107 research outputs found
PrĂĄticas de literacia familiar em benguela (angola): Um estudo exploratĂłrio.
As investigaçÔes mostram que a aprendizagem da linguagem escrita começa muito
antes do ensino formal e que as prĂĄticas e o ambiente de literacia familiar influenciam a literacia
emergente e o desenvolvimento da linguagem escrita. Mas, se estes estudos sĂŁo desenvolvidos no
Ocidente, em Ăfrica pouco se tem feito e em Angola nĂŁo se conhece nenhum estudo. Com base nos
estudos existentes, em diversos contextos culturais, verifica-se que a literacia familiar existe,
podendo as prĂĄticas variar no tipo e frequĂȘncia uma vez que o que se passa num contexto, pode nĂŁo
ser igual ao que se passa noutra realidade cultural diferente. Neste sentido este trabalho, procura
caraterizar as prĂĄticas e o ambiente familiar de literacia em 11 famĂlias de Benguela com um filho a
frequentar o inĂcio da escolaridade. Os dados foram recolhidos atravĂ©s de uma entrevista informal
aos pais. Os resultados mostram que as prĂĄticas de literacia familiar sĂŁo essencialmente prĂĄticas
formais, muito ligadas Ă escola e Ă s tarefas escolares. No mesmo sentido verificĂĄmos que a
responsabilidade pela aprendizagem da linguagem escrita Ă© atribuĂda Ă escola, e a explicadores.
Apesar de surgirem algumas referĂȘncias do uso da literacia associado a prĂĄticas religiosas, poucas
referĂȘncias foram feitas a prĂĄticas informais ou lĂșdicas. Foi clara a quase inexistĂȘncia de materiais
de leitura (jornais, livros, revistas) para além dos escolares. A falta de tempo, a escassez de
bibliotecas pĂșblicas e livrarias, a falta dos recursos financeiras para aquisição do material de literacia
e a iliteracia foram apontados como obstĂĄculos para o desenvolvimento de outro tipo de prĂĄticasinfo:eu-repo/semantics/publishedVersio
Hierarchical CoreâShell Al<sub>2</sub>O<sub>3</sub>@Pd-CoAlO Microspheres for Low-Temperature Toluene Combustion
The high-efficiency catalyst is the
key factor of volatile organic
compounds (VOCs) catalytic combustion. Herein, hierarchical coreâshell
Al<sub>2</sub>O<sub>3</sub>@Pd-CoAlO (Pd-CoAlO-Al) microspheres have
been successfully prepared and used for toluene combustion. The experimental
results reveal that the coreâshell Pd-CoAlO-Al exhibits outstanding
catalytic efficiency due to the homogeneous distribution of Pd-CoAlO
nanosheets on Al<sub>2</sub>O<sub>3</sub> supports and the strong
interaction between the catalytically active Pd-CoAlO nanosheets and
the Al<sub>2</sub>O<sub>3</sub> supports. In particular, the catalytically
active PdO contributes to the excellent catalytic efficiency. In addition,
the <i>in situ</i> DRIFTS results indicate that the benzoate
species are the main intermediate species in toluene combustion
Heterogeneous Reactions between Toluene and NO<sub>2</sub> on Mineral Particles under Simulated Atmospheric Conditions
Heterogeneous
reactions between organic and inorganic gases with
aerosols are important for the study of smog occurrence and development.
In this study, heterogeneous reactions between toluene and NO<sub>2</sub> with three atmospheric mineral particles in the presence
or absence of UV light were investigated. The three mineral particles
were SiO<sub>2</sub>, α-Fe<sub>2</sub>O<sub>3</sub>, and BS
(butlerite and szmolnokite). In a dark environment, benzaldehyde was
produced on α-Fe<sub>2</sub>O<sub>3</sub>. For BS, nitrotoluene
and benzaldehyde were obtained. No aromatic products were produced
in the absence of NO<sub>2</sub> in the system. In the presence of
UV irradiation, benzaldehyde was detected on the SiO<sub>2</sub> surface.
Identical products were produced in the presence and absence of UV
light over α-Fe<sub>2</sub>O<sub>3</sub> and BS. UV light promoted
nitrite to nitrate on mineral particles surface. On the basisi of
the X-ray photoelectron spectroscopy (XPS) results, a portion of BS
was reduced from Fe<sup>3+</sup> to Fe<sup>2+</sup> with the adsorption
of toluene or the reaction with toluene and NO<sub>2</sub>. Sulfate
may play a key role in the generation of nitrotoluene on BS particles.
