Thermal and electrical properties of copoly(1,3,4‐oxadiazole‐ethers) containing fluorene groups

A series of aromatic copolyethers containing 1,3,4‐oxadiazole rings and fluorene groups was prepared by nucleophilic substitution polymerization technique of 9,9‐bis(4‐hydroxyphenyl)fluorene, 1 , or of different amounts of 1 and an aromatic bisphenol, such as 4,4′‐isopropylidenediphenol or phenolphthalein, with 2,5‐bis(p‐fluorophenyl)‐1,3,4‐oxadiazole. The polymers were easily soluble in polar solvents like N‐methylpyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, and chloroform and can be cast from solutions into thin flexible films. They showed high thermal stability, with decomposition temperature being above 425°C. The polymers exhibited a glass‐transition temperature in the range of 195–295°C, with a reasonable interval between glass‐transition and decomposition temperature. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz and 20°C were in the range of 3.16–3.25. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Enhancement of Antimicrobial Photodynamic Therapy of Escherichia Coli by a Functionalized Combination of Photosensitizers: In Vitro Examination of Single Cells by Quantitative Phase Imaging

The prevention of biofilm formation is crucial for the limitation of bacterial infections typically associated with postoperative infections, complications in bedridden patients, and a short-term prognosis in affected cancer patients or mechanically ventilated patients. Antimicrobial photodynamic therapy (aPDT) emerges as a promising alternative for the prevention of infections due to the inability of bacteria to become resistant to aPDT inactivation processes. The aim of this study was to demonstrate the use of a functionalized combination of Chlorin e6 and Pheophorbide as a new approach to more effective aPDT by increasing the accumulation of photosensitizers (PSs) within Escherichia coli cells. The accumulation of PSs and changes in the dry mass density of single-cell bacteria before and after aPDT treatment were investigated by digital holotomography (DHT) using the refractive index as an imaging contrast for 3D label-free live bacteria cell imaging. The results confirmed that DHT can be used in complex examination of the cell–photosensitizer interaction and characterization of the efficiency of aPDT. Furthermore, the use of Pheophorbide a as an efflux pomp inhibitor in combination with Chlorin e6 increases photosensitizers accumulation within E. coli and overcomes the limited penetration of Gram-negative cells by anionic and neutral photosensitizers.     

Aroma compounds in barrel aged apple distillates from two different distillation techniques

The major fermentation and maturation related congeners in apple distillates from two different distillation techniques (alembic and column), matured in oak for 18 months, were measured by GC‐MS and HPLC. Together with a higher ethanol content, column distillates had higher ethyl acetate, methanol and n‐propanol levels compared with alembic distillates. A higher content of acetaldehyde was characteristic of the alembic distillates. The concentrations of i‐butanol, n‐butanol, amyl alcohols and n‐hexanol were not affected by the distillation technique used. Increasing the ageing time of distillates in oak resulted in an increase in the contents of acetaldehyde, ethyl acetate and amyl alcohols while the content of methanol decreased during ageing. Throughout ageing, there were no significant changes in the concentrations of n‐propanol, i‐butanol, n‐butanol and n‐hexanol. Among the maturation related compounds, gallic acid, ellagic acid, vanillin and syringaldehyde were determined in apple distillates with ellagic acid being the most abundant. The contents of gallic acid and ellagic acid increased during ageing whereas vanillin and syringaldehyde slightly increased throughout the 18 months of maturation. © 2019 The Institute of Brewing & Distilling     

Retention of linalool and eugenol in hydrogels

Textural parameters of hydrogels prepared from hydrocolloids (guar gum or xanthan; 0.5 or 1% (w/w)) and disaccharides (sucrose and trehalose) were investigated after preparation and storage for 30 days. Volatile compounds (linalool or eugenol) were added to the hydrogels in order to investigate their behaviour in those systems and to determine whether there is correlation between textural parameters and their retention. Textural parameters that were evaluated were firmness, consistency, cohesiveness and index of viscosity. Regarding textural parameters, there was no significant difference between hydrogels prepared with 0.5% of hydrocolloids. With increase of the amount of added hydrocolloid, textural parameters increased and differences between sucrose- and trehalose-containing hydrogels were observed. Hydrogels prepared with trehalose had lower values of textural parameters. Correlation between texture and retention of volatile compounds was not observed or it was very low.     

