bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterizing nanoscale scanning probes using electron microscopy: A novel fixture and a practical guide
Authors: Jacobs Tevis D. B. , Wabiszewski Graham E. , Goodman Alexander J. , Carpick Robert W.
Published: January 2016

The nanoscale geometry of probe tips used for atomic force microscopy (AFM) measurements determines the lateral resolution, contributes to the strength of the tip-surface interaction, and can be a significant source of uncertainty in the quantitative analysis of results. While inverse imaging of the probe tip has been used successfully to determine probe tip geometry, direct observation of the tip profile using electron microscopy (EM) confers several advantages: it provides direct (rather than indirect) imaging, requires fewer algorithmic parameters, and does not require bringing the tip into contact with a sample. In the past, EM-based observation of the probe tip has been achieved using ad hoc mounting methods that are constrained by low throughput, the risk of contamination, and repeatability issues. We report on a probe fixture designed for use in a commercial transmission electron microscope that enables repeatable mounting of multiple AFM probes as well as a reference grid for beam alignment. This communication describes the design, fabrication, and advantages of this probe fixture, including full technical drawings for machining. Further, best practices are discussed for repeatable, non-destructive probe imaging. Finally, examples of the fixture’s use are described, including characterization of common commercial AFM probes in their out-of-the-box condition.
Liouville quantum gravity on complex tori
Authors: David François , Rhodes Rémi , Vargas Vincent
Published: January 2016

In this paper, we construct Liouville Quantum Field Theory (LQFT) on the toroidal topology in the spirit of the 1981 seminal work by Polyakov [Phys. Lett. B 103, 207 (1981)]. Our approach follows the construction carried out by the authors together with Kupiainen in the case of the Riemann sphere [“Liouville quantum gravity on the Riemann sphere,” e-print arXiv:1410.7318]. The difference is here that the moduli space for complex tori is non-trivial. Modular properties of LQFT are thus investigated. This allows us to integrate the LQFT on complex tori over the moduli space, to compute the law of the random Liouville modulus, therefore recovering (and extending) formulae obtained by physicists, and make conjectures about the relationship with random planar maps of genus one, eventually weighted by a conformal field theory and conformally embedded onto the torus.
Relative entropy convergence for depolarizing channels
Authors: Müller-Hermes Alexander , Stilck França Daniel , Wolf Michael M.
Published: January 2016

We study the convergence of states under continuous-time depolarizing channels with full rank fixed points in terms of the relative entropy. The optimal exponent of an upper bound on the relative entropy in this case is given by the log-Sobolev-1 constant. Our main result is the computation of this constant. As an application, we use the log-Sobolev-1 constant of the depolarizing channels to improve the concavity inequality of the von Neumann entropy. This result is compared to similar bounds obtained recently by Kim and we show a version of Pinsker’s inequality, which is optimal and tight if we fix the second argument of the relative entropy. Finally, we consider the log-Sobolev-1 constant of tensor-powers of the completely depolarizing channel and use a quantum version of Shearer’s inequality to prove a uniform lower bound.
Effect of shear strength on Hugoniot-compression curve and the equation of state of tungsten (W)
Authors: Mashimo Tsutomu , Liu Xun , Kodama Masao , Zaretsky Eugene , Katayama Masahide , Nagayama Kunihiko
Published: January 2016

The Hugoniot data for highly dense polycrystalline tungsten were obtained for pressures above 200 GPa, and the equation of state (EOS) was determined taking into account shear strength effects. For this study, we have made some improvements in measurement system and analyses of the shock wave data. Symmetric-impact Hugoniot measurements were performed using the high-time resolution streak camera system equipped on a one-stage powder gun and two-stage light gas gun, where the effects of tilting and bowing of flyer plate on the Hugoniot data were carefully considered. The shock velocity–particle velocity (US–UP) Hugoniot relation in the plastic regime was determined to be US = 4.137 + 1.242UP km/s (UP < 2 km/s). Ultrasonic and Velocity Interferometer System for Any Reflector measurements were also performed in this study. The zero-intercept value of the US–UP Hugoniot relation was found to be slightly larger than the ultrasonic bulk sound velocity (4.023 km/s). The hypothetical hydrostatic isothermal Us–Up Hugoniot curve, which corresponds to the hydrostatic isothermal compression curve derived from the Hugoniot data using the strength data, converged to the bulk sound velocity, clearly showing shear strength dependence in the Hugoniot data. The EOS for tungsten is derived from the hydrostatic isothermal compression curve using the strength data.
Hyperfine rather than spin splittings dominate the fine structure of the B 4Σ−–X 4Σ− bands of AlC
Authors: Clouthier Dennis J. , Kalume Aimable
Published: January 2016

