Scielo RSS http://bibliotecadigital.uns.edu.ar/rss.php?pid=0327-079320120011&lang=es vol. 42 num. 1 lang. es http://bibliotecadigital.uns.edu.ar/img/en/fbpelogp.gif http://bibliotecadigital.uns.edu.ar http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100001&lng=es&nrm=iso&tlng=es Cardiovascular diseases are one of the leading causes of death in the first world countries nowadays and atherosclerosis is the most relevant among them. It is a disease that affects medium and large size arteries, which causes the formation of plaques within the artery wall. These plaques, called atheromas, develop due to the accumulation of fat, cholesterol, cell debris, smooth muscle cells and other cells and substances. Atheromas may cause temporary or definitive lack of blood supply to organs, such as the heart or the brain. This article proposes a model for cholesterol accumulation and fatty streak formation, which are possible precursors of atheroma. The model is basically a mass balance of low density lipoproteins (LDL) in the intima. The inflow, outflow, oxidation, and consumption of LDL is modeled combining partial models and endothelial LDL permeability correlations available in the literature. A simple zero-dimensional case was run for assessing the sensibility of the model to the initial conditions. A more complex case of a two-dimensional flow in the vecinity of a stagnation point on a rigid wall was used for evaluating the influence of spatial variations of the wall-shear stresses. Blood flow was assumed as an steady flow of an homogeneous newtonian fluid, while blood pressure and LDL blood concentration values were assumed as physiologic. Results showing local LDL mass accumulation and intimal thickening evolution for the first case, and spatial distribution of the initial intimal growth rate for the second one, indicate that there is a very short initial transient behaviour of LDL mass accumulation and intimal thickeness, which may well be considered instantaneous compared to the usual periods involved in the lesion formation. This allows the use of simple quasi-steady solution in future computational implementations of more realistic applications involving 3D arterial geometries with wall remodelling, that will significantly reduce the computational effort. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100002&lng=es&nrm=iso&tlng=es The seeds of Araucaria angustifolia, commonly known as pinhão, are widely consumed in both Southern and Southeastern Brazil due to their high nutritious value. Moisture desorption isotherms of cooked pinhão were determined at 15, 25, 30 and 40 ºC and modeled using well know isotherm models. Results show that Chirife model most appropriately represents the experimental data as reported previously for raw pinhão. The differential enthalpy was calculated and decreased as moisture content increased, becoming almost constant at 0.3 kg water kg-1 dry solids. Values, for each moisture content, were smaller than those reported for raw pinhão. The enthalpy-entropy compensation theory was applied to desorption isotherms providing the isokinetic temperature (401 ± 17 K). It was found that the desorption process investigated was enthalpy controlled as previously reported for raw pinhão. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100003&lng=es&nrm=iso&tlng=es Polymeric surfaces obtained by chemical vapor deposition of HMDSO on aluminum plates using plasma were modified by means of low pressure Argon plasma and vacuum ultraviolet radiation (VUV). The polymeric surface was directly exposed to the plasma -which also acted as a vacuum ultraviolet radiation source- at different conditions. An important contribution of the VUV radiation component in surface modification was observed. The surface free-energy, the chemical composition, and the morphology of the films were determined by contact angle measurement, FTIR spectroscopy, and SEM. It was observed that the action of VUV radiation inside de Argon plasma was responsible for more than 45% of the increase of surface free-energy, and that the influence of VUV radiation on surface free-energy varied significantly as consequence of different exposure times http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100004&lng=es&nrm=iso&tlng=es The aim of this work is the development of a method to obtain the shear layer, which appears in confined co-flowing jet diffusion flames. A convenient formulation, based on the mixture fraction for fluid flow and on flamelet models for the chemistry, using the RANS (Reynolds Averaged Navier-Stokes) and the LES (Large Eddy Simulation) approaches, is chosen. Numerical tests, for the governing equations discretized using the second order finite difference explicit scheme, were carried out for Sandia Flame D to compare the results with data in the literature. Results of the shear layer development comproves the ability of the developed LES method solving diffusion flames. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100005&lng=es&nrm=iso&tlng=es Cibacron Yellow FN-2R dye was degraded by heterogeneous photocatalysis with both titanium dioxide (TiO2), Degussa P-25, and zinc oxide (ZnO). A 3² factorial design was used with photocatalyst amount and pH as factors and the pseudo-first-order constant as response variable. On the optimal conditions the pseudo-first order rate constant was higher when ZnO was used as catalyst. However, the evolution of total zinc (Zn) in solution indicated a significant loss of ZnO on those optimal conditions as consequence of its susceptibility to chemical dissolution and photodissolution. Due to the solubility curve of ZnO has a minimum at pH around 10 and its photodissolution does not occur at pH>10, the photodegradation experiments using ZnO were performed with a pH control near to 10. In this condition, the photocatalytic activity of ZnO was similar to that obtained with TiO2 when it is used in its optimal conditions. