bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of entropy wave generation in a simplified model of gas turbine combustor: A theoretical investigation
Authors: Fattahi Abolfazl , Karimi Nader , Hajialigol Najmeh
Published: October 2020

Entropy noise remains as a largely unexplored mechanism of combustion generated noise. Currently, little is known about the production sources of entropy waves in flames. To address this issue, the present work puts forward a theoretical investigation of the generation of entropy waves in a one-dimensional, ducted flow. A linear theory is developed for the dynamic responses of different sources of unsteady entropy generation including thermal, hydrodynamic, pressure, and chemical irreversibility. For the first time in the literature, dynamics of chemical sources of unsteady entropy generation are investigated extensively. It is found that the mixture fraction fluctuations are responsible for the production of almost all unsteady chemical entropy and the effect of chemical potential is negligibly small. For the Strouhal numbers less than unity, fluctuations in pressure are the most significant source of the overall generation of unsteady entropy. However, at higher frequencies, mixture fraction fluctuations dominate the generation of entropy wave. The cut-off frequency for the generation of entropy wave is shown to depend not only on the thermal and hydrodynamic characteristics of the flame but also on the chemical properties of the downstream gases. It is further argued that the transfer function of entropy generation for a thin flame may feature an unrealistically high amplitude. This study shows that neglecting the chemical sources of an entropy wave can result in wrong predictions of the combustor acoustics and impede the suppression of combustion instabilities and noise.
Isotropic plasma atomic layer etching of Al2O3 using a fluorine containing plasma and Al(CH3)3
Authors: Chittock Nicholas J. , Vos Martijn F. J. , Faraz Tahsin , Kessels Wilhelmus M. M. (Erwin) , Knoops Harm C. M. , Mackus Adriaan J. M.
Published: October 2020

Nanofabrication techniques with atomic level precision are needed for advancement to smaller technology nodes in the semiconductor industry. Thermal atomic layer etching (ALE) is currently being developed to isotropically etch material for future applications. In this Letter, an alternative plasma-based ALE process for isotropic etching of Al2O3 is introduced involving SF6 plasma and trimethylaluminium [TMA, Al(CH3)3] pulses, providing higher etch rates and lower processing temperatures than conventional thermal ALE. This process illustrates that a fluorine-containing plasma can serve as a viable reactant for ALE and that plasmas—besides their conventional use in anisotropic ALE—can be employed for isotropic ALE. In situ spectroscopic ellipsometry measurements confirmed saturation of both SF6 plasma and TMA half-cycles, which results in an etch per cycle (EPC) of 3.1 ± 0.1 Å at 260 °C. The isotropic nature of the plasma ALE process was demonstrated by transmission electron microscopy analysis of Al2O3-coated 3D trench structures after performing ALE cycles. A mechanism of fluorination by F radicals and ligand exchange reactions involving TMA is proposed for this plasma ALE process based on observations from infrared spectroscopy, which are supported by reactant synergy analysis. This work establishes the benefits that a plasma can deliver for isotropic ALE.
Morphological and non-equilibrium analysis of coupled Rayleigh–Taylor–Kelvin–Helmholtz instability
Authors: Chen Feng , Xu Aiguo , Zhang Yudong , Zeng Qingkai
Published: October 2020

In this paper, the coupled Rayleigh–Taylor–Kelvin–Helmholtz instability (RTI, KHI, and RTKHI, respectively) system is investigated using a multiple-relaxation-time discrete Boltzmann model. Both the morphological boundary length and thermodynamic non-equilibrium (TNE) strength are introduced to probe the complex configurations and kinetic processes. In the simulations, RTI always plays a major role in the later stage, while the main mechanism in the early stage depends on the comparison of buoyancy and shear strength. It is found that both the total boundary length L of the condensed temperature field and the mean heat flux strength D3,1 can be used to measure the ratio of buoyancy to shear strength and to quantitatively judge the main mechanism in the early stage of the RTKHI system. Specifically, when KHI (RTI) dominates, LKHI > LRTI LKHI < LRTI, D3,1KHI>D3,1RTI D3,1KHI<D3,1RTI; when KHI and RTI are balanced, LKHI = LRTI, D3,1KHI=D3,1RTI, where the superscript “KHI (RTI)” indicates the type of hydrodynamic instability. It is interesting to find that (i) for the critical cases where KHI and RTI are balanced, both the critical shear velocity uC and Reynolds number Re show a linear relationship with the gravity/acceleration g; (ii) the two quantities, L and D3,1, always show a high correlation, especially in the early stage where it is roughly 0.999, which means that L and D3,1 follow approximately a linear relationship. The heat conduction has a significant influence on the linear relationship. The second set of findings are as follows: For the case where the KHI dominates at earlier time and the RTI dominates at later time, the evolution process can be roughly divided into two stages. Before the transition point of the two stages, LRTKHI initially increases exponentially and then increases linearly. Hence, the ending point of linear increasing LRTKHI can work as a geometric criterion for discriminating the two stages. The TNE quantity, heat flux strength D3,1RTKHI, shows similar behavior. Therefore, the ending point of linear increasing D3,1RTKHI can work as a physical criterion for discriminating the two stages.
A stacked electromagnetic energy harvester with frequency up-conversion for swing motion
Authors: Zhou Ning , Zhang Ying , Bowen Chris R. , Cao Junyi
Published: October 2020

