Generation of persistent currents and their detection in superfluid 3He by nuclear magnetic resonance

1987 ◽  
Vol 65 (11) ◽  
pp. 1481-1485 ◽  
Author(s):  
D. F. Brewer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Larmor Frequency ◽  
Superfluid 3He ◽  
Coupling Constant ◽  
Persistent Currents ◽  
Flow Coupling ◽  
Nmr Techniques ◽  
Set Up ◽  
Nuclear Magnetic

Superflow of 3He–B in a channel can be observed by nuclear magnetic resonance (nmr) techniques, the simplest arrangement being one in which the magnetic field is perpendicular to the flow. Above a certain critical velocity, the transverse resonance frequency shifts away from the Larmor frequency, and the velocity gives a value of the ratio of the flow coupling constant to the dipole coupling constant, which is found to differ substantially from theoretical prediction. The nmr shifts can be used to detect persistent currents in a doubly connected geometry, and some preliminary observations are described as well as an analysis of the way in which currents with multiply quantized circulation may be set up.

Nuclear Magnetic Resonance Spectroscopic Behaviour of Some Selective Natural Flavonoids: A Look Through

2020 ◽  
Vol 17 (2) ◽  
pp. 185-196
Author(s):  
Shyamal K. Jash ◽  
Dilip Gorai ◽  
Lalan C. Mandal ◽  
Rajiv Roy
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Natural Products ◽  
Magnetic Resonance ◽  
Hard Core ◽  
2D Nmr ◽  
Vital Role ◽  
Spectral Technique ◽  
Nmr Techniques ◽  
Significant Class ◽  
Nuclear Magnetic

Flavonoids are considered as a significant class of compounds among the natural products, exhibiting a variety of structural skeletons as well as multidirectional biological potentials. In structural elucidations of natural products, Nuclear Magnetic Resonance (NMR) spectroscopy has been playing a vital role; the technique is one of the sharpest tools in the hands of natural products chemists. The present resume deals with hard-core applications of such spectral technique, particularly in structural elucidation of flavonoids; different NMR techniques including 1H-NMR, 13C-NMR, and 2D-NMR [viz. 1H-1H COSY, COLOC, HMBC, HMQC] are described in detail.

Frequency cycling for compensation of undesired off-resonance effects in surface nuclear magnetic resonance

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. WB33-WB48 ◽  
Author(s):  
Denys Grombacher ◽  
Mike Müller-Petke ◽  
Rosemary Knight
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Larmor Frequency ◽  
Forward Model ◽  
Resonance Excitation ◽  
Entire Volume ◽  
Resonance Effects ◽  
Aquifer Properties ◽  
The Impact ◽  
Nuclear Magnetic

To produce reliable estimates of aquifer properties using surface nuclear magnetic resonance (NMR), an accurate forward model is required. The standard surface NMR forward model assumes that excitation occurs through a process called on-resonance excitation, which occurs when the transmit frequency is set to the Larmor frequency. However, this condition is often difficult to satisfy in practice due to the challenge of accurately determining the Larmor frequency within the entire volume of investigation. As such, in situations where an undesired offset is present between the assumed and true Larmor frequency, the accuracy of the forward model is degraded. This is because the undesired offset leads to a condition called off-resonance excitation, which impacts the signal amplitude, phase, and spatial distribution in the subsurface, subsequently reducing the accuracy of surface NMR estimated aquifer properties. Our aim was to reduce the impact of an undesired offset between the assumed and true Larmor frequency to ensure an accurate forward model in the presence of an uncertain Larmor frequency estimate. We have developed a methodology where data are collected using two different transmit frequencies, each an equal magnitude above and below the assumed Larmor frequency. These data are combined, through a method we refer to as frequency cycling, in a manner that allow the component well-described by our estimate of the Larmor frequency to be stacked coherently, whereas the component related to the presence of an undesired offset is combined destructively. In synthetic and field studies, we have determined that frequency cycling is able to mitigate the influence of an undesired offset providing more accurate estimates of aquifer properties. Furthermore, the frequency-cycling method stabilized the complex inversion of surface NMR data, allowing advantages associated with complex inversion to be exploited.

