Inner Core Seismic Velocities

2007 ◽  
pp. 427-430
Author(s):  
Annie Souriau
Keyword(s):  
Inner Core ◽  
Seismic Velocities

scholarly journals Axial Compressibility and Thermal Equation of State of Hcp Fe–5wt% Ni–5wt% Si

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 98
Author(s):  
Eric Edmund ◽  
Francesca Miozzi ◽  
Guillaume Morard ◽  
Eglantine Boulard ◽  
Alisha Clark ◽  
...  
Keyword(s):  
Equation Of State ◽  
Ambient Temperature ◽  
Inner Core ◽  
Equations Of State ◽  
Axial Ratio ◽  
Seismic Velocities ◽  
X Ray Diffraction ◽  
Thermal Equation ◽  
Planetary Cores ◽  
Ni Addition

Knowledge of the elastic properties and equations of state of iron and iron alloys are of fundamental interest in Earth and planetary sciences as they are the main constituents of telluric planetary cores. Here, we present results of X-ray diffraction measurements on a ternary Fe–Ni–Si alloy with 5 wt% Ni and 5 wt% Si, quasi-hydrostatically compressed at ambient temperature up to 56 GPa, and under simultaneous high pressure and high temperature conditions, up to 74 GPa and 1750 K. The established pressure dependence of the c/a axial ratio at ambient temperature and the pressure–volume–temperature (P–V–T) equation of state are compared with previous work and literature studies. Our results show that Ni addition does not affect the compressibility and axial compressibility of Fe–Si alloys at ambient temperature, but we suggest that ternary Fe–Ni–Si alloys might have a reduced thermal expansion in respect to pure Fe and binary Fe–Si alloys. In particular, once the thermal equations of state are considered together with velocity measurements, we conclude that elements other than Si and Ni have to be present in the Earth’s inner core to account for both density and seismic velocities.

scholarly journals Superionic hcp-Fe alloys and their seismic velocities in Earth’s inner core

2020 ◽  
Author(s):  
Yu He ◽  
Shichuan Sun ◽  
DuckYoung Kim ◽  
Bo Gyu Jang ◽  
He-Ping Li ◽  
...  
Keyword(s):  
Inner Core ◽  
Light Element ◽  
Seismic Velocities ◽  
Light Elements ◽  
Hexagonal Close Packed ◽  
Melting Temperatures ◽  
Superionic State ◽  
Seismological Observation ◽  
Earth’S Inner Core ◽  
Fe Alloys

Abstract Earth’s inner core (IC) is less dense than pure iron, indicating the existence of light elements within it1. Si, S, C, O, and H have been suggested to be the candidates2,3, and the properties of Fe-light-element alloys were studied to constrain the IC composition4-19. Light elements have a significant influence on seismic velocities4-13, melting temperatures15-17, and thermal conductivities of Fe-alloys18,19. However, the state of the light elements in the IC is rarely considered. Using ab initio molecular dynamics (AIMD) simulations, we found that H, O, and C in hexagonal close-packed (hcp) Fe transform to a superionic state under IC conditions, showing high diffusion coefficients like liquid. It suggests the IC can be in superionic state rather than normal solid state. The liquid-like light elements lead to a significant reduction in the seismic velocities approaching the seismological observation of the IC20,21. The significant decrease in shear wave velocity (VS) gives an explanation on the soft IC21. In adddtion, the light-element convection in the IC has potential influence on the IC seismological structure and magnetic field.

scholarly journals CCREM: New reference Earth model from the global coda-correlation wavefield

2021 ◽  
Author(s):  
Xiaolong Ma ◽  
Hrvoje Tkalčić
Keyword(s):  
Inner Core ◽  
Velocity Structure ◽  
Body Waves ◽  
Earth Model ◽  
Seismic Velocities ◽  
New Paradigm ◽  
Reference Models ◽  
First Order ◽  
Global Seismology ◽  
S Period

