bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced thin-sandwich equations on manifolds Euclidean at infinity and on closed manifolds: Existence and multiplicity
Authors: Avalos R. , Lira J. H.
Published: December 2020

The reduced thin-sandwich equations (RTSE) appear within Wheeler’s thin-sandwich approach toward the Einstein constraint equations (ECE) of general relativity. It is known that these equations cannot be well-posed, in general, but, on closed manifolds, sufficient conditions for well-posedness have been established. In particular, it has been shown that the RTSE are well posed in a neighborhood of umbilical solutions of the constraint equations without conformal Killing fields. In this paper, we will analyze such a set of equations on the manifolds Euclidean at infinity in a neighborhood of asymptotically Euclidean (AE) solutions of the ECE. The main conclusion in this direction is that on AE-manifolds admitting a Yamabe positive metric, the solutions of the RTSE parameterize an open subset in the space of solutions of the ECE. In addition, we show that in the case of closed manifolds, these equations are well-posed around umbilical solutions of the ECE admitting Killing fields and present some relevant examples. Finally, it will be shown that in the set of umbilical solutions of the vacuum ECE on closed manifolds, the RTSE are generically well-posed.
Stochastic fluid dynamics simulations of the velocity distribution in protoplasmic streaming
Authors: Egorov Vladislav , Maksimova Olga , Andreeva Irina , Koibuchi Hiroshi , Hongo Satoshi , Nagahiro Shinichiro , Ikai Toshiyuki , Nakayama Madoka , Noro Shuta , Uchimoto Tetsuya , Rieu Jean-Paul
Published: December 2020

Protoplasmic streaming in plant cells is directly visible in the cases of Chara corallina and Nitella flexilis, and this streaming is understood to play a role in the transport of biological materials. For this reason, related studies have focused on molecular transportation from a fluid mechanics viewpoint. However, the experimentally observed distribution of the velocity along the flow direction x, which exhibits two peaks at Vx = 0 and at a finite Vx(≠0), remains to be studied. In this paper, we numerically study whether this behavior of the flow field can be simulated by a 2D stochastic Navier–Stokes (NS) equation for Couette flow in which a random Brownian force is assumed. We present the first numerical evidence that these peaks are reproduced by the stochastic NS equation, which implies that the Brownian motion of the fluid particles plays an essential role in the emergence of these peaks in the velocity distribution. We also find that the position of the peak at Vx(≠0) moves with the variation in the strength D of the random Brownian force, which also changes depending on physical parameters such as the kinematic viscosity, boundary velocity, and diameter of the plant cells.
Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy
Authors: Dang T. H. , Hawecker J. , Rongione E. , Baez Flores G. , To D. Q. , Rojas-Sanchez J. C. , Nong H. , Mangeney J. , Tignon J. , Godel F. , Collin S. , Seneor P. , Bibes M. , Fert A. , Anane M. , George J.-M. , Vila L. , Cosset-Cheneau M. , Dolfi D. , Lebrun R. , Bortolotti P. , Belashchenko K. , Dhillon S. , Jaffrès H.
Published: December 2020

Spintronic structures are extensively investigated for their spin–orbit torque properties, required for magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering for the optimization of spin transmission. Here, we advance the analysis of ultrafast spin-charge conversion phenomena at ferromagnetic-transition metal interfaces due to their inverse spin-Hall effect properties. In particular, the intrinsic inverse spin-Hall effect of Pt-based systems and extrinsic inverse spin-Hall effect of Au:W and Au:Ta in NiFe/Au:(W,Ta) bilayers are investigated. The spin-charge conversion is probed by complementary techniques—ultrafast THz time-domain spectroscopy in the dynamic regime for THz pulse emission and ferromagnetic resonance spin-pumping measurements in the GHz regime in the steady state—to determine the role played by the material properties, resistivities, spin transmission at metallic interfaces, and spin-flip rates. These measurements show the correspondence between the THz time-domain spectroscopy and ferromagnetic spin-pumping for the different set of samples in term of the spin mixing conductance. The latter quantity is a critical parameter, determining the strength of the THz emission from spintronic interfaces. This is further supported by ab initio calculations, simulations, and analysis of the spin-diffusion and spin-relaxation of carriers within the multilayers in the time domain, permitting one to determine the main trends and the role of spin transmission at interfaces. This work illustrates that time-domain spectroscopy for spin-based THz emission is a powerful technique to probe spin-dynamics at active spintronic interfaces and to extract key material properties for spin-charge conversion.
Coupling spins to nanomechanical resonators: Toward quantum spin-mechanics
Authors: Wang Hailin , Lekavicius Ignas
Published: December 2020

Spin-mechanics studies interactions between spin systems and mechanical vibrations in a nanomechanical resonator and explores their potential applications in quantum information processing. In this review, we summarize various types of spin-mechanical resonators and discuss both the cavity-QED-like and the trapped-ion-like spin-mechanical coupling processes. The implementation of these processes using negatively charged nitrogen vacancy and silicon vacancy centers in diamond is reviewed. Prospects for reaching the full quantum regime of spin-mechanics, in which quantum control can occur at the level of both a single spin and a single phonon, are discussed with an emphasis on the crucial role of strain coupling to the orbital degrees of freedom of the defect centers.
Two-band whistler-mode waves excited by an electron bi-Maxwellian distribution plus parallel beams
Authors: Chen Huayue , Sauer Konrad , Lu Quanming , Gao Xinliang , Wang Shaojie
Published: December 2020

