bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and temporal modelling of coupled power and transportation systems: A comprehensive review
Authors: Sun Yingyun , Zhao Pengfei , Wang Liwei , Malik Sarmad Majeed
Published: May 2021

The large‐scale application of electric vehicles can lead to new challenges in the operation of the two complex and coupled networks of electricity and transportation systems, thus creating a new concept—a power—traffic network. The purpose is to provide a comprehensive survey of this emerging field. First, both the transportation system and power grid models are briefly introduced in terms of time and space scales. Then, the power traffic network model and applications at long‐term, mid‐term, and short‐term time scales are summarized, and provided a unified view of these achievements. Based on this analysis, recommendations for future research are presented.
Swarm‐based mean‐variance mapping optimization for optimal placement of energy storage with synthetic inertia control on a low inertia power grid
Authors: Rahman Fathin Saifur , Israjuddin  , Hariyanto Nanang , Liu Chih‐Wen
Published: May 2021

Utilizing energy storage systems equipped with virtual/synthetic inertia control has emerged as one of the solutions to solve low inertia issues in power systems with massive penetration of renewables. However, while the aspect regarding the control of the synthetic inertia control has been widely investigated, the optimal placement of synthetic inertia control is rarely investigated. Therefore, the optimal placement of energy storage system with synthetic inertia control based on swarm‐based mean‐variance mapping optimization is proposed. The performance of the proposed method is tested by considering several cases, both single and multiple contingencies. By utilizing the proposed method, the optimal placement of energy storage system equipped with synthetic inertia control could be obtained, in which the resulting frequency response is better compared to randomly placed ones. The proposed method could also be applied by considering multiple contingencies in different locations. Furthermore, the resulting fitness values for different independent optimization repetitions for various study cases are consistent, leading to the efficacy to be applied in the actual power system planning.
Part‐MOT: A multi‐object tracking method with instance part‐based embedding
Authors: Liu Xiaohu , Luo Yichuang , Yan Keding , Chen Jianfei , Lei Zhiyong
Published: May 2021

Part‐MOT, a one‐stage anchor‐free architecture which unifies the object identification representation and detection in one task for visual object tracking is presented. For object representation, a position relevant feature is obtained using the center‐ness information, which takes advantage of the anchor‐free ideal to encode the feature map as the instance‐aware embedding. To adapt to the object's movement, the clustering‐based method to get the global instance feature is introduced. This enables this approach more robust to make better tracking decisions. Part‐MOT achieves the state‐of‐the‐art performance on public datasets, with especially strong results for object deformation and movement changes.
A discriminative self‐attention cycle GAN for face super‐resolution and recognition
Authors: Li Xiaoguang , Dong Ning , Huang Jianglu , Zhuo Li , Li Jiafeng
Published: May 2021

Face image captured via surveillance videos in an open environment is usually of low quality, which seriously affects the visual quality and recognition accuracy. Most image super‐resolution methods adopt paired high‐quality and its interpolated low‐resolution version to train the super‐resolution network. It is difficult to achieve contented visual quality and restoring discriminative features in real scenarios. A discriminative self‐attention cycle generative adversarial network is proposed for real‐world face image super‐resolution. Based on the cycle GAN framework, unpaired samples are adopted to train a degradation network and a reconstruction network simultaneously. A self‐attention mechanism is employed to capture the contextual information for details restoring. A Siamese face recognition network is introduced to provide a constraint on identify consistency. In addition, an asymmetric perceptual loss is introduced to handle the imbalance between the degradation model and the reconstruction model. Experimental results show that the observation model achieved more realistic low‐quality face images, and the super‐resolved face images have shown better subjective quality and higher face recognition performance.
Analysis of a direct‐drive permanent magnet synchronous generator with novel toroidal winding
Authors: Wei Yanqi , Cheng Zhiping , Si Jikai , Jin Fuli , Gao Caixia , Gan Chun
Published: May 2021

Direct‐drive permanent magnet synchronous generators (DDPMSGs) are gaining more and more attention in the field of wind power because of the advantages of simple structure, high efficiency and high reliability. However, due to the extremely low rotational speed, large volume and heavy weight of DDPMSGs, it poses serious challenges for transportation and installation, which limits its application. Therefore, a DDPMSG with novel toroidal windings (NTW) is proposed to improve power density in this paper. Unlike regular windings, each coil of the NTWs is wound onto the stator yoke in the same direction. The special configuration enables the generator to have higher winding coefficient, so that the DDPMSG with NTWs (NTW‐DDPMSG) can achieve higher power density than traditional fractional slot concentrated windings (FCW). The proposed topology and operating principles are described in detail. To verify the merits of the proposed NTW‐DDPMSG, the electromagnetic parameters of two external rotor surface‐mounted DDPMSGs equipped with NTW and FCW respectively are designed. The characteristics of air‐gap magnetic field, no‐load electromotive force, output power, loss and efficiency are analysed on the conditions of different loads and speeds. Comparison results show that the proposed NTW‐DDPMSG has higher power density than FCW‐DDPMSG.
Performance investigation and parametric optimization of an eco‐friendly sustainable design solar air heater
Authors: Goel Abhishek Kumar , Singh Shailendra Narayan , Prasad B.N
Published: May 2021

