bluuebunny/crossref_metadata_2025 huggingface dataset:
Responses of Poplar to Chilling Temperatures: Proteomic and Physiological Aspects
Authors: Renaut J. , Lutts S. , Hoffmann L. , Hausman J.‐F.
Published: February 2004

Abstract: The effects of cold acclimation on primary metabolism in actively growing poplar (Populus tremula L. ×P. tremuloides Michaux) were studied. Three‐month‐old poplar plants were exposed to chilling stress (4 °C) and compared to plant material kept at a control temperature (23 °C). This treatment did not affect the survival of the plants but growth was almost stopped. The freezing tolerance of the adult leaves increased from ‐ 5.7 °C for the control plants to ‐ 9.8 °C after 14 days of exposure to 4 °C. During acclimation, the evolution of soluble carbohydrate contents was followed in the leaves. Sucrose, glucose, fructose and trehalose accumulated rapidly under chilling conditions, while raffinose content increased after one week at 4 °C. Proteomic analyses, by bidimensional electrophoresis, performed during this stage revealed that a large number of proteins had higher expression, while much less proteins disappeared or had a lower abundance. MALDI‐TOF‐MS analyses enabled ca. 30 spots to be proposed for candidate proteins. Among the accumulating or appearing proteins proposed, about a third presented similarities with chaperone‐like proteins (heat shock proteins, chaperonins). In addition, dehydrins and other late embryogenesis abundant proteins, i.e., stress‐responsive proteins, detoxifying enzymes, proteins involved in stress signalling and transduction pathways were also activated or newly synthesised. Finally, cold exposure induced a decrease in the candidate proteins involved in cell wall or energy production.
Potassium‐Dependent Cambial Growth in Poplar
Authors: Wind C. , Arend M. , Fromm J.
Published: February 2004

Abstract: To study the involvement of potassium in wood formation, poplar plants (Populus tremula L. ×Populus tremuloides Michx.) were grown over a period of one growing season, under different potassium regimes. Seasonal changes in cambial potassium content, osmotic potential, and cambial activity correlated strongly throughout the season, increasing from spring to summer and decreasing from summer to autumn. Moreover, changing the potassium supply during the growing season affected the seasonal changes of these parameters in a similar way. Low potassium supply markedly reduced cambial activity, the number of expanding cambial cell derivatives, the seasonal rate of radial wood increment, and the vessel frequency. The possible effect of hormones on potassium‐dependent cambial growth was investigated and revealed that abscisic acid (ABA) strongly decreased the potassium content within the cambial zone and reduced cambial activity, as well as the number of expanding cambial cell derivatives. In summary, our results indicate a key role for potassium in the regulation of cambial growth and wood formation due to its strong impact on osmoregulation in expanding cambial cells. They also demonstrate involvement of ABA in regulation of potassium‐dependent cambial growth.
Stills Faszienkonzept
Authors: Stark Jane
Published: February 2004

Das Studium von Stills Gesamtwerk erlaubt, dessen Faszienkonzept darzulegen. Faszien waren für ihn nicht wichtiger als andere Organe, er behandelte sie nicht unmittelbar und verwendete den Begriff auch für Membranen. Gemäß seinem Verständnis der Dreieinigkeit des Menschen bezeichnete er mit Faszie oft den materiellen Körper.
Die Bedeutung der Faszien in der manuellen Therapie
Authors: Schleip Robert
Published: February 2004

Faszien üben nicht nur Stütz- und Verbindungsfunktionen aus. Die in ihnen enthaltenen Rezeptoren machen sie zu einem wichtigen Sinnesorgan. Ihre Durchtrittstellen stimmen oft mit Akupunkturpunkten überein. Faszien enthalten kontraktile Zellen und stehen in Wechselwirkung mit dem Vegetativum, so dass über deren Behandlung auf Letzteres eingewirkt werden kann.
Singularity confinement and algebraic integrability
Authors: Lafortune S. , Goriely A.
Published: February 2004

Two important notions of integrability for discrete mappings, algebraic integrability and singularity confinement, have been used for discrete mappings. Algebraic integrability is related to the existence of sufficiently many conserved quantities and singularity confinement is associated with the local analysis of singularities. In this article, the relationship between these two notions is explored for birational autonomous mappings. The main result of this article is that algebraically integrable mappings are shown to have the singularity confinement property. Using this result, the proof of the nonexistence of algebraic conserved quantities for a class of discrete systems is given.
Time dependent transformations in deformation quantization
Authors: Dias Nuno Costa , Prata João Nuno
Published: February 2004

We study the action of time dependent canonical and coordinate transformations in phase space quantum mechanics. We extend the covariant formulation of the theory by providing a formalism that is fully invariant under both standard and time dependent coordinate transformations. This result considerably enlarges the set of possible phase space representations of quantum mechanics and makes it possible to construct a causal representation for the distributional sector of Wigner quantum mechanics.
Stress-strain characteristics in Ni–Ga–Fe ferromagnetic shape memory alloys
Authors: Sutou Y. , Kamiya N. , Omori T. , Kainuma R. , Ishida K. , Oikawa K.
Published: February 2004

