bluuebunny/crossref_metadata_2025 huggingface dataset:
An experimental platform for studying the radiation effects of laser accelerated protons on mammalian cells
Authors: Ehlert J. , Piel M. , Boege F. , Cerchez M. , Haas R. , Iliakis G. E. , Prasad R. , Willi O. , Monzel C.
Published: June 2021

An experimental platform was designed to study the effects of laser accelerated protons (LAPs) on mammalian cells. The protons, in the MeV energy range, originate from the rear side of a thin 5 µm Ti foil target following the interaction with a high power laser pulse and are accelerated by the target normal sheath mechanism. A tape Ti foil target was developed, allowing a shot repetition rate of up to 5 Hz, which corresponds to the rate of the laser system. A dipole magnet arrangement was used for energy dispersion and to separate the proton burst from electrons and x rays. The absorbed radiation dose at the cell port was measured with CR39 plastic detectors and calibrated imaging plates. An epifluorescence microscope with compact open-beam optics was developed to image live cells and their spatiotemporal properties during and after irradiation. To demonstrate the functionality of all components of the platform, biological proof of concept experiments were carried out using two suspension (Jurkat and Ramos) and two adherent (HeLa and A-549) cell lines. A multitude of biological procedures and analytical techniques were established on-site or in laboratories nearby. For example, we analyzed DNA double-strand break (DSB) induction and repair by detecting the γH2A.X signal by fluorescence microscopy and flow cytometry. The observed dose-dependent increase in DSB induction confirms that DNA damage is induced in cells after exposure to LAPs.
Inverse design of locally resonant metamaterial with anisotropic mass density for perfect transmodal Fabry–Pérot interference
Authors: Yang Xiongwei , Chai Yijun , Geng Qian , Li Yueming
Published: June 2021

To realize extraordinary wave phenomena, metamaterials need to attain unique effective material properties. In this work, we propose an inverse design strategy for metamaterials with specific anisotropic EMD (effective mass density). Although the conventional inverse homogenization technique has been extended to various fields, few works have been published to explore the inverse realization of an EMD tensor, each component of which is supposed to gain a given value at a target frequency. To this end, we propose a calculation scheme, in which the EMD tensor can be calculated in a much similar way to the homogenized static stiffness. Therefore, the scheme is quite convenient for sensitivity analysis. The coating layer interfacing the core and matrix is chosen as the design region because it directly determines the motion of the core. The matrix layout, which not only contributes to the stiffness of the metamaterial but also highly affects the core's local motion, is chosen carefully. The perfect transmodal Fabry–Pérot interference phenomenon is considered in this work, and through several numerical examples, the phenomenon is ideally realized. The proposed design strategy could be critically useful in designing locally resonant metamaterials with general anisotropy.
Relaxation of strongly coupled binary ionic mixtures in the coupled mode regime
Authors: Silvestri Luciano G. , Sprenkle R. Tucker , Bergeson Scott D. , Murillo Michael S.
Published: June 2021

Understanding ion transport in plasma mixtures is essential for optimizing the energy balance in high-energy-density systems. In this paper, we focus on one transport property, ion–ion temperature relaxation in a strongly coupled plasma mixture. We review the physics of temperature relaxation and derive a general temperature relaxation equation that includes dynamical correlations. We demonstrate the fidelity of three popular kinetic models that include only static correlations by comparing them to data from molecular dynamics simulations. We verify the simulations by comparing with laboratory data from ultracold neutral plasmas. By comparing our simulations with high fidelity kinetic models, we reveal the importance of dynamical correlations in collisional relaxation processes. These correlations become increasingly significant as the ion mass ratio in a binary mixture approaches unity.
Synchronization of chiral vortex nano-oscillators
Authors: Zeng Zhiyang , Luo Zhaochu , Heyderman Laura J. , Kim Joo-Von , Hrabec Aleš
Published: June 2021

The development of spintronic oscillators is driven by their potential applications in radio frequency telecommunication and neuromorphic computing. In this work, we propose a spintronic oscillator based on the chiral coupling in thin magnetic films with patterned anisotropy. With an in-plane magnetized disk imprinted on an out-of-plane magnetized slab, the oscillator takes a polar vortex-like magnetic structure in the disk stabilized by a strong Dzyaloshinskii–Moriya interaction. By means of micromagnetic simulations, we investigate its dynamic properties under applied spin current, and by placing an ensemble of oscillators in the near vicinity, we demonstrate their synchronization with different resonant frequencies. Finally, we show their potential application in neuromorphic computing using a network with six oscillators.
Quantum W1+∞ subalgebras of BCD type and symmetric polynomials
Authors: Bourgine Jean-Emile
Published: June 2021

The infinite affine Lie algebras of type ABCD, also called gl̂(∞), ô(∞), and sp̂(∞), are equivalent to subalgebras of the quantum W1+∞ algebras. They have well-known representations on the Fock space of a Dirac fermion (Â∞), a Majorana fermion (B̂∞ and D̂∞), or a symplectic boson (Ĉ∞). Explicit formulas for the action of the quantum W1+∞ subalgebras on the Fock states are proposed for each representation. These formulas are the equivalent of the vertical presentation of the quantum toroidal gl(1) algebra Fock representation. They provide an alternative to the fermionic and bosonic expressions of the horizontal presentation. Furthermore, these algebras are known to have a deep connection with symmetric polynomials. The action of the quantum W1+∞ generators leads to the derivation of Pieri-like rules and q-difference equations for these polynomials. In the specific case of B̂∞, a q-difference equation is obtained for Q-Schur polynomials indexed by strict partitions.
Pentagonal prism spherical hohlraums for OMEGA
Authors: Wang W. Y. , Craxton R. S.
Published: June 2021

