The Experts below are selected from a list of 3621714 Experts worldwide ranked by ideXlab platform
James A Sorenson - One of the best experts on this subject based on the ideXlab platform.
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off resonance spin locking for mr imaging
Magnetic Resonance in Medicine, 1994Co-Authors: Giles E Santyr, Jefferson E Fairbanks, Frederick Kelcz, James A SorensonAbstract:: Off-resonance spin locking is investigated as a low power method for achieving low field spin-lattice relaxation contrast using high field clinical MR imaging systems (e.g., 1.5 tesla). Spin-lattice relaxation times and equilibrium magnetizations in the off-resonance rotating frame (T1 rho(off), beta) were measured for tissue-mimicking phantom materials as a function of the ratio of the amplitude to the resonance offset of the spin-locking pulse (f1/delta). The phantom materials consisted of vegetable oil to simulate fat and two different gels containing 2% and 4% agar to simulate nonfatty tissues with different macromolecular compositions. These measurements were used to verify a signal strength equation for a multislice off-resonance spin-locking technique implemented on a clinical MR imaging system operating at 1.5 tesla. Although the oil showed little change in image contrast with increasing f1/delta, the two gels demonstrated a strong variation which provided improved discrimination compared to T1-weighted imaging. Off-resonance spin locking is suggested as a method for improving delineation of breast lesions and a preliminary clinical example from a patient volunteer is presented.
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Off‐resonance spin locking for MR imaging
Magnetic Resonance in Medicine, 1994Co-Authors: Giles E Santyr, E. Jefferson Fairbanks, Frederick Kelcz, James A SorensonAbstract:: Off-resonance spin locking is investigated as a low power method for achieving low field spin-lattice relaxation contrast using high field clinical MR imaging systems (e.g., 1.5 tesla). Spin-lattice relaxation times and equilibrium magnetizations in the off-resonance rotating frame (T1 rho(off), beta) were measured for tissue-mimicking phantom materials as a function of the ratio of the amplitude to the resonance offset of the spin-locking pulse (f1/delta). The phantom materials consisted of vegetable oil to simulate fat and two different gels containing 2% and 4% agar to simulate nonfatty tissues with different macromolecular compositions. These measurements were used to verify a signal strength equation for a multislice off-resonance spin-locking technique implemented on a clinical MR imaging system operating at 1.5 tesla. Although the oil showed little change in image contrast with increasing f1/delta, the two gels demonstrated a strong variation which provided improved discrimination compared to T1-weighted imaging. Off-resonance spin locking is suggested as a method for improving delineation of breast lesions and a preliminary clinical example from a patient volunteer is presented.
Giles E Santyr - One of the best experts on this subject based on the ideXlab platform.
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off resonance spin locking for mr imaging
Magnetic Resonance in Medicine, 1994Co-Authors: Giles E Santyr, Jefferson E Fairbanks, Frederick Kelcz, James A SorensonAbstract:: Off-resonance spin locking is investigated as a low power method for achieving low field spin-lattice relaxation contrast using high field clinical MR imaging systems (e.g., 1.5 tesla). Spin-lattice relaxation times and equilibrium magnetizations in the off-resonance rotating frame (T1 rho(off), beta) were measured for tissue-mimicking phantom materials as a function of the ratio of the amplitude to the resonance offset of the spin-locking pulse (f1/delta). The phantom materials consisted of vegetable oil to simulate fat and two different gels containing 2% and 4% agar to simulate nonfatty tissues with different macromolecular compositions. These measurements were used to verify a signal strength equation for a multislice off-resonance spin-locking technique implemented on a clinical MR imaging system operating at 1.5 tesla. Although the oil showed little change in image contrast with increasing f1/delta, the two gels demonstrated a strong variation which provided improved discrimination compared to T1-weighted imaging. Off-resonance spin locking is suggested as a method for improving delineation of breast lesions and a preliminary clinical example from a patient volunteer is presented.
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Off‐resonance spin locking for MR imaging
Magnetic Resonance in Medicine, 1994Co-Authors: Giles E Santyr, E. Jefferson Fairbanks, Frederick Kelcz, James A SorensonAbstract:: Off-resonance spin locking is investigated as a low power method for achieving low field spin-lattice relaxation contrast using high field clinical MR imaging systems (e.g., 1.5 tesla). Spin-lattice relaxation times and equilibrium magnetizations in the off-resonance rotating frame (T1 rho(off), beta) were measured for tissue-mimicking phantom materials as a function of the ratio of the amplitude to the resonance offset of the spin-locking pulse (f1/delta). The phantom materials consisted of vegetable oil to simulate fat and two different gels containing 2% and 4% agar to simulate nonfatty tissues with different macromolecular compositions. These measurements were used to verify a signal strength equation for a multislice off-resonance spin-locking technique implemented on a clinical MR imaging system operating at 1.5 tesla. Although the oil showed little change in image contrast with increasing f1/delta, the two gels demonstrated a strong variation which provided improved discrimination compared to T1-weighted imaging. Off-resonance spin locking is suggested as a method for improving delineation of breast lesions and a preliminary clinical example from a patient volunteer is presented.
James Rosenfeld - One of the best experts on this subject based on the ideXlab platform.
