Dependence on probe

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. 

Zisman s plot cos 6 varies linearly with yi,. Zzisman = Predicts critical surface tension linearity does not hold universally y depends on probe liquids. [73-76]... 

Many probes are available Dependent on probe concentration... 

STM was the first of a class of techniqnes known as scanning probe microscopy. Atomic force microscopy (AFM), invented later in the 1980s, is currently the most widely used of these techniques. Both STM and AFM depend on probes with atomically sharp tips these probes are manenvred over the snrface of the sample to be imaged, maintaining atom-scale distances between the probe and sample. Both techniques are capable of picking np atoms individnally and placing them precisely on surfaces (7). 

Equation (3) has several other important implications which can be directly confirmed by finite-frequency probes. One example is the motion-narrowing effect in NMR experiments which is expected to disappear when l/r is below the chemical-shift-anisotropy (CSA) width. Indeed the NMR results of Tycko et al. [16] indicate that for a CSA width of 18.2 kHz the line broadens below 190 K and develops a powder pattern at lower temperature. This is in fair agreement with the 200 K calculated from Eq. (3). They also concluded that the thermal activation energy is around 260 meV below TV, again close to the values we calculated. The glassy dynamics can be probed by other experiments such as sound attenuation, microwave absorption, and thermal conductivity. In particular the characteristic temperature will depend on probe frequency. Such studies are essential to fully understand the low-temperature orientational dynamics. 

In Situ STM Hopping Current Dependence on Probe Length and Bias Voltage... 

It is natural to eliminate the influence of these factors, depending on probe parameters, and introduce apparent conductivity which in a uniform medium coincides with its conductivity when parameter Ljh is sufficiently small. In fact this approach has been used widely in several chapters of this monograph. In particular, in accord with eq. 7.53 we have ... 

EIT resonance both the linear and nonlinear refractive indices have very sharp slopes but with opposite signs. Figure 4 shows the derivatives of the linear and nonlinear refractive indices as a function of the probe frequency detuning [16], At small probe frequency detuing, the linear dispersion is normal and positive while the nonlinear dispersion is anomalous and negative. This sensitive dependence on probe frequency detuning can be used to obtain the desired dispersion... 

Direct approaches depend on probes of various types that either accumulate in tissues by binding directly to the DNA, to the RNA message, to the gene product itself (e.g., when that product is a receptor), or are trapped intraceUularly as they are modified by the gene product (e.g., when that product is an enzyme). 

A common approach for imaging near-fields relies on scanning near-field microscopy [SNOM) [51, 52], which offers a lateral resolution, down to tens of nanometers (20-100 nm). However, the measurement involves the insertion of a probe in the immediate vicinity of the object under study, to locally either detect or excite an evanescent field. The presence of the probe generally perturbs the physics of the sample to be characterized and the effective object becomes a complex probe-sample nanosystem, whose physics strongly depends on probe features such as geometry, material, etc. Additionally, producing high quality SNOM probes in a... 

The spectral alterations noted upon addition of vesicant agents to a labelled formulation are caused by changes in (1) motion of the probe, (2) the polarity of the environment of the probe, (3) alteration in fluidity, and/or (4) the permeability profile. If the vesicant agent induces changes that involve radical interactions, the magnitude of the spectral alteration that depends on probe concentration will disappear. 

In conclusion, s(c) almost always follows the stretched-exponential form of Eq. 2.6. When there are measurements on enough members of a homologous series of polymers, a and v can show clear dependences on probe and matrix molecular weights. It appears that the dominant variable determining a is the polymer s extent, not the polymer s molecular weight, so that transferring a polymer from a good to a Theta solvent substantially reduces a. 

Eor another example at the liquid/liquid interface. Steel and Walker used two different solvatochromic probe molecules, para-nitrophenol (PNP) and 2,6-dimethyl-para-nitrophenol (dmPNP), to study the polarity of the water-cyclohexane interface. These probes give spectral shifts as a function of bulk solvent polarity that are very similar because both solutes are mainly sensitive to the nonspecific solvent dipolar interactions. However, when these two dye molecules are adsorbed at the water/cyclohexane interface, they experience quite different polarities. The more polar solute (PNP) has a maximum SHG peak that is close to that of bulk water, and thus it reports a high-polarity environment. In contrast, the less polar solute (dmPNP) reports a much lower interface polarity, having a maximum SHG peak close to that of bulk cyclohexane. Clearly, the more polar solute is adsorbed on the water side of the interface, keeping most of its hydration shell, and thus reports a higher polarity than does the nonpolar solute. Other examples of the surface polarity dependence on probe molecules are discussed in Ref. 363. 

Dependence on probe location and orientation. Prom our discussion of the neat interface we now know that this region is very narrow, and the SHG peak spectrum will likely depend strongly on the solute location and orientation. This was proved by Steel and Walker who designed a series of surfactant solvatochromic probes they call molecular rulers.Each of these surfactant molecules consists of an anionic hydrophilic sulphate group (which is restricted to the aqueous phase), attached to a hydrophobic solvatochromic probe moiety by a variable length alkyl spacer. The probe is based on para-nitroanisole (PNA), whose bulk solution excitation maximum shifts monotonically with solvent polarity. When these surfactant molecules adsorb at the interface, the anionic end is in the aqueous phase, and the probe moiety resides at variable positions relative to the interface. 

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