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Bioindicadores de qualidade do solo em um gradiente de restauração ambiental; Soil quality bioindicators of an environmental restoration gradient

Vasconcellos, Rafael Leandro de Figueiredo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/06/2012 PT
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Impactos ambientais podem interferir nas características da biomassa microbiana, no processo de ciclagem de nutrientes, nas características físicoquímicas e também na diversidade da microbiota e da macrofauna. O objetivo desse trabalho foi conhecer as diferentes interações entre estes atributos e identificar os indicadores da qualidade do solo envolvidos com o tempo de recuperação. Três áreas com estágios diferentes de recuperação (5, 10 e 20 anos) foram comparadas com uma floresta Estacional Semidecídua nativa (NT) com intuito de estudar o comportamento da microbiota, da macrofauna e de suas interações com os atributos físico-químicos. Foram coletadas amostras em 15 pontos por áreas, escolhidos aleatoriamente. Dentre os atributos microbiológicos, a maior atividade das enzimas urease, fosfatase ácida e desidrogeanse foi encontrada na área nativa. O mesmo foi constatado para a respiração basal e para o carbono e nitrogênio da biomassa microbiana. A análise da estrutura da comunidade de Bacteria, feita a partir de TRFLP, separou as áreas, nativa e de 20 anos de recuperação, das demais, somente no verão. A densidade do solo, a umidade e a microporosidade afetaram negativamente os indicadores microbiológicos do solo...

Development of Monolithic Materials with and without a Binder with Carbon Molecular Sieving Properties

Nabais, Joao; Carrott, Peter; Ribeiro Carrott, Manuela; Galacho, Cristina; Padre-Eterno, Ana
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 89940 bytes; application/pdf
ENG
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In this work we studied the production of activated carbon fibres in monolith shape from a commercial textile acrylic fibre. The monoliths were produced with and without a binder. The binders tested were phenolic resin, polystyrene, polymethylmethacrylate and clay. We also tested the influence of using a solvent. The SEM analysis indicates that the monoliths are made of filaments that can be considered activated carbon fibres. The type of binder influences the fibre orientation, degradation and materials shrinkage, the worst results being obtained from the use of polymethylmethacrylate and polystyrene in toluene. The best results are obtained when the monoliths were produced only with acrylic fibre and with phenolic resin as binder. The use of solvents has opposite effects for the carbonised and activated samples. In the former case it seems that the water can be fibre protective but during activation the presence of water leads to an increase in the monolith’s burn-off. The methodology used leads to the formation of excellent samples for performing the gas separations O2/N2 and CO2/CH4. Some samples show maximum selectivity for the referred separations because N2 and CH4 are almost totally excluded from the porous structure which indicates a good potential to be utilised in PSA systems or for natural gas purification. The adsorption capacity is very dependent on the conditions used. Nevertheless...

Relación entre la entalpía de inmersión de monolitos de carbon activado y parametros texturales

Vargas,Diana P.; Gutiérrez,Liliana Giraldo; Moreno,Juan Carlos
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 ES
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In this study, Disc and honeycomb-shaped activated carbon monoliths were obtained using as a precursor coconut shell, without the use of any binder. Textural characterization was performed by adsorption of N2 at 77 K and immersion calorimetry into benzene. The experimental results showed that the activation with zinc chloride produces a wide development of micropores, yielding micropore volumes between 0,38 and 0,79 cm³ g-1, apparent BET surface area between 725 and 1523 m² g-1 and immersion enthalpy between 73,5 and 164,2 J g-1.Were made comparisons between textural parameters and energy characteristics.

Spectroscopic characterization of the oxyferrous complex of prostacyclin synthase in solution and in trapped sol–gel matrix

