bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability and Constancy of Bully-Victim Behavior
Authors: Strohmeier Dagmar , Wagner Petra , Spiel Christiane , von Eye Alexander
Published: September 2010

The present paper (1) focused on variables to investigate the stability of bully-victim behavior over time and constancy across settings in preadolescent and adolescent boys and girls and (2) looked at persons to examine whether patterns of change were the same or different between bully-victim groups identified. Data were drawn from two independent short time longitudinal studies. In Study 1, 100 adolescents (59% female) aged 15–19 years (M = 16.4 years) were asked about their bully-victim behavior in school before and after the summer break. In Study 2, 116 preadolescents (49% female) aged 9–15 years (M = 12.2) were asked about their bully-victim behavior in school and in a summer camp. While adolescents did not enter a new group after the summer break, preadolescents entered a new group in the summer camp. On the whole sample level, both over time and across settings bullying showed moderate to high stability and a decrease. Victimization was moderately stable over time but rather unstable across settings. Victimization also decreased over time. With longitudinal cluster analysis (L-CA) both over time and across settings four bully-victim groups were identified: uninvolved, desisting victims, desisting moderate bullies, and escalating high level bullies. In both studies, escalating high level bullies were only boys. Bullying might be used to establish dominance by only a small group of boys when entering a new group or when returning to an old one after some break. Application of the variable-oriented approach using correlation coefficients and MANOVAs and the person-centered approach using L-CA and Configural Frequency Analysis complements each other.
Along‐strike variations in short‐term slow slip events in the southwest Japan subduction zone
Authors: Sekine Shutaro , Hirose Hitoshi , Obara Kazushige
Published: September 2010

Short‐term slow slip events accompanied by nonvolcanic deep low‐frequency tremors and deep very low frequency earthquakes in southwest Japan were investigated systematically by means of ground tilting studies. The change in tilt usually lasts for several days. By using a genetic algorithm and a least squares method, we inverted the data for tilt steps that were caused by slow slip events and were detected by at least four stations situated near the source of the tremor. Fault parameters were estimated for 54 slow slip episodes that occurred mainly in the western Shikoku, northeastern Kii, and Tokai regions from 2001 to 2008. In eastern Shikoku, two slow slip episodes were detected quantitatively for the first time. The fault geometries of all the slow slip events were located within the belt‐like distribution of tremors in the transition zone between the locked and aseismic slip zones at the plate interface of the subducting Philippine Sea Plate. The spatial extent of the fault geometry corresponds roughly to the distribution of clusters of nonvolcanic tremors and very low frequency earthquakes. The moment magnitudes ranged from 5.4 to 6.2, and the slip was ∼1 cm for each slow slip event. The rate of moment release by the detected slow slip events was 40–60% of the moment accumulation expected from the relative plate motion, and it showed regional differences. They may reflect the along‐strike variations in plate convergence and/or the characteristic size of the slow slip fault plane on the plate interface.
Biogeochemical weathering under ice: Size matters
Authors: Wadham J. L. , Tranter M. , Skidmore M. , Hodson A. J. , Priscu J. , Lyons W. B. , Sharp M. , Wynn P. , Jackson M.
Published: September 2010

The basal regions of continental ice sheets are gaps in our current understanding of the Earth's biosphere and biogeochemical cycles. We draw on existing and new chemical data sets for subglacial meltwaters to provide the first comprehensive assessment of sub‐ice sheet biogeochemical weathering. We show that size of the ice mass is a critical control on the balance of chemical weathering processes and that microbial activity is ubiquitous in driving dissolution. Carbonate dissolution fueled by sulfide oxidation and microbial CO2 dominate beneath small valley glaciers. Prolonged meltwater residence times and greater isolation characteristic of ice sheets lead to the development of anoxia and enhanced silicate dissolution due to calcite saturation. We show that sub‐ice sheet environments are highly geochemically reactive and should be considered in regional and global solute budgets. For example, calculated solute fluxes from Antarctica (72–130 t yr−1) are the same order of magnitude as those from some of the world's largest rivers and rates of chemical weathering (10–17 t km−2 yr−1) are high for the annual specific discharge (2.3–4.1 × 10−3 m). Our model of chemical weathering dynamics provides important information on subglacial biodiversity and global biogeochemical cycles and may be used to design strategies for the first sampling of Antarctic Subglacial Lakes and other sub‐ice sheet environments for the next decade.
North American lithospheric discontinuity structure imaged by Ps and Sp receiver functions
Authors: Abt David L. , Fischer Karen M. , French Scott W. , Ford Heather A. , Yuan Huaiyu , Romanowicz Barbara
Published: September 2010

