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81.
Hasnaa M. Fahmy Hamed M. Kandel Hamdan A. S. Al-shamiri Nabel A. Negm Ahmed H. M. Elwahy Maram T. H. Abou Kana 《Journal of fluorescence》2018,28(6):1421-1430
Novel 7,7′-((anthracene-9,10-diylbis(methylene))bis(oxy))bis(4-methyl-2H-chromen-2-one) (BisCA) was prepared as fluorescent probe. The chemical structure of the novel BisCA was confirmed by spectroscopic data as well as elemental analyses. The solvatochromic characteristics of the new proble and its precursors were investigated in different solvents including, ethanol, DMF and toluene as protic polar, aprotic polar and non-polar solvents, respectively. Photo-physical parameters of probes, such as fluorescence quantum yields, fluorescence lifetime of excited state, radiative and non-radiative decay, were assessed in different media. The intermolecular H-bond effect on absorption and excitation spectra of the novel probe was reported in different solvents. Also, Onsager cavity radius and dipole moment of ground state and excited state of the probe were calculated as described by Bakhshiev and Reichardt methods. 相似文献
82.
L. Escobar-Alarcón E. Camps S. Romero S. Muhl I. Camps E. Haro-Poniatowski 《Applied Physics A: Materials Science & Processing》2010,101(4):771-775
In this work, we used a crossed plasma configuration where the ablation of two different targets in a reactive atmosphere
was performed to prepare nanocrystalline thin films of ternary compounds. In order to assess this alternative deposition configuration,
titanium carbonitride (TiCN) thin films were deposited. Two crossed plasmas were produced by simultaneously ablating titanium
and graphite targets in an Ar/N2 atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates whilst keeping the ablation
conditions of the Ti target constant. By varying the laser fluence on the carbon target it was possible to study the effect
of the carbon plasma on the characteristics of the deposited TiCN films. The structure and composition of the films were analyzed
by X-ray Diffraction, Raman Spectroscopy and non-Rutherford Backscattering Spectroscopy. The hardness and elastic modulus
of the films was also measured by nanoindentation. In general, the experimental results showed that the TiCN thin films were
highly oriented in the (111) crystallographic direction with crystallite sizes as small as 6.0 nm. It was found that the hardness
increased as the laser fluence was increased, reaching a maximum value of about 33 GPa and an elastic modulus of 244 GPa.
With the proposed configuration, the carbon content could be easily varied from 42 to 5 at.% by changing the laser fluence
on the carbon target. 相似文献
83.
A simple, accurate and highly sensitive spectrophotometric methods are proposed for the rapid and accurate determination of amantadine HCl (AMD) using bromocressol green (BCG), bromophenol blue (BPB) and bromothymol blue (BTB). The developed methods involve formation of stable yellow colored chloroform extractable ion-associate complexes of the amino derivative (basic nitrogen) of the AMD with three sulphonphthalein acid dyes, namely; BCG, BPB and BTB, in acidic medium. The ion-associates exhibit absorption maxima at 415, 412 and 414 nm for BCG, BPB and BTB, respectively. AMD can be determined up to 1.5–16.5, 1.4–14.0 and 1.6–17 μg mL?1, respectively. The effect of optimum conditions via acidity, reagent concentration, time, and solvent was studied. The stoichiometry of the reaction was found to be 1:1 in all cases. The low relative standard deviation values indicate good precision and high recovery values. These methods have been successfully applied for the assay of AMD in pharmaceutical formulations. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision. 相似文献
84.
M.M. El-Nahass Abdul-Basit A. Saleh A.A.A. Darwish M.H. Bahlol 《Optics Communications》2012,285(6):1221-1224
Thin films of InSe were prepared by thermal evaporation technique. The as-deposited films have nano-scale crystalline nature and the annealing enhanced the degree of crystallinity. The optical properties of nanocrystalline thin films of InSe were studied using spectrophotometric measurements of transmittance, T, and reflectance, R, at normal incidence of light in the wavelength range 200–2500 nm. The optical constants (refractive index, n, and absorption index, k) were calculated using a computer program based on Murmann's exact equations. The calculated optical constants are independent of the film thickness. The optical dispersion parameters have been analysed by single oscillator model. The type of transition in InSe films is indirect allowed with a value of energy gap equals to 1.10 eV, which increased to 1.23 eV upon annealing. 相似文献
85.
