bluuebunny/crossref_metadata_2025 huggingface dataset:
An efficient and reliable service customized routing mechanism based on deep learning in IPv6 network
Authors: Wang Yufu , Wang Xingwei , Yi Bo , Huang Min
Published: August 2022

Best‐effort service model of traditional routing is gradually hard to meet the personalized demands under the rapid development of network technologies (e.g. 5G and IPv6). Therefore, service customization should be considered. In this work, a service customized routing mechanism based on deep learning in IPv6 network is proposed, which includes deep learning‐based service customization module, reliability evaluation module, and routing calculation module. The first module uses neural network to learn the complex service customization function, which can quickly output win‐win customized service strategies based on user demands. The second module can quantify the reliability of service routing paths, where not only the link status of IPv6 Neighbor Unreachable Detection (NUD) is considered, but also propose link performance weights to ensure the reliability of differentiated service performance. The third module uses the gray wolf optimization algorithm to calculate an optimal routing path to forward services with the customized strategies as the constraints and the maximum reliability and minimum cost as the goal. Finally, the mechanism is tested on the IPv6 Source Address Validation Improvement (SAVI) platform, which can reduce the execution time by 12.25% and improve the average routing reliability, user and ISP satisfaction by 9.0%, 40.45% and 7.4%, respectively.
A parametric design method of observer‐based state feedback controller for quasi‐linear systems
Authors: Gu Da‐Ke , Duan Sheng , Liu Yin‐Dong
Published: August 2022

This paper designs an observer‐based feedback controller for quasi‐linear systems when the entire state vector is unavailable for measurement. First, based on the solution of a type of generalised Sylvester equations, general complete parameterisation of the full‐order observer is proposed. Second, the traditional separation principle is applied to the quasi‐linear systems. In other words, the design of a state feedback and the design of a state observer can be carried out independently. Further, general complete parameterisation of the state feedback controller is also established. Finally, numerical examples and simulations are adopted to verify the effectiveness of the proposed method.
Visual navigation system for generator stator wedge inspection mobile robot
Authors: Jeon BongKyu , Seo Ju‐hwan , Park Jong‐chan , Kwon Dong‐Soo
Published: August 2022

Stator wedge tightness inspection is one of the most important periodic inspections carried out on required for large‐capacity generators. The traditional wedge tightness inspection method enforces inspectors to enter the narrow and uncomfortable inner space of a stator. As an alternative, a wedge tightness inspection mobile robot is developed. This robot has a robotic arm with a wedge tightness test module. A visual navigation system using two cameras is proposed. The proposed system controls the driving of the robot in a stator by using line detection of the bottom view camera image. The system also detects wedges and assigns a location number to them by using the inspection view camera image and an object detector based on a convolutional neural network. The detected wedges are tracked using robot motion to assign location numbers to the new wedges. The inspection points are then determined using the length and position of the detected wedges. The experimental results conducted on the stator testbed demonstrate the potential applicability of the proposed system.
ISM metallicity variations across spiral arms in disk galaxies
Authors: Khoperskov S. , Sivkova E. , Saburova A. , Vasiliev E. , Shustov B. , Minchev I. , Walcher C. J.
Published: August 2022

Chemical abundance variations in the interstellar medium provide important information about the galactic evolution, star-formation, and enrichment histories. Recent observations of disk galaxies suggest that if large-scale azimuthal metallicity variations appear in the ISM, they are linked to the spiral arms. In this work, using a set of chemodynamical simulations of the Milky Way-like spiral galaxies, we quantify the impact of gas radial motions (migration) in the presence of a pre-existing radial metallicity gradient and the local ISM enrichment on both global and local variations of the mean ISM metallicity in the vicinity of the spiral arms. In all the models, we find the scatter of the gas metallicity of ≈0.04 − 0.06 dex at a given galactocentric distance. On large scales, we observe the presence of spiral-like metallicity patterns in the ISM which are more prominent in models with the radial metallicity gradient. However, in our simulations, the morphology of the large-scale ISM metallicity distributions significantly differs from the spiral arm structure in stellar and gas components resulting in both positive and negative residual (after subtraction of the radial gradient) metallicity trends along spiral arms. We discuss the correlations of the residual ISM metallicity values with the star formation rate, gas kinematics and offset to the spiral arms, concluding that the presence of a radial metallicity gradient is essential for the azimuthal variations of metallicity. At the same time, the local enrichment alone is unlikely to drive systematic variations of the metallicity across the spirals.
La chiralité en physique des particules
Authors: Abada Asmaa , Descotes-Genon Sébastien
Published: August 2022

En physique des particules, la chiralité permet de caractériser les particules fondamentales de spin 1/2 qui constituent la matière : d’une part les quarks, d’autre part les leptons. Dans le cadre du Modèle Standard, une seule interaction fondamentale, l’interaction faible, distingue les chiralités gauche et droite. Cela a des conséquences expérimentales profondes et très différentes pour les quarks et les leptons, concernant d’une part, l’asymétrie entre matière et antimatière et d’autre part, la nature et la masse des neutrinos.
Vers une mesure de la brisure de la parité dans les molécules
Authors: Darquié Benoît
Published: August 2022

