bluuebunny/crossref_metadata_2025 huggingface dataset:
Bifurcations of small-amplitude supernonlinear waves of the mKdV and modified Gardner equations in a three-component electron-ion plasma
Authors: Tamang Jharna , Saha Asit
Published: January 2020

Small-amplitude supernonlinear ion-acoustic waves (SIAWs) are examined in a multicomponent electron-ion plasma that is composed of fluid cold ions and two temperature q-nonextensive hot and cold electrons. Implementing the reductive perturbation method, four nonlinear evolution equations are derived: the Korteweg-de-Vries (KdV) equation, the modified KdV (mKdV) equation, the further modified KdV equation, and the modified Gardner (mG) equation. Employing the traveling wave transformation, the nonlinear evolution equations are deduced to their corresponding planar dynamical systems. Applying phase plane theory of dynamical systems, phase portrait profiles including nonlinear homoclinic trajectories, nonlinear periodic trajectories from the KdV equation, and additional supernonlinear periodic trajectories are presented for ion-acoustic waves (IAWs) from the modified KdV equation. Furthermore, supersolitons corresponding to the supernonlinear homoclinic trajectory of IAWs under the modified Gardner equation are shown in a phase plane and confirmed by the potential plot with a specified set of physical parameters q, σc, σh, f, and U. Nonlinear and SIAWs are displayed using computation for distinct parametric values.
A new method for measurement and quantification of tracer diffusion in nanoconfined liquids
Authors: Ajith V. J. , Patil Shivprasad
Published: January 2020

We report development of a novel instrument to measure tracer diffusion in water under nanoscale confinement. A direct optical access to the confinement region, where water is confined between a tapered fiber and a flat substrate, is made possible by coating the probe with metal and opening a small aperture (0.1 μm–1 μm) at its end. A well-controlled cut using an ion beam ensures desired lateral confinement area as well as adequate illumination of the confinement gap. The probe is mounted on a tuning-fork based force sensor to control the separation between the probe and the substrate with nanometer precision. Fluctuations in fluorescence intensity due to diffusion of a dye molecule in water confined between the probe and the sample are recorded using a confocal arrangement with a single photon precision. A Monte Carlo method is developed to determine the diffusion coefficient from the measured autocorrelation of intensity fluctuations which accommodates the specific geometry of confinement and the illumination profile. The instrument allows for measurement of diffusion laws under confinement. We found that the diffusion of a tracer molecule is slowed down by more than 10 times for the probe-substrate separations of 5 nm and below.
Optimal design of SiC piezoresistive pressure sensor considering material anisotropy
Authors: Wu Chen , Fang Xudong , Guo Xin , Zhao Libo , Tian Bian , Jiang Zhuangde
Published: January 2020

Material properties of SiC determine the application potential of corresponding sensors in a high temperature and harsh environment. However, few reports are available to describe basic design principles of SiC sensors. In this paper, aiming at improving the sensitivity of the sensor, the structural design of a full-SiC piezoresistive pressure sensor is studied from the aspects of diaphragm structure, material, piezoresistor arrangement, and dimension. The differences between the isotropy theoretical calculation and the anisotropy simulation are analyzed. Furthermore, in order to conform to the anisotropic intrinsic properties of the SiC material, a fitting curve between the diaphragm stress and the corresponding design parameter a/h is obtained by using a quadratic function. Through comparison, a square diaphragm can obtain more stress than a circular diaphragm; however, it is not suitable for SiC pressure sensors due to the process difficulties in anisotropic etching. Both experiment and simulation results show that higher output sensitivity can be obtained when the four piezoresistors are distributed along the radial direction of the diaphragm. With the control variable method, we found that when the area of the edge piezoresistors is increased by 10 times, output sensitivity will decline by 23.66%. Instead, the size of the two piezoresistors at the center shows a minor impact. Therefore, the size of edge piezoresistors has a significant effect on output sensitivity, which is worth paying attention to and should be minimized. Sensor prototypes were fabricated with optimal design, and preliminary experimental results show that zero output is only slightly affected by temperature due to the good thermal stability of SiC materials.
A finite element method to simulate dislocation stress: A general numerical solution for inclusion problems
Authors: Ahn Chihak , Nishizawa Yutaka , Choi Woosung
Published: January 2020

We developed a simple and efficient way to simulate stress from arbitrary shape dislocations within the finite element method (FEM) framework. The new method is implemented as a single-step FEM simulation using analytic solutions in an infinite medium as input terms of FEM solver with special internal boundary treatment. It is fundamentally equivalent to the multistep “image method” proposed by Van der Giessen and Needleman [Modell. Simul. Mater. Sci. Eng. 3, 689 (1995)], but the force equilibration is achieved by a single step FEM method. The singularity at the dislocation core line is removed without mesh modification, which removes many technical difficulties to couple the dislocation stress model to other process/device simulation models.
Toughness and strength anisotropy among high-symmetry directions in 3C-SiC
Authors: Elahi Fazle , Zhang Zhaocheng , Hossain Zubaer M.
Published: January 2020

