NMR


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magnetic resonance

magnetic resonance, in physics and chemistry, phenomenon produced by simultaneously applying a steady magnetic field and electromagnetic radiation (usually radio waves) to a sample of atoms and then adjusting the frequency of the radiation and the strength of the magnetic field to produce absorption of the radiation. The resonance refers to the enhancement of the absorption that occurs when the correct combination of field and frequency is reached. The procedure is analogous to tuning a radio dial exactly to a desired station.

Several distinct kinds of magnetic resonance exist. In cyclotron resonance the magnetic field is adjusted so that the frequency of revolution of a charged particle around the field lines is exactly equal to the frequency of the radiation. This principle is used to produce beams of energetic particles in particle accelerators.

Other magnetic resonance phenomena depend on the fact that both the proton and electron exhibit intrinsic spin about their own axes and thus act like microscopic magnets. Electron paramagnetic resonance (EPR) arises from unpaired electron spins in liquids or solid crystals. Because of their own magnetism, the spins line up with the external magnetic field. For a given magnetic field the spins can be made to “flip” to the opposite direction when they absorb radiation at a corresponding “resonant” frequency. From the point of view of quantum mechanics, the spin flips can be considered as transitions between states that become separated in energy when the magnetic field is applied. The effect is related to the splitting of spectral lines when an atom is subjected to a magnetic field (see spectrum; Zeeman effect).

Nuclear magnetic resonance (NMR) is analogous to EPR; however NMR is produced by the much smaller magnetism associated with unpaired nuclear spins. The NMR resonant frequency (usually that of protons in complex molecules) is slightly shifted by interactions with nearby atoms in the sample, thus providing information about the chemical structure of organic molecules and other materials. NMR is now extensively employed in medicine, although the use of the word “nuclear” is avoided, the preferred name being magnetic resonance imaging (MRI). The technique provides high-quality cross-sectional images of internal organs and structures. Paul Lauterbur, an American physicist, and Peter Mansfield, a British physicist, shared the 2003 Nobel Prize in Physiology or Medicine for pioneering contributions that later led to the application of magnetic resonance in medical imaging.

Magnetic resonance can also occur without an external magnetic field from interactions of the electron and nuclear spins; such resonance produces the fine and hyperfine structure of atomic spectra.

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NMR

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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The limits of detection for the 600-MHz [sup.1]H NMR spectra were acquired using 160 scans (8 min) and acquisition parameters similar to the abovementioned [sup.1]H NMR spectra.
The identified chemical structure is plotted in Figure 1(b), and the detailed information about [sup.1]H NMR (500 MHz, DMSO-[d.sub.6]) and [sup.13]C NMR (125 MHz, DMSO-[d.sub.6]) is listed in Table S1.
The appearance of a singlet of 2H integration at 4.11 ppm in 1H NMR and the appearance of a quaternary C and a CH2 in BB/DEPT-135Adeg at 55.0 and 57.7 ppm confirms the formation of 2,2-dibromoindan-1-one 16.
Selectivity of the proposed method was evaluated by determining the resolution between fluorine signals and other nuclei while precision was investigated by consecutive NMR measurements of a fluvastatin sample (including sample preparation) over 5 different days.
took an additional step toward diverse clinical applications of quantitative NMR spectroscopy by incorporating GlycA as a part of their methodology (2), which has previously explicitly focused on lipopro tein subclass and lipid analytics (1, 13, 14).
"The frequency at which nuclei respond creates a unique spectral 'fingerprint' of their local environment within a material," said Marek Pruski, Ames Laboratory's Lead Scientist in Solid-State NMR.
The equipment and maintenance cost of [sup.1]H-NMR is also typically higher than conventional GC-MS and LC-MS platforms, but low-end bench-top NMR machines are now available which are comparably priced.
A small-scale solution to Velazquez's problem lies just a few hours south along Highway 2 in Calgary at the offices of Nanalysis Corp., creator of the NMReady, a bench-top NMR spectroscopy instrument.
Similarly, NMR technology is emerging as a standard of care in management of cardiovascular and metabolic diseases.
The polyimide and colloids were characterized by IR and NMR. The films were characterized using SEM and UV--visible spectroscopy.