[en] Time-resolved two-dimensional infrared (2D IR) spectroscopy has been applied to analyse an electro-optic switching ferroelectric liquid crystal (FLC) mixture. The 2D IR correlation technique clearly shows that the Goldstone mode in the SmC* phase is suppressed by an applied electric field. The field-induced reorientation process initiates from intramolecular motions in about 10 μs. The intramolecular motions then propagate from the molecular segments attached to the same molecule to those fragments on other surrounding molecules. During the field-induced switching, the IR dipoles undergo a collective reorientation but with hindered rotation about the molecular long axis

[en] The capacitance-voltage (C-V) characteristics of surface-stabilized ferroelectric liquid crystal (SSFLC) cells doped with zinc oxide nanocrystals (nc-ZnO) have been studied and fitted to the Preisach model to reveal the behaviours of dipolar species. To explain the experimental results, we propose a physical picture depicting an interaction of nc-ZnO dipole with surrounding SSFLC dipolar species. Our study shows that doping nc-ZnO into FLC not only increases the contrast ratio of the cells by 10 times but also enhances the dynamic polarization of the beneficial dipolar species while minimizing the polarization response of the species with counter effects.

[en] Ligand-induced receptor dimerization plays a crucial role in the signaling process of living cells. In this study, we developed a theoretical model and performed single-molecule tracking to explore the correlated diffusion processes of liganded epidermal growth factor receptors prior to dimer formation. We disclosed that both an attractive potential between liganded receptor proteins in proximity and correlated fluctuations in the local environments of the proteins play an important role to produce the observed correlated movement of the receptors. This result can serve as the foundation to shed light on the way in which receptor functions are regulated in plasma membranes in vivo

[en] We analyse the electronic structure of the perovskite crystal CsGeI₃ by means of first-principles calculations and compare our findings to experimental results. Our calculation indicates that CsGeI₃ has a direct-transition gap of 0.74 eV at k-vector=(π/{a})(111). The top of the valence bands was found to mainly comprise the 5p orbitals of iodine, while the bottom of the conduction bands is dominated by the 4p orbital of germanium. Photoluminescence (PL) measurements on a single crystal of CsGeI₃ indicate two peaks, one at 0.82 μm (1.51 eV) and the other at 1.15 μm (1.08 eV). The shorter-wavelength PL peak is assigned as arising from an interband transition at k-vector=(π/{a})(111) and the longer-wavelength PL is presumably ascribable as originating from a transition involving an energy level within the fundamental band gap. Fourier-transformed infrared spectroscopy reveals that the transparent range of CsGeI₃ could extend from ∼2 μm to >12 μm. The short-wavelength cut-off is mainly limited by the energy band gap, while the long-wavelength limit possibly originates from lattice phonon absorption. Raman spectra of the crystal exhibit two major peaks at 105 cm^-1 and 151 cm^-1 and the corresponding overtones at 220 cm^-1 and 293 cm^-1. (author)

[en] The structural, optical and mechanical properties of orthorhombic ternary nitride crystals have been analysed theoretically with first-principles calculation. Our results indicate that these nitrides possess fairly large optical bandgap (4-6 eV), second-order nonlinear optical susceptibility (13-18 pm V^-1), and bulk modulus 170-370 GPa. Therefore these materials could be useful for optical and protective coating applications. Our analysis with the band-by-band and atomic species projection techniques not only yields useful information about material properties, but also provides deep insight into the fundamental understanding of the mechanical and optical properties of orthorhombic ternary nitrides. (author)

[en] In this paper, single-grain-boundary (GB)-position-induced electrical characteristic variations in 300 nm surrounding-gate (i.e., gate-all-around (GAA)) polysilicon thin film transistors (TFTs) are numerically investigated. For a 2T1C active-matrix circuit, a three-dimensional device–circuit coupled mixed-mode simulation shows that the switching speed of GAA TFT can be improved by nine times, compared with the result of the circuit using single-gate (SG) polysilicon TFTs. The position of a single GB near the drain side has an bad effect on device performance, but the influence can be suppressed in the GAA polysilicon TFTs. We found that under the same threshold voltage, the variation of the threshold voltage can be reduced from 15% to 5%, with varying gate structures of the GAA polysilicon TFT

[en] Intra- and inter-particle coupling effects are important but have not been properly taken into account in modeling the optical response of an array of nano-objects. In this paper, we present a method to analyze the impact of electric quadrupolar coupling on the optical response of a layer of silver nanorods fabricated with oblique-angle deposition (OAD). Our technique can render the non-locally coupled nano-objects into an array of coarse-grained induced charges. The retrieved polarizability tensor of the silver nanorods exhibits non-zero off-diagonal components, revealing information about the array structure and inter-particle quadrupolar couplings. Thus, a more transparent picture of the correlation between the function and structure of an optical metamaterial can be yielded.

[en] The first step in many cellular signaling processes occurs at various types of receptors in the plasma membrane. Membrane cholesterol can alter these signaling pathways of living cells. However, the process in which the interaction of activated receptors is modulated by cholesterol remains unclear. In this study, we measured single-molecule optical trajectories of epidermal growth factor receptors moving in the plasma membranes of two cancerous cell lines and one normal endothelial cell line. A stochastic model was developed and applied to identify critical information from single-molecule trajectories. We discovered that unliganded epidermal growth factor receptors may reside nearby cholesterol-riched regions of the plasma membrane and can move into these lipid domains when subjected to ligand binding. The amount of membrane cholesterol considerably affects the stability of correlated motion of activated epidermal growth factor receptors. Our results provide single-molecule evidence of membrane cholesterol in regulating signaling receptors. Because the three cell lines used for this study are quite diverse, our results may be useful to shed light on the mechanism of cholesterol-mediated interaction between activated receptors in live cells