Poly(aniline)/poly(methylmethacrylate) films obtained from waterborne latex nanoparticles

This paper presents the characterization of poly(aniline) (PANI) and poly(methyl methacrylate) (PMMA) coatings obtained by mixing PANI with PMMA aqueous dispersions (latex particles). These dispersions were characterized by using dynamic light scattering for sizing, zeta-potential analysis and thermal analysis. PMMA and PANI/PMMA dispersions show negative charged particles with zeta potential greater than |40| mV, a zeta-average diameter of 64 nm for pure PMMA and a bi-modal particle-size distribution centered at 45 and 120 nm for a mixture with 25% w/w of PANI. Films obtained by casting were characterized by using scanning electron microscopy and they show a conductivity increase upon PANI content reaching a value of 1 mS cm(-1) for a film with 25% w/w of PANI. In addition, Raman spectroscopy have shown the presence of the conducting form of PANI in the films and cyclic voltammetry experiments corroborated that they are electroactive in both acid and neutral solutions.

Ionic mobility of the solvated proton and acid-base titration in a four-compartment capillary electrophoresis system

Although H(+) and OH(-) are the most common ions in aqueous media, they are not usually observable in capillary electrophoresis (CE) experiments, because of the extensive use of buffer solutions as the background electrolyte. In the present work, we introduce CE equipment designed to allow the determination of such ions in a similar fashion as any other ion. Basically, it consists of a four-compartment piece of equipment for electrolysis-separated experiments (D. P. de Jesus et at, Anal. Chem., 2005, 77, 607). In such a system, the ends of the capillary are placed in two reservoirs, which are connected to two other reservoirs through electrolyte-filled tubes. The electrodes of the high-voltage power source are positioned in these reservoirs. Thus, the electrolysis products are kept away from the inputs of the capillary. The detection was provided by two capacitively coupled contactless conductivity detectors (CD), each one positioned about 11 cm from the end of the capillary. Two applications were demonstrated: titration-like procedures for nanolitre samples and mobility measurements. Strong and weak acids (pK(a) < 5), pure or mixtures, could be titrated. The analytical curve is linear from 50 mu M up to 10 mM of total dissociable hydrogen (r = 0.99899 for n =10) in 10-nL samples. By including D(2)O in the running electrolyte, we could demonstrate how to measure the mixed proton/deuteron mobility. When H(2)O/D(2)O (9 : 1 v/v) was used as the solvent, the mobility was 289.6 +/- 0.5 x 10(-5) cm(2) V(-1) s(-1). Due to the fast conversion of the species, this value is related to the overall behaviour of all isotopologues and isotopomers of the Zundel and Eigen structures, as well as the Stokesian mobility of proton and deuteron. The effect of neutral (o-phenanthroline) and negatively charged (chloroacetate) bases and aprotic solvent (DMSO) over the H(+) mobility was also demonstrated.

Lignin phenols used to infer organic matter sources to Sepetiba Bay - RJ, Brasil

Lignin phenols were measured in the sediments of Sepitiba Bay, Rio de Janeiro, Brazil and in bedload sediments and suspended sediments of the four major fluvial inputs to the bay: Sao Francisco and Guandu Channels and the Guarda and Cacao Rivers. Fluvial suspended lignin yields (Sigma 8 3.5-14.6 mgC 10 g dw(-1)) vary little between the wet and dry seasons and are poorly correlated with fluvial chlorophyll concentrations (0.8-50.2 mu gC L(-1)). Despite current land use practices that favor grassland agriculture or industrial uses, fluvial lignin compositions are dominated by a degraded leaf-sourced material. The exception is the Guarda River, which has a slight influence from grasses. The Lignin Phenol Vegetation Index, coupled with acid/aldehyde and 3.5 Db/V ratios, indicate that degraded leaf-derived phenols are also the primary preserved lignin component in the bay. The presence of fringe Typha sp. and Spartina sp. grass beds surrounding portions of the Bay are not reflected in the lignin signature. Instead, lignin entering the bay appears to reflect the erosion of soils containing a degraded signature from the former Atlantic rain forest that once dominated the watershed, instead of containing a significant signature derived from current agricultural uses. A three-component mixing model using the LPVI, atomic N:C ratios, and stable carbon isotopes (which range between -26.8 and -21.8 parts per thousand) supports the hypothesis that fluvial inputs to the bay are dominated by planktonic matter (78% of the input), with lignin dominated by leaf (14% of the input) over grass (6%). Sediments are composed of a roughly 50-50 mixture of autochthonous material and terrigenous material, with lignin being primarily sourced from leaf. (C) 2010 Elsevier Ltd. All rights reserved.

