The Experts below are selected from a list of 5595 Experts worldwide ranked by ideXlab platform
Jose Palomar - One of the best experts on this subject based on the ideXlab platform.
-
a cosmo rs based guide to analyze quantify the polarity of ionic liquids and their mixtures with organic cosolvents
Physical Chemistry Chemical Physics, 2010Co-Authors: Jose Palomar, Jose S Torrecilla, Jesus Lemus, Victor R Ferro, Francisco B RodriguezAbstract:A COSMO-RS descriptor (Sσ-profile) has been used in quantitative structure–property relationship (QSPR) studies by a neural network (NN) for the prediction of empirical solvent polarity ENT scale of neat ionic liquids (ILs) and their mixtures with organic solvents. Sσ-profile is a two-dimensional quantum chemical parameter which quantifies the polar electronic charge of chemical structures on the polarity (σ) scale. Firstly, a radial basis neural network exact fit (RBNN) is successfully optimized for the prediction of ENT, the solvatochromic parameter of a wide variety of neat organic solvents and ILs, including imidazolium, pyridinium, ammonium, phosphonium and pyrrolidinium families, solely using the Sσ-profile of individual molecules and ions. Subsequently, a quantitative structure–activity map (QSAM), a new concept recently developed, is proposed as a valuable tool for the molecular understanding of IL polarity, by relating the ENT polarity parameter to the electronic structure of cations and anions given by quantum-chemical COSMO-RS calculations. Finally, based on the Additive Character of the Sσ-profile descriptor, we propose to simulate the mixture of IL–organic solvents by the estimation of the SMixtureσ-profile descriptor, defined as the weighted mean of the Sσ-profile values of the components. Then, the ENT parameters for binary solvent mixtures, including ILs, are accurately predicted using the SMixtureσ-profile values from the RBNN model previously developed for pure solvents. As result, we obtain a unique neural network tool to simulate, with similar reliability, the ENT polarity of a wide variety of pure ILs as well as their mixtures with organic solvents, which exhibit significant positive and negative deviations from ideality.
-
prediction of non ideal behavior of polarity polarizability scales of solvent mixtures by integration of a novel cosmo rs molecular descriptor and neural networks
Physical Chemistry Chemical Physics, 2008Co-Authors: Jose Palomar, Jose S Torrecilla, Jesus Lemus, Victor R Ferro, Francisco RodriguezAbstract:A new COSMO-RS descriptor (Sσ-profile) has been used in quantitative structure–property relationship (QSPR) studies based on neural networks (NN) for the prediction of polarity/polarizability scales of pure solvents and mixtures. Sσ-profile is a two-dimensional quantum chemical parameter which quantifies the polar electronic charge on the polarity (σ) scale. Firstly, radial base neural networks (RBNN) are successfully optimized for the prediction of polarizability (SP) and polarity/polarizability (SPP) scales of pure solvents using the Sσ-profile of individual molecules. Subsequently, based on the Additive Character of the Sσ-profile parameter, we propose to simulate the solvents mixture by the estimation of SMixtureσ-profile descriptor, defined as the weighted mean of Sσ-profile values of the components. Then, the SPP parameters for binary and ternary mixtures are accurately predicted using the SMixtureσ-profile values into the RBNN model previously developed for pure solvents. As result, we obtain a unique neural network tool to simulate, with similar reliability, the polarity/polarizability of a wide variety of pure organic solvents as well as binary and ternary mixtures which exhibit significant deviations from ideality.
Arne Winterhof - One of the best experts on this subject based on the ideXlab platform.
-
Incomplete Additive Character Sums and Applications
Finite Fields and Applications, 2001Co-Authors: Arne WinterhofAbstract:We prove some bounds on incomplete Additive Character sums of polynomials over finite fields. We also apply results on incomplete Additive Character sums to get a distribution property of irreducible polynomials, we estimate the maximum running digital sums of some dc-constrained codes, and we describe a variant of Waring’s problem in finite fields.
Francisco B Rodriguez - One of the best experts on this subject based on the ideXlab platform.
-
a cosmo rs based guide to analyze quantify the polarity of ionic liquids and their mixtures with organic cosolvents
Physical Chemistry Chemical Physics, 2010Co-Authors: Jose Palomar, Jose S Torrecilla, Jesus Lemus, Victor R Ferro, Francisco B RodriguezAbstract:A COSMO-RS descriptor (Sσ-profile) has been used in quantitative structure–property relationship (QSPR) studies by a neural network (NN) for the prediction of empirical solvent polarity ENT scale of neat ionic liquids (ILs) and their mixtures with organic solvents. Sσ-profile is a two-dimensional quantum chemical parameter which quantifies the polar electronic charge of chemical structures on the polarity (σ) scale. Firstly, a radial basis neural network exact fit (RBNN) is successfully optimized for the prediction of ENT, the solvatochromic parameter of a wide variety of neat organic solvents and ILs, including imidazolium, pyridinium, ammonium, phosphonium and pyrrolidinium families, solely using the Sσ-profile of individual molecules and ions. Subsequently, a quantitative structure–activity map (QSAM), a new concept recently developed, is proposed as a valuable tool for the molecular understanding of IL polarity, by relating the ENT polarity parameter to the electronic structure of cations and anions given by quantum-chemical COSMO-RS calculations. Finally, based on the Additive Character of the Sσ-profile descriptor, we propose to simulate the mixture of IL–organic solvents by the estimation of the SMixtureσ-profile descriptor, defined as the weighted mean of the Sσ-profile values of the components. Then, the ENT parameters for binary solvent mixtures, including ILs, are accurately predicted using the SMixtureσ-profile values from the RBNN model previously developed for pure solvents. As result, we obtain a unique neural network tool to simulate, with similar reliability, the ENT polarity of a wide variety of pure ILs as well as their mixtures with organic solvents, which exhibit significant positive and negative deviations from ideality.
