On the properties of ITO, ZnO, ZnO:Al and NiO thin films obtained by thermal oxidation

Date du colloque : 10/2014International audienc

Vibrational spectra of C60C8H8 and C70C8H8 in the rotor-stator and polymer phases

C60-C8H8 and C70-C8H8 are prototypes of rotor-stator cocrystals. We present infrared and Raman spectra of these materials and show how the rotor-stator nature is reflected in their vibrational properties. We measured the vibrational spectra of the polymer phases poly(C60C8H8) and poly(C70C8H8) resulting from a solid state reaction occurring on heating. Based on the spectra we propose a connection pattern for the fullerene in poly(C60C8H8), where the symmetry of the C60 is D2h. On illuminating the C60-C8H8 cocrystal with green or blue light a photochemical reaction was observed leading to a similar product to that of the thermal polymerization.Comment: 26 pages, 8 figures, to appear in Journal of Physical Chemistry B 2nd version: minor changes in wording, accepted version by journa

VOLCANIC HAZARD ASSESSMENT AT SANTORINI VOLCANO: A REVIEW AND A SYNTHESIS IN THE LIGHT OF THE 2011-2012 SANTORINI UNREST

Το 2011 και το πρώτο εξάμηνο του 2012 η Σαντορίνη γνώρισε την πρώτη σεισμο-ηφαιστειακή κρίση από το 1950, όπως αυτή ανιχνεύθηκε από τα μόνιμα εγκατεστημένα δίκτυα παρακολούθησης και ένα μεγάλο αριθμό παροδικών μετρήσεων. Η διέγερση αυτή χαρακτηρίστηκε από μικρού μεγέθους, αλλά έντονη σεισμική δραστηριότητα, σημαντική ανύψωση και διόγκωση του νησιού, αλλαγές της θερμοκρασίας του νερού και των γεωχημικών αερίων. Ενώ η διέγερση έληξε την άνοιξη του 2012, το παγκόσμιο ενδιαφέρον οδήγησε στην εκπόνηση αρκετών μελετών, σε μια προσπάθεια να αξιολογηθούν τα πιθανά σενάρια για την εξέλιξη της διέγερσης. Στο πλαίσιο αυτό, συνοψίζουμε τα σημαντικότερα ευρήματα σχετικά με την επικινδυνότητα του ευρύτερου ηφαιστειακού συγκροτήματος της Σαντορίνης, καθώς και τις πληροφορίες που πρέπει να ληφθούν υπόψη για τη διαχείριση μιας πιθανής μελλοντικής ηφαιστειακής κρίσης.In 2011 and the first half of 2012 Santorini experienced its first seismo-volcanic unrest since 1950, as detected by the permanently installed monitoring networks and a large number of campaign measurements. The unrest was characterized by small magnitude but intense seismic activity, significant uplift and inflation deformation rates, and changes of water temperature as well as of fluid and soil gases. While the unrest ended in the spring of 2012, the world-wide interest led to the performance of several studies, in an attempt to assess the possible scenarios for the unrest evolution. Within this framework, we summarize the most important findings regarding the volcanic hazard assessment of the broader Santorini volcanic complex, as well as the constraints that need to be taken into account for a possible future volcanic crisis management

