bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum dynamics of hydrogen atoms on graphene. I. System-bath modeling
Authors: Bonfanti Matteo , Jackson Bret , Hughes Keith H. , Burghardt Irene , Martinazzo Rocco
Published: September 2015

An accurate system-bath model to investigate the quantum dynamics of hydrogen atoms chemisorbed on graphene is presented. The system comprises a hydrogen atom and the carbon atom from graphene that forms the covalent bond, and it is described by a previously developed 4D potential energy surface based on density functional theory ab initio data. The bath describes the rest of the carbon lattice and is obtained from an empirical force field through inversion of a classical equilibrium correlation function describing the hydrogen motion. By construction, model building easily accommodates improvements coming from the use of higher level electronic structure theory for the system. Further, it is well suited to a determination of the system-environment coupling by means of ab initio molecular dynamics. This paper details the system-bath modeling and shows its application to the quantum dynamics of vibrational relaxation of a chemisorbed hydrogen atom, which is here investigated at T = 0 K with the help of the multi-configuration time-dependent Hartree method. Paper II deals with the sticking dynamics.
Guiding supersonic projectiles using optically generated air density channels
Authors: Johnson Luke A. , Sprangle Phillip
Published: September 2015

We investigate the feasibility of using optically generated channels of reduced air density to provide trajectory correction (guiding) for a supersonic projectile. It is shown that the projectile experiences a force perpendicular to its direction of motion as one side of the projectile passes through a channel of reduced air density. A single channel of reduced air density can be generated by the energy deposited from filamentation of an intense laser pulse. We propose changing the laser pulse energy from shot-to-shot to build longer effective channels. Current femtosecond laser systems with multi-millijoule pulses could provide trajectory correction of several meters on 5 km trajectories for sub-kilogram projectiles traveling at Mach 3.
Enhanced Li capacity in functionalized graphene: A first principle study with van der Waals correction
Authors: Chouhan Rajiv K. , Raghani Pushpa
Published: September 2015

We have investigated the adsorption of Li on graphene oxide using density functional theory. We show a novel and simple approach to achieve a positive lithiation potential on epoxy and hydroxyl functionalized graphene, compared to the negative lithiation potential that has been found on prestine graphene. We included the van der Waals correction into the calculation so as to get a better picture of weak interactions. A positive lithiation potential suggests a favorable adsorption of Li on graphene oxide sheets that can lead to an increase in the specific capacity, which in turn can be used as an anode material in Li-batteries. We find a high specific capacity of ∼860 mAhg−1 by functionalizing the graphene sheet. This capacity is higher than the previously reported capacities that were achieved on graphene with high concentration of Stone-Wales (75%) and divacancy (16%) defects. Creating such high density of defects can make the entire system energetically unstable, whereas graphene oxide is a naturally occurring substance.
Band gap tuning and orbital mediated electron–phonon coupling in HoFe1−xCrxO3 (0 ≤ x ≤ 1)
Authors: Kotnana Ganesh , Jammalamadaka S. Narayana
Published: September 2015

We report on the evidenced orbital mediated electron–phonon coupling and band gap tuning in HoFe1−xCrxO3 (0 ≤ x ≤ 1) compounds. From the room temperature Raman scattering, it is apparent that the electron-phonon coupling is sensitive to the presence of both the Fe and Cr at the B-site. Essentially, an Ag like local oxygen breathing mode is activated due to the charge transfer between Fe3+ and Cr3+ at around 670 cm−1, this observation is explained on the basis of Franck-Condon mechanism. Optical absorption studies infer that there exists a direct band gap in the HoFe1−xCrxO3 (0 ≤ x ≤ 1) compounds. Decrease in band gap until x = 0.5 is ascribed to the broadening of the oxygen p-orbitals as a result of the induced spin disorder due to Fe3+ and Cr3+ at B-site. In contrast, the increase in band gap above x = 0.5 is explained on the basis of the reduction in the available unoccupied d-orbitals of Fe3+ at the conduction band. We believe that above results would be helpful for the development of the optoelectronic devices based on the ortho-ferrites.
Construction of exchange-correlation functionals through interpolation between the non-interacting and the strong-correlation limit
Authors: Zhou Yongxi , Bahmann Hilke , Ernzerhof Matthias
Published: September 2015

Drawing on the adiabatic connection of density functional theory, exchange-correlation functionals of Kohn-Sham density functional theory are constructed which interpolate between the extreme limits of the electron-electron interaction strength. The first limit is the non-interacting one, where there is only exchange. The second limit is the strong correlated one, characterized as the minimum of the electron-electron repulsion energy. The exchange-correlation energy in the strong-correlation limit is approximated through a model for the exchange-correlation hole that is referred to as nonlocal-radius model [L. O. Wagner and P. Gori-Giorgi, Phys. Rev. A 90, 052512 (2014)]. Using the non-interacting and strong-correlated extremes, various interpolation schemes are presented that yield new approximations to the adiabatic connection and thus to the exchange-correlation energy. Some of them rely on empiricism while others do not. Several of the proposed approximations yield the exact exchange-correlation energy for one-electron systems where local and semi-local approximations often fail badly. Other proposed approximations generalize existing global hybrids by using a fraction of the exchange-correlation energy in the strong-correlation limit to replace an equal fraction of the semi-local approximation to the exchange-correlation energy in the strong-correlation limit. The performance of the proposed approximations is evaluated for molecular atomization energies, total atomic energies, and ionization potentials.
A self-consistent two-fluid model of a magnetized plasma-wall transition
Authors: Gyergyek T. , Kovačič J.
Published: September 2015

