Medical Physics
Fraction-variant VMAT planning for patients with complex gynecological and head-and-neck cancer
Nathan Torelli, Madalyne Day and Jan Unkelbach
Background and Purpose: Increasing the number of arcs in volumetric modulated arc therapy (VMAT) allows for better intensity modulation and may improve plan quality. However, this leads to longer delivery times, which may cause patient discomfort and increase intra-fractional motion. In this study, it was investigated whether the delivery of different VMAT plans in different fractions may improve the dosimetric quality and delivery efficiency for the treatment of patients with complex tumor geometries. Materials and Methods: A direct aperture optimization
algorithm was developed which allows for the simultaneous optimization of different VMAT plans to be delivered in different fractions, based on their cumulative physical dose. Each VMAT plan is constrained to deliver a uniform dose within the target volume, such that the entire treatment does not alter the fractionation scheme and is robust against inter-fractional setup errors. This approach was evaluated in-silico for ten patients with gynecological and head-and-neck cancer. Results: For all patients, fraction-variant treatments achieved better target coverage and reduced the dose to critical organs-at-risk compared to fraction-invariant treatments that deliver the same plan in every fraction, where the dosimetric benefit was shown to increase with the number of different plans to be delivered. In addition, 1-arc and 2-arc fraction-variant treatments could approximate the dosimetric quality of 3-arc fraction-invariant treatments, while reducing the delivery time from 180 s to 60 s and 120 s, respectively. Conclusions: Fraction-variant VMAT treatments may achieve excellent dosimetric quality for patients with complex tumor geometries, while keeping the delivery time per fraction viable.
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Fluid Dynamics
Study of arbitrarily low shear rate rheology using dissipative particle dynamics
Francesco De Roma, Luca Maffioli, Edward R. Smith et al. (+1 more)
The use of dissipative particle dynamics (DPD) simulation to study the rheology of fluids under shear has always been of great interest to the research community. Despite being a powerful tool, a limitation of DPD is the need to use high shear rates to obtain viscosity results with a sufficiently high signal-to-noise ratio (SNR). This often leads to simulations with unrealistically large deformations that do not reflect typical stress conditions on the fluid. In this work, the transient time correlation function (TTCF) technique is used for a simple Newtonian DPD fluid to achieve high SNR results even at arbitrarily low shear rates. The applicability of the TTCF on DPD systems is assessed, and the modifications required by the nature of the DPD force field are discussed. The results showed that the standard error (SE) of viscosity values obtained with TTCF is consistently lower than that of the classic averaging procedure across all tested shear rates. Moreover, the SE resulted proportional to the shear rate, leading to a constant SNR that does not decrease at lower shear rates. Additionally, the effect of trajectory mapping on DPD is studied, and a TTCF approach that does not require mappings is consolidated. Remarkably, the absence of mappings has not reduced the precision of the method compared with the more common mapped approach.
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All authors Francesco De Roma, Luca Maffioli, Edward R. Smith, Antonio Buffo
Computational Physics
Patch-MLP-Based Predictive Control: Simulation of Upstream Pointing Stabilization for PHELIX Laser System
Jiaying Wang, Jonas Benjamin Ohland, Yen-Yu Chang et al. (+8 more)
High-energy
laser facilities such as PHELIX at GSI require excellent beam pointing stability for reproducibility and relative independence for future experiments. Beam pointing stability has been traditionally achieved using simple proportional-integral-derivative (PID) control which removes the problem of slow drift, but is limited because of the time delay in knowing the diagnosis and the inertia in the mechanical system associated with mirrors. In this work, we introduce a predictive control strategy where the
forecasting of beam pointing errors is performed by a patch-based multilayer perceptron (Patch-MLP) designed to capture local temporal patterns for more robust short-term jitter prediction. The subsequent conversion of these predicted errors into correction signals is handled by a PID controller. The neural network has been trained on diagnostic time-series data to predict beam pointing error. Using the feed-forward controller compensates for system delays. Simulations with a correction mirror placed upstream of the PHELIX pre-amplifier bridge confirm that the predictive control scheme reduces residual jitter compared to conventional PID control. Over a 10-hour
dataset the controller maintained stable performance without drift, while standard pointing metrics showed consistent improvements of the order of 10 to 20 percent. The predictive controller operates without drift, and therefore may improve reproducibility and operational efficiency in high energy, low repetition rate
laser experiment conditions.
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All authors Jiaying Wang, Jonas Benjamin Ohland, Yen-Yu Chang, Vedhas Pandit, Stefan Bock, Andrew-Hiroaki Okukura, Udo Eisenbarth, Arie Irman, Michael Bussmann, Ulrich Schramm, Jeffrey Kelling
Fluid Dynamics
Filament inclination effect on turbulent canopy flows
Shane Nicholas, Mohammad Omidyeganeh, Alfredo Pinelli et al. (+3 more)
Inspired by the spontaneous behaviour observed in filamentous layers – where the balance between flow-induced drag and structural elasticity dictates the filaments'
equilibrium streamlined posture – we perform a series of large-eddy simulations to investigate how filament inclination affects turbulent shear flows developing both above and within a canopy of filaments. We examine six distinct filament inclination angles ranging from 0\deg to 90\deg. The in-plane solid fraction and filament length are chosen to achieve a fully dense canopy at zero inclination, and these parameters remain constant throughout our study. By setting a nominal bulk Reynolds number of 6000, we provide a detailed statistical characterisation of the turbulent flow. Our findings illustrate distinct changes in the flow regime with varying filament inclination. At lower angles, the canopy remains dense and significantly influences the flow, conforming to a classical canopy-flow regime. However, as the inclination approaches 90\deg, the intra-canopy region progressively becomes shielded from the outer flow. Remarkably, at 90\deg inclination, the flow drag reduces significantly, and the total drag becomes lower than that typically seen in an open, filament-free flow. We document this transition from a canopy-dominated regime to a scenario where the canopy becomes largely sheltered from the outer turbulent flow, highlighting key alterations in intra-canopy dynamics as filament inclination increases. Our observations are substantiated by an analysis of the velocity spectra, providing deeper insight into the interactions between the canopy and the developing turbulent boundary layer.