VOLCANIC HAZARD ASSESSMENT AT SANTORINI VOLCANO: A REVIEW AND A SYNTHESIS IN THE LIGHT OF THE 2011-2012 SANTORINI UNREST

Το 2011 και το πρώτο εξάμηνο του 2012 η Σαντορίνη γνώρισε την πρώτη σεισμο-ηφαιστειακή κρίση από το 1950, όπως αυτή ανιχνεύθηκε από τα μόνιμα εγκατεστημένα δίκτυα παρακολούθησης και ένα μεγάλο αριθμό παροδικών μετρήσεων. Η διέγερση αυτή χαρακτηρίστηκε από μικρού μεγέθους, αλλά έντονη σεισμική δραστηριότητα, σημαντική ανύψωση και διόγκωση του νησιού, αλλαγές της θερμοκρασίας του νερού και των γεωχημικών αερίων. Ενώ η διέγερση έληξε την άνοιξη του 2012, το παγκόσμιο ενδιαφέρον οδήγησε στην εκπόνηση αρκετών μελετών, σε μια προσπάθεια να αξιολογηθούν τα πιθανά σενάρια για την εξέλιξη της διέγερσης. Στο πλαίσιο αυτό, συνοψίζουμε τα σημαντικότερα ευρήματα σχετικά με την επικινδυνότητα του ευρύτερου ηφαιστειακού συγκροτήματος της Σαντορίνης, καθώς και τις πληροφορίες που πρέπει να ληφθούν υπόψη για τη διαχείριση μιας πιθανής μελλοντικής ηφαιστειακής κρίσης.In 2011 and the first half of 2012 Santorini experienced its first seismo-volcanic unrest since 1950, as detected by the permanently installed monitoring networks and a large number of campaign measurements. The unrest was characterized by small magnitude but intense seismic activity, significant uplift and inflation deformation rates, and changes of water temperature as well as of fluid and soil gases. While the unrest ended in the spring of 2012, the world-wide interest led to the performance of several studies, in an attempt to assess the possible scenarios for the unrest evolution. Within this framework, we summarize the most important findings regarding the volcanic hazard assessment of the broader Santorini volcanic complex, as well as the constraints that need to be taken into account for a possible future volcanic crisis management

Nitrogen, helium, and argon reveal the magmatic signature of fumarole gases and episodes of outgassing from upper-crustal magma reservoirs. The case of the Nisyros caldera (Aegean Arc, Greece)

The chemical composition of gases emitted by active volcanoes reflects both magma degassing and shallower processes, such as fluid-rock hydrothermal interaction and mixing with atmospheric-derived fluids. Untangling the magmatic fluid endmember within surface gas emission is therefore challenging, even with the use of well-known magma degassing tracers such as noble gases. Here, we investigate the deep magmatic fluid composition at the Nisyros caldera (Aegean Arc, Greece) by measuring nitrogen and noble gas abundances and isotopes in naturally degassing fumaroles. Gas samples were collected from 32 fumarolic vents at water-boiling temperature between 2018 and 2021. These fumaroles are admixtures of magmatic fluids typical of subduction zones, groundwater (or air saturated water, ASW), and air. The N2, He, and Ar composition of the magmatic endmember is calculated by reverse mixing modeling and shows N2/He = 31.8 ± 4.5, N2/Ar = 281.6, d15N = +7 ± 3 ‰, 3He/4He = 6.2 Ra (where Ra is air 3He/4He), and 40Ar/36Ar = 551.6 ± 19.8. Although N2/He is significantly low with respect to typical values for arc volcanoes (1,000–10,000), the contribution of subducted sediments to the Aegean Arc magma generation is reflected by the positive d15N values of Nisyros fumaroles. The low N2/He ratio indicates N2-depletion due to solubility-controlled differential degassing of an upper-crustal silicic (dacitic/ rhyodacitic) melt in a high-crystallinity reservoir. We compare our 2018–2021 data with N2, He, and Ar values collected from the same fumaroles during a hydrothermal unrest following the seismic crisis in 1996–1997. Results show additions of both magmatic fluid and ASW during this unrest. In the same period, fumarolic vents display an increase in magmatic species relative to hydrothermal gas, such as CO2/CH4 and He/CH4 ratios, an increase of 50 C in the equilibrium temperature of the hydrothermal system (up to 325 C), and greater amounts of vapor separation. These variations reflect an episode of magmatic fluid expulsion during the seismic crisis. The excess of heat and mass supplied by the magmatic fluid injection is then dissipated through boiling of deeper and peripheral parts of the hydrothermal system. Reverse mixing modeling of fumarolic N2-He-Ar has therefore important ramifications not only to disentangle the magmatic signature from gases emitted during periods of dormancy, but also to trace episodes of magmatic outgassing and better understand the state of the upper crustal reservoir

Data on unveiling the occurrence of transient, multi-contaminated mafic magmas inside a rhyolitic reservoir feeding an explosive eruption (Nisyros, Greece)

