University of Belgrade
  • Belgrade, Serbia
Recent publications
Mushrooms are experiencing a kind of renaissance as a part of the contemporary human diet. These valuable organisms are more than food, they fit in perfectly as a novel market group known as nutra-mycoceuticals. Immune-balancing mushroom dietary fibers and secondary metabolites such as polyphenols are the main focus of the healthcare industry. Wellness and cosmetic companies are increasingly using mushroom extracts rich in these ingredients. This review considers the basic molecular immunomodulatory mechanisms of action of the most commonly used mushroom dietary fibers, β-glucans. The literature data on their bioavailability, metabolic transformations, preclinical and human clinical research, and safety are discussed. Immunomodulatory mechanisms of polyphenol ingredients are also considered. These molecules present great potential in the design of the new immunity balancer formulations according to their widespread structural diversity. Finally, we draw attention to the perspectives of modern trends in mushroom nutraceutical and cosmeceutical formulations to strengthen and balance immunity.
In 1977, Smith has characterized graphs with exactly one positive eigenvalue. Since then, many particular results related to graphs with exactly two positive eigenvalues have emerged. In this paper we conclude this investigation by giving a full characterization of these graphs.
This paper explores the possibilities of providing fast frequency support as an emergency support service to the disturbed AC system through the MTDC grid. A two-layer hierarchical control structure of the MTDC grid is proposed to assure the minimum cost of the frequency control actions, the minimum voltage deviations, or the minimal impact on the frequencies of not-affected AC systems while ensuring the stable operation of MTDC grid. An optimization algorithm is executed at the secondary control level to find the optimal reference values for the voltage-droop characteristics of the voltage-regulating converters, and consequently their DC voltages and active power references. Then, at the primary control level, the reference values are tuned with the optimization results. Implemented control structure confirms that MTDC can provide set values at its terminals without endangering its stability. The secondary control layer is implemented in MATLAB, while the performance of the controller is successfully evaluated through simulation in RSCAD.
The novel method for tuning proportional-integral-derivative controller with second order derivative term (PIDD2) for the automatic voltage regulator (AVR) of synchronous generator is presented. The design method minimizes load disturbance response regarding constraints on sensitivity functions: maximum sensitivity Ms, maximum complementary sensitivity Mp and measurement noise sensitivity Mn. Simple solution is obtained by shifting PIDD2 controller in a new parameter space and by employing an iterative procedure. In each iteration the five controller parameters are obtained by solving the constrained optimization problem concerning sensitivities Ms and Mn for the fixed value of controller zeros damping factor ξ. The robustness index Mp is calculated subsequently. In that manner, maximum of complementary sensitivity Mp is met by means of auxiliary parameter ξ. The performance improvements are achieved in comparison with traditional PID controller, while robustness is retained. Further, the comparison is made with an optimization method using amplitude optimum principle that also minimizes load disturbance response with different optimality criterion. Experiments are carried out on a small lab synchronous generator setup in order to demonstrate practical potential in real noisy environment of the proposed method and to justify the increased order of AVR controller.
Deactivation by NH4HSO4 deposition is one of the major problems faced by commercial SCR catalysts at low temperatures. In this study, NH4NO3 was added to the SCR reaction atmosphere in the presence of H2O and SO2 at 250 °C, which is lower than the typical temperatures suitable for the V2O5-WO3/TiO2 catalyst. After a long test, the catalyst activity decreased from 82 % to 75 %, which is much smaller than the activity drop in the atmosphere without NH4NO3. The characterization results indicate that the addition of NH4NO3 effectively reduced the deposition of NH4HSO4 on the catalyst surface, thus weakening the degree of catalyst poisoning deactivation. In addition, we examined the effect of NH4NO3 addition on the regeneration of catalysts deactivated by NH4HSO4. The activity of the catalyst deactivated by 5 wt% NH4HSO4 recovered efficiently after the deactivated catalyst was treated by NH4NO3, NO and O2 for 1 h at 250 °C. The SEM, FTIR, and BET characterization results reveal the positive effect of NH4NO3 in promoting the decomposition of NH4HSO4.
