The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Alain Coron - One of the best experts on this subject based on the ideXlab platform.
-
Time-Frequency and Time-Scale Approach to Magnetic Resonance Spectroscopy
Journal of Computational Methods in Sciences and Engineering, 2020Co-Authors: Jeanpierre Antoine, Alain CoronAbstract:We review various applications of time-frequency and time-scale representations of signals in magnetic resonance spectroscopy (MRS). First we give a brief survey of the mathematical tools, essentially the wavelet transform and the Gabor transform, both continuous and discrete. Then we turn to the applications and review the literature on signal correction and rephasing, solvent Peak Suppression, denoising, metabolite quantification, etc. We conclude with some indications on available software.
-
the filtering approach to solvent Peak Suppression in mrs a critical review
Journal of Magnetic Resonance, 2001Co-Authors: Alain Coron, Jeanpierre Antoine, Leentje Vanhamme, Paul Van Hecke, Sabine Van HuffelAbstract:Suppressing the solvent Peak is important in many applications of biomedical NMR spectroscopy in order to quantify the metabolites with a great accuracy. Among the postprocessing methods proposed in the literature, many deal with the concept of filtering. However, several proposals lack a theoretical perspective and some have not been explicitly applied to quantification problems. The present article is intended to bridge this gap: five methods are analyzed from a theoretical perspective. Subsequently the different methods are applied to the same set of data, and then the latter are quantified using the model fitting method AMARES. With our set, the scheme proposed by T. Sundin et al. (J. Magn. Reson. 139(2), 189-204 (1999)) proved to be the most reliable method. (C) 2001 Academic Press.
-
water Peak Suppression time frequency vs time scale approach
Journal of Magnetic Resonance, 2000Co-Authors: Jeanpierre Antoine, Alain Coron, Jeanmarie DereppeAbstract:Wavelets are the most popular time-scale analysis tool. A well-known application of wavelets in nuclear magnetic resonance spectroscopy is water Peak extraction/Suppression. However, spectroscopists are more familiar with frequency than scale. So, from a spectroscopist point of view, a time-scale analysis tool (i.e., wavelets) is not natural and a time-frequency approach would be much more satisfactory. We explain a time-frequency solution to this problem based on Gabor analysis. As the two formalisms are closely linked together we continuously emphasize their similarities and differences. In particular we show that, here, the Gabor method is as efficient as the wavelet approach, and we give some examples. Those remarks also apply to other NMR problems solved previously with the continuous wavelet transform, such as quantification or dynamical phase correction.
Jeanpierre Antoine - One of the best experts on this subject based on the ideXlab platform.
-
Time-Frequency and Time-Scale Approach to Magnetic Resonance Spectroscopy
Journal of Computational Methods in Sciences and Engineering, 2020Co-Authors: Jeanpierre Antoine, Alain CoronAbstract:We review various applications of time-frequency and time-scale representations of signals in magnetic resonance spectroscopy (MRS). First we give a brief survey of the mathematical tools, essentially the wavelet transform and the Gabor transform, both continuous and discrete. Then we turn to the applications and review the literature on signal correction and rephasing, solvent Peak Suppression, denoising, metabolite quantification, etc. We conclude with some indications on available software.
-
the filtering approach to solvent Peak Suppression in mrs a critical review
Journal of Magnetic Resonance, 2001Co-Authors: Alain Coron, Jeanpierre Antoine, Leentje Vanhamme, Paul Van Hecke, Sabine Van HuffelAbstract:Suppressing the solvent Peak is important in many applications of biomedical NMR spectroscopy in order to quantify the metabolites with a great accuracy. Among the postprocessing methods proposed in the literature, many deal with the concept of filtering. However, several proposals lack a theoretical perspective and some have not been explicitly applied to quantification problems. The present article is intended to bridge this gap: five methods are analyzed from a theoretical perspective. Subsequently the different methods are applied to the same set of data, and then the latter are quantified using the model fitting method AMARES. With our set, the scheme proposed by T. Sundin et al. (J. Magn. Reson. 139(2), 189-204 (1999)) proved to be the most reliable method. (C) 2001 Academic Press.
