bluuebunny/crossref_metadata_2025 huggingface dataset:
Shock wave refraction patterns at a slow–fast gas–gas interface at superknock relevant conditions
Authors: de Gouvello Yann , Dutreuilh Mathilde , Gallier Stany , Melguizo-Gavilanes Josué , Mével Rémy
Published: November 2021

Shock wave refraction theory and high-resolution numerical simulations were employed to predict the refraction pattern under superknock relevant conditions at slow–fast gas–gas interfaces which are characterized by a higher acoustic impedance in the incident phase than in the transmitted phase. First, our theoretical and computational methodologies were validated against results from the literature for planar shock–straight oblique interface interactions. Second, our framework was applied to planar shock-/cylindrical shock–cylindrical interface interactions. The theoretical regime diagram agrees well with the numerical predictions for the former configuration whereas significant discrepancies were observed for the latter. Numerical results show the formation of temperature and pressure peaks as the refraction structure transits from a free precursor refraction to a twin von Neumann refraction. This change in thermodynamic state can induce a significant reduction in ignition delay time, potentially leading to detonation onset.
Differences of turbulence modulation by heavy particles on solid wall and erodible bed surface
Authors: Wang Ping , Wei Qingqing , Zheng Xiaojing
Published: November 2021

In this paper, wall-resolved large-eddy simulation of turbulence, Lagrangian point-force model of particle tracking, and two-way coupling approach are used to simulate the particle-laden flow over a rigid wall. The flow is a turbulent open channel flow with the particle-free friction Reynolds number of Reτ=4200. Together with the simulated results over an erodible bed from Zheng et al. [J. Fluid Mech. 918, 1–27 (2021)], the influence of the lower boundary condition of particle motion with the wall-normal gravity on turbulence modulation is thoroughly compared. It is found that high-inertia (St+=244.5) particles studied in this work moving over a rigid wall increase the mean fluid velocity and the scales of turbulence structures away from the wall, suppress turbulence fluctuations and Reynolds stress, and reduce the scales of turbulence structures near the wall as compared with the particle-free flow. Gravitational settling of particles accounts for most of the changes, and the crossing trajectory caused by particles bouncing near the rigid wall is responsible for the reduction of the scales of the near-wall turbulence structures. On the contrary, the splashing process of particles over the erodible bed leads to the decrease in the mean fluid velocity, the anisotropic variation of turbulent kinetic energy, the shrink of the outer turbulence structure, and the enlargement of the near-wall streaks. The results reveal the significance of the near-wall particle motion (rebound or splashing) on turbulence modulation.
Architecture of zero-latency ultrafast amplitude detector for high-speed atomic force microscopy
Authors: Umeda Kenichi , Okamoto Chihiro , Shimizu Masahiro , Watanabe Shinji , Ando Toshio , Kodera Noriyuki
Published: November 2021

The advent of high-speed atomic force microscopy has revolutionized the field of biological science. However, there remains a myriad of phenomena that cannot be observed due to their near-instantaneous dynamics. Improving the temporal resolution is the first step toward observing these biofunctional dynamics. So far, the narrow bandwidth of the amplitude detector circuit has been a major obstacle to this objective. Here, we invent a differential-based ultrafast amplitude detection method with zero intrinsic latency based on the basic trigonometric theorem. We demonstrate that our method manifests superior performance over the conventional methods in respect of the bandwidth and noninvasiveness. This will be a breakthrough in the development of faster high-speed atomic force microscopy.
Anatomy of π-hole bonds: Linear systems
Authors: Scheiner Steve
Published: November 2021

The list of σ-hole bonds is long and growing, encompassing both H-bonds and its closely related halogen, chalcogen, etc., sisters. These bonds rely on the asymmetric distribution of electron density, whose depletion along the extension of a covalent bond leaves a positive region of electrostatic potential from which these bonds derive their name. However, the density distributions of other molecules contain analogous positive regions that lie out of the molecular plane known as π-holes, which are likewise capable of engaging in noncovalent bonds. Quantum calculations are applied to study such π-hole bonds that involve linear molecules, whose positive region is a circular belt surrounding the molecule, rather than the more restricted area of a σ-hole. These bonds are examined in terms of their most fundamental elements arising from the spatial dispositions of their relevant molecular orbitals and the π-holes in both the total electron density and the electrostatic potential to which they lead. Systems examined comprise tetrel, chalcogen, aerogen, and triel bonds, as well as those involving group II elements, with atoms drawn from various rows of the Periodic Table. The π-hole bonds established by linear molecules tend to be weaker than those of comparable planar systems.
Effect of losses on hydrogen–oxygen–argon detonation cell sizes
Authors: Xiao Qiang , Weng Chunsheng
Published: November 2021

