bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoscale thermal transport across an GaAs/AlGaAs heterostructure interface
Authors: Gorfien Matthew , Wang Hailong , Chen Long , Rahmani Hamidreza , Yu Junxiao , Zhu Pengfei , Chen Jie , Wang Xuan , Zhao Jianhua , Cao Jianming
Published: March 2020

We studied the thermal transport across a GaAs/AlGaAs interface using time-resolved Reflection High Energy Electron Diffraction. The lattice temperature change of the GaAs nanofilm was directly monitored and numerically simulated using diffusive heat equations based on Fourier's Law. The extracted thermal boundary resistances (TBRs) were found to decrease with increasing lattice temperature imbalance across the interface. The TBRs were found to agree well with the Diffuse Mismatch Model in the diffusive transport region, but showed evidence of further decrease at temperatures higher than Debye temperature, opening up questions about the mechanisms governing heat transfer at interfaces between very similar semiconductor nanoscale materials under highly non-equilibrium conditions.
Strain-tuned magnetic anisotropy in sputtered thulium iron garnet ultrathin films and TIG/Au/TIG valve structures
Authors: Vilela Gilvânia , Chi Hang , Stephen Gregory , Settens Charles , Zhou Preston , Ou Yunbo , Suri Dhavala , Heiman Don , Moodera Jagadeesh S.
Published: March 2020

Defining the magnetic anisotropy for in-plane or out-of-plane easy axis in ferrimagnetic insulators films by controlling the strain while maintaining high-quality surfaces is desirable for spintronic and magnonic applications. We investigate ways to tune the anisotropy of amorphous sputtered ultrathin thulium iron garnet (TIG) films and, thus, tailor their magnetic properties by the thickness (7.5–60 nm), substrate choice (GGG and SGGG), and crystallization process. We correlate morphological and structural properties with the magnetic anisotropy of post-growth annealed films. 30 nm thick films annealed at 600 °C show compressive strain favoring an in-plane magnetic anisotropy, whereas films annealed above 800 °C are under a tensile strain leading to a perpendicular magnetic anisotropy. Air-annealed films present a high degree of crystallinity and magnetization saturation close to the bulk value. These results lead to the successful fabrication of trilayers TIG/Au/TIG with coupling between the TIG layers depending on Au thickness. These results will facilitate the use of TIG to create various in situ clean hybrid structures for fundamental interface exchange studies and toward the development of complex devices. Moreover, the sputtering technique is advantageous as it can be easily scaled up for industrial applications.
Global organization of three-dimensional, volume-preserving flows: Constraints, degenerate points, and Lagrangian structure
Authors: Ravu Bharath , Metcalfe Guy , Rudman Murray , Lester Daniel R. , Khakhar Devang V.
Published: March 2020

Global organization of three-dimensional (3D) Lagrangian chaotic transport is difficult to infer without extensive computation. For 3D time-periodic flows with one invariant, we show how constraints on deformation that arise from volume-preservation and periodic lines result in resonant degenerate points that periodically have zero net deformation. These points organize all Lagrangian transport in such flows through coordination of lower-order and higher-order periodic lines and prefigure unique transport structures that arise after perturbation and breaking of the invariant. Degenerate points of periodic lines and the extended 3D structures associated with them are easily identified through the trace of the deformation tensor calculated along periodic lines. These results reveal the importance of degenerate points in understanding transport in one-invariant fluid flows.
Evaluating higher moments in the transverse Kelvin–Helmholtz instability by full kinetic simulation
Authors: Umeda Takayuki
Published: March 2020

Approximated forms of the third and fourth moments of a velocity distribution function are derived by using a perturbed velocity distribution function around a characteristic spatial scale on the gyroradius derived by Thompson [Rep. Prog. Phys. 24, 363–424 (1961)]. Then, they are evaluated by using a two-dimensional full kinetic Vlasov simulation result of the transverse Kelvin–Helmholtz instability. It is shown that the derived form of the fourth moment is in agreement with the one calculated from the distribution function data of the Vlasov simulation. On the other hand, the derived form of the third moment is quite different from the one (i.e., heat flux tensor) calculated from the distribution function data of the Vlasov simulation. The results suggest that the perturbed velocity distribution function of Thompson needs an improvement.
Hole expansion from a bubble at a liquid surface
Authors: Krishnan Sangeeth , Puthenveettil Baburaj A. , Hopfinger E. J.
Published: March 2020

For millimetre to micron sized bubbles, floating at the free surface of different low viscosity fluids with different surface tensions, and then collapsing, we study the ensuing expansion of the outer radius of the hole (ro) at the free surface, as well as its velocity of expansion (uo). Since the thin film cap of the bubble disintegrates before the hole in it reaches the static rim, the hole expansion at intermediate times occurs as if it initiates at the bubble’s static rim of radius Rr; the evolution of ro then results to be a strong function of gravity, since Rr depends strongly on the bubble radius R. A scaling analysis, which includes the increase in the tip radius due to mass accumulation and the resulting change in the retraction force, along with the gravity effects by considering the hole radius in excess of its initial static radius, re = ro − Rr, results in a novel scaling law re/R∼(t/tc)4/7, where tc=ρR3/σ is the capillary time scale; this scaling law is shown to capture the evolution of the hole radii in the present study. The dimensionless velocities of hole expansion, namely, the Weber numbers of hole expansion, Weo=ρuo2R/σ, scale as Weo∼(t/tc)−6/7, independent of gravity effects, matching the observations. We also show that these Weber numbers, which reduce with time, begin with a constant initial Weber number of 64, while the viscous limit of the present phenomena occurs when the bubble Ohnesorge number Oh=μ/σρR≃0.24.
Magnetization switching induced by magnetic field and electric current in perpendicular TbIG/Pt bilayers
Authors: Chen Huanjian , Cheng Dashuai , Yang Huanglin , Wang Daike , Zhou Shiming , Shi Zhong , Qiu Xuepeng
Published: March 2020

