bluuebunny/crossref_metadata_2025 huggingface dataset:
One-Pot Synthesis of γ-Azidobutyronitriles and Their Intramolecular Cycloadditions
Authors: Budynina Ekaterina M. , Ivanov Konstantin L. , Tukhtaev Hamidulla B. , Tukhtaeva Feruza O. , Bezzubov Stanislav I. , Melnikov Mikhail Ya.
Published: August 2020

Efficient gram-scale, one-pot approaches to azidocyanobutyrates and their amidated or decarboxylated derivatives have been developed, starting from commercially available aldehydes and cyanoacetates. These techniques combine (1) Knoevenagel condensation, (2) Corey–Chaykovsky cyclopropanation and (3) nucleophilic ring opening of donor-acceptor cyclopropanes with the azide ion, as well as (4) Krapcho decarboxylation or (4′) amidation. The synthetic utility of the resulting γ-azidonitriles was demonstrated by their transformation into tetrazoles via intramolecular (3+2)-cycloaddition. A condition-dependent activation effect of the α-substituent was revealed in that case. Thermally activated azide–nitrile interaction did not differentiate the presence of an α-electron-withdrawing substituent in γ-azidonitriles, whereas the Lewis acid mediated (SnCl4 or TiCl4) reaction proceeded much easier for azidocyanobutyrates. This allowed us to develop an efficient procedure for converting azidocyanobutyrates into the corresponding tetrazoles.
Scalable Synthesis of 3-Ethyl-4-methyl-1,5-dihydro-2H-pyrrol-2-one: An Important Building Block of the Antidiabetic Drug Glimepiride
Authors: Chavan Subhash P. , Pawar Ambaji A. , Patil Niteen B. , Kadam Appasaheb L. , Shinde Shrikrishna S.
Published: August 2020

A four-step, practical, and easily scalable synthesis of 3-ethyl-4-methyl-1,5-dihydro-2H-pyrrol-2-one, an important building block of the antidiabetic drug glimepiride, has been accomplished. Key features are the synthesis of 3-methyl-4-hydroxy-2-butenolide in water and triflic acid mediated N-benzyl lactam N-deprotection. The main advantages of this process are the scalable synthetic route and decreased number of reaction steps, which paves the way for the industrial-scale synthesis of 3-ethyl-4-methyl-1,5-dihydro-2H-pyrrol-2-one.
Laser-driven collisionless shock acceleration of ions from near-critical plasmas
Authors: Tochitsky S. , Pak A. , Fiuza F. , Haberberger D. , Lemos N. , Link A. , Froula D. H. , Joshi C.
Published: August 2020

This paper overviews experimental and numerical results on acceleration of narrow energy spread ion beams by an electrostatic collisionless shockwave driven by 1 μm (Omega EP) and 10 μm (UCLA Neptune Laboratory) lasers in near critical density CH and He plasmas, respectively. Shock waves in CH targets produced high-energy ∼50 MeV protons (ΔE/E of ≤30%) and 314 MeV C6+ ions (ΔE/E of ≤10%). Observation of acceleration of both protons and carbon ions to similar velocities is consistent with reflection of particles off the moving potential of a shock front. For shocks driven by CO2 laser in a gas jet, ∼30 MeV peak in He ion spectrum was detected. Particle-in-cell simulations indicate that regardless of the target further control over its density profile is needed for optimization of accelerated ion beams in part of energy spread, yield and maximum kinetic energy.
On quasi-parallel whistler waves in the solar wind
Authors: Vasko I. Y. , Kuzichev I. V. , Artemyev A. V. , Bale S. D. , Bonnell J. W. , Mozer F. S.
Published: August 2020

Recent simulations showed that the whistler heat flux instability, which presumably produces the most of quasi-parallel coherent whistler waves in the solar wind, is not efficient in regulating the electron heat conduction. In addition, recent spacecraft measurements indicated that some fraction of coherent whistler waves in the solar wind may propagate anti-parallel to the electron heat flux, being produced due to a perpendicular temperature anisotropy of suprathermal electrons. We present the analysis of properties of parallel and anti-parallel whistler waves unstable at electron heat fluxes and temperature anisotropies of suprathermal electrons typical of the pristine solar wind. Assuming the electron population consisting of counterstreaming dense thermal core and tenuous suprathermal halo populations, we perform a linear stability analysis to demonstrate that anti-parallel whistler waves are expected to have smaller frequencies, wave numbers, and growth rates compared to parallel whistler waves. The stability analysis is performed over a wide range of parameters of core and halo electron populations. Using the quasi-linear scaling relation, we show that anti-parallel whistler waves saturate at amplitudes of one order of magnitude smaller than parallel whistler waves, which is about 10−3 B0 in the pristine solar wind. The analysis shows that the presence of anti-parallel whistler waves in the pristine solar wind is more likely to be obscured by turbulent magnetic field fluctuations because of lower frequencies and smaller amplitudes compared to parallel whistler waves. The presented results will also be valuable for numerical simulations of the electron heat flux regulation in the solar wind.
Significant correlation of bone material strength index as measured by the OsteoProbe with Vickers and Rockwell hardness
Authors: Ly Franklin S. , Proctor Alexander , Hoffseth Kevin , Yang Henry T. , Hansma Paul K.
Published: August 2020

