bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconfigurable cavity-based plasmonic platform for resonantly enhanced sub-bandgap photodetection
Authors: McPolin Cillian P. T. , Romero-Gómez Mayela , Krasavin Alexey V. , Dickson Wayne , Zayats Anatoly V.
Published: November 2020

Sub-bandgap photodetection based on plasmonic excitations represents a promising route for expanding the spectral range of photodetectors, enabling, for instance, silicon-based devices to be employed at telecom wavelengths. This approach harnesses internal photoemission, where hot carriers are generated via nonradiative plasmonic decay and are subsequently emitted from the metal to a semiconductor, yielding a photocurrent not spectrally limited by the bandgap. However, many schemes based on this approach suffer from low responsivities that hinder their uptake in real-world technologies. Here, we demonstrate a cavity-based platform for both enhancing the generated photocurrent and providing a means for dynamic reconfiguration of the operating wavelength. The proposed device is composed of an optical cavity where one of the mirrors is patterned with a nanoscale grating and interfaced at the other side with a semiconductor. Fabry–Pérot resonances supported by the cavity provide resonant excitation of plasmonic modes at the metal/semiconductor interface, leading to augmented hot-carriers and photocurrent generation compared to the non-resonant case. By employing this cavity-grating geometry, we experimentally demonstrate a fivefold increase in photocurrent due to the presence of cavity resonances. Electromechanical reconfiguration of the photodetector cavity length is also achieved, illustrating dynamic control over the detection wavelength. This cavity-based architecture is compatible with a variety of plasmonic nanostructures, including nanoparticles and nanoantennas, thus providing a flexible means of significantly increasing the photoresponse and hence bringing on-chip plasmonic hot-carrier technologies closer to realization for sub-bandgap photodetection, energy harvesting, and sensing.
Defect states and their electric field-enhanced electron thermal emission in heavily Zr-doped
β
-Ga2O3 crystals
Authors: Sun Rujun , Ooi Yu Kee , Bhattacharyya Arkka , Saleh Muad , Krishnamoorthy Sriram , Lynn Kelvin G. , Scarpulla Michael A.
Published: November 2020

Performing deep level transient spectroscopy (DLTS) on Schottky diodes, we investigated defect levels below the conduction band minima (Ec) in Czochralski-grown unintentionally doped (UID) and vertical gradient freeze-grown Zr-doped β-Ga2O3 crystals. In UID crystals with an electron concentration of 1017 cm−3, we observe levels at 0.18 eV and 0.46 eV in addition to the previously reported 0.86 (E2) and 1.03 eV (E3) levels. For 1018 cm−3 Zr-doped Ga2O3, signatures at 0.30 eV (E15) and 0.71 eV (E16) are present. For the highest Zr doping of 5 × 1018 cm−3, we observe only one signature at 0.59 eV. Electric field-enhanced emission rates are demonstrated via increasing the reverse bias during measurement. The 0.86 eV signature in the UID sample displays phonon-assisted tunneling enhanced thermal emission and is consistent with the widely reported E2 (FeGa) defect. The 0.71 eV (E16) signature in the lower-Zr-doped crystal also exhibits phonon-assisted tunneling emission enhancement. Taking into account that the high doping in the Zr-doped diodes also increases the electric field, we propose that the 0.59 eV signature in the highest Zr-doped sample likely corresponds to the 0.71 eV signature in lower-doped samples. Our analysis highlights the importance of testing for and reporting on field-enhanced emission, especially the electric field present during DLTS and other characterization experiments on β-Ga2O3 along with the standard emission energy, cross section, and lambda-corrected trap density. This is important because of the intended use of β-Ga2O3 in high-field devices and the many orders of magnitude of possible doping.
Modulation of thermal stability and spin–orbit torque in IrMn/CoFeB/MgO structures through atom thick W insertion
Authors: Xiong Danrong , Peng Shouzhong , Lu Jiaqi , Li Weixiang , Wu Hao , Li Zhi , Cheng Houyi , Wang Yuyan , Back Christian H. , Wang Kang L. , Zhao Weisheng
Published: November 2020

Antiferromagnet (AFM)/ferromagnet (FM) systems such as IrMn/CoFeB/MgO enable spin–orbit-torque- (SOT-) induced switching of perpendicular magnetization in the absence of an external magnetic field. However, the low thermal stability, weak perpendicular magnetic anisotropy (PMA), and indistinctive SOT of these AFM/FM heterostructures pose challenges to the practical application. Here, through the insertion of a thin W layer between the IrMn and CoFeB layers, we show that much larger effective PMA fields are obtained with annealing stability to 300 °C, which is guaranteed by the prevention of Mn diffusion via W insertion as shown in spherical aberration corrected transmission electron microscopy and atomic-resolution electron energy-loss spectroscopy measurement results. Furthermore, the spin–orbit torque is effectively tuned by changing the W layer thickness via modulation of the interfacial spin–orbit coupling at IrMn/W/CoFeB interfaces, which was reported to degrade the interface spin transparency for the spin currents. Finally, field-free magnetization switching was achieved with comparable exchange bias fields to samples without W insertion. This work demonstrates an effective strategy for improving the performance of the thermally robust AFM-based SOT device.
Intramolecular-rotation driven triplet-to-singlet upconversion and fluctuation induced fluorescence activation in linearly connected donor–acceptor molecules
Authors: Shimoda Yuushi , Miyata Kiyoshi , Saigo Masaki , Tsuchiya Youichi , Adachi Chihaya , Onda Ken
Published: November 2020