This work revisits the effect of losses on detonation characteristic length scales. Low-pressure experiments of the very regular hydrogen–oxygen–argon detonations in the straight narrow channel and along the exponentially diverging ramp were reported, demonstrating the significant role of losses in increasing detonation velocity deficits and cell sizes. Both the theoretically established and experimentally obtained relationships show the exponential sensitivity of detonation cell sizes to losses in terms of flow divergence, which is controlled by the global activation energy. The presence of losses modulates the lengthening of the characteristic detonation reaction zones and thus results in larger cell sizes, as indicated by the linear correlation characterizing the amplification of cell sizes and induction length. Moreover, the present work proposed an effective method for calibrating the ideal Chapman–Jouguet (CJ) detonation cell size from experiments, by adopting a revised formulism of Mirels' laminar-boundary-layer theory and also the generalized Zeldovich–von Neumann–Doering (ZND) model in the presence of flow divergence. Comparisons of the ZND-model calibrated ideal CJ detonation cell sizes from experiments with those from detailed numerical simulations show that, while differences still exist for the relatively high pressure cases, accounting for wall losses could excellently reconcile the discrepancy for the lower pressure cases, which appears to suggest no evident influence of the vibrational non-equilibrium effects for the hydrogen–oxygen–argon reactive system.
Epitaxial lateral overgrowth of r-plane α-Ga2O3 with stripe masks along ⟨1¯21¯⟩
Authors: Oshima Yuichi , Yagyu Shingo , Shinohe Takashi
Published: November 2021

We demonstrated the epitaxial lateral overgrowth (ELO) of (1¯012) (r-plane) α-Ga2O3 using a striped mask pattern along ⟨1¯21¯0⟩. α-Ga2O3 stripes with an asymmetric cross-sectional shape were formed selectively on the windows at the initial growth stage. They grew vertically and laterally to coalesce with each other, and a compact film was obtained. The film surface exhibited wave-like morphology with macro-scale inclined terraces and steps because of the asymmetric cross-sectional stripe shape. The macrosteps moved laterally like traveling waves as the growth proceeded. Transmission electron microscopy revealed that a domain on a window grew toward the inclined c-axis direction to cover the adjacent domain after the coalescence. As a result, the dislocations, which propagated into the α-Ga2O3 stripe from the seed layer through the window, bent toward the c axis and concentrated in a narrow area. This concentration should enhance the pair annihilation. Therefore, the dislocation density was markedly reduced on the top surface including the areas above the windows and coalesced boundaries in contrast to the cases of conventional c-, a-, and m-plane ELO.
Fabrication of multilayered carbon fibrous membranes for high-efficiency electromagnetic absorption
Authors: Ren Fang , Lu Zhenxia , Fu Baiqiao , Dai Zhong , Guo Zhengzheng , Zhao Yuchen , Jin Yanling , Chen Zhengyan , Ren Penggang , Yan Dingxiang
Published: November 2021

Carbon fibrous (CF) membranes were fabricated by electrospinning, thermal stabilization, and the carbonization process. The in-depth analyses of the CF membranes’ composition, structure, and microwave absorption (MA) property demonstrate that the MA performance of the membranes is strongly correlated with the C/O ratio and CF framework's microstructure. A maximum absorption value of −23.4 dB is achieved at 800 °C, and this was synergistically enhanced to −42.5 dB with the addition of graphene nanosheets (GNSs). The special multilayered membranes containing dielectric loss CNSs and CFs making the balance between excellent impedance matching and the high loss characteristic could deliver an excellent MA property. With the facile and controllable synthesis of the GNS/CF membranes, a new approach to efficiently optimize and regulate its MA behavior is now possible.
Q-factor optimization for high-beta 650 MHz cavities for PIP-II
Authors: Martinello M. , Bice D. J. , Boffo C. , Chandrasekeran S. K. , Eremeev G. V. , Furuta F. , Grassellino A. , Melnychuk O. , Sergatskov D. A. , Wu G. , Reid T. C.
Published: November 2021

High Q-factors are of utmost importance to minimize losses of superconducting radio-frequency cavities deployed in continuous wave particle accelerators. This study elucidates the surface treatment that can maximize the Q-factors in high-beta 650 MHz elliptical niobium cavities. State-of-the-art surface treatments are applied in many single-cell cavities, and surface resistance studies are performed to understand the microwave dissipation at this unexplored frequency. The nitrogen doping treatment is confirmed to be necessary to maximize the Q-factors at medium RF fields. We applied this treatment in five-cell high-beta 650 MHz cavities and demonstrated that extremely high Q-factors were obtained at medium RF fields with this treatment. We also demonstrated that adding a cold electropolishing step after N-doping is crucial to push the quench field of multicell cavities to higher gradients.
Strain-driven phase manipulation of α- and κ-Ga2O3 by nanoepitaxial lateral overgrowth on embedded α-In2O3 submicron dots
Authors: Kuang Y. , Ma T. C. , Chen X. H. , Hao J. G. , Ren F.-F. , Gu S. L. , Zhang R. , Zheng Y. D. , Ye J. D.
Published: November 2021

