Improvement of an Automated Sample Injection System for Pillar Array Columns to Increase Analytical Reproducibility

In our previous study, we developed an automatic sample injection system for pillar array columns for quantitative analysis. An autosampler was used to maintain a constant sample injection volume. However, the sample was diluted during injection using the autosampler, thus deteriorating the analytical reproducibility. In this study, we have substituted the autosampler with a syringe pump to overcome the abovementioned problem and improve the system. Sample dilution was avoided by filling the entire capillary with the sample at a constant rate. This improved system also increased the analytical reproducibility. In the previous system, the relative standard deviation (RSD) exceeded 17% of the peak height for coumarin dyes. In contrast, the improved system decreased the RSD to the range 1.2–1.8%. The analytical reproducibility was evaluated by using five types of amino acids. The RSD of each peak height was within 3.0%, confirming good reproducibility. These results indicate that the sample injection method developed in this study can be applied to biological sample analyses as a simple quantitative analysis method for pillar array columns.     

Charge density-dependent coil–globule transition of alkali metal polycarboxylates in aqueous organic solvent mixtures

The effects of polymer charge density on the counterion-specific and solvent-specific coil–globule transition of polycarboxylates were investigated for alkali metal salts of poly(styrene-alt-maleic acid) (PSaltMA) and poly(acrylic acid) (PAA) in aqueous organic solvent mixtures. The order of the transition region, namely, the counterion specificity for the transition in, e.g., aqueous dimethyl sulfoxide (DMSO), was the same for both polyelectrolytes, Na⁺?>?K⁺?>?Cs⁺?>?Li⁺, while the discrepancy of the transition region between Na⁺ and Li⁺ systems was appreciably narrower for PSaltMA (approximately 20 vol%) than that of PAA (approximately 29 vol%). Such diminished counterion specificity for the former was ascribed to the nonuniform charge array. Namely, PSaltMA has two kinds of nearest charge arrays, one is the shorter spacing between the maleic acid carboxyl groups and the other is the longer one via one styrene group. Thus, the former may be favorable for binding of the smaller counterion (i.e., Li⁺) and the latter for the larger one (Cs⁺). Such a “size-fitting effect” for the counterion binding was in fact further confirmed with variously neutralized PAAs. For example, the counterion specificity in aqueous DMSO of PAA40 that was neutralized to 40 % was Cs⁺?>?K⁺?>?Na⁺?>?Li⁺, showing that the largest counterion becomes most favorable in inducing the transition with increasing average charge spacing. In fact, the nuclear magnetic resonance line width measurement for ¹³³Cs suggested that the counterion binding strength of the large counterion for PAA increases with decreasing charge density from 100 to 40 % neutralization.     

Incommensurate spin fluctuations in hole-overdoped superconductor KFe2As2

A neutron scattering study of heavily hole-overdoped superconducting KFe2As2 revealed a well-defined low-energy incommensurate spin fluctuation at [π(1 ± 2 δ),0] with δ = 0.16. The incommensurate structure differs from the previously observed commensurate peaks in electron-doped AFe2As2 (A = Ba, Ca, or Sr) at low energies. The direction of the peak splitting is perpendicular to that observed in Fe(Te,Se) or in Ba(Fe,Co)2As2 at high energies. A band structure calculation suggests interband scattering between bands around the Γ and X points as an origin of this incommensurate peak. The perpendicular direction of the peak splitting can be understood within the framework of multiorbital band structure. The results suggest that spin fluctuation is more robust in hole-doped than in electron-doped samples, which can be responsible for the appearance of superconductivity in the heavily hole-doped samples.     

Classification of torus manifolds with codimension one extended actions

The purpose of this paper is to classify torus manifolds (M ²ⁿ , T ⁿ ) with codimension one extended G-actions (M ²ⁿ , G) up to essential isomorphism, where G is a compact, connected Lie group whose maximal torus is T ⁿ . For technical reasons, we do not assume torus manifolds are orientable. We prove that there are seven types of such manifolds. As a corollary, if a nonsingular toric variety or a quasitoric manifold has a codimension one extended action then such manifold is a complex projective bundle over a product of complex projective spaces.     

Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor

For the iron-based high T_c superconductor LaFeAsO_1?xF_x, we construct a minimal model, where all of the five Fe d bands turn out to be involved. We then investigate the origin of superconductivity with a five-band random-phase approximation by solving the Eliashberg equation. We conclude that the spin fluctuation modes arising from the nesting between the disconnected Fermi pockets realise, basically, an extended s-wave pairing, where the gap changes sign across the nesting vector.     

Superdrawing of polytetrafluoroethylene nascent powder by solid‐state coextrusion

A film of nascent powder of polytetrafluoroethylene (PTFE), compacted below the ambient melting temperature (T_m, 335 °C), was drawn by two‐stage draw techniques consisting of a first‐stage solid‐state coextrusion followed by a second‐stage solid‐state coextrusion or tensile draw. Although the ductility of extrudates was lost for the second‐stage tensile draw at temperatures above 150 °C due to the rapid decrease in strength, as previously reported, the ductility of extrudates increased with temperature even above 150 °C when the second‐stage draw was made by solid‐state coextrusion, reflecting the different deformation flow fields in a free space for the former and in an extrusion die for the latter. Thus, a powder film initially coextruded to a low extrusion draw ratio (EDR) of 6–20 at 325 °C was further drawn by coextrusion to EDRs up to ～?400 at 325–340 °C, near the T_m. Extremely high chain orientation (f_c = 0.998 ± 0.001), crystallinity (96.5 ± 0.5)%, and tensile modulus (115 ± 5 GPa at 24 °C, corresponding to 73% of the X‐ray crystal modulus) were achieved at high EDRs. Despite such a morphological perfection and a high modulus, the tensile strength of a superdrawn tape, 0.48 ± 0.03 GPa, was significantly low when compared with those (1.4–2.3 GPa) previously reported by tensile drawing above the T_m. Such a low strength of a superdrawn, high‐modulus PTFE tape was ascribed to the low intermolecular interaction of PTFE and the lack of intercrystalline links along the fiber axis, reflecting the initial chain‐extended morphology of the nascent powder combined with the fairly high chain mobility associated with the crystal/crystal transitions at around room temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3369–3377, 2006     

Functional renormalization group beyond the static approximation and its application to the two-dimensional Hubbard model

While the functional renormalization group is a powerful theoretical method, the static approximation has been usually adopted in which the Matsubara frequency dependence of vertex functions is ignored. We propose a formalism beyond the static approximation with an efficient parameterization in the Matsubara frequency space for the vertex functions to incorporate the self-energy.     

On SL(3, ℝ)-actions on 4-spheres

We construct a natural, continuous SL(3, ℝ)-action on S ⁴ which is an extension of the SO(3)-action ψ of Uchida. The construction is based on the Kuiper theorem asserting that the quotient space of ℂP(2) by complex conjugation is S ⁴. We also give a new proof of the Kuiper theorem. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 5, pp. 99–105, 2005.