Search Results (1,065)

Phenetole derivatives with dual ethoxy substituents exhibit rich conformational diversity and complex vibronic characteristics, making them important model compounds for understanding substituent effects on molecular structure and spectroscopy. In this work, we systematically investigated the stable rotamers, vibronic spectra, and cationic ground-state features of p-diethoxybenzene (PDEB) using resonance-enhanced multiphoton ionization (REMPI), UV-UV hole-burning (HB), and mass-analyzed threshold ionization (MATI) spectroscopies, combined with density functional theory (DFT) calculations. The ground-state potential energy surface (PES) of PDEB was calculated at the B3LYP/6-311++G(d,p) level, identifying eight rotamers with distinct statistical weights and relative energies. Hole-burning spectroscopy resolved two dominant rotamers (cis/up–up and trans/up–down) in the supersonic molecular beam, with their S₁←S₀ transition origins determined as 33,824 cm⁻¹ and 33,613 cm⁻¹, respectively. Franck-Condon simulations of the vibronic transitions showed excellent agreement with the experimental REMPI spectra, enabling precise assignment of substituent and benzene ring vibrational modes. MATI experiments yielded accurate adiabatic ionization energies (AIEs) of the cis and trans rotamers as 59,629 ± 5 cm⁻¹ and 59,432 ± 5 cm⁻¹, respectively, and identified active cationic vibrational modes in the D₀ state. Geometric parameters of PDEB in the S₀, S₁, and D₀ states were calculated at the B3PW91/aug-cc-pVTZ, TD-B3PW91/aug-cc-pVTZ, and UB3PW91/aug-cc-pVTZ levels, revealing structural evolution during electronic excitation and ionization. The effects of ethoxy substituent orientation on molecular energy, vibrational frequencies, and ionization energy are discussed, and differences in spectral characteristics between PDEB and its meta isomer (MDEB) are compared. This work provides a comprehensive spectral and structural database for p-diethoxybenzene and deepens the understanding of structure–property relationships in diethoxybenzene isomers. Full article

This study investigates the mechanisms of nonlinear modal interactions in a circularly curved cantilever beam, utilizing the geometrically exact Timoshenko beam formulation. The governing equations take into account shear deformation, rotary inertia, and the geometric nonlinearities associated with significant deflections. A Chebyshev pseudospectral scheme is employed to achieve highly accurate linear eigenvalues, which are subsequently used in a nonlinear modal projection to develop a reduced-order model. Explicit expressions for the quadratic and cubic modal coupling coefficients are derived. The Harmonic Balance Method is then applied to explore internal resonance phenomena, frequency modulation behavior, and the transfer of energy between non-commensurate lateral and normal vibration modes. Full article

Experimental studies on the spontaneous nucleon emission in nuclei around the drip line enable us to explore new isotopes or resonant states, and to reveal exotic structures and decay properties of nuclei located far from the $\mathsf{\beta }$ stability line; consequently, they are of critical importance for probing limits of nuclear stability and understanding nucleon–nucleon interactions under extreme conditions of isospin asymmetry. With the radioactive isotope beam ²⁰Mg provided by the National Superconducting Cyclotron Laboratory at Michigan State University, we studied the proton decays of nuclei around the proton drip line at $A\sim 20$ mass region. Complete-kinematics measurements were performed for proton decays of one-proton resonant states in ¹⁸Na, two-proton resonant states in ²⁰Mg, three-proton resonant states in ²¹Al, and four-proton resonant states in ¹⁸Mg, yielding decay energy spectra for all four nuclei. With the invariant mass method, the ground state of ¹⁸Na was firmly identified, clarifying previous ambiguities of its position. The isotope ¹⁸Mg, which is located two neutrons beyond the proton drip line, was experimentally observed for the first time. Multi-body correlation analysis of emitted protons from ²⁰Mg, ²¹Al, and ¹⁸Mg, combined with Monte Carlo simulations, reveals that the identified resonant states in ²⁰Mg and ²¹Al predominantly decay via two and three sequential steps of $1p$ emission, respectively, whereas the ¹⁸Mg ground state decays mainly through a two-step cascade of prompt $2p$ emission. Full article

