bluuebunny/crossref_metadata_2025 huggingface dataset:
Outcome after Combined Lateral Extra-articular Tenodesis and Anterior Cruciate Ligament Revision in Professional Soccer Players
Authors: Alessio-Mazzola Mattia , Formica Matteo , Russo Antonio , Sanguineti Francesca , Capello Andrea Giorgio , Lovisolo Stefano , Felli Lamberto
Published: September 2018

We report the functional outcome after combined anterior cruciate ligament (ACL) reconstruction and lateral extra-articular tenodesis (LET) for ACL re-rupture and high-grade pivot shift in professional soccer players. For this retrospective review, the medical records of 24 professional soccer players were analyzed. The mean age at surgery was 23.8 ± 4.2 years and the mean follow-up was 42.2 ± 16.9 months. Pre- and postoperative assessment included the KT-1000 Lachman test, pivot shift test, International Knee Documentation Committee (IKDC) subjective knee evaluation, Tegner activity scale (TAS), and Lysholm score. The rate of return to sports and the level of play at final follow-up were recorded. ACL revision was performed with an autologous bone–patellar tendon–bone autograft or a hamstring graft. LET was performed using an extra-articular MacIntosh procedure as modified by Arnold–Coker. Anterior–posterior laxity was significantly reduced at the final clinical assessment (p < 0.0001): 22 patients (91.7%) had a negative pivot shift and 2 (8.3%) had residual glide (+), with significant improvement (p < 0.0001). The mean subjective IKDC and Lysholm score improved from 69.5 ± 11.1 (range: 56–90) to 88.4 ± 8.9 (range: 62.1–100) and from 58.1 ± 11.7 (range: 33–72) to 97.4 ± 3.2 (range: 88–100), respectively, with significant improvement (p < 0.0001) over preoperative values. The overall failure rate was 8.3%. There were no differences between mean preinjury and final TAS scores (p > 0.05). The rate of return to sports at the same level was 91.7% and the mean time to return to sports was 9.2 ± 2.2 months. Mid-term functional outcome after combined extra-articular reconstruction and ACL revision surgery was satisfactory, with a reduction in residual postoperative rotatory instability and degree of pivot shift.
Is Arthrodesis a Reliable Salvage Option following Two-Stage Revision for Suspected Infection in Proximal Tibial Replacements? A Multi-Institutional Study
Authors: Sambri Andrea , Bianchi Giuseppe , Parry Michael , Frenos Filippo , Campanacci Domenico , Donati Davide , Jeys Lee
Published: September 2018

The aim of this multicentric retrospective study was to verify whether knee arthrodesis (KA) is a viable reconstructive option after two-stage revision for infection of proximal tibia (PT) endoprosthetic reconstruction (EPR). Sixty patients who underwent a two-stage revision were included. Definitive EPR or a KA with a modular system was performed following consideration of soft tissue and extensor mechanism conditions. Patients were evaluated with Musculoskeletal Tumor Society Score and Oxford Knee Score. Implant survival was assessed on the basis of recurrence of infection. Five patients did not receive any reconstruction after the first stage. In 14 cases, a KA was performed, and in 41, an EPR was implanted. At 5 years follow-up, reinfection rate in the KA group was lower (10 vs. 17.5% in KA and EPR groups, respectively). In reinfected patients, the KA group had a reduced rate of amputation when compared with those with EPR (50 vs. 88%). Functional evaluation did not show any significant differences between the two groups. A successful KA using a modular implant can eradicate infection and allow preservation of the limb with good function and good pain relief in after two-stage revision for an infected PT EPR.
Does Chronic Ankle Instability Influence Knee Biomechanics of Females during Inverted Surface Landings?
Authors: Li Yumeng , Ko Jupil , Walker Marika , Brown Cathleen , Schmidt Julianne , Kim Seock-Ho , Simpson Kathy
Published: September 2018

The primary purpose of the study was to determine whether atypical knee biomechanics are exhibited during landing on an inverted surface. A seven-camera motion analysis system and two force plates were used to collect lower extremity biomechanics from two groups of female participants: 21 subjects with chronic ankle instability (CAI) and 21 with pair-matched controls. Subjects performed ten landings onto inverted and flat platforms on the CAI/matched and non-test limbs, respectively. Knee and ankle joint angles, joint angular displacements, joint moments and eccentric work were calculated during the landing phase and/or at the initial contact. Paired t-tests were used to compare between-group differences (p<0.05). We observed that CAI group displayed a significantly increased knee flexion angle, knee flexion displacement, peak knee extension moment and internal rotation moment, and eccentric work in the sagittal plane, possibly due to altered ankle biomechanics. Participants with CAI employed some compensatory strategy to improve their ankle and postural stability during landing onto the tilted surface. The increased knee extension and internal rotation moments of CAI participants could potentially result in a greater ACL loading. In future studies, it may be worthwhile to measure or estimate the ACL loading to confirm whether CAI could relate to the mechanism of ACL injury.
Two-dimensional quantum scattering by non-isotropic interactions localized on a circle, applications to open billiards
Authors: de Prunelé E.
Published: September 2018