Tensile and compressive stress–strain characteristics for Ni–Ga–Fe ferromagnetic shape memory alloys at several temperatures were investigated by mechanical test and a critical stress versus temperature diagram was obtained. The crystal structure of the martensite phase obtained by tensile-stress-induced martensitic transformation was estimated from the degree of the transformation strain. Stress-induced martensite transformed from the parent phase with an L21 structure showed a 14M structure by tensile stress and by further applying stress, the 14M structure martensitically was transformed into an L10 structure. Moreover, it was found in the compressive test that variant rearrangement occurred by very low compressive stress less than 3 MPa, which is similar to the phenomenon seen in Ni–Mn–Ga alloys.
The Potts model on Zd with countable set of spin values
Authors: Ganikhodjaev Nasir
Published: February 2004

The Potts model with countable set Φ of spin values on Zd is considered. It is proved that with respect to Poisson distribution on Φ the set of limiting Gibbs measures is not empty.
Hyperelliptic Nambu flow associated with integrable maps
Authors: Saito Satoru , Saitoh Noriko , Yoshida Katsuhiko
Published: February 2004

We study hyperelliptic Nambu flows associated with some n dimensional maps and show that discrete integrable systems can be reproduced as flows of this class.
Galerkin analysis for Schrödinger equation by wavelets
Authors: Dai Dao-Qing , Han Bin , Jia Rong-Qing
Published: February 2004

We consider the perturbed Schrödinger equation, which is an elliptic operator with unbounded coefficients. We use wavelets adapted to the Schrödinger operator to deal with problems on the unbounded domain. The wavelets are constructed from Hermite functions, which characterizes the space generated by the Schrödinger operator. We show that the Galerkin matrix can be pre-conditioned by a diagonal matrix so that its condition number is uniformly bounded. Moreover, we introduce a periodic pseudo-differential operator and show that its discrete Galerkin matrix under periodic wavelet system is equal to the Galerkin matrix for the equation with unbounded coefficients under the Hermite system. The convergence is proved in the L2 topology.
On the Clebsch–Gordan problem for SU(1,1): Coupling nonstandard representations
Authors: Gerry Christopher C.
Published: February 2004

The Clebsch–Gordan coefficients coupling two unitary, irreducible, positive discrete series representations of SU(1,1), are constructed. In contrast to the Clebsch–Gordan coefficients obtained a long time ago by Holman and Biedenharn [Ann. Phys. (N.Y.) 39, 1 (1966)], the derived coefficients are valid even when coupling nonstandard representations such as those for which the corresponding Bargmann indices k may be k=14 and/or 34, values associated with the “two-photon” realization of the su(1,1) Lie algebra, the corresponding representations covering the even and odd number states, respectively, of the single-mode boson system. These nonstandard cases are actually representations associated with the covering group SU¯(1,1). The results are extended to the coupling of three positive discrete series and the corresponding SU(1,1) Racah coefficients are obtained.
Quasiperiodic functions theory and the superlattice potentials for a two-dimensional electron gas
Authors: Maltsev Andrei Ya.
Published: February 2004

We consider Novikov problem of the classification of level curves of quasiperiodic functions on the plane and its connection with the conductivity of two-dimensional electron gas in the presence of both orthogonal magnetic field and the superlattice potentials of a special type. We show that the modulation techniques used in the recent papers on the two-dimensional (2-D) heterostructures permit us to obtain the general quasiperiodic potentials for 2-D electron gas and consider the asymptotic limit of conductivity when τ→∞. We use the quasiclassical approach introduced by Beenakker for the modulated electron gas and investigate the level curves of quasiperiodic potentials (Novikov problem) to get the asymptotic behavior of conductivity in this limit. Using the theory of quasiperiodic functions we introduce here the topological characteristics of the quasiperiodic potentials observable in the conductivity. The corresponding characteristics are the direct analog of the “topological numbers” introduced recently by Novikov and the present author in the conductivity of normal metals.
“Squashed entanglement”: An additive entanglement measure
Authors: Christandl Matthias , Winter Andreas
Published: February 2004

In this paper, we present a new entanglement monotone for bipartite quantum states. Its definition is inspired by the so-called intrinsic information of classical cryptography and is given by the halved minimum quantum conditional mutual information over all tripartite state extensions. We derive certain properties of the new measure which we call “squashed entanglement”: it is a lower bound on entanglement of formation and an upper bound on distillable entanglement. Furthermore, it is convex, additive on tensor products, and superadditive in general. Continuity in the state is the only property of our entanglement measure which we cannot provide a proof for. We present some evidence, however, that our quantity has this property, the strongest indication being a conjectured Fannes-type inequality for the conditional von Neumann entropy. This inequality is proved in the classical case.
Nonintegrability of the Suslov problem
Authors: Maciejewski Andrzej J. , Przybylska Maria
Published: February 2004

In this paper we investigate the Suslov problem in the case when the vector of nonholonomic constraint coincides with the third principal axis of the body, and the fixed point of the body lies in the principal plane defined by the third and the first principal axes but is out of these axes. We called this version of the Suslov problem the generalized Kozlov case, and we prove that in this case a third real meromorphic first integral functionally independent together with the energy and geometrical integrals does not exist.
Geometric integrators and nonholonomic mechanics
Authors: de León M. , Martı́n de Diego D. , Santamarı́a-Merino A.
Published: February 2004

A geometric derivation of nonholonomic integrators is developed. It is based in the classical technique of generating functions adapted to the special features of nonholonomic systems. The theoretical methodology and the integrators obtained are different from those obtained in Cortés and Martı́nez [“Nonholonomic integrators,” Nonlinearity 14, 1365–1392 (2001)]. In the case of mechanical systems with linear constraints a family of geometric integrators preserving the nonholonomic constraints is given.
Quantum mechanics of damped systems. II. Damping and parabolic potential barrier
Authors: Chruściński Dariusz
Published: February 2004

