bluuebunny/crossref_metadata_2025 huggingface dataset:
Photo electric properties during streamer-to-leader transition in a long positive sphere–plane gap
Authors: Geng Jianghai , Chen Yaxi , Lv Fangcheng , Wang Ping , Ding Yujian
Published: August 2020

In this work, a combined photoelectric detecting system is established using devices such as a photomultiplier, an electric field sensor based on optoelectronic integration, and a high-speed camera. The system is used to measure the instantaneous optical power, spatial electric field strength, and optical image during discharge of a 3-m-long sphere–plane gap under standard switching surge voltage of positive polarity. The test results show that the initial streamer of the 3-m-long sphere–plane gap can be divided into strong and weak ionization according to the rate of rise of optical power and electric field strength. Within the dark discharge period in the sphere–plane air gap, the intensity of the spatial electric field slightly jumps when the streamer-to-leader transition is completed, with an increase of about 162.59 kV/m. It is proposed to take the time when the intensity of the spatial electric field jumps in the dark discharge period as the criterion for the streamer-to-leader transition. The measured duration ta of the streamer-to-leader transition is calculated according to instantaneous optical power and spatial electric field strength. Based on the thermodynamic equilibrium equation, a Gallimberti simulation model for this streamer-to-leader transition is established. The duration ts for completing the streamer-to-leader transition is obtained according to the quantity Q of injected electric charges. By comparing the measured duration ta with the calculated duration ts of the streamer-to-leader transition, the rationality of the criterion is verified. The research results provide a basis for establishing an improved model for the inception of a leader in a long air gap.
Dependence of the impurity transport on the dominant turbulent regime in ELM-y H-mode discharges on the DIII-D tokamak
Authors: Odstrčil T. , Howard N. T. , Sciortino F. , Chrystal C. , Holland C. , Hollmann E. , McKee G. , Thome K. E. , Wilks T. M.
Published: August 2020

Laser blow-off injections of aluminum and tungsten have been performed on the DIII-D tokamak to investigate the variation of impurity transport in a set of dedicated ion and electron heating scans with a fixed value of the external torque. The particle transport is quantified via the Bayesian inference method, which, constrained by a combination of a charge exchange recombination spectroscopy, soft x-ray measurements, and vacuum ultraviolet spectroscopy provides a detailed uncertainty quantification of transport coefficients. Contrasting discharge phases with a dominant electron and ion heating reveal a threefold drop in the impurity confinement time and order of magnitude increase in midradius impurity diffusion, when additional electron heating is applied. Furthermore, the calculated stationary aluminum density profiles reverse from peaked in electron heated to hollow in the ion heated case, following a similar trend to electron and carbon density. Comparable values of a core diffusion have been observed for W and Al ions, while differences in the propagation dynamics of these impurities are attributed to pedestal and edge transport. Modeling of the core transport with non-linear gyrokinetics code CGYRO [J. Candy and E. Belly, J. Comput. Phys. 324, 73 (2016)], significantly underpredicts the magnitude of the variation in Al transport. Diffusion increases three-times steeper with additional electron heat flux, and 10-times lower diffusion is observed in ion heated case than predicted by the modeling. The CGYRO model quantitatively matches the increase in the Al diffusion when approaching the linear threshold for the transition from the ion temperature gradient to trapped electron mode.
Magnetic impurities in thin films and 2D Ising superconductors
Authors: Möckli David , Haim Menashe , Khodas Maxim
Published: August 2020

In the theory of dilute magnetic impurities in superconductors, the effect of all impurity spin-components is expressed via a single magnetic scattering rate Γm. In a more realistic setting, magnetic impurities are anisotropic. In this case, the spatial randomness of three spin-components of impurities gives rise to generally different scattering rates Γi (i=1,2,3). We explore the effects of anisotropic magnetic impurities on the in-plane critical field in 2D superconductors. We discuss singlet, triplet, and parity-mixed order parameters allowed in systems without the inversion center. Also, the addition of a small amount of magnetic impurities may cause singlet to triplet crossovers. In all cases, different components of impurity spin affect the magnetic field—temperature phase diagram differently. We show that anisotropy of the magnetic impurities can serve as a probe of unconventional triplet or parity-mixed superconductivity.
Carrier suppression system to measure phase noise of acoustic resonators with low motional resistance
Authors: Pokharel A. , Vaillant E. , Imbaud J. , Boy J. J. , Esnault F. X. , Sthal F.
Published: August 2020

A carrier suppression system is implemented in order to measure the phase noise of acoustic resonators that have a low motional resistance. A special adapters’ system using transformers is proposed to improve the loaded quality factor of the resonators. With this developed device and described protocol, the inherent noise of resonators can be obtained without the usual electronical oscillator conditioning that could take part in the results. The loaded quality factor is improved from about 10% to 60% of the intrinsic quality factor. As an example, the system is used to study Langatate crystal resonators vibrating at 10 MHz. Langatate crystals can be an alternative to substitute for the quartz crystal resonators for frequency and time applications. Their coupling coefficient and the product quality factor-frequency are normally higher than those in quartz crystal resonators. For ultrastable resonators, the motional resistance obtained with Langatate crystals is about five times lower than that for the quartz crystal; it can reach typically few ohms. These resonators have been characterized in terms of impedance, Q-factors, turnover temperature, amplitude–frequency effect, and phase noise. The short-term stability of these resonators is given in terms of Allan standard deviation. The influence of the driving power is presented.
Photoelectron based soft x-ray detector for removing high order x rays
Authors: Nagasaka Masanari , Iwayama Hiroshi
Published: August 2020

