Lead-free Zr-doped ceria ceramics with low permittivity displaying giant electrostriction.

Electrostrictors, materials developing mechanical strain proportional to the square of the applied electric field, present many advantages for mechanical actuation as they convert electrical energy into mechanical, but not vice versa. Both high relative permittivity and reliance on Pb as the key component in commercial electrostrictors pose serious practical and health problems. Here we describe a low relative permittivity (<250) ceramic, ZrCeO (x < 0.

The effect of intramolecular cross links on the mechanochemical fragmentation of polymers in solution.

Addition of intramolecular cross-links to linear polymers significantly improves their resistance to mechanochemical fragmentation, and hence the physical properties of polymer solutions are maintained under shear. However, while fragmentation is suppressed, mechanochemistry of chemical bonds still occurs. In linear polymers, the rate of mechanochemistry has been shown to increase linearly with the degree of polymerisation.

[A bilateral posterior shoulder dislocation caused by humeral head osteonecrosis].

We report a case of simultaneous bilateral posterior shoulders dislocations in a 46-year-old male with antecedent of high-dose corticotherapy. The mechanism was non-traumatic after a contraction of the sub scapularis muscle in internal rotation. The interscapular pain was not initially diagnosed although a tomodensitometry was realized to eliminate a cardiovascular emergency.