From this research, the heterogeneous reactions between organic and
inorganic gases with aerosols that occur during smog events will be
better understood
Extraordinary Deactivation Offset Effect of Arsenic and Calcium on CeO<sub>2</sub>âWO<sub>3</sub> SCR Catalysts
An extraordinary deactivation offset
effect of calcium and arsenic
on CeO<sub>2</sub>âWO<sub>3</sub> catalyst had been found for
selective catalytic reduction of NO with NH<sub>3</sub> (NH<sub>3</sub>âSCR). It was discovered that the maximum NO<sub><i>x</i></sub> conversion of AsâCa poisoned catalyst reached up to
89% at 350 °C with the gaseous hourly space velocity of 120âŻ000
mL·(g·h)<sup>â1</sup>. The offset effect mechanisms
were explored with respect to the changes of catalyst structure, surface
acidity, redox property and reaction route by XRD, XPS, H<sub>2</sub>-TPR, O<sub>2</sub>-TPD, NH<sub>3</sub>-TPD and in situ Raman, in
situ TG, and DRIFTS. The results manifested that Lewis acid sites
and reducibility originating from CeO<sub>2</sub> were obviously recovered,
because the strong interaction between cerium and arsenic was weakened
when Ca and As coexisted. Meanwhile, the CaWO<sub>4</sub> phase generated
on Ca poisoned catalyst almost disappeared after As doping together,
which made for BrĂžnsted acid sites reformation on catalyst surface.
Furthermore, surface Ce<sup>4+</sup> proportion and oxygen defect
sites amount were also restored for two-component poisoned catalyst,
which favored NH<sub>3</sub> activation and further reaction. Finally,
the reasons for the gap of catalytic performance between fresh and
AsâCa poisoned catalyst were also proposed as follows: (1)
surface area decrease; (2) crystalline WO<sub>3</sub> particles generation;
and (3) oxygen defect sites irreversible loss
Comparison of the Structures and Mechanism of Arsenic Deactivation of CeO<sub>2</sub>âMoO<sub>3</sub> and CeO<sub>2</sub>âWO<sub>3</sub> SCR Catalysts
The mechanism of
arsenic poisoning of CeO<sub>2</sub>âWO<sub>3</sub> (CW) and
CeO<sub>2</sub>âMoO<sub>3</sub> (CM) catalysts
during the selective catalytic reduction (SCR) of NO<sub><i>x</i></sub> with NH<sub>3</sub> was investigated. It was found that the
ratio of activity loss of the CW catalyst decreases as the temperature
increases, while the opposite tendency was observed for the CM catalyst.
The fresh and poisoned catalysts were characterized using X-ray diffraction
(XRD) temperature-programmed reduction with H<sub>2</sub> (H<sub>2</sub>-TPR), X-ray photoelectron spectra (XPS), NH<sub>3</sub>-temperature-programmed
desorption (NH<sub>3</sub>-TPD), in situ DRIFTS, and in situ Raman
spectroscopy. The results indicate that arsenic oxide primarily destroys
the structure of the surface CeOx species in the CM catalyst but prefers
to interact with WO<sub>3</sub> in the CW catalyst. Additionally,
the BET surface area, the number and stability of Lewis acid sites,
and the NO<sub><i>x</i></sub> adsorption for these two types
of catalysts clearly decrease after deactivation. According to the
DRIFTS and Raman investigations, at low temperatures, the greater
number of sites with adsorbed NH<sub>3</sub> in the poisoned CM catalyst
leads to less loss of activity than the poisoned CW catalyst. However,
at high temperatures, the greater number of Lewis acid sites remaining
in the poisoned CW catalyst may play an important role in maintaining
the activity of this catalyst
Pt Nanoparticles Embedded in Colloidal Crystal Template Derived 3D Ordered Macroporous Ce<sub>0.6</sub>Zr<sub>0.3</sub>Y<sub>0.1</sub>O<sub>2</sub>: Highly Efficient Catalysts for Methane Combustion
Three-dimensionally
ordered macro/mesoporous Ce<sub>0.6</sub>Zr<sub>0.3</sub>Y<sub>0.1</sub>O<sub>2</sub> (3DOM CZY) supported high-dispersion Pt nanoparticles
(<i>x</i> wt % Pt/3DOM CZY, <i>x</i> = 0.6, 1.1,
and 1.7) were successfully synthesized via the cetyltrimethylammonium
bromide/triblock copolymer P123 assisted gas bubbling reduction route.
