Instituto Superior Técnico

About: Instituto Superior Técnico is a based out in . It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 10085 authors who have published 30226 publications receiving 667524 citations. The organization is also known as: IST & Instituto Superior Tecnico.

High-energy collision of two black holes.

Abstract: We study the head-on collision of two highly boosted equal mass, nonrotating black holes. We determine the waveforms, radiated energies, and mode excitation in the center of mass frame for a variety of boosts. For the first time we are able to compare analytic calculations, black-hole perturbation theory, and strong field, nonlinear numerical calculations for this problem. Extrapolation of our results, which include velocities of up to 0.94c, indicate that in the ultrarelativistic regime about 14±3% of the energy is converted into gravitational waves. This gives rise to a luminosity of order 10^-2c^5/G, the largest known so far in a black-hole merger.

CO2 hydrogenation into CH4 on NiHNaUSY zeolites

Abstract: CO2 hydrogenation into methane was carried out over catalysts containing nickel and cerium species supported on a HNaUSY zeolite, using an H2/CO2 ratio of 4 and temperatures ranging from 250 to 450 °C. Interesting CO2 conversions and CH4 selectivities were achieved for Ni-zeolite catalysts prepared by impregnation. Conversion increased with the Ni content from 2 to 14%, due to the higher amount of Ni0 species after reduction. A further enhancement of the catalysts performances was noticed when doping the Ni-zeolites catalysts with 3–15% of Ce. Actually, the presence of CeO2 after reduction might promote CO2 activation into CO, the final catalyst properties being due to the synergetic effect between the metal active sites and the promoter. Furthermore, almost no deactivation due to sintering was observed after 10 h of reaction at 400 °C. Comparing these results with those reported in literature it is possible to conclude that zeolites have great potential to be used as catalyst supports for the CO2 methanation reaction. In fact, taking the commercially available and widely used HNaUSY zeolite, it was possible to reach conversions and selectivities similar to those previously found in the literature for the best CO2 methanation catalysts that use potentially more expensive bulk cerium oxide supports, even without performing any optimization of the zeolite support.

Unusually Strong Delayed Fluorescence of C70

Abstract: C70 (like other fullerenes) is known to have a very weak fluorescence (ΦF ≅ 5 × 10-4), owing to the high efficiency of triplet formation. In this work we show that, under appropriate conditions, the fluorescence quantum yield increases by one or two orders of magnitude (up to an estimated maximum value ΦF = 0.08), through the mechanism of delayed thermal fluorescence. We also report a new estimate of the singlet−triplet gap (26 ± 2 kJ mol-1), obtained from the temperature dependence of the delayed thermal fluorescence. This value is shown to be in agreement with the phosphorescence spectrum recorded in the same temperature range. An accurate value of the quantum yield of triplet formation (0.994 ± 0.001) is obtained from a new method of data analysis.