bluuebunny/crossref_metadata_2025 huggingface dataset:
Upper mantle structure beneath the eastern Pacific Ocean ridges
Authors: Gu Yu J. , Webb Spahr C. , Lerner‐Lam Arthur , Gaherty James B.
Published: June 2005

We analyze vertical component body and surface waves for 10 Mw > 5 earthquakes, recorded by ocean bottom seismometers at regional and teleseismic distances. Through waveform modeling, we place new constraints on along‐axis variation in temperature and partial melt beneath the eastern Pacific ridges. The resulting best fit models show over 9% variation in average lithosphere shear velocities between different ridge segments. We demonstrate that lid velocity correlates with the square root of plate age, consistent with a conductive cooling process, but we find a more rapid dependence on age close to the rise axis. We map the average plate age into a mean lithospheric temperature for each of our profiles using a half‐space cooling model, and the temperature derivatives (dVs/dT) determined from least squares linear fits are −1.1 and −0.26 m s−1 deg−1, respectively, for temperatures above and below ∼1000°C. The former estimate is more negative than values determined by earlier reports (−0.4 to −0.7 m s−1 deg−1), using global or regional data from a much wider range of seafloor age but with less resolution at young ages. The high ∣dVs/dT∣ value may suggest the presence of limited partial melt at shallow mantle depths, even after accounting for the strong effect of anelasticity and anharmonicity resulting from temperature and grain size variations. Our data also show a strong north‐south difference in mantle structure: the surface waves that traverse the southern East Pacific Rise (EPR) experience shear velocities as low as ∼3.75 km s−1, more than 0.2 km s−1 slower than the average mantle structure at comparable depths beneath the northern EPR and the Galapagos spreading center. This difference cannot be explained by the simple conductive cooling process or spreading rate variations between ridge segments. The slow seismic speeds in the low‐velocity zone (LVZ) appear to require partial melt. The velocity difference might be solely caused by higher temperatures under the southern EPR, but it may also suggest more melt in the LVZ beneath the southern ridge axis due to potential differences in melt production or extraction compared to the north. In addition, differences in width or symmetry of the partial melt zones can affect the observed path‐averaged velocities beneath these two segments. Finally, we determine more accurate depths for ocean transform earthquakes by analyzing the amplitude ratios between body and surface waves. The depths of these transform earthquakes are consistent with brittle deformation within the oceanic crust.
Annual and semiannual variations of the Earth's gravitational field from satellite laser ranging and CHAMP
Authors: Moore P. , Zhang Q. , Alothman A.
Published: June 2005

Temporal variability in the Earth's gravity field has been estimated from 4 years of satellite laser ranging (SLR) to five geodetic satellites, Lageos 1 and 2, Stella, Starlette, and Ajisai supplemented by over 2 years of CHAMP precise orbital positioning, attitude quaternions, and accelerometry. The study considers variability at the annual and semiannual periodicities in the full field of degrees 2–6. A singular value decomposition has been employed in an attempt to recover variability from stand‐alone CHAMP data. Temporal gravity field variability from SLR and from SLR and CHAMP has been computed and compared against geophysical models for surface mass redistribution. For a 4 × 4 field best agreement of the annual variation results in an RMS geoid difference of 0.76 mm with correlation coefficients above 0.85. On extending to a 6 × 6 field agreement decreases to about 1.5 mm RMS in geoid height with correlations of 0.6 at the annual cycle. For the extended field the ocean mass redistribution from Ocean Circulation and Climate Advanced Modeling project and TOPEX is seen to be deficient with near comparable correlations being obtained by neglecting the ocean contribution. The semiannual signal is weaker and less well determined. For the 4 × 4 field, correlations are no better than 0.6 with RMS of 1 mm between the SLR and geophysical models. Results show that CHAMP has a positive effect on the annual variation for a 4 × 4 field but marginal for the extended 6 × 6 field. CHAMP has a negative impact at the semiannual frequency.
Sea‐ice draft from submarine‐based sonar: Establishing a consistent record from analog and digitally recorded data
Authors: Wensnahan Mark , Rothrock D. Andrew
Published: June 2005

Measurements of arctic sea‐ice draft have been taken by Navy submarines for nearly five decades. The data are in two inherently different forms, analog paper charts and digitally recorded data. “Raw” analog drafts digitized from paper charts are biased toward thicker ice by over 30 cm compared with the digital drafts. This is due to the coarser temporal resolution of the paper charts compared the digital data. We examine coincident analog and digital data to determine how they can be made equivalent in mean draft and draft distribution (the histogram of draft vs. fractional frequency of observation). Image processing techniques are used to thin vertical features in the scanned chart images; this produces a “final” analog mean draft that is essentially unbiased (2 ± 6 cm) relative to the digital mean and final draft distributions that are in good agreement.
Observations of multiple X‐line structure in the Earth's magnetotail current sheet: A Cluster case study
Authors: Eastwood J. P. , Sibeck D. G. , Slavin J. A. , Goldstein M. L. , Lavraud B. , Sitnov M. , Imber S. , Balogh A. , Lucek E. A. , Dandouras I.
Published: June 2005

