The Finite Element Method in Thermosetting Polymers' and FRPs' Supramolecular Structure and Thermomechanical Properties' Modeling.

The object of research is cured thermosetting epoxy polymer and FRP on the base of the same polymer matrix. The purpose of this research is to develop the finite element (FE) method in the modeling of cured thermosetting polymers and FRPs to predict their mechanical and thermal properties. The structural mathematical modeling with subsequent computer FE modeling was performed.

Cyclic Thermomechanical Loading of Epoxy Polymer: Modeling with Consideration of Stress Accumulation and Experimental Verification.

Developing a viscoelastic model for the cyclic thermomechanical loading of thermosetting polymers is the main goal of this study. The model includes memory for residual thermal stresses and can consider stress accumulation across many loading cycles. By considering stress accumulation, we can improve predictions and understand how thermosetting polymers' stress-strain state changes under cyclic thermomechanical loading.

Effect of Thermal Aging on Viscoelastic Behavior of Thermosetting Polymers under Mechanical and Cyclic Temperature Impact.

Development of load-bearing fiber reinforced plastic (hereinafter referred to as FRP) composite structures in civil engineering, exploited under high temperatures, such as industrial chimneys and gas ducts, requires the knowledge of their long-term behavior under constant and cyclic mechanical and temperature loads. Such conditions mean that the viscoelasticity of FRP should be considered along with the thermal aging effect. This research is devoted to the effects of thermal aging on the viscoelastic behavior of polymers.

Eubiotic effect of rifaximin is associated with decreasing abdominal pain in symptomatic uncomplicated diverticular disease: results from an observational cohort study.

Background: Rifaximin effectively treats symptomatic uncomplicated diverticular disease (SUDD) and has shown eubiotic potential (i.e., an increase in resident microbial elements with potential beneficial effects) in other diseases.

Relaxation Model of the Relations between the Elastic Modulus and Thermal Expansivity of Thermosetting Polymers and FRPs.

This research was completed in the development of studies devoted to relations between the elastic modulus (MoE) and thermal expansivity (CTe) of different materials. This study, based on experimental data, confirmed the models of the relations between MoE and CTe under normal and heating temperatures for thermosetting epoxy polymers and glass-fiber FRPs in two variants (unfilled and filled by mineral additives), after the usual glassing and prolonged thermal conditioning (thermo-relaxation). The experiment was based on dilatometric and elastic deformation testing.

Solid Particle Erosion of Filled and Unfilled Epoxy Resin at Room and Elevated Temperatures.

Solid particle erosion at room and elevated temperatures of filled and unfilled hot-cured epoxy resin using an anhydride hardener were experimentally tested using an accelerated method on a special bench. Micro-sized dispersed industrial wastes were used as fillers: fly ash from a power plant and spent filling material from a copper mining and processing plant. The results showed that the wear of unfilled epoxy resin significantly decreases with increasing temperature, while the dependence on the temperature of the wear intensity at an impingement angle of 45° is linear and inversely proportional, and at an angle of 90°, non-linear.

Impact of the Polymer Backbone Structure on the Separation Properties of New Stationary Phases Based on Tricyclononenes.

The main purpose of this paper is to compare the chromatographic properties of capillary columns prepared with polymers with different backbone structures and to demonstrate the possibility of polymer differentiation via inverse gas chromatography. With the use of addition and metathesis types of polymerization of tricyclononenes, two new stationary phases were prepared. The metathesis polymer contained double bonds in the polymeric backbone while the backbone of the addition polymer was fully saturated and relatively mobile.

Non-Linearity of Thermosetting Polymers' and GRPs' Thermal Expanding: Experimental Study and Modeling.

Thermal expanding is the important property that defines the stress-strain condition of GRP structures exploited under heating and having limited thermal resistance. So, the GRPs' thermal expanding prediction is the actual requirement of such structures design. The experimental accurate dilatometric study resulted in the non-linearity of thermosetting polymers and plastics thermal expanding under heating.

Effect of Long-Term Thermal Relaxation of Epoxy Binder on Thermoelasticity of Fiberglass Plastics: Multiscale Modeling and Experiments.

