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排序方式: 共有157条查询结果,搜索用时 12 毫秒
21.
Eslam Badr 《代数通讯》2013,41(10):4327-4340
22.
Mohamed M. Azaam El-Refaie Kenawy Ahmed S. Badr El-din Abeer A. Khamis Mohammed A. El-Magd 《Journal of Saudi Chemical Society》2018,22(1):34-41
In the current study, α-aminophosphonates containing thiadiazole moiety (1–4) was synthesized, characterized and their antioxidant and anticancer activities were carried out. The compounds (1–4) were synthesized from the reaction of 2-amino-5-methyl-1,3,4-thiadiazole with various aldehydes, triphenylphosphite and mixed valence Cu(I)/Cu(II) inorganic coordination polymer as a catalyst. The elucidation of compounds structures were carried out using different spectroscopic techniques. The antioxidant properties were carried out using radical scavenging methods (DPPH) which exhibited excellent scavenging activity particularly with compound 3. The cytotoxic effects of the five compounds on the human hepato cellular carcinoma (HepG2) and breast adeno carcinoma (MCF7) cell lines were evaluated using MTT assay which revealed the presence of cytotoxic effect with highest activity for compound 3 on HepG2 and compound 1 on MCF7. This suggests that these five compounds, particularly compounds 1 and 3, have antioxidant and anticancer effect and could be used as novel chemotherapeutic compounds but this needs further in vivo investigation to confirm our in vitro results. 相似文献
23.
Emara AA El-Sayed BA Ahmed el-SA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(3):757-769
4,6-Diacetylresorcinol (DAR) serves as precursor for the formation of different hydrazone ligands, which are di-, tetra- or hexa-basic with two symmetrical sets of O(2)N tridentate, O(2)N(2) tetradentate or O(4)N(2) hexadentate chelating sites. The condensation of 4,6-diacetylresorcinol (DAR) with oxalyldihydrazine (ODH), in the molar ratio 1:1 and 1:2, yields the corresponding hydrazone, H(6)L(a) and H(4)L(b), ligands, respectively. The structures of these ligands were elucidated by elemental analyses and IR, mass, (1)H NMR and UV-vis spectra. Reactions of the hydrazone ligands with cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), iron(III) and chromium(III) ions in 1:2 molar ratio afforded the corresponding transition metal complexes. A variety of binuclear transition metal complexes were obtained in its di-, tetra- or hexa-deprotonated forms. The structures of the newly prepared complexes were identified by elemental analyses and IR, UV-vis, mass, (1)H NMR and ESR spectra, as well as, magnetic susceptibility measurements and thermal gravimetric analysis (TGA). The bonding sites are the azomethine and CO oxygen atoms in either keto or enol forms and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical structures such as tetrahedral and octahedral arrangements. 相似文献
24.
In this paper, transient and steady natural convection heat transfer
in an elliptical annulus has been investigated. The annulus occupies
the space between two horizontal concentric tubes of elliptic
cross-section. The resulting velocity and thermal fields are
predicted at different annulus orientations assuming isothermal
surfaces. The full governing equations of mass, momentum and energy
are solved numerically using the Fourier Spectral method. The heat
convection process between the two tubes depends on Rayleigh number,
Prandtl number, angle of inclination of tube axes and the geometry
and dimensions of both tubes. The Prandtl number and inner tube axis
ratio are fixed at 0.7 and 0.5, respectively. The problem is solved
for the two Rayleigh numbers of $10^4$ and $10^5$ considering a
ratio between the two major axes up to 3 while the angle of
orientation of the minor axes varies from $0^\circ$ to $90^\circ$. The
results for local and average Nusselt numbers are obtained and
discussed together with the details of both flow and thermal fields.
For isothermal heating conditions, the study has shown an optimum
value for major axes ratio that minimizes the rate of heat transfer
between the two tubes. Another important aspect of this paper is to
prove the successful use of the Fourier Spectral Method in solving
confined flow and heat convection problems. 相似文献
25.
Photoconductivity measurements are carried out in this work for single crystals of Tl4S3 compound by using both pulsed excitation (a.c) and steady state (a.c) methods in order to elucidate the nature of photoconductivity (PC) in this compound. Results are reported in the temperature range from 77 to 300 K, excitation intensity range from 1800 to 3300 Lux, applied voltage range from 8 to 14 V, and wavelength range from 840 to 1450 nm. Both of the ac‐photoconductivity (ac‐PC) and the spectral distribution of the photocurrent are studied at different values of light intensity, applied voltage and temperature. Dependencies of carrier lifetime on light intensity, applied voltage and temperature are also investigated as results of the ac‐PC measurements. By using the results of the dc‐photoconductivity (dc‐PC) measurements, the temperature dependence of the energy gap width is described. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
26.
