National Centre of Scientific Research "Demokritos"

Panagopoulos V., Sigalos A., Anyfantis D.I., Niarchos D.

Fe2P (iron phosphide) alloys have garnered significant interest in recent years due to their potential applications in permanent magnet materials, particularly in the context of energy-efficient and environmentally friendly technologies. We have sought to tailor the magnetic properties, such as magnetization, coercivity, and Curie temperature, to meet the specific requirements of rare-earth-free permanent magnets for various industrial sectors. In this work, we review recent advancements in the exploration of substitutions (Si, Co, Mn, and Ni) within Fe2P alloys aimed at enhancing their magnetic performance as candidates for permanent magnets. The X-ray patterns of (Fe,Co)2P show great crystallinity with a pure Fe2P phase even with Mn and Ni substitutions. The Fe2P structure crystallizes in the P-62m space group. It has been confirmed that the transition metals substitute the 3g Fe-site, sometimes with adverse effects regarding magnetic properties with Co vs. Ni substitution, and that Si substitutes the 2c P-site. The saturation magnetization increases (MS=87 Am2/kg) with Mn substitution, while the Curie temperature decreases with these substitutions. The impact of various substitutional elements on the magnetic properties of Fe2P alloys is highlighted, and challenges encountered in this field are reported.

Kanellopoulos P., Nock B.A., Krenning E.P., Maina T.

Background/Objectives: Radiotheranostics of neurotensin subtype 1 receptor (NTS1R)-expressing tumors, like pancreatic, gastrointestinal, or prostate cancer, has attracted considerable attention in recent years. Still, the fast degradation of neurotensin (NT)-based radioligands, by angiotensin-converting enzyme (ACE), neprilysin (NEP), and other proteases, has considerably compromised their efficacy. The recently introduced [99mTc]Tc-DT11 (DT11, N4-Lys(MPBA-PEG4)-Arg-Arg-Pro-Tyr-Ile-Leu-OH; N4, 6-(carboxy)-1,4,8,11-tetraazaundecane) has displayed promising uptake in NTS1R-positive tumors in mice and enhanced resistance to both ACE and NEP by virtue of the lateral MPBA-PEG4 (MPBA, 4-(4-methylphenyl)butyric acid; PEG4, 14-amino-3,6,9,12-tetraoxatetradecan-1-oic acid) chain attached to the ε-NH2 of Lys7. We were next interested in investigating whether these qualities could be retained in DT14D, likewise modified at Lys7 but carrying the universal chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) via a (βAla)3 spacer at the α-NH2 of Lys7. This chelator switch enables the labeling of DT14D with a wide range of trivalent radiometals suitable for true theranostic applications, not restricted to the diagnostic imaging of NTS1R-positive lesions only by single-photon emission computed tomography (SPECT). Methods: DT14D was labeled with Ga-67 (a surrogate for the positron emission tomography radionuclide Ga-68), In-111 (for SPECT), and Lu-177 (applied in radiotherapy). The resulting radioligands were tested in NTS1R-expressing pancreatic cancer AsPC-1 cells and mice models. Results: [67Ga]Ga/[111In]In/[177Lu]Lu-DT14D displayed high affinity for human NTS1R and internalization in AsPC-1 cells. They remained >70% intact 5 min after entering the mice’s circulation, displaying NTS1R-specific uptake in AsPC-1 xenografts. Conclusions: Suitably side-chain modified NT analogs show enhanced metabolic stability and hence better prospects for radiotheranostic application in NTS1R-positive cancer.

Provata A., Almirantis Y., Li W.

Chimera states and bump states are collective synchronization phenomena observed independently (in different parameter regions) in networks of coupled nonlinear oscillators. And while chimera states are characterized by coexistence of coherent and incoherent domains, bump states consist of alternating active and inactive domains. The idea of multistable plasticity in the network connections originates from brain dynamics where the strength of the synapses (axons) connecting the network nodes (neurons) may change dynamically in time; when reaching the steady state the network connections may be found in one of many possible values depending on various factors, such as local connectivity, influence of neighboring cells etc. The sign of the link weights is also a significant factor in the network dynamics: positive weights are characterized as excitatory connections and negative ones as inhibitory. In the present study we consider the simplest case of bistable plasticity, where the link dynamics has only two fixed points. During the system/network integration, the link weights change and as a consequence the network organizes in excitatory or inhibitory domains characterized by different synaptic strengths. We specifically explore the influence of bistable plasticity on collective synchronization states and we numerically demonstrate that the dynamics of the linking may, under special conditions, give rise to co-existence of bump-like and chimera-like states simultaneously in the network. In the case of bump and chimera co-existence, confinement effects appear: the different domains stay localized and do not travel around the network. Memory effects are also reported in the sense that the final spatial arrangement of the coupling strengths reflects some of the local properties of the initial link distribution. For the quantification of the system’s spatial and temporal features, the global and local entropy functions are employed as measures of the network organization, while the average firing rates account for the network evolution and dynamics. In particular, the spatial minima of the local entropy designate the transition points between domains of different synaptic weights in the hybrid states, while the number of minima corresponds to the number of different domains. In addition, the entropy deviations signify the presence of chimera-like or bump-like states in the network.

