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91.
Quadrivalent uranium is found to be a suitable reducing agent in potentiometric titrations, for the estimation of ferric and ceric salts. The stability of the reagent increases by raising the acidity and becomes considerable in the presence of HCl. The stability is not seriously affected by H3PO4 although Zn+2 and Co+2 ions enhance its oxidation. Light affects the stability of the reagent only in the presence of air.The redox potential varies with l'acidity, being 0.3 volt at 0.1N HCl or H2SO4 rising to 0.53 or 0.61 in 1-7 N HCl or 1–9.N H2SO4 and increasing thereafter to ~ 1 volt. 相似文献
92.
We consider the contribution to the depolarization of elastically scattered nucleons which involves transfer of two units of angular momentum to the target nucleus. Our estimates for the depolarization approximate measured values for 9Be, 10B, and 27Al. 相似文献
93.
Sherif M. H. Sanad Ahmed E. M. Mekky Ahmed Y. Said Mohamed A. A. Elneairy 《Journal of heterocyclic chemistry》2021,58(7):1461-1471
In the current study, we report a facile procedure for the preparation of a new series of nicotinonitrile-thiazoles, in excellent isolated yields. For this purpose, pyridine-2(1H)-thiones were investigated as key building blocks for the synthesis of new nicotinonitrile-linked 2-hydroxybenzaldehyde derivatives. To prepare the target thiazole hybrids, a facile one-pot procedure was developed involving amine-mediated reaction of the prior aldehydes, thiosemicarbazide, and the appropriate of hydrazonyl chlorides. The reaction conditions of this one-pot protocol were optimized by repeating the reaction using different solvents and amines. The optimized conditions were conducting the reaction in dioxane containing triethylamine at 100°C for 5 h. The prior protocol gave, in each case, new series of nicotinonitrile-linked thiazole and thiazol-4(5H)-one hybrids, bearing aryldiazenyl or arylhydrazineylidene units. Repeating the prior one-pot protocol using the appropriate halogen containing reagents instead of hydrazonyl chlorides afforded the target thiazoles in excellent isolated yields. By considering their elemental analyses and spectral findings, the structures of the new hybrids were clarified. 相似文献
94.
Zhen Liu Natialia Borisenko Sherif Zein El Abedin Frank Endres 《Journal of Solid State Electrochemistry》2014,18(9):2581-2587
The electrodeposition of Zn on Au(111) was investigated with cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM) in the air and water stable ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate ([EMIm]TfO) with a Zn(TfO)2 concentration of 0.2 M. It has been found that the structure [EMIm]TfO/Au(111) is very complex. Furthermore, the addition of Zn(TfO)2 changes the interfacial structure significantly. The first STM-probed Zn islands appear at +0.3 V, and their growth leads to the formation of a thin zinc layer. A bulk deposition of Zn is obtained with in situ STM at ?0.1 V. Furthermore, in situ STM reveals that the deposition of Zn is accompanied by the formation of Au-Zn surface alloys. 相似文献
95.
Sadeek Sadeek A. Abd El-Hamid Sherif M. El-Shwiniy Walaa H. 《Research on Chemical Intermediates》2016,42(4):3183-3208
Research on Chemical Intermediates - The mixed ligand Zn(II), Zr(IV), Pd(II), Ce(IV), Th(IV), and U(VI) complexes of gemifloxacin and N-donor 2,2′-bipyridine have been prepared. These... 相似文献
96.
A new HB (Harmonic Balance)/AFT (Alternating Frequency Time) method is further developed to obtain synchronous and subsynchronous whirling response of nonlinear MDOF rotor systems. Using the HBM, the nonlinear differential equations of a rotor system can be transformed to algebraic equations with unknown harmonic coefficients. A technique is applied to reduce the algebraic equations to only those of the nonlinear coordinates. Stability analysis of the periodic solutions is performed via perturbation of the solutions. To further reduce the computational time for the stability analysis, the reduced system parameters (mass, damping, and stiffness) are calculated in terms of the already known harmonic coefficients. For illustration, a simple MDOF rotor system with a piecewise-linear bearing clearance is used to demonstrate the accuracy of the calculated steady-state solutions and their bifurcation boundaries. Employing ideas from modern dynamics theory, the example MDOF nonlinear rotor system is shown to exhibit subsynchronous, quasi-periodic and chaotic whirling motions. 相似文献
97.
