bluuebunny/crossref_metadata_2025 huggingface dataset:
A quaternion-based indirect Gaussian particle filter for nonlinear attitude estimation
Authors: Zhou Zhaihe , Zeng Chuanwei , Tian Xiangrui , Zeng Qingxi , Lu Xiong
Published: May 2021

A recursively indirect quaternion estimator based on the Gaussian particle filter (GPF) is proposed for nonlinear attitude estimation. The key idea is to estimate an on-tangent-plane Gaussian distribution in the GPF scheme for interpreting the uncertainty of the unit quaternion manifold. The unit quaternion is provided with a global nonsingular attitude description in the prediction step, and the three-dimensional attitude error is estimated in the update step. Based on the framework of the GPF, the proposed filter does not need resampling and regularization compared with the PF. The performance of the proposed filter is verified theoretically and evaluated by experiments. The results show that the proposed filter has a faster convergence speed, lower complexity, and lower computational cost than the existing quaternion PF under a comparable accuracy.
Dual feedback based bipolar current source with high stability for driving voice coil motors in wide temperature ranges
Authors: Wang Nong , Fang Huachao , Lei Haijun , Ye Dongdong
Published: May 2021

Bipolar current sources with a stability better than 0.1% in the temperature range of −30 to +70 °C are demanded for driving voice coil motors applied in a new ultra-quiet satellite platform, but almost none of the existing designs satisfy the harsh requirements. This paper presents a possible solution, which is essentially a floating-load, bipolar current source circuit with a dual feedback path. The key circuit is a composite amplifier (co-amp) composed of a high precision amplifier for error correction and a high power amplifier for load driving. The first feedback path comprises a specially designed four-wire current-sense resistor for current-to-voltage conversion and a discrete instrumentation amplifier for amplifying the converted voltage and closing the loop. The second feedback path is a proposed compensation network for loop stability. Error budgets for evaluating current stability and choosing key components of the circuit are comprehensively studied based on a derived rigorous current equation. Loop-stability problems attributable to the inductive load and the high open-loop gain of the co-amp are analyzed, and the proposed dual feedback compensation method is verified by theory, simulation, and measurement. All these contributions are demonstrated by three implemented prototypes with an output of up to ±2 A. The measured results agree well with theoretical predictions. The best and the worst stability performances of the three prototypes at +2 and −2 A are, respectively, 394 and 986 ppm in the temperature range of −30 to +70 °C, which are close to the theoretical value of 776 ppm.
Upgrade of far infrared three-wave polarimeter–interferometer system on Joint-TEXT
Authors: Yang Qinglong , Gao Li , Shi Peng , Zhou Yinan , Wang Yuhan , Zhou Chengxi
Published: May 2021

The far infrared polarimeter–interferometer system (POLARIS) on the Joint-TEXT has been upgraded recently. A new support structure has been applied to the mixer array of the POLARIS for adjusting the position of the mixers precisely. Five detection chords have been added to the system on the low field side by optimizing the utilization efficiency of the laser beams on both sides of the beam splitting grid. The spatial resolution can be improved from 3 to 1.5 cm. A better measurement on plasma electron density and current density has been obtained after the system is upgraded. The initial experimental result will be introduced along with the upgrade details.
Twist-angle-dependent thermal conduction in single-crystalline bilayer graphene
Authors: Han Shuo , Nie Xianhua , Gu Shangzhi , Liu Wenyu , Chen Luchen , Ying Hao , Wang Le , Cheng Zhihai , Zhao Li , Chen Shanshan
Published: May 2021

Thermal conductivity (κ) of the single-crystalline bilayer graphene (BLG) is investigated experimentally as a function of the interlayer twist angle (θ) and temperature using the optothermal Raman technique. The results show that a slight 2° twist angle leads to a κ decrease in 15% at ∼320 K. With the regulation of θ from 0° to 30°, the in-plane κ of the BLG decreases first and then increases showing an asymmetry V shape. The local maximum value of κ was reached when the twist angle is 30° and the highest value was found on the Bernal stacked BLG. The obtained κ is further found to be sensitive to the Moire periodicity but insensitive to the commensurate lattice constant of the twisted BLG. The non-equilibrium molecular dynamics simulation reveals that the twist angle in t-BLG affects the proportion of low-frequency phonons and finally changes the κ. The quantitative study validates the regulation of thermal conduction through the interlayer twist angle and favors the further understanding of thermal transport in the van der Waals bilayer systems.
Electrical contacts to few-layer MoS2 with phase-engineering and metal intercalation for tuning the contact performance
Authors: Zhang Wenjun , Wang Qian , Hu Liang , Wu Jiansheng , Shi Xingqiang
Published: May 2021