Le vivant n’a sélectionné qu’une seule des deux formes, droite ou gauche, de molécules chirales aussi essentielles que les acides aminés ou les sucres. Les causes de cette asymétrie restent un mystère mais, d’après les prédictions théoriques, l’interaction nucléaire faible serait à l’origine d’une infime différence d’énergie entre les deux formes. Les enjeux relatifs à une première mesure de cette différence d’énergie sont présentés ici. Cette mesure apporterait une lumière précieuse sur un sujet qui touche à la fois à l’origine de la vie et à la physique fondamentale.
Enhancing the Follow-up Assessment of Very Preterm Children with
Regard to 5-Year IQ Considering Socioeconomic Status
Authors: Hoberg Kathrin , Häusler Martin , Orlikowsky Thorsten , Lidzba Karen
Published: August 2022

Background Specifying peri- and postnatal factors in children born very
preterm (VPT) that affect later outcome helps to improve long-term
treatment.

Aim To enhance the predictability of 5-year cognitive outcome by
perinatal, 2-year developmental and socio-economic data. Subjects and outcome
measures: 92 VPT infants, born 2007–2009, gestational age<32
weeks and/or birthweight of 1500 g, were assessed longitudinally
including basic neonatal, socio-economic (SES), 2-year Mental Developmental
Index (MDI, Bayley Scales II), 5-year Mental Processing Composite (MPC,
Kaufman-Assessment Battery for Children), and Language Screening for
Preschoolers data. 5-year infants born VPT were compared to 34 term
controls.

Results The IQ of 5-year infants born VPT was 10 points lower than that of
term controls and influenced independently by preterm birth and SES. MDI, SES,
birth weight and birth complications explained 48% of the variance of
the MPC. The MDI proved highly predictive (r=0.6,
R2=36%) for MPC but tended to underestimate the cognitive
outcome. A total of 61% of the 2-year infants born VPT were already
correctly classified (specificity of .93, sensitivity of .54). CHAID decision
tree technique identified SES as decisive for the outcome for infants born VPT
with medium MDI results (76–91): They benefit from effects associated to
a higher SES, while those with a poor MDI outcome and a birth
weight≤890 g do not.

Conclusion Developmental follow-up of preterm children enhances the
quality of prognosis and later outcome when differentially considering perinatal
risks and SES.
A Dose-Limited Dexamethasone and Bubble Continuous Positive Airway Pressure in Ventilation-Dependent Extremely Premature Infants
Authors: Mohamed Mohamed A. , Bergman Aaron , Abdelatif Dinan , Massa-Buck Beri
Published: August 2022

Objective Dexamethasone has been associated with early extubation and shorter duration of mechanical ventilation in preterm infants. High doses or prolonged courses of dexamethasone may be associated with poor neurodevelopmental outcomes.

Study Design This is an observational cohort study assessing the efficacy of a low-dose short dexamethasone course combined with postextubation bubble continuous positive airway pressure (bCPAP) strategy on rates of successful extubation and reduction of the duration of invasive mechanical ventilation in extremely preterm infants. We compared the short-term outcomes of implementing such strategy on a group of infants with birth weight <750 g to a historical cohort.

Results Among infants intubated for at least 10 days, median time to extubation from starting the dexamethasone course was 2 days (interquartile range: 1–3). Total duration of intubation was significantly shorter in infants who received dexamethasone compared with the control groups (21 ± 6 vs. 30 ± 10 days, p = 0.03), and although statistically nonsignificant, duration to wean to 21% bCPAP was shorter compared with the control group (48 ± 13 vs. 74 ± 29 days, p = 0.06).

Conclusion A low-dose short dexamethasone course combined with postextubation bCPAP intervention may be associated with successful early extubation and shorter duration of mechanical ventilation.

Key Points
Framing effect method in vaccination status discrimination research
Authors: Gurevich Lyubov
Published: August 2022

According to Chong and Druckman (J Commun 57:99–118 2007), the “framing effect” is a phenomenon that occurs when even small changes in an issue’s representation cause large changes in people’s opinions. Being a cognitive bias, the framing effect encourages people to disregard their own viewpoints and decide in favour of options, represented in surveys (or articles) with positive or negative connotations. It leads to misrepresentation of findings, which contravenes the accuracy of scientific research. This paper intends to analyse the frame “Discrimination” in relation to the cases of public health (namely vaccination status discrimination) in order to find out which frame dimensions and options can influence people’s opinions on these issues, and to which extent these perspectives can be liable to changes due to the framing effect method. The analysis of social discrimination cases demonstrates how different manipulative technologies form a negative opinion towards the out-group members in public.
Breath monitoring, sleep disorder detection, and tracking using thin-film acoustic waves and open-source electronics
Authors: Vernon Jethro , Canyelles-Pericas Pep , Torun Hamdi , Binns Richard , Ng Wai Pang , Wu Qiang , Fu Yong-Qing
Published: August 2022