Observations of the Earth's magnetotail made by the four Cluster spacecraft on October 2 2003 are presented. Multi‐spacecraft analysis is used to show that the variations in field and flow observed in the vicinity of the magnetotail current sheet are most consistent with a series of two active reconnection sites bounding an Earthward moving flux rope. We demonstrate that a single spacecraft analysis of the same data leads to the incorrect conclusion that a single X‐line is moving tailward. The implications of this in relation to the interpretation of single spacecraft observations are outlined. These results show that reconnection can occur simultaneously at different points in the near‐Earth magnetotail current sheet, providing (further) important experimental validation of multiple X – line reconnection theories on the mesoscale (tens of ion inertial length) level.
Sea ice drift and its relationship to altimetry‐derived ocean currents in the Labrador Sea
Authors: Häkkinen S. , Cavalieri D. J.
Published: June 2005

Low frequency sea ice drift variability and its oceanic and atmospheric forcing are investigated for the Labrador Sea over the period 1979–2002. Our objective is to separate the ocean forced component of ice drift in order to corroborate the changes in the subpolar gyre circulation found by Häkkinen and Rhines (2004). The atmospheric and oceanic forcing components can be approximately separated by comparing the time series resulting from an Empirical Orthogonal Function (EOF) analysis of sea ice motion with local sea level pressure gradients and altimetry‐derived oceanic velocities. The first ice motion EOF is found to be associated with wind driven ice drift. The second mode is associated with oceanic forcing, because its time series is similar in its fluctuations to the oceanic velocities derived from altimetry. These two data sets confirm a major weakening of the subpolar ocean circulation between the early 1990s and the latter 1990s.
Helium‐3 plume over the East Pacific Rise at 25°S
Authors: Takahata Naoto , Agarwal Meetu , Nishizawa Manabu , Shirai Kotaro , Inoue Yumiko , Sano Yuji
Published: June 2005

We have measured helium isotopic ratios of sixty‐eight water samples collected in the southeastern Pacific at 25°S. The maximum excess 3He of 47.5% is observed just above the East Pacific Rise, which is comparable to that of 50.5% at 15°S in literature. A negative correlation between helium isotopes and neon to helium ratios of seawater samples suggests that the source of excess helium‐3 in the mid‐depth water is considered to be a MORB‐type mantle. Contour of excess 3He shows symmetrical pattern, that is, plume of 30% excess can be traced up to 1000 km on both east and west of the East Pacific Rise. This pattern is consistent with a northward flow along the rise at 25°S estimated by a physical model. Our observation also supports a flow pattern of deep ocean currents, which has been suggested by contour of excess 3He obtained from previous studies.
The Agent Visualization System: A Graphical and Textual Representation for Multi-Agent Systems
Authors: Mostafa Hala , Bahgat Reem
Published: June 2005

As scientists from various domains increasingly resort to agent-based simulation for a more thorough understanding of real-world phenomena, the need for a simulation environment that facilitates rapid development of multi-agent systems is growing. Such a platform should provide means of visualizing the simulated scenario. In this paper we present the agent visualization system, the first system of its kind to specifically focus on catering to the visualization needs of agent-based simulation. The proposed system is a generic add-on that equips a simulation environment with a rich set of visualization facilities offering a variety of textual and graphical browsers that allow the modeler to detect trends and relationships in the simulation scenario. Some techniques from the field of information visualization were adapted and added to the system, while others were devised especially to be used in it. Regardless of their origin, all visualization techniques were thoroughly revised to make them generic enough to fit in our generic system. Agent visualization is more challenging than traditional information visualization in more than one respect. One of them is that the data to be visualized is not static; the simulation system is constantly producing data with every time step. Moreover, the sheer amount of data, together with its diversity, call for special adaptations to ensure that the system remains responsive and generic. To illustrate the various features of the proposed agent visualization system, we present a visualization of MicroTerra; a simulation scenario involving a group of beings trying to maximize their food intake.
Extending Taxonomic Visualisation to Incorporate Synonymy and Structural Markers
Authors: Graham Martin , Kennedy Jessie
Published: June 2005

The visualisation of taxonomic hierarchies has evolved from indented lists of names to techniques that can display thousands of nodes and onto hundreds of thousands of nodes over multiple taxonomies. However, challenges remain within multiple hierarchy visualisation, and for taxonomic hierarchy visualisation in particular. Firstly, at present, there is no support for handling specific taxonomic information such as synonymy, with current visualisations matching solely on names. Synonymy is extremely important as it reflects expert opinion on the compatibility of data held in separate taxonomies, and is needed to produce an accurate picture of taxonomic overlap. Also, current techniques for exploring large hierarchies find it difficult to convey internal re-organisations between hierarchies, with most systems showing only addition, removal or wide-ranging fragmentation of information between taxonomies. Finding the source of changes that have occurred within an existing structure is currently only achievable through exhaustive drill-down exploration. This paper describes work that tackles these problems, incorporating synonymy information into a model for multiple hierarchy visualisation of large taxonomies, and also detailing techniques that aid navigation for discovering structural re-organisations between hierarchies and for revealing information about nodes that lie below the effective display resolution of the hierarchy layout. Two examples on real taxonomic data sets are annotated to show the effectiveness of these techniques in operation.
Analytic gradients for the spin-conserving and spin-flipping equation-of-motion coupled-cluster models with single and double substitutions
Authors: Levchenko Sergey V. , Wang Tao , Krylov Anna I.
Published: June 2005

