Jožef Stefan Institute
  • Ljubljana, Slovenia
Recent publications
Despite offering low-carbon and reliable energy, the utilization of nuclear energy is declining globally due to high upfront capital costs and longer returns on investments. Nuclear cogeneration of valuable chemicals from waste biomass-derived feedstocks could have beneficial impacts while harnessing the underutilized resource of ionizing energy. Here, we demonstrate selective methanol or acetaldehyde production from ethylene glycol, a feedstock derived from glycerol, a byproduct of biodiesel, using irradiations from a nuclear fission reactor. The influence of radiation quality, dose rate, and the absorbed dose of irradiations on radiochemical yields (G-value) has been studied. Under low-dose-rate, γ-only radiolysis during reactor shutdown rate (<0.018 kGy min–1), acetaldehyde is produced at a maximum G-value of 8.28 ± 1.05 μmol J–1 and a mass productivity of 0.73 ± 0.06% from the 20 kGy irradiation of neat ethylene glycol. When exposed to a high-dose-rate (6.5 kGy min–1), 100 kGy mixed-field of neutron + γ-ray radiations, the radiolytic selectivity is adjusted from acetaldehyde to generate methanol at a G-value of 2.91 ± 0.78 μmol J–1 and a mass productivity of 0.93 ± 0.23%. Notably, utilizing 422 theoretical systems could contribute to 4.96% of worldwide acetaldehyde production using a spent fuel pool γ-ray scheme. This research reports G-values and production capacities for acetaldehyde for high-dose scenarios and shows the potential selectivity of a nuclear cogeneration process to synthesize chemicals based on their irradiation conditions from the same reagent.
Water interaction with mineral surfaces is a complex living system decisive for any photocatalytic process. Resolving atomistic structure of mineral–water interfaces is thus crucial for understanding these processes. Fibrous rutile TiO 2 , grown hydrothermally on twinned rutile seeds under acidic conditions, was studied in terms of interface translation, atomic structure and surface chemistry in the presence of water, by means of advanced microscopy and spectroscopy methods combined with structure modeling and density functional theory calculations. We show that fibers while staying in stable separation during their growth, adopt special crystallographic registry that is controlled by repulsion forces between fully hydroxylated and protonated (110) surfaces. During relaxation, a turbulent proton transfer and cracking of O–H bonds is observed, generating a strong acidic character via proton jump from bridge –OH b to terminal –OH t groups, and spontaneous dissociation of interfacial water via a transient protonation of the –OH t groups. It is shown, that this specific interface structure can be implemented to induce acidic response in initially neutral medium, when re–immersed. To our knowledge this is the first demonstration of a 2D, quantum confined mineral–water interface, capable of memorizing its past and conveying its structurally encoded properties into a new environment. This article is protected by copyright. All rights reserved
Hyperaccumulators are a group of plant species that accumulate high concentrations of one or more metal(loid)s in their above-ground tissues without showing any signs of toxicity. Several hyperaccumulating species belong to the Brassicaceae family, among them the Cd and Zn hyperaccumulator Noccaea praecox . In this paper, we present de novo transcriptome assembled from two naturally occurring N. praecox populations growing in (i) metal-enriched soil and (ii) soil non-contaminated with metals (control site). Total RNA was extracted from the leaves of both populations. We obtained 801,935,101 reads, which were successfully assembled and annotated. The resulting assembly contains 135,323 transcripts, with 103,396 transcripts (76.4%) annotated with at least one function and encoding 53,142 putative proteins. Due to its close relationship with the hyperaccumulating model species N. cearulescens , it will be possible to derive protein functions from sequence comparisons with this species. Comparisons will highlight common and differing pathways of metal acquisition, storage, and detoxification which will allow us to expand our knowledge of these processes.