Two-dimensional quantum scattering by isotropic and non-isotropic interactions localized on a circle is considered. The expansion of the interaction on the circle in a Fourier series allows us to express basic objects of scattering theory (resolvent, T operator, differential cross length, cross length, and cross length averaged over all orientations of the incident particle), in terms of operations on matrices. For numerical applications, these matrices are truncated to a given order. If the interaction is isotropic, this general formulation reduces to the usual one, and the resonances in the isotropic cases are studied because they allow us to interpret resonances in some non-isotropic cases. Applications to open circular billiards are given. A first approach to the open quantum circular billiard is an interaction equal to zero on some parts of the circle and to a great value λ on the other parts. Then, it turns out that the limit λ → +∞ does not lead to an explicit result in this approach. A second approach to the open circular billiard is given by replacing apertures (where the interaction is zero) by pseudo-apertures (where the interaction is small but non-zero), and the limit λ → +∞ then leads to an explicit result. In the high energy regime, the two approaches give similar results and allow interpretation of numerous results, in particular, for differential cross lengths, in terms of classical mechanics.
Transition to chaos in wave memory dynamics in a harmonic well: Deterministic and noise-driven behavior
Authors: Perrard S. , Labousse M.
Published: September 2018

A walker is the association of a sub-millimetric bouncing drop moving along with a co-evolving Faraday wave. When confined in a harmonic potential, its stable trajectories are periodic and quantised both in extension and mean angular momentum. In this article, we present the rest of the story, specifically the chaotic paths. They are chaotic and show intermittent behaviors between an unstable quantised set of attractors. First, we present the two possible situations we find experimentally. Then, we emphasise theoretically two mechanisms that lead to unstable situations. It corresponds either to noise-driven chaos or low-dimensional deterministic chaos. Finally, we characterise experimentally each of these distinct situations. This article aims at presenting a comprehensive investigation of the unstable paths in order to complete the picture of walkers in a two dimensional harmonic potential.
Breakdown mechanism in 1 kA/cm2 and 960 V E-mode β-Ga2O3 vertical transistors
Authors: Hu Zongyang , Nomoto Kazuki , Li Wenshen , Zhang Zexuan , Tanen Nicholas , Thieu Quang Tu , Sasaki Kohei , Kuramata Akito , Nakamura Tohru , Jena Debdeep , Xing Huili Grace
Published: September 2018

A high current density of 1 kA/cm2 is experimentally realized in enhancement-mode Ga2O3 vertical power metal-insulator field-effect transistors with fin-shaped channels. Comparative analysis shows that the more than doubled current density over the prior art arises from a larger transistor channel width; on the other hand, a wider channel also leads to a more severe drain-induced barrier lowering therefore premature transistor breakdown at zero gate-source bias. The observation of a higher current density in a wider channel confirms that charge trapping in the gate dielectric limits the effective field-effect mobility in these transistor channels, which is about 2× smaller than the electron mobility in the Ga2O3 drift layer. The tradeoff between output-current density and breakdown voltage also depends on the trap density. With minimal trap states, the output current density should remain high while breakdown voltage increases with decreasing fin-channel width.
Enhanced photorefractive properties of indium co-doped LiNbO3:Mo crystals
Authors: Zhu Ling , Zheng Dahuai , Liu Hongde , Saeed Shahzad , Wang Shuolin , Liu Shiguo , Chen Shaolin , Kong Yongfa , Xu Jingjun
Published: September 2018

We grew a set of indium and molybdenum co-doped lithium niobate crystals with various indium doping concentrations and investigated their photorefractive properties at different wavelengths (442, 488 and 532 nm). It was found that the diffraction efficiency of 1.0 mol% indium and 0.5 mol% molybdenum co-doped lithium niobate crystal could reach 61.57% at 488 nm. Moreover for 3.0 mol% indium and 0.5 mol% molybdenum co-doped lithium niobate crystal, the response time was greatly shortened to 0.61, 0.76, and 0.74 s at 442, 488, and 532 nm, respectively, while the photorefractive sensitivity reached as high as 7.35 cm/J at 442 nm. These results indicate that co-doping of indium is an efficient way to further enhance the photorefractive properties of molybdenum-doped lithium niobate crystal.
A spectroscopic electric field vector imaging diagnostic for electron cyclotron heating systems
Authors: Martin E. H. , Lau C. , Brookman M. W. , Lohr J.
Published: September 2018

An experimental measurement of the wave electric field vector provides important data that can be used to directly compare against 3D full-wave simulations. This direct comparison yields the fastest approach toward identifying missing physics in computational models and providing a high fidelity validation platform. In this paper, we present a diagnostic that is capable of imaging the Electron Cyclotron (EC) wave electric field vector by acquiring filtered images of polarized Dβ spectral satellites. The diagnostic is designed to have a spatial and temporal resolution on the order of 100 μm and 100 μs, respectively. The diagnostic purpose is to provide experimental data for the direct validation of full-wave codes used to predict EC beam propagation and absorption and to provide real-time monitoring of EC waves.
Effect of buffer iron doping on delta-doped β-Ga2O3 metal semiconductor field effect transistors
Authors: Joishi Chandan , Xia Zhanbo , McGlone Joe , Zhang Yuewei , Arehart Aaron R. , Ringel Steven , Lodha Saurabh , Rajan Siddharth
Published: September 2018