Sp and Ps converted seismic waves at 93 permanent seismic stations are used to image upper mantle velocity discontinuities across the contiguous United States and portions of southeast Canada and northwest Mexico. Receiver functions are calculated with frequency‐domain deconvolution and migrated with 1D models that account for variations in crustal structure and mantle velocities between stations. Strong positive Ps phases from the Moho are observed and agree well with previous crustal thickness estimates. In the tectonically active western U.S., high amplitude, negative Sp phases are interpreted as the lithosphere‐asthenosphere boundary (LAB) at depths of 51–104 km. These phases indicate a large and rapid LAB velocity gradient and are consistent with an anomalously hot asthenosphere that is rich in water or contains partial melt. In the regions of the Phanerozoic southern and eastern U.S where Sp phases are interpretable as the LAB, the discontinuity lies at depths of 75–111 km and is also too sharp to be explained by temperature alone. In contrast, no Sp phases are observed at depths comparable to the base of the thick high velocity lithosphere that lies beneath cratonic North America and certain portions of the Phanerozoic eastern U.S. At these stations, negative Sp phases occur at depths of 59–113 km and are interpreted as the top of a low velocity zone internal to the lithosphere. The absence of an observable LAB discontinuity in regions of thick lithosphere indicates that the LAB velocity gradient is distributed over more than 50–70 km in depth and is consistent with a purely thermal boundary.
EGATEC: A new high‐resolution engineering model of the global atmospheric electric circuit—Currents in the lower atmosphere
Authors: Odzimek A. , Lester M. , Kubicki M.
Published: September 2010

We present a new high‐resolution model of the Earth's global atmospheric electric circuit (GEC) represented by an equivalent electrical network. Contributions of clouds to the total resistance of the atmosphere and as current generators are treated more realistically than in previous GEC models. The model of cloud current generators is constructed on the basis of the ISCCP cloud data and the OTD/LIS lightning flash rates and TRMM rainfall data. The current generated and the electric resistance can be estimated with a spatial resolution of several degrees in latitude and longitude and 3 hour time resolution. The resistance of the atmosphere is calculated using an atmospheric conductivity model which is spatially dependent and sensitive to the level of solar activity. An equivalent circuit is constructed assuming the ionosphere and ground are ideal conductors. The circuit solution provides diurnal variations of the ionospheric potential and the GEC global current at the 3 hour time resolution as well as the global distributions and diurnal variations of the air‐Earth current density and electric field. The model confirms that the global atmospheric electric activity peaks daily at ∼21 UT. The diurnal variation of the ionospheric potential and the global current have a maximum at 12 and 21–24 UT in July and at 9 and 21 UT in December, and a global minimum at 3–6 UT independent of season. About 80% of the current is generated by thunderstorm convective clouds and 20% by mid‐level rain clouds.
Bathymetry and absorptivity of Titan's Ontario Lacus
Authors: Hayes A. G. , Wolf A. S. , Aharonson O. , Zebker H. , Lorenz R. , Kirk R. L. , Paillou P. , Lunine J. , Wye L. , Callahan P. , Wall S. , Elachi C.
Published: September 2010

Ontario Lacus is the largest and best characterized lake in Titan's south polar region. In June and July 2009, the Cassini RADAR acquired its first Synthetic Aperture Radar (SAR) images of the area. Together with closest approach altimetry acquired in December 2008, these observations provide a unique opportunity to study the lake's nearshore bathymetry and complex refractive properties. Average radar backscatter is observed to decrease exponentially with distance from the local shoreline. This behavior is consistent with attenuation through a deepening layer of liquid and, if local topography is known, can be used to derive absorptive dielectric properties. Accordingly, we estimate nearshore topography from a radar altimetry profile that intersects the shoreline on the East and West sides of the lake. We then analyze SAR backscatter in these regions to determine the imaginary component of the liquid's complex index of refraction (κ). The derived value, κ = (6.1−1.3+1.7) × 10−4, corresponds to a loss tangent of tan Δ = (9.2−2.0+2.5) × 10−4 and is consistent with a composition dominated by liquid hydrocarbons. This value can be used to test compositional models once the microwave optical properties of candidate materials have been measured. In areas that do not intersect altimetry profiles, relative slopes can be calculated assuming the index of refraction is constant throughout the liquid. Accordingly, we construct a coarse bathymetry map for the nearshore region by measuring bathymetric slopes for eleven additional areas around the lake. These slopes vary by a factor of ∼5 and correlate well with observed shoreline morphologies.
Patterns in the recent 2007–2008 activity of Mount Etna volcano investigated by integrated geophysical and geochemical observations
Authors: Aiuppa A. , Cannata A. , Cannavò F. , Di Grazia G. , Ferrari F. , Giudice G. , Gurrieri S. , Liuzzo M. , Mattia M. , Montalto P. , Patanè D. , Puglisi G.
Published: September 2010

Seismic, deformation, and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment. In spite of their wide use, there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques. Here we combine seismic (volcanic tremor and long‐period seismicity), deformation (GPS), and geochemical (volcanic gas plume CO2/SO2 ratios) measurements in an attempt to interpret trends in the recent (2007–2008) activity of Etna volcano. We show that each eruptive episode occurring at the Southeast Crater (SEC) was preceded by a cyclic phase of increase‐decrease of plume CO2/SO2 ratios and by inflation of the volcano's summit captured by the GPS network. These observations are interpreted as reflecting the persistent supply of CO2‐rich gas bubbles (and eventually more primitive magmas) to a shallow (depth of 1–2.8 km asl) magma storage zone below the volcano's central craters (CCs). Overpressuring of the resident magma stored in the upper CCs' conduit triggers further magma ascent and finally eruption at SEC, a process which we capture as an abrupt increase in tremor amplitude, an upward (>2800 m asl) and eastward migration of the source location of seismic tremor, and a rapid contraction of the volcano's summit. Resumption of volcanic activity at SEC was also systematically anticipated by declining plume CO2/SO2 ratios, consistent with magma degassing being diverted from the central conduit area (toward SEC).
Water ice clouds over the Martian tropics during northern summer
Authors: Heavens N. G. , Benson J. L. , Kass D. M. , Kleinböhl A. , Abdou W. A. , McCleese D. J. , Richardson M. I. , Schofield J. T. , Shirley J. H. , Wolkenberg P. M.
Published: September 2010

