We use simulated Hubble parameter data in the redshift range 0 ≤ z ≤ 2 to explore the role and power of observational H(z) data in constraining cosmological parameters of the ΛCDM model. The error model of the simulated data is empirically constructed from available measurements and scales linearly as z increases. By comparing the median figures of merit calculated from simulated datasets with that of current type Ia supernova data, we find that as many as 64 further independent measurements of H(z) are needed to match the parameter constraining power of SNIa. If the error of H(z) could be lowered to 3%, the same number of future measurements would be needed, but then the redshift coverage would only be required to reach z = 1. We also show that accurate measurements of the Hubble constant H 0 can be used as priors to increase the H(z) data's figure of merit.

This paper is a review on the observational Hubble parameter data that have gained increasing attention in recent years for their illuminating power on the dark side of the universe -the dark matter, dark energy, and the dark age. Currently, there are two major methods of independent observational H(z) measurement, which we summarize as the "differential age method" and the "radial BAO size method". Starting with fundamental cosmological notions such as the spacetime coordinates in an expanding universe, we present the basic principles behind the two methods. We further review the two methods in greater detail, including the source of errors. We show how the observational H(z) data presents itself as a useful tool in the study of cosmological models and parameter constraint, and we also discuss several issues associated with their applications. Finally, we point the reader to a future prospect of upcoming observation programs that will lead to some major improvements in the quality of observational H(z) data.PACS numbers: 98.80. Es, 95.36.+x, 95.35.+d, 98.62.Ai, 98.62.Py, 98.65.Dx

Design and fabrication of photomechanical soft actuators has attracted intense scientific interest because of their potential in the manufacture of untethered intelligent soft robots and advanced functional devices. Trifunctional and monofunctional polymerizable molecular motors are judiciously designed and synthesized. Novel light-driven liquid crystalline networks (LCN) are prepared by crosslinking overcrowded-alkene-based molecular motors with different degrees of freedom into the anisotropic LCN. The photoisomerization and thermal helix inversion of light-driven molecular motors are reversible when only the upper part of the molecular motor is linked to the network, endowing the LCN film with remarkable photoactive performance. However, photochemical geometric change of the light-driven molecular motor does not work after crosslinking both the upper and lower part of the motor by polymer chains. Interestingly, it is found that the fastened motor can transfer the light energy into localized heat instead of performing photoisomerization. The light-driven molecular-motor-based LCN soft actuators are demonstrated to function as a grasping hand, where the continuous motions of grasping, moving, lifting, and releasing an object are successfully achieved. This work may provide inspiration to the preparation of next-generation photoactive advanced functional materials toward their wide applications in the areas of photonics, optoelectronics, soft robotics, and beyond.

We test the distance-duality relation η ≡ d L /[(1 + z) 2 d A ] = 1 between cosmological luminosity distance (d L ) from the JLA SNe Ia compilation and angular-diameter distance (d A ) based on Baryon Oscillation Spectroscopic Survey (BOSS) and WiggleZ baryon acoustic oscillation measurements. The d L measurements are matched to d A redshift by a statistically consistent compression procedure. With Monte Carlo methods, nontrivial and correlated distributions of η can be explored in a straightforward manner without resorting to a particular evolution template η(z). Assuming independent constraints on cosmological parameters that are necessary to obtain d L and d A values, we find 9% constraints consistent with η = 1 from the analysis of SNIa + BOSS and an 18% bound results from SNIa + WiggleZ. These results are contrary to previous claims that η < 1 has been found close to or above the 1σ level. We discuss the effect of different cosmological parameter inputs and the use of the apparent deviation from distance-duality as a proxy of systematic effects on cosmic distance measurements. The results suggest possible systematic overestimation of SNIa luminosity distances compared with d A data when a Planck ΛCDM cosmological parameter inference is used to enhance the precision. If interpreted as an extinction correction due to a gray dust component, the effect is broadly consistent with independent observational constraints.