bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheology of a crowd: from faster-is-slower to shear thickening
Authors: Hernández-Delfin Dariel , García Ander , Ellero Marco
Published: May 2024

The evacuation speed of pedestrians through bottlenecks usually leads to the faster-is-slower (FIS) phenomenon, which relies on frictional clogging and clusters’ size. However, less attention is given in literature to the rheology of pedestrian crowds and the forces ruling their dynamics. Here, we establish a link between the faster-is-slower phenomenon (FIS) in pedestrian crowds and the shear-thickening rheological behavior of (non)Brownian suspensions. We analyze pedestrian room egress through particle-based simulations using the Social Force Model, revealing an S-shaped shear rate dependency characteristic of discontinuous shear thickening (DST). At the same time, the crowd flow viscosity near the exit exhibits a steep increase coinciding with FIS occurrence, establishing a correlation between FIS and shear thickening. Our results prove that crowd evacuations are governed by two distinct critical jamming densities, one frictional and another frictionless, and that contact forces alone cannot lead to FIS, but social force interactions are necessary to avoid contacts at low desired speeds. Our results point at the suitability of (non)Brownian suspensions as models that provide an original rheological perspective to pedestrian dynamics.
Bridging the gap: leveraging data science to equip domain experts with the tools to address challenges in maternal, newborn, and child health
Authors: Tadesse Girmaw Abebe , Ogallo William , Cintas Celia , Speakman Skyler , Walcott-Bryant Aisha , Wayua Charity
Published: May 2024

The United Nations Sustainable Development Goals (SDGs) advocate for reducing preventable Maternal, Newborn, and Child Health (MNCH) deaths and complications. However, many low- and middle-income countries remain disproportionately affected by high rates of poor MNCH outcomes. Progress towards the 2030 sustainable development targets for MNCH remains stagnated and uneven within and across countries, particularly in sub-Saharan Africa. The current scenario is exacerbated by a multitude of factors, including the COVID-19 pandemic’s impact on essential services and food access, as well as conflict, economic shocks, and climate change.

Traditional approaches to improve MNCH outcomes have been bifurcated. On one side, domain experts lean heavily on expert-driven analyses, often bypassing the advantages of data-driven methodologies such as machine learning. Conversely, computing researchers often employ complex models without integrating essential domain knowledge, leading to solutions that might not be pragmatically applicable or insightful to the community. In addition, low- and middle-income countries are often either data-scarce or with data that is not readily structured, curated, or digitized in an easily consumable way for data visualization and analytics, necessitating non-traditional approaches, data-driven analyses, and insight generation. In this perspective, we provide a framework and examples that bridge the divide by detailing our collaborative efforts between domain experts and machine learning researchers. This synergy aims to extract actionable insights, leveraging the strengths of both spheres. Our data-driven techniques are showcased through the following five applications: (1) Understanding the limitation of MNCH data via automated quality assessment; (2) Leveraging data sources that are available in silos for more informed insight extraction and decision-making; (3) Identifying heterogeneous effects of MNCH interventions for broader understanding of the impact of interventions; (4) Tracking temporal data distribution changes in MNCH trends; and (5) Improving the interpretability of “black box” machine learning models for MNCH domain experts. Our case studies emphasize the impactful outcomes possible through interdisciplinary collaboration. We advocate for this joint collaborative research approach, believing it can accelerate the extraction of actionable insights at scale. Ultimately, this will catalyse data-driven interventions and contribute towards achieving SDG targets related to MNCH.
Deletion of Tmem268 in mice suppresses anti-infectious immune responses by downregulating CD11b signaling
Authors: Duan Mengyuan , Zhang Xuan , Lou Yaxin , Feng Jinqiu , Guo Pengli , Ye Shufang , Lv Ping , Chen Yingyu
Published: May 2024

Transmembrane protein 268 (TMEM268) is a novel, tumor growth-related protein first reported by our laboratory. It interacts with the integrin subunit β4 (ITGB4) and plays a positive role in the regulation of the ITGB4/PLEC signaling pathway. Here, we investigated the effects and mechanism of TMEM268 in anti-infectious immune response in mice. Tmem268 knockout in mice aggravated cecal ligation and puncture-induced sepsis, as evidenced by higher bacterial burden in various tissues and organs, congestion, and apoptosis. Moreover, Tmem268 deficiency in mice inhibited phagocyte adhesion and migration, thus decreasing phagocyte infiltration at the site of infection and complement-dependent phagocytosis. Further findings indicated that TMEM268 interacts with CD11b and inhibits its degradation via the endosome–lysosome pathway. Our results reveal a positive regulatory role of TMEM268 in β2 integrin-associated anti-infectious immune responses and signify the potential value of targeting the TMEM268–CD11b signaling axis for the maintenance of immune homeostasis and immunotherapy for sepsis and related immune disorders.
Lack of p38 activation in T cells increases IL-35 and protects against obesity by promoting thermogenesis
Authors: Nikolic Ivana , Ruiz-Garrido Irene , Crespo María , Romero-Becerra Rafael , Leiva-Vega Luis , Mora Alfonso , León Marta , Rodríguez Elena , Leiva Magdalena , Plata-Gómez Ana Belén , Alvarez Flores Maria Beatriz , Torres Jorge L , Hernández-Cosido Lourdes , López Juan Antonio , Vázquez Jesús , Efeyan Alejo , Martin Pilar , Marcos Miguel , Sabio Guadalupe
Published: May 2024

