Search Results (3,529)

The global cancer burden continues to increase worldwide. Among the various treatment options, radiotherapy (RT), which employs high-energy ionizing radiation to destroy cancer cells, is one of the primary modalities for cancer. However, increasing the absorbed dose to the target volume also increases the risk of damage to surrounding healthy tissues. This radiation-induced toxicity to normal tissues limits the desirable dosage that can be delivered to the tumor, thereby constraining the effectiveness of radiation therapy in achieving tumor control. FLASH radiotherapy (FLASH-RT) has emerged as a promising technique due to its biological advantages. FLASH-RT involves the delivery of radiation at an ultra-high dose rate (≥40 Gy/s). Unlike conventional RT, FLASH-RT achieves comparable tumor control rates while significantly reducing damage to surrounding normal tissues, a phenomenon known as the FLASH effect. Although the mechanism behind the FLASH effect is not fully understood, this approach shows considerable promise for future cancer treatment. The development of specialized treatment planning systems (TPS) becomes imperative to facilitate the clinical implementation of FLASH-RT from experimental studies. These systems must account for the unique characteristics of FLASH-RT, including ultra-high dose rate delivery and its distinctive radiobiological effects. Critical reassessment and optimization of treatment planning protocols are essential to fully leverage the therapeutic potential of the FLASH effect. This review examines key considerations for the TPS development of electron and proton FLASH-RT, including electron and proton FLASH techniques, biological models, crucial beam parameters, and dosimetry, providing essential insights for optimizing TPS and advancing the clinical implementation of this promising therapeutic modality. Full article

The adjustable-ring-mode (ARM) scanning laser was used to perform butt welding on 0.5 mm thick TA1 titanium alloy and 304 stainless steel (SS304) thin sheets, with 1.2 mm diameter AZ61S magnesium alloy welding wire as the filling material. Microhardness test results show that the hardness distribution presented a trend of being higher in the base metals on both sides and lower in the middle filling area, with no hardening observed in the weld zone. For all specimens subjected to horizontal and axial weld bending tests, the bending angle reached 108° without any cracks occurring. When the ring power was in the range of 800–1000 W, or the scanning frequency was between 100 and 200 Hz, all the average tensile strengths of the welded joints were more than 80% of that of the AZ61S filling material (approximately 240 MPa); the maximum average tensile strength stood at 281.2 MPa, which is equivalent to 93.7% of the AZ61S. As the ring power or scanning frequency increased further, the tensile strengths of the joints showed a decreasing trend. The remelting effect of the trailing edge of the ARM laser under high energy conditions, or the scouring of the turbulent molten flow induced by the scanning beam, damages the weak links at the newly formed solid–liquid interface and increases the Fe concentration in the molten pool. This leads to a thicker FeAl interface layer during growth, thereby resulting in a decline in the mechanical properties of the welded joints. Full article

The widespread adoption of low-power devices and microelectronic systems has intensified the need for efficient energy harvesting solutions. While cantilever-beam piezoelectric energy harvesters (PEHs) are popular for their simplicity, their performance is often limited by conventional mass block designs. This study addresses this by proposing a comprehensive structural optimization framework for a triangular cantilever PEH to significantly enhance its electromechanical conversion efficiency. The methodology involved a multi-stage approach: first, an embedded coupling design was introduced to connect the mass block and cantilever beam, improving space utilization and strain distribution. Subsequently, the mass block’s shape was optimized. Furthermore, a negative Poisson’s ratio (NPR) honeycomb structure was integrated into the cantilever beam substrate to induce biaxial strain in the piezoelectric layer. Finally, a variable-density mass block was implemented. The synergistic combination of all optimizations—embedded coupling, NPR substrate, and variable-density mass block—culminated in a total performance enhancement of 69.07% (17.76 V) in voltage output and a 44.34% (28.01 Hz) reduction in resonant frequency. Through experimental testing, the output performance of the prototype machine showed good consistency with the simulation results, successfully verifying the effectiveness of the structural optimization method proposed in this study. These findings conclusively show that strategic morphological reconfiguration of key components is highly effective in developing high-performance, low-frequency adaptive piezoelectric energy harvesting systems. Full article