A new configuration is proposed for spherical hohlraums on OMEGA in which seven laser entrance holes (LEHs) are used—five around the equator and one at each pole [Farmer et al., Phys. Plasmas 26, 032701 (2019)]. This is known as the PEPR (pentagonal prism) hohlraum. A new view-factor code LORE is used to model the PEPR hohlraum and compare its performance with tetrahedral hohlraums shot on OMEGA. With optimization of beam pointings, the PEPR hohlraum produces a nonuniformity ranging from 1.1% (rms) at low albedos to 0.6% at high albedos. The tradeoffs between hohlraum-to-capsule ratio, uniformity, and background radiation temperature have been explored, and it has been shown that larger LEH radii on the poles can result in a modest improvement in uniformity. The seven-hole PEPR hohlraum is well matched to the OMEGA symmetry and promises to provide insight into the performance of spherical hohlraums including octahedral (six-LEH) hohlraums.
CTRAMER: An open-source software package for correlating interfacial charge transfer rate constants with donor/acceptor geometries in organic photovoltaic materials
Authors: Tinnin Jacob , Aksu Huseyin , Tong Zhengqing , Zhang Pengzhi , Geva Eitan , Dunietz Barry D. , Sun Xiang , Cheung Margaret S.
Published: June 2021

In this paper, we present CTRAMER (Charge-Transfer RAtes from Molecular dynamics, Electronic structure, and Rate theory)—an open-source software package for calculating interfacial charge-transfer (CT) rate constants in organic photovoltaic (OPV) materials based on ab initio calculations and molecular dynamics simulations. The software is based on identifying representative donor/acceptor geometries within interfacial structures obtained from molecular dynamics simulation of donor/acceptor blends and calculating the corresponding Fermi's golden rule CT rate constants within the framework of the linearized-semiclassical approximation. While the methods used are well established, the integration of these state-of-the-art tools originating from different disciplines to study photoinduced CT processes with explicit treatment of the environment, in our opinion, makes this package unique and innovative. The software also provides tools for investigating other observables of interest. After outlining the features and implementation details, the usage and performance of the software are demonstrated with results from an example OPV system.
Memory effects in a gas of viscoelastic particles
Authors: Mompó E. , López-Castaño M. A. , Lasanta A. , Vega Reyes F. , Torrente A.
Published: June 2021

We study a granular gas of viscoelastic particles (kinetic energy loss upon collision is a function of the particles' relative velocities at impact) subject to a stochastic thermostat. We show that the system displays anomalous cooling and heating rates during thermal relaxation processes, this causing the emergence of thermal memory. In particular, a significant Mpemba effect is present, i.e., an initially hotter/cooler granular gas can cool down/heat up faster than an in comparison cooler/hotter granular gas. Moreover, a Kovacs effect is also observed, i.e., a nonmonotonic relaxation of the granular temperature—if the gas undergoes certain sudden temperature changes before fixing its value. Our results show that both memory effects have distinct features, very different and eventually opposed to those reported in theory for granular fluids under simpler collisional models. We study our system via three independent methods: approximate solution of the kinetic equation time evolution and computer simulations (both molecular dynamics simulations and direct simulation Monte Carlo method), finding good agreement between them.
Analytical drain current and performance evaluation for inversion type InGaAs gate-all-around MOSFET
Authors: Rahman I. K. M. Reaz , Khan Md. Irfan , Khosru Quazi D. M.
Published: June 2021

This paper presents an analytical investigation of the drain current model for symmetric short channel InGaAs gate-all-around (GAA) MOSFETs valid from depletion to strong inversion using a continuous expression. The development of the core model is facilitated by the solution of the quasi-2D Poisson equation in the doped channel, accounting for interface trap defects and fixed oxide charges. Correction to short channel effects such as threshold voltage roll-off, drain induced barrier lowering, and subthreshold slope degradation is later introduced, complemented with channel length modulation, velocity saturation, and mobility degradation from surface roughness, leading to accurate mobile charge density for electrostatic capacitance–voltage and transport characterization. The effect of physical process parameters such as fin width, oxide thickness, and channel length scaling is thoroughly investigated in both on and off states of the transistor. The robustness of the model is reflected by the precise match with published experimental reports in the literature. An Ron of 1160 Ω μm is obtained from output characteristics and a switching efficiency improvement of 2.5 times is estimated by incorporating a high-κ dielectric into the GAA transistor. Numerical 3D simulations from TCAD corroborate the validity of the proposed model in all regions of operation.
Evaluating the anharmonicity contributions to the molecular excited state internal conversion rates with finite temperature TD-DMRG
Authors: Wang Yuanheng , Ren Jiajun , Shuai Zhigang
Published: June 2021

