Esterification kinetics of glycerol with fatty acids in the presence of sodium and potassium soaps

The kinetics of the direct esterification of glycerol with fatty acids in the presence of sodium and potassium soaps, synthesized in situ to obtain modified acylglycerol emulsifiers, were investigated. The effect of temperature, soap concentration and fatty acid hydrocarbon chain length on the concentration of monoacylglycerols in the reaction mixture was examined. The kinetic studies proved that esterification of glycerol with fatty acids by our method is a first order consecutive reaction with monoacylglycerol as stable intermediate product. The corresponding rate constants and activation energies were evaluated. With the known reaction rate constants, the maximum concentration of monoacylglycerol may be calculated. It was stated that the proposed method opens up possibilities for a specific adjustment of the acylglycerol composition and, thus, of the hydrophilic-lipophilic properties and the characteristics of the emulsifier.     

Synthesis of Gonadoliberin,a gonadotropin releasing hormone

A simple laboratory synthesis of gonadoliberin was elaborated basing on classical solution methods and using minimal protection of side-chain functions. In the final step a hexapeptide segment was condensed with the corresponding tetrapeptide and the obtained product was purified by a single step silica gel chromatography. The total efficiency of the whole synthesis was 15%.     

Colour appearance in immersive three‐dimensional virtual environments

Technology is constantly evolving and, consequently, all the technological advances taking place are regularly integrated into the daily life of society. During recent years, there has been a trend towards virtual resources such as teleworking, telemedicine and e‐commerce. In many countries, this virtualisation process has been accelerated by the changing circumstances caused by the COVID‐19 pandemic. In any case, there is a growing demand for virtual systems, and virtual reality is a suitable field for the application of a multitude of solutions. However, advances in virtual reality occur without any regard to colour science, and there are several challenges to be overcome to improve the visual appearance and fidelity of colour reproduction in all types of related devices. This paper discusses three open issues related to the visual appearance and visual fidelity of virtual reality systems. We believe it is necessary to direct future research efforts in each of these directions to secure improvements in the visual fidelity of virtual reality systems.     

Bacteria Single-Cell and Photosensitizer Interaction Revealed by Quantitative Phase Imaging

Quantifying changes in bacteria cells in the presence of antibacterial treatment is one of the main challenges facing contemporary medicine; it is a challenge that is relevant for tackling issues pertaining to bacterial biofilm formation that substantially decreases susceptibility to biocidal agents. Three-dimensional label-free imaging and quantitative analysis of bacteria–photosensitizer interactions, crucial for antimicrobial photodynamic therapy, is still limited due to the use of conventional imaging techniques. We present a new method for investigating the alterations in living cells and quantitatively analyzing the process of bacteria photodynamic inactivation. Digital holographic tomography (DHT) was used for in situ examination of the response of Escherichia coli and Staphylococcus aureus to the accumulation of the photosensitizers immobilized in the copolymer revealed by the changes in the 3D refractive index distributions of single cells. Obtained results were confirmed by confocal microscopy and statistical analysis. We demonstrated that DHT enables real-time characterization of the subcellular structures, the biophysical processes, and the induced local changes of the intracellular density in a label-free manner and at sub-micrometer spatial resolution.     

One-Step Synthesis of W/O and O/W Emulsifiers in the Presence of Surface Active Agents

The main goal of this study was to describe the method of the synthesis of the dodecyl-, tetradecyl-, hexadecyl- and octadecyl-propylene glycol emulsifiers in the presence of selected anionic and nonionic surfactants. Acyl propylene glycol emulsifiers were produced by esterification of propane–1,2-diol (propylene glycol, PG) with C_12:0–C_18:0 fatty acids in the presence of anionic sodium dodecyl sulfate (SDS) and nonionic-poly(ethylene glycol) monolaurate (PEGML). The presence of SDS and PEGML in the reaction system caused microemulsion formation. Depending on the structure and amount of the surfactant in the system reactions proceeded at different rates and with different efficiency levels. The esterification of propylene glycol carried out under applied conditions causes products with the desired contents of propylene glycol monoesters (MAPG) to be obtained in a one-step reaction. Knowledge of the reaction kinetics creates the possibility to program the composition and properties of the synthesized emulsifiers. The interaction of nonionic, lipophilic MAPG with anionic, hydrophilic SDS or nonionic, hydrophilic PEGML influences the hydrophile–lipophile balance (HLB) values of the products which may be used to stabilize water-in-oil (W/O) and oil-in-water (O/W) emulsions. Use of the synthesized compounds allows stable emulsions to be prepared which include the following vegetable fats in the oil phase: mango oil, palm oil, shorea butter and hydrogenated soybean oil.     

