Página 1 dos resultados de 2151 itens digitais encontrados em 0.040 segundos

Relações entre ciência, tecnologia e sociedade em museus de ciências; Relations between science, technology, and society in science museums

Contier, Djana
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/04/2009 Português
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55.53%
Este trabalho analisa como museus de ciências no Brasil exploram as relações e as interferências mútuas entre ciência, tecnologia e sociedade, utilizando como principais referenciais a educação com enfoque ciência, tecnologia e sociedade (CTS), e a comunicação pública da ciência. A escolha da educação com enfoque CTS está relacionada à discussão sobre a importância da formação de cidadãos críticos diante das questões de ciência e tecnologia (C&T), incluindo a abordagem ciência, tecnologia, sociedade e meio ambiente (CTSA). Já a escolha da comunicação pública da ciência se dá pelo seu debate sobre a mudança na forma de participação do público nas tomadas de decisão sobre C&T. Esses dois referenciais desafiam as instituições que atuam na interface ciência e público a repensar seus objetivos e propósitos. Um questionamento ainda mais relevante, se levados em consideração o crescimento e o fortalecimento dos museus de ciências no Brasil nos últimos anos. Para este projeto, foram selecionadas e analisadas três exposições de diferentes museus de ciências nacionais: Educação Ambiental, do Museu de Ciências e Tecnologia/PUC-RS; Reprodução e genética, do Espaço Biodescoberta do Museu da Vida/Fiocruz...

Recent Changes in Central and Eastern Pacific El Niño

Washam, Peter M
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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55.42%
Recent research indicates that characteristics of El Niño and the Southern Oscillation (ENSO) have changed over the past several decades. Here, I examined different flavors of El Niño in the observational record and the recent changes in the character of El Niño events. The fundamental physical processes that drive ENSO were described and the Eastern Pacific (EP) and Central Pacific (CP) types or flavors of El Niño were defined. Using metrics from the peer-reviewed literature, I examined several historical data sets to interpret El Niño behavior from 1950-2010. A Monte Carlo Simulation was then applied to output from coupled model simulations to test the statistical significance of recent observations surrounding EP and CP El Niño. Results suggested that EP and CP El Niño had been occurring in a similar fashion over the past 60 years with natural variability, but no significant increase in CP El Niño behavior.

Las pruebas de acceso a la universidad en la asignatura de Ciencias de la Tierra y del Medio Ambiente en la Comunidad de Madrid: análisis de las pruebas y evaluación de los resultados de los alumnos y su incidencia en la mejora de la práctica docente y el aprendizaje

Rebollo Ferreiro, Luis F.; Nieda Oterino, Juana
Fonte: Escuela Cardenal Cisneros. Centro Adscrito a la UAH Publicador: Escuela Cardenal Cisneros. Centro Adscrito a la UAH
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
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65.6%
En este trabajo se aborda el papel que pueden desempeñar las Pruebas de Acceso a los Estudios Universitarios como instrumento de actualización pedagógica. Por medio de un proyecto de investigación educativa llevado a cabo por los miembros de la Comisión Elaboradora de los exámenes de Ciencias de la Tierra y del Medio Ambiente en la Comunidad de Madrid se ha realizado el análisis del proceso de diseño de las pruebas correspondientes a esta asignatura, de su tipología, contenido y formato a lo largo de diez cursos, y de los resultados de la aplicación de las mismas a los alumnos de 2º curso de Bachillerato. La finalidad de la investigación es contrastar la coherencia de las pruebas con los elementos curriculares de la asignatura y con los postulados del aprendizaje significativo y de la educación ambiental, y, finalmente, evaluar el aprendizaje de los alumnos de esta materia y extraer conclusiones para trasladar a los profesores y mejorar la práctica docente.; This work deals with the role that university entrance exams can play as a tool for pedagogic updating. The members of the committee that elaborate the exams in Earth and Environment Sciences in the Community of Madrid have carried out an educational investigation through the analysis of the design...

