MAGMA INTRUSION IN 'PROTO-CALDERA CALDERA' SYSTEMS: EXAMPLE FROM THE NISYROS VOLCANO

Στην αμοιβαία σχέση ηφαιστειότητας και τεκτονικής έχει εστιαστεί η προσοχή των ερευνητών την τελευταία δεκαετία λόγω του αυξανομένου όγκου ηφαιστειοτεκτονικών εργασιών και εφαρμογής τεχνικών τηλεπισκόπησης και στα δύο αυτά πεδία της γεωλογικής έρευνας. Τα ηφαίστεια εξαρτώνται από τεκτονικά φαινόμενα όπως είναι τα ρήγματα για την θέση τους, την ^τουργία τους και από το πετροτεκτονικό περιβάλλον για την χημεία των μαγμάτων τους. Τα ρήγματα παρέχουν το 'υδραυλικό σύστημα ' για την άνοδο του μάγματος και ως εκ τούτου η θέση και η χωρική κατανομή των ηφαιστείων εξαρτάται από την τεκτονική δομή μιας περιοχής. Από την άλλη πλευρά, τα ηφαίστεια τοπικά εντυπώνουν τα δικά τους ηφαιστειοτεκτονικά στοιχεία σε μία περιοχή όπως τα ακτινωτά και τα δακτυλοειδή ρήγματα που προκύπτουν από κύκλους επανατροφοδοσίας με μάγμα (διαστολής) και εκκένωσης (συστολής) των μαγματικών θαλάμων. Με αυτή την προοπτική επανεξετάστηκε το πιο ανατολικό άκρο του Τόξου του Αιγαίου, τα κύρια πρόδρομα αποτελέσματα της συνεχιζόμενης έρευνας που διεξάγουμε στην περιοχή χρησιμοποιώντας συνδυασμό μεθόδων πεδίου και τηλεπισκόπησης, δείχνουν ότι η ηφαιστειότητα στην Κω και στην απέναντι ακτή της Μικράς Ασίας από την εποχή του Μειόκαινου επικεντρώνεται στα ρήγματα που ορίζουν το βόρειο όριο του Graben της Datca. Ο γεωμετρικός τόπος των ηφαιστειακών πόρων και καλδερών στην περιοχή της Κω-Νισύρου ορίζεται από μια μεγάλη τεκτονική γραμμή, την γραμμή 'Κω-Νίσυρος-Τήλος' με κατεύθυνση γύρω στα Β320° και τις τομές αυτής της γραμμής με Β50°Α, Β30°Α and Β20°Δ κατευθυνόμενα ρήγματα. Η αρχιτεκτονική του καλά διατηρημένου ηφαιστειακού οικοδομήματος της Νισύρου έχει σημαντικά επηρεαστείαπό την ηφαιστειοτεκτονική 'trap-door' μιας μεγάλης ηφαιστειακής υποδομής της περιοχής, της καλδέρας της Κω.The interdependence of volcanism and tectonism has been focused upon in the last decade as a result of previously accumulated evidence, as well as, due to the application of remote sensing techniques in both these fields. Volcanoes depend on tectonic features such as faults for their positioning and operation and on petrotectonic environment for the chemistry of their magmas. Faults provide the plumbing system for magma ascent and therefore volcano localisation and distribution in space greatly depends on the tectonic pattern of an area. On the other hand, volcanoes locally imprint their volcanotectonic features such as radial and ring faults which result from cycles of magma replenishment (inflation) and evacuation (deflation) of magmatic reservoirs (magma chambers). Under this light, the area in the easternmost extremity of the Aegean Arc is being reconsidered. Our main preliminary findings of ongoing research in the area, using field and remote sensing methods indicate localization of volcanic activity on Kos and on the Datca Peninsula of Asian Minor since Miocene due to the northbounding faults of the Datca Graben. Localisation of volcanic vents and calderas in the Kos-Nisyros area follows intersection of a major tectonic line of northnorthwesterly trending faults the 'Kos-Nisyros-Tilos Line' with N50°E, N30°E and N20°W trending faults. On the well-preserved volcano ofNisyros the architecture of the volcanic edifice has significantly been affected by 'trap-door' volcanotectonics of a major volcanic infrastructure in the area namely the Kos-Calder

Study of the Use of Sawdust and Mycelium Composite as a Substitute of EPS

Expanded polystyrene foams are a petroleum-origin material that is usually used in some applications such as motorcyclist helmets. Despite it notably mechanical properties, it low density and its capability to absorb energy during an impact, it is necessary to find a renewable-origin substitute material. Thus, it has been studied the use of a sawdust and mycelium composite material under quasi-static and dynamic efforts. Sawdust is a waste material that has very small grains that are totally disaggregated so it has very low material properties. The use of oyster mushroom mycelium generates an internal structure that joins grains and, consequently, the resultant material has notably high mechanical properties. Then it has been compared the resultant properties (stress-strain curve, absorbed energy, decelerations, etc.) with the different densities EPS ones and it has been concluded that this composite material, despite it high density, it could be a suitable substitute material and in some cases it has better properties

