Determination of nanogram levels of lanthanoids in a marine macro-alga by neutron activation analysis combined with separation by selective precipitation

Preseparation of lanthanoids by substoichiometric precipitation of calcium oxalate and simple radiochemical separation of lanthanoids by lanthanum oxalate have been developed. They were combined with neutron activation analysis of a marine macro-alga (Laminaria religiosa, brown alga) sample. Quantitative recovery of lanthanoids throughout the procedure was examined by radiotracer technique. Eleven lanthanoids, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Er, Yb and Lu, at 0.7–140 ng g^–1 were determined with a relative standard deviation of 1–7% (n=3). Concentrations of lanthanoids in the marine macro-alga were compared with land plant and sea water.     

A stereoselective total synthesis of (±)-oxylubimin

(±)-Oxylubimin (1), the highest oxidized spirovetivane-type phytoalexin, was totally synthesized with high stereoselectivity using a novel method for α′-hydroxylation of α,β-unsaturated ketones.     

Novel syntheses of hydantoin derivativesK

N-Substituted hydantoin derivatives have been synthesized by the condensation of an α-amino acid derivative, a primary amine and diphenyl carbonate. The method has been applied to the synthesis of hydantoin derivatives with two hydroxyl and/or carboxyl groups.     

Synthesis of Distorted 1,8,13-Trisilyl-9-hydroxytriptycenes by Triple Cycloaddition of Ynolates to 3-Silylbenzynes

1,8,13-Trialkyl(aryl)silyl-9-hydroxytriptycenes (trisilyltriptycenes) were synthesized by the triple addition of ynolates and 3-silylbenzynes with high regioselectivity. Benzene rings in the resulting triptycenes were highly distorted where the dihedral angles between the substituents were as high as 35°. The distortion energy induced step-by-step halogenation reactions to yield halogenated triptycenes, including chiral triptycenes. The 1,8,13-trihalogenated triptycenes were then converted to 1,8,13-functionalized triptycenes.     

Uniaxial alignment of nematic liquid crystals filling vacant spaces in surface-treated nanofibre nonwoven

ABSTRACT

Nematic liquid crystals (NLCs) absorbed in a nonwoven of surface-treated silica nanofibres (SiO₂-NFs) orient the director along the nonwoven thickness direction if the NLCs prefer homeotropic anchoring onto the fibre surface. The nonwoven has vacant spaces with the dimensions of 0.3 and 0.6 μm in the thickness and cross directions, respectively, bordered with SiO₂-NFs with 93 nm in diameter. The SiO₂-NF surface was treated with a silane-coupling agent to induce the homeotropic anchoring of NLC mesogens onto the surface. The nematic director is arranged radially from the fibres although it is more severely constrained by the proximity between fibre surfaces along the thickness direction. Consequently, the NLCs can align along the nonwoven thickness direction involving ?1/2 wedge disclinations on both sides of the fibres.     

One‐Pot Evolution of Ageladine A through a Bio‐Inspired Cascade towards Selective Modulators of Neuronal Differentiation

A bio‐inspired cascade reaction has been developed for the construction of the marine natural product ageladine A and a de novo array of its N1‐substituted derivatives. This cascade features a 2‐aminoimidazole formation that is modeled after an arginine post‐translational modification and an aza‐electrocyclization. It can be effectively carried out in a one‐pot procedure from simple anilines or guanidines, leading to structural analogues of ageladine A that had been otherwise synthetically inaccessible. We found that some compounds out of this structurally novel library show a significant activity in modulating the neural differentiation. Namely, these compounds selectively activate or inhibit the differentiation of neural stem cells to neurons, while being negligible in the differentiation to astrocytes. This study represents a successful case in which the native biofunction of a natural product could be altered by structural modifications.     

Numerical study of unsteady compressible flow driven by supersonic jet injected into elliptical cell with small exit hole

The unsteady behavior of flow driven by a jet suddenly injected into an elliptical cell is numerically studied by solving the axisymmetric two-dimensional compressible Navier–Stokes equations. This system is a model of laser ablation of a certain duration followed by a discharging process through the exit hole at the downstream end of the cell. The parameters for the calculations are the exit diameter of the cell, the Mach number and duration of the injected jet. The injected jet becomes a traveling plume approaching the downstream end of the elliptical cell and discharges from the cell through an exit hole. The plume generates and interacts with a shock wave in the elliptical cell. The unsteady flow properties downstream of the cell are found to be attenuated by the combination of the phenomena occurring in the cell and at the exit. Monitoring the velocity at the exit hole is used to clarify the characteristics of the flow and apply them to applications in pulse laser ablation. The results show that the vortex in the plume head with the same radius as the exit diameter (i.e., D_e/D_j = 2.7, where D_e is the exit diameter and D_j is the injected jet diameter) causes a relatively constant velocity at the exit for about 10 μs. In the downstream flow characteristics, the suddenly injected jet makes a single or double peak in the velocity variation outside the cell depending on the combination of parameters. This suggests that a single laser pulse might generate two beams through the exit hole of a cell, which could increase the efficiency of beam generation with the combination of an elliptical cell and the laser ablation. It is also found that the wave form of the variations and their level are roughly determined by the durations of the jet and the exit diameters of the cell exit, respectively. PACS 51.35.+a; 47.40.Nm     

Franck-Condon factors based on anharmonic vibrational wave functions of polyatomic molecules

Franck-Condon (FC) integrals of polyatomic molecules are computed on the basis of vibrational self-consistent-field (VSCF) or configuration-interaction (VCI) calculations capable of including vibrational anharmonicity to any desired extent (within certain molecular size limits). The anharmonic vibrational wave functions of the initial and final states are expanded unambiguously by harmonic oscillator basis functions of normal coordinates of the respective electronic states. The anharmonic FC integrals are then obtained as linear combinations of harmonic counterparts, which can, in turn, be evaluated by established techniques taking account of the Duschinsky rotations, geometry displacements, and frequency changes. Alternatively, anharmonic wave functions of both states are expanded by basis functions of just one electronic state, permitting the FC integral to be evaluated directly by the Gauss-Hermite quadrature used in the VSCF and VCI steps [Bowman et al., Mol. Phys. 104, 33 (2006)]. These methods in conjunction with the VCI and coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] method have predicted the peak positions and intensities of the vibrational manifold in the X 2B1 photoelectron band of H2O with quantitative accuracy. It has revealed that two weakly visible peaks are the result of intensity borrowing from nearby states through anharmonic couplings, an effect explained qualitatively by VSCF and quantitatively by VCI, but not by the harmonic approximation. The X 2B2 photoelectron band of H2CO is less accurately reproduced by this method, likely because of the inability of CCSD(T)/cc-pVTZ to describe the potential energy surface of open-shell H2CO+ with the same high accuracy as in H2O+.