Analytic gradient expressions for the spin-conserving and spin-flipping equation-of-motion coupled-cluster models with single and double substitutions are derived using a Lagrangian approach for the restricted and unrestricted Hartree–Fock references, both for the case of all orbitals being active in correlated calculations and for the frozen core and/or virtual orbitals. Details of the implementation within the Q-CHEM electronic structure package are discussed. The capabilities of the new code are demonstrated by application to cyclobutadiene.
Theoretical study of the effects of solvent environment on photophysical properties and electronic structure of paracyclophane chromophores
Authors: Masunov Artëm , Tretiak Sergei , Hong Janice W. , Liu Bin , Bazan Guillermo C.
Published: June 2005

We use first-principles quantum-chemical approaches to study absorption and emission properties of recently synthesized distyrylbenzene (DSB) derivative chromophores and their dimers (two DSB molecules linked through a [2.2]paracyclophane moiety). Several solvent models are applied to model experimentally observed shifts and radiative lifetimes in Stokes nonpolar organic solvents (toluene) and water. The molecular environment is simulated using the implicit solvation models, as well as explicit water molecules and counterions. Calculations show that neither implicit nor explicit solvent models are sufficient to reproduce experimental observations. The contact pair between the chromophore and counterion, on the other hand, is able to reproduce the experimental data when a partial screening effect of the solvent is taken into account. Based on our simulations we suggest two mechanisms for the excited-state lifetime increase in aqueous solutions. These findings may have a number of implications for organic light-emitting devices, electronic functionalities of soluble polymers and molecular fluorescent labels, and their possible applications as biosensors and charge/energy conduits in nanoassemblies.
Spin evolution of radical pair with radical containing two groups of equivalent magnetic nuclei
Authors: Bagryansky V. A. , Ivanov K. L. , Borovkov V. I. , Lukzen N. N. , Molin Yu. N.
Published: June 2005

Analytical solution is obtained for time-resolved magnetic field effects (TR-MFE) on recombination fluorescence of radical-ion pair (RIP) containing radical ion with two groups of magnetically equivalent nuclei. The present theoretical approach is applied to three experimental systems: RIPs containing radical cations of 2,3-dimethylbutane, 2,2,6,6-tetramethylpiperidine, or diisopropylamine and radical anion of p-terphenyl-d14 in nonpolar alkane solutions. Good agreement between theory and experiment is found for all the three systems, hyperfine coupling constants of radical cations are obtained by fitting the experimental TR-MFE traces. The potential of the TR-MFE technique for studying radical ions with nonequivalent nuclei is discussed in detail. The wide applicability of the theoretical model and the experimental technique make them useful for studying short-lived radical species that are often beyond the reach of the conventional electron paramagnetic resonance spectroscopy.
Comment on “Oxidation of alloys containing aluminum and diffusion in Al2O3” [J. Appl. Phys. 95, 3217 (2004)]
Authors: Åkermark Torbjörn
Published: June 2005

The introduction of AlO as the diffusing species can be seen as an attempt to bridge the gap between the two scientific communities: those working on the oxidation of metals and those working on the oxidation of silicon. The attempt is, however, not successful and would have been more successful if the Wagner theory [O. Wagner, Z. Phys. Chem. Abt. B 21, 25 (1993)] would have been used to evaluate the mechanisms. There is also a lack of agreement with the two-stage oxidation experiment, oxidation first in O16 and then in O18. The experimental O18 profile in the oxides formed cannot be explained by the diffusion of AlO, so it is unlikely that AlO is the diffusing species during oxidation.
Accurate vibrational spectra and magnetic properties of organic free radicals: The case of H2CN
Authors: Barone Vincenzo , Carbonniere Philippe , Pouchan Claude
Published: June 2005

We present the structural, magnetic, and vibrational properties of H2CN computed using a second-order perturbative approach in which equilibrium values and harmonic frequencies evaluated at the coupled-cluster level are combined with anharmonic and vibrational averaging contributions obtained by hybrid Hartree–Fock/Kohn–Sham methods. Our computations lead to remarkably accurate results and suggest some revision of the experimental vibrational assignments.
On the convergence of isolated neutral oxygen vacancy and divacancy properties in metal oxides using supercell models
Authors: Carrasco Javier , Lopez Nuria , Illas Francesc
Published: June 2005

The properties of isolated neutral oxygen vacancies and divacancies of metal oxides of increasing complexity (MgO, CaO, α-Al2O3, and ZnO) have been studied by means of density-functional theory within a supercell periodic approach. Vacancy formation energies, vacancy–vacancy interactions, and geometry rearrangements around these point defects have been investigated in detail. The characterization of the electronic structure of these point defects has been established by analysis of the density of states and of the topology of the electron density and of electron localization function. It is found that the chemical character of the oxide determines the properties of the oxygen vacancies. For the covalent ZnO oxide, a more complex scheme arises in which the relaxation around the oxygen vacancy is much larger leading to the formation of Zn4-like almost metallic particles in the crystal. The relationship of these structures with the crystal shear planes is discussed. The present study shows that supercells containing ∼200–300 atoms provide converged values for the geometric and electronic structure of oxygen vacancies of these metal oxides in the point defect low concentration limit.
Arrested phase separation in a short-ranged attractive colloidal system: A numerical study
Authors: Foffi G. , De Michele C. , Sciortino F. , Tartaglia P.
Published: June 2005

