Publications by Year: 2025

We perform a theoretical investigation of the electron–surface optical phonon (SOP) interaction in Van der Waals heterostructures (vdWHs) formed by monolayer graphene (1LG) and transition metal dichalcogenides (TMDCs), using eigenenergies obtained from the tight-binding Hamiltonian for electrons. Our analysis reveals that the SOP interaction strength strongly depends on the specific TMDC material. TMDC layers generate localized SOP modes near the 1LG/TMDC interface, serving as effective scattering centers for graphene carriers through long-range Fröhlich coupling. This interaction leads to resonant coupling of electronic sub-levels with SOP, resulting in Rabi splitting of the electronon energy levels. We further explore the influence of different TMDCs, such as WS2, WSe2, MoS2, and MoSe2, on transport properties such as SOP-limited mobility, resistivity, conductivity, and scattering rates across various temperatures and charge carrier densities. Our analysis confirms that at elevated temperatures and low carrier densities, surface optical phonon scattering becomes a dominant factor in determining resistivity. Additionally, we investigate the Auger recombination process at the 1LG/TMDC interface, showing that both Auger and SOP scattering rates increase significantly at room temperature and higher, ultimately converging to constant values as the temperature rises. In contrast, their impact is minimal at lower temperatures. These results highlight the potential of 1LG/TMDC-based vdWHs for controlling key processes, such as SOP interactions and Auger recombination, paving the way for high-performance nanoelectronic and optoelectronic devices.

Heterojunction formation between BiVO4 nanomaterials and benchmark semiconductor photocatalysts has been keenly pursued as a promising approach to improve charge transport and charge separation via interfacial electron transfer for the photoelectrocatalytic degradation of recalcitrant pharmaceutical pollutants. In this work, a heterostructured TiO2/Mo-BiVO4 bilayer photoanode was fabricated by the deposition of a mesoporous TiO2 overlayer using the benchmark P25 titania catalyst on top of Mo-doped BiVO4 inverse opal films as the supporting layer, which intrinsically absorbs visible light below 490 nm, while offering improved charge transport. A porous P25/Mo-BiVO4 bilayer structure was produced from the densification of the inverse opal underlayer after post-thermal annealing, which was evaluated on photocurrent generation in aqueous electrolyte and the photoelectrocatalytic degradation of the refractory anti-inflammatory drug ibuprofen under back-side illumination by visible and UV–Vis light. Significantly enhanced photoelectrochemical performance on both photocurrent density and pharmaceutical degradation was achieved for the bilayer structure with respect to the additive effect of the constituent layers, which was related to the improved light harvesting arising from the backscattering by the mesoporous TiO2 layer in combination with the favorable charge transfer at the TiO2/Mo-BiVO4 interface.

A new giant outburst of the Be X-ray binary RX J0520.5-6932 was detected and subsequently observed with several space-borne and ground-based instruments. This study presents a comprehensive analysis of the optical and X-ray data, focusing on the spectral and timing characteristics of selected X-ray observations. A joint fit of spectra from simultaneous observations performed by the X-ray telescope (XRT) on the Neil Gehrels Swift Observatory (Swift) and Nuclear Spectroscopic Telescope ARray (NuSTAR) provides broad-band parameter constraints, including a cyclotron resonant scattering feature (CRSF) at $32.2_{-0.7}^{+0.8}$ keV with no significant energy change since 2014, and a weaker Fe line. Independent spectral analyses of observations by the Lobster Eye Imager for Astronomy, Einstein Probe (EP), Swift-XRT, and NuSTAR demonstrate the consistency of parameters across different bands. Luminosity variations during the current outburst were tracked. The light curve of the Optical Gravitational Lensing Experiment (OGLE) aligns with the X-ray data in both 2014 and 2024. Spin evolution over 10 yr is studied after adding Fermi Gamma-ray Burst Monitor data, improving the orbital parameters, with an estimated orbital period of 24.39 d, slightly differing from OGLE data. Despite intrinsic spin-up during outbursts, a spin-down of $\sim$0.04 s over 10.3 yr is suggested. For the new outburst, the pulse profiles indicate a complicated energy-dependent shape, with decreases around 15 and 25 keV in the pulsed fraction, a first for an extragalactic source. Phase-resolved NuSTAR data indicate variations in parameters such as flux, photon index, and CRSF energy with rotation phase.