Soft x-ray absorption spectroscopy (XAS) in the low energy region below 200 eV is important to investigate chemical and biological phenomena under an atmospheric condition since it covers K-edges of Li and B and L-edges of Si, P, S, and Cl. Monochromatic soft x rays usually include not only first order x rays but also high order x rays due to the high order diffraction of a plane grating monochromator. It is difficult to measure XAS in the low energy region under an atmospheric helium condition since the transmitted soft x rays mostly consist of the high order x rays due to the low transmission of the first order x rays. In this study, we have developed a photoelectron based soft x-ray (PBSX) detector, where the Au 4f photoelectrons emitted by the first order x rays are separated from those by the high order x rays using a difference in kinetic energies of photoelectrons. By using the PBSX detector, we have successfully obtained Si L-edge XAS spectra of the SiC and polymer/SiC films that mainly include the first order x rays by removing the major contributions of the second order x rays at the C K-edge and the fifth order x rays at the O K-edge. In the future, several physical, chemical, and biological phenomena in solution will be investigated by XAS in the low energy region with the PBSX detector.
Stability of ferroelectric and antiferroelectric hafnium–zirconium oxide thin films
Authors: Chae Kisung , Hwang Jeongwoon , Chagarov Evgueni , Kummel Andrew , Cho Kyeongjae
Published: August 2020

Hafnium–zirconium oxide (HZO) thin films are of interest due to their ability to form ferroelectric (FE) and antiferroelectric (AFE) oxide phases. Density functional theory is employed to elucidate the stabilization mechanisms of both FE HZO thin films and AFE ZrO2 films. The FE orthorhombic phase is primarily stabilized by in-plane tensile strain, which spontaneously occurs during the synthesis process, and this is more effective for HZO than HfO2. Layer-by-layer stack models and core-matrix three-dimensional models of the polymorphs reveal that the electrostatic component of interfacial free energy can play a critical role in the formation of the AFE tetragonal phase in ZrO2 and the “wake-up” effect for FE HZO.
Representation of the conformational ensemble of peptides in coarse grained simulations
Authors: Ozgur Beytullah , Sayar Mehmet
Published: August 2020

In their native state, many proteins/peptides display an ensemble of conformations, rather than a unique tertiary structure. Novel experimental techniques have enabled a quantitative analysis of this structural heterogeneity. In molecular dynamics simulations, however, capturing this conformational ensemble quantitatively remains a major challenge even with all atom simulations. In coarse grained (CG) simulations, with fewer degrees of freedom, representation of the conformational ensemble becomes more problematic. Here, we revisit a CG model from our group, which was designed to address the conformational transferability problem by using the LKα14 peptide as a model system. The LKα14 peptide transitions from a random/unstructured state in dilute solution to a solely α-helical conformation upon aggregation as evidenced by circular dichroism. Here, we demonstrate that the structure/physics based approach, used in the original parameterization of our CG model, strongly depends on the reference system chosen and excluded volume interactions that are often considered to be of secondary importance. We first tune the excluded volume parameters by using both α-helix and β-sheet type structures as reference and then update the nonbonded interactions by using a goodness-of-fit metric for representation of the conformational ensemble of LKα14. We demonstrate that the updated model can recover the whole conformational ensemble quantitatively while maintaining the aggregation driven conformational transition. This balanced parametrization with regard to alternative secondary structures opens the door for the generalization of the CG model to other sequences, which we demonstrate on a β-sheet forming triblock peptide.
Two-plasmon-decay induced fast electrons in intense femtosecond laser–solid interactions
Authors: Singh Prashant Kumar , Adak Amitava , Lad Amit D. , Chatterjee Gourab , Kumar G. Ravindra
Published: August 2020

The nonlinear coupling of intense laser pulse with plasma leads to excitation of several parametric instabilities, featuring plasmon, acoustic or electromagnetic modes. Specifically, the two-plasmon decay (TPD) instability, relevant to the generation of fast electrons, originates at the quarter critical surface, where the incident photon decays into a pair of electron plasmon waves. Although well explored by nanosecond lasers, the TPD instability is rarely seen in femtosecond laser–plasmas, mainly due to steep plasma profiles and the ultrashort duration of the driving pulse. Our experiments show TPD boosting of fast electrons in the femtosecond regime using low intensity contrast and temporally stretched laser pulses. The fast electron spectrum and 3ω0/2 harmonic emission from plasma show significant enhancement for stretched pulses (120 fs) in comparison to transform-limited short pulses (30 fs). The generation of fast electrons is found to be linked with the growth of 3ω0/2 harmonic. The effect of longer femtosecond pulses on TPD growth is observed using several fast electron diagnostics such as electron kinetic energy spectra, hard x-ray emission, rear side plasma emission, Cherenkov emission, and time-space resolved shadowgrams up to laser intensity of 1.5 × 1018 W cm−2. We, thus, provide robust and unambiguous demonstration of TPD instability driven generation of fast electrons in femtosecond laser–plasma interactions.
On the limits of multipactor in rectangular waveguides
Authors: Shaw Z. C. , Silvestre L. , Sugai T. , Esser B. , Mankowski J. J. , Dickens J. C. , Neuber A. A.
Published: August 2020

