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排序方式: 共有69条查询结果,搜索用时 15 毫秒
1.
Novaković MM Stevanović SM Gorjanović SŽ Jovanovic PM Tešević VV Janković MA Sužnjević DŽ 《Journal of food science》2011,76(4):C663-C668
This study was conducted to investigate the influence of different drying treatments on antioxidant (AO) activity and phenolic content of raspberry (Rubus idaeus), cultivar Willamette. Whole raspberry fruits were dried convectively (air-drying), osmotically, and freeze-dried. Acetone-water extracts of fresh and dried raspberries were assessed for total phenolic content by standard Folin-Ciocalteau method. Two AO assays were applied, a recently developed direct current (DC) polarographic assay based on decrease of anodic oxidation current of hydrogen peroxide and widely used radical scavenge against the 1,1-diphenyl-2-picrylhydrazyl (DPPH). Strong correlation has been obtained between both AO assays and total phenolic content. In addition, some individual phenolic compounds present in raspberry have been assessed using DPPH and DC polarographic assay. Comparison and evaluation of drying methods has been based on preservation of AO activity and total phenolic content. Obtained results confirmed superiority of freeze-drying; convective drying caused slight changes while osmotic dehydration showed a significant decrease of phenolic compounds and AO activity. 相似文献
2.
The problems related to our strong dependency on fossil fuels, i.e. greenhouse effect, energy dependency, urban pollution, are of growing importance in recent years. European Union (EU) Action plan of 2003, which had originated from Kyoto Agreement, defined a strategy for substitution of 20% of conventional fuel with the alternative one by 2020. Proved advantages of biodiesel usage in the system of public transport of passengers, with regard to exhaust gases emission above all, have been the decisive determinants for the actual promotion of biodiesel as ecologically “clean” fuel, while its wider usage gives important contribution to sustainable development of cities. This paper presents results of biodiesel-test run in Belgrade, as a part of the project BIO-PEX, which relates to the usage of this alternative fuel in real operating conditions in urban public transport system, with special emphasis on technical, ecological and operational aspects of biofuel usage. 相似文献
3.
Branko Matović Jelena Dukić Biljana Babić Dušan Bučevac Zorana Dohčević-Mitrović Marko Radović Snežana Bošković 《Ceramics International》2013,39(5):5007-5012
Nanometric ceria powders with fluorite-type structure were obtained by applying self-propagating room temperature method. The obtained powders were subsequently thermally treated (calcined) at different temperatures for different times. Powder properties such as specific surface area, crystallite size, particle size and lattice parameter have been studied. Roentgen diffraction analysis (XRD), BET and Raman scattering measurements were used to characterize the as-obtained (uncalcined) powder as well as powders calcined at different temperatures.It was found that the average diameter of the as-obtained crystallites is in the range of 3–5 nm whereas the specific surface area is about 70 m2/g. The subsequent, 15 min long, calcination of as-obtained powder at different temperatures gradually increased crystallite size up to ~60 nm and reduced specific surface down to 6 m2/g. Raman spectra of synthesized CeO2?y depicts a strong red shift of active triply degenerate F2 g mode as well as additional peak at 600 cm?1. The frequency of F2 g mode increased while its line width decreased with an increase in calcination temperature. Such a behavior is considered to be the result of particle size increase and agglomeration during the calcination. After the heat treatment at 800 °C crystallite size reached value larger than 50 nm. Second order Raman mode, which originates from intrinsic oxygen vacancies, disappeared after calcination. 相似文献
4.
Dragan P. Popovi? Sne?ana V. Mijailovi? 《International Journal of Electrical Power & Energy Systems》1997,19(8):525-532
The paper presents the development of a simple method for the fast and sufficiently accurate assessment of dynamic changes of power systems frequency during the time period of primary control. Also, this model gives corresponding values of the total mechanical power of synchronous generators, during the some period. The development of a proposed low-order system frequency response model is based on the main assumption of uniform movement of generators, which enables representation of the power system through an equivalent controlled synchronous machine. The characteristics of the developed method were determined on an example of a real electric power system and a comparison was made with the results of a stricter approach. 相似文献
5.
This statistical study considers two basic hypotheses on industrial and traffic accidents the accident proneness theory and the spell theory. The two hypotheses were tested on the basis of a correlation analysis of accident distribution in a group of tram drivers over a five year observation period. Using the chi-square goodness of the test. the analysis showed the negative binomial distribution and the “short” distribution were successfully fitted,while the Poisson distribution significantly differed from the observations. Correlation analysis showed a significant correlation between the number of tram driver accidents over different periods, and that this correlation. although decreasing with an increase of the interval between observation periods, remained significant. The conclusion is that the proneness hypothesis explains more satisfactorily than the spell hypothesis the occurrence of accidents in tram drivers during tlie observation period. 相似文献
6.
Prediction of the chemical equilibrium constant for peracetic acid formation by hydrogen peroxide 总被引:1,自引:0,他引:1
Milovan?Jankovi? Sne?ana?Sinadinovi?-Fi?erEmail author 《Journal of the American Oil Chemists' Society》2005,82(4):301-303
An expression for temperature dependence of the chemical equilibrium constant for peracetic acid synthesis from acetic acid
and hydrogen peroxide in an aqueous solution, derived on the basis of the van't Hoff and Kirchhoff equations, was proposed.
The reverse trend of the chemical equilibrium constant vs. temperature was apparent when the predicted values of the constant
were compared with experimental ones taken from the literature. However, using the proposed model to calculate the chemical
equilibrium constant resulted in better prediction of the equilibrium composition for peracetic acid synthesis at 297.5 K
than using experimental data from the literature. 相似文献
7.
