An eco-compatible multicomponent strategy for the synthesis of new 2-amino-6-(1H-indol-3-yl)-4-arylpyridine-3,5-dicarbonitriles in aqueous micellar medium promoted by thiamine-hydrochloride

A thiamine hydrochloride (VB₁) accelerated, one-pot synthesis of 2-amino-6-(1H-indol-3-yl)-4-arylpyridine-3,5-dicarbonitriles was achieved via four-component reaction of 3-cyanoacetyl indole, aromatic aldehydes, ammonium acetate, and malononitrile in aqueous micellar conditions by a Knoevenagel condensation reaction followed by Michael-addition, which upon cyclization and dehydration yielded the corresponding product in excellent proportion.     

An Eu(III) sensor based on N,N-diethyl-N-(4-hydroxy-6-methylpyridin-2-yl)guanidine.

A highly selective poly(vinyl chloride)-based membrane sensor produced by using N,N-diethyl-N-(4-hydroxy-6-methylpyridin-2-yl)guanidine (GD) as active material is described. The electrode displays Nernstian behavior over the concentration range 7.0 x 10(-5) - 1.0 x 10(-1) M. The detection limit of the electrode is 5.0 x 10(-5) M. The best performance was obtained with the membrane containing 30% PVC, 55% benzyl acetate, 5% GD and 10% oleic acid. The response of the sensor is pH-independent in the range of 3.0 - 7.0. The sensor possesses satisfactory reproducibility, fast response time (< 20 s), and specially excellent discriminating ability for Eu(III) ion with respect to the alkali, alkaline earth, transition and heavy metal ions. The membrane sensor was used as an indicator electrode in potentiometric titration of Eu(III) ion with EDTA. It was also applied in determination of fluoride ions in mouth wash preparations.     

CABC–CSA: a new chaotic hybrid algorithm for solving optimization problems

Recently a lot of methods have been presented for solving optimization problems. In this paper, we are trying to propose a new hybrid algorithm for solving these kinds of problem. The proposed algorithm is based on chaotic artificial bee colony and chaotic simulated annealing, CABC–CSA. The chaotic artificial bee colony finds new locations chaotically. Actually, the proposed algorithm provides a combination of local search accuracy of simulated annealing and the ability of global search of artificial bee colony. Furthermore, we used a different method for generating the initial population. The proposed algorithm is validated using 12 benchmark functions. The results are compared with those of the artificial bees’ algorithm, the hybrid algorithm of artificial bee colony and simulated annealing and particle swarm optimization. Simulation results show the efficiency of the proposed algorithm.     

Fragmentation reaction of highly sterically hindered TsiSiPhCl2 with some alcoholic sodium alkoxides

TsiSiPhCl₂(1) was treated with boiling NaOEt/EtOH to give the fragmentation product of the type (Me₃Si)₂CHSiPh(OEt)₂. Treatment of 1 with various alkoxides NaOR/ROH (R = n-Pr, n-Bu, iso-Bu, 2-Bu, amyl, iso-amyl, 2-amyl, CH₂Ph) gave Me₃SiCH₂SiPh(OR)₂ rather than the expected (Me₃Si)₂CHSiPh(OR)₂. Study of the products showed that alkoxides as a nucleophile can not attack the silicon center bearing the (Me₃Si)₃C– group because of steric hindrance. It is suggested that the reaction proceeds through an elimination, analogous to E2 eliminations of alkyl halides, involving synchronous attack of RO⁻ at a Me₃Si group, liberation of X⁻, and formation of (Me₃Si)₂C=SiPhCl. The reaction of NaOEt/EtOH with dichloride 1 takes different route from other alkoxides.     

High-twist contribution to large-p T dilepton production

The high-twist contribution to large-transversemomentum lepton pair production in pion-hadron collisions is investigated. In calculations, various pion model wave functions are used. The high-twist contribution is shown to depend on the choice of wave functions and to exceed the leading one by an order of magnitude in the phase space boundary.     

