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Pritish Sinha - One of the best experts on this subject based on the ideXlab platform.
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absolute molar mass determination in mixed solvents 1 solving for the sec mals dri Trivial Case
Analytica Chimica Acta, 2019Co-Authors: André M. Striegel, Pritish SinhaAbstract:Abstract Size-exclusion chromatography (SEC) with on-line static light scattering, specifically multi-angle static light scattering (MALS), and differential refractometry (DRI) detection remains the premier method by which to determine absolute, calibrant-independent molar masses of polymers. The method is restricted to the use of either neat solvents or solvents with a small amount of additive. In mixed solvents, preferential solvation (i.e., the enrichment, within the solvated volume of the polymer in solution, of one solvent over the other as compared to the solvent ratio outside said volume) leads to errors in the areas of the MALS and DRI chromatograms, as the solvent baseline does not accurately represent the solvent contribution to these detectors’ peaks. A seemingly Trivial way by which to overcome this problem is through the use of an isorefractive solvent pair. This “Trivial” solution is complicated by the fact that the solvents in the pair must be miscible with each other in all proportions; the individual solvents as well as the mix must be able to fully dissolve the analyte; the solvents must possess sufficient optical contrast with the solution so as to generate an adequate detector signal; the solvent mix must be compatible with the chromatographic stationary phase, such that enthalpic contributions to the separation are minimal and analyte recovery from the columns is quantitative; and the difference in the Rayleigh factors of the solvents can be ignored. Herein, we present the analysis of narrow dispersity polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples, across a four-fold range in molar mass, using SEC/MALS/DRI in a mix of tetrahydrofuran (THF) and methyl isoamyl ketone (MIAK), solvents which are shown to be isorefractive with each other at the temperature and wavelength of the experiments. Molar mass averages and dispersities are demonstrated to be statistically independent of solvent composition and to correspond well to the values in neat THF. The experiments were augmented by the use of on- and off-line quasi-elastic light scattering and of off-line MALS and DRI, to study the effect of solvent composition on polymer size in solution and on dilute solution thermodynamics. Additionally, 1H nuclear magnetic resonance spectroscopy was used to study the effect of tacticity on the insolubility of PMMA100 in 100% MIAK. We believe this constitutes the first example of obtaining accurate molar masses of polymers by SEC/MALS/DRI employing mixed solvents. The value of these experiments to other forms of macromolecular liquid chromatographic separations is also noted.
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Absolute molar mass determination in mixed solvents. 1. Solving for the SEC/MALS/DRI Trivial Case
Analytica chimica acta, 2018Co-Authors: André M. Striegel, Pritish SinhaAbstract:Abstract Size-exclusion chromatography (SEC) with on-line static light scattering, specifically multi-angle static light scattering (MALS), and differential refractometry (DRI) detection remains the premier method by which to determine absolute, calibrant-independent molar masses of polymers. The method is restricted to the use of either neat solvents or solvents with a small amount of additive. In mixed solvents, preferential solvation (i.e., the enrichment, within the solvated volume of the polymer in solution, of one solvent over the other as compared to the solvent ratio outside said volume) leads to errors in the areas of the MALS and DRI chromatograms, as the solvent baseline does not accurately represent the solvent contribution to these detectors’ peaks. A seemingly Trivial way by which to overcome this problem is through the use of an isorefractive solvent pair. This “Trivial” solution is complicated by the fact that the solvents in the pair must be miscible with each other in all proportions; the individual solvents as well as the mix must be able to fully dissolve the analyte; the solvents must possess sufficient optical contrast with the solution so as to generate an adequate detector signal; the solvent mix must be compatible with the chromatographic stationary phase, such that enthalpic contributions to the separation are minimal and analyte recovery from the columns is quantitative; and the difference in the Rayleigh factors of the solvents can be ignored. Herein, we present the analysis of narrow dispersity polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples, across a four-fold range in molar mass, using SEC/MALS/DRI in a mix of tetrahydrofuran (THF) and methyl isoamyl ketone (MIAK), solvents which are shown to be isorefractive with each other at the temperature and wavelength of the experiments. Molar mass averages and dispersities are demonstrated to be statistically independent of solvent composition and to correspond well to the values in neat THF. The experiments were augmented by the use of on- and off-line quasi-elastic light scattering and of off-line MALS and DRI, to study the effect of solvent composition on polymer size in solution and on dilute solution thermodynamics. Additionally, 1H nuclear magnetic resonance spectroscopy was used to study the effect of tacticity on the insolubility of PMMA100 in 100% MIAK. We believe this constitutes the first example of obtaining accurate molar masses of polymers by SEC/MALS/DRI employing mixed solvents. The value of these experiments to other forms of macromolecular liquid chromatographic separations is also noted.
André M. Striegel - One of the best experts on this subject based on the ideXlab platform.
