bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced photocatalytic water splitting of TiO2 by decorating with facet-controlled Au nanocrystals
Authors: Guan Xiangjiu , Liu Maochang , Mao Samuel S. , Shen Shaohua
Published: October 2021

Localized surface plasmon resonance (LSPR) has drawn much interest in photocatalysis due to the advantages in extending light-absorption and improving charge-separation efficiency. In this work, Au nanocubes with exposed {100} facets and Au nanotrioctahedrons with exposed {221} facets are synthesized via the seed-growth method with the aim of demonstrating the photocatalytic performance under the LSPR effect using a typical TiO2 photocatalyst. The modification of Au nanocrystals results in accelerated charge separation in the TiO2 photocatalyst, which is attributed to the synergetic effect of local electromagnetic field enhancement from the LSPR effect and the Schottky junction established in Au and TiO2. Consequently, the photocatalytic hydrogen-production from the TiO2 photocatalyst is greatly improved. Moreover, Au nanotrioctahedrons modified TiO2 exhibits superior photocatalytic performance due to the stronger local electromagnetic field of the LSPR and the more efficient electron trapping originated from the unique morphology with exposed {221} facets.
Ultrafast vibrational dynamics of a solute correlates with dynamics of the solvent
Authors: Crum Vivian F. , Kiefer Laura M. , Kubarych Kevin J.
Published: October 2021

Two-dimensional infrared (2D-IR) spectroscopy is used to measure the spectral dynamics of the metal carbonyl complex cyclopentadienyl manganese tricarbonyl (CMT) in a series of linear alkyl nitriles. 2D-IR spectroscopy provides direct readout of solvation dynamics through spectral diffusion, probing the decay of frequency correlation induced by fluctuations of the solvent environment. 2D-IR simultaneously monitors intramolecular vibrational energy redistribution (IVR) among excited vibrations, which can also be influenced by the solvent through the spectral density rather than the dynamical friction underlying solvation. Here, we report that the CMT vibrational probe reveals solvent dependences in both the spectral diffusion and the IVR time scales, where each slows with increased alkyl chain length. In order to assess the degree to which solute–solvent interactions can be correlated with bulk solvent properties, we compared our results with low-frequency dynamics obtained from optical Kerr effect (OKE) spectroscopy—performed by others—on the same nitrile solvent series. We find excellent correlation between our spectral diffusion results and the orientational dynamics time scales from OKE. We also find a correlation between our IVR time scales and the amplitudes of the low-frequency spectral densities evaluated at the 90-cm−1 energy difference, corresponding to the gap between the two strong vibrational modes of the carbonyl probe. 2D-IR and OKE provide complementary perspectives on condensed phase dynamics, and these findings provide experimental evidence that at least at the level of dynamical correlations, some aspects of a solute vibrational dynamics can be inferred from properties of the solvent.
Polarization-controlled amplified spontaneous emission in 2D semiconductors with birefringent microcavity
Authors: Jung Jin-Woo , Choi Hyeon-Seo , Lee Taejin , Lee Young-Jun , Hong Sang-Hyun , Kang Jang-Won , Cho Chang-Hee
Published: October 2021

We report on the polarization-controlled amplification of excitonic emission in the monolayer WS2 coupled with ZnO microcavity. From polarization-resolved micro-photoluminescence spectroscopy and numerical modeling, we found that the polarization of WS2 excitonic emission can be tailored by the whispering gallery modes of the birefringent ZnO microcavity. Furthermore, the light input–light output curves exhibit the clear threshold kink and the superlinear increase in the output intensity for both the TM and TE polarization modes, indicating the polarization-dependent amplification of excitonic emission. Our results suggest an approach to realize the polarization-controlled photonic devices based on 2D materials.
Support vector machines for learning reactive islands
Authors: Naik Shibabrat , Krajňák Vladimír , Wiggins Stephen
Published: October 2021

We develop a machine learning framework that can be applied to data sets derived from the trajectories of Hamilton’s equations. The goal is to learn the phase space structures that play the governing role for phase space transport relevant to particular applications. Our focus is on learning reactive islands in two degrees-of-freedom Hamiltonian systems. Reactive islands are constructed from the stable and unstable manifolds of unstable periodic orbits and play the role of quantifying transition dynamics. We show that the support vector machines are an appropriate machine learning framework for this purpose as it provides an approach for finding the boundaries between qualitatively distinct dynamical behaviors, which is in the spirit of the phase space transport framework. We show how our method allows us to find reactive islands directly in the sense that we do not have to first compute unstable periodic orbits and their stable and unstable manifolds. We apply our approach to the Hénon–Heiles Hamiltonian system, which is a benchmark system in the dynamical systems community. We discuss different sampling and learning approaches and their advantages and disadvantages.
Holographic tomography of dynamic three-dimensional acoustic vortex beam in liquid
Authors: Cao Junmei , Yang Kexin , Fang Xinsheng , Guo Ling , Li Yong , Cheng Qian
Published: October 2021

