Base de dados : MEDLINE
Pesquisa : G01.060.075.730.700.831 [Categoria DeCS]
Referências encontradas : 291 [refinar]
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  1 / 291 MEDLINE  
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[PMID]:28408557
[Au] Autor:Seewald JS
[Ad] Endereço:Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. jseewald@whoi.edu.
[Ti] Título:Detecting molecular hydrogen on Enceladus.
[So] Source:Science;356(6334):132-133, 2017 04 14.
[Is] ISSN:1095-9203
[Cp] País de publicação:United States
[La] Idioma:eng
[Mh] Termos MeSH primário: Hidrogênio
Saturno
[Mh] Termos MeSH secundário: Meio Ambiente Extraterreno
[Pt] Tipo de publicação:JOURNAL ARTICLE; COMMENT
[Nm] Nome de substância:
7YNJ3PO35Z (Hydrogen)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170926
[Lr] Data última revisão:
170926
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170415
[St] Status:MEDLINE
[do] DOI:10.1126/science.aan0444


  2 / 291 MEDLINE  
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[PMID]:28103106
[Au] Autor:Brassé C; Buch A; Coll P; Raulin F
[Ad] Endereço:1 Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR CNRS 7583, Université Paris Est Créteil et Université Paris Diderot , Institut Pierre Simon Laplace, C.M.C., Créteil, France .
[Ti] Título:Low-Temperature Alkaline pH Hydrolysis of Oxygen-Free Titan Tholins: Carbonates' Impact.
[So] Source:Astrobiology;17(1):8-26, 2017 Jan.
[Is] ISSN:1557-8070
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Titan, the largest moon of Saturn, is one of the key planetary objects in the field of exobiology. Its dense, nitrogen-rich atmosphere is the site of important organic chemistry. This paper focuses on the organic aerosols produced in Titan's atmosphere that play an important role in atmospheric and surface processes and in organic chemistry as it applies to exobiological interests. To produce reliable laboratory analogues of these aerosols, we developed, tested, and optimized a device for the synthesis of clean tholins. The potential chemical evolution of Titan aerosols at Titan's surface has been studied, in particular, the possible interaction between aerosols and putative ammonia-water cryomagma. Modeling of the formation of Saturn's atmosphere has permitted the characterization of a composition of salts in the subsurface ocean and cryolava. From this new and original chemical composition, a laboratory study of several hydrolyses of tholins was carried out. The results obtained show the formation of many organic compounds, among them, species identified only in the presence of salts. In addition, a list of potential precursors of these compounds was established, which could provide a database for research of the chemical composition of tholins and/or aerosols of Titan. Key Words: Titan tholins-Titan aerosols-Hydrolysis-Carbonates-Titan's surface. Astrobiology 17, 8-26.
[Mh] Termos MeSH primário: Aerossóis/química
Álcalis/química
Carbonatos/química
Temperatura Baixa
Oxigênio/química
Saturno
[Mh] Termos MeSH secundário: Aminoácidos/análise
Cromatografia Gasosa-Espectrometria de Massas
Concentração de Íons de Hidrogênio
Hidrólise
Oceanos e Mares
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Aerosols); 0 (Alkalies); 0 (Amino Acids); 0 (Carbonates); S88TT14065 (Oxygen)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171009
[Lr] Data última revisão:
171009
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170120
[St] Status:MEDLINE
[do] DOI:10.1089/ast.2016.1524


  3 / 291 MEDLINE  
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[PMID]:27798575
[Au] Autor:Postberg F; Tobie G; Dambeck T
[Ti] Título:Under the Sea of Enceladus.
[So] Source:Sci Am;315(4):38-45, 2016 Sep 20.
[Is] ISSN:0036-8733
[Cp] País de publicação:United States
[La] Idioma:eng
[Mh] Termos MeSH primário: Meio Ambiente Extraterreno
Oceanos e Mares
Saturno
[Mh] Termos MeSH secundário: Exobiologia
Fontes Hidrotermais
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1706
[Cu] Atualização por classe:170615
[Lr] Data última revisão:
170615
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161101
[St] Status:MEDLINE
[do] DOI:10.1038/scientificamerican1016-38