This paper undertakes theoretical and experimental investigations of a stacked magnetic modulation harvester with frequency up-conversion for energy harvesting performance enhancement from swing motion. The harvester includes stacked rings including a coil ring, an energy harvesting magnetic ring, a ferromagnetic ring, and a frequency up-conversion magnetic ring with a proof mass, which are axially designed in the same rotating axis to increase the rotation speed of the magnetic field due to swing excitations from human motion. The magnetic flux density produced by frequency up-conversion mechanisms is calculated to derive the governing theoretical model for harvester performance prediction. The rotation speeds and inductive voltages of theoretical results show good agreement with the experimental results in a range of rotational speeds. A range of motion speed tests on a treadmill are performed to demonstrate the advantage of the stacked electromagnetic harvesters on harvested energy from human motion. The average output power improves from approximately 1.5 mW to 11.8 mW when motion speed increases from 4 km/h to 8 km/h. The maximum power density under human motion is 61.9 μW·g−1, with a total weight of 190.7 g.
High internal quantum efficiency and optically pumped stimulated emission in AlGaN-based UV-C multiple quantum wells
Authors: Murotani Hideaki , Tanabe Ryohei , Hisanaga Keisuke , Hamada Akira , Beppu Kanta , Maeda Noritoshi , Khan M. Ajmal , Jo Masafumi , Hirayama Hideki , Yamada Yoichi
Published: October 2020

Internal quantum efficiency (IQE) and stimulated emission properties of AlGaN-based UV-C multiple quantum wells grown on c-plane sapphire substrates were assessed using photoluminescence spectroscopy. The IQEs were estimated to be 53% at room temperature and 16% at 750 K. Furthermore, optically pumped stimulated emission was clearly observed at room temperature. The threshold excitation power densities were estimated to be 13 kW/cm2 at 10 K and 69 kW/cm2 at room temperature. The temperature dependence of the threshold excitation power density suggested that the mechanism of optical gain formation changed from excitonic transition to degenerated electron–hole plasma between 200 and 250 K.
Reducing chances of COVID-19 infection by a cough cloud in a closed space
Authors: Agrawal Amit , Bhardwaj Rajneesh
Published: October 2020

The cough of a COVID-19 infected subject contaminates a large volume of surrounding air with coronavirus due to the entrainment of surrounding air in the jet-like flow created by the cough. In the present work, we estimate this volume of the air, which may help us to design ventilation of closed spaces and, consequently, reduce the spread of the disease. Recent experiments [P. P. Simha and P. S. M. Rao, “Universal trends in human cough airflows at large distances,” Phys. Fluids 32, 081905 (2020)] have shown that the velocity in a cough-cloud decays exponentially with distance. We analyze the data further to estimate the volume of the cough-cloud in the presence and absence of a face mask. Assuming a self-similar nature of the cough-cloud, we find that the volume entrained in the cloud varies as V=0.666 c2dc3, where c is the spread rate and dc is the final distance traveled by the cough-cloud. The volume of the cough-cloud without a mask is about 7 and 23 times larger than in the presence of a surgical mask and an N95 mask, respectively. We also find that the cough-cloud is present for 5 s–8 s, after which the cloud starts dissipating, irrespective of the presence or absence of a mask. Our analysis suggests that the cough-cloud finally attains the room temperature, while remaining slightly more moist than the surrounding. These findings are expected to have implications in understanding the spread of coronavirus, which is reportedly airborne.
Pasteur, rabbits and Cumberland disease
Authors: Blackall Pat J
Published: October 2020

This article outlines the generally well known story of the attempt by Louis Pasteur to win the significant reward offered by the colonial governments of what would become Australia for biological control of the rabbit plague then infesting the continent. While the Pasteur bid, led by his nephew Adrien Loir, was not awarded the prize, there were significant flow-on benefits for agriculture in the colonies. The major benefit was the production of an effective vaccine for what the colonials called Cumberland disease (now known as anthrax). Loir also developed and/or provided vaccines for bovine pleuropneumonia and blackleg of cattle. Benefits also flowed back to France as the funds from the Cumberland disease vaccine sales to the colonial farmers helped support the newly established Pasteur Institute. The on-going controversy in the colonies and in the early days of the new nation of Australia over the use of a biological control agent (the organism we now know as Pasteurella multocida) is covered. This includes how a proposed biological control program using P. multocida became part of a class war. Finally, the irony that history continues to repeat itself – Hollywood’s recently most famous dogs (Pistol and Boo) were simply repeating the story line of Star and Chouette - is covered.
Gonorrhoea: past, present and future
Authors: Semchenko Evgeny A , Chen Xiaofan , Thng Caroline , O’Sullivan Maree , Seib Kate L
Published: October 2020

The sexually transmitted infection (STI) gonorrhoea is an ancient human disease caused by the Gram-negative bacterial pathogen Neisseria gonorrhoeae. Despite decades of research focused on preventing, diagnosing, and treating gonorrhoea, it remains a major global health concern due to its high prevalence, high rates of asymptomatic cases, the severe sequelae that can result from untreated infections, and the increasing difficulty in treating infections caused by multi-drug resistant strains of N. gonorrhoeae. It is estimated that there are more than 87 million cases of gonorrhoea worldwide each year, and the WHO, CDC and Australian National Antimicrobial Resistance (AMR) Strategy have prioritised N. gonorrhoeae as an urgent public health threat for which new therapeutics and a vaccine are needed.
A brief history of AAHL
Authors: Selleck Paul
Published: October 2020

