Search Results (578)

Spacetime singularities, in the sense that curvature invariants are infinite at some point or region, are thought to be impossible to observe, and must be hidden within an event horizon. This conjecture is called Cosmic Censorship (CC), and was formulated by Penrose. Here we review another type of CC where spacetime singularities are causally disconnected from the universe, because the throat of a wormhole “sucks in” the geodesics and prevents them from making contact with the singularity. In this work, we present a series of exact solutions to the Einstein–Maxwell–Dilaton equations that feature a ring singularity; that is, the curvature invariants are singular in this ring, but the ring is causally disconnected from the universe so that no geodesics can touch it. This extension of CC is called Wormhole Cosmic Censorship. Full article

Pigeon paramyxovirus type 1 (PPMV-1) poses a significant threat to pigeon farming in China, and understanding its biological characteristics and pathogenicity is critical for vaccine development and disease control. In this study, we characterized a PPMV-1 QY strain, performed full-length genome sequencing, and constructed a phylogenetic tree based on the F gene. Then, the biological properties and the pathogenicity of the QY strain were assessed and evaluated in vitro and in vivo. The results showed that phylogenetic analysis classified the QY strain within subgenotype VI.2.1.1.2.2, the predominant circulating strain in China. The QY strain exhibited a 50% egg infectious dose (EID₅₀) of 10^−6.8/0.1 mL, mean death time (MDT) in chicken embryos of 68.7 ± 2.1 h, and intracerebral pathogenicity index (ICPI) in one-day-old chicks of 1.12, which indicate it is a moderately virulent strain. Animal experiments showed that the QY strain resulted in a mortality rate of 66.7% in healthy pigeons. Necropsy findings included cerebral congestion and swelling, hemorrhagic glandular stomach papillae, tracheal ring hemorrhages, and duodenal congestion and swelling. Histopathological analysis revealed extensive inflammatory infiltration in the lungs and liver, widespread intestinal erosion, and severe necrosis of splenic red pulp cells. In conclusion, the QY strain belongs to subgenotype VI.2.1.1.2.2 and exhibits moderate virulence, causing high mortality and severe pathological lesions in infected pigeons. These findings provide valuable insights into the pathogenicity of PPMV-1 and the specific mutations in the F protein can serve as potential attenuation targets in vaccine development against the emerging subgenotype VI.2.1.1.2.2. Full article

A compact bio-inspired terahertz wideband antenna is presented in this work. The proposed antenna is based on Viburnum tinus leaf shape, a defective ground plane, a folded-ring slot, and parasitic elements. The footprint of the proposed antenna is $0.46\times 0.18{\lambda }_g^2$ at 0.18 THz. A bandwidth of 0.536 THz (0.18–0.72 THz) is achieved with a band notch at 0.35 THz (0.3–0.36 THz). The proposed antenna has a peak gain of 5 dBi and the stable radiation patterns. The proposed antenna is validated through a finite difference time domain simulator and the equivalent circuit analysis. The results from show a good correlation. Also, an extensive parametric analysis is performed, and the comparative analysis of the proposed antenna with the existing antennas shows that the proposed antenna is compact with competitive performance metrics such as gain, efficiency, and notch-band characteristics. Therefore, the proposed antenna (hereafter referred to as VTB-A) is a promising candidate for future terahertz wireless communications (5G, 6G, and beyond) and terahertz imaging. Full article

We introduce and study a class of rings, which we call NRW rings, distinguished by the condition that the set of nilpotent elements forms a Wedderburn radical subring. This class includes symmetric and semicommutative rings, as well as many other well-known and important classes. We also define nilpotent-semicommuting rings as those satisfying the semicommutativity condition restricted to nilpotent elements and prove that every nilpotent-semicommuting ring is an NRW ring. We provide an element-wise characterization of NRW rings and show that the NRW property is symmetric with respect to one-sided principal ideals. Based on the right ideals of a ring that are NRW, for any ring R we inductively construct the ideal $\overline{\mathcal{W}}\left(R\right)$ and prove that the prime radical of R equals the intersection of $\overline{\mathcal{W}}\left(R\right)$ with the sum of all nil right ideals of R. As a consequence, a positive solution to the Köthe conjecture follows for all rings R satisfying $R=\overline{\mathcal{W}}\left(R\right)$. We also characterize when certain classical ring constructions, such as direct sums, matrix rings, and the Dorroh extension, yield an NRW ring. Full article