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All authors Shane Nicholas, Mohammad Omidyeganeh, Alfredo Pinelli, Alessandro Monti, Giulio Foggi Rota, Marco E. Rosti
Physics and Society
Life-cycle Modeling and the Walking Behavior of the Pedestrian-Group as an Emergent Agent: With Empirical Data on the Cohesion of the Group Formation
Saleh Albeaik, Mohamad Alrished and Faisal Alsallum
This article investigates the pedestrian group as an emergent
agent. The article explores empirical data to derive emergent agency and formation state spaces and outline recurring patterns of walking behavior. In this analysis, pedestrian trajectories extracted from surveillance
videos are used along with manually annotated pedestrian group memberships. We conducted manual expert evaluation of observed groups, produced new manual annotations for relevant events pertaining to group behavior and extracted metrics relevant group formation. This information along with quantitative analysis was used to model the life-cycle and formation of the group
agent. Those models give structure to expectations around walking behavior of groups; from pedestrian walking independently to the emergence of a collective intention where group members tended to maintain bounded distance between each other. Disturbances to this bounded distance often happened in association with changes in either their agency or their formation states. We summarized the patterns of behavior along with the sequences of state transitions into abstract patterns, which can aid in the development of more detailed group
agents in simulation and in the design of engineering systems to interact with such groups.
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Atomic Physics · Cross-listed from quant-ph
An introduction to Markovian open quantum systems
Shovan Dutta
This is a concise, pedagogical introduction to the dynamic field of open
quantum systems governed by Markovian master equations. We focus on the mathematical and physical origins of the widely used Lindblad equation, its unraveling in terms of
stochastic pure-state trajectories and the corresponding continuous measurement protocols, the structure of steady states with emphasis on the role of
symmetry and conservation laws, and a sampling of the novel physical phenomena that arise from nonunitary dynamics (dissipation and measurements). This is far from a comprehensive summary of the field. Rather, the objective is to provide a conceptual foundation and physically illuminating examples that are useful to graduate students and researchers entering this subject. There are exercise problems and references for further reading throughout the notes.
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Fluid Dynamics
Evolving wrinkles: time-dependent buckling of an elastic sheet on a liquid substrate
Daniel J. Netherwood, Ben S. Humphries, Connor Robbins et al. (+1 more)
We model the formation and
evolution of wrinkles in a floating elastic sheet under uniaxial compression. This is a canonical setup in the study of wrinkling, and whilst its static
equilibrium configuration is well characterised, its dynamics are not. In this work, we focus on modelling the transition from early, inertia-dominated wrinkle growth to late-time
gravity-moderated
equilibrium. For an initial configuration in which the sheet is flat, an initial disturbance will first grow at the shortest available wavelengths, because this requires the least kinetic energy, but will subsequently transition to a longer preferred wavelength that minimises potential energy. We observe that the evolving wave pattern must be a spectrum, as opposed to a fundamental wrinkle mode whose wavelength evolves in time. Our results demonstrate that changes in the dominant wrinkle wavelength are coupled to a decay in the compressive force, which is to be expected from
equilibrium theory.
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All authors Daniel J. Netherwood, Ben S. Humphries, Connor Robbins, Doireann O'Kiely
Physics and Society
Emergence, Evolution and Manipulation of Swing Voters in Presidential Election
Ziqian Liu, Xin Wang, Junyu Lu et al. (+3 more)
Political polarization, fueled by public discourse and echo chambers, threatens the foundation of democratic elections. However, traditional one-dimensional opinion models – assuming “support for one party equals opposition to another” – fail to capture the nuanced dynamics of swing voters (including neutrals, left leaners and right leaners), who are critical for the final election outcomes. This study introduces a two-dimensional opinion model that classifies voters into five groups, enabling precise characterization of the swing group's interactive behaviors. Importantly, we introduce antagonism effect to describe the intensities with which the two camps incite opposition and exert voting pressure in the run-up to the election, typically via Us-versus-Them framing. By integrating the open-mindedness of voters, the stubbornness of opinion interactions, and the antagonism effect manipulated by the two parties, we systematically explore the intricate interplay between top-down political campaigns and bottom-up interpersonal opinion dynamics, unveiling their nonlinear coupling impacts on the emergence, and
evolution of swing voters. Counterintuitively, we find that extreme antagonism effects might backfire in presidential election: when both parties adopt intense antagonistic strategies, the party that polarizes more strongly risks alienating swing voters, thereby enabling its ostensibly weaker opponent to prevail. These insights are also validated on the core retweet networks during 2020 U.S. presidential election. Building upon multidimensional opinion model, our results highlight the possibility of manipulating swing voters and shaping electoral outcomes through antagonistic strategies of political parties. Our work also provides a nuanced and generalizable framework for analyzing opinion dynamics in other polarized public discourse.
