The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Ravinder Reddy - One of the best experts on this subject based on the ideXlab platform.
-
effect of il 1β induced macromolecular depletion on residual Quadrupolar Interaction in articular cartilage
Journal of Magnetic Resonance Imaging, 2002Co-Authors: Arijitt Borthakur, Erik M Shapiro, Jennifer Beers, Sagar Kudchodkar, Bruce J Kneeland, Ravinder ReddyAbstract:Purpose Sodium multiple-quantum filtered (MQF) NMR spectroscopy may potentially be used to measure proteoglycan (PG) depletion in cartilage caused by osteoarthritis (OA). The purpose of this work was to quantify the effect of interleukin-1 (IL-1β)-induced macromolecule depletion on the residual Quadrupolar Interaction (RQI) of sodium in bovine cartilage plugs.
-
detection of residual Quadrupolar Interaction in the human breast in vivo using sodium 23 multiple quantum spectroscopy
Journal of Magnetic Resonance Imaging, 1999Co-Authors: Umamaheswar Duvvuri, John S Leigh, Ravinder ReddyAbstract:Sodium multiple quantum (MQ) spectroscopy of the human breast in vivo was performed. Double quantum (DQ) filtered spectra were used to demonstrate the existence of a non-vanishing (residual) Quadrupolar Interaction in the tissue. Triple quantum (TQ) filtered spectra were used to measure the two time constants associated with the biexponential transverse relaxation times of sodium in biological tissues. The two time constants were found to be 0.64 and 26.57 msec. The potential applications of this finding are discussed. J. Magn. Reson. Imaging 1999;9:391–394. © 1999 Wiley-Liss, Inc.
-
Detection of residual Quadrupolar Interaction in the human breast in vivo using sodium‐23 multiple quantum spectroscopy
Journal of Magnetic Resonance Imaging, 1999Co-Authors: Umamaheswar Duvvuri, John S Leigh, Ravinder ReddyAbstract:Sodium multiple quantum (MQ) spectroscopy of the human breast in vivo was performed. Double quantum (DQ) filtered spectra were used to demonstrate the existence of a non-vanishing (residual) Quadrupolar Interaction in the tissue. Triple quantum (TQ) filtered spectra were used to measure the two time constants associated with the biexponential transverse relaxation times of sodium in biological tissues. The two time constants were found to be 0.64 and 26.57 msec. The potential applications of this finding are discussed. J. Magn. Reson. Imaging 1999;9:391–394. © 1999 Wiley-Liss, Inc.
-
detection of residual Quadrupolar Interaction in human skeletal muscle and brain in vivo via multiple quantum filtered sodium nmr spectra
Magnetic Resonance in Medicine, 1995Co-Authors: Ravinder Reddy, Lizann Bolinger, Meir Shinnar, Elizabeth A Noyszewski, John S LeighAbstract:Using sodium multiple quantum filtered methods, we have, for the first time, demonstrated the presence of residual Quadrupolar Interaction in human skeletal muscle and brain in vivo. Surface coils were used in both skeletal muscle and brain studies on healthy human volunteers. Theoretical analysis shows that even with arbitrary flip angles the double quantum filter retains filtering capability; it passes even rank two quantum coherence more efficiently than odd rank two quantum coherence. Multiple quantum filtered spectra were obtained from the gastrocnemius muscle in the leg and from the parietal lobe region of the brain. In double quantum filtered spectra, we observed different proportions of narrow and broad components with preparation time, while the line shape of triple quantum filtered spectra remained similar to the one observed in isotropic environment. These results suggest that, in human skeletal muscle and brain, sodium ions are bound to some ordered structures.
F. B. Anders - One of the best experts on this subject based on the ideXlab platform.
-
influence of the nuclear electric Quadrupolar Interaction on the coherence time of hole and electron spins confined in semiconductor quantum dots
Physical Review Letters, 2015Co-Authors: Johannes Hackmann, Ph Glasenapp, A. Greilich, Manfred Bayer, F. B. AndersAbstract:: The real-time spin dynamics and the spin noise spectra are calculated for p and n-charged quantum dots within an anisotropic central spin model extended by additional nuclear electric Quadrupolar Interactions and augmented by experimental data. Using realistic estimates for the distribution of coupling constants including an anisotropy parameter, we show that the characteristic long time scale is of the same order for electron and hole spins strongly determined by the Quadrupolar Interactions even though the analytical form of the spin decay differs significantly consistent with our measurements. The low frequency part of the electron spin noise spectrum is approximately 1/3 smaller than those for hole spins as a consequence of the spectral sum rule and the different spectral shapes. This is confirmed by our experimental spectra measured on both types of quantum dot ensembles in the low power limit of the probe laser.