We investigate the resonant states for the parabolic potential barrier known also as inverted or reversed oscillator. They correspond to the poles of meromorphic continuation of the resolvent operator to the complex energy plane. As a by-product we establish an interesting relation between parabolic cylinder functions (representing energy eigenfunctions of our system) and a class of Gel’fand distributions used in our recent paper.
A random matrix approach to the crossover of energy-level statistics from Wigner to Poisson
Authors: Datta Nilanjana , Kunz Hervé
Published: February 2004

We analyze a class of parametrized random matrix models, introduced by Rosenzweig and Porter, which is expected to describe the energy level statistics of quantum systems whose classical dynamics varies from regular to chaotic as a function of a parameter. We compute the generating function for the correlations of energy levels, in the limit of infinite matrix size. The crossover between Poisson and Wigner statistics is measured by a renormalized coupling constant. The model is exactly solved in the sense that, in the limit of infinite matrix size, the energy-level correlation functions and their generating function are given in terms of a finite set of integrals.
Decomposition of tensor product representations of the unitary matrix quantum group SUq(2)
Authors: Arik M. , Peker-Dobie A.
Published: February 2004

Representations of SUq(2) are labeled by a phase playing the role of a Casimir operator. The coproduct SUq(2) is used to form direct product representations which can be reduced to irreducible ones. Direct product of two representations with given phases can be reduced to a representation with any given phase. Coefficients necessary for this procedure are calculated. The calculation can also be performed in the Fourier transformed space which replaces the phase by an integer.
Equations of arbitrary order invariant under the Kadomtsev–Petviashvili symmetry group
Authors: Lou S. Y. , Tang Xiao-Yan
Published: February 2004

By means of a simple new approach, a general Kadomtsev–Petviashvili (KP) family with an arbitrary function of group invariants of arbitrary order is proposed. It is proved that the general KP family possesses a common infinite dimensional Kac–Moody–Virasoro Lie point symmetry algebra. The known fourth order one can be re-obtained as a special example. The finite transformation group is presented in a clearer form. The Kac–Moody–Virasoro group invariant solutions and the Kac–Moody group invariant solutions of the KP family are determined by the Boussinesq and KdV families, respectively.
The BMS group and generalized gravitational instantons
Authors: Melas Evangelos
Published: February 2004

The ordinary Bondi–Metzner–Sachs (BMS) group B is the best candidate for the fundamental symmetry group of General Relativity. It has been shown that B admits generalizations to real space–times of any signature, and also to complex space–times. It has been suggested that certain continuous unitary irreducible representations (IRs) of B and of its generalizations correspond to gravitational instantons. Here I make this correspondence more precise and I take this suggestion one step further by arguing that a subclass of IRs of B and of its generalizations correspond to generalized gravitational instantons. Some of these generalized gravitational instantons involve in their definition certain subgroups of the Cartesian product group Cn×Cm, where Cr is the cyclic group of order r. With this motivation, I give the subgroups of Cn×Cm explicitly.
Chemical structure of the interface in ultrathin HfO2/Si films
Authors: Lee Jong-Cheol , Oh S.-J. , Cho Moonju , Hwang Cheol Seong , Jung Ranju
Published: February 2004

The chemical states of the HfO2/Si (100) interface were investigated using transmission electron microscopy and high-resolution x-ray photoelectron spectroscopy. The depth distributions of Hf chemical states showed that the Hf 4f binding energy remains unchanged with the depth and there is no signature of more than one Hf-O state. These facts strongly suggest that the chemical state of the interfacial layer is not Hf-silicate, as previously believed. Instead, the compositions are mainly Si2O3 and SiO2, judging from the deconvolution of Si 2p spectra. The dielectric constant κ=4.8 of the interfacial layer is also consistent with the above conclusions.
Multiplicative anomaly and zeta factorization
Authors: Elizalde E. , Tierz M.
Published: February 2004

Some aspects of the multiplicative anomaly of zeta determinants are investigated. A rather simple approach is adopted and, in particular, the question of zeta function factorization, together with its possible relation with the multiplicative anomaly issue is discussed. We look primordially into the zeta functions instead of the determinants themselves, as was done in previous work. That provides a supplementary view, regarding the appearance of the multiplicative anomaly. Finally, we briefly discuss determinants of zeta functions that are not in the pseudodifferential operator framework.
Pseudounitary operators and pseudounitary quantum dynamics
Authors: Mostafazadeh Ali
Published: February 2004

We consider pseudounitary quantum systems and discuss various properties of pseudounitary operators. In particular we prove a characterization theorem for block-diagonalizable pseudounitary operators with finite-dimensional diagonal blocks. Furthermore, we show that every pseudounitary matrix is the exponential of i=−1 times a pseudo-Hermitian matrix, and determine the structure of the Lie groups consisting of pseudounitary matrices. In particular, we present a thorough treatment of 2×2 pseudounitary matrices and discuss an example of a quantum system with a 2×2 pseudounitary dynamical group. As other applications of our general results we give a proof of the spectral theorem for symplectic transformations of classical mechanics, demonstrate the coincidence of the symplectic group Sp(2n) with the real subgroup of a matrix group that is isomorphic to the pseudounitary group U(n,n), and elaborate on an approach to second quantization that makes use of the underlying pseudounitary dynamical groups.
Nondestructive high spatial resolution imaging with a 60 GHz near-field scanning millimeter-wave microscope
Authors: Kim Myungsik , Kim Jooyoung , Kim Hyun , Kim Songhui , Yang Jongil , Yoo Hyunjun , Kim Sunmi , Lee Kiejin , Friedman Barry
Published: February 2004