Yeh, Hui-Chun; Hsu, Pei-Yung; Tsai, Ah-Lim; Wang, Lee-Ho
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Prostacyclin synthase (PGIS) is a member of the cytochrome P450 family in which the oxyferrous complexes are generally labile in the absence of substrate. At 4 °C, the on-rate constants and off-rate constants of oxygen binding to PGIS in solution are 5.9 × 105 m−1 ·s−1 and 29 s−1, respectively. The oxyferrous complex decays to a ferric form at a rate of 12 s−1. We report, for the first time, a stable oxyferrous complex of PGIS in a transparent sol–gel monolith. The encapsulated ferric PGIS retained the same spectroscopic features as in solution. The binding capabilities of the encapsulated PGIS were demonstrated by spectral changes upon the addition of O-based, N-based and C-based ligands. The peroxidase activity of PGIS in sol–gel was three orders of magnitude slower than that in solution owing to the restricted diffusion of the substrate in sol–gel. The oxyferrous complex in sol–gel was observable for 24 h at room temperature and displayed a much red-shifted Soret peak. Stabilization of the ferrous–carbon monoxide complex in sol–gel was observed as an enrichment of the 450-nm species over the 420-nm species. This result suggests that the sol–gel method may be applied to other P450s to generate a stable intermediate in the di-oxygen activation.

Incorporation of carbon nanotubes in porous polymer monolithic capillary columns to enhance the chromatographic separation of small molecules

Chambers, Stuart D.; Svec, Frantisek; Fréchet, Jean M.J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Multiwalled carbon nanotubes have been entrapped in monolithic poly(glycidyl methacrylate-co-ethylene dimethacrylate) capillary columns to afford stationary phases with enhanced liquid chromatographic performance for small molecules in the reversed phase. While the column with no nanotubes exhibited an efficiency of only 1800 plates/m, addition of a small amount of nanotubes to the polymerization mixture increased the efficiency to over 15,000 and 35,000 plates/m at flow rates of 1 and 0.15 μL/min, respectively. Alternatively, the native glycidyl methacrylate-based monolith was functionalized with ammonia and, then, shortened carbon nanotubes, bearing carboxyl functionalities, were attached to the pore surface through the aid of electrostatic interactions with the amine functionalities. Reducing the pore size of the monolith enhanced the column efficiency for the retained analyte, benzene, to 30,000 plates/m at a flow rate of 0.25 μL/min. Addition of tetrahydrofuran to the typical aqueous acetonitrile eluents improved the peak shape and increased the column efficiency to 44,000 plates/m calculated for the retained benzene peak.

Porous Polymer Monoliths Functionalized through Copolymerization of C60 Fullerene-Containing Methacrylate Monomer for Highly Efficient Separations of Small Molecules

Chambers, Stuart D.; Holcombe, Thomas W.; Svec, Frantisek; Fréchet, Jean M.J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Monolithic poly(glycidyl methacrylate-co-ethylene dimethacrylate) and poly(butyl methacrylate-co-ethylene dimethacrylate) capillary columns, which incorporate the new monomer [6,6]-phenyl-C61-butyric acid 2-hydroxyethyl methacrylate ester, have been prepared and their chromatographic performance tested for the separation of small molecules in the reversed phase. While addition of the C60-fullerene monomer to the glycidyl methacrylate-based monolith enhanced column efficiency 18-fold, to 85,000 plates/m at a linear velocity of 0.46 mm/s and a retention factor of 2.6, when compared to the parent monolith, the use of butyl methacrylate together with the carbon nanostructured monomer afforded monolithic columns with an efficiency for benzene exceeding 110,000 plates/m at a linear velocity of 0.32 mm/s and a retention factor of 4.2. This high efficiency is unprecedented for separations using porous polymer monoliths operating in an isocratic mode. Optimization of the chromatographic parameters affords near baseline separation of 6 alkylbenzenes in 3 minutes with an efficiency of 64,000 plates/m. The presence of 1 wt% or more of water in the polymerization mixture has a large effect on both the formation and reproducibility of the monoliths. Other important factors such as nitrogen exposure...

An adsorbent monolith device to augment the removal of uraemic toxins during haemodialysis

Sandeman, Susan R.; Howell, Carol A.; Phillips, Gary J.; Zheng, Yishan; Standen, Guy; Pletzenauer, Robert; Davenport, Andrew; Basnayake, Kolitha; Boyd, Owen; Holt, Stephen; Mikhalovsky, Sergey V.
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
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397.10555%
Adsorbents designed with porosity which allows the removal of protein bound and high molecular weight uraemic toxins may improve the effectiveness of haemodialysis treatment of chronic kidney disease (CKD). A nanoporous activated carbon monolith prototype designed for direct blood contact was first assessed for its capacity to remove albumin bound marker toxins indoxyl sulphate (IS), p-cresyl sulphate (p-CS) and high molecular weight cytokine interleukin-6 in spiked healthy donor studies. Haemodialysis patient blood samples were then used to measure the presence of these markers in pre- and post-dialysis blood and their removal by adsorbent recirculation of post-dialysis blood samples. Nanopores (20–100 nm) were necessary for marker uraemic toxin removal during in vitro studies. Limited removal of IS and p-CS occurred during haemodialysis, whereas almost complete removal occurred following perfusion through the carbon monoliths suggesting a key role for such adsorbent therapies in CKD patient care.

