1
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Clericò V, Wójcik P, Vezzosi A, Rocci M, Demontis V, Zannier V, Díaz-Fernández Á, Díaz E, Bellani V, Domínguez-Adame F, Diez E, Sorba L, Bertoni A, Goldoni G, Rossella F. Spin-Resolved Magneto-Tunneling and Giant Anisotropic g-Factor in Broken Gap InAs-GaSb Core-Shell Nanowires. Nano Lett 2024; 24:790-796. [PMID: 38189790 PMCID: PMC10811674 DOI: 10.1021/acs.nanolett.3c02559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 12/20/2023] [Accepted: 12/26/2023] [Indexed: 01/09/2024]
Abstract
We experimentally and computationally investigate the magneto-conductance across the radial heterojunction of InAs-GaSb core-shell nanowires under a magnetic field, B, up to 30 T and at temperatures in the range 4.2-200 K. The observed double-peak negative differential conductance markedly blue-shifts with increasing B. The doublet accounts for spin-polarized currents through the Zeeman split channels of the InAs (GaSb) conduction (valence) band and exhibits strong anisotropy with respect to B orientation and marked temperature dependence. Envelope function approximation and a semiclassical (WKB) approach allow to compute the magnetic quantum states of InAs and GaSb sections of the nanowire and to estimate the B-dependent tunneling current across the broken-gap interface. Disentangling different magneto-transport channels and a thermally activated valence-to-valence band transport current, we extract the g-factor from the spin-up and spin-down dI/dV branch dispersion, revealing a giant, strongly anisotropic g-factor in excess of 60 (100) for the radial (tilted) field configurations.
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Affiliation(s)
- Vito Clericò
- Nanolab-Nanotechnology
Group, Departamento de Física Fundamental, Universidad de Salamanca, Plaza de la Merced, s/n., 37008-Salamanca, Spain
| | - Pawel Wójcik
- AGH
University of Krakow, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Krakow, Poland
| | - Andrea Vezzosi
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via Campi 213/a, I-41125 Modena, Italy
| | - Mirko Rocci
- NEST,
Scuola Normale Superiore e Istituto di Nanoscienze-CNR, Piazza san Silvestro 12, I-56127 Pisa, Italy
| | - Valeria Demontis
- NEST,
Scuola Normale Superiore e Istituto di Nanoscienze-CNR, Piazza san Silvestro 12, I-56127 Pisa, Italy
- Department
of Physics, University of Cagliari, S.P. Monserrato-Sestu, Monserrato, 09042, Italy
| | - Valentina Zannier
- NEST,
Scuola Normale Superiore e Istituto di Nanoscienze-CNR, Piazza san Silvestro 12, I-56127 Pisa, Italy
| | - Álvaro Díaz-Fernández
- GISC, Departamento
de Física de Materiales, Universidad
Complutense de Madrid, Avenida Complutense, s/n, Ciudad Universitaria, 28040 Madrid, Spain
| | - Elena Díaz
- GISC, Departamento
de Física de Materiales, Universidad
Complutense de Madrid, Avenida Complutense, s/n, Ciudad Universitaria, 28040 Madrid, Spain
| | - Vittorio Bellani
- Nanolab-Nanotechnology
Group, Departamento de Física Fundamental, Universidad de Salamanca, Plaza de la Merced, s/n., 37008-Salamanca, Spain
- Dipartimento
di Fisica, Università di Pavia, Via Agostino Bassi, 6, 27100 Pavia, Italy
| | - Francisco Domínguez-Adame
- GISC, Departamento
de Física de Materiales, Universidad
Complutense de Madrid, Avenida Complutense, s/n, Ciudad Universitaria, 28040 Madrid, Spain
| | - Enrique Diez
- Nanolab-Nanotechnology
Group, Departamento de Física Fundamental, Universidad de Salamanca, Plaza de la Merced, s/n., 37008-Salamanca, Spain
| | - Lucia Sorba
- NEST,
Scuola Normale Superiore e Istituto di Nanoscienze-CNR, Piazza san Silvestro 12, I-56127 Pisa, Italy
| | - Andrea Bertoni
- S3,
Istituto Nanoscienze-CNR, Via Campi 213/a, I-41125 Modena, Italy
| | - Guido Goldoni
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via Campi 213/a, I-41125 Modena, Italy
| | - Francesco Rossella
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via Campi 213/a, I-41125 Modena, Italy
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2
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Krishnan R, Biswas S, Hsueh YL, Ma H, Rahman R, Weber B. Spin-Valley Locking for In-Gap Quantum Dots in a MoS 2 Transistor. Nano Lett 2023. [PMID: 37363814 DOI: 10.1021/acs.nanolett.3c01779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Spins confined to atomically thin semiconductors are being actively explored as quantum information carriers. In transition metal dichalcogenides (TMDCs), the hexagonal crystal lattice gives rise to an additional valley degree of freedom with spin-valley locking and potentially enhanced spin life and coherence times. However, realizing well-separated single-particle levels and achieving transparent electrical contact to address them has remained challenging. Here, we report well-defined spin states in a few-layer MoS2 transistor, characterized with a spectral resolution of ∼50 μeV at Tel = 150 mK. Ground state magnetospectroscopy confirms a finite Berry-curvature induced coupling of spin and valley, reflected in a pronounced Zeeman anisotropy, with a large out-of-plane g-factor of g⊥ ≃ 8. A finite in-plane g-factor (g∥ ≃ 0.55-0.8) allows us to quantify spin-valley locking and estimate the spin-orbit splitting 2ΔSO ∼ 100 μeV. The demonstration of spin-valley locking is an important milestone toward realizing spin-valley quantum bits.
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Affiliation(s)
- Radha Krishnan
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Sangram Biswas
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Yu-Ling Hsueh
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Hongyang Ma
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Rajib Rahman
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Bent Weber
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
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3
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Fukumoto N, Ohshima R, Aoki M, Fuseya Y, Matsushima M, Shigematsu E, Shinjo T, Ando Y, Sakamoto S, Shiga M, Miwa S, Shiraishi M. Observation of large spin conversion anisotropy in bismuth. Proc Natl Acad Sci U S A 2023; 120:e2215030120. [PMID: 36952378 PMCID: PMC10068794 DOI: 10.1073/pnas.2215030120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 02/21/2023] [Indexed: 03/24/2023] Open
Abstract
While the effective g-factor can be anisotropic due to the spin-orbit interaction (SOI), its existence in solids cannot be simply asserted from a band structure, which hinders progress on studies from such viewpoints. The effective g-factor in bismuth (Bi) is largely anisotropic; especially for holes at T-point, the effective g-factor perpendicular to the trigonal axis is negligibly small (<0.112), whereas the effective g-factor along the trigonal axis is very large (62.7). We clarified in this work that the large anisotropy of effective g-factor gives rise to the large spin conversion anisotropy in Bi from experimental and theoretical approaches. Spin-torque ferromagnetic resonance was applied to estimate the spin conversion efficiency in rhombohedral (110) Bi to be 17 to 27%, which is unlike the negligibly small efficiency in Bi(111). Harmonic Hall measurements support the large spin conversion efficiency in Bi(110). A large spin conversion anisotropy as the clear manifestation of the anisotropy of the effective g-factor is observed. Beyond the emblematic case of Bi, our study unveiled the significance of the effective g-factor anisotropy in condensed-matter physics and can pave a pathway toward establishing novel spin physics under g-factor control.
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Affiliation(s)
- Naoki Fukumoto
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
| | - Ryo Ohshima
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
| | - Motomi Aoki
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
| | - Yuki Fuseya
- Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo182-8585, Japan
| | - Masayuki Matsushima
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
| | - Ei Shigematsu
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
| | - Teruya Shinjo
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
| | - Yuichiro Ando
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
- PRESTO, Japan Science and Technology Agency, Honcho, Kawaguchi, Saitama332-0012, Japan
| | - Shoya Sakamoto
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba227-8581, Japan
| | - Masanobu Shiga
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba227-8581, Japan
| | - Shinji Miwa
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba227-8581, Japan
| | - Masashi Shiraishi
- Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto615-8510, Japan
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4
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Li G, Ma X, Li S, Ye X, Börnert P, Zhou XJ, Guo H. Comparison of uniform-density, variable-density, and dual-density spiral samplings for multi-shot DWI. Magn Reson Med 2023; 90:133-149. [PMID: 36883748 DOI: 10.1002/mrm.29633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 02/17/2023] [Accepted: 02/21/2023] [Indexed: 03/09/2023]
Abstract
PURPOSE To compare the performances of uniform-density spiral (UDS), variable-density spiral (VDS), and dual-density spiral (DDS) samplings in multi-shot diffusion imaging, and determine a sampling strategy that balances reliability of shot navigator and overall DWI image quality. THEORY AND METHODS UDS, VDS, and DDS trajectories were implemented to achieve four-shot diffusion-weighted spiral imaging. First, the static B0 off-resonance effects in UDS, VDS, and DDS acquisitions were analyzed based on a signal model. Then, in vivo experiments were performed to verify the theoretical analyses, and fractional anisotropy (FA) fitting residuals were used to quantitatively assess the quality of spiral diffusion data for tensor estimation. Finally, the SNR performances and g-factor behavior of the three spiral samplings were evaluated using a Monte Carlo-based pseudo multiple replica method. RESULTS Among the three spiral trajectories with the same readout duration, UDS sampling exhibited the least off-resonance artifacts. This was most evident when the static B0 off-resonance effect was severe. The UDS diffusion images had higher anatomical fidelity and lower FA fitting residuals than the other two counterparts. Furthermore, the four-shot UDS acquisition achieved the best SNR performance in diffusion imaging with 12.11% and 40.85% improvements over the VDS and DDS acquisitions with the same readout duration, respectively. CONCLUSION UDS sampling is an efficient spiral acquisition scheme for high-resolution diffusion imaging with reliable navigator information. It provides superior off-resonance performance and SNR efficiency over the VDS and DDS samplings for the tested scenarios.
