Vítor Cardoso, Leonel Queimada,
The "cosmic censorship conjecture" asserts that all singularities arising from gravitational collapse are hidden within black holes. We investigate this conjecture in a setup of interest for tests of general relativity: black hole solutions which are parametrically small deviations away from the Kerr solution. These solutions have an upper bound on rotation, beyond which a naked singularity is visible to outside observers. We study whether these (generic) spacetimes can be spun-up past extremality ...
Tópico(s): Cosmology and Gravitation Theories
2015 - Springer Science+Business Media | General Relativity and Gravitation
Produção Nacional
Revisado por pares
Fátima Cibéle Soares, Rosmary Panno Mello, Márcia Xavier Peiter, Rogério Antônio Bellé, Adroaldo Dias Robaina, Gisele Aparecida Vivan, Ana Rita Costenaro Parizi,
... arroz carbonizada - CAC, cinza da casca de arroz queimada - CZ, fibra de coco - FC, terra do paraíso - TP, TP+CAC, TP+CZ, FC+ ...
Tópico(s): Banana Cultivation and Research
2012 - UNIVERSIDADE FEDERAL DE SANTA MARIA | Ciência Rural
José Natário, Leonel Queimada, Rodrigo Vicente,
We prove that (possibly charged) test fields satisfying the null energy condition at the event horizon cannot overspin/overcharge extremal Kerr–Newman or Kerr–Newman–anti de Sitter black holes, that is, the weak cosmic censorship conjecture cannot be violated in the test field approximation. The argument relies on black hole thermodynamics (without assuming cosmic censorship), and does not depend on the precise nature of the fields. We also discuss generalizations of this result to other extremal ...
Tópico(s): Astrophysical Phenomena and Observations
2016 - IOP Publishing | Classical and Quantum Gravity
Lucia M. Garozzo, Leonel Queimada, Oliver Schlotterer,
A bstract We construct new representations of tree-level amplitudes in D -dimensional gauge theories with deformations via higher-mass-dimension operators α ′ F 3 and α ′ 2 F 4 . Based on Berends-Giele recursions, the tensor structure of these amplitudes is compactly organized via off-shell currents. On the one hand, we present manifestly cyclic representations, where the complexity of the currents is systematically reduced. On the other hand, the duality between color and kinematics due to Bern, Carrasco ...
Tópico(s): Particle physics theoretical and experimental studies
2019 - Springer Nature | Journal of High Energy Physics
Kanato Goto, Hugo Marrochio, Robert C. Myers, Leonel Queimada, Beni Yoshida,
A bstract We revisit the complexity = action proposal for charged black holes. We investigate the complexity for a dyonic black hole, and we find the surprising feature that the late-time growth is sensitive to the ratio between electric and magnetic charges. In particular, the late-time growth rate vanishes when the black hole carries only a magnetic charge. If the dyonic black hole is perturbed by a light shock wave, a similar feature appears for the switchback effect, e.g. it is absent for purely ...
Tópico(s): Noncommutative and Quantum Gravity Theories
2019 - Springer Nature | Journal of High Energy Physics
Produção Nacional
Revisado por pares
Daniel Borini Alves, Swanni T. Alvarado,
... com base no produto MCD64A1 v006 de área queimada e a base de dados de uso e cobertura da terra do projeto Mapbiomas. O Cerrado apresentou 62,2% ...
Tópico(s): Fire effects on ecosystems
2020 - | GEOGRAFIA
Mariana B. Oliveira, João A. P. Coutinho, António J. Queimada,
Ester compounds are widely used in applications such as solvents, plasticizers, polymers, lubricants, cosmetics, medicinals, agrochemicals, soaps and other surface active agents, to mention a few. In many of these applications the simultaneous knowledge of the phase behavior and interfacial properties is an advantage for designing better products and improved processes. The van der Waals density gradient theory is an interesting theory providing such information. In this work it is applied for the ...
Tópico(s): Chemical Thermodynamics and Molecular Structure
2011 - Elsevier BV | Fluid Phase Equilibria
Mariana B. Oliveira, Vera L. Oliveira, João A. P. Coutinho, António J. Queimada,
Polycyclic aromatic hydrocarbons (PAHs) are a family of compounds characterized by having two or more condensed aromatic rings. They are important environmental contaminants associated with oil spills and the incomplete combustion of organic materials. Different models are available in the literature for estimating the aqueous solubilities of organic compounds, but the most accurate are frequently based on the correlation of experimental data, which hampers their use as predictive tools. In this ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2009 - American Chemical Society | Industrial & Engineering Chemistry Research
Mariana B. Oliveira, Isabel M. Marrucho, João A. P. Coutinho, António J. Queimada,
Despite the interest in systems containing non-associating compounds such as alkanes and fluoroalkanes or associating compounds like alkanols, their vapor–liquid interfaces have received little quantitative attention. Aiming at modeling the interfacial tensions of several families of chain molecules, a combination of the density gradient theory of fluid interfaces with the Cubic-Plus-Association (CPA) equation of state was developed. The density gradient theory is based on the phase equilibria of ...
