Spin mechanism

Melt spinning is not used for polyacrylics because they are sensitive to high temperatures. They actually begin to decompose before they reach melting temperature. Solution spinning is used instead. The dried polymer is dissolved in a polar solvent like acetone or dimethyl formamide (DMF). The spinning mechanics are otherwise the same, except the solvent is recovered as it vaporizes, immediately after the extrusion through the spinneret. Most acrylics are sold and used in the form of staple fiber. 

Polypropylene fibers. A small part of the total fibers market (and therefore at the tail end of this section on fibers) is fiber grade polypropylene. The chemistry for polypropylene fibers is the same as for thermoplastics. The spinning mechanics are the same as that for nylon. Polypropylene fibers are particularly resistant to abrasion and chemicals, and they are lightweight. However, they dont take colors very well, and the materials have low softening points and low resilience (they wrinkle). The major applications for polypropylene fibers are carpet-face fiber and backing (because its tough) and rope (because it is strong and floats in water). 

The sequence of operations is as follows Azimuth and range to the target are determined. Hie primary fuze is set and the correct amount of propint charge is loaded into the gun to deliver the round to the area above the target. Launch setback activates the safe and arm device. As the projectile continues on its ballistic path, the pre-set primary fuze initiates when the round passes into the desired delivery area. Primary fuze initiation causes an expl pusher charge to eject the three submunitions from the aft end of the round, which continues on its trajectory. After ejection, a de-spin mechanism slows the speed to allow for parachute deployment. Once de-spin occurs, the vortex ring parachute is deployed, initiating... 

These spectra, taken at variable temperatures and a small polarizing applied magnetic field, show a temperature-dependent transition for spinach ferredoxin. As the temperature is lowered, the effects of an internal magnetic field on the Mossbauer spectra become more distinct until they result at around 30 °K, in a spectrum which is characteristic of the low temperature data of the plant-type ferredoxins (Fig. 11). We attribute this transition in the spectra to spin-lattice relaxation effects. This conclusion is preferred over a spin-spin mechanism as the transition was identical for both the lyophilized and 10 mM aqueous solution samples. Thus, the variable temperature data for reduced spinach ferredoxin indicate that the electron-spin relaxation time is around 10-7 seconds at 50 °K. The temperature at which this transition in the Mossbauer spectra is half-complete is estimated to be the following spinach ferredoxin, 50 K parsley ferredoxin, 60 °K adrenodoxin, putidaredoxin, Clostridium. and Axotobacter iron-sulfur proteins, 100 °K. 

Kinetic isotope effects for C-H hydroxylation of /V,/V-dimethylaniline by cytochrome P450 enzymes indicate that a low-spin mechanism applies.292... 

Hawker Siddeley Dynamics Limited, Space Division, Final Report on De-Spin Mechanism, ESRO Contractor Report CR-30. 

Spectral spin diffusion in the solid state involves simultaneous flipflop transitions of dipolar-coupled spins with different resonance frequencies 11,39,63-76], whereas spatial spin diffusion transports spin polarization between spatially separated equivalent spins. In this review we deal only with the first case. The interaction of spins undergoing spin diffusion with the proton reservoir provides compensation for the energy imbalance (extraneous spins mechanism) [68,70,73,74]. Spin diffusion results in an exchange of magnetization between the nuclei responsible for resolved NMR signals, which can be conveniently detected by observing the relevant cross-peaks in the 2D spin-diffusion spectrum [63-65]. This technique, formally analogous to the NOESY experiment in liquids, is already well established for solids and can also be applied to the study of catalysts. 

The formation of cellulose fibrils in plant cell walls is associated with distinct aggregates of spherical structures in the plasmalemma, originally postulated by Preston before they were found. It is now uncertain whether these contain an appreciable part of the required glycosyltransferase, or are simply a kind of organising or spinning mechanisms for bringing cellulose molecules together to form fibrils. 

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