Sample dynamic

SFM s can be also classified according to static and dynamic operating modes. Under quasi-static conditions, the microscope measures the instantaneous response of the cantilever when it interacts with the sample. Dynamic SFM enables separation of the elastic and inelastic component in the cantilever deflection when the sample surface is exposed to a periodically varying stress field. The dynamic modes are useful for investigation of viscoelastic materials such as polymers and results in additional improvements in the signal-to-noise ratio. 

Can react with sample. Dynamic preferred over static. 

One should note that the CRAMPS technique is not necessarily a panacea for H NMR studies on surfaces, or for any other type of sample. Dynamics associated with motion and/or chemical reactions with a time constant that is comparable to the cycle time of the multiple-pulse sequence interferes with a multiple pulse averaging of H- H dipolar interactions [3b,4f]. Of course, an analogous problem can also arise with MAS, for which the critical period is i as. where v as is the MAS frequency [26]. To quench this kind of dynamic interference with the linenarrowing efficiency of any cyclic technique, like MAS and/or a multiple-pulse sequence, one would have to... 

Variations in the surface topography of a material are depicted as variations in grey level of the image. Detail as small as 70 A can be resolved on most samples. Dynamic experiments can be documented with the aid of a conventional video recorder. 

C and N NMR SS NMR experiments to distinguish between poly-morphs/solvatomorphs of Leu-enkephalin were published by Saito and coworkers [164,165]. The SS NMR spectra of various crystaUine forms of Leu-enkephalin revealed different amount of molecules and solvents in the asymmetric unit of crystal lattice and due to that the assignments of signals were ambiguous. On the basis of REDOR NMR experiment and relaxation studies, the differences in dynamics of the backbone and side chains for polymorphs have been shown. Based on that, authors also proved the less-restricted molecular motion of side residues in more hydrated sample. Dynamics of phenylalanine ring of enkephalin crystals have heen examined utihzing sohd-state NMR patterns (Fig. 2.28) and relaxation time (T ) measurements [166]. Results obtained for HsPhe-labelled samples were consistent with data from previous studies. 

The discussion of headspace methods for blood alcohol and solid-phase micro extraction (SPME) in Section 4.2 introduced the concept of creating an enriched head-space above a sample. Headspace methods may be passive or active and may involve heating the sample. Dynamic headspace (DHS) methods, used in arson analyses, exploit the equilibrium at the liquid-sample interface by sweeping tire headspace with a constant stream of gas, usually helium. DHS is also referred to as purge-and-trap (FT), allhough the latter can also mean a specific t) of sample preconcentrator used in environmental analysis. The trap material can be thermally desorbed or desorbed wifii a solvent. The thermal method is preferred, but is not always possible. The choice of trapping or sorbent materials depends on fire application arson typically requires charcoal or charcoal combinations. 

The explicit analytical expressions given by Equations (FI 6) and (F24), obtained for the synchronous and asynchronous spectrum, are well suited for the efficient machine computation of correlation intensities from discretely sampled and digitized spectral data. If a discretely sampled dynamic spectrum y(v -, t,) with the total of n points of wavenumber Vj is obtained for m times at each point of time tj, with a constant time increment, that is, t,+i - t, i = At, the integrations in Equations (FI6) and (F24) ean be replaced with summations. 

Method B tests the samples dynamically, at a constant force, deflecting the material both vertically and laterally. The fatigue test may be carried out by either procedure A, which uses 8000 cycles, or procedure B, which uses 20,000 cycles. The apparatus consists of a roller that moves back and forth over the specimen at a specified force. The final fatigue value is expressed as a total loss number. The total... 

Purge-and-trap sampling, dynamic headspace procedure, a concentration technique for volatile solutes. The sample is purged with an inert gas that entrains volatile components onto an adsorptive trap. The trap is then heated to desorb trapped components into a GC column. 

Rotating Sample Versus Stationary Sample Dynamic... 

---