bluuebunny/crossref_metadata_2025 huggingface dataset:
Small RNA‐mediated switch‐like regulation in bacterial quorum sensing
Authors: Liu Xi , Zhou Peipei , Wang Ruiqi
Published: September 2013

Quorum sensing (QS) is a signalling mechanism by which bacteria produce, release and then detect and respond to changes in their density and biosignals called autoinducers (AIs). There are multiple feedback loops in the QS system of Vibrio harveyi. However, how these feedback loops function to control signal processing remains unclear. In this study, the authors present a computational model for the switch‐like regulation of signal transduction by small regulatory RNA‐mediated QS based on intertwined network involving AIs, LuxO, LuxU, Qrr sRNAs and LuxR. In agreement with experimental observations, the model suggests that different feedbacks play critical roles in the switch‐like regulation. The authors results reveal that V. harveyi uses multiple feedbacks to precisely control signal transduction.
Self‐align method for improving sensitivity and resolution of infrared focal plane array
Authors: Xia Zhang , DaCheng Zhang
Published: September 2013

In this Letter, it is discussed whether a non‐self‐align process based on microelectronics technology causes the alignment error (AE) between two material layers in a gold–silicon nitride (Au–SiN) bi‐material uncooled optic readout infrared focal plane array (UOR IR FPA). That the AE reduces sensitivity of the FPA and causes extra noise to the FPA is analysed. A self‐align method including both process and pattern design, related to an aluminium–silicon nitride (Al–SiN) bi‐material UOR IR FPA, is proposed. The method effectively eliminates the AE. As a result, the measured value of thermomechanical response of an Al–SiN pixel is closer to the design value in comparison with the Au–SiN FPA fabricated by the non‐self‐align process. The measured value of the thermomechanical response of an Al–SiN pixel is 3.73 × 10−3 rad/°C and is 3.3 times as large as that of the Au–SiN FPA. Thus, the sensitivity of the FPA is improved. There is also no the extra noise. In addition, without the AE, a certain amount of alignment distance is not required while designing the FPA patterns. Therefore it is possible to improve the resolution of the FPA through increasing the quantity of pixels for a given FPA size.
Nonlinear circuit analysis for time‐variant microelectromechanical system capacitor systems
Authors: Dean Robert N. , Wilson Christopher G.
Published: September 2013

Electrostatic transducers, consisting of time‐variant capacitors, are utilised in many types of microelectromechanical system (MEMS) devices. Linear circuit theory is based on the premise of time‐invariant passive devices. Time‐variant capacitors generally result in one or more nonlinear differential equations that must be solved to obtain expressions for the voltage across or the current through the capacitor. An iterative approach can be used to provide an approximate solution to the nonlinear differential equation model of the Thévenin equivalent RC circuit. This solution technique is verified through comparison with a MATLAB Simulink® simulation of a MEMS capacitor that sinusoidally varies with time because of external stimuli.
Experimental investigation of microheat pipes for high‐power light‐emitting diode modules
Authors: Luo Yi , Liu Gang , Zou Liangliang , Yang Yanxia , Wang Xiaodong
Published: September 2013

A light‐emitting diode (LED) is a novel electronic light source that provides a direct conversion of electrical energy into light. A typical LED power package has a heat flux of 100 W/cm2, thus high power LEDs face severe thermal challenges because of their small size and general lack of a proper thermal path. The advantage of microheat pipes (MHPs) which are largely used in heat dissipation of microdevices is based on phase change. With the trend of using a silicon wafer as the substrate in LED manufacturing, a silicon‐glass MHP was fabricated for the quick spread of heat from the LEDs. Flat plate grooved MHPs are introduced. The grooves were fabricated on the silicon wafer and followed by bonding with Pyrex 7740 glass. Water was selected as the working liquid and the charge rate was 40%. The temperature test experiments were carried out to test the feasibility of the MHPs in LED heat conduction, and the preliminary experimental results indicate that the heat conductivity of MHPs without a vapour chamber is better than that of MHPs with a vapour chamber, which is even better than that of the silicon wafer.
Facile synthesis of CuO–NiO nanocomposites with high surface areas and their application for lithium‐ion batteries
Authors: Chen Han , Li Chun‐Long , Li Na , Xiang Kai‐Xiong , Hu Zhong‐Liang
Published: September 2013

CuO–NiO nanocomposites with high surface areas, which are used as anode materials for lithium‐ion batteries (LIBs), are successfully prepared by a facile wet‐chemical method. The CuO microspheres, NiO nanosheets and CuO–NiO nanocomposites were characterised by nitrogen adsorption, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. The CuO–NiO nanocomposites composed of CuO microspheres and NiO nanosheets possess a high surface area of 158.0 m2 g−1. When the CuO–NiO nanocomposites are used as anode materials, they show an initial discharge and charge capacity of 886.7 and 638.8 mAh g−1. A high capacity of 562.5 mAh g−1 at 0.1 C was observed after 50 cycles, which is higher than CuO (345.9 mAh g−1 at 0.1 C after 50 cycles) and NiO (334.4 mAh g−1 at 0.1 C after 50 cycles), demonstrating that the CuO–NiO nanocomposites with high surface area show a better cycling performance than pure CuO and NiO. Therefore the CuO–NiO nanocomposites materials have a great potential application in LIBs.
Hydrothermal synthesis and visible‐light‐driven oxygen production from water splitting of InVO4 micron–rods
Authors: Hu Bo , Wu Yafan , Yan Xu , Shi Weidong
Published: September 2013