Acoustic vortex beams have attracted significant research interest in the last decade. The orbital angular momentum provides an additional degree-of-freedom, hence attracting attention in physics and technology. Generation and measurement are important parts of acoustic vortex research. For the production of acoustic vortices, it is convenient and less costly to use passive materials. Moreover, a point-by-point scanning procedure with a hydrophone still remains the commonly used method and is cumbersome to measure a three-dimensional acoustic field. However, an acoustic vortex field is usually three-dimensional, dynamic, and complex. Thus, the demand for imaging methods for complex pressure distributions has emerged. Herein, we introduced an improved hybrid single-arm coiling slit to generate an acoustic vortex with a deep potential well and infirm focusing. In addition, we proposed a method for holographic reconstruction and visualization of a three-dimensional acoustic field, which does not destroy the acoustic field information. The spatial-temporal properties of the acoustic vortex in the experiment closely match that of theoretical prediction. This study provides a reference for the manipulation and representation of a three-dimensional underwater acoustic wave.
Hydrodynamics of fringing-field induced defects in nematic liquid crystals
Authors: James Richard , Willman Eero , Ghannam Rami , Beeckman Jeroen , Fernández F. Aníbal
Published: October 2021

Consumer demand for high resolution and high refresh-rate displays has naturally led to the fabrication of liquid crystal displays with ever smaller pixels. As a consequence, fringing fields between adjacent pixels grow in magnitude, leading to abrupt changes in orientation. Electric field strengths above some threshold can lead to order melting and, in turn, disclinations. This paper presents accurate modeling of disclinations induced by fringing fields due to interdigitated electrodes in a nematic liquid crystal calculated by means of the Landau–de Gennes theory. Disclination paths are determined while taking into account the flow of the liquid crystal. Making use of interdigitated electrodes, precise electrical control over the creation and positioning of defects is demonstrated for homeotropic, planar, hybrid, and in-plane surface alignments.
Magnetic-field-induced transformation and strain in polycrystalline FeMnGa ferromagnetic shape memory alloys with high cold-workability
Authors: Zhang Yajiu , Wu Zhigang , Hou Zhipeng , Liu Zhuhong , Liu Enke , Xi Xuekui , Wang Wenhong , Wu Guangheng
Published: October 2021

Poor mechanical properties severely impede the practical application of ferromagnetic shape memory alloys. In this Letter, we report cold deformation-induced B2-γ phase transformation in polycrystalline FeMnGa alloys. Due to this property, the alloy achieved a high strength of ∼1000 MPa and a ductility of ∼75% in a compressive test, and a 90% deformation in thickness in a cold rolling experiment, indicating excellent cold-workability. The recrystallization annealing transformed the cold rolled γ phase to a textured B2 phase, which exhibited magnetic-field-induced phase transformation and anisotropic transformation strains. These properties indicate that FeMnGa is a promising candidate for future applications in actuator devices.
Synthetic antiferromagnetic layer based on Pt/Ru/Pt spacer layer with 1.05 nm interlayer exchange oscillation period for spin–orbit torque devices
Authors: Saito Yoshiaki , Ikeda Shoji , Endoh Tetsuo
Published: October 2021

We investigated interlayer exchange coupling through Pt/Ru/Pt and Pt/Ru multilayers as candidates of nonmagnetic spacer layers in the synthetic antiferromagnetic (AF) layer, which is available for studying AF spintronics using current-induced spin–orbit torque (SOT) switching originating from the spin Hall effect. The AF interlayer exchange coupling with the oscillation period of Λ2 ∼ 1.05 nm was observed even for the face-centered cubic (fcc) Pt (tPt)/hexagonal Ru/fcc Pt (tPt) nonmagnetic spacer layer structures in the wide range of both Pt and total nonmagnetic spacer layer thicknesses (0 ≤ tPt ≤ 0.8 nm, 1.0 ≤ ttotal ≤ 2.3 nm), which would be useful for the systematic investigation of the SOT on the AF structure. Moreover, we observed the disappearance of the one oscillation period (Λ1 ∼ 1.65 nm) in the case of Pt(111)/Ru(0001) and Pt(111)/Ru(0001)/Pt(111) spacer layers, whereas the existence of two oscillation periods of AF interlayer exchange coupling (Λ1 ∼ 1.65 nm and Λ2 ∼ 1.05 nm) in the case of Ru spacer layer was observed. We expect that the Pt/Ru/Pt spacer layer with the oscillation period of Λ2 ∼ 1.05 nm will pave a way to the AF spintronics based on the multilayer systems.
Composition dependencies of crystal structure and electrical properties of epitaxial tetragonal (Bi, Na)TiO3–BaTiO3 films grown on (100)cSrRuO3//(100)SrTiO3 substrates by pulsed laser depositions
Authors: Ishihama Keisuke , Shimizu Takao , Yamaoka Wakiko , Tsurumaru Risako , Yoshimura Shintaro , Sato Yusuke , Funakubo Hiroshi
Published: October 2021

Lead-free piezoelectric (1 − x)(Bi, Na)TiO3–xBaTiO3 (x = 0.06–1.0) thin films were deposited, and their crystal structures, ferroelectricity, and piezoelectric properties were studied. These films were epitaxially grown on SrRuO3 covered (100) SrTiO3 substrates by pulsed laser deposition using ceramic targets. For all the compositions, the tetragonal films were found to be grown with (001), polar-axis orientation, mainly due to the thermal strain caused by the different thermal expansion coefficients between the substrate and films. Tetragonal films with x = 0.3 and 0.5 showed higher tetragonality, c/a ratio, than the reported values for the bulk ceramics due to the clamp of the in-plane a-axis by underlying SrRuO3 lattice. Here, a and c are the lattice parameters along in-plane and out-of-plane directions, respectively. This larger c/a ratio results in higher Curie temperature. It was revealed that remanent polarization and coercive electric field correlate with the increase in the c/a ratio of the films. The film with x = 0.06 exhibits the maximum piezoelectric property.
Low thermal conductivity of complex thermoelectric barium silicide film epitaxially grown on Si
Authors: Ishibe Takafumi , Chikada Jinichiro , Terada Tsukasa , Komatsubara Yuki , Kitaura Reona , Yachi Suguru , Yamashita Yudai , Sato Takuma , Suemasu Takashi , Nakamura Yoshiaki
Published: October 2021