Atmospheric models suggest that infrared heating due to water ice clouds over the tropics of Mars during early northern summer has a significant impact on the thermal structure of the tropics at cloud level and of the middle atmosphere near the south pole. Retrievals from limb observations by the Mars Climate Sounder on Mars Reconnaissance Orbiter during early northern summer show that water ice clouds over the northern tropics are thinner and higher than in published model results. Later in this season, the latitudinal extent, apparent mass mixing ratio (and infrared heating rate), and altitude of nighttime tropical clouds significantly increase, reaching a maximum just before northern fall equinox. Published model results do not show this transition. By underestimating the altitude at which water ice clouds form, models also may underestimate the intensity of the meridional circulation at higher altitudes in the tropics during northern summer.
Nonlinear evolution of resistive tearing mode with sub‐Alfvenic shear flow
Authors: Li J. H. , Ma Z. W.
Published: September 2010

Nonlinear evolution of resistive tearing mode with different sub‐Alfvenic shear flow is investigated using incompressible magnetohydrodynamics simulations. The sub‐Alfvenic shear flow can have either stabilization or destabilization effects on the tearing mode development, which is mostly determined by the shear flow thickness (av). The shear flow tends to boost the tearing mode instability when the thickness of the shear flow is above av ∼ 0.35a (where a is the normalization unit). The boosting effect of the shear flow on the tearing mode becomes strongest at av ∼ 0.6a. But the strength of the boosting and suppressing effects is controlled by the asymptotic velocity (V0) of the shear flow. The suppressing and boosting effects of the shear flow increase with increase of the shear flow velocity. The kinetic energy associated with initial shear flow is reduced when the shear flow has a boosting effect on the tearing mode growth.
Explicit validation of a surface shortwave radiation balance model over snow‐covered complex terrain
Authors: Helbig N. , L'we H. , Mayer B. , Lehning M.
Published: September 2010

A model that computes the surface radiation balance for all sky conditions in complex terrain is presented. The spatial distribution of direct and diffuse sky radiation is determined from observations of incident global radiation, air temperature, and relative humidity at a single measurement location. Incident radiation under cloudless sky is spatially derived from a parameterization of the atmospheric transmittance. Direct and diffuse sky radiation for all sky conditions are obtained by decomposing the measured global radiation value. Spatial incident radiation values under all atmospheric conditions are computed by adjusting the spatial radiation values obtained from the parametric model with the radiation components obtained from the decomposition model at the measurement site. Topographic influences such as shading are accounted for. The radiosity approach is used to compute anisotropic terrain reflected radiation. Validations of the shortwave radiation balance model are presented in detail for a day with cloudless sky. For a day with overcast sky a first validation is presented. Validation of a section of the horizon line as well as of individual radiation components is performed with high‐quality measurements. A new measurement setup was designed to determine terrain reflected radiation. There is good agreement between the measurements and the modeled terrain reflected radiation values as well as with incident radiation values. A comparison of the model with a fully three‐dimensional radiative transfer Monte Carlo model is presented. That validation reveals a good agreement between modeled radiation values.
Two-Photon NADH Imaging Exposes Boundaries of Oxygen Diffusion in Cortical Vascular Supply Regions
Authors: Kasischke Karl A , Lambert Elton M , Panepento Ben , Sun Anita , Gelbard Harris A , Burgess Robert W , Foster Thomas H , Nedergaard Maiken
Published: September 2010

Oxygen transport imposes a possible constraint on the brain's ability to sustain variable metabolic demands, but oxygen diffusion in the cerebral cortex has not yet been observed directly. We show that concurrent two-photon fluorescence imaging of endogenous nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation exposes well-defined boundaries of tissue oxygen diffusion in the mouse cortex. The NADH fluorescence increases rapidly over a narrow, very low pO2 range with a p 50 of 3.4±0.6 mm Hg, thereby establishing a nearly binary reporter of significant, metabolically limiting hypoxia. The transient cortical tissue boundaries of NADH fluorescence exhibit remarkably delineated geometrical patterns, which define the limits of tissue oxygen diffusion from the cortical microcirculation and bear a striking resemblance to the ideal Krogh tissue cylinder. The visualization of microvessels and their regional contribution to oxygen delivery establishes penetrating arterioles as major oxygen sources in addition to the capillary network and confirms the existence of cortical oxygen fields with steep microregional oxygen gradients. Thus, two-photon NADH imaging can be applied to expose vascular supply regions and to localize functionally relevant microregional cortical hypoxia with micrometer spatial resolution.
Reduced Ischemic Brain Injury by Partial Rejuvenation of Bone Marrow Cells in Aged Rats
Authors: Taguchi Akihiko , Zhu Pengxiang , Cao Fang , Kikuchi-Taura Akie , Kasahara Yukiko , Stern David M , Soma Toshihiro , Matsuyama Tomohiro , Hata Ryuji
Published: September 2010

