bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic band structure of nitrogen diluted Ga(PAsN): Formation of the intermediate band, direct and indirect optical transitions, and localization of states
Authors: Polak M. P. , Kudrawiec R. , Rubel O.
Published: November 2019

The electronic band structure of Ga(PAsN) with a few percent of nitrogen is calculated in the whole composition range of Ga(PAs) host using density functional methods including the modified Becke-Johnson functional to correctly reproduce the bandgap and unfolding of the supercell band structure to reveal the character of the bands. Relatively small amounts of nitrogen introduced to Ga(PAs) lead to the formation of an intermediate band below the conduction band, which is consistent with the band anticrossing model, widely used to describe the electronic band structure of dilute nitrides. However, in this study, calculations are performed in the whole Brillouin zone and they reveal the significance of the correct description of the band structure near the edges of the Brillouin zone, especially for the indirect bandgap P-rich host alloy, which may not be properly captured with simpler models. The influence of nitrogen on the band structure is discussed in terms of the application of Ga(PAsN) in optoelectronic devices such as intermediate band solar cells, light emitters, as well as two color emitters. Additionally, the effect of nitrogen incorporation on the carrier localization is studied and discussed. The theoretical results are compared with experimental studies, confirming their reliability.
Surface spin waves propagation in tapered magnetic stripe
Authors: Kalyabin D. V. , Sadovnikov A. V. , Beginin E. N. , Nikitov S. A.
Published: November 2019

We analytically investigate properties of magnetostatic surface spin wave propagation in irregular narrow ferromagnetic waveguides that are important elements of magnonic logic. The developed mathematical model is based on the Galerkin method. Theoretical investigations are proved by Brillouin light scattering spectroscopy. We demonstrate that the confinement effect in the narrow waveguide leads to multimode regime propagation, wave beats, and energy redistribution. These processes can be controlled by tuning the structure and excitation parameters. A gradual change in the waveguide width can be used to vary the spin wave energy density. Our results show that the impact of the width effect and the irregularity of the waveguide on the spin wave propagation are crucial.
The snowball Earth transition in a climate model with drifting parameters: Splitting of the snapshot attractor
Authors: Kaszás Bálint , Haszpra Tímea , Herein Mátyás
Published: November 2019

Using an intermediate complexity climate model (Planet Simulator), we investigate the so-called snowball Earth transition. For certain values (including its current value) of the solar constant, the climate system allows two different stable states: one of them is the snowball Earth, covered by ice and snow, and the other one is today’s climate. In our setup, we consider the case when the climate system starts from its warm attractor (the stable climate we experience today), and the solar constant is changed according to the following scenario: it is decreased continuously and abruptly, over one year, to a state, where only the Snowball Earth’s attractor remains stable. This induces an inevitable transition or climate tipping from the warm climate. The reverse transition is also discussed. Increasing the solar constant back to its original value in a similar way, in individual simulations, depending on the rate of the solar constant reduction, we find that either the system stays stuck in the snowball state or returns to warm climate. However, using ensemble methods, i.e., using an ensemble of climate realizations differing only slightly in their initial conditions we show that the transition from the snowball Earth to the warm climate is also possible with a certain probability, which depends on the specific scenario used. From the point of view of dynamical systems theory, we can say that the system’s snapshot attractor splits between the warm climate’s and the snowball Earth’s attractor.
True random number generation based on arrival time and position of dark counts in a multichannel silicon photomultiplier
Authors: Lin Jianming , Wang Yonggang , Cao Qiang , Kuang Jie , Wang Liwei
Published: November 2019

Silicon photomultiplier (SiPM) arrays normally contain tens of photon detection channels, with each channel consisting of several thousand microcells and each microcell being a normal single-photon avalanche diode with a quenching resistor. The dark counts of SiPM arrays have independent spatial and temporal randomness, which will be used for true random number generation in this paper. Since the arrival times of the high dark count rate in each channel are measured with a fast, high precision time-to-digital converter, along with the number of channels, the entropy can be extracted with very high efficiency. The bias in the raw data due to the exponential distribution of the arrival time differences between successive dark counts is removed using the transformation of the cumulative distribution function. Except for the preamplifiers for a signal readout from a 4-channel SiPM, all electronics components in our prototype are implemented inside of one chip of a field programmable gate array. The prototype has a 63.54 Mbps generation throughput, and the statistical quality of the generated random numbers is evaluated. Since the property of the dark count is compatible with single-photons from laser beams, one can easily increase the generation bitrate by either adding more SiPM channels or irradiating the SiPM with extra laser beams.
High on/off ratio black phosphorus based memristor with ultra-thin phosphorus oxide layer
Authors: Wang Yudan , Wu Facai , Liu Xingqiang , Lin Jun , Chen Jui-Yuan , Wu Wen-Wei , Wei Jingsong , Liu Yuan , Liu Qi , Liao Lei
Published: November 2019

