Other Experimental Approaches

Although most of the ellipsometric works are performed in reflection mode (i.e., polarization change on reflection is measured), transmission ellipsometry is also possible and sometimes used as a complementary experiment with the reflection mode experiment. In electrochemical systems, however, transmission ellipsometry is of little use for practical reasons. 

Spectra of n and k, or equivalently of the dielectric constants a and a , are obtained from the sets of ellipsometric measurements as functions of photon energy, a and a are the real and imaginary parts of the complex dielectric constants, respectively. They are related to n and k by 

Such spectra reveal the nature of the material of the surface film, and often can be used for identifying the material. Often, a k spectrum (or the a and a spectra) shows the absorption edge of the optical transition in the material which gives the electronic band structure. 

The thickness determined from the ellipsometry measurements at various wavelengths should be the same if the measurements are made of the same interfacial system. Therefore, the accuracy of the determination can be checked. Films absorbing light k O) at certain frequency ranges can be studied at another range where it is completely transparent for unambiguous determination of the thickness. This in turn can be used in optical characterization at 

In a motor-driven self-nuUing ellipsometer, the dc feedback currents are used to drive servomotors instead of being passed through the Faraday cell. As an alternative to the polarizer modulation described above, crystals with electro-optic effect (e.g., Pockels effect) can be used to modulate the relative phase retardation by an electric ac field. Independent modulations of polarizer 

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This section will cover other experimental approaches that are less frequently applied (yet are not insignificant) toward the structural elucidation of stationary-phase surfaces. This includes electron paramagnetic resonance (EPR), small angle neutron... 

It is highly recommended that microarray findings be verified using other experimental approaches. We usually confirm our results by at least one of the alternative immunoassays, such as enzyme-linked immunosorbent assay (ELISA), dot blot, Western blot, flow cytometry, or immunohistology (16,18). 

Detailed kinetic schemes have also been proposed for many other polymers and the work of Bockhom et al.6-8 is representative of this large area of the literature for schemes relating to polyamide 6, PP, PE, and other polymers. Other experimental approaches, mainly aimed at identifying Arrhenius parameters in similar schemes, are discussed by Howell,9 Lehrle et al.,10 Shyichuk,11 Wilkie,12 and Holland and Hay.1314... 

The estimate on the complexation modes provided by the above thermodynamic approach should be verified by other experimental approaches. Spectroscopic measurements are expected to give straightforward evidence for the coordination state of a metal ion in polymer ligand systems. The... 

One might use a gas-purge method, bubbling air or some inert gas through the sample and measuring the concentration in the air, Cair using procedures similar to that used to determine vapor pressures. The concentration in water, Cw would then be defined by the Henry s law constant as discussed in Section 2.3. Other experimental approaches to this problem have been outlined. ... 

We conclude that one of the important advantages of EXAFS-spectroscopy is, that it is sensitive to the occurrence of fcc-moieties in clusters, so that these are found at considerably lower N) than in other experimental approaches. 

In the context of experiments, subjecting a molecule to F typically involves the mechanical manipulation of groups within that molecule. For example, a polymer subjected to mechanochemical conditions in an AFM experiment may be attached to a surface at one end and the AFM tip at the other. In this context, the polymer corresponds to the molecule being exposed to mechanochemical conditions, and the surface and AFM tip may be thought of as external groups used to impose those conditions. To do this, the distance between the AFM tip and the surface is increased, which in turn subjects the polymer to F. Similar scenarios occur in other experimental approaches to mechanochemistry, where large structural changes in macromolecules are used to apply F to molecules attached to force probes, and the movement of polymers attached to reactive species is used to apply F in sonication experiments, for example. 

While it is clear that multiple factors may underlie ethanol-mediated apoptotic death of neurons in the developing brain, there is abundant evidence that one important causal factor is the production of oxidative stress. While the consistent correlations between the generation of ethanol-mediated oxidative stress and apoptotic death are telling, two other experimental approaches support a causal relationship. The first approach has been to establish time lines related to the onset of oxidative... 

The research chemist usually obtains IR and NMR spectra of an unknown substance even before obtaining an elemental analysis or performing solubility tests because these types of spectra are easily and quickly measured on a small amount of sample. Only after analyzing them does the researcher undertake other experimental approaches for determining the structure. This process can save many hours of unnecessary laboratory work. Other useful information about a compound may be obtained from mass spectrometry (Sec. 8.5), which provides the molar mass of the compound and, if high-resolution data are available, its elemental composition. 

New techniques in such studies— radioisotopes, litter bags, use of insecticides, and other experimental approaches—can provide a fresh insight into the ecological problems confronting biologists and agronomists alike. Such experimentation is best approached from a functional viewpoint that is, an over-all consideration of the ecosystem as a dynamic unit, and the soil fauna and soil microflora as parts of that unit... 

An important application of theoretically calculated electric field gradients at the nucleus is in the determination of nuclear quadrupole moments. The interaction between the nuclear quadrupole moments and the electric field gradient at the nucleus can be measured with unprecedented accuracy (compared to other experimental approaches for determining nudear quadrupole moments) in microwave spectroscopy. These interactions give rise to the fine structure in the rotational spectrum of the molecule. Highly accurate estimates for the electric field gradient at the nucleus can often be calculated theoretically (since this is a first-order molecular property). By combining these theoretical results with experimental observations, accurate values of the nuclear quadrupole moments can be obtained, and this approach has been used to revise previously estimated nudear quadrupole moments (see, e.g., KeUo and Sadlej 1998). 

NMR techniques are frequently used, combined with other experimental approaches, for the chracterization of phase behaviour of L.C.s. Microscopic diffusion processes in thermotropic 5CB L.C. with imbedded surfactant-stabilized water microemulsions have been studied using PFG NMR. The formation of the microemulsion is found to be crucial for the macroscopic separation of the mixture into L.C.- and surfactant-rich phases. ... 

Apart from the traditional fatigue methods, other experimental approaches have been used to reproduce fatigue conditions mechanically similar to those in clinical service of total joint replacements. As an example, we present here two of the smdies present in the UHMWPE literature. 

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