We report on the effect of iron (Fe)-doped semi-insulating buffers on the electron transport and DC-RF dispersion in Si delta (δ)-doped β-Ga2O3 metal-semiconductor field effect transistors. The effect of the distance between the 2-dimensional electron gas and the Fe-doped region was investigated, and Fe doping in the buffer was found to have a significant effect on the transport properties. It was found that buffers thicker than 600 nm can enable better transport and dispersion properties for field effect transistors, while maintaining relatively low parasitic buffer leakage. This work can provide guidance for the use of Fe-doped insulating buffers for future Ga2O3 based electronics.
Mapping between charge-monopole and position-dependent mass systems
Authors: Schmidt Alexandre G. M. , de Jesus Anderson L.
Published: September 2018

We study the non-relativistic charge-monopole system when the charged particle has a position-dependent mass written as M(r) = m0rw. The angular wave functions are the well-known monopole harmonics, and the radial ones are ordinary Bessel functions which depend on the magnetic and electric charge product as well as on the w parameter. We investigate mappings—approximate and exact—between the charge-monopole system with constant mass and the charge with a position-dependent mass solving the position-dependent mass Schrödinger equation for the mass distribution.
Infrared dielectric response, index of refraction, and absorption of germanium-tin alloys with tin contents up to 27% deposited by molecular beam epitaxy
Authors: Imbrenda Dominic , Hickey Ryan , Carrasco Rigo A. , Fernando Nalin S. , VanDerslice Jeremy , Zollner Stefan , Kolodzey James
Published: September 2018

The dielectric spectral response of Ge1-xSnx thin film alloys with relatively high Sn contents (0.15 ≤ x ≤ 0.27) and thickness from 42 to 132 nm was characterized by variable angle spectroscopic ellipsometry over the wavelength range from 0.190 to 6 μm. The Ge1-xSnx thin films were deposited on Ge substrates by molecular beam epitaxy using an electron-beam source for Ge to achieve a substrate temperature below 150 °C to prevent the surface segregation of Sn. From the measured dielectric function, the complex refractive index was calculated indicating an increase in the real index with the Sn content at mid-infrared wavelengths. The ellipsometry revealed that the band structure critical point energies red-shifted with the increasing Sn content. The optical absorption coefficient was calculated from the imaginary index and showed a strong absorption into, and beyond, the mid-infrared with the increasing Sn content.
Boundary interface condition of magnetic fluid determines the magnetic levitation force experienced by a permanent magnet suspended in the magnetic fluid
Authors: Yu Jun , He Xinzhi , Li Decai , Li Wenyi
Published: September 2018

The buoyancy experienced by a permanent magnet suspended in magnetic fluid is studied, and the expression for calculating the magnetic fluid buoyancy is derived. The magnetic fluid buoyancy or magnetic fluid levitation force, which can be obtained by calculating the sum of Archimedes levitation force and magnetic levitation force, depends on the boundary interface condition of magnetic fluid. The type of the boundary interface and the pressure over it determine the boundary interface condition, and the dependence of boundary interface condition of magnetic fluid and magnetic fluid levitation force is studied. If the boundary interface of the magnetic fluid is a liquid-gas interface in contact with air, the magnetic fluid levitation force will be equal to the gravity of the magnetic fluid. A sudden change in magnetic fluid levitation force can be seen when the liquid-gas boundary interface of magnetic fluid is broken by the wall of a container. Or, in other words, the emergence of a solid-liquid boundary interface will influence the magnetic fluid levitation force, and the magnitude of the change is proportional to magnetic field intensity over the solid-liquid boundary interface. Once the liquid-gas boundary interface is close to a horizontal plane, the magnitude of magnetic fluid levitation force will reach a relatively stable value. In the experiments, the volume of magnetic fluid, the location of the magnet, and the magnetic particle concentration in magnetic fluid are used to control and change the boundary interface condition of magnetic fluid.
Measurements of thermal conductivity across the B1-B2 phase transition in NaCl
Authors: McGuire Christopher , Sawchuk Krista , Kavner Abby
Published: September 2018

We present measurements of the pressure dependence of thermal conductivity for high pressure phases of KCl and NaCl using the laser-heated diamond anvil cell (LHDAC) and a 3D finite element model for heat flow. Temperature measurements are made in the LHDAC of KCl in the B2 phase, from 15 GPa to 24 GPa, and of NaCl from 14 GPa to 43 GPa, across the B1-B2 phase transition. The measurements are forward modeled, using the geometry and material properties of the cell as inputs, solving for the change in thermal conductivity between pressure steps. The results for B2 KCl indicate increasing thermal conductivity over the experimental pressure range and give dlnκdlnρ=3.75 ± 0.9. For NaCl, thermal conductivity increases in the B1 and B2 phases, dlnκdlnρ=1.6 ± 0.5 and dlnκdlnρ=2.9 ± 0.8, respectively. Our results constrain the reduction in thermal conductivity across the NaCl B1-B2 transition to 37% ± 7%.
Tutorial: Brain-inspired computing using phase-change memory
devices
Authors: Sebastian Abu , Le Gallo Manuel , Burr Geoffrey W. , Kim Sangbum , BrightSky Matthew , Eleftheriou Evangelos
Published: September 2018