We demonstrate a nondestructive millimeter-wave surface imaging technique using a near-field scanning millimeter-wave microscope (NSMM) with a resonant standard waveguide probe at an operation frequency f=60 GHz. A chemically etched metallic probe tip was coupled to the resonant rectangular waveguide. By properly tuning the tunable resonator and the probe tip we could improve sensitivity and spatial resolution of the NSMM. By measuring the change of the quality factor in the near-field zone, near-field scanning millimeter-wave images of patterned metal films and YBa2Cu3Oy thin films were obtained with a spatial resolution better than 1 μm. We observed the dependence of the current density NSMM images of patterned indium tin oxide films on the bias currents.
Femtosecond spectral snapshots based on electronic optical Kerr effect
Authors: Nakamura R. , Kanematsu Y.
Published: February 2004

On the basis of an optical Kerr-gate method, we have constructed a high performance system for femtosecond spectral snapshots to measure ultrafast behavior of time-dependent spectrum of weak luminescence. Optical components and their configurations have been investigated to optimize the system. We have measured nonlinear refractive indices and two-photon absorption coefficients of cubic crystals and glasses by the z-scan technique in order to evaluate their performances for an optical Kerr gate. SrTiO3 has been found to be highly efficient and suitable as a Kerr-gate material. Simulations based on the Gaussian-beam propagation were performed to find appropriate configurations to obtain high time resolution. Observation for time-resolved luminescence spectra of β-carotene has revealed that time resolution of 200 fs is achieved in a wide range of wavelengths, which is limited by the pulse width of the gating light.
Removing interference and optical feedback artifacts in atomic force microscopy measurements by application of high frequency laser current modulation
Authors: Kassies Roel , van der Werf Kees O. , Bennink Martin L. , Otto Cees
Published: February 2004

Atomic force microscopy measurements based on optical beam deflection can seriously be affected by two specific types of artifacts. Disturbances of the first type are caused by interference on the quadrant photodiode between the beam reflected directly from the cantilever and stray light from the sample surface. The second type is optical feedback effects caused by light scattering from the surface back into the laser cavity. We demonstrate that both types can be significantly reduced by application of high frequency laser current modulation. Residual noise is dominated by electronic and mechanical noise, shot noise, and noise caused by the thermal motion of the cantilever.
Molybdenum cell for x-ray diffraction measurements of fluid alkali metals at high temperatures and high pressures
Authors: Matsuda Kazuhiro , Tamura Kozaburo , Katoh Masahiro , Inui Masanori
Published: February 2004

We have developed a sample cell for x-ray diffraction measurements of fluid alkali metals at high temperatures and high pressures. All parts of the cell are made of molybdenum which is resistant to the chemical corrosion of alkali metals. Single crystalline molybdenum disks electrolytically thinned down to 40 μm were used as the walls of the cell through which x rays pass. The crystal orientation of the disks was controlled in order to reduce the background from the cell. All parts of the cell were assembled and brazed together using a high-temperature Ru–Mo alloy. Energy dispersive x-ray diffraction measurements have been successfully carried out for fluid rubidium up to 1973 K and 16.2 MPa. The obtained S(Q) demonstrates the applicability of the molybdenum cell to x-ray diffraction measurements of fluid alkali metals at high temperatures and high pressures.
Actuation and control of a turbulent channel flow using Lorentz forces
Authors: Breuer Kenneth S. , Park Jinil , Henoch Charles
Published: February 2004

Results concerning the design and fabrication of electromagnetic actuators, and their application to affect the wall shear stress in a fully turbulent channel flow are discussed. The actuators utilize a Lorentz force to induce fluid motion due to the interaction between a magnetic field and a current density. The actuators are comprised of spanwise-aligned rows of permanent magnets interlaced with surface-mounted electrodes, segmented to allow the Lorentz force to be propagated in the spanwise direction. Problems commonly associated with electromagnetic flow control—electrolysis, bubble formation, and electrode corrosion are substantially reduced, and in most cases eliminated by the use of a conductive polymer coating. The actuators generate velocity profiles with a penetration depth into the flow of approximately 1 mm (set by the electrode/magnet pitch) and maximum velocities of approximately 4 cm/s. The actuation velocities are found to scale linearly with forcing voltage and frequency. The electrical to mechanical efficiency is found to be very low (≈10−4), primarily due to the limitations on the magnetic field strength and the low conductivity of the working fluid (saltwater). The actuators are used in a fully turbulent low Reynolds number channel flow and their effect on the turbulent skin friction is measured using a direct measurement of drag. Maximum drag reductions of approximately 10% are measured when the flow is forced using a spanwise oscillating Lorentz force. A scaling argument for the optimal amplitude of the current density is developed. The efficiency of this method for drag reduction, and its application at higher Reynolds numbers is also discussed.
Mechanism for small electron current fraction in a vacuum arc cathode spot on a refractory cathode
Authors: Beilis I. I.
Published: February 2004