Heteroepitaxy of corundum-structured α-Ga2O3 and intriguing ferroelectric κ-Ga2O3 is proven as an alternative strategy to solve current challenges in heat dissipation and large-scale productivity for Ga2O3-based power electronic devices, whereas the fundamental growth dynamics and phase control of metastable Ga2O3 are still far unexplored. In this Letter, we demonstrate the strategy of strain engineering for the in situ phase manipulation of metastable Ga2O3 by embedding α-In2O3 submicrometer dots. Phase transition is modulated by the surface coverage of α-In2O3 due to the competitive growth of κ-Ga2O3 upon α-In2O3 and the homoepitaxy of α-Ga2O3 on the exposed α-Ga2O3 seed region. Upon discrete α-In2O3 submicrometer dots with a low surface coverage, the growth undergoes a nano-scale epitaxial lateral overgrowth mode, in which the selective homoepitaxy of α-Ga2O3 is dominant, and embedded α-In2O3 serves as nano-masks to prevent the threading dislocation propagation into the lateral overgrown Ga2O3 layer. In comparison, κ-Ga2O3 is energetically favorable on the interconnected α-In2O3 submicrometer dots, which are driven by the in-plane tensile strain as probed by the geometric phase analysis of transmission electron microscopy. Phase manipulation by embedded sub micrometer dots allows us to deliver high-quality Ga2O3 with well-defined phases and to conceive advanced devices with ultra-low loss, high frequency, and memorizing functionality.
Electron beam irradiation of gallium nitride-on-silicon betavoltaics fabricated with a triple mesa etch
Authors: Heuser T. , Braun M. , McIntyre P. , Senesky D. G.
Published: November 2021

A process for growing gallium nitride (GaN) vertical p–i–n homojunctions on (111) silicon substrates using metalorganic chemical vapor deposition was developed, and a triple mesa etch technique was used to fabricate efficient betavoltaic energy converters. Monte Carlo simulation platform CASINO was used to model beta radiation penetration into GaN to aid device design. The resulting devices were tested under irradiation from a scanning electron microscope electron beam (e-beam) tuned to imitate the energies of the 63Ni beta emission spectrum. Based on current–voltage measurements taken under e-beam illumination, a maximum open-circuit voltage of ∼412 mV and a maximum short-circuit current density of ∼407 nA/cm2 were measured. A high fill factor of ∼0.77 and power conversion efficiency of ∼6.6% were obtained. Additionally, the proposed triple mesa etch technique used to create these betavoltaics has the potential for further use in fabricating many types of electronic devices using a wide variety of material platforms.
Activation energy of silicon diffusion in gallium oxide: Roles of the mediating defects charge states and phase modification
Authors: Azarov Alexander , Venkatachalapathy Vishnukanthan , Vines Lasse , Monakhov Edouard , Lee In-Hwan , Kuznetsov Andrej
Published: November 2021

Silicon (Si) is an efficient n-type dopant in gallium oxide (Ga2O3)—an ultra-wide bandgap semiconductor promising in a number of applications. However, in spite of the technological importance for device fabrication, the activation energy for Si diffusion in Ga2O3 is missing in the literature. In the present work, we do such measurements in ion implanted monoclinic β-Ga2O3 samples employing anneals in air ambient, also admitting the influence of potential ion beam induced phase modifications on diffusion. Importantly, we show that Si diffusion in β-Ga2O3 fits with the concentration dependent diffusion model, involving neutral and single negatively charged point defects to mediate the process; so that we assumed gallium vacancies in the corresponding charge states to assist Si diffusion in β-Ga2O3 with activation energies of 3.2 ± 0.3 and 5.4 ± 0.4 eV, respectively. Moreover, we also found that a preexisting phase modified surface layer efficiently suppressed Si diffusion in β-Ga2O3 for temperatures up to 1000 °C.
Mixed-signal data acquisition system for optically detected magnetic resonance of solid-state spins
Authors: Zhou Feifei , Song Shupei , Deng Yuxuan , Zhang Ting , Chen Bing , Xu Nanyang
Published: November 2021

We report a mixed-signal data acquisition (DAQ) system for optically detected magnetic resonance (ODMR) of solid-state spins. This system is designed and implemented based on a field-programmable-gate-array chip assisted with high-speed peripherals. The ODMR experiments often require high-speed mixed-signal data acquisition and processing for general and specific tasks. To this end, we realized a mixed-signal DAQ system that can acquire both analog and digital signals with precise hardware synchronization. The system consisting of four analog channels (two inputs and two outputs) and 16 optional digital channels works at up to 125 MHz clock rate. With this system, we performed general-purpose ODMR and advanced lock-in detection experiments of nitrogen-vacancy (NV) centers, and the reported DAQ system shows excellent performance in both single and ensemble spin cases. This work provides a uniform DAQ solution for the NV center quantum control system and could be easily extended to other spin-based systems.
Simultaneous measurements of time-resolved velocity and concentration fields behind a sand dune-inspired jet in crossflow
Authors: Zhou Wenwu , Zhang Xu , He Chuangxin , Wen Xin , Zhao Jisheng , Liu Yingzheng
Published: November 2021

The flow field and scalar concentration behind a sand dune-inspired jet-in-crossflow were measured to quantify the characteristics of flow and scalar mixing. The velocity was resolved from particle image velocimetry measurements, and the time-resolved concentration was simultaneously captured by planar laser-induced fluorescence. During the experiments, the velocity ratio was set to 0.4, 0.6, 0.8, 1.0, and 1.2. The corresponding jet flow statistics, concentration statistics, and flow-concentration dynamics were comparatively analyzed. Aided by the dune, all jets were found to discharge tangentially into the mainstream, forming an energetic shear layer in the dune upper region that not only affects the jet attachment but also influences the flow mixing dynamics. The measured turbulent flow statistics (vorticity, turbulent kinetic energy, and Reynolds stress), concentration statistics (scalar standard deviation and turbulent scalar flux), and dynamics of the flow-concentration fields (instantaneous evolutions, scalar dissipation, and strain rate) revealed not only the complex nature of the generated shear layer but also the significant correlations between the shear flow and scalar mixing. Proper orthogonal decomposition (POD) analysis successfully decomposed the instantaneous velocity and concentration fields into a series of energetic POD modes, vividly demonstrating the modulating effect of the energetic shear layer on the flow and scalar mixing.
A method and the limitations of broadband mechanical frequency tuning in a subgigawatt relativistic Cherenkov microwave generator
Authors: Totmeninov E. M. , Pegel I. V. , Tarakanov V. P.
Published: November 2021

