Data-Driven Insights into the Fluorescence of Asphaltene Aggregates Using Extended Frenkel Exciton Model

The origin of the fluorescence redshift during asphaltene aggregation remains debated due to the great diversity of asphaltene molecules, while the extended Frenkel exciton model provided a theoretical framework for studying multi-chromophore systems such as asphaltene aggregates. We investigated the fluorescence energy of hundreds of asphaltene dimers based on 132 experimentally determined asphaltene monomer structures. Our result shows that the dimer’s fluorescence energy is always lower than both of its monomers regardless of its intermolecular conformation, with its redshift dominated by superexchange. The dimer oscillator strength predominantly depends on the monomer with the lower fluorescence energy, and the involvement of charge-transfer states and the cancellation between monomer transition dipole moments suppressed the fluorescence especially when two monomers have similar fluorescence energy. The above findings hold for all asphaltene dimers despite their diversity, which offers a theoretical interpretation for comprehending the relationship between asphaltene aggregation and its fluorescence variation. Furthermore, this work provides theoretical insights into other research areas related to organic planar conjugated systems with multiple chromophores

Impacts of Polarizable Continuum Models on the SCF Convergence and DFT Delocalization Error of Large Molecules

Advances in algorithm developments have enabled density functional theory (DFT) description of large molecules, including whole proteins, but the self-consistent field (SCF) convergence issues often hamper practical applications. The conductor-like polarizable continuum model (CPCM), although initially introduced as an implicit solvent model, was reported to improve SCF convergence in some large molecules. However, the underlying mechanisms and applicable use cases were unclear. We investigated the impacts of CPCM on the SCF convergence of 25 peptides and found that the CPCM only effectively reduced the SCF iterations for molecules with charge separations (e.g., the zwitterionic form of peptides) but had little effect on non-charge-separated molecules. We observed that CPCM increased the HOMO-LUMO gap of both the zwitterionic and non-charge-separated molecules, but only the charge-separated molecules suffered from the vanishing HOMO-LUMO gap problem in the gas phase which is the origin of the convergence issue. We revealed CPCM’s gap-opening mechanism as the selective stabilization/destabilization of molecular orbitals (MO) based on their local electrostatic environment. Compared to level-shifting, a traditional SCF improvement technique, CPCM has superior performance because the stabilization/destabilization of MOs is consistent through SCF iterations. Finally, we examined CPCM’s impacts on DFT density delocalization error (DDE) when used as an SCF accelerator. CPCM can mitigate the DDE and reproduce the density-derived properties (e.g., dipole moments) matching high-level methods when a very low dielectric constant is used but tends to over-localize the electron density at higher dielectric constants

Difference-based M-estimator of generalized semiparametric model with NSD errors

Abstract In this paper, we consider the generalized semiparametric model (GSPM) yi=h(xiTβ)+f(ti)+ei,1≤i≤n, $$y_{i}=h\bigl(\mathbf{x}_{i}^{T}\beta \bigr)+f(t_{i})+e_{i} , \quad 1\leq i\leq n,$$ where h(⋅) $h(\cdot )$ is a known function, ei $e_{i}$ are dependent errors. We obtain an estimator of the parametric component β for the model by a difference-based M-estimator. In addition, we prove the asymptotic normality of the proposed estimator and investigate the weak convergence rate of the wavelet estimator of f(⋅) $f(\cdot )$. Furthermore, we apply these results to a partially linear model with dependent errors

Synergistic activity of tetrasodium EDTA, ethanol and chlorhexidine hydrochloride against planktonic and biofilm cells of clinically relevant pathogens

Objectives: Biofilms associated with implantable medical devices and wounds are clinically relevant, often requiring repeated use of antibiotics without success. A search for non-antibiotic antimicrobial and antibiofilm solutions is warranted, in line with antimicrobial stewardship. Our study aimed to evaluate the broad-spectrum antimicrobial efficacy of tetrasodium EDTA, ethanol and chlorhexidine hydrochloride (HCl) alone and in combination against clinically relevant planktonic and biofilm cells of bacterial and fungal pathogens. Methods: MICs and MBCs were determined for tetrasodium EDTA, ethanol and chlorhexidine HCl against planktonic cells of test pathogens. The MBEC Assay® biofilm inoculator device was used to evaluate the biofilm eradication ability of test antimicrobials alone and in combination against clinically relevant pathogens. The checkerboard microbroth dilution assay was performed to analyze the synergism between test antimicrobials. Results: Against planktonic cells, the combination of tetrasodium EDTA with ethanol or chlorhexidine HCl resulted in synergistic to indifferent activity, with no antagonism observed. Against mature biofilms, all combinations were synergistic. The MBEC of each test antimicrobial was decreased from 4- to -64-fold when used in combination as compared to when agents were used alone. We optimised the concentration of antimicrobials to achieve rapid eradication of pre-formed biofilms. A triple combination of 3% tetrasodium EDTA, 20% ethanol and 2.5 μg/mL chlorhexidine HCl completely eradicated 48-h-old biofilms of all test strains within 2 h. Conclusion: All three antimicrobial agents can be used together for prevention and treatment of biofilms and biofilm-related infections. The observed in vitro efficacy should be tested further through in vivo and clinical studies