A mechanism for refractory cathode spot operation in a vacuum arc is proposed, based on the presence of a finite electric field Ep at the cathode sheath–plasma interface. The proposed model determines the relationship between the electron current and the total spot current density j and includes a system of equations solved for cathode plasma containing a mixture of ion states. The calculation shows that Ep reaches a value, ∼106 V/cm, and j is 104–108 A/cm2, when the electron current fraction s increases from 0.5 to 0.9. It is discovered that for a refractory cathode, ions with high ionicity (from 2 to 4) can be generated in the spot region for a relatively small s, 0.7–0.9, in contrast to ionization in the plasma jet, as predicted previously for copper cathodes.
Lithography-free high aspect ratio submicron quartz columns by reactive ion etching
Authors: Zeze D. A. , Cox D. C. , Weiss B. L. , Silva S. R. P.
Published: February 2004

We describe lithography-free fabrication of sub-micron surface features on quartz substrates by the reactive ion etching (RIE) in a CF4/Ar atmosphere. These submicron glass columns are well defined, have a high aspect ratio, with the underlying substrate being very flat. The geometry of the fabricated surface columns is dependent on the RIE process parameters. The analysis of these glass columns shows that a differential etching process takes place. The optical characterization of these samples shows a significant absorption at visible wavelengths whereas the relative transmission is very high in the infrared range, suggesting that these samples could potentially be used for wavelength selection device applications.
Fabrication of high-density nanostructures with an atomic force microscope
Authors: Liu Jun-Fu , Von Ehr James R. , Baur Christof , Stallcup Richard , Randall John , Bray Ken
Published: February 2004

High-density alternating nanostructures of octadecanethiol and decanethiol have been fabricated on Au surfaces by nanografting with an atomic force microscope. Fabrication of nanostructures with a step size of less than 1 nm in the vertical direction has been demonstrated. Feature sizes at the full width at half maximum of 8.3 nm with a lattice periodicity of 13.7 nm are achieved. Nanostructures of changing sizes are fabricated by scaling down the gap between grafted nanopatterns. It is found that the measured height of the thiol nanostructures decreases with decreasing size. The effect of tip penetration on the height and on the shape of the fabricated nanostructures is discussed.
Circuit and technique for characterizing switching delay history effects in silicon-on-insulator logic gates
Authors: Ketchen Mark B. , Bhushan Manjul , Anderson Carl J.
Published: February 2004

The delay of a partially depleted silicon-on-insulator complementary metal oxide semiconductor (MOS) logic gate can vary by 10% or more due to history effects. We describe and demonstrate a circuit and measurement technique with which one can measure history effects dominated by either the output rising (pMOS) or output falling (nMOS) characteristics of a multiple-input silicon-on-insulator gate. To precondition the floating-body voltages, any combination of inputs and number of switching events, arbitrarily configured with respect to timing and sequence, may precede an event to be measured.
Technique for measuring the groove density of a diffraction grating with elimination of the eccentricity effect
Authors: Lim Jun , Rah Seungyu
Published: February 2004

For absolute measurement of groove density of diffraction gratings, we suggest a simple method that utilizes two parallel beams, a rotary beam splitter and single-beam long trace profiler. We use the fact that two parallel beams are focused on a point in the focal plane of a Fourier transform lens. Especially, with elimination of the eccentricity effect, the groove density of a diffraction grating was measured for higher precision than ever before. The eccentricity effect is a shift of the interaction points due to the off-centered rotating mount of grating, which is the essential error source in previous measurements. The method was applied to measure the groove density of a varied line spacing plane grating with a central groove density of 400 line/mm. The groove density error was measured to be 0.01 line/mm rms, with a period measurement error of 0.3 nm rms.
Surface photovoltage effects on the isomeric semiconductors of boron-carbide
Authors: Caruso A. N. , Balaz Snjezana , Xu Bo , Dowben P. A. , McMullen-Gunn A. S. , Brand J. I. , Losovyj Y. B. , McIlroy D. N.
Published: February 2004

During exposure to synchrotron radiation, closo 1,7-dicarbadodecaborane (metacarborane) and closo 1,2-dicarbadodecaborane (orthocarborane) decompose, and are accompanied by increasingly evident photoemission surface photovoltage effects. We show that metacarborane and orthocarborane form self-doped n-type and p-type boron-carbides, respectively. Surface photovoltage effects dominate the photoemission final state, not the changes in electronic structure due to decomposition.
Manipulation of electronic states in single quantum dots by micromachined air-bridge
Authors: Nakaoka Toshihiro , Kakitsuka Takaaki , Saito Toshio , Arakawa Yasuhiko
Published: February 2004

We demonstrate an approach to manipulate the quantum states of single self-assembled quantum dots via strain. We fabricate a micromachined air-bridge with microelectromechanical systems (MEMS), in which quantum dots are embedded. The air-bridge is deformed by electrostatic force, which produces additional strain on the dots to modify the confining potential. Our method with MEMS technique will allow functional manipulation of the electronic states through the direct modification of the confining potential.
Measurements of composition and electronic structure in an operating light-emitting diode using analytical electron microscopy
Authors: Bosman M. , Sitarz M. , Sikorski A. Z. , Keast V. J.
Published: February 2004