In this work, we propose a new method to calculate molecular nonradiative electronic relaxation rates based on the numerically exact time-dependent density matrix renormalization group theory. This method could go beyond the existing frameworks under the harmonic approximation (HA) of the potential energy surface (PES) so that the anharmonic effect could be considered, which is of vital importance when the electronic energy gap is much larger than the vibrational frequency. We calculate the internal conversion (IC) rates in a two-mode model with Morse potential to investigate the validity of HA. We find that HA is unsatisfactory unless only the lowest several vibrational states of the lower electronic state are involved in the transition process when the adiabatic excitation energy is relatively low. As the excitation energy increases, HA first underestimates and then overestimates the IC rates when the excited state PES shifts toward the dissociative side of the ground state PES. On the contrary, HA slightly overestimates the IC rates when the excited state PES shifts toward the repulsive side. In both cases, a higher temperature enlarges the error of HA. As a real example to demonstrate the effectiveness and scalability of the method, we calculate the IC rates of azulene from S1 to S0 on the ab initio anharmonic PES approximated by the one-mode representation. The calculated IC rates of azulene under HA are consistent with the analytically exact results. The rates on the anharmonic PES are 30%–40% higher than the rates under HA.
Geometrical considerations to discern the transverse spin Nernst effect in an all-metallic permalloy/platinum bilayer system
Authors: Park Seondo , Park Yun Daniel
Published: June 2021

Most spin caloritronics research utilizes thin films on substrates with an in-plane heat flow, where an unintended out-of-plane thermal gradient may develop by heat dissipation through the substrate. In systems exploiting metallic ferromagnets to generate or detect spin currents, such out-of-plane thermal gradients might confuse the signal via undesirable thermomagnetic effects, such as the anomalous Nernst effect. Here, we report direct measurement of the spin current created by the spin Nernst effect in platinum, using ferromagnetic metal contacts as spin accumulation detectors. By comparing the voltage measured transverse and longitudinal to the thermal gradient, we find that the device geometry is crucial in all-metallic systems. Exploiting the orthogonality in the angular dependence on the external magnetic field of the transversely measured voltage, we quantitatively separate the spin Nernst signal from the parasitic anomalous Nernst voltage, which are of the same order of magnitude. As a result, we estimate the spin Nernst angle of platinum to be comparable to the spin Hall angle in magnitude with an opposite sign.
Electric quadrupole transitions in carbon dioxide
Authors: Yachmenev Andrey , Campargue Alain , Yurchenko Sergei N. , Küpper Jochen , Tennyson Jonathan
Published: June 2021

Recent advances in high sensitivity spectroscopy have made it possible, in combination with accurate theoretical predictions, to observe, for the first time, very weak electric quadrupole transitions in a polar polyatomic molecule of water. Here, we present accurate theoretical predictions of the complete quadrupole rovibrational spectrum of a non-polar molecule CO2, important in atmospheric and astrophysical applications. Our predictions are validated by recent cavity enhanced absorption spectroscopy measurements and are used to assign few weak features in the recent ExoMars Atmospheric Chemistry Suite mid-infrared spectroscopic observations of the Martian atmosphere. Predicted quadrupole transitions appear in some of the mid-infrared CO2 and water vapor transparency regions, making them important for detection and characterization of the minor absorbers in water- and CO2-rich environments, such as those present in the atmospheres of Earth, Venus, and Mars.
Eulerian formulation for the triboelectric charging of polydisperse powder flows
Authors: Zeybek Metin , Grosshans Holger
Published: June 2021

We propose an Eulerian formulation for the triboelectric charging of powder flows. Recently, continuum descriptions of the charging of monodisperse and bidisperse powder appeared. Now, we propose the first Eulerian formulation for this type of flows that can fully account for polydisperse particle size distributions. To this end, the joint particle size, velocity, and charge distribution function are solved through the direct quadrature method of moments. The newly established approach includes the uptake of electrostatic charge by the particles when contacting a solid wall and the exchange of charge in-between particles during collisions. The electrostatic field induced by the charge of the particles and the drag forces of the surrounding gas affects the particle dynamics. Test cases of two-dimensional steady channel flows demonstrate the charging of the flow from the walls toward the center and in the downstream direction. Further, the method predicts the effect of variations of the particle size and initial velocity distribution and the charge diffusion coefficient. The ability to handle polydispersity is a step toward the simulation of the electric charge buildup of real powder flows in full-scale technical applications.
Robust ferromagnetism in single-atom-thick ternary chromium carbonitride CrN4C2
Authors: Liu Dapeng , Zhang Shuo , Gao Miao , Yan Xun-Wang , Xie Z. Y.
Published: June 2021

