bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Knowledge Acquisition in Younger and Elderly Adults
Authors: Jansen Petra , Schmelter Andrea , Heil Martin
Published: October 2009

This study investigated the process of spatial knowledge acquisition in younger adults (20–30 years), middle-aged adults (40–50 years), and older adults (60–70 years) in a desktop virtual environment, where participants learned a way through a virtual maze, had to recall landmarks that were present in the maze, and had to draw an overview of the maze. The results revealed a general decline in spatial memory of the elderly, that is, in the time needed to learn a new route, in the retrieval of landmarks from memory (landmark knowledge), and in the ability to draw a map (configurational knowledge). When the route with landmarks was perfectly learned, however, there was no age dependent difference in finding the correct route without landmarks in the virtual maze (retrieval of route knowledge). Therefore, we conclude that not all aspects of spatial knowledge acquisition and spatial memory degrade with increasing age during adulthood.
Using the Implicit Association Test as a Measure of Causal Learning does not Eliminate Effects of Rule Learning
Authors: De Houwer Jan , Vandorpe Stefaan
Published: October 2009

Given that human causal judgments may be based on propositional reasoning processes rather than reflecting the strength of associations between cause and outcome representations (e.g., De Houwer, 2009, for a review), the question arises whether there are measures of causal learning that are sensitive only to the strength of associations. We investigated the potential of the Implicit Association Test (IAT) in this context. The results showed evidence for rule learning even when IAT effects were used as an index of learning. This suggests that the IAT does not allow one to measure causal learning in a manner that excludes an impact of conscious propositional knowledge.
The Involuntary Capture of Attention by Sound
Authors: Parmentier Fabrice B. R. , Andrés Pilar
Published: October 2009

The presentation of auditory oddball stimuli (novels) among otherwise repeated sounds (standards) triggers a well-identified chain of electrophysiological responses: The detection of acoustic change (mismatch negativity), the involuntary orientation of attention to (P3a) and its reorientation from the novel. Behaviorally, novels reduce performance in an unrelated visual task (novelty distraction). Past studies of the cross-modal capture of attention by acoustic novelty have typically discarded from their analysis the data from the standard trials immediately following a novel, despite some evidence in mono-modal oddball tasks of distraction extending beyond the presentation of deviants/novels (postnovelty distraction). The present study measured novelty and postnovelty distraction and examined the hypothesis that both types of distraction may be underpinned by common frontally-related processes by comparing young and older adults. Our data establish that novels delayed responses not only on the current trial and but also on the subsequent standard trial. Both of these effects increased with age. We argue that both types of distraction relate to the reconfiguration of task-sets and discuss this contention in relation to recent electrophysiological studies.
NW Australian intraplate seismicity and stress regime
Authors: Revets S. A. , Keep M. , Kennett B. L. N.
Published: October 2009

The interrelations between stress orientation, regional deformation, and seismic activity in the context of intraplate seismicity continue to pose difficult questions. Stress models of the Australian continent are largely based on nonseismic information. Our study of 26 microearthquakes in NW Australia shows that they are good indicators of the seismogenic stress field. By inverting focal mechanisms calculated from the events we obtained deviatoric stress tensors in full agreement with the known in‐situ stress field. The stress tensors corroborate the elastic modeling of the continent. The methods used here have widespread applicability in determining crustal stress field parameters in regions where in‐situ stress data are sparse or absent.
Dipolar self‐potential anomaly associated with carbon dioxide and radon flux at Syabru‐Bensi hot springs in central Nepal
Authors: Byrdina S. , Revil A. , Pant S. R. , Koirala B. P. , Shrestha P. L. , Tiwari D. R. , Gautam U. P. , Shrestha K. , Sapkota S. N. , Contraires S. , Perrier F.
Published: October 2009

The Syabru‐Bensi hot springs are located at the Main Central Thrust (MCT) zone in central Nepal. High carbon dioxide and radon exhalation fluxes (reaching 19 kg m−2 d−1 and 5 Bq m−2 s−1, respectively) are associated with these hot springs, making this site a promising case to study the relationship between self‐potential and fluids (gas and water) exhalation along a fault zone. A high‐resolution self‐potential map, covering an area of 100 m by 150 m that surrounds the main gas and water discharge spots, exhibits a dipolar self‐potential anomaly with a negative peak reaching −180 mV at the main gas discharge spot. The positive lobe of the anomaly reaching 120 mV is located along the terraces above the main gas and water discharge spots. Several electrical resistivity tomograms were performed in this area. The resistivity tomogram crossing the degassing area shows a dipping resistive channel interpreted as a fracture zone channeling the gas and the hot water. We propose a numerical finite difference model to simulate the flow pattern in this area with the constraints imposed by the electrical resistivity tomograms, the self‐potential data, the position of the gas vents, and hot water discharge area. This study provides insights on the generation of electrical currents associated with geothermal circulation in a geodynamically active area, a necessary prerequisite to study, using self‐potentials, a possible modulation of the geothermal circulation by tectonic activity.
Estimation of mixing in the troposphere from Lagrangian trace gas reconstructions during long‐range pollution plume transport
Authors: Pisso I. , Real E. , Law K. S. , Legras B. , Bousserez N. , Attié J. L. , Schlager H.
Published: October 2009

