遥测数据的无损压缩技术

桑地亚国家实验室面临着各种测试传感器产生的数字化数据的无损压缩问题。他们所关心的数据一旦产生，就对其进行压缩，即处于实时状态。     

Application of isotopically labeled methylmercury for isotope dilution analysis of biological samples using gas chromatography/ICPMS

An isotope dilution (ID) procedure for the determination of methylmercury (MMHg) in biological samples using an inductively coupled plasma mass spectrometer as detector after the capillary gas chromatographic separation (CGC/ICPMS) has been developed. For the first time, open-focused-microwave pretreatment has been used in conjunction with ID. Optimum conditions for the measurement of isotope ratios on the fast transient chromatographic peaks have been established. Mass bias was found to be about 1.5%/mass unit and was corrected by using the simultaneously measured thallium signals at 203Tl and 205Tl. After mass-bias correction, deviation of the theoretical mercury ratio values was found to be as low as 0.2%. Isotope ratio precisions based on the peak areas measurements were 0.3% RSD for 20 pg injected (as Hg absolute). The absolute detection limits were in the range of 20-30 fg for 202Hg and 201Hg. Methylmercury enriched in 201Hg has been synthesized by direct reaction with methylcobalamine. The concentration of the MMHg spike has been measured by reverse isotope dilution with a natural MMHg standard. The capabilities of CGC/ICPMS to measure isotope ratios were used to optimize sample derivatization by aqueous ethylation with NaBEt4 with respect to MMHg degradation pathways and quantitative recovery. The accuracy of the method developed has been validated with biological certified reference materials (CRM-463, DORM-1).     

Using speciated isotope dilution with GC-inductively coupled plasma MS to determine and unravel the artificial formation of monomethylmercury in certified reference sediments

Speciated isotope-dilution mass spectrometry (SID-MS) is claimed to be an absolute method; however, it has been found to be affected by artifact monomethylmercury (MMHg) formation in sediments. The determination of MMHg in sediments was carried out by SID-MS after open-focused microwave extraction. The extracted mercury species were then ethylated and separated by capillary gas chromatography (CGC). Isotope ratios (peak area ratios at different masses) were measured by on-line ICP-MS detection of the CGC-separated compounds. Reproducibility of 202Hg/201Hg isotope ratio measurements were 0.60% for MeEtHg and 0.69% for Et2Hg; for 202Hg/199Hg, 0.43 and 0.46%, respectively, were determined. The absolute detection limits for CGC-ICPMS measurements were better than 26 fg for 202Hg, 20 fg for 201Hg, and 24 fg for 199Hg. For the direct determination of MMHg in sediment reference materials (CRM 580, IAEA 356, and IAEA 405), higher values than the certified were always found. Systematic experiments were carried out to localize the sources of the unintentional abiotic methylmercury formation during analysis. Different spiking and derivatization procedures (either ethylation, propylation, or derivatization by Grignard reagents) were tested. In addition, isotopically enriched inorganic mercury was spiked. The amount of inorganic mercury initially present in the sample was found to be the critical factor that should be known and carefully controlled. A simple solvent extraction technique involving no critical cleanup steps was applied in order to reduce high Hg2+ amounts. The method was applied to the determination of MMHg in sediment reference material IAEA-405 with satisfactory results after organic solvent extraction. The limitations of applicability of the proposed method are evaluated as related to inorganic mercury, organic carbon, and sulfur contents. The results obtained confirmed that available sediment reference materials are adequate to achieve traceable mercury speciation analysis and to detect potential sources of MMHg artifact formation.     

Analysis of particle sizes, concentration, and refractive index in measurement of light transmittance in the forward-scattering-angle range

A simple method for determining the mean size, the concentration, and the refractive index of the monodispersion and the polydispersion of particles has been presented. The method is based on the empirical inversion of measurements of forward-angle light-scattering transmittance. The effects of particle size distribution and optical constants on forward-angle-scattering transmittance have been considered by using Mie theory. The proposed method has been used successfully for single latex spheres in water and polydispersed weakly absorbing particles of Al(2) O(3) and SiO(2) in the flow of the propane-air flame combustion products.     