This paper presents a quantitative understanding of toughness and strength anisotropy in 3C-SiC under uniaxial deformation. We consider four high-symmetry crystallographic directions including [100], [110], [111], and [112¯] for loading, and find that both toughness and strength are the maximum along the [100] direction and the minimum along the [111] direction. The maximum anisotropy in crack nucleation-toughness is 145% and in fracture toughness 126%, relative to the [111] direction. The corresponding anisotropies in fracture strain and fracture strength are found to be 62% and 36%, respectively. An atomistic analysis shows that bonds deform uniformly for loading along the [100] direction, whereas for loading along the [110], [111], or [112¯] directions, bonds deform nonuniformly and it breaks the symmetry of the local atomic structure. The nonuniform bond deformation creates different sets of bond lengths and forms the atomistic basis for the direction-dependent mechanical behavior. The simulations are conducted with four different interatomic potentials including the Stillinger-Weber, Tersoff, Vashishta, and Environment Dependent Interatomic Potentials. It is found that only the Stillinger-Weber potential exhibits first-principles accurate strength and toughness as well as brittlelike fracture. Also, there is a sizeable difference among the potentials in terms of the crack nucleation toughness and strength. We find the difference to originate from the dissimilarity in the forcing function and its derivative in the nonlinear regime of mechanical deformation. A mathematical analysis suggests that it is essential for the forcing function to accurately represent the first-principles accurate forcing function, at least up to the maximum bond force, to produce accurate fracture properties and patterns.
Analysis of the focal spot by variation of immersion medium for nanostructured metasurfaces
Authors: Xiao Yanqiu , Wang Tong , Shao Jianmin
Published: January 2020

The refractive index of the immersion medium has a significant influence on the shape of the focal spot in the field of diffraction optics. For a refractive index of the immersion medium that varies from the designed one, the change in the focal properties of the diffractive optical elements needs to be verified. By combining the vectorial angular spectrum (VAS) theory with a genetic algorithm, multiannular nanostructured metasurfaces with super-resolution focusing abilities were designed with a linearly polarized beam in an oil immersion medium. The intensity distribution of the focusing field was calculated via the finite-difference time-domain, and the results agreed well with calculations using the VAS theory. The results of the theoretical calculations demonstrated an obvious shift of the focal spot and change in the spot size as the refractive index varied. The calculations showed that the refractive index had an impact on the focal properties of multiannular metasurfaces. This work provides theoretical guidance for super-resolution focusing and imaging.
TEM observation of nitrogen-tunable bcc–bct–fcc transformation of iron-cobalt with added vanadium
Authors: Hasegawa Takashi , Shirai Chihiro , Takemasa Yusuke , Seki Yuki
Published: January 2020

We used transmission electron microscopy (TEM) to observe tunable bcc–bct–fcc transformation of FeCo films caused by the addition of auxiliary elements. The crystal structure of the FeCo with added V was bcc, and the transformation of the bcc structure through the bct to fcc was found to depend on the N content (x). TEM observation revealed that bct structure with c/a = 1.12 was obtained for x = 1.7 atomic%, while fcc structure with c/a = 2 was obtained for x = 9.6 atomic%. The c/a-values depended on x, so the bcc–bct–fcc transformation of the FeCoV was tunable by N content. This research was made possible by special preventative measures taken during preparation to avoid compressive stress, which could otherwise induce the bct FeCo lattice of axial ratio c/a > 1.00 to transform to bcc structure. A FeCo coating of thickness 20 nm was therefore deposited directly on a MgO substrate without any other metallic layers.
Analysis of a single-mode waveguide at sub-terahertz frequencies as a communication channel
Authors: Westig Marc , Thierschmann Holger , Katan Allard , Finkel Matvey , Klapwijk Teun M.
Published: January 2020

We study experimentally the transmission of an electromagnetic waveguide in the frequency range from 160 to 300 GHz. Photo-mixing is used to excite and detect the fundamental TE10 mode in a rectangular waveguide with two orders-of-magnitude lower impedance. The large impedance mismatch leads to a strong frequency dependence of the transmission, which we measure with a high-dynamic range of up to 80 dB and with high frequency-resolution. The modified transmission function is directly related to the information rate of the waveguide, which we estimate to be about 1 bit per photon. We suggest that the results are applicable to a Josephson junction employed as a single-photon source and coupled to a superconducting waveguide to achieve a simple on-demand narrow-bandwidth free-space number-state quantum channel.
Estimating ion confinement times from beam current transients in conventional and charge breeder ECRIS
Authors: Marttinen M. , Angot J. , Annaluru A. , Jardin P. , Kalvas T. , Koivisto H. , Kosonen S. , Kronholm R. , Maunoury L. , Tarvainen O. , Toivanen V. , Ujic P.
Published: January 2020

Cumulative ion confinement times are probed by measuring decaying ion current transients in pulsed material injection mode. The method is applied in a charge breeder and conventional ECRIS yielding mutually corroborative results. The cumulative confinement time estimates vary from approximately 2 ms–60 ms with a clear dependence on the ion charge-to-mass ratio—higher charges having longer residence times. The long cumulative confinement times are proposed as a partial explanation to recently observed unexpectedly high ion temperatures. The results are relevant for rare ion beam (RIB) production as the confinement time and the lifetime of stable isotopes can be used for estimating the extracted RIB production efficiency.
Impact of surfactant addition on non-Newtonian fluid behavior during viscous fingering in Hele-Shaw cell
Authors: Ahmadikhamsi Seyedarash , Golfier Fabrice , Oltean Constantin , Lefèvre Eric , Bahrani S. Amir
Published: January 2020