The bone material strength index (BMSi), as measured by the OsteoProbe, is significantly correlated with Vickers hardness and Rockwell (RW) hardness measurements on conventional materials. The Vickers and RW measurements were carried out according to American Society for Testing and Materials standard test methods, and OsteoProbe measurements followed published standardized testing methods. The correlations between the BMSi and RW hardness, r = 0.93, and between the BMSi and Vickers hardness, r = 0.94, are comparable with the correlation between RW and Vickers hardness, r = 0.87. The correlation between the BMSi and RW is significant at p < 0.01, and the correlation between the BMSi and Vickers hardness is significant at p < 0.01. These results show that the indentation measurement performed by the OsteoProbe may be considered as a type of hardness measurement comparable to widely used conventional methods, with specific applications targeted by its portable and narrow design.
Anormal diffusion enhancement of resonant responses for coupled oscillator networks to weak signals
Authors: Yao Chenggui , He Zhiwei
Published: August 2020

The normal diffusion effect is introduced as a new regulating factor into the established diffusive coupling model for bistable oscillator networks. We find that the response of the system to the weak signal is substantially enhanced by the anormal diffusion, which is termed anormal-diffusion-induced resonance. We also reveal that the diffusive coupling-induced transition, which changes the system from a bistable to a monostable state, is of fundamental importance for the occurrence of resonance. The proposed approach is validated using simulation studies and theoretical analyses. Our results suggest that diffusion induced resonance can be more easily observed in nonlinear oscillator networks.
Resonator-based reflective metasurface for low-frequency underwater acoustic waves
Authors: Chen Zhong , Yan Fei , Negahban Mehrdad , Li Zheng
Published: August 2020

A novel resonator-based metasurface is devised to control reflected underwater waves. Each metasurface unit is constructed with an aluminum plate attached to a lead mass. By tailoring the thickness of the plate, full 2π phase shift of the reflected wave can be achieved. Examples of redirection, focusing, and directional carpet cloaking are demonstrated as applications. The target frequency can be as low as 500 Hz and it can operate in a broadband range. Slight modifications allow the design to perform excellently from tens to thousands of hertz. This metasurface provides a new design paradigm when there is a need to manipulate low frequency underwater waves, such as in submarines for stealth operation or detection-signal manipulation to provide deceptive information.
Numerical solution of a highly nonlinear and non-integrable equation using integrated radial basis function network method
Authors: Bhanot Rajeev P. , Strunin Dmitry V. , Ngo-Cong Duc
Published: August 2020

In this paper, we investigate a wide range of dynamical regimes produced by the nonlinearly excited phase (NEP) equation (a single sixth-order nonlinear partial differential equation) using a more advanced numerical method, namely, the integrated radial basis function network method. Previously, we obtained single-step spinning solutions of the equation using the Galerkin method. First, we verify the numerical solver through an exact solution of a forced version of the equation. Doing so, we compare the numerical results obtained for different space and time steps with the exact solution. Then, we apply the method to solve the NEP equation and reproduce the previously obtained spinning regimes. In the new series of numerical experiments, we find regimes in the form of spinning trains of steps/kinks comprising one, two, or three kinks. The evolution of the distance between the kinks is analyzed. Two different kinds of boundary conditions are considered: homogeneous and periodic. The dependence of the dynamics on the size of the domain is explored showing how larger domains accommodate multiple spinning fronts. We determine the critical domain size (bifurcation size) above which non-trivial settled regimes become possible. The initial condition determines the direction of motion of the kinks but not their sizes and velocities.
Simulated field-modulated x-ray absorption in titania
Authors: Darapaneni Pragathi , Meyer Alexander M. , Sereda Mykola , Bruner Adam , Dorman James A. , Lopata Kenneth
Published: August 2020

In this paper, we present a method to compute the x-ray absorption near-edge structure (XANES) spectra of solid-state transition metal oxides using real-time time-dependent density functional theory, including spin–orbit coupling effects. This was performed on bulk-mimicking anatase titania (TiO2) clusters, which allows for the use of hybrid functionals and atom-centered all electron basis sets. Furthermore, this method was employed to calculate the shifts in the XANES spectra of the Ti L-edge in the presence of applied electric fields to understand how external fields can modify the electronic structure, and how this can be probed using x-ray absorption spectroscopy. Specifically, the onset of t2g peaks in the Ti L-edge was observed to red shift and the eg peaks were observed to blue shift with increasing fields, attributed to changes in the hybridization of the conduction band (3d) orbitals.
A single unsteady DBD plasma actuator excited by applying two high voltages simultaneously for flow control
Authors: Mahdavi Hoda , Daliri Abbas , Sohbatzadeh Farshad , Shirzadi Meisam , Rezanejad Mohammad
Published: August 2020

