bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristic Chromatogram: A Method of Discriminate and Quantitative Analysis for Quality Evaluation of Uncaria Stem with Hooks
Authors: Hou Jinjun , Feng Ruihong , Zhang Yibei , Pan Huiqin , Yao Shuai , Han Sumei , Feng Zijin , Cai Luying , Wu Wanying , Guo De-an
Published: December 2017

It remains a challenge to establish new monographs for herbal drugs derived from multiple botanical sources. Specifically, the difficulty involves discriminating and quantifying these herbs with components whose levels vary markedly among different samples. Using Uncaria stem with hooks as an example, a characteristic chromatogram was proposed to discriminate its five botanical origins and to quantify its characteristic components in the chromatogram. The characteristic chromatogram with respect to the components of Uncaria stem with hooks with the five botanical origins was established using 0.02% diethylamine and acetonitrile as the mobile phase. The total analysis time was 50 min and the detection wavelength was 245 nm. Using the same chromatogram parameters, the single standard to determine multicomponents method was validated to simultaneously quantify nine indole alkaloids, including vincosamide, 3α-dihydrocadambine, isocorynoxeine, corynoxeine, isorhynchophylline, rhynchophylline, hirsuteine, hirsutine, and geissoschizine methyl ether. The results showed that only the Uncaria stem with hooks from Uncaria rhynchophylla, the most widely used in the herbal market, showed the presence of these nine alkaloids. The conversion factors were 1.27, 2.32, 0.98, 1.04, 1.00, 1.02, 1.26, 1.33, and 1.25, respectively. The limits of quantitation were lower than 700 ng/mL. The total contents of 31 batches of Uncaria stem with hooks were in the range of 0.1 – 0.6%, except for Uncaria hirsuta Havil and Uncaria sinensis (Oliv.) Havil. The results also showed that the total content of indole alkaloids tended to decrease with an increase in the hook diameter. This showed that the characteristic chromatogram is practical for controlling the quality of traditional Chinese medicines with multiple botanical origins.
A facile alternative technique for large-area graphene transfer via sacrificial polymer
Authors: Auchter Eric , Marquez Justin , Yarbro Stephen L. , Dervishi Enkeleda
Published: December 2017

A novel method of transferring large-area graphene sheets onto a variety of substrates using Formvar (polyvinyl formal) is presented. Due to the ease at which formvar can be dissolved in chloroform this method allows for a consistent, a clean, and a more rapid transfer than other techniques including the PMMA assisted one. This novel transfer method is demonstrated by transferring large-area graphene onto a range of substrates including commercial TEM grids, silicon dioxide and glass. Raman spectroscopy was used to confirm the presence of graphene and characterize the morphological properties of the large-area sheets. SEM and AFM analyses demonstrated the effectiveness of our rapid transfer technique for clean crystalline large-area graphene sheets. The removal of the sacrificial polymer was found to be one to two orders of magnitude faster than PMMA methods. Ultimately this facile transfer technique offers new opportunities for a wide range of applications for large-area graphene through the utilization of a new sacrificial polymer.
Effect of nitrogen-accommodation ability of electrodes in SiNx-based resistive switching devices
Authors: Yang Mei , Wang Hong , Ma Xiaohua , Gao Haixia , Wang Bin
Published: December 2017

Nitrides could create opportunities of tuning resistive-switching (RS) characteristics due to their different electrical properties and ionic chemistry with oxides. Here, we reported on the effect of nitrogen-accommodation ability of electrodes in SiNx-based RS devices. The Ti/SiNx/Pt devices show a self-compliance bipolar RS with excellent reliability. The W/SiNx/Pt devices provide an unstable RS and fall to an intermediate resistance state (IRS) after a set process. The low resistance states of the Ti/SiNx/Pt devices obey Ohmic conduction and Frenkel-Poole emission from a conductive channel. The IRS of the W/SiNx/Pt devices conforms to Schottky emission and Fowler-Nordheim tunneling from a conductive channel/insulator/electrode structure. A nitrogen-ion-based model is proposed to explain the experimental results. According to the model, the nitrogen-accommodation ability of the electrodes dominates the nitrogen-reservoir size and the nitrogen-ion migration at the metal/SiNx interface, modulating the RS characteristics of the SiNx memory devices.
Mesoscale simulations of confined Nafion thin films
Authors: Vanya P. , Sharman J. , Elliott J. A.
Published: December 2017

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.
Note: Low-temperature scanning tunneling microscope with detachable scanner and reliable transfer mechanism for tip and sample exchange
Authors: Ge Weifeng , Wang Jihao , Wang Junting , Zhang Jing , Hou Yubin , Lu Qingyou
Published: December 2017

A homebuilt low-temperature scanning tunneling microscope (STM) featuring a detachable scanner based on a double slider design, along with a reliable transfer mechanism for tip and sample exchange, is present. The coarse motor is decoupled from the scanner, which prevents the motor instabilities including vibrations and drifts from entering the tip-sample loop and thus improves the performance of the STM. In addition, in situ exchange of tips and samples can be implemented easily and reliably using a winch-type transfer mechanism. Atomically resolved images on graphite are demonstrated to show the performance of the proposed STM.
Clearing out a maze: A model of chemotactic motion in porous media
Authors: Schilling Tanja , Voigtmann Thomas
Published: December 2017