Multipactor in WR-284-like geometries is measured utilizing local and global detection techniques. To emulate conditions one may find in a waveguide filter structure while maintaining the fundamental microwave mode, a standard rectangular waveguide geometry with the reduced waveguide height set to 2.1 or 5.5 mm was adopted. Two high power RF sources were used to investigate a large range of input power (few kWs to MWs): a solid state source using GaN HEMTs allowing for larger pulse widths than standard magnetrons (100 μs as opposed to ∼4 μs) and a MW level S-band coaxial magnetron for the high power end. Particular interest was taken in capturing the lower and upper limits of multipactor threshold. Lower multipactor thresholds for finite pulse duration are governed by the appearance of one or more electrons in the multipactor gap during the applied pulse as well as a minimum power (electric field) level that affects a secondary electron emission yield above unity. As shown, such initial electrons(s) may easily be seeded via an external UV source illuminating the gap. However, wall collisions of excited metastable molecules may be another source of electrons, an observation based on the experiment and prior research. A multipactor upper threshold was non-existent in the experiment, even at powers over 200 kW within a 2.1 mm test gap, which numerically yielded a gap transit time significantly shorter than one half-period of the GHz wave. This is attributed to the electric field distribution within the waveguide structure, which results in the multipactor's spatial position moving to more favorable locations within the test gap.
A new compact dual-band perfect absorption ultrathin planar metasurface energy harvester in X- and V-bands with a wide incident angle
Authors: Ghaneizadeh Alireza , Mafinezhad Khalil , Joodaki Mojtaba
Published: August 2020

In this paper, we design and simulate a new dual-band ultrathin metasurface energy harvester (EH) in X- and V-bands. One of the significant advantages of the proposed EH is the efficiency, which is more than 70% over 170° of the TM-polarized oblique incident angles at f = 10 GHz. The full-wave simulation results show that the maximum harvesting efficiencies of 93.4% (in 10.1 GHz) and 84.3% (in 42.86 GHz) are obtained by the TM 75°-polarized and the normal incident waves, respectively. Besides, half-power bandwidths (ratios) are about 1.12 GHz (11.08%) and 2.36 GHz (5.5%), respectively. The designed unit-cell is miniaturized using a C-shaped slot with the dimensions of 0.1λ0 × 0.1λ0 × 0.008λ0 at the lowest resonance frequency (λ0 = 30.12 mm). To analyze the physical mechanism of energy harvesting, the full-wave simulation results of the current and electric field distributions at two resonance frequencies are presented. We demonstrate how the rotation of the load around the metallic via can affect the resonance frequency and the other characteristics of the EH at the X-band. We validate the load’s rotation effects using the waveguide measurement method as well. Finally, we show that the location of the metallic via has a greater impact compared to the load’s rotation using the full-wave numerical simulation at the X-band.
A multilayer multi-configurational approach to efficiently simulate large-scale circuit-based quantum computers on classical machines
Authors: Ellerbrock Roman , Martinez Todd J.
Published: August 2020

A multilayer multi-configurational theory framework is adapted to simulate circuit-based quantum computers. Quantum addition of superpositions of an exponential number of summands is performed in polynomial time with high accuracy. We demonstrate numerically accurate calculations including up to one million qubits for entangling benchmarks. Simulation cost can be assessed by entropy-based entanglement measures. For the considered systems, we show that the entanglement only grows weakly with the system size. The present simulations demonstrate how quantum algorithms in low-entropy regimes can be used efficiently on classically simulated quantum computers.
Si-ring quantum-well GAA nanowire FET for 5 nm node CMOS integration
Authors: Bahrami Payman , Shayesteh Mohammad Reza , Pourahmadi Majid , Safdarkhani Hadi
Published: August 2020

A novel structure for gate all-around (GAA) NW FET in the 5 nm scale has been proposed in this paper. This device consists of a germanium nanowire structure, the channel of which is surrounded by a ring-shaped silicon layer. In addition, a high-K dielectric has been used as the gate insulator. The performance of the device and its electrical characteristics have been determined using three-dimensional numerical simulation. The simulation results indicated that the proposed structure exhibits better performance compared to conventional GAA FET and Ge-ring QW GAA FET. Moreover, the on-current in nFET and pFET states was determined to be almost symmetrical, an essential factor in the design of integrated circuits. Subsequently, the efficiency of the proposed device was evaluated in the CMOS inverter and the static random access memory cell and was shown to be a remarkable improvement over the reported devices.
Vanadium oxide coatings to self-regulate current sharing in high-temperature superconducting cables and magnets
Authors: Yang Zhenghuai , Araujo Martínez Aurora Cecilia , Muley Sachin V. , Wang Xiaorong , Ji Qing , Anders André
Published: August 2020

