bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption of Chromium (VI) from Aqueous Solutions Using Sol-Gel Anionic Clays with Mg/ Al=7
Authors: Esthela Ramos R. , Norma Gutiérrez O. , Cesar Contreras S. , Javier Álvarez R. , Rosalba Fuentes R. 
Published: April 2011

ABSTRACTAnionic clays has been used in the adsorption of anionic species of toxic heavy metals, such as chromium (VI), which is considered to be a dangerous pollutant, due to its deleterious effects on human health such as epithelial irritation and cancer. In this work the removal of chromium in aqueous solutions using anionic clays with Mg/Al=7 was determined. The anionic clays were synthesized by the sol-gel method at pH 10 and 11.5, and were characterized by X-ray diffraction, thermal analysis, infrared spectroscopy and N2 adsorption Brunauer-Emmett-Teller (BET). By this method, anionic clay containing brucite was obtained. The solids exhibited meso-porosity, high surface areas and thermal stability until 500°C. The data obtained from the adsorption experiments of chromium fitted to the Langmuir adsorption isotherm model and the adsorbent capacity was determined using the Langmuir adsorption equation. The maximum chromium uptake was 45 mg of Cr/g sorbent and 43 mg Cr/g sorbent for anionic clays prepared to pH 10 and 11.5, respectively. The Cr saturation point was attained after eight minutes stirring time. According to chromium adsorption values, the solution pH does not have a significant affect on the adsorption capacity of the anionic clays.
Macro and Microstructural Effects of the Application of an Induced Axial Magnetic Field During the Deposition of Aluminum Weld Beads
Authors: García M. A. , López M. V. H. , García H. R. , Curiel L. F. F. , Ambríz R. R. R. 
Published: April 2011

ABSTRACTIn this work, aluminum weld beads were deposited on aluminum plates of commercial purity (12.7 mm thick), using an ER-5356 filler wire. The aim of the experiments was to assess the effects that yield the induction of an axial magnetic field (AMF) during the application of the weld beads using the direct current gas metal arc welding process (DC-GMAW). An external power source was use to induce magnetic fields between 0 to 28 mT. The effects of the magnetic fields were assessed in terms of the macrostructural features of the deposits, morphology of the grain structure, grain size and grain size distribution in the weld metal. Macrostructural characteristics of the weld beads revealed that increasing the intensity of the magnetic induction to produce a magnetic field above 14 mT, leads to a significant loss of feeding material and there is a tendency of the deposits to increase their width and reduce penetration. Perturbation of the weld pool induced by the application of the AMF noticeably modified the grain structure in the weld metal. In particular, for the intensities of 5 and 14 mT, columnar growth was essentially non-existent. Grain size distribution plots showed, generally speaking, that the use of magnetic fields is an efficient method to produce homogeneous grain structures within the weld metal. Finite element analysis was used to explain the weld bead geometry with the intensity of the magnetic field.
Secondary Phases Precipitation in the 2510 Duplex Stainless Steel
Authors: Reyes Arturo , Calliari Irene , Ramous Emilio , Zanellato Michela , Merlin Mattia 
Published: April 2011

ABSTRACTA lot of duplex and super duplex stainless steels are prone to secondary phases but with different sequence and kinetic which depend on the chemical composition and thermo-mechanical history of the steel. In this paper the results of secondary phase's determination in a welding grade 2510 duplex steel, heat treated at 850–1050°C for 3–30 min are presented. The precipitation stars at grain boundaries with a consistent ferrite transformation for short times. The noses of the TTP curves are at 1000°C (sigma phase) and at 900°C (chi phase) with a partial transformation of chi to sigma, as evidenced in 2205 and 2507 grades.
Growth and Characterization of Organic Polymeric Thin Films From Isopropanol by PECVD.
Authors: Martínez-Gutiérrez J. O. , Romero-Paredes G. , Peña-Sierra R. , Ávila-García A. , Juárez-Díaz G. 
Published: April 2011

