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71.
Mohamed Mahmoud Nasef Jahanbakhsh Asadi Ebrahim Abouzari-Lotf Arshad Ahmad Reihaneh Malakooti 《Green Chemistry Letters and Reviews》2016,9(1):76-84
Regioselective ring opening of aliphatic and aromatic epoxides with nitrogen heterocycles such as indoles and imidazoles was accelerated using an ultrasonic technique as a green approach. An optimized procedure with the catalyst of choice, MCM-41, represents a real alternative to the conventional reaction protocols owing to the catalyst recyclability, simplicity, green conditions and time-saving aspects. 相似文献
72.
Ebrahim Salehi 《Applications of Mathematics》2016,61(5):565-584
In this paper, we consider the linear and circular consecutive k-out-of-n systems consisting of arbitrarily dependent components. Under the condition that at least n?r+1 components (r ≤ n) of the system are working at time t, we study the reliability properties of the residual lifetime of such systems. Also, we present some stochastic ordering properties of residual lifetime of consecutive k-out-of-n systems. In the following, we investigate the inactivity time of the component with lifetime Tr:n at the system level for the consecutive k-out-of-n systems under the condition that the system is not working at time t > 0, and obtain some stochastic properties of this conditional random variable. 相似文献
73.
Mothi Mohamed Ebrahim Antonia Neels Helen Stoeckli-Evans Krishnaswamy Panchanatheswaran 《Polyhedron》2007
The reaction of mercury(II) halides with 1,2-bis(diphenylphosphino)ethane monoxide (dppeO) in 1:1 molar ratio yielded P,O-coordinated polymers having the empirical formula [HgX2(dppeO)]n [X = Cl (1), Br (2), I (3)]. In contrast, the reaction between the same reactants in a 1:2 molar ratio yielded the P, P-coordinated monomeric complexes, HgX2(dppeO)2[X = Cl (4), Br (5), I (6)]. The structures of 2, 3, 4 and 5 have been characterized crystallographically. The results indicate that the geometry around the mercury atom in each of these molecules is tetrahedral with considerable distortion. The 31P NMR spectra of the 1:1 complexes indicate the dissociation of the Hg–O bond in solution. 相似文献
74.
Let R be a semiprime left Goldie ring with
a monomorphism and
an α-derivation, then
is semiprimitive left Goldie ring. 相似文献
75.
76.
Ebrahim Momoniat 《Acta Mechanica Sinica》2012,28(2):300-307
A third-order ordinary differential equation (ODE) for thin film flow with both Neumann and Dirichlet boundary conditions is transformed into a second-order nonlinear ODE with Dirichlet boundary conditions.Numerical solutions of the nonlinear second-order ODE are investigated using finite difference schemes.A finite difference formulation to an Emden-Fowler representation of the second-order nonlinear ODE is shown to converge faster than a finite difference formulation of the standard form of the second-order nonlinear ODE.Both finite difference schemes satisfy the von Neumann stability criteria.When mapping the numerical solution of the second-order ODE back to the variables of the original third-order ODE we recover the position of the contact line.A nonlinear relationship between the position of the contact line and physical parameters is obtained. 相似文献
77.
Performance enhancement of the power penalty in DWDM FSO communication using DPPM and OOK modulation
Ebrahim Eld. Elsayed Bedir B. Yousif Mahmoud M. Alzalabani 《Optical and Quantum Electronics》2018,50(7):282
This paper presents the design and performance enhancement of the power penalty (PP) in a dense wavelength division multiplexing based on free space optical communication (FSOC) link using digital pulse position modulation (DPPM) and on–off keying (OOK) modulation. Such a system has a high performance, low cost, robust and power efficient, reliable, excessive flexibility, and higher data rate for access networks. The system performance is evaluated for an 8-channel wavelength-division-multiplexing for hybrid fiber FSOC system at 2.5 Gbps on widely accepted modulation schemes under various atmospheric turbulence (AT) regimes conditions. The performance of system is introduced in terms of PP, bit-error rate (BER), transmission distance and the average received optical power. The numerical results shows that the improvement of the PP using DPPM modulation of 0.2–3.0 dB for weak turbulence (WT) regimes for BER of 10?6 and above 20, 25 dB for strong turbulence (ST) regimes are reported for BER of 10?6 and 10?9, as respectively (depending on the AT level). Further, we develop of improvement the PP caused by multiple-access interference about 6.686 dB which is predicted for target BER of 10?9 in WT and 1 dB at target BER of 10?6 in ST when the 8 user are active on the system of optical network units. Additionally, the optical power budget and margin losses of a system are calculated with different link length. The proposed approach of DPPM merges superiority with higher enhancement of PP about 0.8 dB for BER equal 10?9 at FSO link length lfso?=?2000 m compared to OOK at 1 dB for WT. An improvement of 2 dB is observed using the DPPM scheme over an OOK due to capability of detect pulses under background noise conditions with increased receiver sensitivity. 相似文献
78.
Based on the irradiance moment definition and the analytical expression of waveform propagation for hypergeometricGaussian type-Ⅱ beams passing through an ABCD system, the kurtosis parameter is derived analytically and illustrated numerically. The kurtosis parameters of the Gaussian beam, modified Bessel modulated Gaussian beam with quadrature radial and elegant Laguerre–Gaussian beams are obtained by treating them as special cases of the present treatment. The obtained results show that the kurtosis parameter depends on the change of the beam order m and the hollowness parameter p, such as its decrease with increasing m and increase with increasing p. 相似文献
79.
Ladan Rashidi Ebrahim Vasheghani-Farahani Masoud Soleimani Amir Atashi Khosrow Rostami Fariba Gangi Masoud Fallahpour Mohammad Taher Tahouri 《Journal of nanoparticle research》2014,16(3):1-14
In this study, the effects of intracellular delivery of various concentrations of gallic acid (GA) as a semistable antioxidant, gallic acid-loaded mesoporous silica nanoparticles (MSNs-GA), and cellular uptake of nanoparticles into Caco-2 cells were investigated. MSNs were synthesized and loaded with GA, then characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, N2 adsorption isotherms, X-ray diffraction, and thermal gravimetric analysis. The cytotoxicity of MSNs and MSNs-GA at low and high concentrations were studied by means of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test and flow cytometry. MSNs did not show significant toxicity in various concentrations (0–500 μg/ml) on Caco-2 cells. For MSNs-GA, cell viability was reduced as a function of incubation time and different concentrations of nanoparticles. The in vitro GA release from MSNs-GA exhibited the same antitumor properties as free GA on Caco-2 cells. Flow cytometry results confirmed those obtained using MTT assay. TEM and fluorescent microscopy confirmed the internalization of MSNs by Caco-2 cells through nonspecific cellular uptake. MSNs can easily internalize into Caco-2 cells without deleterious effects on cell viability. The cell viability of Caco-2 cells was affected during MSNs-GA uptake. MSNs could be designed as suitable nanocarriers for antioxidants delivery. 相似文献
80.
Spin-polarized transport through an Aharonov–Bohm (AB) semiconductor mesoscopic ring is investigated in the presence of both the Rashba spin–orbit interaction (RSOI) and the Dresselhaus spin–orbit interaction (DSOI). The ring symmetrically bridges two input and output electrodes. Based on tight-binding model and Green?s function formalism, we find that for AB fluxes other than integer or half-integer multiples of the flux quanta the ring acts as a spin selective device with unit efficiency only when the difference between strengths of RSOI and DSOI is nonzero and small. Results of this study can be used to design a nonmagnetic-material-based perfect spin filter. 相似文献