[1] The temperature of the deposits left by different types of pyroclastic density currents (PDCs) of the A.D. 79 ''Pompei'' eruption of Vesuvius was estimated by measuring the thermal remanent magnetization (TRM) of lithic clasts carried by the currents. More than 200 lava clasts and roof tile fragments were collected at different sites and distances from the vent. The estimated temperatures fall in the range 180-380°C, although most of the samples show temperatures (T) in the range 240-340°C. This interval occurs for both the deposits of the same eruptive unit sampled at different sites and those derived from PDCs with similar physical characteristics. The sedimentological features coupled with the TRM data allow us to highlight the main processes controlling the T variability of the deposits and of their emplacing currents. The results reveal that air ingestion, involvement of external water, as well as transport and emplacement processes of the PDC are the most important factors in decreasing the emplacement T. The amount of lithic clasts carried by the currents does not play an important role in changing the final temperature because of the grain size and initial high T of these fragments.

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S U M M A R YVolcanic rocks forming sills, dykes or lava flows may display a magnetic anisotropy derived from the viscous flow during their emplacement. We model a sill as a steadystate flow of a Bingham fluid, driven by a pressure gradient in a horizontal conduit. The magma velocity as a function of depth is calculated from the motion and constitutive equations. Vorticity and strain rate are determined for a reference system moving with the fluid. The angular velocity and the orientation of an ellipsoidal magnetic grain immersed in the fluid are calculated as functions of time or strain. Magnetic susceptibility is then calculated for a large number of grains with a uniform distribution of initial orientations. It is shown that the magnetic lineation oscillates in the vertical plane through the magma flow direction, and that the magnetic foliation plane changes periodically from horizontal to vertical. The results are compared with the magnetic fabric of Ferrar dolerite sills (Victoria Land, East Antarctica) derived from low-field susceptibility measurements.

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Highly monodispersed CuO nanoparticles (NPs) were synthesized via continuous hydrothermal flow synthesis (CHFS) and then tested as catalysts for CO 2 hydrogenation. The catalytic behavior of unsupported 11 nm sized nanoparticles from the same batch was characterized by diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), extended X-ray absorption fine structure (EXAFS), X-ray diffraction (XRD), and catalytic testing, under CO 2 /H 2 in the temperature range 25− 500 °C in consistent experimental conditions. This was done to highlight the relationship among structural evolution, surface products, and reaction yields; the experimental results were compared with modeling predictions based on density functional theory (DFT) simulations of the CuO system. In situ DRIFTS revealed the formation of surface formate species at temperatures as low as 70 °C. DFT calculations of CO 2 hydrogenation on the CuO surface suggested that hydrogenation reduced the CuO surface to Cu 2 O, which facilitated the formation of formate. In situ EXAFS supported a strong correlation between the Cu 2 O phase fraction and the formate peak intensity, with the maxima corresponding to where Cu 2 O was the only detectable phase at 170 °C, before the onset of reduction to Cu at 190 °C. The concurrent phase and crystallite size evolution were monitored by in situ XRD, which suggested that the CuO NPs were stable in size before the onset of reduction, with smaller Cu 2 O crystallites being observed from 130 °C. Further reduction to Cu from 190 °C was followed by a rapid decrease of surface formate and the detection of adsorbed CO from 250 °C; these results are in agreement with heterogeneous catalytic tests where surface CO was observed over the same temperature range. Furthermore, CH 4 was detected in correspondence with the decomposition of formate and formation of the Cu phase, with a maximum conversion rate of 2.8% measured at 470 °C (on completely reduced copper), supporting the indication of independent reaction pathways for the conversion of CO 2 to CH 4 and CO that was suggested by catalytic tests. The resulting Cu NPs had a final crystallite size of ca. 44 nm at 500 °C and retained a significantly active surface.