Heavy Particles Research Articles

Residence Time Distribution of Non-Spherical Particles in a Continuous Rotary Drum

The motion of non-spherical particles with sharp edges, as they are commonly involved in practice, was characterized by residence time distribution (RTD) measurement in a continuous drum. Particles with two sizes, 6 and 10 mm, and two densities, 750 and 2085 kg/m3, were used in the experiments. The effects of rotation speed (3–11 rpm), incline angle (2–4°), feed rate, and mixture composition were investigated and compared to the results of other researchers on particles without sharp edges. We also fitted the RTD with an axial dispersion model to obtain a better insight into the flow behavior. MRT of non-spherical particles with sharp edges depends on ω−α similar to other shapes, while the value of alpha is higher for particles with sharp edges (0.9 < α < 1.24), especially at high incline angles. The MRT depends on incline angle, β−b, where b varies between 0.81 (at low ω) and 1.34 (at high ω), while it is close to 1 for other shapes. Feed rate has a slight effect on the MRT of particles with sharp edges and the effect of particle size diminishes when rotation speed increases. The MRT linearly increases with volume fraction of light particles in a mixture of light and heavy particles (from pure heavy to pure light particles).

Axion instability supernovae

New particles coupled to the Standard Model can equilibrate in stellar cores if they are sufficiently heavy and strongly coupled. In this work, we investigate the astrophysical consequences of such a scenario for massive stars by incorporating new contributions to the equation of state into a state of the art stellar structure code. We focus on axions in the ``cosmological triangle,'' a region of parameter space with $300\text{ }\text{ }\mathrm{keV}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}2\text{ }\text{ }\mathrm{MeV}$, ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}\ensuremath{\sim}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$ that is not presently excluded by other considerations. We find that for axion masses ${m}_{a}\ensuremath{\sim}{m}_{e}$, axion production in the core drives a new stellar instability that results in explosive nuclear burning that either drives a series of mass-shedding pulsations or completely disrupts the star resulting in a new type of optical transient---an Axion Instability Supernova. We predict that the upper black hole mass gap would be located at $37\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}\ensuremath{\le}M\ensuremath{\le}107\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}$ in these theories, a large shift down from the standard prediction, which is disfavored by the detection of the mass gap in the LIGO/Virgo/KAGRA GWTC-2 gravitational wave catalog beginning at ${46}_{\ensuremath{-}6}^{+17}\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}$. Furthermore, axion-instability supernovae are more common than pair-instability supernovae, making them excellent candidate targets for James Webb Space Telescope. The methods presented in this work can be used to investigate the astrophysical consequences of any theory of new physics that contains heavy bosonic particles of arbitrary spin. We provide the tools to facilitate such studies.

Measurement of the Higgs boson branching ratio BR(H→γγ) at a 3 TeV CLIC

In this paper we address the potential of a 3 TeV center-of-mass energy Compact Linear Collider (CLIC) to measure the branching fraction of the Higgs boson decay to two photons, $\mathrm{BR}(H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})$. Since photons are massless, the Higgs boson coupling to photons is realized through higher order processes involving heavy particles either from the Standard Model or beyond. Any deviation of the measured $\mathrm{BR}(H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})$, and consequently of the Higgs coupling ${g}_{H\ensuremath{\gamma}\ensuremath{\gamma}}$ from the predictions of the Standard Model, may indicate new physics. The Higgs decay to two photons is thus an interesting probe of the Higgs sector. This study is performed using the simulation of the detector for CLIC and by considering all relevant physics and beam-induced processes in a full reconstruction chain. It is shown that the product of the Higgs production cross section in ${W}^{+}{W}^{\ensuremath{-}}$ fusion and $\mathrm{BR}(H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})$ can be measured with a relative statistical uncertainty of 5.5%, assuming the integrated luminosity of $5\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$ and unpolarized beams.

