The Experts below are selected from a list of 382308 Experts worldwide ranked by ideXlab platform
Jun Shen - One of the best experts on this subject based on the ideXlab platform.
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13C saturation Transfer Effect of carbon dioxide–bicarbonate exchange catalyzed by carbonic anhydrase in vivo
Magnetic resonance in medicine, 2008Co-Authors: Jehoon Yang, Sujata Singh, Jun ShenAbstract:Carbonic anhydrase catalyzes reversible hydration of carbon dioxide and dehydration of bicarbonate. In this article we report that the rapid exchange catalyzed by carbonic anhydrase causes a large magnetization (saturation) Transfer Effect on the 13C signal of bicarbonate at 160.7 ppm in vivo when the resonance of the undetectable carbon dioxide at 125.0 ppm is irradiated with RF pulses. In isoflurane-anesthetized adult rat brain the unidirectional, pseudo first-order rate constant of this exchange in the dehydration direction was determined to be 0.47 ± 0.05 sec−1 following intravenous infusion of uniformly 13C-labeled glucose for labeling bicarbonate. Intralateral ventricular administration of the highly specific carbonic anhydrase inhibitor acetazolamide, which is a drug used for treating glaucoma and epilepsy, was also shown to significantly attenuate the observed 13C magnetization Transfer Effect of the carbon dioxide–bicarbonate exchange in the rat brain. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc.
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Inverse polarization Transfer for detecting in vivo 13C magnetization Transfer Effect of specific enzyme reactions in 1H spectra.
Magnetic resonance imaging, 2007Co-Authors: Jehoon Yang, Jun ShenAbstract:Abstract The wide chemical shift dispersion and long T1 of 13C have allowed determination of in vivo magnetization Transfer Effects caused by aspartate aminoTransferase and lactate dehydrogenase reactions using 13C magnetic resonance spectroscopy. In this report, we demonstrate that these Effects can be observed in the proton spectra by Transferring the equilibrium magnetization of 13C via the one-bond scalar coupling between 13C and 1H using an inverse insensitive nuclei enhanced by polarization Transfer-based heteronuclear polarization Transfer method. This inverse method allows a combination of the advantages of the long 13C T1 for maximum magnetization Transfer and the high sensitivity of proton detection. The feasibility of this in vivo inverse polarization Transfer approach was evaluated for detecting the 13C magnetization Transfer Effect of aspartate aminoTransferase and lactate dehydrogenase reactions from a 72.5-μl voxel in the rat brain at 11.7 T.
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In vivo 13C saturation Transfer Effect of the lactate dehydrogenase reaction.
Magnetic resonance in medicine, 2007Co-Authors: Jehoon Yang, Jun ShenAbstract:Lactate dehydrogenase (LDH, EC 1.1.1.27) catalyzes an exchange reaction between pyruvate and lactate. It is demonstrated here that this reaction is sufficiently fast to cause a significant magnetization (saturation) Transfer Effect when the 13C resonance of pyruvate is saturated by a continuous-wave (CW) RF pulse. Infusion of [2-13C]glucose was used to allow labeling of pyruvate C2 at 207.9 ppm to determine the pseudo first-order rate constant of the unidirectional lactate pyruvate flux in vivo. During systemic administration of GABAA receptor antagonist bicuculline, this pseudo first-order rate constant was determined to be 0.08 ± 0.01 s−1 (mean ± SD, N = 4) in halothane-anesthetized adult rat brains. In 9L and C6 rat glioma models, the 13C saturation Transfer Effect of the LDH reaction was also detected in vivo. Our results demonstrate that the 13C magnetization Transfer Effect of the LDH reaction may be useful as a novel marker for utilizing noninvasive in vivo MRS to study many physiological and pathological conditions, such as cancer. Magn Reson Med 57:258–264, 2007. © 2007 Wiley-Liss, Inc.
Jehoon Yang - One of the best experts on this subject based on the ideXlab platform.