Due to Fermi-level pinning in metal–two-dimensional MoS2 junctions, improving the performance of MoS2-based electrical devices is still under extensive study. The device performance of few-layer MoS2 depends strongly on the number of layers. In this work, via density-functional theory calculations, a comprehensive understanding from the atomistic view was reached for the interlayer interaction between metal and few-layer MoS2 with phase-engineering and intercalation doping, which are helpful for improving the contact performance. These two methods are probed to tune the performance of few-layer MoS2-based field-effect transistors, and both of them can tune the Schottky barrier height. Phase-engineering, which means that the MoS2 layer in contact with metal is converted to the T phase, can transform the Schottky barrier from n- to p-type. Intercalation doping, which takes advantage of annealing and results in metal atom interaction in between MoS2 layers, makes the MoS2 layers become quasi-freestanding and converts the indirect bandgap into direct bandgap. Our atomistic insights help improve the performance of few-layer MoS2-based electronic devices.
Creation of an axially uniform plasma channel in a laser-assisted capillary discharge
Authors: Bagdasarov G. A. , Bobrova N. A. , Olkhovskaya O. G. , Gasilov V. A. , Benedetti C. , Bulanov S. S. , Gonsalves A. J. , Pieronek C. V. , van Tilborg J. , Geddes C. G. R. , Schroeder C. B. , Sasorov P. V. , Bulanov S. V. , Korn G. , Esarey E.
Published: May 2021

Dissipative capillary discharges form plasma channels which allow for high power laser guiding, enabling efficient electron acceleration in a laser wakefield accelerator. However, at the low plasma densities required to produce high-energy electrons, in order to avoid capillary wall damage, high power lasers need a tighter transverse confinement that cannot be achieved by the capillary discharge powered by Ohmic heating alone. The introduction of an additional laser for heating of the plasma leads to deeper and narrower plasma channels. Here we investigate the formation of laser-heated axially uniform plasma channels. We show that a high degree of longitudinal uniformity can be achieved despite significant evolution of the heater laser during its propagation through the channel.
Dynamics of a spherical colloid at a liquid interface: A lattice Boltzmann study
Authors: Gidituri Harinadha , Würger Alois , Stratford Kevin , Lintuvuori Juho S.
Published: May 2021

We study the dynamics of a spherical colloidal particle pulled along the fluid–fluid interface using lattice Boltzmann (LB) simulations. We consider an interface with a finite width and include both the effects of the thermodynamics of the interface and the particle wetting, characterized by the contact angle θ between the particle surface and the interface, in addition to the viscosity ratio λ between the two fluids. We characterize the particle dynamics by applying a constant pulling force along the interface and measure both the translational and the rotational dynamics as a function of the contact angle and the viscosity ratio. We observe that the hydrodynamic drag is reduced and the particle rotation is increased when the particle resides more in the low viscosity fluid, in agreement with previous hydrodynamic theories. We also study the case where the particle rotation is suppressed, and find an overall increase of the drag coefficient.
Simple pair-potentials and pseudo-potentials for warm-dense matter applications
Authors: Dharma-wardana M. W. C.
Published: May 2021

We present computationally simple parameter-free pair potentials useful for solids, liquids, and plasmas at arbitrary temperatures. They successfully treat warm-dense matter (WDM) systems like carbon or silicon with complex tetrahedral or other structural bonding features. Density functional theory asserts that only one-body electron densities and one-body ion densities are needed for a complete description of electron–ion systems. Density functional theory (DFT) is used here to reduce both the electron many-body problem and the ion many-body problem to an exact one-body problem, namely, that of the neutral pseudoatom (NPA). We compare the Stillinger–Weber (SW) class of multi-center potentials, the embedded-atom approaches, and N-atom DFT, with the one-atom DFT approach of the NPA to show that many-ion effects are systematically included in this one-center method via one-body exchange-correlation functionals. This computationally highly efficient one-center DFT-NPA approach is contrasted with the usual N-center DFT calculations that are coupled with molecular dynamics simulations to equilibrate the ion distribution. Comparisons are given with the pair-potential parts of the SW, “glue” models, and the corresponding NPA pair-potentials to elucidate how the NPA potentials capture many-center effects using single-center one-body densities.
Temperature dependence of magnetization processes in Sm(Co, Fe, Cu, Zr)z magnets with different nanoscale microstructures
Authors: Pierobon Leonardo , Schäublin Robin E. , Kovács András , Gerstl Stephan S. A. , Firlus Alexander , Wyss Urs V. , Dunin-Borkowski Rafal E. , Charilaou Michalis , Löffler Jörg F.
Published: May 2021

The characteristic microstructure of Sm(Co,Fe,Cu,Zr)z (z=6.7–9.1) alloys with SmCo5 cell walls in Sm2Co17 cells, all intersected by Zr-rich platelets, makes them some of the best performing high-temperature permanent magnets. Plentiful research has been performed to tailor their microstructure at the nanoscale; but due to its complexity, many questions remain unanswered about the effect of the individual phases on the magnetic performance at different temperatures. Here, we explore this effect for three different Sm(Co,Fe,Cu,Zr)z alloys by deploying high-resolution magnetic imaging via in situ transmission electron microscopy and three-dimensional chemical analysis via atom probe tomography. We show that their microstructures differ in terms of SmCo5 cell-wall and Z-phase size and density as well as the Cu concentration in the cell walls and demonstrate how these features influence the magnetic domain size and density, thus forming different micromagnetic spin structures. Moreover, we illustrate that the dominant coercivity mechanism at room temperature is domain-wall pinning and show that magnets with a denser cell-wall network, a steeper Cu gradient across the cell-wall boundary, and thinner Z-phase platelets have a higher coercivity. We also show that the coercivity mechanism at high temperatures is domain-wall nucleation at the cell walls. Increasing the Cu concentration inside the cell walls decreases the temperature of transition between pinning and nucleation, significantly decreasing the coercivity with increasing temperature. We, therefore, provide a detailed explanation of how the microstructure on the atomic to nanoscale directly affects the magnetic performance and provide detailed guidelines for an improved design of Sm(Co,Fe,Cu,Zr)z magnets.
Flow-induced vibrations of circular cylinder in tandem arrangement with D-section cylinder at low Reynolds number
Authors: Darbhamulla Nihar B. , Bhardwaj Rajneesh
Published: May 2021