Apnoea, a major sleep disorder, affects many adults and causes several issues, such as fatigue, high blood pressure, liver conditions, increased risk of type II diabetes, and heart problems. Therefore, advanced monitoring and diagnosing tools of apnoea disorders are needed to facilitate better treatment, with advantages such as accuracy, comfort of use, cost effectiveness, and embedded computation capabilities to recognise, store, process, and transmit time series data. In this work we present an adaptation of our apnoea-Pi open-source surface acoustic wave (SAW) platform (Apnoea-Pi) to monitor and recognise apnoea in patients. The platform is based on a thin-film SAW device using bimorph ZnO and Al structures, including those fabricated as Al foils or plates, to achieve breath tracking based on humidity and temperature changes. We applied open-source electronics and provided embedded computing characteristics for signal processing, data recognition, storage, and transmission of breath signals. We show that the thin-film SAW device out-performed standard and off-the-shelf capacitive electronic sensors in terms of their response and accuracy for human breath-tracking purposes. This in combination with embedded electronics makes a suitable platform for human breath monitoring and sleep disorder recognition.
Including effects of coastal terrain increases wind farm power output, improves wake recovery
Authors: Frank Jodi Ackerman
Published: August 2022

Large-eddy simulations show need to consider land influence on nearshore offshore wind farms.
Peering into the optical properties of tunable window technology
Authors: Piccone Ashley
Published: August 2022

Microscopic structural changes in windows can modulate the amount of heat and light throughput, but optimal application requires an in-depth understanding of the material’s optical properties.
High spatial resolution and contrast radiography of hydrodynamic instabilities at the National Ignition Facility
Authors: Do A. , Angulo A. M. , Nagel S. R. , Hall G. N. , Bradley D. K. , Hsing W. W. , Pickworth L. A. , Izumi N. , Robey H. F. , Zhou Y.
Published: August 2022

We are developing techniques for studying the Rayleigh–Taylor (RT) and Richtmyer–Meshkov (RM) instabilities in a planar geometry at high-energy-densities at the National Ignition Facility (NIF). In particular, through the improvement of experimental imaging quality, we are progressing toward the study of the turbulent regime of the mixing regions in capsule implosion experiments for inertial confinement fusion, which requires few micrometers resolution. Using 60 NIF beams, a solid shock tube is driven launching a shock wave that crosses the interface between a dense and a light material pre-machined in the target to obtain sinusoidal ripples, which results in RM and RT instabilities that are imaged using the NIF Crystal Backlighter Imager. High-quality images were obtained with a mean resolution of 7 μm and improved contrast. While the obtained resolution does not allow the observation of the smallest scale of the “turbulent” energy spectrum, the generated image encompasses 63% of the total flow energy, a 50% improvement over previous studies, which is observed for the first time a roll-up feature in a high energy density-type RT experiment.
Kagome network with vertex coupling of a preferred orientation
Authors: Baradaran Marzieh , Exner Pavel
Published: August 2022

We investigate spectral properties of periodic quantum graphs in the form of a kagome or a triangular lattice in the situation when the condition matching the wave functions at lattice vertices is chosen of a particular form violating the time-reversal invariance. The positive spectrum consists of an infinite number of bands, some of which may be flat; the negative one has at most three and two bands, respectively. The kagome lattice example shows that even in graphs with such an uncommon vertex coupling, spectral universality may hold: if its edges are incommensurate, the probability that a randomly chosen positive number is contained in the spectrum is ≈0.639.
Enhanced growth and properties of non-catalytic GaAs nanowires via Sb surfactant effects
Authors: Ajay A. , Jeong H. , Schreitmüller T. , Döblinger M. , Ruhstorfer D. , Mukhundhan N. , Koolen P. A. L. M. , Finley J. J. , Koblmüller G.
Published: August 2022

We report the effects of antimony (Sb) surfactant on the growth and correlated structural and optical properties of non-catalytic GaAs nanowires (NW) grown by selective area epitaxy on silicon. Strong enhancements in the axial growth with very high aspect ratio up to 50 are observed by the addition of small traces of Sb (1%–2%), contrasting the commonly reported growth limiting behavior of Sb in GaAs(Sb) NWs. The Sb surfactant effect modifies the growth facet structure from a pyramidal-shaped growth front terminated by {1–1–0} planes to a flat (111)B growth plane, that is even further improved by the presence of Si co-dopants. Additional benefits are seen by the substantial change in microstructure, from a heavily defected layer stacking in Sb-free GaAs NWs to a twinned phase-pure zinc blende structure in Sb-mediated GaAs(Sb) NWs. We directly confirm the impact of the altered microstructure on the optical emission and carrier recombination dynamics via observation of long, few-ns carrier lifetimes in the GaAs(Sb) NWs using steady-state and time-resolved photoluminescence spectroscopy.
Optimization of linearity at high electrical field for dual threshold coupling AlGaN/GaN HEMT applied in Ka-band applications
Authors: Wang Peng-Fei , Mi Min-Han , Du Xiang , Zhou Yu-Wei , Liu Jie-Long , Chen Zhi-Hong , An Si-Rui , Chen Yi-Lin , Zhu Jie-Jie , Zheng Xue-Feng , Ma Xiao-Hua , Hao Yue
Published: August 2022

