1,535 research outputs found
Kinetic signatures of the region surrounding the X-line in asymmetric (magnetopause) reconnection
Kinetic particle-in-cell simulations are used to identify signatures of the
electron diffusion region (EDR) and its surroundings during asymmetric magnetic
reconnection. A "shoulder" in the sunward pointing normal electric field (EN >
0) at the reconnection magnetic field reversal is a good indicator of the EDR,
and is caused by magnetosheath electron meandering orbits in the vicinity of
the x-line. Earthward of the X-line, electrons accelerated by EN form strong
currents and crescent-shaped distribution functions in the plane perpendicular
to B. Just downstream of the X-line, parallel electric fields create
field-aligned crescent electron distribution functions. In the immediate
upstream magnetosheath, magnetic field strength, plasma density, and
perpendicular electron temperatures are lower than the asymptotic state. In the
magnetosphere inflow region, magnetosheath ions intrude resulting in an
Earthward pointing electric field and parallel heating of magnetospheric
particles. Many of the above properties persist with a guide field of at least
unity.Comment: Submitted to Geophysical Research Letter
The silicon trypanosome
African trypanosomes have emerged as promising unicellular model organisms for the next generation of systems biology. They offer unique advantages, due to their relative simplicity, the availability of all standard genomics techniques and a long history of quantitative research. Reproducible cultivation methods exist for morphologically and physiologically distinct life-cycle stages. The genome has been sequenced, and microarrays, RNA-interference and high-accuracy metabolomics are available. Furthermore, the availability of extensive kinetic data on all glycolytic enzymes has led to the early development of a complete, experiment-based dynamic model of an important biochemical pathway. Here we describe the achievements of trypanosome systems biology so far and outline the necessary steps towards the ambitious aim of creating a , a comprehensive, experiment-based, multi-scale mathematical model of trypanosome physiology. We expect that, in the long run, the quantitative modelling enabled by the Silicon Trypanosome will play a key role in selecting the most suitable targets for developing new anti-parasite drugs
The mechanism of thickness selection in the Sadler-Gilmer model of polymer crystallization
Recent work on the mechanism of polymer crystallization has led to a proposal
for the mechanism of thickness selection which differs from those proposed by
the surface nucleation theory of Lauritzen and Hoffman and the entropic barrier
model of Sadler and Gilmer. This has motivated us to reexamine the model used
by Sadler and Gilmer. We again find a fixed-point attractor which describes the
dynamical convergence of the crystal thickness to a value just larger than the
minimum stable thickness, l_min. This convergence arises from the combined
effect of two constraints on the length of stems in a layer: it is unfavourable
for a stem to be shorter than l_min and for a stem to overhang the edge of the
previous layer. The relationship between this new mechanism and the explanation
given by Sadler and Gilmer in terms of an entropic barrier is discussed. We
also examine the behaviour of the Sadler-Gilmer model when an energetic
contribution from chain folds is included.Comment: 15 pages, 13 figures, revte
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