Circulating bone marrow-derived immature cells, including endothelial progenitor cells, have been implicated in homeostasis of the microvasculature. Decreased levels of circulating endothelial progenitor cells, associated with aging and/or cardiovascular risk factors, correlate with poor clinical outcomes in a range of cardiovascular diseases. Herein, we transplanted bone marrow cells from young stroke-prone spontaneously hypertensive rats (SHR-SP) into aged SHR-SP, the latter not exposed to radiation or chemotherapy. Analysis of recipient peripheral blood 28 days after transplantation revealed that 5% of circulating blood cells were of donor origin. Cerebral infarction was induced on day 30 posttransplantation. Animals transplanted with bone marrow from young SHR-SP displayed an increase in density of the microvasculature in the periinfarction zone, reduced ischemic brain damage and improved neurologic function. In vitro analysis revealed enhanced activation of endothelial nitric oxide synthase and reduced activation p38 microtubule-associated protein (MAP) kinase, the latter associated with endothelial apoptosis, in cultures exposed to bone marrow-derived mononuclear cells from young animals versus cells from aged counterparts. Our findings indicate that partial rejuvenation of bone marrow from aged rats with cells from young animals enhances the response to ischemic injury, potentially at the level of endothelial/vascular activation, providing insight into a novel approach ameliorate chronic vascular diseases.
Susceptibility of Tmax to Tracer Delay on Perfusion Analysis: Quantitative Evaluation of Various Deconvolution Algorithms Using Digital Phantoms
Authors: Kudo Kohsuke , Sasaki Makoto , Østergaard Leif , Christensen Soren , Uwano Ikuko , Suzuki Masako , Ogasawara Kuniaki , Shirato Hiroki , Ogawa Akira
Published: September 2010

The time-to-maximum of the tissue residue function ( Tmax) perfusion index has proven very predictive of infarct growth in large clinical trials, yet its dependency on simple tracer delays remains unknown. Here, we determine the dependency of computed tomography (CT) perfusion (CTP) Tmax estimates on tracer delay using a range of deconvolution techniques and digital phantoms. Digital phantom data sets simulating the tracer delay were created from CTP data of six healthy individuals, in which time frames of the left cerebral hemisphere were shifted forward and backward by up to ±5 seconds. These phantoms were postprocessed with three common singular value decomposition (SVD) deconvolution algorithms—standard SVD (sSVD), block-circulant SVD (bSVD), and delay-corrected SVD (dSVD)—with an arterial input function (AIF) obtained from the right middle cerebral artery (MCA). The Tmax values of the left hemisphere were compared among different tracer delays and algorithms by a region of interest-based analysis. The Tmax values by sSVD were positively correlated with ‘positive shifts’ but unchanged with ‘negative shifts,’ those by bSVD had an excellent positive linear correlation with both positive and negative shifts, and those by dSVD were relatively constant, although slightly increased with the positive shifts. The Tmax is a parameter highly dependent on tracer delays and deconvolution algorithm.
A simplified quantum mechanical model for nanowire transistors based on non-linear variational calculus
Authors: Carrillo-Nuñez H. , Magnus Wim , Peeters F. M.
Published: September 2010

A simplified quantum mechanical model is developed to investigate quantum transport features such as the electron concentration and the current flowing through a silicon nanowire metal-oxide-semiconductor field-effect transistor (MOSFET). In particular, the electron concentration is extracted from a self-consistent solution of the Schrödinger and Poisson equations as well as the ballistic Boltzmann equation which have been solved by exploiting a nonlinear variational principle within the framework of the generalized local density approximation. A suitable action functional has been minimized and details of the implementation and its numerical minimization are given. The current density and its related current-voltage characteristics are calculated from the one-dimensional ballistic steady-state Boltzmann transport equation which is solved analytically by using the method of characteristic curves. The straightforward implementation, the computational speed and the good qualitative behavior of the transport characteristics observed in our approach make it a promising simulation method for modeling quantum transport in nanowire MOSFETs.
Enhanced multiferroic properties in Ti-doped Bi2Fe4O9 ceramics
Authors: Tian Z. M. , Qiu Y. , Yuan S. L. , Wu M. S. , Huo S. X. , Duan H. N.
Published: September 2010

Structural, magnetic, and ferroelectric properties have been investigated for Bi2Fe4(1−x)Ti4xO9 (0≤x≤0.2) bulk ceramics, which were synthesized by a modified Pechini method. X-ray diffraction reveals that all samples are single phase with no impurities detected. Compared with antiferromagnetic Bi2Fe4O9 compound, doping with Ti ions induces the appearance of weak ferromagnetism at room temperature, which is discussed in terms of the collapse of the frustrated antiferromagnetic spin structure. Moreover, appropriate Ti doping also significantly reduces electric leakage and leads to the enhancement of electrical polarization. Among all samples, the optimal multiferroics with Mr∼0.0188 emu/g and Pr∼0.262 μC/cm2 at room temperature is found for x=0.15 ceramics. It is thus shown that Ti-doped Bi2Fe4O9 is a promising candidate for preparing multiferroic materials.
High-resolution elastic and rotationally inelastic diffraction of D2 from NiAl(110)
Authors: Barredo Daniel , Laurent Guillaume , Nieto Pablo , Farías Daniel , Miranda Rodolfo
Published: September 2010

