3,780 research outputs found

    Curvature Fields, Topology, and the Dynamics of Spatiotemporal Chaos

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    The curvature field is measured from tracer particle trajectories in a two-dimensional fluid flow that exhibits spatiotemporal chaos, and is used to extract the hyperbolic and elliptic points of the flow. These special points are pinned to the forcing when the driving is weak, but wander over the domain and interact in pairs at stronger driving, changing the local topology of the flow. Their behavior reveals a two-stage transition to spatiotemporal chaos: a gradual loss of spatial and temporal order followed by an abrupt onset of topological changes.Comment: 5 pages, 5 figure

    Alien Registration- Ouellette, Ernest J. (Lewiston, Androscoggin County)

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    https://digitalmaine.com/alien_docs/27702/thumbnail.jp

    Hair Cortisol Concentrations in High- and Low-Stress Mother-Daughter Dyads

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    Hair cortisol concentrations (HCC) are receiving increased attention as a novel biomarker of psychophysiological responses to chronic stress. I examined the validity of HCC as a marker of psychosocial stress in mother-daughter dyads characterized by high (n = 30) or low (n = 30) maternal chronic stress. Additionally, I examined whether early care and daughters’ symptoms moderated similarity of HCC levels within dyads. Finally, I examined chronic stress and early caregiving as potential mediators of children’s cortisol stability. High-stress mothers had significantly lower HCC compared to low-stress mothers. Further, HCC in daughters were significantly associated with previously assessed salivary cortisol reactivity. Mother-daughter HCC associations were significantly moderated by negative parenting styles and children’s internalizing symptoms. Results did not support the mediating roles of either chronic stress or caregiving in the stability of children’s cortisol. Findings overall indicate that HCC may be a useful marker of cortisol responses to chronic stress

    From Unrest to Occupation

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    The repeated occurrences of protest violence during or following Black Lives Matter (BLM) demonstrations has been an issue for the United States since the mass demonstrations of Ferguson, MO in August of 2014. Since then, the United States has experienced a trend of organized demonstrations which follow officer-involved shootings of primarily African American civilians. How and why communities around the nation react to police violence can vary, as do the explanations for the responses of community members, demonstrators, and police officers. The protests of Ferguson, MO (2014) and of North Minneapolis, MN (2015) were similarly prompted by police shootings but each experienced a different kind of protest and police response. This thesis explores how different theoretical perspectives illuminate differences between how Ferguson and North Minneapolis reacted to police violence and argues that multiple theories are needed for analyzing such protests

    Alien Registration- Ouellette, Sylvio J. (Lewiston, Androscoggin County)

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    https://digitalmaine.com/alien_docs/27824/thumbnail.jp

    Alien Registration- Ouellette, Aurele J. (Fort Kent, Aroostook County)

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    https://digitalmaine.com/alien_docs/36322/thumbnail.jp

    Alien Registration- Ouellette, Marie Bertha J. (Lewiston, Androscoggin County)

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    https://digitalmaine.com/alien_docs/27945/thumbnail.jp

    Interaction of Supernova Ejecta with Nearby Protoplanetary Disks

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    The early Solar System contained short-lived radionuclides such as 60Fe (t1/2 = 1.5 Myr) whose most likely source was a nearby supernova. Previous models of Solar System formation considered a supernova shock that triggered the collapse of the Sun's nascent molecular cloud. We advocate an alternative hypothesis, that the Solar System's protoplanetary disk had already formed when a very close (< 1 pc) supernova injected radioactive material directly into the disk. We conduct the first numerical simulations designed to answer two questions related to this hypothesis: will the disk be destroyed by such a close supernova; and will any of the ejecta be mixed into the disk? Our simulations demonstrate that the disk does not absorb enough momentum from the shock to escape the protostar to which it is bound. Only low amounts (< 1%) of mass loss occur, due to stripping by Kelvin-Helmholtz instabilities across the top of the disk, which also mix into the disk about 1% of the intercepted ejecta. These low efficiencies of destruction and injectation are due to the fact that the high disk pressures prevent the ejecta from penetrating far into the disk before stalling. Injection of gas-phase ejecta is too inefficient to be consistent with the abundances of radionuclides inferred from meteorites. On the other hand, the radionuclides found in meteorites would have condensed into dust grains in the supernova ejecta, and we argue that such grains will be injected directly into the disk with nearly 100% efficiency. The meteoritic abundances of the short-lived radionuclides such as 60Fe therefore are consistent with injection of grains condensed from the ejecta of a nearby (< 1 pc) supernova, into an already-formed protoplanetary disk.Comment: 57 pages, 16 figure
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