bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of new porphyrinoid dyads linked with a butenyne bridge via the Sonogashira reaction
Authors: Shkirdova Alena O. , Tyurin Vladimir S. , Chernyadyev Andrey Y. , Zamilatskov Ilya A.
Published: August 2024

Porphyrin dyads linked via a butenyne bridge were obtained for the first time. The strong interaction of units through the bridge provided energy flow between the chromophores and panchromatic light absorption, making them promising photosensitizers.
Ultrahigh-speed absolute temperature sensing using ferroelectric HfO2 enabled by transient negative differential capacitance
Authors: Kumar Mohit , Park Hayoung , Seo Hyungtak
Published: August 2024

Using short electric pulse, our sensor, made from ferroelectric hafnium zirconium oxide nanolaminates, offers ultrafast response time of ∼50 ns and high accuracy (1.0 K). This technology is compatible with USB interfaces for real-time monitoring.
Visible light-mediated radical addition cascade cyclization of aryl isocyanides with tricarbonyls: rapid access to substituted phenanthridines and isoquinolines
Authors: Manna Sabyasachi , Sreedhara Rahul Halanuru , Prabhu Kandikere Ramaiah
Published: August 2024

A visible light-mediated synthesis of substituted phenanthridines and isoquinolines from ortho-substituted aryl isocyanides and tricarbonyl compounds is unveiled via the radical addition cascade cyclization (RACC) strategy.
Moisture-induced ionovoltaic electricity generation using lead free 2-dimensional Cs3SbBiBr9 perovskite
Authors: Pramod Ashna K. , Batabyal Sudip K.
Published: August 2024

Harvesting of electricity from the environment is an easy, effective and sustainable method for energy production: this is based on the ionovoltaic effect, a process where moisture absorption induces ionic motion in a material, thus driving the movement of charge carriers and generating electricity.
Critical insights into eutectic molten hydroxide electrolysis for sustainable green hydrogen production
Authors: Sher Farooq , Ziani Imane , Al-Shara Nawar K. , Chupin Alexander , Horo Nađa , Wang Bohong , Rahman Saba , Fareed Bilal , Nemţanu Monica R.
Published: August 2024

In addressing global energy demands, the focus on hydrogen gas production from renewable sources intensifies.
Approximation for probability of coverage in softly inhibitive cellular networks
Authors: Chen Chunlin
Published: August 2024

The Strauss point process is a very popular model for describing the random cellular networks, yet several key statistical properties such as intensity, empty space function, and probability generating functional have remained elusive. This article addresses these issues by first leveraging the Poisson saddle point method to approximate the distance‐conditioned intensity for Strauss point processes. Subsequently, the author derives an analytically tractable expression for the distribution of empty space distance based on a conditional thinning mechanism. Additionally, the author establishes an upper bound for the probability generating functional in Strauss point processes, which is crucial for evaluating the Laplace transform of cumulative interference in relevant cellular networks. These findings facilitate the systematic derivation of spatially averaged probability of coverage, and the accuracy of analytic results is validated through simulations.
Embedded circuit analysis and design method for reconfigurable metasurface element
Authors: Wu Bincai , Xuan Xingqi , Chen Yuqi , Wen Jun , Hu Qijun , Zheng Shilie , Pratt Ian , Hui Xiaonan , Zhang Xianmin
Published: August 2024

Implementation of reconfigurable metasurfaces demands a complex structure. The design methodology for metasurface elements based on PIN diodes requires targeted optimisation tailored to the varying application environments and cannot be directly transplanted from one methodological approach to another. In addition, inclusion of varactors often imposes undesirable high‐power consumption with complex analog drive circuitry. Furthermore, the design method for the reconfigurable metasurface element has not been simplified and unified, hindering the rapid deployment of metasurface applications. The authors propose a general design model based on low‐power embedded circuitry for a multi‐function metasurface element and give the corresponding numerical analysis. The authors present a reconfigurable method based on the general design model and prove that the method achieves independent regulation of amplitude and phase for the reflected electromagnetic wave. Through analysis of the sensitive area at the bottom of the embedded circuit, a gradient descent algorithm is proposed to find the optimised phase points according to device sensitivity of the application scenario and suitable strategy. Finally, the authors demonstrate that the designed metasurface element possesses phase control capability and decent phase consistency obtained via far‐field scanning experiments. The proposed element design method will provide a theoretical reference for the integrated design of metasurface.
Multi‐data classification detection in smart grid under false data injection attack based on Inception network
Authors: Pan H. , Yang H. , Na C. N. , Jin J. Y.
Published: August 2024

During operation, the smart grid is subject to different false data injection attacks (FDIA). If the different kinds of FDIAs and typical failures have been detected, the system operator can develop various defenses to protect the smart grid in multiple categories. Therefore, this article aims to propose a multi‐data classification detection model to differentiate the data of regular operation, faults, and FDIAs when the smart grid suffers FDIAs. Due to the unbalanced number of different kinds of samples in the dataset, Affinitive Borderlinen SMOTE is used to pre‐process the data by oversampling to improve the training accuracy. A multi‐data detection model based on the Inception network is established, and the overall structure of the network and the individual Inception modules are given. A small power system is an example of simulating a smart grid suffering from FDIAs. The designed classification detection model is simulated, validated, and compared with two‐dimensional convolutional neural networks and existing research results. The qualitative analysis of the evaluation metrics can show that the Inception network model has high accuracy and real‐time performance for detecting different data.
Full non-LTE spectral line formation
Authors: Sampoorna M. , Paletou F. , Bommier V. , Lagache T.
Published: August 2024

