2,178 research outputs found
Behavior of Clayey Soil Existing in the Portoviejo Canton and Its Neutralization Characteristics
An investigation has been carried out on soil characterization and behavior in the canton of Portoviejo province of Manabí, in the Eloy Alfaro street sector of the Andrés de Vera Parish; where pits or open-air surveys were carried out and experimental laboratory tests of soils. It was demonstrated that soils have expansive properties of different characteristics, from medium to high degree of expansively according to the results of Laboratory of Soil Mechanics, where samples were tested analyzing the behavior according to the soil type. In this context, the results obtained by incorporating lime into the mixture are presented in 3 and 6%, thus obtaining a reduction by contraction to the volumetric change of the soil between 8 and 13%, allowing to improve its physical and mechanical properties; as well as its increase to bearing capacity by the California Bearing Ratio (CBR) test method from 9 to 16%, thus improving soil plasticity. With the results obtained, a description of the soil could be elaborated to determine the variations and changes according to the lime content, which was added to the soil, which allowed to reduce the deformations and damages caused to the superficial and structural pavement caused by the clays expansive, because in contact with the water the soil expands and at the same time when it drains the water contracts, proving that stabilizing the expansive clays with hydrated lime would improve the conditions of the pavement and its useful life
Path-integral molecular dynamics simulation of 3C-SiC
Molecular dynamics simulations of 3C-SiC have been performed as a function of
pressure and temperature. These simulations treat both electrons and atomic
nuclei by quantum mechanical methods. While the electronic structure of the
solid is described by an efficient tight-binding Hamiltonian, the nuclei
dynamics is treated by the path integral formulation of statistical mechanics.
To assess the relevance of nuclear quantum effects, the results of quantum
simulations are compared to others where either the Si nuclei, the C nuclei or
both atomic nuclei are treated as classical particles. We find that the
experimental thermal expansion of 3C-SiC is realistically reproduced by our
simulations. The calculated bulk modulus of 3C-SiC and its pressure derivative
at room temperature show also good agreement with the available experimental
data. The effect of the electron-phonon interaction on the direct electronic
gap of 3C-SiC has been calculated as a function of temperature and related to
results obtained for bulk diamond and Si. Comparison to available experimental
data shows satisfactory agreement, although we observe that the employed
tight-binding model tends to overestimate the magnitude of the electron-phonon
interaction. The effect of treating the atomic nuclei as classical particles on
the direct gap of 3C-SiC has been assessed. We find that non-linear quantum
effects related to the atomic masses are particularly relevant at temperatures
below 250 K.Comment: 14 pages, 15 figure
Determination of Physical and Mechanical Properties of Quarries Dos Bocas Mouths and Mine Copeto for High Resistance Concretes
The importance of the use, the type and the correct quality of the aggregate (aggregate) cannot be underestimated. Thin and coarse aggregates occupy about 60% to 80% of the volume of the concrete (70% to 85% of the mass) and strongly influence the properties both in the fresh and hardened state, in the proportions of the mixture and the economy of the concrete. Due to the great importance of the quality of the materials that must be used for high strength concretes, this research has been conducted to determine if the aggregates of the Dos Bocas and Copeto quarries meet the requirements outlined in the standards MOP-001 - F- 2002 for high resistance concretes. The bulk material was taken from the Dos Bocas quarry located in Puerto Cayo, Province of Manabí, and the fine aggregate was obtained from the Copeto Mine that is located in the Santo Domingo sector, Santo Domingo de los Tsáchilas Province. The tests executed in the Laboratory of Soil Mechanics, consisted in determining the quality index of the aggregate, calculating the maximum percentage of mass wear, determination of minimum and maximum percentages that pass through the standard sieves, volumetric mass, absorption and surface moisture. For a better understanding and interpretation of the results obtained from the different tests. We proceeded to graphically represent each of them for the two types of aggregates, allowing us to compare the property of each material with its respective specification, as mentioned in the Technical Specifications of the Ministry of Public Works MOP-001 - F- 2002
Hydrogen and muonium in diamond: A path-integral molecular dynamics simulation
Isolated hydrogen, deuterium, and muonium in diamond have been studied by
path-integral molecular dynamics simulations in the canonical ensemble.