-
water Peak Suppression time frequency vs time scale approach
Journal of Magnetic Resonance, 2000Co-Authors: Jeanpierre Antoine, Alain Coron, Jeanmarie DereppeAbstract:Wavelets are the most popular time-scale analysis tool. A well-known application of wavelets in nuclear magnetic resonance spectroscopy is water Peak extraction/Suppression. However, spectroscopists are more familiar with frequency than scale. So, from a spectroscopist point of view, a time-scale analysis tool (i.e., wavelets) is not natural and a time-frequency approach would be much more satisfactory. We explain a time-frequency solution to this problem based on Gabor analysis. As the two formalisms are closely linked together we continuously emphasize their similarities and differences. In particular we show that, here, the Gabor method is as efficient as the wavelet approach, and we give some examples. Those remarks also apply to other NMR problems solved previously with the continuous wavelet transform, such as quantification or dynamical phase correction.
Arthur Schweiger - One of the best experts on this subject based on the ideXlab platform.
-
Peak Suppression in eseem spectra of multinuclear spin systems
Journal of Magnetic Resonance, 2005Co-Authors: Stefan Stoll, Carlos Calle, George Mitrikas, Arthur SchweigerAbstract:Abstract We have observed a disturbing Suppression effect in three-pulse ESEEM and HYSCORE spectra of systems with more than one nucleus coupled to the electron spin. For such systems, the ESEEM signal contains internuclear combination Peaks of varying intensity. At the same time, the Peaks at the basic ESEEM frequencies are reduced in intensity, up to the point of complete cancellation. For both three-pulse ESEEM and HYSCORE, the amplitude of a Peak of a given nucleus depends not only on its modulation depth parameter k and the τ -dependent blind-spot term b , but also on k and b of all other nuclei. Peaks of nuclei with shallow modulations can be strongly suppressed by nuclei with deep modulations. This cross-Suppression effect explains the observation that HYSCORE 1 H Peaks are often very weak or even undetectable in the presence of strong 14 N Peaks. Due to this distortion of intensities, ESEEM spectra have to be analysed very carefully. We present a theoretical analysis of this effect based on the product rules, numerical computations, and illustrative experimental data on Cu(gly) 2 . In experiments, the impact of this cross Suppression can be alleviated by a proper choice of τ values, remote echo detection, and matched pulses.
-
Novel analytical treatments of electron spin-echo envelope modulation with short and extended pulses
Journal of Magnetic Resonance, 1991Co-Authors: C. Gemperle, Arthur Schweiger, Richard R. ErnstAbstract:Abstract The analytical description of two-pulse electron spin-echo envelope modulation experiments is extended by the derivation of two generalized expressions for the echo amplitude. At first, the effect of a variable position of the observer window is computed for delta function pulses. A new type of Peak Suppression effect, the so-called “observer blind spots,” is discussed. Second, a novel procedure for handling pulses of extended length is introduced. It is based on a pulse representation in terms of a sequence of pulse slices and leads to the first analytical expression that correctly describes an ESEEM experiment performed with pulses of any length, provided the EPR linewidth is much larger than the inverse pulse length. The predicted features are verified experimentally, in particular, the formation of blind spots and the influence of the position and the duration of the observer window.
Jesus Munoz Romero - One of the best experts on this subject based on the ideXlab platform.
-
the determination of 3 nitrophenol and some other aromatic impurities in 4 nitrophenol by reversed phase hplc with Peak Suppression diode array detection
Journal of Pharmaceutical and Biomedical Analysis, 2000Co-Authors: Kazimierz Wrobel, Katarzyna Wrobel, Edith Madai Colunga Urbina, Jesus Munoz RomeroAbstract:Abstract In this work the Peak Suppression technique is used for the determination of 3-nitrophenol and some other aromatic impurities in 4-nitrophenol by reversed phase HPLC with diode array detection. Taking into account the differences between the absorption spectra of the two compounds, two wavelengths were selected in order to obtain the maximum difference between the spectral contribution for 3-nitrophenol and to maintain a small, similar spectral contribution for 4-nitrophenol (the main compound). Then we used the wavelength corresponding to a small spectral contribution of 3-nitrophenol as the reference wavelength. It was shown that taking λ an =266 nm and λ ref =364 nm, a broad elution Peak of 4-nitrophenol was suppressed deconvoluting the Peak of 3-nitrophenol. Moreover, quantitation of 3-nitrophenol was achieved without chemometric tools. Under the proposed conditions the detection limits for 3-nitrophenol and other common impurities of 4-nitrophenol used in the pharmaceutical industry (4-chlorophenol, 4-nitrophenol, 1-chloro-2-nitrobenzene, 1-chloro-4-nitrobenzene, 4,4′-bisfenilether, and 4,4′-dichloroazobenzene) were not significantly affected as compared with respective detection limits evaluated in the absence of 4-nitrophenol and using standard detection conditions ( λ an =280 nm and λ ref =420 nm).