The characteristics of whistler-mode waves excited by temperature anisotropic electrons, whose velocity distribution is a combination of bi-Maxwellian distribution and beam-like shapes, are investigated by both linear theory analysis and particle-in-cell simulation. A frequency gap is formed between two peaks, which is caused by the mode splitting of beam-like electrons. We have further investigated the influences of different parameters and found that the position of beam-like shape is the key parameter in determining the frequency of power gap. Moreover, the beam-like component on one direction will lead to the gap in the spectra of waves propagating in the opposite direction. Our study can shed light on the effects of beam-like electrons on the spectra of whistler-mode waves.
Temperature dependence of diffusion length and mobility in mid-wavelength InAs/InAsSb superlattice infrared detectors
Authors: Soibel Alexander , Ting David Z. , Fisher Anita M. , Khoshakhlagh Arezou , Pepper Brian , Gunapala Sarath D.
Published: December 2020

In the past decade, infrared detectors with InAs/InAsSb (Gallium-free) type-II strained layer superlattice absorbers became a technology of interest for many imaging applications. In this work, we study the dependence of minority carrier (hole) transport, absorption coefficient, and quantum efficiency (QE) of a 5.6 μm cutoff wavelength mid-wavelength infrared InAs/InAsSb detector on temperatures and applied bias. We found that the minority carrier lifetime is very long (τ ≈ 5.5 μs) and is temperature independent in the temperature range T = 50–150 K. The back-side illuminated QE without anti-reflection coating increases from ∼30% at T = 50 K to ∼60% at T = 180 K. The minority carrier (hole) diffusion length, Ldh, was found from QE and absorption coefficient. The hole diffusion length at T = 50 K is Ldh = 2.4 μm and increases monotonically to Ldh = 7.2 μm at T = 180 K. The hole mobility, calculated from diffusion length and minority carrier lifetime, is μh = 4.5 cm2/V s at T = 50 K and increases with temperature to reach μh = 7.2 cm2/V s at T = 150 K. In addition, we find that at lower temperatures where the diffusion length is shorter, the stronger QE dependence on applied bias is due to minority carrier collection from the depletion region, whose width increases with applied bias.
Nanoscale compositional analysis of wurtzite BAlN thin film using atom probe tomography
Authors: Sarker Jith , Tran Tinh Binh , AlQatari Feras , Liao Che-Hao , Li Xiaohang , Mazumder Baishakhi
Published: December 2020

In this work, the local atomic level composition of BAlN films with ∼20% B was investigated using atom probe tomography. Dislocations and elemental clustering were confirmed along which Al atoms tend to segregate. The presence of local compositional heterogeneities (dislocations and small clusters) and impurities is related to the variation of local alloy stoichiometry of the BAlN films. The roughness and interface abruptness of BAlN/AlN were investigated, and a few nm of B and Al composition gradient in BAlN adjacent to the interface was observed. The nanoscale compositional analysis reported here will be crucial for developing BAlN films with a high B content and larger thickness for future high power electronics and optical applications.
Hydrodynamic computations of high-power laser drives generating metal ejecta jets from surface grooves
Authors: Mackay K. K. , Najjar F. M. , Ali S. J. , Eggert J. H. , Haxhimali T. , Morgan B. E. , Park H. S. , Ping Y. , Rinderknecht H. G. , Stan C. V. , Saunders A. M.
Published: December 2020

Understanding dynamic fragmentation in shock-loaded metals and predicting properties of the resulting ejecta are of considerable importance for both basic and applied science. The nature of material ejection has been shown to change drastically when the free surface melts on compression or release. In this work, we present hydrodynamic simulations of laser-driven microjetting from micron-scale grooves on a tin surface. We study microjet formation across a range of shock strengths from drives that leave the target solid after release to drives that induce shock melting in the target. The shock-state particle velocity (Up) varies from 0.3 to 3 km/s and the shock breakout pressure is 3–120 GPa. The microjet tip velocity is 1–8 km/s and the free-surface velocity varies from 0.1 to 5 km/s. Two tin equations of state are examined: a “soft” model (LEOS 501) where the target melts for Up>1 km/s and a more detailed multiphase model (SESAME 2161) that melts for Up>1.4 km/s. We use these two models to examine the influence of phase change and the choice of the material model on microjet formation and evolution. We observe in our computational results that jet formation can be classified into three regimes: a low-energy regime where material strength affects jet formation, a moderate-energy regime dominated by the changing phase of tin material, and a high-energy regime where results are insensitive to the material model and jet formation is described by an idealized steady-jet theory. Using an ensemble of 2D simulations, we show that these trends hold across a wide range of drive energies and groove angles.
Thermodynamic free-energy spectrum theory for open quantum systems
Authors: Gong Hong , Wang Yao , Zhang Hou-Dao , Xu Rui-Xue , Zheng Xiao , Yan YiJing
Published: December 2020

