Instituto Zuliano Of Investigaciones Tecnologicas

Maracaibo, Venezuela

Instituto Zuliano Of Investigaciones Tecnologicas

Maracaibo, Venezuela

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Mendez F.J.,Venezuelan Institute for Scientific Research | Llanos A.,Instituto Universitario Of Tecnologia Dr Federico Rivero Palacio | Echeverria M.,Venezuelan Institute for Scientific Research | Echeverria M.,Instituto Universitario Of Tecnologia Dr Federico Rivero Palacio | And 8 more authors.
Fuel | Year: 2013

(Figure Presented) A series of tungsten and molybdenum catalysts supported on MCM-41 were prepared using Keggin heteropolyacids (H3PM 12O40, M = Mo or W) as active phase sources and compared with their analogues unsupported. The physicochemical characterization was carried out by, small angle and wide angle X-ray diffraction; thermogravimetric analysis/differential scanning calorimetry; ultraviolet-visible diffuse reflectance and Fourier transform infrared spectroscopies; N2 physisorption and potentiometric titration with N-butylamine, for determination, respectively, of the structure; thermal stabilities; integrity of heteropolyacids; textural properties and superficial acidity. The solids were tested in the thiophene hydrodesulfurization reaction at 400°C, atmospheric pressure and weight hourly space velocity of 0.48 h-1. In this study, it has been demonstrated the importance of supporting heteropolyacids to increase the catalytic activity. Furthermore, it was proved a correlation between surface acidity and calcination temperature with the activity and stability of these catalysts in the hydrodesulfurization reaction. © 2012 Elsevier Ltd. All rights reserved.


Oscar Mauricio Castellanos A.,University of Pamplona | Carlos Alberto Rios R.,Industrial University of Santander | Miguel Angel Ramos G.,Instituto Zuliano Of Investigaciones Tecnologicas | Eric Vinicio Plaza P.,Instituto Zuliano Of Investigaciones Tecnologicas
Boletin de Geologia | Year: 2012

Mineralogical transformations during firing of clays from the Laboyos Valley at the Upper Magdalena Basin (Colombia) were studied. Firing of clays was carried out in the temperature range 800-1200 oC under oxidizing conditions. The mineralogical transformations were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Important compositional differences in the neoformed phases were observed in the clays. Typical assemblages with quartz, illite, kaolinite, mica, halloysite, potassium feldspar and plagioclase were observed. Several mineral phases were identified in the fired clays, with the reaction products including mullite, residual quartz, hematite, amorphous phase (glass generated by melting of feldspars and clays) in the fired clays.


Avendano C.,Venezuelan Institute for Scientific Research | Briceno A.,Venezuelan Institute for Scientific Research | Mendez F.J.,Venezuelan Institute for Scientific Research | Brito J.L.,Venezuelan Institute for Scientific Research | And 4 more authors.
Dalton Transactions | Year: 2013

Novel MoO2/C nano/microcomposites were prepared via a bottom-up approach by hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of polyoxometalates (POMs: phosphomolybdic acid [H3PMo12O40] and ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O24] ·4H2O). The structural characterization by FT-IR, XRPD, SEM and TEM analyses revealed the controlled formation of hierarchical MoO 2/C composites with different morphologies: strawberry-like, based on carbon microspheres decorated with MoO2 nanoparticles; MoO 2/C core-shell composites; and irregular aggregates in combination with ring-like microstructures bearing amorphous Mo species. These composites can be fine-tuned by varying reaction time, glucose/POM ratio and type of POM precursor. Subsequent transformations in the solid state through calcinations of MoO2/C core-shell composites in air lead to hollow nanostructured molybdenum trioxide microspheres together with nanorods and plate microcrystals or cauliflower-like composites (MoO2/C). In addition, the MoO 2/C composite undergoes a morphology evolution to urchin-like composites when it is calcined under nitrogen atmosphere (MoO 2/C-N2). The MoO2/C strawberry-like and MoO2/C-N2 composites were transformed into Mo carbide and nitride supported on carbon microspheres (Mo2C/C, MoN/C, and MoN/C-N2). These phases were tested as precursors in thiophene hydrodesulphurization (HDS) at 400°C, observing the following trend in relation to the thiophene steady-state conversion: MoN/C-N2 > MoN/C > Mo2C/C > MoO2/C-N2 > MoO 2/C. According to these conversion values, a direct correlation was observed between higher HDS activity and decreasing crystal size as estimated from the Scherrer equation. These results suggest that such composites represent interesting and promising precursors for HDS catalysts, where the activity and stability can be modified either by chemical or structural changes of the composites under different conditions. © 2013 The Royal Society of Chemistry.


