bluuebunny/crossref_metadata_2025 huggingface dataset:
Chiral bifacial indacenodithiophene-based π-conjugated polymers with chirality-induced spin selectivity
Authors: Li Shuang , Ishiwari Fumitaka , Zorn Scott , Murotani Kazuharu , Pylnev Mikhail , Taniguchi Kouji , Saeki Akinori
Published: August 2024

Chiral bifacial indacenoditiophene-containing π-conjugated polymers were synthesized and exhibited pronounced spin filtering function based on chirality induced spin selectivity.
Carbon–sulfur bond elongation as the promoting reaction coordinate in the efficient sub-nanosecond intersystem crossing in thianaphthene derivatives
Authors: Griffith Cameron , Mao Erqian , Hoehn Sean J. , Krul Sarah E. , Crespo-Hernández Carlos E.
Published: August 2024

It is shown that C7a–S bond elongation promotes efficient intersystem crossing in the thianaphthene derivatives.
A facile methodology for side- and upcycling of HDPE waste via partial creation of unsaturated double bonds
Authors: Wu Klingler Wenyu , Perret Lucie , Rupper Patrick , Lehner Sandro , Zhou Xiaoyu , Eliasson Henrik , Muff Rico , Heuberger Manfred , Gaan Sabyasachi
Published: August 2024

We present a facile chemical method for converting HDPE waste into valuable long-chain dicarboxylic acids (LCDCAs), thus transforming polymer waste into monomers for potentially novel polyester synthesis.
Constructing highly efficient multiple resonance fluorescence materials by inserting benzothiophene within B/N-skeletons
Authors: Zhao He , Han Wenkun , Xu Jianan , Bi Yan , Li He , Yang Tianyu , Ma Xiaoyu , Su Chunhui
Published: August 2024

Two new multi-resonance (MR) blue emitters with benzothiophene within B/N skeletons exhibit blue emissions with narrow FWHMs, achieving high PLQYs and long device lifetimes.
Introduction to Computational Organic Chemistry
Authors: Goodman Jonathan M. , Reid Jolene P. , Wu Judy I.
Published: August 2024

Jonathan Goodman, Jolene Reid and Judy Wu introduce the Organic & Biomolecular Chemistry themed collection on Computational Organic Chemistry.
Deep-learning optical flow for measuring velocity fields from experimental data
Authors: Tran Phu N. , Ray Sattvic , Lemma Linnea , Li Yunrui , Sweeney Reef , Baskaran Aparna , Dogic Zvonimir , Hong Pengyu , Hagan Michael F.
Published: August 2024

Deep learning-based optical flow (DLOF) extracts features in video frames with deep convolutional neural networks to estimate the inter-frame motions of objects. DLOF computes velocity fields more accurately than PIV for densely labeled systems.
Reshaping and enzymatic activity may allow viruses to move through the mucus
Authors: Ziebert Falko , Dokonon Kenan G. , Kulić Igor M.
Published: August 2024

Filamentous viruses can attain toroidal states due to axial spike–spike interactions. Upon binding and cutting of mucus glycans spontaneous rotation can emerge. The induced virus reshaping leads to a vortex-like spinning propelling it through the mucus.
Nature of barriers determines first passage times in heterogeneous media
Authors: Dasgupta Moumita , Guha Sougata , Armbruster Leon , Das Dibyendu , Mitra Mithun K.
Published: August 2024

The nature of barriers control the first passage times in heterogenous media. For entropic barriers, the first passage times increases monotonically with increasing number of barriers, while for energetic barriers, passage times show a non-monotonic behaviour with increasing barriers.
Regulation of PARP1/2 and the tankyrases: emerging parallels
Authors: Jessop Matthew , Broadway Benjamin J. , Miller Katy , Guettler Sebastian
Published: August 2024

ADP-ribosylation is a prominent and versatile post-translational modification, which regulates a diverse set of cellular processes. Poly-ADP-ribose (PAR) is synthesised by the poly-ADP-ribosyltransferases PARP1, PARP2, tankyrase (TNKS), and tankyrase 2 (TNKS2), all of which are linked to human disease. PARP1/2 inhibitors have entered the clinic to target cancers with deficiencies in DNA damage repair. Conversely, tankyrase inhibitors have continued to face obstacles on their way to clinical use, largely owing to our limited knowledge of their molecular impacts on tankyrase and effector pathways, and linked concerns around their tolerability. Whilst detailed structure-function studies have revealed a comprehensive picture of PARP1/2 regulation, our mechanistic understanding of the tankyrases lags behind, and thereby our appreciation of the molecular consequences of tankyrase inhibition. Despite large differences in their architecture and cellular contexts, recent structure-function work has revealed striking parallels in the regulatory principles that govern these enzymes. This includes low basal activity, activation by intra- or inter-molecular assembly, negative feedback regulation by auto-PARylation, and allosteric communication. Here we compare these poly-ADP-ribosyltransferases and point towards emerging parallels and open questions, whose pursuit will inform future drug development efforts.
Preliminary evaluation of the value of small molecular nutrients in depression-specific local metabolic network in preventing and treating depression
Authors: Xu Jiacheng
Published: August 2024

