Propagating chemoattractant waves coordinate periodic cell movement inDictyosteliumslugs

Development ◽  
2001 ◽  
Vol 128 (22) ◽  
pp. 4535-4543 ◽  
Author(s):  
Dirk Dormann ◽  
Cornelis J. Weijer
Keyword(s):  
Wave Propagation ◽  
Optical Density ◽  
Cell Movement ◽  
Camp Phosphodiesterase ◽  
Periodic Cell ◽  
Propagating Waves ◽  
On Line ◽  
Camp Receptor ◽  
The Waves ◽  
Slug Movement

Migration and behaviour of Dictyostelium slugs results from coordinated movement of its constituent cells. It has been proposed that cell movement is controlled by propagating waves of cAMP as during aggregation and in the mound. We report the existence of optical density waves in slugs; they are initiated in the tip and propagate backwards. The waves reflect periodic cell movement and are mediated by cAMP, as injection of cAMP or cAMP phosphodiesterase disrupts wave propagation and results in effects on cell movement and, therefore, slug migration. Inhibiting the function of the cAMP receptor cAR1 blocks wave propagation, showing that the signal is mediated by cAR1. Wave initiation is strictly dependent on the tip; in decapitated slugs no new waves are initiated and slug movement stops until a new tip regenerates. Isolated tips continue to migrate while producing waves. We conclude from these observations that the tip acts as a pacemaker for cAMP waves that coordinate cell movement in slugs.Movies available on-line

scholarly journals Anomalous Anderson localization behavior in gain-loss balanced non-Hermitian systems

Nanophotonics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 443-452
Author(s):  
Tianshu Jiang ◽  
Anan Fang ◽  
Zhao-Qing Zhang ◽  
Che Ting Chan
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Waves ◽  
Anderson Localization ◽  
Random Media ◽  
Normal Incidence ◽  
Disordered Media ◽  
One Dimensional ◽  
Gain Loss ◽  
The Waves ◽  
Localization Behavior

AbstractIt has been shown recently that the backscattering of wave propagation in one-dimensional disordered media can be entirely suppressed for normal incidence by adding sample-specific gain and loss components to the medium. Here, we study the Anderson localization behaviors of electromagnetic waves in such gain-loss balanced random non-Hermitian systems when the waves are obliquely incident on the random media. We also study the case of normal incidence when the sample-specific gain-loss profile is slightly altered so that the Anderson localization occurs. Our results show that the Anderson localization in the non-Hermitian system behaves differently from random Hermitian systems in which the backscattering is suppressed.

scholarly journals Airglow Measurements of Gravity Wave Propagation and Damping over Kolhapur (16.5°N, 74.2°E)

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
R. N. Ghodpage ◽  
A. Taori ◽  
P. T. Patil ◽  
S. Gurubaran ◽  
A. K. Sharma ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Gravity Wave ◽  
Meridional Wind ◽  
Vertical Wavelength ◽  
Emission Layer ◽  
Positive Correlation ◽  
Intensity Measurements ◽  
Wind Shears ◽  
The Waves ◽  
Airglow Intensity

Simultaneous mesospheric OH and O  (1S) night airglow intensity measurements from Kolhapur (16.8°N, 74.2°E) reveal unambiguous gravity wave signatures with periods varying from 01 hr to 9 hr with upward propagation. The amplitudes growth of these waves is found to vary from 0.4 to 2.2 while propagating from the OH layer (~87 km) to the O (1S) layer (~97 km). We find that vertical wavelength of the observed waves increases with the wave period. The damping factors calculated for the observed waves show large variations and that most of these waves were damped while traveling from the OH emission layer to the O (1S) emission layer. The damping factors for the waves show a positive correlation at vertical wavelengths shorter than 40 km, while a negative correlation at higher vertical wavelengths. We note that the damping factors have stronger positive correlation with meridional wind shears compared to the zonal wind shears.

scholarly journals Accelerating numerical wave propagation using wavefield adapted meshes. Part I: forward and adjoint modelling

2020 ◽  
Vol 221 (3) ◽  
pp. 1580-1590 ◽  
Author(s):  
M van Driel ◽  
C Boehm ◽  
L Krischer ◽  
M Afanasiev
Keyword(s):  
Wave Propagation ◽  
Adaptive Mesh Refinement ◽  
Waveform Inversion ◽  
Computational Cost ◽  
Model Space ◽  
Adaptive Mesh ◽  
Order Of Magnitude ◽  
Speed Up ◽  
Adjoint Modelling ◽  
The Waves

SUMMARY An order of magnitude speed-up in finite-element modelling of wave propagation can be achieved by adapting the mesh to the anticipated space-dependent complexity and smoothness of the waves. This can be achieved by designing the mesh not only to respect the local wavelengths, but also the propagation direction of the waves depending on the source location, hence by anisotropic adaptive mesh refinement. Discrete gradients with respect to material properties as needed in full waveform inversion can still be computed exactly, but at greatly reduced computational cost. In order to do this, we explicitly distinguish the discretization of the model space from the discretization of the wavefield and derive the necessary expressions to map the discrete gradient into the model space. While the idea is applicable to any wave propagation problem that retains predictable smoothness in the solution, we highlight the idea of this approach with instructive 2-D examples of forward as well as inverse elastic wave propagation. Furthermore, we apply the method to 3-D global seismic wave simulations and demonstrate how meshes can be constructed that take advantage of high-order mappings from the reference coordinates of the finite elements to physical coordinates. Error level and speed-ups are estimated based on convergence tests with 1-D and 3-D models.

