Rolled-up sheet

Figure 5.3 Electron micrographs of diastereomers of A-octyl-D-aldonamide (a) helical rods from D-Glu-8 (1, bar = 50 nm), (b) rolled-up sheets from D-Man-8 (2, bar = 300 nm), and (c) twisted ribbons from D-Gal-8 (3, bar = 300 nm). Reprinted with permission from Ref. 31. Copyright 1990 by the American Chemical Society.

Fig. 12 An electronic device based on a single rolled-up sheet of carbon atoms. (From Ref. () In the figure, a CNT (red about 1 nm in diameter) bridges two closely spaced (400 nm apart) platinum electrodes (labeled source and drain) atop a silicon surface coated with an insulating silicon oxide layer. Applying an electric field to the silicon (via a gate electrode, not shown) turns on and off the fiow of current across the nanotube, by controlling the movement of charge carriers onto the nanotube. (View this art in color at www.dekker.com.)...

As we have seen in Drosophila, many developmental signals act in a graded fashion, inducing different cell fates depending on their concentration. The same phenomenon exists in vertebrates, for example, in the development of the mammalian central nervous system from the neural tube, which forms early in embryogenesis. The neural tube is a simple rolled-up sheet of cells, initially one cell thick. Cells in the ventral part will form motor neurons lateral cells will form a variety of interneurons. The different cell types can be distinguished prior to morphological differentiation by the proteins that they produce. 

S-layer tubes are formed by rolling up sheets that were assembled by the adhesion of individual protein monomers to each other. 

Programs for the preparation of self-assembling nanotubes have aimed at a variety of different structures (some inspired by nature), including helically folded linear molecules, hollow bundles of rod-like units, rolled-up sheets, helically juxtaposed truncated wedges, and stacked rings (Figure la-e, respectively). 

These compounds, which are called nanotubes, can be thought of as a rolled-up sheet of graphite capped on either end by half of a buckyball. Nanotubes have many potential applications. They can be spun into fibers that are stronger and ligher than steel, and they can also be made to carry electrical currents more efficiently than metals. The next several decades are likely to see many exciting applications of buckyballs and nanotubes. 

Current batteries are hybrid structures in which low molar mass solvents are added to increase the amorphous content and decrease the melting temperature. The batteries are constructed by rolling up sheets of electrodes with the polymer electrolyte as a separator (Figure 14.7). 

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