Dielectric barrier discharge plasma actuators have attracted a lot of attention to use as new technologies for active flow control. In this paper, an experimental investigation of a single unsteady plasma actuator driven by two simultaneous sinusoidal high voltages is carried out. The aerodynamic performance of this plasma actuator is investigated for flow control of a wind turbine blade. Leading edge separation control at Reynolds number of 0.26×106 and in a wide range of angles of attack including linear, stall, and post-stall regions is considered as the test case. The momentum imparted by the plasma actuator to flow is investigated via measuring induced electric wind velocity, which represents that the induced velocities in the steady mode, with vmax≅5 m/s, are higher than that of the unsteady mode. The important aspect of exciting the unsteady dielectric barrier discharge plasma actuator in this new approach is improving its efficiency through increasing the authority of momentum addition to flow and reducing the minimum input power for discharge ignition relative to its typical grounded structure. This can be very important practically in flow control applications where the amount of consumed energy is a substantial factor in determining the actuator's efficiency. The obtained aerodynamic results reveal that the unsteady plasma actuator has the best operation in post-stall angles of attack, which is of great importance for operation characteristics of wind turbine blades. The power spectral density of pressure time series illustrates that the unsteady plasma actuator affects the flow through instabilities of the separation layer and vortex shedding structure.
Chemically vapor deposited Eu3+:Y2O3 thin films as a material platform for quantum technologies
Authors: Harada Nao , Ferrier Alban , Serrano Diana , Persechino Mauro , Briand Emrick , Bachelet Romain , Vickridge Ian , Ganem Jean-Jacques , Goldner Philippe , Tallaire Alexandre
Published: August 2020

Rare earth ions hosted in solids are good candidates for quantum technologies due to their chemical stability and optical and spin transitions exhibiting long coherence lifetimes. While bulk oxide crystals are usually the preferred host material, the development of a scalable silicon-compatible thin film platform would be desirable. In this paper, we report on the growth of Y2(1−x)Eu2xO3 thin films on silicon in the full range of Eu3+ concentration by direct liquid injection chemical vapor deposition (CVD). Our sub-micrometer polycrystalline films with a strong-(111) texture were grown for all compositions into the bixbyite cubic phase. The variation of growth rates with temperature and flow indicated that deposition occurred through a mass-transport controlled regime. Optical assessment of the Eu-doped thin films showed inhomogeneous linewidths as narrow as 50 GHz and fluorescence lifetimes of 1 ms for the lowest concentrations. Finally, a spectral hole was successfully burned in a 200 nm-thin film with a 2% Eu doping leading to a homogeneous linewidth of 11 MHz. These values are still below those reported for bulk single crystals indicating that additional decoherence mechanisms exist in such nanometric films, which might be alleviated by further improvement of the crystalline quality. Nevertheless, these results pave the way to the use of CVD-grown Eu:Y2O3 thin films as a platform for integrated quantum devices.
Computational modeling of charge hopping dynamics along a disordered one-dimensional wire with energy gradients in quantum environments
Authors: Chen Ning , Devi Murali , Jang Seogjoo J.
Published: August 2020

This computational study investigates the effects of energy gradients on charge hopping dynamics along a one-dimensional chain of discrete sites coupled to quantum bath, which is modeled at the level of Pauli master equation (PME). This study also assesses the performance of different approximations for the hopping rates. Three different methods for solving the PME, a fourth order Runge–Kutta method, numerical diagonalization of the rate matrix followed by analytic propagation, and kinetic Monte Carlo simulation method, are tested and confirmed to produce virtually identical values of time dependent mean square displacement, diffusion constant, and mobility. Five different rate expressions, exact numerical evaluation of Fermi’s Golden Rule (FGR) rate, stationary phase interpolation (SPI) approximation, semiclassical approximation, classical Marcus rate, and Miller–Abrahams rate, are tested to help understand the effects of approximations in representing quantum environments in the presence of energy gradients. The results based on direct numerical evaluation of FGR rate exhibit transition from diffusive to non-diffusive behavior with the increase in the gradient and show that the charge transport in the quantum bath is more sensitive to the magnitude of the gradient and the disorder than in the classical bath. Among all the four approximations for the hopping rates, the SPI approximation is confirmed to work best overall. A comparison of two different methods to calculate the mobility identifies drift motion of the population distribution as the major source of non-diffusive behavior and provides more reliable information on the contribution of quantum bath.
Energy loss and developing length during reciprocating flow in a pipe with a free-end
Authors: Hasan M. K. , Manasseh R. , Leontini J. S.
Published: August 2020

Direct numerical simulations of reciprocating pipe flow in a straight pipe with a free-end are presented. The range of amplitudes and frequencies studied span the laminar regime and the beginning of transition toward a conditionally turbulent flow. Two primary results are reported: the measurement of the flow development length and the loss of energy, both due to the presence of the free-end. Two regimes of flow are identified with distinct length scales. For low frequencies, the development length scales with the pipe diameter D. However, for higher frequencies, the development length scales with the Stokes layer thickness δ=2ν/ω. The energy loss is studied by calculating the viscous dissipation function, indicating where energy is lost, and allowing the energy lost due to the presence of the free-end to be isolated. While strong vortices are formed and convected from the exit, most of the energy they dissipate is lost within a few pipe diameters of the exit. It is shown that these trends continue even as the amplitude and frequency are increased so that the flow begins to transition from a laminar toward a turbulent state. Two modes of instability are observed in the Stokes layers near the free-end, one short wavelength mode with a wavelength set by the Stokes layer thickness and the other long wavelength mode with a wavelength set by the amplitude of the oscillatory flow. These modes are related to those observed in the fully developed oscillatory flow.
Advanced ASDEX Upgrade pellet guiding system design
Authors: Ploeckl B. , Köhnlein H. , Engelhardt T. M. J. , Herrmann A. , Lang P. T. , Team ASDEX Upgrade
Published: August 2020