Nicolas A. F. Jaeger - One of the best experts on this subject based on the ideXlab platform.
-
Nested silicon-on-insulator Vernier effect microring resonators
Silicon Photonics XIV, 2019Co-Authors: Mustafa Hammood, Lukas Chrostowski, Ajay Mistry, Nicolas A. F. JaegerAbstract:Vernier effect, series-coupled microring resonators (MRRs) are used to extend the free-spectral-range (FSR) of MRRs. In this work we demonstrate integrating two MRRs in a compact Vernier configuration (compact as compared to previously demonstrated Vernier effect devices). our design was realized by using two waveguide crossings to form a major, outer ring that was coupled to a minor ring nested within the major ring. The ratio of the path length of the major ring to the path length of minor ring was 5:2. The spectral response of the device had an FSR of 27.94 nm, a drop port 3 dB bandwidth of 0.87 nm, a minimum extinction ratio of 16.1 dB, a minimum interstitial Peak Suppression of 10.6 dB, and a footprint of only 540 μm2 .
-
Experimental demonstration of a silicon-on-insulator high-performance double microring filter using MZI-based coupling
Optics Letters, 2015Co-Authors: Robert Boeck, Lukas Chrostowski, Michael Caverley, Nicolas A. F. JaegerAbstract:We have experimentally demonstrated, in silicon, a double microring resonator with Mach–Zehnder interferometer-based coupling that meets many commercial specifications. Our device has a ripple of 0.5 dB, an adjacent channel isolation of at least 41.0 dB, a nonadjacent channel isolation of at least 38.6 dB, an interstitial Peak Suppression of at least 37.5 dB, an express channel isolation of 10.0 dB, and a free spectral range greater than the span of the C-band of 37.23 nm.
-
Thermally tunable quadruple Vernier racetrack resonators.
Optics Letters, 2013Co-Authors: Robert Boeck, Lukas Chrostowski, Nicolas A. F. JaegerAbstract:The spectral responses of series-coupled racetrack resonators exhibiting the Vernier effect have many attractive features as compared to the spectral responses of identical series-coupled racetrack resonators, such as free spectral range (FSR) extension and enhanced wavelength tunability. Here we present experimental results of a thermally tunable quadruple series-coupled silicon racetrack resonator exhibiting the Vernier effect. We thermally tune two of the four racetrack resonators to enable discrete switching of the major Peak by 15.54 nm. Also, our device has an interstitial Peak Suppression of 35.4 dB, a 3 dB bandwidth of 0.45 nm, and an extended FSR of 37.66 nm.
-
Experimental performance of DWDM quadruple Vernier racetrack resonators.
Optics Express, 2013Co-Authors: Robert Boeck, Jonas Flueckiger, Lukas Chrostowski, Nicolas A. F. JaegerAbstract:We demonstrate that one can meet numerous commercial requirements for filters used in dense wavelength-division multiplexing applications using quadruple Vernier racetrack resonators in the silicon-on-insulator platform. Experimental performance shows a ripple of 0.2 dB, an interstitial Peak Suppression of 39.7 dB, an adjacent channel isolation of 37.2 dB, an express channel isolation of 10.2 dB, and a free spectral range of 37.52 nm.
-
High performance Vernier racetrack resonators
Optics Letters, 2012Co-Authors: Robert Boeck, Jonas Flueckiger, Lukas Chrostowski, Nicolas A. F. JaegerAbstract:We demonstrate record performance of series-coupled silicon racetrack resonators exhibiting the Vernier effect. Our device has an interstitial Peak Suppression (IPS) of 25.5 dB, which is 14.5 dB larger than previously reported results. We also demonstrate the relationship between the inter-ring gap distance and the IPS as well as the 3 dB bandwidth (BW) both theoretically and experimentally. Namely, we show that as the inter-ring gap distance increases, the IPS increases and the 3 dB BW decreases.