There is a significant need to build efficient non-von Neumann computing systems for highly data-centric artificial intelligence related applications. Brain-inspired computing is one such approach that shows significant promise. Memory is expected to play a key role in this form of computing and, in particular, phase-change memory (PCM), arguably the most advanced emerging non-volatile memory technology. Given a lack of comprehensive understanding of the working principles of the brain, brain-inspired computing is likely to be realized in multiple levels of inspiration. In the first level of inspiration, the idea would be to build computing units where memory and processing co-exist in some form. Computational memory is an example where the physical attributes and the state dynamics of memory devices are exploited to perform certain computational tasks in the memory itself with very high areal and energy efficiency. In a second level of brain-inspired computing using PCM devices, one could design a co-processor comprising multiple cross-bar arrays of PCM devices to accelerate the training of deep neural networks. PCM technology could also play a key role in the space of specialized computing substrates for spiking neural networks, and this can be viewed as the third level of brain-inspired computing using these devices.
Luminescence methodology to determine grain-boundary, grain-interior, and surface recombination in thin-film solar cells
Authors: Moseley John , Rale Pierre , Collin Stéphane , Colegrove Eric , Guthrey Harvey , Kuciauskas Darius , Moutinho Helio , Al-Jassim Mowafak , Metzger Wyatt K.
Published: September 2018

We determine the grain-boundary (GB) recombination velocity, SGB, and grain-interior (GI) lifetime, τGI, parameters in superstrate CdS/CdTe thin-film solar cell technology by combining cathodoluminescence (CL) spectrum imaging and time-resolved photoluminescence (TRPL) measurements. We consider critical device formation stages, including after CdTe deposition, CdCl2 treatment, and Cu diffusion. CL image analysis methods extract GB and GI intensities and grain size for hundreds of grains per sample. Concurrently, a three-dimensional CL model is developed to simulate the GI intensity as a function of τGI, SGB, grain size, and the surface recombination velocity, Ssurf. TRPL measurements provide an estimate of Ssurf for the CL model. A fit of GI intensity vs. grain size data with the CL model gives a self-consistent and representative set of SGB and τGI values for the samples: SGB(τGI)= 2.6 × 106 cm/s (68–250 ps), SGB(τGI)= 4.1 × 105 cm/s (1.5–3.3 ns), and SGB(τGI)= 5.5 × 105 cm/s (1.0–3.8 ns) for as-deposited, CdCl2-treated, and CdCl2- and Cu-treated samples, respectively. Thus, we find that the CdCl2 treatment both helps to passivate GBs and significantly increase the GI lifetime. Subsequent Cu diffusion increases GB recombination slightly and has nuanced effects on the GI lifetime. Finally, as a partial check on the SGB and τGI values, they are input to a Sentaurus device model, and the simulated performance is compared to the measured performance. The methodology developed here can be applied broadly to CdTe and CdSeTe thin-film technology and to other thin-film solar cell materials including Cu(In1-xGax)Se2, Cu2ZnSnS4, and perovskites.
The EXP pair-potential system. I. Fluid phase isotherms, isochores, and quasiuniversality
Authors: Bacher Andreas Kvist , Schrøder Thomas B. , Dyre Jeppe C.
Published: September 2018

It was recently shown that the exponentially repulsive EXP pair potential defines a system of particles in terms of which simple liquids’ quasiuniversality may be explained [A. K. Bacher et al., Nat. Commun. 5, 5424 (2014); J. C. Dyre, J. Phys.: Condens. Matter 28, 323001 (2016)]. This paper and its companion [A. K. Bacher et al., J. Chem. Phys. 149, 114502 (2018)] present a detailed simulation study of the EXP system. Here we study how structure monitored by the radial distribution function and dynamics monitored by the mean-square displacement as a function of time evolve along the system’s isotherms and isochores. The focus is on the gas and liquid phases, which are distinguished pragmatically by the absence or presence of a minimum in the radial distribution function above its first maximum. A constant-potential-energy (NVU)-based proof of quasiuniversality is presented, and quasiuniversality is illustrated by showing that the structure of the Lennard-Jones system at four state points is well approximated by those of EXP pair-potential systems with the same reduced diffusion constant. Paper II studies the EXP system’s isomorphs, focusing also on the gas and liquid phases.
The EXP pair-potential system. II. Fluid phase isomorphs
Authors: Bacher Andreas Kvist , Schrøder Thomas B. , Dyre Jeppe C.
Published: September 2018

This paper continues the investigation of the exponentially repulsive EXP pair-potential system of Paper I [A. K. Bacher et al., J. Chem. Phys. 149, 114501 (2018)] with a focus on isomorphs in the low-temperature gas and liquid phases. As expected from the EXP system’s strong virial potential-energy correlations, the reduced-unit structure and dynamics are isomorph invariant to a good approximation. Three methods for generating isomorphs are compared: the small-step method that is exact in the limit of small density changes and two versions of the direct-isomorph-check method that allows for much larger density changes. Results from the latter two approximate methods are compared to those of the small-step method for each of the three isomorphs generated by 230 one percent density changes, covering one decade of density variation. Both approximate methods work well.
Writing skyrmions with a magnetic dipole
Authors: Garanin Dmitry A. , Capic Daniel , Zhang Senfu , Zhang Xixiang , Chudnovsky Eugene M.
Published: September 2018

