Helical thread

Figure 2.30. Domain structure of fibrinogen. The fibrinogen molecule is composed of globular end regions separated from a central domain by helical threads. The central domain has cross-links that hold all the polypeptide chains together. Fibrinopeptides A and B (FPA and FPB) are found in the central domain.

In his 1949 paper Gross also reported the presence of regularly (-oiled helical threads in elastica but this was discounted by Franchi and dc Robertis (1951) and by Gross himself in 1951. However there seems little doubt from Gross electron micrographs that elastic fibers are not homogeneous filaments and that a tendency for the material to be laid down as bundles of closely adh( rcnt fibrils is discernible. 

In [295] the following correlation was obtained for ro by using an experimental plant containing a tube of diameter of 14 mm with a helical thread on the internal surface (to prevent the slip of the foam column in the piston mode of operation) ... 

Figure 8.2. Pyrolysis block and accessory apparatus as described by Rogers et al. 30)./. Pyrolysis chamber 2. nickel plug J. carrier gas inlet 4. carrier gas outlet 5. cartridge heater wells 12) 6, helical threads cut in inner body of block 7. outer shell of block 8, cooling jacket inlet 9, cooling jacket outlet. A. carrier gas supply B. pressure regulator C, flow-control needle valve D. reference thermal conductivity E. pyrolysis chamber F, combustion tube C. active cell H. manometer 1, pressure-control needle valve J. rotameter.

Fig. 5.1 Pin features produced on polycrystalline cubic boron nitride friction stir processing tools, including (a) flats, (b) helical threads, and (c) a combination of convex scrolled shoulder and helical threaded pin...

We may consider a plane to be an element of chirality if part of a structure lies in the plane but other parts of the structure leave the plane so as to produce chirality. An example is trans-cyclooctene (28), which is chiral with respect to a plane that includes the two double-bonded carbon atoms and one of the carbon atoms adjacent to the double bond. More than one chain can pass through the double bond, as illustrated by "[8.10]-betwee-nanene" (29). Another example is the [6]paracyclophane 30, in which the plane of chirality can be defined by the three positions marked with an asterisk. In many cases we may consider the chiral element to be either an axis or a plane, and Schlogl has noted the difficulty in defining a plane of chirality. Helical (threaded) structures can also be considered chiral with... 

Braided rope is now available that resembles the finger trap even more closely than conventional rope. This rope has more than four helical threads spiraling left and right around a central core. The advantages of this rope are that it will not twist when loaded in tension, it runs more smoothly over pulleys (due to symmetry), and gripping of the core will be more uniform. 

The finite element method can model the change of physical or chemical variables, the concentration of a chemical species for example, over space and time in a device. The most powerful aspect of the method is that it can deal with devices of any shape, no matter whether this is a screw with a helical thread, a scaffold with random pores, or a coronary stent of any complicated design. 

The individual objects that compose the model are screws which simulate the molecules of the helical polymer their individual chirality is responsible for the spontaneous formation of the overall helical structure. In the model, the screws are left-handed and have a rather compact thread, that is, the pitch-to-diameter ratio of the individual screws is small In this case, left-handed screws generate a left-handed overall helical structure. If instead the thread is loose, left-handed screws may generate a right-handed superstructure (see discussion in Section 3). 

MA Dragline radial threads MASp 1 and 2 ( ) (GA) /(A) / -structure GPGGX/GPGQQ /Lspiral GGX 3j helix =2-8 Gly (38), Ala (29), SSC (70), PC (21) Low concentration disorder/PPII High concentration helical/molten globule 0-Sheet 15-30 35... 

Upon threading the oligosilane molecules into the asymmetric y-cyclodextrin cavity to form a pseudorotaxane-type aggregate,335 a bisignate Cotton effect became apparent at about 290 nm, indicating induced PSS helicity. The reason for the bisignate nature of the signal was not clear. 

Madej, T., Boguski, M. S., and Bryant, S. H. (1995). Threading analysis suggests that the obese gene product may be a helical cytokine. FEES Lett. 373, 13-18. 

The mechanism of the guest binding offers an interesting question. During the formation of a host-guest complex, does the guest thread itself into the interior of the helical cavity (pathway 1), or does the mPE oligomer wrap around... 

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