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Metal oxide nanoparticles as active food packaging components
Get PDFReplacement of non-degradable food packaging materials with a biodegradable alternative
enables reduction of environmental pollution. Metal oxides nanoparticles are good candidates
for enhancing and ensuring good mechanical, thermal and barrier properties of biodegradable
polymer packaging films. Their incorporation in biodegradable food packaging films has also
lead to enhanced antioxidant, antifungal and antibacterial properties of the food packaging
and also oxygen barrier properties, UV protection, oxygen and ethylene scavenging resulting
in an active food packaging material. The synthesis method has a significant influence on the
resulting properties of metal oxide nanoparticles. Green synthesis using plant extracts and
extracts of plant bio-waste as reducing and capping agents are one direction for obtaining
metal oxide nanoparticles with improved antioxidant and antimicrobial properties. Utilization
of bio-waste materials both for metal oxide nanoparticle synthesis and as a source of
biopolymers for packaging enables better environmental protection and ensures a circular bioeconomy. In selection of metal oxide nanoparticles suitable for application in active
packaging bio-nano-composites special attention needs to be paid to nanoparticle migration
and cytotoxic activity in order to produce safe, active and biodegradable food packaging
materials for the future
Thermoelectric Cu doped sodium cobaltite – structural, magnetic and mechanical properties
Get PDFWith the increase of the consumption of electrical energy, the need for new energy sources is growing. Conversion of waste heat into electricity, based on the thermoelectric effects is one of the ways to produce the electrical energy. Layered cobalt oxides have been the subject of many investigations in past decade as candidates for application in energy conversion. The ceramic sodium cobaltite became a promising candidate for potential thermoelectric applications, because of its large thermopower and low resistivity. In this work, polycrystalline samples of NaCo2–xCuxO4 (x = 0, 0.01, 0.03, 0.05) were synthesized from the powder precursors obtained by the citric acid complex method (CAC) and mechanochemically assisted solid state reaction method (MASSR). The obtained powders were uniaxially pressed into disc-shaped pellets and subsequently sintered at 880 °C in inert argon atmosphere. Thermoelectric parameters (the electrical resistivity (ρ), the thermal conductivity (κ) and the Seebeck coefficient (S)) were measured in two temperature regions. In the first one (between 2 and 300 K) κ and S were measured by a Quantum Design physical property measurement system (PPMS 9T) equipped with a 9 T magnet and ρ by a standard four-terminal technique using the direct current. In the second, all parameters were measured simultaneously, in the temperature gradient (ΔT) between hot and cold sides of the samples using Z- meter, based on the “large ΔT method”, and the figure of merit (ZT) was subsequen tly calculated. Accordingly, ρ, κ and S were determined for a temperature gradient that is established between the hot and cold sides of the samples at the time of each measurement; thus the obtained values represented the actual thermoelectric response of a material under conditions of application. In the low temperature range the highest figure of merit of 0.022 at 300 K was observed for the CAC sample doped with 1 mol% Cu, and it was almost twice higher than in the undoped sample confirming the significant influence of Cu-doping with even small concentrations. As for the results obtained in the temperature gradient, the highest ZT value of 0.061 at T = 473 K was observed for the sample with 5 mol% of Cu prepared by the CAC method. Sample magnetization was measured using a Quantum Design SQUID MPMS-XL-5 magnetometer in zero field cooled (ZFC) and field cooled (FC) regimes, between 2 K and 300 K and in the applied field of 100 Oe. The magnetic susceptibility (χ) of all samples followed the Curie-Weiss law in the temperature range between 50 K and 300 K, while a negative Weiss constant (θ) implied an antiferromagnetic interaction. Indentation experiments were carried out to investigate mechanical properties, therefore, the hardness (H) and the Young's modulus of elasticity (Y) were determined using Agilent Nanoindenter G200. It was found that the highest Y (65.2 GPa) and H (1.41 GPa) were obtained for the CAC sample containing 1 mol% of Cu. These results indicated a significant improvement of mechanical properties even in the case of the sample with the lowest dopant concentration. In general, better thermoelectric and mechanic properties showed the samples synthesized by the CAC method, confirming that fine, homogeneous precursor powders present a good base for obtaining material with improved thermoelectric performances
Two-way reaction of versatile peroxidase with artificial lignin enhances low-molecular weight fractions
No full textIn recent years, versatile peroxidase (VP) has emerged as a promising enzyme for biotechnological applications, as it can oxidize lignin without the external mediators. To gain insights into the breakdown process of artificial lignin by VP, reaction between the two was studied. Degradation products were fractionated using ultrafiltration and analyzed by RP- high performance liquid chromatography with mass detection (HPLC-MS) chromatography. Four fractions were obtained based on their molecular sizes: >10, 3–10, 1–3, and <1 kDa. Interestingly, while VP did not significantly alter the yields of these fractions, the chromatograms revealed the presence of oligomers with different molecular weights (MWs) resulting from the enzymatic activity. The VP exhibits a dual role in its enzymatic activity: both degrading and synthesizing these oligomers. This was confirmed by principal component analysis (PCA). The positive correlations were found between certain oligomers (D1 and D2, D5 and D6, as well as between D7, D10, T2, and T4), suggesting their simultaneous degradation. On the other hand, a negative correlation was found between the monomer and some oligomers (D7, D10, T2, and T4), indicating the decomposition of these oligomers into monomers. These findings shed light on the intricate interplay between VP and artificial lignin, offering valuable insights for potential applications in lignin valorization
Changes to fish assemblage following the selective removal of black bullhead (Ameiurus melas)
No full text1. Black bullhead is among the most abundant and successful non-native fish species in European freshwaters. A number of studies have indicated that its physical removal could be a potential solution to minimize possible negative impacts that it may have on native fishes; however, so far there have been no field studies to confirm this.