We present an experimental study of viscous fingering caused by the displacement of an oil phase by non-Newtonian fluids such as Carbopol® 940 with and without surfactant (SDS) addition in a radial Hele-Shaw cell. When polymer solutions are injected, a variety of fingering patterns as a function of flow rate are observed, which differ from the classical Saffman-Taylor instability. We have shown that if the surfactant concentration locally decreases the interfacial tension, it also leads to a reduction of viscosity and hence results in an increasing impact on the capillary number. We found that surfactant-polymer solutions have wider fingers with increasing flow rates in contrast with Newtonian solutions. Our study also revealed that the relative finger width of both non-Newtonian experiments with and without the surfactant converge asymptotically to the same value. We think that this phenomenon is caused by the decrease in surfactant concentration in the vicinity of the tip as the finger is growing so that the shear-thinning features of polymer prevail at long time.
Temporal decay of strong solutions to the magnetohydrodynamics with power-law type nonlinear viscous fluid
Authors: Kim Jae-Myoung
Published: January 2020

We show that the energy norm of strong solutions to the power-law type magnetohydrodynamics in three dimensions has a decay rate of t−34.
Demand response based desynchronization of thermostatically controlled loads with hardware implementation
Authors: Singh Kshitij , Bajaria Pratik
Published: January 2020

Smart buildings are the need of the day with increasing demand-supply ratios and considerable deficiency to generate them. In any modern nonindustrial infrastructure, these demands mainly comprise thermostatically controlled loads (TCLs), which can be maneuvered. TCLs, such as air-conditioners, heaters, and refrigerators, are ubiquitous and their operating times can be controlled to achieve desired aggregate power. This power aggregation, in turn, helps achieve load management targets and thereby serves as an ancillary service (AS) to the power grid. In this work, a distributed averaging protocol is used to achieve the desired power aggregate set by the utility using steady-state desynchronization. The results are verified using a computer program for a homogeneous and heterogeneous population of TCLs. Furthermore, a load following scenario has been implemented using the utility as a reference. Apart from providing a significant AS to the power grid, the proposed idea also helps reduce the amplitude of power system oscillations imparted by the TCLs. Hardware-based results are obtained to verify its implementation feasibility in real-time.
Ultra-high sensitive trace gas detection based on light-induced thermoelastic spectroscopy and a custom quartz tuning fork
Authors: Ma Yufei , He Ying , Patimisco Pietro , Sampaolo Angelo , Qiao Shunda , Yu Xin , Tittel Frank K. , Spagnolo Vincenzo
Published: January 2020

A highly sensitive trace gas sensor based on light-induced thermoelastic spectroscopy (LITES) and a custom quartz tuning fork (QTF) is reported. The QTF has a T-shaped prong geometry and grooves carved on the prongs' surface, allowing a reduction of both the resonance frequency and the electrical resistance but retaining a high resonance quality factor. The base of the QTF prongs is the area maximizing the light-induced thermoelastic effect. The front surface of this area was left uncoated to allow laser transmission through the quartz, while on the back side of the QTF, a gold film was coated to back-reflect the laser beam and further enhance the light absorption inside the crystal. Acetylene (C2H2) was chosen as the target gas to test and validate the LITES sensor. We demonstrated that the sensor response scales linearly with the laser power incident on the prong base, and the optimum signal to noise ratio was obtained at an optical power of 4 mW. A minimum detection limit of ∼325 ppb was achieved at an integration time of 1 s, corresponding to a normalized noise equivalent absorption coefficient of 9.16 × 10−10 cm−1W/√Hz, nearly one order of magnitude better with respect to the value obtained with a standard 32.768 kHz QTF-based LITES sensor under the same experimental conditions.
Electrophoretic deposition of iron oxide nanoparticles to achieve thick nickel/iron oxide magnetic nanocomposite films
Authors: Mills Sara C. , Smith Connor S. , Arnold David P. , Andrew Jennifer S.
Published: January 2020

For modern switching power supplies, current bulk magnetic materials, such as ferrites or magnetic metal alloys, cannot provide both low loss and high magnetic saturation to function with both high power density and high efficiency at high frequencies (10-100 MHz). Magnetic nanocomposites comprised of a ferrite and magnetic metal alloy provide the opportunity to achieve these desired magnetic properties, but previously investigated thin-film fabrication techniques have difficulty achieving multi-micrometer film thicknesses which are necessary to provide practical magnetic energy storage and power handling. Here, we present a versatile technique to fabricate thick magnetic nanocomposites via a two-step process, consisting of the electrophoretic deposition of an iron oxide nanoparticle phase into a mold on a substrate, followed by electro-infiltration of a nickel matrix. The deposited films are imaged via scanning electron microscopy and energy dispersive X-ray spectroscopy to identify the presence of iron and nickel, confirming the infiltration of the nickel between the iron oxide nanoparticles. A film thickness of ∼7 μm was measured via stylus profilometry. Further confirmation of successful composite formation is obtained with vibrating sample magnetometry, showing the saturation magnetization value of the composite (473 kA/m) falls between that of the iron oxide nanoparticles (280 kA/m) and the nickel matrix (555 kA/m). These results demonstrate the potential of electrophoretic deposition coupled with electro-infiltration to fabricate magnetic nanocomposite films.
Magnetic field control of moiré fringes on guanine crystal plate surface using its optical interference pattern
Authors: Asada Hironori , Muneyama Etsuhiro , Nagai Ryosuke , Kimura Takayuki , Iwasaka Masakazu
Published: January 2020

