bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of a bend on vortex formation and evolution in a three-dimensional stenosed geometry during pulsatile flow
Authors: Owais Mohammad , Usmani Abdullah Y. , Muralidhar K.
Published: February 2023

Stenosis at arterial bends alters hemodynamics and instigates abnormal disease progression. This configuration is addressed numerically by exploring pulsatile flow (Reynolds number Re = 300–1200; Womersley number Wo = 7.62–15.24) in arteries encountering bend angles of θ = 20°–60°. Individual influences of stenosis and bend on flow dynamics are investigated. Validations against particle image velocimetry experiments for Re = 800 and Wo = 7.62 are carried out in straight and 60° bend stenosed models. For Re = 300–800, the shear layer along the stenosis rolls up into a primary vortex, that is, constrained by the outer wall forming a secondary vortex. At Re = 1200, shear layers undergo instabilities along the post-stenotic region and develop new vortices that promote disturbances and induce asymmetries over the cross-plane flow structures. These features are not present in a straight stenosed tube, showing that the bend is responsible for flow distortion. During the pulsatile cycle, increasing bend angles intensify the size and strength of vortices, while these are suppressed at higher frequencies. A higher bend of 60° experiences large time-averaged wall shear stress and oscillatory loads. In time, wall loading spatially circumscribes the post-stenotic region followed by wall loading during cycle deceleration. These features are consistent with the skewing of a three-dimensional ring structure formed in a stenosed tube that evolves into disintegrated structures in the post-stenotic region. Overall, simulations reveal that strongly bent stenosed arteries experience aggravated oscillatory loading. In the biomedical context, such arterial geometries will require special attention.
Phase equilibria and interface properties of hydrocarbon propellant–oxygen mixtures in the transcritical regime
Authors: Nitzke Isabel , Stierle Rolf , Stephan Simon , Pfitzner Michael , Gross Joachim , Vrabec Jadran
Published: February 2023

Vapor–liquid equilibria and fluid interface properties of binary mixtures containing either methane or cyclohexane representing fuel and nitrogen or oxygen are reported. The mixtures are studied at different temperatures and pressures, which are chosen such that the temperature of the fuel component is subcritical, while that of the gaseous component is mainly supercritical. Data are obtained from molecular dynamics (MD) simulation, as well as density functional theory and density gradient theory in combination with the PC-SAFT equation of state (EOS). The studied interface properties include surface tension, interface thickness, enrichment, and relative adsorption. Furthermore, bulk vapor–liquid equilibrium properties are computed with two distinct MD methods as well as the PC-SAFT EOS. All approaches are compared to data from highly accurate empirical EOS. Despite the fundamental differences between these methods, very good agreement between the results of MD, density functional theory, and density gradient theory and EOS data is observed for the phase equilibria and interface properties, reinforcing the present predictions. It is found that the equivalence of nitrogen to oxygen is rather limited, in particular for the methane propellant. The disparities are particularly pronounced for low temperatures, where the compositions of the bulk phases differ significantly. As a result, enthalpy of vaporization as well as surface tension attains much higher values for mixtures containing oxygen.
Large negative electrocaloric response induced by nanoscale phase transition in (Bi, Na)TiO3-based thin films
Authors: Sun Yunlong , Du Jianhao , Jiang Chenlu , Liang Jun , Geng Xun , Wang Yu , Wang Danyang
Published: February 2023

Electrocaloric effect (ECE) offers an efficient and environmentally friendly route for solid-state cooling. Either positive or negative ECE could exhibit a large adiabatic temperature change (ΔT). Compared to the positive electrocaloric response, the investigation of negative ECE is lagging behind, largely due to the fact that its origin is still elusive. In this work, the negative ECE behavior of conventional ferroelectric thin films, namely 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNBT), was studied. A remarkable ΔT of −26.1 K was acquired near 160 °C under a moderate electric field of 875 kV/cm, attributing to the ferroelectric phase transition in the polar nanoregions from rhombohedral (R3c) to tetragonal (P4bm), as confirmed by temperature-dependent dielectric permittivity, Raman spectra, and x-ray reciprocal space mapping. The BNBT thin film presents a high electrocaloric coefficient (ΔT/ΔE) of 0.0298 K cm kV−1, transcending that of the most reported negative electrocaloric response of thin films.
Multidimensional infrared diffusion-ordered spectroscopy in depletion mode distinguishes protein amyloids and monomers
Authors: Giubertoni Giulia , Caporaletti Federico , van Diest Rianne , Woutersen Sander
Published: February 2023

Conventional and two-dimensional infrared (2D-IR) spectroscopy are well suited to study amyloid aggregates, because the amide I mode is a sensitive probe of the aggregate structure. However, these methods are not so useful to study mixtures of aggregates and monomers, which generally have overlapping amide I spectra. Here, we show that IR-Diffusion-Ordered Spectroscopy can disentangle the contributions of protein monomers and aggregates (amyloids) in FTIR and 2D-IR spectra by separating the spectral contributions based on molecular size. We rely on the fact that the diffusion coefficient of a molecule is determined by its size through the Stokes–Einstein relation, and achieve sensitivity to the diffusion coefficient by creating a concentration gradient inside an IR sample cell and tracking its equilibration in an IR-frequency-resolved manner. The amyloid diffusion is too slow to be experimentally observable, so instead of tracking the arrival of molecular species diffusing into the initially empty region of the sample cell, we track the depletion of the more rapidly diffusing species as they leave the sample-filled region. This way, we can still obtain the spectrum of very slowly diffusing species, although we cannot determine their diffusion coefficient. We first demonstrate this depletion method on a mixture of two small organic molecules and then show how it can be used to separate the spectrum of a mixture of bovine-serum-albumin amyloids and monomers into its component spectra, both in the FTIR and 2D-IR case.
Underwater gas bubbles produced by droplet impact: Mechanism to trigger volumetric oscillations
Authors: Prokhorov V. E.
Published: February 2023