This data article includes the description and the geochemical and mineralogical dataset of 67 pyroclastic rock samples from the Upper Pumice (UP) explosive activity of Nisyros volcano (eastern South Aegean Active Volcanic Arc). A detailed field and petrographic description of the studied outcrops and samples are reported, including representative photomicrographs and SEM images, whole-rock major and trace elements compositions of 31 representative samples and Sr-Nd isotope ratios on 22 selected samples. Analytical methods and conditions used for data acquisition are also reported. The UP eruption produced a stratigraphic sequence constituted by a basal fallout deposit, gradually substituted by pyroclastic density current (PDC) deposits; these are overlaid by a lag-breccia unit, and the sequence is closed by a grey ash flow level. The juvenile is mainly constituted by white-yellow, moderately crystalline pumice with rhyolitic composition and homogenous Sr-Nd isotope values. Variable amounts of dense, grey, crystalline juvenile lapilli clasts (CRC, Crystal-Rich Clast), with rounded shape and less evolved composition (andesite to dacite) are also present in the deposit. These mafic CRCs are peculiar due to their large variability in textures (from distinctive diktytaxitic to strongly fragmented structure without a defined fabric) and in the geochemical and isotopic composition. The data acquired were fundamental to reconstruct the complex and peculiar history of ascent, storage and differentiation/assimilation processes of these mafic melts before their intrusion into the shallow, rhyolitic magma chamber, with important implication on the possible eruption trigger during the more recent explosive phase of activity at Nisyros volcano. Moreover, the geochemical and isotopic analyses provide new original data to the general knowledge of the Aegean volcanics. All the data reported in this paper are related to the research article Braschi et al. (2022

DEFORMATION PATTERN IN THE WESTERN NORTH AEGEAN TROUGH: PRELIMINARY RESULTS

Πρώτα αποτελέσματα της επεξεργασίας βυθομετρικών δεδομένων και σεισμικών τομών που συλλέχθηκαν στη διάρκεια τεσσάρων πλόων του προγράμματος ΕΣΠΑ "YPOTHER/Aegean Explorations" με το Ω/Κ Αιγαίο παρέχουν νέα στοιχεία για τον τεκτονικό ιστό, την κινηματική των ρηγμάτων και το είδος της παραμόρφωσης στο δυτικό τμήμα της Τάφρου του Βορείου Αιγαίου (NAT). Το δυτικό τμήμα του Ρήγματος Βόρειας Ανατολίας (NAF), με διεύθυνση N40°E, εντοπίζεται κατά μήκος του νότιου περιθωρίου της NAT. Πολυάριθμα δευτερεύοντα ρήγματα με μεγάλη γωνία κλίσης αρχίζουν από το ίχνος του NAF και με μικρή γωνία ως προς αυτό. Η διεύθυνση τους αλλάζει σταδιακά από NE SW σε SE-NW και δημιουργούν ένα σύνολο επάλληλων και διακλαδιζόμενων, καμπύλων ρηγμάτων, μια καλοσχηματισμένη δομή "ουράς αλόγου" (horsetail structure) στο δυτικό άκρο του NAF. H δομή αυτή παραμορφώνει την ιζηματογενή ακολουθία της NAT δημιουργώντας επιμήκη, ατρακτοειδούς και καμπύλου σχήματος, ανυψούμενα και βυθιζόμενα, τεκτονικά μπλοκ. Σε αντίθεση με το αναμενόμενο πλαγιο-εφελκυστικό καθεστώς, το δυτικό τμήμα της NAT παραμορφώνεται με διάτμηση και πλαγιο-συμπίεση που συνάδουν με συμπίεση σε διεύθυνση NW-SE. Η πιθανή εξήγηση της παραμόρφωσης αυτής σχετίζεται με την αλλαγή της διεύθυνσης του NAF από N40°E σε N70°E στο ανατολικό τμήμα της NAT.Preliminary interpretation of swath bathymetry data and seismic profiles acquired during four cruises of "YPOTHER/Aegean Explorations" project aboard R/V Aegaeo provides insights into the fault network, fault kinematics and deformation pattern of the western part of the North Aegean Trough (NAT). The N40°E trending western part of the dextral North Anatolian Fault (NAF) runs along the southern margin of the NAT. Numerous high-angle fault splays initiate from and at low angle to NAF. They run firstly in NE-SW direction and then gradually turn to SE-NW forming an imbricate fault pattern, a nicely developed horsetail structure at the western termination of the NAF. The horsetail pattern deforms the NAT's sedimentary infill forming elongate, curved, uplifting or subsiding tectonic blocks arranged along the fault splays. Instead of the expected transtension, the Western NAT's infill displays dextral shearing and transpression associated with a major stress axis in NW-SE direction. The possible explanation for the transpressional deformation of the Western NAT infill may be related with the change of the trend of NAF from N40°E in the western trough to N70°E east of Lemnos Island

Optimal Heterojunction Organic Photovoltaics bearing Self‐Organized Active Layers

Date du colloque : 07/2014International audienc