Applications Fields, Status Quo and Prospects

CARMONA MORENO CESAR; BELWARD ALAN; BARTHOLOME' ETIENNE; FUAT Ince; KRISCHKE Manfred; BRIESS Klaus; KONECNY Gottfried; NEUMANN Andreas; OLSSON Hakan; PARLOW Eberhard; SCHERER Dieter; WYNNE Randolph; PAXTON Larry
Fonte: A. Taylor & Francis, SAR and QSAR in Environment Research, James Devillers Publicador: A. Taylor & Francis, SAR and QSAR in Environment Research, James Devillers
Tipo: Articles in books Formato: Printed
Português
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45.69%
There is an increasing need for cost effective Earth Observation (EO) missions to meet the information requirements of an almost ever growing range of applications. This is perhaps most clearly seen in the many current moves for international co-operation in the field of environment where measurements from Earth Observing satellites are an essential element. This is especially so where we need to acquire, analyse and use data documenting the condition of the Earth's resources and environment on a long-term (permanent) basis. As can be seen from the list of topics addressed in this chapter, uses range from essential mapping activities to global climate, with information needs arising because of legislation and through international commitments. Hazards, agriculture, land degradation, desertification, deforestation, sustainable forest management, climate, our cryosphere and others topics are all highlighted here. The international community is addressing these needs. Not just through environmental conventions such as the UNFCCC and its Kyoto Protocol, but also through commitments entered into at the 2002 World Summit on Sustainable Development (WSSD) in Johannesburg. The heads of state of 191 nations called for improved global observations for better decision-making...

Assessing the impacts of ocean acidification, global warming and terrestrial runoff on the cross-shelf variability of coral calcification in the central Great Barrier Reef

D'Olivo Cordero, Juan Pablo
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
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55.42%
Ocean acidification and thermal stress due to anthropogenic greenhouse gas emissions present significant, potentially interacting, threats to the future of coral reefs. Coastal reef environments, as in the case of the Great Barrier Reef (GBR), can also be exposed to terrestrial stressors. This thesis evaluates the combined effects of ocean acidification, rising temperatures and river inputs on the calcification of Porites corals along a transect across-shelf the central GBR, north of Townsville. Calcification rates were obtained for 41 long-lived Porites corals from 7 reefs, in an inshore to offshore transect across the central GBR. The boron isotope composition (d11B) of selected cores was used to reconstruct annual and sub-annual changes in seawater pH in inner-shelf and mid-shelf environments. These unique seawater pH records are integrated with sea-surface temperature, river discharge and rainfall records to assess the nature and cause of seasonal, interannual, decadal and long-term (̃50 years) trends in coral calcification. Significant across-shelf differences in the temporal variability and long-term evolution of coral calcification are documented and can be related to local and global-scale changes in environmental conditions and water quality. Corals in the mid-shelf and outer-reef regions of the GBR exhibit an increase in calcification of 10.9% (1.1% S.E.) and 11.1% (3.9% S.E.) respectively since ̃1950 which are associated to the rise in sea-surface temperatures. However...

Modeling, simulation, and characterization of space debris in low-Earth orbit

McCall, Paul David
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
Português
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45.68%
Every space launch increases the overall amount of space debris. Satellites have limited awareness of nearby objects that might pose a collision hazard. Astrometric, radiometric, and thermal models for the study of space debris in low-Earth orbit have been developed. This modeled approach proposes analysis methods that provide increased Local Area Awareness for satellites in low-Earth and geostationary orbit. Local Area Awareness is defined as the ability to detect, characterize, and extract useful information regarding resident space objects as they move through the space environment surrounding a spacecraft. ^ The study of space debris is of critical importance to all space-faring nations. Characterization efforts are proposed using long-wave infrared sensors for space-based observations of debris objects in low-Earth orbit. Long-wave infrared sensors are commercially available and do not require solar illumination to be observed, as their received signal is temperature dependent. The characterization of debris objects through means of passive imaging techniques allows for further studies into the origination, specifications, and future trajectory of debris objects. Conclusions are made regarding the aforementioned thermal analysis as a function of debris orbit...

UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution

Rugheimer, S.; Segura, A.; Kaltenegger, L.; Sasselov, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/06/2015 Português
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The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars at the 1AU equivalent distance for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present day levels at 2.0 Gyr ago, 0.8 Gyr ago and modern Earth (Following Kaltenegger et al. 2007). In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth-Sun levels. A pre-biotic Earth orbiting GJ 581 (M3.5V) receives 300 times less biologically effective radiation, about 2 times modern Earth-Sun levels. The UV fluxes calculated here provide a grid of model UV environments during the evolution of an Earth-like planet orbiting a range of stars. These models can be used as inputs into photo-biological experiments and for pre-biotic chemistry and early life evolution experiments.; Comment: 10 pages...