We study the anomalous dynamics of a biased “hungry” (or “greedy”) random walk on a percolating cluster. The model mimics chemotaxis in a porous medium: In close resemblance to the 1980s arcade game PAC-MAN®, the hungry random walker consumes food, which is initially distributed in the maze, and biases its movement towards food-filled sites. We observe that the mean-squared displacement of the process follows a power law with an exponent that is different from previously known exponents describing passive or active microswimmer dynamics. The change in dynamics is well described by a dynamical exponent that depends continuously on the propensity to move towards food. It results in slower differential growth when compared to the unbiased random walk.
A kinetic model for the characteristic surface morphologies of thin films by directional vapor deposition
Authors: Li Kun-Dar , Huang Po-Yu
Published: December 2017

In order to simulate a process of directional vapor deposition, in this study, a numerical approach was applied to model the growth and evolution of surface morphologies for the crystallographic structures of thin films. The critical factors affecting the surface morphologies in a deposition process, such as the crystallographic symmetry, anisotropic interfacial energy, shadowing effect, and deposition rate, were all enclosed in the theoretical model. By altering the parameters of crystallographic symmetry in the structures, the faceted nano-columns with rectangular and hexagonal shapes were established in the simulation results. Furthermore, for revealing the influences of the anisotropic strength and the deposition rate theoretically on the crystallographic structure formations, various parameters adjusted in the numerical calculations were also investigated. Not only the morphologies but also the surface roughnesses for different processing conditions were distinctly demonstrated with the quantitative analysis of the simulations.
L-edge spectroscopy of dilute, radiation-sensitive systems using a transition-edge-sensor array
Authors: Titus Charles J. , Baker Michael L. , Lee Sang Jun , Cho Hsiao-Mei , Doriese William B. , Fowler Joseph W. , Gaffney Kelly , Gard Johnathon D. , Hilton Gene C. , Kenney Chris , Knight Jason , Li Dale , Marks Ronald , Minitti Michael P. , Morgan Kelsey M. , O’Neil Galen C. , Reintsema Carl D. , Schmidt Daniel R. , Sokaras Dimosthenis , Swetz Daniel S. , Ullom Joel N. , Weng Tsu-Chien , Williams Christopher , Young Betty A. , Irwin Kent D. , Solomon Edward I. , Nordlund Dennis
Published: December 2017

We present X-ray absorption spectroscopy and resonant inelastic X-ray scattering (RIXS) measurements on the iron L-edge of 0.5 mM aqueous ferricyanide. These measurements demonstrate the ability of high-throughput transition-edge-sensor (TES) spectrometers to access the rich soft X-ray (100–2000 eV) spectroscopy regime for dilute and radiation-sensitive samples. Our low-concentration data are in agreement with high-concentration measurements recorded by grating spectrometers. These results show that soft-X-ray RIXS spectroscopy acquired by high-throughput TES spectrometers can be used to study the local electronic structure of dilute metal-centered complexes relevant to biology, chemistry, and catalysis. In particular, TES spectrometers have a unique ability to characterize frozen solutions of radiation- and temperature-sensitive samples.
Irreducible forms of matrix product states: Theory and applications
Authors: De las Cuevas Gemma , Cirac J. Ignacio , Schuch Norbert , Perez-Garcia David
Published: December 2017

The canonical form of Matrix Product States (MPS) and the associated fundamental theorem, which relates different MPS representations of a state, are the theoretical framework underlying many of the analytical results derived through MPS, such as the classification of symmetry-protected phases in one dimension. Yet, the canonical form is only defined for MPS without non-trivial periods and thus cannot fully capture paradigmatic states such as the antiferromagnet. Here, we introduce a new standard form for MPS, the irreducible form, which is defined for arbitrary MPS, including periodic states, and show that any tensor can be transformed into a tensor in irreducible form describing the same MPS. We then prove a fundamental theorem for MPS in irreducible form: If two tensors in irreducible form give rise to the same MPS, then they must be related by a similarity transform, together with a matrix of phases. We provide two applications of this result: an equivalence between the refinement properties of a state and the divisibility properties of its transfer matrix, and a more general characterisation of tensors that give rise to matrix product states with symmetries.
Modeling and numerical simulation of anode activity and arc motion in a transverse magnetic field
Authors: Wang Ting , Xiu Shixin , Feng Dingyu , Liu Zixi , Yuan Bo , Li Mengru
Published: December 2017