In this work, we develop the free-energy spectrum theory for thermodynamics of open quantum impurity systems that can be either fermionic or bosonic or combined. We identify two types of thermodynamic free-energy spectral functions for open quantum systems and further consider the thermodynamic limit, which supports the Gaussian–Wick description of hybrid environments. We can then relate the thermodynamic spectral functions to the local impurity properties. These could be experimentally measurable quantities, especially for the cases of quantum dots embedded in solid surfaces. Another type of input is the bare–bath coupling spectral densities, which could be accurately determined with various methods. For illustration, we consider the simplest noninteracting systems, with focus on the strikingly different characteristics between the bosonic and fermionic scenarios.
A new high-pressure aerosol shock tube for the study of liquid fuels with low vapor pressures
Authors: Hargis Joshua W. , Guo Bing , Petersen Eric L.
Published: December 2020

A new shock-tube facility for studying gas-phase and condensed-phase mixtures has been developed for the investigation of various hydrocarbon species at the Qatar campus of Texas A&M University. At present, the facility is intended for studying combustion behaviors of long-chain hydrocarbon molecules and mixtures thereof under realistic engine conditions. Equipped with an aerosol generation and entrainment apparatus, the facility also possesses an enlarged driver section and double-diaphragm interface between the driver and driven sections. The driver section diameter is 19.37 cm with a configurable length of 1 m–6 m. Additionally, the stainless-steel driven section has an inner surface with a mirror finish and internal diameter of 15.24 cm. The driven section is also configurable in length up to approximately 5.2 m. As with most modern shock tubes, this shock tube is equipped for use with current methods of shock velocity detection, optical diagnostics, and other diagnostic techniques. In addition to the study of aerosolized liquids (fuels and non-fuels) related to combustion chemistry, reaction kinetics, evaporation studies, and particle–fluid interactions, among others, the facility is capable of investigating traditional gas-phase mixtures like those previously undertaken in a similar facility in the Petersen Group Laboratory at Texas A&M University. The operating limits of the title facility include temperatures and pressures up to 4000 K and 100 atm, respectively. The design and characterization of a novel aerosol introduction method is also presented, which yielded measured aerosol loading uniformities of 92%–97%. Finally, ignition delay time measurements of stoichiometric mixtures of decane in air are presented, which show excellent agreement with those recently recorded in heated shock tubes.
Soliton locking phenomenon over finite magnetic field region in the monoaxial chiral magnet CrNb3S6
Authors: Ohkuma M. , Mito M. , Kousaka Y. , Tajiri T. , Akimitsu J. , Kishine J. , Inoue K.
Published: December 2020

Previous magnetic measurements for the chiral magnet CrNb3S6 have shown that the soliton penetration and soliton dissipation in the chiral soliton lattice state strongly depend on the crystal's size and shape. We performed magnetic measurements for a thin single crystal of CrNb3S6 with a thickness 3 μm, permitting the existence of approximately 60 solitons, and observed the magnetization (M)—magnetic field (H) curve with a remarkable full M–H loop. By investigating the minor loop of the M–H curve in detail, we found that the inside of the full M–H loop allows an infinite number of quasi-stable states for each eigen number of solitons, utilizing a non-negligible distribution of the thickness around 3 μm. This study reveals that in a microcrystal with a chiral axis length of a few micrometers, any magnetic state with an arbitrary soliton number can be created in a certain H range within the full M–H loop.
Grain size effects in donor doped lead zirconate titanate ceramics
Authors: Picht Gunnar , Khansur Neamul H. , Webber Kyle G. , Kungl Hans , Hoffmann Michael J. , Hinterstein Manuel
Published: December 2020

The ferroelectric, ferroelastic, and dielectric properties as well as the crystal structure were investigated for polycrystalline donor doped lead zirconate titanate (PZT) with grain sizes ranging from 0.25 to 5 μm, which were prepared using a novel zirconium titanium hydrate precursor (ZTH) with a specific surface area of 310 m2/g. Piezoforce microscopy was used to investigate the change in the domain structure, revealing a change in the domain configuration from a complex 3D structure to a simple lamellar domain formation at a 1 μm grain size that corresponded to a rapidly increasing internal mechanical stress observed with in situ synchrotron x-ray experiments. The correlation between the change in domain configuration, increasing internal stresses, effects of poling on the crystal structure, and the macroscopic ferroelectric and ferroelastic properties are discussed in detail, allowing a deeper understanding of size effects in polycrystalline donor doped PZT ceramics.
Representing molecular ground and excited vibrational eigenstates with nuclear densities obtained from semiclassical initial value representation molecular dynamics
Authors: Aieta Chiara , Bertaina Gianluca , Micciarelli Marco , Ceotto Michele
Published: December 2020

We present in detail and validate an effective Monte Carlo approach for the calculation of the nuclear vibrational densities via integration of molecular eigenfunctions that we have preliminary employed to calculate the densities of the ground and the excited OH stretch vibrational states in the protonated glycine molecule [Aieta et al., Nat Commun 11, 4348 (2020)]. Here, we first validate and discuss in detail the features of the method on a benchmark water molecule. Then, we apply it to calculate on-the-fly the ab initio anharmonic nuclear densities in the correspondence of the fundamental transitions of NH and CH stretches in protonated glycine. We show how we can gain both qualitative and quantitative physical insight by inspection of different one-nucleus densities and assign a character to spectroscopic absorption peaks using the expansion of vibrational states in terms of harmonic basis functions. The visualization of the nuclear vibrations in a purely quantum picture allows us to observe and quantify the effects of anharmonicity on the molecular structure, also to exploit the effect of IR excitations on specific bonds or functional groups, beyond the harmonic approximation. We also calculate the quantum probability distribution of bond lengths, angles, and dihedrals of the molecule. Notably, we observe how in the case of one type of fundamental NH stretching, the typical harmonic nodal pattern is absent in the anharmonic distribution.
Three-dimensional high-order least square-based finite difference-finite volume method on unstructured grids
Authors: Liu Y. Y. , Yang L. M. , Shu C. , Zhang H. W.
Published: December 2020

