Chain-growth Click Copolymerization for Synthesis of Branched Copolymers with Tunable Branching Density

In this work, we reported a facile synthesis of (hyper)branched copolymers with tunable degree of branching (DB) via one-pot chain-growth copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. By using a tri-azido core...

Lactic Acid Bacteria Isolated from Fermented Doughs in Spain Produce Dextrans and Riboflavin

Many lactic acid bacteria (LAB) produce metabolites with applications in the food industry, such as dextran-type exopolysaccharides (EPS) and riboflavin (vitamin B2). Here, 72 bacteria were isolated from sourdoughs made by Spanish bread-makers. In the presence of sucrose, colonies of 22 isolates showed a ropy phenotype, and NMR analysis of their EPS supported that 21 of them were dextran producers. These isolates were identified by their random amplified polymorphic DNA (RAPD) patterns and their rrs and pheS gene sequences as LAB belonging to four species (Weissella cibaria, Leuconostoc citreum, Leuconostoc falkenbergense and Leuconostoc mesenteroides). Six selected strains from the Leuconostoc (3) and Weissella (3) genera grew in the absence of riboflavin and synthesized vitamin B2. The EPS produced by these strains were characterized as dextrans by physicochemical analysis, and the L. citreum polymer showed an unusually high degree of branching. Quantification of the riboflavin and the EPS productions showed that the W. cibaria strains produce the highest levels (585–685 μg/and 6.5–7.4 g/L, respectively). Therefore, these new LAB strains would be good candidates for the development of fermented foods bio-fortified with both dextrans and riboflavin. Moreover, this is the first report of riboflavin and dextran production by L. falkenbergense.

Nanostructural crystallization of metals

Based on thermodynamic calculations, it is shown that metal crystallization is an equilibrium nanostructural process. At the beginning, trigonal or tetragonal structure-forming nanocrystals are formed from elementary nanocrystals. Then crystallization centers are formed from them. Further, tetragonal or hexagonal dendrites are formed from them and tetragonal or trigonal structure-forming nanocrystals. Their forms depend on the degree of branching of dendrites. The most branched of them (compact dendrites) are tetragonal or hexagonal crystals.

Microcalorimetric investigation of amylopectin branching and the content of amylose in potato starches

Hydroxyethylated starches are of particular interest for applications in infusion therapy because of their high volemic effect. The duration of this effect depends on the circulation time of the drug in the blood, i.e., the volume of circulating blood increases with an increase in the concentration, molecular weight and degree of polymer substitution. It is known that hydroxyethylated starches have a wide range of molecular weight and degree of substitution. This allows their solutions to circulate for a long time (up to 10 hours) in the bloodstream without leakage of the active substance into the interstitium of vital organs. The dependence of the melting point of the crystalline starch lamella on the number of glucose residues can be described using the modified Fox - Loshaek ratio, which takes into account the degree of branching of amylopectin molecules and the content of amylose in starch. We proposed an analytical expression for the evaluation of the degree of branching of amylopectin from potato starch based on microcalorimetric data. The proposed methodology allows the genotypes of potatoes with the highest degree of amylopectin branching and a minimum quantity of amylose in starch to be selected. Starches of such potato varieties can be used in the blood plasma substitutes production - hydroxyethylated starches that have good pharmacodynamic properties. Within the developed approach, it is possible to determine the effect of the degree of substitution on the thermodynamic properties of the studied starches through a change in the melting temperature of the lamella, Tm, hence estimating the main pharmacodynamic parameters of substituted starches.

