Oscillatory behaviour in melting of a GaSb/InSb/GaSb system

The effect of coexistence of Marangoni and natural convections was studied numerically in melting of a GaSb/InSb/GaSb sandwich sample. Fluid flow and concentration fields are oscillatory when the solutal natural convection coexists with the thermal Marangoni convection. The coexistence of solutal and thermal natural convections, without Marangoni convection, however, does not lead to fluid flow oscillations in spite of the existence of two flow cells in opposite directions. The conclusion is that not the presence of two opposite flow cells but the flow structure itself, due to the presence of a free surface, is responsible for such an oscillatory behaviour.     

Weak shock waves in isotropic solids at finite temperatures up to the melting point

Propagation speeds and Rankine–Hugoniot relations for weak shock waves in isotropic solids are derived analytically in order to elucidate mechanical and thermal properties of the waves. In the analysis, we adopt a new continuum model for the solids, which takes into account explicitly microscopic thermal vibration of the constituent atoms. As the model is valid in a wide temperature range up to the melting point, we can discuss the relations at high temperatures even near the melting point. Typical numerical results are also shown and discussed as illustrations.      

Dirac electrons in solids

Electronic band structures in solids sometimes have features similar to Dirac electrons in vacuum. Well-known examples are bismuth and graphite; 4×4 original Dirac matrix in three dimension (3d) in the former with strong spin–orbit interaction, while 2×2 massless Dirac in two dimension (2d) with weak inter-layer coupling described essentially by Weyl equation in the latter. Recently one layer of graphite, graphene, is realized and studied both extensively and intensively. Other recent examples include a molecular solid, α-(BEDT-TTF)₂I₃$\mathrm{\alpha }\mathrm{-}(\mathrm{BEDT}\mathrm{-}\mathrm{TTF}{)}_2{\mathrm{I}}_3$, which has a layered structure with electronic states described by tilted-Weyl equation, and Fe-pnictides. There is also a theoretical proposal that one of inverse perovskites, Ca₃PbO, can be a candidate in 3d with strong spin–orbit interaction similar to bismuth. The particular feature of Dirac electrons in solids is a small, or even vanishing, band gap and then thermodynamic or transport properties are affected by inter-band coupling of electronic states. Typical ones are responses to external magnetic field. Actually, it has long been known that orbital susceptibility of these Dirac electrons has very particular features resulting from inter-band effects of magnetic field. It is of interest to see such inter-band effects on Hall effects to be compared with orbital susceptibility, which will be introduced in this paper, together with possible consequences of mutual interaction between valleys triggered by tilting in molecular solids.     

Biosorption of precious metal ions by chicken feather

Chicken feather (C-feather) is an intricate network of stable and water-insoluble protein fibers with high surface area and is an abundant bioresource. C-feather protein was found to accumulate various precious metal ions (gold and platinum metals) selectively from their dilute aqueous solutions in high yield and in short contact time, depending on pH and characteristics of the individual precious metal ions. Under certain condition, the sequestering level of precious ions, Au(III), Pt(II), and Pd(II) approaches about 17, 13, and 7% of dry wt of C-feather, respectively. Gold(III) potassium cyanade was also accumulated up to 5.5% at pH 2.0. The presence of 100-fold (mol) of coexisting cations, such as Na⁺, Fe(III), Cu(II), and Ni(II), did not show a discernible effect on the precious metal uptake rate and capacity of C-feather. Experiment suggested C-feather is promising for use in the removal/recovery of precious metals as well as water pollution control. A qualitative discussion is given about the excellent adsorption behavior of C-feather.

     

Interplay between a homogeneous magnetic field and an antiferromagnetic field in one-dimensional superconductors

Mean-field theory applied to superconductors with one-dimensional band in the presence of both the homogeneous magnetic field H₀ and the antiferromagnetic field H_Q, the second-order phase transition temperature is investigated for the arbitrary angle θ between H₀ and H_Q. It is found that the remarkable superconducting region in the case of θ = 0 is retained only for small θ and that the spatially dependent order parameter coexists with the spatially uniform order parameter except for θ = τ/2.     

Lanthanide organometallic sandwich nanowires: formation mechanism

A molecular beam of europium-cyclooctatetraene sandwich nanowires Eu(n)()(COT)(m)() was produced by a laser vaporization synthesis method. The formation mechanism of the nanowires was quantitatively revealed by photoelectron and photoionization spectroscopies of the Eu-COT species, together with supporting theoretical calculations. From these results, it is confirmed that growth processes extending the length of Eu-COT nanowires involve a series of elementary reactions in which efficient charge transfer occurs at the terminal reaction sites. In every elementary step, the reaction proceeds between one reactant having low ionization energy and the other reactant having high electron affinity, probably via a "harpoon" mechanism.     

Application of LC-NMR for characterization of rat urinary metabolites of zonampanel monohydrate (YM872)

Zonampanel monohydrate (YM872) has a potent and selective antagonistic effect on the glutamate receptor subtype, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor. Metabolic fingerprinting in rat urine after a single intravenous administration of (14)C-labeled YM872 ((14)C-YM872) revealed the presence of two metabolites, R1 and R2. The two metabolites were semi-purified by preparative HPLC from rat urine after a single intravenous administration of non-labeled YM872, and their structures were elucidated by various instrumental analyses involving LC-NMR. The results showed that R1 and R2 have a hydroxyamino group and an amino group at the C-7 position of the quinoxalinedione skeleton, respectively. Therefore, the proposed metabolic pathway of YM872 in rats involves the reduction of the nitro group to a hydroxyamino group and then subsequent reduction to an amino group.     

Geometric and electronic structures of multiple-decker one-end open sandwich clusters: Eu(n)(C8H8)n- (n = 1-4)

We have measured the photoelectron spectra of the multiple-decker 1:1 sandwich clusters of Eu(n)(COT)n- (n = 1-4; COT = 1,3,5,7-cyclooctatetraene), synthesized in the gas phase, and studied theoretically the bonding scheme, charge distribution, valence orbital energies, and photodetachment energies. We calculated the ground electronic state X- and the first excited electronic state A-, both of which have strong ionic bonding and a characteristic charge distribution. Moreover, we found that the valence orbital energies of Eu (6s) and COT (L delta) depend strongly on cluster size and their positions in the clusters. With the calculated vertical detachment energies for these valence orbitals, we assigned the peaks in the experimental photoelectron spectra and analyzed the origin of their interesting behavior by employing simple point charge models. From these analyses, it became clear that the characteristic behavior of the spectra is due to the strong ionic bonding and the charge distribution. In addition, using the point charge models, we estimated the vertical detachment energies of the one-dimensional polymer [Eu(COT)]infinity-.     

Precise frequency-difference measurement between the 1.66-mum transitions of methane

We determined 66 frequency differences (FD's) between rovibrational lines of methane at the 1.66-mum region. Following the technique developed by Nakagawa et al.[Opt.Lett.20, 410 (1995)], we measured the FD's as the optical beat frequency between two external-cavity diode lasers locked at 1-MHz-wide saturated absorption dips of the methane lines. Even though the methane lines often overlap in Doppler-limited resolution, the spectrometer that we use resolves them and determines their FD's with better than 40-kHz precision. This fact demonstrates that the methane lines are promising candidates for frequency reference and that this technique has great potential for high-resolution molecular spectroscopy.