Understanding the equation of state of neutron stars (NSs) is a fundamental challenge in astrophysics and nuclear physics. A first-order phase transition at high densities could lead to the formation of a quark core, significantly affecting NS properties. This review explores observational and theoretical constraints on such transitions from observational effects. X-ray observations, including mass-radius measurements from NICER and spectral features like Quasi-Periodic Oscillations, Cyclotron Resonance Scattering Features and Fast Radio Bursts, provide indirect evidence of EOS modifications. Gravitational wave detections, particularly from binary NS mergers GW170817, constrain tidal deformability and post-merger oscillations, which may carry signatures of phase transitions. Measurements of mass, spin evolution, and glitches, with millisecond pulsars exceeding 2M posing challenges to purely hadronic EOSs. Theoretical models and numerical simulations predict that an FOPT could impact gravitational wave signals, twin-star configurations, and NS cooling. Future advancements, including next-generation gravitational wave detectors, high-precision X-ray telescopes, and improved theoreti-cal modeling, will enhance our ability to probe phase transitions in NSs. A combination of these approaches will provide crucial insights into the existence and properties of deconfined quark matter in NS interiors.

Abstract Little Red Dots (LRDs) are compact sources at z > 5 discovered through JWST spectroscopy. Their spectra exhibit broad Balmer emission lines ($\gtrsim 1000\rm ~km~s^{-1}$), alongside absorption features and a pronounced Balmer break – evidence for a dense, neutral hydrogen medium, in which the n = 2 state is significantly populated. When interpreted as arising from AGN broad-line regions, inferred black hole masses from local scaling relations exceed expectations given their stellar masses, challenging models of early black hole–galaxy co-evolution. However, radiative transfer effects in dense media may also impact the formation of hydrogen emission lines. We model three scattering processes shaping hydrogen line profiles: resonance scattering by hydrogen in the n = 2 state, Raman scattering of UV radiation by ground-state hydrogen, and Thomson scattering by free electrons. Using 3D Monte Carlo radiative transfer simulations, we examine their imprint on line shapes and ratios. Resonance scattering produces strong deviations from Case B flux ratios, clear differences between Hα and Hβ, and encodes gas kinematics in line profiles but cannot broaden Hβ due to conversion to Paα. While Raman scattering can yield broad wings, scattering of the UV continuum is disfavored given the absence of strong FWHM variations across transitions. Raman scattering of higher Lyman-series emission can produce Hα/Hβ wing width ratios of ≳ 1.28, agreeing with observations. Thomson scattering can reproduce the observed $\gtrsim 1000~\rm km\, s^{-1}$ wings under plausible conditions – e.g., Te ∼ 104 K and $N_{\rm e}\sim 10^{24}\rm ~cm^{-2}$ – and lead to black hole mass overestimates by factors ≳ 10. Our results provide a framework for interpreting hydrogen lines in LRDs and similar systems.

In this study, nine novel cationic gemini surfactants were designed, synthesized, and comprehensively characterized for potential application in chemical enhanced oil recovery (EOR). The molecular architecture was systematically varied by combining three alkyl chain lengths (C12, C14, C16) with three polymethylene spacers (2, 3, and 4 carbon atoms), enabling a detailed investigation of structure–property relationships. Successful synthesis was confirmed via Fourier Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance (1H-NMR), Thermogravimetric Analysis (TGA), and Dynamic Light Scattering (DLS), which provided insights into morphological features, thermal stability, and aggregation behavior. Surface tension and conductivity measurements revealed that the critical micelle concentration (CMC) decreases with increasing alkyl chain length, but increases with spacer length, highlighting the interplay between hydrophobic and hydrophilic interactions. Thermodynamic analysis indicated that both micellization and adsorption are spontaneous processes, with micellization predominantly entropy-driven. Notably, adsorption was significantly more favorable, contributing to substantial interfacial tension reduction, a key requirement for efficient EOR. Furthermore, DLS confirmed the tunability of micelle and aggregate formation as a function of surfactant architecture and concentration, offering a rational pathway for designing tailored surfactant systems under demanding oil recovery conditions.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-21090-7.

This study investigates resonance phenomena caused by magnon excitations at low temperatures, which are important for understanding the magnetic characteristics of high-temperature superconductors (HTS) and other correlated electron systems. Magnons, being quantize spin waves, have a major influence on collective magnetic behaviour, and their interactions lead to detectable resonance effects in neutron scattering experiments. This study investigates the dispersion relations and neutron scattering intensity in reduced lattice units (𝑟.𝑙.𝑢.), focusing on the formation of resonance peaks corresponding to magnon energy levels. These peaks are demonstrate to vary with exchange interaction. Theoretical predictions, validated by experimental data, demonstrate a strong link between magnons and other quasi-particles, providing new insights into low-temperature magnetic dynamics and their implications for superconductivity and quantum materials.

