bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin state driven weighted mobility and thermal conductivity properties of electron (Hf) doped strongly correlated Mott insulator LaCoO3 for thermoelectric applications
Authors: K. P. Mohamed Jibri , John Simon Sajan , J. Archana , S. Harish , M. Navaneethan
Published: July 2024

Here, we report the temperature-dependent electrical resistivity and thermopower of hole (Sr) and electron (Hf) doped LaCoO3 in the range of 303–753 K. With increasing temperature, the insulating behavior (303–503 K) with dominance of small polaron hopping to metallic transition (>503 K) is observed. The electron doped sample shows an insulating behavior (19.5 Ω cm) and positive thermopower (139 μV K−1) value due to the spin state blockade, i.e., electron hopping from high spin Co2+ to low spin Co3+ is strongly inhibited. The calculated weighted mobility (μW) of 0.01 to 0.96 cm2 V−1 s−1 validates the observed spin blockade mechanism in electron doped LaCoO3. The fluctuation of spin/orbital ordering and point defect scattering results in the low thermal conductivity of 0.5 W m−1 K−1 for Hf doped LaCoO3. The spin state blockade observed in the electrical resistivity and low lattice thermal conductivity reveals that spin state transition drives the thermoelectric response in Mott insulator LaCoO3.
Rotationally induced ingress in rotor–stator systems
Authors: Graikos D. , Tang H. , Carnevale M. , Bailey N. Y. , Scobie J. A.
Published: July 2024

The presence of a rotating disk adjacent to a stationary disk forms a rotor–stator cavity known as a wheel-space. It is necessary for gas turbine wheel-spaces to be purged with sealing flow bled from the compressor to counteract the harmful effects of ingress. This paper presents a combined experimental, theoretical, and computational study of rotationally induced ingress in rotor–stator systems. Measurements were made in a wheel-space with an axial clearance rim seal under axisymmetric conditions in the absence of a mainstream annulus through-flow. Ingress was quantified using a gas concentration technique and the flow structure in the cavity was explored with static and total pressure measurements to determine the swirl ratio. A low-order theoretical model was developed based on the boundary layer momentum-integral equations. The theory gave excellent results when predicting the effects of ingress and purge flows on the radial pressure and swirl gradients. Unsteady Reynolds-Averaged Navier–Stokes computations were conducted to provide greater fluid dynamic insight into the wheel-space flow structure and ingress through the rim seal. The computational results demonstrated some of the closest agreement with experimental measurements of ingress available in the literature, showing that rotationally induced ingress is dominated by unsteady large-scale structures in the rim seal gap instead of the previously ascribed disk-pumping effect. The study serves as an important validation case for investigations of ingress in rotor–stator systems in more complex environments.
Vacuum deposition of χ(2) nonlinear organic single crystal films on silicon
Authors: Krainova Nina , Johnson Holly M. , Lampande Raju , Gao Siyu , Marom Noa , Rand Barry P. , Giebink Noel C.
Published: July 2024

Integrating second order nonlinear (χ(2)) optical materials on chip is an ongoing challenge for Si photonics. Noncentrosymmetric molecular crystals have the potential to deliver high χ(2) nonlinearity with good thermal stability, but so far have been limited to growth from solution or the melt, which are both difficult to control and scale up in manufacturing. Here, we show that large (>100 μm) single crystal domains of the nonlinear molecule 2-[3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene] malononitrile (OH1) can be grown monolithically on either glass or Si via vacuum evaporation, followed by a short thermal annealing step. The crystallites are tens of nanometer thick and exhibit strong second harmonic generation with their primary χ(2) tensor component lying predominantly in plane. Remarkably, we find that a single domain can grow uninterrupted through nearby channels etched on a Si wafer, which may provide a path to integrate OH1 on Si or Si3N4 waveguides for a broad range of χ(2)-based photonic integrated circuit functionality.
In situ grazing incidence synchrotron x-ray diffraction studies on the wakeup effect in ferroelectric Hf0.5Zr0.5O2 thin films
Authors: Ahn Dante , Anoop Gopinathan , Lee Jun Young , Goh Youngin , Seol WooJun , Unithrattil Sanjith , Samanta Shibnath , Choi Je Oh , Park Seong Min , Lee Su Yong , Lee Hyeon Jun , Park Jong Bae , Jeon Sanghun , Jo Ji Young
Published: July 2024

The discovery of ferroelectricity in HfO2 ultrathin films has gathered considerable interest from the microelectronic industry owing to their compatibility with complementary metal oxide semiconductor technology. However, a significant challenge in utilizing HfO2 thin films for commercial devices is the wakeup effect, which is an increase in polarization with the number of electric field cycles in HfO2-based capacitors. Despite efforts to develop wakeup-free HfO2 thin films, the root cause of this effect remains elusive. Some studies attribute it to the tetragonal (T) to orthorhombic (O) phase transformation, while others suggest it is due to the redistribution of oxygen vacancies within the HfO2 layer during electric field cycling. This study investigated the phase transformation dynamics and oxygen vacancy distributions in TiN/Hf0.5Zr0.5O2/TiN capacitors subjected to electric field cycling using in situ grazing incidence synchrotron x-ray diffraction and ex situ x-ray photoelectron spectroscopy. The as-grown HZO films were crystallized in a mixed phase consisting of monoclinic (M), tetragonal, and orthorhombic fractions. The T-phase volume fraction decreased continuously up to 10k electric field cycles. In contrast, the O-phase fraction increased within the first 100 cycles and then stabilized with further cycling. The redistribution of oxygen vacancies occurred continuously throughout the cycling process. The results revealed that continuous oxygen vacancy redistribution during electric field cycling resulted in phase transformation between the T-, O-, and M-phases. The study provides insight into the phase transformation dynamics and oxygen vacancy redistribution in TiN/Hf0.5Zr0.5O2/TiN capacitors during electric field cycling, shedding light on the underlying mechanisms of the wakeup effect.
Discrete spectrum of the magnetic Laplacian on almost flat magnetic barriers
Authors: Miranda Germán
Published: July 2024

