169,963 research outputs found
Deep explosive focal depths during maar forming magmatichydrothermal eruption: Baccano Crater, Central Italy
No full textAbstract We describe the eruptive activity of the
Pleistocene composite Baccano maar crater in the
Sabatini Volcanic Complex (Central Italy) combining
stratigraphy, grain size/componentry and rare earth
element and Yttrium (REY) composition of its eruptive
products with the stratigraphy and geothermal data
derived from deep wells drilled on the Baccano structural
high. The main lithological characteristics of the basal
Baccano maar pyroclastic deposit, composed of more
than 60% wt of non-thermometamorphosed lithic clasts
from the sedimentary basement, show that the first
eruption was magmatic-hydrothermal in nature. The
lithology of the sedimentary lithic clasts indicates that
the fragmentation level was at a depth of −1,000 to −1,200 m,
with fragment depth verified by deep well stratigraphy. The
15% wt juvenile non-vesicular glass components suggest that
magma played a minor role in powering the eruption.
Assuming that the high-salinity hot hydrothermal fluids
(365<T<410°C and P∼25 MPa), hosted in the highly
permeable and confined aquifer below the Baccano maar
are representative of those at the time of the eruption, we
propose that hydrofracturing would have triggered the
eruption caused by overpressure at the top of the geothermal
aquifer. REY analysis performed on pyroclastic fragments
and basement rocks suggest that partial dissolution of the
deeper limestones (>−1,400 m) by the aggressive hydrothermal
fluids enriched in acid components (HF, HCl, and
H2SO4) may have contributed to increased CO2 partial
pressure that helped to drive the hydrofracturing. This could
have caused rapid vapour separation and pressure drop,
allowing the almost simultaneous breaking of the aquifer
cover and brecciation of the calcareous units down to −1,000
to −1,200 m depth. The relative abundance of calcareous
lithics in the basal part of the first Baccano eruptive unit,
representing about the upper 200 m of stratigraphy below the
top of the Baccano structural high, reveals the descent of the
piezometric surface during the eruption. Combining deep
well information and maar product stratigraphy, using also
REY data from maar pyroclastic fragments and the basement
rocks we draw an interpretative model for the Baccano maarforming
eruption, concluding that a) magmatic-hydrothermal
eruptions may originate deeper than previously thought,
and b) hydrothermal fluids circulating in limestone
aquifers m
Hemianopic ataxic hemiparesis. A case report.
No full textAtaxic hemiparesis and homonimous hemianopia developed in a hypertensive 60-year-old woman. Magnetic resonance imaging detected multiple lesions in the territory of distribution of the posterior cerebral artery and in the inferior region of the left cerebellar hemisphere. At computed tomography only a right hypodense area involving the posterior right thalamus, the postero-medial region of the temporal lobe and the occipital lobe was evident
Sul processo di marforming di un acciaio inossidabile martensitico a 16% di cromo e 2% di nichel
No full text
Mitoxantrone treatment in multiple sclerosis: a 5-year clinical and MRI follow-up
No full textMitoxantrone (MTX) is an antineoplastic agent approved for treatment of secondary progressive and rapidly worsening relapsing-remitting multiple sclerosis (MS). We designed a longitudinal open-label prospective study to evaluate the efficacy and toxicity of MTX over a 2-year treatment period with a further 3-year follow-up. Fifty consecutive MS patients were included and received MTX intravenously (8 mg/m(2) every 2 months for a total of 12 infusions). Efficacy was assessed clinically and by brain MRI performed before MTX therapy, at the end of treatment and at the end of each year of follow-up. Forty-nine patients completed the 5-year study, 44 (89.8%) completed the MTX course, five (10.2%) interrupted the treatment because of side effects. Fifteen (30.6%) patients showed Expanded Disability Status Scale (EDSS) progression on treatment and nine (18.4%) during follow-up. Seventeen (34.7%) patients had enhancing lesions at baseline, nine (18.4%) at the end of treatment, but none at the end of follow-up. In conclusion, we observed EDSS progression in about 1/3 of the patients during the treatment period and in 115 during the further 3-year follow-up period. This evidence suggests a delayed beneficial effect after MTX treatment is completed with only a minority of patients showing disability progression once the drug was suspended
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