High-temperature superconductors (HTSCs) exhibit unconventional normal state electrical resistivity, diverging from standard Fermi-liquid behaviour. Resonance scattering is a major contributing factor to this anomalous resistivity, where charge carriers strongly interact with collective excitations like spin fluctuations or impurity-induced localized states. This mechanism is particularly relevant for cuprates, where strong electron correlations and a complex energy landscape result in non-trivial temperature dependence of resistivity. This behaviour often manifests as a linear behaviour over a wide range. We discuss the microscopic origins of resonance scattering, its impact on the transport properties of HTSCs, and its role in understanding the crossover between the normal and superconducting states. We also examine experimental signatures and theoretical models that describe this phenomenon, highlighting.

Abstract Acoustic metamaterials based on the principle of localized resonance tend to have a narrow absorption band, which limits their potential application for fan noise control. To address this challenge, a spiral acoustic metamaterial is developed that combines the local resonance mechanism with the Bragg scattering mechanism. This design not only effectively broadens the absorption bandwidth at the target frequency and achieves broadband absorption centered on multiple harmonic frequencies, but also compensates for the size‐related limitations associated with the Bragg scattering mechanism. The theoretical model of the acoustic metamaterial, based on the coupling mechanism, is developed using the transfer matrix method. The bandgap analysis demonstrates that the acoustic absorption bandwidth increases by ≈50% following the coupling process. Simultaneously, the design of the spiral structure results in an overall size reduction of ≈67% compared to conventional periodic metamaterials. It is verified through numerical simulations that the designed metamaterial exhibits efficient ventilation capabilities, but the ventilation efficiency decreases with the increase of the number of periodic units. Samples are fabricated for experimental validation via 3D printing technology, and the experimental results demonstrated that the designed acoustic metamaterials are effective in attenuating fan noise.

Resonance Scattering and Absorption of an Extraordinary Plane Wave by a Cylindrical Irregularity in a Magnetoplasma

As well known, the cross sections of the resonance and Quasi-Elastic (QE) scattering off nucleons depend on quantities known as form factors that describe the nucleon structure. There are alternative approaches to determine the values of these non-perturbative quantities, some of them relying on the Neutral Current (NC) scattering of neutrinos off nucleons. In the presence of NC Non-Standard Interactions (NSI), such derivations must be revisited. The aim of the present paper is to discuss how information on NSI can be extracted by combining alternative approaches for deriving the form factors. We discuss how the KamLAND atmospheric neutrino data with Eν< GeV (used to determine the axial strange form factor gAs) can already constrain the axial NSI of ντ with nucleons. We also argue that if the precision measurement of νμ NC QE scattering establishes unexpectedly large vector strange form factor (e.g., F1s(Q2) ∼ 0.01), it will be an indication for nonzero NSI coupling with u and d quarks (ϵμμAu/d∼ 0.01). We study the QE and resonance scattering cross sections of ντ and νe off Argon and show that if their axial NSI is of the order of (but of course below) the present bounds, the deviation of QE cross sections from the SM prediction will be sizable and distinct from the uncertainties induced by the form factors.

This study proposes a composite bandgap metamaterial pipeline (CBMP) integrating local resonance and Bragg scattering mechanisms for simultaneous vibration and noise suppression in fluid‐conveying systems. Through the transfer matrix method (TMM), finite element method (FEM), and experiment, the CBMP demonstrates dual axial bandgaps (180–380 and 1075–2080 Hz) in nonfluid conditions. Numerical and experimental results show ≤ 6.7% deviation, confirming model accuracy. Fluid‐structure interaction (FSI) analysis reveals that liquid filling introduces periodic transmission peaks in Bragg bandgaps, reducing vibration attenuation efficiency. Increasing inlet pressure amplifies circumferential breathing modes, causing axial displacement at pipeline ends to exceed excitation points. Notably, FSI‐induced circumferential modes weaken both local resonance and Bragg bandgap performance, with attenuation effects diminishing as pressure rises. Bragg scattering narrows local resonance bandgaps due to nonlinear mechanism coupling. This work provides critical insights for studying metamaterial pipelines in practical fluid‐structure coupling systems.