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13C saturation Transfer Effect of carbon dioxide–bicarbonate exchange catalyzed by carbonic anhydrase in vivo
Magnetic resonance in medicine, 2008Co-Authors: Jehoon Yang, Sujata Singh, Jun ShenAbstract:Carbonic anhydrase catalyzes reversible hydration of carbon dioxide and dehydration of bicarbonate. In this article we report that the rapid exchange catalyzed by carbonic anhydrase causes a large magnetization (saturation) Transfer Effect on the 13C signal of bicarbonate at 160.7 ppm in vivo when the resonance of the undetectable carbon dioxide at 125.0 ppm is irradiated with RF pulses. In isoflurane-anesthetized adult rat brain the unidirectional, pseudo first-order rate constant of this exchange in the dehydration direction was determined to be 0.47 ± 0.05 sec−1 following intravenous infusion of uniformly 13C-labeled glucose for labeling bicarbonate. Intralateral ventricular administration of the highly specific carbonic anhydrase inhibitor acetazolamide, which is a drug used for treating glaucoma and epilepsy, was also shown to significantly attenuate the observed 13C magnetization Transfer Effect of the carbon dioxide–bicarbonate exchange in the rat brain. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc.
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Inverse polarization Transfer for detecting in vivo 13C magnetization Transfer Effect of specific enzyme reactions in 1H spectra.
Magnetic resonance imaging, 2007Co-Authors: Jehoon Yang, Jun ShenAbstract:Abstract The wide chemical shift dispersion and long T1 of 13C have allowed determination of in vivo magnetization Transfer Effects caused by aspartate aminoTransferase and lactate dehydrogenase reactions using 13C magnetic resonance spectroscopy. In this report, we demonstrate that these Effects can be observed in the proton spectra by Transferring the equilibrium magnetization of 13C via the one-bond scalar coupling between 13C and 1H using an inverse insensitive nuclei enhanced by polarization Transfer-based heteronuclear polarization Transfer method. This inverse method allows a combination of the advantages of the long 13C T1 for maximum magnetization Transfer and the high sensitivity of proton detection. The feasibility of this in vivo inverse polarization Transfer approach was evaluated for detecting the 13C magnetization Transfer Effect of aspartate aminoTransferase and lactate dehydrogenase reactions from a 72.5-μl voxel in the rat brain at 11.7 T.
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In vivo 13C saturation Transfer Effect of the lactate dehydrogenase reaction.
Magnetic resonance in medicine, 2007Co-Authors: Jehoon Yang, Jun ShenAbstract:Lactate dehydrogenase (LDH, EC 1.1.1.27) catalyzes an exchange reaction between pyruvate and lactate. It is demonstrated here that this reaction is sufficiently fast to cause a significant magnetization (saturation) Transfer Effect when the 13C resonance of pyruvate is saturated by a continuous-wave (CW) RF pulse. Infusion of [2-13C]glucose was used to allow labeling of pyruvate C2 at 207.9 ppm to determine the pseudo first-order rate constant of the unidirectional lactate pyruvate flux in vivo. During systemic administration of GABAA receptor antagonist bicuculline, this pseudo first-order rate constant was determined to be 0.08 ± 0.01 s−1 (mean ± SD, N = 4) in halothane-anesthetized adult rat brains. In 9L and C6 rat glioma models, the 13C saturation Transfer Effect of the LDH reaction was also detected in vivo. Our results demonstrate that the 13C magnetization Transfer Effect of the LDH reaction may be useful as a novel marker for utilizing noninvasive in vivo MRS to study many physiological and pathological conditions, such as cancer. Magn Reson Med 57:258–264, 2007. © 2007 Wiley-Liss, Inc.