The design and exploration of ferromagnetic two-dimensional materials is an important research topic due to their potential applications in spintronic devices. By the first-principles calculations, we examine the structural stability and the electronic properties of transition metal carbonitrides MN4C2 (M = 3d transition metals) and find out that chromium carbonitride CrN4C2 is a ferromagnetic two-dimensional material. CrN4C2 is made up of CrN4 unit and C2 dimer, stacked alternatively to form a planar single-atom-thick sheet. For the Cr 3d electronic states, there is a complete spin splitting between Cr 3d spin-up and spin-down states, leading to a large moment up to 3.76 μB around Cr atoms. The magnetic interaction among Cr atoms can be described by Ising model, and the ferromagnetic couplings are energetically favorable, which indicates that there must be a ferromagnetic phase transition and a ferromagnetic ground state. The Curie temperature of CrN4C2 is evaluated to be 226.6 K in terms of the tensor renormalization group method. With Hubbard U of 3 eV and 5 eV being considered, the Curie temperatures reach up to 331.1 and 283.6 K. Consequently, our results demonstrate that CrN4C2 is a graphene-like two-dimensional material with robust ferromagnetism.
Effect of uniform laser irradiation on thermal response of temperature sensitive structures
Authors: Liu Jing-yi , Long Lian-chun , Zhang Chao-ya
Published: June 2021

The analysis of the temperature distribution, thermal deformation, and stress of thin plate structures attributed to laser irradiation is of great significance because the thermal effects substantially affect a suite of properties. In this paper, based on the theory of thin plate thermal bending, the analytical expressions of deflection and thermal stress in the local uniform temperature field are derived and compared with the numerical simulation results. The influence of the boundary constraint and irradiation factor on the thermal response is analyzed. Considering the temperature sensitivity of material parameters, the effect of heat flux density on the structural response is analyzed by the finite element method. The results show that the analytical solutions of the circular plate deflections are consistent with the numerical results. The maximum values of both deflection and compressive stresses occur at the center. The maximum tensile stress occurs near the boundary of the spot. In the heat affected zone (HAZ), the deflection of a point shows a trend of the Gaussian decrease with the increase in the distance to the center, while the thermal stress almost does not change with the distance. Outside the HAZ, both deflection and thermal stress are related to the boundary conditions and irradiation factors. Considering that the material parameters change with temperature, the HAZ area, deflection, and von Mises stress are positively correlated with the heat flux density, but the change patterns are different.
Identification, management and care of refugee patients at a metropolitan public health service: a healthcare worker perspective
Authors: Novak Anna , Hitch Danielle , Bongiovanni Lyn , Mucic Angela
Published: June 2021

Objective To describe the perceptions of healthcare workers employed at a metropolitan public health service, with respect to how they identify, manage and care for refugee patients. Methods This study surveyed healthcare workers using a cross-sectional, mixed methods descriptive design, which partially replicates a previous Australian study. A total of 215 responses to a brief online survey were received (n = 48 medical, n = 100 nursing and midwifery, n = 50 allied health, n = 4 other). Results Nurses and allied health respondents were more likely to record working with refugees rarely or never (P = 0.00). Most respondents (70.3%) identified no negative effects from working with refugees, and perceived this patient group enhanced (71.3%) their work. Insufficient identification, interpreter availability, education, healthcare worker capacity and providing culturally specific treatment were all identified as potential service barriers. Allied health respondents were more likely to report low confidence about working with refugees in general (P = 0.04). Respondents with more than 10 years’ experience with refugees (P = 0.02), and those with good self-perceived awareness of community services (P = 0.01), were more confident in their ability to manage social issues. Conclusions This study suggests that contextual factors influence the perceptions of healthcare workers who provide care to refugee patients; however, communication, health literacy and healthcare worker capacity were consistently raised as key issues when working with refugees. What is known about the topic? Refugee and asylum seeker patients may present with complex health needs to any part of the Australian health system. The majority of previous research has occurred in primary care settings. What does this paper add? This study adds an acute and subacute perspective to the evidence base, and also includes medical respondents for the first time. Compared to previous research, respondents of this study saw refugee patients more frequently in their practice, and also reported fewer negative effects from working with them. Most demographic characteristics had no significant effect on worker-reported confidence in this study; however, greater experience of working with refugees and good self-perceived awareness of community services were both identified as positive influences. What are the implications for practitioners? Practitioners should prioritise remedying barriers that are consistently identified as affecting the service provided to refugee patients (communication, health literacy and healthcare worker capacity) as part of their quality and service improvement efforts.
Foliar elemental microprobe data and leaf anatomical traits consistent with drought tolerance in
Authors: Fernando Denise R. , Lynch Jonathan P. , Hanlon Meredith T. , Marshall Alan T.
Published: June 2021

In food-productive river basins, ecosystems reliant on natural flows are affected by climate change and water removal. One such example is Australia’s Murray–Darling Basin (MDB), to which the ecologically important black box tree Eucalyptus largiflorens (Myrtaceae) is unique. Little is known about its mineral nutrition and response to flooding. A field study conducted at Hattah Kulkyne National Park on the MDB examined nutrient and Al distribution in mature and young foliage of trees whose status varied with respect to the presence of surface floodwaters. Black box is also of interest due to emerging evidence of its capacity to accumulate high foliar salt concentrations. Here, cryo scanning electron microscopy alone (SEM), combined with energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF) spectroscopy were applied to evaluate leaf anatomy and elemental patterns at the cellular and whole-leaf levels. Variation in whole-leaf elemental levels across flooded and dry trees aligned with known nutritional fluctuations in this drought-tolerant species reliant on occasional infrequent flooding. The microprobe data provide evidence of drought tolerance by demonstrating that extended conditions of lack of water to trees do not elicit leaf anatomical changes nor changes to leaf cellular storage of these elements. Foliar Na concentrations of ~2000–6000 mg kg–1 DW were found co-localised with Cl in mesophyll and dermal cells of young and mature leaves, suggesting vacuolar salt disposal as a detoxification strategy.
Robustness and innovation along the endocytic route: Lessons from darkness
Authors: Singleton Kaela S. , Faundez Victor
Published: June 2021

