HF-VHF dual-channel multifunctional radio astronomy terminal system

The high frequency-very high frequency(HF-VHF)frequency band is of significant importance in astronomical observations,with applications studying various phenomena such as space weather,solar radio emissions,planetary eruptions in the solar system,pulsars,transient sources,and reionization of the early universe.This article introduces the HF-VHF frequency band multifunctional radio astronomical terminal system based on a dual-channel high-speed acquisition board with a frequency observation range of 1-250 MHz and a sampling rate of 500 Msps(Mega samples per second).The maximum quantization bit of the system is 14 bits,with a maximum time resolution of 0.1 s and a maximum spectral resolution of 16 kHz.The system combines spectral analysis of solar radio signals and recording of time-domain data of signals interfering with long baselines,and adopts a server-client separation mode to allow remote operation with separate permissions.It is used in the China-Malaysia joint astronomy project,which can carry out single-site observation of solar radio signals as well as interferometric observation of signals from multiple sites.

肌电图对肌萎缩侧索硬化症的早期诊断价值

目的:探讨肌萎缩侧索硬化症(ALS)患者的神经电生理特点及肌电图检测在肌萎缩侧索硬化症早期诊断中的临床意义。方法:对32例临床诊断为肌萎缩侧索硬化症的患者回顾性分析其神经传导速度检测和针极肌电图的检测。结果:32例ALS患者均呈广泛神经源性损害,其中胸锁乳突肌的异常率为93.8%,低于上下肢肌肉的异常率100.0%。结论:EMG和神经传导速度检测有助于ALS的早期诊断,而胸锁乳突肌的针极肌电图检测对ALS的诊断和鉴别诊断有重要的临床意义。

Investigation on the Formation Mechanism of Double-Layer Vertically Aligned Carbon Nanotube Arrays via Single-Step Chemical Vapour Deposition

The mechanism for the formation of double-layer vertically aligned carbon nanotube arrays(VACNTs) through single-step CVD growth is investigated. The evolution of the structures and defect concentration of the VACNTs are tracked by scanning electron microscopy(SEM) and Raman spectroscopy. During the growth, the catalyst particles are stayed constantly on the substrate. The precipitation of the second CNT layer happens at around 30 min as proved by SEM.During the growth of the first layer, catalyst nanoparticles are deactivated with the accumulation of amorphous carbon coatings on their surfaces, which leads to the termination of the growth of the first layer CNTs. Then, the catalyst particles are reactivated by the hydrogen in the gas flow, leading to the precipitation of the second CNT layer. The growth of the second CNT layer lifts the amorphous carbon coatings on catalyst particles and substrates. The release of mechanical energy by CNTs provides big enough energy to lift up amorphous carbon flakes on catalyst particles and substrates which finally stay at the interfaces of the two layers simulated by finite element analysis. This study sheds light on the termination mechanism of CNTs during CVD process.

Preliminary Study on Water Demand Law of 1-0 Rooted Cuttings of Populus szechuanica

In order to provide theoretical basis and technical support for the afforestation and artificial water supply of P.szechuanica in arid areas,the characteristics of water consumption of P.szechuanica were explored,and the law of water demand of P.szechuanica was grasped.In this paper,potted seedlings of 1-0 rooted cuttings of P.szechuanica were taken as research objects,and change situation of water consumption under different water control gradients was measured regularly by using weighing method,further analyzing dynamic change of water consumption of P.szechuanica and revealing water demand law of 1-0 rooted cuttings of P.szechuanica.The results showed that total change of water consumption of 1-0 rooted cuttings of P.szechuanica had"slow-fast-slow-fast"double-peak trend in the growth period of the current year,and corresponded with univariate linear relation(R^(2)=0.7137),with significant difference.In whole growth period,water consumption in August was the highest,which was 2.7 times of that in June and July and 1.5 times of that after September.In different water control treatments,the dynamic changes of daily and monthly water consumption were significantly different.In seven water control treatments,monthly water consumption was between(6315.95±1690.70)and(10105.28±3065.30)g/month,and mean was(8211.07±2308.23)g/month.With intensification of water control treatment,water consumption increased,but there was no seedling death due to water shortage.P.szechuanica has great plasticity in water demand,and can survive in both arid and humid environments.Meanwhile,it is revealed that P.szechuanica is the most widely distributed tree species in the region.

Nanoscale color sensors made on semiconducting multi-wall carbon nanotubes

Sub-micron color sensors are developed, using carbon nanotubes （CNTs）. The color sensor consists of an array of two photodiodes with different spectral responses, fabricated using controlled electric peeling-off and doping-free techniques on a single semiconducting double-wall CNT. The CNT photodiodes exhibit intrinsic broad spectral responses from 640 to 2,100 nm, large linear dynamic ranges of over 60 dB, and sub-micron pixel size. This method explores the unique properties of multi-wall CNTs, and may be readily used for large-scale fabrication of high performance color sensor arrays, when arrays of parallel multi-wall CNTs become available.

Screening transition metal-based polar pentagonal monolayers with large piezoelectricity and shift current

Two-dimensional(2D)materials entirely composed of pentagon motifs are of interest for their wide applications.Here,we demonstrate that in-plane polar symmetry can exist in ternary pentagonal monolayers,where the induced electric polarization is not associated with specific conditions,such as ferroelectric phase transition,strain gradient,and layer stacking,but is an intrinsic structural property coming from the orderly arranged polar bonds.Based on the high-throughput screening method and first-principles calculations,we find eight stable 2D polar transition metal compounds with a number of intriguing properties.In particular,their piezoelectric coefficients are three orders of magnitude larger than those of 2D elemental and binary pentagonal structures,and their bulk photovaltaic shift current can reach up to 300μA V^(−2),superior to that of 2D conventional ferroelectric materials such as GeS.Our identified pentagonal monolayers not only expand the family of 2D pyroelectric materials,but also hold potential for energy conversions.