Oscillating gas bubbles formed when droplets collide with a water surface are studied experimentally. Over a short time interval, before and after the bubble detachment, the bubble surface curvature changes drastically, causing a pulse of Laplace pressure. The leading edge of the pulse occurs before the bubble detachment, and the rear (negative) edge falls on the stage of an already closed bubble, which, like a resonator, is excited into volume oscillations on the natural frequency while simultaneously emitting an acoustic wavepacket. The amplitude and steepness of the pulse are inversely related to the size of the bubble, thereby ensuring that the dynamic parameters of the triggering pulse correspond to the natural frequency of the bubble. The release of pressure during the negative trailing edge of the pulse initiates the beginning of volumetric oscillations from the expansion phase and the acoustic packet from the positive half-wave.
Fluid–structure interaction and flow sensing of primary cilia in oscillating fluid flows
Authors: Cui Jingyu , Jin Yuzhen , Liu Yang , Fu Bingmei M. , Yan Weiwei
Published: February 2023

This study systematically investigates the interaction between an oscillating flow and primary cilia using numerical simulations. The primary cilia are modeled as elastic filaments with rotatable basal ends to mimic real ciliary deflections. How some governing parameters [i.e., the peak Reynolds number (Repeak), Womersley number (Wo), cilium length (L*), and streamwise spacing interval (Ld*)] regulate fluid–cilia interaction is explored. Our results indicate that within a certain range, both the span of deflection (SD) and the maximal curvature increase with the increase in Repeak, L*, and Ld*, while they decrease as the Wo increases. Compared with other parameters, Ld* affects ciliary deflection less significantly and its impact becomes nearly negligible when the cilia are separated over twice their length. Three typical stretch states are captured. For primary cilia with a short or medium length, an increase in the SD is accompanied by a greater propagation distance of the location of the maximal tensile stress (LMTS). However, this is not the case for long cilia that protrude into 1/3 of the lumen, as the arising third stretch state may greatly suppress the LMTS propagation. Our study further confirms the role of primary cilia in decreasing the wall shear stress (WSS) and altering its oscillating feature. The WSS decrease is more significant for cilia undergoing a larger SD and/or when Ld* is reduced. For a constant Ld*, a larger SD corresponds to a more uneven oscillatory shear index distribution, and the affected (i.e., less oscillatory) region appears to greatly depend on Ld*.
Investigation of conductivity modulation in vertical GaN-on-GaN PiN diode under high current density
Authors: Li Yanjun , Yang Shu , Ji Fengwei , Tang Xi , Sheng Kuang
Published: February 2023

This work studies the conductivity modulation in the vertical GaN-on-GaN PiN diode (PND) under high current density and its impact on surge current capability. Thanks to the direct-bandgap of GaN, the junction temperature at different current densities could be characterized by both photo-luminescence and electro-luminescence measurements. The junction temperature rises from 300 K at ∼0.1 kA/cm2 to 620 K at ∼9.0 kA/cm2 with emission peaks shifted from 3.38 to 3.21 eV. Meanwhile, the electro-thermal behavior of the vertical GaN PND shows that the hole concentration in p-GaN is increased due to self-heating, leading to enhanced conductivity modulation and negative temperature-dependence of ON-resistance, which is desirable for surge current capability. The heat accumulation in GaN under surge current condition could be suppressed by the enhanced conductivity modulation. The surge energy density can reach ∼200 J/cm2 in the GaN PND, showing the potential of vertical GaN-on-GaN power devices in the high electro-thermal-ruggedness application.
Conformation and dynamics of an active filament in crowded media
Authors: Yan Ran , Tan Fei , Wang Jingli , Zhao Nanrong
Published: February 2023

The structural and dynamical properties of active filamentous objects under macromolecular crowding have a great relevance in biology. By means of Brownian dynamics simulations, we perform a comparative study for the conformational change and diffusion dynamics of an active chain in pure solvents and in crowded media. Our result shows a robust compaction-to-swelling conformational change with the augment of the Péclet number. The presence of crowding facilitates self-trapping of monomers and, thus, reinforces the activity mediated compaction. In addition, the efficient collisions between the self-propelled monomers and crowders induce a coil-to-globulelike transition, indicated by a marked change of the Flory scaling exponent of the gyration radius. Moreover, the diffusion dynamics of the active chain in crowded solutions demonstrates activity-enhanced subdiffusion. The center of mass diffusion manifests rather new scaling relations with respect to both the chain length and Péclet number. The interplay of chain activity and medium crowding provides a new mechanism to understand the non-trivial properties of active filaments in complex environments.
Slip and jump coefficients for general gas–surface interactions according to the moment method
Authors: Li Ruo , Yang Yichen
Published: February 2023

