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41.
Old Egyptian pottery samples have been in-depth microchemically analyzed using laser induced breakdown spectroscopy (LIBS), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) techniques. Samples from two different ancient Islamic eras, Mamluk (1250–1517 AD), Fatimid (969–1169 AD) in addition to samples from the Roman period (30 BC–395 AD) were investigated. LIBS provided the analytical data necessary to study in micrometric steps the depth profiling of various elements in each sample. Common elements such as silicon, calcium, and aluminum relevant to the originally manufactured and processed clay, showed up in all the investigated samples. EDX and XRD techniques that have been used in the present work provided important chemical insight about the structure of the samples. The obtained analytical results demonstrated the possibility of using LIBS technique in performing in situ spectrochemical analysis of archaeological pottery. This leads to fast in-depth spatial characterization of the samples in the micron range with nearly invisible surface destructive effects. There is no doubt that this can help in restoration and conservation of such precious objects. 相似文献
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Saad F. A. El-Metwaly N. M. Refat M. S. Khedr A. M. 《Russian Journal of General Chemistry》2018,88(6):1258-1265
Russian Journal of General Chemistry - Here we report the studies on selenium coordination compounds, in particular selenium nanoparticles (Nps), that can be used in pharmacology. The Se Nps were... 相似文献
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The synthesis and characterization of new transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3‐(2‐hydroxynaph‐1‐ylazo)‐1,2,4‐triazole ( HL1 ) and 3‐(2‐hydroxy‐3‐carboxynaph‐1‐ylazo)‐1,2,4‐triazole ( HL2 ) have been carried out. Their structures were confirmed by elemental analyses, thermal analyses, spectral and magnetic data. The IR and 1H NMR spectra indicated that HL1 and HL2 coordinated to the metal ions as bidentate monobasic ligands via the hydroxyl O and azo N atoms. The UV‐Vis, ESR spectra and magnetic moment data revealed the formation of octahedral complexes [Mn L1 (AcO)(H2O)3] ( 1 ), [Co L1 (AcO)(H2O)3]·H2O ( 2 ), [Mn L2 (AcO)(H2O)3] ( 6 ) and [Co L2 (AcO)(H2O)3] ( 7 ), [Ni L1 (AcO)(H2O)] ( 3 ), [Zn L1 (AcO)(H2O)]·H2O ( 5 ), [Ni L2 (AcO)(H2O)] ( 8 ), [Zn L2 (AcO)(H2O)]·10H2O ( 10 ) have tetrahedral geometry, whereas [Cu L1 (AcO)(H2O)2] ( 4 ) and [Cu L2 (AcO)(H2O)2]·5H2O ( 9 ) have square pyramidal geometry.. The mass spectra of the complexes under EI‐con‐ ditions showed the highest peaks corresponding to their molecular weights, based on the atomic weights of 55Mn, 59Co, 58Ni, 63Cu and 64Zn isotopes; besides, other peaks containing other isotopes distribution of the metal. Kinetic and thermodynamic parameters of the thermal decomposition stages were computed from the thermal data using Coats‐Redfern method. HL2 and complexes 6 – 10 were found to have moderate antimicrobial activities against Staphylococcus aureus (gram positive), Escherichia coli (gram negative) and Salmonella sp bacteria, and antifungal activity against Fusarium oxysporum, Aspergillus niger and Candida albicans. Also, in most cases, metallation increased the activity compared with the free ligand. 相似文献
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合成了9种3-(2-羟基萘基-1-偶氮)-1,2,4-三氮唑(HL1),3-(2,4-二羟苯基-1-偶氮)-1,2,4-三氮唑(HL2),3-(2-羟基-3-羧基萘基-1-偶氮)-1,2,4-三氮唑(HL3),3-(2-羟基-5-溴苯基-1-偶氮)-1,2,4-三氮唑(HL4)和3-(2-羟基-5-甲基苯基-1-偶氮)-1,2,4-1,2,4-三氮唑(HL5)的Zr(Ⅱ)配合物并用元素分析,摩尔电导,磁矩,IR,UV-Vis,1H-NMR以及热分析(TGA和DTA)对其进行了表征。结果表明HL1-HL5以二齿一元配体方式通过偶氮的氮原子和羟基基团的氧原子与Zr(Ⅱ)离子配位生成单核配合物。用4种革兰氏阴性菌,即大肠杆菌(Escherichia coli),粘质沙雷氏菌(Serratia marcescens),阴沟肠杆菌(Enterobacter cloacae)和普通变形杆菌(Proteus vulgaris),以及2种真菌,即白色念珠菌(Candida albicans)和黑曲霉菌(Aspergillus niger)对配体及其配合物的生物学活性进行了研究。最小抑菌浓度(MICs)用纸上杯碟琼脂扩散法测定,结果表明在大多数情况下,金属化的配合物的抗微生物活性与自由配体相比有所增强。 相似文献
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Wireless Broadband Cognitive Networks (WBCN) are new trend to better utilization of spectrum and resources. However, in multiservice WBCN networks, call admission control (CAC) is a challenging point to effectively control different traffic loads and prevent the network from being overloaded and thus provide promised quality of service. In this paper, we propose a CAC framework and formulate it as an optimization problem, where the demands of both WBCN service providers and cognitive subscribers are taken into account. To solve the optimization problem, we developed an opportunistic multivariate CAC algorithm based on a joint optimization of utility, weighted fairness, and greedy revenue algorithms. Extensive simulation results show that, the proposed call admission control framework can meet the expectations of both service providers and subscribers in wireless broadband cognitive networks. 相似文献
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M. Bahgat A.A. FarghaliW.M.A. El Rouby M.H. Khedr 《Journal of Analytical and Applied Pyrolysis》2011,92(2):307-313
