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La Serena, Chile

The University of La Serena ) is a university in Chile. It is part of the Chilean Traditional Universities. It is located 350 miles north of Santiago. The university has five campuses: three in La Serena, one in Coquimbo, and one in Ovalle. It was founded in 1981, and approximately 8,000 students are currently enrolled there. Wikipedia.

Lazzus J.A.,University of La Serena
Journal of Molecular Liquids | Year: 2012

A new model based on group contribution method to predict the decomposition temperature of several ionic liquids is developed. Experimental data of 120 ionic liquids were used to obtain the contributions for the cation-anion groups in a correlation set. The optimum parameters of the method were obtained using a genetic algorithm-based on multivariate linear regression. Then, the melting temperatures of another 78 ionic liquids were predicted, and the results were compared with experimental data available in the literature. The results show that the group contribution method represents an excellent alternative for the estimation of the decomposition point of diverse ionic liquids from the knowledge of their molecular structure with a correlation coefficient of 0.9359 and average deviation of 4%. © 2012 Elsevier B.V. All rights reserved.

Lazzus J.A.,University of La Serena
Journal of Supercritical Fluids | Year: 2010

A method to estimate the solid vapor pressures of biomolecules using a biologically deriver algorithm is presented. The solid vapor pressure is usually small for most solid compounds and in many cases available experimental techniques cannot be used to obtain accurate values. Therefore, estimation methods must be used to obtain these data. Five binary gas-solid phase systems of supercritical CO2 + biomolecule containing caffeine, artemisinin, capsaicin, cholesterol, and β-carotene are considered in this study. Particle swarm optimization is used for minimize the difference between calculated and experimental solubility. Then, the solid vapor pressures of biomolecules are calculated from solubility data. The Peng-Robinson equation of state with the Wong-Sandler mixing rules are used to evaluate the fugacity coefficient on the systems. The results show that the method presented is reliable enough and can be used with confidence to estimate the solid vapor pressure of any organic biomolecule. © 2009 Elsevier B.V. All rights reserved.

Solid vapor pressures (PS) of pure compounds have been estimated at several temperatures using a hybrid model that includes an artificial neural network with particle swarm optimization and a group contribution method. A total of 700 data points of solid vapor pressure versus temperature, corresponding to 70 substances, have been used to train the neural network developed using Matlab. The following properties were considered as input parameters: 36 structural groups, molecular mass, dipole moment, temperature and pressure in the triple point (upper limit of the sublimation curve), and the limiting value PS → 0 as T → 0 (lower limit of the sublimation curve). Then, the solid vapor pressures of 28 other solids (280 data points) have been predicted and results compared to experimental data from the literature. The study shows that the proposed method represents an excellent alternative for the prediction of solid vapor pressures from the knowledge of some other available properties and from the structure of the molecule. © 2009 Elsevier B.V. All rights reserved.

Roman-Lopes A.,University of La Serena
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2012

In this work we report the discovery of a new Galactic O2If*/WN6 star, a rare member of the extremely massive hydrogen core-burning group of stars that, because of their high intrinsic luminosity (close to the Eddington limit), possess an emission-line spectrum at the beginning of their main-sequence evolution, mimicking the spectral appearance of classical Wolf-Rayet (WR) stars. The new star is named WR 42e and is found in isolation at 2.7arcmin (~6 pc) from the core of the starburst cluster NGC 3603. From the computed E(B - V) colour excess and observed visual magnitude it is possible to estimate its absolute visual magnitude as M V =-6.3 mag, which is a value similar to those obtained by other researchers for stars of similar spectral type both in the Galaxy and in the Large Magellanic Cloud. Considering the derived absolute visual magnitude, we compute a bolometric stellar luminosity of about 3.2 × 10 6 L⊙ Finally, we estimate the mass of the new O2If*/WN6 star by comparing its MTSY.-1.circledot observed magnitudes and colours with those of other probable NGC 3603 cluster members, finding that the initial mass of WR 42e possibly exceeds 100M⊙. © 2012 The Author. Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Roman-Lopes A.,University of La Serena
Monthly Notices of the Royal Astronomical Society | Year: 2013

In this paper, we report on the discovery of an O2 If*/WN6 star probably still partiallyembedded in its parental cocoon in the starburst cluster NGC 3603. From the observed size ofthe associated compact HII region, it has been possible to derive a probable dynamic age ofno more than 600 000 yr. Using the computed visual extinction value AV ~ 6.0 ± 0.2 mag, anabsolute visual magnitude MV = -5.7 mag has been obtained. For the assumed heliocentricdistance of 7.6 kpc, this results in a bolometric luminosity of 8 × 105 L. Also, from the Vmagnitude and the V - I colour of the new star, and from previous models for the massive starpopulation of NGC 3603, we estimate the mass of the binary (O2 If*/WN6 + O3 If) and thesingle star (O2 If*/WN6). For the binary, we find that the initial masses of each componentpossibly exceed 80 and 40 M·, respectively, while for the single star the initial mass of MTT58 is possibly in excess of 100 M·. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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