-
Influence of the Nuclear Electric Quadrupolar Interaction on the Coherence Time of Hole and Electron Spins Confined in Semiconductor Quantum Dots
Physical Review Letters, 2015Co-Authors: Johannes Hackmann, Ph Glasenapp, A. Greilich, Manfred Bayer, F. B. AndersAbstract:The real-time spin dynamics and the spin noise spectra are calculated for p and n-charged quantum dots within an anisotropic central spin model extended by additional nuclear electric Quadrupolar Interactions (QC) and augmented by experimental data studied using identical excitation conditions. Using realistic estimates for the distribution of coupling constants including an anisotropy parameter, we show that the characteristic long time scale is of the same order for electron and hole spins strongly determined by the QC even though the analytical form of the spin decay differs significantly consistent with our measurements. The low frequency part of the electron spin noise spectrum is approximately $1/3$ smaller than those for hole spins as a consequence of the spectral sum rule and the different spectral shapes. This is confirmed by our experimental spectra measured on both types of quantum dot ensembles in the low power limit of the probe laser.
John S Leigh - One of the best experts on this subject based on the ideXlab platform.
-
detection of residual Quadrupolar Interaction in the human breast in vivo using sodium 23 multiple quantum spectroscopy
Journal of Magnetic Resonance Imaging, 1999Co-Authors: Umamaheswar Duvvuri, John S Leigh, Ravinder ReddyAbstract:Sodium multiple quantum (MQ) spectroscopy of the human breast in vivo was performed. Double quantum (DQ) filtered spectra were used to demonstrate the existence of a non-vanishing (residual) Quadrupolar Interaction in the tissue. Triple quantum (TQ) filtered spectra were used to measure the two time constants associated with the biexponential transverse relaxation times of sodium in biological tissues. The two time constants were found to be 0.64 and 26.57 msec. The potential applications of this finding are discussed. J. Magn. Reson. Imaging 1999;9:391–394. © 1999 Wiley-Liss, Inc.
-
Detection of residual Quadrupolar Interaction in the human breast in vivo using sodium‐23 multiple quantum spectroscopy
Journal of Magnetic Resonance Imaging, 1999Co-Authors: Umamaheswar Duvvuri, John S Leigh, Ravinder ReddyAbstract:Sodium multiple quantum (MQ) spectroscopy of the human breast in vivo was performed. Double quantum (DQ) filtered spectra were used to demonstrate the existence of a non-vanishing (residual) Quadrupolar Interaction in the tissue. Triple quantum (TQ) filtered spectra were used to measure the two time constants associated with the biexponential transverse relaxation times of sodium in biological tissues. The two time constants were found to be 0.64 and 26.57 msec. The potential applications of this finding are discussed. J. Magn. Reson. Imaging 1999;9:391–394. © 1999 Wiley-Liss, Inc.
-
detection of residual Quadrupolar Interaction in human skeletal muscle and brain in vivo via multiple quantum filtered sodium nmr spectra
Magnetic Resonance in Medicine, 1995Co-Authors: Ravinder Reddy, Lizann Bolinger, Meir Shinnar, Elizabeth A Noyszewski, John S LeighAbstract:Using sodium multiple quantum filtered methods, we have, for the first time, demonstrated the presence of residual Quadrupolar Interaction in human skeletal muscle and brain in vivo. Surface coils were used in both skeletal muscle and brain studies on healthy human volunteers. Theoretical analysis shows that even with arbitrary flip angles the double quantum filter retains filtering capability; it passes even rank two quantum coherence more efficiently than odd rank two quantum coherence. Multiple quantum filtered spectra were obtained from the gastrocnemius muscle in the leg and from the parietal lobe region of the brain. In double quantum filtered spectra, we observed different proportions of narrow and broad components with preparation time, while the line shape of triple quantum filtered spectra remained similar to the one observed in isotropic environment. These results suggest that, in human skeletal muscle and brain, sodium ions are bound to some ordered structures.
