bluuebunny/crossref_metadata_2025 huggingface dataset:
Down-regulation of cyclin G2 by insulin, IGF-I (insulin-like growth factor 1) and X10 (AspB10 insulin): role in mitogenesis
Authors: Svendsen Angela M. , Winge Sofia B. , Zimmermann Maike , Lindvig Anne B. , Warzecha Caroline B. , Sajid Waseem , Horne Mary C. , De Meyts Pierre
Published: September 2013

The mechanisms whereby insulin analogues may cause enhanced mitogenicity through activation of either the IR (insulin receptor) or the IGF-IR (insulin-like growth factor 1 receptor) are incompletely understood. We demonstrate that in L6 myoblasts expressing only IGF-IRs as well as in the same cells overexpressing the IR, IGF-I (insulin-like growth factor 1), insulin and X10 (AspB10 insulin) down-regulate the mRNA expression level of the cell cycle inhibitor cyclin G2, as measured by qRT-PCR (quantitative reverse transcription–PCR), and induce cell growth measured by [6-3H]thymidine incorporation into DNA. Western blotting showed a marked down-regulation of cyclin G2 at the protein level in both cell lines. Overexpression of cyclin G2 in the two cell lines diminished the mitogenic effect of all three ligands. The use of specific inhibitors indicated that both the MAPK (mitogen-activated protein kinase) and the PI3K (phosphoinositide 3-kinase) pathways mediate the down-regulation of Ccng2. The down-regulation of CCNG2 by the three ligands was also observed in other cell lines: MCF-7, HMEC, Saos-2, R−/IR and INS-1. These results indicate that regulation of cyclin G2 is a key mechanism whereby insulin, insulin analogues and IGF-I stimulate cell proliferation.
Angiotensin II and the ERK pathway mediate the induction of leptin by mechanical cyclic stretch in cultured rat neonatal cardiomyocytes
Authors: Chiu Chiung-Zuan , Wang Bao-Wei , Shyu Kou-Gi
Published: September 2013

Mechanical cyclic stretch of cardiomyocytes causes cardiac hypertrophy through cardiac-restricted gene expression. Leptin induces cardiomyocyte hypertrophy in response to myocardial stress. In the present study, we evaluated the expression of leptin under cyclic stretch and its role in regulating genetic transcription in cardiomyocytes. Cultured rat neonatal cardiomyocytes were subjected to cyclic stretch, and the expression levels of leptin, ROS (reactive oxygen species) and AngII (angiotensin II) were evaluated. Signal transduction inhibitors were used to identify the pathway of leptin expression. EMSAs were used to identify the binding of leptin/STAT3 (signal transducer and activator of transcription 3) and luciferase assays were used to identify the transcription of leptin in cardiomyocytes. The study also used an in vivo model of AV (aortocaval) shunt in rats to investigate leptin, ROS and AngII expression. Leptin and leptin receptor levels increased after cyclic stretch with the earlier expression of AngII and ROS. Leptin expression was suppressed by AngII receptor blockers, an ROS scavenger [NAC (N-acetylcysteine)], an ERK (extracellular-signal-regulated kinase) pathway inhibitor (PD98059) and ERK siRNA. Binding of leptin/STAT3 was identified by EMSAs, and luciferase assays confirmed the transcription of leptin in neonatal cardiomyocytes after cyclic stretch. Increased MHC (myosin heavy chain) expression and [3H]-proline incorporation in cardiomyocytes was detected after cyclic stretch, which were inhibited by leptin siRNA and NAC. The in vivo model of AV shunt also demonstrated increased levels of plasma and myocardial leptin, ROS and AngII expression after cyclic stretch. Mechanical cyclic stretch in cardiomyocytes increased leptin expression mediated by the induction of AngII, ROS and the ERK pathway to cause cardiomyocyte hypertrophy. Myocardial hypertrophy can be identified by increased transcriptional activity and an enhanced hypertrophic phenotype of cardiomyocytes.
Efficient scaling registration algorithm for partially overlapping point sets
Authors: Ma Liang , Zhu Jihua
Published: September 2013

An efficient iterative closest point (ICP) variant is proposed for solving the scaling registration of partially overlapping point sets. By adopting the backward distance measurement and the overlapping rate, the aforementioned registration problem can be formulated as a least squares function, which can be solved in the iterative manner, inspired by the ICP algorithm. During each iteration, the inverse correspondences are set up to compute the overlapping percentage, scale and rigid transformation simultaneously between two m‐D point sets. The experimental results clearly demonstrate its superior performances over previous approaches.
AlGaN/GaN HEMTs on diamond substrate with over 7 W/mm output power density at 10 GHz
Authors: Dumka D.C. , Chou T.M. , Faili F. , Francis D. , Ejeckam F.
Published: September 2013