Cryogenic pellet injection will be the prime candidate to fuel future fusion power plants. In order to harvest optimum fueling performance, it is essential to inject pellets from the magnetic high field side of the tokamak. The pellet launching system of the tokamak ASDEX Upgrade injects cryogenic hydrogen pellets with a speed of up to 1000 m/s from the magnetic high field side via curved guiding tubes. Pellets passing the guiding tube are sliding on a gas cushion, generated by the Leidenfrost effect. The actual track has a rectangular cross section and is composed of a series of ellipses in order to generate the required 270° looping type turn; the path length is 17 m. The last part of this track is marked by strong geometrical constraints from the vacuum vessel port. The previous design was composed of a sequence of three sections of ellipses too, tangentially constant but discontinuous with regard to the curvature. It had been in operation for almost 20 years. Its steps in the curvature are supposed to limit the system performance. A novel and advanced geometry concept, adopting a method well-known from civil engineering (e.g., for the railroad track design), has been applied to develop an improved design. It relies on clothoid shape sections keeping the track curvatures continuous and, thus, provides a smooth transition between all the elements. The new design presented improves the pellet launching system performance on ASDEX Upgrade and provides knowledge for an advanced design of pellet guiding tubes in future fusion devices.
Electrostatic quasi-neutral formulation of global cross-separatrix particle simulation in field-reversed configuration geometry
Authors: Lau C. K. , Fulton D. P. , Bao J. , Lin Z. , Dettrick S. , Binderbauer M. , Tajima T. , Schmitz L.
Published: August 2020

A quasi-neutral blended drift-Lorentz particle model of the field-reversed configuration (FRC) has been developed and implemented in the particle-in-cell code named ANC. A field-aligned mesh and corresponding mesh operations are constructed for solving self-consistent electric fields in FRC geometry. Particle dynamics are described in cylindrical coordinates to allow for cross-separatrix simulation coupling the core and scrape-off layer regions of the FRC. This new model is successfully verified against analytically derived dispersion relations, and FRC turbulence is studied using the blended model for the first time.
Surface-enhanced ultrafast two-dimensional vibrational spectroscopy with engineered plasmonic nano-antennas
Authors: Chuntonov Lev , Rubtsov Igor V.
Published: August 2020

Development of noble metal nanostructure substrates that provide strong near-field enhancements enables applications of linear and nonlinear infrared (IR) spectroscopies to study minute sample quantities, such as nanometer thick films and molecular monolayers. Large near-field enhancements of the electric fields used for spectroscopic interrogation of molecules at the nanostructure surface result in enhancement of the spectroscopic signatures. This enhancement scales with the nonlinear order of the method, providing particularly large signal gains for third- and fifth-order IR methods, reaching 106 and 108 raw enhancement factors, not adjusted to the amount of interrogated sample. In this perspective, we overview the advances in the development of nano-arrays of antenna-like nanostructures for mid-IR measurements and illustrate their use in linear and especially nonlinear two-dimensional IR approaches. We discuss how studies of the interaction mechanisms between light, plasmonic antennas, and molecular excitations benefit from the nonlinear two-dimensional time-resolved methods, which involve high-order scaling of the signal with the excitation field, high sensitivity to signal localization, and coherence of the excitation over a broad bandwidth. On the other hand, we demonstrate how studies of molecular structure and ultrafast dynamics by these advanced spectroscopic methods benefit from surface enhancement of signals by plasmonic antennas.
Basin of attraction for chimera states in a network of Rössler oscillators
Authors: dos Santos Vagner , Borges Fernando S. , Iarosz Kelly C. , Caldas Iberê L. , Szezech J. D. , Viana Ricardo L. , Baptista Murilo S. , Batista Antonio M.
Published: August 2020

Chimera states are spatiotemporal patterns in which coherent and incoherent dynamics coexist simultaneously. These patterns were observed in both locally and nonlocally coupled oscillators. We study the existence of chimera states in networks of coupled Rössler oscillators. The Rössler oscillator can exhibit periodic or chaotic behavior depending on the control parameters. In this work, we show that the existence of coherent, incoherent, and chimera states depends not only on the coupling strength, but also on the initial state of the network. The initial states can belong to complex basins of attraction that are not homogeneously distributed. Due to this fact, we characterize the basins by means of the uncertainty exponent and basin stability. In our simulations, we find basin boundaries with smooth, fractal, and riddled structures.
Spin filtering in germanium/silicon core/shell nanowires with pseudo-helical gap
Authors: Sun Jian , Deacon Russell S. , Liu Xiaochi , Yao Jun , Ishibashi Koji
Published: August 2020