We numerically investigate the competition between phase separation and dynamical arrest in a colloidal system interacting via a short-ranged attractive potential. Equilibrium fluid configurations are quenched at two different temperatures below the critical temperature and followed during their time evolution. At the lowest studied T, the phase-separation process is interrupted by the formation of an attractive glass in the dense phase. At the higher T, no arrest is observed and the phase-separation process proceeds endlessly in the simulated time window. The final structure of the glass retains memory of the interrupted phase-separation process in the form of a frozen spinodal decomposition peak, whose location and amplitude is controlled by the average packing fraction. We also discuss the time evolution of the nonergodicity parameter, providing evidence of a progressively decreasing localization length on increasing the packing fraction. Finally, we confirm that the reported results are independent of the microscopic dynamics.
Theoretical study of single-bubble sonochemistry
Authors: Yasui Kyuichi , Tuziuti Toru , Sivakumar Manickam , Iida Yasuo
Published: June 2005

Numerical simulations of bubble oscillations in liquid water irradiated by an ultrasonic wave are performed under the experimental condition for single-bubble sonochemistry reported by Didenko and Suslick [Nature (London) 418, 394 (2002)]. The calculated number of OH radicals dissolving into the surrounding liquid from the interior of the bubble agrees sufficiently with the experimental data. OH radicals created inside a bubble at the end of the bubble collapse gradually dissolve into the surrounding liquid during the contraction phase of an ultrasonic wave although about 30% of the total amount of OH radicals that dissolve into the liquid in one acoustic cycle dissolve in 0.1μs at around the end of the collapse. The calculated results have indicated that the oxidant produced by a bubble is not only OH radical but also O atom and H2O2. It is suggested that an appreciable amount of O atom is produced by bubbles inside a standing-wave-type sonochemical reactor filled with water in which oxygen is dissolved as in the case of air.
Accurate ab initio predictions of ionization energies of hydrocarbon radicals: CH2, CH3, C2H, C2H3, C2H5, C3H3, and C3H5
Authors: Lau K.-C. , Ng C. Y.
Published: June 2005

The ionization energies for methylene (CH2), methyl (CH3), ethynyl (C2H), vinyl (C2H3), ethyl (C2H5), propargyl (C3H3), and allyl (C3H5) radicals have been calculated by the wave-function-based ab initio CCSD(T)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled-cluster level with single and double excitations plus a quasiperturbative triple excitation [CCSD(T)]. When it is appropriate, the zero-point vibrational energy correction, the core–valence electronic correction, the scalar relativistic effect correction, the diagonal Born–Oppenheimer correction, and the high-order correlation correction have also been made in these calculations. The comparison between the computed ionization energy (IE) values and the highly precise experimental IE values determined in previous pulsed field ionization-photoelectron (PFI-PE) studies indicates that the CCSD(T)/CBS method is capable of providing accurate IE predictions for these hydrocarbon radicals achieving error limits well within ±10meV. The benchmarking of the CCSD(T)/CBS IE predictions by the PFI-PE experimental results also lends strong support for the conclusion that the CCSD(T)/CBS approach with high-level energy corrections can serve as a valuable alternative for reliable IE determination of radicals, particularly for those radicals with very unfavorable Franck–Condon factors for photoionization transitions near their ionization thresholds.
Overcoming computational uncertainties to reveal chemical sensitivity in single molecule conduction calculations
Authors: Solomon Gemma C. , Reimers Jeffrey R. , Hush Noel S.
Published: June 2005

In the calculation of conduction through single molecule’s approximations about the geometry and electronic structure of the system are usually made in order to simplify the problem. Previously [G. C. Solomon, J. R. Reimers, and N. S. Hush, J. Chem. Phys. 121, 6615 (2004)], we have shown that, in calculations employing cluster models for the electrodes, proper treatment of the open-shell nature of the clusters is the most important computational feature required to make the results sensitive to variations in the structural and chemical features of the system. Here, we expand this and establish a general hierarchy of requirements involving treatment of geometrical approximations. These approximations are categorized into two classes: those associated with finite-dimensional methods for representing the semi-infinite electrodes, and those associated with the chemisorption topology. We show that ca. 100 unique atoms are required in order to properly characterize each electrode: using fewer atoms leads to nonsystematic variations in conductivity that can overwhelm the subtler changes. The choice of binding site is shown to be the next most important feature, while some effects that are difficult to control experimentally concerning the orientations at each binding site are actually shown to be insignificant. Verification of this result provides a general test for the precision of computational procedures for molecular conductivity. Predictions concerning the dependence of conduction on substituent and other effects on the central molecule are found to be meaningful only when they exceed the uncertainties of the effects associated with binding-site variation.
Covariant q-differential operators and unitary highest weight representations for Uqsun,n
Authors: Shklyarov Dmitry , Zhang Genkai
Published: June 2005

