Photoluminescence in ZrO2 doped with Y and La

O objetivo deste trabalho é descrever a síntese e a caracterização óptica de uma solução sólida de óxido de zircônio contendo ítrio e lantânio. Foram misturados citrato de zircônio, nitrato de ítrio e nitrato de lantânio nas proporções 94 mol% ZrO2-6 mol% Y2O3 e 92 mol% ZrO2-6 mol % Y2O3-2 mol % La2O3. A análise de espectroscopia de absorção no infravermelho com tranformada de Fourier mostra material orgânico em decomposição e a análise térmica mostra a transformação de fases da zircônia tetragonal para monoclínica, a perda de água e a desidroxilação do zircônio. A análise por difração de raios X mostra formação de fases homogênea de ZrO2-Y2O3-La2O3 demonstrando que a adição de lantânio não provoca formação de fases, promovendo uma solução sólida baseada em zircônia cúbica. Os espectros de fotoluminescência mostram bandas de absorção em 562 nm e 572 nm (350 ºC) e bandas de absorção específicas em 543 nm, 561 nm, 614 nm e 641 nm (900 ºC). O efeito fotoluminescente a baixas temperaturas é causado por defeitos como (Y Zr,Y O)', (2Y Zr,V O)'' e V O. As emissões em 614 nm e 641 nm são causadas pela transição O-2p -> Zr-4d. Uma emissão em 543 nm pode ser atribuída a centros LaO8 com transição O-2p -> La-5d.

Soluções de manutenção na pós-colheita de Chrysanthemum morifolium cv. Dragon

O desenvolvimento e uso de técnicas que prolonguem a durabilidade das flores, mantendo a qualidade do produto, é imprescindível para redução de perdas pós-colheita. Objetivou-se, neste trabalho, avaliar soluções de manutenção, associadas ou não a sacarose, na manutenção da qualidade pós-colheita de hastes de crisântemos. O experimento foi conduzido sob delineamento inteiramente casualizado, em esquema fatorial, com cinco tratamentos e três repetições, com 2 hastes florais cada uma. Os tratamentos utilizaram água destilada; 8-HQC a 100 mg L-1; 8-HQC a 100 mg L-1 + sacarose a 50 g L-1, 8-HQC a 200 mg L-1; 8-HQC a 200 mg L-1 + sacarose a 50 g L-1. Foram feitas avaliações físicas: coloração, massa fresca e conteúdo relativo de água (CRA); avaliações químicas: açúcares redutores e pigmentos; e avaliações qualitativas: turgescência, cor das flores, e número de botões, flores entreabertas e abertas. A combinação de 8-HQC 200 mg L-1 + sacarose a 50 g L-1 foi a que apresentou melhor desempenho para a manutenção da qualidade das hastes florais, favorecendo a abertura de botões e a turgescência das lígulas. A sacarose contribuiu para uma melhor manutenção de substâncias de reserva na haste, que tiveram a sua vida de vaso estendida.

Epitaxially grown LiNbO3 thin films by polymeric precursor method

LiNbO3 thin films were grown on (0001) sapphire substrates by a chemical route, using the polymeric precursor method. The overall process consists of preparing a coating solution from the Pechini process, based on metallic citrate polymerization, the precursor films, deposited by dip coating, are then heat treated to eliminate the organic material and to synthesize the phase. In this work, we studied the influence of the heat treatment on the structural and optical properties of single-layered films. Two routes were also investigated to increase the film thickness: increasing the viscosity of the coating solution and/or increasing the number of successively deposited layers. The x-ray diffraction theta -2 theta scans revealed the c-axis orientation of the single- and multilayered films and showed that efficient crystallization can be obtained at temperatures as low as 400 degreesC, the phi-scan diffraction evidenced the epitaxial growth with two in-plane variants, A microstructural study revealed that the films were crack free, homogeneous, and relatively dense. Finally, the investigation of the optical properties (optical transmittance and refractive index) confirmed the good quality of the films. These results indicate that the polymeric precursor method is a promising process to develop lithium niobate waveguides.

Microstructure of organometallic derived PLZT ceramics

The PLZT powders with the formula Pb0.905La0.095(Zr0.65Ti0.35)(0.976)O-3+3.5 wt.% PbO were prepared by the organometallic precursor method (Pechini and partial oxalate processes). The microstructure of sintered 9.5/65/35 PLZT ceramics obtained from a partial oxalate procedure shows that the outstanding feature of this microstructure is its fairly uniform grains of about 1.8 mum. The microstructure of sintered PLZT ceramics obtained by the Pechini process consists of uniform small randomly- oriented grains tightly bonded together in the central part of the sample with,a grain size of about 1.2 mum. Cubic and elongated grains are formed at the sample's border. The microstructures of hot pressed PLZT ceramics obtained from both processes are dense and rather uniform. After a double stage of hot pressing (2 plus 20 h) the microstructure of PLZT is fully dense, uniform and homogeneous with a grain size of approximately 2.5 mum. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Kinetic aspects of rat (Rattus-norvegicus albinus) submandibular glands lactic-dehydrogenase

