Search Results (14)

According to CIGRE, the usual arrangement of electrodes in a shoreline electrode station for HVDC interconnections is straight with the following form: forming straight frames with the electrodes at equal distances and placing the frames parallel to the longitudinal axis of the breakwater, successively at fixed distances between them. In a previous paper by the authors, 10 alternative configurations of placement of such straight frames were examined to determine which placements mainly affect the near-field results. In particular, radial or circumferential arrangements of the straight frames on a central base in the open sea improve the overall field results, such as the absolute potential and electrode station resistance to remote earth, satisfying the requirements of the maximum electric field strength. In this paper, the nonlinear configuration of the frames will be studied from an electric field perspective at the level of a preliminary study forming innovative configurations in order to check their suitability with respect to the relevant requirements of the CIGRE guidelines B4.61/2017. These arrangements, located in electrode stations, are evaluated and compared with the older configurations for two cases, those of Korakia in Crete and Stachtoroi in Aegina, Attica, for the HVDC Crete-mainland Greece interconnection of 1 GW, ±500 kV. Full article

Protection of coastal cultural heritage is among the most urgent global priorities, as these sites face increasing threats from climate change, sea level rise, and human activity. This study emphasises the value of innovative geospatial tools and data ecosystems for timely risk assessment. The role of land administration systems, geospatial documentation of coastal cultural heritage sites, and the adoption of innovative techniques that combine various methodologies is crucial for timely action. The coastal management infrastructure in Greece is presented, outlining the key public authorities and national legislation, as well as the land administration and geospatial ecosystems and the various available geospatial ecosystems. We profile the Hellenic Cadastre and the Hellenic Archaeological Cadastre along with open geospatial resources, and introduce TRIQUETRA Decision Support System (DSS), produced through the EU’s Horizon project, and a Digital Twin methodology for hazard identification, quantification, and mitigation. Particular emphasis is given to the role of Digital Twin technology, which acts as a continuously updated virtual replica of coastal cultural heritage sites, integrating heterogeneous geospatial datasets such as cadastral information, photogrammetric 3D models, climate projections, and hazard simulations, allowing for stakeholders to test future scenarios of sea level rise, flooding, and erosion, offering an advanced tool for resilience planning. The approach is validated at the coastal archaeological site of Aegina Kolona, where a UAV-based SfM-MVS survey produced using high-resolution photogrammetric outputs, including a dense point cloud exceeding 60 million points, a 5 cm resolution Digital Surface Model, high-resolution orthomosaics with a ground sampling distance of 1 cm and 2.5 cm, and a textured 3D model using more than 6000 nadir and oblique images. These products provided a geospatial infrastructure for flood risk assessment under extreme rainfall events, following a multi-scale hydrologic–hydraulic modelling framework. Island-scale simulations using a 5 m Digital Elevation Model (DEM) were coupled with site-scale modelling based on the high-resolution UAV-derived DEM, allowing for the nested evaluation of water flow, inundation extents, and velocity patterns. This approach revealed spatially variable flood impacts on individual structures, highlighted the sensitivity of the results to watershed delineation and model resolution, and identified critical intervention windows for temporary protection measures. We conclude that integrating land administration systems, open geospatial data, and Digital Twin technology provides a practical pathway to proactive and efficient management, increasing resilience for coastal heritage against climate change threats. Full article

(1) Background: High temperatures and water scarcity, intensified by climate change, present major challenges to Mediterranean viticulture. In this study morphological, anatomical, and physiological responses of leaves at two developmental stages of Vitis vinifera L. cv. Assyrtiko were examined. (2) Methods: Young expanding and fully expanded leaves of two-year-old grapevines grown in pots in a controlled growth chamber, grown in soil in an open-air vineyard, and an adjacent greenhouse on Aegina Island (Greece), were used. The plants were subjected to water deficit (WD), elevated temperature (ET), and combined water deficit and elevated temperature (WD_ET) conditions for four months, and compared with control plants (C). (3) Results: Stress conditions caused contrasting effects on specific leaf area (SLA), which declined in young expanding leaves, except for a significant increase under elevated temperatures, while it increased in fully expanded leaves exposed to stress treatments. Concerning the anatomical traits, the thickness of spongy and palisade parenchyma did not change in young expanding leaves exposed to the three stress treatments, but increased in fully expanded leaves exposed to WD_ET. Metabolic traits (phenolic compounds, soluble sugars, and starch content) further highlighted these differences. (4) Conclusions: The findings reveal distinct stress responses between young expanding and fully expanded leaves of the grapevine Assyrtiko, underscoring the influence of water deficit and elevated temperatures on leaf developmental stage. Full article