The scaling down of switching media encounters high leakage current in the traditional oxide material based memristors, resulting in high power consumption of chips. Two-dimensional (2D) materials promise an ultimate device scaling down to atomic layer thickness. Herein, black phosphorus (BP) and its self-assembly phosphorous oxide (BP) memristors are constructed, which leverages the high on/off ratio operation of oxides and low leakage current of 2D materials with high performance. The memristors exhibit reproducible and reliable switching characteristics with the on/off ratio >107 and data retention >104 s. Depending on the high reproducibility, basic “AND” and “OR” gates have been constructed on flexible substrates. Moreover, on the basis of the symmetry and linearity of conductance in the devices, the neural network simulation for supervised learning presents an online learning accuracy of 91.4%. This work opens an avenue for future flexible electronics.
Equivariant quasi modules at infinity for vertex Γ-algebras
Authors: Li Haisheng , Mu Qiang
Published: November 2019

In this paper, we continue previous studies on quasimodules at infinity for (weak) quantum vertex algebras, focusing on equivariant quasimodules at infinity for vertex Γ-algebras. Among the main results, we obtain a commutator formula and certain general conceptual results. As an application, we establish a category equivalence between the category of lowest weight modules for a certain family of Lie algebras and the category of equivariant quasimodules at infinity for a certain family of vertex Γ-algebras.
Design and verification of TCP/IP offload engine in quantum key distribution system
Authors: Zhong Xiaodong , Chen Lian , Li Yinjie , Jin Ge
Published: November 2019

Since the quantum key distribution (QKD) system is designed based on the basic principles of quantum mechanics, the theoretical security of information can be achieved by encrypting the communication content using the key generated by the QKD system. As the key generation rate increases, the QKD system has an increasing demand for information interaction through the network. This paper optimizes the network interaction part of the QKD system, unloading the TCP/IP protocol from the central processing unit to the hardware. Compared with the TCP/IP implemented in the dual-core processor, the interaction speed is increased by 114%, up to 560 Mbps. In addition, this paper designs identity authentication and encryption protection algorithms for all the interactive data, preventing a third-party from tampering and eavesdropping, further improving the security of the system.
Coherent perfect absorption of single photons in a fiber network
Authors: Vetlugin Anton N. , Guo Ruixiang , Xomalis Angelos , Yanikgonul Salih , Adamo Giorgio , Soci Cesare , Zheludev Nikolay I.
Published: November 2019

Large distance implementation of quantum communication technologies requires coherent control of single photons in optical fiber networks. Here we demonstrate the phenomenon of coherent perfect absorption of single photons in a fully fiberized ultrathin plasmonic metamaterial fabricated at the end facet of an optical fiber. Continuous control of single-photon absorption probability is achieved by driving the network between the regimes of coherent total absorption and coherent total transmission. To circumvent phase fluctuations inherent to optical fiber networks, we implemented a reference-based postselection technique which yielded interference fringe visibility comparable to that of free space experiments. Coherent absorption of quantum light in fiber environment provides new opportunities for dissipative single-photon switching, filtering, and measurement, as well as for manipulation of entangled, weak coherent, and NOON states in optical fiber networks.
Thermal conductance of aluminum oxy-fluoride passivation layers
Authors: Tomko John A. , Boris David R. , Rosenberg Samantha G. , Walton Scott G. , Hopkins Patrick E.
Published: November 2019

The thermal properties of plasma-generated aluminum oxyfluoride passivation layers at the surface of aluminum thin films are measured. The oxyfluoride layers are generated using plasmas produced in mixtures of NH3 and SF6 to simultaneously remove oxygen and add fluorine to the aluminum surface, an alternative approach to the more conventional two-step methods that utilize HF treatments to remove the native oxide followed by metal-fluoride (e.g., MgF2, LiF, and AlF3) thin film deposition that serves to protect the aluminum surface from further oxidation. Here, the change in thermal properties of the layers as a function of plasma processing time is determined. A significant reduction in thermal boundary conductance is measured with the increasing treatment time, which can be related to the increasing fluorine content in the layers. Acoustic reflection measurements indicate this reduced thermal boundary conductance is associated with lower bonding strength to aluminum with increasing fluorine.
Multiphoton dissociation dynamics of the indenyl radical at 248 nm and 193 nm
Authors: Sullivan Erin N. , Nichols Bethan , von Kugelgen Stephen , da Silva Gabriel , Neumark Daniel M.
Published: November 2019

Photofragment translational spectroscopy is used to investigate the unimolecular photodissociation of the indenyl radical (C9H7). C9H7 radicals are generated by photodetachment of C9H7− anions and are dissociated at 248 nm (5.00 eV) and 193 nm (6.42 eV). The following product channels are definitively observed at both wavelengths: C2H2 + C7H5, C2H2 + C3H3 + C4H2, and C2H2 + C2H2 + C5H3. The three-body product channels are energetically inaccessible from single photon excitation at either dissociation wavelength. This observation, in combination with calculated dissociation rates and laser power studies, implies that all dissociation seen in this experiment occurs exclusively through multiphoton processes in which the initial C9H7 radical absorbs two photons sequentially prior to dissociation to two or three fragments. The corresponding translational energy distributions for each product channel peak well below the maximum available energy for two photons and exhibit similar behavior regardless of dissociation wavelength. These results suggest that all products are formed by internal conversion to the ground electronic state, followed by dissociation.
Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes
Authors: Giovannini Tommaso , Riso Rosario Roberto , Ambrosetti Matteo , Puglisi Alessandra , Cappelli Chiara
Published: November 2019