Laser-induced fluorescence and wavelength resolved emission spectra of the B 4Σ−–X 4Σ− band system of the gas phase cold aluminum carbide free radical have been obtained using the pulsed discharge jet technique. The radical was produced by electron bombardment of a precursor mixture of trimethylaluminum in high pressure argon. High resolution spectra show that each rotational line of the 0-0 and 1-1 bands of AlC is split into at least three components, with very similar splittings and intensities in both the P- and R-branches. The observed structure was reproduced by assuming bβS magnetic hyperfine coupling in the excited state, due to a substantial Fermi contact interaction of the unpaired electron in the aluminum 3s orbital. Rotational analysis has yielded ground and excited state equilibrium bond lengths in good agreement with the literature and our own ab initio values. Small discrepancies in the calculated intensities of the hyperfine lines suggest that the upper state spin-spin constant λ′ is of the order of ≈0.025–0.030 cm−1.
Abnormal positive bias stress instability of In–Ga–Zn–O thin-film transistors with low-temperature Al2O3 gate dielectric
Authors: Chang Yu-Hong , Yu Ming-Jiue , Lin Ruei-Ping , Hsu Chih-Pin , Hou Tuo-Hung
Published: January 2016

Low-temperature atomic layer deposition (ALD) was employed to deposit Al2O3 as a gate dielectric in amorphous In–Ga–Zn–O thin-film transistors fabricated at temperatures below 120 °C. The devices exhibited a negligible threshold voltage shift (ΔVT) during negative bias stress, but a more pronounced ΔVT under positive bias stress with a characteristic turnaround behavior from a positive ΔVT to a negative ΔVT. This abnormal positive bias instability is explained using a two-process model, including both electron trapping and hydrogen release and migration. Electron trapping induces the initial positive ΔVT, which can be fitted using the stretched exponential function. The breakage of residual AlO-H bonds in low-temperature ALD Al2O3 is triggered by the energetic channel electrons. The hydrogen atoms then diffuse toward the In–Ga–Zn–O channel and induce the negative ΔVT through electron doping with power-law time dependence. A rapid partial recovery of the negative ΔVT after stress is also observed during relaxation.
Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures
Authors: Smirnov A. M. , Young E. C. , Bougrov V. E. , Speck J. S. , Romanov A. E.
Published: January 2016

We calculate the critical thickness for misfit dislocation (MD) formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs). It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ∼70° for Al0.13Ga0.87N/GaN (h0h̄1) semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1−xN/GaN heterostructures.
Evidence for breathing modes in direct current, pulsed, and high power impulse magnetron sputtering plasmas
Authors: Yang Yuchen , Zhou Xue , Liu Jason X. , Anders André
Published: January 2016

We present evidence for breathing modes in magnetron sputtering plasmas: periodic axial variations of plasma parameters with characteristic frequencies between 10 and 100 kHz. A set of azimuthally distributed probes shows synchronous oscillations of the floating potential. They appear most clearly when considering the intermediate current regime in which the direction of azimuthal spoke motion changes. Breathing oscillations were found to be superimposed on azimuthal spoke motion. Depending on pressure and current, one can also find a regime of chaotic fluctuations and one of stable discharges, the latter at high current. A pressure-current phase diagram for the different situations is proposed.
Effects of nitrogen plasma treatment on the electrical property and band structure of few-layer MoS2
Authors: Su Ting-Hong , Lin Yow-Jon
Published: January 2016

Few-layer MoS2 prepared by the chemical vapor deposition method was treated with nitrogen plasma under different radio-frequency (rf) power conditions in order to experimentally study the change in the electrical property. Control of the rf power could change the work function of MoS2 from 5.40 eV to 5.06 eV. It is shown that the increased rf power leads to the increased (reduced) number of nitrogen (oxygen) atoms, increasing the electron concentration and shifting the Fermi level toward conduction band. The sensitivity of the work function to the rf power provides an opportunity to tune the work function of MoS2.
Low insertion loss of 200 μm-long graphite coplanar waveguide
Authors: Wang Zidong , Shu Xiongjun , Peng Pei , Jia Yuehui , Ren Liming , Gong Xin , Zhang Xing , Huang Ru , Wen Jincai , Fu Yunyi
Published: January 2016

The graphene coplanar waveguide (CPW) has recently been found to have large insertion loss (typically larger than 50 dB/100 μm), which mainly results from the large resistance of graphene. The poor radio-frequency transmission property of graphene hampers its application in interconnect, a low loss material is thus required. In this paper, low-resistance graphite CPWs with effective graphite length up to 200 μm were fabricated. A record low insertion loss of graphite CPW (2.76 dB/100 μm) is demonstrated, and the average insertion loss of our graphite CPWs is only ∼1/5 of that of our monolayer graphene CPWs. Moreover, we find the insertion loss of graphite CPW may be even smaller at higher frequencies. Our investigation shows that graphite is a possible candidate for interconnect and may even be more applicable at ultra-high frequencies.
Wetting transitions on patterned surfaces with diffuse interaction potentials embedded in a Young-Laplace formulation
Authors: Pashos G. , Kokkoris G. , Papathanasiou A. G. , Boudouvis A. G.
Published: January 2016