Depression, a severe mental disease, has become increasingly prevalent worldwide, leading to many negative social impacts. The discovery of a small molecular nutrient capable of preventing and treating depression is of great importance. In this study, the results of signal pathways involved in 19 depressionrelated genes show that only four depression-related genes (HIBADH, TKT, GMPPB, B3GAT3) are directly connected to the metabolic network, while the remaining genes are connected to the non-metabolic network. Additionally, based on the information in KEGG and STRING, we have constructed a local metabolic network (LMN) for depression. Using this network, we found a small molecule nutrient, 3-hydroxyisobutyrate (3-HIB), which has potential value in preventing and treating depression. Finally, we made a preliminary evaluation of its therapeutic potential for depression. In future, we can categorize patients with varying depression symptoms based on molecular profiles and provide nutrient prevention and treatment strategies in different metabolic pathways.
Investigation on AIDS Awareness and Testing Willingness among Freshmen in 4 Higher Vocational Colleges in Chongqing City
Authors: Yu Jingyu , Feng Sheng , Zeng Xiaofei , Zhu Jing
Published: August 2024

Objectives: To understand the knowledge and testing willingness of new students in vocational colleges in Chongqing City towards HIV/AIDS, and provide reference for HIV/AIDS prevention education for vocational college students. Methods: A combined method of cluster sampling and random sampling was used to conduct the survey. In November 2022, four vocational colleges in Chongqing City were selected, and classes of new students were randomly chosen to participate in the survey. In addition, the questionnaire was distributed to new students of the four colleges through WeChat public platform, and students voluntarily responded to the survey. Results: The awareness rate of HIV/AIDS-related knowledge among new students in the four vocational colleges was 67.53% (938/1389), and the awareness rate among students in medical majors was 78.59% (P<0.05). Female students had a significantly higher testing willingness after engaging in high-risk sexual behavior than male students, with statistical differences (P<0.05). Male students had a more friendly attitude towards AIDS patients compared to female students (P<0.05). Conclusion: The awareness rate of AIDS among freshmen in vocational colleges in Chongqing is lower than in other regions of the country. Carrying out various forms of AIDS prevention and education in colleges plays a significant role in improving students’ awareness of AIDS. By strengthening knowledge contents such as “Knowing that one cannot judge whether a person is infected with AIDS based on their appearance”, the testing rate for AIDS can be increased. Male students have a higher level of friendliness towards people with AIDS compared to female students. Destigmatizing AIDS and guiding university students to adopt the correct attitude towards AIDS patients are also key focuses of education.
Control of western corn rootworm with entomopathogenic nematodes in maize monoculture
Authors: Vörös Levente , Kerekes Gábor , Ábrahám Rita
Published: August 2024

Western corn rootworm is one of the most dangerous pests of maize, and both the larvae and the imagoes thereof may cause significant damage to the plants. The options of controlling these pests have recently become highly limited, thus creating a great demand for new control methods complying with sustainable plant protection. These requirements are met by the natural enemies of these pests, such as entomopathogenic nematodes (e.g. Heterorhabditis bacteriophora, Gerritsen, 1994). The objective of this study was to determine whether the viability and larvicide effect of a single injection into the soil of 2 billion nematodes using various amounts of water (50, 100 or 200 L/hectare) was maintained even with the lower quantities. Our studies proved that the entomopathogenic nematodes retain their viability and larvicide effect when applied using 50 L/ha of water. The efficacy of the biological agent did not differ from that of Force 1.5G, a product containing Tefluthrin as active ingredient, which was used as positive control.
Research on B30 fuel use in people’s shipping
Authors: Prasutiyon Hadi , Supartono  , Prayogi Urip , Sugianto Erik , Felayati Frengki Mohamad
Published: August 2024

The usage of biodiesel is necessary to be more suited to manufacturing development, notably diesel engines, both addressing engine performance and exhaust emission issues. Biodiesel is a renewable, sustainable, and alternative fuel for internal combustion engines. The effects of using biodiesel, specifically on the content of PM, HC, and CO emissions, increasing fuel consumption and increasing NOx, as well as carbon deposits in the primary engine components, are brought on by the emergence of new regulations and standards with reference to international regulations. As a result, the B30 fuel mixture is anticipated to aid in the control of air pollution and the alleviation of resource shortages without considerably reducing engine power and being cost-effective. Comparable to 58 Kw, so the HSD-based SFOC is 0.162927 and the B30 value is 0.137527. For the same engine power, it can be stated that using B30 is more effective than using HSD. However, when diesel oil is totally replaced with biodiesel, the engine must be optimized and modified in terms of engine performance, instrumentation, and new testing procedures.
Improved Over Current Relay (OCR) Coordination Using Time Multiple Setting (TMS)
Authors: Prasetijo Hari , Fadli Ari , Renaldi Feby
Published: August 2024