In the present paper we consider the full nonlocal thermodynamic equilibrium (non-LTE) radiation transfer problem. This formalism allows us to account for deviation from equilibrium distribution of both the radiation field and the massive particles. In the present study, two-level atoms with broadened upper level represent the massive particles. In the absence of velocity-changing collisions, we demonstrate the analytic equivalence of the full non-LTE source function with the corresponding standard non-LTE partial frequency redistribution (PFR) model. We present an iterative method based on operator splitting techniques that can be used to numerically solve the problem at hand. We benchmark it against the standard non-LTE transfer problem for a two-level atom with PFR. We illustrate the deviation of the velocity distribution function of excited atoms from the equilibrium distribution. We also discuss the dependence of the emission profile and the velocity distribution function on elastic collisions and velocity-changing collisions.
Gas-phase Fe/O and Fe/N abundances in star-forming regions
Authors: Méndez-Delgado J. E. , Kreckel K. , Esteban C. , García-Rojas J. , Carigi L. , Sander A. A. C. , Palla M. , Chruślińska M. , De Looze I. , Relaño M. , van der Giessen S. A. , Reyes-Rodríguez E. , Sánchez S. F.
Published: August 2024

Context. In stars, metallicity is usually traced using Fe, while in nebulae, O serves as the preferred proxy. Both elements have different nucleosynthetic origins and are not directly comparable. Additionally, in ionized nebulae, Fe is heavily depleted onto dust grains.

Aims. We investigate the distribution of Fe gas abundances in a sample of 452 star-forming nebulae with [Fe III] λ4658 detections and their relationship with O and N abundances. Additionally, we analyze the depletion of Fe onto dust grains in photoionized environments.

Methods. We homogeneously determined the chemical abundances with direct determinations of electron temperature (Te), considering the effect of possible internal variations of this parameter. We adopted a sample of 300 Galactic stars to interpret the nebular findings.

Results. We find a moderate linear correlation (r = −0.59) between Fe/O and O/H. In turn, we report a stronger correlation (r = −0.80) between Fe/N and N/H. We interpret the tighter correlation as evidence that Fe and N are produced on similar timescales while Fe- dust depletion scales with the Fe availability. The apparently flat distribution between Fe/N and N/H in Milky Way stars supports this interpretation. We find that when 12+log(O/H)<7.6, the nebulae seem to reach a plateau value around log(Fe/O) ≈ −1.7. If this trend were confirmed, it would be consistent with a very small amount of Fe dust in these systems, similar to what is observed in high-z galaxies discovered by the James Webb Space Telescope (JWST). We derive a relationship that allows us to approximate the fraction of Fe trapped into dust in ionized nebulae. If the O-dust scales in the same way, its possible contribution in low-metallicity nebulae would be negligible. After analyzing the Fe/O abundances in J0811+4730 and J1631+4426, we do not see evidence of the presence of very massive stars with Minit > 300 M⊙ in these systems.

Conclusions. The close relation observed between the N and Fe abundances has the potential to serve as a link between stellar and nebular chemical studies. This requires an expansion of the number of abundance determinations for these elements in both stars and star-forming nebulae, especially at low metallicities.
PineTree: A generative, fast, and differentiable halo model for wide-field galaxy surveys
Authors: Ding Simon , Lavaux Guilhem , Jasche Jens
Published: August 2024

Context. Accurate mock halo catalogues are indispensable data products for developing and validating cosmological inference pipelines. A major challenge in generating mock catalogues is modelling the halo or galaxy bias, which is the mapping from matter density to dark matter halos or observable galaxies. To this end, N-body codes produce state-of-the-art catalogues. However, generating large numbers of these N-body simulations for big volumes, especially if magnetohydrodynamics are included, requires significant computational time.

Aims. We introduce and benchmark a differentiable and physics-informed neural network that can generate mock halo catalogues of comparable quality to those obtained from full N-body codes. The model design is computationally efficient for the training procedure and the production of large mock catalogue suites.

Methods. We present a neural network, relying only on 18 to 34 trainable parameters, that produces halo catalogues from dark matter overdensity fields. The reduction in network weights was realised through incorporating symmetries motivated by first principles into our model architecture. We trained our model using dark-matter-only N-body simulations across different resolutions, redshifts, and mass bins. We validated the final mock catalogues by comparing them to N-body halo catalogues using different N-point correlation functions.

Results. Our model produces mock halo catalogues consistent with the reference simulations, showing that this novel network is a promising way to generate mock data for upcoming wide-field surveys due to its computational efficiency. Moreover, we find that the network can be trained on approximate overdensity fields to reduce the computational cost further. We also present how the trained network parameters can be interpreted to give insights into the physics of structure formation. Finally, we discuss the current limitations of our model as well as more general requirements and pitfalls of approximate halo mock generation that became evident from this study.
ChatGPT Performs Worse on USMLE-Style Ethics Questions Compared to Medical Knowledge Questions
Authors: Danehy Tessa , Hecht Jessica , Kentis Sabrina , Schechter Clyde B. , Jariwala Sunit P.
Published: August 2024

Objectives The main objective of this study is to evaluate the ability of the Large Language Model Chat Generative Pre-Trained Transformer (ChatGPT) to accurately answer the United States Medical Licensing Examination (USMLE) board-style medical ethics questions compared to medical knowledge-based questions. This study has the additional objectives of comparing the overall accuracy of GPT-3.5 to GPT-4 and assessing the variability of responses given by each version.