Radiogenomics examines associations between imaging phenotypes and underlying biological characteristics across cancer types. This structured narrative review focuses on oropharyngeal squamous cell carcinoma (OPSCC) and evaluates how genomic programs characteristic of HPV-positive and HPV-negative tumors have been investigated across computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) as variations in heterogeneity, diffusion patterns, perfusion and metabolic activity. A structured literature search was conducted in PubMed/MEDLINE, Scopus and Web of Science to identify studies on radiomics and radiogenomics in OPSCC and related head and neck cancers. After screening and eligibility assessment, 81 studies were included in the narrative synthesis. The reviewed literature indicates that imaging-derived features have been associated with HPV status, hypoxia-related signatures, extranodal extension and treatment outcomes. However, the current evidence base remains heterogeneous and is largely composed of retrospective, single-institution studies with relatively small cohorts. Methodological challenges, including variability in imaging acquisition, segmentation and feature harmonization, limit reproducibility and generalizability. Although cone-beam computed tomography (CBCT) is not used for primary OPSCC staging and no CBCT-based radiogenomic studies in OPSCC have been reported, existing radiomics research in dentomaxillofacial imaging suggests its potential as a hypothesis-generating modality for future investigation. Overall, current evidence supports the biological plausibility of radiogenomic imaging signatures in OPSCC, while emphasizing the need for larger multicenter datasets, standardized imaging protocols and prospective validation before clinical implementation. Full article

This study presents an assessment of forced vibration responses of cracked beam-type aerospace structures using VIbration BehaviouR ANalysis Tool (VIBRANT), a high-fidelity time-marching analysis platform. The methodology captures contact-induced nonlinearities arising when crack surfaces intermittently open and close during vibration, producing time-varying stiffness and damping. Frequency-domain behaviour is extracted from time-domain simulations of beams representing aero-engine blades and wing structures under various crack configurations. Results reveal that a crack-induced nonlinearity is strongly configuration-dependent: only specific combinations of crack depth, position relative to the moment distribution, and excitation amplitude produce detectable nonlinear signatures, whilst other configurations—including cracks representing significant structural compromise—exhibit quasi-linear response that would evade conventional vibration-based detection. The deeper crack configuration activates breathing behaviour at higher forcing levels, leading to rightward resonance frequency shifts and amplitude reductions due to impact and frictional contact damping, whereas the baseline and repositioned crack configurations maintain a quasi-linear response across all forcing levels examined. This configuration-dependent character of the breathing crack nonlinearity—and in particular the conditions under which nonlinear signatures are absent despite active damage—represents a critical finding for structural health monitoring and maintenance planning in aerospace applications. Full article

Objective: This study aimed to explore the association between magnetic resonance imaging (MRI)-derived volumetric parameters and oncological outcomes, and to develop an exploratory predictive model based on these variables in patients treated with radio-chemotherapy followed by interventional radiotherapy (modern brachytherapy). Methods: Between 2021 and 2024, 300 patients with cervical cancer were included. Treatment was pelvic external beam radiotherapy with platinum-based chemotherapy followed by interventional radiotherapy boost. Volumetric MRI variables for each patient were collected. Time-to-event analyses were performed using Cox proportional hazards regression models. Model performance was assessed using Harrell’s concordance index (C-index). Internal validation was performed using bootstrap resampling. Based on the final multivariable Cox models, an interactive web-based nomogram was developed as an exploratory tool to visualize model-derived associations. Results: Median tumor volume decreased from 69.4 cm³ at diagnosis to 2.2 cm³ at the time of pre-interventional radiotherapy MRI, with a median reduction rate of 96.5%. Tumor volume at diagnosis, pre-interventional radiotherapy residual tumor volume, and tumor volume reduction rate were significantly associated with loco-regional relapse and distant metastases in Cox regression analyses. These findings were consistent across univariate and multivariable models. Internal validation confirmed the stability of the model estimates. Conclusions: MRI-derived volumetric parameters are associated with oncological outcomes in patients with locally advanced cervical cancer and may contribute to early risk stratification. The proposed model should be considered exploratory and hypothesis-generating and requires external validation before any potential clinical application. Full article

