Contribution to the evolution of the Perama Cave (Ioannina, NW Greece).

Με την έρευνα αυτή δίδεται η συστηματική ταξινόμηση τριάντα τριών τύπων σπηλαιοθεμάτων από το σπήλαιο Περάματος Ιωαννίνων, μαζί με την ερμηνεία σχηματισμού τους, σύμφωνα με τη διεθνή βιβλιογραφία, για πρώτη φορά στην Ελλάδα. Η λεπτομερής μελέτη των σπηλαιοθεμάτων σε συνδυασμό με παρατηρήσεις αναφορικά με τον τρόπο και τη θέση σχηματισμού συγκεκριμένων ομάδων σπηλαιοθεμάτων μας οδήγησαν να προτείνουμε την εξέλιξη του σπηλαίου Περάματος μέσω μιας σειράς διαδοχικών επεισοδίων, τα οποία συμπεριλαμβάνουν τη διάλυση των Σενώνιων ασβεστόλιθων, την κατάρρευση της οροφής του σπηλαίου, καθώς και εναλλασσόμενα επεισόδια σχηματισμού σπηλαιοθεμάτων σταλακτιτικού και σταλαγμιτικού τύπου με εκτεταμένες ροές νερού ή/και πλημμύρες, οι οποίες οδήγησαν στην ανάπτυξη μορφών ροήςThis study includes the description of thirty three speleothem types, which were found in the Perama cave, Ioannina, NW Greece, according to the international literature, along with the interpretation of their formation, for the first time in Greece. The detailed study of these speleothems coupled with observations of the way of their formation and their spatial distribution enabled us to suggest that the Perama cave evolved through a sequence of episodes that include dissolution of the host Senonian limestone, collapse of its roof formations, as well as alternating events of formation of stalactitic- and stalagmitic-type speleothems with excess water flow and/or flooding, which resulted in the development of stream formation

Widespread abiotic methane in chromitites

Recurring discoveries of abiotic methane in gas seeps and springs in ophiolites and peridotite massifs worldwide raised the question of where, in which rocks, methane was generated. Answers will impact the theories on life origin related to serpentinization of ultramafic rocks, and the origin of methane on rocky planets. Here we document, through molecular and isotopic analyses of gas liberated by rock crushing, that among the several mafic and ultramafic rocks composing classic ophiolites in Greece, i.e., serpentinite, peridotite, chromitite, gabbro, rodingite and basalt, only chromitites, characterized by high concentrations of chromium and ruthenium, host considerable amounts of 13C-enriched methane, hydrogen and heavier hydrocarbons with inverse isotopic trend, which is typical of abiotic gas origin. Raman analyses are consistent with methane being occluded in widespread microfractures and porous serpentine- or chlorite-filled veins. Chromium and ruthenium may be key metal catalysts for methane production via Sabatier reaction. Chromitites may represent source rocks of abiotic methane on Earth and, potentially, on Mars

Grammatikopoulosite, NiVP, a New Phosphide from the Chromitite of the Othrys Ophiolite, Greece

Grammatikopoulosite, NiVP, is a new phosphide discovered in the podiform chromitite and hosted in the mantle sequence of the Othrys ophiolite complex, central Greece. The studied samples were collected from the abandoned chromium mine of Agios Stefanos. Grammatikopoulosite forms small crystals (from 5 μm up to about 80 μm) and occurs as isolated grains. It is associated with nickelphosphide, awaruite, tsikourasite, and an undetermined V-sulphide. It is brittle and has a metallic luster. In plane-polarized light, it is creamy-yellow, weakly bireflectant, with measurable but not discernible pleochroism and slight anisotropy with indeterminate rotation tints. Internal reflections were not observed. Reflectance values of mineral in air (R1, R2 in %) are: 48.8–50.30 at 470 nm, 50.5–53.5 at 546 nm, 51.7–55.2 at 589 nm, and 53.2–57.1 at 650 nm. Five spot analyses of grammatikopoulosite give the average composition: P 19.90, S 0.41, Ni 21.81, V 20.85, Co 16.46, Mo 16.39, Fe 3.83, and Si 0.14, total 99.79 wt %. The empirical formula of grammatikopoulosite—based on Σ(V + Ni + Co + Mo + Fe + Si) = 2 apfu, and taking into account the structural results—is (Ni0.57Co0.32Fe0.11)Σ1.00(V0.63Mo0.26Co0.11)Σ1.00(P0.98S0.02)Σ1.00. The simplified formula is (Ni,Co)(V,Mo)P and the ideal formula is NiVP, which corresponds to Ni 41.74%, V 36.23%, P 22.03%, total 100 wt %. The density, calculated on the basis of the empirical formula and single-crystal data, is 7.085 g/cm3. The mineral is orthorhombic, space group Pnma, with a = 5.8893(8), b = 3.5723(4), c = 6.8146(9) Å, V = 143.37(3) Å3, and Z = 4. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2019-090). The mineral honors Tassos Grammatikopoulos, geoscientist at the SGS Canada Inc., for his contribution to the economic mineralogy and mineral deposits of Greece.This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Methane flux and origin in the Othrys ophiolite hyperalkaline springs, Greece

