Optimization of ultrasound heating with Pickering droplets using core-shell scattering theory.

Nanoparticles find widespread application in various medical contexts, including targeted nanomedicine and enhancing therapeutic efficacy. Moreover, they are employed to stabilize emulsions, giving rise to stabilized droplets known as Pickering droplets. Among the various methods to improve anti-cancer treatment, ultrasound hyperthermia stands out as an efficient approach. This research proposes Pickering droplets as promising sonosensitizer candidates, to enhance the attenuation of ultrasound with simultaneous potential to act as drug carriers. The enhanced ultrasound energy dissipation could be, therefore, optimized by changing the parameters of Pickering droplets. The ultrasound scattering theory, based on the core-shell model, was employed to calculate theoretical ultrasound properties such as attenuation and velocity. Additionally, computer simulations, based on a bioheat transfer model, were utilized to compute heat generation in agar-based phantoms of tissues under different ultrasound wave frequencies. Two types of phantoms were simulated: a pure agar phantom and an agar phantom incorporating spherical inclusions. The spherical inclusions, with a diameter of 10 mm, were doped with various sizes of Pickering droplets, considering their core radius and shell thickness. Computer simulation of these spherical inclusions incorporated within agar phantom resulted in different enhancement of achieved temperature elevation, which depending on the core radius, shell thickness, and the material properties of the system. Notably, spherical inclusions doped with Pickering droplets stabilized by magnetite nanoparticles exhibited a higher temperature rise compared to droplets stabilized by silica nanoparticles. Moreover, nanodroplets with a core radius below 400 nm demonstrated better heating performance compared to microdroplets. Furthermore, Pickering droplets incorporated into agar phantom could allow obtaining a similar effect of local heating as sophisticated focused ultrasound devices.

Solving Maxwell's Equations Using Polarimetry Alone.

Maxwell's equations are solved when the amplitude and phase of the electromagnetic field are determined at all points in space. Generally, the Stokes parameters can only capture the amplitude and polarization state of the electromagnetic field in the radiation (far) zone. Therefore, the measurement of the Stokes parameters is, in general, insufficient to solve Maxwell's equations. In this Letter, we solve Maxwell's equations for a set of objects widely used in Nanophotonics using the Stokes parameters alone. These objects are lossless, axially symmetric, and well described by a single multipolar order. Our method for solving Maxwell's equations endows the Stokes parameters an even more fundamental role in the electromagnetic scattering theory.

A Degraded Finger Vein Image Recovery and Enhancement Algorithm Based on Atmospheric Scattering Theory.

With the development of biometric identification technology, finger vein identification has received more and more widespread attention for its security, efficiency, and stability. However, because of the performance of the current standard finger vein image acquisition device and the complex internal organization of the finger, the acquired images are often heavily degraded and have lost their texture characteristics. This makes the topology of the finger veins inconspicuous or even difficult to distinguish, greatly affecting the identification accuracy. Therefore, this paper proposes a finger vein image recovery and enhancement algorithm using atmospheric scattering theory. Firstly, to normalize the local over-bright and over-dark regions of finger vein images within a certain threshold, the Gamma transform method is improved in this paper to correct and measure the gray value of a given image. Then, we reconstruct the image based on atmospheric scattering theory and design a pixel mutation filter to segment the venous and non-venous contact zones. Finally, the degraded finger vein images are recovered and enhanced by global image gray value normalization. Experiments on SDUMLA-HMT and ZJ-UVM datasets show that our proposed method effectively achieves the recovery and enhancement of degraded finger vein images. The image restoration and enhancement algorithm proposed in this paper performs well in finger vein recognition using traditional methods, machine learning, and deep learning. The recognition accuracy of the processed image is improved by more than 10% compared to the original image.

Optically Transparent Lead Halide Perovskite Polycrystalline Ceramics.

