Vinča Institute of Nuclear Sciences
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X-ray imaging dosimeter performance in standard and non-standard radiography radiation fields in terms of air kerma
No full textIntroduction X-ray medical imaging developments have introduced needs for updated dosimetry practices. Methods Performance of commercially available dosimeters used for air kerma measurements in diagnostic and interventional radiology was examined. Ionization chambers and X-ray multimeters were tested in a wide range of air kerma rates, photon energies (using standard and non-standard radiation qualities), and angles of incidence with different dosimeter orientation and rotation. Stability and repeatability of the measured value, the influence of pulse duration, non-linearity of dosimeter response, energy and angular dependence were studied against the IEC 61674:2024 limits of variation. Energy response was tested using the standard RQR and RQT radiation qualities defined in IEC 61267:2005, as well as non-standard copper-filtered beams with added 0.9 mm Cu filtration. Results Most dosimeters complied with the IEC 61674:2024 standard limits of variation, for both standard and non-standard radiation fields. In some cases, observed performance was significantly better than the current limits allowing for the introduction of more stringent values. Conclusion Modification of the performance requirements was proposed, considering differences between reference-class and field-class dosimeters, while introducing more stringent requirements for reference-class dosimeters
Unveiling crystalline modifications on the energy landscape of Cr3Si3N8 using the multi-methodological approach
No full textA multi-methodological approach combining global energy landscape exploration, systematic structure design, and data mining that had been previously successfully applied to Cr2SiN4 and CrSi2N4, was also employed to explore the range of potential modifications in Cr3Si3N8. The global optimization method identified eight promising low-energy structure candidates and successfully determined the global minimum. Additionally, the data mining method identified one promising structure candidate, while the Primitive Cell for Atom Exchange (PCAE) approach generated two additional promising candidates, bringing the total number of energetically favorable structures to eleven. All candidates were re-optimized by ab initio calculations employing two functionals, GGA-PBE and LDA-PZ, and their chemical bonding was investigated. To assess the stability and mechanical properties of the predicted crystal structures and their behavior under extreme conditions, the E(V) and H(p) curves were computed on the ab initio level, the Born stability criteria were checked, and the bulk modulus, volume, total energy, and Gibbs free energy were calculated within a pressure range of up to 10 GPa
Machine learning-assisted luminescence thermometry using Mn5 + -doped near-infrared phosphor with improved accuracy and precision
No full textThis study provides a thorough investigation of machine learning-assisted luminescent thermometry using a Mn5+-doped Ca6Ba(PO4)4O phosphor. A novel, slightly modified Principal Component Analysis (PCA), where data normalization was observation-based rather than feature-based, was used to analyze near-infrared emission spectra collected over a temperature range of 293–373 K. This method showed significantly improved thermometric performance compared to traditional single-parameter and multiparametric approaches. Based on statistical analysis of cross-validation experimental data, the PCA-based method achieved exceptional average temperature resolution (δT = 0.135 K) and accuracy (ΔT = 0.077 K) across the entire temperature range, with even better performance in the physiological temperature range (δTphy = 0.074 K, ΔTphy = 0.032 K). This method utilizes full spectral data through dimensionality reduction, offering insights into the most thermometrically significant spectral regions while keeping the computation simple with basic mathematical operations. Compared to traditional thermometry techniques, which involve calculating emission band intensity ratios, finding spectral positions, and fitting emission decays, PCA-assisted thermometry greatly simplifies and speeds up the computational process, while also enhancing the accuracy and precision of temperature measurement
Advanced nanosystem for target recognition and precise dual-mode imaging-guided photothermal therapy against triple-negative breast cancer