  4 / 291 MEDLINE  
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[PMID]:27552160
[Au] Autor:Nadeau J; Lindensmith C; Deming JW; Fernandez VI; Stocker R
[Ad] Endereço:1 GALCIT, California Institute of Technology , Pasadena, California.
[Ti] Título:Microbial Morphology and Motility as Biosignatures for Outer Planet Missions.
[So] Source:Astrobiology;16(10):755-774, 2016 Oct.
[Is] ISSN:1557-8070
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Meaningful motion is an unambiguous biosignature, but because life in the Solar System is most likely to be microbial, the question is whether such motion may be detected effectively on the micrometer scale. Recent results on microbial motility in various Earth environments have provided insight into the physics and biology that determine whether and how microorganisms as small as bacteria and archaea swim, under which conditions, and at which speeds. These discoveries have not yet been reviewed in an astrobiological context. This paper discusses these findings in the context of Earth analog environments and environments expected to be encountered in the outer Solar System, particularly the jovian and saturnian moons. We also review the imaging technologies capable of recording motility of submicrometer-sized organisms and discuss how an instrument would interface with several types of sample-collection strategies. Key Words: In situ measurement-Biosignatures-Microbiology-Europa-Ice. Astrobiology 16, 755-774.
[Mh] Termos MeSH primário: Archaea/citologia
Bactérias/citologia
Exobiologia/métodos
Meio Ambiente Extraterreno
Voo Espacial
[Mh] Termos MeSH secundário: Corrente Citoplasmática
Terra (Planeta)
Camada de Gelo/microbiologia
Júpiter
Microscopia
Oceanos e Mares
Saturno
Microbiologia da Água
[Pt] Tipo de publicação:JOURNAL ARTICLE; REVIEW
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170926
[Lr] Data última revisão:
170926
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160824
[St] Status:MEDLINE


  5 / 291 MEDLINE  
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[PMID]:27108425
[Au] Autor:Zymak I; Zabka J; Polásek M; Spanel P; Smith D
[Ad] Endereço:J. Heyrovský Institute of Physical Chemistry of the ASCR, Dolejskova 2155/3, 182 23, Prague 8, Czech Republic. illia.zymak@jh-inst.cas.cz.
[Ti] Título:A Pilot Study of Ion - Molecule Reactions at Temperatures Relevant to the Atmosphere of Titan.
[So] Source:Orig Life Evol Biosph;46(4):533-538, 2016 Nov.
[Is] ISSN:1573-0875
[Cp] País de publicação:Netherlands
[La] Idioma:eng
[Ab] Resumo:Reliable theoretical models of the chemical kinetics of the ionosphere of Saturn's moon, Titan, is highly dependent on the precision of the rates of the reactions of ambient ions with hydrocarbon molecules at relevant temperatures. A Variable Temperature Selected Ions Flow Tube technique, which has been developed primarily to study these reactions at temperatures within the range of 200-330 K, is briefly described. The flow tube temperature regulation system and the thermalisation of ions are also discussed. Preliminary studies of two reactions have been carried out to check the reliability and efficacy of kinetics measurements: (i) Rate constants of the reaction of CH ions with molecular oxygen were measured at different temperatures, which indicate values in agreement with previous ion cyclotron resonance measurements ostensibly made at 300 K. (ii) Formation of CH ions in the reaction of N ions with CH molecules were studied at temperatures within the range 240-310 K which showed a small but statistically significant decrease of the ratio of product CH ions to reactant N ions with reaction temperature.
[Mh] Termos MeSH primário: Atmosfera/química
Meio Ambiente Extraterreno
Saturno
[Mh] Termos MeSH secundário: Íons/química
Cinética
Modelos Químicos
Projetos Piloto
Temperatura Ambiente
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Ions)
[Em] Mês de entrada:1704
[Cu] Atualização por classe:171031
[Lr] Data última revisão:
171031
[Sb] Subgrupo de revista:IM; S
[Da] Data de entrada para processamento:160425
[St] Status:MEDLINE


