Synthesis and characterization of the SBA-15/carbon cryogel nanocomposites

The ordered mesoporous silica SBA-15 materials were synthesized using Pluronic P123 (non-ionic triblock copolymer, EO₂₀PO₇₀O₂₀), under acidic conditions. SBA-15/carbon cryogel composites were obtained by sol–gel polycondensation of resorcinol and formaldehyde followed by freeze drying, and subsequent pyrolysis, in the presence of different amounts of SBA-15. For comparison purpose, SBA-15/carbon composite was also prepared using sucrose as carbon source. These materials were characterized by room temperature nitrogen adsorption–desorption measurement, X-ray diffraction, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. It was revealed that the samples have amorphous structure, high specific surface area (350–520 m² g^?1) and developed meso- as well as microporosity. The porosity of structure depends on the carbon source and Si/C ratio which can be easily controlled by varying concentration of starting solution.     

Geodetic method of the fuel tank form inspection

Fuel tanks are usually built of metal and have got a cylindrical form. Due to permanent exposition to different weather conditions, they change their form in time. However, the calculation of fuel volume is calculated using the original tank dimensions, which yields to huge differences in the actual volume. Dimensions of the tank shall be calculated with the measurement uncertainty of 1 mm, according to requested accuracy of the tank volume. A geodetic method of tank dimensions determination is presented in the paper. We estimated the measurement accuracy of geometrical quantities in order to reach the requested measurement uncertainty of tank dimensions. The method is tested with a real example.     

Possibilities of application of waste wood biomass as an energy source in Vojvodina

The Autonomous Province of Vojvodina is an autonomous province in Serbia, containing about 27% of its total population according to the 2002 Census. It is located in the northern part of the country, in the Pannonian plain. Fruska Gora is a lonely island mountain in the Pannonian plain. The research presented in this paper highlights the potential of significant contributing to waste wood biomass in the Park “Fruska Gora (Vojvodina, Serbia) and points to the possibility of using biomass for briquettes production—the final product that can be used for energy purposes. The amount of woody biomass per hectare can be calculated if the data about the average number of trees per hectare are known. For the analyzed case, the value found in 1 ha was 383.1 m³/ha or 272 ± 14 tons, and practically measured value was 402 m³/ha, or 289 tons. The relative deviation of calculated and obtained values of Canadian poplar wood biomass per hectare was 5.88%. Quantities of planned wood waste biomass can be used to produce high-quality briquettes for thermal energy generation purposes in the equivalent of 4.8 million kWh. The large energy potentials, in Vojvodina are still substantially unused, and besides of using waste wood from forestry, it is necessary to consider the sustainable use of available waste biomass from the timber industry.     

Antioxidant and antimicrobial potentials of Serbian red wines produced from international Vitis vinifera grape varieties

BACKGROUND: Antioxidant and antimicrobial potentials of Serbian red wines produced from different international Vitis vinifera grape varieties and their correlation with contents of phenolic compounds were studied by spectrophotometric and chromatographic methods. The antioxidant activity of red wines was estimated through their ability to scavenge 2,2′‐diphenyl‐1‐picrylhydrazyl free radical (DPPH^?). The red wines, gallic acid, (+)‐catechin and quercetin were screened in vitro for antimicrobial activity against Gram‐positive and Gram‐negative strains using microdilution and disc diffusion techniques. RESULTS: Excellent correlations between the contents of quercetin‐3‐glucoside (R² = 0.9463) and quercetin (R² = 0.9337) and DPPH^?‐scavenging ability of the red wines were found. Serbian red wines exhibited significant activity against Staphylococcus aureus, Listeria inocua, Micrococcus flavus, Sarcina lutea, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis and Shigella sonnei strains, which was in correlation with their phenolic composition and antioxidant activity. The compounds gallic acid, quercetin and (+)‐catechin showed high activity against B. subtilis, S. aureus, S. lutea and M. flavus Gram‐positive and S. enteritidis and P. aeruginosa Gram‐negative strains. CONCLUSION: The results show that quercetin‐3‐glucoside and quercetin concentrations can be used as markers for the determination of antioxidant and antimicrobial potentials of red wines. Copyright © 2012 Society of Chemical Industry     

Influence of winemaking techniques on the resveratrol content, total phenolic content and antioxidant potential of red wines

In this paper, the influence of winemaking techniques and cultivars on the resveratrol content, total phenolic content and antioxidant potential of red wines was studied. Wines were made from the cultivars Merlot, Cabernet Sauvignon, Pinot Noir and Prokupac. Applied winemaking technologies included thermovinification and separation of must from pomace. The analysis of trans- and cis-resveratrol in wines was performed by HPLC, while the total phenolic content and antioxidant potential was determined by spectrophotometric methods. The total resveratrol content in analysed samples ranged from 0.35 to 4.85 mg/l; Merlot wines had the highest average resveratrol content, while the lowest was found for native cultivar Prokupac. Although the resveratrol content depended on grape variety, correlation between the winemaking technology applied and the resveratrol level in wines was not observed. The total phenolic content (TPC) varied from 544.4 to 1410.4 mg/l expressed as gallic acid equivalents, and the antioxidant potential, assayed by DPPH in terms of SC₅₀ (mean scavenging concentration), ranged from 0.58 to 2.91 μl/ml. Obtained results showed that thermovinificated wine samples had higher amount of phenolic compounds. Significant negative correlation was observed (p < 0.05) between the total phenolic content and SC₅₀, but there was no significant correlation (p > 0.05) between the resveratrol content and SC₅₀ or TPC. This study could contribute to the establishment of optimal conditions for producing red wines which contain more beneficial phenolic compounds.     