Gil Navon - One of the best experts on this subject based on the ideXlab platform.
-
measurement of dipolar Interaction of Quadrupolar nuclei in solution using multiple quantum nmr spectroscopy
Journal of Magnetic Resonance Series A, 1996Co-Authors: Uzi Eliav, Gil NavonAbstract:Abstract Relaxation resulting from the modulation of dipolar Interaction is commonly used for estimating distances in molecules in solutions. However, for most nuclei with spin I > 1 2 the single-quantum-transition relaxation by dipolar Interaction is masked by Quadrupolar relaxation. In the present study, it is shown that even in systems where single-quantum relaxation times are dominated by Quadrupolar Interaction, dipolar relaxation can be measured by following the − m [formula] m transitions. This is demonstrated for 7 Li in the complex [Li–Kryptofix 211] + X − (X = Cl, Br) dissolved in glycerol at temperatures for which slow motion prevails and no 1 H– 7 Li NOE can be observed. The relaxation times that are most important for the assessment of the dipolar Interaction of 7 Li are − 1 2 [formula] 1 2 and −[formula][formula][formula]and they are measured by multiple-quantum-filtration techniques. For estimating the Quadrupolar Interaction, the relaxation times of the populations and those of the transitions ± 1 2 [formula]±[formula]were measured. The longitudinal and transverse relaxation times of 6 Li as well as the 1 H– 6 Li NOE were also measured and, together with the 7 Li measurements, were used to obtain the strengths of dipolar ( D ) and Quadrupolar (χ) Interactions. The experimental data were analyzed using several models to describe the motion. The model that gave the best fit and resulted in parameters that were physically meaningful encompassed a whole-body isotropic motion as well as internal anisotropic motion. For this particular model, the following values for the Quadrupolar and the dipolar Interactions strength were obtained: D ( 7 Li)/2π = 6.8 kHz, χ( 7 Li)/2π = 85 kHz and D ( 6 Li)/2π = 1.4 kHz, χ( 6 Li)/2π = 2.6 kHz. From the value of D , an estimate of the average lithium–proton distance was calculated to be 3.3 A, which is in fair agreement with crystallographic studies. The sizes of the Quadrupolar and dipolar Interactions were independently confirmed by the 7 Li NMR powder spectra of the complexes that were used for the solution studies.
-
Quadrupole-echo techniques in multiple-quantum-filtered NMR spectroscopy of heterogeneous systems
Journal of Magnetic Resonance Series A, 1995Co-Authors: Uzi Eliav, Gil NavonAbstract:Abstract Multiple-quantum-filtered quadrupole-echo pulse sequences for spin I = 1 and I = 3 2 are suggested. A general condition for obtaining simultaneously Zeeman and Quadrupolar echo is formulated. A theoretical analysis of the various pulse sequences was performed on the basis of second-order perturbation approximation of the Liouville equation for the density matrix. The extent of refocusing as a function of the ratio of the residual Quadrupolar Interaction and the relaxation rates was calculated. Experimental results are presented for 2H and 23Na in cartilage as an example of a heterogeneous system with residual Quadrupolar Interaction. The difference between relaxation times measured by the multiple-quantum-filtered echo techniques and those measured by conventional multiple-quantum-filtered NMR spectroscopy is a simple diagnostic of anisotropic motion that leads to a residual Quadrupolar Interaction. The results of the echo experiments are compared with the relaxation times computed on the basis of lineshape analysis of double-quantum-filtered spectra of a heterogeneous system.
