In the framework of second-order perturbation theory and model potential formalism we investigate the effect of variation of depletion charge on the prediction of stable crystal structures of K, Rb, and Cs. In the formal calculation the HCP structure is found to have the lowest energy for all three metals, even though the phonon contributions were added in case of K. Nevertheless, we were able to predict correctly the observed BCC structure by changing the sign of the depletion hole charge. 相似文献
The solid–solid interactions between pure and alumina-doped cobalt and ferric oxides have been investigated using DTA, IR and XRD techniques. Equimolar proportions of basic cobalt carbonate and ferric oxide and different amounts of aluminum nitrate were added as dopant substrate. The amounts of dopant were 0.75, 1.5, 3.0 and 4.5 mol% Al2O3.
The results obtained revealed that solid–solid interaction between Fe2O3 and Co3O4 takes place at temperatures starting from 700°C to produce cobalt ferrite. The degree of propagation of this reaction increases progressively as a function of precalcination temperature and Al2O3-doping of the reacting solids. However, the heating of pure mixed solids at 1000°C for 6 h. was not sufficient to effect the complete conversion of the reacting solids into CoFe2O4, while the addition of a small amount of Al2O3 (1.5 mol%) to ferric/cobalt mixed solids followed by precalcination at 1000°C for 6 h conducted the complete conversion of the reacting solids into cobalt ferrite. The heat treatment of pure and the 0.75 mol%-doped solids at 900 and 1000°C effected the disappearance of most of IR transmission bands of the free oxides with subsequent appearance of new bands characteristic for the CoFe2O4 structure. An increase in the amount of Al2O3 added from 1.5–4.5 mol% to the mixed solids precalcined at 1000°C led to the disappearance of all bands of free oxides and appearance of all bands of cobalt ferrite. The promotion effect of Al2O3 in cobalt ferrite formation was attributed to an effective increase in the mobility of the various reacting cations. The activation energy of formation (ΔE) of CoFe2O4 phase was determined for pure and doped solids. The computed values of ΔE were, respectively, 99.6, 87.8, 71.9, 64.7 and 48.7 kJ mol−1 for the pure solid and those treated with 0.75, 1.5, 3 and 4.5 mol% Al2O3. 相似文献
In our continuous study for some African plants as a source for antitrypanosomally and cytotoxic active drugs, nine different plants belonging to the Crassulaceae family have been selected for the present study. Sedum sieboldii leaves extract showed an antitrypanosomal activity against Trypanosoma brucei with an IC50 value of 8.5 µg/mL. In addition, they have cytotoxic activities against (HCT-116), (HEPG-2) and (MCF-7), with IC50 values of 28.18 ± 0.24, 22.05 ± 0.66, and 26.47 ± 0.85 µg/mL, respectively. Furthermore, the extract displayed inhibition against Topoisomerase-1 with an IC50 value of 1.31 µg/mL. It showed the highest phenolics and flavonoids content among the other plants’ extracts. In order to identify the secondary metabolites which may be responsible for such activities, profiling of the polar secondary metabolites of S. sieboldii extract via Ultra-Performance Liquid Chromatography coupled to High-Resolution QTOF-MS operated in negative and positive ionization modes, which revealed the presence of 46 metabolites, including flavonoids, phenolic acids, anthocyanidins, coumarin, and other metabolites. 相似文献
A measure of functionality of agricultural sower is the layout of grains sown in the soil and labelled by radioisotope a method. To determine the precise position of the grains which are sown is a figure of merite. To resolve the problem, a detection system with focusing multihole collimator was used. A probe with collimator travelled on a self-propelled carriage. The detector pulses were ratio transmited to the field isotope lab. To label the grains of cereals, cucumber and beet the isotope 99mTc obtained from Mo–Tc generator was applied. 相似文献
