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Development of PMMA–silica–alumina nanocomposites for enhanced performance
No full textThis study focuses on alumina–silica oxide mixtures synthesised via sol–gel processing using rice husk and aluminium chloride hydroxide as precursors followed by calcination, yielding submicron particles suitable for reinforcing poly(methyl methacrylate) (PMMA). These hybrid oxide particles exhibit a well-dispersed phase composition of alumina and silica, enhancing mechanical properties when homogeneously distributed within the brittle PMMA matrix. X-ray diffraction (XRD) confirmed the crystallinity and phase structure of the particles. The PMMA composites were formulated with 1 wt.%, 3 wt.%, and 5 wt.% Al2O3/SiO2, then analysed using scanning electron microscopy (SEM), optical microscopy, and indentation testing. Vickers microhardness and tensile tests showed significant improvements in the hardness, strength, and creep resistance of the hybrid nanocomposites. The hardness increased by approximately 25.94% and creep resistance by 4.4% when 3 wt.% of Al2O3/SiO2 particles was added to PMMA, while the tensile strength increased to approximately twice that of the pure PMMA matrix. Wettability was evaluated via sessile drop measurements using water and glycerine, representing polar liquids with differing viscosities. The surface free energy and work of adhesion were calculated using the Owens–Wendt–Rabel–Kaelble (OWRK) model. The results show that even low concentrations of hydrophilic particles markedly influence the wetting behaviour, with modular surface properties emerging as a function of filler loading. Among tested compositions, the 3 wt.% oxide-reinforced composite achieved the most favourable balance of mechanical reinforcement and wettability control, identifying it as the optimal formulation for enhanced PMMA-based dental applications
Steroidal semicarbazones and carbazate esters: drug-likeness and lipophilicity
No full textSteroidal semicarbazones (SCs) and ethyl carbazates (ECs) were
evaluated for drug-likeness, ADME-related properties, and lipophilicity using
multiple in silico tools and experimental shake-flask measurements. All
compounds complied with Lipinski’s criteria and showed acceptable predicted
absorption and distribution profiles. However, calculated log P values varied
markedly among models (up to ~1.5 units). Experimental data confirmed lower
lipophilicity of SCs and revealed class-dependent agreement between predicted
and measured values, with iLOGP best describing SCs and XLOGP3 ECs,
highlighting the need for combined computational and experimental assessment
Insights into adaptation mechanisms and survival strategies of Pseudomonas chlororaphis subsp. aurantiaca: A comparative proteomic study under PFOA exposure
No full textPerfluorooctanoic acid (PFOA), increasingly detected at extreme concentrations in industrial hotspots, caused a reduction in growth and a prolonged lag phase in Pseudomonas chlororaphis subsp. aurantiaca. In order to reveal microbial adaptation mechanisms and survival strategies under exposure to PFOA, a comparative proteomic analysis was undertaken. The up-regulation of phosphoglycerol transferase, lipoproteins, and long-chain fatty acid synthesis, together with the down regulation of cis unsaturation of fatty acids and changes in specific membrane-embedded porins, indicate alterations in membrane structure, fluidity, and permeability. The up-regulation of the divalent cation–regulated outer membrane protein H1, accompanied by the down-regulation of zinc and other metal transporters, reflect changes in metal ion homeostasis. In particular, altered iron homeostasis and expression of iron-, Fe-S clusters-, and heme-containing proteins were detected, along with the reduced activity of some iron-containing enzymes, as a result of inhibition by PFOA. Up-regulated enzymes of the methylcitrate and the glyoxylate cycles indicate alterations in central metabolic pathways associated with lipid metabolism in PFOA-treated cells. Changes in the respiratory chain may influence enhanced superoxide radical formation, triggering increased ROS production and the up-regulation of antioxidant enzymes, except those involved in thiol-based redox processes. In addition, PFOA alters the regulation of virulence-associated proteins
Winning of rare earth elements from ores and concentrates
No full textPrezentacija kolege iz dijaspore koji je odžao predavanje u okviru diseminacije projekta REMEDIS koji je finansiran od strane Fonda za nauku Republike Srbije. Za sva dodatna pitanja se možete obratiti rukovodiocu projekta dr Nataši Petrović ([email protected]
