Transducers, single-walled

AuNPs, magnetic nanoparticles, single-wall carbon nanotubes (SWNTs), and QDs have been used in immunosen-sors. According to the different types of transducers, immunosensors can be classified as electrochemical, mass-sensitive, and optical sensors. Some interesting examples are discussed herein. 

Novel technologies using CNTs coupled to ME have also explored in food analysis. Single-walled carbon nanotube press-transferred electrodes (SWPTEs) are new disposable electrodes where CNTs act as exclusive electrochemical transducer [54, 55], being... 

Akle BJ, Leo DJ (2008) Single-walled earbon nanotubes ionic polymer electroactive hybrid transducers. J Intell Mater Syst Struct 19 905-915 Akle BJ, Bennett MD, Leo DJ (2006) High-strain ionomeric-ionic hquid electroactive actuators. 

In the last 5 years, our attention has been paid to the development of novel electrochemical DNA biosensors based on carbon-based transducers as substrates for immobilization of DNA. Among others, following four electrodes exhibited the best properties for these purposes GCE (supplied by Metrohm, Herisau, Switzerland), microcrystalline natural graphite-polystyrene composite film-modified electrode (CFE), SPCE (supplied by Food Research Institute, Bratislava, Slovakia), and SPCE modified with single-walled carbon nanotubes (SWCNTs). 

In one of the representative work, Patolsky et al. [24] demonstrated the reconstitution of apo-GOx on FAD cofactor electrically contacted to the electrode via single-walled carbon nanotubes (SWCNTs), which act as conductive nanoneedles that electrically wire the enzyme redox-active site to the transducer surface (Fig. 4A). Before immobilisation, the commercially obtained SWCNTs were chemically shortened by treatment with strong acids. The formation of carboxylic (and phenolic) groups at the nanotube ends (and sidewall defect sites) as a result of acid treatment allowed the covalent immobilisation of the SWCNTs on thioethanol/ cysteamine-modified Au electrode in the presence of the coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as depicted in Fig. 4A. The incorporation of 2-thioethanol in the mixed monolayer prevented... 

Compaction simulators can be fitted with instrumented dies to measure the stress that the powder exerts on the die wall during the compaction and ejection cycle. Different types of instrumented dies have been constructed with single or multiple transducers to measure the die wall stress. The literature reports some examples of different config-urations of the pressure transducers within the instrumented die (13), as shown in Figure 7. 

Ultrasonic Flowmeters. Ultrasonic methods have been used to measure flow velocity and concentration in slurry pipelines (22) and emulsion pipelines (65). There are three methods of ultrasonic flow meter applications transmission of ultrasonic wave, beam deflection, and frequency shift method (22). The frequency shift method (the ultrasonic Doppler flowmeter) consists of a transducer and an electronic control box. The transducer is either clamped on the outside of the pipe or inserted into the pipe so that it is flush with the inside of the pipe wall. The transducer comprises the sensors to transmit and receive the Doppler signal. These sensors are either in a single transducer or in two separate transducers. The control box processes transmitted and received signals (Figure 25). 

All vessels were fitted with external wall thermocouples (3 mm, stainless steel, sheathed type K). Interior fluid temperatures, vapor and liquid, were measured on several levels at a single, near-eentral, vertieal position eorresponding to the fill-level gauge connection with similar, though 1.5-mm diameter, thermocouples. Both vapor and liquid pressures were determined from remote ealibrated pressure transducers. The target tank was mounted on a frame supported on four fire-proteeted load cells these were used to determine the variation in propane mass with PRV aetion. 

Capacitance probes (Fig. 18.18(a)) are widely used in liquid level measurements. It is possible, when the tank waUs are metal, to use a single bare or insulated metal rod as one capacitor plate and the tank walls as the other. More frequently, capacitance probes consist of a metal rod within a concentric cylinder open at the ends, which makes the transducer independent of the tank construction. An interesting appHcation of this type of capacitance probe is in aircraft fuel quantity indicators. Capacitance switches can be utilized as depicted in Fig. 18.18(b) to provide noncontact point measurements of Hquid level. 

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