[Stress, anxiety, depression and insomnia in adults outside Hubei province during the COVID-19 pandemic].

Objective: To investigate the severity of stress, anxiety, depression and insomnia during the novel coronavirus disease (COVID-19) pandemic in adults outside Hubei Province, China. Methods: An online survey of psychological and sleep by using Questionnaire Star program from 5th to 19th February 2020 was conducted. The Impact of Event Scale-Revised was used to assess COVID-19 outbreak-related stress symptoms. Meanwhile, Questionnaires of Generalized Anxiety Disorder-7, Patient Health Questionnaire-9 and the Insomnia Severity Index were respectively used to assess the severity of anxiety, depression and insomnia symptoms prior to and during the COVID-19 pandemic. Results: A total of 3 134 subjects were included. Among the included subjects, 15.5% (487), 24.9% (779), 28.7% (899) and 30.9% (968) of the subjects had COVID-19-related stress symptoms, anxiety, depression and insomnia after the COVID-19 outbreak, respectively. The severity levels of anxiety, depression and insomnia were significantly increased during the COVID-19 pandemic compared to prior to the outbreak (all P<0.01). Furthermore, the subjects' stress response to the COVID-19 outbreak was an independent risk factor for increased anxiety, depression and insomnia after the outbreak. Conclusion: The COVID-19 outbreak resulted in related stress response and widespread increase in anxiety, depression, and insomnia outside Hubei Province, China in the general population. The aggravation of anxiety, depression and insomnia is associated with stress levels. Our data demonstrate that the widespread psychological and insomnia problems in the general population need to be addressed at the early phase of the pandemic.

Electric-field-induced chirality flipping in smectic liquid crystals: the role of anisotropic viscosity.

We demonstrate the homogeneous and permanent reversal of the chirality of a condensed phase by an applied electric field. Tilted chiral smectic layers exhibit a coupled polarization density and molecular orientation fields which reorient about the layer normal as couple of fixed handedness in response to small applied electric fields. Experiments on some bent-core smectics show that above a threshold field the induced rotation can occur instead about the molecular long axis and that, as a result, the handedness of the phase can be flipped. The effect is quantitatively described by a nonequilibrium dissipative model of chiral smectic dynamics with anisotropic rotational viscosities.

Giant-block twist grain boundary smectic phases.

Study of a diverse set of chiral smectic materials, each of which has twist grain boundary (TGB) phases over a broad temperature range and exhibits grid patterns in the Grandjean textures of the TGB helix, shows that these features arise from a common structure: "giant" smectic blocks of planar layers of thickness l(b) > 200 nm terminated by GBs that are sharp, mediating large angular jumps in layer orientation between blocks (60 degrees < Delta < 90 degrees ), and lubricating the thermal contraction of the smectic layers within the blocks. This phenomenology is well described by basic theoretical models applicable in the limit that the ratio of molecular tilt penetration length-to-layer coherence length is large, and featuring GBs in which smectic ordering is weak, approaching thin, melted (nematic-like) walls. In this limit the energy cost of change of the block size is small, leading to a wide variation of block dimension, depending on preparation conditions. The models also account for the temperature dependence of the TGB helix pitch.

Control of molecular orientation in electrostatically stabilized ferroelectric liquid crystals.

The continuously reorientable (XY-like) ferroelectric polarization density of a chiral smectic liquid crystal is shown experimentally to produce nearly complete screening of the applied electric field in an appropriate cell geometry. This screening, combined with the expulsion of polarization charge for large polarization materials, is shown to produce electrostatic control of the orientation of a uniform optic axis or polarization field.

Polarization-modulated smectic liquid crystal phases.

Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for polarization is to be nonuniform, i.e., to be locally bouquet-like or "splayed." However, it is impossible to achieve splay of a preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, in materials like ferroelectric crystals or liquid crystals, such defects are not thermally stable, so that the local preference is globally frustrated and the polarization field remains uniform. Here, we report a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves. The polar domains are locally chiral, and organized into patterns of alternating handedness and polarity. The fluid-layer undulations enable an extraordinary menagerie of filament and planar structures that identify such phases.