bluuebunny/crossref_metadata_2025 huggingface dataset:
White House and agencies focus on space weather concerns
Authors: Showstack Randy
Published: June 2012

“Space weather is a serious matter that can affect human economies around the world,” Tamara Dickinson, a senior policy analyst with the White House Office of Science and Technology Policy (OSTP), told attendees at the 2012 Space Weather Enterprise Forum, held 5 June in Washington, D. C. With the 2013 solar maximum nearing, researchers and government agencies are focusing on how the greater solar activity could affect our increasingly technological society and what measures can be taken to help prevent or mitigate any threats to the electricity grid, GPS, and other potentially vulnerable technologies. Dickenson said that there has been an increased awareness about space weather in the White House and that President Barack Obama recently has requested briefing memos on the topic. She highlighted several efforts the administration is taking related to space weather, including a forthcoming national Earth observation strategy, which could be released in July and will include an assessment of space weather. She explained that the strategy document will be part of the fiscal year 2014 presidential budget request and that it will be updated every 3 years.
The rapidly changing greenhouse gas budget of Asia
Authors: Patra Prabir K. , Canadell Josep G. , Lal Shyam
Published: June 2012

International Workshop on Asian Greenhouse Gases Budgets; Ahmedabad, India, 27–29 September 2011 An international workshop assessed the availability of data and modeling capability to work toward the establishment of the greenhouse gas (GHG) budget for South and Southeast Asia. The workshop was organized with support from the Asia‐Pacific Network (APN) and the Indian Space Research Organisation Geosphere‐Biosphere Programme at the Physical Research Laboratory, in Ahmedabad, India. The effort is based on the synthesis and reconciliation of top‐down (atmospheric observations and inverse models) and bottom‐up estimates (ground‐based fux observations and terrestrial models). While inverse estimates provide a regional net GHG balance, bottomup estimates provide the necessary process attribution to shed light into future dynamics and the components of the balance that can be managed by human activity.
New software system to improve AGU membership management
Authors: McEntee Chris
Published: June 2012

Almost 2 years ago, AGU began investigating how it could more efficiently manage member and customer records as well as support processes that currently run on multiple systems. I am pleased to announce that on 25 June, as the result of intense efforts, AGU will migrate to a new database software system that will house the majority of AGU operations. AGU staff will have more tools at their disposal to assist members, and members will have more intuitive and user‐friendly options when using the online interface to update their profiles or make purchases. I am particularly excited about this major improvement to our infrastructure because it better positions AGU to achieve goals in its strategic plan.
Dunne receives 2011 G. K. Gilbert Award: Citation
Authors: Dietrich William E.
Published: June 2012

Thomas Dunne received the 2011 G. K. Gilbert Award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. The award recognizes “a scientist who has either made a single significant advance or sustained significant contributions to the field of Earth and planetary surface processes, and who has in addition promoted an environment of unselfish cooperation in research and the inclusion of young scientists into the field.”
Perron receives 2011 Luna B. Leopold Young Scientist Award: Citation
Authors: Howard Alan D.
Published: June 2012

J. Taylor Perron received the 2011 Luna B. Leopold Young Scientist Award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. The award recognizes “a young scientist for making a significant and outstanding contribution that advances the field of Earth and planetary surface processes.”
Coupling between Greenland blocking and the North Atlantic Oscillation pattern
Authors: Davini P. , Cagnazzo C. , Neale R. , Tribbia J.
Published: June 2012

Through the adoption of a bidimensional blocking index based on geopotential height, it is shown that the blocking frequency over Greenland is not only a key element in describing the North Atlantic Oscillation (NAO) index, but it also operates as an essential element in modulating its pattern. When Greenland blocking is lower than average, the first Empirical Orthogonal Function (EOF) of the 500 hPa geopotential height over the Euro‐Atlantic region no longer resembles the NAO. Moreover, the typical trimodal variability observed in the Atlantic eddy‐driven jet stream is reduced to a bimodal variability. Consistent with this result, we link the eastward displacement of the NAO pattern observed in recent years to the decreasing frequency of Greenland Blocking. Considering the large bias seen in the simulated blocking frequency in climate models, such strong coupling might have important consequences in the analysis of the NAO in climate simulations.
Micromechanics of brittle creep in rocks
Authors: Brantut N. , Baud P. , Heap M. J. , Meredith P. G.
Published: June 2012

In the upper crust, the chemical influence of pore water promotes time dependent brittle deformation through sub‐critical crack growth. Sub‐critical crack growth allows rocks to deform and fail at stresses well below their short‐term failure strength, and even at constant applied stress (“brittle creep”). Here we provide a micromechanical model describing time dependent brittle creep of water‐saturated rocks under triaxial stress conditions. Macroscopic brittle creep is modeled on the basis of microcrack extension under compressive stresses due to sub‐critical crack growth. The incremental strains due to the growth of cracks in compression are derived from the sliding wing crack model ofAshby and Sammis(1990), and the crack length evolution is computed from Charles' law. The macroscopic strains and strain rates computed from the model are non linear, and compare well with experimental results obtained on granite, low porosity sandstone and basalt rock samples. Primary creep (decelerating strain) corresponds to decelerating crack growth, due to an initial decrease in stress intensity factor with increasing crack length in compression. Tertiary creep (accelerating strain as failure is approached) corresponds to an increase in crack growth rate due to crack interactions. Secondary creep with apparently constant strain rate arises as an inflexion between those two end‐member phases. The minimum strain rate at the inflexion point can be estimated analytically as a function of model parameters, effective confining pressure and temperature, which provides an approximate creep law for the process. The creep law is used to infer the long term strain rate as a function of depth in the upper crust due to the action of the applied stresses: in this way, sub‐critical cracking reduces the failure stress in a manner equivalent to a decrease in cohesion. We also investigate the competition with pressure solution in porous rocks, and show that the transition from sub‐critical cracking to pressure solution dominated creep occurs with increasing depth and decreasing strain rates.
Resuspension onset and crater erosion by a vortex ring interacting with a particle layer
Authors: Bethke N. , Dalziel S. B.
Published: June 2012

