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Alleviating the toxicity of quantum dots to Phanerochaete chrysosporium by sodium hydrosulfide and cysteine
摘要： Quantum dots (QDs) have caused large challenges in clinical tests and biomedical applications due to their potential toxicity from nanosize effects and heavy metal components. In this study, the physiological responses of Phanerochaete chrysosporium (P. chrysosporium) to CdSe/ZnS QDs with either an inorganic sulfide NaHS or an organic sulfide cysteine as antidote have been investigated. Scanning electron microscope analysis showed that the hyphal structure and morphology of P. chrysosporium have obviously changed after exposure to 100 nM of COOH CdSe/ZnS 505, NH2 CdSe/ZnS 505, NH2 CdSe/ZnS 565, or NH2 CdSe/ZnS 625. Fourier transform infrared spectroscopy analysis indicated that the existence of hydroxyl, amino, and carboxyl groups on cell surface could possibly conduct the stabilization of QDs in an aqueous medium. However, after NaHS or cysteine treatment, the cell viability of P. chrysosporium exposed to CdSe/ZnS QDs increased as compared to control group, since NaHS and cysteine have assisted P. chrysosporium to alleviate oxidative damage by regulating lipid peroxidation and superoxide production. Meanwhile, NaHS and cysteine have also stimulated P. chrysosporium to produce more antioxidant enzymes (superoxide dismutase and catalase), which played significant roles in the defense system. In addition, NaHS and cysteine were used by P. chrysosporium as sulfide sources to promote the glutathione biosynthesis to relieve CdSe/ZnS QDs-induced oxidative stress. This work revealed that sulfide sources (NaHS and cysteine) exerted a strong positive effect in P. chrysosporium against the toxicity induced by CdSe/ZnS QDs.
关键词： Detoxification,Cysteine,CdSe/ZnS quantum dots,Sodium hydrosulfide,Antioxidant enzymes,Oxidative stress
更新于2025-09-23 15:19:57
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Hot cracking in autogenous welding of 6061-T6 aluminum alloy by rectangular pulsed Nd:YAG laser beam
摘要： Due to high hot crack susceptibility of Al-Mg-Si alloys, autogenous welding by rectangular pulsed laser beam has not been generally successful in the removal of cracks. In this research, the effect of pulsed Nd:YAG laser parameters and preheating on the creation of hot cracks in the 6061-T6 aluminum alloy was investigated. The sample that was fabricated by the laser parameters including 1 Hz, 0.12 mm/s, 10 ms, and without preheating exhibited the highest cooling rate and the smallest dendrite arm spacing but no hot crack was observed. The tensile test specimens of this sample fractured at a point far from the weld metal and a decrease in the precipitation of silicon and magnesium in the inter-dendritic space and the reduction of thermal stresses resulted in the elimination of hot cracks. However, according to macro-scale models for the creation of hot cracks, preheating decreased the tensile stresses in the BTR (brittle temperature range), but increasing the preheating temperature led to increasing rather than decreasing the hot crack length. In this case, the formation of hydrogen porosity, the segregation of silicon and magnesium, and the creation of low melting point compounds were the important parameters affecting the hot crack initiation and growth.
关键词： Laser welding,6061 aluminum alloy,Stress simulation,Solidification microstructure,Hot crack modeling,Rectangular pulse
更新于2025-09-23 15:19:57
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Tunable Substrate Integrated Waveguide Phase Shifter Using High Dielectric Constant Slab
摘要： This paper deals with precise insertion processing (peg-in-hole task) for speeding up and increasing flexibility of assembly process in factory automation. When a gap between a peg and a hole is narrower than positioning accuracy of robotic manipulator, it is impossible to succeed the peg-in-hole task by conventional position control methods. Moreover, in the case that a robotic hand holds a deformable thin ring and put it around a shaft, the insertion process becomes increasingly difficult because the gripping force deforms the ring and the narrow gap is crushed. We propose a novel mating technique based on passive alignment principle (PAP) in order to solve the twin problems of accuracy and deformation. The PAP mechanism can correct the ring position in nanoorder and remove the ring deformation. We derived the limitations of the PAP, which are remaining position errors after the PAP applied, based on Hertz stress. We also analyzed accuracy requirements of industrial robotic manipulator for applying the PAP and calculated allowance diagrams. We conducted 280 mating and insertion experiments with four kinds of materials of rings and shafts with three different insertion directions. The success rate 97.8% validates our proposed PAP-based mating algorithm.