The CSIRO Australian Animal Health Laboratory (AAHL) was officially opened on 1 April 1985. After that day the laboratory switched to secure mode and has operated as such ever since. AAHL was constructed to be the primary national diagnostic facility for exotic animal diseases but has expanded its role to become a national and international reference laboratory for many diseases. AAHL has supported disease control within the region by providing training, reagents and proficiency testing, both within Australia and internationally. AAHL’s role has evolved even further to include a focus on one-health which resulted in AAHL being renamed the Australian Centre for Disease Preparedness (ACDP) in March 2020.
Global diversity of microbial communities in marine sediment
Authors: Hoshino Tatsuhiko , Doi Hideyuki , Uramoto Go-Ichiro , Wörmer Lars , Adhikari Rishi R. , Xiao Nan , Morono Yuki , D’Hondt Steven , Hinrichs Kai-Uwe , Inagaki Fumio
Published: October 2020

Significance

Marine sediment covers 70% of Earth’s surface and harbors as much biomass as seawater. However, the global taxonomic diversity of marine sedimentary communities, and the spatial distribution of that diversity remain unclear. We investigated microbial composition from 40 globally distributed sampling locations, spanning sediment depths of 0.1 to 678 m. Statistical analysis reveals that oxygen presence or absence and organic carbon concentration are key environmental factors for defining taxonomic composition and diversity of marine sedimentary communities. Global marine sedimentary taxonomic richness predicted by species–area relationship models is 7.85 × 103to 6.10 × 105for Archaea and 3.28 × 104to 2.46 × 106for Bacteria as amplicon sequence variants, which is comparable to the richness in seawater and that in topsoil.
Revealing mechanisms of mating plug function under sexual selection
Authors: Stockley Paula , Franco Catarina , Claydon Amy J. , Davidson Amanda , Hammond Dean E. , Brownridge Philip J. , Hurst Jane L. , Beynon Robert J.
Published: October 2020

Significance

Promiscuous mating by females leads to competition between males for fertilization success. When fertilization is internal, this means that rival males’ sperm must compete within the female reproductive tract to reach the eggs. Males of diverse species deposit a mating plug during copulation, which is hypothesized to assist in the race for fertilization following multiple mating. Here, we tested this by using stable isotope labeling to discriminate the ejaculates of competing male voles in direct competition. This revealed that the mating plug simultaneously inhibits the sperm of rival males while promoting transport of a male’s own sperm, both of which are beneficial in the competition for fertilizations.
Changing nutrient cycling in Lake Baikal, the world’s oldest lake
Authors: Swann George E. A. , Panizzo Virginia N. , Piccolroaz Sebastiano , Pashley Vanessa , Horstwood Matthew S. A. , Roberts Sarah , Vologina Elena , Piotrowska Natalia , Sturm Michael , Zhdanov Andre , Granin Nikolay , Norman Charlotte , McGowan Suzanne , Mackay Anson W.
Published: October 2020

Significance

Lake Baikal (Siberia) is the world’s oldest and deepest lake and a UNESCO World Heritage Site. Containing an exceptionally high level of biodiversity and endemism, in addition to a fifth of global freshwater not stored in ice sheets, the lake has been cited by UNESCO as the “most outstanding example of a freshwater ecosystem.” Using geochemical and climate data, we demonstrate that rates of nutrient supply to the lake’s photic zone have risen to unprecedented levels in the last 2,000 y through the 20th and 21st centuries. Linked to increases in wind speed enhancing deep ventilation, we show that these changes are capable of altering lake primary production and community dynamics, including the balance between endemic and cosmopolitan species.
Frequency doubling in a pendulum
Authors: Reinhold S , Ziese M
Published: October 2020

A smartphone is used as a pendulum bob to simultaneously measure the angular velocity and the acceleration of a pendulum. The data show a frequency doubling in the radial acceleration component compared with the angular velocity and the azimuthal acceleration component. This is mainly due to the centrifugal force and is an illustration of frequency doubling in a simple mechanical system. This experiment might be used in first year university physics courses to teach frequency analysis and frequency doubling in a home laboratory.
Adaptive spectral decompositions for inverse medium problems
Authors: Baffet Daniel H , Grote Marcus J , Tang Jet Hoe
Published: October 2020

Inverse medium problems involve the reconstruction of a spatially varying unknown medium from available observations by exploring a restricted search space of possible solutions. Standard grid-based representations are very general but all too often computationally prohibitive due to the high dimension of the search space. Adaptive spectral decompositions instead expand the unknown medium in a basis of eigenfunctions of a judicious elliptic operator, which depends itself on the medium. Here the AS decomposition is combined with a standard inexact Newton-type method for the solution of time-harmonic scattering problems governed by the Helmholtz equation. By repeatedly adapting both the eigenfunction basis and its dimension, the resulting adaptive spectral inversion (ASI) method substantially reduces the dimension of the search space during the nonlinear optimization. Rigorous estimates of the AS decomposition are proved for a general piecewise constant medium. Numerical results illustrate the accuracy and efficiency of the ASI method for time-harmonic inverse scattering problems, including a salt dome model from geophysics.
Fabrication and characterization of micro electromagnetic linear actuators
Authors: Zhi Chao , Qu Mingshan , Wang Yue , Li Yanjun , Xie Jin , Feng Wei , Tang Bin
Published: October 2020