Proper coordination between overcurrent relay (OCR) is needed to improve the reliability of the power distribution system. By choosing the proper time multiple setting (TMS), an optimum setting of OCR coordination can be achieved. This study improve working time coordination of OCR bay transformer using time multiple setting. Simulations were carried out to see the performance of the OCR bay transformer against a 3 phase short circuit on the 20 kV outgoing bus. The 3 phase short circuit was chosen because it produces the largest fault current among other types of short circuits. The discussion focuses on the OCR bay transformer, consist of OCR incoming 20 kV and OCR outgoing 150 kV. Existing data and calculation results were used as a parameter in the simulation. Simulation results with existing tms 0.21 and 0.23 for OCR incoming 20 kV and OCR outgoing 150 kV, respectively, have the potential to cause miscoordination of the OCR working time. Smaller short circuit current, bigger potential miscoordination. Resetting tms improves coordination of OCR bay transformer working time according to the standard used. Bigger value of tms, as long as it meets the standar, better OCR working time coordination to protect phase-phase fault current.
Menanga Formation as volcanic submarine fan deposit of Woyla Arc in Sumatra, Indonesia
Authors: Widiatama Angga Jati , Santy Lauti Dwita , Nahar Rikza Nur Faqih An , Hendrawan Rezki Naufan , Natalia Happy Christin , Ogara Evan Rosyadi , Christi Dea Ananda Gita
Published: August 2024

The Menanga Formation is part of the Woyla terrane, the last large terrane amalgamated formed island of Sumatra. Woyla terrane consist of Cretaceous arc assemblage and relatively lack of research has been done on this formation in Lampung and surrounding areas. This study aims to identify the facies of the Menanga Formation. Research was carried out by making a measured stratigraphic and dividing it into facies and facies associations. The data were taken from two places, in Gunungkasih, Tanggamus and Way Sabu, Pesawaran, Lampung. The results showed that the Menanga Formation has nine facies, there are graded bedding sandstone (F1), loadcast sandstone (F2), parallel lamination coarse sandstone (F3), parallel lamination medium sandstone (F4), parallel bedding fine sandstone (F5), ripple fine sandstone (F6), lamination red sandstone (F7), grey claystone (F8), and parallel lamination red claystone (F9). The Menanga Formation facies were grouped into three facies associations, AF1 consist of F1, F2, F3, F4, and F5 shown channel geometry, fining upward trend, and Bouma classical turbidite deposit, while AF2 consist of monotonous interbedded of F5, F6, and F7 as upper part of the turbidite sequence, while AF3 shown distal facies association (AF3) consist monotonous interbedded of F8, and F9. The stacking pattern shows fining upwards and thining upwards trend interpreted to be channel-levee deposits in the midfan lobe of the submarine fan, while the monotonous of interbedded claystone with thin layers of sandstone in upper part interpreted to be deposited in the outer fan lobe submarine fan. Menanga Formation sandstone consists of lithic graywacke whose grains are dominated by lithic minerals, small amounts of feldspar and minor quartz. The discovery of indicates the relative age this formation ranging from Jurassic to Cretaceous. The discovery of radiolaria Pantanellium sp. indicates the relative age this formation ranging from Jurassic to Cretaceous. The Menanga Formation interpreted to be deposited in submarine fan environment whose sediment with material originates from the Woyla volcanic arc.
Aza-BODIPY-Based Bifunctional Photocatalyst for Red-Light-Driven Asymmetric Hydroxylation of β‑Ketoesters
Authors: Guo Yonghong , Zhao Jiayi , He Chuan , Zu Bing
Published: August 2024

A novel bifunctional photocatalyst combining an aza-BODIPY and a chiral oxazoline has been developed. This photocatalyst enables the asymmetric hydroxylation of β‑ketoesters under an oxygen atmosphere and irradiation with 18-W red LEDs. This procedure offers a convenient and potentially general approach to obtain enantioenriched α-hydroxy-β-dicarbonyl products. The results reported in this manuscript demonstrate the promise of this new organic photocatalyst design and will help expand the application of BODIPY-based chiral photocatalysts.
Epidemiological, Clinical, Etiological, and Therapeutic Aspects of Cerebral Palsy in Dakar
Authors: Diagne Rokhaya , Mbaye Khalifa Ababacar , Nepetsoun Inès Nkongni , Ndiaye Moustapha
Published: August 2024

Cerebral palsy is one of the most frequent causes of motor disability in children. The aim of our study was to characterize the epidemiological, clinical, paraclinical, etiological, and therapeutic aspects in Dakar. This was a retrospective and descriptive study from March 2010 to March 2020 at the Albert Royer National Children's Hospital and the Neurology Department of the Fann National University Hospital. We collected 913 patients, 13.7% of all pediatric neurology consultations, out of which 556 (60.9%) were males. The average age of the patients was 32.99 months (ranging between 25 days and 17 years). The most common subtype was isolated axial hypotonia (50%) followed by pyramidal (40.5%) and 45% had epilepsy. Brain imaging revealed cortico-subcortical atrophy in 15% of cases. Five hundred and fifty-two children (60.5%) had an electroencephalogram out of which 19.4% had diffuse irritative anomalies. In terms of treatment, 73% had received motor kinesitherapy. Sodium valproate was the most commonly used antiseizure medication at 76.67%. The average follow-up was 12 months. Seven hundred and ninety-two children (86.8%) were lost to follow-up and 5 children (0.5%) died. Psychomotor development improved in 219 children (13.4%) who acquired standing. Note that 267 children (30%) in a stable sitting position and 29 children had acquired language. Cerebral palsy is a disabling condition that needs to be diagnosed early and early interventions can improve the quality of life of the child.
Comparison of Clinical Characteristics of Viral and Bacterial Sepsis in Children: a Single-Center Retrospective Analysis
Authors: Saito Yuya , Kawasaki Tatsuya
Published: August 2024

Objective This study aimed to elucidate the characteristics of viral sepsis in children by comparing viral and bacterial sepsis.

