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We deposit Au films on single crystal sapphire substrates by sputtering and evaporation methods. The microstructure characteristics such as crystal textures, grain sizes, and fraction of contacted area of the films are examined by x-ray diffraction and transmission electron microscopy. The sputtered films have an average grain size of about 200 nm and perfectly attach to the substrates; the as-evaporated films partially attach to the substrate; the grain size varies from 10 to 30 nm, and after annealing, increases to 50 nm. Au2Al phase is observed in the annealed samples. The interfacial thermal resistance is measured by a frequency domain thermoreflectance method. The thermal resistance of the sputtered Au/sapphire interfaces is 35.5×10-9 m2 K W-1, and those of the evaporated samples are up to three times as large as this value. The change in interfacial thermal resistance is explained by the effect of detachment using a parallel arranged thermal resistance model, the effect of grain size, and the influence of chemical bonding at the interfaces. [ABSTRACT FROM AUTHOR]

The PII proteins from the cyanobacteria Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803 have been crystallized and high-resolution structures have been obtained using X-ray crystallography. The core of these new structures is similar to that of the PII proteins from Escherichia coli, although the structures of the T- and C-loops differ. The T-loop of the Synechococcus protein is ordered, but appears to be stabilized by crystal contacts. The same loop in the Synechocystis protein is discordered. The C-termious of the Synechocystis protein is stabilized by hydrogen bonding to the same region of a crystallographically related molecule. The same terminus in the Synechococcus protein is stabilized by coordination with a metal ion. These observations are consistent with the idea that both the T-loop and the C-terminus of PII proteins are flexible in solution and that this flexibility may be important for receptor recognition. Sequence comparisons are used to identify regions of the sequence unique to the cyanobacteria. [ABSTRACT FROM AUTHOR]