Radionuclide imaging of miniaturized chemical analysis systems

We propose radionuclide imaging as a valuable tool for the study of molecular interactions in miniaturized systems for chemical analysis. Sensitive and quantitative imaging can be performed with compounds labeled with short-lived positron-emitting radionuclides, such as (11)C and (68)Ga, within selected parts of the system. Radionuclide imaging is not restricted to transparent materials since the relatively energetic positrons can penetrate high optical density materials. Experimentally, a radiotracer is introduced into the object of study, which is subsequently placed on a phosphor storage plate. After exposure, the plate is scanned with a laser and a digital, quantitative image can be reconstituted. To demonstrate the concept, three types of microstructures suited for integration in chemical analysis systems were imaged with (11)C- and (68)Ga-labeled tracers. The influence of factors such as geometry of the object and type of radionuclide on resolution and sensitivity was investigated. The resolution ranged from 0.9 to 2.7 mm (fwhm). Measuring low amounts of radioactivity in the three structures, 2-20 Bq could be detected, which corresponded to 2.3-500 amol or 2.4-110 pM tracer. The imaging approach was applied to study analyte concentration and sample dilution effects on the performance of a capillary extraction column integrated in an automated LC-ESI-MS system. The utility of the technique was further illustrated by imaging of microchannels in a zeonor plastic compact disk and in a poly(dimethylsiloxane) material for the study of nonspecific peptide adsorption.     

Sample preparation using a miniaturized supported liquid membrane device connected on-line to packed capillary liquid chromatography

A miniaturized supported liquid membrane device has been developed for sample preparation and connected on-line to a packed capillary liquid chromatograph. The device consists of hydrophobic polypropylene hollow fiber, inserted and fastened in a cylindrical channel in a Kel-F piece. The pores of the fiber are filled with an organic solvent, in this study 6-undecanone, thus forming a liquid membrane. The sample is pumped on the outside of the hollow fiber (donor), and the analytes are selectively enriched and trapped in the fiber lumen (acceptor). With this approach, the volume of the acceptor solution can be kept as low as 1-2 μL. This stagnant acceptor solution is then transferred through capillaries attached to the fiber ends to the LC system. The system was tested with a secondary amine (bambuterol), as a model substance in aqueous standard solutions as well as in plasma. The best extraction efficiency in aqueous solution, with an acceptor volume of 1.9 μL, was 32.5% at a donor flow rate of 2.5 μL/min. At flow rates above 20 μL/min, the concentration enrichment per time unit was approximately constant, at 0.9 times/min, i.e., 9 times enrichment in about 10 min. The overall repeatability (RSD) for spiked plasma samples was ～4% (n = 12). Linear calibration curves of peak area versus bambuterol concentration were obtained for both aqueous standard solutions and spiked plasma samples. The detection limit for bambuterol in plasma, after 10 min of extraction at a flow rate of 24 μL/min, was 80 nM.     

Fourier transform infrared detection in miniaturized total analysis systems for sucrose analysis

In this work, a flow system containing a micromachined lamella-type porous silicon reactor and a novel mid-IR fiber-optic flow cell were used for the enzymatic determination of sucrose in aqueous solution. The method relies on the enzymatic hydrolysis of sucrose to fructose and glucose catalyzed by β-fructosidase and on the acquisition of FT-IR spectra before and after complete reaction. β-Fructosidase was covalently bound to the porous silicon surface of the channels in the microreactor. The porous silicon was achieved by anodization of the silicon reactor in a HF/ethanol mixture. For the measurement of small amounts of aqueous solution, a miniaturized flow cell was developed which consisted of two AgCl(x)Br(1)(-)(x) fiber tips (diameter, 0.75 mm) coaxially mounted in a PTFE block at a distance of 23 μm. The flowing stream was directed through the gap of the two fiber tips which served to define the optical path length and to bring the focused mid-IR radiation to the place of measurement. Using this construction, a probed volume of ～10 nL was obtained. The calibration curve was linear between 10 and 100 mmol/L sucrose. Furthermore, the potential of this method was demonstrated by the analysis of binary sucrose/glucose mixtures showing no interference from glucose and by the successful determination of sucrose in real samples.     