The dispersion and mixing of pollutant plumes during long‐range transport across the North Atlantic is studied using ensembles of diffusive backward trajectories in order to estimate turbulent diffusivity coefficients in the free troposphere under stratified flow conditions. Values of the order of 0.3–1 m2 s−1 and 1 × 104 m2 s−1 for the vertical and horizontal diffusivity coefficients Dv and Dh, respectively, are derived. Uncertainties related to the method are discussed, and results are compared with previous estimates of atmospheric mixing rates. These diffusivity estimates also yield an estimate of the vertical/horizontal aspect ratio of tracer structures in the troposphere. Results from this case study are used to estimate grid resolutions needed to accurately simulate the intercontinental transport of pollutants as being of the order of 500 m in the vertical and at least 40 km in the horizontal. This work forms the basis of high‐resolution chemical simulations using ensembles of diffusive backward trajectories.
Late Quaternary left‐lateral slip rate of the Haiyuan fault, northeastern margin of the Tibetan Plateau
Authors: Li Chuanyou , Zhang Pei‐zhen , Yin Jinhui , Min Wei
Published: October 2009

Slip rates of major active strike‐slip faults within and around the Tibetan Plateau provide constraints for understanding the dynamics of continental deformation in general because large slip rates can be taken to imply localized deformation between rigid blocks and low slip rates on faults are more consistent with distributed deformation. Several major strike‐slip faults have been studied during the last 3 decades. As one of important active strike‐slip faults in and around the Tibetan Plateau, the slip rate of the Haiyuan fault has been discrepantly estimated to be high by proponents of “escape tectonics” or low by others and GPS observations. To better constrain its slip rate and then to better understand the mechanics of intracontinental deformation, we try to more carefully consider offset geomorphic features and age constraints along the Haiyuan fault. In this paper, we select three sites where both upper and lower bounds of slip rate can be obtained. We find that slip rates are 4.2 ± 0.8 mm/yr at the Shaomayin, 4.5 ± 0.7 mm/yr at Gaowanzi, and 5.0 ± 2.5 mm/yr at Huangliangtan site. Combinations of these rates with those published previously yield an average slip rate of 4.5 ± 1.0 mm/yr on the Haiyuan fault. This rate agrees with the present‐day slip rate of 4.3 ± 1.5 mm/yr measured by GPS, 4.2–8 mm/yr by interferometric synthetic aperture radar, and ∼5 mm/yr through paleoseismological studies. The temporal consistency suggests a steady state process of strain accumulation and release along the Haiyuan fault. The low slip rate suggests that the Haiyuan fault, similar to the Altyn Tagh fault, does not transfer a significant portion of the convergence between India and Asia out of India's path into Eurasia but merely redistributes crustal thickening.
A conditional random field–based downscaling method for assessment of climate change impact on multisite daily precipitation in the Mahanadi basin
Authors: Raje Deepashree , Mujumdar P. P.
Published: October 2009

Downscaling to station‐scale hydrologic variables from large‐scale atmospheric variables simulated by general circulation models (GCMs) is usually necessary to assess the hydrologic impact of climate change. This work presents CRF‐downscaling, a new probabilistic downscaling method that represents the daily precipitation sequence as a conditional random field (CRF). The conditional distribution of the precipitation sequence at a site, given the daily atmospheric (large‐scale) variable sequence, is modeled as a linear chain CRF. CRFs do not make assumptions on independence of observations, which gives them flexibility in using high‐dimensional feature vectors. Maximum likelihood parameter estimation for the model is performed using limited memory Broyden‐Fletcher‐Goldfarb‐Shanno (L‐BFGS) optimization. Maximum a posteriori estimation is used to determine the most likely precipitation sequence for a given set of atmospheric input variables using the Viterbi algorithm. Direct classification of dry/wet days as well as precipitation amount is achieved within a single modeling framework. The model is used to project the future cumulative distribution function of precipitation. Uncertainty in precipitation prediction is addressed through a modified Viterbi algorithm that predicts the n most likely sequences. The model is applied for downscaling monsoon (June–September) daily precipitation at eight sites in the Mahanadi basin in Orissa, India, using the MIROC3.2 medium‐resolution GCM. The predicted distributions at all sites show an increase in the number of wet days, and also an increase in wet day precipitation amounts. A comparison of current and future predicted probability density functions for daily precipitation shows a change in shape of the density function with decreasing probability of lower precipitation and increasing probability of higher precipitation.
Ice shelf thickness over Larsen C, Antarctica, derived from satellite altimetry
Authors: Griggs J. A. , Bamber J. L.
Published: October 2009

Satellite radar altimetry can be used to infer the thickness of floating ice shelves around Antarctica under the assumption of hydrostatic equilibrium. Ice shelf thickness is an essential parameter in mass budget calculations and is one of the more poorly characterised. Using data from the ERS‐1 radar altimeter recorded in 1994–5, we calculate the thickness of Larsen C ice shelf on the Antarctic Peninsula. The surface elevation was determined to an accuracy of −2.3 ± 4.35 m as compared to elevations from the laser altimeter onboard ICESat. Using a model for firn depth and density, we created a 1 km grid of ice shelf thickness for Larsen C. The accuracy of the ice thickness retrieval was determined from independent airborne radio echo sounding data. The results indicated a bias of −0.22 m and random error of 36.7 m, which is equivalent to 12.7% of the mean thickness for this ice shelf.
Modeling the ratios of SKKS and SKS amplitudes with ultra‐low velocity zones at the core‐mantle boundary
Authors: Zhang Yang , Ritsema Jeroen , Thorne Michael S.
Published: October 2009