A new type of InVO4 micron–rods photocatalyst was successfully synthesised by a facile additive‐assisted hydrothermal method as a novel O2 evolution photocatalyst. The as‐obtained micro–rods are well‐crystallised with about 2 μm lengths and 500 nm widths. In the authors system, the sodium dodecyl sulfate amount, as well as the reaction time and temperature, plays an important role in the formation of the InVO4 micronrods. From the UV–vis absorption spectrum, the bandgap energy of as‐obtained InVO4 microrods is 2.3 eV. Under visible‐light irradiation, InVO4 microrods show excellent photocatalytic O2 production activity (2.663 mmol h−1 g−1) with AgNO3 as sacrifice reagents.
Controlled synthesis and photocatalytic performance of ZnO nano/microstructures via facile aqueous solution route
Authors: Zhang Wenlong , Sun Yangang
Published: September 2013

Nanosheet‐assembled ZnO flower‐like ensembles, urchin‐like ZnO nanorod assemblies and ZnO nanorods, were synthesised by a facile solution‐based route. The Zn2+ :OH− molar ratio was adjusted to obtain ZnO with different morphologies. Scanning electron microscopy, X‐ray diffraction and an ultraviolet spectrophotometer were used to observe the morphology, crystal structure and photocatalytic activity of obtained ZnO in detail. The flower‐like ZnO ensembles composed of ultra‐thin nanosheets exhibited a much better photocatalytic activity than ZnO in the other morphologies, and the decomposition efficiency was 90.26%. It can be concluded that the presence of the photocatalytic activity depends on the morphology of the ZnO samples.
Laser ion acceleration by using the dynamic motion of a target
Authors: Morita Toshimasa
Published: September 2013

Proton acceleration by using a 620 TW, 18 J laser pulse of peak intensity of 5×1021 W/cm2 irradiating a disk target is examined using three-dimensional particle-in-cell simulations. It is shown that protons are accelerated efficiently to high energy for a “light” material in the first layer of a double-layer target, because a strongly inhomogeneous expansion of the first layer occurs by a Coulomb explosion within such a material. Moreover, a large movement of the first layer for the accelerated protons is produced by radiation-pressure-dominant acceleration. A time-varying electric potential produced by this expanding and moving ion cloud accelerates protons effectively. In addition, using the best material for the target, one can generate a proton beam with an energy of 200 MeV and an energy spread of 2%.
Efficient stochastic simulation of chemical kinetics networks using a weighted ensemble of trajectories
Authors: Donovan Rory M. , Sedgewick Andrew J. , Faeder James R. , Zuckerman Daniel M.
Published: September 2013

We apply the “weighted ensemble” (WE) simulation strategy, previously employed in the context of molecular dynamics simulations, to a series of systems-biology models that range in complexity from a one-dimensional system to a system with 354 species and 3680 reactions. WE is relatively easy to implement, does not require extensive hand-tuning of parameters, does not depend on the details of the simulation algorithm, and can facilitate the simulation of extremely rare events. For the coupled stochastic reaction systems we study, WE is able to produce accurate and efficient approximations of the joint probability distribution for all chemical species for all time t. WE is also able to efficiently extract mean first passage times for the systems, via the construction of a steady-state condition with feedback. In all cases studied here, WE results agree with independent “brute-force” calculations, but significantly enhance the precision with which rare or slow processes can be characterized. Speedups over “brute-force” in sampling rare events via the Gillespie direct Stochastic Simulation Algorithm range from ∼1012 to ∼1018 for characterizing rare states in a distribution, and ∼102 to ∼104 for finding mean first passage times.
Rapid high-resolution spin- and angle-resolved photoemission spectroscopy with pulsed laser source and time-of-flight spectrometer
Authors: Gotlieb K. , Hussain Z. , Bostwick A. , Lanzara A. , Jozwiak C.
Published: September 2013

A high-efficiency spin- and angle-resolved photoemission spectroscopy (spin-ARPES) spectrometer is coupled with a laboratory-based laser for rapid high-resolution measurements. The spectrometer combines time-of-flight (TOF) energy measurements with low-energy exchange scattering spin polarimetry for high detection efficiencies. Samples are irradiated with fourth harmonic photons generated from a cavity-dumped Ti:sapphire laser that provides high photon flux in a narrow bandwidth, with a pulse timing structure ideally matched to the needs of the TOF spectrometer. The overall efficiency of the combined system results in near-EF spin-resolved ARPES measurements with an unprecedented combination of energy resolution and acquisition speed. This allows high-resolution spin measurements with a large number of data points spanning multiple dimensions of interest (energy, momentum, photon polarization, etc.) and thus enables experiments not otherwise possible. The system is demonstrated with spin-resolved energy and momentum mapping of the L-gap Au(111) surface states, a prototypical Rashba system. The successful integration of the spectrometer with the pulsed laser system demonstrates its potential for simultaneous spin- and time-resolved ARPES with pump-probe based measurements.
Specific heat measurement of thin suspended SiN membrane from 8 K to 300 K using the 3ω-Völklein method
Authors: Ftouni Hossein , Tainoff Dimitri , Richard Jacques , Lulla Kunal , Guidi Jean , Collin Eddy , Bourgeois Olivier
Published: September 2013

