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Possible flat band bending of the Bi1.5Sb0.5Te1.7Se1.3 crystal cleaved in an ambient air probed by terahertz emission spectroscopy.

ABSTRACT: We investigate an evolution of the surface electronic state of the Bi1.5Sb0.5Te1.7Se1.3 single crystal, which is one of the most bulk insulating topological insulators, by examining terahertz light emitted from the sample surface upon the illumination of the near-infrared femtosecond laser pulses. We find that the surface state with a flat band bending can appear in the course of the natural maturation process of the surface state in an ambient air. Furthermore, we demonstrate that the evolution of the surface electronic state can be accelerated, decelerated, or even stopped by controlling environmental conditions to contain different amount of H2O, in particular.

SUBMITTER: Park SH

PROVIDER: S-EPMC5090861 | biostudies-other | 2016 Nov

REPOSITORIES: biostudies-other

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Possible flat band bending of the Bi1.5Sb0.5Te1.7Se1.3 crystal cleaved in an ambient air probed by terahertz emission spectroscopy.

Park Soon Hee SH Hamh Sun Young SY Park Joonbum J Kim Jun Sung JS Lee Jong Seok JS

Scientific reports 20161102

We investigate an evolution of the surface electronic state of the Bi1.5Sb0.5Te1.7Se1.3 single crystal, which is one of the most bulk insulating topological insulators, by examining terahertz light emitted from the sample surface upon the illumination of the near-infrared femtosecond laser pulses. We find that the surface state with a flat band bending can appear in the course of the natural maturation process of the surface state in an ambient air. Fu ...[more]

PMID: 27805036

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Project description:ImportanceAmyloid-β (Aβ) deposition is a feature of Alzheimer disease (AD) and may be promoted by exogenous factors, such as ambient air quality.ObjectiveTo examine the association between the likelihood of amyloid positron emission tomography (PET) scan positivity and ambient air quality in individuals with cognitive impairment.Design, setting, and participantsThis cross-sectional study used data from the Imaging Dementia-Evidence for Amyloid Scanning Study, which included more than 18 000 US participants with cognitive impairment who received an amyloid PET scan with 1 of 3 Aβ tracers (fluorine 18 [18F]-labeled florbetapir, 18F-labeled florbetaben, or 18F-labeled flutemetamol) between February 16, 2016, and January 10, 2018. A sample of older adults with mild cognitive impairment (MCI) or dementia was selected.ExposuresAir pollution was estimated at the patient residence using predicted fine particulate matter (PM2.5) and ground-level ozone (O3) concentrations from the Environmental Protection Agency Downscaler model. Air quality was estimated at 2002 to 2003 (early, or approximately 14 [range, 13-15] years before amyloid PET scan) and 2015 to 2016 (late, or approximately 1 [range, 0-2] years before amyloid PET scan).Main outcomes and measuresPrimary outcome measure was the association between air pollution and the likelihood of amyloid PET scan positivity, which was measured as odds ratios (ORs) and marginal effects, adjusting for demographic, lifestyle, and socioeconomic factors and medical comorbidities, including respiratory, cardiovascular, cerebrovascular, psychiatric, and neurological conditions.ResultsThe data set included 18 178 patients, of which 10 991 (60.5%) had MCI and 7187 (39.5%) had dementia (mean [SD] age, 75.8 [6.3] years; 9333 women [51.3%]). Living in areas with higher estimated biennial PM2.5 concentrations in 2002 to 2003 was associated with a higher likelihood of amyloid PET scan positivity (adjusted OR, 1.10; 95% CI, 1.05-1.15; z score = 3.93; false discovery rate [FDR]-corrected P < .001; per 4-μg/m3 increments). Results were similar for 2015 to 2016 data (OR, 1.15; 95% CI, 1.05-1.26, z score = 3.14; FDR-corrected P = .003). An average marginal effect (AME) of +0.5% (SE = 0.1%; z score, 3.93; 95% CI, 0.3%-0.7%; FDR-corrected P < .001) probability of amyloid PET scan positivity for each 1-μg/m3 increase in PM2.5 was observed for 2002 to 2003, whereas an AME of +0.8% (SE = 0.2%; z score = 3.15; 95% CI, 0.3%-1.2%; FDR-corrected P = .002) probability was observed for 2015 to 2016. Post hoc analyses showed no effect modification by sex (2002-2003: interaction term β = 1.01 [95% CI, 0.99-1.04; z score = 1.13; FDR-corrected P = .56]; 2015-2016: β = 1.02 [95% CI, 0.98-1.07; z score = 0.91; FDR-corrected P = .56]) or clinical stage (2002-2003: interaction term β = 1.01 [95% CI, 0.99-1.03; z score = 0.77; FDR-corrected P = .58]; 2015-2016: β = 1.03; 95% CI, 0.99-1.08; z score = 1.46; FDR-corrected P = .47]). Exposure to higher O3 concentrations was not associated with amyloid PET scan positivity in both time windows.Conclusions and relevanceThis study found that higher PM2.5 concentrations appeared to be associated with brain Aβ plaques. These findings suggest the need to consider airborne toxic pollutants associated with Aβ pathology in public health policy decisions and to inform individual lifetime risk of developing AD and dementia.

Dataset Information

Possible flat band bending of the Bi1.5Sb0.5Te1.7Se1.3 crystal cleaved in an ambient air probed by terahertz emission spectroscopy.

Publications

Possible flat band bending of the Bi<sub>1.5</sub>Sb<sub>0.5</sub>Te<sub>1.7</sub>Se<sub>1.3</sub> crystal cleaved in an ambient air probed by terahertz emission spectroscopy.

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