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absolute molar mass determination in mixed solvents 1 solving for the sec mals dri Trivial Case
Analytica Chimica Acta, 2019Co-Authors: André M. Striegel, Pritish SinhaAbstract:Abstract Size-exclusion chromatography (SEC) with on-line static light scattering, specifically multi-angle static light scattering (MALS), and differential refractometry (DRI) detection remains the premier method by which to determine absolute, calibrant-independent molar masses of polymers. The method is restricted to the use of either neat solvents or solvents with a small amount of additive. In mixed solvents, preferential solvation (i.e., the enrichment, within the solvated volume of the polymer in solution, of one solvent over the other as compared to the solvent ratio outside said volume) leads to errors in the areas of the MALS and DRI chromatograms, as the solvent baseline does not accurately represent the solvent contribution to these detectors’ peaks. A seemingly Trivial way by which to overcome this problem is through the use of an isorefractive solvent pair. This “Trivial” solution is complicated by the fact that the solvents in the pair must be miscible with each other in all proportions; the individual solvents as well as the mix must be able to fully dissolve the analyte; the solvents must possess sufficient optical contrast with the solution so as to generate an adequate detector signal; the solvent mix must be compatible with the chromatographic stationary phase, such that enthalpic contributions to the separation are minimal and analyte recovery from the columns is quantitative; and the difference in the Rayleigh factors of the solvents can be ignored. Herein, we present the analysis of narrow dispersity polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples, across a four-fold range in molar mass, using SEC/MALS/DRI in a mix of tetrahydrofuran (THF) and methyl isoamyl ketone (MIAK), solvents which are shown to be isorefractive with each other at the temperature and wavelength of the experiments. Molar mass averages and dispersities are demonstrated to be statistically independent of solvent composition and to correspond well to the values in neat THF. The experiments were augmented by the use of on- and off-line quasi-elastic light scattering and of off-line MALS and DRI, to study the effect of solvent composition on polymer size in solution and on dilute solution thermodynamics. Additionally, 1H nuclear magnetic resonance spectroscopy was used to study the effect of tacticity on the insolubility of PMMA100 in 100% MIAK. We believe this constitutes the first example of obtaining accurate molar masses of polymers by SEC/MALS/DRI employing mixed solvents. The value of these experiments to other forms of macromolecular liquid chromatographic separations is also noted.
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Absolute molar mass determination in mixed solvents. 1. Solving for the SEC/MALS/DRI Trivial Case
Analytica chimica acta, 2018Co-Authors: André M. Striegel, Pritish SinhaAbstract:Abstract Size-exclusion chromatography (SEC) with on-line static light scattering, specifically multi-angle static light scattering (MALS), and differential refractometry (DRI) detection remains the premier method by which to determine absolute, calibrant-independent molar masses of polymers. The method is restricted to the use of either neat solvents or solvents with a small amount of additive. In mixed solvents, preferential solvation (i.e., the enrichment, within the solvated volume of the polymer in solution, of one solvent over the other as compared to the solvent ratio outside said volume) leads to errors in the areas of the MALS and DRI chromatograms, as the solvent baseline does not accurately represent the solvent contribution to these detectors’ peaks. A seemingly Trivial way by which to overcome this problem is through the use of an isorefractive solvent pair. This “Trivial” solution is complicated by the fact that the solvents in the pair must be miscible with each other in all proportions; the individual solvents as well as the mix must be able to fully dissolve the analyte; the solvents must possess sufficient optical contrast with the solution so as to generate an adequate detector signal; the solvent mix must be compatible with the chromatographic stationary phase, such that enthalpic contributions to the separation are minimal and analyte recovery from the columns is quantitative; and the difference in the Rayleigh factors of the solvents can be ignored. Herein, we present the analysis of narrow dispersity polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples, across a four-fold range in molar mass, using SEC/MALS/DRI in a mix of tetrahydrofuran (THF) and methyl isoamyl ketone (MIAK), solvents which are shown to be isorefractive with each other at the temperature and wavelength of the experiments. Molar mass averages and dispersities are demonstrated to be statistically independent of solvent composition and to correspond well to the values in neat THF. The experiments were augmented by the use of on- and off-line quasi-elastic light scattering and of off-line MALS and DRI, to study the effect of solvent composition on polymer size in solution and on dilute solution thermodynamics. Additionally, 1H nuclear magnetic resonance spectroscopy was used to study the effect of tacticity on the insolubility of PMMA100 in 100% MIAK. We believe this constitutes the first example of obtaining accurate molar masses of polymers by SEC/MALS/DRI employing mixed solvents. The value of these experiments to other forms of macromolecular liquid chromatographic separations is also noted.
Massimo Merro - One of the best experts on this subject based on the ideXlab platform.
