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Efeito do silício na utilização do fósforo pelas plantas de arroz; Effect of silicon on phosphorus utilization by rice plants

Fehr, Rafhael Mendes
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 27/08/2014 PT
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Com o objetivo de avaliar os efeitos da interação entre o silício (Si) e o fósforo (P) na planta e no solo, foram realizados três experimentos. No primeiro experimento, avaliou-se o efeito de duas fontes de Si (wollastonita e filossilicato) em diferentes doses (0 a 250 mg dm-3) sobre o aproveitamento do P do superfosfato triplo marcado com o radioisótopo 32P. Utilizouse o arroz (Oryza sativa) como planta teste. Neste primeiro experimento, as duas fontes de Si promoveram incremento na quantidade do elemento nas plantas, porém tiveram comportamento diferente quanto à produção de matéria seca da parte aérea e de P acumulado, tendo apenas o filossilicato promovido ganhos para estas variáveis. Constatou-se que o maior acúmulo do P pela planta em relação ao tratamento controle (sem Si) foi devido à maior absorção do nutriente do solo e não do fertilizante, sendo baixo o aproveitamento do superfosfato triplo pelas plantas para as duas fontes de Si. No entanto, a wollastonita liberou maiores quantidades de Si no solo em relação ao filossilicato. No segundo experimento foram avaliadas as formas de aplicação (em sulco ou misturado ao solo) de Si e P no aproveitamento do P do superfosfato triplo pelo arroz. Aplicou-se uma dose de Si (125 mg dm-3) intermediária daquelas utilizadas no primeiro experimento para ambas as fontes de Si...

Novos agentes sililantes aplicaveis em imobilização, processo sol-gel, filossilicato e termoquimica de interação; New silylating agents used in immobilization, sol-gel process phyllosilicate and thermochemical of interaction

Andrea Sales de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 23/02/2006 PT
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Novos agentes sililantes foram preparados através da reação do precursor -3glicidoxipropiltrimetoxissilano com a molécula de interesse 2-aminofenildissulfeto, que contém centros básicos distintos nitrogênio e enxofre. Os novos agentes sintetizados foram covalentemente fixados na estrutura polimérica da silica gel por imobilização, utilizando as rotas homogênea e heterogênea e através do processo sol-gel. Nessa metodologia o novo agente sililante hídrolisa juntamente com o tetraetoxidossilano em meio básico, possibilitando a incorporação de grupos pendentes derivados dos agentes de partida. A sílica mesoporosa foi obtida através do processo sol-gel no qual ocorre a cocondensação entre grupos silanóis, que são formados na hidrólise, e a conseqüente polimerização para chegar ao produto final, sendo que a presença do direcionador dodecilamina funciona na formação de micela. Neste processo a rnicela é envolta pelo reagente tetraetoxissilano, que também permite a agregação do novo agente sililante, antes que ocorra o direcionamento da co-condensação da estrutura inorgâníca. O emprego de um sal de magnésio, em meio básico, juntamente com o agente resulta numa estrutura lametar do filossilicato, contendo a parte orgânica no espaço intertamelar. As propriedades de adsorção com as novas superfícies foram utilizadas na remoção de metais divalentes como cobre...

Organofuncionalização de silica e filossilicato a partir de agentes sililantes incoporados com tioureia; Organofunctionalization of silica and phyllosilicate from silylating agents incorporating thiourea

Fernando Jose Volpi Eusebio de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/07/2006 PT
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Novas matrizes de sílica gel organofuncionalizadas foram preparadas através da incorporação da molécula de tiouréia nos agentes sililantes comerciais de cadeias lineares contendo de um a três átomos de nitrogênio em suas estruturas, na presença de sulfato de amônio, como catalisador. Utilizou-se um novo método de preparação do novo agente modificado não envolvendo a presença de solvente na etapa inicial, o que difere daqueles que usam algum tipo de solvente orgânico, não só na etapa inicial, como também em reações sucessivas de imobilização. As matrizes foram denominadas conforme o número de nitrogênios contidos em suas superfícies, sendo S-NT, S-2NT e S-3NT, de acordo com os crescentes átomos de nitrogênio contidos no agente de origem. Através do processo sol-gel foram sintetizados os filossilicatos correspondentes às superfícies de sílica modificada. Nessa etapa, os agentes incorporados com tiouréia foram dissolvidos em etanol e adicionados a uma solução de nitrato de níquel em meio básico, obedecendo a relação molar Si/Ni como sendo 4/3. Assim, foram obtidos filossilicatos similares ao talco, que apresenta o magnésio nos sítios octaédricos, envoltos por duas camadas de silicato, onde o silício está acomodado nos sítios tetraédricos. Para a síntese da estrutura similar ao talco natural é fundamental que a razão molar mencionada seja obedecida. As técnicas de caracterização utilizadas permitiram a compreensão das estruturas...