ABSTRACTPolymerized organic thin films were synthesized on a variety of substrates by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique using isopropanol as precursor. Hydrogen peroxide, ammonium hydroxide, and iodine dissolved in isopropanol were used as dopants and chlorobenzene as copolymerization precursor. The structural, optical and electrical properties of the films were studied as functions of the dopant type and concentration.The polymeric films were characterized by variable angle ellipsometry (VAE), atomic force microscopy (AFM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible transmission spectroscopy and photoluminescence. The electrical film behavior was explored by the four points probe method.The growth rate, refractive index, optical bandgap, chemical structure and resistivity of the films strongly depend on the concentration and type of dopant added. The AFM microphotographs showed smooth surfaces with RMS roughness less than 10 nm. The optical bandgap values of the films were in the range of 2.6 to 3.26 eV, the resistivity was in the order of 103 – 104 ohm-cm. The photoluminescence response of the polymerized films was obtained in the visible region, by exciting with a UV laser.
Rietveld Structure Refinement of Hydrothermally Grown Zinc Peroxide Nanoparticles
Authors: García-Ruiz A. , Aguilar M. , Aguilar A. , Escobedo-Morales A. , Esparza R. , Pérez R. 
Published: April 2011

ABSTRACTNanocrystals of zinc oxides have demonstrated to be very important materials for several applications in many fields, particularly in catalysis. Nanocrystalline zinc peroxide (ZnO2), which is a precursor of zinc oxide (ZnO), has been prepared by means of a hydrothermal process from zinc acetate dehydrates. On the other hand, it is of great interest to have a detailed structural characterization, in order to correlate it with the catalytic properties of the synthesized material. In this work, some results are presented about the nanostructure of the prepared zinc peroxide. By using X-ray diffraction followed of a pattern refinement by the Rietveld techniques, refined average cell parameters and crystallite size were calculated and, from these refined values, crystallite morphology was simulated in an averaged manner. With the aim to get a more complete characterization, besides these results, some micrographs of the crystalline structure of ZnO2, observed by TEM, were also included in this work.
Evaluation of Modulus of Elasticity, Mineral Composition and Bone Mineral Density of Trabecular Bone L3- Vertebrae Samples Extracted From Mexican Men
Authors: Valdés R. , Solis A. L. , Godínez F. A. , Martínez E. , Villegas C.H. , Navarrete M. 
Published: April 2011

ABSTRACTExtracted samples of L3 vertebrae, the healthy, osteopenic and osteoporotic from Mexican men, were fixed to carry out measurements of the modulus of elasticity (ME) and the minerals content, on the trabecular zone to study their behavior as a function of age.To determine the ME the immersion ultrasonic method (IUM) was used, X-ray dispersion was applied to know the chemical element concentration (Ca++, Na++, P, and Mg++) and computerized axial tomography (CAT) to obtain bone mineral density (BMD).The samples were organized in four groups by decade. The samples in the range of 30-39 years revealed: a normal BMD and a concentration [% w/w] between pairs of Ca++/P, Ca++/Mg++, P/Mg++ and Mg++/ Na ++ with correlation positive due to the strong dependence between them.The average ME results were: 2.79±0.326, 2.68±0.45, 2.66±0.43 and 2.70±0.397 [GPa] for each decade respectively. The ME profiles show a nonlinear behavior as a function of age, indicating a minimum value in the third decade, similar behavior is observed in the Ca++. An exponential behavior between ME and T-score was obtained. The plotted Ca++ and ME as a function of area showed a homogeneous distribution for the first and a non homogeneous for the second.
Biocompatibility and bio-corrosion resistance of amorphous oxide thin films
Authors: Rojas P. N. , Rodil S. E. , Muhl S. , Ramírez G. G. , Arzate H 
Published: April 2011

ABSTRACTThe corrosion resistance of biocompatible materials in body fluids is one of the essential factors in the determination of the lifetime of medical implants. Therefore, it is of great relevance to understand the interface processes that occur when a surface is exposed to body fluids. To this end, amorphous titanium and niobium oxide films were deposited on medical grade stainless steel using a magnetron sputtering system. The biocompatibility of the films was evaluated by adhesion and viability/proliferation assays using human cells, showing non-toxic response. The electrochemical response of the films was evaluated by poteontiodynamic polarization and electrochemical impedance spectroscopy (EIS) as a function of time, up to 500 hrs, using three different simulated body fluids; the NaCl solution and Hartman (Ringer's + Lactate) and Gey's (Ringer's + Phosphates + Glucose) solution. The results indicated that the chemical composition of the solution was very important since different electrochemical behavior was observed for each case. For example, NbOxshowed a better resistance than the TiOxfilms in the Hartman's solution but it failed when Gey's solution was used. Meanwhile TiOxshowed a well passivated response for both NaCl and Gey's solution.
In VitroEffects of Cementum Protein 1 (CEMP1) on Calcium Phosphate Crystal Formation and its Role During the Mineralization Process
Authors: Romo-Arévalo Enrique , Villarreal-Ramírez Eduardo , Chávez-Pacheco Juan L. , Piña-Barba Cristina , Aguilar-Franco M. , Arzate Higinio 
Published: April 2011