Between 105–115° degrees, the SKS waveform is complicated by the formation of SPdKS, a wave that has segments of P diffraction along the core mantle boundary. While previous studies have primarily focused on the move‐out of SPdKS from SKS, we analyze the concomitant reduction of the SKS amplitude. Long‐period SKKS/SKS amplitude ratios present a coherent global pattern. SKKS/SKS is relatively large in North and South American recordings of deep Tonga‐Fiji earthquakes but PREM‐like in European recordings of earthquakes in South America and North American recordings of earthquakes in Indonesia. Modeling of SKKS/SKS indicate that Ultra‐Low Velocity Zones (ULVZs), layers at the base of the mantle with a thickness of about 10–20 km and a shear velocity reduction between 20–30%, are required to explain high SKKS/SKS ratios and the early move‐out of SPdKS.
Penetration of ELF currents and electromagnetic fields into the Earth's equatorial ionosphere
Authors: Eliasson B. , Papadopoulos K.
Published: October 2009

The penetration of extremely low frequency (ELF) transient electromagnetic fields and associated currents in the Earth's equatorial E‐region plasma is studied theoretically and numerically. In the low‐frequency regime, the plasma dynamics of the E‐region is characterized by helicon waves since the ions are viscously coupled to neutrals while the electrons remain mobile. For typical equatorial E‐region parameters, the plasma is magnetically insulated from penetration of very long timescale magnetic fields by a thin diffusive sheath. Wave penetration driven by a vertically incident pulse localized in space and time leads to both vertical penetration and the triggering of ELF helicon/whistler waves that carry currents obliquely to the magnetic field lines. The study presented here may have relevance for ELF wave generation by lightning discharges and seismic activity and can lead to new concepts in ELF/ULF injection in the earth‐ionosphere waveguide.
Influence of ice crystal shape on retrieval of cirrus optical thickness and effective radius: A case study
Authors: Eichler H. , Ehrlich A. , Wendisch M. , Mioche G. , Gayet J.‐F. , Wirth M. , Emde C. , Minikin A.
Published: October 2009

Airborne measurements of spectral upwelling radiances (350–2200 nm) reflected by cirrus using the Spectral Modular Airborne Radiation measurement sysTem (SMART)‐Albedometer were made over land and water surfaces. Based on these data, cloud optical thickness τ and effective radius Reff of the observed cirrus were retrieved. By using different crystal shape assumptions (hexagonal plates, solid and hollow columns, rough aggregates, planar and spatial rosettes, ice spheres, and a mixture of particle habits) in the retrieval, the influence of crystal shape on the retrieved τ and Reff was evaluated. With relative differences of up to 70%, the influence of particle habit on τ is larger than on Reff (up to 20% differences). Retrieved τ values agreed with values derived from concurrent lidar measurements within the measurement uncertainties.
A Consultative Itinerant Approach to Service Delivery: Considerations for the Early Childhood Community
Authors: Dinnebeil Laurie , Pretti-Frontczak Kristie , McInerney William
Published: October 2009

Purpose

This article, written by experts in itinerant early childhood special education, describes and differentiates approaches to itinerant early childhood special education as a primary service delivery option. Consultative itinerant early childhood special education services, in particular, are a means of ensuring that young children with disabilities have access to the general early childhood curriculum as offered in community-based programs.

Method

A discussion of the empirical literature that supports a consultative approach, literature that focuses on behavioral consultation and principles of distributed practice and embedded learning opportunities, is included. In addition, this article outlines a set of assumptions that program personnel make when implementing a consultative itinerant approach to service delivery. The need for and challenges associated with a consultative itinerant approach are discussed.

Conclusion

Itinerant early childhood special educators face similar challenges as speech-language pathologists with regard to providing high-quality interventions to children in inclusive settings.
Kaluza–Klein theory as a dynamics in a dual geometry
Authors: Gershon Avi , Horwitz Lawrence
Published: October 2009

It has been shown that the orbits of motion for a wide class of nonrelativistic Hamiltonian systems can be described as geodesic flow on a manifold and an associated dual. This method can be applied to a four dimensional manifold of orbits in space-time associated with a relativistic system. One can study the consequences on the geometry of the introduction of electromagnetic interaction. We find that resulting geometrical structure in the dual space is that of Kaluza and Klein.
A completeness study on discrete, 2×2 Lax pairs
Authors: Hay Mike
Published: October 2009

We propose a method to identify and examine every partial difference Lax pair that consists of two 2×2 discrete linear problems, where the matrices contain one separable term in each entry. We thereby derive new, higher order versions of the lattice sine-Gordon and lattice modified Korteweg–de Vries equations, while showing that there can be no other partial difference equations associated with this type of Lax pair.
An extension of Wiener integration with the use of operator theory
Authors: Jorgensen Palle E. T. , Song Myung-Sin
Published: October 2009

