Pinch-off zones

With injection BM the preform only has a pinch-off at the neck. In EBM the pinch-off zone performs two functions. It must weld the parison to make a closed vessel that will contain blowing air, and it must leave pinched-off waste material in a condition to be removed easily from the blown product.164... 

With the wet resin technique, the closure of the die and the consequent hydraulic pressure forces the resin through the reinforcement, pushing a front of air to, and through, the pinch-off area. When SMC or DMC are used the closure of the press compresses and heats it. Its viscosity reduces rapidly and it is able to flow to the pinch-off zone of the die. 

In the classic model of synaptic vesicle recycling in nerve terminals, synaptic vesicles fuse completely with the plasma membrane and the integrated vesicle proteins move away from the active zone to adjacent membrane regions (Fig. 9-9A). In these regions, clathrin-mediated synaptic vesicle endocytosis takes place rapidly after neurotransmitter release (within seconds) [64]. The process starts with the formation of a clathrin-coated pit that invaginates toward the interior of the cell and pinches off to form a clathrin-coated vesicle [83]. Coated vesicles are transient organelles that rapidly shed their coats in an ATP/chaperone dependent process. Once uncoated, the recycled vesicle fuses with a local EE for reconstitution as a synaptic vesicle. Subsequently, the recycled synaptic vesicle is filled with neurotransmitter and it returns to the release site ready for use. This may be the normal pathway when neurotransmitter release rates are modest. Clathrin/ EE-based pathways become essential when synaptic proteins have been incorporated into the presynaptic plasma membrane. 

Figure 10 Poincare map for two noniinearly coupled oscillators at fixed energy. The energetic periphery is labeled X. (A) The elliptic fixed point of an orbit with a),/o)2 = /i. (B, C) Elliptic fixed points of two distinct orbits with mjuiz - Vj. (D) Sep-aratrix surrounding the Wj/wj = Vi resonance zone. The separatrix pinches off at four hyperbolic fixed points, three of which are more or less clearly visible. (E) One of four elliptic fixed points of an orbit with V (the other three are not visi-...

Equation (4) corresponds to the so-called linear regime, where Vb < Vb - Vr-As Vd increases, the voltage at the drain electrode gradually decreases, up to a point where it falls to zero. This occurs at the so-called pinch off point, when Vd = Vg - Vt. Beyond pinch off, a narrow depletion zone forms next to the drain because the local potential there drops below threshold. Further increase of Vd leads to a slight extension of the depletion zone and a subsequent shift of the pinch off point towards the source. Because the potential at the pinch off point remains equal to Vg - Vr, the drain current becomes independent of the drain voltage this is the saturation regime. Here, the current is obtained by equating Vd to Vg — Vt in Eq. (4) ... 

In case C (Fig. 13-82c), increasing the boil-up ratio to 6 brings the MIPK product back within specifications, but the production rate and recovery have dropped off. In addition, the profile has switched back to the right side of the region and the temperatures on trays in the pinched zone (trays 4 through 18) are back to 93°C. Such a drastic fluctuation in tray temperature with a relatively minor adjustment of the manipulated variable (boil-up in this case) can make control diffi-... 

Case hardening only becomes obvious when wood is recut or when more material is dressed off one face than the other. When case hardened boards are ripped the two halves crook or bow and pinch the saw. The distortion is towards the saw cut because the surface zones of the board are in compression while the centre of the board is under tension. An edge groove, for tongue and grooving, will pinch too. Similarly a board that is machined more heavily on one face will bow towards that face. Kiln-dried lumber ought to be dimensionally stable, and such distortion on processing is undesirable. 

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