Thermally activated triplet-to-singlet upconversion is attractive from both fundamental science and exciton engineering, but controlling the process from molecular configuration is still unrevealed. In particular, the flexibility of the freedom of molecular geometry is of major importance to understand the kinetics of the phonon-induced upconversion. Here, we focus on two linearly connected donor–acceptor molecules, 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine (DMAC-TRZ) and hexamethylazatriangulene-2,4,6-triphenyl-1,3,5-triazine (HMAT-TRZ), as the model system. While DMAC-TRZ possesses a rotational degree of freedom in the dihedral angle between the donor and acceptor moieties, i.e., C–N bond in tertiary amine, the rotation is structurally restricted in HMAT-TRZ. The rotationally flexible DMAC-TRZ showed significant triplet-to-singlet upconversion caused by thermal activation. On the other hand, the rotation-restricted HMAT-TRZ showed negligible thermal upconversion efficiency. We elaborate on the origin of the photophysical properties from the viewpoint of the geometries in the excited states using time-resolved infrared spectroscopy and quantum chemical calculations. We uncovered that the structural restriction of the intramolecular flexibility significantly affects the optimized geometry and phonon modes coupled to the spin conversion. As a result of the rotation restriction, the spin flipping in HMAT-TRZ was coupled to bending motion instead of the rotation. In contrast, the free rotation fluctuation in the DMAC-TRZ mixes local-excitation and charge-transfer characters, leading to successful activation of the delayed fluorescence as well as the reverse intersystem crossing. Our discovery sheds light on the mechanism of the triplet-to-singlet upconversion, providing a microscopic strategy to control the optoelectronic properties from a molecular viewpoint.
Noise effects in the nonlinear thermoelectricity of a Josephson junction
Authors: Marchegiani G. , Braggio A. , Giazotto F.
Published: November 2020

We investigate the noise current in a thermally biased tunnel junction between two superconductors with different zero-temperature gaps. When the Josephson effect is suppressed, this structure can support a nonlinear thermoelectric effect due to the spontaneous breaking of electron–hole symmetry, as we recently theoretically predicted. We discuss the possibly relevant role played by the noise in the junction. While a moderate noise contribution assists the generation of the thermoelectric signal, further unveiling the spontaneous nature of the electron–hole symmetry breaking, a large noise contribution can induce a switching between the two stationary thermoelectric values, thus hardening the detection of the effect and its application. We demonstrate that the thermoelectric effect is robust to the presence of noise for a wide range of parameters and that the spurious fluctuations of the thermoelectric signal can be lowered by increasing the capacitance of the junction, for instance, by expanding the junction's size. Our results pave the way to the future experimental observation of the thermoelectric effect in superconducting junctions and to improved performance in quantum circuits designed for thermal management.
A study on MoS2-based multilevel transistor memories for neuromorphic computing
Authors: Li Da , Ryu Byunghoon , Liang Xiaogan
Published: November 2020

We study the validity of implementing MoS2 multilevel memories in future neuromorphic networks. Such a validity is determined by the number of available states per memory and their retention characteristics within the nominal computing duration. Our work shows that MoS2 memories have at least 3-bit and 4.7-bit resolvable states suitable for hour-scale and minute-scale computing processes, respectively. The simulated neural network conceptually constructed on the basis of such memory states predicts a high learning accuracy of 90.9% for handwritten digit datasets. This work indicates that multilevel MoS2 transistors could be exploited as valid and reliable nodes for constructing neuromorphic networks.
Influence of nonstoichiometry point defects on electronic thermal conductivity
Authors: Liang Xin , Wang Changan , Jin Dou
Published: November 2020

Electronic contribution to thermal conductivity (κe) is proportional to electrical conductivity (σ) as given by the Wiedemann–Franz law (κe=LσT). The Lorenz number (L) scales the thermal current associated with the electrical current and implies the electrons' capability of carrying heat. By experimental transport measurements and first-principles calculations, we show that electron transport overwhelmingly dominates thermal conductivity in β-Ag2Se, which has intrinsically low lattice thermal conductivity. The Lorenz number linearly decreases from Ag1.95Se to Ag2.03Se, as the point defect changes from a cation vacancy to a self-interstitial. This striking behavior reveals the inelastic electron scattering process due to nonstoichiometry point defects and suggests that the cation vacancies increase while self-interstitials reduce the amount of heat carried by electrons. Remarkably, the Lorenz number varies by 40% for such a narrow nonstoichiometry window, with the deviation as large as 36% from the Sommerfeld value. Finally, we predict the maximum Lorenz number that can be achieved in β-Ag2Se for various electron scattering mechanisms. This work provides insights into the physics of electronic heat conduction in solids containing point defects.
Prenatal establishment of the foal gut microbiota: a critique of the in utero colonisation hypothesis
Authors: Mols Kirsty L. , Boe-Hansen Gry B. , Mikkelsen Deirdre , Bryden Wayne L. , Cawdell-Smith A. Judy
Published: November 2020