Hyper-aging dynamics of nanoclay suspension

Aqueous suspension of nanoclay Laponite undergoes structural evolution as a function of time, which enhances its elasticity and relaxation time. In this work, we employ an effective time approach to investigate long-term relaxation dynamics by carrying out creep experiments. Typically, we observe that the monotonic evolution of elastic modulus shifts to lower aging times, while maxima in viscous moduli get progressively broader for experiments carried out on a later date after preparation (idle time) of the nanoclay suspension. Application of effective time theory produces a superposition of all the creep curves irrespective of their initial state. The resulting dependence of the relaxation time on aging time shows very strong hyper-aging dynamics at short idle times, which progressively weakens to demonstrate a linear dependence in the limit of very long idle times. Remarkably, this behavior of nanoclay suspensions is akin to that observed for polymeric glasses. Consideration of aging as a first-order process suggests that continued hyper-aging dynamics causes cessation of aging. The dependence of relaxation time on aging time, therefore, must attenuate eventually producing linear or weaker dependence on time in order to approach a progressively low-energy state in the limit of very long times as observed experimentally. We also develop a simple scaling model based on a concept of aging of an energy well, which qualitatively captures various experimental observations very well, leading to profound insight into the hyper-aging dynamics of nanoclay suspensions.     

The Johari-Goldstein β-relaxation of glass-forming binary mixtures

The present paper shows, by means of broadband dielectric measurements, that the primary α- and the secondary Johari-Goldstein (JG) β-processes in binary mixtures are strongly correlated. This occurs for different polar rigid probes dissolved in apolar glass-forming solvents, over a wide temperature and pressure range.We found that the coupling parameter n = 1 − β_KWW and the ratio between α- and β-relaxation time reduce on increasing the size of the solute solved within the same apolar matrix. Moreover, such a ratio is invariant when calculated at different combinations of P and T maintaining either the primary or the JG relaxation times constant. Dielectric spectra measured at different T-P combinations but with an invariant α-relaxation time are well superposed in both the α- and β-frequency ranges. Experimental results can be rationalized by Coupling Model equation.     

Cramér–Karhunen–Loève representation and harmonic principal component analysis of functional time series

We develop a doubly spectral representation of a stationary functional time series, and study the properties of its empirical version. The representation decomposes the time series into an integral of uncorrelated frequency components (Cramér representation), each of which is in turn expanded in a Karhunen–Loève series. The construction is based on the spectral density operator, the functional analogue of the spectral density matrix, whose eigenvalues and eigenfunctions at different frequencies provide the building blocks of the representation. By truncating the representation at a finite level, we obtain a harmonic principal component analysis of the time series, an optimal finite dimensional reduction of the time series that captures both the temporal dynamics of the process, as well as the within-curve dynamics. Empirical versions of the decompositions are introduced, and a rigorous analysis of their large-sample behaviour is provided, that does not require any prior structural assumptions such as linearity or Gaussianity of the functional time series, but rather hinges on Brillinger-type mixing conditions involving cumulants.     

Synthesis and desilylation of some bis(trimethylsilyl)alkenes and polymers bearing bis(silyl)alkenyl groups

The synthesis of various vinylbis(silanes) from some aryl and heteroaryl aldehydes and (Me₃Si)₃CLi in Et₂O is described. Friedel-Crafts reaction of 1,1-bis(trimethylsilyl)-2-(2-naphthyl)ethene with various acyl chlorides (RCOCl, R = Me, Et, i-Pr, i-Bu, n-pent) gave the corresponding α-silyl-α,β-unsaturated enones with high E steroselectivity. Moreover, poly(styrene)-co-[2,2-bis(trimethylsilyl)ethenyl(styrene)] obtained via the reaction of polymers bearing pendant enone functions and (Me₃Si)₃CLi, reacts with the same acyl chlorides in the presence of catalytic amount of AlCl₃ to give the new macromolecules bearing α-silyl-α,β-unsaturated enones and α,β-unsaturated enones.     

Removal of chromate from aqueous solution by reduction with nanoscale Fe–Al layered double hydroxide

Nanoscale layered double hydroxides of Fe^II and Al^III (Fe–Al LDH) have been applied for removal of chromate (Cr^VI) from aqueous solution. Given the reaction stoichiometry, Cr^VI was completely reduced to Cr^III and coprecipitated with Fe^III and Al^III oxyhydroxides. The extent of Cr^VI removal decreased with increasing initial pH and decreasing molar ratio of Cr^VI/structural Fe^II in the LDH. The chromate reduction rate at different initial concentrations of Cr^VI was well described by the pseudo-second-order model with reaction rate constant ranging from 197.4 to 13.53 (mmol min)^?1. Initial pH and substitution of various amounts of Fe^III in the LDH structure had little effect on the reaction rate. Backtransformation of Cr^III to Cr^VI by birnessite Mn oxide (δ-MnO₂) after 40 days of reaction was less than 1% of the initial Cr (as Cr^III solid), indicating high stability of the final reaction products and high efficiency of nanoscale Fe–Al LDHs for removal of chromate from aqueous solution.