Mohamed A. Shenashen Sherif A. El‐Safty Emad A. Elshehy 《Particle & Particle Systems Characterization》2014,31(3):293-316
Nanostructured materials, especially nanoparticles (NPs), of noble metal NPs such as silver (Ag) have been the focus of research in recent decades because of their distinct physical, chemical, and biological properties. These materials have attracted considerable attention because of their potential applications, such as catalysis, biosensing, drug delivery, and nanodevice fabrication. Previous studies on Ag NPs have clearly demonstrated that their electromagnetic, optical, and catalytic properties are strongly influenced by their shape, size, and size distribution, which can be varied by using different synthetic methods, reducing agents, and stabilizers. The valuable optical properties of Ag NPs have allowed for new approaches in sensing and imaging applications, offering a wide range of detection modes, such as colorimetric, scattering, and surface‐enhanced Raman scattering techniques, at extremely low detection limits. Here, an overview of the various chemical, physical, and biological properties of Ag NP fabrication approaches to obtain the various shapes and sizes is presented. 相似文献
98.
Ayman M. Atta Maher A. Elsockary Osama F. Kandil Zakaa M. Mohamed 《Journal of Dispersion Science and Technology》2013,34(1):7-19
Polyethylene acrylic acid copolymer (PEAA) was modified with different types of alkanols and hydroxybenzoic acids to produce three types of esterified grafts. The molecular structures of the synthesized dispersants were performed using 1H NMR analysis. The molecular weights of the synthesized dispersants were determined by GPC technique. The activity of PEAA derivatives as asphaltene stabilizer in the crude oil was evaluated by means of flocculation measurements. The effect of asphaltenes on the rheological behavior of highly asphaltenic crude oils was studied to evaluate the transportation parameters of crude oils. The rheological properties were measured at different temperature ranges of 5°C to 25°C in presence and absence of PEAA additives. It was observed that the PEAA having side chain lengths below C16 show non‐Newtonian pseudoplastic relationships at temperatures from 25°C to 5°C. While, PEAA additives having side chain lengths equal or above C16 show Newtonian relationship even at low temperature (5°C) for all tested crude oils. 相似文献
99.
Samir S. Kandil 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2455-2463
Palladium(II) and platinum(II) complexes of N-ethyl-N′-pyrimidin-2-ylthiourea(HL1) and N-phenyl-N′-pyrimidin-2-ylthiourea (HL2) have been prepared, and the complexes [M(HL)Cl2], [Pt(L)2], [Pd(HL1)2]Cl2, and [Pd(L2)2] (where M = PdII or PtII) were characterized. The spectroscopic data are consistent with coordination of thioureas as neutral or monoanionic ligands to PdII and PtII through S and a pyrimidine-N. The IR spectra show shifts of CS and pyrimidine ring stretch bands to lower and higher frequencies, respectively. The 1H NMR spectra differentiate between H(4′) and H(6′) resonances and indicate downfield shifts for all protons of pyrimidine [H(4′), H(5′), and H(6′)], two resonances for two N?H protons for complexes containing the neutral ligand (HL), and only one N?H proton chemical shift for complexes containing the monoanion (L). 13C NMR chemical shifts of pyrimidine carbons are correlated with the type of bonding between PdII or PtII and pyrimidine-N. The magnetic susceptibilities suggest a diamagnetic planar structure for all complexes. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
100.
Sanaa Eissa Hassan M. E. Azzazy Marwa Matboli Sherif M. Shawky Hebatallah Said Fatin A. Anous 《Applied biochemistry and biotechnology》2014,174(2):751-761
The aim of is this study is to explore the role of tissue histidine-rich glycoprotein (HRG) RNA as a promising clinically useful biomarker for breast cancer patients prognosis using nanogold assay. Expression of the HRG RNA was assessed by gold nanoparticles and conventional RT-PCR after purification by magnetic nanoparticles in breast tissue samples. The study included 120 patients, 60 of which were histologically proven breast carcinoma cases, 30 had benign breast lesions and 30 were healthy individuals who had undergone reductive plastic surgery. ER, PR and HER2 status were also investigated. The prognostic significance of tissue HRG RNA expression in breast cancer was explored. The magnetic nanoparticles coated with specific thiol modified oligonucleotide probe were used successfully in purification of HRG RNA from breast tissue total RNAs with satisfactory yield. The developed HRG AuNPs assay had a sensitivity and a specificity of 90 %, and a detection limit of 1.5 nmol/l. The concordance rate between the HRG AuNPs assay with RT-PCR after RNA purification using magnetic nanoparticles was 93.3 %. The median follow-up period was 60 months. Among traditional prognostic biomarkers, HRG was a significant independent prognostic marker in relapse-free survival (RFS). HRG RNA is an independent prognostic marker for breast cancer and can be detected using gold NPs assay, which is rapid, sensitive, specific, inexpensive to extend the value for breast cancer prognosis. 相似文献