Climate projections suggest ecosystems could face drastic changes due to global climate change, including more severe and frequent droughts than those recorded in the last century. Paleoclimatic series provide more extensive information than that available with instrumental records, allowing for the analysis of trends and recurrence of extreme events over a longer time periods. The objective of this research was to reconstruct the precipitation variability for southwestern Chihuahua, based on the tree-ring records of Pinus arizonica Engelm. and to assess the influence of ocean atmospheric circulations like El Niño Southern Oscillation (ENSO) and the North American Monsoon (NAM) on both low- and high-frequency climate variability. We developed three dendrochronological series covering 214 years (1802–2015), 265 years (1750–2014) and 369 years (1647–2015), for the Talayotes (TAL), Predio Particular Las Chinas (PPC) and El Cuervo (CUE) sites, respectively. The 369-year regional chronology was significantly related to cumulative precipitation variability between January and September. Recurring droughts were observed at approximately 50-year intervals. This regional climate variability was significantly related (p < 0.05) to Niño 3 SST and PDSI (JJA) indices. Maximum and minimum extreme events reconstructed in the last 369 years were synchronized with ENSO events, both in the El Niño warm phase and the La Niña cold phase. These results suggest that P. arizonica tree rings record shared a common response to the regional climate that was significantly modulated by ENSO and the NAM. This is the first dendroclimatic study to reconstruct summer precipitation patterns in northern Mexico, which is valuable given the importance of this seasonal precipitation on the regional economy. Full article

We present a concise and self-contained extension of the Finite Ring Continuum (FRC) program, showing that symmetry-complete prime shells ${\mathbb{F}}_{\mathsf{p}}$ with $\mathsf{p}=4\mathsf{t}+1$ exhibit a fundamental Euclidean-Lorentzian dichotomy. A genuine Lorentzian quadratic form cannot be realized within a single space-like prime shell ${\mathbb{F}}_{\mathsf{p}}$, since to split time from space one requires a time coefficient $c^2$ in the nonsquare class of ${\mathbb{F}}_{\mathsf{p}}^{\times }$, but then $c\notin {\mathbb{F}}_{\mathsf{p}}$. An explicit finite-field Lorentz transformation is subsequently derived that preserves the Minkowski form and generates a finite orthogonal group $O(Q_{\nu },{\mathbb{F}}_{p^2})$ of split type (Witt index 1). These results demonstrate that the essential algebraic features of special relativity—the invariant interval and Lorentz symmetry—emerge naturally within finite-field arithmetic, thereby establishing an intrinsic relativistic algebra within FRC. Finally, this dichotomy implies the algebraic origin of causality: Euclidean invariants reside within a space-like shell ${\mathbb{F}}_{\mathsf{p}}$, while Lorentzian structure and causal separation arise in its quadratic spacetime extension ${\mathbb{F}}_{{\mathsf{p}}^2}$. Full article

Industrial bearing surface defect detection faces challenges such as complex image backgrounds, multi-scale defects, and insufficient feature extraction. To address these issues, this paper proposes an improved YOLOv8-GSS defect detection method. Initially, the network substitutes the standard convolution in the C2f module and Concat module within the neck module with lightweight convolutions, GsConv, thereby reducing computational costs. Subsequently, to better capture and represent crucial features in the images, an SENetV2 attention mechanism is integrated before the SPPF module at the backbone end, effectively enhancing the model’s accuracy and robustness in defect detection. Finally, a self-built dataset of surface images of bearing rings collected from industrial sites is utilized as the basis for extensive experimentation. Experimental results show that the network achieves 97.8% AP50, with detection accuracy for large-, medium-, and small-scale defects improved by 2.4%, 3.6%, and 2.3%, respectively.2.3% respectively. The detection speed reaches 115 frames per second (FPS). Compared to mainstream surface defect detection algorithms, the proposed method exhibits significant improvements in both accuracy and detection speed. Full article

A versatile, sustainable feedstock pathway to bio-based polymeric materials was developed utilizing lignin biomass and the ring-opening copolymerization (ROCOP) of cyclic anhydrides and epoxides to synthesize functional, lignin-derived, fully bio-based polyester polyols. The initial goal was to make the ROCOP reaction more applicable to bio-derived starting materials and more attractive to commercialization by conducting the polymerization under less constrained and industrially relevant conditions in air and without the extensive purification of reagents, catalysts, or solvents, typically used in the literature. A refined ROCOP system was applied as a powerful tool in lignin valorization by successfully synthesizing the lignin-derived copolyester prepolymers from lignin models and depolymerized native lignin sourced from the reductive catalytic fractionation of Pinus radiata wood biomass. After mechanistic studies based on NMR characterization, an alternative ROCOP-style mechanism was proposed. This was found to be (1) contributing to the acceleration of the observed reaction rates with added [PPNCl] organo-catalyst and (2) ‘self-initiation/self-promoted’ ROCOP without any added external [PPNCl] catalyst, likely due to the presence of inherent [OH] groups/ species in the lignin-derived glycidyl ether monomer promoting reactivity. As a final goal, the potential of these lignin-derived polyesters as intermediate polyols was demonstrated by applying them in the synthesis of polyurethane (PU) film materials with a high biomass content of 75–79%. A dramatic range of thermomechanical properties was observed for the resulting materials, demonstrating how the ROCOP reaction can be used to tailor the properties of the functional polyester and PU material based on the nature of the epoxide and anhydride substrates used. These findings help endeavors towards predicting the relationship between chemical structure and material thermomechanical properties and performance, relevant for industrial applications. Overall, this study demonstrated the proof of concept that PU materials can be prepared from lignocellulosic biomass utilizing industrially feasible ROCOP of bio-derived cyclic anhydrides and epoxides. Full article

