bluuebunny/crossref_metadata_2025 huggingface dataset:
Synchronization of three electrochemical oscillators: From local to global coupling
Authors: Liu Yifan , Sebek Michael , Mori Fumito , Kiss István Z.
Published: April 2018

We investigate the formation of synchronization patterns in an oscillatory nickel electrodissolution system in a network obtained by superimposing local and global coupling with three electrodes. We explored the behavior through numerical simulations using kinetic ordinary differential equations, Kuramoto type phase models, and experiments, in which the local to global coupling could be tuned by cross resistances between the three nickel wires. At intermediate coupling strength with predominant global coupling, two of the three oscillators, whose natural frequencies are closer, can synchronize. By adding even a relatively small amount of local coupling (about 9%–25%), a spatially organized partially synchronized state can occur where one of the two synchronized elements is in the center. A formula was derived for predicting the critical coupling strength at which full synchronization will occur independent of the permutation of the natural frequencies of the oscillators over the network. The formula correctly predicts the variation of the critical coupling strength as a function of the global coupling fraction, e.g., with local coupling the critical coupling strength is about twice than that required with global coupling. The results show the importance of the topology of the network on the synchronization properties in a simple three-oscillator setup and could provide guidelines for decrypting coupling topology from identification of synchronization patterns.
Microstructure research for ferroelectric origin in the strained Hf0.5Zr0.5O2 thin film via geometric phase analysis
Authors: Bi Han , Sun Qingqing , Zhao Xuebing , You Wenbin , Zhang David Wei , Che Renchao
Published: April 2018

Recently, non-volatile semiconductor memory devices using a ferroelectric Hf0.5Zr0.5O2 film have been attracting extensive attention. However, at the nano-scale, the phase structure remains unclear in a thin Hf0.5Zr0.5O2 film, which stands in the way of the sustained development of ferroelectric memory nano-devices. Here, a series of electron microscopy evidences have illustrated that the interfacial strain played a key role in inducing the orthorhombic phase and the distorted tetragonal phase, which was the origin of the ferroelectricity in the Hf0.5Zr0.5O2 film. Our results provide insight into understanding the association between ferroelectric performances and microstructures of Hf0.5Zr0.5O2-based systems.
Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films
Authors: Chow Philippe K. , Yang Wenjie , Hudspeth Quentin , Lim Shao Qi , Williams Jim S. , Warrender Jeffrey M.
Published: April 2018

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.
Microscopic gate-modulation imaging of charge and field distribution in polycrystalline organic transistors
Authors: Matsuoka Satoshi , Tsutsumi Jun'ya , Kamata Toshihide , Hasegawa Tatsuo
Published: April 2018

In this work, a high-resolution microscopic gate-modulation imaging (μ-GMI) technique is successfully developed to visualize inhomogeneous charge and electric field distributions in operating organic thin-film transistors (TFTs). We conduct highly sensitive and diffraction-limit gate-modulation sensing for acquiring difference images of semiconducting channels between at gate-on and gate-off states that are biased at an alternate frequency of 15 Hz. As a result, we observe unexpectedly inhomogeneous distribution of positive and negative local gate-modulation (GM) signals at a probe photon energy of 1.85 eV in polycrystalline pentacene TFTs. Spectroscopic analyses based on a series of μ-GMI at various photon energies reveal that two distinct effects appear, simultaneously, within the polycrystalline pentacene channel layers: Negative GM signals at 1.85 eV originate from the second-derivative-like GM spectrum which is caused by the effect of charge accumulation, whereas positive GM signals originate from the first-derivative-like GM spectrum caused by the effect of leaked gate fields. Comparisons with polycrystalline morphologies indicate that grain centers are predominated by areas with high leaked gate fields due to the low charge density, whereas grain edges are predominantly high-charge-density areas with a certain spatial extension as associated with the concentrated carrier traps. Consequently, it is reasonably understood that larger grains lead to higher device mobility, but with greater inhomogeneity in charge distribution. These findings provide a clue to understand and improve device characteristics of polycrystalline TFTs.
Pressure sensing element based on the BN–graphene–BN heterostructure
Authors: Li Mengwei , Wu Chenggen , Zhao Shiliang , Deng Tao , Wang Junqiang , Liu Zewen , Wang Li , Wang Gao
Published: April 2018

In this letter, we report a pressure sensing element based on the graphene–boron nitride (BN) heterostructure. The heterostructure consists of monolayer graphene sandwiched between two layers of vertically stacked dielectric BN nanofilms. The BN layers were used to protect the graphene layer from oxidation and pollution. Pressure tests were performed to investigate the characteristics of the BN–graphene–BN pressure sensing element. A sensitivity of 24.85 μV/V/mmHg is achieved in the pressure range of 130–180 kPa. After exposing the BN–graphene–BN pressure sensing element to the ambient environment for 7 days, the relative resistance change in the pressure sensing element is only 3.1%, while that of the reference open-faced graphene device without the BN protection layers is 15.7%. Thus, this strategy is promising for fabricating practical graphene pressure sensors with improved performance and stability.
High-temperature phase transitions in TlInTe2 crystals
Authors: Alekperov O. Z. , Najafov A. I. , Nakhmedov E. , Samedov O. A. , Aliyeva N. A. , Jafarova G.
Published: April 2018

