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The Influence of Al12Mg17 Compound Concentration in High-Energy Mixtures on Thermobaric Systems Characteristics
No full textThe influence of the concentration of Al12Mg17 intermetallic compound in high-energy mixtures (HEMs) on the performances of thermobaric (TB) systems is investigated. Thermobaric charges based on HEM pressed around the high explosive core were detonated in the open area. The pressure measurements of TB and trinitrotoluene reference charges were performed using eight pressure transducers placed around the horizontally positioned charge. A high-speed camera and image processing technique were used to record a fireball evolution and quantify fireball characteristics. The highest values of overpressure peak and positive phase pressure impulse were obtained for HEM with 37 wt.% of Al12Mg17 content. The fireball image analysis shows satisfactory fireball surface area and duration time for HEM with 37 wt.% of Al12Mg17. © 2025 Wiley-VCH GmbH
Where Did Vessels Come from? A Study of Pottery Provenance from the Site of Velika Humska Čuka, Serbia
No full textThe archaeological materials from the Velika Humska Čuka site on the northern fringe of the Niš Basin in southeastern Serbia were analyzed to reveal the provenance of ceramics and other artifacts. This study focused on the elemental analysis of 61 samples, including local clay pits, potsherds, and whole vessels. Samples were chosen based on stylistic and typological characteristics to distinguish local and “foreign” pottery. Elemental analysis was conducted using energy-dispersive X-ray fluorescence (EDXRF) spectrometry, complemented by principal component analysis (PCA) for data interpretation. Results indicated that the majority of pottery samples, over 80%, were produced using local clay from deposits near the site. However, approximately 20% of the analyzed vessels were made using clay from deposits near the Bubanj site, 8 km south of Velika Humska Čuka. A vessel on a hollow high foot combining stylistic elements of the Bubanj-Hum I group and Early Eneolithic Pannonian groups was made of clay not sourced from any identified local deposits, suggesting its non-local origin. While the predominance of local materials suggests self-sufficient production, the use of non-local clays and stylistic influences highlights long-distance connections and exchanges. The study emphasizes the importance of Velika Humska Čuka in understanding the development of ceramic traditions and the cultural dynamics of the Early Eneolithic in the Central Balkans. © 2025 by the authors
Dual activity of newly synthesized Zn(II) and Cu(II) schiff base complexes as a potential solution for global challenges in the fight against priority microorganisms
No full textThe increasing prevalence of antimicrobial resistance (AMR) poses a significant global challenge, necessitating the development of novel and improved therapeutic strategies. Oxidative stress is a major factor in various diseases, emphasizing the need for compounds with dual antimicrobial and antioxidant properties. This study aims to investigate the synthesis, structural characterization, and bioactivity of novel Zn(II) (2a-b) and Cu(II) (3a-b) complexes, derived from structurally related imines incorporating salicylic aldehyde and p-OH benzyl amine (1a) or tyramine (1b). The objective is to explore the relationship between metal coordination and biological activity, focusing on both antimicrobial and antioxidant effects. A comprehensive methodology was employed, including different spectroscopic techniques and molecular docking studies. Antimicrobial activity was assessed through minimum inhibitory concentration (MIC) assays, while antioxidant potential was evaluated via free radical scavenging assays. Molecular docking simulations provided insight into the binding affinities of the complexes with DNA gyrase (DNAg) and cytochrome P450 14-α sterol demethylase (CYP51B). While Zn(II) complexes (2a-b) demonstrated antimicrobial efficacy against priority microorganisms, Cu(II) complex (3a) exhibited notable antioxidant activity. Docking studies revealed that complexes 3a and 3b displayed strong affinity for DNAg (ΔGbind -8.81 and -8.54 kcal mol-1, Ki 0.35 μM for 3a), while complex 2a showed exceptional affinity for CYP51B (-10.22 kcal mol-1, Ki 0.03 μM). Fluorescence spectroscopy confirmed strong interactions between 2a and 3a with Bovine Serum Albumin. These findings demonstrate the promising dual properties of Zn(II) and Cu(II) Schiff base complexes, combining antimicrobial and antioxidant activities, and suggest their potential therapeutic applications in addressing AMR and oxidative stress-related diseases. © 2025 Elsevier B.V
