bluuebunny/crossref_metadata_2025 huggingface dataset:
In silico study of luminal transport of bile salts from the duodenum to the gastric mucosa: Role of small intestinal peristalsis
Authors: Avvari Ravi Kant , Tripathi Dharmendra
Published: April 2024

Biliary reflux plays a key role in the progression of gastric carcinoma over the long term. The reflux of alkaline duodenal contents (Duodenogastric Reflux) is presumed to be mediated by changes in the gastroduodenal motility, with no clear insights into the mechanisms. Considering mechanism comes under the perspective of fluid transport, a mathematical model is formulated for investigating the transport of the bile as a non-reactive species, assuming non-Newtonian nature as the power law fluids in the antropyloroduodenal segment using lubrication approximation. An analytical approach is employed to derive the exact solutions, and further computational results are simulated using MATLAB coding. To assess the pathophysiology of reflux, transport of the bile salt was quantified for various duodenal motility patterns by considering the following peristalsis parameters, such as elementary contraction (Antegrade Propagating Wave, Retrograde Propagating Wave, and Stationary Wave), wavelength, velocity and occlusion of the wave, and frequency of the contraction. Results of the bile transport are presented for the duodenal peristalsis and analyzed for the relative displacement from its initial position across various motility patterns. The particle transport is driven by wave traversal in the vicinity at the duodenum, whereas at the pylorus and proximal pylorus, transport of the imaginary particles, such as bile salts, is accelerated by increased occlusion of the wave (particles travel longer distances owing to higher occlusion, with 90% occlusion showing more transit than 70% occlusion) and wave speed, with pylorus contributing to hydrodynamic hindrance (owing to pyloric channel width, where the resistance scales to 1/R4) with oscillatory excursion.
Influences of coriolis force and friction on fluid dynamics in specific paraboloid basins
Authors: Magdalena I. , Natanael
Published: April 2024

Natural water features, such as rivers, lakes, bays, and straits, exhibit diverse shapes and dynamics. Among these, paraboloid basins, resembling the contours of lakes or closed bays, offer a relatively simple yet intriguing case. This study delves into the dynamics of water waves within two distinct paraboloid basin variations: the parabolic canal and the circular paraboloid. In this investigation, we analyze shoreline movement, considering influential factors such as bottom friction and the Coriolis effect through a mathematical model. The foundation of our analysis lies in the two-dimensional shallow water equations, with the Thacker assumption serving as the basis for deriving an analytical solution. To enhance our understanding, we employ a numerical solution, employing the finite volume method on a staggered grid, to simulate wave behavior within these basin variations. For validation, we compare these numerical findings with our analytical solution. Furthermore, this study conducts a sensitivity analysis of the Coriolis parameter and bottom friction parameter under various conditions. Through this exploration, we gain valuable insights into the interplay of these critical factors in shaping the oscillation of water within paraboloid basins, enriching our understanding of coastal and basin dynamics.
A novel non-adiabatic spin relaxation mechanism in molecular qubits
Authors: Shushkov Philip
Published: April 2024

The interaction of electronic spin and molecular vibrations mediated by spin–orbit coupling governs spin relaxation in molecular qubits. We derive an extended molecular spin Hamiltonian that includes both adiabatic and non-adiabatic spin-dependent interactions, and we implement the computation of its matrix elements using state-of-the-art density functional theory. The new molecular spin Hamiltonian contains a novel spin–vibrational orbit interaction with a non-adiabatic origin, together with the traditional molecular Zeeman and zero-field splitting interactions with an adiabatic origin. The spin–vibrational orbit interaction represents a non-Abelian Berry curvature on the ground-state electronic manifold and corresponds to an effective magnetic field in the electronic spin dynamics. We further develop a spin relaxation rate model that estimates the spin relaxation time via the two-phonon Raman process. An application of the extended molecular spin Hamiltonian together with the spin relaxation rate model to Cu(II) porphyrin, a prototypical S = 1/2 molecular qubit, demonstrates that the spin relaxation time at elevated temperatures is dominated by the non-adiabatic spin–vibrational orbit interaction. The computed spin relaxation rate and its magnetic field orientation dependence are in excellent agreement with experimental measurements.
Anomalous thermal transport and high thermoelectric performance of Cu-based vanadate CuVO3
Authors: Jin Xin , Ou Qiling , Wei Haoran , Ding Xianyong , Zhan Fangyang , Wang Rui , Yang Xiaolong , Lv Xuewei , Yu Peng
Published: April 2024

Thermoelectric (TE) conversion technology, capable of transforming heat into electricity, is critical for sustainable energy solutions. Many promising TE materials contain rare or toxic elements, so the development of cost-effective and eco-friendly high-performance TE materials is highly urgent. Herein, we explore the thermal transport and TE properties of transition metal vanadate CuVO3 by using first-principles calculation. On the basis of the unified theory of heat conduction, we uncover the hierarchical thermal transport feature in CuVO3, where wave-like tunneling makes a significant contribution to the lattice thermal conductivity (κl) and results in the anomalously weak temperature dependence of κl. This is primarily attributable to the complex phononic band structure caused by the heterogeneity of Cu–O and V–O bonds. Simultaneously, we report a high power factor of 5.45 mW·K−2·m−1 realized in hole-doped CuVO3, which arises from a high electrical conductivity and a large Seebeck coefficient enabled by the multiple valleys and large electronic density of states near the valence band edge. Impressively, the low κl and the high power factor make p-typed CuVO3 have ZT of up to 1.39, with the excellent average ZT above 1.0 from 300 to 600 K, which is superior to most reported Cu-based TE materials. Our findings suggest that the CuVO3 compound is a promising candidate for energy conversion applications in innovative TE devices.
Construction of the absorbing boundary condition for the flow of Oldroyd-B fluid over a semi-infinite plate with magnetic effect
Authors: Liu Lin , Zhang Sen , Wang Jihong , Feng Libo , Xie Chiyu
Published: April 2024

