Slow rotation

Wet feed enters the feed tank which has a slow-rotating impeller to break up large particles. The level in the feed tank is maintained by a... 

The slow rotation of the drum and reciprocation of the agitator reduce maintenance requirements to a minimum but the following should be inspected periodically. The strip liner of the trunnion bearing at the valve end will normally wear at the lower half. However, in situations when the slurry has a high specific gravity, the drum has a tendency to become buoyant causing wear to the upper half. 

Thus, under the hydrodynamic conditions prevailing at high rotation rates, the one-electron product is removed more rapidly by convection than by the chemical reaction, while at slow rotation speeds the chemical reaction and further electron transfer predominates. The form of the electrode and the hydrodynamic conditions prevailing in the electrolysis solution are therefore parameters which require controlling but which give additional flexibility in the design of syntheses. 

Polymerization of Lipid 1 by UV Irradiation. The vesicle suspension prepared as described above was transfered into a quartz tube which was then flushed with nitrogen gas for about 20 minutes. After the tube was sealed with a rubber stopper, it was put on a rotator contained in a miniphotoreactor for UV irradiation for 3 minutes with slow rotation. 

Although the underlying physics and mathematics used to convert relaxation rates into molecular motions are rather complex (Lipari and Szabo, 1982), the most important parameter obtained from such analyses, the order parameter. S 2, has a simple interpretation. In approximate terms, it corresponds to the fraction of motion experienced by a bond vector that arises from slow rotation as a rigid body of roughly the size of the macromolecule. Thus, in the interior of folded proteins, S2 for Hn bonds is always close to 1.0. In very flexible loops, on the other hand, it may drop as low as 0.6 because subnanosecond motions partially randomize the bond vector before it rotates as a rigid body. 

It is worth noting that whilst we have restricted discussion in this section to conformational interconversion based on the slow rotation of bonds, the concept of the NMR timescale is equally applicable to other types of interconversion, such as can sometimes be seen in cyclic systems which may exist in two different conformational forms. 

Figure 7 Receptor-induced magnetization enhancement mechanism. The contrast agent consists of two parts the Gdm chelate and the protein-binding moiety. Within the bloodstream, the agent binds to the protein. The bound form is in equilibrium with the small amount of free form, which can be renally excreted steadily over time. The bound form has high relaxivity by virtue of its slow rotation (reproduced by permission of the American Chemical Society from Chem. Rev., 1999, 99, 2293).

This work aims at testing the suggestion of [5] that stellar rotation is faster at lower metallicity by direct measurements, especially in the LMC and SMC, on stars with —3.34 < My < —2.17, i.e. spectral types B0-B6 or masses from 6.7 to 14 M0. This work is complementary to that of [4], which deals with slightly more massive stars. The results are shown on Fig. 1 and commented in the caption. There is an excess of slow rotators in the Galaxy relative to the MCs, but the v sin i distributions of the LMC and the SMC are surprisingly similar. 

To determine the Li abundance we considered only 147 slow rotator cluster members, with membership based on radial velocity and X-ray detection. We first... 

Structural Effects of Rotation Rapid rotation in a fully convective star decreases the core temperature, but actually increases Tt,cz once a radiative core has developed. The net effect on Li depletion seems to be rather small and cannot explain the dispersion of Li abundances seen among the slow rotating ZAMS stars [24]. 

As an example, infrared spectroscopy has shown that the lowest stable hydration state for a Li-hectorite has a structure in which the lithium cation is partially keyed into the ditrigonal hole of the hectorite and has 3 water molecules coordinating the exposed part of the cation in a triangular arrangement (17), as proposed in the model of Mamy (J2.) The water molecules exhibit two kinds of motion a slow rotation of the whole hydration sphere about an axis through the triangle of the water molecules, and a faster rotation of each water molecule about its own C axis ( l8). A similar structure for adsorbed water at low water contents has been observed for Cu-hectorite, Ca-bentonite, and Ca-vermiculite (17). 

This relation shows that the rotational correlation time is uncoupled from the excited-state lifetime, in contrast to classical steady-state or time-resolved fluorescence polarization measurements (see Chapter 5). The important consequence is the possibility of observing slow rotations with fluorophores of short lifetime. This is the case for biological macromolecules labeled with fluorophores (e.g. rhodamine) whose lifetime is of a few nanoseconds. 

Nakamura and Oki (169) prepared 9-benzylthio-l,4-dimethoxytriptycene (121) and oxidized it to the corresponding sulfoxide (122) and sulfone (123). Although the barrier to rotation in 121 was low, slow rotation about the C(9)—S bond of the sulfoxide (122) was detected by H NMR at about -40°C. In contrast, the sulfone (123) showed the presence of stable rotamers, which were isolated by... 

In the nonafulvenes 60 (X = SiMe3), the rotation around the exocyclic double bond is slow below + 50°, whereas it is fast in the contact-ion pairs 60 (X = Li). This is probably due to fast equilibration via a small proportion of 61. In contrast, ordinary enolates like 62 show slow rotation about the C=C bond also at + 200°C (75). 

Boche et al. (208) have studied the temperature-dependent l3CNMR spectra of the Li-enolates of the three acylcyclopentadienes 143a to c in tetrahydrofuran-dt. While the spectrum of 143a indicated slow rotation about the 1-6 bond below... 

P. B. Garland, Phase and modulation optical spectroscopic methods for determining triplet lifetimes and slow rotational diffusion coefficients, Biochem. Soc. Trans. 15, 838-839 (1986). 

G. B. Strambini and W. C. Galley, Detection of slow rotational motions of proteins by steady-state phosphorescence anisotropy, Nature 260, 554-555 (1976). 

M. M. Timbs and N. L. Thompson, Slow rotational mobilities of antibodies and lipids associated with substrate-supported phospholipid monolayers as measured by polarized fluorescence photobleaching recovery, Biophys. J. 58, 413-428 (1990). 

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