We present a specific heat measurement technique adapted to thin or very thin suspended membranes from low temperature (8 K) to 300 K. The presented device allows the measurement of the heat capacity of a 70 ng silicon nitride membrane (50 or 100 nm thick), corresponding to a heat capacity of 1.4 × 10−10 J/K at 8 K and 5.1 × 10−8 J/K at 300 K. Measurements are performed using the 3ω method coupled to the Völklein geometry. This configuration allows the measurement of both specific heat and thermal conductivity within the same experiment. A transducer (heater/thermometer) is used to create an oscillation of the heat flux on the membrane; the voltage oscillation appearing at the third harmonic which contains the thermal information is measured using a Wheatstone bridge set-up. The heat capacity measurement is performed by measuring the variation of the 3ω voltage over a wide frequency range and by fitting the experimental data using a thermal model adapted to the heat transfer across the membrane. The experimental data are compared to a regular Debye model; the specific heat exhibits features commonly seen for glasses at low temperature.
Fabrication of large-area 3D optical fishnet metamaterial by laser interference lithography
Authors: Zhou Y. , Chen X. Y. , Fu Y. H. , Vienne G. , Kuznetsov A. I. , Luk’yanchuk B.
Published: September 2013

Centimeter-scale 3D fishnet metamaterial with negative refractive index in the near infrared spectral range is demonstrated. The large-area fabrication is realized using a conventional laser interference lithography technique in combination with a tri-layer lift-off procedure. This method allows us to effectively achieve a centimeter-scale 3D fishnet structure with a pitch of 600 nm and five functional Ag/SiO2 bi-layers with a total thickness of 300 nm. The experimental transmission spectrum correlates well with simulation results. Effective refractive index versus frequency associated with permittivity and permeability are retrieved. Two negative refractive index regions are found in the near-infrared spectral range.
Hydrophobic and hydrophilic interactions in aqueous mixtures of alcohols at a hydrophobic surface
Authors: Ballal Deepti , Chapman Walter G.
Published: September 2013

Aqueous solutions of alcohols are interesting because of their anomalous behavior that is believed to be due to the molecular structuring of water and alcohol around each other in solution. The interfacial structuring and properties are significant for application in alcohol purification processes and biomolecular structure. Here we study aqueous mixtures of short alcohols (methanol, ethanol, 1-propanol, and 2-propanol) at a hydrophobic surface using interfacial statistical associating fluid theory which is a perturbation density functional theory. The addition of a small amount of alcohol decreases the interfacial tension of water drastically. This trend in interfacial tension can be explained by the structure of water and alcohol next to the surface. The hydrophobic group of an added alcohol preferentially goes to the surface preserving the structure of water in the bulk. For a given bulk alcohol concentration, water mixed with the different alcohols has different interfacial tensions with propanol having a lower interfacial tension than methanol and ethanol. 2-propanol is not as effective in decreasing the interfacial tension as 1-propanol because it partitions poorly to the surface due to its larger excluded volume. But for a given surface alcohol mole fraction, all the alcohol mixtures give similar values for interfacial tension. For separation of alcohol from water, methods that take advantage of the high surface mole fraction of alcohol have advantages compared to separation using the vapor in equilibrium with a water-alcohol liquid.
Investigation of mechanisms for He-I emission radial profile broadening in a weakly ionized cylindrical helium plasma with recombining edge
Authors: Hollmann E. M. , Brandt C. , Hudson B. , Kumar D. , Nishijima D. , Pigarov A. Yu.
Published: September 2013

Spatially resolved spectroscopic measurements of He-I line emission are used to study the causes of emission profile broadening radially across the cylinder of a weakly ionized helium plasma. The plasma consists of an ionizing core (r < 2 cm) surrounded by a recombining edge (r > 2 cm) plasma. The brightness profiles of low-n EUV He-I resonance lines are shown to be strongly radially broadened due to opacity. The brightness profiles of high-n visible lines are also found to be strongly radially broadened, but dominantly due to edge recombination. Visible low-n lines are less strongly radially broadened, apparently by a combination of both recombination and EUV opacity. The low-n visible He-I line ratio method with central opacity correction is found to calculate central electron density and temperature well, with poor agreement at the edge, as expected for recombining plasma. In the recombining edge, high-n Boltzmann analysis is found to accurately measure the cold (Te < 0.2 eV) edge temperature. Near the core, however, high-n Boltzmann analysis can be complicated by electron-impact excitation, giving incorrect (Te≈ 0.1 eV) apparent temperatures. Probe measurements were not able to capture the cold edge temperature accurately, probably due to large potential fluctuations, even when using fast triple probe measurements. Fast spectroscopic measurements show that this discrepancy is not explained by recombining plasma alternating with ionizing plasma in the edge region.
Bi-alkali antimonide photocathodes for high brightness accelerators
Authors: Schubert S. , Ruiz-Osés M. , Ben-Zvi I. , Kamps T. , Liang X. , Muller E. , Müller K. , Padmore H. , Rao T. , Tong X. , Vecchione T. , Smedley J.
Published: September 2013

