Bore magnet

In general, vertical bore magnets are usually cheaper compared with horizontal systems of the same field strength. Moreover, vertical bore magnets can provide much higher magnetic fields, currently 21 T, 900 MHz with an open bore of 52 mm, compared with horizontal bore magnets, currently 11.7 T, 500 MHz with an open bore of up to 300 mm. From the scientific point of view, the main... 

Fig. 2.1.1 Vertical wide bore magnet, 16.44T, 700 MHz, 89-mm inner diameter (Bruker-BioSpin AG, Fallanden, Switzerland).

Fig. 2.1.2 A 7-T and 300-MHz horizontal bore magnet with inner bore diameter of 160 mm (Bruker-BioSpin GmbH, Rheinstetten, Germany).

All experiments were performed in a 1.9-T horizontal bore magnet (Oxford Instruments, Oxford, UK) with a dear bore diameter of 31 cm. Magnetic field gradients were produced by a 12-cm id water-cooled gradient set (Resonance Research, Billerica, MA, USA), capable of a maximum output of 300 mT m-1, and were driven by Techron 7700 amplifiers (Techron Inc., Elkhart, IN, USA). Rf excitation was accomplished using either a quadrature driven birdcage coil (Morris Instruments, Ottawa, ON, Canada), or an 8-tum laboratory-built solenoid coil, driven by an ENI LPI-10 1000 W amplifier or a Matec Model 525 class-C amplifier. 

In this example, extensive use of the available reference samples greatly simplified an otherwise highly complex sample mixture. In addition, utilization of a high-field, wide-bore magnet afforded the necessary spectral resolution to easily resolve the two crystalline forms from each other, as well as from the excipients. A lower field magnet, or a less optimized system, may not have been able to differentiate the two forms, and this significant potential impact on the drug s overall bioavailability may have been overlooked. 

A subsequent study by the same research group focused on pits in olives. This time the olives travelled at various speeds through a 2 T horizontal bore magnet. Segregating 300 pitted and non-pitted olives gave classification errors of 4.3, 4.7, 2.3 and 4% at belt speeds of 0, 5,15 and 25 cm/s, respectively. 

NMR analyses were done on an IBM Instruments NR-300 spectrometer and an Oxford 7 Tesla superconducting narrow-bore magnet. Silicon-29 (Si-29) NMR spectra were recorded at 59.6 MHz and hydrogen (also commonly called proton or H-l) NMR spectra at 300.13 MHz. Spectra were recorded using conventional single-pulse techniques with proton decoupling for Si-29 acquisitions. Si-29 experiments were structured so as to suppress nuclear Overhauser enhancement (NOE). For Si-29 acquisitions, spectral widths were 50 kHz and Fourier transform (FT) sizes were 4K points. For protons, spectral widths were 7.5 kHz and FT sizes were 16K points. Si-29 rf pulse widths were approximately 12 fits and proton rf pulse widths were 8 jj.s. 

Equipment typical for use in material imaging is depicted in Fig. 1.1.8. It consists of a solid-state NMR spectrometer console, a high-field wide-bore magnet (4—I4 l ), high-power rf amplifiers (/ = I kW) for H and for other nuclei, also called X nuclei, three gradient amplifiers, one for each space direction, and an rf receiver. One computer... 

One of the most significant developments that has spurred activity in the area of MRM is the commercial availability of high field (e.g., 14.1 and 17.6 T) wide bore magnets. Assuming that the main source of noise is the receiver coil, SNR is proportional to the 7/4th power of the Bq field. Therefore, imaging with high fields is preferable. 

Historically, the applications of NMR to problems of macromolecular structure and dynamics have preceded extensive studies of biochemistry in vivo by more than a decade. This is a reflection of the development of magnet technology much useful work on the molecular level could be done with the narrow-bore magnets developed first, whereas in vivo biochemical work for the most part requires magnets with a bore wide enough to accommodate at least an isolated organ, and preferably an intact organism such... 

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