The study of optical and photodielectric properties of polymethyl methacrylate and tris-(8-hydroxy-quinoline) aluminum (Alq3) composites

Polymer composite films of tris-(8-hydroxy-quinoline) aluminum (Alq3) and polymethyl methacrylate (PMMA) at two different concentrations were investigated. Dielectric properties of the samples were measured in broad frequency range and results show an increase in specific conductance and susceptance by adding Alq3 in PMMA. Changes in dielectric spectra caused by irradiation of the samples with LED lamps at different wavelengths were also recorded. The samples were examined by UV–Vis and Fourier transform infrared spectroscopy. The interaction between Alq3 and the polymer matrix was observed in the photoluminescence spectroscopy spectra. The doping of the PMMA with different concentrations of the Alq3 leads to the unique photodielectric properties of the resulting composite, and that is the main result of this study. Due to its interesting optical and photodielectric properties, PMMA/Alq3 film may find application in solar cells and optoelectronics.     

The influence of combined emulsifier 2 in 1 on physical and crystallization characteristics of edible fats

The aim of this research was to examine the physical and crystallization characteristics of two type of edible fats with the addition of combination of two kind of emulsifiers and with the addition of, so-called, combined emulsifier 2 in 1. NMR technique was used for measuring the solid fat content (SFC) of fats on different temperatures, as well as for crystallization rate under static conditions, by measuring the change of SFC in a function of time. Also, the possibility of applying of Gompertz’s mathematical method to define kinetics of crystallization was investigated. The hardness of fats was defined by penetration on texture analyser, while the rheological properties were determined using the rotational rheometer. The samples of both fats with emulsifier 2 in 1 added have a lower crystallization rate with less amounts of crystals formed, which indicates better spreadability comparing with samples that contain the combination of two emulsifiers. This is also shown by physical determination, since emulsifier 2 in 1 significantly reduced the values of hardness and work of shearing, as for the values of yield stress and tixotropy curve area. Emulsifier 2 in 1 would significantly facilitate the handling in confectionery industry because it can be used instead of the combination of two different type of emulsifiers, which are usually combined in order to give the necessary technological characteristics of confectionery products that contain the fat phase. Also, this emulsifier would improve the quality of those products since it showed better emulsifying properties than combination of two different emulsifiers.     

One-step method for isolation and purification of native β-lactoglobulin from bovine whey

BACKGROUND: The major whey protein β‐lactoglobulin (BLG) has been widely studied for its functional properties. The aim of this study was to develop an efficient, inexpensive and rapid one‐step method for the isolation and purification of BLG while preserving its native structure. RESULTS: BLG was purified from defatted whey obtained from raw cow's milk by anion exchange chromatography. Protein purity and identity were determined using reverse phase high‐performance liquid chromatography and mass spectrometry. Total BLG yield was 80% with protein purity from 97 to 99%. BLG isoforms A and B were separated into fractions of 91 and 99% purity respectively. The structure and native conformation of the isolated BLG were compared with those of standard commercial BLG by circular dichroism spectrometry, susceptibility to various crosslinking enzymes and enzyme‐linked immunosorbent assay inhibition. CONCLUSION: The proposed method is very useful for the rapid preparation of BLG suitable for studying antigenic and molecular characteristics of this protein, as well as the effect of food processing on these properties. The procedure requires only 1 day for the purification of about 300 mg of BLG from a single run using a small column (2.5 cm × 20 cm) of diethylaminoethyl Sephadex and has potential for scaling up. Copyright © 2011 Society of Chemical Industry     

Valorisation of phenolic composition,antioxidant and cell growth activities of tomato waste

Tomato waste, a by-product in juice processing, obtained from different tomato genotypes, was subjected to evaluation as potential source of phenolic antioxidants and anticancer agents. Some individual phenolic compounds, including phenolic acids and flavonoids, were identified and quantified by HPLC. The antioxidant activity of tomato waste extracts was tested by measuring their ability to scavenge hydroxyl and superoxide anion radicals by ESR spectroscopy. The highest hydroxyl radical scavenging activity (IC₅₀ = 0.03 mg/ml) was obtained in the case of Novosadski niski waste extract. The Rutgers waste extract showed the best performance in scavenging superoxide anion radicals (IC₅₀ = 0.45 mg/ml). Cell growth effects were determined in HeLa, MCF7 and MRC-5 cell lines by SRB test. In all cell lines antiproliferative effects were observed at higher investigated concentrations (?6.3 mg/ml). The strongest activity against cancer cells was observed by Saint Pierre extract in HeLa cell line (IC₅₀ = 13.7 mg/ml).     

Determining the number of postal units in the network – Fuzzy approach,Serbia case study

One of the main, current, goals of the public postal operators in developing countries is to define the model for proper postal network design and access. The access to the postal network represents a set of different elements that interact with each other and have a common aim of providing continuous, of high quality, reliable and sustainable universal postal service. Worldwide experience suggests different approaches in defining the components and criteria for establishing the system of access to the postal network of the public operator. In this paper we present two different approaches. The first one is based on criteria determined in previous study and, here, we develop proper mathematical formulation. The second one is new, general, method created to generate fuzzy rules from numerical data, well known as Wang–Mendel’s method. The authors apply both methods on real data collected from Serbian municipalities and finally, compare results obtained by them.     

Dielectric and optical properties of a poly(ethylene terephthalate) membrane in the temperature interval 150–400 K

In this study, the dielectric and optical properties of poly(ethylene terephthalate) (PET) membranes were examined. The dielectric measurements were carried out in the temperature interval 150–400 K and in the frequency range 20 Hz–60 kHz. We analyzed in detail the temperature dependences of the dielectric permittivity and dielectric loss (tan δ) at various test frequencies. The relaxation tan δ peak, which appeared in the temperature range 150–300 K, was identified as the secondary β relaxation. The increase in tan δ at temperatures higher than 300 K could be explained as approaching the α relaxation. Optical measurements were performed in the UV–visible region from 200 to 400 nm at various temperatures between 150 and 400 K. The values of the direct and indirect band gaps were calculated at various temperatures. These values were lower for higher temperatures. An absorption peak was observed at a wavelength around of 285 nm at temperatures lower than 300 K. Such insight into the dielectric and optical responses of PET track membranes in a wide temperature range is particularly important when this material is used as a matrix for the semiconductor structure in the development of optoelectronic or microfluid devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42834.