Alkali-antimonide photocathodes were grown on Si(100) and studied by means of XPS and UHV-AFM to validate the growth procedure and morphology of this material. The elements were evaporated sequentially at elevated substrate temperatures (first Sb, second K, third Cs). The generated intermediate K-Sb compound itself is a photocathode and the composition of K2.4Sb is close to the favored K3Sb stoichiometry. After cesium deposition, the surface layer is cesium enriched. The determined rms roughness of 25 nm results in a roughness domination of the emittance in the photoinjector already above 3 MV/m.
Photoacoustic transients produced by laser generated, ultrahigh thermal gradients
Authors: Wu Binbin , Frez Clifford , Diebold Gerald J.
Published: September 2013

Irradiation of an absorbing surface in contact with a transparent fluid by a pulsed laser can result in generation of enormous thermal gradients. Here it is shown that the effect of such thermal gradients on photoacoustic waves is the production of fast transients that accompany the leading edge of the wave. Calculations show that the transients can be accounted for by an additional source term in the wave equation for pressure. Experiments are reported showing the predicted transients on waves from absorbing layers submerged in transparent fluids irradiated with 10 ns laser pulses.
Relation between the activation energy of oxygen diffusion and the instantaneous shear modulus in propylene carbonate near the glass transition temperature
Authors: Syutkin V. M.
Published: September 2013

We discuss the transport of small gas molecules in organic glassy matrices using oxygen diffusion in propylene carbonate as an example. The jumps of a penetrant from one interstitial cavity to another require energy to expand the channel between cavities to the size of the penetrant. It has been established that at temperatures below and slightly above the glass transition temperature, the activation energy of oxygen diffusion, E, is related to the instantaneous shear modulus G∞ of propylene carbonate via the equation E = V × G∞, where V is the temperature-independent parameter that characterizes the volume of the channel. Consequently, the E value is the work necessary for elastic deformation of the surrounding matrix to expand the channel available for oxygen diffusion.
Thermoelectric performance of Cu intercalated layered TiSe2 above 300 K
Authors: Bhatt R. , Bhattacharya S. , Patel M. , Basu R. , Singh A. , Sürger C. , Navaneethan M. , Hayakawa Y. , Aswal D. K. , Gupta S. K.
Published: September 2013

High temperature (300–650 K) thermoelectric performance of Cu intercalated CuxTiSe2 (x = 0−0.11) material has been investigated. Cu intercalation transforms the p-type TiSe2 to n-type CuxTiSe2 with significant Seebeck coefficient value saturating to ∼−90 μV/K (x ≥ 0.06) at 650 K. Spanning the entire range of CuxTiSe2 samples, very low thermal conductivity has been observed which is attributed to the layered growth structure and rattling effect of weakly bound Cu atoms in the van der Waals gaps of TiSe2 layers. Figure of merit (ZT) value of 0.1 and 0.15 is achieved for pure TiSe2 and Cu0.11TiSe2 samples, respectively, at 650 K. The 4-element thermoelectric generator fabricated using a combination of p-type TiSe2 and n-type Cu0.11TiSe2 is designed, which gives an output power of 0.64 mW at 650 K.
Theory of hyperfine active nitrogen complexes observed in 4H-SiC diodes
Authors: Tuttle B. R. , Aichinger T. , Lenahan P. M. , Pantelides S. T.
Published: September 2013

Nitrogen complexes have been implicated as defects that limit the performance of SiC-based electronics. Here, we use density functional methods to explore the properties of nitrogen vacancy complexes in bulk 4H-SiC. The stability, electronic levels and hyperfine signatures of defect complexes are reported. A nitrogen substitutional/carbon-antisite complex is found to be the strongest candidate for recently observed hyperfine active defects in 4H-SiC diodes.
Numerical solutions of sheath structures in front of an electron-emitting electrode immersed in a low-density plasma
Authors: Din Alif
Published: September 2013

The exact theoretical expressions involved in the formation of sheath in front of an electron emitting electrode immersed in a low-density plasma have been derived. The potential profile in the sheath region has been calculated for subcritical, critical, and supercritical emissions. The potential profiles of critical and supercritical emissions reveals that we must take into account a small, instead of zero, electric field at the sheath edge to satisfy the boundary conditions used to integrate the Poisson's equation. The I-V curves for critical emission shows that only high values of plasma-electron to emitted-electron temperature ratio can meet the floating potential of the emissive electrode. A one-dimensional fluid like model is assumed for ions, while the electron species are treated as kinetic. The distribution of emitted-electron from the electrode is assumed to be half Maxwellian. The plasma-electron enters the sheath region at sheath edge with half Maxwellian velocity distribution, while the reflected ones have cut-off velocity distribution due to the absorption of super thermal electrons by the electrode. The effect of varying emitted-electron current on the sheath structure has been studied with the help of a parameter G (the ratio of emitted-electron to plasma-electron densities).
On the singularity of the Vlasov-Poisson system
Authors: Zheng Jian , Qin Hong
Published: September 2013

The Vlasov-Poisson system can be viewed as the collisionless limit of the corresponding Fokker-Planck-Poisson system. It is reasonable to expect that the result of Landau damping can also be obtained from the Fokker-Planck-Poisson system when the collision frequency ν approaches zero. However, we show that the collisionless Vlasov-Poisson system is a singular limit of the collisional Fokker-Planck-Poisson system, and Landau's result can be recovered only as the ν approaches zero from the positive side.
Statistical analysis of the ion beam production in a self magnetically insulated diode
Authors: Isakova Y. I. , Pushkarev A. I. , Khaylov I. P.
Published: September 2013

