Showing papers by "Shandong University published in 2023"

Investigation of microstructure evolution, mechanical and corrosion properties of SAF 2507 super duplex stainless steel joints by keyhole plasma arc welding

Abstract: Keyhole plasma arc welding (PAW) of the super duplex stainless steel (SDSS) is expected to achieve full-penetration joints of medium-thickness plates in a single pass with higher efficiency. However, the unique key-holing processes due to the special constricted arc behaviors cause much different thermal cycles of the liquid metals as well as changed microstructures. SDSS 2507 with a thickness of 10 mm was joined by PAW to investigate the joints' microstructure and properties. Microstructure characterization reveals substantial differences in the content of austenite, ranging from 68.9% in weld metal (WM) to 32.1% in the heat-affected zone (HAZ). The oxide inclusions in the WM enhance the hardness of the welded joints, but provide the path for crack propagation to decrease its impact toughness. While complicated microstructure is found in HAZ forming ferrite and diverse austenite, such as grain boundary austenite (GBA), intragrain austenite (IGA), and Widmanstätten austenites (WA). A small amount of secondary austenite (γ2) and chromium nitride are also found in HAZ, and they significantly deteriorate its corrosion resistance. The grain boundary misorientation angle distribution of the austenite in WM is found to be dominated by the low angle boundaries (LABs). However, its content decreases from the WM to base metal (BM). Selective corrosion occurs in all samples, where ferrite is preferentially dissolved when the extrinsic voltage is low (<0.5 V) and austenite is preferentially dissolved when the extrinsic voltage is high (>0.5 V), indicating the different electrochemical activity of the two phases.

Modeling the Expansion Speed of Foreshock Bubbles

Abstract: Foreshock transients, including hot flow anomalies (HFAs) and foreshock bubbles (FBs), are frequently observed in the ion foreshock. Their significant dynamic pressure perturbations can disturb the bow shock, resulting in disturbances in the magnetosphere and ionosphere. They can also contribute to particle acceleration at their parent bow shock. These disturbances and particle acceleration caused by the foreshock transients are not yet predictable, however. In this study, we take the first step in establishing a first-order predictive expansion speed model for FBs (which are simpler than HFAs). Starting with energy conversion from foreshock ions to solar wind ions, we derive the FB expansion speed in the FB's early formation stage and late expansion stage as a function of foreshock and solar wind parameters. We use local hybrid simulations with varying parameters to fit and improve the early stage model and 1D particle-in-cell simulations to test the late-stage model. By comparing model results with Magnetospheric Multiscale (MMS) and Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations, we adjust the late-stage model and show that it can predict the FB expansion speed. Our study provides a foundation for predictive models of foreshock transient formation and expansion, so that we can eventually forecast their space weather effects and particle acceleration at shocks.

Architecting Lignin/Poly(vinyl alcohol) Hydrogel with Carbon Nanotubes for Photothermal Antibacterial Therapy

Abstract: With the development of antimicrobial resistance, rapid and effective killing of bacteria is required for infected wound healing after skin trauma. Herein, we reported a one-pot reaction strategy to prepare a composite hydrogel with antibacterial activity through high-efficiency photothermal therapy. We take poly(vinyl alcohol) as the matrix, and lignin-derived from biomass was introduced into the hydrogel to increase the tensile strength of the prepared hydrogel to 108.58 kPa, and the elongation at break reaches 200.8%. The electrostatic interaction between lignin and chitosan enhanced the reactivity of lignin. Carbon nanotubes endow the hydrogel with photothermal antibacterial activity that can kill more than 97% of either Escherichia coli or Staphylococcus aureus within 5 min, avoiding the problem of bacterial resistance. Experimental evaluation on mice showed that the hydrogel could effectively promote wound healing of full-thickness skin defects. The hydrogels with good mechanical properties, antioxidant activity, and excellent photothermal antibacterial ability show good potential to repair the damaged tissue and are expected to be used in the clinical transformation of wound dressing.