The magnetic Laplacian with a step magnetic field has been intensively studied during the last years. We adapt the construction introduced by Bonnaillie-Noël et al. [Bull. London Math. Soc. 56, 2529 (2024)] to prove the existence of bound states of a new effective operator involving a magnetic step field on a domain with an almost flat magnetic barrier. This result emphasizes the fact that even a small non-smoothness of the discontinuity region can cause the appearance of eigenvalues below the essential spectrum. We also give an example where this effective operator arises.
Plasmon-mediated dynamics and lasing of nanoemitters enhanced by dispersing nanorings
Authors: Burlak Gennadiy , Medina-Ángel Gustavo , Calderón-Segura Yessica
Published: July 2024

We investigate the plasmon-mediated nonlinear dynamics and the optics of a laser emission of random nanoemitters (NEs) embedded in a two-dimensional (2D) lattice of conducting nanorings (NRs) enhanced by plasmon–polariton (PP) excitations. The interaction of quantum NEs with the PP field in the NRs perturbs the dynamics of the electronic populations in NEs, leading to a significant dependence of laser generation (dynamics) on the plasma frequency ωp of PP. This results in a strong coupling of NE field emission with the PP field and sharp variations of the average current in the NR lattice. The phase transition in the system was found when the macroscopic structures of PP fields are excited simultaneously in different regions of the system if ωp (control parameter) reaches critical value ωc. We have established the analytical dependence of the PP current I = I(ωp/ωc) on the plasma frequency, which is in excellent agreement with the results of numerical simulations. This effect may allow the design of new types of PP active devices with the use of conducting NRs in modern nanoelectronics.
STORMM: Structure and topology replica molecular mechanics for chemical simulations
Authors: Cerutti David S. , Wiewiora Rafal , Boothroyd Simon , Sherman Woody
Published: July 2024

The Structure and TOpology Replica Molecular Mechanics (STORMM) code is a next-generation molecular simulation engine and associated libraries optimized for performance on fast, vectorized central processor units and graphics processing units (GPUs) with independent memory and tens of thousands of threads. STORMM is built to run thousands of independent molecular mechanical calculations on a single GPU with novel implementations that tune numerical precision, mathematical operations, and scarce on-chip memory resources to optimize throughput. The libraries are built around accessible classes with detailed documentation, supporting fine-grained parallelism and algorithm development as well as copying or swapping groups of systems on and off of the GPU. A primary intention of the STORMM libraries is to provide developers of atomic simulation methods with access to a high-performance molecular mechanics engine with extensive facilities to prototype and develop bespoke tools aimed toward drug discovery applications. In its present state, STORMM delivers molecular dynamics simulations of small molecules and small proteins in implicit solvent with tens to hundreds of times the throughput of conventional codes. The engineering paradigm transforms two of the most memory bandwidth-intensive aspects of condensed-phase dynamics, particle–mesh mapping, and valence interactions, into compute-bound problems for several times the scalability of existing programs. Numerical methods for compressing and streamlining the information present in stored coordinates and lookup tables are also presented, delivering improved accuracy over methods implemented in other molecular dynamics engines. The open-source code is released under the MIT license.
Micropillar compression of single-crystal single-phase (Co, Cu, Mg, Ni, Zn)O
Authors: Norman Jacob E. , Wang Xin , Dupuy Alexander D. , Schoenung Julie M.
Published: July 2024

Bulk, polycrystalline (Co, Cu, Mg, Ni, Zn)O was synthesized using solid-state sintering. Micropillars were prepared and mechanically deformed along three crystallographic orientations: (001), (101), and (111). Pillars (001) and (111) cracked, while Pillar (101) remained intact. Pillars (001) and (101) exhibited activated slip systems, confirmed by a large stress drop, and the presence of slip bands, respectively. Schmid factor (SF) analysis was performed to examine the effect of grain orientations on dislocation activity and slip behavior. SF values range from 0 to 0.5, with non-zero values indicating potential for slip. Six slip systems exist in the (Co, Cu, Mg, Ni, Zn)O rock salt crystal structure: 1/2⟨110⟩11¯0. For the (001) orientation, four slip systems are potentially active (SF = 0.5). For the (101) orientation, there are four potentially active slip systems (SF = 0.25). For the (111) orientation, no potentially active slips systems exist (SF = 0). Dislocation structures, which were observed post-compression via transmission electron microscopy, demonstrated variations in size, number, and distribution across the pillar, depending on micropillar orientation. Entangled dislocations created misorientation in Pillar (001), which led to the possible formation of subgrains, while singular dislocations were observed in Pillar (101), and a lack of dislocations was observed in Pillar (111). Zener–Stroh type dislocation entanglement-mediated cracking is the proposed cause of the transgranular-type cracks in Pillar (001). The possible subgrain formation, or lack of formation, respectively, caused intergranular-type cracks to additionally form in Pillar (001), while Pillar (111) only exhibited transgranular-type brittle fracture. In combination, these findings highlight the importance of dislocation activity, without the need for elevated temperature, and grain orientation in controlling the mechanical deformation response in single-phase (Co, Cu, Mg, Ni, Zn)O.
Unifying the temperature dependent dynamics of glass formers
Authors: Schlenoff Joseph B. , Akkaoui Khalil
Published: July 2024

Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, Tg, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory (TST), we delve into the atomic/molecular level picture of how microscopic localized unit relaxations, or “cage rattles,” evolve to macroscopic structural relaxations above Tg. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, nα, which ranges from 1 to 4, allowing a systematic classification of glass formers, GFs, that is compared to fragility; and (2) near Tg, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the “primitive” lifetime, τ1, of one unit rattling in its cage. Relaxation maps illustrate how Johari–Goldstein β-relaxations stem from the rattle of nα units. We analyzed a wide variety of glassy materials and materials with a glassy response using literature data. Our four-parameter equation fits “strong” and “weak” GFs over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high “unphysical” apparent frequencies is discussed. Enthalpy–entropy compensation is clearly illustrated using the TST approach.
Explosively driven Richtmyer–Meshkov instability jet suppression and enhancement via coupling machine learning and additive manufacturing
Authors: Sterbentz Dane M. , Kline Dylan J. , White Daniel A. , Jekel Charles F. , Hennessey Michael P. , Amondson David K. , Wilson Abigail J. , Sevcik Max J. , Villena Matthew F. L. , Lin Steve S. , Grapes Michael D. , Sullivan Kyle T. , Belof Jonathan L.
Published: July 2024

The ability to control the behavior of fluid instabilities at material interfaces, such as the shock-driven Richtmyer–Meshkov instability, is a grand technological challenge with a broad number of applications ranging from inertial confinement fusion experiments to explosively driven shaped charges. In this work, we use a linear-geometry shaped charge as a means of studying methods for controlling material jetting that results from the Richtmyer–Meshkov instability. A shaped charge produces a high-velocity jet by focusing the energy from the detonation of high explosives. The interaction of the resulting detonation wave with a hollowed cavity lined with a thin metal layer produces the unstable jetting effect. By modifying the characteristics of the detonation wave prior to striking the lined cavity, the kinetic energy of the jet can be enhanced or reduced. Modifying the geometry of the liner material can also be used to alter jetting properties. We apply optimization methods to investigate several design parameterizations for both enhancing or suppressing the shaped-charge jet. This is accomplished using 2D and 3D hydrodynamic simulations to investigate the design space that we consider. We also apply new additive manufacturing methods for producing the shaped-charge assemblies, which allow for the experimental testing of complicated design geometries obtained through computational optimization. We present a direct comparison of our optimized designs with experimental results carried out at the High Explosives Application Facility at Lawrence Livermore National Laboratory.
Enhancing smoke management in underground parking areas using jet fan systems with a focus on dead-end areas
Authors: Chakheirlou Saeed Hazrati , Omrani Abdolnaser , Param Behnam Heydari , Motallebzadeh Roghayyeh
Published: July 2024

This study delves into the utilization of jet fans in underground parking structures for smoke management during fires, with a specific focus on enhancing smoke control near critical areas adjacent to dead-end sections through innovative jet fan designs. Through the analysis of airflow patterns and computational fluid dynamic simulations, the research aims to effectively contain smoke and prevent its dispersion to unaffected zones. Findings underscore the significance of parking layout designs in ventilation strategies and soot dispersion rates. Altering the downward orientation of the jet fan outlet results in a notable portion of smoke being confined within the parking facility. Additionally, widening the jet fan outlet, as proposed in the design, can enhance smoke evacuation in all directions. Two hazard detection scenarios were executed within the parking structure following the British standard (BS), with one scenario simulated as a fire ignition source. The chosen scenario considers all escape routes and evacuation procedures within the underground parking area based on architectural specifications. By employing OpenFOAM software with the buoyantBoussinesqPimpleFOAM solver, the study assesses the efficacy of this approach, achieving a reduction in airflow irregularities of over 30%. It also provides valuable insights for designers to refine their comprehension of jet fan design, recommending tailored designs for specific zones. This research offers practical guidance for designers to optimize jet fan configurations for effective smoke control in underground parking facilities.
Characterization of the microstructural, magnetic, and thermal behaviors of boron-doped Fe–Co–Ni alloys produced via mechanical alloying
Authors: Khitouni Nawel , Daly Rakia , Daza Jason , Alsulami Abdulelah H. , Suñol Joan-Josep , Khitouni Mohamed
Published: July 2024

