scholarly journals Evidence of log-periodic oscillations and increasing icequake activity during the breaking-off of large ice masses

2008 ◽  
Vol 54 (187) ◽  
pp. 725-737 ◽  
Author(s):  
Jérome Faillettaz ◽  
Antoine Pralong ◽  
Martin Funk ◽  
Nicholas Deichmann
Keyword(s):  
Snow Avalanches ◽  
Velocity Measurements ◽  
Time Singularity ◽  
Periodic Oscillations ◽  
Physical Mechanisms ◽  
Naturally Occurring ◽  
Combined Motion ◽  
Power Law Function ◽  
Finite Time Singularity ◽  
First Time

AbstractIn 1973, surface velocities were measured for the first time on an unstable hanging glacier to predict its collapse. The observed velocities have been shown to increase as a power-law function of time up to infinity at the theoretical time of failure (known as ‘finite time singularity’). This is the characteristic signature of critical phenomena and has been observed in the case of various other naturally occurring ruptures such as earthquakes, landslides and snow avalanches. Recent velocity measurements performed on Weisshorn and Mönch hanging glaciers, Switzerland, confirmed this behaviour, while log-periodic oscillations superimposed on this general acceleration were also detected. Despite different rupture mechanisms in both cases, the log frequency of the oscillations is shown to be the same. The seismic activity was recorded near the unstable Weisshorn hanging glacier, simultaneously with the velocity measurements. Results show dramatically increasing icequake activity 3 days before the final collapse. Combined motion–seismic monitoring seems to be a promising way to accurately predict the breaking-off of hanging glaciers. Such a combined analysis is also useful for capturing the physical mechanisms of rupture in natural heterogeneous materials.

scholarly journals On the predictability of ice avalanches

2005 ◽  
Vol 12 (6) ◽  
pp. 849-861 ◽  
Author(s):  
A. Pralong ◽  
C. Birrer ◽  
W. A. Stahel ◽  
M. Funk
Keyword(s):  
Power Law ◽  
Time Window ◽  
Regression Method ◽  
Linear Regression Method ◽  
Time Singularity ◽  
Periodic Oscillations ◽  
Power Law Function ◽  
Spatially Homogeneous ◽  
Finite Time Singularity ◽  
Time Of Failure

Abstract. The velocity of unstable large ice masses from hanging glaciers increases as a power-law function of time prior to failure. This characteristic acceleration presents a finite-time singularity at the theoretical time of failure and can be used to forecast the time of glacier collapse. However, the non-linearity of the power-law function makes the prediction difficult. The effects of the non-linearity on the predictability of a failure are analyzed using a non-linear regression method. Predictability strongly depends on the time window when the measurements are performed. Log-periodic oscillations have been observed to be superimposed on the motion of large unstable ice masses. The value of their amplitude, frequency and phase are observed to be spatially homogeneous over the whole unstable ice mass. Inclusion of a respective term in the function describing the acceleration of unstable ice masses greatly increases the accuracy of the prediction.

scholarly journals Type II singularities on complete non-compact Yamabe flow

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Beomjun Choi ◽  
Panagiota Daskalopoulos ◽  
John King
Keyword(s):  
Blow Up ◽  
Type Ii ◽  
Conformally Flat ◽  
Time Singularity ◽  
Yamabe Flow ◽  
Blowing Up ◽  
Rotationally Symmetric ◽  
Blow Up Rate ◽  
Finite Time Singularity ◽  
First Time

AbstractThis work concerns with the existence and detailed asymptotic analysis of type II singularities for solutions to complete non-compact conformally flat Yamabe flow with cylindrical behavior at infinity. We provide the specific blow-up rate of the maximum curvature and show that the solution converges, after blowing-up around the curvature maximum points, to a rotationally symmetric steady soliton. It is the first time that the steady soliton is shown to be a finite time singularity model of the Yamabe flow.

Experimental observation of viscoelastic fluid–structure interactions

2017 ◽  
Vol 813 ◽  
Author(s):  
Anita A. Dey ◽  
Yahya Modarres-Sadeghi ◽  
Jonathan P. Rothstein
Keyword(s):  
Flow Instability ◽  
Reynolds Numbers ◽  
Time Dependent ◽  
Flexible Structure ◽  
Fluid Inertia ◽  
Fluid Structure Interactions ◽  
Periodic Oscillations ◽  
Fluid Structure ◽  
Dependent Growth ◽  
First Time

It is well known that when a flexible or flexibly mounted structure is placed perpendicular to the flow of a Newtonian fluid, it can oscillate due to the shedding of separated vortices. Here, we show for the first time that fluid–structure interactions can also be observed when the fluid is viscoelastic. For viscoelastic fluids, a flexible structure can become unstable in the absence of fluid inertia, at infinitesimal Reynolds numbers, due to the onset of a purely elastic flow instability. Nonlinear periodic oscillations of the flexible structure are observed and found to be coupled to the time-dependent growth and decay of viscoelastic stresses in the wake of the structure.