In order to expand the range of mechanical tuning of generation frequency in a subgigawatt Cherenkov microwave oscillator, it is proposed to use а configuration of relativistic backward-wave oscillator (BWO) having no reflectors with the radiation output in the direction opposite to the electron beam. In a numerical experiment using KARAT electromagnetic PiC code, it is demonstrated that in this case, due to only variation of the slow-wave structure (SWS) period, it is possible to change the oscillation frequency by tens of percent preserving the TM01 operation mode. The frequency tuning range is thereby limited from below by the lower boundary of the SWS passband, near which the BWO oscillation regime is displaced by the orotron regime, and from above by high-frequency excitation of the competing TM02 mode. A moderately relativistic microwave oscillator is simulated with a tuning band between 2.73 and 4.15 GHz (frequency ratio 1.52) at the (−3 dB) level of the maximum microwave power (520 MW at 3.85 GHz). The feeding electron beam having 460 keV particle energy and 4.7 kA current is transported by the magnetic field with an induction of 1.0 T. Additional simulations demonstrate that the frequency tuning range is extendable to approximately an octave at the cost of lower generation efficiency.
The role of a porous wall on the solute dispersion in a concentric annulus
Authors: Dejam Morteza , Hassanzadeh Hassan
Published: November 2021

We studied the role of a porous wall on the dispersion of a solute in an annular space in the presence of a pressure-driven flow. The continuity of concentration and mass flux at the annulus–porous medium interface is used to handle the interaction between the two media. The Reynolds decomposition technique and the cross-sectional averaging method are used to derive a reduced-order advective–dispersive transport model with the associated equivalent diffusion and advection terms. The resultant dispersion and advection coefficients for an annulus with a porous wall are fully characterized as a function of the inner solid core radius of the annulus. The findings reveal that dispersion is retarded in the presence of the inner core in an annulus for both porous and non-porous outer walls. The results also indicate that the transition to a fully advective regime occurs at higher Peclet numbers for an annulus with a porous outer wall. The results suggest that dispersion and advection in an annulus can be controlled by proper selection of the inner core diameter. We also identified the inner core size where the solute dispersion in an annulus with a porous wall is minimum compared to a non-porous boundary. The developed model and insights find applications in many engineering processes where a fluid containing a solute in an annulus interacts with a surrounding porous medium.
On the role of the energy loss function in the image force on a charge moving over supported graphene
Authors: Preciado Rivas Maria Rosa , Moshayedi Milad , Mišković Zoran L.
Published: November 2021

We use a dielectric response theory to describe electrodynamic forces on a charged particle moving parallel to a supported two-dimensional layer. Using a Kramers–Kronig relation, we show that the image force on the particle can be expressed in terms of the energy loss function of the target materials. This enables us to analyze the stopping and the image forces on the particle on equal footing in the frequency–momentum domain encompassing all the energy loss channels in the target. Using the example of a graphene layer on a silicon carbide substrate, we show that both the image and stopping forces can be decomposed into contributions coming from two modes arising from hybridization of the sheet plasmon in doped graphene and a transverse optical phonon in the substrate.
Breakthrough instruments and products: Investigation of atomic layer deposited Al:ZnO layer by spectroscopic ellipsometry from the deep-UV to the mid-IR in one instrument
Authors: Makai László , Lehto Tero , Fodor Bálint , King Peter
Published: November 2021

The Semilab SE-2000 spectroscopic ellipsometer is a versatile thin film characterization instrument capable of spectroscopic ellipsometry measurements covering a large spectral range from ultraviolet to near infrared within a few seconds and into the mid-infrared in a few minutes. It is suitable for characterizing thin films from monolayers to complex multi-layer laminates and bulk materials. This article demonstrates the unique capabilities of the SE-2000 system by the wide spectral range investigation of Al doped ZnO layers on different substrates and with different layer structures. Using data fits to the Drude dispersion law, the electrical properties of Al:ZnO were determined despite the presence of other conductive layers. The results were corroborated with four-point-probe measurements on a single Al:ZnO layer deposited on a glass substrate.
Efficient geometrical control of spin waves in microscopic YIG waveguides
Authors: Lake S. R. , Divinskiy B. , Schmidt G. , Demokritov S. O. , Demidov V. E.
Published: November 2021