Dependencies of the lattice parameters and the coefficient of thermal expansion of TlInTe2 crystals on temperature are studied at a wide range of temperatures by using XRD, dilatometer, differential thermal analysis, and impedance spectroscopy (IS) methods. The IS measurements of the dielectric function were done along the c-axis and normal to the (110)-plane. IS for E ⊥ (110)-plane was done for two values of the amplitudes, U0 = 0.04 V and 1 V, of ac-voltage with different frequencies; moreover, the measurements for E∥c were realized at U0 = 0.04 V only. IS measurements demonstrate a sequence of the phase transitions (PTs) to the ferroelectric and the ionic conductivity states, also to a structural phase transition. Tl+ ions are shown to shift in the direction of normal to c-axis in the ferroelectric PT, but they are activated along the c-axis in the ionic conductivity PT. The dielectric function in the ionic conductivity PT is shown to increase to a huge positive value and then to drop to a big negative value, reversing its sign. An explanation of this effect is provided as a competition of Drude and polarization contribution to the dielectric function under ac-electric field. Thermal effects of the phase transitions were determined.
Analysis of retarding field energy analyzer transmission by simulation of ion trajectories
Authors: van de Ven T. H. M. , de Meijere C. A. , van der Horst R. M. , van Kampen M. , Banine V. Y. , Beckers J.
Published: April 2018

Retarding field energy analyzers (RFEAs) are used routinely for the measurement of ion energy distribution functions. By contrast, their ability to measure ion flux densities has been considered unreliable because of lack of knowledge about the effective transmission of the RFEA grids. In this work, we simulate the ion trajectories through a three-gridded RFEA using the simulation software SIMION. Using idealized test cases, it is shown that at high ion energy (i.e., >100 eV) the transmission is equal to the optical transmission rather than the product of the individual grid transparencies. Below 20 eV, ion trajectories are strongly influenced by the electric fields in between the grids. In this region, grid alignment and ion focusing effects contribute to fluctuations in transmission with ion energy. Subsequently the model has been used to simulate the transmission and energy resolution of an experimental RFEA probe. Grid misalignments reduce the transmission fluctuations at low energy. The model predicts the minimum energy resolution, which has been confirmed experimentally by irradiating the probe with a beam of ions with a small energy bandwidth.
Converging shock flows for a Mie-Grüneisen equation of state
Authors: Ramsey Scott D. , Schmidt Emma M. , Boyd Zachary M. , Lilieholm Jennifer F. , Baty Roy S.
Published: April 2018

Previous work has shown that the one-dimensional (1D) inviscid compressible flow (Euler) equations admit a wide variety of scale-invariant solutions (including the famous Noh, Sedov, and Guderley shock solutions) when the included equation of state (EOS) closure model assumes a certain scale-invariant form. However, this scale-invariant EOS class does not include even simple models used for shock compression of crystalline solids, including many broadly applicable representations of Mie-Grüneisen EOS. Intuitively, this incompatibility naturally arises from the presence of multiple dimensional scales in the Mie-Grüneisen EOS, which are otherwise absent from scale-invariant models that feature only dimensionless parameters (such as the adiabatic index in the ideal gas EOS). The current work extends previous efforts intended to rectify this inconsistency, by using a scale-invariant EOS model to approximate a Mie-Grüneisen EOS form. To this end, the adiabatic bulk modulus for the Mie-Grüneisen EOS is constructed, and its key features are used to motivate the selection of a scale-invariant approximation form. The remaining surrogate model parameters are selected through enforcement of the Rankine-Hugoniot jump conditions for an infinitely strong shock in a Mie-Grüneisen material. Finally, the approximate EOS is used in conjunction with the 1D inviscid Euler equations to calculate a semi-analytical Guderley-like imploding shock solution in a metal sphere and to determine if and when the solution may be valid for the underlying Mie-Grüneisen EOS.
How do glycerol and dimethyl sulphoxide affect local tetrahedral structure of water around a nonpolar solute at low temperature? Importance of preferential interaction
Authors: Daschakraborty Snehasis
Published: April 2018

Glycerol and dimethyl sulphoxide (DMSO) have vital roles in cryoprotection of living cells, tissues, etc. The above action has been directly linked with disruption of hydrogen (H-) bond structure and dynamics of water by these cosolvents at bulk region and around various complex units, such as peptide, amino acid, protein, and lipid membrane. However, the disruption of the local structure of the water solvent around a purely hydrophobic solute is still not studied extensively. The latter is also important in the context of stabilization of protein from cold denaturation. Through all-atom molecular dynamics simulation, we have investigated the comparative effect of glycerol and DMSO on the orientational order of water around a nonpolar solute at −5 °C. A steady reduction of the tetrahedral order of water is observed at bulk (>10 Å distance from the solute) and solute interface (<5.5 Å distance from the solute) with increasing the cosolvent concentration. Contrasting roles of glycerol and DMSO have been evidenced. While DMSO affects the H-bond structure of the interfacial water more than that of the bulk water, glycerol affects the water structure almost uniformly at all regions around the solute. Furthermore, while glycerol helps to retain water molecules at the interface, DMSO significantly reduces the water content in that region. We have put forward a plausible mechanism for these contrasting roles of these cosolvents. The solute-cosolvent hydrophobic-interaction-induced orientational alignment of an interfacial cosolvent molecule determines whether the involvement of the cosolvent molecules in H-bonding with solvent water in the interface is akin to the bulk region or not.
Continuous form-dependent focusing of non-spherical microparticles in a highly diluted suspension with the help of microfluidic spirals
Authors: Roth Tanja , Sprenger Lisa , Odenbach Stefan , Häfeli Urs O.
Published: April 2018