Resonance Scattering Due to Magnon Excitation in High-Temperature Superconductors

Objective: This study aims to develop a novel smart formulation based on dual-responsive Polyethylene Glycol Methacrylate-Grafted-Chitosan (PEGMA-g-Cs) copolymers for the controlled delivery of Lactoferrin. The goal is to enhance the bioavailability and therapeutic efficacy of Lactoferrin in treating colorectal cancer, addressing its rapid degradation in a highly acidic gastric environment. Methods: Gold-coated Superparamagnetic Iron Oxide Nanoparticles (Au-SPIONs) were synthesized and loaded into PEGMA-g-Cs microspheres. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Proton Nuclear Magnetic Resonance (HNMR), X-Ray Diffraction (XRD), Infrared Spectroscopy (IR), UV-visible spectrophotometry (UV-Vis), optical microscopy, and Dynamic Light Scattering (DLS) were used to characterise the synthesized materials. Drug loading and release studies of lactoferrin-loaded microbead formulations were conducted to evaluate encapsulation efficiency, loading capacity, and release profiles. Results: The lactoferrin-loaded microbead formulations demonstrated excellent encapsulation efficiency and loading capacity. Specifically, Encapsulation Efficiency (EE) was 77% and Loading Capacity (LC) was 4.99% for the homogenizer batch, while the magnetic stirring batch achieved 86% EE and 3.12% LC. The formulation exhibited minimal release (&lt;20%) in Simulated Gastric Fluid (SGF) and almost complete release in Simulated Colonic Fluid (SCF). The 3-[4,5-Dimethylthiazol-2-Yl]-2,5-Diphenyl Tetrazolium Bromide (MTT) cell cytotoxicity assay in human CaCo-2 colon cancer cells revealed a significant reduction in cell proliferation following treatment with the new formulations. Conclusion: The findings suggest that the new formulation can be a promising approach for the targeted delivery of Lactoferrin, thereby improving the efficacy of colorectal cancer treatment by enhancing the bioavailability of lactoferrin.

The variability of helium abundance in the solar corona and the solar wind is an important signature of solar activity, solar cycle, and solar wind sources, as well as coronal heating processes. Motivated by recently reported remote-sensing UV imaging observations by Helium Resonance Scattering in the Corona and Heliosphere payload sounding rocket of helium abundance in the inner corona on 2009 September 14 near solar minimum, we present the results of the first three-dimensional three-fluid (electrons, protons, and alpha particles) model of tilted coronal streamer belt and slow solar wind that illustrates the various processes leading to helium abundance differentiation and variability. We find good qualitative agreement between the three-fluid model and the coronal helium abundance variability deduced from UV observations of streamers, providing insight on the effects of the physical processes, such as heating, gravitational settling, and interspecies Coulomb friction in the outflowing solar wind that produce the observed features. The study impacts our understanding of the origins of the slow solar wind.

ABSTRACT We conduct a comprehensive analysis of the accreting X-ray pulsar, Hercules X-1, utilizing data from Imaging X-ray Polarimetry Explorer (IXPE) and Nuclear Spectroscopic Telescope Array. IXPE performed five observations of Her X-1, consisting of three in the Main-on state and two in the Short-on state. Our time-resolved analysis uncovers the linear correlations between the flux and polarization degree as well as the pulse fraction and polarization degree. Geometry parameters are rigorously constrained by fitting the phase-resolved modulations of Cyclotron Resonance Scattering Feature and polarization angle with a simple dipole model and Rotating Vector Model, respectively, yielding roughly consistent results. The changes of χp (the position angle of the pulsar’s spin axis on the plane of the sky) between different Main-on observations suggest the possible forced precession of the neutron star crust. Furthermore, a linear association between the energy of Cyclotron Resonance Scattering Feature and polarization angle implies the prevalence of a dominant dipole magnetic field, and their phase-resolved modulations likely arise from viewing angle effects.

The proposed revisit to a classical problem in fluid–structure interaction is due to an interest in the analysis of the narrow resonances corresponding to a low-frequency fluid-borne wave, inspired by modeling and design of metamaterials. In this case, numerical implementations would greatly benefit from preliminary asymptotic predictions. The normal incidence of an acoustic wave is studied for a circular cylindrical shell governed by plane strain equations in elasticity. A novel high-order asymptotic procedure is established considering for the first time all the peculiarities of the low-frequency behavior of a thin fluid-loaded cylinder. The obtained results are exposed in the form suggested by the Resonance Scattering Theory. It is shown that the pressure scattered by rigid cylinder is the best choice for a background component. Simple explicit formulae for resonant frequencies, amplitudes, and widths are presented. They support various important observations, including comparison between widths and the error of the asymptotic expansion for frequencies.