A self-consistent one-dimensional two-fluid model of the magnetized plasma-wall transition is presented. The model includes magnetic field, elastic collisions between ions and electrons, and creation/annihilation of charged particles. Two systems of differential equations are derived. The first system describes the whole magnetized plasma-wall transition region, which consists of the pre-sheath, the magnetized pre-sheath (Chodura layer), and the sheath, which is not neutral, but contains a positive space charge. The second system of equations describes only the neutral part of the plasma-wall transition region—this means only the pre-sheath and the Chodura layer, but not also the sheath. Both systems are solved numerically. The first system of equations has two singularities. The first occurs when ion velocity in the direction perpendicularly to the wall drops below the ion thermal velocity. The second occurs when the electron velocity in the direction perpendicularly to the wall exceeds the electron thermal velocity. The second system of differential equations only has one singularity, which has also been derived analytically. For finite electron to ion mass ratio, the integration of the second system always breaks down before the Bohm criterion is fulfilled. Some properties of the first system of equations are examined. It is shown that the increased collision frequency demagnetizes the plasma. On the other hand, if the magnetic field is so strong that the ion Larmor radius and the Debye length are comparable, the electron velocity in the direction perpendicularly to the wall reaches the electron thermal velocity before the ion velocity in the direction perpendicularly to the wall reaches the ion sound velocity. In this case, the integration of the model equations breaks down before the Bohm criterion is fulfilled and the sheath is formed.
Differentiability of correlations in realistic quantum mechanics
Authors: Cabrera Alejandro , de Faria Edson , Pujals Enrique , Tresser Charles
Published: September 2015

We prove a version of Bell’s theorem in which the locality assumption is weakened. We start by assuming theoretical quantum mechanics and weak forms of relativistic causality and of realism (essentially the fact that observable values are well defined independently of whether or not they are measured). Under these hypotheses, we show that only one of the correlation functions that can be formulated in the framework of the usual Bell theorem is unknown. We prove that this unknown function must be differentiable at certain angular configuration points that include the origin. We also prove that, if this correlation is assumed to be twice differentiable at the origin, then we arrive at a version of Bell’s theorem. On the one hand, we are showing that any realistic theory of quantum mechanics which incorporates the kinematic aspects of relativity must lead to this type of rough correlation function that is once but not twice differentiable. On the other hand, this study brings us a single degree of differentiability away from a relativistic von Neumann no hidden variables theorem.
Electric field controlled nanoscale contactless deposition using a nanofluidic scanning probe
Authors: Geerlings Joël , Sarajlic Edin , Berenschot Erwin J. W. , Sanders Remco G. P. , Siekman Martin H. , Abelmann Leon , Tas Niels R.
Published: September 2015

A technique for contactless liquid deposition on the nanoscale assisted by an electric field is presented. By the application of a voltage between the liquid inside a (FluidFM) nanofountain pen AFM probe and a substrate, accurate contactless deposition is achieved. This technique allows for the deposition of polar liquids on non-wetting substrates. Sodium sulfate dried deposits indicate that the spot size and height increases with t0.33±0.04 and t0.35±0.10, respectively. The minimum observed diameter was 70 nm. By measuring the probe deflection and the electric deposition current, we confirm that deposition is truly non-contact. We propose a simple model based on a constant stream of liquid to the substrate, which explains our observations qualitatively.
On the space of connections having non-trivial twisted harmonic spinors
Authors: Bei Francesco , Waterstraat Nils
Published: September 2015

We consider Dirac operators on odd-dimensional compact spin manifolds which are twisted by a product bundle. We show that the space of connections on the twisting bundle which yields an invertible operator has infinitely many connected components if the untwisted Dirac operator is invertible and the dimension of the twisting bundle is sufficiently large.
Experimental study of intense radiation in terahertz region based on cylindrical surface wave resonator
Authors: Gong Shaoyan , Ogura Kazuo , Yambe Kiyoyuki , Nomizu Shintaro , Shirai Akihiro , Yamazaki Kosuke , Kawamura Jun , Miura Takuro , Takanashi Sho , San Min Thu
Published: September 2015

Periodical corrugations structured on a cylindrical conductor have cylindrical surface waves (CSWs), which are reflected at the corrugation ends and form a CSW-resonator. In this paper, intense radiations in terahertz region based on the CSW-resonator are reported. The CSW-resonators with upper cut off frequencies in the modern IEEE G-band (110–300 GHz) are excited by a coaxially injected annular beam in a weakly relativistic region less than 100 kV. It is shown that there exists an oscillation starting energy for the CSW-resonator. Above the starting energy, very intense terahertz radiations on the order of kW are obtained. The operation frequencies in the range of 166–173 GHz and 182–200 GHz are obtained using two types of CSW-resonator with the different corrugation amplitude. Electromagnetic properties of the CSW-resonator can be controlled by the artificial structure and may play an important role in high-intensity terahertz generations and applications.
Microwave exfoliated graphene oxide/TiO2 nanowire hybrid for high performance lithium ion battery
Authors: Ishtiaque Shuvo Mohammad Arif , Rodriguez Gerardo , Islam Md Tariqul , Karim Hasanul , Ramabadran Navaneet , Noveron Juan C. , Lin Yirong
Published: September 2015