To investigate the fracture behavior of super-absorbent polymer (SAP) internally cured polyvinyl alcohol (PVA) fiber-reinforced concrete (SAP-PVAC), three-point bending tests were carried out. This study systematically examined the effects of (1) PVA fiber content and (2) initial crack-depth-to-beam-height ratios (a₀/D) on the failure modes, fracture toughness (K_IC), and residual flexural tensile strength (f_R,1) of SAP-PVAC beams. The test results demonstrate that SAP particles have a weakening effect on concrete strength (reduce about 6%). Still, the addition of PVA fibers can effectively improve the crack-resistance performance of SAP-PVAC and significantly increase the residual flexural tensile strength by 4.5–42%. The softening performance of the concrete is affected by the initial crack-height ratio. An increase in a₀/D leads to an obvious increase in the crack opening displacement but has little impact on the fracture toughness, while the fracture energy shows a downward trend. SEM microscopic analysis reveals that the synergistic effect of SAP and PVA fibers exhibits a positive promoting effect on the toughening and crack resistance of SAP-PVAC specimens. These results establish a theoretical framework for SAP-PVAC fracture assessment and provide actionable guidelines for its shrinkage-crack mitigation structure engineering applications. Full article

We report a laboratory search for axion-like particles (ALPs) in the eV mass range using a variable-angle three-beam-stimulated resonant photon collider. The scheme independently focuses and collides three laser beams, providing a cosmology- and astrophysics-independent test. By varying the angles of incidence, the center-of-mass energy can be scanned continuously across the eV range. In this work, we operated the collider in a vacuum chamber at a large-angle configuration, verified the spacetime overlap of the three short pulses, and performed a first search centered at $m_a\simeq 2.27\mathrm{eV}$. No excess was observed. Thus, we set a $95\%$ C.L. upper limit on the pseudoscalar two-photon coupling, with a minimum sensitivity of $g/M\simeq 4.2\times {10}^{-10}{\mathrm{GeV}}^{-1}$ at $m_a=2.27\mathrm{eV}$. This provides the first model-independent upper limit on the coupling that reaches the KSVZ benchmark in the eV regime and demonstrates the feasibility of eV-scale mass scans in the near future. Full article

Protons are conventionally regarded as a low-linear energy transfer (low-LET) radiation modality with a relative biological effectiveness (RBE) of 1.1, suggesting direct mechanistic similarity to X-rays in the underpinning biological effects. However, exposure to spread-out Bragg peak (SOBP) protons reveals instructive deviations from this assumption. Indeed, proton beams have a maximum LET of ~5 keV/µm but display reduced reliance on classical non-homologous end joining (c-NHEJ) as well as an increased dependence on homologous recombination (HR) and alternative end joining (alt-EJ). These features are well described in cells exposed to high-LET radiation and typically manifest between 100 and 150 keV/µm. We hypothesized that this apparent discrepancy reflects biological consequences of proton-beam properties that remain uncharacterized. In the present study, we outline exploratory experiments aiming at uncovering such mechanisms. We begin by investigating for both entrance and SOBP protons the dose-dependent engagement of HR we recently showed for X-rays. Consistent with our previous findings with X-rays, HR engagement after exposure to both types of proton beams declined with dose, from ~80% at 0.2 Gy to less than 20% at higher doses. RAD51/γH2AX foci ratios, reflecting HR engagement, were modestly higher following proton irradiation, in line with increased HR utilization. G₂-checkpoint activation, previously linked to HR, was also stronger after exposure to protons, as was DNA end resection. Moreover, the formation of structural chromosomal abnormalities (SCAs) was higher for SOBP than entrance protons and X-rays. Collectively, our results suggest quasi-high-LET characteristics for proton beams and raise the question as to the physical proton properties that underpin them. We discuss that the commonly employed definition of LET may be insufficient for this purpose. Full article