Bacteria colonisation of the foal’s gastrointestinal tract (GIT) is a critical developmental stage, effecting subsequent immunological and health outcomes. It has long been thought that the equine fetus develops in a sterile intrauterine environment and GIT colonisation commences at birth. Research now suggests that bacteria isolated from amniotic fluid are the initial colonisers of the fetal GIT, and exposure to the dam’s microbiota and the external environment during birth provide supplementary colonisation. This in utero colonisation hypothesis has only recently been examined in the horse and microbiota were detected in the amniotic fluid and meconium of healthy equine pregnancies. This review highlights the possible colonisation routes of these bacteria into the fetal compartments and examines their likely origins from the existing maternal microbiome. However, the current data describing the amniotic microbiota of the horse are limited and there is a need for research to fill this gap. Understanding the significance of intrauterine microbes for foal GIT colonisation may provide strategies to improve neonatal health.
So many ‘Africanists’, so few Africans: reshaping our understanding of ‘African politics’ through greater nuance and amplification of African voices
Authors: Zimbalist Zack
Published: November 2020

Who produces knowledge on ‘African politics’? Within political science, our understanding of politics in Africa is overwhelmingly shaped by non-Africans who spend most of their time far removed from Africa. This reality has serious consequences for the academic community, policymakers, students and citizens across the world. Using a new data set of undergraduate syllabi and doctoral exam reading lists, this article sheds further light on this knowledge production and instruction problem and provides suggestions for how we might redress this problem. In doing so, we can generate more nuanced understandings of governance dynamics that are centred on African voices and perspectives.
The distributional stress–energy quadrupole
Authors: Gratus Jonathan , Pinto Paolo , Talaganis Spyridon
Published: November 2020

We investigate stress–energy tensors constructed from the delta function on a worldline. We concentrate on quadrupoles as they make an excellent model for the dominant source of gravitational waves and have significant novel features. Unlike the dipole, we show that the quadrupole has 20 free components which are not determined by the properties of the stress–energy tensor. These need to be derived from an underlying model and we give an example motivated from a divergent-free dust. We show that the components corresponding to the partial derivatives representation of the quadrupole, have a gauge like freedom. We give the change of coordinate formula which involves second derivatives and two integrals. We also show how to define the quadrupole without reference to a coordinate systems or a metric. For the representation using covariant derivatives, we show how to split a quadrupole into a pure monopole, pure dipole and pure quadrupole in a coordinate free way.
The relation between the effective band mass in a solid and the free electron mass
Authors: Forcade G , van Paridon D , Pavelich R L , Marsiglio F
Published: November 2020

The Kronig–Penney model is a model used to study properties of electrons confined in a periodic potential. It is a useful model since the electronic properties can be studied analytically with the aid of Bloch’s theorem. An important concept that emerges from the resultant electron band theory is the electron effective mass. Through the use of the Kronig–Penney model we use the so-called ‘effective mass theorem’, that allows us to ask and answer the question of how the electron effective mass depends on both the free electron mass and the characteristics of the periodic potential. We illustrate the crossover from the case of a weak periodic potential to a strong periodic potential using this theorem and explicit calculations with the Kronig–Penney model. The special case of the Dirac comb model is also treated in this work. Through the use of the ‘effective mass theorem’, we show, among other properties, that an electron–hole effective mass asymmetry is generally expected, even without considering contributions from electron–electron interactions.
Accurate atomic momentum integrals and Compton profiles
Authors: Miguel Beatriz , López Rafael , García de la Vega José M
Published: November 2020

Analytical expressions for integrals involving momentum density have been developed, and an algorithm for the efficient computation of Compton profiles (CPs) based in those equations is reported. The performance of the algorithm is tested by computing the CPs of atoms from helium to xenon for a wide range of incident photon energies. Calculations have been made at Hartree–Fock level (HF), using three different Slater basis sets, showing a good agreement with the experimental results.
Argon 1s
−2 Auger hypersatellites
Authors: Püttner Ralph , Li Yongjun , Zeng Jiaolong , Koulentianos Dimitris , Marchenko Tatiana , Guillemin Renaud , Journel Loïc , Travnikova Oksana , Zmerli Moustafa , Céolin Denis , Azuma Yoshiro , Kosugi Satoshi , Piancastelli Maria Novella , Simon Marc
Published: November 2020

The 1s
−2 Auger hypersatellite spectrum of argon is studied experimentally and theoretically. In total, three transitions to the final states 1s
−12p
−2(2
S

e
,2
D

e
) and 1s
−12s
−1(1
S)2p
−1(2
P

o
) are experimentally observed. The lifetime broadening of the 1s
−2 → 1s
−12p
−2(2
S

e
,2
D

e
) states is determined to be 2.1(4) eV. For the used photon energy of hν = 7500 eV a KK/K ionisation ratio of 2.5(3) × 10−4 is derived. Generally, a good agreement between the experimental and present theoretical energy positions, linewidths, and intensities is obtained.
Recent progresses on metamaterials for optical absorption and sensing: a review
Authors: Yao Yu , Liao Zhefu , Liu Zhengqi , Liu Xiaoshan , Zhou Jin , Liu Guiqiang , Yi Zao , Wang Junqiao
Published: November 2020

