Vinča Institute of Nuclear Sciences
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Nanoscale structural superlubricity in solution-processed graphene films via tribo-induced transfer layers
No full textSo far, nanoscale superlubricity has been demonstrated in well-ordered van der Waals materials, such as graphite and mechanically exfoliated graphene. In contrast, this study demonstrates nanoscale superlubricity in structurally inhomogeneous systems such as solution-processed graphene films, which are promising for scalable and practical applications. The investigated graphene films were obtained via liquid-phase exfoliation (LPE) and deposited by Langmuir–Blodgett assembly technique at the water–air interface, while frictional measurements were performed using atomic force microscopy (AFM)-based techniques. To enable superlubricity in the system consisting of a silica AFM tip and an LPE graphene film, a tribo-induced, graphene-based conformal coating was first formed around the tip. Unlike previous studies that relied exclusively on pristine graphite, we easily transferred small and weakly adhered graphene flakes onto the AFM tip by rubbing it against the LPE graphene film in contact mode. Subsequent friction measurements were performed using these graphene-coated tips. The measurements on LPE films deposited onto silica and polyethylene terephthalate (PET) substrates revealed ultralow friction coefficients of approximately 0.005 on flat regions composed of large graphene flakes thereby confirming the emergence of the superlubric regime. However, the inherently non-uniform morphology of LPE films, with small flakes and numerous exposed edges, introduces localized high-friction regions and wear-prone sites that prevent superlubricity across extended areas. These findings highlight the importance of achieving large flake sizes with reduced density of exposed edges and improved flake adhesion in order to enable robust structural superlubricity in LPE graphene films. © 2025 Elsevier Lt
The influence of backscatter radiation from the image detector on air kerma measurements in mammography
No full textCalibration and routine QC testing in mammography present rather challenging procedures, given the geometry of the X-ray unit and the associated factors that affect the measurements. Some of these factors include the positioning of dosimeters at their respective reference points, backscatter from the image detector, and the presence of the compression paddle in the primary beam. Dosimeters used in calibration and QC procedures are ionization chambers (ICs) or semiconductor X-ray multimeters (XMMs). The main difference is that XMMs have lead shielding on the backside that prevents backscattered radiation from the image detector from reaching the active volume of the dosimeter, while the ICs might be sensitive to backscattered radiation since they can detect radiation from all directions. Mammography X-ray units have a vertical beam with an image detector in place, while calibration laboratories mostly use horizontal beam configurations free-in-air, which may make reproducing realistic clinical conditions difficult. The presence of the image detector cannot be avoided in clinical setups. In opposite, most calibration laboratories don’t use or have an actual image detector that could be used to mimic the realistic clinical conditions. Routine laboratory calibrations are done in terms of air kerma free-in-air which does not take backscattered radiation into consideration. In the scope of the 22NRM01 TraMeXI project, the transfer of calibration procedures from laboratories to clinics is being developed. For this purpose, an image detector has been introduced to the laboratory calibration setup. The measurements in terms of air kerma free-in air have been done with and without the presence of the image detector, to evaluate the influence on measured value. This effect was studied for different positions of dosimeters (3 ICs and 3 XMMs) relative to the image detector. The results can be used to better estimate the uncertainty related to the impact of backscatterInternational conference on radiation applications in Physics, Chemistry, Biology, Medical Sciences, Engineering and Environmental Sciences : May 26-30, Crete, Greece
Evaluation of an in-situ procedure for calibration of well-type brachytherapy chambers in hospitals
No full textBrachytherapy is a specialized form of radiation therapy in which small encapsulated radiation sources are placed directly within or near the target area, with known ability to deliver a high radiation dose to the tumor tissue while minimizing exposure to surrounding healthy tissues. Dosimetry protocols for photonemitting sources in brachytherapy typically rely on reference air kerma rate (RAKR) or air kerma strength (AKS) standards, along with transfer instruments. A well-type ionization chamber, or re-entrant well-type chamber, is the recommended method for measuring the strength of primary brachytherapy sources. In Serbia, no calibration services for brachytherapy ionization chambers were previously available. To address this, the Secondary Standards Dosimetry Laboratory (SSDL) at the Vinca Institute of Nuclear Sciences has initiated the establishment of a calibration service for high dose rate (HDR) brachytherapy sources using a reference well-type chamber, Standard