We introduce a new nonextensive entropic measure that grows like , where N is the size of the sys... more We introduce a new nonextensive entropic measure that grows like , where N is the size of the system under consideration. This kind of nonextensivity arises in a natural way in some N-body systems endowed with long-range interactions described by interparticle potentials. The power law (weakly nonextensive) behavior exhibited by is intermediate between (1) the linear (extensive) regime characterizing the standard Boltzmann-Gibbs entropy and (2) the exponential law (strongly nonextensive) behavior associated with the Tsallis generalized q-entropies. The functional is parametrized by the real number in such a way that the standard logarithmic entropy is recovered when . We study the mathematical properties of the new entropy, showing that the basic requirements for a well behaved entropy functional are verified, i.e., possesses the usual properties of positivity, equiprobability, concavity and irreversibility and verifies Khinchin axioms except the one related to additivity since is nonextensive. For , the entropy becomes superadditive in the thermodynamic limit. The present formalism is illustrated by a numerical study of the thermodynamic scaling laws of a ferromagnetic Ising model with long-range interactions.
It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixtu... more It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in an aerogel with a high degree of porosity (e.g., of the order of 95 to 99%). A Hamiltonian model for this system has recently been introduced . We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations.
We study the one-dimensional Ising model with long-range interactions in the context of Tsallis n... more We study the one-dimensional Ising model with long-range interactions in the context of Tsallis nonextensive statistics by computing numerically the number of states with a given energy. We find that the internal energy, magnetization, entropy, and free energy follow nontrivial scaling laws with the number of constituents N and temperature T. Each of the scaling functions for the internal energy, the magnetization, and the free energy, adopts three different forms corresponding to q . 1, q 1, and q , 1, q being the nonextensivity parameter of Tsallis statistics. 05.50. + q, 05.70.Ce, 75.10.Hk It is generally assumed that thermodynamics and statistical mechanics necessarily imply that the entropy, the internal energy, and other thermodynamic potentials are extensive quantities. For instance, the internal energy E, as a function of temperature T and number of constituents N, scales usually as
Physica A-statistical Mechanics and Its Applications, 2000
We present a new method devised to overcome the intrinsic difficulties associated to the numerica... more We present a new method devised to overcome the intrinsic difficulties associated to the numerical simulations of the Tsallis statistics. We use a standard Metropolis Monte Carlo algorithm at a fictitious temperature T ′ , combined with a numerical integration method for the calculation of the entropy in order to evaluate the actual temperature T . We illustrate the method by applying it to the 2d-Ising model using a standard reweighting technique.
It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixtu... more It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in an aerogel with a high degree of porosity (e.g., of the order of 95 to 99%). A Hamiltonian model for this system has recently been introduced [1]. We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations.
Journal of Polymer Science Part A-polymer Chemistry, 2003
The effect of treating several commercially important emulsion polymers with different initiator ... more The effect of treating several commercially important emulsion polymers with different initiator systems was investigated. The initiator system producing highly reactive tert-butoxyl radicals was able to cause polymer modification. This represented an opportunity to ...
... Daniel Alvarez, Louis Da Cunha, María J. Barandiaran, and José M. Asua*. ... US Patent 588614... more ... Daniel Alvarez, Louis Da Cunha, María J. Barandiaran, and José M. Asua*. ... US Patent 5886140, 1999. (5) Sempio, C.; Saija, LM; Novellara, RE; Montessoro, E. Low VOC Emulsion. EP Patent 0767180 A1, 1997. (6) Moore, JD; Feast, AA Emulsion Polymerization Process. ...
We propose a variant of the simulated annealing method for optimization in the multivariate analy... more We propose a variant of the simulated annealing method for optimization in the multivariate analysis of differentiable functions. The method uses global actualizations via the hybrid Monte Carlo algorithm in their generalized version for the proposal of new configurations. We show how this choice can improve upon the performance of simulated annealing methods (mainly when the number of variables is large) by allowing a more effective searching scheme and a faster annealing schedule.
Journal of Polymer Science Part A-polymer Chemistry, 2002
Emulsion polymerization is the major industrial process for manufacturing a wide range of product... more Emulsion polymerization is the major industrial process for manufacturing a wide range of products such as paints, binders, and adhesives. In this process, as well as in other polymerization processes, polymerization rarely proceeds to 100% conversion, and therefore some ...
A large number of ceramic sherds from Chavin, Peru, as well as recent clay samples from the same ... more A large number of ceramic sherds from Chavin, Peru, as well as recent clay samples from the same region have been studied by Mössbauer spectroscopy. The changes of the Mössbauer spectra of the clay were studied as a function of firing temperature and atmosphere. From a comparison of these data with those form the sherds one can make estimates of the precolumbian firing conditions.
