Ultrafast dynamics observation during femtosecond laser-material interaction

Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.

Continuous subcellular resolution three-dimensional imaging on intact macaque brain

To decipher the organizational logic of complex brain circuits,it is important to chart long-distance pathways while preserving micron-level accuracy of local network.However,mapping the neuronal projections with individual-axon resolution in the large and complex primate brain is still challenging.Herein,we describe a highly efficient pipeline for three-dimensional mapping of the entire macaque brain with subcellular resolution.The pipeline includes a novel poly-N-acryloyl glycinamide(PNAGA)-based embedding method for long-term structure and fluorescence preservation,high-resolution and rapid whole-brain optical imaging,and image post-processing.The cytoarchitectonic information of the entire macaque brain was acquired with a voxel size of 0.32μm×0.32μm×10μm,showing its anatomical structure with cell distribution,density,and shape.Furthermore,thanks to viral labeling,individual long-distance projection axons from the frontal cortex were for the first time reconstructed across the entire brain hemisphere with a voxel size of 0.65μm×0.65μm×3μm.Our results show that individual cortical axons originating from the prefrontal cortex simultaneously target multiple brain regions,including the visual cortex,striatum,thalamus,and midbrain.This pipeline provides an efficient method for cellular and circuitry investigation of the whole macaque brain with individual-axon resolution,and can shed light on brain function and disorders.

Superresolution imaging of DNA tetrahedral nanostructures in cells by STED method with continuous wave lasers

DNA tetrahedral nanostructures are considered to be uew nanocarriers because they can be precisely controlled and hold excellent penetration ability to the cellular membrane. Although the DNA tetrahedral nanostructure is extensively studied in biology and medicine, its behavior in the cells with nanoscale resolution is not understood clearly. In this letter, we demonstrate superrcsolution fluorescence imaging of the distribution of DNA tetrahedral nanostructures in the cell with a simulated emission depletion （STED） microscope, which is built based on a conventional eonfocal microscope and can t）rovide a resolution of 70 nm.