Τhe idea that social influences and social interactions play a central role on individual economic decisions has had a long presence in the history of economics. With the emergence of marginalism, this idea went into background and the concept of atomistic individual became established in mainstream economic rationality. Starting in the 1970’s, there were some attempts to reintroduce non-atomistic preferences in mainstream microeconomic theory in the form of social interactions, interdependent preferences, keeping up with the Joneses, social identity, social preferences, and status concerns. Social preferences have started to have a growing impact among mainstream microeconomics with the advent of behavioral economics, but still they are not in the hard core of the standard theory of choice. The paper argues that atomistic preferences are still prevalent, especially in the form of the assumption of representative agent. It also focuses on the role of methodological individualism and on the theoretical implications of relaxing the assumption of atomistic individual, as main explanations of the resilience of the mainstream economic rationality.

The accurate representation of mixed-phase monsoon clouds and their phase distribution is of great importance for numerical models used to predict monsoon rainfall. Therefore, it is essential for these models to correctly capture the phase fraction of clouds, which includes the proportions of liquid and ice. Ice particle formation in clouds occurs through primary ice production and secondary ice production (SIP). Most weather and climate models tend to overlook secondary SIP mechanisms, often only including rime-splintering. This oversight can introduce biases in the phase partitioning of mixed-phase clouds and monsoon rainfall predictions. In this study, we investigate the roles of three major SIP mechanisms: Hallett-Mossop (HM), droplet shattering (DS), and ice-ice collision (IIC) in mixed-phase monsoon clouds. This investigation is the first of its kind and was conducted using high-resolution simulations of mixed-phase convective clouds observed during the fourth phase of the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) over a rain shadow region of India. The default cloud microphysical scheme, which originally included only the HM process, was modified to incorporate additional SIP mechanisms such as DS and IIC. The simulated cloud parameters, including liquid and ice water content and ice number concentration, showed good agreement with airborne measurements. Our findings indicate that IIC is the predominant SIP mechanism, contributing 90 % to the total ice production through SIP. The inclusion of the three SIP mechanisms resulted in an enhancement of ice concentration by three to four orders of magnitude at temperatures warmer than -20 °C. SIP significantly influenced various cloud parameters between 0 to −20 °C, including total ice number concentration, ice crystal mass, rimed mass, liquid water content, and phase fraction. It also influenced the Ice Water Path (IWP), Liquid Water Path (LWP), and cloud top temperature. The rates of several mixed-phase processes were also affected by the SIP mechanisms. Overall, SIP led to a 15 % reduction in accumulated surface precipitation.

Flash floods have been the cause of some of the most devastating events worldwide. The wide diversity of the effects, as well as the variety in the severity of the impacts, lead to major obstacles in obtaining a realistic understanding of the damages caused by a flood event, thus hampering at the same time our ability to predict future impacts. In assessing flood impacts and their severity, most existing methods use a qualitative characterization (e.g., major, catastrophic, etc.) or view the impacts from a single viewpoint or discipline (e.g., economic losses). In this study, we apply the Flash Flood Impact Severity Scale (FFISS) to assess, map, and classify the impacts of two flash floods from the Lilas River in Greece in 2009 and 2020. This application aims to discuss the different severity levels in terms of how one flood can affect the impacts of the next event. The methodology encompasses comprehensive field research, including the collection of ground-based and aerial observations utilizing UAV technology to document the impacts. These observations are subsequently georeferenced, followed by application of the Flash Flood Impact Severity Scale (FFISS) and generation of detailed maps to assess and evaluate the severity of the impacts associated with the two flood events. The results show that despite the higher water stage of the second flood, the impacts in previously hit areas indicate lower severity values, attributed to the gradual adaptation of the community and its infrastructure, as well as significant local widening of the river channel. On the contrary, high severity remains an issue in newly flooded areas during the second event. Overall, the application of the FFISS can show the spatial patterns of severity impacts, providing insights into the nature of floods locally but also indicating a potential reduction in the overall risk in the post-flood period.

Given the critical role of zeroing neural networks (ZNN) in various fields and the practical demand for models in effectively resisting real-time noise, this study introduces a novel anti-noise integral zeroing neural network (AN-IZNN) model alongside its enhanced counterpart (EAN-IZNN), for the applications of matrix problem solving. Theoretical analysis demonstrates their ability to achieve convergence even under different noise conditions. Both theoretical analyses and simulation validations highlight the superior performance of the proposed models over existing neural network models. Notably, the root mean square error of the proposed AN-IZNN and EAN-IZNN models is reduced by 92.6249% and 91.4178%, respectively, compared to scenarios without the proposed method, demonstrating the effectiveness of the solution.