This paper on the reports design, fabrication and position monitoring of a micro electromagnetic linear actuator. The actuator consists of stator, slider, guide, sensors and affiliated jigs. Actuation is achieved through ampere force between two phase micro-coils (copper) on the stator and permanent magnets (thick NdFeB film) on the slider. During the slider’s movement in the guide slot, tunnelling magneto-resistance (TMR) sensors are utilized to sense the magnetic field to realize position monitoring. TMR is chosen because it owns advantages of small size, large sensitivity and easy integration with micro devices. Purpose of this research is to report the micro fabrication of thick magnet films and testify the possibility of using TMR as position monitoring sensors. Actuators are fabricated by micro-electro-mechanical system process (stator and guide) and precise machining (slider and jigs). Surface magnetic field generated by the slider, driving characteristics of the actuator as well as the position monitoring capabilities of TMR elements are simulated and experimented, respectively. The slider attains 60 mm s−1 speed by sinusoidal input signal at 300 Hz frequency and 0.2 A current magnitude. Actuation bandwidth is between 300 Hz and 500 Hz at open loop condition. The maximum position monitoring error in present work is 2.2% with 101 μm value for 4.5 mm stroke.
Numerical simulation of an atmospheric pressure plasma jet with coaxial shielding gas
Authors: Lin Peng , Zhang Jiao , Nguyen Tam , Donnelly Vincent M , Economou Demetre J
Published: October 2020

A two-dimensional (r, z) numerical simulation of the discharge characteristics of an atmospheric pressure plasma jet (APPJ), with coaxial shielding gas, was performed. The helium working gas flowed in a central capillary tube, engulfing a needle electrode powered by 13.7 MHz radio frequency sinusoidal voltage. The N2 shielding gas flowed in the annular space of a coaxial tube. These gases emerged, in laminar flow, in a 78%N2-21%O2-1%Ar dry air ambient. The characteristics of the APPJ with shielding gas were compared to those of the APPJ without shielding gas. The nitrogen shielding gas hindered the diffusion of oxygen and argon from the ambient air into the helium jet. With the shielding gas present, more nitrogen penetrated into the helium core, causing a shorter plasma ‘plume’. The flow rates of the working and shielding gas, critically affected the gas temperature, and in turn the discharge characteristics. For a He flow of 2 standard liters per minute (slm), switching on the nitrogen shielding gas flow (at 4.5 slm) reduced the on-axis O2 and Ar mole fractions from

3.9
×

10

−
4

to

6.8
×

10

−
5

and from

1.9
×

10

−
5

to

3.3
×

10

−
6

, respectively, at an axial distance of 3 mm downstream of the nozzle. The radial profiles of the mole fractions of the ambient gases were monotonically and strongly decreasing towards the system axis, for short axial distances from the nozzle (∼1 mm), but became progressively flatter at longer distances from the nozzle (3 mm and 5 mm). Simulation predictions captured the salient features of experimental data of ambient species mole fractions in the plasma jet, and the 706 nm optical emission intensity profiles of the He 33S excited state.
Nonlinear electrical transport in Fe3O4-decorated graphene nanoplatelets
Authors: Jaiswar Rajkumar , Mederos-Henry Francisco , Hermans Sophie , Raskin Jean-Pierre , Huynen Isabelle
Published: October 2020

This paper investigates the nonlinear properties of graphene nanoplatelets (GNPs), decorated with Fe3O4 magnetic nanoparticles (MaNPs). Nanocomposite MaNP/GNP samples were prepared by a solvothermal method with three different MaNP loading concentrations of 17 wt%, 28 wt% and 40 wt%, and deposited on a metallic interdigitated electrode (IDE). Three different models are proposed to assess measurements, with the objective to explain the electronic transport in the nanocomposites. At first, a thermionic transport model is proposed to fit the DC nonlinear current–voltage characteristics for the three concentrations. It is observed that the barrier height decreases to 0.312, 0.310 and 0.281 eV, following a decrease in the MaNP loading. A second model, dynamic random resistor network (DRRN) further shows that the impedance of IDE increases following the decreasing MaNP loading rate, 40 wt% > 28 wt% > 17 wt%, and that charge transport takes place through a resistor–capacitor (RC) rectifying percolating network. Finally, impedance spectroscopy performed at different applied DC biases shows that a constant phase element (CPE) is necessary in the equivalent circuit in order to fit the Cole–Cole plot AC response of the IDE, instead of the classical parallel RC circuit. The presence of the CPE confirms the hypothesis of random phenomena occurring in the transport according to the DRRN model. CPE is associated with a spatial distribution of different RC circuits, due to disorderness that arises from inhomogeneities in the Fe3O4–GNP samples.
Magnetism and stability of all primitive stacking patterns in bilayer chromium trihalides
Authors: Gibertini Marco
Published: October 2020

Chromium trihalides, CrX3 (with X = Cl, Br, I), are a family of layered magnetic materials that can be easily exfoliated to provide ferromagnetic monolayers. When two layers are stacked together to form a bilayer the interlayer exchange coupling can be either ferromagnetic or antiferromagnetic depending on the stacking sequence. Here we combine crystallographic arguments based on the close-packing condition with first-principles simulations to enumerate all possible stacking patterns in CrX3 bilayers that preserve the spatial periodicity of each layer. We recover all configurations observed in bulk crystals and disclose stacking sequences with no bulk counterpart where the two layers have opposite chirality. Stacking sequences are ranked according to their relative stability and a preferential interlayer magnetic ordering is assigned to each of them. Simulations provide a consistent picture to frame all current experimental observations on bulk and exfoliated CrX3 crystals, with interesting implications for future measurements, including synthetic bilayers with non-standard stacking patterns.
Magnetic, magnetoresistive and low-frequency noise properties of tunnel magnetoresistance sensor devices with amorphous CoFeBTa soft magnetic layers
Authors: Rasly Mahmoud , Nakatani Tomoya , Li Jiangnan , Sepehri-Amin Hossein , Sukegawa Hiroaki , Sakuraba Yuya
Published: October 2020