Obesity is characterized by low-grade inflammation, energy imbalance and impaired thermogenesis. The role of regulatory T cells (Treg) in inflammation-mediated maladaptive thermogenesis is not well established. Here, we find that the p38 pathway is a key regulator of T cell-mediated adipose tissue (AT) inflammation and browning. Mice with T cells specifically lacking the p38 activators MKK3/6 are protected against diet-induced obesity, leading to an improved metabolic profile, increased browning, and enhanced thermogenesis. We identify IL-35 as a driver of adipocyte thermogenic program through the ATF2/UCP1/FGF21 pathway. IL-35 limits CD8+ T cell infiltration and inflammation in AT. Interestingly, we find that IL-35 levels are reduced in visceral fat from obese patients. Mechanistically, we demonstrate that p38 controls the expression of IL-35 in human and mouse Treg cells through mTOR pathway activation. Our findings highlight p38 signaling as a molecular orchestrator of AT T cell accumulation and function.
Microfluidic isolation of extrachromosomal circular DNA through selective digestion of plasmids and linear DNA using immobilized nucleases
Authors: Zole Egija , Sathyanarayanan Gowtham , Regenberg Birgitte , Kutter Jörg P.
Published: May 2024

Tandem IMER chips to remove unwanted DNA and enrich circular DNA.
A one-pot CRISPR-RCA strategy for ultrasensitive and specific detection of circRNA
Authors: Ke Xinxin , Liang Ajuan , Chen Chuanxia , Hu Tao
Published: May 2024

In this work, we introduce the application of the CRISPR/Cas12a system to establish a one-pot, rapid (30 minutes to 2 hours), specific and ultrasensitive circRNA detection strategy, termed RETA-CRISPR (Reverse Transcription-Rolling Circle Amplification (RT-RCA) with the CRISPR/Cas12a).
Evaluating the native oxide of titanium as an electrocatalyst for oxalic acid reduction
Authors: Sale Halilu , Ertekin Zeliha , Lalaguna Paula L. , Kadodwala Malcolm , Symes Mark D.
Published: May 2024

Titanium electrodes bearing the naturally-forming native oxide coating are competent for the electroreduction of oxalic acid to glyoxylate and glycolate.
Dual-state emission and two-wavelength amplified spontaneous emission behaviors observed from symmetric dyes based on functionalized fluorene and benzotriazole units
Authors: Lin Tzu-Chau , Cho Shu-Tse , Wu Cheng-Lin , Setyatama Novia Eka , Tung Po-Han , Hung Bing-Yi , Lin Ja-Hon , Jan Pei-En , Tsai Ping-Hsun , Lin Hao-Wu
Published: May 2024

A series of D–A–D chromophores were designed, synthesized and characterized to show dual-state emission (DSE) and amplified spontaneous emission (ASE) properties.
Eco-friendly synthesis of an α-Fe2O3/rGO nanocomposite and its application in high-performance asymmetric supercapacitors
Authors: Rahaman Sabiar , Raza Azam , Lone Aadil Rashid , Muaz Mohammad , Zaidi SM Hasan , Adeeb Mohammad Asif , Sama Farasha , Pandey Kavita , Ahmad Absar
Published: May 2024

This work presents an innovative and environmentally friendly biological synthesis approach for producing α-Fe2O3 nanoparticles (NPs) and the successful synthesis of α-Fe2O3/reduced graphene oxide (rGO) nanocomposites (NCs).
Computational prediction of the critical micelle concentration (CMC) of surfactants using the non-Bornian solvation model
Authors: Osakai Toshiyuki , Misaki Tomohiro , Eda Kazuo
Published: May 2024

The non-Bornian solvation model can be used to estimate the adsorption energies of a surfactant from oil and water phases. These adsorption energies are found to be useful for predicting the critical micelle concentration of surfactants.
Ion molecule reactions in the HBr+ + CH4 system: a combined experimental and theoretical study
Authors: Plamper Dominik , Vincent Allen , Fujioka Kazuumi , Sun Rui , Weitzel Karl-Michael
Published: May 2024

Reactions in the system HBr+ + CH4 have been investigated inside a guided ion-beam apparatus under single-collision conditions and rationalized by means of ab initio molecular dynamics.
Fully biobased, catalyst-free vitrimers from tannic acid: a facile combination of mechanical robustness, recyclability and sustainability
Authors: Li Jie , Ju Benzhi , Zhang Shufen
Published: May 2024

The unique hyperbranched structure formed from tannic acid provides both robust mechanical properties and catalyst-free recyclability to fully biobased transesterification vitrimers.
Pipette-operable microfluidic devices with hydrophobic valves in sequential dispensing with various liquid samples: multiplex disease assay by RT-LAMP
Authors: Chang Yen-Wei , Lin Jhih-Pu , Ling Shiu-Jie , Chen Yen-Chun , Liu Helene Minyi , Lu Yen-Wen
Published: May 2024

The pipette-operated microfluidic device allows for sequential dispensing and isolation of liquid into individual chambers through manual pipetting.
Study on the removal of SO42−and Ca2+from potassium chloride brineviaa method combining calcium chloride and carbon dioxide
Authors: Ren Huimin , Wang Qiuchen , Sun Yanzhi , Chen Yongmei , Wan Pingyu , Pan Junqing
Published: May 2024