Integrative lipophilicity assessment and pharmacokinetic correlation of pyrimidine precursors and artesunate–pyrimidine hybrids: development of QSAR models for anticancer activity and interaction with P -glycoprotein
No full textAims: To evaluate chromatographic lipophilicity of novel artesunate–pyrimidine hybrids and precursorsusing reversed-phase thin-layer chromatography (RP-TLC) and assess plasma protein binding (PPB). Theimpact of measured and predicted lipophilicity on pharmacokinetic descriptors was evaluated. Principalcomponent analysis (PCA) explored relationships among lipophilicity, PPB, and physicochemicaldescriptors. Quantitative structure–activity relationship (QSAR) and partial least squares (PLS) modelslinked molecular descriptors to cytotoxicity and resistance modulation in nonsmall cell lung cancer(NSCLC) cells.Materials and methods: Lipophilicity was measured by RP-TLC. PPB was determined using humanserum albumin (HSA)-modified high-performance liquid chromatography (HPLC). PCA characterizedphysicochemical–pharmacokinetic correlations. Cytotoxicity in sensitive NCI-H460 and multidrug-resistant (MDR) NCI-H460/R cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay. QSAR and PLS models identified key descriptors.Results: Lipophilicity strongly influenced adsorption, distribution, and protein binding. Highly lipophilichybrids showed near-complete HSA binding. Compound 2k lost cytotoxicity in the presence of albumin,whereas 4k retained potency. Models indicated steric and electronic features, alongside lipophilicity,dictate efficacy and P-glycoprotein (P-gp) interactions, particularly in resistant cells.Conclusions: Lipophilicity and steric/electronic descriptors govern distribution, protein binding, andanticancer activity. Integrating these features enables design of hybrids overcoming P-gp-mediatedmultidrug resistance, with hybrid 4k emerging as a promising candidate
Green switchable multicomponent reactions for sustainable heterocycle synthesis
No full textAn enzyme-assisted green approach was developed for Hantzsch
and Biginelli multicomponent reactions using benzaldehyde, acetylacetone, and
urea in a glycerol–water buffer. Two known compounds were prepared using
identical temperature profiles, citrate buffers, MgSO₄, and glycerol as an
emulsion stabilizer. Product chemoselectivity was controlled by tuning pH,
reagent ratios, MgSO₄ concentration, and the presence or absence of urease. The
results demonstrate biotechnology-assisted pathway control in competing
multicomponent reactions within a sustainable synthetic framework. Reactions at
65 °C afforded ~40% yields, with fluorescence properties confirming product
formation
Novel well-adhered composite coatings on titanium plates consisted of Sr-doped hydroxyapatite, zein and TiO2 for biomedical applications
No full textComposite coatings based on natural biocompatible polymer impregnated through hydroxyapatite (HAp)/freely-grown titanium oxide matrix were fabricated in one go onto titanium substrates. The substrates were subjected to simultaneous anodization/anaphoretic deposition (A/AD) methodology to check if the methodology can develop biomaterials with the advanced properties of strong adhesion, biocompatibility and bioactivity. HAp and strontium-doped HAp powders were synthesized ex-situ and used to demonstrate A/AD applicability to bone metabolism-enhancing (Sr-doped) materials. Similarly, zein is introduced to check if A/AD preserves its role of impregnating natural and biocompatible polymer. The main finding, emphasizing the improvement by A/AD, indicates the coatings are uniform, compact and well-adhered to the titanium surface, with all of the components present in their expected form. The initially smooth surface of anaphoretic zein coating appears roughened by incorporation of HAp, and especially by Sr-doped HAp. Consequently, the roughening improved the bioactivity and cell attachment with simultaneous excellent adhesion induced by zein. Bone metabolism is also expected to be improved since HAp appears to grow much from the Sr-doped HAp-based coating surface than from its bulk, if compared to the undoped counterpart
Long-term bioelectricity generation in microbial fuel cell exposed to perfluorooctanoic acid
No full textThe long-term performance of microbial fuel cells (MFCs) depends on microbial communities whose composition
strongly influences electron transfer and substrate utilization. The presence of environmental pollutants can
cause changes in microbial abundance and biodiversity and have an effect on the MFC efficacy; however, their
