Numerical study on THz radiation of two-dimensional plasmon resonance of GaN HEMT array

The Ga N high electron mobility transistor(HEMT)has been considered as a potential terahertz(THz)radiation source,yet the low radiation power level restricts their applications.The HEMT array is thought to improve the coupling efficiency between two-dimensional(2D)plasmons and THz radiation.In this work,we investigate the plasma oscillation,electromagnetic radiation,and the integration characteristics of Ga N HEMT targeting at a high THz radiation power source.The quantitative radiation power and directivity are obtained for integrated Ga N HEMT array with different array periods and element numbers.With the same initial plasma oscillation phase among the HEMT units,the radiation power of the two-element HEMT array can achieve 4 times as the single HEMT radiation power when the array period is shorter than 1/8electromagnetic wavelength.In addition,the radiation power of the HEMT array varies almost linearly with the element number,the smaller array period can lead to the greater radiation power.It shows that increasing the array period could narrow the main radiated lobe width while weaken the radiation power.Increasing the element number can improve both the radiation directivity and power.We also synchronize the plasma wave phases in the HEMT array by adopting an external Gaussian plane wave with central frequency the same as the plasmon resonant frequency,which solves the problem of the radiation power reduction caused by the asynchronous plasma oscillation phases among the elements.The study of the radiation power amplification of the one-dimensional(1D)Ga N HEMT array provides useful guidance for the research of compact high-power solid-state terahertz sources.

Research on thermal risk and decomposition behavior of methyl nitrite

The thermal hazards of methyl nitrite(MN)were investigated in the present study.The determination and evaluation of MN decomposition were conducted using a C600 micro thermometer.The thermal runaway reaction characteristics of the compound under different initial pressures were obtained using a VSP2 calorimeter.The kinetic parameters of MN were obtained by regression fitting and calculation of the microthermal experimental data.The experimental and calculated results demonstrated that the potential explosion risk of MN is very high.In addition,there was a high energy barrier in the early stage of the uncontrolled decomposition of MN;however,once the decomposition reaction was initiated,the subsequent decomposition was easily conducted.Under the conditions of adiabatic simulation,the possibility that the reaction was uncontrolled increases with the initial temperature and pressure of the system,and there is a great potential safety risk.

THz trapped ion model and THz spectroscopy detection of potassium channels

Advanced molecular dynamics(MD)simulation and infrared(IR)spectroscopy have been widely adopted to reveal the detailed dynamic process of high-speed selective permeability of potassium channels.Yet these MD simulations cannot avoid the choice of empirical molecular force fields and high transmembrane voltages(as driving electric fields for ions)far exceeding physiological levels.Moreover,the IR spectroscopy method usually requires isotope labels for carbonyl groups of the channels,which may change the original permeation process.Here,we build the terahertz(THz)trapped ion model for the selectivity filter(SF)of potassium channels KcsA based on the density functional theory(DFT)calculation of ion potentials.In this model,the zero-point energy of trapped ions and quantum tunneling effect provide the physical basis for near diffusion limited permeation rates of ions and explain the high driving electric field in MD simulations.Quantitative calculations of zero-point energy and tunneling probability show that the quantum effect assisted knock-on mechanism may help to realize the physiological functions of potassium channels.Furthermore,based on the trapped ion model,we calculated the ion decoherence timescale under the influence of protein environmental noise.We use the quantum optics method to describe the interaction between THz waves and the trapped ion.Then the novel THz spectroscopy approaches through the THz resonance fluorescence and the intense field non-resonant effect are presented theoretically.These are expected to be isotope label-free detective methods of the rapid ion permeation dynamics.

Structure-based design of conformationally constrained cyclic peptidomimetics to target the MLL1-WDR5 protein–protein interaction as inhibitors of the MLL1 methyltransferase activity

We described herein structure-based design, synthesis and evaluation of conformationally constrained, cyclic peptidomimetics to block the MLL1-WDR5 protein-protein interaction as inhibitors of the MLL1 histone methyltransferase activity. Our study has yielded cyclic peptidomimetics with very high binding affinities to WDR5 （Ki values 〈1 nmol/L） and function as antagonists of the MLL1 histone methyltransferase activity.