Explore the vast range of titles available.

As a future abundant and environmentally friendly clean energy source, the decomposition process of natural gas hydrates is significantly regulated by reservoir structural characteristics. Improper extraction can easily trigger geological hazards, yet current research on the coupling mechanism between wellbore microstructure and decomposition remains incomplete. To elucidate the regulatory role of reservoir structural characteristics, this study employed a self-developed physical simulation system to conduct triaxial creep experiments. It compared the mechanical response and decomposition dynamics of sediments under layered and homogeneous hydrate distribution patterns, while simultaneously monitoring gas production and formation displacement parameters. Results indicate that layered distribution significantly influences overall sediment creep behavior and failure patterns: low-saturation sublayers dominate the creep softening–hardening mechanism, while strain evolution at different timescales and long-term bearing capacity are controlled by low- and high-saturation sublayers, respectively. Creep cohesion and internal friction angle exhibit distinct differences between the two distribution patterns, with the influence mechanisms of relevant mechanical indicators closely related to the roles of sublayers with varying saturations. The study also uncovers the intrinsic link between gas production and stratigraphic subsidence during hydrate decomposition, clarifying the core mechanism by which reservoir structures influence decomposition stability through regulating mechanical responses. The methodologies and conclusions of this research provide scientific support for predicting the long-term stability of natural gas hydrate reservoirs and enabling safe, efficient extraction, while laying the groundwork for the systematic development of comprehensive hydrate technologies.

Illumination of noble metal nanostructures by electromagnetic radiation induces coherent oscillations of conductive electrons on their surfaces. These coherent oscillations of electrons, also known as localized surface plasmon resonances (LSPR), are the underlying physical cause of the electromagnetic enhancement of Raman scattering from analytes located in a close proximity to the metal surface. This physical phenomenon is broadly known as surface-enhanced Raman scattering (SERS). LSPR can decay via direct interband, phonon-assisted intraband, and geometry-assisted transitions forming hot carriers, highly energetic species that are responsible for a large variety of chemical transformations. This review critically discusses the most recent progress in mechanistic elucidation of hot carrier-driven chemistry and catalytic processes at the nanoscale. The review provides a brief description of tip-enhanced Raman spectroscopy (TERS), modern analytical technique that possesses single-molecule sensitivity and angstrom spatial resolution, showing the advantage of this technique for spatiotemporal characterization of plasmon-driven reactions. The review also discusses experimental and theoretical findings that reported novel plasmon-driven reactivity which can be used to catalyze redox, coupling, elimination and scissoring reactions. Lastly, the review discusses the impact of the most recently reported findings on both plasmonic catalysis and TERS imaging.

β-Lactamases, biofilms and toxins pose challenges for combating S. aureus infection. Thus, identifying inhibitors that can restore bacterial sensitivity to antibiotics, destroy biofilms, and antitoxins is a promising way to develop alternative agents. In this study, we found that piceatannol (pit), along with its analogues resveratrol (ret) and pterostilbene (pts) bind with β-lactamase to inhibit its activity, and 96TYR, 58ILE and 66LYS were identified as the critical binding residues. Pit and pts reduced the ampicillin (Amp) and gentamicin (Gm) MICs against S. aureus and enhanced the bactericidal ability of Amp. Pit and its analogues inhibited the formation of S. aureus USA300. In addition, the pit analogues bound with α-hemolysin and suppressed the hemolysis activity of the bacterial culture supernatant. The mechanism analysis revealed that pit exhibited multiple potential binding modes with α-hemolysin. Pit significantly decreased the cytotoxicity and the adherence effect mediated by S. aureus and increased the survival rate of Galleria mellonella that infected with S. aureus , the pathological tissue damage of Galleria mellonella was alleviated by treatment with pit alone or in combination with Amp. Taken together, our findings identify promising compounds for the development of S. aureus infection inhibitors.

