Magnetic resonance imaging studies of spontaneous capillary water imbibition in aerated gypsum

International audienceIn this paper we investigate both capillary water imbibition and the sorptivity of aerated gypsum plaster, and how these sorption characteristics are related to the pore structure of the material. These characteristics are examined by monitoring mass change using the conventional gravimetric method and by obtaining water content profiles using nondestructive magnetic resonance imaging (MRI) techniques during capillary imbibition of water. Here, three different gypsum samples are investigated: one non-aerated reference gypsum sample and two aerated gypsum samples produced with different volumetric air fractions. The capillary water absorption into the reference sample follows t 1/2 kinetics (Fickian diffusion), where t is the time of ingress. However, in the aerated gypsum samples there are deviations from t 1/2 kinetics. The MRI results show unambiguously that two wetting fronts advance through the aerated structure ; an observation that cannot be made from the gravimetric data alone. The water content profiles of the aerated gypsum samples are therefore analysed by treating them as the sum of two separate absorption processes using Sharp Front (SF) analysis. The capillary water absorption properties of this material are well described as a parallel combination of fast absorption into fine matrix pores and slow absorption into a modified structure of matrix pores inter-connected to air voids introduced into the slurry by aeration. PACS 47.56.+r. flows through porous media PACS 47.55.nb. capillary and thermocapillary flow

Seeds of Life in Space (SOLIS). III. Zooming Into the Methanol Peak of the Prestellar Core L1544

Toward the prestellar core L1544, the methanol (CH3OH) emission forms an asymmetric ring around the core center, where CH3OH is mostly in solid form, with a clear peak at 4000 au to the northeast of the dust continuum peak. As part of the NOEMA Large Project SOLIS (Seeds of Life in Space), the CH3OH peak has been spatially resolved to study its kinematics and physical structure and to investigate the cause behind the local enhancement. We find that methanol emission is distributed in a ridge parallel to the main axis of the dense core. The centroid velocity increases by about 0.2 km s−1 and the velocity dispersion increases from subsonic to transonic toward the central zone of the core, where the velocity field also shows complex structure. This could be an indication of gentle accretion of material onto the core or the interaction of two filaments, producing a slow shock. We measure the rotational temperature and show that methanol is in local thermodynamic equilibrium (LTE) only close to the dust peak, where it is significantly depleted. The CH3OH column density, N tot(CH3OH), profile has been derived with non-LTE radiative transfer modeling and compared with chemical models of a static core. The measured N tot(CH3OH) profile is consistent with model predictions, but the total column densities are one order of magnitude lower than those predicted by models, suggesting that the efficiency of reactive desorption or atomic hydrogen tunneling adopted in the model may be overestimated; or that an evolutionary model is needed to better reproduce methanol abundance

VizieR Online Data Catalog: SOLIS. II. L1157-B1 NH2CHO image (Codella+, 2017)

Datacube in fits format of the NH2CHO(41,4-31,3) towards L1157-B1 using the IRAM-NOEMA interferometer (see Fig. 1). The L1157-B1 shock was observed at 3mm with the IRAM NOEMA seven-element array during several tracks in July, October, and November 2015 using both the C and D configurations. The shortest and longest baselines are 19m and 237m, respectively, allowing us to recover emission at scales up to ~17". (2 data files)

VizieR Online Data Catalog: SOLIS. I. OMC2-FIR4 HC3N and HC5N images (Fontani+, 2017)

IRAM-NOEMA Interferometer, 3mm receiver, Widex and Narrow-band correlators. Observations with the IRAM NOEMA Interferometer of HC3N (9-8) and HC5N (31-30), at rest frequencies 81.881468GHz and 82.539039GHz , respectively, towards OMC-2 FIR4 have been carried out over 5 days between the 5th and the 19th of August, 2015. The HC3N line was observed in the Widex band correlator, providing a resolution in velocity of ~7.15km/s, while the HC5N line was observed also in the Narrow band correlator with a resolution in velocity of ~0.57km/s. (2 data files)

Radiative properties of expanded polystyrene foams

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Modélisation du transfert de chaleur dans les mousses de PSE de faible densité

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Modeling of Heat Transfer in low-density EPS foams

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Experimental and theoretical study of the hot-wire method applied to low-density thermal insulators

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Experimental and theoretical study of the hot-ring method applied to low-density thermal insulators

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