FeCoNi alloys, both doped and undoped, were synthesized into nanocrystalline forms using a high-energy mechanical milling technique. The study used the x-ray diffraction technique to examine the microstructure characteristics of powder materials. The identified patterns were examined using Maud software. It was found that mechanical alloying produced solid solutions with BCC and FCC structures and crystallite sizes in the range of 25 nm after 100h of milling. The BCC-Fe(Co,Ni,B) and orthorhombic-Fe3B phases were refined for the alloy doped with amorphous boron, while only the bcc-Fe(Co,Ni,B) phase was identified for the alloy doped with crystalline boron. Meanwhile, the FeCoNi alloy revealed a mixture of FCC-Co and BCC-FeCoNi phases. This sample has a soft ferromagnetic behavior, whereas the doped ones have hard ferromagnetic behaviors. The squareness ratios (Mr/Ms) are typically low. The microstructural variations were associated with magnetic characteristics. The thermal stability of the alloyed powder mixtures was investigated by the DSC technique from 25 to 700 °C for 2h. The alloyed samples were first annealed at selected temperatures and then analyzed using x-ray diffraction. The obtained x-ray diffraction results proved that at temperatures below 230 °C, the initial heavy deformed structure’s structural relaxation followed by the recrystallization of the fcc-Co phase and, at higher temperatures, the recrystallization of new phases, such as α-FeCo, fcc-FeNi, fcc-Ni3Fe, and borides of the (FeNi)23B6, -(FeCo)23B6 types. The stability of the crystalline phases that are formed and their magnetic characteristics can be regulated through a carefully calibrated annealing process.
Generation of gamma photons and pairs with transverse orbital angular momentum via spatiotemporal optical vortex pulse
Authors: Zhang Cui-Wen , Zhang De-Sheng , Xie Bai-Song
Published: July 2024

We present the generation of well-collimated gamma photons and pairs with extrinsic transverse orbital angular momentum (TOAM) through the head-on collision of an intense spatiotemporal optical vortex (STOV) pulse carrying intrinsic TOAM and a high-energy electron beam. It is found that the TOAM of STOV pulse remains almost unchanged, and the TOAM is conserved in the center-of-mass frame. Moreover, there exhibits a duality for particles TOAM in the CMF and laboratory frame when the initial location of high-energy electron beam is different. Furthermore, the TOAM of gamma photons in the CMF increases while that of positrons decreases as the topological charge of STOV pulse increases, whereas in the LF, the TOAM of both gamma photons and positrons decreases. The result under the same pulse intensity is better than that under the same pulse energy. The increase in the initial energy of high-energy electrons leads to an enhancement of the TOAM of both gamma photons and positrons in both frames. Gamma photons and electrons/positrons with TOAM as a new degree of freedom may have extensive applications in optical communication, astrophysics, nanomaterials, and other fields.
Simulation of novel Pt-M nanocatalysis for proton exchange membrane fuel cells
Authors: He Yusong , Bai Minli
Published: July 2024

To enhance proton exchange membrane fuel cells, an ultra-thin cathode catalytic layer based on PtPdCu nanowires is analyzed. The purpose is to optimize fuel cell performance by analyzing key parameters of the catalytic layer in detail, such as thickness and porosity. Numerical simulation methods are used to simulate the structural parameters and operating conditions of the catalytic layer using COMSOL Multi-physics software. The paper focuses on analyzing the changes in the transport resistance of electrons, protons, and oxygen within the catalytic layer, as well as the measurement method of the porosity of the catalytic layer. The results demonstrated that when the catalytic layer thickness reached 450 nm, the power density of proton exchange membrane fuel cells reached its peak, which was 801 and 996 mW/cm2, respectively. In catalytic layers with a thickness of less than 1 µm, the transfer efficiency of oxygen and electrons was higher. When the thickness exceeds 5 µm, oxygen transmission was hindered, and the proton transfer path becomes longer. The average porosity was 44.02%, indicating a high structural consistency of the catalytic layer. In terms of redox reaction performance, the area specific activity of PtPdCuNWs was four times that of commercial Pt/C. This study emphasizes the importance of the ultra-thin cathode catalytic layer in optimizing the performance of proton exchange membrane fuel cells and provides insights into improving catalytic efficiency and overall fuel cell performance through micro-structure design.
Jahn–Teller effect driven dielectric anomaly and intrinsic magnetodielectric behaviors in nickel chromate
Authors: Wang L. G. , Cui H. , Zhu C. M. , Wang R. , Yu G. B. , Su X. F. , Jiang X. L. , Jiang Y.
Published: July 2024