Cheap and environmentally friendly calcium chloride is used to remove SO42−in brine and Ca2+is removed by introducing carbon dioxide. The purified brine is suitable for the electrolysis of potassium chloride.
Synthesis of low-cost multi-element Pt-based alloy nanoparticles as catalysts for the oxygen reduction reaction
Authors: Cuya Huaman Jhon L. , Taniguchi Kaneyuki , Iwata Daichi , Shinoda Kozo , Yokoyama Shun , Miyamura Hiroshi , Balachandran Jeyadevan
Published: May 2024

Synthesis of NiPtPd nanostructures by the alcohol reduction method as electrodes for the ORR through the complexation of Pt and Pd ions with surfactants is reported.
First total synthesis of asperilactone B. Revision of absolute stereochemistry of asperilactones B and C
Authors: Djokić Sanja , Benedeković Goran , Kesić Jelena , Rodić Marko V. , Popsavin Mirjana , Popsavin Velimir , Francuz Jovana
Published: May 2024

The first total synthesis of asperilactone B and revision of the absolute stereochemistry of asperilactones B and C are reported. The first total synthesis of the (−)-asperilactone B has also been achieved.
Effects of Exercise-Induced Laryngeal Obstruction in Adolescents: A Qualitative Study
Authors: Fujiki Robert Brinton , Johnson Rebecca , Fujiki Amanda Edith , Thibeault Susan L.
Published: May 2024

Purpose:

The purpose of this study was to examine the influence of exercise-induced laryngeal obstruction (EILO) on adolescents.

Method:

Twenty patients (< 17 years) diagnosed with EILO participated in this study. Patients completed semistructured interviews examining their experience with the health care system, treatment, and the effects of EILO symptoms on quality of life. Interviews were analyzed using a combination of directed and conventional content analyses. Researchers identified seven overarching themes either prior to or during analysis, and 24 subthemes were inductively identified from patient interviews using open, axial, and selective coding.

Results:

On average, patients went 1.9 years between symptom onset and EILO diagnosis. Patients described symptom onset as frightening and confusing. Even after initially reporting symptoms to a medical provider, patients went an average of 10.5 months before diagnosis. Patients perceived that delays in diagnosis prevented efficient management and allowed symptoms to escalate. Patients reported that EILO detrimentally influenced athletic performance, forcing them to pace themselves or cease participation altogether. Social and academic effects of EILO included missed classes, difficulty in physical education courses, and resentment from teammates if athletic performance declined. Both athletes and nonathletes indicated that EILO elicited feelings of fear, frustration, dread, guilt, and embarrassment. Patients reported that therapy with a speech-language pathologist (SLP) effectively addressed symptoms; however, employing rescue breathing techniques was often more difficult than anticipated.

Conclusions:

Physical and emotional sequelae associated with EILO may have widespread influence on patient quality of life. Therapy with an SLP reportedly ameliorated EILO symptoms; however, patients indicated that delayed diagnosis allowed negative effects to intensify prior to treatment.
A Ku‐band wideband low‐profile patch antenna with slot‐loading and parasitic structures
Authors: Yu Sirui , Song Lingnan , Su Donglin
Published: May 2024

This letter introduces a novel bandwidth‐enhanced low‐profile (thin structure) patch antenna adopting double U‐slot loading and parasitic structures. The proposed antenna features single‐layer topology, thin structure of 0.027 , enhanced −10 dB impedance bandwidth of 12.5%, and unidirectional radiation pattern at Ku‐band. Performances of the proposed antenna are validated through full‐wave simulations and measurements. The proposed antenna element is further duplicated to form a patch antenna array, with the parasitic structures shared by adjacent elements. The proposed antenna demonstrates potential in applications demanding wideband, highly directional radiation, and thin structure for seamless integration.
Empowering lightweight video transformer via the kernel learning
Authors: Liu Xiaoxi , Liu Ju , Gu Lingchen
Published: May 2024

Video transformers achieve superior performance in video recognition. Despite the recent advances in video transformers, they still require substantial computation and memory resources. To cater for the computation efficiency, a kernel‐based video transformer is proposed, including: (1) a new formulation of the video transformer via the kernel learning is presented to better understand the individual components of it; (2) a lightweight Kernel‐based spatial–temporal multi‐head self‐attention block is explored to learn the compact joint spatial–temporal video feature; (3) an adaptive‐score position embedding method is conducted to promote the flexibility of video transformer. Experimental results on several action recognition datasets demonstrate the effectiveness of the proposed method. Only pretrained on ImageNet‐1K, the method achieves the preferable balance between computation and accuracy, while requiring 7 fewer parameters and 13 fewer floating point operations than other comparable methods.
Rectification and converter control of the FPSLGs for energy storage applications
Authors: Ali Murad , Haitao Yu , Mobayen Saleh , Zhang Jiahui , Zhilenkov Anton , Din Zakiud
Published: May 2024

