An experimental study on restoration technique for the Acropolis of Athens: developing the experimental set-up for pull-out testing of titanium bars embedded in marble blocks

This work aims at investigating the mechanisms activated during the ex­trac­tion of titanium bars from a marble volume (pull-out phenomenon), used for re­joining fragmented marble structural members at the monuments of the Acropolis of Athens. The restoration protocol includes the insertion of threaded titanium bars into pre-drilled holes in the body of the structural members. The ad­hesion between marble and bars is achieved by an initially liquid cementitious material. There are two main aspects on which this project focuses. Firstly, the weak link of the marble-cement-titanium complex, the marble-cement interface, is inaccess­ible for traditional sensing techniques. In this context, the Acoustic Emission tech­nique is employed in order to detect failure and damages at the interior of the complex. Secondly, the specimens and the experimental procedure should simulate the same stress conditions in which all three phases within the marble-cement-titanium complex are under, while the struc­tural member is in service. For this purpose, two modified tests are proposed aiming at efficiently simulating the bars’ behavior as they are sliding through a marble epistyle. These tests provide promising results with regards to keeping the examined surface between bars and marble free from para­sitic stresses caused by the experimental set-up

An experimental study on restoration technique for the Acropolis of Athens: developing the experimental set-up for pull-out testing of titanium bars embedded in marble blocks

The present work aims at investigating the mechanisms activated during the extraction of titanium bars from a marble volume (pull-out phenomenon), used for rejoining fragmented marble structural members at the monuments of the Acropolis of Athens. The restoration protocol includes the insertion of threaded titanium bars into pre-drilled holes in the body of the structural members. The adhesion between marble and bars is achieved by an initially liquid cementitious material. There are two main aspects on which this project focuses. Firstly, the weak link of the marble-cement-titanium complex, the marble-cement interface, is inaccessible for traditional sensing techniques. In this context, the Acoustic Emission technique is employed in order to detect failure and damages at the interior of the complex. Secondly, the experimental specimen and procedure should simulate the same stress conditions in which all three phases within the marble-cement-titanium complex are under, while the structural member is in service. For this purpose, two modified tests are proposed aiming at efficiently simulating the bars’ behavior as they are sliding through a marble epistyle. The new tests achieve promising results with regards to keeping the examined surface between bars and marble free from the parasitic stresses caused by the experimental set-up

Pre-failure indicators detected by Acoustic Emission: Alfas stone, cement-mortar and cement-paste specimens under 3-point bending

Acoustic Emission (AE) is the technique most widely used nowadays for Structural Health Monitoring (SHM). Application of this technique for continuous SHM of restored elements of stone monuments is a challenging task. The co-existence of different materials creates interfaces rendering “identification” of the signals recorded very complicated. To overcome this difficulty one should have a clear overview of the nature of AE signals recorded when each one of the constituent materials is loaded mechanically. In this direction, an attempt is here described to enlighten the signals recorded, in case a series of structural materials (natural and artificial), extensively used for restoration projects of classic monuments in Greece, are subjected to 3-point bending. It is hoped that obtaining a clear understanding of the nature of AE signals recorded during these elementary tests will provide a valuable tool permitting “identification” and “classification” of signals emitted in case of structural tests. The results appear encouraging. In addition, it is concluded that for all materials tested (in spite their differences in microstructure and composition) clear prefailure indicators are detected, in good accordance to similar indicators provided by other techniques like the Pressure Stimulated Currents (PSC) one

An Unusual Michael-Induced Skeletal Rearrangement of a Bicyclo[3.3.1]nonane Framework of Phloroglucinols to a Novel Bioactive Bicyclo[3.3.0]octane

A novel skeletal rearrangement of bicyclo[3.3.1]nonane-2,4,9-trione (16) to an unprecedented highly functionalized bicyclo[3.3.0]octane system (17), induced by an intramolecular Michael addition, is presented. This novel framework was found to be similarly active to hyperforin (1), against PC-3 cell lines. A mechanistic study was examined in detail, proposing a number of cascade transformations. Also, reactivity of the Δ7,10-double bond was examined under several conditions to explain the above results

A multidisciplinary approach for an effective and rational energy transition in Crete Island, Greece.

