bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal evolution of plasma parameters in a pulse-modulated capacitively coupled Ar/O2 mixture discharge
Authors: Anjum Zakia , Rehman N. U.
Published: November 2020

The time-resolved measurements of the plasma parameters are carried out in a pulse-modulated low pressure capacitively coupled discharge operated in argon and argon–oxygen mixtures. Measurements are performed at a constant radio-frequency (RF) power of 130 W at 13.56 MHz, with the pulse repetition frequency of 1 kHz and 50% duty cycle. A single RF compensated Langmuir probe, synchronized with the modulated signal, is used to investigate the effects of filling gas pressure and O2 content in the discharge on the temporal evolution of electron density ne, electron temperature Te, plasma potential Vp, and electron energy probability function (EEPF). ne shows a rapid increase with time during the start of the pulse-on phase, followed by a gradual increase to attain a steady state value. During the pulse-off phase, ne decreases gradually. ne drops at a higher pressure and with increasing O2 content in the discharge. The temporal variations in Te and Vp, on the other hand, are more abrupt than the temporal variation in ne during the rise and the fall of the pulse. Both Te and Vp show an increase with rising pressure and with increasing O2 content in the discharge. The investigation of the temporal evolution of the EEPF reveals that the discharge is in a highly non-equilibrium state at the start of the pulse and evolves from bi-Maxwellian to Maxwellian distribution with the passage of time. The density of low energy electrons decreases, while the density of high energy electrons increases with increasing pressure and O2 content in the discharge. Moreover, several peaks and broadening in the EEPF profile are also noted with increasing O2 content.
An open, modular, and flexible micro X-ray computed tomography system for research
Authors: Ruf Matthias , Steeb Holger
Published: November 2020

In this paper, a modular and open micro X-ray Computed Tomography (μXRCT) system is presented, which was set up during the last years at the Institute of Applied Mechanics (CE) of the University of Stuttgart and earlier at the Institute of Computational Engineering of Ruhr-University Bochum. The system is characterized by its intrinsic flexibility resulting from the modular and open design on each level and the opportunity to implement advanced experimental in situ setups. On the one hand, the presented work is intended to support researchers interested in setting up an experimental XRCT system for the microstructural characterization of materials. On the other hand, it aims to support scientists confronted with the decision to set up a system on their own or to buy a commercial scanner. In addition to the presentation of the various hardware components and the applied modular software concept, the technical opportunities of the open and modular hard- and software design are demonstrated by implementing a simple and reliable method for the compensation of bad detector pixels to enhance the raw data quality of the projections. A detailed investigation of the performance of the presented system with regard to the achievable spatial resolution is presented. XRCT datasets of three different applications are finally shown and discussed, demonstrating the wide scope of options of the presented system.
Calibration methods of charge sensitive amplifiers at the Colorado dust accelerator
Authors: James David , Fontanese John , Munsat Tobin , Horányi Mihály
Published: November 2020

Charge sensitive amplifiers (CSAs) are electronic integrating circuits frequently used for detecting quick charge pulses such as those produced in semiconductor detector devices and electron multipliers. One of the limitations of highly sensitive CSA circuits is the accuracy with which they can be calibrated due to the necessity of using injection capacitors on the order of a few pF, which are difficult to calibrate and to disentangle from other stray capacitance in calibration circuits. This paper presents an alternate method for calibrating the electronics for CSAs with conductive detectors, referred to as the “external conductor” method, using the detector itself to form the injection circuit. The external conductor method is compared to the traditional injection capacitor method for an example detector. The new method results in an increase to the calibration factor of up to 70% over the value derived from a traditional injection capacitor, with an uncertainty in the new value of 2%. Finally, the results from the external conductor method are compared to a third, independent approach, which uses reference charged particles as calibration sources in the Colorado dust accelerator. The results of the charged particle approach corroborate the external conductor calibration to within the stated uncertainty.
Spatially localized measurement of isotropic and anisotropic thermophysical properties by photothermal radiometry
Authors: Hamaoui Georges , Villarreal Ezekiel , Ban Heng , Chirtoc Mihai , Horny Nicolas
Published: November 2020

This work presents the development of a new photothermal radiometry (PTR) setup using a mix between frequency and spatial domain scans, along with a three-dimensional (3D) heat diffusion model. This newly developed PTR system, with a spatial resolution of 33 μm, is used to measure thermophysical properties of several kinds of materials. These properties include the thermal diffusivity, a, of homogeneous semi-infinite materials, thermal boundary resistance, Rth, and thermal anisotropy of membranes. The measured properties for homogeneous semi-infinite materials and two-layered systems are in good agreement with the literature values. In addition, it was possible to obtain an anisotropic factor of 24.6 between the in-plane and cross-plane thermal diffusivity of a 25 μm anisotropic flexible graphite sheet. Furthermore, it was also possible to measure, both directly and independently, the anisotropic thermal diffusivities for a 1 μm titanium membrane. It is suggested that this new hybrid technique can help us to fill the gap between conventional PTR and other photothermal and thermoreflectance techniques. Using this PTR setup, it is possible to experimentally measure isotropic and anisotropic thermophysical properties of bulk and thin materials, including membranes, with high precision through accurate characterization of the pump beam spots size. This is accomplished without the need for an optical transducer layer.
The opposite pressure dependence of electron temperature with respect to O2/Ar mixing ratio in an inductively coupled plasma
Authors: Lee Moo-Young , Jung Jiwon , Kim Tae-Woo , Kim Kyung-Hyun , Kwon Deuk-Chul , Chung Chin-Wook
Published: November 2020