The Minimum Energy Paths (MEPs) of wetting transitions on pillared surfaces are computed with the Young-Laplace equation, augmented with a pressure term that accounts for liquid-solid interactions. The interactions are smoothed over a short range from the solid phase, therefore facilitating the numerical solution of problems concerning wetting on complex surface patterns. The patterns may include abrupt geometric features, e.g., arrays of rectangular pillars, where the application of the unmodified Young-Laplace is not practical. The MEPs are obtained by coupling the augmented Young-Laplace with the modified string method from which the energy barriers of wetting transitions are eventually extracted. We demonstrate the method on a wetting transition that is associated with the breakdown of superhydrophobic behavior, i.e., the transition from the Cassie-Baxter state to the Wenzel state, taking place on a superhydrophobic pillared surface. The computed energy barriers quantify the resistance of the system to these transitions and therefore, they can be used to evaluate superhydrophobic performance or provide guidelines for optimal pattern design.
Local conditions for the Pauli potential in order to yield self-consistent electron densities exhibiting proper atomic shell structure
Authors: Finzel Kati
Published: January 2016

The local conditions for the Pauli potential that are necessary in order to yield self-consistent electron densities from orbital-free calculations are investigated for approximations that are expressed with the help of a local position variable. It is shown that those local conditions also apply when the Pauli potential is given in terms of the electron density. An explicit formula for the Ne atom is given, preserving the local conditions during the iterative procedure. The resulting orbital-free electron density exhibits proper shell structure behavior and is in close agreement with the Kohn-Sham electron density. This study demonstrates that it is possible to obtain self-consistent orbital-free electron densities with proper atomic shell structure from simple one-point approximations for the Pauli potential at local density level.
Contact resonances of U-shaped atomic force microscope probes
Authors: Rezaei E. , Turner J. A.
Published: January 2016

Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes.
The spectral theorem for quaternionic unbounded normal operators based on the S-spectrum
Authors: Alpay Daniel , Colombo Fabrizio , Kimsey David P.
Published: January 2016

In this paper we prove the spectral theorem for quaternionic unbounded normal operators using the notion of S-spectrum. The proof technique consists of first establishing a spectral theorem for quaternionic bounded normal operators and then using a transformation which maps a quaternionic unbounded normal operator to a quaternionic bounded normal operator. With this paper we complete the foundation of spectral analysis of quaternionic operators. The S-spectrum has been introduced to define the quaternionic functional calculus but it turns out to be the correct object also for the spectral theorem for quaternionic normal operators. The lack of a suitable notion of spectrum was a major obstruction to fully understand the spectral theorem for quaternionic normal operators. A prime motivation for studying the spectral theorem for quaternionic unbounded normal operators is given by the subclass of unbounded anti-self adjoint quaternionic operators which play a crucial role in the quaternionic quantum mechanics.
Counterintuitive strain distribution in axial (In,Ga)N/GaN nanowires
Authors: Krause Thilo , Hanke Michael , Brandt Oliver , Trampert Achim
Published: January 2016

We study the three-dimensional deformation field induced by an axial (In,Ga)N segment in a GaN nanowire. Using the finite element method within the framework of linear elasticity theory, we study the dependence of the strain field on the ratio of segment length and nanowire radius. Contrary to intuition, the out-of-plane-component εzz of the elastic strain tensor is found to assume large negative values for a length-to-radius ratio close to one. We show that this unexpected effect is a direct consequence of the deformation of the nanowire at the free sidewalls and the associated large shear strain components. Simulated reciprocal space maps of a single (In,Ga)N/GaN nanowire demonstrate that nanofocus x-ray diffraction is a suitable technique to assess this peculiar strain state experimentally.
Reconfigurable magnetic logic based on the energetics of pinned domain walls
Authors: López González Diego , Casiraghi Arianna , Van de Wiele Ben , van Dijken Sebastiaan
Published: January 2016

A magnetic logic concept based on magnetic switching in three stripe domains separated by pinned magnetic domain walls is proposed. The relation between the inputs and the output of the logic operator is determined by the energetics of the domain walls, which can be switched between two distinctive states by an external magnetic field. Together with magnetic read-out along two orthogonal directions, non-volatile AND, OR, NAND, and NOR gates can be created. The logic concept is experimentally demonstrated using CoFeB films on BaTiO3 substrates, and micromagnetic simulations are used to analyze the energetics of the system.
A comparative study of three-terminal Hanle signals in CoFe/SiO2/n+-Si and Cu/SiO2/n+-Si tunnel junctions
Authors: Lee Jeong-Hyeon , He Shumin , Grünberg Peter , Jin Mi-Jin , Yoo Jung-Woo , Cho B. K.
Published: January 2016