2. This study quantified population dynamics of both native and non-native fishes in a small slow-running lowland river within the Ponjavica Nature Park in Serbia before and after the black bullhead removal with fyke-nets, which proved to be an efficient tool for this purpose.
3. The removal of black bullhead resulted in statistically significant changes in two native species abundance – an increase of rudd (Scardinius erythrophthalmus) (by 5.3 times), and a decline of bleak (Alburnus alburnus) (by 2.3 times).
4. Significant increase was observed in three non-native fish species: the abundances of topmouth gudgeon (Pseudorasbora parva), pumpkinseed (Lepomis gibbosus), and Prussian carp (Carassius gibelio) increased 25.5, 4.9, and 4.2 times, respectively.
5. There were also substantial changes in the diversity of the fish assemblage after the black bullhead removal, illustrated by changes in diversity indices: Shannon's index doubled, while the Simpson’s dominance index decreased threefold.
6. The catch-per-unit-effort and the biomass-per-unit-effort values indicated the dominance of the black bullhead in the fish assemblage. YOY/adult ratio did not vary in relation to abundance, which confirmed that black bullhead might not compensate for fishing mortality with the increased recruitment.
7. The results suggest that black bullhead plays a significant role in structuring the fish assemblage and that its removal may have both positive and negative effects on species abundance and diversity. These findings can contribute to the conservation of native fish species and improvement of future management programs
VISOKONAPONSKI IZVOR NAPAJANJA ZA KORONA POLARIZACIJU TANKIH PVDF FILMOVA
Get PDFU radu je predstavljen visokonaponski sistem za polarizaciju ultra
tankih filmova poliviniliden fluorida (PVDF) posredstvom visokonaponske korone.
PVDF je polimer sa jedinstvenim karakteristikama, kao što su piezoelektrične i
feroelektrične. Perspektiva primene ovih filmova je u sistemima za sakupljanje energije
iz mehaničkih vibracionih struktura koje generišu široki spektar učestanosti vibracija.
Veoma važan postupak koji obezbeđuje funkcionalnost proizvedenih PVDF tankih
filmova je visokonaponska polarizacija domena (tzv. polingovanje). Ovde su kvalitet i
preciznost visokog napona koji se generiše iz visokonaponskog energetskog pretvarača
veoma bitni sa aspekta kvaliteta polarizacije PVDF uzoraka. U radu je prikazan
konkretno realizovan visokonaponski energetski AC/DC pretvarač 230 V, 50Hz/0-5
kVdc, maksimalne izlazne snage 50 W, koji u potpunosti ispunjava tehničke zahteve
polarizacije PVDF uzoraka
A Realisation of Synchronous Buck Power Converter for Energy Harvesting from Vibrations
Get PDFThe paper presents the implementation of a
synchronous “buck“ power converter that is used to energy
harvesting from vibrating structures that oscillate in the 1Hz-
1kHz range. This range is the most common in real cases. In
addition to the frequency, a very important parameter is also
the amplitude of the vibrations. Usually, low frequencies (<
10Hz) are associated with larger oscillatory masses and larger
oscillation amplitudes, while higher frequencies (1kHz >f >
100Hz) refer to larger oscillatory masses and smaller oscillation
amplitudes. The realized power converter is based on the
integrated circuit LT3588-1, in which it integrates a low-loss
full-wave bridge rectifier with a high efficiency synchronous
“buck” converter to form a complete energy harvesting
solution optimized for high output impedance of
mechanic/electric converter such as piezoelectric lead zirconate
titanate (PZT) ceramics or polymer based on polyvinylidene
fluoride (PVDF), or other composite. The paper presents
experimental results obtained on the vibration platform as
vibration source, in order to testing of the proposed power
converter in laboratory conditions
Cascade luminescence and antibacterial behavior of fluorapatite nanopowder co-doped with Pr3+, NO3− and CO32− ions
No full textIn this study, luminescence and antibacterial behavior of pure fluorapatite (FAp) and praseodymium-
nitrate-carbonate co-doped fluorapatite (PrNCFAp) nanopowders were investigated.