Some spinel chromium oxides with the chemical formula ACr2O4 exhibit magnetic-induced multiferroicity due to the special spiral spin order. However, because of the relatively low temperature of the ordered spiral phase, this kind of multiferroicity generally displays a limited coexistence of magnetic and ferroelectric orders in a narrow temperature range. The Jahn–Teller (JT) effect, serving as a crucial link between charge and orbit degrees of freedom, can facilitate efficient modulation of multiferroic properties. In this work, Ni1−xCuxCr2O4 (0 ≤ x ≤ 0.2) series are synthesized by occupying the same Wyckoff site with two kinds of JT ions. The microstructure and JT distortion can be distinctly influenced by varying the doping level of Cu2+ ions. Particularly, Ni0.85Cu0.15Cr2O4 (x = 0.15) presents the pronounced JT distortion, accompanied by observation of dielectric anomaly at ∼78 K, resulting from spin–orbit coupling. This implies that the JT effect can significantly promote the contribution of spin–orbit coupling in magnetoelectric correlation. Moreover, the magnetodielectric effect induced by intrinsic magnetoelectric coupling is confirmed in Ni0.85Cu0.15Cr2O4 over a wide temperature range of 10–200 K, which is much higher than the Néel temperature of ∼85 K. It indicates that spin–orbit coupling based on the JT effect could overcome the constraint of magnetic order to achieve effective control on electric polarization performance under an applied magnetic field, thereby showing broad application prospects.
Sign reversal of visible to UV photocurrent in core–shell n-InGaN/p-GaN nanowire photodetectors
Authors: Pan Xingchen , Deng Rongli , Hong Hao , Luo Mingrui , Nötzel Richard
Published: July 2024

We demonstrate the change of the sign from negative to positive of the self-powered photovoltaic photocurrent in core–shell n-InGaN/p-GaN nanowire heterojunctions within the visible to UV wavelength range. Such dual-polarity photodetectors are of broad interest to provide extended functionalities for optoelectronic devices, starting with dual-wavelength photodetectors. The physics of the photocurrent sign reversal is understood by a well-balanced selective absorption and photocarrier generation, photocarrier transfer, and thermal excitation paths in the core–shell n-InGaN/p-GaN nanowire functional absorber with different bandgap energies and opposite inner- and surface energy band bendings. The basic dual-wavelength photodetector operation parameters are given.
THz generation by AlGaAs/GaAs heterostructured p-i-n diode
Authors: Trukhin V. , Mustafin I. , Malevich V. , Fan X. , Kalinovskii V. , Kontrosh E. , Prudchenko K.
Published: July 2024

The generation of terahertz radiation by heterostructure p-i-n AlxGa1−xAs/GaAs diodes excited by femtosecond optical pulses was studied experimentally and using the Monte Carlo method. It is shown that when the reverse bias varies, the terahertz generation mechanism changes. With a positive bias on the p-i-n diode, the THz generation mechanism is due to the reflection of the photoexcited electrons from the interface. With a large internal electric field, THz generation in the p-i-n diode occurs due to the acceleration of electrons at the ballistic stage of their movement in the electric field to velocities significantly exceeding the steady state velocity (“velocity overshoot”). The subsequent sharp decrease in velocity of electrons is associated with their inter-valley transitions from the Γ-valley to the L-valley of the conduction band. At electric fields less than 22 kV/cm, the effect of electric field screening by photoexcited carriers has a significant impact on the formation of photocurrent and, accordingly, on the THz generation mechanism. As the reverse bias decreases, this effect leads to a shift in the maximum of the THz pulse toward shorter times and it begins to dominate at electric fields less than 10 kV/cm.
PyDFT-QMMM: A modular, extensible software framework for DFT-based QM/MM molecular dynamics
Authors: Pederson John P. , McDaniel Jesse G.
Published: July 2024

PyDFT-QMMM is a Python-based package for performing hybrid quantum mechanics/molecular mechanics (QM/MM) simulations at the density functional level of theory. The program is designed to treat short-range and long-range interactions through user-specified combinations of electrostatic and mechanical embedding procedures within periodic simulation domains, providing necessary interfaces to external quantum chemistry and molecular dynamics software. To enable direct embedding of long-range electrostatics in periodic systems, we have derived and implemented force terms for our previously described QM/MM/PME approach [Pederson and McDaniel, J. Chem. Phys. 156, 174105 (2022)]. Communication with external software packages Psi4 and OpenMM is facilitated through Python application programming interfaces (APIs). The core library contains basic utilities for running QM/MM molecular dynamics simulations, and plug-in entry-points are provided for users to implement custom energy/force calculation and integration routines, within an extensible architecture. The user interacts with PyDFT-QMMM primarily through its Python API, allowing for complex workflow development with Python scripting, for example, interfacing with PLUMED for free energy simulations. We provide benchmarks of forces and energy conservation for the QM/MM/PME and alternative QM/MM electrostatic embedding approaches. We further demonstrate a simple example use case for water solute in a water solvent system, for which radial distribution functions are computed from 100 ps QM/MM simulations; in this example, we highlight how the solvation structure is sensitive to different basis-set choices due to under- or over-polarization of the QM water molecule’s electron density.
Common anion rule in oxide heterointerfaces: Experimental verification by in situ photoemission spectroscopy
Authors: Hayasaka Ryotaro , Kanda Tatsuhiko , Masutake Yuuki , Nguyen Duy Khanh , Hasegawa Naoto , Inoue Seitaro , Wada Asato , Kitamura Miho , Shiga Daisuke , Yoshimatsu Kohei , Kumigashira Hiroshi
Published: July 2024

