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Background Depression is more frequently associated with akinetic-rigid/postural instability gait difficulty subtypes of Parkinson's disease than with tremor-dominant subtype. Objectives The aim of the study is to investigate the frequency of exposure to antidepressant drugs, as proxy of depression, before motor onset according to Parkinson's disease subtypes. Method Based on a historical cohort design, the exposure to antidepressant drugs before Parkinson's disease motor onset was obtained from the drug prescription database and assessed in the resident population of the Local Healthcare Trust of Bologna (443,117 subjects older than 35 years). Diagnosis of Parkinson's disease and subtype (tremor dominant, non-tremor dominant) at onset were recorded by neurologists and obtained from the “ParkLink Bologna” record linkage system. Exposure to antidepressants was compared both to the general population and between the two subtypes. Results From 2006 to 2018, 198 patients had a tremor dominant subtype at onset whereas 450 did not. Comparison with the general population for antidepressant exposure showed an adjusted hazard ratio of 0.86 (95% CI 0.44–1.70) for the tremor dominant subtype and 1.66 (1.16–2.39) for the non-tremor dominant subtype. Comparison of non-tremor dominant with tremor dominant subtypes showed an adjusted odds ratio of 1.86 (1.05–3.95) for antidepressant exposure. Conclusions In our study, non-tremor dominant Parkinson's disease at onset was significantly associated with exposure to antidepressants in comparison to the general population and in comparison with the tremor dominant subtype. These results support the hypothesis of different biological substrates for different Parkinson's disease subtypes even before motor onset.

Non linear optical, dielectric, magnetic properties of ABO 3 single crystal oxides let the implementation of acousto-optic, electro-optic, photonic, spintronic devices. In particular, significant role is played by the ferroelectric and photorefractive materials, where the photo-induced change in refractive indexes requires charge transport and impurities which support charge transfer, space charge formation and localization with accompanying electric field. Besides, ABO 3 paraelectric perovskites regularly reveal newel effects connected with charge transport, e.g., photo-induced polar state recently reported for SrTiO 3 and KTaO 3 . In this work we review our recent investigation, pointing out our studies of photo-transport in SrTiO 3 , Cu-doped KTaO 3 and LiNbO3:Hf.

We present the first growth of KTaO3:Be (6% at. in the batch) single crystals, together with photoconductivity and thermally stimulated currents studies of this material. It is probably that very small Be2+ ions (ionic radius ∼0.35 A ) mostly substitute K+(1.64 A) and bounded and/or free electronic states formation including polaronic states. As a results Be-doping effect can strongly influence phase instability and electronic properties of KTaO3. It was found that Be2+ doping leads to appreciable photocurrents already at room temperature under irradiation of the samples with photons even at energies just below the fundamental optical gap. Photoconductivity increases strongly at low temperature. Intense thermally stimulated current peaks between 15 and 100 K are probably due to the presence of shallow hole traps and polaronic centres. The obtained results are compared to past observations in pure KTaO3 and KTaO3:Li (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of the antiferrodistorsive phase transition observed at similar to 105 K on the photo-carriers transport and band structure of nominally pure SrTiO3 single crystals was investigated. Simultaneously the ab-initio analysis based on the DFT-HF hybrid approach was performed in order to elucidate the atomic and electronic structure changes. It was found that the structural transition play a minor role in photo-charge transport. However, in highly resistive specimens at low UV-light intensities or under visible-light, 514 nm excitation, weak photoconductivity features are observed in the transition region. Besides, in this region the temperature maximum was found for the photoconductivity spectra. Experimental results are discussed and agree well with theoretical predictions.

42.65.Hw, 72.40.+w, 76.30.–v, 77.84.Dy, 78.30.–j In this work we report on the characterization of structural and defect-related properties of a series of lith-ium niobate single crystals with congruent and stoichiometric composition containing Fe and Mg dopant. In particular we investigate the role of UV and visible irradiation in the charge trapping mechanisms which control the photorefractive (PR) behaviour. Complementary techniques (Raman microscopy, Elec-tron Paramagnetic Resonance, absorption measurements) were used to characterize the degree of crystal imperfections. This is the basic starting point for an exhaustive comprehension of PR behaviour, moni-tored observing photovoltaic current and photoconductivity.

The paper reports on the first crystal growth and Raman scattering studies in K0.992Rb0.008Ta0.96Nb0.04O3 (KRTN) and KTaO3:Rb (3% mol. in the melt), in which Rb+ ions (ionic radius 1.47 angstrom) substitute K+(1.33 angstrom). The experiments were performed in the range 10-300 K and focused on the behavior of TO1 and TO4 modes. The results confirm indications by previous dielectric permittivity data about the ferroelectric nature of the phase transition in KRTN. It appears that a small amount of Rb changes the character of the phase transition induced by Nb from mainly displacive to mainly order-disorder, whereas no evidence of ferroelectricity is revealed in the KTaO3:Rb sample.

A high resolution X-ray photoemission, XPS, study of PbMg 1 3 Nb 2 3 O 3 is reported. The binding energy of the Pb core lines are consistent with a formal valence of 2+, while a valence of 5+ is found for Nb. In addition, on the basis of present data, the existence of different coordination sites for Pb, Nb and Mg is discarded. Finally, within the limit of the present experimental conditions, domains with non-homogeneous electrostatic charges, as proposed by some structural models, are not observed. Instead, the XPS results are consistent with a random distribution of Nb and Mg ions on the cationic site.

The paramagnetic and optical properties of sixfold coordinated Zr3+ ions (T centers) in x-ray-irradiated yttria-stabilized zirconia have been investigated. We propose the attribution of the optical absorption to intracenter transitions as suggested by optical bleaching experiments. Wave functions and energy levels of the possible T-center configurations have been determined by supposing a disorder-induced distribution of oxygen displacements around the anionic vacancies. Electric dipole matrices of these defect structures are evaluated in order to determine the oscillator strength of optical transitions within the 4d1 multiplet. It is shown that local axial distortions without inversion symmetry account for the experimental features of the optical absorption and the paramagnetic resonance spectra. © 1995 The American Physical Society.

X-ray-photoelectron spectroscopy (XPS) and optical measurements have been performed to investigate the structure of electronic states in yttrium-stabilized zirconia. From reflectivity observations, the spectral behavior of the dielectric function, of the energy loss, and of the effective electron number in the range 3--30 eV were obtained for single crystals with an yttria content of 12 and 24 mol %. This information, combined with binding-energy spectra from XPS, was used to infer the structure of valence and conduction states and to discuss the nature of the main optical transitions, also in connection with available theoretical data.

EPR and optical absorption measurements have been performed to detect the defects activated by X-rays in single crystals of zinconium dioxide, stabilized in the cubic phase by the addition of Y 2 O 3 in two different concentrations (12 and 24 mol%). Production yield and thermal stability confirm the attribution of the 375 nm optical absorption band to the defect responsible for the EPR T-signal. Deviations from a random distribution of the stoichiometric oxygen vacancies are evidenced. These results agree with the existence of ordering processes in the vacancy system, as predicted by recent structural models.