Magnetic insulators (MIs) have attracted great attention because of their low Gilbert damping, long spin transmission length, and no Ohmic loss. In this study, the high quality TbIG films with perpendicular magnetic anisotropy were epitaxially grown on GGG (111) substrates. In TbIG/Pt bilayers, the angular dependence of coercivity is found to obey the Kondorsky model, suggesting the magnetization reversal mechanism of magnetic domain nucleation and expansion. The transverse component of spin Hall magnetoresistance (SMR), which is analogous to the planar Hall resistance in a ferromagnetic metal, is found to be about seven times larger than the SMR-induced anomalous Hall resistance (analogous to the anomalous Hall resistance in a ferromagnetic metal). Moreover, the phase diagrams of the current-induced magnetization switching with different angles and magnitudes of the assisting magnetic field were drawn for the TbIG/Pt bilayers. The current-induced damping-like effective field (HDL) characterized by the harmonic measurements was evaluated to be about 164 Oe/108 A cm−2. By providing a comprehensive investigation of magnetization switching behaviors in MIs, our results will promote the application of ultralow-dissipation MI based spintronic devices.
Optical and electronic properties of silver nanoparticles embedded in cerium oxide
Authors: Pelli Cresi Jacopo Stefano , Silvagni Enrico , Bertoni Giovanni , Spadaro Maria Chiara , Benedetti Stefania , Valeri Sergio , D’Addato Sergio , Luches Paola
Published: March 2020

Wide bandgap oxides can be sensitized to visible light by coupling them with plasmonic nanoparticles (NPs). We investigate the optical and electronic properties of composite materials made of Ag NPs embedded within cerium oxide layers of different thickness. The electronic properties of the materials are investigated by x-ray and ultraviolet photoemission spectroscopy, which demonstrates the occurrence of static charge transfers between the metal and the oxide and its dependence on the NP size. Ultraviolet-visible spectrophotometry measurements show that the materials have a strong absorption in the visible range induced by the excitation of localized surface plasmon resonances. The plasmonic absorption band can be modified in shape and intensity by changing the NP aspect ratio and density and the thickness of the cerium oxide film.
Structure of two-dimensional Fe3O4
Authors: Merte Lindsay R. , Olsson Pär A. T. , Shipilin Mikhail , Gustafson Johan , Bertram Florian , Zhang Chu , Grönbeck Henrik , Lundgren Edvin
Published: March 2020

We have investigated the structure of an ultrathin iron oxide phase grown on Ag(100) using surface x-ray diffraction in combination with Hubbard-corrected density functional theory (DFT+U) calculations. The film exhibits a novel structure composed of one close-packed layer of octahedrally coordinated Fe2+ sandwiched between two close-packed layers of tetrahedrally coordinated Fe3+ and an overall stoichiometry of Fe3O4. As the structure is distinct from bulk iron oxide phases and the coupling with the silver substrate is weak, we propose that the phase should be classified as a metastable two-dimensional oxide. The chemical and physical properties are potentially interesting, thanks to the predicted charge ordering between atomic layers, and analogy with bulk ferrite spinels suggests the possibility of synthesis of a whole class of two-dimensional ternary oxides with varying electronic, optical, and chemical properties.
Giant photostriction of CaCu3Ti4O12 ceramics under visible light illumination
Authors: Li Xiu , Chen Chen , Zhang Faqiang , Huang Xintang , Yi Zhiguo
Published: March 2020

Ferroelectrics with a perovskite structure, exhibiting strong coupling between photons, carriers, and phonons, have been demonstrated to show a strong photostrictive response. Limited by the optical bandgap, most of the reported ferroelectric perovskites respond only to UV light or weakly respond to visible light below 550 nm. Herein, the photostrictive performance of CaCu3Ti4O12 (CCTO) ceramics, with a low bandgap of ∼1.5 eV (ideal for solar spectrum absorption), is comprehensively investigated. Although the compound presents no ferroelectricity, in general, a giant photostriction of ∼10−3 with a large photostrictive efficiency of ∼10−11 m3/W in CCTO ceramics is observed by applying purple (405 nm), green (520 nm), and red (655 nm) laser illumination. Evidenced by the XRD peak shifts under external laser illumination and the phonon mode shifts via the power-dependent Raman spectrum, the light-induced non-thermal deformation in CCTO is attributed to the enhanced stretching of O–Ti–O chains and the distortions of TiO6 octahedrons. The excellent and uniform photostrictive performance of CCTO ceramics in the visible-light region makes them potential candidates for practical applications in next-generation photo-driven electromechanical devices.
Enhancement of proton acceleration and conversion efficiency by double laser pulses plasma interactions
Authors: Rahman Obaydur , Tong Sheng-Fei , Sheng Zheng-Mao
Published: March 2020