Moiré fringes are created by superimposing two periodic or quasi-periodic networks of lines. This established technique is an important metrological tool for methods such as super-resolution microscopy. Biogenic guanine crystals show light and dark striped patterns on the broadest surface of their crystal plates when optical interference occurs because of the flatness and transparency of the crystal. In this work, using the optical interference pattern of a goldfish guanine crystal plate, we successfully observe the appearance of moiré fringes on a guanine crystal plate floating in water above herringbone patterns with micron and sub-micron periods. It is demonstrated experimentally that a variety of moiré fringes can be obtained by varying the long-axis direction of the guanine crystal plate using an in-plane magnetic field, which corresponds to a change in the direction of the structured illumination, because of the diamagnetic anisotropy of the crystal. The results of observation of the moiré fringes formed when the tilt angle of the guanine crystal’s (102) plane relative to the substrate is varied using a vertical magnetic field are also presented.
Magnetization reversal mechanisms in Fe/NiO bilayers grown onto nanoporous alumina membranes and Si wafers
Authors: Navarro Enrique , Alonso María , Ruiz Ana , Urdiroz Unai , Sánchez-Agudo Marta , Cebollada Federico , Domíguez-Cañizares Guillermo , Soriano Leonardo , Gutierrez Alejandro , Palomares F. Javier , González Jesús M.
Published: January 2020

We report on the magnetization reversal measured in two ferromagnetic/antiferromagnetic (F/AF) bilayer series: Fe/NiO/Al2O3 (nanoporous membranes, series N) and Fe/NiO/Si (wafers, series W). The Fe and NiO layers were deposited by pulsed laser ablation and magnetron sputtering, respectively. In both series different oxygen partial pressures were implemented in the Ar plasma during the NiO growth. The morphologies of both series (as imaged by atomic force microscopy) reflect those of their substrates and, particularly, the series N samples exhibit a six-fold columnar growth around each one of the membranes nanopores. The in-plane hysteresis loops measured upon field cooling the samples down to different temperatures in the range from 50 K up to 290 K evidenced i) 50 K, 0% oxygen coercivities that decreased markedly in both series samples with the increase of the Fe layer thickness (particularly the Fe 5 nm, series N sample exhibited a coercivity larger than the Fe magneto-crystalline anisotropy field), ii) a decrease of the coercivity with the increase of the NiO deposition oxygen partial pressure, observed in both series independently of the Fe layer thickness, iii) low temperature coercivities larger in the series N samples than in the series W ones. Our data are analyzed in correlation to the deposits morphology and in terms of the occurrence of either propagation mediated reversal (collective mode linked to spatially averaged interactions at the F/AF interface) or localized switching (defect ruled mechanism taking place in a spatially confined environment). It is concluded that i) the magnetization reversal mechanism active in series W samples corresponds to a weak pinning regime propagation of walls interacting with uncompensated moments at the F/AF interface, ii) in series N samples, the magnetization reversal does not involve propagation, and iii) in the latter series the reversal events are spatially restricted to the dot-like tops of the NiO columns surrounding the membrane pores.
Spatial characteristics of optical fields near a gold nanorod revealed by three-dimensional scanning near-field optical microscopy
Authors: Suzuki Hiromasa , Imaeda Keisuke , Mizobata Hidetoshi , Imura Kohei
Published: January 2020

We visualize plasmon mode patterns induced in a single gold nanorod by three-dimensional scanning near-field optical microscopy. From the near-field transmission imaging, we find that 3rd and 4th order plasmon modes are resonantly excited in the nanorod. We perform electromagnetic simulations based on the discrete dipole approximation method under focused Gaussian beam illumination and demonstrate that the observed near-field spectral and spatial features are well reproduced by the simulation. We also reveal from the three-dimensional near-field microscopy that the 4th order plasmon mode confines optical fields more tightly compared with the 3rd order mode. This result indicates that the even-order plasmon modes are promising for enhancing the light−matter interactions.
The effect of zinc fertilisation and arbuscular mycorrhizal fungi on grain quality and yield of contrasting barley cultivars
Authors: Al Mutairi Ahmed A. , Cavagnaro Timothy R. , Khor Shi Fang , Neumann Kylie , Burton Rachel A. , Watts-Williams Stephanie J.
Published: January 2020

Zinc is essential for the functioning of many enzymes and plant processes and the malting process. Arbuscular mycorrhizal fungi (AMF) can improve zinc (Zn) uptake in the important cereal crop barley (Hordeum vulgare) on Zn-deficient soils. Here we investigated the impacts of Zn fertilisation and AMF on the yield and grain quality of malting barley cultivars. Five barley genotypes were inoculated or not with the AMF Rhizophagus irregularis, and grown in pots either fertilised with Zn or not. Measurements of Zn nutrition and yield were made for all cultivars. Further analyses of grain biochemical composition, including starch, β-glucan and arabinoxylan contents, and analysis of ATR-MIR spectra were made in two contrasting cultivars. Mycorrhizal colonisation generally resulted in decreased biomass, but increased grain dimensions and mean grain weight. Barley grain yield and biochemical qualities were highly variable between cultivars, and the ATR-MIR spectra revealed grain compositional differences between cultivars and AMF treatments. Mycorrhizal fungi can affect barley grain Zn concentration and starch content, but grain biochemical traits including β-glucan and arabinoxylan contents were more conserved by the cultivar, and unaffected by AMF inoculation. The ATR-MIR spectra revealed that there are other grain characteristics affected by AMF that remain to be elucidated.
Biodiversity, trait composition and ecological functioning: impacts of coastal urbanisation on subtropical mudflats
Authors: Dissanayake Navodha G. , Frid Christopher L. J. , Caswell Bryony A.
Published: January 2020