Methods We conducted a retrospective cohort study in the pediatric intensive care unit (PICU) of a single pediatric hospital. Patients aged <15 years who were admitted for sepsis to the PICU between January 2011 and December 2019 were included. Sepsis was diagnosed according to the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) criteria, and the degree of organ dysfunction was evaluated using the Pediatric Sequential Organ Failure Assessment (pSOFA) score. The mortality rate was compared as a primary endpoint between patients with viral sepsis and those with bacterial sepsis.

Results We included 28 patients with viral sepsis and 52 patients with bacterial sepsis. The pSOFA scores for viral and bacterial sepsis were 10 (interquartile range [IQR]: 6.75–14) and 9 (IQR: 7–11) points, respectively, with no significant difference between groups. Respiratory disorders were significantly more prevalent in the viral sepsis group. Mortality between patients with viral (n = 8; 29%) and bacterial (n = 7; 13%) sepsis in the PICU showed no significant difference. When analyses were restricted to patients with septic shock, mortality was significantly higher due to viral (70%) than bacterial (27%) sepsis.

Conclusion In pediatric patients, sepsis due to viral and bacterial infections is associated with similar rates of mortality and organ dysfunction.
Developing a piezoresistive sensor based bionic neurological intraoperative monitoring system for spine surgery skill training
Authors: Wu Sin-Syuan , Hsueh Meng Lun , Lin Jang-Chun , Chen Pin-Chuan , Liu Wei-Hsiu
Published: August 2024

This research aims to tackle the limitations faced in surgical education nowadays, particularly in the complex field of spinal cord tumor removal surgery. An innovative flexible piezoresistive sensor designed to mimic a motor nerve was developed and integrated into a bionic spine surgery simulation system, allowing for the intraoperative nerve monitoring possible during simulated tumor removal surgeries. The motor nerve, fabricated using a combination of carbon nanotubes and silicone rubber, exhibited a strong correlation between applied force and resultant changes in resistance, as confirmed by experimental results. This creative system can play an important role in providing valuable feedback for training doctors, facilitating the assessment of surgical precision and success, and enabling doctors to take necessary precautions to minimize the risk of nerve damage in real surgical scenarios. Ultimately, this proposed system has the potential to elevate the standard of surgical education, foster skill development among doctors, and significantly contribute to enhanced patient care and recovery.
A quasi-local, functional analytic detection method for stationary limit surfaces of black hole spacetimes
Authors: Röken Christian
Published: August 2024

We present a quasi-local, functional analytic method to locate and invariantly characterize the stationary limit surfaces of black hole spacetimes with stationary regions. The method is based on ellipticity-hyperbolicity transitions of the Dirac, Klein–Gordon, Maxwell, and Fierz–Pauli Hamiltonians defined on spacelike hypersurfaces of such black hole spacetimes, which occur only at the locations of stationary limit surfaces and can be ascertained from the behaviors of the principal symbols of the Hamiltonians. Therefore, since it relates solely to the effects that stationary limit surfaces have on the time evolutions of the corresponding elementary fermions and bosons, this method is profoundly different from the usual detection procedures that employ either scalar polynomial curvature invariants or Cartan invariants, which, in contrast, make use of the local geometries of the underlying black hole spacetimes. As an application, we determine the locations of the stationary limit surfaces of the Kerr–Newman, Schwarzschild–de Sitter, and Taub–NUT black hole spacetimes. Finally, we show that for black hole spacetimes with static regions, our functional analytic method serves as a quasi-local event horizon detector and gives rise to a relational concept of black hole entropy.
Needle in a haystack: Efficiently finding atomically defined quantum dots for electrostatic force microscopy
Authors: Bustamante José , Miyahara Yoichi , Fairgrieve-Park Logan , Spruce Kieran , See Patrick , Curson Neil , Stock Taylor J. Z. , Grutter Peter
Published: August 2024

The ongoing development of single electron, nano-, and atomic scale semiconductor devices would greatly benefit from a characterization tool capable of detecting single electron charging events with high spatial resolution at low temperatures. In this work, we introduce a novel Atomic Force Microscope (AFM) instrument capable of measuring critical device dimensions, surface roughness, electrical surface potential, and ultimately the energy levels of quantum dots and single electron transistors in ultra miniaturized semiconductor devices. The characterization of nanofabricated devices with this type of instrument presents a challenge: finding the device. We, therefore, also present a process to efficiently find a nanometer sized quantum dot buried in a 10 × 10 mm2 silicon sample using a combination of optical positioning, capacitive sensors, and AFM topography in a vacuum.
Can specific THz fields induce collective base-flipping in DNA? A stochastic averaging and resonant enhancement investigation based on a new mesoscopic model
Authors: Koon Wang Sang , Owhadi Houman , Tao Molei , Yanao Tomohiro
Published: August 2024

