bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(lactic-co-glycolic acid) nanoparticle fabrication, functionalization, and biological considerations for drug delivery
Authors: Marecki Eric K. , Oh Kwang W. , Knight Paul R. , Davidson Bruce A.
Published: September 2024

Nanoparticles can be used for drug delivery and consist of many sizes and chemical compositions. They can accommodate a diverse population of drugs and can be made to target specific areas of the body. Fabrication methods generally follow either top-down or bottom-up manufacturing techniques, which have differing production controls, which determine nanoparticle characteristics including but not limited to size and encapsulation efficiency. Functionalizing these nanoparticles is done to add drugs, prevent aggregation, add positive charge, add targeting, etc. As the nanoparticles reach the target cells, cellular uptake occurs, drug is released, and the nanoparticle is broken down. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles have often been used for drug delivery applications as they have shown minimal toxicity, which has helped with US FDA approval. This review breaks down PLGA nanoparticle fabrication, functionalization, and biological considerations.
How the non-metricity of the connection arises naturally in the classical theory of gravity
Authors: Bąk Bartłomiej , Kijowski Jerzy
Published: September 2024

Spacetime geometry is described by two–a priori independent–geometric structures: the symmetric connection Γ and the metric tensor g. Metricity condition of Γ (i.e. ∇g = 0) is implied by the Palatini variational principle, but only when the matter fields belong to an exceptional class. In case of a generic matter field, Palatini implies non-metricity of Γ. Traditionally, instead of the (first order) Palatini principle, we use in this case the (second order) Hilbert principle, assuming metricity condition a priori. Unfortunately, the resulting right-hand side of the Einstein equations does not coincide with the matter energy-momentum tensor. We propose to treat seriously the Palatini-implied non-metric connection. The conventional Einstein’s theory, rewritten in terms of this object, acquires a much simpler and universal structure. This approach opens a room for the description of the large scale effects in General Relativity (dark matter?, dark energy?), without resorting to purely phenomenological terms in the Lagrangian of gravitational field. All theories discussed in this paper belong to the standard General Relativity Theory, the only non-standard element being their (much simpler) mathematical formulation. As a mathematical bonus, we propose a new formalism in the calculus of variations, because in case of hyperbolic field theories the standard approach leads to nonsense conclusions.
High-quality Ge/SiGe heterostructure with atomically sharp interface grown by molecular beam epitaxy
Authors: Zhang Jie-yin , Ming Ming , Wang Jian-huan , Huang Ding-ming , Gao Han , Chu Yi-xin , Fu Bin-xiao , Xu H. Q. , Zhang Jian-jun
Published: September 2024

Germanium is a versatile material for realization of spin and topological quantum computing. Here, we report on the epitaxial growth of an undoped Ge/SiGe heterostructure in which a hole quantum well is formed in the sandwiched Ge layer. The heterostructure is grown on Si (001) via molecular beam epitaxy (MBE). Atomic force microscopy characterizations display a flat surface with a root mean square roughness of 0.956 nm, and spherical aberration corrected transmission electron microscopy data show a sharp interface with a characteristic length of 0.49 nm. A mobility of up to 1.2 × 105 cm2 V−1 s−1 was achieved in the SiGe/Ge/SiGe two-dimensional hole gas (2DHG). The low percolation density of 3.70 × 1010 cm−2, light effective mass of 0.079 m0 (where m0 is the free electron mass), and large effective g-factor of 9.5 were obtained. These results show the potential of MBE-grown Ge 2DHG for semiconductor quantum computing.
Ku-band 300 kW high power ferrite phase shifter
Authors: Hu Xianggang , Su Jiancang , Bai Bing , Yu Zengqiang , Lu Xiaogang , Li Mei , Li Rui , Cheng Jie , Zhang Jiande , Wu Shaotong
Published: September 2024

Phase shifter (PS) is a key component of a phased array antenna (PAA) system, which controls the microwave phase and realizes the antenna beam forming and scanning. A ferrite PS (FPS) is a current-controlled PS that uses the ferrite’s gyromagnetic properties to realize phase shifting. It has the advantages of short phase switching time, low microwave loss, and high reliability and, therefore, has been widely used in low-power PAA systems. However, the power handling capability of the traditional Ku-band FPS is only a few kW, prohibiting FPS from being used in high-power microwave (HPM) PAA systems. Spurred by this concern, this paper proposes a new dual-toroid FPS structure with an external magnetic excitation. By optimizing the PS configuration, improving the integration process, and enhancing the performance of ferrite materials, a single FPS in the Ku band has reached the power handling capability of more than 300 kW with an insertion loss of less than −1.2 dB, the phase shift range of 0°–360°, the width less than 11.5 mm, and the ability of a one-dimensional array. The FPS has the potential to be used in the PAA of an HPM system, laying a foundation for the research of the HPM PAA system.
Optimized higher-order photon state classification by machine learning
Authors: Xu Guangpeng , Carvalho Jeffrey , Wijesundara Chiran , Thomay Tim
Published: September 2024