Computational insights into the redox properties and electronic structures of [Tc=O]3+ complexes: Implications for 99mTc-radiopharmaceuticals
No full textTechnetium-99m plays a pivotal role in nuclear medicine, offering unique IMAGING capabilities due to its favorable physical and chemical properties. This study investigates the redox behavior and electronic structures of three representative Tc(V) oxo complexes, [TcO(HMPAO)], [TcO(Bicisate)], and [TcO(DMSA)2]-, using computational techniques. Employing relativistic density functional theory with the Zero-Order Regular Approximation (ZORA), we analyze singlet-triplet energy gaps, Gibbs free energy changes, and redox potentials in neutral and acidic environments. The results highlight the significant influence of co-ligands on the electronic stabilization of complexes and their tendencies toward reduction and protonation. The findings also elucidate the role of Jahn-Teller distortions in shaping the redox properties of the studied complexes. Redox potential trends indicate enhanced reducibility in complexes with sulfur-based ligands, impacting their clinical utility. This study provides valuable insights into the design and optimization of technetium-based radiopharmaceuticals, emphasizing their stability and behavior under physiological conditions. © 2025 Elsevier Inc.Peer-reviewed manuscript: [https://vinar.vin.bg.ac.rs/handle/123456789/14986
Structure and Functional Characteristics of Novel Polyurethane/Ferrite Nanocomposites with Antioxidant Properties and Improved Biocompatibility for Vascular Graft Development
No full textNovel ferrite/polyurethane nanocomposites were synthesized using the in situ polymerization method after the addition of different spinel nanoferrite particles (copper, zinc, and copper–zinc) and examined as potential coatings for medical devices and implants in vascular tissue engineering. The influence of the nanoferrite type on the structure and functional characteristics of the polyurethane composites was investigated by FTIR, SWAXS, AFM, TGA, DSC, nanoindentation, swelling behavior, water contact angle, and water absorption measurements. Biocompatibility was evaluated by examining the cytotoxicity and adhesion of human endothelial cells and fibroblasts onto prepared composites and performing a protein adsorption test. The antioxidant activity was detected by UV–VIS spectroscopy using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay. Embedding the different types of nanoparticles in the polyurethane matrix increased phase mixing, swelling ability, and DPPH scavenging, decreased surface roughness, and differently affected the stiffness of the prepared materials. The composite with zinc ferrite showed improved mechanical properties, hydrophilicity, cell adhesion, and antioxidant activity with similar thermal stability, but lower surface roughness and crosslinking density compared to the pristine polyurethane matrix. The in vitro biocompatibility evaluation demonstrates that all nanocomposites are non-toxic, exhibit good hemocompatibility, and promote cell adhesion, and recommends their use as biocompatible materials for the development of coatings for vascular implants. © 2025 by the authors
Microstructure, Hardness, and Wear Behavior of Layers Obtained by Electric Arc Hardfacing Processes
No full textHardfacing is a welding-related technique aimed at depositing a harder and tougher layer onto a softer, less wear-resistant substrate or base metal. This process enhances the abrasion resistance of the component, increasing its durability under working conditions. A key feature of hardfacing is dilution, which refers to the mixing of the hardfacing layer and the base metal. In this study, shielded metal arc welding (SMAW) was employed to hardface structural steel using chromium carbide vanadium consumables, with results compared to AISI D2 cold-work tool steel. Four different SMAW parameters were tested, and the abrasive test was conducted against SiC discs. Wear rate, represented by the wear loss rate, was correlated to microstructure, scanning electron microscopy, energy-dispersive X-ray spectroscopy, hardness, microhardness, and surface roughness. The results showed that key SMAW parameters, such as welding speed and current, significantly influence wear resistance. Specifically, slower welding speeds and higher currents, which result in greater heat input, led to the increased wear resistance of the deposited layer through the mechanism of the inoculation of larger and harder carbides. © 2025 by the authors
