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排序方式: 共有328条查询结果,搜索用时 31 毫秒
71.
S. A. Kandil H. A. Hanafi H. Aglan Z. A. Saleh 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(3):609-614
The adsorption behaviour of La/Ce system on Dowex 50W-X8 in different media, namely, nitric acid, acetate buffer and citrate
buffer was studied as a function of the concentration of nitric acid and buffer pH. In addition, in cation-exchange column
chromatography experiments, three different eluants, namely, citrate buffer of pH 5.5, 0.1 M EDTA and 0.2 M α-HIBA, were employed
for separation of Ce(III) from La(III). The optimum conditions for improvement of radiochemical separation of no-carrier-added
139Ce from proton irradiated lanthanum were applied using the most suitable chelating agent 0.2 M α-HIBA. The purification of
139Ce from macro amount of La(III) was done using two columns in a sequence. The target was prepared by pressing. The production
of high radionuclidic and chemical purity 139Ce via irradiation of lanthanum oxide target at MGC-20 cyclotron of proton energy 14.5 MeV was described. The experimental
yield was found to be 200 kBq/μA h. 相似文献
72.
Semanur Kandil Mine Işıksal-Bostan 《International Journal of Mathematical Education in Science & Technology》2019,50(4):557-576
The purpose of the study was to investigate the effect of inquiry-based instruction enriched with origami activities on 7th grade students’ achievement in reflection symmetry and self-efficacy in geometry. Two classes, instructed by the first author of the paper, were randomly assigned as experimental and control groups. In order to gather data, participants were administered Reflection Symmetry Achievement Test, and Geometry Self-Efficacy Scale as pre-test and post-test. The Analysis of Covariance was performed in order to answer the research questions. Moreover, five participants were interviewed to examine self-efficacy sources which are determinant of the change in self-efficacy levels. Findings revealed that the inquiry-based instruction enriched with origami activities had a significantly positive effect on students’ achievement in reflection symmetry and self-efficacy in geometry. Interviews showed that all four sources were influenced by the intervention. 相似文献
73.
Dr. Nagaraju Mupparapu Lauren Brewster Katrina F. Ostrom Prof. Sherif I. Elshahawi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202104614
The late-stage functionalization of indole- and tryptophan-containing compounds with reactive moieties facilitates downstream diversification and leads to changes in their biological properties. Here, the synthesis of two hydroxy-bearing allyl pyrophosphates is described. A chemoenzymatic method is demonstrated which uses a promiscuous indole prenyltransferase enzyme to install a dual reactive hydroxy-bearing allyl moiety directly on the indole ring of tryptophan-containing peptides. This is the first report of late-stage indole modifications with this reactive group. 相似文献
74.
Sherif M.S. Ibrahim Koushik Banerjee Kara A. Slater Gregory K. Friestad 《Tetrahedron letters》2017,58(52):4864-4866
Tamao–Fleming oxidation of the N-dimethylphenylsilylmethyl group linked to the nitrogen of a peptide bond enables access to dipeptide N,O-acetal functionality. The N-silylmethyl functionality serves as a latent form of the N,O-acetal which is revealed after peptide bond construction. 相似文献
75.
Potentiometric studies on Schiff bases derived from5,7-dihydroxy-6-formyl-2-methylbenzopyran- 4-one were carried out at different
ionic strengths (0.02, 0.04, 0.06, 0.10 and 0.14 M NaCl), at different temperatures (25, 35, 45 and55°C) and in ethanol-water
media of varying compositions (60, 70, 80 and 90% v/v). The ionization constants of the Schiff bases were investigated in
the presence of different organic solvents (70% v/v), e.g. methanol, ethanol, n-propanol, isopropanol, acetone, DMSO and DMF-water
media. The thermodynamic parameters (ΔG, ΔH and ΔS) were also calculated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
77.
Mohamed Hilmy Elnagdi Sherif Mahmoud Fahmy Mohamed Rifaat Hamza Elmoghayar Ezzat Mohamed Kandeel 《Journal of heterocyclic chemistry》1979,16(1):61-64
The behaviour of the aminopyrazole derivatives 1a-c, 2-amino-4-phenylthiazole (2) and 2-amino-5-phenyl-1,3,4-thiadiazole (3) toward the action of ethoxycarbonyl and benzoyl iso-thiocyanate is reported. The data clearly demonstrates the dependence of the nature of the products obtained from the reaction of isothiocyanates with cyclic amidines on the nature of the substituents on the heterocyclic ring. 相似文献
78.
S. H. Kandil M. A. El-Gamal 《Journal of polymer science. Part A, Polymer chemistry》1986,24(11):2765-2771
Methyl acrylate–styrene copolymers of different copolymer compositions were free-radically prepared. The relative intensities of the carbonyl frequencies of the methyl acrylate units at v 1730 cm?1 were correlated with the copolymer composition. The positions and shapes of the carbonyl bands in the infrared absorption spectra of the copolymers-dissolved in chloroform, were shown to depend on the composition of the copolymers and upon the presence of different proportions of methyl acrylate centered triads. The results obtained by infrared spectroscopy were compared with those obtained by 13C-NMR. Infrared spectra may be used to yield information about both the copolymer composition and the triad sequence distribution. 相似文献
79.
Azide has been investigated as a spectrophotometric reagent for uranium(VI). The system is more sensitive than the thiocyanate reaction. It obeys Beer's law in the range 2–180 p.p.m. of uranium. The colour is sensitive to hydrogen ion concentration ; maximum absorbance and stability are attained at pH 5–5.5. Iron(III) interferes seriously, but can be masked by EDTA. Fe+2, Cr+3, Ni+2, Th+4, Cr2O7-2, WO4-2, VO3- and F- interfere. The deep yellow colour cannot be extracted with organic solvents. A mono-azido-uranium(Vl) ion is present in dilute solutions; its dissociation constant is 2.3 ±20.27·10-3. 相似文献
80.
M. E. Kassem E. F. El-Wahidy S. H. Kandil M. A. El-Gamal 《Journal of Thermal Analysis and Calorimetry》1984,29(2):325-331
Thermal analysis, DTA, TG, TMA and DSC were performed on LiKSO4 in the temperature range 300 to 800 K, using a Heraeus TA 500 thermal analyser. The thermal expansion coefficients measured along the three fundamental crystallogrpahic axes, together with the specific heatC p, show anomalous behaviour around the phase transition temperature of these crystals atT c=705 K. Anisotropy in the thermal expansion coefficient as well as endothermic peaks aroundT c were also observed, while no loss of weight was detected. The temperature-dependence of the thermal conductivity of LiKSO4 crystals has been estimated, using the temperature-variation of the thermal diffusivity. 相似文献