This study employs advanced synthetic aperture radar (SAR) techniques, specifically the small baseline subset (SBAS) method, to analyze ground deformation dynamics on Aegina, a volcanic island within the Hellenic Volcanic Arc. Using Sentinel-1 satellite data spanning January 2016 to May 2023, this research reveals different deformation behaviors. The towns of Aegina and Saint Marina portray regions of stability, contrasting with central areas exhibiting subsidence rates of up to 1 cm/year. The absence of deformation consistent with volcanic activity on Aegina Island aligns with geological records and limited seismic activity, attributing the observed subsidence processes to settlement phenomena from past volcanic events and regional geothermal activity. These findings reinforce the need for continuous monitoring of the volcanic islands located in the Hellenic Volcanic Arc, providing important insights for local risk management, and contributing to our broader understanding of geodynamic and volcanic processes. Full article

Probabilistic Seismic Hazard Assessment (PSHA) was carried out for the administrative region of Attica (Greece). Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) values were calculated for return periods of 475 and 950 years for five sub-areas covering the entire region. PGA hazard curves and Uniform Hazard Spectra (UHS) in terms of spectral acceleration (S_a) values were generated for Athens, Methana, and the capitals of each island of Attica (Salamina, Aegina, Poros, Hydra, Spetses, Kythira, and Antikythira). Area sources were adopted from the Euro-Mediterranean Seismic Hazard Model 2013 (ESHM13) and its update, ESHM20, taking into account both crustal and slab tectonic environments. Ground Motion Prediction Equations (GMPEs) proposed for the Greek territory were ranked for PGA and PGV. Each GMPE was reconstructed as a weighted model, accounting for normal and non-normal focal mechanisms for each area source. PGA, PGV, and S_a values were computed using a logic tree, integrating the seismotectonic models as major branches and sub-logic trees, comprised of multiple ranked GMPEs for each area source, as minor branches. The results showed higher seismic hazard values in sub-areas near the Gulf of Corinth and the slab interface, which could indicate a need to revise the active building code in Attica. Full article

During the design of a shoreline electrode station for High-Voltage Direct Current (HVDC) interconnections, the location of the electrodes plays a critical part, especially in the development of the near-electric field. The basic structure is their linear placement, in the form of successive frames, parallel to the longitudinal axis of the breakwater, as proposed by CIGRE and implemented in existing projects. However, this arrangement requires a considerable breakwater length, which may not be permissible, as in the case of Stachtoroi, one of the two electrode stations being built for the 1 GW, ±500 kV HVDC interconnection between Crete and mainland Greece. This troubled the preliminary study team of the electrode stations, which investigated other possible configurations. In this paper, configurations of linear placements of electrode frames are studied and compared at the preliminary study level in terms of electric field effects (especially the near-field), using an analytical simplified model and the superposition method, to determine the most appropriate arrangement of electrodes that will cover the respective requirements of CIGRE directives B4.61/2017. These arrangements are practically evaluated for two different electrode station locations at Korakia in Crete and at Stachtoroi in Aegina for the Crete–mainland-Greece interconnection, resulting in interesting alternative solutions. Full article

