Use Of Multiplexing Techniques Research Articles

Multiplexing techniques for measurement of the immunomodulatory effects of particulate materials: Precautions when testing micro- and nano-particles

Particulate materials at nano- and micro-scales have widespread pharmaceutical and medical applications. Understanding the interactions of these materials with biological systems is crucial for the design of clinically-viable biomaterials of high safety profiles. Immunomodulatory effects of particulate materials can be studied via multiplexing techniques that are capable of measuring up to 500 biomarkers in a few microliters of biological samples. However, there are several challenges towards the use of multiplexing techniques for testing the ability of nanomaterials to induce the release of various biomarkers. As one of the potential challenges, the adsorption of biomarkers on surfaces or within internal structures of nano- or micro-particles has been explored to a lesser extent, although it can lead to biased conclusions and data misinterpretation. Herein, we provide technical details on the use of multiplexing techniques for the evaluation of immunomodulatory effects of nanoparticulates. The same principles can also be applied for the assessment of microparticles. Importantly, precautions to avoid artifacts and data misinterpretation, due to interactions between particles and biomarkers, are provided.

The use of tunable diode laser absorption spectroscopy for atmospheric measurements

We have attempted to describe how tunable diode laser absorption spectroscopy can be applied to measurements of clean and polluted air. Pb salt diodes emit in the infrared region where most gases of atmospheric interest have their strong absorptions, providing the basis for a universal system. The high monochromaticity of these diodes have made TDLAS the most specific method available for unequivocal identification of atmospheric species, a particularly useful property for complex mixtures in polluted air or in automobile stack emissions and for serving as a comparison standard for other, less definitive methods. The combination of modulation and long-path techniques have permitted sensitivities in the parts per trillion range, required for measurements in remote, clean air or for minor, but important constituents in complex mixtures. The rapid tuning rate of these diodes, permitting real-time measurements in the fractions of second range, has been exploited in measurements from fast-flying aircraft, for eddy correlation flux measurements and for studying transients in automobile exhaust. Interesting advances are being made in the use of TDLAS systems for making real-time isotope ratio measurements. Considerable improvements have been made in the operating temperatures and tuning ranges of commercially available diodes which have permitted the use of liquid N2 cryostats or Dewars. A miniature He cryostat cooling system has also been recently developed which weighs 7 kgm and requires only 75 watts of electrical energy. Commercial systems are now available which can fit in a standard instrument rack or small aircraft, and which can be operate automatically, without attendance for long periods of time. The price of these systems have also declined significantly. The main disadvantage of the TDLAS for atmospheric measurements is the limited number of species that can be measured by the same diode. This limitation can be mitigated to some extent by the use of multiplexing techniques which permit simultaneous operation of a number of diodes. The tuning range of modern laser diodes are continuously being extended and is now sufficient in many cases to encompass strong absorption lines from 4 or 5 gases. The high specificity of TDLAS depends on the molecule possessing resolved rotational-vibronic structure. Roughly speaking, this limits the method to molecules having less than 10 atoms or those having symmetrical structures. Extension to larger, asymmetric molecules has not yet been utilized although it is possible that fast scan techniques can be used to measure larger molecules which do not have completely resolved ro-vibrational spectra. Another limitation is that the best specificity and sensitivity is achieved when measurements are made at sub-atmospheric pressure. This necessitates the use of sampling cells which can introduce surface effects for reactive and unstable molecules. The pressure broadening of some molecules, such as N20, CH4, O3, HCI, NO, HNO3 and NH3, are however, sufficiently small that measurement at atmospheric pressure is possible with open paths. Increased interest is being shown in the application of laser diodes made of group III–V compounds to gas measurements. The attractive features of these diodes are that they operate at or near room temperature, while some are relatively inexpensive and of relatively high quality and power due to their wide-spread use in communication and consumer electronic industries. They operate in the near infrared region where absorption coefficients are some two three orders of magnitude lower than those in the fundamental, mid-infrared region. But high frequency modulation techniques can be used to regain some of the sensitivity so that, at present, detection limits approach 1–10% of the sensitivity achievable from the more complex and more expensive mid-infrared systems. In addition both the optical and electronic components are more readily available, less expensive, and much smaller which permits construction of relatively inexpensive, compact instruments. For a certain limited number of species, where ultra-high sensitivity is not required the NIR systems will provide advantages of size, simplicity and cost. For a more universal and sensitive system the Pb salt, mid-infrared diode systems will continue to provide a superior and highly specific measurement system. Improvements both in quality and performance of the Pb-salt diodes and in the hardware and software to operate the system will result in continuing improvements in sensitivity, reliability and performance of these systems as well as in cost reduction.

Realizations of high-order switched-capacitor filters using multiplexing technique

A new SC design methodology using multiplexing technique is proposed to realize arbitrary high-order filters. In this methodology, the filter transfer function is transformed as the combination of biquads and their outputs are computed sequentially by the multiplexing SC biquad circuit. Four basic function SC circuits are introduced and a filter can be implemented by various combinations of these circuits. This makes the proposed method more versatile and practical. Because of the efficient use of multiplexing techniques, the realized high-order filters have less op-amps, switches, and capacitors, and thus small chip area, but at the cost of increasing clock phases. An eighth-order Butterworth low-pass filter design example is presented to demonstrate how to apply the proposed method to the design of high-order filters. Moreover, an eighth-order low-pass filter has been designed and fabricated in 1.2 /spl mu/m CMOS double-poly double-metal process. Both computer simulation and experimental results have successfully verified the function correctness and the performance of the proposed design method. >

Overview of the Data Acquisition Electronics System Design for the SLAC Linear Collider Detector (SLD)

The SLD Detector will contain five major electronics subsystems: Vertex, Drift, Liquid Argon Calorimeter, Cerenkov Ring Imaging, and Warm Iron Calorimeter. To implement the approximately 170,000 channels of electronics, extensive miniaturization and heavy use of multiplexing techniques are required. Design criteria for each subsystem, overall system architecture, and the R & D program are described.