We investigate a one-parameter family of quantum Harish–Chandra modules of Uqsl2n. This family is an analog of the holomorphic discrete series of representations of the group SU(n,n) for the quantum group Uqsun,n. We introduce a q-analog of “the wave” operator (a determinant-type differential operator) and prove certain covariance property of its powers. This result is applied to the study of some quotients of the above-mentioned quantum Harish–Chandra modules. We also prove an analog of a known result by J. Faraut and A. Koranyi on the expansion of reproducing kernels which determines the analytic continuation of the holomorphic discrete series.
An unusual π* shape resonance in the near-threshold photoionization of S1 para-difluorobenzene
Authors: Bellm Susan M. , Davies Julia A. , Whiteside Paul T. , Guo Jingwei , Powis Ivan , Reid Katharine L.
Published: June 2005

Previously reported dramatic changes in photoelectron angular distributions (PADs) as a function of photoelectron kinetic energy following the ionization of S1p-difluorobenzene are shown to be explained by a shape resonance in the b2g symmetry continuum. The characteristics of this resonance are clearly demonstrated by a theoretical multiple-scattering treatment of the photoionization dynamics. New experimental data are presented which demonstrate an apparent insensitivity of the PADs to both vibrational motion and prepared molecular alignment, however, the calculations suggest that strong alignment effects may nevertheless be recognized in the detail of the comparison with experimental data. The apparent, but unexpected, indifference to vibrational excitation is rationalized by considering the nature of the resonance. The correlation of this shape resonance in the continuum with a virtual π* antibonding orbital is considered. Because this orbital is characteristic of the benzene ring, the existence of similar resonances in related substituted benzenes is discussed.
Thermoelectric properties of Yb-filled Ge-compensated CoSb3 skutterudite materials
Authors: Lamberton G. A. , Tedstrom R. H. , Tritt T. M. , Nolas G. S.
Published: June 2005

Over the last several years, a class of materials known as skutterudites has shown substantial promise for potential thermoelectric applications. Specifically, Yb-filled skutterudites have shown high values for the thermoelectric figure of merit. For this work, a series of Yb-filled Ge-compensated skutterudites was synthesized; their thermoelectric properties measured, and the results analyzed. The results from the electrical and thermal transport measurements are presented here and the results are compared with that of previous data.
The effects of photorefraction on electro-optic field sensors
Authors: Garzarella A. , Qadri S. B. , Wieting Terence J. , Wu Dong Ho
Published: June 2005

We have measured the electro-optic response of LiNbO3 and SrxBa1−xNb2O6 crystals to be used for electric-field sensors. Our results indicate that optically induced refractive index variations (photorefractivity) in the crystals affect the temporal stability and sensitivity of the sensors. Spatial distributions of the refractive indices produced from the photorefractivity create incoherence in the polarization of the probing laser passing through the crystal (optical probe). In LiNbO3 crystals, this spatial incoherence was negligible and sensor responsivities close to the theoretical maximum were attained. However, in SrxBa1−xNb2O6 crystals, strong spatial variations of the principal refractive indices resulted in an extremely incoherent polarization of the optical probe and reduced the electro-optic responsivity dramatically. The photorefractive-induced sensitivity loss is modeled using a distribution function (rather than a constant value) to describe the phase of the optical probe. These results emphasize the importance of an optically stable material, with little or no photorefractivity, when designing an electro-optic field sensor.
Fundamental microwave-power-limiting mechanism of epitaxial high-temperature superconducting thin-film devices
Authors: Lahl P. , Wördenweber R.
Published: June 2005

In this paper we present an experimental investigation of the nonlinear microwave properties of coplanar resonators patterned from epitaxial Y1Ba2Cu3O7−δ thin films in zero-field-cooled, field-cooled, and field-sweep experiments in the search for the fundamental limiting mechanism. The impact of magnetization, vortices, intrinsic limitation, grain boundaries, and thermal effects is evaluated. We find that the fundamental limiting mechanism in the absence of thermal and grain-boundary effects is given by the dc critical current density of the superconducting material which masks the intrinsic limitation expected at larger rf current densities. Demagnetizing effects, penetration barriers, vortex penetration, pinning, and relaxation of inhomogeneous vortex distributions are experimentally observed and in agreement with theoretical expectations. The experimental results are modeled in terms of a simple model for the power-handling capability which is based on a superposition of all current densities in the resonator and gives a consistent explanation of all experiments in magnetic fields and in zero field.
Periodic and homoclinic solutions of the modified 2+1 chiral model
Authors: Dai Bo , Terng Chuu-Lian
Published: June 2005

We use algebraic Bäcklund transformations (BTs) to construct explicit solutions of the modified 2+1 chiral model from T2×R to SU(n), where T2 is a 2-torus. Algebraic BTs are parametrized by z∊C (poles) and holomorphic maps π from T2 to Gr(k,Cn). We apply Bäcklund transformations with carefully chosen poles and π’s to construct infinitely many solutions of the 2+1 chiral model that are (i) doubly periodic in space variables and periodic in time, i.e., triply periodic, (ii) homoclinic in the sense that the solution u has the same stationary limit u0 as t→±∞ and is tangent to a stable linear mode of u0 as t→∞ and is tangent to an unstable mode of u0 as t→−∞.
Ab initio studies of two-photon absorption of some stilbenoid chromophores
Authors: Baev Alexander , Prasad Paras N. , Samoc Marek
Published: June 2005

