Special Issue "Applications of Low Field Magnetic Resonance"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Applied Physics".

Deadline for manuscript submissions: 15 June 2019

Special Issue Editors

Guest Editor
Prof. Dr. Robert H. Morris

Physics and Maths, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK
Website | E-Mail
Phone: +44 115 848 3123
Fax: +44 115 848 6636
Interests: Magnetic Resonance Hardware for imaging and for general sensing applications; waste water treatment and monitoring with an emphasis on constructed wetlands; Magnetic Resonance Elastography; Food process control and product stability monitoring; Extrinsic MRI contrast; Surface acoustic wave devices for fluid manipulation
Guest Editor
Dr. Michael I. Newton

Physics and Maths, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK
Website | E-Mail
Phone: 441158483365
Fax: +44 115 848 6636
Interests: Sensor applications of acoustic wave devices; Magnetic resonance based sensors; Applications of Superhydrophobic surfaces

Special Issue Information

Dear Colleagues,

Magnetic resonance finds countless applications, from medical imaging to chemical spectroscopy. It is also becoming more frequently used for sensor type applications, in which the measurement of the longitudinal (T1) relaxation times, effective transverse (T2eff) relaxation times, self-diffusion coefficients, or a mixture of the three, are used in process control or quality management for manufacture and environmental monitoring. One driver in the field has been the availability of strong yet affordable permanent magnets which has given rise to a range of unilateral as well as conventional ‘in bore’ systems. The aim of this Special Issue of Applied Sciences is to highlight the current state of ‘low field’ applications of magnetic resonance where we define low as using a magnetic field below 1 Tesla. We welcome new research or review articles with a clear application focus in these areas.

Prof. Dr. Robert H. Morris
Dr. Michael I. Newton
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • magnetic resonance
  • relaxation time
  • NMR
  • unilateral NMR
  • T1
  • T2
  • process control
  • environmental monitoring
  • earths field NMR

Published Papers (8 papers)

