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81.
Aaron N. Fletcher Dwight A. Fine Dan E. Bliss 《Applied Physics A: Materials Science & Processing》1977,12(1):39-44
A commercial coaxial xenon flashlamp was used to measure laser dye stability. The output energy of each lasing pulse was recorded
and periodic measurements were made of the untuned lasing wavelength, the temporal flashlamp output, and the temporal lasing
output. The present study demonstrates that it is possible to have a number of different types of apparent dye laser system
“half-lifes” through the use of filtration and frequency of flash parameters. The use of near-zero flash frequency and moderate
pore size filters allows a determination of the lifetime that is more representative of the dye as opposed to the lifetime
of the dye laser system. 相似文献
82.
A new analytical clean-up technique, designed specifically for the analysis of N-nitroso compounds with a thermal energy analyzer and a gas Chromatograph, is described. Only two steps are required; vacuum distillation from mineral oil followed by extraction with dichloromethane. The sensitivity for N-nitroso compounds in foodstuffs is at the 5 μg kg-1 level, but if a dichloromethane extract is concentrated on a Kuderna Danish evaporator, a 100-fold increase is attainable. The method can be used for any foodstuff or biological material, and the quantitation of any N-nitroso compounds amenable to gas chromatography is possible. 相似文献
83.
用Eu3+作探针研究硼铅玻璃材料 总被引:3,自引:2,他引:1
利用Eu^3 离子探针技术对所设计的尔组分为(79.5-x)BO3/2-(20 x)PbF2-0.5Eu2O3(x=0,10,20,30,40)玻璃体系进行了研究。测量了不同组份玻璃的激发光谱,得到了各个配比玻璃样品的声子边带(PSB)谱,计算了电声子耦合常数g,讨论了g对组份的依赖关系。在此基础上讨论了该基质中稀土离子的无辐射跃迁行为。测量了在362nm激发下不同配比样品^5Do→^7Fo,^7F1,^7F2,的发射光谱,并利用发射光计算了Eu^3 离子在该玻璃体系中光学跃迁的J-O参量Ω2,进而讨论了其结构特性。 相似文献
84.
Jonathan A. Fine Anand A. Rajasekar Krupal P. Jethava Gaurav Chopra 《Chemical science》2020,11(18):4618
State-of-the-art identification of the functional groups present in an unknown chemical entity requires the expertise of a skilled spectroscopist to analyse and interpret Fourier transform infra-red (FTIR), mass spectroscopy (MS) and/or nuclear magnetic resonance (NMR) data. This process can be time-consuming and error-prone, especially for complex chemical entities that are poorly characterised in the literature, or inefficient to use with synthetic robots producing molecules at an accelerated rate. Herein, we introduce a fast, multi-label deep neural network for accurately identifying all the functional groups of unknown compounds using a combination of FTIR and MS spectra. We do not use any database, pre-established rules, procedures, or peak-matching methods. Our trained neural network reveals patterns typically used by human chemists to identify standard groups. Finally, we experimentally validated our neural network, trained on single compounds, to predict functional groups in compound mixtures. Our methodology showcases practical utility for future use in autonomous analytical detection.A new multi-label deep neural network architecture is used to combine Infrared and mass spectra, trained on single compounds to predict functional groups, and experimentally validated on complex mixtures. 相似文献
85.
LIU Zhen YANG Lin CHEN Bo CHEN Bin & CAO JianLin State Key Laboratory of Applied Optics Changchun Institute of Optics Fine Mechanics Physics Chinese Academy of Sciences Changchun China Graduate University of Chinese Academy of Sciences Beijing 《中国科学:物理学 力学 天文学(英文版)》2011,(3)
This paper first reviews an EUV normal incidence solar telescope that we have developed in our lab. The telescope is composed of four EUV telescopes and the operation wavelengths are 13.0 nm, 17.1 nm, 19.5 nm, and 30.4 nm. These four wavelengths, fundamental to the research of the solar activity and the atmosphere dynamics, are always chosen by the EUV normal incidence solar telescope. In the EUV region, almost all materials have strong absorption, so optics used in this region must be coated by the multila... 相似文献
86.
87.
Chetan Kumar Arya Swati Yadav Jonathan Fine Ana Casanal Gaurav Chopra Gurunath Ramanathan Kutti R. Vinothkumar Ramaswamy Subramanian 《Angewandte Chemie (International ed. in English)》2020,59(39):16961-16966
N,N‐dimethyl formamide (DMF) is an extensively used organic solvent but is also a potent pollutant. Certain bacterial species from genera such as Paracoccus, Pseudomonas, and Alcaligenes have evolved to use DMF as a sole carbon and nitrogen source for growth via degradation by a dimethylformamidase (DMFase). We show that DMFase from Paracoccus sp. strain DMF is a halophilic and thermostable enzyme comprising a multimeric complex of the α2β2 or (α2β2)2 type. One of the three domains of the large subunit and the small subunit are hitherto undescribed protein folds of unknown evolutionary origin. The active site consists of a mononuclear iron coordinated by two Tyr side‐chain phenolates and one carboxylate from Glu. The Fe3+ ion in the active site catalyzes the hydrolytic cleavage of the amide bond in DMF. Kinetic characterization reveals that the enzyme shows cooperativity between subunits, and mutagenesis and structural data provide clues to the catalytic mechanism. 相似文献
88.
基于连续投影算法的土壤总氮近红外特征波长的选取 总被引:13,自引:0,他引:13
讨论了如何利用连续投影算法提取土壤总氮的近红外特征波长.使用连续投影算法对光谱数据进行初步压缩,将优选出的波长按其对总氮贡献值的大小进一步筛选,剔除不敏感的波长,降低模型的复杂度.分析85份土壤样品的近红外光谱,使用连续投影算法得到了总氮的12个波长,贡献值筛选后,波长数量减少到6个,所建模型的预测相关系数(Rp)为0.913,预测均方根误差(RMSEP)为0.011%,模型的预测精度与贡献值筛选前相当,且优于全谱偏最小二乘回归结果.结果表明结合贡献值筛选的连续投影算法能够有效选取待测成分的特征波长,文章所优选的土壤总氮的6个特征波长可以作为小型滤光片式近红外光谱仪波长选择的参考依据. 相似文献
89.
A bifunctional heterogeneous catalyst containing two mutually incompatible acidic and basic sites,which exhibits cooperative catalytic behavior in the aldol condensation of acetone and various aldehydes,was synthesized by postgrafting of 1,5,7- triazabicyclo[4.4.0]dec-5-ene(TBD,a sterically hindered organic base) onto Al-MCM-41 molecular sieve. 相似文献
90.
采用微微秒激光作激发源的时间相关单光子计数系统测量了血卟啉衍生物的肿瘤定位组分(TLF)在缓冲液中不同阳离子表面活性剂浓度下的荧光衰减波形I(t)和时间分辨光谱I(λ,t). 相似文献