Search Results (80)

PSR B1259-63/LS 2883 is a well-studied gamma-ray binary hosting a pulsar in a 3.4-year eccentric orbit around a Be-type star. Its non-thermal emission spans from radio to TeV energies, exhibiting a significant increase near the periastron passage. This paper is dedicated to the analysis of INTEGRAL observations of the system following its last periastron passage in June 2024. We aim to study the spectral evolution of this gamma-ray binary in the soft (0.3–10 keV) and hard (30–300 keV) X-ray energy bands. We performed a joint analysis of the data taken by INTEGRAL/ISGRI in July–August 2024 and quasi-simultaneous Swift/XRT observations. The spectrum of the system in the 0.3–300 keV band is well described by an absorbed power law with a photon index of $\Gamma =1.42\pm 0.03$. We place constraints on potential spectral curvature, limiting the break energy $E_{\mathrm{b}}>30$ keV for $\Delta \Gamma >0.3$ and cutoff energy $E_{\mathrm{cutoff}}>150$ keV at a 95% confidence level. For one-zone leptonic emission models, these values correspond to electron distribution spectral parameters of $E_{\mathrm{b},\mathrm{e}}>0.8$ TeV and $E_{\mathrm{cutoff},\mathrm{e}}>1.7$ TeV, consistent with previous constraints derived by H.E.S.S. Full article

Low-latency and robust beamforming are vital for sustaining signal quality and spectral efficiency in emerging high-mobility 5G and future 6G wireless networks. Conventional beam management approaches, which rely on periodic Channel State Information feedback and static codebooks, as outlined in 3GPP standards, are insufficient in rapidly varying propagation environments. In this work, we propose a Dominance-Enforced Adaptive Clustered Sliding Window Regression (DE-ACSW-R) framework for predictive beamforming in O-RAN Split 7-2x architectures. DE-ACSW-R leverages a sliding window of recent angle of arrival (AoA) estimates, applying in-window change-point detection to segment user trajectories and performing both Linear Regression (LR) and curvature-adaptive Support Vector Regression (SVR) for short-term and non-linear prediction. A confidence-weighted fusion mechanism adaptively blends LR and SVR outputs, incorporating robust outlier detection and a dominance-enforced selection regime to address strong disagreements. The Open Radio Unit (O-RU) autonomously triggers localised MUSIC scans when prediction confidence degrades, minimising unnecessary full-spectrum searches and saving delay. Simulation results demonstrate that the proposed DE-ACSW-R approach significantly enhances AoA tracking accuracy, beamforming gain, and adaptability under realistic high-mobility conditions, surpassing conventional LR/SVR baselines. This AI-native modular pipeline aligns with O-RAN architectural principles, enabling scalable and real-time beam management for next-generation wireless deployments. Full article

With the increasingly complex space environment, the operational safety of spacecraft faces severe challenges, creating an urgent need to develop efficient and reliable space target detection and identification technologies. Traditional optical detection equipment faces significant challenges in space target detection and identification due to the low signal-to-noise ratio of space targets. To address the limited field of view (FOV) of traditional spectrometers, this paper proposes an improved wide-FOV infrared slitless spectrometer system based on the Dyson spectrometer. The system consists of three main components: a front telescope system, a spectral dispersion system, and a relay lens system. The front telescope system adopts a Ritchey–Chrétien structure and incorporates a correction lens group to enhance imaging quality. To overcome the practical challenges of conventional Dyson spectrometers—such as the high difficulty and cost in manufacturing and aligning concave gratings—an improved Dyson spectrometer based on a planar blazed grating is designed. A collimating lens group is incorporated to reduce spectral line curvature and chromatic aberration while ensuring a linear spectral dispersion relationship, achieving “spectrum-value unification” in the system. Additionally, a secondary imaging relay lens system is designed to ensure 100% cold stop matching efficiency, thereby minimizing stray light interference. Through optimization and ray tracing using optical design software, the final system achieves a field of view of 0.69° × 0.55°, a spectral resolution of 8.41 nm/pixel, spectral line curvature and chromatic aberration both below 10 µm, and a nearly linear spectral dispersion relationship, realizing spectrum-value unification to facilitate target identification. This infrared slitless spectrometer can stably acquire the spectral characteristics of space targets without requiring high-precision theodolites, providing a novel technical solution for the identification of dynamic space targets. It holds broad application prospects in space surveillance and related fields. Full article