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All authors Ziqian Liu, Xin Wang, Junyu Lu, Longzhao Liu, Hongwei Zheng, Shaoting Tang
Optics · Cross-listed from cond-mat.other
Bi-isotropic effects on hybrid surface polaritons in bilayer configurations
A. Nonato and Pedro D. S. Silva
In this work, we investigate the bi-isotropic effects in the formation and tunability of hybrid surface polaritons in
bilayer configurations. We consider a
heterostructure composed of a medium with bi-isotropic constitutive relations and an AFM layer. Using the transfer
matrix formalism, we derive general expressions for the dispersion relations of surface polaritonic modes, including the dependence on the bi-isotropic parameter, and analyze their coupling to bulk
magnon-polaritons. As an illustration of application, we consider a
heterostructure formed with Bi$_{2}$Se$_{3}$ interfaced with
antiferromagnetic (AFM) materials that support terahertz-frequency
magnons, specifically Cr$_{2}$O$_{3}$ and FeF$_{2}$. In the strong bi-isotropic coupling regime, the surface Dirac plasmon–
phonon–
magnon polariton (DPPMP) dispersion undergoes a pronounced
redshift, accompanied by suppression of the characteristic anticrossing between the Dirac plasmon and the
phonon. This effect, observed in all AFM materials considered, suggests a weakening of the hybrid interaction, possibly due to saturation or detuning mechanisms induced by increased $\alpha$. Furthermore, increasing the
Fermi energy of the topological
insulator enhances the surface plasmon and
phonon contributions, inducing a blueshift of the DPPP branches and bringing them closer to resonance with the
magnon mode, thereby increasing the hybridization strength. Intriguingly, this
redshift partially compensates the blueshift induced by a higher
Fermi level, restoring the system to a weak-coupling regime analogous to that observed at lower
Fermi energies. Our findings reveal that both the
Fermi level and the bi-isotropic response offer independent and complementary control parameters for tuning the strength of light–
magnon coupling in TI/AFM
heterostructures, with potential implications for reconfigurable THz spintronic and photonic devices.
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Optics
Spatial and temporal study of the post-compressed high-power laser pulses for coherent extreme ultraviolet source development
Cong Zhou, Haina Wu, Chaoneng Wu et al. (+13 more)
We compared the performance of two post-compression techniques, a gas-filled hollow-core fiber (HCF) and a multi-pass
cell (MPC), using a high-power ytterbium-doped fiber
laser. The HCF produced 27 fs pulses from 230 fs inputs at >50% efficiency, whereas the MPC achieved 34 fs pulses with significantly higher efficiency (>88%). Both results aligned well with numerical simulations. Crucially, spatial wavefront analysis revealed that the HCF acts as a modal filter, improving beam quality, whereas the MPC introduces aberrations through cumulative mirror errors. Furthermore, we characterize the
photon flux of high harmonic generation driven by the post-compressed pulses from the HCF and MPC. These finding highlights that post-compression technique based on self-phase modulation is efficient for the intensity boosting of femtosecond
laser system, providing opportunities for generating high quality extreme ultraviolet (XUV) sources. In addition, further improvement of spatial wavefront quality is suggested using the HCF as a single compressor or output component of the cascade compressor.
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All authors Cong Zhou, Haina Wu, Chaoneng Wu, Yitong Zhao, Chen Wang, Jiayue Liu, Zige Qiu, Wei Zhang, Yapei Peng, Mingyuan Shi, Shuyuan Hu, Xiaoliang Liu, Sizhong Wu, Jie Yang, Cangtao Zhou, Lu Li
Chemical Physics
Atomistic Simulations of Oxide-Water Interfaces using Machine Learning Potentials
Jan Elsner, K Nikolas Lausch and Jörg Behler
Oxide-water interfaces govern a wide range of physical and chemical processes fundamental to many fields like catalysis, geochemistry, corrosion, electrochemistry, and sensor technology. Near solid
oxide surfaces, water behaves differently than in the bulk, exhibiting pronounced structuring and increased reactivity, typically requiring ab initio-level accuracy for reliable modeling. However, explicit ab initio calculations are often computationally prohibitive, especially if large system sizes and long simulation time scales are required. By learning the potential energy surface (PES) from data obtained from electronic structure calculations, machine learning potentials (MLPs) have emerged as transformative tools, enabling simulations with ab initio accuracy at dramatically reduced computational expense. Here, we provide an overview of recent progress in the application of MLPs to atomistic simulations of
oxide-water interfaces. Specifically, we review insights that have been gained into the reactivity of interfacial systems involving the dissociation and recombination of water molecules,
proton transfer processes between the solvent and the surface and the dynamic nature of aqueous
oxide surfaces. Moreover, we discuss open challenges and future possible research directions in this rapidly evolving but challenging field.
