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Fluorescence characterisation of bisphenol A in various solvents and drinking water
Get PDFEnvironmental safety may be compromised by the presence of hazardous chemical compounds, such as bisphenol A (BPA), which is commonly used in the production of certain types of plastics. BPA is an emerging organic contaminant that could be found in many matrices, such as drinking water, due to anthropogenic activities. Within this study, we used fluorescence spectroscopy to analyse the photoluminescent characteristics of BPA in various solutions and drinking water. The emission spectra of BPA in various solvents are recorded from 280 nm to 380 nm, after excitation wavelength at 230 nm. These results imply that the fluorescence approach can be used for rapid detection and estimation of the level of BPA in water samples and, hence, for non-invasive monitoring of BPA in drinking water is an important concern for public health and environmental protection
Variability of morpho - anatomical features of needles of Pinus nigra (black pine) in the area of Jastrebac and Goč mountains in central Serbia
Get PDFIn this paper the variability of morphological (needle length and needle width) and anatomical (resin ducts width, epidermis thickness, hypodermis height, number of the hypodermis layers and needle thickness) properties of Pinus nigra J.F. Arnold (black pine) needles were studied at the intra- and inter-population levels. Two mountains in Serbia, Jastrebac and Goč, were selected as experimental plots. Three Pinus nigra trees were selected from both localities (6 in total). Obtained results showed that trees on Goč had bigger dimensions of the following elements: needle length, slightly wider needle width, epidermis thickness, hypodermis height, number of hypodermis layers and needle thickness. On the other hand, resin ducts were only slightly wider by the trees from Jastrebac. The results of the analysis of variance showed that variation between studied populations, as well as variation between trees within populations was statistically significant for all needle traits except resin ducts width and hypodermis height
Dobijanje provodne elektrokeramike na bazi barijum-stanata dopiranog antimonom sa linearnom strujno-naponskom karakteristikom
Get PDFU okviru ove disertacije ispitivani su uticaji koncentracije dopanta i parametara sinterovanja na strukturu i svojstva keramičkih uzoraka barijum-stanata dopiranog antimonom, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 i 0,10) u cilju dobijanja provodne elektrokeramike sa linearnom strujno-naponskom (I-U) karakteristikom. Smeša prahova BaCO3, SnO2 i Sb2O3 mehanički je aktivirana u izopropanolu, kalcinisana na 900 °C i potom sinterovana koristeći tri različite metode: konvencionalno, spark plazma i hladno sinterovanje. Konvencionalno sinterovanje prahova vršeno je na 1200, 1400 i 1600 °C, ali se na nižim temperaturama dobija keramički materijal niskih relativnih gustina. Sinterovanjem na 1600 °C dobijeni su jednofazni uzorci kubne strukture BaSnO3 (BSO). Rezultati skenirajuće elektronske mikroskopije (engl. Scanning Electron Microscopy, SEM) ukazuju na značajno smanjenje veličine zrna nakon dopiranja, ali i na poroznost koja ometa električnu karakterizaciju uzoraka. Transmisiona elektronska mikroskopija visoke rezolucije (engl. High Resolution Transmission Electron Microscopy, HRTEM) ukazuje na prisustvo niskougaonih granica zrna u uzorku BaSn0,92Sb0,08O3. Pouzdana električna merenja izvršena na ovom uzorku ukazuju na njegova poluprovodnička svojstva karakteristična za materijale sa dvostrukom Šotkijevom barijerom (engl. Schottky barrier) na granici zrna. Spark plazma sinterovanje (SPS) vršeno je na temperaturama od 1000, 1100, 1200 i 1250 °C, za vreme od 5, 10, 15 i 30 min, pri pritisku od 60 MPa i sa brzinom zagrevanja od 100 °C min–1. Za dobijanje guste keramike optimalni uslovi sinterovanja su 1100 i 1200 °C, tokom 5 min. Sinterovanjem na 1100 °C dobijeni su jednofazni keramički uzorci kubne strukture BSO. Dopiranje antimonom dovodi do smanjenja veličine zrna, ali i do smanjenja specifične otpornosti u odnosu na nedopirani uzorak. Električna karakterizacija ukazuje na poluprovodnička svojstva svih keramičkih uzoraka, sa najnižom specifičnom otpornošću zabeleženom na uzorku BaSn0,92Sb0,08O3. SPS na 1200 °C dobijaju se keramički uzorci koji osim kubne faze BSO, sadrže i sekundarnu fazu Ba2SnO4, čija se količina u uzorku smanjuje dopiranjem. Na ovoj temperaturi pri visokom pritisku dolazi do reakcije SnO2 iz kalcinisanog praha sa grafitom iz kalupa pri čemu se izdvaja elementarni kalaj i stvaraju uslovi za formiranje sekundarne faze bogate barijumom. Rezultati skenirajuće elektronske mikroskopije emisijom elektrona poljem (engl. Field Emission Scanning Electron Microscopy, FE-SEM) ovih uzoraka potvrđuju da dopiranjem dolazi do smanjenja veličine zrna, ali i smanjenja koncentracije
