切断変形によって生成される核形成溶融の相互接続されたネットワーク
1Department of Geology & Geophysics, University of Minnesota, Minneapolis 55455, USA. bruhn@olivine.geology.umn.edu
Nature
|March 8, 2000
まとめ
惑星の核形成には,マグマの海を必要としないかもしれない. 切断変形は,金属の融解が固体マントルを通して浸透することを可能にし,コア開発のための新しいメカニズムを提供することを実験で示しています.
科学分野:
- * 惑星科学 (惑星科学)
- * 地質物理学について
- * 実験的ペトロロジー
背景:
- * 地球上の惑星の核形成を駆動する正確なメカニズムは,ほとんど不明のままです.
- *現在のモデルでは,しばしばマグマの海や溶けた金属の重力による沈没を提案しています.
- * 固体マトリックス経由の浸透は,水静的実験結果により,割引されています.
研究 の 目的:
- *惑星の核形成の代替メカニズムを調査する.
- * 非水静的条件下での固体マントルの溶融の浸透の生存可能性をテストする.
- * 支配的なマグマ海洋仮説に異議を唱える.
主な方法:
- *惑星の内部条件をシミュレートする高圧実験.
- *金属/金属硫化物溶液による固体ポリクリスタリンオリヴィンに切断変形を適用する.
- * 融解の相互接続性と浸透経路の分析.
主要な成果:
- * 切断変形により,金属と硫化金属の分離したポケットが,固体オリビンのマトリックス内に溶け,成功裏に相互接続された大きな株に変形した.
- * これは,ダイナミックで非水静的環境でも浸透が可能であることを示しています.
- * 発見は,水立体実験に基づく以前の仮定と矛盾しています.
結論:
- * 惑星核の形成は,完全なマグマ海洋がなくても,固いシリケートマントルを通じた溶融の浸透によって起こる可能性があります.
- * 切断変形を含むダイナミックなプロセスは,溶融の移動を可能にするために不可欠です.
- * これは,地上の惑星の核物質を分離するための実行可能な代替メカニズムを提供します.
関連する概念動画
Network Covalent Solids
Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
Production of Formed Elements
Hemangioblasts are multipotent stem cells originating from the mesoderm. They give rise to hematopoietic stem cells (HSCs), which undergo hematopoiesis to produce all the formed elements of blood. This process is regulated by a complex network of hematopoietic growth factors, including transcription factors, growth factors, and cytokines. These factors stimulate the HSCs to divide and differentiate, though some HSCs remain undifferentiated to maintain a self-renewing pool.
Most HSCs commit to...
Most HSCs commit to...
Temperature Dependent Deformation
In a nonhomogeneous rod made up of steel and brass, restrained at both ends and subjected to a temperature change, several steps are involved in calculating the stress and compressive load. Due to the problem's static indeterminacy, one end support is disconnected, allowing the rod to experience the temperature change freely. Next, an unknown force is applied at the free end, triggering deformations in the rod's steel and brass portions. These deformations are then calculated and added together...
Shearing Strain
The shearing strain represents a cubic element's angular change when subjected to shearing stress. This type of stress can transform a cube into an oblique parallelepiped without influencing normal strains. The cubic element experiences a significant transformation when exposed solely to shearing stress. Its shape alters from a perfect cube into a rhomboid, clearly demonstrating the effect of shearing strain. The degree of this strain is considered positive if it reduces the angle between the...
Residual Stresses
Residual stresses reside in a structure even after removing the original stress inducer. This phenomenon often arises from varied plastic deformations across different parts of a structure. Consider a rod stretched beyond its yield point. It will not regain its original length due to permanent deformation. Even after load removal, the rod does not entirely lose stress because of uneven plastic deformations, resulting in residual stresses. The computation of these stresses in structures is...
Elastic Strain Energy for Shearing Stresses
As discussed in previous lessons, strain energy in a material is the energy stored when it is elastically deformed, a concept crucial in materials science and mechanical engineering. This energy results from the internal work done against the cohesive forces within the material. When a material undergoes shearing stress and corresponding shearing strain, the strain energy density, which is the energy stored per unit volume, is calculated. Within the elastic limit, where the stress is...