Elastically mounted circular cylinder in a fluid flow undergoes vortex-induced vibrations (VIV) and exhibits high amplitudes, however in a limited range of reduced velocity (UR). Studies have shown an introduction of asymmetry in the flow around the cylinder may lead to galloping, characterized by large amplitudes over a wide range of UR. Here, flow-induced vibrations of tandem arrangement of a D-section and a circular cylinder of equal diameter and density are studied computationally. The circular cylinder is placed in the wake-interference region. An in-house sharp-interface immersed boundary method has been used to solve for the fluid flow, while the rigid body dynamics of the cylinders are modeled through a linear spring-mass model. Over the range of UR considered (1≤UR≤15), the D-section cylinder shows both VIV and soft-galloping response characteristics. The excitation of galloping instability in the D-section is attributed to wake disruption by the circular cylinder. Oscillation frequencies of both cylinders are found to be in synchronization with the natural frequency of the structure once lock-in is attained. The circular cylinder's oscillations attain high amplitudes only when a transition in vortex shedding mode of the D-section cylinder is observed. The spectral characteristics of the forces and oscillations of the cylinders are studied, and overlapping VIV and galloping characteristics have been observed for both D-section and circular cylinders. In context of relevant literature, the wake-induced response of the cylinder is classified as galloping. The vorticity dynamics associated with the different regimes of response have been investigated.
Predictive models for flame evolution using machine learning: A priori assessment in turbulent flames without and with mean shear
Authors: Ren Jiahao , Wang Haiou , Chen Guo , Luo Kun , Fan Jianren
Published: May 2021

Accurate prediction of temporal evolution of turbulent flames represents one of the most challenging problems in the combustion community. In this work, predictive models for turbulent flame evolution were proposed based on machine learning with long short-term memory (LSTM) and convolutional neural network-long short-term memory (CNN-LSTM). Two configurations without and with mean shear are considered, i.e., turbulent freely propagating premixed combustion and turbulent boundary layer premixed combustion, respectively. The predictions of the LSTM and CNN-LSTM models were validated against the direct numerical simulation (DNS) data to assess the model performance. Particularly, the statistics of the fuel (CH4 for the freely propagating flames and H2 for the boundary layer flames) mass fraction and reaction rate were examined in detail. It was found that generally the performance of the CNN-LSTM model is better than that of the LSTM model. This is because that the CNN-LSTM model extracts both the spatial and temporal features of the flames while the LSTM model only extracts the temporal feature of the flames. The errors of the models mainly occur in regions with large scalar gradients. The correlation coefficient of the mass fraction from the DNS and that from the CNN-LSTM model is larger than 0.99 in various flames. The correlation coefficient of the reaction rate from the DNS and that from the CNN-LSTM model is larger than 0.93 in the freely propagating flames and 0.99 in the boundary layer flames. Finally, the profiles of the DNS values and predictions conditioned on axial distance were examined, and it was shown that the predictions of the CNN-LSTM model agree well with the DNS values. The LSTM model failed to accurately predict the evolution of boundary layer flames while the CNN-LSTM model could accurately predict the evolution of both freely propagating and boundary layer flames. Overall, this study shows the promising performance and the applicability of the proposed CNN-LSTM model, which will be applied to turbulent flames a posteriori in future work.
Flexible and efficient regulation of coalescence-induced droplet jumping on superhydrophobic surfaces with string
Authors: Gao Sihang , Hu Zhifeng , Yuan Zhiping , Wu Xiaomin
Published: May 2021

Coalescence-induced droplet jumping on superhydrophobic surfaces has good application potential in the fields of heat transfer enhancement, self-cleaning, water collection, and microfluidics. However, the direction of droplets jumping on the plane is uncontrollable and the energy conversion rate is low, which limits the application of droplets jumping. In this work, we report a flexible approach to efficiently regulate the direction and velocity of droplet jumping on superhydrophobic surfaces using superhydrophobic string. By changing the inclination angle of the string, the jumping direction of the coalescent droplet shows a maximum deviation of 68.1° from the surface normal. The maximum energy conversion rate is 32.1%, which is about 5.4 times higher than that of jumping on the plane. We analyzed the mechanism of the efficient regulation and found that the string affected the hydrodynamic characteristics of the jumping process, thus changing the jumping direction and the speed of the coalescent droplet.
Time-domain investigation of an external cloak for antiplane elastic waves
Authors: Guenneau S. , Lombard B. , Bellis C.
Published: May 2021

Space folding techniques based on non-monotonic transforms lead to a new class of 2D isotropic cloaks with a constant negative shear modulus and a spatially varying negative density for antiplane elastic waves. We consider an external cloak consisting of a core with positive shear modulus and density, and a shell with simultaneously negative shear modulus and density. Such a core–shell resonant system creates a virtual folded region outside the shell. To handle such negative physical parameters in the time-domain, a two-step strategy is used: (i) assuming resonant (Drude and Lorentz-types) effective parameters in the frequency-domain; (ii) returning to the time-domain by applying the formalism of the auxiliary fields. We numerically show that, at the designed central frequency, scattering of a cylindrical antiplane elastic wave incident upon a finite set of small clamped obstacles is drastically reduced after a lapse of time, when they are placed in the close neighborhood of the external cloak. However, cloaking efficiency decreases when the source is placed in the intense near field of the external cloak and moreover at short times, cloaking breaks down.
Airborne transmission of COVID-19 and mitigation using box fan air cleaners in a poorly ventilated classroom
Authors: He Ruichen , Liu Wanjiao , Elson John , Vogt Rainer , Maranville Clay , Hong Jiarong
Published: May 2021