Falara P.P., Chatzikonstantinou N., Zourou A., Tsipas P., Sakellis E., Alexandratou E., Nasikas N.K., Kordatos K.V., Antoniadou M.

CDs/TiO2 nanohybrids were synthesized and tested for photocatalytic H2 production from aqueous media through simulated solar light-driven photocatalytic reactions. Firstly, three different types of CDs were prepared through green methods, specifically hydrothermal treatment and microwave irradiation, using citric acid and urea as precursors in varying molar ratios. After a multi-step purification procedure, impurity-free CDs were obtained. The as-synthesized CDs were thoroughly characterized using UV-Vis, FT-IR, and PL spectroscopy, along with HR-TEM. The results revealed that the size and optical and physicochemical properties of CDs can be tailored by selecting the precursors’ ratio and the synthetic approach. The heterostructured CDs/TiO2 photocatalysts were formed solvothermally and were analyzed using UV-Vis/DRS, FT-IR, and XPS techniques, which confirmed the effective incorporation of CDs and the improved properties of TiO2. The use of sacrificial reagents is among the most common strategies for enhancing H2 production from water through photocatalytic processes; herein, ethanol was selected as a green liquid organic hydrogen carrier. A maximum H2 production rate of 0.906 μmol H2/min was achieved, while the recyclability study demonstrated that the photocatalyst maintained stable performance during multiple cycles of reuse. Thus, optimizing the synthesis conditions of CDs/TiO2 nanohybrids resulted in the creation of environmentally friendly and reusable photocatalysts.

Rentoumi V., Vassiliou E., Pittaras N., Demiraj A., Papageorgiou M., Sali D., Papatriantafyllou A., Griziotis P., Chardouveli A., Pattakos K., Paliouras G.

Background Most common forms of dementia, including Alzheimer's disease, are associated with alterations in spoken language. Objective This study explores the potential of a speech-based machine learning (ML) approach in estimating cognitive impairment, using inputs of speech audio recordings. Methods We develop an automatic ML pipeline that ingests multimodal inputs of audio and transcribed text, mapping speech and language to domain-specific biomarkers optimized for high explainability and predictive ability. The resulting features are fed through a multi-stage pipeline to determine efficient classification configurations. Results We evaluated the system on large real-world datasets, achieving above 90% and 70% weighted average F1 scores for two-class (AD versus normal controls) and three-class (AD versus mild cognitive impairment versus normal controls) classification tasks, respectively. Model performance remains stable across different population characteristics. Conclusions The study introduces a robust, non-invasive method for gauging the cognitive status of AD and MCI patients from speech samples, with the potential of generalizing effectively to multiple types of diseases/disorders which may burden language.

Bompotis T., Karastergiou E., Giannakopoulos K., Favvas E., Arvanitopoulou M., Arvanitopoulos L., Arvanitopoulos K., Kytherioti G., Vardavoulias M., Giannakoudakis D., Castellsagués L., Soto González S.M., Arkas M.

AbstractThe hydrophilic character and the protection against pathogen proliferation are the most pivotal characteristics of leathers intended for medical purposes. To achieve these goals, dispersions of TiO2 particles incorporating three different formulations of biomimetically synthesized silica xerogels were tested. Emphasis has been given to the role of single and dual solvents employed. Microbiocide capability was induced by benzalkonium chloride along with silver nanoparticles. Particular emphasis should be given to hyperbranched poly(ethylene imine) multifunctional roles. Spontaneous mineralization of silver ions is realized in the dendritic cavities. The same polymer acts as a matrix that interacts with the hydrogen bonding network of orthosilicic acid directing and facilitating gel formation. Furthermore, it contributes to both hydrophilicity and antimicrobial properties. Gel formation and subsequent drying occur in the pores of the impregnated TiO2 substrate. The resistance of the leathers to fungal and bacterial infections and biofilm formation was assessed against Klebsiella Pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. The affinity to water was proved by the contact angle method. The proposed treatment is a prospective environmentally friendly replacement to the standard finishing process of medical leathers.