Methods Using AMBOSS, a third-party USMLE Step Exam test prep service, we selected one group of 27 medical ethics questions and a second group of 27 medical knowledge questions matched on question difficulty for medical students. We ran 30 trials asking these questions on GPT-3.5 and GPT-4 and recorded the output. A random-effects linear probability regression model evaluated accuracy and a Shannon entropy calculation evaluated response variation.

Results Both versions of ChatGPT demonstrated worse performance on medical ethics questions compared to medical knowledge questions. GPT-4 performed 18% points (p < 0.05) worse on medical ethics questions compared to medical knowledge questions and GPT-3.5 performed 7% points (p = 0.41) worse. GPT-4 outperformed GPT-3.5 by 22% points (p < 0.001) on medical ethics and 33% points (p < 0.001) on medical knowledge. GPT-4 also exhibited an overall lower Shannon entropy for medical ethics and medical knowledge questions (0.21 and 0.11, respectively) than GPT-3.5 (0.59 and 0.55, respectively) which indicates lower variability in response.

Conclusion Both versions of ChatGPT performed more poorly on medical ethics questions compared to medical knowledge questions. GPT-4 significantly outperformed GPT-3.5 on overall accuracy and exhibited a significantly lower response variability in answer choices. This underscores the need for ongoing assessment of ChatGPT versions for medical education.
Daily versus Alternate-Day Iron Supplementation for Pregnant Women with Iron Deficiency Anemia: A Randomized Controlled Trial
Authors: Lam Melissa Chu , Khandakar Binny , Heon Isaak , Hussain Farrah , Feldman Kristina , Kaplowitz Elianna , Overbey Jessica R. , Brustman Lois , Rosenn Barak
Published: August 2024

Objective This study aimed to evaluate the most effective regimen to raise hemoglobin (Hb) by comparing alternate-day dosing of iron to daily dosing in pregnant women with iron deficiency anemia.

Study Design Women with Hb < 11.0 g/dL and ferritin ≤ 25 µg/L between 120/7 and 340/7 weeks' gestation were recruited. A total of 88 patients were randomized using block randomization with 1:1 allocation to receive either 1 tablet of 325 mg ferrous sulfate on consecutive days or 2 tablets every other day. The primary outcome, the change in Hb after 6 weeks of treatment was assessed using an analysis of covariance to adjust for baseline level. Secondary outcomes included change in ferritin, hepcidin, side effects, and compliance. Patients completed a questionnaire to assess for adverse symptoms and adherence was monitored by installing a pill reminder app on smartphones of patients.

Results A total of 88 patients were consented. The daily iron group had a greater proportion of nulliparous women (40 vs. 7%). Most patients (98%) had mild anemia (Hb: 9–10.9 g/dL) at recruitment, with a median gestational age of 28.1 weeks (interquartile range [IQR]: 25.6, 30.9) and median duration of treatment of 42 days (IQR: 35, 45). At 6 weeks, the daily iron group had a mean increase in Hb of 0.8 ± 0.9 g/dL, whereas the alternate-day iron group had a mean increase of 0.5 ± 1.0 g/dL (baseline adjusted difference of means: −0.3 [95% confidence interval: −0.7, 0.1], p = 0.15). Frequency of adverse effects attributable to iron were similar between groups. Patient self-reported compliance to treatment was also similar between groups. Among those that used the app, compliance was higher among the daily group compared with the alternate daily group (median: 95.5% [IQR: 75, 100] vs. 85% [IQR: 40, 92]), although this difference was not statistically significant (p = 0.07).

Conclusion This trial suggests that there are no significant differences between alternate-day iron supplementation and daily iron supplementation for treating iron deficiency anemia.

Key Points
Predictors of Vaginal Delivery among Patients Admitted with Severe Preeclampsia
Authors: Myers Sabrena , Pyne Abigail , Darling Alice , Al-Shibli Noor , Cate Jennifer J.M. , Grace Matthew R. , Wheeler Sarahn , Dotters-Katz Sarah K.
Published: August 2024

Objective This study aimed to assess the rates of vaginal delivery (VD) and the predictors of VD in a cohort of patients with early (<34 weeks) preeclampsia with severe features (Early Severe PreEClampsia [ESPEC]).

Study Design We conducted a retrospective cohort study of patients with ESPEC admitted to a single center from 2013 to 2019. Exclusion criteria included patients with contraindications to labor, multifetal gestation, or presenting in spontaneous labor. Patient characteristics were abstracted. The primary outcome was rate of VD. Secondary outcome was factors associated with VD. Secondary analysis performed including only primiparous patients. Bivariate statistics and logistic regression were used to analyze data.