The work is devoted to the prediction and experimental research of the elastic bending modulus of glass-reinforced plastics with an epoxy matrix on anhydride hardener reinforced with different glass fabrics. Experimental studies have been carried out to assess the effect of thermal relaxation of the polymer matrix structure due to long-term exposure to elevated temperatures (above the glass transition temperature of the polymer matrix) on the GRP elastic bending modulus at temperatures ranging from 25 to 180 °C. It has been shown that due to the thermal relaxation of the polymer matrix structure, the GRP modulus increases significantly at temperatures above 110 °C and decreases slightly at lower temperatures.

Compressive and Tensile Elastic Properties of Concrete: Empirical Factors in Span Reinforced Structures Design.

Concretes with the same strength can have various deformability that influences span structures deflection. In addition, a significant factor is the non-linear deformation of concrete dependence on the load. The main deformability parameter of concrete is the instantaneous modulus of elasticity.

Prolonged Thermal Relaxation of the Thermosetting Polymers.

The rigidity of structures made of polymer composite materials, operated at elevated temperatures, is mainly determined by the residual rigidity of the polymer binder (which is very sensitive to elevated temperatures); therefore, the study of ways to increase the rigidity of polymer materials under heating (including prolonged heating) is relevant. In the previous research, cured thermosetting polymer structure's non-stability, especially under heating, is determined by its supra-molecular structure domain's conglomerate character and the high entropy of such structures. The polymer elasticity modeling proved the significance of the entropy factor and layer (EPL) model application.

Preparation and properties of GC capillary column with hypercrosslinked stationary phase.

For the first time, highly porous hypercrosslinked polystyrene layer was synthesized within a gas chromatography capillary column and successfully deposited onto the capillary walls generating porous layer open-tubular capillary column. Elaborated three steps synthetic procedure provides tightly bonded porous polymeric layer and ensues complete elimination of particle shedding and the needs for particle traps. Due to highly developed surface area, porous layer open-tubular column provides strong solute retention that is useful for the separation of various volatile solvents and light gas compounds including ethane, ethylene, ethyne.

Dendritic Iron(III) Carbazole Complexes: Structural, Optical, and Magnetic Characteristics.

This paper focuses on the synthesis, structural characterization, and study of the optical, magnetic, and thermal properties of novel architectures combining metal ions as magnetoactive centers and photoactive blocks formed by carbazole units. For this purpose, a series of azomethine complexes of the composition [Fe(L)]X (L = 3,6-bis[(3',6'-di--butyl-9-carbazol)-9-carbazol]benzoyloxy-4-salicylidene-N'-ethyl-N-ethylenediamine, X = NO, Cl, PF) were synthesized by the reaction of metal salts with Schiff bases in a mixture of solvents. The UV-Vis absorption properties were studied in dichloromethane and rationalized via time-dependent density functional theory (DFT) calculations.

Chromatographic Method for Evaluation of Polymeric GC Stationary Phases Ageing Using the Novel Non-Cross-Linked Poly(3-(Tributoxysilyl)Tricyclononene-7) as the Model Stationary Phase.

The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable than previously studied trimethylsilyl- and trimethoxysilyl- derivatives.

Reconstruction of the Image Metric of Periodic Structures in an Opto-Digital Angle Measurement System.

Measurement of the object angular position and its change is one of the important tasks in measurement technique. Our method is based on determination of the angular position of a 2D periodical optical pattern (2D mark) at the object, captured by the sensor of a digital camera. System performance can be frustrated by errors in determination of the spot coordinates on the camera sensor; by the presence of lens aberrations; by deviations from the parallelism of the pattern planes and the camera sensor; and by differences between the actual spots positions and the ideal grid.

Polymers under Load and Heating Deformability: Modelling and Predicting.

The polymer deformability under load and heating is the determining factor in calculating reinforced polymer structures used under heating. Deformability-load/temperature relations make it possible to calculate temperature stresses and deformations in bearing cross-sections of polymer structures such as chimneys, smokestacks, etc. The present study suggests a method of calculating deformability of polymers subjected to the temperature loads.

The Struggle for Certainty: Ontological Security, the Rise of Nationalism, and Australia-China Tensions after COVID-19.

