Micro-Raman analysis of cubic GaN layers grown by MBE on (001) GaAs substrate

Cubic GaN layers are grown by molecular beam epitaxy on (001) GaAs substrates. Optical micrographs of the GaN epilayers intentionally grown at Ga excess reveal the existence of surface irregularities such as bright rectangular structures, dark dots surrounded by rectangles and dark dots without rectangles. Micro-Raman spectroscopy is used to study the structural properties of these inclusions and of the epilayers in greater detail. We conclude that the observed irregularities are the result of a melting process due to the existence of a liquid Ga phase on the growing surface.

Structural electrical and optical properties of undoped and indium doped ZnO thin films prepared by the pyrosol process at different temperatures

The influence of the substrate temperature on the structural features and opto-electrical properties of undoped and indium-doped ZnO thin films deposited by pyrosol process was investigated. The addition of indium induces a drastic decrease (by a factor approximate to 10(10) for samples deposited at 300 degreesC) in the electrical resistivity of films, the lowest electrical resistivity (6 mOmega-cm) being observed for the film deposited at 450 degreesC. Films are highly transparent (>80%) in the Vis-NIR ranges, and the optical band gap exhibits a blue shift (from 3.29 to 3.33 eV) for the In-doped films deposited at increasing temperature. Preferential orientation of the ZnO crystallites with the c-axis perpendicular to the substrate surface and an anisotropic morphology of the nanoporous structure was observed for films growth at 300 and 350 degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Erbium- and ytterbium-doped sol-gel SiO2-HfO2 crack-free thick films onto silica on silicon substrate

Aware of the difficulties in applying sol-gel technology on the preparation of thin films suitable for optical devices, the present paper reports on the preparation of crack-free erbium- and ytterbium-doped silica: hafnia thick films onto silica on silicon. The film was obtained using a dispersion of silica-hafnia nanoparticles into a binder solution, spin-coating, regular thermal process and rapid thermal process. The used methodology has allowed a significant increase of the film thickness. Based on the presented results good optical-quality films with the required thickness for a fiber matching single mode waveguide were obtained using the erbium- and ytterbium-activated sol-gel silica:hafnia system. The prepared film supports two transversal electric modes at 1550 nm and the difference between the transversal electric mode and the transversal magnetic mode is very small, indicating low birefringence. Photoluminescence of the I-4(13/2) -> I-4(15/2) transition of erbium ions shows a broad band centered at 1.53 mu m with full width at a half maximum of 28 nm. Up-conversion emission was carried out under different pump laser powers, and just one transition at red region was observed. (c) 2006 Elsevier B.V. All rights reserved.

Rhodamine B-containing silica films from TEOS precursor: Substrate surface effects detected by photoluminescence

This work presents the study of substrate surface effects on rhodamine B-containing silica films obtained from TEOS (tetraethylorthosilicate) acid hydrolysis. Soda-lime glass substrates were treated with basic solution under different reaction times and temperatures. Rhodamine B-containing silica films were deposited on pre-treated substrates by the spin-coating method. The substrate surface directly affects film morphology and homogeneity. The films are formed by packed silica spheres which protect the dye against acid-base attack. Luminescence spectra present shifts on the dye emission maximum as expected for different pH values on the substrate surface depending on the alkaline treatment. (c) 2006 Elsevier B.V. All rights reserved.

Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

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

Effect of foliar and substrate fertilization on lady palm seedling growth and development

Lady palm, [Rhapis excelsa (Thunberg) Henry ex. Rehder] is one of the most cultivated ornamental palms in the world, for use as a vase plant or in shaded landscapes. Because limited information exists on lady palm response to fertilizers, the objective of this study was to evaluate the effect of different types of fertilization and substrates on lady palm seedling growth and development. Three year old lady palms were planted in 8-L pots, filled with a mix of soil, manure, and sand 1:1:1 (v:v:v), placed under a 50% shade, and irrigated with microspray. Treatments were substrate fertilization with 500 g P(2)O(5) and 100 g K(2)O per m(3); fertilization with 1.8 kg of P(2)O(5) (simple superphosphate) per m3; 50 g of nitrogen (N), P(2)O(5), and K(2)O of a granulated fertilizer (10:10:10) per m(3), control (without fertilization), and a foliar fertilization in addition to these treatments using the commercial product Biofert (8:9:9). Treatments were replicated four times in a randomized block design. Each treatment plot consisted of four plants. Data were collected at 140, 170, 200, 230, 260, and 290 days after transplanting (DAT) for plant heights, stem diameter at substrate level, number of leaves, shoots, and canopy, roots fresh and dry matter samples were harvest at 290 days. Foliar fertilization resulted in significantly greater plant height in a 140, 120, 200, and 230 DAT and plant diameter on the 140, 260, and 290 DAT. There was interaction among factors for number of leaves with fertilization based on P(2)O(5) and K(2)O when leaf fertilizer was added that resulted in a greater number of leaves.

MINERAL COMPOSITION of RAW MATERIAL, SUBSTRATE and FRUITING BODIES of Pleurotus ostreatus IN CULTURE

In a culture of a Pleurotus ostreatus (oyster mushroom) strain, macro and micronutrients of the raw material and the initial and spent substrates were evaluated. Substrates were formulated with sawdust from Simarouba amara Aubl. and Ochroma piramidale Cav. ex. Lam., crushed Bactris gasipaes Kunth and crushed Saccharum officinarum (sugar cane). Samples were solubilized by means of acid digestion (nitric-peridrol). Ca, Mg, Fe, Cu, Zn and Mn were determined by atomic absorption spectrophotometry, Na and K by atomic emission, and P by colorimetry. The mineral composition of the fruiting body varied with the substrates, which made possible the production of a fruiting body rich in K, P Mg and Fe. Potassium was the mineral with the highest content in the fruiting body in all substrates tested (36.83-42.18g.kg(-1)). There was an increase of protein and mineral content in the spent substrate in relation to the initial one.

