bluuebunny/crossref_metadata_2025 huggingface dataset:
Self‐calibrating circuit for phase correction to support phased array antenna systems
Authors: Shafiq Zain , Anagnostou Dimitris E. , Podilchak Symon K.
Published: November 2023

A self‐calibrating circuit system for use within active phased array antennas is presented. The system addresses the issue of unwanted channel phase imbalances and random phase errors which can deteriorate array performance. Basically, unwanted insertion phase offsets that can originate within each RF channel, due to the supporting and active circuit components and possible temperature variations, can be eliminated by our designed, simulated, and experimentally verified self‐calibrating circuit. With existing technologies and calibration approaches, it is practically difficult and time consuming to check the phase feeding accuracy, as typically a large number of data sets are required to achieve similar channel corrections. As an alternative, our proposed circuit system allows for the consecutive phase shift between RF channels to be inspected and self‐corrected within a feedback loop managed by a MATLAB‐Arduino program. The active S‐band feed system can self‐calibrate in about 25 s (or less), using commercially available phase sensors and voltage controlled phase shifters. To the best knowledge of the authors, no similar computer controlled feed‐back circuit to support the self‐correction of active phased arrays has been previously reported.
Advancing autonomous vehicle control systems: An in‐depth overview of decision‐making and manoeuvre execution state of the art
Authors: Abdallaoui Sara , Ikaouassen Halima , Kribèche Ali , Chaibet Ahmed , Aglzim El‐Hassane
Published: November 2023

This abstract discusses the significant progress made in autonomous vehicles, focusing on decision‐making systems and control algorithms. It explores recent advances, challenges, and contributions in the field, emphasizing the need for precise navigation and control. The paper covers various methodologies, including rule‐based methods, machine learning, deep learning, probabilistic approaches, and hybrid approaches, examining their applications and effectiveness in ensuring safe navigation. Additionally, it reviews ongoing research efforts, emerging trends, and persistent challenges related to decision‐making and manoeuvre execution in autonomous vehicles, addressing complex topics such as sensor measurement uncertainty, dynamic environment modelling, real‐time responsiveness, and safe interactions with other road users. The objective is to provide a comprehensive overview of the state of the art in autonomous vehicle navigation and control for readers.
The GAPS Programme at TNG
Authors: Claudi R. , Bruno G. , Fossati L. , Lanza A. F. , Maggio A. , Micela G. , Maldonado J. , Benatti S. , Biazzo K. , Bignamini A. , Cabona L. , Carleo I. , Danielski C. , Desidera S. , Malavolta L. , Mancini L. , Montalto M. , Nardiello D. , Rainer M. , Scandariato G. , Sozzetti A. , Cosentino R. , Covino E. , Di Fabrizio L. , Ghedina A. , Lorenzi V. , Molinari E. , Molinaro M. , Pagano I. , Piotto G. , Poretti E.
Published: November 2023

Context. Stellar activity is the most relevant types of astrophysical noise that affect the discovery and characterization of extrasolar planets. On the other hand, the amplitude of stellar activity could hint at an interaction between the star and a close-in giant planet. Progress has been made in recent years in understanding how to deal with stellar activity and search for observational evidence of star-planet interactions.

Aims. The aim of this work is to characterize the chromospheric activity of stars hosting short-period exoplanets by studying the correlations between the chromospheric emission (CE) in the Ca II H&K and the planetary parameters.

Methods. We measured CE in the Ca II H&K lines using more than 1900 high-resolution spectra of a sample composed of 76 targets, observed with the HARPS-N spectrograph between 2012 and 2020. We transformed the fluxes into bolometric- and photospheric-corrected chromospheric emission ratios, R′HK. Furthermore, we completed the sample of hosts digging for data in previous works. Stellar parameters Teff, B–V, and V were retrieved homogeneously from the Gaia DR3. Then, M★, R★, and ages were determined from isochrone fitting. We retrieved planetary data from the literature and catalogs. The search for correlations between the log(R′HK) and planetary parameters have been performed through both Spearman’s rank and its statistics as well as the more sophisticated Gaussian mixture model method.

Results. We found that the distribution of log(R′HK) for the transiting planet hosts is different from the distribution of field main-sequence and sub-giant stars. The log(R′HK) of planetary hosts is correlated with planetary parameters proportional to the planetary radius to the power of n (RPn, indicating a common origin for the correlations. The statistical analysis has also highlighted four clusters of host stars with different behavior in terms of their stellar activity with respect to the planetary surface gravity. Some of the host stars have a value of log(R′HK) that is lower than the basal level of activity for main sequence stars. The planets of these systems are very close to filling their Roche lobe, suggesting that they evaporate through hydrodynamic escape under the strong irradiation of the host star, creating shrouds that absorb the core of the chromospheric resonance lines.
Observing the LMC with APEX: Signatures of large-scale feedback in the molecular clouds of 30 Doradus
Authors: Grishunin K. , Weiss A. , Colombo D. , Chevance M. , Chen C.-H. R. , Güsten R. , Rubio M. , Hunt L. K. , Wyrowski F. , Harrington K. , Menten K. M. , Herrera-Camus R.
Published: November 2023

Context. Stellar feedback plays a crucial role in star formation and the life cycle of molecular clouds. The intense star formation region 30 Doradus, which is located in the Large Magellanic Cloud (LMC), is a unique target for detailed investigation of stellar feedback owing to the proximity of the hosting galaxy and modern observational capabilities that together allow us to resolve individual molecular clouds – nurseries of star formation.

