Catalytic properties and crystal structure of UDP-galactose 4-epimerase-like l-threonine 3-dehydrogenase from Phytophthora infestans.

We report, for the first time, the three-dimensional structure and biochemical properties of a UDP-galactose 4-epimerase-like l-threonine 3-dehydrogenase (GalE-like L-ThrDH) from Phytophthora infestans, a plant disease-causing fungus. We identified GalE-like L-ThrDH using Kyoto Encyclopedia of Genes and Genomes (KEGG) database as a candidate target for the development of a new fungicide. The GalE-like L-ThrDH gene was expressed in Escherichia coli, and its product was purified and characterized. N-Acetylglycine was found to act as a competitive inhibitor of the enzyme (Ki =0.18 mM). The crystal structure of the unique hexameric GalE-like L-ThrDH was determined using the molecular replacement method at a resolution of 2.3 Å, in the presence of NAD+ and citrate, an analogue of the substrate. Based on the molecular docking simulation, N-acetylglycine molecule was modeled into the active site and the binding mode and inhibition mechanism of N-acetylglycine were elucidated.

Enhancing Color Images of Extremely Low Light Scenes Based on RGB/NIR Images Acquisition With Different Exposure Times.

We propose a novel method to synthesize a noise- and blur-free color image sequence using near-infrared (NIR) images captured in extremely low light conditions. In extremely low light scenes, heavy noise and motion blur are simultaneously produced in the captured images. Our goal is to enhance the color image sequence of an extremely low light scene. In this paper, we augment the imaging system as well as enhancing the image synthesis scheme. We propose a novel imaging system that can simultaneously capture the red, green, blue (RGB) and the NIR images with different exposure times. An RGB image is taken with a long exposure time to acquire sufficient color information and mitigates the effects of heavy noise. By contrast, the NIR images are captured with a short exposure time to measure the structure of the scenes. Our imaging system using different exposure times allows us to ensure sufficient information to reconstruct a clear color image sequence. Using the captured image pairs, we reconstruct a latent color image sequence using an adaptive smoothness condition based on gradient and color correlations. Our experiments using both synthetic images and real image sequences show that our method outperforms other state-of-the-art methods.

Set of Sellmeier equations for GaS and GaSe and its applications to the nonlinear optics in GaS(x)Se(1-x).

This paper reports a set of Sellmeier equations for GaS and GaSe that provide excellent reproduction of the phase-matching conditions for second- to sixth-harmonic generation of CO2 laser radiation at 10.5910 µm in GaS(0.4)Se(0.6) at 20°C. In addition, this set of Sellmeier equations is found to reproduce well the phase-matching angles for second-harmonic generation of a Ti:Al2O3 laser-pumped BaB2O4 optical parametric generator at 2.14-2.9 µm and CO2 laser radiation at 9.2(9.2007)-10.7(10.6746) µm measured by Kang et al. [Appl. Phys. B 108, 545 (2012)] in GaS(0.09)Se(0.91) and GaS(0.41)Se(0.59).

Estimation of entropy rate in a fast physical random-bit generator using a chaotic semiconductor laser with intrinsic noise.

We analyze the time for growth of bit entropy when generating nondeterministic bits using a chaotic semiconductor laser model. The mechanism for generating nondeterministic bits is modeled as a 1-bit sampling of the intensity of light output. Microscopic noise results in an ensemble of trajectories whose bit entropy increases with time. The time for the growth of bit entropy, called the memory time, depends on both noise strength and laser dynamics. It is shown that the average memory time decreases logarithmically with increase in noise strength. It is argued that the ratio of change in average memory time with change in logarithm of noise strength can be used to estimate the intrinsic dynamical entropy rate for this method of random bit generation. It is also shown that in this model the entropy rate corresponds to the maximum Lyapunov exponent.