Concentric outer rings

In the 1940 s a CVD process using a flame to produce homogeneously nucleated (powder) oxides of titanium, zirconium, iron, aluminum, and silicon was reported. A mixture of metal halide vapor and oxygen is injected through the central nozzle of a burner, with fuel gas and supplemental oxygen provided through two concentric outer rings. At 950°C to 1100 C flame temperature, the metal halide vapor decomposes to form very fine oxide powders. 

In the case of the interaction mode, an interaction probe with a concentric outer ring of illuminator and an inner portion of receptor is usually used. Some companies produce specified NIR devices. The end of the probe is in contact with the surface of the sample. Therefore only the light transmitted through the sample can be detected. The interaction mode is used to determine the Brix value of fruits or vegetables. 

It is more difficult to manufacture these electrodes than the simple disc electrode since the ring must be exactly concentric with the disc. Additionally, in many applications the insulation gap must be thin (0.25 mm or less) as must the ring. For rotating ring—disc electrodes, typical dimensions are a disc radius of 3—4 mm and an outer ring radius of 4—5 mm. For wall-jet ring—disc electrodes, these dimensions can be approximately halved. 

Type I iodothyronine deiodinase is defined as the enzyme which catalyses the (mono)deiodination of the inner or the outer ring of different iodothyronines and which is inhibited by jrM concentrations of PTU [5-8]. In rats and humans, such enzyme activities are present at high levels in liver, kidneys and interestingly also in thyroid, and at low levels in many other tissues [5-8]. The deiodinase is associated with the microsomal fractions of these tissues but is only active in the presence of a cytoplasmic cofactor [5-8], Also, in the absence of cytosol, deiodinase activity is stimulated by simple thiols such as dithiothreitol (DTT) but the physiological cofactor has not yet been identified with certainty. The effects of synthetic and natural thiols will be discussed in Section 2.5. 

Finally, there is electrolysis at the rotating ring-disk electrode. In this experiment the RDE is surrounded by a thin insulating rim and an outer-ring electrode in concentric circles. Electrode products from electrolysis at the inner disk pass by the outer ring, which is held at a different voltage, chosen to allow monitoring of a particular electrolysis product. This technique requires availability of a dual potentiostat". ... 

Walt (1998) described the principle of optical sensing using fibers. An optical fiber consists of two concentrically arranged optically transparent media an inner ring, called the core, carries the optical signal, and a thin outer ring, called the clad (made of a lower refractive index material). The refractive index mismatch at the interface of the two media acts as a mirror to help the transmission of light from one end of the fiber to the other end. The phenomena in play here is that of total internal reflection (Walt 1998). 

The dication of 5-indacene (19), however, provided a 10 7i-electron periphery free optimization gave Z>2h symmetry and bond orders and charges as shown. A quite different electronic structure has been obtained in this case from that in the dianion. Whereas the latter has a peripheral delocalized 7i-electron system, the cation appears to have a 6 n-electron system in the central ring with allyllic 2 7i-electron systems in the outer rings. Charge is largely concentrated on the end atoms of the allyl systems however, there is little interaction between the three delocalized systems <84T4455>. 

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Martinsen and Grimnes used a three-electrode concentric ring system with the outer ring split in two parts, one used as reference electrode (R) and the other as current carrying (C) electrode. In this way, the reference electrode picks up a potential closer to that of the measuring electrode, so that deeper tissue series impedance contribution is reduced. 

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