Synthesis and characterization of cross‐linked poly(sodium acrylate)/sodium silicate hydrogels

Transparent and intumescent polymer‐silicate hydrogels were synthesized by free‐radical polymerization, in the presence of the redox initiators system (potassium persulphate/sodium thiosulphate) and cross‐linking monomer (N,N′‐methylenebisacrylamide). Hydrogels obtained in such a manner were rheologically tested and it was found that the same sample with a different sodium acrylate concentration polymerized faster when its content was lower. The spectroscopic and thermal analysis proved that the polymer combines with sodium silicate by hydrogen bonds and during thermal degradation only small polymer fragments and water molecules were released. NMR studies have shown that the content of water glass causes shorter relaxation times. Conducted fire tests showed that glass panes systems filled with the tested hydrogels meet the relevant construction standards and what is their big advantage, a thin 1 mm layer of polymer‐silicate gel is sufficient for this purpose. We believe that these results will contribute to the development of intumescent hydrogels with enhanced fire‐retardant properties. POLYM. ENG. SCI., 59:1279–1287 2019. © 2019 Society of Plastics Engineers     

Structure‐Based Mechanism of Oleate Hydratase from Elizabethkingia meningoseptica

Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration.     

Multiscale modeling of elastic properties of cortical bone

We model cortical bone as a composite material with hierarchical structure. At a nanostructural level, bone is composed of cross-linked collagen molecules, containing water and non-collagenous proteins in their gaps, reinforced with hydroxyapatite-like nanocrystals. Such a nanocomposite structure represents a mineralized collagen fibril, which serves as a primary building block of bone. At a sub-microstructural level (few microns), the mineralized collagen fibrils are embedded in an extrafibrillar hydroxyapatite matrix to form a single lamella, which also contains the lacunar cavities. At a microstructural level (hundreds of microns) one can distinguish two lamellar structures in the mature cortical bone: osteons, made of concentric layers of lamellae surrounding long hollow Haversian canals, and interstitial lamellae made of remnants of old osteons. At a mesostructural level (several millimeters), the cortical bone is represented by a random collection of osteons and resorption cavities in the interstitial lamellae. A macrostructural level is the whole bone level containing both the cortical (compact) and trabecular (spongy) bone types. In this paper, we predict analytically the effective elastic constants of cortical bone by modeling its elastic response at these different scales, spanning from the nanostructural to mesostructural levels, using micromechanics methods and composite materials laminate theories. The results obtained at a lower scale serve as inputs for the modeling at a higher scale. The predictions are in good agreement with the experimental data reported in literature.     

ZnO Nanoplatelets with Controlled Thickness: Atomic Insight into Facet-Specific Bimodal Ligand Binding Using DNP NMR

Colloidal nanoplatelets (NPLs) and nanosheets with controlled thickness have recently emerged as an exciting new class of quantum-sized nanomaterials with substantially distinct optical properties compared to 0D quantum dots. Zn-based NPLs are an attractive heavy-metal-free alternative to the so far most widespread cadmium chalcogenide colloidal 2D semiconductor nanostructures, but their synthesis remains challenging to achieve. The authors describe herein, to the best of their knowledge, the first synthesis of highly stable ZnO NPLs with the atomically precise thickness, which for the smallest NPLs is 3.2 nm (corresponding to 12 ZnO layers). Furthermore, by means of dynamic nuclear polarization-enhanced solid-state ¹⁵N NMR, the original role of the benzamidine ligands in stabilizing the surface of these nanomaterials is revealed, which can bind to both the polar and non-polar ZnO facets, acting either as X- or L-type ligands, respectively. This bimodal stabilization allows obtaining hexagonal NPLs for which the surface energy of the facets is modulated by the presence of the ligands. Thus, in-depth study of the interactions at the organic–inorganic interfaces provides a deeper understanding of the ligand–surface interface and should facilitate the future chemistry of stable-by-design nano-objects.     

Uranium isotopes in public drinking water and dose assessment for man in Poland

238U, 234U and 235U were determined in tap water from municipal water pipes that drew their supply from surface water or ground water in various locations in Poland. Average activity concentrations of 238U, 234U and 235U in tap water from surface water were 9.6 +/- 7.1, 12.8 +/- 9.7 and 0.41 +/- 0.31 Bq m(-3), respectively, whereas from ground water they were 4.5 +/- 6.0, 5.7 +/- 6.9 and 0.19 +/- 0.27 Bq m(-3), respectively. Activity concentrations of 234U were higher than 238U. Ratios of 234U/238U ranged from 1.07 to 2.60, indicating the lack of equilibrium between these isotopes. The average 235U/238U ratio was 0.043 +/- 0.008, being close to 0.046 for natural uranium. Average annual intake with water and food was 7.6 +/- 5.1 Bq for 238U and 9.5 +/- 6.6 Bq for 234U. Annual committed effective doses calculated from these intakes for adults were 0.34 +/- 0.23 and 0.47 +/- 0.32 microSv, respectively; 235U contributed to the total dose from the uranium isotopes by about 2%.     

