Rope-like

Figure 14.6 A model of intermediate filament construction. The monomer shown in (a) pairs with an identical monomer to form a coiled-coil dimer (b). The dimers then line up to form an antiparallel tetramer (c). Within each tetramer the dimers are staggered with respect to one another, allowing it to associate with another tetramer (d). In the final 10-nm rope-like intermediate filament, tetramers are packed together in a helical array (e).

The nervous system contains an unusually diverse set of intermediate filaments (Table 8-2) with distinctive cellular distributions and developmental expression [21, 22]. Despite their molecular heterogeneity, all intermediate filaments appear as solid, rope-like fibers 8-12 nm in diameter. Neuronal intermediate filaments (NFs) can be hundreds of micrometers long and have characteristic sidearm projections, while filaments in glia or other nonneuronal cells are shorter and lack sidearms (Fig. 8-2). The existence of NFs was established long before much was known about their biochemistry or properties. As stable cytoskeletal structures, NFs were noted in early electron micrographs, and many traditional histological procedures that visualize neurons are based on a specific interaction of metal stains with NFs. 

It was also found that the presence of some metal ions and borates can effectively accelerate the hydrothermal carbonization of starch, which shortens the reaction time to some hours. Thus, iron ions and iron oxide nanoparticles were shown to effectively catalyze the hydrothermal carbonization of starch (< 200 °C) and also had a significant influence on the morphology of the formed carbon nanomaterials [10]. In the presence of Fe2+ ions, both hollow and massive carbon microspheres could be obtained. In contrast, the presence of Fe203 nanoparticles leads to very fine, rope-like carbon nanostructures, reminding one of disordered carbon nanotubes. 

In related work, Dong and coworkers reported using the hydrophobic IL [C4CiIm][PFg] mixed with MWCNs to form two types of MEs [35,36]. In one report, MWCNs were mixed with [C4CiIm][PFJ and applied to a GC electrode [35]. Environmental scanning electron microscopy (ESEM) images of the films showed homogeneously dispersed island-like particles that open up into a number of rope-like 3-D networks. They incorporated GOx into... 

Wash the resulting rope -like polymer with 50% aqueous ethanol or acetone, dry, and weigh to afford 3.16-3.56 g (80-90%) yields of polyamide, Tjinh = 0.4-1.8 (m-cresol, 0.5% cone, at 25°C), m.p. 215°C (soluble in formic acid (see Note 3). 

Morphologically diverse supramolecular assemblies have been formed from long-chain chiral aldonamides [370-378]. Typical compounds include 28 30. Formation of 200- and 300-A-diameter rods and helical rope-like structures in aqueous n-octyl- and n-dodecyl-D-gluconamide (D-28-8 and D-28-12) gpls has been recognized for some time [379]. In a subsequent work, helical double-... 

The plateau region appears when the molecular weight exceeds Mc [(Mc)soln. for solutions], and is taken to be a direct indication of chain entanglement. Indeed the presence of a plateau may be a more reliable criterion than r 0 vs M behavior, especially in solutions of moderate concentration where viscosity may exhibit quite complex concentration and molecular weight behavior. It is postulated that when M greatly exceeds Mc, a temporary network structure exists due to rope-like interlooping of the chains. Rubber-like response to rapid deformations is obtained because the strands between coupling points can adjust rapidly, while considerably more time is required for entire molecules to slip around one another s contours and allow flow or the completion of stress relaxation. 

The addition of water-soluble polymers such as polyethylene oxide (PEO) or polyvinyl alcohol (PVA) into the synthetic mixture of the C TMAX-HN03-TE0S-H20 system (n = 16 or 18 X = Br or Cl) under shear flow is found to promote uniformity and elongation of rope-like mesoporous silica. The millimeter-scaled mesoporous silica ropes are found to possess a three-level hierarchical structure. The addition of water-soluble polymer does not affect the physical properties of the silica ropes. Moreover, further hydrothermal treatment of the acid-made material under basic ammonia conditions effectively promotes reconstruction of the silica nanochannels while maintaining the rope-like morphology. As a result, a notable enhancement in both thermal and hydrothermal stability is found. 

Figure 4.5. Electron micrographs of two-directional cascades. Linear aggregates are formed with flexible alkyl bridges (4.5a) whereas, curved rope-like structures result from the incorporation of bridge structural rigidity such as an alkyne moiety (4.5b).

Figure 1 shows that the type of coke formed from acetylene in the range of about 410°- 460°C depends on the metal surface. The coke on the Incoloy 800 surface appears to be braided or rope-like filaments. In another picture, as shown in Figure 2, two types of filaments were produced—both braided and constant-diameter filaments. Both types of filaments were relatively long compared with their diameters, which were approximately 0.25 /an. Each filament was firmly attached to the metal surface and could not be removed from it easily by mechanical means. 

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