bluuebunny/crossref_metadata_2025 huggingface dataset:
Tsunamigenic ionospheric hole
Authors: Kakinami Yoshihiro , Kamogawa Masashi , Tanioka Yuichiro , Watanabe Shigeto , Gusman Aditya Riadi , Liu Jann‐Yenq , Watanabe Yasuyuki , Mogi Toru
Published: April 2012

Traveling ionospheric disturbances generated by an epicentral ground/sea surface motion, ionospheric disturbances associated with Rayleigh‐waves as well as post‐seismic 4‐minute monoperiodic atmospheric resonances and other‐period atmospheric oscillations have been observed in large earthquakes. In addition, a giant tsunami after the subduction earthquake produces an ionospheric hole which is widely a sudden depletion of ionospheric total electron content (TEC) in the hundred kilometer scale and lasts for a few tens of minutes over the tsunami source area. The tsunamigenic ionospheric hole detected by the TEC measurement with Global Position System (GPS) was found in the 2011 M9.0 off the Pacific coast of Tohoku, the 2010 M8.8 Chile, and the 2004 M9.1 Sumatra earthquakes. This occurs because plasma is descending at the lower thermosphere where the recombination of ions and electrons is high through the meter‐scale downwelling of sea surface at the tsunami source area, and is highly depleted due to the chemical processes.
Remote and in situ observations of an unusual Earth‐directed coronal mass ejection from multiple viewpoints
Authors: Nieves‐Chinchilla T. , Colaninno R. , Vourlidas A. , Szabo A. , Lepping R. P. , Boardsen S. A. , Anderson B. J. , Korth H.
Published: April 2012

During June 16–21, 2010, an Earth‐directed coronal mass ejection (CME) event was observed by instruments onboard STEREO, SOHO, MESSENGER and Wind. This event was the first direct detection of a rotating CME in the middle and outer corona. Here, we carry out a comprehensive analysis of the evolution of the CME in the interplanetary medium comparing in situ and remote observations, with analytical models and three‐dimensional reconstructions. In particular, we investigate the parallel and perpendicular cross section expansion of the CME from the corona through the heliosphere up to 1 AU. We use height‐time measurements and the Gradual Cylindrical Shell (GCS) technique to model the imaging observations, remove the projection effects, and derive the 3‐dimensional extent of the event. Then, we compare the results with in situ analytical Magnetic Cloud (MC) models, and with geometrical predictions from past works. We find that the parallel (along the propagation plane) cross section expansion agrees well with the in situ model and with the Bothmer and Schwenn (1998) empirical relationship based on in situ observations between 0.3 and 1 AU. Our results effectively extend this empirical relationship to about 5 solar radii. The expansion of the perpendicular diameter agrees very well with the in situ results at MESSENGER (∼0.5 AU) but not at 1 AU. We also find a slightly different, from Bothmer and Schwenn (1998), empirical relationship for the perpendicular expansion. More importantly, we find no evidence that the CME undergoes a significant latitudinal over‐expansion as it is commonly assumed. Instead, we find evidence that effects due to CME rotation and expansion can be easily confused in the images leading to a severe overestimation of the proper 3D size of the event. Finally, we find that the reconstructions of the CME morphology from the in situ observations at 1 AU are in agreement with the remote sensing observations but they show a big discrepancy at MESSENGER. We attribute this discrepancy to the ambiguity of selecting the proper boundaries due to the lack of accompanying plasma measurements.
Observations of quasi‐perpendicular propagating electromagnetic waves near the ionopause current sheet of Venus
Authors: Wei H. Y. , Russell C. T. , Daniels J. T. M. , Zhang T. L. , Strangeway R. J. , Luhmann J. G.
Published: April 2012

Due to the lack of an intrinsic magnetic field at Venus, the Venus ionosphere acts as the obstacle to the incoming solar wind flow. Induced currents flowing on the ionopause resist the penetration of the solar wind magnetic fields into the ionosphere. The Venus Express magnetometer occasionally observes plasma waves near the ionopause. These waves propagate quasi‐perpendicularly to the background magnetic field, which are distinctively different from the lightning‐generated whistler waves. Both case and statistical studies are performed on the Venus Express magnetometer data in 32 Hz and 128 Hz resolutions for these quasi‐perpendicular propagating waves. These waves are found to be strongly associated with current sheets near the ionopause, either occurring at the center of a sharp current, or occurring at the edge of a current. The earlier Pioneer Venus Orbiter electric field observations also detected plasma waves associated with field‐aligned currents near the ionopause region, and the wave studies in this paper are possibly the magnetic counterparts of those earlier observations. These waves could be generated from the free energy of currents at the ionopause and could lead to dissipation of those currents.
Contrails developed under frontal influences of the North Atlantic
Authors: Laken B. A. , Pallé E. , Kniveton D. R. , Williams C. J. R. , Kilham D. A.
Published: April 2012

