scholarly journals Water confined in self-assembled ionic surfactant nano-structures

Soft Matter ◽  
2015 ◽  
Vol 11 (12) ◽  
pp. 2469-2478 ◽  
Author(s):  
Samuel Hanot ◽  
Sandrine Lyonnard ◽  
Stefano Mossa
Keyword(s):  
Computer Simulation ◽  
Aqueous Solutions ◽  
Structural Features ◽  
Coarse Grained ◽  
Ionic Surfactants ◽  
Ionic Surfactant ◽  
Coarse Grained Model ◽  
Nano Structures ◽  
Consequent Effect ◽  
The Impact

We present a coarse-grained model for ionic surfactants in explicit aqueous solutions, and study by computer simulation both the impact of water content on the morphology of the system, and the consequent effect of the formed interfaces on the structural features of the absorbed fluid.

The structure of polymer brushes near the transition from dilute to dense systems. A computer simulation study

Soft Matter ◽  
2021 ◽  
Author(s):  
Piotr Polanowski ◽  
Andrzej Sikorski
Keyword(s):  
Computer Simulation ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Simulation Study ◽  
Polymer Brushes ◽  
Polymer Brush ◽  
Coarse Grained ◽  
Computer Simulation Study ◽  
Coarse Grained Model ◽  
Cooperative Motion

Monodisperse polymer brushes were studied by means of Monte Carlo simulations. A coarse-grained model of a polymer brush was designed in order and the Cooperative Motion Algorithm was employed to...

scholarly journals Coarse-grained Simulation of Anionic Surfactant Sodium Dodecyl Sulfate

2021 ◽  
Author(s):  
Xiang-feng Jia ◽  
Jing-fei Chen ◽  
Hui-xue Ren ◽  
Qi Wang ◽  
Wen Xu ◽  
...  
Keyword(s):  
Force Field ◽  
Sodium Dodecyl ◽  
Coarse Grained ◽  
Inversion Method ◽  
Ionic Surfactant ◽  
Coarse Grained Model ◽  
Piecewise Function ◽  
Martini Force Field ◽  
Improved Model ◽  
Vdw Interaction

Abstract Through analyzing the deficiency of the current coarse-grained (CG) model, a new CG model for the ionic surfactant was proposed based on the Martini force field and iterative Boltzmann inversion method. In this model, the electrostatic interaction can be tackled by using a self-defined piecewise function to avoid the disadvantage of using coarse-grained solvents, and the VDW interaction parameters were derived by iterative methods. Using the improved model, the radial distribution function of NaCl and SDS solution in all-atom OPLS can be completely reproduced. The successful setup of the new coarse-grained model provides a good example of the construction of a high-precision coarse-grained force field.

scholarly journals The impact of long-range dispersal on gene surfing

2020 ◽  
Vol 117 (14) ◽  
pp. 7584-7593 ◽  
Author(s):  
Jayson Paulose ◽  
Oskar Hallatschek
Keyword(s):  
Genetic Variation ◽  
Long Range ◽  
Range Expansion ◽  
Spatial Genetic Structure ◽  
Dispersal Distance ◽  
Coarse Grained ◽  
Coarse Grained Model ◽  
Species Invasions ◽  
Dispersal Distances ◽  
The Impact

Range expansions lead to distinctive patterns of genetic variation in populations, even in the absence of selection. These patterns and their genetic consequences have been well studied for populations advancing through successive short-ranged migration events. However, most populations harbor some degree of long-range dispersal, experiencing rare yet consequential migration events over arbitrarily long distances. Although dispersal is known to strongly affect spatial genetic structure during range expansions, the resulting patterns and their impact on neutral diversity remain poorly understood. Here, we systematically study the consequences of long-range dispersal on patterns of neutral variation during range expansion in a class of dispersal models which spans the extremes of local (effectively short-ranged) and global (effectively well-mixed) migration. We find that sufficiently long-ranged dispersal leaves behind a mosaic of monoallelic patches, whose number and size are highly sensitive to the distribution of dispersal distances. We develop a coarse-grained model which connects statistical features of these spatial patterns to the evolution of neutral diversity during the range expansion. We show that growth mechanisms that appear qualitatively similar can engender vastly different outcomes for diversity: Depending on the tail of the dispersal distance distribution, diversity can be either preserved (i.e., many variants survive) or lost (i.e., one variant dominates) at long times. Our results highlight the impact of spatial and migratory structure on genetic variation during processes as varied as range expansions, species invasions, epidemics, and the spread of beneficial mutations in established populations.

scholarly journals Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150556 ◽  
Author(s):  
Radek Erban
Keyword(s):  
Molecular Dynamics ◽  
Differential Equations ◽  
Aqueous Solutions ◽  
Molecular Dynamics Simulations ◽  
Brownian Dynamics ◽  
Md Simulations ◽  
Coarse Grained ◽  
Computational Domain ◽  
Coarse Grained Model ◽  
Dynamics Simulations