The paper presents the results of a study on shot to shot variation in energy density of an ion beam formed by a self-magnetically insulated diode with an explosive emission cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: plasma formation occurs during the first pulse (negative polarity, 300–500 ns, 100–150 kV), and ion extraction and acceleration during the second pulse (positive polarity, 150 ns, 250–300 kV). Crucially, it was found that the standard deviation of energy density does not exceed 11%, whilst the same variation for ion current density was 20%–30%, suggesting the presence of neutrals in the beam. This idea is further supported by the fact that ion current density is only weakly dependant on the accelerating voltage and other output parameters of the accelerator (coefficient of determination < 0.3), whilst the correlation between the energy density of the beam and the output parameters is strong (coefficient of determination > 0.9). We attribute the neutral component as being due to charge exchange between accelerated ions and neutral molecules from a neutral layer near the anode surface. Implementation using a self-magnetically insulated diode with an explosive-emission cathode, having an operational lifetime of up to 107 shots, has promising prospects for various technological applications.
Components of channel capacitance in metal-insulator-semiconductor capacitors
Authors: Grede Alex J. , Rommel Sean L.
Published: September 2013

In metal-insulator-semiconductor (MIS) capacitors, there are several components that influence the channel capacitance. Charges accumulate or deplete from the Γ, X, and L valleys for electrons and light, heavy and split-off bands for holes. Additionally dopants can change occupancy as a result of band-bending. A simple numerical method for calculating these components is presented along with potential implications for MIS capacitor characterization. Calculations for In0.53Ga0.47As indicate capacitance due to changes in dopant impurity ionization becomes significant around ND=1×1017 cm−3. The results also suggest that more detailed transient models are needed to verify the assumptions used in interface state characterization.
Study of weakly damped superconducting quantum interference devices operated in different bias modes in presence of external shunt resistance
Authors: Zeng Jia , Zhang Yi , Mück Michael , Krause Hans-Joachim , Braginski Alex I. , Kong Xiangyan , Xie Xiaoming , Offenhäusser Andreas , Jiang Mianheng
Published: September 2013

We experimentally studied weakly damped superconducting quantum interference devices (SQUIDs) shunted by an external resistor Rs and operated in either current- or voltage-bias mode. The SQUID parameters, such as the flux-to-voltage transfer coefficient ∂V/∂Φ and the dynamic resistance Rd, are reduced due to Rs, while the SQUID intrinsic noise remains unchanged. The reduced parameters can be enhanced again by using voltage feedback circuitry. Furthermore, Rs can be used to damp the SQUID in order to avoid the appearance of hysteresis or oscillation in SQUID characteristics. SQUID shunted by small Rs is always operated in mixed-bias mode.
Complete set of material constants of 0.95(Na0.5Bi0.5)TiO3-0.05BaTiO3 lead-free piezoelectric single crystal and the delineation of extrinsic contributions
Authors: Zheng Limei , Yi Xiujie , Zhang Shantao , Jiang Wenhua , Yang Bin , Zhang Rui , Cao Wenwu
Published: September 2013

Lead-free piezoelectric single crystal 0.95(Na0.5Bi0.5)TiO3 (NBT)-0.05BaTiO3 was grown by top-seeded solution growth method, which has rhombohedral symmetry with composition near morphotropic phase boundary. Full set of dielectric, piezoelectric, and elastic constants for [001]c poled domain-engineered single crystal was determined. Excellent electromechanical properties and low dielectric loss (d33 = 360 pC/N, d31 = −113 pC/N, d15 = 162 pC/N, k33 = 0.720, kt = 0.540, and tan δ = 1.1%) make it a good candidate to replace lead-based piezoelectric materials. The depolarization temperature (Td = 135 °C) is the highest among all NBT-based materials and its electromechanical coupling properties are very stable below Td. Extrinsic contributions to piezoelectric properties were investigated by Rayleigh analysis.
Depletion-mode Ga2O3 metal-oxide-semiconductor field-effect transistors on β-Ga2O3 (010) substrates and temperature dependence of their device characteristics
Authors: Higashiwaki Masataka , Sasaki Kohei , Kamimura Takafumi , Hoi Wong Man , Krishnamurthy Daivasigamani , Kuramata Akito , Masui Takekazu , Yamakoshi Shigenobu
Published: September 2013

Single-crystal gallium oxide (Ga2O3) metal-oxide-semiconductor field-effect transistors were fabricated on a semi-insulating β-Ga2O3 (010) substrate. A Sn-doped n-Ga2O3 channel layer was grown by molecular-beam epitaxy. Si-ion implantation doping was performed to source and drain electrode regions for obtaining low-resistance ohmic contacts. An Al2O3 gate dielectric film formed by atomic layer deposition passivated the device surface and significantly reduced gate leakage. The device with a gate length of 2 μm showed effective gate modulation of the drain current with an extremely low off-state drain leakage of less than a few pA/mm, leading to a high drain current on/off ratio of over ten orders of magnitude. A three-terminal off-state breakdown voltage of 370 V was achieved. Stable transistor operation was sustained at temperatures up to 250 °C.
Time delay induced different synchronization patterns in repulsively coupled chaotic oscillators
Authors: Yao Chenggui , Yi Ming , Shuai Jianwei
Published: September 2013

