bluuebunny/crossref_metadata_2025 huggingface dataset:
Ground-state actinide chemistry with scalar-relativistic multiconfiguration pair-density functional theory
Authors: Adeyiga Olajumoke , Suleiman Olabisi , Dandu Naveen K. , Odoh Samuel O.
Published: October 2019

We have examined the performance of Multiconfiguration Pair-Density Functional Theory (MC-PDFT) for computing the ground-state properties of actinide species. Specifically, we focused on the properties of UN2 and various actinyl species. The properties obtained with MC-PDFT at the scalar-relativistic level are compared to Kohn-Sham DFT (KS-DFT); complete active space self-consistent field theory, CASSCF; coupled-cluster theory, CCSD(T) and CCSDT; as well as multireference perturbation theory (CASPT2). We examine the degree to which MC-PDFT improves over KS-DFT and CASSCF while aligning with CASPT2, CCSD(T), and CCSDT. All properties that we considered were for the CASPT2 electronic ground states. For structural parameters, MC-PDFT confers very little advantage over KS-DFT, especially the B3LYP density functional. For NpO23+, MC-PDFT and local KS-DFT functionals excessively favor the bent structure, whereas CCSDT and CASPT2 predict the bent and linear structures as isoenergetic. For this special case, hybrid KS-DFT functionals like PBE0 and B3LYP provide results closer to CASPT2 and CCSDT than MC-PDFT. On a more positive note, MC-PDFT is very close to CASPT2 and CCSD(T) for the redox potentials, energetics of redox chemical reactions, as well as ligand-binding energies. These are encouraging results since MC-PDFT is more affordable. The best MC-PDFT functional is ft-PBE. Our findings suggest that MC-PDFT can be used to study systems and excited states with larger strong electron correlation effects than were considered here. However, for the systems and properties considered here, KS-DFT functionals do well, justifying their usage as the bulwark of computational actinyl chemistry over the last two to three decades.
Laser-induced fluorescence and dispersed-fluorescence spectroscopy of the Ã2E−X̃2A1 transition of jet-cooled calcium methoxide (CaOCH3) radicals
Authors: Paul Anam C. , Sharma Ketan , Reza Md Asmaul , Telfah Hamzeh , Miller Terry A. , Liu Jinjun
Published: October 2019

Laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of the Ã2E−X̃2A1 electronic transition of the calcium methoxide (CaOCH3) radical have been obtained under jet-cooled conditions. Complete active space self-consistent field and coupled-cluster calculations on the free radical were performed to aid the assignment of vibronic transitions observed in the LIF/DF spectra. In addition to dominant spectral features that are well reproduced by vibrational frequencies and Franck-Condon (FC) factors calculated ab initio, the FC matrix for the Ã2E−X̃2A1 electronic transition contains considerable off-diagonal elements that connect (i) the CaO-stretch (ν4) mode and non-CaO stretch modes and (ii) the asymmetric CaOC stretch (ν3) and the CaOC bending (ν8) modes. The Jahn-Teller and pseudo-Jahn-Teller interactions involving the Ã2E state as well as the spin-orbit interaction induce additional vibronic transitions that are not allowed under the Born-Oppenheimer approximation. Additionally, anharmonic vibrational terms in the ground state induce transitions that are forbidden in the harmonic-oscillator approximation. Spin-orbit splitting has been observed for several vibrational levels of the Ã2E state, and an essentially constant value was measured at all levels accessed in the LIF experiment. Implications of the present spectroscopic investigation to the proposed schemes of laser-cooling MOCH3 (M = alkaline earth metals) molecules and detection of time-reversal-symmetry-violating interactions are discussed.
Free vibration of single-layered MoS2 suspended over a circular hole
Authors: Jiang Jingnong , Wang Lifeng , Zhang Yiqing
Published: October 2019

The vibrational behaviors of circular single-layered molybdenum disulfide (CSLMoS2) suspended over a concentric circular hole are investigated using a two-segment circular Kirchhoff plate (TSCKP) corresponding to different initial stresses and molecular dynamics (MD) simulations. An analytical solution is proposed to analyze the free vibrations of the TSCKP model. van der Waals (vdW) interaction coefficient between the single-layered MoS2 (SLMoS2) and the silicon substrate is derived theoretically. MD simulations show that the TSCKP model can give a good prediction to the vibrational behaviors of the CSLMoS2 suspended over a concentric circular hole. The effects of the overlapped width and radial initial stresses on the vibrational behaviors of the CSLMoS2s are investigated. The natural frequencies of the TSCKP model become much closer to those of a one-segment circular Kirchhoff plate with the clamped supported boundary (OSCKP-CC) as the radius of the inner-segment circular plate increases; however, the value predicted by the TSCKP model is always smaller than that predicted by the OSCKP-CC. The TSCKP model can also give a reasonable prediction to the vibrational behaviors of the square SLMoS2 suspended over a concentric circular hole when the overlapped widths between the circular and square SLMoS2s and elastic substrate along any radial direction are sufficiently large.
Toroidal modeling of thermal particle drift kinetic effects and sub-sonic plasma flow on internal kink mode
Authors: Wu Tingting , Liu Yueqiang , Liu Yue , Zhou Lina , He Hongda
Published: October 2019

