The dual developmental origin of spinal cerebrospinal fluid-contacting neurons gives rise to distinct functional subtypes.

Chemical and mechanical cues from the cerebrospinal fluid (CSF) can affect the development and function of the central nervous system (CNS). How such cues are detected and relayed to the CNS remains elusive. Cerebrospinal fluid-contacting neurons (CSF-cNs) situated at the interface between the CSF and the CNS are ideally located to convey such information to local networks. In the spinal cord, these GABAergic neurons expressing the PKD2L1 channel extend an apical extension into the CSF and an ascending axon in the spinal cord. In zebrafish and mouse spinal CSF-cNs originate from two distinct progenitor domains characterized by distinct cascades of transcription factors. Here we ask whether these neurons with different developmental origins differentiate into cells types with different functional properties. We show in zebrafish larva that the expression of specific markers, the morphology of the apical extension and axonal projections, as well as the neuronal targets contacted by CSF-cN axons, distinguish the two CSF-cN subtypes. Altogether our study demonstrates that the developmental origins of spinal CSF-cNs give rise to two distinct functional populations of sensory neurons. This work opens novel avenues to understand how these subtypes may carry distinct functions related to development of the spinal cord, locomotion and posture

Insights on the source of the 28 September 2018 Sulawesi tsunami, Indonesia based on spectral analyses and numerical simulations

The 28 September 2018 Sulawesi tsunami has been a puzzle because extreme deadly tsunami waves were generated following an Mw 7.5 strike-slip earthquake, while such earthquakes are not usually considered to produce large tsunamis. Here, we obtained, processed and analyzed two sea level records of the tsunami in the near-field (Pantoloan located inside the Palu Bay) and far-field (Mamuju located outside the Palu Bay) and conducted numerical simulations to shed light on the tsunami source. The two tide gauges recorded maximum tsunami trough-to-crest heights of 380 and 24 cm, respectively, with respective dominating wave periods of 3.6-4.4 and 10 min, and respective high-energy wave duration of 5.5 and [14 h. The two observed waveforms were significantly different with wave amplitude and period ratios of *16 and *3, respectively. We infer tsunamigenic source dimen19 sions of 3.4–4.1 km and 32.5 km, for inside and outside of the Palu Bay, respectively. Our numerical simulations fairly well repro21 duced both tsunami observations in Pantoloan and Mamuju; except for the arrival time in Mamuju. However, it was incapable of reproducing the maximum reported coastal amplitudes of 6–11 m. It is possible that these two sources are different parts of the same tectonic source. A bay oscillation mode of *85 min was revealed for the Palu Bay through numerical modeling. Actual sea surface disturbances and landslide-generated waves were captured by two video recordings from inside the Palu Bay shortly after the earthquake. It is possible that a large submarine landslide contributed to and intensified the Sulawesi tsunami. We identify the southern part of the Palu Bay, around the latitude of -0.82o S, as the most likely location of a potential landslide based on our backward tsunami ray tracing analysis. However, marine geological data from the Palu Bay are required to confirm such hypothesis

Finite element analysis of surface instability in hypo-elastic solids

The surface instability of hypo-elastic solids is detected by using numerical stability techniques similar to those used to address the buckling problems of shell and truss structures. The performance of the proposed method is tested by comparing numerical to analytical results in the case of a simple boundary value problem—the plane strain compression test of blocks made of isotropic and anisotropic hypo-elastic materials. Although tested in a simple example, the proposed method can be applied to detect surface instability of more complicated boundary value problems, which are encountered in the fields of solids mechanics, structural geology and rock mechanics

Finite element analysis of rockburst as surface instability

This paper assesses the applicability of finite element methods in detecting the surface instability of bulky solid masses. It provides a numerical technique to analyze rockburst as surface buckling. The proposed approach, which is general enough to be applied to most boundary value problems encountered in engineering practice, is calibrated for a particular boundary value problem - the wedge test

Finite element analysis of two-phase instability for saturated porous hypoelastic solids under plane strain loadings

Investigates the effects of two-phase instability on finite element (FE) solutions for porous hypoelastic solids saturated with an insterstitial fluid. Demonstrates that two-phase instability creates definite problems to the FE computations of coupled solid-fluid systems. The eigenvectors of the tangential finite element matrices which are responsible for problems are not artificial, but are the bifurcating modes of physical solutions. The investigation, although limited to the plane strain undrained compression of hypoelastic models, is relevant to the investigation of the two-phase instability of other materials and boundary value problems, and may lead towards an explanation for numerical problems in soil liquefaction analysis

The damping of saturated poroelastic soils during steady-state vibrations

Herein, we analyze the damping that arises from the soil-water interaction within nearly-saturated soils during steady-state vibrations. Based on the two-phase theory of Biot, we analytically derive the spectral response of a column made of nearly saturated poroelastic soils as a function of soil stiffness, degree of saturation, porosity, specific gravity, and permeability. A parametric study determines the influence of these parameters on the fundamental period, maximum amplitude, energy dissipation, damping factor, and maximum pore pressure. In departure from common beliefs in soil dynamics, we conclude that the soil-water damping within fully-saturated sands is not negligible compared to structural hysteretic damping

Etats stationnaires et régimes évolutifs de la charge d'espace dans les diélectriques. Influence de la nature de l'interface sur les distributions de charges et de potentiel

Time dependent phenomena in dielectrics have been simulated by computing the electric charges, potential and field distributions. Analytical expressions of these physical values have been obtained for several boundary conditions for a one-dimension one-carrier model. They show how simple experimental techniques may determine the charge, mobility and quantity of those carriers present in a dielectric.L'utilisation d'une méthode numérique décrite dans un article antérieur a permis d'obtenir les distributions de charge électrique et de potentiel dans un diélectrique unidimensionnel à un porteur. Les résultats obtenus avec des interfaces injectantes symétriques ou non et des interfaces bloquantes ont été comparés. Des expressions analytiques des différentes variables électriques sont données ainsi que leur domaine de validité. De l'étude théorique il a été possible de déduire des techniques expérimentales simples permettant de déterminer la charge q et la mobilité μ des porteurs, ainsi que la concentration de porteurs aux interfaces et la charge totale du matériau

Finite element analysis of plane strain bifurcation within compressible solids

The plane strain bifurcation of compressible solids is analyzed with finite elements by checking the singularity of the tangential stiffness matrix. The performance of the finite element method is tested by comparing numerical to analytical results in the particular case of the plane strain compression of hypoelastic materials. Although tested for a simple example, the proposed method can be applied to analyze the bifurcation phenomena which are observed in the boundary value problems of solid mechanics, structural geology, and geomechanics