901 research outputs found
Refertazione istopatologica e fattori prognostici del carcinoma mammario: requisiti minimi
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Unraveling the solidification path of a pahoehoe "cicirara" lava from Mount Etna volcano
No full textThe solidified surface of a lava flow reflects the viscosity of its molten fraction and the crystal content during flow; crystal-poor basaltic lavas produce pahoehoe fields, whereas crystal-rich ones solidify with aa carapaces. At Mount Etna volcano aa morphologies are very common, in turn, pahoehoe lavas are rare. The latter are locally named “cicirara” due to the presence of cm-sized plagioclase phenocrysts much more abundant than in aa lavas. The phenocryst content of “cicirara” lavas contrasts with the low viscosity generally associated with pahoehoe morphology. Therefore, to reconcile the discrepancy between textural and volcanic observations, we have studied the most primitive pahoehoe “cicirara” lava sampled until now. Two samples at 0.5 and 1 m from the bottom of the two-meter thick lava flow were investigated on the basis of their mineral compositional variations and textural features, i.e. size frequency and crystal size distribution (CSD). Results coupled with rheological models indicate that only large phenocrysts of plagioclase (>1 mm) and clinopyroxene have grown before eruption. Thermobarometric models and petrological computations based on the composition of plagioclase and clinopyroxene phenocryst cores highlight that only a small amount (10-15 vol.%) of crystals equilibrated at 12 km of depth. Cumulative size frequency and CSD data also indicate that plagioclase and clinopyroxene phenocryst rims grew heterogeneously and coalesced around their cores at depths <1 km, before eruption. In this view, the “cicirara” lava was erupted with a low crystalline content that favoured the formation of its pahoehoe surface; however, crystals with a size <1 mm (~75 vol.%) solidified at post-eruptive conditions.
Our findings underline that the emplacement of high-viscosity aa or low-viscosity pahoehoe lavas is driven by the degree of undercooling imposed by the volatile exsolution rate in the shallowest portion of the Etnean plumbing system. A slow magma ascent rate promotes significant intratelluric degassing and widespread nucleation; consequently, the viscosity of the suspension significantly increases leading to an aa morphology. In contrast, pahoehoe “cicirara” lavas are associated with a rapid rise to the surface of poorly degassed, undercooled magmas
The effect of L-Dopa administration on pursuit ocular movements in suspected Parkinson's disease
No full textThe objective of this study is to evaluate pursuit ocular movements (POM) by using a vision-based non-intrusive eye tracker, in patients with suspected Parkinson's disease (PD), before and after L-Dopa administration. We studied ten patients with suspected diagnosis of idiopathic PD. We compared POM values to those of a group of normal controls (NC), and evaluated them before and after L-Dopa administration. Unified Parkinson's Disease Rating Scale (UPDRS) motor subscores improved significantly (p = 0.001). At baseline, values of POM were lower in suspected PD patients than in NC (p = 0.01). One hour after L-Dopa administration, POM values correlated with UPDRS motor subscore (p = 0.01). We used a recent method, a new vision-based non-intrusive eye tracker, previously described, which can be proposed as a possible tool for supporting the diagnosis of PD in association with levodopa test, as an add-on to the UPDRS score. © Springer-Verlag 2009
The hepatitis B vaccine and celiac disease: more lights than shadows?
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Pharmacokinetic exposure and virological efficacy of a reduced atazanavir dose.
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Il varicocele essenziale: risultati preliminari della nostra esperienza e proposta di un nuovo criterio classificativo.
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Efavirenz dose reduction in HIV-infected patients: a long-term follow-up
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