As a kind of non-Newtonian fluid, the Oldroyd-B fluid has widespread applications. To study the flow characteristics deeply is of great significance. In this paper, we consider a simple model of the Oldroyd-B fluid flow over a semi-infinite plate in a magnetic field. The governing equation is formulated, and the numerical solutions are obtained using the finite difference method. To deal with the semi-infinite region, the artificial boundary method is applied to construct the absorbing boundary condition (ABC) with the (inverse) z-transform, which converts the semi-infinite region to a finite one. To test the accuracy of the numerical scheme, a numerical example by introducing the source term is presented. Graphs show the rationality of the ABC by comparing the fluid flow velocity between the direct truncated boundary condition and the ABC. The effects of the amplitude, the frequency, the relaxation time parameter, the retardation time parameter, and the magnetic field on the magnitude and the cycle of flow velocity are investigated and discussed. The main findings are that the retardation time parameter promotes the velocity of the fluid flow, while the relaxation time and magnetic field hinder the fluid flow. When the relaxation time is equal to the retardation time, the Oldroyd-B fluid can approximate the Newtonian fluid. In addition, the oscillating cycle becomes shorter for a smaller relaxation time parameter or a larger magnetic field and frequency.
Numerical study on the effects of fracture on density-driven flows in CO2 sequestration
Authors: Liu Peiyao , Ju Long , Pu Jun , Guo Zhaoli
Published: April 2024

In this study, CO2 transport in density-driven flows within an ideal model of a fractured porous medium, which contains a single or two intersecting fractures, is investigated numerically. The study employs a multi-scale modeling in which the flow in the matrix is modeled by Darcy's law, while the flow in the fracture is modeled by the Navier–Stokes equations. Our study shows that a horizontal fracture minimally impacts CO2 distribution, and depending on its length, slightly reduces dissolved CO2 during sequestration by 1.5%–2.5%. Vertical fractures play a crucial role in redirecting CO2 movement within the matrix, guiding it toward the fractures and altering its original pathway. Notably, the observed oscillations of CO2-rich water between the interfaces of the vertical fracture highlight the flow consistency with the pore scale. The domain-scale circulation induced by the vertical fracture leads to a rapid increase in flux and dissolved CO2 mass, but early convection shuts down. The results demonstrate that a longer vertical fracture leads to earlier shut down of convection and a potential decrease in storage of over 11%. The flow behaviors observed in inclined fractures are akin to those in vertical fractures, as they disrupt the fingerlike structure of CO2 around the fracture, form the circulation around the fracture, and are accompanied by vortices at the top. Additionally, intersecting fractures can lead to dynamic interactions between the fractures, with high-angle fractures dominating mixing flow. Different fracture angle combinations minimally affect dissolution mass.
Molecular chirality quantification: Tools and benchmarks
Authors: Abraham Ethan , Nitzan Abraham
Published: April 2024

Molecular chirality has traditionally been viewed as a binary property where a molecule is classified as either chiral or achiral, yet in recent decades, mathematical methods for quantifying chirality have been explored. Here, we use toy molecular systems to systematically compare the performance of two state-of-the-art chirality measures: (1) the Continuous Chirality Measure (CCM) and (2) the Chirality Characteristic (χ). We find that both methods exhibit qualitatively similar behavior when applied to simple molecular systems such as a four-site molecule or the polymer double-helix, but we show that the CCM may be more suitable for evaluating the chirality of arbitrary molecules or abstract structures such as normal vibrational modes. We discuss a range of considerations for applying these methods to molecular systems in general, and we provide links to user-friendly codes for both methods. We aim for this paper to serve as a concise resource for scientists attempting to familiarize themselves with these chirality measures or attempting to implement chirality measures in their own work.
An analytical model for permeability of fractal tree-like branched networks composed of converging–diverging capillaries
Authors: Tu Biliang , Xiao Boqi , Zhang Yidan , Long Gongbo
Published: April 2024

Seepage processes in tree-fractal networks have attracted extensive research, but the results of most of these studies presuppose a constant pore cross section. This research investigates fluid flow in a fractal tree-like branching network composed of five different types of circular cross section pipes and establishes the effective permeability of the network. Furthermore, the effective permeability of the fractal tree-like network is compared with that of a typical parallel channel network, and the effect of structural parameters on the seepage process of the tree-like branching network is systematically investigated. The effective permeability of all pipelines increased sharply with an increase in the internal diameter ratio at first and then decreased. Furthermore, a considerable advantage was seen in the permeability of the fractal tree network over the traditional parallel channel network, with the benefit becoming more noticeable as branching levels increased. The clear physics of the model offers a useful framework for studying seepage processes.
High spatial resolution surface plasmon resonance imaging using a plasmonic chip
Authors: Nawa Yasunori , Tawa Keiko
Published: April 2024