The classification of higher-order photon emission becomes important with more methods being developed for deterministic multiphoton generation. The widely used second-order correlation g(2) is not sufficient to determine the quantum purity of higher photon Fock states. Traditional characterization methods require a large amount of photon detection events, which leads to increased measurement and computation time. Here, we demonstrate a machine learning model based on a 2D Convolutional Neural Network (CNN) for rapid classification of multiphoton Fock states up to |3⟩ with an overall accuracy of 94%. By fitting the g(3) correlation with simulated photon detection events, the model exhibits an efficient performance particularly with sparse correlation data, with 800 co-detection events to achieve an accuracy of 90%. Using the proposed experimental setup, this CNN classifier opens up the possibility for quasi-real-time classification of higher photon states, which holds broad applications in quantum technologies.
On the instability of single-axis acoustic levitation under radial perturbations
Authors: Wang Xiaozhen , Chang Qin , Wu Pengfei , Xu Delong , Lin Weijun , Chen Hao
Published: September 2024

Acoustic levitation is widely used in non-container measurement and non-contact manipulation. Particles in the single-axis acoustic levitation are easily unstable in the radial direction under external perturbations. In order to explore the instability in the acoustic levitation during radial perturbations, a nonlinear acoustic levitation model considering the coupling of radial and axial vibration is proposed to analyze the dominant factors influencing the levitation stability, an acoustic levitation system consisting of a transducer and a plane reflector is established, and high-speed photography is used to observe the vibration behavior of the particle with large radial vibration and the levitation stability. The simulation results are compared and verified with the experiments, which indicate that the reduction in axial trapping stiffness due to radial vibration plays a vital role in the levitation instability. The present model can characterize the radial anti-interference ability of different levitators as well as predict the movement trajectories of levitated particles after being disturbed, which is helpful to optimize the design of acoustic levitators and provide guidance for acoustic manipulation.
Solid phase epitaxy of SrRuO3 encapsulated by SrTiO3 membranes
Authors: Zhou Jieyang , Feng Mingzhen , Shih Hudson , Takamura Yayoi , Hong Seung Sae
Published: September 2024

Solid phase epitaxy (SPE) has been widely employed for various thin-film materials, making it valuable for industrial applications due to its scalability. In complex oxides, SPE has been limited to a few materials because of the challenges in maintaining stoichiometric control during growth, particularly when volatile phases are present at high temperatures. Here, we investigate the impact of encapsulation layers on the SPE of complex oxides, using SrRuO3 (SRO) as a model system. An amorphous SRO layer was deposited on a SrTiO3 (STO) substrate, followed by the transfer of a single-crystalline STO membrane as an encapsulation layer in order to suppress the evaporation of volatile species (RuO2) during the SPE process. Whereas both encapsulated and unencapsulated SRO layers were successfully crystallized, the unencapsulated films suffered a substantial loss of Ru ions—exceeding 20%—compared to their encapsulated counterparts. This loss of Ru ions led to a loss of metallicity in the unencapsulated SRO layers, whereas the encapsulated layers retained their metallic ferromagnetic properties. This study demonstrates that the encapsulation provided by oxide membranes effectively suppresses stoichiometric loss during SPE, presenting a new strategy in stabilizing a broader class of functional oxides as epitaxial thin films.
Insights into the fluid dynamics of bioaerosol formation in a model respiratory tract
Authors: Saha Sudipta , Manna Manish Kumar , Chakravarty Aranyak , Sarkar Sourav , Mukhopadhyay Achintya , Sen Swarnendu
Published: September 2024

Bioaerosols produced within the respiratory system play an important role in respiratory disease transmission. These include infectious diseases such as common cold, influenza, tuberculosis, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among several others. It is, therefore, of immense interest to understand how bioaerosols are produced within the respiratory system. This has not been extensively investigated. The present study computationally investigates how bioaerosols are produced in a model respiratory tract due to hydrodynamic interactions between breathed air and a thin mucus layer, which lines the inner surface of the tract. It is observed that Kelvin–Helmholtz instability is established in the thin mucus layer due to associated fluid dynamics. This induces interfacial surface waves which fragment forming bioaerosols under certain conditions. A regime map is created—based on pertinent dimensionless parameters—to enable identification of such conditions. Analysis indicates that bioaerosols may be produced even under normal breathing conditions, contrary to expectations, depending on mucus rheology and thickness of the mucus layer. This is possible during medical conditions as well as during some treatment protocols. However, such bioaerosols are observed to be larger (∼O(100)μm) and are produced in less numbers (∼100), as compared to those produced under coughing conditions. Treatment protocols and therapeutic strategies may be suitably devised based on these findings.
The long road to ignition: An eyewitness account
Authors: Rosen Mordecai D.
Published: September 2024