Preparation of Monolithic Capillary Chromatographic Columns Using Supercritical Fluid as a Porogen Solvent

Szumski, Michał; Buszewski, Bogusław
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Artigo de Revista Científica
EN
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Monolithic polymeric beds were synthesized in fused silica capillaries using either trimethylolpropane trimethacrylate (TRIM) or a mixture of butyl methacrylate (BMA) with ethylene glycol dimethacrylate (EDMA) as monomers. Carbon dioxide at temperature and pressure conditions above its critical values was used as a porogen solvent. The purpose of using the supercritical carbon dioxide was to have the possibility of changing the solvation power (and thus the porosity of the resulting monolith) of the porogen by pressure and temperature changes instead of changing the porogen composition. The experiments were performed using a special setup consisting of a stainless steel high-pressure reactor to which the fused silica capillary was connected. The synthesized monoliths underwent liquid chromatographic evaluation. The polyTRIM capillary monoliths were characterized by different permeability, which depended on the pressure of the synthesis. BMA/EDMA columns were applied for separation of alkylbenzenes and a model mixture of proteins.

Single-walled carbon nanotube-silicon nitride composites

Corral, Erica Lorrane
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
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Colloidal processing methods were developed in order to disperse highly concentrated 1.0, 2.0, and 6.0 vol% single-walled carbon nantoube (SWNT)-Si 3N4 aqueous composite suspensions. Interparticle pair potentials were developed between individual Si3N4 particles and SWNT bundles by coating them with cationic surfactant molecules of cetyltrimethylammonium bromide (CTAB). Zeta potential, viscosity, and sedimentation measurements were conducted on SWNTs and Si3N4 particle suspensions in order to optimize the pH and amount of adsorbed CTAB. The composite suspension viscosity was pH sensitive and adjusted accordingly before consolidation into three-dimensional solid parts using a rapid prototyping fabrication method called robocasting. High-density composites were produced using spark plasma sintering and structurally intact SWNTs were directly observed in the final sintered microstructure using scanning electron microscopy and Raman spectroscopy. When processed with SWNTs the highly insulative ceramic became electrically conductive and resulted in increased grindability for the otherwise hard to machine ceramic. The high hardness, fracture toughness and density of Si 3N4 was maintained for the composite due to the detailed development of colloidal processing and sintering methods used during fabrication. In addition...

Carbon-based honeycomb monoliths for environmental gas-phase applications

Moreno-Castilla, Carlos; P??rez-Cadenas, Agust??n F.
Fonte: Molecular Diversity Preservation International Publicador: Molecular Diversity Preservation International
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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Honeycomb monoliths consist of a large number of parallel channels that provide high contact efficiencies between the monolith and gas flow streams. These structures are used as adsorbents or supports for catalysts when large gas volumes are treated, because they offer very low pressure drop, short diffusion lengths and no obstruction by particulate matter. Carbon-based honeycomb monoliths can be integral or carbon-coated ceramic monoliths, and they take advantage of the versatility of the surface area, pore texture and surface chemistry of carbon materials. Here, we review the preparation methods of these monoliths, their characteristics and environmental applications.

EQUIVALENT CONTINUUM MODELS FOR NONADIABATIC MONOLITH CATALYTIC REACTORS

LIU, YU-HUNG
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: application/pdf
ENG
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An equivalent continuum approach was used to model the heat transfer in the array of channels of a non-adiabatic monolith reactor. The equivalent solid thermal conductivity in the transverse direction was derived for different cross-sectional geometries of the channels. The partial differential equations modeling the heat and mass transfer in a non-adiabatic reactor were solved numerically. The combined global collocation and collocation on finite element method was used to solve for the steady state solutions. And the backward finite difference method with predictor-corrector modification was added to solve for the time dependent solutions. Simulation results for exothermic and endothermic reactions are presented for ceramic and metallic monolith supports. The effects of channel geometry, channel density, wall thickness, reactor length, inlet fluid temperature and concentration were studied. Results showed that monoliths with triangular channels, higher channel density, thinner wall and longer length gave higher overall conversion for carbon monoxide oxidation. The effect of hydrogen on carbon monoxide oxidation was studied. No multiplicity was found. The simulation results for monolith converter with non-uniform flow qualitively confirmed the experimental observations of others' work.

