679 research outputs found
Influence of the sodium/proton replacement on the structural, morphological and photocatalytic properties of titanate nanotubes
Titanate nanotubes (TNT) with different sodium contents have been synthesised
using a hydrothermal approach and a swift and highly controllable post-washing
processes. The influence of the sodium/proton replacement on the structural and
morphological characteristics of the prepared materials was analysed. Different
optical behaviour was observed depending on the Na+/H+ samples' content. A band
gap energy of 3.27\pm0.03 eV was estimated for the material with higher sodium
content while a value of 2.81\pm0.02 eV was inferred for the most protonated
material, which therefore exhibits an absorption edge in the near visible
region. The point of zero charge of the materials was determined and the
influence of the sodium content on the adsorption of both cationic and anionic
organic dyes was studied. The photocatalytic performance of the TNT samples was
evaluated in the rhodamine 6G degradation process. Best photodegradation
results were obtained when using the most protonated material as catalyst,
although this material has shown the lowest R6G adsorption capability.Comment: 22 pages, 8 figures, accepted for publication in Journal of
Photochemistry and Photobiology A: Chemistr
Geochemistry of groundwater from Graciosa Island (Azores): A contribution to the hydrothermal system conceptual model
Graciosa island is located in the Azores Archipelago,
along the so-called Terceira Rift, a major tectonic structure
that makes the NE boundary of the Azores Plateau. In general
terms, it includes a basaltic plataform on the NW and a silicic
poligenetic volcano with caldera on the SE, the Graciosa
Caldera Volcano. This volcano has produced significant
tephra falls, pyroclastic flows, lahars, and lava flows, both of
basaltic s.l. and trachitic s.l. composition.
The hydrothermal system shows fumarolic emissions
inside the volcano caldera and thermal springs located along
the shoreline. This system is exploitated in a thermal building
through shallow and deep (110 m) boreholes, near the coast.
In Graciosa two types of Na-Cl groundwater systems can
be identified: 1) a cold one emerging at springs and exploited
by wells for public water supply, and 2) a hydrothermal
system with temperatures around 40-44 °C. The cold
groundwaters have pH higher than 7 and different degree of
mineralization, according to the proximity to the sea. The
thermal waters show mixing with seawater, pH varying
between 6.20 and 6.94, 166 mg/L of SiO2, and significant
concentration of metals, such as Mn, Fe, Co, Ni, Cu and Zn.
The thermal water mineralization varies strongly, showing EC
from 8.87 mS/cm (shallow water) to 47.4 mS/cm (deeper
water). The higher mineralized water is rich in CO2(g), with
2130 mg/L of total dissolved CO2. Geothermometers
application reveals aquifer temperature around 167 °C and
immature/mixed waters, not reaching complete equilibrium
with reservoir rock.
The geochemistry of the thermal waters indicates the
occurrence of seawater/host rock interaction processes at high
temperature and slightly acid conditions, favored by CO2(g)
input, and a different degrees of mixing with cold and shallow
groundwaters
Solubilization and hydrolysis of porcine coagulated blood protein using sub-critical solvent extraction
Pork represents a major fraction of the meat consumed worldwide but only 30% of the blood generated in slaughterhouses is re-used as raw material for food and feed. Innovative technologies and efficient processing strategies capable of generating added-value products from it are now attracting attention. In this study, the hydrolysis of porcine coagulated blood using sub-critical solvent extraction was investigated. Biomass was hydrolyzed using different temperatures (120–210 °C), applying only water (sub-critical water; SCW) or water with a low concentration of alkali (0.1 mol L−1 NaOH) and different reaction times (30–90 min). Resultant hydrolysates were analyzed for crude and soluble protein, peptide profile, and bioactivity by combining protein quantification, antioxidant activity, and fast protein liquid chromatography measurements. Results showed that increasing temperature increases the degree of hydrolysis and that the addition of NaOH enhances the solubilization of peptides with high molecular weights. Also, hydrolysates showed interesting antioxidant activity, being 60 min the time of reaction with best antioxidant activity. Nevertheless, using only water (SCW) as solvent, without chemical additives, allows the delivering of interesting protein-based bioactive fractions. Sub-critical solvent treatment of porcine blood resulted in added-value fractions with potential bioactivities through a simple and environmentally friendly process.info:eu-repo/semantics/publishedVersio
Multiplet Effects in the Quasiparticle Band Structure of the Anderson Model
In this paper, we examine the mean field electronic structure of the
Anderson lattice model in a slave boson approximation, which should
be useful in understanding the physics of correlated metals with more than one
f electron per site such as uranium-based heavy fermion superconductors. We
find that the multiplet structure of the ion acts to quench the crystal
field splitting in the quasiparticle electronic structure. This is consistent