  6 / 291 MEDLINE  
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[PMID]:27068153
[Au] Autor:Hrusák J; Paidarová I
[Ad] Endereço:J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejskova 3, 182 23, Prague, Czech Republic. jan.hrusak@jh-inst.cas.cz.
[Ti] Título:Step Towards Modeling the Atmosphere of Titan: State-Selected Reactions of O with Methane.
[So] Source:Orig Life Evol Biosph;46(4):419-424, 2016 Nov.
[Is] ISSN:1573-0875
[Cp] País de publicação:Netherlands
[La] Idioma:eng
[Ab] Resumo:Methane conversion and in particular the formation of the C-O bond is one of fundamental entries to organic chemistry and it appears to be essential for understanding parts of atmospheric chemistry of Titan, but, in broader terms it might be also relevant for Earth-like exoplanets. Theoretical study of the reactions of methane with atomic oxygen ion in its excited electronic states requires treating simultaneously at least 19 electronic states. Development of a computational strategy that would allow chemically reasonable and computationally feasible treatment of the CH (X)/O ( D, P) system is by far not trivial and it requires careful examination of all the complex features of the corresponding 19 potential energy surfaces. Before entering the discussion of the rich (photo) chemistry, inspection of the long range behavior of the system with focus on electric dipole transition moments is required. Our calculations show nonzero probability for the reactants to decay before entering the multiple avoided crossings region of the [CH + O â†’ products] reaction. For the CH /O ( P) system non-zero transition moment probabilities occur over the entire range of considered C-O distances (up to 15 Å), while for the CH /O ( D) system these probabilities are lower by one order of magnitude and were found only at C-O distances smaller than 6 Å.
[Mh] Termos MeSH primário: Atmosfera
Meio Ambiente Extraterreno
Modelos Teóricos
Saturno
[Mh] Termos MeSH secundário: Exobiologia
Metano/química
Oxigênio/química
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
OP0UW79H66 (Methane); S88TT14065 (Oxygen)
[Em] Mês de entrada:1704
[Cu] Atualização por classe:171031
[Lr] Data última revisão:
171031
[Sb] Subgrupo de revista:IM; S
[Da] Data de entrada para processamento:160413
[St] Status:MEDLINE


  7 / 291 MEDLINE  
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[PMID]:26701303
[Au] Autor:Grazier KR
[Ad] Endereço:Jet Propulsion Laboratory, California Institute of Technology , Pasadena, California.
[Ti] Título:Jupiter: Cosmic Jekyll and Hyde.
[So] Source:Astrobiology;16(1):23-38, 2016 Jan.
[Is] ISSN:1557-8070
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:It has been widely reported that Jupiter has a profound role in shielding the terrestrial planets from comet impacts in the Solar System, and that a jovian planet is a requirement for the evolution of life on Earth. To evaluate whether jovians, in fact, shield habitable planets from impacts (a phenomenon often referred to as the "Jupiter as shield" concept), this study simulated the evolution of 10,000 particles in each of the jovian inter-planet gaps for the cases of full-mass and embryo planets for up to 100 My. The results of these simulations predict a number of phenomena that not only discount the "Jupiter as shield" concept, they also predict that in a Solar System like ours, large gas giants like Saturn and Jupiter had a different, and potentially even more important, role in the evolution of life on our planet by delivering the volatile-laden material required for the formation of life. The simulations illustrate that, although all particles occupied "non-life threatening" orbits at their onset of the simulations, a significant fraction of the 30,000 particles evolved into Earth-crossing orbits. A comparison of multiple runs with different planetary configurations revealed that Jupiter was responsible for the vast majority of the encounters that "kicked" outer planet material into the terrestrial planet region, and that Saturn assisted in the process far more than has previously been acknowledged. Jupiter also tends to "fix" the aphelion of planetesimals at its orbit irrespective of their initial starting zones, which has the effect of slowing their passages through the inner Solar System, and thus potentially improving the odds of accretion of cometary material by terrestrial planets. As expected, the simulations indicate that the full-mass planets perturb many objects into the deep outer Solar System, or eject them entirely; however, planetary embryos also did this with surprising efficiency. Finally, the simulations predict that Jupiter's capacity to shield or intercept Earth-bound comets originating in the outer Solar System is poor, and that the importance of jovian planets on the formation of life is not that they act as shields, but rather that they deliver life-enabling volatiles to the terrestrial planets.
[Mh] Termos MeSH primário: Júpiter
[Mh] Termos MeSH secundário: Simulação por Computador
Evolução Planetária
Saturno
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Em] Mês de entrada:1610
[Cu] Atualização por classe:161230
[Lr] Data última revisão:
161230
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:151225
[St] Status:MEDLINE
[do] DOI:10.1089/ast.2015.1321