Abstract Ocean water clarity, influenced by marine chlorophyll concentration, significantly alters the distribution of shortwave radiation in the water column. This work aims to assess the effects of varying chlorophyll on the upper-ocean physical properties and their subsequent impact on the atmosphere, using a coupled ocean-atmosphere regional model for the Mediterranean and Black Seas. We performed 11-year (2011–2021) twin-simulation experiments based on different chlorophyll concentrations to estimate the penetration of solar radiation in the ocean. The first simulation used a monthly climatology field of chlorophyll concentrations derived from satellite observations, while in the second experiment, the chlorophyll concentration was kept constant at 0.05 mgm−3 \$\mathrm{m}\mathrm{g}\ {\mathrm{m}}^{-3}\$, representing clear water conditions. Results show that radiative heating driven by chlorophyll amplifies the seasonal cycle of temperature in the upper layers, leading to increased surface warming in summer and surface cooling in winter. Also, higher surface chlorophyll contributes to cooling in subsurface layers throughout the year due to its shading effect. The temperature response to chlorophyll variations is controlled by the mixed layer depth and a balance between (a) direct near-surface radiative heating due to the chlorophyll absorption and (b) indirect cooling resulting from vertical turbulent mixing processes with subsurface waters. The atmosphere moderates the seasonal sea surface temperature (SST) response caused by chlorophyll differential heating primarily through changes in latent heat flux. Ultimately, our simulations suggest that increased surface chlorophyll concentrations enhance the Mediterranean overturning circulation, highlighting the necessity of incorporating realistic optical forcing into regional climate modeling studies.

Metalloporphyrins on interfaces offer a rich playground for functional materials and hence have been subjected to intense scrutiny over the past decades. As the same porphyrin macrocycle on the same surface may exhibit vastly different physicochemical properties depending on the metal center and its substituents, it is vital to have a thorough structural and chemical characterization of such systems. Here, we explore the distinctions arising from coverage and macrocycle substituents on the closely related ruthenium octaethyl porphyrin and ruthenium tetrabenzo porphyrin on Ag(111). Our investigation employs a multitechnique approach in ultrahigh vacuum, combining scanning tunneling microscopy, low-energy electron diffraction, photoelectron spectroscopy, normal incidence X-ray standing wave, and near-edge X-ray absorption fine structure, supported by density functional theory. This methodology allows for a thorough examination of the nuanced differences in the self-assembly, substrate modification, molecular conformation and adsorption height.Metalloporphyrins on interfaces offer a rich playground for functional materials and hence have been subjected to intense scrutiny over the past decades. As the same porphyrin macrocycle on the same surface may exhibit vastly different physicochemical properties depending on the metal center and its substituents, it is vital to have a thorough structural and chemical characterization of such systems. Here, we explore the distinctions arising from coverage and macrocycle substituents on the closely related ruthenium octaethyl porphyrin and ruthenium tetrabenzo porphyrin on Ag(111). Our investigation employs a multitechnique approach in ultrahigh vacuum, combining scanning tunneling microscopy, low-energy electron diffraction, photoelectron spectroscopy, normal incidence X-ray standing wave, and near-edge X-ray absorption fine structure, supported by density functional theory. This methodology allows for a thorough examination of the nuanced differences in the self-assembly, substrate modification, molecular conformation and adsorption height.

The main objective of modern organizations is to acquire a long-term competitive advantage, so that they may cope with the requirements of organizations' complex and unstable environment. In this context, several companies try to transform themselves into Learning Organizations. The aim of this paper is to  reveal whether the awarded companies in Greece, in terms of working environment, provide learning opportunities to their employees within their working environment.  The quantitative method was employed, and a reliable questionnaire was filled by 80 employees, who work for an awarded company as one of the best companies in Greece, by a certified international organization called "Great Place to Work", DLOQ-Dimensions of the Organization Learning Questionnaire with 55 items, was selected as a valid and reliable instrument, in order to evaluate the dimensions of organizational learning and organizational performance. The findings of the current research, indicate that the company under study, has the characteristics of a Learning Organization and that the adoption of the seven dimensions of the Learning Organization has a positive impact on organizational performance. According to the study results, the subject company, identifies the importance of developing a learning culture in order to increase its performance and due to this fact, it takes all actions required for the development and training of human resources, so that it may reach its objectives.