This paper presents results from an experimental investigation of the interaction of a vortex ring with a particle layer. The flow dynamics during the onset of particle resuspension are analysed using particle image velocimetry, while a light attenuation method provides accurate measurements of the final eroded crater shape. This work is a continuation of the research described in R. J. Munro, N. Bethke, and S. B. Dalziel, “Sediment resuspension and erosion by vortex rings,” Phys. Fluids 21, 046601 (2009)10.1063/1.3083318, which focussed on the general resuspension onset dynamics and initial crater formation. Here, we analyse the velocity induced by the vortex ring on the particle layer surface during the resuspension of particles for different particle sizes, and the shape and size of the final craters that are formed by the impact of the vortex ring. We find that the boundary condition is characterised by a quasi-slip velocity at the particle layer surface, independent of the particle size. The particle diameter, and thus bed permeability, is found to have a significant effect on the final crater characteristics.
A theoretical study on structures, energetics, and spectra of Br–.nCO2 clusters: Towards bridging the gap between micro-domain and macro-domain
Authors: Pathak Arup Kumar
Published: June 2012

Structures, energetics, and spectra of Br–.nCO2 (n = 1-8) clusters are studied based on ab initio electronic structure theory. The geometry of each size of clusters is evaluated by employing second-order Moller-Plesset (MP2) perturbation theory. It is observed that the solvent CO2 molecules approach the bromide moiety from one side in an asymmetric fashion except for the Br–.8CO2 cluster. Simple electrostatic model for charge-quadrupole interactions is valid for the Br–.nCO2 clusters. Reduced variational space based energy decomposition method shows that the electrostatic interaction is the major component and polarization and charge transfer energies are the other significant components of the total interaction energy. Both adiabatic and vertical electron detachment energies and solvation energies are calculated at MP2 level of theory. We have observed an excellent agreement between theory and experiment for the vertical detachment and solvation energies. Calculated quantities based on the analytical expression which connects the finite domain to macroscopic one are found to be very good in agreement with the available experimental results. The present study reveals a 2.6 eV increase in the detachment energy of bromide anion due to the solvation effect of CO2, which is relatively small compared to that of the corresponding 4.7 eV increase in detachment energy in water.
Memory characteristics of laser-crystallized polycrystalline-silicon silicon-oxide-nitride-oxide-silicon thin-film transistor with location-controlled grain boundary perpendicular to the channel
Authors: Lee I-Che , Tsai Chun-Chien , Kuo Hsu-Hang , Yang Po-Yu , Wang Chao-Lung , Cheng Huang-Chung
Published: June 2012

An excimer-laser-crystallized polycrystalline-silicon silicon-oxide-nitride-oxide-silicon thin-film transistor with recessed-channel structure has been designed to achieve only one grain boundary with a protrusion perpendicular to the channel for investigating the grain boundary location effects on the memory characteristics. After programming, the devices demonstrated better memory characteristics as the grain boundary was allocated near the source junction. In contrast, the memory characteristics were degraded when the grain boundary was located near the drain junction. The phenomenon was explained by the 2-D device simulation and the energy band diagrams.
Electron localization in olivine materials for advanced lithium-ion batteries
Authors: Craco L. , Leoni S.
Published: June 2012

The olivines FePO4 and LiFePO4 are promising candidates for the next generation of lithium-ion batteries. Motivated thereby, we use a combination of first principles and many-body calculations to show the relevance of electronic correlations in these iron phosphate materials. We apply the theory to clarify relevant features seen in x-ray absorption and electrical transport experiments.
Isotope effect in the superconducting high-pressure simple cubic phase of calcium from first principles
Authors: Errea Ion , Rousseau Bruno , Bergara Aitor
Published: June 2012

It has been recently shown [I. Errea, B. Rousseau, and A. Bergara, Phys. Rev. Lett. 106, 165501 (2011)] that the phonons of the high-pressure simple cubic phase of calcium are stabilized by strong quantum anharmonic effects. This was obtained by a fully ab initio implementation of the self-consistent harmonic approximation including explicitly anharmonic coefficients up to fourth order. The renormalized anharmonic phonons make possible to estimate the superconducting transition temperature in this system, and a sharp agreement with experiments is found. In this work, this analysis is extended in order to study the effect of anharmonicity in the isotope effect. According to our calculations, despite the huge anharmonicity in the system, the isotope coefficient is predicted to be 0.45, close to the 0.5 value expected for a harmonic BCS superconductor.
On determining the strength of the electron-phonon interaction from electron energy relaxation times
Authors: Gadermaier C. , Kabanov V. V. , Alexandrov A. S. , Mihailovic D.
Published: June 2012

