Surface Topology Research Articles

Contact-scale insights into the shear stiffness of non-spherical granular materials

Small-strain shear stiffness (G0) is an essential parameter to predict deformation characteristics and dynamic properties of granular materials. It is empirically known that G0 increases with decreasing a void ratio (e0) and increasing isotropic stress level (p0′). Recently, the effect of particle shape on G0 has been studied; however, the mechanism underlying the evolution of G0 is not fully understood. Using the discrete element method (DEM), this contribution quantifies the G0 of granular materials by performing small-strain probing where multi-sphere clumped particles are used to vary particle shape and surface topology systematically. The Hertzian contact theory is applied for each sphere-element contact to capture the stress-dependent contact stiffness. The results reveal that G0 is well correlated with e0 or mean coordination number for a given particle shape; however, G0 is measurably reduced when finer sphere-elements dominate inter-particle contact responses. The present study proposes two contact-scale expressions of G0 for non-spherical particles based on contact area (CA) and micromechanical effective medium theory (EMT) by extending the EMT expression for spherical particles; both can capture the effects of particle shape and p0′ on G0 under given conditions where particle breakage does not occur.

Anti-Infective Bacteriophage Immobilized Nitric Oxide-Releasing Surface for Prevention of Thrombosis and Device-Associated Infections.

The treatment of critically ill patients has made great strides in the past few decades due to the rapid development of indwelling medical devices. Despite immense advancements in the design of these devices, indwelling medical device-associated infections and thrombosis are two major clinical problems that may lead to device failure and compromise clinical outcomes. Antibiotics are the current treatment choice for these infections; however, the global emergence of antibiotic-resistance and their biofilm formation abilities complicate the management of such infections. Moreover, systemic administration of anticoagulants has been used to counter medical device-induced thrombosis, but a range of serious adverse effects associated with all types of available anticoagulants entails exploring alternative options to counter device-associated thrombosis. In this study, bacteriophages (phages) were covalently immobilized on polydimethylsiloxane (PDMS) surface containing the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine (SNAP) via SNAP impregnation method. This dual strategy combines the targeted antibacterial activity of phages against bacterial pathogens with the antibacterial-antithrombotic activity of NO released from the polymeric surface. The PDMS, SNAP-PDMS, phage-immobilized PDMS (PDMS-Phage), and phage-immobilized SNAP-PDMS (SNAP-PDMS-Phage) surfaces were characterized for their surface topology, elemental composition, contact angle, SNAP loading, NO release and phage distribution. SNAP-PDMS and SNAP-PDMS-Phage surfaces showed similar and consistent NO release profiles over 24 h of incubation. Immobilization of whole phages on PDMS and SNAP-PDMS was achieved with densities of 2.4 ± 0.54 and 2.1 ± 0.33 phages μm-2, respectively. Immobilized phages were found to retain their activity, and SNAP-PDMS-Phage surfaces showed a significant reduction in planktonic (99.99 ± 0.08%) as well as adhered (99.80 ± 0.05%) Escherichia coli as compared to controls in log killing assays. The SNAP-PDMS-Phage surfaces also exhibited significantly reduced platelet adhesion by 64.65 ± 2.95% as compared to control PDMS surfaces. All fabricated surfaces were found to be nonhemolytic and do not exhibit any significant cytotoxic effects toward mammalian fibroblast cells. This study is the first of its kind to demonstrate the combinatorial pertinence of phages and NO to prevent antibiotic-resistant/sensitive bacterial infections and thrombosis associated with indwelling medical devices.

Nested chirality and multimode transfer around exceptional points driven by external forces in electric circuits

Exceptional points (EPs) are non-Hermitian degeneracies or branch points where eigenvalues and their corresponding eigenvectors coalesce. Due to the complex non-trivial topology of Riemann surfaces associated with non-Hermitian Hamiltonians, the dynamical encirclement or proximity of EPs in parameter space has been shown to lead to some novel physical phenomena, such as the chiral modes modulations. However, in the previous studies on dynamically encircling EPs, tuning the chirality for applications requires periodic modulation of the system parameters. Here, we propose theoretically and demonstrate experimentally a way to generate EPs and realize asymmetric multimode switching by tuning external forces. The application of the external force achieves the effect of modifying the system parameters so that the dynamical encircling of the EPs can be easily realized. It is shown theoretically that nested chiral behavior and multimode transfer appear in a two-dimensional non-Hermitian higher-order topological insulator with twofold degenerate second-order EPs by tuning the external forces. Furthermore, we design and fabricate the corresponding circuit networks, and experimentally observe nested chiral behavior and multimode transfer. Our work opens up avenues for practical applications of the non-Hermitian physical phenomena.