Mars Encounters cause fresh surfaces on some near-Earth asteroids

DeMeo, Francesca E.; Binzel, Richard P.; Lockhart, Matthew
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/09/2013 Português
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All airless bodies are subject to the space environment, and spectral differences between asteroids and meteorites suggest many asteroids become weathered on very short (<1My) timescales. The spectra of some asteroids, particularly Q-types, indicate surfaces that appear young and fresh, implying they have been recently been exposed. Previous work found that Earth encounters were the dominant freshening mechanism and could be responsible for all near-Earth object (NEO) Q-types. In this work we increase the known NEO Q-type sample of by a factor of three. We present the orbital distributions of 64 Q-type near-Earth asteroids, and seek to determine the dominant mechanisms for refreshing their surfaces. Our sample reveals two important results: i) the relatively steady fraction of Q-types with increasing semi-major axis and ii) the existence of Q-type near-Earth asteroids with Minimum Orbit Intersection Distances (MOID) that do not have orbit solutions that cross Earth. Both of these are evidence that Earth-crossing is not the only scenario by which NEO Q-types are freshened. The high Earth-MOID asteroids represent 10% of the Q-type population and all are in Amor orbits. While surface refreshing could also be caused by Main Belt collisions or mass shedding from YORP spinup...

Mapping Earth Analogs from Photometric Variability: Spin-Orbit Tomography for Planets in Inclined Orbits

Fujii, Yuka; Kawahara, Hajime
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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55.68%
Aiming at obtaining detailed information of surface environment of Earth analogs, Kawahara & Fujii (2011) proposed an inversion technique of annual scattered light curves named the spin-orbit tomography (SOT), which enables one to sketch a two-dimensional albedo map from annual variation of the disk-integrated scattered light, and demonstrated the method with a planet in a face-on orbit. We extend it to be applicable to general geometric configurations, including low-obliquity planets like the Earth in inclined orbits. We simulate light curves of the Earth in an inclined orbit in three photometric bands (0.4-0.5um, 0.6-0.7um, and 0.8-0.9um) and show that the distribution of clouds, snow, and continents is retrieved with the aid of the SOT. We also demonstrate the SOT by applying it to an upright Earth, a tidally locked Earth, and Earth analogs with ancient continental configurations. The inversion is model independent in the sense that we do not assume specific albedo models when mapping the surface, and hence applicable in principle to any kind of inhomogeneity. This method can potentially serve as a unique tool to investigate the exohabitats/exoclimes of Earth analogs.; Comment: 15 pages, 14 figures, 2 tables; published in The Astrophysical Journal

Lunar Palaeoregolith Deposits as Recorders of the Galactic Environment of the Solar System and Implications for Astrobiology

Crawford, Ian A.; Fagents, Sarah A.; Joy, Katherine H.; Rumpf, M. Elise
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/08/2010 Português
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55.6%
One of the principal scientific reasons for wanting to resume in situ exploration of the lunar surface is to gain access to the record it contains of early Solar System history. Part of this record will pertain to the galactic environment of the Solar System, including variations in the cosmic ray flux, energetic galactic events (e.g, supernovae and/or gamma-ray bursts), and passages of the Solar System through dense interstellar clouds. Much of this record is of astrobiological interest as these processes may have affected the evolution of life on Earth, and perhaps other Solar System bodies. We argue that this galactic record, as for that of more local Solar System processes also of astrobiological interest, will be best preserved in ancient, buried regolith ('palaeoregolith') deposits in the lunar near sub-surface. Locating and sampling such deposits will be an important objective of future lunar exploration activities.; Comment: 23 pages, 1 figure. Accepted for publication in 'Earth Moon and Planets' as part of Special Issue on Lunar Astrobiology

Radiation Environment In Earth-Moon Space: Results From RADOM Experiment Onboard Chandrayaan-1