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dislokacija u keramičkim uzorcima. Svi uzorci osim BaSn0,92Sb0,08O3 ispoljavaju nelinearnu strujno-naponsku karakteristiku, tipičnu za poluprovodnike sa potencijalnom barijerom na granici zrna. Veliki udeo niskougaonih granica u uzorku BaSn0,92Sb0,08O3 dovodi do gubitka potencijalne barijere na granici zrna, što je potvrđeno i impedansnom spektroskopijom, pa ovaj uzorak pokazuje najnižu vrednost specifične otpornosti, konstantnu u temperaturnom opsegu 25–150 °C i linearnu strujno-naponsku karakteristiku. Za razliku od prethodne metode, hladno sinterovanje uzorka BaSn0,92Sb0,08O3 nije dalo zadovoljavajuće rezultate po pitanju faznog sastava, gustine i električnih svojstava. Redukcioni uslovi tipični za spark plazma sinterovanje, uz koncentraciju dopanta od 8 % (mol.) Sb u uzorku BaSnO3 doveli su do formiranja niskougaonih granica zrna, povećanja koncentracije vakancija kiseonika i promene valence Sn, što je dovelo do porasta koncentracije nosilaca naelektrisanja (elektrona) i posledično rezultovalo dobijanjem uzorka sa linearnom I-U karakteristikom i konstantnom vrednosti specifične otpornosti u širem temperaturnom opsegu.The main goal of this doctoral thesis was to investigate the influence of different dopant concentrations and sintering parameters on the structure and properties of antimony-doped barium stannate, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 and 0,10) to obtain conductive electroceramic samples with linear current-voltage (I-U) characteristics. A mixture of BaCO3, SnO2 and Sb2O3 powders was mechanically activated in isopropanol, calcined at 900 °C and then sintered using three different methods: conventional, spark plasma and cold sintering. Conventional sintering at 1200 and 1400 °C resulted in the preparation of low-density ceramic samples. By sintering at 1600 °C, single-phase material with a cubic BaSnO3 (BSO) structure was obtained. The scanning electron microscopy results (SEM) indicate a significant decrease in grain size upon doping but also reveal porosity, which hinders the electrical characterization of the samples. High resolution transmission electron microscopy (HRTEM) indicates the presence of low-angle grain boundaries (LAGBs) in the BaSn0.92Sb0.08O3 sample. Reliable electrical measurements performed on this sample indicate its semiconducting properties characteristic of materials with a double Schottky barrier at the grain boundary. Spark plasma sintering (SPS) was performed at temperatures 1000, 1100, 1200 and 1250 °C, for 5, 10, 15 and 30 min, at a pressure of 60 MPa and with a heating rate of 100 °C min–1. The most optimal conditions for the preparation of dense ceramic materials, in terms of temperatures and sintering time, were 1100 and 1200 °C for 5 min. By sintering at 1100 °C, single-phase ceramic samples with a cubic BSO structure were obtained. In comparison to the undoped sample, doping with Sb leads to a decrease in both grain size and electrical resisitivity. Electrical characterization shows semiconducting properties of all ceramic materials, with the lowest resistivity recorded for the BaSn0.92Sb0.08O3 sample. Apart from the cubic BSO, the spark plasma sintered samples at 1200 °C contained Ba2SnO4 as a secondary phase, whose content decreases upon doping. High sintering temperature and applied pressure created conditions for the reaction of SnO2 from the calcined powder with graphite from the mould, resulting in the evaporation of metallic tin and the formation of the barium-rich secondary phase. The field emission scanning electron microscopy (FE-SEM) results confirm that doping leads to a decrease in grain size and the concentration of dislocations in these ceramic samples. All samples except BaSn0.92Sb0.08O3 exhibit nonlinear current-voltage characteristics, typical for semiconductors with a
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potential barrier at the grain boundary. As a consequence of higher amount of LAGBs present in it, the ceramic BaSn0.92Sb0.08O3, showed linear I-U characteristics in the whole temperature measurement range (25–150 °C) and a significant drop in the electrical resistivity due to the loss of potential barrier at grain boundary. The impedance spectroscopy confirmed these assumptions. Unlike the previous method, cold sintering of the BaSn0.92Sb0.08O3 sample did not give satisfactory results either in phase composition and density or electrical properties. The reducing conditions typical for spark plasma sintering and the dopant concentration of 8 % (mol) Sb in the BaSnO3 sample led to the formation of LAGBs, an increase in the concentration of oxygen vacancies and a change in the valence state of Sn, consequently leading to increase in the charge carriers (electrons) concentration and resulting in the ceramic sample with a linear I-U characteristic and a constant value of electric resistivity in a wide temperature range