We performed three-terminal (3T) Hanle measurement for two types of sample series, CoFe/SiO2/n+-Si and Cu/SiO2/n+-Si, with various tunnel resistances. Clear Hanle signal and anomalous scaling between spin resistance-area product and tunnel resistance-area product were observed in CoFe/SiO2/n+-Si devices. In order to explore the origin of the Hanle signal and the impurity-assisted tunneling effect on the Hanle signal in our devices, Hanle measurement in Cu/SiO2/n+-Si devices was performed as well. However, no detectable Hanle signal was observed in Cu/SiO2/n+-Si, even though a lot of samples with various tunnel resistances were studied in wide temperature and bias voltage ranges. Through a comparative study, it is found that the impurity-assisted tunneling magnetoresistance mechanism would not play a dominant role in the 3T Hanle signal in CoFe/SiO2/n+-Si tunnel junctions, where the SiO2 was formed by plasma oxidation to minimize impurities.
Enhanced sensitivity of graphene ammonia gas sensors using molecular doping
Authors: Mortazavi Zanjani Seyedeh Maryam , Sadeghi Mir Mohammad , Holt Milo , Chowdhury Sk. Fahad , Tao Li , Akinwande Deji
Published: January 2016

We report on employing molecular doping to enhance the sensitivity of graphene sensors synthesized via chemical vapor deposition to NH3 molecules at room temperature. We experimentally show that doping an as-fabricated graphene sensor with NO2 gas improves sensitivity of its electrical resistance to adsorption of NH3 molecules by about an order of magnitude. The detection limit of our NO2-doped graphene sensor is found to be ∼200 parts per billion (ppb), compared to ∼1400 ppb before doping. Electrical characterization and Raman spectroscopy measurements on graphene field-effect transistors show that adsorption of NO2 molecules significantly increases hole concentration in graphene, which results in the observed sensitivity enhancement.
Unusual temperature dependence of the dissociative electron attachment cross section of 2-thiouracil
Authors: Kopyra Janina , Abdoul-Carime Hassan
Published: January 2016

At low energies (<3 eV), molecular dissociation is controlled by dissociative electron attachment for which the initial step, i.e., the formation of the transient negative ion, can be initiated by shape resonance or vibrational Feshbach resonance (VFR) mediated by the formation of a dipole bound anion. The temperature dependence for shape-resonances is well established; however, no experimental information is available yet on the second mechanism. Here, we show that the dissociation cross section for VFRs mediated by the formation of a dipole bound anion decreases as a function of a temperature. The change remains, however, relatively small in the temperature range of 370-440 K but it might be more pronounced at the extended temperature range.
GeSn p-i-n photodetectors with GeSn layer grown by magnetron sputtering epitaxy
Authors: Zheng Jun , Wang Suyuan , Liu Zhi , Cong Hui , Xue Chunlai , Li Chuanbo , Zuo Yuhua , Cheng Buwen , Wang Qiming
Published: January 2016

We report an investigation of normal-incidence GeSn-based p-i-n photodetectors (PDs) with a Ge0.94Sn0.06 active layer grown using sputter epitaxy on a Ge(100) substrate. A low dark current density of 0.24 A/cm2 was obtained at a reverse bias of 1 V. A high optical responsivity of the Ge0.94Sn0.06/Ge p-i-n PDs at zero bias was achieved, with an optical response wavelength extending to 1985 nm. The temperature-dependent optical-response measurement was performed, and a clear redshift absorption edge was observed. This work presents an approach for developing efficient and cost-effective GeSn-based infrared devices.
Performance evaluation and parametric optimum design of a vacuum thermionic solar cell
Authors: Liao Tianjun , Chen Xiaohang , Lin Bihong , Chen Jincan
Published: January 2016

A model of the vacuum thermionic solar cell (VTSC) consisting of a solar concentrator, an emitter, and a collector is proposed, in which the various heat losses including the far- and near-field thermal radiation are taken into account. Formula for the overall efficiency of the system is analytically derived. For given values of the ratio of the front surface area of the absorber to that of the emitter and the vacuum gap between the emitter and the collector, the operating temperatures of the emitter and collector are determined by solving the energy balance equations. The maximum efficiency of the VTSC are calculated for given values of the work functions of the emitter and collector materials, and some key parameters such as the net current density of the VTSC, operating temperatures of the emitter and collector, vacuum gap between the emitter and the collector, and area ratio of the absorber to the emitter are optimally determined. Furthermore, the effects of the work functions and the concentration ratio of the solar irradiation on the performance of the VTSC are discussed and several parametric selection criteria are obtained.
Optically readout write once read many memory with single active organic layer
Authors: Nguyen Viet Cuong , Lee Pooi See
Published: January 2016

An optically readable write once read many memory (WORM) in Ag/Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH PPV)/ITO is demonstrated in this work. Utilising characteristics of the organic light emitting diode structure of Ag/MEH PPV/ITO and electrochemical metallization of Ag, a WORM with light emitting capability can be realised. The simple fabrication process and multifunction capability of the device can be useful for future wearable optoelectronics and photomemory applications, where fast and parallel readout can be achieved by photons.
All-electric spin modulator based on a two-dimensional topological insulator
Authors: Xiao Xianbo , Liu Ying , Liu Zhengfang , Ai Guoping , Yang Shengyuan A. , Zhou Guanghui
Published: January 2016