-
Detection of Anisotropy in Cartilage Using 2H Double-Quantum-Filtered NMR-Spectroscopy
Journal of Magnetic Resonance Series B, 1995Co-Authors: Yehuda Sharf, Uzi Eliav, Hadassah Shinar, Gil NavonAbstract:Double-quantum-filtered (DQF) NMR spectroscopy of I = 1 spin systems is a diagnostic tool for the detection of anisotropy in macroscopically disordered systems. For deuterium, this method reveals the presence of a residual Quadrupolar Interaction for D2O in bovine nasal cartilage. This tissue is not macroscopically ordered and the Quadrupolar splitting is not resolved. Fitting the calculated spectral lineshapes to the experimental results was possible only when a distribution of the residual Quadrupolar Interaction, omega(q), was assumed. The series of DQF lineshapes obtained for different creation times in the DQF experiment could be fitted using a single set of three parameters: the average residual Quadrupolar Interaction ωq/2π = 110 Hz, its standard deviation Δωq/2π = 73 Hz, and the transverse relaxation rate of 63 s−1. Separate deuterium DQF measurements for the constituents of the cartilage, collagen, and chondroitin sulfate indicated that the DQF spectra of cartilage are the result of anisotropic motion of D2O due to binding to the fibrous collagen in the tissue.
D Siminovitch - One of the best experts on this subject based on the ideXlab platform.
-
an optimal strategy for recovering the deuterium 2h Quadrupolar Interaction under magic angle spinning nmr
Solid State Nuclear Magnetic Resonance, 2001Co-Authors: Harold C. Jarrell, D SiminovitchAbstract:Abstract By exploiting the homology in the form of the truncated high-field homonuclear dipole–dipole and quadrupole coupling Hamiltonians, we have previously demonstrated that a simple adaptation of a rotor-synchronized pulse sequence (DRAMA) used for the recovery of dipole–dipole couplings can also be used to resurrect quadrupole couplings (QUADRAMA). In the canonical implementation of these recovery pulse sequences, the couplings are not significantly scaled down from their static sample values. While such minimal scaling is of course desirable in the recovery of typical homonuclear dipolar couplings ( ≤ 2 kHz) and small quadrupole couplings, it is clearly not ideal for the recovery of the much larger quadrupole couplings (20–200 kHz) often encountered in solid-state 2H NMR. In such a case, some prior knowledge of the order of magnitude of the coupling is required to optimize the experimental conditions for QUADRAMA. In order to overcome this drawback, in this study, we have developed a general and optimized strategy for implementing the QUADRAMA technique which does not require any knowledge of the size of the coupling νQ. Experimental tests of the optimized protocol demonstrate that by judicious choices of a combination of scaling factors and recoupling times, 2H quadrupole couplings ranging over an order of magnitude from 3 to 42 kHz can be measured. Since this optimized protocol can reliably be used to recover couplings over a broad range, it expands the range of systems accessible to study by 2H NMR into a realm where static sample NMR and simple MAS NMR may fail.
-
reintroduction of the Quadrupolar Interaction under magic angle spinning nmr
Chemical Physics Letters, 1999Co-Authors: Harold C. Jarrell, D SiminovitchAbstract:Abstract The anisotropy in the dipole–dipole and quadrupole couplings are averaged out in magic-angle spinning (MAS) NMR experiments. Under conditions of axial symmetry (η=0), we exploit the homologous forms of the respective coupling Hamiltonians to show that the quadrupole coupling can also be resurrected by a simple adaptation of a rotor-synchronized pulse sequence previously proposed for the recovery of dipole–dipole couplings. We develop the theory for the recovery of the quadrupole couplings, and then use numerical simulations of the Quadrupolar (double-quantum) dephasing observed in the 2 H MAS NMR spectra of lipid systems to extract the Quadrupolar splitting.
-
Reintroduction of the Quadrupolar Interaction under magic-angle spinning NMR
Chemical Physics Letters, 1999Co-Authors: Harold C. Jarrell, D SiminovitchAbstract:The anisotropy in the dipole-dipole and quadrupole couplings are averaged out in magic-angle spinning (MAS) NMR experiments, Under conditions of axial symmetry (eta = 0), we exploit the homologous forms of the respective coupling Hamiltonians to show that the quadrupole coupling can also be resurrected by a simple adaptation of a rotor-synchronized pulse sequence previously proposed for the recovery of dipole-dipole couplings. We develop the theory for the recovery of the quadrupole couplings, and then use numerical simulations of the Quadrupolar (double-quantum) dephasing observed in the H-2 MAS NMR spectra of lipid systems to extract the Quadrupolar splitting. (C) 1999 Elsevier Science B.V. All rights reserved.