The least square-based finite difference-finite volume (LSFD-FV) method has been developed and successfully applied to solve various two-dimensional flow problems with a high-order of accuracy. In this paper, the extension of the LSFD-FV method to the three-dimensional (3D) case on unstructured grids is presented. Different from other existing high-order methods, the LSFD-FV method combines the good features of the least square-based finite difference (LSFD) scheme for derivative approximation and the finite volume (FV) discretization for conservation of physical laws. Within each control cell, a high-order polynomial resultant from a Taylor series expansion is used to approximate the solution in the FV discretization of governing equations, where the derivatives are approximated by the LSFD scheme. As a result, the mesh-free nature of the LSFD scheme endows the LSFD-FV method with the flexibility on unstructured grids. Additionally, the straightforward algorithm of the LSFD scheme and the direct utilization of the Taylor series polynomial make the LSFD-FV method user-friendly and easy to implement. Furthermore, the inviscid and viscous fluxes are simultaneously evaluated by lattice Boltzmann and gas kinetic flux solvers in this work, which avoids additional and complicated treatment for the viscous discretization. Accuracy studies on unstructured hexahedral and tetrahedral grids validate the third-order of accuracy of the 3D LSFD-FV method. Various 3D incompressible and compressible numerical experiments are also presented. The results show that the proposed method enjoys the higher accuracy than the conventional second-order method on the same mesh. When the same accuracy is achieved, the present high-order method has superior computational efficiency to the second-order counterpart.
Surface anisotropy induced spin wave nonreciprocity in epitaxial La0.33 Sr0.67 MnO3 film on SrTiO3 substrate
Authors: Zhang Jianyu , Burema Arjan Auke , Chen Jilei , Hu Junfeng , Guo Chenyang , Wang Hanchen , Li Ningsheng , Wei Bohang , Han Xiufeng , Banerjee Tamalika , Yu Haiming
Published: December 2020

Spin wave propagation in perovskite La0.33 Sr0.67 MnO3 films epitaxially grown on a SrTiO3 substrate of (001) orientation was investigated using an all electrical spin wave spectroscopy technique. The spin wave nonreciprocity in amplitude, resonance frequency, and group velocity of the transmission spectra were observed. The origin of the spin-wave nonreciprocity is attributed to the out-of-plane surface anisotropy, with a value of 1.3 mJ/m2 at the interface with the substrate, as extracted from the theoretical model. The magnetic field dependence of the frequency shift is attributed to the perpendicular surface anisotropy. The important role of the surface anisotropy in the spin wave nonreciprocity was further confirmed by the angle dependent measurements of the spin wave transmission spectra.
Equation-of-motion coupled-cluster theory for double electron attachment with spin–orbit coupling
Authors: Guo Minggang , Wang Zhifan , Wang Fan
Published: December 2020

We report implementation of the equation-of-motion coupled-cluster (EOM-CC) method for double electron-attachment (DEA) with spin–orbit coupling (SOC) at the CC singles and doubles (CCSD) level using a closed-shell reference in this work. The DEA operator employed in this work contains two-particle and three-particle one-hole excitations, and SOC is included in post-Hartree–Fock treatment. Time-reversal symmetry and spatial symmetry are exploited to reduce computational cost. The EOM-DEA-CCSD method with SOC allows us to investigate SOC effects of systems with two-unpaired electrons. According to our results on atoms, double ionization potentials (DIPs), excitation energies (EEs), and SO splittings of low-lying states are calculated reliably using the EOM-DEA-CCSD method with SOC. Its accuracy is usually higher than that of EOM-CCSD for EEs or DIPs if the same target can be reached from single excitations by choosing a proper closed-shell reference. However, performance of the EOM-DEA-CCSD method with SOC on molecules is not as good as that for atoms. Bond lengths for the ground and the several lowest excited states of GaH, InH, and TlH are underestimated pronouncedly, although reasonable EEs are obtained, and splittings of the 3Σ− state from the π2 configuration are calculated to be too small with EOM-DEA-CCSD.
Combining intermolecular potentials for the prediction of fluid properties: Two-body and three-body interactions
Authors: Sadus Richard J.
Published: December 2020

