Dual-frequency Optoelectronic Oscillator and its Application in Transverse Load Sensing

In this thesis, dual-frequency optoelectronic oscillators (OEOs) and their applications to transverse load sensing are studied. Two configurations of dual-frequency OEOs are proposed and investigated. In the first configuration, a polarization-maintaining phase-shifted fiber Bragg grating (PM-PSFBG) is employed in the OEO loop to the generation of two oscillating frequencies. The beat between the two oscillating frequencies is a function of the load applied to the PM-PSFBG, which is used in transverse load sensing. To avoid the frequency measurement ambiguity, a second configuration is proposed by coupling a dual-wavelength fiber laser to the dual-frequency OEO. A single tone microwave signal with the frequency determined by the birefringence of the grating is generated in the OEO and is fed into the fiber ring laser to injection lock the dual wavelengths. The sensitivity and the resolution are measured to be 9.73 GHz/(N/mm) and 2.06×10-4 N/mm, respectively. The high stability of the single-tone microwave signal permits accurate measurement, while the frequency interrogation allows an ultra-high speed demodulation

Study of fatigue damage behavior in off-axis CFRP composites using digital image correlation technology

This study investigates the fatigue behavior of off-axis carbon fiber reinforced polymer (CFRP) composites under varying stress levels, with a focus on both tensile-tensile and compressive-compressive loading modes. We conduct a comprehensive analysis of energy dissipation and stiffness across various loading conditions, highlighting the critical role of fiber deflection effects in the recovery of tensile-tensile fatigue properties. Utilizing digital image correlation (DIC) technology, we identify both commonalities and distinctions in crack propagation pathways and failure mechanisms between these two fatigue scenarios. In the case of tensile-tensile fatigue, the predominant damage mechanism involves the development of multiple interlaminar shear cracks. These cracks initiate debonding at the fiber/resin interface, propagating from macrocracks at the edges to microcracks at the center, ultimately culminating in fiber pull-out failure. Conversely, in compressive fatigue, damage occurs centrally in the form of intralaminar shear cracks. As damage accumulates, these cracks progressively propagate along the fibers towards the edges, accompanied by localized fiber buckling, ultimately resulting in compressive failure. Furthermore, we determine a critical compressive strain threshold, which serves as a pivotal indicator of failure in compressive-compressive fatigue testing for off-axis CFRP composites

Broadband Chaotic Signals and Breather Oscillations in an Optoelectronic Oscillator Incorporating a Microwave Photonic Filter

We propose a technique to generate broadband chaotic and breather signals employing an optoelectronic oscillator (OEO) comprising a phase modulator (PM) and a linearly chirped fiber Bragg grating (LCFBG). The joint operation of the PM and the LCFBG forms a broadband microwave photonic filter (MPF), which allows the OEO to generate chaotic signals and breathers taking advantage of the interplay between the broadband MPF and the time-delayed feedback loop provided by a long optical fiber delay line. The breather excitations are characterized by nanosecond chaotic oscillations breathing periodically at a significantly lower time-scale determined by the OEO large delay time. A theoretical analysis based on a modified Ikeda time-delayed model to include the effect of the broadband filtering process is provided. The analysis is verified by an experiment. The proposed LCFBG-based OEO and the possibility to control in the optical domain its broadband bandpass characteristics considering the flexibility, accuracy, and precision in FBG fabrication can find applications in chaos-based communications and in fast optical processing systems, such as random number generation, or optical processing in reservoir computing taking advantage of the intrinsic multiple time scales of the LCFBG-based OEO. © 2012 IEEE.Peer Reviewe

Broadband Chaotic Signals and Breather Oscillations in an Optoelectronic Oscillator Incorporating a Microwave Photonic Filter

We propose a technique to generate broadband chaotic and breather signals employing an optoelectronic oscillator (OEO) comprising a phase modulator (PM) and a linearly chirped fiber Bragg grating (LCFBG). The joint operation of the PM and the LCFBG forms a broadband microwave photonic filter (MPF), which allows the OEO to generate chaotic signals and breathers taking advantage of the interplay between the broadband MPF and the time-delayed feedback loop provided by a long optical fiber delay line. The breather excitations are characterized by nanosecond chaotic oscillations breathing periodically at a significantly lower time-scale determined by the OEO large delay time. A theoretical analysis based on a modified Ikeda time-delayed model to include the effect of the broadband filtering process is provided. The analysis is verified by an experiment. The proposed LCFBG-based OEO and the possibility to control in the optical domain its broadband bandpass characteristics considering the flexibility, accuracy, and precision in FBG fabrication can find applications in chaos-based communications and in fast optical processing systems, such as random number generation, or optical processing in reservoir computing taking advantage of the intrinsic multiple time scales of the LCFBG-based OEO. © 2012 IEEE.Peer Reviewe

Curcumin represses NLRP3 inflammasome activation via TLR4/MyD88/NF-κB and P2X7R signaling in PMA-induced macrophages