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Affiliation(s)
- Guangqi Li
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Xiaodong Ma
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Sisi Li
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Xinyu Ye
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Peter Börnert
- Radiology, C.J. Gorter Center for High-Field MRI, Leiden University Medical Center, Leiden, The Netherlands.,Philips Research, Hamburg, Germany
| | - Xiaohong Joe Zhou
- Center for MR Research and Departments of Radiology, Neurosurgery, and Biomedical Engineering, University of Illinois College of Medicine at Chicago, Chicago, Illinois, USA
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China
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5
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Lee PK, Hargreaves BA. A joint linear reconstruction for multishot diffusion weighted non-Carr-Purcell-Meiboom-Gill fast spin echo with full signal. Magn Reson Med 2022; 88:2139-2156. [PMID: 35906924 PMCID: PMC9732866 DOI: 10.1002/mrm.29393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 06/25/2022] [Accepted: 06/27/2022] [Indexed: 12/13/2022]
Abstract
PURPOSE Diffusion weighted Fast Spin Echo (DW-FSE) is a promising approach for distortionless DW imaging that is robust to system imperfections such as eddy currents and off-resonance. Due to non-Carr-Purcell-Meiboom-Gill (CPMG) magnetization, most DW-FSE sequences discard a large fraction of the signal ( 2 - 2 × $$ \sqrt{2}-2\times $$ ), reducing signal-to-noise ratio (SNR) efficiency compared to DW-EPI. The full FSE signal can be preserved by quadratically incrementing the transmit phase of the refocusing pulses, but this method of resolving non-CPMG magnetization has only been applied to single-shot DW-FSE due to challenges associated with image reconstruction. We present a joint linear reconstruction for multishot quadratic phase increment data that addresses these challenges and corrects ghosting from both shot-to-shot phase and intrashot signal oscillations. Multishot imaging reduces T2 blur and joint reconstruction of shots improves g-factor performance. A thorough analysis on the condition number of the proposed linear system is described. METHODS A joint multishot reconstruction is derived from the non-CPMG signal model. Multishot quadratic phase increment DW-FSE was tested in a standardized diffusion phantom and compared to single-shot DW-FSE and DW-EPI in vivo in the brain, cervical spine, and prostate. The pseudo multiple replica technique was applied to generate g-factor and SNR maps. RESULTS The proposed joint shot reconstruction eliminates ghosting from shot-to-shot phase and intrashot oscillations. g-factor performance is improved compared to previously proposed reconstructions, permitting efficient multishot imaging. apparent diffusion coefficient estimates in phantom experiments and in vivo are comparable to those obtained with conventional methods. CONCLUSION Multi-shot non-CPMG DW-FSE data with full signal can be jointly reconstructed using a linear model.
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Affiliation(s)
- Philip K. Lee
- Radiology, Stanford University, Stanford, CA, 94305, USA,Electrical Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Brian A. Hargreaves
- Radiology, Stanford University, Stanford, CA, 94305, USA,Electrical Engineering, Stanford University, Stanford, CA, 94305, USA,Bioengineering, Stanford University, Stanford, CA, 94305, USA
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6
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ten Kate S, Ritter MF, Fuhrer A, Jung J, Schellingerhout SG, Bakkers EPAM, Riel H, Nichele F. Small Charging Energies and g-Factor Anisotropy in PbTe Quantum Dots. Nano Lett 2022; 22:7049-7056. [PMID: 35998346 PMCID: PMC9479220 DOI: 10.1021/acs.nanolett.2c01943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 08/15/2022] [Indexed: 06/15/2023]
Abstract
PbTe is a semiconductor with promising properties for topological quantum computing applications. Here, we characterize electron quantum dots in PbTe nanowires selectively grown on InP. Charge stability diagrams at zero magnetic field reveal large even-odd spacing between Coulomb blockade peaks, charging energies below 140 μeV and Kondo peaks in odd Coulomb diamonds. We attribute the large even-odd spacing to the large dielectric constant and small effective electron mass of PbTe. By studying the Zeeman-induced level and Kondo splitting in finite magnetic fields, we extract the electron g-factor as a function of magnetic field direction. We find the g-factor tensor to be highly anisotropic with principal g-factors ranging from 0.9 to 22.4 and to depend on the electronic configuration of the devices. These results indicate strong Rashba spin-orbit interaction in our PbTe quantum dots.
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Affiliation(s)
- Sofieke
C. ten Kate
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
- University
of Twente, Drienerlolaan
5, 7522 NB Enschede, Netherlands
| | - Markus F. Ritter
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Andreas Fuhrer
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Jason Jung
- Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | | | | | - Heike Riel
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Fabrizio Nichele
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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7
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Wang Z, Wang Z, Zhou X, Fu W, Li H, Liu C, Qiao J, Quek SY, Su C, Feng Y, Loh KP. Giant g-factor in Self-Intercalated 2D TaS 2. Small 2022; 18:e2201975. [PMID: 35989096 DOI: 10.1002/smll.202201975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 07/21/2022] [Indexed: 06/15/2023]
Abstract
Central to the application of spintronic devices is the ability to manipulate spins by electric and magnetic fields, which relies on a large Landé g-factor. The self-intercalation of layered transitional metal dichalcogenides with native metal atoms can serve as a new strategy to enhance the g-factor by inducing ferromagnetic instability in the system via interlayer charge transfer. Here, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are performed to extract the g-factor and characterize the electronic structure of the self-intercalated phase of 2H-TaS2 . In Ta7 S12 , a sharp density of states (DOS) peak due to the Ta intercalant appears at the Fermi level, which satisfies the Stoner criteria for spontaneous ferromagnetism, leading to spin split states. The DOS peak shows sensitivity to magnetic field up to 1.85 mV T-1 , equivalent to an effective g-factor of ≈77. This work establishes self-intercalation as an approach for tuning the g-factor.
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Affiliation(s)
- Ziying Wang
- SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
| | - Zishen Wang
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Xin Zhou
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Wei Fu
- Institute of Materials Research and Engineering, Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, 08-03 Innovis, Singapore, 138634, Singapore
| | - Haohan Li
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Chaofei Liu
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Jingsi Qiao
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Su Ying Quek
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Chenliang Su
- SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China
| | - Yuanping Feng
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
| | - Kian Ping Loh
- SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China
- Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
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8
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Garcia-Arellano G, Trippé-Allard G, Campos T, Bernardot F, Legrand L, Garrot D, Deleporte E, Testelin C, Chamarro M. Unexpected Anisotropy of the Electron and Hole Landé g-Factors in Perovskite CH 3NH 3PbI 3 Polycrystalline Films. Nanomaterials (Basel) 2022; 12:nano12091399. [PMID: 35564108 PMCID: PMC9105229 DOI: 10.3390/nano12091399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/15/2022] [Accepted: 04/15/2022] [Indexed: 12/10/2022]
Abstract
In this work, we studied, at low temperature, the coherent evolution of the localized electron and hole spins in a polycrystalline film of CH3NH3PbI3 (MAPI) by using a picosecond-photo-induced Faraday rotation technique in an oblique magnetic field. We observed an unexpected anisotropy for the electron and hole spin. We determined the electron and hole Landé factors when the magnetic field was applied in the plane of the film and perpendicular to the exciting light, denoted as transverse ⟂ factors, and when the magnetic field was applied perpendicular to the film and parallel to the exciting light, denoted as parallel ∥ factors. We obtained |ge,⟂|=2.600 ± 0.004, |ge,∥|=1.604 ± 0.033 for the electron and |gh,⟂|=0.406 ± 0.002, |gh,∥|=0.299 ± 0.007 for the hole. Possible origins of this anisotropy are discussed herein.
