bluuebunny/crossref_metadata_2025 huggingface dataset:
Eight-dimensional quantum reaction rate calculations for the H+CH4 and H2+CH3 reactions on recent potential energy surfaces
Authors: Zhou Yong , Zhang Dong H.
Published: November 2014

Eight-dimensional (8D) transition-state wave packet simulations have been performed on two latest potential energy surfaces (PES), the Zhou-Fu-Wang-Collins-Zhang (ZFWCZ) PES [Y. Zhou, B. Fu, C. Wang, M. A. Collins, and D. H. Zhang, J. Chem. Phys. 134, 064323 (2011)] and the Xu-Chen-Zhang (XCZ)-neural networks (NN) PES [X. Xu, J. Chen, and D. H. Zhang, Chin. J. Chem. Phys. 27, 373 (2014)]. Reaction rate constants for both the H+CH4 reaction and the H2+CH3 reaction are calculated. Simulations of the H+CH4 reaction based on the XCZ-NN PES show that the ZFWCZ PES predicts rate constants with reasonable high accuracy for low temperatures while leads to slightly lower results for high temperatures, in line with the distribution of interpolation error associated with the ZFWCZ PES. The 8D H+CH4 rate constants derived on the ZFWCZ PES compare well with full-dimensional 12D results based on the equivalent m-ZFWCZ PES, with a maximum relative difference of no more than 20%. Additionally, very good agreement is shown by comparing the 8D XCZ-NN rate constants with the 12D results obtained on the ZFWCZ-WM PES, after considering the difference in static barrier height between these two PESs. The reaction rate constants calculated for the H2+CH3 reaction are found to be in good consistency with experimental observations.
Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B36
Authors: Liu Chun-Sheng , Wang Xiangfu , Ye Xiao-Juan , Yan Xiaohong , Zeng Zhi
Published: November 2014

The synthesis of quasiplanar boron clusters (B36) with a central hexagonal hole provides the first experimental evidence that a single-atomic-layer borophene with hexagonal vacancies is potentially viable [Z. Piazza, H. Hu, W. Li, Y. Zhao, J. Li, and L. S. Wang, Nat. Commun. 5, 3113 (2014)]. However, owing to the hexagonal holes, tunning the electronic and physical properties of B36 through chemical modifications is not fully understood. Based on (van der Waals corrected-) density functional theory, we show that Li adsorbed on B36 and \documentclass[12pt]{minimal}\begin{document}${\rm B}^-_{36}$\end{document}B36− clusters can serve as reversible hydrogen storage media. The present results indicate that the curvature and ionization of substrates can enhance the bond strength of Li due to the energetically favorable B 2p-Li 2p orbitals hybridization. Both the polarization mechanism and the orbital hybridization between H-s orbitals and Li-2s2p orbitals contribute to the adsorption of H2 molecules and the resulting adsorption energy lies between the physisorbed and chemisorbed states. Interestingly, the number of H2 in the hydrogen storage medium can be measured by the appearance of the negative differential resistance behavior at different bias voltage regions. Furthermore, the cluster-assembled hydrogen storage materials constructed by metalized B36 clusters do not cause a decrease in the number of adsorbed hydrogen molecules per Li. The system reported here is favorable for the reversible hydrogen adsorption/desorption at ambient conditions.
Combined effect of relativistic and ponderomotive filamentation on coexisting stimulated Raman and Brillouin scattering
Authors: Vyas Ashish , Singh Ram Kishor , Sharma R. P.
Published: November 2014

This paper presents a model to study the interplay between the stimulated Raman (SRS) and Brillouin scattering (SBS) along with the combined effect of relativistic and ponderomotive nonlinearities, at relativistic laser power. As the intense non-uniform laser beam propagates through the plasma, both the non-linearities are operative and modify the plasma refractive index in such a manner that one enhances the self-focusing (of the pump beam) caused by the other non-linearity. The interplay between the scattering processes (SRS and SBS) affects the pump filamentation process because of pump depletion and at the same time these scattering processes get modified due to this filamentation process. An impact of the filamentation process and coexistence of the scattering processes (SRS and SBS) on the back-reflectivity of scattered beams (SRS and SBS) has been explored and found that the back-reflectivity gets modified significantly. Results are also compared with the three wave interaction case (isolated SRS or SBS case).
Thermopower enhancement in quantum wells with the Rashba effect
Authors: Wu Lihua , Yang Jiong , Wang Shanyu , Wei Ping , Yang Jihui , Zhang Wenqing , Chen Lidong
Published: November 2014

We theoretically demonstrate that the thermopower in two-dimensional quantum wells (QWs) can be significantly enhanced by its Rashba spin-splitting effect, governed by the one-dimensional density of states in the low Fermi energy region. The thermopower enhancement is due to the lower Fermi level for a given carrier concentration in Rashba QWs, as compared with that in normal two-dimensional systems without the spin-splitting effect. The degenerate approximation directly shows that larger strength of Rashba effect leads to higher thermopower and consequently better thermoelectric performance in QWs.
Research Update: Magnetic phase diagram of EuTi1−xBxO3 (B = Zr, Nb)
Authors: Li Ling , Zhou Haidong , Yan Jiaqiang , Mandrus David , Keppens Veerle
Published: November 2014

