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2,931 results on '"Xu, Xiaohui"'

3. Association of Gaseous Ambient Air Pollution and Dementia-Related Neuroimaging Markers in the ARIC Cohort, Comparing Exposure Estimation Methods and Confounding by Study Site

Author

Lynch, Katie M., Bennett, Erin E., Ying, Qi, Park, Eun Sug, Xu, Xiaohui, Smith, Richard L., Stewart, James D., Liao, Duanping, Kaufman, Joel D., Whitsel, Eric A., and Power, Melinda C.

Subjects
Dementia -- Risk factors -- Prevention, Neuroimaging -- Analysis, Air pollution -- Health aspects -- Environmental aspects, Particles -- Analysis, Atherosclerosis -- Diagnosis -- Care and treatment, Environmental issues, Health, Diagnosis, Care and treatment, Prevention, Analysis, Risk factors, Health aspects, Environmental aspects
Abstract

BACKGROUND: Evidence linking gaseous air pollution to late-life brain health is mixed. OBJECTIVE: We explored associations between exposure to gaseous pollutants and brain magnetic resonance imaging (MRI) markers among Atherosclerosis Risk in Communities (ARIC) Study participants, with attention to the influence of exposure estimation method and confounding by site. METHODS: We considered data from 1,665 eligible ARIC participants recruited from four US sites in the period 1987-1989 with valid brain MRI data from Visit 5 (2011-2013). We estimated 10-y (2001-2010) mean carbon monoxide (CO), nitrogen dioxide (N[O.sub.2]), nitrogen oxides (N[O.sub.x]), and 8-and 24-h ozone ([O.sub.3]) concentrations at participant addresses, using multiple exposure estimation methods. We estimated site-specific associations between pollutant exposures and brain MRI outcomes (total and regional volumes; presence of microhemorrhages, infarcts, lacunes, and severe white matter hyperintensities), using adjusted linear and logistic regression models. We compared meta-analytically combined site-specific associations to analyses that did not account for site. RESULTS: Within-site exposure distributions varied across exposure estimation methods. Meta-analytic associations were generally not statistically significant regardless of exposure, outcome, or exposure estimation method; point estimates often suggested associations between higher N[O.sub.2] and N[O.sub.x] and smaller temporal lobe, deep gray, hippocampal, frontal lobe, and Alzheimer disease signature region of interest volumes and between higher CO and smaller temporal and frontal lobe volumes. Analyses that did not account for study site more often yielded significant associations and sometimes different direction of associations. DISCUSSION: Patterns of local variation in estimated air pollution concentrations differ by estimation method. Although we did not find strong evidence supporting impact of gaseous pollutants on brain changes detectable by MRI, point estimates suggested associations between higher exposure to CO, N[O.sub.x], and N[O.sub.2] and smaller regional brain volumes. Analyses of air pollution and dementia-related outcomes that do not adjust for location likely underestimate uncertainty and may be susceptible to confounding bias. https://doi.org/10.1289/EHP13906, Introduction Growing evidence links air pollution to late-life cognitive health. Currently, the strongest evidence supports an effect of particulate matter (PM) air pollution. (1) In comparison with PM, fewer studies [...]

Published
2024
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6. Plasmonic Enhancement of Second Harmonic Generation in Weyl Semimetal TaAs

Author

Yang, Morris M., Ozlu, Mustafa, Peana, Samuel, Mkhitaryan, Vahagn, Sychev, Demid, Xu, Xiaohui, Martin, Zachariah M., Arachchige, Hasitha Suriya, Lagoutchev, Alexei, Mandurus, David, Shalaev, Vladimir, and Boltasseva, Alexandra

Subjects
Physics - Optics
Abstract

In this work a hybrid nanoplasmonic-Weyl Semimetal (WSM) structure is realized for the first time utilizing silver nanopatch antennas and WSM Tantalum Arsenide (TaAs). The studied hybrid WSM-nanoplasmonic structure demonstrated a substantial, over x4.5 enhancement of the second harmonic generation (SHG) process compared to a bare TaAs film. To realize the hybrid structure while preserving TaAs properties, a scalable, non-destructive manufacturing approach was developed that involves the fabrication of TaAs flakes from single crystalline TaAs, overgrowth of a silicon nitride overlayer, and drop-casting of silver nanopatch antennas. The strong polarization response of both the bare flakes, along with the hybrid-nanoplasmonic cavities demonstrates that this approach uniquely preserves the TaAs crystal structure and its optical response while providing significant enhancement of the nonlinear properties. The developed method allows leveraging the capabilities of plasmonics to control and enhance light-matter interactions at the nanometer scale to access and engineer WSM response. This work is the first step towards high-performance nanophotonic devices utilizing WSM topological properties.

Published
2023

10. Greatly Enhanced Emission from Spin Defects in Hexagonal Boron Nitride Enabled by a Low-Loss Plasmonic Nano-Cavity

Author

Xu, Xiaohui, Solanki, Abhishek. B., Sychev, Demid, Gao, Xingyu, Peana, Samuel, Baburin, Aleksandr S., Pagadala, Karthik, Martin, Zachariah O., Chowdhury, Sarah N., Chen, Yong P., Rodionov, Ilya A., Kildishev, Alexander V., Li, Tongcang, Upadhyaya, Pramey, Boltasseva, Alexandra, and Shalaev, Vladimir M.