Nuclear magnetic resonance J coupling constant polarizabilities of hydrogen peroxide: A basis set and correlation study

2012 ◽  
Vol 33 (23) ◽  
pp. 1845-1853 ◽  
Author(s):  
Hanna Kjaer ◽  
Monia R. Nielsen ◽  
Gabriel I. Pagola ◽  
Marta B. Ferraro ◽  
Paolo Lazzeretti ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Correlation Study ◽  
Basis Set ◽  
Coupling Constant ◽  
J Coupling ◽  
Nuclear Magnetic

Elucidation of HIV‐1 5' Leader Secondary Structure Through Novel Long Range Nuclear Magnetic Resonance (NMR) Techniques

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Claudia Walker ◽  
Elisabeth Kan ◽  
Faith Davis ◽  
Jonathan Catazaro ◽  
Michael Summers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Secondary Structure ◽  
Long Range ◽  
Nmr Techniques ◽  
Hiv 1 ◽  
Nuclear Magnetic

scholarly journals Transverse and longitudinal nuclear magnetic resonance in superfluid 3He in anisotropic aerogel

JETP Letters ◽  
2008 ◽  
Vol 86 (9) ◽  
pp. 594-599 ◽  
Author(s):  
V. V. Dmitriev ◽  
D. A. Krasnikhin ◽  
N. Mulders ◽  
V. V. Zavjalov ◽  
D. E. Zmeev
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Superfluid 3He ◽  
Nuclear Magnetic

Comparison of 1-D and 2-D NMR techniques for screening earthworm responses to sub-lethal endosulfan exposure

2010 ◽  
Vol 7 (6) ◽  
pp. 524 ◽  
Author(s):  
Jimmy Yuk ◽  
Jennifer R. McKelvie ◽  
Myrna J. Simpson ◽  
Manfred Spraul ◽  
André J. Simpson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Organochlorine Pesticide ◽  
Environmental Exposure ◽  
Quantum Coherence ◽  
Metabolic Response ◽  
Powerful Approach ◽  
Nmr Techniques ◽  
And Control ◽  
Nuclear Magnetic

Environmental context The application of metabolomics from an environmental perspective depends on the analytical ability to discriminate minute changes in the organism resulting from exposure. In this study, 1-D and 2-D Nuclear Magnetic Resonance (NMR) experiments were examined to characterise the earthworm’s metabolic response to an organochlorine pesticide. 2-D NMR showed considerable improvement in discriminating exposed worms from controls and in identifying the metabolites responsible. This study demonstrates the potential of 2-D NMR in understanding subtle biochemical responses resulting from environmental exposure. Abstract Nuclear Magnetic Resonance (NMR) based metabolomics is a powerful approach to monitoring an organism’s metabolic response to environmental exposure. However, the discrimination between exposed and control groups, depends largely on the NMR technique chosen. Here, three 1-D NMR and three 2-D NMR techniques were investigated for their ability to discriminate between control earthworms (Eisenia fetida) and those exposed to a sub-lethal concentration of a commonly occurring organochlorine pesticide, endosulfan. Partial least-squares discriminant analysis found 1H–13C Heteronuclear Single Quantum Coherence (HSQC) spectroscopy to have the highest discrimination with a MANOVA value (degree of separation) three orders lower than any of the 1-D and 2-D NMR techniques. HSQC spectroscopy identified alanine, leucine, lysine, glutamate, glucose and maltose as the major metabolites of exposure to endosulfan, more than all the other techniques combined. HSQC spectroscopy in combination with a shorter 1-D experiment may prove to be an effective tool for the discrimination and identification of significant metabolites in organisms under environmental stress.

Apsu — A new compact surface nuclear magnetic resonance system for groundwater investigation

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. JM1-JM11 ◽  
Author(s):  
Jakob Juul Larsen ◽  
Lichao Liu ◽  
Denys Grombacher ◽  
Gordon Osterman ◽  
Esben Auken
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Larmor Frequency ◽  
Low Noise ◽  
Quality Data ◽  
Subsurface Water ◽  
Near Surface ◽  
Peak Current ◽  
Multiple Receivers ◽  
Nuclear Magnetic

Surface nuclear magnetic resonance (NMR) is emerging as a competitive method for aquifer exploration due to its direct sensitivity to subsurface water, but the method still has several shortcomings, for example, a signal-to-noise ratio that is often poor, long survey times, and bulky equipment. We have developed Apsu, a new surface NMR system designed for near-surface groundwater investigations. It provides several features such as a compact transmitter unit, separated, small receiver coils, wireless connections between multiple receivers, quasi-zero dead time, and robust phase determination. The transmitter unit is powered by a lightweight generator, and it drives a triangular current in an untuned [Formula: see text] transmitter coil. The peak current of the triangular waveform is up to 145 A, with an effective peak current of 105 A at a Larmor frequency of 2 kHz, corresponding to a 30 m depth of investigation. The frequency and amplitude in each half-oscillation of the transmit pulses can be modulated independently, which gives great flexibility in the pulse design. The receiver uses low-noise preamplifiers and multiple receivers linked to a central unit through Wi-Fi. The use of small receiver coils and wireless connections to multichannel receivers greatly improves the layout configuration flexibility and survey efficiency. The performance of the system under field conditions is demonstrated with high-quality data collected near Silkeborg, Denmark, using on-resonance and numerically optimized modulation pulses.

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