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Pesquisa : G01.060.075.730.700.200 [Categoria DeCS]
Referências encontradas : 1918 [refinar]
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  1 / 1918 MEDLINE  
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[PMID]:29323115
[Au] Autor:Becker S; Schneider C; Okamura H; Crisp A; Amatov T; Dejmek M; Carell T
[Ad] Endereço:Center for Integrated Protein Science Munich CiPSM at the Department of Chemistry, Ludwig-Maximilians-Universität München, 81377, Munich, Germany.
[Ti] Título:Wet-dry cycles enable the parallel origin of canonical and non-canonical nucleosides by continuous synthesis.
[So] Source:Nat Commun;9(1):163, 2018 01 11.
[Is] ISSN:2041-1723
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:The molecules of life were created by a continuous physicochemical process on an early Earth. In this hadean environment, chemical transformations were driven by fluctuations of the naturally given physical parameters established for example by wet-dry cycles. These conditions might have allowed for the formation of (self)-replicating RNA as the fundamental biopolymer during chemical evolution. The question of how a complex multistep chemical synthesis of RNA building blocks was possible in such an environment remains unanswered. Here we report that geothermal fields could provide the right setup for establishing wet-dry cycles that allow for the synthesis of RNA nucleosides by continuous synthesis. Our model provides both the canonical and many ubiquitous non-canonical purine nucleosides in parallel by simple changes of physical parameters such as temperature, pH and concentration. The data show that modified nucleosides were potentially formed as competitor molecules. They could in this sense be considered as molecular fossils.
[Mh] Termos MeSH primário: Biopolímeros/química
Nucleosídeos/química
RNA/química
Água/química
[Mh] Termos MeSH secundário: Terra (Planeta)
Evolução Química
Modelos Químicos
Estrutura Molecular
Origem da Vida
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Biopolymers); 0 (Nucleosides); 059QF0KO0R (Water); 63231-63-0 (RNA)
[Em] Mês de entrada:1803
[Cu] Atualização por classe:180305
[Lr] Data última revisão:
180305
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180112
[St] Status:MEDLINE
[do] DOI:10.1038/s41467-017-02639-1


  2 / 1918 MEDLINE  
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[PMID]:28460085
[Au] Autor:Wadsworth J; Cockell CS
[Ad] Endereço:UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH10 4EP, UK.
[Ti] Título:The Janus face of iron on anoxic worlds: iron oxides are both protective and destructive to life on the early Earth and present-day Mars.
[So] Source:FEMS Microbiol Ecol;93(5), 2017 05 01.
[Is] ISSN:1574-6941
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:The surface of the early Earth was probably subjected to a higher flux of ultraviolet (UV) radiation than today. UV radiation is known to severely damage DNA and other key molecules of life. Using a liquid culture and a rock analogue system, we investigated the interplay of protective and deleterious effects of iron oxides under UV radiation on the viability of the model organism, Bacillus subtilis. In the presence of hydrogen peroxide, there exists a fine balance between iron oxide's protective effects against this radiation and its deleterious effects caused by Photo-Fenton reactions. The maximum damage was caused by a concentration of hematite of ∼1 mg/mL. Concentrations above this confer increasing protection by physical blockage of the UV radiation, concentrations below this cause less effective UV radiation blockage, but also a correspondingly less effective Photo-Fenton reaction, providing an overall advantage. These results show that on anoxic worlds, surface habitability under a high UV flux leaves life precariously poised between the beneficial and deleterious effects of iron oxides. These results have relevance to the Archean Earth, but also the habitability of the Martian surface, where high levels of UV radiation in combination with iron oxides and hydrogen peroxide can be found.
[Mh] Termos MeSH primário: Bacillus subtilis/genética
Dano ao DNA/efeitos dos fármacos
Dano ao DNA/efeitos da radiação
Compostos Férricos/farmacologia
Peróxido de Hidrogênio/farmacologia
Raios Ultravioleta/efeitos adversos
[Mh] Termos MeSH secundário: DNA/efeitos dos fármacos
DNA/efeitos da radiação
Terra (Planeta)
Ferro/química
Marte
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Ferric Compounds); 1K09F3G675 (ferric oxide); 9007-49-2 (DNA); BBX060AN9V (Hydrogen Peroxide); E1UOL152H7 (Iron)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:171224
[Lr] Data última revisão:
171224
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170502
[St] Status:MEDLINE
[do] DOI:10.1093/femsec/fix056


