Magnetic ground-state of perovskite PbVO3 with large tetragonal distortion

The magnetic properties of PbVO 3, a PbTiO 3-type perovskite with a large tetragonal distortion ( c/a = 1.229), were investigated. The temperature dependence of the measured magnetization of multidomain single-crystal samples showed a broad maximum centered around 180 K, indicating a two-dimensional antiferromagnetism. muSR measurement revealed the presence of a long-range order below 43 K. The two-dimensional magnetism is due to the ordering of d xy orbitals, which is thought to also be related to the large tetragonal distortion of PbVO 3.     

Experimental study of a semiconductor laser diode having a Mach–Zehnder interferometer in the cavity

The performance of a semiconductor laser diode that has an asymmetric Mach–Zehnder interferometer all-optical switch in the cavity has been studied experimentally. This novel device was designed to be free from clock pulse insertion, since mode-locked optical pulses are generated internally and change the balance of the interferometer periodically. The device was fabricated using a InGaAsP/InP buried heterostructure and the primary optical properties of the device were investigated. Lasing characteristics that were peculiar to the twin-cavity structure were observed, i.e., continuous-wave lasing power oscillation in relation to the injection current balance between the two arms, and cyclic changes in the single/multiple emission peaks as a function of bias voltage at the saturable absorber. Electrical spectrum analysis indicated 40 GHz modulation of lasing output from the twin-cavity laser.     

Spatially selective modification of optical and magneto-optical properties in Fe- and Au-doped glasses irradiated with femtosecond-laser

The optical property and the magneto-optical response were space-selectively modified in transparent Fe³⁺- and Au³⁺-doped glasses by using infrared femtosecond- (fs-) laser irradiation and subsequent annealing. This irradiation process induces the precipitation of not only magnetic spinel-type Fe-oxide nanoparticles but also Au nanoparticles inside the glasses, which shows localized surface plasmon resonance absorption at the wavelengths larger than 500 nm. As the annealing time and the temperature increases, the position of the LSPR peaks exhibits red shifts, which is due to the growth of Au nanoparticles. Faraday rotation angles as a function of wavelength were measured, and the difference spectra exhibit distinct positive peaks, indicating that the coupling between the LSPR due to the Au nanoparticles and the diamagnetism of the matrix glass is effective. To decrease the coupling with the diamagnetic glass, a two-step annealing process (at 450 °C for 90 min and at 550 °C for 30 min) was carried out after irradiation with fs-laser. The preliminary annealing at the lower temperature contributes to the precipitation of ferrimagnetic magnetite nanoparticles. Au nanoparticles were subsequently grown by annealing at 550 °C. In this case, effective coupling between the LSPR and ferrimagnetic nanoparticles has significantly suppressed the intensity of the positive peak in the Faraday spectra compared with the single annealing process.     

Near–Infrared‐Responsive Peptide that Targets Collagen Fibrils to Induce Cytotoxicity

A novel conjugate, PHG10 dye, was synthesized using a collagen peptide and a near–infrared (NIR)‐responsive dye to achieve targeted cytotoxicity. The collagen peptide motif, ‐(Pro‐Hyp‐Gly)₁₀‐ (PHG10), was incorporated for targeting collagen fibrils that are excessively produced by activated fibroblasts around tumor cells. PHG10 dye was purified by HPLC and identified by MALDI‐MS. The phototoxicity and cytotoxicity of PHG10 dye were examined using human glioma cells (HGCs). Fluorescent images indicated that PHG10 dye preferably assembled to collagen‐coated HGCs compared with noncoated HGCs. Under irradiation with NIR light, effective cytotoxicity was observed on collagen‐coated HGCs within 20 min. Because phototoxicity and cytotoxicity are dependent on the assembled amount of PHG10 dye, the targeting of collagen fibrils by the collagen peptide motif PHG10 is assured.     

The alignment of nematic liquid crystals on photolithographic micro-groove patterns

Abstract

The alignment of nematic liquid crystals on micro-groove patterns was studied. It has been found that the order of the alignments is determined by the edge shape, spacing, and line pitch of the micro-groove patterns. On coarse patterns, with pitches greater than 2 μm, striped patterns of the liquid crystal alignment were observed using polarized light which manifested different orientations of the liquid crystals on the top, edge, and bottom of the grooves, respectively. On fine patterns, with pitches less than 2 μm, a uniform device-quality alignment has been realized, with which twisted nematic cells were constructed in combination with the rubbed alignment layer on the opposite substrate. Their viewing angle characteristics and tilt orientations of the director were also investigated.     

Oxidation of benzyl alcohol aiming at a greener reaction

A highly efficient heterogeneous catalyst Ru-Mn-Fe-Cu-O successfully oxidized benzyl alcohol to benzaldehyde in the presence of oxygen using toluene or water as solvent, and without solvent aiming at greener chemistry. This revised version was published online in June 2006 with corrections to the Cover Date.     

Absolute stereochemistry of TT-1 (rasfonin), an α-pyrone-containing natural product from a fungus, Trichurus terrophilus

The absolute stereochemistry of TT-1 (1=rasfonin), an α-pyrone-containing natural product from a Fungi Imperfecti, Trichurus terrophilus, was determined as 5R,6R,7S,9R, and 6′S on the basis of synthesis of diastereomers of two fragments of 1 in optically active forms, and comparison of their spectral and optical data with those of natural specimens.     

Iron-catalyzed 1,6-addition of aryl Grignard reagents to 2,4-dienoates and -dienamides

1,6-Addition of aryl Grignard reagents to 2,4-dienoates or -dienamides was nicely catalyzed by iron salt to give 5-aryl-3-enoates or the corresponding amides in a highly regio- and stereoselective manner.     

Supramolecular catalysts by encapsulating palladium complexes within dendrimers

Dendrimers are well-defined and highly branched macromolecules. By utilizing their capsular architectures, dendrimers encapsulating various catalytically active species can be prepared, which often bring about unique catalysis. Treatment of the alkylated PPI dendrimer with 4-diphenylphosphinobenzoic acid and [PdCl(C3H5)]2 afforded the dendrimer-encapsulated Pd complex using ionic interactions. The dendrimers encapsulating Pd complexes acted as unique supramolecular catalysts for the Heck reaction and allylic amination. The specific nanoenvironment created by the dense amino groups inside the dendrimers can provide high catalytic activity and stability for the Pd complexes. Facile recovery of the dendritic catalysts could be achieved by thermomorphic systems.