Improved spatiotemporal resolution of anti-scattering super-resolution label-free microscopy via synthetic wave 3D metalens imaging

Super-resolution (SR) microscopy has dramatically enhanced our understanding of biological processes. However, scattering media in thick specimens severely limits the spatial resolution, often rendering the images unclear or indistinguishable. Additionally, live-cell imaging faces challenges in achieving high temporal resolution for fast-moving subcellular structures. Here, we present the principles of a synthetic wave microscopy (SWM) to extract three-dimensional information from thick unlabeled specimens, where photobleaching and phototoxicity are avoided. SWM exploits multiple-wave interferometry to reveal the specimen’s phase information in the area of interest, which is not affected by the scattering media in the optical path. SWM achieves ~0.42 λ/NA resolution at an imaging speed of up to 106 pixels/s. SWM proves better temporal resolution and sensitivity than the most conventional microscopes currently available while maintaining exceptional SR and anti-scattering capabilities. Penetrating through the scattering media is challenging for conventional imaging techniques. Remarkably, SWM retains its efficacy even in conditions of low signal-to-noise ratios. It facilitates the visualization of dynamic subcellular structures in live cells, encompassing tubular endoplasmic reticulum (ER), lipid droplets, mitochondria, and lysosomes

Optimization of a Real-Time Wavelet-Based Algorithm for Improving Speech Intelligibility

The optimization of a wavelet-based algorithm to improve speech intelligibility along with the full data set and results are reported. The discrete-time speech signal is split into frequency sub-bands via a multi-level discrete wavelet transform. Various gains are applied to the sub-band signals before they are recombined to form a modified version of the speech. The sub-band gains are adjusted while keeping the overall signal energy unchanged, and the speech intelligibility under various background interference and simulated hearing loss conditions is enhanced and evaluated objectively and quantitatively using Google Speech-to-Text transcription. A universal set of sub-band gains can work over a range of noise-to-signal ratios up to 4.8 dB. For noise-free speech, overall intelligibility is improved, and the Google transcription accuracy is increased by 16.9 percentage points on average and 86.7 maximum by reallocating the spectral energy toward the mid-frequency sub-bands. For speech already corrupted by noise, improving intelligibility is challenging but still realizable with an increased transcription accuracy of 9.5 percentage points on average and 71.4 maximum. The proposed algorithm is implementable for real-time speech processing and comparatively simpler than previous algorithms. Potential applications include speech enhancement, hearing aids, machine listening, and a better understanding of speech intelligibility.Comment: 16 pages, 7 figures, 4 table

Reconstructing of Embedded High-Aspect-Ratio Nano-Voids Generated by Ultrafast Laser Bessel Beams

International audienceUltrafast non-diffractive Bessel laser beams provide strong light confinement and show robust advantages for fabricating high-aspect-ratio nanoscale structures inside transparent materials. They take the form of nanoscale voids with typical diameters well below the wavelength and aspect ratio of more than 1000. Delivering 3D morphologies of such nanoscale voids is an important issue to evaluate the result for fabrication. However, the characterization of such laser-induced structures is a difficult task. Here, an accurate and time-saving tomography-like methodology is proposed and adopted for reconstructing the morphology of high-aspect-ratio nano-holes. The technique allows an accurate assertion of laser parameters and position on nano-structured features. The reconstructed configuration reveals that nanoholes morphologies have a close relationship with energy distribution in the focal region. It suggests that the configuration of micro-explosion can be controlled by laser energy deposition in the process of laser-matter interaction down to the nanoscale

Nano-spheroid formation on YAG surfaces induced by single ultrafast Bessel laser pulses

International audienceWe report on single pulse ultrafast Bessel laser beam processing of YAG ceramic surfaces as a method for producing contamination-free submicron particles and size adjustable surface hemisphere structures of different curvature signs. The micro-machining process was performed in both air and liquid environments, leading to a variety of surface structures depending on the processing parameters. Particularly, a transformation of the surface structure morphology from micro-hole profiles to hemisphere extrusions was observed. The size of the hemisphere structure is found to be highly sensitive to laser parameters, such as pulse energy, pulse duration and beam focusing position. Through careful analyses of the influence of the laser pulse parameters, a precise regulation of the lateral diameter and height of the hemisphere structure was achieved. Large area hemisphere arrays with low standard deviation in size were fabricated. The detachment of the emerging structures and subsequent particle deposition can be observed in liquid environments when the height-diameter aspect ratio of the hemisphere exceeds a factor of 0.65. The Mechanisms for the formation and detaching of the hemisphere structure are discussed with cross-sectional and morphology imaging via Scanning Electron Microscopy and Atomic Force Microscopy. As a preliminary step towards submicron particle generation in liquid environments, the observation of surface hemispheres has interest in exploring the initial mechanisms of particles formation under laser ablation in liquids. The presented method allows for the fabrication of contamination-free and size adjustable YAG submicron convex structures which have potential applications in integrated optics, biotechnology and other advanced processing techniques

Thermal and mechanical limitations to processing resolution in volume non-diffractive ultrafast laser structuring