High-resolution angular distributions of D2 scattered from NiAl(110) have been measured at incident energies between 20 and 150 meV. The measurements were performed along the [11¯0] azimuth using a high sensitivity time-of-flight apparatus, which allows the recording of diffraction channels not previously studied, including out-of-plane rotationally inelastic diffraction peaks. The attenuation of both elastic and rotationally inelastic diffraction intensities with surface temperature was found to follow a Debye–Waller model. The time-of-flight data analysis allowed us to assign unequivocally the different transition probabilities to each final state. In this way, 0→2, 2→0, and 1→3 transition probabilities were observed, covering relative intensities over two orders of magnitude. In the energy range investigated, the 0→2 transition was found to be a factor of 2–3 larger than the 2→0 one, which lies a factor of 10 above the 1→3 transition probability.
Analysis of a DNA simulation model through hairpin melting experiments
Authors: Linak Margaret C. , Dorfman Kevin D.
Published: September 2010

We compare the predictions of a two-bead Brownian dynamics simulation model to melting experiments of DNA hairpins with complementary AT or GC stems and noninteracting loops in buffer A. This system emphasizes the role of stacking and hydrogen bonding energies, which are characteristics of DNA, rather than backbone bending, stiffness, and excluded volume interactions, which are generic characteristics of semiflexible polymers. By comparing high throughput data on the open-close transition of various DNA hairpins to the corresponding simulation data, we (1) establish a suitable metric to compare the simulations to experiments, (2) find a conversion between the simulation and experimental temperatures, and (3) point out several limitations of the model, including the lack of G-quartets and cross stacking effects. Our approach and experimental data can be used to validate similar coarse-grained simulation models.
Stress-induced nano-oxidation of silicon by diamond-tip in moisture environment: A hybrid quantum-classical simulation study
Authors: Ogata Shuji , Abe Yuya , Ohba Nobuko , Kobayashi Ryo
Published: September 2010

This paper reports a numerical simulation study about the chemical reactions of a nanosized water droplet inserted between H-terminated Si(001) surface and a nanosized, H-terminated diamond-tip when the tip is either slid on or pushed to the surface. The hybrid quantum-classical simulation method, in which the quantum region described with the density-functional theory is embedded in the total system of classical atoms, is used to perform the simulation runs in realistic settings. A feature to select the quantum region adaptively during the run is added to trace the time evolution of the contact area of the tip and surface. When the tip pushes the water droplet, while the Si surface interacts weakly with the water molecule, the tip draws a water molecule from the droplet into a unique metastable state in close proximity to the end of the tip. When the tip is further slid on or pushed to the Si surface, the water molecule in the metastable state decomposes due to high stresses concentrated at the contact area and oxidizes the surface if the molecule is trapped in a dimple structure of the surface. On the other hand, if the water molecule finds enough space between the tip and surface, it runs away without changing the bonding characteristics of both tip and surface.
Light controlled magnetoresonant softening of γ-irradiated KCl:Fe crystals
Authors: Morgunov Roman
Published: September 2010

Magnetoresonant softening of γ-irradiated KCl:Fe crystals controlled by visual light illumination was observed. Resonant magnetoplasticity detected by microhardness before illumination of the crystals is provided by two types of paramagnetic defects: (1) Fe2+-vc ion-vacancy pair with 7.0 and 3.5 g-factors, (2) Fe+ ions with g-factors equal to 2.2 and 4.1. Illumination of the γ-KCl:Fe crystals by λ=500–600 nm light causes disappearance of the electron paramagnetic resonance lines with 7.0 and 3.5 g-factors corresponding to Fe2+-vc resonances. The spectrum of the illuminated sample changes due to recombination of F-electrons with Fe2+-vc centers and their transformation to the Fe+ centers. Two lines with 2.2 and 4.1 g-factors corresponding to the Fe+ resonances were observed before and after light illumination.
Spin dependent tunneling spectroscopy in 1.2 nm dielectrics
Authors: Ryan J. T. , Lenahan P. M. , Krishnan A. T. , Krishnan S.
Published: September 2010

We demonstrate voltage controlled spin dependent tunneling in 1.2 nm effective oxide thickness silicon oxynitride films. Our observations introduce a simple method to link point defect structure and energy levels in a very direct way in materials of great technological importance. We obtain defect energy level resolution by exploiting the enormous difference between the capacitance of the very thin dielectric and the capacitance of the depletion layer of moderately doped silicon. The simplicity of the technique and the robust character of the response make it, at least potentially, of widespread utility in the understanding of defects important in solid state electronics. Since the specific defect observed is generated by high electric field stressing, an important device instability in present day integrated circuitry, the observations are of considerable importance for present day technology. Since the observations involve inherent high sensitivity and tunneling, and since the process can be turned on and off with the application of a narrow range of voltage, our results may also be relevant to the development of spin based quantum computing.
On the microstructure of thin films grown by an isotropically directed deposition flux
Authors: Alvarez R. , Romero-Gomez P. , Gil-Rostra J. , Cotrino J. , Yubero F. , Palmero A. , Gonzalez-Elipe A. R.
Published: September 2010

