bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding biochemistry: basic aspects of statistics for life sciences
Authors: Reid Donald
Published: October 2023

If the biological world is one thing it is variable. As scientists we seek to measure, quantify and explain the causes of this variation. The approach we take to this is remarkably similar whether our research is exploring global temperature, blood pressure, cancer incidence or enzyme kinetics. This approach involves defining clear research questions and applying statistical methods to answer them robustly. This article will introduce a practical example that will be used throughout, specifically whether genetic variation can explain variation in coffee consumption. We assume little experience with statistics and walk through the statistical approach that biologists can use, firstly by describing our data with summary statistics and then by using statistical tests to help arrive at answers to our research question. A General Linear Model (GLM) approach will be used as this is what many common statistical tests are. We explore how to visualise and report results, while checking the assumptions of our analysis. The better we can understand and apply statistics to biological problems, the better we can communicate results and future research to others. The popular statistical programming language R will be used throughout.
Personalized federated learning via directed acyclic graph based blockchain
Authors: Huang Chenglong , Liu Erwu , Wang Rui , Liu Yan , Zhang Hanfu , Geng Yuanzhe , Wang Jie , Han Shaoyi
Published: October 2023

Common federated learning (FL) lacks consideration of clients' personalized requirements, which performs poorly for the scenario with data and resource heterogeneity. In order to overcome the challenge of heterogeneous characteristics, this letter proposes a novel decentralized personalized federated learning (PFL) architecture that first utilizes a directed acyclic graph (DAG) blockchain technology to achieve PFL efficiently, which is called PFLDAG. Simulation results demonstrate that PFLDAG approximately improves accuracy by 80% compared with the classic Google FedAvg algorithm, and by 10% compared with IFCA cluster PFL which considers personalized requirements. In addition, the approach also substantially improves the convergence speed.
Three‐dimensional metal‐only phoenix cell and its application for reflectarrays
Authors: An Zhihang , Makdissy Tony , Garcia Vigueras María , Vaudreuil Sébastien , Gillard Raphaël
Published: October 2023

A 3D metal‐only waveguide‐based phoenix cell for reflectarray is presented. The proposed cell consists of two concentric square waveguides and a metallic block in the centre, which offers two operation modes. The first mode uses its cross section to tune reflection phase while the second mode varies the heights of two waveguides to manipulate reflection phase. The principle of the two different modes is analysed in detail. A metal‐only reflectarray antenna at 20 GHz is designed based on the first mode of the phoenix cell. It is fabricated using selective laser melting 3D printing technology. A good agreement between simulations and measurements is achieved. The measured gain at 19.75 GHz is 30.25 dBi with an aperture efficiency of 51.17% respectively. Also, the measured 1‐dB gain bandwidth is 15% (19–22 GHz). A dual band metal‐only reflectarray operating at 20 and 25 GHz is designed based on the second mode of the phoenix cell. The two metal‐only reflectarray antennas fully demonstrate the capabilities of the proposed 3D metal‐only phoenix cell.
A global view on star formation: The GLOSTAR Galactic plane survey
Authors: Yang A. Y. , Dzib S. A. , Urquhart J. S. , Brunthaler A. , Medina S.-N. X. , Menten K. M. , Wyrowski F. , Ortiz-León G. N. , Cotton W. D. , Gong Y. , Dokara R. , Rugel M. R. , Beuther H. , Pandian J. D. , Csengeri T. , Veena V. S. , Roy N. , Nguyen H. , Winkel B. , Ott J. , Carrasco-Gonzalez C. , Khan S. , Cheema A.
Published: October 2023

As part of the GLObal view of STAR formation in the Milky Way (GLOSTAR) survey, we present the high-resolution continuum source catalog for the regions (ℓ = 2° −28°, 36° −40°, 56° −60°, and |b| < 1.0°), observed with the Karl G. Jansky Very Large Array (VLA) in its B-configuration. The continuum images were optimized to detect compact sources on angular scales up to 4″, and have a typical noise level of 1σ ~ 0.08 mJy beam−1 for an angular resolution of 1″, which makes GLOSTAR currently the highest resolution as well as the most sensitive radio survey of the northern Galactic plane at 4–8 GHz. We extracted 13354 sources above a threshold of 5σ and 5437 sources above 7σ that represent the high-reliability catalog. We determined the in-band spectral index (α) for the sources in the 7σ-threshold catalog. The mean value is α = −0.6, which indicates that the catalog is dominated by sources emitting nonthermal radio emission. We identified the most common source types detected in radio surveys: 251 H II region candidates (113 new), 282 planetary nebulae (PNe) candidates (127 new), 784 radio star candidates (581 new), and 4080 extragalactic radio source candidates (2175 new). A significant fraction of H II regions and PNe candidates have α < −0.1 indicating that these candidates could contain radio jets, winds or outflows from high-mass and low-mass stellar objects. We identified 245 variable radio sources by comparing the flux densities of compact sources from the GLOSTAR survey and the Co-Ordinated Radio “N” Infrared Survey for High-mass star formation (CORNISH), and find that most of them are infrared quiet. The catalog is typically 95% complete for point sources at a flux density of 0.6 mJy (i.e., a typical 7σ level) and the systematic positional uncertainty is ≲ 0″.1.
Very massive stars and nitrogen-emitting galaxies
Authors: Vink Jorick S.
Published: October 2023