Harmonic analysis of sideband signals generated in plasmas

When a small ac voltage with two frequencies was biased to a probe in low pressure inductively coupled plasma, sideband current signals were observed. It was found that two frequencies of the small bias voltage are mutually modulated in the plasma, and this modulation results in the sideband current signals. Experiments for measurement of the sidebands were carried out at various pressures, correlations between the sidebands and the plasma state were investigated. The sidebands were not observed when the plasma was not generated; therefore these signals were produced by the nonlinearity of the sheath. The electron temperature could be obtained from the sideband signals, and it was in good agreement with that from a single Langmuir Probe.     

Fiber-optical sensor with miniaturized probe head and nanometer accuracy based on spatially modulated low-coherence interferogram analysis

Fiber-optical sensors have some crucial advantages compared with rigid optical systems. They allow miniaturization and flexibility of system setups. Nevertheless, optical principles such as low-coherence interferometry can be realized by use of fiber optics. We developed and realized an approach for a fiber-optical sensor, which is based on the analysis of spatially modulated low-coherence interferograms. The system presented consists of three units, a miniaturized sensing probe, a broadband fiber-coupled light source, and an adapted Michelson interferometer, which is used as an optical receiver. Furthermore, the signal processing procedure, which was developed for the interferogram analysis in order to achieve nanometer measurement accuracy, is discussed. A system prototype has been validated thoroughly in different experiments. The results approve the accuracy of the sensor.     

Spectral analysis of the acoustic emission of laser-produced plasmas

A Q-switched frequency Nd:YAG laser was focused on copper, aluminum, and lead targets. The acoustic emission accompanying plasma formation was acquired and analyzed in both the time and the frequency domains. Spectral analysis of the shock wave has proved to be a simple and low-cost diagnostic of plasma phenomena. In the time domain, several propagation mechanisms of the shock wave were observed and the velocity profile of the shock wave estimated. Spectral measurements were performed in the acoustic propagation regime of the shock waves. Spectral features related to the plasma formation mechanism were identified and discussed for copper, aluminum, and lead on the basis of the physical properties of these elements, the expansion mechanisms of the plasma, and an empirical parameter representative of the transported energy.     

Observation and analysis of current carrying plasmas in a railgun

Observation of current-carrying plasma arcs driving solid projectiles in round-bore and square-bore railguns have been made with magnetic induction coils. Both free-running precursor arcs as well as projectile armature arcs are observed. Qualitative behavior of the plasmas is inferred from data and compared to basic physical models. The non-uniform nature of the force on the armature is investigated. Experimental details as well as difficulties in calibration and in quantitative analysis of magnetic probe signals are discussed. Evidence suggesting evolution in the structure of free-running arcs is presented.     

Numerical analysis of oxygen induction thermal plasmas with chemically non-equilibrium assumption for dissociation and ionization

Modeling of induction thermal plasmas has been performed to investigate a chemically non-equilibrium effect for dissociation and ionization. Computations were carried out for oxygen plasmas under atmospheric pressure. The thermofluid and concentration fields were obtained by solving of two-dimensional modeling. This formulation was presented using higher-order approximation of the Chapman-Enskog method for the estimation of transport properties. A deviation from the equilibrium model indicates that oxygen induction plasmas should be treated as non-equilibrium for dissociation and ionization. The present modeling would give the guidance for the rational design of new material processing using thermal plasmas.     