Spatio-Temporal Dynamics of Landscape Connectivity and Ecological Network Construction in Long Yangxia Basin at the Upper Yellow River

Analyzing multi-scale changes in landscape connectivity is an important way to study landscape ecological processes and also an important method to maintain regional biodiversity. In this study, graph-based connectivity was used to analyze the dynamics of the connectivity of natural habitats in the Long Yangxia basin of upper Yellow River valley from 1995 to 2015. We used the core areas of the nature reserves as the source regions to construct ecological networks under different thresholds, so as to identify key areas that can maintain overall landscape connectivity. The results showed that, from 1995 to 2015, the landscape connectivity in the study area increased for the first 10 years, and, since 2005, has declined. On a spatial scale, we found that both the connectivity of the ecological network and the length of the corridor increased with landscape resistance. Our analysis demonstrates the importance of the natural habitat in the southern part of the study area where connectivity was higher, as well as the sensitivity of connectivity of the northern area to human activities. Both large and medium patches contribute greatly to the overall landscape connectivity, while attention needs to be paid to the protection and management of small patches as they played “stepping stone” roles in maintaining and improving landscape connectivity. The proportions of landscape types that served as corridors, listed in order of their contribution to connectivity, were grassland, forestland, wetland and cultivated land. This suggests that, in addition to focusing on the protection of grassland and forest land, the reasonable planning and utilization of wetland and cultivated land will also have an impact on landscape connectivity. In addition, the protection of and improvement in habitats in the Sanjiangyuan Nature Reserve is of great significance to enhance landscape connectivity. Our study provides a scientific basis to support and improve regional landscape connectivity and biodiversity conservation over the next decade

A Novel Transformer-Based Approach for Simultaneous Recognition of Hand Movements and Force Levels in Amputees Using Flexible Ultrasound Transducers

Accurate hand motion intention recognition is essential for the intuitive control of intelligent prosthetic hands and other human-machine interaction systems. Sonomyography, which can detect the changes in muscle morphology and structure precisely, is a promising signal source for fine hand movement recognition. However, sonomyography measured by traditional rigid ultrasound probes may suffer from poor acoustic coupling because the rigid probe surfaces cannot accommodate the curvilinear shape of the human body, particularly in the case of small and irregular residual limbs in amputees. In this study, we used a self-designed lightweight, flexible, and wearable ultrasound transducer to acquire muscle ultrasound images, and proposed a sonomyography transformer (SMGT) model for simultaneous recognition of hand movements and force levels. The performance of SMGT was systematically compared to two commonly used image processing methods, HOG and Gray Gradient, as well as a deep CNN model, in simultaneously recognizing ten classes of hand/finger movements and three force levels. Additionally, ten subjects including seven non-disabled subjects and three trans-radial amputees who are the end users of prosthetic hands were recruited to evaluate the effectiveness of SMGT. Results showed that our proposed method achieved average classification accuracies of 98.4% ± 0.6% and 96.2% ± 3.0% in non-disabled subjects and amputee subjects, respectively, which are much higher than those of other methods. This study provided a valuable approach for ultrasound-based hand motion recognition that may promote the applications of intelligent prosthetic hands

Dynamic Adaptive Low Power Adjustment Scheme for Single-Frequency GNSS/MEMS-IMU/Odometer Integrated Navigation in the Complex Urban Environment

Positioning accuracy and power consumption are essential performance indicators of integrated navigation and positioning chips. This paper proposes a single-frequency GNSS/MEMS-IMU/odometer real-time high-precision integrated navigation algorithm with dynamic power adaptive adjustment capability in complex environments. It is implemented in a multi-sensor fusion navigation SiP (system in package) chip. The simplified INS algorithm and the simplified Kalman filter algorithm are adopted to reduce the computation load, and the strategy of adaptively adjusting the data rate and selecting the observation information for measurement update in different scenes and motion modes is combined to realize high-precision positioning and low power consumption in complex scenes. The performance of the algorithm is verified by real-time vehicle experiments in a variety of complex urban environments. The results show that the RMS statistical value of the overall positioning error in the entire road section is 0.312 m, and the overall average power consumption is 141 mW, which meets the requirements of real-time integrated navigation for high-precision positioning and low power consumption. It supports single-frequency GNSS/MEMS-IMU/odometer integrated navigation SiP chip in real-time, high-precision, low-power, and small-volume applications

Application of Preoperative Ultrasonography in the Percutaneous Minimally Invasive Repair of Acute Closed Achilles Tendon Rupture

Percutaneous minimally invasive surgery involving Achilles tendon (AT) repair has the advantages of a low rerupture rate and fewer postoperative complications. However, due to the inability to operate under direct vision, the injury of the small saphenous vein (SSV) and sural nerve (SN) remains largely a high risk involving many challenges. We propose to introduce the preoperative application and advantages of ultrasonography in percutaneous minimally invasive surgery for acute AT rupture. Our results indicated that ultrasonography could locate the position of the SN more accurately and reduce the risk of iatrogenic nerve injury. Compared with the traditional surface markers, the preoperative localization and marking of AT, SSV, and SN in ultrasonography significantly reduced the risk of intraoperative accidental injury to blood vessels and nerves, which could reduce postoperative complications and promote early rehabilitation of patients. We ultimately exploit the properties of ultrasonography in percutaneous minimally invasive surgery to treat Achilles tendon rupture