We utilize room-temperature uniaxial pressing at applied loads achievable with low-cost, laboratory-scale presses to fabricate freestanding CH3NH3PbX3 (X- = Br-, Cl-) polycrystalline ceramics with millimeter thicknesses and optical transparency up to ∼70% in the infrared. As-fabricated perovskite ceramics can be produced with desirable form factors (i.e., size, shape, and thickness) and high-quality surfaces without any postprocessing (e.g., cutting or polishing). This method should be broadly applicable to a large swath of metal halide perovskites, not just the compositions shown here. In addition to fabrication, we analyze microstructure-optical property relationships through detailed experiments (e.g., transmission measurements, electron microscopy, X-ray tomography, optical profilometry, etc.) as well as modeling based on Mie theory. The optical, electrical, and mechanical properties of perovskite polycrystalline ceramics are benchmarked against those of single-crystalline analogues through spectroscopic ellipsometry, Hall measurements, and nanoindentation. Finally, γ-ray scintillation from a transparent MAPbBr3 ceramic is demonstrated under irradiation from a 137Cs source. From a broader perspective, scalable methods to produce freestanding polycrystalline lead halide perovskites with comparable properties to their single-crystal counterparts could enable key advancements in the commercial production of perovskite-based technologies (e.g., direct X-ray/γ-ray detectors, scintillators, and nonlinear optics).

Asymmetric imaging through engineered Janus particle obscurants using a Monte Carlo approach for highly asymmetric scattering media.

The advancement of imaging systems has significantly ameliorated various technologies, including Intelligence Surveillance Reconnaissance Systems and Guidance Systems, by enhancing target detection, recognition, identification, positioning, and tracking capabilities. These systems can be countered by deploying obscurants like smoke, dust, or fog to hinder visibility and communication. However, these counter-systems affect the visibility of both sides of the cloud. In this sense, this manuscript introduces a new concept of a smoke cloud composed of engineered Janus particles to conceal the target image on one side while providing clear vision from the other. The proposed method exploits the unique scattering properties of Janus particles, which selectively interact with photons from different directions to open up the possibility of asymmetric imaging. This approach employs a model that combines a genetic algorithm with Discrete Dipole Approximation to optimize the Janus particles' geometrical parameters for the desired scattering properties. Moreover, we propose a Monte Carlo-based approach to calculate the image formed as photons pass through the cloud, considering highly asymmetric particles, such as Janus particles. The effectiveness of the cloud in disguising a target is evaluated by calculating the Probability of Detection (PD) and the Probability of Identification (PID) based on the constructed image. The optimized Janus particles can produce a cloud where it is possible to identify a target more than 50% of the time from one side (PID > 50%) while the target is not detected more than 50% of the time from the other side (PD < 50%). The results demonstrate that the Janus particle-engineered smoke enables asymmetric imaging with simultaneous concealment from one side and clear visualization from the other. This research opens intriguing possibilities for modern obscurant design and imaging systems through highly asymmetric and inhomogeneous particles besides target detection and identification capabilities in challenging environments.

Analytic and conformal scattering in general relativity.

This paper is about two important trends of scattering theory in general relativity: time-dependent spectral analytic scattering and conformal scattering. The former was initiated by Jonathan Dimock and Bernard Kay in the mid-1980s and is based on spectral and functional analysis. The latter was proposed by Roger Penrose in 1965 and then constructed for the first time by Gerard Friedlander in 1980 by putting together Penrose's conformal method and another analytic approach to scattering: the Lax-Phillips theory due to Peter Lax and Ralph Phillips. We shall review the history of the two approaches and explain their general principles. We shall also explore an important question: 'can the tools of one approach be used to obtain a complete construction in the other?' This article is part of a discussion meeting issue 'At the interface of asymptotics, conformal methods and analysis in general relativity'.

Architecture Controls Phonon Propagation in All-Solid Brush Colloid Metamaterials.