Role of terbium doping in controlling oxygen vacancies and enhancing conductive performance in BiFeO3 thin films
No full textThe influence of Tb doping on structural and electrical properties of BiFeO3 thin films is investigated, combining the experimental observations and density functional theory. With such an approach we aimed to elucidate the influence of Tb dopant and defects in the form of oxygen vacancies on electronic structure and electrical conductivity of BiFeO3 films. X-ray diffraction confirmed that the rhombohedral (R3c) crystal structure remains stable in the whole doping range without any impurity phases. Relatively large leakage current was generated in pure BiFeO3 and 5% and 20% Tb-doped films. Significant reduction of electrical conductivity was seen only in 10% Tb-doped film. Conductive atomic force microscopy (C-AFM) allowed us to investigate local electrical conduction properties at the microscale level. The 10% Tb doped film exhibited the smallest conductive surface confirming that this sample has the smallest conductivity, whereas the current maps revealed that the conduction takes place across spatially inhomogeneous grain boundaries with enhanced concentration of defects. The Raman and XPS measurements have shown that oxygen vacancies are the dominant defects in Bi1-xTbxFeO3 films. The higher concentration of oxygen vacancies, found in pure, 5% and 20% Tb-doped films can be responsible for higher conductivity of these films. A reduction in oxygen vacancy concentration was registered in 10% Tb-doped film which is in accordance with much lower conductivity of this sample. Density functional theory calculations provide atomic-level insights into the electronic transport mechanisms and are consistent with experimental findings. Undoped and low level Tb-doped samples (∼5%) are conductive due to n-type dopants in the form of oxygen vacancies which are primarily localized on surface. For intermediate Tb doping (~10%), the balance between the effects of oxygen vacancies and dopant-induced states results in the highest electrical resistivity. Increased conductivity at higher doping levels (∼20%) can be attributed to the denser population of Tb states around the Fermi level, which can overlap, presenting dispersive, conducting states. This work underlines the complex interplay of doping concentration, oxygen vacancies, and electronic transport, suggesting that 10% of Tb is an optimal dopant concentration for enhancing the electrical performances of BiFeO3 thin films.Advances in Solid State Physics and New Materials - 30 years of the Center for Solid State Physics and New Materials at the Institute of Physics Belgrade, 19 – 23 May 2025, Belgrade, Serbia
Effective Dielectric Function of a van der Waals Heterostructure Made of Two-Dimensional Materials Separated by Insulating Layers
No full textElectron energy loss spectroscopy (EELS) is a commonly used experimental technique for investigating electronic and plasmonic properties of two-dimensional (2D) materials and van der Waals (vdW) heterostructures [1-3]. Following Ref. [4], we use the continued fraction (CF) method to derive a general expression for the effective 2D dielectric function of a vdW heterostructure made of 2D materials separated by insulating (isotropic or anisotropic) layers. The first objective is to obtain the EEL spectrum of such materials and (if possible) compare it with the available experimental data. We have extensive experience in the theoretical modeling of the experimental EELS data for free-standing (single and multilayer) graphene sheets obtained by scanning transmission electron microscope [5,6], as well as in the theoretical modeling of the experimental EELS data for monolayer graphene supported by different substrates [7-9]. As an implementation of the CF method, we evaluate the wake potential produced by a particle moving parallel to two graphene sheets separated by an isotropic insulator. For the first time, we assign the finite size of the gap between graphene and insulator in a graphene-insulator-graphene composite system. The second objective is to explore the effects of the graphene-insulator distance on the hybridization between the plasmon modes in graphene and phonon modes in the insulating substrate.Advances in Solid State Physics and New Materials - 30 years of the Center for Solid State Physics and New Materials at the Institute of Physics Belgrade, 19 – 23 May 2025, Belgrade, Serbia