Magnetic field sensors using the tunnel magnetoresistance (TMR) effect require linear resistance–magnetic field (R–H) response curves with small hysteresis, for which the soft magnetic property of the free layer (FL) is critical. In this work, we investigated amorphous CoFeBTa (CFBT) as a soft magnetic layer of the FL of CoFeB/MgO/CoFeB-based magnetic tunnel junctions in view of magnetic, TMR, and low-frequency noise properties. A two-step annealing process enabled an orthogonal magnetization configuration between the FL and the reference layer, by which linear R–H curves with small hysteresis were realized. The change in the shape of the R–H curve depending on annealing temperature is explained by the Stoner–Wohlfarth model. The highest TMR ratio of ∼160% and sensitivity of ∼70%/mT were obtained with a CFBT (20 nm)/Ta (0.3 nm)/CoFeB (3 nm) FL. The noise of the TMR devices are dominated by 1/f noise below ∼10 kHz in frequency, which limits the detectivity (D) of the magnetic field of the sensor. The sensor devices patterned to 50 µm diameter circular shapes showed a minimum D of ∼2 nT/

Hz

at 10 Hz, which is superior to the previously reported values for the TMR sensors with NiFe soft magnetic layers.
3D growth of silicon nanowires under pure hydrogen plasma at low temperature (250 °C)
Authors: Yang Kai , Coulon Nathalie , Salaun Anne Claire , Pichon Laurent
Published: October 2020

The synthesis of silicon nanowires (SiNWs) is carried out at 250 °C under pure hydrogen plasma from monocrsytalline silicon substrates or amorphous silicon thin film, using indium as a catalyst. Studies have been carried out in function of the duration of the hydrogen plasma. The results showed a growth of smooth surface nanowire arrays (diameter 100 nm, length 500 nm) from an indium thickness of 20 nm and a hydrogen plasma duration of 30 min. The growth of nanowires for longer hydrogen plasma durations has led to SiNWs with larger diameters and rougher surfaces, revealing the onset of secondary nanowire growth on these surfaces, probably due to the presence of indium residues. The results present a new procedure for the 3D solid liquid solid growth mode of SiNWs.
Complex temperature dependence of coherent and incoherent lattice thermal transport in superlattices
Authors: Chakraborty Pranay , Chiu Isaac Armstrong , Ma Tengfei , Wang Yan
Published: October 2020

Currently, it is still unclear how and to what extent a change in temperature impacts the relative contributions of coherent and incoherent phonons to thermal transport in superlattices. Some seemingly conflicting computational and experimental observations of the temperature dependence of lattice thermal conductivity make the coherent–incoherent thermal transport behaviors in superlattices even more elusive. In this work, we demonstrate that incoherent phonon contribution to thermal transport in superlattices increases as the temperature increases due to elevated inelastic interfacial transmission. On the other hand, the coherent phonon contribution decreases at higher temperatures due to elevated anharmonic scattering. The competition between these two conflicting mechanisms can lead to different trends of lattice thermal conductivity as temperature increases, i.e. increasing, decreasing, or non-monotonic. Finally, we demonstrate that the neural network-based machine learning model can well capture the coherent–incoherent transition of lattice thermal transport in the superlattice, which can greatly aid the understanding and optimization of thermal transport properties of superlattices.
Synchronization in adaptive Kuramoto oscillators for power grids with dynamic voltages
Authors: Li Zhuchun , Zhao Xiaoxue
Published: October 2020

In this paper we are concerned with a coupled system of Kuramoto oscillators for power grids with dynamic voltages. Among various models describing the dynamics of synchronous generators, analytic results are available mainly for the second-order model with constant voltages which describes only the dynamics of rotor angles. It is known that two of the most important forms for power system stability are rotor angle stability and voltage stability. Schmietendorf et al (2014 Eur. Phys. J.
223 2577–2592) derived a model of adaptive Kuramoto oscillators for the power grids with dynamic voltages and carried out some numerical studies. In this model, the transient dynamics of voltages is incorporated and the voltage dynamics could be considered together with rotor angle dynamics. In this article, we will consider this model and derive some analytic results for the synchronization of phase angles and stabilization of voltages. We will find a region of attraction for a class of steady states which is explicitly expressed in the parameters of system.
Thresholds for one-parameter families of affine iterated function systems*
Authors: Vince Andrew
Published: October 2020

This paper examines thresholds for certain properties of the attractor of a general one-parameter affine family of iterated functions systems. As the parameter increases, the iterated function system becomes less contractive, and the attractor evolves. Thresholds are studied for the following properties: the existence of an attractor, the connectivity of the attractor, and the existence of non-empty interior of the attractor. Also discussed are transition phenomena between existence and non-existence of an attractor.
Floer homology in the cotangent bundle of a closed Finsler manifold and noncontractible periodic orbits
Authors: Gong Wenmin , Xue Jinxin
Published: October 2020

