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The role of leached iron from BiFeO3 photocatalyst for water treatment
No full textBismuth ferrite (BiFeO3) powder was synthesized by the auto-combustion method and tested as a photocatalyst for the degradation of methylene blue in water solutions. Structural studies showed good formation of the perovskite BiFeO3 phase with high crystallinity and almost no organic residues as confirmed by thermal analysis. The powder was formed of nanoparticles of several hundred nanometers in diameter agglomerated in bigger, porous particles of several micrometers, as observed by scanning electron microscopy (SEM). Point-of-zero charge of the powder was determined to be at pH 6.5, while the optical band gap of the synthesized BiFeO3 was 2.18 eV, calculated using diffuse reflectance spectroscopy results. Up to 70% of methylene blue was decolorized after four hours of exposure to light in the presence of BiFeO3 as a photocatalyst, with a higher decolorization rate under the visible light than under the mixture of visible and ultraviolet light. The presence of hydrogen peroxide noticeably helped the degradation of methylene blue in acidic conditions through Fenton-like processes, enabling total decolorization in 3 hours. Mechanism study implied the hydroxyl radicals were the main oxidative active species, and the reusability test confirmed good stability after several repetitions. Leached iron plays an important role in photocatalytic properties through homogeneous photocatalysis, showing a significant decolorization rate even at a concentration as low as 10−5 mol/dm3 and contributing to the photocatalytic processes in acidic conditions
The Water Vapor Sensing Ability of Rare-Earth-Doped Barium Cerate
No full textThe ability to conduct protons at high temperatures makes acceptor-doped perovskites suitable for humidity sensors in a high-temperature environment. In this study, the rare-earth-doped barium cerate powders were synthesized by the auto-combustion method and processed into thick porous films (60–70 % porosity) to investigate the water vapor sensing properties in the 400–700 °C temperature range. All samples showed a stable sensitivity to water vapor in the whole temperature range, expressed as impedance ratio in dry and wet argon (ǀZǀdryAr / ǀZǀwetAr), and were able to detect 0.03 vol% of water vapor at 550 °C within the impedance range of 103 Ω at 100 Hz. The sensitivity values increased with the partial pressure of water and decreased with the temperature, whereas the maximal value of 3.41 reached the BCEu10 sample at 550 °C and p(H2O) = 4.28 kPa
PIEZOELECTRIC NANO-BIOCOMPOSITES BASED ON CHITOSAN, GLYCINE, AND ZINC OXIDE NANOPARTICLES
No full textPressure sensors based on materials converting mechanical stress into electrical signals are widely used in fields ranging from industrial automation to medical diagnostics and wearable electronics. These materials offer a unique combination of self-powered operation, high sensitivity, rapid response, mechanical flexibility, and long-term durability. However, rising consumer expectations for sustainability, coupled with stricter environmental regulations, have driven growing demand for economical, biodegradable, and environmentally friendly alternatives. Biopolymers offer a promising solution, combining eco-friendliness, non-toxicity, biodegradability, and biocompatibility. Still, they often suffer from limited piezoelectric and mechanical performance, which presents a key challenge for their broader application in pressure sensing devices.
From this perspective, this study focuses on the development and investigation of novel, natural biopolymer composites based on chitosan (Ch), zinc oxide nanoparticles (ZnO), and glycine (Gly). To fabricate thin-film sensors, solutions with varying weight ratios of Ch, ZnO, and Gly were cast into glass Petri dishes and dried. The resulting films were characterized using optical imaging, atomic force microscopy (AFM), and X-ray diffraction (XRD) to assess their morphology and phase composition. Square samples were then cut from the films, equipped with copper electrodes, connected via wires, and encapsulated in Kapton. The electrical output of the films was measured using a custom-built laboratory setup under mechanical stress applied by finger taps. To ensure more consistent pressure distribution, additional tests were conducted using a Quartz Impulse Hammer (KISTLER, Italy) with a 2 cm rubber tip.