This paper reviews the many twists and turns in the long journey that culminated in ignition in late 2022 using the laser heated indirect-drive approach to imploding DT filled targets at the National Ignition Facility (NIF), located at the Lawrence Livermore National Laboratory (LLNL). We describe the early origins of the Laser Program at LLNL and key developments such as the paradigm shifting birth of high energy density physics (HEDP) studies with lasers, changes in choice of laser wavelength, and the development of key diagnostics and computer codes. Fulfilling the requirements of the multi-faceted Nova Technical Contract was a necessary condition for the approval of the NIF, but more importantly, the end of the Cold War and the cessation of nuclear testing were key catalysts in that approval, along with the ready-and-waiting field of HEDP. The inherent flexibility of the field of laser driven inertial confinement fusion played a fundamental role in achieving success at the NIF. We describe how the ultimately successful ignition target design evolved from the original “point design” target, through the lessons of experiment. All key aspects of that original design changed: The capsule's materials and size were changed; the hohlraum's materials, size, laser entrance hole size, and gas fills were also all changed, as were the laser pulse shapes that go along with all those changes. The philosophy to globally optimize performance for stability (by raising the adiabat and thus lowering the implosion convergence) was also key, as was progress in target fabrication, and in increasing NIF's energy output. The persistence of the research staff and the steadfast backing of our supporters were also necessary elements in this success. We gratefully acknowledge seven decades of researcher endeavors and four decades of the dedicated efforts of many hundreds of personnel across the globe who have participated in NIF construction, operation, target fabrication, diagnostic, and theoretical advances that have culminated in ignition.
Control, bi-stability, and preference for chaos in time-dependent vaccination campaign
Authors: Gabrick Enrique C. , Brugnago Eduardo L. , de Moraes Ana L. R. , Protachevicz Paulo R. , da Silva Sidney T. , Borges Fernando S. , Caldas Iberê L. , Batista Antonio M. , Kurths Jürgen
Published: September 2024

In this work, effects of constant and time-dependent vaccination rates on the Susceptible–Exposed–Infected–Recovered–Susceptible (SEIRS) seasonal model are studied. Computing the Lyapunov exponent, we show that typical complex structures, such as shrimps, emerge for given combinations of a constant vaccination rate and another model parameter. In some specific cases, the constant vaccination does not act as a chaotic suppressor and chaotic bands can exist for high levels of vaccination (e.g., >0.95). Moreover, we obtain linear and non-linear relationships between one control parameter and constant vaccination to establish a disease-free solution. We also verify that the total infected number does not change whether the dynamics is chaotic or periodic. The introduction of a time-dependent vaccine is made by the inclusion of a periodic function with a defined amplitude and frequency. For this case, we investigate the effects of different amplitudes and frequencies on chaotic attractors, yielding low, medium, and high seasonality degrees of contacts. Depending on the parameters of the time-dependent vaccination function, chaotic structures can be controlled and become periodic structures. For a given set of parameters, these structures are accessed mostly via crisis and, in some cases, via period-doubling. After that, we investigate how the time-dependent vaccine acts in bi-stable dynamics when chaotic and periodic attractors coexist. We identify that this kind of vaccination acts as a control by destroying almost all the periodic basins. We explain this by the fact that chaotic attractors exhibit more desirable characteristics for epidemics than periodic ones in a bi-stable state.
300-nm-thick, ultralow-loss silicon nitride photonic integrated circuits by 8-in. foundry production
Authors: Zhang Xuguang , Liang Yuxin , Chen Yujun , Shen Bitao , Huang Jiahui , Lao Chenghao , Wu Yichen , Li Zhihui , Liu Dapeng , Shu Haowen , Hu Weiwei , Wang Xingjun , Cui Naidi , Chang Lin
Published: September 2024

Silicon nitride (Si3N4) photonic integrated circuits are rapidly developing in recent decades. The low loss of Si3N4 attracts significant attention and facilitates a wide range of applications in integrated photonics. In this work, we demonstrate the foundry fabrication of a 300-nm-thick 8-in. wafer-scale Si3N4 platform, with a microresonator intrinsic quality factor of up to 15×106, corresponding to an ultralow loss of 2.2 dB/m. Leveraging this platform, we develop a mature process design kit, achieving a single-mode waveguide propagation loss of less than 5 dB/m, an edge coupler loss of 1.3 dB, and an insertion loss of 0.07 dB for multimode interference couplers. Utilizing the processed Si3N4 chip, we realize a hybrid integrated tunable external cavity laser with a tuning range from 1534 to 1602 nm, a record-high side-mode suppression ratio of up to 76 dB, an optical power of 26 mW, and an intrinsic linewidth of down to 314 Hz. Our work lays a solid foundation for the further development of applications, including nonlinear optics, quantum optics, optical communications, and ranging.
An electro-thermal finite element method (FEM) model for local hotspot kinetics in Cu(In, Ga)Se2 thin-film solar modules
Authors: Nofal Suheir , Vaas Timon S. , Rau Uwe , Pieters Bart E.
Published: September 2024

Partial shading can significantly impair the efficiency of thin-film solar cells. When exposed to partial shading, cells within the array tend to become reverse biased, leading to thermal runaway events and the emergence of hotspots. In Cu(In,Ga)Se2 (CIGS) solar cells such hotspots are also associated with so-called worm-like defects. Both theoretical and experimental studies have shown that in CIGS, a positive-feedback loop leads to instability and thermal runaway events. However, we observe an inconsistency between published simulation results and recently published experimental work. In a recent experimental study, it was shown that under certain conditions, a hotspot develops within 1ms, showing signs of melting of the CIGS in an area with a 5μm radius. However, in published simulation results, the time for such high temperatures to develop is in the order of seconds, a discrepancy of three orders of magnitude. In this work, we argue that this discrepancy is explained by the size of the seed defect, demonstrating that the origin of these experimentally observed, fast-developing hotspots is likely microscopic defects. To this end, we developed an electro-thermal finite element model, with very high temporal and spatial resolution. We demonstrate that, assuming a seed defect with a 10nm radius, we can reproduce the experimental results with respect to the size of the defect and the time it took to develop.
Charge carrier absorption in n-type Sb2Se3
Authors: Herklotz F. , Lavrov E. V. , Hobson T. D. C. , Major J. D. , Durose K.
Published: September 2024

