NO分子光声光谱的理论分析

采用拉普拉斯变换严格求解二能级系统光与物质相互作用的速率方程,获得了强激光诱导气体分子系统光声信号的解析表达式。结果显示光声信号的大小与样品分子的吸收截面、激发光强度、分子共振跃迁吸收的光子数、分子碰撞弛豫速率等因素有关。借助于光声信号随激光强度的变化关系,将NO分子在420.0～470.0 nm波长区间的激光诱导光声光谱归属于NO分子经X 2Π→A 2Σ的双光子激发跃迁及X 2Π→E 2Σ,F 2Σ,R 2Σ的三光子激发跃迁,由此获得NO分子A 2Σ,E 2Σ,F 2Σ和R 2Σ激发电子态的振动常数分别为2 346,2 342,2 397和2 381 cm-1,结果与采用其他方法测量的结果符合得较好。并对光声信号随缓冲气压升高而出现饱和的现象进行了理论解释。     

一类随机变量序列部分和的强大数定律

设{Xn,n≥1}是随机变量序列.文[4]在二阶矩限制下,获得了任意随机变量序列的Hajek-Renyi型不等式,并给出了随机变量序列的强大数定律.本文利用胡舒合等获得的强大数定律,给出了随机变量序列的一些几乎必然收敛性,并给出了结果在PA,NA和两两NQD序列场合下的应用.     

一个4-9GHz 10W 宽带功率放大器

设计并制作了4-9GHz宽带混合集成功率放大器,在6-8GHz频带内功率能达到10W,其余频段内功率也能达到6W以上。电路采用平衡放大器形式,整个频段内增益为7.3dB±0.9dB,在8GHz频点处功率附加效率（PAE）为39%。输入输出驻波均小于-10dB。     

基于增益扩展现象的线性化技术在Doherty功放中的应用

在分析Doherty放大器特性基础上,研究了利用Doherty具有增益扩展特性的放大器线性化技术.深入分析了Doherty功放中辅助功放的栅压变化对增益扩展特性的影响,并讨论了据此将具有增益扩展特性的前级Doherty功放作为模拟射频预失真器与末级Doherty功放进行级联而构成的线性化功放.最后根据这一原理,采用一对MRF21010功放管所设计并优化的Doherty模拟预失真功率放大器与前级为平衡放大器、末级为相同Doherty功放的级联电路相对照,表明三阶互调可以改善15dB,效率提高2%.研究结果对高效率、高线性功放的设计具有实际意义.     

Lipid characterization of embryo zones by silica plate laser desorption ionization mass spectrometry imaging (SP-LDI-MSI)

Lipid pathways play important biological roles in mammalian embryology, directing early developmental pathways to differentiation. Phospholipids and triglycerides, among others, are the main composing lipids of zona pellucida in several embryo species. Lipid analysis in embryos by mass spectrometry usually requires sample preparation and/or matrix application. This novel approach using silica plate laser desorption/ionization mass spectrometry imaging (SP-LDI-MSI) allows direct single-cell imaging and embryo region discrimination with no matrix coating. Its application is herein described for two- and eight-cell embryos. Lipid biomarkers for blastomere and intact zona pellucida are reported and corroborated by both fragmentation reactions (MS/MS) and images. Results obtained in this work are understood to be of great use for further developments on in vitro bovine fertilization. Since much of the processes can be monitored by characteristic biomarkers, it is now possible to precisely identify cell division errors during early embryo stages, as well as evaluate pre-implantation conditions.     

Excitation temperature,degree of ionization of added iron species,and electron density in an exploding thin film plasma

Time and spacially resolved spectra of a cylindrically symmetric exploding thin film plasma were obtained with a rotating mirror camera and astigmatic imaging. These spectra were decouvolved to obtain relative spectral emissivity profiles for nine Fe(II) and two Fe(I) lines. The effective (electronic) excitation temperature at various positions in the plasma and at various times during the first current halfcycle was computed from the Fe(II) emissivity values using the Boltzmann graphical method. The Fe(II)/Fe(I) emissivity ratios together with the temperature were used to determine the degree of ionization of Fe. Finally, the electron density was estimated from the Saha equilibrium. Electronic excitation temperatures range from 10,000–15,000 K near the electrode surface at peak discharge current to 7000–10,000 K at 6–10 mm above the electrode surface at the first current zero. Corresponding electron densities range from 10¹⁷-10¹⁸ cm^?3 at peak current to 10¹⁵-10¹⁶cm^?3 near zero current. Error propagation and criteria for thermodynamic equilibrium are discussed.     

An improved technique for the spectrophotometric determination of nitrate with 2,4-xylenol

An improved method is proposed for the spectrophotometric determination of nitrate with 2,4-xylenol. The sample in aqueous (1.7 + 1 ) sulfuric acid is treated with 2,4-xylenol to produce 6-nitro-2,4-xylenol which is distilled into an ammoniacal water—isopropanol mixture. The intense yellow color of the ammonium salt of 6-nitro-2,4-xylenol is measured at 455 nm. The distillation is done in a Parnas—Wagner Kjeldahl Semimicro distillation apparatus. The isopropanol keeps the excess of 2,4-xylenol in solution. Two procedures are described. In the first (applicable to samples containing alkali nitrates but no chloride, alkaline earth, or ammonium salts), the solution is evaporated to dryness, and (1.7 + 1) sulfuric acid and 2,4-xylenol in acetone are added. In the second (applicable to samples containing chloride, alkaline earth, or ammonium salts), concentrated sulfuric acid is added dropwise to a cooled aliquot and the 2,4-xylenol reagent is then added; if chloride is present, it must be removed by prior precipitation with silver sulfate. Nitrite shows a slight interference which depends on the amount of nitrate and nitrite present.     

Carbocyclization in natural products—II : Brominative cyclization of dihydrocostunolide

Treatment of dihydrocostunolide 1 with NBS in aqueous acetone at room temperature furnished bromolactones 3, 4 and 5. Structural evidence for these bromolactones rests upon spectral data and chemical correlations with santanolide “c” 10. Mass spectral fragmentation patterns for the bromolactones, with special reference to 4, have been also discussed.     

Recent developments in manufacturing emulsions and particulate products using membranes

Membrane emulsification (ME) is a relatively new technique for the highly controlled production of particulates. This review focuses on the recent developments in this area, ranging from the production of simple oil-in-water (O/W) or water-in-oil (W/O) emulsions to multiple emulsions of different types, solid-in-oil-in-water (S/O/W) dispersions, coherent solids (silica particles, solid lipid microspheres, solder metal powder) and structured solids (solid lipid microcarriers, gel microbeads, polymeric microspheres, core-shell microcapsules and hollow polymeric microparticles). Other emerging technologies that extend the capabilities into different membrane materials and operation methods (such as rotating membranes, repeated membrane extrusion of coarsely pre-emulsified feeds) are introduced. The results of experimental work carried out by cited researchers in the field together with those of the current authors are presented in a tabular form in a rigorous and systematic manner. These demonstrate a wide range of products that can be manufactured using different membrane approaches. Opportunities for creation of new and novel entities are highlighted for low throughput applications (medical diagnostics, healthcare) and for large-scale productions (consumer and personal products).