The strength of the electron-phonon interaction is most straightforwardly determined from electron energy relaxation times, provided that an appropriate relaxation scheme is assumed. We use literature data from fs spectroscopy on materials with different strengths of electron-phonon interaction to show that the commonly used two-temperature model is not suitable and a recently proposed non-equilibrium model should be used instead.
Deformation of periclase single crystals at high pressure and temperature: Quantification of the effect of pressure on slip-system activities
Authors: Girard Jennifer , Chen Jiuhua , Raterron Paul
Published: June 2012

In order to investigate the effect of pressure on periclase (MgO) dislocation slip-system activities, creep experiments have been carried out on MgO single crystals, at T and P, respectively, ranging from 1000 °C to 1200 °C and 4 to 9 GPa, in a deformation-DIA apparatus coupled with x-ray synchrotron radiation. Crystals were deformed in compression along either [100], [100], or [111] directions. These orientations were chosen to activate, respectively, either 1/2〈1-10〉{110} dislocation slip systems, 1/2〈1-10〉{100} systems, or simultaneously 1/2〈1-10〉{110} and 1/2〈1-10〉{100} systems. Experiments are carried out in a temperature range of 1000 °C to –1200 °C and a pressure range up to 8 GPa. Experimental results indicate that pressure influences differently the activities of these slip systems, which should yield a transition of dominant slip systems from 1/2〈1-10〉{110} at low pressure to 1/2〈1-10〉{100}. This pressure induced transition is expected to occur at 23 GPa, which would correspond to a pressure in the top portion of the lower mantle.
Fabrication of binary FeSe superconducting wires by diffusion process
Authors: Ozaki Toshinori , Deguchi Keita , Mizuguchi Yoshikazu , Kawasaki Yasuna , Tanaka Takayoshi , Yamaguchi Takahide , Kumakura Hiroaki , Takano Yoshihiko
Published: June 2012

We report successful fabrication of multi- and mono-core FeSe wires with high transport critical current density Jc using a simple in-situ Fe-diffusion process based on the powder-in-tube (Fe-diffusion PIT) method. The seven-core wire showed transport Jc of as high as 1027 A/cm2 at 4.2 K. The superconducting transition temperature Tczero was observed at 10.5 K in the wire-samples, which is about 2 K higher than that of bulk FeSe. The Fe-diffusion PIT method is suitable for fabricating multi-core wires of the binary FeSe superconductors with superior properties.
Electronic structure of La5/3Sr1/3NiO4 by x-ray emission spectroscopy and resonant inelastic x-ray scattering
Authors: Simonelli L. , Saini N. L. , Huotari S. , Giordano V. M. , Monaco G.
Published: June 2012

Here, we report a study of the electronic structure of La5/3Sr1/3NiO4 by x-ray emission spectroscopy (XES) and resonant inelastic x-ray scattering (RIXS). The combination of these techniques has permitted us to reveal a complete picture of the occupied and unoccupied states, and to identify various charge transfer transitions appearing as inelastic features in the RIXS spectra. The results add further information on the electronic excitations in this system, and show how the combination of XES and RIXS can be an important experimental tool to address basic physics of complex systems.
The comprehensive phase evolution for Bi2Te3 topological compound as function of pressure
Authors: Zhang S. J. , Zhang J. L. , Yu X. H. , Zhu J. , Kong P. P. , Feng S. M. , Liu Q. Q. , Yang L. X. , Wang X. C. , Cao L. Z. , Yang W. G. , Wang L. , Mao H. K. , Zhao Y. S. , Liu H. Z. , Dai X. , Fang Z. , Zhang S. C. , Jin C. Q.
Published: June 2012

The recently discovered three-dimensional topological insulator Bi2Te3 is studied as function of pressure in terms of crystal structures, resistance, and Hall coefficient. The superconductivity is found in phase I (ambient phase) Bi2Te3 with Tc ∼ 3 K, which is related to the topological features. The evolution of crystal structure with pressure is investigated by high pressure synchrotron radiation experiments that reveal structural transitions occurring at about 8 GPa, 13 GPa, and 16 GPa, respectively. Furthermore, the high pressure phases of Bi2Te3 are also superconducting but with much higher Tc ∼ 8 K. The superconducting transitions are compared with those for Bi, Te elements. A global phase diagram of Bi2Te3 as function of pressure up to 30 GPa is obtained.
Effect of thermal inhomogeneity for terahertz radiation from intrinsic Josephson junction stacks of Bi2Sr2CaCu2O8+δ
Authors: Kakeya Itsuhiro , Omukai Yuta , Yamamoto Takashi , Kadowaki Kazuo , Suzuki Minoru
Published: June 2012

Terahertz radiation from the mesa structures of Bi2Sr2CaCu2O8+δ is detected in samples with thin electrodes <100 nm. In samples with thick electrodes ≃400 nm, neither radiations nor voltage jumps in current-voltage characteristics are detected. This suggests that the thin electrode helps excite the Josephson plasma oscillation as a result of the poor heat flow through the electrode. The shielding effect by the electrode is not essential. We consider that the local temperature rise is the origin of the synchronization of the phase kink for terahertz radiation.
High resolution synchrotron radiation based photoemission study of the in situ deposition of molecular sulphur on the atomically clean InGaAs surface
Authors: Chauhan Lalit , Hughes Greg
Published: June 2012