The influence of isotropically directed deposition flux on the formation of the thin film microstructure at low temperatures is studied. For this purpose we have deposited TiO2 thin films by two different deposition techniques: reactive magnetron sputtering, in two different experimental configurations, and plasma enhanced chemical vapor deposition. The obtained results indicate that films grown under conditions where deposition particles do not possess a clear directionality, and in the absence of a relevant plasma/film interaction, present similar refractive indices no matter the deposition technique employed. The film morphology is also similar and consists of a granular surface topography and a columnarlike structure in the bulk whose diameter increases almost linearly with the film thickness. The deposition has been simulated by means of a Monte Carlo model, taking into account the main processes during growth. The agreement between simulations and experimental results indicates that the obtained microstructures are a consequence of the incorporation of low-energy, isotropically directed, deposition particles.
Light emission properties of planar source in multilayer structures with photonic crystal patterns
Authors: Zhao Yu , Wang Gang , Wang Xue-Hua
Published: September 2010

Based on scattering matrix method, we investigate the light emission properties of planar source (i.e., an area current source) in multilayer structures with two-dimensional photonic crystal (PC) patterns. Our numerical results show that the outgoing power from planar source is good agreement with the experimental results of multilayer structures with PC patterns reported before, which clarifies the reason of the big differences between experimental results and theoretical simulations based upon point dipole source. Our studies should provide a deep insight into the underlying physics of quantum optoelectronic devices based upon PC structures.
Comment on “Modeling shock waves in orthotropic elastic materials” [J. Appl. Phys. 104, 044904 (2008)]
Authors: Lukyanov Alexander A.
Published: September 2010

This comment identifies two main problems with the paper Vignjevic et al. [J. Appl. Phys. 104, 044904 (2008)] related to shock waves modeling in composites. (1) The authors claim that they have proposed two different stress decompositions based on the assumption that the stress tensor is split into two components: one component is due to volumetric strain and the other is due to deviatoric strain. Following this, the authors defined a pressure as the state of stress resulting only from volumetric deformation. However, neither the first nor second decomposition of the stress tensor proposed by the authors provides a procedure for separating the material volumetric compression from the deviatoric strain tensor which results in a state of stress corresponding to volumetric deformation. Furthermore, the uniquely correct decomposition of the stress tensor based on the same second order material tensors has already been published (see, for example, [Int. J. Plast. 24, 140 (2008)]). Also, the second decomposition of the stress tensor includes serious mistakes and inconsistencies. (2) In addition, the numerical simulation results proposed by the authors cannot be justified. An analytical calculation of the Hugoniot stress levels and the acoustic speed of sound through the thickness orientation for a selected carbon-fiber epoxy composite show that the stress decompositions and material properties reported by the authors do not agree with the experimental data for this material and, more importantly, contradict the shock wave stability requirements.
On application of lubrication approximations to nonunidirectional coating flows with clean and surfactant interfaces
Authors: Krechetnikov R.
Published: September 2010

In this work, the characteristic properties of the lubrication approximation are studied and its weak ellipticity is established, in contradistinction to the commonly accepted parabolic character of the lubrication equations resulting from the underlying unidirectional flow assumption. The weak ellipticity property allows the lubrication analysis to capture flow topologies around stagnation points, contact lines, and flows over edges, all of which normally require elliptic operators to be accounted for. This is used to explain the empirically observed overperformance of the lubrication approximation from the perspective of characteristic analysis. While the analysis is developed in the context of the classical Landau–Levich problem of dip-coating, which is known to possess an interfacial stagnation point both in the clean and surfactant interface cases, the analysis is general since the Landau–Levich equation is common to many other lubrication problems. The analytical approach presented here when applied to the surfactant interface case, also allows one to establish a new physical result: a variation of the bulk surfactant concentration is the necessary condition for the film thickening phenomenon in the Landau–Levich problem to occur due to surfactant-induced Marangoni effects.
Three-dimensional double deck meshlike dye-sensitized solar cells
Authors: Wang Yuanhao , Yang Hongxing , Lu Lin
Published: September 2010

In this paper, we develop a new type of three-dimensional dye-sensitized solar cells (3D DSSCs) with double deck cylindrical Ti meshes as the substrates. One of the Ti meshes is anodized to in situ synthesize the self-organized TiO2 nanotube layer as the photoanode materials. Another Ti mesh is platinized through electrodeposition as the counter electrode. The morphologies of the electrodes are characterized by scanning electron microscopy. We investigate the effect of the mesh number on the 3D DSSCs with the dye adsorption, cyclic voltammetry, and electrochemical impedance spectroscopy. The results show that with the increase in the mesh number, the dye-loadings on the photoanode and the active surface area of Pt on the counter electrode are increased, while the diffusion of the electrolyte becomes more difficult due to the reduced diameter of the openings in the mesh. It has also been demonstrated that the performance of this 3D DSSC is independent of the incident solar beam angle due to its axial symmetrical structure. In the I-V measurement, the 3D DSSC based on the 90-mesh photoanode and the 120-mesh counter electrode shows the highest conversion efficiency of 5.5% under standard AM 1.5 sunlight. The problems of electrical insulator layer are discussed and further investigation is expected.
Nonstoichiometric material transfer in the pulsed laser deposition of LaAlO3
Authors: Droubay T. C. , Qiao L. , Kaspar T. C. , Engelhard M. H. , Shutthanandan V. , Chambers S. A.
Published: September 2010