To observe the evolution of electron temperature and electron density when varying gas mixing ratio and pressure, the measurement of electron energy probability functions (EEPFs) and a kinetic simulation are performed in an O2/Ar inductively coupled plasma. When O2 gas is diluted to pure Ar plasma, the electron density significantly drops regardless of gas pressures and the reduction of electron density increases with gas pressure. This sudden drop of plasma density is due to various inelastic collisions between electrons and O2 molecules. However, the trend of electron temperature variation with respect to the ratio of O2 and Ar is opposite at low and high pressures. At low pressure (5 mTorr), the electron temperature decreases with the addition of O2 up to a 10% O2 ratio. With further addition of O2, the electron temperature increases gradually. On the other hand, at high pressures (25 and 80 mTorr), the electron temperature rises with addition of O2 up to a 10%–20% O2 ratio and then falls gradually with further addition of O2. Simulations show a similar variation of EEPFs to the EEPFs from experiments. In addition, we measured the EEPFs along axial positions and the variation of electron temperature with respect to the ratio of O2 and Ar is opposite at low and high pressures, regardless of spatial positions. This result indicates that the opposite trend of electron temperature variation is mainly affected by the gas mixing ratio and gas pressure.
Helmholtz spacing of thin rectangular magnetic field coils
Authors: Ahrendsen K. J. , Reyes S. , Gay T. J.
Published: November 2020

In this Note, we discuss the Helmholtz spacing for a pair of thin rectangular coils of arbitrary aspect ratio and consider how best to use such coils to compensate for Earth’s magnetic field along the coils’ Cartesian symmetry axes. Such coils are frequently used in conjunction with charged-particle beam machines. The Helmholtz spacing varies non-monotonically between that for square coils and that for four optimally spaced infinite wires. We consider other coil spacings that extend the length over which the field varies by less than some tolerance along the Cartesian symmetry axes. The calculations also provide a convenient means to evaluate when the length of the coils is sufficiently long to be considered infinite at the center point within a fixed tolerance.
Predicting the near-wall velocity of wall turbulence using a neural network for particle image velocimetry
Authors: Wang Hongping , Yang Zixuan , Li Binglin , Wang Shizhao
Published: November 2020

Near-wall velocity prediction for wall-bounded turbulence is useful for constructing a wall model and estimating dissipation and wall shear stress. A convolutional neural network is developed to improve the near-wall velocity prediction and spatial resolution for wall-bounded turbulent velocity fields obtained using particle image velocimetry (PIV). To establish the relationship between the low-resolution and high-resolution fields, this machine learning model is trained on a synthetic PIV dataset generated based on velocity fields obtained from the direct numerical simulation of turbulent channel flows at Reτ = 1000. Using a test dataset with a higher Reynolds number of Reτ = 5200, the performance of this model is assessed in terms of instantaneous fields, error analysis, velocity statistics, and energy spectra. The influences of the interrogation window, image resolution, and particle concentration on the performance of this network are also considered. We further apply this network to practical PIV data from a turbulent boundary layer at Reτ = 2200 to assess the network performance under real experimental conditions. The results indicate that the proposed machine-learning-based model can predict missing near-wall velocity fields and enhance the spatial resolution of PIV fields, but the accuracy for Reynolds shear stress prediction needs to be further improved. The presented approach shows the potential ability to predict the near-wall instantaneous velocity of high-Reynolds-number turbulence from low-Reynolds-number flow fields.
Four-dimensional drift-kinetic model for scrape-off layer plasmas
Authors: Perrone L. M. , Jorge R. , Ricci P.
Published: November 2020

A four-dimensional plasma model able to describe the scrape-off layer region of tokamak devices at arbitrary collisionality is derived in the drift-reduced limit. The basis of the model is provided by a drift-kinetic equation that retains the full nonlinear Coulomb collision operator and describes arbitrarily far from equilibrium distribution functions. By expanding the dependence of the distribution function over the perpendicular velocity in a Laguerre polynomial basis and integrating over the perpendicular velocity, a set of four-dimensional moment equations for the expansion coefficients of the distribution function is obtained. The Coulomb collision operator as well as Poisson's equation are evaluated explicitly in terms of perpendicular velocity moments of the distribution function.
A semi-GCMC simulation study of electrolytic capacitors with adsorbed titrating peptides
Authors: Vo Phuong , Forsman Jan , Woodward Clifford E.
Published: November 2020