We demonstrate numerically, through energy minimization on large spin lattices, that one can write skyrmions in a thin magnetic film with a magnetic dipole of a few tens of nanometer in size. Nucleation of non-chiral skyrmions as well as chiral skyrmions formed by the Dzyaloshinskii-Moriya interaction has been investigated. Analytical model is developed that agrees with the numerical results. It is shown that skyrmions can be written through a number of scenarios that depend on the experimental technique and parameters of the system. In one scenario, which branches into subscenarios of different topology, the magnetic dipole on approaching the film creates a skyrmion-antiskyrmion pair. As the dipole moves closer to the film, it induces collapse of the antiskyrmion and creation of a non-zero topological charge due to the remaining skyrmion. In a different scenario, the dipole moving parallel to the film nucleates a skyrmion at the boundary and then drags it inside the film. Possible implementations of these methods for writing topologically protected information in a magnetic film are discussed.
Thermoelectric efficiency in three-terminal graphene nano-junctions
Authors: Sartipi Zahra , Hayati Amir , Vahedi Javad
Published: September 2018

The thermoelectric efficiency of a thermal machine consisting of a triangular graphene nano-junction connected to three electrodes in the linear response regime is studied. Using the Onsager formalism and a combination of semi-empirical tight-binding calculations as well as Green’s function theory, the efficiency at maximum output power which can be written in terms of generalized figures of merit is investigated. The results for a set temperature and chemical potential parameters have shown that adding a third terminal improves the efficiency at maximum output power compared to the two-terminal setup.
Measured Lamb wave radiation patterns from ⟨011⟩ Mn-PMN-PZT relaxor ferroelectric disks on an isotropic plate
Authors: Vien B. S. , Moss S. D. , Chiu W. K. , Thornton J. , Rosalie C. , Rajic N. , Doughney T. F. , Kissick H. J.
Published: September 2018

Three-dimensional laser Doppler vibrometry is used to quantify the modal composition of the guided plate waves generated by relaxor ferroelectric disk actuators of a ⟨011⟩ poled Mn-Pb(Mg1/3Nb2/3)O-lead zirconate titanate (PZT) single crystal and ⟨100⟩ poled piezoelectric PZT, bonded to an isotropic plate. Disk actuators are excited using a 5.5 cycle Hann-windowed voltage tone-burst at centre frequencies of 100, 200, and 300 kHz. Measured wave fields are processed using a two-dimensional fast Fourier transform to determine the radiation pattern of each contributing mode. For the same applied electric field strength, the single crystal actuators are shown to produce significantly larger wave amplitudes and one additional wave mode, the shear horizontal, as compared with PZT actuators. The wave-mode radiation patterns are shown to be anisotropic, suggesting that the classical theory describing guided-wave modal excitability may need to be revised for these materials.
A thermodynamic supersaturation model for the growth of aluminum gallium nitride by metalorganic chemical vapor deposition
Authors: Washiyama Shun , Reddy Pramod , Kaess Felix , Kirste Ronny , Mita Seiji , Collazo Ramón , Sitar Zlatko
Published: September 2018

A thermodynamic supersaturation model for growth of AlGaN by metalorganic chemical vapor deposition was developed for experimentally accessible growth parameters. The derived non-linear relationships enabled us to estimate Ga and Al supersaturation during AlGaN growth for given growth conditions. Calculations revealed that the GaN phase was close to chemical equilibrium, while the Al supersaturation was as high as 1010 for typical growth conditions. Such a disparity in the supersaturation of reaction species plays a significant role in the stability of the growth of the resulting ternary alloy. The agreement between experiment and simulation suggests that the parasitic gas phase reactions between trimethylaluminum and NH3 were not significant at low NH3 flow rates/partial pressures, indicating that, under these conditions, the AlGaN growth was thermodynamically limited.
Ion dynamics in a magnetized source-collector sheath
Authors: Adhikari S. , Moulick R. , Goswami K. S.
Published: September 2018

A bounded plasma is simulated with a spatially generated source in the presence of an oblique magnetic field. The kinetic particle-in-cell technique has been used to track particles fully kinetically. The plasma facing the surface is considered to be an absorbent for the charged particles. The plasma flow is assumed to be normal with respect to the surface and primarily controlled by the self-consistent internal electric field. The ions are observed to follow interesting dynamical behavior near the collector sheath. The low energetic ions reflect back to the ion source region at certain angles of inclination. The reflection seems to be prominent at a low angle of inclination. The interaction of the magnetic field with the surface in a divertor like scenario of a tokamak is typically at a low angle (∼5°). Even the surface of a space station may be tilted with respect to the earth's magnetic field. The observations made in this paper will find a significant impact in these configurations.
Controlled generation of intrinsic near-infrared color centers in 4H-SiC via proton irradiation and annealing
Authors: Rühl M. , Ott C. , Götzinger S. , Krieger M. , Weber H. B.
Published: September 2018

We report on the generation and annihilation of color centers in 4H silicon carbide (SiC) by proton irradiation and subsequent annealing. Using low-temperature photoluminescence (PL), we study the transformation of PL spectra for different proton doses and annealing temperatures. Among well reported defect signatures, we observe omnipresent but not yet identified PL signatures consisting of three sharp and temperature stable lines (denoted TS1,2,3) at 768.8 nm, 812.0 nm, and 813.3 nm. These lines show a strong correlation throughout all measurement parameters, suggesting that they belong to the same microscopic defect. Further, a clear dependence of the TS1,2,3 line intensities on the initial implantation dose is observed after annealing, indicating that the underlying defect is related to implantation induced intrinsic defects. The overall data suggest a sequential defect transformation: proton irradiation initially generates isolated silicon vacancies which are transformed into antisite vacancy complexes which are, in turn, transformed into presumably intrinsic-related defects, showing up as TS1,2,3 PL lines. We present recipes for the controlled generation of these color centers.
Effects of non-hydrostaticity and grain size on the pressure-induced phase transition of the CoCrFeMnNi high-entropy alloy
Authors: Zhang Fei , Lou Hongbo , Chen Songyi , Chen Xiehang , Zeng Zhidan , Yan Jinyuan , Zhao Wuxin , Wu Yuan , Lu Zhaoping , Zeng Qiaoshi
Published: September 2018