In this work, a high linearity AlGaN/GaN HEMT integrated dual threshold coupling (DT) technology and Schottky–Ohmic drain (SOD) were fabricated and analyzed. Since the architecture of DT synthesized planar- and recess-HEMT periodically along the gate width, SOD alleviated the peak electric field (E-field) around the gate region and the peak transconductance (Gm-max) of 248 mS/mm with the associated transconductance plateau of ∼4.0 V at Vds = 28 V was obtained, which is evidently flatter than that of HEMT without the SOD structure. Attributed to the improved Gm linearity at high E-field, the DT-SOD HEMT exhibits the predicted linearity figure of merit of 5–13 dB when biased at class AB operation, which is ∼10 dB higher than that of DT-HEMT. Moreover, the fabricated device yields a nearly constant fT/fmax of 47/118 GHz over a wide gate voltage, and load-pull measurements at 30 GHz reveal that these devices deliver output power density (Pout) of 7.8 W/mm with the associated 1-dB compression point (P1dB) of 28.5 dBm at Vds = 28 V. The experimental results indicate that the employment of DT technology and SOD structure is an attractive approach to enhance the linearity at high E-field for millimeter wave devices.
A large anomalous Hall conductivity induced by Weyl nodal lines in Fe70Al30
Authors: Lv Bing , Liu Pei , Wang Yongzuo , Gao Cunxu , Si Mingsu
Published: August 2022

Materials with one-dimensional Weyl nodal lines are attracting much attention because of rich exotic properties. In this work, based on the first-principles calculations, we predict the existence of Weyl nodal lines in Fe70Al30. A large intrinsic anomalous Hall conductivity is calculated to be −374 S/cm, which stems from the net Berry curvature induced by Weyl nodal lines. To confirm our calculated results, high quality Fe70Al30 has been prepared and did possess a large anomalous Hall conductivity, where the intrinsic Berry curvature plays a role.
A Perspective on microneedle sensor arrays for continuous monitoring of the body's chemistry
Authors: Freeman D. M. E. , Cass A. E. G.
Published: August 2022

Recent advances in the field of microneedle devices are having an impact on both diagnostic and therapeutic approaches to sustaining healthy populations globally. Whether this is for improving drug and vaccine efficacy or for continuous sensing of key molecular indicators, the past five years have seen increased activity in both the academic and commercial sectors. In this Perspective, we focus on solid microneedle biosensors and discuss the advantages of these devices over alternative clinical diagnostic platforms as well as the technical challenges presented. We will emphasize how their use in continuous measurement of molecules in vivo is made possible with a minimally invasive technique that is simple to perform. This Perspective describes the function and current state of microneedle sensor arrays for the in vivo measurement of both endogenous molecules such as glucose and lactate and drugs such as penicillin.
Conductive mechanism in memristor at the thinnest limit: The case based on monolayer boron nitride
Authors: Li Xiao-Dong , Chen Nian-Ke , Wang Bai-Qian , Li Xian-Bin
Published: August 2022

Atomic picture and electronic transport property are taken into account to investigate the nonvolatile resistive switching mechanism of a memristor at the thinnest limit, just based on one monolayer hexagonal boron nitride (h-BN). It is demonstrated that the intrinsic van der Waals gaps between electrodes and monolayer h-BN ensure the high resistance state (HRS). However, the absorption/desorption of a metallic-electrode atom on the one side of the h-BN can hardly switch the device to hold the experimentally observed ON/OFF current ratio. It is proposed that the electrode atom should penetrate the h-BN sheet via boron vacancy (VB) to form a full conductive atomic filament for an effective low resistance state. The current signal of this VB pinning Au conductive filament can reach up to three orders of magnitude higher than that of the HRS. The energy barrier for one Au atom to pass through VB is also reasonably as low as 0.832 eV. Molecular dynamics simulation further manifests the nonvolatility of this atomic conductive filament at the limit that could even maintain stability at 500 K. This work offers a key working picture in memristors at their thinnest limit, which provides a valuable reference to the development of emerging memory/computing devices at the ultrathin scale.
Theoretical investigation of charged vacancies and clusters in UXO2 (X = La, Ce, Pu, Am)
Authors: Bouchet J. , Dianzinga R. M. , Jomard G.
Published: August 2022

We present our ab initio study of UXO2 (X = La, Ce, Pu, Am) compounds. Depending on the ionization of the associated element, trivalent or tetravalent, either uranium stays tetravalent as in UO2 or it is pentavalent to compensate the charge. We study the evolution of the lattice parameter as a function of X content and in the presence of oxygen vacancies. We also calculate the formation energies of several vacancy defects and show that depending of the ionic state of X the most stable charge state can be either positive (tetravalent: Ce, Pu) or negative (trivalent: La, Am). We also consider the positron lifetime in the presence of these vacancies and we show that it is almost independent of the doping element and its amount. For uranium vacancies, the positron is always trapped, while for oxygen vacancies, the trapping seems to depend on the surrounding cation oxidation states. Finally, we show that different defects have similar positron lifetimes, resulting in extremely difficult defect identification with dedicated experimental studies as the positron annihilation spectroscopy.
Intrinsic electron transport in monolayer MoSi2N4 and WSi2N4
Authors: Li Chunhui , Cheng Long
Published: August 2022

