Role of dynamic Jahn-Teller distortions in Na2C60 and Na2CsC60 studied by NMR

Through 13C NMR spin lattice relaxation (T1) measurements in cubic Na2C60, we detect a gap in its electronic excitations, similar to that observed in tetragonal A4C60. This establishes that Jahn-Teller distortions (JTD) and strong electronic correlations must be considered to understand the behaviour of even electron systems, regardless of the structure. Furthermore, in metallic Na2CsC60, a similar contribution to T1 is also detected for 13C and 133Cs NMR, implying the occurence of excitations typical of JT distorted C60^{2-} (or equivalently C60^{4-}). This supports the idea that dynamic JTD can induce attractive electronic interactions in odd electron systems.Comment: 3 figure

Space-oriented navigation solutions with integrated sensor-suite: the I3DS H2020 project

In all orbital applications, such as on-orbit servicing and repair, rendezvous and docking, active debrisremoval (ADR), and planetary applications, such as exploration of unknown environments for scientificpurposes by means of rovers, GPS-denied navigation aspects have a very large impact on the successfuloutcome of missions. Having a sensor suite, and hence several different sensors, also requires, at the sametime, a suite of navigation algorithms able to deal with different kinds of inputs. Some of them, however,can be shared between multiple sensors, after thorough pre-processing of the raw data. Additionally, thesame kind of sensor can require two different navigation algorithms depending on the scenario. The workdescribed in this paper aims to present and critically discuss the approach to precise relative navigationsolutions with a complete suite of sensors and their performance in different space-oriented applicationscenarios.Standalone navigation filters are examined. In the case of a high-resolution camera for an orbitalscenario, the pose of a target, with respect to a chaser, can be thoroughly obtained with the aid offiducial markers. Stereo camera-based navigation is also addressed with visual odometry. In the case of astereo camera the problem of scale estimation during odometry is solved by means of triangulation. Sincethe outputs of the sensor-suite are also dense 3D point clouds, Iterative Closest Point and Histogram ofDistances (HoD) with Kalman filter approaches are analyzed, paying attention to the provision of correctsensor characterization. The results for each filter are exhaustively examined, highlighting their strengthsand the points where some improvements can be achieve

SENSIBILIDADE DE ESPECTROS DE ONDAS OCEÂNICAS RECUPERADOS POR RADAR DE ABERTURA SINTÉTICA

SAR (Synthetic Aperture Radar ou Radar de Abertura Sintética) é o único sensor transportado por satélites capaz de medir o espectro direcional de ondas. Sua elevada cobertura espacial e temporal permite caracterizar o estado de mar, especialmente a região de baixa frequência do espectro de energia, que vem sendo assimilada em modelos numéricos de previsão de ondas em diversos centros operacionais espalhados pelo globo. Contudo, a extração do espectro de ondas de uma imagem SAR é um procedimento complexo. Alguns modos de operação não permitem o emprego de imagens sequenciais para resolver a ambiguidade direcional de propagação das ondas, o que requer informações adicionais, geralmente obtidas de um modelo de ondas. A dependência destas informações adicionais é investigada aplicando-se a inversão clássica de Hasselmann a alguns estados de mar teóricos. Esta abordagem é baseada na transformação analítica do espectro direcional de ondas sobre o espectro de imagem SAR correspondente. A solução deste problema inverso é determinada por um algoritmo numérico que minimiza um funcional não linear. Apesar de amplamente utilizado por diversos centros operacionais de previsão, este método não foi extensivamente testado em cenários experimentais bem definidos. Os resultados mostram que a dependência investigada é bastante significativa, sobretudo no que diz respeito à direção de propagação das ondas, levantando questionamentos sobre a acurácia da técnica

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Copernicus Marine Service ocean state report, issue 4

This is the final version. Available from Taylor & Francis via the DOI in this record. FCT/MCTE

New pseudonucleosides containing chiral oxazolidin-2-ones and cyclosulfamides as aglycones: Synthesis and antiviral evaluation

9 - conference paper: Proceedings of the 17th International Roundtable of Nucleosides, Nucleotides, and Nucleic Acids MAR 07-SEP 07, 2006 Bern (SWITZERLAND)A series of chiral cyclosulfamides and oxazolidinon-2-ones have been synthesized starting from aminoacids. Regioselective substitution of these pseudopyrimidic heterocyles was carried out under Mitsunobu conditions. Best substitution results were obtained by preliminary deprotection of cyclosulfamides and their condensation with beta-D-ribofuranose. Chiral oxazolidin-2-ones were coupled directly with D-ribofuranose. All compounds were tested against HSV-2, VV and SV viruses. Two compounds 6b and 6e showed significant activities against HSV-type 1

Crystal structure of 4-phenyl-piperazine-1-sulfonamide

1 - ArticleThe structure of 4-phenyl-piperazine-1-sulfonamide was determined by X-ray crystallography. The compound crystallized in a monoclinic system and was characterized as follows: P21/c, a = 24.1829(7), b = 9.5485(3), c = 9.7885(2)Å, β = 92.2337(16)°, Z = 8, V = 2258.55(11)Å3. The crystal structure was solved by direct methods and refined by full-matrix least-squares on F2 to final values of R1 = 0.0427 for 3206 reflections [I > 2σ(I)] and R1 = 0.0739, wR2 = 0.1083 for all the 4589 unique reflections. The crystal structure consists of layers of polar regions that enclose a sulfonamide function linked by hydrogen bonds and hydrophobic regions with π-π stacking interactions

Pharmacological and toxicological effects of Paronychia argentea in experimental calcium oxalate nephrolithiasis in rats

1 - ArticleAim of the study: Renal protection and antiurolithiasic effects of two extracts of Paronychia argentea (PA), a traditional Algerian plant commonly known as Algerian tea, were evaluated. This study was carried out to determine whether the aqueous extract (APA) or the butanolic extract (BPA) of aerial parts could prevent or reduce calculi aggregation in experimental calcium oxalate (Ox) nephrolithiasis in Wistar rats. Materials and methods: The two extracts (APA and BPA) were administrated orally and daily, during 28 days to nephrolithiasic treated rats at the dose of 250, 500 mg/kg b.w. and 10, 20 mg/kg b.w. respectively. Body weight, renal index, liver index, serum level of creatinine, uric acid, urea, K(+), Ca(2+), Mg(2+), Na(+) and transaminase (alanine aminotransferase, ALT; aspartate aminotransferase, AST), phosphatase alkaline activity (PAL) were evaluated following the 28 days treatment in rats. In addition histopathological changes in kidney and liver were stained in hematoxylin eosin (HE). Results: The effect of the extracts could be advantageous in preventing urinary stone retention by reducing renal necrosis and thus inhibit crystal retention. In contradiction with APA, the two doses of BPA attenuated elevation in the serum creatinine (p<0.01) and blood urea levels (p<0.01) (nephroprotective effect). However, the increase in ALT (27%) and PAL (31-51%) serum levels and in the relative liver weights (p<0.01) in the groups treated with doses of APA may indicate that this extract has not a hepatoprotective effect against oxalate toxicity. Conclusions: The presented data indicate that administration of the butanolic extract of aerial parts to rats with NaOx induced lithiasis, and reduced and prevented the growth of urinary stones in experimental calcium oxalate nephrolithiasis in Wistar rats. (C) 2010 Elsevier Ireland Ltd. All rights reserved