Lithium ion battery (LIB) is a key solution to the demand of ever-improving, high energy density, clean-alternative energy systems. In LIB, graphite is the most commonly used anode material; however, lithium-ion intercalation in graphite is limited, hindering the battery charge rate and capacity. To date, one of the approaches in LIB performance improvement is by using porous carbon (PC) to replace graphite as anode material. PC's pore structure facilitates ion transport and has been proven to be an excellent anode material candidate in high power density LIBs. In addition, to overcome the limited lithium-ion intercalation obstacle, nanostructured anode assembly has been extensively studied to increase the lithium-ion diffusion rate. Among these approaches, high specific surface area metal oxide nanowires connecting nanostructured carbon materials accumulation have shown promising results for enhanced lithium-ion intercalation. Herein, we demonstrate a hydrothermal approach of growing TiO2 nanowires (TON) on microwave exfoliated graphene oxide (MEGO) to further improve LIB performance over PC. This MEGO-TON hybrid not only uses the high surface area of MEGO but also increases the specific surface area for electrode–electrolyte interaction. Therefore, this new nanowire/MEGO hybrid anode material enhances both the specific capacity and charge–discharge rate. Scanning electron microscopy and X-ray diffraction were used for materials characterization. Battery analyzer was used for measuring the electrical performance of the battery. The testing results have shown that MEGO-TON hybrid provides up to 80% increment of specific capacity compared to PC anode.
Deuterated polyethylene coatings for ultra-cold neutron applications
Authors: Brenner Th. , Fierlinger P. , Geltenbort P. , Gutsmiedl E. , Hollering A. , Lauer T. , Petzoldt G. , Ruhstorfer D. , Schroffenegger J. , Seemann K. M. , Soltwedel O. , Stuiber St. , Taubenheim B. , Windmayer D. , Zechlau T.
Published: September 2015

We report on the fabrication and use of deuterated polyethylene as a coating material for ultra-cold neutron (UCN) storage and transport. The Fermi potential has been determined to be 214 neV, and the wall loss coefficient η is 1.3 × 104 per wall collision. The coating technique allows for a wide range of applications in this field of physics. In particular, flexible and quasi-massless UCN guides with slit-less shutters and seamless UCN storage volumes become possible. These properties enable the use in next-generation measurements of the electric dipole moment of the neutron.
Coarse-graining and phase behavior of model star polymer–colloid mixtures in solvents of varying quality
Authors: Nikoubashman Arash , Mahynski Nathan A. , Capone Barbara , Panagiotopoulos Athanassios Z. , Likos Christos N.
Published: September 2015

We study the effective interactions and phase behavior of star polymer–colloid mixtures through theory and Monte Carlo simulations. We extend previous theoretical approaches for calculating the effective star–colloid pair potential to take into account attractive contributions, which become significant at worsening solvent conditions. In order to assess the validity of our simulation and theory, we compute the effective interactions via virtual move parallel tempering Monte Carlo simulations using a microscopic bead-spring model for the star polymer and achieve excellent agreement. Finally, we perform grand canonical Monte Carlo simulations of the coarse-grained systems to study the effect of solvent quality on the phase behavior.
Charge transport model to predict intrinsic reliability for dielectric materials
Authors: Ogden Sean P. , Borja Juan , Plawsky Joel L. , Lu T.-M. , Yeap Kong Boon , Gill William N.
Published: September 2015

Several lifetime models, mostly empirical in nature, are used to predict reliability for low-k dielectrics used in integrated circuits. There is a dispute over which model provides the most accurate prediction for device lifetime at operating conditions. As a result, there is a need to transition from the use of these largely empirical models to one built entirely on theory. Therefore, a charge transport model was developed to predict the device lifetime of low-k interconnect systems. The model is based on electron transport and donor-type defect formation. Breakdown occurs when a critical defect concentration accumulates, resulting in electron tunneling and the emptying of positively charged traps. The enhanced local electric field lowers the barrier for electron injection into the dielectric, causing a positive feedforward failure. The charge transport model is able to replicate experimental I-V and I-t curves, capturing the current decay at early stress times and the rapid current increase at failure. The model is based on field-driven and current-driven failure mechanisms and uses a minimal number of parameters. All the parameters have some theoretical basis or have been measured experimentally and are not directly used to fit the slope of the time-to-failure versus applied field curve. Despite this simplicity, the model is able to accurately predict device lifetime for three different sources of experimental data. The simulation's predictions at low fields and very long lifetimes show that the use of a single empirical model can lead to inaccuracies in device reliability.
Spin-orbit torques for current parallel and perpendicular to a domain wall
Authors: Schulz Tomek , Alejos Oscar , Martinez Eduardo , Hals Kjetil M. D. , Garcia Karin , Vila Laurent , Lee Kyujoon , Lo Conte Roberto , Karnad Gurucharan V. , Moretti Simone , Ocker Berthold , Ravelosona Dafiné , Brataas Arne , Kläui Mathias
Published: September 2015