  3 / 1918 MEDLINE  
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[PMID]:28953943
[Au] Autor:Midekisa A; Holl F; Savory DJ; Andrade-Pacheco R; Gething PW; Bennett A; Sturrock HJW
[Ad] Endereço:Malaria Elimination Initiative, Global Health Group, University of California San Francisco, San Francisco, California, United States of America.
[Ti] Título:Mapping land cover change over continental Africa using Landsat and Google Earth Engine cloud computing.
[So] Source:PLoS One;12(9):e0184926, 2017.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Quantifying and monitoring the spatial and temporal dynamics of the global land cover is critical for better understanding many of the Earth's land surface processes. However, the lack of regularly updated, continental-scale, and high spatial resolution (30 m) land cover data limit our ability to better understand the spatial extent and the temporal dynamics of land surface changes. Despite the free availability of high spatial resolution Landsat satellite data, continental-scale land cover mapping using high resolution Landsat satellite data was not feasible until now due to the need for high-performance computing to store, process, and analyze this large volume of high resolution satellite data. In this study, we present an approach to quantify continental land cover and impervious surface changes over a long period of time (15 years) using high resolution Landsat satellite observations and Google Earth Engine cloud computing platform. The approach applied here to overcome the computational challenges of handling big earth observation data by using cloud computing can help scientists and practitioners who lack high-performance computational resources.
[Mh] Termos MeSH primário: Computação em Nuvem
Terra (Planeta)
Sistemas de Informação Geográfica
[Mh] Termos MeSH secundário: África
Modelos Teóricos
Astronave
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171024
[Lr] Data última revisão:
171024
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170928
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0184926


  4 / 1918 MEDLINE  
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[PMID]:28614348
[Au] Autor:Schreiber U; Mayer C; Schmitz OJ; Rosendahl P; Bronja A; Greule M; Keppler F; Mulder I; Sattler T; Schöler HF
[Ad] Endereço:Department of Geology, University Duisburg-Essen, Universitaetsstr. 5, Essen, Germany.
[Ti] Título:Organic compounds in fluid inclusions of Archean quartz-Analogues of prebiotic chemistry on early Earth.
[So] Source:PLoS One;12(6):e0177570, 2017.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The origin of life is still an unsolved mystery in science. Hypothetically, prebiotic chemistry and the formation of protocells may have evolved in the hydrothermal environment of tectonic fault zones in the upper continental crust, an environment where sensitive molecules are protected against degradation induced e.g. by UV radiation. The composition of fluid inclusions in minerals such as quartz crystals which have grown in this environment during the Archean period might provide important information about the first organic molecules formed by hydrothermal synthesis. Here we present evidence for organic compounds which were preserved in fluid inclusions of Archean quartz minerals from Western Australia. We found a variety of organic compounds such as alkanes, halocarbons, alcohols and aldehydes which unambiguously show that simple and even more complex prebiotic organic molecules have been formed by hydrothermal processes. Stable-isotope analysis confirms that the methane found in the inclusions has most likely been formed from abiotic sources by hydrothermal chemistry. Obviously, the liquid phase in the continental Archean crust provided an interesting choice of functional organic molecules. We conclude that organic substances such as these could have made an important contribution to prebiotic chemistry which might eventually have led to the formation of living cells.
[Mh] Termos MeSH primário: Prebióticos/análise
Quartzo/análise
Água/química
[Mh] Termos MeSH secundário: Terra (Planeta)
Seres Humanos
Metano/análise
Origem da Vida
Austrália Ocidental
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Prebiotics); 059QF0KO0R (Water); 14808-60-7 (Quartz); OP0UW79H66 (Methane)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170914
[Lr] Data última revisão:
170914
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170615
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0177570