The stability of the n=1 (n is the toroidal mode number) internal kink mode in a tokamak plasma is numerically investigated, utilizing the full toroidal, ideal magnetohydrodynamic (MHD) code MARS-F [Y. Q. Liu et al., Phys. Plasmas 7, 3681 (2000)] and the nonperturbative MHD-kinetic hybrid code MARS-K [Y. Liu et al., Phys. Plasmas 15, 112503 (2008)]. This study focuses on two physics effects: the sheared toroidal flow of plasma and the drift kinetic effects from thermal particles (ions and electrons) on the internal kink instability. Within the subsonic flow assumption, the flow and flow shear effects on the internal kink are generally weak, but the kinetic effects can be strong. A significant reduction in the mode growth rate is predicted by the nonperturbative MHD-kinetic hybrid computations, when the precessional drift resonance contributions from both particle species are included and when the mode is not too strongly unstable according to the fluid theory. The stabilization/destabilization of sheared toroidal flow depends on the radial location of the local flow shear. Strong destabilization (stabilization) occurs when a negative (positive) flow shear is located near the q=1 rational surface.
Effect of the electron heating transition on the proton acceleration in a strongly magnetized plasma
Authors: Lv Chong , Zhao Bao-Zhen , Wan Feng , Cai Hong-Bo , Meng Xiang-Hao , Xie Bai-Song , Liu Fu-Long , Liu Qiu-Shi , Zhang Xiao-Hua , Zhang Ji , Li Yu-Chen
Published: October 2019

A novel scheme assisted by an external axial magnetic field is proposed to accelerate and collimate protons when a right-hand circularly polarized laser irradiates on an overdense plasma. We find that the transition of heating electron mode plays an important role in proton acceleration. First, the electrons are accelerated by stochastic heating in the case of no external magnetic field. Second, when the ratio of electron cyclotron frequency in the external magnetic field to the laser frequency is smaller than the relativistic factor ωce/ω0≤γ, the cyclotron resonance absorption can occur and a laser front sharpening mechanism greatly improves the energy conversion from the laser to electrons. Meanwhile, the external magnetic field also restrains electrons' transverse motion. Finally, for ωce/ω0>γ, there is a time delay in the electron heating, which can be divided into two stages. In the case of B = 2, a high quality proton beam can be harvested whose cut-off energy is enhanced by a factor of 4 and beam width is reduced to one fifth of that in the case of B = 0. These results may be helpful to understand the electron heating and proton accelerated process in a strongly magnetized plasma.
Selective near-perfect absorbing mirror as a spatial frequency filter for optical image processing
Authors: Wesemann Lukas , Panchenko Evgeniy , Singh Kalpana , Della Gaspera Enrico , Gómez Daniel E. , Davis Timothy J. , Roberts Ann
Published: October 2019

Spatial frequency filtering is a fundamental enabler of information processing methods in biological and technical imaging. Most filtering methods, however, require either bulky and expensive optical equipment or some degree of computational processing. Here, we experimentally demonstrate real-time, on-chip, all-optical spatial frequency filtering using a thin-film perfect absorber structure. We experimentally demonstrate edge enhancement of an amplitude image and conversion of phase gradients to intensity modulation in an image. The device is used to demonstrate enhancement of an image of pond algae.
Thermal simulation of magnetization reversals for a size-distributed assembly of nanoparticles with uniaxial and cubic anisotropies
Authors: Ryon N. , Richy J. , Sheppard C. J. , Prinsloo A. R. E. , Fessant A. , Jay J.-Ph. , Spenato D. , Dekadjevi D. T.
Published: October 2019

A temperature-dependent coherent magnetization reversal model is proposed for size-distributed assemblies of ferromagnetic nanoparticles (NPs). NPs are assumed to be of uniaxial and cubic anisotropies. The thermal dependence is included by considering thermal fluctuations, implemented through the Néel-Arrhenius theory. Theoretically calculated thermal and angular dependences of magnetization reversal loops are obtained. There are similar behaviors for a single NP and an assembly of NPs. In particular, it is shown that the fourfold anisotropy results in double slope loops along the hard axis in both cases. Also, the azimuthal dependence of coercive fields is similar in both cases and with or without the presence of a fourfold anisotropy. There are also important differences in the behaviors observed for a single NP and that of an assembly of NPs. Firstly, the blocking temperature is barely enhanced by the presence of a fourfold anisotropy but is greatly enhanced in the assembly of NPs relative to a single NP. Secondly, along the easy axis, for a single size particle, the shape of the M-H loops is neither temperature dependent nor fourfold anisotropy dependent, as it is always rectangular. However, the shape of the M-H loops for an assembly of NPs is temperature dependent, but this shape is weakly dependent on the anisotropy ratio. Simulations of M-H loops using the model presented here would allow the quantitative determination of the anisotropy constants for either single sized NPs or an assembly with different sizes.
Fast lithiation of NiO investigated by in situ transmission electron microscopy
Authors: Zhu Yuanmin , Li Chan , Wang Qi , Wang Jianping , Chen Lang , Gu Meng
Published: October 2019

As a lithium-ion battery anode material, NiO has attracted a lot of attention owing to its excellent theoretical capacity. In this work, the dynamic lithiation process of NiO nanoplates and nanoparticles was investigated by in situ transmission electron microscopy (TEM). The morphology evolution, phase transformation, and electrochemical reaction of NiO during the lithiation process have been probed in real time by in situ TEM combined with selected area electron diffraction and electron energy loss spectroscopy technologies. We found that the insertion of Li-ions led to huge volume expansion of NiO, resulting in structural changes and breakdown. Li2O formed during lithiation hinders electron transportation through NiO due to its low conductivity, which causes poor cycling performance of NiO. Our findings provide valuable theoretical guidance for the modification of NiO as anode material for next generation high-performance lithium-ion batteries.
Propagation of Bernstein waves in weakly relativistic pair ion plasma
Authors: Ali Muddasir , Khan Waseem , Ehsan Zahida
Published: October 2019