Satellite imagery reveals a visually striking pattern of persistent line‐shaped contrails located to the Northwest of the British Isles on 1 September 2007, just before sunrise. These contrails formed over the heavily trafficked eastbound North Atlantic Track (NAT) flight paths, as they intersected an area of prefrontal mixing. The high relative humidity with respect to ice within the prefrontal mixing zone allowed the contrails to persist, while the strictly regulated flight paths over the region account for their remarkable shapes. The positioning of the NAT flight paths to take advantage of the jet stream likely maximized regional contrail formation. An estimation of the outgoing top of the atmosphere longwave (LW) flux from the CERES instrument shows that the contrails reduced the local instantaneous LW emissivity by 20.96 (±0.26) W/m2. This example demonstrates that for middle latitude regions, prefrontal mixing is an important factor governing the radiative influence of contrails. However, a full estimation of the radiative impact is not possible, as we cannot specify the amount of shortwave forcing caused by the persistence of the contrails into daytime; moreover, several hours after formation the line‐shaped contrails spread and overlapped with pre‐existing cloud structures.
A new global database of Mars impact craters ≥1 km: 2. Global crater properties and regional variations of the simple‐to‐complex transition diameter
Authors: Robbins Stuart J. , Hynek Brian M.
Published: April 2012

We have generated a new, 384,343‐entry global crater database of Mars, statistically complete for craters with diameters D ≥ 1 km. In this release, the database contains detailed morphologic and morphometric data for craters D ≥ 3 km (future releases will extend these to smaller diameters). With detailed topographic data for the largest crater database to‐date, we analyzed crater depth‐to‐diameter ratios for simple and complex morphologies across various terrains and for the planet as a whole and investigated the simple‐to‐complex morphology transition. Our results are similar to those in the published literature, but we found a substantial terrain dependence of the simple‐to‐complex transition that occurs at ∼11‐km‐diameter craters at high latitudes. This suggests a model that requires melting of volatiles during high‐latitude crater formation that fill the crater during the modification phase but will still support the simple morphology to larger diameters. We also use this database to reexamine previously observed distributions and patterns to show its fidelity and to further explore other global relationships of fresh craters, those with central peaks, pits, and summit pits. We present the global distribution of craters with different types of ejecta and morphometric properties. Overall, this database is shown to be comparable to previous databases where there is overlap and to be useful in extending prior work into new regimes.
Morainal bank progradation and sediment accumulation in Disenchantment Bay, Alaska: Response to advancing Hubbard Glacier
Authors: Goff John A. , Lawson Daniel E. , Willems Bryce A. , Davis Marcy , Gulick Sean P. S.
Published: April 2012

Morainal banks are primary features at the margins of advancing and stable to quasi‐stable temperate tidewater glaciers, yet their roles in glacier dynamics and terminus stability are poorly defined by submarine observations. Analysis of new and archival multibeam data and Landsat images of the advancing Hubbard Glacier, southeast Alaska, reveal that between 1978 and 2010 the ice face and morainal bank advanced together at an average rate of ∼34 m/yr, varying spatially and temporally between 14 and 80 m/yr. Morphological features including gullies and a boulder lag suggest cyclical deposition and gravitational erosion on the proximal slope of the morainal bank (15–18°), and possible ice pushing in an area without recent sedimentation. In contrast, the morainal bank of the nearby, quasi‐stable (surging) Turner Glacier advanced steadily since 1978 by proximal sedimentation on the steep fjord wall below its hanging valley. Sedimentation in the deep (>220 m) basin of Disenchantment Bay increased from 0.88 m/yr spanning 1978 to 1999, to 1.22 m/yr thereafter. This change appears to be a combined response to glacier advance and sediment dispersal farther down‐fjord, and to an increase in sediment yield from other glacial and non‐glacial sources. Analysis of Hubbard Glacier illustrates the direct correlation between movement of the terminus and morainal bank in advancing the grounding line of a marine‐terminating glacier, and that morainal banks provide a fundamental stabilizing role for advance into a deep‐water fjord, compensating for changes in water depth at the grounding line.
Plate interaction in the NE Caribbean subduction zone from continuous GPS observations
Authors: ten Brink Uri S. , López‐Venegas Alberto M.
Published: April 2012

Kinematic similarities between the Sumatra and Puerto Rico Trenches highlight the potential for a mega‐earthquake along the Puerto Rico Trench and the generation of local and trans‐Atlantic tsunamis. We used the horizontal components of continuous GPS (cGPS) measurements from 10 sites on NE Caribbean islands to evaluate strain accumulation along the North American (NA) – Caribbean (CA) plate boundary. These sites move westward and slightly northward relative to CA interior at rates ≤2.5 mm/y. Provided this motion originates in the subduction interface, the northward motion suggests little or no trench‐perpendicular thrust accumulation and may in fact indicate divergence north of Puerto Rico, where abnormal subsidence, bathymetry, and gravity are observed. The Puerto Rico Trench, thus, appears unable to generate mega‐earthquakes, but damaging smaller earthquakes cannot be discounted. The westward motion, characterized by decreasing rate with distance from the trench, is probably due to eastward motion of CA plate impeded at the plate boundary by the Bahamas platform. Two additional cGPS sites in Mona Passage and SW Puerto Rico move to the SW similar to Hispaniola and unlike the other 10 sites. That motion relative to the rest of Puerto Rico may have given rise to seismicity and normal faults in Mona Rift, Mona Passage, and SW Puerto Rico.
Distinct functional roles of the two terminal halves of eukaryotic phosphofructokinase
Authors: Martínez-Costa Oscar H. , Sánchez Valentina , Lázaro Antonio , Hernández Eloy D. , Tornheim Keith , Aragón Juan J.
Published: April 2012

