Guiding near-source elastic waves in a semi-infinite medium.

In this work, we propose elastic metamaterials with phase discontinuities to steer the propagation of near-source bulk waves in a semi-infinite elastic medium. Our design exploits an array of embedded subwavelength resonators with tailored masses to attain a complete phase shift spanning [Formula: see text]. This phase control allows for diverse wave functionalities, such as directional refraction and energy focusing. Through the use of dispersion diagrams and the generalized Snell's law, along with a multiple scattering formulation, we analytically demonstrate the effectiveness of our design in achieving the desired wavefront manipulation. The proposed design has the potential to advance the field of guiding elastic waves using metamaterials and find practical applications in areas such as isolating ground-borne vibrations in densely urbanized regions and energy harvesting. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Research on the Improvement of Semi-Global Matching Algorithm for Binocular Vision Based on Lunar Surface Environment.

The low light conditions, abundant dust, and rocky terrain on the lunar surface pose challenges for scientific research. To effectively perceive the surrounding environment, lunar rovers are equipped with binocular cameras. In this paper, with the aim of accurately detect obstacles on the lunar surface under complex conditions, an Improved Semi-Global Matching (I-SGM) algorithm for the binocular cameras is proposed. The proposed method first carries out a cost calculation based on the improved Census transform and an adaptive window based on a connected component. Then, cost aggregation is performed using cross-based cost aggregation in the AD-Census algorithm and the initial disparity of the image is calculated via the Winner-Takes-All (WTA) strategy. Finally, disparity optimization is performed using left-right consistency detection and disparity padding. Utilizing standard test image pairs provided by the Middleburry website, the results of the test reveal that the algorithm can effectively improve the matching accuracy of the SGM algorithm, while reducing the running time of the program and enhancing noise immunity. Furthermore, when applying the I-SGM algorithm to the simulated lunar environment, the results show that the I-SGM algorithm is applicable in dim conditions on the lunar surface and can better help a lunar rover to detect obstacles during its travel.

Single-Frequency GNSS Integer Ambiguity Solving Based on Adaptive Genetic Particle Swarm Optimization Algorithm.

Carrier phase measurements currently play a crucial role in achieving rapid and highly accurate positioning of global navigation satellite systems (GNSS). Resolving the integer ambiguity correctly is one of the key steps in this process. To address the inefficiency and slow search problem during ambiguity solving, we propose a single-frequency GNSS integer ambiguity solving based on an adaptive genetic particle swarm optimization (AGPSO) algorithm. Initially, we solve for the floating-point solution and its corresponding covariance matrix using the carrier-phase double difference equation. Subsequently, we decorrelate it using the inverse integer Cholesky algorithm. Furthermore, we introduce an improved fitness function to enhance convergence and search performance. Finally, we combine a particle swarm optimization algorithm with adaptive weights to conduct an integer ambiguity search, where each generation selectively undergoes half-random crossover and mutation operations to facilitate escaping local optima. Comparative studies against traditional algorithms and other intelligent algorithms demonstrate that the AGPSO algorithm exhibits faster convergence rates, improved stability in integer ambiguity search results, and in practical experiments the baseline accuracy of the solution is within 0.02 m, which has some application value in the practical situation of short baselines.

Improvement of AD-Census Algorithm Based on Stereo Vision.

Problems such as low light, similar background colors, and noisy image acquisition often occur when collecting images of lunar surface obstacles. Given these problems, this study focuses on the AD-Census algorithm. In the original Census algorithm, in the bit string calculated with the central pixel point, the bit string will be affected by the noise that the central point is subjected to. The effect of noise results in errors and mismatching. We introduce an improved algorithm to calculate the average window pixel for solving the problem of being susceptible to the central pixel value and improve the accuracy of the algorithm. Experiments have proven that the object contour in the grayscale map of disparity obtained by the improved algorithm is more apparent, and the edge part of the image is significantly improved, which is more in line with the real scene. In addition, because the traditional Census algorithm matches the window size in a fixed rectangle, it is difficult to obtain a suitable window in the image range of different textures, affecting the timeliness of the algorithm. An improvement idea of area growth adaptive window matching is proposed. The improved Census algorithm is applied to the AD-Census algorithm. The results show that the improved AD-Census algorithm has been shown to have an average run time of 5.3% and better matching compared to the traditional AD-Census algorithm for all tested image sets. Finally, the improved algorithm is applied to the simulation environment, and the experimental results show that the obstacles in the image can be effectively detected. The improved algorithm has important practical application value and is important to improve the feasibility and reliability of obstacle detection in lunar exploration projects.