We use semi-grand canonical Monte Carlo simulations to study an electrolytic capacitor with an adsorbed peptide on the electrode surfaces. Only homogeneous peptides are considered, consisting of only a single residue type. We find that the classical double-hump camel-shaped differential capacitance in such systems is augmented by the addition of a third peak, due to the capacitance contribution of the peptide, essentially superimposed on the salt contribution. This mechanistic picture is justified using a simple mean-field analysis. We find that the position of this third peak can be tuned to various surface potential values by adjusting the ambient pH of the electrolyte solution. We investigate the effect of changing the residue type and the concentration of the adsorbed peptide and of the supporting electrolyte. Varying the residue species and pH allows one to modify the capacitance profile as a function of surface potential, facilitating the design of varying discharging patterns for the capacitor.
Beltrami states in Earth's dusty mesosphere
Authors: Gondal S. M.
Published: November 2020

The study is the description of a three fluid (electrons, ions, and negatively charged dust grains) model of dusty plasmas which is a strong coupling between the magnetic field and the fluid aspects of the plasma. The generalized vorticities and the associated flows become parallel to each other by satisfying the Beltrami condition. Having solved the steady-state solutions with the Ampère's law for the magnetic field has given rise to a quadruple Beltrami state. The self-organized state has four scale parameters. The dynamics of the magnetic field are illustrated graphically in the x–y plane. The characteristics of the self-organized structures are strongly influenced by the scale parameters and the mass of the negatively charged dust grains. The equilibria magnetic field structures for the Earth's mesosphere revealed diamagnetic behavior. A transition into a paramagnetic state from a diamagnetic state was observed by slightly decreasing the mass of the dust grains. This identification can be useful to study and understand the noctilucent cloud and polar mesospheric summer echo in the Earth's mesosphere. The current study will be suitable to study the environmental and defense science. Moreover, this work will be fruitful to understand the environment of the planet Earth in the future.
A three-step model for optimizing coil spacings inside cuboid-shaped magnetic shields
Authors: Liu Tianhao , Schnabel Allard , Voigt Jens , Sun Zhiyin , Li Liyi
Published: November 2020

A three-step model for calculating the magnetic field generated by coils inside cuboid-shaped shields like magnetically shielded rooms (MSRs) is presented. The shield is modeled as two parallel plates of infinite width and one tube of infinite height. We propose an improved mirror method that considers the effect of the parallel plates of finite thickness. A reaction factor is introduced to describe the influence of the vertical tube, which is obtained from finite element method (FEM) simulations. By applying the improved mirror method and then multiplying the result with the reaction factor, the magnetic flux density within the shielded volume can be determined in a fast computation. The three-step model is verified with both FEM and measurements of the field of a Helmholtz coil inside an MSR with a superconducting quantum interference device. The model allows a fast optimization of shield-coupled coil spacings compared to repetitive, time-consuming FEM calculations. As an example, we optimize the distance between two parallel square coils attached to the MSR walls. Measurements of a coil prototype of 2.75 m side length show a magnetic field change of 18 pT over the central 5 cm at the field strength of 2.7 µT. This obtained relative field change of 6 ppm is a factor of 5.4 smaller than our previously used Helmholtz coil.
Pulsed-jet propulsion of a squid-inspired swimmer at high Reynolds number
Authors: Luo Yang , Xiao Qing , Zhu Qiang , Pan Guang
Published: November 2020

An inflation–deflation propulsion system inspired by the jet propulsion mechanism of squids and other cephalopods is proposed. The two-dimensional squid-like swimmer has a flexible mantle body with a pressure chamber and a nozzle that serves as the inlet and outlet of water. The fluid–structure interaction simulation results indicate that larger mean thrust production and higher efficiency can be achieved in high Reynolds number scenarios compared with the cases in laminar flow. The improved performance at high Reynolds number is attributed to stronger jet-induced vortices and highly suppressed external body vortices, which are associated with drag force. Optimal efficiency is reached when the jet vortices start to dominate the surrounding flow. The mechanism of symmetry-breaking instability under the turbulent flow condition is found to be different from that previously reported in laminar flow. Specifically, this instability in turbulent flow stems from irregular internal body vortices, which cause symmetry breaking in the wake. A higher Reynolds number or smaller nozzle size would accelerate the formation of this symmetry-breaking instability.
Photovoltaic properties of all-inorganic lead-free perovskite Cs2PdBr6: A first-principles study
Authors: Xu Peng , Liu Fuxiang
Published: November 2020

Lead halide perovskite has shown amazing optoelectronic performance, while the issues of its toxicity and the thermal instability remain to be intractable. Recently, lead-free halide perovskite Cs2PdBr6 as a narrow bandgap semiconductor with long-term stability has attracted great attention. Herein, through performing first-principles calculations, we find that (i) Cs2PdBr6 has a quasi-direct bandgap with an indirect bandgap of 1.71 eV and a 20 meV smaller direct bandgap. The bandgap increases when the lattice constant enlarges, which is opposite to that of the traditional zincblende semiconductors. (ii) Band offsets between Cs2PdBr6 and popular perovskites indicate that Cs2PdBr6 is more difficult to be doped p-type according to the doping limit rule. The commonly used electron transport materials such as TiO2, SnO2, ZnO, and C60 can also be suitable for Cs2PdBr6 solar cell devices, but the commonly used hole transport materials with a lower highest occupied molecular orbital is an alternative. (iii) Cs2PdBr6 is shown to be difficult to be intrinsic p-type. The electric conductivity would not be too high due to the charge compensation of the defects if there is no suitable external doping. Since the Pd poor and Br rich condition can suppress the formation of the defects with deep levels, this condition is proposed to synthesize Cs2PdBr6 as a solar cell absorber.
Unusual blue to red shifting of C–H stretching frequency of CHCl3 in co-operatively P⋯Cl phosphorus bonded POCl3–CHCl3 heterodimers at low temperature inert matrixes
Authors: Sruthi P. K. , Chandra Swaroop , Ramanathan N. , Sundararajan K.
Published: November 2020