High-temperature superconductors such as REBa2Cu3O7 − δ (REBCO, RE = rare earth) enable high-current cables and high-field magnets. By removing the turn-to-turn insulation in a magnet application, recent experiments demonstrated that REBCO magnets can self-protect against catastrophic damage during a superconducting-to-normal transition (quench), i.e., when the stored magnetic energy rapidly converts to heat. The current can bypass the hot spot during a quench, thereby reducing the localized heat dissipation. The removal of the insulation between turns, however, leads to excessive eddy currents during current ramping, thereby forcing a much-prolonged magnet charging time. To address this issue, we investigate vanadium oxide (VOx) coatings as a temperature-dependent self-switching medium that automatically manages current sharing. VOx coatings (with 1.70 ≤ × ≤ to 2.07) were deposited by reactive cathodic arc deposition, initially on insulating glass to determine the electrical properties, and later on commercial REBCO tapes. The coatings are x-ray amorphous but with a short-range crystalline ordering according to Raman spectrometry. The resistivity of VOx decreased by at least three orders of magnitude when the temperature increased from 80 to 300 K. The coating process is compatible with commercial REBCO tapes as evidenced by the negligible change in the critical current caused by the coating process. The results from current sharing experiments and circuit analysis suggest that the VOx coating can effectively self-regulate current sharing in REBCO magnets, suppress excessive eddy currents, and enable self-protection during quenches.
Global optimization of copper clusters at the ZnO(101¯0) surface using a DFT-based neural network potential and genetic algorithms
Authors: Paleico Martín Leandro , Behler Jörg
Published: August 2020

The determination of the most stable structures of metal clusters supported at solid surfaces by computer simulations represents a formidable challenge due to the complexity of the potential-energy surface. Here, we combine a high-dimensional neural network potential, which allows us to predict the energies and forces of a large number of structures with first-principles accuracy, with a global optimization scheme employing genetic algorithms. This very efficient setup is used to identify the global minima and low-energy local minima for a series of copper clusters containing between four and ten atoms adsorbed at the ZnO(101¯0) surface. A series of structures with common structural features resembling the Cu(111) and Cu(110) surfaces at the metal-oxide interface has been identified, and the geometries of the emerging clusters are characterized in detail. We demonstrate that the frequently employed approximation of a frozen substrate surface in global optimization can result in missing the most relevant structures.
Pulsed-jet propulsion via shape deformation of an axisymmetric swimmer
Authors: Bi Xiaobo , Zhu Qiang
Published: August 2020

By using an axisymmetric immersed-boundary model, we numerically investigate the thrust generation of a deformable body via pulsed jetting. We focus on a single discharging process resulting from the deflation of the body as inspired by the jetting mechanism of cephalopods, such as squids. We examine three jet velocity profiles, namely, impulsive, half-cosine, and cosine, in the relatively low Reynolds number regime. For the impulsive profile, we demonstrate via wake visualization that the leading vortex ring does not pinch off from the trailing jet although its circulation stops growing after a critical formation number (hereby, the formation number is defined as the ratio between the length and diameter of the jet plug) of 6–7. The exact value of the critical formation number depends on the jet velocity profile, suggesting that jet acceleration and viscous dissipation play significant roles in vortex ring evolution. In terms of thrust generation, our results indicate that besides the jet momentum flux, an important source of thrust generation is jet acceleration. The implication is that the jet velocity profile is a key factor in determining the propulsive performance.
Global characteristics of transverse jets of aviation kerosene–long-chain alcohol blends
Authors: Li Fengyu , Shi Weidong , Hu Chao , Bao Lin , Liu Yanju , Lin Qizhao
Published: August 2020

Long-chain alcohol is a promising alternative for commercial fuels. This study aims at experimentally determining the characteristics of transverse jets using long-chain alcohol in aviation applications. The surface wavelength, breakup regime, upper trajectory of a transverse jet, and liquid column breakup point location are investigated. The column breakup and surface breakup are both observed in experiments, and in the surface breakup regime, there exist bag breakup, multimode breakup, and shear breakup. Shear breakup appears in the conditions with Weg lower than 80. An equation for predicting the upper trajectory of aviation kerosene–long chain alcohol (AKL) blends is proposed. Addition of n-butanol makes the upper trajectory lower, whereas addition of n-pentanol makes the upper trajectory higher. Two equations are proposed for predicting the horizontal and vertical positions of the liquid column breakup point, taking Weg, Oh, and q into account. Blending of n-butanol increases xb and zb, whereas the addition of n-pentanol decreases them. By introducing Kelvin–Helmholtz instability and Rayleigh–Taylor instability into the theoretical analysis, λs is showed to be related with Weg and Oh. Using the results of theoretical analysis, as well as the experimental data, a prediction equation for λs is proposed. The variation of λs caused by fuel modification is studied, the λs is shortened with the addition of long-chain alcohol, and aviation kerosene–n-pentanol blends show shorter surface wavelengths than those of aviation kerosene–n-butanol blends with the same blending ratios. This work provides a better understanding of the characteristics of AKL blends, which will be useful in expanding aviation applications of this fuel.
Dynamic behavior of OH and its atomic contrast with O adatom on the Ti site of TiO2(110) at 78 K by atomic force microscopy imaging
Authors: Wen Huan Fei , Sang Hongqian , Sugawara Yasuhiro , Li Yan Jun
Published: August 2020