The ability to combine intermolecular potentials without loss of information is investigated. Molecular simulation results for both vapor–liquid equilibria and supercritical isochoric heat capacities are reported for different combinations of n–m potentials. The role of both additional cohesion and repulsive terms is determined. The 12-8-6 potential obtained by adding an m = 6 contribution to the 12-8 potential significantly broadens the phase envelope, which remains inside of the 12-6 envelope. In contrast, the 12+9-6 potential that involves an additional n = 9 repulsive contribution lifts the phase envelope above the 12-6 values. The 12-8-6 potential significantly reduces the maximum and minimum observed for the isochoric heat capacity at supercritical conditions. In contrast, the additional repulsion of the 12+9-6 potential has a relatively small influence on the supercritical behavior of the isochoric heat capacity. Significantly, a comparison of vapor–liquid equilibria data for two-body only simulations for Ar, Kr, and Xe indicates that there is very good agreement with the 12-8-6 data. This means that the 12-8-6 potential may provide a useful description of two-body only interactions for the noble gases. The 12+9-8 potential at least partially reproduces vapor–liquid properties of noble gases interacting via two-body plus three-body interactions. In general, the combination of potentials provides a mechanism of simplifying the calculation of two-body and two-body plus three-body interactions.
Mechanisms underlying photosynthetic acclimation to high temperature are different between Vitis vinifera cv. Syrah and Grenache
Authors: Gallo Agustina E. , Perez Peña Jorge E. , Prieto Jorge A.
Published: December 2020

Photosynthesis acclimation to high temperature differs among and within species. Grapevine intra-specific variation in photosynthetic acclimation to elevated temperature has been scarcely assessed. Our objectives were to (i) evaluate the mechanisms underlying long-term acclimation of photosynthesis to elevated temperature in grapevine, and (ii) determine whether these responses are similar among two varieties. A warming experiment with well irrigated Grenache and Syrah field-grown plants was performed during two growing seasons comparing plants exposed at ambient temperature (control) with plants in open-top chambers (heating) that increased mean air temperature between 1.5 and 3.6°C. Photosynthetic acclimation was assessed through the response of net assimilation (An), Rubisco carboxylation rate (Vcmax) and electron transport rate (Jmax), at leaf temperatures from 20 to 40°C. Our results evidenced different mechanisms for photosynthetic acclimation to elevated temperature. Compared with control, Grenache heated increased An, maintaining higher Vcmax and Jmax at temperatures above 35°C. By contrast, Syrah heated and control presented similar values of An, Vcmax and Jmax, evidencing an adjustment of photosynthesis without increasing C assimilation. Both varieties increased the optimum temperature for An, but to a lesser extent when growth temperature was higher. Our study provides evidence that grapevine varieties present different acclimation mechanisms to expected warming.
Communication hubs of an asocial cat are the source of a human–carnivore conflict and key to its solution
Authors: Melzheimer Joerg , Heinrich Sonja K. , Wasiolka Bernd , Mueller Rebekka , Thalwitzer Susanne , Palmegiani Ivan , Weigold Annika , Portas Ruben , Roeder Ralf , Krofel Miha , Hofer Heribert , Wachter Bettina
Published: December 2020

Significance

The cheetah is a prominent example for human–carnivore conflicts and mitigation challenges. Its global population suffered a substantial decline throughout its range. Here, we present an in-depth and new understanding of the socio-spatial organization of the cheetah. We show that cheetahs maintain a network of communication hubs distributed in a regular pattern across the landscape, not contiguous with each other and separated by a surrounding matrix. Cheetahs spend a substantial amount of their time in these hubs, resulting in high local cheetah activity, which represents a high local predation risk for livestock. Implementing this knowledge, farmers were able to reduce livestock losses by 86%.
Pharmacoproteomics pinpoints HSP70 interaction for correction of the most frequent Wilson disease-causing mutant of ATP7B
Authors: Concilli Mafalda , Petruzzelli Raffaella , Parisi Silvia , Catalano Federico , Sirci Francesco , Napolitano Francesco , Renda Mario , Galietta Luis J. V. , Di Bernardo Diego , Polishchuk Roman S.
Published: December 2020

Significance

Wilson disease is a disorder of copper homeostasis caused by mutations in
ATP7B
. The most frequent mutation of
ATP7B
results in an H1069Q substitution that affects the localization and stability of the protein product. By interrogating the interactome of ATP7B-H1069Q, we found that this mutant shows stronger interaction with HSP70, which drives mutant degradation. Using an HSP70 inhibitor for structural similarity searches, we identified a Food and Drug Administration-approved drug that increases ATP7B-H1069Q stability in cells and thus improves ATP7B function. This pharmacoproteomic strategy provides an effective shortcut from understanding cellular mechanisms operating in Wilson disease to rapid identification of safe pharmacological tools and therefore might be expanded for drug repurposing to counteract other genetic disorders.
Stable maintenance of multiple representational formats in human visual short-term memory
Authors: Liu Jing , Zhang Hui , Yu Tao , Ni Duanyu , Ren Liankun , Yang Qinhao , Lu Baoqing , Wang Di , Heinen Rebekka , Axmacher Nikolai , Xue Gui
Published: December 2020

Significance

Visual short-term memory (VSTM) is the ability to actively maintain visual information for a short period of time. Classical models posit that VSTM is achieved via persistent firing of neurons in prefrontal cortex. Leveraging the unique spatiotemporal resolution of intracranial EEG recordings and analytical power of deep neural network models in uncovering the neural code of visual processing, our results suggest that visual information is first dynamically extracted in multiple representational formats, including higher-order visual format and abstract semantic format. Both formats are stably maintained across an extended period via coupling to phases of hippocampal low-frequency activity. These results suggest human VSTM is highly dynamic and involves rich and multifaceted representations, which contribute to a mechanistic understanding of VSTM.
The V2 loop of HIV gp120 delivers costimulatory signals to CD4+T cells through Integrin α4β7and promotes cellular activation and infection
Authors: Goes Livia R. , Sajani Alia , Sivro Aida , Olowojesiku Ronke , Ray Jocelyn C. , Perrone Ian , Yolitz Jason , Girard Alexandre , Leyre Louise , Wibmer Constantinos Kurt , Morris Lynn , Gorini Giacomo , Franchini Genoveffa , Mason Rosemarie D. , Roederer Mario , Mehandru Saurabh , Soares Marcelo A. , Cicala Claudia , Fauci Anthony S. , Arthos James
Published: December 2020

