0000000000309445
AUTHOR
P. Porta
Dependence of the Lattice Parameter of Magnesium Oxide on Crystallite Size
Lattice parameters were measured on MgO specimens prepared in air between 450° and 1200°C. The lattice parameter, a, decreases with increase in preparation temperature, Tp, and with increase in crystallite size. A hydroxide layer is present on the MgO particles. If MgO is prepared in vacuum, a increases as Tp increases and as crystallite size, D, increases. It is concluded that a dilatant volume stress is imposed by the hydroxide layer. It is also shown that the oxide surface reactivity toward water is linked to the deviation from perfect order ensuing from low preparation temperatures.
LOFT - A large observatory for x-ray timing
The high time resolution observations of the X-ray sky hold the key to a number of diagnostics of fundamental physics, some of which are unaccessible to other types of investigations, such as those based on imaging and spectroscopy. Revealing strong gravitational field effects, measuring the mass and spin of black holes and the equation of state of ultradense matter are among the goals of such observations. At present prospects for future, non-focused X-ray timing experiments following the exciting age of RXTE/PCA are uncertain. Technological limitations are unavoidably faced in the conception and development of experiments with effective area of several square meters, as needed in order to…
Dalla terra alla mensa attraverso l’arte, fra l’età romana e il Medioevo
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