Spinning high speed

Fig. 3.4 Gentle run-up and balance-controlled high spin speed for laundry spinning.

The critical state of stress-induced crystallization at high spinning speeds is governed by the viscoelasticity of the polymer in combination with its crystallization behavior. Any kind of coarse particle obviously disturbs the structure and affects the resistance against deformation. The development of stress is controlled by the rheological properties of the polymer. Shimizu et al. [4] found that increasing the molecular weight drastically promotes the crystallinity under stress conditions. 

Membranes have been an active focus of NMR research for some time, using techniques appropriate to both solution and oriented samples to determine dynamics and structure. Readers are encouraged to consult several excellent recent reviews on this broad area,4,5,105 as only highlights directly related to HRMAS will be included here. While MAS has been applied for some time at modest rotation rates typical of HRMAS,7 recent applications at high spinning speeds (> 10 kHz) provided high resolution XH NMR... 

EQUATE, can be used in special solid samples, for example where /-coupling is large or other interactions are negligibly weak.203 However, with the recent developments in solid-state NMR, especially very high spinning speed and the invention of powerful decoupling techniques as described in earlier sections, the gap between solid and liquid NMR is decreasing. 

Yesinowski JP, Eckert H (1987) Hydrogen environments in calcium phosphates H MAS NMR at high spinning speeds. J Am Chem Soc 109 6274-6282... 

On the other hand, the poor anode/polymer contact shown in Fig. 6.12b can be improved to some extent by using higher spin speeds (Fig. 6.17). At high spin speeds, the polymer coils are stretched open, allowing the conducting polymer backbone to settle closer to the ITO surface. This results in a better contact and thus a lower hole-injection barrier and lower Vl on-... 

CODEX experiments can be applied at very high spinning speeds, at which undesirable dipolar spin exchange may be suppressed, so that it does not interfere with the detection of motions on the second timescale. An up to 10-fold slow-down of the l3C spin diffusion has been demonstrated by CODEX at 28 kHz for unprotonated equivalent sites in several organic solids.27... 

The pointed brackets indicate the powder average, which also contains the effect of the correlation time rc and mixing time /, . It can be shown that the dephasing is independent of the spinning speed and only depends on the total time Ntr.20 Owing to this cor independence, the CODEX pulse sequence works up to very high spinning speeds (see below). 

In order to increase the sensitivity and resolution, and to reduce the experimental time, of PISEMAMAS technique, it is essential to perform the experiment with fast spinning speeds. While the PISEMA pulse sequence has been successfully used under slow spinning conditions, unfortunately, it cannot be used at high spinning speeds as the heteronuclear dipolar couplings are suppressed. However, changing the S -spin-lock rf field strength (in SEMA) to satisfy the Hartmann-Hahn condition, B s[= " ioi with... 

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