Feasibility of an automatic ultrasonographic image acquisition system associated with an artificial intelligence algorithm for real-time monitoring of cardiac motion during cardiac radio-ablation

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This publication is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 954783. Background Stereotactic arrhythmia radio-ablation (STAR) is a promising strategy for the non-invasive treatment of ventricular arrhythmias (VA). The management of the cardio-respiratory motion of the target and the reduction of the uncertainties related to patients’ positioning are two of the main challenges that STAR has to overcome. A prototype of a system was developed that can automatically acquire and interpret echocardiographic images using an artificial intelligence (AI) algorithm to calculate cardiac displacement in real-time. Purpose To evaluate the feasibility of this automatic acquisition system in patients with a history of VA. Methods We conducted a single center, feasibility study enrolling consecutive patients with a history of VA. Echocardiographic images were automatically acquired from the parasternal and apical views with a dedicated probe. The system was designed to hold the probe fixed to the chest in the supine position during both free-breathing and short expiratory breath-hold sequences, to simulate STAR treatment. The primary endpoint was the percentage of patients reaching a score ≥2 in a multi-parametric assessment evaluating the quality of automatically acquired images in terms of: A - allowing a proper identification of the cardiac cycle phase using the AI algorithm, B - allowing a correct measurement of the heart displacement by the AI algorithm, C - ability to visually distinguish typical cardiac structures, and D - stability of the image throughout the respiration cycle. Moreover, we investigated the potential impact of clinical and demographic characteristics on achieving the primary outcome. Results From May to September 2021, we enrolled 24 patients (63±14 years, 21% females). All of them had a history of VA and 21 (88%) had an ICD. Eight patients (33%) had coronary artery disease, 12 (50%) had non-ischemic cardiomyopathy, and 3 had idiopathic VA. Parasternal as well as apical images were obtained from all patients except from one, in whom parasternal view could not be collected due to the patient’s inability to maintain the supine position. The primary outcome was achieved in 23 patients (96%) for the apical view, in 20 patients (87%) for the parasternal view, and in all patients in at least one of the two views. The images quality was maximal (i.e. score=4) in at least one of the two windows in 19 patients (79%). Atrial fibrillation arrhythmia was the only clinical characteristics associated with a poor score outcome in both imaging windows (apical p=0,022, parasternal p=0,014). Conclusion An automatic ultrasonographic image acquisition system associated with an AI algorithm is feasible for real-time monitoring of cardiac motion in patients with a history of VA. The possibility of real-time, non-invasive monitoring of cardiac position would lead to a significant improvement in the quality and safety of STAR treatment, particularly in case of treatment with heavy particles such as protons and carbon ions.

Wilson coefficients and natural zeros from the on-shell viewpoint

We show how to simplify the calculation of the finite contributions from heavy particles to EFT Wilson coefficients by using on-shell methods. We apply the technique to the one-loop calculation of g − 2 and Hγγ, showing how finite contributions can be obtained from the product of tree-level amplitudes. In certain cases, due to a parity symmetry of these amplitudes, the total contribution adds up to zero, as previously found in the literature. Our method allows to search for new natural zeros, as well as to obtain non-zero contributions in a straightforward way.

Role of the hierarchy of coherent structures in the transport of heavy small particles in turbulent channel flow

To investigate the transport of heavy small particles (inertial particles) in high-Reynolds- number wall turbulence, we conduct direct numerical simulations of inertial particles in turbulent channel flow at the friction Reynolds number $Re_\tau =1000$ . In the statistically steady state, particles distribute inhomogeneously; particles with different relaxation times form voids with different sizes in the bulk of the flow, whereas they form streak-like clusters with different widths along the streamwise direction. To explore the origin of the multiscale voids and clusters of particles, we identify objectively the axes of tubular vortices and the spines of streaks with different sizes. These identifications enable us to show quantitatively that (i) vortices sweep out the particles of the relaxation time comparable with their turnover time, irrespective of their size and existing height, and that, among these particles, (ii) those swept out by wall-detached tubular vortices form clusters isotropically around them, whereas (iii) those swept out by wall-attached vortices are attracted by a nearby low-speed streak. These explain the reason why the multiscale clusterings are well described in terms of the local Stokes number defined by the turnover time of multiscale vortices. Furthermore, these descriptions of the particle transport give us a clear view to understand velocity statistics and wall-deposition mechanism of inertial particles in high-Reynolds-number wall turbulence.