We report the magnetic phase diagram of EuTi1−xBxO3 (B = Zr, Nb), determined from magnetization and heat capacity measurements. Upon Zr-doping, the antiferromagnetic ordering temperature TN of EuTi1−xZrxO3 gradually decreases from 5.6 K (x = 0) to 4.1 K (x = 1). Whereas a similar decrease in TN is observed for small amounts of Nb doping (x ≤ 0.05), ferromagnetism is induced in EuTi1−xNbxO3 with x > 0.05. The ferromagnetic interaction between localized Eu 4f spins mediated by itinerant electrons introduced by Nb doping results in the ferromagnetism in EuTi1−xNbxO3.
Numerical modeling of current-voltage characteristics to extract transport properties of organic semiconductors
Authors: Basile A. F. , Fraboni B.
Published: November 2014

The current vs. voltage (I-V) characteristics of single crystal rubrene Organic Field-Effect Transistors (OFETs) and polycrystalline poly(p-phenylenevinylene) (PPV) films are modeled using the polaron transport theory presented in a previous work [A. F. Basile et al., J. Appl. Phys. 115, 244505 (2014)]. The model is first applied to rubrene OFETs, where transport is two-dimensional and is confined near the interface between the insulator and the organic semiconductor. By considering the effect of image charges in the insulator and by assuming a constant intrinsic mobility, we reproduce both the positive and the negative temperature dependences of the channel mobilities measured on OFETs having a gate dielectric and an air-gap insulator, respectively. In addition, we adapt this model to the three-dimensional transport in PPV films, characterized by effective mobilities which depend on temperature, charge density, and electric field. We show that the I-V characteristics of these materials can be matched by the numerical solution of the Poisson and drift-diffusion equations assuming a constant intrinsic mobility. The polaron binding energy can account for the thermally activated behavior of the I-V characteristics and for the increase of the effective mobility at high applied voltages. Therefore, this model enables to extract the intrinsic transport parameters of organic semiconductors, independent of the device structure, and of the measurement conditions.
Influence of zigzag edges on the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities in graphene nanoribbons
Authors: Akbari-Sharbaf A. , Cottam M. G.
Published: November 2014

Localized magnetic impurity centres in graphene can interact through the π-electrons, leading to an effective Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. A RKKY-type study is presented for graphene ribbons with zigzag edges. Specifically investigations of how the edges modify the interaction between two localized magnetic moments are made by using a tight-binding Hamiltonian to describe the hopping of the π-electrons between adjacent sites and a contact term for interactions with the localized moments. In terms of a Green's function formalism for the excitation spectrum, which comprises modified bulk modes and two different types of localized edge modes, explicit analytical expressions are obtained for the RKKY interaction for any two magnetic sites on the graphene ribbon. The results enable us to determine the RKKY contributions that arise individually from the bulk-like modes and from the two types of edge modes in the zigzag geometry. The importance of these contributions varies depending on the proximity of the magnetic impurities to each other and to an edge.
Filling high aspect ratio trenches by superconformal chemical vapor deposition: Predictive modeling and experiment
Authors: Wang Wenjiao B. , Abelson John R.
Published: November 2014

Complete filling of a deep recessed structure with a second material is a challenge in many areas of nanotechnology fabrication. A newly discovered superconformal coating method, applicable in chemical vapor deposition systems that utilize a precursor in combination with a co-reactant, can solve this problem. However, filling is a dynamic process in which the trench progressively narrows and the aspect ratio (AR) increases. This reduces species diffusion within the trench and may drive the component partial pressures out of the regime for superconformal coating. We therefore derive two theoretical models that can predict the possibility for filling. First, we recast the diffusion-reaction equation for the case of a sidewall with variable taper angle. This affords a definition of effective AR, which is larger than the nominal AR due to the reduced species transport. We then derive the coating profile, both for superconformal and for conformal coating. The critical (most difficult) step in the filling process occurs when the sidewalls merge at the bottom of the trench to form the V shape. Experimentally, for the Mg(DMADB)2/H2O system and a starting AR = 9, this model predicts that complete filling will not be possible, whereas experimentally we do obtain complete filling. We then hypothesize that glancing-angle, long-range transport of species may be responsible for the better than predicted filling. To account for the variable range of species transport, we construct a ballistic transport model. This incorporates the incident flux from outside the structure, cosine law re-emission from surfaces, and line-of-sight transport between internal surfaces. We cast the transport probability between all positions within the trench into a matrix that represents the redistribution of flux after one cycle of collisions. Matrix manipulation then affords a computationally efficient means to determine the steady-state flux distribution and growth rate for a given taper angle. The ballistic transport model predicts a deeper position for the peak of the super-conformal growth rate than the diffusion-reaction model, and successfully explains the observation of complete filling. These models can be used to predict the behavior of any system given a small set of kinetic coefficients to describe the growth rate.
Photo-crystallization in a-Se layer structures: Effects of film-substrate interface-rigidity
Authors: Lindberg G. P. , O'Loughlin T. , Gross N. , Mishchenko A. , Reznik A. , Abbaszadeh S. , Karim K. S. , Belev G. , Weinstein B. A.
Published: November 2014