Brillouin light scattering and elastodynamic theory are concurrently used to determine and interpret the hypersonic phonon dispersion relations in brush particle solids as a function of the grafting density with perspectives in optomechanics, heat management, and materials metrology. In the limit of sparse grafting density, the phonon dispersion relations bear similarity to polymer-embedded colloidal assembly structures in which phonon dispersion can be rationalized on the basis of perfect boundary conditions, i.e., isotropic stiffness transitions across the particle interface. In contrast, for dense brush assemblies, more complex dispersion characteristics are observed that imply anisotropic stiffness transition across the particle/polymer interface. This provides direct experimental validation of phonon propagation changes associated with chain conformational transitions in dense particle brush materials. A scaling relation between interface tangential stiffness and crowding of polymer tethers is derived that provides a guideline for chemists to design brush particle materials with tailored phononic dispersion characteristics. The results emphasize the role of interfaces in composite materials systems. Given the fundamental relevance of phonon dispersion to material properties such as thermal transport or mechanical properties, it is also envisioned that the results will spur the development of novel functional hybrid materials.

Spectral analysis of multiple scattering factors of turbid media for glucose measurement using near-infrared spectroscopy.

Significance: Near-infrared (NIR) diffuse reflectance spectroscopy has been widely used for non-invasive glucose measurement in humans, as glucose can induce a significant and detectable optical signal change in tissue. However, the scattering-dominated glucose spectrum in the range of 1000 to 1700 nm is easily confused with many other scattering factors, such as particle density, particle size, and tissue refractive index. Aim: Our aim is to identify the subtle distinctions between glucose and these factors through theoretical analysis and experimental verification, in order to employ suitable methods for eliminating these interferences, thus increasing the accuracy of non-invasive glucose measurement. Approach: We present a theoretical analysis of the spectra of 1000 to 1700 nm for glucose and some scattering factors, which is then verified by an experiment on a 3% Intralipid solution. Results: We found that both the theoretical and experimental results show that the effective attenuation coefficient of glucose has distinct spectral characteristics, which are distinct from the spectra caused by particle density and refractive index, particularly in the range of 1400 to 1700 nm. Conclusions: Our findings can offer a theoretical foundation for eliminating these interferences in non-invasive glucose measurement, aiding mathematical methods to model appropriately and enhance the accuracy of glucose prediction.

Theoretical prediction of the scattering of spherical bubble clusters under ultrasonic excitation.

Due to the nonlinear vibration of ultrasound contrast agent bubbles, a nonlinear scattered sound field will be generated when bubbles are driven by ultrasound. A bubble cluster consists of numerous bubbles gathering in a spherical space. It has been noted that the forward scattering of a bubble cluster is larger than its backscattering, and some studies have experimentally found the angular dependence of a bubble cluster's scattering signal. In this paper, a theory is proposed to explain the difference of acoustic scattering at different directions of a bubble cluster when it is driven by ultrasound, and predicts the angular distribution of scattered acoustic pressure under different parameters. The theory is proved to be correct under circumstances of small clusters and weak interactions by comparing theoretical results with numerical simulations. This theory not only sheds light on the physics of bubble cluster scattering, but also may contribute to the improvement of ultrasound imaging technology, including ultrasonic harmonic imaging and contrast-enhanced ultrasonography.

Concentration Quantification of TiO2 Nanoparticles Synthesized by Laser Ablation of a Ti Target in Water.

In this work, we present a quantitative method for determining the concentration of metal oxide nanoparticles (NP) synthesized by laser ablation in liquid. The case study was performed with titanium dioxide nanoparticles (TiO2 NP), which were synthesized by laser ablation of a Ti target in water. After synthesis, a colloidal solution was analyzed with UV-Vis spectroscopy. At the same time, the craters that remained on the Ti target after ablation were evaluated with an optical microscope to determine the volume of the ablated material. SEM microscopy was used to determine the TiO2 NP size distribution. It was found that synthesized TiO2 NP followed a Log-Normal diameter distribution with a maximum at about 64 nm. From the volume of ablated material and NP size distribution, under the assumption that most of the ablated material is consumed to form nanoparticles, a concentration of nanoparticles can be determined. The proposed method is verified by comparing the calculated concentrations to the values obtained from the Beer-Lambert law using the Mie scattering theory for the NP cross-section calculation.

