The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform
Horst Weller - One of the best experts on this subject based on the ideXlab platform.
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relaxivity optimization of a pegylated iron oxide based negative magnetic resonance contrast agent for t2 weighted spin echo imaging
ACS Nano, 2012Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst WellerAbstract:Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the Motional Averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 contrast agents by tuning the cluster size of SPIO nanocrystals.
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relaxivity optimization of a pegylated iron oxide based negative magnetic resonance contrast agent for t2 weighted spin echo imaging
ACS Nano, 2012Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst WellerAbstract:Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the Motional Averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 contrast agents by tuning the cluster size of SPIO nanocrystals.
Louiss Bouchard - One of the best experts on this subject based on the ideXlab platform.
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breakdown of carr purcell meiboom gill spin echoes in inhomogeneous fields
Journal of Chemical Physics, 2018Co-Authors: Nanette N Jarenwattananon, Louiss BouchardAbstract:The Carr-Purcell Meiboom-Gill (CPMG) experiment has been used for decades to measure nuclear-spin transverse (T2) relaxation times. In the presence of magnetic field inhomogeneities, the limit of short interpulse spacings yields the intrinsic T2 time. Here, we show that the signal decay in such experiments exhibits fundamentally different behaviors between liquids and gases. In gases, the CPMG unexpectedly fails to eliminate the inhomogeneous broadening due to the non-Fickian nature of the Motional Averaging.
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breakdown of carr purcell meiboom gill spin echoes in inhomogeneous fields
arXiv: Other Condensed Matter, 2018Co-Authors: Nanette N Jarenwattananon, Louiss BouchardAbstract:The Carr-Purcell Meiboom-Gill (CPMG) experiment has been used for decades to measure nuclear-spin transverse ($T_2$) relaxation times. In the presence of magnetic-field inhomogeneities, the limit of short interpulse spacings yields the intrinsic $T_2$ time. Here we show that the signal decay in such experiments exhibits fundamentally different behaviors between liquids and gases. In gases, CPMG unexpectedly fails to eliminate the inhomogeneous broadening due to the non-Fickian nature of the Motional Averaging.
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Motional Averaging of nuclear resonance in a field gradient
Physical Review Letters, 2015Co-Authors: Nanette N Jarenwattananon, Louiss BouchardAbstract:The traditional view of nuclear-spin decoherence in a field gradient due to molecular self-diffusion is challenged on the basis of temperature dependence of the linewidth, which demonstrates different behaviors between liquids and gases. The conventional theory predicts that in a fluid, linewidth should increase with temperature; however, in gases we observed the opposite behavior. This surprising behavior can be explained using a more detailed theoretical description of the dephasing function that accounts for position autocorrelation effects.
Elmar Poselt - One of the best experts on this subject based on the ideXlab platform.
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relaxivity optimization of a pegylated iron oxide based negative magnetic resonance contrast agent for t2 weighted spin echo imaging
ACS Nano, 2012Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst WellerAbstract:Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the Motional Averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 contrast agents by tuning the cluster size of SPIO nanocrystals.
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relaxivity optimization of a pegylated iron oxide based negative magnetic resonance contrast agent for t2 weighted spin echo imaging
ACS Nano, 2012Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst WellerAbstract:Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the Motional Averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 contrast agents by tuning the cluster size of SPIO nanocrystals.
Johannes Borregaard - One of the best experts on this subject based on the ideXlab platform.
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scalable photonic network architecture based on Motional Averaging in room temperature gas
Nature Communications, 2016Co-Authors: Johannes Borregaard, Michael Zugenmaier, J M Petersen, Heng Shen, Georgios Vasilakis, Kasper Jensen, E S Polzik, Anders S SorensenAbstract:Quantum interfaces between photons and atomic ensembles have emerged as powerful tools for quantum technologies. Efficient storage and retrieval of single photons requires long-lived collective atomic states, which is typically achieved with immobilized atoms. Thermal atomic vapours, which present a simple and scalable resource, have only been used for continuous variable processing or for discrete variable processing on short timescales where atomic motion is negligible. Here we develop a theory based on Motional Averaging to enable room temperature discrete variable quantum memories and coherent single-photon sources. We demonstrate the feasibility of this approach to scalable quantum memories with a proof-of-principle experiment with room temperature atoms contained in microcells with spin-protecting coating, placed inside an optical cavity. The experimental conditions correspond to a few photons per pulse and a long coherence time of the forward scattered photons is demonstrated, which is the essential feature of the Motional Averaging.
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room temperature quantum memory and scalable single photon source based on Motional Averaging
arXiv: Quantum Physics, 2015Co-Authors: Johannes Borregaard, Michael Zugenmaier, J M Petersen, Heng Shen, Georgios Vasilakis, Kasper Jensen, E S Polzik, Anders S SorensenAbstract:Quantum interfaces between photons and ensembles of atoms have emerged as powerful tools for quantum technologies. High fidelity storage and retrieval of a photon in a collective quantum state of many atoms requires long-lived collective superposition states typically achieved with immobilized atoms. Thermal atomic vapors, which present a simple and scalable resource, have been so far only used for continuous variable processing or for discrete variable processing on short time scales where atomic motion is negligible. We develop a theory based on the concept of Motional Averaging to enable room temperature discrete variable quantum memories and coherent single photon sources. We show that by choosing the interaction so that atoms can cross the light beam several times during the interaction and by suitable spectral filtering, we erase the "which atom" information and obtain an efficient and homogenous coupling between all atoms and the light. Heralded single excitations can thus be created and stored as collective spinwaves, which can later be read out to produce coherent single photons in a scalable fashion. We demonstrate the feasibility of this approach to scalable quantum memories with a proof of principle experiment with room temperature atoms contained in microcells with spin protecting coating, placed inside an optical cavity.
Christoph Maslo - One of the best experts on this subject based on the ideXlab platform.
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relaxivity optimization of a pegylated iron oxide based negative magnetic resonance contrast agent for t2 weighted spin echo imaging
ACS Nano, 2012Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst WellerAbstract:Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the Motional Averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 contrast agents by tuning the cluster size of SPIO nanocrystals.
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relaxivity optimization of a pegylated iron oxide based negative magnetic resonance contrast agent for t2 weighted spin echo imaging
ACS Nano, 2012Co-Authors: Elmar Poselt, Hauke Kloust, Ulrich I Tromsdorf, Marcus Janschel, Christoph Hahn, Christoph Maslo, Horst WellerAbstract:Concerning the outer sphere relaxation theory, the sensitivity of a T2 MRI contrast agent, expressed by the transverse relaxivity r2, depends on the diffusion length of water molecules relative to the particle size. For T2-weighted spin–echo imaging, theoretical concepts reveal three regimes regarding the r2 relaxivity depending on the nanocrystal size: the Motional Averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r2 maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T2 contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30–200 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T2 contrast agents by tuning the cluster size of SPIO nanocrystals.