ABSTRACTCementum contains specific molecules that could serve to identify, isolate and characterize the cementoblast lineage and to determine the cellular and molecular mechanisms that regulate the cementogenesis process, since it plays a key role during the periodontal regeneration process. One of these molecules is the human cementum protein 1 (CEMP1); which has a molecular weight of 25,9 kDa.In vitroexperiments have shown that CEMP1 promotes cellular adhesion and differentiation. In addition, this protein has been implied in regulating the degree of deposition, composition and morphology of hydroxyapatite crystals formed by putative cementoblastin vitro. Therefore, it is possible that CEMP1 promotes the formation, growth and regulates the morphology of hydroxyapatite crystalsin vitro.We have produced a human recombinant CEMP1 (hrCEMP1) in a prokaryotic system. ThehrCEMP1 purification was realized using the column NiTA HisPrep FF/16. Assays of calcium phosphate crystal growth were realized by means of capillary counterdiffusion system. Our results demonstrated thathrCEMP1 promotes octacalcium phosphate crystal nucleation and possesses high affinity for hydroxyapatite. We infer thathrCEMP1 plays a key role during the regeneration of mineralized tissues.
Deposition of PEDOT/SWCNT Composites by Inkjet Printing
Authors: Angelo Peter David , Farnood Ramin R. 
Published: April 2011

AbstractPoly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), or PEDOT:PSS, a conductive polymer suspension, as well as carbon nanotubes (CNTs), were incorporated into a conductive ink suitable for use in a piezoelectric inkjet printer. Viscosity, surface tension, and particle size of the ink were controlled to achieve stable, high-resolution printing. Passage of the CNTs through the filtration and jetting steps involved in printing was evaluated using scanning transmission electron microscopy (STEM), UV-visible spectroscopy, and zeta-potential measurements of the filtered and printed inks. Only single-walled nanotubes (SWCNTs) passed through the jetting stage in significant amounts. Printed PEDOT/SWCNT sheet resistance was effectively minimized at ˜1 kΩ/on cellulose acetate, in ink containing 6 w/w% of an aqueous SWCNT solution (approximately 0.04 w/w% SWCNTs).
Magnetic Phase Diagram of Transition Metal Doped ZnO from Density Functional Theory Calculations and Monte Carlo Simulations
Authors: Nayak Sanjeev K. , Herper Heike C. , Entel Peter 
Published: April 2011

AbstractTransition metals doped ZnO are possible candidates for multiferroics. Here, we have investigated the evolution of ferromagnetism due to Co dopants. The magnetic properties have been studied for Co concentrations from 0 to 100% by using ab-initio methods, i.e., KKR Green's function techniques. In order to estimate the Curie temperature we have performed Monte Carlo simulations with ab-initio calculated exchange parameters.From our calculations the onset of ferromagnetism occurs between 5 to 20% of Co depending on the numerical details of KKR method used. For Co concentrations larger than 50% the system is dominated by antiferromagnetic coupling and no Curie temperature can be obtained.
Oxidation Products in Inconel Alloys 600 and 690 Under Hydrogenated Steam Environments and Their Role in Stress Corrosion Cracking
Authors: Lopez Hugo F. 
Published: April 2011

AbstractThermodynamic considerations for the stability of Ni and Cr compounds developed under PWR environments (PH2O and PH2) are experimentally tested. In particular, the experimental outcome indicates that Ni(OH)2 and CrOOH are thermodynamically stable products under actual PWR conditions (T < 360°C and Pressures of up to 20 MPa). Accordingly, a mechanism is proposed to explain crack initiation and growth in inconel alloy 600 along the gbs. The mechanism is based on the existing thermodynamic potential for the transformation of a protective NiO surface layer into an amorphous non-protective Ni(OH)2 gel. This gel is also expected to form along the gbs by exposing the gb Ni-rich regions to H2 supersaturated water steam. Crack initiation is then favored by tensile stressing of the gb regions which can easily rupture the brittle gel film. Repeating the sequence of reactions as fresh Ni is exposed to the environment is expected to also account for crack growth in Inconel alloy 600. The proposed crack initiation mechanism is not expected to occur in alloy 690 where a protective Cr2O3 film covers the metal surface. Yet, if a pre-existing crack is present in alloy 690, crack propagation would occur in the same manner as in alloy 600.
Micromechanical Models of Structural Behavior of Concrete
Authors: Avdeev Ilya , Sobolev Konstantin , Amirjanov Adil , Hastert Andrew 
Published: April 2011