Ultrasound Study of Magnetic and Non-Magnetic Nanoparticle Agglomeration in High Viscous Media.

Ultrasound attenuation spectroscopy has found wide application in the study of colloidal dispersions such as emulsions or suspensions. The main advantage of this technique is that it can be applied to relatively high concentration systems without sample preparation. In particular, the use of Epstein-Carhart-Allegra-Hawley's (ECAH) ultrasound scattering theory, along with experimental data of ultrasound velocity or attenuation, provide the method of estimation for the particle or droplet size from nanometers to millimeters. In this study, suspensions of magnetite and silica nanoparticles in high viscous media (i.e., castor oil) were characterized by ultrasound spectroscopy. Both theoretical and experimental results showed a significant difference in ultrasound attenuation coefficients between the suspensions of magnetite and silica nanoparticles. The fitting of theoretical model to experimental ultrasound spectra was used to determine the real size of objects suspended in a high viscous medium that differed from the size distributions provided by electron microscopy imaging. The ultrasound spectroscopy technique demonstrated a greater tendency of magnetic particles toward agglomeration when compared with silica particles whose sizes were obtained from the combination of experimental and theoretical ultrasonic data and were more consistent with the electron microscopy images.

Scattering theory of non-equilibrium noise and deltaTcurrent fluctuations through a quantum dot.

We consider the non-equilibrium zero frequency noise generated by a temperature gradient applied on a device composed of two normal leads separated by a quantum dot. We recall the derivation of the scattering theory for non-equilibrium noise for a general situation where both a bias voltage and a temperature gradient can coexist and put it in a historical perspective. We provide a microscopic derivation of zero frequency noise through a quantum dot based on a tight binding Hamiltonian, which constitutes a generalization of the seminal result obtained for the current in the context of the Keldysh formalism. For a single level quantum dot, the obtained transmission coefficient entering the scattering formula for the non-equilibrium noise corresponds to a Breit-Wigner resonance. We compute the delta-Tnoise as a function of the dot level position, and for a broad range of values of the dot level width, in the Breit-Wigner case, for two relevant situations which were considered recently in two separate experiments. In the regime where the two reservoir temperatures are comparable, our gradient expansion shows that the delta-Tnoise is dominated by its quadratic contribution, and is minimal close to resonance. In the opposite regime where one reservoir is much colder, the gradient expansion fails and we find the noise to be typically linear in temperature before saturating. In both situations, we conclude with a short discussion of the case where both a voltage bias and a temperature gradient are present, in order to address the potential competition with thermoelectric effects.

Structural Asymmetry of Metallic Single-Atom Contacts Detected by Current-Voltage Characteristics.

The complex behavior of the simplest atomic-scale conductors indicates that the electrode structure itself is significant in the design of future nanoscale devices. In this study, the structural asymmetry of metallic atomic contacts formed between two macroscopic Au electrodes at room temperature was investigated. Characteristic signatures of the structural asymmetries were detected by fast current-voltage (I-V) measurements with a time resolution of approximately 100 µs. Statistical analysis of more than 300,000 I-V curves obtained from more than 1000 contact-stretching processes demonstrates that the current rectification properties are correlated with the conductance of the nanocontacts. A substantial suppression of the variation in current rectification was observed for the atomic contacts with integer multiples of the conductance quantum. Statistical analysis of the time-resolved I-V curves revealed that the current rectification variations increased significantly from 500 µs onward before the breakage of the atomic contacts. Ab initio atomistic simulations of the stretching processes and corresponding I-V characteristics confirmed the magnitude of the rectification and related it to the structural asymmetries in the breakdown process of the junctions. Overall, we provide a better understanding of the interplay between geometric and electronic structures at atomically defined metal-metal interfaces by probing charge transport properties in extremely sensitive nanocontacts.

