And phase contrast

The im< e mode produces an image of the illuminated sample area, as in Figure 2. The imj e can contain contrast brought about by several mechanisms mass contrast, due to spatial separations between distinct atomic constituents thickness contrast, due to nonuniformity in sample thickness diffraction contrast, which in the case of crystalline materials results from scattering of the incident electron wave by structural defects and phase contrast (see discussion later in this article). Alternating between imj e and diffraction mode on a TEM involves nothing more than the flick of a switch. The reasons for this simplicity are buried in the intricate electron optics technology that makes the practice of TEM possible. 

Changes in clinical semm and urinary parameters, as well as microscopic examination of tissues, generally indicated severe liver and kidney damage. Acute renal and/or hepatic failure was the probable cause of death. Severe hepatic, renal, and capillary damage was also indicated by light and phase-contrast microscope (Ben-Hur et al. 1972 Ben Hur and Appelbaum 1973). 

Fig. 12.21 Effect of DS-96-rhodamine conjugate on human erythrocytes at 10 p.M Fluorescence left) and phase-contrast (right) micrographs...

The MRA techniques discussed in the following base on gradient echo sequences and can generally be divided into flow-dependent and flow-independent ones. The main flow dependent techniques are time-of-flight MRA (TOF-MRA) and phase contrast MRA. CE-MRA, in contrast, is blood flow-independent, although flow phenomena can still influence... 

Applications of visible light such as the use of polarized light, birefringence, retardation, angles of extinction, dispersion staining, and phase contrast will be explained, discussed and related primarily to asbestos with some discussion of quartz. 

The microscope should be equipped for rapidly switching modes between phase contrast and phase contrast with retardation plates and crossed polars. 

There are three main formation mechanisms of TEM image contrast massthickness contrast, diffraction contrast and phase contrast. When electrons pass... 

Fig. 3. Fluorescence leftpanel) and phase contrast (rightpanel) photomicrographs of EJ bladder carcinoma cells, following exposure to pFI-sensitive liposomes (f 00 p g/ml total lipid) at 37°C for f h. Noncoafed DOPE CHEMs liposomes (top), DDP(EO)g2-coated liposomes (middiri), (DDGG) jEO), -coafed liposomes (bottom). Copolymer content in the formulations is 5 mol%. The homogenous cytosol fluorescence observed in all images shows fhaf the grafted copolymers do not compromise with the cellular internalization of liposomes. (Reproduced from ref. 38 wifh permission from Elsevier)...

The resulting freshly isolated microvessel suspension proves to be mainly composed of capillaries as assessed by light and phase-contrast microscopy. 

Fig. 3.12 TM-AFM height (400 x 400 nm2) (a) and phase contrast (b) pictures acquired simultaneously on 150 kD PEI adsorbed onto mica. The z range in the height image is 2 nm, and the range of phase shifts is 5°. The insets in a and b show corresponding height and phase images of mica incubated with 1 mM KC1 buffered at pH 4 but without polymer. Reproduced with permission from [26]. Copyright 1999. American Chemical Society...

Miscibility of PI blends of different structures was reported by Hasegawa et al. [1991] using charge-transfer fluorescence spectra, dynamic mechanical analysis, and phase-contrast microscopy. These blends were BPDA/PDA PI with PMDA/PDA and PMDA/ODA PFs (BPDA = biphenyltetracarboxylic dianhydride PDA = p-phenylene diamine ODA = oxydianUine PMDA = pyromellitic dianhydride). Two patents issued virtually simultaneously noting the utility of miscible PI blends for gas separating membranes [Burgoyne et al., 1991 Kohn et al., 1991]. 

The confocal laser-scanning microscopy (Laser-scanning microscope 410 Zeiss) is performed on fresh frozen slices, the excitation wavelength is 488/514 nm of the internal argon laser, the fluorescence detection is performed at >590 nm within the red channel and phase contrast within the green channel (Figure 5a, 5b). 

Bright field, dark field, polarized and phase contrast methods are utilized to depict specific features or optical properties of the material. 

Other methods for making the various parts of transparent objects visible in the optical microscope are staining techniques and dark-ground and phase-contrast microscopies. These techniques are explained in the standard optics textbooks and similar methods for use in electron microscopy are described in the next section. 

The preferential interaction of CO2 with individual phases of polymer blends is dictated by the affinity of CO2 to the individual components. Zhou et al. [131] applied atomic force microscopy (AFM) and phase contrast microscopy to study the effect of SCCO2 on the surface structure and phase morphology of PMMA/ PS (50/50 w/w) thin films. AFM was used to monitor the return to thermodynamic equilibrium of the cast film as a function of temperature, pressure, and exposure time. Initially, PMMA appeared as a dispersed surface phase elevated from a continuous PS matrix. The series of AFM images in Fig. 10.7 indicate that the Tg of PMMA/PS blend at 20 MPa is <60°C, and at a temperature of 70 °C the Tg occurs at a pressure greater than 20 MPa, as seen by the initially elevated PMMA phase falhng into the PS phase. 

For X-rays, 6 is very small (10 -10 ) and positive, i.e., the refractive index is slightly less than unity. This property of X-rays causes a near absence of reflection at interfaces and results in very clear images, even of thick specimens. X-ray microscopic samples are amplitude objects as well phase objects and X-ray microscopy can be performed in amplitude (absorption) contrast and phase contrast. Hence, at high photon energies for low-density materials it is much more favorable to image an object in phase contrast rather than in absorption contrast. In addition to natural contrast mechanisms. X-rays can provide chemical bond mapping or trace elements mapping of many elements. 

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