Recently, an irreversible polymorphic transition from face-centered cubic to hexagonal close-packing was surprisingly observed under high pressure in the prototype CoCrFeMnNi high-entropy alloys (HEAs) by various research groups. This unexpected phase transition brings new insights into the stability of HEAs, and its irreversibility stimulates exploration for new HEAs via high-pressure compression synthesis. However, the onset pressure for the phase transition was reported to fluctuate over a vast range from ∼7 to above 49 GPa in the reported experiments. The reason for this inconsistency remains unclear and puzzles the HEA community. To address this problem, this work systematically investigates the effects of non-hydrostaticity and grain size. Our results demonstrate that larger deviatoric stress induced by the non-hydrostaticity of the pressure medium and larger grain size of the initial sample can both promote a phase transition and, therefore, considerably depress the onset pressure.
The low-temperature transport properties of Heusler alloy Mn2CoAl
Authors: Chen Peng , Gao Cunxu , Chen Guilin , Mi Kui , Liu Ming , Zhang Peng , Xue Desheng
Published: September 2018

Epitaxial Mn2CoAl films were grown on MgO(001) substrates by molecular beam epitaxy to study the low-temperature transport properties of a spin gapless semiconductor in view of potential applications in spintronic devices based on this unique class of materials. We present the high-quality epitaxial growth, structure characterization, temperature-dependent resistivity, and magnetoresistance results of the Mn2CoAl films. Derived from these electronic transport properties, we found that the nearly magnetic-field-independent T1/2 term originating from the electron–electron interaction effect was attributed to the resistivity behavior of the Mn2CoAl films at low temperatures. The T1/2-term interaction strength reveals a strong dependence on the structural disorder of the sample, which is in agreement with the disorder-enhanced three-dimensional electron–electron interaction effect.
Molecular screening effects on exciton-carrier interactions in suspended carbon nanotubes
Authors: Uda T. , Tanaka S. , Kato Y. K.
Published: September 2018

Photoluminescence spectroscopy measurements are performed on suspended carbon nanotubes in a field-effect configuration, and the gate voltage dependence of photoluminescence spectra are compared for the pristine and the molecularly adsorbed states of the nanotubes. We quantify the molecular screening effect on the trion binding energies by determining the energy separation between the bright exciton and the trion emission energies for the two states. The voltage dependence shows narrower voltage regions of constant photoluminescence intensity for the adsorbed states, consistent with a reduction in the electronic bandgap due to screening effects. The charge neutrality points are found to shift after molecular adsorption, which suggests changes in the nanotube chemical potential or the contact metal work function.
The electronic structures and optical properties of B, C or N doped BaTiO3
Authors: Teng Zhuang , Jiang Jiajun , Chen Gaoyuan , Ma Chunlan , Zhang Feiwu
Published: September 2018

The electronic structures and optical properties of Boron, Carbon or Nitrogen doped BaTiO3 are calculated by the first-principles calculations. The doped atoms decrease the band gap of BaTiO3 significantly, which could increase the host material ability to absorb the visible light. The absorption spectrum calculations confirm that both Boron and Carbon-doped BaTiO3 have a favorable performance in the absorption of visible light. However, Nitrogen-doped BaTiO3 doesn’t present the improvement. BaTiO3 doped with Boron or Carbon is expected to be a new class of perovskite materials for the field of solar energy.
Graphene/hexagonal boron nitride heterostructures: Mechanical properties and fracture behavior from nanoindentation simulations
Authors: Mallick Govind , Elder Robert M.
Published: September 2018

In-plane or vertically stacked heterostructures containing multiple 2D materials are promising for emerging applications, such as flexible electronics, piezoelectric sensors, and molecular separations. However, utilizing heterostructures requires a fundamental understanding of their mechanics, which is currently lacking. Here, we use reactive molecular dynamics to simulate nanoindentation of stacked hexagonal boron nitride (h-BN) and graphene structures, 2D materials with similar structures but differing electronic properties. We calculate the Young's modulus, bending rigidity, ultimate strength, and the fracture strain of monolayers, homogeneous and heterogeneous bilayers, and alternating trilayers. Their mechanics are broadly similar, although graphene provides mild reinforcement to heterostructures. Further, we characterize the puncture created by nanoindentation, where we find that graphene allows smaller pores with a rougher fracture surface and more cleaved bonds than h-BN, which we attribute to differences in toughness. Our results demonstrate that these layered heterostructures maintain their mechanical robustness regardless of stacking order and provide insight into the influence of layer ordering in separation or passivation applications.
Free-layer-thickness-dependence of the spin galvanic effect with spin rotation symmetry
Authors: Aljuaid Wafa S. , Allen Shane R. , Davidson Angie , Fan Xin
Published: September 2018