This article presents two power converters with controllers attached to the Free‐Piston Stirling Linear Generator (FPSLG) and energy storage system (ESS). The rectifier uses hysteresis‐SVPWM current regulation and CB‐SPWM, while the buck‐boost converter utilizes the dual‐loop PI control method. The storage battery receives energy from a linear‐generator with a rectifier and converter. The FPSE and linear motors in the FPSLG convert thermal to electrical energy. A two‐level electrical energy conversion technique using a three‐phase AC signal to DC and DC‐DC converter has been devised to reduce output electrical energy oscillation as well as stabilize the generating system's DC power. Initially, the FPSE's nonlinear model and the three‐phase permanent magnet linear‐motor's linear mathematical model were created and followed by the ESS and control mechanism simulation. The simulation shows that the ESS system and control approach can give stable power to the storage battery using linear‐generator power. The PR controller replaces the PI controller in the position loop to improve frequency and displacement tracing. The control system design was simulated in MATLAB and the topology's feasibility and correctness were confirmed. Comparative analysis shows that, rectifier uses the H‐SVPWM's unity power factor of AC and stability controllability of the DC‐side voltage is better than the CB‐SPWM approach.
Why English? Exploring Chinese early career returnee academics’ motivations for writing and publishing in English
Authors: Zhao Xiantong , Liu Xu , Yan Shan
Published: May 2024

To improve their research performance in international league tables, many universities in non-English language dominant settings recruit academic returnees in the hope that they will increase the quantity and quality of articles published in English-medium internationally indexed journals. This study explores Chinese early career returnee academics’ motivations for writing and publishing in English. Utilising ecological systems theory, the findings show that the microsystem is reflected in the early career returnee academics’ interaction with collaborators, while national policies constitute the exosystem. The academic culture has a noteworthy impact at the macrosystem level. This study contributes to the understanding of early career returnee academics’ motivations to write and publish in English which will assist policymakers and university administrators to create a more beneficial environment to promote the accomplishments of academic returnees.
Social, economic, and demographic factors drive the emergence of Hinglish code-mixing on social media
Authors: Sengupta Ayan , Das Soham , Akhtar Md. Shad , Chakraborty Tanmoy
Published: May 2024

The advent of globalization and adaptation to multiple cultures has emanated a fusion of Hindi and English, casually known as Hinglish. The phenomenon of mixing multiple languages (such as Hindi and English) within a single utterance is often called code-mixing. Lately, code-mixed Hinglish has emerged as a dominant conversational language for Hindi-speaking citizens both online (on social media platforms) and offline. Although previous studies investigated such linguistic traits of Hinglish over the past few years, some pertinent questions still need to be answered: How did Hinglish evolve? And, what are the factors behind the evolution of Hinglish? Does the fusion of English impact all Hindi words similarly? To this end, we explore the empirical and statistical shreds of evidence behind the rise of Hinglish on social media such as Twitter. We show that adopting Hinglish depends on several socio-economic and demographic factors. We further formulate dynamic models to explore the socio-economic factors driving the growth of Hinglish, derive the future growth of Hinglish in the upcoming years, and estimate the propensity of users to change their linguistic preferences. Our study highlights that the Hinglish population has evolved steadily between 2014 and 2022, with an annualized growth rate of 1.2%, and the usage of Hinglish on Twitter has increased annually by 2%. Further, we find that the impact of Hinglish evolution is not uniform across different word groups and affects the contextual meaning of different words differently. Although our findings are specific to the Indian Hinglish community, our study can be generalized to understand the evolution and dynamics of other code-mixed languages, such as Spanish-English or Chinese-English.
How does digital technology administrative penalty affect big data technology innovation: evidence from China
Authors: Chen Xiaohui , Lu Kongbiao
Published: May 2024

Administrative regulation is an essential institutional arrangement for governing innovation in big data technology. Administrative penalties are one of its main methods. It is worth investigating whether administrative penalties can serve as an institutional safeguard to promote technological innovation. This study collects data on digital technology administrative penalty (DTAP) and big data technology innovation (BDTI) from 2008 to 2020 in 281 cities in China and empirically evaluates the impact and mechanism of DTAP on BDTI. The findings suggest that the normative impact of the DTAP system can foster a conducive business ecosystem for big data innovation. The incentive mechanism motivates firms to increase their long-term investment in technological innovation, while the deterrence mechanism ensures the existence of a regulated competitive market. These mechanisms play a crucial role in facilitating BDTI. Mechanism tests show that the DTAP has the potential to promote novel business models in the digital economy and accelerate progress in industrial digitalisation, which in turn promotes innovation in big data technologies. The impact of the DTAP on promoting BDTI is diverse, with a significantly greater impact in the first-tier cities. DTAP plays a more important role in fostering BDTI in places where the digital factor-driven industry is still in its early stages of development.
The role of leisure activities in enhancing well-being in Saudi’s retired community: a mixed methods study
Authors: Alanazi Homoud Mohammed Nawi
Published: May 2024