Vacuum interrupters based on transverse magnetic field contacts now are widely used in medium voltage circuit breakers. The arc motion under the transverse magnetic field (TMF) plays a decisive role in the interruption. In this paper, we focus on the movement of vacuum arc driven by TMF and anode thermal process during the arcing. Then, based on the principle of conservation, a transient two-dimensional anode activity model (subjected to TMF constricted arc) is established. The state change of material, evaporation from contacts and motion of molten pool are also considered in our model. By considering the arc motion in the anode activity model, the transient anode thermal process and the movement of constrict arc under TMF are studied, respectively. The simulation predicted that average speed of arc is not higher than 200m/s. In the simulation, the anode surface is completely melted near the current peak with 200 μm molten layer. In addition, the influence of movement of molten pool on the arc speed is analyzed, finding that the movement of the bath accelerates arc speed, but weakens the surface melting at the same time.
Time and space resolved current density mapping in three dimensions using magnetic field probe array in a high voltage coaxial gap
Authors: Cordaro S. W. , Bott-Suzuki S. C.
Published: December 2017

We present an experimental analysis of the symmetry of current density in a coaxial geometry, diagnosed using a magnetic field probe array and calculations of the Fowler-Nordheim enhancement factor. Data were collected on the coaxial gap breakdown device (240 A, 25 kV, 150 ns, ∼0.1 Hz), and data from experiments using 2 different gap sizes and different penetration depths are compared over runs comprising 50 shots for each case. The magnetic field probe array quantifies the distribution of current density at three axial locations, on either sides of a vacuum breakdown, and tracks the evolution with time and space. The results show asymmetries in current density, which can be influenced by changes in the gap size and the penetration depth (of the center electrode into the outer electrode). For smaller gap sizes (400 μm), symmetric current profiles were not observed, and the change in the penetration depth changes both the symmetric behavior of the current density and the enhancement factor. For larger gaps (900 μm), current densities were typically more uniform and less influenced by the penetration depth, which is reflected in the enhancement factor values. It is possible that the change in inductance caused by the localization of current densities plays a role in the observed behavior.
One-way transmission of electrons on the topological insulator surface modulated by magnetic potential
Authors: Li Jin-Jing , Zhang Rui-Li , Gao Han-Tian , Peng Ru-Wen , Huang R. S. , Wang Mu
Published: December 2017

We investigate the transport properties of Dirac fermions on the surface of a three-dimensional topological insulator (TI) with magnetic modulation potentials. By using the transfer-matrix method, the transmission coefficients are obtained as a function of incident energy and incident angle. It is shown that the forward and backward propagating carriers possess different transmission coefficients at some incident energies when the charge carriers incident obliquely, which originates from the break of time reversal symmetry. Particularly, the magnetic barrier introduces asymmetric scattering; thus, the scattered angles are different for the forward and backward propagating carriers. As a consequence, the transmission in one direction is permitted while it is blocked in its reversal direction. Therefore, the unidirectional transmission of electrons is achieved on the surface of TI. Furthermore, unidirectional transmission is demonstrated by the electronic charge distributions in the system. The investigations may have potential applications in the design of TI-based one-way quantum devices.
Unusual soft mode dynamics in ferroelectric PbTiO3 nanowire under different mechanical boundary conditions
Authors: Herchig R. , Ponomareva I.
Published: December 2017

First-principles-based atomistic simulations are used to investigate equilibrium phases and soft mode dynamics in ultrathin ferroelectric PbTiO3 nanowire with poor surface charge compensation subjected to a wide range of mechanical boundary conditions. The presence of the depolarizing field along the nanowire's transverse directions leads to the appearance of a unique high-frequency hard phonon mode that can be used to characterize electrical boundary conditions. This mode is insensitive to the mechanical load. Hydrostatic pressure was found to significantly influence the Curie point and ferroelectric soft modes in the nanowire. Uniaxial stress applied either along axial or transverse nanowire's direction is capable of inducing polydomain flux-closure phases that have a unique “dynamical” fingerprint. In such phases, the modes that originate from the soft modes of bulk PbTiO3 become hard, which could open a way to potential identification of such nanodomain phases. In all cases, uniaxial stress significantly increases the Curie temperature.
Detailed balance, internal consistency, and energy conservation in fragment orbital-based surface hopping
Authors: Carof Antoine , Giannini Samuele , Blumberger Jochen
Published: December 2017

We have recently introduced an efficient semi-empirical non-adiabatic molecular dynamics method for the simulation of charge transfer/transport in molecules and molecular materials, denoted fragment orbital-based surface hopping (FOB-SH) [J. Spencer et al., J. Chem. Phys. 145, 064102 (2016)]. In this method, the charge carrier wavefunction is expanded in a set of charge localized, diabatic electronic states and propagated in the time-dependent potential due to classical nuclear motion. Here we derive and implement an exact expression for the non-adiabatic coupling vectors between the adiabatic electronic states in terms of nuclear gradients of the diabatic electronic states. With the non-adiabatic coupling vectors (NACVs) available, we investigate how different flavours of fewest switches surface hopping affect detailed balance, internal consistency, and total energy conservation for electron hole transfer in a molecular dimer with two electronic states. We find that FOB-SH satisfies detailed balance across a wide range of diabatic electronic coupling strengths provided that the velocities are adjusted along the direction of the NACV to satisfy total energy conservation upon a surface hop. This criterion produces the right fraction of energy-forbidden (frustrated) hops, which is essential for correct population of excited states, especially when diabatic couplings are on the order of the thermal energy or larger, as in organic semiconductors and DNA. Furthermore, we find that FOB-SH is internally consistent, that is, the electronic surface population matches the average quantum amplitudes, but only in the limit of small diabatic couplings. For large diabatic couplings, inconsistencies are observed as the decrease in excited state population due to frustrated hops is not matched by a corresponding decrease in quantum amplitudes. The derivation provided here for the NACV should be generally applicable to any electronic structure approach where the electronic Hamiltonian is constructed in a diabatic electronic state basis.
Temperature dependence in magnetic particle imaging
Authors: Wells James , Paysen Hendrik , Kosch Olaf , Trahms Lutz , Wiekhorst Frank
Published: December 2017

