3,294 research outputs found
Hollow vortices and minimal surfaces
We consider an overdetermined elliptic problem known as the hollow vortex
problem. We prove that the solutions to this problem are in 1:1 correspondence
with minimal graphs bounded by horizontal symmetry lines. We use this
correspondence to give various examples of domains with hollow vortices.Comment: 22 pages, 7 figure
Chaco Canyon: A Contested Memory Anchor in the North American Southwest
Natural and archaeological places are powerful loci for social memories and
continually negotiated meanings. As ‘memory anchors’ they are focal points for
the construction of memory and meaning, and can become flashpoints for
disputes over access, land-use, and knowledge claims among stakeholders with
contradictory interests. In the North American Southwest the competing claims
of Native American tribes, archaeologists, government bureaucrats, tourists,
and the mining industry come into sharp relief. In this paper, I explore how
the UNESCO World Heritage Site of Chaco Canyon figures prominently in the
origin stories and sacred geographies of contemporary Pueblo and Navajo
peoples – two indigenous groups with competing political stakes in the
present
Dynamics and efficiency of a self-propelled, diffusiophoretic swimmer
Active diffusiophoresis - swimming through interaction with a self-generated,
neutral, solute gradient - is a paradigm for autonomous motion at the
micrometer scale. We study this propulsion mechanism within a linear response
theory. Firstly, we consider several aspects relating to the dynamics of the
swimming particle. We extend established analytical formulae to describe small
swimmers, which interact with their environment on a finite lengthscale. Solute
convection is also taken into account. Modeling of the chemical reaction
reveals a coupling between the angular distribution of reactivity on the
swimmer and the concentration field. This effect, which we term "reaction
induced concentration distortion", strongly influences the particle speed.
Building on these insights, we employ irreversible, linear thermodynamics to
formulate an energy balance. This approach highlights the importance of solute
convection for a consistent treatment of the energetics. The efficiency of
swimming is calculated numerically and approximated analytically. Finally, we
define an efficiency of transport for swimmers which are moving in random
directions. It is shown that this efficiency scales as the inverse of the
macroscopic distance over which transport is to occur.Comment: 16 pages, 11 figure
Alien Registration- Van Dyke, Frank M. (Portland, Cumberland County)
https://digitalmaine.com/alien_docs/21671/thumbnail.jp
Quadra v. Superior Court of the City and County of San Francisco: A Challenge to the Composition of the San Francisco Grand Jury
Quadra v. Superior Court involves a challenge to the procedures used in the selection of San Francisco\u27s investigative grand jury. The Hastings Law Journal has reprinted plaintiffs\u27 memoranda, which argue that such procedures should be governed by the standards applicable to indicting grand juries
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