Some challenges in the naming and measuring of nanocellulose

Due to its renewable nature, its inherent strength, and many other favorable attributes, nanocellulose (NC) has drawn increasing attention for many potential applications. A diverse and complex assortment of NC products have been reported, and these are most commonly classified based on some contrasting procedures of preparation. The research community is facing a continuing challenge to adequately measure and quantify morphological features of various NC products. In principle, it ought to be possible to quantify and name NC based on such attributes as “degree of branching,” “breadth of particle size,” and “aspect ratio distribution,” etc. However, the ability to measure and compute such quantities still lies beyond what can be achieved in practical amounts of time in typical laboratories. Meanwhile, there has been tension between researchers proposing additional descriptive names, while at the same time there have been efforts at achieving uniformity and simplicity in nomenclature. It is proposed in this essay that this state of affairs is largely a reflection of complexity itself, such that NC products that have the same nominal description can be very different from each other when examined closely. The diversity itself may turn out to be a good thing, as researchers work to come up with varieties of NC that can survive an expected relentless competition from existing plastic-based or cellulose-based materials.

Investigations of polyethylene of raised temperature resistance service performance using autoclave test under sour medium conditions

The chapter deals with the performance evaluation of the polyethylene of raised temperature resistance (PE-RT) and polyethylene (PE) using autoclave test under sour oil and gas medium conditions. The analyses of performance changes showed that PE-RT has good media resistance at 60°C. As the temperature increases, its mechanical properties decrease, accompanied by an increase in weight. Comparative analyses showed that no matter what temperature conditions are, PE-RT media resistance is better than PE80. The better media resistance of PE-RT depends on its higher degree of branching. Short branches are distributed between the crystals to form a connection between the crystals, thereby improving its heat resistance and stress under high-temperature conditions. PE-RT forms an excellent three-dimensional network structure through copolymerization, ensuring that it has better media resistance than PE80. However, the mechanical performance will be attenuated due to the high service temperature.

How unique is unique? Quantifying geometric differences in stripe patterns of Cape mountain zebra, Equus zebra zebra (Perissodactyla: Equidae)

Quantified coat pattern dissimilarity provides a visible surface for individual animal traceability to populations. We determined the feasibility in quantifying uniqueness of stripe patterns of Cape mountain zebra (CMZ; Equus zebra zebra) using geometric morphometrics. We photogrammetrically created dense surface models of CMZ (N = 56). Stripe edges were landmarked, superimposed and compared for shape variation across replicates and the population. Significant allometry in stripe patterns prompted allometric correction to remove increased curvature of stripes at the rump, belly and back with larger adult individuals, to facilitate equilibrated comparison between individuals. Re-landmarked replicates showed lower dissimilarity (Di) than non-replicates (Dp), representing minimal landmarking error. Individuals were 78.07 ± 1.79% unique (U=1−DiDp×100%) relative to the study population. Size, the number of torso stripes and degree of branching in four rear torso stripes described the most shape variation (36.79%) but a significant portion could only be distinguished with geometric morphometrics (41.82%). This is the first known use of geometric morphometrics to quantify coat pattern uniqueness, using a model species to provide baseline individual morphological variation. Measures of coat pattern similarity have a place in phenotypic monitoring and identification.

Effect of Chemical Structure and Degree of Branching on the Stability of Proton Exchange Membranes Based on Sulfonated Polynaphthylimides

Hydrolytic stability and oxidative stability are the core properties of sulfonated polynaphthylimides (SPIs) as proton exchange membranes. The chemical structure of SPIs directly influences the performance. Herein, three different series of branched SPIs were designed and prepared using 1,3,5-tris (2-trifluoromethyl-4-aminophenoxy) benzene as a trifunctional monomer and three non-sulfonated diamine monomers, such as 4,4′-oxydianiline (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (6FODA), and 4,4′-(9-fluorenylidene)dianiline (BFDA). The effect of the chemical structure and degree of branching on SPIs properties is discussed. The results showed that by controlling the chemical structure and degree of branching, the chemical stability of SPIs changed significantly. SPI-6FODA with two ether linkages and a hydrophobic CF3 group has higher hydrolytic stability than SPI-ODA with only one ether linkage. In addition, with the increase of the introduced B3 monomer, the oxidation stability of SPI-6FODA has been greatly improved. We successfully synthesized SPIs with a high hydrolytic stability and oxidative stability.