Eukaryotic PFK (phosphofructokinase), a key regulatory enzyme in glycolysis, has homologous N- and C-terminal domains thought to result from duplication, fusion and divergence of an ancestral prokaryotic gene. It has been suggested that both the active site and the Fru-2,6-P2 (fructose 2,6-bisphosphate) allosteric site are formed by opposing N- and C-termini of subunits orientated antiparallel in a dimer. In contrast, we show in the present study that in fact the N-terminal halves form the active site, since expression of the N-terminal half of the enzymes from Dictyostelium discoideum and human muscle in PFK-deficient yeast restored growth on glucose. However, the N-terminus alone was not stable in vitro. The C-terminus is not catalytic, but is needed for stability of the enzyme, as is the connecting peptide that normally joins the two domains (here included in the N-terminus). Co-expression of homologous, but not heterologous, N- and C-termini yielded stable fully active enzymes in vitro with sizes and kinetic properties similar to those of the wild-type tetrameric enzymes. This indicates that the separately translated domains can fold sufficiently well to bind to each other, that such binding of complementary domains is stable and that the alignment is sufficiently accurate and tight as to preserve metabolite binding sites and allosteric interactions.
Simulation of microtearing turbulence in national spherical torus experiment
Authors: Guttenfelder W. , Candy J. , Kaye S. M. , Nevins W. M. , Wang E. , Zhang J. , Bell R. E. , Crocker N. A. , Hammett G. W. , LeBlanc B. P. , Mikkelsen D. R. , Ren Y. , Yuh H.
Published: April 2012

Thermal energy confinement times in National Spherical Torus Experiment (NSTX) dimensionless parameter scans increase with decreasing collisionality. While ion thermal transport is neoclassical, the source of anomalous electron thermal transport in these discharges remains unclear, leading to considerable uncertainty when extrapolating to future spherical tokamak (ST) devices at much lower collisionality. Linear gyrokinetic simulations find microtearing modes to be unstable in high collisionality discharges. First non-linear gyrokinetic simulations of microtearing turbulence in NSTX show they can yield experimental levels of transport. Magnetic flutter is responsible for almost all the transport (∼98%), perturbed field line trajectories are globally stochastic, and a test particle stochastic transport model agrees to within 25% of the simulated transport. Most significantly, microtearing transport is predicted to increase with electron collisionality, consistent with the observed NSTX confinement scaling. While this suggests microtearing modes may be the source of electron thermal transport, the predictions are also very sensitive to electron temperature gradient, indicating the scaling of the instability threshold is important. In addition, microtearing turbulence is susceptible to suppression via sheared E × B flows as experimental values of E × B shear (comparable to the linear growth rates) dramatically reduce the transport below experimental values. Refinements in numerical resolution and physics model assumptions are expected to minimize the apparent discrepancy. In cases where the predicted transport is strong, calculations suggest that a proposed polarimetry diagnostic may be sensitive to the magnetic perturbations associated with the unique structure of microtearing turbulence.
Gyrokinetic prediction of microtearing turbulence in standard tokamaks
Authors: Doerk H. , Jenko F. , Görler T. , Told D. , Pueschel M. J. , Hatch D. R.
Published: April 2012

First global gyrokinetic simulations of microtearing instabilities in ASDEX Upgrade geometry provide increasing evidence for the existence of these modes in standard tokamaks. It is found that even in only moderately large devices, nonlocal effects like profile shearing are negligible, supporting the use of an efficient flux-tube approach. Nonlinear gyrokinetic simulations show that the resulting level of magnetic electron heat flux can be experimentally relevant.
Transport characteristics of tunnel heterostructures: Transition from the quantum to the classical limit
Authors: Svistunov V. M. , Boylo I. V. , Belogolovskii M. A.
Published: April 2012

Two possible mechanisms for the partial or complete loss of information contained in the quantum-mechanical phase of an electron moving in a stochastic solid-state structure are examined. The first involves phase randomization of the electron characteristics (for example, by elastic scattering of electrons on defects in thin metallic layers) and the second arises from inelastic interactions of current carriers with external degrees of freedom. With a double-barrier heterostructure as an example, it is shown that in the first case the quantum-mechanical approach reduces to a semiclassical method, in which the probabilities of individual events appear, rather than the quantum-mechanical probability amplitudes. The second case corresponds to a transition to the classical theory of charge transport. The effect of decoherence on the differential conductivity and shot noise in double-barrier tunnelling systems with a superconducting electrode is evaluated and the changes in these owing to the transition from quantum to incoherent classical electron transport are analyzed.
Coupled superconductors and beyond
Authors: Josephson Brian D.
Published: April 2012

This paper describes the events leading to the discovery of coupled superconductors, the author’s move in the 1970s to a perspective where mind plays a role comparable to matter, and the remarkable hostility sometimes encountered by those who venture into unconventional areas.
Comparison of phase slippage processes in Josephson junctions and charge-density wave stacked junctions
Authors: Latyshev Yu. I.
Published: April 2012

