Effect of vacuum‐packaging on the changes of Russian sturgeon muscle lipids during frozen storage

The changes in fatty acid composition, non‐polar (triglycerols) and polar lipids (phospholipids), total free fatty acids and total cholesterol of Russian sturgeon (Acipenser gueldenstaedtii) were studied during 360 days of storage at ?18°C. It was established that total neutral lipids and phospholipids content decreased and total free fatty acids concentration increased significantly during the frozen storage. Lower non‐polar and polar lipids content and higher free fatty acids concentration of vacuum‐packaged samples in comparison with air‐packaged samples were found. The changes in total cholesterol concentration and phospholipid classes of frozen stored sturgeon were not influenced by the frozen storage period and the type of packaging. It was established that the sturgeon polar lipids consisted mainly of phosphatidylcholine – 54.98 ± 0.85%, phosphatidylethanolamine – 28.42 ± 0.61%, and phosphatidylserine – 8.64 ± 0.45%. The increase of the total free fatty acids concentration was associated with the free n ? 3 PUFA accumulation as a result of hydrolysis of non‐polar and polar lipids. During the frozen storage DHA percentage of non‐polar lipids and phospholipids decreased approximately 3 and 1.75%, respectively. After 360 days of storage at ?18°C the n ? 3/n ? 6 PUFA ratio of total lipids decreased 4.9%.     

The specific chemical profile of Mediterranean propolis from Malta

Seventeen Maltese propolis samples were studied by GC–MS after silylation. They exhibited the typical Mediterranean chemical profile, rich in diterpene compounds (18–92% of TIC, GC–MS): 32 individual diterpenes were identified; 22 of them were present in each specimen. The other abundant compound group was that of sugars and sugar derivatives. In some samples, however, another compound group was observed (0–12% of TIC, GC–MS); the corresponding mass spectra were consistent with mono- and sesquiterpenyl esters of substituted benzoic acids. Two new propolis constituents of this group, daucane diterpene esters of hydroxybenzoic acids, were isolated. Their origin is suggested to be Ferula communis, as they are taxonomic markers for this species. All propolis samples were active against Staphylococcus aureus but only those with high concentrations of terpenyl esters showed antifungal activity against Candida albicans. The present results confirm that Mediterranean propolis is a valuable natural product with potential to improve human health.     

Synthesis and studies of phosphorus-containing polyurethane foams based on tetrakis(hydroxymethyl) phosphonium chloride derivatives

A phosphorus- and nitrogen-containing polyl is prepared by condensing tetrakis(hydroxymethyl)phosphonium chloride with diethanol amine in aqueous medium. The newly synthesized polyol-bis(hydroxymethyl)-N, N-bis(2-hydroxyethyl)aminomethylphosphine oxide (AMPO) is used in the preparation of rigid polyurethane foams with a various phosphorus content. With the view to comparing their properties, polyurethane foams are also prepared on the basis of the commercially available flame retardant diethyl-N, N-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6). The flammability, thermal stability, and thermoechanical properties of the polyurethane foams obtained are studied. A certain difference in the behavior of the two modified polyurethane foams is observed. The polyurethane foams with AMPO exhibit a slight increase in the resistance to combustion (oxygen index) and a noticeable improvement in the thermal and mechanical properties. These differences probably arise as a result of structural and functional differences between the two types of phosphorus-containing flame retardants.     

Development of horizontal elements in 3-D microcontacts

This paper describes the development and production of horizontal elements in three-dimensional (3-D) microcontacts, implemented in package to PCB assembly. Instead of the standard vacuum deposition process of metal films onto dielectric interfaces, an alternative method aiming at simplicity and lower-cost relative to the technology roadmap, is proposed. This method employs chemical activation and pretreatment of the dielectric photoresist surface with fluid carbon content substance, thus providing also electrical conductivity for direct metal electroplating. A special regime of reverse electrochemical deposition is applied in order to enhance the adhesion of the layer deposited onto the activated surface. This paper presents experimental results of the horizontal elements investigation relative to 3-D microcontacts.     

A Negotiation Scheme for Access Rights Establishment in Autonomic Communication

Autonomic computing and communication has become a new paradigm for dynamic service integration and resource sharing in today's ambient networks. Devices and systems need to dynamically collaborate and federate with little known or even unknown parties in order to perform everyday tasks. Those devices and systems act as independent nodes that autonomously manage and enforce their own security policies. Thus in autonomic pervasive communications clients may not know a priori what access rights they need in order to execute a service nor service providers know a priori what credentials and privacy requirements clients have so that they can take appropriate access decisions. To solve this problem we propose a negotiation scheme that protects security and privacy interests with respect to information disclosure while still providing effective access control to services. The scheme proposes a negotiation protocol that allows entities in a network to mutually establish sufficient access rights needed to grant a service.

