Genetic algorithm-tuned entropy-based fuzzy C-means algorithm for obtaining distinct and compact clusters

A modified approach had been developed in this study by combining two well-known algorithms of clustering, namely fuzzy c-means algorithm and entropy-based algorithm. Fuzzy c-means algorithm is one of the most popular algorithms for fuzzy clustering. It could yield compact clusters but might not be able to generate distinct clusters. On the other hand, entropy-based algorithm could obtain distinct clusters, which might not be compact. However, the clusters need to be both distinct as well as compact. The present paper proposes a modified approach of clustering by combining the above two algorithms. A genetic algorithm was utilized for tuning of all three clustering algorithms separately. The proposed approach was found to yield both distinct as well as compact clusters on two data sets.     

OH radical reactions with ethanolamines: formation of reducing as well as oxidizing radicals

OH radical reactions with ethanolamine, diethanolamine and triethanolamine were studied at pH values below and above the pK_a values of these compounds. The rate constants were found to be lower for the protonated amines than those for their neutral forms. The OH radical reaction led to the formation of both oxidizing, as well as reducing species, as observed by their reactions with methyl viologen and ascorbic acid. The oxidizing species formed by OH radical reaction at the amine site was not found to react with the parent molecules and thereby no secondary yield of reducing species was obtained, as in the case of glycine (except in the case of triethanolamine at pH 9.2).     

Lewis acid-mediated cross-coupling reaction of 7-azaindoles and aldehydes: Cytotoxic evaluation of C3-linked bis-7-azaindoles

The synthesis of 3,3′-bis-7-indolylmethane derivatives is important for their further development as pharmaceutical compounds and other synthetic purposes. Herein, we describe the zinc- or acid-mediated cross-coupling reaction of 7-azaindoles with aldehydes, such as paraformaldehyde, alkyl aldehydes, aryl aldehydes, enal, and α-ketoaldehyde, providing the corresponding C3-linked bis-7-azaindole derivatives, which are a crucial class towards the development of novel bioactive compounds. High levels of site selectivity and functional group tolerance were observed. Synthesized 3,3′-bis-7-azaindole derivatives were evaluated against human breast adenocarcinoma cells (MCF-7) and human ovarian carcinoma cells (SKOV-3), respectively. Notably, compounds 3s and 4e displayed promising anticancer properties competitive with anticancer doxorubicin as a positive control.     

Surface plasmon enhanced ultra-low threshold second harmonic generation in periodically poled whispering gallery resonator

The surface plasmon enhanced ultra-low threshold second harmonic generation is observed, designed and simulated in whispering gallery resonator made of MgO doped periodically poled LiNbO₃. Here the electric field associated with incident optical radiation of picowatt level is amplified to milliwatt level through surface plasmon resonance in Kretschmann geometry which is formed by a BK₇ prism plane, 29 nm thin gold layer and 20 nm thin GaAs layer. This enhanced electric field then coupled to a whispering gallery resonator, which facilitated the generation of second harmonic for an incident laser radiation of picowatt level. In this proposed configuration with an incident optical power of 94.6 pW, generated second harmonic through whispering gallery resonator is found to be 14.6 mW.     

Fixed point of contractive mappings in generalized metric spaces

We prove a fixed point theorem for contractive mappings of Boyd and Wong type in generalized metric spaces, a concept recently introduced in [BRANCIARI, A.: A fixed point theorem of Banach-Caccioppoli type on a class of generalized metric spaces, Publ. Math. Debrecen 57 (2000), 31–37].      

Dispersion-free solvent extraction of U(VI) in macro amount from nitric acid solutions using hollow fiber contactor

The applicability of dispersion-free solvent extraction (DFSX), through microporous hydrophobic membrane has been studied. The hollow fiber membrane contactor, with surface area of 381 cm² was employed to extract U(VI) in macro concentration (35 g dm⁻³) from aqueous acidic solutions. Prior to deployment of this technique for recovery of U(VI) from oxalate supernatant waste, chemical parameters such as extractant concentration, feed acidity, concentration of U(VI) in feed were studied. The study revealed that 30% tri-n-butyl phosphate (TBP) in n-dodecane as an extractant and feed in 3 M HNO₃ gave an optimum extraction of U(VI) and it was possible to strip back utilizing 0.05 M HNO₃. It was established to recover more than 90% of U(VI) from oxalate supernatant waste, which was often generated from nuclear chemical facilities.     

Conductometric studies on the precipitation of thorium hydroxide

This paper presents the effect of age on the conductance of hydroxide precipitated from thorium chloride with progressive addition of alkali. The effect of age on reverse titration has also been studied. Conductance study on the aged samples reveals that in every case there is at first a decrease in the electrical conductance of mixture and then an increase on prolonged ageing. This phenomenon is more marked with the concentrated solutions where it is presumed that adsorption of ions is more marked resulting in the diminution of electrical conductance. With dilute solutions, the precipitated mass being very small in amount does not adsorb appreciable amount of electrolytes from the system. On prolonged ageing there is a decrease of the surface reactivity of the precipitated mass, resulting in the release of adsorbed electrolytes and hence the increase in conductance of the system.

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Zusammenfassung Diese Arbeit behandelt die Wirkung der Alterung auf die Leitfähigkeit von Hydroxid, ausgefällt aus Thoriumchlorid mit fortschreitender Zufügung von Alkali. Auch der Alterungseinfluß auf den umgekehrten Vorgang: Zufügung von Thoriumchlorid zu Alkali, wurde untersucht. Die Leitfähigkeitsmessungen an gealterten Proben zeigen, daß zunächst stets eine Abnahme der elektrischen Leitfähigkeit der Mischungen und später eine Zunahme mit fortschreitender Alterung stattfindet. Dieses Phänomen ist für konzentriertere Lösungen ausgeprägter, bei denen ja wohl auch die Adsorption der Ionen stärker ist und damit die Abnahme der elektrischen Leitfähigkeit. Bei verdünnten Lösungen adsorbiert die dem Betrag nach sehr kleine ausgefällte Masse keine wesentlichen Beträge von Elektrolyten aus dem System. Mit verlängerter Alterung findet eine Abnahme der Oberflächenreaktivität des Fällproduktes statt, was die Freigabe von adsorbierten Elektrolyten und damit eine Zunahme der Leitfähigkeit des Systems zur Folge hat.

     

A comparison of generalized multinomial logit and latent class approaches to studying consumer heterogeneity with some extensions of the generalized multinomial logit model

We calibrate and contrast the recent generalized multinomial logit model and the widely used latent class logit model approaches for studying heterogeneity in consumer purchases. We estimate the parameters of the models on panel data of household ketchup purchases, and find that the generalized multinomial logit model outperforms the best‐fitting latent class logit model in terms of the Bayesian information criterion. We compare the posterior estimates of coefficients for individual customers based on the two different models and discuss how the differences could affect marketing strategies (such as pricing), which could be affected by applying each of the models. We also describe extensions to the scale heterogeneity model that includes the effects of state dependence and purchase history. Copyright © 2011 John Wiley & Sons, Ltd.