Semiconductors with strong spin–orbit interactions can exhibit a helical gap with spin-momentum locking opened by a magnetic field. Such a gap is highly spin selective as a result of a topologically protected spin-momentum locking, which can be used for spin filtering. We experimentally demonstrate such a spin filtering effect in a quasi-ballistic p-type germanium/silicon core/shell nanowire (NW), which possesses a pseudo-helical gap without the application of magnetic field. Polarized hole spin injection to the NW is achieved using cobalt ferromagnetic contacts with controlled natural surface oxide on the NW as a tunnel barrier. Local and nonlocal spin valve effects are measured as the verification of polarized spin transport in the NW outside the helical gap. We electrically tune the NW into the helical gap by scanning its chemical potential with a gate. A hysteresis loop with three resistance states is observed in the local spin valve geometry, as an evidence of spin filtering in the helical gap.
Stratification of polymer mixtures in drying droplets: Hydrodynamics and diffusion
Authors: Howard Michael P. , Nikoubashman Arash
Published: August 2020

We study the evaporation-induced stratification of a mixture of short and long polymer chains in a drying droplet using molecular simulations. We systematically investigate the effects of hydrodynamic interactions (HI) on this process by comparing hybrid simulations accounting for HI between polymers through the multiparticle collision dynamics technique with free-draining Langevin dynamics simulations neglecting the same. We find that the dried supraparticle morphologies are homogeneous when HI are included but are stratified in core–shell structures (with the short polymers forming the shell) when HI are neglected. The simulation methodology unambiguously attributes this difference to the treatment of the solvent in the two models. We rationalize the presence (or absence) of stratification by measuring phenomenological multicomponent diffusion coefficients for the polymer mixtures. The diffusion coefficients show the importance of not only solvent backflow but also HI between polymers in controlling the dried supraparticle morphology.
Biohybrid electrodes for photoelectrochemical solar energy conversion
Authors: Shiyani T. , Mahapatra Santosh K. , Bogle Kashinath A. , Banerjee Indrani
Published: August 2020

Photoelectrochemical (PEC) properties have been investigated in natural basil dye-sensitized hybrid photoelectrodes for solar energy conversion. Basil dye was used as a photosensitizer. A layer of basil dye was drop cast on the sputtered ZnO film and dried at various temperatures. The effect of heat treatment on the growth of the dye layer was studied in this work. The results suggest that heat treatment plays an important role in the performance of PECs. Biohybrid photoelectrodes were demonstrated for PEC and photoswitching applications. The hybrid structure showed an increase in device efficiency until 50 °C, which further decreases with increasing temperature. The energy conversion efficiency is 0.021% to 0.11%. The present studies will play an important role in designing and developing better performance PEC devices to generate clean electricity and solar fuels.
Foil backlighter development at the OMEGA laser facility for extended x-ray absorption fine structure experiments
Authors: Do A. , Coppari F. , Ping Y. , Krygier A. , Kemp G. E. , Schneider M. B. , McNaney J. M.
Published: August 2020

Extended x-ray absorption fine structure (EXAFS) measurements require a bright and continuous x-ray source and a detection system with high spectral resolution to capture the modulations of the absorption coefficient above the material absorption edge. When performing EXAFS measurements under laser-driven dynamic compression, it is hence critical to optimize the backlighter x-ray emission. A series of experiments has been conducted at the OMEGA laser facility to characterize titanium (Z = 22), iron (Z = 26), germanium (Z = 32), molybdenum (Z = 42), silver (Z = 47), and gold (Z = 79) foil backlighters irradiated with 3 kJ–12 kJ of laser energy. The spectra have been recorded using a dual crystal spectrometer (DCS), a two-channel transmission spectrometer covering 11 keV–45 keV and 19 keV–90 keV energy bands. The DCS has been calibrated so that the spectral intensities can be compared between different campaigns.
Novel similarities in the free-surface profiles and velocities of solitary waves traveling over a very steep beach
Authors: Lin Chang , Kao Ming-Jer , Raikar Rajkumar Venkatesh , Yuan Juan-Ming , Yang James , Chuang Po-Yu , Syu Jie-Ming , Pan Wei-Chih
Published: August 2020

This study investigates experimentally similarity and Froude number similitude (FNS) in the dimensionless flow features of three solitary waves traveling on a 1:3 sloping beach. These three waves, designated as cases A, B, and C, respectively, have different heights H0 (=5.8 cm, 2.9 cm, and 1.815 cm) and still water depths h0 (=16.0 cm, 8.0 cm, and 5.0 cm), but identical ratios H0/h0 (=0.363). A high-speed particle image velocimetry system is employed to obtain the free surface profiles (FSPs) and velocity fields/profiles. These features include the free surface elevation (FSE)/FSP time series; velocity fields and profiles, positions, and propagation speeds of flow demarcation curves; times and maximum onshore distances of the maximum run-up heights (MRHs); and times and onshore distances of hydraulic jumps for cases A and B. When the swash tip of a solitary wave reaches the MRH, the contact point becomes almost immobile for a short time interval, with the contact angle changing from obtuse, via right, to acute angle. For cases A and B, the similarities in the dimensionless MRHs and times, at which the run-down motions of the wave tips start, are affirmed. These facts highlight that the swash tips and contact points are subject to complex interactions among gravity force, viscous friction, and surface tension of fluid. Case C, having the smallest length scale, is only focused on the arrival or starting time of the MRH or run-down motion and the MRH and used as a counterexample to demonstrate the absence of similarity or FNS due to the relatively prominent effects of viscous friction and surface tension.
Optimizing bags of artificial neural networks for the prediction of viability from sparse data
Authors: Daly Clyde A. , Hernandez Rigoberto
Published: August 2020