The results indicate that modifying chitosan with zinc oxide nanoparticles enhances its piezoelectric performance, highlighting the potential of the developed composite for use in pressure sensing technologies
A Data-Driven Outlook on the Characterization of Ferritic Steels in the Ductile-Brittle Transition Region
No full textSince the 1980s, there has been sustained interest in the size effect, recognized as one of important outcomes of fracture mechanics. In this article, the size effect is investigated through the estimation of the Weibull cumulative distribution function (CDF) for the fracture toughness KJc defined as an elasticplastic equivalent stress intensity factor derived from the J-integral at the point of onset of cleavage fracture, Jc. This fracture toughness of ferritic steels within the ductile-brittle (DBT) transition temperature region is a stochastic extrinsic property characterized by significant experimental variability, making a statistical approach essential for accurate DBT characterization. This inherent variability and irreducible uncertainty in the fracture properties of ferritic steels align with weakest-link theory, which attributes scatter in strength and fracture toughness to flaws, inhomogeneities, or other local imperfections within the material texture. According to this theory, even a small number of defects—especially near the tip of a pre-existing macrocrack or notch—can trigger localized microseparation events that may evolve into macro-fracture, particularly when dislocation activity is suppressed due to low temperature. Weibull statistics traditionally provides a framework for estimating the likelihood of encountering such defects and assessing their impact on the overall probability of cleavage fracture. Recently, the two-step-scaling (2SS) method was introduced to model size effects throughout the DBT temperature region. This method is based on weakest-link theory and Weibull distribution, incorporating the size dependence of both the scale and shape Weibull parameters within an appropriate framework. In this article, the 2SS method is examined from a practical standpoint to demonstrate its application in engineering contexts. The 2SS approach is evaluated using the EURO fracture toughness dataset, with the results underscoring its broad applicability and versatility
Potential of indigenous biological agents for the control of grapevine trunk diseases in montenegrin viticulture
No full textGrapevine trunk diseases (GTDs) are a group of diseases caused by a large number of fungal
phytopathogens that infect and colonize the woody tissue of grapevine, causing chronic or
apoplectic decline of plants, and as such posing a serious threat to viticulture. Among the
most virulent pathogens are Neofusicoccum parvum, the causal agent of Botryosphaeria
dieback, and Fomitiporia mediterranea considered as the main causal agent of grapevine rot
within the Esca disease complex. This study aimed to isolate and select potent indigenous
bacteria collected from Montenegrin vineyards to serve in the control of GTDs. Isolations
were performed from soil samples taken in a zone of grapevine root (Montenegro) on NA
after soil was dissolved in water and heating at 80°C for 20 min. A total of 262 isolates were
tested for antagonistic activity in a direct in vitro test on PDA. The appearance of a clear zone
was checked after fungi development. Results showed that 32 Montenegrin isolates inhibited
the growth of N. parvum by 34.0-65.0%, and F. mediterranea by 34.8-71.0%. Neighbourjoining
phylogenetic analysis based on the 16S rRNA (primers P0/P6) sequences differentiated
those isolates into six clusters but lacked the resolution to differentiate between several
species. Six groups were as follows: I (21 isolates: Bacillus amyloliquefaciens/B. velezensis/B.
siamensis/B. subtilis), II (2: B. subtilis/B. velezensis/B. tequilensis), III (5: B. halotolerans/B.
mojavensis/B. subtilis/B. velezensis/B. tequilensis/B. spizizenii), IV (1: B. licheniformis/B.