Heterodimers of POCl3—CHCl3 were generated in Ne, Ar, and Kr matrixes at low temperatures and were studied using infrared spectroscopy. The remarkable role of co-operative pentavalent phosphorus bonding in the stabilization of the structure dictated by hydrogen bonding is deciphered. The complete potential energy surface of the heterodimer was scanned by ab initio and density functional theory computational methodologies. The hydrogen bond between the phosphoryl oxygen of POCl3 and C—H group of CHCl3 in heterodimers induces a blue-shift in the C—H stretching frequency within the Ne matrix. However, in Ar and Kr matrixes, the C—H stretching frequency is exceptionally red-shifted in stark contrast with Ne. The plausibility of the Fermi resonance by the C—H stretching vibrational mode with higher order modes in the heterodimers has been eliminated as a possible cause within Ar and Kr matrixes by isotopic substitution (CDCl3) experiments. To evaluate the influence of matrixes as a possible cause of red-shift, self-consistent Iso-density polarized continuum reaction field model was applied. This conveyed the important role of the dielectric matrixes in inducing the fascinating vibrational shift from blue (Ne) to red (Ar and Kr) due to the matrix specific transmutation of the POCl3—CHCl3 structure. The heterodimer produced in the Ne matrix possesses a cyclic structure stabilized by hydrogen bonding with co-operative phosphorus bonding, while in Ar and Kr the generation of an acyclic open structure stabilized solely by hydrogen bonding is promoted. Compelling justification regarding the dispersion force based influence of matrix environments in addition to the well-known dielectric influence is presented.
Functions universal with respect to the trigonometric system
Authors: Grigoryan M. G. , Galoyan L. N.
Published: November 2020

We construct an integrable function whose Fourier series possesses the following property. After an appropriate choice of signs of the coefficients of this series, the partial sums of the resulting series are dense in

,

.
On the standard conjecture for projective compactifications of Néron models of

-dimensional Abelian varieties
Authors: Tankeev S. G.
Published: November 2020

We prove that the Grothendieck standard conjecture of Lefschetz type holds for a smooth complex projective

-dimensional variety

fibred by Abelian varieties (possibly, with degeneracies) over a smooth projective curve if the endomorphism ring

of the generic geometric fibre is not an order of an imaginary quadratic field. This condition holds automatically in the cases when the reduction of the generic scheme fibre

at some place of the curve is semistable in the sense of Grothendieck and has odd toric rank or the generic geometric fibre is not a simple Abelian variety.
On a real caustic of type
Authors: Sedykh V. D.
Published: November 2020

We prove that the manifold of non-singular points of a stable real caustic germ of type

and the manifolds of points of transversal intersection of its smooth branches consist only of contractible connected components. We also calculate the number of these components.
Solubility of unsteady equations of the three-dimensional motion of two-component viscous compressible heat-conducting fluids
Authors: Mamontov A. E. , Prokudin D. A.
Published: November 2020

We consider equations for the three-dimensional unsteady motion of mixtures of viscous compressible heat-conducting fluids in the multi-velocity approach. We prove the existence, globally in time and the input data, of a generalized (dissipative) solution of the initial-boundary value problem corresponding to flows in a bounded domain.
Investigation of the weak solubility of the fractional Voigt alpha-model
Authors: Zvyagin A. V.
Published: November 2020

This paper is devoted to investigating the weak solubility of the alpha-model for a fractional viscoelastic Voigt medium. The model involves the Voigt rheological relation with a left Riemann–Liouville fractional derivative, which accounts for the medium’s memory. The memory is considered along the trajectories of fluid particles determined by the velocity field. Since the velocity field is not smooth enough to uniquely determine the trajectories for every initial value, we introduce weak solutions of this problem using regular Lagrangian flows. On the basis of the approximation-topological approach to the study of hydrodynamical problems, we prove the existence of weak solutions of the alpha-model and establish the convergence of solutions of the alpha-model to solutions of the original model as the parametertends to zero.
Criteria for

-approximability of functions on compact sets in

,

, by solutions of second-order homogeneous elliptic equations
Authors: Paramonov P. V.
Published: November 2020

We obtain capacitive criteria for the approximability of individual functions by solutions of second-order homogeneous elliptic equations with constant complex coefficients in the norm of a Whitney-type

-space on a compact set in

,

. The case

was studied in a recent paper by the author and Tolsa. For

-approximations by harmonic functions (with any

), weaker criteria were earlier found by the author. We establish some metric properties of the capacities considered.
The derivative of the Minkowski function
Authors: Gayfulin D. R. , Kan I. D.
Published: November 2020

We prove new results on the derivative of the Minkowski question mark function.
Inequalities for the average exit time of a random walk from an interval
Authors: Lotov V. I.
Published: November 2020

Two-sided inequalities are obtained for the average exit time from an interval for a random walk with zero and negative drift.
Adjunction in 2-categories
Authors: Kaledin D. B.
Published: November 2020

The aim of the paper is to introduce an approach to the theory of 2-categories which is based on systematic use of the Grothendieck construction and the Segal Machine and to show how adjunction questions can be investigated by means of this approach and what its connections are with more traditional approaches. As an application, the derived Morita 2-category and the Fourier–Mukai 2-category over a Noetherian ring are constructed and the embedding of the latter in the former is demonstrated.