Cointeracting dark matter and conformally coupled light scalars

The increasing observational pressure on the standard cosmological model motivates analyses going beyond the paradigm of the collisionless cold dark matter (DM). Since the only clear evidence for the existence of DM is based on gravitational interactions, it seems particularly fitting to study them in this sector where extensions to the standard model can be naturally introduced. A promising avenue can be obtained using modifications of the space-time metric coupled to DM and induced by the presence of a new ultralight scalar field $\ensuremath{\phi}$. The $\ensuremath{\phi}$ field can contribute to the DM density and can couple all the matter species universally, including additional heavy DM particles. We present a simple two-component DM model employing derivative conformal interactions between the two DM species. This can simultaneously (1) guarantee the necessary symmetries to stabilize the dark species, (2) predict a subdominant thermal relic density of the heavy DM component, and (3) alleviate small-scale structure tensions of the cold DM scenario due to the possible cointeractions in the dark sector. The scenario is highly predictive with future observational prospects ranging from the Large Hadron Collider to gravitational-wave searches and can be generalized to more rich and realistic dark sector models.

Scalar field couplings to quadratic curvature and decay into gravitons

Any field, even if it lives in a completely hidden sector, interacts with the visible sector at least via the gravitational interaction. In this paper, we show that a scalar field in such a hidden sector generically couples to the quadratic curvature via dimension five operators, i.e., ϕR2, ϕRμνRμν, ϕRμνρσRμνρσ, ϕRμνρσ {overset{sim }{R}}^{mu nu rho sigma} , because they can emerge if there exist particles heavier than it. We derive these scalar couplings to the quadratic curvature by integrating out heavy particles in a systematic manner. Such couplings are of phenomenological interest since some of them induce the scalar decay into the graviton pair. We point out that the decay of a scalar field can produce a substantial amount of the stochastic cosmic graviton background at high frequency since the suppression scale of these operators is given by the mass of heavy particles not by the Planck scale. The resultant graviton spectrum is computed in some concrete models.

The Unified Approach of Ionizing Radiation on Biological Matter: Action of Heavy Charged Particles on Mammalian Cells

Damaging effects to mammalian cells by heavy charged particles have been realized in terms of the mean free path for linear primary ionization (the spacing of ionizing events along the charged particle tracks) using in vitro radiobiological experimentation data. Damage is found to be optimum when the mean free path for linear primary ionization along the tracks in the cell nucleus matches the mean chord length of approximately 1.8 nm through a DNA segment. A simple semi-theoretical model is proposed to define absolute biological effectiveness based on effect inactivation cross section s (mm2) which is interrelated to the mean free path for linear primary ionization l. For heavy charged particles, the model shows a saturation region for the effect cross section, ss = 60 mm2 for l ≤ 1.8 nm. The model explains the mechanisms leading to cell death via DNA strand scissions. In the saturation region, double strand breaks of the DNA are predominant, unrepaired or mismatched repair processes lead to maximum damage. At higher mean free path; l > 1.8 nm, single strand breaks of the DNA is the main basic mechanism and thus repairable processes are possible.

Experimental Study of a Rotating Electrode Plasma Reactor for Hydrogen Production from Liquid Petroleum Gas Conversion