Many indoor places, including aged classrooms and offices, prisons, homeless shelters, etc., are poorly ventilated but resource-limited to afford expensive ventilation upgrades or commercial air purification systems, raising concerns on the safety of opening activities in these places in the era of the COVID-19 pandemic. To address this challenge, using computational fluid dynamics, we conducted a systematic investigation of airborne transmission in a classroom equipped with a single horizontal unit ventilator (HUV) and evaluate the performance of a low-cost box fan air cleaner for risk mitigation. Our study shows that placing box fan air cleaners in the classroom results in a substantial reduction of airborne transmission risk across the entire space. The air cleaner can achieve optimal performance when placed near the asymptomatic patient. However, without knowing the location of the patient, the performance of the cleaner is optimal near the HUV with the air flowing downwards. In addition, we find that it is more efficient in reducing aerosol concentration and spread in the classroom by adding air cleaners in comparison with raising the flow rate of HUV alone. The number and placement of air cleaners need to be adjusted to maintain their efficacy for larger classrooms and to account for the thermal gradient associated with a human thermal plume and hot ventilation air during cold seasons. Overall, our study shows that box fan air cleaners can serve as an effective low-cost alternative for mitigating airborne transmission risks in poorly ventilated spaces.
Nanoglobular carbon and palladium–nanoglobular carbon catalysts for liquid-phase hydrogenation of organic compounds
Authors: Mironenko R. M. , Likholobov V. A. , Belskaya O. B.
Published: May 2021

The results of studies related to the development of synthesis, determination of formation conditions and elucidation of the mechanism of palladium–carbon catalyst action are integrated and critically analyzed. The attention is focused on Pd/NGC compositions (NGC is nanoglobular carbon). Methods for NGC preparation with an emphasis on its most common form, carbon black, are considered. The following issues are addressed: mechanisms of formation of carbon nanoglobules and their aggregates, methods of varying the size of nanoglobules, functionalization of the NGC surface to make it suitable as a support for palladium nanoparticles, views on the formation mechanism of palladium clusters and nanoparticles on the carbon support surface and effect of the structure and surface chemistry of carbon nanoglobules on the state of palladium sites in Pd/NGC compositions. The published data on selective hydrogenation of organic compounds in the presence of Pd/NGC catalytic compositions are integrated and systematized. The catalytic properties of Pd/NGC are analyzed in comparison with the properties of palladium catalysts supported on other carbon materials (activated carbon, carbon nanotubes). The influence of preparation conditions of NGC-based palladium compositions on their catalytic properties in practically important hydrogenation reactions is discussed. Promising trends for further research on the development of molecular design methods, study of the genesis of Pd/NGC compositions and extension of their applications in hydrogenation processes are considered.
 The bibliography includes 623 references.
Bioenergetics of blue swimmer crab (
Authors: Junk Emily J. , Smith James A. , Suthers Iain M. , Taylor Matthew D.
Published: May 2021

Stock enhancement is a contemporary management method employed to support fisheries productivity. Blue swimmer crab (Portunus armatus) is a widely distributed species that has been identified as a candidate for stock enhancement; however, the release strategy and ecological impact of releases have not yet been assessed. Here, we (1) quantify the bioenergetics of blue swimmer crab, (2) estimate consumption rates, and (3) develop these relationships in a stocking model to assess appropriate release densities and associated trophic impacts. Static respirometry was used to measure the resting metabolic rate (RMR) of blue swimmer crab at three temperatures (19, 24, and 29°C). RMR was found to increase with temperature (Q10 = 2.32), and was 73% higher when crabs were at a premoult or moulting stage. Parameters derived from respirometry experiments were applied to estimate blue swimmer crab stocking density in a south-eastern Australian estuary, by adapting an existing production-based simulation model. The model estimated a median stocking density of ~1.2 crabs per 100 m2. A sensitivity analysis showed that the growth rate was the most influential parameter in this model, showing the importance of this parameter when assessing stocking scenarios.
The Acrotylaceae (Gigartinales) revisited: molecular data indicate family-level differences in one of the most enigmatic red-algal families
Authors: Kraft Gerald T. , Saunders Gary W.
Published: May 2021

