Search Results (272)

In this work, three 3-carboxamidecoumarin derivatives (3b, 3c, and 4) were synthesized and characterized by NMR, IR, and single-crystal X-ray. All compounds maintain an essentially planar coumarin scaffold stabilized by an intramolecular N–H⋯O hydrogen bond (S(6) motif), though compound 4 exhibits a more complex bifurcated S₃²(11)[S(6)S(6)S(5)] network that enhances its conformational rigidity. The crystal packing analysis reveals that while all derivatives form one-dimensional (1D) supramolecular tapes through C–H⋯O interactions, their 3D architectures differ significantly: 3b and 3c rely on a diverse combination of π⋯π stacking and lone pair⋯π contacts, whereas 4 is governed by highly directional stacking between the pyran and pyridine rings. Hirshfeld surface analysis and CE-B3LYP energy framework calculations quantified the balance between intermolecular forces, showing that 3b is dispersion-dominated (H⋯H, 43.5%), while 3c achieves a balanced electrostatic–dispersion regime due to the nitro group, which increases O⋯H/H⋯O contacts to 37.1% and yields the highest stabilization energy (−69.1 kJ/mol). These results demonstrate that the electronic nature of the substituents at the 3- and 6-positions drastically modulates the hierarchy of non-covalent interactions, providing key insights for the crystal engineering of coumarin-based supramolecular systems. Full article

Background: Long-term stent healing after primary PCI of culprit unprotected left main (ULM) lesions is insufficiently explored. In this setting, large vessel size and bifurcation anatomy may limit angiographic stent optimization and contribute to persistent strut malapposition and incomplete coverage. Objectives: To identify OCT-derived geometric and healing parameters associated with long-term strut coverage and malapposition after angiography-guided primary PCI of culprit ULM lesions. Methods: This single-center exploratory study included 30 patients with long-term OCT follow-up after angiography-guided primary PCI of culprit ULM lesions. OCT analysis was performed separately in three prespecified subsegments: the left main (LM), polygon of confluence (POC), and distal main branch (dMB). Five predefined strut-level healing outcomes were analysed: covered struts, malapposed struts, malapposed and uncovered struts, significantly malapposed struts (>400 μm), and significantly malapposed and uncovered struts. Associations between patient-level healing outcomes and OCT-derived measures of lumen geometry, stent dimensions, neointimal response, and an exploratory lumen–stent mismatch variable were assessed using univariable and multivariable linear regression. Results: A total of 31,703 struts were analysed. Overall strut coverage was 90.7 ± 6.6%. Compared with the dMB, proximal ULM segments (LM and POC) showed lower strut coverage (82.8% and 84.2% vs. 93.9%, p < 0.001) and higher malapposition rates (17.4% and 14.2% vs. 0.4%, p < 0.001). In regression analysis, larger native lumen dimensions were associated with lower strut coverage and higher malapposition, whereas larger achieved stent area was associated with better strut healing. The exploratory lumen–stent mismatch variable in multivariable models with all five healing outcomes in multivariable models (all p < 0.01). Conclusions: After angiography-guided primary PCI of culprit unprotected left main lesions, long-term strut healing was significantly influenced by the mismatch between native reference lumen area and the achieved mean stent area. Whether intravascular imaging–guided optimization of stent sizing and expansion in large-calibre left main anatomy improves strut healing requires further investigation. Full article