This mixed-methods study delves into the impact of leisure activities on the well-being of retirees in Saudi Arabia, focusing on health, emotional balance, social integration, and self-fulfillment. In the quantitative phase, 545 retirees were selected through a snowball sampling, providing a diverse sample of age, gender, socio-economic status, and educational background. Data were collected using a structured questionnaire and analyzed using SPSS. The qualitative phase involved randomly selecting 23 participants from the initial cohort for semi-structured interviews, with the data subjected to thematic analysis for deeper insights. Findings revealed a moderate overall enhancement in well-being attributed to leisure activities, with health benefits being most significantly improved. Emotional and social well-being showed moderate enhancements, while self-fulfillment benefits were less pronounced. Demographic variations were evident, with gender, socio-economic status, and education level influencing the perceived benefits. Qualitatively, the importance of cultural alignment in leisure activities was highlighted, underscoring their role in social connectivity and personal development. The study underscores the need for culturally sensitive and accessible leisure programs tailored to the varied needs of the retired population in Saudi Arabia. It provides crucial insights for policymakers and community planners, emphasizing the importance of demographic considerations in leisure interventions to improve retirees’ quality of life. This research contributes significantly to understanding leisure’s role in enhancing post-retirement well-being, offering a comprehensive perspective for future leisure-related initiatives and policies.
A novel class of phase space representations for the exact population dynamics of two-state quantum systems and the relation to triangle window functions
Authors: Cheng Xiangsong , He Xin , Liu Jian
Published: May 2024

Isomorphism of the two-state system is heuristic in understanding the dynamical or statistical behavior of the simplest yet most quantum system that has no classical counterpart. We use the constraint phase space developed in J. Chem. Phys.145, 204105 (2016); 151, 024105 (2019); J. Phys. Chem. Lett.12, 2496 (2021), non-covariant phase space functions, time-dependent weight functions, and time-dependent normalization factors to construct a novel class of phase space representations of the exact population dynamics of the two-state quantum system. The equations of motion of the trajectory on constraint phase space are isomorphic to the time-dependent Schrodinger equation. The contribution of each trajectory to the integral expression for the population dynamics is always positive semi-definite. We also prove that the triangle window function approach, albeit proposed as a heuristic empirical model in J. Chem. Phys.145, 144108 (2016), is related to a special case of the novel class and leads to an isomorphic representation of the exact population dynamics of the two-state quantum system.
On metric controlled operator-valued frames and their applications
Authors: Poumai Khole Timothy , Khanna Nikhil , Kaushik S. K.
Published: May 2024

The exploration of pseudo-Hermitian quantum mechanics has led to rapid progress in the methods of constructing inner products and determining the observables of the theory in quantum sciences. In this paper, we introduce metric controlled operator-valued frames and our motivation is to find the applications in the generalized setting of quantum mechanics. We give various characterizations of metric controlled operator-valued frames. We also explore various spectral properties of pseudo-Hermitian and pseudo-unitary operators. Finally, we give the method of representing infinte quantum channels in pseudo-Hermitian quantum mechanics using metric controlled operator-valued frames.
Multivortex traveling waves for the Schrödinger map equation
Authors: Tianpei Guo
Published: May 2024

We construct traveling wave solutions for the Schrödinger map equation in R2. These solutions have n(n + 1)/2 pairs of degree ±1 vortices. The locations of those vortices are symmetric in the plane and determined by the roots of a special class of Adler–Moser polynomials. With a few modifications, a similar construction allows for the creation of traveling wave solutions of the Schrödinger map equation in R3. These solutions have the shape of 2n + 1 vortex rings, whose locations are given by a sequence of polynomials with rational coefficients and are far away from each other.
Enhanced torque efficiency in ferromagnetic multilayers by introducing naturally oxidized Cu
Authors: Zheng Kun , Cao Cuimei , Lu Yingying , Meng Jing , Pan Junpeng , Zhao Zhenjie , Xu Yang , Shang Tian , Zhan Qingfeng
Published: May 2024

Spin–orbit torque (SOT) in the heavy elements with a large spin–orbit coupling (SOC) has been frequently used to manipulate the magnetic states in spintronic devices. Recent theoretical works have predicted that the surface oxidized light elements with a negligible SOC can yield a sizable orbit torque (OT), which plays an important role in switching the magnetization. Here, we report anomalous-Hall-resistance and harmonic-Hall-voltage measurements on perpendicularly magnetized Ta/Cu/[Ni/Co]5/Cu-CuOx multilayers. Both torque efficiency and spin-Hall angle of these multilayers are largely enhanced by introducing a naturally oxidized Cu-CuOx layer, where the SOC is negligible. Such an enhancement is mainly due to the collaborative driven of the SOT from the Ta layer and the OT from the Cu/CuOx interface and can be tuned by controlling the thickness of Cu-CuOx layer. Compared to the Cu-CuOx-free multilayers, the maximum torque efficiency and spin-Hall angle were enhanced by a factor of ten, larger than most of the reported values in the other heterostructures.
Ion solvation free energy calculations based on first-principles molecular dynamics thermodynamic integration
Authors: Lin Chao , He Xiaojun , Xi Cong , Zhang Qianfan , Wang Lin-Wang
Published: May 2024

Numerous electrochemistry reactions require the precise calculation of the ion solvation energy. Despite the significant progress in the first-principles calculations for crystals and defect formation energies for solids, the liquid system free energy calculations still face many challenges. Ion solvation free energies can be calculated via different semiempirical ways, e.g., using implicit solvent models or cluster of explicit molecule models; however, systematically improving these models is difficult due to their lack of a solid theoretical base. A theoretically sound approach for calculating the free energy is to use thermodynamic integration. Nevertheless, owing to the difficulties of self-consistent convergence in first-principles calculations for unphysical atomic configurations, the computational alchemy approach has not been widely used for first-principles calculations. This study proposes a general approach to use first-principles computational alchemy for calculating the ion solvation energy. This approach is also applicable for other small molecules. The calculated ion solvation free energies for Li+, Na+, K+, Be2+, Mg2+, and Ca2+ are close to the experimental results, and the standard deviation due to molecular dynamics fluctuations is within 0.06 eV.
Novel barostat implementation for molecular dynamics
Authors: Janek Jiří , Kolafa Jiří
Published: May 2024