The characteristics of Bernstein waves like overlapping, propagation region, and harmonic structure are examined in the symmetric and asymmetric pair ion plasma. We observe that asymmetry (in temperature and mass) in pair ion plasma alters the dispersion curves and overlapping between the harmonics seems to vanish for such a plasma system.
Reducing ambipolar off-state leakage currents in III-V vertical nanowire tunnel FETs using gate-drain underlap
Authors: Krishnaraja Abinaya , Svensson Johannes , Lind Erik , Wernersson Lars-Erik
Published: October 2019

Tunnel Field-Effect Transistors (TFETs) are an emerging alternative to CMOS for ultralow power and neuromorphic applications. The off current (Ioff) and, hence, the subthreshold swing (S) in these devices are limited by ambipolarity, which degrades its capabilities in complementary circuits. Here, we investigate experimentally vertical InAs/InGaAsSb/GaSb nanowire TFETs with gate-drain underlap as a potential solution to avoid ambipolarity and study the temperature dependence of the tunneling current. We compare two different TFET designs, one with an underlap between the gate and drain and the other with an overlap. The introduction of a 25-nm-long underlap region reduced the minimum achievable current Imin from 92 pA/μm to 23 pA/μm by suppressing the ambipolarity and simultaneously improved the minimum S at room temperature from 46 mV/dec to 41 mV/dec at Vds = 0.1 V. We also observe a reduction in the measured on current (Ion) from 0.1 μA/μm in the overlapped device to 0.01 μA/μm in the underlapped device at a drain bias (Vds) = 0.1 V and Ioff = 1 nA/μm. Temperature dependent measurements reveal a potential barrier at the drain junction due to the ungated region at the underlap. We determine a barrier height of 63 meV at Vds = 0.1 V based on thermionic emission combined with a ballistic transport model. Thus, we conclude that gate placement on the drain side is crucial to obtain the low off-currents in TFETs required for ultralow power electronic applications but that the trade-off between Ion and Ioff has to be considered.
All-optical tuning of symmetry protected quasi bound states in the continuum
Authors: Karl Nicholas , Vabishchevich Polina P. , Liu Sheng , Sinclair Michael B. , Keeler Gordon A. , Peake Gregory M. , Brener Igal
Published: October 2019

We demonstrate all-optical switching of high quality factor quasibound states in the continuum resonances in broken symmetry GaAs metasurfaces. By slightly breaking the symmetry of the GaAs nanoresonators, we enable leakage of symmetry protected bound states in the continuum (BICs) to free space that results in sharp spectral resonances with high quality factors of ∼500. We tune the resulting quasi-BIC resonances with ultrafast optical pumping at 800 nm and observe a 10 nm spectral blue shift of the resonance with pump fluences of less than 100 μJ cm−2. The spectral shift is achieved in an ultrafast time scale (<2.5 ps) and is caused by a shift in the refractive index mediated by the injection of free carriers into the GaAs resonators. An absolute reflectance change of 0.31 is measured with 150 μJ cm−2. Our results demonstrate a proof-of-concept that these broken symmetry metasurfaces can be modulated or switched at ultrafast switching speeds with higher contrast at low optical fluences (<100 μJ cm−2) than conventional Mie-metasurfaces.
Apparatus for Seebeck coefficient measurement of wire, thin film, and bulk materials in the wide temperature range (80–650 K)
Authors: Kumar Ashish , Patel Ashutosh , Singh Saurabh , Kandasami Asokan , Kanjilal D.
Published: October 2019

A Seebeck coefficient measurement apparatus has been designed and developed, which is very effective for accurate characterization of different types of samples in a wide temperature range (80–650 K) simultaneously covering low as well as high temperature regimes. Reducing the complexity of technical design of the sample holder and data collections has always been challenging to implement in a single instrument when samples are in different geometrical shapes and electronic structures. Our unique design of the sample holder with pressure probes covers measurements of different sample shapes (wires, thin films, and pellets) as well as different resistivity ranges (metals, semiconductors, and insulators). It is suitable for characterization of different sample sizes (3–12 mm). A double heater configuration powered by using a dual channel source meter is employed for maintaining a desired constant temperature difference across the sample for the whole temperature range. Two K-type thermocouples are used for simultaneously reading temperatures and Seebeck voltages by utilizing different channels of a multichannel digital multimeter. Calibration of the system has been carried out using constantan, chromel, and alumel materials, and recorded data are found to be very accurate and consistent with earlier reports. The Seebeck coefficients of standard samples of constantan (wire) and GaN (thin film) have been reported, which shows the measurement capability of the designed setup with versatile samples.
Experimental study of drop impact on a thin fiber
Authors: Zhu Pingan , Wang Wei , Chen Xiang , Lin Fangye , Wei Xiaofeng , Ji Chen , Zou Jun
Published: October 2019