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Fluid Dynamics
Height-Dependent Rotor Noise and Thrust in Urban Air Mobility: An Experimental Study
Qiyu Huang, Jingwen Deng, Zishuo Lin et al. (+1 more)
The present study investigates the aerodynamic and aeroacoustic characteristics of a propeller operating under varying rotational speeds (RPM) and heights ("H" ), with a particular focus on the effects of upstream obstruction modelled as a tall building. Unlike previous studies that primarily examined rotor noise under axial inflow conditions, this work explores how
vortex shedding and flow ingestion from different elevations influence rotor performance and noise emissions. Experiments were carried out in an anechoic wind tunnel, where a tall cylinder was positioned above the propeller to replicate real-world obstruction scenarios. Results revealed that lower propeller heights led to increased broadband noise due to intensified
turbulence interactions and reduced aerodynamic efficiency, while higher positions improved thrust performance and mitigated noise effects under certain conditions. The findings contribute to understanding noise sources in eVTOL propulsion systems and provide insights for optimizing propeller placement to enhance aerodynamic efficiency and noise reduction in urban environments
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All authors Qiyu Huang, Jingwen Deng, Zishuo Lin, Mahdi Azarpeyvand
Atmospheric and Oceanic Physics
Finding optimal Noah-MP parameterizations for the characterization of surface heat fluxes in the Iberian Peninsula
David Donaire-Montaño, Matilde García-Valdecasas Ojeda, Nicolás Tacoronte et al. (+4 more)
Land surface models (LSMs) play a crucial role in characterizing land-atmosphere interactions by providing boundary conditions to regional
climate models (RCMs). This is particularly true over the Iberian Peninsula (IP), where a water-limited regime governs much of the territory. We optimize the configuration of the Noah land surface model with multiparameterization options (Noah-MP) for characterizing heat fluxes in the IP when the Weather Research and
Forecasting (WRF) model v3.9.1 is used as an RCM. We perform 70 one-year simulations using 35 Noah-MP combinations, for a dry year (2005) and a wet year (2010). Land-surface heat fluxes and soil moisture from WRF/Noah-MP are evaluated against FLUXNET station data and the CERRA-Land reanalysis. In general, WRF/Noah-MP reproduces soil moisture and surface heat fluxes well over the IP, especially under wetter conditions. Clustering identifies an optimal configuration from 10 groups (A to J). The Noah-MP options with greatest impact are canopy stomatal resistance (CRS), surface exchange coefficient for heat (SFC), soil-moisture factor controlling stomatal resistance (BTR), runoff and groundwater (RUN), and surface resistance to evaporation/sublimation (RSF); dynamic vegetation (DVEG) also matters. Several configurations performed reasonably; experiment s27I (Jarvis CRS, Chen97 SFC, CLM-type BTR, BATS RUN, and adjusted Sellers RSF for wet soils) provides a particularly good characterization of heat fluxes over the IP.
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All authors David Donaire-Montaño, Matilde García-Valdecasas Ojeda, Nicolás Tacoronte, Juan José Rosa-Cánovas, Yolanda Castro-Díez, María Jesús Esteban-Parra, Sonia Raquel Gámiz-Fortis
Optics · Cross-listed from quant-ph
Generation and detection of squeezed states via a synchronously pumped optical parametric oscillator
Edoardo Suerra, Samuele Altilia, Stefano Olivares et al. (+7 more)
A synchronously pumped optical parametric oscillator (SPOPO) operating at 93 MHz is used to generate squeezed states at 1035 nm. The system features a counter-propagating beam at the same wavelength as the
quantum state, which simultaneously actively stabilizes the cavity and, after transmission, acts as the local oscillator for homodyne detection. By deriving the local oscillator directly from the SPOPO cavity, the setup establishes an intrinsically excellent spatial mode overlap and high interference visibility, forming a distinctive self-referenced architecture. Two spatial light modulators enable precise spectral shaping of both the pump and the local oscillator in amplitude and phase, allowing investigation of the spectral properties of the generated states. The versatility of the setup further allows exploration of different SPOPO configurations, including regimes with varied finesse and escape efficiency. Representative measurements, including homodyne traces and squeezing levels as functions of pump power and local oscillator bandwidth, demonstrate the performance of the system. Theoretical simulations based on a multimode singular-value-decomposition model reproduce well the measured dependence of squeezing on pump power and LO bandwidth, confirming the accuracy of the description and the robustness of the setup. Measured squeezing levels up to -3.3 dB are achieved, corresponding to -5.7 dB at SPOPO output, evidencing the robustness and versatility of this platform for stable pulsed squeezed-light generation and advanced
quantum optical applications.
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All authors Edoardo Suerra, Samuele Altilia, Stefano Olivares, Alessandro Ferraro, Francesco Canella, Dario Giannotti, Gianluca Galzerano, Sebastiano Corli, Enrico Prati, Simone Cialdi
Fluid Dynamics
Asymmetric behaviour of turbulence in the wake of wind farms caused by the Coriolis force
Gabriele Centurelli, Joachim Peinke, Bughsin' Djath et al. (+2 more)
Large offshore wind farm wakes in shallow atmospheric boundary layers (ABL) exhibit often an asymmetric behaviour when observed through Synthetic-Aperture-Radar or simulated through Large-Eddy Simulations (LES). In previous LES of wind farms in the northern hemisphere, the asymmetry manifests as a streak at the left side of the wake, looking downstream, where the
turbulence kinetic energy (TKE) is greater than the surrounding flow. This work aims at clarifying the physical mechanism that leads to the formation of such a phenomenon. Identifying the Coriolis force as one possible source of asymmetry in the resolved physics, we simulate a real wind farm located in the German Bight operating under different ABLs: one representative of the northern hemisphere; one of the southern hemisphere; and three fictitious ABLs where the Coriolis effects on the inflow and wake, i.e. veer and the wake deflecting force, are removed individually or altogether. Our results show that the TKE streak appears on the opposite side of the wake, i.e. the right one, in the southern hemisphere, and it is primarily caused by veer in the incoming flow, a result of the Coriolis force in a marine ABL. The process involves a larger TKE production which originates from a larger vertical shear promoted where the undisturbed veer profile converges towards the wake in the top part of the ABL. We find that the TKE streak improves the farm wake recovery modestly. Finally, we compare the asymmetry modelled by LES with those observed in several on-field measurements, finding striking similarities.