Submandibular glands of male rats were homogenized with 33 mM sodium potassium phosphate buffer, pH 6.5, containing 1 mM MgCl2 and 0.1 mM DTT and purified with ammonium sulphate, phosphocellulose chromatography, eluted with KC1 0.5 M, followed by Blue Sepharose CL-6B chromatography, eluted with NADH 0.5 mM. The enzyme kepts stable for 60 days when stored at -15-degrees-C in 33 mM phosphate buffer. In other experiment the enzyme was purified by oxamate-agarose chromatography from a crude extract of submandibular gland and the results obtained were better than by phosphocellulose and Sepharose CL-6B chromatography. The Km values for pyruvate. NADH, lactate and NAD+ were established. Sodium oxamate at 0.1 and 0.9 mM concentrations inhibited the LDH activity by 40 and 85%, respectively (competitive); with sodium oxalate the inhibition was of 30% (uncompetitive) and with 3-acetyl pyridine adenine dinucleotide was 80%.

Demulsification of water/sunflower oil emulsions by a tangential filtration process using chemically impregnated ceramic tubes

A tangential filtration process was implemented in this study using porous ceramic tubes made of alpha-alumina produced by the slip-casting technique. These tubes were sintered at 1450 degrees C and characterized by mercury intrusion porosimetry, which revealed a mean pore size of 0.5 mu m. The tubes were chemically impregnated with a zirconium citrate solution, after which they were calcined and heat treated at temperatures of up to 600 and 900 degrees C to eliminate volatile organic compounds and transform the zirconium citrate into zirconium oxide impregnated in the alumina in the form of nanoparticle agglomerates. The microporous pipes were tested on a microfiltration hydraulic system to analyze their performance in the demulsification of sunflower oil and water mixtures. The fluid-dynamic parameters of Reynolds number and transmembrane pressure were varied in the process. The volume of permeate was analyzed by measuring the Total Organic Carbon concentration (TOC), which indicated 99% of oil phase retention. The emulsified mixture was characterized by optical microscopy, while the morphology and composition of the impregnated microporous tubes were analyzed by scanning electron microscopy (SEM). Quantification of the TOC values for the tube impregnated once at 600 degrees C showed the best demulsification performance, with the concentration on permeate smaller than 10 mg/L. The impregnated tube sintered once at 900 degrees C presented low carbon concentration (smaller than 20 mg/L), has the advantage of presenting the greatest trans-membrane flux in relation to the other microporous tube. (c) 2006 Elsevier B.V. All rights reserved.

Effects of powder preparation and sintering procedure on microstructure and dielectric properties of PLZT ceramics

PLZT ceramics belong to one of the very important groups of functional materials that make a basis for the production of a large range of electronic devices. The microstructure and properties of ceramics depend on the powder preparation and thermal processing conditions. Various techniques have been used to obtain chemically homogeneous and fine starting powders. PLZT powders have been prepared by two different production routes: by a modified Pechini method, using a polymeric precursor method (PMM) and by a partial oxalate method. A two-step sintering process, including a hot pressing, was carried out at 1100 and 1200degreesC Distinct phases obtained during the sintering process have been investigated by SEM and EDS techniques and dielectric properties such as permittivity and dielectric loss were measured in a frequency range from 1 to 20 kHz.. A significant difference in microstructure and dielectric properties, depending on powder origin and sintering procedure, has been noticed.

5-AMINOLEVULINIC ACID-INDUCED ALTERATIONS OF OXIDATIVE-METABOLISM IN SEDENTARY AND EXERCISE-TRAINED RATS

5-Aminolevulinic acid (ALA), a heme precursor that accumulates in acute intermittent porphyria patients and lead-exposed individuals, has previously been shown to autoxidize with generation of reactive oxygen species and to cause in vitro oxidative damage to rat liver mitochondria. We now demonstrate that chronically ALA-treated rats (40 mg/kg body wt every 2 days for 15 days) exhibit decreased mitochondrial enzymatic activities (superoxide dismutase, citrate synthase) in liver and soleus (type I, red) and gastrocnemius (type IIb, white) muscle fibers. Previous adaptation of rats to endurance exercise, indicated by augmented (cytosolic) CuZn-superoxide dismutase (SOD) and (mitochondrial) Mn-SOD activities in several organs, does not protect the animals against liver and soleus mitochondrial damage promoted by intraperitoneal injections of ALA. This is suggested by loss of citrate synthase and Mn-SOD activities and elevation of serum lactate levels, concomitant to decreased glycogen content in soleus and the red portion of gastrocnemius (type IIa) fibers of both sedentary and swimming-trained ALA-treated rats. In parallel, the type IIb gastrocnemius fibers, which are known to obtain energy mainly by glycolysis, do not undergo these biochemical changes. Consistently, ALA-treated rats under swimming training reach fatigue significantly earlier than the control group. These results indicate that ALA may be an important prooxidant in vivo.