In this work, a new plasma reactor operating with a butane/propane (C4H10/C3H8) gaseous mixture, designed for hydrogen molecule production, was experimentally studied. This reactor is based on a rotating electrode, biased by an AC high voltage. The plasma discharge was investigated for different AC voltages, rotational frequencies, and gas flow rates. A discharge in the filamentary mode was produced as proved by the electrical characterization. Gas Chromatography (GC) was applied to study the LPG remediation. The maximum conversion factors of 70% and 60% were found for the C3H8 and C4H10, respectively, with an H2 selectivity of 98%. Hydrogen atomic lines from the Balmer series and various molecular bands were detected by optical emission spectroscopy (OES). The stark broadening of the Hα Balmer line was used for the determination of the electron density. The spectra simulation of the C2 band was permitted to obtain the gas temperature while the first five lines of hydrogen atoms were used to calculate the electron temperature. A non-equilibrium plasma with two very different temperatures for electrons and heavy particles was found. The spectroscopic study allowed us to explain the experimental results of the LPG conversion and its dependence on the plasma conditions, resulting in optimizing the H2 formation.

Optical and thermal luminescence efficiencies of BeO exposed to low-energy protons and carbon ions

Optically stimulated luminescence (OSL) and thermoluminescence (TL) are well-described phenomena utilized to measure the absorbed dose of crystalline materials. The techniques are used to monitor low linear energy transfer (LET) radiation (β, γ) as well as high-LET heavy charged particles (HCPs). Detector efficiency ƞdet, defined as the ratio of the luminescence per unit dose from a non-reference radiation field compared to the identical quantity from the reference field, is particle and energy dependent. The responses of BeO ceramics exposed to low-energy HCPs were investigated in this work. Dosimeters were bombarded with 1, 2, and 4 MeV protons, as well as 2 and 4 MeV carbon ions; these radiation qualities constitute a mean LET range of 37.6 keV/μm - 628 keV/μm and were realized using the 2 MV tandem Pelletron particle accelerator at East Carolina University. Each dosimeter was calibrated using a dose response constructed with a90Sr/90Y β source, which was calibrated against a137Cs γ source. This enabled ƞdet to be calculated. It was observed that optical and thermal signal shape and magnitude depend on the mean LET. Furthermore, thermal efficiencies are significantly higher than optical efficiencies for all ions investigated.

Clustering of fast gyrotactic particles in low-Reynolds-number flow.

Systems of particles in turbulent flows exhibit clustering where particles form patches in certain regions of space. Previous studies have shown that motile particles accumulate inside the vortices and in downwelling regions, while light and heavy non-motile particles accumulate inside and outside the vortices, respectively. While strong clustering is generated in regions of high vorticity, clustering of motile particles is still observed in fluid flows where vortices are short-lived. In this study, we investigate the clustering of fast swimming particles in a low-Reynolds-number turbulent flow and characterize the probability distributions of particle speed and acceleration and their influence on particle clustering. We simulate gyrotactic swimming particles in a cubic system with homogeneous and isotropic turbulent flow. Here, the swimming velocity explored is relatively faster than what has been explored in other reports. The fluid flow is produced by conducting a direct numerical simulation of the Navier-Stokes equation. In contrast with the previous results, our results show that swimming particles can accumulate outside the vortices, and clustering is dictated by the swimming number and is invariant with the stability number. We have also found that highly clustered particles are sufficiently characterized by their acceleration, where the increase in the acceleration frequency distribution of the most clustered particles suggests a direct influence of acceleration on clustering. Furthermore, the acceleration of the most clustered particles resides in acceleration values where a cross-over in the acceleration PDFs are observed, an indicator that particle acceleration generates clustering. Our findings on motile particles clustering can be applied to understanding the behavior of faster natural or artificial swimmers.

Predicting the composition of W-B-C coatings sputtered from industrial cylindrical segmented target

Computational methods have been gaining more and more attention as they provide a powerful tool for increasing efficiency in the industrial use of magnetron sputtering and provide results from which experimental work benefits. This work presents an approach for the prediction of the composition and the deposition rate of the coatings. The combination of SDTrimSP and SiMTra provides a framework for the simulation of the deposition process. The chemical composition and the deposition rate of industrially sputtered W-B-C coatings were investigated. An industrial batch coater with a complex geometry was modelled. A cylindrical rotating sputter source was mounted with a segmented target composed of W, B4C, and C segments. The simulated chemical composition and the relative deposition rate were verified and validated by experiments. A correlation between the chemical composition and target segment placement is presented, and the influence of substrate movement on the chemical composition is discussed. A single-axis rotation of the substrate placed on an industrial carousel causes a lowering of the content of tungsten in the coatings in comparison to statically placed substrates in front of the sputter source. The simulations uncover the distinct trajectories of the heavy and light particles. The different transport of particles from target to substrate results in the observed shift of chemical composition and also explains the inherent nanolayering of the non-reactively deposited coatings in the industrial batch coater.

