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Marcella Contini 《Astrophysics and Space Science》1996,238(2):217-222
It is suggested that X-ray diffraction rings by small silicate crystals included into small cloudlets of dust grains or space debris within the Galaxy could be observable. 相似文献
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Michael A. Dopita Marcella Marconi Gisella Clementini Enzo Brocato 《Astrophysics and Space Science》2012,338(1):1-2
In recent papers we had developed a unified picture of black hole entropy and curvature which was shown to lead to Hawking
radiation. It was shown that for any black hole mass, holography implies a phase space of just one quantum associated with
the interior of the black hole. Here we study extremal rotating and charged black holes and obtain unique values for ratios
of angular momentum to entropy, charge to entropy, etc. It turns out that these ratios can be expressed in terms of fundamental
constants in nature, having analogies with other physical systems, like in condensed matter physics. 相似文献
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Chow-Choong Ngeow Shashi M. Kanbur Earl P. Bellinger Marcella Marconi Ilaria Musella Michele Cignoni Ya-Hong Lin 《Astrophysics and Space Science》2012,341(1):105-113
This paper discusses two aspects of current research on the Cepheid period-luminosity (P-L) relation: the derivation of mid-infrared (MIR) P-L relations and the investigation of multi-phase P-L relations. 相似文献
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Mafic enclaves in the rhyolitic products of Lipari historical eruptions; relationships with the coeval Vulcano magmas (Aeolian Islands, Italy) 总被引：1，自引：0，他引：1
The recent finding of mafic enclaves in the Rocche Rosse (RR) lava flow, the last magmatic product on Lipari (Aeolian Islands,
Italy) (AD 1230 ± 40), opens the possibility to investigate in detail the most recent magmatic system of the island, an important
issue for the volcanic hazard assessment of the area. The RR lava flow is an aphyric rhyolitic coulée consisting of grey and
black pumice and black and grey obsidian. Enclaves have ellipsoidal to spheroidal shape and vary from mm-sized in the central
portion of the flow, to cm-sized, at the top and in the flow front, where they are also more abundant. Enclaves are shoshonitic-latitic
(group A) and trachytic (group B) in composition. The mineralogy of group A consists of dominant clinopyroxene crystals with
minor abundance of feldspar (plagioclase > K-feldspar), olivine and biotite, while group B is composed of feldspar (K-feldspar > plagioclase)
with minor clinopyroxene, olivine and biotite. Geochemical modeling suggests that the host rhyolitic rocks could be the product
of AFC (Assimilation plus Fractional Crystallization) of a magma compositionally similar to the associated shoshonitic-latitic
enclaves, which, in turn, could be obtained, through an AFC process, from the primitive melts erupted as olivine hosted melt
inclusions during the last 15 ka at Vulcano. The already-known last 42 ka relationship between Lipari and Vulcano Islands
is here reinforced until historical time, especially for the last 1 ka. The geochemical and petrological overlap between Lipari
and Vulcano is interpreted to reflect the existence of a similar magmatic system underneath the two islands. The nearly aphyric
RR rhyolites are interpreted to be the products of a superheated (temperature far above the liquidus) and initially water-undersaturated
magma that underwent degassing close to the surface inhibiting microlite crystallization. 相似文献
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Marcella Contini 《Monthly notices of the Royal Astronomical Society》2009,399(3):1175-1190
We present consistent modelling of line and continuum infrared (IR) spectra in the region close to the Galactic Centre. The models account for the coupled effect of shocks and photoionization from an external source. The results show that the shock velocities range between ∼65 and 80 km s−1 and the pre-shock densities between 1 cm−3 in the interstellar medium (ISM) to 200 cm−3 in the filamentary structures. The pre-shock magnetic field increases from 5 × 10−6 G in the surrounding ISM to ∼8 × 10−5 G in the arched filaments. The stellar temperatures are ∼38 000 K in the Quintuplet cluster and ∼27 000 K in the Arches Cluster. The ionization parameter is relatively low (<0.01) with the highest values near the clusters, reaching a maximum >0.01 near the Arches Cluster. Depletion from the gaseous phase of Si is found throughout the whole observed region, indicating the presence of silicate dust. Grains including iron are concentrated throughout the arched filaments. The modelling of the continuum spectral energy distribution in the IR range indicates that a component of dust at temperatures of ∼100–200 K is present in the central region of the Galaxy. Radio emission appears to be thermal bremsstrahlung in the E2–W1 filaments crossing strip; however, a synchrotron component is not excluded. More data are necessary to resolve these questions. 相似文献
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The Early Christian Munazio Ireneo cubicle in Cagliari (Sardinia) is carved into the rock and is one of the rare monuments of Sardinia belonging to Early Christian Age. It is 166 cm under the planking level and is a semi-confined chamber in which a gate allows exchange with the outside. In 1888, when it was discovered, it was completely painted, but over the years, it suffered a serious damage and all the paintings are nearly disappeared. Now the site shows a high moisture and a differential damage characterised by delamination, powdering, salt crystallisation and biological colonisation. The research offers a multidisciplinary approach to study the salt crystallisation damage, which is a phenomenon still not completely understood today. Studies and analyses highlight that different kinds of damage can be recognised. The cement mortar and the air pollution cause crystallisation of the sulphates. Constant capillary rising and the presence of water infiltration due to the rains, which travelled into the site from the vault, were detected during qualitative inspection. Although the microclimate did not change much in the site and the humidity was almost constant during the monitoring period, the variations in temperature allowed the phase transitions of sodium sulphate, especially in summer. The greatest damage of the porous stone is associated with the phase transitions and crystallisation inside the stone of sodium sulphate, one of the most harmful salts for porous materials because of its high crystallisation pressure. 相似文献
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Marcella Leonardi Filippo Azzaro Maurizio Azzaro Gabriella Caruso Monique Mancuso Luis Salvador Monticelli Giovana Maimone Rosabruna La Ferla Francesco Raffa & Renata Zaccone 《Marine Ecology》2009,30(S1):33-42
In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C/N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH4 , NO2 , NO3 , PO4 ]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes. 相似文献