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A Semantic Theory of the Internet of Things
Information and Computation, 2018Co-Authors: Ruggero Lanotte, Massimo MerroAbstract:We propose a process calculus for modelling and reasoning on systems in the Internet of Things paradigm. Our systems interact both with the physical environment, via sensors and actuators, and with smart devices, via short-range and Internet channels. The calculus is equipped with a standard notion of labelled bisimilarity which represents a fully abstract characterisation of a well-known contextual equivalence. We use our semantic proof-methods to prove run-time properties of a non-Trivial Case study as well as system equalities.
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LATA - A Calculus of Cyber-Physical Systems
Language and Automata Theory and Applications, 2017Co-Authors: Ruggero Lanotte, Massimo MerroAbstract:We propose a hybrid process calculus for modelling and reasoning on cyber-physical systems (CPSs). The dynamics of the calculus is expressed in terms of a labelled transition system in the SOS style of Plotkin. This is used to define a bisimulation-based behavioural semantics which support compositional reasonings. Finally, we prove run-time properties and system equalities for a non-Trivial Case study.
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A Semantic Theory of the Internet of Things
Lecture Notes in Computer Science, 2016Co-Authors: Ruggero Lanotte, Massimo MerroAbstract:International audienceWe propose a process calculus for modelling and reasoning on systems in the Internet of Things paradigm. Our systems interact both with the physical environment, via sensors and actuators, and with smart devices, via short-range and Internet channels. The calculus is equipped with a standard notion of labelled bisimilarity which represents a fully abstract characterisation of a well-known contextual equivalence. We use our semantic proof-methods to prove run-time properties of a non-Trivial Case study as well as system equalities
Patrick Ahern - One of the best experts on this subject based on the ideXlab platform.
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a theorem of brown halmos type for bergman space toeplitz operators
Journal of Functional Analysis, 2001Co-Authors: Patrick Ahern, željko CuckovicAbstract:Abstract We study the analogues of the Brown–Halmos theorem for Toeplitz operators on the Bergman space. We show that for f and g harmonic, T f T g = T h only in the Trivial Case, provided that h is of class C 2 with the invariant laplacian bounded. Here the Trivial Cases are f or g holomorphic. From this we conclude that the zero-product problem for harmonic symbols has only the Trivial solution. Finally, we provide examples that show that the Brown–Halmos theorem fails for general symbols, even for symbols continuous up to the boundary.
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A Theorem of Brown–Halmos Type for Bergman Space Toeplitz Operators
Journal of Functional Analysis, 2001Co-Authors: Patrick Ahern, Željko ČučkovićAbstract:Abstract We study the analogues of the Brown–Halmos theorem for Toeplitz operators on the Bergman space. We show that for f and g harmonic, T f T g = T h only in the Trivial Case, provided that h is of class C 2 with the invariant laplacian bounded. Here the Trivial Cases are f or g holomorphic. From this we conclude that the zero-product problem for harmonic symbols has only the Trivial solution. Finally, we provide examples that show that the Brown–Halmos theorem fails for general symbols, even for symbols continuous up to the boundary.
Ruggero Lanotte - One of the best experts on this subject based on the ideXlab platform.
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A Semantic Theory of the Internet of Things
Information and Computation, 2018Co-Authors: Ruggero Lanotte, Massimo MerroAbstract:We propose a process calculus for modelling and reasoning on systems in the Internet of Things paradigm. Our systems interact both with the physical environment, via sensors and actuators, and with smart devices, via short-range and Internet channels. The calculus is equipped with a standard notion of labelled bisimilarity which represents a fully abstract characterisation of a well-known contextual equivalence. We use our semantic proof-methods to prove run-time properties of a non-Trivial Case study as well as system equalities.
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LATA - A Calculus of Cyber-Physical Systems
Language and Automata Theory and Applications, 2017Co-Authors: Ruggero Lanotte, Massimo MerroAbstract:We propose a hybrid process calculus for modelling and reasoning on cyber-physical systems (CPSs). The dynamics of the calculus is expressed in terms of a labelled transition system in the SOS style of Plotkin. This is used to define a bisimulation-based behavioural semantics which support compositional reasonings. Finally, we prove run-time properties and system equalities for a non-Trivial Case study.
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A Semantic Theory of the Internet of Things
Lecture Notes in Computer Science, 2016Co-Authors: Ruggero Lanotte, Massimo MerroAbstract:International audienceWe propose a process calculus for modelling and reasoning on systems in the Internet of Things paradigm. Our systems interact both with the physical environment, via sensors and actuators, and with smart devices, via short-range and Internet channels. The calculus is equipped with a standard notion of labelled bisimilarity which represents a fully abstract characterisation of a well-known contextual equivalence. We use our semantic proof-methods to prove run-time properties of a non-Trivial Case study as well as system equalities