Aims. We study the impact of large-scale feedback on the molecular gas using the new observational data in the 12CO(3 − 2) line obtained with the APEX telescope.

Methods. Our data cover an unprecedented area of 13.8 sq. deg. of the LMC disc with a spatial resolution of 5 pc and provide an unbiased view of the molecular clouds in the galaxy. Using these data, we located molecular clouds in the disc of the galaxy, estimated their properties, such as the areal number density, relative velocity and separation, width of the line profile, CO line luminosity, size, and virial mass, and compared these properties of the clouds of 30 Doradus with those in the rest of the LMC disc.

Results. We find that, compared with the rest of the observed molecular clouds in the LMC disc, those in 30 Doradus show the highest areal number density; they are spatially more clustered, they move faster with respect to each other, and they feature larger linewidths. In parallel, we do not find statistically significant differences in such properties as the CO line luminosity, size, and virial mass between the clouds of 30 Doradus and the rest of the observed field.

Conclusions. We interpret our results as signatures of gas dispersal and fragmentation due to high-energy large-scale feedback.
Evidence for saturated and disrupted magnetic braking from samples of detached close binaries with M and K dwarfs
Authors: Belloni Diogo , Schreiber Matthias R. , Moe Maxwell , El-Badry Kareem , Shen Ken J.
Published: November 2023

Context. Recent observations of close detached eclipsing M and K dwarf binaries have provided substantial support for magnetic saturation when stars rotate sufficiently fast, leading to a magnetic braking (MB) torque proportional to the spin of the star.

Aims. We investigated here how strong MB torques need to be to reproduce the observationally inferred relative numbers of white dwarf plus M dwarf post-common-envelope binaries under the assumption of magnetic saturation.

Methods. We carried out binary population simulations with the BSE code adopting empirically derived inter-correlated main-sequence binary distributions as initial binary populations and compared the simulation outcomes with observations.

Results. We found that the dearth of extreme mass ratio binaries in the inter-correlated initial distributions is key to reproduce the large fraction of post-common-envelope binaries hosting low-mass M dwarfs (∼0.1 − 0.2 M⊙). In addition, orbital angular momentum loss rates due to MB should be high for M dwarfs with radiative cores and orders of magnitude smaller for fully convective stars to explain the observed dramatic change of the fraction of short-period binaries at the fully convective boundary.

Conclusions. We conclude that saturated but disrupted, that is, dropping drastically at the fully convective boundary, MB can explain the observations of both close main-sequence binaries containing M and K dwarfs and post-common-envelope binaries. Whether a similar prescription can explain the spin down rates of single stars and of binaries containing more massive stars needs to be tested.
The GAPS programme at TNG
Authors: Carleo I. , Malavolta L. , Desidera S. , Nardiello D. , Wang S. , Turrini D. , Lanza A. F. , Baratella M. , Marzari F. , Benatti S. , Biazzo K. , Bieryla A. , Brahm R. , Bonavita M. , Collins K. A. , Hellier C. , Locci D. , Hobson M. J. , Maggio A. , Mantovan G. , Messina S. , Pinamonti M. , Rodriguez J. E. , Sozzetti A. , Stassun K. , Wang X. Y. , Ziegler C. , Damasso M. , Giacobbe P. , Murgas F. , Parviainen H. , Andreuzzi G. , Barkaoui K. , Berlind P. , Bignamini A. , Borsa F. , Briceño C. , Brogi M. , Cabona L. , Calkins M. L. , Capuzzo-Dolcetta R. , Cecconi M. , Colon K. D. , Cosentino R. , Dragomir D. , Esquerdo G. A. , Henning T. , Ghedina A. , Goeke R. F. , Gratton R. , Horta F. Grau , Gupta A. F. , Jenkins J. M. , Jordán A. , Knapic C. , Latham D. W. , Mireles I. , Law N. , Lorenzi V. , Lund M. B. , Maldonado J. , Mann A. W. , Molinari E. , Pallé E. , Paegert M. , Pedani M. , Quinn S. N. , Scandariato G. , Seager S. , Winn J. N. , Wohler B. , Zingales T.
Published: November 2023

Context. Different theories have been developed to explain the origins and properties of close-in giant planets, but none of them alone can explain all of the properties of the warm Jupiters (WJs, Porb = 10–200 days). One of the most intriguing characteristics of WJs is that they have a wide range of orbital eccentricities, challenging our understanding of their formation and evolution.

Aims. The investigation of these systems is crucial in order to put constraints on formation and evolution theories. TESS is providing a significant sample of transiting WJs around stars bright enough to allow spectroscopic follow-up studies.

Methods. We carried out a radial velocity (RV) follow-up study of the TESS candidate TOI-4515 b with the high-resolution spectrograph HARPS-N in the context of the GAPS project, the aim of which is to characterize young giant planets, and the TRES and FEROS spectrographs. We then performed a joint analysis of the HARPS-N, TRES, FEROS, and TESS data in order to fully characterize this planetary system.