Bibliography: 15 titles.
Necessary and sufficient conditions for extending a function to a Schur function
Authors: Buslaev V. I.
Published: November 2020

A criterion for a function given by its values (with multiplicities) at a sequence of points in the disc

to extend to a holomorphic function in

with modulus at most

is stated and proved. In the case when the function is defined by the values of its derivatives at

, this coincides with Schur’s well-known criterion.

Bibliography: 16 titles.
The rise of angiosperms pushed conifers to decline during global cooling
Authors: Condamine Fabien L. , Silvestro Daniele , Koppelhus Eva B. , Antonelli Alexandre
Published: November 2020

Significance

Competition for common resources can make some species groups thrive and others decline. Flowering plants rose to dominance between 125 and 80 Ma, undergoing an explosive radiation that is believed to have impacted long-established plant groups like gymnosperms. Here, we show that the decline of conifers is strongly and directly linked to the increasing diversity of flowering plants. Both the fossil record and molecular data converge in clarifying the effects of abiotic or biotic factors on the speciation and extinction rates of conifers. These results imply that long-term biological interactions through clade competition can play a more important role in the rise and demise of major organism groups than mass extinctions.
Systematic integrated analysis of genetic and epigenetic variation in diabetic kidney disease
Authors: Sheng Xin , Qiu Chengxiang , Liu Hongbo , Gluck Caroline , Hsu Jesse Y. , He Jiang , Hsu Chi-yuan , Sha Daohang , Weir Matthew R. , Isakova Tamara , Raj Dominic , Rincon-Choles Hernan , Feldman Harold I. , Townsend Raymond , Li Hongzhe , Susztak Katalin
Published: November 2020

Significance

Diabetic kidney disease (DKD) is the most common cause of chronic and end-stage renal failure in the world. In a genetically susceptible host, poor metabolic control contributes to DKD development. The epigenome integrates signals from sequence variations and environmental alterations. We performed genome-wide DNA methylation association analysis in one of the best-characterized kidney disease cohorts: The Chronic Renal Insufficiency Cohort study. Complex computational integration analysis indicated the key role of genetic variations in DNA methylation. Our analysis highlighted loci, where methylation and gene-expression changes likely mediate the genotype effect on kidney disease development. Functional annotation of high-confidence genes suggested the causal role of inflammation, specifically, complement activation and apoptotic cell clearance in kidney disease development.
Outdoor air pollution in India is not only an urban problem
Authors: Ravishankara A. R. , David Liji M. , Pierce Jeffrey R. , Venkataraman Chandra
Published: November 2020

Significance

The pollution in major cities in India is immense, and they are in the news often. In general, air pollution is viewed as an urban problem. Here, we show that outdoor air pollution due to particulate matter is just as harmful in nonurban (rural) areas as in urban areas in India based on satellite data and calculated health impacts. This finding has a far-reaching impact on how pollution is viewed in India and other developing countries. It is also very timely given that India, and countries like India, are turning attention to addressing air pollution, and they need to be aware of this vast issue.
Early life of Neanderthals
Authors: Nava Alessia , Lugli Federico , Romandini Matteo , Badino Federica , Evans David , Helbling Angela H. , Oxilia Gregorio , Arrighi Simona , Bortolini Eugenio , Delpiano Davide , Duches Rossella , Figus Carla , Livraghi Alessandra , Marciani Giulia , Silvestrini Sara , Cipriani Anna , Giovanardi Tommaso , Pini Roberta , Tuniz Claudio , Bernardini Federico , Dori Irene , Coppa Alfredo , Cristiani Emanuela , Dean Christopher , Bondioli Luca , Peresani Marco , Müller Wolfgang , Benazzi Stefano
Published: November 2020

Significance

The extent to which Neanderthals differ from us is the focus of many studies in human evolution. There is debate about their pace of growth and early-life metabolic constraints, both of which are still poorly understood. Here we use chemical and isotopic patterns in tandem with enamel growth rates of three Neanderthal milk teeth from northeastern Italy to explore the early life of these individuals. Our study shows that these Neanderthals started to wean children at 5 to 6 months, akin to modern humans, implying similar energy demands during early infancy. Dental growth rates confirm this and follow trajectories comparable with modern humans. Contrary to previous evidence, we suggest that differences in weaning age did not contribute to Neanderthals’ demise.
The inhibition of LSD1 via sequestration contributes to tau-mediated neurodegeneration
Authors: Engstrom Amanda K. , Walker Alicia C. , Moudgal Rohitha A. , Myrick Dexter A. , Kyle Stephanie M. , Bai Yu , Rowley M. Jordan , Katz David J.
Published: November 2020