We describe in detail two numerical simulation methods valid to study systems whose thermostatist... more We describe in detail two numerical simulation methods valid to study systems whose thermostatistics is described by generalized entropies, such as Tsallis. The methods are useful for applications to non-trivial interacting systems with a large number of degrees of freedom, and both short-range and long-range interactions. The first method is quite general and it is based on the numerical evaluation of the density of states with a given energy. The second method is more specific for Tsallis thermostatistics and it is based on a standard Monte Carlo Metropolis algorithm along with a numerical integration procedure. We show here that both methods are robust and efficient. We present results of the application of the methods to the one-dimensional Ising model both in a short-range case and in a long-range (non-extensive) case. We show that the thermodynamic potentials for different values of the system size N and different values of the non-extensivity parameter q can be described by scaling relations which are an extension of the ones holding for the Boltzmann-Gibbs statistics (q = 1). Finally, we discuss the differences in using standard or non-standard mean value definitions in the Tsallis thermostatistics formalism and present a microcanonical ensemble calculation approach of the averages.
Physica A-statistical Mechanics and Its Applications, 2002
We compute numerically the distribution of energies (E; N ) for the XY-model with shortand long-r... more We compute numerically the distribution of energies (E; N ) for the XY-model with shortand long-range interactions. We ÿnd that in both cases the distribution can be ÿtted to the functional form: (E; N ) ∼ exp (N (E; N )), with (E; N ) an intensive function of the energy. (R. Salazar). 1 A quantity is said to be non-extensive if its asymptotic dependence on the system's size N is non-linear. On the contrary, extensive quantities exhibit a linear dependence on N .
Physica A-statistical Mechanics and Its Applications, 2001
We describe in detail two numerical simulation methods valid to study systems whose thermostatist... more We describe in detail two numerical simulation methods valid to study systems whose thermostatistics is described by generalized entropies, such as Tsallis. The methods are useful for applications to non-trivial interacting systems with a large number of degrees of freedom, and both short-range and long-range interactions. The first method is quite general and it is based on the numerical evaluation of the density of states with a given energy. The second method is more specific for Tsallis thermostatistics and it is based on a standard Monte Carlo Metropolis algorithm along with a numerical integration procedure. We show here that both methods are robust and efficient. We present results of the application of the methods to the one-dimensional Ising model both in a short-range case and in a long-range (non-extensive) case. We show that the thermodynamic potentials for different values of the system size N and different values of the non-extensivity parameter q can be described by scaling relations which are an extension of the ones holding for the Boltzmann-Gibbs statistics (q = 1). Finally, we discuss the differences in using standard or non-standard mean value definitions in the Tsallis thermostatistics formalism and present a microcanonical ensemble calculation approach of the averages.
To obtain information on the firing of inca ceramics, 7 samples from different locations were stu... more To obtain information on the firing of inca ceramics, 7 samples from different locations were studied by Mössbauer spectroscopy including a detailed laboratory refiring procedure. The glaze typical for the surface of this ware was studied by Mössbauer scattering.
Several knowledge-based strategies for the efficient and consistent production of high performanc... more Several knowledge-based strategies for the efficient and consistent production of high performance emulsion polymers are discussed. These strategies involve the understanding of the effect of the process variables on polymer microstructure, as well as the development of quantitative polymer microstructure/product properties relationships. Case studies included tailoring adhesive properties, efficient use of reactive surfactants and optimal monomer removal by postpolymerization.
An illite separated from mylonites from the southern rim of the Bohemian massif was studied by Mö... more An illite separated from mylonites from the southern rim of the Bohemian massif was studied by Mössbauer spectroscopy at temperatures between 300 and 1.8 K. The iron is mainly contained in oxides associated with the illite. Only 13% of the iron are structural Fe3+ and Fe2+ within the clay mineral matrix. The transformations of the oxidic iron during heating at temperatures up to 1250°C were followed by Mössbauer measurements at 300 and 4.2 K.
The performance of devolatilization for cleaning industrial latexes was investigated. It was foun... more The performance of devolatilization for cleaning industrial latexes was investigated. It was found that both steam and air saturated with water were very efficient in volatile organic compound (VOC) removal, as well as in controlling the solids content. No dependence of ...
We report a patient with simultaneous presentation of two histologically grade 2 conventional cho... more We report a patient with simultaneous presentation of two histologically grade 2 conventional chondrosarcomas non-derived from pre-existing cartilaginous lesions, in the absence of pulmonary or visceral involvement. One tumour was located at the right proximal femur and the other one at the right scapula. There was no evidence of local recurrence or pulmonary or visceral involvement three years and a half after total scapulectomy and resection of the proximal third of the femur. To the best of our knowledge, this is the first report of a patient with two nonmonomelic synchronous chondrosarcomas arising in two previously normal bones of the skeleton. Such cases are often difficult to differentiate from metastatic disease.