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Affiliation(s)
- Guadalupe Garcia-Arellano
- Institut des NanoSciences de Paris, CNRS, Sorbonne Université, F-75005 Paris, France; (G.G.-A.); (F.B.); (C.T.); (M.C.)
| | - Gaëlle Trippé-Allard
- LuMIn (Laboratoire Lumière, Matière et Interfaces), CentraleSupélec, CNRS, ENS Paris-Saclay, Université Paris-Saclay, F-91190 Gif-sur-Yvette, France; (G.T.-A.); (T.C.); (E.D.)
| | - Thomas Campos
- LuMIn (Laboratoire Lumière, Matière et Interfaces), CentraleSupélec, CNRS, ENS Paris-Saclay, Université Paris-Saclay, F-91190 Gif-sur-Yvette, France; (G.T.-A.); (T.C.); (E.D.)
- Institut Photovoltaïque d’Île-de-France (IPVF), F-91120 Palaiseau, France
| | - Frédérick Bernardot
- Institut des NanoSciences de Paris, CNRS, Sorbonne Université, F-75005 Paris, France; (G.G.-A.); (F.B.); (C.T.); (M.C.)
| | - Laurent Legrand
- Institut des NanoSciences de Paris, CNRS, Sorbonne Université, F-75005 Paris, France; (G.G.-A.); (F.B.); (C.T.); (M.C.)
- Correspondence:
| | - Damien Garrot
- GEMaC (Groupe d’Etude de la Matière Condensée), CNRS, UVSQ, Université Paris-Saclay, F-78000 Versailles, France;
| | - Emmanuelle Deleporte
- LuMIn (Laboratoire Lumière, Matière et Interfaces), CentraleSupélec, CNRS, ENS Paris-Saclay, Université Paris-Saclay, F-91190 Gif-sur-Yvette, France; (G.T.-A.); (T.C.); (E.D.)
| | - Christophe Testelin
- Institut des NanoSciences de Paris, CNRS, Sorbonne Université, F-75005 Paris, France; (G.G.-A.); (F.B.); (C.T.); (M.C.)
| | - Maria Chamarro
- Institut des NanoSciences de Paris, CNRS, Sorbonne Université, F-75005 Paris, France; (G.G.-A.); (F.B.); (C.T.); (M.C.)
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9
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Liu Y, Ma L, Jiang S, Han C, Tang P, Yang H, Duan X, Liu N, Yan H, Lan X. DNA Programmable Self-Assembly of Planar, Thin-Layered Chiral Nanoparticle Superstructures with Complex Two-Dimensional Patterns. ACS Nano 2021; 15:16664-16672. [PMID: 34636539 DOI: 10.1021/acsnano.1c06639] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Planar, thin-layered chiral plasmonic superstructures with complex two-dimensional (2D) patterns, namely, double-layered binary stars (bi-stars) and pinwheels, were realized through DNA programmable 2D supramolecular self-assembly of gold nanorods (AuNRs). The chirality of the chiral superstructures was defined by a finite number of AuNR pairs as enantiomeric motifs, and their sizes (∼240 nm) were precisely defined by the underlying DNA template. These planar, thin-layered chiral nanoparticle superstructures exhibited prescribed shapes and sizes at the dried state on the substrate surface and are characteristic of giant anisotropy of chiroptical responses, with enhanced g-factors from the axial incident excitation as compared to the in-plane excitation. This work will inspire possibilities for the construction of 2D chiral materials, for example, chiral metasurfaces, for the on-chip manipulation of chiral light-matter interactions via programmable self-assembly of nanoparticles.
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Affiliation(s)
- Yan Liu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China
- Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, People's Republic of China
| | - Li Ma
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China
- Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, People's Republic of China
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
| | - Shuoxing Jiang
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, Arizona 85287, United States
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Cong Han
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China
- Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, People's Republic of China
| | - Pan Tang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China
- Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, People's Republic of China
| | - Hao Yang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China
- Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, People's Republic of China
| | - Xiaoyang Duan
- 2nd Physics Institute, University of Stuttgart, Pfaffenwaldring 57, Stuttgart 70569, Germany
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, Stuttgart 70569, Germany
| | - Na Liu
- 2nd Physics Institute, University of Stuttgart, Pfaffenwaldring 57, Stuttgart 70569, Germany
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, Stuttgart 70569, Germany
| | - Hao Yan
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, Arizona 85287, United States
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Xiang Lan
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China
- Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, People's Republic of China
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10
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Qiu Z, Jia S, Su S, Zhu Y, Liu X, Zheng H, Liang D, Wang H. Highly accelerated parallel MRI using wave encoding and virtual conjugate coils. Magn Reson Med 2021; 86:1345-1359. [PMID: 33856078 DOI: 10.1002/mrm.28803] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 03/22/2021] [Indexed: 11/11/2022]
Abstract
PURPOSE To propose a novel model incorporating virtual conjugate coil (VCC) reconstruction and wave encoding (Wave) for improved parallel MRI. THEORY AND METHODS A novel model (VCC-Wave) incorporating VCC and Wave is proposed. The correlation matrix of the encoding operator is introduced to analyze the encoding capability. In addition, simulation experiments are conducted to gain insights into VCC-Wave. In vivo experiments are performed to compare VCC-Wave with alternative methods. RESULTS The correlation matrix and the simulation experiments show that the proposed VCC-Wave can utilize more priors of Wave under the VCC framework. In vivo experiments show that the proposed VCC-Wave can achieve good image quality at a 6-fold acceleration in high-resolution and high-bandwidth cases, indicating an improvement over the original Wave technique. CONCLUSION The proposed VCC-Wave can not only combine the advantages of both the VCC and Wave but also exploit more priors of Wave under the VCC framework. The improvement in VCC-Wave alleviates the limitation of Wave in high-resolution and high-bandwidth cases.
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Affiliation(s)
- Zhilang Qiu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Sen Jia
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Shi Su
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Yanjie Zhu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Xin Liu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Dong Liang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China.,Research Center for Medical AI, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Haifeng Wang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
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11
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Lee Y, Wilm BJ, Brunner DO, Gross S, Schmid T, Nagy Z, Pruessmann KP. On the signal-to-noise ratio benefit of spiral acquisition in diffusion MRI. Magn Reson Med 2020; 85:1924-1937. [PMID: 33280160 DOI: 10.1002/mrm.28554] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/15/2020] [Accepted: 09/22/2020] [Indexed: 12/20/2022]
Abstract
PURPOSE Spiral readouts combine several favorable properties that promise superior net sensitivity for diffusion imaging. The purpose of this study is to verify the signal-to-noise ratio (SNR) benefit of spiral acquisition in comparison with current echo-planar imaging (EPI) schemes. METHODS Diffusion-weighted in vivo brain data from three subjects were acquired with a single-shot spiral sequence and several variants of single-shot EPI, including full-Fourier and partial-Fourier readouts as well as different diffusion-encoding schemes. Image reconstruction was based on an expanded signal model including field dynamics obtained by concurrent field monitoring. The effective resolution of each sequence was matched to that of full-Fourier EPI with 1 mm nominal resolution. SNR maps were generated by determining the noise statistics of the raw data and analyzing the propagation of equivalent synthetic noise through image reconstruction. Using the same approach, maps of noise amplification due to parallel imaging (g-factor) were calculated for different acceleration factors. RESULTS Relative to full-Fourier EPI at b = 0 s/mm2 , spiral acquisition yielded SNR gains of 42-88% and 40-89% in white and gray matter, respectively, depending on the diffusion-encoding scheme. Relative to partial-Fourier EPI, the gains were 36-44% and 34-42%. Spiral g-factor maps exhibited less spatial variation and lower maxima than their EPI counterparts. CONCLUSION Spiral readouts achieve significant SNR gains in the order of 40-80% over EPI in diffusion imaging at 3T. Combining systematic effects of shorter echo time, readout efficiency, and favorable g-factor behavior, similar benefits are expected across clinical and neurosciences uses of diffusion imaging.
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Affiliation(s)
- Yoojin Lee
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.,Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Zoltan Nagy
- Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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12
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Abstract
Transition metal dichalcogenides are promising semiconductors to enable advances in photonics and electronics and have also been considered as a host for quantum emitters. Particularly, recent advances demonstrate site-controlled quantum emitters in WSe2 through strain deformation. Albeit essential for device integration, the dipole orientation of these strain-induced quantum emitters remains unknown. Here we employ angular-resolved spectroscopy to experimentally determine the dipole orientation of strain-induced quantum emitters. It is found that with increasing local strain the quantum emitters in WSe2 undergo a transition from in-plane to out-of-plane dipole orientation if their emission wavelength is longer than 750 nm. In addition, the exciton g-factor remains with average values of g = 8.52 ± 1.2 unchanged in the entire emission wavelength. These findings provide experimental support of the interlayer defect exciton model and highlight the importance of an underlying three-dimensional strain profile of deformed monolayer semiconductors, which is essential to optimize emitter-mode coupling in nanoplasmonics.