The impacting air jet type collector equipped with fins underneath the absorber surface has been investigated experimentally. Real outdoor conditions were preferred for a specific range of operational parameters (mentioned in Table 1). The experimental investigation covers the analysis of temperature rise parameter (TRP) and instantaneous collector thermal efficiency. The thermal enhancement and other performance characteristics as a result of combining both (impacting air jet mechanism and fins) methods have been studied in detail. It has been observed that TRP decreases and collector efficiency increases with an increase in flow rate. The influence of variable duct aspect ratio has been examined as a function of relevant geometrical parameters of the duct. In the time span of 12.00 hrs–01.00 pm maximum rise in air temperature has been reported at different fin parameters. In conjunction with jet and fin parameters, a parametric optimization model is discussed which yields the optimum values of design parameters to attain maximum efficiency. The experimental and analytical results are validated with similar works. The comparative analysis reports a mean deviation of ±12.7% in TRP and ±7.8% in collector efficiency at w/Dh = 0.23, Dj/Dh = 0.076. The optimum values will be of great help for the researchers and designers exploring this area.
Optimal investment and operation of a microgrid to provide electricity and heat
Authors: Angarita Jorge L , Jafari Hossein , Mohseni Mojtaba , Al‐Sumaiti Ameena Saad , Heydarian‐Forushani Ehsan , Kumar Rajesh
Published: May 2021

This paper proposes a robust investment and operation model to attend the power and heat needs of a microgrid (MG) connected to the distribution system. The optimization algorithm decides on the best investment and operation of combined heat and power (CHP), boilers, PV power generation and battery energy storage systems (BESS). For the BESS, the algorithm estimates the optimal energy storage capacity (MWh) as well as the maximum hourly delivery capacity (MW). The non‐linear and non‐concave heat rate chart is recast by a mix‐integer linear model to have a tractable and precise model. The model considers the uncertain in some parameters using probability density function (pdf) to portrait its behavior. Thus, the problem has been modeled using stochastic programming approach, and its objective function is the expected value of the annual operational cost. The model is tested using a real case where two adjacent consumers share the power and heat facilities to minimize the overall up to 17% depending on the gas price scenario. The results demonstrate the benefits of employing different technologies and the synergies of all technologies operating together.
Method for functional state recognition of multifunction radars based on recurrent neural networks
Authors: Xu Xinsong , Bi Daping , Pan Jifei
Published: May 2021

Radar signal recognition plays a vital role in electronic warfare. For the multifunction radars (MFRs) with complex dynamical modes, the signal recognition needs to identify not only the emitter but also its current functional state. Existing research on MFR recognition mainly focuses on hierarchical modelling approaches. Inspired by recent progress of deep neural networks, the authors propose to further develop radar signal modelling with recurrent neural networks. Here, the authors propose a more efficient method for functional state recognition of MFRs based on a gated recurrent unit (GRU). The method makes full use of the ability of GRUs to automatically learn the characteristics of radar signal sequences, and the nonlinear modelling of GRUs can deal with the corrupted data well. Simulation results on the Mercury radar show that the proposed method achieves a great recognition accuracy with little prior information, and the designed GRU model outperforms the predictive state representation model under the same condition.
Real‐time capable multiple‐input–multiple‐output SONAR systems—An algorithmic approach
Authors: Kaak Thorben , Abshagen Jan , Schmidt Gerhard
Published: May 2021

In recent years, significant effort has been allocated to research on multiple‐input–multiple‐output (MIMO) sound navigation and ranging (SONAR) and RADAR systems. Most work has been conducted on the general theoretical functionality of such systems. Less effort has been applied to considerations of the real‐time MIMO capability, although this is an important factor for the application of these new algorithms in real SONAR systems. To account for this, the following work focusses, after introducing the used methodology and revisiting the general MIMO idea and considered system, on more effective permutations of the involved algorithms in the reduction of floating‐point operations. In this context, the general necessity of the algorithms utilized is shown. Furthermore, it is proven that the reduction in computational load does not affect the performance of the system. In addition, the main algorithmic parts of MIMO systems can be exchanged almost arbitrarily under given restrictions without changing the result. Therefore, the performance differences in floating‐point operations are depicted to give an estimate of the achievable degree of complexity reduction. The results for the investigated systems and algorithms are obtained by applying a system simulation of a simple underwater channel. The obtained results were also verified using a real MIMO SONAR system operating in real time.
Low‐slow‐small target detection using stepped‐frequency signals in a strong folded clutter environment
Authors: Guo Jinpeng , Chang Shaoqiang , Yang Fawei , Cai Jinjian , Liu Quanhua , Long Teng
Published: May 2021

The popularisation of unmanned aerial vehicles (UAVs) and the security threats that follow have made the detection of low‐slow‐small (LSS) targets a hotspot in the radar field. For ground‐based surveillance radars (GSR), the folded‐clutter is an important factor affecting LSS target detection performance. Herein, the stepped‐frequency (SF) signal is used to improve the performance of the folded‐clutter suppression and the LSS target detection for the GSR. Furthermore, an optimisation method for the SF signal parameter design is proposed to maximise the folded‐clutter improvement factor. Specifically, signal parameters including the frequency step number and the step sequence are optimised based on the clutter cognition results. To verify the effectiveness of the well‐designed SF signals in the LSS target detection, simulation experiments and field tests using an L‐band SF‐GSR and a DJI M600‐Pro UAV are conducted. Compared to the results achieved by a simple chirp signal, the detection probabilities of the LSS target with different velocities are significantly increased when the SF signals are used in a typical strong folded‐clutter background.
Non‐stationary clutter suppression method for bistatic airborne radar based on adaptive segmentation and space–time compensation
Authors: Xiong Yuanyi , Xie Wenchong
Published: May 2021