The evolution of a W, Au-Ag-Te and Au-Ag hydrothermal system, Tinos Island, Cyclades, Greece

At Tinos Island, Greece, the physicochemical evolution of the hydrothermal system and the associated stages of metallic mineralization that are developed in the vicinity of the Tinos granodiorite-leucogranite has been studied, based on fluid inclusion studies and chemical reactions modeling. Early tungsten mineraliozation was related to the metasomatic stage of contact metamorphism and precipitated at ~ 350oC, from moderate saline (10.4 to 14.8 wt% NaCl eq.), CO2- effervescing fluids, that contained variable amounts of CaCl2 and MgCl2. Panormos Bay Au-Ag-Te mineralization, located 16 km away from the intrusive site, was deposited from cooler 200° to 300oC, and low to moderate saline (0.2 to 13.2 wt% NaCl eq.) mineralizing fluids. Au-Ag mineralization at Apigania Bay, which represents a late evolutionary phase, was deposited from even cooler (125o to 235oC) and dilute (0.2 to 6.8 wt % NaCl eq.) fluids. In all, the mineralization stage precipitation was controlled by two principal factors: the exsolution of gaseous phase and an increase in pH from 3.3 to 7.6

T-antigen expression in proliferating and non-proliferating simian virus 40-transformed mouse cells

Previous studies with simian virus 40-transformed mouse 3T3 cells which are temperature sensitive for the expression of the transformed phenotype (ts SV3T3 cells) have shown that T-antigen expression and viral DNA transcription are under cell cycle control. Using these ts SV3T3 cells, we studied the expression of the viral genome under proliferating and non-proliferating conditions, in the presence and absence of inhibitors of macromolecular synthesis and of the tumor promoter phorbol myristate acetate. ts SV3TE cells which are growth arrested at 39 degrees C by low serum concentration or saturation density accumulated in G1 and did not express T-antigen. When these cells were induced to proliferate, at either 32 or 39 degrees C, T-antigen synthesis preceded the entry of the cells into the S-phase and was not coupled to DNA replication. G1-arrested ts SV3T3 cells were induced to synthesize T-antigen by phorbol myristate acetate treatment, but T-antigen alone was not sufficient to induce cellular DNA synthesis. Isoleucine deprivation arrested growth of ts SV3T3 cells, but these cells, as well as normal 3T3, did not accumulate in G1 and continued to express T-antigen. The temperature-sensitive expression of the transformed phenotype in the ts SV3T3 cells does not appear to be due to a lack of transcription of specific regions of the integrated simian virus 40 genome at 39 degrees C.</jats:p

State of the viral DNA in rat cells transformed by polyoma virus. I. Virus rescue and the presence of nonintergrated viral DNA molecules

The interaction of polyoma virus with a continuous line of rat cells was studied. Infection of these cells with polyoma did not cause virus multiplication but induced transformation. Transformed cells did not produce infectious virus, but in all clones tested virus was rescuable upon fusion with permissive mouse cells. Transformed rat cells contained, in addition to integrated viral genomes, 20 to 50 copies of nonintegrated viral DNA equivalents per cell (average). "Free" viral DNA molecules were also found in cells transformed by the ts-a and ts-8 polyoma mutants and kept at 33 C. This was not due to a virus carrier state, since the number of nonintegrated viral DNA molecules was found to be unchanged when cells were grown in the presence of antipolyoma serum. Recloning of the transformed cell lines produced subclones, which also contained free viral DNA. Most of these molecules were supercoiled and were found in the muclei of the transformed cells. The nonintegrated viral DNA is infectious. Its specifici infectivity is, however, about 100-fold lower than that of polyoma DNA extracted from productively infected cells, suggesting that these molecules contain a large proportion of defectives.</jats:p

State of the viral DNA in rat cells transformed by polyma virus. II. Identification of the cells containing nonintegrated viral DNA and the effect of viral mutations

F2408 rat cells transformed by polyoma virus contained integrated and nonintegrated viral DNA. The presence of nonintegrated viral DNA is under control of the A early viral function. Polyoma ts-a-transformed rat cells lose the free viral DNA when growth at the nonpermissive temperature (40 degrees C), but they reexpress it 1 to 3 days after they are shifted back to the permissive temperature. In contrast, rat cells transformed by a late viral mutant, ts-8, contain free viral DNA at both permissive and nonpermissive temperatures. Treatment of the transformed rat cells with mitomycin C produces a large increase in the quantity of free viral DNA and some production of infectious virus. Experiments of in situ hybridization, with 3H-labeled polyoma complementary RNA as a probe, show that only a minority (approximately 0.1%) of the transformed cells contain nonintegrated viral DNA at any given time. These results suggest that the presence of free viral DNA in polyoma-transformed rat cells is caused by a spontaneous induction of viral DNA replication, occurring with low but constant probability in the transformed cell population, and that the free viral DNA molecules originate from the integrated ones, probably through a phenomenon of excision and limited replication.</jats:p