Significance

We have made the discovery that pathological tau functions through the histone demethylase LSD1 in the Alzheimer’s disease pathway. Thus, we have identified a mechanism that links tau to the downstream neuronal dysfunction pathways. This step can potentially be targeted therapeutically, after the onset of dementia symptoms, to block the progression of dementia in Alzheimer’s disease patients.
The evolution of altruism and the serial rediscovery of the role of relatedness
Authors: Kay Tomas , Keller Laurent , Lehmann Laurent
Published: November 2020

Significance

The canonical explanation for the evolution of altruism (“kin selection”)—which was mathematically derived in the 1960s by W. D. Hamilton—emphasizes the importance of genetic relatedness. Over the past three decades, numerous authors claim to have discovered alternative explanations. We systematically analyze the models substantiating these claims and reveal that in every model the interacting individuals are genetically related and that the authors have therefore unwittingly rediscovered Hamilton’s insight.
Evidence that coronavirus superspreading is fat-tailed
Authors: Wong Felix , Collins James J.
Published: November 2020

Superspreaders, infected individuals who result in an outsized number of secondary cases, are believed to underlie a significant fraction of total SARS-CoV-2 transmission. Here, we combine empirical observations of SARS-CoV and SARS-CoV-2 transmission and extreme value statistics to show that the distribution of secondary cases is consistent with being fat-tailed, implying that large superspreading events are extremal, yet probable, occurrences. We integrate these results with interaction-based network models of disease transmission and show that superspreading, when it is fat-tailed, leads to pronounced transmission by increasing dispersion. Our findings indicate that large superspreading events should be the targets of interventions that minimize tail exposure.
αv-Class integrin binding to fibronectin is solely mediated by RGD and unaffected by an RGE mutation
Authors: Benito-Jardón María , Strohmeyer Nico , Ortega-Sanchís Sheila , Bharadwaj Mitasha , Moser Markus , Müller Daniel J. , Fässler Reinhard , Costell Mercedes
Published: November 2020

Fibronectin (FN) is an essential glycoprotein of the extracellular matrix; binds integrins, syndecans, collagens, and growth factors; and is assembled by cells into complex fibrillar networks. The RGD motif in FN facilitates cell binding­ and fibrillogenesis through binding to α5β1 and αv-class integrins. However, whether RGD is the sole binding site for αv-class integrins is unclear. Most notably, substituting aspartate with glutamate (RGE) was shown to eliminate integrin binding in vitro, while mouse genetics revealed that FNRGE preserves αv-class integrin binding and fibrillogenesis. To address this conflict, we employed single-cell force spectroscopy, engineered cells, and RGD motif–deficient mice (Fn1ΔRGD/ΔRGD) to search for additional αv-class integrin–binding sites. Our results demonstrate that α5β1 and αv-class integrins solely recognize the FN-RGD motif and that αv-class, but not α5β1, integrins retain FN-RGE binding. Furthermore, Fn1ΔRGD/ΔRGD tissues and cells assemble abnormal and dysfunctional FNΔRGD fibrils in a syndecan-dependent manner. Our data highlight the central role of FN-RGD and the functionality of FN-RGE for αv-class integrins.
Numerical study of evaporative cooling in the space station
Authors: Fan Bo , Zhao Luheng , Zhang Yin , Sun Jingxin , Xiong Wei , Chen Jinqiang , Chen Xuzong
Published: November 2020

In this paper, we numerically studied the effects of mechanical vibration and magnetic fields on evaporative cooling process carried in space station by direct simulation Monte Carlo method. Simulated with the vibration data of international space station, we found that the cooling process would suffer great atomic losses until the accelerations reduced tenfold at least. In addition, if we enlarge the s-wave scattering length five times by feshbach resonance, the phase space density increased to 50 compared to 3 of no magnetic fields situation after 5 s evaporative cooling. We also simulated the two stages crossed beam evaporative cooling process under both physical impacts and obtain 4 × 105
85Rb atoms with a temperature of 8 pK. These results are of significance to the cold atom experiments carried out on space station in the future.
Arc fault power balance in AC and DC electrical aeronautic networks: influence of pressure and cable material
Authors: Vazquez T , Teulet P , Valensi F , Risacher A , Masquère M
Published: November 2020

A systematic study of arc faulting between two cables in aeronautic conditions is performed and a power balance of the arc is realized. Electrical characteristics and radiative heat flux are recorded. The effect of the current mode (AC/DC), cable material and pressure is highlighted with the assessment of the power balance, which includes the mean power of the arc, power transferred to the cables that can cause melting and vaporization, and the power lost by radiation, conduction and convection in the arc column. The evaporated mass of the cables can be estimated in this way. Optical emission spectroscopy measurements of the induced plasma are performed rendering the overall temperature of the arc using a Boltzmann plot method. The overall temperature is higher for copper-contaminated plasma than for aluminium-contaminated plasma. Despite the erratic behaviour of the plasma, the trend shows that the DC as well as the use of lighter aluminium-based cables lead to higher power.
Role of thermionic emission in the formation of negative electric potential and oscillations in low pressure discharges
Authors: Volkov L S , Babaeva N Yu , Antonov N N
Published: November 2020

