Helicity Dependent Directional Surface Plasmon Polariton Excitation Using A Metasurface with Interfacial Phase Discontinuity

Surface plasmon polaritons (SPPs) have been widely exploited in various scientific communities, ranging from physics, chemistry to biology, due to the strong confinement of light to the metal surface. For many applications it is important that the free space photon can be coupled to SPPs in a controllable manner. In this Letter, we apply the concept of interfacial phase discontinuity for circularly polarizations on a metasurface to the design of a novel type of polarization dependent SPP unidirectional excitation at normal incidence. Selective unidirectional excitation of SPPs along opposite directions is experimentally demonstrated at optical frequencies by simply switching the helicity of the incident light. This approach, in conjunction with dynamic polarization modulation techniques, opens gateway towards integrated plasmonic circuits with electrically reconfigurable functionalities.Comment: 17 pages, 5 figures. Published on <Light:Science & Applications

Heating or cooling: temperature effects on the synthesis of atomically precise gold nanoclusters

Developing an efficient, well-controlled synthesis strategy for gold nanoclusters (Au NCs) is crucial for delivering their expected applications in many fields; and such development requires fundamental understandings on the synthetic chemistry. The synthesis of Au NCs typically consists of a pair of reversible reactions: a fast reduction-growth reaction and a slow size-focusing reaction. Here we demonstrate that the above two reactions can be well-balanced while accelerated in a heated synthesis protocol, thus providing an efficient and scalable synthesis method to obtain thermodynamically favorable Au25(SR)18 NCs (SR denotes thiolate ligand) with high yield (>95% on gold atom basis) and fast kinetics. By investigating the Au NC formation behavior at different temperature, we identified the endothermic nature of the reductive formation of Au25(SR)18 NCs from Au(I)-thiolate complex precursors. More interestingly, if overheated, after the formation of Au25(SR)18, there exists an irreversible first-order reaction, which could transform Au25(SR)18 into Au NCs of mixed sizes. As a result, 40 °C is identified as the optimal temperature to synthesize Au25(SR)18 in aqueous solution, as the half-life of the transformation reaction (67.8 h) is much longer than the time needed to obtain high yield Au25(SR)18. The detailed understandings on the temperature effects of Au NC synthesis would facilitate the development of efficient synthesis strategies for atomically precise Au NCs with predesigned size, composition and structure

Toward greener synthesis of gold nanomaterials: from biological to biomimetic synthesis

In the past two decades, the use of biomolecules, either from biological or biomimetic systems (or so-called biological or biomimetic synthesis), has emerged as a promising green approach to synthesize gold nanomaterials (Au NMs). Here, we describe recent progress on the biological and biomimetic syntheses of Au NMs. We focus our discussions on the selection principles of biomolecules, synthesis mechanisms involving biomolecules, recent evolution from biological to biomimetic synthesis, and the contributions of bioinspired synthesis to green production of Au NMs. We hope this review will provide a guideline for the green synthesis of Au NMs and other metal NMs, further paving their way toward practical applications in the field of biomedicine

Space- and intensity-constrained reconstruction for compressed ultrafast photography

The single-shot compressed ultrafast photography (CUP) camera is the fastest receive-only camera in the world. In this Letter, we introduce an external CCD camera and a space- and intensity-constrained (SIC) reconstruction algorithm to improve the image quality of CUP. The external CCD camera takes a time-unsheared image of the dynamic scene. Unlike the previously used unconstrained algorithm, the proposed algorithm incorporates both spatial and intensity constraints based on the additional prior information provided by the external CCD camera. First, a spatial mask is extracted from the time-unsheared image to define the zone of action. Next, an intensity threshold is determined based on the similarity between the temporally projected image of the reconstructed datacube and the time-unsheared image. Both simulation and experimental studies show that the SIC reconstruction improves the spatial resolution, contrast, and general quality of the reconstructed image

Ursolic acid reduces oxidative stress injury to ameliorate experimental autoimmune myocarditis by activating Nrf2/HO-1 signaling pathway

Background: Oxidative stress is crucial in experimental autoimmune myocarditis (EAM)-induced inflammatory myocardial injury. Ursolic acid (UA) is an antioxidant-enriched traditional Chinese medicine formula. The present study aimed to investigate whether UA could alleviate inflammatory cardiac injury and determine the underlying mechanisms.Methods: Six-week-old male BALB/c mice were randomly assigned to one of the three groups: Sham, EAM group, or UA intervention group (UA group) by gavage for 2 weeks. An EAM model was developed by subcutaneous injection of α-myosin heavy chain derived polypeptide (α-MyHC peptide) into lymph nodes on days 0 and 7. Echocardiography was used to assess cardiac function on day 21. The inflammation level in the myocardial tissue of each group was compared using hematoxylin and eosin staining (HE) of heart sections and Interleukin-6 (IL-6) immunohistochemical staining. Masson staining revealed the degree of cardiac fibrosis. Furthermore, Dihydroethidium staining, Western blot, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) were used to determine the mechanism of cardioprotective effects of UA on EAM-induced cardiac injury, and the level of IL-6, Nrf2, and HO-1.Results: In EAM mice, UA intervention significantly reduced the degree of inflammatory infiltration and myocardial fibrosis while improving cardiac function. Mechanistically, UA reduced myocardial injury by inhibiting oxidative stress (as demonstrated by a decrease of superoxide and normalization of pro- and antioxidant enzyme levels). Interestingly, UA intervention upregulated the expression of antioxidant factors such as Nrf2 and HO-1. In vitro experiments, specific Nrf2 inhibitors reversed the antioxidant and antiapoptotic effects of ursolic acid, which further suggested that the amelioration of EAM by UA was in a Nrf2/HO-1 pathway-dependent manner.Conclusion: These findings indicate that UA is a cardioprotective traditional Chinese medicine formula that reduces EAM-induced cardiac injury by up-regulating Nrf2/HO-1 expression and suppressing oxidative stress, making it a promising therapeutic strategy for the treatment of EAM