Based on the data from a continuous fishery resource survey conducted in the Shandong province area of the Yellow River from the summer and autumn of 2022 to the winter and spring of 2023, this study constructed fish biomass particle-size spectra. It compared and analyzed the differences in the characteristics of the fish biomass particle-size spectrum parameters across four different seasons in various survey areas. The results indicated that the fish biomass particle-size spectra in the Shandong province area of the Yellow River exhibited significant seasonal and spatial variations. Overall, the shape of the Sheldon-type biomass particle-size spectra across the four seasons showed a unimodal pattern. The peak values in spring and summer ranged between 32–64 g, while in autumn, it reached 64–128 g, and in winter, it was 1024–2048 g. The dominant species shifted from small individuals in spring and summer to larger individuals in autumn and winter. The fitted curves of the standardized biomass particle-size spectra for the four seasons displayed a dome-shaped parabola, generally arranged from high to low in the biomass particle-size spectra lines from spring to winter, with winter experiencing the least external disturbance. In terms of the regional distribution, the peak particle-size classes for fish in the areas of Gaocun, Dong’a, and Gaoqing all corresponded to the particle-size class of 16–32 g, predominantly featuring small fish species such as Carassius auratus and Pseudobrama simoni. In contrast, the peak particle-size class in the estuarine waters corresponded to 512–1024 g, mainly comprising larger fish species like Cyprinus carpio, Hypophthalmichthys molitrix, and Liza haematocheila. The differences in the standardized biomass particle-size spectra among the four regions were not significant, but the curvature of the estuarine waters was the highest, indicating the least external disturbance. The abundance–biomass comparison (ABC) curve suggested that the fish community in the Shandong province area of the Yellow River is in a severely disturbed state. Full article

Background/Objectives: Autism spectrum disorder (ASD) is a heterogeneous condition with diverse symptoms influenced by factors like gender, severity and the involvement of family and therapists. While many risk factors that contribute to ASD development are known, the exact etiology remains unclear. The relationship between speech ability and postural/gait patterns in ASD has not been extensively studied. This study aimed to verify if the ability to speak can affect body posture and gait patterns. Methods: The study involved 28 boys aged 6–17. The postural assessment used the Adams test, Bunnell scoliometer, goniometer, and inclinometer to measure trunk rotation, joint range of motion, and spinal curvature. Trunk muscle strength was assessed via a flexion test measuring position maintenance time. This study compare body posture parameters in speaking and non-speaking children with Autism Spectrum Disorders. Moreover the parameters were compared to the general norms. Results: The study observed a tendency for speaking children to deviate more from normative body posture. They presented shoulder protraction more often, increased lumbar lordosis angle, and anterior pelvic tilt. Additionally, non-speaking children were more prone to toe-walking, which, according to other studies, is present in approximately 8–9% of all children with autism spectrum disorders. Both groups presented a decreased angle of dorsal flexion in the ankle joint. Conclusions: This study suggests that speaking children with ASD exhibit greater anterior-posterior postural deviations (increased lumbar lordosis, shoulder protraction, anterior pelvic tilt) than non-speaking children. ASD did not affect scoliosis or trunk rotation. Non-speaking children showed a higher incidence of toe-walking. However, the small sample size limits the generalizability of these findings. Full article

This work numerically investigates the fully nonlinear evolution of the free surface of a deep non-conducting liquid in a strong tangential electric field based on the method of dynamic conformal transformations. Direct numerical simulation revealed two possible scenarios for the evolution of nonlinear surface electro-hydrodynamic waves: collapse at finite time (in the non-viscous case) and turbulence generated by strongly nonlinear shock-like waves (taking into account both dissipation and pumping of energy). In the process of wave breaking, regions with a steep wave front arise, in which the curvature of the boundary increases infinitely. The inclusion of viscosity prevents the formation of singularities, and the system transfers to a strongly turbulent mode of motion. The spectrum of surface disturbances is very well described by the Kuznetsov spectrum $k^{-4}$, which corresponds to the second-order singularities in the liquid boundary. The measured probability density functions demonstrate a high level of intermittency in the turbulent regime, i.e., extreme events such as shocks play a dominant role in the evolution of the system. The results of calculations such as the turbulence spectrum, type of surface singularity, and the presence of intermittency are in good qualitative agreement with recent experiments carried out by Ricard and Falcon for a ferrofluid in a magnetic field. Full article