We develop a moment method based on the Hermite series of the arbitrary order to calculate viscous-slip, thermal-slip, and temperature-jump coefficients for general gas-surface scattering kernels. Under some usual assumptions of scattering kernels, the solvability is obtained by showing the positive definiteness of the symmetric coefficient matrix in the boundary conditions. For gas flows with the Cercignani–Lampis gas–surface interaction and inverse-power-law intermolecular potentials, the model can capture the slip and jump coefficients accurately with elegant analytic expressions. On the one hand, the proposed method can apply to the cases of arbitrary order moments with increasing accuracy. On the other hand, the explicit formulas for low-order situations are simpler and more accurate than some existing results in references. Therefore, one may apply these formulas in slip and jump conditions to improve the accuracy of macroscopic fluid dynamic models for gas flows.
Long-term persistence and functionality of adoptively transferred antigen-specific T cells with genetically ablated PD-1 expression
Authors: Dötsch Sarah , Svec Mortimer , Schober Kilian , Hammel Monika , Wanisch Andreas , Gökmen Füsun , Jarosch Sebastian , Warmuth Linda , Barton Jack , Cicin-Sain Luka , D’Ippolito Elvira , Busch Dirk H.
Published: February 2023

Engagement of the inhibitory T cell receptor programmed cell death protein 1 (PD-1) associates with dysfunctional states of pathogen- or tumor-specific T cells. Accordingly, systemic antibody-mediated blockade of PD-1 has become a central target for immunotherapies but is also associated with severe toxicities due to loss of peripheral tolerance. Therefore, selective ablation of PD-1 expression on adoptively transferred T cells through direct genetic knockout (KO) is currently being explored as an alternative therapeutic approach. However, since PD-1 might also be required for the regulation of physiological T cell function and differentiation, the suitability of PD-1 as an engineering target is controversial. In this study, we systematically investigated the maintenance of T cell functionality after CRISPR/Cas9-mediated PD-1 KO in vivo during and after acute and chronic antigen encounter. Under all tested conditions, PD-1 ablation preserved the persistence, differentiation, and memory formation of adoptively transferred receptor transgenic T cells. Functional PD-1 KO T cells expressing chimeric antigen receptors (CARs) targeting CD19 could be robustly detected for over 390 d in a syngeneic immunocompetent mouse model, in which constant antigen exposure was provided by continuous B cell renewal, representing the longest in vivo follow-up of CAR-T cells described to date. PD-1 KO CAR-T cells showed no evidence for malignant transformation during the entire observation period. Our data demonstrate that genetic ablation of PD-1 does not impair functionality and longevity of adoptively transferred T cells per se and therefore may be pursued more generally in engineered T cell-based immunotherapy to overcome a central immunosuppressive axis.
The pleiotropic AMPK–CncC signaling pathway regulates the trade-off between detoxification and reproduction
Authors: Jiang Heng , Meng Xiangkun , Zhang Nan , Ge Huichen , Wei Jiaping , Qian Kun , Zheng Yang , Park Yoonseong , Reddy Palli Subba , Wang Jianjun
Published: February 2023

The association of decreased fecundity with insecticide resistance and the negative sublethal effects of insecticides on insect reproduction indicates the typical trade-off between two highly energy-demanding processes, detoxification and reproduction. However, the underlying mechanisms are poorly understood. The energy sensor adenosine monophosphate-activated protein kinase (AMPK) and the transcription factor Cap “n” collar isoform C (CncC) are important regulators of energy metabolism and xenobiotic response, respectively. In this study, using the beetle
Tribolium castaneum
as a model organism, we found that deltamethrin-induced oxidative stress activated AMPK, which promoted the nuclear translocation of CncC through its phosphorylation. The CncC not only acts as a transcription activator of cytochrome P450 genes but also regulates the expression of genes coding for ecdysteroid biosynthesis and juvenile hormone (JH) degradation enzymes, resulting in increased ecdysteroid levels as well as decreased JH titer and vitellogenin (Vg) gene expression. These data show that in response to xenobiotic stress, the pleiotropic AMPK–CncC signaling pathway mediates the trade-off between detoxification and reproduction by up-regulating detoxification genes and disturbing hormonal homeostasis.
Cyanovirin-N binds to select SARS-CoV-2 spike oligosaccharides outside of the receptor binding domain and blocks infection by SARS-CoV-2
Authors: Muñoz-Basagoiti Jordana , Monteiro Fábio Luís Lima , Krumpe Lauren R. H. , Armario-Najera Victoria , Shenoy Shilpa R. , Perez-Zsolt Daniel , Westgarth Harrison James , Villorbina Gemma , Bomfim Larissa Maciel , Raïch-Regué Dàlia , Nogueras Lara , Henrich Curtis J. , Gallemí Marçal , Moreira Filipe Romero Rebello , Torres Pascual , Wilson Jennifer , D’arc Mirela , Marfil Silvia , Herlinger Alice Laschuk , Pradenas Edwards , Higa Luiza Mendonça , Portero-Otin Manuel , Trinité Benjamin , Twyman Richard M. , Capell Teresa , Tanuri Amilcar , Blanco Julià , Izquierdo-Useros Nuria , Rech Elibio L. , Christou Paul , O’Keefe Barry R.
Published: February 2023