Record RF performance of AlGaN/GaN high electron mobility transistors (HEMTs) on a diamond substrate with over 7 W/mm output power density at 10 GHz is reported. It is achieved along with the peak power‐added‐efficiency over 46% and power gain over 11 dB for 2 × 100 µm gate‐width HEMTs at 40 V drain bias. Device wafers are prepared by first removing the host Si (111) substrate and nitride transition layers beneath the channel, depositing a 50 nm dielectric onto the exposed GaN buffer, and finally growing 100 µm of a chemical vapour deposition diamond onto the dielectric adhering to the epitaxial AlGaN/GaN. This approach enables the active GaN channel to be brought within 1 µm of the diamond substrate. Test HEMTs are fabricated using a dielectrically defined 0.25 µm gate length process.
Effect of output capacitor ESR on dynamic performance of voltage‐mode hysteretic controlled buck converter
Authors: Bao B.C. , Yang J. , Xu J.P. , Zhang X. , Zhou G.H.
Published: September 2013

Different types of capacitors have different parameters, e.g. equivalent series resistance (ESR) and capacitance. In switching DC–DC converters with voltage‐mode (VM) hysteretic control, the output capacitor ESR has a significant effect on dynamic performance. In this reported work, two critical conditions of the output capacitor ESR for mode shifting and normal operation of the VM hysteretic controlled buck converter are derived. These results, verified by circuit simulations, illustrate that the larger output capacitor ESR is necessary for the converter operating normally; otherwise, the converter operates abnormally.
Prediction‐based picture prioritisation method for hierarchical B‐structure of high efficiency video coding
Authors: Ryu E.‐S.
Published: September 2013

The current high efficiency video coding standard does not provide any syntax for prioritising pictures in the same temporal level of hierarchical structure. Thus, this reported work reveals how the current uniform prioritisation method in hierarchical B pictures can cause severe video quality degradation when video packets are transmitted over error‐prone channels. To solve this problem, a new picture prioritisation method using prediction information is proposed.
High reliability sensing circuit for deep submicron spin transfer torque magnetic random access memory
Authors: Kang Wang , Zhao Weisheng , Klein J.‐O. , Zhang Youguang , Chappert C. , Ravelosona D.
Published: September 2013

A high reliability offset‐tolerant sensing circuit is presented for deep submicron spin transfer torque magnetic tunnel junction (STT‐MTJ) memory. This circuit, using a triple‐stage sensing operation, is able to tolerate the increased process variations as technology scales down to the deep submicron nodes, thus improving significantly the sensing margin. Meanwhile, it clamps the bit‐line voltage to a predefined small bias voltage to avoid any read disturbance during the sensing operations. By using the STMicroelectronics CMOS 40 nm design kit and a precise STT‐MTJ compact model, Monte Carlo simulations have been carried out to evaluate its sensing performance.
Harvesting energy at resonance from standing waves on polymer piezoelectric ribbon‐like membrane
Authors: Prakash K. , Mahidhar R. , Sambandan S.
Published: September 2013

Energy harvesting from standing waves on ribbon like membranes of polyvinylidene fluoride is investigated. At resonance, the energy density of 2 mW/gm suffices to power a ring oscillator load. A scaling law for harvestable energy as a function of ribbon length is developed.
Strategic placement of distribution network operator owned wind turbines by using market‐based optimal power flow
Authors: Mokryani Geev , Siano Pierluigi
Published: September 2013

In this study, a new methodology to optimally allocate wind turbines (WTs) in distribution networks is proposed. A market‐based optimal power flow is used to determine the optimal numbers and capacities of WTs in a way that maximises the social welfare. The method is conceived for distribution network operators to strategically allocate WTs in distribution networks. The proposed method by yielding location‐specific WTs capacity settlement both in terms of cost reduction and consumers’ benefits is consistent with distribution network topology and constraints. The method is solved by using step‐controlled primal dual interior point method considering network constraints. The effectiveness of the proposed method is demonstrated with two radial distribution systems including an 84‐bus 11.4 kV and a 69‐bus 11 kV network.
Inkjet-based deposition of polymer thin films enabled by a lubrication model incorporating nano-scale parasitics
Authors: Singhal Shrawan , Meissl Mario J. , Bonnecaze Roger T. , Sreenivasan S. V.
Published: September 2013

Thin film lubrication theory has been widely used to model multi-scale fluid phenomena. Variations of the same have also found application in fluid-based manufacturing process steps for micro- and nano-scale devices over large areas where a natural disparity in length scales exists. Here, a novel inkjet material deposition approach has been enabled by an enhanced thin film lubrication theory that accounts for nano-scale substrate parasitics. This approach includes fluid interactions with a thin flexible superstrate towards a new process called Jet and Coat of Thin-films (JCT). Numerical solutions of the model have been verified, and also validated against controlled experiments of polymer film deposition with good agreement. Understanding gleaned from the experimentally validated model has then been used to facilitate JCT process synthesis resulting in substantial reduction in the influence of parasitics and a concomitant improvement in the film thickness uniformity. Polymer films ranging from 20 to 500 nm mean thickness have been demonstrated with standard deviation of less than 2% of the mean film thickness. The JCT process offers advantages over spin coating which is not compatible with roll-to-roll processing and large area processing for displays. It also improves over techniques such as knife edge coating, slot die coating, as they are limited in the range of thicknesses of films that can be deposited without compromising uniformity.
One-dimensional embedded cluster approach to modeling CdS nanowires
Authors: Buckeridge J. , Bromley S. T. , Walsh A. , Woodley S. M. , Catlow C. R. A. , Sokol A. A.
Published: September 2013