We achieved substantially low thermal conductivity by introducing some crystal disorder into complex material BaSi2 films on Si substrates for realization of a high-performance thermoelectric material. The BaSi2 films/Si exhibited a low thermal conductivity of 0.96 W m−1 K−1 without nanostructuring, which is less than about two-thirds value of bulk BaSi2 and is the lowest among ecofriendly silicide materials. This substantially low thermal conductivity was brought by both the use of complex material with intrinsically low phonon group velocity and the introduction of point defects as the crystal disorder. The first-principles calculations revealed that the point defect modulates the phonon dispersion relation lowering longitudinal acoustic phonon group velocity. However, the transverse acoustic phonon group velocity was increased at the same time, resulting in a negligible change in average acoustic phonon group velocity. This indicated that the crystal disorder effect related to point defects in this system is enhancement of phonon scattering, not lowering phonon group velocity. The BaSi2 films/Si with point defects exhibited a higher thermoelectric power factor (2.9 μW cm−1 K−2) than bulk BaSi2. These results highlight that complex material BaSi2 film/Si with point defects, having substantially low thermal conductivity, is a candidate as a thermoelectric power generator material in the sensor network.
Active control for enhancing vortex induced vibration of a circular cylinder based on deep reinforcement learning
Authors: Mei Yu-Fei , Zheng Chun , Aubry Nadine , Li Meng-Ge , Wu Wei-Tao , Liu Xianglei
Published: October 2021

In the current paper, the active flow control for enhancing vortex induced vibration (VIV) of a circular cylinder, which can be potentially applied in ocean energy harvesting, is achieved by an artificial neural network (ANN) trained through deep reinforcement learning (DRL). The flow past a circular cylinder with and without jet control located on the cylinder is numerically investigated using OpenFOAM, and the ANN is applied to learn an active flow control strategy through experimenting with different mass flow rates of the jets. According to our results, the jets on the cylinder are able to dramatically destabilize the periodic shedding of the cylinder wake, which leads to a much larger VIV and work capability of the cylinder. Through controlling the flow rate of the jets based on the observation of the instantaneous flow field, the ANN successfully increases the drag by 30.78%, and the magnitude of the fluctuation of the drag and lift coefficient by 785.71% and 139.62%, respectively, while the energy consumption of the jets is almost negligible. Furthermore, the net energy output by VIV with jet control increases by 357.63% (case of water) compared with the uncontrolled situation. The results demonstrate that the performance of the active jet control strategy established by DRL for enhancing VIV is outstanding and promising for realizing the transformation from the ocean energy to electrical energy. Therefore, it is encouraged to perform further investigations on VIV enhancement using active flow control based on DRL.
Wake-up and fatigue mechanisms in ferroelectric Hf0.5Zr0.5O2 films with symmetric RuO2 electrodes
Authors: Fields Shelby S. , Smith Sean W. , Jaszewski Samantha T. , Mimura Takanori , Dickie Diane A. , Esteves Giovanni , David Henry M. , Wolfley Steve L. , Davids Paul S. , Ihlefeld Jon F.
Published: October 2021

The mechanisms leading to wake-up and fatigue in ferroelectric hafnium zirconium oxide thin film devices with symmetric RuO2 electrodes are investigated via polarization, relative permittivity, dielectric nonlinearity, pyroelectric coefficient, and microfocus x-ray diffraction (XRD) measurements. The devices are observed to wake-up for up to 103 bipolar pulsed field cycles, after which fatigue occurs with polarization approaching zero following 108 cycles. Wake-up is accompanied by a decrease in both high-field permittivity and hysteresis loop pinching and an increase in the pyroelectric coefficient, indicating that the wake-up process involves a combination of transformations from the tetragonal to the orthorhombic phase and domain depinning from defect redistribution. Fatigue is observed to coincide with an increase in irreversible domain wall motion and a decrease in pyroelectric coefficient. Finite pyroelectric coefficients are measured on fully fatigued devices, indicating that domain pinning is a strong contributor to fatigue and that fatigued devices contain domain structures that are unable to switch under the fields applied for measurement. Microfocus XRD patterns measured on each device reveal that the phase constitution is qualitatively unaffected by field cycling and resultant polarization fatigue. These data indicate that the wake-up process has contributions from both phase transformations and domain depinning, whereas the fatigue process is driven primarily by domain pinning, and the near-zero measured switchable polarization is actually a poled device with immobile domains. These observations provide insight into the physical changes occurring during field cycling of HfO2-based ferroelectrics while examining a possible oxide electrode material for silicon CMOS device implementation.
Spin–orbit torque switching in a single (Ga,Mn)(As,P) layer with perpendicular magnetic anisotropy
Authors: Park Seongjin , Lee Kyung Jae , Lee Sanghoon , Liu Xinyu , Dobrowolska Margaret , Furdyna Jacek K.
Published: October 2021

