Magnetic force imaging

Figure Bl.19.22. Magnetic force microscopy image of an 8 pm wide track on a magnetic disk. The bit transitions are spaced every 2 pm along the track. Arrows point to the edges of the DC-erased region. (Taken from [109], figure 7.)...

The second mode of operation is the non-contact mode, in which the distance between tip and sample is much larger, between 2 and 30 nm. In this case one describes the forces in terms of the macroscopic interaction between bodies. Magnetic force microscopy, in which the magnetic domain structure of a solid can be imaged, is an example of the non-contact mode operation. 

A new suspension array concept based on sedimentation and microscopic imaging was introduced by Moser et al. [98], Magnetic microbeads settle to the bottom of a microplate well by magnetic forces and form randomly ordered arrays, which are examined by fluorescence microscopy and automated imaging analysis. Each bead carries specific capture molecules and can be identified by a defined luminescent code. 

The force microscope, in general, has several modes of operation. In the repulsive-force or contact mode, the force is of the order of 1-10 eV/A, or 10 -10 newton, and individual atoms can be imaged. In the attractive-force or noncontact mode, the van der Waals force, the exchange force, the electrostatic force, or magnetic force is detected. The latter does not provide atomic resolution, but important information about the surface is obtained. Those modes comprise different fields in force microscopy, such as electric force microscopy and magnetic force microscopy (Sarid, 1991). Owing to the limited space, we will concentrate on atomic force microscopy, which is STM s next of kin. 

The exit slit of the magnetic field is located on the imaging curve, e.g., at the focal point A2" (see Figure 3.3). By changing the magnitude of the magnetic force all separated ion beams continuously pass the exit slit and can be detected using a suitable ion detection system (see Chapter 4). 

Miquel, M.E., Carli, S., Couzens, P.J., Wille, H.J., and Hall, L.D. 2001. Kinetics of the migration of lipids in composite chocolate measured by magnetic resonance imaging. Food Res. Int. 34,773-781. Morris, V.J. 2004. Probing molecular interactions in foods. Trends Food Sci. Technol. 15, 291-297. Morris, V.J., Kirby, A.J., and Gunning, A.P. 1999. Atomic Force Microscopy for Biologists . Imperial College Press, London. 

MALDI MCM-41 MCR MD ME MEM MI MPM MRI MS MVA Matrix-assisted Laser Desorption/Ionization Mobile Crystalline Material-41 Multivariate Curve Resolution Molecular Dynamics Matrix-enhanced Magnetic Force Micrscopy Multivariate Image Multiphoton Microscopy Magnetic Resonance Imaging Mass Spectroscopy Multivariate Analysis... 

Magnetic resonance imaging permitted direct observation of the liquid hold-up in monolith channels in a noninvasive manner. As shown in Fig. 8.14, the film thickness - and therefore the wetting of the channel wall and the liquid hold-up -increase nonlinearly with the flow rate. This is in agreement with a hydrodynamic model, based on the Navier-Stokes equations for laminar flow and full-slip assumption at the gas-liquid interface. Even at superficial velocities of 4 cm s-1, the liquid occupies not more than 15 % of the free channel cross-sectional area. This relates to about 10 % of the total reactor volume. Van Baten, Ellenberger and Krishna [21] measured the liquid hold-up of katapak-S . Due to the capillary forces, the liquid almost completely fills the volume between the catalyst particles in the tea bags (about 20 % of the total reactor volume) even at liquid flow rates of 0.2 cm s-1 (Fig. 8.15). The formation of films and rivulets in the open channels of the structure cause the further slight increase of the hold-up. 

Nishide, H., Ozawa, T., Miyasaka, M. and Tsuchida, E. (2001). Nanometer-sized high-spin polyradical poly(4-phenoxyl-l,2-phenylenevinylene) planarily extended in a non-kekule fashion and its magnetic force microscopic images. J. Am. Chem. Soc. 123, 5942-5946... 

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