Imaging HDR-1000 Plus, coupled with a PTW Unidos Webline electrometer. The chamber’s 20 mm thick aluminum outer wall helps reduce the influence of scattered radiation. A unique source holder is provided for each radiation source to ensure reproducible geometry within the chamber well. The calibration of the system can be done either as a whole (system calibration) or separately (component calibration). In system calibration, both the well-type chamber and the electrometer are calibrated together, while in component calibration the chamber and electrometer are individually calibrated and the overall calibration is derived from the two separate calibrations. Due to the lack of a radiation source generator for brachytherapy at the SSDL, calibrations are performed on-site, using sources and dose delivery systems that are available. The calibration procedure for high-dose-rate brachytherapy (HDRBT) is conducted using the substitution method, in which the user’s well-type ionization chamber is calibrated against the reference HDR-1000 Plus chamber. The calibration process includes several steps: prior to measurements the ionization chambers need to be in thermal equilibrium with the ambient conditions, conducting a dummy source test, pre-irradiating the well-type chamber, measuring the first leakage, determining the “sweet spot” of the chamber, recording reference and measured values, measuring the second leakage, and applying corrections to the measured values. If the ionization chamber is used with different holders or catheters, calibration must be performed for each configuration, and it is crucial to specify the conditions under which the calibration coefficient was determined. In accordance with the guidelines outlined in the IAEA document “Calibration of Photon and Beta Ray Sources Used in Brachytherapy (IAEA TRS 492:2023)”, well-type ionization chambers should undergo periodic stability checks to ensure consistent and reliable performance. These checks are an essential part of maintaining the accuracy of brachytherapy dosimetry and should be conducted at regular intervals to adhere to established quality assurance standards.International conference on radiation applications in Physics, Chemistry, Biology, Medical Sciences, Engineering and Environmental Sciences : May 26-30, Crete, Greece
The prospects for the development of Small Modular Reactors (SMRs)
No full textThe twenty-first century brings about a growing demand for higher energy production, coupled with the urgent need to protect the environment, which has already suffered significant damage. In response to this challenge, several countries, including the Republic of Serbia, are considering nuclear energy as a key component of their energy mix. Utilizing nuclear energy for electricity generation offers several advantages, including stable production and supply, low greenhouse gas emissions, and high safety standards. Several countries, including the Republic of Serbia, are considering turning to nuclear energy as a staple in the energy mix. The use of nuclear energy for the production of electricity is positive in terms of production and supply stability, low greenhouse gas emissions, as well as high safety. In contrast to the benefits of nuclear energy, there are significant drawbacks, such as the high cost of constructing and operating traditional nuclear power plants, the challenges associated with treating and disposing of radioactive waste, and the potential for large-scale accidents, which contribute to public fear. To address these issues, the development of small modular reactors (SMRs) has started. SMRs have lower costs compared to conventional reactors, and their potential for serial production can further reduce expenses by shortening both construction and licensing times. Additionally, because SMRs are more compact, they require reduced number of components necessary for transporting steam, such as pipes and pumps. Serial production enables the repetition of knowledge for operational work, especially since there will be multiple reactors of the same type. In addition to their economic development potential, Small Modular Reactors (SMRs) have significant opportunities for applications beyond electricity generation. For instance, they can be utilized in hydrogen production, which might be essential for various industries such as chemical manufacturing, metal processing, and as fuel for vehicles. There is also the potential to use Small Modular Reactors (SMRs) for applications such as process heating, district heating, thermal desalination, and reverse osmosis in the production of drinking water or for wastewater treatment. Although they are still in development, SMRs have the capacity to be widely adopted in the future, not only for power generation but also across various industries. This paper provides an overview of the benefits of SMRs as a promising new technology.International conference on radiation applications in Physics, Chemistry, Biology, Medical Sciences, Engineering and Environmental Sciences : May 26-30, Crete, Greece
Investigating the impact of COX-2 and LOX-5 inhibition on cancer cells irradiated with conventional and hadronic beams