A compact dual-polarized beam-steerable patch antennas with filtering characteristics is proposed in this paper. By digging two orthogonal coupling slots on the ground plate, dual polarization is achieved while ensuring the isolation between the ports. By constructing properly arranged parallel microstrip resonators and open-circuited stubs, the effect of suppressing a broad stopband is produced. The beam steering characteristic is accomplished through the integration of a driven patch antenna with two dual-element metallic walls, each incorporating PIN diodes for electronic tuning. A prototype antenna has been fabricated to substantiate the efficacy of the proposed methodology. The simulated and measured results agree well, demonstrating good performance in terms of impedance bandwidth, stopband suppression, isolation and beam-steering capability. Under six radiation states, the proposed antenna operates from 2.3 GHz to 2.5 GHz with isolation exceeding 20 dB. Additionally, the antenna gain remains below −10 dBi over the 2.6 GHz to 10 GHz band, achieving out-of-band suppression greater than 15.8 dB within the wide stopband. When port 1 is excited, the antenna generates three distinct radiation patterns, enabling beam scanning at 0° and ±30° in the yoz plane. Similarly, exciting port 2 yields three radiation patterns, allowing beam scanning at 0° and ±30° in the xoz plane. This work presents the first integration of dual-polarized, beam-steering, and filtering characteristics into a single compact antenna. Full article

Long-distance coal gangue slurry transportation pipelines are critical components of underground coal mine green backfilling systems, yet blockage failures severely threaten their safe and efficient operation. Existing distributed acoustic sensing (DAS)-based monitoring methods for such pipelines suffer from three key limitations: insufficient fixed-point quantitative accuracy, lack of verified blockage-specific characteristic indicators, and limited quantitative severity assessment capability. To address these gaps, this paper proposes a novel feature-level fusion monitoring method integrating DAS, fiber Bragg grating (FBG), and piezoelectric accelerometers for accurate blockage identification and quantitative evaluation in coal gangue slurry pipelines. A slurry pipeline circulation test platform with gradient blockage simulation (0% to 76.42%) and a synchronous multi-sensor monitoring system were developed. Through multi-domain signal analysis, three blockage-correlated characteristic frequencies were identified and cross-validated by synchronous multi-sensor data: 1.5 Hz (system background vibration), 26 Hz (blockage-induced fluid–structure resonance, verified by the Euler–Bernoulli beam theory with a theoretical value of 25.7 Hz), and 174 Hz (transient flow impact). The DAS phase change rate exhibited a unimodal nonlinear response to blockage degree, with the peak occurring at 40.94% blockage. On this basis, a sine-fitting quantitative inversion model was developed, achieving a high goodness of fit (R² = 0.985), and leave-one-out cross-validation confirmed its excellent robustness with a mean relative prediction error of 3.77%. Finally, a collaborative monitoring framework was built to fully leverage the complementary advantages of each sensor, realizing full-process blockage monitoring covering global blockage localization, precise quantitative severity calibration, and high-frequency transient risk early warning. The proposed method provides a robust experimental and technical foundation for real-time early warning, precise localization, and quantitative diagnosis of long-distance slurry pipeline blockages and holds important engineering application value for the safe and efficient operation of underground coal mine green backfilling systems. Full article

The mode-locking mechanism of Kerr-lens mode-locked lasers is analyzed using the nonlinear ABCD matrix formalism. Our findings demonstrate that positioning the Kerr medium at the beam waist and operating the resonator near the stability boundary significantly enhances the nonlinear effect, thereby facilitating self-starting mode-locking without requiring any external initiation mechanisms. Full article