with experimental observations in such metals as .Comment: 9 pages, revtex, 3 uuencoded postscript figures attached at en
O movimento de mulheres piauienses para obter sua formação profissional como enfermeiras 1959-1973
O estudo objetivou descrever a luta de mulheres piauienses por sua formação como enfermeiras em outros estados do Brasil. Tratase de uma pesquisa histórico- social produzida a partir de fontes orais e secundárias. Os dados foram analisados à luz dos conceitos de espaço social, campo, capital, poder simbólico, luta e violência simbólica de Pierre Bourdieu. Os resultados apontam as lutas simbólicas no processo de formação profissional dessas piauienses, em sua maioria, em universidades na região nordeste. Ao realizarem o curso de enfermagem fora do Estado, essas jovens tiveram um conjunto de conhecimentos incorporados, que aliados à diversidade de culturas favoreceram o ganho de capital científico e cultural. Conclui-se que as lutas desenvolvidas por essas mulheres resultaram em ganhos simbólicos e sociais, além da incorporação do habitus profissional. O estudo contribuirá para a história da enfermagem, na construção de novos registros, além de abrir portas para a realização de novas pesquisas sobre a temática.El estudio tuvo como objetivo describir la lucha de las mujeres Piauí para su formación como enfermeras en otros estados de Brasil. Se trata de una investigación histórico-social producida a partir de fuentes orales y secundarias. Los datos se analizaron de acuerdo a los conceptos de espacio social, campo, el capital, el poder simbólico, la lucha y la violencia simbólica de Pierre Bourdieu. Los resultados muestran las luchas simbólicas en el proceso de formación de éstos mujeres piauienses, en su mayoría en las universidades en el noreste. En la realización del programa de enfermería fuera del estado, estos jóvenes tenían un conjunto de conocimientos incorporados, lo que combinado con la diversidad de culturas favoreció el capital científico y cultural de ganancia. En conclusión, las luchas que estas mujeres resultaron en ganancias simbólicas y sociales así como la incorporación de habitus profesional. El estudio contribuirá a la historia de la enfermería en la construcción de nuevos registros, y abrir las puertas a nuevas investigaciones sobre el tema.The study aimed to describe the struggle of Piauí women for their training as nurses in other Brazilian states. It is a social-historical research produced from oral and secondary sources. Data were analyzed according to the concepts of social space, field, capital, symbolic power, struggle and symbolic violence of Pierre Bourdieu. The results show the symbolic struggles in the training process of these women do Piauí, mostly at universities in the Northeast. When conducting the nursing course outside the state, these young people had a set of embedded knowledge, which combined with the diversity of cultures promoted the gain scientific and cultural capital. In conclusion, the fights undertaken by these women resulted in symbolic and social gains as well the incorporation of professional habitus. The study will contribute to the history of nursing in the construction of new records, and open doors to new research on the subject
Synthesis of titanate nanofibers co-sensitized with ZnS and Bi2S3 nanocrystallites and their application on pollutants removal
The synthesis of nanocomposite materials combining titanate nanofibers (TNF)
with nanocrystalline ZnS and Bi2S3 semiconductors is described in this work.
The TNF were produced via hydrothermal synthesis and sensitized with the
semiconductor nanoparticles, through a single-source precursor decomposition
method. ZnS and Bi2S3 nanoparticles were successfully grown onto the TNF's
surface and Bi2S3-ZnS/TNF nanocomposite materials with different layouts were
obtained using either a layer-by-layer or a co-sensitization approach. The
samples' photocatalytic performance was first evaluated through the production
of the hydroxyl radical using terephthalic acid as probe molecule. All the
tested samples show photocatalytic ability for the production of this oxidizing
species. Afterwards, the samples were investigated for the removal of methylene
blue. The nanocomposite materials with best adsorption ability for the organic
dye were the ZnS/TNF and Bi2S3ZnS/TNF. The removal of the methylene blue was
systematically studied, and the most promising results were obtained
considering a sequential combination of an adsorption-photocatalytic
degradation process using the Bi2S3ZnS/TNF powder as a highly adsorbent and
photocatalyst material.Comment: 26 pages, 10 figure
Influência da qualidade dos materiais de reprodução na reflorestação com sobreiro
O sobreiro ocupa em Portugal cerca de 721000 ha o que corresponde a 21,5 % da área fl orestal nacional e 33% da área
mundial (APCOR, 2005). A sua distribuição no território nacional traduz não só a sua adaptação a determinadas
condições edafo-climaticas, mas tem sido condicionada por várias circunstancias, como o arroteamento, o fogo, o
abuso do pastoreio, a exploração agrícola intensiva e as plantações fl orestais que contrariaram ou favoreceram a sua
existência nesses locais (Natividade, 1950). A distribuição desta espécie é particularmente signifi cativa em zonas
onde têm ocorrido acontecimentos climáticos graves e onde os níveis de desertifi cação humana são críticos.