We study the metastability, internal frequencies, activation mechanism, energy transfer, and the collective base-flipping in a mesoscopic DNA via resonance with specific electric fields. Our new mesoscopic DNA model takes into account not only the issues of helicity and the coupling of an electric field with the base dipole moments, but also includes environmental effects, such as fluid viscosity and thermal noise. Also, all the parameter values are chosen to best represent the typical values for the opening and closing dynamics of a DNA. Our study shows that while the mesoscopic DNA is metastable and robust to environmental effects, it is vulnerable to certain frequencies that could be targeted by specific THz fields for triggering its collective base-flipping dynamics and causing large amplitude separation of base pairs. Based on applying the Freidlin–Wentzell method of stochastic averaging and the newly developed theory of resonant enhancement to our mesoscopic DNA model, our semi-analytic estimates show that the required fields should be THz fields with frequencies around 0.28 THz and with amplitudes in the order of 450 kV/cm. These estimates compare well with the experimental data of Titova et al., which have demonstrated that they could affect the function of DNA in human skin tissues by THz pulses with frequencies around 0.5 THz and with a peak electric field at 220 kV/cm. Moreover, our estimates also conform to a number of other experimental results, which appeared in the last couple years.
Influence of phospholipid head and tail molecular structures on cell membrane mechanical response under tension
Authors: Vo Anh T. N. , Murphy Michael A. , Prabhu Raj K. , Stone Tonya W.
Published: August 2024

Biological cell membranes are primarily comprised of a diverse lipid bilayer with multiple phospholipid (lipid) types, each of which is comprised of a hydrophilic headgroup and two hydrophobic hydrocarbon tails. The lipid type determines the molecular structure of head and tail groups, which can affect membrane mechanics at nanoscale and subsequently cell viability under mechanical loading. Hence, using molecular dynamics simulations, the current study investigated seven membrane phospholipids and the effect of their structural differences on physical deformation, mechanoporation damage, and mechanical failure of the membranes under tension. The inspected phospholipids showed similar yield stresses and strains, as well as pore evolution and damage, but significantly different failure strains. In general, failure occurred at a lower strain for lipids with a larger equilibrium area per lipid. The obtained results suggest that larger headgroup structure, greater degree of unsaturation, and tail-length asymmetry influenced the phospholipids’ ability to pack against each other, increased the fluidity and equilibrium area per lipid of the membrane, and resulted in lower failure strain. Overall, this study provides insights on how different phospholipid structures affect membrane physical responses at the molecular level and serves as a reference for future studies of more complex membrane systems with intricate biophysical properties.
Unfolding the distribution of periodicity regions and diversity of chaotic attractors in the Chialvo neuron map
Authors: Ramírez-Ávila Gonzalo Marcelo , Muni Sishu Shankar , Kapitaniak Tomasz
Published: August 2024

We performed an exhaustive numerical analysis of the two-dimensional Chialvo map by obtaining the parameter planes based on the computation of periodicities and Lyapunov exponents. Our results allowed us to determine the different regions of dynamical behavior, identify regularities in the distribution of periodicities in regions indicating regular behavior, find some pseudofractal structures, identify regions such as the “eyes of chaos” similar to those obtained in parameter planes of continuous systems, and, finally, characterize the statistical properties of chaotic attractors leading to possible hyperchaotic behavior.
Partial tipping in bistable ecological systems under periodic environmental variability
Authors: Basak Ayanava , Dana Syamal K. , Bairagi Nandadulal
Published: August 2024

Periodic environmental variability is a common source affecting ecosystems and regulating their dynamics. This paper investigates the effects of periodic variation in species growth rate on the population dynamics of three bistable ecological systems. The first is a one-dimensional insect population model with coexisting outbreak and refuge equilibrium states, the second one describes two-species predator–prey interactions with extinction and coexistence states, and the third one is a three-species food chain model where chaotic and limit cycle states may coexist. We demonstrate with numerical simulations that a periodic variation in species growth rate may cause switching between two coexisting attractors without crossing any bifurcation point. Such a switchover occurs only for a specific initial population density close to the basin boundary, leading to partial tipping if the frozen system is non-chaotic. Partial tipping may also occur for some initial points far from the basin boundary if the frozen system is chaotic. Interestingly, the probability of tipping shows a frequency response with a maximum for a specific frequency of periodic forcing, as noticed for equilibrium and non-equilibrium limit cycle systems. The findings suggest that unexpected outbreaks or abrupt declines in population density may occur due to time-dependent variations in species growth parameters. Depending on the selective frequency of the periodic environmental variation, this may lead to species extinction or help the species to survive.
Numerical simulations of downburst wind fields: A comparative analysis of stationary and moving storms using the impinging jet model
Authors: Fang Zhiyuan , Wang Zhisong , Huang Hanjie , Yang Longquan , Guo Ying
Published: August 2024