The world’s coastlines have become heavily modified over the last century, with the adjacent natural habitats declining in biodiversity and health under increasing pressure from urbanisation. In this study we assessed the structure and biological traits of macrofaunal assemblages from 24 south-east Queensland mudflats in order to determine whether ecological functioning (e.g. primary production, nutrient cycling) and the delivery of ecosystem services was affected by urbanisation. This work represents the most comprehensive assessment of mudflat assemblages in the region to date. The mudflats contained 50 macrofaunal taxa and so were comparable to other local intertidal systems. Summer assemblages contained more species, more individuals and had differing taxonomic composition. When indexed as a proportion of subcatchment area, urbanisation did not correspond to a clear impact on macrofaunal composition; rather, the nature of the industry or activity was critical. Mudflats from subcatchments with industries producing organic wastes significantly differed from subcatchments with <1.3% cover of these industries. Functioning was conserved in mudflats experiencing current levels of enrichment, but this may decline with growing pressure from human populations. The results of this study illustrate that large-scale spatial data, such as from satellites, can be used to detect the cumulative effects of urbanisation when the pressures are highly resolved.
Molecular mechanism of the chitinolytic peroxygenase reaction
Authors: Bissaro Bastien , Streit Bennett , Isaksen Ingvild , Eijsink Vincent G. H. , Beckham Gregg T. , DuBois Jennifer L. , Røhr Åsmund K.
Published: January 2020

Significance

Biomass decomposition by microorganisms relies on a battery of enzymes, of which lytic polysaccharide monooxygenases (LPMOs) constitute a central player. LPMOs are notably able to disrupt the abundant recalcitrant carbohydrates cellulose and chitin and thus increase the overall rate of their degradation. It has recently been demonstrated that LPMOs prefer hydrogen peroxide over molecular oxygen to oxidize and cleave their substrates. Here, we explain through molecular simulations and experiments how a chitin-active LPMO activates hydrogen peroxide and catalyzes substrate hydrogen abstraction. Thereby, we reveal the molecular details of this unusual bioinorganic chemistry, which is of high relevance for the understanding of pathogenesis-defense mechanisms and biomass turnover.
Presynaptic MAST kinase controls opposing postsynaptic responses to convey stimulus valence in
Caenorhabditis elegans
Authors: Nakano Shunji , Ikeda Muneki , Tsukada Yuki , Fei Xianfeng , Suzuki Takamasa , Niino Yusuke , Ahluwalia Rhea , Sano Ayana , Kondo Rumi , Ihara Kunio , Miyawaki Atsushi , Hashimoto Koichi , Higashiyama Tetsuya , Mori Ikue
Published: January 2020

Presynaptic plasticity is known to modulate the strength of synaptic transmission. However, it remains unknown whether regulation in presynaptic neurons can evoke excitatory and inhibitory postsynaptic responses. We report here that the
Caenorhabditis elegans
homologs of MAST kinase, Stomatin, and Diacylglycerol kinase act in a thermosensory neuron to elicit in its postsynaptic neuron an excitatory or inhibitory response that correlates with the valence of thermal stimuli. By monitoring neural activity of the valence-coding interneuron in freely behaving animals, we show that the alteration between excitatory and inhibitory responses of the interneuron is mediated by controlling the balance of two opposing signals released from the presynaptic neuron. These alternative transmissions further generate opposing behavioral outputs necessary for the navigation on thermal gradients. Our findings suggest that valence-encoding interneuronal activity is determined by a presynaptic mechanism whereby MAST kinase, Stomatin, and Diacylglycerol kinase influence presynaptic outputs.
Neoproterozoic origin and multiple transitions to macroscopic growth in green seaweeds
Authors: Del Cortona Andrea , Jackson Christopher J. , Bucchini François , Van Bel Michiel , D’hondt Sofie , Škaloud Pavel , Delwiche Charles F. , Knoll Andrew H. , Raven John A. , Verbruggen Heroen , Vandepoele Klaas , De Clerck Olivier , Leliaert Frederik
Published: January 2020

The Neoproterozoic Era records the transition from a largely bacterial to a predominantly eukaryotic phototrophic world, creating the foundation for the complex benthic ecosystems that have sustained Metazoa from the Ediacaran Period onward. This study focuses on the evolutionary origins of green seaweeds, which play an important ecological role in the benthos of modern sunlit oceans and likely played a crucial part in the evolution of early animals by structuring benthic habitats and providing novel niches. By applying a phylogenomic approach, we resolve deep relationships of the core Chlorophyta (Ulvophyceae or green seaweeds, and freshwater or terrestrial Chlorophyceae and Trebouxiophyceae) and unveil a rapid radiation of Chlorophyceae and the principal lineages of the Ulvophyceae late in the Neoproterozoic Era. Our time-calibrated tree points to an origin and early diversification of green seaweeds in the late Tonian and Cryogenian periods, an interval marked by two global glaciations with strong consequent changes in the amount of available marine benthic habitat. We hypothesize that unicellular and simple multicellular ancestors of green seaweeds survived these extreme climate events in isolated refugia, and diversified in benthic environments that became increasingly available as ice retreated. An increased supply of nutrients and biotic interactions, such as grazing pressure, likely triggered the independent evolution of macroscopic growth via different strategies, including true multicellularity, and multiple types of giant-celled forms.
What music makes us feel: At least 13 dimensions organize subjective experiences associated with music across different cultures
Authors: Cowen Alan S. , Fang Xia , Sauter Disa , Keltner Dacher
Published: January 2020