We propose a novel implementation of the extended-dynamics equations for isothermal–isobaric ensemble in molecular dynamics, as the Martyna–Tobias–Klein thermostat and barostat. This method is suitable for systems with constraints and the Verlet-family integrators. Instead of iterations or the Trotter-expansion-based methods, both velocities and box sizes (scaling of bond lengths) are predicted. The algorithm begins with force calculation, requiring neither quarter nor half time steps, and necessitating iterations only inside SHAKE. Several tests demonstrate that the quality is comparable to other implementations. It is found that the formula relating the extended barostat mass to the characteristic time of volume fluctuations is inaccurate for condensed systems, which has consequences for the parameter setup. Emphasis is also put on the verification of the precise isothermal–isobaric ensemble and finite-size effects.
Increasing terahertz spintronic emission with planar antennas
Authors: Pacé Matthias , Kovalenko Oleksandr , Solano José , Hehn Michel , Bailleul Matthieu , Vomir Mircea
Published: May 2024

Spintronic THz emitters, consisting of Ta/Co/Pt trilayers patterned into lateral-sized rectangles in the 10 μm range, have been integrated in planar electromagnetic antennas of various types (dipole, bow-tie, and spiral). The antenna dimensions and shapes have been optimized with the help of electromagnetic simulations so as to maximize antenna efficiency in both narrow-band and broadband geometries at/around 1 THz. The THz emission has been studied using a pump–probe free space electro-optic sampling setup, both for single-emitter geometry and for arrays of emitters. The results show an increase in the detected THz signal for all antenna geometries, with enhancement ratios in the range of three to fifteen, depending on the antenna type and frequency range, together with changes in the emission bandwidth consistent with simulated characteristics.
Theory of 2D electronic spectroscopy of water soluble chlorophyll-binding protein (WSCP): Signatures of Chl b derivate
Authors: Riedl Michael , Renger Thomas , Seibt Joachim
Published: May 2024

We investigate how electronic excitations and subsequent dissipative dynamics in the water soluble chlorophyll-binding protein (WSCP) are connected to features in two-dimensional (2D) electronic spectra, thereby comparing results from our theoretical approach with experimental data from the literature. Our calculations rely on third-order response functions, which we derived from a second-order cumulant expansion of the dissipative dynamics involving the partial ordering prescription, assuming a fast vibrational relaxation in the potential energy surfaces of excitons. Depending on whether the WSCP complex containing a tetrameric arrangement of pigments composed of two dimers with weak excitonic coupling between them binds the chlorophyll variant Chl a or Chl b, the resulting linear absorption and circular dichroism spectra and particularly the 2D spectra exhibit substantial differences in line shapes. These differences between Chl a WSCP and Chl b WSCP cannot be explained by the slightly modified excitonic couplings within the two variants. In the case of Chl a WSCP, the assumption of equivalent dimer subunits facilitates a reproduction of substantial features from the experiment by the calculations. In contrast, for Chl b WSCP, we have to assume that the sample, in addition to Chl b dimers, contains a small but distinct fraction of chemically modified Chl b pigments. The existence of such Chl b derivates has been proposed by Pieper et al. [J. Phys. Chem. B 115, 4042 (2011)] based on low-temperature absorption and hole-burning spectroscopy. Here, we provide independent evidence.
Small multimodal thermometry with detonation-created multi-color centers in detonation nanodiamond
Authors: So Frederick T.-K. , Hariki Nene , Nemoto Masaya , Shames Alexander I. , Liu Ming , Tsurui Akihiko , Yoshikawa Taro , Makino Yuto , Ohori Masanao , Fujiwara Masanori , Herbschleb Ernst David , Morioka Naoya , Ohki Izuru , Shirakawa Masahiro , Igarashi Ryuji , Nishikawa Masahiro , Mizuochi Norikazu
Published: May 2024

Detonation nanodiamond (DND) is the smallest class of diamond nanocrystal capable of hosting various color centers with a size akin to molecular pores. Their negatively charged nitrogen-vacancy center (NV−) is a versatile tool for sensing a wide range of physical and even chemical parameters at the nanoscale. The NV− is, therefore, attracting interest as the smallest quantum sensor in biological research. Nonetheless, recent NV− enhancement in DND has yet to yield sufficient fluorescence per particle, leading to efforts to incorporate other group-IV color centers into DND. An example is adding a silicon dopant to the explosive mixture to create negatively charged silicon-vacancy centers (SiV−). In this paper, we report on efficient observation (∼50% of randomly selected spots) of the characteristic optically detected magnetic resonance (ODMR) NV− signal in silicon-doped DND (Si-DND) subjected to boiling acid surface cleaning. The NV− concentration is estimated by continuous-wave electron spin resonance spectroscopy to be 0.35 ppm without the NV− enrichment process. A temperature sensitivity of 0.36K/Hz in an NV− ensemble inside an aggregate of Si-DND is achieved via the ODMR-based technique. Transmission electron microscopy survey reveals that the Si-DNDs core sizes are ∼11.2 nm, the smallest among the nanodiamond’s temperature sensitivity studies. Furthermore, temperature sensing using both SiV− (all-optical technique) and NV− (ODMR-based technique) in the same confocal volume is demonstrated, showing Si-DND’s multimodal temperature sensing capability. The results of the study thereby pave a path for multi-color and multimodal biosensors and for decoupling the detected electrical field and temperature effects on the NV− center.
Effect of oxygen defects on ferroelectric oxides: Correlation between linear and nonlinear dielectric responses
Authors: Cao Zixin , Li Yawei , Shang Liyan , Jiang Kai , Zhu Liangqing , Zhang Jinzhong , Hu Zhigao
Published: May 2024