Recent studies of high-redshift galaxies with James Webb Space Telescope (JWST), such as GN-z11 at z = 10.6, show unexpectedly significant amounts of nitrogen (N) in their spectra. As this phenomenology appears to extend to gravitionally lensed galaxies at Cosmic noon such as the Sunburst Arc at z = 2.37, as well as globular clusters overall, we suggest that the common ingredient among them are very massive stars (VMSs) with zero-age main sequence (ZAMS) masses in the range of 100–1000 M⊙. The He II in the Sunburst Arc might also be the result of the disproportionally large contribution of VMS to the total stellar contribution. We analyse the pros and cons of the previous suggestions, including classical Wolf–Rayet (cWR) stars and supermassive stars (SMSs), to conclude that only our VMS alternative ticks all the relevant boxes. We discuss the VMS mass-loss history via their peculiar vertical evolution in the HR diagram resulting from a self-regulatory effect of these wind-dominated VMSs and we estimate that the large amounts of N present in star-forming galaxies may indeed result from VMSs. We conclude that VMSs should be included in population synthesis and chemical evolution models. Moreover, that it is critical for this to be done self-consistently, as a small error in their mass-loss rates would have dramatic consequences for their stellar evolution, as well as their ionising and chemical feedback.
Acquired Thrombocytopenia in Contemporary Transcatheter Aortic Valve Prosthesis
Authors: Petrov Asen , Taghizadeh-Waghefi Ali , Diab Abdel-Hannan , Breuer Linda , Arzt Sebastian , Matschke Klaus Ehrhard , Alexiou Konstantin
Published: October 2023

Background Postprocedural thrombocytopenia is a known phenomenon following transcatheter aortic valve implantation (TAVI). The aim of this study is to evaluate whether postinterventional platelet kinetics differ when comparing the current generation of balloon-expandable valve (BEV) and self-expanding valve (SEV) prostheses.

Methods We performed a retrospective analysis of patients undergoing TAVI at our facility between 2017 and 2019. Patients were stratified according to the type of prosthesis used: BEV or SEV. Hematocrit-corrected platelet counts were calculated to account for dilution. Nadir platelet counts (lowest recorded platelet count), drop platelet counts (DPC; highest relative platelet drop from baseline), and severity of thrombocytopenia during the discourse and at discharge were assessed.

Results Of the 277 included patients, 212 received SEV and 65 BEV. BEV patients were younger (81.8 ± 4.4 years vs 79.7 ± 6.8 years, p = 0.03). Further demographic characteristics were similar between groups. Implanted SEV were larger (p < 0.001) and had shorter procedural times (p < 0.01). There were no significant differences in postprocedural discourse. Postinterventional platelet drop was more pronounced in BEV patients in several evaluated metrics: mean DPC (24.3 ± 10.9% vs 18.8 ± 14.8%, p < 0.01), patients with DPC > 30% (n = 19, 29.2%, vs n = 33, 15.6%, p = 0.02), and also when comparing platelet kinetics.

Conclusion Despite improvements in outcome, the current generation of balloon-expandable TAVI prostheses carries a predisposition for postprocedural thrombocytopenia even when the effects of dilution are accounted for.
Concepts, Terminology, and Innovations in Follicular Unit Excision Hair Restoration Surgery
Authors: Gupta Aditya K. , Polla Ravi Shruthi
Published: October 2023

Follicular unit excision (FUE) has emerged as the preferred method for hair transplants. Standardized terms and definitions established by members of the International Society of Hair Restoration Surgery and prominent hair restoration surgeons have become the standard, enabling effective knowledge sharing. This chapter provides an overview of the terminology relating to the field.

The historical evolution of FUE and its pivotal role in modern hair transplantation is summarized. Anatomical terminology and graft-related definitions follow, providing insights into the scalp's complex structures and graft characteristics. The subsequent sections detail the terminology associated with graft excision and extraction, shedding light on the precise techniques and procedures employed. An exploration of various FUE techniques and the evolving landscape of FUE devices underscores the continual refinement of hair restoration practices. The chapter proceeds to discuss the “safe'” scalp donor zones, donor assessment terminology, and elements in identifying the optimal donor area for a successful FUE procedure. Additionally, punch dynamics and technique characteristics are examined, emphasizing their pivotal role in achieving superior FUE outcomes. The chapter concludes by discussing the classification of punches and graft evaluation terms, offering insights into the tools, and criteria used to assess graft quality and viability.
Evaluation of a Bidentate ‘Clamp-Like’ Halogen-Bond Donor Motif Based on Iodonium(III) Moieties
Authors: Huber Stefan M. , Reinhard Dominik L. , Kutzinski Dana , Hatta Masahito , Engelage Elric
Published: October 2023

A new motif for iodine(III)-based halogen-bond donors consisting of a 1,3-phenylene core and two cyclic five-membered diaryliodonium(III) wings was designed and its potential as a catalyst was evaluated. Its properties were analyzed in the solid state by X-ray crystallography and in solution by benchmark catalytic activation of a nitro-Michael addition between 5-methoxyindole and trans-β-nitrostyrene.
Desmopressin Dose Requirements in Adults with Congenital and Acquired
Central Diabetes Insipidus
Authors: Pedersen Aslak Nykjær , Andreassen Mikkel , Rasmussen Aase Krogh , Krogh Jesper
Published: October 2023