We report the observation of current induced spin–orbit torque (SOT) switching of magnetization in a (Ga,Mn)(As,P) film using perpendicular magnetic anisotropy. Complete SOT switching of magnetization was achieved with current densities as low as 7.4 × 105 A/cm2, which is one to two orders of magnitude smaller than that normally used for SOT switching in ferromagnet/heavy metal bilayer systems. The observed magnetization switching chirality during current scans is consistent with SOT arising from spin polarization caused by the Dresselhaus-type spin–orbit-induced (SOI) fields. The magnitudes of effective SOI fields corresponding to the SOT were obtained from shifts of switching angles in angular dependent Hall measurements observed for opposite current polarities. By measuring effective SOI fields for the [11̄0] and the [110] current directions, we were then able to separate the values of the Dresselhaus-type (HeffD) and Rashba (HeffR) SOI fields. At a current density of 6.0 × 105 A/cm2, these values are HeffD=6.73Oe and HeffR=1.31Oe, respectively. The observed ratio of about 5:1 between Dresselhaus-type and Rashba SOI fields is similar to that observed in a GaMnAs film with an in-plane magnetic anisotropy.
A digital feedback system for advanced ion manipulation techniques in Penning traps
Authors: Herkenhoff Jost , Door Menno , Filianin Pavel , Huang Wenjia , Kromer Kathrin , Lange Daniel , Schüssler Rima X. , Schweiger Christoph , Eliseev Sergey , Blaum Klaus
Published: October 2021

The possibility of applying active feedback to a single ion in a Penning trap using a fully digital system is demonstrated. Previously realized feedback systems rely on analog circuits that are susceptible to environmental fluctuations and long term drifts, as well as being limited to the specific task they were designed for. The presented system is implemented using a field-programmable gate array (FPGA)-based platform (STEMlab), offering greater flexibility, higher temporal stability, and the possibility for highly dynamic variation of feedback parameters. The system’s capabilities were demonstrated by applying feedback to the ion detection system primarily consisting of a resonant circuit. This allowed shifts in its resonance frequency of up to several kHz and free modification of its quality factor within two orders of magnitude, which reduces the temperature of a single ion by a factor of 6. Furthermore, a phase-sensitive detection technique for the axial ion oscillation was implemented, which reduces the current measurement time by two orders of magnitude, while simultaneously eliminating model-related systematic uncertainties. The use of FPGA technology allowed the implementation of a fully-featured data acquisition system, making it possible to realize feedback techniques that require constant monitoring of the ion signal. This was successfully used to implement a single-ion self-excited oscillator.
Thiophene- and selenophene-based conjugated polymeric mixed ionic/electronic conductors
Authors: Sachinthani K. A. Niradha , Panchuk Jenny R. , Wang Yuhang , Zhu Tong , Sargent Edward H. , Seferos Dwight S.
Published: October 2021

Mixed ionic/electronic conductors (MIECs) are desirable materials for next-generation electronic devices and energy storage applications. Polymeric MIECs are attractive from the standpoint that their structure can be controlled and anticipated to have mechanically robust properties. Here, we prepare and investigate conjugated copolymers containing thiophene and selenophene repeat units and their homopolymer counterparts. Specifically, thiophene bearing a triethylene glycol (EG3) side chain was polymerized and copolymerized with dodecyl thiophene/selenophene monomers. The synthesis leads to a class of copolymers that contain either S or Se and are blocky in nature. The Li-ion conductivity of ionically doped copolymers, P3DDT-s-P3(EG3)T and P3DDS-s-P3(EG3)T (9.7 × 10−6 and 8.2 × 10−6 S/cm, respectively), was 3–4 fold higher than that of the ionically doped constituent homopolymer, P3(EG3)T (2.2 × 10−6 S/cm), at ambient conditions. The electronic conductivity of the oxidatively doped copolymers was significantly higher than that of the constituent homopolymer P3(EG3)T, and most notably, P3DDS-s-P3(EG3)T reached ∼7 S/cm, which is the same order of magnitude as poly(3-dodecylthiophene) and poly(3-dodecylselenophene), which are the highest oxidatively doped conductors based on control experiments. Our findings provide implications for designing new MIECs based on copolymerization and the incorporation of heavy atom heterocycles.
Fabrication and analysis of InAlN/GaN metal–insulator–semiconductor high-electron-mobility transistors based on AlN/GaN superlattice channel
Authors: Nguyen Trung Huu , Takahashi Tokio , Chonan Hiroshi , Van Nguyen Hoang , Yamada Hisashi , Yamada Toshikazu , Shimizu Mitsuaki
Published: October 2021

In this work, InAlN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) based on the AlN/GaN superlattice channel have been demonstrated. The devices fabricated with the AlN/GaN superlattice channel perform superior characteristics over other relative devices consisted of the conventional single GaN channel. The effective channel-electron mobility, maximum drain current, ON-resistance, and the ION/IOFF ratio of the superlattice-channel-based MIS-HEMTs are approximately 932 cm2 V−1 s−1, 57 mA/mm, 62 Ω mm, and 108 and those of the conventional structure are 820 cm2 V−1 s−1, 48 mA/mm, 92 Ω mm, and 104, respectively. Additionally, this work has shown that the AlN/GaN superlattice channel has the ability to suppress leakage currents. As a result, the breakdown voltage of the device based on the superlattice structure without the back barrier is approximately 500 V, which is 430 V higher than that based on the single GaN channel.
Metastability engineering of partially recrystallized C-doped non-equiatomic CoCrFeNiMo medium-entropy alloy
Authors: Kwon Hyeonseok , Zargaran Alireza , Asghari-Rad Peyman , Kim Eun Seong , Gu Gang Hee , Lee Jungwan , Moon Jongun , Bae Jae Wung , Kim Hyoung Seop
Published: October 2021