AbstractA three-dimensional numerical model capable of predicting structural behavior of concrete under various loading conditions is developed. Concrete, as a composite material, is represented by the mechanically strong aggregates of various shapes and sizes incorporated into a cement matrix. The most important aspect of concrete modeling involves an accurate representation of the spatial distribution of the aggregate particles.A micromechanical heterogeneous model based on prescribed spatial distribution of aggregates is developed. This model allows to compute the effective material properties of concrete using a representative cell homogenization approach. The results of numerical analysis of this model are compared to the models of particulate composite material.
Preparation and Mechanical Characterization of Composite Material of Polymer–Matrix with Starch Reinforced with Coconut Fibers
Authors: Torres-Hernández- Yaret G. , Altamirano-Torres Alejandro , Sandoval-Pérez Francisco , Rangel Enrique Rocha 
Published: April 2011

AbstractIn this work the synthesis and mechanical characterization of a polymer matrix composite is reported. An epoxy resin is used as matrix with addition of starch and coconut fibers as reinforcement. Vickers hardness and impact tests are used for mechanical characterization. Starch is used to promote degradability of the polymer matrix with clear benefits for the environment. Natural fibers have been used for reinforcing the composite materials. Natural fibers have several advantages such as price, low density and relatively high mechanical properties, they are also biodegradable and non abrasive In this investigation, the composite material samples are fabricated with epoxy resin, 5, 10, 15 wt % of starch and 5, 10 wt % of coconut fibers with the help of silicon molds which have the dimensions and geometry according to ASTM Standards for make Impact and Vickers hardness tests. The obtained results show that increases in the amount of coconut fibers cause an enhancement of the mechanical properties of the material, due to a good adhesion between the polymeric matrix and the natural fibers.
Synthesis of La4Ni3O10 Cathode Material (SOFC) by SOL-GEL Process
Authors: Cienfuegos Rene Fabian , Carranza Sugeheidy , Chávez Leonardo , Jouanin Laurie , Marie Guillaume , Hinojosa Moisés 
Published: April 2011

AbstractThe goal in this study is to synthesize a Ruddleden-Poper La-Ni phase (La4Ni3O10) using a polymeric route. This material exhibits mixed ionic and electronic conduction (MIEC) properties and can be used as cathode material in the manufacture of Solid Oxide Fuel Cells (SOFC). In addition, an easy and inexpensive synthesis method is presented The polymeric precursors are prepared following the Castillo method using optimized the complexation ratios (HMTA/metallic salts) from 1 to 6. The obtained powders are characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) in order to determine the processing conditions for formation of the crystalline phase. Experiments performed using complexation ratios of 5 and 6 do not show coagulation. However, the solution prepared using a complexation ratio of 5, is transformed into a gel after few days. Gels produced from solutions prepared with complexation ratios from 2 to 5 were heated at 800, 900 and 1000°C to obtain solid materials. These powders are characterized by TGS, DSC and XRD and it is found that the temperature needed to obtain crystalline La4Ni3O10 was 1000°C.
A Practical Approach for Prioritizing The Replacement of Water Pipes in Mexico City
Authors: Tzatchkov V. , Hansen M. P. , Ramírez H. 
Published: April 2011