Study of plasma immersion ion implantation into silicon substrate using magnetic mirror geometry

The effect of magnetic field enhanced plasma immersion ion implantation (PIII) in silicon substrate has been investigated at low and high pulsed bias voltages. The magnetic field in magnetic bottle configuration was generated by two magnetic coils installed outside the vacuum chamber. The presence of both, electric and magnetic field in PIII creates a system of crossed E x B fields, promoting plasma rotation around the target. The magnetized electrons drifting in crossed E x B fields provide electron-neutral collision. Consequently, the efficient background gas ionization augments the plasma density around the target where a magnetic confinement is achieved. As a result, the ion current density increases, promoting changes in the samples surface properties, especially in the surface roughness and wettability and also an increase of implantation dose and depth. (C) 2012 Elsevier B. V. All rights reserved.

Weekend ethanol consumption and high-sucrose diet: resveratrol effects on energy expenditure, substrate oxidation, lipid profile, oxidative stress and hepatic energy metabolism

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

Influence of doping on the preferential growth of alpha-MoO3

MoO3 is a lamellar material with applications in different areas, as solid lubricants, catalysis, solar cells, etc. In the present work, MoO3 powders, synthesized by the polymeric precursor method, were doped with nickel or cobalt. The powder precursors were characterized by TG/DTA. After calcination between 500 and 700 degrees C, the samples were characterized by X-ray diffraction, infrared and Raman spectroscopy and scanning electron microscopy. beta-MoO3 was obtained after calcination at low temperatures. With the temperature increase, alpha-MoO3 is observed, with a preferential growth of the (0 2k 0) planes, when the material is doped and calcined at 700 degrees C. Doping with nickel increases five times the preferential growth. As a consequence, plate-like particles are observed. (c) 2007 Elsevier B.V. All rights reserved.

Bacterial cellulose membrane as flexible substrate for organic light emitting devices

Bacterial cellulose (BC) membranes produced by gram-negative, acetic acid bacteria (Gluconacetobacter xylinus), were used as flexible substrates for the fabrication of Organic Light Emitting Diodes (OLED). In order to achieve the necessary conductive properties indium tin oxide (ITO) thin films were deposited onto the membrane at room temperature using radio frequency (r.f) magnetron sputtering with an r.f. power of 30 W, at pressure of 8 mPa in Ar atmosphere without any subsequent thermal treatment. Visible light transmittance of about 40% was observed. Resistivity, mobility and carrier concentration of deposited ITO films were 4.90 x 10(-4) Ohm cm, 8.08 cm(2)/V-s and -1.5 x 10(21) cm(-3), respectively, comparable with commercial ITO substrates. In order to demonstrate the feasibility of devices based on BC membranes three OLEDs with different substrates were produced: a reference one with commercial ITO on glass, a second one with a SiO(2) thin film interlayer between the BC membrane and the ITO layer and a third one just with ITO deposited directly on the BC membrane. The observed OLED luminance ratio was: 1; 0.5; 0.25 respectively, with 2400 cd/m(2) as the value for the reference OLED. These preliminary results show clearly that the functionalized biopolymer, biodegradable, biocompatible bacterial cellulose membranes can be successfully used as substrate in flexible organic optoelectronic devices. (C) 2008 Elsevier B.V. All rights reserved.

Glucose-induced insulin secretion is impaired and insulin-induced phosphorylation of the insulin receptor and insulin receptor substrate-1 are increased in protein-deficient rats

Malnutrition is related to diabetes in tropical countries. In experimental animals, protein deficiency may affect insulin secretion. However, the effect of malnutrition on insulin receptor phosphorylation and further intracellular signaling events is not known. Therefore, we decided to evaluate the rate of insulin secretion and the early molecular steps of insulin action in insulin-sensitive tissues of an animal model of protein deficiency. Pancreatic islets isolated from rats fed a standard (17%) or a low (6%) protein diet were studied for their secretory response to increasing concentrations of glucose in the culture medium. Basal as well as maximal rates of insulin secretion were significantly lower in the islets isolated from rats fed a low protein diet. Moreover, the dose-response curve to glucose was significantly shifted to the right in the islets from malnourished rats compared with islets from control rats. During an oral glucose tolerance test, there were significantly lower circulating concentrations of insulin in the serum of rats fed a low protein diet in spite of no difference in serum glucose concentration between the groups, suggesting an increased peripheral insulin sensitivity. Immunoblotting and immunoprecipitation were used to study the phosphorylation of the insulin receptor and the insulin receptor substrate-1 as well as the insulin receptor substrate-1-p85 subunit of phosphatidylinositol 3-kinase association in response to insulin. Values were greater in hind-limb muscle from rats fed a low protein diet compared with controls. No differences were detected in the total amount of protein corresponding to the insulin receptor or insulin receptor substrate-1 between muscle from rats fed the two diets. Therefore, we conclude that a decreased glucose-induced insulin secretion in pancreatic islets from protein-malnourished rats is responsible, at least in part, for an increased phosphorylation of the insulin receptor, insulin receptor substrate-1 and its association with phosphatidylinositol 3-kinase. These might represent some of the factors influencing the equilibrium in glucose concentrations observed in animal models of malnutrition and undernourished subjects.