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Reactive compatibilizer precursors for LDPE/PA6 blends. III: ethylene-glycidylmethacrylate copolymer

The effectiveness of a commercial ethylene-glycidylmethacrylate copolymer (Lotader GMA AX 8840) as a compatibilizer precursor (CP) for blends of low density polyethylene (LDPE) with polyamide-6 (PA) has been evaluated by an investigation of the thermal properties and the morphology of binary (LDPE/CP and PA/CP) and ternary (LDPE/PA/CP) blends, as well as by solvent fractionation experiments. It has been demonstrated that the epoxy groups of the CP react quite easily, during melt blending, with both the amine and the carboxyl end groups of PA to give CP-g-PA copolymers, which, depending on the relative amounts of PA and CP, may be partially cross-linked. The composition of the graft copolymers has been approximately determined by gravimetric and calorimetric measurements. The compatibilizing efficiency of the CP employed in this work has been found to be comparable to that of the ethylene-acrylic acid copolymers, and lower than that of a maleic anhydride-functionalized polyethylene, which had been used in previous works.     

Functional amphiphilic block copolyethers as carriers of caffeic acid phenethyl ester

Amphiphilic diblock copolymers consisting of hydrophilic polyglycidol (PG) and hydrophobic poly(allylglycidyl ether) (PAGE) were prepared by sequential anionic ring‐opening polymerization of allylglycidyl ether and ethoxyethyl glycidyl ether followed by removal of the protective ethoxyethyl groups. The polymerization was initiated by partially deprotonated dodecanol and performed in solvent‐free conditions. The copolymers were composed of a hydrophobic dodecyl residue attached to a block of PAGE with a fixed degree of polymerization (dp = 44) and differing in length of the PG block (dp = 16 and 66, corresponding to PG contents of 25 and 60 mol%, respectively). The two copolymers were spontaneously soluble in water. Above a certain critical concentration, they formed well‐defined self‐assembled nanoparticles. Their characterization parameters were determined by static and dynamic light scattering. The aggregates of the more hydrophobic copolymer, C₁₂‐PAGE‐PG25, were characterized by considerably larger dimensions and molar mass, reaching 78.6 nm and 253.0 × 10⁶ g mol^?1, respectively, than those of the more hydrophilic copolymer, C₁₂‐PAGE‐PG60. The hydrophobic moieties were proved to create a favorable environment for solubilization of caffeic acid phenethyl ester (CAPE) (the main active ingredient of propolis with cytotoxic and antioxidant activities), whereas the numerous hydroxyl groups from the PG moieties brought additional benefits related to the biocompatibility of the copolymers. Preliminary experiments with L929 fibroblast cells showed that the aggregates displayed no signs of toxicity in the applied in vitro test system, suggesting their appropriateness as a drug delivery platform. The CAPE‐loaded aggregates, however, showed dose‐dependent cytotoxic effects, indicating that CAPE retained its cytotoxic activity. © 2019 Society of Chemical Industry     

Radiative exciton recombination dynamics in QD-tagged polystyrene microspheres

Fluorescent polystyrene microspheres are prepared by the incorporation of fluorescent CdSe/CdS core/shell semiconductor nanocrystals (quantum dots, QDs) using the emulsification/solvent evaporation method. The radiative exciton recombination dynamics is investigated by nanosecond time-resolved fluorescence spectroscopy at ambient conditions. The time constants of fast and slow fluorescence decay in QDs, dispersed in toluene, were 3.5 and 17.8 ns, respectively. For the QD-tagged microspheres, the time constants of fast and slow processes were ~2–3 and ~11–12 ns, respectively, and did not depend significantly on the QD-content of the microspheres. The fast decay component could be attributed to the recombination of delocalized exciton in the internal core states, and the slow component was attributed to the localized exciton in the surface states. It was found that the ratio of amplitudes of the fast and slow processes also changed after incorporation of QDs in microspheres. The observed differences in fluorescence decay between non-entrapped QDs and QD-tagged microspheres were probably due to energy transfer between the nanocrystals, which were in close proximity inside the microspheres. The obtained fluorescent QD-tagged microspheres are characterized by the other methods as well, which makes them of value for various applications as optical materials.     

Probing diffusion of single nanoparticles at water-oil interfaces

The diffusion of nanoparticles at a water-alkane interface is studied using fluorescence correlation spectroscopy. Hydrophilic and hydrophobic quantum dots of 5, 8, and 11 nm radius are used. A slow-down of nanoparticle diffusion at the liquid-liquid interface is observed. The effect is most evident when the viscosities of both liquid phases are similar, here, at the water-decane interface. In this case, the interfacial diffusion coefficients of the hydrophilic particles are 1.5 times and those of the hydrophobic particles 2 times lower than the corresponding bulk values.