We propose and investigate a spin modulator device consisting of two ferromagnetic leads connected by a two-dimensional topological insulator as the channel material. It exploits the unique features of the topological spin-helical edge states, such that the injected carriers with a non-collinear spin-polarization direction would travel through both edges and show interference effect. The conductance of the device can be controlled in a simple and all-electric manner by a side-gate voltage, which effectively rotates the spin-polarization of the carrier. At low voltages, the rotation angle is linear in the gate voltage, and the device can function as a good spin-polarization rotator by replacing the drain electrode with a non-magnetic material.
Design and application of ion-implanted polySi passivating contacts for interdigitated back contact c-Si solar cells
Authors: Yang Guangtao , Ingenito Andrea , van Hameren Nienke , Isabella Olindo , Zeman Miro
Published: January 2016

Ion-implanted passivating contacts based on poly-crystalline silicon (polySi) are enabled by tunneling oxide, optimized, and used to fabricate interdigitated back contact (IBC) solar cells. Both n-type (phosphorous doped) and p-type (boron doped) passivating contacts are fabricated by ion-implantation of intrinsic polySi layers deposited via low-pressure chemical vapor deposition and subsequently annealed. The impact of doping profile on the passivation quality of the polySi doped contacts is studied for both polarities. It was found that an excellent surface passivation could be obtained by confining as much as possible the implanted-and-activated dopants within the polySi layers. The doping profile in the polySi was controlled by modifying the polySi thickness, the energy and dose of ion-implantation, and the temperature and time of annealing. An implied open-circuit voltage of 721 mV for n-type and 692 mV for p-type passivating contacts was achieved. Besides the high passivating quality, the developed passivating contacts exhibit reasonable high conductivity (Rsh n-type = 95 Ω/□ and Rsh p-type = 120 Ω/□). An efficiency of 19.2% (Voc = 673 mV, Jsc = 38.0 mA/cm2, FF = 75.2%, and pseudo-FF = 83.2%) was achieved on a front-textured IBC solar cell with polySi passivating contacts as both back surface field and emitter. By improving the front-side passivation, a VOC of 696 mV was also measured.
Oxygen influencing the photocarriers lifetime of CH3NH3PbI3−xClx film grown by two-step interdiffusion method and its photovoltaic performance
Authors: Yuan Shuai , Qiu Zhiwen , Zhang Hailiang , Gong Haibo , Hao Yufeng , Cao Bingqiang
Published: January 2016

During the growth of CH3NH3PbI3−xClx (MAPbI3−xClx) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI3−xClx grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells.
Probing complementary memristive characteristics in oxide based memory device via non-conventional chronoamperometry approach
Authors: Younis Adnan , Zhang Lepeng , Chu Dewei , Li Sean
Published: January 2016

In this letter, the resistive switching characteristics of CeO2 based memristor are investigated by utilizing an unusual, non-conventional, and a unique approach of “chronoamperometry.” This methodology provides useful insights into memristive characterization for achieving configurable device functionalities such as categorization of minimum threshold potential to prompt switching behaviour, tuneable on/off ratios with accessible multi-level data storage states, etc. Moreover, the analytical studies on carrier drift/diffusion controlled-memristor response and the estimation of time constants at various applied fixed potentials provide tangible evidence to support valence change mechanism in CeO2 based memristors.
Communication: Accurate higher-order van der Waals coefficients between molecules from a model dynamic multipole polarizability
Authors: Tao Jianmin , Rappe Andrew M.
Published: January 2016

Due to the absence of the long-range van der Waals (vdW) interaction, conventional density functional theory (DFT) often fails in the description of molecular complexes and solids. In recent years, considerable progress has been made in the development of the vdW correction. However, the vdW correction based on the leading-order coefficient C6 alone can only achieve limited accuracy, while accurate modeling of higher-order coefficients remains a formidable task, due to the strong non-additivity effect. Here, we apply a model dynamic multipole polarizability within a modified single-frequency approximation to calculate C8 and C10 between small molecules. We find that the higher-order vdW coefficients from this model can achieve remarkable accuracy, with mean absolute relative deviations of 5% for C8 and 7% for C10. Inclusion of accurate higher-order contributions in the vdW correction will effectively enhance the predictive power of DFT in condensed matter physics and quantum chemistry.
Topological phononic states of underwater sound based on coupled ring resonators
Authors: He Cheng , Li Zheng , Ni Xu , Sun Xiao-Chen , Yu Si-Yuan , Lu Ming-Hui , Liu Xiao-Ping , Chen Yan-Feng
Published: January 2016

We report a design of topological phononic states for underwater sound using arrays of acoustic coupled ring resonators. In each individual ring resonator, two degenerate acoustic modes, corresponding to clockwise and counter-clockwise propagation, are treated as opposite pseudospins. The gapless edge states arise in the bandgap resulting in protected pseudospin-dependent sound transportation, which is a phononic analogue of the quantum spin Hall effect. We also investigate the robustness of the topological sound state, suggesting that the observed pseudospin-dependent sound transportation remains unless the introduced defects facilitate coupling between the clockwise and counter-clockwise modes (in other words, the original mode degeneracy is broken). The topological engineering of sound transportation will certainly promise unique design for next generation of acoustic devices in sound guiding and switching, especially for underwater acoustic devices.
Note: A valve-type piezoelectric reciprocating pump with secondary resonant vibrator
Authors: Ma Yu Ting , Wang Ce , Yan Xin Tao , Feng Zhi Hua
Published: January 2016