Hybrid numerical simulation of the generation and distribution characteristics of SF6 heavy particles under different DC PD energies

To investigate the decomposition law of SF6 under negative direct current partial discharge (PD) at different energies, a SF6 PD hybrid numerical model based on fluid dynamics and plasma chemical reaction models, in which 14 particle species and 24 chemical reactions are considered, is proposed. The effectiveness of the proposed model is validated with the current pulse waveform and the V–I discharge curve obtained by experiment. The influence of discharge energy on SF6 PD characteristic quantities and SF6 decomposition products is investigated with simulation and experiment. The results show that most of the discharge area of SF6 is neutral, and the cation clouds only exist in the ionosphere (4.79–5 mm). With the increase in applied voltage, the electric field intensity of the needle plate gap does not increase completely and even decreases in some areas. Moreover, different from the traditional opinion, the generation of SO2F2 under PD is mainly generated by the hydrolysis reaction of SOF4, which is formed by [SF5], [SF4], and [OH], [O]. The reaction path of [SF2] with O2 is not important. Thus, c(SO2F2)/c(SOF2 + SO2) can be used as the energy characteristic component ratio because of its ability to represent the low-fluorine sulfide ratio n([SF5])/n([SF4]).

A versatile setup for studying size and charge-state selected polyanionic nanoparticles.

Using the example of metal clusters, an experimental setup and procedure is presented, which allows for the generation of size and charge-state selected polyanions from monoanions in a molecular beam. As a characteristic feature of this modular setup, the further charging process via sequential electron attachment within a three-state digital trap takes place after mass-selection. In contrast to other approaches, the rf-based concept permits access to heavy particles. The procedure is highly flexible with respect to the preparation process and potentially suitable for a wide variety of anionic species. By adjusting the storage conditions, i.e., the radio frequency, to the change in the mass-to-charge ratio, we succeeded in producing clusters in highly negative charge states, i.e., Ag800 7-. The capabilities of the setup are demonstrated by experiments extracting electronic and optical properties of polyanionic metal clusters by analyzing the corresponding photoelectron spectra.

Analysis of Arc Electron and Heavy Particle Temperature Distribution with Lateral Flow Velocity for Elucidation of Re-strike

Analysis of Arc Electron and Heavy Particle Temperature Distribution with Lateral Flow Velocity for Elucidation of Re-strike

A Boronated Derivative of Temozolomide Showing Enhanced Efficacy in Boron Neutron Capture Therapy of Glioblastoma.

There is an incontestable need for improved treatment modality for glioblastoma due to its extraordinary resistance to traditional chemoradiation therapy. Boron neutron capture therapy (BNCT) may play a role in the future. We designed and synthesized a 10B-boronated derivative of temozolomide, TMZB. BNCT was carried out with a total neutron radiation fluence of 2.4 ± 0.3 × 1011 n/cm2. The effects of TMZB in BNCT were measured with a clonogenic cell survival assay in vitro and PET/CT imaging in vivo. Then, 10B-boronated phenylalanine (BPA) was tested in parallel with TMZB for comparison. The IC50 of TMZB for the cytotoxicity of clonogenic cells in HS683 was 0.208 mM, which is comparable to the IC50 of temozolomide at 0.213 mM. In BNCT treatment, 0.243 mM TMZB caused 91.2% ± 6.4% of clonogenic cell death, while 0.239 mM BPA eliminated 63.7% ± 6.3% of clonogenic cells. TMZB had a tumor-to-normal brain ratio of 2.9 ± 1.1 and a tumor-to-blood ratio of 3.8 ± 0.2 in a mouse glioblastoma model. BNCT with TMZB in this model caused 58.2% tumor shrinkage at 31 days after neutron irradiation, while the number for BPA was 35.2%. Therefore, by combining the effects of chemotherapy from temozolomide and radiotherapy with heavy charged particles from BNCT, TMZB-based BNCT exhibited promising potential for therapeutic applications in glioblastoma treatment.

