577 research outputs found

    Behavior of a Friction-Piled Box Foundation for an Urban Bridge in Mexico City Clay

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    Severe seismic effects and regional ground subsidence are well recognized conditions that should be considered for the design of foundations in Mexico City. These phenomena are magnified by lacustrine clayey soft deposits with very high compressibility and very low shear strength, which are found at the extensive Lake Zone of the city. To clarify the soil-structure interaction phenomena, a prototype foundation was instrumented, selecting a friction-piled support of an urban bridge located in the Metropolitan area of Mexico City. Soil-raft contact pressures, loads on selected piles, and pore water pressures in the subsoil below the foundation have been monitored continuously, since the beginning of the foundation construction eight years ago. The long-term performance of the foundation is known in terms of these state variables. The response of the soil-foundation system has been recorded during the occurrence of ten mild to strong earthquakes. Time-records of those geotechnical variables were obtained at the very moment of the earthquakes, additionally to the accelerograms. This case history yielded valuable information about the foundation performance before, during and after seismic events, regarding the analysis, design and regulations for this kind of foundation

    Quantification and mapping of domestic plastic waste using GIS/GPS approach at the city of Guayaquil

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    [Abstract] A significant contributor to the waste stream is the domestic single-use plastic used in households, being the final disposal in most cases the local landfill. There is a significant opportunity to promote resource recovery and efficiency through the introduction of circular economy strategies. However, the knowledge and management of post-consumer plastic waste in the country is poor, and there is a lack of an efficient collection and sorting system. In this context, spatial information on domestic plastic waste generation (DPWG) is essential for recycling decision-making. The integration of Geographic Information Systems (GIS) and the Global Positioning System (GPS) shows an opportunity to collect, mapping, and analyse spatial DPWG issues. Thus, this paper had a double objective. The first was to assess the evolution of eight different types of plastic waste in the city鈥檚 households and their daily per capita generation between 2019 and 2021. The second objective was to provide a complete geo-referenced information on the quantities and typologies of domestic plastic waste (DPW) produced in Guayaquil and analyse how the flows have shifted throughout the years. The results showed that PET is the most generated, recording 97.76% and 100.00 % of the households who generate this type of plastic for 2019 and 2021, respectively, with an average of 13.08 and 15.13 g/day/c. Following, we had HDPE, PP and PVC occupying the second, third and fourth place for 2019 with 5.86, 3.05, 2.54 g/day/c, respectively. On the other hand, for 2021, PP (7.43 g/day/c), HDPE (5.92 g/day/c), and LDPE (3.99 g/day/c) occupied the second, third and fourth, respectively. According to the spatial maps, the DPW increment is in most of the popular zones. These popular zones are neighborhoods with a considerable quantity of population and limited basic services. Most of these people live in extreme poverty, being a possible relation between the COVID-19 lockdown and the increasement of DPW

    Numerical Study of the Seismic Response of an Urban Overpass Support System

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    A strategic urban overpass is to be built in the so-called transition and hill zones in Mexico City. The subsoil conditions at these zones typically consist on soft to stiff clay and medium to dense sand deposits, randomly interbedded by loose sand lenses, and underlain by rock formations that may outcrop in some areas. Several critical supports of this overpass are going to be instrumented with accelerometers, inclinometers and extensometers to assess their seismic performance during future earthquakes and to generate a database to calibrate soil-structure-interaction numerical models. This paper presents the seismic performance evaluation of one of these supports. The support foundation is a 3.6 by 4.6 m mat, structurally connected to four cast-in-place 0.80 m diameter piles. A finite elements model of the soil-foundation-structure system was developed. Initially, the model was calibrated analyzing the seismic response that an instrumented bridge support exhibited during the June 15th, 1999 Tehuacan (Mw=7) Earthquake. This bridge is located also within the surroundings of Mexico City, but at the lake zone, where highly compressible clays are found. The computed response was compared with the measured response in the free field, box foundation, and structure. Once the model prediction capabilities were established, the seismic response of the critical support of the urban overpass was evaluated for the design earthquake in terms of transfer functions and displacement time histories

