Molecules with new topologies derived from hydrogen-bonded dimers of tetraurea calix[4]arenes

Tetraurea calix[4]arenes 2 have been synthesized in which two adjacent aryl urea residues are connected to a loop by an aliphatic chain -O-(CH(2))(n)-O-. The remaining urea residues have a bulky 3,5-di-tert-butylphenyl residue and an omega-alkenyloxyphenyl residue. Since this bulky residue cannot pass through the loop, only one homodimer (22) is formed in apolar solvents, for steric reasons, in which the two alkenyl residues penetrate the two macrocyclic loops. Covalent connection of these alkenyl groups by olefin metathesis followed by hydrogenation creates compounds 3, which consist of molecules with hitherto unknown topology. Their molecular structure was confirmed by (1)H NMR spectroscopy and ESIMS, and for one example by single-crystal X-ray analysis.     

Bayesian Dimensionality Reduction With PCA Using Penalized Semi-Integrated Likelihood

We discuss the problem of estimating the number of principal components in principal components analysis (PCA). Despite the importance of the problem and the multitude of solutions proposed in literature, it comes as a surprise that there does not exist a coherent asymptotic framework, which would justify different approaches depending on the actual size of the dataset. In this article, we address this issue by presenting an approximate Bayesian approach based on Laplace approximation and introducing a general method of developing criteria for model selection, called PEnalized SEmi-integrated Likelihood (PESEL). Our general framework encompasses a variety of existing approaches based on probabilistic models, like the Bayesian Information Criterion for Probabilistic PCA (PPCA), and enables the construction of new criteria, depending on the size of the dataset at hand and additional prior information. Specifically, we apply PESEL to derive two new criteria for datasets where the number of variables substantially exceeds the number of observations, which is out of the scope of currently existing approaches. We also report results of extensive simulation studies and real data analysis, which illustrate the desirable properties of our proposed criteria as compared to state-of-the-art methods and very recent proposals. Specifically, these simulations show that PESEL-based criteria can be quite robust against deviations from the assumptions of a probabilistic model. Selected PESEL-based criteria for the estimation of the number of principal components are implemented in the R package pesel, which is available on github (https://github.com/psobczyk/pesel). Supplementary material for this article, with additional simulation results, is available online. The code to reproduce all simulations is available at https://github.com/psobczyk/pesel_simulations.     

Feller’s Scheme in Approximation by Nonlinear Possibilistic Integral Operators

By analogy with Feller’s general probabilistic scheme used in the construction of many classical convergent sequences of linear operators, in this paper, we consider a Feller-kind scheme based on the possibilistic integral, for the construction of convergent sequences of nonlinear operators. In particular, in the discrete case, all the so-called max-product Bernstein-type operators and their qualitative convergence properties are recovered. Also, discrete nonperiodic nonlinear possibilistic convergent operators of Picard type, Gauss–Weierstrass type and Poisson–Cauchy type are studied and the possibility of introduction of discrete periodic(trigonometric) nonlinear possibilistic operators of de la Vallée–Poussin type, of Fejér type and of Jackson type is mentioned as future directions of research.     

Synthesis,crystal structures,characterization and antitumor activities of two copper(II) complexes of a sulfonamide ligand

An N-sulfonamide (HL = N-(5-(4-methoxyph-enyl)-[1, 3, 4]–thiadiazole–2-yl)-naphtalenesulfonamide) and two of its Cu(II) complexes, [Cu(L)₂(py)₂] (C1) and [Cu(L)(phen)₂](L)1.25(MeOH) (C2), were synthesized. The X-ray crystal structures of the complexes have been determined. In complex C1, the copper atom is four-coordinated, forming a CuN₄ chromophore, while in complex C2, the copper atom is five-coordinated, forming a CuN₅ chromophore. The ligand acts as monodentate, coordinating the metal through a single thiadiazole N atom. The molecules from the reaction medium (pyridine and phenanthroline) are also involved in coordination to the copper atoms. The complexes have a square planar (C1) and slightly distorted square pyramidal (C2) geometries. The compounds were characterized by physicochemical and spectroscopic methods. Nuclease activity studies of the complexes confirm their capacity to cleave DNA. Both complexes also have SOD-like activity, but weaker than the native Cu₂Zn₂SOD activity. Cytotoxicity studies were carried out on melanoma cell line B16F10 and on normal retinal epithelial cell line (D407) and confirmed that C2 inhibits the growth of B16F10 cells, in a dose-dependent manner. Also, C2 displays a cytoselective profile, since it is not toxic to the D407 cell line. The results of the cell cytotoxicity studies are in concordance with the DNA cleavage and SOD mimetic activity studies and indicate that complex C2 has a high biological activity.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Chemical activation of ultrasonic cavitation

A method for intensifying ultrasonic cavitation in water and aqueous solutions has been proposed, which consists of a chemical fixation of dissolved oxygen. The influence of selected reducing agents on the intensity of cavitation in water and alkaline solutions has been investigated.     

Nonlinear neutral inclusions: Assemblages of spheres

The problem of determining nonlinear neutral inclusions in (electrical or thermal) conductivity is considered. Neutral inclusions, inserted in a matrix containing a uniform applied electric field, do not disturb the field outside the inclusions. The well known Hashin coated sphere construction is an example of a neutral inclusion. In this paper, we consider the problem of constructing neutral inclusions from nonlinear materials. In particular, we discuss assemblages of coated spheres and the two-dimensional analogous problem of assemblages of coated disks.     

Interactions of di- and trivalent anionic azo dyes with polycations of integral type

The spectral changes of Crystal Ponceau 6R and Ponceau 4R induced by the interaction with polycations having N,N-dimethyl-2-hydroxypropane-1,3-diylammonium chloride units in the main chain were followed. The stoichiometry of the polycation-dye complex related to the dye structure was elaborated by UV-VIS spectrophotometry and viscosimetric measurements. Formation of a tricomponent complex between the polycation/dye complex and poly(sodium acrylate) was also revealed.     

Polycondensation vs. cyclization of divinylsubstituted silicon compounds catalyzed by transition metal complexes

In the presence of ruthenium complexes divinyldiorganosilicon compounds undergo de‐ethenated coupling polycondensation yielding under optimum conditions trans‐tactic polysilylene(siloxylene, silazanylene)vinylenes and poly(silylene‐arylene‐vinylenes). Rhodium‐ ([RhX(cod)]₂ X = Cl, OSiMe₃) catalyzed ring closure of oligomeric (dimeric, trimeric) products of intermolecular condensation opens a new route to synthesizing organosilicon exo‐cyclic methylenes. In the presence of Ru‐complexes the cross‐coupling (poly)condensation of di‐ and trivinylsilicon monomers with organic dienes allows syntheses of a series of linear and dendrimeric poly(arylene‐silylene‐vinylene)s.