Isolation of Phyllosilicate–Iron Redox Cycling Microorganisms from an Illite–Smectite Rich Hydromorphic Soil

Shelobolina, Evgenya; Konishi, Hiromi; Xu, Huifang; Benzine, Jason; Xiong, Mai Yia; Wu, Tao; Blöthe, Marco; Roden, Eric
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 04/04/2012 EN
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The biogeochemistry of phyllosilicate–Fe redox cycling was studied in a Phalaris arundinacea (reed canary grass) dominated redoximorphic soil from Shovelers Sink, a small glacial depression near Madison, WI. The clay size fraction of Shovelers Sink soil accounts for 16% of the dry weight of the soil, yet contributes 74% of total Fe. The dominant mineral in the clay size fraction is mixed layer illite–smectite, and in contrast to many other soils and sediments, Fe(III) oxides are present in low abundance. We examined the Fe biogeochemistry of Shovelers Sink soils, estimated the abundance of Fe redox cycling microorganisms, and isolated in pure culture representative phyllosilicate–Fe oxidizing and reducing organisms. The abundance of phyllosilicate–Fe reducing and oxidizing organisms was low compared to culturable aerobic heterotrophs. Both direct isolation and dilution-to-extinction approaches using structural Fe(II) in Bancroft biotite as a Fe(II) source, and O2 as the electron acceptor, resulted in recovery of common rhizosphere organisms including Bradyrhizobium spp. and strains of Cupriavidus necator and Ralstonia solanacearum. In addition to oxidizing biotite and soluble Fe(II) with O2, each of these isolates was able to oxidize Fe(II) in reduced NAu-2 smectite with NO3- as the electron acceptor. Oxidized NAu-2 smectite or amorphous Fe(III) oxide served as electron acceptors for enrichment and isolation of Fe(III)-reducing microorganisms...

Improved cell disruption of Pichia pastoris utilizing aminopropyl magnesium phyllosilicate (AMP) clay

Kim, Sun-Il; Wu, Yuanzheng; Kim, Ka-Lyun; Kim, Geun-Joong; Shin, Hyun-Jae
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
EN
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An efficient method for Pichia cell disruption that employs an aminopropyl magnesium phyllosilicate (AMP) clay-assisted glass beads mill is presented. AMP clay is functionalized nanocomposite resembling the talc parent structure Si8Mg6O20(OH)4 that has been proven to permeate the bacterial membrane and cause cell lysis. The recombinant capsid protein of cowpea chlorotic mottle virus (CCMV) expressed in Pichia pastoris GS115 was used as demonstration system for their ability of self-assembly into icosahedral virus-like particles (VLPs). The total protein concentration reached 4.24 mg/ml after 4 min treatment by glass beads mill combined with 0.2 % AMP clay, which was 11.2 % higher compared to glass beads mill only and the time was half shortened. The stability of purified CCMV VLPs illustrated AMP clay had no influence on virus assembly process. Considering the tiny amount added and simple approach of AMP clay, it could be a reliable method for yeast cell disruption.