This article proposes a mixture of actions for the development of an effective and rational energy transition plan for all sectors and for all types of onshore final energy use in Crete. Energy transition is initiated with an appropriate capacity building campaign. The plan is based on the introduction of energy saving measures and the exploitation of all the locally available energy resources (wind, solar, geothermal potential, biomass), integrated in a cluster of centralized and decentralized power plants and smart grids to produce electricity and heat and for the transition to e-mobility. The core of the energy transition in Crete will be a set of 14 wind parks and Pumped Hydro Storage systems (PHS) for electricity generation and 12 Combined Heat and Power plants, properly designed and dispersed in the insular territory. Economic analysis is executed for the proposed essential power plants on the island. Biomass, solar and geothermal potential can cover the heating demand in Crete several times. Heat can be produced with a specific cost of 0.05 EUR/kWhth from cogeneration plants fired with solid biomass and biogas. The wind parks-PHS systems exhibit payback periods of approximately 10 years with a final electricity selling price at 0.12 EUR/kWhel. The article shows that 100% energy transition in Crete constitutes a feasible target

Acoustic Emissions versus Pressure Stimulated Currents during bending of restored marble epistyles: Preliminary results

The efficiency of two modern sensing techniques, namely the “Acoustic Emissions” and the “Pressure Stimulated Currents” ones, when they are used as Continuous Structural Health Monitoring tools, is assessed experimentally. The protocol includes multi-point bending of an accurate copy of a fractured marble epistyle of the Parthenon’s Temple on the Acropolis of Athens, under a scale of 1:3. The integrity of the epistyle is restored with three pairs of bolted titanium bars, according to the pioneering technique developed by the scientists of the “Committee for the Conservation of the Acropolis Monuments”. The data provided by the above techniques are considered in juxtaposition to each other and also in comparison to data provided by the “Digital Image Correlation” technique. It is concluded that, at least from a qualitative point of view, the data of all three techniques are in good mutual agreement. Combined exploitation of the various sets of experimental data enlightens interesting aspects concerning the succession of failure mechanisms activated during the loading procedure, revealing the critical role of the internal interfaces characterizing the restored epistyle. Moreover it is definitely indicated that both the “Acoustic Emissions” and the “Pressure Stimulated Currents” techniques provide clear signs of upcoming failure well before macroscopically visible damages are detected at the external surface of the specimen

Μελέτη της παρουσίας των αλειφατικών και πολικυκλικών αρωματικών υδρογονανθράκων σε μονάδες ιχθυοκαλλιέργειας στη Σητεία και στο Σούνιο

