Structural sampling methods

The coarse-graining approach is commonly used for thermodynamic properties whereas the systematic or random sampling methods are appropriate for static structural properties such as the radial distribution function. 

The number of sampling iterations must be sufficient to give stable results for output distributions, especially for the tails. There are no simple rules, because the necessary number of runs depends on the number of variables entered as distributions, model complexity (mathematical structure), sampling technique (random or Latin hypercube), and the percentile of interest in the output distribution. There are formal methods to establish the number of iterations (Cullen and Frey 1999) however, the simulation iterations could simply be increased to a reasonable point of convergence. 

Hard X-ray Spectroscopy. Hard X-ray spectroscopy has been applied in a wide variety of scientific disciplines (physics, chemistry, life sciences, and geology) to investigate and image geometric and electronic structures. The method is element, oxidation, state, and symmetry specific. The technique has been particularly useful in the characterization of new materials. It has also been used in the elucidation of chemical speciation in dilute samples of environmental concern. 

Similar to previous structure identification methods described for metabolites, impurities, and degradants, the knowledge of the physiological or chemical process, in this case the adhesive synthesis process, helped in the rapid interpretation of the MS/MS spectra of the unknown components. No user input about the sample composition is needed for the data-dependent analysis scheme thus, these experiments are simple and rapid to perform. The result is a fairly routine approach to structural screening of unknown mixtures during the manufacturing stage. 

The uncertainty on the redshift estimate using this method is, however, typically 0.1. With such uncertainties, friend-of-friend algorithms become inefficient. The best method to detect clusters is to use photometric redshifts to cut the galaxy samples in several redshift slices and, then, to use classical galaxy density maps in order to detect structures. This method simply increases the constrast between the structure and the field galaxies. 

Electron microscopy (5,40,52,63, 64), on the other hand, can provide direct information on the domain structure under favorable conditions, such as when the domains are crystalline. When the samples exhibit a semicrystalline superstructure, small-angle light scattering and polarized microscopy have been used in addition to electron microscopy to study the spherulitic structure. These methods are complemented by differential scanning calorimetry, and various techniques for studying dynamic mechanical behavior which can be interpreted to give additional, if somewhat less direct, information on domain structure. 

Acoustic emission can detect movement of defects in the sample due to applied load, is sensitive to the material sample, is not geometry sensitive, can be used in a plant or process without much intrusion, and is capable of testing a whole structure. The method requires that the acoustic signal be distinct from background noise. It is also useful to note that, as with... 

Perform simulation either employ MD to determine trajectories and, provided the simulation is long enough, calculate equilibrium properties, or employ molecular mechanics to probe the structure of low energy configurations and subsequently use MC sampling methods to compute equilibrium properties. 

---