We systematically studied the intrinsic electron transport of the recently fabricated two-dimensional (2D) monolayer MoSi2N4 and WSi2N4 (belong to the MA2Z4 family, where M is a transition metal; A is Si or Ge; and Z is N, P, or As) by using the Boltzmann transport theory with the scattering rates calculated from first-principles calculations. It is found that both materials have moderate room temperature electron mobility of 87 cm2/V s for MoSi2N4 and 119 cm2/V s for WSi2N4. Our detailed analysis shows that their electron mobility difference is attributed to the different average effective mass. Moreover, by comparing studies with monolayer MoS2 and WS2, we reveal that the polar optical phonon pattern of MoSi2N4 and WSi2N4 is governed by the antiparallel silicon–nitrogen bond oscillation, different from MoS2 and WS2, in which is governed by the antiparallel transition metal–sulfur bond oscillation. This feature is arising from the large electronegativity difference between N and Si. Nitrogen has the fourth largest electronegativity, so it always tends to attract plenty of electrons from Si and thus Si has a large Born effective charge, thereby resulting in strong Fröhlich interaction. We further found that all the 2D semiconducting MA2Z4 have large Born effective charges, thereby indicating a generally strong electron–phonon coupling strength.
Single molecule DNA origami nanoarrays with controlled protein orientation
Authors: Cervantes-Salguero K. , Freeley M. , Gwyther R. E. A. , Jones D. D. , Chávez J. L. , Palma M.
Published: August 2022

The nanoscale organization of functional (bio)molecules on solid substrates with nanoscale spatial resolution and single-molecule control—in both position and orientation—is of great interest for the development of next-generation (bio)molecular devices and assays. Herein, we report the fabrication of nanoarrays of individual proteins (and dyes) via the selective organization of DNA origami on nanopatterned surfaces and with controlled protein orientation. Nanoapertures in metal-coated glass substrates were patterned using focused ion beam lithography; 88% of the nanoapertures allowed immobilization of functionalized DNA origami structures. Photobleaching experiments of dye-functionalized DNA nanostructures indicated that 85% of the nanoapertures contain a single origami unit, with only 3% exhibiting double occupancy. Using a reprogrammed genetic code to engineer into a protein new chemistry to allow residue-specific linkage to an addressable ssDNA unit, we assembled orientation-controlled proteins functionalized to DNA origami structures; these were then organized in the arrays and exhibited single molecule traces. This strategy is of general applicability for the investigation of biomolecular events with single-molecule resolution in defined nanoarrays configurations and with orientational control of the (bio)molecule of interest.
Molecular dynamics study on spallation fracture in single crystal and nanocrystalline tin
Authors: Yang Xin , Zhao Han , Gao Xuejun , Chen Zhenlin , Zeng Xiangguo , Wang Fang
Published: August 2022

Spallation fracture in ductile metals with low melting points is an important scientific concern of dynamic fracture. Classical spallation and micro-spallation simulations of single crystal (SC) and nanocrystalline (NC) tin were carried out using non-equilibrium molecular dynamics at shock pressures of 13.5–61.0 GPa. The shock wave velocity had no effect on the waveform evolution in the SC Sn but not in the NC Sn. The front width of the stress wave in the classical spallation of the NC Sn was predominantly affected by grain boundary sliding. The atomic trajectory technique was first introduced to reproduce the evolutionary processes of void growth and coalescence quite effectively. In the classical spallation, the differences in void evolution behavior of SC and NC Sn were mainly reflected in nucleation position, spatial distribution, and growth zone, while their evolutionary behaviors were shared in the micro-spallation. In the NC model, for the classic spallation, voids mostly nucleated at grain boundaries and grew along grain boundaries, resulting in intergranular fractures; for the micro-spallation, voids nucleated at the grain boundary and inside the grain, resulting in intergranular, intragranular, and transgranular fractures. Furthermore, the void volume fraction followed the bilinear rise at the early nucleation and growth stages, and the critical transition point fundamentally signified the initiation of void nucleation to growth.
Atomic-scale characterization of structural damage and recovery in Sn ion-implanted β-Ga2O3
Authors: Yoo Timothy , Xia Xinyi , Ren Fan , Jacobs Alan , Tadjer Marko J. , Pearton Stephen , Kim Honggyu
Published: August 2022

β-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of β-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of β-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted β-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic β-phase to the defective cubic spinel γ-phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the γ-Al2O3, which has the same space group as β-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 ⟨110⟩ type in cubic structure. We show that post-implantation annealing at 1100 °C under the N2 atmosphere effectively recovers the β-phase; however, nano-sized voids retained within the β-phase structure and a γ-phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of β-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability.
Universal predictability of large avalanches in the Manna sandpile model
Authors: Shapoval Alexander , Savostianova Dayana , Shnirman Mikhail
Published: August 2022