We discuss a time-space symmetry in phase slippage processes in Josephson junctions and charge density wave (CDW) stacked junctions. In Josephson junctions, above a critical current a phase slip of 2π occurs periodically in time with a period T corresponding to the rate given by the Josephson relation ν = 1/ T= 2eV/h, where V is the voltage on the junction. In CDW stacks, a CDW dislocation appears in the weakest junction of the stack when the voltage on the stack exceeds a threshold value. This phase dislocation corresponds to a local phase slippage of 2π. As the voltage is increased, new dislocations show up and form a periodic array of dislocations with period L. The inverse spacing 1/L obeys an analog of Josephson equation, vF/L = 2eV/h.
Nanoelectromechanics of superconducting weak links (Review Article)
Authors: Parafilo A. V. , Krive I. V. , Shekhter R. I. , Jonson M.
Published: April 2012

Nanoelectromechanical effects in superconducting weak links are considered. Three different superconducting devices are studied: (i) a single-Cooper-pair transistor, (ii) a transparent SNS junction, and (iii) a single-level quantum dot coupled to superconducting electrodes. The electromechanical coupling is due to electrostatic or magnetomotive forces acting on a movable part of the device. It is demonstrated that depending on the frequency of mechanical vibrations the electromechanical coupling could either suppress or enhance the Josephson current. Nonequilibrium effects associated with cooling of the vibrational subsystem or pumping energy into it at low bias voltages are discussed.
Superposition of states in flux qubits with a Josephson junction of the ScS type (Review Article)
Authors: Shnyrkov V. I. , Soroka A. A. , Korolev A. M. , Turutanov O. G.
Published: April 2012

The consequences of the transition to a quantum description of magnetic flux motion in the superconducting ring closed by an ScS type Josephson junction are considered. Here we review the principal results regarding macroscopic quantum tunneling (MQT) of Bose condensate consisting of a macroscopically large number of Cooper electron pairs. These phenomena are illustrated by the original data obtained from the study of MQT and coherent states in a modified flux qubit with energy level depletion ΔE01 ≈ 2·10–23 J (ΔE01/h ≈ 30 GHz). State superposition properties in a two-well potential and the issues associated with quantum measurements of local curvature of qubits’ superposition energy levels are analyzed.
Application of SQUIDs for registration of biomagnetic signals
Authors: Voitovych I. D. , Primin M. A. , Sosnytskyy V. N.
Published: April 2012

Supersensitive magnetometric systems based on low-temperature SQUIDs have been designed to conduct research in cardiology (magnetocardiography) and to examine distribution of magnetic nanoparticles in biologic objects. Such SQUID magnetometric systems are distinguished by their noise immunity enabling research in nonscreened rooms. High repeatability of research outcomes has been confirmed. The use of magnetocardiographic systems has permitted a new screening information technology to be developed to diagnose heart diseases at early stages. Magnetic imaging of heart’s action currents is an ideal way to test local electrical heterogeneity of myocardium. It is shown that magnetocardiography has a significant potential for both basic science of analysis of heart’s biosignals and clinical cardiologic practice. A SQUID magnetometric system measuring magnetic signals radiated by the organs of laboratory animals is described. Information technology for automatic recording and transforming magnetometric data has been developed; the measurement of signals over rats’ livers while injecting intravenously the nanoparticles of iron oxides and lead solutions are presented.
An ultrasonic stage for controlled spin of micro particles
Authors: Zhou Yujie , Li Huaqing , Hu Junhui
Published: April 2012

In this work, we proposed and developed an ultrasonic stage which can make different kinds of micro particles spin at its center. The stage consists of a circular copper plate and two piezoelectric half-rings bonded onto the bottom surface of the copper plate. The two piezoelectric half-rings have the same size and property, but opposite polarization in the thickness direction. They form a ring concentric with the copper plate. The spin direction of micro particles can be reversed by changing the operating frequency of stage. The spin speed can be controlled by operating frequency and voltage of the stage, and it reaches 955 rpm for a single glass ball with 0.51 mm diameter. The spin of micro particles is caused by travelling waves around the center of the stage, and the travelling waves are generated by anti-symmetric flexible vibration of the stage, excited by the two piezoelectric half-rings.
Multiphoton transitions in Josephson-junction qubits (Review Article)
Authors: Shevchenko S. N. , Omelyanchouk A. N. , Il’ichev E.
Published: April 2012

Two basic physical models, a two-level system and a harmonic oscillator, are realized on the mesoscopic scale as coupled qubit and resonator. The realistic system includes moreover the electronics for controlling the distance between the qubit energy levels and their populations and to read out the resonator’s state, as well as the unavoidable dissipative environment. Such rich system is interesting both for the study of fundamental quantum phenomena on the mesoscopic scale and as a promising system for future electronic devices. We present recent results for the driven superconducting qubit–resonator system, where the resonator can be realized as an LC circuit or a nanomechanical resonator. Most of the results can be described by the semiclassical theory, where a qubit is treated as a quantum two-level system coupled to the classical driving field and the classical resonator. Application of this theory allows to describe many phenomena for the single and two coupled superconducting qubits, among which are the following: the equilibrium-state and weak-driving spectroscopy, Sisyphus damping and amplification, Landau–Zener–Stückelberg interferometry, the multiphoton transitions of both direct and ladder-type character, and creation of the inverse population for lasing.
Josephson effect in cuprate superconducting structures
Authors: Ovsyannikov G. A. , Constantinian K. Y.
Published: April 2012

