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1.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities. 相似文献
2.
3.
We consider the isothermal flow through a cylindrical flat chamber, a model of some particular heat exchanger, for which LDV measurements and a numerical simulation have been performed. Experimental results show the establishment of an important vortex zone, the secondary flow extending all along the chamber radius. This observation leads to an expected significant increase of the fluid mixing. Results issued from the numerical simulation appear to be in close agreement with experimental data. Nevertheless, the k–ε model used here must be improved to obtain a better approach near the vortex centre. To cite this article: S. Petitot et al., C. R. Mecanique 330 (2002) 593–599. 相似文献
4.
Abdel Raouf F. Elhefnawy Galal M. Moatimid Abd Elmonem Khalil Elcoot 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,86(2):63-91
The nonlinear electrohydrodynamic stability of
cylindrical interface, supporting surface charge, among two
conducting fluids is investigated. The two fluids are subjected to
a radial electric field. The analysis based on the multiple scale
technique. It is shown that the evolution of the amplitude is
governed by two partial differential equations. These equations
are combined to yield two alternate Schrödinger equations with
cubic nonlinearity. One of which calculates the nonlinear cutoff
electric field, separating stable and unstable disturbances, while
the other is used to analyze the stability of the system. The
stability criteria are analytically discussed and numerically
confirmed. Numerical calculations resulted in set of graphs to
indicate the stability picture of the considered system. 相似文献
5.
Abdel Raouf F. Elhefnawy 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1993,44(3):495-509
A weakly nonlinear evolution of two dimensional wave packets on the surface of a magnetic fluid in the presence of an uniform magnetic field is presented, taking into account the surface tension. The method used is that of multiple scales to derive two partial differential equations. These differential equations can be combined to yield two alternate nonlinear Schrödinger equations. The first equation is valid near the cutoff wavenumber while the second equation is used to show that stability of uniform wave trains depends on the wavenumber, the density, the surface tension and the magnetic field. At the critical point, a generalized formulation of the evolution equation governing the amplitude is developed which leads to the nonlinear Klein-Gordon equation. From the latter equation, the various stability crteria are obtained. 相似文献
6.
F. El Akkad H. F. Ragaie M. Abdel Naby 《Applied Physics A: Materials Science & Processing》1989,48(5):493-495
Zn
x
Cd1–x
S thin films (0x0.20) were prepared using rf sputtering in argon atmosphere and characterized using X-ray diffraction, optical transmission, electrical resistivity and photoconductive decay measurements. The films were found to possess hexagonal structure. The crystallite size and degree of preferential orientation were found to decrease with the increase ofx and to improve upon annealing in vacuum at 250 °C. The transmission edge shifted towards shorter wavelengths with the increase ofx in agreement with the expected shift in the energy band gap. The films were found to exhibit room temperature resistivity in the range 100–1000 cm. The obtained values of long wavelength transmission (70–80%) and minority carrier diffusion length (30 m) are high enough for the application of these films in the field of solar cells. 相似文献
7.
Abdel -Aziz M. Wahbi Mona M. Bedair Shereen M. Galal Mohamed H. Abdel-Hay Azza A. Gazy 《Mikrochimica acta》1993,111(1-3):83-91
A sensitive and rapid Spectrofluorimetric method for the determination of guanethidine sulphate, guanfacine hydrochloride, guanoclor sulphate and guanoxan sulphate in tablets and spiked human serum and urine samples is described. The method is based on the reaction of monosubstituted guanidino compounds in an aqueous potassium hydroxide solution with benzoin, in the presence of -mercaptoethanol and sodium sulphite. Highly fluorescent derivatives were obtained, with excitation and emission maximum wavelengths around 325 and 430 nm, respectively. In optimal reaction conditions, the linearity ranges were 0.04–0.28 g/ml, with relative standard deviations less than 2%. The method has been successfully applied to the determination of these drugs in tablets. The results are highly correlated with the B.P. method. Chloroform (or for guanoxan dichloromethane) was used to extract the drugs from serum and urine at basic pH, followed by the proposed fluorimetric method. The limit of detection is 0.02 g/ml for the selected drugs. 相似文献
8.
Nagwa Rashed Abdel Moneim El Massry El Sayed H. El Ashry Adel Amer Hans Zimmer 《Journal of heterocyclic chemistry》1990,27(3):691-694
A series of 1-aryl-s-triazolo[4,3-a]quinoxalin-4-ones, 3 , were synthesized via the pyrolysis of the corresponding hydrazones, 6 . Thus, the cyclodehydrogenation occurred by refluxing them in an inert solvent (e.g. ethylene glycol) to give the triazoloquinoxalin-4-ones in a satisfactory yield. Using DMSO as a solvent for the above transformation afforded as a minor by-product an S-ylid. In contrast to earlier findings, annelation of a six-membered ring was successful and achieved through the pyrolysis of the pyruvate hydrazones derived of the quinoxalin-4-ones at ?230° to give the as-triazino[4,3-a]quinoxalin-5-ones, 4 . The reaction of 5 with acetylacetone afforded 3-(3′,5′-dimethylpyrazol-1-yl)-2(1H)-quinoxalinone, 10 . The structural assignments for the new compounds were based on their elemental analysis and spectroscopic data as well as an independent synthesis. 相似文献
9.
D. Fennell Evans Martin Allen B. W. Ninham Abdel Fouda 《Journal of solution chemistry》1984,13(2):87-101
Critical micelle concentrations were determined by conductance measurements for decyl-, dodecyl-, tetradecyl- and hexadecyltrimethylammonium bromide in water at 25, 60, 95, 130, and 160°C. The results are discussed in terms of the equilibrium model and the nonlinear Poisson-Boltzmann model for micelle formation. The free energies of transferring a methylene group from water to the oil-like interior of the micelle are found to be –781 at 25°C, –796 at 60°C, –819 at 95°C, –815 at 130°C, and –787 at 160°C cal-mol–1. 相似文献
10.
Abdel Raouf F. Elhefnawy 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1995,46(2):239-254
The nonlinear evolution of interfacial waves separating two magnetic fluids subjected to an oblique magnetic field is studied in two dimensions, with the use of the method of multiple scales. It is shown that the evolution of the envelope is governed by two partial differential equations. These equations can be combined to yield two alternate Schrödinger equations with cubic nonlinearity; one of them leads to the determination of the cutoff wave number separating stable from unstable deformations while the other Schrödinger equation is used to analyze the stability of the system. The stability of the system is discussed both theoretically and computationally, and the stability diagrams are obtained. It is found in the linear theory that the oblique magnetic field has a stabilizing influence if 0 1 + 2 < /2, or 3/2 < 1 + 2 2 and a destabilizing influence if /2 < 1 + 2 < 3/2, where 0 j
, (j=1, 2) and , is the angle between the field and the horizontal axis.In the nonlinear theory, the stability analysis reveals that there exist different regions of stability and instability. It is reported that the oblique magnetic field plays a dual role in the stability criterion and the angles 1 and 2 play a distinctive role in this analysis besides the effect of the variation of the magnetic permeabilities. 相似文献