Results. We find that TOI-4515 b orbits a 1.2 Gyr-old G-star, has an orbital period of Pb = 15.266446 ± 0.000013 days, a mass of Mb = 2.01 ± 0.05 MJ, and a radius of Rb = 1.09 ± 0.04 RJ. We also find an eccentricity of e = 0.46 ± 0.01, placing this planet among the WJs with highly eccentric orbits. As no additional companion has been detected, this high eccentricity might be the consequence of past violent scattering events.
The possible evolution of pitch angles of spiral galaxies
Authors: Reshetnikov V. P. , Marchuk A. A. , Chugunov I. V. , Usachev P. A. , Mosenkov A. V.
Published: November 2023

Aims. The origin and maintenance of spiral structure in galaxies, the correlation between different types of spiral structure and several proposed mechanisms for their generation, and the evolution of spiral arms of galaxies with time are questions that are still controversial. In this note we study the spiral structure in a sample of distant galaxies in order to infer the evolution of spiral arm characteristics with redshift.

Methods. We considered a sample of 171 face-on spiral galaxies in the Hubble Space Telescope COSMOS (The Cosmic Evolution Survey) field. The galaxies are distributed up to z ≈ 1 with a mean value of 0.44. For all galaxies, we determined the pitch angles of the spiral arms and analysed their dependence on redshift; a total of 359 arms were measured.

Results. Analyses of our measurements combined with the literature data suggest a possible evolution of the pitch angles of spiral galaxies: by the modern epoch the spiral pattern, on average, becomes more tightly wound. This may be a consequence of the general evolution of the structure of galaxies as galaxies become more massive over time and their bulges grow. In addition, the distribution of the cotangent of pitch angle of galaxies indicates the possibility that the dominant mechanism of spiral pattern generation changes over time.
Complete F9 Gene Deletion, Duplication, and Triplication Rearrangements: Implications for Factor IX Expression and Clinical Phenotypes
Authors: Ma YuXin , Li Yang , Sun Jie , Liang Qian , Wu Runhui , Ding Qiulan , Dai Jing
Published: November 2023

Background Factor IX (FIX) plays a critical role in blood coagulation. Complete deletion of F9 results in severe hemophilia B, whereas the clinical implications of complete F9 duplication and triplication remain understudied.

Objective To investigate the rearrangement mechanisms underlying complete F9 deletion (cases 1 and 2), duplication (cases 3 and 4), and triplication (case 5), and to explore their association with FIX expression levels and clinical impacts.

Methods Plasma FIX levels were detected using antigen and activity assays. CNVplex technology, optical genome mapping, and long-distance polymerase chain reaction were employed to characterize the breakpoints of the chromosomal rearrangements.

Results Cases 1 and 2 exhibited FIX activities below 1%. Case 3 displayed FIX activities within the reference range. However, cases 4 and 5 showed a significant increase in FIX activities. Alu-mediated nonallelic homologous recombination was identified as the cause of F9 deletion in case 1; FoSTeS/MMBIR (Fork Stalling and Template Switching/microhomology-mediated break-induced replication) contributed to both F9 deletion and tandem duplication observed in cases 2 and 3; BIR/MMBIR (break-induced replication/microhomology-mediated break-induced replication) mediated by the same pair of low-copy repeats results in similar duplication–triplication/inversion–duplication (DUP–TRP/INV–DUP) rearrangements in cases 4 and 5, leading to complete F9 duplication and triplication, respectively.

Conclusion Large deletions involving the F9 gene exhibit no apparent pattern, and the extra-hematologic clinical phenotypes require careful analysis of other genes within the deletion. The impact of complete F9 duplication and triplication on FIX expression might depend on the integrity of the F9 upstream sequence and the specific rearrangement mechanisms. Notably, DUP–TRP/INV–DUP rearrangements significantly elevate FIX activity and are closely associated with thrombotic phenotypes.
Role of Cytogenetics and Fluorescence In Situ Hybridization in the Laboratory Workup of Acute Myeloid Leukemias
Authors: Jain Hemani , Shetty Dhanlaxmi
Published: November 2023

A new understanding of acute myeloid leukemia as a varied group of unique biologic entity has emerged, as a result of the identification of various chromosomal aberrations and their association with clinical prognosis and diagnosis. Following induction treatment, cytogenetic examination can establish the presence of any residual malignant cells, it's recurrence, clonal evolution if any, or the formation of novel abnormalities. The G-banded karyotype has been the gold standard method for detecting all of these aberrations for years. The capacity to examine the entire genome through karyotype analysis quickly enabled the detection of deletions, duplications, and structural rearrangements across every chromosome, and the more frequent ones were associated with particular aberrant clinical symptoms. Fluorescence in situ hybridization (FISH) is a sensitive technology that aids in differential diagnosis or therapeutic planning and provides rapid results. Furthermore, the combination of cytogenetic and molecular profiling enables a more precise evaluation of disease prognosis, diagnosis, classification, risk stratification, and patient treatment. Interphase FISH analysis, in conjunction with G-banded chromosomal analysis, can be used as a major testing tool for the evaluation of hematological neoplasms. For accurate and consistent descriptions of genomic changes identified by karyotyping and FISH, a specified terminology is necessary. The International System for Human Cytogenomic Nomenclature is the main source and provides instructions for documenting cytogenetic and molecular findings in laboratory reports. This review discusses the two methods, karyotyping and FISH, their advantages and limitations, sample requirements, various FISH probes that are used, nomenclature for results reporting, and the necessary quality control measures.
A Scientometric Analysis of the most Highly Cited Publications on Fracture Research from India: 1989-2022
Authors: Vaishya Raju , Gupta Brij Mohan , Kappi Mallikarjun , Vaish Abhishek
Published: November 2023

