1,072 research outputs found
A Discrete Ion Stochastic Continuum Overdamped Solvent Algorithm for Modeling Electrolytes
In this paper we develop a methodology for the mesoscale simulation of strong
electrolytes. The methodology is an extension of the Fluctuating Immersed
Boundary (FIB) approach that treats a solute as discrete Lagrangian particles
that interact with Eulerian hydrodynamic and electrostatic fields. In both
cases the Immersed Boundary (IB) method of Peskin is used for particle-field
coupling. Hydrodynamic interactions are taken to be overdamped, with thermal
noise incorporated using the fluctuating Stokes equation, including a "dry
diffusion" Brownian motion to account for scales not resolved by the
coarse-grained model of the solvent. Long range electrostatic interactions are
computed by solving the Poisson equation, with short range corrections included
using a novel immersed-boundary variant of the classical Particle-Particle
Particle-Mesh (P3M) technique. Also included is a short range repulsive force
based on the Weeks-Chandler-Andersen (WCA) potential. The new methodology is
validated by comparison to Debye-H{\"u}ckel theory for ion-ion pair correlation
functions, and Debye-H{\"u}ckel-Onsager theory for conductivity, including the
Wein effect for strong electric fields. In each case good agreement is
observed, provided that hydrodynamic interactions at the typical ion-ion
separation are resolved by the fluid grid.Comment: 30 pages, 12 figures, 2 table
Homogenization via formal multiscale asymptotics and volume averaging: How do the two techniques compare?
A wide variety of techniques have been developed to homogenize transport equations in multiscale and multiphase systems. This has yielded a rich and diverse field, but has also resulted in the emergence of isolated scientific communities and disconnected bodies of literature. Here, our goal is to bridge the gap between formal multiscale asymptotics and the volume averaging theory. We illustrate the methodologies via a simple example application describing a parabolic transport problem and, in so doing, compare their respective advantages/disadvantages from a practical point of view. This paper is also intended as a pedagogical guide and may be viewed as a tutorial for graduate students as we provide historical context, detail subtle points with great care, and reference many fundamental works
The Iowa Homemaker vol.3, no.7
Table of Contents
Home Economics Cleans House â Division Ready for New Year by Anna E. Richardson, page 1
Storing the Winterâs Supply of Vitamines by C. L. Fitch, page 2
First Hand Acquaintance With Tokyoâs Earthquake by Katherine Cranor, page 3
Hurrah for the Pumpkin Pie by Ruth Elaine Wilson, page 4
Choosing the Fall Hat by Florence Faust, page 5
Who is Responsible for the Child? by An âOld â Maid Auntâ, page 6
A Review of Farm Meats by Viola M. Bell, page 6
Color Hints From Gay October by Ruth Spencer, page 7
Paying Homage to the King of Fruits by Jeanette Beyer, page 8
Sheppard-Towner Bill by Lois Miller Herd, page 9
Buttons and _______ Buttons by Esther Ellen Rayburn, page 9
Candy Popularity by Esther Ellen Rayburn, page 13
Before the Bar of Science by Eda Lord Murphy, page 15
Gingered Pears by Elizabeth Storm, page 1
A systematic variation of the stellar initial mass function in early-type galaxies
Much of our knowledge of galaxies comes from analysing the radiation emitted
by their stars. It depends on the stellar initial mass function (IMF)
describing the distribution of stellar masses when the population formed.
Consequently knowledge of the IMF is critical to virtually every aspect of
galaxy evolution. More than half a century after the first IMF determination,
no consensus has emerged on whether it is universal in different galaxies.
Previous studies indicated that the IMF and the dark matter fraction in galaxy
centres cannot be both universal, but they could not break the degeneracy
between the two effects. Only recently indications were found that massive
elliptical galaxies may not have the same IMF as our Milky Way. Here we report
unambiguous evidence for a strong systematic variation of the IMF in early-type
galaxies as a function of their stellar mass-to-light ratio, producing
differences up to a factor of three in mass. This was inferred from detailed
dynamical models of the two-dimensional stellar kinematics for the large
Atlas3D representative sample of nearby early-type galaxies spanning two orders
of magnitude in stellar mass. Our finding indicates that the IMF depends
intimately on a galaxy's formation history.Comment: 4 pages, 2 figures, LaTeX. Accepted for publication as a Nature
Letter. More information about our Atlas3D project is available at
http://purl.org/atlas3
Argumentation in school science : Breaking the tradition of authoritative exposition through a pedagogy that promotes discussion and reasoning
The value of argumentation in science education has become internationally recognised and has been the subject of many research studies in recent years. Successful introduction of argumentation activities in learning contexts involves extending teaching goals beyond the understanding of facts and concepts, to include an emphasis on cognitive and metacognitive processes, epistemic criteria and reasoning. The authors focus on the difficulties inherent in shifting a tradition of teaching from one dominated by authoritative exposition to one that is more dialogic, involving small-group discussion based on tasks that stimulate argumentation. The paper builds on previous research on enhancing the quality of argument in school science, to focus on how argumentation activities have been designed, with appropriate strategies, resources and modelling, for pedagogical purposes. The paper analyses design frameworks, their contexts and lesson plans, to evaluate their potential for enhancing reasoning through foregrounding the processes of argumentation. Examples of classroom dialogue where teachers adopt the frameworks/plans are analysed to show how argumentation processes are scaffolded. The analysis shows that several layers of interpretation are needed and these layers need to be aligned for successful implementation. The analysis serves to highlight the potential and limitations of the design frameworks
US SOLAS Science Report
The article of record may be found at https://doi.org/10.1575/1912/27821The Surface Ocean â Lower Atmosphere Study (SOLAS) (http://www.solas-int.org/) is an international research initiative focused on understanding the key biogeochemical-physical interactions and feedbacks between the ocean and atmosphere that are critical elements of climate and global biogeochemical cycles. Following the release of the SOLAS Decadal Science Plan (2015-2025) (BrĂ©viĂšre et al., 2016), the Ocean-Atmosphere Interaction Committee (OAIC) was formed as a subcommittee of the Ocean Carbon and Biogeochemistry (OCB) Scientific Steering Committee to coordinate US SOLAS efforts and activities, facilitate interactions among atmospheric and ocean scientists, and strengthen US contributions to international SOLAS. In October 2019, with support from OCB, the OAIC convened an open community workshop, Ocean-Atmosphere Interactions: Scoping directions for new research with the goal of fostering new collaborations and identifying knowledge gaps and high-priority science questions to formulate a US SOLAS Science Plan. Based on presentations and discussions at the workshop, the OAIC and workshop participants have developed this US SOLAS Science Plan. The first part of the workshop and this Science Plan were purposefully designed around the five themes of the SOLAS Decadal Science Plan (2015-2025) (BrĂ©viĂšre et al., 2016) to provide a common set of research priorities and ensure a more cohesive US contribution to international SOLAS.This report was developed with federal support of NSF (OCE-1558412) and NASA (NNX17AB17G).This report was developed with federal support of NSF (OCE-1558412) and NASA (NNX17AB17G)
- âŠ