scholarly journals Microbialite-like structures in Cladophora sp. (Ulvophyceae) mats from a subtropical Andean basin: ecological implications

2019 ◽  
Vol 67 (1) ◽  
Author(s):  
Hugo R. Fernández ◽  
Ana Lucia Gonzalez Achem ◽  
Marcela Correa ◽  
Virginia H. Albarracín
Keyword(s):  
Organic Pollution ◽  
Biological Factors ◽  
X Ray Diffraction ◽  
Calcite Precipitation ◽  
Annual Cycles ◽  
X Ray ◽  
Naturally Occurring ◽  
Ecological Implications ◽  
First Time ◽  
Solubility Equilibrium

The solubility equilibrium of calcite is influenced by physicochemical, climatic and biological factors. Annual cycles of exceptionally prolonged drought, in conjunction with naturally occurring diffuse organic pollution, generate the unique conditions for the precipitation of lithified carbonate structures (microbialites). The aim of this article is to analyze the possible implications of calcite precipitation produced in mats of Cladophora sp. in an Andean subtropical basin, considering it is the first time this phenomenon is described for the region. We collected samples from selected sites at the Lules River Basin, in four sampling dates between the years 2003 and 2004, within a monitoring work of 15 years. Samples were analyzed using an electron microscope and X-ray diffraction analysis. We found that Gomphonema sp. attached to Cladophora sp. contributes to precipitation of calcite and formation of microbialite like structures, in the studied area. This work presents an initial discussion of the discovery of microbialites-like structures attached to Cladophora sp. mats in a subtropical Andean stream and the environmental conditions that lead to their production, as well as the possible ecological implications of these microbialites.

scholarly journals Inverse cascade anomalies in fourth-order Leith models

2021 ◽  
Author(s):  
Simon Thalabard ◽  
Sergey Medvedev ◽  
Vladimir Grebenev ◽  
Sergey Nazarenko
Keyword(s):  
Fourth Order ◽  
Field Model ◽  
Kinetic Equations ◽  
Vacuum Field ◽  
Wave Turbulence ◽  
Anomalous Scaling ◽  
Time Singularity ◽  
Linear Diffusion ◽  
Local Approximations ◽  
Finite Time Singularity

Abstract We analyze a family of fourth-order non-linear diffusion models corresponding to local approximations of 4-wave kinetic equations of weak wave turbulence. We focus on a class of parameters for which a dual cascade behaviour is expected with an infrared finite-time singularity associated to inverse transfer of waveaction. This case is relevant for wave turbulence arising in the Nonlinear Schrödinger model and for the gravitational waves in the Einstein’s vacuum field model. We show that inverse transfer is not described by a scaling of the constant-flux solution but has an anomalous scaling. We compute the anomalous exponents and analyze their origin using the theory of dynamical systems.

scholarly journals Finite-time singularity versus global regularity for hyper-viscous Hamilton–Jacobi-like equations

Nonlinearity ◽  
2003 ◽  
Vol 16 (6) ◽  
pp. 1967-1989 ◽  
Author(s):  
Hamid Bellout ◽  
Said Benachour ◽  
Edriss S Titi
Keyword(s):  
Finite Time ◽  
Global Regularity ◽  
Time Singularity ◽  
Finite Time Singularity

scholarly journals Pharmacologic Activities¬ of 3’-Hydroxypterostilbene: Cytotoxic, Anti-Oxidant, Anti-Adipogenic, Anti-Inflammatory, Histone Deacetylase and Sirtuin 1 Inhibitory Activity

2015 ◽  
Vol 18 (4) ◽  
pp. 713 ◽  
Author(s):  
Jody K Takemoto ◽  
Connie M. Remsberg ◽  
Neal M. Davies
Keyword(s):  
Histone Deacetylase ◽  
Inhibitory Activity ◽  
Sirtuin 1 ◽  
In Vitro Assays ◽  
Naturally Occurring ◽  
Anti Oxidant ◽  
Anti Inflammatory ◽  
First Time ◽  
Stilbene Compounds

Purpose: Delineate the selected pharmacodynamics of a naturally occurring stilbene 3’-Hydroxypterostilbene. Objective: Characterize for the first time the pharmacodynamics bioactivity in several in-vitro assays with relevant roles in heart disease, inflammation, cancer, and diabetes etiology and pathophysiology. Methods: 3’-Hydroxypterostilbene was studied in in-vitro assays to identify possible bioactivity. Results: 3’-Hydroxypterostilbene demonstrated anti-oxidant, anti-inflammatory, cytotoxic, anti-adipogenic, histone deacetylase, and sirtuin-1 inhibitory activity. Conclusions: The importance of understanding individual stilbene pharmacologic activities were delineated.  Small changes in chemical structure of stilbene compounds result in significant pharmacodynamic differences. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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