Oxygen defects are introduced into PbZr0.5Ti0.5O3 films and their impact on ferroelectric behavior, linear dielectric response (LDR), and nonlinear dielectric response (NDR) is studied. Apart from a notable decrease in both polarization and LDR permittivity, the frequency spectra of LDR exhibit a distinctive loss peak. The peak position varies with temperature and oxygen defect concentration. NDR parameters, including the Rayleigh coefficient (α1), the slope (α2) correlating the imaginary part of permittivity with the ac electric field, and the slope (k) between the real and the imaginary parts of permittivity, demonstrate diverse behaviors in response to temperature and oxygen defect concentration. The similarity in the frequency spectra of tanδ and 1/k reveals the correlation between LDR and NDR induced by the presence of oxygen defects. These observations are attributed to the behavior of the single and composite defects associated with oxygen vacancies.
Mitigating inflow acceleration effects in twin mountains using air jets: Emphasis on anti-wind for high-speed railways
Authors: Wang Jian , Deng E , Ni Yi-Qing , He Xu-Hui , Chan Pak-Wai , Yang Wei-Chao , Li Huan , Xie Zu-Yu
Published: May 2024

The twin mountains, a common terrain in mountainous areas, tend to induce the acceleration effect under crosswinds, which enhances the wind speed and the turbulence performance of the flow field. To mitigate the impact of the acceleration effect on high-speed trains, structures, and aircraft near the twin mountains, this study investigates the effectiveness of the jet strategies, which are realized on natural mountain slopes by mechanical ventilation, with different jet angles on the flow field and the train. Wind speed tests, flow visualization, wind field prediction, and research on the train's aerodynamic behavior are conducted in this paper using the wind tunnel and the improved delayed detached eddy simulation dynamic models. The results indicate that the wind velocity on the leeward side of the twin mountains increases up to 1.42 folds of the wind velocity of the incoming flow under crosswinds. The jet streams with 0° and 30° angles are the most effective in mitigating the acceleration effect among those tested (0°, 15°, 30°, and 45°), reducing the maximum wind speed by 11.87% and 16%, respectively. Compared with the mitigation effect of the jet stream with the 30° angle, the jet stream with the 0° angle has a better mitigation effect on the aerodynamic loads (4.0%–13.2%) and its fluctuation amplitude (24.4%–42.7%) of the train. These findings are valuable for studying the flow field characteristics of the twin mountains and the designing anti-wind measures for high-speed railways.
Fast and flexible solid-state linear transformer driver for plasma discharge based on metal oxide semiconductor field effect transistor
Authors: Xue Haorui , Yuan Qi , Ding Weidong , Meng Yang , Wan Zhenbo , Wang Yanan
Published: May 2024

A pulsed power supply with a short rise time and high repetition frequency is favorable to driving diffusive plasma for strongly oxidizing radical (O3, OH) generation and increasing the system’s energy efficiency. In this paper, a 10-stage solid-state linear transformer driver (LTD) with a nanosecond rise time is developed to drive plasma for wastewater treatment. To decrease the rise time, a control system with low jitter is developed to improve the synchronization of pulses using an optocoupler isolation chip. A 10-stage LTD with a rise time of 6.2 ns is realized in the case that the rise time of the single-stage LTD is 5.4 ns. The results show that the LTD can generate pulses on a 300 Ω resistive load with a repetition frequency of 10 kHz, an amplitude of 8.80 kV, an overshoot less than 3.97%, and a reverse overshoot less than 4.82%. The rise time (6.2–33.0 ns), the pulse width (35.9–200.0 ns), and the fall time (10.5–27.6 ns) can be adjusted flexibly and independently by controlling the drive signals of metal oxide semiconductor field effect transistors. The pulsed generator is utilized to drive plasma in the needle-water electrode system. The preliminary experimental results show that the plasma includes abundant oxygen atoms and hydroxyl radicals with high activity, and it is suitable for wastewater treatment.
Influence of location of twin-adiabatic blocks on magnetohydrodynamics-based double-diffusive convection and entropy generation for a liquid metal
Authors: Karki Pawan , Gangawane Krunal M.
Published: May 2024

