高精度光谱辐射标准探测器的温度特性研究

高精度辐射定标技术是现代空间遥感的主要支撑技术之一。基于滤光片辐射计的新型光辐射标准探测器在野外、机载和星上高精度辐射定标中具有广阔的应用前景。温度特性是工程应用中影响标准探测器绝对精度和稳定性的一项关键因素。在20～60℃的宽温度范围内,对基于硅陷阱探测器的滤光片辐射计温度特性进行了系统测试和定量研究,在所获取的完备的实验数据基础上设计并研制了一套精密温控系统。实验结果显示在加入精密温控后,滤光片辐射计的温度系数降低了约一个数量级,从而有利于在不同温度工作平台上保持标准探测器的高精度。     

爆轰波对碰加载下平面金属样品动载行为实验研究

进行冲击波对碰加载简易平面金属Sn和W样品实验,采用X射线照相和激光干涉测速系统进行联合诊断,给出了2种材料冲击波对碰区表面微喷及主体破碎物质的直观图像,研究了Sn和W样品对碰区动力学行为,并比较分析2种材料对碰区特征的异同,给出了定性物理解释,实验结果可为爆轰波对碰加载下材料动力学特性的理论研究提供数据支撑。     

基于CFD的民用飞机水上迫降动力学仿真研究

针对民用飞机水上迫降动态冲击问题,采用数值仿真方法进行了研究。基于计算流体力学采用雷诺平均N-S方程求解,结合流体体积模型和全流场运动网格捕捉水-气交界面,求解六自由度方程获得飞机的位置和姿态。采用该方法研究了尾吊-高平尾布局飞机的水上迫降过程。结果表明,该方法可以较好地模拟水上迫降的运动和受力,入水早期飞机受到较大水冲击载荷,后体吸力使得飞机抬头,之后随着速度降低吸力减小,飞机逐渐低头并趋于稳定。     

An efficient ancestry informative SNPs panel for further discriminating East Asian populations

In forensic genetics, the use of ancestry informative single-nucleotide polymorphisms (AISNPs) panels can narrow the direction of the investigation by estimating an individual's biogeographic ancestry. However, distinguishing subgroups within continental regions requires more specific panels. In this study, we screened 19 AISNPs from the 1000 Genomes Project (1KG) based on their F_ST values to distinguish target populations in East Asia and obtained genotypes through SNaPshot. The 19 AISNPs could divide the global population of the 1KG into five clusters and could further divide the East Asian population into four clusters: Japanese, Han Chinese, Dai Chinese, and Kinh in Ho Chi Minh City of Vietnam. In summary, the 19-AISNP panel may serve as a useful and cost-effective tool for forensic ancestry inference in East Asian populations at a finer scale.     

Dearomatization of (Hetero)arenes through Photodriven Interplay between Polysulfide Anions and Formate**

The facile construction of C(sp³)-rich carbo- and heterocyclic compounds is a pivotal synthetic strategy to foster contemporary drug discovery programs. The downstream dearomatization of readily accessible two-dimensional (2D) planar arenes represents a direct pathway towards accessing three-dimensional (3D) aliphatic scaffolds. Here, we demonstrate that polysulfide anions are capable of catalyzing a dearomatization process of substituted naphthalenes, indoles, and other related heteroaromatic compounds in the presence of potassium formate and methanol under visible light irradiation. The developed protocol exhibits broad functional group tolerance, operational simplicity, scalability, and cost-effectiveness, representing a practical and sustainable synthetic tool for the arene dearomatization.     

