An underdamped and delayed tri-stable model-based stochastic resonance

Stochastic resonance(SR) is investigated in an underdamped tri-stable potential system driven by Gaussian colored noise and a periodic excitation, where both displacement and velocity time-delayed states feedback are considered. It is challenging to study SR in a second-order delayed multi-stable system analytically. In this paper, the improved energy envelope stochastic average method is developed to derive the analytical expressions of stationary probability density(SPD)and spectral amplification. The effects of noise intensity, damping coefficient, and time delay on SR are analyzed. The results show that the shapes of joint SPD can be adjusted to the desired structure by choosing the time delay and feedback gains. For fixed time delay, the SR peak is increased for negative displacement or velocity feedback gain. Meanwhile, the SR peak is decreased while the optimal noise intensity increases with increasing correlation time of noise. The Monte Carlo simulations(MCS) confirm the effectiveness of the theoretical results.

A highly selective C-rhamnosyltransferase from Viola tricolor and insights into its mechanisms

C-Glycosides are important natural products with various bioactivities.In plant biosynthetic pathways,the C-glycosylation step is usually catalyzed by C-glycosyltransferases(CGTs),and most of them prefer to accept uridine 5’-diphosphate glucose(UDP-Glc)as sugar donor.No CGTs favoring UDP-rhamnose(UDP-Rha)as sugar donor has been reported,thus far.Herein,we report the first selective C-rhamnosyltransferase VtCGTc from the medicinal plant Viola tricolor.VtCGTc could efficiently catalyze C-rhamnosylation of 2-hydroxynaringenin 3-C-glucoside,and exhibited high selectivity towards UDP-Rha.Mechanisms for the sugar donor selectivity of VtCGTc were investigated by molecular dynamics(MD)simulations and molecular mechanics with generalized Born and surface area solvation(MM/GBSA)binding free energy calculations.Val144 played a vital role in recognizing UDP-Rha,and the V144T mutant could efficiently utilize UDP-Glc.This work provides a new and efficient approach to prepare flavonoid C-rhamnosides such as violanthin and iso-violanthin.

An all-silicon laser based on silicon nanocrystals with high optical gains

Silicon(Si)has become the most promising material for monolithic integrated photonic circuits with a wide range of scientific and industrial applications.A variety of Si photonic components,such as optical waveguides,optical modulators and photodetectors,have been successfully demonstrated,however,silicon lasers have not yet been achieved due to the low efficiency of Si emission.In 2000,Pavesi et al.[1]reported the first observation of

Genetic profile of Chinese patients with Charcot-Marie-Tooth disease

To the Editor:Charcot-Marie-Tooth disease(CMT)encompasses a genetically heterogeneous group of inherited neuropathies,characterized by progressive distal muscle weakness and atrophy,sensory deficits,impaired tendon reflexes,and foot deformities.[1]To date,more than 80 causative genes have been identified in CMT patients,associated with either autosomal dominant or recessive inheritance,or X-linked transmission.The traditional classification of CMT was based on peripheral neuropathy type,as determined by nerve conduction velocity.As more causative genes were identified and the overlap of neuropathy phenotypes became apparent,the traditional classification system proved unwieldy and inadequate.Moreover,CMT needs to be distinguished from several entities including systemic disorders with neuropathy and other types of hereditary neuropathy.In clinical practice,overlap of phenotypes can present a major challenge in reaching the correct diagnosis.This study aimed to investigate the genetic profile in a cohort of Chinese CMT patients and evaluate the role of genetic testing in the diagnosis and subtyping of CMT.