Bistatic airborne radar has excellent performance due to the separate transmitter and receiver, but its clutter distribution is usually non‐stationary, which causes the performance of the traditional Space time adaptive processing (STAP) method to fail. Herein, firstly a bistatic airborne radar clutter signal model established, followed by an analysis of its clutter distribution characteristics in detail, and finally a bistatic airborne radar space–time compensation STAP method based on adaptive segmentation is proposed. The method first uses the distribution characteristics of the peak spectral centre in the first pulse data of the airborne radar to adaptively segment the clutter data, including extremely non‐stationary, severely non‐stationary, and non‐stationary clutter regions. Then the clutter data are compensated based on the estimation value of the space–time peak spectrum centre. Finally, each range section is processed by using STAP, and the detected target Doppler frequency is adaptively moved. Simulation results verify the effectiveness of the proposed method.
Empirically revealed properties of Rieger-type cycles of stellar activity
Authors: Arkhypov O. V. , Khodachenko M. L.
Published: May 2021

Context. The Rieger cycles were discovered in the Sun as a specific 154-day periodicity of flare occurrence; they strongly influence terrestrial space weather. This phenomenon is far from being understood. Various proposed mechanisms for this periodicity need further verification in stars with stellar parameters different from those of the Sun.

Aims. In this work, we study the Rieger-type cycle (RTC) periods PRTC of stellar activity surveyed in the photometric data of the Kepler space telescope.

Methods. The processing of 1726 stellar light curves reveals statistics of PRTC values for different main-sequence stars with different effective temperatures Teff and periods of rotation P. This study uses as an index of stellar activity the squared amplitude of the first rotational harmonic A12 of the stellar light curve variability.

Results. The obtained information on PRTC of the considered stars confirms the phenomenological analogy between stellar RTCs and the solar Rieger cycles. Two types of RTCs were found: (1) activity cycles with PRTC independent on the stellar rotation, which are typical for the stars with Teff ≲ 5500 K, and (2) activity cycles with PRTC proportional to the stellar rotation period P, which take place on stars with Teff ≳ 6300 K. These two types of RTCs can be driven by the Kelvin and Rossby waves, respectively. The Rossby wave-driven RTCs show a relation with the location of tachocline at shallow depths in the hot stars. This confirms the theoretical predictions of the connection of the RTC with the tachocline. At the same time, the Kelvin wave-driven RTCs do not show this connection. Apparently, both types of wave drivers of RTCs can coexist, resulting in the joint modulation of the magnetic flux tubes emergence by Kelvin and Rossby waves, and the corresponding behavior of PRTC.

Conclusions. The signatures of two types of wave drivers discovered for RTCs and their different relations with the tachocline call for a revision and further elaboration of the theory of RTCs.
An algorithm with LightGBM + SVM fusion model for the assessment of dynamic security region
Authors: Liang Lulu , Hu Wei , Zhang Yiwei , Ma Kun , Gu Yujia , Tian Bei , Li Hongqiang
Published: May 2021

With the development of energy transition, the complexity of power systems’ structure, planning and operation is continuously increasing. As to quickly and accurately assess the dynamic security region of power system, there are prominent problems with traditional manual analysis method, i.e. the rules’ roughness and a low calculation efficiency while data mining approach could provide a new way to get off such problems. Considering that the performance of SVM algorithm depends on feature selection and the LightGBM, a fast and efficient classification algorithm, can be used for feature selection, this paper proposes a new algorithm based on a fusion model. With the CEPRI-36 bus power system, the results of different algorithms are compared and the proposed algorithm verified.
Catalytic Enantioselective Synthesis of Silicon-Stereogenic Alkoxy­silanes and Siloxanes
Authors: He Chuan , Zhu Jiefeng
Published: May 2021

A Rh-catalyzed enantioselective intermolecular dehydrogenative Si–O coupling of dihydrosilanes with alcohols and silanols is demonstrated. Rh(I) catalyst equipped with a Josiphos ligand enables the highly enantioselective alcoholysis process of dihydrosilanes, giving access to a variety of functionalized triorgano-substituted silicon-stereogenic alkoxysilanes and siloxanes in decent yields and ee, which significantly expand the chemical space of the silicon-centered chiral molecules. Utility of this methodology is illustrated by the construction of circularly polarized luminescence (CPL) active chiral alkoxysilane small organic molecules.