Vadawale, S. V.; Goswami, J. N.; Dachev, T. P.; Tomov, B. T.; Girish, V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/12/2010 Português
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The Radiation Monitor (RADOM) payload is a miniature dosimeter-spectrometer onboard Chandrayaan-1 mission for monitoring the local radiation environment in near-Earth space and in lunar space. RADOM measured the total absorbed dose and spectrum of the deposited energy from high energy particles in near-Earth space, en-route and in lunar orbit. RADOM was the first experiment to be switched on soon after the launch of Chandrayaan-1 and was operational till the end of the mission. This paper summarizes the observations carried out by RADOM during the entire life time of the Chandrayaan-1 mission and some the salient results.; Comment: Accepted for publication in Advances in Geosciences

The Effects of Refraction on Transit Transmission Spectroscopy: Application to Earth-like Exoplanets

Misra, Amit; Meadows, Victoria; Crisp, Dave
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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45.66%
We quantify the effects of refraction in transit transmission spectroscopy on spectral absorption features and on temporal variations that could be used to obtain altitude-dependent spectra for planets orbiting stars of different stellar types. We validate our model against altitude-dependent transmission spectra of the Earth from ATMOS and against lunar eclipse spectra from Palle et al. (2009). We perform detectability studies to show the potential effects of refraction on hypothetical observations of Earth analogs with the James Webb Space Telescope (JWST) Near-Infrared Spectrograph (NIRSPEC). Due to refraction, there will be a maximum tangent pressure level that can be probed during transit for each given planet-star system. We show that because of refraction, for an Earth-analog planet orbiting in the habitable zone of a Sun-like star only the top 0.3 bars of the atmosphere can be probed, leading to a decrease in the signal to noise ratio (SNR) of absorption features by 60%, while for an Earth-analog planet orbiting in the habitable zone of an M5V star it is possible to probe almost the entire atmosphere with minimal decreases in SNR. We also show that refraction can result in temporal variations in the transit transmission spectrum which may provide a way to obtain altitude-dependent spectra of exoplanet atmospheres. Additionally...

Exploring Io's atmospheric composition with APEX: first measurement of 34SO2 and tentative detection of KCl

Moullet, A.; Lellouch, E.; Moreno, R.; Gurwell, M.; Black, J.; Butler, B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/08/2013 Português
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55.52%
The composition of Io's tenuous atmosphere is poorly constrained. Only the major species SO2 and a handful of minor species have been positively identified, but a variety of other molecular species should be present, based on thermochemical equilibrium models of volcanic gas chemistry and the composition of Io's environment. This paper focuses on the spectral search for expected yet undetected molecular species (KCl, SiO, S2O) and isotopes (34SO2). We analyze a disk-averaged spectrum of a potentially line-rich spectral window around 345 GHz, obtained in 2010 at the APEX-12m antenna (Atacama Pathfinder EXperiment). Using different models assuming either extended atmospheric distributions or a purely volcanically-sustained atmosphere, we tentatively measure the KCl relative abundance with respect to SO2 and derive a range of 4x10^{-4}-8x10^{-3}. We do not detect SiO or S2O and present new upper limits on their abundances. We also present the first measurement of the 34S/32S isotopic ratio in gas phase on Io, which appears to be twice as high as the Earth and ISM reference values. Strong lines of SO2 and SO are also analyzed to check for longitudinal variations of column density and relative abundance. Our models show that, based on their predicted relative abundance with respect to SO2 in volcanic plumes...

Constraining the Radiation and Plasma Environment of the Kepler Circumbinary Habitable Zone Planets

Zuluaga, Jorge I.; Mason, Paul A.; Cuartas, Pablo A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/01/2015 Português
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45.74%
The remarkable discovery of many planets and candidates using the Kepler telescope even includes ten planets orbiting eight binaries. Three out of the eight, Kepler 16, Kepler 47, and KIC 9632895, have at least one planet in the circumbinary habitable zone (BHZ). In previous work (Mason et al. 2013), we investigated the potential habitability of Earth-like circumbinary planets. In particular, we highlighted the role of mutual stellar tidal interaction and the resulting impact on terrestrial planet habitability. The Kepler binaries with planets in the BHZ are studied in order to constrain the high energy radiation and plasma environment of potentially habitable circumbinary planets. The limits of the BHZ in these binaries as a function of time are estimated and the habitability lifetime is calculated. A self-consistent model of the evolution of stellar rotation including the effect of tidal interaction is key to establishing the plasma and radiation environment. A comprehensive model of the evolution of stellar activity and radiation properties, as proxies for stellar aggression towards planetary atmospheres is developed. We find that Kepler-16 has had a plasma environment favorable for the survival of atmospheres of Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47 making its radiation environment less harsh than solar system and a good example of the mechanism first proposed by Mason et al. (2013). KIC-9632895 has a plasma and radiation environment similar to that of solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ.; Comment: 15 pages...