Background Optical coherence tomography angiography (OCTA) is an emerging imaging modality that enables noninvasive visualization and analysis of tumor vasculature. OCTA has been particularly useful in clinical ocular oncology, while in this article, we evaluated OCTA in assessing microvascular changes in clinical nonocular oncology through a systematic review of the literature. Method The inclusion criterion for the literature search in PubMed, Web of Science and Scopus electronic databases was the use of OCTA in nonocular clinical oncology, meaning that all ocular clinical studies and all ocular and nonocular animal, phantom, ex vivo, experimental, research and development, and purely methodological studies were excluded. Results Eleven articles met the inclusion criteria. The anatomic locations of the neoplasms in the selected articles were the gastrointestinal tract (2 articles), head and neck (1 article) and skin (8 articles). Conclusions While OCTA has shown great advancements in ophthalmology, its translation to the nonocular clinical oncology setting presents several limitations, with a lack of standardized protocols and interpretation guidelines posing the most significant challenge.
Objectives The aim of the present study was to establish the population- and laboratory-specific reference intervals (RIs) for the Slovenian adult population for 24 trace elements (TEs) in blood, plasma and erythrocytes and to evaluate the impact of gender, age, seafood consumption, smoking habits and amalgam fillings on TEs levels. Methods TEs (Mn, Co, Cu, Zn, Se and Mo, Li, Be, V, Cr, Ni, Ga, As, Rb, Sr, Ag, Cd, Sn, Cs, Au, Hg, Tl, Pb and U) were determined in 192 a priori selected blood donors (107 women and 85 men, aged 18–65 years), using inductively coupled plasma mass spectrometry (ICP-MS) with the Octopole Reaction System. Participants filled out a questionnaire, and RIs were established according to the Clinical and Laboratory Standards Institute (CLSI) guidelines for TEs. Results Uniform RIs for non-essential and gender-specific for essential TEs in blood, plasma and erythrocytes were established. In our population, higher blood and plasma Cu, and erythrocyte Mn levels in women were found. In men, blood Zn, plasma Zn, Mn and Se, and erythrocyte Cu levels were higher. Zn levels were higher in 30–39 years age group. Pb and Sr increased with age. Smoking positively affected Cd, Pb, Cs and Rb; seafood consumption increased As, Hg and Zn; and amalgam increased Hg, Ag and Cu levels. Conclusions Essential TEs were inside recommended levels, and the non-essential ones were far below critical levels. Established RIs will provide an important foundation for clinical diagnostics, safety erythrocyte transfusions assessment, toxicology and epidemiological studies.
When verifying the validity of the exponential-decay law through 137 precise decay rate measurement series at various nuclear laboratories, minor violations have been observed in the shape of annual cycles in the residuals with different amplitudes and phase shifts. The timing and amplitude of these deviations have been compared with local weather data and it appears that ambient humidity is highly correlated with the observed instabilities in these radioactivity measurements. In fact, when compensating the residuals for a linear relationship with absolute humidity in air, most of the annual cycles are no longer statistically significant. As a result, the validity of the exponential-decay law can now be demonstrated with even higher fidelity.
State-of-the-art approaches to extract transport coefficients of many-body quantum systems broadly fall into two categories: (i) they target the linear-response regime in terms of equilibrium correlation functions of the closed system; or (ii) they consider an open-system situation typically modeled by a Lindblad equation, where a nonequilibrium steady state emerges from driving the system at its boundaries. While quantitative agreement between (i) and (ii) has been found for selected model and parameter choices, also disagreement has been pointed out in the literature. Studying magnetization transport in the spin-1/2 XXZ chain, we here demonstrate that at weak driving, the nonequilibrium steady state in an open system, including its buildup in time, can remarkably be constructed just on the basis of correlation functions in the closed system. We numerically illustrate this direct correspondence of closed-system and open-system dynamics, and show that it allows the treatment of comparatively large open systems, usually only accessible to matrix product state simulations. We also point out potential pitfalls when extracting transport coefficients from nonequilibrium steady states in finite systems.