关键词： peg-in-hole,Close tolerances fit,robotic assembly,Hertz contact stress
更新于2025-09-23 15:19:57
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The effects of laser stimulation at acupoint ST36 on anxiety-like behaviors and anterior cingulate cortex c-Fos expression in a rat post-traumatic stress disorder model
摘要： Post-traumatic stress disorder (PTSD) is a mental disorder that is linked with the onset of multiple anxiety-like behaviors. This study was designed to assess how these behaviors and anterior cingulate cortex (ACC) c-Fos expression were impacted by 10.6-μm laser stimulation at acupoint ST36 a rat model of PTSD. A rat model of PTSD was prepared via prolonged exposure of animals to a stressor, followed by a 7-day period during which animals were allowed to rest undisturbed in their cages. Rats were randomized into four experimental groups (n = 12/group): the control, PTSD, LS, and sham LS groups. Control group animals were not subjected to SPS procedures prior to behavioral testing. LS and sham LS animals were administered LS treatment at bilateral ST36 acupoints or non-acupoints, respectively, for a 7-day period. Animals were then assessed for performance in elevated plus maze (EPM) tests and open-field tests (OFT), and their plasma corticosterone levels were measured. In addition, c-Fos-positive nuclei in the ACC were detected via immunohistochemical staining. Relative to sham LS treatment and PTSD model control rats, LS was associated with increased time spent in both open EPM test arms and in the central area in the OFT (P < 0.05). The PTSD model group exhibited a significant reduction in ACC c-Fox expression, while LS treatment significantly increased this expression (P < 0.001). In addition, a correlation was detected between anxiety-like behaviors and altered ACC neuronal activation. The results of this study indicate that LS at acupoint ST36 can have a previously unreported effect on anxiety-like behaviors in the context of PTSD, with ACC neuronal activation potentially being implicated as a driver of this effect.
关键词： Anterior cingulate cortex,Anxiety-like behavior,Post-traumatic stress disorder,Laser stimulation
更新于2025-09-23 15:19:57
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Analytical mechanics modeling of residual stress in laser powder bed considering flow hardening and softening
摘要： Residual stress builds up during the fabrication of components via laser powder bed fusion (L-PBF) process which causes parts to fail due to the crack initiation and growth, low fatigue life, and fall outside of the specified dimensions. During the thermal loading, the grain size affected by strain hardening and flow softening is altered at the subsurface through dynamic recrystallization (DRx) and subsequent recovery. The yield strength of the alloys is largely determined by the size of nucleated grains, and it has a substantial influence on flow stress and residual stress build-up. In this work, a physics-based analytical model is proposed to predict the residual stress affected by the strain hardening, flow softening, and microstructural evolution during L-PBF process with IN718 as a material system for exploration. The temperature field is predicted using a transient moving point heat source approach. Due to the non-uniform heating, materials experience high thermal stress which may exceed the yield strength of the material. The thermal stress is obtained from Green’s functions of stresses due to the point body load. A material constitutive flow stress model known as Johnson-Cook is used to determine the yield surface. This flow stress model is modified to incorporate the effects of flow softening and grain size. The dynamic recrystallization and grain refinement models are used to calculate the grain size using recrystallized volume fraction from nucleation and growth rates. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Results from the analytical residual stress model showed good agreement with X-ray diffraction measurements used to determine the residual stresses in the IN718 specimens built via L-PBF.
关键词： Residual stress,Microstructure evolution,Strain hardening,Flow softening,Laser powder bed fusion
更新于2025-09-23 15:19:57
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The New Technologies Developed from Laser Shock Processing
摘要： Laser shock processing (LSP) is an advanced material surface hardening technology that can significantly improve mechanical properties and extend service life by using the stress effect generated by laser-induced plasma shock waves, which has been increasingly applied in the processing fields of metallic materials and alloys. With the rapidly development of modern industry, many new technologies developed from LSP have emerged, which broadens the application of LSP and enriches its technical theory. In this work, the technical theory of LSP was summarized, which consists of the fundamental principle of LSP and the laser-induced plasma shock wave. The new technologies, developed from LSP, are introduced in detail from the aspect of laser shock forming (LSF), warm laser shock processing (WLSP), laser shock marking (LSM) and laser shock imprinting (LSI). The common feature of LSP and these new technologies developed from LSP is the utilization of the laser-generated stress effects rather than the laser thermal effect. LSF is utilized to modify the curvature of metal sheet through the laser-induced high dynamic loading. The material strength and the stability of residual stress and micro-structures by WLSP treatment are higher than that by LSP treatment, due to WLSP combining the advantages of LSP, dynamic strain aging (DSA) and dynamic precipitation (DP). LSM is an effective method to obtain the visualized marks on the surface of metallic materials or alloys, and its critical aspect is the preparation of the absorbing layer with a designed shape and suitable thickness. At the high strain rates induced by LSP, LSI has the ability to complete the direct imprinting over the large-scale ultrasmooth complex 3D nanostructures arrays on the surface of crystalline metals. This work has important reference value and guiding significance for researchers to further understand the LSP theory and the new technologies developed from LSP.
关键词： laser shock processing,stress effect,warm laser shock processing,laser shock marking,laser shock imprinting,laser shock forming
更新于2025-09-23 15:19:57
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Improved output voltage of 0–3 cementitious piezoelectric composites with basalt fibers
摘要： In this paper, basalt fibers (BF) was employed as high modulus component with good interface bonding with cement matrix to enhance local stress applied on piezoelectric ceramic particles in 0–3 cementitious piezoelectric composites (0–3 CPCs). The effect of content of BF varying from 0.00 vol% to 0.23 vol% on the mechanical, piezoelectric and dielectric properties of 0–3 CPCs and the output voltage of 0–3 CPCs sensor was evaluated. The results showed that amplitude of output voltage of the 0–3 CPCs sensor with 0.12 vol% BF maximized at 4.98 V, which was 60.0% higher than that of the 0–3 CPCs sensor without fibers for the compact structure of the 0–3 CPCs and good interface bonding between BF and cement matrix as a reason of good stress transfer in the composites. While the split tensile strength, piezoelectric voltage constant (g33), piezoelectric strain constant (d33), relative dielectric constant (εr) and dissipation factor (tanδ) was 13.1 MPa, 11.36 × 10?3 V m/N, 43 pC/N, 430.0 and 0.43, respectively. It provided a novel method to improve the mechanical-electrical response of piezoelectric sensor by enhancing local stress applied on piezoelectric ceramic particles in the piezoelectric composites.
