Eveningness and Seasonality are Associated with the Bipolar Disorder Vulnerability Trait

Trait theories of vulnerability to bipolar disorder (BD) are increasingly common in the literature, yet poorly understood. The aim of the current study was to complement existing knowledge of trait theories by investigating two biological rhythm features often associated with BD – eveningness and seasonality – in a sample assessed as vulnerable to the disorder. Two hundred and thirteen participants completed an online survey consisting of the General Behavior Inventory, Seasonal Pattern Assessment Questionnaire, and Morningness-Eveningness Questionnaire. Hierarchical regressions controlling for sex and age showed that greater levels of seasonality and a tendency towards an eveningness chronotype were weak, but significant predictors of the BD vulnerability trait. When the traits of vulnerability to depression and mania were investigated separately, seasonality and eveningness were significant predictors of the former, but only seasonality was a significant predictor of the latter. The Autumn/Winter pattern of seasonality was a weak predictor of trait vulnerability to mania but not depression. The current findings advance understanding of the BD vulnerability trait, and may have consequences for the behavioural management of those who are considered to be ‘at risk’ of the disorder

Nonlinear Optics

This chapter provides a brief introduction into the basic nonlinear-optical phenomena and discusses some of the most significant recent advances and breakthroughs in nonlinear optics, as well as novel applications of nonlinear-optical processes and devices. Nonlinear optics is the area of optics that studies the interaction of light with matter in the regime where the response of the material system to the applied electromagnetic field is nonlinear in the amplitude of this field. At low light intensities, typical of non-laser sources, the properties of materials remain independent of the intensity of illumination. The superposition principle holds true in this regime, and light waves can pass through materials or be reflected from boundaries and interfaces without interacting with each other. Laser sources, on the other hand, can provide sufficiently high light intensities to modify the optical properties of materials. Light waves can then interact with each other, exchanging momentum and energy, and the superposition principle is no longer valid. This interaction of light waves can result in the generation of optical fields at new frequencies, including optical harmonics of incident radiation or sum- or difference-frequency signals