We report an efficient scheme to improve the proton acceleration and energy conversion efficiency by using double laser pulses with foil interaction. We find a significant increase in the peak energy, the total number, and the maximum energy of the accelerated protons for the double laser pulses with foil interaction compared to those in the single laser pulse case, while the total laser energy is kept constant. The role of the first pulse (pre-pulse) is to change the target electron distribution and reduce the reflection of succeeding laser pulse and hence enhance the laser absorption so that more energy of the second laser pulse (main pulse) is converted into the particle energy. The main pulse preferentially accelerates the slower electrons located deeper in the plasma, and it also accelerates the fast electrons due to volumetric heating. Finally, the protons are accelerated to high energy due to the laser break-out afterburner, when the target becomes relativistically transparent to the laser pulse.
Unsteady behaviors of separated flow over a finite blunt plate at different inclination angles
Authors: Deng Yifan , He Chuangxin , Wang Peng , Liu Yingzheng
Published: March 2020

This study comprises an extensive analysis of unsteady behaviors of a separated flow over a finite blunt plate at three different inclination angles, θ = 0°, 3°, and 6°. It was found that these three distinctly different flow patterns resulted from increasing inclination angles: reattachment, intermittent reattachment, and non-reattachment. The separated flow fields and wall-pressure fluctuations were experimentally measured with planar particle image velocimetry (PIV) operating at 1 Hz and a microphone array sampling at 5 kHz, respectively. Flow patterns were discussed in terms of the time-averaged flow fields and distributions of the statistical quantities (i.e., the reverse-flow intermittency, or velocity fluctuation intensity). A slender separation bubble formed in the front area of the plate (0 < x/D < 4.6) in the system where θ = 0° and then it enlarged to the whole surface of the plate in the system where θ = 3°. In contrast, in the system where θ = 6°, the plate surface was entirely engulfed by a large recirculation zone extending to the near-wake region. In the wall-pressure fluctuation analysis, two characteristic frequencies, St = 0.036 and 0.107, could be readily identified in all three systems; these corresponded to the flapping of separation bubble and the shedding of large-scale vortical structures, respectively. In addition, in the system where θ = 0°, wall-pressure fluctuations of the Karman vortex were detected at St = 0.154 but were suppressed in the systems where θ = 3° and 6° due to the extensive interaction between the shedding of large-scale vortical structures and the unsteady wake. Subsequently, a field-programmable gate array taking full advantage of dynamic mode decomposition (DMD) on the wall-pressure fluctuations was constructed, and a real-time conditional signal corresponding to individual unsteady behavior was generated to fire the phase-locking PIV measurement. High-resolution spatiotemporal evolutions of dominant flow behaviors (i.e., enlargement-and-shrinkage motion of the separation bubble and shedding motion of the large-scale vortical structures) were determined. In the system where θ = 6°, a separation bubble enlarged and shrank dramatically together with the shedding of large-scale vortical structures, leading to a large recirculation zone over the blunt plate, distinct from the behavior in the systems where θ = 0° and 3°. Finally, a joint dominant mode analysis of flow structures and wall-pressure fluctuations was further evaluated, which delineated the complex unsteady processes in separated flow clearly and provided more information and references for other studies on wind engineering, fluid-induced structure vibrations, and acoustic emissions.
Tunable hierarchical wrinkling: From models to applications
Authors: Ma Long , He Linghui , Ni Yong
Published: March 2020

Wrinkled surfaces have attracted enormous interest during the past years due to their various wrinkling patterns and impressive multifunctional properties. With the growing demand of numerous potential applications, it is desirable to uncover the formation mechanism and develop fabrication methods for tunable wrinkles, in particular, for hierarchical wrinkle that has spatially varying wavelength and amplitude. In this tutorial, we comprehensively discuss the possible mechanism of the formation of hierarchical wrinkles, including the role of elasticity gradient in film–substrate systems, the effect of boundary confinement, the sequential multistep strain-releasing method in a multilayer system, etc. The formation conditions and morphological features of various hierarchical wrinkling patterns are outlined. Lastly, representative applications of hierarchical wrinkling are briefly summarized as well.
Dynamic evolutionary metamodel analysis of the vulnerability of complex systems
Authors: Wang Binglin , Duan Xiaojun , Yan Liang , Zhao Hua
Published: March 2020

Because the collapse of complex systems can have severe consequences, vulnerability is often seen as the core problem of complex systems. Multilayer networks are powerful tools to analyze complex systems, but complex networks may not be the best choice to mimic subsystems. In this work, a cellular graph (CG) model is proposed within the framework of multilayer networks to analyze the vulnerability of complex systems. Specifically, cellular automata are considered the vertices of a dynamic graph-based model at the microlevel, and their links are modeled by graph edges governed by a stochastic model at the macrolevel. A Markov chain is introduced to illustrate the evolution of the graph-based model and to obtain the details of the vulnerability evolution with low-cost inferences. This CG model is proven to describe complex systems precisely. The CG model is implemented with two actual organizational systems, which are used on behalf of the typical flat structure and the typical pyramid structure, respectively. The computational results show that the pyramid structure is initially more robust, while the flat structure eventually outperforms it when being exposed to multiple-rounds strike. Finally, the sensitivity analysis results verify and strengthen the reliability of the conclusions.
Linear global stability of liquid metal mixed convection in a horizontal bottom-heating duct under strong transverse magnetic field
Authors: Hu Jun
Published: March 2020