In this work, we propose a new crystal plasticity finite element model to simulate the mechanical behavior of austenitic stainless steel subjected to operational conditions typical for internal structures of light water reactors. In particular, we address the coupling of (i) hydrogen and (ii) irradiation defects (Frank loops) with mobile dislocations on microscale to study the emergence of irradiation hardening, plastic strain localization and embrittlement on macroscale. The constitutive equations accounting for neutron-irradiation and hydrogen-concentration effects are derived theoretically for the austenitic stainless-steel single crystals within the crystal plasticity framework. A crystalline lattice is equipped with two types of residing hydrogen atoms: normal interstitial lattice sites and trapping sites attributed to the gliding dislocations. Both hydrogen site concentrations are assumed to be in equilibrium during the mechanical loading. In this respect, the total deformation gradient tensor is multiplicatively decomposed into three distinct configurations: the elastic (volumetric), hydrogen (hydrostatic) and plastic (isochoric) parts. The combined effects of hydrogen concentration and irradiation damage are studied within a polycrystalline aggregate in a series of uniaxial tension simulations. The proposed model, based on dislocation dynamics inferred mechanisms, is able to capture the neutron-irradiation-induced hardening followed by softening due to the formation of defect-free channels on each slip plane during plastic deformation. The effect of hydrogen is manifested in a higher yield stress, due to activation of immobile dislocations, and in a reduced work hardening, in accordance with the increase of dislocation mobility observed experimentally. The overall softening response, accompanied with plastic strain localization, is predicted ”at smaller applied strains for higher neutron fluences and higher hydrogen concentrations” due to combined effects of clear channel formation and increased dislocation mobility. In this regime, the embrittlement is predicted for austenitic stainless steel.
Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1 T -TaS 2 upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Using a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden state are key for device applications at the nexus of electronics and photonics.
The next years will see the completion of several new facilities at Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali del Sud (LNS) opening up new possibilities in the fields of nuclear structure, nuclear dynamics, nuclear astrophysics and applications. These include a new line for high-intensity cyclotron beams, a new facility for in-flight production of radioactive ion beams, the PANDORA plasma trap for multidisciplinary studies and a high-power laser for basic science and applied physics. The nuclear physics community has organized a workshop to discuss the new physics opportunities that will be possible in the middle term (5–7 years) by employing state-of-the-art detection systems. A detailed discussion of the outcome from the workshop is presented in this report.
The European Association of National Metrology Institutes (EURAMET) within its research programme European Metrology Programme for Innovation and Research (EMPIR) funded project EMPIR 19NET03 supportBSS that contributes to the establishment of a European Metrology Network (EMN) for Radiation Protection (RP). The EMN-RP was established in September 2021 with the intent to work as a meeting point for the metrology community and all stakeholders in the field of ionising radiation regulation, thus providing quality assurance for measurements in each of the exposure situations contemplated in the European Legislation. Within project EMPIR 19NET03, work package 3 aims at the preparation of a Strategic Research Agenda (SRA) by identifying the metrology needs to support the European legislation and regulation in Radiation Protection and of two Roadmaps for metrology services, one under the European Council Directive 2013/59/EURATOM and the other under the EURATOM Treaty. Following a Gaps Workshop held in September 2020 and a second internal workshop that took place in April 2022, a questionnaire was prepared for distribution to the stakeholders, e.g. RP platforms and authorities, academia, industry, among other, together with an accompanying paper. In this paper, the authors present the state of the art of European legislation in RP, address the importance of metrology, the practices and activities that need metrology to meet the requirements set in the regulations, emphasise the need for quality assured measurements in all fields, highlight the stakeholders contributions in their specific area and show their vision of the EMN-RP.