Background

India bears a huge burden of accidents and fractures. This study aimed to study the bibliometric characteristics of India's fracture research output during last three decades. The most highly cited publications (HCPs; with 20 or more citations) on orthopaedic fracture research from India were analyzed on various parameters.

Methodology

The Scopus database was used to identify publications on fractures that originated from India, between 1989 to 2022. The top HCPs were retrieved. A bibliometric and network analysis was used to identify the key players, such as organizations, authors and journals, and important keywords besides identifying their collaborative interactions and visual co-occurrences of significant keywords using VOSviewer and Biblioshiny software.

Results

Of the total 1,048 Indian publications, 126 (10.02%) were HCPs (cited 4,695 times). External funding was received in 1.59%, and international collaboration in 15.08%. The most productive organizations were All India Institute of Medical Sciences (AIIMS), New Delhi, followed by Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, and Pandit Bhagwat Dayal Sharma Post Graduate Institute of Medical Sciences (PGIMS), Rohtak. The most impactful organizations were Maulana Azad Medical College (MAMC), Delhi, followed by the Jawaharlal Institute of Postgraduate Medical Education & Research (JIPMER), Pondicherry, and Sancheti Institute of Orthopaedic Research & Rehabilitation, Pune. The most productive authors were R. Malhotra, M.S. Dhillon, and N.K. Magu, and the most impactful authors were U.K. Meena, A.P. Singh, and P. Sancheti. Delhi was the epic of research, followed by Karnataka, Tamil Nadu, and Chandigarh.

Conclusion

This study provides an insight into the research trends, the most influential contributions, and the performance of Indian organizations and authors. It gives some ideas about the past, present, and future hotspots in research.
Ser252Asn Mutation Introduces a New N-Linked Glycosylation Site and Causes Type IIb Protein C Deficiency
Authors: Zhou Shijie , Wu Xi , Song Ying , Li Lei , Shi Chunli , Lai Zhe , Ding Qiulan , Wu Wenman , Dai Jing , Wang Xuefeng , Lu Yeling
Published: November 2023

Background Protein C (PC) is a vitamin K-dependent anticoagulant serine protease zymogen which upon activation by the thrombin–thrombomodulin (TM) complex downregulates the coagulation cascade by degrading cofactors Va and VIIIa by limited proteolysis. We identified a thrombosis patient who carried a heterozygous mutation c.881G > A, p.Ser252Asn (S252N) in PROC. This mutation was originally described in a report of novel mutations in patients presenting with defective PC anticoagulant activity in Paris. The research identified PC-S252N (the “Paris” mutation) in a propositus and her family members and highlighted the critical role of Ser252 in the anticoagulation process of activated PC (APC).

Material and Methods We expressed the PC-S252N mutant in mammalian cells and characterized the properties in coagulation assays to decipher the molecular basis of anticoagulant defect of this mutation.

Results We demonstrated that PC-S252N had a diminished ability to TM binding, which resulted in its impaired activation by the thrombin-TM complex. However, APC-S252N exhibited a slightly stronger cleavage capacity for the chromogenic substrate. Meanwhile, the catalytic activity of APC-S252N toward FVa was significantly reduced. Sequence analysis revealed that Ser252 to Asn substitution introduced a new potential N-linked glycosylation site (252NTT254) in the catalytic domain of PC, which adversely affected both the activation process of PC and anticoagulant activity of APC.

Conclusion The new N-glycosylation site (252NTT254) resulting from the mutation of Ser252 to Asn252 in PROC affects the overall structure of the protease, thereby adversely affecting the anticoagulant function of protein C. This modification has a negative impact on both TM-promoted activation of protein C and APC cleavage of FVa, ultimately leading to thrombosis in the patient.
Solitary Fibrous Tumor of the Pleura: Surgical Treatment and Recurrence
Authors: Bove Mary , Natale Giovanni , Messina Gaetana , Tiracorrendo Matteo , Rendina Erino Angelo , Fiorelli Alfonso , D'Andrilli Antonio
Published: November 2023

Background Solitary fibrous tumors of the pleura (SFTPs) are primary pleural tumors originating from the mesenchymal tissue. Surgical treatment was the first choice for management of SFTPs. There were no defined guidelines for the follow-up of these tumors and the postoperative therapy due to the rarity of these tumors.

Methods We conducted a retrospective, multicenter study from two high-volume centers in Italy. Data of patients diagnosed with pleural solitary fibrous tumors between January 2003 and October 2022 were prospectively recorded and retrospectively analyzed. The aim of this study was to identify predictive prognostic factors and the correlation between tumor characteristics and recurrence.