The band alignment at the interface is one of the fundamental parameters for designing electronic devices and artificial functional materials. However, there is no firmly established guideline for oxide heterostructures, limiting the functional design of oxide heterostructures. Here, we provide spectral evidence that the band diagram of oxide heterointerfaces is well described by the Zhong and Hansmann scheme based on the common anion rule [Z. Zhong and P. Hansmann, Phys. Rev. X 7, 011023 (2017)]. By utilizing the elemental selectivity of Ti 2p–3d resonant photoemission for the Ti 3d state near the Fermi level, we directly visualize the presence or absence of charge transfer from the overlayer films to SrTiO3 in prototypical heterointerfaces of SrVO3/SrTiO3 and SrNbO3/SrTiO3. It is found that the charge transfer occurs in SrNbO3/SrTiO3 but not in SrVO3/SrTiO3, as predicted by the Zhong and Hansmann scheme, indicating that the presence or absence, as well as the sign and amount, of interfacial charge transfer is predicted by this scheme. Our findings provide guidelines for designing and controlling the functionalities in oxide nanostructures.
Rab10-CAV1 mediated intraluminal vesicle transport to migrasomes
Authors: Li Yong , Wen Yiling , Li Ying , Tan Xinyi , Gao Shuaixin , Fan Peiyao , Tian Wenmin , Wong Catherine C.L. , Chen Yang
Published: July 2024

Migrasomes, vesicular organelles generated on the retraction fibers of migrating cells, play a crucial role in migracytosis, mediating intercellular communication. The cargoes determine the functional specificity of migrasomes. Migrasomes harbor numerous intraluminal vesicles, a pivotal component of their cargoes. The mechanism underlying the transportation of these intraluminal vesicles to the migrasomes remains enigmatic. In this study, we identified that Rab10 and Caveolin-1 (CAV1) mark the intraluminal vesicles in migrasomes. Transport of Rab10-CAV1 vesicles to migrasomes required the motor protein Myosin Va and adaptor proteins RILPL2. Notably, the phosphorylation of Rab10 by the kinase LRRK2 regulated this process. Moreover, CSF-1 can be transported to migrasomes through this mechanism, subsequently fostering monocyte–macrophage differentiation in skin wound healing, which served as a proof of the physiological importance of this transporting mechanism.
Parallel vector memories in the brain of a bee as foundation for flexible navigation
Authors: Patel Rickesh N. , Roberts Natalie S. , Kempenaers Julian , Zadel Ana , Heinze Stanley
Published: July 2024

Insects rely on path integration (vector-based navigation) and landmark guidance to perform sophisticated navigational feats, rivaling those seen in mammals. Bees in particular exhibit complex navigation behaviors including creating optimal routes and novel shortcuts between locations, an ability historically indicative of the presence of a cognitive map. A mammalian cognitive map has been widely accepted. However, in insects, the existence of a centralized cognitive map is highly contentious. Using a controlled laboratory assay that condenses foraging behaviors to short distances in walking bumblebees, we reveal that vectors learned during path integration can be transferred to long-term memory, that multiple such vectors can be stored in parallel, and that these vectors can be recalled at a familiar location and used for homeward navigation. These findings demonstrate that bees meet the two fundamental requirements of a vector-based analog of a decentralized cognitive map: Home vectors need to be stored in long-term memory and need to be recalled from remembered locations. Thus, our data demonstrate that bees possess the foundational elements for a vector-based map. By utilizing this relatively simple strategy for spatial organization, insects may achieve high-level navigation behaviors seen in vertebrates with the limited number of neurons in their brains, circumventing the computational requirements associated with the cognitive maps of mammals.
Time-scale invariant contingency yields one-shot reinforcement learning despite extremely long delays to reinforcement
Authors: Gallistel Charles R. , Shahan Timothy A.
Published: July 2024

Reinforcement learning inspires much theorizing in neuroscience, cognitive science, machine learning, and AI. A central question concerns the conditions that produce the perception of a contingency between an action and reinforcement—the assignment-of-credit problem. Contemporary models of associative and reinforcement learning do not leverage the temporal metrics (measured intervals). Our information-theoretic approach formalizes contingency by time-scale invariant temporal mutual information. It predicts that learning may proceed rapidly even with extremely long action–reinforcer delays. We show that rats can learn an action after a single reinforcement, even with a 16-min delay between the action and reinforcement (15-fold longer than any delay previously shown to support such learning). By leveraging metric temporal information, our solution obviates the need for windows of associability, exponentially decaying eligibility traces, microstimuli, or distributions over Bayesian belief states. Its three equations have no free parameters; they predict one-shot learning without iterative simulation.
Functional transition from hear
to nonvisual sensory and hearsay evidential categories
Authors: Suzuki Hiroyuki
Published: July 2024

This article presents a development of evidential categories derived from a verb related to the auditory sense in
the evidential system attested in rGyalthang Tibetan varieties. The language varieties under study possess a morphological
distinction of at least five evidentials in the access-to-information category and two evidentials in the source-of-information
category. The discussion focuses on one morpheme derived from the Literary Tibetan verb grag ‘resound, hear’ used
for both categories, and examines its process of grammaticalisation and degrammaticalisation. Elicited data illustrate the
following functions: (1) grag as a nonvisual sensory evidential suffix that was further degrammaticalised as a
copulative nonvisual sensory verb stem; (2) grag as a hearsay marker in a separate syntactic slot, which extended
from (1); and (3) grag as a lexical verb stem meaning ‘hear’ [the common origin to (1) and (2)], which underwent
two grammaticalisation processes.
De novo lipid synthesis and polarized prenylation drive cell invasion through basement membrane
Authors: Park Kieop , Garde Aastha , Thendral Siddharthan B. , Soh Adam W.J. , Chi Qiuyi , Sherwood David R.
Published: July 2024