A valve-type piezoelectric diaphragm pump using secondary resonant vibrator is introduced in this paper. The secondary resonant vibrator, which is mainly composed of a first vibrator and a second vibrator, is used to coordinate the frequency incompatibility between piezoelectric elements and check valves. The intermittent vibration of the first vibrator excites the resonant vibration of the second vibrator. The diaphragm in the pump chamber moves with the second vibrator, resulting in chamber volume and pressure variations. Control circuit capable of frequency tracking is designed. Vibration displacement and flow rate changing with driving voltage amplitude, frequency, and backpressure are studied in experiments. The flow rate of a prototype driven by voltage of 712 Vpp is 13.94 ml/min at secondary resonant frequency of 6 Hz.
Large reversible magnetocaloric effect in a Ni-Co-Mn-In magnetic shape memory alloy
Authors: Huang L. , Cong D. Y. , Ma L. , Nie Z. H. , Wang Z. L. , Suo H. L. , Ren Y. , Wang Y. D.
Published: January 2016

Reversibility of the magnetocaloric effect in materials with first-order magnetostructural transformation is of vital significance for practical magnetic refrigeration applications. Here, we report a large reversible magnetocaloric effect in a Ni49.8Co1.2Mn33.5In15.5 magnetic shape memory alloy. A large reversible magnetic entropy change of 14.6 J/(kg K) and a broad operating temperature window of 18 K under 5 T were simultaneously achieved, correlated with the low thermal hysteresis (∼8 K) and large magnetic-field-induced shift of transformation temperatures (4.9 K/T) that lead to a narrow magnetic hysteresis (1.1 T) and small average magnetic hysteresis loss (48.4 J/kg under 5 T) as well. Furthermore, a large reversible effective refrigeration capacity (76.6 J/kg under 5 T) was obtained, as a result of the large reversible magnetic entropy change, broad operating temperature window, and small magnetic hysteresis loss. The large reversible magnetic entropy change and large reversible effective refrigeration capacity are important for improving the magnetocaloric performance, and the small magnetic hysteresis loss is beneficial to reducing energy dissipation during magnetic field cycle in potential applications.
Unique Occurrence of Cationic and Anionic Bis-1,2-diaminocyclohexane Copper(II) Units in a Double Complex Salt
Authors: Kelly Norman , Wenzel Marco , Doert Thomas , Gloe Kerstin , Weigand Jan J. , Lindoy Leonard F. , Gloe Karsten
Published: January 2016

The reaction of (±)-trans-diaminocyclohexane (dach) with copper(ii) sulfate in water resulted in the spontaneous formation of a double complex salt of type [Cu(dach)2(H2O)2][Cu(dach)2(SO4)2]·6H2O, whose X-ray structure confirmed the presence of the same square-planar Cu(dach)22+ coordination motif in both the complex cation and anion. Each copper centre adopts a Jahn–Teller-distorted octahedral geometry. Both axial positions of the metal centre in the complex cation are occupied by water molecules, whereas two monodentate sulfato ions occupy the corresponding sites in the complex anion, leading to a trans N4O2-donor coordination environment in each ion.
Intending, knowing how, infinitives
Authors: Hornsby Jennifer
Published: January 2016

Intellectualists tell us that a person who knows how to do something therein knows a proposition. Along with others, they may say that a person who intends to do something intends a proposition. I argue against them. I do so by way of considering ‘know how ——’ and ‘intend ——’ together. When the two are considered together, a realistic conception of human agency can inform the understanding of some infinitives: the argument need not turn on what semanticists have had to say about (what they call) ‘the subjects of infinitival clauses’.
Impact properties of low-alloy transformation-induced plasticity-steels with different matrix
Authors: Hojo T. , Kobayashi J. , Sugimoto K.
Published: January 2016

The effects of matrix types on Charpy impact properties were investigated in Fe–0.2%C–1.5%Si–1.5%Mn (mass%) transformation-induced plasticity steels. The steels with annealed martensite and bainitic ferrite matrix possessed higher upper shelf Charpy impact absorbed energy than the steel with polygonal ferrite and martensitic matrix. In addition, the low ductile–brittle fracture appearance transition temperatures were achieved in annealed martensite and martensite types in comparison with those of other steels.
Statistical evaluation of very high cycle fatigue property of high carbon chromium bearing steel under axial loading
Authors: Li W. , Sakai T. , Deng H.
Published: January 2016

Axial loading test was performed to investigate the S–N characteristics and the failure mechanisms of a high carbon chromium bearing steel under very high cycle fatigue (VHCF). Compared with the experimental results under rotating bending, the bearing steel under axial loading also exhibited two failure modes including surface failure and interior inclusion-induced failure. In the life regime beyond about 106 cycles, the fine granular area can occur around the inclusion. But under the axial loading with the uniform stress distribution on the cross-section of specimen, the duplex S–N characteristics of bearing steel was not so distinct. In view of the limitation of common statistical method, a statistical method based on mixed Weibull distribution and parameter optimisation was proposed to evaluate the VHCF property of bearing steel corresponding to two failure modes. Based on the proposed statistical method, the P–S–N curves of bearing steel under axial loading can be better established.