Tópico(s): Advanced Thermodynamics and Statistical Mechanics
2008 - Elsevier BV | Fluid Phase Equilibria
Nuno M. Garrido, Miguel Jorge, António J. Queimada, Eugénia A. Macedo, Ioannis G. Economou,
A methodology is proposed for the prediction of the Gibbs energy of solvation (Δ(Solv)G) based on MD simulations. The methodology is then used to predict Δ(Solv)G of four solutes (namely propane, benzene, ethanol and acetone) in several solvents of different polarities (including n-hexane, n-hexadecane, ethylbenzene, 1-octanol, acetone and water) while testing the validity of the TraPPE force field parameters. Excellent agreement with experimental data is obtained, with average deviations of 0.2, 1. ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2011 - Royal Society of Chemistry | Physical Chemistry Chemical Physics
Miguel Jorge, Nuno M. Garrido, António J. Queimada, Ioannis G. Economou, Eugénia A. Macedo,
Although calculations of free energy using molecular dynamics simulations have gained significant importance in the chemical and biochemical fields, they still remain quite computationally intensive. Furthermore, when using thermodynamic integration, numerical evaluation of the integral of the Hamiltonian with respect to the coupling parameter may introduce unwanted errors in the free energy. In this paper, we compare the performance of two numerical integration techniques—the trapezoidal and Simpson' ...
Tópico(s): Advanced Chemical Physics Studies
2010 - American Chemical Society | Journal of Chemical Theory and Computation
Nuno M. Garrido, Miguel Jorge, António J. Queimada, Ioannis G. Economou, Eugénia A. Macedo,
In the present work, molecular dynamics calculations of the Gibbs energy of hydration of 10 different substituted barbiturates in SPC/E water were performed using thermodynamic integration. Given that experimental determination of the Gibbs hydration energy for this class of compounds is currently unfeasible, computer simulations appear as the only alternative for the estimation of this important quantity. Several simulation parameters are discussed and optimized based on calculations for barbituric ...
Tópico(s): Protein Structure and Dynamics
2009 - Elsevier BV | Fluid Phase Equilibria
F.L. Mota, António J. Queimada, Simão P. Pinho, Eugénia A. Macedo,
In this work, the aqueous solubilities of two hydroxybenzoic acids (gallic and salicylic acid) and three phenylpropenoic acids (trans-cinnamic, ferulic, and caffeic acids) are addressed. Measurements were performed, as a function of temperature, between 288.15 and 323.15 K, using the shake-flask method for generating the saturated aqueous solutions, followed by compositional analysis by spectrophotometric and gravimetric methods. The pH values of the saturated aqueous solutions were measured by potentiometry. ...
Tópico(s): Crystallization and Solubility Studies
2008 - American Chemical Society | Industrial & Engineering Chemistry Research
Produção Nacional
Newton Paulo de Souza Falção, Eluise S. Lopes, Erlon H. Martins Ferreira, Danielle Monteiro de Oliveira, Bráulio S. Archanjo, Carlos A. Achete, Joyce R. Araújo,
... locally known, in Amazon basin, as burnt earth (Terra Queimada).Among burnt earth soils, there are differences on ...
Tópico(s): Soil Management and Crop Yield
2019 - | Net Journal of Agricultural Science
Produção Nacional
Revisado por pares
Leonardo Waisman de Azevedo, Silvia Moehlecke Copé, Rita Scheel-Ybert,
... base côncava, conjuntos de pedras e presença de terra queimada. Tais características indicam o conhecimento de tecnologias determinantes ...