Microfluidic spirals are able to focus non-spherical microparticles in diluted suspension due to the Dean effect. A secondary flow establishes in a curved channel, consisting of two counter-rotating vortices, which transport particles to an equilibrium position near the inner wall of the channel. The relevant size parameter, which is responsible for successful focusing, is the ratio between the particle diameter of a sphere and the hydraulic diameter, which is a characteristic of the microfluidic spiral. A non-spherical particle has not one but several different size parameters. This study investigated the minor and major axes, the equivalent spherical diameter, and the maximal rotational diameter as an equivalent to the spherical diameter. Using a polydimethylsiloxane (PDMS)-based microfluidic device with spirals, experiments were conducted with artificial peanut-shaped and ellipsoidal particles sized between 3 and 9 μm as well as with the bacteria Bacillus subtilis. Our investigations show that the equivalent spherical diameter, the major axis, and the maximal rotational diameter of a non-spherical particle can predict successful focusing. The minor axis is not suitable for this purpose. Non-spherical particles focused when the ratio of their equivalent spherical diameter to the hydraulic diameter of the channel was larger than 0.07. The particles also focused when the ratio between the maximal rotational diameter or the major axis and the hydraulic diameter was larger than 0.01. These results may help us to separate non-spherical biological particles, such as circulating tumor cells or pathogenic bacteria, from blood in future experimental studies.
Modeling to study the role of catalyst in the formation of graphitic shells during carbon nanofiber growth subjected to reactive plasma
Authors: Gupta Ravi , Gupta Neha , Sharma Suresh C.
Published: April 2018

An analytical model to study the role of a metal catalyst nanofilm in the nucleation, growth, and resulting structure of carbon nanofibers (CNFs) in low-temperature hydrogen diluted acetylene plasma has been developed. The model incorporates the nanostructuring of thin catalyst films, growth of CNF, restructuring of catalyst nanoparticles during growth, and its repercussion on the resulting structure (alignment of rolled graphene sheets around catalyst nanoparticles) by taking into account the plasma sheath formalization, kinetics of neutrals and positively charged species in the reactive plasma, flux of plasma species onto the catalyst front surface, and numerous surface reactions for carbon generation. In order to examine the influence of the catalyst film on the growth of CNFs, the numerical solutions of the model equations have been obtained for experimentally determined initial conditions and glow discharge plasma parameters. From the solutions obtained, we found that nanostructuring of thin films leads to the formation of small nanoparticles with high surface number density. The CNF nucleates over these small-sized nanoparticles grow faster and attain early saturation because of the quick poisoning of small-sized catalyst particles, and contain only a few graphitic shells. However, thick nanofilms result in shorter CNFs with large diameters composed of many graphitic shells. Moreover, we found that the inclination of graphitic shells also depends on the extent up to which the catalyst can reconstruct itself during the growth. The small nanoparticles show much greater elongation along the growth axis and also show a very small difference between their tip and base diameter during the growth due to which graphitic shells align at very small angles as compared to the larger nanoparticles. The present study is useful to synthesize the thin and more extended CNFs/CNTs having a smaller opening angle (inclination angle of graphene layers) as the opening angle has a significant influence on their field emission properties. The comparisons of these theoretical findings to the experimental observations confirm the adequacy of the proposed model.
Turbulent structure of stably stratified inhomogeneous flow
Authors: Iida Oaki
Published: April 2018

Effects of buoyancy force stabilizing disturbances are investigated on the inhomogeneous flow where disturbances are dispersed from the turbulent to non-turbulent field in the direction perpendicular to the gravity force. Attaching the fringe region, where disturbances are excited by the artificial body force, a Fourier spectral method is used for the inhomogeneous flow stirred at one side of the cuboid computational box. As a result, it is found that the turbulent kinetic energy is dispersed as layered structures elongated in the streamwise direction through the vibrating motion. A close look at the layered structures shows that they are flanked by colder fluids at the top and hotter fluids at the bottom, and hence vertically compressed and horizontally expanded by the buoyancy related to the countergradient heat flux, though they are punctuated by the vertical expansion of fluids at the forefront of the layered structures, which is related to the downgradient heat flux, indicating that the layered structures are gravity currents. However, the phase between temperature fluctuations and vertical velocity is shifted by π/2 rad, indicating that temperature fluctuations are generated by the propagation of internal gravity waves.
Implementing Bayesian networks with embedded stochastic MRAM
Authors: Faria Rafatul , Camsari Kerem Y. , Datta Supriyo
Published: April 2018