J. M. Rubi - One of the best experts on this subject based on the ideXlab platform.
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Magnetization reversal driven by spin injection: A diffusive spin-Transfer Effect
Physical Review B, 2008Co-Authors: Jean-eric Wegrowe, S. M. Santos, M.-c. Ciornei, Henri-jean Drouhin, J. M. RubiAbstract:An out-of-equilibrium description of spin-Transfer Effect is proposed, based on the spin-injection mechanism occurring at the junction with a ferromagnet. The Effect of spin injection is to locally modify, in the ferromagnetic configuration space, the density of magnetic moments. The corresponding gradient leads to a currentdependent diffusion process of magnetization. In order to describe this Effect, the dynamics of the magnetization of a ferromagnetic single domain is reconsidered in the framework of the thermokinetic theory of mesoscopic systems. Assuming an Onsager cross coefficient that couples the currents, it is shown that spindependent electric transport leads to a correction of the Landau–Lifshitz–Gilbert equation of the ferromagnetic order parameter with supplementary diffusion terms. The consequence of spin injection in terms of the activation process of the ferromagnet is deduced, and the expressions of the Effective energy barrier and of the critical current are derived. Magnetic fluctuations are calculated: the correction to the fluctuations is similar to that predicted for the activation. These predictions are consistent with the measurements of spin Transfer obtained both in the activation regime and for ferromagnetic resonance under spin injection.
Kangping Yan - One of the best experts on this subject based on the ideXlab platform.
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The phase Transfer Effect of sulfur in lithium–sulfur batteries
RSC Advances, 2019Co-Authors: Ziyi Deng, Lei Sun, Yan Sun, Chunhui Luo, Qiang Zhao, Kangping YanAbstract:Lithium–sulfur (Li–S) batteries are considered to be among the most promising energy storage technologies owing to their high theoretical capacity (1675 mA h g−1). At present, however, discharge mechanisms are complicated and remain a controversial issue. In this work, elemental sulfur, used as an electrical insulator for the cathode, was introduced into batteries for its potential chemical reactions in the electrolyte. A film, prepared by loading elemental sulfur onto glass fiber, was introduced as an interlayer in a Li–S battery. The results demonstrate that elemental sulfur may be reduced to polysulfides even when it functions as an electrical insulator for the cathode. Furthermore, it can improve the overall capacity of the Li–S battery and cycle life. This was verified by simulating the phase equilibrium of the chemical system in Li–S batteries using HSC Chemistry software. We hypothesize that the insulating elemental sulfur could be reduced by polysulfides generated on the cathode, after which they are dissolved in the electrolyte and participate in cathode reactions. This phase Transfer Effect of sulfur in Li–S batteries revealed a chemical equilibrium in the electrolyte of the Li–S battery, which may form a chemical path embedded into the discharge process of Li–S batteries.
Jean-eric Wegrowe - One of the best experts on this subject based on the ideXlab platform.
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Magnetization reversal driven by spin injection: A diffusive spin-Transfer Effect
Physical Review B, 2008Co-Authors: Jean-eric Wegrowe, S. M. Santos, M.-c. Ciornei, Henri-jean Drouhin, J. M. RubiAbstract:An out-of-equilibrium description of spin-Transfer Effect is proposed, based on the spin-injection mechanism occurring at the junction with a ferromagnet. The Effect of spin injection is to locally modify, in the ferromagnetic configuration space, the density of magnetic moments. The corresponding gradient leads to a currentdependent diffusion process of magnetization. In order to describe this Effect, the dynamics of the magnetization of a ferromagnetic single domain is reconsidered in the framework of the thermokinetic theory of mesoscopic systems. Assuming an Onsager cross coefficient that couples the currents, it is shown that spindependent electric transport leads to a correction of the Landau–Lifshitz–Gilbert equation of the ferromagnetic order parameter with supplementary diffusion terms. The consequence of spin injection in terms of the activation process of the ferromagnet is deduced, and the expressions of the Effective energy barrier and of the critical current are derived. Magnetic fluctuations are calculated: the correction to the fluctuations is similar to that predicted for the activation. These predictions are consistent with the measurements of spin Transfer obtained both in the activation regime and for ferromagnetic resonance under spin injection.