We show that the existence of noncontractible periodic orbits for compactly supported time-dependent Hamiltonian on the disk cotangent bundle of a Finsler manifold provided that the Hamiltonian is sufficiently large over the zero section. We generalize the Biran–Polterovich–Salamon capacities and earlier constructions of Weber (2006 Duke Math. J.
133 527–568) and other authors Biran et al (2003 Duke Math. J.
119 65–118) to the Finsler setting. We then obtain a number of applications including: (1) generalizing the main theorem of Xue (2017 J. Symplectic Geom.
15 905–936) to the Lie group setting, (2) preservation of minimal Finsler length of closed geodesics in any given free homotopy class by symplectomorphisms, (3) existence of periodic orbits for Hamiltonian systems separating two Lagrangian submanifolds, (4) existence of periodic orbits for Hamiltonians on noncompact domains, (5) existence of periodic orbits for Lorentzian Hamiltonian in higher dimensional case, (6) partial solution to a conjecture of Kawasaki (2016 Heavy subsets and non-contractible trajectories (arXiv:1606.01964)), (7) results on squeezing/nonsqueezing theorem on torus cotangent bundles, etc.
Detection of subjects with ischemic heart disease by using machine learning technique based on heart rate total variability parameters
Authors: Accardo Agostino , Silveri Giulia , Merlo Marco , Restivo Luca , Ajčević Miloš , Sinagra Gianfranco
Published: October 2020

Objective: Ischemic heart disease (IHD), in its chronic stable form, is a subtle pathology due to its silent behavior before developing in unstable angina, myocardial infarction or sudden cardiac death. The clinical assessment is based on typical symptoms and finally confirmed, invasively, by coronary angiography. Recently, heart rate variability (HRV) analysis as well as some machine learning algorithms like artificial neural networks (ANNs) were used to identify cardiovascular arrhythmias and, only in few cases, to classify IHD segments in a limited number of subjects. The goal of this study was the identification of the ANN structure and the HRV parameters producing the best performance to identify IHD patients in a non-invasive way, validating the results on a large sample of subjects. Moreover, we examined the influence of a clinical non-invasive parameter, the left ventricular ejection fraction (LVEF), on the classification performance. Approach: To this aim, we extracted several linear and non-linear parameters from 24 h RR signal, considering both normal and ectopic beats (heart rate total variability), of 251 normal and 245 IHD subjects, matched by age and gender. ANNs using several different combinations of these parameters together with age and gender were tested. For each ANN, we varied the number of hidden neurons from 2 to 7 and simulated 100 times, changing randomly the training and test dataset. Main results: The HRTV parameters showed significant greater variability in IHD than in normal subjects. The ANN applied to mean RR, LF, LF/HF, beta exponent, SD2 together with age and gender reached a maximum accuracy of 71.8% and, by adding as input LVEF, an accuracy of 79.8%. Significance: The study provides a deep insight into how a combination of some HRTV parameters and LVEF could be exploited to reliably detect the presence of subjects affected by IHD.
Detection of coronary artery disease using multi-modal feature fusion and hybrid feature selection
Authors: Zhang Huan , Wang Xinpei , Liu Changchun , Liu Yuanyuan , Li Peng , Yao Lianke , Li Han , Wang Jikuo , Jiao Yu
Published: October 2020

Objective: Coronary artery disease (CAD) is a common fatal disease. At present, an accurate method to screen CAD is urgently needed. This study aims to provide optimal detection models for suspected CAD detection according to the differences in medical conditions, so as to assist physicians to make accurate judgments on suspected CAD patients. Approach: Electrocardiogram (ECG) and phonocardiogram (PCG) signals of 32 CAD patients and 30 patients with chest pain and normal coronary angiograms (CPNCA) were simultaneously collected for this paper. For each subject, the ECG and PCG multi-domain features were extracted, and the results of Holter monitoring, echocardiography (ECHO), and biomarker levels (BIO) were obtained to construct a multi-modal feature set. Then, a hybrid feature selection (HFS) method was developed using mutual information, recursive feature elimination, random forest, and weight of support vector machine to obtain the optimal feature subset. A support vector machine with nested cross-validation was used for classification. Main results: Results showed that the Holter model achieved the best performance as a single-modal feature model with an accuracy of 82.67%. In terms of multi-modal feature models, PCG-Holter, PCG-Holter-ECHO, PCG-Holter-ECHO-BIO, and ECG-PCG-Holter-ECHO-BIO were the optimal bimodal, three-modal, four-modal, and five-modal models, with accuracies of 90.38%, 91.92%, 95.25%, and 96.67%, respectively. Among them, the ECG-PCG-Holter-ECHO-BIO model, which was constructed by combining ECG and PCG signals features with Holter, ECHO, and BIO examination results, achieved the best classification results with an average accuracy, sensitivity, specificity, and F1-measure of 96.67%, 96.67%, 96.67%, and 96.64%, respectively. Significance: The study indicated that multi-modal feature fusion and HFS can obtain more effective information for CAD detection and provide a reference for physicians to diagnose CAD patients.
Donor-acceptor nature of orange photoluminescence in AlN
Authors: Aleksandrov Ivan A , Malin Timur V , Milakhin Denis S , Ber Boris Ya , Kazantsev Dmitrii Yu , Zhuravlev Konstantin S
Published: October 2020