We study, experimentally and by micromagnetic simulations, the propagation of spin waves in 100-nm thick YIG waveguides, where the width linearly decreases from 2 to 0.5 μm over a transition region with varying lengths between 2.5 and 10 μm. We show that this geometry results in a downconversion of the wavelength, enabling efficient generation of waves with wavelengths down to 350 nm. We also find that this geometry leads to a modification in the group velocity, allowing for almost-dispersionless propagation of spin-wave pulses. Moreover, we demonstrate that the influence of energy concentration outweighs that of damping in these YIG waveguides, resulting in an overall increase in the spin-wave intensity during propagation in the transition region. These findings can be utilized to improve the efficiency and functionality of magnonic devices that use spin waves as an information carrier.
Functional genomics and metabolomics advance the ethnobotany of the Samoan traditional medicine “matalafi”
Authors: Molimau-Samasoni Seeseei , Woolner Victoria Helen , Foliga Su’emalo Talie , Robichon Katharina , Patel Vimal , Andreassend Sarah K. , Sheridan Jeffrey P. , Te Kawa Tama , Gresham David , Miller Darach , Sinclair Daniel J. , La Flamme Anne C. , Melnik Alexey V. , Aron Allegra , Dorrestein Pieter C. , Atkinson Paul H. , Keyzers Robert A. , Munkacsi Andrew B.
Published: November 2021

Significance

Medicinal plants with extensive ethnobotanical histories, particularly those from Asia, have contributed to the approval of natural compounds as pharmaceutical drugs. In contrast, Samoan traditional medicine is relatively understudied. Working with traditional healers via an ethical, data sovereignty–driven collaboration led by indigenous Samoan researchers, we elucidate the chemical biology of the poorly understood but often-used Samoan traditional medicine “matalafi,” the homogenate of
Psychotria insularum
leaves commonly used to treat inflammation-associated illnesses. Our approach unifies genomics, metabolomics, analytical biochemistry, immunology, and traditional knowledge to delineate the mode of action of the traditional medicine rather than by the more common reductionist approach of first purifying the bioactive principles, which can be used to better understand the ethnobotany of traditional medicine.
Dendritic cell paucity in mismatch repair–proficient colorectal cancer liver metastases limits immune checkpoint blockade efficacy
Authors: Ho William W. , Gomes-Santos Igor L. , Aoki Shuichi , Datta Meenal , Kawaguchi Kosuke , Talele Nilesh P. , Roberge Sylvie , Ren Jun , Liu Hao , Chen Ivy X. , Andersson Patrik , Chatterjee Sampurna , Kumar Ashwin S. , Amoozgar Zohreh , Zhang Qixian , Huang Peigen , Ng Mei Rosa , Chauhan Vikash P. , Xu Lei , Duda Dan G. , Clark Jeffrey W. , Pittet Mikael J. , Fukumura Dai , Jain Rakesh K.
Published: November 2021

Significance

Immune checkpoint blockade (ICB) has been efficacious in several cancer types. However, mismatch repair–proficient (pMMR) metastatic colorectal cancer (CRC), ∼95% of total metastatic CRC cases, typically does not respond to ICB. Here, we show that orthotopic liver metastasis mouse models of pMMR CRC cell lines are unresponsive to ICB and recapitulate the resistance of human disease, unlike subcutaneous tumors of the same cell lines. We also show that just like the human disease, orthotopic pMMR CRC liver metastases have a paucity of T cells and dendritic cells, and that treatment with Flt3L sensitizes the liver metastases to ICB. Our findings highlight that orthotopic tumor models, and not subcutaneous models, should be used for preclinical studies of cancer immunotherapy.
Paleoclimate-conditioning reveals a North Africa land–atmosphere tipping point
Authors: Hopcroft Peter O. , Valdes Paul J.
Published: November 2021

Significance

Understanding of climate “tipping points” is extremely limited. Their representation within Earth System models (ESMs) is completely unconstrained because of a lack of any actual occurrences of these events in recent times. As an example, most ESMs fail to simulate the rapid desertification of the Sahara during the Holocene. Here, we overcome this by tuning uncertain aspects of one ESM using the climate of 6,000 y ago. This approach reveals a hitherto-absent tipping point within this ESM that produces excellent agreement between the modeled and observed timing of abrupt change in North Africa. This demonstrates how paleoclimate information can be used to radically improve the representation of abrupt changes in the ESMs that are employed for future projections.
Anthropogenic pressures and life history predict trajectories of seagrass meadow extent at a global scale
Authors: Turschwell Mischa P. , Connolly Rod M. , Dunic Jillian C. , Sievers Michael , Buelow Christina A. , Pearson Ryan M. , Tulloch Vivitskaia J. D. , Côté Isabelle M. , Unsworth Richard K. F. , Collier Catherine J. , Brown Christopher J.
Published: November 2021

Significance

Seagrasses are important for ecosystem services, including climate regulation and fisheries production. But they are threatened by multiple pressures including poor water quality and coastal development. Seagrass extent is not monitored in many places, so areas at most risk of decline and the management actions needed in these places are largely unknown. We examine associations between change in seagrass meadow area and key pressures globally, helping predict the trajectory of meadows in unmonitored regions. We find rapidly shrinking seagrass meadows in areas where water quality is poor and destructive fishing occurs. Trajectories of change also vary with seagrass life-history strategy. Finally, we identify several unmonitored locations at risk of decline, highlighting where urgent monitoring and management are required.
Structural differences in amyloid-β fibrils from brains of nondemented elderly individuals and Alzheimer's disease patients
Authors: Ghosh Ujjayini , Yau Wai-Ming , Collinge John , Tycko Robert
Published: November 2021