  8 / 291 MEDLINE  
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[PMID]:26559966
[Au] Autor:Taubner RS; Leitner JJ; Firneis MG; Hitzenberger R
[Ad] Endereço:Research Platform: ExoLife, University of Vienna, Türkenschanzstraße 17, 1180, Vienna, Austria. ruth-sophie.taubner@univie.ac.at.
[Ti] Título:Modelling the Interior Structure of Enceladus Based on the 2014's Cassini Gravity Data.
[So] Source:Orig Life Evol Biosph;46(2-3):283-8, 2016 Jun.
[Is] ISSN:1573-0875
[Cp] País de publicação:Netherlands
[La] Idioma:eng
[Ab] Resumo:We present a model for the internal structure of Saturn's moon Enceladus. This model allows us to estimate the physical conditions at the bottom of the satellite's potential subsurface water reservoir and to determine the radial distribution of pressure and gravity. This leads to a better understanding of the physical and chemical conditions at the water/rock boundary. This boundary is the most promising area on icy moons for astrobiological studies as it could serve as a potential habitat for extraterrestrial life similar to terrestrial microbes that inhabit rocky mounds on Earth's sea floors.
[Mh] Termos MeSH primário: Meio Ambiente Extraterreno
Gravitação
Modelos Estatísticos
Saturno
[Mh] Termos MeSH secundário: Exobiologia
Seres Humanos
Gelo/análise
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Ice)
[Em] Mês de entrada:1611
[Cu] Atualização por classe:171031
[Lr] Data última revisão:
171031
[Sb] Subgrupo de revista:IM; S
[Da] Data de entrada para processamento:151113
[St] Status:MEDLINE
[do] DOI:10.1007/s11084-015-9475-9


  9 / 291 MEDLINE  
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[PMID]:26204935
[Au] Autor:Kirk BB; Savee JD; Trevitt AJ; Osborn DL; Wilson KR
[Ad] Endereço:Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 6R2100, Berkeley, CA 94720-8226, USA. krwilson@lbl.gov.
[Ti] Título:Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡CË™) with small alkenes and alkynes.
[So] Source:Phys Chem Chem Phys;17(32):20754-64, 2015 Aug 28.
[Is] ISSN:1463-9084
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.
[Mh] Termos MeSH primário: Alcenos/química
Alquinos/química
Atmosfera/química
Saturno
[Mh] Termos MeSH secundário: Radicais Livres/química
Estrutura Molecular
Peso Molecular
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Nm] Nome de substância:
0 (Alkenes); 0 (Alkynes); 0 (Free Radicals)
[Em] Mês de entrada:1601
[Cu] Atualização por classe:150806
[Lr] Data última revisão:
150806
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:150725
[St] Status:MEDLINE
[do] DOI:10.1039/c5cp02589c


  10 / 291 MEDLINE  
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[PMID]:25761113
[Au] Autor:McLendon C; Opalko FJ; Illangkoon HI; Benner SA
[Ad] Endereço:1 Foundation for Applied Molecular Evolution , Gainesville, Florida.
[Ti] Título:Solubility of polyethers in hydrocarbons at low temperatures. A model for potential genetic backbones on warm titans.
[So] Source:Astrobiology;15(3):200-6, 2015 Mar.
[Is] ISSN:1557-8070
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Ethers are proposed here as the repeating backbone linking units in linear genetic biopolymers that might support Darwinian evolution in hydrocarbon oceans. Hydrocarbon oceans are found in our own solar system as methane mixtures on Titan. They may be found as mixtures of higher alkanes (propane, for example) on warmer hydrocarbon-rich planets in exosolar systems ("warm Titans"). We report studies on the solubility of several short polyethers in propane over its liquid range (from 85 to 231 K, or -188 °C to -42 °C). These show that polyethers are reasonably soluble in propane at temperatures down to ca. 200 K. However, their solubilities drop dramatically at still lower temperatures and become immeasurably low below 170 K, still well above the ∼ 95 K in Titan's oceans. Assuming that a liquid phase is essential for any living system, and genetic biopolymers must dissolve in that biosolvent to support Darwinism, these data suggest that we must look elsewhere to identify linear biopolymers that might support genetics in Titan's surface oceans. However, genetic molecules with polyether backbones may be suitable to support life in hydrocarbon oceans on warm Titans, where abundant organics and environments lacking corrosive water might make it easier for life to originate.
[Mh] Termos MeSH primário: Temperatura Baixa
Éteres/química
Meio Ambiente Extraterreno/química
Hidrocarbonetos/química
Modelos Teóricos
[Mh] Termos MeSH secundário: Evolução Biológica
Biopolímeros/química
Estruturas Genéticas
Saturno
Solubilidade
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Nm] Nome de substância:
0 (Biopolymers); 0 (Ethers); 0 (Hydrocarbons)
[Em] Mês de entrada:1510
[Cu] Atualização por classe:150312
[Lr] Data última revisão:
150312
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:150312
[St] Status:MEDLINE
[do] DOI:10.1089/ast.2014.1212



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