The prediction of organismal viability in response to exposure to different nanoparticles and conditions characterized at the molecular scale is challenging because several orders of magnitude must be bridged. A so-called bag of artificial neural networks has recently been shown to provide such a connection when trained through the use of relatively small databases. In the present work, we found that individual neural networks do not always converge under training. The use of bags and weighted means for consensus predictions provides a mechanism for effectively pruning the effects from the diverging networks without requiring prior conditioning. The optimized structure of these machines was also found to be effective in predicting the relative viability of nanoparticles that had not been used in developing the major findings of this work.
Creating Gaussian process regression models for molecular simulations using adaptive sampling
Authors: Burn Matthew J. , Popelier Paul L. A.
Published: August 2020

FFLUX is a new force field that combines the accuracy of quantum mechanics with the speed of force fields, without any link to the architecture of classical force fields. This force field is atom-focused and adopts the parameter-free topological atom from Quantum Chemical Topology (QCT). FFLUX uses Gaussian process regression (also known as kriging) models to make predictions of atomic properties, which in this work are atomic energies according to QCT’s interacting quantum atom approach. Here, we report the adaptive sampling technique maximum expected prediction error to create data-compact, efficient, and accurate kriging models (sub-kJ mol−1 for water, ammonia, methane, and methanol and sub-kcal mol−1 for N-methylacetamide). The models cope with large molecular distortions and are ready for use in molecular simulation. A brand new press-one-button Python pipeline, called ICHOR, carries out the training.
Half-Heusler thermoelectric materials: NMR studies
Authors: Tian Yefan , Ghassemi Nader , Ren Wuyang , Zhu Hangtian , Li Shan , Zhang Qian , Wang Zhiming , Ren Zhifeng , Ross Joseph H.
Published: August 2020

We report 59Co, 93Nb, and 121Sb nuclear magnetic resonance measurements combined with density functional theory (DFT) calculations on a series of half-Heusler semiconductors, including NbCoSn, ZrCoSb, TaFeSb, and NbFeSb, to better understand their electronic properties and general composition-dependent trends. These materials are of interest as potentially high efficiency thermoelectric materials. Compared to the other materials, we find that ZrCoSb tends to have a relatively large amount of local disorder, apparently antisite defects. This contributes to a small excitation gap corresponding to an impurity band near the band edge. In NbCoSn and TaFeSb, Curie–Weiss-type behavior is revealed, which indicates a small density of interacting paramagnetic defects. Very large paramagnetic chemical shifts are observed associated with a Van Vleck mechanism due to closely spaced d bands splitting between the conduction and valence bands. Meanwhile, DFT methods were generally successful in reproducing the chemical shift trend for these half-Heusler materials, and we identify enhancement of the larger-magnitude shifts, which we connect to electron interaction effects. The general trend is connected to changes in d-electron hybridization across the series.
Trapping of sub-wavelength microparticles and cells in resonant cylindrical shells
Authors: Lin Qin , Zhou Wei , Cai Feiyan , Li Fei , Xia Xiangxiang , Wang Jieqiong , Zhao Degang , Yan Fei , Meng Long , Zheng Hairong
Published: August 2020

Acoustic tweezers based on the focused field hold the promise of contactless manipulation of microparticles. However, acoustic diffraction severely limits the trapping strength and the minimum size of the trapped particles in conventional diffraction-limited systems. Here, we propose and demonstrate a simple cylindrical shell structure for the trapping of microparticles with a radius as small as 1/400 of the corresponding acoustic wavelength, and its trapping ability is much stronger than that of the standing wave. This mechanism is attributed to the significantly enhanced acoustic radiation force originating from the resonant excitation of low order circumferential modes intrinsically existing in the cylindrical shell, which is a highly localized field around its surfaces. Cylindrical shell-based acoustic tweezers are simple, disposable, low cost, biocompatible, and functional, which may be of interest for nano-scale manufacturing and biomedical applications such as bio-printing, cell culturing, and tissue engineering.
The dispersion of spherical droplets in source–sink flows and their relevance to the COVID-19 pandemic
Authors: Cummins C. P. , Ajayi O. J. , Mehendale F. V. , Gabl R. , Viola I. M.
Published: August 2020

In this paper, we investigate the dynamics of spherical droplets in the presence of a source–sink pair flow field. The dynamics of the droplets is governed by the Maxey–Riley equation with the Basset–Boussinesq history term neglected. We find that, in the absence of gravity, there are two distinct behaviors for the droplets: small droplets cannot go further than a specific distance, which we determine analytically, from the source before getting pulled into the sink. Larger droplets can travel further from the source before getting pulled into the sink by virtue of their larger inertia, and their maximum traveled distance is determined analytically. We investigate the effects of gravity, and we find that there are three distinct droplet behaviors categorized by their relative sizes: small, intermediate-sized, and large. Counterintuitively, we find that the droplets with a minimum horizontal range are neither small nor large, but of intermediate size. Furthermore, we show that in conditions of regular human respiration, these intermediate-sized droplets range in size from a few μm to a few hundred μm. The result that such droplets have a very short range could have important implications for the interpretation of existing data on droplet dispersion.
'Casey did very good work for Wheeler and you are lucky to have him': Dermot Casey's under-appreciated importance in Australian archaeology
Authors: Spriggs Matthew
Published: August 2020