International audienceThe minimum feature size and spatial resolution are key factors for ultrafast laser structuring, defining the resulting function of the structured material. With the aim to improve the processing resolution achievable for non-diffractive beams, we analyze in volume the hydrodynamic and thermomechanical material responses during laser structuring defining the affected zone. The extent of laser induced cavitation on a 100 nm scale, accompanied by local annealing, and internal fracture under stress on µm scale are revealed using a combination ion beam milling, chemical etching and electron microscopy. Melting and mechanical stress acting at different planes are proved to be primary factors for restricting the structuring resolution to a critical distance where cooperative effects appear. Their extent is controllable via the local intensity and, hence, the pulse duration. A parametric control on the accumulated energy density limiting the thermomechanical action range and maximizing resolution is then reported

Comparative genomics revealed the gene evolution and functional divergence of magnesium transporter families in Saccharum

Abstract Background Sugarcane served as the model plant for discovery of the C4 photosynthetic pathway. Magnesium is the central atom of chlorophyll, and thus is considered as a critical nutrient for plant development and photosynthesis. In plants, the magnesium transporter (MGT) family is composed of a number of membrane proteins, which play crucial roles in maintaining Mg homeostasis. However, to date there is no information available on the genomics of MGTs in sugarcane due to the complexity of the Saccharum genome. Results Here, we identified 10 MGTs from the Saccharum spontaneum genome. Phylogenetic analysis of MGTs suggested that the MGTs contained at least 5 last common ancestors before the origin of angiosperms. Gene structure analysis suggested that MGTs family of dicotyledon may be accompanied by intron loss and pseudoexon phenomena during evolution. The pairwise synonymous substitution rates corresponding to a divergence time ranged from 142.3 to 236.6 Mya, demonstrating that the MGTs are an ancient gene family in plants. Both the phylogeny and Ks analyses indicated that SsMGT1/SsMGT2 originated from the recent ρWGD, and SsMGT7/SsMGT8 originated from the recent σ WGD. These 4 recently duplicated genes were shown low expression levels and assumed to be functionally redundant. MGT6, MGT9 and MGT10 weredominant genes in the MGT family and werepredicted to be located inthe chloroplast. Of the 3 dominant MGTs, SsMGT6 expression levels were found to be induced in the light period, while SsMGT9 and SsMTG10 displayed high expression levels in the dark period. These results suggested that SsMGT6 may have a function complementary to SsMGT9 and SsMTG10 that follows thecircadian clock for MGT in the leaf tissues of S. spontaneum. MGT3, MGT7 and MGT10 had higher expression levels Insaccharum officinarum than in S. spontaneum, suggesting their functional divergence after the split of S. spontaneum and S. officinarum. Conclusions This study of gene evolution and expression of MGTs in S. spontaneum provided basis for the comprehensive genomic study of the entire MGT genes family in Saccharum. The results are valuable for further functional analyses of MGT genes and utilization of the MGTs for Saccharum genetic improvement

Rising Importance of Organosulfur Species for Aerosol Properties and Future Air Quality

Acid-driven multiphase chemistry of isoprene epoxydiols (IEPOX), a key isoprene oxidation product, with inorganic sulfate aerosol yields substantial amounts of secondary organic aerosol (SOA) through the formation of organosulfur. The extent and implications of inorganic-to-organic sulfate conversion, however, are unknown. Herein, we reveal that extensive consumption of inorganic sulfate occurs, which increases with the IEPOX-to-inorganic sulfate ratio (IEPOX:Sulfinorg), as determined by laboratory and field measurements. We further demonstrate that organosulfur greatly modifies critical aerosol properties, such as acidity, morphology, viscosity, and phase state. These new mechanistic insights reveal that changes in SO2 emissions, especially in isoprene-dominated environments, will significantly alter biogenic SOA physicochemical properties. Consequently, IEPOX:Sulfinorg will play a central role in understanding historical climate and determining future impacts of biogenic SOA on global climate and air quality.</div

Increasing Isoprene Epoxydiol-to-Inorganic Sulfate Aerosol Ratio Results in Extensive Conversion of Inorganic Sulfate to Organosulfur Forms: Implications for Aerosol Physicochemical Properties

International audienceAcid-driven multiphase chemistry of isoprene epoxydiols (IEPOX), key isoprene oxidation products, with inorganic sulfate aerosol yields substantial amounts of secondary organic aerosol (SOA) through the formation of organosulfur compounds. The extent and implications of inorganic-to-organic sulfate conversion, however, are unknown. In this report, we demonstrate that extensive consumption of inorganic sulfate occurs, which increases with the IEPOX-to-inorganic sulfate concentration ratio (IEPOX:Sulf inorg), as determined by laboratory measurements. Characterization of total sulfur aerosol observed at Look Rock, Tennessee, from 2007-2016 shows that organosulfur mass fractions will likely continue to increase with ongoing declines in anthropogenic Sulf inorg , consistent with our laboratory findings. We further demonstrate that organosulfur compounds greatly modifies critical aerosol properties, such as acidity, morphology, viscosity, and phase state. These new mechanistic insights demonstrate that changes in SO 2 emissions, especially in isoprene-dominated environments, will significantly alter biogenic SOA physicochemical properties. Consequently, IEPOX:Sulf inorg will play an important role in understanding historical climate and determining future impacts of biogenic SOA on global climate and air quality