Coiling bridge

Figure 31.14 Coiling bridge. (Photos oourtesy of Bridges" Jul.-Aug. 2005).

A common known method to get eddy-current informations about material flaws is the measurement of real- and imaginary part of the complex impedance of a coil in absolute circuit. The measurement, shown in this paper, are done with an impedance analyzer (HP4192A). The device measures the serial inductance L, and the serial resistance Rs of the complex impedance with an auto-balance bridge measurement circuit [5]. 

Let us consider a conductive material with the conductivity a, in which have been machined relatively small discontinuities shaped like dead hole. The surface has been inspected with a transducer with orthogonal coils connected in an impedance bridge [11]. 

Equation (8.97) shows that the second virial coefficient is a measure of the excluded volume of the solute according to the model we have considered. From the assumption that solute molecules come into surface contact in defining the excluded volume, it is apparent that this concept is easier to apply to, say, compact protein molecules in which hydrogen bonding and disulfide bridges maintain the tertiary structure (see Sec. 1.4) than to random coils. We shall return to the latter presently, but for now let us consider the application of Eq. (8.97) to a globular protein. This is the objective of the following example. 

Reducing the residual ripple from single-phase rectifiers for currents up to about 20 A and voltages of up to about 20 V can be achieved by filter circuits of choke coils and condensers. For greater output and constant residual ripple independent of load, the only possibility is the three-phase bridge circuit. It is always more satisfactory than a filter circuit. 

Formation of helical-like peptides stabilized due to heterocyclic bridges formed between coils by natural and artificial amino acids 99T11711. 

The sensor usually consists of a coil of wire made from the material that is wound on a former and the whole sealed to prevent oxidization, although a film of the metal deposited on a ceramic substrate can also be used. The resistor is connected in a Wheatstone bridge network (Figure 17.17), using fixed resistors in the other three arms. The instrument connected across the bridge is calibrated directly in terms of temperature. The range is limited by the linearity of the device and the upper temperature, which can be measured, must be well below the melting point of the material. 

To answer the question whether the ds-transisomerization of the bridged polypeptides with a Ala-Gly-Pro sequence represents the rate-determining step, the following experiment was carried out The polypeptide with a chain length n = 8 was denaturated in a rapid reaction with a temperature jump from 9.2 to 30 °C and subjected to renatura-tion at 9.2 °C after an incubation time of 25 s. In a second and a third experiment, the incubation in the coiled state was prolonged respectively to 75 and 125 s. It could be observed that the amplitude of the rapid phase depends on the time that lapses between the denaturation and renaturation (Fig. 32). 

In 1% aqueous acetic acid, the peptides of the sequence (Ala-Gly-Pro)n, bridged with Lys-Lys and beginning with n = 8 show a cooperative transition, which was interpreted as a triple helix-coil transition (see Figs. 35, 36). 

The CD spectra of nine proteins in 6 M Gdm-HCl were studied by Cortijo etal. (1973). Those proteins with disulfide bridges were reduced and carboxymethylated. The spectra of individual proteins were not reported, but the range of values at wavelengths from 240 to 210 nm was given. The [0]222 values ranged from —800 to —2400 deg cm2/dmol. From this substantial variation, Cortijo etal. (1973) concluded that the proteins studied are not true random coils in 6 M Gdm-HCl, because random coils should have CD spectra essentially independent of amino acid composition and sequence. The observed variation was attributed to differences in the conformational distribution between allowed regions of the Ramachandran map or to residual interactions between different parts of the chain that are resistant to Gdm-HCl denaturation. 

Turn on the cooling water (to magnet coils, magnet power supply, microwave bridge). 

During the reaction of the hot catalyst surface with a flammable gas the temperature of the device increases. The Platinum coil itself serves at the same time as a resistance thermometer. The resistance increase of the coil then is a direct measure for the amount of combusted gas. Usually the amount of heat that develops during combustion is small and amounts to 800 kj/mol for methane, for example [8], Therefore the sensor is connected in a bridge circuit to a second resistor which shows the same setup as the pellistor but is catalytically inactive. The bridge voltage is then controlled by the temperature difference of the two sensors (see Fig. 5.34). 

The platinum resistance may have the form of a coil supported on a crossed mica web or of a bird-cage element, or of a bifilar wire wound on a ceramic bobbin or of a film deposited on a small ceramic substrate. The resistance can be measured using a bridge (Wheatstone bridge) or a four-wire ohmmeter (Hewlett Packard 1997). For curve fitting of the data the following equation is frequently used ... 

Fig. 10.6. Proteolytic site of the yeast fi subunit. The protein backbone is drawn as a white coil with the active-site residues Thrl, Aspl7, Lys33, Seri 29, Aspl66 and Seri 69 shown in ball-and-stick mode. Owing to the salt-bridge with Aspl 7, the amino group of Lys33 should be positively charged and thus be...

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