2,672 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
Methodology for hand-tool vibration analysis using bond graph
This paper presents an efficient and easy methodology for modeling the vibrational behavior of common portable tools using as example a hand-driller. The work described in this paper uses a Hand-Tool model previously developed by the authors and couples it with different Hand-Arm-System (HAS) in order to evaluate which one reproduces the most realistic vibrational behavior. Although proposed for hand-tools, it can be extended for any kind of tool that produces vibration during its operation. This methodology summarizes different techniques in order to analyze the vibrational system. The different components of the hand-driller are represented as lumped masses and the connections between them with a spring and a damper. The elastic constant for the structural elements are determined by FEA using SolidWorks simulations, while the damping constant values used are the recommended by the software 20-sim for structural damping. Once the model is developed, it will be shown how the corresponding Bond-Graph diagram can be obtained and how it helps in obtaining the equations that describe the model. The software 20-sim is used to simulate the developed Bond-Graph model and to determine the Hand-Arm system vibrational response for a specific excitation force
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
Effect of temperature in bursting of thalamic reticular cells
Objective: To show the relation between the four parameters associated to bursting discharges of the thalamic reticular cells (TRNn): the maximum firing frequency (fmax) and the temperature at which it occurs (Tfmax), the range of temperatures defined as the full width at half maximum (∆Th) and the maximum specific low threshold calcium conductance (GT). Materials and Methods: In order to simulate the TRNn bursting activity a computational simulation model was implemented using the NEURON software, which incorporates morphological and electrophysiological data and stimuli properties closely related to reality. Results: It was found that there are nonlinear relations between the parameters. The fmax frequency follows a quadratic grow with temperature and tends asymptotically towards a limit value with the maximum calcium conductance. In the same manner, ∆Th increases until reaching a limit value as function of fmax and GT. However, the increment per frequency unit is bigger than the increment per conductance unit. Conclusions: There were obtained four equations that model the relations between the parameters associated to bursting discharges of the TRNn in rats and other neurons with similar characteristics in different animal species
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
Chiral Mono- and α-Diimines and Their Pd(II) Complexes with Anticancer Activity
The aim of this review is to provide mainly an outlook of the synthesis and characterization of chiral mono- and α-diimines ligands and their Pd(II) complexes carried out in our group in the last few years. Some other issues with simple chiral imines synthesized in our lab are also outlined. The report includes details about their versatile coordination patterns, biological activity in cancer cell lines, and engaging properties in different fields, such as materials science
A review of a priori defined oxidative balance scores relative to their components and impact on health outcomes
Oxidative Balance Scores (OBSs) are tools that have emerged to evaluate the global balance
of individuals’ oxidation—reduction status. The aim was to compare OBSs available in the literature
regarding their characteristics and associations with chronic diseases in epidemiological studies.
Studies that developed OBSs were searched in PubMed until August 2018. A total of 21 OBSs were
identified. These OBSs presented different scoring schemes and different types of anti- and pro-oxidant
components, including dietary factors (dietary intake and/or nutrient biomarkers), lifestyle factors,
and medications. Most OBSs were based on over 10 components, and some included only dietary
factors. Few considered weighted components in the score. Only three OBSs were validated as
potential surrogates of oxidative balance through inflammation and OS-related biomarkers. Notably,
all the OBSs were associated—to a varying degree—with a reduced risk of cardiovascular diseases,
chronic kidney disease, colorectal adenomas, and different cancer types (colorectal and breast cancer),
as well as with all-cause and cancer-related mortality. For other outcomes, e.g., prostate cancer,
contradictory results were reported. In summary, there is a great heterogeneity in the definition
of OBSs. Most studies are concordant in supporting that excessive OS reflected by a lower OBS
has deleterious effects on health. Unified criteria for defining the proper OBSs, valuable to gauge
OS-related aspects of the diet and lifestyle that may lead to adverse health outcomes, are needed
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
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