Downburst is a hazardous strong wind commonly encountered in thunderstorm weather. Influenced by ambient wind, the downdraft often accompanies horizontal movement while descending. Based on the impinging jet model, this study employs the large eddy simulation method to conduct computational fluid dynamics numerical simulations of stationary and moving downbursts. The evolution process, time-varying wind speed, and wind profile characteristics of the two types of wind fields are compared. This study also discusses the influence of η—which represents the ratio of the storm traveling speed (Vtr) to the jet velocity (Vjet)—on the wind field structure and verifies the applicability of the vector superposition principle in the simulation of the moving downburst. The results show the following: The wind speed and direction time histories obtained from the numerical simulation of moving downbursts have good consistency with the actual wind field records. The movement of the storm causes the near-surface wind field to lose its central symmetry, resulting in a bow-shaped distribution of extreme wind speeds at the storm's leading edge. As η increases, the non-central symmetry of the wind field becomes more pronounced, the maximum horizontal wind speed at the storm's leading edge gradually moves closer to the storm's center, peak wind speeds gradually increase, and the wind speed distribution at the storm's trailing edge shows the opposite trend. The vector superposition principle is not entirely applicable in the simplified analysis of moving downburst, causing significant errors when η is larger than 0.1.
Improved delayed detached-eddy simulation on aerodynamic characteristics of biomimetic Coleoptera pantograph deflectors installed on a high-speed train
Authors: Gai Jie , Yu Yizheng , Wang Yuechen , Ding Yansi , Zhang Jie
Published: August 2024

With continuous increase in the train speed, the aerodynamic drag forces of high-speed trains increase sharply in a square relationship. As an important source of train aerodynamic drag, pantograph regions have become the key areas to share the contribution to the train's total drag. Thus, improving the pressure distribution in pantograph regions can be a potential and effective method to reduce train aerodynamic drag. Coleoptera has smooth and hard elytra to protect the hindwings, which provides a new design concept for the pantograph deflectors. Based on the biological pattern of Coleoptera, the geometric shape of pantograph biomimetic elytra (i.e., deflector) was constructed in a three-car group mode. Therefore, four calculation cases were set up, i.e., the original unraised pantograph model, original raised pantograph model, unraised pantograph + deflector model, and raised pantograph + deflector model. A time-dependent numerical method improved delayed detached-eddy simulation (IDDES), first validated by the previous wind tunnel test, was employed to analyze the aerodynamic drag forces in different schemes, and the drag reduction mechanism of deflectors was studied. The results show that although an extra drag force is introduced from the deflector, a larger drag reduction is obtained from the pantograph itself. Thus, the aerodynamic drag of pantograph regions is significantly reduced after installing pantograph deflectors. The air flows over the pantograph region in a smoother way with less blocking effect, and the flow above the deflector is accelerated. After the deflector separately installed on three-car high-speed train models with unraised/raised pantographs, the drag reduction for the unraised/raised pantograph regions can be up to 83.88% and 35.29%, while for a three-car grouping model, it can be achieved by 10.76% and 4.49%, respectively.
Exploring relaxation dynamics in warm dense plasmas by tailoring non-thermal electron distributions with a free electron laser
Authors: Shi Y.-F. , Ren S. , Chung H.-K. , Wark J. S. , Vinko S. M.
Published: August 2024

Knowing the characteristic relaxation time of free electrons in a dense plasma is crucial to our understanding of plasma equilibration and transport. However, experimental investigations of electron relaxation dynamics have been hindered by the ultrafast, sub-femtosecond timescales on which these interactions typically take place. Here, we propose a novel approach that uses x rays from a free electron laser to generate well-defined non-thermal electron distributions, which can then be tracked via emission spectroscopy from radiative recombination as they thermalize. Collisional radiative simulations reveal how this method can enable the measurement of electron relaxation timescales in situ, shedding light on the applicability and accuracy of the Coulomb logarithm framework for modeling collisions in dense plasmas.
Simulation study of hemodynamic commonality of umbrella-shaped inferior vena cava filter using computational fluid dynamics
Authors: Li Mingrui , Song Xue , Wang Jingying , Zhou Yue , Zhang Shiyue , Lee Chunhian
Published: August 2024

The inferior vena cava filter (IVCF) has been used in clinical practice for decades to prevent fatal pulmonary embolism. One of the most commonly used types of IVCFs features a conical umbrella-like design. The geometric similarity among these umbrella-shaped IVCFs suggests a potential commonality in their hemodynamic behavior. However, many previous studies have primarily analyzed the blood flow around a single umbrella-shaped IVCF, failing to capture the general hemodynamic characteristics of this filter type. This paper uses computational fluid dynamics to simulate the blood flow around five typical umbrella-shaped IVCFs, aiming to investigate their hemodynamic commonality. For all five IVCFs, prothrombotic stagnation zones are observed downstream of the filter head, extending nearly 12 times the diameter of the inferior vena cava (IVC). The “viscous block” effect of the filter wires accelerates blood flow within the conical region of the filter, enhancing the potential for clot capture and dissolution. The deployment of umbrella-shaped IVCF remarkably increases the wall shear stress (WSS) on the IVC wall, and the WSS on the filter wire continuously increases in the flow direction. Additionally, the viscous resistance of each umbrella-shaped IVCF contributes several times more to the total flow resistance than the pressure resistance. Our results suggest that alterations in the morphology of the filter wires of umbrella-shaped IVCFs significantly impact the flow resistance of the filter and the WSS distribution pattern of the IVC. These hemodynamic changes may lead to life-threatening conditions, such as IVC lesions, filter rupture, and displacement.
Adaptive tau-leaping methods for microscopic-lattice kinetic Monte Carlo simulations
Authors: Che Tianshi , Zhou Yang , Han Xiaoying , Najm Habib N.
Published: August 2024