Significance

Understanding the early events in HIV transmission will aid in the development of an efficacious HIV vaccine. Productive infection requires that virions access metabolically activated CD4+T cells. These cells are, in general, limited in number, which contributes to inefficient viral transmission. This report describes a mechanism whereby the HIV gp120 envelope protein can deliver activating signals to CD4+T cells. This activity may increase both productive infection in mucosal tissues around the time of transmission and the formation of viral reservoirs. gp120 mediates activating signals by binding to integrin α4β7. Antibodies specific to the V2 domain of gp120 block this interaction and may contribute to the efficacy of an HIV vaccine.
A Middle Eocene lowland humid subtropical “Shangri-La” ecosystem in central Tibet
Authors: Su Tao , Spicer Robert A. , Wu Fei-Xiang , Farnsworth Alexander , Huang Jian , Del Rio Cédric , Deng Tao , Ding Lin , Deng Wei-Yu-Dong , Huang Yong-Jiang , Hughes Alice , Jia Lin-Bo , Jin Jian-Hua , Li Shu-Feng , Liang Shui-Qing , Liu Jia , Liu Xiao-Yan , Sherlock Sarah , Spicer Teresa , Srivastava Gaurav , Tang He , Valdes Paul , Wang Teng-Xiang , Widdowson Mike , Wu Meng-Xiao , Xing Yao-Wu , Xu Cong-Li , Yang Jian , Zhang Cong , Zhang Shi-Tao , Zhang Xin-Wen , Zhao Fan , Zhou Zhe-Kun
Published: December 2020

Significance

The ancient topography of the Tibetan Plateau and its role in biotic evolution are still poorly understood, mostly due to a lack of fossil evidence. Our discovery of ∼47-Mya plant fossils from a present elevation of 4,850 m in central Tibet, diminishes, significantly, that lack of knowledge. The fossils represent a humid subtropical vegetation and some of the 70 different plant forms show affinity to Early-Middle Eocene floras in both North America and Europe. Using leaf architecture, we calculate that the forest grew at ∼1,500-m elevation within an east–west trending valley under a monsoonal climate. Our findings highlight the complexity of Tibet’s ancient landscape and emphasize the importance of Tibet in the history of global biodiversity.
Dissociating antibacterial from ototoxic effects of gentamicin C-subtypes
Authors: O’Sullivan Mary E. , Song Yohan , Greenhouse Robert , Lin Randy , Perez Adela , Atkinson Patrick J. , MacDonald Jacob P. , Siddiqui Zehra , Lagasca Dennis , Comstock Kate , Huth Markus E. , Cheng Alan G. , Ricci Anthony J.
Published: December 2020

Significance

Gentamicin is a potent aminoglycoside antibiotic with significant ototoxic side-effects. Although it is administered as a mixture of five main C-subtypes and <10% impurities, the significance of mixture is unclear, partly because of the difficulty in chemically separating the individual components. We established methods purifying gentamicin C-subtypes, and found C2b to be the least and sisomicin the most ototoxic, with both antimicrobial comparable to the gentamicin mixture. Ototoxicity varies among C-subtypes and impurities and highly correlates with their affinity for cochlear hair cell mechanotransducer channels, representing a mechanism to alleviate aminoglycoside ototoxicity. Finally, reconstituted mixtures consisting of only C-subtypes remained antimicrobial but were less ototoxic. Our study reveals structure–activity relationships that dissociate ototoxicity from antimicrobial actions of aminoglycosides.
TCRα reporter mice reveal contribution of dual TCRα expression to T cell repertoire and function
Authors: Yang Letitia , Jama Burhan , Wang Huawei , Labarta-Bajo Lara , Zúñiga Elina I. , Morris Gerald P.
Published: December 2020

Significance

This study utilizes novel transgenic reporter mice to definitively evaluate T cells coexpressing two T cell antigen receptors. These experiments demonstrate that T lymphocytes naturally coexpressing two different antigen receptors are significantly more abundant than previous estimates and that these cells have a previously unappreciated role in physiologic immune responses.
The plasticity of well-being: A training-based framework for the cultivation of human flourishing
Authors: Dahl Cortland J. , Wilson-Mendenhall Christine D. , Davidson Richard J.
Published: December 2020