Significance

Do our subjective experiences when listening to music show evidence of universality? And if so, what is the nature of these experiences? With data-driven methodological and statistical approaches, we examined the feelings evoked by 2,168 music excerpts in the United States and China. We uncovered 13 distinct types of experiences that people across 2 different cultures report in listening to music of different kinds. Categories such as “awe” drive the experience of music more so than broad affective features like valence. However, emotions that scientists have long treated as discrete can be blended together. Our results provide answers to long-standing questions about the nature of the subjective experiences associated with music.
Cotranslational folding allows misfolding-prone proteins to circumvent deep kinetic traps
Authors: Bitran Amir , Jacobs William M. , Zhai Xiadi , Shakhnovich Eugene
Published: January 2020

Many large proteins suffer from slow or inefficient folding in vitro. It has long been known that this problem can be alleviated in vivo if proteins start folding cotranslationally. However, the molecular mechanisms underlying this improvement have not been well established. To address this question, we use an all-atom simulation-based algorithm to compute the folding properties of various large protein domains as a function of nascent chain length. We find that for certain proteins, there exists a narrow window of lengths that confers both thermodynamic stability and fast folding kinetics. Beyond these lengths, folding is drastically slowed by nonnative interactions involving C-terminal residues. Thus, cotranslational folding is predicted to be beneficial because it allows proteins to take advantage of this optimal window of lengths and thus avoid kinetic traps. Interestingly, many of these proteins’ sequences contain conserved rare codons that may slow down synthesis at this optimal window, suggesting that synthesis rates may be evolutionarily tuned to optimize folding. Using kinetic modeling, we show that under certain conditions, such a slowdown indeed improves cotranslational folding efficiency by giving these nascent chains more time to fold. In contrast, other proteins are predicted not to benefit from cotranslational folding due to a lack of significant nonnative interactions, and indeed these proteins’ sequences lack conserved C-terminal rare codons. Together, these results shed light on the factors that promote proper protein folding in the cell and how biomolecular self-assembly may be optimized evolutionarily.
Object clitic production in French-speaking L2 children and children with SLI
Authors: Scheidnes Maureen , Tuller Laurice , Prévost Philippe
Published: January 2020

This study examines French object clitic production in 20 typically developing L2 children (L1 English) compared to 19
monolingual children with SLI. We collected spontaneous and elicitation data twice at a one-year interval (T1, T2) in order to better
evaluate the impact of age- and time-related factors on the L2-SLI comparison, as well as the impact of proficiency and working memory on
object clitic production. The data revealed considerable group overlap at T1 in both tasks, but the L2 children produced significantly more
object clitics than the SLI group at T2 in spontaneous language, thus suggesting that the L2-SLI overlap decreases when the L2 children have
more language exposure. In elicitation, clitic production in both groups increased from T1 to T2 when all clitic types were included, but
when only 3p accusative clitics were analyzed, the L2 children outperformed the SLI group. Age played an important role in elicitation in
both groups, thus suggesting that mature performance systems, including unimpaired working memory, are required for object clitic production
in this task. Language-related measures were linked to both tasks, thus suggesting that object clitic production is particularly sensitive
to overall language proficiency, possibly because of issues with resource allocation.
Has “Grain for Green” threaten food security on the Loess Plateau of China?
Authors: Shi Peng , Feng Zhaohong , Gao Haidong , Li Peng , Zhang Xiaoming , Zhu Tiantian , Li Zhanbin , Xu Guoce , Ren Zongping , Xiao Lie
Published: January 2020

There is debating over the question of whether the large-scale ‘Grain for Green’ program on the Loess Plateau of China threatens regional food security. Self-sufficiency index and cropland pressure index were used to assess food security on the Loess Plateau after the implementation of revegetation program. The results showed that the ‘Grain for Green’ program initially had a considerable impact on regional food security, where grain yield fell from 1999 to 2001, resulting in a lower grain self-sufficiency and increased farmland stress. Subsequently, grain yield in this region increased due to the elevated agricultural material input and increased construction of terraces and check dams. The grain self-sufficiency index would have increased to 96.55% if there were improvements to the agricultural conditions, such as fertilization and irrigation, which would have resulted in an increase in the crop yield per unit of 20%. However, the grain self-sufficiency increased to 105.25% via the construction of terraces and check dams. Thus, the government should further expand the ‘Grain for Green’ program in coordination with improvements to the agricultural production conditions and the construction of terraces and check dams on the Loess Plateau.
Coherent Transfer of Excitation in a Nanomechanical Artificial Lattice*
Authors: Zhang Liang , Tian Tian , Huang Pu , Lin Shaochun , Du Jiangfeng
Published: January 2020

