Raman scattering investigation and symmetry analysis of ferroelectric/ferroelastic Sb5O7I polytype 2MA

The polytype 2MA (beta-Sb5O7I) has the simplest acentric structure of the antimony oxideiodide family. It undergoes an antiferrodistortive phase transition at 438K and is both ferroelectric and ferroelastic below that temperature. The complete polarized Raman spectra in the ferroic phase have been measured and compared with those of the ferroelastic, centric polytype 2MC (agr-Sb5O7I). Several lines could be attributed to Sb—0 and Sb—I vibrations. A factor group analysis has been performed and compatibility relations have been established connecting phonon species in the low and high temperature phase. As a function of temperature the spectra revealed a strongly temperature dependent central line and several phonon lines whose intensities vanish aboveT c . Using these phonon line intensities the temperature variation of the order parameter could be determined. The experimental results indicate that the phase transition is of first order

The NMR Laser - A Nonlinear Solid State System Showing Chaos

Pathways from simple to complex behavior of nonlinear systems is a topic of intense theoretical and experimental interest after J.M. Feigenbaum, J.P. Eckmann and others have demonstrated universal features of a sequence of period-doubling bifurcations leading to chaotic states.</jats:p

Biophysical parameters modification could overcome essential hearing gaps

A majority of hearing defects are due to malfunction of the outer hair cells (OHCs), those cells within the mammalian hearing sensor (the cochlea) that provide an active amplification of the incoming signal. Malformation of the hearing sensor, ototoxic drugs, acoustical trauma, infections, or the effect of aging affect often a whole frequency interval, which leads to a substantial loss of speech intelligibility. Using an energy-based biophysical model of the passive cochlea, we obtain an explicit description of the dependence of the tonotopic map on the biophysical parameters of the cochlea. Our findings indicate the possibility that by suitable local modifications of the biophysical parameters by microsurgery, even very salient gaps of the tonotopic map could be bridged