1,274 research outputs found
Correlação entre o conteúdo inorgânico e a polimerização da matriz orgânica das resinas compostas para restaurações dentárias: uma revisão narrativa
Introduction: In recent years, resin-matrix composite materials have revealed a fast technological improvement for dental applications. However, there are still some drawbacks related to the chemical composition, polymerization, and mechanical properties of resin-matrix composites with consequences in long-term clinical success. Objective: This study aimed to perform a narrative review regarding the effects of inorganic fillers on the organic matrix polymerization of resin-matrix composites. Materials and Methods: A search was performed in PubMed using relevant related key terms related to the chemical composition, properties and polymerization of resin matrix composites. Relevant studies published between 2001 and 2021 were selected. Results: The studies included in the present research provided relevant information on the chemical composition and properties of resin composites and polymerization factors, including the time, wavelength mode, and equipment. Studies have reported that silica and silicate nano-scale particles improve light transmission through resin-matrix composites and the degree of conversion of monomers in the organic matrix. Micrometric particles with a high refractive index can decrease the degree of conversion of monomers in the organic matrix. Conclusion: The polymerization of resin-matrix composites is affected by light scattering due to the type of inorganic particles and the differences in refractive indexes of inorganic and organic contents.Introdução: Nos últimos anos, as resinas compostas têm sido melhoradas em termos tecnológicos, permitindo o
alcance de melhores prognósticos na medicina dentária. Entretanto, subsistem algumas limitações relacionadas com
a composição química e as propriedades das resinas compostas com consequências no sucesso clínico a longo prazo.
Objetivo: O objetivo deste trabalho foi realizar uma revisão narrativa sobre a influência da componente inorgânica na
polimerização da matriz orgânica das resinas compostas usadas para restauração dentária. Materiais e Métodos: A
pesquisa foi realizada na plataforma PubMed utilizando termos de pesquisa relacionados com a composição química,
propriedades e a polimerização das resinas compostas, para seleção de artigos relevantes ao tema. Resultados:
Os estudos identificados reportam diferentes fatores relacionados com a polimerização incluindo modo, tempo,
equipamento e a composição química das resinas compostas. Os estudos indicam que partículas nanométricas à
base de sílica ou silicatos promovem uma maior transmissão de luz à matriz orgânica o que favorece a polimerização
do material. Por outro lado, partículas micrométricas com um alto índice de refração podem diminuir o grau de
conversão dos monómeros da matriz orgânica. Conclusão: A polimerização das resinas compostas é afetada pela
dispersão da luz, devido ao tamanho das partículas inorgânicas e aos índices de refração da componente orgânica e
inorgânica. De fato, um maior controlo da composição química e do tamanho de partículas inorgânicas aumenta o
grau de polimerização das resinas compostas
Alterações Físicas Em Latossolos Cultivados Com Plantas De Cobertura Em Rotação Com Soja E Milho
This study was conducted to evaluate the effect of different covers, grown in rotation with soybean and corn on the physical attributes of two Oxisols. The experiments were installed in Votuporanga, SP, Brazil and Selvíria, MS, Brazil in March 2008, after conventional tillage. The experimental design was a randomized complete block with four replications, using the following cover crops at different amounts of seeds: Sorghum bicolor, Pennisetum americanum, S. sudanense, hybrid of S. bicolor with S. sudanense, Urochloa ruziziensis and a control with spontaneous vegetation. We evaluated the dry matter yield of different covers, and macroporosity, microporosity, total porosity and bulk density, in the layers of 0-0.05, 0.05-0.20 and 0.20-0.40 m. It concludes that, different covers plants and seed amounts used for grains, seeds and forage after two years did not cause effects on some soil physical properties of the two Oxisols.11314915
Estabilidade De Agregados Em Latossolos Sob Plantas De Cobertura Em Rotação Com Soja E Milho