Results In all, 107 patients undergoing R0 surgical resection of pleural solitary fibrous tumor were included in the study. Patients were divided in two groups: benign and malignant. All the patients were treated with surgery with the aim to obtain R0 resection. Lung resection was necessary when the tumor adhered strongly to the lung parenchyma or infiltrated it. Twenty of the 107 patients had tumor recurrence. At a multivariate analysis, histological characteristics (high mitotic index) and maximum standardized uptake values (maxSUV) were related to recurrence. The mean disease-free survival (DFS) was 143.3 ± 6.1 months.

Conclusion In our experience, histological features of malignancy and maxSUV are significantly related to recurrence, which can occur even years after the first diagnosis. Surgical excision with negative surgical margins results in good long-term outcomes. After surgery, a long-term and strict follow-up should be done, in order to detect recurrence early. R0 of the recurrence is associated with long-term survival.
Reframing the narrative of magic wind in Arthur Waley’s translation of Journey to the West: another look at the abridged translation
Authors: Wang Feng , Liu Keqiang , Humblé Philippe
Published: November 2023

This article examines Arthur Waley’s abridged translation of “Journey to the West”, titled “Monkey”, and its influence on magic wind narrativity using narrative theory and (re)framing concepts. The research categorises the narrative significance of the magical wind in the source text and highlights its powers as destruction, transport and transformation. In contrast, these elements seem subdued in “Monkey”. Waley’s reframing employs strategies, such as (I) temporal and spatial reframing; (II) selective appropriation, emphasising stories of pilgrims saving their lands, while overshadowing important cultural and religious aspects of the original; and (III) modifying specific labelling techniques that include references to the magical wind.
The functional differentiation of brain–computer interfaces (BCIs) and its ethical implications
Authors: Sun Xiao-yu , Ye Bin
Published: November 2023

The growth of research and applications of brain–computer interfaces (BCIs) has spurred extensive discussion about their ethical implications. However, most existing research has primarily examined ethical issues related to BCIs from a general perspective, with little attention paid to the specific functions of the technology. This has resulted in a mismatch between governance and ethical issues, due to the lack of differentiation between write-in and read-out BCIs. By providing detailed descriptions of the functions and technical approaches of both write-in and read-out BCIs, we argue that ethical governance of BCIs should follow the principle of precise governance and develop refined governance strategies for different functional types of BCIs.
Uniform bound of the entanglement for the ground state of the one-dimensional quantum Ising model with non-homogeneous transverse field
Authors: Campanino Massimo
Published: November 2023

We consider the ground state of the one-dimensional quantum Ising model with transverse field hx in one dimension depending on the site x∈Z in a finite volume Λm ≔ {−m, −m + 1, …, m + L}. We make suitable assumptions on the regions where the field is small and prove that if the field is sufficiently large on the complementary set, then the entanglement of the interval Λ0≔0,..,L relative to its complement Λm\Λ0 is bounded uniformly in m and L. The result applies in particular to periodic transverse fields. The bound is established by means of a suitable cluster expansion.
Role of Pauli blocking for enhancement of saturable absorption in MoS2/PEDOT:PSS nanocomposite films
Authors: Arjun K. , Karthikeyan B.
Published: November 2023

We have effectively shown a technique for significantly altering the nonlinear saturable absorption (SA) properties of nanocomposite films (NCFs) based on poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) and molybdenum disulfide (MoS2) by regulating MoS2 concentration and input pulse energy of the laser. The NCFs are made using the straightforward drop-cast process on a glass substrate with varying quantities of MoS2. The produced NCFs’ refractive index (n) and extinction coefficient (k) values are determined using the Kramers–Kronig equations. Nonlinear studies show that the optical nonlinearity of pure PEDOT:PSS changes when mixed with MoS2. The Pauli blocking has been observed in MoS2/PEDOT:PSS NCFs. This leads to enhanced SA in NCF. The open-aperture Z-scan approach is used for the nonlinear optical research, and a nanosecond pulsed laser with a wavelength of 532 nm is used for the excitation. The findings obtained show the NCFs’ strong SA qualities.
Learning nonlinear projections for reduced-order modeling of dynamical systems using constrained autoencoders
Authors: Otto Samuel E. , Macchio Gregory R. , Rowley Clarence W.
Published: November 2023

Recently developed reduced-order modeling techniques aim to approximate nonlinear dynamical systems on low-dimensional manifolds learned from data. This is an effective approach for modeling dynamics in a post-transient regime where the effects of initial conditions and other disturbances have decayed. However, modeling transient dynamics near an underlying manifold, as needed for real-time control and forecasting applications, is complicated by the effects of fast dynamics and nonnormal sensitivity mechanisms. To begin to address these issues, we introduce a parametric class of nonlinear projections described by constrained autoencoder neural networks in which both the manifold and the projection fibers are learned from data. Our architecture uses invertible activation functions and biorthogonal weight matrices to ensure that the encoder is a left inverse of the decoder. We also introduce new dynamics-aware cost functions that promote learning of oblique projection fibers that account for fast dynamics and nonnormality. To demonstrate these methods and the specific challenges they address, we provide a detailed case study of a three-state model of vortex shedding in the wake of a bluff body immersed in a fluid, which has a two-dimensional slow manifold that can be computed analytically. In anticipation of future applications to high-dimensional systems, we also propose several techniques for constructing computationally efficient reduced-order models using our proposed nonlinear projection framework. This includes a novel sparsity-promoting penalty for the encoder that avoids detrimental weight matrix shrinkage via computation on the Grassmann manifold.
Effect of isothermal rough boundaries on the statistics of velocity and temperature fluctuations in turbulent Rayleigh–Bénard convection
Authors: Chand Krishan , Laskar Debojyoti N. , Sharma Mukesh , De Arnab Kr.
Published: November 2023