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Affiliation(s)
- Yue Luo
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
- Center for Nanoscale Systems, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Na Liu
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Stefan Strauf
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
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13
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Abstract
Nanozymes have been widely applied in bio-assays in the field of biotechnology and biomedicines. However, the physicochemical basis of nanozyme catalytic activity remains elusive. To test whether nanozymes exhibit an inactivation effect similar to that of natural enzymes, we used guanidine chloride (GuHCl) to disturb the iron oxide nanozyme (IONzyme) and observed that GuHCl induced IONzyme aggregation and that the peroxidase-like activity of IONzyme significantly decreased in the presence of GuHCl. However, the aggregation appeared to be unrelated to the quick process of inactivation, as GuHCl acted as a reversible inhibitor of IONzyme instead of a solo denaturant. Inhibition kinetic analysis showed that GuHCl binds to IONzyme competitively with H2O2 but non-competitively with tetramethylbenzidine. In addition, electron spin resonance spectroscopy showed that increasing GuHCl level of GuHCl induced a correlated pattern of changes in the activity and the state of the unpaired electrons of the IONzymes. This result indicates that GuHCl probably directly interacts with the iron atoms of IONzyme and affects the electron density of iron, which may then induce IONzyme inactivation. These findings not only contribute to understanding the essence of nanozyme catalytic activity but also suggest a practically feasible method to regulate the catalytic activity of IONzyme.
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Affiliation(s)
- Wei-Chuan Mo
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, University of the Chinese Academy of Sciences, CAS, Beijing, China
| | - Jia Yu
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, University of the Chinese Academy of Sciences, CAS, Beijing, China
| | - Li-Zeng Gao
- CAS Engineering Laboratory for Nanozyme, Institute of Biophysics Key Laboratory of Protein and Peptide Drugs, Institute of Biophysics, CAS, Yangzhou, China
| | - Ying Liu
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, University of the Chinese Academy of Sciences, CAS, Beijing, China.,School of Life Sciences, Beijing University of Chinese Medicine, Beijing, China
| | - Yan Wei
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, University of the Chinese Academy of Sciences, CAS, Beijing, China.,CAS Key Laboratory of Mental Health Laboratory, Institute of Psychology, Beijing, China
| | - Rong-Qiao He
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, University of the Chinese Academy of Sciences, CAS, Beijing, China.,Southwest Medical University, Luzhou, China
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14
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Kettinger AO, Setsompop K, Kannengiesser SAR, Breuer FA, Vidnyanszky Z, Blaimer M. Full utilization of conjugate symmetry: combining virtual conjugate coil reconstruction with partial Fourier imaging for g-factor reduction in accelerated MRI. Magn Reson Med 2019; 82:1073-1090. [PMID: 31081561 DOI: 10.1002/mrm.27799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 02/27/2019] [Accepted: 04/13/2019] [Indexed: 11/10/2022]
Abstract
PURPOSE In this study we propose a method to combine the parallel virtual conjugate coil (VCC) reconstruction with partial Fourier (PF) acquisition to improve reconstruction conditioning and reduce noise amplification in accelerated MRI where PF is used. METHODS Accelerated measurements are reconstructed in k-space by GRAPPA, with a VCC reconstruction kernel trained and applied in the central, symmetrically sampled part of k-space, while standard reconstruction is performed on the asymmetrically sampled periphery. The two reconstructed regions are merged to form a full reconstructed dataset, followed by PF reconstruction. The method is tested in vivo using T1-weighted spin-echo and T2*-weighted gradient-echo echo planar imaging (EPI) sequences, using both in-plane and simultaneous multislice (SMS) acceleration, at 1.5T and 3T field strengths. Noise amplification is estimated with theoretical calculations and pseudo-multiple-replica computations, for different PF factors, using zero-filling, homodyne, and projection onto convex sets (POCS) PF reconstruction. RESULTS Depending on the PF algorithm and the inherent benefit of VCC reconstruction without PF, approximately 35% to 80%, 15% to 60%, and 5% to 30% of that intrinsic SNR gain can be retained for PF factors 7/8, 6/8, and 5/8, respectively, by including the VCC signals in the reconstruction. Compared with VCC-reconstructed acquisitions of higher acceleration, without PF, but having the same net acceleration, the combined method can provide a higher SNR if the inherent benefit of VCC is low or moderate. CONCLUSION The proposed technique enables the partial application of VCC reconstruction to measurements with PF using either in-plane or SMS acceleration, and therefore can reduce the noise amplification of such acquisitions.
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Affiliation(s)
- Adam O Kettinger
- Brain Imaging Centre, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary.,Department of Nuclear Techniques, Budapest University of Technology and Economics, Budapest, Hungary.,Siemens Healthcare GmbH, Erlangen, Germany
| | - Kawin Setsompop
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts.,Department of Radiology, Harvard Medical School, Boston, Massachusetts.,Harvard-MIT Health Sciences and Technology, MIT, Cambridge, Massachusetts
| | | | - Felix A Breuer
- Magnetic Resonance and X-ray Imaging Department, Fraunhofer Development Center X-ray Technology (EZRT), Würzburg, Germany
| | - Zoltan Vidnyanszky
- Brain Imaging Centre, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Martin Blaimer
- Magnetic Resonance and X-ray Imaging Department, Fraunhofer Development Center X-ray Technology (EZRT), Würzburg, Germany
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15
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Luo T, Noll DC, Fessler JA, Nielsen JF. A GRAPPA algorithm for arbitrary 2D/3D non-Cartesian sampling trajectories with rapid calibration. Magn Reson Med 2019; 82:1101-1112. [PMID: 31050011 DOI: 10.1002/mrm.27801] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 04/03/2019] [Accepted: 04/16/2019] [Indexed: 12/11/2022]
Abstract
PURPOSE GRAPPA is a popular reconstruction method for Cartesian parallel imaging, but is not easily extended to non-Cartesian sampling. We introduce a general and practical GRAPPA algorithm for arbitrary non-Cartesian imaging. METHODS We formulate a general GRAPPA reconstruction by associating a unique kernel with each unsampled k-space location with a distinct constellation, that is, local sampling pattern. We calibrate these generalized kernels using the Fourier transform phase shift property applied to fully gridded or separately acquired Cartesian Autocalibration signal (ACS) data. To handle the resulting large number of different kernels, we introduce a fast calibration algorithm based on nonuniform FFT (NUFFT) and adoption of circulant ACS boundary conditions. We applied our method to retrospectively under-sampled rotated stack-of-stars/spirals in vivo datasets, and to a prospectively under-sampled rotated stack-of-spirals functional MRI acquisition with a finger-tapping task. RESULTS We reconstructed all datasets without performing any trajectory-specific manual adaptation of the method. For the retrospectively under-sampled experiments, our method achieved image quality (i.e., error and g-factor maps) comparable to conjugate gradient SENSE (cg-SENSE) and SPIRiT. Functional activation maps obtained from our method were in good agreement with those obtained using cg-SENSE, but required a shorter total reconstruction time (for the whole time-series): 3 minutes (proposed) vs 15 minutes (cg-SENSE). CONCLUSIONS This paper introduces a general 3D non-Cartesian GRAPPA that is fast enough for practical use on today's computers. It is a direct generalization of original GRAPPA to non-Cartesian scenarios. The method should be particularly useful in dynamic imaging where a large number of frames are reconstructed from a single set of ACS data.
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Affiliation(s)
- Tianrui Luo
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Douglas C Noll
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Jeffrey A Fessler
- Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan
| | - Jon-Fredrik Nielsen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
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16
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Lin J, Han T, Piot BA, Wu Z, Xu S, Long G, An L, Cheung P, Zheng PP, Plochocka P, Dai X, Maude DK, Zhang F, Wang N. Determining Interaction Enhanced Valley Susceptibility in Spin-Valley-Locked MoS 2. Nano Lett 2019; 19:1736-1742. [PMID: 30720286 DOI: 10.1021/acs.nanolett.8b04731] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMDCs) are recently emerged electronic systems with various novel properties, such as spin-valley locking, circular dichroism, valley Hall effect, and superconductivity. The reduced dimensionality and large effective masses further produce unconventional many-body interaction effects. Here we reveal strong interaction effects in the conduction band of MoS2 by transport experiment. We study the massive Dirac electron Landau levels (LL) in high-quality MoS2 samples with field-effect mobilities of 24 000 cm2/(V·s) at 1.2 K. We identify the valley-resolved LLs and low-lying polarized LLs using the Lifshitz-Kosevitch formula. By further tracing the LL crossings in the Landau fan diagram, we unambiguously determine the density-dependent valley susceptibility and the interaction enhanced g-factor from 12.7 to 23.6. Near integer ratios of Zeeman-to-cyclotron energies, we discover LL anticrossings due to the formation of quantum Hall Ising ferromagnets, the valley polarizations of which appear to be reversible by tuning the density or an in-plane magnetic field. Our results provide evidence for many-body interaction effects in the conduction band of MoS2 and establish a fertile ground for exploring strongly correlated phenomena of massive Dirac electrons.
