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1.
Astrobiology ; 15(7): 587-600, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26154779

RESUMO

Serpentinization involves the hydrolysis and transformation of primary ferromagnesian minerals such as olivine ((Mg,Fe)2SiO4) and pyroxenes ((Mg,Fe)SiO3) to produce H2-rich fluids and a variety of secondary minerals over a wide range of environmental conditions. The continual and elevated production of H2 is capable of reducing carbon, thus initiating an inorganic pathway to produce organic compounds. The production of H2 and H2-dependent CH4 in serpentinization systems has received significant interdisciplinary interest, especially with regard to the abiotic synthesis of organic compounds and the origins and maintenance of life in Earth's lithosphere and elsewhere in the Universe. Here, serpentinization with an emphasis on the formation of H2 and CH4 are reviewed within the context of the mineralogy, temperature/pressure, and fluid/gas chemistry present in planetary environments. Whether deep in Earth's interior or in Kuiper Belt Objects in space, serpentinization is a feasible process to invoke as a means of producing astrobiologically indispensable H2 capable of reducing carbon to organic compounds.


Assuntos
Objetos Astronômicos , Hidrogênio/química , Metano/síntese química , Fenômenos de Química Orgânica , Hidrólise , Minerais , Pressão , Temperatura
2.
Proc Natl Acad Sci U S A ; 111(26): 9379-83, 2014 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-24979770

RESUMO

Hot methane spectra are important in environments ranging from flames to the atmospheres of cool stars and exoplanets. A new spectroscopic line list, 10to10, for (12)CH4 containing almost 10 billion transitions is presented. This comprehensive line list covers a broad spectroscopic range and is applicable for temperatures up to 1,500 K. Previous methane data are incomplete, leading to underestimated opacities at short wavelengths and elevated temperatures. Use of 10to10 in models of the bright T4.5 brown dwarf 2MASS 0559-14 leads to significantly better agreement with observations and in studies of the hot Jupiter exoplanet HD 189733b leads to up to a 20-fold increase in methane abundance. It is demonstrated that proper inclusion of the huge increase in hot transitions which are important at elevated temperatures is crucial for accurate characterizations of atmospheres of brown dwarfs and exoplanets, especially when observed in the near-infrared.


Assuntos
Objetos Astronômicos , Astronomia/métodos , Metano/análise , Modelos Teóricos , Análise Espectral/métodos , Temperatura
3.
4.
Proc Natl Acad Sci U S A ; 111(7): 2409-16, 2014 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-24477692

RESUMO

Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.


Assuntos
Objetos Astronômicos , Astronomia/métodos , Modelos Teóricos
5.
Science ; 340(6132): 570-1, 2013 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-23641109
6.
Isis ; 103(4): 760, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23488245
9.
Brain Behav Evol ; 75(3): 156-73, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20733292

RESUMO

With their highly sensitive visual systems, the arthropods have evolved a remarkable capacity to orient and navigate at night. Whereas some navigate under the open sky, and take full advantage of the celestial cues available there, others navigate in more difficult conditions, such as through the dense understory of a tropical rainforest. Four major classes of orientation are performed by arthropods at night, some of which involve true navigation (i.e. travel to a distant goal that lies beyond the range of direct sensory contact): (1) simple straight-line orientation, typically for escape purposes; (2) nightly short-distance movements relative to a shoreline, typically in the context of feeding; (3) long-distance nocturnal migration at high altitude in the quest to locate favorable feeding or breeding sites, and (4) nocturnal excursions to and from a fixed nest or food site (i.e. homing), a task that in most species involves path integration and/or the learning and recollection of visual landmarks. These four classes of orientation--and their visual basis--are reviewed here, with special emphasis given to the best-understood animal systems that are representative of each.


