High magnetic fields

The most widely used development in HTS wire production is tlie powder-in-tube procedure with BSCCO ceramic materials. In this procedure very fine HTS powder, placed inside of a hollow silver tube, is fused as the tube lengtn is mechanically increased to form a wire. Very high magnetic fields with this wire have been reported at 4 K however, the performance degrades substantially above 20 to 30 K. 

Special applications, such as in high-magnetic fields, require special thermometers. The carbon-glass and strontium-titinate resistance thermometers have the least magnetoresistance effects. 

Eddy currents are circular currents induced in wide areas within the core in the surrounding wires and structures by the presence of high magnetic fields. There is not much that a typical designer can do to reduce these losses. 

Fig. 8. Field dependence of the momenl of carbon nanolubes al ihe temperaiures shown at high magnetic fields (after Here-mans et al.[26]).

The situation changes drastically in the presence of a high magnetic field perpendicular to the axis. As has been discussed in Sec. 2, Landau levels without dispersion appear at the Fermi level considerably, leading to a magnetic-field induced distortion [13,14]. 

Fig. 9. An example of calculated in-plane lattice distortions induced by a high magnetic field (left) and the dependence of the maximum gap due to in-plane lattice distortions on a magnetic field (right).

The electron wave function becomes localised in the top and bottom part of the cylindrical surface where the effective magnetic field perpendicular to the tube surface is the largest. Thus the boundary condition along the circumference direction becomes less important in high magnetic fields as has been discussed in Sec. 2. Consequently the distinction between metallic and semiconducting... 

Metals and semiconductors are electronic conductors in which an electric current is carried by delocalized electrons. A metallic conductor is an electronic conductor in which the electrical conductivity decreases as the temperature is raised. A semiconductor is an electronic conductor in which the electrical conductivity increases as the temperature is raised. In most cases, a metallic conductor has a much higher electrical conductivity than a semiconductor, but it is the temperature dependence of the conductivity that distinguishes the two types of conductors. An insulator does not conduct electricity. A superconductor is a solid that has zero resistance to an electric current. Some metals become superconductors at very low temperatures, at about 20 K or less, and some compounds also show superconductivity (see Box 5.2). High-temperature superconductors have enormous technological potential because they offer the prospect of more efficient power transmission and the generation of high magnetic fields for use in transport systems (Fig. 3.42). 

Only Tg-S mixing will be considered now since it is responsible for most CIDNP spectra, certainly at zero and at high magnetic fields. 

Bousseksou A, Varret F, Goiran M, Boukheddaden K, Tuchagues J-P (2004) The Spin Crossover Phenomenon Under High Magnetic Field. 235 65-84 Bousseksou A, see Tuchagues J-P (2004) 235 85-103 Bowers MT, see Wyttenbach T (2003) 225 201-226... 

Yamagishi, A., Takeuchi, T., Higashi, T. and Date, M. (1989) Diamagnetic orientation of polymerized molecules under high magnetic field. J. Phys. Soc. Jpn., 58, 2280-2283. 

Tanimoto, Y, Katsuki, A., Yano, H. and Watanabe, S. (1997) Effect of high magnetic field on the silver deposition from its aqueous solution. J. Phys. Chem. A 101, 7357363. 

Uechi, 1., Katsuki, A., Dunin-Barkovskiy, L. and Tanimoto, Y. (2004) 3D-morphological chirality induction in zinc silicate membrane tube using a high magnetic field. J. Phys. Chem. B, 108,... 

The application of superconductivity in electrical engineering offers revolutionary possibilities huge current densities with no resistive loss very high magnetic fields with no power supply required the possible elimination of iron in electrical machines and the reduction in size and cost of plant. The first wide-scale application of superconductivity has... 

For a manufacturer the difficulty is to estimate future developments or trends in NMR microscopy. Based on dedicated laboratory-made hardware developed by the NMR microscopy users and on their requests for new commercial hardware and software, the following topics could become more important micro-coil applications, multiple receiver systems and multi-coil arrangements, NMR microscopy at very high magnetic fields, MAS imaging and localized 1H MAS spectroscopy and localized single-shot 2D spectroscopy. There are no clear-cut distinctions between most of the individual topics, as will be discussed in the following sections. 

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