This paper discusses the current status of the European research reactor (RR) fleet and identified opportunities for its utilization. The data for this analysis was collected through a specific questionnaire from which a database of the European RR fleet was created. The questionnaire was designed to assess the degree of exploitation of different RR applications and to identify gaps and opportunities for future utilization. The results indicate that the European RR fleet is older compared to the world average, with no new research reactors built in Europe since 1992. The majority of RRs reported low levels of exploitation across all applications, and a desire to expand utilization was expressed by 78% of respondents. Lack of manpower, finance, and customers were identified as the main obstacles preventing expansion, while the need for more nuclear engineers was identified as a clear opportunity to attract people to the field. The findings of this study emphasize the need for actions to be taken to combat future needs and to improve the utilization of the European RR fleet. Overall, this study provides valuable insights for policymakers, industry professionals, and researchers working in the field of nuclear energy.
The Cherenkov power meter developed at the Jožef Stefan Institute (JSI) is an independent, reliable and cost-effective measurement system based on Cherenkov radiation detection, used to measure fast power transients during pulse operation at the JSI TRIGA research reactor. It is based on a closed tube in order to avoid interference from external light sources and radiation damage experienced by optical fibers. The tube is placed in the reactor core periphery, the bottom part of the tube is filled with water, serving as the source of Cherenkov light. The measurements obtained in the framework of an extensive experimental campaign in collaboration with the French Atomic and Alternative Energy Commission (CEA) focused on reactor pulse operation using the Cherenkov power meter show excellent agreement with existing nuclear instrumentation (TRIGA pulse recorder), especially for high peak power pulses. However, the Cherenkov power meter outperforms the TRIGA pulse recorder in accurately recording low peak power pulses. The power vs. time behavior measured with the Cherenkov power meter is in accordance with measurements using miniature fission and ionization chambers developed at the CEA. The possibility of reactor pulse characterization based on measurements with the Cherenkov power meter combined with neutron dosimetry measurements sets the basis for enabling irradiation during pulse operation at JSI TRIGA research reactor in the future.
A closed-water activation loop is being built at the Jožef Stefan Institute TRIGA reactor in Slovenia to serve as a well-defined and stable source of high-energy gamma rays and neutrons. The radial piercing port, which penetrates the graphite reflector and touching the reactor core was chosen for the installation of the closed-water loop due to the high neutron flux and favourable shielding conditions of the surrounding concrete bioshield. The main objective of this work is to assess the neutron and gamma dose field outside the port to obtain important details for the final design of the inner part of the irradiation facility and to assess the background noise for the detectors. The main part of the work consists of the design of the shielding plugs and the construction of a detailed MCNP model of the whole irradiation facility. The dose field calculations were performed with a two-step hybrid transport approach using ADVANTG for variance reduction and MCNP for particle transport. Such deep penetration and shielding calculations are challenging and computationally intensive. The results showed that the dose rate using shielding plugs is more than 7 orders of magnitude lower compared to an empty open port. To reduce the computational uncertainty, further optimisation of the ADVANTG input is essential. The final design of the shielding plugs is described. Additional lead shielding blocks will be added outside the port afterwards if needed.
Three novel heterometallic Ni/Cd coordination compounds [Ni(en)3][CdCl4]∙3dmso (1), [Ni(en)2(dmf)2][CdBr4] (2), and [Ni(en)3]2[CdI4](I)2 (3) have been synthesized through the self-assembly process in a one-pot reaction of cadmium oxide, nickel salt (or nickel powder), NH4X (X = Cl, Br, I), and ethylenediamine in non-aqueous solvents dmso (for 1) or dmf (for 2 and 3). Formation of the one- (1) or three-dimensional (2 and 3) hydrogen-bonded frameworks has been observed depending on the nature of the [CdX4]²⁻ counter-anion, as well as on the nature of the solvent. The electronic structures of [Ni(en)3]²⁺ and [Ni(en)2(dmf)2]²⁺ cations were studied at the DFT and CASSCF levels, including the ab initio ligand field theory (AILFT) calculations. The non-covalent intermolecular contacts between the cationic nickel and anionic cadmium blocks in the solid state were investigated by the QTAIM analysis. The mechanism of ligand substitution at the nickel center in [Ni(en)2(dmf)2]²⁺ was theoretically investigated at the ωB97X-D4/ma-def2-TZVP//DLPNO-CCSD(T)/ma-def2-TZVPP level. The results demonstrate that thermodynamic factors are structure-determining ones due to low energy barriers of the rotation of dmf ligands in [Ni(en)2(dmf)2]²⁺ (below 3 kcal mol⁻¹) and the reversible transformation of [Ni(en)2(dmf)2]²⁺ into [Ni(en)3]²⁺ (below 20 kcal mol⁻¹).