Research indicates that core dimensions of psychological well-being can be cultivated through intentional mental training. Despite growing research in this area and an increasing number of interventions designed to improve psychological well-being, the field lacks a unifying framework that clarifies the dimensions of human flourishing that can be cultivated. Here, we integrate evidence from well-being research, cognitive and affective neuroscience, and clinical psychology to highlight four core dimensions of well-being—awareness, connection, insight, and purpose. We discuss the importance of each dimension for psychological well-being, identify mechanisms that underlie their cultivation, and present evidence of their neural and psychological plasticity. This synthesis highlights key insights, as well as important gaps, in the scientific understanding of well-being and how it may be cultivated, thus highlighting future research directions.
Reconstructing orogens without biostratigraphy: The Saharides and continental growth during the final assembly of Gondwana-Land
Authors: Şengör A. M. Celâl , Lom Nalan , Zabcı Cengiz , Sunal Gürsel , Öner Tayfun
Published: December 2020

Significance

A method without biostratigraphy is employed to delineate a hitherto unknown, major orogenic system of Neoproterozoic age in North Africa and Arabia in which some 5 million km2of juvenile continental crust may have been generated in some 400 Ma, i.e., 0.44 km3/a assuming a minimum thickness of 35 km for the generated crust, thus slightly less than the 1/3 of the annual average crustal growth rate globally and similar to the crustal growth rate in the Altaids of Asia between 600 and 140 Ma, supporting the idea that the formation of the continental crust has been continuous throughout earth history, albeit with fluctuating intensity. Our method can be applied to reconstruct other complex Precambrian orogenic systems.
Glucose-TOR signaling regulates PIN2 stability to orchestrate auxin gradient and cell expansion in
Arabidopsis
root
Authors: Yuan Xinbo , Xu Ping , Yu Yongdong , Xiong Yan
Published: December 2020

The plant growth hormone auxin controls cell identity, cell division, and expansion. In the primary root of
Arabidopsis
there is a robust auxin gradient with a peak concentration at the tip of the meristem and a significant decrease throughout the elongation zone. The molecular mechanisms of how such a steep auxin gradient is established and maintained, and how this auxin gradient within the root dynamically adjusts in response to environmental stimuli are still largely unknown. Here, using a large-scale
Arabidopsis
mutant screening, we described the identification of PIN2 (PIN-FORMED 2), an auxin efflux facilitator, as a key downstream regulator in glucose-TOR (target of rapamycin) energy signaling. We demonstrate that glucose-activated TOR phosphorylates and stabilizes PIN2 and therefore influences the gradient distribution of PIN2 in the
Arabidopsis
primary root. Interestingly, dysregulation of TOR or PIN2 disrupts the glucose-promoted low auxin region located in the elongation zone that is essential for cell elongation. Taken together, our results shed light on how carbon and metabolic status can be tightly integrated with the hormone-driven processes to orchestrate complex plant growth programs.
Fluid interfaces with very sharp tips in viscous flow
Authors: Courrech du Pont Sylvain , Eggers Jens
Published: December 2020

Significance

Turn a shampoo bottle upside down, and the rising bubble develops a very sharp tip at its rear. Similar conical structures have been observed placing a drop in an electrical field. Owing to the significance of such structures in chemical processing or in geophysics, they have been studied for almost a century. Here we present a consistent analysis of the shape near the tip in flow. We show that the size of the tip always remains finite, but decreases so rapidly in size with the flow strength that it may be considered zero for practical purposes.
Identification of signaling pathways, matrix-digestion enzymes, and motility components controlling
Vibrio cholerae
biofilm dispersal
Authors: Bridges Andrew A. , Fei Chenyi , Bassler Bonnie L.
Published: December 2020

Significance

The global pathogen
Vibrio cholerae
alternates between free swimming and existing in sessile multicellular communities known as biofilms. Transitioning between these lifestyles is key for disease transmission.
V. cholerae
biofilm formation is well studied; however, almost nothing is known about how
V. cholerae
cells disperse from biofilms, precluding our understanding of a central pathogenicity step. Here, we conducted an imaging screen for
V. cholerae
mutants that failed to disperse. Our screen revealed three classes of components required for dispersal: signal transduction, matrix degradation, and motility factors. We characterized these components to reveal the sequence of molecular events that choreograph
V. cholerae
biofilm dispersal. Our report provides a framework for developing strategies to modulate biofilm dispersal to prevent or treat disease.
Political discourse analysis in operation
Authors: Liu Nancy Xiuzhi
Published: December 2020

After implementing of the Belt and Road Initiative (BRI) for four years, the Chinese government convened the BRI Summits
in Beijing in 2017 and 2019, respectively. This article will address the questions of how the summits were covered in translated news by
using empirical data from news published on the Reference News, a state-owned newspaper that publishes translated news, in
comparison to news carried in People’s Daily, an authoritative national newspaper in China. Situated in the framework of
political discourse analysis (PDA) within critical discourse analysis (CDA) and using the method of qualitative thematic analysis, the study
shows that translated news is a platform where contentious ideologies are at play and where dominant ones leave little room for the
confrontational. In this process, translators are submissive actors whose work is navigated by the agenda set by the authorities in either
legitimizing or representing frames in mainstream media.
Creaming off commodity profits: Europe’s re-export boom and Africa’s earnings crisis in the coffee and cocoa sectors
Authors: Elsby Angus
Published: December 2020