Atypical proliferative retinopathy as the presenting feature of chronic myeloid leukemia in a patient with diabetes mellitus

Abstract: In Brief Purpose: To describe a case of proliferative retinopathy as the presenting manifestation of chronic myeloid leukemia in a patient with poorly controlled diabetes mellitus (DM). Undiagnosed chronic myeloid leukemia in a patient with pre-existing poorly controlled DM is rarely encountered but must be recognized to treat appropriately with systemic chemotherapy. Significant fundus finding overlaps with DM making the recognition of chronic myeloid leukemia challenging. Methods: Case report. Results: Fundoscopy revealed scattered dot–blot hemorrhages, venous beading, and numerous Roth spots in all quadrants, in both eyes. In the right eye, there was also a vitreous hemorrhage with evidence of neovascularization near the inferior arcade. Intravenous fluorescein angiography showed significant peripheral capillary nonperfusion without evidence of exudation in both eyes. No macular edema was observed on optical coherence tomography. A review of systems and physical examination was negative for constitutional symptoms, lymphadenopathy, organomegaly, and other symptoms. Retinal findings prompted a complete blood count, which revealed significant leukocytosis. A bone marrow biopsy confirmed a diagnosis of chronic myeloid leukemia. Systemic chemotherapy and pan-retinal photocoagulation successfully normalized the leukocyte count and resolved the vitreous hemorrhage and neovascularization. Conclusion: The presence of numerous Roth spots in all quadrants, extensive areas of capillary nonperfusion on intravenous fluorescein angiography, and neovascularization in the absence of exudation or macular edema should prompt investigations to rule out hematologic disorders. Proliferative retinopathy was the presenting manifestation of chronic myeloid leukemia in a patient with diabetes mellitus. The fundus finding overlaps with diabetes mellitus making the recognition of chronic myeloid leukemia challenging. The presence of diffuse Roth spots, extensive areas of capillary nonperfusion, and neovascularization without exudation or macular edema should prompt hematological investigations.

The Glutaminase Inhibitor Compound 968 Exhibits Potent In vitro and In vivo Anti-tumor Effects in Endometrial Cancer

Abstract: Glutamine is one of the primary nutrients utilized by cancer cells for energy production and biosynthesis. Hence, interfering with glutamine metabolism may impose anti-tumor effects.In this study, we assessed the anti-tumorigenic effects of glutaminase-1 enzyme (GLS1) inhibition in endometrial cancer in vitro and in vivo.The human endometrial cancer cell lines Ishikawa and HEC-1B were used. The effects of compound 968 on cell proliferation, cell cycle, apoptosis, cellular stress, and AKT/mTOR pathway inhibition were assessed. The synergistic effects of compound 968 and paclitaxel were also analyzed. The in vivo effect of compound 968 was evaluated using tumor xenografts.We found that the GLS1-targeting compound 968 was able to reduce cancer cell proliferation in a dose- and time-dependent manner. Compound 968 combined with a low concentration of paclitaxel showed stronger inhibitory effects. Further analyses indicated that compound 968 induced cell cycle arrest at the G1 phase, as well as increased the production of cellular reactive oxygen species (ROS) and promoted cellular stress and cancer cell apoptosis. Additionally, the treatment of endometrial cancer with compound 968 downregulated the expression of GLS1 and cyclin D1 and upregulated the expression of P21 and E-cadherin. Moreover, the treatment of endometrial cancer cells with compound 968 significantly reduced the levels of phospho-S6 ribosomal protein and phospho-AKT (Ser473), indicative of AKT/mTOR/S6 signaling pathway inhibition. In xenograft mouse models of endometrial cancer, compound 968 significantly suppressed tumor growth. In addition, western blotting analysis indicated that GLS1 expression was upregulated in human endometrial cancer tissues.Compound 968 may be a promising approach for the management of human endometrial cancer.

Organosilicon Fluorescent Materials

Abstract: In the past few decades, organosilicon fluorescent materials have attracted great attention in the field of fluorescent materials not only due to their abundant and flexible structures, but also because of their intriguing fluorescence properties, distinct from silicon-free fluorescent materials. Considering their unique properties, they have found broad application prospects in the fields of chemosensor, bioimaging, light-emitting diodes, etc. However, a comprehensive review focusing on this field, from the perspective of their catalogs and applications, is still absent. In this review, organosilicon fluorescent materials are classified into two main types, organosilicon small molecules and polymers. The former includes fluorescent aryl silanes and siloxanes, and the latter are mainly fluorescent polysiloxanes. Their synthesis and applications are summarized. In particular, the function of silicon atoms in fluorescent materials is introduced. Finally, the development trend of organosilicon fluorescent materials is prospected.