No full textTriple-negative breast cancer (TNBC) presents significant diagnostic and therapeutic challenges due to the lack of targeted treatments, rapid progression, high recurrence and metastasis rates, and overall poorer prognosis. Herein, the targeted theranostic platform of cysteine-modified gold nanodots-sulfhydrated luteinizing hormone releasing hormone (CGN-SLR) nanosystem was designed for target recognition and precise dual-mode imaging-guided photothermal therapy (PTT) against TNBC. On the one hand, the CGN-SLR nanosystem can serve as an ideal targeting fluorescent probe and computed tomography (CT) enhancer to facilitate the accurate diagnosis and surgical guidance of TNBC. On the other hand, the CGN-SLR nanosystem with great targeting and PTT ability can significantly inhibit the growth of TNBC, without causing harm to normal tissues and healthy organs. It provides an effective strategy for the diagnosis and treatment of TNBC through the rational design of multifunctional nanoplatform with target recognition, multiple imaging guidance/monitoring, and high-efficiency PTT
Structural and optical properties of mixed phase WO3-ZnWO4 films synthesized from thermally oxidized metallic Zn–W films
No full textTungsten-bearing compounds have attracted significant interest in recent years, especially in thin films or nano powder form, due to their photocatalytic activity stemming from their wide band gap semiconductor properties. This study presents the synthesis of mixed phase WO3–ZnWO4 films synthesized by thermal oxidation of co-sputtered metallic Zn–W films. From XRD analysis it appeared that annealing at 600 °C leads to the formation of the monoclinic Zn-tungstate phase within the WO3 matrix with crystallite size about 50 nm for both phases. The XPS analysis of the O1s peak showed mixed phase compound of WO3 matrix with about 13 at.% of ZnWO4. Raman and infrared spectroscopy further characterize the structural features, revealing the WO6 octahedral unit as main building block in the structure. The optical band gap of the annealed film was found to be 3.34 eV, indicating a wide gap semiconductor. The films displayed a UV induced Photoluminescence with broad PL spectra with emission maximum at about 2.48 eV. The study demonstrates that co-sputtering and annealing at 600 °C approach is effective for synthesizing of tungstate phase ZnWO4 within WO3 matrix
Effects of 147 MeV Kr Ions on the Structural, Optical and Luminescent Properties of Gd3Ga5O12
No full textThe optical and vibrational responses of Gd3Ga5O12 (GGG) single crystals to 147 MeV Kr-ion irradiations were systematically investigated to clarify defect formation pathways and their influence on luminescence mechanisms. Absorption spectra measured at room temperature reveal a stepwise redshift of the fundamental edge and the progressive development of a broad sub-band-gap tail between 4.4 and 5.3 eV, indicating the accumulation of F- and F+-type oxygen-vacancy centers and increasing structural disorder. Raman spectroscopy shows that, despite substantial track overlap at fluences up to 1014 ions/cm2, the crystal preserves its phonon frequencies and linewidths, while peak intensities decrease due to a growing disordered volume fraction. Low-temperature (13 K) photoluminescence demonstrates the persistence of a dominant broad band near 2.4 eV and the emergence of an additional irradiation-induced band at ~2.75 eV whose width increases with fluence, reflecting the formation of vacancy-related defect complexes. Excitation spectra transform from band-edge-dominated behavior in the pristine crystal to defect-tail-mediated excitation in heavily irradiated samples. These results provide a consistent spectroscopic picture of ion-track-induced disorder in GGG and identify the defect states governing its luminescence under extreme irradiation conditions
Novel N-doped carbon/Co/Co3O4 ternary composites derived by direct carbonization of ZIF-67: Efficient electrocatalysts for oxygen reduction reaction
No full textCobalt-containing zeolitic imidazole framework ZIF-67 was synthesized in high yield, and directly carbonized by different heating routes at 800 and 900 °C. The products of carbonization, C(ZIF-67)s, were comprehensively characterized in terms of elemental composition (FAAS, EDX, XPS), crystalline (XRD) and molecular structure (FTIR and Raman spectroscopies), morphology (SEM), electrical conductivity, textural (N2 physisorption), and electrochemical properties. It was found that C(ZIF-67)s represent novel meso/microporous ternary composites of the type N-doped carbon/Co/Co3O4, containing metallic Co nanoparticles (NPs) with cubic body-centred crystalline structure, and predominately amorphous Co3O4. They exhibited high electrical conductivity (up to 4.2 S cm−1), notable BET specific surface area (197–265 cm2 g−1), and almost doubled mesopore volume compared to the parent ZIF-67. The effects of carbonization conditions on the