In this paper, we discuss the results from the two-dimensional computational investigation of the role of thermionic cathode emission in the formation of the negative (reverse) potential near the emissive cathode (LaB6 tablet). Two modes of discharge behavior are considered—high- and low-pressure modes. We show that the region of the negative potential (for that of the emitting cathode) is enclosed in a semi-sphere bounded by the line where the electric field changes its direction. This sheath region was distorted by the movement of the emitting points in horizontal and vertical directions. The unstable behavior of the high pressure discharge and self-excited oscillations of plasma parameters were observed. At low pressure the potential reversal and oscillations were not so pronounced.
Accidental neutron exposure in a medical setting: a case study
Authors: Ainsbury Elizabeth A , Eakins Jonathan , Güçlü İnci , Kırbaşoğlu Çiğdem , Peet Debbie , Tosun Idris
Published: November 2020

In May 2016, a new linear accelerator (Linac) was installed at a hospital oncology department. A team of individuals supervised the installation, including a Radiation Oncologist who acted as an independent observer to the installation, calibration, beam data collection and shielding measurements. In order to ensure the shielding was correct, a licensed representative of the Turkish Atomic Energy Authority carried out formal measurements of the gamma and neutron dose rates at a variety of locations in and around the Linac facility. At 18 MV, the maximum neutron dose rate was 172 μSv h−1 and the maximum gamma dose rate was approximately 2 μSv h−1 (ambient dose equivalent in both cases), significantly higher than the expected and local background doses. As the neutron dose rates in particular were so high, it was concluded that the shielding was not sufficient, potentially due to an inadequate design. In order to rule out overexposure during the installation, biological dosimetry was carried out for a number of the individuals involved. The estimated doses were closely aligned with the doses measured using commercially available neutron dosemeters and were also within the tolerance dose ranges estimated using Monte Carlo simulations, which also supported the investigation. The results underline the need for careful planning before and after installation of new radiation exposure facilities, especially high MV Linac operation for which photo-neutrons might need to be mitigated. The results clearly indicate the importance of such checks, in addition to demonstrating the relevance of biological dosimetry supported by modelling strategies complex or unclear exposure scenarios.
Understanding radiological protection systems among diagnostic radiology facilities in Mumbai, India
Authors: Singh Thokchom Dewan
Published: November 2020

This study aims to understand radiological protection systems in diagnostic radiology practices among 30 diagnostic radiology facilities in Mumbai, India. It assesses the status of radiological protection systems in the facilities, continuous professional development (CPD) of workers and their risky working behaviour and perceptions using a semi-structured questionnaire. Then, we examine the perceptions of workers when they were working in facilities without proper protection systems. We also, attempt to understand the reasons why workers engage in risky behaviour despite the availability of protective systems. In doing so, we examine the influence of CPD on their work behaviour. The study observed that about 20% of the diagnostic radiology facilities in Mumbai had lack of implementation of the regulatory requirements and establishment of radiological protection systems. Obviously, it is expected that the workers of regulated facilities would comply with regulatory requirements, and their working behaviour would be better than those of their counterparts of unregulated facilities would. However, our study observes that some workers in the regulated practices also indulge in risky working behaviour. About 30% of workers were not using personal monitoring device during work procedures. Although lead aprons were available in the facilities, about 51% of workers were not wearing it wherever required. It was observed that about 10% of workers engaged in the activities like opening the door during radiation exposure, chatting with others on mobile phone during procedure and not checking collimator light before radiation exposure etc. The factors that contributed to workers’ engagement in risky work behaviour are the non-availability of protection systems, lack of exposure to CPD, low-risk perception of workers and dearth of communication between institutes and regulator.
Mechanical properties of graphene-reinforced aluminium composite with modified substrate surface: a molecular dynamics study
Authors: Liu Jun , Zhang Yingyan , Zhang Henin , Yang Jie
Published: November 2020

Due to its extraordinary properties, graphene has been widely used as reinforcing nanofillers to enhance the mechanical properties of polymer- or metal-based composites. However, the weak interfacial interaction between the matrix and graphene is still a major bottleneck that considerably hinders its reinforcing effectiveness and efficiency. This study presents an atomistic study via molecular dynamics simulation on a chemical modification strategy where the aluminium (Al) substrate is modified with Al2O3 (with or without covalent bonds formed between Al2O3 and graphene) or Al4C3 to achieve significantly improved interfacial shear strength and overall mechanical properties of graphene-reinforced aluminium (Al/Gr) composites. Numerical results show that this strategy works very well and among the three cases considered, modifying Al substrate by Al2O3 without covalent bonds formed at the interface between Al2O3 and graphene produces the strongest interfacial interaction and the best mechanical properties. In the presence of covalent bonds, however, the reinforcing effect is adversely affected due to the sp2–sp3 bond transformation which partially degrades graphene. The present work provides, for the first time, valuable insight into the role of substrate surface modification on the mechanical performance of Al/Gr nanocomposites.
Approaching ultra-low turn-on voltage in GaN lateral diode
Authors: Wang Zeheng , Yang Di , Shi Junjie , Yao Yuanzhe
Published: November 2020

