Luminescence tuning of imidazole-based lanthanide(III) complexes [Ln = Sm, Eu, Gd, Tb, Dy

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me(3)L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(3)L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(2)L). The general formulas are [Ln(Me(3)L)(H(2)O)(2)](NO(3))(3)·3H(2)O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H(3)L)(NO(3))](NO(3))(2)·MeOH (Ln(3+) = Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H(2)L)(NO(3))(2)(MeOH)](NO(3))·MeOH (Ln(3+) = Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me(3)L and H(3)L ligands and 10-coordinate in the complexes with the H(2)L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me(3)L, H(3)L, and H(2)L are 21?000, 22?700, and 23?000 cm(-1), respectively, which were determined from the phosphorescence spectra of their Gd(3+) complexes. The Me(3)L ligand is an effective sensitizer for Sm(3+) and Eu(3+) ions. Efficient luminescence of Sm(3+), Eu(3+), Tb(3+), and Dy(3+) ions was observed in complexes with the H(3)L and H(2)L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions.     

Unified approach to catechin hetero-oligomers: first total synthesis of trimer EZ-EG-CA isolated from Ziziphus jujuba

A catechin hetero-trimer isolated from Ziziphus jujuba has been synthesized. Among three constituent monomers, (-)-epiafzelechin and (-)-epigallocatechin were prepared by de novo synthesis. Trimer formation relied on the unified approach to oligomers based on the bromo-capping and the orthogonal activation, reaching the reported structure of the natural product.     

Synthesis and luminescence properties of dye-doped deoxyribonucleic acid films

Dye-doped deoxyribonucleic acids (DNA)–tetradecyltrimethylammonium (TTA) films have been prepared. Rhodamine 6G, known as laser dyes, can be spontaneously doped by immersing the DNA–TTA film in rhodamine 6G-acetonitrile solutions. It is surmised that rhodamine 6G monomers and dimers diffuse within the hydrophobic TTA sites, and then monomers presumably intercalate between adjacent base pairs of DNA. Optical absorption spectra reveal that rhodamine 6G molecules in the sample undergo an unusual transformation from the dimer state to the monomer state with the elapse of time. Rhidamine 6G molecules doped in DNA–TTA show enhanced photostability and concentration quenching than those in PMMA. The environment, conformation and chemical stability of rhodamine 6G are different between DNA–TTA and PMMA, and are presumably modified by the intercalation.     

Wind tunnel test of Japanese arrows with the JAXA 60-cm magnetic suspension and balance system

In order to understand the aerodynamic properties of Japanese arrows, several types of shafts without fletching and various types of Japanese arrows were examined in a low-speed wind tunnel equipped with the JAXA 60-cm magnetic suspension and balance system. The main component of drag acting on the shaft is viscous drag from the boundary layer. This viscous drag can be evaluated analytically. A simple new method to estimate the effects of fletching on the lift of the arrow was proposed in which we found that lift is proportional to the angle of attack of the arrow but not to the rotation speed or angle. Time history results for the lift on rotating arrows in the magnetic suspension and balance system indicate that this method effectively estimates the lift on an actual rotating arrow in flight. The lift and pitching moment were mainly generated by fletching, and the drag from the fletching was similar in magnitude to that of the arrow shaft. For Japanese bamboo arrows tested with a field point, the drag, lift, and pitching moment coefficients were evaluated to be in the ranges of 3.5?C3.7, 0.4?C0.8, and ?0.15 to ?0.25, respectively, at Reynolds numbers of an arrow in flight.     

First-principles supercell calculations for simulating a shallow donor state in Si

We present first-principles simulations of As-doped Si carried out using several cubic supercells of up to 10 648 atoms. The 1s As donor level in each supercell splits into three states, which have A₁, T₂, and E symmetries, respectively. The 1s(A₁) wavefunction is well converged in the largest cell, and its spread is close to those of the effective-mass theories. However, the calculated binding energies are smaller than experimental values. This discrepancy would be due to the self-interaction error within the approximated exchange-correlation density functional used in this calculation. Therefore, we also show perturbative calculations based on an impurity potential without the self-interaction error to estimate the binding energies of the 1s(A₁) donor state. The estimated binding energy in the largest supercell agrees well with the experimental value.     

Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.     

Electrochemical Detection of Triglycerides Based on an Enzymatic Reaction and Electrocatalytic Oxidation with Nortropine‐N‐oxyl

This work investigated a simple triglycerides (TGs) detection method combining an enzymatic reaction, using only lipase, and the electrocatalytic oxidation of glycerol with nortropine‐N‐oxyl (NNO). Tributyrin was employed as a model TG. In this method, TGs are degraded by lipase to glycerol and fatty acids, after which the glycerol reacts with NNO. Preliminary cyclic voltammetry trials demonstrated that the anodic peak current increased along with the glycerol concentration, giving currents of 53.2 and 97.3 μA (at +0.6 V vs. Ag/AgCl) in response to 10 and 100 mM glycerol, respectively. Amperometry confirmed the same response during constant potential electrolysis at+0.6 V vs. Ag/AgCl. This behavior was also observed in a system incorporating tributyrin and lipase, with increases in current proportional to the tributyrin concentration over the range of 0.1 to 10 mM.     

Total Synthesis of Carthamin,a Traditional Natural Red Pigment

The first total synthesis of carthamin ( 3 ), a historic natural red pigment, has been achieved. The molecular structure was efficiently constructed by assembling two equivalents of the in situ generated lithiated monomers and triisopropyl orthoformate. This synthesis confirms the structure proposed in 1996.     

Bound diquarks and their Bose–Einstein condensation in strongly coupled quark matter

We explore the formation of diquark bound states and their Bose–Einstein condensation (BEC) in the phase diagram of three-flavor quark matter at nonzero temperature, T, and quark chemical potential, μ  . Using a quark model with a four-fermion interaction, we identify diquark excitations as poles of the microscopically computed diquark propagator. The quark masses are obtained by solving a dynamical equation for the chiral condensate and are found to determine the stability of the diquark excitations. The stability of diquark excitations is investigated in the T–μ$T\text{–}\mu$ plane for different values of the diquark coupling strength. We find that diquark bound states appear at small quark chemical potentials and at intermediate coupling strengths. Bose–Einstein condensation of non-strange diquark states occurs when the attractive interaction between quarks is sufficiently strong.     

Tadpole resummations in string theory

While R–R tadpoles should be canceled for consistency, string models with broken supersymmetry generally have uncanceled NS–NS tadpoles. Their presence signals that the background does not solve the field equations, so that these models are in “wrong” vacua. In this Letter we investigate, with reference to some prototype examples, whether the true values of physical quantities can be recovered resumming the NS–NS tadpoles, hence by an approach that is related to the analysis based on String Field Theory by open–closed duality. We show that, indeed, the positive classical vacuum energy of a Dp-brane of the bosonic string is exactly canceled by the negative contribution arising from tree-level tadpole resummation, in complete agreement with Sen's conjecture on open-string tachyon condensation and with the consequent analysis based on String Field Theory. We also show that the vanishing classical vacuum energy of the SO(8192) unoriented bosonic open-string theory does not receive any tree-level corrections from the tadpole resummation. This result is consistent with the fact that this (unstable) configuration is free from tadpoles of massless closed-string modes, although there is a tadpole of the closed string tachyon. The application of this method to superstring models with broken supersymmetry is also discussed.