Optimal Factorization of Three-Way Binary Data Using Triadic Concepts

We present a new approach to factor analysis of three-way binary data, i.e. data described by a 3-dimensional binary matrix I, describing a relationship between objects, attributes, and conditions. The problem consists in finding a decomposition of I into three binary matrices, an object-factor matrix A, an attribute-factor matrix B, and a condition-factor matrix C, with the number of factors as small as possible. The scenario is similar to that of decomposition-based methods of analysis of three-way data but the difference consists in the composition operator and the constraint on A, B, and C to be binary. We show that triadic concepts of I, developed within formal concept analysis, provide us with optimal decompositions. We present an example demonstrating the usefulness of the decompositions. Since finding optimal decompositions is NP-hard, we propose a greedy algorithm for computing suboptimal decompositions and evaluate its performance.     

Synthesis of novel thienonorbornylpurine derivatives

The synthesis and antiviral evaluation of 6-amino- and 6-chloro-9-(exo-bicyclo[2.2.1]hept-2yl)-9H-purine derivatives with thiophene and tetrahydrothiophenes annelated to a norbornane moiety are described. The key step in the synthesis of derivatives with the symmetrically annelated thiophene was the Mitsunobu reaction of endo-4-thiatricyclo[5.2.1.0^2,6]deca-2,5-dien-8-ol with 6-chloropurine. The key alcohol was obtained by DDQ mediated aromatization of the corresponding tetrahydro derivatives, which were used for the preparation of the target tetrahydrothieno analogs. The key intermediate for the synthesis of derivatives with the asymmetrically annelated thiophene was 8-exo-azido-3-thiatricyclo[5.2.1.0^2,6]deca-2(6),4-diene, which was prepared from 5-exo-azido[2.2.1]heptan-2-one by aldol condensation with O-ethyl S-(2-oxoethyl) carbonodithioate, deprotection and cyclization. The target compounds were obtained by the construction of the purine base on an amine, which was obtained by LAH reduction of the key azide. The synthesized compounds were evaluated for antiviral and cytostatic activity.     

The effect of the number of carbohydrate moieties on the azaphthalocyanine properties

A series of azaphthalocyanines (AzaPc) bearing one, two, four or eight isopropylidene-protected galactosyl units was prepared by azide-alkyne click reaction or by classical Pc template cyclotetramerization of the corresponding dicyanopyrazine and AzaPc properties important for photodynamic therapy were compared. All compounds absorbed at long wavelengths (above 650 nm) and belonged to strong singlet oxygen producers (Φ(Δ) = 0.58-0.64) retaining significant fluorescence emission (Φ(F) = 0.026-0.23). The only exception was the compound with four isopropyliden-protected galactosyl units where partial aggregation was observed. Removal of protecting groups increased the polar character of all AzaPc. However, only AzaPc bearing eight galactoses was found to be water-soluble (105 mg mL(-1)) but noticeably aggregated in water as well as in organic solvents (DMF, DMSO). Amphiphilic AzaPc bearing one deprotected galactose was incorporated into the lipidic bilayer of liposomes in a nonaggregated form. Liposomes may therefore be a suitable delivery system for this amphiphilic photosensitizer.     

Enhanced performance of surface-modified TiO(2) photocatalysts prepared via a visible-light photosynthetic route

Benzene can be activated by visible light (λ > 455 nm) in the presence of TiO(2), which leads to formation of carbonaceous polymeric deposits on the titania surface. These photosynthesized surface-modified materials exhibit enhanced photoactivity in degradation of phenolic compounds, particularly under visible light irradiation.     

Mechanical and optical properties of SiO<Subscript>2</Subscript> thin films deposited on glass

The optical and mechanical properties of amorphous SiO₂ films deposited on soda-lime silicate float glass by reactive RF magnetron sputtering at room temperature were investigated in dependence of the process pressure. The densities of the films are strongly influenced by the process pressure and vary between 2.38 and 1.91 g cm^?3 as the pressure changes from 0.27 to 1.33 Pa. The refractive indices of the films shift between 1.52 and 1.37, while the residual compressive stresses in the deposited films vary in the range from 440 to 1 MPa. Hardness and reduced elastic modulus values follow the same trend and decline with the increase of process pressure from 8.5 to 2.2 GPa and from 73.7 to 30.9 GPa, respectively. The abrasive wear resistance decreases with the density of the films.     

Synthesis of 2-alkenyl-3-hydroxyquinolin-4(1H)-ones as promising antimicrobial and fluorescent agents

2-Alkenyl-3-hydroxyquinolin-4(1H)-ones were prepared by the rearrangement of anthranilic acid esters synthesized by two alternative methods. The prepared derivatives were screened for their antimicrobial activities against representative Gram-positive and Gram-negative bacteria, displaying notable minimum inhibitory concentration values against specific strains. The emission spectra of the target quinolines exhibited two well-separated emission bands, and the maximum excitation wavelengths of the selected compounds were detected at relatively high values.     

Experimental test of the quantum non-Gaussian character of a heralded single-photon state

We report on the experimental verification of quantum non-Gaussian character of a heralded single-photon state with a positive Wigner function. We unambiguously demonstrate that the generated state cannot be expressed as a mixture of Gaussian states. Sufficient information to witness the quantum non-Gaussian character is obtained from a standard photon anticorrelation measurement.     

Silicon-(thio)urea Lewis acid catalysis

We present a new class of catalysts based on the combination of N,N'-diaryl(thio)ureas and weak silicon Lewis acids (e.g., SiCl(4)). Such silicon-(thio)urea catalysts effectively catalyze the stereospecific rearrangement of epoxides to quaternary carbaldehydes.