What mechanisms ensure the loading of a SNARE into a nascent carrier? In this issue, Bowman et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202005173) describe an unprecedented mechanism where two sorting complexes, AP-3 and BLOC-1, the latter bound to syntaxin 13, work as a fail-safe to recognize sorting signals in VAMP7, a membrane protein required for fusion to melanosomes. Their observations define one of the first examples of distributed robustness in membrane traffic mechanisms.
Fano Resonance Enabled Infrared Nano-Imaging of Local Strain in Bilayer Graphene
Authors: Du Jing , Lyu Bosai , Shan Wanfei , Chen Jiajun , Zhou Xianliang , Xie Jingxu , Deng Aolin , Hu Cheng , Liang Qi , Xie Guibai , Li Xiaojun , Luo Weidong , Shi Zhiwen
Published: June 2021

Detection of local strain at the nanometer scale with high sensitivity remains challenging. Here we report near-field infrared nano-imaging of local strains in bilayer graphene by probing strain-induced shifts of phonon frequency. As a non-polar crystal, intrinsic bilayer graphene possesses little infrared response at its transverse optical phonon frequency. The reported optical detection of local strain is enabled by applying a vertical electrical field that breaks the symmetry of the two graphene layers and introduces finite electrical dipole moment to graphene phonon. The activated phonon further interacts with continuum electronic transitions, and generates a strong Fano resonance. The resulted Fano resonance features a very sharp near-field infrared scattering peak, which leads to an extraordinary sensitivity of ∼ 0.002% for the strain detection. Our results demonstrate the first nano-scale near-field Fano resonance, provide a new way to probe local strains with high sensitivity in non-polar crystals, and open exciting possibilities for studying strain-induced rich phenomena.
Highly Robust Reentrant Superconductivity in CsV3Sb5 under Pressure
Authors: Chen Xu , Zhan Xinhui , Wang Xiaojun , Deng Jun , Liu Xiao-Bing , Chen Xin , Guo Jian-Gang , Chen Xiaolong
Published: June 2021

We present the superconducting (SC) property and high-robustness of structural stability of kagome CsV3Sb5 under in situ high pressures. For the initial SC-I phase, its T
c is quickly enhanced from 3.5 K to 7.6 K and then totally suppressed at P ∼ 10 GPa. With further increasing pressure, an SC-II phase emerges at P ∼ 15 GPa and persists up to 100 GPa. The T
c rapidly increases to the maximal value of 5.2 K at P = 53.6 GPa and slowly decreases to 4.7 K at P = 100 GPa. A two-dome-like variation of T
c in CsV3Sb5 is concluded here. The Raman measurements demonstrate that weakening of E
2g mode and strengthening of E
1g mode occur without phase transition in the SC-II phase, which is supported by the results of phonon spectra calculations. Electronic structure calculations reveal that exertion of pressure may bridge the gap of topological surface nontrivial states near E
F, i.e., disappearance of Z
2 invariant. Meanwhile, the Fermi surface enlarges significantly, consistent with the increased carrier density. The findings here suggest that the change of electronic structure and strengthened electron-phonon coupling should be responsible for the pressure-induced reentrant SC.
Characterising a tunable, pulsed atomic beam using matter-wave interferometry
Authors: Morley J , Flack R , Hiley B J , Barker P F
Published: June 2021

We describe the creation and characterisation of a velocity tunable, spin-polarized beam of slow metastable argon atoms. We show that the beam velocity can be determined with a precision below 1% using matter-wave interferometry. The profile of the interference pattern was also used to determine the velocity spread of the beam, as well as the Van der Waals (VdW) co-efficient for the interaction between the metastable atoms and the multi-slit silicon nitride grating. The VdW co-efficient was determined to be C
3 = 1.84 ± 0.17 a.u., in good agreement with values derived from spectroscopic data. Finally, the spin polarization of the beam produced during acceleration of the beam was also measured, demonstrating a spatially uniform spin polarization of 96% in the m = +2 state.
Key outcome summaries of the scientific programme of the IRPA15 congress
Authors: Weiss Wolfgang , Salomaa Sisko , Giorgio Marina Di , Boyd Mike , Thurston Jim , Takala John , Tokonami Shinji , Vaillant Ludovic , Coates Roger , Kim Jong Kyung
Published: June 2021