Turbulent flow of two-phase fluids occurs in many industrial systems. One of the manifestations of the two-phase flow in a pipe is slug flow, which consist of large gas bubbles (i.e. Taylor bubbles) separated from each other by liquid slugs. We are particularly interested in the phenomena of coalescence and breakup in the slug flow regime and the development of numerical models for the Large Eddy Simulation (LES) method as they are still in early stages of development for two-phase flows [1].
Automatic genre identification (AGI) is a text classification task focused on genres, i.e., text categories defined by the author’s purpose, common function of the text, and the text’s conventional form. Obtaining genre information has been shown to be beneficial for a wide range of disciplines, including linguistics, corpus linguistics, computational linguistics, natural language processing, information retrieval and information security. Consequently, in the past 20 years, numerous researchers have collected genre datasets with the aim to develop an efficient genre classifier. However, their approaches to the definition of genre schemata, data collection and manual annotation vary substantially, resulting in significantly different datasets. As most AGI experiments are dataset-dependent, a sufficient understanding of the differences between the available genre datasets is of great importance for the researchers venturing into this area. In this paper, we present a detailed overview of different approaches to each of the steps of the AGI task, from the definition of the genre concept and the genre schema, to the dataset collection and annotation methods, and, finally, to machine learning strategies. Special focus is dedicated to the description of the most relevant genre schemata and datasets, and details on the availability of all of the datasets are provided. In addition, the paper presents the recent advances in machine learning approaches to automatic genre identification, and concludes with proposing the directions towards developing a stable multilingual genre classifier.
Objectives Erbium lasers have become an accepted tool for performing both ablative and non‐ablative medical procedures, especially when minimal invasiveness is desired. Hard‐tissue desiccation during Er:YAG laser procedures is a well‐known phenomenon in dentistry, the effect of which is to a certain degree being addressed by the accompanying cooling water spray. The desiccation of soft tissue has attracted much less attention due to the soft tissue's high‐water content, resulting in a smaller effect on the ablation process. Materials and methods In this study, the characteristics of skin temperature decay following irradiations with Er:YAG laser pulses were measured using a fast thermal camera. Results The measurements revealed a substantial increase in temperature decay times and resulting thermal exposure times following irradiations with Er:YAG pulses with fluences below the laser ablation threshold. Based on an analytical model where the skin surface cooling time is calculated from the estimated thickness of the heated superficial layer of the stratum corneum (SC), the observed phenomena is attributed to the accelerated evaporation of water from the SC's surface. By using an Arrhenius damage integral‐based variable heat shock model to describe the dependence of the critical temperature on the duration of thermal exposure, it is shown that contrary to what an inexperienced practitioner might expect, the low‐to‐medium level fluences may result in a larger thermal damage in comparison to treatments where higher fluences are used. This effect may be alleviated by hydrating the skin before Er:YAG treatments. Conclusion Our study indicates that tissue desiccation may play a more important role than expected for soft‐tissue procedures. It is proposed that its effect may be alleviated by hydrating the skin before Er:YAG treatments.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
964 members
Boris Turk
  • Department of Biochemistry, Molecular and Structural Biology
Eva Zerovnik
  • Department of Biochemistry, Molecular and Structural Biology
Matjaz Gams
  • Department of Intelligent Systems
Jamova 39, 1000, Ljubljana, Slovenia
Head of institution
Prof. dr. Boštjan Zalar