Scanning transmission electron microscopy (STEM) is a useful technique for the study of the morphology, composition, and electronic structure of quantum wells. However, most previous studies have been on epitaxially grown structures, before they had been used in devices. In this work we show that, with careful specimen preparation, advanced STEM techniques can be used to study a packaged commercially available light-emitting diode. The composition and morphology of both the quantum wells and the superlattices in this device have been determined and the electronic structure was measured with electron energy-loss spectroscopy.
Direct measurement of trapped and free charge distributions in semiconductors
Authors: Holé Stéphane , Lewiner Jacques
Published: February 2004

The nonuniform distribution of charges in semiconductors is of direct influence on their behavior. It is therefore of great interest to estimate these distributions in order to optimize semiconductor structures and designs. Until now only indirect methods have been used which require the application of a bias voltage. We show, that it should be possible to perform direct measurements of the distribution of trapped charges and of mobile carriers in semiconductors independently to the biasing conditions. Theoretical developments and experimental results are shown.
On the universality of nonclassical nonlinear phenomena and their classification
Authors: Hirsekorn Sigrun , Delsanto Pier Paolo
Published: February 2004

Recent discoveries of nonclassical nonlinear effects in materials have suggested the existence of a nonlinear mesoscopic elasticity (NME) universality class. In the present contribution, we go beyond NME and look for the underlying mathematical foundations that may justify conjectured universality. Using a completely general “response box” formalism, we classify the response according to its spectral contents and obtain the analyticity conditions. We prove that, under the assumption of no conditioning, from the result of a single experiment at a certain amplitude Ā the response of the system to any excitation of the same frequency and amplitude A<Ā can be derived.
Impedance of photonic crystals and photonic crystal waveguides
Authors: Biswas R. , Li Z. Y. , Ho K. M.
Published: February 2004

We develop and demonstrate the concept of impedance for a photonic crystal by generalizing the transverse wave impedance of conventional waveguides. The impedance involves a ratio of transverse fields and power flux. The calculated impedance for a two-dimensional photonic crystal is very well defined using the transfer matrix method. The predicted frequency-dependent reflectance from this impedance agrees very well with rigorous transfer matrix calculations for band modes and waveguiding modes in the band gap. This impedance concept will be very powerful in minimization of insertion loss into photonic crystal waveguides, designing waveguide splitters, and for modeling reflectance/transmittance from photonic crystals.
Fast-response and scattering-free polymer network liquid crystals for infrared light modulators
Authors: Fan Yun-Hsing , Lin Yi-Hsin , Ren Hongwen , Gauza Sebastian , Wu Shin-Tson
Published: February 2004

A fast-response and scattering-free homogeneously aligned polymer network liquid crystal (PNLC) light modulator is demonstrated at λ=1.55 μm wavelength. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. The strong polymer network anchoring assists LC to relax back quickly as the electric field is removed. As a result, the PNLC response time is ∼250× faster than that of the E44 LC mixture except that the threshold voltage is increased by ∼25×.
Effect of Mn concentration on the structural, optical, and magnetic properties of GaMnN
Authors: Thaler G. , Frazier R. , Gila B. , Stapleton J. , Davidson Mark , Abernathy C. R. , Pearton S. J. , Segre Carlos
Published: February 2004

The room temperature magnetization of GaMnN films grown by molecular beam epitaxy on (0001) sapphire substrates with Mn concentrations varying from 0 to 9 at. % was found to depend on Mn concentration, with a maximum magnetization found at ∼3 at. % Mn. High-resolution x-ray diffraction measurements show that the c-plane lattice constant initially decreases with increasing Mn concentration, then increases when the Mn content increases above ∼3 at. %. This increase is accompanied by a decrease in the full width at half maximum of the rocking curves. Extended x-ray absorption fine structure results indicate that the nonsubstitutional Mn is not present in the form of GaxMny clusters and thus is most likely present in the form of an interstitial. Optical absorption measurements show only a slight increase in the band gap for material with 3 at. % Mn, relative to undoped GaN.
Non-Debye dielectric dispersion of barium titanate stannate in the relaxor and diffuse phase-transition state
Authors: Mueller V. , Beige H. , Abicht H.-P.
Published: February 2004

Frequency dependence Tm(f ) of the permittivity maximum temperature observed in BaTi1−xSnx03, x=0.2 (BTS20), confirms that this composition is close above threshold xc for relaxor behavior in BTS. The low-frequency permittivity carries a ln(1/f )-frequency dependence in the vicinity of Tm, both for x=0.2 and x=0.125<xc. At temperatures T<Tm, the non-Debye contribution of both compositions shows a qualitatively different temperature dependence, indicating basic differences between the diffuse phase-transition state and the relaxor state of BTS.
1:2 Cation order in A(Li1/3(Nb,Ta)2/3)O3 microwave perovskites
Authors: Borisevich Albina , Davies Peter K.
Published: February 2004

In a family of perovskites with the general stoichiometry (A2/32+La1/3)(B1/31+B2/35+)O3, three 1:2 ordered perovskites were prepared with A=Sr, B1+=Li, B5+=Nb, Ta and with A=Ca, B1+=Li, B5+=Nb. These compounds can be sintered to high density at temperatures ⩽1350 °C, have dielectric constants in the range 25–30, microwave quality factors as high as 26 000, and negative temperature coefficients of resonant frequency. A 1:2 polymorph was not observed for (Ca2/3La1/3)(Li1/3Ta2/3)O3 which adopted a 1:1 ordered structure. The larger charge difference between the ions involved in the B-site ordering in these systems compared to other 1:2 ordered microwave perovskites such as Ba(Zn1/3Nb2/3)O3, is reflected by a higher stability of the order which is stable up to their decomposition/melting temperature.
Photon antibunching at high temperature from a single InGaAs/GaAs quantum dot
Authors: Mirin Richard P.
Published: February 2004