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All authors Gabriele Centurelli, Joachim Peinke, Bughsin' Djath, Johannes Schulz-Stellenfleth, Gerald Steinfeld
Medical Physics
Monitoring Head Movement in a Brain PET Scanner
Machiel Kolstein, Mokhtar Chmeissani and Andreu Pacheco
When acquiring PET images, body motions are unavoidable, given that the acquisition time could last 10-20 minutes or more. These motions can seriously deteriorate the quality of the final image at the level of image reconstruction and attenuation corrections. Movements can have rhythmic patterns, related to respiratory or cardiac motions, or they can be abrupt reflexive actions caused by the patient's discomfort. Many approaches, software and hardware, have been developed to mitigate this problem where each approach has its own advantages and disadvantages. In this work we present a simulation study of a head monitoring device, named CrowN@22, intended to be used in conjunction with a dedicated
brain PET scanner. The CrowN@22 device consists of six point sources of non-pure positron emitter isotopes, such as 22Na or 44Sc, mounted in crown-like rings around the head of the patient. The relative positions of the point sources are predefined and their actual position, once mounted, can be reconstructed by tagging the extra 1274 keV
photon (in the case of 22Na). These two factors contribute to a superb signal-to-noise ratio, distinguishing between the signal from the 22Na monitor point sources and the background signal from the FDG in the
brain. Hence, even with a low activity for the monitor point sources, as low as 10 kBq per point source, in the presence of 75 MBq activity of 18F in the
brain, one can detect
brain movements with a precision of less than 0.3 degrees, or 0.5 mm, which is of the order of the PET spatial resolution, at a sampling rate of 1 Hz.
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Applied Physics
Microwave Cytometry with Machine Learning for Shape-Resolved Microplastic Detection
Sayedus Salehin, Syed Shaheer Uddin Ahmed, Uzay Tefek et al. (+2 more)
Microplastics are increasingly recognized as a global environmental health threat, yet their detection and characterization remain constrained by the cost, form factor, and throughput of existing analytical tools. Portable micro/nanotechnology-based sensors are emerging to address this need, but most rely on the assumption of spherical particle geometry in their operating principle, limiting their relevance for environmental analysis. Here, we overcome this limitation by advancing microwave cytometry with machine learning-enabled shape recognition. Microwave cytometry is a flow-through electronic platform that integrates microwave resonator responses with low-frequency impedance signals to capture the dielectric signatures of individual particles. Using microscopy-derived shape measurements as ground truth, we trained a random forest model to decode these information-rich waveforms. Once trained, the system operates without optical input, enabling electronic-only determination of particle geometry. We demonstrate extraction of the major and minor axes of ellipsoidal microparticles with <8% relative error on average and use these predictions to derive the dielectric permittivity of ellipsoid particles. This approach removes long-standing shape assumptions in microplastic sensing and establishes a pathway toward portable, high-throughput, morphology-aware detection technologies.
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All authors Sayedus Salehin, Syed Shaheer Uddin Ahmed, Uzay Tefek, Laura Weirauch, M. Selim Hanay
Applied Physics
Self-Assembled hBN Wrinkles as Planar Optofluidic Channels
Xiliang Yang, Tetsuo Martynowicz, Allard Katan et al. (+3 more)
Optically accessible, scalable planar nanofluidic channels are attractive for studying transport and localization under confinement. Two dimensional (2D) materials provide large area, atomically flat interfaces for generating such platforms, yet achieving long range one-dimensional (1D) confinement with top-down nanofabrication remains challenging because it requires reproducible nanoscale feature control over extended distances, high yield, and low nonspecific adsorption of analytes under aqueous conditions. Here we demonstrate that thermally induced wrinkling of exfoliated hexagonal boron nitride (hBN) produces self-assembled,
liquid-accessible, channel-like networks through a lithography-free process. By varying flake thickness and substrate choice, we quantify statistical trends in wrinkle density and morphology, thereby establishing a practical fabrication design space. Atomic force microscopy and electron microscopy reveal wrinkle-derived geometries with vertical confinement ranging from <2 nm to >100 nm depending on flake thickness and substrate. We further employ time-sequence optical imaging upon droplet-contact, which together with Raman mapping of the water OH-stretch band and capacitance-gradient mapping (dC/dz) by scanning dielectric microscopy (KPFM-based) measurements, demonstrates
liquid infiltration and long-term
liquid retention within the wrinkle network for more than 10 h. We finally show a proof-of-concept biomolecule confinement application in which we integrate a
graphene overlayer as a background suppression interface, enabling wide-field fluorescence localization of ATTO647N labeled DNA along hBN wrinkle-induced nanochannels. Overall, this work establishes self-assembled hBN wrinkles as a scalable, and optically addressable planar nanofluidic platform for confinement of fluids and biomolecules.
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All authors Xiliang Yang, Tetsuo Martynowicz, Allard Katan, Kenji Watanabe, Takashi Taniguchi, Sabina Caneva
Classical Physics
Momentum-Transfer Framework Unifies High-Velocity Impact and Failure Across Materials, Geometries, and Scales
Yasara Dharmadasa, Nicholas Jaegersberg, Ara Kim et al. (+2 more)
Materials that dissipate energy efficiently under high-speed impacts, from micrometeoroid strikes on spacecraft to ballistic penetration in protective systems, are essential for maintaining structural integrity in extreme environments. Yet, despite decades of study, predicting and comparing impact performance across materials, geometries, and length scales remains challenging because conventional projectile-impact models often rely on conservation-based or empirically partitioned descriptions that assume the projectile-target interaction is a closed system. Here, we relax this assumption and directly observe the momentum and energy transferred out of the projectile during impact. We find that the momentum transferred to the target consistently reaches its maximum at the ballistic-limit velocity, demonstrated through a coordinated suite of micro-projectile impact experiments spanning varied projectile diameters, target thicknesses, and impact velocities, and further supported by targeted macroscale tests. This behavior is reinforced across a broad range of independent studies encompassing metals,
polymers, composites, sandwich panels, and reinforced concrete, with thicknesses ranging from nanometers to hundreds of millimeters and projectiles of spherical, blunt, ogive, and conical shape, under both normal and oblique impacts. Together, these observations reveal a consistent impact behavior across all available data: maximum momentum transfer occurs at the ballistic limit. Extending this bound into the energy absorption landscape addresses an entrenched misconception in the field by revealing that specific energy absorption inherently inflates the performance of thinner targets due to
geometric normalization, rather than reflecting genuine material enhancement.