SHORT INTERNODE (SHI)-Related Sequence (SRS) transcription factors play crucial roles in plant growth, development, and stress responses and have been extensively studied in various plant species. However, the molecular functions and regulatory mechanisms of SRS genes in the economically important tropical fruit crop pitaya (Hylocereus undatus) remain poorly understood. This study identified 9 HuSRS genes in pitaya via bioinformatics analysis, with subcellular localization predicting nuclear distributions for all. Gene structure analysis showed 1–4 exons, and conserved motifs (RING-type zinc finger and IXGH domains) were shared across subclasses. Phylogenetic analysis classified the HuSRS genes into three subfamilies. Subfamily I (HuSRS1–HuSRS4) is closely related to poplar and tomato homologs and subfamily III (HuSRS6–HuSRS8) contains a recently duplicated paralogous pair (HuSRS7/HuSRS8) and shows affinity to rice SRS genes. Protein structure prediction revealed dominance of random coils, α-helices, and extended strands, with spatial similarity correlating to subfamily classification. Interaction networks showed HuSRS1, HuSRS2, HuSRS7 and HuSRS8 interact with functional proteins in transcription and hormone signaling. Promoter analysis identified abundant light/hormone/stress-responsive elements, with HuSRS5 harboring the most motifs. Transcriptome and qPCR analyses revealed spatiotemporal expression patterns: HuSRS4, HuSRS5, and HuSRS7 exhibited significantly higher expression levels in callus (WG), which may be associated with dedifferentiation capacity. In seedlings, HuSRS9 exhibited extremely high transcriptional accumulation in stem segments, while HuSRS1, HuSRS5, HuSRS7 and HuSRS8 were highly active in cotyledons. This study systematically analyzed the characteristics of the SRS gene family in pitaya, revealing its evolutionary conservation and spatio-temporal expression differences. The research results have laid a foundation for in-depth exploration of the function of the SRS gene in the tissue culture and molecular breeding of pitaya. Full article

Gallium nitride high electron mobility transistors (GaN HEMTs), characterized by their extremely high switching speeds and superior high-frequency performance, have demonstrated significant advantages, and gained extensive applications in fields such as aerospace and high-power-density power supplies. However, their unique internal architecture renders these devices highly sensitive to circuit parasitic parameters. Conventional circuit design methodologies often induce severe issues such as overshoot and high-frequency oscillations, which significantly constrain the realization of their high-frequency performance. To solve this problem, this paper investigates the nonlinear dynamic behavior of GaN HEMTs during switching transients by establishing an equivalent impedance model. Based on this model, a detailed analysis is implemented to elucidate the mechanism by which RC Snubber circuits influence the system’s resonance frequency and the amplitude at the resonant frequency. Through this analysis, an optimal RC Snubber circuit parameter is derived, enabling effective suppression of high-frequency oscillations during the switching transient of GaN HEMT. Experimental results demonstrate that the proposed design achieves a maximum reduction of 40% in voltage overshoot, shortens the ringing time to one-twentieth of the original value, and suppresses noise by 20 dB in the high-frequency range of 20 MHz to 30 MHz, thereby significantly enhancing the stability and reliability of circuit operation. Additionally, considering the heat dissipation requirements in high power density scenarios, this work optimizes the layout of devices, and heat sinks to maintain operational temperatures within safe limits, further mitigating the impact of parasitic parameters on overall system performance. Full article

In this paper, we provide the necessary and sufficient conditions for a Lie centralizer to be proper and a Jordan centralizer to be a centralizer on graded rings. Since every Lie centralizer naturally induces an anti-symmetric mapping and every Jordan centralizer naturally induces a symmetric mapping, our results provide the underlying graded structures reflected in these mappings. As applications, we recover known results for trivial extension algebras and triangular algebras, and additionally characterize Lie (Jordan) centralizers on exterior algebras, whose operations are inherently anti-symmetric. Full article

