Search Results (8,491)

The High-Energy Ray Observatory (HERO) is a space-based experiment designed to measure the spectrum and composition of cosmic rays using an ionization calorimeter. The instrument’s effective geometric factor is at least 12 m²·sr for protons and 16 m²·sr or more for nuclei and electrons. Over an exposure period of approximately 5 to 7 years, the mission will enable high-resolution, element-by-element measurements of cosmic ray spectra in the energy range of 10¹² to 10¹⁶ eV per particle. A Monte Carlo simulation of the calorimeter—based on a scintillation detector with and without boron additives—was carried out using the GEANT4 software package. In this study, we examine the impact of boron additives in scintillator materials on energy resolution and their potential for discriminating between electromagnetic and hadronic components of cosmic rays. The primary objectives are to demonstrate that boron does not degrade detector characteristics and that it enables an additional timing-based method for cosmic-ray component rejection. The planned launch of the orbital experiment is scheduled for no earlier than 2029. Full article

The accurate prediction of the point-ahead angle (PAA) is crucial for applications of inter-satellite laser links (ISLLs), especially laser ranging and continuous communication. Herein, a real-time and high-precision point-ahead-angle algorithm is presented; the principle of the algorithm is mathematically characterized, and its performance is simulated and verified using typical on-orbit scenarios. The maximum PAAs of a typical geosynchronous equatorial orbit (GEO)–GEO link and low Earth orbit (LEO)–GEO link were simulated with this algorithm, and the results are consistent with those of typical calculation methods, proving the algorithm’s accuracy. The performance of the proposed algorithm was verified using a practical engineering application of ISLLs, where it was used to calculate the point-ahead angle during stable on-orbit communication. The Pearson correlations between the curves of azimuth, elevation, and total point-ahead angles, and the actual experimental data are 99.91%, 52.32%, and 98.01%, respectively. The corresponding average deviations are −5.8510 nrad, −1.0945 nrad, and −79.5403 nrad, respectively. The maximum calculation error is 5.2103%, and the calculation accuracy exceeds 94%. The above results show that the algorithm produces results that closely match actual on-orbit experimental data with high calculation accuracy, enabling the accurate prediction of the point-ahead angle and the improvement of ISLL stability. Additionally, with this method, the measurement error of the laser ranging is smaller than 50 μm, further enhancing the accuracy of precision measurements based on ISLLs. Full article

Extra-osseous calcification refers to the pathological deposition of calcium salts in soft tissues. Its most recognized forms affect the cardiovascular system, leading to vascular and heart valve calcifications. This process is active and regulated, involving the phenotype transition of resident cells into osteo/chondrogenic lineage. Chronic kidney disease (CKD) patients frequently suffer from vascular and other soft tissue calcification. OsteoSense dyes are fluorescent imaging agents developed to visualize calcium deposits during bone formation. In addition to its application in bone physiology, it has been used to detect vascular smooth muscle cell calcification in vitro and to evaluate calcification ex vivo. Here, we investigated CKD-associated soft tissue calcification by applying OsteoSense in vivo. CKD was induced by a diet containing adenine and elevated phosphate. OsteoSense (80 nmol/kg body weight) was injected intravenously through the retro-orbital venous sinus 18 h before the measurement on an IVIS Spectrum In Vivo Imaging System. OsteoSense staining detected calcium deposition in the aorta, kidney, heart, lung, and liver in CKD mice. On the other hand, no calcification occurred in the brain, eye, or spleen. OsteoSense positivity in the calcified soft tissues in CKD mice was associated with increased mRNA levels of osteo/chondrogenic transcription factors. Our findings demonstrate that OsteoSense is a sensitive and effective tool for detecting soft tissue calcification in vivo, and may be particularly valuable for studies of CKD-related ectopic calcification. Full article

We present new spectroscopic orbits for the bright binaries Mizar B, 3 Pup, $\nu$ Gem, 2 Lac, and $\varphi$ Aql. Our analysis is based on medium-resolution ($R\approx$ 12,000) échelle spectra obtained with the 0.81-m telescope and fiber-fed eShel spectrograph of the Three College Observatory (Greensboro, NC, USA) between 2015 and 2024. Orbital elements were inferred with an affine-invariant Markov-chain Monte-Carlo sampler; convergence was verified through the integrated autocorrelation time and the Gelman–Rubin statistic. Errors quote the 16th–84th-percentile credible intervals. Compared with previously published orbital solutions for the studied stars, our method improves the root-mean-square residuals by 25–50% and bring the 1$\sigma$ uncertainties on the radial velocity (RV) semi-amplitudes down to 0.02–0.15 km $s^{-1}$. These gains translate into markedly tighter mass functions and systemic RVs, providing a robust dynamical baseline for future interferometric and photometric studies. A complete Python analysis pipeline is openly available in a GitHub repository, ensuring full reproducibility. The results demonstrate that a Bayesian RV analysis with well-motivated priors and rigorous convergence checks yields orbital parameters that are both more precise and more reproducible than previous determinations, while offering fully transparent uncertainty budgets. Full article