We report field- and current-induced domain wall (DW) depinning experiments in Ta\Co20Fe60B20\MgO nanowires through a Hall cross geometry. While purely field-induced depinning shows no angular dependence on in-plane fields, the effect of the current depends crucially on the internal DW structure, which we manipulate by an external magnetic in-plane field. We show depinning measurements for a current sent parallel to the DW and compare its depinning efficiency with the conventional case of current flowing perpendicularly to the DW. We find that the maximum efficiency is similar for both current directions within the error bars, which is in line with a dominating damping-like spin-orbit torque (SOT) and indicates that no large additional torques arise for currents perpendicular to the DW. Finally, we find a varying dependence of the maximum depinning efficiency angle for different DWs and pinning levels. This emphasizes the importance of our full angular scans compared with previously used measurements for just two field directions (parallel and perpendicular to the DW) to determine the real torque strength and shows the sensitivity of the SOT to the precise DW structure and pinning sites.
Thermoelectric properties of sintered type-II clathrates (K, Ba)24(Ga, Sn)136 with various carrier concentrations
Authors: Kishimoto Kengo , Koda Shota , Akai Koji , Koyanagi Tsuyoshi
Published: September 2015

We reported the thermoelectric properties of the sintered type-II clathrate K8Ba16Ga40Sn96 in a previous paper [S. Koda et al., J. Appl. Phys. 116, 023710 (2014)]. The clathrate had a high dimensionless figure of merit ZT, namely, 0.93. In this study, we optimized the carrier concentration n by modifying the chemical compositions of (K, Ba)24(Ga, Sn)136 samples, and heat treated the sintered samples. The carrier mobilities μ were improved because of the reduction in potential barrier scattering at grain boundaries. The room-temperature (RT) n values varied from 7.7 × 1017 to 3.7 × 1019 cm−3; the maximum RT μ value was 170 cm2V−1s−1. Consequently, we obtained a high ZT value of 1.19 at 630 K for n = 2.5 × 1019 cm−3. This material therefore has good thermoelectric properties.
Parametrized dielectric functions of amorphous GeSn alloys
Authors: D'Costa Vijay Richard , Wang Wei , Schmidt Daniel , Yeo Yee-Chia
Published: September 2015

We obtained the complex dielectric function of amorphous Ge1−xSnx (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge0.75Sn0.25 and Ge0.50Sn0.50 alloys from literature. The compositional dependence of band gap energy Eg and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.
Effect of Group-III precursors on unintentional gallium incorporation during epitaxial growth of InAlN layers by metalorganic chemical vapor deposition
Authors: Kim Jeomoh , Ji Mi-Hee , Detchprohm Theeradetch , Dupuis Russell D. , Fischer Alec M. , Ponce Fernando A. , Ryou Jae-Hyun
Published: September 2015

Unintentional incorporation of gallium (Ga) in InAlN layers grown with different molar flow rates of Group-III precursors by metalorganic chemical vapor deposition has been experimentally investigated. The Ga mole fraction in the InAl(Ga)N layer was increased significantly with the trimethylindium (TMIn) flow rate, while the trimethylaluminum flow rate controls the Al mole fraction. The evaporation of metallic Ga from the liquid phase eutectic system between the pyrolized In from injected TMIn and pre-deposited metallic Ga was responsible for the Ga auto-incorporation into the InAl(Ga)N layer. The theoretical calculation on the equilibrium vapor pressure of liquid phase Ga and the effective partial pressure of Group-III precursors based on growth parameters used in this study confirms the influence of Group-III precursors on Ga auto-incorporation. More Ga atoms can be evaporated from the liquid phase Ga on the surrounding surfaces in the growth chamber and then significant Ga auto-incorporation can occur due to the high equilibrium vapor pressure of Ga comparable to effective partial pressure of input Group-III precursors during the growth of InAl(Ga)N layer.
Negative hydrogen ion production in a helicon plasma source
Authors: Santoso J. , Manoharan R. , O'Byrne S. , Corr C. S.
Published: September 2015

In order to develop very high energy (>1 MeV) neutral beam injection systems for applications, such as plasma heating in fusion devices, it is necessary first to develop high throughput negative ion sources. For the ITER reference source, this will be realised using caesiated inductively coupled plasma devices, containing either hydrogen or deuterium discharges, operated with high rf input powers (up to 90 kW per driver). It has been suggested that due to their high power coupling efficiency, helicon devices may be able to reduce power requirements and potentially obviate the need for caesiation due to the high plasma densities achievable. Here, we present measurements of negative ion densities in a hydrogen discharge produced by a helicon device, with externally applied DC magnetic fields ranging from 0 to 8.5 mT at 5 and 10 mTorr fill pressures. These measurements were taken in the magnetised plasma interaction experiment at the Australian National University and were performed using the probe-based laser photodetachment technique, modified for the use in the afterglow of the plasma discharge. A peak in the electron density is observed at ∼3 mT and is correlated with changes in the rf power transfer efficiency. With increasing magnetic field, an increase in the negative ion fraction from 0.04 to 0.10 and negative ion densities from 8 × 1014 m−3 to 7 × 1015 m−3 is observed. It is also shown that the negative ion densities can be increased by a factor of 8 with the application of an external DC magnetic field.
All-optical transistors and logic gates using a parity-time-symmetric Y-junction: Design and simulation
Authors: Ding Shulin , Wang Guo Ping
Published: September 2015