3-aminopropyl functionalized magnesium phyllosilicate as an organoclay based drug carrier for improving the bioavailability of flurbiprofen

Yang, Liang; Choi, Soo-Kyung; Shin, Hyun-Jae; Han, Hyo-Kyung
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
EN
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This study aimed to develop an oral delivery system using clay-based organic–inorganic hybrid materials to improve the bioavailability of the drug, flurbiprofen, which is poorly soluble in water. 3-aminopropyl functionalized magnesium phyllosilicate (AMP clay) was synthesized by a one-pot direct sol-gel method, and then flurbiprofen (FB) was incorporated into AMP clay (FB-AMP) at different drug/clay ratios. The structural characteristics of AMP and FB-AMP formulation were confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. Among tested formulations, FB-AMP(3), dramatically increased the dissolution of FB and achieved rapid and complete drug release within 2 hours. More than 60% of FB was released from FB-AMP(3) after 30 minutes; the drug was completely dissolved in the water within 2 hours. Under the acidic condition (pH 1.2), FB-AMP(3) also increased the dissolution of FB by up to 47.1% within 1 hour, which was three-fold higher than that of untreated FB. Furthermore, following an oral administration of FB-AMP(3) to Sprague-Dawley rats, the peak plasma concentration and area under the plasma concentration-time curve of FB increased two-fold, and the time to reach the peak plasma concentration was shortened compared with that in the untreated FB. This result suggests that the oral drug delivery system using clay-based organic–inorganic hybrid material might be useful to improve the bioavailability of FB.

Fe-phyllosilicate redox cycling organisms from a redox transition zone in Hanford 300 Area sediments

Benzine, Jason; Shelobolina, Evgenya; Xiong, Mai Yia; Kennedy, David W.; McKinley, James P.; Lin, Xueju; Roden, Eric E.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 16/12/2013 EN
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Microorganisms capable of reducing or oxidizing structural iron (Fe) in Fe-bearing phyllosilicate minerals were enriched and isolated from a subsurface redox transition zone at the Hanford 300 Area site in eastern Washington, USA. Both conventional and in situ “i-chip” enrichment strategies were employed. One Fe(III)-reducing Geobacter (G. bremensis strain R1, Deltaproteobacteria) and six Fe(II) phyllosilicate-oxidizing isolates from the Alphaproteobacteria (Bradyrhizobium japonicum strains 22, is5, and in8p8), Betaproteobacteria (Cupriavidus necator strain A5-1, Dechloromonas agitata strain is5), and Actinobacteria (Nocardioides sp. strain in31) were recovered. The G. bremensis isolate grew by oxidizing acetate with the oxidized form of NAu-2 smectite as the electron acceptor. The Fe(II)-oxidizers grew by oxidation of chemically reduced smectite as the energy source with nitrate as the electron acceptor. The Bradyrhizobium isolates could also carry out aerobic oxidation of biotite. This is the first report of the recovery of a Fe(II)-oxidizing Nocardioides, and to date only one other Fe(II)-oxidizing Bradyrhizobium is known. The 16S rRNA gene sequences of the isolates were similar to ones found in clone libraries from Hanford 300 sediments and groundwater...

Effect of coating phyllosilicate clays with hydrous oxides on organic carbon stabilisation.

Saidy, Akhmad Rizalli
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2013
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Phyllosilicate clays and hydrous oxides are recognised as important minerals in soils for organic carbon (OC) stabilisation. Most studies on the influence that hydrous oxides have on OC stabilisation have been carried out using different soils that contain different amounts of Fe or Al oxides or in experiments where OC stabilisation was measured separately on phyllosilicate clays and oxides. Consequently, the interactive effect of different types of phyllosilicate clays and hydrous oxides on OC stabilisation remains poorly understood. In this work, a series of experiments was carried out to obtain a better understanding of the effect of different phyllosilicate clays on OC stabilisation in the presence and absence of different hydrous oxides. In the first set of experiments, stabilisation of plant-derived OC by three different phyllosilicate clays (kaolinite, illite, smectite) with and without goethite coating and illitic clay coated with different oxides (goethite, haematite, ferrihydrite, imogolite) was quantified by measuring mineralisation of added OC to these clays or clay-oxide associations in a model system consisting of sand mixed with clay. The amount of OC added to mineral was the same for all treatments (5 mg C g⁻¹ sand-clay mixture). These conditions correspond to a relatively high OC loading...