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped positive stranded RNA virus which has caused the recent deadly pandemic called COVID-19. The SARS-CoV-2 virion is coated with a heavily glycosylated Spike glycoprotein which is responsible for attachment and entry into target cells. One, as yet unexploited strategy for preventing SARS-CoV-2 infections, is the targeting of the glycans on Spike. Lectins are carbohydrate-binding proteins produced by plants, algae, and cyanobacteria. Some lectins can neutralize enveloped viruses displaying external glycoproteins, offering an alternative therapeutic approach for the prevention of infection with virulent β-coronaviruses, such as SARS-CoV-2. Here we show that the cyanobacterial lectin cyanovirin-N (CV-N) can selectively target SARS-CoV-2 Spike oligosaccharides and inhibit SARS-CoV-2 infection in vitro and in vivo. CV-N neutralizes Delta and Omicron variants in vitro better than earlier circulating viral variants. CV-N binds selectively to Spike with a Kd as low as 15 nM and a stoichiometry of 2 CV-N: 1 Spike but does not bind to the receptor binding domain (RBD). Further mapping of CV-N binding sites on Spike shows that select high-mannose oligosaccharides in the S1 domain of Spike are targeted by CV-N. CV-N also reduced viral loads in the nares and lungs in vivo to protect hamsters against a lethal viral challenge. In summary, we present an anti-coronavirus agent that works by an unexploited mechanism and prevents infection by a broad range of SARS-CoV-2 strains.
Metastasis from the tumor interior and necrotic core formation are regulated by breast cancer-derived angiopoietin-like 7
Authors: Yamamoto Ami , Huang Yin , Krajina Brad A. , McBirney Margaux , Doak Andrea E. , Qu Sixuan , Wang Carolyn L. , Haffner Michael C. , Cheung Kevin J.
Published: February 2023

Necrosis in the tumor interior is a common feature of aggressive cancers that is associated with poor clinical prognosis and the development of metastasis. How the necrotic core promotes metastasis remains unclear. Here, we report that emergence of necrosis inside the tumor is correlated temporally with increased tumor dissemination in a rat breast cancer model and in human breast cancer patients. By performing spatially focused transcriptional profiling, we identified angiopoietin-like 7 (Angptl7) as a tumor-specific factor localized to the perinecrotic zone. Functional studies showed that Angptl7 loss normalizes central necrosis, perinecrotic dilated vessels, metastasis, and reduces circulating tumor cell counts to nearly zero. Mechanistically, Angptl7 promotes vascular permeability and supports vascular remodeling in the perinecrotic zone. Taken together, these findings show that breast tumors actively produce factors controlling central necrosis formation and metastatic dissemination from the tumor core.
Transcranial magnetic stimulation to frontal but not occipital cortex disrupts endogenous attention
Authors: Fernández Antonio , Hanning Nina M. , Carrasco Marisa
Published: February 2023

Covert endogenous (voluntary) attention improves visual performance. Human neuroimaging studies suggest that the putative human homolog of macaque frontal eye fields (FEF+) is critical for this improvement, whereas early visual areas are not. Yet, correlational MRI methods do not manipulate brain function. We investigated whether rFEF+ or V1/V2 plays a causal role in endogenous attention. We used transcranial magnetic stimulation (TMS) to alter activity in the visual cortex or rFEF+ when observers performed an orientation discrimination task while attention was manipulated. On every trial, they received double-pulse TMS at a predetermined site (stimulated region) around V1/V2 or rFEF+. Two cortically magnified gratings were presented, one in the stimulated region (contralateral to the stimulated area) and another in the symmetric (ipsilateral) nonstimulated region. Grating contrast was varied to measure contrast response functions (CRFs) for all attention and stimulation combinations. In experiment 1, the CRFs were similar at the stimulated and nonstimulated regions, indicating that early visual areas do not modulate endogenous attention during stimulus presentation. In contrast, occipital TMS eliminates exogenous (involuntary) attention effects on performance [A. Fernández, M. Carrasco,
Curr. Biol.
 
30
, 4078–4084 (2020)]. In experiment 2, rFEF+ stimulation decreased the overall attentional effect; neither benefits at the attended location nor costs at the unattended location were significant. The frequency and directionality of microsaccades mimicked this pattern: Whereas occipital stimulation did not affect microsaccades, rFEF+ stimulation caused a higher microsaccade rate directed toward the stimulated hemifield. These results provide causal evidence of the role of this frontal region for endogenous attention.
The competence in little words
Authors: Schirm Sam , Uskokovic Budimka , Taleghani-Nikazm Carmen
Published: February 2023

L2 frameworks, such as the Common European Framework of Reference for Languages, describe expected linguistic abilities at different levels of L2 development. These frameworks, and the assessment rubrics they inform, only peripherally address how L2 speakersrespondto informings in interaction. Through responses interactants show their understanding of, and stance toward, a previous informing. In question-answer sequences in which a participant requests new information, the response to the answer may additionally reveal the questioning participant’s orientation to the answer in terms of its fit with the question. Responses to informings are thus a site of important interactional work. In our paper, we draw on the notion of ‘Interactional Competence’ and propose a conversation-analytic approach to assessing L2 speakers’ responses to elicited informings in German in question-answer sequences. We analyze L2 speakers’ use of tokens (e.g.,oh, okay, wirklich) in sequentially third position in dyadic, video-mediated everyday conversations with L1 speakers, as, in the turns following the third-position token, participants make visible their understanding of the token. We thereby attempt to describe how competent an L2 speaker’s use of a third-position token is. We end our paper by using our findings to make recommendations for language assessment frameworks and rubrics.
The p97/VCP segregase is essential for arsenic-induced degradation of PML and PML-RARA
Authors: Jaffray Ellis G. , Tatham Michael H. , Mojsa Barbara , Liczmanska Magda , Rojas-Fernandez Alejandro , Yin Yili , Ball Graeme , Hay Ronald T.
Published: February 2023