Impact of Pressure on Metavalent Bonding in BiTe Influencing Electronic Topological Transitions

AbstractBiTe, a member of the (Bi2)m(Bi2Te3)n homologous series, possesses natural van der Waals‐like heterostructure with a Bi2 bilayer sandwiched between the two [Te−Bi−Te−Bi−Te] quintuple layers. BiTe exhibits both the quantum states of weak topological and topological crystalline insulators, making it a dual topological insulator and a suitable candidate for spintronics, quantum computing and thermoelectrics. Herein, we demonstrate that the chemical bonding in BiTe is to be metavalent, which plays a significant role in the pressure dependent change in the topology of the electronic structure Fermi surface. The enhancement of the metavalent bonding character with pressure in BiTe is evidenced from first‐principles density functional theory (DFT) calculations. Due to the change in the Fermi surface topology, we have visualized electronic topological transitions (ETT) at ~1 and ~3 GPa through pressure dependent synchrotron X‐ray diffraction analysis and Raman spectroscopy. The correlation between the metavalent bonding and ETT offers insights into chemical bonding influenced transitions in quantum materials.

Unbiased picture of the ligand docking process for the hevein protein–oligosaccharide complex

The ligand-docking behavior of hevein, the major latex protein from the rubber tree Hevea brasiliensis (Euphorbiaceae), has been investigated by the unguided molecular dynamics (MD) simulation method. An oligosaccharide molecule, initially placed in an arbitrary position, was allowed to move around hevein for a prolonged simulation time, on the order of microseconds, with the expectation of spontaneous ligand docking of the oligosaccharide molecule to the binding site of hevein. In the binary solution system consisting of a hevein molecule and a chito-trisaccharide (GlcNAc3) molecule, three out of the six separate simulation runs successfully reproduced the complex structure of the observed binding from. It appeared that the surface topology formed by two aromatic side chains of the hevein molecule played a role in orienting the GlcNAc3 molecule in the correct direction. We also performed MD simulations of the ternary solution system containing a cello-hexasaccharide (Glc6) molecule in addition to hevein and a chito-hexasaccharide (GlcNAc6) molecule. Formation of hevein–GlcNAc6 complex structures was exclusively observed, while the Glc6 molecule remained in the solvent phase throughout the simulations. Obviously, the acetamide groups of GlcNAc play a role in detecting the binding site and its vicinity on the protein surface.

The influence of halogen-mediated interactions on halogen abstraction reactions by formyl radicals.

This article reports a theoretical study on the halogen exchange reactions YX + CHO → Y + XCHO (with Y = F, Cl, Br; X = Cl, Br, I) carried out at a high level of accuracy using coupled-cluster based methodologies including CCSD(T)-F12, CCSD(T)/CBS and CCSDT(Q)Λ. Most of the reactions are exothermic at room temperature, with the exception of the reactions FI + CHO → F + ICHO and ClI + CHO → Cl + ICHO. Exothermicity follows two concurrent trends established by the strength of the bonds being cleaved and formed: Y = F < Cl < Br (X-Y bond strength) and X = Cl > Br > I (C-X bond strength). Regarding the topology of the potential energy surfaces, we find that at the CCSD level of theory only some processes present the expected reaction profile: a pre-reactive complex (preRC) followed by a transition state (TS) and a post-reactive complex (postRC). However, when triple excitations are taken into account, all reactions become barrierless with no preRC/TS along the reaction profile. We propose that halogen-mediated interactions through the σ-hole, which represent the driving force in the early stages of the title reactions, are responsible for the absence of a tight transition state. We suggest that the strength of these interactions formed during these processes triggers the onset of the halogen atom exchange, before the preRC is formed. Therefore, this study aims to show the relevant role of halogen-mediated interactions in the mechanism of reactions in which a halogen atom is abstracted by the formyl radical (CHO).