Severe coronary artery calcification (CAC) is a frequent finding in patients undergoing percutaneous coronary intervention (PCI) and represents a significant procedural challenge. CAC is commonly associated with ageing and comorbidities such as diabetes, hypertension, and chronic kidney disease, and contributes to vessel rigidity, impaired device delivery, and suboptimal stent expansion. These factors increase the risk of angiographic complications, as well as major adverse cardiac events compared with non-calcified lesions, negatively impacting both immediate and long-term clinical outcomes. In cases of severe calcification, traditional balloon angioplasty is often inadequate, necessitating the use of dedicated calcium modification techniques. Devices such as rotational atherectomy (RA), orbital atherectomy (OA), excimer laser coronary atherectomy (ELCA), and intravascular lithotripsy (IVL) have been developed to address these challenges. Among these, orbital atherectomy offers a potential unique dual mechanism of action and has shown promise in enhancing lesion preparation and facilitating optimal stent deployment. This review provides an overview of the role of orbital atherectomy in the management of calcified coronary lesions, evaluates current evidence on its safety and efficacy, and discusses how it may be positioned in the future, underscoring the need for a personalised, lesion-specific approach to optimise PCI outcomes. Full article

This study investigates the impact of assimilating FY-3D Microwave Radiation Imager (MWRI) radiance data into the Weather Research and Forecasting (WRF) model, utilizing a 3D-Var data assimilation system, on the forecast accuracy of Typhoon Muifa (2022). The research focuses on the selection of data from different channels, land/ocean coverage, and orbits of the MWRI, along with the synergistic assimilation strategy with MWHS-2 data. Ten assimilation experiments were conducted, starting from 0600 UTC on 14 September 2022, covering a 42 h forecast period. The results show that after assimilating the microwave radiometer data, the brightness temperature deviation in the ocean area was significantly reduced compared to the simulation without data assimilation. This led to an improvement in the accuracy of typhoon track and intensity predictions, particularly for predictions beyond 24 h. Furthermore, the assimilation of land data and single-orbit data (particularly from the western orbit) further enhanced forecast accuracy, while the joint assimilation of MWHS-2 and MWRI data yielded additional error reductions. These findings underscore the potential of satellite data assimilation in improving typhoon forecasting and highlight the need for optimal land observation and channel selection techniques. Full article

Advances in satellite miniaturisation have led to a steep rise in the number of Earth-observation platforms, turning the downlink of the resulting high-volume remote-sensing data into a critical bottleneck. Low-Earth-Orbit (LEO) communication constellations offer a high-throughput relay for these data, yet also introduce intricate scheduling requirements. We term the associated task the Remote Sensing Data Transmission in Communication Constellations (DTIC) problem, which comprises two sequential stages: inter-satellite routing, and satellite-to-ground delivery. This problem can be cast as a Hybrid Flow Shop Scheduling Problem (HFSP). Unlike the classical HFSP, every processor (e.g., ground antenna) in DTIC can simultaneously accommodate multiple jobs (data packets), subject to two-dimensional spatial constraints. This gives rise to a new variant that we call the Hybrid Flow Shop Problem with Two-Dimensional Processor Space (HFSP-2D). After an in-depth investigation of the characteristics of this HFSP-2D, we propose a constructive heuristic, denoted NEHedd-2D, and a Two-Stage Memetic Algorithm (TSMA) that integrates an Inter-Processor Job-Swapping (IPJS) operator and an Intra-Processor Job-Swapping (IAJS) operator. Computational experiments indicate that when TSMA is initialized with the solution produced by NEHedd-2D, the algorithm attains the optimal solutions for small-sized instances and consistently outperforms all benchmark algorithms across problems of every size. Full article

