Pitch height

Helical structures also are encountered in proteins. Three conformational types characterize their secondary structure the a-structure (helix), the P-helix is a right-handed screw with 3.6 amino acids forming one turn — its pitch height is 540 pm. 

Amylose has a marked tendency to adopt a single coiled helical conformation (10.26) and this has been shown to occur in the variety known as W amylose . It contains a left-handed helix with six glucose units per turn, with pitch height 8 A, and an internal channel diameter of 5 A. Both... 

The redox-active ferrocenoyl moieties are surrounding a central H-bonded peptide core. Fcl is involved in the square helix having a right-handed twist, as observed in most p sheets, and Fc2 is involved in the twisted helix. Both helices have a pitch height of 14A. The square helix and twisted helix have an inner diameter of 3.8 A and 4.1 A, respectively. Although peptide-disulfides often exhibit unusual structural features, a supramolecular assembly as exhibited by Fc-glycylcystamine was never before observed in peptide conjugates. 

A rarer type is a helix 2.2-j (the hydrogen bond is between atoms 1 and 7 of the polypeptide chain). A right-handed hehx 3 (three units per turn, pitch height 0.6 nm), which is narrower and also steeper than an a-helix (the hydrogen bond is between atoms 1 and 10 of the polypeptide chain), sometimes occurs as an a-hehx junction with another part of the polypeptide chain. The so-cahed hehx 4.4jg (n-helix) only exists at the end of several hehces (4.4 units per turn, pitch height 0.52 nm, the hydrogen bond is between atoms 1 and 16 of the polypeptide chain). 

Hou H, Reuning A, Wendorff JH, Greiner A (2000) Tuning of the pitch height of thermotropic cellulose esters. Macromol Chem Phys 201(15) 2050-2054 Huang B, Ge JJ, Li Y, Hou H (2007) Aliphatic acid esters of (2-hydroxypropyl) cellulose—effect of side chain length on properties of cholesteric liquid crystals. Polymer 48(l) 264-269 Isogai A, Saito T, Fukuzumi H (2011) TEMPO-oxidized cellulose nanofibers. Nanoscale 3(l) 71-85... 

Tubing The 25.4-mm (I-in) outside-diameter tube is most commonly used. Fin heights vary from 12.7 to 15.9 mm (0.5 to 0.625 in), fin spacing from 3.6 to 2.3 mm (7 to II per linear inch), and tube triangular pitch from 50.8 to 63.5 mm (2.0 to 2.5 in). Ratio of extended surface to bare-tube outside surface varies from about 7 to 20. The... 

A basic stirred tank design is shown in Fig. 23-30. Height to diameter ratio is H/D = 2 to 3. Heat transfer may be provided through a jacket or internal coils. Baffles prevent movement of the mass as a whole. A draft tube enhances vertical circulation. The vapor space is about 20 percent of the total volume. A hollow shaft and impeller increase gas circulation (as in Fig. 23-31). A splasher can be attached to the shaft at the hquid surface to improve entrainment of gas. A variety of impellers is in use. The pitched propeller moves the liquid axially, the flat blade moves it radially, and inclined blades move it both axially and radially. The anchor and some other designs are suited to viscous hquids. 

Optimum depth of immersion depends on pitch-line speed. Deep immersion is permissible at low speeds because power losses from churning are low, but at moderate speeds the immersion depth should not be more than three times the tooth height. At the highest speeds, only the addenda of the teeth need be submerged (Figure 52.8). 

D Diameter of agitator Dt Diameter of tank ZA Height of agitator from base of tank H Depth of liquid R No. of baffles WB Width of baffles N Speed of agitator P Pitch of agitator... 

Fig. 20—Effects of slider attitude on the floating force and moment. (a) influence of flying height on the floating force (b) Influence of pitch angle on the pitch moment.

Contrary to commonly held opinion (e.g. [62, 63]), this comparison shows that axial-flow impellers such as pitched-blade impellers and propellers lead to particularly high stresses at the same specific impeller power. The impeller geometry, such as the impeller-to-tank diameter ratio d/D and the relative blade height h/d (see Fig. 5), also has a distinct influence. 

ESR characterization was performed in situ in order to avoid any contact of the pretreated solids with air. Spectra, recorded as the first derivative of the absorption, were obtained at room temperature or 77K using a Varian E9 spectrometer working in the X band. The g values were measured relative to a DPPH reference (g = 2.0036). The sample tubes were filled with the solid to a height greater than the depth of the resonant cavity and the number of paramagnetic species was calculated by double integration of the recorded spectra normalized to that of Varian Strong Pitch sample (g = 2.0028, 3. lO spins, cm" ). 

Fins are used to increase the effective surface area of heat-exchanger tubing. Many different types of fin have been developed, but the plain transverse fin shown in Figure 12.66 is the most commonly used type for process heat exchangers. Typical fin dimensions are pitch 2.0 to 4.0 mm, height 12 to 16 mm ratio of fin area to bare tube area 15 1 to 20 1. 

A jacketed, agitated reactor consists of a vertical cylinder 1.5 m diameter, with a hemispherical base and a flat, flanged, top. The jacket is fitted to the cylindrical section only and extends to a height of 1 m. The spacing between the jacket and vessel walls is 75 mm. The jacket is fitted with a spiral baffle. The pitch between the spirals is 200 mm. 

Recently, a low-resolution model of the chromatin core particle has been derived from a combination of single-crystal X-ray diffraction and electron microscopic data (Finch et al., 1977). The particle is described as a flat cylinder 110 A in diameter and 57 A in height. A similar shape and similar dimensions were found to be consistent with the low-angle neutron scattering from core particles in solution (Pardon et al., 1977 Suau et al., 1977). Some conclusions may be drawn concerning the conformation of the DNA. Presumably, the strong 28 A periodicity apparent in the crystal data (Finch et al., 1977) corresponds to the pitch of the DNA superhelix wound about the histone core. X-Ray and spectroscopic data suggest that the DNA super-... 

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