Magnetic tunnel junctions (MTJ’s) with low barrier magnets have been used to implement random number generators (RNG’s) and it has recently been shown that such an MTJ connected to the drain of a conventional transistor provides a three-terminal tunable RNG or a p-bit. In this letter we show how this p-bit can be used to build a p-circuit that emulates a Bayesian network (BN), such that the correlations in real world variables can be obtained from electrical measurements on the corresponding circuit nodes. The p-circuit design proceeds in two steps: the BN is first translated into a behavioral model, called Probabilistic Spin Logic (PSL), defined by dimensionless biasing (h) and interconnection (J) coefficients, which are then translated into electronic circuit elements. As a benchmark example, we mimic a family tree of three generations and show that the genetic relatedness calculated from a SPICE-compatible circuit simulator matches well-known results.
Two-dimensional photonic crystal slab nanocavities on bulk single-crystal diamond
Authors: Wan Noel H. , Mouradian Sara , Englund Dirk
Published: April 2018

Color centers in diamond are promising spin qubits for quantum computing and quantum networking. In photon-mediated entanglement distribution schemes, the efficiency of the optical interface ultimately determines the scalability of such systems. Nano-scale optical cavities coupled to emitters constitute a robust spin-photon interface that can increase spontaneous emission rates and photon extraction efficiencies. In this work, we introduce the fabrication of 2D photonic crystal slab nanocavities with high quality factors and cubic wavelength mode volumes—directly in bulk diamond. This planar platform offers scalability and considerably expands the toolkit for classical and quantum nanophotonics in diamond.
Molecular dynamics simulations of ejecta production from sinusoidal tin surfaces under supported and unsupported shocks
Authors: Wu Bao , Wu FengChao , Zhu YinBo , Wang Pei , He AnMin , Wu HengAn
Published: April 2018

Micro-ejecta, an instability growth process, occurs at metal/vacuum or metal/gas interface when compressed shock wave releases from the free surface that contains surface defects. We present molecular dynamics (MD) simulations to investigate the ejecta production from tin surface shocked by supported and unsupported waves with pressures ranging from 8.5 to 60.8 GPa. It is found that the loading waveforms have little effect on spike velocity while remarkably affect the bubble velocity. The bubble velocity of unsupported shock loading remains nonzero constant value at late time as observed in experiments. Besides, the time evolution of ejected mass in the simulations is compared with the recently developed ejecta source model, indicating the suppressed ejection of unmelted or partial melted materials. Moreover, different reference positions are chosen to characterize the amount of ejecta under different loading waveforms. Compared with supported shock case, the ejected mass of unsupported shock case saturates at lower pressure. Through the analysis on unloading path, we find that the temperature of tin sample increases quickly from tensile stress state to zero pressure state, resulting in the melting of bulk tin under decaying shock. Thus, the unsupported wave loading exhibits a lower threshold pressure causing the solid-liquid phase transition on shock release than the supported shock loading.
Flexible scheme to truncate the hierarchy of pure states
Authors: Zhang P.-P. , Bentley C. D. B. , Eisfeld A.
Published: April 2018

The hierarchy of pure states (HOPS) is a wavefunction-based method that can be used for numerically modeling open quantum systems. Formally, HOPS recovers the exact system dynamics for an infinite depth of the hierarchy. However, truncation of the hierarchy is required to numerically implement HOPS. We want to choose a “good” truncation method, where by “good” we mean that it is numerically feasible to check convergence of the results. For the truncation approximation used in previous applications of HOPS, convergence checks are numerically challenging. In this work, we demonstrate the application of the “n-particle approximation” to HOPS. We also introduce a new approximation, which we call the “n-mode approximation.” We then explore the convergence of these truncation approximations with respect to the number of equations required in the hierarchy in two exemplary problems: absorption and energy transfer of molecular aggregates.
Taming axial dispersion in hydrodynamic chromatography columns through wall patterning
Authors: Adrover Alessandra , Cerbelli Stefano , Giona Massimiliano
Published: April 2018

A well-known limitation of hydrodynamic chromatography arises from the synergistic interaction between transverse diffusion and streamwise convection, which enhances axial dispersion through the Taylor-Aris mechanism. We show that a periodic sequence of slip/no-slip conditions at the channel walls (e.g., representing wall indentations hosting stable air pockets) can significantly reduce axial dispersion, thus enhancing separation performance. The theoretical/numerical analysis is based on a generalization of Brenner’s macrotransport approach to solute transport, here modified to account for the finite-size of the suspended particles. The most effective dispersion-taming outcome is observed when the alternating sequence of slip/no-slip conditions yields non-vanishing cross-sectional flow components. The combination of these components with the hindering interaction between the channel boundaries and the finite-sized particles gives rise to a non-trivial solution of Brenner’s problem on the unit periodic cell, where the cross-sectional particle number density departs from the spatially homogeneous condition. In turn, this effect impacts upon the solution of the so-called b-field defining the large-scale dispersion tensor, with an overall decremental effect on the axial dispersion coefficient and on the Height Equivalent of a Theoretical Plate.
On the formation of thermal drift
Authors: Abtahi Arman , Floryan J. M.
Published: April 2018