Influence of agricultural biomass burning on aerosol size distribution and dry deposition in southeastern Brazil

The size distributed composition of ambient aerosols is used to explore seasonal differences in particle chemistry and to show that dry deposition fluxes of soluble species, including important plant nutrients, increase during periods of biomass (sugar cane trash) burning in São Paulo State, Brazil. Measurements were made at a single site centrally located in the State's sugar cane growing region but away from the immediate vicinity of burns, so that the air sampled was representative of the regional background. Calculation of ion equivalent balances showed that during burning periods smaller particles (Aitken and accumulation modes) were more acidic, containing higher concentrations of SO(4)(2-), oxalate, NO(3)(-), HCOO(-), CH(3)COO(-), and Cl(-), but insufficient NH(4)(+) and K(+) to achieve neutrality. Larger particles showed an anion deficit due to the presence of unmeasured ions and comprised resuspended dusts modified by accumulation of nitrate, chloride, and organic anions. Increases of resuspended particles during the burning season were attributed to release of earlier deposits from the surfaces of burning vegetation as well as increased vehicle movement on unsurfaced roads. During winter months the relative contribution of combined emissions from road transport and industry diminished due to increased emissions from biomass combustion and other activities specifically associated with the harvest period. Positive increments in annual particulate dry deposition fluxes due to higher fluxes during the sugar cane harvest were 44.3% (NH(4)(+)), 42.1 % (K(+)), 31.8% (Mg(2+)), 30.4% (HCOO(-)), 12.8% (Cl(-)), 6.6% (CH(3)COO(-)), 5.2% (Ca(2+)), 3.8% (SO(4)(2-)), and 2.3% (NO(3)(-)). Na(+) and oxalate fluxes were seasonally invariant. Annual aerosol dry deposition fluxes (kg ha(-1)) were 0.5 (Na(+)), 0.25 (NH(4)(+)), 0.39 (K(+)), 0.51 (Mg(2+)), 3.19 (Ca(2+)), 1.34 (Cl(-)), 4.47 (NO(3)(-)), 3.59 (SO(4)(2-)), 0.58 (oxalate), 0.71 (HCOO(-)), and 1.38 (CH(3)COO(-)). Contributions of this mechanism to combined aerosol dry deposition and precipitation scavenging (inorganic species, excluding gaseous dry deposition) were 31% (Na(+)), 8% (NH(4)(+)), 26% (K(+)), 63% (Mg(2+)), 66% (Ca(2+)), 32% (Cl(-)), 33% (NO(3)(-)), and 36% (SO(4)(2-)).

Development and characterization of an equine behaviour chamber and the effects of amitraz and detomidine on spontaneous locomotor activity

This report describes the development of a behaviour chamber and the validation of the chamber to measure locomotor activity of a horse, Locomotor activity was detected by four Mini-beam sensors and recorded on a data logger every 5 min for 22 h. Horses were more active during daytime than in the evening, which was at least partially related to human activity in their surroundings. To validate the ability of the chambers to detect changes in activity, fentanyl citrate and xylazine HCl, agents well-characterized as a stimulant and a depressant, respectively, were administered to five horses. Fentanyl citrate (0.016 mg/kg) significantly increased locomotor activity which persisted for 30 min, Xylazine HCl (1 mg/kg) significantly reduced locomotor activity for 90 min. Amitraz produced a dose-dependent decrease in locomotor activity, lasting 75 min for the 0.05 mg/kg dose, 120 min for the 0.10 mg/kg dose, and 180 min for the 0.15 mg/kg dose, In a separate experiment, yohimbine administration immediately reversed the sedative effect of amitraz, This suggests there is a similarity in the mode of action of amitraz, xylazine and detomidine, as yohimbine acts primarily by blocking central alpha 2-adrenoceptors that are stimulated by agents like xylazine, There was also a significant decrease in locomotor activity following injection of detomidine (0.02, 0.04 and 0.08 mg/kg) for 1.5, 3.5 and 5.0 h, respectively, the locomotor chamber is a useful, sensitive and highly reproducible tool for measuring spontaneous locomotor activity in the horse, which allows investigators to determine an agent's average time of onset, duration and intensity of effect on movement.