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100006&lng=es&nrm=iso&tlng=es In this paper, we present the results and a discussion of microflotation tests performed with manganese minerals (rhodonite and rhodochrosite) and quartz mineral, using sodium oleate as the collector. We also explore the influence of water glass (sodium silicate) as a depressant in the recovery of these minerals with sodium oleate. Potential zeta determinations were carried out with the three minerals conditioned with deionised water and with the previously mentioned reagents. It was found that, at a pH of 9, the recoveries of rhodonite and quartz were maximised, and for the rodhocrhosite mineral, the maximum recovery was achieved at pH 11. The water glass at pH 9 was more efficient in depressing quartz than rhodonite, especially for smaller concentrations, whereas the flotation response of rhodochrosite was only slightly affected at both pH 9 and pH 11. The potential zeta curves indicate that the IEP of rhodonite (pH=2.8) is similar to values reported in the literature, whereas the IEP values of quartz (pH=2.2) and rhodochrosite (pH=10.8) differ slightly from those in the literature. The zeta potentials of rhodonite, quartz and rhodochrosite in the presence of sodium oleate and water glass become more negative in a basic medium. Finally, based on the experimental results with a collector of sodium oleate and a depressant of water glass, some inferences on the adsorption mechanisms of these reagents on rhodonite, quartz and rhodochrosite surfaces are made. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100007&lng=es&nrm=iso&tlng=es Kinetic studies of the photocatalytic degradation of tartrazine are carried out in a batch stirred reactor built in quartz at laboratory scale using TiO2 as catalyst and irradiating the photoreactor with ultraviolet light. An experimental design is performed using as independent variables or factors the catalyst concentration, the calcination temperature of the catalyst and the initial concentration of tartrazine. The obtained kinetic model indicates that the value of the kinetic constant, k, for a first order reaction is high, in the operating conditions studied. This is consistent with the low value of the adsorption constant, K. The experimental data fitted, with the Langmuir-Hinshelwood model, lead to an equation that, in the range of concentrations studied, allows the evaluation of photodegradation and describes well the photoreactivity results. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100008&lng=es&nrm=iso&tlng=es The aim of the present work was to verify the influence of the type of metal used in the presence of niobium pentoxide on the photocatalytic degradation of an industrial leather dye. Niobium oxide alone showed low photocatalytic activity, but with the impregnation of small quantities of metal, this material showed highly activity. It was observed that the type of metal significantly influenced the catalytic activity of niobium oxide. The results indicate that metal/Nb2O5 could be employed for the removal of dyes from wastewater. The order of photocatalytic activity of metal-doped Nb2O5 was as follows: (La, Zn, Ti) > (Sr, Sn, Ag) > (Co, V, Ga) > (Ni, Y, Cu). The metals Ce, Mn and Mo showed not efficient catalytic activity in degrading the leather dye http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100009&lng=es&nrm=iso&tlng=es TiO2 powder was prepared by a hydrothermal process at 200°C for 12 h. The material was characterized by X-ray diffraction and N2 adsorption-desorption isotherm. The synthesized sample presented a pure phase anatase, with nanometric particle size. Its activity was tested for adsorption and degradation of the azo leather dye, Direct Black 38. The adsorption isotherm obtained followed the S-type in terms of the classification of Giles. Thermodynamic parameters were calculated, and the results revealed that the adsorption process is endothermic in nature. The material showed highly photocatalytic activity in the degradation of the dye, similar to that of the TiO2 (P25 Degussa) photocatalyst. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100110&lng=es&nrm=iso&tlng=es Porous silicon (PSi) has attracted much attention for biosensing due to its large surface area and easy preparation. In this paper, an optical immunoassay method based on a macro-PSi silicon resonant waveguide, with pore size much larger than that of large molecules such as bovine serum albumin, has been developed for the detection of the antigen-antibody reaction between hydroxysafflor yellow A (HSYA, i.e., the component of Carthamus tinctorius L.) and the specificity of the polyclonal anti-HSYA antibodies. HSYA antibodies were immobilized into the macro-PSi silicon waveguide using standard amino-silane and glutaraldehyde chemistry. The waveguide resonance angle was increased by binding HSYA onto the immobilized antibodies. The label-free immunosensor is simple and exhibits high sensitivity to HSYA. Therefore, this research is expected to have applications for quick and accurate determination of HSYAand can also be used for various immunoassays with other antigens.. