Correction to: Multivariate cluster weighted models using skewed distributions

Advances in Data Analysis and Classification - In the original publication of the article, the line after equation (5) has been published incorrectly     

Chaos break and synchrony enrichment within Hindmarsh–Rose-type memristive neural models

Nonlinear Dynamics - The fluctuation of ions concentration across the cell membrane of neuron can generate a time varying electromagnetic field. Thus, memristors are used to realize the coupling...     

An infeasible-start framework for convex quadratic optimization,with application to constraint-reduced interior-point and other methods

Mathematical Programming - A framework is proposed for solving general convex quadratic programs (CQPs) from an infeasible starting point by invoking an existing feasible-start algorithm tailored...     

Compactness and convergence rates in the combinatorial integral approximation decomposition

The combinatorial integral approximation decomposition splits the optimization of a discrete-valued control into two steps: solving a continuous relaxation of the discrete control problem, and computing a discrete-valued approximation of the relaxed control. Different algorithms exist for the second step to construct piecewise constant discrete-valued approximants that are defined on given decompositions of the domain. It is known that the resulting discrete controls can be constructed such that they converge to a relaxed control in the \(\hbox {weak}^*\) topology of \(L^\infty \) if the grid constant of this decomposition is driven to zero. We exploit this insight to formulate a general approximation result for optimization problems, which feature discrete and distributed optimization variables, and which are governed by a compact control-to-state operator. We analyze the topology induced by the grid refinements and prove convergence rates of the control vectors for two problem classes. We use a reconstruction problem from signal processing to demonstrate both the applicability of the method outside the scope of differential equations, the predominant case in the literature, and the effectiveness of the approach.

     

High Blocking Temperature of Magnetization and Giant Coercivity in the Azafullerene Tb2@C79N with a Single‐Electron Terbium–Terbium Bond

The azafullerene Tb₂@C₇₉N is found to be a single‐molecule magnet with a high 100‐s blocking temperature of magnetization of 24 K and large coercivity. Tb magnetic moments with an easy‐axis single‐ion magnetic anisotropy are strongly coupled by the unpaired spin of the single‐electron Tb?Tb bond. Relaxation of magnetization in Tb₂@C₇₉N below 15 K proceeds via quantum tunneling of magnetization with the characteristic time τ_QTM=16 462±1230 s. At higher temperature, relaxation follows the Orbach mechanism with a barrier of 757±4 K, corresponding to the excited states, in which one of the Tb spins is flipped.     

Imidazotetrazines as Weighable Diazomethane Surrogates for Esterifications and Cyclopropanations

Diazomethane is one of the most versatile reagents in organic synthesis, but its utility is limited by its hazardous nature. Although alternative methods exist to perform the unique chemistry of diazomethane, these suffer from diminished reactivity and/or correspondingly harsher conditions. Herein, we describe the repurposing of imidazotetrazines (such as temozolomide, TMZ, the standard of care for glioblastoma) for use as synthetic precursors of alkyl diazonium reagents. TMZ was employed to conduct esterifications and metal‐catalyzed cyclopropanations, and results show that methyl ester formation from a wide variety of substrates is especially efficient and operationally simple. TMZ is a commercially available solid that is non‐explosive and non‐toxic, and should find broad utility as a replacement for diazomethane.     

Phenazine Radical Cations as Efficient Homogeneous and Heterogeneous Catalysts for the Cross-Dehydrogenative Aza-Henry Reaction

The redox activity of molecular phenazine catalysts has been previously exploited for aerobic oxidative amine homo- and cross-coupling reactions. In this contribution, we have extended the reaction scope of this novel type of organocatalyst and used them in the cross-dehydrogenative aza-Henry coupling of isoquinolines with nitromethane under aerobic conditions. Additionally, we have designed and prepared a novel porous organic polymer by cross-linking of tetrakis(4-bromophenyl)silane and dihydrophenazine through Pd-catalyzed Buchwald-Hartwig cross-coupling. This new type of heterogeneous catalyst, apart from being robust and easily reusable, also showed outstanding catalytic activities and improved selectivity compared to its molecular counterpart. A plausible reaction mechanism was proposed based on spectroscopic and kinetic measurements.     

New oxacalix[4]arene carboxylate detects viologen in protic media

ABSTRACT

We demonstrate that Ullman fragment-coupling can be used to synthesise an oxacalix[4]arene monocarboxylic acid, which provides easy access to its water-soluble carboxylato derivatives. Crystallographic and computational data suggest that the new carboxyl-substituted oxacalix[4]arene adopts a 1,3-alternate conformation both in the solid-state and in methanol solution. Its water-soluble tetrabutylammonium derivate can detect the herbicide paraquat at neutral pH in aqueous media (K _a = 111 ± 3 M^–1) and in methanol (K _a = 2020 ± 70 M^–1).     

Global and local performance metric with inertia effects

Nonlinear Dynamics - A complex system’s structural–dynamical interplay plays a profound role in determining its collective behavior. Irregular behavior in the form of macroscopic chaos,...     

Rapid and cost-effective LC–MS/MS method for determination of hydroxycitric acid in plasma: Application in the determination of pharmacokinetics in commercial Garcinia preparations

Garcinia cambogia is one of the most commonly used anti-obesity dietary supplements, and hydroxycitric acid (HCA) is a major constituent in the commercial preparations of Garcinia. High doses of HCA are often consumed without much awareness of its pharmacokinetic and toxicokinetic parameters, and therefore, a complete understanding of its effects is lacking. The first step in understanding these parameters is the availability of a reliable bioanalytical method. Here, we present the first report on a UPLC–MS/MS method for analysis of HCA in rat plasma after a simplified and cost-effective protein precipitation. Chromatographic separation of the analytes in the supernatant was achieved using hydrophilic interaction liquid chromatography, where mass parameters were optimized and a rapid 5-min quantitative assay was developed. The method was highly sensitive, accurate, precise and linear in the concentration range of 10.5–5000 ng/mL (validated according to the United States Food and Drug Administration guidelines). Further, the method was successfully used to describe the pharmacokinetic profile of HCA in rat plasma after the administration of pure HCA and commercial Garcinia preparations.