The optical and electrical properties of n-type chlorine-doped Sb2Se3 single crystals, with free carrier concentrations above 1016 cm−3 at room temperature, have been studied. The experiments reveal a strongly polarized temperature-dependent long-wavelength infrared absorption attributable to conduction band electrons within the material. For wavelengths between 1.6 and 6 μm, the room temperature absorption varies as λ2.5±0.3, suggesting that longitudinal optical mode scattering is the dominant electron scattering mechanism. The results are most consistent with the hypothesis that electron transport in Sb2Se3 is band-like and not intrinsically limited by small-polaron self-trapping.
Hydrodynamic stability of magnetic boundary layer flow of viscoelastic Walters' liquid B embedded in a porous medium
Authors: Amrutha H. , Gogate S. Shashi Prabha
Published: September 2024

The present study investigates the linear stability of stagnation boundary layer flow of viscoelastic Walters' liquid B in the presence of magnetic field and porous medium by solving modified Orr–Sommerfeld equation numerically using the Chebyshev collocation method. The model is characterized mainly by the elasticity number (E), the magnetic number (Q), and the permeability parameter (K) in addition to the Reynolds number(Re). The Prandtl boundary layer equations derived for the present model are converted through appropriate similarity transformations, to an ordinary differential equation whose solution describes the velocity, which has oscillatory behavior. The solution of generalized eigenvalue problem governing the stability of the boundary layer has an interesting eigenspectrum. The spectra for different values of E, K, and Q are shown to be a continuation of Newtonian eigenspectrum with the instability belongs to viscoelastic wall mode for certain range of parameters. It is shown that the role of elasticity number is to destabilize the viscoelastic boundary layer flow, whereas both magnetic field and porous medium have the stabilizing effect on the flow. These interesting features are further confirmed by performing the energy budget analysis on the perturbed quantities. Region of negative production due to the Reynolds stress as well as production due to viscous dissipation and viscoelastic contributions in the positive region, and there is reduction in the growth rate of kinetic energy that causes stability. Other physical mechanisms related to flow stability are discussed in detail.
Non-Foster approach to broadband optical metamaterials based on Lorentzian gain materials
Authors: Hrabar Silvio , Ziolkowski Richard W.
Published: September 2024

All passive metamaterials are inherently narrowband due to fundamental dispersion-energy constraints, and their dispersive properties are usually approximated by a Lorentz model. However, there are broadband active metamaterials in the radio frequency (RF) regime based on negative capacitors with non-Foster dispersion properties. Non-Foster dispersion is usually considered as an “electronic-engineering trick” that cannot be applied at optical frequencies. Here, we demonstrate that the dispersion relation of a RF non-Foster capacitor is similar to that of an optical gain material described by a Lorentz model. This insight paves the way to realize non-Foster optical metamaterial structures. As the simplest example, we develop a broadband non-Foster optical epsilon-near-zero slab with a 1:10 bandwidth.
Effect of three-dimensionality of turbulence on the along-wind loads of square cross-sectional structures
Authors: Wang Yuxia , Li Mingshui
Published: September 2024

The existing theories for along-wind loads on slender structures, based on the “strip assumption” overlook the three-dimensionality of turbulence. However, numerous experimental phenomena contradicting the “strip assumption” highlight the need to consider the effects of three-dimensional turbulence (3D effect). This study develops an analysis model that considers the three-dimensionality of turbulence and derives a function containing the section-shape-dependent characteristic parameters to represent the 3D effect. A method for identifying the parameters through a wind tunnel test is proposed to solve this function. The parameters for the square cross section are then identified in two different turbulence fields, revealing that the identification parameters of both cases are nearly identical. This similarity indicates that the parameters are independent of the turbulence validating the proposed theories. Finally, the 3D effect on square cross-sectional structures with different aspect ratios under various turbulence integral scales is analyzed. The results showed that as the ratio of the turbulence integral scale to the windward width of the structures increases, the 3D effect reduces, but the rate of reduction slows down. In addition, increasing the aspect ratios of structures further mitigates the 3D effect, enhancing the accuracy of the “strip assumption.” These results can be a reference for evaluating the accuracy of the “strip assumption” theory for square cross-sectional high-rise buildings in atmospheric boundary layer turbulence. The proposed method can be applied to investigate the 3D effect on along-wind loads of slender structures with various cross-sectional shapes.
XUV-beamline for photoelectron imaging spectroscopy with shaped pulses
Authors: Behrens M. , Englert L. , Bayer T. , Wollenhaupt M.
Published: September 2024