To breach the basement membrane, cells in development and cancer use large, transient, specialized lipid-rich membrane protrusions. Using live imaging, endogenous protein tagging, and cell-specific RNAi during Caenorhabditis elegans anchor cell (AC) invasion, we demonstrate that the lipogenic SREBP transcription factor SBP-1 drives the expression of the fatty acid synthesis enzymes POD-2 and FASN-1 prior to invasion. We show that phospholipid-producing LPIN-1 and sphingomyelin synthase SMS-1, which use fatty acids as substrates, produce lysosome stores that build the AC’s invasive protrusion, and that SMS-1 also promotes protrusion localization of the lipid raft partitioning ZMP-1 matrix metalloproteinase. Finally, we discover that HMG-CoA reductase HMGR-1, which generates isoprenoids for prenylation, localizes to the ER and enriches in peroxisomes at the AC invasive front, and that the final transmembrane prenylation enzyme, ICMT-1, localizes to endoplasmic reticulum exit sites that dynamically polarize to deliver prenylated GTPases for protrusion formation. Together, these results reveal a collaboration between lipogenesis and a polarized lipid prenylation system that drives invasive protrusion formation.
Machine learning-based rapid analysis of the failure progress of thin-film electrodes from electric impedance spectroscopy (EIS) data
Authors: Li Shucai , Zhao Yuqi , Wu Zhenyu , Li Lei , Luo Chuan
Published: July 2024

Parylene C is a common substrate and encapsulation material used in implantable microelectrodes. Its reliability and failure are of great significance in the research and application of microelectrodes. In this study, three different failure stages of Parylene C thin-film electrodes were modeled using equivalent circuits, and the electric impedance spectroscopy of the electrodes were rapidly analyzed 9 different machine learning algorithms to identify the failure stages. The results showed that the three equivalent circuit models (ECMs) can represent the dynamics of the three failure stages of the Parylene C thin-film electrodes. The support vector machine (SVM) algorithm achieves more than 93% accuracy in identifying the ECMs from electric impedance spectroscopy data with an average time of 0.0273 s. The SVM algorithm has great potential in fast analysis of electric impedance spectroscopy for the endurability study and application of implantable microelectrodes.
First-principles explorations on 2D transition metal diborides featuring inverse sandwich structures and their gas sensing properties
Authors: Wang Shukai , Shi Kai , Li Jie , Lyu Juan , Li Fengyu
Published: July 2024

First-principles calculations were carried out to investigate the stability of two dimensional (2D) MB2 monolayers (TiB2-I, VB2-I, MnB2-I, TiB2-II, ScB2-II, NiB2-II) with an inverse sandwich configuration and their potential as efficient gas sensors to detect toxic gas molecules. We first identified six stable 2D MB2 configurations, based on stability evaluation covering thermodynamical, dynamical, and thermal aspects. To investigate the performance of these novel structures as gas sensors, the adsorption behavior of five toxic gas molecules (CO, NO, NO2, NH3, SO2) on MB2 has been explored, and the charge transfer and magnetic changes of these adsorption systems were analyzed. It is found that five gases are all chemisorbed on 2D MB2. Particularly, when CO is adsorbed on TiB2-II, the magnetism of the system undergoes a significant change from non-magnetism to antiferromagnetism, showing selectivity for CO. Furthermore, the current−voltage characteristics obtained from simulations confirm gas sensing performance. The TiB2-II is expected to be a candidate material for CO gas sensor with short recovery time (7.50 × 10−10 s). Our theoretical study provides new ideas for designing gas sensor nanomaterials with magnetism alteration as the indicator featuring easy measurement and fast response.
Spectral and microstructural analysis of the effect of the Ga+ implantation on diamond: a CL-EELS study
Authors: Valendolf J , Piñero J C , Lloret F , Alba G , Eon D , Araujo D
Published: July 2024

Due to its capacity to achieve nanometre-scale machining and lithography, a focused ion beam (FIB) is an extended tool for semiconductor device fabrication and development, in particular, for diamond-based devices. However, some technological steps are still not fully optimized for its use. Indeed, ion implantation seems to affect the crystalline structure and electrical properties of diamond. For this study, a boron-doped ([B] ∼ 1017 atoms·cm−3) diamond layer grown by chemical vapour deposition was irradiated using Ga+ by FIB, with 1 nA current and 5, 20, and 30 keV of acceleration voltage. The Ga+ implanted diamond layer has been analysed through cathodoluminescence (CL) and scanning transmission electron microscopy (STEM)-related techniques. The beam penetration depth has been simulated by Monte Carlo calculations of both Ga+ (FIB) and e− (CL) beams at different energies. The comparative CL analysis of the layer as-grown and after implantation revealed peaks related to defects, such as A band, H3 centre, and defects present in the green band region. The STEM studies for the 30 keV implanted sample showed that the diamond lattice is affected by the damage, evidencing amorphisation in the layer with a sp2/sp3 ratio of 1.37, estimated by electron energy loss spectroscopy. Therefore, this study highlights the effects of the Ga+ implantation on the optical and structural characteristics of diamond, using different methods.
Relative equilibria of mechanical systems with rotational symmetry
Authors: Arathoon Philip
Published: July 2024