Central diabetes insipidus is a rare disorder characterized by a deficiency of
vasopressin. The first line drug to treat this disorder is a synthetic analogue
of vasopressin, desmopressin.The primary aim of this retrospective register
study was to compare desmopressin dose requirements in patients with acquired
and congenital DI, and secondly to assess the influence of BMI on dose
requirement and risk of hyponatremia with different drug administrations. We
included all patients with suspected DI attending the endocrine department at
Rigshospitalet, Copenhagen, Denmark in 2022. We identified 222 patients who were
included whereof 130/222 (58.6%) were females and median age was
53 years (IQR 35 to 63). The etiology included 7/222 (3.2%)
congenital and 215/222 (96.8%) acquired. After converting nasal
and sublingual doses to equivalent oral doses, the median daily dose requirement
was 600 μg in patients with congenital etiology compared to
200 μg in patients with acquired etiology (p=0.005). We
found no association between BMI and desmopressin dose requirements
(p=0.6). During the past 12 months, 66/215 (30.7%) had
sodium levels<136 mmol/l including 20/215
(9.3%) with sodium levels<131 mmol/l. No
increased risk of hyponatremia was found, when nasal and oral were compared
(p=0.9). Daily desmopressin dose requirements were higher in patients
with congenital DI compared to patients with acquired DI. However, this result
was associated with uncertainty due to the small congenital group. BMI did not
influence daily dose requirements and nor did type of administration influence
the risk of hyponatremia.
Acquired Hemophilia A: A Rare, Acquired Coagulopathy in the Postpartum Setting
Authors: Oberlin Austin , Krenitsky Nicole M. , Gandhi Christy , Akpan Imo Joseph , Eisenberger Andrew , Landau Ruth , Yurteri-Kaplan Ladin , Nathan Lisa , Sheen Jean-Ju , LaSala Anita , D'Alton Mary
Published: October 2023

Postpartum hemorrhage (PPH) remains a leading cause of maternal morbidity. Pregnancy-associated acquired hemophilia A (AHA) caused by autoantibodies against factor VIII can present with recurrent episodes of postpartum bleeding.

Case 1 A 50-year-old G2P0112 presented with vaginal bleeding 22 days postcaesarean. She underwent dilation and curettage, hysterectomy, and interventional radiology (IR) embolization before AHA diagnosis. She was hospitalized for 32 days and received 23 units of blood product. She remains without relapse of AHA after 5 years.

Case 2 A 48-year-old G3P1021 presented with vaginal bleeding 8 days postcaesarean. She underwent three surgeries and IR embolization before AHA diagnosis. She was hospitalized for 18 days and received 39 units of blood product. Prednisone and cyclophosphamide were continued after discharge.

AHA is a rare cause of PPH. An isolated prolonged activated partial thromboplastin time (aPTT) should prompt further workup in postpartum patients with refractory bleeding. Rapid recognition of AHA can prevent significant morbidity related to hemorrhage, massive transfusion, and multiple surgeries.
Increased Body Mass Index is Associated with Worse Mid- To Long-Term Patient Outcomes after Surgical Repair of Multiligamentous Knee Injuries
Authors: Tan Danny , Ferrante Stephanie , DiBartola Alex , Magnussen Robert , Welder Eric , Crouser Nisha , Kaeding Christopher , Flanigan David , Duerr Robert A.
Published: October 2023

We evaluated the relationship between elevated body mass index (BMI) and mid- to long-term outcomes after surgical treatment of multiligamentous knee injury (MLKI). Records identified patients treated surgically for MLKI at a single institution. Inclusion criteria: minimum 2 years since surgery, complete demographics, surgical data, sustained injuries to two or more ligaments in one or both knees, and available for follow-up. Patients were contacted to complete patient-reported outcomes assessments and were classified according to mechanism of injury. Multivariate logistic regression analysis was used to predict the impact of BMI on outcome scores. A total of 77 patients (72.7% male) were included with a mean age at the time of injury of 29.4 ± 11.0 years and a mean BMI of 30.5 ± 9.4 kg/m2. The mean length of follow-up was 7.4 years. For each 10 kg/m2 increase in BMI, there is a 0.9-point decrease in Tegner activity scale (p = 0.001), a 5-point decrease in Knee Injury and Osteoarthritis Outcome Score (KOOS)-pain (p = 0.007), a 5-point decrease in KOOS-ADL (p = 0.003), a 10-point decrease in KOOS-QOL (p = 0.002), and an 11-point decrease in KOOS-Sport (p = 0.002). There were no significant correlations with BMI and Pain Catastrophizing Scale or Patient Health Questionnaire scores. Increasing BMI has a negative linear relationship with mid- to long-term clinical outcomes including pain, ability to perform activities of daily living, quality of life, and ability to perform more demanding physical activity after MLKI. BMI does not appear to have a significant relationship with knee swelling and mechanical symptoms or patients' mental health.
Oxidative C–H Sulfonylation of Hydrazones Enabled by Electrochemistry
Authors: Yang Qi-Liang , Lei Ping-Ping , Guo Hai-Ming , Hao Er-Jun , Zhang Bei-Ning , Zhou Hong-Hao , Li Wan-Wan
Published: October 2023