paralicheniformis), V (2: B. cereus/B. thuringiensis/B. albus/B. anthracis), VI (1: Paenibacillus
peoriae/P. polymyxa). Sequencing of housekeeping genes would provide more accurate
identification.ISBN број није доступан
Computational modeling of CO2 adsorption on orange carbon dots to enhance the photosynthesis capacity in plants
No full textPlants’ photosynthetic capacity is not sufficiently exploited. Due to their high light-harvesting capability, orange carbon dots (o-CDs) can improve photosynthesis without showing toxic effects on plants, which opens the way for their applications in agriculture. Our aim is to investigate if o-CDs may act as a CO2 carrier, thus importing a higher amount of CO2 for photosynthesis and increasing the plant productivity. To study the action mechanism of o-CDs in plants, computational simulations and modeling of o-CD-CO2 interaction were performed. Classical annealing and molecular dynamics (MD) simulations were used to find the best geometries for CO2 adsorption on o-CD. According to previously reported characteristics, computational model of o-CDs was built with a similar atomic composition (89.5% of carbon, 8.9% of oxygen, and 1.5% of nitrogen atoms) and size (average diameter of 1.7 nm). Three different modes of CO2 adsorption on the surface of o-CD were evaluated: (1) parallel deposition on top of the aromatic ring, which provides the weakest interaction, (2) side-on approximation to the negatively charged oxygen atom of the phenolate group, and (3) side-on approximation to the lone pair of the amine nitrogen atom. The bicarbonate ion is highly soluble in water and coexists in equilibrium with CO2. MD simulations and quantum mechanics calculations revealed that in water, o-CD has more affinity for CO2 molecules than bicarbonate ions, due to the charge repulsion between the net negative charges present on their surfaces. The results show that o-CD binds CO2 preferably in this form (the form of CO2 present in C3 plants) and not in the form of bicarbonate (the form of CO2 present in C4 plants). This information may be useful for the enhancement of crop yield. Therefore, computational simulations confirmed that o-CDs are capable of enhancing photosynthetic efficiency, acting as a “CO2 delivery” system
IMPROVING MAIZE AGRONOMIC POTENTIAL: THE IMPACT OF Ag-N@MOF ON GERMINATION AND PHYSIOLOGICAL TRAITS
No full textMetal-Organic Frameworks (MOFs) have emerged as promising materials in modern agriculture, particularly due to their high porosity, large surface area, and chemical versatility. The aim of this work was to study the influence of different concentrations (1, 5 and 10 mg L-1) of silver-based metal-organic framework MOF (Ag-N@MOF) on maize (Zea mays L.) seeds germination for 4 days. Afterward, the seedlings were grown on KNOP/2 hydroponic solution under controlled conditions (16h light/ 8h dark photoperiod) for 7 days. The physiological and morphological parameters of root and shoot length, and dry/fresh weight ratio (DW/FW) were determined. Also, the parameters of chlorophyll (Chl), flavonoids (Flav), and nitrogen balance index (NBI) in the leaves at the same stem-positions of non-treated (control) and treated plants were determined using Dualex. The germination rate exceeded 90% following treatment with 5 and 10 mg L-1 of Ag-N@MOF, whereas the control samples achieved only about 60%. Our results that the highest chlorophyl and flavonoid contents were recorded with MOF concentration of 5 mg L-1 and 1 mg L-1, respectively. NBI reached its highest value (~90) at mg L-1 MOF, suggesing improved nitrogen status in plants. Additionally, the results indicate that the studied types of MOFs affect the morphology and physiological parameters of the maize. Considering the potential of Ag-N@MOF as agricultural additives to enhance maize agronomic potential, this research could significantly improve agricultural practices and increase crop yields for sustainable food production
Investigation of doped lanthanum manganite thin films
No full textLanthanum manganite, LaMnO? (LMO) with its perovskite structure has
been extensively studied due to its unique electric and magnetic
properties, which enable various applications. The LMO structure
allows substitutions at different ion sites, enhancing its functional
properties. Particularly, doping at the La site with lower-valence cations
(e.g., Na+, Sr²? and Ca²?) introduces heterovalent manganese ions
(Mn³? and Mn??) to maintain charge neutrality. This results in the socalled
double exchange mechanism—an electric charge transfer
between Mn³? and Mn?? mediated by oxygen ions—which gives rise to
ferromagnetism, metallic conductivity, and colossal magnetoresistance.