A detailed numerical optimization of side-pumped cerium- and neodymium-codoped yttrium aluminum garnet (Ce:Nd:YAG) solar laser architectures was performed using Zemax^® and LASCAD^TM, aiming for both high-power multimode and TEM₀₀-mode performances. Multiple rod configurations and laser resonator geometries were evaluated to maximize absorbed pump power, improve mode overlap, and ensure thermal stability. For multimode operation, the optimal design was a four-rod cross side-pumped configuration employing 4.0 mm diameter, 25 mm length rods, which numerically delivered a solar laser output power of 134 W (resulting in a collection efficiency of 49.1 W/m² and solar-to-laser conversion efficiency of 4.91%), representing a 1.50-times improvement over the best previously reported value of 89.29 W. For TEM₀₀-mode generation, the best performance was obtained with a three-rod horizontal side-pumped configuration using 2.5 mm diameter, 34 mm length rods, achieving a collection efficiency of 21.1 W/m² and solar-to-laser conversion efficiency of 2.11%, surpassing the record 16.49 W/m² reported in earlier literature. Thermal analyses revealed low peak temperatures, reduced thermally induced stress, and minimized refractive-index gradients in both architectures, confirming that multirod side pumping significantly improves the thermal environment and enables stable operation at high absorbed pump powers. These results demonstrate that carefully engineered multirod geometries can simultaneously enhance collection efficiency, beam quality, and thermal robustness, highlighting multirod side-pumped solar lasers as a promising pathway for further power scaling and next-generation high-performance solar laser systems. Full article

This review summarizes recent experimental progress in the structure and correlations of light neutron-rich nuclei. We first highlight achievements based on quasi-free scattering reactions in inverse kinematics at the Radioactive Isotope Beam Factory (RIBF), including investigations of the single-particle composition of halo systems—for example, revealing the minimal s-wave component in the “weak-halo” nucleus ¹⁷B—and the mapping of universal, surface-localized dineutron correlations in Borromean nuclei such as ¹¹Li, ¹⁴Be and ¹⁷B. We then discuss recent advances in the study of multineutron correlations and cluster states, addressing both experimental challenges and major breakthroughs. These include the observation of a candidate $4n$ resonance, the absence of a resonant state in the $3n$ system, the characterization of direct two-neutron decay in ¹⁶Be, and evidence for a condensate-like $\alpha +{}^{2}n+{}^{2}n$ cluster structure in the ${}^8\mathrm{He}\left(0_2^{+}\right)$ state. Finally, we discuss prospects for extending such investigations to heavier halo candidates and more complex multineutron systems, and outline the development of next-generation neutron detector arrays that will drive future progress in this field. Full article

The Nd:GYSAG crystal enables multi-wavelength near-infrared laser output, with adjustable wavelengths tailored for specific application requirements, making it highly valuable for space-borne water vapor detection. This study reports, for the first time, the side-pumping characteristics and electro-optical Q-switching performance of this crystal. Using Ø3 × 73 mm and Ø4 × 73 mm crystal rods doped with 1.21 at.% Nd:GYSAG (chemical formula Nd_0.033Gd_0.93Y_1.79Sc_0.70Al_4.54O_11.99), 1060.4 nm laser output was achieved under 808 nm laser diode (LD) side-pumping at a repetition rate of 100 Hz and a pump pulse width of 250 μs. The experimental results show that the Ø4 × 73 mm rod had a higher laser threshold but exhibited significantly superior slope efficiency and maximum output power compared to the Ø3 × 73 mm rod. Using a flat–flat resonator, optimal laser performance was obtained with an output coupler transmission of 35%, yielding a slope efficiency of 37.2%. A maximum output energy of 179.4 mJ was achieved at a pump energy of 646 mJ. Thermal lensing effects were compensated using a flat–convex cavity, leading to improved laser performance and beam quality. Electro-optical Q-switching experiments were conducted using a KD*P crystal. A comparison between voltage-applied and voltage-removed Q-switching techniques revealed superior performance for the voltage-applied method. High-performance laser output was realized, achieving a maximum pulse energy of 59.6 mJ, a pulse width of 14.93 ns, and a peak power of 3.99 MW. This study provides an important foundation for the development of near-infrared laser devices based on Nd:GYSAG. Full article