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Affiliation(s)
- Jiangxiazi Lin
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Tianyi Han
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Benjamin A Piot
- Laboratoire National des Champs Magnétiques Intenses, LNCMI-CNRS-UGA-UPS-INSA-EMFL , F-38042 Grenoble , France
| | - Zefei Wu
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Shuigang Xu
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Gen Long
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Liheng An
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Patrick Cheung
- Department of Physics , The University of Texas at Dallas , Richardson , Texas 75080 , United States
| | - Peng-Peng Zheng
- Department of Physics , The University of Texas at Dallas , Richardson , Texas 75080 , United States
| | - Paulina Plochocka
- Laboratoire National des Champs Magnétiques Intenses, LNCMI-CNRS-UGA-UPS-INSA-EMFL , F-31400 Toulouse , France
| | - Xi Dai
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Duncan K Maude
- Laboratoire National des Champs Magnétiques Intenses, LNCMI-CNRS-UGA-UPS-INSA-EMFL , F-31400 Toulouse , France
| | - Fan Zhang
- Department of Physics , The University of Texas at Dallas , Richardson , Texas 75080 , United States
| | - Ning Wang
- Department of Physics and Center for Quantum Materials , The Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
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17
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Rabanillo-Viloria I, Zhu A, Aja-Fernández S, Alberola-López C, Hernando D. Computation of exact g-factor maps in 3D GRAPPA reconstructions. Magn Reson Med 2018; 81:1353-1367. [PMID: 30229566 DOI: 10.1002/mrm.27469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 07/05/2018] [Accepted: 07/06/2018] [Indexed: 11/12/2022]
Abstract
PURPOSE To characterize the noise distributions in 3D-MRI accelerated acquisitions reconstructed with GRAPPA using an exact noise propagation analysis that operates directly in k-space. THEORY AND METHODS We exploit the extensive symmetries and separability in the reconstruction steps to account for the correlation between all the acquired k-space samples. Monte Carlo simulations and multi-repetition phantom experiments were conducted to test both the accuracy and feasibility of the proposed method; a high-resolution in-vivo experiment was performed to assess the applicability of our method to clinical scenarios. RESULTS Our theoretical derivation shows that the direct k-space analysis renders an exact noise characterization under the assumptions of stationarity and uncorrelation in the original k-space. Simulations and phantom experiments provide empirical support to the theoretical proof. Finally, the high-resolution in-vivo experiment demonstrates the ability of the proposed method to assess the impact of the sub-sampling pattern on the overall noise behavior. CONCLUSIONS By operating directly in the k-space, the proposed method is able to provide an exact characterization of noise for any Cartesian pattern sub-sampled along the two phase-encoding directions. Exploitation of the symmetries and separability into independent blocks through the image reconstruction procedure allows us to overcome the computational challenges related to the very large size of the covariance matrices involved.
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Affiliation(s)
| | - Ante Zhu
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin
| | | | | | - Diego Hernando
- Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin.,Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin
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18
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Ziegler M, Peikert A. How Specific Abilities Might Throw ' g' a Curve: An Idea on How to Capitalize on the Predictive Validity of Specific Cognitive Abilities. J Intell 2018; 6:E41. [PMID: 31162468 PMCID: PMC6480727 DOI: 10.3390/jintelligence6030041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 07/05/2018] [Accepted: 07/17/2018] [Indexed: 11/20/2022] Open
Abstract
School grades are still used by universities and employers for selection purposes. Thus, identifying determinants of school grades is important. Broadly, two predictor categories can be differentiated from an individual difference perspective: cognitive abilities and personality traits. Over time, evidence accumulated supporting the notion of the g-factor as the best single predictor of school grades. Specific abilities were shown to add little incremental validity. The current paper aims at reviving research on which cognitive abilities predict performance. Based on ideas of criterion contamination and deficiency as well as Spearman's ability differentiation hypothesis, two mechanisms are suggested which both would lead to curvilinear relations between specific abilities and grades. While the data set provided for this special issue does not allow testing these mechanisms directly, we tested the idea of curvilinear relations. In particular, polynomial regressions were used. Machine learning was applied to identify the best fitting models in each of the subjects math, German, and English. In particular, we fitted polynomial models with varying degrees and evaluated their accuracy with a leave-one-out validation approach. The results show that tests of specific abilities slightly outperform the g-factor when curvilinearity is assumed. Possible theoretical explanations are discussed.
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Affiliation(s)
- Matthias Ziegler
- Psychological Institute, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.
| | - Aaron Peikert
- Psychological Institute, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.
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19
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Mizokuchi R, Maurand R, Vigneau F, Myronov M, De Franceschi S. Ballistic One-Dimensional Holes with Strong g-Factor Anisotropy in Germanium. Nano Lett 2018; 18:4861-4865. [PMID: 29995419 DOI: 10.1021/acs.nanolett.8b01457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report experimental evidence of ballistic hole transport in one-dimensional quantum wires gate-defined in a strained SiGe/Ge/SiGe quantum well. At zero magnetic field, we observe conductance plateaus at integer multiples of 2 e2/ h. At finite magnetic field, the splitting of these plateaus by Zeeman effect reveals largely anisotropic g-factors with absolute values below 1 in the quantum-well plane, and exceeding 10 out-of-plane. This g-factor anisotropy is consistent with a heavy-hole character of the propagating valence-band states, which is in line with a predominant confinement in the growth direction. Remarkably, we observe quantized ballistic conductance in device channels up to 600 nm long. These findings mark an important step toward the realization of novel devices for applications in quantum spintronics.
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Affiliation(s)
- R Mizokuchi
- Université Grenoble Alpes & CEA, INAC-PHELIQS , F-38000 Grenoble , France
| | - R Maurand
- Université Grenoble Alpes & CEA, INAC-PHELIQS , F-38000 Grenoble , France
| | - F Vigneau
- Université Grenoble Alpes & CEA, INAC-PHELIQS , F-38000 Grenoble , France
| | - M Myronov
- Department of Physics , University of Warwick , Coventry CV4 7AL , United Kingdom
| | - S De Franceschi
- Université Grenoble Alpes & CEA, INAC-PHELIQS , F-38000 Grenoble , France
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20
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Li X, Shepard GD, Cupo A, Camporeale N, Shayan K, Luo Y, Meunier V, Strauf S. Nonmagnetic Quantum Emitters in Boron Nitride with Ultranarrow and Sideband-Free Emission Spectra. ACS Nano 2017; 11:6652-6660. [PMID: 28521091 DOI: 10.1021/acsnano.7b00638] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Hexagonal boron nitride (hBN) is an emerging material in nanophotonics and an attractive host for color centers for quantum photonic devices. Here, we show that optical emission from individual quantum emitters in hBN is spatially correlated with structural defects and can display ultranarrow zero-phonon line width down to 45 μeV if spectral diffusion is effectively eliminated by proper surface passivation. We demonstrate that undesired emission into phonon sidebands is largely absent for this type of emitter. In addition, magneto-optical characterization reveals cycling optical transitions with an upper bound for the g-factor of 0.2 ± 0.2. Spin-polarized density functional theory calculations predict possible commensurate transitions between like-spin electron states, which are in excellent agreement with the experimental nonmagnetic defect center emission. Our results constitute a step toward the realization of narrowband quantum light sources and the development of spin-photon interfaces within 2D materials for future chip-scale quantum networks.
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Affiliation(s)
- Xiangzhi Li
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
| | - Gabriella D Shepard
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
| | - Andrew Cupo
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
- Department Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
| | - Nicolas Camporeale
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
| | - Kamran Shayan
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
| | - Yue Luo
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
| | - Vincent Meunier
- Department Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
| | - Stefan Strauf
- Department of Physics & Engineering Physics, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States
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21
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Long G, Maryenko D, Shen J, Xu S, Hou J, Wu Z, Wong WK, Han T, Lin J, Cai Y, Lortz R, Wang N. Achieving Ultrahigh Carrier Mobility in Two-Dimensional Hole Gas of Black Phosphorus. Nano Lett 2016; 16:7768-7773. [PMID: 27960491 DOI: 10.1021/acs.nanolett.6b03951] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate that a field-effect transistor (FET) made of few-layer black phosphorus (BP) encapsulated in hexagonal boron nitride (h-BN) in vacuum exhibits a room-temperature hole mobility of 5200 cm2/(Vs), being limited just by the phonon scattering. At cryogenic temperatures, the FET mobility increases up to 45 000 cm2/(Vs), which is five times higher compared to the mobility obtained in earlier reports. The unprecedentedly clean h-BN-BP-h-BN heterostructure exhibits Shubnikov-de Haas oscillations and a quantum Hall effect with Landau level (LL) filling factors down to v = 2 in conventional laboratory magnetic fields. Moreover, carrier density independent effective mass of m* = 0.26 m0 is measured, and a Landé g-factor of g = 2.47 is reported. Furthermore, an indication for a distinct hole transport behavior with up- and down-spin orientations is found.
