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10. Evolution of the electronic structure of ultrathin MnBi2Te4 Films

Author

Xu, Runzhe, Bai, Yunhe, Zhou, Jingsong, Li, Jiaheng, Gu, Xu, Qin, Na, Yin, Zhongxu, Du, Xian, Zhang, Qinqin, Zhao, Wenxuan, Li, Yidian, Wu, Yang, Ding, Cui, Wang, Lili, Liang, Aiji, Liu, Zhongkai, Xu, Yong, Feng, Xiao, He, Ke, Chen, Yulin, and Yang, Lexian

Subjects
Condensed Matter - Materials Science
Abstract

Ultrathin films of intrinsic magnetic topological insulator MnBi2Te4 exhibit fascinating quantum properties such as quantum anomalous Hall effect and axion insulator state. In this work, we systematically investigate the evolution of the electronic structure of MnBi2Te4 thin films. With increasing film thickness, the electronic structure changes from an insulator-type with a large energy gap to one with in-gap topological surface states, which is, however, still drastically different from the bulk material. By surface doping of alkali-metal atoms, a Rashba split band gradually emerges and hybridizes with topological surface states, which not only reconciles the puzzling difference between the electronic structures of the bulk and thin film MnBi2Te4 but also provides an interesting platform to establish Rashba ferromagnet that is attractive for (quantum) anomalous Hall effect. Our results provide important insights into the understanding and engineering of the intriguing quantum properties of MnBi2Te4 thin films., Comment: Online published in Nano Letters

Published
2022
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11. Persistent exchange splitting in a chiral helimagnet Cr1/3NbS2

Author

Qin, Na, Chen, Cheng, Du, Shiqiao, Du, Xian, Zhang, Xin, Yin, Zhongxu, Zhou, Jingsong, Xu, Runzhe, Gu, Xu, Zhang, Qinqin, Zhao, Wenxuan, Li, Yidian, Mo, Sung-Kwan, Liu, Zhongkai, Zhang, Shilei, Guo, Yanfeng, Tang, P. Z., Chen, Yulin, and Yang, Lexian

Subjects
Condensed Matter - Materials Science
Abstract

Using high-resolution angle-resolved photoemission spectroscopy (ARPES) and ab-initio calculation, we systematically investigate the electronic structure of the chiral helimagnet Cr1/3NbS2 and its temperature evolution. The comparison with NbS2 suggests that the electronic structure of Cr1/3NbS2 is strongly modified by the intercalation of Cr atoms. Our ab-initio calculation, consistent with experimental result, suggests strong hybridization between Nb- and Cr-derived states near the Fermi level. In the chiral helimagnetic state (below the Curie temperature Tc), we observe exchange splitting of the energy bands crossing EF, which follows the temperature evolution of the magnetic moment, suggesting an important role of the conduction electrons in the long-range magnetic ordering. Interestingly, the exchange splitting persists far above Tc with negligible temperature dependence, in drastic contrast to the itinerant ferromagnetism described by the Stoner model, indicating the existence of short-range magnetic order. Our results provide important insights into the microscopic mechanism of the chiral helimagnetic ordering in Cr1/3NbS2.

Published
2022
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12. Persistent exchange splitting in the chiral helimagnet Cr1/3NbS2

Author

Qin, Na, Chen, Cheng, Du, Shiqiao, Du, Xian, Zhang, Xin, Yin, Zhongxu, Zhou, Jingsong, Xu, Runzhe, Gu, Xu, Zhang, Qinqin, Zhao, Wenxuan, Li, Yidian, Mo, Sung-Kwan, Liu, Zhongkai, Zhang, Shilei, Guo, Yanfeng, Tang, Peizhe, Chen, Yulin, and Yang, Lexian

Subjects
Physical Sciences, Condensed Matter Physics, Chemical sciences, Engineering, Physical sciences
Abstract

Using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structure of the chiral helimagnet Cr1/3NbS2 and its temperature evolution. The comparison with NbS2 suggests that the electronic structure of Cr1/3NbS2 is strongly modified by the intercalation of Cr atoms. Our ab initio calculation, consistent with experimental results, suggests strong hybridization between Nb- and Cr-derived states near the Fermi level. In the chiral helimagnetic state (below the Curie temperature, Tc), we observe exchange splitting of the energy bands crossing the Fermi level, which follows the temperature evolution of the magnetic moment, suggesting a strong interaction between the conduction electrons and Cr spin moments. Interestingly, the exchange splitting persists far above Tc with weak temperature dependence, in drastic contrast to the itinerant ferromagnetism described by the Stoner model, indicating the existence of short-range magnetic order. Our results provide important insights into the interplay between the electronic structure and magnetism in Cr1/3NbS2, which is helpful for understanding the microscopic mechanism of chiral helimagnetic ordering.

