Micrographs defocus

Fig. 10.4. Effect of focused and defocused laser beam, (a) SEM micrographs of DHB single crystals after exposure to 10 laser shots (337 nm) under focused (right column) and defocused (left column) irradiation with corresponding sum spectra of horse heart cytochrome C (Mr = 12,360 u) black and white bars correspond to 10 pm (b) Resulting MALDI spectra. Reproduced from Ref. [48] by permission. Elsevier Science, 1991.

HP Erickson, A King. Measurement and compensation of defocusing and aberrations by Fourier processing of electron micrographs, Phil. Trans. Roy. Soc. Lond. B261 105-118, 1971. 

Figure 8. Bright field, defocus micrographs of solution cast films of (a) sample 1/5/4 and (b) sample 1/6/5 (underfocus for both micrographs = 2 pm)...

The defocus values for electron micrographs can be readily estimated on the basis of the CTF rings visible in the incoherently averaged Fourier transforms of individual particle images (Zhou et at., 1994, 1996). This method has become a routine practice universally adapted for the initial evaluation and determination of CTF parameters as defined in Eqs. (2) and (3). So far, the determination of the cumulative B factors for 3-D reconstruction has been somewhat ad hoc. The cumulative B factor used in these studies is determined either by trial and error with the initial value derived from previous results, or from the incoherently averaged Fourier transforms of particle images. Different approaches have been adopted to make corrections for the CTF and the function of the micrographs. They differ in the steps where these corrections are made and in whether or how the E function is corrected. 

A potentially difficult problem is ice thickness variations across a micrograph, which would result in defocus difference at different regions... 

Figure Bl.17.6. A protein complex (myosin SI decorated fdamentous actin) embedded in a vitrified ice layer. Shown is a defocus series at (a) 580 nm, (b) 1130 nm, (c) 1700 nm and (d) 2600 nm underfocus. The pictures result from averaging about 100 individual images from one electron micrograph the decorated filament length shown is 76.8 nm.

Pre-processing is a set of operations designed to transform the data into the format required for the software, to determine the defocus at which the micrograph was... 

The next degree of complexity is the single-sideband hologram, which is a defocused micrograph obtained with... 

The application of the Porod equation or of the Debye-Bueche approach are particularly attractive because they offer the possibility to evaluate the interfacial area between the phases of the blend, and they are probably the only way to quantify such feature in polymer blends and composites. In fact, when the two polymers are mixed together in a blend, traditional methods based on the adsorption of small molecules, i.e. the BET approach, are inapplicable. Image analysis of TEM micrographs can in principle be an option, but it is extremely time consuming and it suffers from a number of limitations, such as dependence on sample preparation, on projection effects, and on image defocus. The validity of SAXS for the study of interpenetrating networks has been shown for several systems. ... 

Fig. 5.20 Electron diffraction (top left) and defocus phase contrast micrographs of melt drawn polyethylene films. Optical diffraction patterns from the micrographs are at top right. As drawn film (A) is well oriented. Annealing (B) increases orientation and crystal size. Bright regions are interlamellar the crystalline regions are gray or dark if they diffract. (From Yang and Thomas [95] reproduced with permission.)...

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