Results Of 229 patients with ESPEC, 184 (80%) were candidates for labor. Of those, 74 (40%) underwent prelabor cesarean delivery (CD). Among the 110 remaining patients who attempted VD, 47 (43%) were successful. No significant differences in characteristics between VD and CD patients were found on bivariate analysis. In regression models, BMI ≥ 40 was associated with increased odds of CD (adjusted odds ratio [aOR]: 2.83, 95% confidence interval [CI]: 1.01, 7.95), whereas private insurance was associated with reduced odds of CD (aOR: 0.37, 95% CI: 0.16, 0.86). In planned secondary analysis of primiparous patients, 101/123 (82%) were candidates for labor. Of those, 29 underwent prelabor CD. The VD rate among primiparous patients attempting labor was 40% (29/72). In this subgroup, private insurance was associated with VD (71 vs. 46%, p = 0.03). In regression models, only private insurance remained associated with CD (aOR: 0.30, 95% CI: 0.10, 0.92).

Conclusion Patients with ESPEC who attempted VD were successful less than half of the time, with similar rates among the subset of primiparous patients. BMI ≥ 40 was associated with increased odds of CD, whereas private insurance was associated with reduced odds of CD. These data may aid providers in counseling patients with ESPEC on the likelihood of successful VD.

Key Points
Clinicopathological Implication of HER2/neu Expression in Carcinoma Stomach
Authors: Asnani Ritu , Shetty Padma K. , Shetty Vijith V. , Patil Prakash , Shetty Jayaprakash K.
Published: August 2024

Background and Objectives Metastatic gastric carcinoma makes the current treatment options unsatisfactory. There is HER2 directed therapy like transtuzumab are used in metastatic gastric cancer. This study aimed to determine the tissue HER2/neu status by immunohistochemistry (IHC) and find their relation with clinicopathological parameters for assessing the prognosis.

Study Design, Materials, and Methods In this descriptive study, 30 patients of gastric cancer with metastasis were studied for HER2/neu expression by IHC. The chi-square test was used to determine the association between HER2/neu expression and clinicopathological parameters of patients.

Results and Conclusion The majority of samples (90%) were endoscopic biopsies from patients with a mean age of 61.4 years. Tumors were majorly of intestinal type (67%) with moderately differentiated grade located at the fundus of the stomach. The common site of metastasis was the lymph node (53.33%) followed by lymph node and liver metastasis (13.33%). The overexpression of HER2/neu by IHC was observed in 13.3% of cases. Furthermore, no significant association was observed between HER2/neu and gender, diet, age, tumor site, subtype, and grade. Overall, HER2/neu overexpression can be considered an independent prognostic factor for carcinoma stomach. Therefore, the patients identified with HER2/neu overexpression are targeted for trastuzumab therapy.
An electroporation cytometry system for long-term, live cell cycle analysis
Authors: Nesmith Thomas , Vieira Christian , Rackus Darius G. , Gupta Gagan D.
Published: August 2024

Electric fields are used in biology to address a broad range of questions and through a variety of techniques, including electroporation, gene electrotransfer (GET), electrostimulation (ES), and electrochemotherapy. Each of these modalities requires specific conditions and has drastically different target outcomes on the cell. ES has demonstrated that non-pore forming electric fields alter cell cycle progression. However, pore forming electric fields such as with GET have not been as widely explored despite major clinical advancements. Additionally, the real-time visual analysis of electrical field effects on mammalian cell culture is currently lacking among most commercial systems. To facilitate investigations into these research areas, an electroporation cytometry system was developed including a custom chamber compatible with live cell imaging and exponential decay pulse generator for live cell analysis. The functionality of the system was demonstrated using a recombinant cell line using U-2 OS cells and FUCCI(CA)5 cell cycle reporter. The exposure of the cells to a 180 V pulse in both unsynchronized and synchronized populations revealed an effect on the cell cycle.
Photoelectric charge from metallic filters: An online XUV pulse energy diagnostics
Authors: Staněk Matyáš , Hort Ondřej , Jurkovičová Lucie , Albrecht Martin , Finke Ondřej , Nagyillés Balázs , Farkas Balázs , Csizmadia Tamás , Grósz Tímea , Körmöczi Andor , Divéki Zsolt , Nejdl Jaroslav
Published: August 2024

Extreme ultraviolet (XUV) radiation is a tool of choice for studying ultrafast processes and atomic physics. Most experiments employing sources of XUV radiation, such as high harmonic generation (HHG) or x-ray lasers, benefit from knowing the number of photons delivered to target in every single shot, because of the possible shot-to-shot pulse fluctuation of the sources. Nonetheless, many setups lack noninvasive XUV pulse energy diagnostics, hindering the simultaneous measurement of pulse energy and utilization of the XUV beam for applications. We present an online XUV pulse energy monitoring method based on the detection of photoelectric charge from thin metallic foil filters transmitting the XUV beam, which can be easily implemented at every pulsed XUV source that includes a high-pass filter system in the form of metallic filters. Consequently, implementation of our method is as straightforward as connecting the filter to an oscilloscope. In the paper, we describe all the physics aspects of such measurement and show the dependence of measured photoelectric charge on the incident pulse energy. To prove the versatility of our approach, we performed this measurement on two different high-flux HHG beamlines, taking consecutive shots at 1 kHz.
Thermal stability and phase transformation of α-, κ(ε)-, and γ-Ga2O3 films under different ambient conditions
Authors: Tang Jingyu , Jiang Kunyao , Tseng Po-Sen , Kurchin Rachel C. , Porter Lisa M. , Davis Robert F.
Published: August 2024