We report the observation of photon antibunching from a single, self-assembled InGaAs/GaAs quantum dot at temperatures up to 135 K. The second-order intensity correlation, g(2)(0), is measured to be less than 0.260 for temperatures up to 100 K. At 120 K, g(2)(0) increases to about 0.471, which is slightly less than the second-order intensity correlation expected from two independent single emitters. At 135 K, g(2)(0) is 0.667, which still indicates nonclassical light emission that is equivalent to having three independent single emitters.
Limit of validity of the drift-diffusion approximation for simulation of photodiode characteristics
Authors: Konno K. , Matsushima O. , Navarro D. , Miura-Mattausch M.
Published: February 2004

We have investigated the photoresponse of a Si p–n photodiode under different illumination and bias conditions. Under high illumination and low applied reverse bias, a clear discrepancy between experimental results and conventional two-dimensional device simulation results is observed. The discrepancy is found to be caused by the fact that the space-charge limitation effect under the drift-diffusion approximation used in conventional simulations does not describe the real situation. Thus, in the framework of the drift-diffusion approximation, modification of the mobility model is needed for the early stage of carrier transport under such operating conditions.
THz near-field imaging employing synchrotron radiation
Authors: Schade U. , Holldack K. , Kuske P. , Wüstefeld G. , Hübers H.-W.
Published: February 2004

Terahertz scanning near-field infrared microscopy below 1 THz is demonstrated at an electron storage ring using coherent synchrotron radiation. Spatial resolution below the diffraction limit down to about λ/40 at 2 cm−1 is derived from the transmittance spectra of a conical aperture probe. The potential of the technique is exemplified by imaging wet biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 μm at about 12 cm−1. The THz near-field images reveal distinct structural differences in the mesophytic and xerophytic leaves investigated.
Current quantization due to single-electron transfer in Si-wire charge-coupled devices
Authors: Fujiwara Akira , Zimmerman Neil M. , Ono Yukinori , Takahashi Yasuo
Published: February 2004

We observe a quantized current due to single-electron transfer in a small charge-coupled device, which consists of a narrow Si-wire channel with fine gates; the gate is used to form a tunable barrier potential. By modulating two barrier potentials under the fine gates with phase-shifted pulse voltages, quantized numbers of electrons are injected into and extracted from the charge island sandwiched by the two barriers. Current plateaus due to single-electron transfer are clearly observed at 20 K with frequencies up to 100 MHz and a current level of 16 pA.
Enhanced formation of luminescent nanocrystal Si embedded in Si/SiO2 superlattice by excimer laser irradiation
Authors: Cha Daigil , Shin Jung H. , Song In-Hyuk , Han Min-Koo
Published: February 2004

The effect of excimer laser annealing on the formation of luminescent nanocrystal Si (nc-Si) embedded in Si/SiO2 superlattice is investigated. An amorphous Si/SiO2 superlattice consisting of 20 periods of 2 nm thin Si layers and 5 nm thin SiO2 layers was deposited on Si using electron cyclotron resonance plasma-enhanced chemical vapor deposition. Excimer laser annealing alone did not result in any nc-Si luminescence even at an energy density sufficient to melt the Si layers. However, if the nc-Si is preformed by a thermal anneal, subsequent excimer laser annealing will result in a threefold increase of the nc-Si luminescence intensity. The temperature dependence of the nc-Si luminescence spectrum, lifetime, and intensity indicates that excimer laser annealing activates luminescent nc-Si by removing defects and amorphous regions in thermally crystallized Si layers without significant changes in the size or shape of nc-Si.
Confinement effects and surface-induced charge carriers in Bi quantum wires
Authors: Huber T. E. , Nikolaeva A. , Gitsu D. , Konopko L. , Foss C. A. , Graf M. J.
Published: February 2004

We present measurements of Shubnikov–de Haas oscillations in arrays of bismuth nanowires. For 80 nm wires, the hole concentration is less than 30% that of bulk Bi, a finding that is consistent with current models of quantum confinement effects. However, 30-nm-diam nanowires which are predicted to be semiconductors show a nearly isotropic short period of 0.025 T−1, consistent with a heavy carrier concentration five times that of bulk Bi. These results are discussed in terms of surface-induced charge carriers in a spherical Fermi surface pocket that are uniformly distributed in the 30 nm nanowire volume and that inhibit the semimetal-to-semiconductor transition.
Multimode and multifrequency gigahertz surface acoustic wave sensors
Authors: Seidel Werner , Hesjedal Thorsten
Published: February 2004

A simple surface acoustic wave sensor system is presented that combines the advantages of multifrequency/multimode operation and GHz frequencies in a single acoustic device structure. Analyzing multiple frequencies and modes is the basis for the multicomponent analysis of gases and liquids. The sensor system is based on floating electrode unidirectional transducers that allow efficient excitation of two modes and up to 48 harmonics (or 5 GHz). It can be fabricated without the need of costly nanofabrication techniques. Higher sensor frequencies are advantageous as the sensitivity increases with the frequency. We tested the basic operation of our sensor system by applying it to humidity sensing without a sensitive layer.
Ferromagnetism in Fe-doped SnO2 thin films
Authors: Coey J. M. D. , Douvalis A. P. , Fitzgerald C. B. , Venkatesan M.
Published: February 2004