Traditional Kinetic Monte Carlo (KMC) approaches, rooted in Gillespie’s stochastic simulation algorithm, become computationally demanding in systems with a large range of timescales. The goal of this work is to propose and study new adaptive lattice-KMC time integration strategies for spatially non-uniform systems. To that end, two novel adaptive tau-leaping methods and their corresponding time integration strategies are developed based on the idea of the “n-fold” direct KMC method. These strategies allow for the simultaneous execution of multiple reactions, advancing time by adaptively selected coarse increments. We present numerical experiments comparing the proposed methods with existing approaches in a catalytic surface kinetics application involving ammonia decomposition.
High voltage determination and stabilization for collinear laser spectroscopy applications
Authors: König Kristian , Köhler Finn , Palmes Julian , Badura Henrik , Dockery Adam , Minamisono Kei , Meisner Johann , Müller Patrick , Nörtershäuser Wilfried , Passon Stephan
Published: August 2024

Fast beam collinear laser spectroscopy is the established method to investigate nuclear ground state properties such as the spin, the electromagnetic moments, and the charge radius of exotic nuclei. These are extracted with high precision from atomic observables, i.e., the hyperfine splitting and the isotope shift, which become possible due to a large reduction of the Doppler broadening by compressing the velocity width of the ion beam through electrostatic acceleration. With the advancement of experimental methods and applied devices, e.g., to measure and stabilize the laser frequency, the acceleration potential became the dominant systematic uncertainty contribution. To overcome this, we present a custom-built high-voltage divider, which was developed and tested at the German metrology institute, and a feedback loop that enabled collinear laser spectroscopy to be performed at a 100-kHz level. Furthermore, we describe the impact of field penetration into the laser–ion interaction region. This affects the determined isotope shifts and hyperfine splittings if Doppler tuning is applied, i.e., the ion beam energy is altered instead of scanning the laser frequency. Using different laser frequencies that were referenced to a frequency comb, the field penetration was extracted laser spectroscopically. This allowed us to define an effective scanning potential to still apply the faster and easier Doppler tuning without introducing systematic deviations.
Glow-to-arc discharge transitions in a radio frequency atmospheric pressure plasma jet
Authors: T. P. Radhika , Kar Satyananda
Published: August 2024

This study investigates the mechanism of discharge transitions in a radio frequency atmospheric pressure plasma jet (RF APPJ), with the aim of unraveling the underlying mechanisms behind the unexpected arcing-like filament formation on power electrode observed at lower power levels and the subsequent glow-to-arc transition (GAT) at higher powers. Through meticulous analysis of plasma parameter variations under varying power increment rates, this research offers crucial insights into the complex dynamics of plasma behavior. Detailed analysis of discharge current under different power increment rates exhibited distinct discharge phases as power increased, i.e., the normal glow phase, the abnormal glow phase, and the glow-to-arc transition. Notably, the arcing-like filament formation observed on the power electrode during the abnormal glow phase is indicative of complex plasma dynamics driven by the combined effect of thermal instability and the resulting thermo-field emission. Particularly noteworthy is the dynamic relationship between power increment rates and the duration of the abnormal glow discharge phase, shedding light on the multifaceted nature of thermal instability phenomena. Moreover, the ponderomotive force plays a crucial role in restricting thermo-field emission, thereby preventing the transition from glow to arc at low power levels. Additionally, the observed rise in electron density, electron temperature, and the emission intensity of reactive oxygen and nitrogen species during the abnormal glow discharge phase presents exciting possibilities for novel operational regimes characterized by lower gas temperatures. This study paves the way for enhanced understanding and control of atmospheric pressure plasma processes by highlighting the intricate interplay between power increment rates and discharge behavior, offering promising avenues for developing more efficient and stable plasma-based technologies.
Characterization of a CMOS camera based film digitization platform for gated x-ray imaging diagnostics at the National Ignition Facility
Authors: Ruof N. W. , Trosseille C. , Holder J. P. , Nagel S. R.
Published: August 2024

Hardened gated x-ray detectors use photographic film as the data recording medium due to its low sensitivity to the high-yield neutron environments at the National Ignition Facility (NIF). The photographic film is digitized with a Photometric Data Systems (PDS) microdensitometer, which measures the film’s optical density. The PDS scanner is able to measure a dynamic range of 0–5 OD; however, raster scanning the film is time consuming and maintenance of the instrument is challenging due to legacy technology. Since film usage at NIF is expected to continue in the foreseeable future, a digitization platform that is faster and more maintainable would benefit the NIF’s current and future operations. This work presents the characterization of the digital transitions (DT) atom, a CMOS camera-based digitization platform that records film data in a single image capture very quickly and has widely available user support. The preliminary results suggest that the DT atom is able to reconstruct exposures accurately enough to be a competitive alternative to the PDS Scanner.
Vortex-induced vibration of a sinusoidal wavy cylinder: The effect of wavelength
Authors: Zhao Fuwang , Zeng Lingwei , Bai Honglei , Alam Md. Mahbub , Wang Zhaokun , Dong You , Tang Hui
Published: August 2024

