Uniform-Penalty Inversion of Multiexponential Decay Data

Borgia, G.C.; Brown, R. James; Fantazzini, Paola

doi:10.1006/jmre.2000.2197

Cited by 232 publications

(167 citation statements)

References 6 publications

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“…The ILT was performed using the method described by Borgia et al 13 PCA was used to find the main variations in the full T 2 relaxation curve decays, whereas SIMCA was used to develop classification models based on oil type. PCA and SIMCA models were performed in Pirouette ® software, version 4.5 (Infometrix Inc., Woodville, WA, USA).…”

Section: Discussionmentioning

confidence: 99%

“…5,6 However, these methods are laborious (extensive sample preparation/derivatization), time consuming, and quite expensive. Consequently, several alternative methods have been proposed, including vibrational spectroscopies (UV-Vis, near infrared (NIR), middle infrared (MIR) and Raman), electrochemical and high-and mid-resolution 1 H, 13 C and 31 P nuclear magnetic resonance (NMR) methods. [7][8][9][10] Although these methods have become an attractive alternative due to the ability to analyze samples with little or no sample preparation, they do not allow the analysis in a completely non-invasive fashion.…”

Section: Introductionmentioning

confidence: 99%

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Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry

Santos¹,

Kock²,

Santos³

et al. 2016

Journal of the Brazilian Chemical Society

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A fast procedure using time-domain nuclear magnetic resonance (TD-NMR) to detect olive oil adulteration with polyunsaturated vegetable oils in filled bottles is proposed. The 1 H transverse relaxation times (T 2 ) of 37 commercial samples were measured using low-field nuclear magnetic resonance (LF-NMR) spectrometer and a unilateral nuclear magnetic resonance (UNMR) sensor. Results obtained with LF-NMR revealed better feasibility when compared with the UNMR sensor, with higher signal-to-noise (S/N) ratio and larger difference in the T 2 decays. Principal component analysis (PCA) exhibited tight and well-separated clusters of pure olive oil (OO), pure soybean oil (SO), and blends of OO/SO (adulterated samples). Soft independent modeling of class analogies analysis (SIMCA) classification model indicated that five brands of olive oil commercialized in Brazil were adulterated with polyunsaturated fatty acids, further confirmed by high-resolution NMR. Overall, LF-NMR provided a fast procedure for screening olive oil authenticity directly in the sealed bottles.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry

Santos¹,

Kock²,

Santos³

et al. 2016

Journal of the Brazilian Chemical Society

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show abstract

“…Eq. [8]). Then the ML estimates of A and are found by maximizing L, or equivalently log L, with respect to A and .…”

Section: Region Of Constant Amplitude and Phasementioning

confidence: 99%

“…For example, in the case of noise filtering the parameter to be estimated is given by the true signal component underlying the noise-corrupted data, whereas in the construction of T 1 and T 2 maps the parameters to be estimated are given by the relaxation time constants (2)(3)(4)(5)(6)(7)(8)(9)(10).…”

mentioning

confidence: 99%

Maximum likelihood estimation of signal amplitude and noise variance from MR data

Sijbers

Dekker

2004

Magnetic Resonance in Med

248

211

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In MRI, the raw data, which are acquired in spatial frequency space, are intrinsically complex valued and corrupted by Gaussian-distributed noise. After applying an inverse Fourier transform, the data remain complex valued and Gaussian distributed. If the signal amplitude is to be estimated, one has two options. It can be estimated directly from the complex valued data set, or one can first perform a magnitude operation on this data set, which changes the distribution of the data from Gaussian to Rician, and estimate the signal amplitude from the obtained magnitude image. Similarly, the noise variance can be estimated from both the complex and magnitude data sets. This article addresses the question whether it is better to use complex valued data or magnitude data for the estimation of these parameters using the maximum likelihood method. As a performance criterion, the mean-squared error (MSE) is used. Magn Reson Med 51:586 -594, 2004.

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“…Provencher's MULTIFIT [37] routine was then used to fit a sum of exponentials to the data, and distinctions between single and multiple exponential fits were based on the statistical tests in the program. The relative weightings for multiple exponential components also were analyzed using Brown's UPEN routines [38,39]. The quality of the fits to the experimental curves was judged from a sum of squares of the residuals.…”

Section: Calculation Of Relaxation Ratesmentioning

confidence: 99%

Electron spin relaxation enhancement measurements of interspin distances in human, porcine, and Rhodobacter electron transfer flavoprotein–ubiquinone oxidoreductase (ETF–QO)

Fielding

Usselman

Watmough

et al. 2008

Journal of Magnetic Resonance

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Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is a membrane-bound electron transfer protein that links primary flavoprotein dehydrogenases with the main respiratory chain. Human, porcine, and Rhodobacter sphaeroides ETF-QO each contain a single [4Fe-4S] 2+,1+ cluster and one equivalent of FAD, which are diamagnetic in the isolated enzyme and become paramagnetic on reduction with the enzymatic electron donor or with dithionite. The anionic flavin semiquinone can be reduced further to diamagnetic hydroquinone. The redox potentials for the three redox couples are so similar that it is not possible to poise the proteins in a state where both the [4Fe-4S] + cluster and the flavoquinone are fully in the paramagnetic form. Inversion recovery was used to measure the electron spin-lattice relaxation rates for the [4Fe-4S] + between 8 and 18 K and for semiquinone between 25 and 65 K. At higher temperatures the spin-lattice relaxation rates for the [4Fe-4S] + were calculated from the temperature-dependent contributions to the continuous wave linewidths. Although mixtures of the redox states are present, it was possible to analyze the enhancement of the electron spin relaxation of the FAD semiquinone signal due to dipolar interaction with the more rapidly relaxing [4Fe-4S] + and obtain point dipole interspin distances of 18.6 ± 1 Å for the three proteins. The point-dipole distances are within experimental uncertainty of the value calculated based on the crystal structure of porcine ETF-QO when spin delocalization is taken into account. The results demonstrate that electron spin relaxation enhancement can be used to measure distances in redox poised proteins even when several redox states are present.

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Uniform-Penalty Inversion of Multiexponential Decay Data

Cited by 232 publications

References 6 publications

Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry

Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry

Maximum likelihood estimation of signal amplitude and noise variance from MR data

Electron spin relaxation enhancement measurements of interspin distances in human, porcine, and Rhodobacter electron transfer flavoprotein–ubiquinone oxidoreductase (ETF–QO)

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