Acute Promyelocytic Leukemia is caused by expression of the oncogenic Promyelocytic Leukemia (PML)–Retinoic Acid Receptor Alpha (RARA) fusion protein. Therapy with arsenic trioxide results in degradation of PML-RARA and PML and cures the disease. Modification of PML and PML-RARA with SUMO and ubiquitin precedes ubiquitin-mediated proteolysis. To identify additional components of this pathway, we performed proteomics on PML bodies. This revealed that association of p97/VCP segregase with PML bodies is increased after arsenic treatment. Pharmacological inhibition of p97 altered the number, morphology, and size of PML bodies, accumulated SUMO and ubiquitin modified PML and blocked arsenic-induced degradation of PML-RARA and PML. p97 localized to PML bodies in response to arsenic, and siRNA-mediated depletion showed that p97 cofactors UFD1 and NPLOC4 were critical for PML degradation. Thus, the UFD1-NPLOC4-p97 segregase complex is required to extract poly-ubiquitinated, poly-SUMOylated PML from PML bodies, prior to degradation by the proteasome.
About hysteresis in Shaker: A note on Cowgill and Chanda
Authors: Villalba-Galea Carlos A.
Published: February 2023

This letter proposes an alternative explanation to the work published by Cowgill and Chanda on the nature of hysteresis in the voltage-gated, potassium-selective channel Shaker.
An 8-inch commercial aluminum nitride MEMS platform for the co-existence of Lamb wave and film bulk acoustic wave resonators
Authors: Hsu Tzu-Hsuan , Tung Shao-Siang , Huang Yan-Ming , Wu Guan-Lin , Chang Chin-Yu , Ho Yens , Chen Yung-Hsiang , Pradeep Yelehanka , Chand Rakesh , Li Ming-Huang
Published: February 2023

This work investigates a co-design approach for fundamental symmetric Lamb wave (S0) resonators (LWR) and film bulk acoustic wave resonators (FBAR) in a commercial 8-inch aluminum nitride (AlN) microelectromechanical system (MEMS) platform to enable multi-band operation. The platform utilizes surface micromachining to define local release cavities, providing an undercut-free solution for acoustic resonators to achieve a high quality factor (Q). However, being based on a standardized platform initially tailored for FBAR devices, many design considerations and trade-offs need to be investigated for the co-existence between LWR and FBAR design. Hence, to capture the optimal design window for S0 LWRs while analyzing its performance impact on existing FBARs, the electrode configuration and its thickness are thoroughly investigated by the finite element method. In this work, a 2.2 GHz FBAR, a 700 MHz S0 LWR, and a 2.19 GHz S0 Lamé LWR are demonstrated for performance evaluation across different types of devices in this platform. The measurement results revealed a baseline performance for the FBAR device with an electromechanical coupling factor (

k

t

2

) of 6.73% and Q of 3017 at 2.2 GHz, resulting in a high figure-of-merit (FoM =

k

t

2

⋅
Q

) over 200. In comparison, the 700 MHz S0 LWR exhibits a high Q of 2532 as well and a

k

t

2

of 1.1% (FoM = 27.8), while the 2.19 GHz S0 Lamé LWR also exhibits a high Q of 1752 and a

k

t

2

of 2.44% (FoM = 42.7), respectively. These performance indexes are all comparable with the current state-of-the-art, revealing the excellent potential of this AlN MEMS platform being implemented for future LWR development design or even mass production.
MEMS piezoelectric resonant microphone array for lung sound classification
Authors: Liu Hai , Barekatain Matin , Roy Akash , Liu Song , Cao Yunqi , Tang Yongkui , Shkel Anton , Kim Eun Sok
Published: February 2023

This paper reports a highly sensitive piezoelectric microelectromechanical systems (MEMS) resonant microphone array (RMA) for detection and classification of wheezing in lung sounds. The RMA is composed of eight width-stepped cantilever resonant microphones with Mel-distributed resonance frequencies from 230 to 630 Hz, the main frequency range of wheezing. At the resonance frequencies, the unamplified sensitivities of the microphones in the RMA are between 86 and 265 mV Pa−1, while the signal-to-noise ratios (SNRs) for 1 Pa sound pressure are between 86.6 and 98.0 dBA. Over 200–650 Hz, the unamplified sensitivities are between 35 and 265 mV Pa−1, while the SNRs are between 79 and 98 dBA. Wheezing feature in lung sounds recorded by the RMA is more distinguishable than that recorded by a reference microphone with traditional flat sensitivity, and thus, the automatic classification accuracy of wheezing is higher with the lung sounds recorded by the RMA than with those by the reference microphone, when tested with deep learning algorithms on computer or with simple machine learning algorithms on low-power wireless chip set for wearable applications.
Effect of simultaneous electrical and mechanical stressing on porosity of Ti3C2T
x
MXene films
Authors: Sharp Logan C , Al-Mamun Nahid Sultan , Wetherington Maxwell , Haque Aman
Published: February 2023