We introduce an extreme ultraviolet (XUV)-beamline designed for the time-resolved investigation and coherent control of attosecond (as) electron dynamics in atoms and molecules by polarization-shaped as-laser pulses. Shaped as-pulses are generated through high-harmonic generation (HHG) of tailored white-light supercontinua (WLS) in noble gases. The interaction of shaped as-pulses with the sample is studied using velocity map imaging (VMI) techniques to achieve the differential detection of photoelectron wave packets. The instrument consists of the WLS-beamline, which includes a hollow-core fiber compressor and a home-built 4f polarization pulse shaper, and the high-vacuum XUV-beamline, which combines an HHG-stage and a versatile multi-experiment vacuum chamber equipped with a home-built VMI spectrometer. The VMI spectrometer allows the detection of photoelectron wave packets from both the multiphoton ionization (MPI) of atomic or molecular samples by the tailored WLS-pulses and the single-photon ionization (SPI) by the shaped XUV-pulses. To characterize the VMI spectrometer, we studied the MPI of xenon atoms by linearly polarized WLS pulses. To validate the interplay of these components, we conducted experiments on the SPI of xenon atoms with linearly polarized XUV-pulses. Our results include the reconstruction of the 3D photoelectron momentum distribution (PMD) and initial findings on the coherent control of the PMD by tuning the spectrum of the XUV-pulses with the spectral phase of the WLS. Our results demonstrate the performance of the entire instrument for HHG-based photoelectron imaging spectroscopy with prototypical shaped pulses. Perspectively, we will employ polarization-tailored WLS-pulses to generate polarization-shaped as-pulses.
Periodic orbits in Fermi–Pasta–Ulam–Tsingou systems
Authors: Karve Nachiket , Rose Nathan , Campbell David
Published: September 2024

The Fermi–Pasta–Ulam–Tsingou (FPUT) paradox is the phenomenon whereby a one-dimensional chain of oscillators with nonlinear couplings shows long-lived nonergodic behavior prior to thermalization. The trajectory of the system in phase space, with a long-wavelength initial condition, closely follows that of the Toda model over short times, as both systems seem to relax quickly to a non-thermal, metastable state. Over longer times, resonances in the FPUT spectrum drive the system toward equilibrium, away from the Toda trajectory. Similar resonances are observed in q-breather spectra, suggesting that q-breathers are involved in the route toward thermalization. In this article, we first review previous important results related to the metastable state, solitons, and q-breathers. We then investigate orbit bifurcations of q-breathers and show that they occur due to resonances, where the q-breather frequencies become commensurate as mΩ1=Ωk. The resonances appear as peaks in the breather energy spectrum. Furthermore, they give rise to new “composite periodic orbits,” which are nonlinear combinations of multiple q-breathers that exist following orbit bifurcations. We find that such resonances are absent in integrable systems, as a consequence of the (extensive number of) conservation laws associated with integrability.
Electronic structures and magnetism of MTe2 (M = Cr, V, and Fe) monolayer nanoribbons
Authors: Chen Wei , Chen Qi , Zhang Jianmin , Zheng Yu , Long Ying
Published: September 2024

Inspired by the fabrication of the transition metal dichalcogenide nanoribbons with well-defined atomically precise edges, we study the stability, electronic structures, and magnetism of MTe2 (M = Cr, V, and Fe) monolayer nanoribbons. The calculations indicate that all three types of monolayers can form structurally stable zigzag (ZNR) and armchair (ANR) nanoribbons, which significantly alter the properties of the monolayer films, as shown in Table I. For the zigzag nanoribbons, CrTe2-ZNR transitions from a non-magnetic semiconductor to a ferrimagnetic metal. VTe2-ZNR transforms from a ferromagnetic semiconductor to a ferrimagnetic metal. FeTe2-ZNR mostly maintains the characteristics of the monolayer. For the armchair nanoribbons, CrTe2-ANR exhibits ferrimagnetism. The electrical conductivity is related to the width. CrTe2-ANR with narrow width is semiconducting, while wider ones are metallic. VTe2-ANR displays ferromagnetic or ferrimagnetic metallic behavior depending on the width. FeTe2-ANR with widths larger than 11 remains ferromagnetic metal, while with narrow widths are unstable. In addition, the magnetism of all MTe2 monolayer nanoribbons primarily originates from the 3d transition metal atoms. These findings are essential for applications of MTe2 nanoribbons-based low-dimensional spintronic devices.
Symmetry and structure in the “Generalized Plasma Focus problem”
Authors: Auluck S. K. H.
Published: September 2024

The “Generalized Plasma Focus problem” refers to a generic class of plasma propagation phenomena that share many features of a dense plasma focus device. Its recent theoretical development has been shown to predict some features of the pinch phase in PF-1000 and POSEIDON. The theory attempts to decompose the plasma propagation problem into two weakly interdependent subproblems. This is achieved by expressing every physical variable of an applicable continuum model of the plasma as the product of a scaling parameter, which contains device-related information and represents its numerical magnitude, and a scaled variable that is devoid of device-related information, is of order unity, and represents the spatiotemporal structure of that variable. The first subproblem seeks a traveling surface of revolution whose local normal velocity equals the scaling parameter for velocity and is aligned with the magnetic force density. Spatiotemporal distributions of all the scaled variables must move along with this reference surface by definition. This paper explores the resulting scaling theory and its symmetry properties. A new coordinate transformation results in a formula for the spatiotemporal distribution of the magnetic field of the curved and non-steady plasma sheath. New insights into the snowplow effect are obtained. A current sheath with a rear boundary exists only when the current is decreasing and only when the current carrying plasma is less dense than the fill gas. The current sheath thickness is the same for small and large devices. The geomagnetic flux compression problem has an exact solution.
Co-evolving networks for opinion and social dynamics in agent-based models
Authors: Djurdjevac Conrad Nataša , Quang Vu Nhu , Nagel Sören
Published: September 2024