Phase transitions in metastable α-, κ(ε)-, and γ-Ga2O3 films to thermodynamically stable β-Ga2O3 during annealing in air, N2, and vacuum have been systematically investigated via in situ high-temperature x-ray diffraction (HT-XRD) and scanning electron microscopy (SEM). These respective polymorphs exhibited thermal stability to ∼471–525 °C, ∼773–825 °C, and ∼490–575 °C before transforming into β-Ga2O3, across all tested ambient conditions. Particular crystallographic orientation relationships were observed before and after the phase transitions, i.e., (0001) α-Ga2O3 → (2¯01) β-Ga2O3, (001) κ(ε)-Ga2O3 → (310) and (2¯01) β-Ga2O3, and (100) γ-Ga2O3 → (100) β-Ga2O3. The phase transition of α-Ga2O3 to β-Ga2O3 resulted in catastrophic damage to the film and upheaval of the surface. The respective primary and possibly secondary causes of this damage are the +8.6% volume expansion and the dual displacive and reconstructive transformations that occur during this transition. The κ(ε)- and γ-Ga2O3 films converted to β-Ga2O3 via singular reconstructive transformations with small changes in volume and unchanged surface microstructures.
Development of an atomic spectra research platform based on a 30-keV electron beam ion trap
Authors: Ji H. J. , Zhang H. M. , Lyu B. , Yang Y. , Bin B. , Bae C. , Lin Z. C. , Zeng C. , Huang S. H. , Shen Y. C. , Yin X. H. , Dai S. Y.
Published: August 2024

Electron Beam Ion Traps (EBITs) serve as efficient tools for producing and studying highly charged ions. In response to the diagnostic requirements of upcoming magnetic confinement fusion devices, a medium-energy atomic spectra research platform based on a compact EBIT is developed. This platform achieves a central magnetic field of up to 1.0 T, with electron beam currents reaching 20 mA and electron energies up to 30 keV, similar to the electron temperature on fusion reactors. The developed atomic spectra platform successfully provided spectral data for elements such as argon, xenon, iron, and tungsten. This platform stands as a valuable asset for advancing research in nuclear fusion, particularly concerning impurity spectroscopic diagnostics.
Improvement of memory storage capacity and prolongation of endurance/retention through H2 plasma treatment of IGZO/HZO structure
Authors: Liu Cheng-Rui , Tsai Yu-Tzu , Chen Yu-Ting , Chen Zheng-Kai , Huang Zi-Rong , Wang Sheng-Min , Pai Chia-Shuo , Tang Ying-Tsan
Published: August 2024

In this study, we integrated an Indium Gallium Zinc Oxide (IGZO) channel with a superlattice of HfO2/ZrO2 (HZO) under low-thermal-budget microwave annealing to produce nearly wake-up-free ferroelectric capacitors. To eliminate the impact of trap-charges during the atomic layer deposition process, we conducted H2 plasma treatment to eliminate leak defects induced by carbon contamination and maintain neutrality to achieve high-quality IGZO/HZO interfaces, confirmed by x-ray photoelectron spectroscopy. The H2 plasma treatment improved polarization (Pr) and coercive field (Ec), reaching 2Pr: 40 μC/cm2 and Ec: 2.33 MV/cm, enabling a low-power writing speed of 30 ns with eight states (three bits per cell). The defect engineering method ensures endurance of up to 108 cycles and retains ten-year data storage at 90 °C. This research provides a new avenue for improving emerging oxide interfaces controlled by ferroelectric polarization.
Hydration structure and dynamics of phosphoric acid and its anions—Ultrafast 2D-IR spectroscopy and ab initio molecular dynamics simulations
Authors: Kundu Achintya , Fingerhut Benjamin P. , Elsaesser Thomas
Published: August 2024

The hydration shells of phosphate ions and phosphate groups of nucleotides and phospholipid membranes display markedly different structures and hydrogen-bond strengths. Understanding phosphate hydration requires insight into the spatial arrangements of water molecules around phosphates and in thermally activated structure fluctuations on ultrafast time scales. Femtosecond two-dimensional infrared spectroscopy of phosphate vibrations, particularly asymmetric stretching vibrations between 1000 and 1200 cm−1, and ab initio molecular dynamics (AIMD) simulations are combined to map and characterize dynamic local hydration structures and phosphate–water interactions. Phosphoric acid H3PO4 and its anions H2PO4−, HPO42−, and PO43− are studied in aqueous environments of different pH value. The hydration shells of phosphates providing OH donor groups in hydrogen bonds with the first water layer undergo ultrafast structural fluctuations, which induce a pronounced spectral diffusion of vibrational excitations on a sub-300 fs time scale. With a decreasing number of phosphate OH groups, the hydration shell becomes more ordered and rigid. The 2D-IR line shapes observed with hydrated PO43− ions display a pronounced inhomogeneous broadening, reflecting a distribution of hydration geometries without fast equilibration. The AIMD simulations allow for an in-depth characterization of the hydration geometries with different numbers of water molecules in the first hydration layer and different correlation functions of the fluctuating electric field that the water environment exerts on the vibrational phosphate oscillators.
Realization of a shock-tube facility to study the Richtmyer–Meshkov instability driven by a strong shock wave
Authors: Jiang Shuaishuai , Cai Wei , Xie Jin , He Dong , Wang He , Si Ting , Luo Xisheng
Published: August 2024