Substantiated explanations of the unpredictability regarding sandpile models of self-organized criticality (SOC) gave way to efficient forecasts of extremes in a few models. The appearance of extremes requires a preparation phase that ends with general overloading of the system and spatial clustering of the local stress. Here, we relate the predictability of large events to the system volume in the Manna and Bak–Tang–Wiesenfeld sandpiles, which are basic models of SOC. We establish that in the Manna model, the events located to the right of the power-law segment of the size-frequency relationship are predictable and the prediction efficiency is described by the universal linear dependence on the event size scaled by a power-law function of the lattice volume. Our scaling-based approach to predictability contributes to the theory of SOC and may elucidate the forecast of extremes in the dynamics of such systems with SOC as neuronal networks and earthquakes.
Mechanism of reverse gate leakage current reduction in AlGaN/GaN high-electron-mobility-transistor after 3-MeV proton irradiation
Authors: Sun Chang-Hao , Peng Chao , Zhang Zhan-Gang , Wang Jin-Bin , Yue Shao-Zhong , Zhang Hong , Chen Zi-Wen , Ou-Yang Xiao-Ping , Lei Zhi-Feng , Zhong Xiang-Li
Published: August 2022

A 3-MeV proton irradiation experiment was carried out on an AlGaN/GaN high-electron-mobility-transistor (HEMT). The results showed that the device's saturation drain current decreased, the threshold voltage drifted positively, and the maximum transconductance decreased after irradiation. Interestingly, the forward gate leakage current was almost unchanged, and the reverse gate leakage current was reduced by two orders of magnitude. We found that this experimental phenomenon can be well explained by the Poole–Frenkel emission model. Proton irradiation led to deeper defect energy levels and higher defect concentrations of the device. Deeper defect energy levels made it more difficult for electrons to be excited from the trap state into the conduction band. Thus, the reverse gate leakage current decreased. Higher defect concentrations led to degradation of the output and transfer curves of the device. The deep level transient spectroscopy characterization defect further proved the correctness of this model. The reduction in the reverse gate leakage current had a positive impact on AlGaN/GaN HEMT devices in high power or high frequency applications.
Out-of-plane longitudinal sound velocity in SnS2 determined via broadband time-domain Brillouin scattering
Authors: Cheng Meixin , Pichugin Kostyantyn , Maas André , Schleberger Marika , Sciaini Germán
Published: August 2022

Here, we report time-resolved broadband transient reflectivity measurements performed in a single crystal of SnS2. We made use of time-domain Brillouin scattering and a broadband probe to measure the out-of-plane longitudinal sound velocity, υL=(2950±100)ms–1, in this semiconducting two-dimensional metal dichalcogenide. Our study illustrates the potential of this non-invasive all-optical pump–probe technique for the study of the elastic properties of transparent brittle materials and provides the value of the elastic constant c33=(39±3)GPa.
Flow transition on the suction surface of a controlled-diffusion compressor blade using a large-eddy simulation
Authors: Katiyar S. , Sarkar S.
Published: August 2022

Separation-induced transition is discussed here on a suction surface of a controlled-diffusion compressor blade using a large eddy simulation, where the Reynolds number based on the chord is 210 000. The filtered, incompressible Navier–Stokes and energy equations in the covariant form are solved with second-order spatial and temporal accuracy, where the subgrid stress tensor and temperature flux are assessed by a dynamic model. Flow features are resolved with appreciable accuracy, exhibiting a separation bubble on the suction surface in the vicinity of mid-chord. Excitation of the shear layer is evident with the evolution of Kelvin–Helmholtz (K–H) rolls, depicting amplification of the selective frequency in the first half of the bubble, where the normalized shedding frequency based on the momentum thickness at the point of separation becomes 0.011. The secondary instability appears in the second half of the bubble, which is attributed to the spanwise deformation of K–H rolls. This leads to significant growth of perturbations in the braid region, resulting in breakdown near reattachment. In brief, outer shear layer activities are initiated via inviscid instability, while the near-wall region might be susceptible to the viscous effect in the second half with increasing levels of velocity fluctuations, production, and wall-normal turbulent heat flux. The validity of the universal intermittency curve also bears evidence of a significant viscous effect. The instantaneous temperature contours closely follow the vorticity field, illustrating a strong correlation between species and momentum transport.
Explosive breakup and evolution of the thermal boundary layer around a pulse-heated microwire in sub- and supercritical CO2
Authors: Wang Gaoyuan , Hu Zhan-Chao
Published: August 2022

This paper reports our experimental findings aimed to understand the importance of compressibility in fluid flow and heat transfer. A platinum microwire of diameter 50 μm was immersed in a pressure vessel filled with CO2 at different thermodynamic states around the critical point. The microwire was heated by an electric pulse resulting in a temperature rise of about 667 K during 0.35 ms. The snapshots of CO2 and the temporal profiles of mean temperature of the microwire were recorded. An explosive breakup of the thermal boundary layer is identified, manifested by a radial spreading fluid layer with a “fluffy” boundary. Since buoyancy can only drive upward motions, such a phenomenon is closely related to compressibility, as a result of complex interactions between thermoacoustic waves and large-density-gradient interfaces. This phenomenon is also responsible for the efficient cooling observed in the first 10 ms because expansion is a cooling process and can also help to evacuate high-temperature fluid. Afterward, the flow exhibits various buoyancy-driven patterns depending on the existence and intensity of surface tension: garland-like cluster, unstable gas column, or normal bubble, followed by a continuously thinning thermal boundary layer. Both the classic and the newly revised thermodynamic phase diagrams are employed and compared in this paper, suggesting the latter is proper and informative.
Interaction of molecular nitrogen with vanadium oxide in the absence and presence of water vapor at room temperature: Near-ambient pressure XPS
Authors: Balogun K. , Chukwunenye P. , Anwar F. , Ganesan A. , Adesope Q. , Willadsen D. , Nemšák S. , Cundari T. R. , Bagus P. S. , D’Souza F. , Kelber J. A.
Published: August 2022