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The Long‐Run Performance of Sponsored and Conventional Spin‐Offs
Financial Management, 2010Co-Authors: April Klein, James RosenfeldAbstract:A sponsored Spin-off takes place when an equity stake in a subsidiary is sold to an outside investor before going public. The stock return performance of a sample of 57 sponsored Spin-offs from 1994 to 2005 is significantly negative over a three-year period following the Spin-off date. The parent firms' stock performance for the year preceding (following) the Spin-off date are below average (average) suggesting that their earlier performances were adversely affected by their subsidiaries and motivated the parents to spin them off. We also find that parent firms underinvest in the subsidiary prior to the Spin-off, which could have motivated the subsidiary to seek outside funding sources before going public.
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The Long-Run Performance of Sponsored and Conventional Spin-offs
SSRN Electronic Journal, 2008Co-Authors: April Klein, James RosenfeldAbstract:Unlike a conventional Spin-off, a sponsored Spin-off takes place when the subsidiary to be divested sells an equity stake to an outside investor before going public, thereby receiving a substantial capital infusion. We find that the stock return performance of a sample of 57 sponsored Spin-offs from 1994 through 2005 is significantly negative over a three-year period following the Spin-off date. In contrast, 182 conventional Spin-offs over same interval record an average return performance. The parent firms' stock performance for the year preceding (following) the Spin-off date is below-average (average), suggesting that their earlier performance was adversely affected by the subsidiary and motivated the parent to spin it off. In support of this contention, we find that parent firms tended to under-invest in the subsidiary prior to the Spin-off, due to the subsidiary's limited growth opportunities. This under-investment, in turn, could have motivated the subsidiary to seek outside funding sources before going public.
Thomas Schleich - One of the best experts on this subject based on the ideXlab platform.
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off resonance rotating frame nuclear overhauser effect spectroscopy
Journal of Magnetic Resonance Series A, 1994Co-Authors: Kazuo Kuwata, Thomas SchleichAbstract:The incorporation of off-resonance spin-lock effects into the ROESY experiment enables the evaluation of nuclear motion and internuclear distances in macromolecules by employing the functional dependence of the cross-peak intensity on off-resonance spin-lock frequency. The salient difference between the off-resonance ROESY and the ROESY experiments is that the on-resonance spin lock was replaced by an off-resonance spin lock applied at frequency νoff and at field strength B2 delivered in the form of a shifted laminar pulse. Variation of νoff at constant B2 creates a suite of two-dimensional spectra with frequency-dependent dispersion behavior in the cross-peak intensity established by the interacting spin-12 nuclei. Simulations are presented describing the functional dependence of cross-peak intensity dispersion behavior on macromolecular parameters. This experiment, designated O-ROESY, was implemented in compensated form and yields an amplitude-corrected cross-peak intensity dispersion curve with a smoothly increasing NOESY contribution, at the expense of ROESY, as the off-resonance spin-lock frequency is increased. Application of the O-ROESY experiment was made to lysozyme, demonstrating the feasibility of obtaining the correlation time of specific internuclear vectors, the internuclear vector order parameter, the correlation time of overall reorientational motion, and the relative internuclear distance, from an analysis of O-ROESY cross-peak intensity dispersion curve behavior for several Cα proton pairs in the stable β-strand region of the protein.
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Off-Resonance Rotating Frame Spin—Lattice Relaxation
In Vivo Spectroscopy, 1992Co-Authors: Thomas Schleich, G. Herbert Caines, Jan M. RydzewskiAbstract:The off-resonance rotating frame spin-lattice relaxation experiment represents a class of magnetic resonance techniques in which a low-power, continuous-wave radiofrequency (RF) field is applied off-resonance from a selected resonance. Application of such an irradiation field establishes nuclear spin polarization along an effective field inclined at an angle Θ away from the z axis of the rotating frame. In its original form, this approach was employed for the determination of the rotational correlation time, i.e., the rotational diffusion characteristics of a reorienting macromolecule (James et al., 1978; Schleich et al., 1989). More generally, the off-resonance rotating frame spin-lattice relaxation experiment can be thought of as a form of off-resonance saturation, in which a selected resonance is either completely or partially saturated. Viewed in these terms, the off-resonance rotating frame spin-lattice relaxation formalism, modified to include magnetization transfer phenomena, may be used to obtain chemical exchange kinetic and magnetic cross-relaxation information.
A. O. Sboychakov - One of the best experts on this subject based on the ideXlab platform.
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Dynamical spin susceptibility of a spin-valley half-metal
Physical Review B, 2020Co-Authors: D. A. Khokhlov, A. L. Rakhmanov, A. V. Rozhkov, A. O. SboychakovAbstract:A few years ago we predicted theoretically that in systems with nesting of the Fermi surface the spin-valley half-metal has lower energy than the spin density wave state. In this paper we suggest a possible way to distinguish these phases experimentally. We calculate dynamical spin susceptibility tensor for both states in the framework of the Kubo formalism. Discussed phases have different numbers of the bands: four bands in the spin-valley half-metal and only two bands in the spin density wave. Therefore, their susceptibilities, as functions of frequency, have different number of peaks. Besides, the spin-valley half-metal does not have rotational symmetry, thus, in general the off-diagonal components of susceptibility tensor are non-zero. The spin density wave obeys robust rotational symmetry and off-diagonal components of the susceptibility tensor are zero. These characteristic features can be observed in experiments with inelastic neutron scattering.
