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Dopant deactivation in pure Si and pure Ge nanowires (NWs) can compromise the efficiency of the doping process at nanoscale. Quantum confinement, surface segregation and dielectric mismatch, in different ways, strongly reduce the carrier generation induced by intentional addition of dopants. This issue seems to be critical for the fabrication of high-quality electrical devices for various future applications, such as photovoltaics and nanoelectronics. By means of Density Functional Theory simulations, we show how this limit can be rode out in core-shell silicon-germanium NWs (SiGe NWs), playing on the particular energy band alignment that comes out at the Si/Ge interface. We demonstrate how, by choosing the appropriate doping configurations, it is possible to obtain a 1-D electron or hole gas, which has not to be thermally activated and which can furnish carriers also at very low temperatures. Our findings suggest core-shell NWs as possible building blocks for high-speed electronic device and new generation solar cells.

The Ca-Looping (CaL) technology, based on a dual gas-fluidized bed system of CaO/CaCO3 particles operated at high temperature, is a viable technological process for highly efficient pre-combustion and post-combustion CO2 capture. In this paper we show a lab-scale experimental study on the carbonation/ decarbonation of a fluidized bed of CaO particles at CaL conditions as affected by the application of a high-intensity acoustic field. The results obtained demonstrate that both carbonation and decarbonation are remarkably enhanced for sound intensity levels above 140 dB and frequencies of about 100 Hz. Fine particles (of size smaller than dp 100 lm) are entrained in the oscillating gas flow induced by an acoustic field of such low frequency, which yields a strong agitation of the bed and improves the gas-solid contact efficiency. On the other hand, an intense convection of gas flow (acoustic streaming) is generated on the surface of larger particles unmovable by the sound wave, which promotes the heat/mass transfer at the gas-solid boundary in this case. Either of these mechanisms, whose relative importance will depend on the average particle size and sound frequency, will contribute to increase the carbonation and decarbonation rates of CaO fluidized beds in the CaL technology.

Libro focalizzato sulle tecniche di caratterizzazione di sistemi e materiali per accumulo termico

Physical review letters 121(5), 051101 (2018). doi:10.1103/PhysRevLett.121.051101 Published by APS, College Park, Md.

Photocatalytic reforming of renewable raw materials in aqueous solutions represents a valid possibility for the valorization of wastes from agricultural and industrial processes. In this study, we prepared TiO2 materials with different phase compositions by changing the urea/Ti molar ratio employed during the hydrothermal preparation method. After deposition of Pt nanoparticles, the photocatalytic H2 production was investigated using ethanol and glycerol as sustainable sacrificial agent. While anatase/rutile nanocomposites showed poor catalytic activity, the anatase/brookite nanocomposites showed more promising performances. Specifically, the anatase-rich materials showed the best performances on mass bases. When normalized with respect to the surface area of the photocatalysts, the activity continuously increased with the brookite content, indicating that exposed facets of brookite possess an intrinsic higher activity than that of the other polymorphs.

The cosmopolitan solitary deep-water scleractinian coral Desmophyllum dianthus (Esper, 1794) was selected as a representative model species of the polyphyletic Caryophylliidae family to (1) examine phylogenetic relationships with respect to the principal Scleractinia taxa, (2) check population structure, (3) test the widespread connectivity hypothesis and (4) assess the utility of different nuclear and mitochondrial markers currently in use. To carry out these goals, DNA sequence data from nuclear (ITS and 28S) and mitochondrial (16S and COI) markers were analyzed for several coral species and for Mediterranean populations of D. dianthus. Three phylogenetic methodologies (ML, MP and BI), based on data from the four molecular markers, all supported D. dianthus as clearly belonging to the "robust" clade, in which the species Lophelia pertusa and D. dianthus not only grouped together, but also shared haplotypes for some DNA markers. Molecular results also showed shared haplotypes among D. dianthus populations distributed in regions separated by several thousands of kilometers and by clear geographic barriers. These results could reflect limited molecular and morphological taxonomic resolution rather than real widespread connectivity. Additional studies are needed in order to find molecular markers and morphological features able to disentangle the complex phylogenetic relationship in the Order Scleractinia and to differentiate isolated populations, thus avoiding the homoplasy found in some morphological characters that are still considered in the literature.

Multimedia data concern visual, audio, textual, information involving voice, gestures and others, so there are several challenges related to their storage and retrieval. Context awareness and personalization are key aspects to consider to manage any information-related content. In this paper we propose a general profiling model to define the user and context profiles in order to preserve and use their interrelationships. This general profiling model can be used tofilter the user query in a more precise and selective way and to filter the multimedia contents in the repository that match the user query. In this paper the personalization relies on the combined use of the user profiles and context profiles, and the combination driving in particular the choice of the interaction mode in order to make relevant information available to people in the appropriate form.