Experimental results are presented demonstrating how temperature can influence the dynamics of magnetic nanoparticles (MNPs) in liquid suspension, when exposed to alternating magnetic fields in the kilohertz frequency range. The measurements used to probe the nanoparticle systems are directly linked to both the emerging biomedical technique of magnetic particle imaging (MPI), and to the recently proposed concept of remote nanoscale thermometry using MNPs under AC field excitation. Here, we report measurements on three common types of MNPs, two of which are currently leading candidates for use as tracers in MPI. Using highly-sensitive magnetic particle spectroscopy (MPS), we demonstrate significant and divergent thermal dependences in several key measures used in the evaluation of MNP dynamics for use in MPI and other applications. The temperature range studied was between 296 and 318 Kelvin, making our findings of particular importance for MPI and other biomedical technologies. Furthermore, we report the detection of the same temperature dependences in measurements conducted using the detection coils within an operational preclinical MPI scanner. This clearly shows the importance of considering temperature during MPI development, and the potential for temperature-resolved MPI using this system. We propose possible physical explanations for the differences in the behaviors observed between the different particle types, and discuss our results in terms of the opportunities and concerns they raise for MPI and other MNP based technologies.
Imaging pulsed laser deposition oxide growth by in situ atomic force microscopy
Authors: Wessels W. A. , Bollmann T. R. J. , Post D. , Koster G. , Rijnders G.
Published: December 2017

To visualize the topography of thin oxide films during growth, thereby enabling to study its growth behavior quasi real-time, we have designed and integrated an atomic force microscope (AFM) in a pulsed laser deposition (PLD) vacuum setup. The AFM scanner and PLD target are integrated in a single support frame, combined with a fast sample transfer method, such that in situ microscopy can be utilized after subsequent deposition pulses. The in situ microscope can be operated from room temperature up to 700 °C and at (process) pressures ranging from the vacuum base pressure of 10−6 mbar up to 1 mbar, typical PLD conditions for the growth of oxide films. The performance of this instrument is demonstrated by resolving unit cell height surface steps and surface topography under typical oxide PLD growth conditions.
Self-adaptive tensor network states with multi-site correlators
Authors: Kovyrshin Arseny , Reiher Markus
Published: December 2017

We introduce the concept of self-adaptive tensor network states (SATNSs) based on multi-site correlators. The SATNS ansatz gradually extends its variational space incorporating the most important next-order correlators into the ansatz for the wave function. The selection of these correlators is guided by entanglement-entropy measures from quantum information theory. By sequentially introducing variational parameters and adjusting them to the system under study, the SATNS ansatz achieves keeping their number significantly smaller than the total number of full-configuration interaction parameters. The SATNS ansatz is studied for manganocene in its lowest-energy sextet and doublet states; the latter of which is known to be difficult to describe. It is shown that the SATNS parametrization solves the convergence issues found for previous correlator-based tensor network states.
Nonadiabatic semiclassical dynamics in the mixed quantum-classical initial value representation
Authors: Church Matthew S. , Hele Timothy J. H. , Ezra Gregory S. , Ananth Nandini
Published: December 2017

We extend the Mixed Quantum-Classical Initial Value Representation (MQC-IVR), a semiclassical method for computing real-time correlation functions, to electronically nonadiabatic systems using the Meyer-Miller-Stock-Thoss (MMST) Hamiltonian in order to treat electronic and nuclear degrees of freedom (dofs) within a consistent dynamic framework. We introduce an efficient symplectic integration scheme, the MInt algorithm, for numerical time evolution of the phase space variables and monodromy matrix under the non-separable MMST Hamiltonian. We then calculate the probability of transmission through a curve crossing in model two-level systems and show that MQC-IVR reproduces quantum-limit semiclassical results in good agreement with exact quantum methods in one limit, and in the other limit yields results that are in keeping with classical limit semiclassical methods like linearized IVR. Finally, exploiting the ability of the MQC-IVR to quantize different dofs to different extents, we present a detailed study of the extents to which quantizing the nuclear and electronic dofs improves numerical convergence properties without significant loss of accuracy.
Switching the magnetically induced polarization of Co4Nb2O9 by dielectric-relaxation-related internal electric field
Authors: Xie Y. M. , Zang H. , Ceng W. D. , Wang C. C.
Published: December 2017