structure, physico-chemical properties, and performance of C(ZIF-67)s as electrode materials in electrocatalysis of oxygen reduction reaction (ORR) and charge storage were studied. All C(ZIF-67) composites showed excellent ORR electrocatalytic activity in 0.1 M KOH, with four-electron reduction pathway. The highest ORR activity (the onset potential of −0.13 V vs. SCE) showed the composite produced by gradual heating up to 800 °C followed by holding at that temperature for 3 h. This is attributed to its highest mesopore volume, appropriate meso/micropore structure, high surface content of heteroatom-containing active sites (C–O–C, Co–N, Co–O), high surface Co2+/Co3+ ratio and the presence of Co NPs. The applied direct carbonization of ZIF-67, without additives and post-synthetic modifications, was shown as a simple way to produce meso/microporous electroconducting composites with high potential in energy related applications
Critical current density in advanced superconductors
No full textThis review paper delves into the concept of critical current density (Jc) in high-temperature superconductors (HTS) across macroscopic, mesoscopic, and microscopic perspectives. Through this exploration, a comprehensive range of connections is unveiled aiming to foster advancements in the physics, materials science, and the engineering of applied superconductors. Beginning with the macroscopic interpretation of Jc as a central material law, the review traces its development from C.P. Bean’s foundational work to modern extensions. Mesoscopic challenges in understanding vortex dynamics and their coherence with thermodynamic anisotropy regimes are addressed, underscoring the importance of understanding the limitations and corrections implicit in the macroscopic measurement of Jc, linked with mesoscopic phenomena such as irradiation effects, defect manipulation, and vortex interactions. The transition to supercritical current densities is also discussed, detailing the superconductor behaviour beyond critical thresholds with a focus on flux-flow instability regimes relevant to fault current limiters and fusion energy magnets. Enhancing Jc through tailored material microstructures, engineered pinning centers, grain boundary manipulation, and controlled doping is explored, along with radiation techniques and their impact on large-scale energy systems. Emphasizing the critical role of Jc, this review focuses on its physical optimization and engineering manipulation, highlighting its significance across diverse sectors
Integrated assessment of radiological and heavy metal(loid) hazards in soil at a remediated oil drilling site
No full textThis study investigated the heavy metal (loid) and radionuclide contamination in the soil at a remediated oil drilling site. Radionuclide activity concentrations were within acceptable levels, while elevated concentrations were detected for Cd, Hg, Zn, As, and Cu. Positive matrix factorization identified four distinct sources: oil drilling, remediation process, industrial activities, and natural sources. The radiological risk indices indicated no significant gamma radiation hazard, and non-carcinogenic and carcinogenic indices were within the acceptable levels. The spatial distribution maps of health risk indices followed the distribution pattern of the five heavy metal(loid)s, revealing a single hotspot
Triangular-ordered Co atoms activate substrates for ampere-level durable hydrogen production
No full textPractical electrolyzer-level hydrogen production, exemplified by alkaline anion exchange membrane (AEM) ones, typically operates at harsh conditions, e.g., high-current densities (> 1 A cm−2) and long-term duration, which present significant challenges for the durability of catalysts. These challenges are amplified in atomically dispersed catalysts due to their weak point-to-point interactions. Here, we present an atom-ordering strategy to fabricate Co triangular orders that enable the activation of the substrate for durable AEM electrolyzers. We demonstrate that Co atoms thermodynamically favor triangular arrangements within the VN lattice, which are successfully synthesized via a photo-induced self-assembly method. This Co-triangular order enables the activation of adjacent V atoms, driving the exponential propagation of active sites for hydrogen production under high currents. Notably, this catalyst exhibits an extended linear region in the Tafel slope and performs stably at a current density of 1 A cm–2. The assembled AEM water electrolyzer achieves a cell voltage of 1.97 V with long-term operational durability. Our work provides a strategy for designing atom-ordered catalysts that strike a balance between activity and long-term stability under industrial operating conditions