Electron transport and microwave properties of cuprate superconducting structures (bicrystal junctions and hybrid mesa heterostructures) are discussed here. Superconducting current in junctions from cuprate superconductors with the dominant dx2−y2-wave symmetry is determined by the barrier properties, characterized by the mid-gap bound states due to the multiple Andreev reflection. In bicrystal junctions it is revealed via linear dependence of critical current density on square root of the transparency, and an increase of spectral density of shot noise at low voltages are observed. The experiments demonstrate that the superconducting hybrid mesa-heterostructures have the critical current density jс = 1–700 A/cm2 for an antiferromagnetic interlayer with thickness dM = 10–50 nm and the characteristic decay length of superconducting correlations on the order of 7 nm, due to the anomalous long range proximity effect, analyzed in the model of coupled superconductors via multilayer magnetic layer with antiferromagnetic ordering of magnetization in the layers. It is found that the hybrid mesa–heterostructures have much greater sensitivity to external magnetic field than conventional Josephson junctions because of the strong dependence of superconducting current on interlayer spin state.
Monte Carlo studies of the intrinsic time-domain response of nanoscale three-branch junctions
Authors: Iñiguez-de-la-Torre I. , Rodilla H. , Mateos J. , González T. , Irie H. , Sobolewski Roman
Published: April 2012

We present a Monte Carlo time-domain study of nanostructured ballistic three-branch junctions (TBJs) excited by both step-function and Gaussian picosecond transients. Our TBJs were based on InGaAs 2-dimensional electron gas heterostructures and their geometry followed exactly the earlier experimental studies. Time-resolved, picosecond transients of both the central branch potential and the between-the-arms current demonstrate that the bandwidth of the intrinsic TBJ response reaches the THz frequency range, being mainly limited by the large-signal, intervalley scattering, when the carrier transport regime changes from ballistic to diffusive.
Characterization and luminescence properties of AlON:Eu2+ phosphor for white-emitting-diode illumination
Authors: Zhang F. , Chen S. , Chen J. F. , Zhang H. L. , Li J. , Liu X. J. , Wang S. W.
Published: April 2012

AlON phosphors with different Eu2+ doping concentrations were synthesized by solid-state reaction method. Two Eu2+ doping sites were confirmed by temperature-dependent emission intensity, band shift and biexponential decay studies. High internal quantum efficiency and tunable chromaticity coordinates make AlON:Eu2+ phosphor a suitable candidate for white light-emitting diodes application.
Life cycle cost analysis of building re-lamping alternatives
Authors: Boubekri M.
Published: April 2012

With rising energy costs and cuts in expenditures, institutions around the country are trying to find ways to cut energy consumption and operational costs. As many academic institutions have old buildings in service, one of the most considered and relatively easy energy saving alternatives is to change old and inefficient lighting to those that are newer and more energy efficient. This paper deals with the cost savings question of re-lamping existing buildings on the campus of the University of Illinois at Urbana-Champaign using life cycle cost procedures. We examined the energy and costs savings potential by comparing existing prevalent T12 fluorescent lighting fixtures to two T8 fixtures and two T5 fixtures. The results show that, although there may be energy savings potential for some of these newer systems, the economic benefits are not always obvious or real.
Complementary cellophane optic gate and its use for a 3D iPad without glasses
Authors: Iizuka K.
Published: April 2012

A complementary cellophane optic gate was fabricated using a birefringent cellophane sheet. Previous versions of the optic gate required the retardance of the cellophane to be as close to 180° as possible throughout the entire visible wavelength range, which meant it was often difficult to find a cellophane sheet with the right thickness and dispersion characteristics to meet this requirement. The complementary optic gate reported in this paper has no restriction on the thickness, composition, or wavelength range of the cellophane sheet except that the cellophane must have some birefringence. Even with an arbitrary retardance, an extinction ratio of 5 × 10−3 was achieved at λ = 0.63 μm. The optic gate was used to convert an iPad into a 3D display without the need for the observer to wear glasses. The high extinction ratio of the optic gate resulted in a 3D display of supreme quality.
Resonant planar antenna as an inductive plasma source
Authors: Guittienne Ph. , Lecoultre S. , Fayet P. , Larrieu J. , Howling A. A. , Hollenstein Ch.
Published: April 2012

A resonant planar antenna as an inductive plasma source operating at 13.56 MHz inside a low pressure vacuum vessel is presented for potential plasma processing applications. Its principle consists in interconnecting elementary resonant meshes composed of inductive and capacitive elements. Due to its structure, the antenna shows a set of resonant modes associated with peaks of the real input impedance. Each of these modes is defined by its own current and voltage distribution oscillating at the frequency of the mode. A rectangular antenna of 0.55m×0.20m has been built, and first results obtained with argon plasmas are presented. Plasma generation is shown to be efficient as densities up to 4·1017m-3 at 2000 W have been measured by microwave interferometry at a distance of 4 cm from the source plane. It is also demonstrated that the plasma couples inductively with the resonating currents flowing in the antenna above a threshold power of about 60 W. A non-uniformity of less than ±5% is obtained at 1000 W at a few centimeters above the antenna over 75% of its surface.
The systematic study and simulation modeling on nano-level dislocation edge stress effects
Authors: Liao M.-H. , Chen C.-H. , Chang L.-C. , Yang C.
Published: April 2012