Shparlinski, Igor E. - One of the best experts on this subject based on the ideXlab platform.
-
Additive energy of cyclic matrix groups and Character sums with matrix exponential functions
2021Co-Authors: Ostafe Alina, Shparlinski, Igor E.Abstract:We obtain a nontrivial bound on the number of solutions to the equation $A^{x_1} + A^{x_2} = A^{x_3} + A^{x_4}$, $1 \le x_1,x_2,x_3,x_4 \le \tau$, with a fixed $n\times n$ matrix $A$ over a finite field ${\mathbb F}_q$ of $q$ elements of multiplicative order $\tau$. For $n=2$ this equation has been considered by Kurlberg and Rudnick (2001) in their study of quantum ergodicity for linear maps over ${\mathbb F}_q$. Furthermore, its multivariate analogue (also with $n=2$) has been studied by Bourgain (2005). We give applications of our result to obtaining a new bound of Additive Character sums with a matrix exponential function, which is nontrivial beyond the square-root threshold, and also to a certain Additive problem with matrices. Our results are especially strong for ${\rm SL}(n,q)$ matrices with an irreducible Characteristic polynomial.Comment: The submission is superseded by arXiv:2110.1094
-
Equations and Character sums with matrix powers, Kloosterman sums over small subgroups and quantum ergodicity
2021Co-Authors: Ostafe Alina, Shparlinski, Igor E., Voloch, José FelipeAbstract:We obtain a nontrivial bound on the number of solutions to the equation $$ A^{x_1} + \ldots + A^{x_\nu} = A^{x_{\nu+1}} + \ldots + A^{x_{2\nu}}, \quad 1 \le x_1, \ldots,x_{2\nu} \le \tau, $$ with a fixed $n\times n$ matrix $A$ over a finite field $\mathbb F_q$ of $q$ elements of multiplicative order $\tau$. We give applications of our result to obtaining a new bound of Additive Character sums with a matrix exponential function, which is nontrivial beyond the square-root threshold. For $n=2$ this equation has been considered by Kurlberg and Rudnick (2001) (for $\nu=2$) and Bourgain (2005) (for large $\nu$) in their study of quantum ergodicity for linear maps over residue rings. Here we use a new approach to improve their results. We also obtain a bound on Kloosterman sums over small subgroups, of size below the square-root threshold.Comment: This paper supersedes our previous submission: arXiv:2108.13146 which is now obsolet
Igor E Shparlinski - One of the best experts on this subject based on the ideXlab platform.
-
Additive energy of cyclic matrix groups and Character sums with matrix exponential functions
arXiv: Number Theory, 2021Co-Authors: Alina Ostafe, Igor E ShparlinskiAbstract:We obtain a nontrivial bound on the number of solutions to the equation $A^{x_1} + A^{x_2} = A^{x_3} + A^{x_4}$, $1 \le x_1,x_2,x_3,x_4 \le \tau$, with a fixed $n\times n$ matrix $A$ over a finite field ${\mathbb F}_q$ of $q$ elements of multiplicative order $\tau$. For $n=2$ this equation has been considered by Kurlberg and Rudnick (2001) in their study of quantum ergodicity for linear maps over ${\mathbb F}_q$. Furthermore, its multivariate analogue (also with $n=2$) has been studied by Bourgain (2005). We give applications of our result to obtaining a new bound of Additive Character sums with a matrix exponential function, which is nontrivial beyond the square-root threshold, and also to a certain Additive problem with matrices. Our results are especially strong for ${\rm SL}(n,q)$ matrices with an irreducible Characteristic polynomial.
-
on Character sums with distances on the upper half plane over a finite field
Finite Fields and Their Applications, 2009Co-Authors: Nicholas M Katz, Igor E Shparlinski, Maosheng XiongAbstract:For the finite field F"q of q elements (q odd) and a quadratic non-residue (that is, a non-square) @[email protected]?F"q, we define the distance [email protected]([email protected],[email protected])=(u-x)^[email protected](v-y)^2vy on the upper half plane H"q={[email protected]|[email protected]?F"q,[email protected]?F"q^*}@?F"q"^"2. For two sets E,[email protected]?H"q with #E=E, #F=F and a non-trivial Additive Character @j on F"q, we give the following estimate|@[email protected]?E,[email protected][email protected](@d(w,z))|==E) is non-trivial if EF/q^2->~ as q->~.