The Complicity Model of Action: Variation of Complicity in the Making of Student-Athletes in a Chinese Elite University

This study proposes the “complicity model” as an alternative to investigate the relationship between action and institutional environment. The author argues that extant literature on action is prevented from advancement by the separation between disposition and capacity, and by the separation between motivation and environment. The former separation is done by scholars’ injection of intention with global knowledge into action, and the latter is due to a lack of temporality. To avoid these two separations, the “complicity model” is demonstrated in the case of Chinese student-athletes. A three-month ethnography and forty interviews are done in a Chinese elite university to extract patterns of how student-athletes cope with and fit in the college environment with their different dispositions. Three levels of complicity are used to identify the subjectless disposition-institution cooperation and the temporal dimension of the position-making of student-athletes, advancing the explanation of action

Path analysis to identify factors influencing osteoporosis: A cross-sectional study

Background: Osteoporosis is characterized by low bone mass and deterioration of bone tissue, which is influenced by both environmental factors and nutritional metabolism. The relationship between biochemical indicators and bone mineral density (BMD) is intricate and involves complex mechanisms. Path analysis, a statistical method that investigates causal relationships and the strength of associations among multiple factors, can be valuable in elucidating the connection between biochemical indicators and BMD. Methods: In this study, we employed advanced statistical techniques, specifically structural equation modeling (SEM) to investigate the intricate interrelationships among a myriad of factors that exert influence on BMD. This analytical approach facilitated not only the identification of the direct relationships between specific variables and BMD but also the exploration of the intricate of indirect pathway through which other variables contribute to the oval impact on BMD. By delving into the direct and indirect effects, we aimed to unravel the complex influences that collectively shape the state of bone health, providing a nuanced understanding of the multifaceted nature of the factors affecting BMD. Results: Our findings revealed that lipid levels had a significant indirect influence on BMD, which was mediated by body mass index (BMI). BMI exhibited both direct and indirect effects on BMD. Uric acid (UA) exerted a significant direct and indirect influence on BMD, with glomerular filtration rate (GFR) acting as the mediator. However, the total effect of UA on BMD was not significant due to the cancellation of positive effect UA on BMD but negative indirect effects of UA through GFR. For females, albumin had a significant direct effect on BMD, whereas this effect was not observed in males. The path analysis models generated results that demonstrated an acceptable fit for both female data (χ2 = 9.63, df = 7, p = 0.21, comparative fit index (CFI) = 0.98, root mean square error of approximation (RMSEA) = 0.05) and male data (χ2 = 6.26, df = 4, p = 0.18, CFI = 0.97, RMSEA = 0.06). Conclusions: Nutritional metabolism plays a crucial role in maintaining BMD in elderly females and males

Application of Improved Combined Deterministic-Stochastic Subspace Algorithm in Bridge Modal Parameter Identification

Modal parameter identification is considered to be one of the most important tasks in structural health monitoring because it provides a reliable reference for structural vibration control, damage severity, and operational state. Moreover, at present, the combined deterministic-stochastic subspace algorithm is cogitated as one of the key algorithms in the modal parameter identification, which is why it is widely used in the modal parameter identification of bridge structures. In this paper, a novel method is proposed, which is a time-domain identification algorithm, based on sliding window-fuzzy C-means clustering algorithm-combined with deterministic-stochastic subspace identification (SC-CDSI), to achieve online intelligent tracking and identification of modal parameters for nonlinear time-varying structures. First of all, to realize the online tracking and identification process, it is necessary to divide the input and output signal of the nonlinear time-varying structure by windowing; for that, to determine the window function, window size and window step length according to the characteristics of the signal are analyzed. Secondly, in order to satisfy the intelligent identification of effective modals in stability diagram, the fuzzy C-means clustering algorithm is kept as a base, whereas frequency, damping ratio, and modal shapes serve as clustering elements, applied to fuzzy C-means clustering algorithm, and then the intelligent selection of effective modals is achieved. Finally, a shaking table test bridge is used as a modal parameter identification in lab, and its results are compared with the MIDAS finite element results. The compared results show that the proposed SC-CDSI identification algorithm can accurately achieve the intelligent identification of online tracking of the structural frequency, and the identification results are reliable to be used in real-life bridge structures