Ferrous medium-entropy alloys (FeMEAs) are coming into attention these days for their excellent mechanical properties. Most of the FeMEAs developed so far form metastable face-centered cubic (FCC) matrix, and “metastability engineering” that utilizes deformation-induced martensitic transformation (DIMT) from FCC to body-centered cubic (BCC) as a method to enhance work hardenability has been the key to the exceptional mechanical behaviors. However, the FeMEAs have a significant weakness: low yield strength compared with high tensile strength and ductility. In this study, partial recrystallization is presented as a solution to the current drawback of the FeMEAs. A Co18.5Cr12Fe55Ni9Mo3.5C2 (at. %) FeMEA was annealed at 800 °C for 10 and 30 min and partially recrystallized microstructures with relatively coarse non-recrystallized grains that contain profuse mechanical twins and ultrafine recrystallized grains were attained. In addition, nanosized Cr-rich M23C6-type and Mo-rich M6C-type carbides were precipitated during the annealing. The partially recrystallized FeMEA showed a yield strength of ∼1.07 GPa, significantly enhanced from ∼600 MPa of the recrystallized counterpart. Dislocation strengthening, precipitation strengthening, grain boundary strengthening, and twin boundary strengthening led to the improved strength of the partially recrystallized FeMEA. Back stress hardening owing to the heterogeneity also contributed to the high strength and work hardenability. Moreover, the transformation-induced plasticity effect from the FCC-to-BCC DIMT activated by BCC nucleation at defects within the non-recrystallized grains effectively enhanced the work hardenability, leading to ∼1.34 GPa of tensile strength and ∼30% of elongation. This study provides an insight to optimize the microstructure and corresponding mechanical properties of metastable metallic materials.
Full control of superconducting qubits with combined on-chip microwave and flux lines
Authors: Manenti Riccardo , Sete Eyob A. , Chen Angela Q. , Kulshreshtha Shobhan , Yeh Jen-Hao , Oruc Feyza , Bestwick Andrew , Field Mark , Jackson Keith , Poletto Stefano
Published: October 2021

As the field of quantum computing progresses to larger-scale devices, multiplexing will be crucial to scale quantum processors. While multiplexed readout is common practice for superconducting devices, relatively little work has been reported about the combination of flux and microwave control lines. Here, we present a method to integrate a microwave line and a flux line into a single “XYZ line.” This combined control line allows us to perform fast single-qubit gates as well as to deliver flux signals to the qubits. The measured relaxation times of the qubits are comparable to state-of-the-art devices employing separate control lines. We benchmark the fidelity of single-qubit gates with randomized benchmarking, achieving a fidelity as high as 99.93±0.04%, and we demonstrate that XYZ lines can in principle be used to run parametric entangling gates.
An enhanced plasma injection method for triggering a 10 cm-magnitude high-pressure SF6 gas gap for a megavolt ultrafast bypass switch
Authors: Li Xiaoang , Gao Gan , Jiang Pan , Zhang Ningbo , Li Zhibing , Zhang Qiaogen
Published: October 2021

Aiming at developing a megavolt ultrafast bypass switch (UFBPS) that operates at a very low working coefficient, an enhanced plasma injection (EPI) method was proposed, which ejected high-density plasmas up to several centimeters in height in a high-pressure SF6 and thus has an extremely strong triggering ability. The EPI method employed a thin polytetrafluoroethylene microcavity embedded inside the ground electrode and a metal wire electrically exploded inside the microcavity, generating a high-density metal vapor plasma that was rapidly ejected outward from the nozzle and inducing a breakdown of the residual gas gap. In this study, the ejected plasma properties by EPI and main influencing factors were examined and the EPI triggering ability was experimentally verified. The results showed that EPI evolution presented three stages: ellipsoid-shaped, mushroom-shaped, and dissipation stages. In 0.5-MPa SF6, when the trigger energy was 960 J and the exploded aluminum wire was 300 µm in radius, the EPI maximum height reached over 9 cm within 0.7 ms, with an initial evolution velocity >800 m/s. Then, an EPI cavity array was set to repetitively trigger a 10 cm-magnitude SF6 gas gap at 0.5 MPa, with a theoretical breakdown voltage >2 MV. The gas gap was successfully triggered with an average trigger delay of 538 µs when a DC 100 kV voltage (undervoltage ratio <5%) was applied. These results indicated that EPI was an effective method for triggering megavolt-magnitude high-pressure SF6 gas gaps at a low undervoltage ratio and meeting the submillisecond trigger requirement of the UFBPS.
Ubiquity of ring structures in the control space of complex oscillators
Authors: Ramírez-Ávila Gonzalo Marcelo , Kurths Jürgen , Gallas Jason A. C.
Published: October 2021