This research deals with a rectangular cavity encompassing two adiabatic rectangular and impermeable obstacles at various positions. This study serves as a platform to explore the interplay between diverse flow-governing parameters, such as the buoyancy ratio (N = −1, 0, and +1), Hartmann number (Ha = 0, 50, and 100), Lewis number (Le = 1, 5, and 10), Rayleigh number (Ra = 103 and 104), and geometric arrangements of twin-blocks (C1, C2, and C3) to help in developing insights into such complex transport phenomenon driven under the influence of buoyancy and concentration. The arrangements are chosen such that C1 and C3 represent the off-center position of the first obstacle, while C2 represents the in-line position with the second obstacle. The influence of liquid sodium–potassium alloy (Pr = 0.054) on fluid flow, heat, and mass transfer, and entropy generation characteristics due to double-diffusive natural convection in the twin obstacle-filled rectangular enclosure are observed using the lattice Boltzmann method. The results reveal that the maximum amount of heat and mass transfer occurs at the C2 position, making it the most efficient for heat and mass transfer among all. In contrast, the C2 configuration is a thermodynamically inefficient arrangement as entropy generation is maximum, while the C3 configuration is obtained to be more efficient thermodynamically. Furthermore, the results reveal that the average total entropy generation is directly related to the Lewis number, while it has an inverse relation with the Hartmann number.
Tuning structural and electronic properties of metal-organic framework 5 by metal substitution and linker functionalization
Authors: Edzards Joshua , Saßnick Holger-Dietrich , Andreo Julia Santana , Cocchi Caterina
Published: May 2024

The chemical flexibility of metal-organic frameworks (MOFs) offers an ideal platform to tune structure and composition for specific applications, from gas sensing to catalysis and from photoelectric conversion to energy storage. This variability gives rise to a large configurational space that can be efficiently explored using high-throughput computational methods. In this work, we investigate from first principles the structural and electronic properties of MOF-5 variants obtained by replacing Zn with Be, Mg, Cd, Ca, Sr, and Ba and by functionalizing the originally H-passivated linkers with CH3, NO2, Cl, Br, NH2, OH, and COOH groups. To build and analyze the resulting 56 structures, we employ density-functional theory calculations embedded in an in-house developed library for automatized calculations. Our findings reveal that structural properties are mainly defined by metal atoms and large functional groups, which distort the lattice and modify coordination. The formation energy is largely influenced by functionalization and enhanced by COOH and OH groups, which promote the formation of hydrogen bonds. The charge distribution within the linker is especially influenced by functional groups with electron-withdrawing properties, while the metal nodes play a minor role. Likewise, the bandgap size is crucially determined by ligand functionalization. The smallest gaps are found with NH2 and OH groups, which introduce localized orbitals at the top of the valence band. This characteristic makes these functionalizations particularly promising for the design of MOF-5 variants with enhanced gas uptake and sensing properties.
Absorption and fluorescence spectroscopy of cold proflavine ions isolated in the gas phase
Authors: Lindkvist Thomas Toft , Kjær Christina , Langeland Jeppe , Vogt Emil , Kjaergaard Henrik G. , Nielsen Steen Brøndsted
Published: May 2024

Proflavine, a fluorescent cationic dye with strong absorption in the visible, has been proposed as a potential contributor to diffuse interstellar bands (DIBs). To investigate this hypothesis, it is essential to examine the spectra of cold and isolated ions for comparison. Here, we report absorption spectra of proflavine ions, trapped in a liquid-nitrogen-cooled ion trap filled with helium-buffer gas, as well as fluorescence spectra to provide further information on the intrinsic photophysics. We find absorption- and fluorescence-band maxima at 434.2 ± 0.1 and 434.7 ± 0.3 nm, corresponding to a Stokes shift of maximum 48 cm−1, which indicates minor differences between ground-state and excited-state geometries. Based on time-dependent density functional theory, we assign the emitting state to S2 as its geometry closely resembles that of S0, whereas the S1 geometry differs from that of S0. As a result, simulated spectra involving S1 exhibit long Franck-Condon progressions, absent in the experimental spectra. The latter displays well-resolved vibrational features, assigned to transitions involving in-plane vibrational modes where the vibrational quantum number changes by one. Dominant transitions are associated with vibrations localized on the NH2 moieties. Experiments repeated at room temperature yield broader spectra with maxima at 435.5 ± 1 nm (absorption) and 438.0 ± 1 nm (fluorescence). We again conclude that prevalent fluorescence arises from S2, i.e., anti-Kasha behavior, in agreement with previous work. Excited-state lifetimes are 5 ± 1 ns, independent of temperature. Importantly, we exclude the possibility that a narrow DIB at 436.4 nm originates from cold proflavine cations as the band is redshifted compared to our absorption spectra.
Uncertainties of predictions from temperature replica exchange simulations
Authors: Kříž Pavel , Beránek Jan , Spiwok Vojtěch
Published: May 2024

Parallel tempering molecular dynamics simulation, also known as temperature replica exchange simulation, is a popular enhanced sampling method used to study biomolecular systems. This method makes it possible to calculate the free energy differences between states of the system for a series of temperatures. We developed a method to easily calculate the errors (standard errors or confidence intervals) of these predictions using a modified version of our recently introduced JumpCount method. The number of transitions between states (e.g., protein folding events) is counted for each temperature. This number of transitions, together with the temperature, fully determines the value of the standard error or the confidence interval of the free energy difference. We also address the issue of convergence in the situation where all replicas start from one state by developing an estimator of the equilibrium constant from simulations that are not fully equilibrated. The prerequisite of the method is the Markovianity of the process studied.