Visualization techniques microscopy

Dark field Visualization technique for ashes produced by microincineration and fluorescence microscopy useful for low-contrast subjects Electron systems imaging EM shadowing Detection, localization, and quantitation of light elements Structural information from ordered arrays of macromolecules... 

Mieroscopic visualization techniques have also been used to investigate mucus-polymer interactions [36-39]. Transmission electron microscopy was used by Fiebrig et al. [36], whereas different microscopical techniques were used by Lehr et al. [37] for the visualization of mucoadhesive interfaces. Transmission electron microscopy in combination with near-fleld Fourier transform infrared microscopy (FT-IR) has been shown to be suitable for investigating the adhesion-promoting effect of polyethyleneglycol added in a hydrogel [38]. Moreover, scanning force microscopy may be a valuable approaeh to obtain information on mueoadhesion and specific adhesion phenomena [39]. 

Advances in light microscopy have allowed the magnification of objects up to 1,000 times their original size and improved the resolution of the human eye from 0.1 mm to 0.2 Xm (see Table 1 for a comparison of the different visualization techniques). With the aid of histochemical, fluorescence, and autoradiographic methods, in particular, the use of light microscopy in the biological sciences has revealed the substructure of tissues and dynamic processes within cells. 

A EXPERIMENTAL FIGURE 5-44 Live cells can be visualized by microscopy techniques that generate contrast by interference. These micrographs show live, cultured macrophage cells viewed by bright-field microscopy (/eft), phase-contrast microscopy middle), and differential interference contrast (DIC) microscopy righti. In a phase-contrast image, cells... 

During the last few years optical visualization techniques have also been introduced. Among them the total internal reflection fluorescence excitation (TIFR) microscopy [4] and optical interference-enhanced reflection microscopy [5] appear to be the most promising nonintrusive techniques. Their resolution, however, does not even approach the resolution of atomic force microscope and optical techniques may thus serve as an image survey of nanobubbles at 300 nm level (diameter) which is so far their resolution limit. 

Importantly, detection must be via simple inspection utilizing light microscopy, without the need for sophisticated mounting and visualization techniques, since this is preclusive to the ability to screen large numbers of individual broods. 

Variations of this method include the use of a fluorescent dye such as fluorescein or Rhodamine. Depending on the visualization technique used, the uncertainty between perfect mixing and multi-lamellae flow may still be detrimental to proper quantification of the mixing quality. Nevertheless, the use of confocal scanning microscopy enables one to perform three-dimensional imaging of the flow and distinguish between these conflgurations [17, 34, 38]. 

X-ray diffraction (XRD) is a useful, complementary tool in the structural characterization of porous silicon (pSi), providing information not readily available from direct visualization techniques such as electron microscopies. This review outlines key considerations in the use of diffraction techniques for analyses of this material in both thin film form and freestanding porous Si nano or microparticles. Examples of the range of content in the analysis of pSi are provided, ineluding formation mechanisms, layer thickness, extent of pSi oxidation, and degree of crystallinity. Such properties influence practical properties of pSi such as its biodegradability. We also focus on selected key properties where XRD has been particularly informative (a) strain, (b) the structural analysis of pSi multilayers, and (c) an analysis of pSi loaded with small molecules of fundamental or therapeutic interest. 

In the last decade confocal laser scanning microscopy (CLSM) was shown to be a helpful tool for various further tasks of microparticle characterization (Lamprecht et al., 2000a, b, c). It minimizes the light scattered from out-of-focus structures, and permits the identification of several compounds through use of different fluorescence labels. Therefore, CLSM can be applied as a non-destructive visualization technique for microparticles. Moreover, CLSM allows visualization and characterization of structures not only on the surface, but also inside the particles, provided the carrier matrices are sufficiently transparent and can be fluorescently labeled by collecting several coplanar cross-sections, a three-dimensional reconstruction of the inspected objects is possible. Figure 6.13 shows the application of CLSM to investigatation of the cross-sectional structures of spray-dried powders of maltodextrin (MD) with a dextrose equivalent value of DE = 2 and 20. Florescein sodium salt was dissolved in the feed solution as a fluorescent probe of the carrier... 

Visual inspection of microscopical structure is an invaluable tool for a deep knowledge of filters. This is why the visualizing techniques were very early used to characterize them. Nevertheless, as the developed filters included relevant structures with submicron sizes, optical microscopy was no longer useful to achieve a... 

In many investigations of the properties of double-emulsion systems, the use of microscopic visualization in conjunction with the experimental techniques mentioned above has correlated the information gained and in many cases enhanced the understanding of detected mechanisms. In other investigations, visualization techniques alone provide direct detection of changes in the stability and properties of double-emulsion systems. This chapter provides an overview of microscopy techniques applied in investigations of stabihty and transport in double-emulsion systems. 

To understand the principles at which biological systems operate, detailed studies on ultrastructure, material properties, force range, and motion pattern during locomotion are necessary. Such studies have become possible in the past several years due to new developments (1) in microscopical visualization techniques (atomic force microscopy, freezing and environmental scanning electron microscopy), (2) in characterisation of mechanical properties of biological materials and structures in situ and in vivo (measurements of stiffness, hardness, adhesion, friction) at local and global scales, and (3) in computer simulations. 

While field ion microscopy has provided an effective means to visualize surface atoms and adsorbates, field emission is the preferred technique for measurement of the energetic properties of the surface. The effect of an applied field on the rate of electron emission was described by Fowler and Nordheim [65] and is shown schematically in Fig. Vlll 5. In the absence of a field, a barrier corresponding to the thermionic work function, prevents electrons from escaping from the Fermi level. An applied field, reduces this barrier to 4> - F, where the potential V decreases linearly with distance according to V = xF. Quantum-mechanical tunneling is now possible through this finite barrier, and the solufion for an electron in a finite potential box gives... 

Scanning acoustic microscopy (SAM) is a relatively new technique which broke through in the mid-seventies and was commercialized recently. The SAM uses sound to create visual images of variations in the mechanical properties of samples. The ability of acoustic waves to penetrate optically opaque materials makes it possible to provide surface or subsurface stmctural images nondestmctively, which might... 

First-order phase transitions can be detected by various thermoanalytical techniques, such as DSC, thermogravimetric analysis (TGA), and thermomechanical analysis (TMA) [31]. Phase transitions leading to visual changes can be detected by optical methods such as microscopy [3], Solid-solid transitions involving a change in the crystal structure can be detected by X-ray diffraction [32] or infrared spectroscopy [33], A combination of these techniques is usually employed to study the phase transitions in organic solids such as drugs. 

A variation on this method, called fluorescent in situ hybridization (FISH), uses fluorescent-labeled DNA and RNA probes for detection and visualization of single cells by microscopy or flow cytometry.7 80 The FISH technique is popular because of its sensitivity and speed of visualization fluorescent dyes can be used to produce probes with different colors for simultaneous detection of several organisms.76,81,82... 

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