High resolution synchrotron radiation core level photoemission studies were performed on atomically clean 0.5 μm thick In0.53Ga0.47As (100) epilayers lattice matched to InP substrates following the removal of a 100 nm protective arsenic cap at 410  °C. Both n-type (Si doped 5 × 1017 cm−3) and p-type (Be doped 5 × 1017 cm−3) InGaAs samples were subsequently exposed in situ to molecular sulphur at room temperature, and the resulting changes in the surface chemical composition were recorded. The photoemission spectra indicate evidence of As-S, Ga-S, and In-S bond formation and the substitution of As in the near surface region by sulphur. Annealing to 400  °C results in the complete removal of the As-S bonding component with both Ga-S and In-S bonding configurations remaining. After the anneal, the Fermi level position for both n-type and p-type samples resides at the top of the bandgap indicating a near flat band condition for n-type and significant band bending on the p-type sample. The results of angle resolved photoemission measurements suggest that the sulphur has substituted arsenic in the near surface region resulting in both samples displaying n-type surface behaviour. Annealing to higher temperatures results in the loss of In from the surface without any significant change in the Ga, As, or S signals. Work function measurements on both doping types after sulphur deposition and anneal show similar behaviour displaying a value close to 6 eV which is indicative of the formation of a surface dipole layer related to the presence of sulphur on the surface.
Mean field renormalization group: A theoretical approach to the Fe1−qAlq in the bcc lattice
Authors: Freitas A. S. , de Albuquerque Douglas F. , Moreno N. O.
Published: June 2012

In this work, the site diluted Heisenberg model is applied to study the magnetic properties of the bcc disordered phase of FeAl alloys by employing mean field renormalization group theory. We suggest a new approach to exchange interaction between nearest neighbors of Fe that depends on de powers of the Al (q) instead of the linear dependence proposed in other papers. Excellent agreement with the experimental data in the T – q plane have been obtained, in particular, in the region with anomalous behavior of the alloy concerned.
Experimental and ab initio investigations of the x-ray absorption near edge structure of orthorhombic LuMnO3
Authors: Hu Y. , Borca C. N. , Kleymenov E. , Nachtegaal M. , Delley B. , Janousch M. , Dönni A. , Tachibana M. , Kitazawa H. , Takayama-Muromachi E. , Kenzelmann M. , Niedermayer C. , Lippert T. , Wokaun A. , Schneider C. W.
Published: June 2012

X-ray near edge absorption spectroscopy was used to probe the electronic structure of multiferroic orthorhombic LuMnO3 polycrystalline samples and strained, twin-free orthorhombic (1–10) LuMnO3 films grown by pulsed laser deposition on (1–10) YAlO3 substrates. For all o-LuMnO3 samples x-ray near edge absorption spectroscopy spectra reveal that the pre-edge structure is influenced by the increase in MnO6 distortion as a result of the smaller Re-ion or film strain. Furthermore there is clear evidence of anisotropic Mn-O bonding and Mn orbital ordering along the c- and [110] direction. The experimental film and bulk data are in agreement with ab initio simulations.
Optically addressed near and long-wave infrared multiband photodetectors
Authors: Cellek O. O. , Reno J. L. , Zhang Y.-H.
Published: June 2012

Optically addressed dual-band photodetector incorporating of a 0.82 μm cut-off wavelength near-infrared (NIR) AlGaAs/GaAs p-i-n photodetector and a 8.2 μm peak wavelength long-wave infrared (LWIR) AlGaAs/GaAs quantum well infrared photodetector on GaAs substrate is fabricated and characterized. Switching between NIR and LWIR bands is demonstrated by using external light bias. The dual-band photodetector gives 65% quantum efficiency in NIR band and specific detectivity of 2 × 109 cm Hz1/2/W in LWIR band at 68 K. Spectral crosstalk is better than 25 dB. These devices enable the use of only a single indium-bump per pixel for multiband image sensor arrays to have maximum fill factor.
Room temperature femtotesla radio-frequency atomic magnetometer
Authors: Chalupczak W. , Godun R. M. , Pustelny S. , Gawlik W.
Published: June 2012

A radio-frequency tunable atomic magnetometer with a sensitivity of about 1 fT/Hz1/2 in a range of 10–500 kHz is demonstrated. The magnetometer is operated in the orientation configuration in which atoms are pumped to the stretched atomic state by a scheme based on indirect optical pumping using only one unmodulated, low-power laser. The magnetometer operates with cesium atoms, which have sufficient vapor pressure near room temperature to enable high magnetometric sensitivities. The technique enables a compact and robust module to be constructed that could become an in-the-field device.
Monodisperse water microdroplets generated by electrohydrodynamic atomization in the simple-jet mode
Authors: Agostinho L. L. F. , Yurteri C. U. , Fuchs E. C. , Marijnissen J. C. M.
Published: June 2012

Experiments were conducted in order to investigate the influences of flow rate, applied voltage, and electric conductivity on droplet size and size distribution of water electrosprays in the simple-jet mode. The results show that the electric potential decreases significantly the relative standard deviation (RSD) of the spray size distribution, with the best result obtained for Weber number, We = 3.3 (240 ml/h) when the RSD decreases from 0.50 at 0 kV to 0.18 at 5 kV. We conclude that simple-jet mode electrosprays are a good option for applications which require monodisperse micrometer droplets with high throughput.
Photoexcited carrier dynamics in AlInN/GaN heterostructures
Authors: Liuolia V. , Marcinkevičius S. , Billingsley D. , Shatalov M. , Yang J. , Gaska R. , Shur M. S.
Published: June 2012