Hyperspectral image classification (HSIC) plays a crucial role in fine-grained Earth observation tasks. However, balancing efficient long-range dependency modeling with the extraction of fine-grained local features remains a significant challenge, primarily due to the inherent high-dimensional spectral redundancy and complex spatial variability of hyperspectral data. Existing modeling paradigms exhibit distinct limitations: Convolutional Neural Networks (CNNs) are constrained by localized receptive fields, while Vision Transformers (ViTs), despite their global receptive capabilities, incur prohibitive quadratic computational complexity. Meanwhile, the emerging Mamba architecture has demonstrated remarkable effectiveness in sequence modeling with linear complexity, but it often lacks sufficient sensitivity to local textures when directly applied to non-causal 2D images. To address these limitations, this paper proposes a novel parallel hybrid architecture termed DualMambaFormer. Deviating from the traditional serial stacking paradigm, the proposed network utilizes a dual-stream design to achieve the complementary fusion of global static attention and dynamic sequence reasoning. Specifically, the model first employs an SS-ResNet for spectral dimensionality reduction and local feature embedding. Subsequently, the architecture bifurcates into a parallel encoding stage: one branch leverages Multi-Head Self-Attention (MHSA) to capture global spatial correlations, while the other introduces a Local Enhanced Mamba (LEM) branch. By integrating State Space Models (SSM) with depthwise separable convolutions, the LEM branch simultaneously captures long-range causal dependencies and local spatial context. Finally, a dual class token fusion strategy is designed to integrate heterogeneous representations at the decision level. Extensive experiments on four benchmark datasets—Indian Pines, Pavia University, Salinas, and WHU-HongHu—show that DualMambaFormer achieves OA values of 96.56%, 98.95%, 97.60%, and 96.09%, respectively, with consistently high AA and Kappa coefficients. These results demonstrate the effectiveness, robustness, and generalization capability of the proposed method for hyperspectral image classification. Compared with the second-best competing methods, DualMambaFormer improves OA by 5.55, 2.30, 1.68, and 4.30 percentage points on the Pavia University, Indian Pines, Salinas, and WHU-HongHu datasets, respectively. Full article

We study a perturbed coupled system of generalized hybrid pantograph equations involving the deformable derivative of Zulfeqarr–Ujlayan–Ahuja. A central point of the revision is made explicit: for classically differentiable functions this derivative is local and satisfies $D^{\tau }u=(1-\tau )u+\tau u^{\prime }$. Therefore, in the present differentiable setting the memory or aftereffect is produced by the proportional pantograph delays, while the deformable order $\tau$ supplies an order-dependent local relaxation/drift term. After rewriting the system as an equivalent integral equation on $\mathcal{X}=C(I,{\mathbb{R}}^2)$, we establish invariant-ball conditions, existence and uniqueness within invariant balls, generalized Ulam–Hyers stability, and Lipschitz continuous dependence on the perturbation amplitude $\epsilon$. The assumptions and constants are stated so that the restrictive roles of the Lipschitz bounds, the interval length, and $\left|\epsilon \right|$ are transparent. We then provide numerical parameter sensitivity diagrams for illustrative pantograph systems and include step-size refinement checks and performance indices. The numerical and plasma-inspired sections are deliberately framed as exploratory delay-feedback examples rather than as first-principles plasma models or rigorous bifurcation theory. Full article

Hill’s problem plays an important role in analyzing the local dynamics of an infinitesimal body under the gravitational influence of a distant massive primary and a nearby secondary body of smaller mass. When radiation pressure is included, the resulting model becomes particularly relevant for studying the motion of dust particles and solar-sail spacecraft in the vicinity of minor celestial bodies, such as planets or asteroids. This inclusion breaks the symmetry with respect to the Oy axis that characterizes the configurations of motion in the classical Hill’s problem. Thus, the location of the collinear equilibrium points, and the evolution of the Lyapunov families must be studied independently. Although the planar dynamics of the photogravitational Hill’s problem have been extensively investigated, its three-dimensional structure remains largely unexplored. The present study undertakes a systematic numerical investigation of branches of spatial periodic orbits that bifurcate from the planar Lyapunov families. Specifically, we compute all three-dimensional bifurcations up to multiplicity four and classify them according to their symmetry properties. The analysis reveals that these families exhibit distinct evolutionary patterns in the space of initial conditions, with most of them terminating in collision orbits with the secondary body. Full article