The Acrotylaceae (Gigartinales) has been an obscure, puzzling red-algal family composed of six genera (Acrotylus, Amphiplexia, Antrocentrum, Claviclonium, Hennedya and Ranavalona) that have virtually no habit and vegetative features remotely in common. Excepting Amphiplexia, with two species, all are monotypic and, save for Ranavalona, endemic to the southern half of Australia, Ranavalona being known only by a single collection from southern Madagascar. The most noteworthy unifying feature of the genera is the cystocarps, in which carposporangial filaments grow into a hollow cavity from inner hull layers. In almost all other respects, apart from zonate tetrasporangia, there are no anatomical features that appear uniformly throughout the complex. Molecular studies indicate that the family is composed of the Acrotylaceae sensu stricto (for Acrotylus, Hennedya and Ranavalona) and the newly proposed Clavicloniaceae (for Claviclonium, Amphiplexia and Antrocentrum). We recognise a new species of Acrotylus (A. cryptographicus) and transfer Rhabdonia mollis Harvey and R. hamata Zanardini to Antrocentrum. Closest affinities of both families lie with the Dicranemataceae, Mychodeaceae and Mychodeophyllaceae of the Gigartinales. The South African genus Reinboldia, which is based on a single 19th century collection, has been questionably included in the Acrotylaceae previously but should, in our opinion, be excluded.
Comparative survey techniques for a cryptic Australian snake (
Authors: Shelton Michael B. , Goldingay Ross L.
Published: May 2021

Ecologists endeavour to develop survey techniques that are cost-effective for the species they target and robust enough for statistical analysis. Using time as a measure of effort, we compared visual encounter surveys with artificial cover objects (strapped to trees), targeting an arboreal elapid, the pale-headed snake (Hoplocephalus bitorquatus) and its potential prey (geckos). Within a red gum forest vegetation community with relatively high snake density, capture rates were 0.6 ± 0.1 (s.e.) snakes/person-hour using visual encounter surveys, compared with only 0.1 ± 0.1 snakes/person-hour using cover objects. The probability of detection of pale-headed snakes was estimated from occupancy modelling at 0.70 ± 0.06 in visual encounter surveys and 0.19 ± 0.09 in cover object surveys. Gecko capture rates (among all vegetation communities) were significantly greater (P < 0.001) using cover objects. The probability of detection of geckos was estimated from occupancy modelling at 0.77 ± 0.05 in visual encounter surveys and 0.97 ± 0.02 in cover object surveys. Geckos favoured (P < 0.001) cover objects facing south during all seasons except winter. Artificial cover objects may provide some value in detecting pale-headed snakes in vegetation communities where habitat resources are limited; however, where resources are plentiful, visual encounter surveys are likely to remain the most cost-effective survey option.
HBD1 protein with a tandem repeat of two HMG-box domains is a DNA clip to organize chloroplast nucleoids in
Chlamydomonas reinhardtii
Authors: Takusagawa Mari , Kobayashi Yusuke , Fukao Yoichiro , Hidaka Kumi , Endo Masayuki , Sugiyama Hiroshi , Hamaji Takashi , Kato Yoshinobu , Miyakawa Isamu , Misumi Osami , Shikanai Toshiharu , Nishimura Yoshiki
Published: May 2021

Significance

Compaction of bulky DNA is a universal issue for all DNA-based life forms. Both chloroplasts and mitochondria maintain their own multicopy genomes organized as nucleoids, but the mechanism of DNA compaction remains obscure. Here, we discovered a chloroplast nucleoid protein (HBD1) that is highly similar to major mitochondrial nucleoid proteins transcription factor A, mitochondrial (TFAM), and ARS binding factor 2 protein (Abf2p) in terms of possessing two DNA-binding high mobility group box (HMG-box) domains. Our analyses of HBD1 based on DNA origami/atomic force microscopy showed that HBD1 is capable of compacting DNA by introducing U-turns and cross-strand bridges with the two HMG-box domains, indicating that proteins with two HMG-box domains could compact DNA in both mitochondrial and chloroplast nucleoids.
Peptidic boronic acids are potent cell-permeable inhibitors of the malaria parasite egress serine protease SUB1
Authors: Lidumniece Elina , Withers-Martinez Chrislaine , Hackett Fiona , Collins Christine R. , Perrin Abigail J. , Koussis Konstantinos , Bisson Claudine , Blackman Michael J. , Jirgensons Aigars
Published: May 2021

Significance

Malaria remains a major global health threat. In the face of increasing resistance to available chemotherapeutics, new antimalarial drugs with new modes of action are urgently needed. The causative agent of malaria is a single-celled parasite that invades and replicates within red blood cells. Escape from the red cell, a process called egress, involves a proteolytic pathway triggered by an essential parasite subtilisin-like serine protease called SUB1. Here, we describe the development and rational optimization of a potent, membrane-permeable substrate-based boronic acid compounds that block egress and parasite proliferation by direct inhibition of SUB1 activity. The compounds could form the basis of a new type of antimalarial medicine that would both protect against infection and treat disease.
Isoelectronic perturbations to
f
-
d
-electron hybridization and the enhancement of hidden order in URu
2
Si
2
Authors: Wolowiec Christian T. , Kanchanavatee Noravee , Huang Kevin , Ran Sheng , Breindel Alexander J. , Pouse Naveen , Sasmal Kalyan , Baumbach Ryan E. , Chappell Greta , Riseborough Peter S. , Maple M. Brian
Published: May 2021