We present an embedded cluster model to treat one-dimensional nanostructures, using a hybrid quantum mechanical/molecular mechanical (QM/MM) approach. A segment of the nanowire (circa 50 atoms) is treated at a QM level of theory, using density functional theory (DFT) with a hybrid exchange-correlation functional. This segment is then embedded in a further length of wire, treated at an MM level of theory. The interaction between the QM and MM regions is provided by an embedding potential located at the interface. Point charges are placed beyond the ends of the wire segment in order to reproduce the Madelung potential of the infinite system. We test our model on the ideal system of a CdS linear chain, benchmarking our results against calculations performed on a periodic system using a plane-wave DFT approach, with electron exchange and correlation treated at the same level of approximation in both methods. We perform our tests on pure CdS and, importantly, the system containing a single In or Cu impurity. We find excellent agreement in the determined electronic structure using the two approaches, validating our embedded cluster model. As the hybrid QM/MM model avoids spurious interactions between charged defects, it will be of benefit to the analysis of the role of defects in nanowire materials, which is currently a major challenge using a plane-wave DFT approach. Other advantages of the hybrid QM/MM approach over plane-wave DFT include the ability to calculate ionization energies with an absolute reference and access to high levels of theory for the QM region which are not incorporated in most plane-wave codes. Our results concur with available experimental data.
Radial scale effect on the performance of low-power cylindrical Hall plasma thrusters
Authors: Seo Mihui , Lee Jongsub , Seon Jongho , June Lee Hae , Choe Wonho
Published: September 2013

Investigation of the radial scale effect on low-power cylindrical Hall thrusters has been undertaken by comparing the thrusters with three different channel diameters of 28, 40, and 50 mm. The investigation found that both the anode efficiency and the thrust of the larger thruster are higher as the anode power is raised. On the other hand, higher current and propellant utilizations are achieved for the smaller thruster, which is due to higher neutral density and better electron confinement. The large plume angle of the small cylindrical Hall thruster causes thrust loss, resulting in the reduction of anode efficiency.
Synchronization of finite-size particles by a traveling wave in a cylindrical flow
Authors: Melnikov D. E. , Pushkin D. O. , Shevtsova V. M.
Published: September 2013

Motion of small finite-size particles suspended in a cylindrical thermocapillary flow with an azimuthally traveling wave is studied experimentally and numerically. At certain flow regimes the particles spontaneously align in dynamic accumulation structures (PAS) of spiral shape. We find that long-time trajectories of individual particles in this flow fall into three basic categories that can be described, borrowing the dynamical systems terminology, as the stable periodic, the quasiperiodic, and the quasistable periodic orbits. Besides these basic types of orbits, we observe the “doubled” periodic orbits and shuttle-like particle trajectories. We find that ensembles of particles having periodic orbits give rise to one-dimensional spiral PAS, while ensembles of particles having quasiperiodic orbits form two-dimensional PAS of toroidal shape. We expound the reasons why these types of orbits and the emergence of the corresponding accumulation structures should naturally be anticipated based on the phase locking theory of PAS formation. We give a further discussion of PAS features, such as the finite thickness of PAS spirals and the probable scenarios of the spiral PAS destruction. Finally, in numerical simulations of inertial particles we observe formation of the spiral structures corresponding to the 3:1 “resonance” between the particle turnover frequency and the wave oscillations frequency, thus confirming another prediction of the phase locking theory. In view of the generality of the arguments involved, we expect the importance of this structure-forming mechanism to go far beyond the realm of the laboratory-friendly thermocapillary flows.
Ultrafast x-ray photoelectron spectroscopy in the microsecond time domain
Authors: Höfert O. , Gleichweit C. , Steinrück H.-P. , Papp C.
Published: September 2013

We introduce a new approach for ultrafast in situ high-resolution X-ray photoelectron spectroscopy (XPS) to study surface processes and reaction kinetics on the microsecond timescale. The main idea is to follow the intensity at a fixed binding energy using a commercial 7 channeltron electron analyzer with a modified signal processing setup. This concept allows for flexible switching between measuring conventional XP spectra and ultrafast XPS. The experimental modifications are described in detail. As an example, we present measurements for the adsorption and desorption of CO on Pt(111), performed at the synchrotron radiation facility BESSY II, with a time resolution of 500 μs. Due to the ultrafast measurements, we are able to follow adsorption and desorption in situ at pressures of 2 × 10−6 mbar and temperatures up to 500 K. The data are consistently analyzed using a simple model in line with data obtained with conventional fast XPS at temperatures below 460 K. Technically, our new approach allows measurement on even shorter timescales, down to 20 μs.
Broadband anisotropy of femtosecond laser induced nanogratings in fused silica
Authors: Beresna M. , Gecevičius M. , Lancry M. , Poumellec B. , Kazansky P. G.
Published: September 2013