We consider the task of classifying relative equilibria for mechanical systems with rotational symmetry. We divide relative equilibria into two natural groups: a generic class which we call normal, and a non-generic abnormal class. The eigenvalues of the locked inertia tensor descend to shape-space and endow it with the geometric structure of a three-web with the property that any normal relative equilibrium occurs as a critical point of the potential restricted to a leaf from the web. To demonstrate the utility of this web structure we show how the spherical three-body problem gives rise to a web of Cayley cubics on the three-sphere, and use this to fully classify the relative equilibria for the case of equal masses.
PET digitization chain for Monte Carlo simulation in GATE
Authors: Salvadori Julien , Merlet Antoine , Presles Benoit , Cabello Jorge , Su Kuan-Hao , Cochet Alexandre , Etxebeste Ane , Vrigneaud Jean-Marc , Sarrut David
Published: July 2024

Objective. We introduce a versatile methodology for the accurate modelling of PET imaging systems via Monte Carlo simulations, using the Geant4 application for tomographic emission (GATE) platform. Accurate Monte Carlo modelling involves the incorporation of a complete analytical signal processing chain, called the digitizer in GATE, to emulate the different count rates encountered in actual positron emission tomography (PET) systems. Approach. The proposed approach consists of two steps: (1) modelling the digitizer to replicate the detection chain of real systems, covering all available parameters, whether publicly accessible or supplied by manufacturers; (2) estimating the remaining parameters, i.e. background noise level, detection efficiency, and pile-up, using optimisation techniques based on experimental single and prompt event rates. We show that this two-step optimisation reproduces the other experimental count rates (true, scatter, and random), without the need for additional adjustments. This method has been applied and validated with experimental data derived from the NEMA count losses test for three state-of-the-art SiPM-based time-of-flight (TOF)-PET systems: Philips Vereos, Siemens Biograph Vision 600 and GE Discovery MI 4-ring. Main results. The results show good agreement between experiments and simulations for the three PET systems, with absolute relative discrepancies below 3%, 6%, 6%, 7% and 12% for prompt, random, true, scatter and noise equivalent count rates, respectively, within the 0–10 kBq·ml−1 activity concentration range typically observed in whole-body 18F scans. Significance. Overall, the proposed digitizer optimisation method was shown to be effective in reproducing count rates and NECR for three of the latest generation SiPM-based TOF-PET imaging systems. The proposed methodology could be applied to other PET scanners.
Electric and dielectric responses of Au/n-Si structure by Mn doped PVC interfacial layers
Authors: Badali Yosef , Güçlü Çiğdem Şükriye
Published: July 2024

This paper has investigated and compared the impact of polyvinyl chloride (PVC) without/with manganese (Mn) metallic nanoparticles interfacial layer on the electric and impedance characteristics of Schottky diode (SD) with a structure of Au/n-Si (MS). The structures of these two metal-polymer-semiconductor (MPS) SDs are Au/PVC/n-Si and Au/PVC:Mn/n-Si. A detailed description of the SDs manufacturing process is given. The x-ray diffraction (XRD) analysis, Scanning Electron Microscope (FE-SEM) images, and Electron Dispersive x-ray (EDX) spectroscopy are three methods that have been utilized to examine mean size of crystallite, morphology of surface, purity specification. The fundamental electronic variables of these devices are ascertained and contrasted with one another using the I-V characteristic measurement at ±6 V. Ohm’s law, Thermionic Emission (TE) theory, modified Norde, and Cheung functions are used to calculate the SDs’ leakage current (I0), ideality coefficient (n), potential barrier height (BH), shunt (Rsh), and series (Rs) resistances. Investigations are conducted on the energy dependence of surface states density (Nss) and the current conduction mechanisms (CCMs) for both reverse and forward biases. These interfacial layers are known to decrease the n, Rs, and Nss. The PVC polymer interlayer leads to improve the efficiency of the MS-type SD, but it does not when doped by Mn nanoparticles. Additionally, by measuring impedance at a bias of 1.5 V and 100 Hz-1 MHz frequency range, the frequency dependence of dielectric properties of the prepared SDs is studied. The dielectric permittivity, dielectric loss tangent, electronic modulus, and ac electronic conductivity of these SDs are all studied.
A unimodular Kaluza-Klein theory
Authors: Fabris Júlio C , Kerner Richard
Published: July 2024

Unimodular gravity became an object of increasing interest in the late 80-ties (see, e.g. M. Henneaux and C. Teitelboim, (1989 Phys. Lett. B
222, 195), W. Buchmüller and N. Dragon, N. (1989 Phys. Lett. B
223, 313), W.G. Unruh, (1989 Phys. Rev. D, 40, 1048) and was recently used in primordial Universe modeling with cosmological constant, in the context of the Brans-Dicke gravity including scalar field A. M. Almeida et al (2023 Universe
8, 429). In the present article we investigate the possibility of imposing the unimodular condition within the 5-dimensional Kaluza-Klein theory including the scalar field. The variational principle is formulated in 5 dimensions first, and dimensional reduction is applied to the resulting set of equations. A cosmological model based on these equations is then presented and discussed.