We experimentally observed the dynamic behavior of OH on the Ti site (OHt) of TiO2(110) at 78 K in detail by atomic force microscopy (AFM). OHt was imaged as a dimer shape or a fuzzy round shape corresponding to the motion of OHt that OHt swings along the [1–10] direction. The frequency of swing positively responds to the applied bias voltage between the tip and the sample, and it is proposed that the applied bias voltage decreases the barrier of the OHt transition between two or more equilibrium states. Such specific response of OHt to the applied bias voltage can be used as the fingerprint. In addition, the atomic contrast of O adatom (Oad) and OHt is compared with the contrast of other surface species by AFM, and it is demonstrated that the contrast of Oad and OHt is similar to the contrast of the surface defects due to the effect of tip apex polarity. H atom desorption of OHt is performed by Kelvin probe force spectroscopy, and it is resulted from the reduction of barrier width together with the tunneling electron excitation. The present study is expected to be useful to explore the property of H-involved species and the surface reactions on the oxide surface by AFM.
Rock salt structure GdO epitaxial thin film with a high ferromagnetic Curie temperature
Authors: Yamamoto Taku , Kaminaga Kenichi , Saito Daichi , Oka Daichi , Fukumura Tomoteru
Published: August 2020

GdO with unusual valence of Gd2+ (4f75d1) has been known as the only gas phase so far. In this study, we report on the growth of solid phase rock salt structure GdO epitaxial thin films. The GdO thin film was an n-type semiconductor with the bandgap of 0.1 eV. The ferromagnetic Curie temperature (TC) was as high as 276 K, which was much higher than that of archetypal ferromagnetic rare earth monoxide EuO (TC = 69 K). TC increased slightly with electron doping similar to non-stoichiometric EuO1−δ, while decreased significantly with La doping probably caused by the magnetic dilution effect due to substitution of Gd with divalent La.
Ferro-advection aided evaporation kinetics of ferrofluid droplets in magnetic field ambience
Authors: Chattopadhyay Ankur , Dwivedi Raghvendra Kumar , Harikrishnan A. R. , Dhar Purbarun
Published: August 2020

The present article discusses the physics and mechanics of evaporation of pendant, aqueous ferrofluid droplets, and modulation of the same by an external magnetic field. We show experimentally and by mathematical analysis that the presence of a horizontal magnetic field augments the evaporation rates of pendant ferrofluid droplets. First, we tackle the question of improved evaporation of the colloidal droplets compared to water and propose physical mechanisms to explain the same. Experiments show that the changes in evaporation rates aided by the magnetic field cannot be explained on the basis of changes in surface tension or based on classical diffusion driven evaporation models. Probing via particle image velocimetry shows that the internal advection kinetics of such droplets plays a direct role toward the augmented evaporation rates by modulating the associated Stefan flow. Infrared thermography reveals changes in thermal gradients within the droplet and evaluating the dynamic surface tension reveals the presence of solutal gradients within the droplet, both brought about by the external field. Based on the premise, a scaling analysis of the internal magneto-thermal and magneto-solutal ferroadvection behavior is presented. The model incorporates the role of the governing Hartmann number, the magneto-thermal Prandtl number, and the magneto-solutal Schmidt number. The analysis and stability maps reveal that the magneto-solutal ferroadvection is the more dominant mechanism, and the model is able to predict the internal advection velocities with accuracy. Furthermore, another scaling model to predict the modified Stefan flow is proposed and is found to accurately predict the improved evaporation rates.
Investigate on structure for transparent anti-icing surfaces
Authors: Duc Nguyen Ba , Binh Nguyen Thanh
Published: August 2020

The ice-phobic and transparent surface based on the distinctive structure of a coating material has been investigated. Moth eye structure fabricated on the quartz substrate was covered with a flat paraffin layer to isolate it in a cold and humid environment. Paraffin wax was chosen as the coating material due to low thermal conductivity, easy coating, and original water repellency. The paraffin layer only stayed on the top of the nanostructure, separated it from the outside environment to obstruct heat energy being transferred to the cold substrate, and prevented the wetting transition, which was observed regularly on the rough surface. The uncountable number of air blocks trapped inside the nanostructure also contributed to delayed heat transfer, leading to an increase in the freezing time of the attached water droplet. The anti-icing performance was evaluated in terms of adhesion strength, freezing time, and freezing rain sustainability. The nanostructure coated sample was compared with barely coated and superhydrophobic nanostructure surface and demonstrated a preeminent performance.
Stable isotopes in hair reveal dietary protein sources with links to socioeconomic status and health
Authors: Ehleringer James R. , Covarrubias Avalos Stephannie , Tipple Brett J. , Valenzuela Luciano O. , Cerling Thure E.
Published: August 2020

Significance

As Americans, our diets have among the highest protein consumption rates and we are experiencing increased rates of obesity across all age groups. Here we reveal that consumption of corn-fed animal proteins are more common among lower socioeconomic status populations, which places these populations at a potentially greater risk for increased health problems.
Genome-wide RNA interference screening reveals a COPI-MAP2K3 pathway required for YAP regulation
Authors: Kim Yong Joon , Jung Eunji , Shin Eunbie , Hong Sin-Hyoung , Jeong Hui Su , Hur Gayeong , Jeong Hye Yun , Lee Seung-Hyo , Lee Ji Eun , Kim Gun-Hwa , Kim Joon
Published: August 2020

Significance

YAP is a transcriptional regulator governing gene expression programs underlying cell proliferation and survival. In addition, YAP has been highlighted as a key player in various stages of cancer pathogenesis. Currently, our understanding of the regulation of YAP activity is incomplete in part because there is no comprehensive list of genes related to the regulation. In this paper, we report the result of a genome-wide RNA interference screen to identify genes whose loss of function affects the activity of YAP. We discovered a number of genes that can be classified as positive or negative factors of YAP stability or nuclear enrichment. Our data will be valuable for gaining a deeper insight into complex YAP regulation.
Global snow drought hot spots and characteristics
Authors: Huning Laurie S. , AghaKouchak Amir
Published: August 2020