With the use of tensor product of Hilbert space and a diagonalization procedure from operator theory, we derive an approximation formula for a general class of stochastic integrals. Further we establish a generalized Fourier expansion for these stochastic integrals. In our extension, we circumvent some of the limitations of the more widely used stochastic integral due to Wiener and Ito, i.e., stochastic integration with respect to Brownian motion. Finally we discuss the connection between the two approaches, as well as a priori estimates and applications.
Euclidean Epstein–Glaser renormalization
Authors: Keller Kai J.
Published: October 2009

In the framework of perturbative algebraic quantum field theory recently developed by Brunetti, Dütsch, and Fredenhagen (http://arxiv.org/abs/0901.2038) I give a general construction of so-called Euclidean time-ordered products, i.e., algebraic versions of the Schwinger functions, for scalar quantum field theories on spaces of Euclidean signature. This is done by generalizing the recursive construction of time-ordered products by Epstein and Glaser, originally formulated for quantum field theories on Minkowski space [Epstein and Glaser, Ann. Inst. Henri Poincare 19, 211 (1973)]. An essential input of Epstein–Glaser renormalization is the causal structure of Minkowski space. The absence of this causal structure in the Euclidean framework makes it necessary to modify the original construction of Epstein and Glaser at two points. First, the whole construction has to be performed with an only partially defined product on (interaction) functionals. This is due to the fact that the fundamental solutions of the Helmholtz operator (−Δ+m2) of Euclidean quantum field theory have a unique singularity structure, i.e., they are unique up to a smooth part. Second, one needs to (re)introduce a (rather natural) “Euclidean causality” condition for the recursion of Epstein and Glaser to be applicable.
Ellipsoids of U(3) model
Authors: Cerkaski M.
Published: October 2009

The Cartan model of SO(3)/SO(2) matrices is applied to reduce the rotational degrees of freedom on coadjoint orbits of u∗(3) Poisson algebra. The seven-dimensional Poisson algebra uSO(3) obtained by SO(3) reduction in u∗(3) algebra is found and canonical parametrization of u∗(3) orbits [p1,p2,p3]∗ is studied. The structure of bands formed by so-called families of S and P ellipsoids obtained by searching extremes of many-body SO(3) invariant Hamiltonians is investigated. The reduced four-dimensional system of equations of motion describing the simple schematic Hamiltonian based on the volume conservation is presented. A new set of canonical coordinates regarding the separation of motion for independent modes is found with the help of the Jacobi approach. Bohr–Somerfield quantization of new momentum space is studied.
A group theoretical identification of integrable equations in the Liénard-type equation ẍ+f(x)ẋ+g(x)=. II. Equations having maximal Lie point symmetries
Authors: Pandey S. N. , Bindu P. S. , Senthilvelan M. , Lakshmanan M.
Published: October 2009

In this second of the set of two papers on Lie symmetry analysis of a class of Liénard-type equation of the form ẍ+f(x)ẋ+g(x)=0, where overdot denotes differentiation with respect to time and f(x) and g(x) are smooth functions of their variables, we isolate the equations which possess maximal Lie point symmetries. It is well known that any second order nonlinear ordinary differential equation which admits eight parameter Lie point symmetries is linearizable to free particle equation through point transformation. As a consequence all the identified equations turn out to be linearizable. We also show that one can get maximal Lie point symmetries for the above Liénard equation only when fxx=0 (subscript denotes differentiation). In addition, we discuss the linearizing transformations and solutions for all the nonlinear equations identified in this paper.
Studies on monodromy preserving deformation of linear differential equations on elliptic curves
Authors: Mano Toshiyuki
Published: October 2009

We study a monodromy preserving deformation (MPD) of linear differential equations on elliptic curves. As the first of our results, we describe asymptotic behaviors of solutions to the MPD system when the elliptic curve degenerates to a rational curve. As the second, we find explicit solutions for special values of parameters where the MPD system is linearizable. Our solutions are written in terms of integrals of theta functions. We also show that they converge to the hypergeometric functions applying the above asymptotic formula when the elliptic curve degenerates to a rational curve.
A note of Sasakian metrics with constant scalar curvature
Authors: Zhang Xi
Published: October 2009

In this paper, we consider compact Sasakian manifolds with constant scalar curvature. Under some positive curvature assumption, we prove that such Sasakian metrics must be η-Einstein metrics.
The tunneling solutions of the time-dependent Schrödinger equation for a square-potential barrier
Authors: Elçi A. , Hjalmarson H. P.
Published: October 2009

The exact tunneling solutions of the time-dependent Schrödinger equation with a square-potential barrier are derived using the continuous symmetry group GS for the partial differential equation. The infinitesimal generators and the elements for GS are represented and derived in the jet space. There exist six classes of wave functions. The representative (canonical) wave functions for the classes are labeled by the eigenvalue sets, whose elements arise partially from the reducibility of a Lie subgroup GLS of GS and partially from the separation of variables. Each eigenvalue set provides two or more time scales for the wave function. The ratio of two time scales can act as the duration of an intrinsic clock for the particle motion. The exact solutions of the time-dependent Schrödinger equation presented here can produce tunneling currents that are orders of magnitude larger than those produced by the energy eigenfunctions. The exact solutions show that tunneling current can be quantized under appropriate boundary conditions and tunneling probability can be affected by a transverse acceleration.
Final state problem for the cubic nonlinear Klein–Gordon equation
Authors: Hayashi Nakao , Naumkin Pavel I.
Published: October 2009