Ferrer V.,University of Zulia | Finol D.,University of Zulia | Solano R.,University of Zulia | Moronta A.,University of Zulia | Ramos M.,Instituto Zuliano Of Investigaciones Tecnologicas
Journal of Environmental Sciences (China) | Year: 2015

The catalytic activity of Pd catalysts supported on Ce0.73Tb0.27Ox/SiO2, Ce0.6Zr0.4Ox/SiO2, Ce0.73Tb0.27Ox/La2O3-Al2O3 and Ce0.6Zr0.4Ox/La2O3-Al2O3 was studied using the reduction of NO by CO. The catalysts were characterized by X-ray fluorescence, surface area, X-ray diffraction, temperature-programmed reduction, CO chemisorption and oxygen storage capacity. Temperature-programmed reduction results indicated that Tb or Zr incorporation improves the reducibility and oxygen storage capacity. CO chemisorption data suggested the presence of large PdO particles due to the low CO/Pd ratio. No significant differences were obtained in light off temperatures (TLight off) for all Pd catalysts and the most active was 1.5%Pd/Ce0.6Zr0.4Ox/SiO2. © 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.


Faneite A.M.,University of Zulia | Rincon A.,Rafael Urdaneta University | Ferrer A.,Instituto Zuliano Of Investigaciones Tecnologicas | Angos I.,Technical University of Ambato | Arguello G.,Instituto Nacional Of Investigaciones Agricolas Inia
International Food Research Journal | Year: 2016

In this work green plantain peel was characterized in terms of moisture, and dry basis hemicellulose (HC), cellulose, lignin, crude fiber (CB), crude protein (CP), ether extract (EE), starch, nitrogen free extract (NFE), total digestible nutrients (TDN) and ash. According to the high proportion found of hydrophilic components (carbohydrates) and water (76.15 % and 87.62 % respectively) a slow drying period was determined. Drying kinetics of peels at 60, 70, 80, 90, 100 and 110 °C was studied. Isothermal drying curves for green plantain peels showed a monotonic decreasing of moisture content in the whole range of temperatures studied, until a point where the changes of the moisture content were very little in function of time, indicating that the transition state of dynamic pseudo-equilibrium (TSDPE) was reached. Best fit was found when modified Henderson-Pabis model was used. Desorption, drying rate, and effective diffusivity curves showed a non fickian process, a drying period of decreasing rate with internal control, and a concentration-dependence diffusion, respectively. © All Rights Reserved.


San-Blas E.,Venezuelan Institute for Scientific Research | Cubillan N.,University of Zulia | Guerra M.,Instituto Zuliano Of Investigaciones Tecnologicas | Portillo E.,Venezuelan Institute for Scientific Research | Esteves I.,Instituto Zuliano Of Investigaciones Tecnologicas
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2012

The use of Fourier transform mid-infrared spectroscopy with attenuated total reflection for characterizing entomopathogenic bacteria from genera Xenorhabdus and Photorhabdus is evaluated for the first time. The resulting spectra of Xenorhabdus poinarii and Photorhabdus luminiscens were compared with the spectrum of Escherichia coli samples. The absorption spectra generated by the bacteria samples, were very different at the region below 1400 cm -1 which represents the stretching vibrations of phosphate and carbohydrates. Star diagrams of the fingerprint section of nematodes spectra (between 1350 and 1650 cm -1) for separation between spectra was used and showed to be a useful tool for classification purposes. © 2012 Elsevier B.V. All rights reserved.


San-Blas E.,Venezuelan Institute for Scientific Research | Guerra M.,Instituto Zuliano Of Investigaciones Tecnologicas | Portillo E.,Venezuelan Institute for Scientific Research | Esteves I.,Instituto Zuliano Of Investigaciones Tecnologicas | And 2 more authors.
Vibrational Spectroscopy | Year: 2011

The use of Fourier transform mid-infrared spectroscopy with attenuated total reflection for characterizing entomopathogenic nematodes is evaluated for the first time. The resulting spectra of Steinernema glaseri and Heterorhabditis indica were compared with the spectrum of Caenorhabditis elegans. In the absorption spectra generated by the nematodes samples, the absorption bands were assigned to the molecular species and some important components were identified including triglycerides, trehalose, glycogen and collagen. Also, the use of star diagrams for the fingerprint section of nematode spectra for separating genera is discussed. © 2011 Elsevier B.V.