Differential Abundance Analysis of "Core" Bacteriobiota During Key Growth Stages of Maize
No full textNumerous microbial taxa are used as biofertilizers because they have the potential to competitively colonize the rhizosphere or root interior of plants and promote nutrient uptake. The aim was to investigate the shifts of keystone bacterial species in maize roots and rhizosphere during seedling stage, flowering, and harvest, under different treatments of bacterial phytobiotic (PHY), poultry
manure (PM) and their combination (PHY_PM). Soil bacterial communities remained largely unchanged regardless of the treatment applied or phenophase studied, with uncultured Gaiellales and Bacillus being the most abundant. In contrast, bacterial communities in roots differed in terms of distribution and relative abundance (RA) of different taxa between growth stages and treatments. The most abundant bacterial taxa in the roots during the initial seedling stage was
Pseudomonas. In the flowering, Bacillus occurred with a two- to threefold higher RA in treatments with PHY or PM compared to the negative control, while Lechevalieria dominated during the harvest. Differential abundance analysis at the seedling stage showed a reduction of Pseudomonas in roots treated with PHY, while Pseudonocardia was significantly more abundant in roots treated with PM than in the other samples. Massilia, Streptomyces, Lechevalieria, Microbacteriaceae, Aeromicrobium, Sphingomonas and Roseiflexaceae were significantly higher in the PHY_PM treated root samples. Steroidobacter and Bdellovibrio were absent in PHY and PM treated root samples during flowering, while Bdellovibrio was significantly reduced in PHY_PM treatment compared to the negative control. RA of Bradyrhizobium and Polaromonas was reduced in PHY treated root samples, and Dongia was completely absent. Gaiellales was significantly more abundant, while Sphingomonas was less abundant in roots treated with PM and PHY_PM. Solirubrobacter and Bdellovibrio were absent from roots during harvest in all three treatment types. Pajaroellobacter was completely absent in PHY and PM treatments, while Steroidobacteraceae were present only in PHY and Cyclobacteriaceae in PM. Mucilaginibacter calamicampi showed
significantly higher RA in PHY_PM treatment, while Sphingomonas was reduced. Considering the non-disruptive effect of PHY on the "core" bacteriobiota and the positive effects on the presence of beneficial bacterial genera, such products could be proposed as a promising alternative to chemicals and organic fertilizers in maize cultivation
Nova formulacija ulja karanfilića (Syzygium aromaticum L.) u kontroli brojnosti krompirovog moljca (Phthorimaea operculella)
No full textU okviru ove studije, prvi je put u svetu uspešno sintetizovana nova stabilna i homogena EC formulacije ulja karanfilića (S. aromaticum) zasnovana na biopolimerima kao što je zeolit. Nova formulacija ulja karanfilića (F-CSZ) prema fizičkim svojstvima ispunjava kriterijume za EC formulaciju u obliku kojem je sintetizovana. Novoformulisano, inkapsulirano ulje karanfilića obezbeđuje ekološki prihvatljivu zamenu sintetičkim pesticidima u kontroli štetočina na osnovu ispoljavanja visoke biološke efikasnosti u kontroli brojnosti imaga krompirovog moljca ali i bezbeđivanjem produžene efikasnosti ulja do 14 dana u odnosu na čisto etarsko ulje karanfilića koje je izgubilo insekticidnu aktivnost nakon 24 h od tretmana. Nova formulacija ulja karanfilića (F-CSZ) je ispoljila visoku efikasnost u suzbijanju imaga krompirovog moljca, a da pri tome nije uticala na kvalitet krompira te se može komercijalno koristiti kao fumigant ili zaštitni premaz za suzbijanje štetočina u skladištu, a samim tim i za smanjenje gubitaka tokom skladištenja i čuvanja proizvoda
Correlation between the microstructure and electrical properties of Sb-doped BaSnO3 ceramics
Get PDFThe non-magnetic, non-inductive electroconductive materials with linear current-voltage characteristic and low and almost constant electrical resistivity in the wide temperature range could be used in conditions unfavorable for metals and alloys. Particular emphasis is placed on the performance and endurance of these materials in conditions at constant high voltage, current, and energy, as well as operating in acidic and humid environmental conditions.