AbstractAims: In the NOD-like receptor (NLR) family, the pyrin domain containing 3 (NLRP3) inflammasome is closely related to the progression of atherosclerosis. This study aimed to assess the effects of curcumin on NLRP3 inflammasome in phorbol 12-myristate 13-acetate (PMA)-induced macrophages and explore its underlying mechanism.Methods: Human monocytic THP-1 cells were pretreated with curcumin for 1 h and subsequently induced with PMA for 48 h. Total protein was collected for Western blot analysis. Cytokine interleukin (IL)-1β release and nuclear factor kappa B (NF-κB) p65 translocation were detected by ELISA assay and cellular NF-κB translocation kit, respectively.Results: Curcumin significantly reduced the expression of NLRP3 and cleavage of caspase-1 and IL-1β secretion in PMA-induced macrophages. Moreover, Bay (a NF-κB inhibitor) treatment considerably suppressed the expression of NLRP3 inflammasome in PMA-induced THP-1 cells. Curcumin also markedly inhibited the upregulation of toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), phosphorylation level of IκB-α, and activation of NF-κB in PMA-induced macrophages. In addition, purinergic 2X7 receptor (P2X7R) siRNA was administered, and it significantly decreased NLRP3 inflammasome expression in PMA-induced macrophages. Furthermore, curcumin reversed PMA-stimulated P2X7R activation, which further reduced the expression of NLRP3 and cleavage of caspase-1 and IL-1β secretion. Silencing of P2X7R using siRNA also suppressed the activation of NF-κB pathway in PMA-induced macrophages, but P2X7R-silenced cells did not significantly decrease the expression of TLR4 and MyD88.Conclusions: Curcumin inhibited NLRP3 inflammasome through suppressing TLR4/MyD88/NF-κB and P2X7R pathways in PMA-induced macrophages

Ulinastatin Ameliorates IL-1β-Induced Cell Dysfunction in Human Nucleus Pulposus Cells via Nrf2/NF-κB Pathway

Low back pain (LBP) has been a wide public health concern worldwide. Among the pathogenic factors, intervertebral disc degeneration (IDD) has been one of the primary contributors to LBP. IDD correlates closely with inflammatory response and oxidative stress, involving a variety of inflammation-related cytokines, such as interleukin 1 beta (IL-1β), which could result in local inflammatory environment. Ulinastatin (UTI) is a kind of acidic protein extracted from human urine, which inhibits the release of tumor necrosis factor alpha (TNF-α) and other inflammatory factors to protect organs from inflammatory damage. However, whether this protective effect of UTI on human nucleus pulposus (NP) exists, and how UTI affects the biological behaviors of human NP cells during IDD remain elusive. In this current study, we revealed that UTI could improve the viability of NP cells and promote the proliferation of NP cells. Additionally, UTI could protect human NP cells via ameliorating IL-1β-induced apoptosis, inflammatory response, oxidative stress, and extracellular matrix (ECM) degradation. Molecular mechanism analysis suggested that the protective effect from UTI on IL-1β-treated NP cells were through activating nuclear factor- (erythroid-derived 2-) like 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway and the suppression of NF-κB signaling pathway. Therefore, UTI may be a promising therapeutic medicine to ameliorate IDD

Salidroside Ameliorates Mitochondria-Dependent Neuronal Apoptosis after Spinal Cord Ischemia-Reperfusion Injury Partially through Inhibiting Oxidative Stress and Promoting Mitophagy

Ischemia-reperfusion injury is the second most common injury of the spinal cord and has the risk of neurological dysfunction and paralysis, which can seriously affect patient quality of life. Salidroside (Sal) is an active ingredient extracted from Herba Cistanche with a variety of biological attributes such as antioxidant, antiapoptotic, and neuroprotective activities. Moreover, Sal has shown a protective effect in ischemia-reperfusion injury of the liver, heart, and brain, but its effect in ischemia-reperfusion injury of the spinal cord has not been elucidated. Here, we demonstrated for the first time that Sal pretreatment can significantly improve functional recovery in mice after spinal cord ischemia-reperfusion injury and significantly inhibit the apoptosis of neurons both in vivo and in vitro. Neurons have a high metabolic rate, and consequently, mitochondria, as the main energy-supplying suborganelles, become the main injury site of spinal cord ischemia-reperfusion injury. Mitochondrial pathway-dependent neuronal apoptosis is increasingly confirmed by researchers; therefore, Sal’s effect on mitochondria naturally attracted our attention. By means of a range of experiments both in vivo and in vitro, we found that Sal can reduce reactive oxygen species production through antioxidant stress to reduce mitochondrial permeability and mitochondrial damage, and it can also enhance the PINK1-Parkin signaling pathway and promote mitophagy to eliminate damaged mitochondria. In conclusion, our results show that Sal is beneficial to the protection of spinal cord neurons after ischemia-reperfusion injury, mainly by reducing apoptosis associated with the mitochondrial-dependent pathway, among which Sal’s antioxidant and autophagy-promoting properties play an important role