This special issue of JRP includes a selection of research papers and review articles presented at the 15th Congress of the International Radiation Protection Association (IRPA15) as chosen by the scientific committee. All invited journal contributions are suitably expanded beyond the initial conference presentations to meet the criteria for a full journal article and include (a) presentation within a comprehensive radiological protection context and (b) additional data/interpretation. Published contributions address a wide spectrum of scientific topics and concepts to further develop the radiation protection (RP) system. They are based on scientific evidence and available experience in a wide spectrum of applications of the protection system. The IRPA is the international voice of the RP profession. It promotes excellence in RP by providing benchmarks of good practice, enhancing professional competence, and encourages the application of the highest standards of professional conduct, skills and knowledge for the benefit of individuals and society. Within the overarching theme of the conference ‘Bridging RP Culture and Science—Widening Public Empathy’ IRPA15 provided an invaluable opportunity to discuss and strengthen the relations between RP culture and science, and share developing scientific knowledge and related experience in RP among members of the scientific community, between representatives of key international organizations, including ICRP, IAEA, WHO, and NEA but also with the public. Some discussions focused on the rationale of available RP programmes and priorities, with an opportunity to identify and further develop key scientific issues of the current RP system as well as key processes for the interaction between members of the scientific community and society. The scientific programme of IRPA15 included eight topics and four thematic areas. The topical areas were: Underpinning Science; Dosimetry and Measurement; the System of Protection; Standards and Regulation; Practical Implementation—Medical Sector, as well as Industry and Research; Emergency Preparedness and Response; Existing Exposures and Non-ionizing Radiation. The thematic areas addressed were: Ethics; Communication and Public Understanding; RP Culture; Human Capital and Competency.
Quantification and mitigation of PIV bias errors caused by intermittent particle seeding and particle lag by means of large eddy simulations
Authors: Martins Fabio J W A , Kirchmann Jonas , Kronenburg Andreas , Beyrau Frank
Published: June 2021

In the present work, a standard large eddy simulation is combined with tracer particle seeding simulations to investigate the different PIV bias errors introduced by intermittent particle seeding and particle lag. The intermittency effect is caused by evaluating the velocity from tracer particles with inertia in a region where streams mix with different seeding densities. This effect, which is different from the vastly-discussed particle lag, is frequently observed in the literature but scarcely addressed. Here, bias errors in the velocity are analysed in the framework of a turbulent annular gaseous jet weakly confined by low-momentum co-flowing streams. The errors are computed between the gaseous flow velocity, obtained directly from the simulation, and the velocities estimated from synthetic PIV evaluations. Tracer particles with diameters of 0.037, 0.37 and 3.7 µm are introduced into the simulated flow through the jet only, intermediate co-flowing stream only and through both regions. Results quantify the influence of intermittency in the time-averaged velocities and Reynolds stresses when only one of the streams is seeded, even when tracers fulfil the Stokes-number criterion. Additionally, the present work proposes assessing unbiased velocity statistics from large eddy simulations, after validation of biased seeded simulations with biased PIV measurements. The approach can potentially be applied to a variety of flows and geometries, mitigating the bias errors.
Photoionization of Rydberg atoms in optical lattices
Authors: Cardman R , MacLennan J L , Anderson S E , Chen Y-J , Raithel G
Published: June 2021

We develop a formalism for photoionization (PI) and potential energy curves (PECs) of Rydberg atoms in ponderomotive optical lattices and apply it to examples covering several regimes of the optical-lattice depth. The effect of lattice-induced PI on Rydberg-atom lifetime ranges from noticeable to highly dominant when compared with natural decay. The PI behavior is governed by the generally rapid decrease of the PI cross sections as a function of angular-momentum (ℓ), lattice-induced ℓ-mixing across the optical-lattice PECs, and interference of PI transition amplitudes from the lattice-mixed into free-electron states. In GHz-deep lattices, ℓ-mixing leads to a rich PEC structure, and the significant low-ℓ PI cross sections are distributed over many lattice-mixed Rydberg states. In lattices less than several tens-of-MHz deep, atoms on low-ℓ PECs are essentially ℓ-mixing-free and maintain large PI rates, while atoms on high-ℓ PECs trend towards being PI-free. Characterization of PI in GHz-deep Rydberg-atom lattices may be beneficial for optical control and quantum-state manipulation of Rydberg atoms, while data on PI in shallower lattices are potentially useful in high-precision spectroscopy and quantum-computing applications of lattice-confined Rydberg atoms.
The POEMMA (Probe of Extreme Multi-Messenger Astrophysics) observatory
Authors: Olinto A.V. , Krizmanic J. , Adams J.H. , Aloisio R. , Anchordoqui L.A. , Anzalone A. , Bagheri M. , Barghini D. , Battisti M. , Bergman D.R. , Bertaina M.E. , Bertone P.F. , Bisconti F. , Bustamante M. , Cafagna F. , Caruso R. , Casolino M. , Černý K. , Christl M.J. , Cummings A.L. , De Mitri I. , Diesing R. , Engel R. , Eser J. , Fang K. , Fenu F. , Filippatos G. , Gazda E. , Guepin C. , Haungs A. , Hays E.A. , Judd E.G. , Klimov P. , Kungel V. , Kuznetsov E. , Mackovjak Š. , Mandát D. , Marcelli L. , McEnery J. , Medina-Tanco G. , Merenda K.-D. , Meyer S.S. , Mitchell J.W. , Miyamoto H. , Nachtman J.M. , Neronov A. , Oikonomou F. , Onel Y. , Osteria G. , Otte A.N. , Parizot E. , Paul T. , Pech M. , Perkins J.S. , Picozza P. , Piotrowski L.W. , Plebaniak Z. , Prévôt G. , Reardon P. , Reno M.H. , Ricci M. , Romero Matamala O. , Sarazin F. , Schovánek P. , Scotti V. , Shinozaki K. , Soriano J.F. , Stecker F. , Takizawa Y. , Ulrich R. , Unger M. , Venters T.M. , Wiencke L. , Winn D. , Young R.M. , Zotov M.
Published: June 2021