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All authors Yasara Dharmadasa, Nicholas Jaegersberg, Ara Kim, Jizhe Cai, Ramathasan Thevamaran
Biological Physics
Capillarity Reveals the Role of Capsid Geometry in HIV Nuclear Translocation
Alex W. Brown, Sami C. Al-Izzi, Jack L. Parker et al. (+4 more)
The protective capsid encasing the genetic material of Human Immunodeficiency Virus (HIV) has been shown to traverse the
nuclear pore complex (NPC) intact, despite exceeding the passive
diffusion threshold by over three orders of magnitude. This remarkable feat is attributed to the properties of the capsid surface, which confer solubility within the NPC's phase-separated, condensate-like barrier. In this context, we apply the classical framework of wetting and capillarity – integrating analytical methods with sharp- and diffuse-interface numerical simulations – to elucidate the physical underpinnings of HIV
nuclear entry. Our analysis captures several key phenomena: the reorientation of incoming capsids due to torques arising from asymmetric capillary forces; the role of confinement in limiting capsid penetration depths; the classification of translocation mechanics according to changes in
topology and interfacial area; and the influence of (spontaneous) rotational
symmetry-breaking on energetics. These effects are all shown to depend critically on capsid geometry, arguing for a physical basis for HIV's characteristic capsid shape.
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All authors Alex W. Brown, Sami C. Al-Izzi, Jack L. Parker, Sophie Hertel, David A. Jacques, Halim Kusumaatmaja, Richard G. Morris
Optics
Refractive Index-Correlated Pseudocoloring for Adaptive Color Fusion in Holotomographic Cytology
Minseok Lee, Tal Lifshitz, Young Ki Lee et al. (+6 more)
Conventional bright-field (BF) cytology of thyroid fine-needle aspiration biopsy (FNAB) suffers from staining variability and limited subcellular contrast. Here, we present a refractive index-correlated pseudocoloring (RICP) framework that integrates quantitative refractive index (RI) maps obtained by holotomography (HT) with color BF images to enhance diagnostic interpretability. The imaging platform combines a digital micromirror device (DMD)-based HT system with an RGB LED illumination module, enabling simultaneous acquisition of RI tomograms and BF images from PAP-stained thyroid samples. The RICP
algorithm adaptively embeds RI-derived structural information into the least-occupied hue channel, preserving color fidelity while enhancing
nuclear and cytoplasmic contrast. Applied to benign and malignant thyroid clusters, RICP revealed diagnostically relevant features such as nucleoli, lipid droplets, and
nuclear irregularities, and hue-saturation analysis quantitatively differentiated cytological categories. This perceptually grounded, label-free framework bridges conventional color cytology and quantitative optical imaging for improved diagnostic precision.
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All authors Minseok Lee, Tal Lifshitz, Young Ki Lee, Geon Kim, Seog Yun Park, Hayoung Lee, Juyeon Park, Eun Kyung Lee, YongKeun Park
Optics
Incoherent dielectric tensor tomography for quantitative 3D measurement of biaxial anisotropy
Juheon Lee, Yeon Wook Kim, Hwanseok Chang et al. (+4 more)
Biaxial anisotropy, arising from distinct optical responses along three principal directions, underlies the complex structure of many crystalline, polymeric, and biological materials. However, existing techniques such as X-ray diffraction and electron microscopy require specialized facilities or destructive preparation and cannot provide full three-dimensional (3D) information. Here we introduce incoherent dielectric tensor
tomography (iDTT), a non-interferometric optical imaging method that quantitatively reconstructs the 3D dielectric tensor under incoherent, polarization-diverse illumination. By combining polarization diversity and angular-spectrum modulation, iDTT achieves speckle-free and vibration-robust mapping of biaxial birefringence with submicron resolution. Simulations and experiments on uniaxial and biaxial samples validate its quantitative accuracy. Applied to mixed and polycrystalline materials, iDTT distinguishes
crystal types by their birefringent properties and reveals 3D grain orientations and boundaries. This approach establishes iDTT as a practical and accessible tool for quantitative, label-free characterization of biaxial anisotropy in diverse materials.
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All authors Juheon Lee, Yeon Wook Kim, Hwanseok Chang, Herve Hugonnet, Seung-Mo Hong, Seokwoo Jeon, YongKeun Park
Optics
Dinosaur Photonic Crystal Cavity Interfaces for Color Center Coupling to Triangular Nanostructures
Julian M. Bopp, Lucca Valerius and Tim Schröder
Waveguide-coupled photonic
crystal cavities with a triangular cross section fabricated by angled etching are suitable to interface embedded color centers with flying photonic
qubits in
quantum information applications. Moreover, their fabrication requires fewer processing steps compared to nanostructures produced by quasi-isotropic undercutting. As an alternative to established hole-based photonic
crystal cavities, we introduce corrugated triangular 'Dinosaur' photonic
crystal cavities, and develop a tapered, quasi loss-free cavity-waveguide interface to adiabatically interconvert Bloch and waveguide modes. We optimize the cavity-waveguide interface to minimize
photon losses and demonstrate that its adjustment allows precise tuning of the light-matter interaction.