Significance

Alzheimer's disease (AD) patients develop amyloid deposits, containing amyloid-β (Aβ) fibrils, in their brain tissue. Although amyloid is a likely contributor to AD dementia, similar amyloid loads occur in some nondemented elderly individuals. Molecular structures of Aβ fibrils are known to be variable. We, therefore, investigate whether structures of Aβ fibrils derived from cerebral cortical tissue of nondemented elderly subjects differ from structures from AD patients. We find statistically significant, but subtle, differences between NMR spectra of Aβ fibrils from nondemented elderly subjects and analogous spectra of fibrils from AD patients. Thus, similar structures develop but with different relative populations on average. Other factors may be primary determinants of cognitive status in individuals with high amyloid loads.
Microchromosomes are building blocks of bird, reptile, and mammal chromosomes
Authors: Waters Paul D. , Patel Hardip R. , Ruiz-Herrera Aurora , Álvarez-González Lucía , Lister Nicholas C. , Simakov Oleg , Ezaz Tariq , Kaur Parwinder , Frere Celine , Grützner Frank , Georges Arthur , Graves Jennifer A. Marshall
Published: November 2021

Significance

Genomes of birds and reptiles, but not mammals, consist of a few large chromosomes and many tiny microchromosomes. Microchromosomes are gene-rich and highly conserved among birds and reptiles and share homology with one or more of the tiny chromosomes of an invertebrate that diverged from the vertebrate lineage 684 Ma. Microchromosomes interact strongly and crowd together at the center of cells, suggesting functional coherence. Many microchromosomes have been lost independently in turtles, snakes, and lizards as they have fused with each other or with larger chromosomes. In mammals they have completely disappeared, yet some chromosomes of the basal platypus line up with several microchromosomes, suggesting that they are the building blocks of the atypically variable chromosomes of mammals.
Content and language integrated learning (CLIL) and the linguistic difficulties of Saudi students learning
algebra
Authors: Eltoum Russina A
Published: November 2021

This study explores the type of linguistic difficulties that Saudi students encounter in Introductory Algebra
courses at college level and how an integrated pedagogical approach, such as Content and Language Integrated Learning (CLIL),
might impact students’ learning of both algebra and the language needed to learn it. A mixed-method design was implemented for 12
weeks to collect and analyze data in three phases. The study sample comprised of a study group of 28 students from an Introductory
Algebra class. Findings identified and classified the types of difficulties that the students encountered and suggested a CLIL
instructional model to overcome or minimize them.
Numerical simulation of contact and separation of magnetic particles under uniform magnetic field
Authors: Xu Zhiqiang , Bo Xinqian , Wu Heng , Tang Zhifa , Chen Feng , Chen Kewen , Wang Xiaodong , Zhang Gaofeng , Jiang Shengqiang
Published: November 2021

Under the action of an external magnetic field, the magnetic particles will be arranged along the direction of the magnetic field. The laws of physics that control these processes are well described in the literature. However, when the magnetic particles move in the fluid, the magnetic particles with different initial distances have different mutual influences, so there will be different laws of motion. Therefore, based on the motion theory of magnetic particles in Stokes fluid, this article discusses the motion law of the contact and separation of two circular magnetic particles in Newtonian fluid. First, we conduct theoretical and simulation modeling of two magnetic particles under the action of a uniform magnetic field, and verify the correctness of the simulation through experiments; secondly, we use numerical simulation to study the angle of repulsion and attraction of magnetic particles at different initial distances, and analyze at the same time the changes in the trajectory, speed, torque and force of magnetic particles in the process of motion are studied. Finally, the influence of external field conditions on the phenomenon of contact and separation of magnetic particles is studied. The study found that even when the initial angle between the magnetic particles is 90° with the direction of the magnetic field, the magnetic particles with different initial distances will repel under the action of repulsive force and then contact again and keep repelling these two states, a better explanation the reason for the agglomeration of magnetic particles at close range is explained.
Transfer of correlations from photons to electron excitations and currents induced in semiconductor quantum wells by non-classical twisted light
Authors: Tikhonova Olga V , Voronina Ekaterina N
Published: November 2021

In this paper the excitations of collective electronic modes and currents induced in nanostructured semiconductor systems by two-mode quantum light with non-zero orbital angular momenta are investigated. Transfer of photon correlations to the excitations and currents induced in the semiconductor system is demonstrated. Birth of correlated electrons arising in the conduction band of the nanostructure due to the interaction with correlated photons of quantum light is found. Azimuthal and radial spatial distributions of the entangled electrons are established. The obtained results make possible to register the correlated electrons experimentally and to implement quantum information and nanoelectronics circuits in nanosystems using the found azimuthal and radial electron entanglement.
Fabrication of junction-free Cu nanowire networks via Ru-catalyzed electroless deposition and their application to transparent conducting electrodes
Authors: Song Jinkyu , Kim Mee-Ree , Kim Youngtae , Seo Darae , Ha Kyungryul , Song Tae-Eun , Lee Wan-Gyu , Lee Yonghee , Kim Ki-Chul , Ahn Chi Won , Han Hee
Published: November 2021