Quantum Confinement Suppressing Electronic Heat Flow below the Wiedemann-Franz Law.

The Wiedemann-Franz law states that the charge conductance and the electronic contribution to the heat conductance are proportional. This sets stringent constraints on efficiency bounds for thermoelectric applications, which seek a large charge conduction in response to a small heat flow. We present experiments based on a quantum dot formed inside a semiconducting InAs nanowire transistor, in which the heat conduction can be tuned significantly below the Wiedemann-Franz prediction. Comparison with scattering theory shows that this is caused by quantum confinement and the resulting energy-selective transport properties of the quantum dot. Our results open up perspectives for tailoring independently the heat and electrical conduction properties in semiconductor nanostructures.

Multi-Particle Interference in an Electronic Mach-Zehnder Interferometer.

The development of dynamic single-electron sources has made it possible to observe and manipulate the quantum properties of individual charge carriers in mesoscopic circuits. Here, we investigate multi-particle effects in an electronic Mach-Zehnder interferometer driven by a series of voltage pulses. To this end, we employ a Floquet scattering formalism to evaluate the interference current and the visibility in the outputs of the interferometer. An injected multi-particle state can be described by its first-order correlation function, which we decompose into a sum of elementary correlation functions that each represent a single particle. Each particle in the pulse contributes independently to the interference current, while the visibility (given by the maximal interference current) exhibits a Fraunhofer-like diffraction pattern caused by the multi-particle interference between different particles in the pulse. For a sequence of multi-particle pulses, the visibility resembles the diffraction pattern from a grid, with the role of the grid and the spacing between the slits being played by the pulses and the time delay between them. Our findings may be observed in future experiments by injecting multi-particle pulses into a Mach-Zehnder interferometer.

Simultaneous Trapping of Two Types of Particles with Focused Elegant Third-Order Hermite-Gaussian Beams.

The focusing properties of elegant third-order Hermite-Gaussian beams (TH3GBs) and the radiation forces exerted on dielectric spherical particles produced by such beams in the Rayleigh scattering regime have been theoretically studied. Numerical results indicate that the elegant TH3GBs can be used to simultaneously trap and manipulate nanosized dielectric spheres with refractive indexes lower than the surrounding medium at the focus and those with refractive indexes larger than the surrounding medium in the focal vicinity. Furthermore, by changing the radius of the beam waist, the transverse trapping range and stiffness at the focal plane can be changed.

Turbidity compensation method based on Mie scattering theory for water chemical oxygen demand determination by UV-Vis spectrometry.

In view of the problem that chemical oxygen demand (COD) measurement in water using UV-Vis spectrometry was easily affected by turbidity, this paper proposed an analytical method for determining the complex refractive index of particles in water based on Lambert-Beer's law and K-K (Kramers-Kronig) relationship. The obtained complex refractive index was used to establish the turbidity compensation model in the COD characteristic spectral region, and the COD concentration inversion were achieved by using the PLS algorithm. The results show that the turbidity compensation method based on Mie scattering theory can improve the accuracy of COD measurement by UV-Vis spectroscopy. Compared with before turbidity compensation, R2 (determination coefficient) between true values and predicted values of COD increased from 0.2274 to 0.9629, and RMSE (root mean square error) of predicted values decreased from 21.73 to 3.12 mg L-1. Compared with 350 nm PC, derivative method, and improved MSC method, the turbidity compensation method for COD measurement based on Mie scattering theory is simple, fast, and highly accurate. And the calculated spectrum can represent the scattering characteristics of the measured spectrum. The average relative error between the fitted spectrum and the original normalized spectrum in the 55 mixed solutions was 0.52%, and the maximum relative error was 6.65%. This method can be useful for online COD measurement. Graphical abstract.

Tests on the Accuracy and Scalability of the Full-Potential DFT Method Based on Multiple Scattering Theory.