Metamaterials (MMs) offer great potential for achieving optical absorption due to their novel electromagnetic properties. MM absorbers can overcome the thickness limitation and provide excellent absorption performance over the wide frequency range, thereby enable the swift emergence of some promising applications. Moreover, the optical sensors based on MM absorbers have shown great potential in several fields. This review concentrates on the recent progresses in MM-based optical absorbers and spectral sensing. We present four aspects of MM-based optical absorption: the metal-insulation-metal arrangements, the optical coherence, the functional materials, and some novel approaches. Also, we present three aspects of MM-based optical sensing: the refractive index sensing, gas and molecule sensing, and surface-enhanced Raman scattering. Finally, the current challenges and prospects in device designs, fabrications have been discussed. This review is with the purpose to give a generalized knowledge of MMs for optical absorption and sensing, thus inspiring the investigations on MMs for other devices and their practical applications.
Symmetry analysis of trimer-based all-dielectric metasurfaces with toroidal dipole modes
Authors: Dmitriev Victor , Kupriianov Anton S , Silva Santos Silvio Domingos , Tuz Vladimir R
Published: November 2020

Herein, we discuss the conditions for excitation of symmetry-protected toroidal dipole modes in all-dielectric metasurfaces composed of trimer or twin-trimer clusters of dielectric disks. Such metasurfaces permit enhanced light–matter interaction due to spatially confined light in resonant systems with a high-quality factor. To describe characteristics of toroidal modes existing in the clusters, we use the magnetic dipole moments approximation, group-theoretical methods, group representation theory, symmetry-adapted linear combination method, and circuit theory. To validate the obtained theoretical results, we fulfill both full-wave numerical simulations and microwave experiments. In particular, we have shown that the toroidal dipole mode appears as a quasi-dark state of the trimer. It can be excited in the metasurface by the field of a linearly polarized wave, providing the symmetry of the trimer is properly reduced. In the metasurface, the properties of the toroidal dipole mode are determined primarily by the parameters of a single trimer and are not a consequence of the periodicity of the array. The coupling of the toroidal dipole modes in the twin-trimers can appear in both bonding and anti-bonding fashion resulting in different orders of the net toroidal dipole moment. Due to the unique field configuration of these modes, the proposed metasurfaces can be considered as a platform for efficient light–matter interaction for enhanced absorption, non-linear switching, and sensing.
Application of molecular convergent close-coupling cross sections in a collisional radiative model for the triplet system of molecular hydrogen
Authors: Wünderlich D , Scarlett L H , Briefi S , Fantz U , Zammit M C , Fursa D V , Bray I
Published: November 2020

Collisional radiative (CR) models for molecular hydrogen are of high relevance for performing qualitative and quantitative analysis of excited-state population densities measured in plasmas or predicting the dependence of plasma emission on parameter variations. Although the development of such models for H2 started decades ago, major uncertainties still exist regarding the most important set of input parameters, namely the cross sections for electron-impact excitation. The deviations between cross sections from different datasets are particularly pronounced in the energy region close to the threshold energy, strongly increasing the uncertainty of CR models applied to low-temperature plasmas. This paper presents experimental validation of a set of newly calculated non ro-vibrationally resolved electron-impact cross sections calculated for the triplet system of H2 using the molecular convergent close-coupling method in the adiabatic-nuclei formulation. These cross sections are implemented into a CR model based on the flexible solver Yacora. A first comparison of CR calculations with the different datasets to experimentally-determined population densities is performed at a planar ICP discharge for varying pressure (between 1 and 10 Pa) and RF power (between 700 and 1100 W). For the experimentally-accessible electron temperature and density range (2.5–10 eV and 1.8–3.3 × 1016 m−3, respectively), very good agreement between the model and experiment is obtained using the new data set, in contrast to previously used cross sections.
Batch production of uniform graphene films via controlling gas-phase dynamics in confined space
Authors: Zhang Yongna , Huang Deping , Duan Yinwu , Chen Hui , Tang Linlong , Shi Mingquan , Li Zhancheng , Shi Haofei
Published: November 2020

Batch production of continuous and uniform graphene films is critical for the application of graphene. Chemical vapor deposition (CVD) has shown great promise for mass producing high-quality graphene films. However, the critical factors affected the uniformity of graphene films during the batch production need to be further studied. Herein, we propose a method for batch production of uniform graphene films by controlling the gaseous carbon source to be uniformly distributed near the substrate surface. By designing the growth space of graphene into a rectangular channel structure, we adjusted the velocity of feedstock gas flow to be uniformly distributed in the channel, which is critical for uniform graphene growth. The monolayer graphene film grown inside the rectangular channel structure shows high uniformity with average sheet resistance of 345 Ω sq−1 without doping. The experimental and simulation results show that the placement of the substrates during batch growth of graphene films will greatly affect the distribution of gas-phase dynamics near the substrate surface and the growth process of graphene. Uniform graphene films with large-scale can be prepared in batches by adjusting the distribution of gas-phase dynamics.
Design and fabrication of CuInS2/ZnS-based QLED for automotive lighting systems
Authors: Santaella J J , Critchley K , Rodríguez-Bolívar S , Gómez-Campos F M
Published: November 2020