MXenes are atomically layered carbides and nitrides of transition metals that have potential for micro-devices applications in energy storage, conversion, and transport. This emerging family of materials is typically studied as nanosheets or ultra-thin films, for which the internal defects are mostly nanoscale flake-flake interface separation type. However, micro-devices applications would require thicker films, which exhibit very high density of microscale pores. Electrical conductivity of thicker MXenes is significantly lower than nanosheets, and the physics of defect size and density control are also different and less understood. Current art is to perform high temperature annealing to improve the electrical conductivity, which can structurally alter or degrade MXene. The key contribution of this study is a room-temperature annealing process that exploits the synergy between electrical pulses and compressive mechanical loading. Experimental results indicate over a 90% increase in electrical conductivity, which reflects a decrease in void size and density. In the absence of compressive loading, the same process resulted in a conductivity increase of approximately 75%. Analytical spectroscopy and microscopy indicated that the proposed multi-stimuli process kept the MXene composition intact while significantly decreasing the void size and density.
Developing a multi-sample acoustofluidic device for high-throughput cell aggregation
Authors: Yang Renhua , Huang Siping , Zhang Yiwen , Zhang Chao , Qian Jingui , Lam Raymond H W , Lee Joshua E-Y , Wang Zuankai
Published: February 2023

Plug-and-play acoustofluidic devices are highly promising for dexterously aggregating microparticles owing to the advantages of being contactless, label-free, and cost-efficient. Despite the extensive progress, existing acoustofluidic devices are largely limited to addressing a single sample per device, lacking the ability to address multiple samples for high-throughput operations in a single acoustofluidic device. In this work, we report a high-throughput multi-sample acoustofluidic aggregation device that enables manipulation of up to 12 samples simultaneously using a single reusable acoustic tweezer. The key design of the multi-sample acoustofluidic device lies in the utilization of a polydimethylsiloxane frame as a selective acoustic-absorbing feature to create asymmetric acoustic waves over multiple detachable superstrates in a single device. This approach is distinct from conventional strategies which mostly have involved modifying the superstrates or tuning the settings for individual superstrates. We demonstrate that the proposed acoustofluidic device can efficiently aggregate multiple samples of various compositions ranging from non-bioactive microparticles to bioactive cells, as well as a range of object sizes spanning from 0.6 µm to 13 µm. Given its merits of simplicity, cost-efficiency and high throughput, the proposed platform could be useful for biomedical applications requiring large-scale operations, such as 3D tumor spheroids and bio-sensors.
Effect of dielectric target properties on plasma surface ionization wave propagation
Authors: Morsell Joshua , Bhatt Naman , Dechant Corey , Shannon Steven
Published: February 2023

Surface ionization waves (SIWs) propagating along dielectric covered, grounded surfaces have been studied for various dielectric bulk and surface conditions; a dependence on the propagation velocity with respect to dielectric electrical thickness and near surface permittivity profiles are observed. SIWs generated by an atmospheric pressure plasma source are imaged interacting with planar dielectric surface. Surface wave velocity is obtained by tracking emission intensity as a function of time. Target dielectric thickness is varied from

d
=
0.15
−
10

mm and dielectric constant is varied from

ϵ
r

=
6.21
−
9.4

. The propagation of SIWs can be generally predicted by relating their velocity to the RC time constant of the circuit generated between the plasma and the dielectric surface, but it is found that this approximation breaks down for dielectric substrates of sufficient thickness and wave velocity becomes constant. The results show that wave velocity is stable and predictable for target thicknesses beyond a certain point determined by the permittivity of the target material. It is also shown that SIW propagation is strongly driven by the dielectric material near to the surface of the target in addition to the bulk material. The possible mechanisms driving these thickness dependent behaviors is discussed.
Theoretical studies on electronic, magnetic and optical properties of two dimensional transition metal trihalides
Authors: Basak Krishnanshu , Ghosh Mainak , Chowdhury Suman , Jana Debnarayan
Published: February 2023

Two dimensional transition metal trihalides have drawn attention over the years due to their intrinsic ferromagnetism and associated large anisotropy at nanoscale. The interactions involved in these layered structures are of van der Waals types which are important for exfoliation to different thin samples. This enables one to compare the journey of physical properties from bulk structures to monolayer counterpart. In this topical review, the modulation of electronic, magnetic and optical properties by strain engineering, alloying, doping, defect engineering etc have been discussed extensively. The results obtained by first principle density functional theory calculations are verified by recent experimental observations. The relevant experimental synthesis of different morphological transition metal trihalides are highlighted. The feasibility of such routes may indicate other possible heterostructures. Apart from spintronics based applications, transition metal trihalides are potential candidates in sensing and data storage. Moreover, high thermoelectric figure of merit of chromium trihalides at higher temperatures leads to the possibility of multi-purpose applications. We hope this review will give important directions to further research in transition metal trihalide systems having tunable band gap with reduced dimensionalities.
Topological skyrmion phases of matter
Authors: Cook Ashley M
Published: February 2023