The fully polarizable Quantum Mechanics/Molecular Mechanics (QM/MM) approach based on fluctuating charges and fluctuating dipoles, named QM/FQFμ [T. Giovannini et al., J. Chem. Theory Comput. 15, 2233 (2019)], is extended to the calculation of vertical excitation energies of solvated molecular systems. Excitation energies are defined within two different solvation regimes, i.e., linear response (LR), where the response of the MM portion is adjusted to the QM transition density, and corrected-Linear Response (cLR) in which the MM response is adjusted to the relaxed QM density, thus being able to account for charge equilibration in the excited state. The model, which is specified in terms of three physical parameters (electronegativity, chemical hardness, and polarizability) is applied to vacuo-to-water solvatochromic shifts of aqueous solutions of para-nitroaniline, pyridine, and pyrimidine. The results show a good agreement with their experimental counterparts, thus highlighting the potentialities of this approach.
Large-deviations of the basin stability of power grids
Authors: Feld Yannick , Hartmann Alexander K.
Published: November 2019

Energy grids play an important role in modern society. In recent years, there was a shift from using few central power sources to using many small power sources, due to efforts to increase the percentage of renewable energies. Therefore, the properties of extremely stable and unstable networks are of interest. In this paper, distributions of the basin stability, a nonlinear measure to quantify the ability of a power grid to recover from perturbations, and its correlations with other measurable quantities, namely, diameter, flow backup capacity, power-sign ratio, universal order parameter, biconnected component, clustering coefficient, two core, and leafs, are studied. The energy grids are modeled by an Erdős-Rényi random graph ensemble and a small-world graph ensemble, where the latter is defined in such a way that it does not exhibit dead ends. Using large-deviation techniques, we reach very improbable power grids that are extremely stable as well as ones that are extremely unstable. The 1/t-algorithm, a variation of Wang-Landau, which does not suffer from error saturation, and additional entropic sampling are used to achieve good precision even for very small probabilities ranging over eight decades.
Unitary circuit synthesis for tomography of generalized coherent states
Authors: Somma Rolando D.
Published: November 2019

We present a method that outputs a sequence of simple unitary operations to prepare a given quantum state that is a generalized coherent state. Our method takes as inputs the expectation values of some relevant observables. Such expectations can be estimated by performing projective measurements on O(M3⁡log(M/δ)/ε2) copies of the state, where M is the dimension of an associated Lie algebra, ɛ is a precision parameter, and 1 − δ is the required confidence level. The method can be implemented on a classical computer and runs in time O(M4⁡log(M/ε)). It provides O(M⁡log(M/ε)) simple unitaries that form the sequence. The overall complexity is then polynomial in M, being very efficient in cases where M is significantly smaller than the Hilbert space dimension, as for some fermion algebras. When the algebra of relevant observables is given by certain Pauli matrices, each simple unitary may be easily decomposed into two-qubit gates. We discuss applications to efficient quantum state tomography and classical simulations of quantum circuits.
Holographic acoustic admittance surface for acoustic beam steering
Authors: Kim Jedo , Park Sungjun , Anzan-Uz-Zaman Md. , Song Kyungjun
Published: November 2019

Efficient beam steering using elements in the subwavelength scale is an exciting field, which can significantly miniaturize the existing acoustic systems and may lead to promising applications of sonic devices. In this study, we build an acoustic metasurface, which functions as a holographic leaky wave antenna and achieves effective beam steering in the designed direction. It is demonstrated that carefully designing the depth of the cylindrically grooved elements, arranged in a hexagonal pattern, allows the refractive index and surface admittance to be manipulated and can be used to generate acoustic surface modes below the cutoff frequency. The hologram principle, originally used for holographic reactance surfaces in the electromagnetic regime, is used to introduce admittance patterns, which allow effective beam steering results. We present a detailed construction methodology of the holographic acoustic admittance surface and verify its beam steering effectiveness both experimentally and numerically. The present work presents an effective method for acoustic beam steering and brings us one step closer in achieving freely steering wave beams.
Numerical and experimental investigation of the stability of a drop in a single-axis acoustic levitator
Authors: Andrade Marco A. B. , Marzo Asier
Published: November 2019