  5 / 1918 MEDLINE  
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[PMID]:28541338
[Au] Autor:Popkin G
[Ti] Título:Earth-observing companies push for more-advanced science satellites.
[So] Source:Nature;545(7655):397, 2017 05 23.
[Is] ISSN:1476-4687
[Cp] País de publicação:England
[La] Idioma:eng
[Mh] Termos MeSH primário: Terra (Planeta)
Ciências da Terra/economia
Ciências da Terra/instrumentação
Setor Privado/economia
Imagens de Satélites/economia
Imagens de Satélites/instrumentação
[Mh] Termos MeSH secundário: Agricultura/economia
Radar/instrumentação
Pesquisa/economia
Pesquisa/instrumentação
Estados Unidos
United States National Aeronautics and Space Administration/economia
Tempo (Meteorologia)
[Pt] Tipo de publicação:NEWS
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170914
[Lr] Data última revisão:
170914
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170526
[St] Status:MEDLINE
[do] DOI:10.1038/545397a


  6 / 1918 MEDLINE  
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[PMID]:28538733
[Au] Autor:Meyers S
[Ad] Endereço:Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
[Ti] Título:Climate science: Cracking the palaeoclimate code.
[So] Source:Nature;546(7657):219-220, 2017 06 08.
[Is] ISSN:1476-4687
[Cp] País de publicação:England
[La] Idioma:eng
[Mh] Termos MeSH primário: Ciclo do Carbono
Mudança Climática/história
Terra (Planeta)
Geologia
[Mh] Termos MeSH secundário: Atmosfera/química
Dióxido de Carbono/análise
Ecossistema
Sedimentos Geológicos
Efeito Estufa/história
História Antiga
Rotação
[Pt] Tipo de publicação:HISTORICAL ARTICLE; NEWS
[Nm] Nome de substância:
142M471B3J (Carbon Dioxide)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171010
[Lr] Data última revisão:
171010
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170525
[St] Status:MEDLINE
[do] DOI:10.1038/nature22501


  7 / 1918 MEDLINE  
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[PMID]:28418704
[Au] Autor:Reinhard CT; Olson SL; Schwieterman EW; Lyons TW
[Ad] Endereço:1 NASA Astrobiology Institute .
[Ti] Título:False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth.
[So] Source:Astrobiology;17(4):287-297, 2017 Apr.
[Is] ISSN:1557-8070
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth-oxygen (O ), ozone (O ), and methane (CH ). We suggest that the canonical O -CH disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O /O levels have been a poor proxy for the presence of Earth's biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures-Oxygen-Methane-Ozone-Exoplanets-Planetary habitability. Astrobiology 17, 287-297.
[Mh] Termos MeSH primário: Terra (Planeta)
Exobiologia
Meio Ambiente Extraterreno
Oceanos e Mares
Planetas
[Mh] Termos MeSH secundário: Atmosfera/química
Metano/análise
Oxigênio/análise
Ozônio/análise
Análise Espectral
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
66H7ZZK23N (Ozone); OP0UW79H66 (Methane); S88TT14065 (Oxygen)
[Em] Mês de entrada:1705
[Cu] Atualização por classe:170508
[Lr] Data última revisão:
170508
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170419
[St] Status:MEDLINE
[do] DOI:10.1089/ast.2016.1598