We introduce topological phases of matter defined by skyrmions in the ground state spin—or pseudospin—expectation value textures in the Brillouin zone, the chiral and helical topological skyrmion phases of matter. These phases are protected by a symmetry present in centrosymmetric superconductors. We consider a tight-binding model for spin-triplet superconductivity in transition metal oxides and find it realizes each of these topological skyrmion phases. The chiral phase is furthermore realized for a parameter set characterizing Sr2RuO4 with spin-triplet superconductivity. We also find two types of topological phase transitions by which the skyrmion number can change. The second type occurs without the closing of energy gaps in a system described by a quadratic Hamiltonian without breaking the protecting symmetries when atomic spin–orbit coupling is non-negligible and there is a suitable additional degree of freedom. This contradicts the ‘flat band’ limit assumption important in use of entanglement spectrum and Wilson loops, and in construction of the ten-fold way classification scheme of topological phases of matter. We furthermore predict two kinds of bulk-boundary correspondence signatures—one for measurements which execute a partial trace over degrees of freedom other than spin, which yields quantized transport signatures—and a second resulting from skyrmions trapping defects with their own non-trivial topology that is discussed in a second work, which yields generalizations of unpaired Majorana zero-modes.
Resonances and antiresonances in heat generation by spin current in a quantum dot
Authors: Zhou Li-Ling , Yang Mou , Zhou Xue-Yun , Zeng Zhao–Yang
Published: February 2023

We study the heat generation in a quantum dot exposed to a rotating magnetic field and coupled to a normal lead. Both electron-phonon interaction and electron-electron interaction are considered in the dot. We show the emergence of resonances and antiresonances in the heat generation, which we attribute to constructive interference and destructive interference between phonon waves emitted from opposite spin channels in the dot.
Oxygen-vacancy-dependent high-performance α-Ga2O3 nanorods photoelectrochemical deep UV photodetectors
Authors: Qu Lihang , Ji Jie , Liu Xin , Shao Zhitao , Cui Mengqi , Zhang Yunxiao , Fu Zhendong , Huang Yuewu , Yang Guang , Feng Wei
Published: February 2023

Ga2O3 is a good candidate for deep ultraviolet photodetectors due to its wide-bandgap, good chemical, and thermal stability. Ga2O3-based photoelectrochemical (PEC) photodetectors attract increasing attention due to the simple fabrication and self-powered capability, but the corresponding photoresponse is still inferior. In this paper, the oxygen vacancy (Vo) engineering towards α-Ga2O3 was proposed to obtain high-performance PEC photodetectors. The α-Ga2O3 nanorods were synthesized by a simple hydrothermal method with an annealing process. The final samples were named as Ga2O3-400, Ga2O3-500, and Ga2O3-600 for annealing at 400 ℃, 500 ℃, and 600 ℃, respectively. Different annealing temperatures lead to different Vo concentrations in the α-Ga2O3 nanorods. The responsivity is 101.5 mA W−1 for Ga2O3-400 nanorod film-based PEC photodetectors under 254 nm illumination, which is 1.4 and 4.0 times higher than those of Ga2O3-500 and Ga2O3-600 nanorod film-based PEC photodetectors, respectively. The photoresponse of α-Ga2O3 nanorod film-based PEC photodetectors strongly depends on the Vo concentration and high Vo concentration accelerates the interfacial carrier transfer of Ga2O3-400, enhancing the photoresponse of Ga2O3-400 nanorod film-based PEC photodetectors. Furthermore, the α-Ga2O3 nanorod film-based PEC photodetectors have good multicycle, long-term stability, and repeatability. Our result shows that α-Ga2O3 nanorods have promising applications in deep UV photodetectors.
A novel Riemann–Hilbert approach via t-part spectral analysis for a physically significant nonlocal integrable nonlinear Schrödinger equation
Authors: Wu Jianping
Published: February 2023

In this paper, a novel Riemann–Hilbert (RH) approach is reported for a physically significant nonlocal integrable nonlinear Schrödinger equation. In this RH approach, the spectral analysis is performed from the t-part of the Lax pair rather than the x-part to formulate the desired RH problem. As a consequence, the resulting RH problem is determined by the t-part of the Lax pair with the x-part playing an auxiliary role. Compared with the traditional RH method, the novel RH approach in this paper has the merits that (a) the symmetry relations of the scattering data are found to be simple, (b) the general multi-soliton solutions of the equation can be easily obtained in the reflectionless cases. Additionally, to show the remarkable features of the obtained multi-soliton solutions, some special soliton dynamics are theoretically explored and then graphically illustrated by demonstrating their three-dimensional profiles.
Quaternion attention multi-scale widening network for endoscopy image super-resolution
Authors: Lin Junyu , Huang Guoheng , Huang Jun , Yuan Xiaochen , Zeng Yiwen , Shi Cheng
Published: February 2023