No full textDespite recent advancements in the management of cancer, there is still a large necessity to identify more effective strategies while minimizing undesirable side effects. A promising option is to use hadronic particle beams applied combined with drugs that increase sensitivity to radiation therapy. Moreover, the improved modeling of irradiation-induced DNA damage with Monte Carlo Track Structure (MCTS) codes results from validation with experimentally obtained data. These MCTS codes also provide possibilities for dose determination in treatment planning. The abnormal activation of the cyclooxygenase-2 (COX-2) and/or prostaglandin E2 (PGE2) pathway is commonly observed in various tumor types. This points to the anti-inflammation therapy as a promising cancer treatment option. The activation of the COX-2 pathway decreases the response of tumor cells to radiation therapy while enhancing radiation-induced unwanted late effects in healthy cells. In this regard, COX-2 inhibitors, a structurally diverse class of compounds, can be useful. Also, the increased activity of the 5-LOX signaling pathway in cells exposed to COX-2 inhibitors suggests that dual COX-2 and 5-LOX inhibitors could be the most optimal. In this work, several newly synthesized COX-2 and dual COX-2 and 5-LOX inhibitors were tested on selected cancer cell lines. Based on the results of their cytotoxicity, the most potent inhibitors were selected for combined treatment with radiation. Irradiation with increasing doses of γ-rays was performed at the Laboratory for Molecular Biology and Endocrinology of the Vinča Institute of Nuclear Sciences. Clonogenic assay was done using BxPC-3 (ATCC CRL-1687, pancreatic adenocarcinoma) and HT-29 (ATCC HTB-38, colorectal cancer) cell lines. The obtained survival data was used both for the evaluation of the sensitivity of cells to conventional irradiation and for an investigation of the radiosensitizing potential of tested compounds. The cell geometries were added to the online library of Geant4-DNA, which is openly available to users. To further extend the investigation to irradiation-induced effects on selected cancer models, low-energy protons (≅5 MeV) and alpha-particles (≅ 7.5 MeV) will be used to reproduce the LET values that occur at the mid-SOBP of clinical proton and 12C beams (i.e. around 7 and 75 keV/um, respectively) and will be performed at the 3-MV TANDEM accelerator of the University of Caserta, in Italy. The obtained results will show if the combination of COX-2 and dual COX-2 and 5-LOX inhibitors with radiation of different types has the potential to improve tumor control and whether it can be introduced into clinical routine.International conference on radiation applications in Physics, Chemistry, Biology, Medical Sciences, Engineering and Environmental Sciences : May 26-30, Crete, Greece
Plasma, UV Radiation and Ozone for Microplastics Degradation: Optical Characterization of Polystyrene, Polyethylene and Polypropylene Degradation using FTIR and Raman Spectroscopy
No full textThis study comprehensively examined the alterations in the optical and structural properties of three commonly encountered microplastic polymers—polypropylene (PP), polyethylene (PE), and polystyrene (PS)—when subjected to different degradation treatments. The microplastic samples were exposed to three distinct experimental conditions: ozone (O₃) treatment, ultraviolet (UV) radiation, and cold plasma, each representing an advanced oxidation or energetic degradation environment relevant to both environmental and industrial contexts. Controlled laboratory experiments were designed to simulate realistic degradation pathways and to systematically assess how each treatment influences the integrity and chemical structure of the selected polymers. The progression of degradation was monitored through Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, which provided detailed spectral fingerprints of the evolving chemical bonds and functional groups [1]. The spectroscopic data revealed treatment-specific molecular transformations, such as oxidation, chain scission, and the formation of new surface functionalities. These changes were manifested through the appearance or shifting of characteristic peaks, indicating alterations in crystallinity, the emergence of carbonyl and hydroxyl groups, and the breakdown of polymer backbones. This multi-technique approach enabled a nuanced understanding of the degradation mechanisms and the relative persistence of each microplastic type under different environmental stressors [2]. Overall, the study contributes valuable insights into the photochemical and oxidative degradation behavior of microplastics, with implications for environmental monitoring, remediation strategies, and the design of more degradable polymeric materials.X International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; 25 - 29 August 2025 Belgrade, Serbia
Effect of pulse energy on the formation of Laser-Induced Periodic Surface Structure on Nb/Ti multilayer thin films