Australia-China relations have been relatively stable over the last decade. However, soon after the outbreak of COVID-19, Australia took an increasingly assertive stance toward China, one that is arguably even more assertive than those of its Western allies. What prompted Australia to adopt a tougher policy against China? This article argues that COVID-19 has brought significant uncertainty to the international system and, hence, to Australia's external environment, which has affected the country's decision-making, accelerating the formation of a hardline policy toward China.

Heteroarene-fused anthraquinone derivatives as potential modulators for human aurora kinase B.

The quest for effective anticancer therapeutics continues to be extensively pursued. Over the past century, several drugs have been developed, however, a majority of these drugs have a poor therapeutic index and increased toxicity profile. Hence, there still exists ample opportunity to discover safe and effective anticancer drugs.

Synthesis and antibacterial activity of novel arylbis(indol-3-yl)methane derivatives.

A series of new compounds-arylbis(indol-3-yl)methylium derivatives-were synthesized and their antimicrobial activity was evaluated. All the compounds turned out to be highly active, with MIC depending on their structure and the length of N-alkyl residues. The parent triarylmethane compounds possess weaker activity.

Synthesis, antimicrobial and antiproliferative properties of epi-oligomycin A, the (33)-diastereomer of oligomycin A.

We describe the synthesis of epi-oligomycin A, a (33)-diastereomer of the antibiotic oligomycin A. The structure of (33)-oligomycin A was determined by elemental analysis, spectroscopic studies, including 1D and 2D NMR spectroscopy, and mass spectrometry. Isomerization of C33 hydroxyl group led to minor changes in the potency against , , and filamentous fungi whereas the activity against decreased by approximately 20-fold compared to oligomycin A.

Synthesis and evaluation of biological activity for dual-acting antibiotics on the basis of azithromycin and glycopeptides.

One of the promising directions of the combined approach is the design of dual-acting antibiotics - heterodimeric structures on the basis of antimicrobial agents of different classes. In this study a novel series of azithromycin-glycopeptide conjugates were designed and synthesized. The structures of the obtained compounds were confirmed using NMR spectroscopy and mass spectrometry data including MS/MS analysis.

Synthesis and evaluation of biological activity of benzoxaborole derivatives of azithromycin.

Novel benzoxaborole derivatives of azithromycin in which benzoxaborole residue is attached to the 4″-hydroxy-group of azithromycin have been synthesized. Antibacterial activity of synthesized derivatives in comparison with azithromycin was tested on a panel of Gram-positive and Gram-negative bacterial strains. All the investigated compounds demonstrated broad spectrum of antibacterial activity being in general more active against Gram-positive strains.

Thermal stability of poly[1-(trimethylsilyl)-1-propyne] and the gas chromatographic stationary phase based on it.

The thermal stability of poly[1-(trimethylsilyl)-1-propyne] is investigated by heating the capillary column with this polymer as the stationary phase with the subsequent separation of the test mixture of light hydrocarbons. It is shown that heating of the column up to 130°C does not cause a decrease in efficiency or in the retention time of solutes. A further increase in temperature results in both decrease in column efficiency and sorbate retention.

Investigation of poly[oligo(ethylene glycol)diacrylates] as potential stationary phases in GC.

Poly[oligo(ethylene glycol)diacrylate]s were investigated as potential candidates for application as stationary phases in capillary gas chromatography. Depending on the molar mass of the monomer, up to three different phase transitions were observed in calorimetric scans of the polymers. Two transitions have been identified as the glass transition and melting of crystallites while the nature of the third effect remains unknown.

Verification of oligomycin A structure: synthesis and biological evaluation of 33-dehydrooligomycin A.

Although, the structure of oligomycin A (1) was confirmed by spectroscopic and chemical evaluations, some crystallographic data cast doubt on the originally adopted structure of the side 2-hydroxypropyl moiety of this antibiotic. It was suggested that the side chain of the oligomycin is enol-related (2-hydroxy-1-propenyl). To clarify this matter we synthesized and evaluated 33-dehydrooligomycin A (2) prepared by the Kornblum oxidation of 33-O-mesyloligomycin A (3) by dimethyl sulfoxide.