The surface plasmon resonance (SPR) technique has been widely applied to biosensing technologies for the rapid quantification of biomolecules without enzyme and fluorescent labeling. However, the conventional prism-coupling SPR method generally has a detection area of a few mm2, and the large contribution of the background signal forms a barrier to highly sensitive detection. Based on a highly spatially resolved SPR method, the present study constructed a scanning GC-SPR imaging instrument using an objective lens with a high numerical aperture and a plasmonic chip that could be used for grating-coupled SPR. Focusing light on the diffraction limit can suppress background signals and improve detection sensitivity. SPR imaging can also be performed by scanning a focal spot. Using this method, the refractive index of a mixture of water and dimethyl sulfoxide was measured with a detection accuracy of 2.43 × 10−3 RIU. Polydopamine films prepared with a thickness of <5 nm were also measured, and each film thickness was evaluated with high sensitivity from the effective refractive index detected in a small area of <1 µm2.
Light-induced photoluminescence enhancement in chiral CdSe quantum dot films
Authors: Wang Yang , Liang Pan , Men Yumeng , Jiang Meizhen , Cheng Lin , Li Jinlei , Jia Tianqing , Sun Zhenrong , Feng Donghai
Published: April 2024

Chiral quantum dots (QDs) are promising materials applied in many areas, such as chiral molecular recognition and spin selective filter for charge transport, and can be prepared by facile ligand exchange approaches. However, ligand exchange leads to an increase in surface defects and reduces the efficiencies of radiative recombination and charge transport, which restricts further applications. Here, we investigate the light-induced photoluminescence (PL) enhancement in chiral L- and D-cysteine CdSe QD thin films, providing a strategy to increase the PL. The PL intensity of chiral CdSe QD films can be significantly enhanced over 100 times by continuous UV laser irradiation, indicating a strong passivation of surface defects upon laser irradiation. From the comparative measurements of the PL intensity evolutions in vacuum, dry oxygen, air, and humid nitrogen atmospheres, we conclude that the mechanism of PL enhancement is photo-induced surface passivation with the assistance of water molecules.
Investigation of carrier transport and recombination at type-II band aligned p-NiO/AlGaN interface in p-NiO gate AlGaN/GaN HEMTs under forward bias
Authors: Peng Yanghu , Guo Hui , Gong Ruiling , Liu Huaize , Shao Pengfei , Sun Na , Ren Fangfang , Ye Jiandong , Zheng Youdou , Lu Hai , Zhang Rong , Chen Dunjun
Published: April 2024

In this work, fine carrier transport and recombination processes in p-NiO gate AlGaN/GaN high electron mobility transistors were investigated by analyzing their electroluminescence under forward gate bias, with photoluminescence spectrum as a reference. Red luminescence with a peak of 1.9 eV was captured when the gate bias voltage exceeded 4 V, which was verified to originate from the tunneling enhanced interface recombination of injected holes from the gate metal and spilled electrons from the 2DEG channel at the type-II band aligned p-NiO/AlGaN heterostructure interface. Under higher gate bias voltage, holes were further injected into the GaN buffer layer, producing ultraviolet luminescence and yellow luminescence, corresponding respectively to the band edge emission and defect-assisted radiative recombination of GaN. Threshold voltage shift measurements under forward gate bias were conducted to further investigate the carrier transport and recombination processes.
Shock compression experiments using the DiPOLE 100-X laser on the high energy density instrument at the European x-ray free electron laser: Quantitative structural analysis of liquid Sn
Authors: Gorman M. G. , McGonegle D. , Smith R. F. , Singh S. , Jenkins T. , McWilliams R. S. , Albertazzi B. , Ali S. J. , Antonelli L. , Armstrong M. R. , Baehtz C. , Ball O. B. , Banerjee S. , Belonoshko A. B. , Benuzzi-Mounaix A. , Bolme C. A. , Bouffetier V. , Briggs R. , Buakor K. , Butcher T. , Di Dio Cafiso S. , Cerantola V. , Chantel J. , Di Cicco A. , Clarke S. , Coleman A. L. , Collier J. , Collins G. W. , Comley A. J. , Coppari F. , Cowan T. E. , Cristoforetti G. , Cynn H. , Descamps A. , Dorchies F. , Duff M. J. , Dwivedi A. , Edwards C. , Eggert J. H. , Errandonea D. , Fiquet G. , Galtier E. , Laso Garcia A. , Ginestet H. , Gizzi L. , Gleason A. , Goede S. , Gonzalez J. M. , Harmand M. , Hartley N. J. , Heighway P. G. , Hernandez-Gomez C. , Higginbotham A. , Höppner H. , Husband R. J. , Hutchinson T. M. , Hwang H. , Lazicki A. E. , Keen D. A. , Kim J. , Koester P. , Konopkova Z. , Kraus D. , Krygier A. , Labate L. , Lee Y. , Liermann H.-P. , Mason P. , Masruri M. , Massani B. , McBride E. E. , McGuire C. , McHardy J. D. , Merkel S. , Morard G. , Nagler B. , Nakatsutsumi M. , Nguyen-Cong K. , Norton A.-M. , Oleynik I. I. , Otzen C. , Ozaki N. , Pandolfi S. , Peake D. J. , Pelka A. , Pereira K. A. , Phillips J. P. , Prescher C. , Preston T. R. , Randolph L. , Ranjan D. , Ravasio A. , Redmer R. , Rips J. , Santamaria-Perez D. , Savage D. J. , Schoelmerich M. , Schwinkendorf J.-P. , Smith J. , Sollier A. , Spear J. , Spindloe C. , Stevenson M. , Strohm C. , Suer T.-A. , Tang M. , Toncian M. , Toncian T. , Tracy S. J. , Trapananti A. , Tschentscher T. , Tyldesley M. , Vennari C. E. , Vinci T. , Vogel S. C. , Volz T. J. , Vorberger J. , Walsh J. P. S. , Wark J. S. , Willman J. T. , Wollenweber L. , Zastrau U. , Brambrink E. , Appel K. , McMahon M. I.
Published: April 2024

