Screening phenomenon

Another factor that influences strongly the evolution of polarization reversal in fe bulk crystals is the limited minimization of the depolarization field by means of screening charges. In the case of the afm tip of R 50 nm the screening charge is limited both by the size of the tip and its non-ohmic contact with the sample surface. Such an effect is especially pronounced in the case of indirect electron beam exposure method described in this paper. The strong limitation of the screening phenomenon provides a necessary condition for the observed effect of fdb [13-15],... 

These parameters have the same signs and their values are close. From these facts, we may take it that the ligand electrostatic contributions form a great part of the B4 (exp) and, moreover, that the rare-earth ion will not be very sensitive to the electrostatic field of the farthest ions. This screening phenomenon had been seen up to that time for the B2° parameter only. 

Beeause of their aromatie character, aramids absorb UV light, which results in an oxidative color change. Substantial exposure can lead to the loss of yam tensile properties [24]. UV absorption by p-aramids is more pronounced than with w-aramids. In this case a self-screening phenomenon is observed, which makes thin stmctures more susceptible to degradation than thiek ones. Very frequently p-aramids are covered with another material in the final applieation to protect them. 

The sensitivity of the luminescence IP s in the systems employed here decreases with increasing x-ray energy more strongly than in the case of x-ray film. Therefore, this phenomenon must be compensated by using thicker lead front and back screens. The specific contrast c,p [1,3] is an appropriate parameter for a comparison between IP s and film, since it may be measured independently of the spatial resolution. Since the absorption coefficient p remains roughly constant for constant tube voltage and the same material, it suffices to measure and compare the scatter ratio k. Fig. 2 shows k as a function of the front and back screen thickness for the IP s for 400 keV and different wall thicknesses. The corresponding measured scatter ratios for x-ray films with 0,1 mm front and back screens of lead are likewise shown. The equivalent value for the front and back screen thicknesses is found from the intersection of the curves for the IP s and the film value. 

Barrier Phenomenon. In red cell filtration, the blood first comes into contact with a screen filter. This screen filter, generally a 7—10-) m filter, does not allow micro aggregate debris through. As the blood product passes through the deeper layer of the filter, the barrier phenomenon continues as the fiber density increases. As the path becomes more and more tortuous the cells are more likely to be trapped in the filter. 

Watei has an unusually high (374°C) ctitical tempeiatuie owing to its polarity. At supercritical conditions water can dissolve gases such as O2 and nonpolar organic compounds as well as salts. This phenomenon is of interest for oxidation of toxic wastewater (see Waste treatments, hazardous waste). Many of the other more commonly used supercritical fluids are Hsted in Table 1, which is useful as an initial screening for a potential supercritical solvent. The ultimate choice for a specific appHcation, however, is likely to depend on additional factors such as safety, flammabiUty, phase behavior, solubiUty, and expense. 

Cathodoluminescence (CL), i.e., the emission of light as the result of electron-beam bombardment, was first reported in the middle of the nineteenth century in experiments in evacuated glass tubes. The tubes were found to emit light when an electron beam (cathode ray) struck the glass, and subsequendy this phenomenon led to the discovery of the electron. Currendy, cathodoluminescence is widely used in cathode-ray tube-based (CRT) instruments (e.g., oscilloscopes, television and computer terminals) and in electron microscope fluorescent screens. With the developments of electron microscopy techniques (see the articles on SEM, STEM and TEM) in the last several decades, CL microscopy and spectroscopy have emerged as powerfirl tools for the microcharacterization of the electronic propenies of luminescent materials, attaining spatial resolutions on the order of 1 pm and less. Major applications of CL analysis techniques include ... 

Exact solutions to the electronic Schrodinger equation are not possible for many-electron atoms, but atomic HF calculations have been done both numerically and within the LCAO model. In approximate work, and for molecular applications, it is desirable to use basis functions that are simple in form. A polyelectron atom is quite different from a one-electron atom because of the phenomenon of shielding", for a particular electron, the other electrons partially screen the effect of the positively charged nucleus. Both Zener (1930) and Slater (1930) used very simple hydrogen-like orbitals of the form... 

It has been proposed that a combination of various molecular forces is responsible for the phenomenon of condensation [38]. Probably, electrostatic forces play the most important role in the screening of phosphate repulsion by counterions, thus helping in the collapse of... 

Unconsolidated or weakly consolidated sediments sometimes collapse around the well screen before the filter pack can be installed. This phenomenon is called formation collapse . Formation collapse can occur as a result of the inherently unstable nature of certain sediments or the disruptive nature of the drilling process. Formation collapse is most common below the water table. Although steps can be taken to minimize the amount of collapse, it may not be entirely preventable. The groundwater monitoring plan may need to accept natural formation material as the filter pack for some or all of the screen section. Well development activities (see Section 2.1.6) can be designed to maximize the effectiveness of the formation collapse materials as a filter pack. 

A comparison with Burchard s first cumulant calculations shows qualitative agreement, in particular with respect to the position of the minimum. Quantitatively, however, important differences are obvious. Both the sharpness as well as the amplitude of the phenomenon are underestimated. These deviations may originate from an overestimation of the hydrodynamic interaction between segments. Since a star of high f internally compromises a semi-dilute solution, the back-flow field of solvent molecules will be partly screened [40,117]. Thus, the effects of hydrodynamic interaction, which in general eases the renormalization effects owing to S(Q) [152], are expected to be weaker than assumed in the cumulant calculations and thus the minimum should be more pronounced than calculated. Furthermore, since for Gaussian chains the relaxation rate decreases... 

In addition, an interesting phenomenon was observed when pumping the sample gas through the sampling probe. The chamber air is pulled through the screens and filter, and through a dry test meter with a Metal Bellows pump. When pump is on, a steadily increasing number of detectable condensation nuclei is found. 

However, in contrast to XPS, electrons are promoted into bound or continuum states and still provide partial screening to the excited atom, so that these absorption energies are less sensitive to relaxation effects. Shifts in absorption energies are thus often more easily detected than those in XPS BEs. Moreover, XANES is a bulk-sensitive technique, and avoids the ambiguities associated with XPS in attributing trends to a bulk vs. surface phenomenon. 

Superconductivity provides an illustration of the Higgs mechanism. It is the property of materials that show no electrical resistance, usually at low temperatures. Such materials are capable to carry persistent currents. These currents effectively screen out magnetic flux, which is therefore zero in a superconductor (the Meisner effect). Another way of describing the Meisner effect is to say that the photons are effectively massive, as in the Higgs phenomenon. These conclusions can be shown to follow from the Lagrangian (46). In this instance it is sufficient to consider a static situation, i.e. d4 = 0, etc, leading to the Lagrangian... 

Simplified mathematical models These models typically begin with the basic conservation equations of the first principle models but make simplifying assumptions (typically related to similarity theory) to reduce the problem to the solution of (simultaneous) ordinary differential equations. In the verification process, such models must also address the relevant physical phenomenon as well as be validated for the application being considered. Such models are typically easily solved on a computer with typically less user interaction than required for the solution of PDEs. Simplified mathematical models may also be used as screening tools to identify the most important release scenarios however, other modeling approaches should be considered only if they address and have been validated for the important aspects of the scenario under consideration. 

Some models carry the surface tension approach to extreme, and attempt to include even the electrostatic contributions in the surface tensions. These pure SASA models are obviously limited in their ability to account for such phenomenon as dielectric screening, but they have the virtue of being very easy to compute. Thus, they can be used to augment molecular mechanics calculations on very large molecules with a qualitative accounting for solvation. 

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