This work reports the design, manufacturing and numerical simulation approach of a 6-pixel (4.5 mm2/pixel) electroluminescent quantum dot light emitting device (QLED) based on CuInS2/ZnS quantum dots as an active layer. The QLED device was fabricated using a conventional multi-layer thin film deposition. In addition, the electrical I–V curves were measured for each pixel independently, observing how the fabrication process and layer thickness have an influence in the shape of the plot. This experimental device, enabled us to create a computational model for the QLED based on the Transfer Hamiltonian approach to calculate the current density J (mA cm−2), the band diagram of the system, and the accumulated charge distribution. Besides, it is worth highlighting that the simulator allows the possibility to study the influence of different parameters of the QLED structure like the junction capacitance between the distinct multilayer set. Specifically, we found that the Anode-HIL interface capacitance has a greater influence in the I–V curve. This junction capacitance plays an important role in the current density increase and the QLED turn-on value when a forward voltage is applied to the device. The simulation enabled that influence could be controlled by the selection of the optimal thickness and transport layers during the experimental fabrication process. This work is remarkable since it achieves to fit simulation and experiment results in an accurate way for electroluminescent QLED devices; particularly the simulation of the device current, which is critical when designing the automotive electronics to control these new nanotechnology lighting devices in the future.
Interpretation and visualization techniques for deep learning models in medical imaging
Authors: Huff Daniel T , Weisman Amy J , Jeraj Robert
Published: November 2020

Deep learning (DL) approaches to medical image analysis tasks have recently become popular; however, they suffer from a lack of human interpretability critical for both increasing understanding of the methods’ operation and enabling clinical translation. This review summarizes currently available methods for performing image model interpretation and critically evaluates published uses of these methods for medical imaging applications. We divide model interpretation in two categories: (1) understanding model structure and function and (2) understanding model output. Understanding model structure and function summarizes ways to inspect the learned features of the model and how those features act on an image. We discuss techniques for reducing the dimensionality of high-dimensional data and cover autoencoders, both of which can also be leveraged for model interpretation. Understanding model output covers attribution-based methods, such as saliency maps and class activation maps, which produce heatmaps describing the importance of different parts of an image to the model prediction. We describe the mathematics behind these methods, give examples of their use in medical imaging, and compare them against one another. We summarize several published toolkits for model interpretation specific to medical imaging applications, cover limitations of current model interpretation methods, provide recommendations for DL practitioners looking to incorporate model interpretation into their task, and offer general discussion on the importance of model interpretation in medical imaging contexts.
Magnetic tracking of gastrointestinal motility
Authors: Brinck Christian Emil , Mark Esben Bolvig , Klinge Mette Winther , Ejerskov Cecilie , Sutter Nanna , Schlageter Vincent , Scott S Mark , Drewes Asbjørn Mohr , Krogh Klaus
Published: November 2020

Capsule-based methods for assessment of gastrointestinal (GI) motility have seen great improvements in recent decades. The most recent development is the electromagnetic Motilis 3D-Transit system (3D-Transit). The aim of this paper is to review and discuss the development and technical properties of magnetic tracking of GI motility. We performed a comprehensive literature review on magnetic tracking in GI research. The motility tracking system was the first capsule-based magnetic system to be used in GI motility research. However, the potential of the system was hampered by its stationary and hospitalizing nature. This led to the development of the electromagnetic Motilis 3D-Transit system. The 3D-Transit system is a portable system that allows for assessment of both whole gut and regional transit times and contraction patterns in a fully ambulatory setting in the patients’ home environment with only minor restrictions on movements. The spatiotemporal resolution of 3D-Transit allows assessment of segmental colonic transit times and permits an analysis of gastric and colonic movements with a degree of detail unrivalled by other ambulatory methods, such as the wireless motility capsule. Recently, robust normative data on 3D-Transit have been published. This review provides a current perspective on the use of capsule-based magnetic tracking systems in GI research and how they represent a potentially valuable clinical resource for GI physicians and in GI research.
Effects of three different rehabilitation games’ interaction on brain activation using functional near-infrared spectroscopy
Authors: Wang Zilin , Liao Minyan , Li Qinbiao , Zhang Yanjie , Liu Heshan , Fan Zhijun , Bu Lingguo
Published: November 2020