We study the final state problem for the nonlinear Klein–Gordon equation, utt+u−uxx=μu3, t∊R,x∊R, where μ∊R. We prove the existence of solutions in the neighborhood of the approximate solutions 2 Re U(t)w+(t), where U(t) is the free evolution group defined by U(t)=F−1e−it⟨ξ⟩F, ⟨x⟩=1+x2, F and F−1 are the direct and inverse Fourier transformations, respectively, and w+(t,x)=F−1(û+(ξ)e(3/2)iμ⟨ξ⟩2|û+(ξ)|2log t), with a given final data u+ is a real-valued function and ‖⟨ξ⟩3⟨i∂ξ⟩û+(ξ)‖L∞ is small.
On uniformization of Burnside’s curve y2=x5−x
Authors: Brezhnev Yu. V.
Published: October 2009

The main objects of uniformization of the curve y2=x5−x are studied: its Burnside’s parametrization, corresponding Schwarz’s equation, and accessory parameters. As a result we obtain the first examples of solvable Fuchsian equations on torus and exhibit number-theoretic integer q-series for uniformizing functions, relevant modular forms, and analytic series for holomorphic Abelian integrals. A conjecture of Whittaker for hyperelliptic curves and its hypergeometric reducibility are discussed. We also consider the conversion between Burnside’s and Whittaker’s uniformizations.
Global existence of classical solutions to the minimal surface equation in two space dimensions with slow decay initial value
Authors: Wang Yu-Zhu
Published: October 2009

In this paper, we prove the global existence of classical solutions to the Cauchy problem for the minimal surface equation in the Minkowski space R1+2 with slow decay initial value.
Exactly solvable birth and death processes
Authors: Sasaki Ryu
Published: October 2009

Many examples of exactly solvable birth and death processes, a typical stationary Markov chain, are presented together with the explicit expressions of the transition probabilities. They are derived by similarity transforming exactly solvable “matrix” quantum mechanics, which is recently proposed by Odake and the author [S. Odake and R. Sasaki, J. Math. Phys. 49, 053503 (2008)]. The (q-) Askey scheme of hypergeometric orthogonal polynomials of a discrete variable and their dual polynomials play a central role. The most generic solvable birth/death rates are rational functions of qx (with x being the population) corresponding to the q-Racah polynomial.
Rapid identification of structural phases in combinatorial thin-film libraries using x-ray diffraction and non-negative matrix factorization
Authors: Long C. J. , Bunker D. , Li X. , Karen V. L. , Takeuchi I.
Published: October 2009

In this work we apply a technique called non-negative matrix factorization (NMF) to the problem of analyzing hundreds of x-ray microdiffraction (μXRD) patterns from a combinatorial materials library. An in-house scanning x-ray microdiffractometer is used to obtain μXRD patterns from 273 different compositions on a single composition spread library. NMF is then used to identify the unique μXRD patterns present in the system and quantify the contribution of each of these basis patterns to each experimental diffraction pattern. As a baseline, the results of NMF are compared to the results obtained using principle component analysis. The basis patterns found using NMF are then compared to reference patterns from a database of known structural patterns in order to identify known structures. As an example system, we explore a region of the Fe–Ga–Pd ternary system. The use of NMF in this case reduces the arduous task of analyzing hundreds of μXRD patterns to the much smaller task of identifying only nine μXRD patterns.
Explicit blow-up solutions to the Schrödinger maps from R2 to the hyperbolic 2-space H2
Authors: Ding Qing
Published: October 2009

In this article, we prove that the equation of the Schrödinger maps from R2 to the hyperbolic 2-space H2 is SU(1,1)-gauge equivalent to the following 1+2 dimensional nonlinear Schrödinger-type system of three unknown complex functions p, q, r, and a real function u: iqt+qzz¯−2uq+2(p¯q)z−2pqz¯−4|p|2q=0, irt−rzz¯+2ur+2(p¯r)z−2prz¯+4|p|2r=0, ipt+(qr)z¯−uz=0, p¯z+pz¯=−|q|2+|r|2, −r¯z+qz¯=−2(pr¯+p¯q), where z is a complex coordinate of the plane R2 and z¯ is the complex conjugate of z. Although this nonlinear Schrödinger-type system looks complicated, it admits a class of explicit blow-up smooth solutions: p=0, q=(ei(bzz¯/2(a+bt))/a+bt)αz¯, r=e−i(bzz¯/2(a+bt))/(a+bt)αz¯, u=2α2zz¯/(a+bt)2, where a and b are real numbers with ab<0 and α satisfies α2=b2/16. From these facts, we explicitly construct smooth solutions to the Schrödinger maps from R2 to the hyperbolic 2-space H2 by using the gauge transformations such that the absolute values of their gradients blow up in finite time. This reveals some blow-up phenomenon of Schrödinger maps.
Note on spin modules associated to Z-graded Lie superalgebras
Authors: Iohara Kenji , Koga Yoshiyuki
Published: October 2009