Using direct numerical simulations, we investigate the effect of surface roughness on the statistics of fluctuations in a 2D rectangular cell of aspect ratio Γ = 2 with air as the working fluid. We consider roughly two decades of Rayleigh number, 108≤Ra≤4.64×109, with three roughness configurations of R1, R2, and R3 characterized by their maximum heights of 5%, 10%, and 20% of the cell height, respectively. We show that roughened cells trigger stronger fluctuations, which further gets augmented with increasing Ra. Vertical variations of velocity and temperature fluctuations show different trends. While the temperature fluctuation becomes homogeneous in the bulk, it exhibits strong inhomogeneous vertical velocity fluctuations. The comparison of global heat flux with smooth case shows a significant increment beyond Ra=2.15×108. Surface roughness impacts local heat flux through augmented plumes, which is qualitatively ascertained by instantaneous temperature field. Furthermore, probability distribution functions reveal no particular trend for the taller roughness configurations, though the magnitude is amplified. Through identification of plumes and background regions, we show their behavior as a function of Ra for different rough cases. Finally, we decompose the shear production into its three components (based on the nature of mechanical forces) to understand the energy interaction between the mean flow and fluctuating flow field.
High figure of merit spin polarized electron sources grown via MOCVD
Authors: Belfore Benjamin , Masters Adam , Poudel Deewakar , Blume Greg , Polly Stephen , Wang Erdong , Hubbard Seth M , Stutzman Marcy , Grames Joseph Michael , Poelker Matt , Grau Matt , Marsillac Sylvain
Published: November 2023

Spin polarized photocathodes are key to the future operation of electron accelerators such as the ones at Thomas Jefferson National Accelerator Facility and Brookhaven National Laboratory. Currently, these photocathodes come in short supply due to limited production by molecular beam epitaxy. By developing a process to implement similar structures using metal organic chemical vapor deposition, the availability of these devices can be increased. In this paper, we detail the implementation of recent photocathode advancements via metal organic chemical vapor deposition process and show an improvement in both polarization and quantum efficiency of our devices compared to those fabricated via molecular beam epitaxy, with devices reaching 82% polarization and 2.9% quantum efficiency.
Anisotropic optical characteristics of WS2/ReS2 heterostructures with broken rotational symmetry
Authors: Xie Xing , Ding Junnan , Wu Biao , Zheng Haihong , Li Shaofei , He Jun , Liu Zongwen , Wang Jian-Tao , Liu Yanping
Published: November 2023

High-symmetry transition-metal dichalcogenides (TMDs) have garnered substantial attention in the fields of sensors, optoelectronics, and valleytronics. However, the inherent C3 rotational symmetry of TMDs engenders highly isotropic properties, impeding their further technological progress. To overcome this limitation, we embarked on a study to investigate the effects of isotropic/anisotropic heterostructures engineering on WS2, aiming to break its C3 rotational symmetry. In this work, we designed and fabricated heterostructures composed of WS2 and ReS2 layers. Our comprehensive investigations revealed a remarkable emergence of anisotropic characteristics in excitons originating from the WS2 layers within the engineered WS2/ReS2 heterostructures. Moreover, we observed an enhancement in the valley polarizations of WS2 layers within the heterostructures, which is attributed to the reduced intervalley scattering facilitated by the WS2/ReS2 heterostructure configuration. This observation indicates the potential for leveraging heterostructure engineering to tailor and optimize anisotropic devices, thereby opening promising avenues for future applications in various technological domains.
Unraveling the interplay of leaf structure and wettability: A comparative study on superhydrophobic leaves of Cassia tora, Adiantum capillus-veneris, and Bauhinia variegata
Authors: Ganar Shubham S. , Das Arindam
Published: November 2023

