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Armin Ferse - One of the best experts on this subject based on the ideXlab platform.
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Numerical values of individual activity coefficients of single-ion species in concentrated aqueous electrolyte solutions and the attempt of a qualitative interpretation on a model of electrostatic interaction
Journal of Solid State Electrochemistry, 2013Co-Authors: Armin FerseAbstract:Individual activity coefficients of single-ion species can be achieved by the factorizing of a new Concentration Function for the mean activity coefficient to the required power applying a purely mathematical method. These single-ion activity coefficients, calculated in this manner, are listed for some aqueous strong electrolytes. The reasons for the magnitude and variation of the activity coefficients as a Function of the Concentration are, without a doubt, of complex nature. Activity coefficients have their meaning as practical values. In relation to the analytical Concentration, the individual activity coefficients represent the macroscopic effectiveness of the single-ion species in solution an easy manner. However, with increasing deviations from Debye–Hückel conditions of an infinitely diluted electrolyte solution, a physically correct interpretation of the macroscopically visible activity coefficient is becoming more and more difficult, if not impossible to find. On the basis of a model of electrostatic interaction, an attempt has been made to create a qualitative interpretation of the individual ion activity coefficients in concentrated aqueous electrolyte solutions which were calculated applying the purely mathematical method by Ferse.
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Factorizing of a Concentration Function for the mean activity coefficients of aqueous strong electrolytes into individual Functions for the ionic species
Journal of Solid State Electrochemistry, 2011Co-Authors: Armin Ferse, Hans-otfried MüllerAbstract:The Concentration curve of mean activity coefficients to the required power was approximated by a product Function. The product Function parameters were optimized by experimental data for the mean activity coefficients using a nonlinear regression model. Assuming that the product Function parameters can be determined, the factor Functions are clearly known. The mathematical complexity and a concept solution are presented. Clear, reliable results were obtained with the help of asymptotic theory when corresponding approximations were used. The method described makes it possible to split the experimentally determinable Concentration curve of the mean activity coefficients to the required power in individual factor Functions of complementary ion species, $$ {\bar{\gamma }_{\text{C}}}(m) $$ and $$ {\bar{\gamma }_{\text{A}}}(m) $$ . The results are verified by comparing them with experimentally determined quotients of single-ion activity coefficients of ternary systems. The calculated individual parts for single-ion species are plausible and show a characteristic, typical Concentration curve for cations as well as for anions. They correlate with the ion parameters.
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Reply to the comment by F. Malatesta on: “Factorizing of a Concentration Function for the mean activity coefficients of aqueous strong electrolytes into individual Functions for ionic species” by A. Ferse and H.-O. Müller
Journal of Solid State Electrochemistry, 2011Co-Authors: Armin FerseAbstract:The arguments of Malatesta (J Solution Chem 29:771–779, 2000; Fluid Phase Equil 295:244–248, 2010) exclude the experimental determination of individual ion activity coefficients. I agree that a measurement of single-ion activity coefficients is impossible. But the comment of Malatesta (J Solid State Electrochem (in press), 2011) in the connection with the purely mathematical procedure developed by Ferse and Muller (J Solid State Electrochem (in press), 2011) is senseless because there is no new aspect which is not also given in the paper of Ferse and Muller (J Solid State Electrochem (in press), 2011). All of the mentioned problems are already discussed and clarified in the publication by Ferse and Muller (J Solid State Electrochem (in press), 2011). The purely mathematical method is a possibility to obtain the Concentration Functions for the individual activity coefficients of the complementary ion species by factorizing a product Function of the experimentally accessible Concentration dependence of the mean activity coefficients to the required power.
Michael Graham Espey - One of the best experts on this subject based on the ideXlab platform.
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vitamin c a Concentration Function approach yields pharmacology and therapeutic discoveries
Advances in Nutrition, 2011Co-Authors: Mark Levine, Sebastian J. Padayatty, Michael Graham EspeyAbstract:A Concentration-Function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C Concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue Concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma Concentrations do not exceed 100 μmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma Concentrations are always <250 μmol/L and frequently <150 μmol/L. By contrast, when ascorbate is i.v. injected, tight control is bypassed until excess ascorbate is eliminated by glomerular filtration and renal excretion. With i.v. infusion, pharmacologic ascorbate Concentrations of 25–30 mmol/L are safely achieved. Pharmacologic ascorbate can act as a pro-drug for hydrogen peroxide (H2O2) formation, which can lead to extracellular fluid at Concentrations as high as 200 μmol/L. Pharmacologic ascorbate can elicit cytotoxicity toward cancer cells and slow the growth of tumors in experimental murine models. The effects of pharmacologic ascorbate should be further studied in diseases, such as cancer and infections, which may respond to generation of reactive oxygen species via H2O2.
