We report the preparation of composite foils consisting of two layers, one solid gold and one nanoporous gold. Tip displacements of several millimeters are observed when the foils are immersed in aqueous electrolytes and the electrochemical potential varied. This suggests that nanoporous metals could be used as the active component in actors, and it demonstrates for the first time that changes in the surface stress f of the metal−electrolyte interface can induce a macroscopic strain, orders of magnitude larger than the amplitudes which are reached in conventional cantilever bending experiments used to measure f.

The last two decades have seen considerable research activity on the use of riblets for viscous drag reduction. Experimental results concerning the performance of 3 M riblets on airfoils, wings and wing-body or aircraft configurations at different speed regimes are reviewed; these applications bring in additional effects like pressure gradients and three dimensionality. In addition to drag reduction, aspects of altered flow features due to riblets are discussed based on detailed wind tunnel measurements at low speeds. The available results obtained from wind tunnels as well as flight tests firmly establish the effectiveness of riblets from low speed to moderate supersonic Mach numbers. With optimized riblets, skin friction drag reduction in the range of 5-8% have been measured on 2D airfoils at low incidence and in mild adverse pressure gradients; strong evidence exist at low speeds to indicate that riblets are more effective in adverse pressure gradients. On wings of moderate sweep relevant to transport aircraft, riblets remain effective providing drag reduction comparable to 2D airfoils, as long as the local angle between the surface streamlines and riblet orientation is relatively small (o101). Limited data available on wing-body configurations show that total drag reduction of about 2-3% is likely. Certain suggestions for future research are outlined.

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In the present investigation, we have reported the fabrication of a low-cost, magnetically separable, solar light active NiFe 2−x Nd x O 4 photocatalyst with different neodymium contents. The synthesized photocatalyst samples were characterized by a combination of various physicochemical techniques such as PXRD, SEM, EDS, FTIR, and UV−vis spectroscopy. It was observed that Nd substitution can greatly enhance absorption in the whole visible region. With an increase in Nd concentration, NiFe 2−x Nd x O 4 samples show a red shift in absorption. Interestingly, Nd substitution into nickel ferrite results in a dramatic conversion of the inert NiFe 2 O 4 into a highly solar light active photocatalyst for the degradation of organic pollutants and also shows excellent recyclability and durability properties. The significant enhancement in photoactivity under solar light irradiation can be ascribed to the reduction of the nickel ferrite band gap by Nd 3+ substitution. Therefore, these unusual properties of NiFe 2−x Nd x O 4 encourage us to extend photocatalytic degradation to another few organic pollutants. This new photocatalyst system, NiFe 2−x Nd x O 4 , can have other potential environmental and energy applications that only need visible light as energy input.

Die Eigenschaften der kondensierten Materie sind durch die elektronische Bandstruktur bestimmt. Daher sind sie in Raumladungszonen an Oberflächen abhängig von der Ladungsdichte. Ein Team des Forschungszentrums Karlsruhe machte sich nun diesen Effekt zu Nutze und induzierte in metallischen Nanostrukturen durch eine elektrische Spannung reversible Änderungen der makroskopischen Eigenschaften [1].