Effect of Mg-Ga powder addition on the superconducting properties of MgB2 samples

MgB2 bulk samples containing different proportions of Mg-Ga powder were prepared by an in situ reaction technique. The Mg-Ga powder was obtained via high energy ball milling of a Mg-10 at.% Ga composite, which was fabricated by melting of pure magnesium and gallium metals inside encapsulated stainless steel tube at 655 °C in a controlled atmosphere. The MgB2 samples containing 0, 1, 3, 5 and 7 wt.% of MgGa addition were sintered at 650 °C for 30 min in argon atmosphere. Magnetic measurements performed at 5 K and 20 K showed improved critical current density, Jc, in the low magnetic field range for samples with MgGa addition. The critical temperature, Tc, for all samples with gallium additions is consistently higher when compared to the pure MgB2. © 2007 Elsevier B.V. All rights reserved.

The mechanism of dephosphorylation of bis(2,4-dinitrophenyl) phosphate in mixed micelles of cationic surfactants and lauryl hydroxamic acid

(Figure Presented) Mixed micelles of cetyltrimethylammonium bromide (CTABr) or dodecyltrimethylammonium bromide (DTABr) and the α-nucleophile, lauryl hydroxamic acid (LHA) accelerate dephosphorylation of bis(2,4-dinitrophenyl) phosphate (BDNPP) over the pH range 4-10. With a 0.1 mole fraction of LHA in DTABr or CTABr, dephosphorylation of BDNPP is approximately 10 4-fold faster than its spontaneous hydrolysis, and monoanionic LHA - is the reactive species. The results are consistent with a mechanism involving concurrent nucleophilic attack by hydroxamate ion (i) on the aromatic carbon, giving an intermediate that decomposes to undecylamine and 2,4-dinitrophenol, and (ii) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement yielding a series of derivatives including N,N-dialkylurea, undecylamine, undecyl isocyanate, and carbamyl hydroxamate. © 2009 American Chemical Society.

Rietveld analyses and piezoelectric properties of niobium doped bismuth titanate systems

Bi 4Ti 3- xNbxO 12 (BITNb) samples, with × ranging from 0 to 0.40 were obtained using a polymeric precursor solution. Rietveld analyses confirmed that the powders crystallize in an orthorhombic structure free of secondary phases with space group Fmmm. Raman analysis evidenced a sharp increase in the bands intensity located at 129 cm -1 and 190 cm -1 due the lattice distortion in BIT02Nb and BIT04Nb compositions. UV-vis spectra indicated that addition of niobium causes a reduction of defects in the BIT lattice due the suppression of oxygen vacancies located at BO-6 octahedral. Size and morphology of particles as well as electrical behavior of BIT ceramics were affected by addition of donor dopant. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning and was investigated by piezoresponse force microscopy (PFM). PFM measurements revealed a decrease in piezoelectric response with increasing Nb concentration originating from a reduced polarizability along the a-axis. High spontaneous polarization is noted for the less doped sample due the reduction of strain energy and pin charged defects after niobium addition. Copyright © 2010 American Scientific Publishers.

Um olhar semiótico sobre o processo de indexação: a questão da representação e do referente

The indexing process is determined the subject of the document and its relation with the representation information. To cultivate the interdisciplinary contributions is essential, especially when the relationship allows substantial additions to the area of research. Rehearse some contributions in this article of Semiotics of Charles Sanders Peirce in the field of study of the indexing process, in particular, the notions of representation and referent. It is concluded that the tripartite division of the sign provides basis for to understanding the process of thematic representation, discussing the relationship of the sign with the object and the phenomenon presented, in the indexer sees the documentary language as referent.

Effect of Ag addition on phase transitions of the Cu-22.26 at.%Al-9.93 at.%Mn alloy

The phase transitions that occur in the Cu-22.26 at.%Al-9.93 at.%Mn and Cu-22.49 at.%Al-10.01 at.%Mn-1.53 at.%Ag alloys after slow cooling were studied using differential scanning calorimetry at different heating rates, microhardness changes with temperature, magnetization changes with temperature, scanning electron microscopy and energy dispersion X-ray spectroscopy. The results indicated that the presence of Ag does not modify the transition sequence of Cu-Al-Mn alloy, introduces a new transition due to the (Ag-Cu)-rich precipitates dissolution at about 800 K, and changes the mechanism of DO 3 phase dissolution. This mechanistic change was analyzed and a sequence of phase transitions was proposed for the reaction. © 2013 Elsevier B.V.