Objective: This study reveals the changes in brain activation due to different game interaction states based on functional near-infrared spectroscopy signals and discusses their significance for stroke rehabilitation. Approach: The oxygenated hemoglobin concentration (Delta [HbO2]) signals and the deoxygenated hemoglobin (Delta [HbR]) signals were recorded from the prefrontal cortex (PFC), the motor cortex (MC), the occipital lobe (OL) and the temporal lobe of 21 subjects (mean age: 24.6 ± 1.9 years old) in three game interaction states: physical, motion-sensing, and button-push training. The subjects were also asked to complete user-satisfaction survey scales after the experiment. Main results: Compared with the button-training state, several channels in the PFC and MC region of the physical-training state were significantly altered as were several channels in the RMC region of the motion-sensing training state (P < 0.05 after adjustment). The motion-sensing state of the PFC had a significant correlation with that of the MC and the OL. The subjective scale results show that the acceptability of the physical and motion-sensing states was greater than the acceptability of the button-push training state. Significance: The results show that the brain regions responded more strongly when activated by the physical and motion-sensing states compared with the button-push training state, and the physical and motion-sensing states are more conducive to the rehabilitation of the nervous system. The design of rehabilitation products for stroke patients is discussed and valuable insights are offered to support the selection of better interactive training methods.
A novel GaN vertical junction field-effect transistor with intrinsic reverse conduction capability and kilo-volt breakdown voltage
Authors: Chen Kuangli , Zhou Qi , Zhu Liyang , Dong Zhiwen , Huang Peng , Deng Chao , Cai Yonglian , Gao Wei , Zhou Chunhua , Chen Wanjun , Zhang Bo
Published: November 2020

In this work, a novel GaN vertical junction field-effect transistor (JFET) with intrinsic reverse conduction capability (RC-JFET) is proposed and studied by simulation. The RC-JFET features two separate source electrodes, one of which performs as an embedded freewheeling diode that can enable the reverse conduction function of the device. Benefiting from a structure with two separate source electrodes, the forward and reverse current conduction paths are also separated, which allows us to independently design the forward and reverse conduction characteristics of the RC-JFET. The forward threshold voltage V
TH is 1.6 V while the reverse turn-on voltage V
on,rev is as low as 0.7 V. In addition, the buried floating p-base can effectively modulate the E-field in the GaN drift region, which can achieve a high breakdown voltage of 1720 V with an R
on,sp of 2.79 mΩ cm2. Due to the embedded freewheeling diode, the device exhibits a short reverse recovery time T
rr of 13 ns. By featuring an intrinsic reverse conduction capability, the proposed RC-JFET is capable of eliminating the externally connected diode, which is beneficial for improved switching speed and switching power loss due to the reduction of parasitic effects and chip size of power circuits.
Enhancing photoelectric current by nonclassical light
Authors: Yao Hai-Yan , Li Sheng-Wen
Published: November 2020

We study the photoelectric current generated by a driving light with nonclassical photon statistics. Due to the nonclassical input photon statistics, it is no longer enough to treat the driving light as a planar wave as in classical physics. We make a quantum approach to study such problems, and find that: when the driving light starts from a coherent state as the initial state, our quantum treatment well returns the quasi-classical driving description; when the the driving light is a generic state with a certain P function, the full system dynamics can be reduced as the P function average of many ‘branches’—in each dynamics branch, the driving light starts from a coherent state, thus again the system dynamics can be obtained in the above quasi-classical way. Based on this quantum approach, it turns out the different photon statistics does make differences to the photoelectric current. Among all the classical light states with the same light intensity, we prove that the input light with Poisson statistics generates the largest photoelectric current, while a nonclassical sub-Poisson light could exceed this classical upper bound.
A study on the bifurcation of stagnation points for a peristaltic transport of micropolar fluids with slip condition
Authors: Ullah Kaleem , Ali Nasir
Published: November 2020

The objective of present work is to investigate the impacts of embedded parameters on various flow phenomena and the bifurcations of stagnation points. This analysis is made for peristaltic transports of micropolar fluids through symmetric channel with slip condition. Exact analytic expressions for velocity profile and stream function are obtained under the constraints of long wavelength and vanishing Reynolds number. Three various flow phenomena (backward, trapping and augmented flow) and two bifurcation conditions due to their transitions are encountered in the flow by employing the dynamical system theory. The local bifurcation diagrams are used to explore the influences of micropolar parameter, coupling number and slip parameter on these bifurcations. The backward region experiences contraction by enlarging the micropolar parameter up to a critical value and after that an opposite trend is observed. The augmented flow and trapping regions expand by increasing the coupling number, while slip parameter shows an opposite behavior. At the end, the results of this analysis are summarized by using global bifurcation diagrams.
Modulation and enhancement of photonic spin Hall effect with graphene in broadband regions*
Authors: Dong Peng , Wang Gaojun , Cheng Jie
Published: November 2020

The photonic spin Hall effect (SHE) holds great potential applications in manipulating spin-polarized photons. However, the SHE is generally very weak, and previous studies of amplifying photonic SHE were limited to the incident light in a specific wavelength range. In this paper, we propose a four-layered nanostructure of prism-graphene-air-substrate, and the enhanced photonic SHE of reflected light in broadband range of 0 THz–500 THz is investigated theoretically. The spin shift can be dynamically modulated by adjusting the thickness of air gap, Fermi energy of graphene, and also the incident angle. By optimizing the structural parameter of this structure, the giant spin shift (almost equal to its upper limit, half of the incident beam waist) in broadband range is achieved, covering the terahertz, infrared, and visible range. The difference is that in the terahertz region, the Brewster angle corresponding to the giant spin shift is larger than that of infrared range and visible range. These findings provide us with a convenient and effective way to tune the photonic SHE, and may offer an opportunity for developing new tunable photonic devices in broadband range.
Polarization-resolved Raman spectra of α-PtO2
*
Authors: Lei Zhanhong , Wang Weiliang , She Juncong
Published: November 2020