Changes in hairiness of woven fabrics at the production and finishing stages

Advances in the textile industry have led to a shift from using empirical experience to design fabrics to using computer-aided systems. Objective fabric properties related to appearance, feel, and comfort are predicted based on the physical models. The look and feel of fabrics are greatly influenced by their complex surface topology, which can be defined by two main properties: roughness and hairiness. In this study, a roughness contactless measurement system originally designed for evaluating only the surface roughness was extended to evaluating the hairiness, which is quantified by spatial parameters obtained by the quadrat method. The modified system of Roughness Contactless Measurement system was applied to assessing work shirts across five production stages, and the experimental results demonstrated variations between gray and treated woven fabrics that could be attributed to shrinkage during water-based processes, subsequent drying under tension, and singeing. The gray and pretreated fabrics exhibited the highest hairiness, which was greatly reduced by singeing and stabilized during the finishing stage by an easy-care treatment.

Effects of Ionizing Radiation on the Color and Morphology Properties of Leather

Effective conservation strategies for leather artifacts and art objects are essential for preserving cultural heritage, particularly given the inherent vulnerability of the material to biodegradation, as leather, an organic material, is especially susceptible to this process. Gamma radiation has emerged as a promising method for the disinfestation and disinfection of cultural heritage objects and archival materials. This study aimed to advance the understanding of gamma radiation as a conservation technique for vegetable-tanned snake and chrome-tanned bovine leather, specifically focusing on its effects on chromaticity, surface topology, fiber structure and thermal behavior. Gamma radiation was applied at controlled doses of 1 and 3 kGy, and its impact on the morphology of the leather was assessed using colorimetry within the CIELAB color space and field emission gun scanning electron microscopy (FEGSEM). The findings indicated that gamma radiation at these doses induced minimal alterations in the morphological properties of the leather. The color differences for irradiated and non-irradiated samples were negligible, with total color differences (ΔE) remaining within acceptable limits (ΔE &lt; 3). Moreover, FEGSEM analysis demonstrated that the fiber structure and surface morphology were not significantly compromised by the irradiation process. Thermogravimetric analyses showed similar thermal decomposition between non-irradiated and irradiated samples for both bovine and snake leather, with detailed data analysis indicating thermal stability. The results supported the efficiency of gamma radiation as a conservation technique for both bovine and snake leather artifacts, preserving their aesthetic and structural integrity.

Optimizing Abrasive Water Jet Parameters for Enhanced Interactivity in Metal-Stacked Hybrid Fiber Laminates

High strength and shock-absorbing hybrid Fibre Laminate (HFL) machining is required to get the required geometric shape and size and to test the functioning under various impact protection circumstances. The compression molding process was adopted to fabricate the HFL. Skin titanium metal and alternately interlaced durable jute and high strength Kevlar fiber. A Central Composite Design (CCD)-Response Surface Technique (RST) was used to conduct the experiments with varying abrasive water jet parameters like WP-water pressure, TS-traverse speed, SOD-stand-off distance, and AQ-abrasive quantity. The desirability optimization technique adopted to minimize the surface roughness (Ra) and kerf angle (KA). An experimental examination shows that when water jet pressure was raised to its maximum value, the Ra and KA considerably reduced by 28.69% and 8.25%, respectively. Similar to how the Ra and KR significantly reduced by an extent of 7.4% and 3.5% when the abrasive quantity was increased to its higher value. However, when SOD and TS increased, a reversal impact on Ra and KA was seen. According to surface topology study, the brittle fracture occurs with micro-chipping, and for the kevlar fiber, bulk machining.

Impact of Pressure on Metavalent Bonding in BiTe Influencing Electronic Topological Transitions.

BiTe, a member of the (Bi2)m(Bi2Te3)n homologous series, possesses natural van der Waals-like heterostructure with a Bi2 bilayer sandwiched between the two [Te-Bi-Te-Bi-Te] quintuple layers. BiTe exhibits both the quantum states of weak topological and topological crystalline insulators, making it a dual topological insulator and a suitable candidate for spintronics, quantum computing and thermoelectrics. Herein, we demonstrate that the chemical bonding in BiTe is to be metavalent, which plays a significant role in the pressure dependent change in the topology of the electronic structure Fermi surface. The enhancement of the metavalent bonding character with pressure in BiTe is evidenced from first-principles density functional theory (DFT) calculations. Due to the change in the Fermi surface topology, we have visualized electronic topological transitions (ETT) at ~1 and ~3 GPa through pressure dependent synchrotron X-ray diffraction analysis and Raman spectroscopy. The correlation between the metavalent bonding and ETT offers insights into chemical bonding influenced transitions in quantum materials.