Significance

Given the importance of snow to global food, water, and energy security, characterizing snow deficits (snow droughts) in a changing climate has emerged as a critical knowledge gap. We identify snow drought hot spots and determine how drought duration and intensity vary globally. We show that eastern Russia, Europe, and the western United States experienced longer, more intense snow droughts in the second half of the period 1980 to 2018. During this period, droughts became less intense over the Hindu Kush, Himalayas, extratropical Andes, and Patagonia regions. Natural and human-driven factors (e.g., atmospheric circulation patterns, polar vortex movement, and Arctic warming) likely contribute to snow droughts. We urge the community to further investigate the complex physical drivers of snow drought.
Ancestral regulatory mechanisms specify conserved midbrain circuitry in arthropods and vertebrates
Authors: Bridi Jessika C. , Ludlow Zoe N. , Kottler Benjamin , Hartmann Beate , Vanden Broeck Lies , Dearlove Jonah , Göker Markus , Strausfeld Nicholas J. , Callaerts Patrick , Hirth Frank
Published: August 2020

Significance

Comparative developmental genetics indicate insect and mammalian forebrains form and function in comparable ways. However, these data are open to opposing interpretations that advocate either a single origin of the brain and its adaptive modification during animal evolution; or multiple, independent origins of the many different brains present in extant Bilateria. Here, we describe conserved regulatory elements that mediate the spatiotemporal expression of developmental control genes directing the formation and function of midbrain circuits in flies, mice, and humans. These circuits develop from corresponding midbrain-hindbrain boundary regions and regulate comparable behaviors for balance and motor control. Our findings suggest that conserved regulatory mechanisms specify cephalic circuits for sensory integration and coordinated behavior common to all animals that possess a brain.
Spatiotemporal mapping of bacterial membrane potential responses to extracellular electron transfer
Authors: Pirbadian Sahand , Chavez Marko S. , El-Naggar Mohamed Y.
Published: August 2020

Significance

Past studies on extracellular electron transfer (EET) have mainly employed bulk techniques, overlooking the subpopulation variation in EET and the potentially complex spatial patterns of activity in microbial communities. Here, by performing simultaneous electrochemical and in vivo single-cell-level fluorescence microscopy, we demonstrate the link between EET and the cell membrane potential, revealing the utility of membrane potential as a single-cell-level bioenergetic indicator of EET by
Shewanella oneidensis
MR-1 cells. Our findings pave the way for understanding the factors underlying EET at a fundamental level, which could, in turn, lead to improvements in the design of bioelectrochemical systems that enhance their overall performance.
Identification of MYC as an antinecroptotic protein that stifles RIPK1–RIPK3 complex formation
Authors: Seong Daehyeon , Jeong Manhyung , Seo Jinho , Lee Ji-Yoon , Hwang Chi Hyun , Shin Ho-Chul , Shin Jeong Yoon , Nam Young Woo , Jo Jeong Yeon , Lee Haeseung , Kim Hye-Jung , Kim Hwa-Ryeon , Oh Ji Hoon , Ha Sang-Jun , Kim Seung Jun , Roe Jae-Seok , Kim Wankyu , Cheong June-Won , Bae Kwang-Hee , Lee Sang Chul , Oberst Andrew , Vandenabeele Peter , Shin Dong Hoon , Lee Eun-Woo , Song Jaewhan
Published: August 2020

Significance

A major yet perplexing question in the field of necroptosis is the role and involvement of necroptosis in cancer cells. Many cancer cells have protective mechanisms against necroptosis, but the underlying mechanism remains elusive. We report findings of cross-talk and a regulatory pathway that exist between MYC, a potent oncogene, and RIPK3, a pivotal factor in necroptosis. We find that MYC pathway is downregulated upon necroptotic, while MYC inhibits TNF-α–induced necroptosis. The inhibitory effect of MYC on necroptosis is unexpected because no transcriptional activity by MYC is required. Mechanistically, a direct interaction between MYC and RIPK3 takes place in the cytosol, preventing RIPK1–RIPK3 complex formation. Finally, MYC depletion enhances antitumor activity of necroptosis-inducing agents in a xenograft model.
Geometric anomaly detection in data
Authors: Stolz Bernadette J. , Tanner Jared , Harrington Heather A. , Nanda Vidit
Published: August 2020

Significance

The problem of fitting low-dimensional manifolds to high-dimensional data has been extensively studied from both theoretical and computational perspectives. As datasets get more heterogeneous and complicated, so must the spaces that are used to approximate them. Stratified spaces, built out of manifold pieces coherently glued together, form natural candidates for such geometric models. The key difficulty encountered when fitting stratified spaces to data is that none of the sampled points can be expected to lie exactly on the low-dimensional singular strata. The present work uses local cohomology to overcome this difficulty. Here, we describe an efficient and practical framework for singularity detection from finite samples and demonstrate its ability to detect interfaces in real and simulated data.
An objective evaluation of the beholder’s response to abstract and figurative art based on construal level theory
Authors: Durkin Celia , Hartnett Eileen , Shohamy Daphna , Kandel Eric R.
Published: August 2020