Published
2022

21. Tripartite motif containing 26 prevents steatohepatitis progression by suppressing C/EBPδ signalling activation

Author

Xu, Minxuan, Tan, Jun, Liu, Xin, Han, Li, Ge, Chenxu, Zhang, Yujie, Luo, Fufang, Wang, Zhongqin, Xue, Xiaoqin, Xiong, Liangyin, Wang, Xin, Zhang, Qinqin, Wang, Xiaoxin, Tian, Qin, Zhang, Shuguang, Meng, Qingkun, Dai, Xianling, Kuang, Qin, Li, Qiang, Lou, Deshuai, Hu, Linfeng, Liu, Xi, Kuang, Gang, Luo, Jing, Chang, Chunxiao, Wang, Bochu, Chai, Jie, Shi, Shengbin, and Han, Lianyi

Published
2023
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35. CommunityGAN: Community Detection with Generative Adversarial Nets

Author

Jia, Yuting, Zhang, Qinqin, Zhang, Weinan, and Wang, Xinbing

Subjects
Computer Science - Artificial Intelligence, Computer Science - Social and Information Networks
Abstract

Community detection refers to the task of discovering groups of vertices sharing similar properties or functions so as to understand the network data. With the recent development of deep learning, graph representation learning techniques are also utilized for community detection. However, the communities can only be inferred by applying clustering algorithms based on learned vertex embeddings. These general cluster algorithms like K-means and Gaussian Mixture Model cannot output much overlapped communities, which have been proved to be very common in many real-world networks. In this paper, we propose CommunityGAN, a novel community detection framework that jointly solves overlapping community detection and graph representation learning. First, unlike the embedding of conventional graph representation learning algorithms where the vector entry values have no specific meanings, the embedding of CommunityGAN indicates the membership strength of vertices to communities. Second, a specifically designed Generative Adversarial Net (GAN) is adopted to optimize such embedding. Through the minimax competition between the motif-level generator and discriminator, both of them can alternatively and iteratively boost their performance and finally output a better community structure. Extensive experiments on synthetic data and real-world tasks demonstrate that CommunityGAN achieves substantial community detection performance gains over the state-of-the-art methods., Comment: 11 pages, 9 figures, 7 tables

Published
2019

39. OCT Angiography to Predict Geographic Atrophy Progression using Choriocapillaris Flow Void as a Biomarker.

Author

Nattagh, Khashayar, Zhou, Hao, Rinella, Nicholas, Zhang, Qinqin, Dai, Yining, Foote, Katharina G, Keiner, Cathrine, Deiner, Michael, Duncan, Jacque L, Porco, Travis C, Wang, Ruikang K, and Schwartz, Daniel M

Subjects
AMD, OCTA, choriocapillaris, flow void, geographic atrophy, Biomedical Engineering, Opthalmology and Optometry
Abstract

PurposeTo investigate the relationship between choriocapillaris (CC) flow void (FV) percentage and geographic atrophy (GA) growth rate, and study how variations in FV percentage surrounding GA predict regional GA growth.MethodsThis prospective, longitudinal study enrolled subjects with GA secondary to nonexudative age-related macular degeneration. Optical coherence tomography angiography imaged the CC and FV percentage was evaluated using a validated algorithm. GA growth rate was measured as the difference in the square root of GA area divided by the months between baseline and follow-up imaging.ResultsTwelve eyes from 7 subjects with a mean age of 80 ± 5 years (range 74-86) were studied once at baseline and 7 to 16 months later. GA expansion rate was positively correlated with increased CC FV percentage (Spearman rank correlation coefficient r = 0.69 [P = 0.038] and 0.76 [P = 0.013]) within the 6 x 6 mm scanned macular region and the 2° margin surrounding each GA lesion, respectively. Regions with CC FV at baseline located within 480 µm from the GA margin showed 33% greater chance of becoming atrophic compared with regions within 480 µm from the GA margin that did not show CC FV at baseline.ConclusionsGA expansion rate and CC FV density throughout the macular region and surrounding the GA margin were significantly correlated. The regional magnitude of FV immediately surrounding GA was associated with GA growth into that region.Translational relevanceCC FV analysis may facilitate prediction of GA growth over time for patients with advanced nonneovascular age-related macular degeneration.