Simultaneous preconcentration of copper, zinc, cadmium, and nickel in water samples by cloud point extraction using 4-(2-pyridylazo)-resorcinol and their determination by inductively coupled plasma optic emission spectrometry

A procedure for simultaneous separation/preconcentration of copper. zinc, cadmium, and nickel in water samples, based on cloud point extraction (CPE) as a prior step to their determination by inductively coupled plasma optic emission spectrometry (ICP-OES), has been developed. The analytes reacted with 4-(2-pyridylazo)-resorcinol (PAR) at pH 5 to form hydrophobic chelates, which were separated and preconcentrated in a surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-I 14). The parameters affecting the extraction efficiency of the proposed method, such as sample pH, complexing agent concentration, buffer amount, surfactant concentration, temperature, kinetics of complexation reaction, and incubation time were optimized and their respective values were 5, 0.6 mmol L(-1). 0.3 mL, 0.15% (w/v), 50 degrees C, 40 min, and 10 min for 15 mL of preconcentrated solution. The method presented precision (R.S.D.) between 1.3% and 2.6% (n = 9). The concentration factors with and without dilution of the surfactant-rich phase for the analytes ranged from 9.4 to 10.1 and from 94.0 to 100.1, respectively. The limits of detection (L.O.D.) obtained for copper, zinc, cadmium, and nickel were 1.2, 1.1, 1.0. and 6.3 mu g L(-1), respectively. The accuracy of the procedure was evaluated through recovery experiments on aqueous samples. (C) 2009 Published by Elsevier B.V.

Stretching and folding mechanism in foams

We have described the stretching and folding of foams in a vertical Hele-Shaw cell containing air and a surfactant solution, from a sequence of upside-down flips. Besides the firactal dimension of the foam, we have observed the logistic growth for the soap film length. The stretching and folding mechanism is present during the foam formation, and this mechanism is observed even after the foam has reached its respective maximum fractal dimension. Observing the motion of bubbles inside the foam, large bubbles present power spectrum associated with random walk motion in both directions, while the small bubbles are scattered like balls in a Galton board. (C) 2008 Published by Elsevier B.V.

Characterization and greenhouse evaluation of Brazilian calcined nonapatite phosphate rocks for rice