Enzyme use in kibble diets formulated with wheat bran for dogs: Effects on processing and digestibility

Recently, there is an interest in technologies that favour the use of coproducts for animal nutrition. The effect of adding two enzyme mixtures in diets for dogs formulated with wheat bran (WB) was evaluated. Two foods with similar compositions were formulated: negative control (NC; without WB) and test diet (25% of WB). The test diet was divided into four treatments: without enzyme (positive control), enzyme mixture 1 (ENZ1; added before extrusion β-glucanase, xylanase, cellulase, glucoamylase, phytase); enzyme mixture 2 (ENZ2; added before extrusion the ENZ1 more α-amylase); enzyme mixture 2 added after the extrusion (ENZ2ex). ENZ1 and ENZ2 were used to evaluate the enzyme effect on extruder pre-conditioner (processing additive) and ENZ2ex to evaluate the effect of enzyme supplementation for the animal. Digestibility was measured through total collection of faeces and urine. The experiment followed a randomized block design with five treatments (diets) and six dogs per diet, totalling 30 dogs (7.0 ± 1.2 years old and 11.0 ± 2.2 kg of body weight). Data were submitted to analysis of variance and means compared by Tukey's test and orthogonal contrasts (p < 0.05). Reducing sugars showed an important reduction after extrusion, suggesting the formation of carbohydrate complexes. The apparent total tract digestibility (ATTD) of dry matter, organic matter, crude protein, acid-hydrolysed fat and energy was higher in NC than in diets with WB (p < 0.001), without effects of enzyme additions. WB diets resulted in higher faecal production and concentration of short-chain fatty acids (SCFA) and reduced pH and ammonia concentration (p < 0.01), with no effect of enzyme addition. The enzyme addition did not result in improved digestibility of a diet high in non-starch polysaccharides; however, only ATTD was measured and nutrient fermentation in the large intestine may have interfered with the results obtained. WB modified fermentation product formation in the colon of dogs. © 2013 Blackwell Verlag GmbH.

Source-driven remobilizations of nutrients within stem wood in Eucalyptus grandis plantations

Nutrient remobilizations in tree ligneous components have been little studied in tropical forests. A complete randomized block design was installed in Brazilian eucalypt plantations to quantify the remobilizations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) within stem wood. Three treatments were studied: control with neither K nor Na addition (C), 3 kmol ha-1 K applied (+K), and 3 kmol ha-1 Na applied (+Na). Biomass and nutrient contents were measured in the stem wood of eight trees destructively sampled at 1, 2, 3 and 4 years after planting in each treatment and annual rings were localized on discs of wood sampled every 3 m in half of the trees. Chemical analyses and wood density measurements were performed individually for each ring per level and per tree sampled. Nutrient remobilizations in annual rings were calculated through mass balance between two successive ages. Our results show that nutrient remobilizations within stem wood were mainly source-driven. Potassium and Na additions largely increased their concentration in the outer rings as well as the amounts remobilized in the first 2 years after the wood formation. The amount of Na remobilized in annual rings was 15 % higher in +Na than in +K the fourth year after planting despite a 34 % higher production of stem wood in +K leading to a much higher nutrient sink. A partial substitution of K by Na in the remobilizations within stem wood might contribute to enhancing Eucalyptus grandis growth in K-depleted soils. © 2013 Springer-Verlag Berlin Heidelberg.

Propriedade antimicrobiana de óleos essenciais de plantas condimentares com potencial de uso como conservante em carne e hambúrguer bovino e testes de aceitação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da adição da espécie Acidithiobacillus ferrooxidans e de íons Cl- na dissolução da calcopirita (CuFeS'IND2')

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigação comparativa das propriedades estruturais do diboreto de magnésio dopado com compostos de carbono

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Efeito da adição de argilas modificadas na estrutura e propriedades funcionais de biofilmes produzidos a base de zeína

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudo das propriedades supercondutoras e da microestrutura do supercondutor Mg'B IND. 2' puro e dopado com compostos de carbono

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ensaios comparativos de mistura asfáltica pré-misturado a frio com adição de borracha de pneu

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Encapsulamento do cromo proveniente do lodo de curtume, em matrizes de cimento, visando a resistência mecânica à compressão e os limites de lixiviação e solubilização

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Imobilização de invertase comercial e de Saccharomyces cerevisiae em sabugo de milho e bagaço de cana-de-açúcar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)