While considerable research has addressed flow around stationary sinusoidal wavy cylinders, studies on vortex-induced vibration (VIV) of elastic-supported wavy cylinders still remain limited. This study aims to address this gap through a series of water tunnel experiments, focusing on the effects of the cylinder's spanwise wavelength. Three typical spanwise wavelengths (λ* = 1.8, 3.6, and 6.0) are considered, with the first and third identified as the optimal for reducing fluid forces (lift forces by over 90%) in previous stationary cylinder studies. The cylinder oscillates transversally at a range of reduced velocities Ur = 3.0–12.0, corresponding to the Reynolds numbers (1.5–7.0) × 103. Results indicate that, compared with a smooth cylinder, the λ* = 1.8 cylinder experiences reduced oscillation throughout the VIV regime, while the cylinders with λ* = 3.6 or 6.0 undergo enhanced oscillation over a broader lock-in range. The oscillation of the wavy cylinders with λ* = 3.6 or 6.0 tend to occur at a higher Ur, leading to an extension of the lower branch. Frequency analysis shows that, despite affecting vibration amplitude, the wavy surface retains typical VIV features. These results reveal a notable dependence of fluid forces and force-displacement phase lag on the cylinder's wavelength. Finally, we provide a detailed discussion of the phase-averaged and time-averaged flow structures from the time-resolved particle image velocimetry measurement. Overall, this study addresses the research gap concerning the impact of wavelength on the behavior of elastically supported wavy cylinders, providing significant insights for the development of practical strategies for VIV suppression and enhancement.
The role of band-tail states on the electric properties of amorphous chalcogenides: A simulative approach
Authors: Brunetti R. , Jacoboni C. , Rudan M.
Published: August 2024

Band-tail states, i.e., charge-carrier energy states located in the bandgap at the valence and conduction band edges of amorphous materials, even though not delocalized, exhibit nonzero mobility; thus, they are expected to contribute to the charge-conduction process. A microscopic model based on hydrodynamic transport equations for unipolar conduction, including trap, band-tail, and band states, and coupled to the Poisson equation is presented here. The equations are self-consistently solved by means of a numerical procedure, and the results provide qualitative and quantitative estimates of the influence of band-tail states (namely, of their energy distribution, density, and mobility) on the carrier heating, precursor of the Ovonic threshold switch.
Comparative study of wind and turbulence characteristics during Super Typhoon Saola based on stationary and nonstationary models
Authors: Xue Yu-Cheng , He Jun-Yi , Chan Pak-Wai , Li Qiu-Sheng
Published: August 2024

An in-depth understanding of typhoon wind and turbulence characteristics in the atmospheric boundary layer is of crucial importance to structural design of high-rise structures. This study utilizes observational wind records collected from the 356-m-high Shenzhen Meteorological Gradient Tower, which is currently the tallest in Asia and the world's second tallest meteorological tower during Super Typhoon Saola to investigate typhoon wind and turbulence characteristics based on the stationary and nonstationary models. The mean wind speed and direction, power law exponent, friction velocity, and wind speed profiles are analyzed using the stationary model. Moreover, a comparative analysis employing the stationary and nonstationary models is carried out to study turbulence characteristics involving turbulence intensity, gust factor, turbulence integral length scale, power spectral density (PSD), and turbulence parameter profiles, along with a comparison to those stipulated in several building or structural design codes and standards. The results indicate that the typhoon wind speed signals exhibit strong nonstationarity, especially for longitudinal wind direction. The turbulence parameters calculated within the nonstationary framework are lower than those from the stationary model. In addition, the PSDs of the three orthogonal wind components obtained from the stationary and nonstationary model display similarities at the frequency above 0.01 Hz, and von Kármán spectra perform better in fitting the observed PSDs compared to the Kaimal spectra. The findings of this research reveal notable disparities in typhoon wind and turbulence characteristics yielded from the stationary and nonstationary models, highlighting the necessity of accounting for nonstationarity under typhoon wind conditions.
Dipole engineering to achieve interface dependent electric contact in Janus MoSO/graphene heterostructure
Authors: Zhang Wei , Ji Weixiao
Published: August 2024

Large Schottky barriers formed at the interfaces between graphene and 2D semiconductors often degrade device performance. Here, taking the Janus MoSO as a prototype and using the first-principles calculations together with the band unfolding technique, we demonstrate that the Ohmic contact (OC), which is absent in pristine graphene/MoXY (X/Y = S, Se, Te. X ≠ Y), is realized in the pristine graphene/MoSO (G/MoSO) heterostructure. G/OMoS shows the n-type OC (OC-n) that leads to the p-doping of the graphene layer with a hole density of 1.17×1013/cm2, while G/SMoO exhibits the p-type Schottky contact with a tunable Schottky barrier height. The realization of OC and the interface dependent contact type are mainly attributed to the large intrinsic dipole between asymmetric S and O layers, which dominate the different behaviors of charge transfer and the associated interface dipole in heterostructures. Inspired by the finding, considering the larger dipole moment in Janus MoSeO and MoTeO, we further confirm that both OC-n and OC-p exist in pristine G/MoSeO and G/MoTeO. Moreover, on comparison with MoSO, both G/OMoS and G/SMoO show enhanced optical absorptions (∼105 cm−1) in most of the visible light range. Our results not only show the potential application of G/MoSO in nanoelectronic devices such as field-effect transistors but also indicate that dipole engineering would help us to predict or design desirable electric contacts of Janus-transition metal dichalcogenide-based metal/semiconductor systems in advance.