A wideband coaxial-to-waveguide transition devised with topology optimization

Topology optimization is a powerful technique that utilizes the distribution of material properties along with surface topology as parameters to expand a specified performance. While primarily used as a foundational step in regenerative design for structural mechanics, the general TO framework is also applicable to many of the complex issues in electromagnetics such as frequency agile mode converters. This is considered a difficult parameter to optimize since RF components operate on resonance. TO is used on the coaxial-to-rectangular waveguide converter in the range X band. The radiative element chosen is a patch antenna with a ground stop. The original design is transformed into a binary material distribution matrix, where each cell is assigned a value of 0 or 1, while ensuring connectivity between the cells. Then the cell values are altered via a BPSO algorithm to optimize the width of the operating band, resulting in a complex structure that yields a bandwidth 38% larger than the control. The optimized patch structure is fabricated and its performance verified in the frequency range 8-12 GHz.

Rescuing ACE2-Deficiency-Mediated Nucleus Pulposus Senescence and Intervertebral Disc Degeneration by a Nanotopology-Enhanced RNAi System.

Nucleus pulposus cell (NPC) senescence contributes to intervertebral disc degeneration (IVDD). However, the underlying molecular mechanisms are not fully understood. In this study, it is demonstrated that angiotensin-converting enzyme 2 (ACE2) counteracted the aging of NPCs and IVDD at the cellular and physiological levels. The expression of ACE2 correlates negatively with the degree of NPC senescence and IVDD. Using both loss- and gain-of-function mouse models, it is revealed that ACE2 deficiency increased the senescence of NPCs and exacerbated injury- or instability-induced IVDD, whereas ACE2 overexpression counteracted these detrimental effects. Mechanistically, integrated analysis of single-cell and bulk transcriptomics shows that ACE2 deficiency results in the activation of TGFβ2/Smads signaling pathway and the transcription of Serpine1, ultimately triggering NPC senescence and IVDD. A nanomedical delivery system (virus-like nanovectors, VNs) composed of nanovectors with a virus-like surface topology and small interfering RNA targeting Serpine1 (VN-siSer) is developed. With nanotopology-enhanced transfection efficiency, RNA-interfering treatment by VN-siSer effectively alleviated NPC senescence and IVDD at both the cellular and animal levels. Overall, the data reveal the underlying mechanisms of ACE2 in NPC senescence and IVDD pathogenesis and propose a distinct paradigm of precise nanomedical senescence-blockade RNAi for IVDD treatment.

Survey of Inter‐Prediction Methods for Time‐Varying Mesh Compression

AbstractTime‐varying meshes (TVMs), that is mesh sequences with varying connectivity, are a greatly versatile representation of shapes evolving in time, as they allow a surface topology to change or details to appear or disappear at any time during the sequence. This, however, comes at the cost of large storage size. Since 2003, there have been attempts to compress such data efficiently. While the problem may seem trivial at first sight, considering the strong temporal coherence of shapes represented by the individual frames, it turns out that the varying connectivity and the absence of implicit correspondence information that stems from it makes it rather difficult to exploit the redundancies present in the data. Therefore, efficient and general TVM compression is still considered an open problem. We describe and categorize existing approaches while pointing out the current challenges in the field and hint at some related techniques that might be helpful in addressing them. We also provide an overview of the reported performance of the discussed methods and a list of datasets that are publicly available for experiments. Finally, we also discuss potential future trends in the field.

The role of the single-particle state in the topology of the potential energy surface of 72Kr

The relativistic Hartree–Bogoliubov formalism was employed to explore the role of the nucleon single-particle state in defining the potential energy surface of the [Formula: see text]Kr isotope utilizing density-dependent zero and finite range NN interactions. It is discovered that a significant influence on identifying the ground state minima is the density of states near to the Fermi level.

Microfluidic paper-based analytical soft actuators (μPAC).

Soft actuators have developed over the last decade for diverse applications including industrial machines and biomedical devices. Integration of chemical sensors with soft actuators would be beneficial in analyzing chemical and environmental conditions, but there have been limited devices to achieve such sensing capabilities. In this work, we developed a thin-film soft actuator integrated with a paper-based chemical sensor, termed a microfluidic paper-based analytical soft actuator (μPAC). μPAC consists of (1) a silicone thin film with a 3D-printed pneumatic chamber and (2) a cellulose paper. This cellulose paper offers dual functions: the strain-limiting layer of a soft actuator and the substrate for the chemical sensor for a paper-based analytical device (μPAD). We characterized the design parameters of the actuators-namely, (1) thickness of silicone thin film, (2) chamber length, and (3) Young's modulus of silicone thin film-to evaluate the actuation performance. These characterizations suggested that the cellulose paper served as a suitable self-straining layer of the actuator, making μPAC a chemical sensor that can actuate simultaneously. Highlighting the unique capability of μPAC, we demonstrated the local detection of pH on the curved target surface. Overall, this research demonstrated the rapid fabrication of actuating chemical sensors with a unique design by combining soft actuators and μPAD, enabling chemical sensing on various surface topologies by dynamically making conformal contact.

