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In this paper, the non-weldable precipitation-hardened superalloy Inconel 738 thin-wall parts were fabricated by laser directed energy deposition (LDED). The influence of post heat treatments including solution and aging heat treatments on the microstructures and mechanical properties of LDED-manufactured IN738 parts were investigated. The research results show that the phase composition of as-built and heat-treated IN738 alloys consisted of γ/γ’ and MC carbide. The microstructure of as-built IN738 alloy included fine columnar dendrites with a strong <100> fibre texture parallel to the build direction. The smallest size of γ′ precipitates in the matrix led to the highest hardness value. By applying the post-heat treatment of 1120°C-2h+850°C-24 h, intense dislocation lines formed the network around the cuboidal γ′ precipitates. Moreover, the elongation of transverse and longitudinal tensile specimens reached the highest value of 26% and 17.4% respectively. With the increase of solution temperature, the fine columnar dendrites gradually enlarged along the direction vertical to the building direction. When the solution temperature increased to 1270 °C, the elongation of samples decreased obviously due to the enlarged columnar grains and the disappearance of dislocation network.

The spinal cord dorsal horn is a relay hub that receives sensory information from the peripheral nervous system and transmits bioelectrical signals to the brain. In vivo imaging of neuronal and glial activity in the dorsal horn can provide insights into both functions and dysfunctions of the neuronal network in the spinal cord. With multimodal NLO microscopy, we identified a thin-myelin sheath region allowing to image over 200 μm deep below pia with subcellular resolution. By using an optically cleared intervertebral window, dorsal horn neuron and microglia activities can be observed without activating spinal cord inflammation. Two-photon imaging of neurons and microglia as well as the optical clearing improvement at different tissue depths were further characterized over time. Using this inflammation-free imaging method, we conducted a longitudinal study of dorsal horn microglia dynamics following sciatic nerve transection. Furthermore, stable in vivo calcium imaging of neurons in the dorsal horn was performed with electrical stimulation on the mouse's hind paw. The subcellular-resolution imaging enabled characterization of the distinct calcium transients of neuronal somas and dendrites. This minimally invasive imaging approach to spinal dorsal horn through an optically cleared intervertebral window provides a reliable platform for studying and understanding cellular activities in the spinal dorsal horn.

Quantitative methods to precisely measure cellular states in vivo have become increasingly important and desirable in modern biology. Recently, stimulated Raman scattering (SRS) microscopy has emerged as a powerful tool to visualize small biological molecules tagged with alkyne (C≡C) or carbon–deuterium (C–D) bonds in the cell-silent region. In this study, we developed a technique based on SRS microscopy of vibrational tags for quantitative imaging of lipid synthesis and lipolysis in live animals. The technique aims to overcome the major limitations of conventional fluorescent staining and lipid extraction methods that do not provide the capability of in vivo quantitative analysis. Specifically, we used three bioorthogonal lipid molecules (the alkyne-tagged fatty acid 17-ODYA, deuterium-labeled saturated fatty acid PA-D31, and unsaturated fatty acid OA-D34) to investigate the metabolic dynamics of lipid droplets (LDs) in live Caenorhabditis elegans(C. elegans). Using a hyperspectral SRS (hsSRS) microscope and subtraction method, the interfering non-Raman background was eliminated to improve the accuracy of lipid quantification. A linear relationship between SRS signals and fatty acid molar concentrations was accurately established. With this quantitative analysis tool, we imaged and determined the changes in concentration of the three fatty acids in LDs of fed or starved adult C. elegans. Using the hsSRS imaging mode, we also observed the desaturation of fatty acids in adult C. elegansvia spectral analysis on the SRS signals from LDs. The results demonstrated the unique capability of hsSRS microscopy in quantitative analysis of lipid metabolism in vivo.

The femtosecond laser ablation in biological tissue produces highly fluorescent compounds that are of great significance for intrinsically labelling ablated tissue in vivo and achieving imaging-guided laser microsurgery. In this study, we analyzed the molecular structures of femtosecond laser-ablated tissues using Raman spectroscopy and transmission electron microscopy. The results showed that though laser ablation caused carbonization, no highly fluorescent nanostructures were found in the ablated tissues. Further, we found that the fluorescence properties of the newly formed compounds were spatially heterogeneous across the ablation site and the dominant fluorescent signals exhibited close similarity to the tissue directly heated at a temperature of 200 °C. The findings of our study indicated that the new fluorescent compounds were produced via the laser heating effect and their formation mechanism likely originated from the Maillard reaction, a chemical reaction between amino acids and reducing sugars in tissue.