Time delayed coupling plays a crucial role in determining the system's dynamics. We here report that the time delay induces transition from the asynchronous state to the complete synchronization (CS) state in the repulsively coupled chaotic oscillators. In particular, by changing the coupling strength or time delay, various types of synchronous patterns, including CS, antiphase CS, antiphase synchronization (ANS), and phase synchronization, can be generated. In the transition regions between different synchronous patterns, bistable synchronous oscillators can be observed. Furthermore, we show that the time-delay-induced phase flip bifurcation is of key importance for the emergence of CS. All these findings may light on our understanding of neuronal synchronization and information processing in the brain.
Growth of deformation twins in tantalum via coherent twin boundary migration
Authors: Sandoval Luis A. , Surh Michael P. , Chernov Alexander A. , Richards David F.
Published: September 2013

In order to investigate the process of twinning growth, the nucleation of twinning dislocation loops on the coherent boundary of a Tantalum twin superlattice is studied via a molecular dynamics approach. We get homogeneous nucleation rates by means of a stationarity test and the mean first-passage method. We study their dependence on driving force and temperature in a framework given by the Kolgomorov-Johnson-Mehl-Avrami theory. Correspondingly, the contribution to the twinning growth dictated by this nucleation mechanism, as compared to the pole mechanism, is discussed. The homogeneous loop nucleation and growth mechanism can be relevant to twinning in high strain-rate experiments as in shock waves.
Thomson scattering measurement of a shock in laser-produced counter-streaming plasmas
Authors: Morita T. , Sakawa Y. , Tomita K. , Ide T. , Kuramitsu Y. , Nishio K. , Nakayama K. , Inoue K. , Moritaka T. , Ide H. , Kuwada M. , Tsubouchi K. , Uchino K. , Takabe H.
Published: September 2013

We report the first direct measurement of temporally and spatially resolved plasma temperatures at a shock as well as its spatial structure and propagation in laser-produced counter-streaming plasmas. Two shocks are formed in counter-streaming collisionless plasmas early in time, and they propagate opposite directions. This indicates the existence of counter-streaming collisionless flows to keep exciting the shocks, even though the collisional effects increase later in time. The shock images are observed with optical diagnostics, and the upstream and downstream plasma parameters of one of the shocks are measured using Thomson scattering technique.
Erratum: “Boundary based on exchange symmetry theory for multilevel simulations. I. Basic theory” [J. Chem. Phys. 139, 044120 (2013)]
Authors: Shiga Motoyuki , Masia Marco
Published: September 2013

The error in Eq. (19) of the original article is corrected. This error will not affect other parts of the paper. All the calculations have been done using the correct formula.
Exploring semiconductor substrates for silicene epitaxy
Authors: Bhattacharya Amrita , Bhattacharya Saswata , Das Gour P.
Published: September 2013

We have carried out first-principles density functional theory based calculations on electronic properties of silicene monolayer on various (111) semi-conducting surfaces. We find that the relative stability and other properties of the silicene overlayer depend sensitively on whether the interacting top layer of the substrate is metal or non-metal terminated. The nature of silicene-monolayer on the metal terminated surface can be metallic or even magnetic, depending upon the choice of the substrate. The silicene overlayer undergoes n-type doping on metal terminated surface while it undergoes p-type doping on nonmetal terminated surfaces of the semiconductor substrates.
A ZnO nanowire resistive switch
Authors: Karthik K. R. G. , Ramanujam Prabhakar Rajiv , Hai L. , Batabyal Sudip K. , Huang Y. Z. , Mhaisalkar S. G.
Published: September 2013

An individual ZnO nanowire resistive switch is evaluated with Pt/ZnO nanowire/Pt topology. A detailed DC I-V curve analysis is performed to bring both the conduction mechanism and the device characteristics to light. The device is further studied at various vacuum pressures to ascertain the presence of polar charges in ZnO nanowires as the phenomenon leading to the formation of the switch. The disappearance of the resistive switching is also analyzed with two kinds of fabrication approaches Focused Ion/Electron Beam involved in the making the device and a summary of both length and fabrication dependences of resistive switching in the ZnO nanowire is presented.
Co-spectrum and mean velocity in turbulent boundary layers
Authors: Katul Gabriel G. , Porporato Amilcare , Manes Costantino , Meneveau Charles
Published: September 2013

Connections are explored between spectral descriptions of turbulence and the mean velocity profile in the equilibrium layer of wall-bounded flows using a modeled budget for the co-spectral density. Using a standard model for the wall normal velocity variance and a Rotta-like return-to-isotropy closure for the pressure-strain effects, the co-spectrum is derived. The approach establishes a relation between the von Kármán (κ), one-dimensional Kolmogorov (\documentclass[12pt]{minimal}\begin{document}$C^\prime _K$\end{document}CK′), and Rotta (A) constants, namely, \documentclass[12pt]{minimal}\begin{document}$\kappa = (4 A/7C^\prime _K)^{-3/4}$\end{document}κ=(4A/7CK′)−3/4. Depending on the choices made about small-scale intermittency corrections, the logarithmic mean velocity profile or a power-law profile with an exponent that depends on the intermittency correction are derived thereby offering a new perspective on a long standing debate.
Destabilization of a liquid ring in the binormal direction
Authors: Zhao Sicheng , Tao Jianjun
Published: September 2013

