Common fixed point results for new Ciric-type rational multivalued <Emphasis Type="Italic">F</Emphasis>-contraction with an application

In this article, common fixed point theorems for a pair of multivalued mappings satisfying a new Ciric-type rational F-contraction condition in complete dislocated metric spaces are established. An example is constructed to illustrate our results. An application to the system of integral equations is presented to support the usability of proved results. Our results combine, extend and infer several comparable results in the existing literature.     

Separation of no-carrier-added radioactive scandium from neutron irradiated titanium

In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found at pH < 8.0, whereas a negative effect was observed at pH > 8.0. The Langmuir, Freundlich, and D-R models were applied to simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na⁺/H⁺ on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH.     

Synthesis and properties ofN-substituted azacalix[n]arenes

Side arm modifications of hexahomotriazacalix[3]arene (1) were achieved by simple synthetic methods. Compound5 has picolyl side arms and liquid-liquid extraction experiments showed that the alkali cation affinity of5 is much stronger than that of1. A chiral group was also introduced into the azacalixarene structure. Calix[4]arene was converted into dihomoazacalix[4]arene (2) in 8% yield. Clathrate formation of2 with various solvents is described. MM3 calculations were carried out onp-substituted analogs of2. The self-filled structure, in which the benzyl side arm is placed in its cavity, is the most stable structure when thep-positions of the aromatic rings carry small substituents. Strong hydrogen bonds between nitrogen and phenolic hydroxyl groups in dihomoazacalix[4]arene (2) were observed at low temperatures. The¹H-NMR signals of phenolic hydroxyl groups appeared as six singlets in the range of 9.817.1 ppm at –70°C.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

First natural urease inhibitor from Euphorbia decipiens

Three new diterpene esters with a myrsinol-type skeleton have been isolated from Euphorbia decipiens BOISS. & BUHSE. The structure elucidation of the isolated compounds was based primarily on two-dimensional (2D)-NMR techniques including correlation spectroscopy (COSY), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC) and nuclear Overhauser effect spectroscopy (NOESY) experiments. Compounds 1 and 3 are active against prolyl endopeptidase and compound 2 showed inhibitory activity against urease enzyme.     

Dye-sensitized photooxygenation of the C=N bond. 5. substituent effects on the cleavage of the C=N bond of C-aryl-N-aryl-N-methylhydrazones

The title compounds are cleaved cleanly at the C=N bond by singlet oxygen ((1)O(2), (1)Delta(g)) yielding arylaldehydes and N-aryl-N-methylnitrosamines. These reactions take place more rapidly at -78 degrees C than at room temperature. The effects of substituent variation at both the C-aryl and N-aryl groups were studied using a competitive method. Good correlations of the resulting rate ratios with substituent constants (sigma(-) or sigma(+)) were obtained yielding small to very small rho values indicative of small to very small changes in charge distribution between the reactant and the rate determining transition state. Electron withdrawing groups on the C-aryl moiety retard reaction somewhat by preferential stabilization of the hydrazone. Electron donors on the other hand slightly stabilize the rate determining transition state. Substituents on the N-aryl group have almost no effect. Inhibition by 3,5-di-tert-butylphenol was not observed showing that free (uncaged) radical intermediates are not involved in the mechanism. We postulate a mechanism in which the initial event is exothermic electron transfer from the hydrazone to (1)O(2) leading to an ion-radical caged pair. Subsequent covalent bond formation between the hydrazone carbon and an oxygen atom is rate controlling. The transition state for this step also has a lower enthalpy than the starting reactants, but the free energy of activation is dominated by a large negative TDeltaS++term leading to the negative temperature dependence. Direct formation of a C-O bond in the initial step is not unambiguously ruled out. Subsequent steps lead to C-N cleavage.     

Two new triterpene saponins from Eryngium campestre

Two new triterpene saponins, 3-O-beta-D-glucopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucuronopyranosyl-22-O-angeloyl-R1-barrigenol (1) and 3-O-beta-D-glucopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucuronopyranosyl-22-O-beta,beta-dimethylacryloyl-A1-barrigenol (2), were isolated from the roots of Eryngium campestre (Apiaceae). Their structures were established mainly by 2D NMR techniques and mass spectrometry.