Uniform nanopowders were synthesized by precipitation reaction followed by
centrifugation and systematically characterized by XRD, FTIR, SEM–EDS, TG and PL
methods. XRD analysis revealed the formation of hexagonal FAp crystals, and FTIR spectra
indicate the presence of nitrate (
NO3
−) and carbonate (
CO3
2−) species. SEM analyzes
confirm agglomerates composed of irregular nanometer-sized spheres. Emission of FAp
nanopowder occurred in the violet-blue region of the visible part of the spectrum, with
redshift to the blue-green color region when Pr3+,
NO3
− and CO3
2− co-doped in the lattice.
Analysis of luminescence spectra by MCR-ALS method extract three fluorophores from
the PrNCFAp sample and showed simultaneous existents of emission-reabsorption-emission
between dopants in FAp lattice. Antibacterial activity against pathogen Staphylococcus
aureus was investigated before and after treatment of nanopowders by UVA radiation
of 365 nm. Nanopowders irradiated with UVA compared to non-irradiated reduced Staphylococcus
aureus by 84.9% for PrNCFAp and 33.3% for FAp in the first 0.5 h of contact, and
76.1% and 42.9% after 24 h of contact. In addition, the obtained luminescent nanomaterials
showed a low degree of hemolytic activity and could potentially be candidates for further
research in dentistry
Intestinal content analyses of pumpkinseed Lepomis gibbosus (Linnaeus, 1785) in five small reservoirs – central Serbia
Get PDFLepomis gibbosus (pumpkinseed) was first recorded as a non-native fish in Serbia in the
1930s in the Tisza River. The species currently inhabits almost the entire region of the Black
Sea basin in Serbia, but has no economic value. The current range of the pumpkinseed
covers more than 50% of the total Serbian area and is also naturalised in Serbian waters.
The pumpkinseed feeds on bottom fauna, small fish, fish roe and juvenile fish, which
together with competition for habitat and spawning sites can have a negative impact on
native species. The most common prey of younger specimens is zooplankton, while adult
specimens feed on larger organisms such as larvae and pupae of insects, molluscs or
crustaceans. The composition of the prey varies seasonally and depends on the
composition of the community. The main objective of the study was to analyse the
differences in the feeding habits of pumpkinseed in five reservoir.
Samples were collected from five reservoirs in central Serbia (<200 asl, Markovačko,
Topola, Vlaški Do, Jatagan, Kudreč) using standard electrofishing equipment. All sampled
reservoirs had mud substrate, except Jatagan Reservoir, which had gravel substrate. The
sampled fish were identified on site based on morphological characteristics using
identification keys. The sampled fish were measured using total body length and weight.
The total sample consisted of 354 pumpkinseed individuals whose body weight ranged
from 3.66–9.52 g and body length from 6.01–8.41 cm. The number of individuals with
intestinal content was 282, while the number of individuals with empty stomachs was 72.