Assuntos
Artrópodes/fisiologia , Olho Composto de Artrópodes/fisiologia , Visão Noturna/fisiologia , Comportamento Espacial/fisiologia , Percepção Visual/fisiologia , Migração Animal/fisiologia , Animais , Objetos Astronômicos , Olho Composto de Artrópodes/ultraestrutura , Crustáceos/fisiologia , Sinais (Psicologia) , Reação de Fuga/fisiologia , Comportamento Alimentar/fisiologia , Voo Animal/fisiologia , Geografia , Comportamento de Retorno ao Território Vital/fisiologia , Insetos/fisiologia , Aprendizagem/fisiologia , Orientação/fisiologia , Reconhecimento Visual de Modelos/fisiologia
10.
Cold Spring Harb Perspect Biol ; 2(12): a002097, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20554702

RESUMO

Astronomical observations have shown that carbonaceous compounds in the gas and solid state, refractory and icy are ubiquitous in our and distant galaxies. Interstellar molecular clouds and circumstellar envelopes are factories of complex molecular synthesis. A surprisingly large number of molecules that are used in contemporary biochemistry on Earth are found in the interstellar medium, planetary atmospheres and surfaces, comets, asteroids and meteorites, and interplanetary dust particles. In this article we review the current knowledge of abundant organic material in different space environments and investigate the connection between presolar and solar system material, based on observations of interstellar dust and gas, cometary volatiles, simulation experiments, and the analysis of extraterrestrial matter. Current challenges in astrochemistry are discussed and future research directions are proposed.


Assuntos
Objetos Astronômicos , Carbono/química , Poeira Cósmica/análise , Evolução Química , Meio Ambiente Extraterreno , Compostos Orgânicos/química , Simulação por Computador
11.
Hawaii Med J ; 69(4): 93-8, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20481234

RESUMO

Energy absorbtion from particles and photons moving at relativistic speeds has been a fundamental part of life on earth and wherever else life might exist. Heat and visible light have deeply influenced the course of human evolution, affecting habitat and nutrition. The photons of ionizing radiation that over time can possibly affect evolution, contribute to the more immediate problem of morbidity and mortality of cancer This review addresses our radiative energy absorbtion, from both natural and manmade sources, and its relationship with disease and death. Educational Public Health efforts to offset the dangers of solar ultraviolet overexposure are presented, together with data on the significant mortality of metastatic melanoma.


Assuntos
Objetos Astronômicos , Radiação Cósmica , Astronomia , Fenômenos Eletromagnéticos , Humanos , Neoplasias Cutâneas/epidemiologia , Raios Ultravioleta
12.
13.
Opt Express ; 16(25): 20249-57, 2008 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-19065163

RESUMO

We introduce a novel telescope consisting of a pinhole-like camera with rotatable MEMS micromirrors substituting for pinholes. The design is ideal for observations of transient luminous phenomena or fast-moving objects, such as upper atmospheric lightning and bright gamma ray bursts. The advantage of the MEMS "obscura telescope" over conventional cameras is that it is capable both of searching for events over a wide field of view, and fast zooming to allow detailed investigation of the structure of events. It is also able to track the triggering object to investigate its space-time development, and to center the interesting portion of the image on the photodetector array. We present the proposed system and the test results for the MEMS obscura telescope which has a field of view of 11.3 degrees, sixteen times zoom-in and tracking within 1 ms.


Assuntos
Objetos Astronômicos , Astronomia/instrumentação , Aumento da Imagem/instrumentação , Lentes , Sistemas Microeletromecânicos/instrumentação , Dispositivos Ópticos , Fotometria/instrumentação , Astronomia/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Aumento da Imagem/métodos , Fotometria/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
14.
Guang Pu Xue Yu Guang Pu Fen Xi ; 25(7): 1155-7, 2005 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-16241080

RESUMO

This paper presents a novel method for redshift determination of quasars. Firstly, a group of redshifts were determined using the emission line info extracted from the observed spectrum; Secondly, the template was redshifted according to the candidates, and the correlation between the observed spectrum and the redshifted template was measured. Finally, the redshift candidate corresponding to the highest correlation was chosen as the redshift. Compared with the existing methods based on spectral line matching, the proposed method has a lower dependence on the quality of spectral line extraction. Experiments show that this method is robust and superior to the methods based on spectral linematching.


Assuntos
Objetos Astronômicos , Fenômenos Astronômicos , Análise Espectral/métodos , Algoritmos , Processamento de Imagem Assistida por Computador , Reprodutibilidade dos Testes
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