Acoustic levitation can be employed to hold liquid drops in midair, enabling novel applications in X-ray scattering of proteins, amorphous crystallization of solutions, or contactless mixing. Multiple studies have characterized the physical behavior of a levitated drop inside an acoustic field. Here, we present a numerical and experimental study on the acoustic levitation of water drops in a single-axis acoustic levitator consisting of an ultrasonic transducer and an opposing reflector. Instead of modeling an abstract incident acoustic field, our model considers the shape of the drop as well as the real geometry of the levitator. We also use a high-speed camera to observe the disintegration and the undesired oscillations of the drops. Our results show that the insertion of a drop in the levitator provokes a shift in its resonant frequency that depends on the shape of the drop. Second, the levitation behavior depends on whether the levitator operates slightly below or above the resonance. Third, if the levitator is driven above the resonant frequency, it is possible to levitate with more strength and avoid disintegration of the drop. This research provides an insight on how to achieve more stable experiments that avoid the bursting and undesired oscillations of the levitated sample. We hope that it will facilitate numerous experiments involving acoustically levitated liquid drops.
High rectification sensitivity of radiofrequency signal through adiabatic stochastic resonance in nanoscale magnetic tunnel junctions
Authors: Algarín J. M. , Ramaswamy B. , Chen Y. J. , Weinberg I. N. , Krivorotov I. N. , Katine J. A. , Shapiro B. , Waks E.
Published: November 2019

Rectification is an important stage in electronic circuits for any wireless radio frequency power transfer application. Currently, Schottky diodes are widely used as rectifiers; however, they are inefficient at low power levels of microwatts or less (providing maximum sensitivities around 4 mV/μW). Nanoscale magnetic tunnel junctions can serve as alternative rectifiers by utilizing the so-called spin-torque diode effect, demonstrating a much higher rectification sensitivity (200 mV/μW) compared to Schottky diodes. However, for this mechanism to work, the signal frequency must match the ferromagnetic resonance frequency, which typically lies in the gigahertz range. For signals in the megahertz range or lower, Schottky diodes remain the only option for rectification. Here, we demonstrate a mechanism based on thermally activated adiabatic stochastic resonance in magnetic tunnel junctions to produce low frequency (up to tens of megahertz) signal rectification at low input power (submicrowatt), with a sensitivity of up to 35 mV/μW—higher than state-of-the-art Schottky diode rectifiers at this frequency and power range. These findings suggest magnetic tunnel junctions as potential alternatives to Schottky diodes for low frequency and low power applications.
Size-dependence of the photothermal response of a single metal nanosphere
Authors: Un Ieng-Wai , Sivan Yonatan
Published: November 2019

We study the thermal response of a single spherical metal nanoparticle to continuous wave illumination as a function of its size. We show that the particle temperature increases nonmonotonically as the particle size increases, indicating that the photothermal response can be optimized by tuning the particle size and illumination wavelength. We also compare the size-dependence of the photothermal effects of gold and silver nanoparticles and find somewhat surprisingly that Ag nanoparticles are more efficient heat generators only for sufficiently small sizes. These results have importance for applications such as plasmon-assisted photocatalysis, photothermal cancer therapy, etc. and provide a first step toward the study of the size-dependence of the thermo-optic nonlinearity of metal nanospheres.
Compensation between radiative and Auger recombinations in III-nitrides: The scaling law of separated-wavefunction recombinations
Authors: David Aurelien , Young Nathan G. , Lund Cory , Craven Michael D.
Published: November 2019

The magnitude of radiative and Auger recombinations in polar InGaN quantum wells is studied. Lifetime measurements show that these two processes are related by a power law as the electron-hole wavefunction overlap varies, leading to a near-compensation of their relative contributions. Theoretical investigation reveals that, in systems with wavefunction separation, recombination rates are controlled by the spatial tails of decaying wavefunctions. Such recombinations observe a general power law whose exponent is determined only by the ratio of the carriers' effective masses. These findings explain why III-nitride emitters remain efficient despite significant wavefunction separation.
Numerical investigations on stability of the spatially oscillating planar two-phase liquid jet in a quiescent atmosphere
Authors: Arote Ashish , Bade Mukund , Banerjee Jyotirmay
Published: November 2019

The liquid jet when perturbed sinusoidally will lead to instability under certain conditions. Understanding the causes and consequences of such a behavior is still obscure. Hence, numerical investigations are reported in the present study for a two phase spatially oscillating planar jet in a quiescent air. Simulations are performed by solving the Navier-Stokes equations and using the volume of fluid method to track the air-water interface. It is demonstrated that an increase in amplitude of oscillation is caused due to the formation of a low pressure region created by the vortical structures in air near the leading edge of the jet when deflected. This two way coupling between air and water is analyzed with the help of enstrophy, divergence of the Lamb vector, and vortex forces. It is found through a parametric study that surface tension and viscosity stabilize the perturbations in an oscillating planar jet. On the other hand, an increase in Froude number (Fr) initially leads to an augmentation of perturbation amplitude and later causes its damping when surface tension forces become dominant. The numerical analysis for different inlet velocity profiles establishes that the jet is more stable when subjected to a parabolic inlet velocity profile as compared to a uniform profile due to lower relative velocity at the interface. The present work also reveals the role of capillary instability in addition to Kelvin-Helmholtz and Rayleigh-Taylor instabilities that induce primary breakup in the jet.
Exact Solov'ev equilibrium with an arbitrary boundary
Authors: Aydemir A. Y. , Park B. H. , Han K. S.
Published: November 2019