The instability of a circular inviscid ring in its binormal direction is investigated theoretically by linear analysis. The analytical solutions of growth rates are obtained for both the simple sinuous mode and the varicose mode, namely, the classical Rayleigh mode. Different from the varicose mode, the unstable sinuous mode is caused not by the surface tension but by the aerodynamic lift force. The superimposition of these two modes provides a surface shape, which is qualitatively consistent with experimental observations on drop splash.
Spin-transfer force acting on vortex induced by current gradient in a planar polarizer geometry
Authors: Liu Yan , Li Huanan , Hu Yong , Du An
Published: September 2013

We discuss a new mechanism of changing the magnetic vortex gyrotropic motion in a permalloy/nonmagnet bi-layers system. In this system, a spin current characterized by an in-plane polarizer is injected from the nonmagnetic layer to the permalloy disk. We introduce current density gradient to the spin current, and find that the interplay between the planar polarizer and current gradient can change the damping of the vortex motion. This change originates from a spin-transfer force acting on the vortex. The influence of the spin-transfer force on the vortex motion is dependent on the direction of the planar polarizer, the orientation of the current density gradient, and the vortex state.
Visualization of Bi3+ off-centering in the average cubic structure of (Ba0.70Bi0.30)(Ti0.70Fe0.30)O3 at the electron density level
Authors: Singh Anar , Moriyoshi Chikako , Kuroiwa Yoshihiro , Pandey Dhananjai
Published: September 2013

We present here evidence for the off-centering of Bi3+ symmetrically distributed along the six ⟨100⟩ directions of a pseudocubic composition (Ba0.70Bi0.30)(Ti0.70Fe0.30)O3 at the electron density distribution level. We also calculate the strength of covalent bonding between the oxygen (O2−) anions with A-site (Ba2+/Bi2+) and B-site (Ti4+/Fe3+) cations, which provides evidence for the stabilization of average cubic symmetry. We believe that Bi3+ positional disorder may be ubiquitous in all the lead free piezoceramic solid solutions of the type (Ba1−xBix)(Ti1−xMex)O3, where Me = Fe3+, Sc3+, Al3+, (Mg1/2Ti1/2)3+, and (Zn1/2Ti1/2)3+.
Enhanced photocurrent in solution processed electronically coupled CdSe nanocrystals thin films
Authors: Dondapati Hareesh , Ha Duc , Pradhan A. K.
Published: September 2013

We have demonstrated the fabrication of highly continuous and smooth CdSe semiconductor films containing self-assembled nanocrystals (NCs) using a simple, low cost solution-processed deposition technique. The impact of thermal annealing and ethanedithiol (EDT) treatment on oleate capped CdSe NCs films is illustrated. Post deposition EDT treatment enhances strong electron coupling between NCs by reducing the inter-particle distance, which enhances four orders of magnitude of photocurrent in the pn-device. Mild thermal annealing of NC films cause large redshift and significant broadening. Our findings suggest that NCs with short-range organic ligands are suitable for high-performance Thin-Film-Transistors and next generation high-efficiency photovoltaics.
A tension stress loading unit designed for characterizing indentation response of single crystal silicon under tension stress
Authors: Huang Hu , Zhao Hongwei , Shi Chengli , Hu Xiaoli , Cui Tao , Tian Ye
Published: September 2013

In this paper, a tension stress loading unit is designed to provide tension stress for brittle materials by combining the piezo actuator and the flexible hinge. The structure of the tension stress loading unit is analyzed and discussed via the theoretical method and finite element simulations. Effects of holding time, the installed specimen and hysteresis of the piezo actuator on output performances of the tension stress loading unit are studied in detail. An experiment system is established by combing the indentation testing unit and the developed tension stress loading unit to characterize indentation response of single crystal silicon under tension stress. Experiment results indicate that tension stress leads to increasing of indentation displacement for the same inden-tation load of single crystal silicon. This paper provides a new tool for studying indentation response of brittle materials under tension stress.
Polymer composite microtube array produced by meniscus-guided approach
Authors: Won Kyu Hwang , Weon Byung Mook , Je Jung Ho
Published: September 2013

Single freestanding microtubes of poly(methyl methacrylate)/polypyrrole (PMMA/PPy) are produced based on a meniscus-guided approach. A ring-deposit of nanoparticles is first formed in a meniscus solution of PMMA/PPy nanoparticles by outward liquid flow in fast solvent evaporation. Continuous accumulation of nanoparticles on the ring-deposit is then made by guiding the meniscus upward under the outward flow, thereby forming single composite microtube with controlled outer diameter and wall thickness. The meniscus-guiding enables us to produce an array of freestanding microtubes that are individually controlled in size at the desired positions. We demonstrate individually addressable gas sensors by integrating PMMA/PPy microtubes on electrodes.
Comparison of the characteristics of atmospheric pressure plasma jets using different working gases and applications to plasma-cancer cell interactions
Authors: Joh Hea Min , Kim Sun Ja , Chung T. H. , Leem S. H.
Published: September 2013

Atmospheric pressure plasma jets employing nitrogen, helium, or argon gases driven by low-frequency (several tens of kilohertz) ac voltage and pulsed dc voltage were fabricated and characterized. The changes in discharge current, optical emission intensities from reactive radicals, gas temperature, and plume length of plasma jets with the control parameters were measured and compared. The control parameters include applied voltage, working gas, and gas flow rate. As an application to plasma-cancer cell interactions, the effects of atmospheric pressure plasma jet on the morphology and intracellular reactive oxygen species (ROS) level of human lung adenocarcinoma cell (A549) and human bladder cancer cell (EJ) were explored. The experimental results show that the plasma can effectively control the intracellular concentrations of ROS. Although there exist slight differences in the production of ROS, helium, argon, or nitrogen plasma jets are found to be useful in enhancing the intracellular ROS concentrations in cancer cells.
The potential for pharmacological supply of 25-hydroxyvitamin D to increase phosphorus utilisation in cattle
Authors: McGrath J. J. , Savage D. B. , Godwin I. R.
Published: September 2013