An efficient electrochemical oxidative C(sp2)–H sulfonylation of aldehyde hydrazones is described. A variety of sodium sufinates or sulfinic acids participate effectively in this protocol, which provides facile access to an array of alkyl and aromatic sulfonylated hydrazones with up to 96% yield. Large-scale synthesis and product derivatization show the potential utility of this methodology. Preliminary mechanistic investigations including radical-inhibition, electricity on/off experiments, and cyclic voltammetry support a radical pathway.
A lexical network approach to second language development
Authors: Chen Heng
Published: October 2023

This study investigates lexical development in second language (L2) learning from the perspective of complex dynamic system theory (CDST) using a complex network method. Based on authentic written output texts from L2 Chinese learners of different proficiency levels and language backgrounds, we successfully differentiate between different proficiency levels using a bi-gram lexical network model at a corpus level. A more in-depth investigation reveals that when compared to traditional lexical complexity indices, such as average word length and hapax legomena percentage (though Guiraud proves to be a robust predictor), the lexical network indices, such as network density and network clusters, provide a more profound understanding of L2 proficiency distinctions and a more precise approximation of the target language. Moreover, our findings illuminate the consistent manifestation of complex network characteristics within L2 Chinese lexical networks across all proficiency levels. Additionally, word association features, encompassing more than just word frequency information, provide comprehensive properties of the interlanguage system, as supported by their information gain values. We argue that studies within the CDST framework should integrate both lexical frequency and lexical network features to gain a comprehensive understanding of L2 lexical development.
Implications of ideology on school buildings and cultural pluralistic context of Gazimağusa, North Cyprus
Authors: Ukabi Ejeng B. , Gurdalli Huriye
Published: October 2023

This paper aims to answer the pertinent question: What are the implications of ideology on school buildings and the culturally pluralistic context of Gazimağusa in Northern Cyprus? It traces the social and communication qualities of architecture to restructure the architectural identity of schools and the cultural patterns of this city during the British Period (1878–1960). The colonialists relied on education as an ideological tool for perceiving social and economic stability through training a new, educated middle class to replace the existing traditional authorities: Ottoman leaders and Church structures. Their failure to recognize the diverse cultural layers of the context led to unsustainable outcomes. An interpretative case research approach that involved descriptive and historical techniques was utilized to investigate this situation. Ideology had two separate but related consequences in the context chosen at both urban and architectural scales. Resulting in a cultural shift from intrinsic to extrinsic living that contradicts previous cultural alignments of the place. The urban syntax for communal life shifted to exclusivity, and cultural coexistence was divided between Turkish and Greek Cypriots on the one side; on the other, schools copied a globalized character of transformation. Based on contextual perceptions, the study advocates for a creative cultural mix of local and global concepts. The island went through modernization, hosting the two communities under British Colonial Rule who were both struggling with the colonizers on one hand and experiencing ethnic and political clashes on the other; they formed the conditions for a wide variety of school buildings. Within this context, the paper highlights school buildings as an ideological space, symbol, and tool of nationalism and colonization/decolonization.
Spectral analysis on ruled surfaces with combined Dirichlet and Neumann boundary conditions
Authors: Amorim Rafael T. , Verri Alessandra A.
Published: October 2023

Let Ω be an unbounded two dimensional strip on a ruled surface in Rn+1, n > 1. Consider the Laplacian operator in Ω with Dirichlet and Neumann boundary conditions on opposite sides of Ω. We prove some results on the existence and absence of the discrete spectrum of the operator; which are influenced by the twisted and bent effects of Ω. Provided that Ω is thin enough, we show an asymptotic behavior of the eigenvalues. The interest in those considerations lies on the difference from the purely Dirichlet case. Finally, we perform an appropriate dilatation in Ω and we compare the results.
Rota–Baxter family Ω-associative conformal algebras and their cohomology theory
Authors: Zhang Yuanyuan , Zhao Jun , Liu Genqiang
Published: October 2023

In this paper, we first propose the concept of Rota–Baxter family Ω-associative conformal algebras, then we study the cohomology theory of Rota–Baxter family Ω-associative conformal algebras of any weight and justify it by interpreting the lower degree cohomology groups as formal deformations.
Charge transport in highly acidic glass-forming protic ionic liquids tailored by zwitterionic precursors
Authors: You Jinhai , Li Bing-Yu , De Borggraeve Wim , Wübbenhorst Michael
Published: October 2023

Highly acidic protic ionic liquids (PILs) are promising materials for potential electrochemical applications due to their high proton conductivity and excellent thermal stability. Still, little is known about the correlation between charge transport and structural dynamics as well as the proton transport mechanism despite the large body of literature on this topic. Here, we have examined the charge transport and structural dynamics by employing broadband dielectric spectroscopy in two highly acidic PILs in their supercooled liquid and glassy states, which included the same anion [TfO]− and different cations, [Tau]+ vs [Ahs]+. Unlike many other ionic liquids, the conductivity relaxation time τe of two studied PILs is substantially faster than the structural relaxation time τα. The decoupling behavior between charge transport and structural dynamics of two materials, which is manifested by a decoupling index Rτ, varies between 0.3 and 2.3 over the temperature range above Tg. Moreover, “Walden” plots of the molar conductivity vs the viscosity qualify both compounds as “Super ILs.” All findings support the physical picture of large, polar, and orientationally correlated ion clusters, where the slow α-relaxation can be identified as structural relaxation associated with cooperative reorientations of the cluster macrodipole. In contrast, the shortest timescale for diffusive charge transport, τe, is 1–2 decades shorter than τα, implying that proton hopping is triggered by “single particle” (ions or ion pair) rotations and jumps on a sub-length scale of the cluster size, a dynamics being present even in the glassy state as indicated by a strong β-relaxation. These results demonstrate the practicality of employing highly acidic PILs in electrochemical fields.
Parametric study of the polarization dependence of nonlinear Breit–Wheeler pair creation process using two laser pulses
Authors: Qian Qian , Seipt Daniel , Vranic Marija , Grismayer Thomas E. , Blackburn Thomas G. , Ridgers Christopher P. , Thomas Alexander G. R.
Published: October 2023