Classical nonlinear or quantum all-optical transistors are dependent on the value of input signal intensity or need extra co-propagating beams. In this paper, we present a kind of all-optical transistors constructed with parity-time (PT)-symmetric Y-junctions, which perform independently on the value of signal intensity in an unsaturated gain case and can also work after introducing saturated gain. Further, we show that control signal can switch the device from amplification of peaks in time to transformation of peaks to amplified troughs. By using these PT-symmetric Y-junctions with currently available materials and technologies, we can implement interesting logic functions such as NOT and XOR (exclusive OR) gates, implying potential applications of such structures in designing optical logic gates, optical switches, and signal transformations or amplifications.
Note: Model-based identification method of a cable-driven wearable device for arm rehabilitation
Authors: Cui Xiang , Chen Weihai , Zhang Jianbin , Wang Jianhua
Published: September 2015

Cable-driven exoskeletons have used active cables to actuate the system and are worn on subjects to provide motion assistance. However, this kind of wearable devices usually contains uncertain kinematic parameters. In this paper, a model-based identification method has been proposed for a cable-driven arm exoskeleton to estimate its uncertainties. The identification method is based on the linearized error model derived from the kinematics of the exoskeleton. Experiment has been conducted to demonstrate the feasibility of the proposed model-based method in practical application.
Controlled emission and coupling of small-size YAG:Ce3+ nanocrystals to gold nanowire
Authors: Birowosuto Muhammad Danang , Isnaeni  , de Mello Donegá Celso , Meijerink Andries
Published: September 2015

We report a controlled emission of Ce3+ ions inside single Yttrium Aluminum Garnet Y3Al5O12 (YAG:Ce3+) nanocrystals with a diameter of 22 ± 10 nm as a result of a coupling of a surface plasmon mode propagating along single gold nanowire (NW). From the photoluminescence images, the intensity for single YAG:Ce3+ nanocrystals in the proximity of the single gold NW increases by a factor of two in comparison with that without the NW. Also, we observe a maximum of 3.8-fold emission rate enhancements for the single nanocrystal close to the single gold NW. The emission rate enhancements of YAG:Ce3+ nanocrystals are two folds the enhancements of 100-nm fluorescent nanospheres. This value is in agreement with the calculation of a combination from the analytical scattering model and boundary element method. We also confirm that the small size light sources are more efficient for the emission rate enhancements. Thus, the controlled emission of small YAG:Ce3+ nanocrystals with the perfect photostabilities will pave the way for the ultimate efficient nanoscale light sources.
Enhanced field emission of plasma treated multilayer graphene
Authors: Khare Ruchita T. , Gelamo Rogerio V. , More Mahendra A. , Late Dattatray J. , Rout Chandra Sekhar
Published: September 2015

Electron emission properties of multilayer graphene (MLG) prepared by a facile exfoliation technique have been studied. Effect of CO2 Ar, N2, plasma treatment was studied using Raman spectroscopy and investigated for field emission based application. The CO2 plasma treated multilayer graphene shows an enhanced field emission behavior with a low turn on field of 0.18 V/μm and high emission current density of 1.89 mA/cm2 at an applied field of 0.35 V/μm. Further the plasma treated MLG exhibits excellent current stability at a lower and higher emission current value.
Anomalous change in leakage and displacement currents after electrical poling on lead-free ferroelectric ceramics
Authors: Borkar Hitesh , Tomar M. , Gupta Vinay , Scott J. F. , Kumar Ashok
Published: September 2015

We report the polarization, displacement current, and leakage current behavior of a trivalent nonpolar cation (Al3+) substituted lead free ferroelectric (Na0.46Bi0.46−xAlxBa0.08)TiO3 (NBAT−BT) (x = 0, 0.05, 0.07 and 0.10) electroceramics with tetragonal phase and P4 mm space group symmetry. Almost, three orders of magnitude decrease in leakage current were observed under electrical poling, which significantly improves microstructure, polarization, and displacement current. Effective poling neutralizes the domain pinning, traps charges at grain boundaries and fills oxygen vacancies with free charge carriers in matrix, thus saturated macroscopic polarization in contrast to that in unpoled samples. E-poling changes “bananas” type polarization loops to real ferroelectric loops.
Spin relaxation characteristics in Ag nanowire covered with various oxides
Authors: Karube S. , Idzuchi H. , Kondou K. , Fukuma Y. , Otani Y.
Published: September 2015

We have studied spin relaxation characteristics in a Ag nanowire covered with various oxide layers of Bi2O3, Al2O3, HfO2, MgO, or AgOx by using non-local spin valve structures. The spin-flip probability, a ratio of momentum relaxation time to spin relaxation time at 10 K, exhibits a gradual increase with an atomic number of the oxide constituent elements, Mg, Al, Ag, and Hf. Surprisingly, the Bi2O3 capping was found to increase the probability by an order of magnitude compared with other oxide layers. This finding suggests the presence of an additional spin relaxation mechanism such as Rashba effect at the Ag/Bi2O3 interface, which cannot be explained by the simple Elliott-Yafet mechanism via phonon, impurity, and surface scatterings. The Ag/Bi2O3 interface may provide functionality as a spin to charge interconversion layer.
Plasmonic gain in long-range surface plasmon polariton waveguides bounded symmetrically by dye-doped polymer
Authors: Hahn Choloong , Song Seok Ho , Oh Cha Hwan , Berini Pierre
Published: September 2015