Thin films grown by pulsed-laser deposition from targets of Sn0.95Fe0.05O2 are transparent ferromagnets with Curie temperature and spontaneous magnetization of 610 K and 2.2 A m2 kg−1, respectively. The Fe57 Mössbauer spectra show the iron is all high-spin Fe3+ but the films are magnetically inhomogeneous on an atomic scale, with only 23% of the iron ordering magnetically. The net ferromagnetic moment per ordered iron ion, 1.8 μB, is greater than for any simple iron oxide with superexchange interactions. Ferromagnetic coupling of ferric ions via an electron trapped in a bridging oxygen vacancy (F center) is proposed to explain the high Curie temperature.
Development of high-operating-temperature infrared detectors with gold-doped Hg0.70Cd0.30Te
Authors: Shih H. D. , Kinch M. A. , Aqariden F. , Liao P. K. , Dreiske P. D. , Ohlson M. J. , Orent T. W. , Robinson J. E. , Schaake H. F. , Teherani T. H. , Kalma A. H. , Roush F. M.
Published: February 2004

Excellent high-operating-temperature infrared photodiodes in the medium-wavelength infrared spectral band with cutoff wavelengths ∼5 μm at 77 K were fabricated on Hg1−xCdxTe samples (x∼0.30) prepared by liquid-phase epitaxy in a tellurium-melt reactor. The samples were doped with indium to ∼1×1014 cm−3 and gold to ∼5×1015 cm−3. Thick planar diodes (∼80 μm thick) and thin cylindrical diodes (∼10 μm thick) of the n-on-p type were fabricated, and they gave comparable, excellent detector dark values within a factor of two. At 130 K, dark currents as low as 5×10−7 A/cm2 were obtained.
Influence of a two-dimensional SiO2 nanorod structure on the extraction efficiency of ZnS:Mn thin-film electroluminescent devices
Authors: Do Young Rag , Kim Yoon Chang , Cho Sang-Hwan , Zang Dong Sik , Huh Young-Duk , Yun Sun Jin
Published: February 2004

To improve light extraction from thin-film electroluminescent (TFEL) devices, we have introduced a two-dimensional (2-D) SiO2 nanorod pattern into the glass substrate of a TFEL. This periodic modulation converts the guided waves in the high refractive index ZnS:Mn phosphor layers into leaked external waves. We used the finite-difference time-domain method to optimize the structural parameters of the 2-D nanorod pattern. Using a nanorod pattern with a depth of 300 nm, a lattice constant of 600 nm, and a radius of 180 nm, the extraction efficiency of the TFEL is theoretically predicted to increase by a factor of more than 4.8. We compare the calculated efficiency and that of the actual TFEL structure, with a view to decreasing diameter of nanorod.
Low-temperature chemical vapor deposition and scaling limit of ultrathin Ru films
Authors: Wang Q. , Ekerdt J. G. , Gay D. , Sun Y.-M. , White J. M.
Published: February 2004

Thermal chemical vapor deposition at temperatures as low as 423 K, using Ru3(CO)12 with no accompanying reactive gas, forms pure, uniform, and smooth Ru films on Ta and low-resistivity films on SiO2. A 2.5-nm-thick Ru film fully covers the underlying Ta and the Ru film is thermally stable up to 573 K. Unlike Ta, Ru films exhibit excellent wetting by Cu even when the Ru surface is contaminated with small amounts of oxygen.
Influence of mounting on continuous-wave photoluminescence from midinfrared PbSrSe/PbSe multiple quantum wells
Authors: Zhao F. , Lv X. , Majumdar A. , Shi Z.
Published: February 2004

Strong continuous-wave photoluminescence from midinfrared lead–salt PbSrSe/PbSe multiple quantum wells grown on (111) BaF2 substrates by molecular-beam epitaxy was observed at temperatures from 100 to 300 K. The maximum output power was 2.9 and 0.6 mW at room temperature with episide down and episide up mounting, respectively. At 225 K, the temperature difference between the active region and the heat sink was about 32 °C for episide down mounting and 75 °C for episide up mounting. The peak energies shifted toward high energy with increasing temperature. The temperature-tuning coefficient obtained from episide down and episide up mounting was 0.45 and 0.50 meV/K.
Microstructural evolution of a-plane GaN grown on a-plane SiC by metalorganic chemical vapor deposition
Authors: Craven M. D. , Wu F. , Chakraborty A. , Imer B. , Mishra U. K. , DenBaars S. P. , Speck J. S.
Published: February 2004

This letter describes the relationship between the morphological evolution of heteroepitaxial a-plane GaN films and the formation of the extended defect structure. The initial a-plane GaN growth on a-plane SiC substrates (via a high temperature AlN buffer layer) follows a Volmer–Weber growth mode. Consequently, the coalescence of three-dimensional (3D) islands generates threading dislocations which dominate the nonpolar GaN film’s microstructure (3×1010 cm−2). Exposed nitrogen-face surfaces, identified using x-ray diffraction measurements and convergent beam electron diffraction analysis, are present throughout the 3D growth and are the likely source of basal plane faulting (7×105 cm−1) within the film. Atomic force microscopy and scanning electron microscopy were used to image the morphological transition, which was correlated to changes in the a-GaN crystal tilt mosaic measured by x-ray rocking curves.