Significance of phyllosilicate mineralogy and mineral chemistry in the epithermal environment. Insights from the Palai-Islica Au-Cu deposit (Almer??a, SE Spain)

Carrillo-Ros??a, Javier; Morales-Ruano, Salvador; Esteban-Arispe, I??aki; Fenoll Hach-Al??, Purificaci??n
Fonte: Clay Minerals Society Publicador: Clay Minerals Society
Tipo: Artigo de Revista Científica
ENG
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X-ray diffraction, optical and electronic microscopy (scanning and transmitted), electron microprobe and Fourier transform infra red spectroscopy has been used to study phyllosilicates in the Palai-Islica Au-Cu epithermal, volcanic-hosted deposit, in order to link phyllosilicate mineralogy and mineral chemistry to ore genesis. Thus, different phyllosilicate assemblages characterize two types of mineralization, and related hydrothermal alteration. Chlorite and mica appear in polymetallic quartz veins with sulfides, and in the related chloritic and sericitic hydrothermal alteration. These minerals have notable textural and chemical differences (i.e. Fe/(Fe+Mg), Si and Al in chlorite and illitic and phengitic components in mica) amongst veins and altered rocks, revealing different genetic conditions. These chemical features also distinguish propylitic and regional, non ore-related, low-temperature alteration. Hot hydrothermal fluids of near-neutral pH are responsible for vein mineralization and alteration. Illite, interstratified illite-smectite, kaolinite and pyrophyllite are characteristic, with a distribution pattern by zones, for the intermediate argillic and advanced argillic alteration around areas of silicification. In the latter...

Spitzer infrared spectrograph spectroscopy of the 10 Myr old EF Cha debris disk: Evidence for phyllosilicate-rich dust in the terrestrial zone

Currie, Thayne M.; Lisse, Carey Michael; Sicilia-Aguilar, Aurora; Rieke, George H.; Su, Kate
Fonte: The American Astronomical Society Publicador: The American Astronomical Society
Tipo: Artigo de Revista Científica
ENG
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The Astrophysical Journal 734.2 (2011): 115 reproduced by permission of the AAS; We describe Spitzer Infrared Spectrograph spectroscopic observations of the ∼10 Myr old star, EF Cha. Compositional modeling of the spectra from 5 μm to 35 μm confirms that it is surrounded by a luminous debris disk with LD /L⊙ ∼ 10-3, containing dust with temperatures between 225 K and 430 K, characteristic of the terrestrial zone. The EF Cha spectrum shows evidence for many solid-state features, unlike most cold, low-luminosity debris disks but like some other 10-20 Myr old luminous, warm debris disks (e.g., HD 113766A). The EF Cha debris disk is unusually rich in a species or combination of species whose emissivities resemble that of finely powdered, laboratory-measured phyllosilicate species (talc, saponite, and smectite), which are likely produced by aqueous alteration of primordial anhydrous rocky materials. The dust and, by inference, the parent bodies of the debris also contain abundant amorphous silicates and metal sulfides, and possibly water ice. The dust's total olivine to the pyroxene ratio of ∼2 also provides evidence of aqueous alteration. The large mass volume of grains with sizes comparable to or below the radiation blow-out limit implies that planetesimals may be colliding at a rate high enough to yield the emitting dust but not so high as to devolatize the planetesimals via impact processing. Because phyllosilicates are produced by the interactions between anhydrous rock and warm...

Exploring the potential of phyllosilicate minerals as potassium fertilizers using sodium tetraphenylboron and intensive cropping with perennial ryegrass

Li, Ting; Wang, Huoyan; Wang, Jing; Zhou, Zijun; Zhou, Jianmin
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 18/03/2015 EN
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283.2302%
In response to addressing potassium (K) deficiency in soil and decreasing agricultural production costs, the potential of K-bearing phyllosilicate minerals that can be directly used as an alternative K source has been investigated using sodium tetraphenylboron (NaTPB) extraction and an intensive cropping experiment. The results showed that the critical value of K-release rate and leaf K concentration was 3.30 g kg−1 h−1 and 30.64 g (kg dry matter)−1, respectively under the experimental conditions. According to this critical value, the maximum amount of released K that could be utilized by a plant with no K deficiency symptoms was from biotite (27.80 g kg−1) and vermiculite (5.58 g kg−1), followed by illite, smectite and muscovite with 2.76, 0.88 and 0.49 g kg−1, respectively. Ryegrass grown on phlogopite showed K deficiency symptoms during the overall growth period. It is concluded that biotite and vermiculite can be directly applied as a promising and sustainable alternative to the use of classical K fertilizers, illite can be utilized in combination with soluble K fertilizers, whereas muscovite, phlogopite and smectite may not be suitable for plant growth. Further field experiments are needed to assess the use of these phyllosilicate minerals as sources of K fertilizer.