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Affiliation(s)
- Gen Long
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Denis Maryenko
- RIKEN Center for Emergent Matter Science (CEMS) , Wako 351-0198, Japan
| | - Junying Shen
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Shuigang Xu
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Jianqiang Hou
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Zefei Wu
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Wing Ki Wong
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Tianyi Han
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Jiangxiazi Lin
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Yuan Cai
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Rolf Lortz
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
| | - Ning Wang
- Department of Physics and Center for Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong, China
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22
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Watzinger H, Kloeffel C, Vukušić L, Rossell MD, Sessi V, Kukučka J, Kirchschlager R, Lausecker E, Truhlar A, Glaser M, Rastelli A, Fuhrer A, Loss D, Katsaros G. Heavy-Hole States in Germanium Hut Wires. Nano Lett 2016; 16:6879-6885. [PMID: 27656760 PMCID: PMC5108027 DOI: 10.1021/acs.nanolett.6b02715] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/12/2016] [Indexed: 05/14/2023]
Abstract
Hole spins have gained considerable interest in the past few years due to their potential for fast electrically controlled qubits. Here, we study holes confined in Ge hut wires, a so-far unexplored type of nanostructure. Low-temperature magnetotransport measurements reveal a large anisotropy between the in-plane and out-of-plane g-factors of up to 18. Numerical simulations verify that this large anisotropy originates from a confined wave function of heavy-hole character. A light-hole admixture of less than 1% is estimated for the states of lowest energy, leading to a surprisingly large reduction of the out-of-plane g-factors compared with those for pure heavy holes. Given this tiny light-hole contribution, the spin lifetimes are expected to be very long, even in isotopically nonpurified samples.
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Affiliation(s)
- Hannes Watzinger
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Christoph Kloeffel
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Lada Vukušić
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Marta D. Rossell
- Electron Microscopy
Center, Empa, Swiss Federal Laboratories for Materials Science and
Technology, Überlandstrasse
129, 8600 Dübendorf, Switzerland
- IBM Research Zürich, CH-8803 Rüschlikon, Switzerland
| | - Violetta Sessi
- Chair for Nanoelectronic Materials, Technical University Dresden, 01062 Dresden, Germany
| | - Josip Kukučka
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Raimund Kirchschlager
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Elisabeth Lausecker
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Alisha Truhlar
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Martin Glaser
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | - Armando Rastelli
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
| | | | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Georgios Katsaros
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
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23
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Stemkens B, Sbrizzi A, Andreychenko AA, Crijns SPM, Lagendijk JJW, van den Berg CAT, Tijssen RHN. An optimization framework to maximize signal-to-noise ratio in simultaneous multi-slice body imaging. NMR Biomed 2016; 29:275-283. [PMID: 26684245 DOI: 10.1002/nbm.3457] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 10/17/2015] [Accepted: 11/10/2015] [Indexed: 06/05/2023]
Abstract
Parallel imaging is essential for the acceleration of abdominal and pelvic 2D multi-slice imaging, in order to reduce scan time and mitigate motion artifacts. Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration (CAIPIRINHA) accelerated imaging has been shown to increase the signal-to-noise ratio (SNR) significantly compared with in-plane parallel imaging with similar acceleration. We hypothesize that for CAIPIRINHA-accelerated abdominal imaging the consistency of image quality and SNR is more difficult to achieve due to the subject-specific coil sensitivity profiles, caused by (1) flexible coil placement; (2) variations in anatomy; and (3) variations in scan coverage along the superior-inferior direction. To test this, a mathematical framework is introduced that calculates the (retained) SNR for in-plane and simultaneous multi-slice (SMS)-accelerated acquisitions. Moreover, this framework was used to optimize the sampling pattern by maximizing the local SNR within a region of interest (ROI) through non-linear, RF-induced CAIPIRINHA slice shifts. The framework was evaluated on 14 healthy subjects and the optimized sampling pattern was compared with in-plane acceleration and CAIPIRINHA acceleration with linear slice shifts, which are primarily used in brain imaging. We demonstrate that the field of view (FOV) in the superior-inferior direction, the coil positioning and the individual anatomy have a large impact on the image SNR (changes up to 50% for varying coil positions and 40% differences between subjects) and image artifacts for simultaneous multi-slice acceleration. Consequently, sampling patterns have to be optimized for acquisitions employing different FOVs and ideally on an individual basis. Optimization of the sampling pattern, which exploits non-linear shifts between slices, showed a considerable SNR increase (10-30%) for higher acceleration factors. The framework outlined in this article can be used to optimize sampling patterns for a broad range of accelerated body acquisitions on an individual basis. Copyright © 2015 John Wiley & Sons, Ltd.
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Affiliation(s)
- Bjorn Stemkens
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Alessandro Sbrizzi
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Anna A Andreychenko
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Sjoerd P M Crijns
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jan J W Lagendijk
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | | | - Rob H N Tijssen
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
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24
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Jen YJ, Chan S, Huang JW, Jheng CY, Liu WC. Self-Shadowing Deposited Pure Metal Nanohelix Arrays and SERS Application. Nanoscale Res Lett 2015; 10:498. [PMID: 26714860 PMCID: PMC4695490 DOI: 10.1186/s11671-015-1205-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 12/10/2015] [Indexed: 06/05/2023]
Abstract
In this work, one-step glancing angle deposition is utilized to fabricate gold and silver nanohelix arrays (NHAs) on smooth glass substrates. During deposition, the substrate is cooled using liquid nitrogen and rotated with a tunable spin rate. The substrate spin rate is tuned to match the deposition rate to yield a spiral-like helix structure. The morphologies and optical properties of spiral-like Ag and Au NHAs are measured and compared. The polarization-dependent reflectance of Au NHA leads to a strong g-factor. The three-dimensional nanohelical structures are demonstrated to be a highly sensitive surface-enhanced Raman scattering (SERS) substrate.
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Affiliation(s)
- Yi-Jun Jen
- Department of Electro-Optical Engineering, National Taipei University of Technology, 10608 No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei, Taiwan.
| | - San Chan
- Department of Electro-Optical Engineering, National Taipei University of Technology, 10608 No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei, Taiwan.
| | - Jyong-Wei Huang
- Department of Electro-Optical Engineering, National Taipei University of Technology, 10608 No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei, Taiwan.
| | - Ci-Yao Jheng
- Department of Electro-Optical Engineering, National Taipei University of Technology, 10608 No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei, Taiwan.
| | - Wei-Chih Liu
- Department of Electro-Optical Engineering, National Taipei University of Technology, 10608 No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei, Taiwan.
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25
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Ritchie SJ, Booth T, Valdés Hernández MDC, Corley J, Maniega SM, Gow AJ, Royle NA, Pattie A, Karama S, Starr JM, Bastin ME, Wardlaw JM, Deary IJ. Beyond a bigger brain: Multivariable structural brain imaging and intelligence. Intelligence 2015; 51:47-56. [PMID: 26240470 PMCID: PMC4518535 DOI: 10.1016/j.intell.2015.05.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 04/15/2015] [Accepted: 05/01/2015] [Indexed: 10/29/2022]
Abstract
People with larger brains tend to score higher on tests of general intelligence (g). It is unclear, however, how much variance in intelligence other brain measurements would account for if included together with brain volume in a multivariable model. We examined a large sample of individuals in their seventies (n = 672) who were administered a comprehensive cognitive test battery. Using structural equation modelling, we related six common magnetic resonance imaging-derived brain variables that represent normal and abnormal features-brain volume, cortical thickness, white matter structure, white matter hyperintensity load, iron deposits, and microbleeds-to g and to fluid intelligence. As expected, brain volume accounted for the largest portion of variance (~ 12%, depending on modelling choices). Adding the additional variables, especially cortical thickness (+~ 5%) and white matter hyperintensity load (+~ 2%), increased the predictive value of the model. Depending on modelling choices, all neuroimaging variables together accounted for 18-21% of the variance in intelligence. These results reveal which structural brain imaging measures relate to g over and above the largest contributor, total brain volume. They raise questions regarding which other neuroimaging measures might account for even more of the variance in intelligence.