小型化线列阵研究

介绍了一种小型化线列阵,阵结构与常规线列阵最大的不同在于阵元间距小于四分之一波长。通过理论分析和仿真计算优化了各阵元的最佳权系数,获得了良好的指向性,得到了实验的证明。小型化线列阵的指向性图具有四大特点：①单向性：仅在半空间出现一个轴对称的主波束,无栅瓣和次瓣。②端射特性：主波束出现在线阵的轴射方向。③超指向性：在阵的尺寸远小于二分之一波长条件下不仅可以获得良好的指向性图,并且波束宽度随阵元间距的减小而减小。④恒定束宽特性：在阵元间距小于八分之一波长条件下,波束宽度随频率变化非常平缓。这种小型化基阵也可用于大型基阵如拖曳阵和展开式体积阵的子基阵,进行低频宽带信号的检测。     

Failure analysis of miniaturized multilayer ceramic capacitors in surface mount printed circuit board assemblies

New failure analysis results of miniaturized multilayer ceramic capacitors (sizes 0402, 0603, 0805 and 1206) which have been subjected to various degrees of thermal shock up to 450°C by ice-water or dry ice quenching are reported. The thermal shock resistance of 0402 multilayer ceramic capacitors was found to be about 400°C and considerably better than those of the larger ones. Microstructural and layer-by-layer insulation resistance analyses have clearly identified the physical locations responsible for the electrical leakage of defective capacitors. Further, no evidence of silver migration as a dominant failure mechanism has been observed for any of the defective capacitors under usual operating stresses. Comparisons ofI–V characteristics for multilayer ceramic capacitors quenched by ice-water and dry ice confirm that water plays a significant role in causing electrical failure at nominal bias. Comparisons with results obtained from practical surface mount printed circuit board assembly of mobile telephones is discussed. From these, failure mechanisms are proposed to explain the failure of miniaturized multilayer ceramic capacitors under normal service conditions.     

One- and two-dimensional miniaturized electrophoresis of proteins with native fluorescence detection

Miniaturized electrophoresis was successfully coupled with native fluorescence detection for direct analysis of proteins in one- and two-dimensional separations. The detection setup was based on direct observation of the UV-induced fluorescence of proteins using a CCD camera and a Hg (Xe) lamp for sample excitation. Protein mixtures were readily separated by size on a 1-cm segment of the one-dimensional gel in 8 min, and a detection limit of 0.04 ng per band was achieved. The dynamic range of the system was larger than 2 orders of magnitude. Miniaturized slab gel electrophoresis was performed on a special holder designed to couple isoelectric focusing with SDS-PAGE. Two-dimensional separation, including rehydration of IEF strip and fluorescence detection was completed in 2.5 h. Approximately 200 protein spots from Escherichia coli were detected on a 1 cm(2) area. A detection limit of 0.1 microg of total protein was achieved. The operation should be amenable to total automation.     

Lam e-mode miniaturized quartz temperature sensors

Lam e-mode is very useful for realization of a miniaturized quartz crystal resonator because its resonant frequency principally depends only on the contour dimensions. Because the heat capacitance for the miniaturized quartz crystal resonator is small and the frequency response versus temperature is very rapid, the quartz crystal resonator is useful for application in temperature sensors. In addition, because a Lam e-mode quartz crystal resonator has zero temperature coefficients, designated LQ(1) cut and LQ(2) cut, and, particularly, the resonator for LQ(1) cut has a comparatively large value of the second-order temperature coefficient beta, a Lam e-mode quartz crystal resonator can be obtained with the large first-order temperature coefficient or when beta=0. In this paper, when cut angles phi=45 degrees and theta=45 degrees , alpha has a value of 44.6x10(-6)/ degrees C in the calculation and 39.9x10(-6)/ degrees C in the experiments with beta=0; when phi=51.5 degrees and theta=45 degrees , alpha=68.1x10(-6)/ degrees C in the calculation and 62.0x10(-6)/ degrees C in the experiments with a value of beta larger than that of phi=45 degrees and theta=45 degrees . For both cut angles, the calculated frequency change vs. temperature is found to be sufficiently large and slightly larger than the measured one.     