  8 / 1918 MEDLINE  
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[PMID]:28323456
[Au] Autor:Khodadad CL; Wong GM; James LM; Thakrar PJ; Lane MA; Catechis JA; Smith DJ
[Ad] Endereço:1 Sierra Lobo, Inc., Kennedy Space Center , Florida.
[Ti] Título:Stratosphere Conditions Inactivate Bacterial Endospores from a Mars Spacecraft Assembly Facility.
[So] Source:Astrobiology;17(4):337-350, 2017 Apr.
[Is] ISSN:1557-8070
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Every spacecraft sent to Mars is allowed to land viable microbial bioburden, including hardy endospore-forming bacteria resistant to environmental extremes. Earth's stratosphere is severely cold, dry, irradiated, and oligotrophic; it can be used as a stand-in location for predicting how stowaway microbes might respond to the martian surface. We launched E-MIST, a high-altitude NASA balloon payload on 10 October 2015 carrying known quantities of viable Bacillus pumilus SAFR-032 (4.07 × 10 spores per sample), a radiation-tolerant strain collected from a spacecraft assembly facility. The payload spent 8 h at ∼31 km above sea level, exposing bacterial spores to the stratosphere. We found that within 120 and 240 min, spore viability was significantly reduced by 2 and 4 orders of magnitude, respectively. By 480 min, <0.001% of spores carried to the stratosphere remained viable. Our balloon flight results predict that most terrestrial bacteria would be inactivated within the first sol on Mars if contaminated spacecraft surfaces receive direct sunlight. Unfortunately, an instrument malfunction prevented the acquisition of UV light measurements during our balloon mission. To make up for the absence of radiometer data, we calculated a stratosphere UV model and conducted ground tests with a 271.1 nm UVC light source (0.5 W/m ), observing a similarly rapid inactivation rate when using a lower number of contaminants (640 spores per sample). The starting concentration of spores and microconfiguration on hardware surfaces appeared to influence survivability outcomes in both experiments. With the relatively few spores that survived the stratosphere, we performed a resequencing analysis and identified three single nucleotide polymorphisms compared to unexposed controls. It is therefore plausible that bacteria enduring radiation-rich environments (e.g., Earth's upper atmosphere, interplanetary space, or the surface of Mars) may be pushed in evolutionarily consequential directions. Key Words: Planetary protection-Stratosphere-Balloon-Mars analog environment-E-MIST payload-Bacillus pumilus SAFR-032. Astrobiology 17, 337-350.
[Mh] Termos MeSH primário: Atmosfera
Bacillus/fisiologia
Meio Ambiente Extraterreno
Marte
Astronave
Esporos Bacterianos/fisiologia
[Mh] Termos MeSH secundário: Terra (Planeta)
Viabilidade Microbiana/efeitos da radiação
Análise de Sequência de DNA
Raios Ultravioleta
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1705
[Cu] Atualização por classe:170508
[Lr] Data última revisão:
170508
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170322
[St] Status:MEDLINE
[do] DOI:10.1089/ast.2016.1549


  9 / 1918 MEDLINE  
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[PMID]:28230127
[Au] Autor:Ma C; Meyers SR; Sageman BB
[Ad] Endereço:Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, USA.
[Ti] Título:Theory of chaotic orbital variations confirmed by Cretaceous geological evidence.
[So] Source:Nature;542(7642):468-470, 2017 02 22.
[Is] ISSN:1476-4687
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Variations in the Earth's orbit and spin vector are a primary control on insolation and climate; their recognition in the geological record has revolutionized our understanding of palaeoclimate dynamics, and has catalysed improvements in the accuracy and precision of the geological timescale. Yet the secular evolution of the planetary orbits beyond 50 million years ago remains highly uncertain, and the chaotic dynamical nature of the Solar System predicted by theoretical models has yet to be rigorously confirmed by well constrained (radioisotopically calibrated and anchored) geological data. Here we present geological evidence for a chaotic resonance transition associated with interactions between the orbits of Mars and the Earth, using an integrated radioisotopic and astronomical timescale from the Cretaceous Western Interior Basin of what is now North America. This analysis confirms the predicted chaotic dynamical behaviour of the Solar System, and provides a constraint for refining numerical solutions for insolation, which will enable a more precise and accurate geological timescale to be produced.
[Mh] Termos MeSH primário: Terra (Planeta)
Geologia
[Mh] Termos MeSH secundário: Clima
História Antiga
Modelos Teóricos
Fatores de Tempo
Incerteza
[Pt] Tipo de publicação:HISTORICAL ARTICLE; JOURNAL ARTICLE; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Em] Mês de entrada:1706
[Cu] Atualização por classe:170626
[Lr] Data última revisão:
170626
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170224
[St] Status:MEDLINE
[do] DOI:10.1038/nature21402


  10 / 1918 MEDLINE  
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[PMID]:28230120
[Au] Autor:Paillard D
[Ad] Endereço:Laboratory of Climate and Environmental Sciences, Centre d'Etudes de Saclay, 91191 Gif-sur-Yvette, France.
[Ti] Título:Climate science: Predictable ice ages on a chaotic planet.
[So] Source:Nature;542(7642):419-420, 2017 02 22.
[Is] ISSN:1476-4687
[Cp] País de publicação:England
[La] Idioma:eng
[Mh] Termos MeSH primário: Gelo
[Mh] Termos MeSH secundário: Clima
Terra (Planeta)
Ciência
[Pt] Tipo de publicação:NEWS; COMMENT
[Nm] Nome de substância:
0 (Ice)
[Em] Mês de entrada:1705
[Cu] Atualização por classe:170530
[Lr] Data última revisão:
170530
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170224
[St] Status:MEDLINE
[do] DOI:10.1038/542419a



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