The comprehensive investigation on the effect of dislocation edge stress for Si N-type metal-oxide-semiconductor field-effect transistors is presented in this work by the experimental measurement and proposed simulation model. The accurate stress measurement in Si OD region with and without dislocation edge stress treatment is extracted by atomic force microscope-Raman technique with the nanometer level space resolution. Less compressive stress in Si OD region on the real transistor with dislocation edge stress treatment is observed successfully and has its corresponding higher electron carrier mobility, agreed with the strained Si theory. Main reasons for the less compressive stress in the device with dislocation edge stress treatment are the more stress relaxation of the STI intrinsic compressive stress in modern CMOS process and one layer Si atom missing near the source and drain region along the dislocation line. The measured stress from AFM-Raman spectra experimentally, the simulated stress from proposed finite element method, and its corresponding electrical characteristics agrees well with each other in this work. After the comprehensive understanding and calibrated model for the dislocation edge stress, the relationship between channel stress and dislocation edge shapes, including the angle and length of dislocation lines is simulated and investigated clearly. It can be found that longer dislocation line and smaller dislocation angle can relax the intrinsic STI compressive stress more and should have the better electron carrier mobility and device performance for N-MOSFETs.
Space charge effects on externally injected current in planar diodes: Existence of multiple stationary states
Authors: Rokhlenko A. , Lebowitz J. L.
Published: April 2012

We study the effects of space charge on the properties of a system with a specified steady current. The problem is solved exactly for a planar one dimensional geometry, but we expect similar results for more realistic systems. We find that in many cases, the stationary current density cannot exceed some fixed value Jmax and in other cases be lower than a fixed Jmin depending on the method of injection. There are also intervals of intermediate current densities, which cannot exist in the stationary conditions. In general, there are values of J in some range where there are two different stationary regimes, which correspond to two different electric fields at the emitter surface. Connection with results obtained from numerical simulations and possible applications are also considered.
Stress relaxation and critical thickness for misfit dislocation formation in (101¯) and (3031¯) InGaN/GaN heteroepitaxy
Authors: Shan Hsu Po , Hardy Matthew T. , Young Erin C. , Romanov Alexey E. , DenBaars Steven P. , Nakamura Shuji , Speck James S.
Published: April 2012

Cathodoluminescence imaging was used to study the onset of plastic relaxation and critical thickness for misfit dislocation (MD) formation by basal plane (BP) or nonbasal plane (NBP) slip in In0.09Ga0.91N/GaN heterostructures grown on nonpolar (101¯0) and semipolar (3031¯) substrates. Layers grown on both orientations were shown to stress relax initially via generation of NBP MDs as a result of prismatic slip on inclined m-planes. Analysis of the resolved shear stress on the two slip planes (i.e., basal and an inclined m-plane) reveals a crossover at which the resolved shear stress on the m-planes becomes larger than that on the BP.
Note: Unique characterization possibilities in the ultra high vacuum scanning transmission x-ray microscope (UHV-STXM) “MAXYMUS” using a rotatable permanent magnetic field up to 0.22 T
Authors: Nolle D. , Weigand M. , Audehm P. , Goering E. , Wiesemann U. , Wolter C. , Nolle E. , Schütz G.
Published: April 2012

Using the x-ray magnetic circular dichroism effect, the soft x-ray range provides powerful detection capabilities concerning element specific structural, chemical, and magnetic properties. We present the implementation of a variable 0.22 T magnet system based on permanent magnets into the new UHV scanning microscope “MAXYMUS” at HZB/BESSY II, allowing surface sensitive and simultaneous standard transmission microscopic investigations in a variable external magnetic field. The outstanding potential of these new investigation possibilities will be demonstrated showing the development of the magnetic domain structure concurrently at the surface and in the bulk, providing a profound understanding of fundamental mechanisms in coupled magnetic systems.
Coexistence of two cycloid-phases in multiferroic RMnO3: Consequence of the next-nearest-neighbor spin interaction modulations
Authors: Tao Y. M. , Chen D. P. , Qin M. H. , Dong S. , Gao X. S. , Liu J.-M.
Published: April 2012

The modulation of the next-nearest-neighbor spin interaction in RMnO3-type manganites is considered and its effect on the multiferroic behaviors is investigated within the framework of classical Heisenberg model using Monte Carlo simulation. Two types of the modulations, i.e., the symmetric perturbations in which the interactions over the lattice are symmetrically modulated with an equal distribution to maintain the mean interaction invariant and the asymmetric perturbations in which the interactions over the lattice are randomly modulated with variable mean interaction, are taken into account. It is shown that both the types of modulations can drive the reorientation of the spiral spin order and thus lead to the coexistence of two cycloid-phases within appropriate magnitudes of modulation. The two multiferroic phase coexistence can be understood as the consequence of the competition between the single-ion anisotropy and the Dzyaloshinskii-Mariya interaction. A comparison of the simulated results with recent relevant experiments on multiferroic manganites is also presented.
Effect of gold composition on the orientations of oxide nuclei during the early stage oxidation of Cu-Au alloys
Authors: Luo Langli , Kang Yihong , Yang Judith C. , Zhou Guangwen
Published: April 2012