The possibility of switching the magnetically induced polarization (MIP) in magnetoelectric antiferromagnet Co4Nb2O9 by a dielectric-relaxation-related internal electric field was investigated. The MIP at a lower temperature is more difficult to be reversed, and this can be explained based on the Landau-Ginzburg-Devonshire theory as well as the domain nucleation and growth theory.
The second virial coefficient of bounded Mie potentials
Authors: Heyes D. M. , Pereira de Vasconcelos T.
Published: December 2017

The second virial coefficient (SVC) of bounded generalizations of the Mie m:n potential ϕ(r)=λ[1/(aq+rq)m/q−1/(aq+rq)n/q], where λ, a, q, m, and n are constants (a ≥ 0), is explored. The particle separation distance is r. This potential could be used as an effective interaction between polymeric dispersed colloidal particles of various degrees of interpenetrability. The SVC is negative for all temperatures for a, greater than a critical value, ac, which coincides with the range of a, where the system is thermodynamically unstable. The Boyle temperature and the temperature at which the SVC is a maximum diverge to +∞ as a → ac from below. Various series expansion expressions for the SVC are derived following on from those derived for the Mie potential itself (i.e., a = 0) in the study of Heyes et al. [J. Chem. Phys. 145, 084505 (2016)]. Formulas based on an expansion of the exponential in the Mayer function definition of the SVC are formally convergent, but pose numerical problems for the useful range of a < 1. High temperature expansion (HTE) formulas extending those in the previous publication are derived, which in contrast converge rapidly for the full a range. The HTE formulas derived in this work could be useful in guiding the choice of nucleation and growth experimental conditions for dispersed soft polymeric particles. Inter alia, the SVC of the inverse power special case of the Bounded Mie potential, i.e., ϕ(r)=1/(aq+rq)m/q, are also derived.
Magnetically-assembled micro/mesopixels exhibiting light intensity enhancement in the (012) planes of fish guanine crystals
Authors: Chikashige T. , Iwasaka M.
Published: December 2017

In this study, a new method was investigated to form light-reflecting dots at the micrometer scale using the magnetic orientations of biogenic guanine crystals obtained from fish skin and scales. The crystal platelets, possessing average dimensions of 5 μm×20 μm×100 nm, were dispersed in water and observed during exposure to vertical magnetic fields up to 5 T. The magnetic field direction was parallel to Earth’s gravity, and allowed the narrowest edges of the crystals to be observed at the micrometer scale for the first time. The magnetic orientation process was initiated under conditions where the crystal platelets in water were laid on a glass substrate or where the platelets had random orientations. In the former case, the crystal platelets followed a two-stage magnetic orientation process where, in the first step, the platelet widths were aligned in the magnetic field direction. The second step required rotation of the ∼20-μm-long plates with respect to the Earth’s gravity, where application of a 5 T magnetic field enabled their orientation. Real-time images of the magnetically aligning platelets provided new evidence that the crystal platelets also emitted reflected light from a very narrow window at two crystal planes (i.e., (01¯2¯) and (01¯2)). In the latter case with random platelet orientation, spatially-condensed light-reflecting dots appeared while the guanine crystal platelets were floating and maintaining their orientation. The technique developed for controlling light-reflecting microscale objects in an aqueous medium can be applied to produce a type of microfluidic optical tool.
Enhanced tunability of magneto-impedance and magneto-capacitance in annealed Metglas/PZT magnetoelectric composites
Authors: Leung Chung Ming , Zhuang Xin , Xu Junran , Li Jiefang , Zhang Jitao , Srinivasan G. , Viehland D.
Published: December 2017

This report is on a new class of magnetostatically tunable magneto-impedance and magneto-capacitance devices based on a composite of ferromagnetic Metglas and ferroelectric lead zirconate titanate (PZT). Layered magneto-electric (ME) composites with annealed Metglas and PZT were studied in a longitudinal in-plane magnetic field-transverse electric field (L-T) mode. It was found that the degree of tunability was dependent on the annealing temperature of Metglas. An impedance tunability (ΔZ/Z0) of ≥400% was obtained at the electromechanical resonance (EMR) frequency (fr) for a sample with Metglas layers annealed at Ta = 500oC. This tunability is a factor of two higher than for composites with Metglas annealed at 350oC. The tunability of the capacitance, (ΔC/C0), was found to be 290% and -135k% at resonance and antiresonance, respectively, for Ta = 500oC. These results provide clear evidence for improvement in static magnetic field tunability of impedance and capacitance of ME composites with the use of annealed Metglas and are of importance for their potential use in tunable electronic applications.
High-quality single-crystal thulium iron garnet films with perpendicular magnetic anisotropy by off-axis sputtering
Authors: Wu C. N. , Tseng C. C. , Lin K. Y. , Cheng C. K. , Yeh S. L. , Fanchiang Y. T. , Hong M. , Kwo J.
Published: December 2017