In this article, superhydrophobic leaves of Cassia tora, Adiantum capillus-veneris (ACV), and Bauhinia variegata are reported for the first time, and the wettability of these leaf's surfaces was correlated with their surface morphology at micro- and nanoscale. Field Emission Scanning Electron Microscopy (FESEM) images of the surfaces were used to get surface morphological information at the micro-nanoscale structures. A special drying method was implemented to ensure the minimal structural collapse of these surfaces under the high vacuum of FESEM. FESEM images of Cassia tora leaves showed widely spaced, low aspect ratio nanopetals distributed on bumpy blunt microfeatures, responsible for high contact angle hysteresis, and high roll angle measured on the Cassia tora leaves. ACV leaves showed the presence of micrometer-scale spherical morphology made of nanoscale hair-like features. These hierarchical re-entrant surface features generated a very high contact angle and low roll-off angle. Leaves of Bauhinia variegata showed similar superhydrophobic and self-cleaning properties. However, surface features were different, which consisted of a higher aspect ratio and closely spaced nanopetals uniformly distributed over flat surfaces consisting of micro-scale ridges. Our comprehensive investigation covers a detailed analysis of droplet impact studies, shedding light on the intricate dynamics governing droplet behavior on these superhydrophobic surfaces. Furthermore, we extended our analysis to encompass droplet impact on macrostructures to assess their influence on droplet receding and rebound phases. Notably, it was observed that only the microstructure of Cassia tora had a discernible impact on the receding and rebound phases of droplets. Additionally, our experiments examining maximum spreading diameter demonstrated good agreement with established models, further strengthening the scientific basis of our findings. These findings not only contribute to the advancement of our understanding of surface wetting phenomena but also bear practical implications for the development of water-repellent and self-cleaning materials.
Large-eddy simulation of non-isothermal flow and heat transfer in an enclosed rotor–stator cavity
Authors: Wang Ruonan , Du Qiang , Xie Yaguang , Xie Lei , Lu Lin
Published: November 2023

This paper presents a numerical study of non-isothermal flow and heat transfer in an enclosed rotor–stator disk cavity. Wall-resolved large-eddy simulation is implemented with attention focused on the Reynolds number effect (Reϕ=105 and 5×105) and non-isothermal effects, including different thermal Rossby numbers (βΔT=0.05–0.25) and heat convection types (axial heat convection, axial and radial heat convection). Verification and validation are implemented by comparing with available experimental data and examining the resolution of the present LES. Although the Batchelor flow type is unchanged, the non-isothermal effect is found to be responsible for the acceleration of flow in both disk boundary layers and cavity core. Temperature in the cavity is negatively correlated with the Rayleigh number. The radial inward temperature gradient is found to be responsible for destabilizing the flow near the cylinders, due to the effect of centrifugal buoyant force. Transition from laminar to turbulent is shown in the rotor boundary layer for Reϕ=5×105 conditions. The non-isothermal effect increases flow unsteadiness in both rotor and stator boundary layers, but it has little to no effect on the transition position, as well as the kinematic and thermal boundary layer thicknesses, which are mainly controlled by Reϕ. Spectral proper orthogonal decomposition is implemented to explore the Reynolds number effect. Analyzing the most energetic mode and its energy spectra provides some insights into the understanding of non-isothermal rotor–stator disk cavity flows.
Direct current conductance and 1/f-noise in cellulose nanofiber–multi-walled carbon nanotube composites for applications in flexible electronic devices
Authors: Banerjee Arnab , Sathwane Manoj , Das Sutanu , Chattopadhyay Bidisa , Maji Pradip K. , Nandi Upendranath , Ghosh Aswini
Published: November 2023

We report on the studies of conduction mechanism, direct current conductance, and 1f-noise of cellulose nanofiber (CNF) and multiwalled carbon nanotube (MWCNT) composites. The composites were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The temperature- and voltage-dependence of the dc conductance Σ were, respectively, probed to investigate the charge transport mechanism and the electrical response of the composite. At room temperature, the increase in Σ with wt. % of MWCNT ϕ showed typical percolation behavior. The Σ−T behavior was fitted to the combination of one-dimensional variable range hopping and the fluctuation-induced tunneling, which were attributed to hopping of charge carriers through 1D MWCNTs and the tunneling of charge carriers between the bundles of MWCNTs, respectively. The non-Ohmic electrical conduction was characterized by the onset voltage V0(T) which scaled with Ohmic conductance Σ0 as V0(T)∼Σ0(T)xT, with xT being the onset exponent increased with ϕ. A scaling description based on the data collapse method was adopted to find the parameters V0(T) and xT. The noise power spectrum SV(f) followed the relation SV(f)∼Vβ with two different power-laws: β1 in the Ohmic and β2 in the non-Ohmic region (β1>β2). Interestingly, this change in power-laws occurs at the same V0(T) obtained from Σ−V curves. A simple model was proposed to explain the noise behavior after V0(T). It is expected that such electrical characterization of CNF-MWCNT nanopaper composite would open up their possibility of application in flexible electronic devices, intelligent networks, sensors, and actuators.
Thermomechanic behavior of epitaxial GeTe ferroelectric films
Authors: Croes Boris , Cheynis Fabien , Texier Michaël , Müller Pierre , Curiotto Stefano , Leroy Frédéric
Published: November 2023

A key development toward new electronic devices integrating memory and processing capabilities could be based on the electric control of the spin texture of charge carriers in semiconductors. In that respect, GeTe has been recently recognized as a promising ferroelectric Rashba semiconductor, with giant spin splitting of the band structure, due to the inversion symmetry breaking arising from ferroelectric polarization. Here, we address the temperature dependence of the ferroelectric structure of GeTe thin films grown on Si(111). We demonstrate the hysteretic behavior of the ferroelectric domain density upon heating/cooling cycles by low energy electron microscopy. This behavior is associated with an abnormal evolution of the GeTe lattice parameter as shown by x-ray diffraction. We explain these thermomechanical phenomena by a large difference of thermal expansion coefficients between the film and the substrate and to the pinning of the GeTe/Si interface. The accumulated elastic energy by the GeTe thin film during sample cooling is released by the formation of a-nanodomains with in-plane ferroelectric polarization components.
Simulation of quantum walks on a circle with polar molecules via optimal control
Authors: Ding Yi-Kai , Zhang Zuo-Yuan , Liu Jin-Ming
Published: November 2023