The rise of digital social media has strengthened the coevolution of public opinions and social interactions that shape social structures and collective outcomes in increasingly complex ways. The existing literature often explores this interplay as a one-directional influence, focusing on how opinions determine social ties within adaptive networks. However, this perspective overlooks the intrinsic dynamics driving social interactions, which can significantly influence how opinions form and evolve. In this work, we address this gap, by introducing the co-evolving opinion and social dynamics using stochastic agent-based models. Agents’ mobility in a social space is governed by both their social and opinion similarity with others. Similarly, the dynamics of opinion formation is driven by the opinions of agents in their social vicinity. We analyze the underlying social and opinion interaction networks and explore the mechanisms influencing the appearance of emerging phenomena, such as echo chambers and opinion consensus. To illustrate the model’s potential for real-world analysis, we apply it to General Social Survey data on political identity and public opinion regarding governmental issues. Our findings highlight the model’s strength in capturing the coevolution of social connections and individual opinions over time.
Compact widely tunable laser integrated on an indium phosphide membrane platform
Authors: Kabir Tasfia , Wang Yi , Tondini Stefano , Williams Kevin , Jiao Yuqing , Heck Martijn J. R.
Published: September 2024

We present the design, fabrication, and characterization results of a compact, widely tunable laser realized on an indium phosphide membrane-on-silicon (IMOS) platform. The laser features a compact Mach–Zehnder interferometric structure as the wavelength-selective intracavity filter with a footprint of 0.13 mm2. The filter design is optimized to ensure narrow filter transmission and high side-mode-to-main-mode-ratio, enabling single-mode operation for the laser. The high optical confinement on the IMOS platform can support tight waveguide bends. Leveraging this, the laser achieves a short cavity length, further enhancing the single-mode operation. Measurement results indicate a threshold current of 29 mA and a maximum on-chip output power of approximately 3.6 dBm and wall plug efficiency of 1.8%. The side-mode suppression ratio ranges from 30 to 44 dB, with a tuning range spanning 40 nm, from 1555 to 1595 nm. A complete tuning lookup table is generated via an automated setup incorporating a stochastic search algorithm.
An implicit solution for Asay foil trajectories generated by separable, sustained-production ejecta source models
Authors: Tregillis I. L. , Koskelo Aaron
Published: September 2024

We present a simple implicit solution for the time-dependent trajectory of a thin Asay foil ejecta diagnostic for the general case where the impinging ejecta cloud is generated by a source function characterized by an arbitrary (sustained) time dependence and a time-independent (stationary) particle velocity distribution. In the limit that the source function time dependence becomes a delta function, this solution—which is amenable to rapid numerical calculations of arbitrary accuracy—exactly recovers a previously published solution for the special case of instantaneous ejecta production. We also derive simple expressions for the free-surface arrival (catch-up) time as well as the true ejecta areal mass accumulation on the accelerating foil and place bounds on the level of error incurred when applying instant-production mass solutions to a sustained-production trajectory. We demonstrate these solutions with example calculations for hypothetical source functions spanning a wide range of ejecta production durations, velocity distributions, and temporal behaviors. These calculations demonstrate how the foil trajectory is often insensitive to the temporal dependence of the source function, instead being dominated by the velocity distribution. We quantify this insensitivity using a “compatibility score” metric. Under certain conditions, one may capitalize upon this insensitivity to obtain a good approximation of the second integral of the velocity distribution from the observed foil trajectory.
ScAlInN/GaN heterostructures grown by molecular beam epitaxy
Authors: Ye Haotian , Wang Rui , Yang Liuyun , Wang Jinlin , Wang Tao , Feng Ran , Xu Xifan , Lee Wonseok , Wang Ping , Wang Xinqiang
Published: September 2024

Rare-earth (RE) elements doped III-nitride semiconductors have garnered attention for their potential in advanced high-frequency and high-power electronic applications. We report on the molecular beam epitaxy of quaternary alloy ScAlInN, which is an encouraging strategy to improve the heterointerface quality when grown at relatively low temperatures. Monocrystalline wurtzite phase and uniform domain structures are achieved in ScAlInN/GaN heterostructures, featuring atomically sharp interface. ScAlInN (the Sc content in the ScAlN fraction is 14%) films with lower In contents (less than 6%) are nearly lattice matched to GaN, exhibiting negligible in-plane strain, which are excellent barrier layer candidates for GaN high electron mobility transistors (HEMTs). Using a 15-nm-thick Sc0.13Al0.83In0.04N as a barrier layer in GaN HEMT, a two-dimensional electron gas density of 4.00 × 1013 cm−2 and a Hall mobility of 928 cm2/V s, with a corresponding sheet resistance of 169 Ω/□, have been achieved. This work underscores the potential of alloy engineering to adjust lattice parameters, bandgap, polarization, interfaces, and strain in emerging RE-III-nitrides, paving the way for their use in next-generation optoelectronic, electronic, acoustic, and ferroelectric applications.
Numerical assessment of transient flow and energy dissipation in a Pelton turbine during startup
Authors: Sun Longgang , Wang Zhihu , Zhou Hengte , Wang Zhaoning , Guo Pengcheng
Published: September 2024