An Adaptive and Robust Control Strategy for Real-Time Hybrid Simulation.

A real-time hybrid simulation (RTHS) is a promising technique to investigate a complicated or large-scale structure by dividing it into numerical and physical substructures and conducting cyber-physical tests on it. The control system design of an RTHS is a challenging topic due to the additional feedback between the physical and numerical substructures, and the complexity of the physical control plant. This paper proposes a novel RTHS control strategy by combining the theories of adaptive control and robust control, where a reformed plant which is highly simplified compared to the physical plant can be used to design the control system without compromising the control performance. The adaptation and robustness features of the control system are realized by the bounded-gain forgetting least-squares estimator and the sliding mode controller, respectively. The control strategy is validated by investigating an RTHS benchmark problem of a nonlinear three-story steel frame The proposed control strategy could simplify the control system design and does not require a precise physical plant; thus, it is an efficient and practical option for an RTHS.

The chromatin-remodeling enzyme BRG1 coordinates CIITA induction through many interdependent distal enhancers.

The chromatin-remodeling enzyme BRG1 is critical for interferon-gamma (IFN-gamma)-mediated gene induction. Promoter-proximal elements are sufficient to mediate BRG1 dependency at some IFN-gamma targets. In contrast, we show here that at CIITA, which encodes the 'master regulator' of induction of major histocompatibility complex class II, distal elements conferred BRG1 dependency. At the uninduced locus, many sites formed BRG1-independent loops. One loop juxtaposed a far downstream element adjacent to a far upstream site. Notably, BRG1 was recruited to the latter site, which triggered the appearance of a histone 'mark' linked to activation. This subtle change was crucial, as subsequent IFN-gamma-induced recruitment of the transcription factors STAT1, IRF1 and p300, as well as histone modifications, accessibility and additional loops, showed BRG1 dependency. Like BRG1, each remote element was critical for the induction of CIITA expression. Thus, BRG1 regulates CIITA through many interdependent remote enhancers, not through the promoter alone.

Frequent interferon regulatory factor 1 (IRF1) binding at remote elements without histone modification.

Transcriptional activators bind DNA and recruit cofactors to modify chromatin. The extent to which these two events are separable is unclear. Here, using a custom ChIP tiling array to map chromatin modifications, we show that interferon-γ-induced DNA binding of signal transducer and activator of transcription 1 (STAT1), typically associated with the transcription factor interferon regulatory factor 1 (IRF1), causes histone acetylation (H3ac, H4ac). In contrast, among IRF1 sites lacking concomitant STAT1 recruitment, only 25% underwent inducible histone acetylation, 31% exhibited constitutive histone acetylation, and 44% had no histone acetylation. These latter "orphan sites" also lacked other activating modifications (e.g. H3K4me1, H3K4me2) and were typically remote from transcription start sites. In these cases the closest gene was typically an IFNγ-inducible locus that did not respond to IFNγ in this setting. Orphan sites were detected in different cell types, suggesting broad relevance. Despite an atypical downstream response (i.e. no histone modifications), IRF1 binding depended on SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4 or BRG1), as is typical of active IRF1 enhancers. Although SMARCA4 permitted IRF1 access to the orphan sites, there was no corecruitment of the histone acetyltransferases CREB-binding protein (CBP) and p300. Orphan sites were constitutively unacetylated, and several were marked with repressive chromatin modifications (e.g. H3K27me3). In conclusion, although IRF1 can trigger enhanceosome formation independently of STAT1, its ability to do so depends on local chromatin cues.