The objective was to evaluate the effect of different covers on the stability of soil aggregates in two areas of Oxisols, grown in rotation with crops of soybean and corn. The experiments were installed in Votuporanga, São Paulo, Brazil and Selvíria, Mato Grosso do Sul, Brazil in March 2008. The experimental design was a randomized block with four replicates and the following cover crops in different spending ha-1 seeds, were the treatments: Sorghum bicolor, 6, 7 and 8 kg ha-1; Pennisetum americanum, 10, 15 and 20 kg ha-1; S. sudanense, 12, 15 and 18 kg ha-1; hybrid of S. bicolor and S. sudanense, 8, 9 and 10 kg ha-1; Urochloa ruziziensis, 8, 12 and 16 kg ha-1; plus, control treatment with spontaneous vegetation. We evaluated the dry matter yield of different covers and were separate classes of soil aggregates and calculated the average diameter. It is noted that the cover crops had similar behavior on aggregates stability in the surface layer, and in the greater depth, the S. sudanense was more efficient in improving the class mean diameter between 2.0-1.0 mm, in Votuporanga, and the P. americanum was more efficient from 4.0 to 2.0 mm and 2.0-1.0 mm in Selvíria. Lower spending seeds was more promising on aggregate stability.11315616
Insights into the mechanism of MCT8 oligomerization
Supplemental material related to this submitted article will be made available here
Transfer-matrix scaling from disorder-averaged correlation lengths for diluted Ising systems
A transfer matrix scaling technique is developed for randomly diluted
systems, and applied to the site-diluted Ising model on a square lattice in two
dimensions. For each allowed disorder configuration between two adjacent
columns, the contribution of the respective transfer matrix to the decay of
correlations is considered only as far as the ratio of its two largest
eigenvalues, allowing an economical calculation of a configuration-averaged
correlation length. Standard phenomenological-renormalisation procedures are
then used to analyse aspects of the phase boundary which are difficult to
assess accurately by alternative methods. For magnetic site concentration
close to , the extent of exponential behaviour of the curve
is clearly seen for over two decades of variation of . Close to the
pure-system limit, the exactly-known reduced slope is reproduced to a very good
approximation, though with non-monotonic convergence. The averaged correlation
lengths are inserted into the exponent-amplitude relationship predicted by
conformal invariance to hold at criticality. The resulting exponent
remains near the pure value (1/4) for all intermediate concentrations until it
crosses over to the percolation value at the threshold.Comment: RevTeX 3, 11 pages +5 figures, uuencoded, to appear in Phys. Rev. B
(1994), PUC/RJ preprin
Expanded Bed Adsorption Of Bromelain (e.c. 3.4.22.33) From Ananas Comosus Crude Extract
This work focuses on the adsorption of Bromelain in expanded bed conditions, such as the adsorption kinetics parameters. The adsorption kinetics parameters showed that after 40 minutes equilibrium was achieved and maximum adsorption capacity was 6.11 U per resin mL. However, the maximum adsorption capacity was only determined by measuring the adsorption isotherm. Only by the Langmuir model the maximum adsorption capacity, Qm, and dissociation constant, kd, values could be estimated as 9.18 U/mL and 0.591, respectively, at 25°C and 0.1 mol/L phosphate buffer pH 7.5. A column made of glass with an inner diameter of 1 cm was used for the expanded bed adsorption (EBA). The residence time was reduced 10 fold by increasing the expansion degree 2.5 times; nonetheless, the plate number (N) value was reduced only 2 fold. After adsorption, the bromelain was eluted in packed bed mode, with a downward flow. The purification factor was about 13 fold and the total protein was reduced 4 fold. EBA showed to be feasible for purification of bromelain.261149157Amersham Pharmacia Biotech. EBA Handbook: Principles and Methods. Uppsala, ISBN 91-630-5519-8 (1997)Anspach, F.B., Curbelo, D., Hartman, R., Garke, G., Deckwer, W.D., Expanded-bed chromatography in primary protein purification (1999) J. Chromatogr. A, 865, p. 129Bruce, L.J., Chase, H.A., Hydrodynamics and adsorption behaviour within an expanded bed adsorption column studied using in-bed sampling (2001) Chem. Eng. Sci, 56, p. 3149Camprubi, S., Bruguera, M., Canalias, F., Purification of recombinant histidine-tag streptolysin O using immobilized metal affinity expanded bed adsorption (IMA-EBA). International (2006) J. Biol. 