In this paper, we investigate the geometric realization of $\mathrm{Spin}\left(8\right)$ triality through vector fields on the octonionic algebra $\mathbb{O}$. The triality automorphism group of $\mathrm{Spin}\left(8\right)$, isomorphic to ${\mathfrak{S}}_3$, cyclically permutes the three inequivalent 8-dimensional representations: the vector representation V and the spinor representations $S_{+}$ and $S_{-}$. While triality automorphisms are well known through representation theory, their concrete geometric realization as flows on octonionic space has remained unexplored. We construct explicit smooth vector fields $X_{\sigma }$ and $X_{{\sigma }^2}$ on $\mathbb{O}\cong {\mathbb{R}}^8$ whose flows generate infinitesimal triality transformations. These vector fields have a linear structure arising from skew-symmetric matrices that implement simultaneous rotations in three orthogonal coordinate planes, providing the first elementary geometric description of triality symmetry. The main results establish that these vector fields preserve the octonionic multiplication structure up to automorphisms in $G_2=\mathrm{Aut}\left(\mathbb{O}\right)$, demonstrating fundamental compatibility between geometric flows and octonionic algebra. We prove that the standard Euclidean metric on $\mathbb{O}$ is triality-invariant and classify all triality-invariant Riemannian metrics as conformal to the Euclidean metric with a conformal factor depending only on the isotonic norm. This classification employs Schur’s lemma applied to the irreducible $\mathrm{Spin}\left(8\right)$ action, revealing the rigidity imposed by triality symmetry. We provide a complete classification of triality-symmetric minimal surfaces, showing they are locally isometric to totally geodesic planes, surfaces of revolution about triality-fixed axes, or surfaces generated by triality orbits of geodesic curves. This trichotomy reflects the threefold triality symmetry and establishes correspondence between representation-theoretic decomposition and geometric surface types. For complete surfaces with finite total curvature, we establish global classification and develop explicit Weierstrass-type representations adapted to triality symmetry. Full article

The rapid development of spacecraft on-orbit services has increased the requirements for docking technology, especially for large-scale payloads that exceed the launch envelope. Docking technology based on astronaut extravehicular activities is one of the most promising directions for on-orbit services. In view of this, this paper designs and characterizes a handheld double-point docking mechanism for assembling large-scale payloads that is suitable for extravehicular activity (EVA) in dual-astronaut collaborative operations. It achieves the functional decoupling of docking, locking, unlocking, and separation throughout the whole process. The mechanism also has excellent design for human factors engineering, allowing astronauts to change hands, operate with one hand, and apply limited force. The mechanism adopts a dual-point probe–drogue configuration, while the misalignment tolerance design guarantees the docking accuracy and the operating range, and forms a rigid structural connection through a force amplification mechanism. Theoretical analysis and numerical simulations are implemented to estimate the dynamics, statics, and kinematics of the docking process. Corresponding experiments of the prototype are also conducted, including high–low temperature dynamics, docking tests, and kinematic tolerance experiments. The experiments validate the finite element analysis and verify the actual performance of the mechanism. The designed handheld dual-point docking mechanism was successfully applied for the first time by the Shenzhou 15 crew on China’s Space Station in March 2023. This paves a new road for spacecraft on-orbit service of large-scale payloads by EVAs, providing guidance as well as a technical foundation for the on-orbit construction of large spacecraft in the future. Full article

In this paper, we design a new type of terahertz orbital angular momentum (OAM) optical fiber with excellent transmission characteristics over a wide frequency range. Within the 0.8–1.8 THz frequency band, it shows stable support for transmission of the fifth-order OAM mode. Its dispersion control effect is excellent; it maintains the confinement loss of most modes at the extremely low level of 10⁻¹⁰ dB/m; its maximum dispersion is only 5.57 ps/THz/cm; and its effective mode field area is greater than 1.11 × 10⁻⁷ m². These characteristics jointly endow this optical fiber with broad application prospects and significant research value in the field of terahertz communication. With the continuous advancement of technology in this field, this optical fiber is expected to become a key component when building efficient, reliable, and large-capacity communication systems. Full article

As the next generation of time–space infrastructure, low-earth-orbit navigation augmentation (LEO-NA) technology has become a hot research topic, since it can overcome the vulnerabilities and limitations of global navigation satellite systems (GNSSs). Meanwhile, a LEO-NA signal can serve as a better cooperative illuminator to build more powerful passive radar (PR). This paper proposes and investigates a new and promising PR system, LEO-NA signal-based PR (LNAS-PR), which utilizes LEO-NA signals as the illuminator and utilizes an unmanned aerial vehicle (UAV) to carry the receiver. Taking advantage of higher landing power and global coverage, LNAS-PR can be used to detect maritime targets with benefits of low cost and high efficiency. However, new technical challenges of information capture and processing need to be dealt with. Therefore, this paper presents the system model, signal model, and performance analyses within a maritime monitoring scenario, providing a foundation for future in-depth research. Full article

