Imaging direct

K Cgq multilayers, direct imaging with scanning tunneling microscopy Science 253 429-33... 

Blodgett films direct imaging by scanning tunneling microscopy and high-resolution transmission electron... 

Figure C2.17.1. Transmission electron micrograph of a Ti02 (anatase) nanocrystal. The mottled and unstmctured background is an amorjihous carbon support film. The nanocrystal is centred in die middle of die image. This microscopy allows for die direct imaging of die crystal stmcture, as well as the overall nanocrystal shape. This titania nanocrystal was syndiesized using die nonhydrolytic niediod outlined in [79].

One technique that does probe the foam stmcture directly is cryomicroscopy. The foam is rapidly frozen, and the soHd stmcture is cut open and imaged with an optical or electron microscope (14). Such methods are widely appHcable and provide a direct image of the foam stmcture however, they destroy the sample and may also perturb the foam stmcture in an uncontroUed manner during the freezing. 

Other methods attempt to probe the stmcture of the foam indirectly, without directly imaging it. Eor example, since the Hquid portion of the foam typically contains electrolytes, it conducts electrical current, and much work has been done on relating the electrical conductivity of a foam to its Hquid content, both experimentally (15) and theoretically (16). The value of the conductivity depends in a very complex fashion on not only the Hquid content and its distribution between films and borders, but the geometrical stmcture of the bubble packing arrangement. Thus electrical measurements offer only a rather cmde probe of the gas Hquid ratio, a quantity that can be accurately estimated from the foam s mass density. 

Today dynamic SIMS is a standard technique for measurement of trace elements in semiconductors, high performance materials, coatings, and minerals. The main advantages of the method are excellent sensitivity (detection limit below 1 pmol mol ) for all elements, the isotopic sensitivity, the inherent possibility of measuring depth profiles, and the capability of fast direct imaging and 3D species distribution. 

Fig. 3.19. Basic set-up of a direct imaging magnetic sector instrument. The stigmatic secondary ion optics consists of an electrostatic analyzer (ESA) and a magnet sector field.

The direct imaging magnetic sector mass analyzer (Fig. 3.19) has the unique property that all parts (lenses, electrostatic analyzer and magnetic sector field) of the secondary ion optics are stigmatic (comparable with light microscopes). This means that all points of the surface are simultaneously projected into the analyzer. 

For measurement of local ion intensities in the direct imaging mode (see Fig. 3.19), amplification ensuring laterally uniform-single ion detection is necessary. Depending on the sensitivity of the detector a single or double channel plate is used. Two imaging devices are in use ... 

Economy, J., Daley, M., Hippo, E. J. and Tandon, D., Elucidating the pore structure of activated carbon fibers through direct imaging using scanning tunneling microscopy (STM), Carbon, 1995, 33(3), 344 345... 

Meanwhile orbitals cannot be observed either directly, indirectly since they have no physical reality contrary to the recent claims in Nature magazine and other journals to the effect that some d orbitals in copper oxide had been directly imaged (Scerri, 2000). Orbitals as used in ab initio calculations are mathematical figments that exist, if anything, in a multi-dimensional Hilbert space.19 Electron density is altogether different since it is a well-defined observable and exists in real three-dimensional space, a feature which some theorists point to as a virtue of density functional methods. 

For image slicers, contiguous slices of the sky are re-arranged end-to-end to form the pseudo-slit. In that case it is obvious that the sky can be correctly sampled (according to the Nyquist sampling theorem) by the detector pixels on which the slices are projected in the same way as required for direct imaging. 

Viswanathan, R. and Heaney, M.B., Direct imaging of the percolation network in a three-dimensional disordered conductor-insulator composite, Phys. Rev. Lett., 75, 4433, 1995. 

Direct images of the three counterflow twin flames with decreasing stretch rate through the reduction of the mixture flow rate (from top photo to bottom photo), while keeping the flow mixture composition constant. 

TEM is conventionally used as a tool to evaluate the size and shape of the cores by direct imaging. However, the core size cannot be determined with atomic resolution from low contrast and 2-D projection of the 3-D core. There are several subjective factors in the estimation of size e.g., how to select the area from which the core size is derived and how to measure this precisely from the vague projections of cores in the TEM micrographs. 

Extensive experimental techniques have been developed for porous material characterization [1], including direct imaging [2-5] and bulk measurement techniques for the statistical properties of the pore space. NMR is one such bulk measurement that is both non-destructive and compatible with large samples. 

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