Silicon compounds as additives improving coating performance: fixation of silicon compounds with cellulose

In this study the reactivity of cellulose with new solvent born preparations containing organosilanes, alkyd resin and natural oil was analysed. Structural analysis of cellulose after reaction with organosilanes and after extraction was performed using Fourier-transform infrared spectroscopy (FTIR). In IR spectra the analyzed bands included 1250 cm⁻¹ responsible for vibrations of the SiC group and 800 cm⁻¹ responsible for vibrations of SiC and/or SiO groups. These bands are characteristic of silicon bonds with atoms of carbon and oxygen originating from the methoxy groups found in organosilanes. The presence of these bands in the spectra proves the occurrence of a reaction between cellulose and organosilanes. The concentration of silicon was determined by AAS in cellulose after reaction with preparations and after extraction.     

Overexpression of the genes of glycerol catabolism and glycerol facilitator improves glycerol conversion to ethanol in the methylotrophic thermotolerant yeast Ogataea polymorpha

Production of fuel ethanol is one of the possible ways to utilize crude glycerol, substantial amounts of which are produced by biodiesel industry. Earlier, we have described construction of the recombinant strains of methylotrophic thermotolerant yeast Ogataea polymorpha with simultaneous overexpression of the genes PDC1 and ADH1, which produced increased amounts of ethanol from glycerol. In this work, we have further improved these strains by overexpression of genes involved either in oxidative (through dihydroxyacetone) or phosphorylative (through glycerol-3-phosphate) pathway of glycerol catabolism, as well as heterologous gene coding for glycerol transporter FPS1 from Komagataella phaffii (formerly, Pichia pastoris). Obtained recombinant strains produced up to 10.7 g/L of ethanol (with ethanol productivity 30 mg/g of biomass/hr and yield 132 mg/g of consumed glycerol) from pure glycerol and up to 3.55 g/L of ethanol (with ethanol productivity 11.6 mg/g of biomass/hr and yield 72.3 mg/g of consumed glycerol) from crude glycerol as a carbon source, which is approximately 15 times more relative to that of the O. polymorpha wild-type strain and 2.2 more relative to the earlier constructed strain.     

Differences in content and composition of free lipids and carotenoids in flour of spring and winter wheat cultivated in Poland

The work presents the content and composition of free lipids and carotenoids in spring and winter classes of wheat flour. It discusses genetical and physiological aspects of their synthesis and accumulation in wheat kernels and also indicates how methodological differences explain differences in results presented in the literature. It has been reported that spring wheat flours are richer in free lipids, especially in the non-polar fraction. The content of glycolipids ranged from 134 to 215 mg/100 g flour and was more stable within the winter wheat class. The percentages of the two main fractions, namely DGDG and MGDG, were similar in both wheat classes and reached ca. 77%. Phospholipids constituted the smallest fraction of the flour free lipids in both wheat classes; however, spring wheat flours were richer in these compounds, which is likely associated with a greater content of spherosomes in the endosperm of this wheat class. The free lipids of spring wheat flour contained more oleic and slightly less linoleic and linolenic acids. Spring wheat flour was also richer in carotenoids, although there were varieties in both classes that deviated from this. The main carotenoid was lutein, whose total percentage in the form of different isomers ranged from 71.3% to 83.3% and was slightly lower for spring wheat flour. Lutein, in the form of a trans-isomer, constituted about 62% and 70% of all carotenoids in spring and winter wheat flours, respectively.     

Convective cooling optimization of a blade for a supercritical steam turbine

This paper discusses the problem of blade cooling system optimization connected with conjugate heat transfer (CHT) analysis for reliable thermal field prediction within a steam cooled component. Since the full CHT solution, which involves the main flow, blade material and the coolant flow domains is computationally expensive from the point of view of optimization process, it was decided to reduce the problem by fixing the boundary conditions at the blade surface and solving the task for the interior only (both solid material and coolant). Such assumption, on one hand, makes the problem computationally feasible, and on the other, provides more reliable thermal field prediction than it used to be with the empirical relationships.The analysis involves shape optimization of internal cooling passages within an airfoil. The cooling passages are modeled with a set of four Bezier splines joined together to compose a closed contour. Each passage is fed with cooling steam of constant parameters at the inlet. In the present study the airfoil profile is taken as aerodynamically optimal. The search problem is solved with evolutionary algorithm and the final configuration is to be found among the Pareto optimal cooling candidates.