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ATS mechanically despun communications satellite antenna

The antenna system described is one of the experiments on NASAs ATS-III spin stabilized satellite that was launched on November 5, 1967. It was put into synchronous orbit shortly thereafter and has been operating satisfactorily since. Using a line source feed illuminating a parabolic cylindrical reflector, a linearly polarized gain over 17 dB is achieved. The antenna is positioned by means of a vernier type stepping motor-drive system that points the antenna beam towards earth within approximatelypm0.7degree in accordance with instructions received on the satellite from the ground control station. Prior to launch, the antenna system was subjected to extensive qualification testing. Confidence in a desired five-year life in orbit for the motor-drive system was obtained by testing the lubrication system and bearings for 7800 hours at temperatures ranging from-80degF to+120degF at vacuum pressures as low as1 times 10^{-8}torr.     

Synthesis and Characterization of Ligand-Linked Pt Nanoparticles: Tunable,Three-Dimensional,Porous Networks for Catalytic Hydrogen Sensing

Porous networks of Pt nanoparticles interlinked by bifunctional organic ligands have shown high potential as catalysts in micro-machined hydrogen gas sensors. By varying the ligand among p-phenylenediamine, benzidine, 4,4‘‘-diamino-p-terphenyl, 1,5-diaminonaphthalene, and trans-1,4-diaminocyclohexane, new variants of such networks were synthesized. Inter-particle distances within the networks, determined via transmission electron microscopy tomography, varied from 0.8 to 1.4 nm in accordance with the nominal length of the respective ligand. While stable structures with intact and coordinatively bonded diamines were formed with all ligands, aromatic diamines showed superior thermal stability. The networks exhibited mesoporous structures depending on ligand and synthesis strategy and performed well as catalysts in hydrogen gas microsensors. They demonstrate the possibility of deliberately tuning micro- and mesoporosity and thereby transport properties and steric demands by choice of the right ligand also for other applications in heterogeneous catalysis.     

Ein neuer mikrochemischer Bleinachweis

Ohne ZusammenfassungDiese Arbeit wurde noch von der früheren Schriftleitung der Mikrochemie redigiert.     

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Ma?analytische Bestimmung des Thiocarbamids

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