Amorphous selenium (a-Se) films deposited on rigid substrates can undergo photo-induced crystallization (PC) even at temperatures (T) well below the glass transition, Tg ∼ 313 K. Substrate-generated shear strain is known to promote the PC process. In the present work, we explore the influence of different substrates (Si and glass), and different film-layer-substrate combinations, on the PC in a variety of a-Se films and film-structures. The intermediate layers (indium tin oxide and polyimide) are chosen to promote conductivity and/or to be a buffer against interface strain in structures of interest for digital imaging applications. The PC characteristics in these samples are evaluated and compared using optical microscopy, atomic-force microscopy, Raman mapping, and T-dependent Raman spectroscopy. Both the presence of a soft intermediate layer, and the thermal softening that occurs for T increasing through Tg, inhibit the tendency for the onset of PC. The extensive PC mapping results in the wide range of samples studied here, as well as the suppression of PC near Tg in this array of samples, strongly support the generality of this behavior. As a consequence, one may expect that the stability of a-Se films against PC can be enhanced by decreasing the rigidity of the film-substrate interface. In this regard, advanced film structures that employ flexible substrates, soft intermediate layers, and/or are designed to be operated near Tg should be explored.
Influence of shape, size and internal structure on magnetic properties of core-edge nanodots with perpendicular anisotropy
Authors: Milińska E. , Wawro A.
Published: November 2014

The properties of perpendicularly magnetized isolated nanodots different in shape, size, and internal structure are simulated by micromagnetic calculations. Investigated dots are magnetically uniform, or they are composed of a core and an edge characterized by different anisotropy—stronger or weaker than that of the core. Based on calculated hysteresis loops, we discuss in details the magnetization reversal processes, stability of magnetic structures, and spin configurations in the dots.
Structure, composition and microwave dielectric properties of bismuth zinc niobate pyrochlore thin films
Authors: Wang Zhao , Ren Wei , Zhan Xuelei , Shi Peng , Wu Xiaoqing
Published: November 2014

(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 (BZN) pyrochlore thin films were deposited onto both Pt/TiO2/SiO2/Si and polycrystalline alumina substrates using pulsed laser deposition technique and then post-annealed using rapid thermal processing. The deposition temperature varies from 300 °C to 600 °C, and all the BZN films showed cubic pyrochlore structure after annealing at 650 °C for 30 min in air. The influence of the substrate associated with crystal structure is significant in the as-deposited films and disappears after post-annealing. The dielectric properties as a function of frequency up to the microwave frequency in both films were measured by LCR meter and split-post dielectric resonator technique. It is found that the BZN film deposited at 400 °C and post-annealed at 650 °C shows excellent dielectric properties with low loss in the microwave frequency range. This result indicates that the BZN thin film is a potential microwave material.
Exchange bias in strained SrRuO3 thin films
Authors: Sow Chanchal , Pramanik A. K. , Anil Kumar P. S.
Published: November 2014

Recently, it was found that the ferromagnetic SrRuO3 when combined with another ferromagnet in thin film form gives rise to exchange bias (EB) effect. However, we observed EB in single, strained, SrRuO3 thin films grown on diamagnetic LaAlO3 (100) substrates. It displays the training effect, which essentially confirms EB. The temperature dependence of the EB reveals the blocking temperature to be around ∼75 K. The strength of the exchange bias decreases with the increase in thickness of the film. We observe tensile strain in the out of plane direction. Further, the presence of in-plane compressive strain is observed through asymmetric reciprocal space mapping. Finally, we find a direct link between strain and EB. The evolution of strain with thickness matches well with the nature of scaled EB. It has been shown earlier by first principle calculations that this strain can induce EB in thin films.
Doping dependence and anisotropy of minority electron mobility in molecular beam epitaxy-grown p type GaInP
Authors: Haegel N. M. , Christian T. , Scandrett C. , Norman A. G. , Mascarenhas A. , Misra Pranob , Liu Ting , Sukiasyan Arsen , Pickett Evan , Yuen Homan
Published: November 2014

Direct imaging of minority electron transport via the spatially resolved recombination luminescence signature has been used to determine carrier diffusion lengths in GaInP as a function of doping. Minority electron mobility values are determined by performing time resolved photoluminescence measurements of carrier lifetime on the same samples. Values at 300 K vary from ∼2000 to 400 cm2/V s and decrease with increasing doping. Anisotropic diffusion lengths and strongly polarized photoluminescence are observed, resulting from lateral composition modulation along the [110] direction. We report anisotropic mobility values associated with carrier transport parallel and perpendicular to the modulation direction.
Note: Optical receiver system for 152-channel magnetoencephalography
Authors: Kim Jin-Mok , Kwon Hyukchan , Yu Kwon-kyu , Lee Yong-Ho , Kim Kiwoong
Published: November 2014

An optical receiver system composing 13 serial data restore/synchronizer modules and a single module combiner converted optical 32-bit serial data into 32-bit synchronous parallel data for a computer to acquire 152-channel magnetoencephalography (MEG) signals. A serial data restore/synchronizer module identified 32-bit channel-voltage bits from 48-bit streaming serial data, and then consecutively reproduced 13 times of 32-bit serial data, acting in a synchronous clock. After selecting a single among 13 reproduced data in each module, a module combiner converted it into 32-bit parallel data, which were carried to 32-port digital input board in a computer. When the receiver system together with optical transmitters were applied to 152-channel superconducting quantum interference device sensors, this MEG system maintained a field noise level of 3 fT/√Hz @ 100 Hz at a sample rate of 1 kSample/s per channel.
The effect of voltage waveform and tube diameter on transporting cold plasma strings through a flexible dielectric tube
Authors: Sohbatzadeh Farshad , Omran Azadeh Valinataj
Published: November 2014