    Bioactivity of wollastonite/aerogels composites obtained from a TEOS-MTES matrix

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    Organic-inorganic hybrid materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS), methyltrimethoxysilane (MTES), synthetic wollastonite powders and polydimethylsiloxane (PDMS) in an ethanol solution. Aerogels were prepared from acid hydrolysis of TEOS and MTES with different volume ratio in ethanol, followed by addition of wollastonite powder and PDMS in order to obtain aerogels with 20 wt% of PDMS and 5 wt% of CaO of the total silica. Finally, when the wet gels were obtained, they were supercritically dried at 260掳C and 90 bar, in ethanol. In order to obtain its bioactivity, one method for surface activation is based on a wet chemical alkaline treatment. The particular interest of this study is that we introduce hybrid aerogels, in a 1 M solution of NaOH, for 30 s at room temperature. We evaluate the bioactivity of TEOS-MTES aerogel when immersed in a static volume of simulated body fluid (SBF). An apatite layer of spherical-shaped particles of uniform size smaller than 5 microns is observed to form on the surface of the aerogels after 25 days soaking in SBF.Ministerio de Ciencia e Innovaci贸n MAT2005-01583Junta de Andaluc铆a TEP 79

    Topographic characterisation of dental implants for commercial use

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    To characterize the surface topography of several dental implants for commercial use. Dental implants analyzed were Certain (Biomet 3i), Tissue Level (Straumann), Interna (BTI), MG-InHex (MozoGrau), SPI (Alphabio) and Hikelt (Bioner). Surface topography was ascertained using a confocal microscope with white light. Roughness parameters obtained were: Ra, Rq, Rv, Rp, Rt, Rsk and Rku. The results were analysed using single-factor ANOVA and Student-Neuman-Keuls(p<0.05) tests. Certain and Hikelt obtained the highest Ra and Rq scores, followed by Tissue Level. Interna and SPI obtained lower scores, and MG-InHex obtained the lowest score. Rv scores followed the same trend. Certain obtained the highest Rp score, followed by SPI and Hikelt, then Interna and Tissue Level. MG-InHex obtained the lowest scores. Certain obtained the highest Rt score, followed by Interna and Hikelt, then SPI and Tissue Level. The lowest scores were for MG-InHex. Rsk was negative (punctured surface) in the MG-InHex, SPI and Tissue Level systems, and positive (pointed surface) in the other systems. Rku was higher than 3 (Leptokurtic) in Tissue Level, Interna, MG-InHex and SPI, and lower than 3 (Platykurtic) in Certain and Hikelt. The type of implant determines surface topography, and there are differences in the roughness parameters of the various makes of implants for clinical use

    Cytogenetic Mapping of 35 New Markers in the Alpaca (Vicugna pacos)

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    Universidad Nacional Agraria La Molina. Escuela de Posgrado. Maestr铆a en Producci贸n AnimalAlpaca is a camelid species of broad economic, biological and biomedical interest, and an essential part of the cultural and historical heritage of Peru. Recently, efforts have been made to improve knowledge of the alpaca genome, and its genetics and cytogenetics, to develop molecular tools for selection and breeding. Here, we report cytogenetic mapping of 35 new markers to 19 alpaca autosomes and the X chromosome. Twenty-eight markers represent alpaca SNPs, of which 17 are located inside or near protein-coding genes, two are in ncRNA genes and nine are intergenic. The remaining seven markers correspond to candidate genes for fiber characteristics (BMP4, COL1A2, GLI1, SFRP4), coat color (TYR) and development (CHD7, PAX7). The results take the tally of cytogenetically mapped markers in alpaca to 281, covering all 36 autosomes and the sex chromosomes. The new map assignments overall agree with human鈥揷amelid conserved synteny data, except for mapping BMP4 to VPA3, suggesting a hitherto unknown homology with HSA14. The findings validate, refine and correct the current alpaca assembly VicPac3.1 by anchoring unassigned sequence scaffolds, and ordering and orienting assigned scaffolds. The study contributes to the improvement in the alpaca reference genome and advances camelid molecular cytogenetics. View Full-Tex