Over the past few years, metal nanowire networks have attracted attention as an alternative to transparent conducting oxide materials such as indium tin oxide for transparent conducting electrode applications. Recently, electrodeposition of metal on nanoscale template is widely used for formation of metal network. In the present work, junctionless Cu nanowire networks were simply fabricated on a substrate by forming a nanostructured Ru with 80 nm width as a seed layer, followed by direct electroless deposition of Cu. By controlling the density of Ru nanowires or the electroless deposition time, we readily achieve desired transmittance and sheet resistance values ranging from ∼1 kΩ sq−1 at 99% to 9 Ω sq−1 at 89%. After being transferred to flexible substrates, the nanowire networks exhibited no obvious increase in resistance during 8000 cycles of a bending test to a radius of 2.5 mm. The durability was verified by evaluation of its heating performance. The maximum temperature was greater than 180 °C at 3 V and remained constant after three repeated cycles and for 10 min. Transmission electron microscopy and x-ray diffraction studies revealed that the adhesion between the electrolessly deposited Cu and the seed Ru nanowires strongly influenced the durability of the core–shell structured nanowire-based heaters.
Selectively triggering photoelectrons for CO2 to CH4 reduction over SrTiO3 {110} facet with dual-metal sites
Authors: Lu Lei , Zhu Xiaopeng , Wang Shaomang , Li Taozhu , Yan Shicheng , Zou Zhigang
Published: November 2021

In this article, the roles of surface-active sites in dominating photoelectron selectivity for CO2 reduction products are well demonstrated over photocatalyst models of SrTiO3 {100} and {110} facets. On the easily exposed {100} facets terminated with Sr-O atoms, photoelectrons are of 8 mol % for CH4 and 92 mol % for CO generation. The Sr-O-Ti configuration in the {110} facets could enrich the surface charge density due to the lower interface resistance for higher photocatalytic efficiency (1.6 fold). The dual sites of Ti and adjacent Sr atoms are active for strong adsorption and activation of the generated CO* species from primary CO2 reduction on the surface, thus kinetically favoring the activity of photoelectrons (73 mol %) in hydrogenation for CH2* species and hence CH4 product. Inversely, the poor CH4 selectivity is due to difficulty in the subsequent photoelectron reduction reaction by the weak adsorption of CO* at the single-Sr site on the {100} facets, independent of the electron and proton concentration. Our results may offer some illuminating insights into the design of a highly efficient photocatalyst for selective CO2 reduction.
Transition from ballistic to thermalized transport of metal-sputtered species in a DC magnetron
Authors: Revel Adrien , Farsy Abderzak El , de Poucques Ludovic , Robert Jacques , Minea Tiberiu
Published: November 2021

Tunable diode-laser induced fluorescence technique has been optimized to accurately measure the titanium (Ti)-sputtered atom velocity distribution functions (AVDFs) in a magnetron discharge operating in DC mode. The high spatial and spectral resolution achieved reveals some features of the transport of the metal-sputtered atoms and their thermalization. The two groups of thermalized and energetic atoms have been very well separated compared to previous works. Hence, the fitting of the energetic atom group shows dumping from modified Thompson to Gauss distribution when the product pressure-distance from the target increases. In parallel, sputtered metal transport from the target has been simulated using the Monte Carlo collision (MCC) approach. Direct comparison between numerical and experimental results led to an improved cross-section for Ti–Ar momentum transfer, based on the ab initio formulas of the interaction potential derived from noble gas interaction. The accuracy of the experimental data enabled the numerical parametric study of the angular distribution and cut-off energy for the initial distribution of sputtered atoms to reveal the precise characterization of the initial conditions. A very good overall agreement is obtained for measured and calculated AVDFs. Comparison between the measured and modeling results emphasized the major role played by the argon (Ar) ions, not only in the sputtering process, but in the neutral metal transport by the gas rarefaction near the target. The microscopic description provided by the MCC model clearly reveals different transport regimes: ballistic, diffusive and back-scattering, which provide new insight into the thermalization of sputtered species in the intermediate pressure range.
Identification and manipulation of spin wave polarizations in perpendicularly magnetized synthetic antiferromagnets
Authors: Chen Xing , Zheng Cuixiu , Zhang Yu , Zhou Sai , Liu Yaowen , Zhang Zongzhi
Published: November 2021

Interlayer exchange-coupled synthetic antiferromagnets (SAFs) have the combined advantages of both high frequency of antiferromagnets and easy detection of ferromagnets. Here, magnetic excitations are investigated by theoretical analysis and micromagnetic simulations in SAFs that consist of two identical ferromagnetic layers with perpendicular magnetic anisotropy. Different from the common in-phase acoustic mode and out-of-phase optic mode, linearly or circularly polarized spin wave modes can be excited at zero bias field by using different types of microwave magnetic fields. Once a bias magnetic field is applied along the easy-axis, left-handed (LH) and right-handed (RH) polarization modes are observed, and the resonance frequency of RH (LH) mode of the SAFs increases (decreases) linearly with the increase of bias magnetic fields until a critical spin-flop field is reached, which is in accordance with collinear antiferromagnets with easy-axis anisotropy. These simulation results agree with the theoretical derivation and provide fundamental insight into the nature of dynamic properties of the perpendicularly magnetized SAFs, which may provide new prospects for spintronic applications.
In silico investigation of Alliin as potential activator for AMPA receptor
Authors: Ozturk Hilal , Yorulmaz Nuri , Durgun Mustafa , Basoglu Harun
Published: November 2021