High-quality single-crystal thulium iron garnet (TmIG) films of 10-30 nm thick were grown by off-axis sputtering at room temperature (RT) followed by post-annealing. X-ray photoelectron spectroscopy (XPS) was employed to determine the TmIG film composition to optimize the growth conditions, along with the aid of x-ray diffraction (XRD) structural analysis and atomic force microscope (AFM) for surface morphology. The optimized films exhibited perpendicular magnetic anisotropy (PMA) and the saturation magnetization at RT was ∼99 emu/cm3, close to the RT bulk value ∼110 emu/cm3 with a very low coercive field of ∼2.4 Oe. We extracted the H⊥ of 1734 Oe and the peak-to-peak linewidth ΔH of ferromagnetic resonance are only about 99 Oe, significantly lower than that of PLD grown TmIG film and bulk single crystals. The high-quality sputtered single-crystal TmIG films show great potential to be integrated with topological insulators or heavy metals with strong spin-orbit coupling for spintronic applications.
Antidamping spin-orbit torques in epitaxial-Py(100)/β-Ta
Authors: Tiwari Dhananjay , Behera Nilamani , Kumar Akash , Dürrenfeld Philipp , Chaudhary Sujeet , Pandya D. K. , Åkerman Johan , Muduli P. K.
Published: December 2017

We perform spin torque ferromagnetic resonance measurements on the Si(100)/TiN(100)/epi-Py(100)/β-Ta system. We demonstrate current induced modulation of the Gilbert damping constant, which is about 30% for a current density of 6.25 × 109 A/m2. We show that the observed modulation of the Gilbert damping constant cannot be explained by spin transfer torques arising from the spin Hall effect of the β-Ta layer. An additional mechanism such as antidamping spin-orbit torque resulting from the interface or the crystalline structure of Py thin films needs to be considered.
A double-helix and cross-patterned solenoid used as a wirelessly powered receiver for medical implants
Authors: Mao Shitong , Wang Hao , Mao Zhi-Hong , Sun Mingui
Published: December 2017

Many medical implants need to be designed in the shape of a cylinder (rod), a cuboid or a capsule in order to adapt to a specific site within the human body or facilitate the implantation procedure. In order to wirelessly power these types of implants, a pair of coils, one is located inside the human body and one is outside, is often used. Since most organs such as major muscles, blood vessels, and nerve bundles are anatomically parallel to the body surface, the most desired wireless power transfer (WPT) direction is from the external power transmission pad (a planar coil) to the lateral surface of the implant. However, to obtain optimal coupling, the currently used solenoid coil requires being positioned perpendicular to the body surface, which is often medically or anatomically unacceptable. In this research, a concentric double-helix (DH) coil with an air core is presented for use in implantable devices. Two helical coils are tilted at opposite angles (±45 degrees) to form a cross pattern. The WPT system is designed using the magnetic resonance concept for wireless power transfer (MR-WPT). The power transfer efficiency (PTE) relies on the near-field magnetic coupling which is closely related to the location and orientation of the DH coil. We explain how the novel structure of the DH solenoid magnifies the mutual inductance with the widely adopted circular planner coil and how the PTE is improved in comparison to the case of the conventional solenoid coil. We also study an important case where the double-helix power reception coil is laterally and angularly misaligned with the transmitter. Finally, our computational study using the finite element method and experimental study with actually constructed prototypes are presented which have proven our new double-helix coil design.
A high-pressure metallic core holder for magnetic resonance based on Hastelloy-C
Authors: Shakerian M. , Marica F. , Afrough A. , Goora F. G. , Li M. , Vashaee S. , Balcom B. J.
Published: December 2017

A metallic core holder, fabricated from non-magnetic Hastelloy-C276, has been designed for Magnetic Resonance (MR) and Magnetic Resonance Imaging (MRI) of core plug samples at high pressures and temperatures. Core plug samples, 1.5″ in diameter and 2″ in length, can be tested in the core holder at elevated pressures and temperatures, up to 5000 psi and 80 °C. These are conditions commonly found in petroleum reservoirs. A radio frequency probe, which excites and detects magnetic resonance signals, was placed inside the metal vessel. Proximity to the sample improves the signal to noise ratio of the resulting measurements. The metallic core holder is positioned between the poles of a 0.2 T permanent magnet and subjected to rapidly switched magnetic field gradients as part of the imaging process. This switching induces eddy currents on the conductive core holder, which degrades the magnetic field gradient waveform in the sample space. The low electrical-conductivity of Hastelloy-C276 minimizes the duration and the magnitude of such eddy currents. A recently developed pre-equalization technique was employed to ensure that magnetic field gradient pulses, required for MRI, are near ideal in the sample space. A representative core flooding experiment was undertaken in conjunction with MR/MRI measurements.
Exploring a multi-scale method for molecular simulation in continuum solvent model: Explicit simulation of continuum solvent as an incompressible fluid
Authors: Xiao Li , Luo Ray
Published: December 2017