A shock-tube facility capable of generating a planar shock with the Mach number higher than 3.0 is developed for studying Richtmyer–Meshkov instability induced by a strong shock wave (referred to as strong-shock RMI). Shock enhancement is realized through the convergence of shock within a channel with the profile determined by using shock dynamics theory. The facility is designed considering the repeatability of shock generation, transition of shock profile, and effects of viscosity and flow choking. By measuring the dynamic pressure of the tube flow using pressure sensors and capturing the shock movement through the high-speed shadowing technique, the reliability and repeatability of the shock tube for generating a strong planar shock are first verified. Particular emphasis is then placed on the ability of the facility to study strong-shock RMI, for which a thin polyester film is adopted to form the initial interface separating gases of different densities. The results indicate that the shock tube is reliable for conducting strong-shock RMI experiments.
Fabrication of high-Q suspended AlGaAs microresonators for efficient Kerr comb generation
Authors: Zhang Yuqian , Sun Changzheng , Xiong Bing , Wang Jian , Hao Zhibiao , Wang Lai , Han Yanjun , Li Hongtao , Luo Yi
Published: August 2024

AlGaAs is a promising integrated nonlinear photonics material with enormous optical nonlinearity and high refractive index. Nevertheless, presently AlGaAs microring resonators exhibiting high-quality factors and tight optical confinement rely predominantly on wafer bonding techniques, which entail an intricate fabrication process. Here, we present suspended AlGaAs waveguides and resonators as a viable platform for high efficiency integrated nonlinear photonics. The suspended microring resonator formed by combined plasma dry etching and chemical wet etching exhibits an intrinsic quality factor Q of 2.1×106, corresponding to an optical loss of 0.28 dB/cm, and Kerr comb generation with milliwatt level threshold is recorded. The proposed scheme can be implemented with a relatively simple fabrication process, as it eliminates the need for wafer bonding. Without the hinderance of SiO2 or Al2O3 claddings, the air-clad suspended AlGaAs platform lends itself directly to applications in the mid-infrared region. Our demonstration opens up a prospect for employing AlGaAs devices in integrated nonlinear photonics.
Impact of static disorder and dynamic disorder on the thermal conductivity of sodium superoxide (NaO2)
Authors: Ramasubramanian Hariharan , Shao Cheng , McGaughey Alan J. H.
Published: August 2024

The pyrite phase of sodium superoxide, NaO2, is studied using equilibrium molecular dynamics simulations and lattice dynamics calculations to understand the impacts of static disorder and dynamic disorder on its thermal conductivity. Three structural regimes are observed based on the rotational dynamics and orientations of O2− ions. At low temperatures, where the O2− ions librate and the system is fully ordered, thermal conductivity exhibits a crystal-like temperature dependence, decreasing with increasing temperature. As temperature increases, the static disorder regime emerges, where the O2− ions transition between different orientations on a time scale larger than the librational period. In this regime, the thermal conductivity continues to decrease and then becomes temperature independent. At higher temperatures, where the O2− ions freely rotate, the system is dynamically disordered and the thermal conductivity is temperature independent, as in an amorphous solid. Using instantaneous normal mode analysis and Allen–Feldman theory, 80% of the thermal conductivity in the dynamic disorder regime is attributed to diffusons, vibrational modes that are non-propagating and non-localized. When increasing the lattice constant at a constant temperature, transitions from librations to static disorder to dynamic disorder are also observed, with the thermal conductivity decreasing monotonically. The presented methodology can be applied to other crystals with rotational degrees of freedom, offering strategies for the design of thermal conductivity switches that are responsive to external stimuli.
Recovering particle velocity and size distributions in ejecta with photon Doppler velocimetry
Authors: Don Jayamanne J. A. , Outerovitch R. , Ballanger F. , Bénier J. , Blanco E. , Chauvin C. , Hereil P. , Tailleur J. , Durand O. , Pierrat R. , Carminati R. , Hervouët A. , Gandeboeuf P. , Burie J.-R.
Published: August 2024

When a solid metal is struck, its free surface can eject fast and fine particles. Despite the many diagnostics that have been implemented to measure the mass, size, velocity, or temperature of ejecta, these efforts provide only a partial picture of this phenomenon. Ejecta characterization, especially in constrained geometries, is an inherently ill-posed problem. In this context, Photon Doppler Velocimetry (PDV) has been a valuable diagnostic, measuring reliably particles and free surface velocities in the single scattering regime. Here, we present ejecta experiments in gas and how, in this context, PDV allows one to retrieve additional information on the ejecta, i.e., information on the particles’ size. We explain what governs ejecta transport in gas and how it can be simulated. To account for the multiple scattering of light in these ejecta, we use the Radiative Transfer Equation (RTE) that quantitatively describes PDV spectrograms, and their dependence not only on the velocity but also on the size distribution of the ejecta. We remind how spectrograms can be simulated by solving numerically this RTE and we show how to do so on hydrodynamic ejecta simulation results. Finally, we use this complex machinery in different ejecta transport scenarios to simulate the corresponding spectrograms. Comparing these to experimental results, we iteratively constrain the ejecta description at an unprecedented level. This work demonstrates our ability to recover particle size information from what is initially a velocity diagnostic, but more importantly it shows how, using existing simulation of ejecta, we capture through simulation the complexity of experimental spectrograms.
Instability of double-diffusive magnetoconvection in a non-Newtonian fluid layer with cross-diffusion effects
Authors: Sangamesh  , Raghunatha K. R. , Shivakumara I. S.
Published: August 2024