The design and the synthesis of functional films with enhanced functionality represent a significant step forward in sustainable material development due to their potential applications. In this study, a novel chitosan derivative (CS-MeIm) was synthetized by chemically modifying chitosan (CS) structure with 1-methyl-1H-imidazole (MeIm), a heterocyclic compound known for its biological properties. This functionalization not only enhances the intrinsic capabilities of CS but also provides a strategic platform for advanced material engineering. The modified compound, CS-MeIm, was incorporated at 10 wt% into films based on CS matrix, which was also reinforced with 1 or 5 wt% of chitin nanowhiskers (ChNw), to improve their functionality for its potential applications. The fabrication process was optimized to ensure the homogeneity and the structural integrity of the films, which were extensively evaluated to study their thermal stability, mechanical integrity, and bioactivity. The incorporation of the imidazole ring into the CS backbone provided a marked enhancement in antioxidant capacity from 3 to 15 μmol Trolox/gram of film; and excellent antimicrobial activity against common microbes, particularly against E. coli with an efficacy of 99.999%. The findings reveal that this chemical modification not only raises the intrinsic properties of CS but also introduces a versatile platform for creating biodegradable films with high functionality. Full article

This review of thiazolidinedione or glitazone, which have a five-membered heterocyclic ring C₃NS, shows their versatile properties in terms of pharmacological actions such as antimicrobial, antifungal, insecticidal, pesticidal, antidiabetic, anti-inflammatory, anti-proliferative, anti-neurotoxicity, anticonvulsant, anti-thyroidal, and anti-tubercular uses. While having a wide range of biological activities, the TZDs mainly act via binding to the peroxisome proliferator-activated receptor (PPAR) members. PPAR-γ are ligand-activated transcription factors, which are members of the nuclear hormone receptors group. Activations of PPAR-γ regulate cell proliferation and differentiation, glucose homeostasis, apoptosis, lipid metabolism, and inflammatory responses. This review explores the synthesis of a thiazolidinedione and its derivatives, focusing on their pharmacological profiles and antidiabetic activity. It highlights the benefits of synthesis, reaction profiles, and catalyst recovery, which may encourage further investigation into these scaffolds by researchers. Based on synthesized derivatives, some glimpses of the structure–activity relationships of some compounds have been compiled. All the synthesized derivatives have been reviewed concerning their standard drugs already available and concluded with the highly or moderately active synthesized derivatives of thiazolidinedione. The data for this review was collected by an extensive review of current scientific literature, including on the synthesis, biological evaluation, SAR, and patents (2015–25). Full article

Pipelines are extensively used in offshore equipment. Accurate and non-destructive measurement of hoop stress conditions within pipes is critical for ensuring the integrity of offshore structures. However, the existing technology to measure the hoop stress of the pipeline needs to planarize the surface of the pipeline, which greatly limits the detection efficiency. This study proposes a method for pipeline hoop stress measurement using a planar longitudinal critically refracted (LCR) probe, based on correcting LCR wave-propagation paths, which solves the problem of pipeline planarization in pipeline hoop stress measurement. First, a linear relationship between stress variations and ultrasonic time-of-flight changes in the material was established based on the acoustoelastic effect. Finite element analysis was then used to construct an acoustic simulation model for the hoop direction of the pipeline. Simulation results showed that LCR waves propagated within a wedge as quasi-plane waves and, upon oblique incidence into the pipeline, traveled along the chordal direction. Furthermore, using ray tracing methods, a mapping relationship between the pipeline geometry and the ultrasonic propagation path was established. Based on this, the LCR pipeline hoop stress measurement (LCR-HS) method was proposed. Finally, a C-shaped ring was employed to verify the measurement accuracy of the LCR-HS method. Experimental results indicated that the measurement error decreased with increasing pipe diameter and fell below 8% when the diameter exceeded 400 mm. This method enables precise measurement of hoop stress on curved surfaces by revealing the hoop propagation behavior of LCR waves in pipelines. The findings provide a technical reference for evaluating pipeline stress states, which is of significant importance for assessment of pipeline integrity. Full article

We provide a new proof of the Arason–Pfister Hauptsatz (APH) in the setting of reduced special groups, as developed by Dickmann and Miraglia. Our approach avoids the use of Boolean invariants and instead relies on a construction inspired by Marshall’s quotient, suitably adapted to the context of special groups. We establish structural properties of this quotient and show that it generalizes the Pfister quotient by a Pfister subgroup. Using this framework, we define iterated quadratic extensions of special groups and develop a theory of Arason–Pfister sequences. These tools allow us to prove that any anisotropic form $\phi \in I^n\left(G\right)$ over a reduced special group G satisfies the inequality $dim\left(\phi \right)\ge 2^n$, where $I^n\left(G\right)$ denotes the n-th power of the fundamental ideal of the Witt ring of G. Our methods are purely algebraic and internal to the theory of special groups, contributing with novel tools to the categorical study of abstract theories of quadratic forms. Full article