Preparation and Characterization of Energetic Nanocomposites of Organic Gel – Inorganic Oxidizers

Two types of polymeric sols, resorcinol‐formaldehyde (RF) and resorcinol‐furfural (RFur), were mixed in a water‐containing medium with aqueous solutions of inorganic salts: NH₄ClO₄, Mg(ClO₄)₂, and NH₄NO₃. After gelation and an ambient pressure drying, hybrid nanocomposites with properties of energetic materials were obtained. It was stated that salt concentration and addition of a second solvent (e.g., methanol or N,N‐dimethylformamide) to the mixture of reagents have crucial meaning for gel formation. In the case when only water was used, the mixture of organic sol/inorganic salt did not transfer from sol to gel, and precipitates were formed. Conventional drying of wet gelled composites leads to rigid material called xerogels. The RF xerogels are red and RFur xerogels are black. Typically, xerogels are transparent at low salt concentration (below 30%). The microstructure, morphology, and some other properties of chosen composites were studied by means of HR SEM, AFM, XRD, DTA/TG, and N₂ adsorption isotherm techniques. SEM observation revealed that sizes of the oxidizer particles vary from less than 100 nm to ca. 1000 nm. XRD analyses also confirmed the presence of nanometer‐sized crystals of oxidizers in some formulations. The specific surface area of polymeric matrix/oxidizer composites was found to be in the range from 0.002 to 0.3 m² g⁻¹. After removing the salt from the composites (by extraction with boiling water), the specific surface area grows even up to 210 m² g⁻¹. TG/DTA analyses showed that the tested composites decompose as typical energetic materials. If pre‐heated and exposed to flame, some of them (especially RF/Mg(ClO₄)₂ composites) undergo violent deflagration with loud sound and flash effect.     

Improved conformational space annealing method to treat β-structure with the UNRES force-field and to enhance scalability of parallel implementation

Successful application of physics-based protein-structure prediction methods depends on sophisticated computational approaches to global optimization of the conformational energy of a polypeptide chain. One of the most effective procedures for the global optimization of protein structures appears to be the Conformational Space Annealing (CSA) method. CSA is a hybrid method which combines genetic algorithms, essential aspects of the build-up method and a local gradient-based minimization. CSA evolves the population of conformations through genetic operators (mutations, i.e. perturbations of selected geometric parameters, and crossovers, i.e. exchange of selected subsets of geometric parameters between conformations) to a final population optimizing their conformational energy. Implementation of the CSA method with the united-residue force field (UNRES, in which each amino-acid residue is represented by two interaction sites, namely the united peptide group and the united side-chain) was enhanced by introducing new crossover operations consisting of (i) copying β-hairpins, (ii) copying remote strand pairs forming non-local β-sheets, and (iii) copying α-helical segments. A mutation operation, which shifts the position of a β-turn, was also introduced. The new operations promote β-structure, and are essential for searching the conformational space of proteins containing both α- and β-structure; without these operations, excessive preference of α-helical structures is obtained, even though these structures are high in energy. Parallelization of the CSA method has also been enhanced by removing most of the synchronization steps; the improved algorithm scales almost linearly up to 1,000 processors with over 75% average performance.     

SELECTIVITY OF RESINS WITH GUANIDYL GROUPS TOWARDS DICYANOAURATE ANIONS

ABSTRACT

Resins having two types of ligands: guanidine and aminoguanidine on copolymers of vinylbenzyl chloride (VBC)/ methyl methacrylate (MM)/ divinylbenzene (DVB) and on styrene (S)/DVB have been investigated in respect to their selectivity towards dicyanoaurate anions Resins coded CH and CP displayed high selectivity and sorption of gold from its diluted solution. They sorbed 10 - 11?mg of gold/g and dicyanoaurate distribution coefficient reached 1890 and 2290, respectively. Resins have the following selectivity order when sorption was carried out from solution of 5.08?mg Au/dm³: resin U-BIS Zn>Ag>Au>Cu; resin CP Au>Zn»Cu»Ag; resin CH Au>Zn=Ag»Cu. Resins have weak affinity towards iron complexes.     

Modeling of Drying of Highly Shrinking Materials Using Hydrogels as an Example

The work presents a model of convective drying of a highly shrinking material of cylindrical shape. To identify the effective diffusivity as a function of local temperature and moisture content the problem was solved as an inverse problem. A set of experimental data served for model validation. The optimization algorithms were used to solve PDE system and fit numerically obtained curves to the experimental data using the effective diffusivity as the only adjustable parameter.     

