Numerically optimized modulations for adiabatic pulses in surface nuclear magnetic resonance

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. JM1-JM14 ◽  
Author(s):  
Denys Grombacher
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Signal To Noise Ratio ◽  
Effective Means ◽  
Reducing Power ◽  
Large Signal ◽  
Hyperbolic Tangent ◽  
Adiabatic Pulse ◽  
Adiabatic Pulses ◽  
Nuclear Magnetic

Adiabatic pulses, which provide an effective means of generating a large-amplitude nuclear magnetic resonance (NMR) signal in the presence of a heterogeneous magnetic field, have the potential to greatly improve the signal-to-noise ratio of the surface NMR experiment. To ensure efficient implementation of adiabatic pulses into the surface NMR framework, a numerically optimized modulation (NOM) approach is used to design adiabatic pulses specifically intended for application in surface NMR. The scenario in which the frequency response of the tuned transmit coil is used to modulate the current amplitude is considered. The performance of a NOM pulse is contrasted against two alternative adiabatic pulses (described by a linear frequency sweep and a hyperbolic tangent sweep) that are currently implemented with the existing hardware. The NOM approach provides equivalent excitation as the chirp and hyperbolic tangent pulse while shortening pulse durations and reducing power consumption. Furthermore, the NOM approach also provides sharp resolution and large signal amplitudes. Considerations for the design of the NOM adiabatic pulse for surface NMR are given, as well as a discussion about their implementation into the surface NMR experimental framework.

Adiabatic pulses enhance surface nuclear magnetic resonance measurement and survey speed for groundwater investigations

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. WB85-WB96 ◽  
Author(s):  
Elliot Grunewald ◽  
Denys Grombacher ◽  
David Walsh
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Field Experiments ◽  
Signal Amplitude ◽  
Pulse Frequency ◽  
Adiabatic Pulse ◽  
Adiabatic Pulses ◽  
Wide Range ◽  
Measurement Efficiency ◽  
Nuclear Magnetic

Surface nuclear magnetic resonance (surface NMR) is an extremely powerful tool for groundwater resource investigations. However, the technique suffers from an inherently low signal-to-noise ratio (S/N), which commonly necessitates extensive signal averaging, resulting in very long measurement times. Previous approaches to improve S/N and measurement efficiency have focused primarily on reducing noise, through hardware and processing advancements. We introduce a new and divergent approach to actually increase the signal amplitude by modifying the form of the transmitted pulse used to excite the groundwater signals. An on-resonance pulse, the only form of excitation pulse previously used in surface NMR, has a fixed frequency and induces coherent excitation over a narrow range of transmit field strengths. Given spatially inhomogeneous fields underlying the surface coil, an on-resonance pulse excites water, a limited volume of water, producing a similarly limited signal amplitude. An adiabatic pulse, one of many pulse forms used for medical imaging and chemical spectroscopy, modulates pulse frequency and provides excitation over a much larger range of transmit field amplitudes. Numerical simulations of surface NMR with adiabatic pulses demonstrate almost a factor of three improvement in the peak signal amplitude compared to an on-resonance pulse. Simulations also show that a single measurement using an adiabatic pulse with high transmit current provides sensitivity to water over a wide range of depth. In contrast, multiple on-resonance measurements using a range of transmit currents are required to span sensitivity over a similar range of depths. Numerical simulation results are validated by the first field experiments comparing on-resonance and adiabatic pulses. We have considered how improvements in S/N can be used for dramatically improved measurement speed and how other advantages of adiabatic pulses may more generally be used to enhance surface NMR measurements.

Oil in and under Ice Detection using Nuclear Magnetic Resonance

2017 ◽  
Vol 2017 (1) ◽  
pp. 1877-1889
Author(s):  
David Palandro ◽  
Tim Nedwed ◽  
Steve Altobelli ◽  
Eiichi Fukushima ◽  
Mark Conradi ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Crude Oil ◽  
Signal To Noise Ratio ◽  
Field Tests ◽  
Thick Layer ◽  
Research Area ◽  
Active Research ◽  
Ice Detection ◽  
Nuclear Magnetic

