10,387 research outputs found
An improved reconstruction procedure for the correction of local magnification effects in three-dimensional atom-probe
A new 3DAP reconstruction procedure is proposed that accounts for the
evaporation field of a secondary phase. It applies the existing cluster
selection software to identify the atoms of the second phase and, subsequently,
an iterative algorithm to homogenise the volume laterally. This Procedure,
easily implementable on existing reconstruction software, has been applied
successfully on simulated and real 3DAP analyses
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Global morphogenetic flow is accurately predicted by the spatial distribution of myosin motors.
During embryogenesis tissue layers undergo morphogenetic flow rearranging and folding into specific shapes. While developmental biology has identified key genes and local cellular processes, global coordination of tissue remodeling at the organ scale remains unclear. Here, we combine in toto light-sheet microscopy of the Drosophila embryo with quantitative analysis and physical modeling to relate cellular flow with the patterns of force generation during the gastrulation process. We find that the complex spatio-temporal flow pattern can be predicted from the measured meso-scale myosin density and anisotropy using a simple, effective viscous model of the tissue, achieving close to 90% accuracy with one time dependent and two constant parameters. Our analysis uncovers the importance of a) spatial modulation of myosin distribution on the scale of the embryo and b) the non-locality of its effect due to mechanical interaction of cells, demonstrating the need for the global perspective in the study of morphogenetic flow
A Note on Easy and Efficient Computation of Full Abelian Periods of a Word
Constantinescu and Ilie (Bulletin of the EATCS 89, 167-170, 2006) introduced
the idea of an Abelian period with head and tail of a finite word. An Abelian
period is called full if both the head and the tail are empty. We present a
simple and easy-to-implement -time algorithm for computing all
the full Abelian periods of a word of length over a constant-size alphabet.
Experiments show that our algorithm significantly outperforms the
algorithm proposed by Kociumaka et al. (Proc. of STACS, 245-256, 2013) for the
same problem.Comment: Accepted for publication in Discrete Applied Mathematic
Early out-of-equilibrium beam-plasma evolution
We solve analytically the out-of-equilibrium initial stage that follows the
injection of a radially finite electron beam into a plasma at rest and test it
against particle-in-cell simulations. For initial large beam edge gradients and
not too large beam radius, compared to the electron skin depth, the electron
beam is shown to evolve into a ring structure. For low enough transverse
temperatures, the filamentation instability eventually proceeds and saturates
when transverse isotropy is reached. The analysis accounts for the variety of
very recent experimental beam transverse observations.Comment: to appear in Phys. Rev. Letter
Anticorrelation between Ion Acceleration and Nonlinear Coherent Structures from Laser-Underdense Plasma Interaction
In laser-plasma experiments, we observed that ion acceleration from the
Coulomb explosion of the plasma channel bored by the laser, is prevented when
multiple plasma instabilities such as filamentation and hosing, and nonlinear
coherent structures (vortices/post-solitons) appear in the wake of an
ultrashort laser pulse. The tailoring of the longitudinal plasma density ramp
allows us to control the onset of these insabilities. We deduced that the laser
pulse is depleted into these structures in our conditions, when a plasma at
about 10% of the critical density exhibits a gradient on the order of 250
{\mu}m (gaussian fit), thus hindering the acceleration. A promising
experimental setup with a long pulse is demonstrated enabling the excitation of
an isolated coherent structure for polarimetric measurements and, in further
perspectives, parametric studies of ion plasma acceleration efficiency.Comment: 4 pages, 5 figure
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