Little information is available on the agronomic effectiveness of calcined nonapatite phosphate rock (PR) sources containing crandallite minerals in the form of Ca-Fe-Al-P for flooded and upland rice (Oryza sativa L.). We conducted laboratory and greenhouse studies to (i) characterize the mineralogical composition, (ii) investigate the solubility and dissolution behavior, and (iii) evaluate the agronomic effectiveness of two nonapatite PR sources (Juquia and Sapucaia) from Brazil and compared them with (i) a highly reactive Gafsa PR (Tunisia) containing apatite in the form of Ca-P and (ii) a reference water-soluble triple superphosphate (TSP) for flooded and upland rice. After calcination at 500 degrees C for 4 h, the solubility of Juquia PR and Sapucaia PR in neutral ammonium citrate (NAC) significantly increased from almost nil to a maximum of 39.3 and 114 g P kg(-1), respectively. X-ray diffraction showed that crystalline crandallite mineral was transformed to an amophorus form after calcination. The solubility behavior of the two calcined PR sources followed the same trend as Gafsa PR, that is, P release decreased with increasing equilibrium pH in the 0.01 M KCl solution (PH 3.0-8.0). At PH 3, the solubility followed: Gafsa PR > calcined Sapucaia PR > calcined Juquia PR. No P release was detected from any of the PR sources at pH >= 5.0 in the solution, indicating the Ca-P characteristic of the Ca-Fe-Al-P mineral controlled P dissolution of the calcined PR. Without calcination, both Juquia PR and Sapucaia PR were totally ineffective for upland rice grown on a Hiwassee clay loam (fine, kaolinitic, thermic Rhodic Kanhapludult) with pH 5.4 whereas a significant P response was observed with the calcined PR samples. For flooded rice grown on Hiwassee soil, the calcined Juquia PR and Sapucaia PR were 66 and 72%, respectively, as effective as TSP in increasing rice grain yield whereas Gafsa PR was ineffective. For upland rice grown on the unlimed soil, Gafsa PR was as effective as TSP in increasing rice grain yield whereas calcined Juquia PR and Sapucaia PR were 89 and 83% of TSP. The effectiveness of Gafsa PR was reduced to 0% after the soil was limed to pH 7.0 whereas the two calcined PR sources were reduced to 49% of TSP. Soil available P extracted by iron oxide impregnated filter paper (Pi test) or anion-exchange resin after rice harvest correlated well with P uptake by rice grain for flooded and upland rice.

Agronomic evaluation of calcined crandallite from three Brazilian phosphate deposits

Samples from the weathering mantle containing crandallite of three Brazilian phosphate deposits, Tapira, Catalo, and Juqui, were characterized, calcined, and agronomically evaluated. The calcination process increased total phosphorus (P) and neutral ammonium citrate soluble (NAC) P contents of all samples. The NAC solubility of original Tapira, Catalo, and Juqui was about 5% of total P, whereas for calcined samples it was 54, 16, and 53%, respectively. In a greenhouse study, rates of P were applied at 0, 10, 20, 40, 80, and 120mg P kg(-1) from the calcined materials and MCP (monocalcium phosphate) to an Ultisol cropped with upland and flooded rice for 65 days. The results showed that the calcined P samples increased dry-matter yield and P uptake with increasing rates of P applied for both crops. Tapira and Juqui were more effective for flooded than for upland rice. The calculated values of relative agronomic effectiveness of Tapira, Catalo, and Juqui with respect to MCP were 57, 48, and 53% in dry-matter yield for upland rice and 64, 50, and 69% for flooded rice, respectively.

Successful maintenance of a stingless bee population despite a severe genetic bottleneck

Stingless bees play an important ecological role as pollinators of many wild plant species in the tropics and have significant potential for the pollination of agricultural crops. Nevertheless, conservation efforts as well as commercial breeding programmes require better guidelines on the amount of genetic variation that is needed to maintain viable populations. In this context, we carried out a long-term genetic study on the stingless bee Melipona scutellaris to evaluate the population viability consequences of prolonged breeding from a small number of founder colonies. In particular, it was artificially imposed a genetic bottleneck by setting up a population starting from only two founder colonies, and continued breeding from it for a period of over 10 years in a location outside its natural area of occurrence. We show that despite a great reduction in the number of alleles present at both neutral microsatellite loci and the sex-determining locus relative to its natural source population, and an increased frequency in the production of sterile diploid males, the genetically impoverished population could be successfully bred and maintained for at least 10 years. This shows that in stingless bees, breeding from a small stock of colonies may have less severe consequences than previously suspected. In addition, we provide a simulation model to determine the number of colonies that are needed to maintain a certain number of sex alleles in a population, thereby providing useful guidelines for stingless bee breeding and conservation efforts.

High Solids Content, Soap-Free, Film-Forming Latexes Stabilized by Laponite Clay Platelets

High solids content film-forming poly[styrene-co-(n-butyl acrylate)] [poly(Sty-co-BuA)] latexes armored with Laponite clay platelets have been synthesized by soap-free emulsion copolymerization of styrene and n-butyl acrylate. The polymerizations were performed in batch in the presence of Laponite and a methyl ether acrylateterminated poly(ethylene glycol) macromonomer in order to promote polymer/clay association. The overall polymerization kinetics showed a pronounced effect of clay on nucleation and stabilization of the latex particles. Cryo-transmission electron microscopy observation confirmed the armored morphology and indicated that the majority of Laponite platelets were located at the particle surface. The resulting nanostructured films displayed enhanced mechanical properties.