Performance of Dual Branch SSC Receiver in Correlated <Emphasis Type="Italic">α</Emphasis>-<Emphasis Type="Italic">μ</Emphasis> Fading Channels

In this paper, the performance analysis of dual branch switch and stay combining (SSC) receivers operating over correlated and identically distributed (i.d.) α-μ fading channels is presented. Assuming this diversity technique, infinite series expressions with fast converging properties are derived for the probability density function (pdf), cumulative distribution function (cdf) and the moments of the output envelope. The proposed analysis is used for evaluating the important performance criteria, such as the outage probability, the mean square output envelope, the amount of fading and the average bit error probability (ABEP). The effects of fading severity, branch correlation and optimum choice of switching threshold are considered and numerically presented. Monte Carlo simulations confirm the validity and accuracy of the derived analytical expressions.     

Fumonisin B1 and its co-occurrence with other fusariotoxins in naturally-contaminated wheat grain

The natural occurrence of fumonisin B₁ (FB₁) and its co-occurrence with zearalenone (ZEA), T-2 toxin and deoxynivalenol (DON) were surveyed in 103 winter wheat samples collected after four to six-month storage in family barns from different locations in Serbia. All 103 samples were mycotoxin positive. The mean concentrations of all mycotoxins except ZEA were greater in 2005 than in 2007. FB₁ was detected in 82.1% and 92.0% of all samples with ranges of 750-5400 μg kg⁻¹ (mean, 2079.45 μg kg⁻¹) and 750-4900 μg kg⁻¹ (mean 918.76 μg kg⁻¹) in 2005 and 2007, respectively. Moderate positive correlations were found between FB₁ and DON concentrations (r = 0.56 in 2005 and r = 0.54 in 2007) and between FB₁ and ZEA concentrations (r = 0.48 in 2005 and r = 0.60 in 2007), while a moderate negative correlation was detected between the production of FB₁ and T-2 toxin in 2007 (r = −0.33). This is the first report of FB₁ occurrence in naturally-contaminated wheat grain and its simultaneous occurrence with ZEA, DON and T-2 toxin in Serbia. Moreover, this is one of the rare reports presenting the occurrence of FB₁ on wheat in the world.     

CYCLIC CONJUGATION IN FLUORANTHENE AND ITS BENZO-DERIVATIVES. PART 1. CATACONDENSED SYSTEMS

Continuing our investigations of π -electron properties of fluoranthene-type polycyclic conjugated compounds [Gutman, ?ur?evi?, Balaban, Polycyclic Aromatic Compounds 29 (2009): 3–11], we studied the energy effects of individual rings in fluoranthene and its catacondensed benzo-derivatives (i.e., benzo-annelated fluoranthenes possessing exactly one internal carbon atom). A number of general regularities were observed: (a) the PCP effect (six-membered rings connected by a single bond to the five-membered ring increase in it the intensity of cyclic conjugation), (b), the retro-PCP effect (the five-membered ring increases the intensity of cyclic conjugation in the six-membered rings to which it is connected by a single bond), (c) the linear effect (six-membered rings, linearly annelated to fluoranthene, decrease the cyclic conjugation in the five-membered ring), (d) the magnitude of the PCP effect differs, depending on whether the six-membered ring belongs to the “male” or “female” benzenoid fragment, and (e) the pattern of cyclic conjugationin of isoarithmic benzofluoranthenes is essentially identical.     

Experimental investigation and thermodynamic calculation of the Ga–Sb–Zn phase diagram

Phase equilibrium of ternary Ga–Sb–Zn system was investigated by applying CALPHAD method and using literature thermodynamic data for constitutive binary systems. The liquidus surface and isothermal section at 673 K were calculated. Calculated results were verified experimentally on the alloys samples with the compositions corresponding to the characteristic vertical sections: SbZn (1:1)–Ga; GaZn(1:1)–Sb; and GaSb(1:1)–Zn. Phase transitions temperatures were determined by differential thermal analysis and differential scanning calorimetry. Microstructure and phase composition investigation were investigated by using scanning electronic microscopy with energy dispersive spectrometry. The experimental and analytical results showed good agreement, concerning the temperatures of phase transitions and phase compositions of alloys concerned.     

Binding affinity between dietary polyphenols and β-lactoglobulin negatively correlates with the protein susceptibility to digestion and total antioxidant activity of complexes formed

Non-covalent interactions between β-lactoglobulin (BLG) and polyphenol extracts of teas, coffee and cocoa were studied by fluorescence and CD spectroscopy at pH values of the gastrointestinal tract (GIT). The biological implications of non-covalent binding of polyphenols to BLG were investigated by in vitro pepsin and pancreatin digestibility assay and ABTS radical scavenging activity of complexes formed. The polyphenol–BLG systems were stable at pH values of the GIT. The most profound effect of pH on binding affinity was observed for polyphenol extracts rich in phenolic acids. Stronger non-covalent interactions delayed pepsin and pancreatin digestion of BLG and induced β-sheet to α-helix transition at neutral pH. All polyphenols tested protected protein secondary structure at an extremely acidic pH of 1.2. A positive correlation was found between the strength of protein–polyphenol interactions and (a) half time of protein decay in gastric conditions (R² = 0.85), (b) masking of total antioxidant capacity of protein–polyphenol complexes (R² = 0.95).