Quantum walks are the quantum counterpart of classical random walks and have various applications in quantum information science. Polar molecules have rich internal energy structure and long coherence time and thus are considered as a promising candidate for quantum information processing. In this paper, we propose a theoretical scheme for implementing discrete-time quantum walks on a circle with dipole–dipole coupled SrO molecules. The states of the walker and the coin are encoded in the pendular states of polar molecules induced by an external electric field. We design the optimal microwave pulses for implementing quantum walks on a four-node circle and a three-node circle by multi-target optimal control theory. To reduce the accumulation of decoherence and improve the fidelity, we successfully realize a step of quantum walk with only one optimal pulse. Moreover, we also encode the walker into a three-level molecular qutrit and a four-level molecular ququart and design the corresponding optimal pulses for quantum walks, which can reduce the number of molecules used. It is found that all the quantum walks on a circle in our scheme can be achieved via optimal control fields with high fidelities. Our results could shed some light on the implementation of discrete-time quantum walks and high-dimensional quantum information processing with polar molecules.
Memristive devices with short-term and long-term memory behaviors for processing temporal information
Authors: Ki Seung Jun , Kim Jisoo , Chen Mingze , Liang Xiaogan
Published: November 2023

Memristors based on 2D semiconductors such as MoS2 and its derivative materials exhibit analog switching behaviors capable of emulating some synaptic functions, including short-term plasticity, long-term potentiation, and spike-time-dependent-plasticity. Additional investigation is needed to realize reliable control of such synaptic behaviors for practical device implementation. To meet this scientific need, we fabricated MoS2-based memristors and studied their paired-pulse facilitation (PPF) and long-term memory characteristics under different pulse programming settings. This research has provided a guideline for identifying the programming settings for different neuromorphic processes. For example, a specific setting resulting in PPF > 30% and long-term conductance change < 20% has been identified to be suited for processing real-time temporal information. Furthermore, this research also indicates that the MoS2 memristor keeps having an almost constant relative change in conductance but greatly enhanced drive current level under laser illumination. This behavior can enable an easy integration of such memristive devices with state-of-the-art controller circuits for practice neuromorphic control applications.
A fast natural convection algorithm based on dividing fluid development stages
Authors: Zhao Banghua , Zhou Yuanye , Ding Chen , Dong Sujun
Published: November 2023

We develop a numerical method for fast computation of natural convection, which proposes a new dimensionless number (Fs) to characterize the degree of influence of convection on the temperature field in the flow field and determines the moment of pause for the updating of the flow field by designing judgmental conditions to delineate the stage of development of the flow field, where the loosely coupled computation is turned on to improve the efficiency of the transient temperature field computation. The accuracy of the algorithm is verified using an experimental case of a standard model of natural convection, and the robustness of the algorithm is verified by specifying different monitoring boundaries and setting different numbers of monitoring steps, and the algorithm is applied to a model of natural convection in the equipment in the cabin of the vehicle. The results show that the computational speed is increased by 8.8, 6.4, and 3.5 times after turning on the loosely coupled computation in the first, second, and third development phases, respectively, and the average errors of the monitored point temperatures are 0.7%, 0.1%, and 0.028%, respectively. By monitoring the change in Fs during the loosely coupled computation, the error of the first development stage under the variable boundary is reduced by 95.1%, and the computation speed is 2.2 times faster than that of the second development stage.
Vortex-induced energy loss and pressure fluctuations in a closed sump under various conditions: An experimental investigation
Authors: Zhang Bowen , Yang Anlong , Cheng Li , Jiao Weixuan , Xu Jiameng , Luo Can
Published: November 2023

The roof-attached vortices (RAVs), floor-attached vortices (FAVs), and complex combined submerged vortices (CSVs) excited in a closed pump sump will induce irregular pressure fluctuations that can decrease the energy efficiency of the pump and the stability of its input flow. This article presents an experimental investigation of the energy loss and pressure fluctuations induced by these vortices under various conditions. A transparent closed-loop test rig was used for high-speed visualization and pressure-fluctuation tests. The findings demonstrate that as the flow rate is increased, the head and efficiency of the pump device significantly decrease. A CSV, which is composed of an RAV and an FAV, has the highest head-loss value, reaching 0.21 m, with an efficiency decrease in up to 2.8%. The typical evolution stages of RAV are divided into newborn, developing, fully developed, and dissipative collapsing. The typical evolution stages of FAV are divided into germinating, growing, maintaining, decaying, and disappearance. The maximum diameter of the FAV core is approximately 0.05 times the maximum vortex-core scale of the RAV. Based on the proposed vortex-identification method, as the bellmouth height decreases, the strength of the FAV increases during the CSV period, and the degree of pressure fluctuation becomes more severe. In addition, regardless of the flow rate, the strength of the FAV structure is always much greater than that of the RAV.