Two-dimensional steady-state solutions of liquid metal mixed convection in a horizontal bottom-heating duct under a strong magnetic field are first computed numerically by the Newton iteration method along with the spatial discretization of the Taylor–Hood finite element. Two branches of steady solutions with symmetrical rolls and a pair of asymmetrical solutions with a single roll are identified and can be regarded as the base flow for linear global stability analysis. The symmetrical steady solution for the first branch has a nearly uniform distribution for the temperature field in the transverse direction, while the second branch occurs at much larger Grashof numbers and the temperature field becomes nonuniform transversely. The linear stability analysis is performed for a fixed Reynolds number and Prandtl number with Re = 5000 and Pr = 0.0321. For the symmetrical rolls of the first branch, with an increase in the Grashof number, two-dimensional stationary instabilities first occur at small Hartmann numbers, while three-dimensional oscillatory instabilities first appear at moderate or large Hartmann numbers. From the further study of the two-dimensional instabilities, it is revealed that the asymmetrical solution is actually bifurcated supercritically from the symmetrical solution at a two-dimensional critical Grashof number. In addition, the critical curve of the Grashof number with respect to the Hartmann number for the three-dimensional oscillatory mode shows that there exists a minimum critical Grashof number, which occurs at a moderate Hartmann number. The critical curves of the one-roll asymmetrical solution are also exhibited and determined by two three-dimensional oscillatory unstable modes. It is revealed that there exists a minimum Hartmann number below which the asymmetrical steady-state can always remain stable for all Grashof numbers (5 × 105–107). The energy analyses at the oscillatory critical thresholds with different Hartmann numbers are performed to exhibit that buoyancy is the dominant destabilizing term, and the magnetic force is always the main stabilization term for both symmetrical and asymmetrical solutions. In addition, both streamwise and cross-sectional shears of the basic flow are important for the determination of the linear stability boundary of the asymmetrical solution.
Tuning magnetic anisotropy in thin films helps create magnon valves
Authors: Bandari Anashe
Published: March 2020

Tuning of perpendicular magnetic anisotropy in iron garnets is used to create trilayer valve structures.
Recovery kinetics in high temperature annealed AlN heteroepitaxial films
Authors: Washiyama Shun , Guan Yan , Mita Seiji , Collazo Ramón , Sitar Zlatko
Published: March 2020

Based on the experimental dislocation annihilation rates, vacancy core diffusion-controlled dislocation climb was found as a dominant recovery mechanism in high temperature annealing of AlN heteroepitaxial films. Dislocation annihilation mechanisms via dislocation glide (with or without kinks) and vacancy bulk diffusion were found to be less significant. Cross-slip was also ruled out as a possible mechanism as a majority of dislocations in heteroepitaxial AlN films are threading edge dislocations. While dislocation climb through both vacancy bulk and core diffusion could offer a plausible explanation of the recovery process, the activation energy for the vacancy core diffusion-controlled dislocation climb was relatively low (4.3 ± 0.1 eV), as estimated from an Arrhenius plot. The validity of the vacancy core diffusion mechanism was also supported by a large vacancy mean free path (∼240 nm), which was comparable to the sample thickness and thus the average dislocation length. Finally, the experimentally observed dislocation density reduction as a function of the annealing temperature and time was in good agreement with the vacancy core diffusion mechanism.
Development of a solvent-polarizable three-dimensional reference interaction-site model theory
Authors: Yoshida Norio , Yamaguchi Tsuyoshi
Published: March 2020

Solvent polarization around a polar solute molecule plays an essential role in determining the electronic and thermodynamic properties of solutions. In this study, a solvent-polarizable model in response to solute polarization is proposed, which is coupled with a three-dimensional reference interaction-site model theory. The charge-response kernel is used to describe solvent polarizability, and four different coupling schemes are assessed. The most feasible behavior scheme among them is the one that incorporates responses not only to solute polarization but also to solute-induced solvent polarization. The numerical results indicated that solvent molecules near the polar solute show significant polarization, and therefore, the model proposed here is useful for considering the solvation process and thermodynamics of polar solute molecules.
Review of Scientific Instruments New Products
Authors: Mandelis Andreas
Published: March 2020

In order to supplement manufacturers’ information, this department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials which supersede earlier data or suggest new research applications.
Ecological improvement by restoration on the Jialu River: water quality, species richness and distribution
Authors: Kong Xiangshi , Tian Kai , Jia Yanyan , He Zaihua , Song Siyuan , He Xingbing , Xiang Changguo , An Shuqing , Tian Xingjun
Published: March 2020

