Disordered interfaces, functional

An alternative route to understanding the complications of disordered interfaces is to achieve functional control of intrinsically disordered materials interfaces as well. Such enhanced control can, for example, be achieved by construction of molecular sensitizers capable of binding in a functionally equivalent manner even to disordered nanostructured substrates. An important step in this direction is to find molecular sensitizers that can form interfaces with nanostructured substrates that display consistent interfacial electronic contacting capabilities, enabling systematic investigations of the distance dependence of surface electron transfer processes. 

Patterns of ordered molecular islands surrounded by disordered molecules are common in Langmuir layers, where even in zero surface pressure molecules self-organize at the air—water interface. The difference between the two systems is that in SAMs of trichlorosilanes the island is comprised of polymerized surfactants, and therefore the mobihty of individual molecules is restricted. This lack of mobihty is probably the principal reason why SAMs of alkyltrichlorosilanes are less ordered than, for example, fatty acids on AgO, or thiols on gold. The coupling of polymerization and surface anchoring is a primary source of the reproducibihty problems. Small differences in water content and in surface Si—OH group concentration may result in a significant difference in monolayer quahty. Alkyl silanes remain, however, ideal materials for surface modification and functionalization apphcations, eg, as adhesion promoters (166—168) and boundary lubricants (169—171). 

In Figure 7 a comparison is made of the frequency of the CHj antisymmetric stretching vibration as a function of molecular area for DPPC monolayer films at the A/W and A/Ge interfaces. As described above, the frequency of (his vibration is related to the overall macromolecular conformation of the lipid hydrocarbon chains. For the condensed phase monolayer (-40-45 A2 molecule 1), the measured frequency of the transferred monolayer film is virtually the same as that of the in-situ monolayer at the same molecular area, indicating a highly ordered acyl chain, predominately all-trans in character. For LE films as well as films transferred in the LE-LC phase transition region, however, the measured frequency appears independent (within experimental uncertainty) of the surface pressure, or molecular area, at which the film was transferred. The hydrocarbon chains of these films are more disordered than those of the condensed phase transferred films. However, no such easy comparison can be made to the in-situ monolayers at comparable molecular areas. For the LE monolayers (> ca. 70 A2 molecule 1), the transferred monolayers are more ordered than the in-situ film. In the LE-LC phase transition region ( 55-70 A2 molecule 1), the opposite behavior occurs. 

The most welcome technical achievements in life science are the ones that enhance well-being or restore impaired or lost biological functions. Rehabilitation engineering is a research field that has devoted its full spectrum of efforts to compensate for malfunctions and disorders in human biological systems. This includes the development of devices for the rehabilitation of neural disorders which are termed neural prostheses. Neural prostheses directly interface with the central and peripheral nervous system. The most commonly known neural prosthesis is the cardiac pacemaker, which has existed for more than 30 years. A variety of other lesser known devices have been developed to partially restore neural functions in disabled people. 

Fig. 13. Plot of the amplitude (envelope) function B(Z) vs Z, for a planar interface between coexisting disordered (Z— >o) and lamellar (Z—>-< >) phases of block copolymer melts in the bulk. The midpoint of the profile (Z,B)=(0,1/2) is denoted by an open circle, while the inflection point (solid circle) is at [—(1/2) ln(3/2), 1/V3]. From Fredrickson and Binder [234]...

In addition to the striatum, the bed nucleus of the stria terminalis and interface islands (apparent homolog to the islands of Calleja in rodents) within the ventral striatum show intense Di mRNA expression levels in the human brain (Hurd et al., 2001 Fig. 7). These regions are implicated in limbic function and thus have important relevance for the impaired Di transmission in psychiatric disorders. The Di mRNA is normally not detected in the thalamus, hypothalamus, hippocampus, pallidum, cerebellum, substantia nigra, pons, raphe and other brainstem nuclei of the normal human brain. 

A New Model. The results of the studies on anodic oxide films (see section 5.9 and chapter 3 on passive film and anodic oxides) show that anodic oxide properties (oxidation state, degree of hydration, 0/Si ratio, degree of crystallinity, electronic and ionic conductivities, and etch rate) are a function of the formation field (the applied potential). Also, they vary from the surface to the oxide/silicon interface, which means that they change with time as the layer of oxide near the oxide/silicon interface moves to the surface during the formation and dissolution process. The oxide near the silicon/oxide interface is more disordered in composition and structure than that in the bulk of the oxide film. Also, the degree of disorder depends on the formation field which is a function of thickness and potential. The range of disorder in the oxide stmcture is thus responsible for the variation in the etch rate of the oxide formed at different times during a period of the oscillation. The etch rate of silicon oxides is very sensitive to the stmcture and composition (see Chapter 4). 

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