1 Introduction

2 Conditions Optimization

3 Substrate Scope

4 Application

5 Conclusions

6 Experimental Procedure
Lewis Acid Mediated [3+2] and [3+3] Annulations of an Azomethine Imine with Donor–Acceptor Cyclopropanes
Authors: Sikervar Vikas , Sonawane Ravindra , Mandadapu Raghuramaiah , Dehade Amol Satish , Shete Shrikant Abhiman , Montgomery Mark
Published: May 2021

Two different Lewis acids were used for developing [3+2] and [3+3] regioselective cycloaddition reactions of an azomethine imine with activated cyclopropanes. Scandium(III) triflate catalyzes a [3+2] cycloaddition reaction of the azomethine imine with cyclopropanes to form tetrahydropyrazolone derivatives and tricyclic tetrahydrofuran derivatives in moderate yields. Complementary to this, a novel [3+3] cycloaddition reaction of the azomethine imine with activated cyclopropanes was developed by using EtAlCl2 as a Lewis acid to form hexahydropyridazinone derivatives in high regioselectivity.
Regio- and Stereoselective (SN2) N-, O-, C- and S-Alkylation Using Trialkyl Phosphates
Authors: Banerjee Amit , Hattori Tomohiro , Yamamoto Hisashi
Published: May 2021

Bimolecular nucleophilic substitution (SN2) is one of the most well-known fundamental reactions in organic chemistry to generate new molecules from two molecules. In principle, a nucleophile attacks from the back side of an alkylating agent having a suitable leaving group, most commonly a halide. However, alkyl halides are expensive, very harmful, toxic and not so stable, which makes them problematic for laboratory use. In contrast, trialkyl phosphates are inexpensive, readily accessible and stable at room temperature, under air, and are easy to handle, but rarely used as alkylating agents in organic synthesis. Here, we describe a mild, straightforward and powerful method for nucleophilic alkylation of various N-, O-, C- and S-nucleophiles using readily available trialkyl phosphates. The reaction proceeds smoothly in excellent yield, and quantitative yield in many cases, and covers a wide range of substrates. Further, the rare stereoselective transfer of secondary alkyl groups has been achieved with inversion of configuration of chiral centers (up to 98% ee).
Physicians' Opinions on Anticoagulant Therapy in Patients with a Limited Life Expectancy
Authors: Huisman Bregje A.A. , Geijteman Eric C.T. , Kolf Nathalie , Dees Marianne K. , van Zuylen Lia , Szadek Karolina M. , Steegers Monique A.H. , van der Heide Agnes
Published: May 2021

Patients with a limited life expectancy have an increased risk of thromboembolic and bleeding complications. Anticoagulants are often continued until death, independent of their original indication. We aimed to identify the opinions of physicians about the use of anticoagulants at the end of life. A mixed-method research design was used. A secondary analysis was performed on data from a vignette study and an interview study. Participants included general practitioners and clinical specialists. Physicians varied in their opinions: some would continue and others would stop anticoagulants at the end of life because of the risk of thromboembolic or bleeding complications. The improvement or preservation of patients' quality of life was a reason for both stopping and continuing anticoagulants. Other factors considered in the decision-making were the types of anticoagulant, the indication for which the anticoagulant was prescribed, underlying diseases, and the condition and life expectancy of the patient. Factors that made decision-making difficult were the lack of evidence on either strategy, uncertainty about patients' life expectancy, and the fear of harming patients. Which decision was eventually made seems largely dependent on the choice of the patient. In conclusion, there is a substantial variation in physicians' opinions regarding the use of anticoagulants in patients with a limited life expectancy. Physicians agree that the primary goal of medical care at end of life is the improvement or preservation of patients' quality of life. An important barrier to decision-making is the lack of evidence about the risks and benefits of stopping anticoagulants.
A scheme to excite transverse electric graphene plasmon polariton with positive value of imaginary part of conductivity
Authors: Liu Daqing , Wang Lijun , Fan Yazhou , Zhang Lei , Jiang Xingfang , Zhao Xiang
Published: May 2021

We proposed a scheme to generate a transverse electric graphene plasmon polariton in which the imaginary part of conductivity need not be negative. In a three-dimensional periodic structure with graphene ribbons embedded in a medium, at a suitable frequency and wavelength, the periodic modification factor is not a real number but a purely imaginary one, which makes dispersion relations possibly satisfied, that is, a transverse electric graphene plasmon polariton can be excited in this case. The spectrum of the plasmon polariton is broadband. Furthermore, the coupling between the plasmon polariton and electromagnetic wave was enhanced and the enhancement is beneficial to design high efficiency optoelectronic devices.
Shock-ramp analysis test problem
Authors: Rothman S. D. , Ali S. J. , Brown J. L. , Eggert J. H. , Seagle C. T.
Published: May 2021

Quasi-isentropic (ramp) compression is now a well-established experimental method and so are the analysis techniques to give Lagrangian sound speed, pressure, and density along the sample material's isentrope. A shock followed by ramp compression is a natural extension to investigate, for example, shock melt and refreeze on compression, or isentropes of states off the Hugoniot or principal isentrope. In practice, graded-density impactors produce initial shocks, compression by shaped laser pulses may be unable to produce a smooth pressure increase from zero, and incidental perturbations on the drive pulse may also give rise to shocks, so robust shock-ramp analysis methods will be needed. Appropriate analysis methods are needed for shock-ramp experiments, based on those for quasi-isentropic compression, and these require validation. This paper describes three different analyses of a shock-ramp test problem, including an assessment of their estimated errors. The methods tested were based on hydrodynamic characteristics or integration backward in space. All methods gave the known Lagrangian sound speed to within ∼1%, and pressure and volume to within less than 2% and 1%, demonstrating that the analysis methods of isentropic compression experiments can be confidently extended to the analysis of shock and ramp compression.
Perspectives on photodetectors based on selenides and their van der Waals heterojunctions
Authors: Yan Faguang , Hu Ce , Wang Ziao , Lin Hailong , Wang Kaiyou
Published: May 2021