Nebojša D. Cekić Snežana D. Savić Miroslav M. Savić Žarko Jović Rolf Daniels 《Drug development and industrial pharmacy》2013,39(9):1092-1102
Background: The potential for use of chitosan-treated alginate microparticles as a vehicle for oral phenytoin delivery has not been thoroughly exploited. Aim: We studied the influence of preparation procedure and chitosan type on physicochemical properties and release behavior of alginate-chitosan microparticles. Method: The total number of 24 microparticles formulations prepared by varying contents of calcium gelling ions and varying contents and type of chitosan was examined. As an additional variable, two different hardening times (1 and 24 hours) were employed. Possible interactions of components, surface morphology of microparticles as well as release profile of phenytoin were studied. Results: Both series of formulations with regard to hardening times, irrespective of the chitosan type and/or concentration employed appeared to be highly loaded with the model drug (above 90%). The drug release studies showed that the kinetics of phenytoin cannot be straightforwardly predicted based on the molecular weight of chitosan alone. On the other hand, prolonging the hardening time from 1 to 24 hours had significantly improved phenytoin kinetics, and gave rise to a formulation with the liberation half-time of about 2.5 hours. Conclusion: This study showed that the latter formulation is eligible for further modifications aimed at improving the regularity of phenytoin absorption. 相似文献
8.
Curčić MG Stanković MS Mrkalić EM Matović ZD Banković DD Cvetković DM Dačić DS Marković SD 《International journal of molecular sciences》2012,13(2):2521-2534
The aim of this study is to examine the growth inhibitory effects of methanolic leaf and fruit extracts of L. vulgare on HCT-116 cells over different time periods and their synergistic effect with a Pd(apox) complex. The antiproliferative activity of plant extracts alone or in combination with the Pd(apox) complex was determined using MTT cell viability assay, where the IC(50) value was used as a parameter of cytotoxicity. Results show that antiproliferative effects of L. vulgare extracts increase with extension of exposure time, with decreasing IC(50) values, except for 72 h where the IC(50) values for methanolic leaf extract were lower than for the fruit extract. The Pd(apox) complex alone had a weak antiproliferative effect, but combination with L. vulgare extracts caused stronger effects with lower IC(50) values than with L. vulgare extracts alone. The type of cell death was explored by fluorescence microscopy using the acridin orange/ethidium bromide method. Treatments with plant extracts caused typical apoptotic morphological changes in HCT-116 cells and co-treatments with Pd(apox) complex caused higher levels of apoptotic cells than treatment with plant extracts alone. The results indicate that L. vulgare is a considerable source of natural bioactive substances with antiproliferative activity on HCT-116 cells and which have a substantial synergistic effect with the Pd(apox) complex. 相似文献
9.
Radmila V. Hercigonja Danijela D. Maksin Aleksandra B. Nastasović Snežana S. Trifunović Pavle B. Glodić Antonije E. Onjia 《应用聚合物科学杂志》2012,123(2):1273-1282
The possibility of sorption of technetium‐99 in the form of pertechnetate anion (TcO4?) and the sorption kinetics for removing TcO4? from aqueous solution by chelating polymers based on glycidyl methacrylate (GMA) were investigated. Two samples of macroporous crosslinked poly(glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) (PGME), with different amount of the crosslinker (ethylene glycol dimethacrylate, EGDMA), were synthesized by suspension copolymerization and functionalized with diethylene triamine (deta). We propose that nonspecific sorption of pertechnetate anion via electrostatic interactions takes place at the protonated amino groups of macroporous crosslinked copolymer. The results of batch experiments performed at pH 1–14 showed fast sorption kinetics for removing TcO4? by amino‐functionalized PGME‐deta in a wide range of pH, that is, from 1.0 to 9.0. Almost complete removal of TcO4? (91–98%) was reached within 180 min in the stated pH range (1.0–9.0), with the sorption half‐times of under 25 min. The partitioning coefficients of linear adsorption isotherms, with 180‐min equilibrium time, reach the high values of 2130 mL g?1 and 1698 mL g?1 for the two samples of synthesized PGME‐deta. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
10.
Snežana Filip Branimir Pavlić Senka Vidović Jelena Vladić Zoran Zeković 《Food Analytical Methods》2017,10(7):2270-2280
Microwave-assisted extraction (MAE) was optimized by response surface methodology in order to enhance the extraction of polyphenols from basil (Ocimum basilicum L). Box–Behnken experimental design on three levels and three variables was used for optimization. Influence of ethanol concentration (50, 70, and 90%); microwave power (400, 600, and 800 W); and extraction time (15, 25, and 35 min) on each response were investigated. Experimental results were fitted to a second-order polynomial model, and multiple regression analysis and analysis of variance were used to evaluate model fitness and optimal conditions. Considering the maximum content of extracted total phenols, total flavonoids, and antioxidant activity, the optimal conditions for all investigated response were ethanol concentration of 50%, microwave power of 442 W, and extraction time of 15 min. Under the optimal conditions, obtained basil liquid extract contained 4.299 g gallic acid equivalents/100 g dry weight (DW) of total polyphenols, 0.849 g catechin equivalents/100 g DW of total flavonoids, and IC50 and EC50 values of 9.602 and 82.889 μg/mL, respectively. The development of simultaneous MAE procedure for extraction of total phenols, total flavonoids, and potential antioxidants from basil, represented valorization of basil as valuable source of bioactive compounds. 相似文献