We demonstrate operation of femtosecond laser imprinted birefringent optical elements from 200 to 2100 nm. The absorption losses in the UV can substantially reduced by the post-annealing of the structures. The birefringence is also accompanied with the weak dichroism which is related to the polarization dependent scattering. The transition from the isotropic modification to nanostructures is accompanied by occurrence of ODC(II) defect.
Mapping variable ring polymer molecular dynamics: A path-integral based method for nonadiabatic processes
Authors: Ananth Nandini
Published: September 2013

We introduce mapping-variable ring polymer molecular dynamics (MV-RPMD), a model dynamics for the direct simulation of multi-electron processes. An extension of the RPMD idea, this method is based on an exact, imaginary time path-integral representation of the quantum Boltzmann operator using continuous Cartesian variables for both electronic states and nuclear degrees of freedom. We demonstrate the accuracy of the MV-RPMD approach in calculations of real-time, thermal correlation functions for a range of two-state single-mode model systems with different coupling strengths and asymmetries. Further, we show that the ensemble of classical trajectories employed in these simulations preserves the Boltzmann distribution and provides a direct probe into real-time coupling between electronic state transitions and nuclear dynamics.
Improved renormalization group theory for critical asymmetry of fluids
Authors: Wang Long , Zhao Wei , Wu Liang , Li Liyan , Cai Jun
Published: September 2013

We develop an improved renormalization group (RG) approach incorporating the critical vapor-liquid equilibrium asymmetry. In order to treat the critical asymmetry of vapor-liquid equilibrium, the integral measure is introduced in the Landau-Ginzbug partition function to achieve a crossover between the local order parameter in Ising model and the density of fluid systems. In the implementation of the improved RG approach, we relate the integral measure with the inhomogeneous density distribution of a fluid system and combine the developed method with SAFT-VR (statistical associating fluid theory of variable range) equation of state. The method is applied to various fluid systems including square-well fluid, square-well dimer fluid and real fluids such as methane (CH4), ethane (C2H6), trifluorotrichloroethane (C2F3Cl3), and sulfur hexafluoride (SF6). The descriptions of vapor-liquid equilibria provided by the developed method are in excellent agreement with simulation and experimental data. Furthermore, the improved method predicts accurate and qualitatively correct behavior of coexistence diameter near the critical point and produces the non-classical 3D Ising criticality.
Computational studies of the glass-forming ability of model bulk metallic glasses
Authors: Zhang Kai , Wang Minglei , Papanikolaou Stefanos , Liu Yanhui , Schroers Jan , Shattuck Mark D. , O'Hern Corey S.
Published: September 2013

Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate Rc below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing Rc, and thus good glass-formers possess small values of Rc. We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change Rc significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ∼1011 K/s, which is several orders of magnitude higher than Rc for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.
Temperature-dependent characteristics of junctionless bulk transistor
Authors: Han Ming-Hung , Chen Hung-Bin , Yen Shiang-Shiou , Shao Chi-Shen , Chang Chun-Yen
Published: September 2013

The temperature-dependent performance, including drain current (Id) and gate capacitance (Cgg) of multi-gate junctionless (JL) bulk transistor for temperature (T) ranging from 150 K to 500 K, was investigated using 3D thermodynamic quantum-corrected device simulation. The combination effect of impurity scattering and phonon scattering is observed owing to the different temperature-dependent of mobility at low and high temperature. Since the Cgg of the JL device consists of a series combination of oxide capacitance (Cox) and semiconductor channel capacitance (CS) due to bulk conduction of the current, the Cgg at on-state (Vg = 1 V) shows much sensitive to the temperature than a conventional inversion-mode transistor.
Modeling of high contrast partially electroded resonators by means of a polynomial approach
Authors: Rabotovao P. M. , Ratolojanahary F. E. , Lefebvre J. E. , Raherison A. , Elmaimouni L. , Gryba T. , Yu J. G.
Published: September 2013

This work presents the modeling of high contrast partially electroded resonators by means of a polynomial approach. This method allows easily solving the equations that govern the structure. The boundary, symmetry, and continuity conditions are automatically incorporated into the equations of motion by the use of delta functions for the variables stress (T) and electric displacement (D) and appropriate analytical expression forms for the independent variables, mechanical displacements (u), and electric potential (ϕ). Structure symmetry was used to reduce the number of unknowns. For the zinc oxide (ZnO) resonator in extreme geometrical cases (thin plate and bar cases), a good agreement was obtained between the results of the proposed polynomial approach and those of an analytical approach for both the modal and harmonic analyses. The proposed polynomial approach was used to calculate the 2D resonator electrical admittance (full and partial metallization) near the 1D thickness fundamental mode, and the results highlight the presence of spurious modes. Influence of the metallization rate on the number of spurious modes in the bandwidth is studied. This model can also easily calculate the electromechanical coupling coefficient and the field profiles. Illustrations for both electromechanical coupling coefficient and particle displacement profiles are given for aluminium nitride (AlN), lead zirconate titanate, and ZnO resonators.
Zinc oxide and metal phthalocyanine based hybrid P-N junction diodes
Authors: Singh Budhi , Ghosh Subhasis
Published: September 2013