Exact Solov'ev equilibria for arbitrary plasma cross sections are calculated using a constrained least squares method. The boundary, with or without X-points, can be specified with an arbitrarily large number of constraints to ensure an accurate representation. Thus, the order of the polynomial basis functions in the homogeneous solution of the Grad-Shafranov equation becomes an independent parameter determined only by the accuracy requirements of the overall solution. Examples of exact, highly shaped equilibria are presented.
Internal flow during mixing induced in acoustically levitated droplets by mode oscillations
Authors: Hasegawa K. , Watanabe A. , Kaneko A. , Abe Y.
Published: November 2019

In this paper, we describe a mixing method with mode oscillation on the internal flow field of a levitated droplet. The effect of internal flow on the mixing performance of droplets acoustically levitated via ultrasonic phased arrays remains unclear. To better understand the mixing mechanism of a levitated droplet, clarifying the effect of the internal flow field on droplet mixing from mode oscillation during acoustic levitation is necessary. We used a 50 wt. % glycerol aqueous solution with 6th mode oscillation. We applied particle image velocimetry (PIV) to study the internal flow fields under interfacial oscillation. The PIV results indicated that the visualized flow field enhanced mixing performance with increasing Reynolds number. We demonstrated the nonlinear characteristics of droplet mixing compared to potential flow. The nonlinearity of the droplet oscillation was driven by the nonlinear acoustic field exerted on the levitated droplet. Mode oscillation on the droplet surface induced a pressure gradient and caused internal flow in the droplet. The pressure gradient in the droplet from the interfacial oscillation was quantitatively analyzed. Pressure induced by the interfacial oscillation, which can be roughly ten times larger than the hydrostatic pressure in the droplet, drastically enhanced the mixing performance in the droplet. Our experimental findings provide deeper physical insights into noncontact fluid manipulation for potential lab-in-a-drop applications.
Stability of organic permeable base transistors
Authors: Subedi Kashi N. , Al-Shadeedi Akram , Lüssem Björn
Published: November 2019

Organic Permeable Base Transistors (OPBTs) reach a very high transit frequency and large on-state currents. However, for a later commercial application of this technology, a high operational stability is essential as well. Here, the stability of OPBTs during continuous cycling and during base bias stress is discussed. It is observed that the threshold voltage of these transistors shifts toward more positive base voltages if stressed by applying a constant potential to the base electrode for prolonged times. With the help of a 2D device simulation, it is proposed that the observed instabilities are due to charges that are trapped on top of an oxide layer formed around the base electrode. These charges are thermally released after removing the stress, and the device reaches its initial performance after around 24–48 h.
Particle size effect on the Langmuir-Hinshelwood barrier for CO oxidation on regular arrays of Pd clusters supported on ultrathin alumina films
Authors: Sitja Georges , Tissot Héloïse , Henry Claude R.
Published: November 2019

The Langmuir-Hinshelwood barrier (ELH) and the pre-exponential factor (νLH) for CO oxidation have been measured at high temperatures on hexagonal arrays of Pd clusters supported on an ultrathin alumina film on Ni3Al (111). The Pd clusters have a sharp size distribution, and the mean sizes are 174 ± 13, 360 ± 19, and 768 ± 28 atoms. ELH and νLH are determined from the initial reaction rate of a CO molecular beam with a saturation layer of adsorbed oxygen on the Pd clusters measured at different temperatures [493 ≤ T(K) ≤ 613]. The largest particles (3.5 nm) give values of ELH and νLH similar to those measured on Pd (111) [T. Engel and G. Ertl, J. Chem. Phys. 69, 1267 (1978)]. However, smaller particles (2.7 and 2.1 nm) show very different behaviors. The origin of this size effect is discussed in terms of variation of the electronic structure and of the atomic structure of the Pd clusters.
Influence of dipolar interactions on the magnetic properties of superparamagnetic particle systems
Authors: Fabris F. , Tu Kun-Hua , Ross C. A. , Nunes W. C.
Published: November 2019

Magnetic effects caused by dipolar interactions in single-domain magnetic ensembles at finite temperatures are described. A modified superparamagnetic approach based on the mean field theory and random anisotropy model has been developed to describe the magnetization curves of nanoparticle assemblies. The model was used to fit experimental zero-field-cooled and field-cooled magnetization curves in Fe3O4 nanoparticles embedded in paraffin. The fitting parameters were based on structural properties of the materials and the strength of the interactions between nanoparticles. The model provides a quantitative description of the effects of the nanoparticle interaction with good agreement with the experiment. In addition, the model was adapted to describe magnetic properties of a NiFe thin film patterned into a nanodot array, showing potential to be used as a framework to predict magnetic interaction effects in high-density 2D arrays such as bit patterned media.
A mechanical wave switch with tunable frequency output
Authors: Fu Congyi , Xu Jingxian , Zhao Tianfei , Chen C. Q.
Published: November 2019

