Highly Crystalline and Semiconducting Imine-Based Two-Dimensional Polymers Enabled by Interfacial Synthesis

Single-layer and multi-layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long-range transport properties. Here we employ a surfactant-monolayer-assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine-based 2D polymer (PI-2DP) films with square and hexagonal lattices, respectively. The synthetic PI-2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100–150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI-2DP are investigated by time-resolved terahertz spectroscopy. Typically, the porphyrin-based PI-2DP 1 film exhibits a p-type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm² V⁻¹ s⁻¹, superior to the previously reported polyimine based materials.     

New compounds with a TGBA-TGBC-SmC* phase sequence

A new series of lactic acid derivatives has been prepared with molecular cores consisting of two laterally substituted biphenyls connected by an ester group. The compounds exhibited the TGBA phase in a broad temperature range. In addition, for some compounds, a narrow blue phase was found above the TGBA phase on cooling from the isotropic phase. Except for the compound with the shortest chain, the TGBC phase appeared below the TGBA phase. The low temperature SmC* phase existed within the interval up to 80 K, including the overcooled state, which was down to room temperature. In the compounds studied a strong pre-transitional phenomenon took place manifested as a broad peak on the differential scanning calorimetry plot in the isotropic phase. The phases were established on the basis of a planar sample and free-standing film microscope observation. Small angle X-ray diffraction measurements provided information about layer spacing, d, and confirmed the phase assignment. Dielectric spectroscopy revealed the soft and Goldstone modes in the respective TGBA and SmC* phases.     

Thermodynamic and kinetic analysis of the polymetallic copper concentrate oxidation process

This paper presents the experimental investigation results of the polymetallic copper concentrate oxidation process with the oxygen from the air. Concentrate characterization included chemical analysis, X-ray diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), and light microscopy. Chemical analysis and EDXRF results showed that the investigated copper concentrate consisted mainly of copper, iron and sulphur, with small amounts of zinc, lead, arsenic and other minor elements. XRD analysis showed that metals were bonded to sulphur in sulphide minerals: chalcopyrite, pyrite, luzonite, sphalerite and enargite. Those minerals were mutually bonded into aggregates, confirmed by light microscopy. The results of DTA/TG analysis were used for determining the mechanism of the oxidation process. Comparison between experimental data obtained by XRD, DTA/TG and data obtained from the phase stability diagrams, implied that the oxidation process of the investigated concentrate can be divided in two stages: the first stage consisted of sulphide oxidation reactions with the characteristic exothermal effects below 973 K while forming sulphates and oxysulphates, and the second stage, which consisted of sulphates and oxysulphates decomposition reactions and forming copper and iron oxides, with endothermal effects above 973 K. Kinetic studies were carried out in isothermal conditions in the temperature range (573–873) K. Calculations were done according to Sharp’s method of reduced half-time reaction. Calculated values for the activation energies were 82 kJ mol^?1 for the initial stage of the oxidation process (up to 723 K), and 42 kJ mol^?1 for the stage of the process where desulphurization degree reached 68–86 % for the oxidation temperatures 748 K and higher. Calculated activation energy values indicated that the reaction of oxidation is a chemically controlled reaction.     

Geometric Arveson–Douglas conjecture

We prove the Arveson–Douglas essential normality conjecture for graded Hilbert submodules that consist of functions vanishing on a given homogeneous subvariety of the ball, smooth away from the origin. Our main tool is the theory of generalized Toeplitz operators of Boutet de Monvel and Guillemin.     

Normally Admissible Stratifications and Calculation of Normal Cones to a Finite Union of Polyhedral Sets

This paper considers computation of Fréchet and limiting normal cones to a finite union of polyhedra. To this aim, we introduce a new concept of normally admissible stratification which is convenient for calculations of such cones and provide its basic properties. We further derive formulas for the above mentioned cones and compare our approach to those already known in the literature. Finally, we apply this approach to a class of time dependent problems and provide an illustration on a special structure arising in delamination modeling.     

Transferral of entailment in duality theory: Dualisability

A number of new results that say how to transfer the entailment relation between two different finite generators of a quasi-variety of algebras is presented. As their consequence, a well-known result saying that dualisability of a quasi-variety is independent of the generating algebra is derived. The transferral of endodualisability is also considered and the results are illustrated by examples.     

On Double Basic Algebras and Pseudo-effect Algebras

Double basic algebras are a counterpart of bounded lattices with order-antiautomorphisms on principal filters. In the paper, an independent axiomatization of double basic algebras is given and lattice pseudo-effect algebras are characterized in the setting of double basic algebras.     

Reversible aggregation of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) block copolymer micelles in acidic aqueous Solutions

Micelles of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-PVP-PEO) were studied in acidic aqueous solutions by static and dynamic light scattering, alkalimetric titration, fluorescence correlation spectroscopy, and after deposition on a mica surface by atomic force microscopy. The PS-PVP-PEO micelles prepared by dialysis in ternary 1,4-dioxane-methanol-acidic water mixtures have a very low association number and show a strong tendency to form aggregates. The aggregation, which is promoted at low pH, seems to be fully reversible. Possible mechanisms of the aggregation are discussed. Atomic force microscopy scans of PS-PVP-PEO micelles deposited on a mica surface reveal the formation of micellar aggregates and support the general concept of aggregation upon changes in conditions and deterioration of the stability of small micelles.     

Impregnated fly ash sorbent for cesium-137 removal from water samples

Journal of Radioanalytical and Nuclear Chemistry - Cesium-137 is an important indicator of radioactive pollution in the aquatic environment. The aim of this study was to increase the sorption...