X-ray free electron laser (XFEL) sources coupled to high-power laser systems offer an avenue to study the structural dynamics of materials at extreme pressures and temperatures. The recent commissioning of the DiPOLE 100-X laser on the high energy density (HED) instrument at the European XFEL represents the state-of-the-art in combining x-ray diffraction with laser compression, allowing for compressed materials to be probed in unprecedented detail. Here, we report quantitative structural measurements of molten Sn compressed to 85(5) GPa and ∼3500 K. The capabilities of the HED instrument enable liquid density measurements with an uncertainty of ∼1% at conditions which are extremely challenging to reach via static compression methods. We discuss best practices for conducting liquid diffraction dynamic compression experiments and the necessary intensity corrections which allow for accurate quantitative analysis. We also provide a polyimide ablation pressure vs input laser energy for the DiPOLE 100-X drive laser which will serve future users of the HED instrument.
Cation effects in hydrogen evolution and CO2-to-CO conversion: A critical perspective
Authors: Hsu Yu-Shen , Rathnayake Sachinthya T. , Waegele Matthias M.
Published: April 2024

The rates of many electrocatalytic reactions can be strongly affected by the structure and dynamics of the electrochemical double layer, which in turn can be tuned by the concentration and identity of the supporting electrolyte’s cation. The effect of cations on an electrocatalytic process depends on a complex interplay between electrolyte components, electrode material and surface structure, applied electrode potential, and reaction intermediates. Although cation effects remain insufficiently understood, the principal mechanisms underlying cation-dependent reactivity and selectivity are beginning to emerge. In this Perspective, we summarize and critically examine recent advances in this area in the context of the hydrogen evolution reaction (HER) and CO2-to-CO conversion, which are among the most intensively studied and promising electrocatalytic reactions for the sustainable production of commodity chemicals and fuels. Improving the kinetics of the HER in base and enabling energetically efficient and selective CO2 reduction at low pH are key challenges in electrocatalysis. The physical insights from the recent literature illustrate how cation effects can be utilized to help achieve these goals and to steer other electrocatalytic processes of technological relevance.
Droplet impact simulation with Cahn–Hilliard phase field method coupling Navier-slip boundary and dynamic contact angle model
Authors: Fu Zunru , Jin Haichuan , Yao Guice , Wen Dongsheng
Published: April 2024

As a highly promising interface capture tool, the phase field method (PFM) has gained fast development in the past 20 years or so including in the simulation of droplet impact. The mobility tuning parameter χ of PFM, however, is hard to determine since it ambiguously reflects the relative strength between advection and diffuse effects that are difficult to quantify. This problem becomes even more complex when it is coupled with the contact line movement modeling, i.e., the dynamic contact angle (DCA) model, which is closely related to the effective slip (Ls,e) and the Navier-slip (Ls). This study systematically investigated the factors that would take effect at the interface capture and the contact line movement in droplet impact simulation. The value and the scaling law of Ls,e as for its dependence on χ and interface thickness (ε) was first confirmed, and an approximation scheme for defining the DCA model was proposed based on the difference between the apparent contact line moving velocity (Ucl) and the Navier-slip velocity at the contact line (Ucl′), which is inherently determined by Ls,e and Ls, respectively. After validation with the experiments, the scaling law of χ with ε, i.e., the sharp-interface limit, was finally obtained, which provides improved droplet impact simulation.
Secondary flows in the actuator-disk simulation of wind-turbine wakes
Authors: Zehtabiyan-Rezaie Navid , Amarloo Ali , Abkar Mahdi
Published: April 2024

This study explores the generation of secondary flows of Prandtl's second kind in the actuator-disk simulation of wind-turbine wakes. Leveraging large-eddy simulation data and conducting an analysis of the mean streamwise vorticity budget, we uncover the physical mechanisms contributing to this phenomenon. Our investigations attribute the emergence of such flows to the spatial gradients of the Reynolds stresses in the wake downstream of the turbines, which are, in turn, influenced by ground effects. To further investigate the phenomenon, we specifically isolate the impact of secondary flows on the wake by employing a model recognized for its incapacity to capture such dynamics: a two-equation Reynolds-averaged Navier–Stokes (RANS) model founded on the linear eddy-viscosity hypothesis. By comparing the predictions of the RANS model with those of large-eddy simulations and wind-tunnel experiments, we highlight the effect of secondary flows on the wake structure and, in particular, the upward shift of the wake. Motivated by the obtained results, we then enhance the baseline RANS model by introducing a non-linear term within the Reynolds stress tensor. This modification leads to a more accurate representation of Reynolds stresses, enabling the RANS model to capture the secondary flows in the wake. Our analysis emphasizes the importance of employing advanced RANS models in the simulation of wind farms.
Efficient heuristic approach for minimization of phonon mean free path in large-area nanostructured thin films
Authors: Taniguchi Ryusei , Tomabechi Riku , Hori Takuma
Published: April 2024