Various acoustic and mechanical wave components have been developed. Most of them focused on the control of energy flow. However, these waves are not only energy flow but also wave signals with a frequency dependence. In this Letter, we propose a mechanical wave switch (MWS) capable of controlling energy flow and output frequency simultaneously. It consists of a difference frequency generation (DFG) unit and a wave filter. The DFG unit consists of two mass blocks and a tension/compression asymmetrical bilinear spring, and the wave filter is a one-dimensional mass-spring lattice. Systematical calculations were carried out to identify the critical condition for the design of MWSs. Both numerical and experimental results demonstrate the capability of the proposed MWS to tune the energy flow and the output frequency of acoustic waves via a small amplitude control wave signal. The scale-independent MWS can be implemented at micro- and nanoscales.
High frequency H-diamond MISFET with output power density of 182 mW/mm at 10 GHz
Authors: Yu Xinxin , Zhou Jianjun , Zhang Song , Cao Zhengyi , Kong Yuechan , Chen Tangsheng
Published: November 2019

RF power characteristics of hydrogen-terminated diamond metal-insulator-semiconductor field-effect transistors operating at 10 GHz have been reported, and an output power density of 182 mW/mm has been achieved. The diamond devices were fabricated by using a self-aligned process combined with 0.1 μm gate-length T-shaped gates. A high quality atomic layer deposition Al2O3 film with low leakage current was deposited as a gate dielectric by using H2O as the oxidant at a low temperature of 90 °C. The direct current output characteristics of the devices were measured by applying gate voltage in opposite directions, and a maximum drain current density of 741 mA/mm has been obtained. By small-signal measurements, the diamond device demonstrates a high extrinsic cutoff frequency fT of 66 GHz and a maximum frequency of oscillation fmax of 55 GHz.
Effect of peak power enhancement of ferrite phase shifter from full-height to increased-height rectangular waveguide
Authors: Deng G. J. , Huang W. H. , Li J. W. , Shao H. , Guo L. T. , Xie S. Y.
Published: November 2019

In order to enhance the high-power performance of the ferrite phase shifter (PS), a method of increasing waveguide height is proposed and experimentally demonstrated. Dual-toroid geometry is utilized as a high-power structure. Two configurations of X-band PSs with full-height (FH) and increased-height (IH) waveguides are designed and fabricated while keeping other parameters consistent. Comparative analysis based on simulation and high-power experiments is conducted. The simulation results agree well with experiments. Compared with the FHPS, the IHPS can enhance the peak-power-capacity from 90 kW to 140 kW while maintaining almost the same insertion loss of 0.5 dB with a slight increase in differential phase shift from 360° to 380°.
Fantasy versus reality in fragment-based quantum chemistry
Authors: Herbert John M.
Published: November 2019

Since the introduction of the fragment molecular orbital method 20 years ago, fragment-based approaches have occupied a small but growing niche in quantum chemistry. These methods decompose a large molecular system into subsystems small enough to be amenable to electronic structure calculations, following which the subsystem information is reassembled in order to approximate an otherwise intractable supersystem calculation. Fragmentation sidesteps the steep rise (with respect to system size) in the cost of ab initio calculations, replacing it with a distributed cost across numerous computer processors. Such methods are attractive, in part, because they are easily parallelizable and therefore readily amenable to exascale computing. As such, there has been hope that distributed computing might offer the proverbial “free lunch” in quantum chemistry, with the entrée being high-level calculations on very large systems. While fragment-based quantum chemistry can count many success stories, there also exists a seedy underbelly of rarely acknowledged problems. As these methods begin to mature, it is time to have a serious conversation about what they can and cannot be expected to accomplish in the near future. Both successes and challenges are highlighted in this Perspective.
A multiferroic molecular magnetic qubit
Authors: Johnson Alexander I. , Islam Fhokrul , Canali C. M. , Pederson Mark R.
Published: November 2019

The chiral Fe3O(NC5H5)3(O2CC6H5)6 molecular cation, with C3 symmetry, is composed of three six-fold coordinated spin-carrying Fe3+ cations that form a perfect equilateral triangle. Experimental reports demonstrating the spin-electric effect in this system also identify the presence of a magnetic uniaxis and suggest that this molecule may be a good candidate for an externally controllable molecular qubit. Here, we demonstrate, using standard density-functional methods, that the spin-electric behavior of this molecule could be even more interesting as there are energetically competitive reference states associated with both high and low local spins (S = 5/2 vs S = 1/2) on the Fe3+ ions. Each of these structures allow for spin-electric ground states. We find that qualitative differences in the broadening of the Fe(2s) and O(1s) core levels, shifts in the core-level energies, and the magnetic signatures of the single-spin anisotropy Hamiltonian may be used to confirm whether a transition between a high-spin manifold and a low spin manifold occurs.
Probing basis set requirements for calculating hyperfine coupling constants
Authors: Jakobsen Philip , Jensen Frank
Published: November 2019

A series of basis sets optimized for the calculation of the hyperfine coupling constant is proposed. The pcH-n basis sets are defined in qualities from double-ζ to pentuple-ζ for the elements H to Ar. They are derived from the polarization consistent basis sets by addition of two tight s-functions and one tight p-, d-, and f-function and are shown to provide an exponential convergence toward the complete basis set limit, and they have significantly lower basis set errors than other commonly used basis sets for a given ζ quality. The pcH basis sets display very similar basis set convergence with a range of density functional theory methods and may also be suitable for wave function based methods.
Evidence that glycosaminoglycan storage and collagen deposition in the cauda epididymidis does not impair sperm viability in the Mucopolysaccharidosis type I mouse model
Authors: do Nascimento Cinthia Castro , Aguiar Odair , Viana Gustavo Monteiro , D'Almeida Vânia
Published: November 2019