We explored a multi-scale algorithm for the Poisson-Boltzmann continuum solvent model for more robust simulations of biomolecules. In this method, the continuum solvent/solute interface is explicitly simulated with a numerical fluid dynamics procedure, which is tightly coupled to the solute molecular dynamics simulation. There are multiple benefits to adopt such a strategy as presented below. At this stage of the development, only nonelectrostatic interactions, i.e., van der Waals and hydrophobic interactions, are included in the algorithm to assess the quality of the solvent-solute interface generated by the new method. Nevertheless, numerical challenges exist in accurately interpolating the highly nonlinear van der Waals term when solving the finite-difference fluid dynamics equations. We were able to bypass the challenge rigorously by merging the van der Waals potential and pressure together when solving the fluid dynamics equations and by considering its contribution in the free-boundary condition analytically. The multi-scale simulation method was first validated by reproducing the solute-solvent interface of a single atom with analytical solution. Next, we performed the relaxation simulation of a restrained symmetrical monomer and observed a symmetrical solvent interface at equilibrium with detailed surface features resembling those found on the solvent excluded surface. Four typical small molecular complexes were then tested, both volume and force balancing analyses showing that these simple complexes can reach equilibrium within the simulation time window. Finally, we studied the quality of the multi-scale solute-solvent interfaces for the four tested dimer complexes and found that they agree well with the boundaries as sampled in the explicit water simulations.
Growth of Brahman cross heifers to 2 years of age in the dry tropics
Authors: Fordyce Geoffry , Chandra Kerri
Published: December 2017

Growth of 1368 Brahman cross heifers from 6 year cohorts was monitored over the 2 years post-weaning in Australia’s northern forest, a low-animal-growth dry tropical environment. Heifers weighing 47–266 kg at weaning were managed in groups weighing <100 kg, 100–149 kg, 150–199 kg, and >199 kg during the post-weaning dry season. Weaner heifers were allocated to receive 300 g/day of a protein meal during the dry season or to basic nutritional management to sustain health. Heifers in three cohorts were allocated to first mating at 1 or 2 years of age, in four cohorts to vaccination against androstenedione, and in a small proportion of two cohorts to ovariectomy post-weaning. Growth was highly variable between seasons and years; average cohort liveweight by the start of 2-year-old mating was 256–319 kg. Heifer groups not receiving protein supplementation gained –16 to 21 kg (2 kg average) during 6-month dry seasons, and 49–131 kg (101 kg average) during wet seasons to reach an average of two-thirds of mature liveweight (445 kg) and 95% of mature hip height (1350 mm) by the start of mating at 2 years. Average body condition score (1–5) fluctuated by 1–2 units between seasons. Hip height gain continued, irrespective of season, commencing at ~0.60 mm/day at 6 months of age, and decelerating by ~0.00075 mm/day through to 2.5 years of age. Standard errors of predicted means across analyses were ~0.015 for average daily weight gains, 0.4 mm for average monthly height gain and 0.06 score units for average seasonal body condition score change. Post-weaning dry-season supplementation increased gains in liveweight, height and body condition score by an average of 0.1 kg/day, 0.1 mm/day and 0.5 units, respectively, during the supplementation period. Periods of poor nutrition or high nutritional demand secondary to reproduction suppressed daily gains in liveweight and hip height, at which times body condition score was also reduced. Subsequent to this, partial to full compensation occurred for all measures. Ovariectomy had negative effects on growth. Androstenedione vaccination had no effect on growth. The main conclusion is that heifer growth in Australia’s dry tropical northern forest region is highly variable between seasons and years, thus limiting significant proportions of some cohorts from reaching target weights for mating at 2 years of age, even after compensatory growth.
Simultaneous measurements of ammonia volatilisation and deposition at a beef feedlot
Authors: Redding M. R. , Lewis R. , Shorten P. R.
Published: December 2017

The nitrogen (N) excreted at intensive livestock operations is vulnerable to volatilisation, and, subsequently, may form a source of indirect nitrous oxide (N2O) emissions. The present study simultaneously investigated volatilisation and deposition of N at a beef feedlot, semi-continuously over a 129-day period. These data were examined relative to pen manure parameters, management statistics and emission-inventory calculation protocols. Volatilisation measurements were conducted using a single, heated air-sampling inlet, centrally located in a feedlot pen area, with real time concentration analysis via cavity ring-down spectroscopy and backward Lagrangian stochastic (bLS) modelling. Net deposited mineral-N was determined via two transects of soil-deposition traps, with samples collected and re-deployed every 2 weeks. Total volatilised ammonia amounted to 210 tonnes of NH3-N (127 g/animal.day), suggesting that the inventory volatilisation factor probably underestimated volatilisation in this case (inventory, 30% of excreted N; 65 g N volatilised/animal.day; a value of ~60% of excreted N is indicated). Temperature contrast between the manure and air was observed to play a significant role in the rate of emission (R2 = 0.38; 0.46 Kendall’s tau; P < 0.05). Net deposition within 600 m of the pen boundary represented only 1.7% to 3% of volatilised NH4+-N, between 3.6 and 6.7 tonnes N. Beyond this distance, deposition approached background rates (~0.4 kg N/ha.year).
A simple numerical model to estimate water availability in saline soils
Authors: Mohammadi Mohammad Hossein , Khataar Mahnaz
Published: December 2017