On the other hand, doping at the Mn sites with different
transition metals (e.g. Co, Ni, Fe) enables the magnetic and electrical
properties fine-tuning. These characteristics make doped lanthanum
manganites suitable for various applications such as magnetic sensors
and actuators.
In this study, La0.6Sr0.25Na0.05Gd0.1MnO? and
La0.6Sr0.25Na0.05Gd0.1Mn0.9Co0.1O? thin films were prepared starting from
acetates and by the deposition on the Si and Si/Pt substrates. The
structure and morphology of the thin films were evaluated using X-ray
diffraction (XRD) and scanning electron microscopy (SEM). The
influence of used dopants on the functional properties of thin films was
analyzed through the four probe sheet resistivity and magnetic
measurements
Between-year nest re-occupation by the european bee-eater (Merops apiaster)
No full textThe European bee-eater (Merops apiaster) is a cavity-nesting bird that digs its nests,
usually in loess, clay, or sand cliffs, forming colonies that range from a few to several hundred
breeding pairs. Due to the lack of nest sanitation, previous research suggested that bee-eaters
obligatorily construct new breeding burrows each year. However, while bee-eaters are capable
of excavating new nests annually, they may also reuse old burrows – a nesting behavior that
has only recently been thoroughly documented. In this study, we investigated nest reoccupation
by bee-eaters in a mixed colony of bee-eaters, common starlings (Sturnus vulgaris),
and common swifts (Apus apus) in Višnjička Kosa (44.8°N, 20.6°E), Belgrade, Serbia.
The study was conducted during the 2023 and 2024 breeding seasons in a colony situated within
a 550-meter-long loess bank, created by previous clay excavation. To identify active nest holes,
we recorded the colony using high-definition digital camcorders and examined selected nests
with an endoscope camera. The recorded footage was reviewed multiple times on a computer
screen to ensure data accuracy. Of the 138 burrows examined in 2024, 66 (48%) had been used
in a previous breeding year, demonstrating a high level of nest re-occupation. Our results align
with recent research from another colony, which showed that over 50% of nests can be reused
by bee-eaters between breeding seasons. These findings suggest that nest reuse may be the rule
rather than the exception in bee-eaters, as using existing burrows allows birds to save energy
and time required for excavating new ones
Đordje Stanojević’s Patents for the Storage and Sorting of Photographic Plates
No full textProfesor Đorđe Stanojević je 1913. godine aplicirao za patentiranje uređaja za skladištenje i sortiranje fotografskih negativa na staklenim pločama u britanskom i francuskom patentnom zavodu, gde su patenti zatim i registrovani. Izum predstavlja kutiju u obliku knjige sa žlebovima za smeštaj 35 negativa. Žlebovi su numerisani, a predviđen je i prostor za beleške koji je, takođe, numerisan, kao i prostor za obeležavanje zbirke. Ovaj način skladištenja omogućava zaštitu i sistematizaciju ploča. Patentima se danas može pristupiti preko Evropskog patentnog zavoda, u okviru kojeg nose oznake GB191313077A i FR459097A. Ovo praktično rešenje moglo je doprineti arhiviranju i sistematizaciji fotografskog materijala. Ipak, njegov potencijal ostao je nedovoljno iskorišćen.Versatile physics professor and rector Đorđe Stanojević was significantly dedicated to photography. In 1913, he applied for a patent for a device for storing and sorting photographic glass plate negatives in both the British and French patent offices, where the patents were registered, as well. The invention consists of a book-shaped box with grooves designed to hold 35 negatives. The grooves are numbered, and there is also a designated space for notes, which is likewise numbered, as well as an area for marking the belonging inside collection. This storage method allows the protection and organization of the plates. The design of the invention suggests the professor’s "bibliophilic" approach to problem-solving. Today, these patents can be accessed via the European Patent Office under the designations GB191313077A and FR459097A. This practical solution could have contributed to the archiving and systematization of photographic material. However, its potential remained largely underutilized