It has been recently shown [A. Abtahi and J. M. Floryan, “Natural convection and thermal drift,” J. Fluid Mech. 826, 553 (2017)] that a horizontal flow, the thermal drift, can be created by applying spatially periodic heating to a corrugated plate. The presence of corrugations and its proper placement with respect to the heating pattern are essential. This analysis demonstrates that such drift can result from the interaction of the corrugated plate with any temperature field of the same spatial periodicity regardless of how this field is created. This principle is demonstrated through an analysis of convection in a horizontal slot with one plate heated and the opposite plate corrugated.
Modelling and simulation of particle-particle interaction in a magnetophoretic bio-separation chip
Authors: Alam Manjurul , Golozar Matin , Darabi Jeff
Published: April 2018

A Lagrangian particle trajectory model is developed to predict the interaction between cell-bead particle complexes and to track their trajectories in a magnetophoretic bio-separation chip. Magnetic flux gradients are simulated in the OpenFOAM CFD software and imported into MATLAB to obtain the trapping lengths and trajectories of the particles. A connector vector is introduced to calculate the interaction force between cell-bead complexes as they flow through a microfluidic device. The interaction force calculations are performed for cases where the connector vector is parallel, perpendicular, and at an angle of 45° with the applied magnetic field. The trajectories of the particles are simulated by solving a system of eight ordinary differential equations using a fourth order Runge-Kutta method. The model is then used to study the effects of geometric positions and angles of the connector vector between the particles as well as the cell size, number of beads per cell, and flow rate on the interaction force and trajectories of the particles. The results show that the interaction forces may be attractive or repulsive, depending on the orientation of the connector vector distance between the particle complexes and the applied magnetic field. When the interaction force is attractive, the particles are observed to merge and trap sooner than a single particle, whereas a repulsive interaction force has little or no effect on the trapping length.
Assessment of interaction-strength interpolation formulas for gold and silver clusters
Authors: Giarrusso Sara , Gori-Giorgi Paola , Della Sala Fabio , Fabiano Eduardo
Published: April 2018

The performance of functionals based on the idea of interpolating between the weak- and the strong-interaction limits the global adiabatic-connection integrand is carefully studied for the challenging case of noble-metal clusters. Different interpolation formulas are considered and various features of this approach are analyzed. It is found that these functionals, when used as a correlation correction to Hartree-Fock, are quite robust for the description of atomization energies, while performing less well for ionization potentials. Future directions that can be envisaged from this study and a previous one on main group chemistry are discussed.
A method for generating reduced-order combustion mechanisms that satisfy the differential entropy inequality
Authors: Ream Allen E. , Slattery John C. , Cizmas Paul G. A.
Published: April 2018

This paper presents a new method for determining the Arrhenius parameters of a reduced chemical mechanism such that it satisfies the second law of thermodynamics. The strategy is to approximate the progress of each reaction in the reduced mechanism from the species production rates of a detailed mechanism by using a linear least squares method. A series of non-linear least squares curve fittings are then carried out to find the optimal Arrhenius parameters for each reaction. At this step, the molar rates of production are written such that they comply with a theorem that provides the sufficient conditions for satisfying the second law of thermodynamics. This methodology was used to modify the Arrhenius parameters for the Westbrook and Dryer two-step mechanism and the Peters and Williams three-step mechanism for methane combustion. Both optimized mechanisms showed good agreement with the detailed mechanism for species mole fractions and production rates of most major species. Both optimized mechanisms showed significant improvement over previous mechanisms in minor species production rate prediction. Both optimized mechanisms produced no violations of the second law of thermodynamics.
Numerical study of the collisionless interaction between positive and negative ion beams
Authors: Lounes-Mahloul S. , Oudini N. , Bendib A.
Published: April 2018

We study, through two dimensional Particle-In-Cell simulations, the expansion of an ion-ion beam in vacuum. This beam is generated by a continuous extraction of positive and negative ions from two adjacent gridded ion sources. The grid systems are biased to extract and accelerate, continuously, positive and negative ions from two distinct ion sources. The ion sources are positioned such that their grid systems form an angle θ. In this work, we study two configurations, θ = π and θ = π/2. The proposed device constitutes an alternative approach to the usual positive ion beam neutralized by electrons. This work aims, on the one hand, to demonstrate that the neutralization of a continuously extracted ion beam space charge might be achieved by the use of oppositely charged ions. On the other hand, this work investigates the physical properties of the generated ion-ion beam. Our results show that, for θ = π, potential barriers form in the close vicinity of the acceleration grids. These potential barriers oppose to extraction and induce an ion backflow. This backflow increases with the increase in extracted ion current density. It represents ∼60% to ∼80% of extracted ions for an extracted ion current density ranging from 1 to 10 A/m2. Moreover, for θ = π/2, the potential barriers are located downstream the grids, typically at one source diameter. For this configuration, we found that the backflow is drastically reduced to about 25% of the extracted ions.
Rate equation description of quantum noise in nanolasers with few emitters
Authors: Mork J. , Lippi G. L.
Published: April 2018