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full celestial sky. POEMMA will observe the air fluorescence produced by extensive air showers (EASs) from UHECRs and potentially UHE neutrinos above 20 EeV. Additionally, POEMMA has the ability to observe the Cherenkov signal from upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The POEMMA spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain currently unparalleled neutrino flux sensitivity. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical satellites flying in loose formation in 525 km altitude orbits. Each POEMMA instrument incorporates a wide field-of-view (45∘) Schmidt telescope with an optical collecting area of over 6 m2. The hybrid focal surface of each telescope includes a fast (1 μs) near-ultraviolet camera for EAS fluorescence observations and an ultrafast (10 ns) optical camera for Cherenkov EAS observations. In a 5-year mission, POEMMA will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these extreme energies.
Relativistic viscous effects on the primordial gravitational waves spectrum
Authors: Mirón-Granese Nahuel
Published: June 2021

We study the impact of the viscous effects of the primordial plasma on the evolution of the primordial gravitational waves (pGW) spectrum from Inflation until today, considering a self-consistent interaction that incorporates the back-reaction of the GW into the plasma. We use a relativistic causal hydrodynamic framework with a positive entropy production based on a Second-Order Theory (SOT) in which the viscous properties of the fluid are effectively described by a new set of independent variables. We study how the spin-2 modes typical of SOTs capture the simplest GW-fluid viscous interaction to first order. We consider that all non-ideal properties of the primordial plasma are due to an extra effectively massless self-interacting scalar field whose state becomes a many-particles one after Reheating and for which an effective fluid description is suitable. We numerically solve the evolution equations and explicitly compute the current GW spectrum obtaining two contributions. On the one hand we have the viscous evolution of the pGW: for the collision-dominated regime the GW source becomes negligible while in the collisionless limit there exists an absorption of the pGW energy due to the damping effect produced by the free-streaming spin-2 modes of the fluid and driven by the expansion of the Universe. The latter effect is characterized by a relative amplitude decrease of about 1 to 10 % with respect to the GW free evolution spectrum. On the other hand we get the GW production due to the decay of the initial spin-2 fluctuations of the fluid that is negligible compared with the above-mentioned contribution.

This SOT framework captures the same qualitative effects on the evolution of GW coupled to matter reported in previous works in which a kinetic theory approach has been used.
Molecular dynamics simulations of dopant effects on lattice trapping of cracks in Ni matrix*
Authors: Liu Shulan , Yang Huijing
Published: June 2021

Molecular dynamic analysis was performed on pure and doped (by Re, Ru, Co or W) Ni at 300 K using the embedded-atom-method (EAM) potentials to understand the crack formation of the doped Ni matrix in the (010)[001] orientation. When Ni was doped with Re, Ru, and W, the matrix demonstrated increased lattice trapping limits and, as a result, improved the mechanical properties. Consequently, this prevented the bond breakage at the crack tips and promoted crack healing. The average atomic and surface energy values increased when Re, Ru, and W were added. Analysis of these energy increase helpedus to understand the influence these elements had on the lattice trapping limits. The fracture strength of the Ni matrixat 300 K increased because of the formation of the stronger Ni–Re, Ni–Ru, and Ni–W bonds. At the same time, doping the Ni matrix with Co did not demonstrate any strengthening effects because of the formation of Co–Ni bonds, which are weaker than the Ni–Ni bonds. Out of all dopants tested in this work, Ni doping with W showed the best results.
Intrinsic two-dimensional multiferroicity in CrNCl2 monolayer*
Authors: Shen Wei , Pan Yuanhui , Shen Shengnan , Li Hui , Nie Siyuan , Mei Jie
Published: June 2021

Two-dimensional multiferroics, which simultaneously possess ferroelectricity and magnetism in a single phase, are well-known to possess great potential applications in nanoscale memories and spintronics. On the basis of first-principles calculations, a CrNCl2 monolayer is reported as an intrinsic multiferroic. The CrNCl2 has an antiferromagnetic ground state, with a Néel temperature of about 88 K, and it exhibits an in-plane spontaneous polarization of 200 pC/m. The magnetic moments of CrNCl2 mainly come from the d5
xy
orbital of the Cr cation, but the plane of the d
xy
orbital is perpendicular to the direction of the ferroelectric polarization, which hardly suppresses the occurrence of ferroelectricity. Therefore, the multiferroic exits in the CrNCl2. In addition, like CrNCl2, the CrNBr2 is an intrinsic multiferroic with antiferromagnetic-ferroelectric ground state while CrNI2 is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state. These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.
A novel receiver-transmitter metasurface for a high-aperture-efficiency Fabry-Perot resonator antenna*
Authors: Xie Peng , Wang Guangming , Zong Binfeng , Zou Xiaojun
Published: June 2021