三通道气相色谱法监测大气中CH_(4)、CO、CO_(2)、N_(2)O和SF_(6)北大核心CSCD

我国正处于“碳达峰、碳中和”的关键时期,准确认识我国温室气体浓度时空格局以及变化对于评估“碳达峰”和“碳中和”行动成效非常重要。当前我国近地面温室气体高精度监测主要依赖进口的光学监测主机,单台仪器成本高且监测要素有限。为此,该研究基于传统的气相色谱法,自主设计了一套三通道气相色谱分析系统,在单台仪器上实现了5种主要长寿命温室气体(CH_(4)、CO、CO_(2)、N_(2)O和SF_(6))的高精度监测。对该系统的精密度、线性响应情况和准确度进行的针对性测试实验表明系统检测性能满足世界气象组织/全球大气观测(WMO/GAW)质控标准。针对环境浓度的CH_(4)、CO、CO_(2)、N_(2)O和SF_(6)的连续分析精密度分别达0.08%、1.90%、0.05%、0.08%、0.66%。准确度测试中,5种气体(CH_(4)、CO、CO_(2)、N_(2)O和SF_(6))使用回归方程计算所得值与标称摩尔分数间的偏差分别达0.15×10-9、0.20×10-9、0.37×10-6、0.35×10-9、0.02×10-12(摩尔分数),CH_(4)、CO、CO_(2)、N_(2)O和SF_(6)仪器响应值与标称摩尔分数的线性拟合相关系数(R2)均为0.9999,线性拟合残差和准确度基本达到WMO/GAW拓展质控目标。该系统对杭州城区大气温室气体在线连续监测结果显示,2021年5~7月期间大气CH_(4)、CO、CO_(2)和N_(2)O呈明显的日变化特征,主要受人为活动影响。综合测试和试运行结果表明,该研发系统具备良好的精密度、准确度、线性和稳定性,与目前国内广泛进口的仪器相比,具有技术自主可控、运行成本更低、自动化水平更高等优势,能满足多种温室气体在线监测研究的需求。     

Gasification and combustion kinetics of a high-ash-fusion-temperature coal using thermogravimetric analysis

Journal of Thermal Analysis and Calorimetry - The gasification/combustion kinetics of a typical Chinese high-ash-fusion-temperature (AFT) coal char, Huainan (HN) coal char, are analyzed using a...     

Thixotropy of Aqueous Suspensions Containing Mg‐Al Hydrotalcite‐like Compound and Low‐substituted Cationic Starch: Comparison between Oscillatory Shear and Thixotropic Loop Measurements

The rheological properties of aqueous suspensions consisting of positively charged aluminum magnesium hydrotalcite‐like compound (HTlc) and low‐substituted cationic starch (LCS) were investigated. Special emphasis was placed on the thixotropic phenomenon. Thixotropic behavior was investigated by two thixotropic methods: thixotropic loop and oscillatory shear measurements. LCS molecules could be adsorbed onto HTlc particles due to the hydrogen bonding between ether groups or hydroxyl groups of LCS and hydroxyl groups of HTlc. The elastic dynamic response of the HTlc/LCS suspension increased with increasing mass ratio (R) of HTlc and a three‐dimensional network structure could be formed in the suspension with higher R value. The thixotropic type of the HTlc/LCS suspension transformed from negative to positive and then to complex thixotropy when R changed from 0 to 0.5. By comparing between the thixotropic results obtained by thixotropic loop and oscillatory shear measurements, it was validated that the thixotropic loop for the suspension showing complex thixotropy had a crossover point.     

Small open reading frames: current prediction techniques and future prospect

Evidence is accumulating that small open reading frames (sORF, <100 codons) play key roles in many important biological processes. Yet, they are generally ignored in gene annotation despite they are far more abundant than the genes with more than 100 codons. Here, we demonstrate that popular homolog search and codon-index techniques perform poorly for small genes relative to that for larger genes, while a method dedicated to sORF discovery has a similar level of accuracy as homology search. The result is largely due to the small dataset of experimentally verified sORF available for homology search and for training ab initio techniques. It highlights the urgent need for both experimental and computational studies in order to further advance the accuracy of sORF prediction.     

Flow rate gradient high-speed counter-current chromatography separation of five diterpenoids from Triperygium wilfordii and scale-up

In this paper, high-speed counter-current chromatography (HSCCC) instruments with different gravitational forces were applied for the separation of bioactive compounds from Triperygium wilfordii Hook.f. The critical parameters including sample concentration, sample volume and flow rate were first optimized on an analytical Mini-DE HSCCC system, and then scaled up to a preparative TBE 300A HSCCC system. Although this scale-up process was performed using different CCC instruments with different centrifuges and gravitational forces, the same resolutions were obtained and the elution time could be predictable. Five diterpenoid compounds and one unknown compound were separated from Triperygium wilfordii Hook.f. by HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (HEMW) (3:2:3:2, v/v/v/v). This one-step flow gradient separation produced triptonide (25 mg), isoneotriptophenolide (77 mg), hypolide (83 mg), unknown compound (1 mg), triptophenolide (42 mg), triptonoterpene methyl ether VI (37 mg) from 320 mg crude extract with purities of 98.2%, 96.6%, 98.1%, 95.3%, 95.1%, and 96.5%, respectively. Their purities and structures were identified by high-performance liquid chromatography, mass spectrometry and NMR. This paper demonstrates that analytical CCC plays an important role in optimizing parameters and scale-up process when analytical CCC and preparative CCC are supplied by different manufacturers with different gravitational forces, and the scale-up process from analytical CCC to preparative CCC is still predictable.