Rate equations for micro- and nanocavity lasers are formulated which take account of the finite number of emitters, Purcell effects as well as stochastic effects of spontaneous emission quantum noise. Analytical results are derived for the intensity noise and intensity correlation properties, g(2), using a Langevin approach and are compared with simulations using a stochastic approach avoiding the mean-field approximation of the rate equations. Good agreement between the two approaches is found even for large values of the spontaneous emission beta-factor, i.e., for threshold-less lasers, as long as more than about ten emitters contribute to lasing. A large value of the beta-factor improves the noise properties.
Specimen's plane misaligned installation solution based on charge fluctuation inside SEM
Authors: Lu Haojian , Liu Yanting , Yang Yuanyuan , Wang Panbing , Shen Yajing
Published: April 2018

Precise specimen's installation is a sticking point to ensure the characterization accuracy of the in-situ material property test. Although it is common knowledge that specimen's plane misaligned installation (PMI) would cause extra force loading during mechanical testing, there are few effective solutions available to deal with it at the current stage, especially during the in-situ scanning electron microscopy (SEM) test. Taking into consideration the charge fluctuation phenomenon under SEM, this paper proposes a highlight area variation (HAV) method for specimen deformation judgment, i.e., the specimen deformation is defined when the highlight area changes greater than 20% of the initial value of the specimen surface. Three types of specimens with different resistivities, i.e., human hair (electrical resistivity ∼3 × 1012 Ω cm), optical fiber (electrical resistivity ∼1017 Ω cm), and magnetic wire (electrical resistivity ∼2 × 10−5 Ω cm), are chosen to verify the effectiveness of the HAV method. Furthermore, combined with the developed robot-aided alignment system, the specimen's PMI problem can also be solved. In the demonstration, the human hair specimen is installed across two specimen stages and its in-situ twisting (in 360°) test is implemented. The results clearly indicate that the HAV method and the robot-aided alignment system are practical and reliable, and the specimen can be aligned on the same plane and installed precisely with accuracy up to 3 μm. This method will benefit the in-situ SEM material mechanical property test and has a significant impact in fundamental material research.
Comparison on mechanical properties of heavily phosphorus- and arsenic-doped Czochralski silicon wafers
Authors: Yuan Kang , Sun Yuxin , Lu Yunhao , Liang Xingbo , Tian Daxi , Ma Xiangyang , Yang Deren
Published: April 2018

Heavily phosphorus (P)- and arsenic (As)-doped Czochralski silicon (CZ-Si) wafers generally act as the substrates for the epitaxial silicon wafers used to fabricate power and communication devices. The mechanical properties of such two kinds of n-type heavily doped CZ silicon wafers are vital to ensure the quality of epitaxial silicon wafers and the manufacturing yields of devices. In this work, the mechanical properties including the hardness, Young’s modulus, indentation fracture toughness and the resistance to dislocation motion have been comparatively investigated for heavily P- and As-doped CZ-Si wafers. It is found that heavily P-doped CZ-Si possesses somewhat higher hardness, lower Young’s modulus, larger indentation fracture toughness and stronger resistance to dislocation motion than heavily As-doped CZ-Si. The mechanisms underlying this finding have been tentatively elucidated by considering the differences in the doping effects of P and As in silicon.
An application area of C60: Overall improvement of insulating oil's electrical performance
Authors: Sun Potao , Sima Wenxia , Chen Jiaqi , Zhang Dingfei , Jiang Xiongwei , Chen Qiulin
Published: April 2018

We prepared nano-C60 based insulating oil, which has the potential to overcome the application barriers of nanomodified insulating oil. We find that nano-C60 based insulating oil has an excellent stability. Its electrical performance increases by 17.9%, 9.3%, and 8.3% for AC and positive/negative lightning impulse voltage, respectively. We believe that C60 molecules have a strong capacity to absorb electrons and can capture photons in a streamer, which may weaken photoionization in the streamer and thereby improve the electrical performance of insulating oil.
Seagrass habitat metabolism increases short-term extremes and long-term offset of CO
2
under future ocean acidification
Authors: Pacella Stephen R. , Brown Cheryl A. , Waldbusser George G. , Labiosa Rochelle G. , Hales Burke
Published: April 2018

Significance

The impacts of ocean acidification in nearshore estuarine environments remain poorly characterized, despite these areas being some of the most ecologically important habitats in the global ocean. Here, we quantify how rising atmospheric CO
2
from the years 1765 to 2100 alters high-frequency carbonate chemistry dynamics in an estuarine seagrass habitat. We find that increasing anthropogenic carbon reduces the ability of the system to buffer natural extremes in CO
2
. This reduced buffering capacity leads to preferential amplification of naturally extreme low pH and high pCO
2(s.w.)
events above changes in average conditions, which outpace rates published for atmospheric and open-ocean CO
2
change. Seagrass habitat metabolism drives these short-term extreme events, yet ultimately reduces organismal exposure to harmful conditions in future high-CO
2
scenarios.
The computational form of craving is a selective multiplication of economic value
Authors: Konova Anna B. , Louie Kenway , Glimcher Paul W.
Published: April 2018