    Atomic Data and Spectral Model for Fe 瑟瑟

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    We present extensive calculations of radiative transition rates and electron impact collision strengths for Fe ii. The data sets involve 52 levels from the 3d7, 3d64s, and 3d54s2 configurations. Computations of A-values are carried out with a combination of state-of-the-art multiconfiguration approaches, namely the relativistic Hartree鈥揊ock, Thomas鈥揊ermi鈥揇irac potential, and Dirac鈥揊ock methods, while the R-matrix plus intermediate coupling frame transformation, Breit鈥揚auli R-matrix, and Dirac R-matrix packages are used to obtain collision strengths. We examine the advantages and shortcomings of each of these methods, and estimate rate uncertainties from the resulting data dispersion. We proceed to construct excitation balance spectral models, and compare the predictions from each data set with observed spectra from various astronomical objects. We are thus able to establish benchmarks in the spectral modeling of [Fe 瑟瑟] emission in the IR and optical regions as well as in the UV Fe 瑟瑟 absorption spectra. Finally, we provide diagnostic line ratios and line emissivities for emission spectroscopy as well as column densities for absorption spectroscopy. All atomic data and models are available online and through the AtomPy atomic data curation environment

    Composici贸n y estructura de la ictiofauna del r铆o Hondo, M茅xico-Belice, con base en el uso del arp贸n

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    ResumenSe determin贸 la composici贸n y estructura de la ictiofauna del r铆o Hondo y la variaci贸n espacial de 茅stas en funci贸n de los par谩metros ambientales. Se realizaron 3 muestreos durante marzo, abril y mayo de 2012, en 6 sitios a lo largo del r铆o. Los datos usados para determinar la estructura se obtuvieron con ayuda de un arp贸n de 58.5cm, utilizado durante 2h de buceo libre en cada punto de muestreo. Para complementar la lista de especies se utilizaron redes agalleras, palangres, nasas y anzuelos. Adem谩s, se realiz贸 una revisi贸n bibliogr谩fica y se consult贸 material de la colecci贸n de peces de ECOSUR en Chetumal. La lista sistem谩tica se conform贸 por 40 especies en 33 g茅neros, 18 familias y 11 贸rdenes. La familia mejor representada fue Cichlidae, incluida la especie ex贸tica Oreochromis niloticus. Los par谩metros ambientales que mejor describieron la variaci贸n de la distribuci贸n y abundancia en los peces en el r铆o Hondo fueron: la anchura del r铆o, distancia a la boca, transparencia, profundidad, concentraci贸n de ox铆geno disuelto y conductividad. La relaci贸n entre las especies y las variables ambientales fue alta en ambos ejes (0.89 y 0.79). Ambientalmente, el r铆o se puede zonificar en 3 partes, aunque su ictiofauna puede dividirse en 2 conjuntos principales.AbstractComposition and structure of the Hondo River ichthyofauna and its spatial variation were determined as a function of environmental parameters. Six sites along the river were sampled in March, April and May 2012. Data for estimating structure of fish assemblages was obtained by means of a 58.5cm harpoon during 2 hours of free diving at each sampling site. The species list for the study area was completed with the aid of gillnets, longlines, double-cone traps, and hook-and-line. In addition, a bibliographical research performed as well as the ichthyological collection of ECOSUR at Chetumal was checked. The systematic list includes 40 species in 33 genera, 18 families and 11 orders. The richest family was Cichlidae, including the exotic Oreochromis niloticus. The environmental parameters that best described distribution and abundance of fish in the Hondo River were river width, distance to mouth, transparency, depth, dissolved oxygen concentration, and conductivity. Correlation between species and environmental parameters was high in both axis (0.89 and 0.79). The river was classified into 3 environmental zones, although its fish fauna could be divided in 2 main assemblages
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