Improving the multicaloric properties of Pb(Fe0.5Nb0.5)O3 by controlling the sintering conditions and doping with manganese

Designing multicaloric single-phase materials with combined electro- and magnetocaloric effects is still at its initial stage and presents a number of challenges. One of the main challenges encountered so far is to reduce the excessive electrical conductivity, which leads to the appearance of Joule heating that might completely degrade the electrocaloric response. In this work, multicaloric Pb(Fe_0.5Nb_0.5)O₃ material was successfully prepared exhibiting pronounced electrocaloric effect above room temperature and maximum magnetocaloric effect at cryogenic temperature. The conductivity was suppressed by controlling the sintering temperature. The ceramic sintered at 1000 °C exhibits maximum electrocaloric effective cooling of 0.88 °C at 28 °C and maximum magnetocaloric effect of 0.14 °C at ?271 °C. The caloric properties can be further improved by doping Pb(Fe_0.5Nb_0.5)O₃ with manganese. In comparison to the undoped sample, Pb(Fe_0.5Nb_0.5)O₃ doped with 0.5 mol% of manganese exhibits three times higher maxima of electrocaloric effective cooling (2.47 °C at 80 °C) and magnetocaloric temperature change (0.44 °C at ?271 °C).     

Brown rice proteins as delivery system of phenolic and volatile compounds of raspberry juice

Development of novel food ingredients with health benefits as well as desired sensory attributes is of great importance for food industry. For that purpose, complexes (BRP/R) between brown rice proteins (amounts varied; 2%, 6% and 10%) and raspberry juice were prepared. Obtained complexes were evaluated for the amount of volatile compounds, phenolic content, anthocyanin content and antioxidant activity. Those parameters depended on proteins amount. The highest adsorption of total phenolics and anthocyanins (18.18 mg g⁻¹ and 4.59 mg g⁻¹, respectively) was observed on complexes obtained with the lowest amount of proteins (2%). Regarding volatiles, dominant flavour note in raspberry juice was berry (40% of overall flavour), followed by citrus and woody notes (each around 18%), while dominant flavour note on complexes was citrus note (60%) followed by green note (15%). These results suggest an efficient plant-based approach to produce value-added protein-based complexes with possible utility as food colourant and flavouring.     

Optimization and Applicability of a Novel Sensor for Potentiometric Determination of Anionic Surfactants

Novel potentiometric sensors for anionic surfactant (AS) determination, with different percentages of tetraoctadecylammonium tetraphenylborate (TODA-TPB) as sensing materials and different electrolytes (sodium chloride, lithium chloride, sodium dodecyl sulfate (NaDS), sodium tetraphenylborate, sodium acetate, and potassium chloride) at varied concentration levels, were developed and compared. The sensor with best response characteristics was further characterized. It had a fast response time (5 s), a low signal drift (2.0 and 2.9 mV h⁻¹ in a detergent solution and NaDS, respectively), a wide pH working range (3–11), and a longer lifetime of 6 months. This novel sensor was characterized with Nernstian response toward NaDS (−58.0 mV decade⁻¹ of activity), a wide working range (1.3 · 10⁻⁷–5 · 10⁻³ M), and a low limit of detection (1.0 · 10⁻⁷ M). It proved to be an accurate and reliable sensor for AS determination in multicomponent mixtures of AS and household wastewater using a potentiometric titration method. Nonionic surfactants, which are commonly mixed with AS in commercial products to obtain better properties of products, had an insignificant impact on AS determination.     

Microstructure and dielectric properties of Ag-BaTiO3 composite ceramics

Di-phase composite ceramics based on BaTiO₃ with 5?vol% of Ag filler have been prepared by sintering the mixture of powders at temperatures above the silver melting point (1000?°C–1300?°C/2?h). As predicted by finite element calculations, the addition of metallic particles should produce a field concentration in some regions of the BaTiO₃ matrix and therefore, an enhanced dielectric response with respect to pure BaTiO₃. The role of oxygen vacancies on the dielectric relaxation mechanisms of Ag-BaTiO₃ composites has been investigated. The sintering temperature of 1200?°C provided optimized ceramics with excellent dielectric properties, i.e. with low losses (tanδ?<?3%) and room temperature permittivity measured at 50?kHz exceeding 6500 (and above 13,000 at the Curie temperature), as result of a good densification (94% relative density) and a synergy effect of the metallic particles inclusions and ceramic grain size in the range of ≈1?μm, where BaTiO₃ has a well-known maximum of its permittivity.