Properties of STAT1 and IRF1 enhancers and the influence of SNPs.

BACKGROUND: STAT1 and IRF1 collaborate to induce interferon-γ (IFNγ) stimulated genes (ISGs), but the extent to which they act alone or together is unclear. The effect of single nucleotide polymorphisms (SNPs) on in vivo binding is also largely unknown. RESULTS: We show that IRF1 binds at proximal or distant ISG sites twice as often as STAT1, increasing to sixfold at the MHC class I locus. STAT1 almost always bound with IRF1, while most IRF1 binding events were isolated. Dual binding sites at remote or proximal enhancers distinguished ISGs that were responsive to IFNγ versus cell-specific resistant ISGs, which showed fewer and mainly single binding events. Surprisingly, inducibility in one cell type predicted ISG-responsiveness in other cells. Several dbSNPs overlapped with STAT1 and IRF1 binding motifs, and we developed methodology to rapidly assess their effects. We show that in silico prediction of SNP effects accurately reflects altered binding both in vitro and in vivo. CONCLUSIONS: These data reveal broad cooperation between STAT1 and IRF1, explain cell type specific differences in ISG-responsiveness, and identify genetic variants that may participate in the pathogenesis of immune disorders.

Pt@UiO-66 heterostructures for highly selective detection of hydrogen peroxide with an extended linear range.

In this study, a good core-shell heterostructure of Pt NPs@UiO-66 was fabricated by encapsulating presynthesized platinum nanoparticles (Pt NPs) into the host matrix of UiO-66 which possesses the slender triangular windows with a diameter of 6 Å. The transmission electron microscopy images exhibited that the number of the encapsulated Pt NPs and the crystalline morphology of as-synthesized core-shell heterostructure samples had a series of changes with increasing the volume of the injected Pt NPs precursor solution. Among these samples, the Pt NPs@UiO-66-2 sample had a good crystalline morphology with several well-dispersed Pt NPs encapsulated in UiO-66 frameworks. But there were no obvious Pt NPs observed in the Pt NPs@UiO-66-1 sample, and for the Pt NPs@UiO-66-3 sample, the number of Pt NPs encapsulated in UiO-66 matrix notably reduced and the metal organic framework (MOF) crystals became small and aggregated. The electrochemical measurements showed that the Pt NPs@UiO-66-2 sample modified glass carbon electrode (GCE) presented a remarkable electrocatalytic activity toward hydrogen peroxide (H2O2) oxidation, including an excellent anti-interference performance even if the concentration of the interference species was the same as the H2O2, an extended linear range from 5 µM to 14.75 mM, a low detection limit, as well as good stability and reproducibility. The results indicate the superiority of MOFs in H2O2 detection. And more importantly, it will provide a new opportunity to promote the anti-interference performance of the nonenzyme electrochemical sensors.

[Study on UPLC fingerprint of Xiasangju Granules].

OBJECTIVE: To establish a UPLC fingerprint method of Xiasangju Granules. METHODS: UPLC analysis was performed on a Waters ACQUITY UPLC H-Class system and carried out at 30 °C on a Waters Column ACQUITY UPLC BEH C18 (2.1 mm x 50 mm, 1.7 µm). A binary gradient elution system was composed of acetonitrile (phase A)and 0.5% acetic acid solution (phase B). Detection was performed at the wavelength of 320 nm,the mobile flow rate was at 0.4 mL/min. A matrix including 16 variations (characteristic peaks area)and 12 samples was constructed for similarity evaluation, cluster analysis and principle component analysis. RESULTS: The results showed that the collected samples had a good similarity. A specificity fingerprint was produced and 16 characteristic peaks were designated. 12 samples were divided into 6 groups. CONCLUSION: It is a reliable, available and quick method for quality control of Xiasangju Granules.