Natural products from plants, such as flavonoids, arouse immense interest in medicine because of the therapeutic and many other bioactive properties. The molecular docking is a very useful method to screen the molecules based on their free binding energies and give important structural suggestions about how molecules might activate or inhibit the target receptor by comparing reference molecules. Alliin and Allicin differ from many other flavonoids because of containing no benzene rings and having nitrogen and sulfur atoms in their structure. In this study Alliin and Allicin affinity on AMPA, NMDA and GABA-A receptors were evaluated in the central nervous system by using the molecular docking method. Both Alliin and Allicin indicated no inhibitory effects. However Alliin showed significant selectivity to human AMPA receptor (3RN8) as an excitatory. The binding energy of glutamate to 3RN8 was −6.61 kcal mol−1, while the binding energy of Allin was −8.08 kcal mol−1. Furthermore Alliin’s affinity to the other AMPA and NMDA receptors is quite satisfactory compared to the reference molecule glutamate. In conclusion based on the molecular docking study, Alliin can be useful for synaptic plasticity studies whereas might be enhance seizure activity because of the increased permeability to cations. It also can be beneficial to improve learning and memory and can be used as a supportive product to the hypofunction of NMDA associated problems.
Micromolding fabrication of biocompatible dry micro-pyramid array electrodes for wearable biopotential monitoring
Authors: Alban Marco Vinicio , Lee Haechang , Moon Hanul , Yoo Seunghyup
Published: November 2021

Thin dry electrodes are promising components in wearable healthcare devices. Assessing the condition of the human body by monitoring biopotentials facilitates the early diagnosis of diseases as well as their prevention, treatment, and therapy. Existing clinical-use electrodes have limited wearable-device usage because they use gels, require many preparation steps, and can be uncomfortable to wear. Dry electrodes can improve these issues and have demonstrated performance on par with gel-based electrodes, providing advantages in mobile and wearable applications. However, the materials and fabrication methods used are not yet at the level of disposable gel electrodes for low-cost mass manufacturing and wide adoption. Here, a low-cost manufacturing process for thin dry electrodes with a conductive micro-pyramidal array (MPA) is presented for large-scale on-skin wearable applications. The electrode is fabricated using micromolding techniques in conjunction with solution processes in order to guarantee ease of fabrication, high device yield, and the possibility of mass production compatible with current semiconductor production processes. Fabricated using a conductive paste and an epoxy resin that are both biocompatible, the developed MPA electrode operates in a conformal, non-invasive manner, with low skin irritation, which ensures improved comfort for brief or extended use. The operation of the developed electrode was examined by analyzing electrode-skin-electrode impedance, electroencephalography, electrocardiography, and electromyography signals and comparing them with those measured simultaneously using gel electrodes.
Model-based electron density profile estimation and control, applied to ITER
Authors: Bosman T O S J , van Berkel M , de Baar M R
Published: November 2021

In contemporary magnetic confinement devices, the density distribution is sensed with interferometers and actuated with feedback controlled gas injection and open-loop pellet injection. This is at variance with the density control for ITER and DEMO, that will depend mainly on pellet injection as an actuator in feed-back control. This paper presents recent developments in state estimation and control of the electron density profile for ITER using relevant sensors and actuators. As a first step, Thomson scattering is included in an existing dynamic state observer. Second, model predictive control is developed as a strategy to regulate the density profile while avoiding limits associated with the total density (Greenwald limit) or gradients in the density distribution (e.g. neoclassical impurity transport). Simulations show that high quality density profile estimation can be achieved with Thomson Scattering and that the controller is capable of regulating the distribution as desired.
Spoiled for choice: number of signalers constrains mate choice based on acoustic signals
Authors: Tanner Jessie C , Simmons Leigh W
Published: November 2021

Animal communication mediates social interactions with important fitness consequences for individuals. Receivers use signals to detect and discriminate among potential mates. Extensive research effort has focused on how receiver behavior imposes selection on signalers and signals. However, animals communicate in socially and physically complex environments with important biotic and abiotic features that are often excluded from controlled laboratory experiments, including noise. “Noise” is any factor that prevents signal detection and discrimination. The noise caused by aggregates of acoustic signalers is a well-known impediment to receivers, but how many individual signalers are required to produce the emergent effects of chorus noise on receiver behavior? In Teleogryllus oceanicus, the Australian field cricket, we assayed female preferences for a temporal property of male advertisement signals, the number of long chirp pulses, using two-, four-, six-, and eight-choice phonotaxis experiments. We found that, as the number of individual signalers increased, receivers became less likely to respond phonotactically and less likely to express their well-documented preference for more long chirp pulses. We found that very few individual signalers can create a sufficiently noisy environment, due either to acoustic interference or choice overload, to substantially impair female preference expression. Our results suggest that receivers may not always be able to express their well-documented mating preferences in nature.
Neuron, control thyself!
Authors: Rubin Daniel B , Paulk Angelique C
Published: November 2021

This scientific commentary refers to ‘Volitional control of individual neurons in the human brain’ by Patel et al. (doi:10.1093/brain/awab370).