On oscillators in phyllosilicate excitable automata

Adamatzky, Andrew
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/05/2013
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Phyllosilicate is a sheet of silicate tetrahedra bound by basal oxygens. A phyllosilicate excitable automaton is a regular network of finite state machines, which mimics structure of a silicate sheet. A node of the silicate sheet is an automaton, which takes resting, excited and refractory states, and updates its state in discrete time depending on a sum of excited states of its three (silicon automata) or six (oxygen automata) closest neighbours. Oscillator is a localised compact configuration of non-quiescent states which undergoes finite growth and modification but returns to its original state in a finite number of steps. We show that phyllosilicate excitable automata exhibit spiral and target waves, and oscillating localisation dynamics. Basic types of oscillators are classified and characterised.

Game of Life on Phyllosilicates: Gliders, Oscillators and Still Life

Adamatzky, Andrew
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/06/2013
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A phyllosilicate is a sheet of silicate tetrahedra bound by basal oxygens. A phyllosilicate automaton is a regular network of finite state machines --- silicon nodes and oxygen nodes --- which mimics structure of the phyllosilicate. A node takes states 0 and 1. Each node updates its state in discrete time depending on a sum of states of its three (silicon) or six (oxygen) neighbours. Phyllosilicate automata exhibit localizations attributed to Conway's Game of Life: gliders, oscillators, still lifes, and a glider gun. Configurations and behaviour of typical localizations, and interactions between the localizations are illustrated.

Phyllosilicate Emission from Protoplanetary Disks: Is the Indirect Detection of Extrasolar Water Possible?

Morris, Melissa A.; Desch, Steven J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/04/2013
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Phyllosilicates are hydrous minerals formed by interaction between rock and liquid water and are commonly found in meteorites originating in the asteroid belt. Collisions between asteroids contribute to zodiacal dust, which therefore reasonably could include phyllosilicates. Collisions between planetesimals in protoplanetary disks may also produce dust containing phyllosilicates. These minerals possess characteristic emission features in the mid-infrared and could be detectable in extrasolar protoplanetary disks. Here we determine whether phyllosilicates in protoplanetary disks are detectable in the infrared using instruments such as those on board the Spitzer Space Telescope and SOFIA (Stratospheric Observatory for Infrared Astronomy). We calculate opacities for the phyllosilicates most common in meteorites and compute the emission of radiation from a protoplanetary disk using a 2-layer radiative transfer model. We find that phyllosilicates present at the 3% level lead to observationally significant differences in disk spectra, and should therefore be detectable using infrared observations and spectral modeling. Detection of phyllosilicates in a protoplanetary disk would be diagnostic of liquid water in planetesimals in that disk and would demonstrate similarity to our own Solar System. We also discuss use of phyllosilicate emission to test the "waterworlds" hypothesis...

Spitzer IRS Spectroscopy of the 10 Myr-old EF Cha Debris Disk: Evidence for Phyllosilicate-Rich Dust in the Terrestrial Zone

Currie, Thayne; Lisse, Carey M.; Sicilia-Aguilar, Aurora; Rieke, George H.; Su, Kate
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/04/2011
Relevância na Pesquisa
272.8264%
We describe Spitzer IRS spectroscopic observations of the 10 Myr-old star, EF Cha. Compositional modeling of the spectra from 5 {\mu}m to 35 {\mu}m confirms that it is surrounded by a luminous debris disk with LD/L\star ~ 10-3, containing dust with temperatures between 225 K and 430 K characteristic of the terrestrial zone. The EF Cha spectrum shows evidence for many solid-state features, unlike most cold, low-luminosity debris disks but like some other 10-20 Myr-old luminous, warm debris disks (e.g. HD 113766A). The EF Cha debris disk is unusually rich in a species or combination of species whose emissivities resemble that of finely powdered, laboratory-measured phyllosilicate species (talc, saponite, and smectite), which are likely produced by aqueous alteration of primordial anhydrous rocky materials. The dust and, by inference, the parent bodies of the debris also contain abundant amorphous silicates and metal sulfides, and possibly water ice. The dust's total olivine to pyroxene ratio of ~ 2 also provides evidence of aqueous alteration. The large mass volume of grains with sizes comparable to or below the radiation blow-out limit implies that planetesimals may be colliding at a rate high enough to yield the emitting dust but not so high as to devolatize the planetesimals via impact processing. Because phyllosilicates are produced by the interactions between anhydrous rock and warm...