Two-photon absorption of a series of donor-acceptor trans-stilbene derivatives is studied by means of density functional theory applied to second-order response function. Several important issues in modeling are highlighted which must be addressed for a reliable reproduction of the experimental results. It is evident that the correct order of magnitude of calculated two-photon absorption cross sections can only be obtained if proper account is taken of vibrational broadening of the absorption profiles. A comparison of the theoretical results with the experimental ones indicates that the computed two-photon absorption cross sections are in rough agreement with our previous report, although the observed systematic increase of the cross sections with the electron acceptor strength is not well reproduced. It is suggested that this disagreement may be due not only to the deficiencies of the computations but also to a variety of factors contributing to the experimental value of the effective two-photon absorption cross section, which are not taken into account in the ab initio calculations.
Eckart axis conditions and the minimization of the root-mean-square deviation: Two closely related problems
Authors: Kudin Konstantin N. , Dymarsky Anatoly Y.
Published: June 2005

We highlight the fact that the rotation matrix minimizing the root-mean-square deviation between two molecular conformations [W. Kabsch, Acta Cryst. A32, 922 (1976)] also satisfies the Eckart axis conditions [C. Eckart, Phys. Rev. 47, 552 (1935)].
Multiple-species model for electrokinetic instability
Authors: Oddy Michael H. , Santiago Juan G.
Published: June 2005

In this paper we present a multiple-species electrokinetic instability (MSEKI) model. We consider a high aspect ratio flow geometry, a base state where the conductivity gradient is orthogonal to the applied electric field (i.e., a spanwise gradient configuration), and a four-species chemistry model. A linear stability analysis (LSA) of the depth-averaged governing equations is shown to have unstable eigenmodes for conductivity ratios as close to unity as 1.01. We present the experimental image data and full nonlinear simulations of the governing equations for a conductivity ratio of 1.05. Images of the disturbance dye field from the nonlinear simulations show good qualitative agreement with the experiment. Both the trend and absolute value of the temporal evolution of the critical wave number are captured by the MSEKI model. Growth rates extracted from the experimental data also compare favorably with those predicted by LSA. Species electromigration is shown to have a significant influence on the development of the conductivity field and instability dynamics in multi-ion configurations. We anticipate this model to be of practical interest to researchers developing electrokinetically driven, chip-based bioanalytical devices.
Response to “Comment on ‘Computation of the pseudorotation matrix to satisfy the Eckart axis conditions’ ” [J. Chem. Phys. 122, 227101 (2005)]
Authors: Dymarsky Anatoly Y. , Kudin Konstantin N.
Published: June 2005

In this response, we rebut the statements made by Dierksen in his comment on our paper [J. Chem. Phys. 122, 124103 (2005)]. Specifically, we discuss how our solution to the Eckart axis conditions differs from the one described by Pickett and Strauss [J. Am. Chem. Soc. 92, 7281 (1970).]
Marangoni convection and heat transfer in thin liquid films on heated walls with topography: Experiments and numerical study
Authors: Alexeev Alexander , Gambaryan-Roisman Tatiana , Stephan Peter
Published: June 2005

Thermocapillary-induced motion in thin liquid films on a heated horizontal wall with parallel grooves on its upper surface is studied experimentally and numerically. The results of velocity and temperature measurements are reported. A numerical model for a liquid film on a structured wall is developed. The full incompressible Navier–Stokes equations and the energy equation are integrated by a finite difference algorithm, whereas the mobile gas-liquid interface is tracked by the volume-of-fluid method. The numerical model is verified by comparison with the experimental data showing a good agreement. The model is used to study flow patterns and film rupture caused by the thermocapillary forces. Heat transfer in the liquid is also investigated. In particular, it is found that the thermocapillary convection enhances heat transfer in liquid, though the effect depends on the shape of the wall surface.
Pulse-echo measurements of unsteady propellant deflagration
Authors: Di Salvo Roberto , Frederick Robert A. , Moser Marlow D.
Published: June 2005

This article discusses a laboratory test method for the measurement of nonsteady deflagration rates and combustion-stability properties of solid propellants. The method combines ultrasonic pulse-echo measurement, fluidic pressure modulation, and digital signal processing techniques to compute the real and imaginary components of pressure-coupled response functions of solid propellants. A description of the apparatus identifies the major components and their functions. A section on the experimental procedure illustrates the steps necessary to conduct a test, and a section on the data reduction technique describes the sequence of steps employed to compute the nonsteady burn rate and the pressure-coupled response. A detailed implementation of the technique as it applies to two representative tests follows, in which graphs and tables illustrate the intermediate data reduction steps. Details of the evaluation of the uncertainties associated with the technique and the data reduction algorithms are also presented.
Transportable real-time single-particle ion trap mass spectrometer
Authors: Harris William A. , Reilly Peter T. A. , Whitten William B. , Ramsey J. Michael
Published: June 2005