AbstractIn Mexico City, one of the largest cities in the world, large losses occur in the drinking water distribution system, mainly due to the age of the pipes and the type of materials used in water delivery to the end user. In the past, most of the water distribution networks in the city were built with asbestos-cement pipes. Currently, policies dictate that they be replaced by polyethylene pipes. While the size of the city leads to limited financial resources, it is important to prioritize pipe replacement; therefore, a practical approach based on Deterioration Point Allocation (DPA) is proposed to define the priority level. In the next set of factors, each is represented by appropriate indicators:1. Failures in pipes and service connectionsa. Number of failures (leaks) in pipes repaired in one year for every 100 km of pipeline.b. Number of failures (leaks) repaired in one year per 1000 service connections.c. Spatial concentration of failures (leaks) in a pipe2. Annual pipe and service connections rehabilitation or replacement level per year.3. Operating parameters of the network: intermittent water supply, water pressure, and water losses4. Deterioration status of pipes and service connections5. Land subsidenceA score and a weight are assigned to each factor. The score depends on the values of the indicator, and the weight on the relative importance of the factor. The final score is used to prioritize the replacement and it is calculated by adding up the scores of each factor.Considering that available information is incomplete and unstructured, two levels of use are proposed: basic (with available data, using MS Excel) and advanced (using a GIS).
Infrared Characterization of PMMA-SiO2 Hybrid Glasses Obtained by Sol-Gel Process
Authors: Díaz-Flores L.L. , Rodríguez A. S. López , SifuentesGallardo P. , Rivera M.A. Hernàndez , Romo M.a Garnica , Bernal R. , Yáñez-Limón J.M. 
Published: April 2011

AbstractThis work is about the production of hybrid coatings of the system SiO2-PMMA (PMMA, polymethylmethacrylate). These materials have interesting mechanical and chemical properties useful for anticorrosive and wear resistance applications. SiO2-PMMA hybrids were obtained by the sol-gel traditional process, using tetraethylorthosilicate (TEOS) and methylmethacrylate (MMA) by Aldrich Co, as starting reagents. The SiO2:PMMA ratio was varied from 0:1 to about 1:1 at air atmosphere deposition. The coatings were obtained on acrylic sheets and silicon wafers. A diversity of coatings with chemical composition ranging from SiO2 and PMMA to obtain the SiO2-PMMA hybrids were obtained. Infrared (IR) and atomic force microscopy (AFM), were performed to determinate structural and morphological behavior.
Thermoluminescence of Beta Particle Irradiated LiMgF3:X (X=Ce, Er)
Authors: Muñoz I. C. , Brown F. , Baldenevro R. I. , Orante-Barrón V. R. , Cruz-Vázquez C. , Furetta C. , Bernal R. 
Published: April 2011

AbstractThe thermoluminescence (TL) properties of beta particle irradiated Ce and Er doped LiMgF3 phosphors are presented. Pellet-shaped samples were prepared by cool-pressing 74 μm size particle powder, followed by thermal annealing at 700 °C during 5 h in air atmosphere. Some samples were irradiated with beta particles in the dose range from 8 up to 128 Gy. The sensitivity of Er doped samples was greater than the one of Ce-doped. In both cases, a 2 % mol of dopant concentration was used. The TL fading was between 19 % for Ce-doped samples, and 24 % for the Er-doped. The integrated TL increases as dose increases, with no saturation clues. The TL sensitivity of samples exhibited a loss in successive irradiation – readout cycles.
Thermal Stability of Pt Nanoparticles Supported on WOx/Al2O3 for n-Heptane Hydroconversion
Authors: Contreras J. L. , Fuentes G.A. , Salmones J. , Zeifert B. 
Published: April 2011

AbstractThe thermal stabilization of γ-Al2O3 using W+6 ions has been found useful to the synthesis of Pt/Al2O3 catalysts. The sequential impregnation method was used to study the effect of W6+ upon Pt/ γ-Al2O3 reducibility, Pt dispersion, Raman spectroscopy and n-heptane hydroconversion. The W/Pt atomic ratios varied from 3.28 to 75. We found that the W6+ ions delayed reduction of a fraction of Pt+4 atoms beyond 773 K. At the same time, W6+inhibited sintering of the metallic crystallites once they were formed on the surface. For the sample with a W/Pt atomic ratio of 3.28, W6+ did not inhibit the H2 reduction of Pt oxides even below of 773 K, the Pt oxides were reduced completely, however, the Pt dispersion decreased for this sample with respect to the Pt/γ-Al2O3 catalyst. After reduction at 1073 K, sequential samples impregnating Pt on WOx/γAl2O3 were more active and stable during n-heptane hydroconversion than monometallic Pt/γAl2O3 catalyst. Selectivities for dehydrocyclization, isomerization and Hydrocracking changed significantly when the W/Pt atomic ratio and reduction temperature increased. Initial and final reaction rates were more sensitive to reduction temperature. W6+ ions promoted high thermal stability of Pt crystallites when sequential catalysts were reduced at 1073 K and deactivation of bimetallic catalysts reduced at 773 K and 1073 K was less than the deactivation of Pt/Al2O3 catalyst.