In this paper, we present an experimental study of drop impact on a thin flexible fiber. Detailed dynamics of the collision was captured with a high-speed video camera. Previous studies have presented three modes: capturing, single drop falling, and splitting. However, in our experiments, we observed that a low-speed drop could bounce off a thin fiber. Moreover, the splitting mode was segmented into two different types: low-speed splitting and high-speed splitting. Based on systematic experiments, we rebuilt a regime map consisting of capturing, low-speed splitting, single drop falling, and high-speed splitting. Both the upper and the lower limits of the low-speed splitting were presented. Fiber wettability was found to play an important role in the impact results. Low-speed splitting vanished when a water drop impacts on a nylon fiber coated with a layer of hydrophilic material. Meanwhile, a theoretical model was proposed to predict the fiber dynamics, which fitted well with the experimental results.
Quantitative characterization of viscoelastic fracture induced by time-dependent intratumoral pressure in a 3D model tumor
Authors: Tran Quang D. , Marcos  , Gonzalez-Rodriguez David
Published: October 2019

In the tumor environment, interstitial pressure drives interstitial flow drainage from the tumor core to the lymphatic vessels. Recent studies have highlighted the key role of interstitial pressure in tumor development and cell migration. High intratumoral pressures, up to 60mmHg, have been reported in cancer patients. In a previous study, we showed that such pressure levels induce fracture in an experimental tumor model consisting of a microfluidic system holding a cellular aggregate. Here, we investigate and quantify the characteristics of tumor model fracture under a range of flow conditions. Our findings suggest a strong dependence of viscoelastic fracture behavior on the loading rate exerted by flow. The aggregate exhibits fragile fracture at high loading rates and ductile fracture at lower rates. The loading rate also modifies the permeability of the cellular aggregate, as well as the persistence time of the load required to induce fracture. The quantification parameters we propose here, evaluated for an in vitro model tumor without the extracellular matrix, could be applied to characterize tumor fracture under more realistic interstitial flow conditions.
Effective one-particle energies from generalized Kohn–Sham random phase approximation: A direct approach for computing and analyzing core ionization energies
Authors: Voora Vamsee K. , Galhenage Randima , Hemminger John C. , Furche Filipp
Published: October 2019

Generalized-Kohn-Sham (GKS) orbital energies obtained self-consistently from the random phase approximation energy functional with a semicanonical projection (spRPA) were recently shown to rival the accuracy of GW quasiparticle energies for valence ionization potentials. Here, we extend the scope of GKS-spRPA correlated one-particle energies from frontier-orbital ionization to core orbital ionization energies, which are notoriously difficult for GW and other response methods due to strong orbital relaxation effects. For a benchmark consisting of 23 1s core electron binding energies (CEBEs) of second-row elements, chemical shifts estimated from GKS-spRPA one-particle energies yield mean absolute deviations from experiment of 0.2 eV, which are significantly more accurate than the standard GW and comparable to Δ self-consistent field theory without semiempirical adjustment of the energy functional. For small ammonia clusters and cytosine tautomers, GKS-spRPA based chemical shifts capture subtle variations in covalent and noncovalent bonding environments; GKS-spRPA 1s CEBEs for these systems agree with equation-of-motion coupled cluster singles and doubles and ADC(4) results within 0.2–0.3 eV. Two perturbative approximations to GKS-spRPA orbital energies, which reduce the scaling from O(N6) to O(N5) and O(N4), are introduced and tested. We illustrate the application of GKS-spRPA orbital energies to larger systems by using oxygen 1s CEBEs to probe solvation and packing effects in condensed phases of water. GKS-spRPA predicts a lowering of the oxygen 1s CEBE of approximately 1.6–1.7 eV in solid and liquid phases, consistent with liquid-jet X-ray photoelectron spectroscopy and gas phase cluster experiments. The results are rationalized by partitioning GKS-spRPA electron binding energies into static, relaxation, and correlation parts.
Poly(2-alkyl-2-oxazoline) electrode interlayers for improved n-type organic field effect transistor performance
Authors: Nam Sungho , de la Rosa Victor R. , Cho Yuljae , Hamilton Rick , Cha SeungNam , Hoogenboom Richard , Bradley Donal D. C.
Published: October 2019

Thin film interlayer materials inserted at the metal/semiconductor interface provide an effective means to improve charge injection and reduce the threshold voltage for organic field-effect transistors. Here, we report the use of poly(2-alkyl-2-oxazoline) interlayers for gold electrodes within n-type poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] field-effect transistors. We specifically show that the use of poly(2-ethyl-2-oxazoline) yields a reduction in the work function from 5.07 to 4.73 eV (ΔE = 0.34 eV), an increase in the electron mobility from 0.04 to 0.15 cm2/V s (3.75 times), and a reduction in the threshold voltage from 27.5 to 16.5 V (ΔV = 11 V) relative to bare gold. The alkyl side chain of the poly(2-alkyl-2-oxazoline) has a significant influence on the film microstructure and, as a consequence, also device performance.
The atmospheric Rayleigh-Bénard problem on the f-plane
Authors: Fantini M.
Published: October 2019

When applied to a system of sizeable vertical extent that can undergo adiabatic expansion/compression, the Rayleigh-Bénard treatment of convection between two parallel plates, kept at constant temperature, needs to be amended with the consideration of potential temperature as the conserved thermodynamic variable. The fixed-temperature boundary conditions are therefore expressed as a combination of potential temperature and pressure, and this causes the solutions to be a mixture of the odd and even modes of the classical problem. Here, solutions are presented for a rotating system, which supports both stationary and oscillatory modes. While the stationary modes are all stabilized by this mechanism, as was shown previously for a nonrotating system, the oscillatory modes can have a lower critical Rayleigh number than their traditional counterpart, when the Prandtl number is approximately between 0.2 and 1.0.
Electrical tuning of a terahertz quantum cascade laser based on detuned intersubband absorption
Authors: Gao Liang , Zhao Le , Reno John L. , Kumar Sushil
Published: October 2019