This study employed numerical simulations to investigate the aerodynamic characteristics of a flapping wing by solving the governing incompressible Navier–Stokes equations. Using computational fluid dynamics (CFD), the effect of frequency acceleration on the aerodynamic performance of a two-degrees-of-freedom (DoF) flapping wing in hovering was examined. The results indicate that the pitching frequency acceleration significantly influences the aerodynamic force: positive acceleration enhances lift by up to 2.0 times while maintaining propulsion compared to the case under negative acceleration. This mechanism is attributed to the delayed shedding of the leading-edge vortex (LEV) and the shedding of the trailing-edge vortex (TEV). Moreover, aerodynamic forces are also affected by plunge acceleration, with both negative and positive acceleration contributing to performance improvement. An increase in the acceleration coefficient leads to a notable enhancement in the aerodynamic force; however, the improvement becomes marginal when the coefficient n exceeds 0.4. The underlying flow evolution is illustrated and analyzed through pressure and vorticity contours. These findings on the acceleration effect will be applied to optimize the kinematics and design of flapping wing drones.

To investigate the aerodynamic characteristics and multi-objective optimization of the variable camber airfoils, the influence of leading- and trailing-edge deflections on aerodynamic performance is conducted. A novel prediction model is presented using the Kriging surrogate model, with leading and trailing edge deflection angles as inputs and lift coefficients and drag coefficients as outputs. The Non-dominated Sorting Genetic Algorithm II (NSGA II) multi-objective optimization technique is applied to ascertain the ideal deflection parameters. The results show that upward deflection of the leading edge raises the lift, whereas downward deflection increases the value of the critical angle of attack. The deflection of the trailing edge increases the value of the critical angle of attack, while the downward deflection can enhance the lift coefficient. Appropriate upward deflections of both leading and trailing edges can delay the critical Mach number, while downward deflections of both the leading and trailing edges can enhance the value of the critical Mach number. The discrepancies between the Kriging model prediction and the CFD simulation are less than 2%. Compared to the basic airfoil, the aerodynamic performance of the optimized airfoil has been improved, with the lift coefficient increasing by 7.55% and 7.37% and the lift-to-drag ratio rising by 6.97% and 10.27% at two Mach numbers, respectively. The efficiency and reliability of this method have been verified.

Streptococcus pneumoniae (S. pneumoniae) Sortase A (SrtA) anchors virulence proteins to the surface of the cell wall by recognizing and cleaving the LPXTG motif. These toxins help bacteria adhere to and colonize host cells, promote biofilm formation, and trigger host inflammatory responses. Therefore, SrtA is an ideal target for the development of new preparations for S. pneumoniae. In this study, we found that phloretin (pht) and phlorizin (phz) exhibited excellent affinities for SrtA based on virtual screening experiments. We analyzed the interactive mechanism between pht, phz, and alnusone (aln, a reported S. pneumoniae SrtA inhibitor) and SrtA based on molecular dynamics simulation experiments. The results showed that these inhibitors bound to the active pocket of SrtA, and the root mean square deviation (RMSD) and distance analyses showed that these compounds and SrtA maintained stable configuration and binding during the assay. The binding free energy analysis showed that both electrostatic forces (ele), van der Waals forces (vdw), and hydrogen bonds (Hbonds) promoted the binding between pht, phz, and SrtA; however, for the binding of aln and SrtA, the vdw force was much stronger than ele, and Hbonds were not found. The binding free energy decomposition showed that HIS141, ILE143, and PHE119 contributed more energy to promote pht and SrtA binding; ARG215, ASP188, and LEU210 contributed more energy to promote phz and SrtA binding; and HIS141, ASP209, and ARG215 contributed more energy to promote aln and SrtA binding. Finally, the transpeptidase activity of SrtA decreased significantly when treated with different concentrations of pht, phz, or aln, which inhibited S. pneumoniae biofilm formation and adhesion to A549 cells without affecting normal bacterial growth. These results suggest that pht, phtz, and aln are potential materials for the development of novel inhibitors against S. pneumoniae infection.