We report the discovery of two types of stability rings in the control parameter space of a vertical-cavity surface-emitting semiconductor laser. Stability rings are closed parameter paths in the laser control space. Inside such rings, laser stability thrives even in the presence of small parameter fluctuations. Stability rings were also found in rather distinct contexts, namely, in the way that cancerous, normal, and effector cells interact under ionizing radiation and in oscillations of an electronic circuit with a junction-gate field-effect transistor (JFET) diode. We argue that stability-enhancing rings are generic structures present in the control parameter space of many complex systems.
Realizing high thermoelectric performance in N-type Bi2Te3 compounds by Sb nano-precipitates
Authors: Sun Jiepu , Shu Zhong , Yang Jianmin , Wang Tiancheng , Zhu Bin , He Jiaqing
Published: October 2021

Driven by the prospective application of thermoelectric (TE) materials, massive efforts have been devoted to improving its performance. However, strong-coupled thermal and electrical transport is still the largest block for the promotion of TE techniques. Here, we report a peak ZT over 1.2 at 400 K in an n-type Bi2Te2.7Se0.3 sample doped by 5 wt. % Sb under the spark plasma sintering method. This high performance is attributed to the synergistically optimized thermal and electrical transport properties. Sb nano-precipitates, which have been observed directly by spherical aberration-corrected transmission electron microscopy, substantially decrease the lattice thermal conductivity of the sample, leading to a low value of 0.35 W m−1 K−1. Meanwhile, band bending caused by the nano-precipitates significantly enhances the Seebeck coefficient, resulting in a high PF of 35 μW cm−1 K−2. The study about optimizing electrical and thermal properties simultaneously opens the door to the high performance of Bi2Te3-based materials.
Determining the enantioselectivity of asymmetric hydrogenation through parahydrogen-induced hyperpolarization
Authors: Jiang Wenlong , Peng Qiwei , Sun Huijun , Zhang Qi , Huang Chengda , Cao Shuohui , Wang Xinchang , Chen Zhong
Published: October 2021

Asymmetric hydrogenation plays an essential role for both academic research and industry to produce enantiomeric pure chiral molecules. Although nuclear magnetic resonance (NMR) is powerful in determining the yields of hydrogenation, it is still challenging to use NMR for chirality-related analysis. Herein, we applied parahydrogen-induced hyperpolarization (PHIP) NMR to determine the enantioselectivity of asymmetric hydrogenation and the absolute chirality of products. We hyperpolarized two types of unsaturated amino acid precursors, i.e., methyl-α-acetoamido cinnamate and (E)-ethyl 3-acetamidobut-2-enoate. Hydrogenation of prochiral substrates with parahydrogen gave temporary hyperpolarized diastereoisomers, which exhibit different PHIP patterns distinguishable in 1H NMR. After assigning the NMR peaks by density functional theory calculations, we simulated the PHIP patterns of all the possible temporary hyperpolarized diastereoisomers and unambiguously assigned the chirality of the products and the enantioselectivity of asymmetric hydrogenation. Our work demonstrates the application and potential of PHIP in revealing the mechanism of asymmetric hydrogenation.
High frequency focal transducer with a Fresnel zone plate for intravascular ultrasound
Authors: Su Min , Xia Xiangxiang , Liu Baoqiang , Zhang Zhiqiang , Liu Rong , Cai Feiyan , Qiu Weibao , Sun Lei
Published: October 2021

The diameter of an intravascular ultrasound (IVUS) catheter is always less than 1 mm, because it must be inserted into a blood vessel to obtain ultrasound images. Owing to this requisite small size, it is difficult to perform geometric focusing on the surface of an IVUS transducer to improve the spatial resolution of the image. This study proposes a high frequency transducer with a Fresnel zone plate (FZP) for intravascular ultrasound imaging. Through theoretical calculations, the parameters and structure of the transducer are optimized for high-frequency ultrasound. The acoustic beam is simulated using COMSOL software. The aperture size of the ultrasound element is 0.778 × 0.9 mm2. Transducers with or without the FZP layer are designed and fabricated in this study. The center frequency and –6 dB bandwidth of the FZP transducer are 52.5 MHz and 42%, respectively. Meanwhile, the center frequency and –6 dB bandwidth of the plane-shape transducer are 51.3 MHz and 58%, respectively. Wire phantom and porcine artery imaging experiments were performed to evaluate the performance of the designed transducers. The spatial resolution of the FZP transducer is 46.8 μm axially and 183.6 μm laterally, and the resolution of the plane-shape transducer is 44.3 μm axially and 313.5 μm laterally. The results demonstrate that the FZP transducer provides superior lateral imaging resolution for IVUS applications.
Feasibility Analysis of Net Metering Execution in Hybrid Energy Systems
Authors: Akhtar Iram , Kirmani Sheeraz , Jamil Majid
Published: October 2021

Net metering is a system that gives owners of hybrid energy systems credits for the energy they add to the utility grid during the off-peak period. Extra power from hybrid energy systems can be sent to the grid and “cycled back” when the hybrid energy system is not generating power. Customers are billed only for their “net” energy use. This makes hybrid energy systems more affordable, attractive, and economic from both the utility's and the user's perspectives. On the one hand, it brings down the energy cost drastically; and on the other, it helps in creating small power generation units meant for residential users. In this way, net metering can be used in hybrid energy systems. This chapter shows the feasibility analysis of a net metering implementation in residential buildings in Ramapuram, Chennai, India, using a solar–wind hybrid energy system. The analysis shows that, with the help of the proposed scheme, a lower payback period and an annual saving in electricity bills are achieved. As an outcome, grid costs are shifted to customers working without hybrid energy systems through higher utility bills. The recent policies of the Government of India regarding the use of hybrid energy systems are also discussed in this chapter. Therefore, net metering implementation with a solar–wind hybrid energy system ensures a sustainable and happy future for a hybrid energy system that improves the welfare of all power customers.
Synchrophasor Applications to Support Power Distribution Networks
Authors: Arghandeh Reza
Published: October 2021