We introduce a new nonextensive entropic measure that grows like , where N is the size of the sys... more We introduce a new nonextensive entropic measure that grows like , where N is the size of the system under consideration. This kind of nonextensivity arises in a natural way in some N-body systems endowed with long-range interactions described by interparticle potentials. The power law (weakly nonextensive) behavior exhibited by is intermediate between (1) the linear (extensive) regime characterizing the standard Boltzmann-Gibbs entropy and (2) the exponential law (strongly nonextensive) behavior associated with the Tsallis generalized q-entropies. The functional is parametrized by the real number in such a way that the standard logarithmic entropy is recovered when . We study the mathematical properties of the new entropy, showing that the basic requirements for a well behaved entropy functional are verified, i.e., possesses the usual properties of positivity, equiprobability, concavity and irreversibility and verifies Khinchin axioms except the one related to additivity since is nonextensive. For , the entropy becomes superadditive in the thermodynamic limit. The present formalism is illustrated by a numerical study of the thermodynamic scaling laws of a ferromagnetic Ising model with long-range interactions.
It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixtu... more It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in an aerogel with a high degree of porosity (e.g., of the order of 95 to 99%). A Hamiltonian model for this system has recently been introduced . We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations.
We study the one-dimensional Ising model with long-range interactions in the context of Tsallis n... more We study the one-dimensional Ising model with long-range interactions in the context of Tsallis nonextensive statistics by computing numerically the number of states with a given energy. We find that the internal energy, magnetization, entropy, and free energy follow nontrivial scaling laws with the number of constituents N and temperature T. Each of the scaling functions for the internal energy, the magnetization, and the free energy, adopts three different forms corresponding to q . 1, q 1, and q , 1, q being the nonextensivity parameter of Tsallis statistics. 05.50. + q, 05.70.Ce, 75.10.Hk It is generally assumed that thermodynamics and statistical mechanics necessarily imply that the entropy, the internal energy, and other thermodynamic potentials are extensive quantities. For instance, the internal energy E, as a function of temperature T and number of constituents N, scales usually as
Physica A-statistical Mechanics and Its Applications, 2000
We present a new method devised to overcome the intrinsic difficulties associated to the numerica... more We present a new method devised to overcome the intrinsic difficulties associated to the numerical simulations of the Tsallis statistics. We use a standard Metropolis Monte Carlo algorithm at a fictitious temperature T ′ , combined with a numerical integration method for the calculation of the entropy in order to evaluate the actual temperature T . We illustrate the method by applying it to the 2d-Ising model using a standard reweighting technique.
It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixtu... more It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in an aerogel with a high degree of porosity (e.g., of the order of 95 to 99%). A Hamiltonian model for this system has recently been introduced [1]. We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations.
Journal of Polymer Science Part A-polymer Chemistry, 2003
The effect of treating several commercially important emulsion polymers with different initiator ... more The effect of treating several commercially important emulsion polymers with different initiator systems was investigated. The initiator system producing highly reactive tert-butoxyl radicals was able to cause polymer modification. This represented an opportunity to ...
... Daniel Alvarez, Louis Da Cunha, María J. Barandiaran, and José M. Asua*. ... US Patent 588614... more ... Daniel Alvarez, Louis Da Cunha, María J. Barandiaran, and José M. Asua*. ... US Patent 5886140, 1999. (5) Sempio, C.; Saija, LM; Novellara, RE; Montessoro, E. Low VOC Emulsion. EP Patent 0767180 A1, 1997. (6) Moore, JD; Feast, AA Emulsion Polymerization Process. ...
We propose a variant of the simulated annealing method for optimization in the multivariate analy... more We propose a variant of the simulated annealing method for optimization in the multivariate analysis of differentiable functions. The method uses global actualizations via the hybrid Monte Carlo algorithm in their generalized version for the proposal of new configurations. We show how this choice can improve upon the performance of simulated annealing methods (mainly when the number of variables is large) by allowing a more effective searching scheme and a faster annealing schedule.
Journal of Polymer Science Part A-polymer Chemistry, 2002
Emulsion polymerization is the major industrial process for manufacturing a wide range of product... more Emulsion polymerization is the major industrial process for manufacturing a wide range of products such as paints, binders, and adhesives. In this process, as well as in other polymerization processes, polymerization rarely proceeds to 100% conversion, and therefore some ...
A large number of ceramic sherds from Chavin, Peru, as well as recent clay samples from the same ... more A large number of ceramic sherds from Chavin, Peru, as well as recent clay samples from the same region have been studied by Mössbauer spectroscopy. The changes of the Mössbauer spectra of the clay were studied as a function of firing temperature and atmosphere. From a comparison of these data with those form the sherds one can make estimates of the precolumbian firing conditions.