Finite-temperature properties of these point defects were analyzed in the range
from 100 to 800 K. Interatomic interactions were modeled by a tight-binding
potential fitted to density-functional calculations. The most stable position
for these hydrogenic impurities is found at the C-C bond center. Vibrational
frequencies have been obtained from a linear-response approach, based on
correlations of atom displacements at finite temperatures. The results show a
large anharmonic effect in impurity vibrations at the bond center site, which
hardens the vibrational modes with respect to a harmonic approximation.
Zero-point motion causes an appreciable shift of the defect level in the
electronic gap, as a consequence of electron-phonon interaction. This defect
level goes down by 70 meV when replacing hydrogen by muonium.Comment: 11 pages, 8 figure
Use of Concrete Debris
Natural disasters in a very short time are capable of destroying what man has built using different types of resources, the construction of buildings, houses, etc. In their construction processes, they use different materials in a separate way that mixes and this process give them hardness and resistance to these materials. When they are destroyed they lose their individual properties and become waste; this research aims to make a study of the NEVI-12-MTOP standards, to be able to reuse the debris materials generated by the destruction of the earthquake on April 16. A bibliographic search was carried out related to the use given to waste caused by earthquakes in different countries. In the city of Portoviejo, the largest amount of debris was a concrete waste, and it can be concluded that these materials can be used as sub-base material in the road structures, so the reuse method was proposed. In particular, the characteristics of the residual materials were obtained as a result of the analysis of environmental, economic and material safety feasibility
Population-based prevalence of cervical infection with human papillomavirus genotypes 16 and 18 and other high risk types in Tlaxcala, Mexico
This study was supported by the National Institute of Public Health of
Mexico, the Coordinación de Investigación en Salud del Instituto Mexicano
del Seguro Social, the Secretaría de Salud Tlaxcala, the Instituto Nacional de
las Mujeres, and the Consejo Nacional de Ciencia y Tecnología [FOSISS 2013
202468]. Additional support has been provided by Roche Diagnostics, BD
Diagnostics, DICIPA and Arbor Vita Corporation. The study sponsors did not
played a role in designing the study, collecting, analyzing or interpreting the
data, writing the report, or submitting this paper for publication. UC Berkeley
Center for Global Public Health, Schoeneman Grant, Joint Medical Program
Thesis Grant, and Cancer Research UK (C569/A10404)
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic
data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data
release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median
z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar
spectra, along with the data presented in previous data releases. These spectra
were obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline, which
determines radial velocities, surface temperatures, surface gravities, and
metallicities of stars, has been updated and refined with improvements in
temperature estimates for stars with T_eff<5000 K and in metallicity estimates
for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars
presented in DR8, including stars from SDSS-I and II, as well as those observed
as part of the SDSS-III Sloan Extension for Galactic Understanding and
Exploration-2 (SEGUE-2).
The astrometry error introduced in the DR8 imaging catalogs has been
corrected in the DR9 data products. The next data release for SDSS-III will be
in Summer 2013, which will present the first data from the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) along with another year of
data from BOSS, followed by the final SDSS-III data release in December 2014.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at
http://www.sdss3.org/dr
The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with
new instrumentation and new surveys focused on Galactic structure and chemical
evolution, measurements of the baryon oscillation feature in the clustering of
galaxies and the quasar Ly alpha forest, and a radial velocity search for
planets around ~8000 stars. This paper describes the first data release of
SDSS-III (and the eighth counting from the beginning of the SDSS). The release
includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap,
bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a
third of the Celestial Sphere. All the imaging data have been reprocessed with
an improved sky-subtraction algorithm and a final, self-consistent photometric
recalibration and flat-field determination. This release also includes all data
from the second phase of the Sloan Extension for Galactic Understanding and
Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars
at both high and low Galactic latitudes. All the more than half a million
stellar spectra obtained with the SDSS spectrograph have been reprocessed
through an improved stellar parameters pipeline, which has better determination
of metallicity for high metallicity stars.Comment: Astrophysical Journal Supplements, in press (minor updates from
submitted version
The state of the Martian climate
60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
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