Hybrid p-n junction diode based on zinc oxide (ZnO) and metal phthalocyanine (MePc) has been demonstrated using highly conducting Al doped ZnO as transparent electrode. Three different MePcs: copper phthalocyanine, zinc phthalocyanine (ZnPc), and cobalt phthalocyanine are used as p-type layer in hybrid p-n junction. It is found that most desirable performance can be achieved in ZnO/ZnPc based hybrid p-n junction. The depletion region in hybrid p-n junctions has been measured using current-voltage and capacitance-voltage characteristics.
An improved semiclassical theory of radical pair recombination reactions
Authors: Manolopoulos D. E. , Hore P. J.
Published: September 2013

We present a practical semiclassical method for computing the electron spin dynamics of a radical in which the electron spin is hyperfine coupled to a large number of nuclear spins. This can be used to calculate the singlet and triplet survival probabilities and quantum yields of radical recombination reactions in the presence of magnetic fields. Our method differs from the early semiclassical theory of Schulten and Wolynes [J. Chem. Phys. 68, 3292 (1978)] in allowing each individual nuclear spin to precess around the electron spin, rather than assuming that the hyperfine coupling-weighted sum of nuclear spin vectors is fixed in space. The downside of removing this assumption is that one can no longer obtain a simple closed-form expression for the electron spin correlation tensor: our method requires a numerical calculation. However, the computational effort increases only linearly with the number of nuclear spins, rather than exponentially as in an exact quantum mechanical calculation. The method is therefore applicable to arbitrarily large radicals. Moreover, it approaches quantitative agreement with quantum mechanics as the number of nuclear spins increases and the environment of the electron spin becomes more complex, owing to the rapid quantum decoherence in complex systems. Unlike the Schulten-Wolynes theory, the present semiclassical theory predicts the correct long-time behaviour of the electron spin correlation tensor, and it therefore correctly captures the low magnetic field effect in the singlet yield of a radical recombination reaction with a slow recombination rate.
Single-shot readout of a superconducting flux qubit with a flux-driven Josephson parametric amplifier
Authors: Lin Z. R. , Inomata K. , Oliver W. D. , Koshino K. , Nakamura Y. , Tsai J. S. , Yamamoto T.
Published: September 2013

We report single-shot readout of a superconducting flux qubit by using a flux-driven Josephson parametric amplifier (JPA). After optimizing the readout power, gain of the JPA, and timing of the data acquisition, we observe the Rabi oscillations with a contrast of 74%, which is mainly limited by the bandwidth of the JPA and the energy relaxation of the qubit. The observation of quantum jumps between the qubit eigenstates under continuous monitoring indicates the nondestructiveness of the readout scheme.
Irradiation-induced composition patterns in binary solid solutions
Authors: Dubey Santosh , El-Azab Anter
Published: September 2013

A theoretical/computational model for the irradiation-driven compositional instabilities in binary solid solutions has been developed. The model is suitable for investigating the behavior of structural alloys and metallic nuclear fuels in a reactor environment as well as the response of alloy thin films to ion beam irradiation. The model is based on a set of reaction-diffusion equations for the dynamics of vacancies, interstitials, and lattice atoms under irradiation. The dynamics of these species includes the stochastic generation of defects by collision cascades as well as the defect reactions and diffusion. The atomic fluxes in this model are derived based on the transitions of lattice defects. The set of reaction-diffusion equations are stiff, hence a stiffly stable method, also known as the Gear method, has been used to numerically approximate the equations. For the Cu-Au alloy in the solid solution regime, the model results demonstrate the formation of compositional patterns under high-temperature particle irradiation, with Fourier space properties (Fourier spectrum, average wavelength, and wavevector) depending on the cascade damage characteristics, average composition, and irradiation temperature.
Glassy domain wall matter in KH2PO4 crystal: Field-induced transition
Authors: Kumar Jitender , Awasthi A. M.
Published: September 2013

We have investigated the domain wall (DW) dielectric response of potassium dihydrogen phosphate (KH2PO4) crystal under 0–500 V dc-bias electric field. Activated DW-contribution onsets freezing at Tf(ω, V), some 30 K below the ferroelectric TC; timescale τf(T, V) exhibiting Vogel-Fulcher (VFT) divergence. Sharply distinct low- and high-field behaviors of TC(V), DW-Tg(V), VFT-T0(V), barrier energy Ua(V), and DW glass-fragility m(V) signify a field-induced transition from randomly pinned/vitreous to clustered/glass-ceramic phases of domain wall matter. Field-hysteresis (ε′poled>ε′unpoled) observed at high dc-bias indicates coexistent unclustered DW phase, quenched-in during the field-cooling. We construct a paradigm T-E phase diagram depicting the complex glassy patterns of domain wall matter.
Thermal emission from large area chemical vapor deposited graphene devices
Authors: Luxmoore I. J. , Adlem C. , Poole T. , Lawton L. M. , Mahlmeister N. H. , Nash G. R.
Published: September 2013

