The experimentally obtained time-resolved fluorescence spectra of photosystem II (PS II) core complexes, purified from a thermophilic cyanobacterium Thermosynechococcus vulcanus, at 5–180 K are compared with simulations. Dynamic localization effects of excitons are treated implicitly by introducing exciton domains of strongly coupled pigments. Exciton relaxations within a domain and exciton transfers between domains are treated on the basis of Redfield theory and generalized Förster theory, respectively. The excitonic couplings between the pigments are calculated by a quantum chemical/electrostatic method (Poisson-TrEsp). Starting with previously published values, a refined set of site energies of the pigments is obtained through optimization cycles of the fits of stationary optical spectra of PS II. Satisfactorily agreement between the experimental and simulated spectra is obtained for the absorption spectrum including its temperature dependence and the linear dichroism spectrum of PS II core complexes (PS II-CC). Furthermore, the refined site energies well reproduce the temperature dependence of the time-resolved fluorescence spectrum of PS II-CC, which is characterized by the emergence of a 695 nm fluorescence peak upon cooling down to 77 K and the decrease of its relative intensity upon further cooling below 77 K. The blue shift of the fluorescence band upon cooling below 77 K is explained by the existence of two red-shifted chlorophyll pools emitting at around 685 and 695 nm. The former pool is assigned to Chl45 or Chl43 in CP43 (Chl numbering according to the nomenclature of Loll et al. Nature2005, 438, 1040) while the latter is assigned to Chl29 in CP47. The 695 nm emitting chlorophyll is suggested to attract excitations from the peripheral light-harvesting complexes and might also be involved in photoprotection.

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Fig. 1. Our two-scale topology optimization framework allows to optimize continuous material properties mapping to printable microstructures (lee) to fabricate high-resolution functional objects (middle) and minimum compliant structures (right). In this paper we present a novel two-scale framework to optimize the structure and the material distribution of an object given its functional specii-cations. Our approach utilizes multi-material microstructures as low-level building blocks of the object. We start by precomputing the material property gamut-the set of bulk material properties that can be achieved with all material microstructures of a given size. We represent the boundary of this material property gamut using a level set eld. Next, we propose an eecient and general topology optimization algorithm that simultaneously computes an optimal object topology and spatially-varying material properties constrained by the precomputed gamut. Finally, we map the optimal spatially-varying material properties onto the microstructures with the corresponding properties in order to generate a high-resolution print-able structure. We demonstrate the eecacy of our framework by designing, optimizing, and fabricating objects in diierent material property spaces on the level of a trillion voxels, i.e several orders of magnitude higher than what can be achieved with current systems.

Summary This study presents a level set–based topology optimization with isogeometric analysis (IGA) for controlling high‐frequency electromagnetic wave propagation in a domain with periodic microstructures (unit cells). The high‐frequency homogenization method is applied to characterize the macroscopic high‐frequency waves in periodic heterogeneous media whose wavelength is comparative to or smaller than the representative length of a unit cell. B‐spline basis functions are employed for the IGA discretization procedure to improve the performance of electromagnetic wave analysis in a unit cell and topology optimization. Also, to keep the same order of continuity on the periodic boundaries as on other element edges in the domain, we propose the extended domain approach, while incorporating Floquet periodic boundary condition (FPBC). Two types of optimization problems are taken as examples to demonstrate the effectiveness of the proposed method in comparison with the standard finite element analysis (FEA). The optimization results provide optimized topologies of unit cells qualified as anisotropic metamaterials with hyperbolic and bidirectional dispersion properties at the macroscale.

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