Photoexcited carrier dynamics and localization potentials in Al0.86In0.14N/GaN heterostructures have been examined by time-resolved and scanning near-field photoluminescence (PL) spectroscopy. The large GaN and AlInN PL intensity difference, and the short AlInN PL decay and GaN PL rise times indicate efficient photoexcited hole transfer from AlInN to GaN via sub-band-gap states. These states are attributed to extended defects and In clusters. Near-field PL scans show that diameter of the localization sites and the distance between them are below 100 nm. Spatial variations of the GaN PL wavelength have been assigned to the electric field inhomogeneities at the heterostructure interface.
Large magnetic moment of gadolinium substituted topological insulator: Bi1.98Gd0.02Se3
Authors: Song Y. R. , Yang Fang , Yao Meng-Yu , Zhu Fengfeng , Miao Lin , Xu Jin-Peng , Wang Mei-Xiao , Li H. , Yao X. , Ji Fuhao , Qiao S. , Sun Z. , Zhang G. B. , Gao B. , Liu Canhua , Qian Dong , Gao C. L. , Jia Jin-Feng
Published: June 2012

The crystal structure, electronic, and magnetic properties of Gadolinium (Gd) substituted Bi2Se3—represented by Bi1.98Gd0.02Se3—were investigated systematically by scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and superconducting quantum interference device. Gd dopants with valence of 3+ were mainly found to substitute Bi atoms. Each Gd3+ ion has a magnetic moment as large as ∼6.9μB in the bulk paramagnetic state.
Josephson comparator with modified dynamic behavior for improved sensitivity
Authors: Ortlepp T. , Miyajima S. , Toepfer H. , Fujimaki A.
Published: June 2012

The decision of a Josephson comparator is influenced by thermal noise which is limiting the practical sensitivity in many applications of superconductor electronics. We analyzed the Gaussian state distribution theoretically and identified the most effective way to improve the practical sensitivity of a Josephson comparator. We suggest a modified damping concept and demonstrate a gray zone width as low as 840 nA experimentally. This value is about ten times smaller than for conventional Josephson comparators and very close to the theoretical limit at liquid helium temperature.
Electronic band gaps and transport in aperiodic graphene superlattices of Thue-Morse sequence
Authors: Ma Tianxing , Liang Chun , Wang Li-Gang , Lin Hai-Qing
Published: June 2012

We have studied the electronic properties in aperiodic graphene superlattices of Thue-Morse sequence. Although the structure is aperiodic, an unusual Dirac point (DP) does exist and its location is exactly at the energy corresponding to the zero-averaged wave number (zero-k¯). Furthermore, the zero-k¯ gap associated with the DP is robust against the lattice constants and the incident angles, and multi-DPs may appear under the suitable conditions. A resultant controllability of electronic transport in Thue-Morse sequence is predicted, which may facilitate the development of many graphene-based electronics.
Simple adaptive output-feedback lag-synchronization of multiple time-delayed chaotic systems
Authors: Pourdehi Shabnam , Karimaghaee Paknosh
Published: June 2012

In this letter, a simple adaptive output-feedback controller is designed for lag-synchronization of two multiple time-delayed chaotic systems in the presence of uncertainty, external disturbances, and input nonlinearity. Based on Lyapunov stability theorem and adaptive techniques, sufficient conditions for lag-synchronization of these two systems are achieved. To deal with the existence of unknown time-delays in the system dynamics, the novel Lyapunov–Krasovskii functionals are used. Finally, a numerical simulation is presented to show the effectiveness of the proposed chaos lag-synchronization scheme.
Optical manipulation of shape-morphing elastomeric liquid crystal microparticles doped with gold nanocrystals
Authors: Sun Yaoran , Evans Julian S. , Lee Taewoo , Senyuk Bohdan , Keller Patrick , He Sailing , Smalyukh Ivan I.
Published: June 2012

We demonstrate facile optical manipulation of shape of birefringent colloidal microparticles made from liquid crystal elastomers. Using soft lithography and polymerization, we fabricate elastomeric microcylinders with weakly undulating director oriented on average along their long axes. These particles are infiltrated with gold nanospheres acting as heat transducers that allow for an efficient localized transfer of heat from a focused infrared laser beam to a submicrometer region within a microparticle. Photothermal control of ordering in the liquid crystal elastomer using scanned beams allows for a robust control of colloidal particles, enabling both reversible and irreversible changes of shape. Possible applications include optomechanics, microfluidics, and reconfigurable colloidal composites with shape-dependent self-assembly.
Magnetic anisotropy engineering: Single-crystalline Fe films on ion eroded ripple surfaces
Authors: Liedke M. O. , Körner M. , Lenz K. , Grossmann F. , Facsko S. , Fassbender J.
Published: June 2012

We present a method to preselect the direction of an induced in-plane uniaxial magnetic anisotropy (UMA) in thin single-crystalline Fe films on MgO(001). Ion beam irradiation is used to modulate the MgO(001) surface with periodic ripples on the nanoscale. The ripple direction determines the orientation of the UMA, whereas the intrinsic cubic anisotropy of the Fe film is not affected. Thus, it is possible to superimpose an in-plane UMA with a precision of a few degrees—a level of control not reported so far that can be relevant for example in spintronics.
Dielectric relaxation and magneto-dielectric effect in polycrystalline Bi0.9Ca0.1FeO2.95
Authors: Ramachandran B. , Dixit A. , Naik R. , Lawes G. , Ramachandra Rao M. S.
Published: June 2012

