Modelling-orientated teaching (A theoretical development for teaching mathematics through the modelling process)

It is of our belief that modelling must constitute one of the essential components of teaching mathematics in secondary education. And it is worth noting the fact, that while this process has attracted interest from at least the early 1980s, few researchers and educators believe in the teaching of mathematics through the modelling process. Prompted by the problems we have spotted in the curriculum of Greek secondary education, we have developed modellingorientated teaching, a didactic model with which we can teach new mathematical concepts. This model is a three-part approach with the following stages: conceptual modelling; abstraction and formalization of mathematical concepts; applied modelling. In this paper we also quote elements from the international discussion about the role and place of modelling in mathematical education, a discussion that still goes on. In the last part we present some of the conclusions of wider research, in the context of which we have developed modelling-orientated teaching. © 1994 Taylor & Francis Ltd

The parabolas of Artzt in the solution of a geometric problem of minimum length

The article describes the solution of a geometric problem and how this problem was formed. During the investigation process, I discovered that the inscribed parabola in a triangle, known as the parabola of Artzt, a mathematical subject developed almost 120 years ago, was the decisive idea which directed me towards the solution. Moreover, in the solution, I also used notions that some mathematicians of the present generation, probably, are not familiar with, such as the symmedian and the Simson line. © 2011 Taylor & Francis

Capture Fisheries and Aquaculture Exploitation in the Aegean Sea Archipelago

The Aegean Sea is an insular archipelago in North Mediterranean Sea. It exhibits 60 inhabited islands, more than 1,400 small islands and more than 2,500 outcrops and rocks. Its total area is in excess of 215,000 km2. Fisheries and aquaculture are the second most important economic activities after tourism, from the point of view of contribution to the national GDP. However, as segments of the primary production, they are more important than tourism for job and income security of the numerous rural fishery-dependent communities in the region, as tourism activity is limited in certain areas and islands. The fishing fleet in the Aegean Sea amounts to 11,580 vessels approximately from which 95% belongs to the smallscale fishery segment and operates from over 100 ports, harbours and fishing refuges on the mainland and the islands. Fisheries production reached almost 69,000 t in 2018. Aquaculture in Greece is a fast developing industry with export orientation. The total national aquaculture production today amounts to 133,000 t of sea bass and sea bream for 2016, compared to 400 t in 1984. Aquaculture production in the Aegean Sea amounts to 83,000 t (63% of total) and fetching approximately 370 million €. From the economic point of view, the fisheries sector in the Aegean Sea faces many challenges. Even though demand for high-quality fishery products is stable and increasing, mainly due to tourism, the market structure is such that net income margins for capture fisheries are low between 8 and 12% at the producer level. Aquaculture suffers from very low prices close or seasonally below production cost levels due to the market competition of aquaculture production of the same species (whole, fresh or chilled sea bass and sea bream) by most Mediterranean States. Finally, fishery product processing industry faces drops in the demand of traditional products in the region (canned in oil, smoked) and low market prices for other types of products (fillets, frozen, etc.) which has forced many companies to diverse their production to vegetables and other local high-market value produce. © Springer Nature Switzerland AG 202

Spatial and temporal effects of fish farming on benthic community structure in a semi-enclosed gulf of the Eastern Mediterranean

Spatial and temporal effects of fish farming on the benthic community structure at 2 fish farms in the Eastern Mediterranean were investigated between July 2004 and April 2005. In the area of each fish farm, 3 stations were sampled. At each station, sediment samples were collected for analysis of organic carbon, organic matter and benthic community parameters. There were statistically significant differences in organic matter and organic carbon among all stations. This impact seems to be only spatial, since 1-way ANOVA indicated no significant differences in organic matter and organic carbon between seasons for both farms. Furthermore, significant differences were found in species number, abundance and species richness among stations and seasons for one of the farms (2-way ANOVA). One-way ANOVA indicated that the significant differences, detected in the benthic community parameters of this farm, were spatio-temporal for species number, temporal for abundance and spatial for species richness. The spatial effect of fish farming on benthic community structure was present up to 50 m from the centre of cages on one farm and between 50 and 300 m from the other farm. Capitella capitata was the most dominant species at the farm sites, while Nephthys hystricis was the most dominant species at the control sites. In all cases, the benthic assemblages in the immediate vicinity showed symptoms of disturbance, but the spatial and temporal extent of this effect was less than one would expect considering the fact that the study area is located in a semi-enclosed gulf

Studies on Migratory Movements of the Prawn Penaeus kerathurus (Forskal, 1775) at Amvrakikos Gulf, Western Greece