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Computational Physics
Generative Artificial Intelligence for Air Shower Simulation
C. Bozza, A. Calivà, A. De Caro et al. (+7 more)
The detailed simulation of extensive air showers, produced by primary
cosmic rays interacting in the atmosphere, is a task that is traditionally undertaken by means of Monte Carlo methods. These processes are computationally intensive, accounting for a major fraction of the computational resources used in the large-scale simulations required by current and future experiments in the field of astroparticle physics. In this work, we present a novel approach based on Generative
Adversarial Networks (GANs) to accelerate air shower simulations. We developed and trained a GAN on a
dataset of high-energy
proton-induced air showers generated with CORSIKA; our model reproduces key distributions of secondary particles, such as energy spectra and spatial distributions at ground level of
muons. Once the model has been trained, which takes approximately 74 hours, the generation real time per shower is reduced by a factor of $10^4$ with respect to the full CORSIKA simulation, leading to a substantial decrease in both computational time and energy consumption.
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All authors C. Bozza, A. Calivà, A. De Caro, D. De Gruttola, S. De Pasquale, L.A. Fusco, G. Messuti, C. Poirè, S. Scarpetta, T. Virgili
Optics
Dual-domain Microwave Photonic Radar for Non-contact High-resolution Monitoring of Vital Signs in Multiple Individuals
Dongyu Li, Ziqun Zhang, Hongyi Wang et al. (+8 more)
We present a dual-domain microwave photonic radar system for multi-parameter vital sign monitoring, utilizing ultra-wideband radiofrequency signals to achieve high-precision chest displacement measurements, while high-frequency optical signals enable accurate Doppler detection of pulse-induced micro-motions. We experimentally validated the system by simultaneously monitoring respiratory and pulse rate of two male volunteers, demonstrating high performance with average accuracies of 98.1% for pulse detection and 99.85% for respiratory detection. Additionally, the system facilitates rapid, indirect blood pressure estimation, achieving a coefficient of determination of 0.905. With the help of low-loss distribution capability of optical fibers, the system can be scaled into a distributed, non-contact multiple vital signs monitoring platform, highlighting its potential for clinical and healthcare applications.
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All authors Dongyu Li, Ziqun Zhang, Hongyi Wang, Yukang Jia, Siyue Zeng, Hong Chen, Jin Zhang, Xiaotong Liu, Yalan Wang, Dangwei Wang, Anle Wang
Medical Physics
Simultaneous optimization of non-coplanar beam orientations and cumulative EQD2 distribution for high-dose reirradiation of locoregionally recurrent non-small cell lung cancer
Nathan Torelli, Jonas Willmann, Katja Daehler et al. (+3 more)
Background and Purpose: Reirradiation for non-small
cell lung cancer (NSCLC) is commonly delivered using coplanar techniques. In this study, we developed a beam orientation optimization
algorithm for reirradiation planning to investigate whether the selection of favorable non-coplanar beam orientations may limit cumulative doses to critical organs-at-risk (OARs) and thus improve the therapeutic window. Materials and Methods: Fifteen cases of challenging high-dose reirradiation for locoregionally recurrent NSCLC were included in this in-silico study. For each patient, the dose distribution from the previous treatment was first mapped to the reirradiation planning CT using rigid dose registration, and subsequently converted to equivalent dose in 2 Gy fractions (EQD2). A 2-arc non-coplanar reirradiation plan, combining dynamic gantry and couch rotation, was then generated using an EQD2-based direct aperture optimization
algorithm, which allows for the simultaneous optimization of the dynamic gantry-couch path and the cumulative EQD2 distribution. Non-coplanar reirradiation plans were benchmarked against 2-arc coplanar VMAT plans, which mimic state-of-the-art practice for reirradiation of NSCLC. Results: Non-coplanar reirradiation plans could reduce the maximum cumulative EQD2 to critical OARs such as bronchial tree, esophagus, thoracic wall and trachea by at least 5 Gy2 for 6 out of 15 patients compared to coplanar reirradiation plans. At the same time, target coverage and lung EQD2 metrics were comparable for both methods. Conclusions: The automated selection of favorable non-coplanar beam orientations may reduce the maximum cumulative EQD2 to critical OARs in challenging thoracic reirradiation cases. This allows to explore either better OAR sparing or dose-escalation in future clinical studies.