The existing Earth reference models have provided an excellent one-dimensional representation of Earth’s properties as a function of its radius and explained many seismic observations in a broad frequency band. However, some discrepancies still exist among these models near the first-order discontinuities (e.g., the core-mantle and the inner-core boundaries) due to different datasets and approaches. As a new paradigm in global seismology, the analysis of coda-correlation wavefield is fundamentally different from interpreting direct observations of seismic phases or free oscillations of the Earth. The correlation features exist in global correlograms due to the similarity of body waves reverberating through the Earth’s interior. As such, there is a great potential to utilize the information stored in the coda-correlation wavefield in constraining the Earth’s internal structure. Here, we deploy the global earthquake-coda correlation wavefield as an independent data source in the 15-50 s period interval to increase the Earth's radial structure constraints. We assemble a dataset of multiple pronounced correlation features and fit both their travel times and waveforms by computing synthetic correlograms through a series of candidate models. Misfit measurements for correlation features are then computed to search for the best-fitting model. The model that provides an optimal representation of the correlation features in the coda-correlation wavefield is CCREM. It displays differences in radial seismic velocities, especially near the first-order discontinuities, relative to previously proposed Earth-reference models. This is the first application of the earthquake-coda correlation wavefield in constraining the whole Earth's radial velocity structure.

scholarly journals Toward a mineral physics reference model for the Moon’s core

2015 ◽  
Vol 112 (13) ◽  
pp. 3916-3919 ◽  
Author(s):  
Daniele Antonangeli ◽  
Guillaume Morard ◽  
Nicholas C. Schmerr ◽  
Tetsuya Komabayashi ◽  
Michael Krisch ◽  
...  
Keyword(s):  
High Pressures ◽  
Inner Core ◽  
Reference Model ◽  
Velocity Model ◽  
Face Centered Cubic ◽  
Seismic Velocities ◽  
Planetary Interiors ◽  
Ε Phase ◽  
Face Centered ◽  
Seismic Models

The physical properties of iron (Fe) at high pressure and high temperature are crucial for understanding the chemical composition, evolution, and dynamics of planetary interiors. Indeed, the inner structures of the telluric planets all share a similar layered nature: a central metallic core composed mostly of iron, surrounded by a silicate mantle, and a thin, chemically differentiated crust. To date, most studies of iron have focused on the hexagonal closed packed (hcp, or ε) phase, as ε-Fe is likely stable across the pressure and temperature conditions of Earth’s core. However, at the more moderate pressures characteristic of the cores of smaller planetary bodies, such as the Moon, Mercury, or Mars, iron takes on a face-centered cubic (fcc, or γ) structure. Here we present compressional and shear wave sound velocity and density measurements of γ-Fe at high pressures and high temperatures, which are needed to develop accurate seismic models of planetary interiors. Our results indicate that the seismic velocities proposed for the Moon’s inner core by a recent reanalysis of Apollo seismic data are well below those of γ-Fe. Our dataset thus provides strong constraints to seismic models of the lunar core and cores of small telluric planets. This allows us to propose a direct compositional and velocity model for the Moon’s core.

An Electron Microscopic Study of an Avian Reovirus that Causes Arthritis

1971 ◽  
Vol 29 ◽  
pp. 254-255
Author(s):  
E, R. Walker ◽  
N. O. Olson ◽  
M. H. Friedman
Keyword(s):  
Electron Microscopy ◽  
Viral Genome ◽  
Inner Core ◽  
Avian Reovirus ◽  
Electron Microscopic ◽  
Outer Coat ◽  
Acid Type ◽  
Chicken Eggs ◽  
Icosahedral Particle ◽  
Mature Virus

An unidentified virus, responsible for an arthritic-like condition in chickens was studied by electron microscopy and other methods of viral investigation. It was characterized in chorio-allantoic membrane (CAM) lesions of embryonating chicken eggs and in tissue culture as to: 1) particle size; 2) structure; 3) mode of replication in the cell; and 4) nucleic acid type.The inoculated virus, coated and uncoated, is first seen in lysosomal-like inclusions near the nucleus; the virions appear to be uncoated in these electron dense inclusions (Figure 1), Although transfer of the viral genome from these inclusions is not observable, replicating virus and mature virus crystals are seen in the cytoplasm subsequent to the uncoating of the virions.The crystals are formed in association with a mass of fibrils 50 to 80 angstroms in diameter and a ribosome-studded structure that appears to be granular endoplasmic reticulum adapted to virus replication (Figure 2). The mature virion (Figure 3) is an icosahedral particle approximately 75 millimicrons in diameter. The inner core is 45 millimicrons, the outer coat 15 millimicrons, and the virion has no envelope.

