The SARS-CoV-2 Omicron variant with increased fitness is spreading rapidly worldwide. Analysis of cryo-EM structures of the spike (S) from Omicron reveals amino acid substitutions forging ...interactions that stably maintain an active conformation for receptor recognition. The relatively more compact domain organization confers improved stability and enhances attachment but compromises the efficiency of the viral fusion step. Alterations in local conformation, charge, and hydrophobic microenvironments underpin the modulation of the epitopes such that they are not recognized by most NTD- and RBD-antibodies, facilitating viral immune escape. Structure of the Omicron S bound with human ACE2, together with the analysis of sequence conservation in ACE2 binding region of 25 sarbecovirus members, as well as heatmaps of the immunogenic sites and their corresponding mutational frequencies, sheds light on conserved and structurally restrained regions that can be used for the development of broad-spectrum vaccines and therapeutics.
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•Omicron spike stably maintains an active conformation for receptor recognition•Improved stability of Omicron enhances attachment but compromises viral fusion•Mutations perturb the conformation of antigenic sites recognized by most antibodies•Structurally restrained regions of RBM can be targets for COVID-19 countermeasures
Mutations in the SARS-CoV-2 Omicron variant improve spike trimer stability that supports viral attachment but appears to compromise viral fusion. They also perturb the confirmation of antigenic sites for antibody recognition, which may contribute to immune evasion.
In array signal processing, the inner structure of the signals could possibly be exploited to improve the performance of the direction-of-arrival (DOA) estimations. One typical scenario has been ...discussed in P. Chage, Y. Wang, and J. Saillard, ldquoA Root-MUSIC Algorithm for Non-Circular Sources,rdquo Proc. Int. Conf. Acoustics, Speech, Signal Processing (ICASSP), Salt Lake City, UT, May 2001, pp. 7-11, where all the incoming signals are supposed to be sent by noncircular PAM/BPSK sources. A modified MUSIC algorithm was then developed to improve the DOA estimation accuracy, as well as to increase the maximum number of detectable signals. However, it is more realistic that some users send noncircular symbols while other users still send circular symbols. In this correspondence, we develop an algorithm to cope with this more general scenario. By exploiting the redundancy existing in the noncircular signals, the proposed algorithm can still increase the maximum number of detectable signals and improve the performance accuracy compared to the conventional MUSIC algorithm. Simulation results clearly show the effectiveness of our proposed algorithm.
The development and application of marine current energy are attracting more and more attention around the world. Due to the hardness of its working environment, it is important and difficult to ...study the fault diagnosis of a marine current generation system. In this paper, an underwater image is chosen as the fault-diagnosing signal, after different sensors are compared. This paper proposes a diagnosis method based on the sparse autoencoder (SA) and softmax regression (SR). The SA is used to extract the features and SR is used to classify them. Images are used to monitor whether the blade is attached by benthos and to determine its corresponding degree of attachment. Compared with other methods, the experiment results show that the proposed method can diagnose the blade attachment with higher accuracy.
In the field of civil engineering, sounding the top layer of carriageways, i.e., the pavement layer, is classically performed using standard ground-penetrating radar (GPR), whose resolution is ...bandwidth dependent. The layer thickness is deduced from both the time delays of backscattered echoes and the known dielectric constant of the medium. This paper focuses on superresolution and high-resolution techniques, which serve to improve the time resolution of GPR signals, and presents a parametric technique and five subspace methods, namely, estimation of signal parameters via rotational invariance techniques (ESPRIT), multiple-signal classification (MUSIC) algorithm, Min-Norm, and their polynomial versions root-MUSIC and root-Min-Norm. The performance of these algorithms will be compared in terms of resolution power as well as root-mean-square error on the estimated thickness. The paper also presents the results of computer tests and radar measurements in the far field.
The direction-of-arrivals (DOA) estimation with an unfolded coprime linear array (UCLA) has been investigated because of its large aperture and full degrees of freedom (DOFs). The existing method ...suffers from low resolution and high computational complexity due to the loss of the uniform property and the step of exhaustive peak searching. In this paper, an improved DOA estimation method for a UCLA is proposed. To exploit the uniform property of the subarrays, the diagonal elements of the two self-covariance matrices are averaged to enhance the accuracy of the estimated covariance matrices and therefore the estimation performance. Besides, instead of the exhaustive peak searching, the polynomial roots finding method is used to reduce the complexity. Compared with the existing method, the proposed method can achieve higher resolution and better estimation performance with lower computational complexity.
With the wide application of lithium batteries, battery fault prediction and health management have become more and more important. This article proposes a method for predicting the remaining useful ...life (RUL) of lithium-ion batteries to avoid a series of safety problems caused by continuing to use the battery after reaching its service life threshold. Since the battery capacity is not easy to obtain online, we propose that some measurable parameters should be used in the battery discharge cycle to estimate battery capacity. Then, the estimated capacity is used to replace the measured value of the particle filter (PF) based on the Kendall rank correlation coefficient (KCCPF) to predict the RUL of the lithium batteries. Simulation results show that the proposed method has high prediction accuracy, stability, and practical value.