A low-cost, highly active CaO-based catalyst was prepared from waste filter cake (WFC) from a sugar beet processing factory by calcination in air at 900 °C for 2 h, referred to as the calcined filter cake (CFC). It was used to catalyze the rapeseed oil transesterification with methanol under mild reaction conditions (methanol-to-oil molar ratio of 9:1, catalyst loading of 4–10 %, and reaction temperature of 40–60 °C). Rapeseed oil was characterized regarding the physicochemical properties and fatty acid profile. Low free fatty acid content (about 2.0 mg KOH/g) allowed the direct use of the base CFC catalyst for rapeseed oil transesterification. Rapeseed oil has more unsaturated fatty acids (about 93 %), with oleic acid as the most abundant, than saturated fatty acids (about 7 %). A simplified model combining the changing mechanism of the reaction and the triacylglycerols mass transfer limitation successfully describes the kinetics of transesterification. A good agreement between the model and the experiment was proved by the mean relative percentage deviation for the conversion degree of only ± 7.43 % (based on 42 data). The apparent reaction rate constant follows the Arrhenius equation with the activation energy of 51.9 kJ mol⁻¹. The FAME content higher than 96.5 % can be obtained in wide ranges of the catalyst amount (4–10 %) and the reaction time (about 45–70 min). The following conditions were optimum: the reaction temperature of 59.2 °C, the catalyst loading of 9.1 % (based on the oil weight), and the reaction time of 47 min.
Objectives In order to reveal their structure, Poincaré plots (PP) of electrocardiogram (ECG) RR intervals (RRI) were studied as linear edge planar directed graphs, obtained by connecting all their sequential points. We were also aimed at studying their graph complexity properties. Methods RRI signals were subjected to a series of different window length (WL) Moving Average Low Pass (MALP) filters. For each filtered graph, four standard PP descriptors: Pearson’s coefficient, SD1, SD2, and SD2/SD1 were calculated, as well as four new graph complexity measures: mean angle between adjacent graph edges; mean number of edge crossings; directional complexity and directional entropy. This approach was applied to signals of twenty young healthy subjects, recorded in four experimental conditions – combination of two body postures (supine and standing) and two breathing regimes (spontaneous and slow 0.1 Hz). Results We found that PP graphs consist of two superimposed components: one originating from Respiratory Sinus Arrhythmia (RSA) oscillations, the other from slow variations (SV) of the RRI time series. This result was further corroborated by observing the transformation of a PP cloud shape occurring in filtered graphs. When applied to subjects, the outcome was that three measures significantly differentiated the two breathing regimes in the RSA region of the WL domain, while four other measures were able to differentiate two body postures in the SV WL region. Discussion After obtaining these results in healthy, we expect to successfully apply this approach to patients suffering from different pathological conditions.
Population variability of n-alkanes in the cuticular waxes of Serbian spruce needles from Bosnia and Herzegovina was investigated for the first time. n-Alkanes exhibited composition variability ranging from C18 to C35. The divergence of populations from Bosnia and Herzegovina and previously investigated Serbian populations was statistically confirmed by PCA, DA, and CA (Cluster analysis), which could support the fact that there are two possible spruce chemotypes: one relating to the Bosnian-Herzegovinian and the other to the Serbian populations. Climate parameters (precipitation, temperature, wind, and solar radiation) approved this conclusion.
Severe damage of non-structural elements is noticed in previous earthquakes, causing high economic losses and posing a life threat for the people. Masonry partition walls are one of the most commonly used non-structural elements. Therefore, their behaviour under earthquake loading in out-of-plane (OOP) direction is investigated by several researches in the past years. However, none of the existing experimental campaigns or analytical approaches consider the influence of prior slab deflection on OOP response of partition walls. Moreover, none of the existing construction techniques for the connection of partition walls with surrounding reinforced concrete (RC) is investigated for the combined slab deflection and OOP loading. However, the inevitable time-dependent behaviour of RC slabs leads to high values of final slab deflections which can further influence boundary conditions of partition walls. Therefore, a comprehensive study on the influence of slab deflection on the OOP capacity of masonry partitions is conducted. In the first step, experimental tests are carried out. Results of experimental tests are further used for the calibration of the numerical model employed for a parametric study. Based on the results, behaviour under combined loading for different construction techniques is explained. The results show that slab deflection leads either to severe damage or to a high reduction of OOP capacity. Existing practical solutions do not account for these effects. In this contribution, recommendations to overcome the problems of combined slab deflection and OOP loading on masonry partition walls are given. Possible interaction of in-plane (IP) loading, with the combined slab deflection and OOP loading on partition walls, is not investigated in this study.