Fauna do solo e outros atributos edáficos como indicadores da qualidade ambiental em áreas com Araucaria angustifolia no Estado de São Paulo; Soil fauna and others edaphics attributes as environmental quality indicators in areas with Araucaria angustifolia in São Paulo State, Brazil

Baretta, Dilmar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/09/2007 PT
Relevância na Pesquisa
170.62223%
O estudo de indicadores biológicos da qualidade do solo em áreas com araucária é muito importante para entender os processos ecológicos que ocorrem nestes sistemas, já que a fauna edáfica atua na decomposição e mineralização da matéria orgânica e, também, nas propriedades e processos físicos, químicos e biológicos do solo. O objetivo deste estudo foi verificar a possibilidade de utilizar alguns grupos da fauna edáfica e das variáveis ambientais como indicadores da qualidade do solo em áreas com araucária natural e reflorestada, impactadas ou não pela queima acidental, por meio de técnicas de análise multivariada. As áreas estudadas incluem: 1. floresta nativa com araucária (NF); 2. reflorestamento de araucária (R); 3. reflorestamento de araucária submetido a incêndio acidental (RF); e 4. pastagem natural com araucárias nativas e ocorrência de incêndio (NPF). Em cada área, amostras de solo para avaliação da comunidade da fauna edáfica e das variáveis ambientais foram coletadas em 0,3 ha, perto de dez árvores de araucária selecionadas ao acaso, em três épocas contrastantes, usando diferentes métodos de coleta (monólitos e armadilhas). As análises de componentes principais (ACP), canônica discriminante (ACD) e de correlação canônica (ACC) foram aplicadas às variáveis ambientais [carbono da biomassa microbiana (CBM)...

Fases extratoras para a análise direta de contaminantes orgânicos e inorgânicos em água; Extraction phases for direct analysis of organic and inorganic contaminants in water

Laiane de Moura Fontes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/06/2015 PT
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Este trabalho descreve o desenvolvimento de diferentes fases extratoras para a determinação de hidrocarbonetos aromáticos e de íons metálicos em água. Para o desenvolvimento das fases extratoras de polidimetilsiloxano e nanotubos de carbono (PDMS-NTC), os nanotubos foram tratados com ácido nítrico, octadecilamina e hipoclorito de sódio. Este último produziu grupos carboxílicos na superfície do nanomaterial, aumentando sua afinidade por hidrocarbonetos aromáticos. A fase extratora foi preparada pela dispersão dos NTC no PDMS e, depois de pronta, inserida num frasco preenchido com as soluções aquosas dos analitos. Após 60 minutos sob agitação, a fase extratora foi removida da solução, seca e inserida em um sistema de medidas, empregando-se um espectrofotômetro FT-NIR. A fase extratora com NTC oxidados com NaOCl possibilitou um aumento da capacidade de extração de 40% e 20% para tolueno e benzeno, respectivamente. No segundo momento, foram desenvolvidas membranas poliméricas plastificadas utilizando os reagentes complexantes Br-PADAP e TAN para a determinação de cobre e chumbo em água por espectroscopia de emissão óptica com plasma induzido por laser (LIBS). As membranas de PVC não forneceram resultados satisfatórios como fase extratora...