Contrasting alteration processes in hydrothermally altered dolerites from the Betic Cordillera, Spain

Jiménez-Millán, Juan; Abad, Isabel; Nieto, F.
Fonte: Mineralogical Society (Great Britain) Publicador: Mineralogical Society (Great Britain)
Tipo: Artículo Formato: 13824 bytes; application/vnd.ms-excel
ENG
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189.6325%
Dolerites from the Sierra de San Pedro (Betic Cordillera, southern Spain) develop three main types of microsystems during hydrothermal alteration: (1) centimetre-sized veins cross-cutting the dolerites; (2) microfractures in feldspar and diopside grains; and (3) alterations involving primary-igneous mafic phyllosilicate grains. The vein and microfracture sites developed alteration assemblages of randomly oriented smectites (saponite and beidellite) and halloysite. At these sites, the alteration mechanism was governed by complete dissolution of the parent material with subsequent crystallization of the products, with no parent-mineral crystallographic control. Pseudomorphed mafic phyllosilicate sites are characterized by oriented complex mineral assemblages made of chlorite, chlorite/smectite mixed layers, corrensite, saponite and relicts of biotite. These assemblages formed during the initial high-temperature stage of the hydrothermal process. In these microsites, the alteration sequence was controlled by the parent-mineral structure and chemistry, with products determined by structural relations with the parent phyllosilicate. Alteration of one phyllosilicate to the next most stable proceeds via interstratification of the parent and product phyllosilicates.; Peer reviewed

Phyllosilicate Diversity and Past Aqueous Activity Revealed at Mawrth Vallis, Mars

Bishop, Janice L.; Dobrea, Eldar Z. Noe; McKeown, Nancy K.; Parente, Mario; Ehlmann, Bethany L.; Michalski, Joseph R.; Milliken, Ralph E.; Poulet, Francois; Swayze, Gregg A.; Mustard, John F.; Murchie, Scott L.; Bibring, Jean-Pierre
Fonte: American Association for the Advancement of Science Publicador: American Association for the Advancement of Science
Tipo: Article; PeerReviewed Formato: application/pdf; video/mpeg
Publicado em 08/08/2008
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Observations by the Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars in the Mawrth Vallis region show several phyllosilicate species, indicating a wide range of past aqueous activity. Iron/magnesium (Fe/Mg)–smectite is observed in light-toned outcrops that probably formed via aqueous alteration of basalt of the ancient cratered terrain. This unit is overlain by rocks rich in hydrated silica, montmorillonite, and kaolinite that may have formed via subsequent leaching of Fe and Mg through extended aqueous events or a change in aqueous chemistry. A spectral feature attributed to an Fe^(2+) phase is present in many locations in the Mawrth Vallis region at the transition from Fe/Mg-smectite to aluminum/silicon (Al/Si)–rich units. Fe^(2+)-bearing materials in terrestrial sediments are typically associated with microorganisms or changes in pH or cations and could be explained here by hydrothermal activity. The stratigraphy of Fe/Mg-smectite overlain by a ferrous phase, hydrated silica, and then Al-phyllosilicates implies a complex aqueous history.