The spatial variation of thermal emission from large area graphene grown by chemical vapor deposition, transferred onto SiO2/Si substrates and fabricated into field effect transistor structures, has been investigated using infra-red microscopy. A peak in thermal emission occurs, the position of which can be altered by reversal of the current direction. The experimental results are compared with a one dimensional finite element model, which accounts for Joule heating and electrostatic effects, and it is found that the thermal emission is governed by the charge distribution in the graphene and maximum Joule heating occurs at the point of minimum charge density.
Thermal conductivity of suspended few-layer graphene by a modified T-bridge method
Authors: Jang W. , Bao W. , Jing L. , Lau C. N. , Dames C.
Published: September 2013

We measured the in-plane thermal conductivity of suspended few-layer graphene flakes by a modified T-bridge technique from 300 K to below 100 K. The thermal conductivities at room temperature are 389, 344, 302, and 596 W/m K for 2-, 3-, 4-, and 8-layer graphene, respectively. The thinner (2-, 3-, 4-layer) graphene samples did not show any clear thickness dependence, while the thicker (8-layer) sample clearly has higher thermal conductivity. In situ current annealing was used to remove polymer residues from the central portion of the 3- and 8-layer graphene samples, as confirmed by electrical transport measurements and post-experiment characterization by Raman and scanning electron microscopy, although some residues still remained near both ends (heater and heat sink). Comparing the 2, 3, and 4-layer samples suggests the annealing had little effect near room temperature but leads to increased thermal conductivity at low temperature. These results also show that the thermal conductivities of suspended few-layer graphene are higher than those of encased few-layer graphene of similar thickness measured previously [Jang et al., Nano Lett. 10, 3909 (2010)].
Electrode size dependence of piezoelectric response of lead zirconate titanate thin films measured by double beam laser interferometry
Authors: Sivaramakrishnan S. , Mardilovich P. , Mason A. , Roelofs A. , Schmitz-Kempen T. , Tiedke S.
Published: September 2013

The electrode size dependence of the effective large signal piezoelectric response coefficient (d33,f) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed electrode size dependence is shown to arise from a contribution from the substrate. The intrinsic PZT contribution to d33,f is independent of electrode size and is equal to the theoretical value derived assuming a rigid substrate. The substrate contribution is strongly dependent on the relative size of the electrode with respect to the substrate thickness. For electrode sizes larger than the substrate thickness, the substrate contribution is positive and for electrode sizes smaller than the substrate thickness, the substrate contribution is negative. In the case of silicon substrates, if the electrode size is equal to the substrate thickness, the substrate contribution vanishes, and the measured value of d33,f is equal to the theoretical value under the rigid substrate assumption.
Structure and magnetic properties of ultra thin textured EuO films on graphene
Authors: Klinkhammer Jürgen , Förster Daniel F. , Schumacher Stefan , Oepen Hans P. , Michely Thomas , Busse Carsten
Published: September 2013

We present a straightforward and reproducible method to grow stoichiometric and single phase (100) textured EuO thin films on epitaxial graphene. Depending on coverage, either separated EuO grains or fully closed layers can be prepared. Room temperature preparation followed by annealing in Eu vapor leads to a random distribution of the in-plane orientation, whereas growth under distillation conditions at 720 K induces a fixed orientation with respect to the substrate. Magneto-optical Kerr effect (MOKE) shows that the films are ferromagnetic with an enhanced Curie temperature.
Optical constants and dispersion energy parameters of NiO thin films prepared by radio frequency magnetron sputtering technique
Authors: Usha K. S. , Sivakumar R. , Sanjeeviraja C.
Published: September 2013

In this paper, we report on rf power induced change in the structural and optical properties of nickel oxide (NiO) thin films deposited onto glass substrates by rf magnetron sputtering technique. The crystallinity of the film was found to increase with increasing rf power and the deposited film belong to cubic phase. The maximum optical transmittance of 95% was observed for the film deposited at 100 W. The slight shift in transmission threshold towards higher wavelength region with increasing rf power revealed the systematic reduction in optical energy band gap (3.93 to 3.12 eV) of the films. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal dispersion in the transparent region. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion parameters, dielectric constants, relaxation time, and optical non-linear susceptibility were evaluated. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.
Benchmarking gyrokinetic simulations in a toroidal flux-tube
Authors: Chen Y. , Parker S. E. , Wan W. , Bravenec R.
Published: September 2013

A flux-tube model is implemented in the global turbulence code GEM [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 839 (2007)] in order to facilitate benchmarking with Eulerian codes. The global GEM assumes the magnetic equilibrium to be completely given. The initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, etc.) to be equal to the values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. This implementation shows disagreement with Eulerian codes in linear simulations. An alternative flux-tube model based on a complete local equilibrium solution of the Grad-Shafranov equation [J. Candy, Plasma Phys. Controlled Fusion 51, 105009 (2009)] is then implemented. This results in better agreement between Eulerian codes and the particle-in-cell (PIC) method. The PIC algorithm based on the v||-formalism [J. Reynders, Ph.D. dissertation, Princeton University, 1992] and the gyrokinetic ion/fluid electron hybrid model with kinetic electron closure [Y. Chan and S. E. Parker, Phys. Plasmas 18, 055703 (2011)] are also implemented in the flux-tube geometry and compared with the direct method for both the ion temperature gradient driven modes and the kinetic ballooning modes.
Axisymmetric curvature-driven instability in a model divertor geometry
Authors: Farmer W. A. , Ryutov D. D.
Published: September 2013

