Experimental investigation of the closest parallel pulses in holographic femtosecond laser processing

In holographic femtosecond laser processing, diffractive parallel pulses are distorted by phase discontinuities and mutual interference between the neighborhoods in the reconstructed image of a Fourier computer-generated hologram when the interval is smaller than the beam diameter. We investigated holographic fabrication on a glass surface using parallel pulses with different intervals. We found the closest parallel pulses with sufficient separation to avoid mutual interference in holographic femtosecond laser processing. The minimum interval was 2.8 times larger than the diffracted beam diameter. The experimental results were also supported by a computer simulation. Our findings will be very useful in the design of holographic laser processing systems.     

Theoretical study of inverted sandwich type complexes of 4d transition metal elements: interesting similarities to and differences from 3d transition metal complexes

Inverted sandwich type complexes (ISTCs) of 4d metals, (μ-η(6):η(6)-C(6)H(6))[M(DDP)](2) (DDPH = 2-{(2,6-diisopropylphenyl)amino}-4-{(2,6-diisopropylphenyl)imino}pent-2-ene; M = Y, Zr, Nb, Mo, and Tc), were investigated with density functional theory (DFT) and MRMP2 methods, where a model ligand AIP (AIPH = (Z)-1-amino-3-imino-prop-1-ene) was mainly employed. When going to Nb (group V) from Y (group III) in the periodic table, the spin multiplicity of the ground state increases in the order singlet, triplet, and quintet for M = Y, Zr, and Nb, respectively, like 3d ISTCs reported recently. This is interpreted with orbital diagram and number of d electrons. However, the spin multiplicity decreases to either singlet or triplet in ISTC of Mo (group VI) and to triplet in ISTC of Tc (group VII), where MRMP2 method is employed because the DFT method is not useful here. These spin multiplicities are much lower than the septet of ISTC of Cr and the nonet of that of Mn. When going from 3d to 4d, the position providing the maximum spin multiplicity shifts to group V from group VII. These differences arise from the size of the 4d orbital. Because of the larger size of the 4d orbital, the energy splitting between two d(δ) orbitals of M(AIP) and that between the d(δ) and d(π) orbitals are larger in the 4d complex than in the 3d complex. Thus, when occupation on the d(δ) orbital starts, the low spin state becomes ground state, which occurs at group VI. Hence, the ISTC of Nb (group V) exhibits the maximum spin multiplicity.     

Kobayashi hyperbolic imbeddings into toric varieties

Our main goal of this article is to give a characterization of an algebraic divisor on an algebraic torus whose complement is Kobayashi hyperbolically imbedded into a toric projective variety. As an application of our main theorem, we prove the following: the complement of the union of n + 1 hyperplanes in the n-dimensional projective space ${\mathbb{P}^{n}(\mathbb{C})}$ in general position and a general hypersurface of degree n in ${\mathbb{P}^n(\mathbb{C})}$ is Kobayashi hyperbolically imbedded into ${\mathbb{P}^n(\mathbb{C})}$ .     

Partial Oxidation of Methane into Syngas with Oxygen Permeating Ceramic Membrane Reactors

Partial oxidation of methane (CH₄ +1/2O₂ CO + 2H₂) is considered as an alternative reforming reaction to steam reforming for production of syngas. This reaction is a slightly exothermic reaction and produces syngas of H₂/CO = 2, which is suitable for the synthesis of hydrocarbon or methanol. In this paper, the catalytic partial oxidation of CH₄ with a membrane reactor using oxygen permeating ceramic, in particular, LaGaO₃-based oxide, is reported. Supported Ni or Rh catalysts are active and selective for this reaction. On the other hand, a mixed ionic and electronic conducting (MIEC) ceramic membrane is useful for obtaining pure oxygen from air when the gradient in oxygen partial pressure is obtained. As for a MIEC membrane, mixed electronic–oxide ionic conductors of Fe- or Co-based perovskite oxides are widely investigated. However, the improvement in stability in a reducing atmosphere is critically required for the MIEC membrane for the application to the membrane reactor for CH₄ partial oxidation. Perovskite oxides of LaGaO₃ doped with Sr for a La site and a Fe, Co, or Ni for a Ga site, respectively, are promising as the oxygen-separating membrane for CH₄ partial oxidation because of high stability in a reducing atmosphere as well as high permeability of oxygen. The partial oxidation of CH₄ with solid oxide fuel cells (SOFCs) is also described. Simultaneous generation of electrical power and syngas is demonstrated by the fabricated fuel cell type reactor using a LaGaO₃-based oxide electrolyte.     

Organic light-emitting transistors with a thin metal layer covering a diffraction grating

We fabricated organic light-emitting transistors (OLETs) characterized by an Ag layer deposited on a one-dimensional (1D) or two-dimensional (2D) diffraction grating that acts as a combined gate insulator with SiO₂. The Ag layer was entirely covered with an organic crystal. Upon photoexcitation that crystal showed narrow linewidth emissions (NLEs) parallel to the substrate plane. The narrowed lines were either redshifted or blueshifted with rotation of the crystal around a normal to its surface with respect to the grating wave vector. Strong emissions (～10⁴–10⁶ cd m^?2) accompanied by current-injected NLEs were observed from the 1D and 2D grating OLETs.     

Two-dimensional laser Doppler velocimeter using polarized beams and 90° phase shift for discrimination of velocity direction

A laser Doppler velocimeter (LDV) for two-dimensional velocity measurement using a simple optical configuration without any optical modulator is proposed. The structure using polarized beams and the 90° phase shift of the reference beam is used to discriminate the direction of velocity. The analytical relation among beat frequencies and velocity components is derived and the characteristics of the proposed LDV are simulated. The simulation results indicate that the direction of velocity can be discriminated by the proposed LDV as well as the magnitudes of the components of the velocity.     

A Bäcklund transformation between two integrable discrete hungry systems

The discrete hungry Toda (dhToda) equation and the discrete hungry Lotka-Volterra (dhLV) system are known as integrable discrete hungry systems. In this Letter, through finding the LR transformations associated with the dhToda equation and the dhLV system, we present a Bäcklund transformation between these integrable systems.