arXiv subjects

F. Brouers

Publications and source records attributed to F. Brouers.

12 recordsLinked to original sources

arXiv2019

The use of the fractal Brouers-Sotolongo formalism to analyze the kinetics of drug release

We have applied the Brouers-Sotolongo fractal kinetic equation (BSf(t,n,α)), improving notably the precision, to nine cases reported recently in the literature on drug release. The reason of using this equation is that it contains as approximations some of the mostly used empirical formula used in that field. Moreover, this equation is now successfully employed for the investigation of sorption of contaminants in aqueous media. An important extension of the BSf(t,n,α) has been the introduction of variation of the fractal time coefficient (α(t^ν )). This improvement can lead to a greater precision of the fits and deduce some hint on the nature of the drug release process which can give precious information to propose microscopic molecular ad hoc models. We, therefore, suggest the use of the BSf(t,n,α(t^ν)) formula, as a first step, in any detailed investigation and practical application of drug release data both in vitro and in vivo studies starting with the Weibull and Hill approximations to follow properly the physical solution.

physics.med-ph↗

arXiv2016

The Burr 12 Distribution Family and the Maximum Entropy Principle: Power-Law Phenomena are not necessarily Nonextensive

In this paper we recall for physicists how it is possible, using the principle of maximization of the Boltzmann-Shannon entropy, to derive the Burr-Bingh-Maddala (burr12) double power law probability distribution function and its approximations (Pareto, loglogistic ..) and extension first used in econometrics. this is possible using a deformation of the power function, as this has been done in complex systems for the exponential function. We give to that distribution a deep stochastic interpretation using the theory of Weron et al. applied to thermodynamics the entropy nonextensivity can be accounted for by assuming that the asymptotic exponents are scale dependent. Therefore functions which describe phenomena presenting power-law asymptotic behaviour can be obtained without introducing exotic forms of the entropy.

cond-mat.dis-nn↗

arXiv2016

Dubinin and the Brouers-Sotolongo family isotherms

We show how the Dubinin isotherm and its extensions can be related to the isotherms derived from the general BrouersSotolongo isotherm. We compare them using benzene vapor adsorbed on activated carbon data from one of the original Dubinin paper. We use the same procedure to analyze data from the thesis of MarquezMontesino on the adsorption on activated carbon prepared from pinus caribaea saw dust. We conclude by proposing a simple methodology to determine the macroscopic information given by genuine statistical isotherms.

cond-mat.mtrl-sci↗

arXiv2013

Sorption Isotherms and Probability Theory of Complex Systems

We show that most of the empirical or semi-empirical isotherms proposed to extend the Langmuir formula to sorption (adsorption, chimisorption and biosorption) on heterogeneous surfaces in the gaseous and liquid phase belong to the family and subfamily of the Burr_{XII} cumulative distribution functions. As a consequence they obey relatively simple differential equations which describe birth and death phenomena resulting from mesoscopic and microscopic physicochemical processes. Using the probability theory, it is thus possible to give a physical meaning to their empirical coefficients, to calculate well defined quantities and to compare the results obtained from different isotherms. Another interesting consequence of this finding is that it is possible to relate the shape of the isotherm to the distribution of sorption energies which we have calculated for each isotherm. In particular, we show that the energy distribution corresponding to the Brouers-Sotolongo (BS) isotherm [1] is the Gumbel extreme value distribution Finally we propose a generalized GBS isotherm, calculate its relevant statistical properties and recover all the previous results by giving well defined values to its coefficients. In the course of the discussion we make contact with the Tsallis nonextensive theory [2] and the noninteger order reaction and fractal kinetics theory [3]. In the spirits of the present and previous publications, we propose an alternative formula to include fractality in the Michealis-Menten enzyme catalysis theory. Finally we suggest that the stochastic cluster model introduced by K.Weron [4] to account for the universal character of relaxation in disordered systems should be relevant for other phenomena in particular for heterogeneous sorption

cond-mat.dis-nn↗

arXiv2006

Entropic origin of dielectric relaxation universalities in heterogeneous materials (polymers, glasses, aerogel catalysts)

We have derived a universal relaxation function for heterogeneous materials using the maximum entropy principle for nonextensive systems. The power law exponents of the relaxation function are simply related to a global fractal parameter and for large time to the entropy nonextensivity parameter q. For intermediate times the relaxation follows a stretched exponential behavior. The asymptotic power law behaviors both in the time and the frequency domains coincide with those of the Weron generalized dielectric function derived in the stochastic theory from an extension of the Levy central limit theorem. These results are in full agreement with the Jonscher universality principle and find application in the characterization of the dielectric properties of aerogels catalytic supports as well as in the problem of the relation between morphology and dielectric properties of polymer composites.

cond-mat.soft↗

arXiv2005

Generalized Fractal Kinetics in Complex Systems (Application to Biophysics and Biothechnology)