Two-dimensional layered selenides have attracted intense attention in recent years because of their unique structures and physical properties. Many high-performance electrical and optoelectrical devices based on selenides and their heterostructures have been extensively investigated, and photodetectors have been a particular area of attention. Here, we provide a systematic summary of our recent research progress in selenide-based photodetectors. Three different strategies are introduced and discussed, specifically the use bottom metal contacts, graphene contacts, and bandgap engineering-based vertical van der Waals heterostructures. These approaches are effective for improving the performance of photodetectors based on selenides and their heterostructures. Conclusions are given, and several approaches are proposed for further development of selenide-based optoelectrical devices.
Giant THz Faraday rotation with stacked magnetized graphene
Authors: Gu Minyu , Michalski Krzysztof A.
Published: May 2021

It has been recently discovered that strong magnetoplasmonic effects exist on graphene and may open a new avenue for many novel THz non-reciprocal devices. The magnetoplasmonic response of two-dimensional graphene strongly depends on the electromagnetic properties of the surrounding medium. We develop a modified transmission line analog formulation to investigate the Faraday and Kerr rotation associated with multi-sheet magnetized graphene embedded in the layered medium. The formulation utilizes a junction transformer to model anisotropic conductive sheets at the interfaces and is highly numerically efficient and stable. It is also demonstrated for the first time that a multiple heterojunctions conjugated photonic crystal with graphene embedded at the interfaces will significantly enhance the magneto-optical effect of the system. 15.3° Faraday angle under 0.25 T low static bias magnetic field is achieved at 15 THz with a high transmittance, which enables the design of accessible high-performance non-reciprocal devices in the high THz frequency regime. The proposed formulation and design principle may lay the foundation for future THz graphene-based plasmonic devices.
Rhodium chemistry: A gas phase cluster study
Authors: Zhao Yan-Xia , Zhao Xi-Guan , Yang Yuan , Ruan Man , He Sheng-Gui
Published: May 2021

Due to the extraordinary catalytic activity in redox reactions, the noble metal, rhodium, has substantial industrial and laboratory applications in the production of value-added chemicals, synthesis of biomedicine, removal of automotive exhaust gas, and so on. The main drawback of rhodium catalysts is its high-cost, so it is of great importance to maximize the atomic efficiency of the precious metal by recognizing the structure–activity relationship of catalytically active sites and clarifying the root cause of the exceptional performance. This Perspective concerns the significant progress on the fundamental understanding of rhodium chemistry at a strictly molecular level by the joint experimental and computational study of the reactivity of isolated Rh-based gas phase clusters that can serve as ideal models for the active sites of condensed-phase catalysts. The substrates cover the important organic and inorganic molecules including CH4, CO, NO, N2, and H2. The electronic origin for the reactivity evolution of bare Rhxq clusters as a function of size is revealed. The doping effect and support effect as well as the synergistic effect among heteroatoms on the reactivity and product selectivity of Rh-containing species are discussed. The ingenious employment of diverse experimental techniques to assist the Rh1- and Rh2-doped clusters in catalyzing the challenging endothermic reactions is also emphasized. It turns out that the chemical behavior of Rh identified from the gas phase cluster study parallels the performance of condensed-phase rhodium catalysts. The mechanistic aspects derived from Rh-based cluster systems may provide new clues for the design of better performing rhodium catalysts including the single Rh atom catalysts.
Recombination rate analysis in long minority carrier lifetime mid-wave infrared InGaAs/InAsSb superlattices
Authors: Carrasco Rigo A. , Morath Christian P. , Grant Perry C. , Ariyawansa Gamini , Stephenson Chad A. , Kadlec Clark N. , Hawkins Samuel D. , Klem John F. , Shaner Eric A. , Steenbergen Elizabeth H. , Schaefer Stephen T. , Johnson Shane R. , Webster Preston T.
Published: May 2021

Gallium is incorporated into the strain-balanced In(Ga)As/InAsSb superlattice system to achieve the same mid-wave infrared cutoff tunability as conventional Ga-free InAs/InAsSb type-II superlattices, but with an additional degree of design freedom to enable optimization of absorption and transport properties. Time-resolved photoluminescence measurements of InGaAs/InAsSb superlattice characterization- and doped device structures are reported from 77 to 300 K and compared to InAs/InAsSb. The low-injection photoluminescence decay yields the minority carrier lifetime, which is analyzed with a recombination rate model, enabling the determination of the temperature-dependent Shockley–Read–Hall, radiative, and Auger recombination lifetimes and extraction of defect energy levels and capture cross section defect concentration products. The Shockley–Read–Hall-limited lifetime of undoped InGaAs/InAsSb is marginally reduced from 2.3 to 1.4 μs due to the inclusion of Ga; however, given that Ga improves the vertical hole mobility by a factor of >10×, a diffusion-limited InGaAs/InAsSb superlattice nBn could expect a lower bound of 2.5× improvement in diffusion length with significant impact on photodetector quantum efficiency and radiation hardness. At temperatures below 120 K, the doped device structures are Shockley–Read–Hall limited at 0.5 μs, which shows promise for detector applications.
Effect of Fe atomic layers at the ferromagnet–semiconductor interface on temperature-dependent spin transport in semiconductors
Authors: Yamada M. , Shiratsuchi Y. , Kambe H. , Kudo K. , Yamada S. , Sawano K. , Nakatani R. , Hamaya K.
Published: May 2021