Optimization design of gearbox based on response surface optimization and topology optimization

Optimization design of gearbox based on response surface optimization and topology optimization

Спин-орбитальное взаимодействие в пятиорбитальной модели ферропниктидов

The effect of spin-orbit coupling on the band structure and Fermi surface in the five-orbital model for iron-based superconductors is studied. Since there are two iron ions in the unit cell and their orbitals indirectly coupled through as orbitals, we introduce the constants of the intra- and inter-ion spin-orbit coupling in the effective model to separate the effect of the corresponding contributions on the band structure. We show that the intra- and inter-ion parts of the spinorbit coupling lead to Fermi surface topology change – splitting of the four contours of the Fermi surface around the point M = (π, π).

Surface Structured Quadrilateral Mesh Generation Based on Topology Consistent‐Preserved Patch Segmentation

ABSTRACTSurface‐structured mesh generation is an important part of the Computational Fluid Dynamics (CFD) preprocessing stage. The traditional method cannot automatically divide the 3D surface topology in complex structures. Thus, we propose a surface‐structured quadrilateral mesh generation method based on topology‐consistent‐preserved patch segmentation. The core idea is to segment the complex 3D model into several simple parts according to mesh quality and map each part to the 2D parametric domain based on the conformal parameterization method. Then, we utilize pattern‐based topology partitioning to divide the parametric domain into multiple quadrilateral subdomains, facilitating the generation of 2D structured quadrilateral meshes. By using the inverse mapping algorithm based on barycentric weights, the generated 2D structured mesh is inversely mapped back to the 3D space. Finally, we splice each part accurately according to the structured mesh distribution. Experimental results show that our proposed method can generate higher‐quality structured quadrilateral meshes than previous methods without losing the mesh topology of the original model.

The Golden Ratio Family of Extremal Kerr-Newman Black Holes and Its Implications for the Cosmological Constant

This work explores the geometry of extremal Kerr-Newman black holes by analyzing their mass/energy relationships and the conditions ensuring black hole existence. Using differential geometry in E3, we examine the topology of the event horizon surface and identify two distinct families of extremal black holes, each defined by unique proportionalities between their core parameters: mass (m), charge (Q), angular momentum (L), and the irreducible mass (mir). In the first family, these parameters are proportionally related to the irreducible mass by irrational numbers, with a characteristic flat Gaussian curvature at the poles. In the second family, we uncover a more intriguing structure where m, Q, and L are connected to mir through coefficients involving the golden ratio −ϕ−. Within this family lies a unique black hole whose physical parameters converge on the golden ratio, including the irreducible mass and polar Gauss curvature. This black hole represents the highest symmetry achievable within the constraints of the Kerr-Newman metric. This remarkable symmetry invites further speculation about its implications, such as the potential determination of the dark energy density parameter ΩΛ for Kerr-Newman-de Sitter black holes. Additionally, we compute the maximum energy that can be extracted through reversible transformations. We have determined that the second, golden-ratio-linked family allows for a greater energy yield than the first.

SegCSR: Weakly-Supervised Cortical Surfaces Reconstruction from Brain Ribbon Segmentations.

Deep learning-based cortical surface reconstruction (CSR) methods heavily rely on pseudo ground truth (pGT) generated by conventional CSR pipelines as supervision, leading to dataset-specific challenges and lengthy training data preparation. We propose a new approach for reconstructing multiple cortical surfaces using weak supervision from brain MRI ribbon segmentations. Our approach initializes a midthickness surface and then deforms it inward and outward to form the inner (white matter) and outer (pial) cortical surfaces, respectively, by jointly learning diffeomorphic flows to align the surfaces with the boundaries of the cortical ribbon segmentation maps. Specifically, a boundary surface loss drives the initialization surface to the target inner and outer boundaries, and an inter-surface normal consistency loss regularizes the pial surface in challenging deep cortical sulci. Additional regularization terms are utilized to enforce surface smoothness and topology. Evaluated on two large-scale brain MRI datasets, our weakly-supervised method achieves comparable or superior CSR accuracy and regularity to existing supervised deep learning alternatives.