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All authors Nathan Torelli, Jonas Willmann, Katja Daehler, Madalyne Day, Nicolaus Andratschke, Jan Unkelbach
Fluid Dynamics
Stability of plane Couette and Poiseuille flows rotating about the streamwise axis
Geert Brethouwer
We study the stability of plane Poiseuille flow (PPF) and plane Couette flow (PCF) subject to streamwise system rotation using linear stability analysis and direct numerical simulations. The linear stability analysis reveals two asymptotic regimes depending on the non-dimensional rotation rate ($Ro$): a low-$Ro$ and a high-$Ro$ regime. In the low-$Ro$ regime, the critical Reynolds number $Re_c$ and critical streamwise wavenumber $\alpha_c$ are proportional to $Ro$, while the critical spanwise wavenumber $\beta_c$ is constant. In the high-$Ro$ regime, as $Ro \rightarrow \infty$, we find $Re_c = 66.45$ and $\beta_c = 2.459$ for streamwise rotating PPF, and $Re_c = 20.66$ and $\beta_c = 1.558$ for streamwise rotating PCF, with $\alpha_c\propto 1/Ro$. Our results for streamwise rotating PPF match previous findings by Masuda et al. (2008). Interestingly, the critical values of $\beta_c$ and $Re_c$ at $Ro \rightarrow \infty$ in streamwise rotating PPF and PCF coincide with the minimum $Re_c$ reported by Lezius & Johnston (1976) and Wall & Nagata (2006) for spanwise rotating PPF at $Ro=0.3366$ and PCF at $Ro=0.5$. We explain this similarity through an analysis of the perturbation equations. Consequently, the linear stability of streamwise rotating PCF at large $Ro$ is closely related to that of spanwise rotating PCF and Rayleigh-Benard convection, with $Re_c = \sqrt{Ra_c}/2$, where $Ra_c$ is the critical Rayleigh number. To explore the potential for subcritical transitions, direct numerical simulations were performed. At low $Ro$, a subcritical transition regime emerges, characterized by large-scale turbulent-laminar patterns in streamwise rotating PPF and PCF. However, at higher $Ro$, subcritical transitions do not occur and the flow relaminarizes for $Re < Re_c$. Furthermore, we identify a narrow $Ro$-range where turbulent-laminar patterns develop under supercritical conditions.
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Computational Physics · Cross-listed from cond-mat.mes-hall
Exciton dynamics in equilibrium and nonequilibrium regimes
Pushpendra Yadav
The bound electron-hole pairs known as
excitons govern the optical properties of insulating solids. While their behavior in
equilibrium is well-understood theoretically, the nonequilibrium regime at high excitation densities-where phenomena like electron-hole
liquids emerge - is less explored. This thesis presents a first-principles study of
excitons in two-dimensional materials. We use the GW approximation and the Bethe-Salpeter equation to investigate their properties from
equilibrium to nonequilibrium conditions. We first demonstrate how increasing photo-excited carrier density leads to a
redshift-blueshift crossover of
excitons. We then show that electron-
phonon interactions critically modify optical spectra and
exciton lifetimes at finite temperatures. Finally, we unify these effects to demonstrate the formation of an electron-hole
liquid phase above a critical carrier density and below a critical temperature. Our work identifies how enhanced Coulomb interactions in two dimensions can stabilize this phase at significantly higher temperatures, proposing promising material candidates for observing these collective states.
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Fluid Dynamics · Cross-listed from astro-ph.SR
A new particle-based code for Lagrangian stochastic models applied to stellar turbulent convection
J. Philidet and K. Belkacem
The inclusion of convection in
stellar evolution models lacks realism, especially near convective-radiative interfaces. Furthermore, the interaction of convection with oscillations prevent us from accurately predicting seismic frequencies, and therefore from fully exploiting the asteroseismic data of low-mass
stars. We aim to develop a new formalism to model the one-point statistics of
stellar convection, to implement it in a new numerical code, and to validate this implementation against
benchmark cases. This new formalism is based on Lagrangian Probability Density Function (PDF) methods, where a Fokker-Planck equation for the PDF of particle-based turbulent properties is integrated in time. We then develop a Monte-Carlo implementation of this method, where the flow is represented by a large number of notional particles acting as realisations of the PDF. Notional particles interact with each other through the time- and space-dependent mean flow, which is estimated from the particle realisations through a scheme similar to Smoothed Particle Hydrodynamics. We establish a model for the
evolution of turbulent properties along Lagrangian trajectories applicable to
stellar turbulent convection, with only a minimal number of physical assumptions necessary to close the system. In particular, no closure is needed for the non-linear advection terms, which are included exactly through the Lagrangian nature of formalism. The numerical implementation of this new formalism allows us to extract time-dependent maps of the statistical properties of turbulent convection in a way which is not possible in grid-based large-eddy simulations, in particular the turbulent pressure, Reynolds stress tensor, internal energy variance and convective flux.
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Geophysics
Machine learning-based upscaling of rock permeability from pore scale to core scale: effect of training dataset size and sub-core volumes
Yaotian Guo, Fei Jiang, Takeshi Tsuji et al. (+7 more)
Permeability characterizes the capacity of porous formations to conduct fluids, thereby governing the performance of carbon capture, utilization, and storage (CCUS), hydrocarbon extraction, and subsurface energy storage. A reliable assessment of rock permeability is therefore essential for these applications. Direct estimation of permeability from low-resolution CT images of large rock samples offers a rapid approach to obtain permeability data. However, the limited resolution fails to capture detailed pore-scale structural features, resulting in low prediction accuracy. To address this limitation, we propose a convolutional neural network (CNN)-based upscaling method that integrates high-precision pore-scale permeability information into core-scale, low-resolution CT images. In our workflow, the large core sample is partitioned into sub-core volumes, whose permeabilities are predicted using CNNs. The upscaled permeability at the core scale is then determined through a Darcy flow solver based on the predicted sub-core permeability map. Additionally, we examine the optimal sub-core volume size that balances computational efficiency and prediction accuracy. This framework effectively incorporates small-scale heterogeneity, enabling accurate permeability upscaling from micrometer-scale pores to centimeter-scale cores.
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All authors Yaotian Guo, Fei Jiang, Takeshi Tsuji, Yoshitake Kato, Mai Shimokawara, Lionel Esteban, Mojtaba Seyyedi, Marina Pervukhina, Maxim Lebedev, Ryuta Kitamura