We realize a coherent transfer of mechanical excitation in a finely controlled artificial nanomechanical lattice. We also realize strong dynamic coupling between adjacent high-Q mechanical resonators, via modulated dielectric force at the frequency difference between them. An excitation transfer across a lattice consisting of 7 nanobeams is observed by applying a design sequence of switching for couplings, with the final effective population reaching 0.94. This work not only demonstrates the ability to fully control an artificial lattice but also provides an efficient platform for studying complicated dynamics in one-dimensional systems.
On the Nonlinear Growth of Multiphase Richtmyer–Meshkov Instability in Dilute Gas-Particles Flow*
Authors: Zheng Huan , Chen Qian , Meng Baoqing , Zeng Junsheng , Tian Baolin
Published: January 2020

We discuss evolutions of nonlinear features in Richtmyer–Meshkov instability (RMI), which are known as spikes and bubbles. In single-phase RMI, the nonlinear growth has been extensively studied but the relevant investigation in multiphase RMI is insufficient. Therefore, we illustrate the dynamic coupling behaviors between gas phase and particle phase and then analyze the growth of the nonlinear features theoretically. A universal model is proposed to describe the nonlinear finger (spike and bubble) growth velocity qualitatively in multiphase RMI. Both the effects of gas and particles have been taken into consideration in this model. Further, we derive the analytical expressions of the nonlinear growth model in limit cases (equilibrium flow and frozen flow). A novel compressible multiphase particle-in-cell (CMP-PIC) method is used to validate the applicability of this model. Numerical finger growth velocity matches well with our model. The present study reveals that particle volume fraction, particle density and Stokes number are the three key factors, which dominate the interphase momentum exchange and further induce the unique property of multiphase RMI.
The Unexpected Stability of Hydrazine Molecules in Hydrous Environment under Pressure*
Authors: Jiang Shu-Qing , Yang Xue , Huang Xiao-Li , Huang Yan-Ping , Li Xin , Cui Tian
Published: January 2020

The incomplete decomposition product of metastable hydrazine (N2H4) instead of the energetically favorable ammonia (NH3) upon decompression is one drawback in applications of energetic material oligomeric hydronitrogens. We explore the stability of hydrazine molecules in hydrazine hydrate (N2H4·H2O) under pressure in diamond anvil cells (DACs) combined with in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD) measurements. The results show that one NH2 branch forms NH3 group by hydrogen bonds between hydrazine and water molecules after the sample crystallizes at 3.2 GPa. The strengthening hydrogen bonds cause the torsion of hydrazine molecules and further dominate a phase transition at 7.2 GPa. Surprisingly, the NN single bonds are strengthened with increasing pressure, which keeps the hydrazine molecules stable up to the ultimate pressure of 36 GPa. Furthermore, the main diffraction patterns show continuous shift to higher degrees in the whole pressure range while some weak lines disappear above 8.2 GPa. The present peak-indexing results of the diffraction patterns with Materials Studio show that the phase transition occurs in the same monoclinic crystal system. Upon decompression, all of the hydrazine molecules extract from hydrazine hydrate crystal at 2.3 GPa, which may provide a new way to purify hydrazine from hydrate.
An Incremental Model for Defect Production upon Cascade Overlapping*
Authors: Wang Yi , Lai Wensheng , Li Jiahao
Published: January 2020

An analytic incremental model is proposed to predict the defect production upon cascade overlapping. By resolving the coupled annealing events during cascade overlapping, this model handles cascade overlapping with multiple pre-existing defects of different sizes and number densities. The model is first parameterized and then applied to bcc-Fe. The proposed model satisfyingly reproduces the defect production obtained by molecular dynamics simulations with various radiation damage levels and defect cluster size distributions. The present model provides an essential description of the primary source of radiation damage, especially for high dose irradiation, and could be used in conjunction with reactive diffusion models for better understanding of radiation damage.
Ferromagnetism in Layered Metallic Fe1/4TaS2 in the Presence of Conventional and Dirac Carriers*
Authors: Wang Jin-Hua , Quan Ya-Min , Liu Da-Yong , Zou Liang-Jian
Published: January 2020

We present the microscopic origin of the ferromagnetism of Fe0.25TaS2 and its finite-temperature magnetic properties. The band structures of Fe0.25TaS2 are first obtained by the first-principles calculations and it is found that both conventional and Dirac carriers coexist in metallic Fe0.25TaS2. Accordingly, considering the spin-orbit coupling of Fe 3d ion, we derive an effective Ruderman–Kittle–Kasuya–Yosida-type Hamiltonian between Fe spins in the presence of both the conventional parabolic-dispersion and the Dirac linear-dispersion carriers, which contains a Heisenberg-like, an Ising-like and an XY-like term. In addition, we obtain the ferromagnetic Curie temperature T
c by using the cluster self-consistent field method. Our results could address not only the high ferromagnetic Curie temperature but also the large magnetic anisotropy in Fe
x
TaS2.
Centrality anomalies in complex networks as a result of model over-simplification
Authors: Alves Luiz G A , Aleta Alberto , Rodrigues Francisco A , Moreno Yamir , Nunes Amaral Luís A
Published: January 2020

