Sheet orientation

Wet processes involve mixing a hydrocarbon liquid or some other low-molecular -weight substance with a polyolefin resin, heating and melting the mixture, extruding the melt into a sheet, orientating the sheet either in the machine direction or biaxi-ally, and then extracting the liquid with a volatile solvent [6-8]. 

Figure 5.7 The 2H NMR spectrum of D2O adsorbed on pulp sheets oriented perpendicular to the magnetic field.

Figure 14.5 Proposed model of (a) antiparallel /8-sheet orientation within nanofibers when viewed perpendicular to the /8-sheets plane and (b) the cross section. Amino acid side chains are represented as spheres and Ala-7 and Leu-14 are marked by crosses. Reprinted from Kammerer et al. (2004). Copyright 2004 National Academy of Sciences.

Fig. 9.7 Snapshots of a re-entrant scroll wave in a 6x6x3 cm isotropic and homogeneous epicardial cuboid (left), and a wedge model of the human left ventricular free wall with similar dimensions, and fiber and sheet orientations giving orthotropy of propagation (right). Both examples use the ten Tusscher— Noble—Noble—Panfilov model [42] for excitation kinetics. In the wedge model these kinetics are spatially heterogeneous, with endocardial, mid-myocardial and epicardial tissue occupying approximately equal fractions of the transmural distance. In the cuboid, the diffusion coefficient was 0.154 mm2 ms-1 in all directions. The diffusion coefficient in the wedge was set to 0.154 mm2 ms-1 in the fiber axis direction, with a ratio of...

In addition to the deliberate monoaxial or biaxial orientation carried out to produce an oriented filament or sheet, orientation will often occur during polymer processing, whether desired or not. Thus in injection moulding, extrusion or calendering the shearing of the melt during flow will cause molecular orientation. 

Simulations of amide bands for a /1-sheet oriented parallel to the interface with different angles of incidence and use of p-polarized light are shown in Fig. 8. Comparison of measured and simulated spectra reveals that amyloid-] (Ap) is lying almost flat at the air-water interface, although a slightly tilted conformation cannot be excluded. 

The /3 sheet orientation in porin, a trimeric integral protein which forms channels across E.coli outer membranes, was determined by analyzing the amide I band and its shoulders around 1631 cm and the amide II band around 1530 cm. The results showed that the jS sheets are oriented perpendicularly to the membrane (Nabedryk et al., 1988). 

The ideal diffractometer specimen would be a small sphere cut out of the sheet, because a sphere presents the same aspect to the incident beam whatever its orientation. Normally, however, the sheet is examined directly, and then the paths of incident and diffracted beams within the sheet change with sheet orientation. It is then necessary to correct the measured intensities for these geometrical effects or to design the x-ray optics so that corrections are not required. 

Members of tbe amyloid family bave no sequence homology with each other, but fibers formed from proteins in tiiis group share a similar secondary structure. Two characteristic reflections (at 10 and 4.8 A) are produced when fibers formed from any of the amyloid proteins are analyzed by x-ray diffraction (Sunde et al, 1997). This pattern defines the cross P-pleated sheet structure in which P sheets lie parallel to the long axis of the fiber, with tbe strands of each sheet oriented perpendicular to the fiber axis (Sunde et al, 1997). Fibers formed from tbe NM region of Sup35 share tbis structure (Serio etal, 2000) thus, Sup35 can be defined as an amyloidogenic protein. 

Experimentally, the depolarization ratio may bo obtained by inserting a Polaroid sheet or other polarizer between the sample and the monochromator. Spectra are then obtained with the axis of the sheet oriented parallel with first Ihc.v and then the xy plane shown in Figure 18-5. 

Major Influences are sheet thickness, plastic viscosity, and melt index (Chapter 1), regrind (Chapter 9), sheet orientation (Chapter 1), draw ratio, forming temperature and pressure, and surface blemishes, blisters, blushing, scratch marks, and so on. A guide to troubleshooting the thermoforming process is given in Table 5-5. 

Bias ply n. A layer of reinforcing fiber, cloth, or sheet oriented at an angle, less than 90° and typically 45°, to the fiber direction in the main reinforcing layers. 

A more common structural feature is the presence of Cu02 sheets oriented in the a-b plane, which is common to all high-Tc superconducting cuprates discovered so far. The number of Cu02 sheets in unit cell corresponds to the n value in the formula for the homologous series, Bi2Sr2Ca iCu 02n+4. For the n = 1 member (Bi-2201), there is one Cu02 sheet where each Cu coordinates to... 

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