In this work, we developed transporting atmospheric pressure cold plasma using single electrode configuration through a sub-millimetre flexible dielectric tube beyond 100 cm. It was shown that the waveform of the applied high voltage is essential for controlling upstream and downstream plasma inside the tube. In this regard, sawtooth waveform enabled the transport of plasma with less applied high voltage compared to sinusoidal and pulsed form voltages. A cold plasma string as long as 130 cm was obtained by only 4 kV peak-to-peak sawtooth high voltage waveform. Optical emission spectroscopy revealed that reactive chemical species, such as atomic oxygen and hydroxyl, are generated at the tube exit. The effect of tube diameter on the transported plasma was also examined: the smaller the diameter, the higher the applied voltage. The device is likely to be used for sterilization, decontamination, and therapeutic endoscopy as already suggested by other groups in recent past years.
Transforming dielectric coated tungsten and platinum wires to gaseous state using negative nanosecond-pulsed-current in vacuum
Authors: Wu Jian , Li Xingwen , Wang Kun , Li Zhenghong , Yang Zefeng , Shi Zongqian , Jia Shenli , Qiu Aici
Published: November 2014

With the help of thin dielectric coatings, corona free explosions were achieved in the region of about half a wire length (2 cm) for tungsten wires and nearly the whole wire length for platinum wires under a fast rising (46–170 A/ns) negative polarity current in vacuum. Expansion velocity of the tungsten gas was over 10 km/s. Current waveforms from exploding coated wires were similar to those from bare wires in the air including a current pause stage. Coated wires with different coating parameters had a similar joule energy deposition before voltage collapsed, but a quite different scenario in the region near the electrodes. The axial field under negative current was the main reason for the axial inhomogeneity of coated tungsten wires. Tungsten or platinum gases in the vaporized region were tightly encompassed by the dielectric coating, while gaps or probably low density gases, were observed between the coating and the edge of the dense wire core in the core-corona structure region.
Terahertz generation by two cross focused Gaussian laser beams in magnetized plasma
Authors: Singh Ram Kishor , Sharma R. P.
Published: November 2014

This paper presents a theoretical model for terahertz (THz) radiation generation by two cross-focused Gaussian laser beams in a collisionless magnetoplasma. The plasma is redistributed due to the ponderomotive nonlinearity which leads to the cross focusing of the laser beams. The focusing of the copropagating laser beams increases with increasing the externally applied static magnetic field which is perpendicular to the wave propagation direction. The nonlinear current at THz frequency arises on account of nonlinear ponderomotive force as a result of beating of the two lasers. The generated THz radiation amplitude increases significantly with increasing magnetic field. The cross focusing of two laser beams enhances the THz yield. Optimization of laser-plasma parameters gives the radiated normalized THz power of the order of 10 kW.
Enhanced transmission band in periodic media with loss modulation
Authors: Cebrecos A. , Picó R. , Romero-García V. , Yasser A. M. , Maigyte L. , Herrero R. , Botey M. , Sánchez-Morcillo V. J. , Staliunas K.
Published: November 2014

We study the propagation of waves in a periodic array of absorbing layers. We report an anomalous increase of wave transmission through the structure related to a decrease of the absorption around the Bragg frequencies. The effect is first discussed in terms of a generic coupled wave model extended to include losses, and its predictions can be applied to different types of waves propagating in media with periodic modulation of the losses at the wavelength scale. The particular case of sound waves in an array of porous layers embedded in air is considered. An experiment designed to test the predictions demonstrates the existence of the enhanced transmission band.
Electronic structure and optical properties of CdSxSe1−x solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations
Authors: Murphy M. W. , Yiu Y. M. , Ward M. J. , Liu L. , Hu Y. , Zapien J. A. , Liu Yingkai , Sham T. K.
Published: November 2014

The electronic structure and optical properties of a series of iso-electronic and iso-structural CdSxSe1−x solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.
O-band quantum-confined Stark effect optical modulator from Ge/Si0.15Ge0.85 quantum wells by well thickness tuning
Authors: Chaisakul Papichaya , Frigerio Jacopo , Marris-Morini Delphine , Vakarin Vladyslav , Chrastina Daniel , Isella Giovanni , Vivien Laurent
Published: November 2014

We report an O-band optical modulator from a Ge/Si0.15Ge0.85 multiple quantum well (MQW). Strong O-band optical modulation in devices commonly operating within E-band wavelength range can be achieved by simply decreasing the quantum well thickness. Both spectral photocurrent and optical transmission studies are performed to evaluate material characteristics and device performance from a surface-illuminated diode and a waveguide modulator, respectively. These results demonstrate the potential of using Ge/Si0.15Ge0.85 MQWs for the realization of future on-chip wavelength-division multiplexing systems with optical modulators operating at different wavelengths over a wide spectral range.
Realizing a supercapacitor in an electrical circuit
Authors: Fukuhara Mikio , Kuroda Tomoyuki , Hasegawa Fumihiko
Published: November 2014