A model problem is presented which qualitatively describes a pressure-driven instability which can occur near the null-point in the divertor region of a tokamak where the poloidal field becomes small. The model problem is described by a horizontal slot with a vertical magnetic field which plays the role of the poloidal field. Line-tying boundary conditions are applied at the planes defining the slot. A toroidal field lying parallel to the planes is assumed to be very strong, thereby constraining the possible structure of the perturbations. Axisymmetric perturbations which leave the toroidal field unperturbed are analyzed. Ideal magnetohydrodynamics is used, and the instability threshold is determined by the energy principle. Because of the boundary conditions, the Euler equation is, in general, non-separable except at marginal stability. This problem may be useful in understanding the source of heat transport into the private flux region in a snowflake divertor which possesses a large region of small poloidal field, and for code benchmarking as it yields simple analytic results in an interesting geometry.
Theory of vibrational equilibria and pooling at solid-diatom interfaces
Authors: Boney E. T. D. , Marcus R. A.
Published: September 2013

In the present paper we provide a statistical theory for the vibrational pooling and fluorescence time dependence observed in infrared laser excitation of CO on an NaCl surface. The pooling is seen in experiment and in computer simulations. In the theory, we assume a rapid equilibration of the quanta in the substrate and minimize the free energy subject to the constraint at any time t of a fixed number of vibrational quanta N(t). At low incident intensity, the distribution is limited to one-quantum exchanges with the solid and the Debye frequency of the solid plays a key role in limiting the range of this one-quantum domain. The resulting inverted vibrational equilibrium population depends only on fundamental parameters of the oscillator (ωe and ωeχe) and the surface (ωD and T). The relation to the Treanor gas phase treatment is discussed. Unlike the solid phase system, the gas phase system has no Debye-constraining maximum.
Strain states of AlN/GaN-stress mitigating layer and their effect on GaN buffer layer grown by ammonia molecular beam epitaxy on 100-mm Si(111)
Authors: Ravikiran L. , Radhakrishnan K. , Dharmarasu N. , Agrawal M. , Munawar Basha S.
Published: September 2013

The effect of strain states of AlN/GaN-stress mitigating layer (SML) on buried crack density and its subsequent influence on the residual stresses in GaN buffer layers grown using ammonia-molecular beam epitaxy on 100-mm Si(111) substrate has been investigated. Different stages involved in the formation of buried cracks, which are crack initialization, growth of relaxed AlN layer, and subsequent lateral over growth, are identified using in-situ curvature measurements. While the increase of GaN thickness in AlN/GaN-SML enhanced its compressive strain relaxation and resulted in reduced buried crack spacing, the variation of AlN thickness did not show any effect on the crack spacing. Moreover, the decrease in the crack spacing (or increase in the buried crack density) was found to reduce the residual compression in 1st and 2nd GaN layers of AlN/GaN-SML structure. The higher buried crack density relaxed the compressive strain in 1st GaN layer, which further reduced its ability to compensate the tensile stress generated during substrate cool down, and hence resulted in lower residual compressive stress in 2nd GaN layer.
Note: Automated electrochemical etching and polishing of silver scanning tunneling microscope tips
Authors: Sasaki Stephen S. , Perdue Shawn M. , Perez Alejandro Rodriguez , Tallarida Nicholas , Majors Julia H. , Apkarian V. Ara , Lee Joonhee
Published: September 2013

Fabrication of sharp and smooth Ag tips is crucial in optical scanning probe microscope experiments. To ensure reproducible tip profiles, the polishing process is fully automated using a closed-loop laminar flow system to deliver the electrolytic solution to moving electrodes mounted on a motorized translational stage. The repetitive translational motion is controlled precisely on the μm scale with a stepper motor and screw-thread mechanism. The automated setup allows reproducible control over the tip profile and improves smoothness and sharpness of tips (radius 27 ± 18 nm), as measured by ultrafast field emission.
Macroscopic acoustoelectric charge transport in graphene
Authors: Bandhu L. , Lawton L. M. , Nash G. R.
Published: September 2013

We demonstrate macroscopic acoustoelectric transport in graphene, transferred onto piezoelectric lithium niobate substrates, between electrodes up to 500 μm apart. Using double finger interdigital transducers we have characterised the acoustoelectric current as a function of both surface acoustic wave intensity and frequency. The results are consistent with a relatively simple classical relaxation model, in which the acoustoelectric current is proportional to both the surface acoustic wave intensity and the attenuation of the wave caused by the charge transport.
Two-stage approach for the assessment of distributed generation capacity mixture in active distribution networks
Authors: Jayaweera D. , Islam S. , Neduvelil S.
Published: September 2013

