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Nuclear Magnetic Resonance (NMR) in Food Processing Applications
Published in Azharul Karim, Sabrina Fawzia, Mohammad Mahbubur Rahman, Advanced Micro-Level Experimental Techniques for Food Drying and Processing Applications, 2021
Azharul Karim, Sabrina Fawzia, Mohammad Mahbubur Rahman
After applying the radio frequency pulse, the NMR signal is determined by putting the sample in a coil tuned to the resonance frequency of the nuclei of interest. A slight current is induced in a receiver coil by the nuclei coherently processing magnetic moment, which dissipates as the nuclei revert to equilibrium. The intensity–time signals that results can be recorded and Fourier-transformed to produce an intensity–frequency spectrum. Equation 6.3 gives the maximum magnetisation that can be detected Mo. M0=γ2h2NsB04kT,
Physicochemical Properties of Coal
Published in Vivek Ranade, Sanjay Mahajani, Ganesh Samdani, Computational Modeling of Underground Coal Gasification, 2019
Vivek Ranade, Sanjay Mahajani, Ganesh Samdani
Nuclear Magnetic Resonance (NMR) is a spectroscopic analytical technique that can be used to determine the structure of a molecule and purity of mixtures. The analysis is performed by measuring the local magnetic field around nuclei to deduce the chemical environment of specific nuclei. Solid-state NMR is typically used for fuels or materials that do not have a defined structure and do not dissolve readily, for example, materials like coal (Sethi et al., 1988). The technique can provide information on the structural parameters of the coal matrix, consisting majorly of C, H, and O. This information can be useful for modeling complex reactions like pyrolysis wherein the overall structure of the coal matrix affects the composition of the volatiles produced (Solum et al., 2001). Figure 3.4 shows typical NMR spectra with functional groups identified (Suggate and Dickinson, 2004). The information that can be obtained by NMR includes aliphatic and aromatic ratios and various other functional groups as shown in Figure 3.4.
Manufacturing and Characterisation of Shape-Memory Polymers and Composites
Published in Kishore Debnath, Inderdeep Singh, Primary and Secondary Manufacturing of Polymer Matrix Composites, 2018
Devarshi Kashyap, Charan Mukundan, S. Kanagaraj
NMR technique is one of the most powerful methods for the analysis of organic compounds. NMR spectroscopy provides information about chemical composition, cross-link density, repeating units and distribution, branching, molecular weight and tacticity, degree of conversion and shape-memory transitions at molecular level. Bertmer et al. (2005) investigated the SME in a covalent cross-linked system obtained from UV cross-linking of poly [l-(lactide)-ran-glycolide)] dimethacrylates by double-quantum excitation method, which reflects the strength of dipolar coupling in the network. The temporary shape of SMP fixed by heating and elongation revealed 80% higher dipolar coupling compared to the permanent shape. In temporary shape, the segments between cross-linking points are stretched and partially aligned, resulting in greater dipole moment than the permanent shape.
Noise model of the cryogenic nuclear magnetic resonance spectroscopy system's receiving chain
Published in Automatika, 2022
Petar Kolar, Lovro Blažok, Dario Bojanjac
Nuclear magnetic resonance (NMR) is a physical phenomenon that is used to study materials via the interaction between the radio frequency (RF) electromagnetic (EM) radiation and the observed material's nuclei placed in a strong magnetic field. This phenomenon is analogous to the process of stimulated emission in lasers: while the population inversion of electrons causes the emission of photons (which is the EM field in the optical frequency range between around 400 THz and around 800 THz) in lasers [1], the population inversion of magnetic spins causes the emission of EM field in the High Frequency (HF), Very High Frequency (VHF) or Ultra High Frequency (UHF) band in NMR [2,3]. Furthermore, NMR spectroscopy is a spectroscopic technique, based on the phenomenon of NMR, that is used to observe local magnetic fields around atomic nuclei [4] and thus determine the chemical and physical properties of the atoms or molecules these atoms are placed in.
Non-targeted metabolomics in sport and exercise science
Published in Journal of Sports Sciences, 2019
Liam M. Heaney, Kevin Deighton, Toru Suzuki
NMR spectroscopy uses a high-powered magnet to induce a magnetic field that causes some atomic nuclei to spin. For 1H NMR spectroscopy, commonly employed in metabolomics studies (Want et al., 2010), the induced magnetic field causes the protons to align in an orientation corresponding to low or high energy; these are known as α and β states, respectively. The sample is then subjected to applied radio waves which cause those nuclei in the α state to shift to the β state. Once the applied energy is removed, the nuclei return to their original energy state and an alteration in magnetic field, known as resonance, can be measured and interpreted as peaks on NMR spectra. The magnetic field expressed on the nuclei is influenced by both the externally applied field and the magnetic effect of localised nuclei/electrons, causing changes in the resonance frequency in comparison to that seen from a singular atom. These changes in resonance are compared to a standard, which is defined as zero, and the difference observed is known as the chemical shift. These chemical shifts are characteristic for certain molecular structures and therefore can be used to identify molecules, or parts of molecular structure, present in the sample which aids in identification of the measured metabolites. As not all isotopes exhibit a magnetic spin (e.g., 12C is not magnetic, where 13C is), it means that not all molecules can be studied using NMR spectroscopy and therefore the technique is limited in its application to metabolite measurement on a global scale.
Influencing factors on liquid crystalline properties of cholesterol side-chain liquid crystalline polymers without spacer: molecular weight and copolymerisation
Published in Liquid Crystals, 2019
Xiwen Yang, Sheng Chen, Shaonan Chen, Haoran Xu
Nuclear magnetic resonance (NMR). 1H NMR measurements were performed on a Bruker ARX400 MHz spectrometer using with CDCl3 as solvent, tetramethylsilane (TMS) as the internal standard at room temperature.