Estrella Álvarez

Bio: Estrella Álvarez is an academic researcher from University of Vigo. The author has contributed to research in topics: Aqueous solution & Mass transfer. The author has an hindex of 23, co-authored 61 publications receiving 2562 citations. Previous affiliations of Estrella Álvarez include University of Santiago, Chile & University of Santiago de Compostela.

Surface Tension of Alcohol Water + Water from 20 to 50 .degree.C

Abstract: The surface tension of mixtures is a physical property of great importance for mass transfer processes such as distillation, extraction, or absorption. The surface tension of aqueous solutions of methanol, ethanol, 1-propanol, and 2-propanol was measured over the entire concentration range at temperatures of 20--50 C. The experimental values were correlated with temperature and with mole fraction. The maximum deviation was in both cases always less than 3%.

Surface Tension of Binary Mixtures of Water + Monoethanolamine and Water + 2-Amino-2-methyl-1-propanol and Tertiary Mixtures of These Amines with Water from 25 °C to 50 °C

Abstract: The surface tension of aqueous solutions of monoethanolamine, 2-amino-2-methyl-1-propanol, and monoethanolamine + 2-amino-2-methyl-1-propanol was measured at temperatures from 25 °C to 50 °C. The concentration ranges were 0−100 mass % monoethanolamine and 2-amino-2-methyl-1-propanol, and for tertiary mixtures 50 mass % total amine concentration (the concentration range for each amine was 0−50 mass %). The experimental values were correlated with temperature and mole fraction. The maximum deviation was in both cases always less than 0.5%.

Surface Tension of Organic Acids + Water Binary Mixtures from 20 °C to 50 °C

Abstract: The surface tensions of aqueous solutions of formic acid, acetic acid, and propionic acid were measured over the entire concentration range at temperatures (20 to 50) °C. The experimental values were correlated with temperature and mole fraction. Maximum deviations were in both cases always less than 1%.

The size, shape, albedo, density, and atmospheric limit of transneptunian object (50000) quaoar from multi-chord stellar occultations

Abstract: Fil: Braga Ribas, F.. Ministerio de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasil; . Laboratoire d;

Introduction to rheology

Abstract: Common to liquids, solids and substances in between the former two is that if a stress is applied to them, they will strain. Stress may be visualized by placing a small amount of fluid between two parallel plates. When one plate slides over the other, forces act on the fluid dependent upon the rate of the plate movement. This causes a shear stress on the liquid. Recall laminar flow of fluids through a tubular vessel. Strain is the response to the stress. If solids are elastic, they deform and return to their original shape. Since fluids are not elastic and, hence, viscous, their deformation is irreversible.

Methods Used to Evaluate Pain Behaviors in Rodents

Abstract: Rodents are commonly used to study the pathophysiological mechanisms of pain as studies in humans may be difficult to perform and ethically limited. As pain cannot be directly measured in rodents, many methods that quantify "pain-like" behaviors or nociception have been developed. These behavioral methods can be divided into stimulus-evoked or non-stimulus evoked (spontaneous) nociception, based on whether or not application of an external stimulus is used to elicit a withdrawal response. Stimulus-evoked methods, which include manual and electronic von Frey, Randall-Selitto and the Hargreaves test, were the first to be developed and continue to be in widespread use. However, concerns over the clinical translatability of stimulus-evoked nociception in recent years has led to the development and increasing implementation of non-stimulus evoked methods, such as grimace scales, burrowing, weight bearing and gait analysis. This review article provides an overview, as well as discussion of the advantages and disadvantages of the most commonly used behavioral methods of stimulus-evoked and non-stimulus-evoked nociception used in rodents.

Magnetically Driven Floating Foams for the Removal of Oil Contaminants from Water

Abstract: In this study, we present a novel composite material based on commercially available polyurethane foams functionalized with colloidal superparamagnetic iron oxide nanoparticles and submicrometer polytetrafluoroethylene particles, which can efficiently separate oil from water. Untreated foam surfaces are inherently hydrophobic and oleophobic, but they can be rendered water-repellent and oil-absorbing by a solvent-free, electrostatic polytetrafluoroethylene particle deposition technique. It was found that combined functionalization of the polytetrafluoroethylene-treated foam surfaces with colloidal iron oxide nanoparticles significantly increases the speed of oil absorption. Detailed microscopic and wettability studies reveal that the combined effects of the surface morphology and of the chemistry of the functionalized foams greatly affect the oil-absorption dynamics. In particular, nanoparticle capping molecules are found to play a major role in this mechanism. In addition to the water-repellent and oil-ab...

Interfacial tension of alkane + water systems

Abstract: Interfacial tension was measured for hexane + water, heptane + water, octane + water, nonane + water, decane + water, undecane + water, and dodecane + water, using the emergent drop experimental technique with a numerical method based on a fourth degree spline interpolation of the drop profile. The experimental equipment used to generate the drop consists of a cell with a stainless steel body and two Pyrex windows. The inner cell was previously filled with water. A surgical needle (at the bottom of the cell) was used to introduce the organic phase into the cell (forming the emergent drop). Water was used to keep the temperature constant inside the cell (between 10 °C and 60 °C). The cell was illuminated from the back using a fiber optic lamp and a diffuser. A video camera (with a 60 mm microlens and an extension ring) was located at the front window. The emergent drop image was captured and sent to the video recording system. The cell and the optical components were placed on an optical table with vibration isolation legs. A new correlation was found to predict interfacial tension (γ) as a function of temperature (t) and the number of carbon atoms (n) with a deviation of less than 0.05% from experimental values.

Density, viscosity, and surface tension of water+ethanol mixtures from 293 to 323K

Abstract: Density, viscosity, and surface tension of liquids are important physicochemical properties which affect mass and heat transfer in solutions. The density, viscosity, and surface tension of binary mixture of water+ethanol at 293, 298, 303, 308, 313, 318, and 323 K are reported and compared with the available literature data. The findings of these comparisons show how the measured data are reproducible from different laboratories. The molar volume of water+ ethanol mixtures are also calculated using measured density values. The Jouyban-Acree model was used for mathematical correlation of the data. The relative deviation (RD) was used as an error criterion and the RD values for correlation of density, viscosity, surface tension and molar volume data at investigated temperatures are 0.1±0.1%, 10.4±9.5%, 4.2±3.6%, and 0.3±0.3%, respectively. The corresponding RDs for the predicted properties after training using the experimental data at 298 K are 0.2±0.2%, 14.1±15.8%, 5.4±4.6% and 0.4±0.3%, respectively, for density, viscosity, surface tension, and molar volume data. This study shows that the Jouyban-Acree model can correlate/predict physicochemical properties of the mixtures of solvents at different temperatures with acceptable error in calculation.