The aromaticity of small boron clusters remains under scrutiny due to persistent inconsistencies between magnetic and electronic descriptors. Here, we reexamine B₃⁻, B₃⁺, B₄, B₄²⁺, and B₄²⁻ using a multidimensional approach that integrates Adaptive Natural Density Partitioning, Electron Density of Delocalized Bonds, magnetically induced current density, and the z-component of the induced magnetic field. We introduce a model in which σ-aromaticity arises from two distinct delocalization topologies: a radial 2e⁻ σ-pathway and a tangential multicenter circuit formed by alternating filled and vacant sp² orbitals. This framework accounts for the evolution of aromaticity upon oxidation or reduction, preserving coherence between electronic structure and magnetic response. B₃⁻ features cooperative radial and tangential σ-delocalization, together with a delocalized 2e⁻ π-bond, yielding robust double aromaticity. B₃⁺ retains σ- and π-aromaticity, but only via a tangential 6e⁻ σ-framework, leading to a more compact delocalization and slightly attenuated ring currents. In B₄, the presence of a radial 2e⁻ σ-bond and a 4c–2e π-bond confers partial aromatic character, while the tangential 8e⁻ σ-framework satisfies the 4n rule and induces a paratropic current. In contrast, B₄²⁺ lacks the radial σ-component but retains a tangential 8e⁻ σ-circuit and a 2e⁻ 4c–2e π-bond, leading to a σ-antiaromatic and π-aromatic configuration. Finally, B₄²⁻, exhibits delocalized π- and σ-circuits, yielding consistent diatropic ring currents, which confirms its fully doubly aromatic nature. Altogether, this analysis underscores the importance of resolving σ-framework topology and demonstrates that, when radial and tangential contributions are correctly distinguished, Hückel’s rule remains a powerful tool for interpreting aromaticity in small boron rings. Full article

Sea surface temperature (SST) is vital for climate monitoring and extreme weather forecasting. Existing global SST datasets are typically provided at daily to seasonal resolutions, while hourly data remain limited to regional scales. Polar-orbiting satellites offer global coverage but low temporal resolution, providing only 1–2 observations per day. Geostationary satellites provide high temporal resolution but cover only part of the region. These limitations create a gap in the availability of global, hourly SST data. To address this, we propose a Triple-Collocation (TC)-based fusion algorithm for generating accurate global hourly SST data through multi-source integration. The method includes data preprocessing (quality control and linear interpolation), merging five geostationary SST datasets into two global sets by priority, applying TC fusion to three polar-orbiting datasets, and finally combining all sources via multi-source TC fusion. Results show improved temporal resolution and increased spatial coverage to 32%. The fused dataset achieves high accuracy, with a daily mean Bias below 0.0427 °C, RMSE about 0.5938 °C to 0.6965 °C, and R² exceeding 0.9879. These outcomes demonstrate the method’s reliability and its potential for supporting climate and environmental research. Full article

Thermal analyses of space station windows in Low Earth Orbit (LEO) are usually focused on a specific orbiting scenario, namely the one with the longest eclipse duration and the greatest temporal fluctuation in solar radiation, that is typically considered the most critical for satellites. However, for windows made of materials such as acrylic glass, whose mechanical properties are sensitive to temperature, alternative orbital configurations can lead to significantly higher heating than previously estimated. In particular, this study identifies a critical condition, occurring when the orbit plane is highly inclined with respect to the Sun rays, so that one surface is exposed to prolonged and intense radiation. Here, it is demonstrated that, under this scenario, the Sun-facing surface may reach temperatures above the glass transition point, risking material degradation and structural failure, while the opposite surface experiences low temperatures, potentially leading to embrittlement. These findings emphasize the need to evaluate transient thermal behavior under diverse orbital geometries when designing large windows for future space stations. The results highlight key trade-offs between material properties, glazing dimensions, and orbital parameters to ensure safety and performance. Full article

To study the adsorption of lanthanide (Ln) atoms on graphene containing a Stone–Wales defect, we used a cluster model (SWG) and performed calculations at the PBE-D2/DNP level of the density functional theory. Our previous study, where the above combination was complemented with the ECP pseudopotentials, was only partially successful due to the impossibility of calculating terbium-containing systems and a serious error found for the SWG complex with dysprosium. In the present study we employed the DSPP pseudopotentials and completely eliminated the latter two failures. We analyzed the optimized geometries of the full series of fifteen SWG + Ln complexes, along with their formation energies and electronic parameters, such as frontier orbital energies, atomic charges, and spins. In many regards, the two series of calculations show qualitatively similar features, such as roughly M-shaped curves of the adsorption energies and trends in the changes in charge and spin of the adsorbed Ln atoms, as well as the spin density plots. However, the quantitative results can differ significantly. For most characteristics we found no evident correlation with the lanthanide contraction. The only dataset where this phenomenon apparently manifests itself (albeit to a limited and irregular degree) is the changes in the closest Ln^…C approaches. Full article