This briefing uses historical export data and a combination of institutional sources to track how mark-ups on African coffee and cocoa exports have changed relative to European coffee and cocoa re-exports in recent decades. It finds that African coffee is now re-exported from Europe at an average mark-up of over 300%, compared to just over 50% in the 1970s and 1980s. These trends have prompted a crisis for producers, and reflect the growth, expansion and extended control over production of European agribusiness, which European governments have encouraged through the implementation of competition, corporate tax and regulatory policies favourable to agribusiness, in addition to the suppression of national and international initiatives to manage global supply.
First-principles electronic structure, phonon properties, lattice thermal conductivity and prediction of figure of merit of FeVSb half-Heusler
Authors: Shastri Shivprasad S , Pandey Sudhir K
Published: December 2020

In this work, we have studied the electronic structure of a promising thermoelectric half-Heusler FeVSb using FP-LAPW method and SCAN meta-GGA including spin–orbit coupling. Using the obtained electronic structure and transport calculations we try to address the experimental Seebeck coefficient S of FeVSb samples. The good agreement between the experimental and calculated S suggests the band gap could be ∼0.7 eV. This is supported by the obtained mBJ band gap of ∼0.7 eV. Further, we study and report the phonon dispersion, density of states and thermodynamic properties. The effect of long range Coulomb interactions on phonon frequencies are also included by nonanalytical term correction. Under quasi-harmonic approximation, the thermal expansion behaviour up to 1200 K is calculated. Using the first-principles anharmonic phonon calculations, the lattice thermal conductivity κ
ph of FeVSb is obtained under single-mode relaxation time approximation considering the phonon-phonon interaction. At 300 K, the calculated κ
ph is ∼18.6 W m−1 K−1 which is higher compared to experimental value. But, above 500 K the calculated κ
ph is in good agreement with experiment. A prediction of figure of merit ZT and efficiency for p-type and n-type FeVSb is made by finding out optimal carrier concentration. At 1200 K, a maximum ZT of ∼0.66 and ∼0.44 is expected for p-type and n-type FeVSb, respectively. For p-type and n-type materials, maximum efficiency of ∼12.2% and ∼6.0% are estimated for hot and cold temperature of 1200 K and 300 K, respectively. A possibility of achieving n-type and p-type FeVSb by elemental doping/vacancy is also discussed. Our study is expected to help in further exploring the thermoelectric material FeVSb.
A wearable contact lens sensor for noninvasive in-situ monitoring of intraocular pressure
Authors: Fan Yanyan , Tu Hailing , Zhao Hongbin , Wei Feng , Yang Yi , Ren Tianling
Published: December 2020

Glaucoma is the second leading cause of blindness in the world. Intraocular pressure (IOP) is a primary indicator of glaucoma which can be measured for the treatment of the disease. This paper presents a piezo-resistive principle pressure sensor to monitor IOP continuously and non-invasively. The sensor is designed based on the Wheatstone bridge circuit and fabricated by the spray-coating method. The hybrid nanomaterials of graphene and carbon nanotubes are introduced as sensing layers which are embedded inside the soft contact lens substrate composed of flexible polydimethyl siloxane (PDMS) and parylene. The sensing performance is discussed followed by a brief description of our sensor design and fabrication. Tests on a PDMS eyeball model indicate that it has a high sensitivity of 36.01 μV mmHg−1. Also, the frequency response and the ability to track dynamic pressure change cycles are demonstrated in normal IOP variation range from 9 to 34 mmHg. It shows good repeatability and linearity, and can accurately track fluctuating IOP. Thus, this sensor, with its ease of fabrication and simple design, as well as allowance for continuous pressure measurement, offers a promising approach for IOP monitoring in clinical diagnosis of glaucoma.
Electron acceleration and electromagnetic emission in the field of intersecting Gaussian pulses
Authors: Borovskiy A V , Galkin A L
Published: December 2020

Numerical simulations of the acceleration of an electron by a pair of phased intersecting Gaussian laser beams and of the electromagnetic emissions by the electrons are carried out. The study is based on solving equations of the relativistic electron dynamic with the corresponding Lorentz force. The electron emissions are calculated with the help of the Lienard–Wiechert potentials, taking into account the retardation of the propagating fields. Differences between the electron acceleration and emissions in intersecting laser beams and in a single Gaussian beam are examined. It is shown that the integral emission energy is maximal for the symmetric trajectory and that the acceleration and emission are competing processes.
Multiscale characteristics of pool boiling in vacuum
Authors: Serdyukov V , Malakhov I , Surtaev A , Pavlenko A
Published: December 2020

In this paper the results of comprehensive study on the multiscale characteristics and heat transfer rate during water boiling in the pressure range from 8.8 to 103 kPa are presented. The experimental data are obtained using the modern experimental techniques, including high-speed video recording and infrared thermography. The usage of the special design of a transparent heating surface allows gaining a full set of major multiscale pool boiling characteristics. In particular, new data have been revealed on the vapor bubble growth rate and departure diameter, bubble emission frequency and nucleation site density during pool boiling in vacuum. The simple expression to predict the effect of pressure reduction on nucleation site density value is also presented.
Structuring of water molecules near a copper surface
Authors: Andryushchenko V A , Boyko E V
Published: December 2020

Using the molecular dynamics method, the structuring of water molecules near copper surfaces at various temperatures is studied. Samples with crystallographic orientations of 100 and 111 are considered at temperatures from 300 K to 350 K. It is found that the planes of water molecules in the near-surface region with the size is about six angstroms are oriented mainly parallel to the copper surface. However, the character of the structuring of water molecules near the copper surface weakly depends on the considered crystallographic orientations and temperatures.