10,480 research outputs found
A Statistical Model of Magnetic Islands in a Large Current Layer
We develop a statistical model describing the dynamics of magnetic islands in
very large current layers that develop in space plasma. Two parameters
characterize the island distribution: the flux contained in the island and the
area it encloses. We derive an integro-differential evolution equation for this
distribution function, based on rules that govern the small-scale generation of
secondary islands, the rates of island growth, and island merging. Our
numerical solutions of this equation produce island distributions relevant to
the magnetosphere and corona. We also derive and analytically solve a
differential equation for large islands that explicitly shows the role merging
plays in island growth.Comment: 4 pages, 3 figure
Four-way regulation of mosquito yolk protein precursor genes by juvenile hormone-, ecdysone-, nutrient-, and insulin-like peptide signaling pathways.
Anautogenous mosquito females require a meal of vertebrate blood in order to initiate the production of yolk protein precursors by the fat body. Yolk protein precursor gene expression is tightly repressed in a state-of-arrest before blood meal-related signals activate it and expression levels rise rapidly. The best understood example of yolk protein precursor gene regulation is the vitellogenin-A gene (vg) of the yellow fever mosquito Aedes aegypti. Vg-A is regulated by (1) juvenile hormone signaling, (2) the ecdysone-signaling cascade, (3) the nutrient sensitive target-of-rapamycin signaling pathway, and (4) the insulin-like peptide (ILP) signaling pathway. A plethora of new studies have refined our understanding of the regulation of yolk protein precursor genes since the last review on this topic in 2005 (Attardo et al., 2005). This review summarizes the role of these four signaling pathways in the regulation of vg-A and focuses upon new findings regarding the interplay between them on an organismal level
Super-Alfv\'enic propagation of reconnection signatures and Poynting flux during substorms
The propagation of reconnection signatures and their associated energy are
examined using kinetic particle-in-cell simulations and Cluster satellite
observations. It is found that the quadrupolar out-of-plane magnetic field near
the separatrices is associated with a kinetic Alfv\'en wave. For magnetotail
parameters, the parallel propagation of this wave is super-Alfv\'enic
(V_parallel ~ 1500 - 5500 km/s) and generates substantial Poynting flux (S ~
10^-5 - 10^-4 W/m^2) consistent with Cluster observations of magnetic
reconnection. This Poynting flux substantially exceeds that due to frozen-in
ion bulk outflows and is sufficient to generate white light aurora in the
Earth's ionosphere.Comment: Submitted to PRL on 11/1/2010. Resubmitted on 4/5/201
The Effects of Turbulence on Three-Dimensional Magnetic Reconnection at the Magnetopause
Two- and three-dimensional particle-in-cell simulations of a recent encounter
of the Magnetospheric Multiscale Mission (MMS) with an electron diffusion
region at the magnetopause are presented. While the two-dimensional simulation
is laminar, turbulence develops at both the x-line and along the magnetic
separatrices in the three-dimensional simulation. The turbulence is strong
enough to make the magnetic field around the reconnection island chaotic and
produces both anomalous resistivity and anomalous viscosity. Each contribute
significantly to breaking the frozen-in condition in the electron diffusion
region. A surprise is that the crescent-shaped features in velocity space seen
both in MMS observations and in two-dimensional simulations survive, even in
the turbulent environment of the three-dimensional system. This suggests that
MMS's measurements of crescent distributions do not exclude the possibility
that turbulence plays an important role in magnetopause reconnection.Comment: Revised version accepted by GR
Evaluation of a Coping Kit of Items to Support Children with Developmental Disorders in the Hospital Setting
This study attempted to answer the question, Do nurses perceive coping kits to be effective at meeting the needs of hospitalized children with developmental disabilities who are at increased risk for challenging behaviors? A cross-sectional post-test survey study design was used, with a convenience sample of 24 registered nurses at a Midwestern free-standing children\u27s hospital. A coping kit with simple communication cards, social script book, and distraction items (toys) was developed to enhance communication and distract children with developmental disabilities (including autism spectrum disorder) undergoing procedures in the hospital. A modified version of Hudson\u27s (2006) intervention effectiveness survey was used to measure the nurse\u27s perception of the effectiveness of the coping kit. Nurses perceived the coping kits to be effective for decreasing their patient\u27s anxiety, calming the child\u27s behavior, and increasing cooperation during procedures. The nurse can develop a plan of care that includes a coping kit to help gain cooperation with the hospitalized child with challenging behaviors
Quality control of EUVE databases
The publicly accessible databases for the Extreme Ultraviolet Explorer include: the EUVE Archive mailserver; the CEA ftp site; the EUVE Guest Observer Mailserver; and the Astronomical Data System node. The EUVE Performance Assurance team is responsible for verifying that these public EUVE databases are working properly, and that the public availability of EUVE data contained therein does not infringe any data rights which may have been assigned. In this poster, we describe the Quality Assurance (QA) procedures we have developed from the approach of QA as a service organization, thus reflecting the overall EUVE philosophy of Quality Assurance integrated into normal operating procedures, rather than imposed as an external, post facto, control mechanism
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