Signaling response

Fig. 3 Maximum. signal response as a function of craek tilt for a surfaee-breaking erack of width...

The field that generates these eddy currents is, by its nature, anisotropic, i e the eddy current signal response is directionally dependent on probe orientation. This can be used advantageously if one bears in mind that the corroded material one aims to detect usually displays random peaks and valleys, while man-made edges have a definite orientation. 

The operation is quite simple One sets the frequency to the lowest value, adjusts the gain and phase to the desired sensitivity using a special calibration standard discussed below and performs a zero-compensation on a defect free zone of the standard. Now one is ready to test. As one slides the probe across the surface of an aluminum structure, a signal response will be indicative of the presence of corrosion or of the presence of a subsurface edge. 

When using the gradient method described above, conventional flat-bottom hole standards can not be used. Tbe probe will see only the edges of the holes and they all have the same gradient, i.e. vertical steepness, and will give the same signal responses. 

The pulse-echo and resonance impedance techniques are capable of determining which layer contains a disbond, given an appropriate standard to compare against. Inspection standards are bond assemblies made to simulate specific areas of a part with disbonds purposefully placed in them. By comparing the signal response of a suspected void to that of a known disbond in the standard, the... 

Figure 5.1 Pesticides included in the systematic investigations on APCI-MS signal response dependence on eluent flow rate the parameter IsTow represents the distribution coefficient of the pesticide between n-octanol and water. Reprinted from J. Chromatogr, A, 937, Asperger, A., Efer, 1., Koal, T. and Engewald, W., On the signal response of various pesticides in electrospray and atmospheric pressure chemical ionization depending on the flow rate of eluent applied in liquid chromatography-mass spectrometry , 65-72, Copyright (2001), with permission from Elsevier Science.

Table 5.15 Relative signal responses from various injection volumes for the LC-MS-MS analysis of a wheat forage matrix sample. Reprinted from J. Chromatogr., A, 907, Choi, B. K., Hercules, D. M. and Gusev, A. L, Effect of liquid chromatography separation of complex matrices on liquid chromatography-tandem mass spectrometry signal suppression , 337-342, Copyright (2001), with permission from Elsevier Science...

Signal response is expressed as a percentage of that obtained from standard samples 100% is indicative of no signal suppression. 

Table 5.16 LC-MS-MS signal responses" obtained from wheat forage matrix samples using various mobile-phase additives (injection volumes of 50 p,l). From Choi, B. K., Hercules, D. M. and Gusev, A. I., LC-MS/MS signal suppression effects in the analysis of pesticides in complex environmental matrices , Fresenius J. Anal. Chem., 369, 370-377, Table 2, 2001. Springer-Verlag GmbH Co. KG. Reproduced with permission...

A cell subjected to a stress of any kind can potentially exhibit a wide range of responses. Severe stress may lead to cell death and, ultimately, to cell lysis imposition of less severe conditions may result in a metabolically perturbed system, which may either revert to its initial state or adapt in some way to the imposed conditions. Figure 10 shows a hypothetical scheme, presented by Prokop and Bajpai [12], for the signal-response cascade associated with hydrodynamic shear stress. The signal reception/transduction mechanisms are, as yet, poorly understood. While Fig. 10 can be applied to any biological system, Namdev and... 

Fig. 10. Hypothetical scheme of the signal-response cascade for hydrodynamic shear stress [12]. Redrawn with permission of Academic Press, Inc.

A nearly universal response to organic compounds, high sensitivity, long term stability, sli liclty of operation and construction, low dead volume and fast signal response, and... 

Fig. 2.9. Current transient and mass signal responses during oxidation of methanol adsorbate in pure base electrolyte (flow cell procedure). Methanol was adsorbed from a 10 2 M CD3OH + 10 4 M HC104 + 0.1 M NaC104. ad = 356 mV tad = 400 s. Potential step to 975 mV vs. Pd-H for 0.5s to produce C02 (m/e = 44) and hydrogen ions, followed by a step to —574 mV vs. Pd-H to detect HD...

As we have pointed out in Section 1.1 the mass signal response for a given reaction is proportional to the respective current (see Eq. 1.1). The result in Fig. 4.1 shows that at 0.58 V an increase in current by a factor of 7.5 is obtained. At the same time, the mass signal for C02 increases by a factor of 13 and that for HCOOCH3 by a factor of 3. This result indicates that tin affects the current efficiency for both parallel reaction pathways to a different extent. 

A voltammogram recorded after 15 min of interaction with tin is shown in Fig. 4.7a, together with the mass signal response for C02. The current signal shows... 

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