Kanellopoulou D., Giannakopoulos G., Terlixidis P., Karkaletsis V.

The Smart Attica European Digital Innovation Hub constitutes a driver of innovation with Artificial Intelligence (AI) in Greece by bridging the adoption gap encountered by businesses and public organisations in the country. Treating AI as a cross-sector (horizontal) enabler for a wide range of state-of-the-art services, this paper explores the hub’s value proposition and emphasises the key success factors for ensuring the sustainability of AI adoption efforts. Moreover, the paper introduces a novel holistic approach to the design of AI-powered innovation projects, aiming to enhance impact and cost efficiency. Each such project involves multiple service providers and targets a wide range of beneficiaries. The initial results of this approach are showcased through the hub’s initiative to improve resilience in the face of natural disasters by combining the mobilisation of organisations and society as a whole with technological providers, as a response to recent crises experienced in the country. This established a methodology which is now adopted by the Greek State.

Ketikis P., Syrmos A., Klonos P.A., Pilatos G., Giannakopoulou T., Kyritsis A., Trapalis C., Tarantili P.A.

In this study, composites of hydroxyl-terminated polydimethylsiloxane (PDMS) reinforced with multiwall carbon nanotubes (MWCNTs) were prepared using solution mixing assisted by sonication. The vulcanization behavior of PDMS was investigated using modulated temperature DSC, revealing a decrease in the reaction rate at higher MWCNT loadings. The prepared nanocomposites were characterized for their thermomechanical and dielectric properties, as well as for oxygen permeability and electromagnetic interference shielding effectiveness (EMI SE). Thermogravimetric Analysis (TGA) showed that thermal degradation of the specimens began at lower temperatures and ended at higher temperatures compared to pure PDMS. Enhancements in tensile strength and Young’s modulus were also recorded, particularly at higher filler concentrations. Swelling after immersion in toluene was lower for all MWCNT/PDMS composites compared to pure PDMS. Notably, membranes made from MWCNT/PDMS composites demonstrated a significant decrease in O2 permeability. Dielectric Relaxation Spectroscopy (DRS) revealed that the percolation threshold was reached at a low CNT content of 0.036 phr. The Electromagnetic interference (EMI) Shielding Effectiveness (SE) of the prepared MWCNT/PDMS membranes -recorded in the X-band- was strongly dependent on the CNTs loading. Membranes with thickness of ∼1.1 mm exhibited SE values of 5 and 17 dB, for loadings of 0.5 and 4.0 phr, respectively. Based on these results, it is concluded that MWCNTs/PDMS composites prepared via solution mixing demonstrate improvement in their performance in many critical properties, even at very low reinforcement levels.

Aad G., Aakvaag E., Abbott B., Abdelhameed S., Abeling K., Abicht N. ., Abidi S. ., Aboelela M., Aboulhorma A., Abramowicz H., Abreu H., Abulaiti Y., Acharya B. ., Ackermann A., Adam Bourdarios C., et. al.

This Letter presents a search for highly ionizing magnetic monopoles in 262  μb−1 of ultraperipheral Pb+Pb collision data at sNN=5.36  TeV collected by the ATLAS detector at the LHC. A new methodology that exploits the properties of clusters of hits reconstructed in the innermost silicon detector layers is introduced to study highly ionizing particles in heavy-ion data. No significant excess above the background, which is estimated using a data-driven technique, is observed. Using a nonperturbative semiclassical model, upper limits at 95% confidence level are set on the cross section for pair production of monopoles with a single Dirac magnetic charge in the mass range of 20–150 GeV. Depending on the model, monopoles with a single Dirac magnetic charge and mass below 80–120 GeV are excluded. © 2025 CERN, for the ATLAS Collaboration 2025 CERN

Aad G., Aakvaag E., Abbott B., Abdelhameed S., Abeling K., Abicht N. ., Abidi S. ., Aboelela M., Aboulhorma A., Abramowicz H., Abulaiti Y., Acharya B. ., Ackermann A., Adam Bourdarios C., Adamczyk L., et. al.