We describe in detail two numerical simulation methods valid to study systems whose thermostatist... more We describe in detail two numerical simulation methods valid to study systems whose thermostatistics is described by generalized entropies, such as Tsallis. The methods are useful for applications to non-trivial interacting systems with a large number of degrees of freedom, and both short-range and long-range interactions. The first method is quite general and it is based on the numerical evaluation of the density of states with a given energy. The second method is more specific for Tsallis thermostatistics and it is based on a standard Monte Carlo Metropolis algorithm along with a numerical integration procedure. We show here that both methods are robust and efficient. We present results of the application of the methods to the one-dimensional Ising model both in a short-range case and in a long-range (non-extensive) case. We show that the thermodynamic potentials for different values of the system size N and different values of the non-extensivity parameter q can be described by scaling relations which are an extension of the ones holding for the Boltzmann-Gibbs statistics (q = 1). Finally, we discuss the differences in using standard or non-standard mean value definitions in the Tsallis thermostatistics formalism and present a microcanonical ensemble calculation approach of the averages.
Physica A-statistical Mechanics and Its Applications, 2002
We compute numerically the distribution of energies (E; N ) for the XY-model with shortand long-r... more We compute numerically the distribution of energies (E; N ) for the XY-model with shortand long-range interactions. We ÿnd that in both cases the distribution can be ÿtted to the functional form: (E; N ) ∼ exp (N (E; N )), with (E; N ) an intensive function of the energy. (R. Salazar). 1 A quantity is said to be non-extensive if its asymptotic dependence on the system's size N is non-linear. On the contrary, extensive quantities exhibit a linear dependence on N .
Physica A-statistical Mechanics and Its Applications, 2001
We describe in detail two numerical simulation methods valid to study systems whose thermostatist... more We describe in detail two numerical simulation methods valid to study systems whose thermostatistics is described by generalized entropies, such as Tsallis. The methods are useful for applications to non-trivial interacting systems with a large number of degrees of freedom, and both short-range and long-range interactions. The first method is quite general and it is based on the numerical evaluation of the density of states with a given energy. The second method is more specific for Tsallis thermostatistics and it is based on a standard Monte Carlo Metropolis algorithm along with a numerical integration procedure. We show here that both methods are robust and efficient. We present results of the application of the methods to the one-dimensional Ising model both in a short-range case and in a long-range (non-extensive) case. We show that the thermodynamic potentials for different values of the system size N and different values of the non-extensivity parameter q can be described by scaling relations which are an extension of the ones holding for the Boltzmann-Gibbs statistics (q = 1). Finally, we discuss the differences in using standard or non-standard mean value definitions in the Tsallis thermostatistics formalism and present a microcanonical ensemble calculation approach of the averages.
To obtain information on the firing of inca ceramics, 7 samples from different locations were stu... more To obtain information on the firing of inca ceramics, 7 samples from different locations were studied by Mössbauer spectroscopy including a detailed laboratory refiring procedure. The glaze typical for the surface of this ware was studied by Mössbauer scattering.
Several knowledge-based strategies for the efficient and consistent production of high performanc... more Several knowledge-based strategies for the efficient and consistent production of high performance emulsion polymers are discussed. These strategies involve the understanding of the effect of the process variables on polymer microstructure, as well as the development of quantitative polymer microstructure/product properties relationships. Case studies included tailoring adhesive properties, efficient use of reactive surfactants and optimal monomer removal by postpolymerization.
An illite separated from mylonites from the southern rim of the Bohemian massif was studied by Mö... more An illite separated from mylonites from the southern rim of the Bohemian massif was studied by Mössbauer spectroscopy at temperatures between 300 and 1.8 K. The iron is mainly contained in oxides associated with the illite. Only 13% of the iron are structural Fe3+ and Fe2+ within the clay mineral matrix. The transformations of the oxidic iron during heating at temperatures up to 1250°C were followed by Mössbauer measurements at 300 and 4.2 K.
The performance of devolatilization for cleaning industrial latexes was investigated. It was foun... more The performance of devolatilization for cleaning industrial latexes was investigated. It was found that both steam and air saturated with water were very efficient in volatile organic compound (VOC) removal, as well as in controlling the solids content. No dependence of ...
We report a patient with simultaneous presentation of two histologically grade 2 conventional cho... more We report a patient with simultaneous presentation of two histologically grade 2 conventional chondrosarcomas non-derived from pre-existing cartilaginous lesions, in the absence of pulmonary or visceral involvement. One tumour was located at the right proximal femur and the other one at the right scapula. There was no evidence of local recurrence or pulmonary or visceral involvement three years and a half after total scapulectomy and resection of the proximal third of the femur. To the best of our knowledge, this is the first report of a patient with two nonmonomelic synchronous chondrosarcomas arising in two previously normal bones of the skeleton. Such cases are often difficult to differentiate from metastatic disease.
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Papers by Rafael Salazar