With the rapid development of high-power petawatt class lasers worldwide, exploring physics in the strong field QED regime will become one of the frontiers for laser–plasma interactions research. Particle-in-cell codes, including quantum emission processes, are powerful tools for predicting and analyzing future experiments where the physics of relativistic plasma is strongly affected by strong field QED processes. The spin/polarization dependence of these quantum processes has been of recent interest. In this article, we perform a parametric study of the interaction of two laser pulses with an ultrarelativistic electron beam. The first pulse is optimized to generate high-energy photons by nonlinear Compton scattering and efficiently decelerate electron beam through the quantum radiation reaction. The second pulse is optimized to generate electron–positron pairs by the nonlinear Breit–Wheeler decay of photons with the maximum polarization dependence. This may be experimentally realized as a verification of the strong field QED framework, including the spin/polarization rates.
Ordering kinetics and steady state of Malthusian flock
Authors: Jena A. Pratikshya , Mishra B. Shradha
Published: October 2023

We study a collection of polar self-propelled particles or polar flock on a two dimensional substrate involving birth and death. Most of the previous studies of polar flock with birth and death have focused on the steady state characteristics of Malthusian flock. We emphasize on the significance of rate of birth and death on the kinetics as well as steady state of the system. Our system is modeled using coarse-grained hydrodynamic equations of motion for local density and velocity of the flock. Results are obtained for different birth and death rates by solving the hydrodynamic equations using numerical integration and linearized calculation about the broken symmetry state. The presence of finite birth and death rate affects the density field significantly, whereas the effect on velocity field is moderate. The early time growth of velocity field slows down in the presence of finite birth and death rate, whereas at late times it approaches the value of non-conserved growth kinetics for all birth and death rates. The density field shows the strong time dependent growth kinetics. The asymptotic growth law for density depends on the birth and death rates and shows a crossover from 5/6 for the immortal flock to 1/4 for large birth and death rates. In the steady state, the presence of birth and death rate leads to the suppression of speed of sound wave, velocity, and density fluctuations in the system.
Multi-criteria thermo-economic analysis of solar-driven tri-generation systems equipped with organic Rankine cycle and bottoming absorption refrigeration and Kalina cycles
Authors: Dehghan Masood , Akbari Ghasem , Montazerin Nader , Maroufi Arman
Published: October 2023

Optimal thermo-economic integration of renewable energy sources with multi-generation energy systems is a prime research topic today. The present study proposes a multi-criteria evaluation method of such integration, based on combined heating and power (CHP), and combined cooling and power (CCP) scenarios, for three different solar intensities. Three novel solar-driven tri-generation systems are selected. They include different organic Rankine cycle (ORC) architectures and a Kalina cycle system (KCS) and a double-effect absorption refrigeration cycle as bottoming cycles. Evaluation of the tri-generation systems, both with and without the KCS system, indicates a performance improvement of up to 23% in various thermoeconomic characteristics when the KCS system is present. Selection of the suitable tri-generation system for each condition and optimization of the working fluid are carried out based on a multi-attribute decision-making method. P-xylene is found as the optimal organic working fluid for ORC and ORC (ORC integrated with internal heat exchanger) based systems, and benzene for the regenerative ORC-based system in both CHP and CCP scenarios. Multi-criteria analysis shows that ORC-based system outperforms other systems with net outranking flow of 0.44 (0.39) for CHP (CCP) application. The optimal configuration gives 95.6 M$ and 1.99 years for net present value and dynamic payback period, and 83.03% and 34.55% for energy and exergy efficiencies, respectively.
Advanced space charge limited field emission cathodes
Authors: Exelby S. C. , Leach C. J.
Published: October 2023

Several novel field emission cathodes are constructed by attaching a variety of materials to a steel substrate using multiple methods of bonding. These cathodes are tested using a pulsed relativistic (350–550 kV) vircator in a space charge limited operating regime. The viability of these cathodes as advanced or alternative components in high power microwave systems is evaluated. The currents measured from the cathodes are compared to values predicted from a 3D space charge limited flow model. The performance of the cathode is determined by how the current deviates from the model, as well as the consistency and durability.
Three-dimensional wake transition of a heated square cylinder in the presence of cross-buoyancy
Authors: Ali Mohd Perwez , Hasan Nadeem , Sanghi Sanjeev
Published: October 2023

