The effect of microstructure on the anodic behaviour of Cu-Be-Ni-Zr alloy system

The effect of heat treatment on the anodic behaviour of the Cu-Be-Ni-Zr alloy in 65% phosphoric acid has been investigated by the potentiostatic method. Different anode states obtained by quenching from temperatures of 900,950 and 1000°C were examined under the microscope. It was found that the position and shape of the polarization curves, especially in the active and passive parts, are dependent upon the quenching temperature and colling rate. For pre-quenching temperatures up to 950°C, at which there are no appreciable changes in microstructure, the polarization curves are similar. For higher pre-quenching temperatures up to 1000°C where substantial microstructural changes occur, the active part of the polarization curves becomes more negative, by almost 100 mV, while the passivation decreases.     

Milk-based beverages obtained by Kombucha application

This paper investigates the manufacture of milk-based beverages by application of several Kombucha starters. Local Kombucha culture was grown up on three substrates: sweetened black and green tea, and topinambur. Their concentrates were obtained by vacuum-evaporation and amounts of 10% and 15% (v/v) were applied to milk (2.2% fat). The traditional yoghurt starter (B3) was applied for producing control samples. All fermentations were stopped when the pH reached 4.4. Fermentation curves were registered, linear for yoghurt and sigmoidal for Kombucha. Two times faster process was achieved with yoghurt starter. Influence of inoculum concentration on the rate of fermentation was insignificant. Viscosities were higher for Kombucha beverages at lower speeds of spindle, but lower at higher speeds of spindle. Very high sensory scores were achieved for all beverages, after production and after 5-days’ storage.     

Alternating phenylenevinylene and thienylenevinylene copolymers with cyano groups: Synthesis,photophysics and photovoltaics

Two alternating conjugated copolymers TTP and TTT were synthesized by Heck coupling of 2,3-bis-(5-bromothiophene-2-yl)acrylonitrile with 1,4-dihexyloxy-2,5-divinylbenzene and 3-hexyl-2,5-divinylthiophene, respectively. The absorption spectra of the copolymers in THF solution showed three maxima around 270, 370 and 460 nm with optical band gaps of 2.30–2.34 eV. The electrochemically estimated band gaps of copolymers were 2.04–2.10 eV. The thin film absorption spectra were broad and extended about from 250 to 600 nm with a long wavelength maximum near 470 nm. The copolymers emitted yellow-orange light with maximum at 528–551 nm in THF solution and 567–610 nm in thin film. TTP showed the most red shifted emission maximum between the copolymers. The performance of the photovoltaic cells which were fabricated using blends of the copolymers with 6,6-phenyl C61-butyric acid methyl ester (PCBM) (1:1 and 1:4, w/w) as well as pure copolymers was investigated.     

Ruthenium complex containing block copolymer for the enhancement of carbon nanotube photoconductivity

We report the synthesis of a multifunctional block copolymer incorporated with pyrene and ruthenium terpyridyl thiocyanato complex moieties by reversible addition-fragmentation chain transfer polymerization. The pyrene block in the copolymer facilitates the dispersion of multiwalled carbon nanotubes in DMF solution because of the strong π-π interaction between the pyrene moieties and nanotube surface. On the other hand, the ruthenium complexes greatly enhance the photosensitivity of the functionalized nanotubes in the visible region. The photocurrent responses of the nanotubes at different wavelength measured by conductive AFM spectrum strongly agree with the absorption spectrum of the ruthenium complex. The results demonstrate a new and versatile approach in enhancing and fine-tuning the photosensitivity or other opto-electronic properties of carbon nanotubes by multifunctional block copolymers.     

Comparison of the products of Kombucha fermentation on sucrose and molasses

Fermentation of 1.5 g/L of Indian black tea, sweetened either with 70 g/L of sucrose or an adequate quantity of three kinds of molasses, was conducted by domestic Kombucha (Acetobacter strains in symbiosis with Saccharomycodes ludwigii, Saccharomyces cerevisiae, Saccharomyces bisporus, Torulopsis sp. and Zygosaccharomyces sp.). Inoculation was performed with 10% of fermentation broth from the previous process. The fermentation in cylindrical vessels containing 2 L of liquid phase, was carried out at 22 ± 1 °C for 14 days, with periodical sampling to measure pH, content of acids (total, acetic and l-lactic), content of remaining sucrose and the yield of biomass at the end of fermentation. Significance of the differences of the results obtained in the fermentations on different substrates was analyzed by applying Duncan’s multiple range test. The molasses that yielded the beverage richest in l-lactic acid was suggested for Kombucha fermentation.     

Epithelial cells in bronchial asthma

The paper deals with the current data on the morphologic and functional damages to the epithelium in asthma. Structure of the normal airway epithelium is briefly described. Damage to the epithelium disrupts the barrier to the external environment, and may result in changes in mucous secretion, and mucociliary clearance; induce bronchoconstriction; promote chemotaxis of inflammatory cells. Epithelial cells can present antigens to T-lymphocytes. Epithelium is both target and effector in asthma. Hypothesis that eosinophils contribute to the damage of the epithelium gained increasing recognition.     

Mechanisms of noise sources in microelectromechanical systems

It is well known that several mechanisms of noise generation appear in microelectronic devices, causing thermal noise, shot noise, generation–recombination noise and 1/f noise. Besides these noises, in the case of microelectromechanical systems, specific additional noises appear as a consequence of the fact that the “building blocks” (microcantilevers or membranes) of micromechanical systems have very small geometrical dimensions and mass. Most often, these noises are the consequences of temperature fluctuations caused by dissipative processes in various vibrational structures within the micromechanical systems. This work presents a methodology of calculation of noises, characteristic of microelectromechanical systems and applies it to the calculation of limiting performances of accelerometers, sensing probe cantilevers and thermal infrared detectors.     

Alternating electrical conductivity of polyphenylenes and their pyrolysis residues after doping

o,m,p-Polyphenylenes were prepared by oxidation-cationic polymerization of biphenyl and then pyrolyzed up to 800°C. The o,m,p-polyphenylenes as well as their pyrolysis residues were doped with anhydrous FeCl₃ from their solution in acetonitrile. The real part of the alternating electrical conductivity σ′ of the undoped and doped materials was determined at room temperature. Decreasing σ′-values of pyrolyzed residues at 600°C without doping were observed because of the large weight losses during the pyrolysis leading to chain scission reactions within the polymer. At higher pyrolysis temperatures (i.e. 700°C, 800°C) the σ′-values are increased due to the formation of closed aromatic systems in the polymer. The doped materials have higher σ′-values in relation to the corresponding specimens without doping, with the exception of the pyrolysis residues at 800°C. The dependence of doping effect and time was also determined. The transition of the organic polymer to the pyropolymers can be followed and characterized by the measurement of alternating electrical conductivity.