Preliminary Studies on Non-Reactive Flow Vortex Cooling

2019 ◽  
Vol 12 (3) ◽  
pp. 262-271
Author(s):  
T.N. Rajesh ◽  
T.J.S. Jothi ◽  
T. Jayachandran
Keyword(s):  
Combustion Chamber ◽  
Inner Core ◽  
Rocket Engine ◽  
Injection Pressure ◽  
Chamber Pressure ◽  
Reactive Flow ◽  
Stoichiometric Ratio ◽  
Gaseous Oxygen ◽  
Mixture Ratio ◽  
Vortex Combustion

Background: The impulse for the propulsion of a rocket engine is obtained from the combustion of propellant mixture inside the combustion chamber and as the plume exhausts through a convergent- divergent nozzle. At stoichiometric ratio, the temperature inside the combustion chamber can be as high as 3500K. Thus, effective cooling of the thrust chamber becomes an essential criterion while designing a rocket engine. Objective: A new cooling method of thrust chambers was introduced by Chiaverni, which is termed as Vortex Combustion Cold-Wall Chamber (VCCW). The patent works on cyclone separators and confined vortex flow mechanism for providing high propellant mixing with improved degree of turbulence inside the combustion chamber, providing the required notion for studies on VCCW. The flow inside a VCCW has a complex structure characterised by axial pressure losses, swirl velocities, centrifugal force, flow reversal and strong turbulence. In order to study the flow phenomenon, both the experimental and numerical investigations are carried out. Methods: In this study, non-reactive flow analysis was conducted with real propellants like gaseous oxygen and hydrogen. The test was conducted to analyse the influence of mixture ratio and injection pressure of the propellants on the chamber pressure in a vortex combustion chamber. A vortex combustor was designed in which the oxidiser injected tangentially at the aft end near the nozzle spiraled up to the top plate and formed an inner core inside the chamber. The fuel was injected radially from injectors provided near the top plate and the propellants were mixed in the inner core. This resulted in enhanced mixing and increased residence time for the fuel. More information on the flow behaviour has been obtained by numerical analysis in Fluent. The test also investigated the sensitivity of the tangential injection pressure on the chamber pressure development. Results: All the test cases showed an increase in chamber pressure with the mixture ratio and injection pressure of the propellants. The maximum chamber pressure was found to be 3.8 bar at PC1 and 2.7 bar at PC2 when oxidiser to fuel ratio was 6.87. There was a reduction in chamber pressure of 1.1 bar and 0.7 bar at PC1 and PC2, respectively, in both the cases when hydrogen was injected. A small variation in the pressure of the propellant injected tangentially made a pronounced effect on the chamber pressure and hence vortex combustion chamber was found to be very sensitive to the tangential injection pressure. Conclusion: VCCW mechanism has been to be found to be very effective for keeping the chamber surface within the permissible limit and also reducing the payload of the space vehicle.

Ups and Downs

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Mantle Convection ◽  
Laboratory Experiments ◽  
Inner Core ◽  
Computer Modelling ◽  
Great Depth ◽  
New Horizons ◽  
The Core ◽  
The Earth ◽  
The World ◽  
The 1960S

Despite the dumbing-down of education in recent years, it would be unusual to find a ten-year-old who could not name the major continents on a map of the world. Yet how many adults have the faintest idea of the structures that exist within the Earth? Understandably, knowledge is limited by the fact that the Earth’s interior is less accessible than the surface of Pluto, mapped in 2016 by the NASA New Horizons spacecraft. Indeed, Pluto, 7.5 billion kilometres from Earth, was discovered six years earlier than the similar-sized inner core of our planet. Fortunately, modern seismic techniques enable us to image the mantle right down to the core, while laboratory experiments simulating the pressures and temperatures at great depth, combined with computer modelling of mantle convection, help identify its mineral and chemical composition. The results are providing the most rapid advances in our understanding of how this planet works since the great revolution of the 1960s.

scholarly journals Simple, green, ultrasound-assisted preparation of novel core–shell microcapsules from octyl methoxycinnamate and oligomeric proanthocyanidins for UV-stable sunscreen

RSC Advances ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 6374-6382
Author(s):  
Jie Song ◽  
Siqi Chen ◽  
Xu Zhao ◽  
Junbo Cheng ◽  
Yanli Ma ◽  
...  
Keyword(s):  
Inner Core ◽  
Outer Shell ◽  
Core Shell ◽  
Uv Resistance ◽  
Oligomeric Proanthocyanidins ◽  
Ultraviolet Absorbers ◽  
Ultrasound Assisted

With oligomeric proanthocyanidins (OPCs) as the outer shell and ultraviolet absorbers (OMC) as the inner core, OMC/OPCs composite microcapsules were prepared and characterized, and their UV resistance was studied.

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