The three-dimensional flow transition is examined in the wake of a heated square cylinder subjected to horizontal cross-flow perpendicular to gravity utilizing a direct numerical simulation approach. The surface of the square cylinder is heated uniformly to an elevated temperature Tw, and the amount of excess temperature is represented as the over-heat ratio ε=(Tw−T∞)/T∞, where T∞ represents the surrounding temperature. The effects of large-scale heating on the transport properties and thermal straining of the fluid particles are captured using an in-house non-Oberbeck–Boussinesq compressible model. The compressible flow governing equations (in a body-fitted coordinate system) are solved using a variant of flux-based particle velocity upwind-modified+ (PVU-M+) technique [Ahmad et al., “On the formation and sustenance of the compressible vortex rings in starting axisymmetric jets: A phenomenological approach,” Phys. Fluids 32, 126114 (2020)]. In this investigation, all computations are conducted at a low Mach number (Ma = 0.1) and air (Prandtl number, Pr = 0.71) is used as the working fluid. As the heating level rises, the shape and wavelength of the vortical structure undergo significant alterations. At Re = 250, the mode-B transition with a shorter spanwise wavelength and the mode-D transition with a longer wavelength are observed, respectively, for heating levels ε=0.0−0.2 and ε=0.8−1.0. Furthermore, for heating levels in the range 0.4≤ε≤0.6, an intermediate wavelength of the mode-E transition is detected. The temporal variation of fluid properties such as the force coefficient (CL, CD) and the Nusselt number (Nu) are shown at various heating levels. In addition, surface vorticity is examined in order to comprehend the flow dynamics near the surface of a heated square cylinder.
Analysis of the spreading radius in droplet impact: The two-dimensional case
Authors: Náraigh Lennon Ó , Mairal Juan
Published: October 2023

We study droplet impact problems in a 3D cylindrical or equivalent 2D Cartesian geometry. Such structures do have an approximate experimental realization, and they are often simulated as a testbed for computational methods. We focus on droplet impact on a smooth homogeneous surface as well as head-on collision of two droplets. We perform an energy-budget analysis and introduce a correlation, which predicts the maximum spreading radius as a function of Reynolds number and Weber number. We show how the dissipation term in this analysis can be decomposed into boundary-layer dissipation in the droplet lamella (where applicable) and head loss. We use existing results in the literature (simulations and experiments) as well as our own simulation results to validate the correlation. Dissipation by head loss is a key term in the analysis: only by modeling it accurately, one can obtain good agreement between the simulations and the theory.
Transition from viscous fingers to foam during drainage in heterogeneous porous media
Authors: Lanza Federico , Sinha Santanu , Hansen Alex , Rosso Alberto , Talon Laurent
Published: October 2023

We investigate the behavior of drainage displacements in heterogeneous porous media finding a transition from viscous fingering to foam-like region. A pore network model incorporating the formation of blobs is adopted to study this phenomenon. By imposing a pressure difference between the inlet and outlet, we observe that the displacement pattern undergoes a significant transition from a continuous front of growing viscous fingers to the emergence of foam, which develops and propagates until breakthrough. This transition occurs at a specific distance from the inlet, which we measure and analyze as a function of the viscosity ratio and the capillary number, demonstrating that it follows a non-trivial power-law decay with both the parameters. Moreover, we discuss the relationship between the evolution of the total flow rate and the local pressure drop, showing that the foam developed reduces global mobility. We observe that foam is formed from the fragmentation of viscous fingers beneath the front, and this instability mechanism is connected with fluctuations of the local flow rate, which we analyze both in the viscous fingering region and in the foam region.
Statistical quantum conductance of porous and random alloys
Authors: Sharafedini Elham , Hamzehpour Hossein , Alidoust Mohammad
Published: October 2023

Performing statistical evaluations, coupling Schrödinger's equation and Poisson's equation self-consistently, and employing an iterative fitting process, we have obtained a simple parametric formula for the charge conductance of nonmagnetic two-phase porous and random alloys. The formula exhibits remarkable agreement in describing the response of a system to an applied voltage difference, system size, bandgap, and density of conductive grains as parameters. Exploiting the obtained formula, we parametrically determine the activation threshold functionality of each parameter to other parameters where the charge conductance switches “on” and “off.” The results of our study can be directly utilized to guide experiments.
Temporal characteristics of hypersonic flows over a double wedge with Reynolds number
Authors: Tumuklu Ozgur , Hanquist Kyle M.
Published: October 2023

Laminar hypersonic flows at Mach 7.10 with unit Reynolds numbers of 5.2×104, 1.04×105, and 4.14×105 m−1 over a 30°/55° double-wedge configuration were studied to investigate the spatial–temporal characteristics of the flow in a time-accurate manner. Close comparisons were made between previous kinetic and current continuum approaches to test the validity of the continuum assumption, especially considering the presence of large gradients associated with shock–shock and shock–boundary layer interactions, as well as spanwise instabilities. Previous results from direct simulation Monte Carlo, which inherently predicts rarefied effects such as velocity slip and temperature jumps, were found to be in very close agreement with the current work, even for the lowest Reynolds number. The impact of velocity slip and temperature jumps on flow and surface parameters was investigated, and comparisons were made with a no-slip and constant temperature wall model. The temporal and spatial variation of two- and three-dimensional flows were thoroughly investigated using two-dimensional (2D), three-dimensional (3D) periodic sidewall boundary conditions, and a full 3D configuration consistent with existing experimental data. Close comparisons among the 2D and 3D cases were made. The characteristics of 2D periodic oscillations were reported for the moderate Reynolds number case for the first time. The presence of spanwise instabilities, even at a relatively low free stream pressure of about 100 Pa, establishes that the flow field depends on spanwise effects and is fully 3D. High-fidelity numerical schlieren videos captured strong spanwise oscillations for 3D configurations.
Full quantum scattering calculations of the line-shape parameters for the P and R branches of HF perturbed by Ar
Authors: Chai Shijie , Yang Dongzheng , Zhou Yanzi , Xie Daiqian
Published: October 2023

