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Proposta de diretrizes para o desenvolvimento da arquitetura em terra no Rio Grande do Sul, a partir da interpretação de estratégias uruguaias; Proposal of guidelines for the development of earth architecture in the state of Rio Grande do Sul, through the interpretation of Uruguayan strategies

Bayer, Ana Paula
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.21%
A construção civil é, atualmente, apontada como responsável pela extração de grande parte dos recursos naturais do planeta consumidos pela humanidade. Nesse sentido, a utilização de materiais construtivos nãoconvencionais, como a terra, surge como alternativa para construir edificações mais amigáveis com o meioambiente e, assim, também, modos de vida mais saudáveis, mais sustentáveis. Entretanto, a falta de informações, por parte de grande parte da população, inclusive de instituições de ensino e de profissionais atuantes no ramo da construção civil, em relação ao tema, faz com que o preconceito para com esse tipo de bioconstrução seja considerável. Surge, pois, a possibilidade de promoção da utilização da terra enquanto material construtivo, para que esse método de construção amigável com o meio-ambiente possa, aos poucos, recuperar o importante papel que desempenhava no passado, quando tais construções eram tidas como convencionais por nossos ancestrais. Através da investigação das técnicas de construção em terra e dos programas que favorecem esse tipo de iniciativa, o presente estudo tem como meta estabelecer um conjunto de diretrizes para orientar profissionais do ramo da construção civil e entidades interessadas em contribuir com a promoção da arquitetura em terra. Além disso...

Relações diplomaticas oficiais de contato Brasil/Alemanha para a preservação do meio ambiente e da qualidade de vida : um estudo sobre os lugares de interlocução ocupados por brasileiros e alemães, a partir da configuração de necessidades especificas; Official diplomatic contact relations between Brazil/Germany, in relation to partnerships for the protection and conservation of the environment and quality of life on Earth : a study about Brazilians and Germans interlocutory positions

Ian Oliveira de Assis
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/02/2008 PT
Relevância na Pesquisa
36.06%
A partir de postulados da Análise do Discurso tais como: Efeitos de verdade estão relacionados ao poder, estão estabelecidos discursivamente por ele e fora dele inexistem (Foucault, 1969); Todo sujeito fala a partir de lugares de interlocução constituídos discursivamente e ideologicamente definidos ? ou seja, todo sujeito é constituído pelo discurso e, ao falar, põe em movimento a memória e a história da sua cultura, da sua sociedade, do seu país (Orlandi, 1993); Há sempre um jogo de força na memória sob o choque do acontecimento: jogo que visa manter uma regularização pré-existente, com os implícitos que ela veicula, que visa confrontá-la como estabilização parafrástica, negociando a integração do acontecimento até absorvê-lo e, eventualmente dissolvê-lo, mas também, ao contrário, jogo de força de uma desregulação que vem perturbar a rede de implícitos (Pêcheux, 1983), e com base na pesquisa efetuada por Zink (1996), acerca das relações de contato entre brasileiros e alemães, este trabalho analisa características das relações diplomáticas oficiais de contato Brasil/Alemanha, no que tange a parcerias de ação para a preservação do meio ambiente e da qualidade de vida no Planeta. Nele, além de serem pesquisadas características desse discurso oficial...

Ver para aprender com o Google Earth

Freitas, Elisabete Maria Pacheco de
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em //2010 POR
Relevância na Pesquisa
36.27%
Dissertação mestrado em Estudos da Criança (área de especialização em Tecnologias de Informação e Comunicação); Estando os nossos alunos habituados a conviver fora da Escola com meios tecnológicos, como televisão, computador, telemóvel e muitos outros, onde o processo de comunicação se desencadeia sobretudo através da imagem, optamos neste projecto por aproximar a sala de aula da vida quotidiana destes alunos. Neste sentido, e para a aprendizagem dos elementos básicos do Meio Físico envolvente (Formas de Relevo), através da sua visualização, criamos o Microworld “Caça às Formas de Relevo”, respeitando as características de um ambiente de aprendizagem significativa, onde o Google Earth serviu de apoio/parceria para a construção destes conceitos. A metodologia escolhida foi o estudo de caso, levado a cabo com um grupo de alunos do 2º ano de escolaridade, sendo o método da recolha de dados a observação participante, os artefactos físicos e as entrevistas. Os resultados obtidos levam-nos a acreditar que programas como o Google Earth ao providenciar/servir de apoio à visualização de conceitos “deu-lhes vida”, sendo o conhecimento construído neste ambiente significativo, pessoal e presumivelmente perdurável...