Οι ιχθυοκαλλιέργειες αποτελούν έναν από τους τρεις γρηγορότερους τομείς ανάπτυξης της παγκόσμιας οικονομίας (ηλεκτρονικοί υπολογιστές, κινητή τηλεφωνία). Η ανάπτυξη τους την τελευταία δεκαετία είναι αλματώδης. Οι ιχθυοκαλλιέργειες της Ελλάδας ασχολούνται με την παραγωγή τσιπούρας και λαβρακίου και η ετήσια παραγωγή τους (60.000tones, 2004) ανέρχεται στο μισό ποσοστό της συνολικής παραγωγής στην Ευρώπη. Προκύπτουν επομένως ερωτηματικά σχετικά με το αν η ραγδαία αυτή ανάπτυξη των υδατοκαλλιεργειών επιφέρει ρύπανση στο θαλάσσιο περιβάλλον. Η παρούσα εργασία περιλαμβάνει την μελέτη της παρουσίας δύο σημαντικών κατηγοριών οργανικών ρυπαντών, των αλειφατικών και πολυκυκλικών αρωματικών υδρογονανθράκων (ΠΑΥ) σε ιζήματα από δύο μονάδες ιχθυοκαλλιέργειας της Ελλάδας, στη Σητεία και στο Σούνιο, καθώς και σε διάφορες αποστάσεις από αυτές. Η ιχθυοκαλλιέργεια της Σητείας βρίσκεται στα βορειοανατολικά παράλια της Κρήτης και σε απόσταση 10km από το κοντινότερο χωριό. Θεωρείται μια από της μεγαλύτερες μονάδες στη Ευρώπη, με την ετήσια παραγωγή να ανέρχεται στους 1,3ktones. Η ιχθυοκαλλιέργεια του Σουνίου βρίσκεται στα νότια παράλια της Αττικής σε απόσταση 500m από την ακτής και 100m από ένα μικρό νησί που ονομάζεται Πάτροκλος. H ετήσια παραγωγή είναι 400tones. Μελετήθηκε επίσης δείγμα της τροφής η οποία χρησιμοποιείται για την εκτροφή της τσιπούρας και του λαβρακίου και ίζημα από παγίδα η οποία βρίσκεται στο κάτω μέρος κλουβιού εκτροφής ψαριών στην ιχθυοκαλλιέργεια της Σητείας. Η παρουσία των υπό μελέτη οργανικών ρυπαντών εντοπίστηκε τόσο στα δείγμα της τροφής και της παγίδας, όσο και στα δείγματα των θαλάσσιων ιζημάτων, οδηγώντας μας στο συμπέρασμα της πιθανής συνεισφοράς της ρύπανσης που εμφανίζει η τροφή σε αυτή των ιζημάτων . Οι υψηλότερες συγκεντρώσεις και των δύο οργανικών ρυπαντών εντοπίστηκαν στο δείγμα της παγίδας, όπου εμφάνιζε υψηλή συσσώρευση περιττωμάτων από τα ψάρια. Η συνολική συγκέντρωση των ΠΑΥ στο δείγμα της τροφής βρέθηκε σχεδόν σε τριπλάσια επίπεδα από αυτή που έχει μετρηθεί σε τροφή ιχθυοκαλλιέργειας σολομού, ενώ δεν υπάρχουν συγκριτικά αποτελέσματα για τη συνολική συγκέντρωση των αλειφατικών υδρογονανθράκων . Υψηλότερες συγκεντρώσεις αλειφατικών υδρογονανθράκων και ΠΑΥ εμφανίστηκαν στην ιχθυοκαλλιέργεια της Σητείας, όπου πρόκειται για μια μεγαλύτερη μονάδα σε σχέση με αυτήν του Σουνίου και με τα φυσικοχημικά χαρακτηριστικά του ιζήματος να είναι πιο προσφορά στην κατακράτηση των ημιπτητικών ενώσεων. Στα ιζήματα και των δύο ιχθυοκαλλιεργειών, εντοπίστηκαν μεγαλύτερα επίπεδα ρύπανσης στην απόσταση των 5m, όπου πιθανότατα παρασύρεται από ρεύματα το οργανικό υλικό. Παρατηρήθηκε, επίσης, μείωση της ρύπανσης αυτής κατά την απομάκρυνση από τις μονάδες. Οι συνολικές συγκεντρώσεις των κ-αλκανίων στα ιζήματα και των δύο ιχθυοκαλλιεργειών κυμαίνονται σε υψηλότερα επίπεδα σε σχέση με αυτές μελετών οι οποίες έχουν πραγματοποιηθεί σε θαλάσσια ιζήματα στην Κρήτη. Όσον αφορά τις συνολικές συγκεντρώσεις των ΠΑΥ στη μονάδα της Σητείας βρίσκονται σε υψηλότερα επίπεδα σε σχέση με αυτές θαλάσσιων ιζημάτων της Κρήτης, ενώ στη μονάδα του Σουνίου σε χαμηλότερες. Γενικά η ρύπανση των ΠΑΥ και στις δύο ιχθυοκαλλιέργειες είναι λιγότερη από αυτήν σε ιχθυοκαλλιέργειες στη Σκοτία και την Κίνα. Παράλληλα κατά τον προσδιορισμό του ολικού οργανικού υλικού δεν παρατηρήθηκαν ιδιαίτερες διακυμάνσεις συγκεντρώσεων στα δείγματα των ιζημάτων.Aquaculture consist one of the three faster expanding sectors of the world economy (besides computers & mobile phones). Aquaculture exhibited a very rapid development the last decade. Aquaculture in Greece focuses on the breeding of the sea-bream and the sea-bass and with an annual production of 60.000 tones (2004). This figure makes up to the half percentage of the total European production. Many questions arise relatively to the rapid expansion of aquaculture concerning its pollution input to the marine environment. The present work includes the study of the occurrence of two important categories of organic pollutants, namely the aliphatic and the polyciclic aromatic hydrocarbons (PAH), in sediments of two aquaculture units, in the area of Sitia and Sounio (Greece). The aquaculture unit of Sitia is located at the northeast coast of Crete island. It is considered one of the largest units in Europe as its annual production comes up to 1,3 ktones. The aquaculture of Sounio is located at the south coasts of the Athens metropolitan area, 500 m from the coast and 100 m from a small island called Patroklos. Its annual production comes up to 400 tones. Sediments samples were collected under the cages and at distance: 5, 10, 25, 50, 1000 m from the unit. In addition, samples from sediment traps deployed underneath the cages and fish-food, were also analyzed in respect to their content in aliphatics and PAHs. Both aliphatics and PAHs were determined in the samples of the sediments in fish-food and in sediment trap material. This observation led us to the conclusion that there is a potential contribution of fish-food to the sedimentary content of aliphatics and PAHs. The highest concentrations of both organic pollutants were measured in the sediment trap due to the high accumulation of fish fecal pellets. The total concentration of PAHs in fish-food, used in the studied aquaculture units was three times higher than the corresponding concentration measured in other units (salmons fish-food). Higher concentrations of aliphatic hydrocarbons and PAHs were measured at the sediment of the aquaculture of Sitia, than in the corresponded unit of Sounio. The highest concentration was determinated at a distance of 5 m from the aquaculture unit in both studied locations. This probably due to the streams that transport the suspended matter. We also observed a decrease of contamination in larger distances from the aquaculture areas. The total concentrations of n-alkanes in both units exceeded those measured in marine sediments of other areas of Cretan Sea. The total concentrations of PAH measured in marine sediments sampled in the area of Sitia unit were higher than those collected at the area of Sounio unit and other marine areas of Cretan Sea. However even the highest PAH sediment concentrations were lower than those measured in other aquaculture units in China and Scotland