A mechanism to electrically tune the frequency of terahertz quantum cascade lasers (QCLs) is developed that allows for tuning, while the QCL is operated close to its peak bias and temperature. Two optically coupled but electrically isolated cavities are used in which the bias of a control cavity tunes the resonant-mode of the coupled QCL cavity independent of the QCL's operating bias. Approximately 4 GHz electrical tuning is realized for a 3.6 THz distributed-feedback QCL operating in pulsed mode at 58 K in a Stirling cooler. The single-mode QCL emits near-constant peak-power in the range of 5−5.3 mW through the tuning range and radiates in a narrow single-lobed beam with a far-field divergence of ∼4°×11°. The superlattice structure of the QCL is designed to implement a low-voltage intersubband absorption transition that is detuned from that of its gain transition, the strength of which could be controlled sensitively with applied voltage utilizing resonant-tunneling injection of electrons in the absorption subband. The tuning is realized by the application of small bias voltages (∼6−7 V) and requires a narrow bias range (∼1 V, ∼40 A/cm2) to traverse across the entire tuning range, and the method should be generally applicable to all intersubband lasers including mid-infrared QCLs.
apex: A new commercial off-the-shelf on-board computer platform for sounding rockets
Authors: Maas N. , Willnecker R. , Hemmersbach R. , Hauslage J.
Published: October 2019

In order to supersede the aging Microchip ATMEGA328P as the de facto standard for Commercial off-the-shelf (COTS) On-Board Computers (OBCs) with a more powerful system for different kinds of high-speed sensors and image acquisition applications, we developed advanced processors, encryption, and security experiment (apex). The platform consisting of a newly developed OBC using COTS components has been flight tested during the ATEK/MAPHEUS-8 sounding rocket campaign. The main advantages of the apex OBC lies in the speed and simplicity of the design while maintaining operational security with a redundant master-master microcontroller system, as well as dual flash storage within each master. Additionally, a single board computer with a containerized and failure-resistant Operating System (OS) (balenaOS) was included to allow usage of a high-definition camera or other more compute-intensive tasks. The bench and flight tests were performed successfully and already showed feasible ways to further improve operational performance.
State-to-state inelastic rotational cross sections in five-atom systems with the multiconfiguration time dependent Hartree method
Authors: Ndengué Steve , Scribano Yohann , Gatti Fabien , Dawes Richard
Published: October 2019

We present a MultiConfiguration Time Dependent Hartree (MCTDH) method as an attractive alternative approach to the usual quantum close-coupling method that approaches some computational limits in the calculation of rotational excitation (and de-excitation) between polyatomic molecules (here collisions between triatomic and diatomic rigid molecules). We have performed a computational investigation of the rotational (de-)excitation of the benchmark rigid rotor H2O–H2 system on a recently developed Potential Energy Surface of the complex using the MCTDH method. We focus here on excitations and de-excitations from the 000, 111, and 110 states of H2O with H2 in its ground rotational state, looking at all the potential transitions in the energy range 1–200 cm−1. This work follows a recently completed study on the H2O–H2 cluster where we characterized its spectroscopy and more generally serves a broader goal to describe inelastic collision processes of high dimensional systems using the MCTDH method. We find that the cross sections obtained from the MCTDH calculations are in excellent agreement with time independent calculations from previous studies but does become challenging for the lower kinetic energy range of the de-excitation process: that is, below approximately 20 cm−1 of collision energy, calculations with a relative modest basis become unreliable. The MCTDH method therefore appears to be a useful complement to standard approaches to study inelastic collision for various collision partners, even at low energy, though performing better for rotational excitation than for de-excitation.
A new scheme for fixed node diffusion quantum Monte Carlo with pseudopotentials: Improving reproducibility and reducing the trial-wave-function bias
Authors: Zen Andrea , Brandenburg Jan Gerit , Michaelides Angelos , Alfè Dario
Published: October 2019

Fixed node diffusion quantum Monte Carlo (FN-DMC) is an increasingly used computational approach for investigating the electronic structure of molecules, solids, and surfaces with controllable accuracy. It stands out among equally accurate electronic structure approaches for its favorable cubic scaling with system size, which often makes FN-DMC the only computationally affordable high-quality method in large condensed phase systems with more than 100 atoms. In such systems, FN-DMC deploys pseudopotentials (PPs) to substantially improve efficiency. In order to deal with nonlocal terms of PPs, the FN-DMC algorithm must use an additional approximation, leading to the so-called localization error. However, the two available approximations, the locality approximation (LA) and the T-move approximation (TM), have certain disadvantages and can make DMC calculations difficult to reproduce. Here, we introduce a third approach, called the determinant localization approximation (DLA). DLA eliminates reproducibility issues and systematically provides good quality results and stable simulations that are slightly more efficient than LA and TM. When calculating energy differences—such as interaction and ionization energies—DLA is also more accurate than the LA and TM approaches. We believe that DLA paves the way to the automation of FN-DMC and its much easier application in large systems.
Detection of cyclotron resonance using photo-induced thermionic emission at graphene/MoS2 van der Waals interface
Authors: Wakafuji Yusai , Moriya Rai , Park Sabin , Kinoshita Kei , Masubuchi Satoru , Watanabe Kenji , Taniguchi Takashi , Machida Tomoki
Published: October 2019

