Screw opposite

As compression occurs concurrently in both halves of the compressor, radial forces are oppositely directed, resulting in negligible net-radial loads on the rotor bearings (uuhke twin screw compressors), but there are some loads on the star wheel shafts. 

Tray Classifier A hybrid like the screw-conveyor classifier, the tray classifier rakes pulp up the sloping bottom of a tank while solvent flows in the opposite direction. The solvent is forced by a baffle to the bottom of the tank at the lower end before it overflows. The sohds must be rugged enough to stand the stress of raking. 

The typical rotary screw compressor stage is made up of two rotating shafts, or screws. One is a female rotor and the other a male rotor. These two rotating components turn counter to one another (counterrotating). The two rotating elements are designed so that as they rotate opposite to one another their respective helix forms intermesh (see Figure 3-78). As with all rotary compressors, there are no valves. The gas is sucked into the inlet post and is squeezed between the male and female... 

Fig. 15 Sketch of two screws with opposite chirality fitting tightly into each other. From [70], Copyright 2002 American Chemical Society...

Optically Active Polysilanes with Diastereomeric Helidties Containing Opposite Screw Senses and Different Screw Pitches... 

This knowledge and understanding may be helpful to characterize local conformations of other optically active polysilanes in solution. For example, poly(methyl-(-)-(3-pinanylsilane) [(+)-7 Mw = 10,200] prepared by Shinohara and co-workers.281 showed a bisignate CD band at 280 and 303 nm, associated with a broad UV absorption at 300 nm in chloroform at 15°C. Since the spectroscopic features are quite similar to those of i,28d-28e it is possible that the main chain in 7 may contain diastereomeric helical motifs with opposite screw senses and different screw pitches. 

Another significant cooperativity effect in preferential helical screw sense optically active copolymers is the majority rule phenomenon.18bl8q In this case, the screw sense of a helical main chain with unequal proportions of opposite chirality enantiopure chiral side groups is controlled by the enantiomeric excess only. Since this phenomenon was first reported from poly-a-olefins made of vinyl co-monomers bearing nonenantiopure chiral moieties by Green et al.8b and Pino et al.,16b this majority rule has been established in... 

We also reported an intriguing chiral termini effect in rodlike poly(n-hexyl-(2-methylpropyl)silane) with (5)-2-me(hylbu(yl termini (15).28g Although the value of gabs is only +1 x 10-5, which indicates a very weak preferential screw sense in 15, it is noted that the preferential screw sense of 15 was opposite to that of 4, bearing the same (5)-2-me(hylbutyl side groups.28d,28f,28k... 

By contrast, in the CD spectrum of the p derivative (39), no bands were observed even at —80°C, as shown in Figure 4.19b. This is because the Cotton band of the p derivative is canceled by an oppositely signed CD band originating in an equivalent proportion of opposite screw sense helical segments (which may be referred to as masked helicity or masked circular dichro-ism ). The difference between the helical conformations of m and p derivatives may be due to the degree of steric hindrance of (S>2-methylbutoxyphenyl rings, since the p derivative may have enough space to freely rotate the... 

In contrast, the CD spectra of 50, 51, and 52 exhibit negative Cotton effects, as shown in Figure 4.36 for 50. This implies a helical conformation, but of the opposite preferential screw sense to 48 and 49, even though the enantiopure chiral moiety in all cases is the (5 )-2-methylbutyl group. Similarly, the Cotton effect is of greatest magnitude (negative) at low temperature and almost very much reduced at 80°C. 

It is possible that the helicity is a result of the chiral substitution itself and that the polymers with achiral substituents have, in fact, all-anti conformations. While this possibility cannot be directly ruled out, comparison of the spectroscopic data for the polymers with chiral substituents and achiral substituents, for example, 47 and 48, respectively, indicates similar main-chain dihedral angles, since the UV absorption maxima are so similar. Both polymers should therefore be latent helical, that is, contain segments of opposite screw sense separated by strong kinks (helix reversal points), with the difference being that in the case of 47 the overall numbers of P and M turns are equal, whereas for 48, one of the screw senses predominates, resulting in net helicity and optical activity. 

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