We evaluate the numerical accuracy of finite-difference time-domain (FDTD) analysis of optical transport in a three-dimensional scattering medium illuminated by an isotropic point source. This analysis employs novel boundary conditions for the diffusion equation. The power radiated from an isotropic point source located at a depth equal to the reciprocal of the reduced scattering coefficient (1/μ'(s)) below the surface at the irradiated position is introduced to the integral form of the diffusion equation. Finite-difference approximations of the diffusion equation for a surface cell are derived by utilizing new boundary conditions that include an isotropic source even in a surface cell. Steady-state and time-resolved reflectances are calculated by FDTD analysis for a semi-infinite uniform scattering medium illuminated by an isotropic point source. The numerical results agree reasonably with the analytical solutions for μ'(s)=1-3 mm(-1) without resizing the mesh elements.
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http://dx.doi.org/10.1364/AO.50.001697 | DOI Listing |
Adv Mater
January 2025
Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund Platz 1, 37077, Göttingen, Germany.
In the burgeoning field of super-resolution fluorescence microscopy, significant efforts are being dedicated to expanding its applications into the 3D domain. Various methodologies have been developed that enable isotropic resolution at the nanometer scale, facilitating the visualization of 3D subcellular structures with unprecedented clarity. Central to this progress is the need for reliable 3D structures that are biologically compatible for validating resolution capabilities.
View Article and Find Full Text PDFGround Water
January 2025
School of Earth Sciences, University of Western Australia, Perth, Australia.
In simulations of groundwater flow through dipping aquifers, layers of model cells are often "deformed" to follow the top and bottom elevations of the aquifers. When this approach is used in MODFLOW, adjacent cells within the same model layer are vertically offset from one another, and the standard conductance-based (two-point) formulation for flow between cells does not rigorously account for these offsets. The XT3D multi-point flow formulation in MODFLOW 6 is designed to account for geometric irregularities in the grid, including vertical offsets, and to provide accurate results for both isotropic and anisotropic groundwater flow.
View Article and Find Full Text PDFNat Commun
January 2025
Research Laboratory of Electronics, MIT, Cambridge, MA, USA.
Three-dimensional subcellular imaging is essential for biomedical research, but the diffraction limit of optical microscopy compromises axial resolution, hindering accurate three-dimensional structural analysis. This challenge is particularly pronounced in label-free imaging of thick, heterogeneous tissues, where assumptions about data distribution (e.g.
View Article and Find Full Text PDFPhys Med
January 2025
Department of Radiation Oncology (Maastro), GROW School for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, the Netherlands. Electronic address:
Purpose: Proton therapy of moving targets is considered a challenge. At Maastro, we started treating lung cancer patients with proton therapy in October 2019. In this work, we summarise the developed treatment strategies and gained clinical experience from a physics point of view.
View Article and Find Full Text PDFJ Phys Chem B
January 2025
Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan.
As a liquid is supercooled toward the glass transition point, its dynamics slow significantly, provided that crystallization is avoided. With increased supercooling, the particle dynamics become more spatially heterogeneous, a phenomenon known as dynamic heterogeneity. Since its discovery, this characteristic of metastable supercooled liquids has garnered considerable attention in glass science.
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