The 3DOM CZY and <i>x</i> wt % Pt/3DOM CZY samples exhibited
a high surface area of 84â94 m<sup>2</sup>/g. Pt nanoparticles
(NPs) with a size of 2.6â4.2 nm were uniformly dispersed on
the surface of 3DOM CZY. The 1.1 wt % Pt/3DOM CZY sample showed excellent
catalytic performance, giving a <i>T</i><sub>90%</sub> value
at 598 °C at gas hourly space velocity (GHSV) of 30000 mL/(g
h) and the highest turnover frequency (TOF<sub>Pt</sub>) of 6.98 Ă
10<sup>â3</sup> mol/(mol<sub>Pt</sub> s) at 400 °C for
methane combustion. The apparent activation energy (64 kJ/mol) over
1.1 wt % Pt/3DOM CZY was much lower than that (95 kJ/mol) over Bulk
CZY. The effects of water vapor and SO<sub>2</sub> on the catalytic
activity of 1.1 wt % Pt/3DOM CZY were also examined. It is concluded
that the excellent catalytic activity of 1.1 wt % Pt/3DOM CZY was
associated with its high oxygen adspecies concentration, good low-temperature
reducibility, and strong interaction between Pt NPs and CZY as well
as large surface area and unique nanovoid-walled 3DOM structure
Additional file 1: of Association of Interleukin-1 gene clusters polymorphisms with primary open-angle glaucoma: a meta-analysis
The full details of databases searching terms. (DOCX 36ĂÂ kb)s (DOCX 36 kb
Novel MnâCeâTi Mixed-Oxide Catalyst for the Selective Catalytic Reduction of NO<sub><i>x</i></sub> with NH<sub>3</sub>
MnâCeâTi
mixed-oxide catalyst prepared by the hydrothermal method was investigated
for the selective catalytic reduction (SCR) of NO<sub><i>x</i></sub> with NH<sub>3</sub> in the presence of oxygen. It was found
that the environmentally benign MnâCeâTi catalyst exhibited
excellent NH<sub>3</sub>-SCR activity and strong resistance against
H<sub>2</sub>O and SO<sub>2</sub> with a broad operation temperature
window, which is very competitive for the practical application in
controlling the NO<sub><i>x</i></sub> emission from diesel
engines. On the basis of the catalyst characterization, the dual redox
cycles (Mn<sup>4+</sup> + Ce<sup>3+</sup> â Mn<sup>3+</sup> + Ce<sup>4+</sup>, Mn<sup>4+</sup> + Ti<sup>3+</sup> â Mn<sup>3+</sup> + Ti<sup>4+</sup>) and the amorphous structure play key
roles for the high catalytic deNO<sub><i>x</i></sub> performance.
Diffuse reflectance infrared Fourier transform spectroscopy studies
showed that the synergetic effect between Mn and Ce contributes to
the formation of reactive intermediate species, thus promoting the
NH<sub>3</sub>-SCR to proceed
Design Strategies for Development of SCR Catalyst: Improvement of Alkali Poisoning Resistance and Novel Regeneration Method
Based on the ideas of the additives modification and
regeneration
method update, two different strategies were designed to deal with
the traditional SCR catalyst poisoned by alkali metals. First, ceria
doping on the V<sub>2</sub>O<sub>5</sub>âWO<sub>3</sub>/TiO<sub>2</sub> catalyst could promote the SCR performance even reducing
the V loading, which resulted in the enhancement of the catalystâs
alkali poisoning resistance. Then, a novel method, electrophoresis
treatment, was employed to regenerate the alkali poisoned V<sub>2</sub>O<sub>5</sub>âWO<sub>3</sub>/TiO<sub>2</sub> catalyst. This
novel technique could dramatically enhance the SCR activities of the
alkali poisoned catalysts by removing approximately 95% K or Na ions
from the catalyst and showed less hazardous to the environment. Finally,
the deactivation mechanisms by the alkali metals were extensively
studied by employing both the experimental and DFT theoretical approaches.
Alkali atom mainly influences the active site V species rather than
W oxides. The decrease of catalyst surface acidity might directly
reduce the catalytic activity, while the reducibility of catalysts
could be another important factor
Additional file 4: Table S2. of Association of Interleukin-1 gene clusters polymorphisms with primary open-angle glaucoma: a meta-analysis
Quality of included studies. (DOC 68ĂÂ kb) (DOC 68 kb
- âŠ