Apart from traditional medicine use, the fruit of Lycium barbarum L., known as red goji berry or wolfberry, is recognized and consumed as a functional food. Beyond nutritional properties, goji berry exerts many biological activities and health-promoting effects due to wide-range phytochemicals. Rising global popularity and high demand have spread the production of goji berries from traditional Asian regions into various parts of the world. In addition, other native species, as Lycium ruthenicum Murr., or black goji berry, also have been started to generate attention by the scientific community as a valuable source of nutritional and functional components. This chapter reviews data on nutritional value and bioactive compounds of red and black goji berries from different regions, highlighting the influence of many pre-harvest and post-harvest factors that affect their chemical compositions, sensory quality, and bioactivities.
Today, as always throughout the history of nature, it is an inexhaustible source of inspiration. One of the main goals of creating new biophilic/biomimetic forms inspired by natural structures and patterns is to create a positive psychological impact on people (especially in urban areas) by using geometrical methods and the graphical representation of the plants should convey the symbolism of life. With the progress of civilization and the development of digital technologies, significant biodesign is growing rapidly and becoming necessary in the humanization of today's sustainable way of life. This paper deals with leaf of dandelion (Leontodon taraxacum L.) as bio-inspiration to gain land-art installation as result by using digital modelling throughout Blender, SketchUp and Lumion software tools.
This paper combines the k-means clustering method in combination with PCA and the system dynamic modeling approach to derive a better insight into the behavior of airline profitability during the time span of 1995 until 2020. The model includes various explanatory variables that capture different aspects of airline economic and operational metrics, whose fluctuations may affect the airline profitability. By forecasting these exogenous variables, the system dynamic model is used to predict airline profitability through 2025 and answer the question of whether the US airline industry will return to its pre-COVID 19 pandemic state. The latter research question can be agreed with, as the effect of introducing a fourth dimension derived from Principal Component Analysis (PCA) to sufficiently cover the variation within the dataset during the years of COVID-19 pandemic diminishes towards the end of the forecast period. Furthermore, the key measures from PCA imply that under the assumption of continuous growth and a non-exogenous shock, future years will not cluster in past years. The six different clusters from 2019 to 2025 showed how the system stays in a certain state for a few years and then drifts further to a new state. There are only a few variables that change to transfer from one cluster to the next.
The second-hand vessel market has quite different dynamics than the market of the new-building vessel, and highly complicated and conflicting criteria and many uncertainties affect the ship selection process. Therefore, it is required to use a robust mathematical model to solve these kinds of decision-making problems. For this purpose, this paper presents an extended version of WASPAS (Weighted Aggregated Sum Product ASsessment) techniques with the help of T2NN based on the Bonferroni function (T2NN WASPAS’B). The three main focal points of the proposed approach are (i) setting the influential criteria to select the appropriate Ro-Ro vessel in the second-hand vessel market; and (ii) presenting a flexible group decision-making approach, which is proper to real decision-making problems. (iii) detecting the interrelations among criteria and eliminating the negative impacts of undesirable and excessive values in input variables on the results. Practical use of the proposed approach is demonstrated to select the appropriate Ro-Ro vessel in the second-hand market. The analysis results show that the most effective and determinative factor is Trailer Lane length, and the most effective alternative is GREIFSWALD. Besides, the consistency and validity of the obtained results have been verified with the help of a stability and robustness check. The results prove that the proposed novel T2NN WASPAS’B model is robust, powerful, and reliable for making rational and realistic decisions.