In situ environmental transmission electron microscopy is employed to study the effect of Au composition in Cu-Au alloys on the orientations of oxide islands during the initial-stage oxidation of Cu-Au(100) alloys. An orientation transition from nucleating epitaxial Cu2O islands to randomly oriented oxide islands is observed upon increasing the oxygen gas pressure. By increasing the Au composition in the Cu-Au alloys, both the oxide nucleation time and saturation density of oxide islands increase, but the critical oxygen pressure leading to nucleating randomly oriented Cu2O islands decreases. It is shown by a kinetic model that such a dependence of the critical oxygen pressure on the alloy composition is related to its effect on two competing processes, the oxide-alloy structure match and the effective collision of oxygen atoms, in determining the overall nucleation rate of oxide islands during the oxidation.
Influence of boron doping on magnetic properties and microwave characteristics of MnIr/FeCoB multilayers
Authors: Phuoc Nguyen N. , Ong C. K.
Published: April 2012

A detailed investigation of the influence of B doping on the magnetic properties and high frequency characteristics of FeCoB/MnIr multilayered thin films was carried out. Exchange bias was found to decrease monotonically with B doping possibly due to less favorable of AF phase of MnIr in the samples with rich B concentration. However, with small amount of doping up to 9% of B concentration, the MnIr fcc (111) peaks become more prominent and the real part of permeability enhanced. Our results suggest no correlation between the structural phase of MnIr and the exchange bias. Also, the influences of B doping on several static and dynamic parameters, such as rotational magnetic anisotropy field, coercivity, saturation magnetization, resonance frequency, and effective damping factor are presented and discussed. Our results support the claim that the coercivity enhancement and the arising of rotational anisotropy may have the same physical origin.
Symmetrically tunable optical properties of InGaN/GaN multiple quantum disks by an external stress
Authors: Shih H. Y. , Chen Y. F. , Lin T. Y.
Published: April 2012

The influence of an external stress on the optical properties of InGaN/GaN multiple quantum disks (MQDs) has been investigated. As a transversal force is applied on the MQDs, both photoluminescence and Raman scattering spectra are altered due to the piezoelectric potential accompanied by the quantum confined Stark effect. Quite interestingly, it is found that the optical spectra possess a sixfold symmetry about the c-axis. This intriguing phenomenon can be attributed to the inherent nature of hexagonal lattice as well as the good flexibility of the composite consisting of polydimethylsiloxane and MQDs. Our results can provide an alternative route to optimize and extend the application of nitride-based devices.
High-Q silicon optomechanical microdisk resonators at gigahertz frequencies
Authors: Sun Xiankai , Zhang Xufeng , Tang Hong X.
Published: April 2012

We report disk-shaped silicon optomechanical resonators with frequency up to 1.75 GHz in the ultrahigh frequency band. Optical transduction of the thermal motion of the disks’ in-plane vibrational modes yields a displacement sensitivity of 4.1 × 10−17 m/Hz1/2. Due to the reduced clamping loss, these disk resonators possess high mechanical quality factors (Q), with the highest value of 4370 for the 1.47 GHz mode measured in ambient air. Numerical simulation on the modal frequency and mechanical Q for disks of varying undercut shows modal coupling and suggests a realistic pedestal size to achieve the highest possible Q.
GaAs/AlGaAs resonant tunneling diodes with a GaInNAs absorption layer for telecommunication light sensing
Authors: Hartmann F. , Langer F. , Bisping D. , Musterer A. , Höfling S. , Kamp M. , Forchel A. , Worschech L.
Published: April 2012

Al0.6Ga0.4As/GaAs/Al0.6Ga0.4As double-barrier resonant-tunneling diodes (RTD) were grown by molecular beam epitaxy with a nearby, lattice-matched Ga0.89In0.11N0.04As0.96 absorption layer. RTD mesas with ring contacts and an aperture for optical excitation of charge carriers were fabricated on the epitaxial layers. Electrical and optical properties of the RTDs were investigated for different thicknesses of a thin GaAs spacer layer incorporated between the AlGaAs tunnel barrier adjacent to the GaInNAs absorption layer. Illumination of the RTDs with laser light of 1.3 μm wavelength leads to a pronounced photo-effect with a sensitivities of around 103 A/W.
Anabolic action of parathyroid hormone regulated by the β
2
-adrenergic receptor
Authors: Hanyu Ryo , Wehbi Vanessa L. , Hayata Tadayoshi , Moriya Shuichi , Feinstein Timothy N. , Ezura Yoichi , Nagao Masashi , Saita Yoshitomo , Hemmi Hiroaki , Notomi Takuya , Nakamoto Tetsuya , Schipani Ernestina , Takeda Shu , Kaneko Kazuo , Kurosawa Hisashi , Karsenty Gerard , Kronenberg Henry M. , Vilardaga Jean-Pierre , Noda Masaki
Published: April 2012

