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The recent discovery of more than a thousand planets outside our Solar System, together with the significant push to achieve inertially confined fusion in the laboratory, has prompted a renewed interest in how dense matter behaves at millions to billions of atmospheres of pressure. The theoretical description of such electron-degenerate matter has matured since the early quantum statistical model of Thomas and Fermi, and now suggests that new complexities can emerge at pressures where core electrons (not only valence electrons) influence the structure and bonding of matter. Recent developments in shock-free dynamic (ramp) compression now allow laboratory access to this dense matter regime. Here we describe ramp-compression measurements for diamond, achieving 3.7-fold compression at a peak pressure of 5 terapascals (equivalent to 50 million atmospheres). These equation-of-state data can now be compared to first-principles density functional calculations and theories long used to describe matter present in the interiors of giant planets, in stars, and in inertial-confinement fusion experiments. Our data also provide new constraints on mass-radius relationships for carbon-rich planets. [ABSTRACT FROM AUTHOR]

Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry-driven actuation can be realized in high-surface-area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes of the order of a few tenths of a per cent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into a mechanical response, thus opening the door to surface-chemistry-driven actuator and sensor technologies. [ABSTRACT FROM AUTHOR]

The reaction of sulfur and oxygen with the gold surface is important in many technological applications, including heterogeneous catalysis, corrosion, and chemical sensors. We have studied reactions on Au(111) using scanning tunneling microscopy (STM) in order to better understand the surface structure and the origin of gold’s catalytic activity. We find that the Au(111) surface dynamically restructures during deposition of sulfur and oxygen and that these changes in structure promote the reactivity of Au with respect to SO2 and O2 dissociation. Specifically, the Au(111) herringbone reconstruction lifts when either S or O is deposited on the surface. We attribute this structural change to the reduction of tensile surface stress via charge redistribution by these electronegative adsorbates. This lifting of the reconstruction was accompanied by the release of gold atoms from the herringbone structure. At high coverage, clusters of gold sulfides or gold oxides form by abstraction of gold atoms from regular terrace sites of the surface. Concomitant with the restructuring is the release of gold atoms from the herringbone structure to produce a higher density of low-coordinated Au sites by forming serrated step edges or small gold islands. These undercoordinated Au atoms may play an essential role in the enhancement of catalytic activity of gold in reactions such as oxygen dissociation or SO2 decomposition. Our results further elucidate the interaction between sulfur and oxygen and the Au(111) surface and indicate that the reactivity of Au nanoclusters on reducible metal oxides is probably related to the facile release of Au from the edges of these small islands. Our results provide insight into the sintering mechanism which leads to deactivation of Au nanoclusters and into the fundamental limitation in the edge definition in soft lithography using thiol-based self-assembled monolayers (SAMs) on Au. Furthermore, the enhanced reactivity of Au after release of undercoordinated atoms from the surface indicate a relatively insignificant role of an oxide support for high reactivity. [ABSTRACT FROM AUTHOR]

We describe a two-step dealloying/compaction process to produce nanocrystalline Au. First, nanocrystalline/nanoporous Au foam was synthesized by electrochemically driven dealloying. The resulting Au foams exhibited porosities of ∼60% with pore sizes of 40 and 100 nm and a typical grain size of <50 nm. Second, the nanoporous foams were fully compacted to produce nanocrystalline monolithic Au. The compacted Au was characterized by transmission electron microscopy and x-ray diffraction and tested by depth-sensing nanoindentation. The compacted nanocrystalline Au exhibited an average grain size of <50 nm and hardness values ranging from 1.4 to 2.0 GPa, which were up to 4.5 times higher than the hardness values obtained from polycrystalline Au. [ABSTRACT FROM AUTHOR]

We have tested whether experimental insulitis induced by multiple subdiabetogenic injections of streptozotocin can be transferred by lymphocytes to normal recipients. C57BL/6J mice were treated on 5 consecutive days with 40 mg streptozotocin /kg body weight. 5×10 nucleated spleen cells from 20 animals which had developed hyperglycaemia with concomitant insulitis three weeks after the first streptozotocin-injection, were transferred into congenic thymusless C57BL/6J-nu/nu mice. The cell transfer led to lymphocytic infiltrations of pancreatic islets in 75% of the recipients. Hyperglycaemia was not observed. It is concluded that lowdose streptozotocin treatment induces cellular immune reactions against pancreatic islets. [ABSTRACT FROM AUTHOR]

By coupling purified horseradish peroxidase with glutaraldehyde and subsequent reaction with insulin, conjugates were obtained. These were partially purified by ion exchange chromatography on DEAE-cellulose. A fraction with an average molar ratio of peroxidase to insulin 1:0.37 was analysed by electrophoresis and gel filtration. The peroxidase activity of this fraction was found to be 19% of normal and the immunological reactivity 0.6% as compared with that of insulin. [ABSTRACT FROM AUTHOR]

To study both the effect of Ag and the relative density on the elastic properties of nanoporous Au (np-Au) foams, partially as well as fully dealloyed np-Au samples with various ligament sizes were prepared. Additionally, Ag-coated np-Au samples were synthesized by immersing np-Au in a 1 M Ag nitrate solution, followed by drying and thermal decomposition of the deposited Ag nitrate salt to Ag, NO2, and O2. Cross-sectional analysis revealed that this method yields a homogeneous Ag distribution and that the Ag concentration can be adjusted within the range of 0 to 20 at.%. Mechanical testing was performed by depth-sensing nanoindentation. It was observed that the effect of the relative density on the elastic properties of np-Au seems to be much stronger than predicted by the Gibson and Ashby relationship: Even Ag contents as low as 1 at.% can significantly change the modulus values. On the other hand, the elastic modulus of np-Au seems to be independent of the ligament size. [ABSTRACT FROM AUTHOR]