The Jialu River has experienced serious water quality deterioration and biodiversity decline. An ecological restoration project was undertaken. We investigated water quality, species richness and distribution before and after restoration to describe ecological improvements on the Jialu River. After the project, total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD) and ammonium nitrogen (NH4+-N) decreased by 38.69, 40.52, 39.06 and 45.07% respectively. Concentrations of these indices were maintained at steady levels after restoration, indicating stable purification capacity had been established. However, TN, TP and NH4+-N concentrations were still higher than Level V of the Chinese surface water standards. In all, 155 species, belonging to 94 families, were found, with shore plants accounting for the largest proportion (26.53%). The biota showed different distribution patterns over space and time, except for species of zooplankton and phytoplankton, which were evenly distributed over space and time. Most species (71.71%) occurred in only one or two sites. Compared with July 2013, by July 2015 species richness had increased, on average, 65.61%. Furthermore, 31 novel native species were found in July 2015, covering the main functional groups (hydrophytes, zoobenthos and fishes). The recovery of an intact food chain as a result of the project facilitated water purification in the short term and the return of birds to the Jialu River in the long term. This study evaluated the recovery of the Jialu River and the results will inform future ecosystem restoration projects.
Walking through a 'phoenix landscape': hiker surveys reveal nuanced perceptions of wildfire effects
Authors: Weill Alexandra M. , Watson Lauren M. , Latimer Andrew M.
Published: March 2020

Public opinion of wildfire is often perceived to be negative and in support of fire suppression, even though research suggests public opinions have become more positive over the past few decades. However, most prior work on this topic has focused on homeowners in forested regions. In this study, we shift the lens to hikers in a chaparral- and oak-savannah-dominated landscape that burned at high severity in 2015. We surveyed hikers before and after their hike about their familiarity and perceptions of local fire, and wildfire in the nation at large. We found hikers were familiar with topics such as prescribed fire and basic fire ecology, but knew little about local ecology or fire regimes. Post-hike perceptions of fire and feelings about wildfire in the USA were complex and heterogeneous, not predominantly negative. Contrary to frequent media descriptions of post-fire landscapes as ‘devastated’ or ‘moonscapes,’ many participants described the burned landscape with awe and admiration. These results suggest that residents of fire-prone landscapes may benefit from programming that emphasises benefits and challenges of fire in the local landscape and incorporates visits to local burned sites throughout the recovery period.
A better Amazon road network for people and the environment
Authors: Vilela Thais , Malky Harb Alfonso , Bruner Aaron , Laísa da Silva Arruda Vera , Ribeiro Vivian , Auxiliadora Costa Alencar Ane , Julissa Escobedo Grandez Annie , Rojas Adriana , Laina Alejandra , Botero Rodrigo
Published: March 2020

Significance

In the next 5 y, more than 10 thousand kilometers of roads will be built or improved in the Amazon. Well-designed projects can increase employment opportunities, reduce transport costs, and support regional development. However, roads will also drive deforestation, threatening biodiversity and ecosystem services, jeopardizing the welfare of indigenous people, and moving the biome toward irreversible shifts in vegetation. Data to support good decisions are remarkably scarce. Typical feasibility studies, where they exist, inadequately address environmental and social impacts and do not facilitate comparison across projects. This study contributes to informed decision-making by quantifying the environmental, social and economic effects of 75 planned projects. It demonstrates that fewer projects in carefully chosen locations would dramatically improve outcomes of all types.
Signing at the beginning versus at the end does not decrease dishonesty
Authors: Kristal Ariella S. , Whillans Ashley V. , Bazerman Max H. , Gino Francesca , Shu Lisa L. , Mazar Nina , Ariely Dan
Published: March 2020

Honest reporting is essential for society to function well. However, people frequently lie when asked to provide information, such as misrepresenting their income to save money on taxes. A landmark finding published in PNAS [L. L. Shu, N. Mazar, F. Gino, D. Ariely, M. H. Bazerman,
Proc. Natl. Acad. Sci. U.S.A.
109, 15197–15200 (2012)] provided evidence for a simple way of encouraging honest reporting: asking people to sign a veracity statement at the beginning instead of at the end of a self-report form. Since this finding was published, various government agencies have adopted this practice. However, in this project, we failed to replicate this result. Across five conceptual replications (
n
= 4,559) and one highly powered, preregistered, direct replication (
n
= 1,235) conducted with the authors of the original paper, we observed no effect of signing first on honest reporting. Given the policy applications of this result, it is important to update the scientific record regarding the veracity of these results.
Decoding across sensory modalities reveals common supramodal signatures of conscious perception
Authors: Sanchez Gaëtan , Hartmann Thomas , Fuscà Marco , Demarchi Gianpaolo , Weisz Nathan
Published: March 2020

