River meanders in a tray: Meanders are a feature of some of the world's noblest rivers, but laboratory models have failed to meander convincingly

Article Abstract:

Theory suggests that meandering is an instability phenomenon, but the mechanism that maintains channel coherence is only partially understood. Meandering alluvial rivers often devolve into a less coherent braided state and Murray and Paola proposed that braiding is the default morphology of alluvial streams, and meandering occurs only when braiding is suppressed. Charles E Smith has made an experimental replication of river meandering, and his technique provides an analogue that reproduces meandering of its own accord.

Meandering rivers

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Why gold is the noblest of all the metals

Article Abstract:

The dissociation of H2 on the surface of gold, copper, nickel, and platinum is studied to show that the degree of filling of the antibonding states on adsorption and the degree of orbital lap with the adsorbate are the factors responsible for the nobleness of gold. Self-consistent density-functional calculations of the activation barriers and chemisorption energies are presented. The detrimental role of the two factors on adsorbate binding and subsequent reactivity of gold is discussed.

Testing, Reactivity (Chemistry), Gold, Precious metals, Assaying

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Enhancement of surface self-diffusion of platinum atoms by adsorbed hydrogen

Article Abstract:

The phenomenon of surface diffusion of atoms is important in materials processing. Self-diffusion has been much studied, and adsorbed hydrogen atoms are known to be able to promote and inhibit self-diffusion. Mechanistic insights into the effect are reported, using observations from a scanning tunnelling microscope, of hydrogen-promoted self-diffusion of platinum on the Pt(100) surface. It is indicated that Pt-H complex comprises a hydrogen atom trapped on a platinum atom.

Platinum, Atoms, Diffusion, Diffusion (Physics)

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