Parathyroid hormone (PTH), the major calcium-regulating hormone, and norepinephrine (NE), the principal neurotransmitter of sympathetic nerves, regulate bone remodeling by activating distinct cell-surface G protein-coupled receptors in osteoblasts: the parathyroid hormone type 1 receptor (PTHR) and the β
2
-adrenergic receptor (β
2
AR), respectively. These receptors activate a common cAMP/PKA signal transduction pathway mediated through the stimulatory heterotrimeric G protein. Activation of β
2
AR via the sympathetic nervous system decreases bone formation and increases bone resorption. Conversely, daily injection of PTH (1–34), a regimen known as intermittent (i)PTH treatment, increases bone mass through the stimulation of trabecular and cortical bone formation and decreases fracture incidences in severe cases of osteoporosis. Here, we show that iPTH has no osteoanabolic activity in mice lacking the β
2
AR. β
2
AR deficiency suppressed both iPTH-induced increase in bone formation and resorption. We showed that the lack of β
2
AR blocks expression of iPTH-target genes involved in bone formation and resorption that are regulated by the cAMP/PKA pathway. These data implicate an unexpected functional interaction between PTHR and β
2
AR, two G protein-coupled receptors from distinct families, which control bone formation and PTH anabolism.
Imaging prior information in the brain
Authors: Gorlin Scott , Meng Ming , Sharma Jitendra , Sugihara Hiroki , Sur Mriganka , Sinha Pawan
Published: April 2012

In making sense of the visual world, the brain's processing is driven by two factors: the physical information provided by the eyes (“bottom-up” data) and the expectancies driven by past experience (“top-down” influences). We use degraded stimuli to tease apart the effects of bottom-up and top-down processes because they are easier to recognize with prior knowledge of undegraded images. Using machine learning algorithms, we quantify the amount of information that brain regions contain about stimuli as the subject learns the coherent images. Our results show that several distinct regions, including high-level visual areas and the retinotopic cortex, contain more information about degraded stimuli with prior knowledge. Critically, these regions are separate from those that exhibit classical priming, indicating that top-down influences are more than feature-based attention. Together, our results show how the neural processing of complex imagery is rapidly influenced by fleeting experiences.
Computational design of a protein crystal
Authors: Lanci Christopher J. , MacDermaid Christopher M. , Kang Seung-gu , Acharya Rudresh , North Benjamin , Yang Xi , Qiu X. Jade , DeGrado William F. , Saven Jeffery G.
Published: April 2012

Protein crystals have catalytic and materials applications and are central to efforts in structural biology and therapeutic development. Designing predetermined crystal structures can be subtle given the complexity of proteins and the noncovalent interactions that govern crystallization. De novo protein design provides an approach to engineer highly complex nanoscale molecular structures, and often the positions of atoms can be programmed with sub-Å precision. Herein, a computational approach is presented for the design of proteins that self-assemble in three dimensions to yield macroscopic crystals. A three-helix coiled-coil protein is designed de novo to form a polar, layered, three-dimensional crystal having the P6 space group, which has a “honeycomb-like” structure and hexameric channels that span the crystal. The approach involves: (
i
) creating an ensemble of crystalline structures consistent with the targeted symmetry; (
ii
) characterizing this ensemble to identify “designable” structures from minima in the sequence-structure energy landscape and designing sequences for these structures; (
iii
) experimentally characterizing candidate proteins. A 2.1 Å resolution X-ray crystal structure of one such designed protein exhibits sub-Å agreement [backbone root mean square deviation (rmsd)] with the computational model of the crystal. This approach to crystal design has potential applications to the de novo design of nanostructured materials and to the modification of natural proteins to facilitate X-ray crystallographic analysis.
Structural basis for the allosteric inhibitory mechanism of human kidney-type glutaminase (KGA) and its regulation by Raf-Mek-Erk signaling in cancer cell metabolism
Authors: Thangavelu K. , Pan Catherine Qiurong , Karlberg Tobias , Balaji Ganapathy , Uttamchandani Mahesh , Suresh Valiyaveettil , Schüler Herwig , Low Boon Chuan , Sivaraman J.
Published: April 2012

Besides thriving on altered glucose metabolism, cancer cells undergo glutaminolysis to meet their energy demands. As the first enzyme in catalyzing glutaminolysis, human kidney-type glutaminase isoform (KGA) is becoming an attractive target for small molecules such as BPTES [bis-2-(5 phenylacetamido-1, 2, 4-thiadiazol-2-yl) ethyl sulfide], although the regulatory mechanism of KGA remains unknown. On the basis of crystal structures, we reveal that BPTES binds to an allosteric pocket at the dimer interface of KGA, triggering a dramatic conformational change of the key loop (Glu312-Pro329) near the catalytic site and rendering it inactive. The binding mode of BPTES on the hydrophobic pocket explains its specificity to KGA. Interestingly, KGA activity in cells is stimulated by EGF, and KGA associates with all three kinase components of the Raf-1/Mek2/Erk signaling module. However, the enhanced activity is abrogated by kinase-dead, dominant negative mutants of Raf-1 (Raf-1-K375M) and Mek2 (Mek2-K101A), protein phosphatase PP2A, and Mek-inhibitor U0126, indicative of phosphorylation-dependent regulation. Furthermore, treating cells that coexpressed Mek2-K101A and KGA with suboptimal level of BPTES leads to synergistic inhibition on cell proliferation. Consequently, mutating the crucial hydrophobic residues at this key loop abrogates KGA activity and cell proliferation, despite the binding of constitutive active Mek2-S222/226D. These studies therefore offer insights into (
i
) allosteric inhibition of KGA by BPTES, revealing the dynamic nature of KGA's active and inhibitory sites, and (
ii
) cross-talk and regulation of KGA activities by EGF-mediated Raf-Mek-Erk signaling. These findings will help in the design of better inhibitors and strategies for the treatment of cancers addicted with glutamine metabolism.