The study explores the initiation of two-dimensional double-diffusive convection in a horizontal layer of an electrically conducting non-Newtonian Navier–Stokes–Voigt fluid, subjected to a uniform vertical magnetic field and cross-diffusion effects. The numerical results are presented by obtaining the analytical solutions for both steady and oscillatory onset scenarios. The viscoelastic nature of the fluid either delays or hastens the onset of oscillatory convection depending on the strength of solute concentration. The analysis also uncovers contradictions in the linear instability characteristics with and without cross-diffusion terms, even when other input parameters are identical. Under specific conditions, three novel phenomena are observed that are not typically seen in double-diffusive cases: (i) an electrically conducting Navier–Stokes–Voigt fluid layer, initially linearly stable in the presence of a magnetic field, can become destabilized with the addition of a heavy solute to the fluid's bottom; (ii) a stable double-diffusive electrically conducting Navier–Stokes–Voigt fluid layer can be destabilized by the application of a magnetic field; and (iii) the requirement of three critical values of the thermal Rayleigh number to determine linear instability, as opposed to the usual single value owing to the existence of disconnected closed convex oscillatory neutral curves. The results are shown to align with previously published findings in the limiting cases.
Multipacting mitigation by atomic layer deposition: The case study of titanium nitride
Authors: Kalboussi Y. , Dadouch S. , Delatte B. , Miserque F. , Dragoe D. , Eozenou F. , Baudrier M. , Tusseau-Nenez S. , Zheng Y. , Maurice L. , Cenni E. , Bertrand Q. , Sahuquet P. , Fayette E. , Jullien G. , Inguimbert C. , Belhaj M. , Proslier T.
Published: August 2024

This study investigates the use of atomic layer deposition (ALD) to mitigate multipacting phenomena inside superconducting radio frequency cavities used in particle accelerators while preserving high quality factors in the 1010 range. The unique ALD capability to control the film thickness down to the atomic level on arbitrary complex shape objects enables the fine-tuning of TiN film resistivity and total electron emission yield (TEEY) from coupons to devices. This level of control allows us to adequately choose a TiN film thickness that provides both high resistivity to prevent Ohmic losses and a low TEEY to mitigate multipacting for the application of interest. The methodology presented in this work can be scaled to other domains and devices subject to RF fields in vacuum and sensitive to multipacting or electron discharge processes with their own requirements in resistivities and TEEY values.
Simultaneously achieving superior pyroelectric performance and ultrahigh depolarization temperature in NaNbO3-based ceramics
Authors: Lv Zhongqian , Guo Shaobo , Liu Zhen , Yao Chunhua , Wang Genshui
Published: August 2024

Pyroelectric materials have been widely studied because of their important role in infrared detectors, sensors, thermal imaging, and other applications, among which, lead-based ceramics are extensively adopted. However, the environmental problems caused by lead-based compounds in production and processing are becoming increasingly serious. Meanwhile, the surface mounting technology is extensively employed in the electronics industry for device miniaturization and integration. However, due to its high processing temperature (∼260 °C), it makes most pyroelectric ceramic materials unsuitable for this process. Therefore, it is of great significance to develop novel high-performance lead-free pyroelectric ceramics with high depolarization temperature (>260 °C). In this work, we report the Na0.995Ag0.005NbO3-0.1%Mn (NANM) pyroelectric ceramics. The antiferroelectric–ferroelectric phase transition field and coercive field of NaNbO3 ceramics were reduced by the introduction of AgNbO3 and Mn, making it easier to induce the ferroelectric phase and realize poling in NANM ceramics. The NANM ceramics exhibited an excellent pyroelectric coefficient of 2.55 × 10−4 C m−2 K−1 and figures of merit as Fi = 0.93 × 10−10 m/V, Fv = 6.46 × 10−2 m2/C, and Fd = 2.92 × 10−5 Pa−1/2 at room temperature. More importantly, a high depolarization temperature of 280 °C was achieved, ensuring the ability to withstand high temperature during production and operation. The NANM ceramics with excellent pyroelectric properties and high depolarization temperature are expected to be a promising lead-free candidate for uncooled infrared detector applications.
Monte Carlo QM/MM simulation studies of the Cannizzaro reaction in ionic liquids for improved biofuel production
Authors: Romero Maria , Kushnir Jamie S. , Mochi Bruno , Velez Caroline , Acevedo Orlando
Published: August 2024

The conversion of biomass to 5-hydroxymethylfurfural (HMF) holds substantial promise as a renewable energy source. Notably, HMF can be transformed into 2,5-bis(hydroxymethyl)furan (BHMF), a crucial reactant in biofuel production, but requires harsh operating conditions, H2, and precious metal catalysts. A recently reported Cannizzaro reaction of HMF to BHMF, characterized by its efficiency, mild conditions, and eco-friendliness, instead employed ionic liquids (ILs) to achieve high yields. In this study, combined quantum mechanical and molecular mechanical (QM/MM) simulations in conjunction with Metropolis Monte Carlo statistical mechanics and free-energy perturbation theory utilized M06-2X/6-31+G(d), PDDG/PM3, and the OPLS-VSIL force field to uncover important solute–solvent interactions present in the HMF to BHMF reaction pathway. The Cannizzaro reaction was examined in water and in five ILs composed of the 1-butyl-3-methylimidazolium [BMIM] cation coupled to hexafluorophosphate, tetrafluoroborate, thiocyanate, chloride, and bromide. Energetic and structural analysis of the rate-determining hydride transfer between HMF and the hydride-donor anion HMFOH− attributed the enhanced reactivity to highly organized solvent interactions featuring (1) hydrogen bonding between the ring protons of [BMIM] and the negatively charged carbonyl oxygen atoms on the transition structure, (2) favorable electrostatic interactions between the IL anions and solute hydroxyl groups, and (3) beneficial π–π stacking interactions between [BMIM] and the two aromatic rings present in HMF and HMFOH−.
Impact forces of drops falling on inclined superhydrophobic surfaces
Authors: Xu Hechen , Zhang Bin , Lv Cunjing
Published: August 2024