We demonstrate the detection of cyclotron resonance in graphene by a photo-induced thermionic emission mechanism at the graphene/MoS2 van der Waals (vdW) Schottky junction. At cyclotron resonance in Landau-quantized graphene, the infrared light is absorbed, and an electron–hole pair is generated. When the energy of a photoexcited electron exceeds the band offset energy at the graphene/MoS2 interface, the electron transfer occurs from graphene to the conduction band of MoS2, and the hole remains in graphene. This creates an electron–hole separation at the graphene/MoS2 interface at cyclotron resonance, and a photovoltage is generated. The proposed method is an infrared photodetection technique through out-of-plane transport at the vdW junction, which is distinct from the previously reported methods that use in-plane transport in graphene for electronic detection of the cyclotron resonance. Despite the simple structure of our device with a single-vdW junction, our method exhibits a very high sensitivity of ∼106 V/W, which shows an improvement of three orders of magnitude over the previously reported values. Therefore, the proposed method displays a high potential for cyclotron resonance-based infrared photodetector applications.
A protein corona primer for physical chemists
Authors: Payne Christine K.
Published: October 2019

Nanoparticles present in any biological environment are exposed to extracellular proteins. These proteins adsorb on the surface of the nanoparticle forming a “protein corona.” These proteins control the interaction of nanoparticles with cells. The interaction of proteins with the nanoparticle surface is governed by physical chemistry. Understanding this process requires spectroscopy, microscopy, and computational tools that are familiar to physical chemists. This perspective provides an overview of the protein corona along with two future directions: first, the need for new computational approaches, including machine learning, to predict corona formation and second, the extension of protein corona studies to more complex environments ranging from lung fluids to waste water treatment.
Relations between skin friction and other surface quantities in viscous flows
Authors: Chen Tao , Liu Tianshu , Wang Lian-Ping , Chen Shiyi
Published: October 2019

This paper presents the derivations of the exact relations between skin friction and other important dynamical and kinematical quantities on a stationary curved surface in a viscous flow by applying the standard methods of differential geometry to the governing partial differential equations in fluid mechanics. In particular, the mathematical structures of the effects of the surface curvature are explicitly expressed, which extend the previous results on a flat surface. These relations reveal that skin friction is intrinsically coupled with surface pressure, temperature, and scalar concentration through the boundary enstrophy flux, heat flux, and mass flux, respectively. As an example, the relation between skin friction and surface pressure is examined in the Oseen flow over a sphere to elucidate the significant effect of the surface curvature at a very small Reynolds number. Two other validation examples are a gravity-driven creeping liquid film flow over a wavy surface and the Falkner-Skan flow over a wedge. Furthermore, the relation is applied to a simulated turbulent channel flow to explore the local near-wall coherent structure and understand its dynamical roles in turbulence production.
Monte Carlo simulation and integral equation study of Hertzian spheres in the low-temperature regime
Authors: Munaò Gianmarco , Saija Franz
Published: October 2019

We investigate the behavior of Hertzian spheres in the fluid phase and in proximity of the freezing threshold by using Monte Carlo (MC) simulations and integral equation theories, based on the Ornstein-Zernike (OZ) approach. The study is motivated by the importance of the Hertzian model in representing a large class of systems interacting via soft interactions, such as star polymers or microgels. Radial distribution functions, structure factors, and excess entropy clearly show the reentrant behavior typical of the Hertzian fluid, well caught by both MC simulations and OZ theory. Then, we make use of some phenomenological one-phase criteria for testing their reliability in detecting the freezing threshold. All criteria provide evidence of the fluid-solid transition with different degrees of accuracy. This suggests the possibility to adopt these empirical rules to provide a quick and reasonable estimate of the freezing transition in model potentials of wide interest for soft matter systems.
Ongoing mentorship works for retaining minorities in STEM
Authors: Feder Toni
Published: October 2019

Improving the academic environment for marginalized groups is aided by a holistic approach and dedicated resources.
HIV and syphilis and sexual risk behaviours among men who have sex with men attending university in China: a systematic review and meta-analysis
Authors: Fan Song , Yang Zuyao , Hou Fengsu , Yu Maohe , Luo Zhenzhou , Liao Meizhen , Gong Yanhua , Meng Xiaojun , Cai Yong , Zou Huachun
Published: October 2019