We derive a universal function for the kinetics of complex systems. This kinetic function unifies and generalizes previous theoretical attempts to describe what has been called "fractal kinetic".The concentration evolutionary equation is formally similar to the relaxation function obtained in the stochastic theory of relaxation, with two exponents a and n. The first one is due to memory effects and short-range correlations and the second one finds its origin in the long-range correlations and geometrical frustrations which give rise to ageing behavior. These effects can be formally handled by introducing adequate probability distributions for the rate coefficient. We show that the distribution of rate coefficients is the consequence of local variations of the free energy (energy landscape) appearing in the exponent of the Arrhenius formula. We discuss briefly the relation of the (n,a) kinetic formalism with the Tsallis theory of nonextensive systems.

cond-mat.dis-nn↗

arXiv2004

Prior Measure for Nonextensive Entropy

We show that if one uses the invariant form of the Boltzmann-Shannon continuous entropy, it is possible to obtain the generalized Pareto-Tsallis density function, using an appropriate "prior" measure m_{q}(x) and a "Boltzman constraint" which formally is equivalent to the Tsallis q-average constraint on the random variable X. We derive the Tsallis prior function and study its scaling asymptotic behavior. When the entropic index q tends to 1, m_{q}(x) tends to 1 for all values of x as this should be.

cond-mat.stat-mech↗

arXiv2004

Burr, Levy, Tsallis

The purpose of this short paper dedicated to the 60th anniversary of Prof.Constantin Tsallis is to show how the use of mathematical tools and physical concepts introduced by Burr, Lėvy and Tsallis open a new line of analysis of the old problem of non-Debye decay and universality of relaxation. We also show how a finite characteristic time scale can be expressed in terms of a $q$-expectation using the concept of $q$- escort probability.The comparison with the Weron et al. probabilistic theory of relaxation leads to a better understanding of the stochastic properties underlying the Tsallis entropy concept.

cond-mat.stat-mech↗

arXiv2003

Universal relaxation function in nonextensive systems

We have derived the dipolar relaxation function for a cluster model whose volume distribution was obtained from the generalized maximum Tsallis nonextensive entropy principle. The power law exponents of the relaxation function are simply related to a global fractal parameter $α$ and for large time to the entropy nonextensivity parameter $q$. For intermediate times the relaxation follows a stretched exponential behavior. The asymptotic power law behaviors both in the time and the frequency domains coincide with those of the Weron generalized dielectric function derived from an extension of the Levy central limit theorem. They are in full agreement with the Jonscher universality principle. Moreover our model gives a physical interpretation of the mathematical parameters of the Weron stochastic theory and opens new paths to understand the ubiquity of self-similarity and power laws in the relaxation of large classes of materials in terms of their fractal and nonextensive properties.

cond-mat.soft↗

arXiv1999

Localization and Absorption of Light in 2D Composite Metal-Dielectric Films at the Percolation Threshold

We study in this paper the localization of light and the dielectric properties of thin metal-dielectric composites at the percolation threshold and around a resonant frequency where the conductivities of the two components are of the same order. In particular, the effect of the loss in metallic components are examined. To this end, such systems are modelized as random $L-C$ networks, and the local field distribution as well as the effective conductivity are determined by using two different methods for comparison: an exact resolution of Kirchoff equations, and a real space renormalization group method. The latter method is found to give the general behavior of the effective conductivity but fails to determine the local field distribution. It is also found that the localization still persists for vanishing losses. This result seems to be in agreement with the anomalous absorption observed experimentally for such systems.

cond-mat.mes-hall↗

arXiv1998

Statistical and Scaling Properties of the $ac$ Conductivity in Thin Metal-Dielectric Composites

We Study in this paper the scaling and statistical properties of the $ac$ conductivity of thin metal-dielectric films in different regions of the loss in the metallic components and particularly in the limit of vanishing loss. We model the system by a 2D $RL-C$ network and calculate the effective conductivity by using a real space renormalization group method. It is found that the real conductivity strongly fluctuates for very small losses. The correlation length, which seems to be equivalent to the localization length, diverges for vanishing losses confirming our previous results for the decay of the real conductivity with the loss. We found also that the distribution of the real conductivity becomes log-normal below a certain critical loss $R_{c}$ which is size dependent for finite systems. For infinite systems this critical loss vanishes and corresponds to the phase transition between localized modes for finite losses and the extended ones at zero loss.

cond-mat.dis-nn↗

arXiv1997

Sandpile Model for Relaxation in Complex Systems

The relaxation in complex systems is in general nonexponential. After an initial rapid decay the system relax slowly following a long time tail. In the present paper a sandpile modelation of the relaxation in complex systems is analysed. Complexity is introduced by a process of avalanches in the Bethe lattice and a feedback mechanism which leads to slower decay with increasing time. In this way, some features of relaxation in complex systems: long time tails relaxation, aging, and fractal distribution of characteristic times, are obtained by simple computer simulations.

cond-mat↗