The Pelton turbine, known for its high application water head, wide efficient operating range, and rapid start-stop capability, is ideal for addressing intermittent and stochastic load issues. This study numerically analyzes the transient two-phase flow and energy dissipation during the startup of a Pelton turbine. Dynamic mesh technology controlled nozzle opening changes, and momentum balance equations managed runner rotation. Findings showed that the runner speed initially increased rapidly and then more slowly, and flow rate matched the nozzle opening variations. Runner torque first rose linearly, then decreased, with the fastest decline during nozzle closing. Hydraulic efficiency peaked early in nozzle reduction but then dropped sharply. Strong vortices formed due to upstream inflow and downstream backflow impact in the distributor pipe. The jet needle and guide vane improved flow in the converging section of nozzle, but flow began to diffuse with increased stroke. Initially, the jet spread fully on the bucket surface, but later only affected the bucket tips. Pressure fluctuations in the water supply mechanism were primarily due to jet needle motion, with higher amplitude during movement and lower when stationary. These fluctuations propagated upstream, weakening over distance. Reynolds stress work and turbulent kinetic energy generation, respectively, dominated energy transmission and energy dissipation, with their maximum contribution exceeding 96% and 70%. High-energy clusters corresponded to jet impact positions, highlighting jet-bucket interference as crucial for energy transport. This study established a performance evaluation method for Pelton turbine startups, supporting further investigation into characteristic parameters, flow evolution, and energy dissipation patterns.
Scaling of coherent structures in compressible wall-bounded turbulence
Authors: Lyu Fuzhou , Xu Chunxiao
Published: September 2024

Semi-local scales have been widely used in compressible wall-bounded turbulence, but it is still unclear whether they are applicable to the scaling of coherent structures, especially under conditions of high Mach number and cold wall temperature. By scrutinizing the direct numerical simulation dataset at different Mach numbers and wall temperatures, this paper demonstrates that the coherent structures normalized by semi-local scales are universal in size. In addition to this, we find that the ratios of Kolmogorov scales to semi-local scales are independent of Mach number and wall temperature. Thus, Kolmogorov scales can achieve the same scaling effect as the semi-local scales. The velocity spectra are also compared to verify the current scaling method quantitatively. A method to determine the threshold for the vortex identification criterion is proposed, allowing the same threshold for different cases to obtain vortices of similar size. The scaling of other statistics including turbulent kinetic energy, streamwise Reynolds normal stress, and root mean square of fluctuating vorticity is also investigated. A new velocity scale is proposed based on the total-stress-based transformation for mean streamwise velocity, which can collapse the profiles of these statistics more accurately than the semi-local velocity scale. The present paper demonstrates that through appropriate normalization, the structures and statistics of compressible turbulence become universal, reaffirming the validity of Morkovin's hypothesis even for the present high Mach number and cold wall cases.
Statistical features of the response of a superconducting hot-electron bolometer to extremely weak terahertz pulses of picosecond and nanosecond duration
Authors: Novikova T. I. , Kuznetsov K. A. , Korolev I. V. , Pentin I. V. , Prudkovskii P. A. , Kitaeva G. Kh.
Published: September 2024

We study the statistical distributions of the output signals of a superconducting hot-electron bolometer (HEB) detector exposed to weak photon pulses of 1 THz (terahertz) frequency. Pulses with variable photon numbers were generated through strongly non-degenerate parametric downconversion (PDC) in a LiNbO3 crystal at 4.8 K. Fundamental differences in histograms are found between two PDC pumping modes, with pulse widths of 28 ps and 10 ns. HEB response to a picosecond THz pulse was detected in the form of a single elementary electrical pulse (SEP), with the average amplitude proportional to radiation intensity and dispersion relative to the bolometer's dark current. HEB responses to extremely weak radiation intensities have been recorded using nanosecond pulsed illumination. We found that nanosecond histograms are asymmetrical and broaden as radiation intensity increases, indicating that the nanosecond response consists of several SEPs. Poisson–Gauss approximation of histograms indicates that not only the average number of SEPs increase but also the average amplitude of a SEP increases with increasing power of incident THz radiation.
Multicaloric response tuned by electric field in cylindrical MnAs/PZT magnetoelectric composite
Authors: Amirov Abdulkarim A. , Koliushenkov Maksim A. , Mukhuchev Abdula A. , Yusupov Dibir M. , Govorina Valeriya V. , Neznakhin Dmitriy S. , Govor Gennady A. , Aliev Akhmed M.
Published: September 2024