The aim of this work was to investigate the influence of antimony concentration and sintering parameters on the structure, microstructure, and electrical properties of antimony-doped barium stannate, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 and 0,10) to obtain conductive electroceramic samples with linear current-voltage (I- U) characteristics and low electrical resistivity. For this purpose three different sintering techniques were used: conventional, spark plasma and cold sintering.
According to the X-ray diffraction (XRD) analysis, single-phase ceramic mater- ials with cubic BaSnO3 structure were obtained by conventional sintering at 1600 °C for 3 h and spark plasma sintering at 1100 °C for 5 min. Raising the spark plasma sintering temperature to 1200 °C induced the formation of Ba-rich secondary phase, Ba2SnO4. XRD analysis confirmed the presence of unreacted SnO2 and BaCO3 in cold sintered BaSn0.92Sb0.08O3 sample (310 °C for 5 min, 20 wt.% 1 M acetic acid). Scanning electron microscopy (SEM) indicates a significant decrease in grain size upon doping, regardless of the sintering technique. High-resolution transmission electron microscopy (HRTEM) revealed the presence of low angle grain boundaries (LAGBs) in conventionally and spark plasma sintered (1200 °C for 5 min) samples with x = 0.08. The results of electrical measurements confirmed the semiconducting properties of all BSSO, except the spark plasma sintered BaSn0.92Sb0.08O3 (1200 °C for 5 min) sample. This sample showed linear current-voltage characteristic, the lowest and almost constant electrical resistivity in the temperature range of 25–150
°C resulting from the loss of potential barriers at grain boundaries due to the large fraction of LAGBs present in BaSn0.92Sb0.08O3 ceramic sample
BaTiO3/NixZn1−xFe2O4 (x = 0, 0.5, 1) Composites Synthesized by Thermal Decomposition: Magnetic, Dielectric and Ferroelectric Properties
Get PDFTo investigate the influence of spinel structure and sintering temperature on the functional properties of BaTiO3/NixZn1−xFe2O4 (x = 0, 0.5, 1), NiFe2O4, ZnFe2O4, and Ni0.5Zn0.5Fe2O4 were in situ prepared by thermal decomposition onto BaTiO3 surface from acetylacetonate precursors. As-prepared powders were additionally sintered at 1150 °C and 1300 °C. X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS) were used for the detailed examination of phase composition and morphology. The magnetic, dielectric, and ferroelectric properties were investigated. The optimal phase composition in the BaTiO3/NiFe2O4 composite, sintered at 1150 °C, resulted in a wide frequency range stability. Additionally, particular phase composition indicates favorable properties such as low conductivity and ideal-like hysteresis loop behavior. The favorable properties of BaTiO3/NiFe2O4 make this particular composite an ideal material choice for further studies on applications of multi-ferroic devices
Characterization of Xanthomonas arboricola pv. pruni from Prunus spp. orchards in Western Balkans
No full textThe present study provides a new insight into the existing Xanthomonas arboricola pv. pruni (Xap) bacterial population originating from peach and apricot in two Western Balkans countries (Serbia and Montenegro). Multilocus sequence typing and analysis of the sequences of nine housekeeping genes revealed homology between the tested Xap strains as well as with the European population of this bacterium. The tested strains share the same haplotype (Haplotype I) with the Xap strains from Italy, France, Spain, United States, Australia and Brazil. The revealed single nucleotide change (G ↔ C) in the sequences of the gyrB1 gene differentiates Haplotype I from Haplotype II (Xap from South Korea, New Zealand, Argentina and Uruguay). The detached-leaf bioassay results confirmed differences in virulence between strains originating