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100111&lng=es&nrm=iso&tlng=es A study was made of the extraction of clavulanic acid (CA) from a fermented medium and its concentration and purification. The fermented broth was obtained by cultivation of Streptomyces clavuligerus in complex medium containing glycerol as the Carbon and energy source, and soybean protein isolate as the Nitrogen source. The extraction steps proposed here were evaluated from the standpoint of Yield, purification factor and concentration factor. The extractions were carried out with ethyl acetate, butyl acetate, 2-butanol, n-butanol and methyl isobutyl ketone. The distribution coefficient was related to the solvent properties and it was found that distribution coefficient is directly proportional to the product of the dielectric constant, with solubility. It was observed that extraction with butanol leads to a higher distribution coefficient than ethyl acetate; however, the higher solubility of water in butanol impairs the final precipitation of clavulanic acid. The optimal condition with ethyl acetate occurs at pH 1.63, yielding an extraction factor of 35.6% with a distribution coefficient of 0.73. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100112&lng=es&nrm=iso&tlng=es Olein production from the residue constituents of hide pre-fleshing is carried out through the unit operations of extraction and subsequent fractionation of the fatty material (tallow). The residue was characterized and the content of fatty matter (31.83% by mass) revealed a high potential for its reuse. By the extraction/ digestion of tallow assays were carried out to quantify the effect of factors such as the presence of agitation, temperature and extraction time in terms of the efficiency of the extraction operation and acidity index of the tallows obtained. The oils were characterized according to the acidity index, iodine index, saponification index, water content, volatile matter content and fractions of saturated and unsaturated fatty acids. The oil composition was quantified using gas chromatography. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100113&lng=es&nrm=iso&tlng=es Scientific studies have shown that mango peel is a rich source of phenolic compounds, which present antioxidant activity. In order to contribute to the future applications of this material, this paper aims the optimization of the extraction process of phenolic compounds from mango peels. The following process parameters were evaluated in this study: mango variety, peel drying time, ethanol concentration and solvent temperature. A two-level, four-factor full- factorial design (2(4)) was used in the design of the experiments and in the analysis of the results. With the preliminary results a star experimental design around the central point was performed to obtain a response surface. A maximum extraction yield of 33.7% of total phenolics was obtained for the "Espada" variety, with ethanol concentration of 70% and 10 hours of mango peel drying time. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100114&lng=es&nrm=iso&tlng=es The effect of surface treatment on the properties of rice husk/polypropylene composites was investigated. Rice husk with particle sizes of 20, 30, 40 and 60 mesh was modified by alkaline treatment and coupling of silanes with and without previous alkaline treatment. The rice husk was characterized by FTIR, TGA, SEM and a qualitative hydrophilicity test by using a water-toluene system. The TGA results and the qualitative hydrophilicity test indicated that silanized rice husk decreased their hydrophilic character and increased their thermal stability. SEM images showed a regular geometry in the 60 mesh husk which consisted of short fibers. Test specimens were obtained according to ASTM D-1708 standard, by molding injection process using a ratio of 30 % rice husk/70 % polypropylene (PP) based on weight. A quantitative improvement in tensile strength was observed in composites filled with alkali treated rice husk and silanized rice husk in comparison with composites filled with untreated rice husk. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100115&lng=es&nrm=iso&tlng=es The design and fabrication of highly porous polymeric or composite scaffolds for tissue engineering and organ regeneration are keystones to advance in these interdisciplinary research areas. The development of biocompatible polymeric matrices with particular morphologies that promote a specific biological response for each type of cell, is strongly needed. To attain this goal, the characterization and quantification of the morphological properties of the scaffolds are necessary to correlate them to mechanical and biological properties. In this work, micro/nanofibrous scaffolds obtained by electrospinning were characterized by scanning electron microscopy (SEM). The use of the granulometric size function, computed from the scaffold images, to develop algorithms that help the specialists in the characterization of the shape, size, stocking density and orientation of the arrays, is proposed. The obtained results show that the analysis of SEM images allows for a good characterization of fibrous scaffolds becoming a useful tool for specialists in this research area. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932012001100116&lng=es&nrm=iso&tlng=es A quasilinearisation method for solving the nonlinear equations is presented. The method works successively in linearizing the nonlinear equations and solving the resulting higher order deformation equations using spectral methods. We illustrate the application of the method by solving the laminar heat transfer problem in a rotating disk. Comparison between the linearisation method and numerical results obtained using the MATLAB in-built bvp4c solver reveals that the linearisation method is accurate and converges at very low orders of the iteration scheme.