The aim of this note is to clarify what can be a correct analog of modules of ‘semi-infinite wedges’ over the Virasoro algebra, considered by Feigin and Fuchs [“Invariant skew-symmetric differential operators on the line and Verma modules over the Virasoro algebra,” Funct. Anal. Appl. 16, 114 (1982)], for a certain class of Lie superalgebras.
Unified expression for the rate constant of the bridged electron transfer derived by renormalization
Authors: Saito Keisuke , Sumi Hitoshi
Published: October 2009

Electron transfer (ET) from a donor to an acceptor through an energetically close intermediary state on a midway molecule is a process found often in natural and artificial solar-energy capturing systems such as photosynthesis. This process has often been thought of in terms of opposing “superexchange” and “sequential or hopping” mechanisms, and the recent theory of Sumi and Kakitani (SK) [J. Phys. Chem. B 105, 9603 (2001)] has shown an interpolation between these mechanisms. In their theory, however, dynamics governing the most interesting intermediary region between them has artificially been introduced by phenomenologies. The dynamics is played by decoherence among electronic states, their decay, and thermalization of phonons in the medium. The present work clarifies the dynamics on a microscopic basis by means of renormalization in electronic coupling among the states, and gives a complete unified expression of the rate constant of the ET. It merges to that given by the SK theory in the semiclassical approximation for phonons interacting with an electron transferred.
Strong uniaxial magnetic anisotropy in CoFe films on obliquely sputtered Ru underlayer
Authors: Fukuma Y. , Lu Z. , Fujiwara H. , Mankey G. J. , Butler W. H. , Matsunuma S.
Published: October 2009

Co 90 Fe 10 films with an in-plane uniaxial magnetic anisotropy have been grown on an obliquely sputtered thin Ru underlayer. The anisotropy field can be increased up to 200 Oe. The hysteresis curves show a very high squareness in the easy axis direction and almost no hysteresis in the hard axis direction, suggesting that the induced uniaxial anisotropy is uniform throughout the films. The switching characteristics of the nanoelements fabricated from the films by e-beam lithography are also investigated. There is no degradation of the magnetic anisotropy after the annealing and lithographical process.
Phase behavior of a de-ionized binary mixture of charged spheres in the presence of gravity
Authors: Lorenz Nina J. , Schöpe Hans Joachim , Palberg Thomas
Published: October 2009

We report on the phase behavior of an aqueous binary charged sphere suspension under exhaustively de-ionized conditions as a function of number fraction of small particles p and total number density n. The mixture of size ratio Γ=0.557 displays a complex phase diagram. Formation of bcc crystals with no compositional order dominates. We observe a region of drastically decreased crystal stability at 0.55
p>0.95 crystal formation is partially assisted by gravity, i.e., gravitational separation of the two species precedes crystal formation for samples in the coexistence range. In the composition range corresponding to the decreased crystal stability only lower bounds of the freezing and melting line are obtained, but the general shape of the phase diagram is retained. At p=0.93 and n=43 μm−3 two different crystalline phases coexist in the bulk, while at p=0.4 additional Bragg peaks appear in the static light scattering experiments. This strongly suggests that we observe an eutectic in the region of decreased stability, while the enhanced stability at p=0.4 seems to correlate with compound formation.
Bogolubov–Hartree–Fock mean field theory for neutron stars and other systems with attractive interactions
Authors: Bach Volker , Fröhlich Jürg , Jonsson Lars
Published: October 2009

A simplification of the Bogolubov–Hartree–Fock theory, which is a natural generalization of the traditional Hartree–Fock theory, is derived. This simplification allows to express the pairing interaction in terms of the one-particle density matrix for systems interacting by attractive pair potentials, such as the Newtonian gravitational potential.
Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles
Authors: Yan Feng , Li Jinhua , Mok Sheung Man
Published: October 2009

Organic phototransistors based on a composite of P3HT and TiO2 nanoparticles have been fabricated, which show high photosensitivity, fast response, and stable performance under both visible and ultraviolet light illumination, and thus they are promising for applications as low cost photosensors. The transfer characteristic of each device exhibits a parallel shift to a positive gate voltage under light illumination, and the channel current increases up to three orders of magnitude in the subthreshold region. The shift in the threshold voltage of the device has a nonlinear relationship with light intensity, which can be attributed to the accumulation of electrons in the embedded TiO2 nanoparticles. It has been found that the device is extremely sensitive to weak light due to an integration effect. The relationship between the threshold voltage change and the intensity of light illumination can be fitted with a power law. An analytical model has been developed to describe the photosensitive behavior of the devices. It is expected that such organic phototransistors can be developed for sensing different wavelengths based on different semiconducting polymers and semiconducting nanoparticles.
Energy and momentum relaxation dynamics of hot holes in modulation doped GaInNAs/GaAs quantum wells
Authors: Sun Y. , Balkan N.
Published: October 2009

We present the studies of energy and momentum relaxation dynamics of nonequilibrium holes in GaxIn1−xNyAs1−y/GaAs quantum well modulation doped with Be. Experimental results show that the real-space transfer (RST) of hot holes occurs via thermionic emission from the high-mobility GaInNAs quantum wells into the low-mobility GaAs barriers at a threshold electric field of F∼6 kV/cm at T=13 K. At this field the hole drift velocity saturates at vd∼1×107 cm/s. A slight increase in the field above the threshold leads to the impact ionization of acceptors in the barriers by the nonequilibrium holes. We observe and model theoretically a negative differential mobility effect induced by RST that occurs at an electric field of F∼7 kV/cm. The observed current surge at electric fields above 7 kV/cm is attributed to the hole multiplication induced by shallow impurity breakdown in the GaAs barrier and impact ionization in the high-field domain regime associated with the packet of RST of holes in the well.
Transport properties of Brownian particles confined to a narrow channel by a periodic potential
Authors: Wang Xinli , Drazer German
Published: October 2009