We investigate a reduced scaling full-potential DFT method based on the multiple scattering theory (MST) code MuST, which is released online (https://github.com/mstsuite/MuST) very recently. First, we test the accuracy by calculating structural properties of typical body-centered cubic (BCC) metals (V, Nb, and Mo). It is shown that the calculated lattice parameters, bulk moduli, and elastic constants agree with those obtained from the VASP, WIEN2k, EMTO, and Elk codes. Second, we test the locally self-consistent multiple scattering (LSMS) mode, which achieves reduced scaling by neglecting the multiple scattering processes beyond a cut-off radius. In the case of Nb, the accuracy of 0.5 mRy/atom can be achieved with a cut-off radius of 20 Bohr, even when small deformations are imposed on the lattice. Despite that the calculation of valence states based on MST exhibits linear scaling, the whole computational procedure has an overall scaling of about O ( N 1 . 6 ) , due to the fact that the updating of Coulomb potential scales almost as O ( N 2 ) . Nevertheless, it can be still expected that MuST would provide a reliable and accessible way to large-scale first-principles simulations of metals and alloys.

Graphene vs. silica coated refractory nitrides based core-shell nanoparticles for nanoplasmonic sensing.

Plasmonic nanoparticles based on conventional metals like gold (Au) and silver (Ag) has attracted significant attention of biosensor researchers. Core-shell nanoparticles (CSNP) have shown specific advantages by virtue of unique combination of strong field enhancement and wide ranging spectral tuneability of localized surface plasmon resonances (LSPR). In view of the remarkable plasmonic properties of refractory nitrides (e.g., ZrN and TiN) like higher degree of spectral tuneability, growth compatibility, high melting point, inherent CMOS and biocompatibility etc., and reported high surface area, excellent bio-molecular compatibility, improvement in the speed, higher sensitivity in graphene, the present work assess the feasibility of graphene coated refractory nitrides based CSNP as an efficient refractive index sensor. Mie theory is employed for the theoretical analysis and simulation of such plasmonic structures. The results reported in the present work have been corroborated using COMSOL. The comparison of plasmonic properties and sensing characteristics e.g., FWHM, quality factor, sensitivity and figure of merit is presented for graphene and silica based sensors. It is reported that the sensitivity = 171.68 (nm/RIU) and figure of merit = 3.57 × 104 (nm/RIU) can be attained. The present work suggests that graphene coated refractory nitrides based core-shell structures may emerge as ultrasensitive biosensor.

Inversion of PM2.5 atmospheric refractivity profile based on AlexNet model from the perspective of electromagnetic wave propagation.

Human civilization has reached an unprecedented height, but the industrialization of economic development also brings global warming, ozone depletion, acid rain, fresh water resources crisis, energy shortage, and environmental problems. In autumn and winter, haze becomes the usual state in the modern society, and PM2.5 has been becoming an important form of air pollution. The research found that PM2.5 brings great influence to the human body or daily life. To some extent, the PM2.5 also affects the propagation of electromagnetic waves near the ground, reducing the transmission performance of electromagnetic wave. Based on Mie scattering theory, this paper qualitatively analyzed the scattering effects of PM2.5 particles on every frequency band of electromagnetic wave in daily use. Then the paper takes the satellite navigation signals as a research example, selecting university of Wyoming Davis stations in Antarctica sounding data by measuring the tropospheric atmospheric meteorological parameters (including the atmosphere pressure, geopotential height of different layers, dew point temperature, relative humidity and specific humidity, wind direction, wind speed, and temperature). The paper inversed the refractive index distribution of the troposphere based on AlexNet model and described the error quantitatively. The simulation results show that the estimated error is less than 5.1455%, proving the high accuracy of the AlexNet model. To test the influence of PM2.5, the paper takes Jiuquan, a city with serious pollution, as an example. Comparison between the inversion results and IGS products shows that high concentration of PM2.5 pollution has little influence on the inversion of refractive index profile.