Disorder, thermal

The region from the Helmholz plane into the solution, across which the potential varies exponentially attaining a value of zero at some distance in this region the ions are subjected to both ordering electrical forces and disordering thermal forces. 

Stern Combination of Parallel-Plate and Diffuse-Charge Models 9m = -9S = "[9h + J t 1 1 C Qi Qi maV=waVhaV Pole r R 1 of ,ial. linear variation V, ions are under the combined influence of the ordering electrical and the disordering thermal forces. Agrees with the experiment only for ions nonspecificaHy adsorbed on the electrode (e g. NaF). 

Koepf, E.K., Petrassi, H.M., Sudol, M., and Kelly, J.W. 1999. WW An isolated three-stranded antiparallel P-sheet domain that unfolds and refolds reversibly evidence for a structured hydrophobic cluster in urea and GdnHCl and a disordered thermal unfolded state. Protein Sci. 8 841-853. 

Notice, however, that the preceding analysis gives only an upper limit and an average, or rms value, of position errors, and further, that the errors result from the limits of accuracy in the data. There are also two important physical (as opposed to statistical) reasons for uncertainty in atom positions thermal motion and disorder. Thermal motion refers to vibration of an atom about its rest position. Disorder refers to atoms or groups of atoms that do not occupy the same position in every unit cell, in every asymmetric unit, or in every molecule within an asymmetric unit. The temperature factor Bj obtained during refinement reflects both the thermal motion and the disorder of atom j, making it difficult to sort out these two sources of uncertainty. 

In Section I, the spectra of e"(ai) consist of Dirac 5 peaks (1.79). In a real crystal these peaks are broadened by static disorder, thermal fluctuations, and excitation-relaxation processes. Discarding for the moment the static disorder, we focus our attention on broadening processes due to lattice phonons, which may be described alternatively in terms of fluctuations of the local energies of the sites, or in terms of exciton relaxation by emission and absorption of phonons. These two complementary aspects of the fluctuation-dissipation theorem64 will allow us to treat the exciton-phonon coupling in the so-called strong and weak cases. The extraordinary (polariton) 0-0 transition of the anthracene crystal will be analyzed on the basis of these theoretical considerations and the semiexperimental data of the Kramers-Kronig analysis. 

First order 19 Crystalline, angular displacement causing disorder Thermal methods, x-ray, NMR... 

This discussion has shown that the diffraction pattern can reveal three types of disorder, as discussed fully by several authors (Wiener and White, 1991a Blaurock, 1982 Hosemann and Bagchi, 1962). Thermal disorder is generally referred to as disorder of the first kind and lattice disorder as disorder of the second kind. The disorder due to the mosaic nature of the sample is referred to as orientational disorder. Thermal disorder and small amounts of orientational disorder are not particularly troublesome in the diffraction experiment. Lattice disorder, on the other hand, can be extremely problematic because one can never achieve a fully resolved image of the stmcture since there are too few stmcture factors available to obtain a faithful model. Thermal disorder simply means that the position of the atoms are .smeared in some fashion, determined by the equation of state of the molecules. If the lattice is excellent so that all of the stmcture factors observable within the limits of the... 

The periodicity of this modulation of the absorption will be dependent upon the inteiatomic distance between the absorbing and back-scat tei i ng atoms, R, and the phase shifts, 5. , encountered when the photoelect i on expeiiences the potentials at these centres. Its intensity will be governed by the number of back-scatterers, Nj and their back-scattering amplitudes, F (k). Finally the amplitude is dampened by disorder (thermal and static), a in the interatomic distance and any inelastic piocesses (related to the mean free path of the election, j)- The recognition of the stiuctural information intrinsic to this phenomenon and the derivation of a tractable formula for the estimation of interatomic distances was the result of the work of Sayers, Lytle and... 

Electronic disorder thermal excitation of electrons from the fully filled valence band to the empty conduction band, which means that electronic conduction by electrons and holes becomes possible. The thermal equilibrium is + /i with... 

Bragg s law (and therefore, the coherent elastic differential cross section) can be exploited for determining the precise crystalline structure. Obviously, neutron scattering from crystals is not restricted to the coherent elastic contribution scattering observed in between Bragg peaks is called diffuse scattering, which is generally connected to some sort of disorder (thermal. 

Figure 3.3. Molecular kinetic energy is disordered thermal movement of atoms and molecules in a system. Macroscopic kinetic energy is an ordered, simultaneous movement of a system of matter. The temperature of a system of matter is a measure of the average molecular kinetic energy of the atoms and molecules of the system.

Thermal stahility. Yor applications of LB films, temperature stability is an important parameter. Different teclmiques have been employed to study tliis property for mono- and multilayers of arachidate LB films. In general, an increase in temperature is connected witli a confonnational disorder in tire films and above 390 K tire order present in tire films seems to vanish completely [45, 46 and 45] However, a comprehensive picture for order-disorder transitions in mono- and multilayer systems cannot be given. Nevertlieless, some general properties are found in all systems [47]. Gauche confonnations mostly reside at tire ends of tire chains at room temperature, but are also present inside tire... 

Thermal stability. The tliennal stability of SAMs is, similarly to LB films, an important parameter for potential applications. It was found tliat SA films containing alkyl chains show some stability before an increase in tire number of gauche confonnations occurs, resulting in melting and irreversible changes in tire film. The disordering of tire... 

Cohen S R, Naaman R and Sagiv J 1986 Thermally induced disorder in organized organic monolayers on solid substrates J. Phys. Chem. 90 3054-6... 

Rothberg L, Higashi G S, Allara D L and Garoff S 1987 Thermal disordering of Langmuir-Blodgett-films of cadmium stearate on sapphire Chem. Phys. Lett. 133 67-72... 

The temperature factor (together with the Cartesian coordinates) is the result of the rcfincincnt procedure as specified by the REMARK 3 record. High values of the temperature factor suggest cither disorder (the corresponding atom occupied different positions in different molecules in the crystal) or thermal motion (vibration). Many visualisation programs (e.g., RasMol [134] and Chime [155]) have a special color scheme designated to show this property. 

The tetrahedral network can be considered the idealized stmcture of vitreous siUca. Disorder is present but the basic bonding scheme is still intact. An additional level of disorder occurs because the atomic arrangement can deviate from the hiUy bonded, stoichiometric form through the introduction of intrinsic (stmctural) defects and impurities. These perturbations in the stmcture have significant effects on many of the physical properties. A key concern is whether any of these defects breaks the Si—O bonds that hold the tetrahedral network together. Fracturing these links produces a less viscous stmcture which can respond more readily to thermal and mechanical changes. 

Step 11. At this point a computer program refines the atomic parameters of the atoms that were assigned labels. The atomic parameters consist of the three position parameters x,j, and for each atom. Also one or six atomic displacement parameters that describe how the atom is "smeared" (due to thermal motion or disorder) are refined for each atom. The atomic parameters are varied so that the calculated reflection intensities are made to be as nearly equal as possible to the observed intensities. During this process, estimated phase angles are obtained for all of the reflections whose intensities were measured. A new three-dimensional electron density map is calculated using these calculated phase angles and the observed intensities. There is less false detail in this map than in the first map. 

Point defects, static disorder, and thermally induced displacements lead to an increase of the background intensity between the spots. Depending on the correlation between the scatters, the background is either homogeneous (no correlation) or... 

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