Status of the singlino-dominated dark matter in general Next-to-Minimal Supersymmetric Standard Model

Abstract: With the rapid progress of dark matter direct detection experiments, the attractiveness of the popular bino-dominated dark matter in economical supersymmetric theories is fading. As an alternative, the singlino-dominated dark matter in general Next-to-Minimal Supersymmetric Standard Model (NMSSM) is paying due attention. This scenario has the following distinct characteristics: free from the tadpole problem and the domain-wall problem of the NMSSM with a $Z_3$-symmetry, predicting more stable vacuum states than the $Z_3$-NMSSM, capable of forming an economical secluded dark matter sector to yield the dark matter experimental results naturally, and readily weaken the restrictions from the LHC search for SUSY. Consequently, it can explain the muon g-2 anomaly in broad parameter space that agrees with various experimental results while simultaneously breaking the electroweak symmetry naturally. In this study, we show in detail how the scenario coincides with the experiments, such as the SUSY search at the LHC, the dark matter search by the LZ experiment, and the improved measurement of the muon g-2. We provide a simple and clear picture of the physics inherent in the general NMSSM.

In vitro degradation and corrosion evaluations of plasma electrolytic oxidized Mg–Zn–Ca–Si alloys for biomedical applications

Abstract: Biodegradable calcium phosphate (CaP) ceramic coatings were prepared on self-designed Mg-2.0Zn-0.6Ca-xSi alloys by plasma electrolytic oxidation (PEO). The effect of calcium (Ca) and silicon (Si) on alloy microstructure and coating formation and biomineralization mechanisms were discussed. The in vitro bioactivity and degradability of CaP coatings were evaluated by immersion tests in simulated body fluid (SBF) solutions and trishydroxymethyl-aminomethane hydrochloric acid (Tris-HCl) buffer, respectively. The microstructure and chemical composition of the coatings, depositions and corrosion products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical corrosion behavior of alloys and coatings was investigated using the electrochemical workstation. Results showed that the shape, quantity, size and distribution of second phases can be changed by the simultaneously addition of Ca and Si in Mg–Zn–Ca–Si alloys. The Si content in Mg-2.0Zn-0.6Ca-xSi alloy should not be higher than 0.8 wt%. The microstructure of Mg-2.0Zn-0.6Ca-xSi alloys can influence the formation and growth of PEO coating by altering the spark discharge characteristics. The plasma electrolytic oxidized Mg-2.0Zn-0.6Ca-0.8Si has potential to be served as biodegradable bone implant and cardiovascular stent.

Electron‐Rich Bi Nanosheets Promote CO ₂ ⋅ ⁻ Formation for High‐Performance and pH‐Universal Electrocatalytic CO ₂ Reduction

Abstract: Electrochemical CO2 reduction reaction (CO2RR) to chemical fuels such as formate offers a promising pathway to carbon-neutral future, but its practical application is largely inhibited by the lack of effective activation of CO2 molecules and pH-universal feasibility. Here, we report an electronic structure manipulation strategy to electron-rich Bi nanosheets, where electrons transfer from Cu donor to Bi acceptor in bimetallic Cu−Bi, enabling CO2RR towards formate with concurrent high activity, selectivity and stability in pH-universal (acidic, neutral and alkaline) electrolytes. Combined in situ Raman spectra and computational calculations unravel that electron-rich Bi promotes CO2⋅− formation to activate CO2 molecules, and enhance the adsorption strength of *OCHO intermediate with an up-shifted p-band center, thus leading to its superior activity and selectivity of formate. Further integration of the robust electron-rich Bi nanosheets into III–V-based photovoltaic solar cell results in an unassisted artificial leaf with a high solar-to-formate (STF) efficiency of 13.7 %.