Capacitors are commonly used in electronic resonance circuits; however, capacitors have not been used for storing large amounts of electrical energy in electrical circuits. Here, we report a superior RC circuit which serves as an electrical storage system characterized by quick charging and long-term discharging of electricity. The improved energy storage characteristics in this mixed electric circuit (R1 + R2C1) with small resistor R1, large resistor R2, and large capacitor C1 are derived from the damming effect by large R2 in simple parallel R2C1 circuit. However, no research work has been carried out previously on the use of capacitors as electrical energy storage devices in circuits. Combined with nanotechnology, we hope that our finding will play a remarkable role in a variety of applications such as hybrid electric vehicles and backup power supplies.
Quasi-phase-matching of the dual-band nonlinear left-handed metamaterial
Authors: Liu Yahong , Zhou Xin , Song Kun , Gu Shuai , Liu Zhaojun , Guo Lei , Zhao Xiaopeng
Published: November 2014

We demonstrate a type of nonlinear meta-atom creating a dual-band nonlinear left-handed metamaterial (DNLHM). The DNLHM operates at two distinct left-handed frequency bands where there is an interval of one octave between the two center frequencies. Under the illumination of a high-power signal at the first left-handed frequency band corresponding to fundamental frequency (FF), second-harmonic generation (SHG) is observed at the second left-handed band. This means that our DNLHM supports backward-propagating waves both at FF and second-harmonic (SH) frequency. We also experimentally demonstrate quasi-phase-matching configurations for the backward SHG. This fancy parametric process can significantly transmits the SH generated by an incident FF wave.
An important mechanism for thermal rectification in graded nanowires
Authors: Liu Yue-Yang , Zhou Wu-Xing , Tang Li-Ming , Chen Ke-Qiu
Published: November 2014

In the quest for the origin of the different thermal rectifying behavior of two graded nanowires, we reveal the important role that standing waves play in the thermal transport properties of such graded structures. Evidence for the existence of standing waves is given from two angles, and one possible scenario of the origin of the standing wave is presented. The key point is that the formation of the standing wave, which greatly hinders the propagation of phonon waves, occurs only when the narrow end of the nanowire is at a higher temperature than the wide end, making the heat current flow preferably from the wide end to the narrow end.
Characterizing intra-exciton Coulomb scattering in terahertz excitations
Authors: Zybell S. , Bhattacharyya J. , Winnerl S. , Eßer F. , Helm M. , Schneider H. , Schneebeli L. , Böttge C. N. , Kira M. , Koch S. W. , Andrews A. M. , Strasser G.
Published: November 2014

An intense terahertz field is applied to excite semiconductor quantum wells yielding strong non-equilibrium exciton distributions. Even though the relaxation channels involve a complicated quantum kinetics of Coulomb and phonon effects, distinct relaxation signatures of Coulomb scattering are identified within time-resolved photoluminescence by comparing the experiment with a reduced model that contains all relevant microscopic processes. The analysis uncovers a unique time scale for the Coulomb scattering directly from experiments and reveals the influence of phonon relaxation as well as radiative decay.
The instability of monodisperse bubbles passing through a confined geometry
Authors: Li Yuting , Wu Ping , Zhang Haifeng , Luo Zhaofeng , Wang Yong , Cheng Zhengdong , He Liqun
Published: November 2014

The dispersed bubble experiences an impact of flow-focusing from the outer viscous liquid, and may break into satellite bubbles after flowing through the narrower section. We show that the number of satellite bubbles can be characterized by a phase diagram that depends on the capillary number and the Weber number. The number of satellite bubbles can be estimated through the Tgrow (the growth time of the daughter bubble), Tpinch (the pinch-off time of the daughter bubble), and Tpass (the time the initial microbubble need to pass the pore). We defined N = Tpass/(Tpinch + Tgrow) as the dimensionless time and the critical condition: N ∼ 1 to evaluate the bubble breakup. Our work shows that the breakup of the microbubble or droplet through a sudden narrowing joint is predictable and controllable.
Band gap engineering of TiO2 through hydrogenation
Authors: Mo Li-Bin , Bai Yang , Xiang Qing-Yun , Li Qun , Wang Jia-Ou , Ibrahim Kurash , Cao Jiang-Li
Published: November 2014

The band gap of rutile TiO2 is reduced remarkably through high-temperature annealing in hydrogen atmosphere, and the absorption of visible light of the hydrogenated-TiO2 can be enhanced. These modifications of hydrogenated-TiO2 become more evident with the increase in annealing hydrogen pressure. A defect band arises near the valence band upon hydrogenation while the conduction band remains almost unchanged, which helps for meeting the requirements for hydrogen production through water splitting. This method could be also indicative for the band gap adjustment of other oxide semiconductors.
Thickness dependence of Young's modulus and residual stress of sputtered aluminum nitride thin films
Authors: Schneider M. , Bittner A. , Schmid U.
Published: November 2014