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease caused by a deficiency of the lysosomal hydrolase, α-L-iduronidase (IDUA). IDUA degrades heparan and dermatan sulfates, two types of glycosaminoglycan (GAG), important signalling and structural molecules of the extracellular matrix. Because many cell types store GAGs, MPS I has been investigated in human and animal models. Enzyme replacement therapy is available for MPS I patients and has improved their life expectancy, allowing them to achieve reproductive age. The aim of this study was to evaluate epididymal and sperm morphology and function in a murine model of MPS I. We used C57BL Idua+/+ and Idua−/− adult male mice (6 months old) to investigate epididymal morphology, sperm ultrastructure, GAG characterisation and mating competence. Epithelial GAG storage, especially in the cauda epididymidis, was seen in Idua−/− mice. Regardless of the morphologic change and GAG storage found in the cauda epididymis, sperm morphology and motility were normal, similar to wild types. In the interstitium, vacuolated cells were found in addition to deposits of GAGs. Mating was not impaired in Idua−/− males and litter sizes were similar between groups. At the time point of the disease evaluated, the deficiency in IDUA affected the morphology of the epididymis in male Idua−/− mice, whereas sperm appearance and motility and the male’s capacity to mate and impregnate females were preserved.
Syntax and working memory in typically-developing children
Authors: Delage Hélène , Frauenfelder Ulrich Hans
Published: November 2019

A growing trend in developmental psycholinguistics is to relate linguistic development to the development of other
cognitive systems. Jakubowicz (2005, 2011)
in particular argued that the processing of a complex sentence requires considerable working memory (WM) resources and that these
resources are limited in young children, which would explain their non-adult grammar. The present research aims to clarify the
relationship between WM and complex syntax, in comprehension, repetition, and spontaneous production, in 48 typically-developing
children aged 5 to 12. Our results demonstrate a strong age effect for all measures of WM and syntax. They also reveal strong
correlations between scores on simple and complex spans and syntactic performance. Finally, we show the highly predictive value of
WM capacities on the acquisition of syntactic skills in both comprehension and production. In particular, the complex-span task,
measuring counting span, explains the largest part of the variance in the spontaneous production of embedded clauses.
L’expression du déplacement en italien L2
Authors: Anastasio Simona
Published: November 2019

Cet article vise à analyser la conceptualisation spatiale dans une tâche narrative orale (Frog story) chez des adultes apprenants d’italien langue seconde (L2) qui se distinguent (a) par leur langue maternelle (L1, anglais ou français) et (b) par leur niveau de compétence en L2 (intermédiairevsavancé). Pour ce faire, nous adoptons une méthodologie impliquant des comparaisons entre les récits de groupes natifs et non natifs ayant accompli la même tâche, afin de comprendre de quelle manière les apprenants se rapprochent de la langue cible (LC) et s’ils sont influencés par leur L1 lors du discours spatial en L2. Les usages natifs des locuteurs des L1 observées confirment les différences inter-typologiques entre les languesà cadrage verbal, le français et l’italien, età cadrage satellitaire, l’anglais (Talmy, 1985,2000). Néanmoins, unevariation intra-typologiqueentre l’italien et le français est attestée : seul l’italien exploite des constructions satellitaires. Les données en L2 révèlent que les productions des apprenants intermédiaires sont assez similaires quelle que soit la L1, alors que des phénomènes évidents detransfert conceptuelsont attestés aux stades avancés lorsqu’il y a des similarités structurelles entre la langue source (LS) et la LC et quel’inputen fournit une évidence positive.
ETAA1 ensures proper chromosome segregation: A matter of S phase or mitosis?
Authors: González Besteiro Marina Alejandra , Gottifredi Vanesa
Published: November 2019

ETAA1 activates the master checkpoint kinase ATR. Bass and Cortez (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201810058) recently reported an intra-mitotic function of ETAA1 that safeguards chromosome stability. In this issue, Achuthankutty et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201905064) describe a mechanism controlling the ATR-activating potential of ETAA1 in S phase to preserve chromosome stability.
Developmental and cellular age direct conversion of CD4+ T cells into RORγ+ or Helios+ colon Treg cells
Authors: Pratama Alvin , Schnell Alexandra , Mathis Diane , Benoist Christophe
Published: November 2019