基于虚拟仪器的数据链测试模拟器研制

针对传统数据链测试设备功能单一且不易重构的问题,借鉴虚拟仪器模块化的设计思想,设计实现了一种基于美国国家仪器公司（National Instruments,NI）通用软件无线电平台的数据链测试模拟器。该模拟器采用线性调频信号叠加（Sum of Linear Frequency Modulation,SoLFM）的方法高效产生具备连续相位的时变信道衰落,包括瑞利衰落、莱斯衰落和对数正态衰落等,并结合多相滤波思想能够精确模拟数据链长时延的多径传播场景。利用矢量网络分析仪对硬件模拟器输出的信道传递函数和信道冲激响应进行实测验证,并对各支路的随机信道衰落包络分布进行统计验证。实测结果表明,该数据链测试模拟器输出的信道函数和统计分布均与理论值吻合,因而可用于数据链装备的系统优化、验证和性能评估。     

Species-specific stable isotope analysis by the hyphenation of chromatographic techniques with MC-ICPMS

This work reviews the basis and all the existing publications on the hyphenation of chromatography-based techniques to MC-ICPMS for isotopic studies that were published until the end of 2010. A brief historical retrospective of the measurement of isotope ratios from transient signals by ICPMS with different sample introduction techniques is also included. The most important experimental parameters and data reduction strategies affecting the accurate and precise measurement of compound-specific isotope ratios by either HPLC or GC coupled to MC-ICPMS are discussed. All the applications are reported and critically reviewed in terms of analytical characteristics, performances, optimization, advantages and disadvantages and future applicability to the environmental, geochemical, or bioinorganic studies.     

Axial superresolution of two-photon microfabrication

An axial superresolution diffraction theory is developed in a two-photon microfabrication system. This method can improve the axial superresolution of the two-photon microfabrication system. A theoretical analysis of the photosensitive resin is discussed based on the exciting power and the concentration of free radical theory. Simulated results of the two-photon microfabrication verify the method and show that it can provide insight into the microfabrication system.     

Combining Fourier transform-ion cyclotron resonance/mass spectrometry analysis and Kendrick plots for silicon speciation and molecular characterization in petroleum products at trace levels

A new method combining FT-ICR/MS analysis and Kendrick plots for the characterization of silicon species at trace levels in light petroleum products is presented. The method provides efficient instrumental detection limits ranging from 80 ng/kg to 5 μg/kg and reliable mass accuracy lower than 0.50 ppm for model silicon molecules in spiked gasoline. More than 3000 peaks could be detected in the m/z 50-500 range depending on the nature of the gasoline sample analyzed. An in-house software program was used to calculate Kendrick plots. Then, an algorithm searched, selected, and represented silicon species classes (O(2)Si, O(3)Si, and O(4)Si classes) in Kendrick plots by incorporating model molecules' information (i.e., exact mass and intensity). This procedure allowed the complete characterization of more than 50 new silicon species with different degrees of unsaturation in petroleum products.     

Thin films of two functional oxides patterned laterally by soft lithography

Thin films of two laterally patterned functional oxides of uniform thickness were obtained in a two-step soft-lithographic micromolding process. CoFe(2)O(4)/ZnO and CoFe(2)O(4)/BaTiO(3) dual-phase patterns were fabricated. The films showed good replication of the pattern that was defined in the first patterning step. X-ray diffraction showed that the films consisted of two distinct phases, and magnetic force microscopy showed that the compounds were laterally separated, the separation pattern being the same as that of the initial soft-lithographic process. The films exhibited slight height variations near the edges of the phases, which were introduced in the first deposition step and were not fully compensated in the second deposition step. The films are sufficiently smooth to allow fabrication of multilayer structures.     

Stacks of functional oxide thin films patterned by micromolding

Stacks of up to five relief patterned functional oxide thin films were obtained by a low-cost and low-tech soft-lithographic patterning technique. Micromolding was used to pattern a film of a metal-organic precursor solution for Y-stabilized ZrO(2) (YSZO). Subsequent drying and pyrolysis yielded a line-patterned YSZO film. The process was repeated up to four times with a precursor solution for BaTiO(3) on top of the YSZO film, resulting in stacks of YSZO and BaTiO(3) lines with well-defined edges. This approach presents a step forward on the way to a versatile additive micropatterning technique with which simple multi-material device structures can be fabricated in a reliable, fast, and cost-effective manner.