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Research

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Open AccessArticle
Hyperpolarised 1H–13C Benchtop NMR Spectroscopy
Appl. Sci. 2019, 9(6), 1173; https://doi.org/10.3390/app9061173
Received: 28 February 2019 / Revised: 14 March 2019 / Accepted: 15 March 2019 / Published: 20 March 2019
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Abstract
Benchtop NMR spectrometers with sub-ppm spectral resolution have opened up new opportunities for performing NMR outside of the standard laboratory environment. However, the relatively weak magnetic fields of these devices (1–2 T) results in low sensitivity and significant peak overlap in 1H [...] Read more.
Benchtop NMR spectrometers with sub-ppm spectral resolution have opened up new opportunities for performing NMR outside of the standard laboratory environment. However, the relatively weak magnetic fields of these devices (1–2 T) results in low sensitivity and significant peak overlap in 1H NMR spectra. Here, we use hyperpolarised 13C{1H} NMR to overcome these challenges. Specifically, we demonstrate the use of the signal amplification by reversible exchange (SABRE) parahydrogen-based hyperpolarisation technique to enhance the sensitivity of natural abundance 1D and 2D 13C{1H} benchtop NMR spectra. We compare two detection methods for SABRE-enhanced 13C NMR and observe an optimal 13C{1H} signal-to-noise ratio (SNR) for a refocused INEPT approach, where hyperpolarisation is transferred from 1H to 13C. In addition, we exemplify SABRE-enhanced 2D 13C benchtop NMR through the acquisition of a 2D HETCOR spectrum of 260 mM of 4-methylpyridine at natural isotopic abundance in a total experiment time of 69 min. In theory, signal averaging for over 300 days would be required to achieve a comparable SNR for a thermally polarised benchtop NMR spectrum acquired of a sample of the same concentration at natural abundance. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessArticle
Analysis of Early Performance of Cement Paste by Low Field NMR
Appl. Sci. 2019, 9(5), 896; https://doi.org/10.3390/app9050896
Received: 29 January 2019 / Revised: 26 February 2019 / Accepted: 27 February 2019 / Published: 2 March 2019
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Abstract
The change of the evaporable water content in the early hydration process of cement paste with different water-to-cement ratios was monitored by low field nuclear magnetic resonance (LF-NMR) relaxometry. The hydration degree and gel/space ratio were accordingly calculated and analyzed. The test results [...] Read more.
The change of the evaporable water content in the early hydration process of cement paste with different water-to-cement ratios was monitored by low field nuclear magnetic resonance (LF-NMR) relaxometry. The hydration degree and gel/space ratio were accordingly calculated and analyzed. The test results show that the first derivative curves of the transverse magnetization are in good agreement with the known five stages of cement hydration process at an early age. The initial and final setting times of the cement paste are closely related to the times the gel/space ratio reaches a fixed value. The early compressive strength of the hardened cement paste exhibits a power function relationship with the gel/space ratio. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessArticle
Effect of Heat Treatment on Water Absorption of Chinese fir Using TD-NMR
Appl. Sci. 2019, 9(1), 78; https://doi.org/10.3390/app9010078
Received: 8 November 2018 / Revised: 12 December 2018 / Accepted: 14 December 2018 / Published: 26 December 2018
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Abstract
Knowledge of the dynamic changes in the water absorption process of heat-treated wood is important for providing a scientific basis for the reasonable application of heat-treated wood, especially for outdoor applications. Nuclear magnetic resonance (NMR) techniques provide detailed information about the moisture components [...] Read more.
Knowledge of the dynamic changes in the water absorption process of heat-treated wood is important for providing a scientific basis for the reasonable application of heat-treated wood, especially for outdoor applications. Nuclear magnetic resonance (NMR) techniques provide detailed information about the moisture components and moisture transport processes in wood, which are not available with other methods. In this work, water absorption of untreated and heat treated Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) heartwood was investigated using various NMR methods. The heat treatment temperatures were varied between 160 °C and 220 °C. According to the spin-spin relaxation time (T2), there were two components of water in the samples heat-treated at 160 °C and 180 °C as well as the untreated sample, while three components of water were found in the samples heat-treated at 200 °C and 220 °C, and the mass of each component was calculated by the integral peak areas of the T2 curve. The amount of bound water and free water in heat-treated samples were less compared to the untreated ones, and the water absorption decreased correspondingly, due to the increasing heat-treated temperature. The results obtained by one dimensional frequency coding indicated that the heat treatment made wood difficult to be accessed by moisture. Besides, NMR images revealed that the free water absorption in latewood was faster than in earlywood, but earlywood could absorb more water than latewood. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessArticle
Low-Field NMR and MRI to Analyze the Effect of Edible Coating Incorporated with MAP on Qualities of Half-Smooth Tongue Sole (Cynoglossus Semilaevis Günther) Fillets during Refrigerated Storage
Appl. Sci. 2018, 8(8), 1391; https://doi.org/10.3390/app8081391
Received: 30 July 2018 / Revised: 10 August 2018 / Accepted: 15 August 2018 / Published: 17 August 2018
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Abstract
Nondestructive and fast measurement and characterization of fish is highly desired during various processing treatments. This research investigated the effectiveness of low field LF-NMR and MRI as fast monitoring techniques to estimate the qualities of half-smooth tongue sole fillets treated with edible coating [...] Read more.
Nondestructive and fast measurement and characterization of fish is highly desired during various processing treatments. This research investigated the effectiveness of low field LF-NMR and MRI as fast monitoring techniques to estimate the qualities of half-smooth tongue sole fillets treated with edible coating combined with modified atmosphere packaging during refrigeration. T2 relaxation spectra showed three peaks representing bound water (T21), immobile water (T22), and free water (T23), respectively. pT22 accounted for the largest proportion of three types of water, followed by pT23. The weighted MRI provided the internal structure information associated with different samples, indicting the combination of edible coating and MAP (70% CO2 + 30% N2) is the best performance in the maintenance of qualities and freshness of HTS fillets. All results demonstrated that the combination of LF-NMR and MRI as fast and nondestructive methods have great potential to monitor qualities deterioration and predict shelf life in of HTS fillets during refrigerated storage. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessArticle
Leaf Development Monitoring and Early Detection of Water Deficiency by Low Field Nuclear Magnetic Resonance Relaxation in Nicotiana tabacum Plants
Appl. Sci. 2018, 8(6), 943; https://doi.org/10.3390/app8060943
Received: 17 May 2018 / Revised: 1 June 2018 / Accepted: 4 June 2018 / Published: 7 June 2018
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Abstract
Drought is the main abiotic stress worldwide affecting harvest quality and quantity of numerous crops. To enable better water management, low field NMR (nuclear magnetic resonance) relaxometry was assessed as a developmental marker and a new method for early detection of water deficiency. [...] Read more.
Drought is the main abiotic stress worldwide affecting harvest quality and quantity of numerous crops. To enable better water management, low field NMR (nuclear magnetic resonance) relaxometry was assessed as a developmental marker and a new method for early detection of water deficiency. The effect of a foliar biostimulant against water stress was also investigated. Two leaves of different ranks (four and eight) were studied. The leaves of different ranks were characterized by different NMR T2 spectra which validated the ability of NMR to describe the developmental stage of tobacco. Results also showed that T2 NMR relaxation spectra allow the detection of mild water stress (80% of the field capacity) through the precise characterization of the leaf water status while other water stress markers (relative water content, photosynthetic related parameters…) were not yet impacted. The agricultural impact of the mild water stress was determined through the nitrogen rate in shoots and amino acids assay six weeks after the beginning of the stress and results shows that foliar application of biostimulant limits the negative consequences of drought. Our results demonstrate the sensitivity of NMR to detect slight changes triggered in the leaf by water stress at the tissue level. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Review