Phonon transport simulations are conducted to unveil the design of nanostructured thin films with the lowest thermal conductivity for enhancing thermoelectric performance. An efficient and effective optimization method that utilizes simulated annealing is realized by tuning and switching a reduction rate of annealing temperature, which is a parameter to facilitate escaping local optima during the process. The superiority of this optimization approach is confirmed by demonstrating it in nanostructured thin films of various sizes. Furthermore, the characteristics of structures with lower thermal conductivities are identified from the optimization results for each size. Based on this, a large-area nanostructured thin film, in which the simulated annealing method is computationally costly, is designed and validated by comparing it with typical nanostructured thin films as a reference.
Numerical solutions for nonlinear mixed integro-differential equation and the neutron transport equation
Authors: Al-Bugami Abeer M.
Published: April 2024

In this work, I will discuss the solution of the new in a nonlinear integro-differential equation (NI-DE) form. The NI-DE is established from the nuclear transport equation, which is a linearized derivative of the equation developed by Boltzmann for the kinetic theory of gases. In this study, I will introduce the basic equations and boundary conditions for the formulation of the problem. Then, the NI-DE is established from the planar geometry problem of the neutron transport equation. In addition, I will prove the existence of a unique solution to the problem. In addition, I will use the numerical method to obtain a system of NI-DEs. Therefore, I will prove, under certain conditions, the existence of a unique solution to this system. Finally, I will present two different effective methods to solve the problem numerically, and I will discuss the results.
Substrate dependence of the self-heating in lead zirconate titanate (PZT) MEMS actuators
Authors: Song Yiwen , Kang Kyuhwe , Tipsawat Pannawit , Cheng Christopher Y. , Zhu Wanlin , LaBella Michael , Choi Sukwon , Trolier-McKinstry Susan E.
Published: April 2024

Lead zirconate titanate (PZT) thin films offer advantages in microelectromechanical systems (MEMSs) including large motion, lower drive voltage, and high energy densities. Depending on the application, different substrates are sometimes required. Self-heating occurs in the PZT MEMS due to the energy loss from domain wall motion, which can degrade the device performance and reliability. In this work, the self-heating of PZT thin films on Si and glass and a film released from a substrate were investigated to understand the effect of substrates on the device temperature rise. Nano-particle assisted Raman thermometry was employed to quantify the operational temperature rise of these PZT actuators. The results were validated using a finite element thermal model, where the volumetric heat generation was experimentally determined from the hysteresis loss. While the volumetric heat generation of the PZT films on different substrates was similar, the PZT films on the Si substrate showed a minimal temperature rise due to the effective heat dissipation through the high thermal conductivity substrate. The temperature rise on the released structure is 6.8× higher than that on the glass substrates due to the absence of vertical heat dissipation. The experimental and modeling results show that the thin layer of residual Si remaining after etching plays a crucial role in mitigating the effect of device self-heating. The outcomes of this study suggest that high thermal conductivity passive elastic layers can be used as an effective thermal management solution for PZT-based MEMS actuators.
Research on pressure pulsation characteristics of a pump-turbine in pump mode with rotating stall: Focus on the broadband frequency
Authors: Zeng Yongshun , Qian Zhaohui , Ye Weixiang , Geng Chen , Luo Xianwu
Published: April 2024

To investigate the adverse effects of rotating stalls on the pressure pulsation characteristics of a pump-turbine in pump mode, an unsteady numerical simulation was carried out by applying the partially averaged Navier–Stokes turbulence model. The numerical methods were carefully verified, and the onset flow rate of the hump at the performance curve and heads were in good agreement with the experimental data. The rotating stall appeared in the guide vane when the flow rate ranged from 0.514 to 0.887 times the best efficiency point (QBEP), with a frequency of 11.7% times the rotational frequency. In the period of a rotating stall, a sudden intensive pressure pulsation in the guide vane channel was observed and named as the component of the broadband frequency, and its corresponding flow mechanism was explained as the vortex evolution between the adjacent guide vane blades based on the dynamic mode decomposition technology. There were three distinct characteristics of broadband frequency: (i) intermittent occurrence when the rotating stall cell propagated to the current flow channel, (ii) a wide range of the frequency varying with flow rate, (iii) a considerable amplitude, e.g., reaching 21.1%–42.2% times that of the rotating stall frequency. In addition, both the frequency range and amplitude of the broadband frequency gradually decreased as the flow rate increased to 0.887QBEP. This study clarified the internal flow mechanism and frequency behaviors of a sudden intensive pressure pulsation if a rotating stall occurred, which was important to assess the stability of pump-turbine units.
Time-resolved solvation of alkali ions in superfluid helium nanodroplets
Authors: García-Alfonso Ernesto , Barranco Manuel , Halberstadt Nadine , Pi Martí
Published: April 2024