A transportable ion trap mass spectrometer for real-time detection and characterization of individual airborne particles was constructed by minimal modification of a commercial ion trap mass spectrometer. A blank flange was replaced with a flange containing an aerodynamic lens based inlet, light scattering detection optics and ablation/ionization laser optics. Four holes were drilled into the ring electrode. Timing electronics boards running off of in-place power systems were added and integrated with the existing software. The modified mass spectrometer and laser system was packaged in a rugged wheeled frame for easy transport. Particles entered the instrument through a 100μm orifice and were passed through an aerodynamic lens system that produced a well-collimated particle beam over a wide range of sizes. The particle beam passed through a skimmer into the main chamber where individual particles were optically detected and sized with two focused 532nm diode lasers on their way to the ion trap. When the particles reached the center of the trap, they were ablated and ionized with a focused 266nm laser. The nascent ions were then mass analyzed using standard ion trap techniques, including tandem mass spectrometry. Each detected particle was characterized with a mass spectrum and an aerodynamically determined particle size. Careful design minimized the weight and size of the instrument to 104kg and 69×71×76cm, with power consumption less than 1.5kW. Tandem mass spectrometry was demonstrated for identification of ions through collision-induced dissociation (CID) up to mass spectrometry (MS).4 Unit mass resolution was observed in both the parent and CID mass spectra.
Hyperspectral surface-enhanced Raman imaging of labeled silver nanoparticles in single cells
Authors: Wabuyele Musundi B. , Yan Fei , Griffin Guy D. , Vo-Dinh Tuan
Published: June 2005

We describe the development of an acousto-optic tunable filter (AOTF)-based hyperspectral surface-enhanced Raman imaging (HSERI) system equipped with an intensified charged coupled device and an avalanche photodiode. The AOTF device is a miniature rapid-scanning solid-state device that has no moving parts and can be rapidly tuned (microseconds) either sequentially or randomly, over a wide spectral range between 600 and 900nm [corresponding to a large relative wave number range (∼0–4500cm−1)], with respect to a 632.8nm excitation and can also acquire images at a fairly narrow band of ∼7cm−1. In this article we describe a confocal surface-enhanced Raman imaging (SERI) system developed in our laboratory that combines hyperspectral imaging capabilities with surface-enhanced Raman scattering (SERS) to identify cellular components with high spatial and temporal resolution. The HSERI system’s application to cellular imaging is demonstrated using SERS-labeled nanoparticles in cellular systems.
Development of a technique for high-temperature chemical kinetics: Shock tube/pulsed laser-induced fluorescence imaging method
Authors: Seta Takamasa , Nakajima Masakazu , Miyoshi Akira
Published: June 2005

A technique for the measurements of high-temperature gas-phase chemical reactions, like those involved in combustion, has been developed and an application to OH-radical measurement has been evaluated. The developed method, shock tube/pulsed laser-induced fluorescence imaging technique, allows us to measure a quantitative concentration-time profile of radical species by a single laser pulse. The detection limit for OH radicals was as low as 1×1012moleculescm−3 at total pressures (mainly argon) of 1.5–2.4bar and temperatures of 1300–1750K, when exciting the 1-0 band of the OH A-X transition with a∼1mJ laser pulse (full width at half maximum 0.15cm−1). The applicability to time-resolved chemical kinetic measurements has been investigated by measuring the rate constants for the reaction of OH radicals with benzene (C6H6). Because of the high detection sensitivity, the initial OH-radical concentration could be kept low enough, ∼1×1013moleculescm−1, to prevent the influence of side reactions. The measured rate constants agreed well with the previous reports and their extrapolation to higher temperatures. These results demonstrate the applicability of the technique to kinetic measurements for reactions of combustion interests.
Capillary optics for micro x-ray fluorescence analysis
Authors: Bjeoumikhov A. , Langhoff N. , Bjeoumikhova S. , Wedell R.
Published: June 2005

Practically achieved parameters of capillary optics are presented. A micro x-ray fluorescence (XRF) arrangement was realized by using a microfocus x-ray tube and a capillary optic. Several examples for application of micro XRF are given. It was shown that polycapillary lenses free of the “halo effect” well suited for micro XRF of heavy elements can be manufactured. Limits of opportunities for micro XRF applications and further development for micro XRF by using capillary optics are analyzed.
Dual-probe scanning tunneling microscope for study of nanoscale metal-semiconductor interfaces
Authors: Yi W. , Kaya I. I. , Altfeder I. B. , Appelbaum I. , Chen D. M. , Narayanamurti V.
Published: June 2005

Using a dual-probe scanning tunneling microscope, we have performed three-terminal ballistic electron emission spectroscopy on Au∕GaAs(100) by contacting the patterned metallic thin film with one tip and injecting ballistic electrons with another tip. The collector current spectra agree with a Monte-Carlo simulation based on modified planar tunneling theory. Our results suggest that it is possible to study nanoscale metal-semiconductor interfaces without the requirement of an externally-contacted continuous metal thin film.
Alternating current loss in a cylinder with power-law current-voltage characteristic
Authors: Chen D.-X. , Gu C.
Published: June 2005

The transport ac loss Q in a superconducting cylinder of radius a with a power-law current-voltage characteristic E=Ec∣J∕Jc∣n as a function of current amplitude Im is numerically calculated for a set of given values of a,Jc, and frequency f at n=5, 10, 20, and 30. After deriving a scaling law and defining a critical frequency fc, the results can be converted and interpolated to those for any values of a, Jc, f, and 5⩽n⩽30. The “power-law” Q(Im) at f=fc is a better alternative of the critical-state Q(Im), used not only for describing the features of Q(Im,f) of high-temperature superconductors but also for planning Q measurements and their interpretation.
Modeling arsenic deactivation through arsenic-vacancy clusters using an atomistic kinetic Monte Carlo approach
Authors: Pinacho R. , Jaraiz M. , Castrillo P. , Martin-Bragado I. , Rubio J. E. , Barbolla J.
Published: June 2005

