Rocking motion

Machinery must be positioned so that all mounts are equally loaded, and failure to do so will result in the possibility of a rocking motion developing. This may... 

Each weight causes a centrifugal force, which results in a rocking motion or rotor wobble. This condition can be simulated by placing a pencil on a table, then at one end pushing the side of the pencil with one finger. At the same time, push in the opposite direction at the other end. The pencil will tend to rotate end-over-end. This end-over-end action causes two imbalance orbits, both 180° out of-phase, resulting in a wobble motion. 

The checkers used a rocking-motion autoclave and the reduction required 48 hours to complete. 

Fluctuations in speed and direction also occur in the subcritical range (down to Re = 270) (GIO). A sphere shows a rocking motion and follows a zigzag or spiral trajectory in this range (C5, Ml, P5) with wavelength about 12[Pg.114]

Fig. 7.11 Wake configurations for drops in water (highly purified systems), reproduced from Winnikow and Chao (W8) with permission, (a) nonoscillating nitrobenzene drop = 0.280 cm, Re = 515 steady thread-like laminar wake (b) nonoscillating m-nitrotoluene drop 4 = 0.380 cm. Re = 688 steady thread accompanied by attached toroidal vortex wake (c) oscillating nitrobenzene drop 4 = 0.380 cm. Re = 686 central thread plus axisymmetric outer vortex sheet rolled inward to give inverted bottle shape of wake (d) oscillating nitrobenzene drop = 0.454 cm. Re = 775 vortex sheet in c has broken down to form vortex rings (e) oscillating nitrobenzene drop d = 0.490 cm. Re = 804 vortex rings in d now shed asymmetrically and the drop exhibits a rocking motion.

It is hard to fit such relatively free-rocking motions into a framework of normally, strongly oriented, covalent bonds.f It appears instead as though, at the distances involved in the transition state the interactions between the alkyl groups must involve a good deal of ionic character. Thus for CH8 recombination we may picture the state as ... 

Returning to our one-dimensional phase line, any oscillatory motion, such as a rocking motion in one of the potential minima, would correspond to... 

Figure 5. Restricted circumrotation of [2]catenane 7 the steric demand of the cyclohexane groups only allows a 90° rocking motion and prevents inner (gray) and outer isophtha-loyl units from exchanging (legend Figure 3) [15].

The NMR spectrum of polycrystalline [PtCl2(C2H4)]2 indicates the presence of a rocking motion perpendicular to the platinum(II)-alkene bond, and a wagging about the carbon-carbon double-bond axis.695 A similar type of motion is observed in the NMR spectrum of single crystals of Zeise s salt.696... 

The HNMR spectrum of this complex showed no inequivalence of the pyrazolyl protons between —60 and 20 °C. This was interpreted in terms of the molecule being fluxional with either (a) a rocking motion of the R3PAg moiety between the two nitrogens or (b) a complete... 

Maintaining continuous physical activity is one of the most commonly used methods in sleep-depriving animals, and often physical activity is encouraged to maintain alertness in human sleep deprivation studies. However, a distinction between rhythmic and arrhythmic activity is important because the two have very different effects on maintaining alertness and reducing the likelihood of sleep. While arrhythmic activity facilitates alertness, rhythmic physical activity, at least a gentle rocking motion, in fact induces sleep. 

It is important to note that the proportional relationship between Amax, Amid, and Amin for these couplings is the same for 100% spin density, and for the present case with approximately 50% spin density. When this is so it indicates that there is no rocking motion at the radical site. This is good evidence therefore that the radical site is essentially planar. The best evidence for radical planarity comes from the analysis of the direction cosines associated with each principal values of the hyperfine coupling tensor. The direction of Amin (Table 18-2) is known to be associated with the direction of the >C-H bond, while the direction associated with the Amid indicates the direction of the n-clcctron orbital. These directions are easily calculated from the crystal structure, and are included in Table 18-2. One sees that the direction associated with Amid deviates only 2.0° from the computed perpendicular to the ring plane, while the direction of Amin, deviates only 2.8° from the computed direction of the C6-H bond. The errors listed on these values are at the 95% confidence level. This is very clear evidence that the radical shown here is planar in the solid-state. Any torsional motion of the C6-H would lead to asymmetries of the hyperfine coupling tensor, and would not produce the observed agreement between the direction cosines and the known directions obtained from the crystal structure. 

Addition of a catalytic amount of BPK to a 14/dppm/THF solution at 288 K affords a quantitative yield of 15, in which the dppm is monodentate, within 1 min (Scheme 6). The thermal reaction of 14 with dppm in hexane affords the dppm-bridged complex, 16. The substitution of equatorial carbonyls to form pt-r -dppm products has been confirmed in a number of cases by X-ray crystallography, for example, [Co2(/a-PhC2Ph) (ja-dppm)(CO)4j (Fig. 7).60 Solution dynamics studies of [Co2( t-aIkyne) (ju.-dppm)(CO)4] complexes show that an effective mirror plane that contains the cobalt-cobalt bond and the two phosphorus atoms is generated on the NMR time scale.61 This can be interpreted as a rocking motion of the alkyne about the cobalt-cobalt bond. Complex 16 is also produced... 

NMR studies have provided evidence of a fast rocking motion between two distorted square-pyramidal conformations (Scheme 8) for the complexes Fe(MeNNNNMe)(CO)(PRj)2, and of fast CO and P(OMe)j exchange in the complexes Fe(MeNNNNMe)(CO)3 and Fe(MeNNNNMe) P(OMe)3 3, respectively (114). 

The four librations (torsional oscillations or rocking motions) arise because the crystal-field potential prevents the I2 molecule from rotating as it would in the gas phase. There are some special crystals, called plastic crystals, in which symmetric molecules that interact weakly can still undergo hindered rotation in the solid phase, but l2( ) is not one of these. The librational motions for each I2 occur about two axes (a, /3) perpendicular to the 1—1 bond direction. The librations of the two I2 molecules in the same unit cell are coupled—giving rise to SL, AL and SL, AL vibrations, where SL denotes symmetric libration (angle displacements in phase) and AL denotes antisymmetric libration (angle displacements out of phase). 

The uneven, rocking motion was quite pleasant, and with the curtains shut the bustle in the streets was less intimidating, but I felt very alone and was suddenly overwhelmed by yearning for that moment yesterday when I had stood by the tomb with Shales and talked about heaven and suffering. 

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