scholarly journals Relationship between the effective attenuation coefficient of spaceborne lidar signal and the IOPs of seawater

2018 ◽  
Vol 26 (23) ◽  
pp. 30278 ◽  
Author(s):  
Qun Liu ◽  
Dong Liu ◽  
Jian Bai ◽  
YuPeng Zhang ◽  
Yudi Zhou ◽  
...  
Keyword(s):  
Attenuation Coefficient ◽  
Lidar Signal ◽  
Effective Attenuation Coefficient

scholarly journals The Optical Effective Attenuation Coefficient as an Informative Measure of Brain Health in Aging

Photonics ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 79
Author(s):  
Antonio M. Chiarelli ◽  
Kathy A. Low ◽  
Edward L. Maclin ◽  
Mark A. Fletcher ◽  
Tania S. Kong ◽  
...  
Keyword(s):  
Attenuation Coefficient ◽  
Near Infrared ◽  
Fluid Layer ◽  
Geometric Mean ◽  
Cortical Atrophy ◽  
Infrared Light ◽  
Scattering Coefficients ◽  
Age Related ◽  
Effective Attenuation Coefficient ◽  
Brain Data

Aging is accompanied by widespread changes in brain tissue. Here, we hypothesized that head tissue opacity to near-infrared light provides information about the health status of the brain’s cortical mantle. In diffusive media such as the head, opacity is quantified through the Effective Attenuation Coefficient (EAC), which is proportional to the geometric mean of the absorption and reduced scattering coefficients. EAC is estimated by the slope of the relationship between source–detector distance and the logarithm of the amount of light reaching the detector (optical density). We obtained EAC maps across the head in 47 adults (age range 18–75 years), using a high-density dual-wavelength optical system. We correlated regional and global EAC measures with demographic, neuropsychological, structural and functional brain data. Results indicated that EAC values averaged across wavelengths were strongly associated with age-related changes in cortical thickness, as well as functional and neuropsychological measures. This is likely because the EAC largely depends on the thickness of the sub-arachnoid cerebrospinal fluid layer, which increases with cortical atrophy. In addition, differences in EAC values between wavelengths were correlated with tissue oxygenation and cardiorespiratory fitness, indicating that information about cortical health can be derived non-invasively by quantifying the EAC.

scholarly journals Low-resolution mapping of the effective attenuation coefficient of the human head: a multidistance approach applied to high-density optical recordings

2017 ◽  
Vol 4 (2) ◽  
pp. 021103 ◽  
Author(s):  
Antonio M. Chiarelli ◽  
Edward L. Maclin ◽  
Kathy A. Low ◽  
Sergio Fantini ◽  
Monica Fabiani ◽  
...  
Keyword(s):  
Attenuation Coefficient ◽  
Human Head ◽  
High Density ◽  
Low Resolution ◽  
Resolution Mapping ◽  
Effective Attenuation Coefficient

scholarly journals The Nonlinear Effective Attenuation Coefficient of Spaceborne Oceanic Lidar Signal

2020 ◽  
Vol 237 ◽  
pp. 08022
Author(s):  
Qun Liu ◽  
Dong Liu ◽  
Jian Bai ◽  
Xiaoyu Cui ◽  
Yudi Zhou ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Attenuation Coefficient ◽  
Radiative Transfer Equation ◽  
Monte Carlo Model ◽  
Retrieval Accuracy ◽  
Inherent Optical Properties ◽  
Scattering Effect ◽  
Multiple Scattering Effect ◽  
Effective Attenuation Coefficient ◽  
Lidar Equation

Multiple scattering is an inevitable effect in spaceborne oceanic lidar because of the large footprint size and the high optical density of seawater. The effective attenuation coefficient klidar in oceanic lidar equation, which indicates the influence of the multiple scattering effect on the formation of lidar returns, is an important parameter in the retrieval of inherent optical properties (IOPs) of seawater. In this paper, the nonlinearity of klidar and the relationships between klidar and the IOPs of seawater are investigated by solving the radiative transfer equation with an improved semianalytic Monte Carlo model. klidar is found to decrease exponentially with the increase of depth in homogeneous waters. klidar is given as an exponential function of depth and IOPs of seawater. The results in this paper can help to have a better understanding of the multiple scattering effect of spaceborne lidar and improve the retrieval accuracy of the IOPs of seawater using spaceborne lidar.

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