Applications of surface-enhanced Raman spectroscopy in environmental detection.

As the human population grows, the anthropogenic impacts from various agricultural and industrial processes produce unwanted contaminants in the environment. The accurate, sensitive and rapid detection of such contaminants is vital for human health and safety. Surface-enhanced Raman spectroscopy (SERS) is a valuable analytical tool with wide applications in environmental contaminant monitoring. The aim of this review is to summarize recent advancements within SERS research as it applies to environmental detection, with a focus on research published or accessible from January 2021 through December 2021 including early-access publications. Our goal is to provide a wide breadth of information that can be used to provide background knowledge of the field, as well as inform and encourage further development of SERS techniques in protecting environmental quality and safety. Specifically, we highlight the characteristics of effective SERS nanosubstrates, and explore methods for the SERS detection of inorganic, organic, and biological contaminants including heavy metals, pharmaceuticals, plastic particles, synthetic dyes, pesticides, viruses, bacteria and mycotoxins. We also discuss the current limitations of SERS technologies in environmental detection and propose several avenues for future investigation. We encourage researchers to fill in the identified gaps so that SERS can be implemented in a real-world environment more effectively and efficiently, ultimately providing reliable and timely data to help and make science-based strategies and policies to protect environmental safety and public health.

A dynamic particle scale-driven interphase force model for water-sand two-phase flow in hydraulic machinery and systems

The water–sand two-phase flow in hydraulic machinery and systems has a strong inter-phase interaction due to the effect of rotating turbulence, but many engineering computations do not consider turbulent effects into the interphase force, affecting the prediction accuracy of inner flow characteristics. The objective of this paper is to provide a new dynamic particle scale-driven interphase force model, and its notable features are shown as follows. In the Euler-Euler framework, the time-scale-driven hybrid URANS/LES model is introduced to extend the resolution scale of rotating turbulence. On this basis, (1) the turbulent factor and the wall factor based on a dynamic particle scale are determined to reflect the effects of turbulent fluctuation and wall surface on the drag force; (2) a new turbulent dispersion force model based on a dynamic particle scale is proposed to characterize the following behavior of heavy particles and their interaction with energetic eddies. Four typical flow cases of sediment-laden flows are tested. It is found that the eddy viscosity of water turbulence is effectively adjusted, thereby allowing more turbulent vortices to be resolved on the same URANS grids. The settling motion and inertial motion of sand are reasonably controlled by the improved interphase force model, thereby giving the prediction results of two-phase flow fields with higher accuracy. The new model improves the simulation accuracy of water–sand two-phase flow with rotation and curvature while does not significantly increase the computational cost, which enables efficient engineering computations of water–sand two-phase flow in hydraulic machinery and systems.

Analyzing Cathode and Anode Spot Movements of Atmospheric Arc Plasma in Parallel Electrodes Using Thermal Field Theory and Thermal Nonequilibrium Model

It is necessary to elucidate the mechanism of atmospheric arc plasma movement and the variation in its physical properties for constructing an accurate virtual model while using digital twin technology to design a next‐generation direct current circuit breaker. In this study, the calculation setting for considering the thermal nonequilibrium effect on an electrode surface was established. Moreover, the thermal field theory was employed for simulating the cathode spot movement and a thermal nonequilibrium model was implemented for analyzing the triggering factor of the re‐strike phenomenon occurrence on the anode surface. It was found that heavy particles (ions and neutral particles) were transported forward by the cathode jet and not only caused an increment in the electrical conductivity on the anode surface, but also increased the electric field between the arc column and the anode surface. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.