Thiazole Analogs of Isoflavolignans

Modified analogs of isoflavolignans are prepared by annelation of dioxole, dioxane, and dioxepan fragments to 3-thiazolyl-7,8-dihydroxychromones     

The catalytic efficiency of Fe-containing nanocomposites based on highly dispersed silica in the reaction of CO2 hydrogenation

Research on Chemical Intermediates - Oxide Ni(80)Fe(20)/SiO2, Co(93)Fe(7)/SiO2, and Ni(19)Co(77)Fe(4)/SiO2 nanocomposites (NCs) were prepared using highly dispersed silica. It was modified by...     

Robustness analysis in Multi-Objective Mathematical Programming using Monte Carlo simulation

In most multi-objective optimization problems we aim at selecting the most preferred among the generated Pareto optimal solutions (a subjective selection among objectively determined solutions). In this paper we consider the robustness of the selected Pareto optimal solution in relation to perturbations within weights of the objective functions. For this task we design an integrated approach that can be used in multi-objective discrete and continuous problems using a combination of Monte Carlo simulation and optimization. In the proposed method we introduce measures of robustness for Pareto optimal solutions. In this way we can compare them according to their robustness, introducing one more characteristic for the Pareto optimal solution quality. In addition, especially in multi-objective discrete problems, we can detect the most robust Pareto optimal solution among neighboring ones. A computational experiment is designed in order to illustrate the method and its advantages. It is noteworthy that the Augmented Weighted Tchebycheff proved to be much more reliable than the conventional weighted sum method in discrete problems, due to the existence of unsupported Pareto optimal solutions.     

Properties of aqueous solutions containing blends of poly-N-vinylformamide with carboxymethyl cellulose of various degrees of ionization and of composite films of these polymers

Rheological properties of mixtures of dilute and moderately concentrated aqueous solutions of poly-N-vinylformamide and carboxymethyl cellulose of various degrees of ionization were studied. Composite film materials were prepared, and their physicomechanical properties and structural organization were studied.     

Structure and dynamics of liquid crystalline pattern formation in drying droplets of DNA

We investigate the formation of ringlike deposits in drying drops of DNA. In analogy with the colloidal "coffee rings," DNA is transported to the perimeter by the capillary flow. At the droplet edge, however, DNA forms a lyotropic liquid crystal (LC) with concentric chain orientations to minimize the LC elastic energy. During the final stages of drying, the contact line retracts, and the radial stress causes undulations at the rim that propagate inward through the LC and form a periodic zigzag structure. We examine the phenomenon in terms of a simple model based on LC elasticity.     

Synthesis of New Amphiphilic Comb-Like Copolymers Based on Maleic Anhydride and α-Olefins

Summary: Novel amphiphilic comb-like poly(α-olefin-co-maleic anhydride) with a controlled ratio of hydrophilic (polyoxyethylene) and hydrophobic (polymethylene) side chains have been synthesized and characterized. The comb-like copolymers are soluble in organic and aqueous media and form micelles whose behaviour could be correlated to the chemical structure of polymers. We foresee that amphiphilic properties of the novel comb-like polymers are obviously the basis of new architectures in solution which could be used in a broad range of applications. Using micelles from these copolymers, silver nanoparticles with a narrow particle size distribution have been obtained as stable dispersion in both polar and non-polar media.     

Syntheses, optical properties and electronic structures of copper(I) tantalates: Cu5Ta11O30 and Cu3Ta7O19

Two copper tantalates, Cu₅Ta₁₁O₃₀ (1) and Cu₃Ta₇O₁₉ (2), were synthesized by solid-state and flux synthetic methods, respectively. A synthetic route yielding 2 in high purity was found using a CuCl flux at 800^oC and its structure was characterized using powder X-ray diffraction (XRD) data (P6₃/m (no. 176), Z=2, a=6.2278(1) Å, and c=20.1467(3) Å). The solid-state synthesis of 1 was performed using excess Cu₂O that helped to facilitate the growth of single crystals and their characterization by XRD (P6¯2c (no. 190), Z=2, a=6.2252(1) Å, and c=32.516(1) Å). The atomic structures of both copper tantalates consist of alternating single and double layers of TaO₇ pentagonal bipyramids that are bridged by a single layer of isolated TaO₆ octahedra and linearly-coordinated Cu⁺. Measured optical bandgap sizes of ∼2.59 and ∼2.47 eV for 1 and 2 were located well within visible-light energies and were consistent with their orange-yellow colours. Each also exhibits optical absorption coefficients at the band edge of ∼700 and ∼275 cm⁻¹, respectively, and which were significantly smaller than that for NaTaO₃ of ∼1450 cm⁻¹. Results of LMTO calculations indicate that their visible-light absorption is attributable mainly to indirect bandgap transitions between Cu 3d¹⁰ and Ta 5d⁰ orbitals within the TaO₇ pentagonal bipyramids.     

A three‐dimensional heterometallic CuI/VIV 1,2‐bis(1,2,4‐triazol‐4‐yl)ethane framework: a new insight into the structure of vanadium oxyfluoride coordination hybrids

The bitopic ligand 1,2‐bis(1,2,4‐triazol‐4‐yl)ethane (tr₂eth) provides an unprecedented short‐distance N¹:N²‐triazole bridging of Cu^I and V^IV ions in poly[bis[μ₄‐1,2‐bis(1,2,4‐triazol‐4‐yl)ethane]di‐μ₂‐fluorido‐tetrafluoridodi‐μ₂‐oxido‐dicopper(I)divanadium(IV)], [Cu₂V₂F₆O₂(C₆H₈N₆)₂]_n. The Cu^I ions and tr₂eth linkers afford a two‐dimensional square‐grid topology involving centrosymmetric (tr)Cu(μ‐tr)₂Cu(tr) [tr is triazole; Cu—N = 1.9525 (16)–2.0768 (18) Å] binuclear net nodes, which are expanded in a third dimension by centrosymmetric [V₂O₂F₆]²⁻ pillars. The concerted μ‐tr and μ‐O bridging between the Cu^I and V^IV ions allows a multi‐centre accommodation of the vanadium oxyfluoride moiety on a cationic Cu/tr₂eth matrix [Cu—O = 2.1979 (15) Å and V—N = 2.1929 (17) Å]. The distorted octahedral coordination of [VONF₄] is completed by two terminal and two bridging F⁻ ions [V—F = 1.8874 (14)–1.8928 (13) and 2.0017 (13)–2.1192 (12) Å, respectively]. The resulting three‐dimensional framework has a primitive cubic net topology and adopts a threefold interpenetration.