Kaolinite/illite (KUb) and sepiolite (SEP) clays were used to study Cr(III) adsorption removal from aqueous solutions so that they could be utilized after saturation for ceramic manufacturing. SEP had a larger specific surface area and a higher PZC than KUb. The removal of Cr(III) was evaluated using a batch equilibration procedure at pHi = 4 and pHi = 6. Fast removal kinetics were observed for both clays. Maximum removal capacity was determined by changing the concentration of Cr(III) while keeping the concentration of clay constant and by altering the amount of clay while keeping the concentration of Cr(III) constant. In all situations, SEP had greater capacity than KUb, and capacity was greater for both clays at higher pHi. Not only did the pHi impact the removal capacity and efficiency, but so did the pH during adsorption and the initial concentration of Cr(III). Because of the higher PZC, the pHf for SEP was higher for the same pHi. The higher the pH and Cr(III) concentration, the higher the probability of Cr(OH)3 precipitation and the higher the removal capacity. Dried saturated clays were uniaxially pressed and sintered at 1000 °C for 2 h. The densities of the sintered materials were nearly identical to those of pure clay-based materials, but the compressive strengths were higher, which is significant for the use of saturated clays as raw materials in ceramic manufacturing. Leaching of Cr from SEP-based material was significantly higher than from KUb-based material probably due to the presence of CaCO3 in the SEP.
Poly(vinylidenefluoride)–ZnO (PVDF–ZnO) nanocomposites with mechanically activated ZnO nanoparticle fillers were investigated using thermal and mechanical analysis and AFM and PFM. Differential scanning calorimetry (DSC) investigated the effect of ZnO nanoparticles on the crystallinity of the polymer, under controlled heating and cooling. Atomic force (AFM) microscopy was used to record the surfaces of the samples. Nanocomposite surface roughness shows the presence of the different phases inside of the matrix, where rough samples contain a higher proportion of the β phase. PFM was performed to investigate the piezoresponse of the composites. Nanoidentation showed that the mechanical activation of the filler (ZnO) increases the Young modulus with the activation time. Molecular simulations in periodic systems (PVDF–ZnO spherical nanocluster and nanocylinder composite) were used to investigate the influence of particle size and shape on the Young modulus of different phases of PVDF.
What is it to be “an ideal parent”? Does the answer differ across countries and social classes? To answer these questions in a way that minimizes bias and ethnocentrism, we used open-ended questions to explore ideal-parent beliefs among 8,357 mothers and 3,517 fathers from 37 countries. Leximancer Semantic Network Analysis was utilized to first determine parenting culture zones (i.e., countries with shared ideal-parent beliefs) and then extract the predominant themes and concepts in each culture zone. The results yielded specific types of ideal-parent beliefs in five parenting culture zones: being “responsible and children/family-focused” for Asian parents, being “responsible and proper demeanor-focused” for African parents, and being “loving and responsible” for Hispanic-Italian parents. Although the most important themes and concepts were the same in the final two zones—being “loving and patient,” there were subtle differences: English-speaking, European Union, and Russian parents emphasized “being caring,” while French-speaking parents valued “listening” or being “present.” Ideal-parent beliefs also differed by education levels within culture zones, but no general pattern was discerned across culture zones. These findings suggest that the country in which parents were born cannot fully explain their differences in ideal-parent beliefs and that differences arising from social class or education level cannot be dismissed. Future research should consider how these differences affect the validity of the measurements in question and how they can be incorporated into parenting intervention research within and across cultures.
Rosehip (Rosa canina L.) seeds are rich in bioactive compounds and nutrients and hence with a great potential to be employed in production of functional foods. This work aimed to evaluate the fatty acid composition of seed oil from wild and cultivated rosehip collected at different locations in the Republic of Serbia. Unsaturated fatty acids were dominant in majority of seed oil samples, with linoleic (LA), α-linolenic (ALA) and oleic (OA) acids (24.53-46.68 %, 4.73-12.39 % and 3.89-13.82 %, respectively) as the most abundant ones. Based on the analyses of most dominant bands in Raman spectra of seeds (~1265 and ~1660 cm-1) characteristic for unsaturated fatty acids, ANOVA revealed significantly higher content in two seed samples (5SW and 10SC). Ratios of UFAs/ SFAs, ω-6/ω-3 and LA/ALA and desirable fatty acids (DFA) indicated that most studied rosehip seed oils showed good quality. Factors such as genetic characteristics and agro-ecological conditions most likely affected FAs composition of seed oils.