Recombination dynamics, photoluminescence and photoluminescence excitation spectra have been investigated for 1.9 eV photoluminescence band in AlN in the temperature range of 5–650 K. The recombination dynamics for the 1.9 eV photoluminescence band has been described by a model of donor-acceptor recombination with taking into account a broadening due to electron coupling with local lattice vibrations of a deep level defect. The experimental results have been compared with density functional theory calculations of luminescence peak energies and line shapes of band to defect and donor-acceptor transitions, and possible origin of the orange photoluminescence band in AlN has been discussed.
Adaptive global weight window generator based on particles density uniformity for Monte Carlo particles transport simulation
Authors: He Peng , Song Jing , Sun Guangyao , Zhang Shu , Hao Lijuan , Wu Bin , Hu Liqin , Wu Yican , Team FDS
Published: October 2020

Variance reduction techniques are necessary for the Monte Carlo (MC) calculations in which obtaining a detailed flux distribution for a large and complex model is required. A new method for generating mesh weight window (WW) parameters is presented, named global weight window generator (GWWG). In the method, MC calculation is performed to generate the importance of each mesh voxel in the user-set region, and then the corresponding WW parameters are obtained. The importance is related to whether the simulated particles can be uniformly transported to each mesh voxel, which is called particles density uniformity. The GWWG method does not rely on user’s design experience and can significantly improve the calculation efficiency. The tests for this method have been conducted on ITER reference neutronics models. In the calculation of ITER C-Lite model, the FoM was improved comparing to the analog FoM by the factor of 637.4.
Generation of rotating multi-vortex laser beams
Authors: Krasnoshchekov Ye A , Yaparov V V , Taranenko V B
Published: October 2020

We study transverse dynamics of the optical field, generated in a single-frequency laser of moderate Fresnel number. The existence of steadily rotating vortex clusters generated spontaneously in laser with degenerate in frequency cavity is demonstrated numerically and experimentally in laser-like two-wave-mixing photorefractive oscillator with plane-mirror cavity and controlled aperture. The observed rotational dynamics of two-, three- and four-vortex clusters is explained within the framework of the general nonlinear pattern forming model.
Quality of Anatomic Staging of Breast Carcinoma in Hospitals in the United States, With Focus on Measurement of Tumor Dimension
Authors: Wu Dolly Y , Spangler Ann E , de Hoyos Alberto , Vo Dat T , Seiler Stephen J
Published: October 2020

Objectives

We investigated the accuracy of clinical breast carcinoma anatomic staging and the greatest tumor dimension measurements.

Methods

We compared clinical stage and greatest dimension values with the pathologic reference standard values using 57,747 cases from the 2016 US National Cancer Institute Surveillance, Epidemiology, and End Results program who were treated by surgical resection without prior neoadjuvant therapy.

Results

Agreement for clinical vs pathologic anatomic TNM group stage, overall, is 74.3% ± 0.4%. Lymph node N staging overall agrees very well (85.1% ± 0.4%). Based on tumor dimension and location, T staging has an agreement of only 64.2% ± 0.4%, worsening to 55% without carcinoma in situ (Tis) cases. In approximately 25% of cases, pathologic T stage is higher than clinical T stage. The mean difference in the greatest dimension is 1.36 ± 9.59 mm with pathologic values being generally larger than clinical values; pathologic and clinical measurements correlate well. T-stage disagreement is associated with histology, tumor grade, tumor size, N stage, patient age, periodic biases in tumor size measurements, and overuse of family T-stage categories. Pathologic measurement biases include rounding and specimen-slicing intervals.

Conclusions

Clinical and pathologic T-staging values agree only moderately. Pathologists face challenges in increasing the precision of gross tumor measurements, with the goal of improving the accuracy of clinical T staging and measurement.
Temporal Dynamics and Neuronal Specificity of Grin3a Expression in the Mouse Forebrain
Authors: Murillo Alvaro , Navarro Ana I , Puelles Eduardo , Zhang Yajun , Petros Timothy J , Pérez-Otaño Isabel
Published: October 2020

GluN3A subunits endow N-Methyl-D-Aspartate receptors (NMDARs) with unique biophysical, trafficking, and signaling properties. GluN3A-NMDARs are typically expressed during postnatal development, when they are thought to gate the refinement of neural circuits by inhibiting synapse maturation, and stabilization. Recent work suggests that GluN3A also operates in adult brains to control a variety of behaviors, yet a full spatiotemporal characterization of GluN3A expression is lacking. Here, we conducted a systematic analysis of Grin3a (gene encoding mouse GluN3A) mRNA expression in the mouse brain by combining high-sensitivity colorimetric and fluorescence in situ hybridization with labeling for neuronal subtypes. We find that, while Grin3a mRNA expression peaks postnatally, significant levels are retained into adulthood in specific brain regions such as the amygdala, medial habenula, association cortices, and high-order thalamic nuclei. The time-course of emergence and down-regulation of Grin3a expression varies across brain region, cortical layer of residence, and sensory modality, in a pattern that correlates with previously reported hierarchical gradients of brain maturation and functional specialization. Grin3a is expressed in both excitatory and inhibitory neurons, with strong mRNA levels being a distinguishing feature of somatostatin interneurons. Our study provides a comprehensive map of Grin3a distribution across the murine lifespan and paves the way for dissecting the diverse functions of GluN3A in health and disease.
Biomarker Research and Development for Coronavirus Disease 2019 (COVID-19): European Medical Research Infrastructures Call for Global Coordination
Authors: Oldoni Emanuela , van Gool Alain , García Bermejo Laura , Scherer Andreas , Mayrhofer Michaela Th , Florindi Francesco , Demotes Jacques , Kubiak Christine , Fauvel Anne-Charlotte , Bietrix Florence , Ussi Anton , Andreu Antonio L
Published: October 2020