Pistachio (Pistacia vera L.) is a nut with a good adaptability to the Mediterranean conditions of cultivation, specifically in the Andalusian region, becoming an emerging crop. Moreover, it has been getting attention in the past years for the great content of bioactive compounds such as polyphenols. Although some studies have reported the polyphenolic profile of pistachios, most of them have analyzed the hull part, considered as a residue, and not the kernel which is the edible part. Therefore, characterization of eleven varieties of pistachios kernels cultivated in Andalusia and harvested in 2019 and 2020 was carried out by UHPLC-MS (ultra-high-performance liquid chromatography high-resolution mass spectrometry). The identification and quantification of 56 polyphenolic compounds was performed, being the hydroxybenzoic acids group the most abundant with a 71–86% of the total amount followed by flavan-3-ols group that accounted for 8–24%. Moreover, 3,4-dihydroxybenzoic acid was the main compound in most of the varieties, followed by vanillic acid hexoside. Larnaka, Avdat, Aegina, and Mateur presented the highest amount of total polyphenols, while Kalehghouchi, Joley, Lost Hills, Kerman, and Golden Hills were the varieties with the lowest content. Regarding the harvest season, no significant differences (p < 0.01) were found in the total amount of polyphenols between 2019 and 2020. In addition, the antioxidant activity was measured by DPPH (1,1-diphenyl-2-picryl-hydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), and ORAC (oxygen radical absorbance capacity) assays, showing a similar trend as that of the polyphenols. Full article

The rising human activities and resource exploitation have increased pressure in the coastal zone and the marine environment, risking the very existence of Marine Priority Habitats (MPH) and Underwater Cultural Heritage (UCH). The delimitation of these two priority areas in a time- and cost-effective way is essential for the sustainable management and exploitation of sea resources and natural-cultural heritage preservation. We propose an Integrated Methodological Approach for the Detection and Mapping of MPH and UCH. To achieve this, we used a downscale methodological approach of increasing spatial resolution based on three main methodological axes: (i) desk-based research, (ii) marine geophysics/seafloor classification, and (iii) in-depth visual inspection/3D mapping. This methodological scheme was implemented at the Saronic Gulf and focused on Aegina island. The methodology proposed, which combines existing and new techniques, proved successful in detecting and mapping the MPH and UCH in detail, while it compiled the information necessary for the establishment of Marine Spatial Planning (MSP) maps. Finally, the MSP map constructed for the Saronic Gulf demonstrated the lack of holistic coastal zone management plans due to impacts on UCH linked to anthropogenic intervention and the sparsity of marine habitats owing to marine pollution. Full article

The documentation of underwater cultural heritage (UCH) is the basis for sustainable maritime development including its protection, preservation, and incorporation in coastal zone management plans. In this study, we present a multidisciplinary, non-intrusive downscale approach for the documentation of UCH implemented on the coastal area of Aegina Island, Greece, where a unique submerged harbour complex is preserved. This approach succeeded in obtaining information that serves both geomorphological and archaeological purposes in a time- and cost-effective way, while obtaining information of centimeters to millimeters scale. The geomorphology of the area was mapped in detail through marine geophysical means while ancient submerged conical rubble structures and breakwaters were documented using automatic seafloor segmentation techniques, revealing previously unknown sites of archaeological interest. The structures’ parameters were extracted from the acoustic data to analyze their morphometry, while photogrammetry was realized using a Remotely Operated Vehicle to expose their micro-structure. The spatial distribution of the structures revealed the construction of a well-planned harbour complex with multiple passages and different possible functionalities. Finally, through the structures’ morphometric analysis (geometry and terrain statistical parameters) their preservation status was revealed, demonstrating the anthropogenic impact on the submerged ancient structures due to the modern harbor activity. Full article

This paper refers to the study of the Voyatzis mansion, in the port of Aegina, Greece. The building complex consists of two discrete structures, which were built at different times (before 1830, 1880 and 1890) and have housed either the Voyatzis family home or its business and work premises. The present research is focused on the documentation of the building, which was never published, and combines the architectural form and elements within its historical context as well as the physicochemical analysis of the painted decoration. The key hypothesis investigated is whether Konstantinos Voyatzis transferred the aesthetic approach and application techniques from Symi to Aegina, when he emigrated from his birthplace. The documentation of the ceiling decoration as well as the physicochemical study of the second floor’s internal wall painting decoration in the main rooms was carried out using in situ modern hyperspectral imaging in specific wavelengths of the visible and near-infrared region, as well as in false color infrared mode. Complementary SWIR imaging, using an InGaAs sensor at the range 900–1700 nm was also applied. The assumption was supported by the findings of the imaging techniques, which showed, apart from the secco method, the use of traditional pigments for the wall paintings, such as cobalt blue, brown, red and yellow earth pigments, chrome oxide green and black, sometimes in admixture with white. The use of guidelines and stencil in the case of the hallway was also recorded. Full article