The occurrence and origin of methane (CH4) generated by serpentinization of ultramafic rocks is of current timely interest in planetary geology, astrobiology and energy resource exploration, as it may contribute, in particular, to decipher the source of methane on Mars, the origin of life and the potential of abiotic hydrocarbon synthesis. Methane of dominant abiotic origin in serpentinized peridotites on continents (ophiolites or igneous intrusions) has been documented so far, with complete carbon and hydrogen isotope composition, in six countries, in the Philippines, Turkey, Oman, New Zealand, Japan and Italy. We report the discovery of two new sites in Greece, at Archani and Ekkara, located in the Othrys ophiolite massif. Portable sensors based on Fourier Transform InfraRed spectrometry (FTIR) and Tunable Diode Laser Absorption Spectroscopy (TDLAS) allowed to realize that out of 21 ophiolitic springs, methane is released only by four hyperalkaline (pH from 10.7 to 11.3) and calcium hydroxide (Ca–OH) type waters; all other 17 springs with pH b 8.7 and magnesium-rich waters in the Pindos, Vourinos and Veria ophiolites, do not show methane. This correlation between gas occurrence and water type seems to occur worldwide; accordingly, CH4 production appears to be intimately related to the depth and residence time of the circulating meteoric waters. Methane is emitted into the atmosphere also from the soil surrounding the hyperalkaline springs, with fluxes of the same order of magnitude (~102–103 mg m−2 day−1) of seepage typically observed over conventional petroleum systems. Othrys CH4 has an isotopic composition (δ13C from −27‰ to −37.3‰ VPDB, δ2H from −250‰ to −311‰ VSMOW) similar to that reported in ultramafic rocks in New Zealand and Japan, and in Precambrian crystalline shields, which were considered dominantly abiotic and probably derived from Fischer–Tropsch Type reactions. The paucity of CO2, which is the norm in hyperalkaline waters, and of other hydrocarbons prevents from evaluating possible mixing of gas of different sources, including microbial methanogenesis. Also the H2 content is trivial, notwithstanding it being a typical product of serpentinization; this could be due to complete H2 consumption by CO2 reduction in a limited or decreased H2 production system due, for example, to a late stage of increased silica activity, as suggested by preliminary petrographic observations. The low geothermal gradient of the area and the present-day serpentinization imply that,whatever the CH4 production mechanism, it took place at temperatures below those traditionally considered for the origin of abiotic methane in hydrothermal systems