We developed a numerical model to predict soil salinity from knowledge of evapotranspiration rate, crop salt tolerance, irrigation water salinity, and soil hydraulic properties. Using the model, we introduced a new weighting function to express the limitation imposed by salinity on plant available water estimated by the integral water capacity concept. Lower and critical limits of soil water uptake by plants were also defined. We further analysed the sensitivity of model results to underlying parameters using characteristics given for corn, cowpea, and barley in the literature and two clay and sandy loam soils obtained from databases. Results showed that, between two irrigation events, soil salinity increased nonlinearly with decreasing soil water content especially when evapotranspiration and soil drainage rate were high. The salinity weighting function depended greatly on the plant sensitivity to salinity and irrigation water salinity. This research confirmed that both critical and lower limits (in terms of water content) of soil water uptake by plants increased with evapotranspiration rate and irrigation water salinity. Since the presented approach is based on a physical concept and well-known plant parameters, soil hydraulic characteristics, irrigation water salinity, and meteorological conditions, it may be useful in spatio-temporal modelling of soil water quality and quantity and prediction of crop yield.
Human-caused fire occurrence modelling in perspective: a review
Authors: Costafreda-Aumedes Sergi , Comas Carles , Vega-Garcia Cristina
Published: December 2017

The increasing global concern about wildfires, mostly caused by people, has triggered the development of human-caused fire occurrence models in many countries. The premise is that better knowledge of the underlying factors is critical for many fire management purposes, such as operational decision-making in suppression and strategic prevention planning, or guidance on forest and land-use policies. However, the explanatory and predictive capacity of fire occurrence models is not yet widely applied to the management of forests, fires or emergencies. In this article, we analyse the developments in the field of human-caused fire occurrence modelling with the aim of identifying the most appropriate variables and methods for applications in forest and fire management and civil protection. We stratify our worldwide analysis by temporal dimension (short-term and long-term) and by model output (numeric or binary), and discuss management applications. An attempt to perform a meta-analysis based on published models proved limited because of non-equivalence of the metrics and units of the estimators and outcomes across studies, the diversity of models and the lack of information in published works.
Molecular chaperones maximize the native state yield on biological times by driving substrates out of equilibrium
Authors: Chakrabarti Shaon , Hyeon Changbong , Ye Xiang , Lorimer George H. , Thirumalai D.
Published: December 2017

Significance

Molecular chaperones have evolved to assist the folding of proteins and RNA, thus avoiding the deleterious consequences of misfolding. Thus, it is expected that increasing chaperone concentrations should enhance the yield of native states. While this has been observed in GroEL-mediated protein folding, experiments on
Tetrahymena
ribozyme folding assisted by CYT-19 surprisingly show the opposite trend. Here, we reconcile these divergent experimental observations by developing a unified theory of chaperone-assisted protein and RNA folding. We show that these ATP-fueled machines drive their substrates out of equilibrium, maximizing the nonequilibrium native yield in a given time rather than the absolute yield or folding rate. The theory predicts that in vivo the number of chaperones is regulated to optimize their functions.
Lipid bilayer mediates ion-channel cooperativity in a model of hair-cell mechanotransduction
Authors: Gianoli Francesco , Risler Thomas , Kozlov Andrei S.
Published: December 2017

Significance

Hearing relies on molecular machinery that consists of springs stretched by mechanical stimuli and mechanosensitive ion channels responding to the generated tension. Reproducing the experimental data theoretically without requiring unrealistically large conformational changes of the channels has been a longstanding hurdle. Here, we propose and develop a model with two mobile channels per spring, coupled by elastic forces within the membrane. The relative motion of the channels following their cooperative opening and closing produces the required change in spring extension. This study lies at the interface between the fields of membrane mechanics and mechanotransduction in the inner ear. It describes a physiological function for the bilayer-mediated cooperativity between mechanosensitive ion channels in a vertebrate sensory system.
Why conceptual competence won’t help the non-naturalist epistemologist
Authors: Werner Preston J.
Published: December 2017

Non-naturalist normative realists face an epistemological objection: They must explain how their preferred route of justification ensures a non-accidental connection between justified moral beliefs and the normative truths. One strategy for meeting this challenge begins by pointing out that we are semantically or conceptually competent in our use of the normative terms, and then argues that this competence guarantees the non-accidental truth of some of our first-order normative beliefs. In this paper, I argue against this strategy by illustrating that this competence based strategy undermines the non-naturalist's ability to capture the robustly normative content of our moral beliefs.
Introduction: revolution and counter-revolution in Egypt
Authors: Tansel Cemal Burak , De Smet Brecht
Published: December 2017

This introduction to the ROAPE debate reasserts the centrality of revolutionary theory to understand the dynamics of social and political struggles in contemporary Middle East and North Africa. Framed around the conceptual and political interventions brought about by Brecht De Smet’s Gramsci on Tahrir (2016), we discuss the utility of Gramscian concepts in explaining the trajectories of social mobilisations in the peripheries of global capitalism.