The optimization of the poor heat transfer characteristics of fluids conventionally employed in solar devices are at present one of the main topics for system efficiency and compactness. In the present work we investigated the optical and thermal properties of nanofluids consisting in aqueous suspensions of single wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption. We found that the thermal conductivity of the nanofluids was higher than pure water. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device.

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In the present work, we investigated the scattering and spectrally resolved absorption properties of nanofluids consisting in aqueous and glycol suspensions of single-wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption with respect to the pure base fluids. Scattered light was found to be not more than about 5% with respect to the total attenuation of light. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device.PACS78.40.Ri, 78.35.+c, 78.67.Bf, 88.40.fh, 88.40.fr, 81.05.U.

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Ultra-high temperature ceramics (UHTCs) are interesting materials for a large variety of applications under extreme conditions. This paper reports on the production and extensive characterization of highly dense, pure zirconium and tantalum diborides, with particular interest to their potential utilization in the thermal solar energy field. Monolithic bulk samples are produced by Spark Plasma Sintering starting from elemental reactants or using metal diboride powders previously synthesized by Self-propagating High-temperature Synthesis (SHS). Microstructural and optical properties of products obtained by the two processing methods have been comparatively evaluated. We found that pure diborides show a good spectral selectivity, which is an appealing characteristic for solar absorber applications. No, or very small, differences in the optical properties have been evidenced when the two investigated processes adopted for the fabrication of dense TaB2 and ZrB2, respectively, are compared

Intralipid 20% was recently suggested as a diffusive reference standard for tissue simulating phantoms. In this work, we extend previously obtained results to other fat emulsions, specifically Intralipid 10%, Intralipid 30%, Lipovenoes 10%, Lipovenoes 10% PhosphoLipid Reduced, Lipovenoes 20%, Lipofundin S 10%, and Lipofundin S 20%. Of particular importance for practical applications, our measurements carried out at a wavelength of 751 nm show the following features. First, these products show high stability and small batch-to-batch variations in their diffusive optical properties, similar to Intralipid 20%. Second, the absorption coefficient of Intralipid, Lipovenoes, and Lipofundin S are very similar and their measured values are within the experimental errors; moreover the reduced scattering coefficient of Intralipid 20%, Lipovenoes 20%, and Lipofundin S 20% are similar and their measured values are within 5%. Third, the reduced scattering coefficient of Intralipid 10% and Intralipid 30% can be scaled from that of Intralipid 20% with an error of 9% and 2%, respectively. A similar scaling property is valid for Lipovenoes and Lipofundin S. We have verified that this scaling property depends on the composition of the fat emulsions: If the ingredients exactly scale with the concentration then the reduced scattering coefficient almost exactly scale as well.

Our experiments, carried out at night and during the day on adults and laboratory-born young of the sandhopper Talitrus saltator, deal with the identification and use of the moon as an orientating factor. Sandhoppers were released in an apparatus (a Plexiglas dome) that produced a scenario similar to the natural one (with artificial sky, moon or sun illuminated at different intensities). When tested at night, the adult and young sandhoppers used the artificial moon like the natural one, independently of the intensity of illumination of the artificial sky and moon. In other words, sandhoppers tested at night always identified the artificial moon as the moon and never as the sun. In daytime releases, the seaward orientation failed at low intensities of artificial sky and sun illumination (3.07 and 1.55 microW cm2, respectively), whereas the sun compass was used effectively at higher levels of artificial sun and sky illumination. The innate ability of moon compass orientation in inexpert young sandhoppers was demonstrated even under artificial light.