Results 261 to 270 of about 184,530 (301)

Differentiation of fentanyl analogues by low-field NMR spectroscopy

Analytica Chimica Acta, 2019
Forensic laboratories commonly receive new psychoactive substances such as fentanyl analogues and other synthetic opioids that are difficult to identify. Slight changes to chemical structures, e.g. shifting the position of functional groups such as methyl groups or halogens on the aromatic ring, may not be distinguished using traditional methods.
Jonathan Duffy, Aaron Urbas, Matthias Niemitz, Katrice Lippa, Ioan Marginean   +4 more
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Gated cardiac imaging using low-field NMR

Physics in Medicine and Biology, 1986
A system for the ECG gating of NMR images is described. It is based on the Aberdeen Mark 1 0.04 T imager and a 280 microprocessor to control data acquisition. The collection of images is discussed including: saturation recovery images; inversion recovery images and phase-encoded images.
D G, Norris, J M, Hutchison
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Perfusion Measurement with Low Field NMR

2023
<p>Blood perfusion is a fundamental parameter of tissue health and function. Measurements of blood perfusion are clinically used to assess the severity of strokes, tumors and other diseases. Nuclear Magnetic Resonance (NMR) is a common modality for these measurements, due to its flexibility, sensitivity and lack of ionising radiation.</p> ...
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Quantitative Analysis of Low-Field NMR Signals in the Time Domain

Analytical Chemistry, 2001
Two novel methods are described for direct quantitative analysis of NMR free induction decay (FID) signals. The methods use adaptations of the generalized rank annihilation method (GRAM) and the direct exponential curve resolution algorithm (DECRA). With FID-GRAM, the Hankel matrix of the sample signal is compared with that of a reference mixture to ...
Nordon, A., Gemperline, P.J., McGill, C.A., Littlejohn, D.   +3 more
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Proton Low‐Field NMR Measurements on Crackers

Journal of Food Science, 1994
ABSTRACT We have shown that the signal obtained for crackers (3.5% water content) by low resolution NMR method using the CPMG sequence, described the relaxation of the protons of fat. For water content up to 7.1% the water signal is not seen by a CPMG sequence, the water has therefore a very short spin‐spin relaxation time (T2 < 0 ...
PASCAL DESBOIS, DENIS LE BOTLAN
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Low field NMR investigations of methyl tunnelling

Physica B: Condensed Matter, 1994
Abstract Low-field dipole-dipole-driven NMR has been used to measure the ground state methyl tunnelling frequencies in dimethylmalonic acid ( ν t = 337 ± 3 kHz), 3-hexanone ( ν t = 210 ± 10 kHz) and 4-heptanone ( ν t = 495 ± 3 kHz).
P.M. Debenham, A.J. Horsewill, I.B.I. Tomsah, S. Clough   +3 more
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Low Field NMR Water Cut Metering

Canadian International Petroleum Conference, 2002
Abstract We have developed a new on line water cut meter using low field Nuclear Magnetic Resonance (NMR) technology. This instrument is designed for use on heavy oil systems where conventional instruments experience difficulties.
Ian Wright, Lastockin David, Allsopp Kevin, Evers-Dakers Maureen, Kantzas Apostolos   +4 more
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A low field NMR imager for clinical use

Journal of Physics E: Scientific Instruments, 1987
The essential design features of a vertical field 0.08 T, 3.4 MHz NMR proton imager are described. The machine was constructed in-house following successful clinical trials with a prototype 1.7 MHz imager. Based on a four-coil air-cored resistive electromagnet, the machine acquires single-slice 128*128 pixel images in about 4 min using an interleaved ...
T W Redpath, J M S Hutchison, L M Eastwood, R D Selbie, G Johnson, R A Jones, J R Mallard   +6 more
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Evaluation of Composites Miscibility by Low Field NMR

International Journal of Polymeric Materials, 2007
Solid state nuclear magnetic resonance (NMR) is a powerful technique to analyze polymer composites. The use of proton relaxation data to evaluate the dispersity of the dispersion phase in the composite and its homogeneity are very wide. In this work PVC/silica composites were prepared using different ratios to obtain a new material to be used in ...
Maria Inês B. Tavares, Otávio Ferreira, Mônica Preto, Eduardo Miguez, Igor L. Soares, Edemilson P. da Silva   +5 more
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Hyphenated low‐field NMR techniques: combining NMR with NIR, GPC/SEC and rheometry

Magnetic Resonance in Chemistry, 2015
Hyphenated low‐field NMR techniques are promising characterization methods for online process analytics and comprehensive offline studies of soft materials. By combining different analytical methods with low‐field NMR, information on chemical and physical properties can be correlated with molecular dynamics and complementary chemical information.
Räntzsch, Volker, Wilhelm, Manfred, Guthausen, Gisela   +2 more
openaire   +3 more sources