Sedimentation process in Ariake Bay using NAA and gamma-spectrometry

In order to assess the effect of marine and terrestrial environmental change in the last decades on the sedimentation environment in Ariake Bay, we collected three sediment cores. The concentrations of natural and anthropogenic radionuclides, major elements, and rare-earth elements were measured using gamma-spectrometry and neutron activation analysis. Vertical distributions of both radionuclides and sedimentation rates, determined using Cs-137 and Pb-210_ex dating methods, varied significantly among the sites.     

Preparation and characteristics of photocross-linkable poly(vinyl alcohol)

The reaction of poly(vinyl alcohol) with styrylpyridinium and quinolinium salts which contain formyl group produced water-soluble photosensitive polymers. The sensitivity was high, although the content of the styryl groups was extraordinarily low. Spectroscopical studies revealed that the high sensitivity is due to the aggregation of photofunctional group in the polymer matrix which leads to cyclodimerization on exposure to ultraviolet (UV) light.     

Quasiparticle picture of quarks near chiral phase transition

We study how the quasiparticle picture of the quark can be modified near but above the critical temperature (T _c) of the chiral phase transition; we incorporate into the quark self-energy the effects of the precursory soft modes of the phase transition, i.e. ‘para-σ(π) meson’. It is found that the quark spectrum has a three-peak structure near T _c: We show that the additional new spectra originate from the mixing between a quark (antiquark) and an antiquark-hole (quark-hole) caused by a “resonant scattering” of the quasi-fermions with the thermally-excited soft modes.     

Use of whole‐body cryosectioning and desorption electrospray ionization mass spectrometry imaging to visualize alkaloid distribution in poison frogs

Ambient mass spectrometry is useful for analyzing compounds that would be affected by other chemical procedures. Poison frogs are known to sequester alkaloids from their diet, but the sequestration pathway is unknown. Here, we describe methods for whole‐body cryosectioning of frogs and use desorption electrospray ionization mass spectrometry imaging (DESI‐MSI) to map the orally administered alkaloid histrionicotoxin 235A in a whole‐body section of the poison frog Dendrobates tinctorius. Our results show that whole‐body cryosectioning coupled with histochemical staining and DESI‐MSI is an effective technique to visualize alkaloid distribution and help elucidate the mechanisms involved in alkaloid sequestration in poison frogs.     

Solid-state photoelectron transfer in powdery nanocomposites comprised of a sensitiser, photoacid generators and silica nanoparticles

The dry beads milling of a mixture of 9,10-dipropoxyanthracene (DPA) as an electron donor and surface-modified silica nanoparticles was conducted in the absence or in the presence of a photoacid generator (PAG) as an electron acceptor to give powdery nanocomposites. Fluorescence measurements indicated no mechanochemical change in the crystal structure of DPA after the nanohybridisation. The co-milling with PAG resulted in solid-state fluorescence quenching, whereas quenching efficiency was considerably dependent on the nature of PAG. The solid-state sensitised photoacid generation through the electron transfer was demonstrated by the solid-state photocolouration of leuco-dye of crystal violet lactone.     

Fermi surfaces and quasi-particle band dispersions of the iron pnictides superconductor KFe2As2 observed by angle-resolved photoemission spectroscopy

We have performed an angle-resolved photoemission study of the iron pnictide superconductor KFe₂As₂ with . Most of the observed Fermi surfaces show almost two-dimensional shapes, while one of the quasi-particle bands near the Fermi level has a strong dispersion along the k_z direction, consistent with the result of a band-structure calculation. However, hole Fermi surfaces α and ζ are smaller than those predicted by the calculation while other Fermi surfaces are larger. These observations are consistent with the result of a de Haas-van Alphen study and a theoretical prediction on inter-band scattering, possibly indicating many body effects on the electronic structure.     

Superconducting gap in iron pnictides studied by optical spectroscopy

We investigated the in-plane optical spectrum of a Co-doped Ba(Fe_0.94Co_0.06)₂As₂ single crystal showing superconductivity below . In the normal state, the low-energy optical conductivity spectrum can be decomposed into a sharp Drude term and a broad “incoherent” term. Below T_c, an s-wave-like superconducting gap appears in both components. We also investigated a magnetic or spin-density-wave gap in the detwinned parent compound.     

Analysis of Diffuser Shift Margin in Spatial Spread-Spectrum Holographic Multiplexing

We present a novel numerical model for analyzing shift margin in spatial spread-spectrum (SSS) multiplexing, in which the spatial phase of signal beams, not in reference beams, is modulated and demodulated by a random diffuser to multiplex holograms. The shift margin is determined not by the Bragg effect of a thick hologram, but mainly by the phase correlation property of the diffuser used. In our model, we simulate signal data patterns and a smooth rough surface of a diffuser using oversampling and zero-padding, which allows us to cover crosstalk calculations and direct bit-errors calculations, with a fine shift resolution and a wide diffusion angle range. Calculation results revealed that the practical shift margin that ensures a signal to noise ratio more than 3.0 and a bit-error rate less than 10⁻² is in the range of 0.3ω_eff−0.5ω_eff, where ω_eff is the effective autocorrelation length of the diffuser transmission function. This model will be helpful in designing the optimum random diffuser profile for SSS multiplexing.     

Nonlinear viscoelasticity of polystyrene solutions. I. Strain-dependent relaxation modulus

Strain-dependent relaxation moduli G(t,s) were measured for polystyrene solutions in diethyl phthalate with a relaxometer of the cone-and-plate type. Ranges of molecular weight M and concentration c were from 1.23 × 10⁶ to 7.62 × 10⁶ and 0.112 to 0.329 g/cm³. Measurements were performed at various magnitudes of shear s ranging from 0.055 to 27.2. The relaxation modulus G(t,s) always decreased with increasing s and the relative amount of decrease (i.e.,–log[G(t,s)/G(t,0)]) increased as t increased. However, the detailed strain dependences of G(t,s) could be classified into two types according to the M and c of the solution. When cM < 10⁶, the plot of log G(t,s) versus log t varied from a convex curve to an S-shaped curve with increasing s. For solutions of cM > 10⁶, the curves were still convex and S-shaped at very small and large s, respectively, but in a certain range of s (approximately 3 < s < 7) log G(t,s) decreased rapidly at short times and then very slowly; a peculiar inflection and a plateau appeared on the plot of log G(t,s) versus log t. The strain-dependent relaxation spectrum exhibited a trough at times corresponding to the plateau of log G(t,s). The longest relaxation time τ₁(s) and the corresponding relaxation strength G₁(s) were evaluated through the “Procedure X” of Tobolsky and Murakami. The relaxation time τ₁(s) was independent of s for all the solutions studied while G₁(s) decreased with s. The reduced relaxation strength G₁(s)/G₁(0) was a simple function of s (The plot of log G₁(s)/G₁(0) against log s was a convex curve) and was approximately independent of M and c in the range of cM <10⁶. This behavior of G₁(s)/G₁(0) was in agreement with that observed for a polyisobutylene solution and seems to have wide applicability to many polymeric systems. On the other hand, log G₁(s)/G₁(0) as a function of log s decreased in two steps and decreased more rapidly when M or c was higher. It was suggested that in the range of cM < 10⁶, a kind of geometrical factor might be responsible for a large part of the nonlinear behavior, while in the range of cM > 10⁶, some “intrinsic” nonlinearity of the entanglement network system might be important.