Using density functional theory, we investigate the vibrational properties and polarization-resolved Raman spectra of α-PtO2 and obtain the Raman tensor and angle-dependent Raman intensity of α-PtO2. It is found that the polar plot of A1g mode in parallel polarization configuration is useful in identifying the orientation of the crystal. The Raman intensity of the Eg mode is about five times stronger than that of the A1g mode. The Raman intensity is about three times stronger when the wave vector of the incident light is in x or y direction than in z direction. Our work will help the material scientists to characterize the α-PtO2 and to identify its orientation by comparing the experimental spectra with our result.
Passivation of PEA+ to MAPbI3 (110) surface states by first-principles calculations*
Authors: Hu Wei , Tian Ying , Xue Hong-Tao , Li Wen-Sheng , Tang Fu-Ling
Published: November 2020

The MAPbI3 (110) surface with low indices of crystal face is a stable and highly compatible photosensitive surface. Since the electronic states on the surface can be detrimental to the photovoltaic efficiency of the device, they should be passivated. Phenylethylamine (PEA+), as a molecular ligand, has been widely used in continuous degradation and interfacial charge recombination experiments, and has satisfactory performance in improving surface defects. Therefore, we construct an adsorption model of MAPbI3 with small molecules, calculating the lattice structure and electronic properties of PEA+-adsorbed MAPbI3 (110) surface. It is found that PEA+ as a passivator can effectively weaken the electronic states and regulate the band gap of the MAPbI3 (110) surface. Before and after adding the passivator, the peak value of electronic state densities at MAPbI3 (110) surface is reduced by about 50%, and the band gap is apparently reduced. Moreover, by comparing the Bader atomic charge and spatial charge distributions before and after PEA+’s adsorption on the surface of MAPbI3, we observe a substantial change of PEA+ charges, which suggests the surface states have been passivated by PEA+.
Instability of AdS black holes with lattices *
Authors: Ling Yi , Wu Meng-He
Published: November 2020

Anti-de Sitter (AdS) black holes with lattices are essential for optical conductivity studies in the holographic approach. We investigate the instability of these black holes that can result in the holographic description of charge density waves. In the presence of homogeneous axion fields, we show that the instability of AdS-Reissner-Nordström (AdS-RN) black holes is always suppressed. However, in the presence of Q-lattices, we find that the unstable region becomes the smallest in the vicinity of the critical region for the metal/insulator phase transition. This novel phenomenon is reminiscent of the behavior of the holographic entanglement entropy during quantum phase transitions.
Revisiting the determining fraction of glueball component in f
0 mesons via radiative decays of J/ψ
*
Authors: Guo Xing-Dao , Ke Hong-Wei , Zhao Ming-Gang , Tang Liang , Li Xue-Qian
Published: November 2020

QCD theory predicts the existence of glueballs, but so far all experimental endeavors have failed to identify any such states. To remedy this discrepancy between QCD, which has proven to be a successful theory for strong interactions, and the failure of experimental searches for glueballs, one is tempted to accept the promising interpretation that the glueballs mix with regular

states of the same quantum numbers. The lattice estimate of the masses of pure

glueballs ranges from 1 to 2 GeV, which is the region of the

family. Thus many authors suggest that the

mesonic series is an ideal place to study possible mixtures of glueballs and

. In this paper, following the strategy proposed by Close, Farrar and Li, we try to determine the fraction of glueball components in

mesons using the measured mass spectra and the branching ratios of

radiative decays into

mesons. Since the pioneering papers by Close et al., more than 20 years have elapsed and more accurate measurements have been done by several experimental collaborations, so it is time to revisit this interesting topic using new data. We suppose

and

to be pure quark states, while for

,

and

, to fit both the experimental data of

radiative decay and their mass spectra, glueball components are needed. Moreover, the mass of the pure

glueball is phenomenologically determined.
How protective is China’s National Ambient Air Quality Standards on short-term PM2.5? Findings from blood pressure measurements of 1 million adults
Authors: Guan Tianjia , Xue Tao , Guo Jian , Wang Xin , Zheng Yixuan , Chao Baohua , Kang Yuting , Chen Zuo , Zhang Linfeng , Zheng Congyi , Jiang Linlin , Yang Ying , Zhang Qiang , Wang Zengwu , Liu Yuanli , Gao Runlin
Published: November 2020