An increasing number of studies highlight common brain regions and processes in mediating conscious sensory experience. While most studies have been performed in the visual modality, it is implicitly assumed that similar processes are involved in other sensory modalities. However, the existence of supramodal neural processes related to conscious perception has not been convincingly shown so far. Here, we aim to directly address this issue by investigating whether neural correlates of conscious perception in one modality can predict conscious perception in a different modality. In two separate experiments, we presented participants with successive blocks of near-threshold tasks involving subjective reports of tactile, visual, or auditory stimuli during the same magnetoencephalography (MEG) acquisition. Using decoding analysis in the poststimulus period between sensory modalities, our first experiment uncovered supramodal spatiotemporal neural activity patterns predicting conscious perception of the feeble stimulation. Strikingly, these supramodal patterns included activity in primary sensory regions not directly relevant to the task (e.g., neural activity in visual cortex predicting conscious perception of auditory near-threshold stimulation). We carefully replicate our results in a control experiment that furthermore show that the relevant patterns are independent of the type of report (i.e., whether conscious perception was reported by pressing or withholding a button press). Using standard paradigms for probing neural correlates of conscious perception, our findings reveal a common signature of conscious access across sensory modalities and illustrate the temporally late and widespread broadcasting of neural representations, even into task-unrelated primary sensory processing regions.
Small-molecule covalent bond formation at tyrosine creates a binding site and inhibits activation of Ral GTPases
Authors: Bum-Erdene Khuchtumur , Liu Degang , Gonzalez-Gutierrez Giovanni , Ghozayel Mona K. , Xu David , Meroueh Samy O.
Published: March 2020

Ral (Ras-like) GTPases are directly activated by oncogenic Ras GTPases. Mutant K-Ras (G12C) has enabled the development of covalent K-Ras inhibitors currently in clinical trials. However, Ral, and the overwhelming majority of mutant oncogenic K-Ras, are devoid of a druggable pocket and lack an accessible cysteine for the development of a covalent inhibitor. Here, we report that covalent bond formation by an aryl sulfonyl fluoride electrophile at a tyrosine residue (Tyr-82) inhibits guanine exchange factor Rgl2-mediated nucleotide exchange of Ral GTPase. A high-resolution 1.18-Å X-ray cocrystal structure shows that the compound binds to a well-defined binding site in RalA as a result of a switch II loop conformational change. The structure, along with additional high-resolution crystal structures of several analogs in complex with RalA, confirm the importance of key hydrogen bond anchors between compound sulfone oxygen atoms and Ral backbone nitrogen atoms. Our discovery of a pocket with features found on known druggable sites and covalent modification of a bystander tyrosine residue present in Ral and Ras GTPases provide a strategy that could lead to therapeutic agent targeting oncogenic Ras mutants that are devoid of a cysteine nucleophile.
Half-precessional cycle of thermocline temperature in the western equatorial Pacific and its bihemispheric dynamics
Authors: Jian Zhimin , Wang Yue , Dang Haowen , Lea David W. , Liu Zhengyu , Jin Haiyan , Yin Yaqian
Published: March 2020

Significance

The precessional insolation plays a critical role in modulating the low-latitude oceanographic changes through ENSO-like dynamics. While previous studies focused on the precessional insolation-induced low-latitude surface water changes, our well-dated, centennial-resolution proxy data and numerical simulation reveal the half-precession cycle of thermocline water temperature (TWT) in the western equatorial Pacific that directly linked to ENSO-like zonal temperature seesaw over the equatorial Pacific. These half-precessional TWT changes are proposed to originate from the interplay of subtropical-to-tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band. This work illustrates that the tropical thermocline water could bridge the meridional climatic processes and the east−west ENSO-like dynamics at orbital timescales.
Extreme weather events recorded by daily to hourly resolution biogeochemical proxies of marine giant clam shells
Authors: Yan Hong , Liu Chengcheng , An Zhisheng , Yang Wei , Yang Yuanjian , Huang Ping , Qiu Shican , Zhou Pengchao , Zhao Nanyu , Fei Haobai , Ma Xiaolin , Shi Ge , Dodson John , Hao Jialong , Yu Kefu , Wei Gangjian , Yang Yanan , Jin Zhangdong , Zhou Weijian
Published: March 2020

Significance

Reconstructing past extreme weather events, such as tropical cyclones and cold surges, using natural paleoclimate archives can lengthen the instrumental data and help us have a broader understanding of the range of weather variability not evident in instrumental record. However, the time resolution of current paleoarchives, from millennial to monthly at best, is usually too low to explore past weather events. Here we found that the
Tridacna
shells from South China Sea, western Pacific, have continuous daily growth bands, and several daily to hourly resolution biogeochemical proxy records were developed. Our results demonstrate that these records can record nearby tropical cyclones and cold surges, indicating that
Tridacna
shells have the potential to be an unprecedented ultra-high-resolution archive for paleoweather reconstructions.
Seasonal hysteresis of surface urban heat islands
Authors: Manoli Gabriele , Fatichi Simone , Bou-Zeid Elie , Katul Gabriel G.
Published: March 2020

