Tubular sensors

NH4 plus alkaline ions 5 Tubular sensors SIA system Fertilizers [51]... 

Mixture of anions 5 Tubular sensors SIA Dynamic system Mineral waters [86]... 

Figure 4.13 The Gecor 6 linear polarization meter with sensor controlled guard ring for corrosion rate measurement (circular sensor A) and concrete cover resistance/resistivity head (tubular sensor B). Courtesy James Instruments USA and Geocisa SA, Spain.

An alternative approach measures the resistivity of the cover concrete by a two electrode method using the reinforcing network as one electrode and a surface probe as the other tubular sensor B in Figure 4.13 (Feliu et ai, 1988 Broomfield et aL, 1993, 1994). 

The manifold is typically a tubular steel structure (similar to a template) which is host to a series of remotely operated valves and chokes. It is common for subsea tree control systems to be mounted on the manifold and not on the individual trees. A complex manifold will generally have its own set of dedicated subsea control modules (for controlling manifold valves and monitoring flowline sensors). 

This extreme condition rarely happens but serious peak distortion and loss of resolution can still result. This is particularly so if the sensor volume is of the same order of magnitude as the peak volume. The problem can be particularly severe when open tubular columns and columns of small diameter are being used. Scott and Kucera measured the effective sensor cell volume on peak shape and their results are shown in Figure 13. 

FfCURE 13.54 Semiconductor gas sensors (o) tubular, (b) thick film, (e) bulk-type one-electrode sensor where a thin Pt wire spiral is embedded Inside a sintered oxide semiconductor button. ... 

Possible mechanisms responsible for the decreased Ca release are changes in the sensitivity of the voltage sensor in the T-tubular system or in the SR Ca channel to the sensor stimulus. A third possibility would be a decreased availability... 

For catalyst testing, conventional small tubular reactors are commonly employed today [2]. However, although the reactors are small, this is not the case for their environment. Large panels of complex fluidic handling manifolds, containment vessels, and extended analytical equipment encompass the tube reactors. Detection is often the bottleneck, since it is still performed in a serial fashion. To overcome this situation, there is the vision, ultimately, to develop PC-card-sized chip systems with integrated microfluidic, sensor, control, and reaction components [2]. The advantages are less space, reduced waste, and fewer utilities. 

D.Z. Levine and M. Iacovitti, Real time microelectrode measurement of nitric oxide in kidney tubular fluid in vivo. Sensors 3, 314 (2003). 

The temperature dependence of the fabricated open cavity FP device was evaluated experimentally. The sensor was placed in a programmable electric tubular furnace. The temperature of the furnace was increased from room temperature to 1,100°C at a step of 50°C. The cavity length as a function of the temperature is plotted in Fig. 7.11, where it increased nearly linearly following the increase of temperature. The temperature sensitivity of the particular FP device under test was estimated to be 0.074 nm °C 1 based on the linear fit of the measurement data. The equivalent coefficient of thermal expansion (CTE) of the fiber FP device was 2.4x10 6oC. ... 

Chemical and Genetic Probes—Nanotube-tipped atomic force microscopes can trace a strand of DNA and identify chemical markers that reveal DNA fine structure. A miniaturized sensor has been constructed based on coupling the electronic properties of nanotubes with the specific recognition properties of immobilized biomolecules by attaching organic molecules handles to these tubular nanostructures. In one study, the pi-electron network on the CNT is used to anchor a molecule that irreversibly adsorbs to the surface of the SWNT. The anchored molecules have a tail to which proteins, or a variety of other... 

Several classical ion-selective electrodes (some of which are commercially available) have been incorporated into continuous systems via suitable flow-cells. In fact, Lima et al. [112] used a tubular homogeneous crystal-membrane (AgjS or AgCl) sensor for the determination of sulphide and chloride in natural and waste waters. However, the search for new active materials providing higher selectivity and/or lower detection limits continues. Thus, Smyth et al [113] tested the suitability of a potentiometric sensor based on calix[4]arene compounds for use in flow injection systems. They found two neutral carriers, viz. methyl-j3-rerr-butylcalix[4]aryl acetate and... 

Some ISEs containing no inner reference solution, as well as tubular potentiometric sensors, has been used in conjunction with FI systems for the determination of vitamins B, and Bg in pharmaceutical preparations. The membranes used for this purpose were prepared from the vitamin tetra(2-chlorophenyl)borate dissolved in o-nitrophenyloctyl ether and immobilized in PVC. The intrinsic behaviour of the tubular electrodes was assessed by using a low-dispersion single-channel FI manifold and compared with those of conventionally-shaped electrodes using the same membrane the results provided by both were very similar [119]. 

In the method proposed by van Staden for the determination of three halides, these are separated in a short colunm packed with a strongly basic ion-exchange resin (Dowex i-X8) that is placed in an FI manifold. A laboratory-made tubular silver/silver halide ion-selective electrode is used as a potentiometric sensor. Van Staden compared the response capabilities of the halide-selective electrodes to a wide concentration range (20-5000 pg/mL) of individual and mixed halide solutions in the presence and absence of the ion-exchange column. By careful selection of appropriate concentrations of the potassixun nitrate carrier/eluent stream to satisfy the requirements of both the ion-exchange column and the halide-selective electrode, he succeeded in separating and determining chloride, bromide and iodide in mixed halide solutions with a detection limit of 5 /xg/mL [130]. 

In the previous papers(12,13), we reported on the vessel access type, i.e. tubular type, glucose sensor. It consisted of a glucose electrode system with a GOX enzyme immobilized Nylon membrane and a glucose semipermeable membrane, and a reference oxygen electrode system. The sensor could directly measure up to 700 mg/dl of BGL in an arterial blood stream when it was placed into an external A-V shunt. This sensor, however, has some problems such as thrombus during in vivo testing without heparin and clinical complexity associated with implanting the sensor in a blood stream. 

Manz, A., Miyahara, Y., Miura, J., Watanabe, Y., Miyagi, H., Sato, K., Design of an open-tubular column liquid chromatograph using silicon chip technology. Sensors Actuators B 1990, 1, 249-255. 

The fluid nature of PTC cocktails allows them to conform to the shape of a surface. Consequently, on evaporation of the tetrahydro-furan the PTC sensor film is left as a particular contour. This has allowed improved designs of ISEs, e.g., coated wires/epoxy, tubular flow-through, micro and all solid-state epoxy models. Thus, a lithiun sensor cast on top of a small epoxy base in a flow injection system is suitable for the assay of lithium in the saliva of manic depressive patients (Beswick,C.W., MDody,G.J., Thomas,J.D.R., diversity of Wales College of Cardiff, unpublished data). 

Flow-cell (or flow-through cell) — is a device through which fluid may be driven using an external force. Often of rectangular or tubular form for electrochemical applications, a cell may incorporate a variety of different - sensors, e.g., voltammetric [i] or potentiometric [ii], these devices can also be used in conjunction with spectroscopic analysis. Flow-through cells are also used extensively in synthetic and technical applications - Swiss-role cell. 

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