AlN, with its ultra-wide bandgap, is highly attractive for modern applications in deep ultraviolet light-emitting diodes and electronic devices. In this study, the surface and cross-sectional properties of AlN films grown on flat and nano-patterned sapphire substrates are characterized by a variety of techniques, including photoluminescence spectroscopy, high-resolution X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Raman spectroscopy. The results indicate that different sapphire substrates have minimal impact on the photoluminescence spectrum of the epitaxial films. As the temperature increased, the radius of curvature of the AlN films increased, while the warpage decreased. The AlN films grown on nano-patterned substrates exhibited superior quality with less surface oxidation. During the growth of AlN thin films on different types of substrates, slight shifts in the energy bands occurred due to differences in the introduction of carbon-related impurities and intrinsic defects. The Raman shift and full width at half maximum (FWHM) of the E₂(low), A₁(TO), E₂(high), E₁(TO), and E₁(LO) phonon modes for the cross-sectional AlN films varied with the depth and temperature. The stress state within the film was precisely determined with specific depths and temperatures. The FWHM of the E₂(high) phonon mode suggests that the films grown on nano-patterned substrates exhibited better crystalline quality. Full article

Iprodione (IDN) is a broad-spectrum fungicide used to treat various fungal infections in plants. Despite its extensive use, assessment of its toxicity in aquatic organisms remains incomplete. This study investigated the deleterious effects of IDN using zebrafish (ZF) as a model organism. ZF embryos, beginning at 2 h post-fertilization (hpf), were exposed to IDN (3.75–40 mg/L), and both mortality and deformities were assessed. The impact of IDN on mortality was concentration-dependent and significant from 14 mg/L. Importantly, IDN induced several deformities at sublethal concentrations, including abnormal somites, reduced retinal pigment accumulation, yolk sac edema, hatching failure, abnormal swim bladders, and spinal curvature. The EC₅₀ values for IDN-induced deformities were 3.44 ± 0.74 to 21.42 ± 6.00 mg/L. The calculated teratogenic index values for all deformities were above 1, indicating that IDN is teratogenic to ZF. IDN-exposed ZF also displayed abnormalities in touch-evoked escape responses. IDN significantly affected heart rate and blood flow, and induced pericardial edema and hyperemia in a concentration-dependent manner, suggesting its influence on cardiac development and the function of ZF. In conclusion, these results suggest that IDN exerts toxic effects on ZF embryos, affecting mortality, development, and behavior. Full article

This article presents a long-period fiber-grating sensor based on a congruent quasi-helical structure (CQH-LPFG) with the two-parameter measurement of both temperature and curvature. The CQH-LPFG sensor was manufactured using a high-frequency CO₂ laser, and an innovative quasi-helical structure was introduced into the two-parameter measurement of the temperature and curvature of the optical fiber sensor with excellent results. The experiment and analysis demonstrate that the curvature sensitivities of the three resonance peaks in the 1440 nm to 1540 nm transmission spectrum were 11.88 nm/m⁻¹, 8.05 nm/m⁻¹, and 11.11 nm/m⁻¹, and the curvature varied ranging from 0.156 m⁻¹ to 0.494 m⁻¹. The three resonance peaks showed temperature responsivities of 29.87 pm/°C, 24.65 pm/°C, and 36.85 pm/°C, respectively, and the linear fit was of excellent quality. In the case of measuring both curvature and temperature changes simultaneously, the resonant peak wavelength of the CQH-LPFG sensor was demodulated through matrix analysis, with dip A and dip C providing superior simultaneous measurements. These features make it a promising candidate for applications such as engineering machinery and the health inspection of buildings. Full article

The light homogenizing element is a crucial component of the illumination system of the lithography machine. Its primary purpose is to realize the uniform distribution of energy. However, it suffers from a common issue, which is angular spectrum discreteness, which significantly impacts light uniformity. To address this, we design and fabricate random micro-cylindrical lens arrays to obtain a small-angle Gaussian optical field, which can compensate for the angular spectrum discreteness. By adjusting the pitches and curvature radii of the micro-cylindrical lenses separately, we are able to manipulate the divergence angle of the emitted sub-beams, enabling precise angular spectrum modulation. By using mask-moving technology, the angular spectrum modulator is fabricated to generate a Gaussian illumination field. The surface profile is measured and determined with a structural roughness below 10 nm. Furthermore, optical test experiments on the modulator have been conducted, achieving an angle error of less than 0.02° and a balance better than 0.5%. Full article