Besides the commercial success in power electronics, GaN-based devices are also considered as a promising candidate in sensors or high-frequency applications. In such applications, ultra-low turn-on voltage (V
T) is highly demanded to realize low power consumption and high sensitivity. In this paper, we approach ultra-low V
T in a novel Γ-shaped anode AlGaN/GaN Schottky barrier diode (SBD) using an ultra-thin barrier (UTB) and fluorine ions implantation (FI). Benefiting from the low-work-function anode and UTB, the proposed device exhibits ultra-low V
T that is lower than 0.1 V. Simultaneously, the trenched anode plate and FI region provide a good reverse blocking capability. According to the numerical analysis, when the fluorine ions implantation length (L
FI) is 3 μm and the fluorine ions concentration (N
FI) is

1
×

10

18

cm−3, a favorable Baliga figure-of-merits (BFOM) of 33.0 KW mm−1 can be achieved. Compared to the conventional SBD and the SBD with pure Γ-shaped anode, the proposed device experiences at least 90% enhancement of BFOM, rendering the proposed ΓF-SBD performs potential in high-power and high-frequency applications such as microwave sensing and wireless power transmission.
Bioglass incorporated methacrylated collagen bioactive ink for 3D printing of bone tissue
Authors: Kajave Nilabh S , Schmitt Trevor , Nguyen Thuy-Uyen , Gaharwar Akhilesh K , Kishore Vipuil
Published: November 2020

Bioactive three-dimensional (3D) printed scaffolds are promising candidates for bone tissue engineering (BTE) applications. Here, we introduce a bioactive ink composed of Bioglass 45S5 (BG) and methacrylated collagen (CMA) for 3D printing of biomimetic constructs that resemble the organic and inorganic composition of native bone tissue. A uniform dispersion of BG particles within the collagen network improved stability and reduced swelling of collagen hydrogels. Rheological testing showed significant improvement in the yield stress and percent recovery of 3D printed constructs upon BG incorporation. Further, addition of BG improved the bone bioactivity of 3D printed constructs in stimulated body fluid. BG incorporated CMA (BG-CMA) constructs maintained high cell viability and enhanced alkaline phosphatase activity of human mesenchymal stem cells. In addition, cell-mediated calcium deposition was significantly higher on BG-CMA constructs, compared to CMA alone. In conclusion, 3D printed BG-CMA constructs have significant potential for use in BTE applications.
Urbanization and fragmentation mediate temperate forest carbon cycle response to climate
Authors: Reinmann Andrew B , Smith Ian A , Thompson Jonathan R , Hutyra Lucy R
Published: November 2020

Forest fragmentation is ubiquitous across urban and rural areas. While there is mounting evidence that forest fragmentation alters the terrestrial carbon cycle, the extent to which differences in ambient growing conditions between urban and rural landscapes mediate forest response to fragmentation and climate remains unexamined. This study integrates field measurements of forest structure, growth, and soil respiration with climate data and high-resolution land-cover maps to quantify forest carbon storage and sequestration patterns along edge-to-interior gradients. These data were used to contrast the response of temperate broadleaf forests to non-forest edges within rural and urban landscapes. We find that forest growth rates in both rural and urban landscapes nearly double from the forest interior to edge. Additionally, these edge-induced enhancements in forest growth are not offset by concurrent increases in total soil respiration observed across our sites. Forest productivity generally increases near edges because of increases in leaf area, but elevated air temperature at the edge tempers this response and imparts greater sensitivity of forest growth to heat. In particular, the adverse impacts of heat on forest growth are two to three times larger in urban than rural landscapes. We demonstrate that the highly fragmented nature of urban forests compared to rural forests makes them a stronger carbon sink per unit area, but also much more vulnerable to a warming climate. Collectively, our results highlight the need to include the effects of both urbanization and fragmentation when quantifying regional carbon balance and its response to a changing climate.
Contrasting yield responses of winter and spring wheat to temperature rise in China
Authors: He Di , Fang Shibo , Liang Hanyue , Wang Enli , Wu Dong
Published: November 2020

Wheat growth, development, and grain yield are affected by global climate warming. The general consensus is that global warming shortens the overall length of wheat growing period and reduces global wheat yield. Here, focusing on China, the largest wheat producer in the world, we show that warming increases wheat yield in most winter wheat growing regions in China. We collated data from field experiments under stress-free conditions and artificial warming from 12 locations over China to assess the impact of warming on wheat yield. The data cover 14 wheat cultivars, 27 site-years, and a range of growing season temperatures from 7.5 °C to 17.2 °C. Our results indicate that warming up to +3 °C increased winter wheat yield by 5.8% per °C (change rate of yield/average of yield), while reduced spring wheat yield by 16.1% per °C. Although artificial warming reduced the total growth duration, warming-induced longer early developmental phases and grain filling duration, and subsequently more and larger grains contributed to the yield increase of winter wheat. The yield decline of spring wheat was due to the opposite changes of those key processes in response to temperature rise.