氷が低温で圧縮されたときに無形な形がない

Chris A Tulk¹, Jamie J Molaison², Adam R Makhluf³

¹Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN, USA. tulkca@ornl.gov.

Nature

|May 24, 2019

まとめ

圧縮運動は無形氷の形成に影響する. 100Kの氷の緩やかな圧縮は,高密度無形氷 (HDA) ではなく,結晶相を生じ,無形氷の2液体水モデルに挑戦する.

科学分野:

材料科学
物理化学
凝縮物質物理学

背景:

アモルフな水氷は,結晶の秩序がない複数の形態で存在します.
高密度無形氷 (HDA) は以前はガラスの状態と考えられ,超冷却水異常の2液体の水モデルに影響を与えていた.
代替理論では,機械的な不安定性と緩やかな運動性によるHDA形態が示唆されている.

研究の目的:

アモルフな氷の形成における運動の役割を調査する.
アモルフな氷と超冷却液体の水を結びつける既存の理論に異議を唱えるために
異なる運動条件下で氷の圧縮経路を探求する.

主な方法:

制御され,ゆっくりとした運動条件下での氷の圧縮 I.
遅い対速い圧縮プロトコルの結果の比較
プロトンの順序と相互浸透を含む,結果の氷の段階の構造分析.

主要な成果:

氷Iを100Kでゆっくり圧縮すると,結晶相:氷IX',氷XV',氷VIII'が生成される.
100Kでの急速な圧縮により,高密度無形氷 (HDA) が生成されたが,IX氷は生成されなかった.
氷Iから氷XV'の直接変換は構造的に阻害されていることが判明した.

結論:

アモルフな氷の形成は,低密度氷Iと高密度氷XV'の間の運動的に停止した変換である.
この研究は,無形氷の相と超冷却水の2液体モデルとの関連に異議を唱える.
熱力学的な融解ではなく,運動学が,無形と結晶の氷の構造の形成を決定する上で重要である.

さらに関連する動画

11:20

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Published on: August 15, 2018

9.0K

09:43

Identification of Plant Ice-binding Proteins Through Assessment of Ice-recrystallization Inhibition and Isolation Using Ice-affinity Purification

Published on: May 5, 2017

9.1K

関連する概念動画

01:21

Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism

685

Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...

685

01:23

Behavior of Concrete Under Compressive Load

617

Concrete exhibits specific behaviors under different compressive loads. Understanding this is crucial for understanding its structural integrity. When concrete undergoes uniaxial compression, it tends to develop cracks that run parallel to the direction of the force. These parallel cracks stem from localized tensile stresses that occur perpendicular to the compression direction. Additionally, angled cracks may appear due to the formation of shear planes.
As the concrete specimen fractures under...

617

02:11

Effects of Temperature on Free Energy

28.0K

The spontaneity of a process depends upon the temperature of the system. Phase transitions, for example, will proceed spontaneously in one direction or the other depending upon the temperature of the substance in question. Likewise, some chemical reactions can also exhibit temperature-dependent spontaneities. To illustrate this concept, the equation relating free energy change to the enthalpy and entropy changes for the process is considered:

28.0K

01:34

Production of Formed Elements

3.8K

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...

3.8K

01:31

Discharge Summary Forms

1.3K

The discharge summary is crucial as it enables a smooth transition from a healthcare facility to a patient's home or another care setting. This critical document facilitates seamless continuity of care, ensuring patients receive the necessary support and attention.
Here's a detailed look at the key components and guidelines for preparing a discharge summary:

1.3K

01:07

Body Temperature

1.4K

Body temperature reflects the equilibrium between heat production and heat loss within the body. Most heat is generated by metabolically active tissues, particularly the liver, heart, brain, kidneys, and endocrine organs. At rest, skeletal muscles contribute 20–30% of total heat production, but during vigorous exercise, this can increase up to 30–40 times.
The average body temperature is approximately 37°C (98.6°F) and typically ranges from 36.1–37.2°C...