Food quality is a topic of utmost importance as more and more emphasis is placed on quality rather than quantity of products. Previous studies have pointed out the interaction of quality with the harvest year. In this study, 22 Pistacia vera (Greek ‘Aegina’ variety) samples (11 from 2017 and 11 from 2018) were differentiated using Fourier transform infrared spectroscopy (FTIR) and (a) diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and (b) KBr/sample disk techniques. In both years, the pistachios trees’ growing followed standard cultivation methods and similar agronomic conditions. Two chemometric models were developed using partial least squares-discrimination analysis (PLS-DA). DRIFTS proved unable to statistically differentiate the samples (R² = 0.96266, Q² = 0.63152). On the contrary, the disk technique completely differentiated the pistachio samples (R² = 0.99705, Q² = 0.97719). The 1720–1800 cm⁻¹ region mostly contributed to the discrimination. The disk-FTIR chemometric model is fast, robust, economical, and environmentally friendly for determining pistachio matrix quality. Full article

Pistachios are a nutritionally beneficial food source widely consumed all over the world. Pistachios exhibit high content of antioxidants, vitamins and other beneficial micronutrients, including nutrient elements and rare earth elements (REEs). Considering that the concentration of REEs depends on the climate and soil characteristics that vary among different geographical regions, REEs could constitute markers responsible for the geographical discrimination of this nut type. In this study, Greek pistachios with a protected designation of origin (PDO) label from Aegina Island and Fthiotida and Turkish pistachios from Adana were analyzed with inductively coupled plasma mass spectrometry (ICP-MS) to assess their REE profile. La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb were determined and quantified. The quantification results were further analyzed using the main effect plot, permutational analysis of variance (PERMANOVA), nonmetric multidimensional scaling (nMDS), principal component analysis (PCA) and hierarchical clustering (HCA) to investigate the similarities between the pistachios. A decision tree (DT) was developed for the classification of pistachios according to their geographical origin proving to be a promising and reliable tool for verifying the authenticity of food products on the basis of their REE profile. Full article

In this study, an integrated environmental risk assessment (ERA) study involving frequent monitoring of both water and soil parameters (24 on total), was carried out to assess and compare the environmental risk quality of three pistachio (Pistacia vera L.) fields (two in Aegina island and one in Kilkis) based upon risk categories identified and assessed in terms of quality and quantity. In this context, vertical profiles and risk matrices were created for a 60-month period for the most important soil and water parameters i.e., soil pH, soil organic matter, soil salinity, heavy metals, and irrigation water quality. According to the obtained results, the two pistachio fields in Aegina exhibited reduced overall risk values, i.e., 17% and 27%, respectively after the adoption of sustainable cultivation practices, thus reflecting a transition from “medium to high risk” to “low to medium risk” environmental quality. On the other hand, overall risk values for the pistachio field in Kilkis were reduced by 34% and were lower compared to the ones obtained for the pistachio fields in Aegina. The better environmental profile identified for the entire period in Kilkis ranging from “medium risk” to “low risk” was the result of lower inherent risk associated with irrigation water quality and soil salinity. The proposed methodology can be easily applied in other agricultural areas and for similar cultivations in Greece and other Mediterranean countries. Full article

The aim of this work was to characterize the pistachio oil of the Greek variety, “Aegina”, evaluate its various quality indices, and investigate the potential use of FTIR as a tool to discriminate different oil qualities. For this purpose, the antioxidant capacity, the tocopherol content and the oxidation and degradation of fatty acids, as described by k, Δk, R-values, and free acidity were evaluated using 45 samples from eight different areas of production and two subsequent years of harvesting. The antioxidant capacity was estimated using 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS) and 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazine (DPPH) assays, and the tocopherol content was quantified through HPLC analysis. FTIR spectra were recorded for all samples and multivariate analysis was applied. The results showed significant differences between the oil samples of different harvesting years, which were successfully discriminated by a representative FTIR spectral region based on R-value, total antioxidant capacity, and scavenging capacity, through ABTS. A similar approach could not be confirmed for the other quality parameters, such as the free acidity and the tocopherol content. This research highlighted the possibility of developing a simple, rapid, economic, and environment friendly method for the discrimination of pistachio oils according to their quality profile, through FTIR spectroscopy and multivariate analysis. Full article