A Bay of Biscay model configuration is used as a test case to assess the data-based consistency of ensemble-based ocean model uncertainties of several types: [A] built-in stochastic parameterizations at regional ocean scales, [B] ocean model response to a global atmospheric model ensemble and [C] both A and B simultaneously. Ensembles of varying length were generated. In addition to a seasonal-range ensemble, three medium-range ensembles were carried out over successive overlapping segments permitting to compare consistency metrics for different lead times. The largest spread was obtained for the C case, although most of the model uncertainties were attributable to the stochastic ocean parameterizations in A. We addressed the question of which ensemble type and lead time was able to provide the most realistic model uncertainties given observations of SST, sea level, and Chlorophyll a, using a theoretical and diagnostic consistency analysis framework expanded from Vervatis et al. (2021a). In our results, consistency was satisfactory for the stochastic ensembles of types A and C, for the “aged” error cases (but only marginally with respect to the “young” error cases), and whenever physical and biogeochemical uncertainty processes were active in the region and could be detected by the observational networks, such as the onset of the spring shoaling of the thermocline and the phytoplankton abundance primary bloom. Sea level empirical consistency was improved when a wide range of low- to high-frequency errors were included in the signal of dynamic atmospheric process in the data and in the model inverse barometer. These findings provide additional insight that can help configure ensemble-based methods in academic studies and in operational ocean forecasting systems.

The macrocyclic biquinazoline ligand, H-Mabiq, presents a central and a peripheral site for the coordination of metal ions, making the adsorption on solid surfaces promising for the creation of self-assembled bimetallic two-dimensional platforms. Here, we apply an on-surface metalation strategy under ultra-high vacuum conditions to guide the synthesis of metalated species and study sequential metalation patterns. We find that cobalt (as well as iron) metalation on the Ag(111) surface preferentially occurs at the macrocyclic centre without further metal coordination to the peripheral site. Nevertheless, starting from a densely packed, self-assembled H-Mabiq monolayer, the modification of the central cavity by Co is accompanied by an unusual, metalation-induced phase transformation which gives evidence of modified lateral / interfacial interactions. The selective metalation of one molecular site opens up an on-surface route to create bimetallic networks incorporating select metal ions at different locations.

We have theoretically investigated surface magnetoplasmons (SMPs) in an yttrium-iron-garnet (YIG) sandwiched waveguide. The dispersion demonstrated that this waveguide can support topological unidirectional SMPs. Based on unidirectional SMPs, magnetically controllable multimode interference (MMI) is verified in both symmetric and asymmetric waveguides. Due to the coupling between the modes along two YIG–air interfaces, the asymmetric waveguide supports a unidirectional even mode within a single-mode frequency range. Moreover, these modes are topologically protected when a disorder is introduced. Utilizing robust unidirectional SMP MMI (USMMI), tunable splitters have been achieved. It has been demonstrated that mode conversion between different modes can be realized. These results provide many degrees of freedom to manipulate topological waves.

Existing research has shown that emotional intelligence (EI) and teacher self-efficacy (TSE) play an important role in the work of in-service teachers. However, there is limited research on these variables and their associations among pre-service teachers. Also, the cultural context is expected to influence EI and TSE. Therefore, this study examined the associations between EI and TSE in two cultures, Finland and Greece. A comprehensive evaluation of EI was done by including both trait EI and ability EI measures. Data from primary education student teachers from Finland (N = 82) and Greece (N = 117) were collected online. The measures of EI and TSE exhibited full configural and metric measurement invariance and partial scalar and residual/strict measurement invariance across cultures. Finnish students had significantly higher scores on all EI variables than Greek students, whereas Greek students scored higher on self-efficacy for student engagement. Structural equation modelling showed that trait EI was moderately associated with one facet of ability EI, namely emotional management, but not with emotional understanding, implying that trait EI and ability EI can be considered as partially distinct constructs. A statistically significant positive association between trait EI and TSE was found in Finland, whereas a statistically significant negative association between ability EI and TSE was found in Greece. The findings have important implications for the models of trait and ability EI, for understanding the links between trait and ability EI and TSE during the critical phase of teacher education in the two cultural contexts studied, and for culturally informed teacher education.