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相关概念视频

Chirality02:25

Chirality

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Chirality is a term that describes the lack of mirror symmetry in an object. In other words, chiral objects cannot be superposed on their mirror images. For example, our feet are chiral, as the mirror image of the left foot, the right foot, cannot be superposed on the left foot.
Chiral objects exhibit a sense of handedness when they interact with another chiral object. For example, our left foot can only fit in the left shoe and not in the right shoe. Achiral objects — objects that have...
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Chirality in Nature02:30

Chirality in Nature

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Chirality is the most intriguing yet essential facet of nature, governing life’s biochemical processes and precision. It can be observed from a snail shell pattern in a macroscopic world to an amino acid, the minutest building block of life. Most of the snails around the world have right-coiled shells because of the intrinsic chirality in their genes. All the amino acids present in the human body exist in an enantiomerically pure state, except for glycine - the sole achiral amino acid.
12.2K
Molecules with Multiple Chiral Centers02:25

Molecules with Multiple Chiral Centers

11.0K
Molecules that possess multiple chiral centers can afford a large number of stereoisomers. For instance, while some molecules like 2-butanol have one chiral center, defined as a tetrahedral carbon atom with four different substituents attached, several molecules like butane-2,3-diol have multiple chiral centers. A simple formula to predict the number of stereoisomers possible for a molecule with n chiral centers is 2n. However, there can be a lower number where some of the stereoisomers are...
11.0K
Prochirality02:05

Prochirality

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The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
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Chirality at Nitrogen, Phosphorus, and Sulfur02:30

Chirality at Nitrogen, Phosphorus, and Sulfur

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Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
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Stereoisomerism02:52

Stereoisomerism

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Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
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模块化形原形材料

Tuo Zhao1, Xiangxin Dang1, Konstantinos Manos2

  • 1Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA.

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|April 24, 2025
PubMed
概括

研究人员开发了模块化合元材料, 这些材料可以独立控制扭曲和收缩,克服以前变形和合的限制.

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科学领域:

  • 材料科学
  • 机械工程
  • 机器人技术

背景情况:

  • 现有的合元材料表现出合的,小变形的多模式运动,限制了它们的机器类应用.
  • 在超材料中,自主功能是可取的,但由于合式执行和微小的应变极限 (≤2%) 造成障碍.

研究的目的:

  • 建立具有脱的模块化超材料,以独立控制多模式变形.
  • 为了克服以前的奇拉元材料设计中的合运动和小变形的局限性.

主要方法:

  • 设计和制造模块化形超材料,结合辅助式平面模块化和灵感来自于原木的柱状阵列.
  • 在单个自由度操作下对变形机制的实验和仿真分析.
  • 演示不同的操作条件:自由转移的扭转和自由旋转的线性移动.

主要成果:

  • 模块化超材料表现出脱的执行,实现很大的平面收缩 (高达25%) 和平面外收缩 (超过50%).
  • 证明了独立的控制:从0°扭转到90°随着自由转移,以及随着自由旋转的线性移位.
  • 由旋转正方形图形 (平面内扭曲/收缩) 和克雷斯林原形阵列 (平面外收缩) 造成的变形.

结论:

  • 开发的模块化合元材料提供了多模式,多稳定和可重编程机器的路径.
  • 潜在的应用包括机器人变压器,温度调节,机械记忆和能量吸收系统.
  • 模块化设计可以实现可调节性,可扩展性和插即用功能,以应对各种工程挑战.