Interpretation potential mapping

The potential map obtained after the CTF correction (Fig. 8f) can be readily interpreted in terms of atomic structures while the map before the CTF correction and imposing the S5mimetry (Fig. 8e)... 

In a similar way, Voigt-Martin et al. [14] have solved the structure of [9,9 -bianthryl]-10-carbonitrile in three dimensions using 150 unique diffraction intensities, and independently verified the result with model building and image simulation techniques. As before, the potential maps are difficult to interpret, and independent validation is an important part of the structure solving procedure. 

Sn2 reactions provide an interesting example of the utility of electrostatic potential maps in rationalizing an experimental result, while challenging conventional wisdom . It is well established that a nucleophile such as bromide reacts much faster with methyl bromide than it does with ter/ -butyl bromide. The reason normally cited is that while the transition state for the Sn2 reaction with methyl bromide is uncrowded , that for the corresponding reaction with tert-hutyl bromide is sterically crowded . However, this interpretation does... 

Graphical models, in particular, electrostatic potential maps and LUMO maps have proven of considerable value, not only as a means to rationalize trends in molecular structure and stability and chemical reactivity and selectivity, but also as tools with which to carry out chemical investigations. A few examples have already been provided in Chapter 4. Those which follow have been chosen to further illustrate both interpretive and predictive aspects of graphical models. 

Today potential mapping is the only widely recognised and standardised nondestructive method for assessing the corrosion state of rebars in concrete structures. In addition to the American standard ASTM C876-91 [1], a RILEM recommendation has been published recently [2] where the extensive recent experience with potential mapping has been included. Several national guidelines (e. g. the Swiss SIA 20061996 [3]) describe the use and interpretation of half[Pg.277]

Interpretation. The presence of an above-critical amount of chloride ions at the rebars leads to depassivation and in the presence of oxygen and water to corrosion attack. From chloride profiles information on the transport of chlorides into the concrete (Chapter 6) can be obtained. In combination with results from potential mapping, the critical chloride content for the specific structure can be obtained. On chloride-contaminated structures an empirical correlation between chloride content and half-cell potential could be established, thus the chloride distribution can be roughly obtained from the potential map. 

Data are normally recorded on a plan reflecting the survey grid. The interpretation and presentation is discussed later. The potential map should... 

Data are normally recorded on a plan reflecting the survey grid. The interpretation and presentation are discussed below. The potential map should be drawn up while still on site in order to check that the date are sensible and that apparent corrosion host spots are investigated as part of the survey. 

Interpretation of results from computer models is straightforward, since the results are usually potential maps that can be related back to current density maps by using the polarization curves of the appropriate materials, or the current density maps, themselves. Faraday s Law can be applied to the current densities to determine the corrosion rates over the various surfaces. The results of this type of analysis always look good intuitively, with the potential... 

The major clinical use of ECG analysis, in all its forms, has been restricted to diagnosis alone. The efforts of many researchers, as well as that of industry, has been devoted quite successfully to the interpretation of the morphology of a single beat from a single (or multiple) lead ECG, or of a single frame of a body surface potential map. An impressive effort has also been invested in the analysis... 

Theoretical considerations and practical experience on a large number of structures (Elsener and Bohni, 1990 Elsener etal., 1996) demonstrate that the results of potential mapping need careful interpretation. It has been found that there are no absolute potential values to indicate corrosion hazard in a structure - in contrast to the interpretation given in the ASTM C876-91 that relies on a fixed potential value of -0.35 V CSE. Depending on moisture content, chloride content, temperature, carbonation of the concrete and cover thickness, different potential values indicate corrosion of the rebars in different structures (Fig. 8-18). Thus the gradient between corroding and passive areas is more important than the absolute... 

The mechanistic interpretation of the pH-rate profiles for quinone methide disappearance relied on Hartree-Fock calculations with 6-31G basis sets as well as on product studies. In Fig. 7.20, we show the potential-density maps of the protonated and neutral pyridoindole quinone methide with negative charge density colored red and positive charge density colored blue. Inspection of the methide... 

The National Institutes of Health (NIH) has characterized "[t]he general aim of metabolomics. .. to identify, measure and interpret the complex, time-related concentration, activity and flux of endogenous metabolites in cells, tissues and other biosamples such as blood, urine and saliva."3 Taken together, the three "omics" disciplines represent a systemic and powerful approach to mapping cellular networks, allowing for faster and more predictive biology in terms of risk assessment, potential therapeutic benefit, as well as diagnosis. 

In the TLC of the toxins (lower part of Figure 5), Rf values are not presented because they show small variations and are potentially misleading. However, the relative elution sequence has proven to be highly reproducible, such that the two-dimensional composition maps produced by this method can be interpreted with a high level of confidence. 

Graphical Models are introduced and illustrated in Chapter 4. Among other quantities, these include models for presentation and interpretation of electron distributions and electrostatic potentials as well as for the molecular orbitals themselves. Property maps, which typically combine the electron density (representing overall molecular size and shape) with the electrostatic potential, the local ionization potential, the spin density, or with the value of a particular molecular orbital (representing a property or a reactivity index where it can be accessed) are introduced and illustrated. 

The photo-dissociation dynamics at 193 nm was analyzed in detail and the observed rotational state distribution was obtained by using the rotation reflection principle by Schinke and Stasemler [53]. All rotational state distributions depend sensitively on the anisotropy of the dissociative potential energy surface. These are interpreted as a mapping of the bound state wave function onto the quantum number axis. The mapping is mediated by the classical excitation function determined by running classical trajectories onto the potential energy surface within the dissociative state. This so-called rotation-reflection principle... 

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