Significance

Art affects our mindset; it can be therapeutic, emotionally evocative, and generative of aesthetic experience. But how art recruits cognitive processes, and how this process differs between abstract and representational art, remain unknown. To quantify differences in mindset evoked by abstract and representational art, we drew on construal level theory (CLT), a psychological theory that has systematically characterized differences in abstract and concrete mindsets. In three different decision making tasks, we found that abstract art evokes a more abstract mindset than representational art. Our data suggest that abstract and representational art have differential effects on cognition and that CLT provides a useful new empirical approach to the analysis of cognitive states evoked by different levels of artistic abstraction.
Structural basis for carotenoid cleavage by an archaeal carotenoid dioxygenase
Authors: Daruwalla Anahita , Zhang Jianye , Lee Ho Jun , Khadka Nimesh , Farquhar Erik R. , Shi Wuxian , von Lintig Johannes , Kiser Philip D.
Published: August 2020

Significance

The formation of apocarotenoids by carotenoid cleavage dioxygenases (CCDs) is a critical process for several biological signaling systems. However, the active site determinants directing CCDs to cleave a specific alkene bond within the polyene backbone of carotenoids have remained unclear. Through analysis of the previously uncharacterized group of archaeal CCDs, we identified an enzyme, closely related to animal CCDs, that could be isolated in complex with its apocarotenoid product. Its crystal structure revealed the precise molecular interactions governing the enzyme’s unique regioselectivity. These insights pave the way toward control of CCD activity in carotenoid/retinoid metabolism through rational design of small-molecule modulators or targeted mutagenesis.
In-place molecular preservation of cellulose in 5,000-year-old archaeological textiles
Authors: Reynaud Corentin , Thoury Mathieu , Dazzi Alexandre , Latour Gaël , Scheel Mario , Li Jiayi , Thomas Ariane , Moulhérat Christophe , Didier Aurore , Bertrand Loïc
Published: August 2020

The understanding of fossilization mechanisms at the nanoscale remains extremely challenging despite its fundamental interest and its implications for paleontology, archaeology, geoscience, and environmental and material sciences. The mineralization mechanism by which cellulosic, keratinous, and silk tissues fossilize in the vicinity of archaeological metal artifacts offers the most exquisite preservation through a mechanism unexplored on the nanoscale. It is at the center of the vast majority of ancient textiles preserved under nonextreme conditions, known through extremely valuable fragments. Here we show the reconstruction of the nanoscale mechanism leading to the preservation of an exceptional collection of ancient cellulosic textiles recovered in the ancient Near East (4,000 to 5,000 years ago). We demonstrate that even the most mineralized fibers, which contain inorganic compounds throughout their histology, enclose preserved cellulosic remains in place. We evidence a process that combines the three steps of water transport of biocidal metal cations and soil solutes, degradation and loss of crystallinity of cellulosic polysaccharides, and silicification.
Hypothalamic extended synaptotagmin-3 contributes to the development of dietary obesity and related metabolic disorders
Authors: Zhang Yi , Guan Yunliang , Pan Susu , Yan Lihong , Wang Ping , Chen Zhuo , Shen Qing , Zhao Faming , Zhang Xin , Li Juan , Li Juxue , Cai Dongsheng , Zhang Guo
Published: August 2020

Significance

The epidemic of obesity has reached an alarming level worldwide. Understanding the etiology of obesity is important for identifying a new approach of prevention or treatment. Accumulating evidence demonstrates that the central nervous system plays a critical role in animal’s energy homeostasis. Here, we show that extended synaptotagmin (E-Syt3) is expressed in the hypothalamus and contributes to diet-induced obesity development. Whole-body or proopiomelanocortin neuron-specific deletion of
E-Syt3
significantly protects mice against DIO and related metabolic disorders. Mechanistically, we show that inhibition of
E-Syt3
can lead to increased hypothalamic content of α-melanocyte-stimulating hormone. Thus, our current work suggests that E-Syt3 might be a relevant target for treating obesity.
ActivatingKRAS,NRAS, andBRAFmutants enhance proteasome capacity and reduce endoplasmic reticulum stress in multiple myeloma
Authors: Shirazi Fazal , Jones Richard J. , Singh Ram K. , Zou Jianxuan , Kuiatse Isere , Berkova Zuzana , Wang Hua , Lee Hans C. , Hong Samuel , Dick Larry , Chattopadhyay Nibedita , Orlowski Robert Z.
Published: August 2020

Significance

KRAS,NRAS, andBRAFmutations that activate MAPK signaling occur in half of myeloma patients and confer a poor prognosis. Our studies link activatingRASandRAFmutations with enhanced proteasome assembly and capacity through the MAPK intermediate ELK1. These downstream changes reduce cellular stress, thereby promoting myeloma cell survival, and confer proteasome inhibitor resistance, which can be overcome by combinations with BRAF or MEK inhibitors. They provide a possible reason for the frequency of MAPK pathway mutations in myeloma, and support use of these combinations specifically in patients withBRAF- orRAS-mutated disease.
Polygenic inheritance, GWAS, polygenic risk scores, and the search for functional variants
Authors: Crouch Daniel J. M. , Bodmer Walter F.
Published: August 2020