Journal of Radioanalytical and Nuclear Chemistry - This work presents a method for simultaneous proton induced gamma-ray emission analysis of fluorine, lithium, and sodium in “as... 相似文献
This paper introduces an approximate solution for Liouville‐Caputo variable order fractional differential equations with order 0 < α(t) ≤ 1 . The solution is adapted using a family of fractional‐order Chebyshev functions with unknown coefficients. These coefficients have been obtained by using an optimization approach based on minimax technique and the least pth optimization function. Several linear and nonlinear fractional‐order differential equations are discussed using the proposed technique for fixed and variable order fractional‐order derivatives. Moreover, the response of RC charging circuit with variable order fractional capacitor is studied for different cases. Several comparisons with related published techniques have been added to illustrate the accuracy of the proposed approach. 相似文献
AbstractThe chemical constituents of Cupressus macrocarpa were investigated. A new neolignan glycoside (1) in addition to nine known compounds were isolated. The acetylcholinesterase (AChE) inhibitory activity and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) of different fractions and isolates of C. macrocarpa were evaluated. The light petroleum fraction showed the highest activity in both assays with IC50 value of 88.79 µg/ml and 152.58 µg/ml for the AChE inhibitory activity and MRSA antibacterial activities, respectively. Weak to moderate activity were detected for the isolated compounds. 相似文献
Abstract 3-amino-4,5-diphenylthieno[2,3-c]pyridazine-2-arylcarboxamide 2 underwent cyclization with triethyl orthoformate and with nitrous acid to give the pyrimidothienopyridazines 3a-c, 4b respectively. 3-amino-4,5-diphenylthieno[2,3-c] pyridazine-2-carbohydrazide 6 reacted with aromatic aldehydes to give the corresponding carbohydrazones 7a-c. Compound 7 reacts with triethyl orthoformate, acetic anhydride or with CS2/pyridine to produce pyrimidothienopyridazines 8,9 and pyridazothienothiazine 11. 相似文献
Bis(triazolo[3,4‐b]thiadiazine) 4 in which the fused system is linked directly to the benzene core can be synthesized in 75% yield by, firstly, preparation of bis(s‐triazole) 2 followed by reaction with phenacyl bromide 3 in refluxing EtOH/DMF mixture containing piperidine. Bis(s‐triazolo[3,4‐b][1,3,4]thiadiazines) 8 and 11 in which the triazolothiadiazines are linked to benzene core via alkyl or ether linkage were synthesized in 70 and 72% yields, respectively, starting from dicarboxylic acids 5 and 9 upon treatment with two moles of thiocarbohydrazide 6 to give the corresponding bis(4‐amino‐5‐mercapto‐s‐triazolo‐3‐y1) derivatives 7 and 10 and subsequent reaction with two equivalents of phenacyl bromide. Bis(6‐phenyl‐7H‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazines) 15a , 15b , 15c , 15d , 15e , 15f , which are linked to arene cores via sulfanylmethylene spacers, were prepared by the reaction of 4‐amino‐4H‐1,2,4‐triazole‐3,5‐dithiol 12 with the appropriate bis(bromomethyl)benzenes 13a , 13b , 13c , 13d , 13e , 13f to give bis(4‐amino‐5‐mercapto‐4H‐3‐sulfanylmethyl)arenes 14a , 14b , 14c , 14d , 14e , 14f and subsequent reaction with phenacyl bromide. Compounds 15a , 15b , 15c , 15d , 15e , 15f were alternatively obtained in 60–70% yields by twofold substitution of 13a , 13b , 13c , 13d , 13e , 13f with two equivalents of 6‐phenyl‐7H‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazine‐3‐thiol 16 in refluxing EtOH/DMF mixture containing KOH. Bis(triazolothiadiazine) 22 attached to the benzene core through the thiadiazine ring via an amine linkage was prepared in 70% yield starting from p‐phenylenediamine 19 by, firstly, acylation with chloroacetyl chloride 18 followed by bis‐alkylation with 1,2,4‐triazole 20 and subsequent intramolecular ring closure upon treatment with phosphorus oxychloride. 相似文献