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Vitamin C: A Concentration-Function Approach Yields Pharmacology and Therapeutic Discoveries
Advances in nutrition (Bethesda Md.), 2011Co-Authors: Mark Levine, Sebastian J. Padayatty, Michael Graham EspeyAbstract:A Concentration-Function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C Concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue Concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma Concentrations do not exceed 100 μmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma Concentrations are always
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Vitamin C: A Concentration-Function Approach Yields Pharmacology and
2011Co-Authors: Mark Levine, Sebastian J. Padayatty, Michael Graham EspeyAbstract:A Concentration-Function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C Concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue Concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma Concentrations do not exceed 100 mmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma Concentrations are always
Mark Levine - One of the best experts on this subject based on the ideXlab platform.
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vitamin c a Concentration Function approach yields pharmacology and therapeutic discoveries
Advances in Nutrition, 2011Co-Authors: Mark Levine, Sebastian J. Padayatty, Michael Graham EspeyAbstract:A Concentration-Function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C Concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue Concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma Concentrations do not exceed 100 μmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma Concentrations are always <250 μmol/L and frequently <150 μmol/L. By contrast, when ascorbate is i.v. injected, tight control is bypassed until excess ascorbate is eliminated by glomerular filtration and renal excretion. With i.v. infusion, pharmacologic ascorbate Concentrations of 25–30 mmol/L are safely achieved. Pharmacologic ascorbate can act as a pro-drug for hydrogen peroxide (H2O2) formation, which can lead to extracellular fluid at Concentrations as high as 200 μmol/L. Pharmacologic ascorbate can elicit cytotoxicity toward cancer cells and slow the growth of tumors in experimental murine models. The effects of pharmacologic ascorbate should be further studied in diseases, such as cancer and infections, which may respond to generation of reactive oxygen species via H2O2.
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Vitamin C: A Concentration-Function Approach Yields Pharmacology and Therapeutic Discoveries
Advances in nutrition (Bethesda Md.), 2011Co-Authors: Mark Levine, Sebastian J. Padayatty, Michael Graham EspeyAbstract:A Concentration-Function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C Concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue Concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma Concentrations do not exceed 100 μmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma Concentrations are always
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Vitamin C: A Concentration-Function Approach Yields Pharmacology and
2011Co-Authors: Mark Levine, Sebastian J. Padayatty, Michael Graham EspeyAbstract:A Concentration-Function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C Concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue Concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma Concentrations do not exceed 100 mmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma Concentrations are always
Hans-otfried Müller - One of the best experts on this subject based on the ideXlab platform.
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Factorizing of a Concentration Function for the mean activity coefficients of aqueous strong electrolytes into individual Functions for the ionic species
Journal of Solid State Electrochemistry, 2011Co-Authors: Armin Ferse, Hans-otfried MüllerAbstract:The Concentration curve of mean activity coefficients to the required power was approximated by a product Function. The product Function parameters were optimized by experimental data for the mean activity coefficients using a nonlinear regression model. Assuming that the product Function parameters can be determined, the factor Functions are clearly known. The mathematical complexity and a concept solution are presented. Clear, reliable results were obtained with the help of asymptotic theory when corresponding approximations were used. The method described makes it possible to split the experimentally determinable Concentration curve of the mean activity coefficients to the required power in individual factor Functions of complementary ion species, $$ {\bar{\gamma }_{\text{C}}}(m) $$ and $$ {\bar{\gamma }_{\text{A}}}(m) $$ . The results are verified by comparing them with experimentally determined quotients of single-ion activity coefficients of ternary systems. The calculated individual parts for single-ion species are plausible and show a characteristic, typical Concentration curve for cations as well as for anions. They correlate with the ion parameters.
Lidia Sacchetto - One of the best experts on this subject based on the ideXlab platform.
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On the definition of a Concentration Function relevant to the ROC curve
METRON, 2020Co-Authors: Mauro Gasparini, Lidia SacchettoAbstract:This work provides a definition of Concentration curve alternative to the one presented on this journal by Schechtman and Schechtman (Metron 77:171–178, 2019). Our definition clarifies, at the population level, the relationship between Concentration and the omnipresent ROC curve in diagnostic and classification problems.
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On the definition of a Concentration Function relevant to the ROC curve.
arXiv: Methodology, 2020Co-Authors: Mauro Gasparini, Lidia SacchettoAbstract:This is a reader's reaction to a recent paper by E. Schechtman and G. Schechtman (Metron, 2019) about the correct definition of a Concentration Function for the diagnostic, i.e. supervised classification, problem. We propose and motivate a different definition and refer to the relevant literature.