Phosphorus (P) is recommended as a supplement for beef cattle grazing rangelands and for dairy cows grazing pastures. However, existing supplementation mechanisms are wasteful, labour intensive, and are becoming increasingly expensive. Cattle have an inability to absorb or retain >70% of the P they consume. Therefore, the need for supplementation could be reduced if the utilisation of dietary P was increased. Vitamin D and its metabolites are involved in the absorption and metabolism of calcium (Ca) and P. However, the use of vitamin D for improving utilisation of P is novel. This review presents information gathered from various studies that demonstrate the potential for vitamin D metabolites to increase P utilisation. The concentration of dietary Ca is demonstrated to be the controlling element for utilisation of endogenous sources of vitamin D. Therefore, the use of exogenous sources of vitamin D in greater than normal concentration is required to overcome the suppression of active absorption mechanisms by normal calcaemia. Use of 25-hydroxyvitamin D in sufficient doses has been shown to increase active absorption of both Ca and P and therefore potentially provide a method of increasing utilisation of existing sources of P or increase the utilisation of P supplements for cattle.
Can precipitation influence landscape controls on wildfire severity? A case study within temperate eucalypt forests of south-eastern Australia
Authors: Collins L. , Bradstock R. A. , Penman T. D.
Published: September 2013

The environmental, economic and social impacts of wildfires depend on spatial patterns of fire severity. An understanding as to how drivers of fire severity vary across broad vegetation communities exists. However, examination of variation within communities in response to gradients of moisture has received little attention so far. This study examined whether relationships between environmental variables (i.e. fire weather, topography and fuel age) and fire severity were modified by increasing mean annual precipitation. Understorey fires were more likely to occur in young fuels (i.e. <5 years since fire) in drier sites, although this effect diminished as precipitation increased. The probability of occurrence of understorey fires under non-extreme weather and on steep slopes was reduced in wetter areas. Relationships between crown fire and weather, topography and fuel age were largely unaltered by the precipitation gradient, with only a marginally significant interaction occurring between weather and mean annual precipitation. Greater fine fuel accumulation associated with increased precipitation presumably reduced fuel limitations imposed by environmental factors (i.e. fire weather, slope, fuel age), altering their relative control on the probability of understorey fire. The probability of crown fires is predominantly driven by fire weather and is consequently less sensitive to precipitation gradients. Consideration of precipitation gradients will be necessary when identifying controls of fire severity and devising effective fire management strategies.
What is a Human?
Authors: Kahn Peter H. , Ishiguro Hiroshi , Friedman Batya , Kanda Takayuki , Freier Nathan G. , Severson Rachel L. , Miller Jessica
Published: September 2013

In this paper, we move toward offering psychological benchmarks to measure success in building increasingly humanlike robots. By psychological benchmarks we mean categories of interaction that capture conceptually fundamental aspects of human life, specified abstractly enough to resist their identity as a mere psychological instrument, but capable of being translated into testable empirical propositions. Nine possible benchmarks are considered: autonomy, imitation, intrinsic moral value, moral accountability, privacy, reciprocity, conventionality, creativity, and authenticity of relation. Finally, we discuss how getting the right group of benchmarks in human–robot interaction will, in future years, help inform on the foundational question of what constitutes essential features of being human.
Working with a robot
Authors: Bernstein Debra , Crowley Kevin , Nourbakhsh Illah
Published: September 2013

Research on human–robot interaction has often ignored the human cognitive changes that might occur when humans and robots work together to solve problems. Facilitating human–robot collaboration will require understanding how the collaboration functions system-wide. We present detailed examples drawn from a study of children and an autonomous rover, and examine how children’s beliefs can guide the way they interact with and learn about the robot. Our data suggest that better collaboration might require that robots be designed to maximize their relationship potential with specific users.
Design and analysis of large-scale biological rhythm studies: a comparison of algorithms for detecting periodic signals in biological data
Authors: Deckard Anastasia , Anafi Ron C. , Hogenesch John B. , Haase Steven B. , Harer John
Published: September 2013

Motivation: To discover and study periodic processes in biological systems, we sought to identify periodic patterns in their gene expression data. We surveyed a large number of available methods for identifying periodicity in time series data and chose representatives of different mathematical perspectives that performed well on both synthetic data and biological data. Synthetic data were used to evaluate how each algorithm responds to different curve shapes, periods, phase shifts, noise levels and sampling rates. The biological datasets we tested represent a variety of periodic processes from different organisms, including the cell cycle and metabolic cycle in Saccharomyces cerevisiae, circadian rhythms in Mus musculus and the root clock in Arabidopsis thaliana.

Results: From these results, we discovered that each algorithm had different strengths. Based on our findings, we make recommendations for selecting and applying these methods depending on the nature of the data and the periodic patterns of interest. Additionally, these results can also be used to inform the design of large-scale biological rhythm experiments so that the resulting data can be used with these algorithms to detect periodic signals more effectively.

Contact:  anastasia.deckard@duke.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.