Radiation therapy is a crucial treatment method that delivers a high dose of radiation to localized areas. Therefore, ensuring the accuracy of the radiation dose from the radiation generator is essential. Alanine dosimetry offers the advantage of being equivalent to water and tissue and is thus a valuable tool for estimating radiation doses in the human body. In this study, we aimed to assess the feasibility of utilizing electron paramagnetic resonance (EPR)/alanine dosimetry for quality control of medical linear accelerators (LINACs). The EPR signal and slope of the dose-response curve were compared with the number of alanine dosimeters per dose using a 10 MV linear accelerator, and the measurement uncertainty was evaluated. The signal increased by approximately 0.03 per 1 Gy per count, in conjunction with the slope of the dose-response curve. The measurement uncertainty, estimated based on the synthesis of eight numerical factors of the uncertainty propagation law, was approximately 2.49–4.19% (k = 1). The findings of this study suggest that the EPR/alanine dosimetry system can be reliably applied for quality control of 10 MV photon beams under the investigated experimental conditions. Full article

Dynamic wavefront control plays a crucial role in advancing terahertz (THz) high-precision non-destructive testing, wireless communication and high-resolution imaging. However, existing approaches to THz dynamic wavefront control suffer from inherent limitations, such complex structures, narrow operational bandwidth, and the ability to tune only a single function, significantly restricting their practical applications. To overcome these challenges, we propose a dynamic reflective THz metasurface based on nested split-ring unit cells. The nested unit cell consists of an outer double-split VO₂ ring resonator and an inner single-split aluminum ring deposited on a central VO₂ circular patch. By, respectively, rotating the inner and outer rings in the insulator and metal states of VO₂, independent full 2π phase coverage at 1.07 THz can be achieved in both VO₂ states while maintaining high polarization-conversion efficiency with a PCR exceeding 0.98, thereby enabling efficient dynamic wavefront control. Using these unit cells, we constructed three distinct reflective metasurfaces that, respectively, generate broadband focusing beams with tunable focal lengths, broadband vortex beams with different topological charges, and a broadband beam that can be switched between focusing and vortex modes by changing the state of VO₂. The design offers considerable flexibility for developing compact, multifunctional THz devices, with promising potential for integrated THz systems, high-capacity communications, and high-resolution imaging. Full article

This study investigates the vibration response and energy transfer characteristics of walnut trees in mechanical vibration harvesting, aiming to improve fruit detachment efficiency and reduce structural damage. Three walnut tree architectures were classified based on branching height, trunk stiffness, canopy size, and geometric regularity. A dynamic model of the trunk was established, modeled as an equivalent conical beam with Rayleigh damping, and the clamping point was simplified to a single-degree-of-freedom system. To quantify energy transfer, three indicators were introduced: energy transfer coefficient, energy attenuation rate, and trunk overload index (OLI). Sweep-frequency experiments (9–17 Hz) were conducted at a clamping height of 80 cm. Triaxial acceleration responses were measured, and branch kinetic energy was calculated. The model-predicted natural frequencies matched the experimental acceleration peaks well, identifying a frequency-sensitive band between 15 and 17 Hz. Significant differences in energy distribution were observed among the three tree architectures. Tree 1 exhibits intense energy concentration near the trunk, with rapid energy decay along branches and the highest canopy vibration index (OLI: 6.13), indicating the highest trunk overload risk. Tree 2 demonstrates whole-tree coordinated vibration and the lowest OLI value (2.10). Tree 3 possesses two sensitive frequency bands with relatively uniform energy distribution and an OLI of 2.89. Trunk stiffness, branching height, canopy structure, and geometric irregularities collectively determine energy distribution within resonance bands and overload risk. The proposed energy metrics and OLI provide quantitative guidance for selecting excitation frequencies and controlling operational duration during walnut vibration harvesting. Full article