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Affiliation(s)
- Stuart J. Ritchie
- Department of Psychology, The University of Edinburgh, United Kingdom
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
| | - Tom Booth
- Department of Psychology, The University of Edinburgh, United Kingdom
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
| | - Maria del C. Valdés Hernández
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Centre for Clinical Brain Sciences, The University of Edinburgh, United Kingdom
- Brain Research Imaging Centre, The University of Edinburgh, United Kingdom
- Scottish Imaging Network, a Platform for Scientific Excellence (SINAPSE), United Kingdom
| | - Janie Corley
- Department of Psychology, The University of Edinburgh, United Kingdom
| | - Susana Muñoz Maniega
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Centre for Clinical Brain Sciences, The University of Edinburgh, United Kingdom
- Brain Research Imaging Centre, The University of Edinburgh, United Kingdom
- Scottish Imaging Network, a Platform for Scientific Excellence (SINAPSE), United Kingdom
| | - Alan J. Gow
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Department of Psychology, School of Life Sciences, Heriot-Watt University, United Kingdom
| | - Natalie A. Royle
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Centre for Clinical Brain Sciences, The University of Edinburgh, United Kingdom
- Brain Research Imaging Centre, The University of Edinburgh, United Kingdom
- Scottish Imaging Network, a Platform for Scientific Excellence (SINAPSE), United Kingdom
| | - Alison Pattie
- Department of Psychology, The University of Edinburgh, United Kingdom
| | - Sherif Karama
- Department of Neurology and Neurosurgery, McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Canada
- Department of Psychiatry, Douglas Mental Health University Institute, McGill University, Canada
| | - John M. Starr
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Alzheimer Scotland Dementia Research Centre, The University of Edinburgh, United Kingdom
| | - Mark E. Bastin
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Centre for Clinical Brain Sciences, The University of Edinburgh, United Kingdom
- Brain Research Imaging Centre, The University of Edinburgh, United Kingdom
- Scottish Imaging Network, a Platform for Scientific Excellence (SINAPSE), United Kingdom
| | - Joanna M. Wardlaw
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
- Centre for Clinical Brain Sciences, The University of Edinburgh, United Kingdom
- Brain Research Imaging Centre, The University of Edinburgh, United Kingdom
- Scottish Imaging Network, a Platform for Scientific Excellence (SINAPSE), United Kingdom
| | - Ian J. Deary
- Department of Psychology, The University of Edinburgh, United Kingdom
- Centre for Cognitive Ageing and Cognitive Epidemiology, The University of Edinburgh, United Kingdom
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26
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Chang YV, Quirk JD, Yablonskiy DA. In vivo lung morphometry with accelerated hyperpolarized (3) He diffusion MRI: a preliminary study. Magn Reson Med 2015; 73:1609-14. [PMID: 24799044 PMCID: PMC4221580 DOI: 10.1002/mrm.25284] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 04/11/2014] [Accepted: 04/15/2014] [Indexed: 12/27/2022]
Abstract
PURPOSE Parallel imaging can be used to reduce imaging time and to increase the spatial coverage in hyperpolarized gas magnetic resonance imaging of the lung. In this proof-of-concept study, we investigate the effects of parallel imaging on the morphometric measurement of lung microstructure using diffusion magnetic resonance imaging with hyperpolarized (3) He. METHODS Fully sampled and under-sampled multi-b diffusion data were acquired from human subjects using an 8-channel (3) He receive coil. A parallel imaging reconstruction technique (generalized autocalibrating partially parallel acquisitions [GRAPPA]) was used to reconstruct under-sampled k-space data. The morphometric results of the generalized autocalibrating partially parallel acquisitions-reconstructed data were compared with the results of fully sampled data for three types of subjects: healthy volunteers, mild, and moderate chronic obstructive pulmonary disease patients. RESULTS Morphometric measurements varied only slightly at mild acceleration factors. The results were largely well preserved compared to fully sampled data for different lung conditions. CONCLUSION Parallel imaging, given sufficient signal-to-noise ratio, provides a reliable means to accelerate hyperpolarized-gas magnetic resonance imaging with no significant difference in the measurement of lung morphometry from the fully sampled images. GRAPPA is a promising technique to significantly reduce imaging time and/or to improve the spatial coverage for the morphometric measurement with hyperpolarized gases.
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Affiliation(s)
- Yulin V Chang
- Biomedical Magnetic Resonance Laboratory, Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri, USA
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27
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Binter C, Ramb R, Jung B, Kozerke S. A g-factor metric for k-t SENSE and k-t PCA based parallel imaging. Magn Reson Med 2015; 75:562-71. [PMID: 25809284 DOI: 10.1002/mrm.25606] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 11/21/2014] [Accepted: 12/12/2014] [Indexed: 11/09/2022]
Abstract
PURPOSE To propose and validate a g-factor formalism for k-t SENSE, k-t PCA and related k-t methods for assessing SNR and temporal fidelity. METHODS An analytical gxf -factor formulation in the spatiotemporal frequency domain is derived, enabling assessment of noise and depiction fidelity in both the spatial and frequency domain. Using pseudoreplica analysis of cardiac cine data the gxf -factor description is validated and example data are used to analyze the performance of k-t methods for various parameter settings. RESULTS Analytical gxf -factor maps were found to agree well with pseudoreplica analysis for 3x, 5x, and 7x k-t SENSE and k-t PCA. While k-t SENSE resulted in lower average gxf values (gx (avg) ) in static regions when compared with k-t PCA, k-t PCA yielded lower gx (avg) values in dynamic regions. Temporal transfer was better preserved with k-t PCA for increasing undersampling factors. CONCLUSION The proposed gxf -factor and temporal transfer formalism allows assessing noise performance and temporal depiction fidelity of k-t methods including k-t SENSE and k-t PCA. The framework enables quantitative comparison of different k-t methods relative to frame-by-frame parallel imaging reconstruction.
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Affiliation(s)
- Christian Binter
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Rebecca Ramb
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, Freiburg, Germany
| | - Bernd Jung
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, Freiburg, Germany.,Institute for Diagnostic, Interventional and Pediatric Radiology, University Hospital Berne, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.,Imaging Sciences and Biomedical Engineering, King's College London, United Kingdom
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28
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Sawada T, Yashiro M, Sentani K, Oue N, Yasui W, Miyazaki K, Kai K, Fushida S, Fujimura T, Ohira M, Kakeji Y, Natsugoe S, Shirabe K, Nomura S, Shimada Y, Tomita N, Hirakawa K, Maehara Y. New molecular staging with G-factor supplements TNM classification in gastric cancer: a multicenter collaborative research by the Japan Society for Gastroenterological Carcinogenesis G-Project committee. Gastric Cancer 2015; 18:119-28. [PMID: 24488015 PMCID: PMC4257995 DOI: 10.1007/s10120-014-0338-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Accepted: 12/30/2013] [Indexed: 02/07/2023]
Abstract
BACKGROUND The G-Project committee was erected by the Japan Society for Gastroenterological Carcinogenesis with an aim of establishing a new classification scheme based on molecular biological characteristics that would supplement the conventional TNM classification to better predict outcome. METHODS In a literature search involving 822 articles on gastric cancer, eight molecules including p53, vascular endothelial growth factor (VEGF)-A, VEGF-C, matrix metalloproteinase-7 (MMP-7), human epidermal growth factor receptor 2, Regenerating islet-derived family, member 4, olfactomedin-4 and Claudin-18 were selected as candidates to be included in the new molecular classification scheme named G-factor. A total of 210 cases of gastric cancer who underwent curative R0 resection were registered from four independent facilities. Immunohistochemical staining for the aforementioned molecules was performed for the surgically resected specimens of the 210 cases to investigate the correlation between clinicopathological factors and expression of each molecule. RESULTS No significant correlation was observed between the immunostaining expression of any of the eight factors and postoperative recurrence. However, the expressions of p53 and MMP-7 were significantly correlated with overall survival (OS). When 210 gastric cancer patients were divided into three groups based on the expression of p53 and MMP-7 (G0 group: negative for both p53 and MMP-7, n = 69, G1 group: positive for either p53 or MMP-7, n = 97, G2 group: positive for both of the molecules, n = 44), G2 group demonstrated significantly higher recurrence rate (59%) compared to 38% in G0 (p = 0.047). The multivariate regression analysis revealed that G2 group was independently associated with a shorter disease-free survival (DFS) (hazard ratio 1.904, 95% CI 1.098-3.303; p = 0.022), although the association with OS was not significant. Stage II patients among the G2 group had significantly inferior prognosis both in terms of OS and DFS when compared with those among the G0/G1 group, with survival curves similar to those of Stage III cases. CONCLUSIONS G-factor based on the expression of p53 and MMP-7 was found to be a promising factor to predict outcome of Stage II/III gastric cancer, and possibly to help select the treatment for Stage II cancer, thus supplementing the conventional TNM system.