Aluminum nitride thin films are commonly used as active layer in micro-/nanomachined devices due to their piezoelectric properties. In order to predict the performance of advanced device architectures, careful modelling and simulation using techniques such as finite element analysis are of the utmost importance. An accurate knowledge of the corresponding thin film material properties is therefore required. This work focuses on the mechanical properties residual stress and Young's modulus over a wide thickness range from 100 to 1200 nm. The load-deflection technique is used to measure the bending curve of a circumferentially clamped, circular aluminum nitride diaphragm under a uniformly distributed pressure load. The bending curves are analyzed using an advanced analytical approach rather than commonly used models for load-deflection methods, thus resulting in a higher accuracy. It is found that the Young's modulus is nearly independent of film thickness, whereas the tensile residual stress exhibits a maximum at a thickness of about 600 nm. A thorough discussion of possible error sources is presented and approaches to minimize their impact are discussed.
Effects of relativistic electron temperature on parametric instabilities for intense laser propagation in underdense plasma
Authors: Zhao Yao , Zheng Jun , Chen Min , Yu Lu-Le , Weng Su-Ming , Ren Chuang , Liu Chuan-Sheng , Sheng Zheng-Ming
Published: November 2014

Effects of relativistic electron temperature on stimulated Raman scattering and stimulated Brillouin scattering instabilities for high intensity lasers propagating in underdense plasma are studied theoretically and numerically. The dispersion relations for these instabilities are derived from the relativistic fluid equation. For a wide range of laser intensity and electron temperature, it is found that the maximum growth rate and the instability region in k-space can be reduced at relativistic electron temperature. Particle-in-cell simulations are carried out, which confirm the theoretical analysis.
Comparison of structural and electrical properties of Lu2O3 and Lu2TiO5 gate dielectrics for α-InGaZnO thin-film transistors
Authors: Pan Tung-Ming , Chen Ching-Hung , Her Jim-Long , Koyama Keiichi
Published: November 2014

We compared the structural properties and electrical characteristics of high-κ Lu2O3 and Lu2TiO5 gate dielectrics for amorphous indium-gallium-zinc oxide (α-InGaZnO) thin-film transistor (TFT) applications. The Lu2O3 film has a strong Lu2O3 (400) peak in the X-ray diffraction pattern, while the Lu2TiO5 sample shows a relatively weak Lu2TiO5 (102) peak. Atomic force microscopy reveals that the Lu2O3 dielectric exhibits a rougher surface (about three times) than Lu2TiO5 one. In X-ray photoelectron spectroscopy analysis, we found that the intensity of the O 1s peak corresponding to Lu(OH)x for Lu2O3 film was higher than that of Lu2TiO5 film. Furthermore, compared with the Lu2O3 dielectric, the α-InGaZnO TFT using the Lu2TiO5 gate dielectric exhibited a lower threshold voltage (from 0.43 to 0.25 V), a higher Ion/Ioff current ratio (from 3.5 × 106 to 1.3 × 108), a smaller subthreshold swing (from 276 to 130 mV/decade), and a larger field-effect mobility (from 14.5 to 24.4 cm2/V s). These results are probably due to the incorporation of TiOx into the Lu2O3 film to form a Lu2TiO5 structure featuring a smooth surface, a low moisture absorption, a high dielectric constant, and a low interface state density at the oxide/channel interface. Furthermore, the stability of Lu2O3 and Lu2TiO5 α-InGaZnO TFTs was investigated under positive gate-bias stress (PGBS) and negative gate-bias stress (NGBS). The threshold voltage of the TFT performed under NGBS is more degradation than that under PGBS. This behavior may be attributed to the electron charge trapping at the dielectric–channel interface under PGBS, whereas the oxygen vacancies occurred in the InGaZnO under NGBS.
Proteresis of Cu2O/CuO core-shell nanoparticles: Experimental observations and theoretical considerations
Authors: Wu Sheng Yun , Ji Jhong-Yi , Shih Po-Hsun , Gandhi Ashish Chhaganlal , Chan Ting-Shan
Published: November 2014

A study of “proteresis (inverted hysteresis)” in core-shell, Cu2O/CuO nanoparticles, is presented. Crystal and characteristic sizes are determined using the x-ray absorption near-edge structure method for the weak ferromagnetic core (Cu2O) and antiferromagnetic shell (CuO) nanoparticles. A core-shell anisotropic energy model is established to describe the observed proteretic behavior in Cu2O/CuO core-shell nanocrystals. The proteresis loop triggered by the applied magnetic field can be tentatively attributed to core-shell exchange coupling induced by the surface of the Cu2O core, hinting at a possible way to tune the strength of the exchange inter-coupling energy that can control the dynamic of proteresis and hysteresis in a core-shell system.
Tuning the emission of ZnO nanorods based light emitting diodes using Ag doping
Authors: Echresh Ahmad , Chey Chan Oeurn , Shoushtari Morteza Zargar , Nur Omer , Willander Magnus
Published: November 2014