Molecular dynamics (MD) simulations of ions (K + , Na + , Ca 2+ and Cl − ) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parametrized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain.

scholarly journals From sectors to speckles: The impact of long-range migration on gene surfing

2019 ◽  
Author(s):  
Jayson Paulose ◽  
Oskar Hallatschek
Keyword(s):  
Genetic Variation ◽  
Long Range ◽  
Range Expansion ◽  
Spatial Genetic Structure ◽  
Dispersal Distance ◽  
Coarse Grained ◽  
Coarse Grained Model ◽  
Species Invasions ◽  
Dispersal Distances ◽  
The Impact

Range expansions lead to distinctive patterns of genetic variation in populations, even in the absence of selection. These patterns and their genetic consequences have been well-studied for populations advancing through successive short-ranged migration events. However, most populations harbor some degree of long-range dispersal, experiencing rare yet consequential migration events over arbitrarily long distances. Although dispersal is known to strongly affect spatial genetic structure during range expansions, the resulting patterns and their impact on neutral diversity remain poorly understood. Here, we systematically study the consequences of long-range dispersal on patterns of neutral variation during range expansion in a class of dispersal models which spans the extremes of local (effectively short-ranged) and global (effectively well-mixed) migration. We find that sufficiently long-ranged dispersal leaves behind a mosaic of monoallelic patches, whose number and size are highly sensitive to the distribution of dispersal distances. We develop a coarse-grained model which connects statistical features of these spatial patterns to the evolution of neutral diversity during the range expansion. We show that growth mechanisms that appear qualitatively similar can engender vastly different outcomes for diversity: depending on the tail of the dispersal distance distribution, diversity can either be preserved (i.e. many variants survive) or lost (i.e. one variant dominates) at long times. Our results highlight the impact of spatial and migratory structure on genetic variation during processes as varied as range expansions, species invasions, epidemics, and the spread of beneficial mutations in established populations.

scholarly journals Causal Geometry

Entropy ◽  
2020 ◽  
Vol 23 (1) ◽  
pp. 24
Author(s):  
Pavel Chvykov ◽  
Erik Hoel
Keyword(s):  
Causal Relationship ◽  
Causal Model ◽  
Information Geometry ◽  
Scientific Models ◽  
Coarse Grained ◽  
Model Parameters ◽  
Coarse Grained Model ◽  
Fundamental Part ◽  
The Impact ◽  
Causal Geometry

Information geometry has offered a way to formally study the efficacy of scientific models by quantifying the impact of model parameters on the predicted effects. However, there has been little formal investigation of causation in this framework, despite causal models being a fundamental part of science and explanation. Here, we introduce causal geometry, which formalizes not only how outcomes are impacted by parameters, but also how the parameters of a model can be intervened upon. Therefore, we introduce a geometric version of “effective information”—a known measure of the informativeness of a causal relationship. We show that it is given by the matching between the space of effects and the space of interventions, in the form of their geometric congruence. Therefore, given a fixed intervention capability, an effective causal model is one that is well matched to those interventions. This is a consequence of “causal emergence,” wherein macroscopic causal relationships may carry more information than “fundamental” microscopic ones. We thus argue that a coarse-grained model may, paradoxically, be more informative than the microscopic one, especially when it better matches the scale of accessible interventions—as we illustrate on toy examples.

Ozonation of Non-Ionic Surfactants in Aqueous Solutions

1985 ◽  
Vol 17 (6-7) ◽  
pp. 1069-1080 ◽  
Author(s):  
Nava Narkis ◽  
Bella Ben-David ◽  
Malka Schneider Rotel
Keyword(s):  
Ethylene Oxide ◽  
Aqueous Solutions ◽  
Reaction Rate ◽  
Oxidation Mechanism ◽  
Ionic Surfactants ◽  
Ionic Surfactant ◽  
Nonyl Phenol ◽  
First Order ◽  
Reaction Rate Constants ◽  
Dilute Aqueous Solutions

The effect of ozone on dilute aqueous solutions of a series of non-ionic surfactants of nonyl phenol ethoxylates, with n=4 to 30 ethylene oxide groups, dinonyl phenol ethoxylate and a polyethylene glycol were investigated. Assuming ozone concentration in solution to remain constant throughout the ozonation, the experiments showed first-order reactions with respect to surfactant concentration, as measured by the Wickbold method, and also with respect to COD & TOC. A linear relationship was established between the first-order reaction rate constants, and between n, the average number of ethylene oxide groups in the ethoxylate chain of the nonyl phenol ethoxylate series. The oxidation mechanism by ozone of non-ionic surfactant molecules is explained as mainly polyethoxylate chains' cleavage into shorter polyethylene glycols and to a smaller extent oxidation of the aromatic ring. High ozone doses do not convert the non-ionic surfactant completely to CO2 and H2O but smaller doses are sufficient to enhance biodegradation.

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