Lipid droplets are highly associated with obesity, diabetes, inflammatory disorders, and cancer. A reliable two-photon dye for specific lipid droplets imaging in live cells and live tissues at ultralow concentration has rarely been reported. In this work, four new aggregation-induced emission luminogens (AIEgens) based on the naphthalene core were designed and synthesized for specific two-photon lipid droplet staining. The new molecules, namely, NAP AIEgens, exhibit large Stokes shift (>110 nm), high solid-state fluorescence quantum yield (up to 30%), good two-photon absorption cross section (45–100 GM at 860 nm), high biocompatibility, and good photostability. They could specifically stain lipid droplets at ultralow concentration (50 nM) in a short time of 15 min. Such ultralow concentration is the lowest value for lipid droplets staining in live cells reported so far. In vitroand ex vivotwo-photon imaging of lipid droplets in live cells and live mice liver tissues were successfully demonstrated. In addition, selective visualization of lipid droplets in live mice liver tissues could be achieved at a depth of about 70 μm. These excellent properties render them as promising candidates for investigating lipid droplet-associated physiological and pathological processes in live biological samples.

Femtosecond laser microsurgery has become an advanced method for clinical procedures and biological research. The tissue treated by femtosecond laser can become highly fluorescent, indicating the formation of new fluorescent compounds that can naturally label the treated tissue site. We systematically characterized the fluorescence signals produced by femtosecond laser ablation in biological tissues in vivo. Our findings showed that they possess unique fluorescence properties and can be clearly differentiated from endogenous signals and major fluorescent proteins. We further demonstrated that the new fluorescent compounds can be used as in vivo labelling agent for biological imaging and guided laser microsurgery.

In this paper, chemically bonded phosphate ceramic coatings (CBPCs) with the addition of carbon nanotubes (CNTs) were prepared on the mild steel (Q235) through sol gel method. The wear and corrosion performance of CBPCs with the addition of CNTs were evaluated by tribological and electrochemical tests combining the analysis of microstructure, phase characterization and curing behavior. Results indicate CNTs nanofiller significantly enhances the wear and corrosion behavior of CBPCs. The enhancement of wear performance for CBPCs with CNTs nanofiller is because CNTs can effectively hinder the dislocation movement through the coating and substrate system and the occurrence of plastic deformation owing to their remarkable mechanical and lubricating properties. The enhancement of corrosion performance for CBPCs with CNTs nanofiller is because that CNTs can help CBPCs to get denser and more compact microstructure, which is contributed to prolong the electrolyte diffusion path. Besides, CNTs exhibit excellent hydrophobicity and can absorb oxygen molecules, which prevents the corrosion process on the anode and cathode sections of coating and substrate system.

Impairment of microglial clearance activity contributes to beta-amyloid (Aβ) pathology in Alzheimer’s disease (AD). While the transcriptome profile of microglia directs microglial functions, how the microglial transcriptome can be regulated to alleviate AD pathology is largely unknown. Here, we show that injection of interleukin (IL)-33 in an AD transgenic mouse model ameliorates Aβ pathology by reprogramming microglial epigenetic and transcriptomic profiles to induce a microglial subpopulation with enhanced phagocytic activity. These IL-33-responsive microglia (IL-33RMs) express a distinct transcriptome signature that is highlighted by increased major histocompatibility complex class II genes and restored homeostatic signature genes. IL-33-induced remodeling of chromatin accessibility and PU.1 transcription factor binding at the signature genes of IL-33RM control their transcriptome reprogramming. Specifically, disrupting PU.1-DNA interaction abolishes the microglial state transition and Aβ clearance that is induced by IL-33. Thus, we define a PU.1-dependent transcriptional pathway that drives the IL-33-induced functional state transition of microglia, resulting in enhanced Aβ clearance.