Interactions of N2 at oxide surfaces are important for understanding electrocatalytic nitrogen reduction reaction (NRR) mechanisms. Interactions of N2 at the polycrystalline vanadium oxide/vapor interface were monitored at room temperature and total pressures up to 10−1 Torr using Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS). The oxide film was predominantly V(IV), with V(III) and V(V) components. XPS spectra were acquired in environments of both pure N2 and equal pressures of N2 and H2O vapor. In pure N2, broad, partially resolved N1s features were observed at binding energies of 401.0 and 398.7 eV, with a relative intensity of ∼3:1, respectively. These features remained upon subsequent pumpdown to 10−9 Torr. The observed maximum N surface coverage was ∼1.5 × 1013 cm−2—a fraction of a monolayer. In the presence of equal pressures of H2O, the adsorbed N intensity at 10−1 Torr is ∼25% of that observed in the absence of H2O. The formation of molecularly adsorbed H2O was also observed. Density functional theory-based calculations suggest favorable absorption energies for N2 bonding to both V(IV) and V(III) cation sites but less so for V(V) sites. Hartree–Fock-based cluster calculations for N2–V end-on adsorption show that experimental XPS doublet features are consistent with the calculated shake-up and normal, final ionic configurations for N2 end-on bonding to V(III) sites but not V(IV) sites. The XPS spectra of vanadium oxide transferred in situ between electrochemical and UHV environments indicate that the oxide surfaces studied here are stable upon exposure to the electrolyte under NRR-relevant conditions.
Trapped-particle microrheology of active suspensions
Authors: Peng Zhiwei , Brady John F.
Published: August 2022

In microrheology, the local rheological properties, such as the viscoelasticity of a complex fluid, are inferred from the free or forced motion of embedded colloidal probe particles. Theoretical machinery developed for forced-probe microrheology of colloidal suspensions focused on either constant-force (CF) or constant-velocity (CV) probes, while in experiments, neither the force nor the kinematics of the probe is fixed. More importantly, the constraint of CF or CV introduces a difficulty in the meaningful quantification of the fluctuations of the probe due to a thermodynamic uncertainty relation. It is known that, for a Brownian particle trapped in a harmonic potential well, the product of the standard deviations of the trap force and the particle position is dkBT in d dimensions, with kBT being the thermal energy. As a result, if the force (position) is not allowed to fluctuate, the position (force) fluctuation becomes infinite. To allow the measurement of fluctuations in theoretical studies, in this work, we consider a microrheology model in which the embedded probe is dragged along by a moving harmonic potential so that both its position and the trap force are allowed to fluctuate. Starting from the full Smoluchowski equation governing the dynamics of N hard active Brownian particles, we derive a pair Smoluchowski equation describing the dynamics of the probe as it interacts with one bath particle by neglecting hydrodynamic interactions among particles in the dilute limit. From this, we determine the mean and the variance (i.e., fluctuation) of the probe position in terms of the pair probability distribution. We then characterize the behavior of the system in the limits of both weak and strong trap. By taking appropriate limits, we show that our generalized model can be reduced to the well-studied CF or CV microrheology models.
Effect of geometric disorder on chaotic viscoelastic porous media flows
Authors: Chauhan A. , Gupta S. , Sasmal C.
Published: August 2022

Many practical applications, such as enhanced oil recovery or groundwater remediation, encounter the flow of viscoelastic fluids in porous media. Once the flow rate exceeds a critical value in such flows, an elastic instability with a fluctuating flow field is observed, which ultimately transits to a more chaotic and turbulence-like flow structure as the flow rate further increases. In this study, we present an extensive numerical investigation of the viscoelastic fluid flows in a model porous media consisting of a microchannel with many micropillars placed in it by considering both their initial staggered and aligned configurations. Within the present range of conditions encompassed in this study, we find that the geometric disorder always increases the chaotic fluctuations irrespective of the initial arrangement of micropillars. We propose that it is due to the formation of preferential paths or lanes and the formation of highly curved streamlines, which results in the local stretching of polymer molecules and, hence, significant origin in the local elastic stresses. We further show that this chaotic flow behavior strongly depends on the competitive influence between the strain-hardening and shear-thinning behaviors of a viscoelastic fluid, which again strongly depends on the polymer extensibility parameter, polymer viscosity ratio, and geometric disorder parameter. In particular, we show that the strain-hardening behavior of a viscoelastic fluid promotes these chaotic fluctuations, whereas the shear-thinning behavior tends to suppress these. Therefore, it is not a general phenomenon that can always be seen in the flows of a viscoelastic fluid in porous media.
Photoinduced charge transfer in the Zn-methanol cation studied with selected-ion photofragment imaging
Authors: Rittgers Brandon M. , Marks Joshua H. , Kellar Douglas J. , Duncan Michael A.
Published: August 2022