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Open AccessReview
Time Domain NMR in Polymer Science: From the Laboratory to the Industry
Appl. Sci. 2019, 9(9), 1801; https://doi.org/10.3390/app9091801
Received: 22 March 2019 / Revised: 15 April 2019 / Accepted: 23 April 2019 / Published: 30 April 2019
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Abstract
Highly controlled polymers and nanostructures are increasingly translated from the lab to the industry. Together with the industrialization of complex systems from renewable sources, a paradigm change in the processing of plastics and rubbers is underway, requiring a new generation of analytical tools. [...] Read more.
Highly controlled polymers and nanostructures are increasingly translated from the lab to the industry. Together with the industrialization of complex systems from renewable sources, a paradigm change in the processing of plastics and rubbers is underway, requiring a new generation of analytical tools. Here, we present the recent developments in time domain NMR (TD-NMR), starting with an introduction of the methods. Several examples illustrate the new take on traditional issues like the measurement of crosslink density in vulcanized rubber or the monitoring of crystallization kinetics, as well as the unique information that can be extracted from multiphase, nanophase and composite materials. Generally, TD-NMR is capable of determining structural parameters that are in agreement with other techniques and with the final macroscopic properties of industrial interest, as well as reveal details on the local homogeneity that are difficult to obtain otherwise. Considering its moderate technical and space requirements of performing, TD-NMR is a good candidate for assisting product and process development in several applications throughout the rubber, plastics, composites and adhesives industry. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessReview
Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR
Appl. Sci. 2019, 9(7), 1312; https://doi.org/10.3390/app9071312
Received: 23 January 2019 / Revised: 20 March 2019 / Accepted: 27 March 2019 / Published: 29 March 2019
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Abstract
This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency [...] Read more.
This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval Tp shorter than the effective transverse relaxation time (T2*), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T1. Therefore, Tp should be as short as possible (limited by hardware). For Tp < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T1/T2; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T1 using a low flip angle (5°) or T2, using θ = 180°. For measuring T1 and T2 simultaneously in a single experiment, it is necessary to use θ = 90°, the values of T* and M0, and the magnitude of CWFP signal |Mss|. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T2. The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessReview
Monitoring Electrochemical Reactions in Situ with Low Field NMR: A Mini-Review
Appl. Sci. 2019, 9(3), 498; https://doi.org/10.3390/app9030498
Received: 30 December 2018 / Revised: 15 January 2019 / Accepted: 21 January 2019 / Published: 1 February 2019
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Abstract
The number of applications of time domain NMR using low-field spectrometers in research and development has been steadily increasing in recent years with applications ranging from quality control of industrial products to the study of physical and chemical properties of a wide array [...] Read more.
The number of applications of time domain NMR using low-field spectrometers in research and development has been steadily increasing in recent years with applications ranging from quality control of industrial products to the study of physical and chemical properties of a wide array of solid and liquid samples to, most recently, electrochemical studies. In this mini-review we summarize the progress that has been achieved in the coupling between time domain NMR (using low-field spectrometers) and electrochemistry and how the challenges that this coupling poses have been overcome over the years. We also highlight the effect that the static magnetic field of the NMR spectrometer has on the electrochemical systems. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Authors: Dr. Meghan Halse and his group
Affiliation: Centre for Hyperpolarisation in Magnetic Resonance (CHyM), Department of Chemistry, University of York, York, UK

Authors: Dr. Shaoying Huang and his group
Affiliation: Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore

Authors: Prof. Wu Yao and his group
Affiliation: Key Laboratory of Advanced Civil Engineering Materials (Tongji University), Ministry of Education, Shanghai 201804, China

Authors: Prof. Jianxiong Lu and his group
Affiliation: Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China

Authors: Dr. Samuel Patz and his group
Affiliation: Center for Pulmonary Functional Imaging, Departments of Radiology and Pulmonary Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA

Article Type: Review
Authors: Dr. Michael Vogel and his group
Affiliation: Centre for Advanced Imaging, University of Queensland, Brisbane, St Lucia, QLD 4072, Australia

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