from peach and apricot towards Prunus armeniaca (apricot), indicating host specialization of the apricot strain towards this host. For the first time, immunity of P. fruticosa (European ground cherry) to Xap was established. According to the AUDPC, PCA and cluster analysis, other Prunus spp. were classified as having low susceptibility (P. mahaleb, P. cerasus and P. avium), as susceptible (P. domestica) and as highly susceptible (P. persica, P. dulcis, P. cerasifera and P. spinosa). Xap strains were also found to be susceptible to 10 tested antibiotics. This study provides valuable knowledge on the Xap population from stone fruit grown in the Western Balkans region as well as the source of immunity, which could serve as a starting point for breeding Prunus cultivars and could be used as the main control strategy
Biological control of major pathogenic bacteria of potato by Bacillus amyloliquefaciens strains SS-12.6 and SS-38.4
Get PDFPotato is ranked as one of the most important food crops. Bacterial wilt caused by Ralstonia solanacearum and blackleg and soft rot caused by different species from genera Pectobacterium and Dickeya are considered two of the most important diseases of the potato. Biological control is the optimal strategy for controlling pathogens in crops generally, including bacteria. The present study aimed to evaluate the antagonistic effects of two Bacillus amyloliquefaciens strains, SS-12.6 and SS-38.4, against bacterial pathogens isolated from the potato in Serbia, such as R. solanacearum, Pectobacterium carotovorum, Pectobacterium brasiliense, and Dickeya dianthicola. The diameter of the inhibition zones formed by ethyl-acetate extracts of SS-12.6 and SS-38.4 strains show much higher values than the inhibition zones of supernatants, which implies the main power of these antagonists’ potential lies in lipopeptides. The effectiveness of the treatment (19.7–44.5%), based on the difference in weight of potato tubers on the fifth and 15th day after treatment (DAT), showed that the antagonistic strains were almost equally effective in the suppression of P. carotovorum, P. brasiliense, and D. dianthicola strains. Strains SS-12.6 and SS-38.4 exhibited the efficacy in the suppression of R. solanacearum wilt from 28.64 to 60.22%. The analysis of the area under the disease progress (AUDPC) confirmed differences among pathogen control treatments and biocontrol treatments with B. amyloliquefaciens strains in all trials. This study shows that the two B. amyloliquefaciens strains, SS-12.6 and SS-38.4, can potentially be used as biocontrol agents against potato pathogens
SYNTHESIS AND CHARACTERIZATION OF PURE AND Sm-, Zr-DOPED TiO2 NANOFIBERS AND ITS PHOTOCATALYTIC ACTIVITY
Get PDFPure, samarium (Sm3+) and zirconium (Zr4+) doped titanium dioxide (TiO2)
nanofibers were synthesized using the electrospinning method followed by
calcination at 500 °C for 1 h. The structure, morphology and optical properties of the
obtained nanofibers were investigated as a function of different Sm3+ and Zr4+
contents (0.5–5 mol%). XRD and FTIR analysis showed that addition of Sm or Zr
suppressed the transformation of anatase to rutile. After calcination all fibers were
smooth, fragile and randomly oriented. HRTEM analysis revealed that doping with
Sm didn’t affect the TiO2 crystal lattice whilst Zr4+ ions replaced the substitutional
sites in the anatase crystalline lattice. The effects of Sm3+ and Zr4+-dopant content
and different doses of photocatalyst on the photodegradation of methylene blue
(MB) were monitored under UV-light illumination. TiO2:0.5%Sm3+ and
TiO2:1.0%Zr4+ nanofibers have shown the highest photocatalytic activity of 97%
and 98% due to red shifting of the band gap towards visible light in the case of Sm
and suppressed electron-hole recombination shown in recorded PL spectra in the
case of Zr