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Progr, 17, pp. 1128-1136Gaspani, L., Limiroli, E., Ferrario, P., Bianchi, M., In vivo and in vitro effects of bromelain on PGE(2) and SP concentrations in the inflammatory exudate in rats (2002) Pharmacology, 65, pp. 83-86Haq, S.K., Rasheedi, S., Khan, R.H., Characterization of a partially folded intermediate of stem bromelain at low pH (2002) Eur. J. Biochem, 269, pp. 47-52Harrach, T., Eckert, K., Maurer, H.R., Machleidt, I., Machleidt, W., Nuck, R., Isolation and characterization of two forms of an acidic bromelain stem proteinase (1998) J. Protein Chem, 17, pp. 351-361Hatano, K., Sawano, Y., Tanokura, M., Structure-function relationship of bromelain isoinhibitors from pineapple stem (2002) Biol. Chem, 383, pp. 1151-1156Hatano, K., Tanokura, M., Takahashi, K., The amino acid sequences of isoforms of the bromelain inhibitor from pineapple stem (1998) J. 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K., Thermostable lipase of Bacillus stearothermophilus, high level production, purification and calciumdependent thermostability. Korea Res. Inst. Biosci. Biotechnol. 64:280-286 (2000)Kordel, M., Hofmann, B., Schomburg, D., Schimid, R.D., Extracelluar lipase of Pseudomonas sp. strain ATCC 21808: Purification, characterization, crystallization and preliminary X-ray diffraction data (1991) J. Bacteriol, 173, pp. 4836-4841Kunitz, M., Crystalline soybean trypsin inhibitor: II general properties (1974) J. Gen. Physiol, 30, pp. 291-310Lali, A.M., Khare, A.S., Joshi, J.B., Behaviour of solid particles in viscous non-newtonian solutions: Settling velocity, wall effects and bed expansion in solid-liquid fluidized beds (1989) Powder Tech, 57, pp. 39-50Maurer, H.R., Bromelain: Biochemistry, pharmacology and medical use (2001) Cell. Mol. 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Synthesis, structural and physical properties of -FeSe
We report on synthesis, structural characterization, resistivity, magnetic
and thermal expansion measurements on the as yet unexplored -phase of
FeSe, here synthesized under ambient- (AP) and high-pressure (HP)
conditions. We show that in contrast to -FeSe, monophasic
superconducting -FeSe can be obtained in off-stoichiometric
samples with excess Fe atoms preferentially residing in the van der Waals gap
between the FeSe layers. The AP -FeSe sample studied here
( 8.5\,K) possesses an unprecedented residual resistivity ratio
RRR 16. Thermal expansion data reveal a small feature around
90\,K, which resembles the anomaly observed at the structural and
magnetic transitions for other Fe-based superconductors, suggesting that some
kind of "magnetic state" is formed also in FeSe. %indicative of a fluctuating
magnetic ordering. For HP samples (RRR 3), the disorder within the
FeSe layers is enhanced through the introduction of vacancies, the saturated
magnetic moment of Fe is reduced and only spurious superconductivity is
observed.Comment: 7 pages, 8 figures, published versio
Activated Random Walkers: Facts, Conjectures and Challenges
We study a particle system with hopping (random walk) dynamics on the integer
lattice . The particles can exist in two states, active or
inactive (sleeping); only the former can hop. The dynamics conserves the number
of particles; there is no limit on the number of particles at a given site.
Isolated active particles fall asleep at rate , and then remain
asleep until joined by another particle at the same site. The state in which
all particles are inactive is absorbing. Whether activity continues at long
times depends on the relation between the particle density and the
sleeping rate . We discuss the general case, and then, for the
one-dimensional totally asymmetric case, study the phase transition between an
active phase (for sufficiently large particle densities and/or small )
and an absorbing one. We also present arguments regarding the asymptotic mean
hopping velocity in the active phase, the rate of fixation in the absorbing
phase, and survival of the infinite system at criticality. Using mean-field
theory and Monte Carlo simulation, we locate the phase boundary. The phase
transition appears to be continuous in both the symmetric and asymmetric
versions of the process, but the critical behavior is very different. The
former case is characterized by simple integer or rational values for critical
exponents (, for example), and the phase diagram is in accord with
the prediction of mean-field theory. We present evidence that the symmetric
version belongs to the universality class of conserved stochastic sandpiles,
also known as conserved directed percolation. Simulations also reveal an
interesting transient phenomenon of damped oscillations in the activity
density
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