We have investigated temperature, frequency, and magnetic field dependent dielectric properties of polycrystalline Bi0.9Ca0.1FeO2.95. Two dielectric anomalies, near 65 K and 260 K, were observed with the anomaly near 65 K exhibiting distinct frequency dependence as the peak temperature shifts with increasing frequency. The low-temperature dielectric relaxation data that can be fitted to a Vogel-Fulcher expression yielding a characteristic relaxation time of ∼10−8 s are four orders larger than that of pure BiFeO3 which may be the resultant of the chemical pressure induced by Ca doping. We also observed a switchable magneto-dielectric response in Bi0.9Ca0.1FeO2.95 at room temperature.
Microscopic energy conversion process in the ion drift region of electrohydrodynamic flow
Authors: Kim Chul , Noh Kwang-Chul , Hyun Junho , Lee Sang-Gu , Hwang Jungho , Hong Hiki
Published: June 2012

We theoretically investigated the momentum transfer and energy conversion process of ion-neutral and ensuing neutral-neutral collisions in the ion drift region of electrohydrodynamic flow. Our results are presented in explicit equations with physical interpretations of the phenomena. The unit conversion process was estimated to sustain for 1.0 nano-second in a very tiny 0.5-μm-sized volume in the air. Also, the continuum-based equation formulations are presented according to the microscopic energy conversion phenomena. Numerical simulations reflecting those formulations are performed to verify the theoretical results and experimentally supported by an air corona discharge.
Anti-phase synchronization of two coupled mechanical metronomes
Authors: Wu Ye , Wang Nianchuang , Li Lixiang , Xiao Jinghua
Published: June 2012

This paper mainly investigates the anti-phase synchronization of two coupled mechanical metronomes not only by means of numerical simulations, but also by experimental tests. It is found that the attractor basin of anti-phase synchronization enlarges as the rolling friction increases. Furthermore, this paper studies the relationship between different initial conditions and synchronization types. The impacts of rolling friction on in-phase and anti-phase synchronization times are also discovered. Finally, in-phase and anti-phase synchronization conditions of non-identical metronomes are discussed. These results indicate the potential complexity of the dynamics of coupled metronomes.
Phase-flip transition in nonlinear oscillators coupled by dynamic environment
Authors: Sharma Amit , Dev Shrimali Manish , Kumar Dana Syamal
Published: June 2012

We study the dynamics of nonlinear oscillators indirectly coupled through a dynamical environment or a common medium. We observed that this form of indirect coupling leads to synchronization and phase-flip transition in periodic as well as chaotic regime of oscillators. The phase-flip transition from in- to anti-phase synchronization or vise-versa is analyzed in the parameter plane with examples of Landau-Stuart and Rössler oscillators. The dynamical transitions are characterized using various indices such as average phase difference, frequency, and Lyapunov exponents. Experimental evidence of the phase-flip transition is shown using an electronic version of the van der Pol oscillators.
Ab initio-based study for adatom kinetics on AlN(0001) surfaces during metal-organic vapor-phase epitaxy growth
Authors: Akiyama Toru , Nakamura Kohji , Ito Tomonori
Published: June 2012

The kinetics of Al and N adatoms on reconstructed AlN(0001) surfaces under growth conditions is investigated by performing first-principles pseudopotential calculations. Our calculations reveal that the adsorption of Al adatom strongly depends on the surface reconstruction while its diffusion is not affected by the reconstruction: the adsorption of Al adatom on the surface under N-rich conditions is much easier than that under H-rich conditions. These results indicate that the growth of AlN during metal-organic vapor-phase epitaxy is prominent under N-rich conditions rather than H-rich conditions, consistent with experimentally reported growth rate difference.
Electrothermal actuation of metal-insulator transition in SmNiO3 thin film devices above room temperature
Authors: Ha Sieu D. , Viswanath B. , Ramanathan Shriram
Published: June 2012

We demonstrate that a metal-insulator phase transition can be electrothermally actuated in the correlated complex oxide SmNiO3 (SNO) above room temperature from current-voltage measurements on thin film two-terminal devices. We simulate the internal temperature of SmNiO3 as a function of applied dc power by a Joule heating mechanism with substrate/electrode dissipation and find good agreement with experiment and device scaling. The results are relevant towards integrating correlated oxide phase transition functionality into semiconductor electronic/optoelectronic platforms.
Single domain vs. polydomain [111] 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystal. Polarization switching, dielectric and pyroelectric properties
Authors: Dietze Matthias , Katzke Hannelore , Es-Souni M. , Neumann Norbert , Luo Hao-Su
Published: June 2012

We introduce a poling treatment to induce a single domain structure in [111] single crystals of 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-PT). The properties obtained differ from those known for domain-engineered [111] PMN-PT single crystals. The dielectric, ferroelectric, and pyroelectric properties of this single domain structure are assessed in comparison to polydomain single crystals that were poled by conventional poling treatment. The attributes of the single domain state are a single switching event that reflects in a discontinuity of polarization at the coercive field, a substantially lower dielectric loss (than the multidomain state), and a higher detectivity for pyroelectric applications.
Electron-dependent thermoelectric properties in Si/Si1-xGex heterostructures and Si1-xGex alloys from first-principles
Authors: Hossain M. Z. , Johnson H. T.
Published: June 2012