The Zn+(methanol) ion molecule complex produced by laser vaporization is studied with photofragment imaging at 280 and 266 nm. Photodissociation produces the methanol cation CH3OH+ via excitation of a charge-transfer excited state. Surprisingly, excitation of bound excited states produces the same fragment via a curve crossing prior to separation of products. Significant kinetic energy release is detected at both wavelengths with isotropic angular distributions. Similar experiments are conducted on the perdeuterated methanol complex. The Zn+ cation is a minor product channel that also exhibits significant kinetic energy release. An energetic cycle using the ionization energies of zinc and methanol together with the kinetic energy release produces an upper limit on the Zn+-methanol bond energy of 33.7 ± 4.2 kcal/mol (1.46 ± 0.18 eV).
Vibration assisted glass-formation in zeolitic imidazolate framework
Authors: Peng Si-Xu , Yin Zheng , Zhang Tao , Yang Qun , Yu Hai-Bin , Zeng Ming-Hua
Published: August 2022

A new glass forming method is essential for broadening the scope of liquid and glassy metal–organic frameworks due to the limitations of the conventional melt-quenching method. Herein, we show that in situ mechanical vibration can facilitate the framework melting at a lower temperature and produce glassy metal–organic frameworks (MOFs) with unique properties. Using zeolitic imidazolate framework (ZIF)-62 as a concept-proofing material, in situ mechanical vibration enables low-temperature melting at 653 K, far below its melting point (713 K). The resultant vibrated ZIF-62 glass exhibited a lower glass transition temperature of 545 K, improved gas accessible porosity, and pronounced short-to-medium range structures compared to the corresponding melt-quenched glass. We propose that vibration-facilitated surface reconstruction facilitates pre-melting, which could be the cause of the lowered melting temperature. The vibration assisted method represents a new general method to produce MOF glasses without thermal decomposition.
Corrigendum to: Regional drought synchronised historical fires in dry forests of the Montane Cordillera Ecozone, Canada
Authors: Chavardès Raphaël D. , Daniels Lori D. , Harvey Jill E. , Greene Gregory A. , Marcoux Hélène , Eskelson Bianca N. I. , Gedalof Ze’ev , Brookes Wesley , Kubian Rick , Cochrane Jared D. , Nesbitt John H. , Pogue Alexandra M. , Villemaire-Côté Olivier , Gray Robert W. , Andison David W.
Published: August 2022

Understanding climate as a driver of low- to moderate-severity fires in the Montane Cordillera Ecozone of Canada is a priority given predicted and observed increases in frequency and severity of large fires due to climate change. We characterised historical fire-climate associations using 14 crossdated fire-scar records and tree-ring proxy reconstructions of summer drought and annual precipitation from the region. We compared fire-climate associations among years when fires burned in multiple study areas. From 1746 to 1945, there were 32 years with moderate fire synchrony in which four to six study areas recorded fire. During four high fire synchrony years, 7 to 10 study areas recorded fire. Below-average annual precipitation and summer drought synchronised fires, whereas infrequent years of high fire synchrony were preceded by a wet summer. After 1945, decreased fire occurrence and synchrony reflects fire exclusion, suppression and climatic variation. Global climate change manifests as blocking high-pressure ridges that superimpose on longer fire-seasons and increased droughts. Combined, they make dry forests increasingly susceptible to synchronous fires, which are difficult to suppress as observed during the record-breaking 2017, 2018 and 2021 fire seasons in British Columbia.
TGF-β promotes stem-like T cells via enforcing their lymphoid tissue retention
Authors: Ma Chaoyu , Wang Liwen , Liao Wei , Liu Yong , Mishra Shruti , Li Guo , Zhang Xin , Qiu Yuanzheng , Lu Qianjin , Zhang Nu
Published: August 2022

Stem-like CD8+ T cells sustain the antigen-specific CD8+ T cell response during chronic antigen exposure. However, the signals that control the maintenance and differentiation of these cells are largely unknown. Here, we demonstrated that TGF-β was essential for the optimal maintenance of these cells and inhibited their differentiation into migratory effectors during chronic viral infection. Mechanistically, stem-like CD8+ T cells carried a unique expression pattern of α4 integrins (i.e., α4β1hi and α4β7lo) controlled by TGF-β. In the absence of TGF-β signaling, greatly enhanced expression of migration-related markers, including altered expression of α4 integrins, led to enhanced egress of stem-like CD8+ T cells into circulation accompanied by further differentiation into transitional states. Blocking α4 integrin significantly promoted their lymphoid tissue retention and therefore partially rescued the defective maintenance of Tcf-1+ subset in the absence of TGF-β signaling. Thus, TGF-β promotes the maintenance and inhibits the further differentiation of stem-like T cells at least partially via enforcing their lymphoid tissue residency.
Superfast fish show superfast coupling
Authors: Short Ben
Published: August 2022

JGP study reveals that adult zebrafish skeletal muscle fibers display the fastest kinetics of excitation–contraction coupling ever measured in vertebrate locomotor muscles.