Temporal dynamics of urban warming have been extensively studied at the diurnal scale, but the impact of background climate on the observed seasonality of surface urban heat islands (SUHIs) remains largely unexplored. On seasonal time scales, the intensity of urban–rural surface temperature differences (ΔTs) exhibits distinctive hysteretic cycles whose shape and looping direction vary across climatic zones. These observations highlight possible delays underlying the dynamics of the coupled urban–biosphere system. However, a general argument explaining the observed hysteretic patterns remains elusive. A coarse-grained model of SUHI coupled with a stochastic soil water balance is developed to demonstrate that the time lags between radiation forcing, air temperature, and rainfall generate a rate-dependent hysteresis, explaining the observed seasonal variations ofΔTs. If solar radiation is in phase with water availability, summer conditions cause strong SUHI intensities due to high rural evaporative cooling. Conversely, cities in seasonally dry regions where evapotranspiration is out of phase with radiation show a summertime oasis effect controlled by background climate and vegetation properties. These seasonal patterns of warming and cooling have significant implications for heat mitigation strategies as urban green spaces can reduceΔTsduring summertime, while potentially negative effects of albedo management during winter are mitigated by the seasonality of solar radiation.
Predictions drive neural representations of visual events ahead of incoming sensory information
Authors: Blom Tessel , Feuerriegel Daniel , Johnson Philippa , Bode Stefan , Hogendoorn Hinze
Published: March 2020

The transmission of sensory information through the visual system takes time. As a result of these delays, the visual information available to the brain always lags behind the timing of events in the present moment. Compensating for these delays is crucial for functioning within dynamic environments, since interacting with a moving object (e.g., catching a ball) requires real-time localization of the object. One way the brain might achieve this is via prediction of anticipated events. Using time-resolved decoding of electroencephalographic (EEG) data, we demonstrate that the visual system represents the anticipated future position of a moving object, showing that predictive mechanisms activate the same neural representations as afferent sensory input. Importantly, this activation is evident before sensory input corresponding to the stimulus position is able to arrive. Finally, we demonstrate that, when predicted events do not eventuate, sensory information arrives too late to prevent the visual system from representing what was expected but never presented. Taken together, we demonstrate how the visual system can implement predictive mechanisms to preactivate sensory representations, and argue that this might allow it to compensate for its own temporal constraints, allowing us to interact with dynamic visual environments in real time.
A regional nuclear conflict would compromise global food security
Authors: Jägermeyr Jonas , Robock Alan , Elliott Joshua , Müller Christoph , Xia Lili , Khabarov Nikolay , Folberth Christian , Schmid Erwin , Liu Wenfeng , Zabel Florian , Rabin Sam S. , Puma Michael J. , Heslin Alison , Franke James , Foster Ian , Asseng Senthold , Bardeen Charles G. , Toon Owen B. , Rosenzweig Cynthia
Published: March 2020

Significance

Impacts of global warming on agricultural productivity have been evaluated extensively. The implications of sudden cooling for global crop growth, however, are as yet little understood. While crop failures after historic volcanic eruptions are documented, a nuclear conflict can cause even more severe and longer-lasting climate anomalies. India and Pakistan are contributing to a de facto Asian arms race and the political instability in South Asia increasingly imposes a global threat. Based on comprehensive climate and crop model ensemble simulations, we provide critical quantitative information on how sudden cooling and perturbations of precipitation and solar radiation could disrupt food production and trade worldwide for about a decade—more than the impact from anthropogenic climate change by late century.
US life expectancy stalls due to cardiovascular disease, not drug deaths
Authors: Mehta Neil K. , Abrams Leah R. , Myrskylä Mikko
Published: March 2020

After decades of robust growth, the rise in US life expectancy stalled after 2010. Explanations for the stall have focused on rising drug-related deaths. Here we show that a stagnating decline in cardiovascular disease (CVD) mortality was the main culprit, outpacing and overshadowing the effects of all other causes of death. The CVD stagnation held back the increase of US life expectancy at age 25 y by 1.14 y in women and men, between 2010 and 2017. Rising drug-related deaths had a much smaller effect: 0.1 y in women and 0.4 y in men. Comparisons with other high-income countries reveal that the US CVD stagnation is unusually strong, contributing to a stark mortality divergence between the US and peer nations. Without the aid of CVD mortality declines, future US life expectancy gains must come from other causes—a monumental task given the enormity of earlier declines in CVD death rates. Reversal of the drug overdose epidemic will be beneficial, but insufficient for achieving pre-2010 pace of life expectancy growth.
Shared vision for a decarbonized future energy system in the United States
Authors: Miniard Deidra , Kantenbacher Joseph , Attari Shahzeen Z.
Published: March 2020

How do people envision the future energy system in the United States with respect to using fossil fuels, renewable energy, and nuclear energy? Are there shared policy pathways of achieving a decarbonized energy system? Here, we present results of an online survey (
n
= 2,429) designed to understand public perceptions of the current and future energy mixes in the United States (i.e., energy sources used for electric power, transportation, industrial, commercial, and residential sectors). We investigate support for decarbonization policies and antidecarbonization policies and the relative importance of climate change as an issue. Surprisingly, we find bipartisan support for a decarbonized energy future. Although there is a shared vision for decarbonization, there are strong partisan differences regarding the policy pathways for getting there. On average, our participants think that climate change is not the most important problem facing the United States today, but they do view climate change as an important issue for the world today and for the United States and the world in the future.
Specialized cytonemes induce self-organization of stem cells
Authors: Junyent Sergi , Garcin Clare L. , Szczerkowski James L. A. , Trieu Tung-Jui , Reeves Joshua , Habib Shukry J.
Published: March 2020