Spin-orbit coupling near the surface of a ferromagnetic metal gives rises to spin-to-charge conversion with symmetry different from the conventional inverse spin Hall effect. We have previously observed this spin galvanic effect with spin rotation symmetry (SGE-SR) in a spin valve under a temperature gradient. Here, we show there are two processes that contribute to the SGE-SR, one of which is sensitive to the free magnetic layer thickness, while the other only depends on the interface of the free layer. Based on the free-layer-thickness-dependent study, we extrapolate the spin diffusion length of Py to be 3.9 ± 0.2 nm. We also propose that the SGE-SR can help to quantitatively study the spin Seebeck effect in metallic magnetic films.
Tailoring arbitrary polarization states of light through scattering media
Authors: Yu Panpan , Zhao Qian , Hu Xinyao , Li Yinmei , Gong Lei
Published: September 2018

Light beams with spatially variant states of polarization (SOPs) have attracted increasing interest recently because their vector nature brings unique perspectives to optics and photonics. Nevertheless, their applications are challenged when transposed to scattering media, because of the inherent depolarization effects arising from multiple scattering. Wavefront shaping techniques are expected to confront these challenges; however, shaping spatially variant SOPs in addition to amplitude and phase of light through scattering media has not been explored yet. Here, we present a general framework based on the vector transmission matrix to simultaneously tailor these properties. Further, we demonstrate its use in producing multiple focal spots and structured light beams with spatially variant SOPs behind the scattering media, which is confirmed by simulations. As a particular application, by encoding information into light's spatially distributed SOPs, we are able to directly encrypt multiplexed grayscale images into a single laser beam behind a scattering medium. Our work is expected to find potential applications such as optical imaging in deep tissues, optical encryption, and communication.
Electron-hole Superconductivity (Review)
Authors: Fil D. V. , Shevchenko S. I.
Published: September 2018

This review is devoted to the theory of electron-hole superfluidity in bilayer systems. This is a discussion of the state in which electrons and holes from adjacent layers form bound pairs, and a nondissipative transfer of charge is caused by the motion of pairs as wholes. The occurrence of the flow of bound pairs is equivalent to the flow in conducting layers of equal in modulus but oppositely directed electric currents. Therefore, such superfluidity can be examined as a unique superconductivity that is often called counterflow superconductivity. Although this phenomenon was predicted about 40 years ago, the intensive study of the problem of electron-hole superconductivity in bilayer systems continues to date. An extensive description of theoretical representations and approaches to the problem of electron-hole superconductivity is presented in this review.
The Nature of Acoustic Emission during Deformation Processes in Metallic Materials
Authors: Vinogradov A. Yu. , Merson D. L.
Published: September 2018

The theoretical foundation of the method of acoustic emission (AE) was established in the pioneering studies by V. Natsik and his colleagues, which were published in the 1960s–1980s. The source functions corresponding to elementary dislocation mechanisms of plastic deformation and fracture were calculated based on continuum dislocation dynamics. The results remain up to date. Despite the existing experimental difficulties in verifying some of the basic formulations, these works clearly demonstrated the differences between potential sources of acoustic emission in materials. Based on these fundamental premises, statistical methods for recognizing the AE mechanisms, utilizing spectral and cluster analysis of AE time series, were recently proposed. This brief communication reviews theoretical models of AE sources, as well as some key experimental findings, to provide insights into the nature of the acoustic emission peak in the early stages of plastic deformation of metals. The methods for analyzing the AE signal and recognizing the AE sources are also discussed.
Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding
Authors: Trojanová Z. , Drozd Z. , Lukáč P. , Minárik P. , Džugan J. , Halmešová K.
Published: September 2018

Fine grained magnesium alloy AZ31 sheets were submitted to the accumulative roll bonding (ARB). After ARB, the microstructure of samples was refined, and the sheets exhibited pronounced texture. The amplitude-dependent internal friction (ADIF) was measured at room temperature. Microstructure changes as the increased dislocation density, grain size refinement, twins, and texture influenced the ADIF. A significant anisotropy of the properties was observed. Experimental results are discussed on the base of physical mechanisms responsible for internal friction.
Advances in understanding the roles and benefits of nursery areas for elasmobranch populations
Authors: Heupel Michelle R. , Kanno Shiori , Martins Ana P. B. , Simpfendorfer Colin A.
Published: September 2018

Nursery areas are critical to the survival of many marine species, and it is widely accepted that elasmobranch species use nursery areas where they improve species fitness. A 2007 review proposed an approach to identify elasmobranch nursery areas to help clarify their location and use. Here we examine progress towards defining elasmobranch nurseries in the intervening ≥10 years. Many studies have used these criteria, and some have tested their effectiveness, but it is apparent that there is still much to learn. Our current understanding of elasmobranch nurseries is biased towards tropical coastal shark species with few studies of temperate, pelagic, deep-water or batoid species. Recent research has used the criteria to more accurately identify nursery areas, determine that some species may not use them and, at times, improve conservation and management. Results are also revealing that some areas considered to be nurseries do not meet the criteria. Although we have learned a great deal about the location and use of elasmobranch nurseries, there are still several questions to be answered and species to be considered. Continued application of nursery criteria and improved knowledge of nursery areas will lead to improved conservation and management systems.
Surface bypass as a means of protecting downstream-migrating fish: lack of standardised evaluation criteria complicates evaluation of efficacy
Authors: Klopries Elena-Maria , Deng Zhiqun Daniel , Lachmann Theresa U. , Schüttrumpf Holger , Trumbo Bradly A.
Published: September 2018

