High Temperature Thermopower in La_{2/3}Ca_{1/3}MnO_3 Films: Evidence for Polaronic Transport

Thermoelectric power, electrical resistivity and magnetization experiments, performed in the paramagnetic phase of La_{2/3}Ca_{1/3}MnO_3, provide evidence for polaron-dominated conduction in CMR materials. At high temperatures, a large, nearly field-independent difference between the activation energies for resistivity (rho) and thermopower (S), a characteristic of Holstein Polarons, is observed, and ln(rho) ceases to scale with the magnetization. On approaching T_c, both energies become field-dependent, indicating that the polarons are magnetically polarized. Below T_c, the thermopower follows a law S(H) prop. 1/rho (H) as in non saturated ferromagnetic metals.Comment: 10 pages, 5 .gif figures. Phys. Rev B (in press

The Noctambuli: Tales of Sleepwalkers and Secrets of the Body in Seventeenth-century England

Seventeenth-century readers were fascinated by marvellous tales of people known as the noctambuli who rose up in their sleep, performed daily chores and attempted dangerous feats, such as clambering onto rooftops. On account of their uncanny nature, commentators noted that sleepers could be mistaken for spectres or those who had been bewitched. Depictions of the noctamubli were also influenced by the Malleus Maleficarum, which had argued that they were acting under the influence of demons and would fall if their Christian name was called. Medical texts explained this behaviour in terms of the escape of hot vapours within the body, the powers of the imaginative faculty, and the impairment of common sense during sleep. While this explanation was widely accepted, in the 1650s it was challenged by alternative views from esoteric writings, which conceptualised the movements of sleepers in terms of mystical powers within the body