A fi leira da cortiça salienta-se por Portugal ocupar o primeiro lugar entre os países produtores, transformadores e
exportadores de cortiça, correspondendo-lhe mais de metade da produção mundial desta matéria-prima. O nosso
País é a origem de aproximadamente 60% das transacções de cortiça a nível mundial, valor que sobe para 80%
quando nos referimos a transacções de produtos transformados. A nível nacional, o valor das exportações de cortiça
representam aproximadamente 0,7% do PIB, 2,24% das exportações e correspondem a mais de 33% do conjunto das
exportações de produtos fl orestais (APCOR, 2005). Para além da importância económica do sector corticeiro a nível
nacional, o aumento da consciência e do interesse da sociedade nas questões ambientais, faz com que o montado de
sobro seja reconhecido cada vez mais como um espaço fl orestal, de elevada biodiversidade, paisagísticamente único,
que potencia micro-economias locais baseadas numa agricultura e pastorícia extensivas, interessante para outras
actividades como o turismo rural e a caça.
O sobreiro tem sido a espécie fl orestal que mais tem benefi ciado dos meios fi nanceiros disponibilizados aos proprietários
fl orestais para a refl orestação no âmbito da aplicação das medidas de reforma da Política Agrícola Comum
da UE, na arborização das terras agrícolas. Contudo, têm-se registado com frequência elevadas taxas de insucesso
na arborização sendo a qualidade dos materiais florestais de reprodução (MFR) apontada como uma das causas.
Neste trabalho abordaremos a a qualidade dos materiais de reprodução, considerando-a do ponto de vista genético
e fisiológicoN/
Conceptual model of the Quenturas hydromineral resource (Furnas volcano, S. Miguel Island): a contribution
RESUMO: O Vulcão das Furnas, na ilha de São Miguel, comporta no seu
interior uma grande variabilidade de nascentes, que se podem classificar
em 5 tipos distintos, nomeadamente frias lisas, frias gasocarbónicas, termais
ácidas, termais básicas e condensado de fumarola, de características
marcadas e variadas, originando a designada “Hidrópole” das Furnas. A
Concessão Hidromineral das Furnas comporta parte importante destas
nascentes, entre elas o Recurso Hidromineral das Quenturas, ou Água Férrea
das Quenturas, referida como “3”. Trata-se de uma água termal ácida, com
59 °C de temperatura, pH ácido e mineralização elevada, cuja origem se
considera corresponder ao aquecimento de aquíferos mais superficiais por
vapor hidrotermal que ascende do aquífero hidrotermal profundo,
conferindo a estas águas temperatura e uma importante componente
gasocarbónica. Dados isotópicos apontam uma altitude de recarga de cerca de
800 m para esta nascente e uma idade compreendida entre os 23 e os 30 anos.ABSTRACT: Furnas Volcano, located on S. Miguel Island, is home to a large
variety of springs, that can be classified in 5 different groups, namely cold
waters, cold CO2-rich waters, thermal waters with low pH, thermal waters
with high pH and fumaroles, each with distinctive characteristics, originating
the “Furnas Hydropolis”. The Furnas Hidromineral Permit includes some of
these springs, including the Quenturas spring, also known as Água Férrea
das Quenturas, which is referred in the permit by the number “3”. Quenturas
is a thermal water with low pH, with a temperature of 59 °C and high
mineralization. It has its origin in the shallower aquifers that are heated by
the hydrothermal steam provided by the deep-seated hydrothermal aquifers,
providing them with temperature and an important gaseous component.
Isotopic data estimates a recharge altitude of approximately 800 m for this
spring, and 23 to 30 years of age.info:eu-repo/semantics/publishedVersio
Castaing Instability and Precessing Domains in Confined Alkali Gases
We explore analogy between two-component quantum alkali gases and
spin-polarized helium systems. Recent experiments in trapped gases are put into
the frame of the existing theory for Castaing instability in transverse channel
and formation of homogeneous precessing domains in spin-polarized systems.
Analogous effects have already been observed in spin-polarized and
mixtures systems. The threshold effect of the confining
potential on the instability is analyzed. New experimental possibilities for
observation of transverse instability in a trap are discussed.Comment: 6 RevTex pages, no figure
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