The sinking of alkali cations in superfluid 4He nanodroplets is investigated theoretically using liquid 4He time-dependent density functional theory at zero temperature. The simulations illustrate the dynamics of the buildup of the first solvation shell around the ions. The number of helium atoms in this shell is found to linearly increase with time during the first stages of the dynamics. This points to a Poissonian capture process, as concluded in the work of Albrechtsen et al. on the primary steps of Na+ solvation in helium droplets [Albrechtsen et al., Nature 623, 319 (2023)]. The energy dissipation rate by helium atom ejection is found to be quite similar between all alkalis, the main difference being a larger energy dissipated per atom for the lighter alkalis at the beginning of the dynamics. In addition, the number of helium atoms in the first solvation shell is found to be lower at the end of the dynamics than at equilibrium for both Li+ and Na+, pointing to a kinetic rather than thermodynamical control of the snowball size for small and strongly attractive ions.
Flocculation rate of locally densely distributed cohesive particles in Taylor–Green vortex flow
Authors: Zhao Kunpeng , Zhao Shuaiqi , Huang Han , Zhang Rui , Meiburg Eckart , Bai Bofeng
Published: April 2024

We employ the three-way coupled numerical simulations to investigate the flocculation of primary cohesive particles which are locally densely distributed in the Taylor–Green cellular vortex flow. The hydrodynamic and inertial forces as well as the direct contact, lubrication, and cohesion forces between particles during the growth, deformation, and breakup of flocs are captured in detail. The flocculation rate of the primary particles decreases gradually from its maximum value at the initial moment, then levels off during flocculation, yielding the flocculation and equilibrium stages. The flocculation rate is determined by the equilibrium floc size and a flocculation coefficient. A larger equilibrium floc size and a smaller value of the flocculation coefficient yield faster flocculation. An initially dense distribution of cohesive particles accelerates the growth of flocs during flocculation but has minor effects on the equilibrium floc size, compared to an initially dilute distribution. A larger particle-to-fluid density ratio, a smaller size ratio between the particle diameter and the Kolmogorov length scale, and stronger cohesion yield a larger equilibrium floc size and a higher flocculation coefficient. Their influence on the flocculation coefficient becomes more evident when the initial particle distribution becomes more concentrated, while their impact on the maximum flocculation rate is very limited. A simple new model is proposed to describe the flocculation process of unevenly distributed cohesive particles in turbulence.
Polymer-coated urea applied at one-time mechanical topdressing increases nitrogen use efficiency and rice yield in the cold area
Authors: Yu Cailian , Lin Yuchen , Li Bolin , Liu Xiaolun , Liu Zhilei , Peng Xianlong
Published: April 2024

Context The application of slow and controlled release fertilisers can reduce nitrogen loss, but the research is still scarce in the cold rice region of China. Aims The study was conducted to screen slow-release or controlled-release fertilisers which can meet the nitrogen demand of rice and reduce NH3 volatilisation in different pH soils. Methods This experiment includes four fertilisation treatments: no fertiliser (control), urea, urea with N-(n-butyl) thiophosphorictriamide (NBPT), and polymer-coated urea (PCU). The amounts of urea-N, pH, ammonium-N (NH4+-N) in the surface water, and NH3 volatilisation were determined. Thereafter, to evaluate the effects of one-time mechanical topdressing of PCU mixed with compound fertilisers along with farmers’ fertilisation practice (FFP), field experiments carried out in wide soil pH differences were conducted. Key results Cumulative NH3 volatilisation was reduced in the NBPT treatment compared with the urea treatment. There was no significant difference between urea-N, NH4+-N, and pH in the surface water under PCU and control. NH3 volatilisation of PCU is negligible and significantly prolongs the soil nitrogen storage time. In the subsequent experiment, PCU blend increased yield, dry matter, nitrogen uptake, and the partial factor productivity of applied nitrogen (PFPN) compared to FFP. Conclusions PCU treatment slows down urea release and reduces ammonia volatilisation from paddy fields. In turn, it reduces ammonia-nitrogen levels and pH in surface water and further slows down the rate of ammonia volatilisation. Implications Application of PCU as a one-time mechanical topdressing fertiliser in rice fields in cold regions saves nitrogen fertiliser, increases crop yields, and reduces labour.
The scaffolding protein AKAP12 regulates mRNA localization and translation
Authors: Smith Madeleine R. , Naeli Parisa , Jafarnejad Seyed M. , Costa Guilherme
Published: April 2024

Regulation of subcellular messenger (m)RNA localization is a fundamental biological mechanism, which adds a spatial dimension to the diverse layers of post-transcriptional control of gene expression. The cellular compartment in which mRNAs are located may define distinct aspects of the encoded proteins, ranging from production rate and complex formation to localized activity. Despite the detailed roles of localized mRNAs that have emerged over the past decades, the identity of factors anchoring mRNAs to subcellular domains remains ill-defined. Here, we used an unbiased method to profile the RNA-bound proteome in migrating endothelial cells (ECs) and discovered that the plasma membrane (PM)–associated scaffolding protein A-kinase anchor protein (AKAP)12 interacts with various mRNAs, including transcripts encoding kinases with Actin remodeling activity. In particular, AKAP12 targets a transcript coding for the kinase Abelson Tyrosine-Protein Kinase 2 (ABL2), which we found to be necessary for adequate filopodia formation and angiogenic sprouting. Moreover, we demonstrate that AKAP12 is necessary for anchoring
ABL2
mRNA to the PM and show that in the absence of AKAP12, the translation efficiency of
ABL2
mRNA is reduced. Altogether, our work identified a unique post-transcriptional function for AKAP12 and sheds light into mechanisms of spatial control of gene expression.
A mammalian tripartite enhancer cluster controls hypothalamic
Pomc
expression, food intake, and body weight
Authors: Rojo Daniela , Hael Clara E. , Soria Agustina , de Souza Flávio S. J. , Low Malcolm J. , Franchini Lucía F. , Rubinstein Marcelo
Published: April 2024