Surface bypasses are downstream migration structures that can help reduce hydropower-induced damage to migrating fish. However, no comprehensive design concept that facilitates good surface bypass performance for a wide range of sites and species is available. This is why fish-passage efficiencies at recently built bypass structures vary widely between 0% and up to 97%. We reviewed 50 surface bypass performance studies and existing guidelines for salmonids, eels and potamodromous species to identify crucial design criteria for surface bypasses employed in North America, Europe and Australia. Two-tailed Pearson correlation of bypass efficiency and bypass design criteria shows that bypass entrance area (r=0.3300, P=0.0036) and proportion of inflow to the bypass (r=0.3741, P=0.0032) are the most influential parameters on bypass efficiency. However, other parameters such as guiding structures (P=0.2181, ordinary Student’s t-test) and trash-rack spacing (r=–0.1483, P=0.3951, Spearman correlation), although not statistically significant, have been shown to have an effect on efficiency in some studies. The use of different performance criteria and efficiency definitions for bypass evaluation hampers direct comparison of studies and, therefore, deduction of design criteria. To enable meta-analyses and improve bypass design considerations, we suggest a list of standardised performance parameters for bypasses that should be considered in future bypass-performance studies.
Predicting hydraulic structure-induced barotrauma in Australian fish species
Authors: Pflugrath Brett D. , Boys Craig A. , Cathers Bruce
Published: September 2018

When fish pass downstream through river infrastructure, such as dams and weirs, barotrauma may occur as a result of rapid decompression. In severe cases, barotrauma may lead to mortality. Different species are likely to respond differently to these decompressions. Therefore, to predict barotrauma for a specific species, surrogate species may not be a valid approach, and it may be necessary to examine each species individually. For the present study, Australian bass and carp gudgeon were exposed to a range of rapid decompressions using hyper- and hypobaric hydro-chambers and examined for injuries and mortality. Rapid decompression data from these two fish species, in addition to previously examined Murray cod and silver perch, were evaluated to determine which injuries were highly associated with and likely to predict mortality. Dose–response logistic regression models were developed for each species to predict injury and mortality over a range of rapid decompressions. These models are valuable for estimating injury and mortality rates for fish passing though river infrastructure and can be applied to specific sites where pressure profiles have been developed. Applying these models to current and future infrastructure can provide important insight into what measures or design alterations may be necessary to reduce negative effects of infrastructure on fish populations.
Genomic responses to selection for tame/aggressive behaviors in the silver fox (
Vulpes vulpes
)
Authors: Wang Xu , Pipes Lenore , Trut Lyudmila N. , Herbeck Yury , Vladimirova Anastasiya V. , Gulevich Rimma G. , Kharlamova Anastasiya V. , Johnson Jennifer L. , Acland Gregory M. , Kukekova Anna V. , Clark Andrew G.
Published: September 2018

Significance

The behavior of domesticated animals differs dramatically from that of wild relatives, and the Russian tame fox experiment demonstrated clearly that these changes can occur in just a few generations of selection. Analysis of gene expression in the brains of tame and aggressive foxes from this experiment allows us to ask what brain pathways have been altered by this recent, strong selection. Pathways that impact the function of both serotonergic and glutaminergic neurons were clearly modulated by selection, consistent with the roles of these neurons in learning and memory. Both allele frequency and gene expression changes also implicate genes important in neural crest cell function, supporting a possible role of neural crest cells in the domestication syndrome.
Targeting intramolecular proteinase NS2B/3 cleavages for
trans
-dominant inhibition of dengue virus
Authors: Constant David A. , Mateo Roberto , Nagamine Claude M. , Kirkegaard Karla
Published: September 2018

Significance

Inhibitors of dengue virus, a mosquito-borne pathogen, are urgently needed. Virally encoded NS2B/3, a two-subunit serine proteinase, is responsible for many cleavages within the viral polyprotein. We demonstrate that two cleavage sites flanking NS3 and one that is internal are self-processing. This strict intramolecular cleavage dictates that, if uncleaved precursors can inhibit viral growth, this phenotype will be
trans
-dominant. Indeed, a mutation that abrogates one of the self-processing sites caused
trans
-dominant inhibition of wild-type virus. This site is also the most susceptible to a dengue proteinase inhibitor, providing a compelling rationale for its efficacy. We suggest that explicit targeting of specific intramolecular cleavage sites will be an effective antiviral strategy that can suppress multiple variants in an intracellular quasispecies.
Two-level masers as heat-to-work converters
Authors: Ghosh Arnab , Gelbwaser-Klimovsky David , Niedenzu Wolfgang , Lvovsky Alexander I. , Mazets Igor , Scully Marlan O. , Kurizki Gershon
Published: September 2018

Significance

We propose a paradigm of heat-powered maser. In contrast to textbook knowledge, it does not require population inversion or coherent driving and hence can operate with a two-level working medium. Therefore, it is a conceptually different type of maser and, more generally, a conceptually different quantum heat machine. Its autonomous character and “free” power source make this machine technologically enticing.