Bulk layer

Coextrusion. An increasingly popular technique to produce tailored film or sheet products is to coextmde one or more polymer types in two or more layers of melt (6). In this fashion the benefits of specific polymer types or formulations may be combined. Thus high cost barrier resins may be combined with a low cost thicker layer of standard resin to achieve an optimum barrier film at lower cost. Thin sUp-control layers may be used on the surface of a bulk layer of opticaUy clear resin to obtain an aesthetic film with good handleabUity. Lower melting outer layers may be used to provide heat sealing for polymers that seal with difficulty by themselves. 

Novotny et al. [41] used p-polarized reflection and modulated polarization infrared spectroscopy to examine the conformation of 1 -1,000 nm thick liquid polyperfluoropropy-lene oxide (PPFPO) on various solid surfaces, such as gold, silver, and silica surfaces. They found that the peak frequencies and relative intensities in the vibration spectra from thin polymer films were different from those from the bulk, suggesting that the molecular arrangement in the polymer hlms deviated from the bulk conformation. A two-layer model has been proposed where the hlms are composed of interfacial and bulk layers. The interfacial layer, with a thickness of 1-2 monolayers, has the molecular chains preferentially extended along the surface while the second layer above exhibits a normal bulk polymer conformation. 

The electrochemistry of Se adsorbate and bulk layers has been studied (and debated) by many research groups (e.g., [81, 82] see also references connected... 

By using a multichamber system [129], exchange of residual gases between successive depositions will be strongly decreased, and very sharp interfaces can be made. Furthermore, the use of a load-lock system ensures high quality of the background vacuum, and thus low levels of contaminants in the bulk layers. Multichamber reactor systems have been used for the fabrication of solar cells, and considerable improvements in energy conversion efficiency have been achieved [130, 131]. 

The chemical composition of the IF phase deviates only very slightly, if at all, from the composition of the bulk layered compound. Deviations from stoichiometry can only occur in the cap of the nanotube. In fact, even the most modem analytical techniques, like scanning probe techniques and high (spatial) resolution electron energy loss spectroscopy, are unable to resolve such a tiny deviation from the stoichiometry, like the excess or absence of a single Mo (W) or S (Se) atom in the nanotube cap. 

It is well known that all low-index clean gold surfaces exhibit reconstructions, in that the outermost layer has always a density larger than the corresponding bulk layers . The genuinely rectangular (100) and (110)... 

It should be pointed out, however, that the interpretation of these electron micrographs are still open to question. For example, many reports of chain-like structures appear in the literature however, it seems that in many cases these chains are turned up edges, which are attached to the bulk layer. Interpretation of the two-dimensional TEM images, which are... 

The only source for the tritium found below the ejecta layer (2-3 inches) in the undisturbed soil below was the missile ejecta. It is our opinion that all of the tritium profiles shown in Figures 3 and 4, including that of the crater lip, were produced by rainfall leaching. We believe the source layer for tritium was in the missile ejecta layer immediately after the detonation and that most of the tritium in the bulk layer has... 

Fig. 19.4. UVRR spectrum of a bacterial bulk layer with genotypic information due to enhanced DNA and protein signals compared with a micro-Raman spectrum of a bacterial cell for phenotypic characterization since all subcellular components DNA, protein, carbohydrates, and lipids contribute to the Raman spectrum...

Hence, in simple cases each bulk layer, each grain boundary plane, and both electrodes of the brick layer model sample, can be represented by separate RC elements (Fig. 7b). The RC elements of the n bulk layers can be combined to a single RC element with the -fold resistance and the 1 / -fold capacitance of a single layer. The n — 1 grain boundary impedances can also be summed, as can the two electrode impedances, and hence the model sample corresponds to a series connection of three RC elements (Fig. 7c) with... 

To first order, we consider the molecular structure of the surface layers to be identical to that of the bulk layers. Consequently, all the characteristics corresponding to short-range intralayer interactions (e.g. Davydov splitting, vibrational frequencies, excitonic band structure, vibronic relaxations are similar for bulk and surface layers). In fact, we shall see that even slight changes may be detected. They will be analyzed in Section III.C, devoted to surface reconstruction. Therefore, our crystal model consists of (a,b) monolayers translated in energy relative to the bulk excitation by 206, 10, and 2cm-1 for the first three layers, as indicated in Fig. 3.5. No other changes are considered in this first-order crystal model. 

To explain the observed width, it is necessary to look for strong surface-to-bulk interactions, i.e. large magnitudes of surface-exciton wave vectors. Such states, in our experimental conditions, may arise from virtual interactions with the surface polariton branch, which contains the whole branch of K vectors. We propose the following indirect mechanism for the surface-to-bulk transfer The surface exciton, K = 0, is scattered, with creation of a virtual surface phonon, to a surface polariton (K / 0). For K 0, the dipole sums for the interaction between surface and bulk layers may be very important (a few hundred reciprocal centimeters). Through this interaction the surface exciton penetrates deeply into the bulk, where the energy relaxes by the creation of bulk phonons. The probability of such a process is determined by the diagram... 

The sums run over surface wave vectors K and bulk layers V.)... 

In the particular case of the (001) plane of the anthracene crystal, we assume that the surface structure is very little different from that of a bulk layer. Indeed, the creation of two surfaces by cleavage is very easy The energy cost is very low and needs no molecular displacements of large amplitude. Thus, we adopt, for the (001) layer, the simplest assumption a 2D layer with periodicity, parallel to the plane of vectors a and b, preserved on the surface. We assume further that the molecules are rigid and that the symmetry plane (a, c) persists. Under these conditions, the surface layer has the monoclinic structure of a bulk layer, and the only parameters susceptible to modification are ... 

Since the range of the cohesive forces is much larger than the range of the repulsive forces, the surface layer will suffer, relative to bulk layers, a dilatation strain. In our model of quasi-independent (001) layers, we are interested only in intralayer quantities, which are thus amenable to the calculation of effects of the dilatation strain, to which the surface layer is assumed to respond linearly, with the elastic constatns of the bulk. Dilatation along the c axis will provide variations on our three parameters (the c distance, the monoclinic angle p, and the orientation of the surface molecules in their unit cells) as well as on the frequencies of the associated librations. 

Perhaps the most compelling evidence for the X-ray induced decomposition of bulk layers of TDF is the fact that a substantial amount of TDF-derived features remained on the surface after the same X-ray irradiated specimen was warmed to room temperature (see curves 3, Figure 7). This behavior is unlike that observed for TDF films condensed on clean Ag and not exposed to the X-ray beam until after the specimen had been heated to ca. 300 K by flowing hot N2 through the cryostat (vide infra), in which case clean Ag was obtained. 

Bulk layer spacing 1.28 A. First layer spacing expanded 25 1.0%, second and third layers contracted by 10 5. 

MgO (100) (rocksalt) (lxl) Terminated bulk structure, no change from bulk layer spacing of 2.10 A. LEED/12/... 

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