In this paper, a spectral efficient hybrid wireless optical broadband access network (WOBAN) is proposed and demonstrated based on the transmission of wireless multi-input multi-output orthogonal frequency division multiplexing (MIMO OFDM) signals over wavelength division multiplexing passive optical network (WDM PON). By using radio over fiber (ROF) techniques, the optical fiber is well adapted to propagate multiple wireless services having different carrier frequencies. It is a known fact that multiple wireless signals having the same carrier frequency cannot propagate over a single optical fiber at the same time, such as MIMO signals feeding multiple antennas in fiber wireless (FiWi) system. A novel optical single-sideband frequency translation technique is designed and simulated to solve this problem. This technique allows four pairs of wireless MIMO OFDM signals with the same carrier frequency for each pair to be transmitted over a single optical fiber by using one optical source per wavelength. The crosstalk between the different MIMO channels with the same frequency is eliminated, since each channel is upconverted on specified wavelength with enough channel spacing between them. Also the maximum crosstalk level between the different MIMO channels with different frequencies is very low around ?76 dB. The physical layer performance of the proposed WOBAN is analyzed in terms of the bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR). The proposed WOBAN achieves 7.68 Gb/s data rate for 20 km for the optical back-end and 240 Mb/s for the outdoor wireless front-end. 相似文献
86.
The electron paramagnetic resonance (EPR) and Mössbauer spectra of ironmolybdenum mixed oxides system have been investigated. Both EPR and Mössbauer measurements revealed the formation of ferric molybdate, Fe2 (MoO4)3 and the existence of two different Fe3+ species. The EPR spectra of Fe2 (MoO4)3, show two resonance lines of Fe3+ ions indicating that a strong exchange interaction is dominates in pure iron molybdate. Mösbauer measurements revealed that the isomer shift (I. S) increases with increasing the iron content. A maximum of quadrupole splitting (Q. S) is observed at the stoichiometric concentration corresponding to the formation of Fe2 (MoO4)3. The effect of a catalytaic dehydration process on the redox behaviour of Fe3+ located in iron molybdate frame work is investigated. Results indicate that the catalytaic dehydration of 2-proppanol over this catalyst reduces Fe3+ ions to Fe2+ leading to the formation of the inactive phase FeMoO4. the essential role of oxygen, in the alcohol gas feed, in regeneration the activity of the catalysts was demonstrated. 相似文献
87.
The magnetohydrodynamics flow and heat transfer in a thin liquid film over an unsteady elastic stretching surface are analyzed by the homotopy analysis method. A more general surface temperature is taken into consideration. The effects of various parameters in this study are discussed and presented graphically. The good agreement between the analytic series solutions and the previous numerical results shows the effectiveness of HAM to this problem. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
88.
Shijun Liao 《Communications in Nonlinear Science & Numerical Simulation》2009,14(4):983-997
We describe, very briefly, the basic ideas and current developments of the homotopy analysis method, an analytic approach to get convergent series solutions of strongly nonlinear problems, which recently attracts interests of more and more researchers. Definitions of some new concepts such as the homotopy-derivative, the convergence-control parameter and so on, are given to redescribe the method more rigorously. Some lemmas and theorems about the homotopy-derivative and the deformation equation are proved. Besides, a few open questions are discussed, and a hypothesis is put forward for future studies. 相似文献
89.
90.
《Superlattices and Microstructures》2005,37(2):115-126
Silicon (Si) with dangling bonds that are fully passivated by hydrogen (H) is investigated using the well-known non-self-consistent perturbative pseudopotential method (PPM) of M. Jaros. The role of H atoms is studied from a different point of view compared with previous works: (i) the modifications due to these atoms are calculated according to the Si bulk states, (ii) the gap variations with the Si–H bond length, and (iii) the gap variations with the Si/H band line-ups are investigated. This work is an attempt to shed light qualitatively on the role of hydrogen in the electronic properties of porous silicon (PSi). 相似文献