Dyes based on a 1,4‐naphthoquinone skeleton as new type II photoinitiators for radical polymerisation

Photoredox pairs consisting of 1,4‐naphthoquinone dyes and commercially available hydrogen donors (2‐mercaptobenzoxazole, 2‐mercaptobenzothiazole, 2‐mercaptobenzimidazole and 2,5‐dimercapto‐1,3,4‐thiadiazole) are found to be effective initiator systems for the radical polymerisation of trimethylolpropane triacrylate under visible light. The efficiency of these initiator systems is discussed in terms of the free energy change for the electron transfer process from the dye to the hydrogen donor. The results show that the photoinitiation ability of tested photoredox pairs depends on the structure of both the dye and the hydrogen donor.     

High temperature monoclinic-to-tetragonal phase transition in magnesium doped lanthanum ortho-niobate

Magnesium doped lanthanum ortho-niobate (La_0.98Mg_0.02NbO₄) was prepared by the molten salt synthesis method. X-ray diffraction and dilatometry methods were used to study high temperature behavior of the ceramic material. Special attention was paid to the phase transition between the monoclinic and tetragonal phases. The values of spontaneous strain on the basis of unit cell parameter, obtained by Rietveld refinement, have been calculated as well as Landau order parameter. The thermal expansion coefficient (TEC) of La_0.98Mg_0.02NbO₄ was determined to be 12×10^?6 1/K and 8×10^?6 1/K below and above 500 °C, respectively.     

A Photoexcited Porphyrin System as a Biomimetic Catalyst for D-limonene Biotransformation

A photoexcited porphyrin system has been found to be an efficient catalyst for D-limonene biotransformation. The catalyst showed high selectivity in hydroxylation of D-limonene. The best catalyst for limonene biotransformation was 5,10,15,20-Tetraphenylporphyrin (H₂TPP), which gave the highest accumulation of carvone and an unknown product with a verbenone-like mass spectrum. The highest conversion yield of these products was favoured at 1:2 molar ratio of H₂TPP to limonene. Some factors affecting the biotransformation yield were also investigated. Maximal yield of carvone was obtained in the medium containing 90% of the substrate, within the period of 18–36 h. Mechanism involved in limonene biotransformation catalysed by H₂TPP is also discussed.     

Effect of ALDH1A1 Gene Knockout on Drug Resistance in Paclitaxel and Topotecan Resistant Human Ovarian Cancer Cell Lines in 2D and 3D Model

Ovarian cancer is the most common cause of gynecological cancer death. Cancer Stem Cells (CSCs) characterized by drug transporters and extracellular matrix (ECM) molecules expression are responsible for drug resistance development. The goal of our study was to examine the role of aldehyde dehydrogenase 1A1 (ALDH1A1) expression in paclitaxel (PAC) and topotecan (TOP) resistant ovarian cancer cell lines. In both cell lines, we knocked out the ALDH1A1 gene using the CRISPR/Cas9 technique. Additionally, we derived an ALDH1A1 positive TOP-resistant cell line with ALDH1A1 expression in all cells via clonal selection. The effect of ALDH1A1 gene knockout or clonal selection on the expression of ALDH1A1, drug transporters (P-gp and BCRP), and ECM (COL3A1) was determined by Q-PCR, Western blot and immunofluorescence. Using MTT assay, we compared drug resistance in two-dimensional (2D) and three-dimensional (3D) cell culture conditions. We did not observe any effect of ALDH1A1 gene knockout on MDR1/P-gp expression and drug resistance in the PAC-resistant cell line. The knockout of ALDH1A1 in the TOP-resistant cell line resulted in a moderate decrease of BCRP and COL3A1 expression and weakened TOP resistance. The clonal selection of ALDH1A1 cells resulted in very strong downregulation of BCPR and COL3A1 expression and overexpression of MDR1/P-gp. This finally resulted in decreased resistance to TOP but increased resistance to PAC. All spheroids were more resistant than cells growing as monolayers, but the resistance mechanism differs. The spheroids’ resistance may result from the presence of cell zones with different proliferation paces, the density of the spheroid, ECM expression, and drug capacity to diffuse into the spheroid.     

Antifungal activity of denture soft lining material modified by silver nanoparticles-a pilot study

Soft liner materials in oral cavity environments are easily colonized both by fungi and dental plaque. These factors are the cause of mucosal infections. The microorganism that most frequently colonizes soft liner materials is Candida albicans. Colonization occurs on the surface of materials and within materials. A solution to this problem might involve modification of soft liner materials with silver nanoparticles (AgNPs). In this article, we present results showing the antifungal efficacy of silicone soft lining materials modified with AgNPs. The modification process was conducted by dissolving both material components (base and catalyst) in a colloidal solution of AgNPs and evaporating the solvent. Composites with various AgNP concentrations (10, 20, 40, 80, 120 and 200 ppm) were examined. The in vitro antifungal efficacy (AFE) of composite samples was 16.3% to 52.5%.