This study develops a two-dimensional numerical model to investigate the hydrodynamic performance of a floating breakwater coupled with flexible wave-dissipating structures (FWDS). The model integrates the immersed boundary method with a finite element structural solver, enabling accurate simulation of fluid–structure interactions under wave excitation. Validation against benchmark cases, including cantilever beam deflection and flexible vegetation under waves, confirms the model’s reliability. Parametric analyses were conducted to examine the influence of the elastic modulus and height of the FWDS on wave attenuation efficiency. Results show that structural flexibility plays a crucial role in modifying wave reflection, transmission, and dissipation characteristics. A lower elastic modulus enhances energy dissipation through large deformation and vortex generation, while higher stiffness promotes reflection with reduced dissipation. Increasing the height of the FWDS improves overall wave attenuation but exhibits diminishing returns for long-period waves. The findings highlight that optimized flexibility and geometry can effectively enhance the energy-dissipating capacity of floating breakwaters. This study provides a theoretical basis for the design and optimization of hybrid floating breakwaters integrating flexible elements for coastal and offshore wave energy mitigation. Full article

Laser-driven ion acceleration is a rapidly developing branch of plasma physics and laser science whose primary practical goal is to provide a physical and technological basis for the construction and development of new types of ion accelerators. Laser-driven accelerators can be less complex and more compact than currently used RF-driven accelerators, while the intensities, fluences, and powers of laser-accelerated ion beams can potentially exceed those achieved in RF accelerators. This paper focuses on the generation of very intense ion beams driven by a multi-PW femtosecond laser. The acceleration mechanisms enabling the generation of such beams are characterized, and the properties of multi-PW laser-driven uranium ion beams are discussed in detail based on the results of advanced particle-in-cell numerical simulations. The feasibility of generating sub-picosecond, multi-GeV, mono-charge uranium beams with extreme intensities (~>10²⁰ W/cm²) and fluences (~>GJ/cm²) is demonstrated, and methods for controlling the beam parameters are identified. It is shown that using such beams, extreme states of matter with parameters unattainable with ion beams from conventional accelerators can be created. The prospects for applications of ultra-intense laser-driven ion beams in high-energy density physics, inertial confinement nuclear fusion, and in certain areas of nuclear physics are outlined. Full article

Underwater acoustic energy transmission (UAET) is critical for sustaining long-term operations of underwater platforms, but its efficiency is constrained by the limited aperture of underwater receivers—requiring acoustic energy to be concentrated within a pre-defined target angular domain. Existing array-weighting methods face inherent limitations: traditional window-based techniques optimize mainlobe–sidelobe trade-offs rather than target-specific energy concentration, while intelligent algorithms suffer from high computational cost, quasi-optimality, and poor reproducibility. To address these gaps, this study proposes an array beam energy aggregation optimization method based on Rayleigh quotient eigenvalues for UAET. First, a rigorous mathematical model of the acoustic energy concentration problem was established: by defining a target-domain energy operator matrix ${\mathrm{R}}_{\mathsf{\Theta }}$ with a Toeplitz–sinc structure (Hermitian positive definite), the energy-focusing problem was transformed into a tractable linear algebra problem. Second, the optimization objective of maximizing target-domain energy was formulated as a generalized Rayleigh quotient maximization problem, where the optimal amplitude weights correspond to the eigenvector of the maximum eigenvalue of ${\mathrm{R}}_{\mathsf{\Theta }}$—solved via Cholesky whitening and eigenvalue decomposition to ensure theoretical optimality and low computational complexity. Comprehensive validations were conducted via simulations and underwater physical experiments. Simulations on 1D uniform linear arrays and 2D 4-layer circular ring arrays showed that the proposed method outperformed traditional weighting methods and PSO in target angular energy concentration: for the 16-element linear array, its energy radiation efficiency in the 30° domain was 14% higher than classical methods (Blackman weighting). Underwater physical tests further confirmed its superiority: for the 4-layer circular ring array at 1 m, the acoustic energy efficiency in the 30° target domain reached 21.5% higher than Blackman weighting. Additionally, the method exhibited strong adaptivity (dynamic weight adjustment with target angular width) and scalability (performance improvement with array size), meeting UAET’s real-time and reliability requirements. This work provides a theoretically optimal and engineering-feasible solution for directional acoustic energy transfer in underwater environments, offering valuable insights for UAET system design. Full article