Inequivalent angular distributions have been found for La and Al in the ablation plume from LaAlO3 single crystal targets using a KrF laser during pulsed laser deposition. Angular distributions and stoichiometries in the condensate were measured and reveal decidedly nonstoichiometric transfer from target to substrate over most of the angular range. Composition varied dramatically for plume angles parallel to the long axis of the laser spot with the on-axis position exhibiting a peak in the La/Al atom ratio at ∼1.5. The distributions were more diffuse in the perpendicular direction. Stoichiometric LaAlO3 was found in the condensate only at an extreme off-axis position.
Temperature and strain-rate dependent fracture strength of graphene
Authors: Zhao H. , Aluru N. R.
Published: September 2010

We investigate the variation in fracture strength of graphene with temperature, strain rate, and crack length using molecular dynamics (MD) simulations, kinetic analysis of fracture with a nonlinear elastic relation, and the quantized fracture mechanics theory. Young’s modulus does not vary significantly with temperature until about 1200 K, beyond which the material becomes softer. Temperature plays a more important role in determining the fracture strength of graphene. Our studies suggest that graphene can be a strong material even, when subjected to variations in temperature, strain rate, and cracks.
Atomic structure of misfit dislocations in nonpolar ZnO/Al2O3 heterostructures
Authors: Zhou H. , Chisholm M. F. , Pant P. , Chang H. J. , Gazquez J. , Pennycook S. J. , Narayan J.
Published: September 2010

Understanding dislocation core structures at the atomic level is of significant theoretical and technological importance because of the role dislocations play in the electronic/optical properties of materials. In this paper, we report our aberration-corrected scanning transmission electron microscopy study on misfit dislocation core structures at non-polar (112¯0)ZnO/(11¯02)Al2O3 (a-ZnO/r-Al2O3) interface. The atomic configuration of the core structure is found to be closely related to the preferred interfacial bonding configuration. A significant number of these misfit dislocations have undergone a core structure modification involving the incorporation of Zn in the Al2O3 side of the dislocation.
Charge transfer and mixed-valence behavior in phtalocyanine-dimer cations
Authors: Monari Antonio , Evangelisti Stefano , Leininger Thierry
Published: September 2010

Phtalocyanine compounds deserved a considerable interest in recent times, particularly because of their possible use in the field of nanoelectronics. In particular, the charge mobility (of both electrons and holes) in phtalocyanine stacked arrangements has been recently extensively investigated. The present work focuses on the study of the hole-transfer mechanism between two phtalocyanine monomers. For an interdisk distance larger than 4.5 bohrs, the eclipsed dimer exhibits a mixed-valence behavior, with a saddle point transition state separating two equivalent minima. This behavior, however, is strongly dependent on the relative angle between the disks. In particular, the mixed-valence character of the compound is strongly enhanced for arrangements that are far from the eclipsed geometry. Moreover, for values of the angle close to π/8 and 3π/8, the ground and excited transition states have exactly the same energy, thus implying the presence of a conical intersection. These results can have deep implication in the charge transfer along phtalocyanine chains.
Dynamical (e, 2e) studies using tetrahydrofuran as a DNA analog
Authors: Colyer C. J. , Bellm S. M. , Lohmann B. , Hanne G. F. , Al-Hagan O. , Madison D. H. , Ning C. G.
Published: September 2010

Triple differential cross sections for the electron-impact ionization of the outer valence orbital of tetrahydrofuran have been measured using the (e, 2e) technique. The measurements have been performed with coplanar asymmetric kinematics, at an incident electron energy of 250 eV and at an ejected electron energy of 10 eV, over a range of momentum transfers. The experimental results are compared with theoretical calculations carried out using the molecular three-body distorted wave model. The results obtained are important for gaining an understanding of electron driven processes at a molecular level and for modeling energy deposition in living tissue.
Remote doping of a pentacene transistor: Control of charge transfer by molecular-level engineering
Authors: Zhao Wei , Qi Yabing , Sajoto Tissa , Barlow Stephen , Marder Seth R. , Kahn Antoine
Published: September 2010

We demonstrate that holes from a p-doped N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layer transfer to an adjacent pentacene film. The spatial separation of carriers from dopants, or remote doping, is demonstrated with a combination of photoemission spectroscopy and current-voltage measurements for a p-doped α-NPD/pentacene heterojunction. Increased conductivity of the pentacene film is observed in both nongated temperature-dependent conductivity and gated thin-film transistor measurements.
Congruent evaporation temperature of GaAs(001) controlled by As flux
Authors: Zhou Z. Y. , Zheng C. X. , Tang W. X. , Jesson D. E. , Tersoff J.
Published: September 2010

