scholarly journals The 2019 Eruptive Activity at Stromboli Volcano: A Multidisciplinary Approach to Reveal Hidden Features of the “Unexpected” 3 July Paroxysm

2021 ◽  
Vol 13 (20) ◽  
pp. 4064
Author(s):  
Mario Mattia ◽  
Bellina Di Lieto ◽  
Gaetana Ganci ◽  
Valentina Bruno ◽  
Pierdomenico Romano ◽  
...  
Keyword(s):  
Multidisciplinary Approach ◽  
Confining Pressure ◽  
Short Time Scale ◽  
Stromboli Volcano ◽  
Lower Section ◽  
Low Viscosity ◽  
Remote Cameras ◽  
Depth Analysis ◽  
Eruptive Period ◽  
Short Time

In July and August 2019, Stromboli volcano underwent two dangerous paroxysms previously considered “unexpected” because of the absence of significant changes in usually monitored parameters. We applied a multidisciplinary approach to search for signals able to indicate the possibility of larger explosive activity and to devise a model to explain the observed variations. We analysed geodetic data, satellite thermal data, images from remote cameras and seismic data in a timespan crossing the eruptive period of 2019 to identify precursors of the two paroxysms on a medium-term time span (months) and to perform an in-depth analysis of the signals recorded on a short time scale (hours, minutes) before the paroxysm. We developed a model that explains the observations. We call the model “push and go” where the uppermost feeding system of Stromboli is made up of a lower section occupied by a low viscosity, low density magma that is largely composed of gases and a shallower section occupied by the accumulated melt. We hypothesize that the paroxysms are triggered when an overpressure in the lower section is built up; the explosion will occur at the very moment such overpressure overcomes the confining pressure of the highly viscous magma above it.

Well-Characterized Low Viscosity Elastic Liquids

2000 ◽  
Vol 10 (4) ◽  
pp. 166-177 ◽  
Author(s):  
Graham M. Harrison ◽  
D. V. Boger
Keyword(s):  
Shear Viscosity ◽  
Swirling Flow ◽  
Dynamic Properties ◽  
Short Time Scale ◽  
Normal Stresses ◽  
Steady Shear Viscosity ◽  
Low Viscosity ◽  
Jet Breakup ◽  
Constant Viscosity ◽  
Short Time

Abstract A series of low and constant viscosity elastic liquids are constructed and are studied rheologically. Steady shear viscosity and normal stresses, dynamic properties, and an apparent extensional viscosity are measured using well-established techniques. The rheological characteristics of the solution are used to help explain the physical basis for non-Newtonian phenomena in short time scale processes such as jet breakup, splash, spray atom-isation and swirling flow. It is demonstrated that even when the shear viscosity is maintained at a constant value, significant differences occur in processes due to the differences in the elasticity of the fluids. Some implications for these observations are discussed. The paper is an overview on our work on elastic effects in the flow of low viscosity fluids. It reflects the verbal presentation made at the Professor John D. Ferry Symposium at the 71st Annual Meeting of the Society of Rheology.

scholarly journals The endgame of gas giant formation: accretion luminosity and contraction post-runaway

2019 ◽  
Vol 490 (3) ◽  
pp. 4334-4343 ◽  
Author(s):  
Sivan Ginzburg ◽  
Eugene Chiang
Keyword(s):  
Time Scale ◽  
Accretion Rate ◽  
High Viscosity ◽  
Giant Planets ◽  
Short Time Scale ◽  
Low Viscosity ◽  
Running Away ◽  
Accretion Rates ◽  
Gas Accretion ◽  
Short Time

ABSTRACT Giant planets are thought to form by runaway gas accretion on to solid cores. Growth must eventually stop running away, ostensibly because planets open gaps (annular cavities) in their surrounding discs. Typical models stop runaway by artificially capping the accretion rate and lowering it to zero over an arbitrarily short time-scale. In reality, post-runaway accretion persists as long as the disc remains. During this final and possibly longest phase of formation, when the planet is still emerging from the disc, its mass can more than double, and its radius contracts by orders of magnitude. By drawing from the theory of how gaps clear, we find that post-runaway accretion luminosities diverge depending on disc viscosity: luminosities fall in low-viscosity discs but continue to rise past runaway in high-viscosity discs. This divergence amounts to a factor of 102 by the time the disc disperses. Irrespective of the specifics of how planets interact with discs, the observed luminosity and age of an accreting planet can be used to calculate its instantaneous mass, radius, and accretion rate. We perform this exercise for the planet candidates embedded within the discs orbiting PDS 70, HD 163296, and MWC 758, inferring masses of 1–10 MJ, accretion rates of 0.1–10 MJ Myr−1, and radii of 1–10 RJ. Our radii are computed self-consistently from the planet’s concurrent contraction and accretion and do not necessarily equal the value of 2RJ commonly assumed; in particular, the radius depends on the envelope opacity as R ∝ κ0.5.

Periodic Variations in the Coronal Green Line Intensity and their Connection with the White-light Coronal Structures

2000 ◽  
Vol 179 ◽  
pp. 197-200
Author(s):  
Milan Minarovjech ◽  
Milan Rybanský ◽  
Vojtech Rušin
Keyword(s):  
Time Resolution ◽  
White Light ◽  
Short Time Scale ◽  
High Time Resolution ◽  
Green Line ◽  
Periodic Intensity ◽  
Coronal Green Line ◽  
Significant Intensity ◽  
Short Time ◽  
Coronal Structures

AbstractWe present an analysis of short time-scale intensity variations in the coronal green line as obtained with high time resolution observations. The observed data can be divided into two groups. The first one shows periodic intensity variations with a period of 5 min. the second one does not show any significant intensity variations. We studied the relation between regions of coronal intensity oscillations and the shape of white-light coronal structures. We found that the coronal green-line oscillations occur mainly in regions where open white-light coronal structures are located.

