of nanoparticles in each dip cycle with narrower pore size distribution. Fibers prepared by the deposition of crystalline TiO2 nanoparticles show higher surface area and higher pore volume than amorphous nanoparticles. Scattering coefficients and backscattering properties of fibers are investigated and compared with those of commercial P25 nanoparticles. Composite P25–fiber films are electrophoretically deposited and employed as the photoanode in DSSC. Photoelectrochemical measurements showed an increase of around 50 % in conversion efficiency. By employing the intensity‐modulated photovoltage and photocurrent spectroscopy methods, it is shown that the performance improvement due to addition of fibers is mostly due to the increase in light‐harvesting efficiency. The high surface area due to the nanoparticulate structure and strong light harvesting due to the hollow structure make these fibers promising scatterers in DSSCs. 相似文献
89.
A high-sensitivity and high-resolution single-particle fluorescence microscopy technique differentiated between homogeneous and heterogeneous metathesis polymerization catalysis by imaging the location of the early stages of polymerization. By imaging single polymers and single crystals of Grubbs II, polymerization catalysis was revealed to be solely homogeneous rather than heterogeneous or both. 相似文献
90.
The subensemble kinetics of a platinum-sulfur covalent chemical reaction at the solution/surface interface of a model industrial catalyst support was examined using single-molecule fluorescence microscopy (SMFM) and was found to exhibit biexponential first-order kinetic behavior. The observed kinetics was a convolution of the observation probability and chemical reaction rate. These results suggest that deconvolution strategies may be broadly important for obtaining accurate chemical reaction kinetics with SMFM. 相似文献