Briceno S.,Venezuelan Institute for Scientific Research | Bramer-Escamilla W.,Venezuelan Institute for Scientific Research | Silva P.,Venezuelan Institute for Scientific Research | Delgado G.E.,University of Los Andes, Venezuela | And 3 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2012

Cobalt ferrite nanoparticles (CoFe 2O 4) have been synthesized using precipitation in water solution with polyethylene glycol as surfactant. Influence of various synthesis variables included pH, reaction time and annealing temperature on the magnetic properties and particle sizes has also been studied. Structural identification of the samples was carried out using Thermogravimetric and Differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, High resolution transmission electron microscopy. Vibrating sample magnetometer was used for the magnetic investigation of the samples. Magnetic properties of nanoparticles show strong dependence on the particle size. The magnetic properties increase with pH of the precipitating medium and annealing temperature while the coercivity goes through a maximum, peaking at around 25 nm. © 2012 Elsevier B.V. All rights reserved.


PubMed | Instituto Zuliano Of Investigaciones Tecnologicas, Central University of Venezuela, CNR Institute of Biophysics and Simon Bolivar University of Venezuela
Type: | Journal: Revista do Instituto de Medicina Tropical de Sao Paulo | Year: 2016

Vibrio cholerae represents a significant threat to human health in developing countries. This pathogen forms biofilms which favors its attachment to surfaces and its survival and transmission by water or food. This work evaluated the in vitro biofilm formation of V. cholerae isolated from clinical and environmental sources on stainless steel of the type used in food processing by using the environmental scanning electron microscopy (ESEM). Results showed no cell adhesion at 4 h and scarce surface colonization at 24 h. Biofilms from the environmental strain were observed at 48 h with high cellular aggregations embedded in Vibrio exopolysaccharide (VPS), while less confluence and VPS production with microcolonies of elongated cells were observed in biofilms produced by the clinical strain. At 96 h the biofilms of the environmental strain were released from the surface leaving coccoid cells and residual structures, whereas biofilms of the clinical strain formed highly organized structures such as channels, mushroom-like and pillars. This is the first study that has shown the in vitro ability of V. cholerae to colonize and form biofilms on stainless steel used in food processing.


Guerra M.,Instituto Zuliano Of Investigaciones Tecnologicas | Lopez M.A.,Instituto Zuliano Of Investigaciones Tecnologicas | Esteves I.,Instituto Zuliano Of Investigaciones Tecnologicas | Zubillaga A.L.,Simon Bolivar University of Venezuela | Croquer A.,Simon Bolivar University of Venezuela
Diseases of Aquatic Organisms | Year: 2014

Yellow band disease (YBD) is a common and wide-spread Caribbean syndrome that affects the genus Orbicella, a group of species that constitute the framework of Caribbean coral reefs. Previous studies have shown that the structure and function of bacterial assemblages vary between healthy tissues and YBD lesions; however, how the molecular composition of tissues varies as tissues transition from healthy to YBD has not been determined before. The present study provides the first survey of macromolecules found from healthy (H), apparently healthy (AH), transition (TR) and YBD tissues of Orbicella faveolata. For this, we used Fourier-transformed mid-infrared spectroscopy (FTIR) to compare absorption profiles as a proxy for the gross molecular composition of decalcified H, AH and YBD tissues. We found a significantly higher level of infrared absorption for bands assigned to lipids in H tissues compared to YBD tissues, suggesting that lipid compounds are more abundant in compromised tissues in relation to other macromolecules. We also found a lower level of intensity of bands assigned to carbohydrates and proteins in YBD tissues, compared to H and AH tissues. A similar pattern was observed for phospholipidic compounds in relation to fatty acids. This study is the first to show that healthy and YBD-compromised tissues have different infrared absorption profiles, suggesting that alterations in the biochemical composition occur during pathogenesis. Future studies should focus on determining the actual concentration of these compounds in H, AH, TR and YBD tissues and on testing the role of translocation of photoassimilates from H tissues and/or from endolithic algae to YBD tissues. © Inter-Research 2014.

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