Dynamic response and wave motion of a periodically supported beam under an ultra-high-speed load: Wave dispersion and critical velocities

In this paper, we present the simple, one-step, self-consistent, and fast resonance scattering model rsapec based on the AtomDB database. This model can be used as an alternative to the commonly used APEC model for fitting X-ray spectra with optically thick lines. The current model is intended, in general, for verifying the presence of the effect and for spectral modeling of galaxy clusters and elliptical galaxies under applicable assumptions. We test rsapec to derive the line suppression in the elliptical galaxy NGC 4636 and the Perseus cluster of galaxies and obtain resonance suppressions of ∼1.24 and ∼1.30, respectively.

Resonance Raman optical activity (RROA) spectra with high sensitivity reveal details on molecular structure, chirality, and excited electronic properties. Despite the difficulty of the measurements, the recorded data for the Co(III) complex with S,S-N,N-ethylenediaminedisuccinic acid are of exceptional quality and, coupled with the theory, spectacularly document the molecular behavior in resonance. This includes a huge enhancement of the chiral scattering, contribution of the antisymmetric polarizabilities to the signal, and the Herzberg-Teller effect significantly shaping the spectra. The chiral component is by about one order of magnitude bigger than for an analogous aluminum complex. The band assignment and intensity profile were confirmed by simulations based on density functional and vibronic theories. The resonance was attributed to the S0®S3 transition, with the strongest signal enhancement of Raman and ROA spectral bands below about 800 cm-1. For higher wavenumbers, other excited electronic states contribute to the scattering in a less resonant way. RROA spectroscopy thus appears as a unique tool to study the structure and electronic states of absorbing molecules in analytical chemistry, biology, and material science.

ABSTRACT We present the timing and spectral analysis of the high-mass X-ray binary source 4U 1538−522 using Nuclear Spectroscopic Telescope Array (NuSTAR) observations. One of the observations partially covers the X-ray eclipse of the source along with eclipse ingress. The source is found to spin down at the rate of 0.163 ± 0.002 s yr−1 between ∼54973 and 58603 MJD. It is evident that at time ∼58620 MJD, a torque reversal occurred; thereafter, the source exhibited a spin-up trend at the rate −(0.305 ± 0.018) s yr−1 until 59275 MJD. A recent NuSTAR observation finds the pulse period of the source: (526.2341 ± 0.0041) s. The pulse profile exhibits a transition from double-peaked to single-peaked nature above ∼30 keV. We analysed the overall trend of the temporal evolution of fundamental cyclotron resonance scattering feature, Ecyc, incorporating recent NuSTAR measurements. Initially, during the time span ∼50452.16–55270.8 MJD, the cyclotron line energy is found to increase at a rate of 0.11 ± 0.03 keV yr−1, which is further followed by a decrease at a rate −0.14 ± 0.01 keV yr−1 between 55270.8 and 59267 MJD. The combined measurements in the time span 50452.16–59267 MJD reveal that the cyclotron line energy is increasing linearly at a rate of 0.08 ± 0.02 keV yr−1.

A new method for directly sampling the resonance upscattering effect is presented. Alternatives have relied on inefficient rejection sampling techniques or large tabular storage of relative velocities. None of these approaches, which require pointwise energy data, are particularly well suited to the windowed multipole cross-section representation. The new method, called multipole analytic resonance scattering, overcomes these limitations by inverse transform sampling from the target relative velocity distribution where the cross section is expressed in the multipole formalism. The closed-form relative speed distribution contains a novel special function we deem the incomplete Faddeeva function, and we present the first results on its efficient numerical evaluation.

Alkali-borosilicate glasses with composition (80-x)SiO2-xB2O3-20Na2O (10 ≤ x ≤ 30) were subjected to a 25 GPa compression and decompression at room temperature, resulting in density increases between 1.4% and 1.9%. The structural changes associated with this process have been investigated and compared with uncompressed glasses having the same thermal history. Systematic trends are identified, using Raman scattering and multinuclear solid-state Nuclear Magnetic Resonance (ssNMR). Perhaps counterintuitively, pressurization tends to increase the concentration of three-coordinated boron species (B(III) units) at the expense of four-coordinated boron (B(IV) units). 23Na NMR spectra show a systematic shift toward higher frequencies in the pressurized glasses, consistent with shorter average Na-O distances. The results are consistently explained in terms of a breakage of Si-O-B4 linkages resulting in the formation of nonbridging oxygen species. Pressure effects on the spectra are reversed by annealing the glasses at their respective glass transition temperatures.