Significance

Phase transitions often manifest themselves in characteristic signatures in the electrical resistivity. Here, we track the temperature increase of the resistive signature of the hidden-order (HO) phase transition in URu
2
Si
2
, a mysterious phase with unknown order parameter. The application of pressure and the isoelectronic substitutions of Fe and Os ions for Ru are the only known perturbations to favor the HO phase. These perturbations are likely to cause increases in

f

-

d

-electron hybridization that lead to degeneracy and instabilities in the electronic band structure. The degeneracy is lifted by partial gapping of electronic states over the Fermi surface during the transition to HO. This and related investigations point to the importance of isoelectronic perturbations in generating emergent electronic phases.
The cytokine FAM3B/PANDER is an FGFR ligand that promotes posterior development in
Xenopus
Authors: Zhang Fangfang , Zhu Xuechen , Wang Pan , He Qing , Huang Huimei , Zheng Tianrui , Li Yongyu , Jia Hong , Xu Linping , Zhao Huaxiang , Colozza Gabriele , Tao Qinghua , De Robertis Edward M. , Ding Yi
Published: May 2021

Significance

How distinct body regions form along the anterior–posterior axis in vertebrate embryos is a fascinating and incompletely understood developmental process. FAM3B/PANDER is a secreted protein involved in glucose metabolism and type 2 diabetes pathogenesis in mammals, but its receptor has been unknown. Here, we report that FAM3B binds to transmembrane fibroblast growth factor receptors (FGFRs) and activates their downstream signaling pathway. In frog embryos, gain-of-function of FAM3B impairs head development and induces ectopic tail-like structures, whereas loss-of-function of FAM3B promotes head development. FGFR is required downstream of FAM3B for head-to-tail patterning. Our results reveal that FAM3B functions by activating the FGFR pathway in frog embryos and mammalian cells and shed light on its possible role in human diseases.
PIEZO ion channel is required for root mechanotransduction in
Arabidopsis thaliana
Authors: Mousavi Seyed A. R. , Dubin Adrienne E. , Zeng Wei-Zheng , Coombs Adam M. , Do Khai , Ghadiri Darian A. , Keenan William T. , Ge Chennan , Zhao Yunde , Patapoutian Ardem
Published: May 2021

Significance

Underground barriers caused by drought or heterogeneous soil components exert mechanical resistance to plants, and plant roots must determine whether to avoid or penetrate these barriers. Yet, very little is known about how roots sense mechanical forces at the molecular level. Using genetics, electrophysiology, and in vivo imaging, we found that
Arabidopsis
PIEZO1, an ortholog of mammalian Piezo, is required for root penetration and that
pzo1
mutants have impaired primary root growth into harder media. These results highlight a conserved function of PIEZOs from plants to mammals.
Determination of effective magnon mass of neodymium magnet by temperature dependence of spontaneous magnetization
Authors: Mishonov Todor M , Andreoni Matteo , Mihaylova Nelly Zh , Varonov Albert M
Published: May 2021

The effective mass of a magnon in a neodymium magnet is evaluated using Bloch temperature dependence of spontaneous magnetization. We use the Hall effect magnetometer and thermo-couple thermometer for measurement of the temperature of the water in which the encapsulated commercial magnet is immersed. The experiment can be repeated in every school and methodological remarks for experimental data processing are given with great detail and attention. The purpose of the paper is to illustrate the simple relation between the quantum spectrum of magnons and the easily measured magnetic field of a permanent magnet.
Heating ability modulation by clustering of magnetic particles for precision therapy and diagnosis
Authors: Barrera Gabriele , Allia Paolo , Tiberto Paola
Published: May 2021

Magnetic and thermal properties of clustered magnetite nanoparticles submitted to a high-frequency magnetic field is studied by means of rate equations. A simple model of large particle clusters (containing more than one hundred individual particles) is introduced. Dipolar interactions among clustered particles markedly modify shape and area of the hysteresis loops in a way critically dependent on particle size and cluster dimensions, thereby modulating the power released as heat to a host medium. For monodisperse and polydisperse systems, particle clustering can lead to either a significant enhancement or a definite reduction of the released power; in particular cases the same particles can produce opposite effects in dependence of the dimensions of the clusters. Modulation by clustering of the heating ability of magnetic nanoparticles has impact on applications requiring optimization and accurate control of temperature in the host medium, such as magnetic hyperthermia for precision therapy or fluid flow management, and advanced diagnostics involving magnetic tracers.
Ultrafast carrier response of CH3NH3PbI3/MoO3/graphene heterostructure for terahertz waves
Authors: Li Xiang , Yang Tingting , Liu Yangqi , Liu Jingyu , Liu Bin , Lv Longfeng , Hou Yanbing , Zhang Yan , Shen Jingling , Zhang Bo
Published: May 2021

Ultrafast carrier response of perovskite/MoO3/graphene heterostructure was investigated by optical-pump terahertz (THz) probe spectroscopy. The high work function of MoO3 changes the tunable graphene Fermi level via hole doping. Compared with monolayer graphene, it generates a more negative photoconductivity and enables ultra-fast THz functional manipulation. The subsequent THz signal decrease is related to hot-carrier cooling and the carrier concentration contributed by the CH3NH3PbI3 layer. The charge transfer and recombination reduce the positive conductance of the hybrid structure relative to that of neat CH3NH3PbI3.
Magnetic anisotropy and exchange interactions of two-dimensional FePS3, NiPS3 and MnPS3 from first principles calculations
Authors: Olsen Thomas
Published: May 2021