This study investigates the flexural performance of geopolymer (zero-cement) concrete (ZCC) beams compared to normal concrete (NC) under monotonic and cyclic loading. Sixteen reinforced beams with compressive strengths of 20 and 30 Mpa and reinforcement configurations of 2Ø10 and 3Ø12 were tested to evaluate load–deflection behavior, ductility, energy absorption, and cracking characteristics. Under monotonic loading, ZCC beams achieved 9–17% higher ultimate strength and 5–30% greater mid-span deflection than NC beams, indicating superior ductility and energy dissipation. Under cyclic loading, ZCC beams demonstrated more stable hysteresis loops, slower stiffness degradation, and 8–32% higher cumulative energy absorption. ZCC specimens also sustained 8–12 cycles, corresponding to 70–90% of the monotonic displacement, whereas NC beams generally failed earlier at lower displacement levels. Increasing reinforcement ratio enhanced stiffness and load capacity but reduced deflection for both materials. Crack mapping showed finer and more uniformly distributed cracking in ZCC beams, confirming improved bond behavior between steel reinforcement and the geopolymer matrix. In addition, geopolymer concrete beams exhibited a significant enhancement in ductility, with the ductility coefficient increasing by nearly 50% compared to normal concrete under cyclic loading. Overall, the findings indicate that ZCC provides comparable or superior structural performance relative to NC, supporting its application as a sustainable, low-carbon material for flexure- and shear-critical members subjected to static and cyclic actions. Full article

Boron Neutron Capture Therapy (BNCT) is a radiotherapeutic modality which couples selective pharmacological delivery of ¹⁰B with irradiation by low-energy neutrons to achieve highly localized tumor cell killing. The BNCT therapeutic approach is undergoing rapid evolution driven primarily by advances in compact accelerator-driven neutron-source and associated facility-level nuclear infrastructure. This review examines the key physical and radiobiological principles of BNCT, with emphasis on the current engineering and operational aspects, such as neutron production and moderation, spectral shaping, beam optimization and dosimetric quantification, that critically influence clinical translation. Recent progress in ¹⁰B production and enrichment, as well as in strategies for efficient ¹⁰B delivery, is also briefly addressed. By tracing the pathway from neutron source to clinical target, this review defines the state of the art in BNCT technology, identifies the main physical and infrastructural challenges, and delineates the multidisciplinary advances needed to support widespread clinical implementation of next-generation BNCT systems. Full article

(1) Purpose: Incoherent processes in production of lepton pairs (dileptons) are studied for the scattering of protons on nuclei. Methods: New quantum mechanical model is constructed on the basis (1) generalization of the nuclear model of emission of photons in the proton-nucleus reactions from low to intermediate energies, (2) formalism of dilepton production. Results: (1) The coherent cross sections of dilepton production in $p+\mathrm{Be}$ at proton beam energy $E_{\mathrm{p}}$ of 2.1 GeV calculated by model are in good agreement with experimental data of DLS Collaboration. (2) Dilepton production for ⁹Be, ¹²C, ¹⁶O, ²⁴Mg, ⁴⁴Ca, ¹⁹⁷Au at $E_{\mathrm{p}}=2.1$ GeV are studied. Coherent cross sections of dilepton production are monotonously decreased with increasing mass of nuclei. (3) At larger $E_{\mathrm{p}}$ dileptons are produced more intensively. (4) Incoherent processes in production of dileptons are studied for p + ⁹Be at E_p = 2.1 GeV. Agreement between experimental data and calculated cross sections is better, in to include incoherent processes to the model. A new phenomenon of suppression of production of dileptons at low energies due to incoherent processes is observed. This is explained by dominant coherent contribution at very low energies. (5) Longitudinal amplitude of virtual photon suppresses the cross section of dilepton production a little (effect is observed for p + ⁹Be at E_p = 2.1 GeV). (6) The contribution from incoherent processes plays a leading role in the dilepton production ((the ratio between the incoherent and coherent terms is 10–100). Also our model provides the tendencies of the full spectrum for p + ⁹³Nb at E_p = 3.5 GeV in good agreement with experimental data obtained by HADES collaboration, and shows large role of incoherent processes. Conclusions: Incoherent processes are much more important than coherent ones in study of dilepton production in this reaction. Full article

