Inducing Motions of Polymers in Liquid Nitrogen with Light.

Polymer materials that show macroscopic deformation in response to external stimuli are feasible for novel soft actuators including microactuators. Incorporation of photochromic moieties, such as azobenzenes, into polymer networks enables macroscopic deformation under irradiation with light through photoisomerization. Under cryogenic conditions, however, it has been difficult to induce macroscopic deformation as polymers lose their soft nature due to the severe restrictions of molecular motions. Here, activation of molecular motions and macroscopic deformation in liquid nitrogen only with light for polymers containing photochromic moieties is reported. Photoinduced bending of polymer networks with normal azobenzenes in liquid nitrogen is enabled by preliminary UV irradiation at room temperature to produce cis-isomers. To realize photoinduced deformation directly in liquid nitrogen, polymer networks are functionalized with bridged azobenzenes, which exist as cis-isomers in thermodynamic equilibrium. The films with bridged azobenzenes exhibit reversible photoisomerization and bending upon irradiation with light in liquid nitrogen without the need of preliminary irradiation, implying that the change in conformation of polymer chains can be isothermally induced even under cryogenic conditions. Achievement of flexible motions under cryogenic conditions through isothermal processes will greatly expand the operating temperature range of soft actuators.

Challenges of COVID-19 outbreak on the cruise ship Diamond Princess docked at Yokohama, Japan: a real-world story.

The event of the Diamond Princess, with a total of 712 (as of 17 March 2020) persons infected on the cruise ship, attracted global attention as the largest disease cluster outside China for the period 7 to 24 February 2020. Representing the Ministry of Health, Labour and Welfare, the authors were heavily engaged in the quarantine operation on the cruise ship ourselves. During the quarantine period from 5 to 23 February 2020, when the last group of the quarantined passengers left the ship, a series of measures have been conducted under the principles of i) zero deaths among all on board, ii) rapid establishment and thorough implementation of an infection control system, and iii) maintenance of health conditions and relief of anxieties among passengers and crew members. The case of Diamond Princess has implications of more than a cruise ship but deserves full scientific analysis to learn lessons from this operation as well as to study the characteristics, particularly the transmission of COVID-19.