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Affiliation(s)
- Tetsuji Sawada
- Department of Surgical Oncology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka, 545-8585, Japan,
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29
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Chang Y, Pipe JG, Karis JP, Gibbs WN, Zwart NR, Schär M. The effects of SENSE on PROPELLER imaging. Magn Reson Med 2014; 74:1598-608. [PMID: 25522132 DOI: 10.1002/mrm.25557] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 10/27/2014] [Accepted: 11/08/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE To study how sensitivity encoding (SENSE) impacts periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) image quality, including signal-to-noise ratio (SNR), robustness to motion, precision of motion estimation, and image quality. METHODS Five volunteers were imaged by three sets of scans. A rapid method for generating the g-factor map was proposed and validated via Monte Carlo simulations. Sensitivity maps were extrapolated to increase the area over which SENSE can be performed and therefore enhance the robustness to head motion. The precision of motion estimation of PROPELLER blades that are unfolded with these sensitivity maps was investigated. An interleaved R-factor PROPELLER sequence was used to acquire data with similar amounts of motion with and without SENSE acceleration. Two neuroradiologists independently and blindly compared 214 image pairs. RESULTS The proposed method of g-factor calculation was similar to that provided by the Monte Carlo methods. Extrapolation and rotation of the sensitivity maps allowed for continued robustness of SENSE unfolding in the presence of motion. SENSE-widened blades improved the precision of rotation and translation estimation. PROPELLER images with a SENSE factor of 3 outperformed the traditional PROPELLER images when reconstructing the same number of blades. CONCLUSION SENSE not only accelerates PROPELLER but can also improve robustness and precision of head motion correction, which improves overall image quality even when SNR is lost due to acceleration. The reduction of SNR, as a penalty of acceleration, is characterized by the proposed g-factor method.
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Affiliation(s)
- Yuchou Chang
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - James G Pipe
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - John P Karis
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Wende N Gibbs
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Nicholas R Zwart
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Michael Schär
- Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.,Philips Healthcare, Cleveland, Ohio, USA.,Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA
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30
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Ramb R, Binter C, Schultz G, Assländer J, Breuer F, Zaitsev M, Kozerke S, Jung B. A g-factor metric for k-t-GRAPPA- and PEAK-GRAPPA-based parallel imaging. Magn Reson Med 2014; 74:125-135. [PMID: 25043689 DOI: 10.1002/mrm.25386] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Revised: 07/01/2014] [Accepted: 07/05/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE The aim of this work is to derive a theoretical framework for quantitative noise and temporal fidelity analysis of time-resolved k-space-based parallel imaging methods. THEORY An analytical formalism of noise distribution is derived extending the existing g-factor formulation for nontime-resolved generalized autocalibrating partially parallel acquisition (GRAPPA) to time-resolved k-space-based methods. The noise analysis considers temporal noise correlations and is further accompanied by a temporal filtering analysis. METHODS All methods are derived and presented for k-t-GRAPPA and PEAK-GRAPPA. A sliding window reconstruction and nontime-resolved GRAPPA are taken as a reference. Statistical validation is based on series of pseudoreplica images. The analysis is demonstrated on a short-axis cardiac CINE dataset. RESULTS The superior signal-to-noise performance of time-resolved over nontime-resolved parallel imaging methods at the expense of temporal frequency filtering is analytically confirmed. Further, different temporal frequency filter characteristics of k-t-GRAPPA, PEAK-GRAPPA, and sliding window are revealed. CONCLUSION The proposed analysis of noise behavior and temporal fidelity establishes a theoretical basis for a quantitative evaluation of time-resolved reconstruction methods. Therefore, the presented theory allows for comparison between time-resolved parallel imaging methods and also nontime-resolved methods. Magn Reson Med 74:125-135, 2015. © 2014 Wiley Periodicals, Inc.
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Affiliation(s)
- Rebecca Ramb
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, University of Freiburg, Freiburg, Germany
| | - Christian Binter
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Gerrit Schultz
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, University of Freiburg, Freiburg, Germany
| | - Jakob Assländer
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, University of Freiburg, Freiburg, Germany
| | - Felix Breuer
- Research Center Magnetic Resonance Bavaria, Diagnostic Imaging, Wuerzburg, Germany
| | - Maxim Zaitsev
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, University of Freiburg, Freiburg, Germany
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.,Imaging Sciences and Biomedical Engineering, King's College London, London, UK
| | - Bernd Jung
- Department of Diagnostic Radiology, Medical Physics, University Medical Center, University of Freiburg, Freiburg, Germany.,Institute of Diagnostic, Interventional and Pediatric Radiology, University Hospital Bern, Bern, Switzerland
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31
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Affiliation(s)
- Richard J Haier
- Emeritus, Pediatrics, School of Medicine, University of California Irvine, CA, USA
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Huang TY, Liang CT, Chen YF, Simmons MY, Kim GH, Ritchie DA. Direct measurement of the spin gaps in a gated GaAs two-dimensional electron gas. Nanoscale Res Lett 2013; 8:138. [PMID: 23522392 PMCID: PMC3626693 DOI: 10.1186/1556-276x-8-138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Accepted: 03/09/2013] [Indexed: 06/02/2023]
Abstract
We have performed magnetotransport measurements on gated GaAs two-dimensional electron gases in which electrons are confined in a layer of the nanoscale. From the slopes of a pair of spin-split Landau levels (LLs) in the energy-magnetic field plane, we can perform direct measurements of the spin gap for different LLs. The measured g-factor g is greatly enhanced over its bulk value in GaAs (0.44) due to electron-electron (e-e) interactions. Our results suggest that both the spin gap and g determined from conventional activation energy studies can be very different from those obtained by direct measurements.
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Affiliation(s)
- Tsai-Yu Huang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Yang Fang Chen
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Michelle Y Simmons
- School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Gil-Ho Kim
- School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746, South Korea
| | - David A Ritchie
- Cavendish Laboratory, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
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Lin FH, Vesanen PT, Nieminen JO, Hsu YC, Zevenhoven KCJ, Dabek J, Parkkonen LT, Zhdanov A, Ilmoniemi RJ. Noise amplification in parallel whole-head ultra-low-field magnetic resonance imaging using 306 detectors. Magn Reson Med 2012; 70:595-600. [PMID: 23023497 DOI: 10.1002/mrm.24479] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2012] [Revised: 08/09/2012] [Accepted: 08/09/2012] [Indexed: 11/08/2022]
Abstract
In ultra-low-field magnetic resonance imaging, arrays of up to hundreds of highly sensitive superconducting quantum interference devices (SQUIDs) can be used to detect the weak magnetic fields emitted by the precessing magnetization. Here, we investigate the noise amplification in sensitivity-encoded ultra-low-field MRI at various acceleration rates using a SQUID array consisting of 102 magnetometers, 102 gradiometers, or 306 magnetometers and gradiometers, to cover the whole head. Our results suggest that SQUID arrays consisting of 102 magnetometers and 102 gradiometers are similar in g-factor distribution. A SQUID array of 306 sensors (102 magnetometers and 204 gradiometers) only marginally improves the g-factor. Corroborating with previous studies, the g-factor in 2D sensitivity-encoded ultra-low-field MRI with 9 to 16-fold 2D accelerations using the SQUID array studied here may be acceptable.
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Affiliation(s)
- Fa-Hsuan Lin
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
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Tanaka A, Nakashima K. DFT studies of ESR parameters for N-O centered radicals, N-alkoxyaminyl and aminoxyl radicals. Magn Reson Chem 2011; 49:603-610. [PMID: 21823164 DOI: 10.1002/mrc.2792] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 05/22/2011] [Accepted: 06/17/2011] [Indexed: 05/31/2023]
Abstract
Theoretical calculations of ESR parameters for aminoxyl radicals have been widely studied using the density functional theory (DFT) calculations. However, the isomer N-alkoxyaminyl radicals have been limitedly studied. With the use of experimental data for 46 N-alkoxyaminyl and 38 aminoxyl radicals, the isotropic (14)N hyperfine coupling constants (aN ) and g-factors have been theoretically estimated by several DFT calculations. The best calculation scheme of aN for N-alkoxyaminyl radicals was PCM/B3LYP/6-31 + + G(d,p) (R(2) = 0.9519, MAE = 0.034 mT), and that for aminoxyl radicals was PCM/BHandHLYP/6-31 + + G(3df,3pd) (R(2) = 0.9336, MAE = 0.057 mT). For aminoxyl radicals, the solvation models in calculations enhanced the accuracy of reproducibility. In contrast, for N-alkoxyaminyl radicals the calculations with solvation models provided no improvement. The differences in the best functionals between two types of radicals were thought to come from the contribution ratios of neutral and dipolar canonical structures in resonance forms. The aN for N-alkoxyaminyl radicals that were stabilized by small contribution of dipolar canonical structures could be precisely reproduced by B3LYP with only 20% HF exact exchange. In contrast, the aN for aminoxyl radicals stabilized by large contribution of dipolar canonical structures was well reproduced by BHandHLYP with 50% HF exchange. The best calculation scheme of g-factors was IEFPCM/B3LYP/6-31 + G(d,p) (R(2) = 0.9767, MAE = 0.0001) for not only aminoxyl but also N-alkoxyaminyl radicals.
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Affiliation(s)
- Akio Tanaka
- Organic Synthesis Research Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka 554-8558, Japan.
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