RORγ+ and Helios+ Treg cells in the colon are phenotypically and functionally distinct, but their origins and relationships are poorly understood. In monocolonized and normal mice, single-cell RNA-seq revealed sharing of TCR clonotypes between these Treg cell populations, potentially denoting a common progenitor. In a polyclonal Treg cell replacement system, naive conventional CD4+ (Tconv) cells, but not pre-existing tTregs, could differentiate into RORγ+ pTregs upon interaction with gut microbiota. A smaller proportion of Tconv cells converted into Helios+ pTreg cells, but these dominated when the Tconv cells originated from preweaning mice. T cells from infant mice were predominantly immature, insensitive to RORγ-inducing bacterial cues and to IL6, and showed evidence of higher TCR-transmitted signals, which are also characteristics of recent thymic emigrants (RTEs). Correspondingly, transfer of adult RTEs or Nur77high Tconv cells mainly yielded Helios+ pTreg cells, recapitulating the infant/adult difference. Thus, CD4+ Tconv cells can differentiate into both RORγ+ and Helios+ pTreg cells, providing a physiological adaptation of colonic Treg cells as a function of the age of the cell or of the individual.
Electrically tunable spin diode effect in a tunneling junction of quantum dot*
Authors: Peng Xukai , Zhang Zhengzhong
Published: November 2019

Control over the tunneling current in spintronic devices by electrical methods is an interesting topic, which is experiencing a burst of activity. In this paper, we theoretically investigate the transport property of electrons in a spin-diode structure consisting of a single quantum dot (QD) weakly coupled to one nonmagnetic (NM) and one half-metallic ferromagnet (HFM) leads, in which the QD has an artificial atomic nature. By modulating the gate voltage applied on the dot, we observe a pronounced decrease in the current for one bias direction. We show that this rectification is spin-dependent, which stems from the interplay between the spin accumulation and the Coulomb blockade on the quantum dot. The degree of such spin diode behavior is fully and precisely tunable using the gate and bias voltages. The present device can be realized within current technologies and has potential application in molecular spintronics and quantum information processing.
Natural oscillation shapes for a heavy fluid in an elliptic vessel
Authors: Kumakshev S A
Published: November 2019

The problem of constructing of shapes of the natural oscillations in a vertical cylindrical basin (vessel) with an elliptic cross-section in linearized form of an ideal incompressible fluid is considered. Only the gravity force is acting on the fluid. It is required to define the frequencies and shapes of the natural oscillations of the fluid as a function of the system’s parameters. The solution algorithm represented here is based on the method of separation of variables in elliptic coordinates, and the special developed method for the high-accuracy solution of the boundary problem. It used the variational principle and the procedure of continuation in the parameter. This approach shows its effectiveness and obtains the almost complete solution of the problem. For five lower oscillation modes, the natural shapes are determined with high degree of accuracy for a wide range of the eccentricity values.
About the k-error linear complexity over

F

p of sequences of length 2p with optimal three-level autocorrelation
Authors: Edemskiy V A
Published: November 2019

We investigate the k-error linear complexity over

F

p
of binary sequences of length 2p with optimal three-level autocorrelation. These balanced sequences are constructed from cyclotomic classes of order four using a method presented by Ding et al.
Compact model of a Schottky diode on GaN
Authors: Fedorov D G , Zhelannov AV , Seleznev B I , Petrov M N
Published: November 2019

In this paper, we consider the synthesis of a compact (SPICE) Schottky diode model on GaN. Synthesis of a compact (SPICE) Schottky diode model is implemented on the basis of a modified model of a conventional diode on a p-n junction by extracting the parameters contained in it from experimental data. To create the structures of the Schottky diodes, epitaxial structures of gallium nitride grown by the MOCVD method on a sapphire substrate were used. Ohmic contacts of diode structures were formed on ion-doped epitaxial layers. The result of the simulation of diode structures is the extraction from experimental data of parameters of the compact model of a Schottky diode on GaN.
The Choice of Solvents for Cleaning Metal Optics in Order to Increase the Threshold of Optical Damage
Authors: Filin S A , Rogalin V E , Kaplunov I A
Published: November 2019

Metal optics is actively used in IR optics, which makes it necessary to clean it from dust and other operational contaminants. This increases the life of these notably expensive products. Usually their mechanical wiping is excluded, since it leads to the appearance of scratches and other defects on the surface, markedly increasing the scattering of radiation. Methods for the selection of solvents have been analyzed and experiments have been carried out that make it possible to accept efficient their use in the purification of metal optics from contaminations. Contaminations have different physicochemical properties and are present, as a rule, together on the surface of metal optics (taking into account the corrosion properties of the latter). Solvent compositions based on azeotrope mixes with freon-114B2, having a solubility parameter (δ) corresponding or close to the solubility parameter (δ) of the main (by weight) contamination or a mixture of contaminants which are present on the optical surface, were used.
On the program implementation of a Markov homogeneous random search algorithm of an extremum with normal distributions
Authors: Tikhomirov A S
Published: November 2019

A program that implements a Markov homogeneous monotonous random search algorithm of an extremum with normal distributions is presented. This program allows to solve a fairly wide class of problems of finding the global extremum of an objective function with a high accuracy.
On the program implementation of one inhomogeneous Markov algorithm of search for extremum
Authors: Tikhomirov A S
Published: November 2019

A program that implements a Markov inhomogeneous monotonous random search algorithm of an extremum is presented. This program allows to solve a fairly wide class of problems of finding the global extremum of an objective function with a high accuracy.