The plasmonic gain of a top-pumped active symmetric metal slab waveguide is investigated theoretically and experimentally. The structure consists of a thin Ag film cladded above and below by gain media (IR140-doped poly (methyl methacrylate)), and operating with long-range surface plasmon polaritons (LRSPPs) at near-infrared wavelengths. We consider the spatial distribution of the pump intensity and the position dependence of the dipole lifetime within the claddings when computing the LRSPP gain. We find that the bottom cladding provides significant gain to the LRSPP, despite the low pump transmittance through the Ag film, as long as the pump intensity is strong enough to saturate the gain material (∼4 MW/cm2). In this situation, the LRSPP gain is doubled compared to the case where the top cladding only is active. The LRSPP gain was measured in a fabricated structure using the variable stripe length method, yielding gmod = 16.7 cm−1 at a pump intensity of ∼4 MW/cm2. The measured LRSPP gain agrees very well with the computed value, implying that the bottom cladding provides significant gain to the mode. Active plasmonic devices based on the symmetric dielectric-metal-dielectric structure can be significantly more efficient by using gain layers as both the top and bottom claddings.
Voltage contrast X-ray photoelectron spectroscopy reveals graphene-substrate interaction in graphene devices fabricated on the C- and Si- faces of SiC
Authors: Aydogan Pinar , Arslan Engin , Cakmakyapan Semih , Ozbay Ekmel , Strupinski Wlodek , Suzer Sefik
Published: September 2015

We report on an X-ray photoelectron spectroscopy (XPS) study of two graphene based devices that were analyzed by imposing a significant current under +3 V bias. The devices were fabricated as graphene layers(s) on hexagonal SiC substrates, either on the C- or Si-terminated faces. Position dependent potential distributions (IR-drop), as measured by variations in the binding energy of a C1s peak are observed to be sporadic for the C-face graphene sample, but very smooth for the Si-face one, although the latter is less conductive. We attribute these sporadic variations in the C-face device to the incomplete electrical decoupling between the graphene layer(s) with the underlying buffer and/or substrate layers. Variations in the Si2p and O1s peaks of the underlayer(s) shed further light into the electrical interaction between graphene and other layers. Since the potential variations are amplified only under applied bias (voltage-contrast), our methodology gives unique, chemically specific electrical information that is difficult to obtain by other techniques.
Oblique collision of dust acoustic solitons in a strongly coupled dusty plasma
Authors: Boruah A. , Sharma S. K. , Bailung H. , Nakamura Y.
Published: September 2015

The oblique collision between two equal amplitude dust acoustic solitons is observed in a strongly coupled dusty plasma. The solitons are subjected to oblique interaction at different colliding angles. We observe a resonance structure during oblique collision at a critical colliding angle which is described by the idea of three wave resonance interaction modeled by Kadomtsev-Petviashvili equation. After collision, the solitons preserve their identity. The amplitude of the resultant wave formed during interaction is measured for different collision angles as well as for different colliding soliton amplitudes. At resonance, the maximum amplitude of the new soliton formed is nearly 3.7 times the initial soliton amplitude.
Reduction in the concentration of cation vacancies by proper Si-doping in the well layers of high AlN mole fraction AlxGa1–xN multiple quantum wells grown by metalorganic vapor phase epitaxy
Authors: Chichibu S. F. , Miyake H. , Ishikawa Y. , Furusawa K. , Hiramatsu K.
Published: September 2015

Appropriate-amount Si-doping in the well layers significantly improved the luminescence efficiency of Al0.68Ga0.32N/Al0.77Ga0.23N multiple quantum wells. To understand the mechanisms, spatio-time-resolved cathodoluminescence measurements and self-consistent Schrödinger-Poisson calculations were carried out. The increase in the luminescence lifetime at room temperature, which reflects the decrease in the concentration of nonradiative recombination centers (NRCs), was correlated with increased terrace width of Si-doped wells. The results suggest the importance of H3SiNH2 doping-reactant formation that gives rise to enhanced decomposition of NH3 and provides wetting conditions by surface Si-N bonds, which reduce the total energy and concentration of NRCs composed of cation vacancies.
Limited effectiveness of divers to mitigate ‘barrens’ formation by culling sea urchins while fishing for abalone
Authors: Sanderson J. C. , Ling S. D. , Dominguez J. G. , Johnson C. R.
Published: September 2015

Climate-driven incursion of the long-spined sea urchin (Centrostephanus rodgersii) in eastern Tasmania has prompted calls for strong management intervention given the urchins’ capacity to overgraze kelp beds and cause local collapse of valuable reef fisheries. We examined the effectiveness of commercial divers culling C. rodgersii while undertaking otherwise normal fishing for black-lip abalone (Haliotis rubra). Diver effort appears to be driven by fishing yield and not the opportunity to maximise numbers of urchins culled; the greatest culls occurred on shorter dives when abalone fishing was poor. Despite culling thousands of urchins, divers culled urchins only from within a small proportion of the total barrens patches on particular reefs. Thus, urchin density, size-frequency of barrens patches, and benthic community structure showed no detectable change relative to ‘no-cull’ control reefs. Nonetheless, divers were effective in culling urchins in the few patches they targeted, and these patches were quickly recolonised by canopy-forming kelps. Ongoing urchin culling by abalone divers will increase resilience of the kelp habitats on which the valuable abalone fishery depends, but only at highly localised spatial scales (10m). The effectiveness of this control strategy is dependent on sustainable local harvest of abalone warranting recurrent diver visitation to affected sites. However, abalone divers culling urchins while fishing are unlikely to control urchin densities at scales ≥102 m.
Active mixing of complex fluids at the microscale
Authors: Ober Thomas J. , Foresti Daniele , Lewis Jennifer A.
Published: September 2015