Tópico(s): History of Colonial Brazil
2013 - UNIVERSIDADE DO SUL DE SANTA CATARINA | Revista Memorare
Pedro J. Carvalho, Mara G. Freire, Isabel M. Marrucho, António J. Queimada, João A. P. Coutinho,
This work addresses surface tension measurements of eight imidazolium-based ionic liquids (ILs) with the bis(trifluoromethylsulfonyl)imide, Tf2N, common anion, and their dependence with temperature, from (293 to 353) K, at atmospheric pressure. The set of selected ionic liquids was chosen to provide a detailed and comprehensive study of the influence of the cation alkyl chain length on the surface tensions of the ionic liquids based on the Tf2N anion. It is shown that, unlike other ionic liquids, ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2008 - American Chemical Society | Journal of Chemical & Engineering Data
Mara G. Freire, Pedro J. Carvalho, Ana M. Fernandes, Isabel M. Marrucho, António J. Queimada, João A. P. Coutinho,
This work addresses the experimental measurements of the surface tension of eight imidazolium based ionic liquids (ILs) and their dependence with the temperature (288–353 K) and water content. The set of selected ionic liquids was chosen to provide a comprehensive study of the influence of the cation alkyl chain length, the number of cation substitutions and the anion on the properties under study. The influence of water content in the surface tension was studied for several ILs as a function of the ...
Tópico(s): Surfactants and Colloidal Systems
2007 - Elsevier BV | Journal of Colloid and Interface Science
André M. Palma, António J. Queimada, João A. P. Coutinho,
One of the major challenges of an equation of state lies in the description of water and aqueous systems. Its abundance and unique properties turn water into one of the most important molecules in the industry. However, because of these peculiar characteristics, its modeling is far more complex than for any other common solvent. In this work, a modified cubic plus association (CPA) model, which includes the correct description of the pure component critical temperature and critical pressure, is expanded ...
Tópico(s): Chemical Thermodynamics and Molecular Structure
2017 - American Chemical Society | Industrial & Engineering Chemistry Research
André M. Palma, Mariana B. Oliveira, António J. Queimada, João A. P. Coutinho,
Although the CPA EoS was initially developed 20 years ago to meet industrial solicitations, namely the need to describe mixtures of hydrocarbons and water, including the formation and dissociation of hydrates, it has only recently received a widespread use in mid-stream and downstream oil and gas processing, or in the petrochemical and chemical industries. One of the reasons for such limited use of the model in the industry is the necessity to parameterize every associating component from saturation ...
Tópico(s): Petroleum Processing and Analysis
2017 - Elsevier BV | Fluid Phase Equilibria
Pedro J. Carvalho, Luís M.C. Pereira, Neusa P.F. Gonçalves, António J. Queimada, João A. P. Coutinho,
A new high pressure cell was developed to measure the high pressure phase behavior of gas + aqueous salt solutions and validated through the measurement, and comparison against literature data, of two systems, the H2O + CO2 and H2O + CO2 + NaCl, at temperatures up to 363 K and pressures up to 13 MPa. As previously reported by others, a salting out effect on the carbon dioxide solubility in water by NaCl is observed, decreasing its solubility as the salt concentration increases. Electrolyte versions of the ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2014 - Elsevier BV | Fluid Phase Equilibria
Mariana B. Oliveira, Vítor Ribeiro, António J. Queimada, João A. P. Coutinho,
Liquid−liquid equilibrium (LLE) and vapor−liquid equilibrium (VLE) data of binary and ternary systems formed at the biodiesel production and purification industrial units were used to evaluate the performance of commonly used excess Gibbs energy (gE) models, cubic equations of state (EoS), equations of state with EoS−gE mixing rules, and association equation of state models. The models used in this study are the UNIFAC, Soave−Redlich−Kwong (SRK) EoS, the SRK-MHV2, the Peng−Robinson (PR) EoS using the ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2011 - American Chemical Society | Industrial & Engineering Chemistry Research
Mariana B. Oliveira, Sofia I. Miguel, António J. Queimada, João A. P. Coutinho,
The knowledge and the capability to describe the phase equilibria of binary systems formed by a fatty acid ester and an alcohol are of great interest in biodiesel production, where these mixtures can be found after the transesterification unit and where they must be separated to purify the biodiesel stream and to recover the unreacted alcohol. Despite this interest, little information is available on the vapor−liquid equilibria (VLE) of fatty acid ester + alcohol systems. To overcome this lack of data, ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2010 - American Chemical Society | Industrial & Engineering Chemistry Research
Nuno M. Garrido, António J. Queimada, Miguel Jorge, Eugénia A. Macedo, Ioannis G. Economou,
The 1-octanol/water partition coefficient is an important thermodynamic variable usually employed to understand and quantify the partitioning of solutes between aqueous and organic phases. It finds widespread use in many empirical correlations to evaluate the environmental fate of pollutants as well as in the design of pharmaceuticals. The experimental evaluation of 1-octanol/water partition coefficients is an expensive and time-consuming procedure, and thus, theoretical estimation methods are needed, ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2009 - American Chemical Society | Journal of Chemical Theory and Computation
Mariana B. Oliveira, Ana Rita R. Teles, António J. Queimada, João A. P. Coutinho,
Biodiesel is nowadays in Europe the most used biofuel for road transportation. During its production, different separation and purification processes are required for the glycerol rich streams such as the recovery of the unreacted alcohol and the removal of water. The adequate design of the recovery and purification steps requires the knowledge about the vapour–liquid equilibria data for water + glycerol and alcohol + glycerol systems that are surprisingly scarce. To overcome this lack of information, ...