The following macroinvertebrate taxa were identified during the examination of the gut
contents: aquatic insects (Chironomidae, Chironomidae-pupae, Diptera, Ceratopogonidae,
Trichoptera, Ephemeroptera, Odonata, Heteroptera, Coleoptera), Gammaridae, Mollusca,
Bivalvia, Gastropoda, Nematoda. Undetermined terrestrial insects were also recorded. Most
prey were found in the Kudreč Reservoir, and the greatest diversity was in the Topola
Reservoir. Jatagan Reservoir had the lowest number of prey items, which may be due to
the substrate type. The high number of aquatic insect taxa could be explained by the small
surface area of the reservoir and the presence of aquatic vegetation
Proučavanje populacija Xanthomonas campestris pv. campestris poreklom sa kupusa u Vojvodini
No full textBakterija Xanthomonas campestris pv. campestris (Xcc) je sveprisutna kao
prouzrokovač crne truleži biljaka iz familije kupusnjača, pre svega kupusa, a zatim i karfiola, brokolija, kelja, prokelja, kelerabe, raštana, ali i uljane repice, slačice, rotkvice, hrena, kres salate, određenih sorti model biljke Arabidopsis thaliana i nekih korovskih vrsta i ukrasnih biljaka. Negativnim uticajem na rast i razvoj domaćina, a time i veličinu i kvalitet prinosa, dovodi do značajnih ekonomskih gubitaka. Beležene štete izazvane ovim patogenom procenjuju se na više od 50% na kupusu, odnosno 50 – 70% na karfiolu. U Srbiji se Xcc nakon
prve pojave na kelju 1960-ih, redovno javlja na svim gajenim kupusnjačama. S obzirom na obim i tradiciju gajenja različitih kupusnjača, ova bakterija je najznačajniji patogen kupusa. Dosadašnje genetičke analize prisutnih populacija Xcc poreklom sa kupusa u Srbiji nisu ukazale na postojanje diverziteta, bez obzira na sortu, godinu ili lokalitet sa kog su izolovane. Cilj ovog rada je da se izoluju i genetički okarakterišu novije populacije bakterije Xcc poreklom
sa kupusa. Tokom avgusta i septembra 2021. godine, listovi kupusa sa simptomima crne truleži, sakupljeni su sa četiri parcele u Vojvodini, dve u lokalitetu Futog (sorta Futoški obe parcele) i dve u Begeču [sorta Futoški i crveni kupus (nepoznata sorta)]. Izolacija prouzrokovača bolesti vršena je na podlogu od kvaščevog ekstrakta, dekstroze i kalcijum karbonata (engl. Yeast extract dextrose-calcium carbonate agar, YDC). Nakon tri dana inkubacije na 26 °C, formirane su svetlo žute, sjajne, konveksne i mukoidne bakterijske kolonije. Četiri reprezentativna izolata (sa svake parcele po jedan, pod šiframa Xc221, Xc321, Xc421, Xc521, redom) su odabrana i analizirana na osnovu sekvenci konzervativnog gena gyrB. Patogenost odabranih izolata je dokazana infiltracijom bakterijske suspenzije u listove kupusa. Lančana reakcija polimeraze (PCR) je korišćena za umnožavanje DNK izolata, očekivane dužine 865 bp, po sledećem programu: inicijalna denaturacija 94 °C 3 min, 30 cikusa denaturacije 94 °C 30 sec, hibridizacije 54 °C 30 sec i elongacije 72 °C 1 min, i finalna elongacija 72 °C 10 min. Amplifikovani produkti su sekvencirani (Eurofins Genomics), a kvalitet dobijenih sekvenci manuelno pregledan. Filogenetsko „Neighbour-joining” stablo je konstruisano primenom MEGA7 programa, sa izolatima iz ove studije i sojevima populacija izolovanih sa kupusa tokom prethodnih godina na području Srbije. Dobijeni rezultati su pokazali genetičku homogenost novijih populacija Xcc sa prethodno opisanim i prisutnim u Srbiji, bez obzira na godinu izolacije, lokalitet ili sortu. Prema dostupnim podacima, dobijeni rezultati ukazuju na održavanje iste populacije ove bakterije tokom poslednje decenije
Fish Migratory behaviour In proximity to the Iron Gate Dams
Get PDFRiver infrastructures, such as hydropower plants Iron Gate I (IG; rkm 943) and II (rkm 863) represent major obstructions to fish migration in the Danube River. Knowledge about fish behaviour and movements in the vicinity of major river structures is required to build effective fish passages to protect migratory fish species, with acoustic telemetry being an useful method for observing such behaviour. From autumn 2019 to the spring 2021, the movement of 185 fish (barbel Barbus barbus, nase Chondrostoma nasus, vimba bream Vimba vimba, asp Leuciscus aspius, Pontic shad Alosa immaculata, and carp Cyprinus carpio) were monitored in the Danube River upstream and downstream of the IG II dam using acoustic telemetry. The movements of tagged fish were recorded by a combination of automatic tracking of fish passing receivers deployed in the river and manual tracking by boat. Of the 101 fish released downstream of IG II, 48% moved upstream from their release site and were detected close to IG II. The remaining 84 tagged fish were released in the reservoir between IG I and II, with 49% of fish moving further upstream in the reservoir and 18% reaching IG I, while 48% of the tagged fish moved in a downstream direction and were recorded below IG II. No fish released downstream of IG II were detected in the reservoir between two dams, which indicates that the ship locks on either side of the river do not represent viable routes for upstream migration around IG II. There was also no clear pattern in which side of the river tagged fish preferred to move along. To conserve migratory fish species, dam management strategies that take into account the behaviour of fish around such structures is necessary. Acoustic telemetry can be used to inform and guide towards construction of the safe fish passage or adapt structures to improve the movement and fish migration