This paper is part of a Themed Issue on Recent developments in bearing steels.
Characterisation of the structure and thermophysical properties of solid electroslag remelting slags
Authors: Plotkowski A. , deBarbadillo J. , Krane M. J. M.
Published: January 2016

The solid structure and thermophysical properties of three electroslag remelting (ESR) slags were characterised. Samples from ESR trials performed by Special Metals Corporation in Burnaugh, KY, were compared to samples solidified in a vacuum induction melter. The microstructures were characterised using a combination of optical and electron microscopy, X-ray diffraction, energy-dispersive spectroscopy and a serial sectioning technique to quantify porosity. The thermophysical properties were measured using differential scanning calorimetry and laser flash diffusivity testing at Thermophysical Property Measurement Laboratory, Inc. in West Lafayette, IN. The two processing routes were found to produce similar phase fractions, but resulted in different properties as a function of phase morphology and porosity content. These results suggest that future modelling and property measurement efforts must account for both the structure and composition of the slags.
Population Dynamics and Evaluation of Alternative Management Strategies for Nonnative Lake Trout in Priest Lake, Idaho
Authors: Ng Elizabeth L. , Fredericks Jim P. , Quist Michael C.
Published: January 2016

Lake Trout Salvelinus namaycush have been introduced widely throughout the western USA to enhance recreational fisheries, but high predatory demand can create challenges for management of yield and trophy fisheries alike. Lake Trout were introduced to Priest Lake, Idaho, during the 1920s, but few fishery-independent data are available to guide current or future management actions. We collected fishery-independent data to describe population dynamics and evaluate potential management scenarios using an age-structured population model. Lake Trout in Priest Lake were characterized by fast growth at young ages, which resulted in young age at maturity. However, adult growth rates and body condition were lower than for other Lake Trout populations. High rates of skipped spawning (>50%) were also observed. Model projections indicated that the population was growing (λ = 1.03). Eradication could be achieved by increasing annual mortality to 0.32, approximately twice the current rate. A protected slot length limit could increase population length-structure, but few fish grew fast enough to exit the slot. In contrast, a juvenile removal scenario targeting age-2 to age-5 Lake Trout maintained short-term harvest of trophy-length individuals while reducing overall population abundance.
Effect of the structure of dietary epoxylignan on its cytotoxic activity: relationship between the structure and the activity of 7,7′-epoxylignan and the introduction of apoptosis by caspase 3/7
Authors: Wukirsari Tuti , Nishiwaki Hisashi , Nishi Kosuke , Sugahara Takuya , Akiyama Koichi , Kishida Taro , Yamauchi Satoshi
Published: January 2016

We compared the cytotoxic activities of dietary epoxylignans and their stereoisomers and found (−)-verrucosin, which is (7S,7′R,8R,8′R)-7,7′-epoxylignan, to be the most cytotoxic epoxylignan against HeLa cells (IC50 = 6.6 μM). On the other hand, the activity was about a factor of 10 less against HL-60. In this research on the relationship between the structure and cytotoxic activity of (−)-verrucosin 13, the 7-(4-methoxyphenyl)-7′-(3,4-dimethoxyphenyl) derivative 60, for which the activity (IC50 = 2.4 μM) is three times greater than (−)-verrucosin 13, was discovered. The induction of apoptosis by caspase 3/7 was observed upon treatment with the (−)-verrucosin derivative.
Tridiagonalization of the hypergeometric operator and the Racah–Wilson algebra
Authors: Genest Vincent , Ismail Mourad , Vinet Luc , Zhedanov Alexei
Published: January 2016

The algebraic underpinning of the tridiagonalization procedure is investigated. The focus is put on the tridiagonalization of the hypergeometric operator and its associated quadratic Jacobi algebra. It is shown that under tridiagonalization, the quadratic Jacobi algebra becomes the quadratic Racah–Wilson algebra associated to the generic Racah–Wilson polynomials. A degenerate case leading to the Hahn algebra is also discussed.
Ergodic Theorems for lower probabilities
Authors: Cerreia–Vioglio S. , Maccheroni F. , Marinacci M.
Published: January 2016

We establish an Ergodic Theorem for lower probabilities, a generalization of standard probabilities widely used in applications. As a by-product, we provide a version for lower probabilities of the Strong Law of Large Numbers.
A Brauer-Wielandt formula (with an application to character tables)
Authors: Navarro Gabriel , Rizo Noelia
Published: January 2016