Dermot Casey (1897–1977) is known in Australian archaeology, if he is remembered at all, for being someone who assisted the premier prehistorian of Australia, John Mulvaney, in his excavations of the late 1950s and 1960s and whose collaboration Mulvaney greatly valued. But when Casey began his collaboration with Mulvaney he was already 58 years old and had had a continuing and significant archaeological career, involving work in England and South Asia with Mortimer Wheeler, as well as in Australia. He had been a key figure both before and after World War 2 in the development of Australian archaeology. His role is virtually unknown, however, not least because he was a man of independent means who did not need to work for a living. His selflessness was partly because that privilege gave him a keen sense of service to society, seen in both world wars and in his archaeological practice.
Priorities for primary health care policy implementation: recommendations from the combined experience of six countries in the Asia–Pacific
Authors: Kassai Ryuki , van Weel Chris , Flegg Karen , Tong Seng Fah , Han Tin Myo , Noknoy Sairat , Dashtseren Myagmartseren , Le An Pham , Ng Chirk Jenn , Khoo Ee Ming , Noh Kamaliah Mohd , Lee Meng-Chih , Howe Amanda , Goodyear-Smith Felicity
Published: August 2020

Primary health care is essential for equitable, cost-effective and sustainable health care. It is the cornerstone to achieving universal health coverage against a backdrop of rising health expenditure and aging populations. Implementing strong primary health care requires grassroots understanding of health system performance. Comparing successes and barriers between countries may help identify mutual challenges and possible solutions. This paper compares and analyses primary health care policy in Australia, Malaysia, Mongolia, Myanmar, Thailand and Vietnam. Data were collected at the World Organization of National Colleges, Academies and Academic Associations of General Practitioners/Family Physicians (WONCA) Asia–Pacific regional conference in November 2017 using a predetermined framework. The six countries varied in maturity of their primary health care systems, including the extent to which family doctors contribute to care delivery. Challenges included an insufficient trained and competent workforce, particularly in rural and remote communities, and deficits in coordination within primary health care, as well as between primary and secondary care. Asia–Pacific regional policy needs to: (1) focus on better collaboration between public and private sectors; (2) take a structured approach to information sharing by bridging gaps in technology, health literacy and interprofessional working; (3) build systems that can evaluate and improve quality of care; and (4) promote community-based, high-quality training programs.
RNA sectors and allosteric function within the ribosome
Authors: Walker Allison S. , Russ William P. , Ranganathan Rama , Schepartz Alanna
Published: August 2020

Significance

The ribosome is a large, complex, and essential biomolecular machine. Despite its importance in all domains of life, the long-range interactions that regulate ribosome function are poorly understood. Here we report that statistical coupling analysis (SCA), a method previously only applied to proteins, can identify networks of coevolving bases within the 23S rRNA of the large ribosomal subunit. Using a continuous culture assay, we show that 23S rRNA bases predicted to be important network members cause growth defects when mutated. These findings inform our understanding of long-range functional couplings in the ribosome and provide a tool for studying the same types of interactions in other large RNAs.
Global enhancement of cortical excitability following coactivation of large neuronal populations
Authors: Zhang Deng , Yan Xingjian , She Liang , Wen Yunqing , Poo Mu-ming
Published: August 2020

Significance

Propagating cortical waves that evoke correlated firing of large neuronal populations may cause long-term modification of neural circuits in the brain. Using optogenetic stimulation, we found that repetitive coactivation of large populations of mouse cortical neurons led to enhanced excitability of cortical neurons in both coactivated areas and distant areas that were not coactivated, including those in the contralateral cortices. This global enhancement of neuronal excitability caused by local neuronal stimulation was accompanied by the potentiation of excitatory synaptic transmission, suggesting activity-dependent synaptic plasticity. The corticothalamocortical circuit could contribute to the propagation of this enhancement effect. These results show that the repetitive correlated excitation of large neuronal populations could lead to global enhancement of neuronal excitability.
Changes in life history and population size can explain the relative neutral diversity levels on X and autosomes in extant human populations
Authors: Amster Guy , Murphy David A. , Milligan William R. , Sella Guy
Published: August 2020

Significance

All else being equal, the ratio of diversity levels on X and autosomes at selectively neutral sites should mirror the ratio of their numbers in the population and thus equal 3/4. In reality, the ratios observed across human populations differ markedly from 3/4 and from each other. Because, from a population perspective, autosomes spend an equal number of generations in both sexes, while the X spends twice as many generations in females, these departures from the naïve expectations plausibly reflect differences between male and female life histories and their effects on mutation processes. Indeed, we show that the ratios observed across human populations can be explained by demographic history, assuming realistic sex-specific mutation rates, generation times, and reproductive variances.
A folding reaction at the C-terminal domain drives temperature sensing in TRPM8 channels
Authors: Díaz-Franulic Ignacio , Raddatz Natalia , Castillo Karen , González-Nilo Fernando D. , Latorre Ramon
Published: August 2020