Light carrying orbital angular momentum (OAM) has emerged as a promising tool for manipulating light–matter interactions, providing an additional degree of freedom to explore chiral-optical phenomena at the nanoscale. When such vortex beams interact with chiral metamaterials, a unique phenomenon of optical asymmetry known as vortical dichroism (VD) arises. Nevertheless, most existing chiral metamaterials exhibit limited VD responses, and the underlying physical mechanisms are yet to be fully clarified. In this work, we propose three-dimensional spiral metamaterials that achieve gigantic VD effect. This pronounced VD effect originates from the intrinsic coupling between the spiral structure and the chirality inherent to optical vortices, which leads to strongly asymmetric scattering intensities for left- and right-handed OAM beams of opposite topological charges. Numerical simulations confirm a remarkable VD value of 0.69. Further analysis of electric field distributions reveals that the asymmetric VD response stems from a handedness-dependent excitation of distinct electromagnetic modes. For opposite handedness, spatial mode mismatch results in enhanced scattering. In contrast, matching handedness enables efficient energy coupling into a guided spiral mode, which suppresses scattering. These findings not only deepen the physical understanding of VD mechanisms but also establish a versatile platform for developing advanced chiral photonic devices and enhancing OAM-based light–matter interactions. Full article

Atmospheric turbulence significantly degrades the performance of High Energy Laser (HEL) systems by distorting the laser wavefront as it propagates through the atmosphere. Conventional correction techniques rely on Adaptive Optics (AO), which preserve beam quality at the object. However, AO systems require wavefront sensors, such as Shack–Hartmann, and a reference beam, increasing system complexity and cost. This work presents a Deep Learning (DL)-based wavefront sensing approach that operates directly on scene imagery, thereby eliminating the need for dedicated wavefront sensors and a reference beam. A DL model was trained to predict wavefront distortions, represented by Zernike coefficients, from aberrated imagery of the Reaper Unmanned Aerial Vehicle (UAV). Reaper imagery utilized in training was aberrated at different levels of turbulence, $D/r_0$, with $D=30$ cm being the aperture diameter of a telescope capturing the object scene and $r_0=3, 5, 7$ cm the Fried parameter that defines weak turbulence for higher values and strong turbulence for lower values. The proposed model, trained across all these turbulence levels, outperformed models trained on a single level by providing superior accuracy and offering practical advantages for deployment. The model also demonstrated strong generalization capabilities for two practical scenarios: (a) Reaper imagery with turbulence levels beyond the training range, and (b) Mongoose UAV imagery not included in the training set. The model predicts turbulence accurately in both cases. The results confirm that if the model is trained for a UAV model for a certain turbulence level, it provides accurate predictions for turbulence levels outside its training range and for other UAV aberrated images. Full article

The seismic performance of a proposed bolted angle connector beam-to-column joint with a stiffener (hereinafter referred to as a BACS joint) was investigated utilizing quasi-static tests on six specimens with H-shaped steel members. The failure modes, hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation capacity were analyzed. The test results indicated that the BACS joint exhibited a 28.1% higher moment resistance and a 12.6% greater equivalent viscous damping coefficient compared to a welded connection with the same specifications. Furthermore, when compared to a short-beam spliced connection with comparable steel consumption, the BACS joint demonstrated advantages in both the load-bearing capacity and the energy dissipation. The numerical analysis results based on ABAQUS software demonstrated that increasing the stiffener height could not only enhance the bending capacity and stiffness of the connection, but also promote the relocation of the plastic hinge towards the beam end, thereby improving the failure mode. The increase in the stiffener thickness led to a minor improvement in the bending capacity of the connection, yet the influence of the stiffener thickness on the connection stiffness was limited. Furthermore, the use of steel with a higher strength grade could substantially increase the bending capacity of the BACS joint, while the enhancement in stiffness was relatively modest. Therefore, economic considerations should be integrated into the engineering design process. Full article