Characterization of phyllosilicates observed in the central Mawrth Vallis region, Mars, their potential formational processes, and implications for past climate

McKeown, Nancy K.; Bishop, Janice L.; Dobrea, Eldar Z. Noe; Ehlmann, Bethany L.; Parente, Mario; Mustard, John F.; Murchie, Scott L.; Swayze, Gregg A.; Bibring, Jean-Pierre; Silver, Eli A.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 26/11/2009
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Mawrth Vallis contains one of the largest exposures of phyllosilicates on Mars. Nontronite, montmorillonite, kaolinite, and hydrated silica have been identified throughout the region using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). In addition, saponite has been identified in one observation within a crater. These individual minerals are identified and distinguished by features at 1.38–1.42, ∼1.91, and 2.17–2.41 μm. There are two main phyllosilicate units in the Mawrth Vallis region. The lowermost unit is nontronite bearing, unconformably overlain by an Al-phyllosilicate unit containing montmorillonite plus hydrated silica, with a thin layer of kaolinite plus hydrated silica at the top of the unit. These two units are draped by a spectrally unremarkable capping unit. Smectites generally form in neutral to alkaline environments, while kaolinite and hydrated silica typically form in slightly acidic conditions; thus, the observed phyllosilicates may reflect a change in aqueous chemistry. Spectra retrieved near the boundary between the nontronite and Al-phyllosilicate units exhibit a strong positive slope from 1 to 2 μm, likely from a ferrous component within the rock. This ferrous component indicates either rapid deposition in an oxidizing environment or reducing conditions. Formation of each of the phyllosilicate minerals identified requires liquid water...

Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis basin

Mustard, J. F.; Ehlmann, B. L.; Murchie, S. L.; Poulet, F.; Mangold, N.; Head, J. W.; Bibring, J.-P.; Roach, L. H.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 12/12/2009
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Definitive exposures of pristine, ancient crust on Mars are rare, and the finding that much of the ancient Noachian terrain on Mars exhibits evidence of phyllosilicate alteration adds further complexity. We have analyzed high-resolution data from the Mars Reconnaissance Orbiter in the well-exposed Noachian crust surrounding the Isidis basin. We focus on data from the Compact Reconnaissance Imaging Spectrometer for Mars as well as imaging data sets from High Resolution Imagine Science Experiment and Context Imager. These data show the lowermost unit of Noachian crust in this region is a complex, brecciated unit of diverse compositions. Breccia blocks consisting of unaltered mafic rocks together with rocks showing signatures of Fe/Mg-phyllosilicates are commonly observed. In regions of good exposure, layered or banded phyllosilicate-bearing breccia rocks are observed suggestive of pre-Isidis sedimentary deposits. In places, the phyllosilicate-bearing material appears as a matrix surrounding mafic blocks, and the mafic rocks show evidence of complex folded relationships possibly formed in the turbulent flow during emplacement of basin-scale ejecta. These materials likely include both pre-Isidis basement rocks as well as the brecciated products of the Isidis basin–forming event at 3.9 Ga. A banded olivine unit capped by a mafic unit covers a large topographic and geographic range from northwest of Nili Fossae to the southern edge of the Isidis basin. This olivine-mafic cap combination superimposes the phyllosilicate-bearing basement rocks and distinctly conforms to the underlying basement topography. This may be due to draping of the topography by a fluid or tectonic deformation of a previously flatter lying morphology. We interpret the draping...

Oxygen and Hydrogen adsorption studies by means of the Kelvin probe on an  iron  Phyllosilicate

Cárdenas,Luis A.; Rodríguez,Alfonso; Rueda,Fulgencio; Casanova,Rodrigo; Mendialdua,Juan; Loaiza-Gil,Alfonso
Fonte: Universidad Simón Bolívar; ; Publicador: Universidad Simón Bolívar; ;
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2004 EN
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The aim of the present work is to study the different oxygen species adsorbed on an iron phyllosilicate catalyst using the Kelvin probe technique. The results of the oxygen and hydrogen adsorption studies on samples with different iron content, Fe(10%)SiO2, Fe(20%)SiO2 and Fe(30%)SiO2 , are presented in the temperature range between 323 K and 723 K. In the Fe(10%)SiO2 sample the oxygen species adsorbed is O-2 for temperatures lower than 473 K, while the O-2 species is found in the temperature range between 573K and 723K. In the Fe(20%)SiO2 sample, the O- oxygen species is adsorbed in this sample at 473K predominantly; while the O-2  is found on the surface in the temperature range between 623 K and 698 K. The oxygen species adsorbed on  the Fe(30%) SiO2  sample is  O-2.