We have fabricated, characterized, and compared ZnO nanorods/p-GaN and n-Zn0.94Ag0.06O nanorods/p-GaN light emitting diodes (LEDs). Current-voltage measurement showed an obvious rectifying behaviour of both LEDs. A reduction of the optical band gap of the Zn0.94Ag0.06O nanorods compared to pure ZnO nanorods was observed. This reduction leads to decrease the valence band offset at n-Zn0.94Ag0.06O nanorods/p-GaN interface compared to n-ZnO nanorods/p-GaN heterojunction. Consequently, this reduction leads to increase the hole injection from the GaN to the ZnO. From electroluminescence measurement, white light was observed for the n-Zn0.94Ag0.06O nanorods/p-GaN heterojunction LEDs under forward bias, while for the reverse bias, blue light was observed. While for the n-ZnO nanorods/p-GaN blue light dominated the emission in both forward and reverse biases. Further, the LEDs exhibited a high sensitivity in responding to UV illumination. The results presented here indicate that doping ZnO nanorods might pave the way to tune the light emission from n-ZnO/p-GaN LEDs.
Ferromagnetic-organic interfacial states and their role on low voltage current injection in tris-8-hydroxyquinloline (Alq3) organic spin valves
Authors: Zhang H. T. , Han S. , Desai P. , Zhan Y. Q. , Li W. , Si W. , Scott K. , Drew A. J. , Gillin W. P. , Zhang S. J. , Kreouzis T.
Published: November 2014

Organic Spin Valves (OSVs) operate at small bias (<100 mV) when carrier injection should not occur due to injection barriers and in built potentials. We explore the consequences of hybrid-interface states between a ferromagnetic electrode and an organic semiconductor in OSV carrier injection. By temperature-dependent Dark Injection measurements, we observe hole trapping due to these filled states and measure a low thermal activation energy (∼100 meV) of the carrier density within OSVs. The small injection barrier is consistent with a significant interfacial potential, due to hybrid-interface state filling, overcoming the injection barrier due to the electrode work function—transport level mismatch.
Superhydrophobic anti-ultraviolet films by doctor blade coating
Authors: Cai Chang-Yun , Lin Kun-Yi Andrew , Yang Hongta
Published: November 2014

This article reports a scalable technology for fabricating polymer films with excellent water-repelling and anti-ultraviolet properties. A roll-to-roll compatible doctor blade coating technology is utilized to prepare silica colloidal crystal-polymer composites. The silica microspheres can then be selectively removed to create flexible self-standing macroporous polymer films with crystalline arrays of pores. The void sizes are controlled by tuning the duration of a reactive ion etching process prior to the removal of the templating silica microspheres. After surface modification, superhydrophobic surface can be achieved. This study further demonstrates that the as-prepared transparent porous films with 200 nm of pores exhibit diffraction of ultraviolet lights originated from the Bragg's diffractive of light from the three-dimensional highly ordered air cavities.
A taxonomy of prospection: Introducing an organizational framework for future-oriented cognition
Authors: Szpunar Karl K. , Spreng R. Nathan , Schacter Daniel L.
Published: November 2014

Prospection—the ability to represent what might happen in the future—is a broad concept that has been used to characterize a wide variety of future-oriented cognitions, including affective forecasting, prospective memory, temporal discounting, episodic simulation, and autobiographical planning. In this article, we propose a taxonomy of prospection to initiate the important and necessary process of teasing apart the various forms of future thinking that constitute the landscape of prospective cognition. The organizational framework that we propose delineates episodic and semantic forms of four modes of future thinking: simulation, prediction, intention, and planning. We show how this framework can be used to draw attention to the ways in which various modes of future thinking interact with one another, generate new questions about prospective cognition, and illuminate our understanding of disorders of future thinking. We conclude by considering basic cognitive processes that give rise to prospective cognitions, cognitive operations and emotional/motivational states relevant to future-oriented cognition, and the possible role of procedural or motor systems in future-oriented behavior.
Rational design and synthesis of an orally bioavailable peptide guided by NMR amide temperature coefficients
Authors: Wang Conan K. , Northfield Susan E. , Colless Barbara , Chaousis Stephanie , Hamernig Ingrid , Lohman Rink-Jan , Nielsen Daniel S. , Schroeder Christina I. , Liras Spiros , Price David A. , Fairlie David P. , Craik David J.
Published: November 2014

Significance

Peptides are valuable leads for drug development, offering advantages over other molecular classes. Specifically, they can bind potently and selectively to drug targets, including protein–protein interactions that are too challenging for small-molecule therapeutics. However, peptides are poor drugs because of their low in vivo stability and poor oral bioavailability. We propose a strategy for improving the oral bioavailability of peptides by identifying appropriate amides for chemical modification using temperature coefficients measured by NMR. The modified peptides have improved solvation properties, making them more membrane permeable. This approach for identifying sites for modification is a rapid method for guiding peptide drug design.
Polyharmonic maps of order 𝑘 with finite 𝐿^{𝑝} k-energy into Euclidean spaces
Authors: Maeta Shun
Published: November 2014

We consider polyharmonic maps

ϕ
:
(
M
,
g
)
→

E

n

\phi :(M,g)\rightarrow \mathbb {E}^n

of order

k
k

from a complete Riemannian manifold into the Euclidean space and let

p
p

be a real constant satisfying

2
≤
p
>
∞

2\leq p>\infty

.

(
i
)

(i)

If

∫
M

|

W

k
−
1

|

p

d

v
g

>
∞

\int _M|W^{k-1}|^{p}dv_g>\infty

and

∫
M

|

∇
¯

W

k
−
2

|

2

d

v
g

>
∞
,

\int _M|\overline \nabla W^{k-2}|^2dv_g>\infty ,

then

ϕ
\phi

is a polyharmonic map of order

k
−
1

k-1

.

