Chemical systems with external control capability and selfrecoverability are promising since they can avoid additional chemical or energy imposition during the working process. However, it remains challenging to employ such a nonequilibrium method for the engineering of optoelectronic function and for visualization. Here, we report a functional molecule that can undergo intense conformational regulation upon photoexcitation. It enables a dynamical change in hydrophobicity and a follow-up molecular aggregation in aqueous media, accordingly leading to an aggregation-induced phosphorescence (AIP) behavior. This successive performance is self-recoverable, allowing a rapid (second-scale cycle) and long-standing (>10 3 cycles) flicker ability under rhythmical control of the AIP. Compared with traditional bidirectional manipulations, such monodirectional photocontrol with spontaneous reset profoundly enhances the operability while mostly avoiding possible side reactions and fatigue accumulation. Furthermore, this material can serve as a type of luminescent probe for dynamically strengthening visualization in bioimaging.A rtificial molecular switches continue to attract research attention due to their fascinating structures and smart control performances (1-5). Nevertheless, most of these chemical systems work between two or more stable states, and the rest of them requires at least a secondary chemical or energy stimuli, imposing additional inconvenience and the possibility of doubling fatigue accumulation (6-8). Inspired by the underlying mechanism of functional natural systems, scientists began to design and develop molecules with self-recoverability for nonequilibrium action control (9-11). Among the control methods, photocontrol is still a superior fashion because light stimuli are usually rapid and precise, and can be operated remotely (12,13). In contrast to well-studied photochemical processes like photoreaction, photocyclization, and photoisomerization (14, 15), a photocontrol approach with selfrecoverability largely connects to a photoexcitation principle. Thus, it may generally suffer from ultrafast energy relaxation and dissipation, and is extremely difficult to be utilized in materials. Engineering of optoelectronic function and visualization via such a photocontrol method is particularly challenging but also desirable.While luminescent probe techniques enabled a significant scientific advancement in visualized analysis, sensing, and imaging (16)(17)(18), in this work, we expect to impose a photocontrol with self-recoverability into the advancing of operating methods for molecular luminescence. Aggregation-induced emission (AIE) is a type of approach where the molecules can exhibit high luminescence in condensed or constraint states by overcoming the aggregation-caused quenching effect (19)(20)(21). Controllable AIE probes that utilize specific chemical reactions have emerged to facilitate a series of frontier biological usage (22)(23)(24)(25). In contrast, the necessity of spontaneous, repeatable, and rhyth...

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Achieving widespread population immunity by voluntary vaccination poses a major challenge for public health administration and practice. The situation is complicated even more by imperfect vaccines. How the vaccine efficacy affects individuals' vaccination behavior has yet to be fully answered. To address this issue, we combine a simple yet effective game theoretic model of vaccination behavior with an epidemiological process. Our analysis shows that, in a population of self-interested individuals, there exists an overshooting of vaccine uptake levels as the effectiveness of vaccination increases. Moreover, when the basic reproductive number, , exceeds a certain threshold, all individuals opt for vaccination for an intermediate region of vaccine efficacy. We further show that increasing effectiveness of vaccination always increases the number of effectively vaccinated individuals and therefore attenuates the epidemic strain. The results suggest that ‘number is traded for efficiency’: although increases in vaccination effectiveness lead to uptake drops due to free-riding effects, the impact of the epidemic can be better mitigated.

Dendrimers and regular hyperbranched polymers are two classic families of macromolecules, which can be modeled by Cayley trees and Vicsek fractals, respectively. In this paper, we study the trapping problem in Cayley trees and Vicsek fractals with different underlying geometries, focusing on a particular case with a perfect trap located at the central node. For both networks, we derive the exact analytic formulas in terms of the network size for the average trapping time (ATT)-the average of node-to-trap mean first-passage time over the whole networks. The obtained closed-form solutions show that for both Cayley trees and Vicsek fractals, the ATT display quite different scalings with various system sizes, which implies that the underlying structure plays a key role on the efficiency of trapping in polymer networks. Moreover, the dissimilar scalings of ATT may allow to differentiate readily between dendrimers and hyperbranched polymers.

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