Abstract. The prawn Penaeus kerathurus completes its life cycle in Amvrakikos Gulf. The reasons for not entering the open sea depend on the status of biotic and abiotic factors of the gulf. The migratory movements of the species in the gulf are described by a simple square model, in each corner of which, the wintering, spawning, nursery, and recruitment area exist. The wintering area is located below the 25m isobath and wintering period lasts from late December to late March. Spermatophores on females are observed throughout the year but the highest percentages between April and August. The spawning season begins late in spring and continues through the summer. The spawning area is located below the 10m isobath, mainly around 25m. The nursery area of Penaeus kerathurus is in shallow waters near river estuaries, and the temporal limits were determined to be between mid‐summer and mid‐autumn. Finally, the recruitment area is located near the nursery area, with recruitment taking place in autumn, while the major stock renewal is restricted to winter. Copyright © 1992, Wiley Blackwell. All rights reserve

Population Characteristics of the Upper Infralittoral Sea Urchin Arbacia lixula (Linnaeus, 1758) in Eastern Mediterranean (Central Greece): An Indicator Species for Coastal Water Quality

The black sea urchin (Arbacia lixula, Linnaeus, 1758) is a non-edible marine echinoderm of high ecological importance with the potential to affect marine ecological communities. A. lixula were sampled monthly for one year from the supralittoral fringe at two locations in the Pagasitikos Gulf, in the north-western Aegean Sea. Morphometric characteristics exhibited significant spatiotemporal variation. The population in closer proximity to treated sewage effluent outflow exhibited significantly higher biometric relationships resulting in possible improved physiological conditions. Spatial distribution exhibited a clumped pattern of dispersion, consisting of predominantly six age classes. The dominant cohort was the four-year age class, comprising 31.2% of the total population. Significant negative allometric relationships were exhibited between all morphometric characteristics. The maximum approximate age of the total A. lixula population was estimated at 15.27 years. The von Bertalanffy growth equation for the entire population was estimated as: test diameter = 62.881 × (1 − e-0.196× (Age+1.147)). The gonadosomatic index indicated a seasonal cycle with a peak in late spring. The approximate age of sexual maturity was estimated at 4.45 years. We observed a significantly higher number of females than expected at the site in closer proximity to the treated sewage effluents (32% of total female number). © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Population characteristics of the mid-littoral chthamalid barnacle c. Stellatus (poli, 1791) in eastern mediterranean (central greece)

Barnacles are key space-occupiers in rocky shore communities on European coasts. Barnacles of the species Chthamalus stellatus (Poli, 1791) were collected between June 2014 and May 2015 from two sites, two stations per each site with varying degree of exposure to wave action and anthropogenic pressure (trampling), in the Eastern Mediterranean (Pagasitikos Gulf, Central Greece). This study addresses a knowledge gap in population characteristics of C. stellatus populations in the Eastern Mediterranean, assessing population structure and allometric relationships. Patterns of distribution and abundance (density and percentage cover) were studied both temporally (seasonally) and spatially (water level and site). Morphometric characteristics exhibited spatiotemporal variation. Population density was significantly higher at the site with higher wave exposure. The population cover exhibited high levels of similarity among shore levels, both spatially and temporally. Spatial distribution exhibited a clumped pattern of dispersion in autumn, winter, and spring, mainly in the sheltered site. Six dominant age groups were identified, with the dominant cohort in the third-year class. Significant negative allometric relationships were exhibited between all morphometric characteristics. Differences in growth patterns among populations were indicated, with a higher rate of growth at the site of lower wave exposure. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Rare earths as authenticity markers for the discrimination of Greek and Turkish pistachios using elemental metabolomics and chemometrics

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. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

A Rapid HPLC-UV Protocol Coupled to Chemometric Analysis for the Determination of the Major Phenolic Constituents and Tocopherol Content in Almonds and the Discrimination of the Geographical Origin

Reversed phase-high-pressure liquid chromatographic methodologies equipped with UV detector (RP-HPLC-UV) were developed for the determination of phenolic compounds and tocopherols in almonds. Nineteen samples of Texas almonds originating from USA and Greece were analyzed and 7 phenolic acids, 7 flavonoids, and tocopherols (−α, −β + γ) were determined. The analytical methodologies were validated and presented excellent linearity (r2 > 0.99), high recoveries over the range between 83.1 (syringic acid) to 95.5% (ferulic acid) for within-day assay (n = 6), and between 90.2 (diosmin) to 103.4% (rosmarinic acid) for between-day assay (n = 3 × 3), for phenolic compounds, and between 95.1 and 100.4% for within-day assay (n = 6), and between 93.2–96.2% for between-day assay (n = 3 × 3) for tocopherols. The analytes were further quantified, and the results were analyzed by principal component analysis (PCA), and agglomerative hierarchical clustering (AHC) to investigate potential differences between the bioactive content of almonds and the geographical origin. A decision tree (DT) was developed for the prediction of the geographical origin of almonds proposing a characteristic marker with a concentration threshold, proving to be a promising and reliable tool for the guarantee of the authenticity of the almonds