Significance

Many questions about how stem cells communicate with neighboring cells and self-organize to initiate tissue formation remain unanswered. We uncovered mechanisms employed by embryonic stem cells (ESCs) and trophoblast stem cells (TSCs) to coform embryo-like structures. We describe ESC-generated cytonemes that react to self-renewal–promoting Wnt ligands secreted by TSCs. We identified glutamatergic activity upon formation of ESC–TSC interaction. This cellular connection is required for the transmission of Wnt signals to ESCs for Wnt/β-catenin pathway activation, a process that regulates morphogenesis. Given that many stem cell types express glutamate receptors and rely on niche-secreted Wnt ligands for self-renewal, we propose that Wnt and glutamatergic signaling crosstalk may prove prevalent in various mammalian tissues to regulate stem cell–niche interactions.
Estimating and leveraging protein diffusion on ion-exchange resin surfaces
Authors: Khanal Ohnmar , Kumar Vijesh , Schlegel Fabrice , Lenhoff Abraham M.
Published: March 2020

Significance

Direct measurement of protein diffusion at a solid–liquid interface, unlike that in a bulk liquid phase, is challenging, particularly in complex adsorbent geometries. As a result there is disagreement as to whether surface diffusion contributes significantly to protein transport into porous ion-exchange chromatography (IEX) beads. We provide complementary evidence supporting the role of surface diffusion in protein transport into IEX media and show that the diffusivity depends explicitly on adsorption affinity. Exploiting this relationship, we further present an innovative procedure for loading protein onto a column that increases the column productivity by 43% for purification of a monoclonal antibody. We therefore provide a multipronged approach for investigating protein surface diffusion and validate its significance in protein transport.
Extraction of mechanical properties of materials through deep learning from instrumented indentation
Authors: Lu Lu , Dao Ming , Kumar Punit , Ramamurty Upadrasta , Karniadakis George Em , Suresh Subra
Published: March 2020

Instrumented indentation has been developed and widely utilized as one of the most versatile and practical means of extracting mechanical properties of materials. This method is particularly desirable for those applications where it is difficult to experimentally determine the mechanical properties using stress–strain data obtained from coupon specimens. Such applications include material processing and manufacturing of small and large engineering components and structures involving the following: three-dimensional (3D) printing, thin-film and multilayered structures, and integrated manufacturing of materials for coupled mechanical and functional properties. Here, we utilize the latest developments in neural networks, including a multifidelity approach whereby deep-learning algorithms are trained to extract elastoplastic properties of metals and alloys from instrumented indentation results using multiple datasets for desired levels of improved accuracy. We have established algorithms for solving inverse problems by recourse to single, dual, and multiple indentation and demonstrate that these algorithms significantly outperform traditional brute force computations and function-fitting methods. Moreover, we present several multifidelity approaches specifically for solving the inverse indentation problem which 1) significantly reduce the number of high-fidelity datasets required to achieve a given level of accuracy, 2) utilize known physical and scaling laws to improve training efficiency and accuracy, and 3) integrate simulation and experimental data for training disparate datasets to learn and minimize systematic errors. The predictive capabilities and advantages of these multifidelity methods have been assessed by direct comparisons with experimental results for indentation for different commercial alloys, including two wrought aluminum alloys and several 3D printed titanium alloys.
Effect of a ketogenic diet on hepatic steatosis and hepatic mitochondrial metabolism in nonalcoholic fatty liver disease
Authors: Luukkonen Panu K. , Dufour Sylvie , Lyu Kun , Zhang Xian-Man , Hakkarainen Antti , Lehtimäki Tiina E. , Cline Gary W. , Petersen Kitt Falk , Shulman Gerald I. , Yki-Järvinen Hannele
Published: March 2020

Significance

Ketogenic diet is an effective treatment for nonalcoholic fatty liver disease (NAFLD). Here, we present evidence that hepatic mitochondrial fluxes and redox state are markedly altered during ketogenic diet-induced reversal of NAFLD in humans. Ketogenic diet for 6 d markedly decreased liver fat content and hepatic insulin resistance. These changes were associated with increased net hydrolysis of liver triglycerides and decreased endogenous glucose production and serum insulin concentrations. Partitioning of fatty acids toward ketogenesis increased, which was associated with increased hepatic mitochondrial redox state and decreased hepatic citrate synthase flux. These data demonstrate heretofore undescribed adaptations underlying the reversal of NAFLD by ketogenic diet and highlight hepatic mitochondrial fluxes and redox state as potential treatment targets in NAFLD.
Little cutie one piece
Authors: Shi Heidi H. , Jing-Schmidt Zhuo
Published: March 2020

This study investigates emerging usages in Chinese cyberspace of the numeral classifierméithat violate syntactic and semantic conventions of canonical grammar of modern Chinese. We treat these usages as constructional variants of the canonical classifier construction and show how they afford users of Weibo a device of social indexicality in the sense of Silverstein (1976,1985,2003) and Eckert (2000,2003,2008). We argue that the constructional variants facilitate the creation of a cute, chic, playful, humorous, and youthful online style and that its popularity draws on multiple indexical resources including contrast to canonical grammar, contemporary language contact with Japanese, influence of the cuteness culture and its commodification, and consumerism in the digital economy. This study contributes to research on the linguistic construction of identity and style, linguistic creativity in the new media and digital culture, and usage-based constructionist approaches to language.