ABSTRACT (2017-387) The application of existing remote sensing sensors and technologies for the detection of oil in and under ice is an ongoing and active research area. Currently, the suite of sensors that have and are being tested include acoustic, radar, optical and fluorosensors. Another technology being tested is Nuclear Magnetic Resonance (NMR) in the earth’s magnetic field. NMR to detect oil in and under ice has undergone extensive testing since 2006 and results to date have been promising. Field tests performed using a prototype 1 × 1 m flat transmitting/receiving antenna coil have differentiated seawater and Crisco® oil, a crude-oil surrogate. Research has been focused on scaling-up the 1 m2 prototype to increase the signal-to-noise ratio (SNR) and allow the sensor to detect oil beneath ice that is up to 1 m thick. The coil currently being tested has a diameter of 6 m in a modified figure-8 pattern. This coil was being tested at Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire, USA. The final phase of feasibility testing was completed in late 2016 with the use of a ruggedized NMR system flown under a helicopter over a pond. The ruggedized NMR system was able to detect a 1.0 cm thick layer of a crude oil surrogate under ~ 110 cm of simulated ice.

Carbon-13 Fourier Transform Nuclear Magnetic Resonance. IX. Complete Assignments of Some Prodigiosins. Bioincorporation of Label

1975 ◽  
Vol 53 (1) ◽  
pp. 148-160 ◽  
Author(s):  
Robert J. Cushley ◽  
Richard J. Sykes ◽  
C.-K. Shaw ◽  
Harry H. Wasserman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Effective Means ◽  
Substituted Pyrroles ◽  
Biosynthetic Studies ◽  
Complete Interpretation ◽  
Comprehensive Study ◽  
Nuclear Magnetic

A comprehensive study has been made of the carbon-13 chemical shifts of substituted pyrroles. The data, together with perdeuteration, single resonance, and off-resonance techniques, formed the basis for the complete interpretation of the carbon-13 spectra of the prodigiosins. Based on these assignments the biosynthetic origin of the prodigiosin carbons was elucidated, with further biosynthetic studies to be reported.Carbon-13 chemical shifts are shown to be an effective means of determining sites of protonation.

scholarly journals Особенности исследования состояния текущей среды методом ядерного магнитного резонанса

2020 ◽  
Vol 46 (2) ◽  
pp. 8
Author(s):  
В.В. Давыдов ◽  
Н.С. Мязин ◽  
В.И. Дудкин ◽  
Р.В. Давыдов
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Signal To Noise Ratio ◽  
Relaxation Times ◽  
The State ◽  
T2 Relaxation ◽  
Signal To Noise ◽  
Flowing Liquid ◽  
Registration System ◽  
Nuclear Magnetic

The features of the state investigation of a flowing liquid by nuclear magnetic resonance was defined. The methodology for the state investigation of the flowing medium by changing the values of the longitudinal T1 and transverse T2 relaxation times is justified. For the parameters of the registration system of the signal of nuclear magnetic resonance and magnetic fields are established relations between them. The implementation of these ratios allows to obtain a signal to noise ratio of more than 5 for carrying out measurements of T1 and T2 values in real time with an error not exceeding 1%. The results of experimental research are presented.

scholarly journals Competing transfer pathways in direct and indirect dynamic nuclear polarization magic anglespinning nuclear magnetic resonance experiments on HIV-1 capsid assemblies: implications for sensitivity and resolution

2021 ◽  
Vol 2 (1) ◽  
pp. 239-249
Author(s):  
Ivan V. Sergeyev ◽  
Caitlin M. Quinn ◽  
Jochem Struppe ◽  
Angela M. Gronenborn ◽  
Tatyana Polenova
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Large Signal ◽  
Experimental Conditions ◽  
Hiv 1 ◽  
Nuclear Magnetic

Abstract. Dynamic nuclear polarization (DNP)-enhanced magic angle spinning (MAS) nuclear magnetic resonance (NMR) of biological systems is a rapidly growing field. Large signal enhancements make the technique particularly attractive for signal-limited cases, such as studies of complex biological assemblies or at natural isotopic abundance. However, spectral resolution is considerably reduced compared to ambient-temperature non-DNP spectra. Herein, we report a systematic investigation into sensitivity and resolution of 1D and 2D 13C-detected DNP MAS NMR experiments on HIV-1 CA capsid protein tubular assemblies. We show that the magnitude and sign of signal enhancement as well as the homogeneous line width are strongly dependent on the biradical concentration, the dominant polarization transfer pathway, and the enhancement buildup time. Our findings provide guidance for optimal choice of sample preparation and experimental conditions in DNP experiments.

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