660 research outputs found
Propagation of social representations
Based on a minimal formalism of social representations as a set of associated cognems, a simple model of propagation of representations is presented. Assuming that subjects share the constitutive cognems, the model proposes that mere focused attention on the set of cognems in the field of common conscience may replicate the pattern of representation from context into subjects, or, from subject to subject, through actualization by language, where cognems are represented by verbal signs. Limits of the model are discussed, and evolutionist perspectives are presented with the support of field data
Parallel flow in Hele-Shaw cells with ferrofluids
Parallel flow in a Hele-Shaw cell occurs when two immiscible liquids flow
with relative velocity parallel to the interface between them. The interface is
unstable due to a Kelvin-Helmholtz type of instability in which fluid flow
couples with inertial effects to cause an initial small perturbation to grow.
Large amplitude disturbances form stable solitons. We consider the effects of
applied magnetic fields when one of the two fluids is a ferrofluid. The
dispersion relation governing mode growth is modified so that the magnetic
field can destabilize the interface even in the absence of inertial effects.
However, the magnetic field does not affect the speed of wave propagation for a
given wavenumber. We note that the magnetic field creates an effective
interaction between the solitons.Comment: 12 pages, Revtex, 2 figures, revised version (minor changes
Moored current meter, AVHRR, CTD, and drifter data from the Agulhas Current and Retroflexion region (1985-1987) Volume XLII
Stored in the Archives of the Woods Hole Oceanographic Institution is the floppy disk on which can be found the one-day average currents, the path of the Agulhas Current, CTD stations in "Live Atlas" format, SST frontal analyses (Chassignet and Olson, personal communcation) as well as
programs written in QuickBASIC which allow one to access and display these observations. The programs are stored in ASCII and
can be run under the Microsoft QuickBasic (Version 4.0 or higher). Instructions for running the programs can be found in a file
entitled "read.me" on the disk.Data are presented from an experiment designed to explore the spatial and temporal structure of the Agulhas Current and
Retroflexion by direct means. Included are the current meter results from 10 moorings in the Retroflexion region, CTD stations
occupied on the deployment cruise in 1985, data from satellite tracked (ARGOS) freely during surface buoys and numerous images
of the sea surface temperature.Funding was provided by the Office of Naval Research through Contract Nos.
NOOO14-84C-O134, NOO014-85-C-0001, and NOOO14-87-K-0007
Rotating Hele-Shaw cells with ferrofluids
We investigate the flow of two immiscible, viscous fluids in a rotating
Hele-Shaw cell, when one of the fluids is a ferrofluid and an external magnetic
field is applied. The interplay between centrifugal and magnetic forces in
determining the instability of the fluid-fluid interface is analyzed. The
linear stability analysis of the problem shows that a non-uniform, azimuthal
magnetic field, applied tangential to the cell, tends to stabilize the
interface. We verify that maximum growth rate selection of initial patterns is
influenced by the applied field, which tends to decrease the number of
interface ripples. We contrast these results with the situation in which a
uniform magnetic field is applied normally to the plane defined by the rotating
Hele-Shaw cell.Comment: 12 pages, 3 ps figures, RevTe
Phase transitions in a ferrofluid at magnetic field induced microphase separation
In the presence of a magnetic field applied perpendicular to a thin sample
layer, a suspension of magnetic colloidal particles (ferrofluid) can form
spatially modulated phases with a characteristic length determined by the
competition between dipolar forces and short-range forces opposing density
variations. We introduce models for thin-film ferrofluids in which
magnetization and particle density are viewed as independent variables and in
which the non-magnetic properties of the colloidal particles are described
either by a lattice-gas entropy or by the Carnahan-Starling free energy. Our
description is particularly well suited to the low-particle density regions
studied in many experiments. Within mean-field theory, we find isotropic,
hexagonal and stripe phases, separated in general by first-order phase
boundaries.Comment: 12 pages, RevTex, to appear in PR
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The Role of Electron Transport and Trapping in MOS Total-Dose Modeling
Deep and shallow electron traps form in irradiated thermal SiO{sub 2} as a natural response to hole transport and trapping. The density and stability of these defects are discussed, as are their implications for total-dose modeling
The Effects On Children Of Depressed Mothers' Remission And Relapse Over 9 Months
Background—The high rate of depression among children of depressed mothers is well known. Suggestions that improvement in maternal acute depression has a positive effect on the child have emerged. However, data on the mechanisms of change have been sparse. The aim was to understand how remission and relapse in the mother might explain the changes in the child’s outcome
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