The congruent evaporation temperature Tc is a fundamental surface characteristic of GaAs and similar compounds. Above Tc the rate of As evaporation exceeds that of Ga during Langmuir (free) evaporation into a vacuum. However, during molecular beam epitaxy (MBE) there is generally an external As flux F incident on the surface. Here we show that this flux directly controls Tc. We introduce a sensitive approach to measure Tc based on Ga droplet stability, and determine the dependence of Tc on F. This dependence is explained by a simple model for evaporation in the presence of external flux. The capability of manipulating Tc via changing F offers a means of controlling congruent evaporation with relevance to MBE, surface preparation methods, and droplet epitaxy.
Induced absorption dynamics in quantum dot based waveguide electroabsorbers
Authors: Piwonski T. , Pulka J. , Viktorov E. A. , Huyet G. , Manning R. J. , Houlihan J. , Mandel P. , Erneux T.
Published: September 2010

Two-color pump-probe measurements are used to study the carrier dynamics of InAs/GaAs quantum dots in a waveguide structure under reverse bias conditions. For the case of initially populating the ground state (GS), we find relaxation dynamics that include both absorptive and bleaching components in the excited state (ES) wavelength range. We reproduce the main features of this induced absorption dynamics using a simple model with an additional term for induced absorption at the ES due to carriers injected at the GS. The induced absorption dynamics includes multiple recovery timescales which can be attributed to phonon-assisted processes of GS/ES interaction.
Tuning perpendicular magnetic anisotropy in (Ga,Mn)(As,P) by thermal annealing
Authors: Casiraghi A. , Rushforth A. W. , Wang M. , Farley N. R. S. , Wadley P. , Hall J. L. , Staddon C. R. , Edmonds K. W. , Campion R. P. , Foxon C. T. , Gallagher B. L.
Published: September 2010

We have investigated the effects of postgrowth low temperature annealing on the magnetic, electrical, and structural properties of (Ga0.94Mn0.06)(As0.9P0.1) layers grown by molecular beam epitaxy. By controlling the annealing time, we are able to tune the magnetic anisotropy between an easy axis in the plane for the as-grown samples, to an easy axis perpendicular to the plane for fully annealed samples. The increase in the carrier density, as a result of annealing, is found to be the primary reason for the sign reversal of the magnetic anisotropy, in qualitative agreement with theoretical predictions.
Impact of ion implantation boundary dimensionality on boron transient diffusion in submicron scale patterns
Authors: Woon Wei Yen , Chen Chia Ling
Published: September 2010

We investigate two-dimensional boron transient diffusion in sub-micron scale patterns by plane view scanning capacitance microscopy (SCM). Submicron long strips and squares ion implantation windows of systematically varying sizes have been designed and fabricated. Boron ion implantation and spike annealing were followed to activate the dopant and cause diffusion. Square opening windows show more enhanced diffusion than the long strip counterparts, especially at larger length scales. We explain the observation and fit the experimental data by a nonlinear logistics model. The implication to modern microelectronic circuit design and conventional dopant profiling methodology are discussed.
The general two-dimensional open-closed cloak with tunable inherent discontinuity and directional communication
Authors: Han Tiancheng , Qiu Chengwei , Tang Xiaohong
Published: September 2010

We propose general two-dimensional open-closed cloaks with controllable and inherent discontinuity, which is manipulated to create fully open, partially open, and fully closed cloaks rigorously. Multiple objects can be concealed separately in multiple controllable touching domains, with or without openings. The openings in proposed open-closed cloaks are introduced by inherent discontinuity without any approximation, and can be much larger compared to the approximate method [H. Ma, S. B. Qu, Z. Xu, and J. F. Wang, Appl. Phys. Lett. 94, 103501 (2009)]. More importantly, quasiperfect cloaking performance is kept while allowing the cloaked objects to communicate with the outer region directionally.
Urinary corticosterone metabolite responses to capture, and annual patterns of urinary corticosterone in wild and captive endangered Fijian ground frogs (Platymantis vitiana)
Authors: Narayan Edward , Molinia Frank , Christi Ketan , Morley Craig , Cockrem John
Published: September 2010

This study was based on the development of a non-invasive glucocorticoid enzyme-immunoassay for the assessment of stress in wild and captive endangered Fijian ground frogs (Platymantis vitiana). Enzyme-immunoassays were developed and validated for the first time to non-invasively measure both cortisol and corticosterone metabolites in frog urine. Frog urine showed parallel displacement with corticosterone but not cortisol standards, therefore corticosterone enzyme immunoassays were used to examine stress in wild and captive frogs. Urinary corticosterone metabolite concentrations increased in frog urine (n = 4) at 6 h, 1 day and 2 days after injection with adrenocorticotropic hormone (0.44 μg g–1 bodyweight), indicating that the corticosterone enzyme-immunoassay could detect changes in circulating corticosterone in frogs. Urinary concentrations of corticosterone were measured in wild frogs (n = 18) after capture in the field. The first measurement beyond the initial sample was at 2–3 h. Mean urinary corticosterone concentrations rose after the initial sample and were significantly elevated in samples collected 3–4 h after capture. This is the first demonstration of a urinary corticosterone response to capture in amphibians. Urinary corticosterone metabolite concentrations for all months combined were lower in captive males than in wild males, and differed between vitellogenic, non-vitellogenic and captive females. Concentrations did not differ between captive and wild females. In conclusion, urinary corticosterone enzyme immunoassays can be used in frogs for assessing stress responses to capture and natural stress profiles of both captive and wild populations.