The van der Waals bonded transition metal phosphorous trichalcogenides FePS3, NiPS3 and MnPS3 have recently attracted renewed attention due to the possibility of exfoliating them into their monolayers. Although the three compounds have similar electronic structure, the magnetic structure differs due to subtle differences in exchange and magnetic anisotropy and the materials thus comprise a unique playground for studying different aspects of magnetism in 2D. Here we calculate the exchange and anisotropy parameters of the three materials from first principles paying special attention to the choice of Hubbard parameter U. We find a strong dependence of the choice of U and show that the calculated Néel temperature of FePS3 varies by an order of magnitude over commonly applied values of U for the Fe d-orbitals. The results are compared with parameters fitted to experimental spin-wave spectra of the bulk materials and we find excellent agreement between the exchange constants when a proper value of U is chosen. However, the anisotropy parameters are severely underestimated by density functional theory and we discuss possible origins of this discrepancy.
Ns-pulsewidth pulsed power supply by regulating electrical parameters for AFM nano EDM of nm-removal-resolution
Authors: Quan Ran , Tong Hao , Li Yong
Published: May 2021

Nano electro discharge machining (nano EDM), as a frontier processing method in the research stage of exploration, has an important application prospect in the machining of metal and alloy materials for achieving nanoscale removal resolution. A pulsed power supply used in nano EDM is expected to limit a single pulse energy to nJ order of magnitude for improving the removal resolution of single pulsed discharge even to nanoscale. One developing direction is to decrease pulsewidth of the pulsed power supply. Conventional pulsed power supplies hardly output a single pulse and continuous pulses with nanosecond (ns) pulsewidth, resulting in too large single pulsed energy of μJ order of magnitude usually. In this research, a novel pulsed power supply is designed for realizing the ns-pulsewidth with controllable pulsewidth and peak voltage. The key novelty lies in a cascaded circuit with two triodes working in the state of ultra-fast avalanche conduction, where pF capacitors are applied to adjust the pulsewidth and pulsed energy precisely. Performance tests verified that a single pulse of 5 ns pulsewidth or continuous pulses up to 9 MHz can be outputted. Furthermore, nano EDM experiments of single pulsed discharge are carried out under the conditions of nanometer (nm) discharge gap and nm-tip tool electrode based on an atomic force microscope (AFM) system. The special results are achieved: a single pulsed energy can reach down to 1.75 nJ by outputting a pulsewidth of 10 ns, and a nano-EDM crater is only about 182 nm in diameter with regular shape and little recasting. Those results verify the possibility of AFM-tip-based nano EDM for machining nanostructures.
Theory of stochastic diffusion in Wendelstein-line stellarators in the presence of radial electric field
Authors: Tykhyy A V , Kolesnichenko Ya I
Published: May 2021

In optimized stellarators of the Wendelstein line prompt losses of fast ions in superbanana orbits are reduced through a modification of the magnetic configuration by high β (ratio of the plasma pressure to the magnetic field pressure), so that most contours of the longitudinal adiabatic invariant

J
∥

of locally trapped particles are closed inside the plasma volume. However, magnetic drift leads to the transformation of some of these particles into the locally passing ones and vice versa. Orbit transformation upon crossing the separatrix between locally trapped and locally passing states is accompanied by jumps in

J
∥

that lead to collisionless stochastic diffusion (SD), which was shown to be an important mechanism of the loss of energetic ions in the optimized Wendelstein-line stellarators (C D Beidler et al 2001 Phys. Plasmas
8 2731). The theory of SD that took into account the phase space asymmetry between locally passing particles with opposite signs of

v
∥

was developed in (A V Tykhyy 2018 Ukr. J. Phys.
63(6) 495). This work extends that theory to consider the effect of radial electric field E

r
on SD. It is found that negative E

r
of such magnitudes as those observed in W7-X and predicted in Helias reactor can mitigate SD losses from the plasma core of NBI ions in W7-X and α-particles in Helias. This loss mitigation occurs because added

E

×

B

drift increases the range of pitch angles for which separatrices are closed inside the plasma volume, even while it increases the SD coefficient. This means that E

r
can be used in addition to magnetic configuration changes for both loss mitigation and energy deposition profile optimization.
Effect of buffer layer on thermal recovery of superconducting nanowire single-photon detector
Authors: Xu T , Chen S , Shi H K , Jia X Q , Zhang L B , Zhao Q Y , Tu X C , Kang L , Chen J , Wu P H
Published: May 2021

Superconducting nanowire single-photon detectors (SNSPDs) wherein ultrathin films are fabricated on Si substrates are greatly affected by lattice mismatch between the thin film and the substrate. A buffer layer can be used to reduce such lattice mismatch or optimize the strain in the film, thereby improving device performance. We prepared and optimized Nb5N6 as a buffer layer and found that it considerably improved the properties of NbN films on Si substrates. The zero-resistance critical temperature (T
C0) of a 3 nm thick NbN film with a 20 nm thick buffer layer was 10.3 K. SNSPDs with Nb5N6-buffered NbN films were fabricated and compared with normal devices; the fabricated devices had high hysteresis current and low timing jitter. Furthermore, we investigated the thermal diffusion process of the device based on the hysteresis current and hotspot relaxation time and found that Nb5N6 buffer layers enhance the thermal coupling between the superconducting film and substrates. The relaxation time of buffered SNSPD was 14.2 ps, which was shorter than that of nonbuffered SNSPD by 17.8 ps. These effects explain the performance improvement observed in the case of the buffered devices.
Single ion thermal wave packet analyzed via time-of-flight detection
Authors: Stopp Felix , Ortiz-Gutiérrez Luis , Lehec Henri , Schmidt-Kaler Ferdinand
Published: May 2021