Significance

Sensory and homeostatic responses in several organisms depend on the exquisite temperature dependence of ion channels of the transient receptor potential family (thermo-TRP). To date, this temperature dependence has been explained either in terms of the existence of a dedicated temperature sensor or by the increase in the molar heat capacity during channel gating. We found that the Carboxy Terminus Domain (CTD) is required for temperature-driven gating of the cold-activated TRPM8 channel and that this domain folds in response to cold. Here we propose that the CTD of the TRPM8 channel is a bona fide temperature sensor that drives channel gating due to an increase in the molar heat capacity during the folded-to-unfolded transition.
Tuning the circadian period of cyanobacteria up to 6.6 days by the single amino acid substitutions in KaiC
Authors: Ito-Miwa Kumiko , Furuike Yoshihiko , Akiyama Shuji , Kondo Takao
Published: August 2020

Significance

Circadian clocks, biological oscillators with temperature-compensated periods close to 24 h, enhance fitness in Earth’s daily cycle. Although many circadian period mutants have helped to elucidate the circadian clock mechanism, the tuning mechanism of 24-h period remains unclear. In this study, we found that mutants at position 402 of cyanobacterial clock protein KaiC alter circadian periods dramatically, from 0.6 to 6.6 d. Despite the wide-range tunability, temperature compensation of period was kept nearly intact. As these astounding results can be observed in in vitro system, residue 402 is the important position for tuning mechanism of period. Furthermore, we found that the volume of residue 402 of KaiC is the key factor in determination of the length of circadian period.
Dielectric response with short-ranged electrostatics
Authors: Cox Stephen J.
Published: August 2020

Significance

Much of a liquid’s ability to act as a solvent stems from its dielectric properties. The intermolecular forces between polar molecules can act over very long ranges, which complicates both theoretical descriptions and molecular simulations. Here the dielectric properties of a model system with only short-ranged intermolecular interactions are investigated, and this short-ranged model’s behavior is rationalized on a theoretical basis. This work will likely facilitate the development of both efficient short-ranged interaction potentials and our understanding of fluids under confinement.
Global patterns and climatic controls of belowground net carbon fixation
Authors: Gherardi Laureano A. , Sala Osvaldo E.
Published: August 2020

Significance

The fraction of fixed carbon allocated belowground in terrestrial ecosystems is the most uncertain component of global carbon cycle assessments. Here we present a novel approach to determining global quantification of belowground productivity, which is estimated at 24.7 Pg y
−1
and accounts for 46% of terrestrial carbon fixation. Carbon allocated belowground has a longer residence than its aboveground counterpart, playing a key role in long-term carbon storage. Total belowground productivity increases with precipitation, but the rate of increase decreases from arid to humid ecosystems. The fraction of total fixed carbon entering the soil decreases with precipitation and varies significantly among biomes. These results are indicative of the possible impacts of climate and land use changes on the global carbon cycle.
Surface polarization effects in confined polyelectrolyte solutions
Authors: Bagchi Debarshee , Nguyen Trung Dac , Olvera de la Cruz Monica
Published: August 2020

Significance

Molecular electrolytes under confinement are crucial materials for energy storage devices and commonly used model systems for understanding biomolecular functions. In particular, understanding the complex interplay of entropy and electrostatic interactions in a polyelectrolyte solution confined inside oppositely charged surfaces gives us important insights into its energy storage and capacitance properties. Here, using molecular dynamics simulations, we analyze polyelectrolyte solutions confined between two oppositely charged planar surfaces with a much lower dielectric constant. We find that such mismatch of dielectric constants and chain flexibility significantly influence the energy storage capability and capacitance of such a confined system. Dielectric mismatch enhances surface charge amplification in flexible polyelectrolyte solutions, increasing their energy storage capabilities.
Genomic analysis of inherited hearing loss in the Palestinian population
Authors: Abu Rayyan Amal , Kamal Lara , Casadei Silvia , Brownstein Zippora , Zahdeh Fouad , Shahin Hashem , Canavati Christina , Dweik Dima , Jaraysa Tamara , Rabie Grace , Carlson Ryan J. , Gulsuner Suleyman , Lee Ming K. , Avraham Karen B. , Walsh Tom , King Mary-Claire , Kanaan Moien N.
Published: August 2020

Significance

The genetic characterization of a common phenotype for an entire population reveals both the genetic epidemiology of that phenotype and the power of family-based, population-wide genomic analysis. We characterized the genetics of hearing loss throughout the Palestinian population of the West Bank and Gaza. In families with no prior history of hearing loss, we estimate that 56% of hearing loss is genetic and 44% is not genetic. For most families with inherited hearing loss, causal genes and mutations were identified. Most inherited hearing loss in the population was attributable to consanguinity. Given the ongoing decline in consanguineous marriage, inherited hearing loss will likely be much rarer in the next generation.