The possibility observation of the electric field controlled multicaloric response through quasi-isostatic compression as a result of the converse piezoelectric effect was demonstrated on the cylindrical type magnetoelectric composite MnAs/PZT. It was shown that an electric voltage of 100 V corresponding to an electric field of E ∼0.3 kV/mm applied to the walls of the piezoelectric component PZT of the MnAs/PZT composite contributes to an increase in the maximum adiabatic temperature change by 0.2 K in the temperature range of the magnetostructural phase transition of MnAs ∼317 K at a magnetic field change of 1.8 T. Numerical analysis using the finite element method has shown that an electric field voltage of 100 V is capable of creating a quasi-isostatic mechanical stress in the region inside a cylindrical PZT tube of ∼3 MPa. Moreover, in the region of weak pressures up to 10 MPa, the contribution to the total adiabatic temperature change from piezo-mechanical compression linearly depends on the electrical voltage that can be used for control by magnetic and caloric properties of multicaloric materials.
Fractal permeability model for power-law fluids in embedded tree-like branching networks based on the fractional-derivative theory
Authors: Zhou Huan , Gao Jun , Xiao Boqi , Chen Lei , Cao Jiyin , Long Gongbo , Zhang Jiacheng
Published: September 2024

The investigation of permeability in tree-like branching networks has attracted widespread attention. However, most studies about fractal models for predicting permeability in tree-like branching networks include empirical constants. This paper investigates the flow characteristics of power-law fluids in the dual porosity model of porous media in embedded tree-like branching networks. Considering the inherent properties of power-law fluids, non-Newtonian behavior effects, and fractal properties of porous media, a power-law fluids rheological equation is introduced based on the fractional-derivative theory and fractal theory. Then, an analytical formula for predicting the effective permeability of power-law fluids in dual porous media is derived. This analytical formula indicates the influences of fractal dimensions and structural parameters on permeability. With increasing length ratio, bifurcation series, and bifurcation angle, as well as decreasing power-law exponent and diameter ratio, the effective permeability decreases to varying degrees. The derived analytical model does not include empirical constants and is consistent with the non-Newtonian properties of power-law fluids, indicating that the model is an effective method for describing the flow process of complex non-Newtonian fluids in porous media in natural systems and engineering. Therefore, this study is of great significance to derive analytical solutions for the permeability of power-law fluids in embedded tree-like bifurcation networks.
Advancing spatial analysis of invasive species movement data to improve monitoring, control programs and decision making: feral cat home range as a case study
Authors: Wilson Cameron , Gentle Matthew , Fancourt Bronwyn
Published: September 2024

Context Many invasive animals are typically active across large areas, making monitoring and control programs expensive. To be efficacious, monitoring devices and control tools need to be strategically located to maximise the probability of encounter. This requires an understanding of how the target species uses the landscape, through identifying key habitat or landscape features that are preferred and used disproportionately more frequently by the species. Spatial analysis of animal movements can help identify high use areas. Aims The variability introduced by different range calculation methods can lead to uncertainty in subsequent habitat analyses. We aimed to determine which method is superior for accurate delineation of core areas for feral cats. Methods We analysed spatial data from 35 collared feral cats across four Australian study sites between 2016 and 2019, and compared the core areas generated using seven commonly used home range estimation methods. Key results We found that the α-hull method provided a higher precision of polygon placement, resulting in lower Type I and II errors and higher conformity to landscape features than other methods. The α-hull used a single default parameter and required no subjective input, making it a more objective, superior method. Conclusions We recommend that the α-hull method be used to define core activity areas for feral cats, enabling more robust habitat analysis, and identification of key habitat and landscape features to strategically target for monitoring and control programs. Implications This strategic approach could significantly improve cost efficiencies, particularly where existing management is widely dispersed, and core activity areas are clumped.
Sex work, syndemic conditions and condomless anal intercourse among men who have sex with men who engage in sex work in Latin America
Authors: Sönmez İbrahim , Lorente Nicolas , Mesías-Gazmuri Jocelyn , Schmidt Axel J. , Jonas Kai J. , Stuardo Avila Valeria , Marcus Ulrich , Veras Maria Amelia , Casabona Barbarà Jordi , Folch Cinta
Published: September 2024

Background In Latin American countries and Suriname, sexual transmission is one of the most common modes of HIV transmission, and men who have sex with men (MSM) who engage in sex work constitute a key population. Methods In a sample of MSM (N = 53,166) from the Latin American Internet Survey (2018) across 18 countries, we examined how sex work engagement is associated with syndemic conditions (multidrug use, homophobic abuse, depression/anxiety, alcohol dependency (CAGE alcohol questionnaire) and internalised homonegativity) and condomless anal intercourse with non-steady male partners using separate logistic regressions. We then used a structural equation model to determine if and how syndemic conditions mediate the relationship between sex work engagement and non-steady male partners. Results We found that getting paid for sex was associated with less condom use for anal intercourse with non-steady male partners and particular syndemic conditions, such as multidrug use, homophobic abuse and alcohol dependency. In our structural equation model, the results showed that the direct relationship between sex work engagement and non-steady male partners was positive and significant, and syndemic conditions partially mediated this relationship. Conclusion Our results highlight the continuing need for including MSM who engage in sex work and those who experience syndemic conditions in the prevention strategies targeted to MSM in Latin America and Suriname, to prevent the transmission of HIV.