关键词： 0–3 cementitious piezoelectric composites,Stress transfer,Basalt fibers,Output voltage
更新于2025-09-23 15:19:57
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Bactericidal action of ferulic acid with ultraviolet-A light irradiation
摘要： The bactericidal activity of ferulic acid (FA) against various microorganisms was remarkably enhanced by ultraviolet-A (UV-A) irradiation (wavelength, 365 nm). However, the bactericidal mechanism in the photo-combination system has not been evaluated. In the present study, this combined treatment was characterized by investigating associated changes in cellular functions of Escherichia coli, including assessments of respiratory activity, lipid peroxidation, membrane permeability, and damage to DNA and the cell surface. FA adsorbed onto and was incorporated into bacterial membranes, and the affinity resulted in decreased respiratory activity and enhanced lipid peroxidation in the cytoplasmic membrane with low-fluence (1.0 J/cm2) UV-A irradiation. Flow cytometry analysis revealed that additional exposure (8 J/cm2) combined with FA (1 mg/mL) induced increased cell permeability, yielding a 4.8-log decrease in the viable cell count. Morphologically, the treated cells exhibited a bacterial membrane dysfunction, producing many vesicles on the cell surface. However, despite this effect on the cell surface, plasmid DNA transformed into FA-treated E. coli maintained supercoiled integrity with negligible DNA oxidation. Our data strongly suggested that FA functions inside and outside the bacterial membrane; UV-A exposure in the presence of FA then causes increased oxidative modification and subsequent disruption of the bacterial membrane, without causing detectable genotoxicity.
关键词： Ultraviolet-A,Bactericidal action,Ferulic acid,Oxidative stress,Membrane damage
更新于2025-09-23 15:19:57
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Selective Visualization of Live-Cell Mitochondrial Thiophenols and Their Induced Oxidative Stress Process by a Rationally Designed Rhodol-Based Fluorescent Probe
摘要： Mitochondria as cellular powerhouses are the preferential targets affected by thiophenols, an important class of highly toxic environmental pollutants, and are linked to the production of pathogenic reactive oxygen species (ROS) induced by trace thiophenol residues. For real-time and accurate sensing, it is critically important to develop highly sensitive fluorescent probes for the specific detection of mitochondrial thiophenols. Herein, we report the first mitochondria-targeted fluorescent probe (ROAL) to image thiophenols in living cells. The development of ROAL was based on a novel red-emitting rhodol derivative (ROAP). ROAL proved to be highly selective to thiophenols among various analytes including aliphatic thiols, and renders an ultrasensitive off-on fluorescence response to thiophenols with a remarkable detection limit (8.1 nM). The probe efficiently stains mitochondria with a high Pearson’s co-localization coefficient (0.95) using Mito Tracker Green FM as reference, thereby ensuring the specific detection of mitochondrial thiophenols in living HepG2 and HeLa cells. In particular, using this probe we for the first time proved that endogenous reactive oxygen species have the capacity to eliminate thiophenols in living cells, suggesting that thiophenols might induce cellular oxidative stress.
关键词： oxidative stress damage,fluorescent probe,live-cell imaging,thiophenol,mitochondria-targeted
更新于2025-09-23 15:19:57
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A phenylboronate-based SERS nanoprobe for detection and imaging of intracellular peroxynitrite
摘要： A surface-enhanced Raman scattering (SERS) based nanoprobe was developed for detection and imaging of endogenous peroxynitrite in living cells. The probe was fabricated by assembling 3-mercaptophenylboronic acid pinacol ester onto the surface of gold nanoparticles (AuNPs). The detection of peroxynitrite is accomplished via measurement of the changes in the SERS spectra (at 882 cm?1) that are caused by the reaction between probe and peroxynitrite. The probe has a fast response (<30 s), a 0.4 μM lower detection limit and a wide linearity range from 5.0 × 10?7 to 1.0 × 10?4 M. It is biocompatible and highly stable on storage and under various pH conditions. Both the reaction and the SERS signal are highly specific over other species. The nanoprobe was successfully applied to SERS imaging of peroxynitrite that is produced in macrophages under oxidative stress. Conceivably, the method has a most viable tool for use in studies on peroxynitrite-related physiological and pathological processes.
关键词： Surface-enhanced Raman scattering,Boronate ester,Specific reaction,Reactive oxygen species,Gold nanoparticles,Living cell,Oxidative stress,Biosensor
更新于2025-09-23 15:19:57