Using artificially controlled ferromagnet (FM)–semiconductor (SC) interfaces, we study the decay of the nonlocal spin signals with increasing temperature in SC-based lateral spin-valve devices. When more than five atomic layers of Fe are inserted at the FM/SC interfaces, the temperature-dependent spin injection/detection efficiency (Pinj/det) can be interpreted in terms of the T32 law, meaning a model of the thermally excited spin waves in the FM electrodes. For the FM/SC interfaces with the insufficient insertion of Fe atomic layers, on the other hand, the decay of Pinj/det is more rapid than the T32 curve. Using magneto-optical Kerr effect measurements, we find that more than five atomic layers of Fe inserted between FM and SC enable us to enhance the ferromagnetic nature of the FM/SC heterointerfaces. Thus, the ferromagnetism in the ultra-thin FM layer just on top of SC is strongly related to the temperature-dependent nonlocal spin transport in SC-based lateral spin-valve devices. We propose that the sufficient ferromagnetism near the FM/SC interface is essential for high-performance FM–SC hybrid devices above room temperature.
Room temperature ferromagnetic stability of SrTi1−
x
M
xO3 (M = V, Cr, Mn, Fe, Co, Ni, Cu): A theoretical perspective
Authors: Zang Tao-Cheng , Chen Gao-Yuan , Ma Chun-Lan
Published: May 2021

The diluted magnetic semiconductor (DMS) has significant potential application in spintronic devices, and DMS oxides have been considered a possibility for high ferromagnetic transition temperature. Here, the first-principles calculation is utilized to comprehensively examine characteristics of high ferromagnetic transition temperature in transition-metal (TM = V, Cr, Mn, Fe, Co, Ni, and Cu)-doped SrTiO3 (STO) at 25%, 12.5%, and 7.4% doping concentrations with respect to their total energy, Curie temperature (TC), formation energy, and Gibbs free energy. We find that high ferromagnetic transition temperature can be obtained in Mn-, Fe-, and Co-doped STO systems with dopant concentration over 7.4%. In addition, TC decreases with the decrease in doping concentration. In particular, above 340 K, Mn-doped STO with 25% doping concentration is in the ferromagnetic state, which resolves the conflict in previous reports that the theoretically calculated Mn-doped STO system has no room-temperature ferromagnetism (RTFM), which has been reported experimentally. V- and Cu-doped STO systems always show the antiferromagnetic ground state. Although the Cr-doped system shows the ferromagnetic ground state at a concentration of 25%, its TC (92.4 K) is much lower than room temperature. Whether Ni-doped STO has ferromagnetism at room temperature needs further experimental verification. The results indicate that Mn-, Fe-, and Co-doped STO systems are very good candidate materials exhibiting RTFM.
Nano-amorphous layers improve the helium swelling resistance of a CAC-type nanocomposite
Authors: Chen Huaican , Hai Yang , Zhan Xiaozhi , Liu Xiao , Xu Juping , Yin Wen
Published: May 2021

Numerous studies pay more attention to the heterophase interfaces of nanocomposites due to their effective sinks for radiation-induced point defects and traps for helium. An amorphous structure with excessive free volume also possesses high He solubility and irradiation resistance, but its effect on helium irradiation of the nanocomposites is not clear. Here, the helium irradiation effect of a crystalline/amorphous/crystalline sandwich structured W/Amorphous/Cu nanocomposite (W/A/Cu) is investigated. The results show that helium swelling resistance of a W/A/Cu nanocomposite is enhanced after introducing an amorphous layer due to strong sink strength of the crystalline/amorphous-W(Cu)/A interface and high He solubility of amorphous layers. This result sheds light on the design of radiation-tolerant materials for advanced nuclear reactor applications.
In situ TEM measurement of electrical properties of individual BaTiO3 nanocubes
Authors: Tian Xinchun , Caruntu Gabriel , Kavey Benard , Tan Xiaoli
Published: May 2021

We report on the measurement of the electrical properties of individual pristine and doped BaTiO3 nanocubes by using in situ transmission electron microscopy with a two-electrode configuration. The dimensions of the nanocubes tested are between 10 and 20 nm, which rendered their in situ electrical characterization challenging. We characterized 4%Cr and 5%La (atomic percentage) doped BaTiO3 nanocubes and compared them with the properties of pristine BaTiO3 nanocubes synthesized by the same solvothermal method. We found that the resistance of all three types of nanocubes when displayed in log-scale shows a nearly linear dependence on the applied electric field (R2 ≥ 0.95) over a wide range of electric fields (50–900 kV/cm). Compared with pristine BaTiO3 nanocubes, the resistance of both 4%Cr and 5%La doped nanocubes showed reduced variation rates with respect to the electric field, with 5%La doping, demonstrating a better reduction in the variation rate. By developing techniques capable of evaluating the properties of individual BaTiO3 nanocubes, we expect that our work to open the door to the use of BaTiO3 nanomaterials in the design of future multilayer ceramic capacitors with improved volumetric efficiency and ferroelectrics-enabled nanodevices with advanced functionality.
Surface modification of BaTiO3 with catechol surfactant and effects on cold sintering
Authors: Sada Takao , Ndayishimiye Arnaud , Fan Zhongming , Fujioka Yoshihiro , Randall Clive A.
Published: May 2021