Development of density-inclination plasmas for analysis of plasma nano-processes via combinatorial method

We have developed a plasma-process analyzer based on the “combinatorial method”, in which process examinations with a continuous variation of sample-preparation conditions can be carried out in one execution of experiment via placing substrates on a substrate holder with an inclined distribution of process parameters (ion flux and radical flux) and the distributions of particle fluxes are finely controlled and characterized via particle diagnostics. In the present study, plasma-fluid simulations have been performed to show the feasibility of the combinatorial plasma-process analyzer, in which density inclinations of the plasma parameters (ion density, radical density) are obtained via sustaining plasmas by localized deposition of discharge power using low-inductance antenna modules. The simulation results showed that density-inclination plasmas were feasible by localized power deposition for sustaining plasmas, indicating that a variety of process conditions can be efficiently analyzed via placing substrates on a substrate holder, along which process parameters are inclined.     

Sample preparation techniques in trace element analysis of water

Sample preparation techniques for the analysis of water for trace elements using X-ray emission spectroscopy are described.Fresh water samples for the analysis of transition metals were prepared by complexation with ammonium-pyrrolidine-dithiocarbamate (APDC) and filtering through a membrane filter. Analyses of water samples for halogenes was done on samples prepared by precipitation with AgNO₃ and subsequent filtration. Two techniques for seawater preparation for uranium determination are described, viz. precipitation with APDC in the presence of iron (II) as a carrier and complexation with APDC followed with adsorption on activated carbon.In all cases trace element levels at 10^?3 μg/g were measured.     

The electro-adsorption chiller: a miniaturized cooling cycle with applications to micro-electronics

A novel modular and miniature chiller is proposed that symbiotically combines adsorption and thermoelectric cooling devices. The seemingly low efficiency of each cycle individually is overcome by an amalgamation with the other. This electro-adsorption chiller incorporates solely existing technologies. It can attain large cooling densities at high efficiency, yet is free of moving parts and comprises harmless materials. The governing physical processes are primarily surface rather than bulk effects, or involve electron rather than fluid flow. This insensitivity to scale creates promising applications in cooling personal computers and other microelectronic appliances.     

Design of miniaturized RF SAW duplexer package

This paper provides a comprehensive methodology for accurate analysis and design of miniaturized radio frequency (RF) surface acoustic wave (SAW) duplexer package. Full-wave analysis based on the three dimensional (3-D) finite element method (FEM) is applied to get the package model. The die model is obtained by combining the parasitics and acoustics models. The modeling of bonding wire is also discussed. The models of package, die, and bonding wires are assembled together to get the total response. Based on this methodology, several novel ideas are proposed to significantly improve the isolation. Simulation and measurement results are compared, and excellent agreement is found. The technique developed in this paper reduces the design cycle time greatly and can be applied to various RF SAW device packages.     

Isotachophoresis in free-flow using a miniaturized device

For the first time, we report a miniaturized approach for isotachophoresis employing the technique of free-flow electrophoresis. Using a micromachined separation chamber with a volume of 200 nL, a sample mixture of fluorescein, eosin G, and acetylsalicylic acid was separated, stacked, and concentrated in less than a minute. Additionally, an isotachophoretic separation of a reaction mixture of myoglobin and fluoresceinisothiocyanate as a fluorescence label has shown the potential of this method for on-line sample preparation.     

Spot size effects in miniaturized moving-optical-wedge interferometer

In this paper we study the effect of diffraction on the performance of a miniaturized moving-optical-wedge interferometer. By using the Gaussian model, we calculate the degradation of the interferometer visibility due to diffraction effects. We use this model to optimize the detector size required to obtain maximum visibility and study its effect on resolution of Fourier transform spectrometers based on a moving-optical-wedge interferometer. A comparison between these effects in Michelson and wedge interferometers is also presented showing the advantage of the moving-optical-wedge interferometer in suppressing the diffraction effects with respect to the Michelson interferometer.