The purpose of this work is to describe an abstract theory of Hardy-Sobolev spaces on doubling Riemannian manifolds via an atomic decomposition. We study the real interpolation of these spaces with Sobolev spaces and finally give applications to Riesz inequalities. 相似文献
27.
The Tl2S compound was prepared in a single crystal form using a special local technique, and the obtained crystals were analysed
by X-ray diffraction. For the resultant crystals, the electrical properties (electrical conductivity and Hall effect) and
steady-state photoconductivity were elucidated in this work. The electrical measurements extend from 170 to 430 K, where it
was found that σ
⊥ = 8.82 × 10−5 Sm−1 when current flow direction makes right angle to the cleavage plane of the crystals. In the same range of temperatures, it
was found that σ
‖ = 4.73 × 10−5 Sm−1 when the current flow is parallel to the cleavage plane. In line with the investigated range of temperatures, the widths
of the band gaps were calculated and discussed as also the results of the electrical conductivity and Hall effect measurements.
In addition, the anisotropy of the electrical conductivity (σ
⊥/σ
‖) for the obtained crystals was also studied in this work. Finally the photosensitivity was calculated for different levels
of illumination as a result of the photoconductivity measurements, which showed that the recombination process in Tl2S single crystals is a monomolecular process.
相似文献
28.
Nadine Badr 《Potential Analysis》2009,31(4):345-374
We hereby study the interpolation property of Sobolev spaces of order 1 denoted by \(W^{1}_{p,V}\), arising from Schrödinger operators with positive potential. We show that for 1?≤?p 1?p?p 2?q 0 with p?>?s 0, \(W^{1}_{p,V}\) is a real interpolation space between \(W_{p_1,V}^{1}\) and \(W_{p_2,V}^{1}\) on some classes of manifolds and Lie groups. The constants s 0, q 0 depend on our hypotheses. 相似文献
29.
Badr IH 《Analytica chimica acta》2006,570(2):176-185
Metallo-salens of cobalt(II) (Co-Sal), chromium(III) (Cr-Sal), and aluminum(III) (Al-Sal) are used as the active ionophores within plasticized poly(vinyl chloride) membranes. It is shown that central metal-ion plays a critical role in directing the ionophore selectivity. Polymer-membrane electrodes based on Co-Sal, Cr-Sal, and Al-Sal are demonstrated to exhibit enhanced responses and selectivity toward nitrite/thiocyanate, thiocyanate, and fluoride anions, respectively. The improved anion selectivity of the three ionophore systems is shown to deviate significantly from the classical Hofmeister pattern that is based only on ion lipophilicity. For example, optimized membrane electrodes for nitrite ion based on Co-Sal exhibit logK(Nitrite,Anion)(pot) values of -5.22, -4.66, -4.48, -2.5 towards bromide, perchlorate, nitrate, and iodide anions, respectively. Optimized membrane electrodes based on Co-Sal and Cr-Sal show near-Nernstian responses towards nitrite (-57.9+/-0.9 mV/decade) and thiocyanate (-56.9+/-0.8 mV/decade), respectively, with fast response and recovery times. In contrast, Al-Sal based membrane electrodes respond to fluoride ion in a super-Nernstian (-70+/-3 mV/decade) and nearly an irreversible mode. The operative response mechanism of Co-Sal, Cr-Sal, and Al-Sal membrane electrodes is examined using the effect of added ionic sites on the potentiometric response characteristics. It is demonstrated that addition of lipophilic anionic sites to membrane electrodes based on the utilized metallo-salens enhances the selectivity towards the primary ion, while addition of cationic sites resulted in Hofmeister selectivity patterns suggesting that the operative response mechanism is of the charged carrier type. Electron spin resonance (ESR) data indicates that Co(II) metal-ion center of Co-Sal ionophore undergoes oxidation to Co(III). This process leads to formation of a charged anion-carrier that is consistent with the response behavior obtained for Co-Sal based membrane electrodes. 相似文献
30.
Hamacek J Poggiali D Zebret S El Aroussi B Schneider MW Mastalerz M 《Chemical communications (Cambridge, England)》2012,48(9):1281-1283
A new tripodal ligand has been designed by connecting pyridine-based coordination units to a rigid triptycene moiety. Its reaction with europium(III) provides three-dimensional tetranuclear edifices, whose structural and photophysical characteristics as well as host-guest interactions are discussed in this contribution. 相似文献