Residual potential

New Techniques for the Construction of Residue Potentials for Protein Folding... 

Keywords, protein folding, tertiary structure, potential energy surface, global optimization, empirical potential, residue potential, surface potential, parameter estimation, density estimation, cluster analysis, quadratic programming... 

M. Oobatake and G.M. Crippen, Residue-residue potential function for conformational analysis of proteins, J.Phys. Chem. 85 (1981), 1187-1197. 

Craig, O.E. (2003). Dairying, dairy products and milk residues potential studies in European prehistory. In Food, Culture and Identity in the Neolithic and Early Bronze Age, ed., Parker Pearson, M., British Archaeological Reports IS 1117, Archaeopress, Oxford, pp. 89-96. 

Small residual voltages are left after exposure, (residual potential)... 

The products formed during cathode polarization are unstable and almost entirely decompose within a few minutes. The products of anode polarization are considerably more stable as evidenced by the stabihty of the residual potential. The residual potential... 

In xerographic measurements, as illustrated in Fig. 5.3, the sample is corona-charged to a voltage Vq and then exposed to a short wavelength (absorption depth S L) step illumination. At the end of the illumination, there is a measurable surface potential, termed the residual potential V because of the bulk trapped charges. If positive charging is used, then is due to trapped holes in the bulk of the specimen. 

Dark discharge rate must be sufficiently low to maintain an ample amount of charge on the photoreceptor during the exposure and development steps. A high dark decay rate will limit the available contrast potential. The residual potential remaining after the xerographic cycle must be small enough that it does not impair the quality... 

In the case of a-Se, these xerographic properties have been extensively studied. In addition to the magnitude of the saturated residual voltage, the rate of decay and the temperature dependence of the cycled-up residual potential are important considerations, because they determine the time required for the photoreceptor to regain its first-cycle xerographic properties. 

Figure 5.5 Typical photoreceptor behavior through xerographic cycles showing dark decay, first-cycle residual potential V i, and cycled-up residual potential after many cycles [2].

Figure 5.9 Hole and electron drift mobility lifetime product /xt and residual potential versus Te content in a-Scj- Te films. The /xt product was xerographically measured by Abkowitz and Markovics [14].

Figure 5.10 Residual potential as a function of xerographic cycle n for a-Se Sb films (L = 50 pm).

This parameter was determined from xerographic residual potential in a-Sei- Te monolayer films. As one can see, even with very little Te alloying, there is a considerable rise in both hole and electron deep traps. The relationship between the trapping time and the residual potential has been evaluated by several authors (see, for example. Refs. [12, 15]). It can be seen that once the Te concentration exceeds 12 wt% Te, the residual potential is more than an order of magnitude larger than typical values for pure selenium. 

If blue light is used for the discharge process, then the absorption is very close to the charged surface, and one can assume that the discharge process involves the transport of photogenerated holes through the bulk. Trapping of these holes in the bulk then results in the observed first residual potential Vri. In the case of amorphous selenium photoreceptor films, it has been found that Ki is predicted by the Waiter expression [16]... 

The observed saturation may be due to the dynamic balance between trapping and release of charge carriers as the xerographic cycle is repeated. As an alternative variant, it may be due to the filling of the deep trap population so that the saturated residual potential is given by... 

Figure 5.11 Dependence of the first and firth residual potentials (for pure a-Se see Ref. [17]).

The rate of decay and the temperature dependence of the saturated voltage can be used to obtain the concentration and energy distribution of the deep traps responsible for the residual potential. Thus, provides a useful means of studying the nature of deep traps in amorphous semiconductors and has been successfully used to derive the energy distribution of deep localized states in the mobility gap of both a-Se and a-Si H [10,18],... 

One can assume that the saturated residual potential, at the end of a large number of cycles, decays. As thermal release proceeds, holes are emitted and swept out from the specimen, resulting in a decrease in the measured surface potential. The decay rate of the saturated potential is strongly temperature dependent due to thermal release from deep mobility gap centers, located approximately 0.9 eV above for holes. The discharge of the saturated potential due to electron trapping occurs much more slowly. The reason is that the energy depth of electron traps from is about 1.2 eV, which is greater than that of hole traps from E. ... 

Figure 7.5 Effect of antimony on the residual potential (measured after first and fifth cycles) of Sb-Se alloy.

The residual potential is due to trapped electrons in the bulk of the specimen. The simplest theoretical model, which is based on range limitation and weak trapping (Vj drift mobility and lifetime r product) via the Warter equation [19] ... 

As described earher [20], the saturation residual potential provides an experimental measure of the integrated number of deep traps (trap-release rates are much slower than those from shallow traps which control drift mobihty). Vk is then simply given by... 

Both the first residual and the cycled-up saturated residual potential are sensitive to alloying. For example, when pure amorphous Se films are alloyed with antimony, the buildup of the residual potential occurs more rapidly toward a much higher saturated residual potential. We obtain, for instance, Aij 2 X lO cm and Ni lO cm" for a-Se and Sbo.osSeo.gT, respectively. 

As apparent from the large xerographic residual potentials for Sbj Sei alloys, the addition of Sb to a-Se seems to greatly increase the concentration of deep locahzed states within the mobihty gap of the material. 

A more detailed model can be constructed for the nucleons in terms of a central potential that holds all the nucleons together plus a residual potential or residual interaction that lumps together all of the other nucleon-nucleon interactions. Other such important one-on-one interactions align the spins of unlike nucleons (p-n) and cause the pairing of like nucleons (p-p, n-n). The nucleons are then allowed to move independently in these potentials, that is, the Schrodinger equation is solved for the... 

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