Objective. In the field of endoscopic imaging, Super-Resolution (SR) plays an important role in Manufactured Diagnosis, physicians and machine Automatic Diagnosis. Although many recent studies have been performed, by using deep convolutional neural networks on endoscopic SR, most of the methods have large parameters, which limits their practical application. In addition, almost all of these methods treat each channel equally based on the real-valued domain, without considering the difference among the different channels. Our objective is to design a SR model named Quaternion Attention Multi-scale Widening Network (QAMWN) for endoscopy images to address the above problem. Approach. QAMWN contains a stacked Quaternion Attention Multi-Scale Widening Block, that composed of Multi-scale Feature Widening Aggregation Module (MFWAM) and Quaternion Residual Channel Attention (QRCA). The MFWAM adopts multi-scale architecture with step-wise widening on feature channels for better feature extraction; and in QRCA, quaternion is introduced to construct Residual Channel Attention Mechanism, which obtains adaptively scales features by considering compact cross-channel interactions in the hyper-complex domain. Main results. To verify the efficacy of our method, it is performed on two public endoscopic datasets, CVC ClinicDB and Kvasir dataset. The experimental results show that our proposed method can achieve a better trade-off in model size and performance. More importantly, the proposed QAMWN outperforms previous state-of-the-art methods in both metrics and visualization. Significance. We propose a lightweight SR network for endoscopy and achieves better performance with fewer parameters, which helps in clinical diagnosis of endoscopy.
Memory efficient model based deep learning reconstructions for high spatial resolution 3D non-cartesian acquisitions
Authors: Miller Zachary , Pirasteh Ali , Johnson Kevin M
Published: February 2023

Objective. Model based deep learning (MBDL) has been challenging to apply to the reconstruction of 3D non-Cartesian MRI due to GPU memory demand because the entire volume is needed for data-consistency steps embedded in the model. This requirement makes holding even a single unroll in GPU memory difficult meaning memory efficient techniques used to increase unroll number like gradient checkpointing and deep equilibrium learning will not work well for high spatial resolution 3D non-Cartesian reconstructions without modification. Here we develop a memory efficient method called block-wise learning that combines gradient checkpointing with patch-wise training to overcome this obstacle and allow for fast and high-quality 3D non-Cartesian reconstructions using MBDL. Approach. Block-wise learning applied to a single unroll decomposes the input volume into smaller patches, gradient checkpoints each patch, passes each patch iteratively through a neural network regularizer, and then rebuilds the full volume from these output patches for data-consistency. This method is applied across unrolls during training. Block-wise learning significantly reduces memory requirements by tying GPU memory for a single unroll to user selected patch size instead of the full volume. This algorithm was used to train a MBDL architecture to reconstruct highly undersampled, 1.25 mm isotropic, pulmonary magnetic resonance angiography volumes with matrix sizes varying from 300–450 × 200–300 × 300–450 on a single GPU. We compared block-wise learning reconstructions against L1 wavelet compressed reconstructions and proxy ground truth images. Main results. MBDL with block-wise learning significantly improved image quality relative to L1 wavelet compressed sensing while simultaneously reducing average reconstruction time 38x. Significance. Block-wise learning allows for MBDL to be applied to high spatial resolution, 3D non-Cartesian datasets with improved image quality and significant reductions in reconstruction time relative to traditional iterative methods.
Unification based on the mysterious cubic-structure grouping of quarks and leptons
Authors: Mehrafarin Mohammad
Published: February 2023

We present a unification model based on the well-known but mysterious cubic-structure grouping of quarks and leptons that suggests an underlying symmetry connection deemed explainable by a unified theory. It results in an extension of the Pati-Salam model that consolidates the fermions into two sixteen-dimensional chiral representations of the gauge group. Moreover, the discrete cubic flavor symmetry arbitrarily conjectured in the literature is found here to be implied by the gauge symmetry. Furthermore, the gauge algebra also describes an eleven-dimensional spacetime decomposed into the usual spacetime and the seven-sphere, which is the manifold of unit octonions. This suggests such a spacetime is apt for embracing all elementary particles and their interactions.
Dynamic diffusion of water inside graphene-reinforced PU/PTFE coatings: A molecular dynamics approach
Authors: Sharma Amit , Sharma Sumit
Published: February 2023

Polymers are extensively used in various applications due to their excellent properties. Recently, graphene-based polymer composites have gotten significant attention due to their superior barrier properties to corrosive media. Although there are lots of experimental studies on graphene-based composites, there are very few works available at the atomistic level using molecular dynamics. The present work investigates the role of temperature on the diffusion of water and the effect of graphene-reinforcement in the polyurethane (PU) and polytetrafluoroethylene (PTFE). The results showed an increase in the diffusion at higher temperatures due to an increase in the mobility of polymeric chains at higher temperatures and hence a smooth path for the travel of water molecules. There is a significant decrease in the diffusion of water molecules in the graphene-reinforced systems when compared with neat PU and PTFE systems. The decrement in the diffusion of water in the range of 273 K to 350 K was around 79–93% for graphene-reinforce PU systems and around 58–62% in the case of graphene-reinforced PTFE systems.
Asymmetry-driven reconfigurability of magnetic vortices in hemispherical shells
Authors: Mary Anija , Edathumkandy Yadhu Krishnan , Thomas Senoy
Published: February 2023

Inhomogeneous magnetic configurations like vortices attract tremendous appeal as an emerging candidate in understanding nanoscale spin behaviours and utilizing their spin configurations for advanced technological applications. For vortex-driven practical applications, independent control and manipulation of both the circularity and polarity of the magnetic vortex is a prerequisite. In this study, we have shown that both the circularity and polarity of the magnetic vortex in an asymmetric hemispherical shell can be controlled by changing a single parameter - the direction of the in-plane external magnetic field. Furthermore, our results demonstrate the influence of geometrical asymmetry on the characteristics of magnetic vortices in ferromagnetic permalloy shells. These findings are expected to be helpful while designing vortex-based advanced technologies.