Food intake and energy balance are tightly regulated by a group of hypothalamic arcuate neurons expressing the proopiomelanocortin (
POMC)
gene. In mammals, arcuate-specific
POMC
expression is driven by two
cis
-acting transcriptional enhancers known as nPE1 and nPE2. Because mutant mice lacking these two enhancers still showed hypothalamic
Pomc
mRNA, we searched for additional elements contributing to arcuate
Pomc
expression. By combining molecular evolution with reporter gene expression in transgenic zebrafish and mice, here, we identified a mammalian arcuate-specific
Pomc
enhancer that we named nPE3, carrying several binding sites also present in nPE1 and nPE2 for transcription factors known to activate neuronal
Pomc
expression, such as ISL1, NKX2.1, and ERα. We found that nPE3 originated in the lineage leading to placental mammals and remained under purifying selection in all mammalian orders, although it was lost in
Simiiformes
(monkeys, apes, and humans) following a unique segmental deletion event. Interestingly, ablation of nPE3 from the mouse genome led to a drastic reduction (>70%) in hypothalamic
Pomc
mRNA during development and only moderate (<33%) in adult mice. Comparison between double (nPE1 and nPE2) and triple (nPE1, nPE2, and nPE3) enhancer mutants revealed the relative contribution of nPE3 to hypothalamic
Pomc
expression and its importance in the control of food intake and adiposity in male and female mice. Altogether, these results demonstrate that nPE3 integrates a tripartite cluster of partially redundant enhancers that originated upon a triple convergent evolutionary process in mammals and that is critical for hypothalamic
Pomc
expression and body weight homeostasis.
Thermodynamic crossovers in supercritical fluids
Authors: Li Xinyang , Jin Yuliang
Published: April 2024

Can liquid-like and gas-like states be distinguished beyond the critical point, where the liquid–gas phase transition no longer exists and conventionally only a single supercritical fluid phase is defined? Recent experiments and simulations report strong evidence of dynamical crossovers above the critical temperature and pressure. Despite using different criteria, many existing theoretical explanations consider a single crossover line separating liquid-like and gas-like states in the supercritical fluid phase. We argue that such a single-line scenario is inconsistent with the supercritical behavior of the Ising model, which has two crossover lines due to its symmetry, violating the universality principle of critical phenomena. To reconcile the inconsistency, we define two thermodynamic crossover lines in supercritical fluids as boundaries of liquid-like, indistinguishable, and gas-like states. Near the critical point, the two crossover lines follow critical scalings with exponents of the Ising universality class, supported by calculations of theoretical models and analyses of experimental data from the standard database. The upper line agrees with crossovers independently estimated from the inelastic X-ray scattering data of supercritical argon, and from the small-angle neutron scattering data of supercritical carbon dioxide. The lower line is verified by the equation of states for the compressibility factor. This work provides a fundamental framework for understanding supercritical physics in general phase transitions.
OTULIN and Muller’s morphs
Authors: Spaan András N.
Published: April 2024

In this issue of JEM, Davidson et al. (https://doi.org/10.1084/jem.20222171) and Takeda et al. (https://doi.org/10.1084/jem.20231941) independently report on a dominant negative form of OTULIN deficiency in three unrelated patients.
Cannabidiol potentiates hyperpolarization-activated cyclic nucleotide–gated (HCN4) channels
Authors: Page Dana A. , Ruben Peter C.
Published: April 2024

Cannabidiol (CBD), the main non-psychotropic phytocannabinoid produced by the Cannabis sativa plant, blocks a variety of cardiac ion channels. We aimed to identify whether CBD regulated the cardiac pacemaker channel or the hyperpolarization-activated cyclic nucleotide–gated channel (HCN4). HCN4 channels are important for the generation of the action potential in the sinoatrial node of the heart and increased heart rate in response to β-adrenergic stimulation. HCN4 channels were expressed in HEK 293T cells, and the effect of CBD application was examined using a whole-cell patch clamp. We found that CBD depolarized the V1/2 of activation in holo-HCN4 channels, with an EC50 of 1.6 µM, without changing the current density. CBD also sped activation kinetics by approximately threefold. CBD potentiation of HCN4 channels occurred via binding to the closed state of the channel. We found that CBD’s mechanism of action was distinct from cAMP, as CBD also potentiated apo-HCN4 channels. The addition of an exogenous PIP2 analog did not alter the ability of CBD to potentiate HCN4 channels, suggesting that CBD also acts using a unique mechanism from the known HCN4 potentiator PIP2. Lastly, to gain insight into CBD’s mechanism of action, computational modeling and targeted mutagenesis were used to predict that CBD binds to a lipid-binding pocket at the C-terminus of the voltage sensor. CBD represents the first FDA-approved drug to potentiate HCN4 channels, and our findings suggest a novel starting point for drug development targeting HCN4 channels.
Mutation in pore-helix modulates interplay between filter gate and Ba2+ block in a Kcv channel pore
Authors: Tewes Noel , Kubitzki Beatrice , Bytyqi Flandrit , Metko Nikola , Mach Sebastian , Thiel Gerhard , Rauh Oliver
Published: April 2024