Although short-term exposure to fine particulate matter (PM2.5) air pollution has been shown to induce elevated blood pressure (BP), limited evidence is available regarding the association between ambient PM2.5 and BP levels in nationwide China and how the association may change. This study sought to explore acute BP changes with exposure to PM2.5 at levels below China’s current National Ambient Air Quality Standards (NAAQS). Based on a spatiotemporal study of over 1 million adults, we linked BP measurements to daily estimates of PM2.5 from multiple sources (i.e. in situ observations, satellite measurements of aerosol and numeric simulations of air quality model) after adjusting for several individual-level covariates and further conduced the below-criteria models by restricting the analyses within subsets of individuals with short-term PM2.5 exposure below 75 μg m−3 (i.e. NAAQS of 24 h PM2.5 in China). We further explored variations in BP-PM2.5 associations by pollution level and for different demographic groups. With full adjustments, a 10 μg m−3 increase in PM2.5 was statistically significantly associated with a 0.049 mmHg (95% confidence interval, CI: 0.041, 0.057) increase in systolic BP, a 0.022 mmHg (95% CI: 0.017, 0.027) increase in diastolic BP and a 0.77% (95% CI: 0.62%, 0.92%) increased risk of hypertension (HPN). For both BP and HPN, the exposure-response curves were linear, with no threshold effects, at the low-concentration ends and sublinear at the high-concentration ends. Below the current NAAQS, the associations in population level remained statistically significant and were even stronger. A 10 μg m−3 increase in below-NAAQS PM2.5 was associated with a 1.95% (95% CI: 1.44%, 2.47%) increased risk of HPN. Specific subpopulations were more susceptible to PM2.5 exposure. These findings can help support decisions by policymakers to revise related environmental regulations to protect public health.
Designing tunable narrowband parametric source in Chalcogenide-based dynamic fiber geometry
Authors: Chatterjee Sudip K , Khan Saba N
Published: November 2020

We numerically investigate the generation of spectrally isolated narrowband tunable parametric sources by continuous-wave pumping a specially designed gelatin-coated chalcogenide-silica dynamic fiber in the normal dispersion regime. The relative humidity (RH) dependent phase matching dominated by fourth order dispersion has been exploited for the first time, to the best of our knowledge, to produce far-detuned new wavelengths. A tunable source in the range of 0.96–2.5 μm with a tuning rate of 1.3 THz/%RH has been designed by milliwatt pumping a 30 cm long fiber at 1.395 μm. Additionally, the sideband tailorability of about 50 THz close to the visible band was achieved by selectively exciting higher-order fiber modes (HE21) in the anomalous dispersion regime at 0.91 μm. We emphasize that the parametric sources from the proposed host would be extremely useful in short-wave infrared spectroscopy and biomedical applications.
Multi-Class classification of vulnerabilities in smart contracts using AWD-LSTM, with pre-trained encoder inspired from natural language processing
Authors: Gogineni Ajay K , Swayamjyoti S , Sahoo Devadatta , Sahu Kisor K , Kishore Raj
Published: November 2020

Vulnerability detection and safety of smart contracts are of paramount importance because of their immutable nature. Symbolic tools like OYENTE and MAIAN are typically used for vulnerability prediction in smart contracts. As these tools are computationally expensive, they are typically used to detect vulnerabilities until some predefined invocation depth. These tools require more search time as the invocation depth increases. Since the use of smart contracts increases rapidly, their analysis becomes difficult using these traditional tools. Recently, a machine learning technique called Long Short Term Memory (LSTM) has been used to predict the vulnerability of a smart contract. In the present article, we present how to classify smart contracts into Suicidal, Prodigal, Greedy, or Normal categories using Average Stochastic Gradient Descent Weight-Dropped LSTM (AWD-LSTM), a variant of LSTM. We reduced the class imbalance by considering only distinct opcode combinations for normal contracts and achieved a weighted average F1 score of 90.0%. Such techniques can be utilized in real-time to analyze a large number of smart contracts and to improve their security.
Contrasting patterns of plant–pollinator interactions among four oil-secreting species of Iridaceae from Pampean and Cerrado provinces (Brazil)
Authors: Báez-Lizarazo Mabel R , Eggers Lilian , Aguiar Antonio J C , Chauveau Olivier
Published: November 2020

Flowers producing oil resources and oil bee pollinators are involved in one of the most specialized pollination strategies. Various species of Iridaceae tribe Tigridieae are characterized by floral oil-secreting structures called elaiophores, but specialized plant–pollinator interactions among these taxa remain poorly understood. This study focused on four South American species of Tigridieae in three genera to assess the nature and extent of ecological specialization related to oil flower/oil bee interactions. Proportion, frequency and behaviour of specialist and generalist pollinators were investigated, and experiments on plant breeding system and observations on floral biology were conducted. Species of Arhysoceble (specialist bees) and Halictidae (generalist bees) formed the most representative taxonomic groups of pollinators. Even though ecological specialization for oil bees was detected in Cypella amplimaculata and Cipura sp., contrasting patterns of specialization were observed not only among the different plant species studied but also between populations of Herbertia pulchella and Cipura formosa. Self-incompatibility was reported for H. pulchella and Cipura sp., whereas C. amplimaculata and C. formosa presented a mixed-breeding system. However, all species were pollinator dependent and patterns of ecological specialization were not dependent of plant breeding system. This study revealed also that interactions between oil bees and elaiophores are not reliable predictors for efficient pollination.