Background
This study was conducted to summarise the HIV epidemic, sexual behaviours and HIV testing among men who have sex with men (MSM) attending university in China. Methods: Five databases were searched for student MSM information in English and Chinese language publications. Meta-analyses were performed to calculate the pooled prevalence of HIV and syphilis, pooled mean age at first anal intercourse (AFAI) and the rate of other HIV-related behaviours among MSM attending university in China. Univariate meta-regression and subgroup analysis were conducted to explore potential sources of heterogeneity. Publication bias was measured using Egger’s test. Results: Thirty-three articles representing 31 studies were included in the analysis. The pooled HIV prevalence was 4.1% (95% CI 3.1–5.0%). The estimated AFAI was 18.7 years, but 37.5% of students had their first anal intercourse before 18 years of age. Most (88.2%) had their first sexual intercourse with a male partner. Of the MSM attending university, 4.2% of MSM engaged in commercial sex (either selling or buying sex), 10.3% had ever engaged in group sex, 13.1% had had sex with a female partner in the past month and 10.1% had ever used drugs. Most (77.7%) sought sex partners via geosocial networking gay apps or the Internet, and 42.9% had ever tested for HIV. There was a tendency for an increase in lifetime HIV testing rate from 32% in 2005–07 to 53% in 2014–16. Conclusions: This review found high HIV prevalence, early AFAI and a high prevalence of sexual risk behaviours among MSM attending university in China. Interventions aimed at increasing HIV testing and reducing sexual risk behaviours are urgently needed among this young population.
IL-2 receptors preassemble and signal in the ER/Golgi causing resistance to antiproliferative anti–IL-2Rα therapies
Authors: Volkó Julianna , Kenesei Ádám , Zhang Meili , Várnai Péter , Mocsár Gábor , Petrus Michael N. , Jambrovics Károly , Balajthy Zoltán , Müller Gabriele , Bodnár Andrea , Tóth Katalin , Waldmann Thomas A. , Vámosi György
Published: October 2019

Significance

Interleukin-2 (IL-2), a cytokine produced by activated T cells, acting in a paracrine/autocrine fashion, is essential for T cell proliferation. In adult T cell leukemia (ATL) and in autoimmune/graft-vs.-host diseases, anti–IL-2Rα antibody therapies were established to inhibit proliferation, with only limited success. We demonstrated that IL-2/15 receptors start to assemble in the endoplasmic reticulum/Golgi and demonstrated signaling by Jak1/Jak3 in the Golgi. Thus, in T cells also producing IL-2 (e.g., ATL cells), signaling can already take place before receptors reach cell membranes. This scenario explains resistance to antibody therapies targeting receptors at cell surfaces. Our study sheds light on an autocrine signaling mechanism, in which an intracellularly synthesized ligand activates its receptor en route toward the cell surface.
Distinct representations of spatial and categorical relationships across human scene-selective cortex
Authors: Persichetti Andrew S. , Dilks Daniel D.
Published: October 2019

Significance

Humans are capable of many sophisticated behaviors. One such behavior is using landmarks to navigate from one place to another, distant place. This type of navigation, known as landmark-based navigation, requires the navigator to extract spatial information from places in the environment. Another sophisticated behavior is recognizing the type of place one is in and acting appropriately in that environment (e.g., recognizing that you are in a kitchen, and thus making a cup of coffee). This type of behavior does not rely on spatial information so much as it relies on extracting cues related to the category membership of different places. Here we show that these complex interactions with our environment, navigating between places and recognizing them, are neurally dissociable.
Gradients of structure–function tethering across neocortex
Authors: Vázquez-Rodríguez Bertha , Suárez Laura E. , Markello Ross D. , Shafiei Golia , Paquola Casey , Hagmann Patric , van den Heuvel Martijn P. , Bernhardt Boris C. , Spreng R. Nathan , Misic Bratislav
Published: October 2019

The white matter architecture of the brain imparts a distinct signature on neuronal coactivation patterns. Interregional projections promote synchrony among distant neuronal populations, giving rise to richly patterned functional networks. A variety of statistical, communication, and biophysical models have been proposed to study the relationship between brain structure and function, but the link is not yet known. In the present report we seek to relate the structural and functional connection profiles of individual brain areas. We apply a simple multilinear model that incorporates information about spatial proximity, routing, and diffusion between brain regions to predict their functional connectivity. We find that structure–function relationships vary markedly across the neocortex. Structure and function correspond closely in unimodal, primary sensory, and motor regions, but diverge in transmodal cortex, particularly the default mode and salience networks. The divergence between structure and function systematically follows functional and cytoarchitectonic hierarchies. Altogether, the present results demonstrate that structural and functional networks do not align uniformly across the brain, but gradually uncouple in higher-order polysensory areas.
Reviving rare chicken breeds using genetically engineered sterility in surrogate host birds
Authors: Woodcock Mark E. , Gheyas Almas A. , Mason Andrew S. , Nandi Sunil , Taylor Lorna , Sherman Adrian , Smith Jacqueline , Burt Dave W. , Hawken Rachel , McGrew Michael J.
Published: October 2019

Significance

In the fields of conservation biology and sustainable agriculture, the ability to cryopreserve and revive animal species is paramount to efforts to preserve genetic diversity. An innovative approach is to use sterile surrogate host animals for the transplantation of reproductive germ cells from rare/endangered animals. This technology has previously been utilized in mammals but is of particular importance for animals with lipid-filled zygotes/embryos, such as fish and birds, which render cryopreservation techniques inefficient. We demonstrate that the female chicken rendered sterile using genome editing technology can be used as a surrogate host for transplanted cryopreserved germ cells and only lay eggs of the transplanted rare chicken breed. Our results suggest a way to preserve the biodiversity of bird species.
Impact of increasing vegetarian availability on meal selection and sales in cafeterias
Authors: Garnett Emma E. , Balmford Andrew , Sandbrook Chris , Pilling Mark A. , Marteau Theresa M.
Published: October 2019