Structural characterization of organometallic-derived 9.5/65/35 PLZT ceramics

This study consisted of an investigation of the influence of powder preparation on the phase and chemical compositions and microstructure of 9.5/65/35 PLZT materials sintered in an oxygen atmosphere. The powders with the formula Pb0.905La0.095(Zr0.65Ti0.35)(0.976)O-3+3.5 wt.% PbO were prepared by the polymeric organometallic precursor method (the Pechini method and the partial oxalate procedure). Phase composition was determined by X-ray diffraction of powder and EDS analysis, while grain size was determined based on the micrograph obtained from SEM. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Walker 256 tumour growth causes marked changes of glutamine metabolism in rat small intestine

The effect of Walker 256 tumour growth on the metabolism of glucose and glutamine in the small intestine of rats was examined. Walker 256 tumour has been extensively used as an experimental model to induce cancer cachexia in rats. Walker 256 tumour growth decreased body weight and small intestine weight and length. The activities of glucose-6-phosphate dehydrogenase and phosphate-dependent glutaminase were reduced in the proximal, median and distal portions of the intestine. Glutamine oxidation was reduced in the proximal portion only. The decrease in glutaminase activity was not due to a low synthesis of the protein as indicated by Western blotting analysis. Hexokinase and citrate synthase activities were not changed by the tumour. These findings led us to postulate that tumour growth impairs glutamine metabolism of small intestine but the mechanism involved remains to be elucidated. Copyright (C) 2001 John Wiley Sons, Ltd.

Cracks developed during SrTiO3 thin-film preparation from polymeric precursors

Strontium titanate (SrTiO3) thin films were prepared by dip-coating Si(111) single-crystal substrates in citrate solutions of ethylene glycol, considering several citric acid/ethylene glycol (CA/EG) ratios. Measurements of intrinsic viscosity indicate that increasing the amount of EG increases the precursors' polymeric chains and increases the weight loss. After deposition the substrates were dried on a hotplate (approximate to 150 degrees C); this was followed by heat treatment at temperatures ranging from 500 to 700 degrees C using heating and cooling rates of 1 degrees C min(-1). SEM and optical microscopy investigations of the sintered films obtained from different CA/EG ratios indicate that there is a critical thickness above which the films present cracks. This critical thickness for SrTiO3 films deposited on the Si(111) substrate is about 150 nm, Measurements of crack spacing as a function of film thickness indicate that the origin of cracks cannot be explained by the elastic behavior of the film but rather by the viscoelastic relaxation of the film during pyrolysis and sintering. Copyright (C) 1999 John Wiley & Sons, Ltd.

Indium tin oxide films prepared via wet chemical route

In this work, indium tin oxide (ITO) films were prepared using a wet chemical route, the Pechini method. This consists of a polyesterification reaction between an alpha-hydroxicarboxylate complex (indium citrate and tin citrate) with a polyalcohol (ethylene glycol) followed by a post annealing at 500 degrees C. A 10 at.% of doping of Sn4+ ions into an In2O3 matrix was successfully achieved through this method. In order to characterize the structure, the morphology as well as the optical and electrical properties of the produced ITO films, they were analyzed using different experimental techniques. The obtained films are highly transparent, exhibiting transmittance of about 85% at 550 nm. They are crystalline with a preferred orientation of [222]. Microscopy discloses that the films are composed of grains of 30 nm average size and 0.63 nm RMS roughness. The films' measured resistivity, mobility and charge carrier concentration were 5.8 x 10(-3) Omega cm, 2.9 cm(2)/V s and -3.5 x 10(20)/cm(3), respectively. While the low mobility value can be related to the small grain size, the charge carrier concentration value can be explained in terms of the high oxygen concentration level resulting from the thermal treatment process performed in air. The experimental conditions are being refined to improve the electrical characteristics of the films while good optical, chemical, structural and morphological qualities already achieved are maintained. (C) 2007 Elsevier B.V. All rights reserved.

SrBi2Nb2O9 thin films deposited by dip coating using aqueous solution

A new approach for SrBi2Nb2O9 (SBN) thin films synthesis using aqueous solution was successfully experienced. The deposition solution was prepared from Sr-Bi-Nb mixed-citrate solution, requiring no special atmosphere and using common reagents. Films were deposited by dip coating onto Pt/Ti/SiO2/Si(100) substrates and hear treated at temperatures ranging from 300 to 700 degrees C. The process of formation and crystallization of SrBi2Nb2O9 thin films, prepared by the aqueous solution method have been studied with particular emphasis on the microstructure of crystallized films. Crystalline phases formation were followed by grazing incident X-ray diffraction (GIXRD), microstructure characterization was evaluated by scanning electron microscopy (SEM) and surface roughness were observed using atomic for ce microscopy (AFM). To reach the desired thickness, substrates were dipped in the deposition solution twice, forming double-layered films. The thickness of each layer ranged from 80 to 100 nm. (C) 1999 Elsevier B.V. Limited. All rights reserved.