A comprehensive atomistic model for arsenic in silicon which includes charge effects and is consistent with first-principles calculations for arsenic-vacancy cluster energies has been developed. Emphasis has been put in reproducing the electrical deactivation and the annealed profiles in preamorphized silicon. The simulations performed with an atomistic kinetic Monte Carlo simulator suggest a predominant role of the mobile interstitial arsenic in deactivation experiments and provide a good understanding of the arsenic behavior in preamorphized silicon during annealing.
Dislocation-free strained silicon-on-silicon by in-place bonding
Authors: Cohen G. M. , Mooney P. M. , Paruchuri V. K. , Hovel H. J.
Published: June 2005

In-place bonding is a technique where silicon-on-insulator (SOI) slabs are bonded by hydrophobic attraction to the underlying silicon substrate when the buried oxide is undercut in dilute HF. The bonding between the exposed surfaces of the SOI slab and the substrate propagates simultaneously with the buried oxide etching. As a result, the slabs maintain their registration and are referred to as “bonded in-place”. We report the fabrication of dislocation-free strained silicon slabs from pseudomorphic trilayer Si/SiGe/SOI by in-place bonding. Removal of the buried oxide allows the compressively strained SiGe film to relax elastically and induce tensile strain in the top and bottom silicon films. The slabs remain bonded to the substrate by van der Waals forces when the wafer is dried. Subsequent annealing forms a covalent bond such that when the upper Si and the SiGe layer are removed, the bonded silicon slab remains strained.
Epitaxial La2∕3Sr1∕3MnO3 thin films with metallic behavior above the Curie temperature
Authors: Bertacco R. , Riva M. , Cantoni M. , Signorini L. , Ciccacci F.
Published: June 2005

Despite its half-metallic character, La2∕3Sr1∕3MnO3 is currently not considered a good candidate for real spin electronic devices due to the dramatic deterioration of its spin polarization at room temperature. Using pulsed-laser deposition, we have grown thin films of La2∕3Sr1∕3MnO3, which display good room-temperature magnetic properties accompanied by a sizable increase of the temperature at which the metal-insulator transition takes place with respect to the Curie temperature. The persistence of the metallic character well above the Curie temperature indicates minor modifications of the electronic structure near the Fermi level, which is responsible for the half-metallicity. These films are good candidates for increasing the operating temperature of devices based on La2∕3Sr1∕3MnO3.
A transparent metal: Nb-doped anatase TiO2
Authors: Furubayashi Yutaka , Hitosugi Taro , Yamamoto Yukio , Inaba Kazuhisa , Kinoda Go , Hirose Yasushi , Shimada Toshihiro , Hasegawa Tetsuya
Published: June 2005

This Letter focuses on the discovery of a transparent conducting oxide (TCO), anatase Ti1−xNbxO2 films with x=0.002–0.2. The resistivity of films with x⩾0.03 is 2–3×10−4Ωcm at room temperature. The carrier density of Ti1−xNbxO2 can be controlled in a range of 1×1019to2×1021cm−3. The internal transmittance for films with x⩽0.03 (40nm thickness) is about 97% in the visible light region. The transport and optical parameters are comparable to those of typical TCOs, such as In2−xSnxO3 and ZnO.
Memory characteristics of silicon nitride with silicon nanocrystals as a charge trapping layer of nonvolatile memory devices
Authors: Choi Sangmoo , Yang Hyundeok , Chang Man , Baek Sungkweon , Hwang Hyunsang , Jeon Sanghun , Kim Juhyung , Kim Chungwoo
Published: June 2005

Silicon nitride with silicon nanocrystals formed by low-energy silicon plasma immersion ion implantation has been investigated as a charge trapping layer of a polycrystalline silicon-oxide-nitride-oxide-silicon-type nonvolatile memory device. Compared with the control sample without silicon nanocrystals, silicon nitride with silicon nanocrystals provides excellent memory characteristics, such as larger width of capacitance-voltage hysteresis, higher program∕erase speed, and lower charge loss rate at elevated temperature. These improved memory characteristics are derived by incorporation of silicon nanocrystals into the charge trapping layer as additional accessible charge traps with a deeper effective trap energy level.
Capacitance pressure sensor based on GaN high-electron-mobility transistor-on-Si membrane
Authors: Kang B. S. , Kim J. , Jang S. , Ren F. , Johnson J. W. , Therrien R. J. , Rajagopal P. , Roberts J. C. , Piner E. L. , Linthicum K. J. , Chu S. N. G. , Baik K. , Gila B. P. , Abernathy C. R. , Pearton S. J.
Published: June 2005

The changes in the capacitance of the channel of an AlGaN∕GaN high-electron-mobility transistor (HEMT) membrane structure fabricated on a Si substrate were measured during the application of both tensile and compressive strain through changes in the ambient pressure. The capacitance of the channel displays a change of 7.19±0.45×10−3pF∕μm as a function of the radius of the membrane at a fixed pressure of +9.5bar and exhibits a linear characteristic response between −0.5 and +1bar with a sensitivity of 0.86pF∕bar for a 600μm radius membrane. The hysteresis was 0.4% in the linear range. These AlGaN∕GaN HEMT membrane-based sensors appear to be promising for both room-temperature and elevated-temperature pressure-sensing applications.