A search for the production of three Higgs bosons (HHH) in the bb¯bb¯bb¯ final state is presented. The search uses 126  fb−1 of proton-proton collision data at s=13  TeV collected with the ATLAS detector at the Large Hadron Collider. The analysis targets both nonresonant and resonant production of HHH. The resonant interpretations primarily consider a cascade decay topology of X→SH→HHH with masses of the new scalars X and S up to 1.5 and 1 TeV, respectively. In addition to scenarios where S is off-shell, the nonresonant interpretation includes a search for Standard Model HHH production, with limits on the trilinear and quartic Higgs self-coupling set. No evidence for HHH production is observed. An upper limit of 59 fb is set, at the 95% confidence level, on the cross section for Standard Model HHH production. © 2025 CERN, for the ATLAS Collaboration 2025 CERN

Asvos X., El Mubarak M.A., Karampelas T., Rampias T., Tamvakopoulos C., Sivolapenko G.B., Papakyriakou A., Topouzis S., Vassilatis D.K., Fokas D.

Aad G., Aakvaag E., Abbott B., Abdelhameed S., Abeling K., Abicht N.J., Abidi S.H., Aboelela M., Aboulhorma A., Abramowicz H., Abreu H., Abulaiti Y., Acharya B.S., Ackermann A., Adam Bourdarios C., et. al.

Abstract A search for the production of a Higgs boson and one or more charm quarks, in which the Higgs boson decays into a photon pair, is presented. This search uses proton-proton collision data with a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV and an integrated luminosity of 140 fb −1 recorded by the ATLAS detector at the Large Hadron Collider. The analysis relies on the identification of charm-quark-containing jets, and adopts an approach based on Gaussian process regression to model the non-resonant di-photon background. The observed (expected, assuming the Standard Model signal) upper limit at the 95% confidence level on the cross-section for producing a Higgs boson and at least one charm-quark-containing jet that passes a fiducial selection is found to be 10.6 pb (8.8 pb). The observed (expected) measured cross-section for this process is 5.3 ± 3.2 pb (2.9 ± 3.1 pb).

Tumasyan A., Adam W., Andrejkovic J.W., Bergauer T., Chatterjee S., Damanakis K., Dragicevic M., Escalante Del Valle A., Frühwirth R., Jeitler M., Krammer N., Lechner L., Liko D., Mikulec I., Paulitsch P., et. al.

Abstract A search is presented for the resonant production of a pair of standard model-like Higgs bosons using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb −1. The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where at least one of the pairs is highly Lorentz-boosted and is reconstructed as a single large-area jet. The other pair may be either similarly merged or resolved, the latter reconstructed using two b-tagged jets. The data are found to be consistent with standard model processes and are interpreted as 95% confidence level upper limits on the product of the cross sections and the branching fractions of the spin-0 radion and the spin-2 bulk graviton that arise in warped extradimensional models. The limits set are in the range 9.74–0.29 fb and 4.94–0.19 fb for a narrow radion and a graviton, respectively, with masses between 1 and 3 TeV. For a radion and for a bulk graviton with widths 10% of their masses, the limits are in the range 12.5–0.35 fb and 8.23–0.23 fb, respectively, for the same masses. These limits result in the exclusion of a narrow-width graviton with a mass below 1.2 TeV, and of narrow and 10%-width radions with masses below 2.6, and 2.9 TeV, respectively.

Vaso A., Tegkelidi E., Kaloudi A.S., Gournis D.P., Tzitzios V., Boukos N., Kolokithas Ntoukas A., Georgakilas V.I.

Hayrapetyan A., Tumasyan A., Adam W., Andrejkovic J.W., Bergauer T., Chatterjee S., Damanakis K., Dragicevic M., Hussain P.S., Jeitler M., Krammer N., Li A., Liko D., Mikulec I., Schieck J., et. al.

Abstract A search for long-lived heavy neutral leptons (HNLs) using proton-proton collision data corresponding to an integrated luminosity of 138 fb −1 collected at $$ \sqrt{s} $$ s = 13 TeV with the CMS detector at the CERN LHC is presented. Events are selected with a charged lepton originating from the primary vertex associated with the proton-proton interaction, as well as a second charged lepton and a hadronic jet associated with a secondary vertex that corresponds to the semileptonic decay of a long-lived HNL. No excess of events above the standard model expectation is observed. Exclusion limits at 95% confidence level are evaluated for HNLs that mix with electron and/or muon neutrinos. Limits are presented in the mass range of 1–16.5 GeV, with excluded square mixing parameter values reaching as low as 2 × 10 −7. For masses above 11 GeV, the presented limits exceed all previous results in the semileptonic decay channel, and for some of the considered scenarios are the strongest to date.