Intrinsic linewidth of the plasmonic resonance in a micrometric metal mesh

The intrinsic linewidth and angular dispersion of Surface Plasmon Polariton resonance of a micrometric metal mesh have been measured with a collimated mid-infrared beam, provided by an External Cavity tunable Quantum Cascade Laser. We show that the use of a collimated beam yields an observed resonance linewidth γ = 12 cm(-1) at the resonance frequency ν0 = 1658 cm(-1), better by an order of magnitude than with a non-collimated beam. The extremely narrow plasmon resonance attained by our mesh is then exploited to reconstruct, by varying the QCL angle of incidence θ, the angular intensity distribution f(θ) of a globar at the focal plane of a conventional imaging setup. We thus show that f(θ) is better reproduced by a Gaussian distribution than by a uniform one, in agreement with ray-tracing simulation.

Observation of charge-density-wave excitations in manganites

In the optical conductivity of four different manganites with commensurate charge order (CO), strong peaks appear in the meV range below the ordering temperature T_{CO}. They are similar to those reported for one-dimensional charge density waves (CDW) and are assigned to pinned phasons. The peaks and their overtones allow one to obtain, for La_{1-n/8}Ca_{n/8}MnO_{3} with n=5, 6, the electron-phonon coupling, the effective mass of the CO system, and its contribution to the dielectric constant. These results support a description of the CO in La-Ca manganites in terms of moderately weak coupling and of the CDW theory.

Phase diagram of La2-xSrxCuO4 probed in the infared: imprints of charge stripe excitations

While there is increasing evidence for antiferromagnetic (AF) ordering in the Cu-O planes of high-T(c) superconductors, either static or fluctuating, there is no direct evidence so far for the charge stripes that should separate the AF domains. By investigating the optical response of La2-xSrxCuO4 for 0<or=x<or=0.26 and 30<or=T<or=295 K, we identify strong far infrared peaks whose energy, width, and intensity are consistent with a scenario of charge stripe dynamics in the Cu-O planes.

Haloperidol administration in humans lowers plasma nerve growth factor level: evidence that sedation induces opposite effects to arousal

Studies reported in recent years have indicated that the level of nerve growth factor (NGF), in both the brain and in the bloodstream, increases following stressful events and anxiety-associated behaviour. These observations prompted us to investigate whether an anti-arousal drug would induce an opposite effect. We have reported that the administration of haloperidol (HA), a neuroleptic drug clinically used for psychiatric disorders, decreases NGF levels in the hypothalamus of adult male mice. In the present study, we showed that HA reduced the basal NGF plasma levels in 8 neuroleptic-free schizophrenic patients. These observations strengthen the hypothesis that NGF may play a functional role in stress-coping responses.