Published
2020

40. Cone Structure Persists Beyond Margins of Short-Wavelength Autofluorescence in Choroideremia

Author

Foote, Katharina G, Rinella, Nicholas, Tang, Janette, Bensaid, Nicolas, Zhou, Hao, Zhang, Qinqin, Wang, Ruikang K, Porco, Travis C, Roorda, Austin, and Duncan, Jacque L

Subjects
Biomedical and Clinical Sciences, Ophthalmology and Optometry, Eye Disease and Disorders of Vision, Clinical Research, Neurosciences, Eye, Adolescent, Adult, Aged, Choroid, Choroideremia, Female, Humans, Male, Middle Aged, Multimodal Imaging, Ophthalmoscopy, Optical Imaging, Radio Waves, Retinal Cone Photoreceptor Cells, Retinal Pigment Epithelium, Tomography, Optical Coherence, Visual Field Tests, Visual Fields, Young Adult, choroideremia, fundus autofluorescence, microperimetry, adaptive optics scanning laser ophthalmoscopy, optical coherence tomography angiography, Biological Sciences, Medical and Health Sciences, Ophthalmology & Optometry, Ophthalmology and optometry
Abstract

PurposeWe studied the relationship between structure and function of the choriocapillaris (CC), retinal pigment epithelium (RPE), and photoreceptors in patients with choroideremia (CHM).MethodsSix CHM patients (12 eyes) and four normal subjects (six eyes) were studied with fundus-guided microperimetry, confocal and nonconfocal adaptive optics scanning laser ophthalmoscopy (AOSLO), near-infrared and color fundus photos, short wavelength fundus autofluorescence (SW-AF), and swept-source optical coherence tomography (SS-OCT) and angiography (SS-OCTA) images. Cone spacing was represented using Z-scores (standard deviations from the mean at that eccentricity). CC flow voids were defined using a threshold of 1 SD below the normal mean.ResultsCone spacing Z-scores were not significantly correlated with distance from the borders of preserved RPE, determined using either the SS-OCT or SW-AF scans. Cone spacing Z-scores were significantly correlated with CC flow voids and retinal sensitivity. Flow voids were abnormal in regions of preserved RPE and increased progressively from within -2° of the preserved area to +2° beyond the border. Visual sensitivity decreased as CC flow voids increased approaching and beyond the border of preserved structure.ConclusionsIn CHM, cone spacing Z-scores correlated with CC flow voids, and were negatively correlated with retinal sensitivity, suggesting cone degeneration accompanied reduced CC perfusion. Functional cones were found outside the presumed borders of preserved outer-retina/RPE as defined by SW-AF, but not outside the borders determined by SS-OCT. The use of SW-AF to identify the border of preserved structures may underestimate regions with cells that may be amenable to treatment.

Published
2019

44. Generating retinal flow maps from structural optical coherence tomography with artificial intelligence

Author

Lee, Cecilia S., Tyring, Ariel J., Wu, Yue, Xiao, Sa, Rokem, Ariel S., Deruyter, Nicolaas P., Zhang, Qinqin, Tufail, Adnan, Wang, Ruikang K., and Lee, Aaron Y.

Subjects
Computer Science - Computer Vision and Pattern Recognition, Computer Science - Artificial Intelligence, Statistics - Machine Learning
Abstract

Despite significant advances in artificial intelligence (AI) for computer vision, its application in medical imaging has been limited by the burden and limits of expert-generated labels. We used images from optical coherence tomography angiography (OCTA), a relatively new imaging modality that measures perfusion of the retinal vasculature, to train an AI algorithm to generate vasculature maps from standard structural optical coherence tomography (OCT) images of the same retinae, both exceeding the ability and bypassing the need for expert labeling. Deep learning was able to infer perfusion of microvasculature from structural OCT images with similar fidelity to OCTA and significantly better than expert clinicians (P < 0.00001). OCTA suffers from need of specialized hardware, laborious acquisition protocols, and motion artifacts; whereas our model works directly from standard OCT which are ubiquitous and quick to obtain, and allows unlocking of large volumes of previously collected standard OCT data both in existing clinical trials and clinical practice. This finding demonstrates a novel application of AI to medical imaging, whereby subtle regularities between different modalities are used to image the same body part and AI is used to generate detailed and accurate inferences of tissue function from structure imaging., Comment: Under revision at Nature Communications. Submitted on June 5th 2017

Published
2018

49. Quantifying choriocapillaris hypoperfusion in patients with choroidal neovascularization using swept-source OCT angiography.