Physico-chemical properties of 3-methoxy-2-nitrobenzoates of some rare earth elements（Ⅲ）

The complexes of 3-methoxy-2-nitrobenzoates of Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Er(III) and Tm(III) with the formula: Ln(C8H6NO5)3·2H2O, where Ln=lanthanides(III), were synthesized and characterized by elemental analysis, Forier transform irtrared (FTIR) spectroscopy, magnetic and thermogravimetric studies and also by X-ray diffraction (XRD) measurements. The complexes had col- ours typical for Ln(III) ions. The carboxylate groups bound as bidentate chelating. On heating to 1173 K in air they decomposed in the same way, at first, dehydrated in one step to anhydrous salts, and then decomposed to the oxides of respective metals with intermediate formation of the oxycarbonates. The enthalpy values of the dehydration process changed from 133.72 to 44.50 kJ/mol. Their solubility in water at 293 K was of the order of 10-4 mol/dm3. The magnetic moments of analysed complexes were determined by Gouy’s method in the range of 76-303 K.     

Effect of ripening stage on thiamin and riboflavin levels in lupin, pea and faba bean seeds

 Seeds of yellow pea lupin (Lupinus luteus L., cv. Juno), pea (Pisum sativum L., cv. Ergo) and faba bean (Vicia faba sp. minor Harz., cv. Tibo) were harvested at different stages of seed maturity. Changes in thiamin and riboflavin levels during growth and maturation were studied. The results obtained showed that thiamin and riboflavin were found in high abundance early in the development of lupins and peas, but that their content decreased during maturation. The thiamin content of faba bean seeds increased from 33 to 47 days after flowering (DAF), then a decrease was observed until 61 DAF; however, no significant differences between these levels in faba bean seeds harvested from 61 to 89 DAF were found. The riboflavin content of faba beans increased after 54 DAF, and no significant changes were observed between then and 89 DAF. The thiamin and riboflavin contents in lupin, pea and faba bean seeds during development were fitted to modelling curves in order to predict the vitamin content at different stages of maturity. Received: 17 July 1997     

Investigation on the Use of the Weakly Basic Polyacrylate AnionExchanger Amberlite IRA-68 for Sorption and Separation of Iminodiacetate Complexes of Rare Earth Elements

Based on the determined affinity series of rare earth element complexes with IMDA for the anion-exchangers, purification of macroquantities of Nd^3 from Y^3 , Sm^3 from Ho^3 , La^3 from Nd^3 and La^3 from Pr^3 on the weakly basic gel anion-exchanger Amberlite IRA-68 was studied. Using the presented method on 1 L of Amberlite IRA-68 in the acetate form, it is possible to obtain about 240 g Nd2O3 purified from Y2O3. Great difference in affinity of La^3 and Nd^3 as well as Pr^3 complexes for this anion-exchanger in the acetate form indicates the possibility of applying this process for purification of lanthanum on the increased scale. On 1 L of Amberihe IRA-68 in the acetate form it is possible to obtain about 1125 g La2O3 purified from Nd2O3. On the basis of these results it can be assumed that unique properties of polyacrylate anion-exchangers enable their application for separation of rare earth elements.     

Effect of high-fat cholesterol enriched diets on hypolipemic action of Oenothera paradoxa oil in rats. Part 2. Blood serum and liver fatty acids

The effect of Oenothera paradoxa oil on blood serum and liver fatty acids composition in rats was studied. Rats were fed high-fat diets containing 15% of lard or sunflower oil with or without 0.5% of cholesterol. Soybean protein isolate (27%) was the source of proteins. Intake of Oe. paradoxa oil resulted in increase of levels of gamma-linolenic acid (GLA) and linoleic acid (LA) in blood serum and liver of experimental animals. The effect of Oe. paradoxa oil on blood serum and liver fatty acids composition depended mainly on the type and to the lower degree on the amount of fat in a diet. The addition of cholesterol did not change the influence of examined oil on the composition of fatty acids.