The distribution-level phasor measurement unit (D-PMU) is a measurement device that measures the synchronized voltage and current values of electric power distribution networks. The synchronized data achieved by D-PMUs supports situational awareness, diagnostic, and control applications in the grid. In this chapter, we review the state of the art in D-PMU design and applications to support power distribution functions. This chapter also provides researchers and practitioners in this field with a deep understanding of the tremendous role of D-PMUs in the distribution network's operation to improve the reliability, resiliency, and efficiency of the grid.
Digital Substations with the IEC 61850 Standard
Authors: Jamil Majid , Rizwan Mohammad , Bhattacharjee Tanushree , Azeem Abdul
Published: October 2021

The IEC 61850 protocols for intelligent electronic devices (IEDs) are becoming popular in various applications of power systems, such as protection, control, monitoring in real-time operation, and integration of modern devices like IEDs, analog merging units and Ethernet networks. To address the problem of the interoperability of devices from various vendors, IEC standards play a vital role. Other than protection functions, the IEC 61850 protocol has a wider role in the communication of devices in an integrated system. With the implementation of IEC 61850 standards, a substation with IEDs may be upgraded as a digital substation. In this chapter, the basics of the IEC 61850 standard with the architecture of a digital substation and applications in power systems are discussed. Hardware devices in block diagram layout and the software needed to develop a digital substation laboratory model have also been included. The chapter discusses the IEC 61850 standard in preference to other standards because the other standards do not have the capability of covering the operational aspects of different levels of substation. All other standards in substation automation use master–slave communication, whereas IEC 61850 uses the client–server communication model. The time lag for master–slave communication in a large system is huge as compared to that for client–server communication. Also, the IEC 61850 standard is self-descriptive, so fetching any information in future will be easy. This study on the IEC 61850 standard and digital substations with real-time hardware condition monitoring will provide readers with a clear idea about IEC standard-based substations and their operation in real time.
Smart Home and Building Energy Management Systems
Authors: Kuzlu Murat , Pipattanasomporn Manisa , Elma Onur
Published: October 2021

Smart home and building energy management (H/BEM) systems are one of the most critical elements to support data exchange between an energy management unit and smart devices, such as smart plugs, smart meters, smart appliances, and electric vehicles in a premises area network. An H/BEM energy management unit is typically embedded with intelligent algorithms to allow energy savings, reduce peak demand consumption, increase energy efficiency, and facilitate demand response applications. The objective of this chapter is to present a typical architecture of a smart H/BEM system, its communication network requirements, communication technologies, and protocols applicable to smart home and building applications, as well as energy savings/peak demand management algorithms. Demand response implementation studies are demonstrated using a smart home located at Yildiz Technical University. Widely used wired and wireless communication technologies for H/BEM systems discussed in this chapter are (wired) Ethernet, power line communication, ITU-T G.hn, and HomePNA, as well as (wireless) Wi-Fi, ZigBee, Z-Wave, 6LoWPAN, and EnOcean. This chapter also discusses widely used standards and protocols for home/building area networks, such as BACnet, SEP 2.0, LonWorks, KNX, X10, DALI, and U-SNAP.
Outcomes of routine screening for reproductive coercion in a family planning service
Authors: Cheng Yan , Wilson Eleanor G. , Botfield Jessica R. , Boerma Clare J. , Estoesta Jane , Peters Leslie James , McGeechan Kevin
Published: October 2021

Background Reproductive coercion (RC) occurs when a person’s autonomous decision-making regarding reproductive health is compromised by another. RC screening, that is, the use of routine, non-invasive screening questions asked of service users/clients, is one strategy that can be used to assess for RC. Routine screening for RC was implemented within Family Planning NSW clinical consultations in December 2018. A cross-sectional study was undertaken to review the outcomes of screening to better understand the situation of RC among women accessing family planning services. Methods A retrospective review of clinical consultation data of eligible women attending Family Planning NSW clinics in 2019 was undertaken. Descriptive analysis was conducted and modified Poisson regression was used to estimate prevalence ratios and assess associations between binary outcomes and client characteristics. Results Of 7943 women eligible for RC screening, 5497 were screened (69%) and 127 women (2.3%) disclosed RC. RC was more likely to be disclosed among clients who were unemployed, had a disability or had more than one visit within 1 year. Conclusions Sexual and reproductive health clinicians, in particular, are well placed to conduct RC screening. However, they must have adequate training and access to resources to implement screening and respond to women who disclose RC.
Effect of moisture content and fuel type on emissions from vegetation using a steady state combustion apparatus
Authors: Garg Priya , Roche Thomas , Eden Matthew , Matz Jacqueline , Oakes Jessica M. , Bellini Chiara , Gollner Michael J.
Published: October 2021