In deep geothermal engineering, concrete slabs are prone to thermal cracking. The aggregates and pores are the core influencing factors for this failure behavior. However, existing research methods are unable to accurately capture the microscopic evolution process of thermal cracking and cannot clarify the intrinsic mechanism of how the characteristics of aggregates and pores affect the initiation and propagation of cracks. This limitation restricts the in-depth understanding of the laws of concrete thermal cracking. To address this deficiency, this study employs the discrete element method (DEM) and combines the particle flow program PFC2D to construct a microscopic model of concrete disks. By setting reasonable temperature parameters and thermal load boundaries, a numerical simulation system matching the actual deep geothermal high-temperature environment is established. Three sets of quantitative variables were designed: aggregate particle size (0.003, 0.004, 0.005, 0.006), aggregate volume fraction (0.35, 0.40, 0.45, 0.50), and porosity (0.11, 0.12, 0.13, 0.14). Through controlled variable simulations, the influence laws of each variable on the formation, propagation path, and time evolution of concrete thermal cracks were explored. The quantitative research results show that an increase in aggregate particle size significantly accelerates the generation and propagation of cracks. When the particle size is 0.006, the number of cracks is the highest and the propagation rate is the fastest. The aggregate volume fraction is negatively correlated with the final number of cracks, and 0.50 is the optimal fraction, at which the number of cracks is the smallest. A decrease in the fraction will lead to intensified stress concentration in the cement paste and a sudden increase in the number of cracks. An increase in porosity significantly disrupts the material continuity. When the porosity is 0.14, the bifurcation and connection of cracks are the most significant, while a low porosity of 0.11 can effectively inhibit the overall development process of thermal cracks. In addition, compared with traditional experimental methods and continuous medium numerical simulation techniques, the discrete element method has unique advantages in revealing the internal mechanism of concrete thermal cracking at the microscopic level. It can achieve real-time tracking of the evolution of discrete micro-cracks and the internal stress distribution characteristics. This study enriches the microscopic theoretical system of concrete thermal cracking and provides reliable quantitative references and technical support for the design of thermal crack resistance of concrete in deep geothermal engineering and the optimization of material composition. Full article

A study was conducted to evaluate the effect of neutral detergent fiber (NDF) levels of calf starter and weaning time on growth, rumen fermentation characteristics, serum metabolites, and rumen microbial diversity of Holstein calves. A total of 24 newly born male Holstein calves were randomly distributed to four groups in a completely randomized design with a 2 × 2 factorial arrangement of NDF levels (14% and 24%) and weaning time (d 44 and d 54). There was no interaction between starter NDF levels and weaning time for any trait except rumen acetic acid in the immediate post-weaning phase (p = 0.013). Starter NDF levels had no effect on growth, feed intake, and hay intake. Late-weaned calves had greater (p = 0.050) weight gain in the pre-weaning phase whereas, early-weaned calves showed greater weight gain (p = 0.004) and starter intake (p = 0.004) in the post-weaning phase although overall weight gain, and starter and hay intakes were not affected by weaning time. Rumen pH, ammonia nitrogen, and most volatile fatty acids remained unaffected by starter NDF levels and weaning except isobutyric acid which was greater in calves fed 24% NDF starter (p = 0.001) in the immediate post-weaning and isovaleric acid which was greater in early-weaned calves (p = 0.044) at the end of experiment. Serum metabolites were largely affected (p < 0.05) by starter NDF levels and weaning time in the pre-weaning phase only. Alpha diversity of rumen microbes was greater and chaotic in 14% NDF starter group (early- and late-weaned) in the pre-weaning phase which converged in the immediate post-weaning phase and diverged on starter NDF basis at the end of experiment. Microbial ecology at phylum and genus levels composition were greatly driven by starter NDF levels in the pre-weaning phase, by weaning time in the immediate post-weaning phase, and two distinct bifurcated microbial ecologies based on starter NDF levels appeared at the end of experiment. In conclusion, the comparable growth with distinct microbial diversity but largely in favor of 24% NDF starter suggests that calves can be subjected to early weaning with 24% starter NDF levels for smooth transition from liquid to solid feed in Holstein calves. Full article

In this work, we present a numerical proof-of-concept study of a device for nanoparticle sorting, targeting size ranges relevant to exosome-like dimensions (typically 40–200 nm), which remains challenging for passive sorting techniques. The system consists of three silicon waveguides embedded in a CYTOP layer and arranged in a two-step directional-coupler configuration, integrated with a microchannel that carries a water-based buffer as the carrier fluid, transporting the suspended nanoparticles. Three-dimensional Finite Element Method (3D-FEM) simulations were performed, incorporating both optical and hydrodynamic forces to track particle dynamics within the microchannel and demonstrate controlled, size-selective particle deflection. First, numerical simulations show that nanospheres with diameters ranging from 500 nm to 700 nm can be effectively separated by the transverse trapping force at a 4:1 power-splitting ratio. Then, to extend the concept toward smaller size ranges, a bifurcated microchannel is introduced, enabling fluid-assisted transport in low-optical-field regions and allowing reliable separation of particles with smaller diameters (between 200 nm and 400 nm), accompanied by an 8:1 power-splitting ratio. These results demonstrate, within a numerical framework, the feasibility of an integrated photonic–microfluidic approach for size-selective nanoparticle sorting. The proposed strategy may support future pre-processing steps in liquid biopsy workflows, particularly for enriching nanoscale components such as exosome-sized vesicles, rather than constituting a direct diagnostic tool. Full article