Unlike phononic thermal conductivity (which is shown in the literature to be reduced due to alloying and has a nearly constant value over a range of compositional variations), electron-dependent thermoelectric properties are shown here, from first-principles, to vary nonlinearly with composition. Of the Si/Si1−xGex systems considered, the maximum thermopower observed, which is 10% higher than that of crystalline Si, is obtained for a Si0.875Ge0.125 alloy. Also, heterostructuring is shown to reduce thermopower, electrical conductivity, and electron thermal conductivity. Additionally, neither Lorenz number nor Seebeck coefficient shows oscillations for heterostructures, regardless of electron/hole energies, contradicting the conclusions obtained with miniband approximations.
Surface load induced electrical impedance shift in relaxor-PbTiO3 crystal piezoelectric resonators
Authors: Kim Kyungrim , Zhang Shujun , Jiang Xiaoning
Published: June 2012

The effect of surface loads on Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal piezoelectric resonators was studied. Electrical impedance shifts at both resonance and anti-resonance frequencies due to surface loads were recorded for comparison among face-shear mode, thickness-shear mode, and thickness mode resonators. It was observed that electrical impedances of face shear mode resonators exhibited significantly higher sensitivity to surface load changes comparing with other resonators with similar dimensions, because of enhanced energy dissipation in face shear mode resonators, indicating a promising innovative face-shear mode single crystal piezoelectric sensing mechanism.
Magnetic properties of CoFe2O4 nanoparticles distributed in a multiferroic BiFeO3 matrix
Authors: Sone Keita , Sekiguchi Sho , Naganuma Hiroshi , Miyazaki Takamichi , Nakajima Takashi , Okamura Soichiro
Published: June 2012

BiFeO3-CoFe2O4 composite thin films were formed on Pt/Ti/SiO2/Si(100) substrates by chemical solution deposition from a mixed precursor solution. X-ray diffraction and transmission electron microscopy analyses confirmed that CoFe2O4 nanoparticles less than 10 nm were uniformly distributed in the BiFeO3 matrix. The BiFeO3-CoFe2O4 composite films exhibited the same ferroelectric switching charge as BiFeO3 thin films, although a larger applied electric field was necessary. However, the magnetic properties were significantly improved by incorporation of CoFe2O4 nanoparticles into BiFeO3; a saturated magnetization of 80 emu/cm3 and a magnetic coercive field of 450 Oe were attained at 300 K. Furthermore, the composite films did not show superparamagnetic behavior in zero-field-cooling and field-cooling measurements, which suggest that the thermal fluctuation of CoFe2O4 nanoparticles was suppressed by exchange coupling with BiFeO3.
Acquiring verbs in Spanish
Authors: Serrat Elisabet , Sanz-Torrent Mònica , Feijóo Sara , Chireac Silvia Maria , Hilferty Joseph
Published: June 2012

The objective of the present study focuses on exploring two proposals about the acquisition of the grammatical category of verb. On the one hand, the study aims at analyzing whether the acquisition of a given mass of verbal lexical items occurs before the emergence of productive verbal morphology. On the other hand, the study also explores the possibility that the acquisition of negative structures emerges before productive verbal morphology as well. The study presents longitudinal data based on the linguistic production of a monolingual Spanish-speaking girl at the age of 19 to 27 months. These data show that the amount of verbal vocabulary is a good indicator of productivity as far as verbal morphology is concerned, but such vocabulary development occurs simultaneous to morphological development. The data also show that the learning and productive use of negation occurs before productivity in verbal morphology. These results are discussed in connection to the approach that claims that distributional analysis is a good mechanism for the acquisition of grammatical categories.
Rice sequences of relations
Authors: Montalbán Antonio
Published: June 2012

We propose a framework to study the computational complexity of definable relations on a structure. Many of the notions we discuss are old, but the viewpoint is new. We believe that all the pieces fit together smoothly under this new point of view. We also survey related results in the area. More concretely, we study the space of sequences of relations over a given structure. On this space, we develop notions of c.e.-ness, reducibility, join and jump. These notions are equivalent to other notions studied in other settings. We explain the equivalences and differences between these notions.
Certifiable quantum dice
Authors: Vazirani Umesh , Vidick Thomas
Published: June 2012

We introduce a protocol through which a pair of quantum mechanical devices may be used to generatenrandom bits that areε-close in statistical distance fromnuniformly distributed bits, starting from a seed ofuniform bits. The bits generated are certifiably random, based only on a simple statistical test that can be performed by the user, and on the assumption that the devices obey the no-signalling principle. No other assumptions are placed on the devices' inner workings: it is not necessary to even assume the validity of quantum mechanics.
Sonographic Gallbladder Abnormality Is Associated with Intravenous Immunoglobulin Resistance in Kawasaki Disease
Authors: Chen Chih-Jen , Huang Fu-Chen , Tiao Mao-Meng , Huang Ying-Hsien , Lin Li-Yan , Yu Hong-Ren , Yang Kuender D. , Huang Yi-Chuan , Chen Chih-Cheng , Chang Wei-Chiao , Kuo Ho-Chang
Published: June 2012

