In order to obtain a clear image of the retina of model eye, an adaptive optics system used to correct the wave-front error is introduced in this paper. The spatial light modulator that we use here is a liquid crystal on a silicon device instead of a conversional deformable mirror. A paper with carbon granule is used to simulate the retina of human eye. The pupil size of the model eye is adjustable (3-7 mm). A Shack-Hartman wave-front sensor is used to detect the wave-front aberration. With this construction, a value of peak-to-valley is achieved to be 0.086 λ, where λ is wavelength. The modulation transfer functions before and after corrections are compared. And the resolution of this system after correction (69lp/m) is very close to the diffraction limit resolution. The carbon granule on the white paper which has a size of 4.7 μm is seen clearly. The size of the retina cell is between 4 and 10 μm. So this system has an ability to image the human eye's retina.
Fully atomistic molecular dynamics (MD) simulations at 293, 303 and 313 K have been performed for the four-component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions (TCFs) were calculated from MD trajectories. The rotational viscosity coefficients (RVCs) of the mixture were calculated using the Nemtsov-Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detail. Reasonable agreement between the simulated and experimental values was found.
This paper investigates the average dielectric permittivity(ε) in the Maier-Meier theory for calculating the dielectric anisotropy(ε) of nematic liquid crystals.For the reason that ε of nematics has the same expression as the dielectric permittivity of the isotropic state,the Onsager equation for isotropic dielectric was used to calculate it.The computed ε shows reasonable agreement with the results of the numerical methods used in the literature.Molecular parameters,such as the polarizability and its anisotropy,the dipole moment and its angle with the molecular long axis,were taken from semi-empirical quantum chemistry(MOCPAC/AM1) modeling.The calculated values of ε according to the Maier-Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.