The selectivity filter of K+ channels catalyzes a rapid and highly selective transport of K+ while serving as a gate. To understand the control of this filter gate, we use the pore-only K+ channel KcvNTS in which gating is exclusively determined by the activity of the filter gate. It has been previously shown that a mutation at the C-terminus of the pore-helix (S42T) increases K+ permeability and introduces distinct voltage-dependent and K+-sensitive channel closures at depolarizing voltages. Here, we report that the latter are not generated by intrinsic conformational changes of the filter gate but by a voltage-dependent block caused by nanomolar trace contaminations of Ba2+ in the KCl solution. Channel closures can be alleviated by extreme positive voltages and they can be completely abolished by the high-affinity Ba2+ chelator 18C6TA. By contrast, the same channel closures can be augmented by adding Ba2+ at submicromolar concentrations to the cytosolic buffer. These data suggest that a conservative exchange of Ser for Thr in a crucial position of the filter gate increases the affinity of the filter for Ba2+ by >200-fold at positive voltages. While Ba2+ ions apparently remain only for a short time in the filter-binding sites of the WT channel before passing the pore, they remain much longer in the mutant channel. Our findings suggest that the dwell times of permeating and blocking ions in the filter-binding sites are tightly controlled by interactions between the pore-helix and the selectivity filter.
Superfluid fraction tensor of a two-dimensional supersolid
Authors: Blakie P B
Published: April 2024

We investigate the superfluid fraction of crystalline stationary states within the framework of mean-field Gross–Pitaevskii theory. Our primary focus is on a two-dimensional Bose–Einstein condensate with a non-local soft-core interaction, where the superfluid fraction is described by a rank-2 tensor. We then calculate the superfluid fraction tensor for crystalline states exhibiting triangular, square, and stripe geometries across a broad range of interaction parameters. Factors leading to an anisotropic superfluid fraction tensor are also considered. We also refine the Leggett bounds for the superfluid fraction of the 2D system. We systematically compare these bounds to our full numerical results, and other results in the literature. This work is of direct relevance to other supersolid systems of current interest, such as supersolids produced using dipolar Bose–Einstein condensates.
Weak abnormal acoustic signal enhancement and recognition using squeeze-and-excitation attention based denoising convolutional neural network during high-dam flood discharging
Authors: Lian Jijian , Xu Wenliang , Liang Chao , Liu Fang , Wang Runxi
Published: April 2024

Acoustic signals (particularly cavitation acoustic signals) generated during the flood discharge of high dams are highly sensitive to various abnormal situations, whereas weak abnormal signal recognition under strong discharge-noise interference is extremely challenging. Based on the prototype and model experiments, the related abnormal acoustic signals and discharge noise were recorded to construct datasets. Subsequently, using the framework of the deep neural network (DNN) speech enhancement method, a squeeze-and-excitation attention based denoising convolutional neural network (DnCNN) based method for weak abnormal acoustic signal enhancement and recognition was proposed and verified using two case studies of cavitation acoustic signal enhancement and multicategory acoustic signal enhancement and recognition. Compared with the DnCNN method and traditional signal processing methods (such as wavelet, empirical mode decomposition, least mean square, and recursive least square), the proposed method achieved excellent signal enhancement performance after training based on limited prior knowledge of signal and noise. It also demonstrated good generalization ability and robustness in multicategory tasks, which significantly improved the abnormal signal recognition accuracy. This study provides technical support for the practical application of acoustic monitoring based on DNN for safety during the flood discharge of high dams.
OxySaver: highly conserving demand oxygen delivery system with increased throughput
Authors: Haque Syed Razwanul , Saha Shovon Sudan , Chowdhury Hasib Ahmed , Nesa Meherun , Choudhury Ju-un Nahar , Choudhury Dewan Ahmad Fawzul Kabir , Rahman Tanzilur
Published: April 2024

Since the beginning of the twentieth century, oxygen has been an essential therapeutic drug. Patients with chronic lung disease and other conditions rely on supplemental oxygen provided by oxygen cylinders for treatment. Because of the sudden increase in oxygen demand caused by the COVID-19 pandemic, combined with a lack of oxygen supply, new methods of oxygen delivery have been investigated as a potential solution. We propose OxySaver, a novel low-cost (∼60$) demand oxygen delivery system that may significantly reduce oxygen consumption. The proposed system consists of a pressure sensor that detects the patient’s demand for oxygen, a normally open solenoid valve that switches the supply ON/OFF on demand, and a processing unit that ensures the supply of oxygen only during the patients’ inhalation. It is simple to install using existing oxygen cylinders and oxygen pipelines in hospitals. The preliminary prototype tests have been promising, with OxySaver able to save up to 67% more oxygen than conventional methods. OxySaver’s pulse setting can reach 18 LPM, as opposed to the 0.2–4 LPM typically found in oxygen concentrators. The system only needs 3.72 W at 50 bpm, which is less than other similar devices. OxySaver in multiplexing mode has the potential to reduce the logistical challenges associated with oxygen refilling and transport. The device is now ready for clinical testing at the bedside.