Emission measurements are available in the literature for a wide variety of field burns and laboratory experiments, although previous studies do not always isolate the effect of individual features such as fuel moisture content (FMC). This study explores the effect of FMC on gaseous and particulate emissions from flaming and smouldering combustion of four different wildland fuels found across the United States. A custom linear tube-heater apparatus was built to steadily produce emissions in different combustion modes over a wide range of FMC. Results showed that when compared with flaming combustion, smouldering combustion showed increased emissions of CO, particulate matter and unburned hydrocarbons, corroborating trends in the literature. CO and particulate matter emissions in the flaming mode were also significantly correlated with FMC, which had little influence on emissions for smouldering mode combustion, when taking into account the dry mass of fuel burned. These variations occurred for some vegetative fuel species but not others, indicating that the type of fuel plays an important role. This may be due to the chemical makeup of moist and recently live fuels, which is discussed and compared with previous measurements in the literature.
Slowed canonical progress in large fields of science
Authors: Chu Johan S. G. , Evans James A.
Published: October 2021

Significance

The size of scientific fields may impede the rise of new ideas. Examining 1.8 billion citations among 90 million papers across 241 subjects, we find a deluge of papers does not lead to turnover of central ideas in a field, but rather to ossification of canon. Scholars in fields where many papers are published annually face difficulty getting published, read, and cited unless their work references already widely cited articles. New papers containing potentially important contributions cannot garner field-wide attention through gradual processes of diffusion. These findings suggest fundamental progress may be stymied if quantitative growth of scientific endeavors—in number of scientists, institutes, and papers—is not balanced by structures fostering disruptive scholarship and focusing attention on novel ideas.
Detecting insulitis in type 1 diabetes with ultrasound phase-change contrast agents
Authors: Ramirez David G. , Ciccaglione Mark , Upadhyay Awaneesh K. , Pham Vinh T. , Borden Mark A. , Benninger Richard K. P.
Published: October 2021

Significance

Methods to detect type 1 diabetes (T1D) progression prior to clinical diagnosis are needed. T1D results from autoreactive T cells infiltrating the islets of Langerhans, destroying insulin-producing β-cells. Overt disease takes years to present, and at diagnosis, there is substantial β-cell loss. Therapeutic intervention to preserve β-cell mass is hampered by an inability to follow presymptomatic T1D progression. Several immunotherapies can delay T1D development. However, identifying “at-risk” individuals and tracking whether therapeutic interventions are impacting disease progression, are lacking. We present ultrasound imaging of nanodroplet (ND) contrast-agent accumulation within the islet. ND accumulation is dependent on immune infiltration; therefore, it tracks presymptomatic T1D development and progression to diabetes. This provides an opportunity to guide therapeutic treatments to prevent T1D.
Decreasing Phanerozoic extinction intensity as a consequence of Earth surface oxygenation and metazoan ecophysiology
Authors: Stockey Richard G. , Pohl Alexandre , Ridgwell Andy , Finnegan Seth , Sperling Erik A.
Published: October 2021

Significance

The decline in extinction rates through geologic time is a well-established but enigmatic feature of the marine animal fossil record. We hypothesize that this trend is driven largely by secular changes in the oxygenation of the atmosphere and oceans, as physiological principles predict that marine animals would have been more vulnerable to ocean warming during intervals of geological time with limited atmospheric oxygenation. We test this at a global oceanographic scale by combining models of ocean biogeochemistry and animal physiology. We show that atmospheric oxygen exerts a first-order control on the simulated extinction vulnerability of marine animals, highlighting its likely importance in controlling extinction trends through geologic time.
Recent increases in tropical cyclone precipitation extremes over the US east coast
Authors: Maxwell Justin T. , Bregy Joshua C. , Robeson Scott M. , Knapp Paul A. , Soulé Peter T. , Trouet Valerie
Published: October 2021

Significance

Using a tree-ring–based reconstruction of tropical cyclone precipitation summed over June 1 through October 15, we found that extremely high tropical cyclone precipitation amounts have increased over the past 300 years. By looking at other characteristics of tropical cyclones, we find that this increase is linked to the longer average duration of tropical cyclones. The extremes (≥0.95 quantile) of summed tropical cyclone precipitation have increased by 2 to 4 mm/decade since 1700, resulting in an increase of 64 to 128 mm compared to extremes in the early 1700s. This study documents increases in extremes of summed tropical cyclone precipitation, which provides another line of evidence that the speed of movement of tropical cyclones is slowing.
Evidence for massive and recurrent toxic blooms of
Alexandrium catenella
in the Alaskan Arctic
Authors: Anderson Donald M. , Fachon Evangeline , Pickart Robert S. , Lin Peigen , Fischer Alexis D. , Richlen Mindy L. , Uva Victoria , Brosnahan Michael L. , McRaven Leah , Bahr Frank , Lefebvre Kathi , Grebmeier Jacqueline M. , Danielson Seth L. , Lyu Yihua , Fukai Yuri
Published: October 2021

Significance

The neurotoxin-producing dinoflagellate
Alexandrium catenella
is shown to be distributed widely and at high concentrations in bottom sediments and surface waters of the Alaskan Arctic. Future blooms are likely to be large and frequent given hydrographic and bathymetric features that support high cell and cyst accumulations, and warming temperatures that promote bloom initiation from cysts in bottom sediments and cell division in surface waters. As the region undergoes an unprecedented regime shift, the exceptionally widespread and dense cyst and cell distributions represent a significant threat to Arctic communities that are heavily dependent upon subsistence harvesting of marine resources. These observations also highlight how warming can facilitate range expansions of harmful algal bloom species into waters where temperatures were formerly unfavorable.