Due to its scientific significance and practical applications, the common natural phenomena of drops impacting on inclined surfaces have attracted extensive attention. Previous research has primarily reported the distinct morphology and dynamic behavior of drops impacting on inclined superhydrophobic surfaces compared to the impact on the horizontal scenarios. One distinguished feature of drop impingement on inclined surfaces is the asymmetric shapes of the drop, which accounts for different underlying physics compared to the impacts on horizontal surfaces. However, the impact forces exerted by the inclined surface during impingement have remained unknown. In this study, we present a direct measurement of the normal impact force of drops on inclined superhydrophobic surfaces using a high-precision force sensor. We observe the temporal evolution of the force and identify two peak forces occurring during the spreading and retraction stages, respectively. Our findings lie on investigating the variation of these two peak forces with the normal Weber number, based on scaling arguments. We reveal that the asymmetrical morphology of the drop must be taken into account especially in the scenarios of large impact velocities and large tilt angles to revise the theoretical model of the second peak force. The physics reported in this work sheds new light on the impingement of drops.
MPSDynamics.jl: Tensor network simulations for finite-temperature (non-Markovian) open quantum system dynamics
Authors: Lacroix Thibaut , Le Dé Brieuc , Riva Angela , Dunnett Angus J. , Chin Alex W.
Published: August 2024

The MPSDynamics.jl package provides an easy-to-use interface for performing open quantum systems simulations at zero and finite temperatures. The package has been developed with the aim of studying non-Markovian open system dynamics using the state-of-the-art numerically exact Thermalized-Time Evolving Density operator with Orthonormal Polynomials Algorithm based on environment chain mapping. The simulations rely on a tensor network representation of the quantum states as matrix product states (MPS) and tree tensor network states. Written in the Julia programming language, MPSDynamics.jl is a versatile open-source package providing a choice of several variants of the Time-Dependent Variational Principle method for time evolution (including novel bond-adaptive one-site algorithms). The package also provides strong support for the measurement of single and multi-site observables, as well as the storing and logging of data, which makes it a useful tool for the study of many-body physics. It currently handles long-range interactions, time-dependent Hamiltonians, multiple environments, bosonic and fermionic environments, and joint system–environment observables.
Improved mixing-width model for the linear stage of reshocked Richtmyer–Meshkov turbulence
Authors: Sun Fang-ping , Song Yu , Wang Yu-hui , Zhang You-sheng
Published: August 2024

Turbulent mixing induced by reshocked Richtmyer–Meshkov instability widely occurs in both natural phenomena, such as supernova explosions, and high-energy-density applications, such as inertial confinement fusion. As the most important global quantity, the mixing width has been used and modeled to describe the reshocked multimode Richtmyer–Meshkov instability flow. Among the available models, Mikaelian's linear/nonlinear matching model has been widely recognized. However, it is unsatisfactory for predicting the linear growth rate immediately after reshock. To overcome this limitation, in this paper, we derived an improved model. Compared with Mikaelian's model, the improved model uses the same model coefficient of the linear growth and ensures the continuity of the mixing-width growth rate before and after reshock. Consequently, it agrees well with the results of experiments and simulations. This result is of great significance for clarifying the long-standing divergences in the model coefficient in the literature, and it sheds light on the study of reshocked Richtmyer–Meshkov turbulence.
A study on maglev force and vibration attenuation characteristics of quasi-zero stiffness cruciform maglev isolator
Authors: Wu Jiafeng , Liu Wentao , Zhang Yun , Li Tiantian , Wang Shouren , Yang Yu’e
Published: August 2024

This paper aims to study the maglev force and vibration attenuation characteristics of quasi-zero stiffness cruciform maglev isolators (CMIs). The maglev force and stiffness of CMIs were analytically computed based on equivalent charge theory, and the transfer function of the system was conducted. The effects of magnet geometry parameters and air gap on the maglev force, stiffness, and vibration transmission characteristics of the CMI system were revealed through parametric analyses. With the increase in magnet length and width, the maximum value of maglev force increases, but the displacement range of near-zero stiffness, amplitude, and phase of the system gradually decrease. With the increase in magnet height, the displacement range of near-zero stiffness increases, while the variation in the amplitude and phase of the system has minimal impact. Meanwhile, in the Halbach array, the height variation of the magnet at different positions has different impacts on the magnetic force. As the air gap increases, the maximum value of maglev force decreases, but the amplitude and phase gradually increase, and the displacement range of near-zero stiffness first rises and then decreases. Finally, an experimental study was carried out to test the vibration attenuation characteristics of CMIs, in which sinusoidal excitation, hammer strike excitation, and random excitation were applied.