Multifunctional lignin bio-based adsorbent, b-LMS, was obtained via inverse copolymerization in the suspension of acryloyl modified kraft lignin (KfL-AA) and bio-based trimethylolpropane triacrylate (bio-TMPTA). Morphological and structural characterization of KfL-AA and b-LMS was performed using BET, FTIR, Raman, NMR, TGA, SEM, and XPS techniques. The b-LMS microspheres with 253 ± 42 μm diameters, 69.4 m² g⁻¹ surface area, and 59% porosity efficiently adsorb Malachite Green (MG), Tartrazine (T), and Methyl Red (MR) dye. The influence of pH, pollutant concentration, temperature, and time on the removal efficiency was studied in a batch mode. Favorable and spontaneous processes with high adsorption capacities e.g. 116.8 mg g⁻¹ for MG, 86.8 mg g⁻¹ for T, and 68.6 mg g⁻¹ for MR indicate the significant adsorptive potential of b-LMS. Results from diffusional and single mass transfer resistance studies indicate that pore diffusion is a rate-limiting step. Theoretical calculations confirmed a higher affinity of b-LMS to cationic dye MG compared with an anionic and neutral one, i.e. T and MR, respectively. The data fitting from a flow system, using semi-empirical equations and Pore Surface Diffusion Modelling (PSDM) provided breakthrough point determination. The results from the desorption and competitive adsorption study proved the exceptional performance of b-LMS. Moreover, sulfation of b-LMS, i.e.production of b-LMS-OSO3H, introduced high-affinity sulfate groups with respect to cationic dye and cations. Developed methodology implements the principle of sustainable development and offers concept whose results contribute to the minimization of environmental pollution.
Four cerium-zeolites were examined as low-cost bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in an alkaline solution. Cerium-exchanged zeolites, synthetic 13X and natural clinoptilolite were employed as prepared and calcined (cal). Four samples (Ce-13X cal, Ce-13X, Ce-Cli cal, and Ce-Cli) were characterized by X-ray powder diffraction analysis (XRPD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy and Brunner-Emmet-Teller (BET) method. All four zeolites exhibited activity for the two studied reactions. Ce-13X cal gave the lowest onset potential accompanied by the highest OER current density. Furthermore, Ce-13X cal showed the most positive ORR onset potential value of 0.84 V and the most positive ORR half-wave potential of 0.75 V (ca. 50 mV more positive than value for the other three cerium-zeolite electrodes) accompanied by the lowest Tafel slope of 80 mV dec⁻¹. Koutecky-Levich analysis indicated that ORR follows 2-electron pathway. Overall, Ce-13X cal showed the best OER/ORR performances in alkaline solution.
Objectives: Due to the role of oxidative stress in the pathophysiology of COVID-19, it is biologically plausible that inter-individual differences in patients’ clinical manifestations might be affected by antioxidant genetic profile. The aim of our study was to assess the distribution of antioxidant genetic polymorphisms Nrf2 rs6721961, SOD2 rs4880, GPX1 rs1050450, GPX3 rs8177412, and GSTP1 (rs1695 and rs1138272) haplotype in COVID-19 patients and controls, with special emphasis on their association with laboratory biochemical parameters. Methods: The antioxidant genetic polymorphisms were assessed by appropriate PCR methods in 229 COVID-19 patients and 229 matched healthy individuals. Results: Among examined polymorphisms, only GSTP1 haplotype was associated with COVID-19 risk (p = 0.009). Polymorphisms of SOD2 and GPX1 influenced COVID-19 patients’ laboratory biochemical profile: SOD2*Val allele was associated with increased levels of fibrinogen (p = 0.040) and ferritin (p = 0.033), whereas GPX1*Leu allele was associated with D-dimmer (p = 0.009). Discussion: Our findings regarding the influence of SOD2 and GPX1 polymorphisms on inflammation and coagulation parameters might be of clinical importance. If confirmed in larger cohorts, these developments could provide a more personalized approach for better recognition of patients prone to thrombosis and those for the need of targeted antiox­idant therapy.
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Tanja Vukov
  • Department of evolutionary biology (IBISS)
Ljubiša Stanisavljević
  • Department of Invertebrate Zoology and Entomology
Ivica Bradaric
  • Vinca Institute of Nuclear Science
Veljko Djokic
  • Department of Chemical Engineering
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Address
Студентски трг 1, 11000, Belgrade, Serbia
Head of institution
Владимир Бумбаширевић
Website
http://www.bg.ac.rs
Phone
+381 11 3207-445
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2638-912, 3207-481