Synthesis of MWCNTs by chemical vapor deposition (CVD) of acetylene is investigated at different temperatures. Fe-Co/CaCO3 catalyst/support prepared by wet impregnation method is used. CaCO3 was found to be a good support as a high selective material for deposition of CNTs with high purity. The effect of temperature on catalyst/support phases and crystal size was identified by using XRD. The crystallite size was decreased with increase temperature. The effect of growing time and temperature on carbon yield was studied and the deposited MWCNTs increased with temperature. The structure and purity of synthesized CNTs at different temperatures was examined by TEM and the effect of temperature on the surface area of the synthesized MWCNTs was investigated, the surface area decreased as the temperature increased. The prepared CNTs were purified using chemical oxidation method and the effect of acid treatment on CNTs surface was examined by TEM and SEM. The function groups produced at CNTs surface were investigated by using FTIR spectroscopy also the effect of CNTs preparation temperature on FTIR spectra was studied. The functionalized CNTs were used for adsorption of some heavy metals and for removal of some organic dyes from water. 相似文献
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Abdalla M. Khedr Morsi M. Abou-Sekkina Fouad G. El-Metwaly 《Journal of Electronic Materials》2013,42(6):1275-1281
Spinel lithium manganese oxide and a series of Sm/LiMn2O4 spinels with different Sm additive contents (x = 0.02%, 0.05%) were prepared for the first time via a coprecipitation method for rechargeable lithium-ion batteries. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive analysis of x-rays (EDAX), infrared (IR), and electron spin resonance spectral studies as well as various electrochemical measurements were used to examine the structural and electrochemical characteristics of LiMn2?x Sm x O4 (x = 0.00%, 0.02%, 0.05%). XRD and SEM studies confirmed the nano materials size for all prepared spinels. From cyclic voltammetry studies, in terms of peak splitting, electrochemical active surface area, and intensity of the peaks, the LiMn1.98Sm0.02O4 sample possesses better electrochemical performance compared with the LiMn1.95Sm0.05O4 sample. Hence, limited addition of a rare-earth dopant is preferable to obtain better efficiency. Direct-current (DC) electrical conductivity measurements indicated that these samples are semiconducting and their activation energies decrease with increasing rare-earth Sm3+ content. 相似文献
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Abu-Eittah RH Khedr MK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,71(5):1688-1694
The electronic absorption spectra of: 2-, 3-, and 4-azidopyridines have been investigated in a wide variety of polar and non-polar solvents. According to Onsager model, the studied spectra indicate that the orientation polarization of solvent dipoles affects the electronic spectrum much stronger than the induction polarization of solvent dipoles. The effect of solvent dipole moment predominates that of solvent refractive index in determining the values of band maxima of an electronic spectrum. The spectra of azidopyridines differ basically from these of pyridine or mono-substituted pyridine. Results at hand indicate that the azide group perturbs the pyridine ring in the case of 3-azidopyridine much more than it does in the case of 2-azidopyridine. This result agrees with the predictions of the resonance theory. Although the equilibrium <==> azide tetrazole is well known, yet the observed spectra prove that such an equilibrium does not exist at the studied conditions. The spectra of the studied azidopyridines are characterized by the existence of overlapping transitions. Gaussian analysis is used to obtain nice, resolved spectra. All the observed bands correspond to pi-->pi* transitions, n-->pi* may be overlapped with the stronger pi-->pi* ones. 相似文献
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K.S. Abdel Halim M.H. Khedr A.H. Zaki 《Journal of Analytical and Applied Pyrolysis》2007,80(2):346-352
Ferrites have continued to attract attention over years. As magnetic materials, ferrites cannot be replaced by any other magnetic material because they are relatively inexpensive, stable and have a wide range of technological applications in transformer core, high quality filters, high frequency circuits and operating devices. Nanocrystallite sizes of Cu0.5 Zn0.5Fe2O4 with 25 nm have been obtained by hydrothermal route. Cu0.5Zn0.5Fe2O4 powder was isothermally reduced in H2 flow at 400–600 °C. The reduction behavior of the produced powder as well as the influence of reduction temperature on the structural characteristics of the products was extensively studied. Microstructure of partially and completely reduced samples was investigated and the activation energy values were calculated from Arrhenius equation. The activation energy for nanocrystallite Cu0.5 Zn0.5Fe2O4 reduced at the initial stage was found to be 37.4 kJ/mole, while that at the final stage is 14 kJ/mole. The approved mathematical formulations for the different crystallite sizes gas solid reaction were applied and it was found that at the final stages the reaction is controlled by the gaseous diffusion while the combined gaseous diffusion and interfacial chemical reaction is the rate controlling mechanisms at the initial stages. The reduction process produce nanoparticles metallic phases of iron, copper and zinc, which have ball and fibers shapes. 相似文献