Subjects
Physics - Optics, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Two-dimensional hexagonal boron nitride (hBN) has been known to host a variety of quantum emitters with properties suitable for a broad range of quantum photonic applications. Among them, the negatively charged boron vacancy (VB-) defect with optically addressable spin states has emerged recently due to its potential use in quantum sensing. Compared to spin defects in bulk crystals, VB- preserves its spin coherence properties when placed at nanometer-scale distances from the hBN surface, enabling nanometer-scale quantum sensing. On the other hand, the low quantum efficiency of VB- has hindered its use in practical applications. Several studies have reported improving the overall quantum efficiency of VB- defects using plasmonic effects; however, the overall enhancements of up to 17 times reported to date are relatively modest. In this study, we explore and demonstrate much higher emission enhancements of VB- with ultralow-loss nano-patch antenna (NPA) structures. An overall intensity enhancement of up to 250 times is observed for NPA-coupled VB- defects. Since the laser spot exceeds the area of the NPA, where the enhancement occurs, the actual enhancement provided by the NPA is calculated to be ~1685 times, representing a significant increase over the previously reported results. Importantly, the optically detected magnetic resonance (ODMR) contrast is preserved at such exceptionally strong enhancement. Our results not only establish NPA-coupled VB- defects as high-resolution magnetic field sensors operating at weak laser powers, but also provide a promising approach to obtaining single VB- defects., Comment: 17 pages, 4 figures

Published
2022
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26. Influencing factors and correlation analysis of population with high risk of cardiovascular diseases

Author

SHEN Xiafen, CAI Qiang, YU Wei, XU Xiaohui

Subjects
cardiovascular disease, high risk group, behavioral factor, cox regression, apriori algorithm, Medicine
Abstract

Objective To highlight the impact of behavioral and non-behavioral factors on cardiovascular health, disease prevention and management. Methods Cox regression and forest plots were used to assess and demonstrate the relationship between their behavioral and non-behavioral factors and cardiovascular disease (CVD) risk in a study population of 20 745 people at high cardiovascular risk from Zhejing province. Apriori algorithm was used to analyze the correlation between behavioral factors and non-behavioral factors for people with at least one of the greatest risk behavioral factors. Results The incidence of cardiovascular risk in Zhejiang province was positively related to age and inversely related to education level of target population. The higher risk was identified in in male and population in urban citities as compared to female and the people in rural areas; The risk was positively related to smoking intensity and showed a U-shaped association with alcohol intake; The incidence was lowest in those who were mainly standing during routine work; The risk was lower in those who had a clear distinction between busy and idle farming activity in farmers; Men who were engaged in general physical labor and never smoked nor drank high dose of alcohol; Women who never smoked and drank, but did not work and at home were important factors related to the higher cardiovascular risk rate. Conclusions There are a wide range of factors affecting the high-risk population of cardiovascular disease, and there is a certain correlation among these factors.

Published
2023
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34. Machine learning assisted quantum super-resolution microscopy

Author

Kudyshev, Zhaxylyk A., Sychev, Demid, Martin, Zachariah, Bogdanov, Simeon I., Xu, Xiaohui, Kildishev, Alexander V., Boltasseva, Alexandra, and Shalaev, Vladimir M.

Subjects
Physics - Optics, Electrical Engineering and Systems Science - Image and Video Processing
Abstract

One of the main characteristics of optical imaging systems is the spatial resolution, which is restricted by the diffraction limit to approximately half the wavelength of the incident light. Along with the recently developed classical super-resolution techniques, which aim at breaking the diffraction limit in classical systems, there is a class of quantum super-resolution techniques which leverage the non-classical nature of the optical signals radiated by quantum emitters, the so-called antibunching super-resolution microscopy. This approach can ensure a factor of $\sqrt{n}$ improvement in the spatial resolution by measuring the n-th order autocorrelation function. The main bottleneck of the antibunching super-resolution microscopy is the time-consuming acquisition of multi-photon event histograms. We present a machine learning-assisted approach for the realization of rapid antibunching super-resolution imaging and demonstrate 12 times speed-up compared to conventional, fitting-based autocorrelation measurements. The developed framework paves the way to the practical realization of scalable quantum super-resolution imaging devices that can be compatible with various types of quantum emitters.

Published
2021

50. Creating Quantum Emitters in Hexagonal Boron Nitride Deterministically on Chip-Compatible Substrates

Author

Xu, Xiaohui, Martin, Zachariah O., Sychev, Demid, Lagutchev, Alexei S., Chen, Yong, Taniguchi, Takashi, Watanabe, Kenji, Shalaev, Vladimir M., and Boltasseva, Alexandra

Subjects
Physics - Optics, Quantum Physics
Abstract

Two-dimensional hexagonal boron nitride (hBN) that hosts bright room-temperature single-photon emitters (SPEs) is a promising material platform for quantum information applications. An important step towards the practical application of hBN is the on-demand, position-controlled generation of SPEs. Several strategies have been reported to achieve the deterministic creation of hBN SPEs. However, they either rely on a substrate nanopatterning procedure that is not compatible with integrated photonic devices or utilize a radiation source that might cause unpredictable damage to hBN and underlying substrates. Here, we report a radiation- and lithography-free route to deterministically activate hBN SPEs by nanoindentation with an atomic force microscope (AFM) tip. The method is applied to thin hBN flakes (less than 25 nm in thickness) on flat silicon-dioxide-silicon substrates that can be readily integrated into on-chip photonic devices. The achieved SPEs yields are above 30% by utilizing multiple indent sizes, and a maximum yield of 36% is demonstrated for the indent size of around 400 nm. Our results mark an important step towards the deterministic creation and integration of hBN SPEs with photonic and plasmonic on-chip devices., Comment: 31 pages, 14 figures

Published
2021
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