TWO DECADES OF EARTH SCIENCE RESEARCH

Silva, A.M.; Araújo, A.A.; Reis, A.H.; Morais, M.; Bezzeghoud, M.
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Livro
ENG
Relevância na Pesquisa
36.11%
In 2012, the Évora Geophysics Centre (CGE) celebrates 20 years of activity. In these two decades, the national scientific system underwent a profound transformation, new organizational structures appeared, and participation in structures and international networks, and scientific integration reached very high levels. The national scientific environment is now more qualified and competitive; however the available funding per researcher became scarcer. Currently the CGE team includes 67 full members, and is organized in two main Lines of Research: (1) Atmosphere and Hydrosphere, (ii) Solid Earth. The first one comprises the centers of activity: Meteorology & Climate, Water, Environment, & Surface Processes, and Energy & Flow Structures, while the latter is composed of the centers of activity: Active Tectonics & Risks, Lithosphere, Mantle & Geological Resources, and Heritage & Archeometry. The time of maturity has come for GCE as a research unit, with a growth trajectory that was not always linear; however it has been progressive with respect to scientific quality, organizational structure, and the scientific and training outputs that were made available to the community. It is also the time to reflect on the past and to define future strategies. This debate is carried out within the evolving framework in which the CGE develops its activity. Actually...

ANALYSIS OF THE EARTH CONSTRUCTION’S THERMAL BEHAVIOR – IN SITU MEASUREMENT AND EVALUATION OF THERMAL PERFORMANCE OF THREE RAMMED EARTH CASE STUDIES

Sampaio, Sofia; Gomes, Maria da Glória; Borges Abel, António
Fonte: Grupo Tierra, Universidad de Valladolid Publicador: Grupo Tierra, Universidad de Valladolid
Tipo: Aula
POR
Relevância na Pesquisa
36.06%
The emergence of the new paradigm of sustainable construction related to the concern of excessive energy consumption of our society, led to the investigation of techniques, materials and construction solutions that could causes less environmental impact. Consequently, the interest given to ancient techniques that dealt with earth constructive solutions aroused, which has captivated the interest of architects, builders and people in general. Although this type of material is associated to a less dignified and poor construction, the search for modern expression in new buildings’ design has shown the physical and plastic potential of the usage of earth in modern architecture. However, the regulation of the constructions’ minimum requirements related to materials’ mechanical strength and thermal performance (such as the Portuguese Thermal Building Regulation- RCCTE), has been one of the biggest obstacles in spreading and growing the application of this technique. This study intends to increase the knowledge of the thermal behavior of this type of construction. In this article, the results of in situ measurement campaigns, carried out during the summer and winter periods, are presented. They were performed on three different single-family dwellings located in Abrantes...

Science, technology and the Earth Charter

Mackey, Brendan G
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Working/Technical Paper Formato: 66644 bytes; application/pdf
EN_AU
Relevância na Pesquisa
36.09%
The Earth Charter aims to describe a set of fundamental principles that underpin sus-tainable development, defining new norms of behaviour of how individuals and socie-ties relate to the environment. The Earth Charter principles are therefore aimed at providing guidance to human and social be-haviour in order to promote environmental protection and sustainable living. The Earth Charter can be viewed as the third pillar of global governance, following (a) The United Nations Convention and (b) the International Declaration of Human Rights. The former governs how nations treat each other, while the latter deals with how people treat people. The aim of the Earth Charter is to provide guidance as to how people and societies in-teract with Earth. Accordingly it must pro- vide a blue print for the protection of Earth as a home for humanity, and for meeting the needs of present and future generations. Further information about the Earth Charter process can be found at the Earth Council Website [1]. This paper discusses the role that sci-ence and technology have to play in the for-mulation of the Earth Charter, and aims to identify a set of scientifically based principles that should be included in such a Charter. By science I mean scientific knowledge and un-derstanding about how Earth works...

Contextualizing Science Education via Earth System Science Events for Meaningful Lifelong Learning

de la Chica, Sebastian
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: articles
ENG
Relevância na Pesquisa
36.08%
Final doctoral research paper presented at JCDL 2005 Inaugural Doctoral Consortium, 7 June 2005, Denver, Colorado, USA.; The widespread deployment of ubiquitous communication technologies, including growing Internet access, in the early 21st century has resulted in a growing number of information sources available for educational purposes. These online information sources contribute to an educational landscape increasingly capable of near real-time access to news coverage, scientific data, and critical analyses about earthquakes, volcanic eruptions, tsunamis, and similar Earth system science (ESS) events. By contrast, traditional science textbooks provide sanctioned quality educational content, but require content updating cycles several orders of magnitude longer than online information sources. Lacking meaningful context, scientific information in traditional textbooks often leads to disconnected rote learning and limited understanding of scientific concepts. Lacking the appropriate cognitive skills, learners often fail to recognize and connect the salient scientific concepts and social issues underlying news coverage of significant ESS events with their existing scientific knowledge. Nationally-recognized science education standards have addressed the importance of learning how to be a scientist through learning goals related to science inquiry and critical thinking skills in authentic settings...

