Supramolecular Systems from Natural Polymers and Maleic Polyelectrolytes

Summary: The formation of polyelectrolyte complexes by interaction between chitosan and maleic acid copolymers as strong/weak dibasic polyanions was investigated. The interaction between the sodium salt of maleic acid copolymers with styrene or vinyl acetate and the chitosan hydrochloride in aqueous solution was followed by potentiometric, conductometric and turbidimetric titration. The effect of the added low molecular salt on the complex formation was also investigated. The precipitated complexes were analyzed by FTIR spectroscopy and TG analysis. Preliminary layer-by-layer deposition experiments were performed to obtain thin films.     

Endpoint Fragmentation Index: A Method for Monitoring the Evolution of Microbial Degradation of Polysaccharide Feedstocks

We describe a simple method for tracking the course of microbial degradation of polysaccharide-rich feedstocks. The method involves determining total polysaccharides present in the feedstock, measured in glucose equivalents, relative to the fractional component of polysaccharides exhibiting 2,3-dinitrosalycylic acid aldehyde activity. The ratio of total polysaccharide to aldehyde activity, defined as the end-point fragmentation (EPF) index, is then calculated and tracked as it shifts as microbial degradation of polysaccharide-rich feedstock progresses. While degradation occurs, the EPF index falls. It bottoms out at an asymptotic limit marking the point in time where further degradation of the polysaccharide-rich feedstock has ceased. The EPF index can be used to follow the progressive breakdown of composting polysaccharide-rich waste. It may also have applicability as a means of tracking the turnover of polysaccharides in other complex environments including soil, sediments, wetlands, and peat bogs.     

Bioactive Polymers. XXVI. Immobilization of Pepsin on Biozan R

Pepsin was immobilized on BIOZAN R (Hercules) with dicyclohexylcarbodiimide as activator. The reaction product obtained has a protein content of 35–110 mg/g of polymer and a proteolytic activity between 20.85–28.75 μmol tyrosine/L·min·g of polymer). The coupling reaction rate is maximum under the following conditions: pepsin/BIOZAN R ratio = 0.52 g/g, DCCI/BIOZAN R ratio = 0.2 g/g, pH = 3.4, reaction time = 4 h.     

The Preparation,Characterization and Properties of Catalase Immobilized on Crosslinked Gellan

In the present paper, the reaction of chemical immobilization of catalase on a crosslinked macromolecular carrier of a polysaccharide structure (gellan) is studied. The influence of some reaction parameters (enzyme/carrier, activator/carrier ratios, duration) on the activity of enzymatic products is analyzed. The kinetics of the biocatalytic process, stability under different pH and temperature conditions, and the inhibitors effect were studied for the immobilized enzymes.     

The low-temperature heat capacity of CaUO4 and SrUO4

The heat capacity of calcium monouranate CaUO₄ and strontium monouranate SrUO₄ have been measured over the temperature range (2 to 300) K. The results are significantly different from earlier measurements, confirming the conclusions from our previous study on BaUO₄. The standard entropy at T = 298.15 K of orthorhombic α-SrUO₄ is consistent with the values for the isostructural BaUO₄ as well as the alkali uranates Na₂UO₄ and Cs₂UO₄. The standard entropy of the rhombohedral CaUO₄ is appreciably different, which is attributed to the different structures of the uranium sublattices.     

Thermogravimetric analysis of layered double hydroxides with chloramphenicol and salicylate in the interlayer space

The thermal behavior of the new inorganic-organic nanohybrid materials obtained by intercalation of chloramphenicol and salicylate into layered double hydroxides (LDHs) by direct synthesis method, anion exchange reaction and the reconstruction method was evaluated by dynamic thermogravimetric analysis in air, at heating rates of 5°C min⁻¹. The XRD patterns of the samples are characteristic for those of well crystallized solids with layered double hydroxide structures. The FTIR spectroscopy results show the presence of the organic compound within the network structure of the synthesized LDHs. The kinetic parameters (reaction order (n) apparent activation energy (E _a) and pre-exponential factor (lnA) were calculated by the Coats-Redfern method. The compensation effects were determined.     

Bioactive polymers 61. synthesis and characterization of some retard antibiotics

Ampicillin and chloramphenicol were coupled on xanthan by activation by dicyclohexyl-carbodiimide. Drug release from the support was studied in vitro for ampicillin, and in vitro and in vivo conditions for chloramphenicol.     

Numerical solutions to singular ϕ-Laplacianwith Dirichlet boundary conditions

In this note we are concerned with numerical solutions to Dirichlet problem $$[\phi(u')]' =f(x) \quad \mbox{in} [\alpha, \beta]; \quad u(\alpha)=A, \; u(\beta)=B, $$ where \(\phi :(-\eta , \eta ) \to \mathbb {R}\) \((\eta <+ \infty )\) is an increasing diffeomorphism with \(\phi '(y)\geq d >0\) for all \(y\in (-\eta , \eta )\) . The obtained algorithm combines the shooting method with Euler’s method and it is convergent whenever the problem is solvable. We provide numerical experiments confirming the theoretical aspects.     

On the stability of the linear functional equation in a single variable on complete metric groups

In this paper we obtain a result on Hyers–Ulam stability of the linear functional equation in a single variable $f(\varphi (x)) = g(x) \cdot f(x)$ on a complete metric group.     

Correction to: convergence rates for Kaczmarz-type algorithms

Numerical Algorithms - We will refer to the paper “Convergence rates for Kaczmarz-type algorithms”, published in Numerical Algorithms, 79(1)(2018), 1-17. It was observed by Dr. Mokhtar...