This paper presents a novel coupled receiver–transmitter metasurface (MS) which is used to realize a high-aperture-efficiency Fabry–Perot resonator antenna. The unit cell of the MS adopts a slot-coupling procedure to realize energy transmission from the receiver patch to the radiator patch. This approach makes it easier to independently control the transmission magnitude and phase. Based on this characteristic, the transmission coefficients of different unit cells on the MS can be optimized by a genetic algorithm. Then, nearly uniform electric amplitude and phase distribution across the aperture field of the antenna are achieved. Therefore, the gain and aperture efficiency of the antenna are improved. A prototype of the optimized antenna is fabricated and measured to validate the design. The measured gain of the fabricated antenna reaches 17.3 dBi with an aperture efficiency of 94.5%. A higher aperture efficiency is obtained with the proposed antenna which has a low profile and simple structure.
Vertical WS2 spin valve with Ohmic property based on Fe3GeTe2 electrodes*
Authors: Hu Ce , Yan Faguang , Li Yucai , Wang Kaiyou
Published: June 2021

The two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have been recently proposed as a promising class of materials for spintronic applications. Here, we report on the all-2D van der Waals (vdW) heterostructure spin valve device comprising of an exfoliated ultra-thin WS2 semiconductor acting as the spacer layer and two exfoliated ferromagnetic Fe3GeTe2 (FGT) metals acting as ferromagnetic electrodes. The metallic interface rather than Schottky barrier is formed despite the semiconducting nature of WS2, which could be originated from the strong interface hybridization. The spin valve effect persists up to the Curie temperature of FGT. Moreover, our metallic spin valve devices exhibit robust spin valve effect where the magnetoresistance magnitude does not vary with the applied bias in the measured range up to 50 μA due to the Ohmic property, which is a highly desirable feature for practical application that requires stable device performance. Our work reveals that WS2-based all-2D magnetic vdW heterostructure, facilitated by combining 2D magnets, is expected to be an attractive candidate for the TMDCs-based spintronic applications.
Origin of anomalous enhancement of the absorption coefficient in a PN junction*
Authors: Tang Xiansheng , Sun Baoan , Yue Chen , Li Xinxin , Zhang Junyang , Deng Zhen , Du Chunhua , Wang Wenxin , Jia Haiqiang , Jiang Yang , Wang Weihua , Chen Hong
Published: June 2021

The absorption coefficient is usually considered as a constant for certain materials at the given wavelength. However, recent experiments demonstrated that the absorption coefficient could be enhanced a lot by the PN junction. The absorption coefficient varies with the thickness of the intrinsic layer in a PIN structure. Here, we interpret the anomalous absorption coefficient from the competition between recombination and drift for non-equilibrium carriers. Based on the Fokker–Planck theory, a non-equilibrium statistical model that describes the relationship between absorption coefficient and material thickness has been proposed. It could predict the experimental data well. Our results can give new ideas to design photoelectric devices.
Distribution of donor states on the surface of AlGaN/GaN heterostructures*
Authors: Liu Yue-Bo , Liu Hong-Hui , Shen Jun-Yu , Yao Wan-Qing , Wang Feng-Ge , Ren Yuan , Zhang Min-Jie , Wu Zhi-Sheng , Liu Yang , Zhang Bai-Jun
Published: June 2021

The uniform distribution model of the surface donor states in AlGaN/GaN heterostructures has been widely used in the theoretical calculation. A common and a triple-channel AlGaN/GaN heterostructure Schottky barrier diodes have been fabricated to verify the models, but the calculation results show the uniform distribution model can not provide enough electrons to form three separate 2DEGs in the triple-channel AlGaN/GaN heterostructure. Our experiments indicate the uniform distribution model is not quite right, especially for the multiple-channel AlGaN/GaN heterostructures. Besides, it is found the exponential distribution model possibly matches the actual distribution of the surface donor states better, which allows the 2DEG to form in each channel structure during the calculation. The exponential distribution model would be helpful in the research field.
Fabrication of Josephson parameter amplifier and its application in squeezing vacuum fluctuations*
Authors: Song Pengtao , Guo Xueyi , Xu Kai , Song Xiaohui , Wang Zhan , Xiang Zhongcheng , Li Hekang , Su Luhong , Jin Yirong , Zheng Dongning
Published: June 2021

Josephson parameter amplifier (JPA) is a microwave signal amplifier device with near-quantum-limit-noise performance. It has important applications in scientific research fields such as quantum computing and dark matter detection. This work reports the fabrication and characterization of broadband JPA devices and their applications in multi-qubit readout and squeezing of vacuum state. We use a process in which transmission lines and electrodes are made of niobium thin film and aluminum Josephson junctions are made by Dolan bridge technique. We believe this process is more convenient than the process we used previously. The whole production process adopts electron beam lithography technology to ensure high structural resolution. The test result shows that the gain value of the manufactured JPA can exceed 15 dB, and the amplification bandwidth is about 400 MHz. The noise temperature is about 400 mK at the working frequency of 6.2 GHz. The devices have been successfully used in experiments involving superconducting multi-qubit quantum processors. Furthermore, the device is applied to squeeze vacuum fluctuations and a squeezing level of 1.635 dB is achieved.