The sintering of functionalized particles is an approach often used to obtain high performance functional ceramics. When molecular surfactants are used to functionalize particles, conventional sintering cannot be applied due to extremely high processing temperatures. Here, BaTiO3 particles are grafted with different coverages using a catechol (CA) surfactant, and then these particles are densified under cold sintering with a (BaOH2)⋅8H2O transient flux. The adsorption of CA is equilibrated with various concentrations on BaTiO3 particles at room temperature. The modeling (Langmuir and Freundlich adsorption) and the quantification (UV–vis absorption and thermogravimetric analysis) of CA coverage enable us to rigorously determine the degree of functionalization and conduct thorough cold sintering kinetics investigations as a function of CA coverage using a dilatometer. Microstructure is observed with electron microscopy techniques to determine the grain and grain boundary interfaces that result with the competition of surfactant coverage and densification driven by the dissolution and reprecipitation processes at the interfaces. A mechanism with the retardation of cold sintering kinetics is discussed based on these experimental observations.
Analytic solutions of the nonlinear radiation diffusion equation with an instantaneous point source in non-homogeneous media
Authors: Krief Menahem
Published: May 2021

Analytical solutions to the nonlinear radiation diffusion equation with an instantaneous point source for a non-homogeneous medium with a power law spatial density profile are presented. The solutions are a generalization of the well-known solutions for a homogeneous medium. It is shown that the solutions take various qualitatively different forms according to the value of the spatial exponent. These different forms are studied in detail for linear and non-linear heat conduction. In addition, by inspecting the generalized solutions, we show that there exist values of the spatial exponent such that the conduction front has constant speed or even accelerates. Finally, various solution forms are compared in detail to numerical simulations, and a good agreement is achieved.
Ion-acoustic shock waves in a magnetized plasma featuring super-thermal distribution
Authors: Heera N. M. , Akter J. , Tamanna N. K. , Chowdhury N. A. , Rajib T. I. , Sultana S. , Mamun A. A.
Published: May 2021

A theoretical investigation has been made on the propagation of ion-acoustic shock waves in a magnetized pair-ion plasma having inertial warm positive and negative ions and inertialess super-thermal electrons and positrons. The well known Burgers equation has been derived by employing the reductive perturbation method. The plasma model supports both positive and negative shock structures under consideration of super-thermal electrons and positrons. It is found that the oblique angle (δ) enhances the magnitude of the amplitude of both positive and negative shock profiles. It is also observed that the steepness of the shock profiles decreases with the kinematic viscosity of the ion and the height of the shock profile increases (decreases) with the mass of the positive (negative) ion. The implications of the results have been briefly discussed for space and laboratory plasmas.
Adsorption of simple gases into the porous glass MCM-41
Authors: Soper Alan K. , Bowron Daniel T.
Published: May 2021

The porous glass MCM-41 is an important adsorbent to study the process of adsorption of gases onto a cylindrical surface. In this work, we study the adsorption of oxygen, nitrogen, deuterium, and deuteriated methane gases into MCM-41 using a combination of neutron diffraction analysis and atomistic computer modeling to interpret the measured data. Adsorption is achieved by immersing a sample of MCM-41 in a bath of the relevant gas, keeping the gas pressure constant (0.1 MPa), and lowering the temperature in steps toward the corresponding bulk liquid boiling point. All four gases have closely analogous behaviors, with an initial layering of liquid on the inside surface of the pores, followed by a relatively sharp capillary condensation (CC) when the pore becomes filled with dense fluid, signaled by a sharp decrease in the intensity of (100) Bragg diffraction reflection. At the temperature of CC, there is a marked distortion of the hexagonal lattice of pores, as others have seen, which relaxes close to the original structure after CC, and this appears to be accompanied by notable excess heterogeneity along the pore compared to when CC is complete. In none of the four gases studied does the final density of fluid in the pore fully attain the value of the bulk liquid at its boiling point at this pressure, although it does approach that limit closely near the center of the pore, and in all cases, the pronounced layering near the silica interface seen in previous studies is observed here as well.
Cryopreservation of spermatozoa obtained postmortem from the European common frog
Authors: Kaurova Svetlana A. , Uteshev Victor K. , Gapeyev Andrew B. , Shishova Natalia V. , Gakhova Edith N. , Browne Robert K. , Kramarova Ludmila I.
Published: May 2021

