A flexible carbon nanotube field emitter fabricated on a polymer substrate by a laser separation method

The fabrication of a sparsely networked carbon nanotube (CNT) thin film on a polycarbonate substrate as the conductor electrode and the emitting cathode by a newly proposed laser separation method is reported. Based on this approach, numerous surface protruding tube tips can be structured straightforwardly, which results in favorable field-emission characteristics. A flexible field emitter with a low turn-on voltage of 1.0 V/μm can be obtained. This method also demonstrates the abilities for fabricating a film with precision patterns and varying CNT concentrations as well as the flexibility of direct film formation on a curved surface. Moreover, all fabrication steps are executed in the ambient environment and at room temperature.     

Intramolecular Diels–Alder reaction in enyne–allenes: a computational investigation and comparison with the Myers–Saito and Schmittel reactions

The reaction mechanisms as well as substituted effect and solvent effect of the enyne–allenes are investigated by Density Functional Theory (DFT) method and compared with the Myers–Saito and Schmittel reactions. The Myers–Saito reaction of non‐substituted enyne–allenes is kinetically and thermodynamically favored as compared to the Schmittel reaction; while the concerted [4 + 2] cycloaddition is only 1.32 kcal/mol higher than the C₂? C₇ cyclization and more exothermic (Δ_RE = ?69.38 kcal/mol). For R₁ = CH₃ and t‐Bu, the increasing barrier of the C₂? C₇ cyclization is higher than that for the C₂? C₆ cyclization because of the steric effect, so the increased barrier of the [4 + 2] cycloaddition is affected by such substituted electron‐releasing group. Moreover, the strong steric effect of R₁ = t‐Bu would shift the C₂? C₇ cyclization to the [4 + 2] cycloaddition. On the other hand, for R₁ = Ph, NH₂, O^?, NO₂, and CN substituents, the barrier of the C₂? C₆ cyclization would be more diminished than the C₂? C₇ cyclization due to strong mesomeric effect; the reaction path of C₂? C₇ cyclization would also shift to the [4 + 2] cycloaddition. The solvation does not lead to significant changes in the potential‐energy surface of the reaction except for the more polar surrounding solvent such as dimethyl sulfoxide (DMSO), or water. Copyright © 2009 John Wiley & Sons, Ltd.     

Painlevé Integrability of Nonlinear Schrödinger Equations with bothSpace- and Time-Dependent Coefficients

We investigate the Painlevé integrability of nonautonomous nonlinearSchrödinger (NLS) equations with both space- and time-dependent dispersion, nonlinearity, and external potentials. The Painlevé analysis is carried out without using the Kruskal's simplification, which results in more generalized form of inhomogeneous equations. The obtained equations are shown to be reducible to the standard NLS equation by using a point transformation. We also construct the corresponding Lax pair and carry out its Kundu-type reduction to the standard Lax pair. Special cases of equations from choosing limited form of coefficients coincide with the equations from the previous Painlevé analyses and/or become unknown new equations.     

Bound states and resonance states of the plasma-embedded tdμ and ddμ molecular ions

We have investigated the bound states and resonance states of plasma-embedded tdμ and ddμ molecular ions using accurate correlated basis functions. The plasma effect has been taken care of by considering the Debye shielding approach of plasma modeling which admits a variety of plasma conditions. The density of resonance states are calculated using the stabilization method. The ground and excited states energies, and the S-wave resonance energies of tdμ and ddμ molecular ions immersed in plasmas are reported for various shielding parameters, along with the 1S and 2S threshold energies of the tμ and dμ atoms.     

Interfaces in perovskite heterostructures

Recent advances in film synthesis have made it possible to investigate the properties of well-controlled interfaces in perovskite metal-oxides. A review of published experimental data and computational results indicate that so far most interfaces that have been analyzed in ferroelectric materials—while necessary to impose large lattice strain on the polar material—contribute little to the ferroelectricity and may instead be detrimental to the desired properties. In contrast, a very different situation arises at interfaces that show changes in the electronic configuration as a consequence of a compositional discontinuity. Data is shown for LaMnO₃/SrTiO₃ superlattices as an example of electronic effects that produce enhanced properties, further illustrating the richness of interfacial properties that can be obtained at interfaces (as shown in numerous published results for different but related interfaces).     

Complex-scaling treatment for high-lying doubly excited resonances for screened Coulomb helium atom

This work presents an investigation on the doubly excited ¹S ^e autoionizing states of screened helium atom lying below the n = 4 threshold of the He⁺ ion. The potential generated in this system is represented by a Yukawa type potential. We have employed complex-coordinate rotation method, as it is a powerful scheme to study high lying resonances. Hylleraas type wave function is used to consider the correlation effect between all the charged particles. Our resonance parameters for the resonances lying below the He⁺ (n = 2) threshold agree well with those of the existing calculations by using the stabilization method. Resonances associated with higher thresholds are new calculations. All the present results are well converged with basis length N = 444.     

Energy of grain boundaries between cusp misorientations

The disclination model of high angle grain boundaries proposed before is used to understand the energy-angle relations between cusp misorientations. It is found that the model predicts the correct relationship within experimental error with only one adjustable parameter which resembles the Burgers vector of dislocations at low angles. Experimental data for [100] symmetric tilt boundaries in Cu and Al and for [110] symmetric tilt boundaries in Al are used for illustration.     

Submanifolds of complex space forms admitting an almost contact metric compound structure

Summary Real hypersurfaces of an almost Hermitian manifold naturally admit an almost contact metric structure and the (f, g, u, v, w, , , )-structure is defined on submanifolds of codimension 3 of an almost Hermitian manifold. We study the so-called semi-invariant submanifolds of a complex space form with almost contact metric compound structure which is a general notion of (f, g, u, v, w, , , )-structure.Dedicated to professor Eulyong Pak on his 60th birthdayThis research was partially supported by Korean Science and Engineering Foundation Grant.     

Approximate ground state in a model with spontaneous symmetry breakdown

The spontaneous symmetry breakdown is treated by means of a variational approach. Use is made of coherent states of Glauber and of pairing states of BCS-type as the translationally invariant vacuum states for the discussion of the real scalar field ⁴ withm ₀ ² 0. The first type of trial states reproduces the usual approach to spontaneous symmetry breakdown (-) in the tree approximation (which is possible only form ₀ ² <0), while the second type of trial states offers the possibility of spontaneous symmetry breakdown even form ₀ ² =0.     

Low-energy electron diffraction and auger electron spectroscopy study of the oxidation of Ti {0001} at room temperature

The reaction of a clean Ti (0001) surface with oxygen gas at low pressure and room temperature has been studied with low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). At low exposures (about 1 Langmuir) ap(2×2) superstructure is observed which gradually converts to 1×1 at high exposures (about 100 Langmuirs). The LEED spectra confirm that the final 1×1 structure is different from that of clean Ti (0001), while the AES spectra indicate that the final oxide is probably TiO, not TiO₂. The plausibility of this indication is discussed.