Tremendous advances have been made in our understanding of the properties and evolution of complex networks. These advances were initially driven by information-poor empirical networks and theoretical analysis of unweighted and undirected graphs. Recently, information-rich empirical data complex networks supported the development of more sophisticated models that include edge directionality and weight properties, and multiple layers. Many studies still focus on unweighted undirected description of networks, prompting an essential question: how to identify when a model is simpler than it must be? Here, we argue that the presence of centrality anomalies in complex networks is a result of model over-simplification. Specifically, we investigate the well-known anomaly in betweenness centrality for transportation networks, according to which highly connected nodes are not necessarily the most central. Using a broad class of network models with weights and spatial constraints and four large data sets of transportation networks, we show that the unweighted projection of the structure of these networks can exhibit a significant fraction of anomalous nodes compared to a random null model. However, the weighted projection of these networks, compared with an appropriated null model, significantly reduces the fraction of anomalies observed, suggesting that centrality anomalies are a symptom of model over-simplification. Because lack of information-rich data is a common challenge when dealing with complex networks and can cause anomalies that misestimate the role of nodes in the system, we argue that sufficiently sophisticated models be used when anomalies are detected.
Measurements of decay branching fractions of

in associated

production at the CEPC *
Authors: Bai Yu , Chen Chun-Hui , Fang Ya-Quan , Li Gang , Ruan Man-Qi , Shi Jing-Yuan , Wang Bo , Kong Pan-Yu , Lan Bo-Yang , Liu Zhan-Feng
Published: January 2020

The high-precision measurement of Higgs boson properties is one of the primary goals of the Circular Electron Positron Collider (CEPC). The measurements of

decay branching fraction in the CEPC experiment is presented, considering a scenario of analysing 5000 fb-1

collision data with the center-of-mass energy of 250 GeV. In this study the Higgs bosons are produced in association with a pair of leptons, dominantly mediated by the ZH production process. The statistical uncertainty of the signal cross section is estimated to be about 1% in the

final state, and approximately 5%-10% in the

final states. In addition, the main sources of the systematic uncertainties and their impacts to the measurements of branching fractions are discussed. This study demonstrates the potential of precise measurement of the hadronic final states of the Higgs boson decay at the CEPC, and will provide key information to understand the Yukawa couplings between the Higgs boson and quarks, which are predicted to be the origin of quarks’ masses in the standard model.
Measurement of the differential cross sections and angle-integrated cross sections of the 6Li(n, t)4He reaction from 1.0 eV to 3.0 MeV at the CSNS Back-n white neutron source *
Authors: Bai Huaiyong , Fan Ruirui , Jiang Haoyu , Cui Zengqi , Hu Yiwei , Zhang Guohui , Chen Zhenpeng , Jiang Wei , Yi Han , Tang Jingyu , Zhou Liang , An Qi , Bao Jie , Cao Ping , Chen Qiping , Chen Yonghao , Cheng Pinjing , Feng Changqing , Gu Minhao , Guo Fengqin , Han Changcai , Han Zijie , He Guozhu , He Yongcheng , He Yuefeng , Huang Hanxiong , Huang Weiling , Huang Xiru , Ji Xiaolu , Ji Xuyang , Jing Hantao , Kang Ling , Kang Mingtao , Li Bo , Li Lun , Li Qiang , Li Xiao , Li Yang , Li Yang , Liu Rong , Liu Shubin , Liu Xingyan , Luan Guangyuan , Ma Yinglin , Ning Changjun , Qi Binbin , Ren Jie , Ruan Xichao , Song Zhaohui , Sun Hong , Sun Xiaoyang , Sun Zhijia , Tan Zhixin , Tang Hongqing , Wang Pengcheng , Wang Qi , Wang Taofeng , Wang Yanfeng , Wang Zhaohui , Wang Zheng , Wen Jie , Wen Zhongwei , Wu Qingbiao , Wu Xiaoguang , Wu Xuan , Xie Likun , Yang Yiwei , Yu Li , Yu Tao , Yu Yongji , Zhang Jing , Zhang Linhao , Zhang Liying , Zhang Qingmin , Zhang Qiwei , Zhang Xianpeng , Zhang Yuliang , Zhang Zhiyong , Zhao Yingtan , Zhou Zuying , Zhu Danyang , Zhu Kejun , Zhu Peng
Published: January 2020

The 6Li(n, t)4He reaction was measured as the first experiment involving neutron-induced charged particle emission reactions at the CSNS (China Spallation Neutron Source) Back-n white neutron source. The differential cross-sections of the 6Li(n,t)4He reaction at 15 detection angles ranging from 19.2° to 160.8° are obtained from 1.0 eV to 3.0 MeV at 80 neutron energy points; for 50 energy points below 0.1 MeV they are reported for the first time. The results indicate that the anisotropy of the emitted tritium is noticeable above E
n = 100 eV. The angle-integrated cross-sections are also obtained. The present differential cross-sections agree in general with the previous evaluations, but there are some differences in the details. More importantly, the present results indicate that the cross-sections of the 6Li(n, t)4He reaction might be overestimated by most evaluations in the 0.5 − 3.0 MeV region, although they are recommended as standards below 1.0 MeV.
Reheating and entropy perturbations in fibre inflation *
Authors: Gu Bao-Min , Brandenberger Robert
Published: January 2020

We study reheating in some one and two field realizations of fibre inflation. We find that reheating begins with a phase of preheating in which long wavelength fluctuation modes are excited. In two field models there is a danger that the parametric amplification of infrared fluctuations in the second scalar field - associated with an entropy mode - might induce an instability of the curvature fluctuations. We show that, at least in the models we consider, the entropy mode has a sufficiently large mass to prevent this instability. Hence, from the point of view of reheating the models we consider are well-behaved.