The reconciliation between Mendelian inheritance of discrete traits and the genetically based correlation between relatives for quantitative traits was Fisher’s infinitesimal model of a large number of genetic variants, each with very small effects, whose causal effects could not be individually identified. The development of genome-wide genetic association studies (GWAS) raised the hope that it would be possible to identify single polymorphic variants with identifiable functional effects on complex traits. It soon became clear that, with larger and larger GWAS on more and more complex traits, most of the significant associations had such small effects, that identifying their individual functional effects was essentially hopeless. Polygenic risk scores that provide an overall estimate of the genetic propensity to a trait at the individual level have been developed using GWAS data. These provide useful identification of groups of individuals with substantially increased risks, which can lead to recommendations of medical treatments or behavioral modifications to reduce risks. However, each such claim will require extensive investigation to justify its practical application. The challenge now is to use limited genetic association studies to find individually identifiable variants of significant functional effect that can help to understand the molecular basis of complex diseases and traits, and so lead to improved disease prevention and treatment. This can best be achieved by 1) the study of rare variants, often chosen by careful candidate assessment, and 2) the careful choice of phenotypes, often extremes of a quantitative variable, or traits with relatively high heritability.
A Zika virus envelope mutation preceding the 2015 epidemic enhances virulence and fitness for transmission
Authors: Shan Chao , Xia Hongjie , Haller Sherry L. , Azar Sasha R. , Liu Yang , Liu Jianying , Muruato Antonio E. , Chen Rubing , Rossi Shannan L. , Wakamiya Maki , Vasilakis Nikos , Pei Rongjuan , Fontes-Garfias Camila R. , Singh Sanjay Kumar , Xie Xuping , Weaver Scott C. , Shi Pei-Yong
Published: August 2020

Significance

ZIKV has “silently” circulated without causing severe diseases for decades since its discovery in 1947. Our study demonstrated that ZIKV acquired an evolutionary mutation in viral envelope gene (E-V473M) that increases virulence, maternal-to-fetal transmission during pregnancy, and viremia in nonhuman primates to facilitate urban transmission since 2013, which may be responsible for the recent emergence and severe diseases. Our results underscore the potential that high genetic mutation frequencies during arbovirus replication and transmission between mosquito and vertebrate hosts could lead to emergence and reemergence of those pathogens. Understanding the mechanisms of emergence and enhanced transmission is essential to detect and respond to future arbovirus outbreaks.
JMJD5 couples with CDK9 to release the paused RNA polymerase II
Authors: Liu Haolin , Ramachandran Srinivas , Fong Nova , Phang Tzu , Lee Schuyler , Parsa Pirooz , Liu Xinjian , Harmacek Laura , Danhorn Thomas , Song Tengyao , Oh Sangphil , Zhang Qianqian , Chen Zhongzhou , Zhang Qian , Tu Ting-Hui , Happoldt Carrie , O’Conner Brian , Janknecht Ralf , Li Chuan-Yuan , Marrack Philippa , Kappler John , Leach Sonia , Zhang Gongyi
Published: August 2020

Significance

RNA polymerase II (Pol II) is stalled at the transcription starting site for a large number of genes in higher eukaryotes. We previously found that JMJD5/7 proteins act as both endopeptidases and exopeptidases to cleave arginine methylated histone tails including those of H2A, H3, and H4, thus generating relatively “tailless nucleosomes”, which can be overcome by Pol II. This report shows that knockout of JMJD5 in mice leads to accumulation of nucleosomes at +1 and loss of expression of a large number of genes. We find that the N-terminal domain of JMJD5 binds to CTD of Pol II with a unique combination of phosphorylation generated by CDK9. We propose that JMJD5 couples with CDK9 to release the paused Pol II.
Molecular biology and structure of a novel penaeid shrimp densovirus elucidate convergent parvoviral host capsid evolution
Authors: Pénzes Judit J. , Pham Hanh T. , Chipman Paul , Bhattacharya Nilakshee , McKenna Robert , Agbandje-McKenna Mavis , Tijssen Peter
Published: August 2020

Significance

Parvoviruses (PVs) are ssDNA viruses, with T = 1 icosahedral symmetry, infecting deuterostome and protostome animals. Most PVs have a highly conserved phospholipase A2 domain (PLA2) in the N-terminal region of their minor capsid protein. Under acidic pH, during endosomal/lysosomal egress, the PLA2 domain is activated to disrupt vesicle membranes. However, certain PVs lack the PLA2 and thus must use a different escape mechanism. Our study offers insight into this enigma, showing how a recently discovered PV of marine crustacean has evolved a cation-dependent mechanism to accomplish this task. We also show how host-driven convergent evolution pushed two PVs, infecting the same host species, to adopt strikingly similar surface morphologies, despite distinct multimer interactions and lack of sequence similarity.
Three-dimensional reconstructions of the putative metazoan
Namapoikia
show that it was a microbial construction
Authors: Mehra Akshay , Watters Wesley A. , Grotzinger John P. , Maloof Adam C.
Published: August 2020

Significance

Animals that build skeletons have an outsized impact on Earth’s biological, geochemical, and sedimentological cycles. To determine when, where, and why metazoan biomineralization first emerged, it is necessary to study the earliest record of skeletal animals. This record is made up of four genera from the Ediacaran period:
Namacalathus
,
Cloudina
,
Sinotubulites
, and
Namapoikia
. Here, we measure three-dimensional reconstructions of
Namapoikia
to test the hypothesis that it is a calcifying sponge. We find that
Namapoikia
lacks the physical characteristics expected of a sponge, or, for that matter, an animal.