(
i
i
)

(ii)

If

∫
M

|

W

k
−
1

|

p

d

v
g

>
∞

\int _M|W^{k-1}|^{p}dv_g>\infty

and

Vol

(
M
,
g
)
=
∞

\textrm {Vol}(M,g)=\infty

, then

ϕ
\phi

is a polyharmonic map of order

k
−
1

k-1

. Here,

W
s

=

Δ
¯

s
−
1

τ
(
ϕ
)
 
(
s
=
1
,
2
,
⋯
)

W^s=\overline \Delta ^{s-1}\tau (\phi )\ (s=1,2,\cdots )

and

W
0

=
ϕ

W^0=\phi

. As a corollary, we give an affirmative partial answer to the generalized Chen conjecture.
Tropicalizing the positive semidefinite cone
Authors: Yu Josephine
Published: November 2014

We study the tropicalization of the cone of positive semidefinite matrices over the ordered field of real Puiseux series. The tropical PSD matrices form the normal cone of the Newton polytope of the symmetric determinant at the vertex corresponding to the product of diagonal entries. We find generators and defining inequalities of the cone. The PSD tropical quadratic forms are those that induce the trivial subdivision on the standard simplex dilated by two. We also show that the tropical PSD cone is the tropical convex hull of the set of symmetric matrices of tropical rank one and that every tropical PSD matrix can be factored as a tropical product of a matrix and its transpose.
Geometric analysis aspects of infinite semiplanar graphs with nonnegative curvature II
Authors: Hua Bobo , Jost Jürgen
Published: November 2014

In a previous paper, we applied Alexandrov geometry methods to study infinite semiplanar graphs with nonnegative combinatorial curvature. We proved the weak relative volume comparison and the Poincaré inequality on these graphs to obtain a dimension estimate for polynomial growth harmonic functions which is asymptotically quadratic in the growth rate. In the present paper, instead of using volume comparison on the graph, we translate the problem to a polygonal surface by filling polygons into the graph with edge lengths 1. This polygonal surface then is an Alexandrov space of nonnegative curvature. From a harmonic function on the graph, we construct a function on the polygonal surface that is not necessarily harmonic, but satisfies crucial estimates. Using the arguments on the polygonal surface, we obtain the optimal dimension estimate for polynomial growth harmonic functions on the graph which is linear in the growth rate.
Multi-scaling limits for relativistic diffusion equations with random initial data
Authors: Liu Gi-Ren , Shieh Narn-Rueih
Published: November 2014

Let

u
(
t
,

x

)
,
 
t
>
0
,
 

x

∈

R

n

,

u(t,\mathbf {x}),\ t>0,\ \mathbf {x}\in \mathbb {R}^{n},

be the spatial-temporal random field arising from the solution of a relativistic diffusion equation with the spatial-fractional parameter

α
∈
(
0
,
2
)

\alpha \in (0,2)

and the mass parameter

m

>
0

\mathfrak {m}> 0

, subject to a random initial condition

u
(
0
,

x

)

u(0,\mathbf {x})

which is characterized as a subordinated Gaussian field. In this article, we study the large-scale and the small-scale limits for the suitable space-time re-scalings of the solution field

u
(
t
,

x

)

u(t,\mathbf {x})

. Both the Gaussian and the non-Gaussian limit theorems are discussed. The small-scale scaling involves not only scaling on

u
(
t
,

x

)

u(t,\mathbf {x})

but also re-scaling the initial data; this is a new type result for the literature. Moreover, in the two scalings the parameter

α
∈
(
0
,
2
)

\alpha \in (0,2)

and the parameter

m

>
0

\mathfrak {m}> 0

play distinct roles for the scaling and the limiting procedures.
Farmland Protection and Agricultural Land Values at the Urban‐Rural Fringe: British Columbia's Agricultural Land Reserve
Authors: Eagle Alison J. , Eagle David E. , Stobbe Tracy E. , van Kooten G. Cornelis
Published: November 2014

Farmland conservation policies typically use zoning and differentiated taxes to prevent urban development of farmland, but little is known about the effectiveness of these policies. This study adds to current knowledge by examining the impact of British Columbia's Agricultural Land Reserve (ALR), established in 1973, which severely restricts subdivision and nonagricultural uses for more than 4.7 million hectares of farmland. To determine the extent to which the ALR preserves farmland by reducing or removing the development option, a multilevel hedonic pricing model is used to estimate the impact of land use, geographic, and zoning characteristics on farmland value near the capital city of Victoria on Vancouver Island. Using sales data from 1974 through 2008, the model demonstrates a changing ALR impact over time that varies considerably by improved and unimproved land types. In 2008, landowners paid 19% less for the typical improved farmland parcel within the ALR versus that outside it. This suggests that would‐be developers expect permanency in the zoning law, and prefer non‐ALR zoned land. However, ALR land that is unimproved has a premium of 55%, suggesting that this land is more valuable for agriculture than for development. Farmland located closer to the city or the commuting highway commands a premium if it has a residence on it, with a residence also explaining why smaller agricultural properties sell at higher prices. However, it appears that zoning by itself is insufficient to protect farmland; other policies likely need to be implemented in conjunction with zoning to protect agricultural land.