This paper proposes a new research method for braided river sedimentation on the beach shore based on the action of tidal currents. This study conducts a statistical analysis of the length and width of a single braided river and channel bar sand body, and establishes the relationship function model of the quantitative scale of a single braided river and the channel bar. According to the core and logging data of the Nanwu area of the target oilfield, a quantitative methodology based on the calculation of a single accretion scale is established from three perspectives: the architecture interface identification of the accretion, the occurrence and scale calculation of the interlayer, and the scale calculation of the single accretion. In the Nanwu area, the inclination angle of the accretion interface in the direction of the long axis is 0.78–1.32°, and the inclination angle of the accretion interface in the direction of the short axis is 2.02–3.78°. The density of a single well group is generally 2–3 per well. The length of the single accretion in the channel bar is 700–1500 m. Based on these findings, this paper completes the construction of the architecture of the channel bar, and establishes the quantitative scale calculation method for architecture elements for different levels of braided river reservoirs. The research results provide support for the prediction of the braided river reservoir architecture and the remaining oil in similar blocks.

The world-wide Coronavirus Disease 2019 (COVID-19) pandemic was triggered by the widespread of a new strain of coronavirus named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Multiple studies on the pathogenesis of SARS-CoV-2 have been conducted immediately after the spread of the disease. However, the molecular pathogenesis of the virus and related diseases has still not been fully revealed. In this study, we attempted to identify new transcriptomic signatures as candidate diagnostic models for clinical testing or as therapeutic targets for vaccine design. Using the recently reported transcriptomics data of upper airway tissue with acute respiratory illnesses, we integrated multiple machine learning methods to identify effective qualitative biomarkers and quantitative rules for the distinction of SARS-CoV-2 infection from other infectious diseases. The transcriptomics data was first analyzed by Boruta so that important features were selected, which were further evaluated by the minimum redundancy maximum relevance method. A feature list was produced. This list was fed into the incremental feature selection, incorporating some classification algorithms, to extract qualitative biomarker genes and construct quantitative rules. Also, an efficient classifier was built to identify patients infected with SARS-COV-2. The findings reported in this study may help in revealing the potential pathogenic mechanisms of COVID-19 and finding new targets for vaccine design.

The heart is an essential organ in the human body. It contains various types of cells, such as cardiomyocytes, mesothelial cells, endothelial cells, and fibroblasts. The interactions between these cells determine the vital functions of the heart. Therefore, identifying the different cell types and revealing the expression rules in these cell types are crucial. In this study, multiple machine learning methods were used to analyze the heart single-cell profiles with 11 different heart cell types. The single-cell profiles were first analyzed via light gradient boosting machine method to evaluate the importance of gene features on the profiling dataset, and a ranking feature list was produced. This feature list was then brought into the incremental feature selection method to identify the best features and build the optimal classifiers. The results suggested that the best decision tree (DT) and random forest classification models achieved the highest weighted F1 scores of 0.957 and 0.981, respectively. The selected features, such as NPPA, LAMA2, DLC1, and the classification rules extracted from the optimal DT classifier played a crucial role in cardiac structure and function in recent research and enrichment analysis. In particular, some lncRNAs (LINC02019, NEAT1) were found to be quite important for the recognition of different cardiac cell types. In summary, these findings provide a solid academic foundation for the development of molecular diagnostics and biomarker discovery for cardiac diseases.

A traditional airfoil NACA0012 is employed to examine the aerodynamic characteristics of a flapping wing in forward flight. Numerical simulations were carried out to determine the effect of frequency acceleration on aerodynamic behavior. The results indicate that acceleration significantly enhances lift and slightly improves propulsion compared to non-acceleration condition. Acceleration applied solely in the sweeping motion had a minimal influence on lift, whereas positive sweeping acceleration considerably reduced propulsion, even turning it negative – a trend explained by shedding strength of tailing edge vortex (TEV). In contrast, pitching acceleration showed no notable effect on propulsion, but negative pitching acceleration increased lift by up to 9 times compared to the AM-10 baseline. Regarding to the acceleration coefficient, lift improvement was observed only when the coefficient n was below 1.2. Additionally, the advanced ratio was found to markedly influence aerodynamic performance, simultaneously reducing both lift and propulsion. The examination of frequency acceleration provides a theoretical foundation for improving aerodynamic performance and guiding the construction of flapping wing drones.