Author

Keiner, Cathrine M, Zhou, Hao, Zhang, Qinqin, Wang, Ruikang K, Rinella, Nicholas T, Oldenburg, Catherine E, Duncan, Jacque L, and Schwartz, Daniel M

Subjects
AMD, OCT angiography, OCTA, flow void, Opthalmology and Optometry
Abstract

Purpose:To compare choriocapillaris flow voids (FV) in patients with neovascular age-related macular degeneration (AMD) with age-matched normal controls using swept-source optical coherence tomography angiography (SS-OCTA). Patients and methods:Eleven eyes of 11 subjects with neovascular AMD and 11 eyes of 11 age-similar normal subjects were imaged using SS-OCTA with a 6x6mm scanning pattern. Choriocapillaris FV, defined as a percentage of regions determined to have flow deficits divided by the total scanned region, was measured using a one standard deviation thresholding algorithm developed from a database of age-similar normal subjects. Results:Choriocapillaris FV was more extensive in patients with choroidal neovascularization (CNV) compared to age-similar normal subjects (FV: 20.56±4.95, 95% CI: 17.64-23.49 vs FV: 10.95±2.08, 95% CI: 9.73-12.18, respectively; P=0.0001). FV within a two-degree margin surrounding CNV in wet AMD subjects (FV: 35.04±9.34; 95% CI: 29.52-40.56) was increased compared to normal subjects (P

Published
2019

50. OCT Angiography and Cone Photoreceptor Imaging in Geographic Atrophy

Author

Qin, Jia, Rinella, Nicholas, Zhang, Qinqin, Zhou, Hao, Wong, Jessica, Deiner, Michael, Roorda, Austin, Porco, Travis C, Wang, Ruikang K, Schwartz, Daniel M, and Duncan, Jacque L

Subjects
Biomedical and Clinical Sciences, Ophthalmology and Optometry, Neurodegenerative, Prevention, Aging, Eye Disease and Disorders of Vision, Macular Degeneration, Neurosciences, Biomedical Imaging, Clinical Research, Bioengineering, Aged, Aged, 80 and over, Choroid, Female, Fluorescein Angiography, Geographic Atrophy, Humans, Male, Middle Aged, Multimodal Imaging, Ophthalmoscopy, Optical Imaging, Retinal Cone Photoreceptor Cells, Tomography, Optical Coherence, adaptive optics scanning laser ophthalmoscopy, geographic atrophy, swept source optical coherence tomography angiography, Biological Sciences, Medical and Health Sciences, Ophthalmology & Optometry, Ophthalmology and optometry
Abstract

PurposeTo compare cone spacing and choriocapillaris (CC) perfusion adjacent to geographic atrophy (GA) in patients with age-related macular degeneration (AMD) and age-similar normal eyes.MethodsSubjects were imaged using adaptive optics scanning laser ophthalmoscopy (AOSLO), fundus autofluorescence (FAF), and swept-source optical coherence tomography angiography. The GA border was identified using FAF images; CC flow void was analyzed in 1° regions extending from the GA border. A grader masked to CC perfusion selected regions of interest (ROIs) with unambiguous cone mosaics in AOSLO images. At each ROI, cone spacing and CC flow void were converted to Z-scores (standard deviations from the mean of 12 normal eyes aged 50 to 81 years for cone spacing, and 60 normal eyes age 51 to 88 years for CC flow void).ResultsExcluding regions of GA and drusen, CC flow void in eight eyes of six patients with AMD was significantly greater than in four age-similar normal eyes (exact permutation test, P = 0.024). CC flow void was negatively correlated with distance from the GA margin (r = -0.35; 95% confidence interval [CI], -0.53 to -0.12). Increased cone spacing was significantly correlated with CC flow void (r = 0.33; 95% CI, 0.12 to 0.59). Cone spacing was increased in 39% of ROIs, while CC flow void was increased in 96% of ROIs.ConclusionsIn eyes with GA due to AMD, CC hypoperfusion was significantly correlated with, and more extensive than, cone photoreceptor loss. The results suggest that reduced CC perfusion contributes to the development of GA.

Published
2018

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