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
SPA
Relevância na Pesquisa
45.95%
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...

The World Bank Group’s Partnership with the Global Environment Facility; Volume 1. Main Report

Independent Evaluation Group
Fonte: Washington, DC: World Bank Publicador: Washington, DC: World Bank
Tipo: Book; Publications & Research; Publications & Research :: Publication
EN_US
Relevância na Pesquisa
45.89%
The World Bank Group was a principal founding partner of the Global Environment Facility (GEF) in its pilot phase in 1991, and of the restructured GEF in 1994. The Bank plays three different roles in the GEF: (a) as trustee of the GEF and related trust funds, (b) as implementing agency, including the implementation of private-sector GEF projects by the International Finance Corporation (IFC), and (c) as the host organization of the functionally independent GEF secretariat. Focusing primarily on the role of the Bank as an implementing agency, this review documents how the partnership that the GEF and the World Bank Group established in the early 1990s has evolved over time, offers explanations for observed changes, and draws a number of lessons. The review addresses the following issues: * The mutual relevance of the World Bank Group and the GEF * Inter-organizational coordination along the World Bank Group-GEF project cycle * The introduction of the GEF’s resource allocation systems in 2006 and 2010 * The evolution and effectiveness of the Bank Group’s GEF portfolio * Catalytic approaches in the Bank Group-GEF partnership: co-financing, blending, and mainstreaming * The World Bank’s corporate activities as a GEF implementing agency. The principal purposes of this review are (a) to help improve the relevance and effectiveness of the Bank Group’s partnership with the GEF...

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
Relevância na Pesquisa
36.29%
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
Relevância na Pesquisa
36.08%
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
Relevância na Pesquisa
36.07%
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

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
Relevância na Pesquisa
36.08%
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
Relevância na Pesquisa
36.04%
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...

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
Relevância na Pesquisa
36.16%
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
Relevância na Pesquisa
36.04%
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
Relevância na Pesquisa
36.08%
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.

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
Relevância na Pesquisa
46.12%
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.

Carbon-driven Chemical Interactions between Alumina and Iron: A possible reaction pathway in Earth's interior

Rita Khanna; Mohammad Ikram-ul Haq; Veena Sahajwalla
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Relevância na Pesquisa
36.06%
Seismological and geochemical observations have revealed a complex structure for the earth's core-mantle boundary (CMB) region, with lateral and chemical heterogeneities. The presence of higher than expected concentrations of siderophile elements (Ni, Co, Pt etc) in the earth's mantle, iron enrichment of the lower mantle relative to the upper mantle, and a possible carbon flux from the core suggest the possibility of continual long-term exchange of materials between the core and the mantle. The chemical interactions of molten iron with complex mantle oxides and diffusion have been postulated as key mechanisms. A number of studies have been carried out on the reduction reactions taking into account the extreme conditions of high-temperature and high-pressure in earth's interior. These studies have, however, neglected to consider the influence of carbon on these reactions. The earth's metallic core is rich in carbon (~ 5 wt% C), and there is a growing evidence for the presence of carbon in the earth's mantle as well. Carbon can affect redox conditions through chemical interactions with oxygen, and is a critical element in determining the oxidation state of siderophile elements. Here we present a study of the interactions between liquid iron and alumina-carbon substrates at 1...

Nanomaterials: Look at the Earth

Siddhartha S. Mukhopadhyay
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Relevância na Pesquisa
36.08%
Nanotechnology promises to be the greatest technological breakthrough in history, doing for our control of matter what computers did for our control of information. The origins of nanoscience can be traced to clay mineralogy and crystallography when it was discovered that clay minerals were crystalline and of micrometer size. The unit cell dimensions of clay minerals are in nanometer scale in all three axes (x, y, and z). The advantages of clays are: (i) their ordered arrangements, (ii) their large adsorption capacity, (iii) their shielding against sunlight (ultraviolet radiation), (iv) their ability to concentrate organic chemicals, and (v) their ability to serve as polymerization templates. Clay minerals in nanoforms played a catalytic role in the synthesis of the ribosome in RNA that led to genesis of life on Earth. The history of Earth suggests that the late Precambrian oxygenation led to the inception of a ‘clay mineral factory’ that triggered the radical evolutionary diversification of Neoproterozoic life due to enhanced burial of organic carbon. High activity clays protected organic matter from reoxygenation, allowing a corresponding quantity of O2 to accumulate in the environment. The inseparable association of clays with lifeforms makes them most desirable in manufacturing nanoparticles. Clays have been extensively used in industry...