33,923 research outputs found
Radar, Insect Population Ecology, and Pest Management
Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives
Exact solution of a model DNA-inversion genetic switch with orientational control
DNA inversion is an important mechanism by which bacteria and bacteriophage
switch reversibly between phenotypic states. In such switches, the orientation
of a short DNA element is flipped by a site-specific recombinase enzyme. We
propose a simple model for a DNA inversion switch in which recombinase
production is dependent on the switch state (orientational control). Our model
is inspired by the fim switch in Escherichia coli. We present an exact
analytical solution of the chemical master equation for the model switch, as
well as stochastic simulations. Orientational control causes the switch to
deviate from Poissonian behaviour: the distribution of times in the on state
shows a peak and successive flip times are correlated.Comment: Revised version, accepted for publicatio
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Magnetotail energy dissipation during an auroral substorm.
Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1km/s. This observed auroral activity appears sufficient to dissipate the released energy
Spacetime structure of static solutions in Gauss-Bonnet gravity: neutral case
We study the spacetime structures of the static solutions in the
-dimensional Einstein-Gauss-Bonnet- system systematically. We
assume the Gauss-Bonnet coefficient is non-negative. The solutions
have the -dimensional Euclidean sub-manifold, which is the Einstein
manifold with the curvature and -1. We also assume , where is the curvature radius, in order for the
sourceless solution (M=0) to be defined. The general solutions are classified
into plus and minus branches. The structures of the center, horizons, infinity
and the singular point depend on the parameters , , ,
and branches complicatedly so that a variety of global structures for the
solutions are found. In the plus branch, all the solutions have the same
asymptotic structure at infinity as that in general relativity with a negative
cosmological constant. For the negative mass parameter, a new type of
singularity called the branch singularity appears at non-zero finite radius
. The divergent behavior around the singularity in Gauss-Bonnet
gravity is milder than that around the central singularity in general
relativity. In the cases the plus-branch solutions do not have any
horizon. In the case, the radius of the horizon is restricted as
) in the plus (minus)
branch. There is also the extreme black hole solution with positive mass in
spite of the lack of electromagnetic charge. We briefly discuss the effect of
the Gauss-Bonnet corrections on black hole formation in a collider and the
possibility of the violation of third law of the black hole thermodynamics.Comment: 19 pages, 11 figure
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