This work studied the rovibrational absorption spectral line-shape parameters of the P(1)–P(10) and R(0)–R(9) lines for Hydrogen fluoride perturbed by argon in the 0–0, 1–0, and 2–0 vibrational bands at 20–1000 K. A dataset of beyond-Voigt line-shape parameters (pressure broadening and shifting parameters, their speed dependencies, and the complex Dicke parameters) has been theoretically determined for the first time from generalized spectroscopic cross-section calculated by the full quantum scattering calculations. Then these parameters were employed to predict the line shape and asymmetry based on the partially-correlated speed-dependent hard-collision and the partially-correlated quadratic-speed-dependent hard-collision profiles. The effect of each parameter on the line shape and line asymmetry was further studied, which revealed that the beyond-Voigt effects were indispensable to accurately describe the line shape contour. Our results are in good agreement with the available experimental observations and provide a comprehensive set of theoretical references for further experimental measurements.
Influence of the chordwise distribution of tip winglets on the stability of a high-load compressor stage
Authors: Zhao Ao , Wu Wanyang , Hu Yi , Zhong Jingjun
Published: October 2023

Compressor rotor blade tip winglet technology has been confirmed to be a passive flow control method that is effective in increasing the operating stability of compressors. As revealed by extensive research, the structural parameters of tip winglets are capable of affecting their stability expansion effect, whereas their mechanism and influence law of the compressor stage remains unclear. In this study, the effect exerted by the chordwise distribution of tip winglets on the stability of a high-load compressor stage was investigated. As indicated by the result of this study, the tip winglet exhibiting a proper widest position and an adequate chordwise length can effectively increase the stall margin. To be specific, the widest position was located at 25% chord, and the stall margin was increased by up to 25.39%. A winglet exhibiting a chordwise length of 50% achieved the stability expansion ability equivalent to winglet with a full chordwise length, which can be increased by 22.58%. The tip leakage flow turned out to be weakened as the axial momentum was increased, and the circumferential momentum of the flow that arose from the tip winglet was reduced. The result of this study also suggested that tip winglets can play a certain role in combing the inflow of the stator, such that the blockage of the stator channel can be reduced.
Surrogate model-based deep reinforcement learning for experimental study of active flow control of circular cylinder
Authors: Dong Xinhui , Hong Hao , Deng Xiaolong , Zhong Wei , Hu Gang
Published: October 2023

The flow around a circular cylinder is a classical problem in fluid mechanics, and the reduction of drag and lift has been a long-standing research focus in flow control. In this study, we apply deep reinforcement learning (DRL) to intelligently determine suction flow rate on a circular cylinder model in wind tunnel, aiming to minimize aerodynamic forces while considering energy dissipation efficiency. However, DRL has been criticized for its low data utilization rate and long training period, leading to high experimental training cost. To address these issues, this study employs a surrogate model to optimize the reward function and hyperparameters, and this method is called SM-DRL. This SM-DRL method efficiently expedites the DRL training process, significantly reducing the experimental training cost. In addition, DRL training was conducted in a variable flow field, and the robustness of the obtained DRL model was tested. The results indicate that the DRL agent can determine the optimal control strategy, i.e., automatically select the optimal suction flow rate in terms of the incoming wind velocity, resulting in a significant reduction in lift fluctuations. For Reynolds number of 1.65×104, the reduction in lift fluctuations of the circular cylinder exceeds 50%.
A versatile platform for gas-phase molecular polaritonics
Authors: Wright Adam D. , Nelson Jane C. , Weichman Marissa L.
Published: October 2023

Cavity coupling of gas-phase molecules will enable studies of benchmark chemical processes under strong light–matter interactions with a high level of experimental control and no solvent effects. We recently demonstrated the formation of gas-phase molecular polaritons by strongly coupling bright ν3, J = 3 → 4 rovibrational transitions of methane (CH4) to a Fabry–Pérot optical cavity mode inside a cryogenic buffer gas cell. Here, we further explore the flexible capabilities of this infrastructure. We show that we can greatly increase the collective coupling strength of the molecular ensemble to the cavity by increasing the intracavity CH4 number density. In doing so, we can tune from the single-mode coupling regime to a multimode coupling regime in which many nested polaritonic states arise as the Rabi splitting approaches the cavity mode spacing. We explore polariton formation for cavity geometries of varying length, finesse, and mirror radius of curvature. We also report a proof-of-principle demonstration of rovibrational gas-phase polariton formation at room temperature. This experimental flexibility affords a great degree of control over the properties of molecular polaritons and opens up a wider range of simple molecular processes to future interrogation under strong cavity-coupling. We anticipate that ongoing work in gas-phase polaritonics will facilitate convergence between experimental results and theoretical models of cavity-altered chemistry and physics.
Effects of rotational excitation on decay rates of long-lived Rydberg states in NO
Authors: Rayment M. H. , Hogan S. D.
Published: October 2023