This paper investigates the performance of a wide variety of radar imaging modes, such as nadir-looking B-scan, or side-looking synthetic aperture radar tomographic acquisitions, performed in both ...back- and forward-scattering geometries, for the inspection and characterization of roadways. Nadir-looking B-scan corresponds to a low-complexity mode exploiting the direct return from the response, whereas side-looking configurations allow the utilization of angular and polarimetric diversity in order to analyze advanced features. The main objective of this paper is to evaluate the ability of each configuration, independently of aspects related to operational implementation, to discriminate and localize shallow underground defects in the wearing course of roadways, and to estimate key geophysical parameters, such as roughness and dielectric permittivity. Campaign measurements are conducted using short-range radar stepped-frequency continuous-waveform (SFCW) devices operated in the C and X bands, at the pavement fatigue carousel of Université Gustave Eiffel, over debonded areas with artificial defects. The results indicate the great potential of the newly proposed forward-scattering tomographic configuration for detecting slight defects and characterizing roadways. Case studies, performed in the presence of narrow horizontal heterogeneities which cannot be detected using classical B-scan, show that both the coherent integration along an aperture using the back-projection algorithm, and the exploitation of scattering mechanisms specific to the forward-looking bistatic geometry, allows anomalous echoes to be detected and further characterized, confirming the efficacy of radar imaging techniques in such applications.
To integrate Meta-analysis and bioinformatics strategies in the preliminary exploration of the potential mechanism of Yinyanghuo () and its extract in treating chronic obstructive pulmonary disease ...(COPD).
First, Meta-analysis was carried out. The Chinese and English literature of Yinyanghuo () in treating COPD was searched using the systematic strategy of combining subject words with free words. The included studies were evaluated by the SYRCLE risk bias assessment tool, after which the review manager software was used to combine the effect quantities for statistical analysis. Then, based on bioinformatics technology, the active ingredients and their targets of Yinyanghuo () were screened, and the intersection genes were obtained by mapping and comparing with the targets of COPD. The "medicinal materials-compounds-targets model" was constructed, and the key pathways were annotated. Finally, the core target was docked with important compounds.
A total of 8 studies were included in the Meta-analysis. The results showed that the Yinyanghuo (Herba Epimedii Brevicornus) group could significantly down-regulate pro-inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin (IL)-8 and increase the expression of anti-inflammatory factors and antioxidant factors such as IL-10 and phospho-protein kinase B (p-AKT) in the COPD model (all P < 0.05). A total of 23 active components and 102 corresponding target genes of Yinyanghuo (Herba Epimedii Brevicornus) were obtained by bioinformatics technology, among which 17 compounds and 63 targets were closely related to COPD. The results of enrichment analysis mainly included TNF signaling pathway, phosphoinositide 3-kinase (PI3K)/Akt signaling pathway, cancer signaling pathway, and other inflammatory reactions, oxidative stress, and tumor-related pathways. The molecular docking results showed that the binding energy fractions of the top five components of 24-epicampesterol with 10 core targets such as IL-6 were all less than ﹣5.0 kcal/mol, suggesting good binding ability.
Meta-analysis and bioinformatics results indicated that the therapeutic effect of Yinyanghuo () and its components on COPD might be related to antagonizing inflammation and oxidative stress. The above findings provide a preliminary basis for the development of Yinyanghuo () as a natural drug for preventing and treating COPD.
The microstructure and mechanical properties of four hot-rolled alloys, Mg-4Li, Mg-4Li-3Al, Mg-4Li-3Al-0.38Si and Mg-4Li-6Al-0.76Si, (weight percent) were investigated. The results showed that the ...addition of Al and Al-Si eutectic results in the precipitation of Al3Li(Mg) within the hot-rolled alloys. The Al3Li(Mg) is present as a solid solution of Mg in Al3Li with an L12 superlattice structure, which precipitates as small spherical particles. Another minor constituent present as a precipitate in the Si-containing alloys, Mg-4Li-3(Al-Si) and Mg-4Li-6(Al-Si), is a Mg2Si phase which is broken into polygonal particles in the hot-rolled alloys. Ultimate tensile strength (UTS) up to 295MPa was measured for the Mg-4Li-6(Al-Si) alloy, compared with 143MPa for the Mg-4Li alloy. This improvement is attributed to precipitation strengthening imparted by the Al3Li(Mg) and Mg2Si phases, as well as solid-solution strengthening due to Al atoms dissolved in the α-Mg matrix of the alloys.
This paper presents a novel adaptive digital predistortion (DPD) technique based on a cascade of an adaptive indirect learning architecture (ILA) and a static direct learning architecture (DLA) using ...a linear interpolation look-up-table (LILUT). The static LILUT-DLA-based DPD is designed to identify the inverse of a radio-frequency power amplifier (PA) model. The cascaded system of the DLA-based predistorter (PD) and PA is theoretically linear. However, in real-time applications, the PA characteristics change with time due to process, supply voltage, and temperature variations, making this cascaded system not strictly linear, which results in some residual nonlinear distortion at the PA output. This residual distortion is effectively compensated by an additional adaptive ILA-based PD using least mean squares or recursive least squares. Thanks to the incorporation of the static DLA, the proposed DPD approach is less sensitive to the PA output noise, ensuring a better preinverse of the PA and also requiring a smaller number of adaptive coefficients than either the adaptive stand-alone DLA- or ILA-based DPDs. The experimental results show that the proposed DPD technique effectively linearizes the PA, even if its characteristics change, and obtains better linearization performance than either the classical stand-alone DLA- or stand-alone ILA-based DPDs.
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