long-term operational stability under environmental stress remains insufficiently explored. This study assessed
the long-term performance of MFCs using river sediment organic matter as the energy, electron, and carbon
source during exposure to perfluorooctanoic acid (PFOA). The MFC-PFOA (MFC with PFOA) system operated
effectively for 10 months, achieving a maximum voltage of 461.9 mV and a peak current density of 14.5 mA/m2,
significantly outperforming the control cell. Liquid chromatography–tandem mass spectrometry (LC-MS/MS)
analysis confirmed a 94.9 % reduction in PFOA concentration and detected perfluoroheptanoic acid (PFHpA) and
perfluorohexanoic acid (PFHxA), indicating possible partial transformation and/or redistribution processes
within the bioelectrochemical system. Additionally, bacterial community analysis revealed a shift in microbial
composition, with Firmicutes and Desulfobacterota becoming dominant, suggesting their roles in current gen-
eration and biotransformation of PFOA. Overall, this work demonstrates long-term bioelectricity generation in
the presence of per- and polyfluoroalkyl substances (PFAS) pollutants, while indicating partial attenuation and
compositional changes of PFOA under bioelectrochemical conditions, thus providing valuable insights into the
robustness of bioelectrochemical systems for energy recovery in contaminated environments
In silico drug-likeness of steroidal heterocyclic derivatives
No full textSteroidal bis-thiosemicarbazones and their cyclic derivatives,
thiadiazolines (TDZs) and triazoline-3-thiones (TATs), were evaluated in silico
(Molinspiration, pkCSM) to assess drug-likeness and pharmacokinetic properties.
With the exception of cholestane-based derivatives, most compounds complied
with Lipinski’s criteria or showed only a single violation. TDZs exhibited the
most balanced predicted absorption–distribution profile, while TATs were
characterized by favorable intestinal absorption and higher predicted volume of
distribution, supporting their consideration for further synthesis and biological
evaluation
Variscan sutures in the Carpathian-Balkan belt revisited: a granitoid perspective on Late Palaeozoic closure of the Rheic Ocean, slab breakoff and tectonic exhumation
No full textThe integration of available geochronological and geophysical data from the Carpathian-Balkan
basement, along with geochemical data related to the Variscan granitoid-decorated suture, indicates
the presence of subduction-driven collision followed by post-collisional exhumation of the Inner
Carpathian-Balkan (Rheic) suture configuration (ICBRS). The ICBRS as a Variscan crustal amalgamation
(exposed in Serbia) collapsed due to slab breakoff (‘high-temperature’ orogeny) that occurred prior to
the start of the Alpine rifting. The advancing edge of the Lower Palaeozoic north Gondwanan
microcontinent, which includes the Serbo-Macedonian, Supragetic, and Getic-Kučaj nappes (Alpine
basements) together with the attached oceanic lithosphere of Devonian age, was involved in
subduction beneath the Danubian and Moesia (an external promontory of the East European craton).
In contrast, the opposite side of the Carpathian-Balkan microcontinent (western Serbo-Macedonian
Unit) exhibits less frequent granitic activity (Paleotethyan suture). Variscan deformation of ICBRS,
characterized by pre-, syn-, and post-collisional magmatism, involves multiple episodes of granitoid
emplacement spanning from the Late Devonian to the Carboniferous. Variscan-age granitoids extend
along a 200-km-long north-south belt across the Getic/Kučaj and Danubian microcontinents, emerging
through the Carpathian-Balkan fold-and-thrust belt of eastern Serbia (Brnjica, Neresnica,
Gornjane, Plavna, Ravno Bučje, Suvodol, Radičevo, Janja). Devonian lithospheric underplating of
the northern Gondwanan microcontinent led to the formation of the (latest Devonian)
Carboniferous syn-collisional ‘high-temperature’ orogeny, associated with the Inner Carpathian-
Balkan Rheic suture, characterized by modest crustal thickening. The combination of geochemical
and geophysical data, including available regional geological reconstructions illustrating Late
Palaeozoic crustal exhumation processes revolving around the ICBRS. Study further highlights the
overlapping processes of reactivation of the Variscan-Alpine suture zones. However, due to the
interference of Cimmerian and Alpine deformation stages, the mechanisms of crustal exhumation
of lower crustal levels remain increasingly ambiguous, thus being absent from the available literature.Appendix: [https://cer.ihtm.bg.ac.rs/handle/123456789/9159]Supplementary Material: [https://cer.ihtm.bg.ac.rs/handle/123456789/9168