We investigate the transport of Brownian particles in a two-dimensional potential moving under the action of an external force or convected by a flow field. The potential is periodic in one direction and confines the particles to a narrow channel of varying cross section in the other direction. We apply the standard long-wave asymptotic analysis in the narrow dimension and show that the leading order term is equivalent to that obtained previously from a direct extension of the Fick–Jacobs approximation. We also show that the confining potential has similar effects on the transport of Brownian particles to those induced by a solid channel. Finally, we compare the analytical results with Brownian dynamics simulations in the case of a sinusoidal variation of the width of a parabolic potential in the cross section. We obtain excellent agreement for the marginal probability distribution, the average velocity of the Brownian particles, and the asymptotic dispersion coefficient over a wide range of Péclet numbers.
On the structure of graded Lie algebras
Authors: Calderón Martín Antonio J.
Published: October 2009

We study the structure of arbitrary graded Lie algebras. We show that any of such algebras L with a symmetric G-support is of the form L=U+∑jIj with U a subspace of L1 and any Ij a well described graded ideal of L, satisfying [Ij,Ik]=0 if j≠k. Under certain conditions, the gr-simplicity of L is characterized and it is shown that L is the direct sum of the family of its minimal graded ideals, each one being a gr-simple graded Lie algebra.
Advanced optical magnetic nanostructures fabricated by anodic aluminum oxide membranes and magnetic fluids
Authors: Di Ziyun , Chen Xianfeng , Zhang Dongchen
Published: October 2009

Optical magnetic nanostructures, based on anodic aluminum oxide membranes and magnetic fluids, were fabricated and investigated in both transmission and magneto-optical properties. A strong enhancement in transmission property has been found compared with the traditional magnetic fluids. Excellent magneto-optical characteristic was obtained: a negative differential magnetic linear dichroism was observed, quite different from the traditional Langevin type of magnetic fluids. This phenomenon was interpreted by an antiferromagnetic coupling between two types of magnetic grains having different average diameters in the nanocomposites. Based on its outstanding magneto-optical effects, it may open potentials for future integral optical devices.
Attractors for nonautonomous two-dimensional space periodic Navier–Stokes equations
Authors: Gong Dongshan , Song Haitao , Zhong Chengkui
Published: October 2009

In this paper, we apply a new theorem which was proven by Lu et al. [“Attractors for non-autonomous 2D Navier-Stokes equations with normal external forces,” Discrete Contin. Dyn. Syst. 8, 701 (2005)] to nonautonomous two-dimensional space periodic Navier–Stokes equation. We obtain the existence of the uniform attractor in D(A) which is the domain of the Stokes operator A with periodic boundary conditions if external forces f(t) are a normal function in Lloc2(R;H1). The uniform attractor attracts all bounded subsets of D(A) in the norm of D(A).
Nonperturbative one-loop effective action for electrodynamics in curved space-time
Authors: Fucci Guglielmo
Published: October 2009

In this paper we explicitly evaluate the one-loop effective action in four dimensions for scalar and spinor fields under the influence of a strong, covariantly constant, magnetic field in curved space-time. In the framework of zeta function regularization, we find the one-loop effective action to all orders in the magnetic field up to linear terms in the Riemannian curvature. As a particular case, we also obtain the one-loop effective action for massless scalar and spinor fields. In this setting, we found that the vacuum energy of charged spinors with small mass becomes very large due entirely to the gravitational correction.
Functional determinants in higher derivative Lagrangian theories
Authors: Di Criscienzo Roberto , Zerbini Sergio
Published: October 2009

Motivated by the considerable success of alternative theories of gravity, we consider the toy model of a higher derivative Lagrangian theory, which reduces, in the Gaussian approximation, to the Pais–Uhlenbeck oscillator studied in a recent paper by [Hawking and Hertog Phys. Rev. D 65, 103515 (2002)]. Its Euclidean path integral is studied with a certain detail and a pedagogical derivation of the propagator, which makes use of a theorem due to Forman, is consequently proposed.
On quantum integrability of the Landau–Lifshitz model
Authors: Melikyan A. , Pinzul A.
Published: October 2009

We investigate the quantum integrability of the Landau–Lifshitz (LL) model and solve the long-standing problem of finding the local quantum Hamiltonian for the arbitrary n-particle sector. The particular difficulty of the LL model quantization, which arises due to the ill-defined operator product, is dealt with by simultaneously regularizing the operator product and constructing the self-adjoint extensions of a very particular structure. The diagonalizibility difficulties of the Hamiltonian of the LL model, due to the highly singular nature of the quantum-mechanical Hamiltonian, are also resolved in our method for the arbitrary n-particle sector. We explicitly demonstrate the consistency of our construction with the quantum inverse scattering method due to Sklyanin [Lett. Math. Phys. 15, 357 (1988)] and give a prescription to systematically construct the general solution, which explains and generalizes the puzzling results of Sklyanin for the particular two-particle sector case. Moreover, we demonstrate the S-matrix factorization and show that it is a consequence of the discontinuity conditions on the functions involved in the construction of the self-adjoint extensions.
Light trapping in thin-film silicon solar cells with integrated diffraction grating
Authors: Dewan Rahul , Knipp Dietmar
Published: October 2009