Significance

The ability to continuously mix complex fluids at the microscale depends on their flow rate, rheology, and mixing rate. New scaling relationships between mixer dimensions and operating conditions are derived and experimentally verified to create a framework for designing active microfluidic mixers that can efficiently homogenize a wide range of materials. Based on this understanding, active mixing printheads are designed and implemented for multimaterial printing of 3D architectures whose local composition and properties can be programmably tailored.
APTANI: a computational tool to select aptamers through sequence-structure motif analysis of HT-SELEX data
Authors: Caroli J. , Taccioli C. , De La Fuente A. , Serafini P. , Bicciato S.
Published: September 2015

Motivation: Aptamers are synthetic nucleic acid molecules that can bind biological targets in virtue of both their sequence and three-dimensional structure. Aptamers are selected using SELEX, Systematic Evolution of Ligands by EXponential enrichment, a technique that exploits aptamer-target binding affinity. The SELEX procedure, coupled with high-throughput sequencing (HT-SELEX), creates billions of random sequences capable of binding different epitopes on specific targets. Since this technique produces enormous amounts of data, computational analysis represents a critical step to screen and select the most biologically relevant sequences.

Results: Here, we present APTANI, a computational tool to identify target-specific aptamers from HT-SELEX data and secondary structure information. APTANI builds on AptaMotif algorithm, originally implemented to analyze SELEX data; extends the applicability of AptaMotif to HT-SELEX data and introduces new functionalities, as the possibility to identify binding motifs, to cluster aptamer families or to compare output results from different HT-SELEX cycles. Tabular and graphical representations facilitate the downstream biological interpretation of results.

Availability and implementation: APTANI is available at http://aptani.unimore.it.

Contact:  silvio.bicciato@unimore.it

Supplementary information:  Supplementary data are available at Bioinformatics online.
Eyelid Necrosis and Secondary Cicatrical Ectropion Secondary to Levamisole-Associated Vasculitis
Authors: Ramesh Sathyadeepak , Sobti Deepak , Mancini Ronald
Published: September 2015

A 56-year-old female presented with eyelid necrosis secondary to systemic levamisole-induced vasculitis. Skin biopsy revealed necrotic epidermis with small-vessel thrombosis, fibrinoid reaction, and neutrophilic infiltration of vessel walls in the dermis with +pANCA. She was treated with plasmapheresis and steroids. Six months later, she developed severe, symptomatic cicatrical ectropion with marked anterior lamellar shortage and middle lamellar contracture. Scar release in the middle lamellar plane with lateral tarsal strip procedures was performed, with full-thickness skin grafts from the upper eyelids. She remained fully epithelialized postoperatively with improvement in symptoms, although she incomplete graft take due to her eyelid necrosis and compromised dermal blood supply.
Protease-Activated Receptor 1 Inhibitors: Novel Antiplatelet Drugs in Prevention of Atherothrombosis
Authors: Al-Khafaji Khalid , Mutyala Monica , Al-Khafaji Nawfal , Harper Yenal , Ismail Imtiaz , Hakim Hosam , Arora Rohit R.
Published: September 2015

Protease-activated receptor (PAR)-1 inhibitors have recently become popular in the use of atherosclerosis among clinicians. Atherosclerosis can cause cardiovascular and cerebrovascular events leading to one of the major causes of mortality worldwide. Thrombin-mediated platelets can cause atherosclerotic plaques, and these platelets are activated by thrombin through the PAR-1. Vorapaxar and atopaxar are novel antiplatelet drugs that inhibit the thrombin-induced platelet activation by antagonizing the PAR-1. The objective of this article is to review the mechanism of action of vorapaxar and atopaxar and explain the rationale for using them in atherothrombosis patients including myocardial infarction, peripheral arterial disease, and stroke.
Novel Associations Between Major Histocompatibility Complex and Pediatric‐onset Inflammatory Bowel Disease
Authors: Kolho Kaija‐Leena , Paakkanen Riitta , Lepistö Anna , Wennerstöm Annika , Meri Seppo , Lokki Marja‐Liisa
Published: September 2015

Purpose:

Major histocompatibility complex (MHC) genes have been widely studied in adult inflammatory bowel disease (IBD), but data on MHC genes are scarce in pediatric IBD. This study focused on MHC association of genes with pediatric‐onset IBD and its different phenotypes.

Methods:

Blood samples of 103 patients with pediatric IBD (Crohn disease or ulcerative colitis) were collected at Children's Hospital, University of Helsinki, Finland. HLA‐A, ‐B, ‐DRB1 alleles and complement C4A and C4B gene copy numbers were determined and constructed into haplotypes by a Bayesian algorithm (PHASE). A general population cohort (n = 149) served as a control. HLA‐alleles and C4 deficiency frequencies were compared between patients and controls with χ2‐squared and Fisher exact test with Bonferroni correction (Pcorr).