A modern method of treating initial caries for children using the infltration method

2020 ◽  
Vol 20 (1) ◽  
pp. 4-8
Author(s):  
A. U. Zamurayeva ◽  
Е. T. Supiyeva ◽  
B Sh. Orynbayeva
Keyword(s):  
Pathogenic Bacteria ◽  
Early Stage ◽  
Modern Method ◽  
Modern Technology ◽  
White Spot ◽  
Tooth Decay ◽  
Low Viscosity ◽  
Initial Caries ◽  
Short Time ◽  
Infiltration Method

Relevance. The modern method of infiltration provides an opportunity to stop the spread of pathogenic bacteria and the development of caries at the white spot stage, replacing the destroyed enamel cells with special polymers having low viscosity and high penetrating ability. The stabilization of the process is achieved in a short time with the maximum safety of their tissues. Purpose. Treatment of initial tooth decay in children by infiltration, assessment of the effectiveness and advantages of modern technology. Materials and methods. Clinical examination was carried out according to generally accepted methods. Additionally, a laser diagnostic method was used using the KaVo DIAGNOdent device (Germany). The LLP Dentistry Center «Zhaik Dent» and the LLP «Concept» used the Icon system for the treatment of initial caries and after orthodontic treatment for 25 children with 54 teeth. Results. At the end of tooth treatment with the Icon infiltration method, parents and the child were given recommendations: from the next day, brush your teeth 2 times a day, rinse your mouth regularly after eating, do not drink drinks, products with coloring substances. To monitor the result of treatment, the child was prescribed for reexamination after 7-10 days, after one month, in the following periods – once a year.After working with the material of the Icon system, the authors noted the pronounced effects of the treatment of initial caries by the method of infiltration.Conclusions. 1. The method of infiltration is a modern and promising technology for the treatment of dental caries at an early stage without losing healthy tissues. 2. The Icon infiltration method makes it possible to stop the spread of pathogenic bacteria and develop tooth decay at the white spot stage, replacing the destroyed enamel cells with special polymers having low viscosity and high penetrating ability. 3. The stabilization of the carious process is achieved in a short time with the maximum preservation of the tooth's tissues. 

Nondiffusive Brownian Motion Studied by Diffusing-Wave Spectroscopy

1989 ◽  
Vol 177 ◽  
Author(s):  
D. J. Pine ◽  
D. A. Weitz ◽  
D. J. Durian ◽  
P. N. Pusey ◽  
R. J. A. Tough
Keyword(s):  
Autocorrelation Function ◽  
Colloidal Particles ◽  
Scattered Light ◽  
Short Time Scale ◽  
Velocity Autocorrelation Function ◽  
Velocity Autocorrelation ◽  
Power Law Decay ◽  
Brownian Particles ◽  
Short Time ◽  
Surrounding Fluid

ABSTRACTOn a short time scale, Brownian particles undergo a transition from initially ballistic trajectories to diffusive motion. Hydrodynamic interactions with the surrounding fluid lead to a complex time dependence of this transition. We directly probe this transition for colloidal particles by measuring the autocorrelation function of multiply scattered light and observe the effects of the slow power-law decay of the velocity autocorrelation function.

scholarly journals On the Short Time Scale Evolutionary History of the Contact Binary VW Cephei

1998 ◽  
Vol 11 (1) ◽  
pp. 396-396
Author(s):  
I. Pustylnik
Keyword(s):  
Evolutionary History ◽  
Light Curves ◽  
Published Data ◽  
Short Time Scale ◽  
Flare Activity ◽  
Considerable Portion ◽  
History Of ◽  
Contact Binary ◽  
Elongation Phase ◽  
Short Time

We study the short-time evolutionary history of the well-known contact binary VW Cep. Our analysis is based partly on the numerous UBV lightcurves obtained at Tartu Observatory, IUE spectra, and samples from the published data. Special attention is given to the effects of asymmetry of the light curves. A higher degree of asymmetry outside the eclipses along with the significant displacements of the brightness maxima in respect to the elongation phase is interpreted as evidence that a considerable portion of the flaring source is concentrated close to the neck connecting the components. We discuss the nature of asymmetry in terms of possible mass exchange and the flare activity and compare the results of our model computations with the record of orbital period variations over the last 60 years.

An Alternative Test Using Algal Cultures for Testing Chemicals for Toxicity

1993 ◽  
Vol 21 (2) ◽  
pp. 196-201
Author(s):  
Søren Achim Nielsen ◽  
Thomas Hougaard
Keyword(s):  
Size Distribution ◽  
Mitotic Activity ◽  
Time Scale ◽  
Test System ◽  
Short Time Scale ◽  
Toxic Substances ◽  
Alternative Test ◽  
Short Time ◽  
Algal Cultures ◽  
Test Cultures

An alternative test is presented, in which algal cultures are used for testing toxic substances. This test system is based on variations in the size distribution of cells in test cultures as a measurement of growth. Thus, inhibition of mitotic activity is used as a measurement for toxic effects. The test can be performed on a short time-scale and is very sensitive to even weak toxic doses.

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