If a

p
p

-group

P
P

acts coprimely on a finite group

G
G

, we give a Brauer-Wielandt formula to count the number of fixed points

|

C

G

(
P
)

|

| \textbf {C}_{G}(P) |

of

P
P

in

G
G

. This serves to determine the number of Sylow

p
p

-subgroups of certain finite groups from their character tables.
Spectral mapping of V348 Puppis: spiral arms in the period gap★
Authors: Saito R. K. , Baptista R.
Published: January 2016

We report the analysis of Hubble Space Telescope (HST) UV–optical spectroscopy of the nova-like variable V348 Puppis with eclipse mapping techniques. We measured the eclipse width at disc centre and determined a lower limit on the mass ratio of q > 0.3, with a tight relation between q and the binary inclination i. For 0.31 ≤ q ≤ 0.6, we have 79$_{.}^{\circ}$5 ≤ i ≤ 88$_{.}^{\circ}$2. Simulations with 3D eclipse mapping give no support to the suggestion of self-shielding of the accretion disc of V348 Pup, indicating a geometrically thin disc. Eclipse maps reveal two structures in the accretion disc interpreted as tidally induced spiral arms, which account for 50–60  per cent of the disc flux in the continuum. The uneclipsed component accounts for 30–50  per cent of the light, indicating that a significant fraction of the light comes from a vertically extended disc chromosphere + wind. Its spectrum can be fitted by an isothermal slab of gas with temperature T = 9600 K and column density Σ ∼1010 g cm−2, corresponding to optically thick thermal emission. Superhumps had faded by the epoch of the HST observations; the disc shrank in size while the disc wind flux increased with respect to observations when superhumps were present. This may be explained if the disc wind outflow is the dominant source of angular momentum loss from the accretion disc. Previously observed accretion disc radii of V348 Pup and of two other binaries with large discs are used to derive an empirical expression for the maximum possible disc radius, which implies that superhumps may be found in systems with up to q ≃ 0.7.
Scaling and universality in urban economic diversification
Authors: Youn Hyejin , Bettencourt Luís M. A. , Lobo José , Strumsky Deborah , Samaniego Horacio , West Geoffrey B.
Published: January 2016

Understanding cities is central to addressing major global challenges from climate change to economic resilience. Although increasingly perceived as fundamental socio-economic units, the detailed fabric of urban economic activities is only recently accessible to comprehensive analyses with the availability of large datasets. Here, we study abundances of business categories across US metropolitan statistical areas, and provide a framework for measuring the intrinsic diversity of economic activities that transcends scales of the classification scheme. A universal structure common to all cities is revealed, manifesting self-similarity in internal economic structure as well as aggregated metrics (GDP, patents, crime). We present a simple mathematical derivation of the universality, and provide a model, together with its economic implications of open-ended diversity created by urbanization, for understanding the observed empirical distribution. Given the universal distribution, scaling analyses for individual business categories enable us to determine their relative abundances as a function of city size. These results shed light on the processes of economic differentiation with scale, suggesting a general structure for the growth of national economies as integrated urban systems.
Voxel size dependency, reproducibility and sensitivity of an
in vivo
bone loading estimation algorithm
Authors: Christen Patrik , Schulte Friederike A. , Zwahlen Alexander , van Rietbergen Bert , Boutroy Stephanie , Melton L. Joseph , Amin Shreyasee , Khosla Sundeep , Goldhahn Jörg , Müller Ralph
Published: January 2016

A bone loading estimation algorithm was previously developed that provides
in vivo
loading conditions required for
in vivo
bone remodelling simulations. The algorithm derives a bone's loading history from its microstructure as assessed by high-resolution (HR) computed tomography (CT). This reverse engineering approach showed accurate and realistic results based on micro-CT and HR-peripheral quantitative CT images. However, its voxel size dependency, reproducibility and sensitivity still need to be investigated, which is the purpose of this study. Voxel size dependency was tested on cadaveric distal radii with micro-CT images scanned at 25 µm and downscaled to 50, 61, 75, 82, 100, 125 and 150 µm. Reproducibility was calculated with repeated
in vitro
as well as
in vivo
HR-pQCT measurements at 82 µm. Sensitivity was defined using HR-pQCT images from women with fracture versus non-fracture, and low versus high bone volume fraction, expecting similar and different loading histories, respectively. Our results indicate that the algorithm is voxel size independent within an average (maximum) error of 8.2% (32.9%) at 61 µm, but that the dependency increases considerably at voxel sizes bigger than 82 µm.
In vitro
and
in vivo
reproducibility are up to 4.5% and 10.2%, respectively, which is comparable to other
in vitro
studies and slightly higher than in other
in vivo
studies. Subjects with different bone volume fraction were clearly distinguished but not subjects with and without fracture. This is in agreement with bone adapting to customary loading but not to fall loads. We conclude that the
in vivo
bone loading estimation algorithm provides reproducible, sensitive and fairly voxel size independent results at up to 82 µm, but that smaller voxel sizes would be advantageous.