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Thin films containing a mixture of aliphatic (glycine) and aromatic (tryptophan or tyrosine) amino acids were exposed to a vacuum ultraviolet radiation (VUV) with wavelenghts 100–200 nm. Dipeptides (glycyl-tryptophan and glycyl-tyrosine) were synthesized in these conditions. We compared the actions of VUV and γ-radiation. Polymerization is an essential step in prebiological evolution and we have shown that this stage probably occured over an early Solar system history.  相似文献   
2.
The Grain Impact Analyser and Dust Accumulator (GIADA) onboard the ROSETTA mission to comet 67P/Churyumov–Gerasimenko is devoted to study the cometary dust environment. Thanks to the rendezvous configuration of the mission, GIADA will be plunged in the dust environment of the coma and will be able to explore dust flux evolution and grain dynamic properties with position and time. This will represent a unique opportunity to perform measurements on key parameters that no ground-based observation or fly-by mission is able to obtain and that no tail or coma model elaborated so far has been able to properly simulate. The coma and nucleus properties shall be, then, clarified with consequent improvement of models describing inner and outer coma evolution, but also of models about nucleus emission during different phases of its evolution. GIADA shall be capable to measure mass/size of single particles larger than about 15 μm together with momentum in the range 6.5 × 10−10 ÷ 4.0 × 10−4 kg m s−1 for velocities up to about 300 m s−1. For micron/submicron particles the cumulative mass shall be detected with sensitivity 10−10 g. These performances are suitable to provide a statistically relevant set of data about dust physical and dynamic properties in the dust environment expected for the target comet 67P/Churyumov–Gerasimenko. Pre-flight measurements and post-launch checkouts demonstrate that GIADA is behaving as expected according to the design specifications. The International GIADA Consortium (I, E, UK, F, D, USA).  相似文献   
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Fulchignoni  M.  Ferri  F.  Angrilli  F.  Bar-Nun  A.  Barucci  M.A.  Bianchini  G.  Borucki  W.  Coradini  M.  Coustenis  A.  Falkner  P.  Flamini  E.  Grard  R.  Hamelin  M.  Harri  A.M.  Leppelmeier  G.W.  Lopez-Moreno  J.J.  McDonnell  J.A.M.  McKay  C.P.  Neubauer  F.H.  Pedersen  A.  Picardi  G.  Pirronello  V.  Rodrigo  R.  Schwingenschuh  K.  Seiff  A.  Svedhem  H.  Vanzani  V.  Zarnecki  J. 《Space Science Reviews》2002,104(1-4):395-431
The Huygens Atmospheric Structure Instrument (HASI) is a multi-sensor package which has been designed to measure the physical quantities characterising the atmosphere of Titan during the Huygens probe descent on Titan and at the surface. HASI sensors are devoted to the study of Titan's atmospheric structure and electric properties, and to provide information on its surface, whether solid or liquid. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
4.
Automatic speaker recognition systems have been largely dominated by acoustic-spectral-based systems, relying in proper modelling of the short-term vocal tract of speakers. However, there is scientific and intuitive evidence that speaker-specific information is embedded in the speech signal in multiple short- and long-term characteristics. In this work, a multilevel speaker recognition system combining acoustic, phonotactic, and prosodic subsystems is presented and assessed by blind submission to NIST 2005 Speaker Recognition Evaluation  相似文献   
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