A single 40Ca ion is confined in the harmonic potential of a Paul trap and cooled to a temperature of a few mK, with a wave packet of sub-μm spatial and sub-m s−1 velocity uncertainty. Deterministically extracted from the Paul trap, the single ion is propagating over a distance of 0.27 m and detected. By engineering the ion extraction process on the initial wave packet, theoretically modeling the ion trajectories, and studying experimentally the time-of-flight distribution, we directly infer the state of the previously trapped ion. This analysis allows for accurate remote sensing of the previous motional excitation in the trap potential, both coherently or incoherently. Our method paves a way to extract, manipulate and design quantum wave packets also outside of the Paul trap.
High-fidelity formation of deeply bound ultracold molecules via non-Hermitian shortcut to adiabaticity
Authors: Zhang Jia-Hui , Dou Fu-Quan
Published: May 2021

Stimulated Raman adiabatic passage allows robust transfer between two ends of a three-state quantum system and has been employed to transfer weakly bound Feshbach molecules into their deeply bound rovibrational ground state. However, the efficient transfer remains to be explored. Here we propose a possible alternative route, based on a recently developed non-Hermitian shortcut to adiabaticity method. It is able to realize single-step transfer efficiencies up to 100% even in the presence of a decaying excited level, surpassing all the previous methods. We also prove that our scheme is robust against the external field parameter fluctuations and is expected to be applicable for abundant molecular species.
Preparation of one 87Rb and one 133Cs atom in a single optical tweezer
Authors: Brooks R V , Spence S , Guttridge A , Alampounti A , Rakonjac A , McArd L A , Hutson Jeremy M , Cornish Simon L
Published: May 2021

We report the preparation of exactly one 87Rb atom and one 133Cs atom in the same optical tweezer as the essential first step towards the construction of a tweezer array of individually trapped 87Rb133Cs molecules. Through careful selection of the tweezer wavelengths, we show how to engineer species-selective trapping potentials suitable for high-fidelity preparation of Rb + Cs atom pairs. Using a wavelength of 814 nm to trap Rb and 938 nm to trap Cs, we achieve loading probabilities of 0.508(6) for Rb and 0.547(6) for Cs using standard red-detuned molasses cooling. Loading the traps sequentially yields exactly one Rb and one Cs atom in 28.4(6)% of experimental runs. Using a combination of an acousto-optic deflector and a piezo-controlled mirror to control the relative position of the tweezers, we merge the two tweezers, retaining the atom pair with a probability of

0.9

9

(

−
0.02

)

(

+
0.01

)

. We use this capability to study hyperfine-state-dependent collisions of Rb and Cs in the combined tweezer and compare the measured two-body loss rates with coupled-channel quantum scattering calculations.
Soliton solutions of a (3+1)-dimensional nonlinear evolution equation for modeling the dynamics of ocean waves
Authors: Jadaun Vishakha
Published: May 2021

The (3+1)-dimensional generalized nonlinear evolution equation (gNLEE) is analyzed to model oceanic waves. One-parameter Lie group of infinitesimal transformations method is applied to the (3+1)-dimensional gNLEE. Invariant condition satisfying fourth-order prolongation and generators of infinitesimal transformations are found. The (3+1)-dimensional gNLEE is reduced to ordinary differential equations (ODEs) for the different vector fields obtained by the Lie group of transformations method. The key finding for the study of breathers and solitons that account for waveform perturbation and dispersion, including nonlinear impacts, is elaborated. Discussion of wave-wave interactions, using graphic interpretation, to explain the formation of directional large-amplitude rogue waves is explained. It is found that the scale in the crest direction becomes finite as the coherence becomes diagonal. In addition, unstable wave fields, beam dynamics, and interactions among solitons are seen.
Nonlinear MHD simulations of external kinks in quasi-axisymmetric stellarators using an axisymmetric external rotational transform approximation
Authors: Ramasamy R. , Hoelzl M. , Strumberger E. , Lackner K. , Günter S.
Published: May 2021

Reduced magnetohydrodynamic (MHD) equations are used to study the nonlinear dynamics of external kinks in a quasi-axisymmetric (QA) stellarator with varying fractions of external rotational transform. The large bootstrap currents associated with high beta plasmas may make QA configurations susceptible to low n external modes, limiting their operational space. The violence of the nonlinear dynamics, and, in particular, when these modes lead to a disruption, is not yet understood. In this paper, the nonlinear phase of external kinks in an unstable QA configuration with an edge safety factor below two is simulated. An axisymmetric approximation of this stellarator is constructed in the nonlinear MHD code, JOREK, capturing the influence of the external rotational transform. The use of this approximation for the considered stellarator is validated by comparing the linear dynamics against the linear viscoresistive MHD code, CASTOR3D. The nonlinear dynamics of this stellarator approximation are compared with an equivalent tokamak to understand the influence of a relatively small external rotational transform. While the external rotational transform does have a stabilizing influence on the MHD activity, it remains violent. To explore the first order influence of a larger external rotational transform, this equilibrium parameter is artificially increased for the considered stellarator, reducing the effective plasma current. The violence of the kink instability is quantified, and shown to reduce with the increasing external rotational transform. At the same time, the external kink triggers internal modes that exacerbate the loss in confinement during the nonlinear phase, such that it remains large over much of the parameter space. It is only with a significant fraction of external rotational transform that these subsequent modes are stabilized.