Methane flux and origin in the Othrys ophiolite hyperalkaline springs, Greece

The occurrence and origin of methane (CH4) generated by serpentinization of ultramafic rocks is of current timely interest in planetary geology, astrobiology and energy resource exploration, as it may contribute, in particular, to decipher the source of methane on Mars, the origin of life and the potential of abiotic hydrocarbon synthesis. Methane of dominant abiotic origin in serpentinized peridotites on continents (ophiolites or igneous intrusions) has been documented so far, with complete carbon and hydrogen isotope composition, in six countries, in the Philippines, Turkey, Oman, New Zealand, Japan and Italy. We report the discovery of two new sites in Greece, at Archani and Ekkara, located in the Othrys ophiolite massif. Portable sensors based on Fourier Transform InfraRed spectrometry (FTIR) and Tunable Diode Laser Absorption Spectroscopy (TDLAS) allowed to realize that out of 21 ophiolitic springs, methane is released only by four hyperalkaline (pH from 10.7 to 11.3) and calcium hydroxide (Ca–OH) type waters; all other 17 springs with pH b 8.7 and magnesium-rich waters in the Pindos, Vourinos and Veria ophiolites, do not show methane. This correlation between gas occurrence and water type seems to occur worldwide; accordingly, CH4 production appears to be intimately related to the depth and residence time of the circulating meteoric waters. Methane is emitted into the atmosphere also from the soil surrounding the hyperalkaline springs, with fluxes of the same order of magnitude (~102–103 mg m−2 day−1) of seepage typically observed over conventional petroleum systems. Othrys CH4 has an isotopic composition (δ13C from −27‰ to −37.3‰ VPDB, δ2H from −250‰ to −311‰ VSMOW) similar to that reported in ultramafic rocks in New Zealand and Japan, and in Precambrian crystalline shields, which were considered dominantly abiotic and probably derived from Fischer–Tropsch Type reactions. The paucity of CO2, which is the norm in hyperalkaline waters, and of other hydrocarbons prevents from evaluating possible mixing of gas of different sources, including microbial methanogenesis. Also the H2 content is trivial, notwithstanding it being a typical product of serpentinization; this could be due to complete H2 consumption by CO2 reduction in a limited or decreased H2 production system due, for example, to a late stage of increased silica activity, as suggested by preliminary petrographic observations. The low geothermal gradient of the area and the present-day serpentinization imply that,whatever the CH4 production mechanism, it took place at temperatures below those traditionally considered for the origin of abiotic methane in hydrothermal systems.Published161-1747A. Geofisica di esplorazioneJCR Journalrestricte

Economic evaluation of nimesulide versus diclofenac in the treatment of osteoarthritis in Greece

Objective: To evaluate, from a social security system perspective, the economic consequences of treating rheumatic diseases with nimesulide or diclofenac. Design: Cost-minimisation analysis was used to estimate the incremental direct medical cost and the cost of gastrointestinal adverse events for 15 days' treatment with nimesulide compared with diclofenac. Cumulative incidence of adverse events was calculated through meta-analysis of the results of double-blind randomised clinical trials. The therapeutic pathway for ambulatory care resource use was determined by a panel of experts, and direct hospital costs were estimated from a sample of 43 patients. Main outcome measures and results: The 15-day treatment cost with nimesulide was 35.9% lower compared with diclofenac due to the lower incidence of adverse events. Our analysis showed that nimesulide generated a cost saving of $US20.98 per patient depending on the dosage of diclofenac used

Non-β-cell progenitors of β-cells in pregnant mice

Pregnancy is a normal physiological condition in which the maternal beta-cell mass increases rapidly about two-fold to adapt to new metabolic challenges. We have used a lineage tracing of beta-cells to analyse the origin of new beta-cells during this rapid expansion in pregnancy. Double transgenic mice bearing a tamoxifen-dependent Cre-recombinase construct under the control of a rat insulin promoter, together with a reporter Z/AP gene, were generated. Then, in response to a pulse of tamoxifen before pregnancy, beta-cells in these animals were marked irreversibly and heritably with the human placental alkaline phosphatase (HPAP). First, we conclude that the lineage tracing system was highly specific for beta-cells. Secondly, we scored the proportion of the beta-cells marked with HPAP during a subsequent chase period in pregnant and non-pregnant females. We observed a dilution in this labeling index in pregnant animal pancreata, compared to nonpregnant controls, during a single pregnancy in the chase period. To extend these observations we also analyzed the labeling index in pancreata of animals during the second of two pregnancies in the chase period. The combined data revealed statistically-significant dilution during pregnancy, indicating a contribution to new beta cells from a non-beta-cell source. Thus for the first time in a normal physiological condition, we have demonstrated not only beta-cell duplication, but also the activation of a non-beta-cell progenitor population. Further, there was no transdifferentiation of beta-cells to other cell types in a two and half month period following labeling, including the period of pregnancy