Significance

Craving is a specific desire state that biases choice toward the desired object. Although extremely common, and in its pathological form a major contributor to negative health outcomes as in addiction and obesity, craving is not well understood. In a laboratory model of craving, we find “craving” is reflected in people’s momentary willingness to pay for the things they desire, and for subjectively similar things, consistent with a transient, good-selective change in subjective valuation. We further find the value of the desired goods increases multiplicatively, which might explain several escalation behaviors associated with craving in real-world environments. This opens more lines of research regarding the computational form of craving in health and disease, with implications for marketing actions and consumer choice.
Precise characterization of KRAS4b proteoforms in human colorectal cells and tumors reveals mutation/modification cross-talk
Authors: Ntai Ioanna , Fornelli Luca , DeHart Caroline J. , Hutton Josiah E. , Doubleday Peter F. , LeDuc Richard D. , van Nispen Alexandra J. , Fellers Ryan T. , Whiteley Gordon , Boja Emily S. , Rodriguez Henry , Kelleher Neil L.
Published: April 2018

Significance

TheKRASgene is frequently mutated in human cancer, especially in pancreatic, lung, and colorectal tumors. We developed an intact protein assay for the detection and quantitation of KRAS protein forms (proteoforms), enabling the measurement of how genetically encoded mutations affect posttranslational modifications on the same protein molecule. The modifications found are known to activate KRAS or interfere with membrane attachment, suggesting cellular mechanisms that control downstream KRAS activity. Analysis of wild-type and mutant-specific forms of the KRAS protein with complete molecular specificity is shown to be possible by top-down proteomics and enables future tests of how an individual’s KRAS proteoforms are linked to disease stage and chance of survival.
Intron retention induced by microsatellite expansions as a disease biomarker
Authors: Sznajder Łukasz J. , Thomas James D. , Carrell Ellie M. , Reid Tammy , McFarland Karen N. , Cleary John D. , Oliveira Ruan , Nutter Curtis A. , Bhatt Kirti , Sobczak Krzysztof , Ashizawa Tetsuo , Thornton Charles A. , Ranum Laura P. W. , Swanson Maurice S.
Published: April 2018

Significance

A number of hereditary neurological and neuromuscular diseases are caused by the abnormal expansion of short tandem repeats, or microsatellites, resulting in the expression of repeat expansion RNAs and proteins with pathological properties. Although these microsatellite expansions may occur in either the coding or noncoding regions of the genome, trinucleotide CNG repeats predominate in exonic coding and untranslated regions while intron mutations vary from trinucleotide to hexanucleotide GC-rich, and A/AT-rich, repeats. Here, we use transcriptome analysis combined with complementary experimental approaches to demonstrate that GC-rich intronic expansions are selectively associated with host intron retention. Since these intron retention events are detectable in both affected tissues and peripheral blood, they provide a sensitive and disease-specific diagnostic biomarker.
China, the United States, and competition for resources that enable emerging technologies
Authors: Gulley Andrew L. , Nassar Nedal T. , Xun Sean
Published: April 2018

Significance

Expanding demand for nonfuel minerals that enable pivotal technologies has elevated concerns regarding supply security, especially for nations that are highly import reliant. Although import reliance has become a prominent concern, few studies assess import reliance and none compare import reliance of countries concurrently. Doing so provides insights into resource interdependency and competition potential. Here, we compare the net import reliance of 42 minerals for the two largest national economies, China and the United States. We find that China relies on imports for over half of its consumption for 19 minerals, compared with 24 for the United States—11 of which are common to both. It is for these 11 minerals that competition between the United States and China may become the most contentious.
Increased autophagy blocks HER2-mediated breast tumorigenesis
Authors: Vega-Rubín-de-Celis Silvia , Zou Zhongju , Fernández Álvaro F. , Ci Bo , Kim Min , Xiao Guanghua , Xie Yang , Levine Beth
Published: April 2018

Significance

Approximately 20% of breast cancers have amplification of a cancer-causing signaling molecule known as human epidermal growth factor receptor 2 (HER2). Decreased mRNA expression of the autophagy gene,
beclin 1/BECN1
, increases the risk of HER2-positive breast cancer. However, the role of Beclin 1-dependent autophagy in regulating HER2-mediated tumorigenesis is unknown. Here, we show that a mutation in
Becn1
that increases basal autophagy prevents HER2-mediated tumorigenesis in mice and prevents HER2-mediated inhibition of autophagy in cultured cells. Furthermore, treatment with a cell-penetrating, autophagy-inducing peptide derived from Beclin 1 inhibits growth of HER2-positive human breast tumor xenografts in mice as efficiently as a clinically used agent that inhibits HER2 receptor tyrosine kinase activity. These findings demonstrate that genetic and pharmacological activation of autophagy inhibits HER2-mediated breast tumorigenesis.
Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability
Authors: Smith Alyson S. , Nowak Roberta B. , Zhou Sitong , Giannetto Michael , Gokhin David S. , Papoin Julien , Ghiran Ionita C. , Blanc Lionel , Wan Jiandi , Fowler Velia M.
Published: April 2018