An effective response to the coronavirus disease 2019 (COVID-19) pandemic requires a better understanding of the biology of the infection and the identification of validated biomarker profiles that would increase the availability, accuracy, and speed of COVID-19 testing. Here, we describe the strategic objectives and action lines of the European Alliance of Medical Research Infrastructures (AMRI), established to improve the research process and tackle challenges related to diagnostic tests and biomarker development. Recommendations include: the creation of a European taskforce for validation of novel diagnostic products, the definition and promotion of criteria for COVID-19 samples biobanking, the identification and validation of biomarkers as clinical endpoints for clinical trials, and the definition of immune biomarker signatures at different stages of the disease. An effective management of the COVID-19 pandemic is possible only if there is a high level of knowledge and coordination between the public and private sectors within a robust quality framework.
Specific Redistribution of Severe Acute Respiratory Syndrome Coronavirus 2 Variants in the Respiratory System and Intestinal Tract
Authors: Du Pengcheng , Song Chuan , Li Rui , Song Yangzi , Li Jiarui , Ding Nan , Zhang Ju , Song Rui , Han Junyan , Gao Guiju , Yue Jinglin , Duan Ang , Huang Yanyi , An Jing , Wang Jianbin , Zhang Fujie , Chen Chen , Zeng Hui
Published: October 2020

Intrahost analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomic sequences identified 2 viral haplotypes comprised of 3 genetically linked mutations from the respiratory and intestinal tracts of a patient with coronavirus disease 2019. Spatiotemporal data suggest that this patient initially had dual infection of 2 SARS-CoV-2 variants, which subsequently redistributed into the 2 systems.
Verification of Harmonization of Serum Total and Free Prostate-Specific Antigen (PSA) Measurements and Implications for Medical Decisions
Authors: Ferraro Simona , Bussetti Marco , Rizzardi Sara , Braga Federica , Panteghini Mauro
Published: October 2020

Background

Previous studies have shown that the harmonization of prostate-specific antigen (PSA) assays remained limited even after the introduction of WHO International Standards. This information needs updating for current measuring systems (MS) and reevaluation according to established analytical performance specifications (APS) and the characteristics of antibodies used.

Methods

Total (tPSA) and free (fPSA) PSA were measured in 135 and 137 native serum samples, respectively, by Abbott Alinity i, Beckman Access Dxl, Roche Cobas e801, and Siemens Atellica IM MSs. Passing–Bablok regression and difference plots were used to compare results from each MS to the all-method median values. Agreement among methods was evaluated against APS for bias derived from biological variation of the 2 measurands.

Results

The median interassay CV for tPSA MSs (11.5%; 25–75th percentiles, 9.2–13.4) fulfilled the minimum APS goal for intermethod bias (15.9%), while the interassay CV for fPSA did not [20.4% (25–75th percentiles, 18.4–22.7) vs goal 17.6%]. Considering the all-method median value of each sample as reference, all tPSA MSs exhibited a mean percentage bias within the minimum goal. On the other hand, Alinity (+21.3%) and Access (−24.2%) were out of the minimum bias goal for fPSA, the disagreement explained only in minimal part by the heterogeneity of employed antibodies.

Conclusions

The harmonization among tPSA MSs is acceptable only when minimum APS are applied and necessitates further improvement. The marked disagreement among fPSA MSs questions the use of fPSA as a second-level test for biopsy referral.
Titin-truncating mutations associated with dilated cardiomyopathy alter length-dependent activation and its modulation via phosphorylation
Authors: Vikhorev Petr G , Vikhoreva Natalia N , Yeung WaiChun , Li Amy , Lal Sean , dos Remedios Cristobal G , Blair Cheavar A , Guglin Maya , Campbell Kenneth S , Yacoub Magdi H , de Tombe Pieter , Marston Steven B
Published: October 2020

Aims 

Dilated cardiomyopathy (DCM) is associated with mutations in many genes encoding sarcomere proteins. Truncating mutations in the titin gene TTN are the most frequent. Proteomic and functional characterizations are required to elucidate the origin of the disease and the pathogenic mechanisms of TTN-truncating variants.

Methods and results 

We isolated myofibrils from DCM hearts carrying truncating TTN mutations and measured the Ca2+ sensitivity of force and its length dependence. Simultaneous measurement of force and adenosine triphosphate (ATP) consumption in skinned cardiomyocytes was also performed. Phosphorylation levels of troponin I (TnI) and myosin binding protein-C (MyBP-C) were manipulated using protein kinase A and λ phosphatase. mRNA sequencing was employed to overview gene expression profiles. We found that Ca2+ sensitivity of myofibrils carrying TTN mutations was significantly higher than in myofibrils from donor hearts. The length dependence of the Ca2+ sensitivity was absent in DCM myofibrils with TTN-truncating variants. No significant difference was found in the expression level of TTN mRNA between the DCM and donor groups. TTN exon usage and splicing were also similar. However, we identified down-regulation of genes encoding Z-disk proteins, while the atrial-specific regulatory myosin light chain gene, MYL7, was up-regulated in DCM patients with TTN-truncating variants.

Conclusion 

Titin-truncating mutations lead to decreased length-dependent activation and increased elasticity of myofibrils. Phosphorylation levels of TnI and MyBP-C seen in the left ventricles are essential for the length-dependent changes in Ca2+ sensitivity in healthy donors, but they are reduced in DCM patients with TTN-truncating variants. A decrease in expression of Z-disk proteins may explain the observed decrease in myofibril passive stiffness and length-dependent activation.