Results:

One MHC haplotype HLA‐A*03; HLA‐B*07; 1 C4A gene; 1 C4B gene; HLA‐DRB1*15 was more common in Crohn disease and ulcerative colitis than in controls (7/61, 11.5%, 6/42, 14.3% and 1/149, 0.7%, respectively, odds ratio (OR) = 19.19, 95% CI 2.31–159.57, Pcorr = 0.004 for Crohn disease vs controls and OR = 24.67, 95% CI 2.88–211.36, Pcorr = 0.002 for ulcerative colitis vs controls). Two MHC markers were associated with clinical characteristics. HLA‐DRB1*01 was more common in patients with milder disease course, that is, no need for anti–tumor necrosis factor (TNF)‐α medication (18/32, 56.2% vs 19/71, 26.8% without and with anti–TNF‐α medication, respectively, OR = 0.28, 95% CI 0.12–0.68, Pcorr = 0.032). C4B deficiency (<2 C4B genes) was associated with complicated recovery after surgery (12/16, 75.0% vs 4/16, 25.0%, respectively, OR = 9.00, 95% CI 1.82–44.59, Pcorr = 0.025).

Conclusions:

One MHC haplotype is strongly linked with pediatric‐onset IBD, whereas the need for immunomodulatory therapy and surgery outcome associates with other distinct MHC gene markers.
Multiscale model of a freeze–thaw process for tree sap exudation
Authors: Graf Isabell , Ceseri Maurizio , Stockie John M.
Published: September 2015

Sap transport in trees has long fascinated scientists, and a vast literature exists on experimental and modelling studies of trees during the growing season when large negative stem pressures are generated by transpiration from leaves. Much less attention has been paid to winter months when trees are largely dormant but nonetheless continue to exhibit interesting flow behaviour. A prime example is sap exudation, which refers to the peculiar ability of sugar maple (
Acer saccharum
) and related species to generate positive stem pressure while in a leafless state. Experiments demonstrate that ambient temperatures must oscillate about the freezing point before significantly heightened stem pressures are observed, but the precise causes of exudation remain unresolved. The prevailing hypothesis attributes exudation to a physical process combining freeze–thaw and osmosis, which has some support from experimental studies but remains a subject of active debate. We address this knowledge gap by developing the first mathematical model for exudation, while also introducing several essential modifications to this hypothesis. We derive a multiscale model consisting of a nonlinear system of differential equations governing phase change and transport within wood cells, coupled to a suitably homogenized equation for temperature on the macroscale. Numerical simulations yield stem pressures that are consistent with experiments and provide convincing evidence that a purely physical mechanism is capable of capturing exudation.
Bifunctional crosslinking ligands for transthyretin
Authors: Mangione P. Patrizia , Deroo Stéphanie , Ellmerich Stephan , Bellotti Vittorio , Kolstoe Simon , Wood Stephen P. , Robinson Carol V. , Smith Martin D. , Tennent Glenys A. , Broadbridge Robert J. , Council Claire E. , Thurston Joanne R. , Steadman Victoria A. , Vong Antonio K. , Swain Christopher J. , Pepys Mark B. , Taylor Graham W.
Published: September 2015

Wild-type and variant forms of transthyretin (TTR), a normal plasma protein, are amyloidogenic and can be deposited in the tissues as amyloid fibrils causing acquired and hereditary systemic TTR amyloidosis, a debilitating and usually fatal disease. Reduction in the abundance of amyloid fibril precursor proteins arrests amyloid deposition and halts disease progression in all forms of amyloidosis including TTR type. Our previous demonstration that circulating serum amyloid P component (SAP) is efficiently depleted by administration of a specific small molecule ligand compound, that non-covalently crosslinks pairs of SAP molecules, suggested that TTR may be also amenable to this approach. We first confirmed that chemically crosslinked human TTR is rapidly cleared from the circulation in mice. In order to crosslink pairs of TTR molecules, promote their accelerated clearance and thus therapeutically deplete plasma TTR, we prepared a range of bivalent specific ligands for the thyroxine binding sites of TTR. Non-covalently bound human TTR–ligand complexes were formed that were stable
in vitro
and
in vivo
, but they were not cleared from the plasma of mice
in vivo
more rapidly than native uncomplexed TTR. Therapeutic depletion of circulating TTR will require additional mechanisms.
Social signals and algorithmic trading of Bitcoin
Authors: Garcia David , Schweitzer Frank
Published: September 2015

The availability of data on digital traces is growing to unprecedented sizes, but inferring actionable knowledge from large-scale data is far from being trivial. This is especially important for computational finance, where digital traces of human behaviour offer a great potential to drive trading strategies. We contribute to this by providing a consistent approach that integrates various datasources in the design of algorithmic traders. This allows us to derive insights into the principles behind the profitability of our trading strategies. We illustrate our approach through the analysis of Bitcoin, a cryptocurrency known for its large price fluctuations. In our analysis, we include economic signals of volume and price of exchange for USD, adoption of the Bitcoin technology and transaction volume of Bitcoin. We add social signals related to information search, word of mouth volume, emotional valence and opinion polarization as expressed in tweets related to Bitcoin for more than 3 years. Our analysis reveals that increases in opinion polarization and exchange volume precede rising Bitcoin prices, and that emotional valence precedes opinion polarization and rising exchange volumes. We apply these insights to design algorithmic trading strategies for Bitcoin, reaching very high profits in less than a year. We verify this high profitability with robust statistical methods that take into account risk and trading costs, confirming the long-standing hypothesis that trading-based social media sentiment has the potential to yield positive returns on investment.