No full textThe possibilities of creating Laser-Induced Periodic Surface Structure (LIPSS) on Nb/Ti multilayer structures were investigated through surface modification with picosecond laser radiation. Using DC ion sputtering, fifteen (Nb/Ti) bilayers were deposited to create multilayer thin films with a total thickness of 440 nm on (100) Si wafers. Dynamic laser modifications, such as laser-etched lines, were performed using picosecond (15 ps) laser pulses of a Nd: YVO4 laser operating at 532 nm, with pulse energies ranging from 1.5 to 2.8 μJ. The development of LIPSS was accompanied by different morphological features depending on the applied pulse energy; the different absorbed energy stimulated diverse processes in a multilayer 15x(Nb/Ti)/Si system. By gradually increasing the pulse energy at a constant scanning speed (5 mm s -1 and 1 mm s-1), the development of LIPSS included the following morphological changes: (i) initial surface melting with the formation of clusters, (ii) elongation of melted regions and formation of HSFL (high spatial frequency LIPSS); (iii) separation of droplets and their arrangement in LSFL (low spatial frequency LIPSS); (iv) cracks appearance corresponding to positions of LSFL; (v) material recrystallization; and (vi) material ablation at the highest pulse energies. The analysis of changes in composition after laser modification revealed the presence of oxygen in a higher concentration than in the untreated area, realizing the possibility of forming an ultra-thin oxide layer composed of Nb- and Ti-oxides. The obtained results for the development of periodic structures in the form of LIPSS, depending on the pulse energy (fluence) at the selected scan speeds, provide a relatively satisfactory prediction of the LIPSS formation with the desired morphological characteristics.X International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; 25 - 29 August 2025 Belgrade, Serbia
Equivalent electrical circuit modeling of the irradiation and NBTS induced threshold voltage shift in p-channel power VDMOSFETs
No full textThirteenth International Conference on Radiation Natural Sciences, Medicine, Engineering, Technology and Ecology : June 16-20, 2025, Herceg Novi, Montenegro
Sustainable gamma irradiation strategy for GO and rGO modification: Impact on electromagnetic interference shielding efficiency
No full textElectromagnetic interference (EMI) has emerged as a significant issue in contemporary electronic systems, particularly within aerospace, defense, and communication technology. Graphene-derived materials, including graphene oxide (GO) and reduced graphene oxide (rGO), present remarkable potential for lightweight, flexible, and EMI shielding solutions owing to their adjustable electrical conductivity and structural integrity. This study introduces an eco-friendly method for adjusting the EMI shielding effectiveness (EMI SE) of free-standing films made from GO and rGO by controlled gamma irradiation at low (50 kGy) and high (300 kGy) doses, conducted in two types of media: air and isopropyl alcohol (IPA). The structural alterations generated by irradiation were characterized by Raman and Infrared spectroscopies, X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements, indicating changes in defect density, surface roughness, and hydrophilicity. Results indicate that gamma irradiation can precisely adjust the oxidation/reduction equilibrium, hence boosting conductivity in rGO and improving interfacial polarization in GO. Remarkably, rGO films exposed to air demonstrated exceptional EMI SE values above 20 dB in the X-band (8–12 GHz), signifying their suitability for advanced shielding applications. This research illustrates the effectiveness of gamma irradiation as an environmentally friendly, scalable method for modifying the characteristics of graphene-based materials, facilitating their incorporation into advanced aeronautical and electronic equipment
Mercury removal from acid mine drainage by natural pyrophyllite schist material
No full textAcid mine drainages (AMD) pose a serious threat, due to their potentially toxic metals content, which can pollute the environment and affect human, animal and plant health. The potential of natural pyrophyllite schist (Prl-sch) material from the Parsovići mine in Bosnia and Herzegovina for Hg removal from acid mine drainage (AMD) was tested. This AMD freely discharges from the abandoned cinnabar (HgS) mine Šuplja Stena, located on Mount Avala in Serbia. The sorption experiment was conducted in duplicate, involving the direct contact of 2 g of Prl-sch with 100 mL of native AMD sample for 2 h at room temperature with agitation of 200 rpm. Prl-sch used in this experiment was mechanochemically modified beforehand to obtain particles less than 0.45 μm in diameter. Concurrently, a control experiment with deionized water was run to determine if the Prl-sch itself releases Hg under the same experimental conditions. The Hg concentrations in native AMD, Prl-sch-treated AMD and control sample were measured by inductively coupled plasma - optical emission spectroscopy. The initial concentration of Hg in the native AMD sample was 9.3 μg/L, while in the control and Prl-sch-treated AMD sample Hg content was below the limit of quantification (<0.4 μg/L). The observed Hg removal efficiency and sorption capacity of Prl-sch from the Prl- sch-treated AMD sample was ˃95.7% and ˃0.4 μg/g, respectively. Mercury sulfides are poorly soluble in water, which could explain the initial low Hg content in the native AMD sample. In this experiment, Prl-sch demonstrated the exceptionally high potential for Hg removal, rendering this natural material a promising treatment for the purification of Hg-contaminated water environments.ICCBIKG 2025 : 3rd International Conference on Chemo and Bioinformatics, September 25-26, 2025; Kragujevac, Serbia