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) coupled with methanol reforming hold promise for distributed energy systems, yet channel hydrodynamics and geometry optimization remain underexplored. This study develops a 3D multiphysics model to investigate coupled behaviors in HT-PEMFCs fueled by methanol reformate. Results reveal bifurcation-induced Dean vortices have dual effects: they cause flow maldistribution (15–18% velocity deviation) and contribute 50% of inlet pressure loss, while generating a lateral pumping effect that enhances local mass transfer. A continuous parametric sweep of channel widths (0.9–1.9 mm) identifies a voltage-dependent performance crossover—narrower channels (1.3 mm) excel at high voltages by improving electronic conduction, whereas wider channels (1.5 mm) perform better at low voltages by mitigating mass transfer limitations. These findings provide quantitative design criteria for optimizing flow field geometry in HT-PEMFC stacks. Full article

In this paper, based on the Caputo-like delta fractional difference operator, we will present a fractional discrete model of a 4D Power System. We present an extension of the popular integer-order single-machine infinite-bus formulation to two fractional cases, one with commensurate (equal) fractional orders and another incommensurate (not equal). This extension captures long-memory effects in dynamics and thus offers a consistent mathematical description of the nonlinear behavior of power systems. The orders of the fractional models are analyzed numerically. Using time series evolution, phase-space plots, bifurcation maps, Lyapunov spectra, and the 0–1 chaos test, spectral entropy and $C_0$ complexity metrics, we identify chaotic regimes. Additionally, techniques for controlling chaos are explored to stabilize and regulate the dynamics of the system. Both the fractional formulations exhibit richer dynamical features than their integer counterparts, and for the incommensurate case, the sensitivity to the fractional variations is larger, generating complex nonlinear oscillations. The fractional discrete power system framework provides a new perspective for studying instability, the voltage collapse phenomenon, and chaotic oscillations in power engineering applications. Full article

The use of computational fluid dynamics (CFD) to study hemodynamics in arteries offers significant potential for addressing complex flow problems. Due to its enhanced performance hardware and software, CFD has become an important approach for studying hemodynamics in human arteries. This approach is utilized to investigate hemodynamics and forecast risk factors for atherosclerotic lesion development and progression, including circulatory flow, and to analyze local flow fields and flow profiles resulting from geometric changes. This foundational study will aid in analyzing blood flow behavior through the abdominal aorta and the origin and courses of renal arteries, as well as investigating the causes of disorders such as atherosclerosis and hypertension. The current study investigates three idealized abdominal aorta–renal artery junction models under varying blood pressure settings. Materialise software V19 was used to extract the geometry data to create idealized 3D abdominal aorta–renal branching models. Unsteady flow simulations were performed in ANSYS Fluent, utilizing rigid walls and Newtonian and Carreau–Yasuda viscosity conditions. Oscillatory shear index (OSI) and Time-averaged wall shear stress (TAWSS) were measured to enhance understanding of atherosclerotic plaque formation and progression. Also, the effect of geometric change at the bifurcation area was explored, and it was discovered that this location causes considerable vortex forming zones. The evident velocity reduction and backflow development were seen, reducing shear stress. The findings indicate that low TAWSS < 0.4 Pa and OSI > 0.15 areas within the bifurcation region are more susceptible to atherosclerosis development. Full article