Distribution networks are limited with spare capacities to integrate increased volumes of distributed generation (DG). Network constraints and congestion, dynamic thermal limits, intermittent outputs, and the need for reduction in greenhouse gas emission increase the complexity of capturing optimal DG mixture that can safely permit the optimal operation. This paper investigates this problem in detail and proposes a two-stage approach for the quantification of optimal DG capacity mixture in an active distribution network. The approach is aimed at operational planning and takes into account dynamic thermal limits, network internal benefit, and network external benefit and then optimizes samples of DG mixtures through sequential simulation. A case study is performed incorporating wind and photovoltaic generation as intermittent DG and diesel units as standing reserve units. Results suggest that specific operating conditions in an active distribution network can dominate the optimal DG mixture. Wind and diesel hybrid operation can be the most beneficial DG mixture compared to any other DG combination. Dynamic thermal limits of assets can potentially control the type of DG of the optimized mixture.
A study of cotton coated with intumescents flame retardant: Kinetics and effect of blends of used vegetable oil methyl ester
Authors: Balakrishnan N. , Mayilsamy K.
Published: September 2013

Oxidative thermal degradation and flame retardant behavior of cotton with intumescent formulations containing nanoclay as well as biodiesel (B0, B23, and B100) are studied by thermogravimetry (TG), differential thermal analysis, and limiting oxygen index (LOI). Activation energy of thermal degradation of cotton and cotton coated samples is determined by applying Coats-Redfern method on TG data. Action of intumescent is found concurrent with the process of decomposition of cotton fabric on heating. Activation energy of cotton coated with intumescent (175.3 kJ mol−1) is found lower than that of uncoated cotton (236.5 kJ mol−1), which further decreased on inclusion of blends of biodiesel in intumescent formulations (112–126 kJ mol−1). Char yield for cotton coated with intumescent increased from zero to 12.9% at 500 °C. LOI value for pure cotton (17%) increased for intumescent-coated (22.3%).
The role of the gas/plasma plume and self-focusing in a gas-filled capillary discharge waveguide for high-power laser-plasma applications
Authors: Ciocarlan C. , Wiggins S. M. , Islam M. R. , Ersfeld B. , Abuazoum S. , Wilson R. , Aniculaesei C. , Welsh G. H. , Vieux G. , Jaroszynski D. A.
Published: September 2013

The role of the gas/plasma plume at the entrance of a gas-filled capillary discharge plasma waveguide in increasing the laser intensity has been investigated. Distinction is made between neutral gas and hot plasma plumes that, respectively, develop before and after discharge breakdown. Time-averaged measurements show that the on-axis plasma density of a fully expanded plasma plume over this region is similar to that inside the waveguide. Above the critical power, relativistic and ponderomotive self-focusing lead to an increase in the intensity, which can be nearly a factor of 2 compared with the case without a plume. When used as a laser plasma wakefield accelerator, the enhancement of intensity can lead to prompt electron injection very close to the entrance of the waveguide. Self-focusing occurs within two Rayleigh lengths of the waveguide entrance plane in the region, where the laser beam is converging. Analytical theory and numerical simulations show that, for a density of 3.0 × 1018 cm−3, the peak normalized laser vector potential, a0, increases from 1.0 to 1.85 close to the entrance plane of the capillary compared with a0 = 1.41 when the plume is neglected.
Examining the usefulness of a Y-maze choice method to measure the preferences of laying hens
Authors: Arnold N. A. , Hemsworth P. H.
Published: September 2013

Measurement of animal preferences can be used as an indirect, but persuasive, method for assessing animal welfare on the basis that preferences may identify resources and behaviours that might be important to animals. The present experiment examined the usefulness of a Y-maze methodology, incorporating alteration of motivational state through prior restriction of resources of potentially differing value in assessing and understanding animal preferences. The choice behaviour of laying hens for feed, a dustbath substrate (sawdust; ‘dust’) and social contact was measured under three pairwise comparisons in a Y-maze apparatus. In each of the three experiments, 48 birds (HyLine Brown Strain; n = 24 per experiment) were offered a choice of two resources in a Y-maze test, with one of the three possible resource pairings. In each experiment, after Y-maze training, an equal number of birds was deprived in a factorial design of Resource 1, Resource 2, both, or neither resource. Analysis of choices over 24 trials per bird in each experiment revealed that birds preferred feed over social contact or dust, irrespective of restriction of any of these resources, and further, were quicker (P < 0.01) to make feed choices than dust or social-contact choices. In the social contact and dust comparison, restriction of dust significantly (P < 0.05) increased choice for dust in the 24 trials (38 vs 53% dust choice), suggesting that dust restriction increased the birds’ motivation to access dust. This result potentially highlights the impact of the resource of comparison in pairwise tests on overall choice response to restriction. The inclusion of measurements of speed of movement through the Y maze proved a useful aspect of the methodology, providing results consistent with choice behaviour in all three experiments. Although overall choices for dust and social contact were not significantly (P = 0.328) different from random, birds were quicker (P < 0.05) to make dust choices than social-contact choices, suggesting that speed of choice may be a particularly sensitive correlate of current motivation levels. The consistency of results across these experiments, together with results reported in the literature on laying-hen preferences, suggests that the methodology is a promising option for assessing the relative preference for resources for laying hens. Additional evidence, particularly on the occurrence of abnormal behaviour, stress physiology and health, when restricted of the resource of interest is necessary to provide a more comprehensive assessment of the impact of the restriction on animal welfare.