Analysis of the new INTEGRAL Earth observations to measure the cosmic X-ray background

Türler, M.; Produit, N.; Pavan, L.; Ferrigno, C.; Bordas, P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/02/2013 Português
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45.66%
A new series of Earth occultation observations has been started in 2012 to refine the determination of the cosmic X-ray background by the INTEGRAL mission. We show here that the new detector lightcurves in the 3 to 160 keV range differ from the ones obtained in 2006. Instead of the expected modulation induced by the passage of the Earth through the field of view of the JEM-X, IBIS/ISGRI and SPI instruments, we record unrelated variability on shorter timescales. We discuss the differences obtained with the datasets of 2006 and 2012 in view of the changes in pointing direction, spacecraft orbit and solar cycle phase. We conclude that the Earth occultation signal in 2012 is likely blended by radioactive decay resulting from the activation of the spacecraft when crossing the proton radiation belt at perigee passage. The observed variability, on the other hand, results most likely from the current solar maximum. In addition to a variable particle environment from inhomogeneities of the solar wind, we also find evidence for hard X-ray auroral emission. While the former can be traced by SPI/ACS counts, the latter - by enhancing unpredictably the Earth emission - is a major disturbance for measuring the diffuse X-ray background through occultation by the Earth.; Comment: Proceedings of "An INTEGRAL view of the high-energy sky (the first 10 years)" the 9th INTEGRAL Workshop...

Effects of Plasma Drag on Low Earth Orbiting Satellites due to Heating of Earth's Atmosphere by Coronal Mass Ejections

Nwankwo, Victor U. J.; Chakrabarti, Sandip K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/05/2013 Português
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45.68%
Solar events, such as coronal mass ejections (CMEs) and solar flares, heat up the upper atmosphere and near-Earth space environment. Due to this heating and expansion of the outer atmosphere by the energetic ultraviolet, X-ray and particles expelled from the sun, the low Earth-Orbiting satellites (LEOS) become vulnerable to an enhanced drag force by the ions and molecules of the expanded atmosphere. Out of various types of perturbations, Earth directed CMEs play the most significant role. They are more frequent and intense during the active (solar maximum) phase of the sun's approximately 11-year cycle. As we are approaching another solar maximum later in 2013, it may be instructive to analyse the effects of the past solar cycles on the orbiting satellites using the archival data of space environment parameters as indicators. In this paper, we compute the plasma drag on a model LEOS due to the atmospheric heating by CMEs and other solar events as a function of the solar parameters. Using the current forecast on the time and strength of the next solar maximum, we predict how an existing satellite orbit may be affected in the forthcoming years.

Giant comets and mass extinctions of life

Napier, W. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/03/2015 Português
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55.61%
I find evidence for clustering in age of well-dated impact craters over the last 500 Myr. At least nine impact episodes are identified, with durations whose upper limits are set by the dating accuracy of the craters. Their amplitudes and frequency are inconsistent with an origin in asteroid breakups or Oort cloud disturbances, but are consistent with the arrival and disintegration in near-Earth orbits of rare, giant comets, mainly in transit from the Centaur population into the Jupiter family and Encke regions. About 1 in 10 Centaurs in Chiron-like orbits enter Earth-crossing epochs, usually repeatedly, each such epoch being generally of a few thousand years duration. On time-scales of geological interest, debris from their breakup may increase the mass of the near-Earth interplanetary environment by two or three orders of magnitude, yielding repeated episodes of bombardment and stratospheric dusting. I find a strong correlation between these bombardment episodes and major biostratigraphic and geological boundaries, and propose that episodes of extinction are most effectively driven by prolonged encounters with meteoroid streams during bombardment episodes. Possible mechanisms are discussed.; Comment: 10 pages, 11 figures