Introduction: The retropharyngeal carotid artery (RCA) is a rare anatomical variant where the carotid artery resides in the retropharyngeal space. The co-occurrence of RCA and significant atherosclerotic stenosis of the carotid bifurcation is even rarer. Recognizing this anatomy is crucial because of the increased risk of adverse events during procedures such as intubation or oropharyngeal surgery. Furthermore, differentiating between the fixed and dynamic forms is essential for guiding appropriate diagnostic and therapeutic strategies. A scoping review was undertaken, and two cases of RCA and significant internal carotid artery stenosis requiring a surgical approach were presented. Materials and Methods: EMBASE and OVID were systematically searched for studies reporting data on RCA and significant internal carotid artery stenosis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) was followed, and we presented two case reports of RCA and significant internal carotid artery stenosis requiring surgical treatment, treated at the Division of Vascular Surgery, IRCCS MultiMedica, Sesto San Giovanni, Milan, Italy. Results and Discussion: Among the 22 papers identified by the scoping review, 6 case reports were ultimately included in the analysis, supplemented by our two cases. The review and the added cases highlight significant heterogeneity in the clinical presentation and management of RCA with stenosis. Therapeutic options include carotid endarterectomy (CEA), transfemoral carotid artery stenting (TF-CAS), and transcarotid artery revascularization (TCAR). Also, the diagnostic with dynamic 3D-CT angiography during swallowing would be important in some symptomatic cases to document mechanical compression by the hyoid bone or thyroid cartilage (dynamic RCA), which standard static imaging failed to detect. Conclusions: Due to the rarity of the condition, no high-level evidence (RCTs) exists. Treatment decisions are based on the qualitative assessment of anatomical risk and isolated case reports. Standard interventions (CEA and TF-CAS) are generally considered high-risk. The final management choice must be individualized based on technical feasibility, neurological risk, and the determination of whether the pathology is fixed or dynamically compressive. Full article

In this study, we develop and investigate a novel fractional discrete-time computer virus dynamics model in two dimensions with a memristive nonlinear coupling mechanism. The memristor introduces nonlinearity by having memory regulation that depends on the state and enhances the propagation dynamics of virus spread. By investigating both matching and non-matching fractional orders, it is then possible to derive useful knowledge with respect to cooperating roles in terms of fractional memory and memristive effects. The complexity behind it is confirmed via 3D phase portraits, bifurcation analysis with LE_max calculation, 0–1 chaos test, and SE complexity. Numerical results reveal rich dynamical phenomena, including periodic oscillations, quasi-periodicity, and strong chaos. In fact, positive LE_max values, Brownian-like trajectories, and high-complexity SE corroborate the chaotic nature of the regimes. Thereby, the fractional-order separation in noncommensurate conditions is a marker of chaotic motion, magnified in the emergently high-dimensional space introduced by the memristive element. As these results indicate that the derivative model proposed here provides an excellent fit for complex viruses present in scaffolds, it may prove to be a useful modeling tool. Full article

This study numerically investigates the flow division at lateral diversions, focusing on the influence of the diversion angle and the ratio of channel widths on flow characteristics and discharge distribution. A total of 68 simulations were performed using FLOW-3D HYDRO 2022R1 software with a Large Eddy Simulation turbulence model. The investigation covered diversion angles of 30°, 45°, 60°, and 90°, combined with width ratios of 0.25, 0.50, and 1.00, under a wide range of upstream and downstream flow parameters. The flow fields were analyzed using cross-sections in both channels; the change in flow depths and velocity fields were evaluated together with organized flow structures. Streamline analyses were performed and three new empirical equations were proposed to predict the width of the divided flow and the discharge distribution in the bifurcation. Finally, the performance of existing equations previously proposed in the literature were assessed against the simulation results. Full article

Recent phytochemical investigations have demonstrated that Luvunga scandens is a rich source of structurally diverse secondary metabolites; however, its potential antioxidant-active constituents and their underlying mechanisms remain largely unexplored. In this study, an NMR-guided fractionation strategy applied to the rhizomes and leaves of L. scandens led to the isolation of ten limonoids, including three new compounds, Luvungas B–D (3, 4, and 8). Their structures and absolute configurations were determined through extensive spectroscopic analysis, X-ray diffraction, and ECD calculations. Based on the isolated analogues, a biosynthetic pathway is proposed, featuring the metabolic bifurcation of a key acyclic intermediate into the isoobacunoic acid and propellane-type lineages. Biological evaluation revealed that 8 inhibits RSL3-induced ferroptosis in HepaRG liver cells with an EC₅₀ of 16.1 µM. Mechanistic studies demonstrated that, unlike classical antioxidants, compound 8 mitigates lipid peroxidation without exhibiting direct radical-scavenging or iron-chelating activities. These findings suggest that 8 suppresses ferroptosis via non-canonical mechanisms. Full article