Cellulose Peroxides with Structures of Peracid and α-Hydroxyhydroperoxide Types

Cellulose peroxides derived from various cellulose derivatives with hydrogen peroxide were investigated. Fibrous carboxy-methyl cellulose, periodic acid-oxidized cellulose, and methyl vinyl ketone-treated cellulose were employed as cellulose derivatives. Carboxyl and carbonyl groups in the cellulose derivatives were believed to react with hydrogen peroxide to form peroxides with structures of peracid and α-hydroxyhydroperoxide types, respectively. The decomposition of the cellulose peroxides and their abilities to initiate grafting reaction were examined.     

Temperature-dependent spectral changes of self-aggregates of zinc chlorophylls esterified by different linear alcohols at the 17-propionate

Systematically synthetic zinc 3-hydroxymethyl-13¹-oxo-chlorins esterified by different linear alcohols (methanol, 1-propanol, 1-hexanol, 1-dodecanol and 1-octadecanol) at the 17-propionate were self-assembled in the presence of cetyltrimethylammonium bromide in an aqueous solution. These zinc chlorins exhibited red-shifted Q _y absorption bands and circular dichroism (CD) signals in the corresponding Q _y region after incubation for 17 h, indicating that the zinc chlorins formed self-aggregates like those in natural chlorosomes of green photosynthetic bacteria. Visible absorption and CD spectra of self-aggregates of the zinc chlorins depended on the length of their esterifying alcohols. Zinc chlorins esterified by shorter alcohols gave larger changes in their visible absorption and CD spectra after incubation above 40°C, whereas zinc chlorins esterified by longer alcohols afforded smaller changes. These results indicate that hydrophobic interaction among esterifying chains of chlorin molecules as well as that between the esterifying chains and peripheral surfactants or lipids play an important role in the stability of chlorosomal self-aggregates.     

Self-assembly of zinc chlorophyll derivatives possessing a pyrenyl group at the 17-propionate residue and effects of additional γ-cyclodextrins on their optical properties

Two kinds of zinc 3¹-hydroxy-13¹-oxo-chlorins 1 and 2 possessing a pyrenyl group at the 17-propionate residue, of which the linker length between the chlorin and the pyrene moieties was varied, were synthesised from naturally occurring chlorophyll a, and were self-assembled in an aqueous solution. Both zinc chlorins 1 and 2 exhibited Q_y absorption bands around 720 nm accompanying circular dichroism signals in the Q_y region, indicating that these zinc chlorins could form self-aggregates like chlorosomes of green photosynthetic bacteria. Addition of γ-cyclodextrin into an aqueous solution containing the self-aggregates of zinc chlorin 1 esterified with 1-pyrenylmethanol induced the appearance of excimer emission of the pyrene moieties around 480 nm as well as increased the fluorescence intensities of the pyrene monomers at 378 and 396 nm, while only an increase in fluorescence from the monomeric pyrene moiety was observed in the case of 2 esterified with 4-(1-pyrenyl)butanol. Exogenous γ-cyclodextrin unchanged the spectral features derived from the chlorin moieties of 1 and 2 in the aqueous phase. These suggest that the encapsulation of the pyrenyl groups in the zinc chlorins unchanged their assembling states under the present conditions.     

Energy structure of Er-2O center in GaAs:Er,O studied by high magnetic field photoluminescence measurement

We perform photoluminescence measurement of GaAs:Er,O under a pulsed magnetic field up to 60 T and succeed to obtain the magnetic field dependence of three main photoluminescence peaks. We also estimate the energy splitting of states ⁴I_15/2 and ⁴I_13/2 using the crystal field theory. Theoretically calculated energy differences between the lowest state of J= and the lowest three states of J= are in good agreement with experimentally obtained energy of three main PL peaks. We discuss the local configuration around the luminescent Er-2O center. By using parameters in the crystal field calculation, our analysis suggest that not only O²⁻ sites but also As³⁻ sites adjacent to Er³⁺ ion are displaced from their original lattice positions.     

Tracking the effects of interactions on spinons in gapless Heisenberg chains

We consider the effects of interactions on spinon excitations in Heisenberg spin-1/2 chains. We compute the exact two-spinon part of the longitudinal structure factor of the infinite chain in zero field for all values of anisotropy in the gapless antiferromagnetic regime, via an exact algebraic approach. Our results allow us to quantitatively describe the behavior of these fundamental excitations throughout the observable continuum, for cases ranging from free to fully coupled chains, thereby explicitly mapping the effects of "turning on the interactions" in a strongly correlated system.     

Long-time asymptotic solutions of convex Hamilton-Jacobi equations with Neumann type boundary conditions

We study the long-time asymptotic behavior of solutions u of the Hamilton-Jacobi equation u _t (x, t)?+?H(x, Du(x, t))?=?0 in ?? × (0, ??), where ?? is a bounded open subset of ${\mathbb{R}^n}$ , with Hamiltonian H?=?H(x, p) being convex and coercive in p, and establish the uniform convergence of u to an asymptotic solution as t ?? ??.     

Enhancement of stability and accuracy of the moving particle semi-implicit method

As a Lagrangian gridless particle method, the MPS (Moving Particle Semi-implicit) method has been proven useful in a wide range of engineering applications. Up to now, most of MPS applications have been limited to problems with compressive stress states. This paper investigates the performance and stability of MPS method in simulation of more general hydrodynamic problems, including those characterized by tensile stresses or by changes in the stress states. It is shown that MPS-based simulations are prone to become destabilized in presence of attractive interparticle forces. This instability appears to be similar to the so-called tensile instability in SPH method. Two new modifications, namely, a modified Poisson Pressure Equation and a corrective matrix for pressure gradient model, are proposed to resolve this shortcoming. These two new modifications together with two previously proposed improvements are shown to stabilize and enhance the performance of MPS method.     

Mössbauer studies of Jarosite, Mikasaite and Yavapaiite, and implication to their Martian counterparts

In order to confirm Mössbauer spectra of Jarosite, unidentified Fe³⁺ species (Fe3D3) and Fe₂O₃ found on Martian surface, some Jarosite specimens produced on Earth were characterized by ⁵⁷Fe Mössbauer spectroscopy. For comparison, anhydrous ferric sulfate minerals, Mikasaite (Fe³⁺ _1.56Al_0.44)(SO₄)₃, and Yavapaiite, KFe (SO₄)₂ were also measured. The thermal decomposition products of Jarosite and their hydration products were also traced by scattering Mössbauer spectra (CEMS and XMS). These data are useful for the identification of hydrous and anhydrous ferric sulfate phases on Mars, including Fe3D3.