The BL Lacertae (BL Lac) object OJ 287 underwent an intense X-ray activity phase, exhibiting its brightest recorded X-ray flare in 2016–2017, characterized by much softer X-ray spectra and, concurrently, its first-ever recorded very-high-energy (VHE) emission (100–560 GeV), reported by the VERITAS observatory. Broadband spectral energy distribution reveals a new jet emission component similar to high-synchrotron-peaked BL Lac objects, thereby implying the soft X-ray spectrum for the synchrotron emission. Using the advantage of simultaneous X-ray and VHE spectral information, as well as the source being a low-synchrotron-peaked BL Lac object, we systematically explored the extragalactic background light (EBL) spectrum by demanding that the VHE spectrum cannot be harder than the X-ray spectrum. We used three different phenomenological forms of the EBL spectral shape (power-law, parabola, and polynomial) motivated by current constraints on the EBL with the Bayesian Monte Carlo approach to infer the credible EBL range. Our study favors an almost flat power-law spectral shape and is consistent with previous studies. The other spectral forms capable of capturing curvature though result in a better statistics value; the improvement is statistically insignificant given the additional parameters. Full article

The common-spectrum process, characterized by the Hellings–Downs angular correlation and observed by pulsar timing array collaborations, such as NANOGrav, PPTA, EPTA, and CPTA, can be explained by the scalar-induced gravitational waves (SIGWs). The energy density of SIGWs exhibits universal behavior in the infrared regions. Utilizing a broken power law parameterization for the primordial curvature power spectrum, we clarify the PTA signal through the infrared characteristics of the SIGWs, using Bayesian analysis to provide posterior distributions. Bayesian factors emphasize the statistical preference for the SIGW model over explanations involving supermassive black hole binaries. Full article

The stochastic signal observed by collaborations such as NANOGrav, PPTA, EPTA +InPTA, and CPTA may originate from gravitational waves induced by primordial curvature perturbations during inflation. This study investigates small-scale properties of inflation and reheating, assuming a log-normal form for the power spectrum of the primordial curvature and a reheating phase equation of state $w=1/9$. Inflation and reheating scenarios are thoroughly examined using Bayesian methods applied to the NANOGrav 15-year dataset. The analysis establishes constraints on the reheating temperature, suggesting $T_{\mathrm{rh}}\gtrsim 0.1\mathrm{Gev}$, consistent with Big Bang nucleosynthesis constraints. Additionally, the NANOGrav 15-year dataset requires the amplitude (A∼0.1) and width ($\mathsf{\Delta }\lesssim 0.001$) of the primordial curvature power spectrum to be within specific ranges. A notable turning point in the energy density of scalar-induced gravitational waves occurs due to a change in the equation of state w. This turning point signifies a transition from the reheating epoch to radiation domination. Further observations of scalar-induced gravitational waves could provide insights into the precise timing of this transition, enhancing our understanding of early Universe dynamics. Full article

Radio observations from normal pulsars indicate that the coherent radio emission is excited by curvature radiation from charge bunches. In this review, we provide a systematic description of the various observational constraints on the radio emission mechanism. We have discussed the presence of highly polarized time samples where the polarization position angle follow two orthogonal well-defined tracks across the profile that closely match the rotating vector model in an identical manner. The observations also show the presence of circular polarization, with both the right and left handed circular polarization seen across the profile. Other constraints on the emission mechanism are provided by the detailed measurements of the spectral index variation across the profile window, where the central part of the profile, corresponding to the core component, has a steeper spectrum than the surrounding cones. Finally, the detailed measurements of the subpulse drifting behaviour can be explained by considering the presence of non-dipolar field on the stellar surface and the formation of the partially screened gap (PSG) above the polar cap region. The PSG gives rise to a non-stationary plasma flow that has a multi-component nature, consisting of highly energetic primary particles, secondary pair plasma, and iron ions discharged from the surface, with large fragmentation resulting in dense plasma clouds and lower-density inter-cloud regions. The physical properties of the outflowing plasma and the observational constraints lead us to consider coherent curvature radiation as the most viable explanation for the emission mechanism in normal pulsars, where propagation effects due to adiabatic walking and refraction are largely inconsequential. Full article

Fracture pattern acquisition and representation in human bones play a crucial role in medical simulation, diagnostics, and treatment planning. This article presents a comprehensive review of methodologies employed in acquiring and representing bone fracture patterns. Several techniques, including segmentation algorithms, curvature analysis, and deep learning-based approaches, are reviewed to determine their effectiveness in accurately identifying fracture zones. Additionally, diverse methods for representing fracture patterns are evaluated. The challenges inherent in detecting accurate fracture zones from medical images, the complexities arising from multifragmentary fractures, and the need to automate fracture reduction processes are elucidated. A detailed analysis of the suitability of each representation method for specific medical applications, such as simulation systems, surgical interventions, and educational purposes, is provided. The study explores insights from a broad spectrum of research articles, encompassing diverse methodologies and perspectives. This review elucidates potential directions for future research and contributes to advancements in comprehending the acquisition and representation of fracture patterns in human bone. Full article