Tópico(s): Chemical and Physical Properties in Aqueous Solutions
2009 - Elsevier BV | Fluid Phase Equilibria
Mariana B. Oliveira, Mara G. Freire, Isabel M. Marrucho, Georgios M. Kontogeorgis, António J. Queimada, João A. P. Coutinho,
Fluorocarbons (FCs) are a family of chemicals that are composed primarily of carbon and fluorine. They present weak intermolecular and strong intramolecular interactions, which confers them unusual thermophysical properties. They can also solubilize large amounts of gases such as oxygen and carbon dioxide, making them interesting for several biomedical applications. In most of these applications, water or aqueous systems are present for which the knowledge of the mutual solubilities between the fluorocarbons ...
Tópico(s): Spectroscopy and Quantum Chemical Studies
2007 - American Chemical Society | Industrial & Engineering Chemistry Research
F.L. Mota, António J. Queimada, Simão P. Pinho, Eugénia A. Macedo,
Although of extreme importance for evaluating the effective therapeutic action, aqueous solubility data involving drug-like molecules are scarce. Thermodynamic models can be used to estimate these solubilities, and different models, namely activity coefficient models, have been applied for that purpose. Still, these frequently cannot describe with accuracy broad temperature and pressure ranges, various solvent compositions or multifunctional molecules. Despite the success of the cubic-plus-association ( ...
Tópico(s): Chemical Thermodynamics and Molecular Structure
2010 - Elsevier BV | Fluid Phase Equilibria
António J. Queimada, F.L. Mota, Simão P. Pinho, Eugénia A. Macedo,
Aqueous solubilities of natural phenolic compounds from different families (hydroxyphenyl, polyphenol, hydroxybenzoic, and phenylpropenoic) were experimentally obtained. Measurements were performed on tyrosol and ellagic, protocatechuic, syringic, and o-coumaric acids, at five different temperatures (from 288.2 to 323.2 K), using the standard shake-flask method, followed by compositional analysis using UV spectrophotometry. To verify the accuracy of the spectrophotometric method, some data points ...
Tópico(s): Chemical Thermodynamics and Molecular Structure
2009 - American Chemical Society | The Journal of Physical Chemistry B
F.L. Mota, Aristides P. Carneiro, António J. Queimada, Simão P. Pinho, Eugénia A. Macedo,
In this work, pure solvent solubilities of drugs, such as paracetamol, allopurinol, furosemide and budesonide, measured in the temperature range between 298.2–315.2 K are presented. The solvents under study were water, ethanol, acetone, ethyl acetate, carbon tetrachloride and n-hexane. Measurements were performed using the shake-flask method for generating the saturated solutions followed by compositional analysis by HPLC. Previous literature values on the solubilities of paracetamol were used to ...
Tópico(s): Thermodynamic properties of mixtures
2009 - Elsevier BV | European Journal of Pharmaceutical Sciences
André M. Palma, Mariana B. Oliveira, António J. Queimada, João A. P. Coutinho,
To create a predictive method for an associative equation of state, the parameters of a specific associative group should be transferrable among molecules. The hydroxyl group, one of the most common associative groups, is a good starting point for this development. On the basis of a previous study where a modified version of the Cubic Plus Association (CPA) EoS was shown to present accurate results for alkanols with almost constant association parameters, this work addresses branched, secondary alcohols, ...
Tópico(s): Petroleum Processing and Analysis
2017 - American Chemical Society | Industrial & Engineering Chemistry Research
Nuno M. Garrido, Ioannis G. Economou, António J. Queimada, Miguel Jorge, Eugénia A. Macedo,
Abstract In recent years molecular simulation has emerged as a useful tool to predict physical properties of complex chemical systems. A methodology to estimate the n ‐hexane/water and 1‐octanol/water partition coefficients of environmentally relevant solutes, namely substituted alkyl‐aromatic molecules, chlorobenzenes, polychlorinated biphenyls (PCBs) and polychlorinated diphenyl ethers (PCDEs) using molecular simulation is elucidated here. The partition coefficients are calculated based on the absolute ...
Tópico(s): Analytical Chemistry and Chromatography
2011 - Wiley | AIChE Journal