Microscopy dynamic

The number of specimens and the number of features to be measured should also be considered. Statistical parameters, such as the variability and size of features and inherent errors in the analysis, must be taken into consideration. For example, in a typical latex particle size analysis, the number of particles measured must be larger for broader distributions. It is equally important to consider the number of grids and the number of different micrographs used to obtain a random sampling. 

Image processing and image analysis are similar fields that are often confused. In image analysis 

A video camera is placed below the fluorescent screen of the TEM or in the camera tube on an optical microscope. The SEM and STEM do not require a camera or a monitor. Video recordings can be made directly from the internal video signal, as long as the scan is at standard video rates. A video system permits acquisition of 

The thickness and density are often difficult to determine, and one method replaces these inputs with the resonant frequency and damping factor [204]. 

Thermal tuning [205, 206] measures the fluctuations in position due to thermal excitation. A sufficiently sensitive system can determine this displacement and the mean must correspond with an energy of V kT. If the optical lever sensitivity is known, this gives the spring constant. 

Alternatively, if the spring constant is calculated, the sensitivity can be determined using thermal tuning, so that it is not necessary to push a tip against the surface and possibly damage it [207]. 

A disadvantage of conducting experiments in the microscope is that the experiments can consume a lot of time and are thus expensive. For mechanical tests, it is rare to observe a statistically significant number of specimens also, neither stress-strain measurements nor microscopy is optimal. Nevertheless, the insight gained from direct observation of deformation and failure mechanisms outweigh these disadvantages in some cases. 

Experiments involving hydrated polymers have been monitored using variable pressure SEMs (e.g., [214]), although recent evidence has shown extensive radiation damage [215, 216] occurs during these studies (see Section 5.5.2). Because the AFM can be operated in a wide range of environments, many other dynamic experiments are possible. The effect of hydration on polymer blends and membranes [135, 217] and the effect of UV irradiation in various gaseous environments on the friction of polymer films [218] are just a few examples of the himdreds of AFM dynamic studies on polymers. 

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The in situ monitoring of high temperature reactions by hpl29Xe magnetic resonance is still in its infancy. Although the previous work on gas phase dynamics in porous media has shown the feasibility of dynamic microscopy and M RI and the first in situ combustion NMR spectra have been collected, much more development remains to be done. To date, hpl29Xe NMR and MRI are currently the only techniques available to study gas dynamics in porous and opaque systems. 

There are two types of stages for dynamic microscopy (a) hot and cold stages and (b) tensile stages [1], Hot stages are most commonly used for the dynamic microscopy of polymers [1,43]. Thermal analysis in the OM is complementary to other thermal analysis methods, such as differential thermal analysis (DTA) [1], Direct observation of the structural changes of a polymer as a function of temperature can determine the nature of phase changes and thermal decomposition [1], It also measures the transformation temperatures. 

A major appUcation of dynamic microscopy is the study of pol)nner structure and its development as a function of temperature in a hot stage. This type of work is rare in electron microscopes. Heating a polymer sample in an electron microscope requires caution, as not only will heating increase the rate of radiation damage, but also the polymer may outgas or degrade and evaporate, contaminating the microscope vacuum system and associated x-ray detectors. 

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