Effect of bioglass additions on the sintering of Y-TZP bioceramics

The objective of this work was to evaluate the influence of bioglass additions on the sintering and mechanical properties of yttria-stabilized zirconia ceramics, Y-TZP Samples containing different bioglass additions, varying between 0 and 30 wt.%, were cold uniaxial pressed at 80 MPa and sintered in air at 1200 degrees C or 1300 degrees C for 120 min. Sintered samples were characterized by X-ray Diffractometry and Scanning Electron Microscopy. Hardness and fracture toughness were determined using Vickers indentation method. As a preliminary biological evaluation, in vitro cytotoxicity tests by Neutral Red Uptake method (using mouse connective tissue cells, NCTC clone L929 from ATCC bank) were realized to determine the cytotoxicity level of ZrO(2)-bioglass ceramics. The increasing of bioglass amount leads to the decreasing of relative density due to martensitic (tetragonal-monoclinic) transformation during cooling of the sintered samples. Y-TZP samples sintered at 1300 degrees C containing 5 wt.% of bioglass presented the best results. with high relative density, hardness and fracture toughness of 11.3 GPa and 6.1 MPa m(1/2), respectively. Furthermore, the un-cytotoxic behavior was observed in all sintering conditions and bioglass amounts used in this study. (C) 2009 Elsevier B.V. All rights reserved.

Characterization of commercial cellulases and their use in the saccharification of a sugarcane bagasse sample pretreated with dilute sulfuric acid

This study aimed to correlate the efficiency of enzymatic hydrolysis of the cellulose contained in a sugarcane bagasse sample pretreated with dilute H(2)SO(4) with the levels of independent variables such as initial content of solids and loadings of enzymes and surfactant (Tween 20), for two cellulolytic commercial preparations. The preparations, designated cellulase I and cellulase II, were characterized regarding the activities of total cellulases, endoglucanase, cellobiohydrolase, cellobiase, beta-glucosidase, xylanase, and phenoloxidases (laccase, manganese and lignin peroxidases), as well as protein contents. Both extracts showed complete cellulolytic complexes and considerable activities of xylanases, without activities of phenoloxidases. For the enzymatic hydrolyses, two 2(3) central composite full factorial designs were employed to evaluate the effects caused by the initial content of solids (1.19-4.81%, w/w) and loadings of enzymes (1.9-38.1 FPU/g bagasse) and Tween 20 (0.0-0.1 g/g bagasse) on the cellulose digestibility. Within 24 h of enzymatic hydrolysis, all three independent variables influenced the conversion of cellulose by cellulase I. Using cellulase II, only enzyme and surfactant loadings showed significant effects on cellulose conversion. An additional experiment demonstrated the possibility of increasing the initial content of solids to values much higher than 4.81% (w/w) without compromising the efficiency of cellulose conversion, consequently improving the glucose concentration in the hydrolysate.

Mechanical properties and cytotoxicity of 3Y-TZP bioceramics reinforced with Al(2)O(3) particles