Nitric oxide (NO) molecules in pulsed supersonic beams have been excited to long-lived Rydberg-Stark states in series converging to the lowest vibrational level in the ground electronic state of NO+ with rotational quantum numbers N+ = 2, 4, and 6. The molecules in these excited states were then guided, or decelerated and trapped in a chip-based Rydberg-Stark decelerator, and detected in situ by pulsed electric field ionization. Time constants, reflecting the decay of molecules in N+ = 2 Rydberg-Stark states, with principal quantum numbers n between 38 and 44, from the electrostatic traps were measured to be ∼300μs. Molecules in Rydberg-Stark states with N+ = 4 and 6, and the same range of values of n were too short-lived to be trapped, but their decay time constants could be determined from complementary sets of delayed pulsed electric field ionization measurements to be ∼100 and ∼25 μs, respectively.
On the dynamics of air disk contraction
Authors: Jian Zhen , Li Ruixuan
Published: October 2023

Contraction of an air disk in liquid was investigated by direct numerical simulations of the Navier–Stokes equations in an axisymmetric framework. Five mechanisms of the first breakup were revealed: End-pinching, center-opening, cross-splitting, vertical splitting and no-breakup, and a parameter space as a function of the Ohnesorge number Oh and the aspect ratio Γ was established. Similar to air film contraction of other geometries, the contraction velocity of the air disk increases from rest to a maximum velocity, then decreases. Theories involving volume conservation, hydrodynamic drag, or added mass were proposed to predict the contraction velocity at different stages. Interaction between complicated morphological changes and vortex dynamics was studied. Generation and shedding of vortices around the bubble were responsible for the complex contraction dynamics.
Transport cross sections and collision integrals for C+(2P)–H(2S), C(3P)–H+(1S), C(1D)–H+(1S), and C+(4P)–H(2S) interactions
Authors: Hou Zhenlu , Qin Zhi , Liu Linhua
Published: October 2023

Transport collision integrals of interacting atoms or ions play a crucial role in modeling transport properties of high-temperature gases and plasmas. Here, we obtained the potential energy curves (PECs) of CH+ using the internally contracted multireference configuration interaction method with the Davidson correction (icMRCI+Q) method. The PECs were then used to investigate the transport cross sections and transport collision integrals for the C+(2P)–H(2S), C(3P)–H+(1S), C(1D)–H+(1S), and C+(4P)–H(2S) interactions using the classical mechanical approach and a quantum mechanical treatment of the scattering with Wentzel–Kramers–Brillouin approximations of the scattering phase shifts. The transport cross sections were obtained in the collision energy of 10−6–1 hartree, which were used to compute transport collision integrals for C–H+ and C+–H systems over the temperature range of 500–40 000 K. The C(1D)–H+(1S) and C+(4P)–H(2S) interactions are considered for the first time. Our transport collision integrals can provide data references for computing transport properties of high-temperature plasmas involving C and H atoms/ions.
Mobility-enhanced normally off hydrogen-terminated diamond FET with low interface state density using Al2O3/Nd gate stack
Authors: Su Jianing , Wang Wei , Shao Guoqing , Chen Genqiang , Wang Hong-Xing
Published: October 2023

A mobility-enhanced normally off hydrogen-terminated diamond (H-diamond) field-effect transistor (FET) with low interface state density has been realized using Al2O3/Nd gate stack deposited by electron beam evaporator. The threshold voltage is extracted to be −1.48 V, indicating an obvious normally off characteristic. The enhancement mode could be ascribed to the large work function difference between Nd and H-diamond. The subthreshold swing is deduced as low as 86.3 mV/dec, revealing a high working speed in the subthreshold region. More importantly, the mobility (518.5 cm2/V·s) has been enhanced due to the fairly low interface state density (3.19 × 1011 cm−2·eV−1). In addition, the device exhibits a relatively low trapped charge density and fixed charge density from the C–V characteristic. This work provides a simple method to realize the normally off device and suggests the great potential of adopting the Al2O3/Nd gate stack for achieving high-performance H-diamond FET.
Reinforcement learning-based active flow control of oscillating cylinder for drag reduction
Authors: Jiang Haokui , Cao Shunxiang
Published: October 2023

This study explores the use of a reinforcement learning (RL)-based active flow control strategy to reduce the drag of a transversely oscillating cylinder confined between two walls. We incorporate wake kinematic information of the oscillating cylinder from direct numerical solution into the agent to actively adjust the oscillating amplitude. Our findings reveal two strategies that significantly improve drag reduction. First, the oscillating frequency should be chosen within the lock-in region. Second, placing probes in the active region of turbulent kinetic energy enables the full utilization of physical information for achieving more efficient and stable control. The results show that an effective control strategy can reduce the drag by 8.4% compared to the case of stationary cylinder at Re = 200. We identify three characteristics of the controlled flow that contribute to drag reduction: an elongated recirculation zone, an increased energy transport coefficient, and asymmetric cylinder oscillation. We observed that this well-behaved controlled flow can be obtained through real-time RL-based control, as it consistently attenuates the asymmetric dynamic mode decomposition modes of the flow. Furthermore, we find that the asymmetry cylinder oscillation synchronizes with the vortex shedding, indicating that the RL-based control can expand the lock-in region.