Synthesis of macro/mesoporous silica and carbon monoliths by using a commercial polyurethane foam as sacrificial template

Álvarez García, Sonia; Fuertes Arias, Antonio Benito
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
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4 pages, 3 figures, 1 table.-- Available online Sep 26, 2006.; A commercial macrocellular polyurethane foam was used as template to fabricate macro/mesoporous silica and carbon monoliths. These materials have a cellular structure which is a faithful replica of that of the polymeric foam. In addition, they have a high surface area and a large porosity made up of accessible mesopores. The synthesis of silica monoliths was carried out by impregnating the polymeric foam with a mixture of a silica precursor and a surfactant. The carbon monoliths were prepared by using the silica monoliths as sacrificial templates. They retain the foamy vesicular structure and exhibit a high surface area of 1800 m2 g−1 and a large porosity made up of framework-confined mesopores of around 3.4 nm.; The financial support for this research work provided by the Spanish MCyT (MAT2005-00262) is gratefully acknowledged. S. Alvarez thanks the Spanish MCyT for her FPI (BES-2003-0134) grant.; Peer reviewed

An activated carbon monolith as an electrode material for supercapacitors

Ruiz Ruiz, Vanesa; Blanco Rodríguez, Clara; Santamaría Ramírez, Ricardo; Ramos-Fernández, J. M.; Martínez-Escandell, M.; Sepúlveda-Escribano, A.; Rodríguez-Reinoso, F.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
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378.89453%
6 pages, 6 figures, 1 table.-- Available online Oct 2, 2008.; Activated carbon binderless monoliths with high consistency and large porosity, synthesised from a mesophase pitch, are studied as electrodes for supercapacitors. The electrochemical cells prepared provided high capacitance values in sulphuric acid media (334 F g−1) and very low electrical resistivity, which results in a very efficient energy storage device (12 Wh Kg−1 maximum energy density and 12,000 W Kg−1 maximum power density). Long-term cycling experiments showed excellent stability with a reduction of the initial capacitance values of 19% after performing 23,000 galvanostatic cycles at ~300 mA g−1.; This work has been performed with financial support from MEC (projects MAT2007-61467 and MAT2007-61734). V. Ruiz acknowledges a predoctoral research grant from FICYT.; Peer reviewed

Positive and negative artifacts in particulate organic carbon measurements with denuded and undenuded sampler configurations

Subramanian, R; Khlystov, AY; Cabada, JC; Robinson, AL
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Artigo de Revista Científica Formato: 27 - 48
Publicado em //2004
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Measurement of ambient particulate organic carbon (POC) with quartz filters is prone to positive and negative sampling artifacts. One approach for estimating these artifacts is to sample with a backup quartz filter placed behind either the main quartz filter or a Teflon filter in a parallel line. Another approach is to use a denuder to reduce the positive artifact in combination with a highly adsorbent backup filter to capture any negative artifact. Results obtained using both of these approaches in parallel for over one year in Pittsburgh, PA are presented in this article. A sampler using an activated carbon monolith denuder has been developed and tested extensively. Transmission losses were found to be negligible, and the denuder is on average 94\% efficient at removing gas-phase organics. Denuder breakthrough is corrected for each run using a dynamic blank in parallel with the sample line. Comparisons with the dynamic blank indicate that the denuder almost eliminates the positive artifact on the quartz filter. Negative artifact from the denuded quartz filter is quantified using a carbon-impregnated glass fiber (CIG) backup filter and was found to be small, typically less than 10\% of the ambient POC. Compared to the denuded sampler POC...

Photoluminescence from Inner Walls in Double-Walled Carbon Nanotubes and Hybrid Carbon/Titanium Dioxide Gels for Energy Conversion and Storage Applications

Yang, Sungwoo
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
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Currently, fossil fuels and nuclear power are our primary energy sources. However, both have critical disadvantages due to the limited supply and the hazard issues. Renewable energy research becomes one of most important research topics in the 21st century. Nanostructured materials show unique electrochemical properties in various energy conversion or storage devices. This dissertation starts with fundamental optical studies of nanomaterials (carbon nanotubes), followed by synthesizing novel nanomaterials for energy conversion (solar cells) and storage (lithium ion batteries) devices.

(1) There is an on-going debate concerning the ability of double walled carbon nanotubes (DWNTs) to exhibit photoluminescence (PL). We aim to clearly resolve this debate through the study of carefully separated DWNTs using density gradient ultra-centrifugation (DGU). Here, we clearly show that light is emitted from the inner wall of DWNTs. Interestingly, it was found that a very narrow range of diameters of the inner walls of DWNTs is required for photoluminescence (PL) to be observable. All other diameters led to complete PL quenching in DWNTs. (2) Inexpensive dye sensitized solar cells (DSSCs) on flexible plastic substrates have a bright future...