The influence of Al(2)O(3) addition and sintering parameters on the mechanical properties and cytotoxicity of tetragonal ZrO(2)-3 mol% Y(2)O(3) ceramics was evaluated. Samples containing 0, 10, 20 and 30 wt.% of Al(2)O(3) particles were prepared by cold uniaxial pressing (80 MPa) and sintered in air at 1500, 1550 and 1600 degrees C for 120 min. The effects of the sintering conditions on the microstructure were analyzed by X-ray diffraction analysis and scanning electron microscopy. Hardness and fracture toughness were determined by the Vickers indentation method and the mechanical resistance by four-point bending tests. As a preliminary biological evaluation, ""in vitro"" cytotoxicity tests were realized to determine the cytotoxic level of the ZrO(2)-Al(2)O(3) composites, using the neutral red uptake method with NCTC clones L929 from the American Type Culture Collection (ATCC) bank. Fully dense ceramic materials were obtained with a hardness ranging between 1340 HV and 1585 HV, depending on the amount of Al(2)O(3) in the ZrO(2) matrix. On the other hand, no significant influence of the Al(2)O(3) addition on fracture toughness was observed, exhibiting values near 8 MPa m(1/2) for all compositions and sintering conditions studied. The non-cytotoxic behavior, the elevated fracture toughness, the good bending strength (sigma(f) = 690 MPa) and the elevated Weibull`s modulus (m = 11) exhibited by the material, show that these ceramic composites are highly suitable biomaterials for dental implant applications. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Sagittal spinal alignment in paraplegics: a new paradigm for the rehabilitation under neuromuscular electrical stimulation

Study design: Radiographic analysis of sagittal spinal alignment of paraplegics in a standing position under surface neuromuscular electrical stimulation (NMES). Objectives: Describing the radiographic parameters of the sagittal spinal alignment of paraplegics going through a rehabilitation program with NMES. Setting: The University Hospital`s Ambulatory (UNICAMP), Campinas, Sao Paulo, Brazil. Methods: Panoramic X-ray images in profile were taken for 10 paraplegics. All patients participated in the rehabilitation program and were able to perform gait through NMES of the femoral quadriceps muscles. The radiographic parameters used for the analysis were the same as those described in the literature for healthy people. The results were didactically organized into three groups: anatomical shape of the spine, morphology and kinetics of the pelvis and spinopelvic alignment. Results: The physiological curvature of the spine in paraplegics showed average values similar to those described in the literature for healthy patients. The inversion of the pelvic tilt and the increase in the sacral slope were defined by the anterior backward rotation of the pelvis. The existing theoretical mathematical formulas that define lumbar lordosis, pelvic incidence and pelvic tilt showed normal values, despite the anterior intense sagittal imbalance. Conclusions: The adaptive posture of the spine in paraplegics standing through the stimulation of the femoral quadriceps does not allow for a neutral sagittal alignment. This novel radiographic detailed description of the various segments of the spine can be of assistance toward the understanding of the global postural control for such subjects. Spinal Cord (2010) 48, 251-256; doi: 10.1038/sc.2009.123; published online 29 September 2009

INFLUENCE OF ROOF MATERIAL ON THERMAL COMFORT IN BROILER HOUSINGS IN THE STATE OF SAO PAULO

This paper presents a different roof tiles influence study on the thermal comfort for broiler housings. The research was conducted at UNESP`s Experimental Campus at Dracena, state of Sao Paulo, Brazil. Four prototypes in real scale were built, each with an area of 28 m(2). The prototype was covered with roof tiles made of recycled long-life packing material, ceramic tiles, ceramic tiles painted with white coating, and fiber/cement tiles. Temperatures inside the structures were recorded in the winter 2007 over a 90-day period. The results obtained indicated that recycled tile thermal behavior was similar to ceramic tiles. However for the winter period all the prototypes had presented comfort thermal index not in the broilers thermo neutral zone.

Estimation of Mass Transfer Velocity Based on Measured Turbulence Parameters

The aim of this study is to quantify the mass transfer velocity using turbulence parameters from simultaneous measurements of oxygen concentration fields and velocity fields. The surface divergence model was considered in more detail, using data obtained for the lower range of beta (surface divergence). It is shown that the existing models that use the divergence concept furnish good predictions for the transfer velocity also for low values of beta, in the range of this study. Additionally, traditional conceptual models, such as the film model, the penetration-renewal model, and the large eddy model, were tested using the simultaneous information of concentration and velocity fields. It is shown that the film and the surface divergence models predicted the mass transfer velocity for all the range of the equipment Reynolds number used here. The velocity measurements showed viscosity effects close to the surface, which indicates that the surface was contaminated with some surfactant. Considering the results, this contamination can be considered slight for the mass transfer predictions. (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 2005-2017; 2010