Objective. Kawasaki disease (KD) is an acute systematic vasculitis in children which causes coronary arterial lesions and hydrops of gallbladder. Our objective is to correlate the clinical significance and influence on disease outcome of patients with gallbladder abnormalities in Kawasaki dissease.Methods. Children who met KD diagnosis criteria and were admitted for IVIG treatment were retrospectively enrolled for analysis. Patients with abdominal sonography were divided into 2 groups based on the absence (Group A,N=61) or presence (Group B,N=16) of gallbladder abnormalities (GBA), defined as hydrops or acalculous cholecystitis. Between the two groups, clinical features, demographic data (including admission days, coronary artery lesions, IVIG resistance), and laboratory data before/after IVIG treatment were collected for analysis.Results. The presence of sonographic gallbladder abnormalities is correlated with higher levels of serum CRP, GPT, and neutrophils. It also points to an increased number of IVIG resistance rates in group B. There was no significant statistical difference among clinical features, age, gender, admission days, or coronary artery lesions between the two groups.Conclusion. Sonographic gallbladder abnormalities are associated with higher CRP, GPT, neutrophil and IVIG resistance in KD. It can be used as a predictor of IVIG resistance in patients with KD.
The Effects of Subchronic Exposure to Metribuzin onDanio rerio
Authors: Plhalova Lucie , Stepanova Stanislava , Praskova Eva , Chromcova Lucie , Zelnickova Lenka , Divisova Lenka , Skoric Misa , Pistekova Vladimira , Bedanova Iveta , Svobodova Zdenka
Published: June 2012

The aim of this study was to assess the impact of metribuzin in surface waters on fish under experimental conditions. The effects of subchronic exposure to metribuzin on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver) and on activity of some biochemical markers (CYP450, EROD) inDanio reriowere investigated during a 28-day toxicity test. Juvenile growth tests were performed onD. rerioaccording to OECD method number 215. Fish at an initial age of 30 days were exposed to a range of metribuzin concentrations (1.5, 5, 16, 33, and 53 mg L−1). Exposure to metribuzin at 53 mg L−1was associated with increased mortality. Negative effects with regard to total body weight, length, and the inhibition of specific growth rate were induced at concentrations of 33 and 53 mg L−1. Histopathological examination revealed pathological lesions in the liver in pesticide-exposed fish only at the highest concentration of 53 mg L−1of metribuzin. Based on the results of growth rate, biochemical markers (CYP450, EROD), and histopathological examination, the lowest observed effect concentration (LOEC) value was 33 mg L−1and the no observed effect concentration (NOEC) value was 16 mg L−1.
Expression and delivery of tetanus toxin fragment C fused to the N‐terminal domain of SipB enhances specific immune responses in mice
Authors: Jang Jung Im , Kim Jin Seok , Eom Jeong Seon , Kim Hyeon Guk , Kim Bae Hoon , Lim Sangyong , Bang Iel‐Soo , Park Yong Keun
Published: June 2012

Live attenuated bacteria can be used as a carrier for the delivery of foreign antigens to a host's immune system. The N‐terminal domain of SipB, a translocon protein of the type III secretion system of Salmonella enterica serovar Typhimurium, is required for secretion and outer membrane localization. In the present study, vaccine plasmids for antigen delivery in which the non‐toxic tetanus toxin fragment C (TTFC), which contains a T cell epitope, is fused to the N‐terminal 160 amino acids of SipB were developed. It was found that the recombinant proteins are secreted into the culture media and localized to the bacterial surface. TTFC‐specific antibody responses are significantly increased in mice orally immunized with attenuated S. Typhimurium BRD509 strains carrying TTFC delivery plasmids. When the TTFC delivery cassettes were introduced into a low copy vector, the plasmid was stably maintained in the BRD509 strain and induced an immune response to the TTFC antigen in mice. These results suggest that expression and delivery of heterologous antigens fused to the N‐terminus of SipB enhance the induction of antigen‐specific immune responses, and that the N‐terminal domain of SipB can be used as a versatile delivery system for foreign antigens.
An environmental epigenetic study of ADRB2 5′‐UTR methylation and childhood asthma severity
Authors: Fu A. , Leaderer B. P. , Gent J. F. , Leaderer D. , Zhu Y.
Published: June 2012

Background

Beta‐2 adrenergic receptor (ADRB2) is the primary target of both short‐ and long‐acting beta‐agonist asthma medications.
ADRB2 5′‐UTR methylation changes in blood have the potential to act as a surrogate biomarker of responsiveness to beta‐agonist treatment and childhood asthma severity.

Objective

To study the association between
ADRB2 5′‐UTR methylation, NO
2 exposure and childhood asthma severity.

Methods

We compared
ADRB2 5′‐UTR methylation levels in blood between 60 children with mild asthma and 122 children with severe asthma using methylation‐specific PCR. We also investigated potential joint effects between NO
2 exposure and
ADRB2 5′‐UTR methylation.

Results

We found a significant association between intermediate (OR: 4.11, 95% CI: 1.58–10.73) and high levels (OR: 7.63, 95% CI: 3.02–19.26) of
ADRB2 methylation and severe childhood asthma. In addition, we found a significant association between indoor exposure to NO
2, an air pollutant and known asthmogen, and severe asthma among children exhibiting high
ADRB2 methylation (OR: 4.59, 95% CI: 1.03–20.55) but no association among children exhibiting low levels of
ADRB2 methylation (OR: 0.35, 95% CI: 0.01–14.13).

Conclusions and Clinical Relevance

These findings support the potential use of
ADRB2 5′‐UTR methylation as a biomarker of both asthma severity and risk for NO
2‐associated asthma exacerbations in children, and present the first evidence of an epigenetic link between an important environmental exposure and childhood asthma severity.