scholarly journals Demonstration and application of diffusive and ballistic wave propagation for drone-to-ground and drone-to-drone wireless communications

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Peter J. Burke
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Path Loss ◽  
Base Station ◽  
Physical Models ◽  
Mapping Technology ◽  
Aerial Vehicle ◽  
A Cell ◽  
Independent Path ◽  
The Waves

Abstract In order to determine how an electromagnetic wave propagates from a base station to a cell phone or a wirelessly connected device, we use a novel Unmanned Aerial Vehicle (UAV) mapping technology to map the cellular network coverage at various altitudes in various terrains (flat, hilly, mountainous). For the flat terrains, the waves are shown to propagate ballistically: They have an altitude independent path loss consistent with minimal scatter in the propagation from transmitter to (aerial) receiver. In mountainous terrain, the waves are shown to propagate in the diffuse regime, and demonstrate a 10 dB increase in received signal intensity per 100′ of altitude gain, up to 400′. In the intermediate case, evidence of coherent wave interference is clearly observed in altitude independent interference patterns. These general observations can be used to build a physical or empirical model for drone-to-ground and drone-to-drone propagation, for which existing models are shown to fail. While important for building physical models of wave propagation in wireless networks, this method can be used more generally to determine the magnitude and phase of an electromagnetic wave at every point in space, as well as usher in the era of drone-to-ground and drone-to-drone communications.

scholarly journals Energy occupation of waves and structures in 3D compressive MHD turbulence

2019 ◽  
Vol 488 (1) ◽  
pp. 859-867 ◽  
Author(s):  
L P Yang ◽  
H Li ◽  
S T Li ◽  
L Zhang ◽  
J S He ◽  
...  
Keyword(s):  
Large Scale ◽  
Mean Field ◽  
Turbulent Energy ◽  
Mhd Turbulence ◽  
Linear Cascade ◽  
Temporal Domain ◽  
Propagating Waves ◽  
Cascade Processes ◽  
Parallel Direction ◽  
The Waves

Abstract Structures and propagating waves are often observed in solar wind turbulence. Their origins and features remain to be uncovered. In this work, we use 3D driven, compressible MHD turbulence simulations to investigate the global signatures of the driven fluctuations in whole spatial and temporal domain. With four-dimensional spatial-temporal (x, y, z, t) Fourier transformations implemented, we have identified two distinct main populations: waves, which satisfy the $\omega -\boldsymbol {k}$ dispersion relations and are propagating; and structures, which satisfy the polarization relations but non-propagating (ω = 0). Whereas the overall turbulent energy spectrum is still consistent with k−5/3, the contributions from waves and structures show very different behaviour in $\boldsymbol {k}$ space, with structures dominating at small k but waves becomes comparable to structures at large k. Overall, the fluctuations in the directions perpendicular to the large-scale mean field $\boldsymbol {B_0}$ are a manifestation of structures, while along the parallel direction, the fluctuations are dominated by waves. Also, a significant portion of the incompressible structures are the Alfvénic nature, and with imbalanced increased, the waves predominantly propagate in one direction and nearly perpendicular to $\boldsymbol {B_0}$. Differentiating the relative contributions from waves and structures could have important implications for understanding the non-linear cascade processes in the inertial range as well as particle-fluctuation interactions at small scales.

Rayleigh surface waves along the boundary between a plasma and a metallic screen

1993 ◽  
Vol 49 (2) ◽  
pp. 227-235 ◽  
Author(s):  
S. T. Ivanov ◽  
K. M. Ivanova ◽  
E. G. Alexov
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Surface Waves ◽  
Electromagnetic Waves ◽  
Electromagnetic Wave Propagation ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Magnetoactive Plasma ◽  
Rayleigh Surface Waves ◽  
The Waves

Electromagnetic wave propagation along the interface between a magnetoactive plasma and a metallic screen is investigated analytically and numerically. It is shown that the waves have a Rayleigh character: they are superpositions of two partial waves. It is concluded that electromagnetic waves propagate only at frequencies lower than min (ωp, ωc), where ωpis the plasma frequency and ωcis the cyclotron frequency. The field topology is found, and the physical character of the waves is discussed.

scholarly journals Wave propagation of junctional remodeling in collective cell movement of epithelial tissue

2017 ◽  
Vol 145 ◽  
pp. S41
Author(s):  
Tetsuya Hiraiwa ◽  
Erina Kuranaga ◽  
Tatsuo Shibata
Keyword(s):  
Wave Propagation ◽  
Cell Movement ◽  
Epithelial Tissue
Sign in / Sign up

Export Citation Format

Share Document