The optics of microcrystalline silicon thin-film solar cells with integrated light trapping structures was investigated. Periodic grating couplers were integrated in microcrystalline silicon thin-film solar cells and the influence of the grating dimensions on the short circuit current and the quantum efficiency was investigated by the numerical simulation of Maxwell’s equations utilizing the finite difference time domain algorithm. The grating structure leads to scattering and higher order diffraction resulting in an increased absorption of the incident light in the silicon thin-film solar cell. The influence of the grating period and the grating height on the short circuit current and the quantum efficiency was investigated. Enhanced quantum efficiencies are observed for the red and infrared parts of the optical spectrum. Optimal dimensions of the grating coupler were obtained.
Double side electroluminescence from p-NiO/n-ZnO nanowire heterojunctions
Authors: Wang Jen-Yi , Lee Chun-Yu , Chen Yung-Ting , Chen Chung-Tse , Chen Yung-Ling , Lin Ching-Fuh , Chen Yang-Fang
Published: October 2009

Double side light emission devices based on p-NiO/n-ZnO nanowire heterojunctions have been fabricated on indium tin oxide substrate by radio frequency magnetron sputtering combined with hydrothermal process. According to the energy band alignment, the detected broad visible and narrow ultraviolet electroluminescence arise from defect and band edge transitions in ZnO nanowires, respectively. The unique property of the double side emission is due to the nature of the large band gap of NiO film. It provides a good opportunity for the emission of a light emitting device with different colors on the top and back sides, simultaneously.
Real time reduction of probe-loss using switching gain controller for high speed atomic force microscopy
Authors: Agarwal Pranav , De Tathagata , Salapaka Murti V.
Published: October 2009

In this article, a switching gain proportional-integral-differential controller is used to reduce probe-loss affected regions in an image, obtained during tapping mode operation. Switching signal is derived from the “reliability index” signal, which demarcates regions where the tip has lost contact with the sample (probe-loss), within couple of cantilever oscillation cycles, thereby facilitating use of higher than optimal controller gain without deteriorating on-sample performance. Efficacy of the approach is demonstrated by imaging calibration sample at tip velocity close to 240 μm/s and plasmid DNA at tip velocity of 60 μm/s indicating significant reduction of probe-loss areas and recovery of lost sample features.
AC thermal imaging of a microwire with a fluorescent nanocrystal: Influence of the near field on the thermal contrast
Authors: Aigouy Lionel , Saïdi Elika , Lalouat Loïc , Labéguerie-Egéa Jessica , Mortier Michel , Löw Peter , Bergaud Christian
Published: October 2009

We have studied the temperature dependence of the visible fluorescence lines of 250 nm large PbF2 nanocrystals codoped with Er3+ and Yb3+ ions. By gluing such a particle at the end of a sharp atomic force microscope tip, we have developed a scanning thermal microscope able to observe the heating of electrically excited micro- and nanowires. By modulating the electrical current that flows in the structure, the resulting temperature variations modulate the particle fluorescence giving rise to the thermal contrast. We will show that the fluorescence is affected both by the near-field optical distribution and by temperature variations. We will show that it is possible to get rid of these optical effects and to keep the thermal contribution by comparing the images to reference images obtained when the device is not driven by a current. The determination of the temperature of the devices is performed by analyzing the thermal quenching of the fluorescent particle and is in good agreement with numerical simulations. The spatial resolution is in the range of the fluorescent particle size (smaller than 500 nm), and the temperature sensitivity is smaller than 5 K.
High temperature dilatation measurements by in situ laser interferometry under high magnetic field
Authors: Rivoirard S. , Garcin T. , Beaugnon E. , Gaucherand F.
Published: October 2009

This article contains a description of a laser interferometer coupled with a furnace for in situ dilatation measurements under high magnetic field. The apparatus fits an 18 T superconducting magnet with a 32 mm diameter room temperature bore. This optical method was chosen for dilatation measurements because it is not perturbated by the magnetic field. The measured sample can be heated up to 1500 K under a controlled atmosphere, and heating and cooling rates can be varied within a range of 10 K/s. The resolution is below 50 nm. As an example of using in situ dilatation measurements to follow phase transformations, the increase in the ferrite/austenite transformation temperature in pure iron in a magnetic field up to 16 T was experimentally evidenced.
Electron spin relaxation in n-type InAs quantum wires
Authors: Lü C. , Schneider H. C. , Wu M. W.
Published: October 2009

We investigate the electron spin relaxation of n-type InAs quantum wires by numerically solving the fully microscopic kinetic spin Bloch equations with the relevant scattering explicitly included. We find that the quantum-wire size and the growth direction influence the spin relaxation time by modulating the spin-orbit coupling. Due to intersubband scattering in connection with the spin-orbit interaction, spin-relaxation in quantum wires can show different characteristics from those in bulk or quantum wells and can be effectively manipulated by various means.