Cryopreserved spermatozoa offers a reliable, efficient and cost-effective means to perpetuate the genetic variation of endangered amphibian species in concert with conservation breeding programs. Here we describe successful cryopreservation of testicular spermatozoa of the common frog Rana temporaria, preliminarily stored in the carcasses of decapitated animals at +4°C for 0, 1 and 4 days. The motility, membrane integrity and fertilisation capability of fresh testicular spermatozoa treated with cryoprotective medium supplemented with 15% dimethylformamide (DMF) or 15% dimethylsulfoxide (DMSO) were examined. DMSO had a significantly greater toxic effect on fresh frog spermatozoa than DMF. Low levels of DNA fragmentation were seen in spermatozoa stored in the testis for different times and then treated with DMF (mean (±s.e.m.) 8.2 ± 0.7% and 18.2 ± 1.8% after 0 and 4 days storage respectively). After 1 day of storage in frog carcasses, the quality of spermatozoa cryopreserved with DMF was not significantly different from that of control spermatozoa (0 days of storage). After 4 days of storage, the quality of frozen–thawed spermatozoa was significantly lower in the DMF-treated than control group: 35% of the spermatozoa cryopreserved with DMF retained motility, 25% maintained the ability to fertilise fresh oocytes and 80% of fertilised oocytes survived to hatch.
Wild-type α-synuclein inherits the structure and exacerbated neuropathology of E46K mutant fibril strain by cross-seeding
Authors: Long Houfang , Zheng Weitong , Liu Yang , Sun Yunpeng , Zhao Kun , Liu Zhenying , Xia Wencheng , Lv Shiran , Liu Zhengtao , Li Dan , He Kai-Wen , Liu Cong
Published: May 2021

Significance

Amyloid deposition of α-syn is a hallmark of PD. Heterozygous point mutations of α-syn are associated with the early-onset and rapid progression of fPD. In this study, we found the fibril strain formed by a familial mutant hE46K induced early-onset motor deficit and enhanced α-syn aggregation in vivo. More importantly, we showed through cryogenic electron microscopy and in vivo studies the E46K fibril strain can template wild-type α-syn monomer to form amyloid fibrils, which inherit both the structure and propagation potency of the template. Our work reveals the structural basis underlying the cross-seeding between wild-type and mutant α-syn, underscores the importance of fibril structure in determining α-syn neuropathology, and provides mechanistic understanding of the pathology of E46K-associated fPD.
Global declines in coral reef calcium carbonate production under ocean acidification and warming
Authors: Cornwall Christopher E. , Comeau Steeve , Kornder Niklas A. , Perry Chris T. , van Hooidonk Ruben , DeCarlo Thomas M. , Pratchett Morgan S. , Anderson Kristen D. , Browne Nicola , Carpenter Robert , Diaz-Pulido Guillermo , D’Olivo Juan P. , Doo Steve S. , Figueiredo Joana , Fortunato Sofia A. V. , Kennedy Emma , Lantz Coulson A. , McCulloch Malcolm T. , González-Rivero Manuel , Schoepf Verena , Smithers Scott G. , Lowe Ryan J.
Published: May 2021

Significance

The growth of coral reefs is threatened by the dual stressors of ocean warming and acidification. Despite a wealth of studies assessing the impacts of climate change on individual taxa, projections of their impacts on coral reef net carbonate production are limited. By projecting impacts across 233 different locations, we demonstrate that the majority of coral reefs will be unable to maintain positive net carbonate production globally by the year 2100 under representative concentration pathways RCP4.5 and 8.5, while even under RCP2.6, coral reefs will suffer reduced accretion rates. Our results provide quantitative projections of how different climate change stressors will influence whole ecosystem carbonate production across coral reefs in all major ocean basins.
The persistence of ancient settlements and urban sustainability
Authors: Smith Michael E. , Lobo José , Peeples Matthew A. , York Abigail M. , Stanley Benjamin W. , Crawford Katherine A. , Gauthier Nicolas , Huster Angela C.
Published: May 2021

We propose a dedicated research effort on the determinants of settlement persistence in the ancient world, with the potential to significantly advance the scientific understanding of urban sustainability today. Settlements (cities, towns, villages) are locations with two key attributes: They frame human interactions and activities in space, and they are where people dwell or live. Sustainability, in this case, focuses on the capacity of structures and functions of a settlement system (geography, demography, institutions) to provide for continuity of safe habitation. The 7,000-y-old experience of urbanism, as revealed by archaeology and history, includes many instances of settlements and settlement systems enduring, adapting to, or generating environmental, institutional, and technological changes. The field of urban sustainability lacks a firm scientific foundation for understanding the long durée, relying instead on narratives of collapse informed by limited case studies. We argue for the development of a new interdisciplinary research effort to establish scientific understanding of settlement and settlement system persistence. Such an effort would build upon the many fields that study human settlements to develop new theories and databases from the extensive documentation of ancient and premodern urban systems. A scientific foundation will generate novel insights to advance the field of urban sustainability.
TMEM16C is involved in thermoregulation and protects rodent pups from febrile seizures
Authors: Wang Tongfei A. , Chen Chao , Huang Fen , Feng Shengjie , Tien Jason , Braz João M. , Basbaum Allan I. , Jan Yuh Nung , Jan Lily Yeh
Published: May 2021

Significance

As the most common convulsive disorder in infancy and childhood, affecting 2 to 5% of American children in their first 5 y of life, febrile seizures (FSs) are associated with genetic risk factors, including the
Tmem16c
(
Ano3
) gene. Whereas central neuronal hyperexcitability has been implicated in FSs, whether FSs may result from compromised body temperature regulation is unknown. To approach this question, we developed rodent models of FSs associated with deficient thermoregulation, including conditional knockout mice with TMEM16C eliminated from a hypothalamic neuronal population important for maintaining body temperature but not from most of the cortical and hippocampal neurons and sensory neurons. Our findings raise the possibility that impaired homeostatic thermoregulation could contribute to the risk of FSs.