Shifting people in higher income countries toward more plant-based diets would protect the natural environment and improve population health. Research in other domains suggests altering the physical environments in which people make decisions (“nudging”) holds promise for achieving socially desirable behavior change. Here, we examine the impact of attempting to nudge meal selection by increasing the proportion of vegetarian meals offered in a year-long large-scale series of observational and experimental field studies. Anonymized individual-level data from 94,644 meals purchased in 2017 were collected from 3 cafeterias at an English university. Doubling the proportion of vegetarian meals available from 25 to 50% (e.g., from 1 in 4 to 2 in 4 options) increased vegetarian meal sales (and decreased meat meal sales) by 14.9 and 14.5 percentage points in the observational study (2 cafeterias) and by 7.8 percentage points in the experimental study (1 cafeteria), equivalent to proportional increases in vegetarian meal sales of 61.8%, 78.8%, and 40.8%, respectively. Linking sales data to participants’ previous meal purchases revealed that the largest effects were found in the quartile of diners with the lowest prior levels of vegetarian meal selection. Moreover, serving more vegetarian options had little impact on overall sales and did not lead to detectable rebound effects: Vegetarian sales were not lower at other mealtimes. These results provide robust evidence to support the potential for simple changes to catering practices to make an important contribution to achieving more sustainable diets at the population level.
KCNQ5 activation is a unifying molecular mechanism shared by genetically and culturally diverse botanical hypotensive folk medicines
Authors: Manville Rían W. , van der Horst Jennifer , Redford Kaitlyn E. , Katz Benjamin B. , Jepps Thomas A. , Abbott Geoffrey W.
Published: October 2019

Significance

Botanical folk medicines have been used by diverse human populations and cultures for several millennia. Many are still in use today, but the underlying molecular mechanisms often remain elusive. Here we report the discovery of a molecular mechanism linking diverse plant extracts used traditionally to lower blood pressure (hypotensives). All of the hypotensive plants tested activated the KCNQ5 vascular-expressed potassium channel, whereas nonhypotensives did not. For one hypotensive plant, we describe discovery of the active small molecule (aloperine) and demonstrate that it KCNQ-dependently relaxes blood vessels. The discovery opens up a new source of potential therapeutic drugs and explains the mechanism behind folk hypotensive medicines used by diverse populations for thousands of years.
RORα is crucial for attenuated inflammatory response to maintain intestinal homeostasis
Authors: Oh Se Kyu , Kim Dongha , Kim Kyeongkyu , Boo Kyungjin , Yu Young Suk , Kim Ik Soo , Jeon Yoon , Im Sun-Kyoung , Lee Su-Hyung , Lee Ji Min , Ko Younhee , Lee Ho , Park Daechan , Fang Sungsoon , Baek Sung Hee
Published: October 2019

Retinoic acid-related orphan receptor α (RORα) functions as a transcription factor for various biological processes, including circadian rhythm, cancer, and metabolism. Here, we generate intestinal epithelial cell (IEC)-specific RORα-deficient (RORα
ΔIEC
) mice and find that RORα is crucial for maintaining intestinal homeostasis by attenuating nuclear factor κB (NF-κB) transcriptional activity. RORα
ΔIEC
mice exhibit excessive intestinal inflammation and highly activated inflammatory responses in the dextran sulfate sodium (DSS) mouse colitis model. Transcriptome analysis reveals that deletion of RORα leads to up-regulation of NF-κB target genes in IECs. Chromatin immunoprecipitation analysis reveals corecruitment of RORα and histone deacetylase 3 (HDAC3) on NF-κB target promoters and subsequent dismissal of CREB binding protein (CBP) and bromodomain-containing protein 4 (BRD4) for transcriptional repression. Together, we demonstrate that RORα/HDAC3-mediated attenuation of NF-κB signaling controls the balance of inflammatory responses, and therapeutic strategies targeting this epigenetic regulation could be beneficial to the treatment of chronic inflammatory diseases, including inflammatory bowel disease (IBD).
Waterproof molecular monolayers stabilize 2D materials
Authors: Su Cong , Yin Zongyou , Yan Qing-Bo , Wang Zegao , Lin Hongtao , Sun Lei , Xu Wenshuo , Yamada Tetsuya , Ji Xiang , Zettsu Nobuyuki , Teshima Katsuya , Warner Jamie H. , Dincă Mircea , Hu Juejun , Dong Mingdong , Su Gang , Kong Jing , Li Ju
Published: October 2019

Significance

A family of strong yet removable 1- to 2-nm-thick ultrathin monolayer is developed as a corrosion inhibitor for 2-dimensional materials that significantly prolong lifetime while protecting optoelectronic properties in both ambient and harsh chemical or thermal environments. This method is low in toxicity and can be applied to arbitrary substrate with no size limit.
β-Catenin is required for radial cell patterning and identity in the developing mouse cochlea
Authors: Jansson Lina , Ebeid Michael , Shen Jessica W. , Mokhtari Tara E. , Quiruz Lee A. , Ornitz David M. , Huh Sung-Ho , Cheng Alan G.
Published: October 2019

Significance

The cochlea is essential for sound detection. It consists of highly differentiated hair cells and nonsensory supporting cells radially patterned into lateral and medial compartments. However, mechanisms regulating radial patterning and specification of hair cell and supporting cell subtypes, each of which serves unique functions, are unclear. Here we show that β-catenin is required for radial patterning and differentiation of sensory and nonsensory cell subtypes in the developing cochlea. β-Catenin-deleted cochleae displayed disrupted compartment borders containing ectopic hair cell and supporting cell subtypes, whereas inhibiting transcriptional and preserving cell adhesion-mediated activities of β-catenin maintained radial patterning and cell identity. This study thus characterizes a role for β-catenin-mediated cell adhesion in the developing cochlea.