Wavelength demultiplexers based on finite photonic lattices
No full textDemand for densely packed wavelength demultiplexers has increased due to the rapid developments in information systems and sensing for biomedical and space applications. The required miniaturisation is problematic due to the crosstalk in high-density photonic circuits, while the feature size complicates design at sub-micrometer wavelengths. As a solution, we propose wavelength demultiplexers based on wavelength-dependent self-imaging in linearly coupled finite optical lattices. The novel semi-analytical design allows for intuitive and efficient control of their spectral characteristics, notably the bandwidth control by changing the number of waveguides in the lattice. The principle is validated using femtosecond laser fabrication of visible/near-infrared demultiplexers in borosilicate glass. The insertion loss did not exceed 0.43 dB with 0.1-0.15 dB for most devices and the crosstalk was lower than 30 dB. The applicability of the proposed design to other fabrication platforms and wavelength ranges is demonstrated by numerical simulations of silicon-on-insulator demultiplexers at telecom wavelengths with highly competitive insertion loss and crosstalk of 0.13 dB and −82 dB, respectively. © 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.This is the peer-reviewed version of the article: Stojanović, M. G., Vildoso, P., Bugarski, K., Parra, P. M., Maluckov, A., Vicencio, R. A., & Petrović, J. (2025). Wavelength demultiplexers based on finite photonic lattices. Journal of Optics, 27(5), 055801. [http://dx.doi.org/10.1088/2040-8986/adcbbe
Assessing bisphenol a degradation via electro-fenton process: the role of lactic acid as an indicator
No full textBisphenol A (BPA) is a commonly used industrial chemical in the manufacturing of plastics and resins; however, its endocrine-disrupting properties pose serious health risks to living organisms. By interfering with hormonal balance, BPA can contribute to reproductive and developmental problems. Due to its extensive use, BPA remains prevalent in the environment, highlighting the importance of developing efficient methods for its degradation and monitoring. The electroFenton process, utilizing a SnO₂-MWCNT (multi-walled carbon nanotube) anode and a stainlesssteel cathode, operated at a current density of 15 mA cm⁻² in 0.1 M Na₂SO₄ at pH 4 with externally added H₂O₂ (30 mM) and Fe²⁺ (3.66 mM), demonstrated high efficiency in removing BPA from water, achieving complete mineralization into carbon dioxide and water through OH radicals. During the oxidation of BPA via the electro-Fenton process, various intermediates are formed, including hydroxylated BPA derivatives (catechol, dicatechol, quinones) and smaller single-ring molecules such as 4-isopropenylphenol, benzoic acid, 4-hydroxybenzoic acid, 4- hydroxyacetophenone, and hydroxyquinone. These intermediates slowly convert into carboxylic acids, such as lactic acid, and eventually break down into carbon dioxide and water. Based on the obtained results, it can be observed that the concentration of lactic acid steadily increases up to the fourth hour of the electro-Fenton process, at which point it reaches its maximum level. After this peak, the concentration of lactic acid suddenly decreases, suggesting that the degradation process is progressing towards the complete mineralization of BPA. This decline in lactic acid concentration indicates the successful breakdown of intermediate products and the further transformation of these compounds into simpler molecules, ultimately resulting in the complete mineralization of BPA into carbon dioxide and water. This study highlighted the potential of utilizing lactic acid as an effective indicator of BPA degradation within the electro-Fenton process. The findings suggest that lactic acid can serve as a reliable marker for tracking the progress of the degradation process and provide valuable insights into its overall effectiveness. By monitoring the concentration of lactic acid, it is possible to predict the efficiency of the electro-Fenton process, offering a practical tool for assessing the extent of BPA removal and the success of the mineralization process over time.EEM2025 - 9th International Congress Engineering, Environment and Materials in Process Industry; 2-4 april 2025; Bijeljina, Republic of Srpska, Bosnia and Herzegovina