Significance

The biconcave disk shape and deformability of the mammalian RBC are vital to its circulatory function and rely upon a 2D viscoelastic spectrin–F-actin network attached to the membrane. A role for nonmuscle myosin II (NMII) contractility in generating tension in this network and controlling RBC shape has not been tested. We show that NMIIA forms bipolar filaments in RBCs, which associate with F-actin at the membrane. NMIIA motor activity regulates interactions with the spectrin–F-actin network to control RBC biconcave shape and deformability. These results provide a previously undescribed mechanism for actomyosin force generation at the plasma membrane, and may apply to spectrin–F-actin–based membrane skeleton networks in other cell types, such as neurons and polarized epithelial cells.
Ablation of insulin receptor substrates 1 and 2 suppresses
Kras
-driven lung tumorigenesis
Authors: Xu He , Lee Min-Sik , Tsai Pei-Yun , Adler Ashley S. , Curry Natasha L. , Challa Saketh , Freinkman Elizaveta , Hitchcock Daniel S. , Copps Kyle D. , White Morris F. , Bronson Roderick T. , Marcotrigiano Michael , Wu Yaotang , Clish Clary B. , Kalaany Nada Y.
Published: April 2018

Significance

To date, therapies are lacking that efficiently target the Kirsten rat sarcoma (
KRAS
) oncogene, which is responsible for approximately a quarter of all lung cancer cases in the United States. This study provides genetic evidence that the insulin/insulin-like growth factor 1 (IGF1) signaling, which modulates cellular survival, growth, and metabolism, is required for
KRAS
-driven lung cancer initiation. It further identifies a metabolic vulnerability in tumors with loss of such signaling, that is, the dependence on autophagy (a self-eating process), and protein degradation, to compensate for decreased amino acid levels. Such vulnerability could be exploited therapeutically using available autophagy and protein degradation inhibitors, in combination with insulin receptor/IGF1 receptor inhibitors, in patients with
KRAS
-mutant lung cancer.
Plasticity in early immune evasion strategies of a bacterial pathogen
Authors: Bernard Quentin , Smith Alexis A. , Yang Xiuli , Koci Juraj , Foor Shelby D. , Cramer Sarah D. , Zhuang Xuran , Dwyer Jennifer E. , Lin Yi-Pin , Mongodin Emmanuel F. , Marques Adriana , Leong John M. , Anguita Juan , Pal Utpal
Published: April 2018

Significance

Borrelia burgdorferiis one of the few extracellular pathogens capable of establishing persistent infection. We show that a spirochete surface protein of unknown function, BBA57, is an unorthodox regulator of multiple virulent determinants. The protein orchestrates unique host immune evasion strategies crucial for early spirochete infection in mammals. It suppresses host complement-mediated killing and neutrophil-derived microbicidal responses, including induction of antimicrobial peptides, and promotes pathogen dissemination by regulating type I interferon. In the absence of BBA57, spirochetes can undergo nonheritable transcriptional reprograming events ultimately favoring pathogen persistence. These studies highlight the evolution of plasticity in immune evasion strategies of atypical pathogens likeB. burgdorferi, which is remarkably adapted to persist in multiple hosts and on a long-term basis without host clearance.
Hominin skeletal part abundances and claims of deliberate disposal of corpses in the Middle Pleistocene
Authors: Egeland Charles P. , Domínguez-Rodrigo Manuel , Pickering Travis Rayne , Menter Colin G. , Heaton Jason L.
Published: April 2018

Significance

Awareness of self-mortality is a uniquely human capacity. Ritualistic treatment of corpses reflects this realization. Two large assemblages of fossil human bones from Spain (Sima de los Huesos, SH) and South Africa (Dinaledi Chamber, DC) are offered as the earliest evidence for mortuary behavior. This interpretation implies that humans had developed a sense of mortal transience by ∼600,000 to 300,000 years ago. Machine-learning statistical analyses of the skeletal part representation data upon which hypotheses of deliberate disposal of corpses at SH and DC are based fail to falsify—but also do not provide unequivocal support for—those hypotheses. We thus argue that it is premature to assert that SH and DC shed particular light on the development of the “human condition.”
Second-order spinal cord pathway contributes to cortical responses after long recoveries from dorsal column injury in squirrel monkeys
Authors: Liao Chia-Chi , Reed Jamie L. , Qi Hui-Xin , Sawyer Eva K. , Kaas Jon H.
Published: April 2018

Significance

Recovery of cutaneous sensation after spinal cord injury relies on reestablishing effective somatotopic pathways from the skin to the cortex. We show that the recovery of cortical activity months after extensive damage to the primary touch pathway in the dorsal column depends on a few surviving primary axons, together with the greater number of preserved axons in a secondary touch pathway from spinal cord neurons. These surviving axons could be targeted for treatments that potentiate their roles in recovery after spinal cord injury.