The low-mass stellar population in the young cluster Tr37: Disk evolution, accretion, and environment

Sicilia-Aguilar, Aurora; Kim, Jinyoung Serena; Sobolev, Andrej; Getman, Konstantin; Henning, Thomas; Fang, Min
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/08/2013 Português
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55.49%
We present a study of accretion and protoplanetary disks around M-type stars in the 4 Myr-old cluster Tr37. With a well-studied solar-type population, Tr37 is a benchmark for disk evolution. We used low-resolution spectroscopy to identify 141 members (78 new) and 64 probable members, mostly M-type stars. H\alpha\ emission provides information about accretion. Optical, 2MASS, Spitzer, and WISE data are used to trace the SEDs. We construct radiative transfer models to explore the structures of full-disks, pre-transition, transition, and dust-depleted disks. Including the new and previously known members, we confirm that a substantial fraction (~2/5) of disks show signs of evolution, either as radial dust evolution (transition/pre-transition disks) or as a more global evolution (low small-dust masses, dust settling, and weak/absent accretion signatures). Accretion is strongly dependent on the SED type. About half of the transition objects are consistent with no accretion, and dust-depleted disks have weak (or undetectable) accretion signatures, especially among M-type stars. The analysis of accretion and disk structure suggests a parallel evolution of dust and gas. We find several distinct classes of evolved disks, based on SED type and accretion...

Below One Earth Mass: The Detection, Formation, and Properties of Subterrestrial Worlds

Sinukoff, E.; Fulton, B.; Scuderi, L.; Gaidos, E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/08/2013 Português
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55.63%
The Solar System includes two planets --- Mercury and Mars --- significantly less massive than Earth, and all evidence indicates that planets of similar size orbit many stars. In fact, one of the first exoplanets to be discovered is a lunar-mass planet around a millisecond pulsar. Novel classes of exoplanets have inspired new ideas about planet formation and evolution, and these "sub-Earths" should be no exception: they include planets with masses between Mars and Venus for which there are no Solar System analogs. Advances in astronomical instrumentation and recent space missions have opened the sub-Earth frontier for exploration: the Kepler mission has discovered dozens of confirmed or candidate sub-Earths transiting their host stars. It can detect Mars-size planets around its smallest stellar targets, as well as exomoons of comparable size. Although the application of the Doppler method is currently limited by instrument stability, future spectrographs may detect equivalent planets orbiting close to nearby bright stars. Future space-based microlensing missions should be able to probe the sub-Earth population on much wider orbits. A census of sub-Earths will complete the reconnaissance of the exoplanet mass spectrum and test predictions of planet formation models...

Solar minimum spectra of galactic cosmic rays and their implications for models of the near-Earth radiation environment

Davis, A. J.; Mewaldt, R. A.; Cohen, C. M. S.; Cummings, A. C.; George, J. S.; Leske, R. A.; Stone, E. C.; Wiedenbeck, M. E.; Yanasak, N. E.; Christian, E. R.; von Rosenvinge, T. T.; Binns, W. R.; Hink, P. L.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/12/2001 Português
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45.71%
The radiation dose from galactic cosmic rays during a manned mission to Mars is expected to be comparable to the allowable limit for space shuttle astronauts. Most of this dose would be due to galactic cosmic rays with energies < 1 GeV nucleon^(−1), with important contributions from heavy nuclei in spite of their low abundance relative to H and He. Using instruments on NASA's Advanced Composition Explorer (ACE) spacecraft, we have made the most statistically precise measurements to date of the solar minimum energy spectra of cosmic ray nuclei with charge Z = 4–28 in the energy range ∼ 40–500 MeV nucleon^(−1). We compare these measurements obtained during the 1997–1998 solar minimum period with measurements from previous solar minima and with models of the near-Earth radiation environment currently used to perform shielding and dose calculations. We find that the cosmic ray heavy-element spectra measured by ACE are as much as 20% higher than previously published solar minimum measurements. We also find significant differences between the ACE measurements and the predictions of available models of the near-Earth radiation environment, suggesting that these models need revision. We describe a cosmic ray interstellar propagation and solar modulation model that provides an improved fit to the ACE measurements compared to radiation environment models currently in use.